Image display device and light emission device (09-Mar-2010)

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional Application of, and claims the benefit of priority under 35 U.S.C. § 120 from U.S. Ser. No. 11/504,682, filed Aug. 16, 2006, which is a continuation of U.S. Ser. No. 11/386,858, filed Mar. 23, 2006, (now U.S. Pat. No. 7,110,061, issued Sep. 19, 2006), which is a divisional application of Ser. No. 10/956,136, filed Oct. 4, 2004, which is continuation application of Ser. No. 10/436,157, filed May 13, 2003 (now U.S. Pat. No. 6,864,627, issued Mar. 8, 2005), which is divisional application of Ser. No. 09/080,300, filed May 18, 1998 (now U.S. Pat. No. 6,586,874, issued Jul. 1, 2003), and claims the benefit of priority under 35 U.S.C. § 119 from Japanese Patent Application No. 127426/1997, filed May 16, 1997, the entire contents of each of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an image display device and a light emission device, more particularly to an image display device of a small size with high performance and high reliability and a light emission device which is suitable for various kinds of uses including a light source of the image display device.

An image display device plays a role as an interface that visually connect various kinds of electrical equipment and human beings. In the present information society, the role of image display devices is essential, and the image display device is a key component in a wide field that includes television sets, computers, information terminals, game machines and household electronic appliances. At the same time, development of new high performance image display devices is desired to meet the needs of the present information society as it rapidly develops and increases in diversity.

For such image displaying devices, a Braun tube and a liquid crystal display device have been mainly used. The Braun tube scans an electron beam in a glass tube sealed to produce a vacuum and excites fluorescent bodies arranged on a shadow mask, thereby displaying an image. The Braun tube can be manufactured relatively low in cost, and is capable of displaying high quality images. Therefore, in general, the Braun tube is widely used as an image display device for television sets, computer monitors, etc.

On the other hand, a liquid crystal display device applies a designated electric field to a liquid crystal layer held between two substrates, thereby changing an optical property of the liquid crystal layer to display changes of intensities of transmitted light and reflected light in the form of a predetermined image. When the liquid crystal display device is compared with the Braun tube, the liquid crystal display device has an advantage that it is thin in thickness and light in weight. Liquid crystal display devices are used in electronic equipment such as notebook computers and various kinds of portable information console units.

With the development of the foregoing electronic equipment and the advancement of the information society, image display devices must be made smaller in size, lighter in weight, and display an image with higher quality and reliability.

However, the Braun tube has structural problems because it is large in length in its tube direction, heavy in weight, and since it is a vacuum glass tube, it has an insufficient durability against vibrations and shocks.

On the other hand, a conventional liquid crystal display device uses a cathode fluorescent tube as its light source, which meets manufacturers needs for a small-sized, thin cathode fluorescent tube having long life, in addition to having display luminance. However, there is a problem in liquid crystal display devices, that the visual field angle is narrower than that of the Braun tube, so that image recognition from an oblique direction is significantly poor.

The present invention was made from the viewpoint of the above described circumstances. Specifically, the object of the present invention is to provide an image display device which is easy to manufacture, small in size, light in weight, having has a wide visual filed angle, capable of displaying a high quality image, and having a high reliability, and to provide a light emission device which is suitably used for a light source of such image display device and for other various kinds of uses.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a novel image display device that comprises a light source section which includes a semiconductor light emitting element as a light source, a light adjustment section which adjusts an intensity of a light emitted from the light source section for each of pixels, and transmits the pixels as a transmission light. The image display device also includes a wavelength change section which receives the transmission light transmitted from the light adjustment section and emits light having an intensity spectrum different from that of the transmission light.

The light adjustment section in the image display device adjusts the intensity of the transmission light by a liquid crystal cell, and the wavelength change section comprises a phosphor.

The semiconductor light emitting element of the light source section is the one which emits a light exhibiting a light emission spectrum having a peak wavelength in a ultraviolet region. The wavelength change section comprises three kinds of phosphors arranged according to a predetermined pixel pattern. The three kinds of the phosphors are the ones which convert the said transmission light into visible rays of lights of red, green and blue wavelength zones, respectively, whereby the image display device can display a clear and bright image with a low power consumption.

Moreover, the semiconductor light emitting element comprises a gallium nitride type semiconductor as a light emitting layer, in which a peak wavelength of a light emission spectrum is set to be at a range of 360 nanometer to 380 nanometer. The wavelength change section uses a phosphor exhibiting an absorption excitation peak in a wavelength region which is substantially the same as that of the said peak wavelength of the foregoing phosphors, whereby an image display device of a high efficiency can be provided.

Moreover, a light transmitting substrate of the light adjustment section is formed of a low alkali glass, a no-alkali glass or a quartz glass, whereby the absorption of a ultra violet ray is reduced so that a luminance is increased.

Moreover, by providing an ultra violet absorption filter in the wavelength change section, it is possible to suppress the entry of a ultra violet ray from the outside as well as the leakage of a ultra violet ray emitted from the semiconductor light emitting element to the outside.

Moreover, the semiconductor light emitting element exhibits a light emission spectrum, in which the peak wavelength is at a blue range. The wavelength conversion section comprises two kinds of phosphors and one kind of filters, arranged according to a predetermined pixel pattern. The two kinds of phosphors are organic phosphors which convert the foregoing transmission light to a visual light in a wavelength zone such as red or green zone and one kind of filter transmit the foregoing transmission light, so that the image display device with a high efficiency can be provided.

On the other hand, the image display of the present invention may be alternatively constituted in such a manner that a light source section including a semiconductor light emitting element as a light source, a wavelength change section which receives light emitted from the semiconductor light emitting element and emits a light exhibiting a different intensity spectrum from that of the received light, and a light adjustment section which adjusts the intensity of the light emitted from said wavelength change section, corresponding to each pixel of an image to be displayed, and transmits it as a transmission light.

Moreover, the semiconductor light emitting element as the light source of the image display device emits a light exhibiting a light emission spectrum, a peak wavelength of which is in an ultraviolet ray range, and the phosphors convert the lights emitted from the said light conduction plate to visible lights having respective peaks in wavelengths zones of red, green and blue thereof.

Moreover, the light adjustment section comprises either a guest-host type liquid crystal or a high polymer diversion type liquid crystal. To keep balance of luminance for every color, the pixel pattern has different pixel area depending on each color, and the light source sections may be constructed in various types, whereby it will make it possible to display a clear image with a high efficiency.

Moreover, the image display device of the present invention comprises a light source section having a semiconductor light emitting element and a movable reflection mirror in the light source section, and a wavelength change section which receives a light emitted from said light source section to emit it after changing its intensity spectrum, wherein the light from the semiconductor light emitting element is reflected by moving the movable reflection mirror and the reflected light is incident onto a predetermined position of said wavelength change section.

Moreover, the image display device of the present invention may comprise a variable lens instead of the movable reflection mirror.

On the other hand, the light emitting element of the present invention comprises a light emitting diode which includes a gallium nitride type compound semiconductor as a light emitting layer and a phosphor which is deposited in at least one portion of a surface of the light emitting diode, wherein the light emitted from the light emitting diode is subjected to a wavelength change by said phosphor and is emitted to an outside of the light emitting diode.

Moreover, the light emitting element of the present invention comprises a mounting material, the light emitting diode which includes a gallium nitride type compound semiconductor as a light emitting layer mounted on the mounting material, and resin molding the light emitting diode, wherein a phosphor is deposited on a surface of the resin and the light emitted from the light emitting diode is subjected to a wavelength change by the phosphor and is emitted to the outside.

Alternatively, the light emitting element of the present invention comprises a mounting member, the light emitting diode mounted on the mounting member, and resin which molds the light emitting diode, wherein said mounting member comprises a reflection plate provided around the mounting member of the light emitting diode and a phosphor deposited on a surface of the reflection plate, and wherein a light emitted from the light emitting diode is subjected to a wavelength change by the phosphor and is emitted to the outside.

Alternatively, the light emitting element of the present invention comprises a light transmission substrate, a layer formed of a phosphor stacked on the light transmission substrate, and a light emitting diode which includes a gallium nitride type compound semiconductor as a light emitting layer, being mounted on the phosphor layer, wherein a light emitted from the light emitting diode is subjected to a wavelength change by the phosphor layer, and is emitted to the outside after transmitting through the light transmission substrate.

Or, the light emitting element of the present invention comprises a light emitting diode having a multi-layered structure composed of a plurality of semiconductor layers including at least one gallium nitride type compound semiconductor, wherein at least one of said semiconductor layers includes a phosphor which performs a wavelength change for a light emitted from said fight emitting diode and emits it to the outside.

Or, the light emitting element of the present invention comprises a plurality of light emitting diodes, each of which emits a light of a wavelength different from those emitted from other light emitting diodes and is stacked so as not to shade the light emitted from other diodes when viewed from a light exiting direction, wherein the light emitted from each of the light emitting diodes can be taken from the light exiting direction.

According to the present invention, it is possible to provide an image display device which is capable of displaying an image with a very wide visual field angle compared to an ordinary liquid crystal display device, the image being recognized clearly even when viewed obliquely.

According to the present invention, it is possible to provide an image display device which is capable of displaying a distinctive image without blur and vagueness.

According to the present invention, since in the image display device of the present invention the light source section employs the semiconductor light emitting element as a light source, the image display device can exhibit an extremely high photoelectric conversion efficiency and has an ability to reduce power consumption compared to the conventional image display device such as the liquid crystal display device.

According to the present invention, the image display device of the present invention employs the semiconductor light emitting element as a light source, whereby a high photoelectric conversion efficiency can be achieved and the power consumption can be reduced compared to the conventional cathode fluorescent tube. For example, the power consumption of a 10.4 inch type thin film transistor (TFT) liquid crystal display device using the conventional cathode fluorescent tube as a light source is about 9 watts. On the contrary, the power consumption of the image display device adopting an ultra violet LED and the phosphor is about 4 watts, specifically, the power consumption is reduced to be less than half of that of the conventional liquid crystal display device. As a result, battery life of portable electronic equipment such as a notebook type computer and various kinds of information portable console units which incorporate the image display device of the present invention can be prolonged.

Moreover, according to the present invention, in the light source section of the image display device, the circuit thereof is simplified compared to the conventional cathode fluorescent tube, where the driving voltage for the light source section can be reduced. Specifically, the conventional cathode fluorescent tube had to be applied with a high voltage via a stabilizing circuit or an inverter. However, according to the present invention, the semiconductor light emitting element serving as a light source has an ability to provide a sufficient light emission intensity with a DC voltage as low as 2 to 3.5 volts. Therefore, there is no need of a stabilizing circuit or an inverter circuit for the semiconductor light emitting element, so that the driving circuit for the light source is greatly simplified and the driving voltage for driving the light source can be reduced.

Moreover, according to the present invention, the life time of the light source incorporated in the image display device can be significantly prolonged than that of the conventional image display device. Specifically, in a conventional cathode fluorescent tube, luminance is rapidly lowered after the passage of a predetermined life time period due to sputtering phenomenon at the light source section, and light emission stops. According to the present invention, reduced luminance is rarely found even when the light source has been used for an extremely long time as long as several tens of thousands of hours, and the life time of the light source can be said to be quasi-permanent.

Moreover, the image display device of the present invention has a very short rise-up time for the light emission. Specifically, the period of time from a signal input for starting of driving to a stationary state in the light emission is very short compared to the conventional cathode fluorescent tube so that the image display device of the present invention is capable of starting an operation instantaneously.

According to the present invention, the reliability of the image display device of the present invention can be increased. Specifically, the conventional cathode fluorescent tube has a structure that seals a specified gas in a glass tube. Therefore, in some cases, the cathode fluorescent tube is broken by excessive shock and vibration. According to the present invention, however, since the semiconductor light emitting element that is a solid state element is used as a light source, reliability against shock and vibration increases remarkably.

Moreover, according to the present invention, there is no need of harmful mercury. Specifically, in the conventional cathode fluorescent tube, a designated amount of mercury is often sealed in its glass tube. The image display device of the present invention need not use such harmful mercury.

Moreover, the light emitting element of the present invention is small in size, thin in thickness, and exhibits high luminance and is reliable. A plurality of emitted lights having different wavelengths such as red, green and blue colors can be simultaneously produced from the light emitting element of the present invention. As described above, according to the present invention, provided are the image display device and the light emitting element which have simple constitutions and are small in size with a high reliability. In addition, excellent industrial advantages, including those described above and hereinafter, can be brought about by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is an illustration of a sectional view showing an outline of a constitution of an image display device according to a first embodiment of the present invention;

FIG. 2 is an illustration of sectional view of an image display device 10a according to the present invention;

FIG. 3 is an illustration of a sectional view showing an outline of a detailed constitution of another image display device 10b according to the present invention;

FIG. 4 is a chart illustrating concrete examples of semiconductor light emitting elements suitably used for a light source section of the image display devices according to the present invention;

FIG. 5 is a graph of light emission efficiency versus wavelength for a phosphor which is suitably used for a wavelength change section 40b of the image display device 10b shown in FIG. 3;

FIG. 6 is an illustration of is a sectional view of an image display device 10c shown in FIG. 3;

FIG. 7 is an illustration of a sectional view of an image display device 10d shown in FIG. 3;

FIG. 8 is a sectional view showing an outline of still another concrete constitutional example of the image display device 10a shown in FIG. 3;

FIG. 9 is a sectional view showing an outline of further still another concrete constitutional example of the image display device 10a shown in FIG. 3;

FIG. 10 is a sectional view showing an outline of further still another concrete constitutional example of the image display device 10a shown in FIG. 3;

FIG. 11 is a sectional view showing an outline of further still another concrete constitutional example of the image display device 10a shown in FIG. 3;

FIG. 12 is a sectional view showing an outline of further still another concrete constitutional example of the image display device 10a shown in FIG. 3;

FIG. 13 is a sectional view showing an outline of a constitution of an image display device according to a second embodiment of the present invention;

FIG. 14 is a sectional view showing an outline of a constitutional example of an image display device 50 of the present invention;

FIG. 15 is a sectional view showing an outline of a constitution of a modification example of an image display device 50a of the present invention;

FIG. 16 is a sectional view showing an outline of a constitution of a modification example of an image display device 50 of the present invention;

FIG. 17 is a sectional view exemplifying a constitution of a transmission type image display device which uses a light adjustment section 30k capable of being used in the present invention;

FIG. 18 is a constitutional view exemplifying an outline of a reflection type image display device which uses a light adjustment section 30k;

FIG. 19 is an explanatory view showing an example in which an area of each pixel is optimized in the image display device of the present invention;

FIG. 20 is a constitutional view showing an outline of a concrete example of the light source section 20 of the image display device 10 or 50 according to the present invention;

FIG. 21 is a constitutional view showing an outline of a second concrete example of the light source section of the image display section according to the present invention;

FIG. 22 is a constitutional view showing a third concrete example of the light source of the image display device according to the present invention;

FIG. 23 is a constitutional view showing a fourth concrete example of the light source of the image display device according to the present invention;

FIG. 24 is a constitutional view showing a fifth concrete example of the light source of the image display device according to the present invention;

FIG. 25 is a constitutional view showing a sixth concrete example of the light source of the image display device according to the present invention;

FIG. 26 is a constitutional view showing a seventh concrete example of the light source of the image display device according to the present invention;

FIG. 27 is a constitutional view showing an eighth concrete example of the light source of the image display device according to the present invention;

FIG. 28 is a constitutional view showing a ninth concrete example of the light source of the image display device according to the present invention;

FIG. 29 is a constitutional view showing a tenth concrete example of the light source of the image display device according to the present invention;

FIG. 30 is a constitutional view showing an eleventh concrete example of the light source of the image display device according to the present invention;

FIG. 31 is a constitutional view showing a twelfth concrete example of the light source of the image display device according to the present invention;

FIG. 32 is a constitutional view showing a thirteenth concrete example of the light source of the image display device according to the present invention;

FIG. 33 is a constitutional view showing a fourteenth concrete example of the light source of the image display device according to the present invention;

FIG. 34 is a constitutional view showing a fifteenth concrete example of the light source of the image display device according to the present invention;

FIG. 35 is a constitutional view showing a sixteenth concrete example of the light source of the image display device according to the present invention;

FIG. 36 is a constitutional view showing a seventeenth concrete example of the light source of the image display device according to the present invention;

FIG. 37 is a constitutional view showing a eighteenth concrete example of the light source of the image display device according to the present invention;

FIG. 38 is a constitutional view showing a nineteenth concrete example of the light source of the image display device according to the present invention;

FIG. 39 is a constitutional view showing a twentieth concrete example of the light source of the image display device according to the present invention;

FIG. 40 is a constitutional view showing a twenty-first concrete example of the light source of the image display device according to the present invention;

FIG. 41 is a constitutional view showing a twenty-second concrete example of the light source of the image display device according to the present invention;

FIG. 42 is a constitutional view showing a twenty-third concrete example of the light source of the image display device according to the present invention;

FIG. 43 is a constitutional view showing a twenty-fourth concrete example of the light source of the image display device according to the present invention;

FIG. 44 is a constitutional view showing a twenty-fifth concrete example of the light source of the image display device according to the present invention;

FIG. 45 is a constitutional view showing a twenty-sixth concrete example of the light source of the image display device according to the present invention;

FIG. 46 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention;

FIG. 47 is a sectional view showing an outline of a concrete example of the light source section 22A;

FIG. 48 is a sectional view showing an outline of a concrete example of the light source section 22A;

FIG. 49 is a sectional view showing an outline of a concrete example of the light source section 22A;

FIG. 50 is a sectional view showing an outline of a conventional light source, which is illustrated for comparison with the present invention;

FIG. 51 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 52 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 53 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 54 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 55 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 56 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 57 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention;

FIG. 58 is a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 59 a sectional view showing an outline of a concrete example of the light source 22A;

FIG. 60 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention;

FIG. 61 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention;

FIG. 62 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention;

FIG. 63 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention;

FIG. 64 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention; and

FIG. 65 is a sectional view showing an outline of a concrete example of the light source of the image display device according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIG. 1, thereof, the present invention provides an image display device which is capable of displaying a high quality image with a wide visual field angle and a low power consumption, by combining in various forms a material having a wavelength conversion function, a light adjustment mechanism for adjusting an intensity of a transmission light and a semiconductor light emitting element. Moreover, the present invention provides a small-sized light emission device which emits a plurality of lights with high luminance, each of the lights having a different wavelength.

In FIG. 1, there is provided a sectional view showing an outline of a constitution of an image display device according to a first embodiment of the present invention. Specifically, the image display device 10 of the present invention comprises a light source section 20, a light adjustment section 30, and a wavelength conversion section 40. Or, the image display device 10 may comprise a wavelength selection section 40 instead of the wavelength conversion section 40. The light source section 20 includes semiconductor light emitting elements appropriately arranged therein, and emit light incident onto the light adjustment section 30. The light has predetermined wavelength and quantity of lights, and exhibits a predetermined luminance distribution.

The light adjustment section 30 adjusts the light incident from the light source section 20 thereinto every pixel, and transmits the adjusted light through the wavelength conversion section 40, which appropriately changes the wavelength of the light incident from the light adjustment section 30, and emits the light outside of the image display device 10.

According to the present invention, a spatial intensity distribution of the light emitted from the wavelength conversion section or the wavelength selection section 40 can be approximated to an intensity distribution displayed by an aggregate of point light sources formed by the wavelength conversion section 40 as the light source. Therefore, there is an extremely wide angle of visual field compared to ordinary liquid crystal display devices, and the image display device of the present invention is capable of displaying an image clearly recognized even when it is observed from an oblique angle.

According to the present invention, the light emitted from the wavelength conversion section 40 is directly output without passing through the light adjustment section 30. The wavelength of the light being changed by the wavelength conversion section 40 is disposed in the front plane of the image display device 10. Therefore, no blur or vignette are produced, and a distinct image can be obtained.

According to the present invention, the light source section 20 employs the semiconductor light emitting element as a light source, resulting in a high photoelectric conversion efficiency and reduction in power consumption compared to conventional image display devices such as liquid crystal display devices.

FIG. 2 is a sectional view showing an outline of the concrete structure of the image display device of the present invention. Specifically, the image display device 10a shown in FIG. 2 comprises a light source section 20, a light adjustment section 30a and a wavelength change section 40a.

The light source section 20 comprises a semiconductor light emitting element as a light source, which posses a designated light emission spectrum.

The light adjustment section 30a has a structure that adjusts the transmission ratio of a light with liquid crystal. Specifically, in the light adjustment section 30a, liquid crystal layer 36 is held between polarizing plates 31 and 39. By applying a designated voltage between pixel electrodes 34 and the opposite electrode 38, the orientation state of molecules in the liquid crystal layer 36 is controlled and the liquid crystal layer 36 acts with the upper and lower polarization plates 31 and 39, whereby the transmission ratio of the light can be controlled. Each pixel electrode 34 is supplied with a designated voltage via switching elements 35. For switching elements 35, a metal-insulating layer-metal (MIM) coupling type element or a thin film transistor (TFT) formed from a hydrogenized amorphous silicon or polycrystalline silicon can be used, for example.

The wavelength conversion section 40a has a structure which phosphors 44 are disposed on the lower surface of transparent substrate 42. Phosphors 44 may be arranged so that the pixels are partitioned from each other by black matrixes formed of a light shading material. Or, the phosphors 44 may be arranged on the upper surface of the transparent substrate 42.

In an image display device such as image display device 10a, the light adjustment section 30a adjusts the amount of light of every pixel emitted from the light source section 20, depending on the voltage applied to the liquid crystal layer 36. Then, the light is incident onto the phosphors 44. Then the wavelength of each pixel is converted at phosphors 44, thereby forming a designated image. Here, the phosphors 44 may be a long wavelength conversion type phosphor, specifically, they may be a phosphor that, upon receipt of an incident light, changes the incident light into a light having a longer wavelength and emits it. Or, the phosphors 44 may be a phosphor that changes the incident light into one having a wavelength shorter than that of the incident light and emits it.

According to the present invention, since the semiconductor light emitting element is used as a light source, the photoelectric conversion efficiency is higher than that of the conventional cathode fluorescent tube, and power consumption can be reduced. Moreover, in the new structure the phosphor is excited by the light emitted from the semiconductor light emitting element which has a high photoelectric conversion efficiency, resulting in reduced power consumption of the image display device as a whole.

As one example, in the case of the 10.4 inch type TFT liquid crystal display device using a conventional cathode fluorescent tube as a light source, the power consumption was about 9 watts. However, in case of the image display device of the present invention, using a ultra violet ray LED and phosphors, the power consumption is about 4 watts, so that power consumption is reduced to less than half of that of the conventional liquid crystal display device. As a result, the battery cells of portable type electronic equipment such as notebook type computers and various kinds of portable information terminal equipment can be prolonged.

Moreover, the image display device of the present invention can achieve a simplification of the circuit constitution and a reduction in the driving voltage, compared to a conventional cathode fluorescent tube. Specifically, a conventional cathode fluorescent tube had to be applied with a high voltage via a stabilizing circuit or an inverter. However, according to the image display device of the present invention, the semiconductor serving as the light source can produce a sufficient light emission intensity with a DC voltage as low as 2 to 3.5 V. Therefore, a stabilizing circuit or an inverter is unnecessary so that the driving circuit of the light source is greatly simplified and at the same time the driving voltage is reduced.

Moreover, according to the image display of the present invention, the life of the light source can be significantly prolonged. Specifically, the luminance of the emitted light declines rapidly in a conventional cathode fluorescent tube and light emission stops after the expiration of a predetermined life time, due to a sputtering phenomenon at its electrode section. However, according to the image display device of the present invention, the semiconductor light emitting element of the light source scarcely exhibits any drop of luminance of the emitted light after it has been used for a long time such as tens of thousands of hours. It can be said that the life time of the semiconductor light emitting element is quasi-permanent. Therefore, the image display device of the present invention has greatly prolonged life compared to a conventional device. Moreover, according to the present invention, the image display device has an extremely short rise-up time to start an operation. Specifically, the time from turning on of the power to a steady state of illumination luminance is very short compared to the conventional cathode fluorescent tube, so that the image display device of the present invention is capable of starting its display operation virtually simultaneously.

According to the present invention, the image display device of the present invention has increased reliability. Specifically, the conventional cathode fluorescent tube has a structure that its glass tube is charged with specified gas. Therefore, the conventional cathode fluorescent tube may be broken due to excessive shock or vibration. However, according to the present invention, since a semiconductor light emitting element which is a solid state element, is employed as the light source, durability against shock and vibration increases remarkably. As a result, the reliability of various kinds of portable electronic equipment mounting the image display device of the present invention can be increased greatly.

Moreover, according to the present invention, harmful mercury is not used. Specifically, in a conventional cathode fluorescent tube, a designated amount of mercury is often charged in its glass tube. However, according to the present invention, it is unnecessary to use such harmful mercury.

FIG. 3 is a sectional view showing an outline of a concrete structure of image display device 10b of the present invention. Specifically, the image display device 10b shown in FIG. 3 comprises a light source section 20, a light adjustment section 30a and a wavelength conversion section 40b.

The light source section 20 comprises a semiconductor light emitting element as a light source, which emits light in an ultraviolet ray range. For example, gallium nitride which is explained in FIG. 4 should preferably be used for a material forming a light emitting layer material of the light emitting element.

The wavelength conversion section 40b includes phosphors 44a, 44b, and 44c, arranged in a predetermined pattern. The phosphors convert light wavelength ranges of light emitted from the light adjustment section 30a into visible rays of red, green, and blue wavelength light, respectively.

FIG. 4 is an explanatory chart concerning a concrete example of a semiconductor light emitting element which is suitably used for the light source of the image display device. In FIG. 4, wavelengths of light, colors corresponding to each of the wavelengths and materials of compound semiconductors, each of which has a light emission peak in the corresponding wavelength zones, is shown.

In the image display device 10b shown in FIG. 3, the wavelength of light from the light source 20 is changed and output by the conversion section 40b. Here, phosphor is a means for changing the wavelength, and the wavelength conversion section 40b performs in many cases what is called long wavelength conversion, which emits light having a longer wavelength than that of the incident light. Therefore, in order to realize a full color display, the wavelength of the semiconductor light emitting element should be shorter than that of blue color which has the shortest in the visible light range. In addition, the semiconductor light emitting element must also exhibit a high light emission luminance at the same time.

For a material of such semiconductor light emitting element satisfying these requirements, gallium nitride can be utilized. A semiconductor light emitting element that uses gallium nitride as a light emitting layer, and emits light of a wavelength ranging from 360 to 380 nanometer, has a high light emission efficiency. Therefore, using such a semiconductor light emitting element as a light source, an image display device which displays a clear image with a high luminance can be realized.

The light adjustment section 30a of the image display device 10b shown in FIG. 3 can be constituted similar to that of the image display device 10a shown in FIG. 2. Accordingly, the same material parts in the light adjustment section 30a and the light adjustment section of image display device 10a are denoted with the same reference numerals, and descriptions for them are omitted.

Moreover, the wavelength change section 40b of the image display device 10b has a constitution in which phosphors 44a, 44b and 44c are arranged on the lower surface of the transparent substrate 42 so as to form a designated pattern. For the material of the phosphors 44a, 44b and 44c, the one that has an excitation characteristic that agrees with the light emission characteristic of the light source of light source section 20 should be preferably used.

FIG. 5 is an explanatory drawing concerning a concrete example of a phosphor suitable to be used in the wavelength conversion section 40b of the image display device 10b. Specifically, in FIG. 5, exemplified is a relation between a relative light emission efficiency of a phosphor and a wavelength of light incident thereto. The phosphor shown in FIG. 5 exhibits the maximum light emission efficiency of the wavelength of the incident light, at the ranges from 340 to 380 nanometer. Specifically, the phosphor shown in FIG. 5 indicates an excitation peak in the wavelength zone of the light emitted from the light emitting element which was explained in FIG. 4. By combining this phosphor with the semiconductor light emitting element explained with FIG. 4, an extremely high photoelectric conversion efficiency can be achieved. Moreover, the wavelength of the light emitted from the phosphor can be suitably selected by introducing specified impurities thereinto. Thus, the image display device 10b of the present invention will be capable of increasing luminance in an image display and displaying a bright and clear image.

For such phosphor, for example, a substance such as Y₂O₂S:Eu for emitting a red color will be mentioned; (Sr, Ca, Ba, Eu)₁₀(PO₄)₆Cl₂ for emitting a blue color; and 3(Ba, Mg, Eu, Mn)0.8Al₂O₃ for emitting a green color.

By using such phosphor, the wavelength of the light in the ultraviolet range emitted from the light source section 20 can be converted with high efficiency. The phosphors 44a, 44b and 44c receive the light in the ultraviolet range from the light source section 20 to convert the wavelengths of the light, and output lights in red (R), green (G) and blue (B) wavelength ranges respectively, thereby forming the designated color image.

Moreover, each pixel of phosphors 44a, 44b and 44c may be partitioned by the black matrix formed of a light shading material. Or, they may be arranged on the upper surface of the transparent substrate 42. When they are arranged on the upper surface of the transparent substrate 42, blurs and vignettes of the image can be suppressed by interposing the transparent substrate 42.

The image display device 10b of the present invention exhibits the following effects, in addition to those of the foregoing image display device 10a.

Specifically, the image display 10b employs the semiconductor light emitting element which emits light at the ultraviolet range as the light source, and at the same time employs a phosphor in the same ultraviolet ray range which exhibits a high photoelectric conversion efficiency, whereby the image display device 10b can display an image with an extremely high display luminance.

FIG. 6 is a sectional view showing an outline of a concrete structure of image display device 10c of the present invention. Specifically, the image display device 10c shown in FIG. 6 comprises a light source section 20, a light adjustment section 30b and a wavelength conversion section 40b.

The light source section 20 comprises a semiconductor light emitting element which emits light at the ultraviolet ray range, similar to the foregoing image display device 10b. Gallium nitride which was described above should be preferably used for a material of a light emitting layer of the semiconductor light emitting element.

The light adjustment section 30b has a constitution in which a light transmission ratio is adjusted by liquid crystal, similar to the foregoing image display device 10b. Specifically, in the light adjustment section 30b, a liquid crystal layer 36 is held between polarization plates 31 and 39.

Similar to the foregoing display device 10b, the wavelength conversion section 40b also has a constitution in which phosphors 44a, 44b and 44c are arranged on the under surface of the transparent substrate 42 so as to form a designated pattern. With respect to a material of the phosphors 44a, 44b and 44c, a material exhibiting a light emission characteristics as shown in FIG. 5 should preferably be used. Using such phosphors, the light in the ultraviolet ray range, which is emitted from the light source section 20, can be subjected to the wavelength conversion with high efficiency. The phosphors 44a, 44b and 44c receives the light in the ultraviolet ray range from the light source section 20 and change the wavelength of the light and emit it, each being in the wavelength ranges of red (R), green (G) and blue (B) colors, respectively.

In the image display device 10c, the transparent substrate 32a in the light adjustment section 30b is formed of low alkali glass containing alkali elements at a low content ratio. Here, “low alkali glass” means glass formed of a neutral silicic acid glass having a lower alkali content ratio than alkali glass formed of soda lime glass. In the case of alkali glass, the alkali content ratio is about 13.5% of weight, but in case of low alkali glass, it is about 7% by weight. By using such low alkali glass, absorption of the ultraviolet ray from the light source section 20 is suppressed so that the display luminance can be increased.

FIG. 7 is a sectional view showing an outline of a concrete structure of the image display device 10d of the present invention. Referring to FIG. 7, the image display device 10d comprises a light source section 20, a light adjustment section 30c and a wavelength conversion section 40b.

The light source section 20 comprises a semiconductor light emitting element as a light source, which emits light at the ultraviolet ray range, similar to the foregoing image display device 10b. Gallium nitride described above should be used for the material of the light emitting layer of the semiconductor light emitting element.

The light adjustment section 30c comprises a structure in which the transmission ratio of light is adjusted by liquid crystal, similar to the foregoing image display device 10b. Specifically in light adjustment section 30c, a liquid crystal layer 36 is held between polarization plates 31 and 39.

Similar to the case of the foregoing image display device 10b, the wavelength conversion section 40b also has a constitution in which the phosphors 44a, 44b and 44c are arranged on the lower surface of the transparent substrate 42 so as to form a designated pattern. A material exhibiting a light emission characteristic as shown in FIG. 5 should preferably be used for the phosphors 44a, 44b and 44c. By using such phosphors, the light at the ultraviolet ray range, which is emitted from the light source section 20, can be subjected to the wavelength conversion with high efficiency. The phosphors 44a, 44b and 44c receive the light at the ultraviolet ray range from the light source section 20 to change the wavelength of the light and output the lights at the red (R), green (G) and blue (B) wavelength regions, respectively.

Here, in the image display device 10d, the transparent substrate 32b of the light adjustment section 30c is formed of non-alkali glass which substantially contains no alkali element. Here, “non-alkali glass” means glass which substantially contains no alkali. By using such non-alkali glass, the absorption of the ultraviolet ray from the light source section 20 is further suppressed so that the display luminance can be increased.

FIG. 8 is a sectional view showing an outline of a concrete structure of the image display device 10e of the present invention. Specifically, the image display device 10e shown in FIG. 8 comprises a light source section 20, a light adjustment section 30d and a wavelength change section 40b.

Similar to the foregoing image display device 10b, the light source section 20 comprises a semiconductor light emitting element as a light source, which emits light in the ultraviolet ray range. For example, gallium nitride which was described above should preferably be used for a material of a light emitting layer of the semiconductor light emitting element.

Similar to the foregoing image display device 10b, also the light adjustment section 30d also has a constitution in which the transmission ratio of the light is adjusted by a liquid crystal. Specifically, in the light adjustment section 30d, a liquid crystal layer 36 is held between polarization plates 31 and 39.

Similar to the foregoing image display device 10b, the wavelength conversion section 40b also has a constitution in which phosphors 44a, 44b and 44c are arranged on the lower surface of the transparent substrate 42 so as to form a designated pattern. A material exhibiting light emission characteristic shown in FIG. 5 should preferably be used for the phosphors 44a, 44b and 44c. By using such phosphors, the light from the light source section 20 at the ultraviolet ray range can be subjected to the wavelength conversion with high efficiency. The phosphors 44a, 44b and 44c receives the light at the ultraviolet ray range, emitted from the light source section 20, and change the wavelengths of the light to output the lights in the red (R), green (G) and blue (B) wavelength ranges, respectively.

Here, in the image display device 10e, the transparent substrate 32c of the light adjustment section 30d is formed of quartz glass. Quartz glass has a low alkali content ratio of about 2 ppm, so it exhibits an extremely low absorption ratio for ultraviolet ray. Therefore, the absorption of the ultraviolet ray is further suppressed, and the display luminance can be further increased.

FIG. 9 is a sectional view showing an outline of a concrete structure of the image display device 10f of the present invention. Specifically, the image display device 10f shown in FIG. 9 comprises a light source section 20, a light adjustment section 30e and a wavelength conversion section 40b.

Similar to the foregoing image display device 10b, the light source section 20 comprises a semiconductor light emitting element as a light source, which emits light at the ultraviolet ray range. Gallium nitride which was mentioned above should preferably be used for a material of the semiconductor light emitting element, for example.

The light adjustment section 30e also has a constitution in which the transmission ratio of light is adjusted by a liquid crystal, similar to the foregoing image display device 10b. Specifically, the light adjustment section 30e has a liquid crystal layer 36 held between polarization plates 31 and 39. Moreover, the transparent substrate 32d should be formed of any one of the low alkali glass, non-alkali glass, or quartz glass.

Similar to the foregoing image display device 10b, the wavelength change section 40b also has a constitution in which phosphors 44a, 44b and 44c are arranged on the lower surface of the transparent substrate 42 so as to form a designated pattern. A material exhibiting a light emission characteristic as shown in FIG. 5 should be used for phosphors 44a, 44b and 44c. By using such phosphors, the light from the light source section 20 in the ultraviolet ray range can be subjected to wavelength conversion with high efficiency. Phosphors 44a, 44b and 44c receive the light from the light source section 20 in the ultraviolet ray range and change the wavelength of the light, thereby outputting lights at red (R), green (G) and blue (B) wavelength ranges, respectively.

Here, in image display device 10f, an ultraviolet ray cutting filter 46 is stacked on the wavelength conversion section 40b. This ultraviolet ray cutting filter 46 should have a low absorption ratio for visible light and a high absorption ratio for ultraviolet ray. By providing such ultraviolet ray cutting filter 46 stacked on the wavelength conversion section 40b, the following effects can be obtained.

First, by employing the ultraviolet ray cutting filter 46, the light emission from the excitation of phosphors 44a, 44b and 44c from disturbance light can be suppressed. Specifically, when the ultraviolet ray is incident from the outside of the image display device 10f, the phosphors 44a, 44b and 44c are excited, whereby unnecessary light emission will be produced by them. However, when the ultraviolet ray cutting filter 46 is provided, filter 46 absorbs the ultraviolet ray from the outside of the image display device 10f, thereby suppressing the unnecessary light emission.

Moreover, it is possible to prevent the ultraviolet ray from the light source section 20 from leaking to the outside.

When the ultraviolet ray cutting filter 46 is provided between the transparent substrate 42 of the wavelength conversion section 40b and the phosphors 44a, 44b and 44c, the same effects can be obtained.

FIG. 10 is a sectional view showing an outline of the concrete structure of image display device log of the present invention. Specifically, the image display device log shown in FIG. 10 comprises a light source section 20, a light adjustment section 30f and a wavelength conversion section 40c.

Here, the light source section 20 comprises a semiconductor light emitting element possessing a peak of light emission in a blue range. For example, a light emitting element employing gallium nitride type semiconductor can be used.

Similar to the foregoing image display device 10a, the light adjustment section 30f has a constitution in which the transmission ratio for light is adjusted by liquid crystal. Specifically, in the light adjustment section 30f, the liquid crystal layer 36 is held between the polarization plates 31 and 39.

The wavelength change section 40c comprises a phosphor 44d emitting light of a red (R) color, a phosphor 44e emitting light of a green (G) color and a window section 44f transmitting light of a blue (B) color. Specifically, the phosphor 44d receives blue colored light which is emitted from the light source section 20 and incident thereto through the light adjusting section 30f. The phosphor 44d changes its wavelength and outputs it as red color light. Moreover, the phosphor 44e receives the blue color light which is emitted from the light source section 20 and incident through the light adjusting section 30f. The phosphor 44e changes its wavelength and outputs it as green color light. Moreover, the window portion 44f receives the blue color light which is emitted from the light source section 20 and travels through the light adjusting section 30f. The window portion 44f then transmits the received blue color light.

Here, phosphors 44d and 44e should be formed of a material exhibiting an absorption excitation peak for the light in a blue color range, the light being emitted by the light source section 20. In addition, in order to achieve a high changing efficiency, it should be preferable that a phosphor formed of an organic material is used. For such organic phosphor, for example, rhodamine B is mentioned for emitting red color light, and brilliant sulfoflavine FF is mentioned for emitting green color light. On the other hand, the window portion 44f may be achromatic transparent, or it may be formed of a transparent material exhibiting a designated absorption ratio in order to balance the luminance of red and blue colors.

Since the image display device log shown in FIG. 10 uses a light emitting element which emits blue color light as a light source, it has an advantage that deterioration of material such as the liquid crystal layer can be avoided, the deterioration being produced when ultraviolet ray is used. Moreover, since the blue color light among the colors to be displayed can be outputted without changing its wavelength, loss in the wavelength conversion is small, so that it has an advantage that it is easy to increase the luminance of an image.

FIG. 11 is a sectional view showing an outline of a concrete example of the structure of an image display device 10h of the present invention. Specifically, the image display device 10h shown in FIG. 11 comprises a light source section 20, a light adjustment section 30g and a wavelength change section 40d.

Here, similar to the foregoing image display device 10b, the light source section 20 can use a semiconductor light emitting element which exhibits a light emission peak in the ultraviolet ray range as a light source. Moreover, like the foregoing image display device log, the light source section 20 can use a semiconductor light emitting element which exhibits a light emission peak in the blue color range as a light source. Still furthermore, the light source section may use a semiconductor light emitting element which exhibits a light emission peak in other wavelength ranges as a light source.

Similar to the foregoing image display device 10a, the light adjustment section 30g also has a constitution in which a light transmission ratio is adjusted by a liquid crystal. Specifically, also in the light adjustment section 30g, a liquid crystal layer 36 is also held between polarization plates 31 and 39.

Similar to the foregoing image display device 10b, the wavelength conversion section 40d can be constituted of phosphors 44a, 44b and 44c which are arranged on the lower surface of the transparent substrate 42 so as to form a designated pattern, where phosphors 44a, 44b and 44c emits lights respectively in red (R), green (G) and blue (B) wavelength ranges. Moreover, in the case where the light source emits a blue colored light, the wavelength conversion section 40d has a structure in which a phosphor 44d emits a red color (R) light, a phosphor 44e emits a green color light (G) and a window portion 44f transmits a blue color light.

Moreover, in the image display device 10h, a light diffusion plate 47 is provided above the phosphors 44 of the wavelength conversion section 40d. This light diffusion plate 47 diffuses the directions of the light incident from phosphors 44 and outputs them. By providing such light diffusion plate 47, it is possible to widen the visual field angle and smoothen the image.

FIG. 12 is a sectional view showing an outline of a concrete example of the structure of image display device 10i of the present invention. Specifically, the image display device 10i in FIG. 12 comprises a light source section 20, a light adjustment section 30g and a wavelength conversion section 40e.

Here, in the image display device 10i, the foregoing light diffusion plate 47 is arranged on the lower layer of phosphors 44. By arranging such light diffusion plate 47, lack of uniformity in luminance of lights incident onto phosphors 44 can be controlled, allowing each of the phosphors 44 to emit lights uniformly.

Next, an image display device of a second embodiment of the present invention will be described.

FIG. 13 is a sectional view showing an outline of a concrete structure of the image display device of the second embodiment of the present invention. Specifically, image display device 50 of the present invention comprises a light source section 20, a wavelength conversion section 40 or a wavelength selection section 40 and a light adjustment section 30.

In the light source section 20, at least one semiconductor light emitting element is properly arranged so as to emit light to wavelength conversion section 40, the light having a designated wavelength, light amount and luminance distribution. The wavelength conversion section 40 changes the wavelength of the light incident from the light source section 20 to output it to the light adjustment section 30. When the wavelength selection section 40 is used, it selects the wavelength of the light to output it to the light adjustment section 30.

The light adjustment section 30 adjusts the amount of light incident from either the wavelength conversion section or the wavelength selection section for each pixel and forms a designated image and outputs it from the observation plane of the image display device 50.

According to the present invention, since the wavelength conversion section 40 is provided between the light source section 20 and the light adjustment section 30, the light from the light source section 20 is never incident directly onto the light adjustment section 30. Therefore, problems of deterioration and malfunction of the light adjustment section 30 due to the direct light from the light source section 20 never occurs. Particularly, the liquid crystal layer and the switching elements in the light adjustment section 30 are prone to deterioration by the irradiation of ultraviolet ray. However, in the image display device 50, such deterioration never occurs.

In addition, according to the present invention, the light adjustment section 30 can be structured so that it has the same structure as that of the conventional liquid crystal display device. Specifically, the light incident into the light adjustment section 30 is converted to visual light, whereby the light adjustment section 30 can be constituted so as to have the same structure as that of the conventional one.

FIG. 14 is a sectional view showing an outline of a concrete example of the structure of the image display device of the present invention. Specifically, the image display device shown in FIG. 50a comprises a light source section 20, a wavelength conversion section 40a and a light adjustment section 30h.

Here, the light source section 20 can use the semiconductor light emitting element as a light source, which possesses a light emission peak in the ultraviolet ray range, like the foregoing image display device 10b. Moreover, like the foregoing image display device log, it can use the semiconductor light emitting element as a light source, which possess a light emission peak at the blue color light region. Moreover, it may use a semiconductor light emitting element as a light source, which exhibits a light emission peak in other wavelength ranges.

The wavelength conversion section 40a is provided between the light source section 20 and the light adjustment section 30h. Phosphors 44 can be used as its material. It is preferable that the wavelength of an absorption excitation peak of the phosphors 44 agrees with that of the light emitting element used in the light source section 20. For example, when the light emitting element formed of gallium nitride as described above is used in the light emission section 20, the phosphor exhibiting the absorption excitation peak as shown in FIG. 5 should be preferably used for the wavelength conversion section.

As such phosphors, Y₂O₂S:Eu is mentioned for one emitting red colored light, (Sr, Ca, Ba, Eu)₁₀(PO₄)₆Cl₂ is mentioned for emitting blue colored light, and 3(Ba, Mg, Eu, Mn)0.8Al₂O₃ is mentioned for emitting green colored light.

Moreover, a second wavelength change section 40b may be provided under the light source section, and a reflection plate 68 may be further provided under the second wavelength conversion section 40b. With such structure, the light emitted downward from the light source section 20 is subjected to the wavelength conversion, and the light is reflected by the reflection plate 68. Then, the reflected light travels through the light source section 20 and the wavelength change section 40a and is incident onto the light adjustment section 30h. So it is possible to use the light effectively.

The light adjustment section 30h has a structure in which a light transmission ratio is adjusted by liquid crystal. Specifically, in the light adjustment section 30h, a liquid crystal layer 36 is held between polarization plates 31 and 39. The liquid adjustment section 30h is designed so that the molecule orientation state of the liquid crystal layer 36 is controlled by applying a designated voltage between pixel electrodes 34 and opposite electrodes, and the liquid crystal layer 36 controls the light transmission ratio in cooperation with the upper and lower polarization plates 31 and 39. Each of the pixel electrodes 34 is supplied with a designated voltage via the switching element 35. A metal/insulating film/metal (MIM) junction type device and a thin film transistor (TFT) formed of hydrogenized amorphous silicon or polycrystalline silicon can be used as switching element 35.

FIG. 15 is a sectional view showing an outline of a concrete example of the structure of an image display device 50b which is a modification of the image display device 50a shown in FIG. 14. The image display device 50b shown in FIG. 15 comprises a light source section 20, a wavelength change section 40g and a light adjustment section 30i.

Here, as has been described concerning the image display device 50a, the transparent substrate 32a is provided between the wavelength conversion section 40g and the light adjustment section 30i. The image display device 50b has a structure in which an optical property of the transparent substrate 32a is changed for each pixel. For example, such change of the optical property of the transparent substrate 32a can be achieved, by providing a range in the substrate 32a, in which the refraction range is different for each pixel. Or, for each pixel, a light shielding partition may be provided in the substrate 32a. Moreover, a light shielding pattern may be formed on either both surfaces of the substrate 32a or on one surface thereof.

By changing the optical property of the transparent substrate 32a for each pixel, leakage of the light can be prevented when the light travels from the wavelength conversion section 40g to the light adjustment section 30j through the transparent substrate 32a. Therefore, pixel blur can be prevented.

FIG. 16 is a sectional view showing an outline of a concrete example of the structure of a modification of the image display device of the present invention. Specifically, the image display device 50c shown in FIG. 16 comprises a light source section 20, a wavelength conversion section 40h and a light adjustment section 30j.

However, in the image display device 50c, the wavelength conversion section 40h is disposed between light guiding plate 26 and light source 22 of the light source section 20. Specifically, the light from the light source 22 is subjected to the wavelength conversion by the wavelength conversion section 40h such that the light has a designated wavelength, and the light is incident onto the light adjustment section 30j through the light guiding plate 26 thereafter.

The phosphor can be employed as a material of the wavelength conversion section 40h, similar to the case of the image display device 50a. It should be preferable that the absorption excitation peak wavelength of the phosphor used for this wavelength change section 40h agrees with the light emission peak wavelength of the light emitting element used in the light source 22. For example, when the light emitting element formed of gallium nitride as is described in FIG. 4 is used in the light source 22, the phosphor exhibiting the absorption excitation peak shown in FIG. 5 should be preferably used for the phosphor of the wavelength conversion section 40h.

Moreover, it should be preferable that three kinds of phosphors, which exhibit light emission peaks in red (R), green (G) and blue (B) wavelength ranges are respectively used in combination with each other. More specifically, the light emission peak wavelengths of the phosphors should be selected so as to agree with the transmission spectrum characteristic of a color filter 60 of the light adjustment section 30j.

Next, a light adjustment section used suitably for the image display devices 10 and 50 of the present invention will be described.

FIG. 17 is a sectional view exemplifying an outline of a structure of a transmission type image display device using a light adjustment device 30k, which can be used in the present invention. In FIG. 17, only the light source section 20 and the light adjustment section 30k are illustrated for convenience. A wavelength conversion section (not shown) can be disposed in a similar manner as that in any of the foregoing image display devices shown in FIGS. 1-3 and 6-16. In FIG. 17, the light emitted from the light source section 20 is emitted through the light adjustment section 30k.

Here, either a guest/host type liquid crystal or high polymer dispersion type liquid crystal is used as the liquid crystal 36a of the light adjustment section 30k. The guest/host type liquid crystal is one which two color dyes (guest) exhibiting anisotropic properties in absorption of visible light depending on the long and short axis directions of molecules dissolved in a liquid crystal (host) of a constant molecular arrangement. When the guest/host type liquid crystal is used, the light adjustment section can function with one polarization plate. Therefore, a high light transmission ratio can be obtained and luminance of the image display device can be increased.

Moreover, the high polymer dispersion type liquid crystal utilizes a light scattering effect of a composite substance composed of nematic liquid crystal and high polymer. The high polymer dispersion type liquid crystal is roughly divided into NCAP (nematic curvulinear aligned phase) type and PN (polymer network) type. In case of the high polymer dispersion type liquid crystal, a polarization plate is not necessary so the image display can be achieved with further brightness and a wider visual field angle.

FIG. 18 is a sectional view showing an outline of a concrete example of the structure of a reflection type image display device using the light adjustment section 30k which has been described above. Specifically, in the image display device shown in FIG. 18, the light adjustment section 30k is stacked on a reflection plate 28, and further the light source section 20 is stacked on the light adjustment section 20. Then, the light emitted from the light source section 20 is reflected by the reflection plate 28 through the light adjustment section 30k, and then passes through the light adjustment section 30k again, and the light reaches the observer through the light source section 20.

Also in the image display device shown in FIG. 18, the light adjusting section 30k uses either a high polymer dispersion type liquid crystal or a guest/host type liquid crystal as liquid crystal 36a. Therefore, the polarization plate is unnecessary so that the transmission ratio can be improved. Thus, the image display device of the present invention can display a bright image.

FIG. 19 is an explanatory view showing an outline of an example in which each area of pixels in the image display device according to the present invention is optimized. Specifically, in any of the foregoing image display devices shown in FIGS. 1 to 18, luminance of each pixel of red (R), green (G) and blue (B) is not necessarily equal to each other. In order to adjust the luminance of each pixel, the area of each pixel is set to an appropriate ratio, as shown in FIG. 19, for example. Therefore, each of colors of red (R), green (G) and blue (B) can be displayed with an optimized balance, and an image reproducing colors with neutral tints can be displayed with precision.

Next, a light source section which is suitably used for the image display device of the present invention will be described. FIGS. 20(a) and 20(b) show an outline of a concrete example of the structure of a light source section 20 of either the image display device 10 or the image display device 50 of the present invention. Specifically, FIG. 20(a) is a sectional view showing an outline in parallel with the observation plane of the image display device. FIG. 20(b) is a sectional view showing an outline perpendicular to the observation plane of the image display device.

A light source section 20a illustrated in FIGS. 20(a) and 20(b) comprises a installation section 25a, to which a light source is installed, and a light guiding plate 26. In the installation section 25a, light emitting diode (LED) chips 22a are arranged as the light source. The LED chip 22a is mounted on, for example, a substrate 24a and a designated wiring is performed on the chip 22a. The LED chip 22a is supplied with a driving electric current, whereby the LED chip 22a is allowed to emit light. The light which is radiated from the LED chip 22a diverges within the light guiding plate 26, and incident onto a light adjustment section 30 or a wavelength conversion section 40, both of which are not shown in FIGS. 20(a) and 20(b). Furthermore, since a light extracting efficiency is increased, a reflection plate 28 can be disposed under the light guiding plate 26, whereby the light emitted from the light guiding plate downward can be returned upward. Moreover, in order to reduce the unevenness of luminance of the light, a diffusion plate 29 may be stacked on the light guiding plate 26.

The image display device of the present invention, which uses the light source section 20a, has the following effects in addition to the various kinds of the foregoing effects described using FIGS. 1 to 22.

Specifically, since the small sized LED chips 22a in a so-called bare chip state are used, it is possible to make the width W of the installation section 25a small. The installation section 25a is often arranged outside of the display region of the image display device, so a frame section of the image display device, namely, the non-display region can be made smaller by narrowing the width W of the installation section 25a.

In addition, since the LED chip 22a in a bare chip state are small, the LED chips 22a can be densely mounted, whereby luminance of the light source can be increased. As a result, a bright and clear image can be displayed.

FIGS. 21(a) and 21(b) are structural views showing an outline of the structure of a second concrete example of the light source of the image display device according to the present invention. Specifically, FIG. 21(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device, and FIG. 21(b) is a sectional view showing an outline of the light source section perpendicular to the observation plane thereof.

The light source section 20b showing in FIGS. 21(a) and 21(b) comprises a installation section 25b to which a light source is installed, and a light guiding plate 26. In the installation section 25b, LED lamps 22b are arranged. Each LED lamp 22b has a structure that an LED chip is mounted on a lead frame, or a stem possessing lead wire, and molded with resin. Each of the LED lamps 22b can be mounted on the substrate 24b, for example. Moreover, a reflection plate 28 and a diffusion plate 29 may be provided therein (not shown).

The image display device using the light source section 20b shown in FIGS. 21(a) and 21(b) has the following effects in addition to those of the image display device 10a described above.

Specifically, since the LED lamps 22b are used, a light collection capability by virtue of the lens effect of the mold resin is increased, whereby a light utilization effect can be improved.

Moreover, since the lead wire of the LED lamp 22b can be inserted into the substrate 24b and it can be mounted by only soldering, assembly steps can be simplified.

FIGS. 22(a) and 22(b) are structural views showing an outline of the structure of a third concrete example of the light source section of the image display device according to the present invention. Specifically, FIG. 22(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device and FIG. 22(b) is a sectional view showing an outline of the light source section perpendicular to the observation plane thereof.

The light source section 20c shown in FIGS. 22(a) and 22(b) comprises a installation section 25c to which the light source is fitted, and a light guiding plate 26. In the installation section 25c, surface mounting (SMD) type lamps 22c are arranged. Each of the SMD lamps 22c has a structure that an LED chip is mounted on a small sized mounting substrate and it is molded with resin. The SMD lamp 22c can be mounted on the substrate 24c, for example. Moreover, a reflection plate 28 and a diffusion plate 29 may be provided therein.

The image display device using the light source section 20c shown in FIGS. 22(a) and 22(b) has the following effects in addition to the effects of the foregoing image display device 10a.

First, since the SMD lamp 22c is used, assembly steps can be simplified. Specifically, the SMD lamp 22c can be simply mounted on the substrate 24c according to a so called soldering reflow method, simultaneously when other parts are mounted such as a chip type resistor or a chip type capacitor. In addition, automation of the mounting steps can easily be realized.

The SMD lamp 22c is short in height, so that the width W of the installation section 25c of the light source section 20c can be set small. As a result, the size of the frame section of the image display device, that is, the non-display region thereof can be made smaller.

FIGS. 23(a) and 23(b) are structural views showing an outline of the structure of a fourth concrete example of the light source section of the image display device according to the present invention. Specifically, FIG. 23(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device, and FIG. 23(b) is a sectional view showing an outline of the light source section perpendicular to the observation plane.

The light source section 20d shown in FIGS. 23(a) and 23(b) comprises a installation section 25d to which a light source is installed, and a light guiding plate 26. In the installation section 25d, LED lamps 22d, 22e and 22f exhibiting light emission peaks respectively in wavelength zones of red (R), green (G) and blue (B), are arranged.

As is described above, the LED lamps 22d, 22e and 22f emitting R, G and B colors are arranged in the installation section 25d, so that an existing illumination section of a conventional image display device can be replaced with them. Specifically, in the conventional liquid crystal display device, a cathode fluorescent tube or an electroluminescence element has been used for the illumination section. However, by using the light source section 20d of the present invention, the image display device of a low power consumption and a long life time can be obtained. In addition, the image display device using the light source section 20d of the present invention has a high reliability and an ability to function with high speed.

FIGS. 24(a) and 24(b) are structural views showing an outline of the structure of a fifth concrete example of the light source section of the image display device according to the present invention. Specifically, FIG. 24(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device, and FIG. 24(b) is a sectional view showing an outline of the light source section perpendicular to the observation plane thereof.

The light source section 20e shown in FIGS. 24(a) and 24(b) comprises SMD lamps 22g, 22h and 22i arranged therein as a light source, which exhibit light emission peaks in wavelength zones of red (R), green (G) and blue (B) colors, respectively. By using the SMD lamps as described above, the light source section 20e has effects that the width W of the installation section 25e can further be made smaller and the image display device can be manufactured to be smaller in size, in addition to the effects of the foregoing light source section 20d.

Moreover, by using LED chips instead of the SMD lamps 22g, 22h and 22i, the width W of the installation section 25e can be reduced more, so that the image display device can be made smaller.

FIGS. 25(a) and 25(b) are structural views illustrating an outline of the structure of a sixth concrete example of a light source section of the image display device according to the present invention. Specifically, FIG. 25(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device, and FIG. 25(b) is a sectional view showing the outline thereof perpendicular to the observation plane of the image display device.

Similar to the foregoing light source sections 20d and 20e, the light source section 20f illustrated in FIGS. 25(a) and 25(b) comprises a installation portion 25f in which semiconductor light emitting elements 22 exhibiting light emission peaks in the wavelength zones of, for example, red (R), green (G) and blue (B), respectively, are arranged as a light source.

Then, a light diffusion plate 28 is provided between the installation section 25 and the light guiding plate 26. By arranging the light diffusion plate 28 near the light sources 22, that is, the semiconductor light emitting elements, the lights of the RGB colors are mixed so that the occurrence of unevenness of color can be suppressed.

FIGS. 26(a) and 26(b) are sectional views showing an outline of the structure of a seventh concrete example of the light source section of the image display device according to the present invention. Specifically, FIG. 26(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device and FIG. 26(b) is a sectional view showing the outline thereof perpendicular to the observation plane.

The light source section 20g illustrated in FIGS. 26(a) and 26(b) comprises a installation section 25g arranged on the right and left ends thereof with the light guiding plate 26 interposed therebetween, LED lamps 22b being arranged in each of 25g. By arranging the LED lamps 22b on both sides of the light guiding plate 26, the number of the light sources increases so that luminance of the light source section can be further increased.

FIGS. 27(a) and 27(b) are sectional views showing an outline of the structure of an eighth concrete example of the light source section of the image display device according to the present invention. Specifically, FIG. 27(a) is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device and FIG. 27(b) is a sectional view showing the outline perpendicular to the observation plane of the image display device.

The light source section 20h illustrated in FIGS. 27(a) and 27(b) comprises installation sections 25h arranged in the left and right end portions thereof with the light guiding plate 26 interposed therebetween, and SMD lamps 22c being arranged in each of the installation sections 25h and 25h. By arranging the LED lamps 22c on both sides of the light guiding plate 26, the number of the light sources is increased so that the luminance of the light source section can be increased. Moreover, the width W of the installation section 25h can be made smaller compared to the case of the LED lamp 22c, whereby the image display device can be made smaller. Furthermore, if the LED chip 22a is used instead of the SMD lamp 22c, the width W of the installation section 25 can be reduced more, whereby the size of the image display device can be made smaller furthermore.

FIG. 28 is a structural view showing an outline of the structure of a ninth concrete example of the light source section of the image display device according to the present invention. Specifically, FIG. 28 is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device. The light source section 20i illustrated in FIG. 28 comprises installation sections 25i arranged at four sides of the light guiding plate 26, and LED lamps 22b arranged in each of the installation sections 25i. By arranging the LED lamps 22b at the four sides of the light guiding plate 26, the number of the light sources increases so that the luminance of the light source section can be improved furthermore.

FIG. 29 is a structural view showing an outline of the structure of a tenth concrete example of the light source section of the image display section according to the present invention. Specifically, FIG. 29 is a sectional view showing an outline of the light source section in parallel with an observation plane of the image display device. The light source section 20j shown in FIG. 29 comprises installation sections 25j arranged on four sides of the light guiding plate 26, and SMD lamps

1. An image display device comprising: a light source section including semiconductor light emitting elements as light sources; a light adjustment section arranged opposite said light source section and which adjusts intensity of light incident thereto; and a wavelength conversion section opposite said light source section and having a plurality of pixels, which adjusts intensity of light incident thereto for said pixels to a different frequency range, wherein lights emitted from said light source section pass through said light adjustment section and said wavelength conversion section to be output as transmitted lights adjusted in intensity and converted in frequency, said light source section includes a light guiding plate for guiding light from said light source section, said light guiding plate being disposed in parallel with an image display plane, and light from said light source section is incident into said light guiding plate.

2. The image display device according to claim 1, wherein said light adjustment section comprises liquid crystal cells including switching elements formed on a transparent substrate and corresponding to respective of said pixels, said liquid crystal cells having voltages applied thereto and said light adjustment section controlling said voltages applied to said liquid crystal cells to adjust intensities of said transmitted lights for said pixels; said wavelength conversion section comprises phosphors which convert wavelengths of incident light transmitted through said wavelength conversion section; and said wavelength conversion section emits the converted wavelength light as said transmitted lights.

3. The image display device according to claim 1, wherein said light adjustment section is interposed between said light source section and wavelength conversion section.

4. The image display device according to claim 1, wherein said semiconductor light emitting elements exhibit a light emission spectrum having a peak wavelength in an ultraviolet range; said wavelength conversion section comprises three kinds of phosphors arranged according to a designated pixel pattern; and three kinds of phosphors changes a corresponding one of lights transmitted through said wavelength conversion section to visible light of one of red, green and blue wavelengths.

5. The image display device according to claim 4, wherein said semiconductor light emitting elements comprise gallium nitride type semiconductor that exhibit a light emission spectrum having a peak wavelength in a range between 360 and 380 nanometers.

6. The image display device according to claim 5, wherein said wavelength conversion section includes a phosphor which exhibits an absorption excitation peak at a wavelength within said peak wavelength range of said semiconductor light emitting elements.

7. The image display device according to claim 6, wherein said light adjustment section comprises a light transmission substrate of a low alkali glass possessing a low absorption ratio for light having ultraviolet wavelengths emitted from said semiconductor light emitting elements.

8. The image display device according to claim 6, wherein said wavelength conversion section comprises a filter which absorbs ultraviolet wavelengths in order to control entry of ultraviolet wavelengths from outside the image display device and leakage of ultraviolet wavelengths emitted from said semiconductor light emitting elements to the outside.

9. The image display device according to claim 1, wherein said wavelength conversion section is interposed between said light source section and said light adjustment section.

10. The image display device according to claim 9, wherein said light adjustment section comprises liquid crystal cells including switching elements formed on a transparent substrate and corresponding to respective of said pixels said liquid crystal cells having voltages applied thereto and said light adjustment section controlling said voltages applied to said liquid crystal cells to adjust intensities of said transmitted lights for said pixels; said wavelength conversion section comprises phosphors which convert wavelengths of incident light transmitted through said wavelength conversion section; and said wavelength conversion section emits the converted wavelength light as said transmitted lights.

11. The image display device according to claim 1, wherein said semiconductor light emitting elements exhibit a light emission spectrum having a peak wavelength in a blue color range; said wavelength conversion section comprises two kinds of phosphors and a light transmitter arranged according to a designated pattern, said two kinds of phosphors being organic phosphors that change a corresponding wavelength range of incident light transmitted through said wavelength conversion section to visible light of one of red and green wavelengths; and said light transmitter is configured to transmit incident light unchanged.

12. The image display device according to claim 1, wherein said light adjustment section comprises a transparent plate which conducts light emitted from said semiconductor light emitting elements; and said wavelength conversion section is a layer including a phosphor, the layer being stacked on said transparent plate.

13. The image display device according to claim 1, wherein said light adjustment section comprises a transparent plate which conducts light emitted from said semiconductor light emitting elements; and said wavelength conversion section comprises a phosphor layer.

14. The image display device according to claim 1, wherein substrates having said light emitting elements are provided on opposite sides of said light guiding plate.

15. The image display device according to claim 1, wherein substrates having said light emitting elements are provided on plural sides of said light guiding plate.

16. The image display device according to claim 1, wherein substrates having said light emitting elements are provided on opposite sides of said light guiding plate and one of the plural sides of said light guiding plate.

17. The image display device according to claim 1, wherein said light source section includes a directional element; and light emitted from said light source section is directed by said directional element to be incident onto a designated position of said wavelength conversion section.

18. The image display device according to claim 17, wherein said directional element comprises a movable reflection mirror provided for pixel arrays of said image display device.

19. The image display device according to claim 17, wherein said directional element comprises a movable lens; and light emitted from said semiconductor light emitting elements is converged and scanned by moving said movable lens, causing the light emitted from said light source section to be incident onto a predetermined position of said wavelength conversion section.

20. The image display device according to claim 17, wherein said directional element comprises a half mirror corresponding to pixels so that light emitted from said light source section is partially reflected toward corresponding pixel portions of said light adjustment section.