JP2000194275A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the device small-sized and low in power consumption irrelevantly to the size of a display image by using a semiconductor light emitting element as a light source. SOLUTION: A projector type image display device for displaying a color image by using the primary colors of a light is equipped with three liquid crystal display panels 12a, 12b, and 12c which are constituted by arranging pixels in matrix and vary the transmissivity of the respective pixels to the light with electric signals, light emitting diodes 11a, 11b, and 11c which are provided for the liquid crystal display panels 12a, 12b, and 12c and emit lights corresponding to red, blue, and green, and optical systems 13, 14, and 15 which form images on an image display screen by putting together three kind of lights transmitted through the respective liquid crystal display panels 12a, 12b, and 12c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for displaying a color image, and more particularly to an image display device with an improved light source.

[0002]

2. Description of the Related Art At present, display methods differ depending on the size of an image display device, such as a liquid crystal display when the display area is 15 inches or less, a cathode ray tube display up to 40 inches, and a plasma display when it exceeds 40 inches. Furthermore, it has a body that is basically larger than the display part. For this reason, usability such as movement and versatility is poor, and in order to obtain an image of a desired size, an image display device of a different size is required each time.

[0003] Recently, a projector-type image display device represented by a liquid crystal projector has been developed, and these points have been solved to some extent. However, in this type of device, the size of the unit is large, the light use efficiency is low, and the power consumption is large due to the heat generation in the main body, the lamp, and the optical system. . In particular, at present, only a few percent of the total light can be used in terms of light use efficiency. Further, since each color of RGB is created by the filter, the color purity is poor and the displayed image is not clear.

[0004]

As described above, the conventional image display device is essentially limited in image size, and the projector type display device has a large main body and a complicated optical system, and is difficult to use. There is a problem that power consumption is large due to short life and low light use efficiency.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to use a semiconductor light emitting device as a light source to reduce the size of a display image regardless of the size of a display image.
An object of the present invention is to provide a projector-type image display device capable of reducing power consumption.

[0006]

(Structure) In order to solve the above problem, the present invention employs the following structure.

That is, according to the present invention, in an image display apparatus for displaying a color image, pixels are arranged in a matrix, and a pixel panel section which varies a light transmittance or a reflectance of each pixel by an electric signal. And an n-side electrode and a p-side electrode joined to the stacked film to supply a current to the pn junction, and a stacked film stacked to form a pn junction,
And a semiconductor light emitting element that emits monochromatic light and irradiates the pixel panel section.

Here, preferred embodiments of the present invention include the following. (1) The pixel panel is a liquid crystal display panel. (2) The pixel panel section and the semiconductor light emitting element are provided corresponding to three colors of R, G, and B, respectively. (3) The semiconductor light emitting device is a light emitting diode made of a group III nitride.

(4) The semiconductor light emitting element is a light emitting diode which can selectively emit each of R, G and B colors.
R, G, B light is emitted in a time series when used in combination with two liquid crystal display panels.

(5) A minute lens group is arranged on the surface of the semiconductor light emitting element. (6) A diffraction grating type lens array is arranged between the semiconductor light emitting element and the pixel panel section.

According to the present invention, in an image display device for displaying a color image using three primary colors of light, pixels are arranged in a matrix, and the light transmittance of each pixel is varied by an electric signal. Three liquid crystal display panels,
Provided for each of these liquid crystal display panels,
A light-emitting diode that emits light corresponding to each of red, blue, and green colors, and an optical system that combines three types of light transmitted through each of the liquid crystal display panels to form an image on an image display surface. It is characterized by.

(Operation) In the present invention, a configuration is used in which a semiconductor light-emitting element having a pn junction as a light source is combined with a pixel panel section capable of electrically varying light transmittance or reflectance. Has important implications.

As described above, in the conventional image display device, it is necessary to create a device larger than the display portion. This is also true of a display device called a flat panel, and it is difficult to make the size smaller than this size because there is always a display portion where an image is displayed.

Therefore, the present invention employs a projector system. In the case of the projector system, if there is an image display engine much smaller than the display portion, the change of only the distance to the screen can be used for mobile applications, that is, from a display device sized by the palm of a home theater exceeding 100 inches. The application can be realized by the same principle.

However, in the projector system, the engine itself tends to be large due to the complicated optical system, the light use efficiency of the light source is several percent, the power consumption is large, and the brightness is low. There have been problems such as that projection can be performed only at a specific size and that the life of the lamp as a light emitting source is short.

Therefore, as in the present invention, it is very important to use a current-driven light-emitting element represented by a semiconductor as a light source. In the conventional optical system, a large number of lenses and reflecting mirrors are used, and the utilization efficiency of each is not 100%, so that the overall utilization efficiency is reduced. further,
Since the three primary colors are created by the filter, only a part of the emission wavelength of the light source is used, and the overall light use efficiency is significantly reduced to about several percent.

On the other hand, in the present invention, as described above, by using a light emitting element typified by a semiconductor, the pixel panel portion and the semiconductor light emitting element can be placed in an arrangement capable of directly optically coupling. Then, a light source is prepared for each of the RGB colors, and if necessary, the light source is optically corrected and coupled to the pixel panel unit. As a result, the light use efficiency is improved to about 40% as a whole.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIGS. 1 (a) and 1 (b)
FIG. 1 is a diagram illustrating a basic configuration of an image display device according to a first embodiment of the present invention. Each of the examples has a light source based on three types of light emitting diodes (LEDs) corresponding to each color of RGB, a pixel panel portion composed of liquid crystal, and an optical system for coupling these.

In FIG. 1A, 11 (11a to 11a)
c) L which emits monochromatic light corresponding to each of R, G and B colors
Reference numerals ED and 12 (12a to 12c) denote liquid crystal display panels corresponding to R, G, and B colors, 13 denotes a dichroic prism, 14 denotes a TIR prism, and 15 denotes a projection lens. The R, G, and B monochromatic lights emitted from the LEDs 11 are respectively radiated to the liquid crystal display panel 12, and the lights transmitted through the respective liquid crystal display panels 12 are combined by the prisms 13 and 14, and the projection surface (not shown) is projected by the projection lens 15. Is imaged. As a result, a color image is displayed.

In the example of FIG. 1B, the reflecting mirrors 16 (16a to 16a) are used instead of the prisms 13 and 14 of FIG.
d) and the RGB 17 are combined using the prism 17. That is, the monochromatic light (R) from the LED 11a is reflected by the reflection mirrors 16a and 16b and
2a, the monochromatic light (G) from the LED 11b is directly irradiated to the liquid crystal display panel 12b,
Is reflected by the reflection mirrors 16c and 16d and is irradiated on the liquid crystal display panel 12c. The colors transmitted through the liquid crystal panels 12a, 12b, and 12c are combined by the prism 17 and further formed on a projection surface by a projection lens (not shown).

As described above, according to the present embodiment, a color image can be displayed by combining the three kinds of LEDs 11 corresponding to each color of RGB and the liquid crystal display panel 12. In this case, unlike the conventional method of separating the three primary colors of light from white light such as a halogen lamp, there is no need to use a color filter that reduces the light use efficiency, so that the light use efficiency can be increased. According to the experiments by the present inventors, the light use efficiency can be increased to about 40% as a whole. Further, the LED is smaller than a halogen lamp or the like, and an optical system for wavelength-separating white light is not required, so that the configuration can be simplified and downsized.

Next, the configuration of each section in the image display device of the present embodiment will be described in more detail.

FIG. 3 is a diagram showing another example of the light source. FIG. 3A shows a laser diode (LD) 31 as a light source.
, And the light emitted from the LD 31 is applied to the liquid crystal display panel 33 through the spread spectrum plate 32. In this case, the spectrum of the laser light that is too sharp for color display can be diffused, and the entire surface of the liquid crystal panel can be irradiated by extending the linear light source in a direction perpendicular to the lines.

FIG. 3B shows a method in which light from a semiconductor light emitting element 36 (LED or LD) is scanned and projected on a liquid crystal display panel 33 by a movable lens 35. In this case, even if the semiconductor light emitting element 36 is a minute light source, light can be applied to the entire surface of the liquid crystal display panel 33 by the movable lens 35.

FIG. 4 is a diagram for explaining how to radiate light from a light source. FIG. 4A is an example in which a microlens-type optical group is formed on a light source, whereby emitted light can be collected at regular positions, and unevenness of a displayed image can be reduced. .

FIG. 4B shows an example in which a diffraction grating is provided to obtain the same effect as in FIG. FIG.
2 shows a cross section of the diffraction grating of FIG. In FIG. 4C, the diffraction grating has a rectangular shape in (1) and a sawtooth shape in (2). However, various forms are possible for the method of forming the diffraction grating, the density, and the angle. FIG. 4 (d)
Is provided with a diffraction grating corresponding to the arrangement of the individual light sources, and the same effect as that of the microlens can be obtained.

FIG. 5 is a diagram showing an example of the arrangement of light sources. FIG. 5A is a diagram in which minute light sources 51 such as LEDs are closely arranged radially on a substrate 50, FIG. 5B is a diagram in which one entire surface is a planar light source 51, and FIG. FIG. 5D shows a case where minute rectangular light sources 51 are arranged in a matrix, and FIG.
Is a circular light source 51 having a relatively large diameter arranged in a line.
Since each of them is a linear light source as a whole, it is possible to cover an area corresponding to the size of the liquid crystal display panel by combining with a movable lens or a diffusion plate as shown in FIG.

FIG. 6 is a diagram showing another example of the arrangement of the light sources. FIGS. 6A and 6B show an arrangement in which a light source 61 such as an LED is disposed inside a concave mirror 62, and FIGS.
A light source 61 is also provided around a pillar 63 provided at the center together with the inside of the light source 61.
Is arranged. In this case, there is an advantage that the light source including the lens is constituted by one device.

FIG. 7 shows an example relating to an electrode pattern of a flat light source. FIG. 7A shows a rectangular pattern 71 at the center and trapezoidal patterns 72a, 72b, 72c, 72d at the periphery.
Are formed by separating the transparent electrodes.
In this case, a different voltage can be applied to each electrode. As a result, a uniform temperature distribution can be provided over a wide area, and it is possible to contribute to improving the uniformity of the light emission output and the light emission wavelength.

FIG. 7B shows a circular pattern 73 at the center.
And peripheral circular patterns 74a, 74b, 74c, 74
The transparent electrode is formed separately for each of the d. In this case, the same effect as that of FIG. 7A can be obtained.

In FIG. 7C, although the transparent electrode 75 is formed entirely without being separated, a thin metal wiring 76 is formed on the transparent electrode 75 in a mesh shape. In this case, ITO
Since the metal wiring 76 has a smaller resistance and better heat conduction than the transparent electrode 75, the formation of the metal wiring 76 makes it possible to equalize the voltage over the entire surface of the transparent electrode and the temperature distribution over the entire surface. .

When there is no problem of non-uniform temperature,
As shown in FIG. 7D, metal electrodes 7 are provided at the four corners of transparent electrode 77.
8 may be arranged. In this case, the metal wiring 78 at the four corners
The contact with the transparent electrode 77 can be taken.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
(A) is a diagram showing an arrangement relationship between a light source, a pixel panel unit, and an optical system, (b) is a diagram showing an element structure of a light source, and (c) is a diagram for explaining an image display device according to the embodiment. FIG. 3 is a diagram illustrating a configuration of a cooling unit of a light source.

In the overall configuration shown in FIG.
Is an LED capable of selectively emitting three colors of R, G, and B;
2 denotes a liquid crystal display panel, 203 denotes a lens group, 204 denotes a projection lens, 205 denotes a heat sink, 206 denotes a Peltier element, 207 denotes a fin, and 208 denotes a fan.

In the configuration of the LED 201 shown in FIG. 2B, 209 is a sapphire substrate, 210 is an n-type GaN contact layer, 211 is an n-type AlGaN cladding layer, 21
2,213,214 are GaN / InGaN /
This is a quantum well layer made of GaN. In these quantum well layers, R, G, and B correspond to each layer. 215 is p-type A
1GaN current diffusion preventing layer, 216 is a p-type AlGaN cladding layer, 217 is a p-type GaN contact layer, 21
8, 219 are n and p electrodes, respectively.

The MOCVD method is used for crystal growth.
In forming such an element structure, a general photoresist was used, and after patterning was performed, a step was formed by dry etching. As a result, an n-electrode formation surface is formed. By causing each layer of the LED to emit light in time series, it is possible to display pixels having each of R, G, and B colors.

In the cooling configuration shown in FIG.
Reference numeral 1 denotes an LED, 205 denotes a heat sink, 206 denotes a Peltier element, 207 denotes a radiation fin, and 208 denotes a fan. In order to prevent the temperature of the LED 201 from rising, a Peltier element 206 and a heat radiation fin 207 are provided.

In this embodiment, an LED 201 capable of selectively emitting three colors of R, G, and B is used as a light source.
By causing the ED 201 to emit light in chronological order and driving one liquid crystal display panel 202 in accordance with R, G, and B, color display can be performed without using a filter despite being a single-panel type.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
It is a figure showing the basic composition of the image display device concerning an embodiment.

The basic configuration is a form in which the elements of the first and second embodiments are partially adopted, and the optimum configuration is obtained by considering the material of the light source. 81 is an LED that emits R light, 82 is an LE that can selectively emit G and B light
D, 83 and 84 are liquid crystal display panels, 85 is a prism, 8
Reference numeral 6 denotes a projection lens, and 87 denotes a polarizing plate and a collimator lens.

In the present embodiment, the same color display as in the second embodiment can be performed by causing the LED 81 to emit continuously and the LED 82 to emit light in time series.

(Fourth Embodiment) FIG. 9 shows a fourth embodiment of the present invention.
It is a figure showing the basic composition of the image display device concerning an embodiment. In this embodiment, the light sources correspond to R, G, and B, respectively.
However, the number of pixel panel units is one.

FIG. 9A uses three LEDs 901, 902, and 903 corresponding to R, G, and B as light sources, but uses one liquid crystal display panel 904. In this case, color display can be performed by causing the LEDs 901, 902, and 903 to emit light sequentially and driving the liquid crystal display panel 904 corresponding to each color.

FIG. 9B shows a configuration in which a mirror 917 is provided in addition to the configuration shown in FIG. 9A. FIG. 9C shows a configuration in which micro mirror groups 921, 922, and 923 are provided in addition to the configuration of FIG.

(Fifth Embodiment) FIG. 10 is a diagram showing a basic configuration of an image display device according to a fifth embodiment of the present invention. In this embodiment, the light source is formed of an organic semiconductor, and the configuration other than the light source may be the same as that of FIG.

As shown in FIG. 10A, the glass substrate 1
An ITO transparent electrode 102 is formed on the substrate 01, a hole transport layer 103 and an electron transport layer 104 are laminated thereon, and a metal cathode 105 is further formed thereon.

As the electron transport layer 104, for example, FIG.
A material (Alq ₃ ) as shown in (b) can be used. As the hole transport layer 103, for example, FIG.
(NPB) can be used. Further, as the polymer LED material, for example, a material (PPV) as shown in FIG. 10D can be used.

The present invention is not limited to the above embodiments. In the embodiment, a GaN-based material is used as the light-emitting element material system. However, the present invention is not limited to this. Also,
A plurality of elements can be integrated on the same substrate.

In the embodiment, a transmissive liquid crystal display panel is used. However, a similar structure can be used using a reflective liquid crystal display panel. Further, the pixel panel section is not necessarily limited to the liquid crystal display panel, but may be any as long as it can change the light transmittance or the reflectance of each pixel by an electric signal. For example, a method of moving a thin film by applying a voltage (digital mirror: DMD) can be used.

In addition, various modifications can be made without departing from the spirit of the present invention.

[0052]

As described in detail above, according to the present invention, L
By using a semiconductor light emitting element that emits monochromatic light such as an ED as a light source, it is possible to realize a projector-type image display device with low power consumption, which has not been obtained conventionally.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an image display device according to a first embodiment.

FIG. 2 is a diagram showing a basic configuration of an image display device according to a second embodiment.

FIG. 3 is a diagram showing another example of a light source.

FIG. 4 is a diagram showing an example in which a lens and a diffraction grating are provided on a light source.

FIG. 5 is a diagram showing an example of the arrangement of light sources.

FIG. 6 is a diagram showing an example in which light sources are arranged not inside a plane but inside a concave mirror.

FIG. 7 is a diagram showing an example relating to a pattern of a planar light source.

FIG. 8 is a diagram showing a basic configuration of an image display device according to a third embodiment.

FIG. 9 is a diagram showing a basic configuration of an image display device according to a fourth embodiment.

FIG. 10 is a diagram showing a basic configuration of an image display device according to a fifth embodiment.

[Explanation of symbols]

11, 201: LED (semiconductor light emitting device) 12, 33, 202: liquid crystal display panel (pixel panel unit) 13, 14, 17: prism 15, 204: projection lens 16: reflecting mirror 31, laser diode 32: spectral diffusion plate 35 movable lens 51, 61 light source 203 lens group 205 heat sink 206 Peltier element 207 fin 208 fan 209 sapphire substrate 210 n-type GaN contact layer 211 n-type AlGaN cladding layer 212, 213, 214 ... GaN / InGaN / GaN
Quantum well layer 215: p-type AlGaN current diffusion preventing layer 216: p-type AlGaN cladding layer 217: p-type GaN contact layer 218, 219: electrode

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masayuki Ishikawa 1st address, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in the Toshiba R & D Center (reference) 5G435 AA16 AA18 BB04 BB12 BB17 CC09 CC12 DD06 DD13 GG02 GG03 GG26 GG27 GG28 LL00

Claims (5)

[Claims] 1. A pixel panel section in which pixels are arranged in a matrix, wherein a pixel panel section which varies the transmittance or reflectance of light in each pixel by an electric signal, and a laminated film laminated so as to form a pn junction. The n-side and p-side junctions of the stacked film to supply current to the pn junction
And a semiconductor light emitting element that emits monochromatic light and irradiates the pixel panel portion with side electrodes. 2. The image display device according to claim 1, wherein said pixel panel section is a liquid crystal display panel. 3. The image display device according to claim 1, wherein said semiconductor light emitting device is a planar light emitting diode made of a group III nitride. 4. The pixel panel section and the semiconductor light emitting element
The image display device according to any one of claims 1 to 3, wherein the image display device is provided for each of three colors of R, G, and B. 5. A projector-type image display device for displaying a color image using three primary colors of light, wherein pixels are arranged in a matrix, and the light transmittance of each pixel is varied by an electric signal. Three liquid crystal display panels to be provided, respectively provided for these liquid crystal display panels,
A light emitting diode that emits light corresponding to each color of red, blue, and green; and an optical system that combines three types of light transmitted through each of the liquid crystal display panels to form an image on an image display surface. An image display device comprising: