JPH117009A - Projection type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the projection type image display device which can display an image of high quality having no decrease in contrast even for high-luminance image display. SOLUTION: The display device is equipped with a means which projects the output light of an optical modulating means that displays an image by modulating the output light and the optical modulating means is equipped with photodetection electrodes 8 and a light shield film 9 which are sandwiched between a glass substrate 3 and a glass substrate 3' where a conductive transparent electrode 2, a photoconductive layer 4, a light absorbing layer 5, and a liquid crystal layer 17 are formed, and electrically insulated from each other on the photoconductive layer; and respective reflecting electrodes 6 which are electrically insulated from each other on the light absorbing layer 5 are electrically connected to the corresponding photodetection electrodes 8 and further a light shield film 9 is formed on the photoconductive layer corresponding to the interval of the rejecting electrodes so as to prevent a light beam which is not absorbed by the light absorbing layer 5 from being made incident on the photoconductive layer 4 when part of the output light made incident from the side of the liquid crystal layer 7 is made incident on the light absorbing layer 5 from the interval of the reflecting electrodes 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type image display device for displaying a high quality screen.

[0002]

2. Description of the Related Art In recent years, since it is difficult to increase the size of a conventional direct-view television, a projection display for enlarging and projecting an image displayed on a liquid crystal panel has been developed.
Above all, a system using a reflective liquid crystal panel of an optical writing system is expected to be capable of realizing a bright and high-definition image display (for example, Japanese Patent Application Laid-Open No. 6-59275, Japanese Patent Application No. 5-138066). .

FIG. 5 is a sectional view of a reflection type liquid crystal panel 17 of a conventional optical writing system. The reflection type liquid crystal panel 17 of the optical writing system has a photoconductive layer 4, a reflection electrode 6, and a liquid crystal layer 7 formed in this order on a first glass substrate 3 on which a conductive transparent electrode 2 is formed. The structure is sandwiched by the second glass substrate 3 'on which the' is formed. The light absorbing layer 5 is provided between the reflective electrodes 6 in a groove formed by etching the photoconductive layer 4.

Next, the operation principle of the conventional optical writing type reflective liquid crystal panel 17 will be described. When an AC voltage is applied between the opposing conductive transparent electrodes 2, 2 ', the photoconductive layer 4
When light is incident on the liquid crystal layer, the impedance of the photoconductive layer 4 is reduced, and most of the applied voltage is applied to the liquid crystal layer 7 to switch the liquid crystal. Since the intensity of the voltage applied to the liquid crystal changes according to the intensity of the incident light, the switching state of the liquid crystal also changes according to the intensity of the incident light. The light that enters the photoconductive layer 4 and reduces the impedance of the photoconductive layer 4 is called writing light. In a portion where the writing light does not enter, most of the applied voltage is applied to the high-resistance photoconductive layer 4, so that the liquid crystal does not switch.

FIG. 6 shows a configuration of a projection type image display apparatus using a conventional reflection type liquid crystal panel 17 of an optical writing system. As the image source 10, generally a cathode ray tube (hereinafter referred to as CR)
T). The image of the image source 10 is imaged by the writing lens 11 on the photoconductive layer 4 of the reflection type liquid crystal panel 17 of the optical writing system, and the liquid crystal layer 7 is switched.

The state of the switched liquid crystal is determined by the light source 12.
Is converted into linearly polarized light by a polarizing beam splitter 14 (hereinafter referred to as PBS) and input to read out. That is, only the S-polarized light is reflected by the PBS 14 and enters the reflective liquid crystal panel 17 of the optical writing system. In the portion where the liquid crystal is switched, the incident S-polarized light is modulated into P-polarized light when passing through the liquid crystal, and is reflected and output by the reflection electrode 6.

Since the PBS 14 has a function of transmitting the P-polarized light component, the light beam modulated to the P-polarized light by the liquid crystal layer 7 passes through the PBS 14 and is enlarged and projected on the screen 16 by the projection lens 15 to be turned ON. Is displayed.
The display of the halftone is realized by increasing the P-polarized light component according to the degree of switching of the liquid crystal and increasing the component transmitted through the PBS 14.

Since the liquid crystal layer 7 corresponding to the portion where the writing light does not enter does not switch, the S-polarized light is output as it is as the S-polarized light and is reflected by the PBS 14 toward the light source 12. This state corresponds to black in the image.

In the reflection type liquid crystal panel 17 of the conventional optical writing system, intrinsic amorphous silicon or rectifying amorphous silicon is used as the photoconductive layer 4. As the liquid crystal material, a ferroelectric liquid crystal, a TN liquid crystal, or the like is used. There is also a configuration in which readout light is reflected by a dielectric multilayer film instead of a reflective electrode such as Al. In this case, the dielectric multilayer does not have a pixel structure, and a light shielding layer is formed between the dielectric multilayer and the photoconductive layer.

[0010]

In order to brighten a display image in a projection type image display device, it is necessary to increase the light output of the light source 12. That is, the display image can be made brighter by increasing the intensity of the reading light 13.

The light-shielding layer 5 has a function of absorbing readout light entering from between the reflective electrodes 6 and preventing the readout light from entering the photoconductive layer 4. However, in the reflection type liquid crystal panel 17 of the conventional optical writing system, when strong reading light is incident, the intensity of light incident on the light absorbing layer 5 from between the reflective electrodes 6 is also increased, so that sufficient light shielding cannot be performed. There were challenges. That is, when the read light becomes strong, the amount of light incident on the photoconductive layer 4 without being absorbed by the light absorption layer 5 increases, so that the liquid crystal layer 7 switches regardless of the presence or absence of the write light. Switching of the liquid crystal layer 7 in the absence of the writing light means that the black level of the image increases, resulting in a significant decrease in contrast.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a projection type image display device capable of displaying a high quality image without lowering the contrast even in a high brightness image display.

[0013]

In order to achieve the above object, a projection type image display apparatus according to the present invention comprises at least an illuminating means and a light modulating means for modulating an output light of the illuminating means to display an image. And a projection unit for projecting output light from the light modulation unit, the light modulation unit comprising: a first glass substrate on which a conductive transparent electrode, a photoconductive layer, and a light absorption layer are sequentially formed; A second glass substrate on which a conductive transparent electrode is formed facing the first glass substrate; and a liquid crystal layer is formed between the first glass substrate and the second glass substrate. And, comprising a plurality of light receiving electrodes and a light shielding film electrically insulated from each other on the photoconductive layer,
And a plurality of reflective electrodes electrically insulated from each other on the light absorbing layer, and each of the reflective electrodes is electrically connected to a corresponding one of the light receiving electrodes, and When a part of the output light of the illuminating means incident from the layer side is incident on the light absorbing layer from the interval between the reflective electrodes,
The light-shielding film is formed on the photoconductive layer corresponding to a distance between the plurality of reflective electrodes in order to prevent light rays not absorbed by the light-absorbing layer from entering the photoconductive layer.

[0014]

FIG. 1 is a sectional view of an optical writing type reflection type liquid crystal panel 1 used in a projection type image display device according to an embodiment of the present invention.

This optical writing type reflection type liquid crystal panel 1
Now, the first glass substrate 3 on which the conductive transparent electrode 2 is formed
On top, a photoconductive layer 4, a light absorbing layer 5, a reflective electrode 6, a liquid crystal layer 7
Are formed in order, and are sandwiched by the second glass substrate 3 ′ on which the conductive transparent electrode 2 ′ is formed. That is, the liquid crystal layer 7 is formed between the first glass substrate and the second glass substrate.

A light receiving electrode 8 is provided on the photoconductive layer 4, and the light receiving electrode 8 forms a pair with the corresponding reflection electrode 6,
They are electrically connected to each other. In addition, a light shielding film 9 is provided on the photoconductive layer 4 in order to prevent the unabsorbed component of the readout light incident on the light absorbing layer 5 from between the reflective electrodes 6 from entering the photoconductive layer 4. It has become.

FIG. 2 shows a pixel structure (a part of a circle is enlarged) as viewed from the liquid crystal layer 7 side. The light receiving electrode 8 is formed one size smaller than the hexagonal reflection electrode 6, and the light shielding film 9 is formed one size larger than the interval between the reflection electrodes 6. With such a configuration, the readout light that enters from between the reflective electrodes 6 and is not absorbed by the light absorbing layer 5 can be used.
Can be prevented.

As the photoconductive layer 4, for example, CdS, C
dTe, CdSe, ZnS, ZnSe, GaAs, Ga
Compound semiconductors such as N, GaP, GaAlAs, InP, amorphous semiconductors such as Se, SeTe, AsSe, S
i, Ge, Si1-xCx, Si1-xGex, Ge1-xCx (0
<X <1) a polycrystalline or amorphous semiconductor, and (1)
Phthalocyanine pigment (abbreviated as Pc)
c, XPc (X = Cu, Ni, Co, TiO, Mg, S
i (OH) ₂ etc.), AlClPcCl, TiOClP
cCl, InClPcCl, InClPc, InBrP
(2) azo dyes such as monoazo dyes and disazo dyes, (3) penylene pigments such as penylene anhydride and penylene imide, (4) indigoid dyes, (5) quinacridone pigments, (6) anthraquinone , Polycyclic quinones such as pyrenequinones, (7) cyanine dyes, (8) xanthene dyes, (9) PVK / TNF
Organic semiconductors such as (10) a eutectic complex formed from a beryllium salt dye and a polycarbonate resin, and (11) an azulenium salt compound.

Also, amorphous Si, Ge, Si1-x Cx, S
i1-xGex, Ge1-xCx (hereinafter a-Si, a-Ge,
When a-Si1-xCx, a-Si1-xGex, or a-Ge1-xCx is used for the photoconductive layer 4, hydrogen or a halogen element may be included, and the dielectric constant can be reduced and the resistivity can be reduced. Oxygen or nitrogen may be included to increase nitrogen.

For controlling the resistivity, p-type impurities B and A
elements such as l and Ga, or n-type impurities P and A
Elements such as s and Sb may be added. The amorphous material to which the impurities are added is stacked to form p / n, p / i, i
The dielectric constant, dark resistance, or operating voltage polarity may be controlled by forming a junction such as / n or p / i / n and forming a depletion layer in the photoconductive layer 4. In addition to such an amorphous material, a depletion layer may be formed in the photoconductive layer 4 by forming a heterojunction by laminating two or more kinds of the above materials.
The thickness of the photoconductive layer 4 is desirably 0.1 to 10 μm.

As the transparent conductive electrodes 2, 2 ', for example, ITO, ZnO, SnO ₂ or the like can be used.

As the reflective electrode 6 and the light receiving electrode 8, an electrode material having conductivity can be used.
Metal thin films of Ti, Cr, Ag, Mo, Ni, Mg, etc.,
Alternatively, a laminate of two or more metal thin films can be used.

As the light shielding film 9, for example, Al, Ti, C
A metal thin film of r, Ag, Mo, Ni, Mg, or the like, a thin film in which two or more metals are stacked, or a dielectric mirror may be used.

The liquid crystal material used for the liquid crystal layer 7 is TN
Liquid crystals and ferroelectric liquid crystals can be used.

The light absorbing layer 5 may be made of a material that absorbs a wavelength band in which the photoconductive layer 4 has sensitivity. For example, an organic high molecular polymer in which carbon or a black pigment or a black dye is dispersed, or aC: H, aG
An inorganic thin film such as e: H or a-Ge _1-x N _x : H can be used.

Next, the principle of operation of the reflective liquid crystal panel 1 of the optical writing system used in the projection type image display device of the present invention will be described. When an AC voltage is applied between the opposing conductive transparent electrodes 2 and 2 ′, when writing light enters the photoconductive layer 4, the impedance of the photoconductive layer 4 decreases, and most of the applied voltage is applied to the liquid crystal layer 7. Switching the liquid crystal. Since the intensity of the voltage applied to the liquid crystal changes according to the writing light intensity, the switching state of the liquid crystal also changes according to the writing light intensity. In a portion where the writing light does not enter, most of the applied voltage is applied to the high-resistance photoconductive layer 4, so that the liquid crystal does not switch.

The projection type image display device shown in FIG. 3 can be constituted by using the reflection type liquid crystal panel 1 of the optical writing system of the present invention. As the image source 10, a CRT or a transmissive liquid crystal panel can be used. The image of the image source 10 is formed on the photoconductive layer 4 of the reflective liquid crystal panel 1 of the optical writing system by the writing lens 11 to switch the liquid crystal layer 7.

The state of the switched liquid crystal is determined by the light source 12.
Is converted into linearly polarized light by a polarizing beam splitter 14 (hereinafter referred to as PBS) and input to read out. That is, only the S-polarized light is reflected by the PBS 14 and is incident on the reflective liquid crystal panel 1 of the optical writing system. In the part where the liquid crystal is switching, when the incident S-polarized light passes through the liquid crystal,
The light is modulated into polarized light, reflected by the reflective electrode 6, and output.

Since the PBS 14 has a function of transmitting the P-polarized light component, the light beam modulated to the P-polarized light by the liquid crystal layer 7 is transmitted through the PBS 14 and is enlarged and projected on the screen 16 by the projection lens 15 to be turned ON. Is displayed.
The display of the halftone is realized by increasing the P-polarized light component according to the degree of switching of the liquid crystal and increasing the component transmitted through the PBS 14.

Since the liquid crystal layer 7 corresponding to the portion where the writing light does not enter does not switch, the S-polarized light is output as it is as the S-polarized light, and is reflected by the PBS 14 toward the light source 12. This state corresponds to black in the image.

In the projection type image display device of the present invention,
When a strong readout light is incident on the liquid crystal panel, the readout light 13 that has not been absorbed in the light incident on the light absorbing layer 5 from between the reflective electrodes 6 is reflected by the light-shielding electrode 9. Can be suppressed from being incident on the photoconductive layer 4, and a decrease in contrast can be reduced.

FIG. 4 shows the relationship between the brightness and the contrast of the projected image. In a conventional projection type image display device using a reflective liquid crystal panel 17 of an optical writing system, the contrast is remarkably reduced when it exceeds 2,000 lumens, whereas in the projection type image display device of the present invention, it is 10,000 lumens. Even when an image was displayed at a brightness higher than the above, almost no decrease in contrast was observed.

In the projection type image display apparatus constructed according to the present invention, as described in detail, even when a high-luminance image is displayed, a high-quality image display can be realized without a decrease in contrast.

It should be noted that the projection type image display device of the present invention is not limited to the above embodiment, and various modifications are possible based on the gist of the present invention.

[0035]

As described above, according to the present invention, it is possible to realize a projection type image display apparatus capable of displaying a high-contrast image even in a high-luminance image display.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical writing type reflection type liquid crystal panel used in a projection type image display device according to an embodiment of the present invention.

FIG. 2 is a pixel structure diagram of an optical writing type reflection type liquid crystal panel used in a projection type image display device according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of a projection type image display device configured according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between brightness and contrast of a projection type image display device configured according to an embodiment of the present invention and a conventional projection type image display device.

FIG. 5 is a sectional view of a reflective liquid crystal panel of an optical writing system used in a conventional projection type image display device.

FIG. 6 is a configuration diagram of a conventional projection type image display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflection type liquid crystal panel of optical writing system 2, 2 'Conductive transparent electrode 3, 3' Glass substrate 4 Photoconductive layer 5 Light absorption layer 6 Reflection electrode 7 Liquid crystal layer 8 Light reception electrode 9 Light shielding film

Claims (1)

[Claims] 1. A projection type image display comprising at least illumination means, light modulation means for modulating output light of the illumination means to display an image, and projection means for projecting output light from the light modulation means. An apparatus, wherein the light modulating means is disposed opposite to a first glass substrate on which a conductive transparent electrode, a photoconductive layer, a light absorbing layer, and a liquid crystal layer are sequentially formed, and the first glass substrate. A plurality of light-receiving electrodes and a light-shielding film that are electrically insulated from each other on the photoconductive layer; A plurality of reflective electrodes electrically insulated from each other on the light absorbing layer, and each of the reflective electrodes is electrically connected to the corresponding light receiving electrode; and the liquid crystal layer A part of the output light of the illumination means incident from the side is In order to prevent light not absorbed by the light absorbing layer from entering the photoconductive layer when entering the light absorbing layer from the interval between the reflective electrodes, the photoconductive layer corresponding to the interval between the plurality of reflective electrodes A projection type image display device, wherein the light shielding film is formed thereon.