JPH08122810A - Space light modulating element - Google Patents

Abstract

PURPOSE: To provide a space light modulating element which can modulate read light having high luminance. CONSTITUTION: In a display device where the first main flat plane 102 of the primary insulated substrate 101 and the first main flat plane 105 of the secondary insulated substrate 104 are mutually opposite, and a liquid crystal layer 109 is held between the first and the second insulated substrate 101, 104, a transparent electrode 107 is provided on the first main flat plane 102 of the primary insulated substrate 101, and a plurality of metal reflecting films 112 divided into minute shapes is provided on the first main flat plane 105 of the secondary insulated substrate 104, and a photoconductive layer 118 and a transparent electrode 119 are provided on the second main flat plane 106 of the secondary insulated substrate 104, and the metal reflecting film 112 is electrically connected to the photoconductive layer 118 through the connecting wiring 114 in a through hole 113 provided within the secondary insulated substrate 104.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a projection type display,
The present invention relates to a spatial light modulator used in a holographic television or an optical arithmetic device.

[0002]

2. Description of the Related Art In recent years, a projection type display (projector) has been actively developed in order to easily enjoy a large screen image. Projectors using CRTs have been developed from an early stage and are now widely produced. However, in recent years, as the image quality of video has advanced, a brighter screen has been desired and it has become necessary to deal with high-definition images represented by high-definition. In principle, it is difficult for a CRT to achieve both high definition and high brightness. In case of CRT,
In order to achieve high definition, it is necessary to reduce the electron beam diameter, and for that reason, it is necessary to limit the intensity of the electron beam to some extent. On the contrary, in order to increase the brightness, it is necessary to increase the intensity of the electron beam, and then the diameter of the electron beam inevitably widens.

Therefore, in recent years, a projector combining a CRT and a spatial light modulator using a liquid crystal has been developed [Technical Report of the Television Society, Vol. 17, No. 10, page 11 (1).
993)]. This spatial light modulator is a video light amplifier that modulates read light with a weak write information light. The projector described above writes a high-definition image to the spatial light modulator by a CRT and modulates strong read light. By doing so, both high definition and high brightness were achieved.

Some structures of the spatial light modulator used in the above projector have already been proposed. The present inventors have already proposed a spatial light modulator using amorphous silicon having a diode structure as a photoconductive layer, providing a minute metal reflection film as a pixel, and using a ferroelectric liquid crystal as a liquid crystal layer (Japanese Patent Laid-Open No. Hei 10 (1999) -242242). 4-136580).

In the case of a projector using a spatial light modulator, it is necessary to make the reading light intense in order to obtain a bright screen. That is, for the spatial light modulator, how important the read light can be modulated is an important issue. In general, when a strong read light is applied to the spatial light modulator, the read light leaks into the photoconductive layer, causing erroneous switching and a decrease in the contrast of the modulated light.

FIG. 5 shows the structure described in Japanese Patent Laid-Open No. 4-136580 mentioned above. In FIG. 5, 501 is a transparent insulating substrate, 502 is a transparent conductive electrode, 503 is an input light shielding film, 504 is a p layer, 505 is an i layer, 506 is an n layer, 507 is an amorphous silicon photoconductive layer, and 508 is light shielding. Layer, 509 is a metal reflection film, 510 is an alignment film, 511 is a liquid crystal layer, 512 is a spacer, 513 is an alignment film, 514 is a transparent conductive electrode, 515 is a transparent insulating substrate,
516 is a spatial light modulator, 517 is a polarizer, 518 is an analyzer, 519
Is a reading light, 520 is an output light, 521 is a writing light, and 522 is an output light shielding film.

In this structure, the output light-shielding film and the light-shielding layer contribute to the shielding of the read light. For the light-shielding layer, an insulator containing a black pigment, dye, carbon or the like to increase the light-shielding ability is used. The role of this light shielding layer is
(1) Auxiliary light-shielding of the output light-shielding film (2) Light-shielding of light incident on the photoconductive layer through the gap between the metal reflection film and the output reflection film. As the output light-shielding film, a metal thin film having a thickness of several tens nm to several hundreds nm is usually used. This prevents light from entering the photoconductive layer below the output light-shielding film. Particularly in the case of an amorphous silicon photoconductive layer, the i layer not doped with impurity ions is shielded from light.

The light blocking ability of the output light blocking film increases as the film thickness increases. However, if the film thickness is too thick, an electrical short circuit with the metal reflective film is likely to occur. When these short circuits occur, the potential of the metal reflective film is not accurately modulated by the writing light.

In particular, when the output light-shielding film is formed by self-alignment using a metal reflection film divided into minute shapes as a mask, the relationship between the thickness of the output light-shielding film and establishment of short circuit becomes more remarkable. The short circuit as described above causes a defect in the image on the display and greatly deteriorates the image quality. Moreover, the number of pixels increases as the display becomes higher definition. Therefore, if the number of pixels is large even if the probability of occurrence of defects is small, the number of defects increases. For example, 2000 × 2000 dots (4
In case of 1,000,000 dots) Even if the occurrence of defects is 10pp
Even with m, there is a defect of 40 dots on the image.

[0010]

In recent years, displays are required to have higher brightness and higher definition images.
However, in the structure as described above, it is necessary to increase the film thickness of the output light-shielding film in order to use the strong reading light for brightening, but this has a problem that it causes an increase in defects.

Further, the light-shielding layer is required to have higher light-shielding performance, and it is necessary to increase the content of the black pigment, dye or carbon, or to increase the thickness of the light-shielding layer, but there is a limit to the increase of the content. In addition, increasing the thickness reduces the volume of the photoconductive layer and lowers the sensitivity of the spatial light modulator, and engraving the back side of the metal reflective film may cause the deflection of the reflective electrode and reduce the amount of reflected light. become.

In view of the above problems, the present invention provides a spatial light modulator capable of modulating strong read light with high contrast and having almost no defects.

[0013]

In order to achieve the above object, the present invention uses a substrate which is opaque to the reading light and uses a liquid crystal layer and a photoconductive layer on the first and second principal planes of the substrate, respectively. It is formed separately, and the thickness of the substrate is used to shield the read light.

[0014]

With the above-described structure, the read light blocks the light with a thickness of several thousand times, which is several millimeters different from the conventional light-shielding layer formed of a thin film or the output light-shielding film. The photoconductive layer is almost unaffected by light being read out.

Further, since the metal reflection film is formed on the substrate, the flatness of the substrate is reflected and a mirror surface is easily obtained, and the reflectance is improved. Further, since the metal reflection film itself is sufficiently thin, the flatness of the substrate surface is improved, the orientation of the liquid crystal layer formed thereon is improved, and the spatial light modulator having a higher contrast ratio is obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A spatial light modulator according to a first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional structural view of a spatial light modulator according to the first embodiment of the present invention.

In FIG. 1, 101 is a first insulating substrate and 102
Is a first main surface of the first insulating substrate, 103 is a second main surface of the first insulating substrate, 104 is a second insulating substrate, 105 is a first main surface of the second insulating substrate, and 106 is a second Second main plane of the insulating substrate, 107 is a transparent electrode, 108 is an alignment film, 109 is a liquid crystal layer, 110 is an alignment film, 111 is a spacer, 112 is a metal reflection film, 113 is a through hole, 114 is a connection wiring, 115 Is n layer, 116 is i layer, 117
Is a p-layer, 118 is an amorphous silicon photoconductive layer, 119 is a transparent electrode, 120 is a polarizer, 121 is an analyzer, 122 is reading light, 123 is output light, and 124 is writing light.

The read light 122 is modulated by the liquid crystal layer 109 which is formed between the first insulating substrate 101 and the second insulating substrate 104. The modulated signal is created by the writing light 124 and the photoconductive layer formed on the second main plane of the second insulating substrate 104. The n-layer 115 is divided into minute regions and is formed on the first main plane with the metal reflection film 112 and the through holes 113.
It is electrically connected by the connection wiring 114 formed therein.

The metal reflecting film 112 is preferably made of a metal having a high reflectance such as an aluminum thin film or a silver thin film. Also, the film thickness is preferably about 50 nm to 500 nm, which improves the orientation of the liquid crystal layer 109 formed thereover. A ceramic substrate or a resin substrate is used as the second insulating substrate 104, and a pigment, a dye, a pigment or the like that absorbs visible light or the like may be dispersed in these. Metal reflective film 112
The n layer 115 is electrically connected to the n layer 115 by a connection wiring 114. In the figure, one through hole is used for connection, but a plurality of through holes may be used for connection. The through hole 113 may be a method in which the electrical connection is anisotropically made only in the direction of the first main plane and the second main plane without being restricted by the shape of the hole. It does not matter even if the conductive filler is connected in one direction.

Although the photoconductive layer in the figure has a rectifying property, the photoconductive layer is not limited to this and the n layer 115 and the p layer 117 may be omitted. At that time, the connection wiring 114 is electrically connected to the i layer 116. The alignment film 108 may not be necessary depending on the material of the liquid crystal layer 109. Further, a protective layer, a protective substrate, or the like may be provided on the side of the transparent electrode 119 on which the writing light 124 is incident.

A spatial light modulator according to a second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional structural view of the spatial light modulator in the second embodiment of the present invention.

In FIG. 2, 201 is a first insulating substrate, 202
Is a first main surface of the first insulating substrate, 203 is a second main surface of the first insulating substrate, 204 is a second insulating substrate, 205 is a first main surface of the second insulating substrate, and 206 is a second main surface. Second plane of the insulating substrate, 207 is a transparent electrode, 208 is an alignment film, 209 is a liquid crystal layer, 210 is an alignment film, 211 is a spacer, 212 is a metal reflection film, 213 is a through hole, 214 is a connection wiring, and 215. Is n layer, 216 is i layer, 217
Is a p-layer, 218 is an amorphous silicon photoconductive layer, 219 is an insulating layer, 220 is a transparent electrode, 221 is a polarizer, 222 is an analyzer, 223
Is the reading light, 224 is the output light, and 225 is the writing light.
Since the basic structure is similar to that of the first embodiment, detailed description of the same parts will be omitted.

The feature of this embodiment is that the photoconductive layer 218 is divided into minute regions. Adjacent photoconductive layer 21
An insulating layer 219 is arranged in the gap of 8.

As a result, the photoconductive layer 218 is independent for each minute region, and the charges generated in this region and the flow thereof do not affect the adjacent region, which contributes to the improvement of resolution as a spatial light modulator. Further, the insulating layer 219 may contain a pigment, a dye or a dye for blocking the writing light 225.

A spatial light modulator according to the third embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a sectional structural view of a spatial light modulator according to the third embodiment of the present invention.

In FIG. 3, 301 is a first insulating substrate, 302
Is a first main surface of the first insulating substrate, 303 is a second main surface of the first insulating substrate, 304 is a second insulating substrate, 305 is a first main surface of the second insulating substrate, and 306 is a second main surface. Second main plane of the insulating substrate, 307 is a transparent electrode, 308 is an alignment film, 309 is a liquid crystal layer, 310 is an alignment film, 311 is a spacer, 312 is a metal reflection film, 313 is a through hole, 314 is a connection wiring, and 315 Is n layer, 316 is i layer, 317
Is a p-layer, 318 is an amorphous silicon photoconductive layer, 319 is a transparent electrode, 320 is a third insulating substrate, 321 is a first main surface of the third insulating substrate, and 322 is a second main surface of the third insulating substrate. , 323 is a polarizer, 324 is an analyzer, 325 is a reading light, 326 is an output light, and 327 is a writing light. Since the basic structure is the same as that of the first embodiment, the details of the same parts will be described. Detailed description is omitted.

The feature of this embodiment is that the first insulating substrate 301 and the second insulating substrate 304 are composed of three substrates to form a liquid crystal layer, and the photoconductive layer 318 is formed on the third insulating substrate 320. This is connected to the second main surface of the second insulating substrate 304 and the connection wiring 3
14 and the photoconductive layer 318 (or the n layer 315) are electrically connected. This forms the liquid crystal layer 309 and the photoconductive layer 3
18 can be formed independently, and the degree of freedom in the creation method increases.

Although the connection wiring 314 and the n layer 315 are in direct contact with each other in the figure, conductive resin or metal bumps may be interposed therebetween. Also, the third insulating substrate 320 must be transparent to the writing light 327.

A spatial light modulator according to the fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a sectional structural view of a spatial light modulator according to the fourth embodiment of the present invention.

In FIG. 4, 401 is a first insulating substrate and 402
Is a first main surface of the first insulating substrate, 403 is a second main surface of the first insulating substrate, 404 is a second insulating substrate, 405 is a first main surface of the second insulating substrate, and 406 is a second main surface. Of the insulating substrate, 407 is a transparent electrode, 408 is an alignment film, 409 is a liquid crystal layer, 410 is an alignment film, 411 is a spacer, 412 is a metal reflection film, 413 is a through hole, 414 is a connection wiring, and 415. Is n layer, 416 is i layer, 417
Is a p-layer, 418 is an amorphous silicon photoconductive layer, 419 is an insulating layer, 420 is a transparent electrode, 421 is a third insulating substrate, 422 is a first main plane of the third insulating substrate, and 423 is a third insulating substrate. Of the second main plane, 424 is a polarizer, 425 is an analyzer, 426 is reading light, 427 is output light, and 428 is writing light. Since the basic structure is the same as that of the first embodiment, Detailed description of the same parts will be omitted.

The feature of this embodiment is that the first insulating substrate 401 and the second insulating substrate 404 are composed of three substrates to form a liquid crystal layer, and the photoconductive layer 418 is divided into minute regions to form a third region. It is formed on the insulating substrate 421, and is opposed to the second main plane of the second insulating substrate 404, and the connection wiring 414 and the photoconductive layer 418 (or the n layer 41).
5) is electrically connected to. As a result, the photoconductive layer 418 is independent for each minute region, and the charges generated in this region and the flow thereof do not affect the adjacent region, which contributes to improvement in resolution as a spatial light modulator.

The insulating layer 419 may contain a pigment, a dye or a dye for blocking the writing light 428. Further, a light shielding layer for shielding the gap between the adjacent photoconductive layers 418 is provided on the first main plane 422 of the third insulating substrate or the transparent electrode 4.
It may be provided between 20 and the p layer 417 or between the transparent electrode 420 and the insulating layer 419.

In the first to fourth embodiments, the photoconductive layer is a diode having a structure of p-layer, i-layer, and n-layer of amorphous silicon, but it is not limited to this.
The material may be a silicon carbide type, a cadmium type, a selenium type, a germanium type, or the like, and the crystal form may be not only amorphous but also microcrystal, polycrystal, or crystal. Organic semiconductor materials can also be used. Further, it is desirable to have a rectifying function, but the structure is not limited to the p, i, n structure.

In the first to fourth embodiments, the liquid crystal layer is preferably a ferroelectric liquid crystal, and the surface-stabilized ferroelectric liquid crystal mode in which the thickness of the operation mode liquid crystal layer is set to a spiral pitch or less is desirable. Ferroelectric liquid crystal is capable of high-speed response and has a wide viewing angle. Alternatively, a twisted nematic mode using a nematic liquid crystal, an electric field control birefringence mode, or the like may be used.

[0035]

As described above, in the spatial light modulator of the present invention, the liquid crystal layer and the photoconductive layer are the first main plane and the second plane of the insulating substrate.
Provided with a spatial light modulator that can modulate read-out light with a higher contrast ratio and a higher contrast ratio, which could not be used in the conventional light-shielding structure with a thin film, because it is created separately from the main plane, and has few display defects. it can.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a spatial light modulator according to a first embodiment of the present invention.

FIG. 2 is a sectional structural view of a spatial light modulator according to a second embodiment of the present invention.

FIG. 3 is a sectional structural view of a spatial light modulator according to a third embodiment of the present invention.

FIG. 4 is a sectional structural view of a spatial light modulator according to a fourth embodiment of the present invention.

FIG. 5 is a sectional structure diagram of a conventional spatial light modulator.

[Explanation of symbols]

 101 first insulating substrate 102 first major surface of first insulating substrate 103 second major surface of first insulating substrate 104 second insulating substrate 105 first major surface of second insulating substrate 106 second insulating substrate Second main plane of substrate 107 Transparent electrode 108 Alignment film 109 Liquid crystal layer 110 Alignment film 111 Spacer 112 Metal reflective film 113 Through hole 114 Connection wiring 115 n layer 116 i layer 117 p layer 118 Amorphous silicon photoconductive layer 119 Transparent electrode 201 First insulating substrate 202 first insulating substrate first major surface 203 first insulating substrate second major surface 204 second insulating substrate 205 second insulating substrate first major surface 206 second insulating substrate Second main plane 207 Transparent electrode 208 Alignment film 209 Liquid crystal layer 210 Alignment film 211 Spacer 212 Metal reflection film 213 Through hole 214 Connection wiring 218 Amorphous silicon photoconductive layer 219 Insulation layer 220 Transparent electrode 301 First insulation substrate 302 First First main plane of insulating substrate 303 First insulating substrate Second main plane 304 Second insulating substrate 305 First main plane of second insulating substrate 306 Second main plane of second insulating substrate 307 Transparent electrode 308 Alignment film 309 Liquid crystal layer 310 Alignment film 311 Spacer 312 Metal reflection film 313 Through Hole 314 Connection Wiring 318 Amorphous Silicon Photoconductive Layer 319 Transparent Electrode 320 Third Insulating Substrate 321 First Main Plane of Third Insulating Substrate 322 Second Main Plane of Third Insulating Substrate 401 First Insulating Substrate 402 First main plane of first insulating substrate 403 Second main plane of first insulating substrate 404 Second insulating substrate 405 First main plane of second insulating substrate 406 Second main plane of second insulating substrate 407 Transparent electrode 408 Alignment film 409 Liquid crystal layer 410 Alignment film 411 Spacer 412 Metal reflection film 413 Through hole 414 Connection wiring 418 Amorphous silicon photoconductive layer 419 Insulating layer 420 Transparent electrode 421 Third insulating substrate 422 First of third insulating substrate Main plane 423 Second main plane of third insulating substrate

Claims (6)

[Claims] 1. A first main surface of a first insulating substrate and a first main surface of a second insulating substrate are opposed to each other, and a liquid crystal layer is sandwiched between the first and second insulating substrates. A transparent electrode is provided on the first main plane of the first insulating substrate, and a plurality of metal reflection films divided into minute shapes are provided on the first main plane of the second insulating substrate. A photoconductive layer and a transparent electrode are provided on the second main surface of the insulating substrate, and the metal reflection film is formed on the photoconductive layer through a through hole provided in the second insulating substrate. A spatial light modulator, which is electrically connected to. 2. A first main surface of a first insulating substrate and a first main surface of a second insulating substrate are opposed to each other, and a liquid crystal layer is sandwiched between the first and second insulating substrates. A transparent electrode is provided on the first main plane of the first insulating substrate, and a plurality of metal reflection films divided into minute shapes are provided on the first main plane of the second insulating substrate. A plurality of photoconductive layers divided into minute regions, an insulating layer, and a transparent electrode are provided on the second main surface of the insulating substrate of, and the insulating layer fills a gap between the adjacent photoconductive layers. The spatial light modulation element is characterized in that the metal reflection film is electrically connected to the photoconductive layer through a through hole provided in the second insulating substrate. 3. A first main surface of the first insulating substrate and a first main surface of the second insulating substrate face each other, and a second main surface of the second insulating substrate and a first main surface of the third insulating substrate. The first main surface is opposed to the first main surface, and the liquid crystal layer is sandwiched between the first and second insulating substrates.
A photoconductive layer is sandwiched between a second insulating substrate and a third insulating substrate, a transparent electrode is provided on the first main plane of the first insulating substrate, and a minute electrode is provided on the first main plane of the second insulating substrate. A plurality of metal reflection films divided into shapes are provided, a plurality of metal electrodes divided into minute shapes are provided on the second main plane of the second insulating substrate, and the metal electrodes are the metal reflection films. And the second
Is electrically connected through a through hole provided in the insulating substrate, and a photoconductive layer and a transparent electrode are provided on the first main plane of the third insulating substrate. Is a spatial light modulator which is electrically connected to the metal electrode. 4. A first main surface of the first insulating substrate and a first main surface of the second insulating substrate face each other, and a second main surface of the second insulating substrate and a third main surface of the third insulating substrate. The first main surface is opposed to the first main surface, and the liquid crystal layer is sandwiched between the first and second insulating substrates.
A photoconductive layer is sandwiched between a second insulating substrate and a third insulating substrate, a transparent electrode is provided on the first main plane of the first insulating substrate, and a minute electrode is provided on the first main plane of the second insulating substrate. A plurality of metal reflection films divided into shapes are provided, a plurality of metal electrodes divided into minute shapes are provided on the second main plane of the second insulating substrate, and the metal electrodes are the metal reflection films. And the second
A plurality of photoconductive layers and insulating layers which are electrically connected to each other through through holes provided in the insulating substrate, and which are divided into minute regions on the first main plane of the third insulating substrate. And a transparent electrode, the insulating layer fills a gap between the photoconductive layers adjacent to each other, and the photoconductive layer is electrically connected to the metal electrode. element. 5. The spatial light modulator according to claim 1, wherein the second insulating substrate is opaque to visible light. 6. The spatial light modulator according to claim 1, wherein the second insulating substrate comprises a plurality of layers including a layer opaque to visible light.