JPH05323358A - Space optical modulating element and its production - Google Patents

Abstract

PURPOSE:To provide the space optical modulating element with which an orientation defect is prevented or the generated orientation defect, if any, is limited to a local part and picture element defects are decreased. CONSTITUTION:This space optical modulator is constituted of at least a photoconductive layer 103, a liquid crystal layer 106 and metallic reflection films 104 divided to microshapes within the same plane between these layers. The film thickness of the liquid crystal layer 106 on the metallic thin films 104 is set smaller than the film thickness of the spacings 105 between the metallic thin films. The photoconductive layer 103 is formed on transparent insulating substrates 101, 110 coated with transparent conductive electrodes 102, 109 and the metallic reflection films 104 are uniformly formed and after the patterns of the microshapes are formed by photolithography, the photoconductive layer 103 is etched by using the metallic reflection films 104 of the microshapes as a mask, by which level differences are provided.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art High-definition televisions having large screens and high-density pixels have been developed and put into practical use in various systems. Above all, the development of a projection display using liquid crystal technology has been active in place of the conventional cathode ray tube method. With the cathode ray tube method, the screen brightness becomes lower and the screen becomes darker for high density pixels.
Also, it is difficult to increase the size of the cathode ray tube itself. On the other hand, although a projection display apparatus using a liquid crystal element of a transistor drive system is a promising method, it has been pointed out that the aperture ratio does not increase and the element is expensive. A liquid crystal light valve using a CRT as an input has attracted attention as a device having a simpler element shape and combining the advantages of a CRT and a liquid crystal element (for example, JP-A-63-1).
09422). In recent years, it has become possible to display moving images on a large screen of 100 inches or more by combining a highly sensitive light receiving layer amorphous silicon and liquid crystal. In addition, the liquid crystal material uses a ferroelectric liquid crystal that can respond at high speed, and liquid crystal light valves with higher speed and higher resolution have become possible. This liquid crystal light valve is also expected to be the core of the next-generation parallel computing device and optical computing device that uses the memory property and binarization characteristics of ferroelectric liquid crystals.

Holography-television has been attracting attention as a device capable of viewing a three-dimensional moving image without glasses. In particular, a liquid crystal display element is expected as a rewritable hologram recording medium. The resolution of the current liquid crystal element of the transistor drive system is 12 to 25 lp / mm, and it is desired to realize an element having 200 lp / mm in the future.

There is a spatial light modulator consisting of a liquid crystal layer and a photoconductive layer or a liquid crystal light valve, which is formed by providing minute electrodes which are independent of each pixel. A liquid crystal light valve using microelectrodes is characterized by being easier to manufacture than when using a reflective layer of a multi-layered dielectric thin film, having no dependence on the incident angle, and having high reflectivity. Can be raised. When used as a spatial light modulator of a projection display, a high-quality television image can be obtained because the aperture ratio is large and the pixel shape is clear.

[0005]

When the liquid crystal layer is composed of a ferroelectric liquid crystal, it is important to control the orientation thereof. The defect alignment such as the zigzag defect peculiar to the ferroelectric liquid crystal causes a reduction in contrast not to mention an image defect when an image is formed. Alignment defects do not occur locally but grow over a large area centered on the nucleus. Therefore, it is necessary to prevent the alignment defect or to limit it to the local portion even if it occurs.

[0006]

A spatial light modulator comprising at least a photoconductive layer, a liquid crystal layer, and a metal reflective film divided into minute shapes in the same plane between the layers, wherein the metal thin film is formed on the metal thin film. The thickness of the liquid crystal layer is different from the thickness of the liquid crystal layer between the metal thin films.

A photoconductive layer is formed on a transparent insulating substrate coated with a transparent conductive electrode, a metal reflection film is uniformly formed, and a fine pattern is formed by photolithography. The photoconductive layer is etched by using the minute metal reflection film as a mask to form a step, and the thickness of the liquid crystal layer between the metal thin films is increased.

[0008]

In the image display device or the spatial light modulation device using the ferroelectric liquid crystal, the surface stabilized state (hereinafter referred to as SS state) is used as the liquid crystal alignment state. This orientation state is likely to cause a defect mode called a zigzag defect, which is the first cause of image defects. It has been clarified that the zigzag defect is caused by the deformation of the liquid crystal alignment surface of the liquid crystal layer into a V shape when the cross section of the liquid crystal layer is viewed. Now consider the case where the film thickness of the liquid crystal layer changes discontinuously. The zigzag defect generated in the region where the film thickness of the liquid crystal layer is small is bent at the center of the layer, resulting in a V-shaped deformation.

This defect continuously grows in a region having a large film thickness, and an asymmetric layer structure is generated in the film thickness direction. The larger the film thickness difference, the more remarkable the asymmetry difference. Therefore, the energy state becomes higher as the film thickness difference increases. On the other hand, when the generated V-shaped orientation is cut into a discontinuous orientation and the V-shaped defects are confined in one region, the state energy becomes low, and the orientation state is easily realized. In this case, the discontinuous plane of orientation concentrates on the interface where the discontinuous change in film thickness occurs.

Therefore, in an element having a metal reflection surface divided into minute areas as a pixel, by making the liquid crystal film thickness on the metal reflection film and the liquid crystal film thickness between the metal reflection films different,
Even if a zigzag defect occurs, it can be confined to only one pixel that is the source.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

1 and 2 are sectional views showing one embodiment of the spatial light modulator of the present invention. In FIG. 1, there is a concave portion 105 between pixels,
This is the case where the film thickness of the liquid crystal layer 106 on the metal reflection surface is thinner than the liquid crystal layer between pixels. The configuration of the spatial light modulator 111 is
A transparent conductive electrode 102 (for example, ITO, SnOx) is provided on a transparent insulating substrate 101 (for example, glass), a photoconductive layer 103 (for example, an amorphous silicon semiconductor having a diode structure) is laminated, and a separation corresponding to a pixel is formed. Aligned film 1 for aligning the liquid crystal layer 104 (for example, a metal thin film of aluminum, chromium, titanium, etc.) having a minute shape and the liquid crystal.
07 (for example, a polymer thin film such as polyimide) is arranged. The cell thickness of the ferroelectric liquid crystal layer 106 is controlled by the dispersed beads 108 serving as a spacer. The alignment layer 107 is evenly formed on the transparent conductive electrode 109 on the opposite side. Incident light from the substrate side on which the photoconductive layer is formed 11
2 is optically written, and the other is read light 113
Is modulated by the liquid crystal layer 106, and output light 114 is emitted from the metal reflective layer 104. The polarizer 115 and the analyzer 116 are arranged so as to be orthogonal to each other.

The material used for the photoconductive layer 103 is, for example,
CdS, CdTe, CdSe, ZnS, ZnSe, Ga
Compound semiconductors such as As, GaN, GaP, GaAlAs, InP, amorphous semiconductors such as Se, SeTe, AsSe, Si, Ge, Si _1-x C _x , Si _1-x Ge _x , Ge _1-x
C _x (0 <x <1) polycrystalline or amorphous semiconductor, and (1)
Phthalocyanine pigment (abbreviated as Pc), for example, metal-free Pc,
XPc (X = Cu, Ni, Co, TiO, Mg, Si
(OH) ₂ ), AlClPcCl, TiOClPc
Cl, InClPcCl, InClPc, InBrPc
Br, etc., (2) azo dyes such as monoazo dyes and disazo dyes, (3) penylene pigments such as penylene anhydride and penylene acid imide, (4) indigoid dyes, (5) quinacridone pigments, (6) anthraquinone , Polycyclic quinones such as pyrenequinones, (7) cyanine dyes, (8) xanthene dyes, (9) PVK / TNF
There are organic semiconductors such as charge transfer complexes such as (10), eutectic complexes formed from (10) pyrrole dyes and polycarbonate resins, and (11) azurenium salt compounds. In addition, amorphous Si, Ge, Si _1-x C _x , Si _1-x Ge _x , Ge _1-x
C _x (hereinafter a-Si, a-Ge, a-Si _1-x C _x , a
-Si _1-x Ge _x, when used for a-Ge _1-x C abbreviated as in _x) photoconductive layer 103, it may be included hydrogen or a halogen element, and of the resistivity to reduce the dielectric constant Oxygen or nitrogen may be included for augmentation. To control the resistivity, an element such as B, Al or Ga which is a p-type impurity, or an element such as P, As or Sb which is an n-type impurity may be added. As described above, the amorphous materials to which impurities are added are stacked to form junctions such as p / n, p / i, i / n, and p / i / n, and a depletion layer is formed in the photoconductive layer 107. In this way, the dielectric constant and dark resistance or the operating voltage polarity may be controlled. Not only such an amorphous material, but also two or more kinds of the above materials are laminated to form a heterojunction to form the photoconductive layer 1.
A depletion layer may be formed in 03. In addition, the photoconductive layer 10
The film thickness of 3 is preferably 0.1 to 10 μm.

The alignment film 107 is set so that the alignment of the ferroelectric liquid crystal molecules is parallel to the layer direction. The thickness of the alignment film is 1000 Å or less, preferably 100 Å or less. As the alignment film, there is a polymer film of nylon, polyimide or the like or a SiO ₂ oblique vapor deposition film. For example, Japanese Patent Application No. 3-1145 discloses an alignment film having excellent electrical characteristics. As the liquid crystal material of the liquid crystal layer 106, a chiral smectic C liquid crystal which is a ferroelectric liquid crystal is used. Since the thickness of the ferroelectric liquid crystal layer is in the case of the reflection type spatial light modulator, the contrast of the output light is set to about 1 μm. The thickness of the metal thin film is 100 to 2000Å, optimally 500 to 1500Å.

FIG. 2 is an example of an element structure in which there are inter-pixel convex portions 205 and the liquid crystal layer 206 on the metal reflection surface is thicker than the liquid crystal layer between pixels. FIG. 3 is a structural example of a conventional spatial light modulator.

4 and 5 are process diagrams showing the manufacturing method of FIGS. In the step of FIG. 4, (1) a transparent conductive electrode 402 is formed on the glass substrate 401 which is one of the transparent insulating substrates of FIG. As the photoconductive layer 403, for example, a p-layer, an i-layer, and an n-layer of an amorphous silicon photoconductive layer are continuously formed by a plasma CVD method. A metal reflection film 404 is formed on the top. (2) A separate reflection film 405 corresponding to a pixel is patterned by photolithography. (3) Part of the photoconductive layer 403 is removed using the separation reflection film 405 as an etching mask. CF ₄ for example
The inter-pixel recess 4 is formed by dry etching using a mixed gas of O ₂ and O ₂ or wet etching using a mixed solution of hydrofluoric acid and nitric acid.
A step difference of 06 can be formed. This step yields one substrate containing the photoconductive layer of the spatial light modulator of FIG.

FIG. 5 is a process diagram for forming the convex portion between pixels, and is for forming the spatial light modulator of FIG.
(1) One transparent insulating substrate glass substrate 501 of FIG.
A transparent conductive electrode 502 is formed on top. Photoconductive layer 503
For example, a p-layer, an i-layer, and an n-layer of the amorphous silicon photoconductive layer are continuously formed by the plasma CVD method. A resist pattern for forming a portion between pixels is formed on the uppermost portion by photolithography. (2) Resist 5
A part of the photoconductive layer 503 is removed by using 04 as an etching mask. For example, the steps in the pixel portion can be formed by dry etching using a mixed gas of CF ₄ and O ₂ or wet etching using a mixed solution of hydrofluoric acid and nitric acid. (3) A metal reflective film is formed on the entire surface of the substrate. The separation reflection film 505 is formed. (4) The inter-pixel convex portion 50 is formed by removing the resist.
6 is formed, and one substrate including the photoconductive layer of the spatial light modulator of FIG. 2 is formed.

The operation will be described with reference to FIG. An image display element or a spatial light modulation element using a ferroelectric liquid crystal uses a surface stabilized state (hereinafter referred to as SS state) as a liquid crystal alignment state. This orientation state is likely to cause a defect mode called a zigzag defect, which is the first cause of image defects.
It has been clarified that the zigzag defect is caused by the deformation of the liquid crystal alignment surface of the liquid crystal layer into a V shape when the cross section of the liquid crystal layer is viewed. Now consider the case where the film thickness of the liquid crystal layer changes discontinuously. In FIG. 6, the zigzag defect generated in the region A where the film thickness of the liquid crystal layer 601 is small is bent at the center of the layer, and a V-shaped deformation occurs. This defect continuously grows in a region B having a large film thickness, and again has a region A ′ having a small film thickness.
The case where it is connected to is shown in (1) of FIG. In the region B (or B '), a layer structure asymmetric in the film thickness direction is generated. The larger the film thickness difference, the more remarkable the asymmetry difference. Therefore, the energy state becomes higher as the film thickness difference increases. On the other hand, the case of discontinuous orientation is shown in (2) of FIG. In the figure, the doglegged orientation generated in A is cut at the interface between A and B. The liquid crystal alignment was made parallel and defect-free alignment in any of B, A'and B '. In this case, the discontinuous plane of orientation concentrates on the interface where the discontinuous change in film thickness occurs. The asymmetric orientation with respect to FIG. 6A is reduced, and the energy state is low. The state energy of (1) and (2) of FIG. 6 becomes lower in the case of confining the dogleg defect in one region as the difference in the liquid crystal film thickness becomes larger, and the orientation is realized. Therefore, in an element having a metal reflection surface divided into minute regions as pixels, when a zigzag defect is generated by making the liquid crystal film thickness Da on the metal reflection film different from the liquid crystal film thickness Db between the metal reflection films. However, it is possible to confine it only to the one pixel that is the source.

Example 1 A spatial light modulator shown in FIG. 7 was produced. An ITO film having a thickness of 0.1 μm was formed on a glass substrate 701 having a size of 55 mm × 45 mm × 1.1 mm by a sputtering method to form a transparent conductive electrode 702. Then, a p / i / n diode with a thickness of 2.2 μm is formed by a plasma CVD method.
An amorphous silicon film having a transparent structure is stacked as the photoconductive layer 706. p layer 703 (thickness 1000Å), i layer 70
4 (film thickness 1.8 μm), n layer 705 (film thickness 3000 Å)
And The effective area is 35 mm × 35 mm. An aluminum thin film 1 is formed on the film within this effective area by a vacuum deposition method.
000A was formed as the metal reflection film 707. A resist pattern is formed and the size of each pixel is 20 μm × 20 μ.
As m, 1000 × 1000 pixels were formed with a pitch of 25 μm. A part of the amorphous silicon film between the pixels was removed by etching. Dry etching is performed by reactive ion etching (hereinafter referred to as RIE) using a mixed gas of CF ₄ and oxygen. 5000 Å is etched almost vertically to remove 3000 Å of the n-layer 705 and the upper 2000 Å of the i-layer 704. In this step, the inter-pixel concave portion 708 is formed.

A polyimide alignment film 711 was laminated, and the alignment treatment was performed by rubbing the surface in a certain direction with a nylon cloth. On a glass substrate 713 on one side, in order to realize a liquid crystal layer thickness of about 1 μm, beads having a diameter of 1 μm dispersed in isopropyl alcohol are scattered by a spray. afterwards,
A liquid crystal cell was produced by enclosing both glass substrates with UV curable resin around the substrates. Ferroelectric liquid crystal ZLI-
Inject 3654 (Merck). In order to obtain uniform orientation after injection, the material was heated to a temperature not lower than the phase transition temperature (62 ° C.) of ZLI-3654 and then returned to room temperature and reoriented at a slow cooling rate of 1 ° C./min or less.

A polarizer 715 and an analyzer 716 were arranged so that the polarization directions were orthogonal to each other, and a spatial light modulator was produced. An AC voltage was applied to this spatial light modulator and white light was used as input light to confirm the operation. As a result, when the intensity of the input light 717 was several μW / cm ² or more, the rising of the output light 719 was observed, and it was confirmed that the operation was sufficient even when the incident light intensity was small.

The spatial light modulator thus produced was evaluated as a projection display. FIG. 9 shows a schematic view of the projection display device. Spatial light modulator 9 of the present invention
01 is optically written by the CRT display 902. The number of pixels of the element used for display is 480 in height and 650 in width. A light source 905 (metal halide lamp) for reading is illuminated by a polarizing beam splitter 903 by a condenser lens 904. The output image is magnified by the lens 906 and displayed on the screen 607. When each dot on the CRT screen is written in the separated pixel of the spatial light modulator, each pixel is converted into a square shape on the screen. The aperture ratio is 80% and a bright image can be obtained.
The image enlarged to a size of 100 inches has an illuminance of 2000 lumens on the screen. The image had a contrast of 250: 1 and a resolution of 650 vertical TV lines. This means that the spatial light modulator has a resolution of 50 lp / mm. When a moving image was output, a clear high-intensity image was obtained with no afterimage due to the movement of the video rate. In order to obtain a color image, three sets of a CRT tube corresponding to each of RGB and a spatial light modulation element were prepared and combined on a screen. A good color image is reproduced in detail, and there is almost no leak light in the area between pixels, which is 1 / the maximum illuminance of the pixel area.
It was 10 ⁴ or less. 55 pixel defects (total number: 10
⁶ pieces), it has been possible to reduce by more than one digit compared to the conventional structure.

The spatial light modulator having the convex portion between pixels shown in FIG. 8 was manufactured by the above method by the process shown in FIG. When a projection type display device was assembled and evaluated, pixel defects 7
High image quality equivalent to 5 was obtained.

(Example 2) In a spatial light modulator having a concave portion between pixels, the number of defective pixels was comparatively evaluated by changing the depth (D (μm)) of the concave portion. The device configuration is shown in FIG. 8 of the first embodiment. The results are shown in Table 1. In the table, D = 0.1 μm
Is the conventional example of FIG. Here, the step corresponds to the reflection film thickness.

[0025]

[Table 1]

It has been shown that a significant effect can be obtained by providing a step of 0.5 μm or more. Therefore, the spatial light modulator 10 shown in FIG. 10 in which the concave portions between pixels have the thickness of the photoconductive layer.
14 was produced. The step difference is 2.2 μm. Although the same process as in Example 1 can be performed, an input light shielding film 1002 that shields input light between pixels is formed on the substrate 1001 in advance. Image evaluation was carried out by the apparatus shown in FIG. 9 in the same manner as in Example 1, and a pixel defect 14 and a favorable element could be manufactured.

(Embodiment 3) FIG. 10 manufactured by the above method.
11 was assembled using the spatial light modulator of No. 1 and the reproduction of the stereoscopic image displayed in real time was confirmed. He as coherent light
-Ne laser 1101 is used to illuminate a subject 1106, and CC is emitted together with the reference light passing through the collimator 1105.
An interference fringe pattern is formed on the image pickup surface of D1107. This image data is transferred to the CRT 1109 and optically written in the spatial light modulator 1110 to reproduce the interference fringe pattern.
He-Ne laser-1101 of coherent light to read
Observe a three-dimensional image in reflection mode using. The pixel pattern
The pixel size is 8 μm square and 100 lp / m with 10 μm pitch.
m elements (3200 × 3200 = 10 ⁷ pixels).

[0028]

According to the present invention, a spatial light modulator having few pixel defects is provided for a projection display device which displays a high-resolution, high-luminance, large-screen image. In addition, a method for manufacturing an element with a simple structure and a small number of steps is provided. Using this element, a holography-television device can obtain a clear stereoscopic image in real time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a spatial light modulator having a concave portion between pixels according to the present invention.

FIG. 2 is a cross-sectional view of a spatial light modulator having convex portions between pixels according to the present invention.

FIG. 3 is a sectional view of an example of a spatial light modulator having a conventional structure.

FIG. 4 is a process drawing showing a method for manufacturing a spatial light modulator having inter-pixel recesses of the present invention.

FIG. 5 is a process diagram showing a method for manufacturing a spatial light modulator having convex portions between pixels according to the present invention.

FIG. 6 is a schematic diagram showing an alignment state of a ferroelectric liquid crystal layer having a step in the film thickness direction.

FIG. 7 is a cross-sectional view of a spatial light modulator having an inter-pixel concave portion according to the first embodiment of the present invention.

FIG. 8 is a cross-sectional view of a spatial light modulator having a convex portion between pixels according to the first embodiment of the present invention.

FIG. 9 is a schematic diagram of a projection display device manufactured using the spatial light modulator of the present invention.

FIG. 10 is a sectional view of a spatial light modulator having a concave portion between pixels according to a second embodiment of the present invention.

FIG. 11 is a schematic diagram of a holography-television device manufactured using the spatial light modulator of the present invention.

[Explanation of symbols]

 101 Transparent Conductive Substrate 102 Transparent Conductive Electrode 103 Photoconductive Layer 104 Metal Reflective Film 105 Inter-pixel Recesses 106 Liquid Crystal Layer 107 Alignment Film 108 Beads 109 Transparent Conductive Electrode 110 Transparent Insulating Substrate 111 Spatial Light Modulation Element 112 Incident Light 113 Read-out light 114 Output light 115 Polarizer 116 Analyzer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuki Zutomi, 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Kuni Ogawa, 1006, Kadoma, Kadoma City, Osaka Prefecture 72) Inventor Yukio Tanaka 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A spatial light modulator comprising at least a photoconductive layer, a liquid crystal layer, and a metal reflective film divided into minute shapes in the same plane between the layers, and a liquid crystal layer on the metal thin film. A spatial light modulation element characterized in that the film thickness and the liquid crystal layer between the metal thin films are different. 2. The spatial light modulator according to claim 1, wherein the difference between the film thickness of the liquid crystal layer on the metal thin film and the film thickness of the liquid crystal layer between the metal thin films is 2000 Å or more. 3. The film thickness of the liquid crystal layer on the metal thin film is smaller than the film thickness of the liquid crystal layer between the metal thin films, and the difference is not less than the film thickness of the photoconductive layer. The spatial light modulator described. 4. A photoconductive layer is formed on a transparent insulating substrate coated with a transparent conductive electrode, a metal reflection film is uniformly formed, and a fine pattern is formed by photolithography. 2. The method for manufacturing a spatial light modulator according to claim 1, wherein the photoconductive layer is etched by using the minute metal reflection film as a mask to form a step, thereby increasing the film thickness of the liquid crystal layer between the metal thin films.