JPH05173171A - Spatial optical modulating element and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the surface inward diffusion of light carriers and a drift on each border surface and to obtain the spatial optical modulating element which has high resolution by forming photoconductors which have rectifying ability in a photoconductive layer in picture element units. CONSTITUTION:The photoconductive layer 13 constitutes a pin type diode which provides rectification in the picture element units and a metallic reflecting layer 14 is formed thereupon while separated in the picture element units. When this spatial optical modulating element 1 is irradiated with light while applied with a reverse bias voltage, a photocurrent is generated in an (i) layer 13b; and the electron drifts to the side of an (n) layer 13c and the positive hole drifts to the side of a (p) layer 13a. In the area between the picture elements, there is neither the (p) layer nor the (n) layer and only the (i) layer 13b is formed, so the part of the photoconductor layer 13 positioned between the picture elements is invariably a high-resistance area since there is not any channel layer having a low-resistance border surface and a light shield layer 27 is present. Therefore, the migration of electric charges such as the electrons and positive holes generated in the picture element units, to adjacent picture elements is suppressed to eliminate crosstalk between the picture elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a projection display,
The present invention relates to a spatial light modulator used in an image display device such as a holographic television or an optical arithmetic device, or an image arithmetic device, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, high-definition televisions having a large screen and high-density pixels have been developed by various methods and partially put into practical use. Above all, the development of projection-type displays using liquid crystal technology is active as an alternative to the conventional CRT method. The conventional cathode ray tube method has a problem that the luminance of the screen tends to decrease and the entire image tends to be dark when aiming at higher pixel density, and it is difficult to increase the size of the cathode ray tube itself.

Further, a projection type display device using a liquid crystal element driven by a thin film transistor is an effective method in terms of downsizing and weight reduction and low power consumption, but the aperture ratio is not large and the element itself is complicated and expensive. Is mentioned as an issue to be solved.

On the other hand, the combination with the CRT-input photo-writing type liquid crystal element has a simpler device structure and CR.
As a device combining the advantages of T and a liquid crystal element (Japanese Patent Laid-Open No. 63-109422, etc.), in recent years, a liquid crystal element having an amorphous silicon thin film as a highly sensitive light receiving layer has been used, and more than 100 inches. It is now possible to project moving images on the large screen. With regard to the liquid crystal material, it has become possible to realize a higher resolution liquid crystal light valve by using a ferroelectric liquid crystal capable of high-speed response. Further, such an optical writing type liquid crystal element is expected to be the core of the next-generation parallel arithmetic device and optical computing device by utilizing the memory characteristic and the binarization characteristic of the ferroelectric liquid crystal. ..

On the other hand, a holographic television has been attracting attention as a device capable of viewing a three-dimensional stereoscopic moving image without glasses, and a liquid crystal element is particularly expected as a rewritable hologram recording medium. Current transistor drive type liquid crystal device has a resolution of 12 to 25 (lp / m
m), and it is desired to realize a high resolution of 200 (lp / mm) or more in the future.

A spatial light modulator used in such an image display device or an image processing device is provided with a liquid crystal layer, a photoconductive layer, a reflective layer, an alignment film for aligning the liquid crystal, etc. In a modulation element, a photoconductor having a rectifying property is generally uniformly formed in the photoconductive layer over the entire element, and the presence of such a photoconductive layer enables high-speed response. In addition, it is possible to return the state of each pixel or the entire surface of the element to the initial state only by the electric signal (Japanese Patent Laid-Open No. 64-18130).

On the other hand, in the conventional spatial light modulator, in order to read out the modulated light output after the optical writing, an element structure in which a metal reflection layer is separately provided between the liquid crystal layer and the photoconductive layer ( JP-A-62-169120) and an element structure in which a dielectric reflection thin film layer is provided instead of the metal reflection layer have been proposed. In such a device structure, the limit resolution for writing a high-density image input is given by, for example, the following equation.

[0008]

[Equation 1]

In the equation (1), f is the resolution, ρ is the volume resistivity of the light receiving layer, C is the sum of the capacitance of the light receiving layer and the liquid crystal layer, and τ is the response time of the liquid crystal. As a typical numerical example, ρ = 10 ¹⁰
From Ω · cm, C = 10 nF / cm ² , τ = 100 μs, f = 100 (lp / mm) is obtained. At present, when a dielectric reflection film is provided, a maximum resolution of 125 (lp / mm) has been confirmed (Autumn Applied Physics Society of Japan 1990 Proceedings 26a-H-9).

On the other hand, when the output image is a metal reflection film having clear pixels, it is required to form fine pixels of 100 (lp / mm) or more. As a fine processing technology in the current silicon semiconductor technology, a photolithography technology capable of processing a pattern line width of the order of μm or less has been developed. By using this technology, one pixel is 10 μm square and the width between pixels is It is possible to form a pattern of 1 μm or less.

In particular, the latter spatial light modulation element has a clear pixel shape and is used as an optical writing element applied to a large-screen and high-density display such as a high-definition television.
It is expected to realize a spatial light modulator having a large aperture ratio and capable of displaying a high brightness screen. Further, an optical arithmetic element utilizing the binarization processing capability of the ferroelectric liquid crystal due to the threshold characteristic has a clear threshold and pixel shape for each element (corresponding to a pixel), and therefore, the optical arithmetic element can be used as a parallel arithmetic device based on optical information. Proposed as a main element (Japanese Patent Application Nos. 3-1145 and 3)
-1146).

[0012]

There is a spatial light modulation element using a ferroelectric liquid crystal as an image display element having high resolution or an optical operation element for performing two-dimensional information processing having high density information. As a factor that gives the limit of
(1) In-plane diffusion length of photo carriers generated in the absorption layer,
(2) Charge drift at each junction interface inside the absorption layer due to its rectifying property, (3) Crosstalk due to electric field strength leakage between adjacent pixels, (4) Size of the minimum domain of ferroelectric liquid crystal, etc. Can be considered.

Particularly, in the element structure provided with the separated metal reflection layer, the resolution is largely deteriorated due to the influence of the factor (1) and the factor (2), and the element is separated due to the resolution limit determined by these factors. The pixel density of a spatial light modulator of the type having a reflective surface is determined.

FIG. 7 is a sectional view of an example of a conventional spatial light modulator. In the conventional spatial light modulator, the photoconductive layer 13 having the pin structure is uniformly formed over the entire surface of the device,
Due to the potential difference and electric field generated between adjacent pixels, electrons move in the n-layer and holes move in the p-layer in the lateral direction of the device, respectively, and crosstalk occurs between the pixels.
There is a problem that the resolution is degraded due to (1) and factor (2).

In order to solve the above-mentioned problems, the present invention is a spatial light modulator having a liquid crystal layer, a photoconductive layer, an alignment film and the like, which has an element structure which prevents the above-mentioned deterioration of resolution which occurs in the photoconductive layer. The object of the present invention is to provide a spatial light modulation element capable of faithfully displaying high-density information, and to provide a space in which the spatial light modulation element according to the present invention can be easily obtained. It is an object of the present invention to provide a method for manufacturing a light modulation element.

[0016]

In order to achieve the above object, the spatial light modulator of the present invention comprises at least a photoconductive layer,
A spatial light modulator including a reflective layer, a ferroelectric liquid crystal layer, and an alignment film for aligning the ferroelectric liquid crystal, wherein a photoconductor having rectifying property is formed in each pixel in the photoconductive layer. Is characterized by.

In the above structure, the photoconductor having a rectifying property is preferably an amorphous silicon semiconductor having a diode structure. Further, in the above configuration,
It is preferable that the reflective layer is divided into pixel units on top of the rectifying photoconductor.

Further, in the method for manufacturing a spatial light modulator of the present invention, after forming a thin film layer made of an amorphous silicon semiconductor having a diode structure, a part of the uppermost layer of the thin film layer is removed to have a rectifying property. A feature is that a photoconductor is formed on a pixel-by-pixel basis, and a reflective layer and an alignment film are sequentially formed on the surface thereof.

In the method for manufacturing a spatial light modulator of the present invention, after forming a thin film layer made of an amorphous silicon semiconductor having a diode structure, a reflective layer is formed, and then the uppermost layer of the reflective layer and the thin film layer. Is partially removed, a reflective layer and a photoconductor having a rectifying property are formed on a pixel-by-pixel basis, and an alignment film is further formed on the surface thereof.

[0020]

According to the above structure, the spatial light modulator having at least the photoconductive layer, the reflective layer, the ferroelectric liquid crystal layer and the alignment film for aligning the ferroelectric liquid crystal, wherein the photoconductive layer has a rectifying property. By forming the photoconductor which it has, the switching speed can be remarkably improved. In addition, by applying a voltage in the forward direction to the rectifying photoconductor in the absence of bias light, a large electric field is applied to the ferroelectric liquid crystal layer, forcing the image memory state to the initial state. Can be returned. On the other hand, when a voltage is applied in the opposite direction to the photoconductor having a rectifying property in the state where some image pattern is received, the pixel having a light input is in a low resistance state, so that the ferroelectric liquid crystal in that portion. And the pixel portion with no light input remains high resistance, and the orientation of the ferroelectric liquid crystal is not reversed.

Further, since the photoconductor having a rectifying property is formed in the pixel unit in the photoconductive layer, the light carriers generated in the light receiving layer are diffused in the in-plane direction, and the photoreceiver has the rectifying property. Since it is possible to prevent charge drift at each junction interface inside the layer, it is possible to suppress resolution degradation due to these influences.

Further, in the above structure, since the photoconductor having rectifying property is an amorphous silicon semiconductor having a diode structure, it is easy to form a film on a large area and the quantum efficiency of photocurrent generation is good. Can be easily formed.

Further, in the above structure, since the reflective layer is divided into pixel units above the photoconductor having a rectifying property, it is possible to suppress light reflection in a region between pixels, and The contrast of the image can be improved, and the blurring and blurring of the image can be improved.

Further, according to the method of manufacturing a spatial light modulator of the present invention, after forming a thin film layer made of an amorphous silicon semiconductor having a diode structure, a part of the uppermost layer of the thin film layer is removed to obtain a rectifying property. A photoconductor having a rectifying property in the photoconductive layer can be easily formed in a pixel unit by forming a photoconductor having a pixel in a pixel unit and further sequentially forming a reflective layer and an alignment film on the surface thereof. it can.

Further, in the method for manufacturing a spatial light modulator of the present invention, after forming a thin film layer made of an amorphous silicon semiconductor having a diode structure, a reflective layer is formed, and then the uppermost layer of the reflective layer and the thin film layer. Is removed to form a reflective layer and a rectifying photoconductor on a pixel-by-pixel basis, and an alignment film is further formed on the surface to form a reflective layer and a rectifying photoconductor on a pixel-by-pixel basis. Can be easily formed.

The operation of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the spatial light modulator of the present invention, and the manner in which the above-mentioned deterioration of resolution is improved will be described with reference to FIG. Photoconductive layer 13
Comprises a rectifying pin diode for each pixel unit, on which a metal reflection layer 14 is formed separately for each pixel unit. The photoconductive layer 13 is preferably an amorphous silicon layer which can be easily formed on a large area and has a quantum efficiency of photocurrent generation close to 1 which is almost ideal. On the other hand, the photoconductive layer 13 located between the pixels forms only the i layer 13b of the amorphous silicon layer. With such an element structure, the pin structure of the portion corresponding to the pixel is two-dimensionally distributed in the plane in a columnar shape, and the region between the pixels has a pattern shape surrounded by the i layer 13b.

When light is applied to such a spatial light modulator 1 while applying a reverse bias voltage, a photocurrent is generated in the i layer 13.
Electrons drift to the n layer 13c side and holes drift to the p layer 13a side. The area between pixels is p
Since only the i layer 13b is formed without the layers and the n layer, the photoconductive layer 13 located between the pixels is provided due to the absence of the channel layer of the low resistance interface and the presence of the light shielding layer 27.
The area of is always a high-resistance region, and charges such as electrons and holes generated in a pixel unit are suppressed from moving to an adjacent pixel, and crosstalk between pixels is eliminated.

In particular, when the photoconductive layer 13 is amorphous silicon, the main carrier having a long traveling length is an electron, so that the electrons in the charge pair generated by light absorption can travel from the substrate side so that the electrons can travel in the layer. The layer 13a, the i layer 13b, and the n layer 13c are formed in this order. At this time, it is most effective to limit the lateral drift of electrons, which are carriers, on the n-layer 13c side.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an embodiment of the spatial light modulator of the present invention. Transparent insulating substrate 1 such as glass
1, a light-shielding film 27 made of chromium or the like is formed between the pixels to prevent light from entering between the pixels during image writing. ITO or SnO _{x on the} surface
Etc., a transparent conductive electrode 12 is formed, and a photoconductive layer 13 made of an amorphous silicon semiconductor or the like is further stacked thereon in the order of a p-layer 13a, an i-layer 13b, and an n-layer 13c in a diode structure. Corresponding to the photoconductive layer 13
In the part of, only the i layer 13b is laminated.

The material used for the photoconductive layer 13 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 , G
e _1-x C _x (0 <x <1) semiconductor such as polycrystalline or amorphous semiconductor, or (1) phthalocyanine pigment (hereinafter referred to as “P
abbreviated as “c”), for example, metal-free Pc, XPc (X = Cu,
Ni, Co, TiO, Mg, Si (OH) _2, etc.), Al
ClPcCl, TiOClPcCl, InClPcC
1, InClPc, InBrPcBr, etc., (2) Azo dyes such as monoazo dyes and disazo dyes, (3) Penylene anhydrides, Penylene pigments such as penylene acid imides, (4) Indigoid dyes, (5) Quinacridone pigments, (6) Polycyclic quinones such as anthraquinones and pyrenequinones, (7) Cyanine dyes, (8) Xanthene dyes, (9) Charge transfer complexes such as PVK / TNF, (10) Formed from pyrylium salt dyes and polycarbonate resins There are organic semiconductors such as eutectic complexes and (11) azurenium salt compounds.

Amorphous Si, Ge, Si
_1-xC_x, Si_1-xGe_x, Ge_1-xC_x(Hereinafter, a-
Si, a-Ge, a-Si_1-xC_x, A-Si_1-xGe
_x, A-Ge _1-xC_xAbbreviated as) to the photoconductive layer 13
When used, hydrogen or halogen elements may be included.
First, use oxygen or nitrogen to reduce the dielectric constant or increase the resistivity.
You can include it. In addition, p-type impurities are used to control the resistivity.
Is an element such as B, Al, or Ga, or is an n-type impurity.
Elements such as P, As, and Sb may be added.

In this way, the amorphous materials doped with impurities are stacked to form junctions of p / n, p / i, i / n, p / i / n, etc., and the depletion layer is formed in the photoconductive layer 13. May be formed to control the dielectric constant, dark resistivity or operating voltage polarity. Not only such an amorphous material, but two or more kinds of the above materials are laminated to form a heterojunction, and the photoconductive layer 13 is formed.
A depletion layer may be formed inside. In addition, the photoconductive layer 13
The film thickness of is preferably in the range of 0.1 μm to 10 μm.

On the surface of the n layer 13c of the photoconductive layer 13, a reflective layer 14 made of a metal thin film of aluminum, chromium, titanium or the like is formed. Therefore, the p layer 13a and the n layer 13c
The reflective layer 14 is formed as a pixel pattern that is separated for each pixel.

On this surface, an alignment film 15 made of a polymer thin film such as nylon or polyimide or a SiO ₂ oblique vapor deposition film for aligning the liquid crystal is uniformly formed over the entire surface of the element. The alignment film 15 is formed so that the alignment of the ferroelectric liquid crystal molecules is parallel to the layer direction, and the thickness thereof is 1000 angstroms or less, and particularly preferably 100 angstroms or less.

The cell thickness of the ferroelectric liquid crystal layer 16 is determined by the spacers 17 such as resin beads. In particular, in order to increase the contrast of output light, the thickness of the ferroelectric liquid crystal layer 16 is about 2 μm in the case of a transmissive spatial light modulator.
In the case of a reflective spatial light modulator, it is preferably set to about 1 μm. Further, the material of the ferroelectric liquid crystal layer 16 is preferably a chiral smectic C liquid crystal which is a ferroelectric liquid crystal.

Similarly, a transparent conductive electrode 19 such as ITO or SnO _x is formed on a transparent insulating substrate 20 such as glass, and an alignment layer 18 similar to the alignment film 15 is formed on the transparent conductive electrode 19. It is formed uniformly over the entire surface.

Next, the operation of the spatial light modulator 1 will be described. Incident light 2 from the substrate side where the photoconductive layer 13 is laminated
1 records pattern information. On the opposite side of the element, the reading light 22 is emitted through the polarizer 23, and the output light 24 modulated according to the recorded pattern information is output through the analyzer 25. The polarization directions of the polarizer 23 and the analyzer 25 are orthogonal to each other.

FIG. 2 is a sectional view of another embodiment of the spatial light modulator of the present invention. The spatial light modulator 1 of the present embodiment is
Although it is almost the same as that shown in FIG. 1, a difference is that a uniform multilayer dielectric reflection film 26 is formed over the entire surface of the element instead of the reflection layer 14 formed separately in pixel units. .. Therefore, by using the multilayer dielectric reflection film as compared with the metal thin film, a reflectance of 90% or more can be achieved, and a read image with high brightness can be obtained.

FIG. 3 is a sectional view of another embodiment of the spatial light modulator of the present invention. The spatial light modulator 1 of the present embodiment is
Although substantially the same as that shown in FIG. 1, the corresponding portions of the photoconductive layer 13 between the pixels are the p layer 13a and the i layer 13b.
Are different in that they are laminated. Therefore, the deterioration of resolution is prevented by suppressing the drift of the photo carriers, particularly the electrons, in the n layer 13c in the lateral direction.

FIG. 4 is a cross-sectional view for explaining the steps of one embodiment of the method for manufacturing a spatial light modulator of the present invention. In the step (a), a chrome film is formed on the glass substrate 11 by a sputtering method to form a light-shielding film 27, and then a portion corresponding to each pixel is removed by using photolithography, and ITO is formed thereon. The electrode 12 was formed by the sputtering method.

In the step (b), after the p layer 13a of the amorphous silicon photoconductive layer is formed over the entire surface by the plasma CVD method, the resist film is formed by photolithography on the portion other than the light shielding film, that is, the portion of each pixel. Thirty
To form.

In step (c), p corresponding to the pixels is
After removing the layer 13a by etching or the like, the resist film 30 is removed, and then the i layer 13b and the n layer 13c of the amorphous silicon photoconductive layer are continuously formed so that the pixel portion has a pin diode structure. To do. Further, an aluminum thin film is formed thereon as the reflection layer 14 by, for example, electron beam evaporation. Next, a resist film 31 is formed on each pixel portion by using photolithography.

In step (d), the resist layer 31 is removed after the reflective layer 14 and the n layer 13c of the amorphous silicon photoconductive layer in the portions between the pixels are removed by etching. Next, as an alignment film 15 for aligning the ferroelectric liquid crystal, a polyimide film is formed by coating, for example. In addition, in order to obtain uniform alignment when performing the alignment treatment,
It is preferable to rub the surface of the polymer film with a cloth such as nylon. Further, when the SiO ₂ film formed by the oblique evaporation method is used as the alignment film 15, the rubbing process is not necessary.

After the step (d), the spatial light modulator shown in FIG. 1 can be manufactured by laminating the spacers 17 together with the dispersed glass substrate 20 on the opposite side.

Specific examples of the spatial light modulator and the method for manufacturing the same according to the present invention will be described below in detail. (Embodiment 1) In this embodiment, the manufacture of the spatial light modulator shown in FIG. 1 will be described with reference to FIG.
As the transparent insulating substrate 11, 55 mm × 45 mm × 1.
Using a 1 mm glass substrate, a chromium film having a thickness of 1000 angstrom is formed thereon by a sputtering method to form a light shielding film on the entire surface. Next, using photolithography, a 40 μm square window corresponding to one pixel and a light shielding film 27 were formed in a pixel pattern of 45 μm pitch in the vertical and horizontal directions. Next, an ITO film having a thickness of 0.05 μm to 0.5 μm was formed thereon by a sputtering method to form the transparent conductive electrode 12 over the entire surface (step a).

In order to form the amorphous silicon of the p layer, after forming the amorphous silicon by the plasma CVD method, 1000 ppm of boron is added within the effective area of 35 mm × 35 mm to form the p layer 13a of 500 angstrom thickness. Formed. Next, this substrate is taken out from the film forming apparatus and a resist film 30 is patterned on portions corresponding to each pixel by photolithography (step b).

After the p layer 13a corresponding to the space between the pixels is removed by etching or the like, the resist film 30 is removed and p
The substrate on which the layer 13a is patterned is again treated with plasma C
Put it in a VD device and add a non-doped i layer 13b with a thickness of 2 μm,
2000-angstrom-thick phosphorus-doped n-layer 13c
Are continuously formed. Next, an aluminum thin film having a thickness of 1500 Å was formed as the reflective layer 14 on the entire surface of the n layer 13c by the electron beam evaporation method. Then, by using photolithography, a resist film 31 is pattern-formed in a portion corresponding to each pixel (step c).

The reflective layer 14 made of an aluminum film is wet-etched with an acid solution, and the resist film 31 remains. A pixel pattern is formed on the amorphous silicon n-layer 13c by wet etching with a hydrofluoric acid-based solution or reactive ion etching with CF ₄ and oxygen. On this, as the alignment film 14,
Polyamic acid, which is a precursor of polyimide, is applied by a spinner to a thickness of 200 angstroms or less, and the entire substrate is placed in a heat treatment furnace and subjected to heat treatment at 230 ° C. for 1 hour, whereby the polyamic acid is imidized to form a polyimide film. Formed (step d).

On the other hand, the transparent insulating substrate 2 on one side shown in FIG.
A transparent conductive electrode 19 made of ITO was formed on the entire surface of No. 0 by sputtering, and then an alignment film 18 of polyimide was laminated on the entire surface in the same manner as in the above method. Then, the alignment film 15,
By rubbing the surface of 18 with nylon cloth in a certain direction,
The alignment process of the alignment film is performed.

Next, the formation of the ferroelectric liquid crystal layer 16 will be described. In order to realize a ferroelectric liquid crystal layer having a thickness of about 1 μm, spacers 17 made of beads with a diameter of 1 μm dispersed in isopropyl alcohol are sprayed on the surface of the alignment film 15 on one side of the substrate, A liquid crystal cell was produced by applying a UV curable resin around the transparent insulating substrates 11 and 20 and adhering them to each other. Ferroelectric liquid crystal (brand name "ZLI-36
54 ", manufactured by Merck & Co., Inc., and then heated to a temperature higher than the phase transition temperature (62 ° C.) of the ferroelectric liquid crystal in order to obtain uniform alignment, and returned to room temperature at a slow cooling rate of 1 ° C./min or less and then re-heated. Oriented.

Thus, the spatial light modulator 1 according to the present invention could be obtained. Next, the characteristic evaluation of the obtained spatial light modulator 1 will be described. FIG. 5 is a schematic configuration diagram of a projection display device used for evaluation of the spatial light modulator. A CRT display 43 having a resolution of 480 pixels in the vertical direction and 650 pixels in the horizontal direction was used as a means for optically writing in the spatial light modulator 1. The readout light is emitted from the light source 40 of the metal halide lamp, condensed by the condenser lens 41, and applied to the spatial light modulator 1 via the polarization beam splitter 42. The output image is reflected by the polarization beam splitter 42 and the lens 4
The image is magnified at 4 and imaged on the screen 45. When each pixel on the screen of the CRT display 43 is written in the divided pixels of the spatial light modulator 1, the pixels are converted into rectangular pixels on the screen 45.

As a result, the image having a large aperture ratio of 80% and enlarged to a size of 100 inches is displayed on the screen 4.
5 gives a bright image with an illuminance of 2000 lumens. Further, it was confirmed that the image contrast was 250: 1 and the resolution was 650 TV lines in the vertical direction.

When a moving image was output, there was no afterimage with respect to the movement at the video rate, and a clear high-luminance image was obtained. Also, a color image could be obtained by preparing three combinations of the CRT display 43 and the spatial light modulator 1 corresponding to the three primary colors of RGB and combining them on the screen.

On the other hand, when the spatial light modulator having the structure shown in FIG. 7 was incorporated into the projection display shown in FIG. 5 for comparison of the characteristic evaluation, the resolution was 45 in the vertical direction.
The result is 0 TV lines.

(Embodiment 2) By the same manufacturing method as in Embodiment 1, the pixel shape is 8 μm square and the pixel pitch is 1.
A spatial light modulator having a pixel pattern of 0 μm and vertical 3200 pixels × horizontal 3200 pixels was produced. Therefore, the total number of pixels is 10 ⁷ or more. Regarding the characteristics of the obtained spatial light modulator, a photographic image for resolution evaluation was recorded, and then the recorded image was read, whereby a resolution of 100 (lp / mm) could be confirmed.

(Embodiment 3) A device structure similar to that of the spatial light modulator shown in FIG. 2 is obtained by the same manufacturing method and pixel pattern as in Embodiment 2, except that the reflective layer 14 is replaced by Zn.
A dielectric reflection film 26 made of an alternating laminated film of S and MgF ₂ was formed by electron beam evaporation. The obtained spatial light modulator has a dielectric reflection film 26 of 90%.
Since the above reflectance can be achieved, the brightness of the image was increased and a resolution of 100 (lp / mm) was achieved.

Example 4 To obtain the spatial light modulator shown in FIG. 3, the manufacturing method is the same as that of Example 1, but in the step (b) shown in FIG. 4, the amorphous silicon layer is used. P layer 13a, i layer 13b, and n layer 13c are continuously laminated. Therefore, the photoconductive layer 13 in the portion of the light shielding film 27, that is, the portion corresponding to the portion between the pixels is p
/ I structure. The pixel shape is 8 μm as in the second embodiment.
When formed in a corner, the obtained spatial light modulator had a resolution of 100 (lp / mm). Therefore, as compared with the element structure shown in FIG. 1, the pattern formation step of the p layer 13a can be omitted, and it has been confirmed that a high resolution spatial light modulator can be obtained by a simpler manufacturing method. Further, from these results, it is expected that in the spatial light modulator using the amorphous silicon layer as the light receiving layer, the drift of electrons in the n layer 13c in the lateral direction is the largest factor that causes deterioration in resolution.

Next, the result of characteristic evaluation of the spatial light modulator of this embodiment as a holographic television device will be described. FIG. 6 is a schematic configuration diagram of a holographic television device used for evaluation of the spatial light modulator. As a means for performing optical writing in the spatial light modulator, the coherent light from the He-Ne laser 51 is split by the half mirror 52, and one of the light fluxes passes through the lens 56 and the subject 50.
The light is radiated to the CCD 58 through the lens 5 and the other light flux is passed through the lens 5.
After passing through a beam expander composed of 4 and 55, the CCD 58 is irradiated with the reference light through the half mirror 57,
An interference fringe pattern is formed on the image pickup surface of the CCD 58.
The image data of the interference fringe pattern is converted into an electric signal and C
It is transferred to RT65 and reproduced.

The image data of the interference fringe pattern reproduced on the screen of the CRT 65 is optically written and recorded in the spatial light modulator 1 by the lens 66. The spatial light modulator 1 has a pixel pattern of 8 μm square pixels having a pitch of 10 μm and 3200 × 3200 = about 10 ⁷ pixels.

The He-Ne laser 61 is used to read out the image.
The coherent light from the laser beam passes through the beam expander composed of the lenses 62 and 63, is irradiated onto the spatial light modulation element 1 via the polarization beam splitter 64, and the modulated output light passes through the polarization beam splitter 64 and passes through the lens 67. , A stereoscopic image in the reflection mode is observed with the naked eye 68.

As a result, the stereoscopic image displayed in real time can be reproduced, and the movement of the subject 50 can be observed in the real time hologram. The aperture ratio is 64%,
It was confirmed that the image contrast was 200: 1 and the resolution was 100 lines / mm.

[0062]

As described above in detail, the spatial light modulator of the present invention is provided with at least a photoconductive layer, a reflective layer, a ferroelectric liquid crystal layer and an alignment film for aligning the ferroelectric liquid crystal. The photoconductor having a rectifying property is formed for each pixel, so that the switching speed of the photoconductive layer is improved and the initialization of the memory state is facilitated, and the in-plane diffusion of photocarriers and Since the drift at each junction interface is prevented, a spatial light modulator having high resolution can be obtained. In particular, by using an amorphous silicon semiconductor as the photoconductor, it is possible to increase the light receiving area of the spatial light modulator, and it is possible to obtain a highly sensitive spatial light modulator because it exhibits high quantum efficiency. .. In addition, since the reflective layer is divided on the photoconductor on a pixel-by-pixel basis, light reflection in a region between pixels is suppressed, and a spatial light modulator having a high resolution can be obtained.

Further, according to the method of manufacturing the spatial light modulator of the present invention, it becomes easy to form the reflective layer, or the reflective layer and the photoconductor having the rectifying property on a pixel-by-pixel basis, and the manufacturing cost is reduced by a simple manufacturing process. A low and high resolution spatial light modulator can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a spatial light modulator of the present invention.

FIG. 2 is a sectional view of another embodiment of the spatial light modulator of the present invention.

FIG. 3 is a sectional view of another embodiment of the spatial light modulator of the present invention.

FIG. 4 is a cross-sectional view for explaining a process of an embodiment of the method for manufacturing the spatial light modulator of the present invention.

FIG. 5 is a schematic configuration diagram of a projection display device used for evaluation of a spatial light modulator.

FIG. 6 is a schematic configuration diagram of a holographic television device used for evaluation of a spatial light modulator.

FIG. 7 is a cross-sectional view of an example of a conventional spatial light modulator.

[Explanation of symbols]

 11 Transparent Insulating Substrate 12 Transparent Conductive Electrode 13 Photoconductive Layer 13a p Layer 13b i Layer 13c n Layer 14 Reflective Layer 15 Alignment Film 16 Ferroelectric Liquid Crystal Layer 17 Spacer 18 Alignment Layer 19 Transparent Conductive Electrode 20 Transparent Insulating Substrate 21 Incident Light 22 Readout Light 23 Polarizer 24 Output Light 25 Analyzer 26 Multilayer Dielectric Reflective Film 27 Light Shielding Film 30, 31 Resist Film 40 Light Source 41 Condenser Lens 42 Polarizing Beam Splitter 43 CRT Display 44 Lens 45 Screen 51, 61 He- Ne laser 52, 57 Half mirror 53 Mirror 54, 55, 56, 62, 63, 66, 67 Lens 58 CCD 64 Polarizing beam splitter 65 CRT 68 Naked eye

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

Claims (5)

[Claims] 1. A spatial light modulator comprising at least a photoconductive layer, a reflective layer, a ferroelectric liquid crystal layer, and an alignment film for aligning the ferroelectric liquid crystal, wherein the photoconductive layer has a rectifying property. A spatial light modulator comprising a photoconductor formed on a pixel-by-pixel basis. 2. The spatial light modulator according to claim 1, wherein the rectifying photoconductor is an amorphous silicon semiconductor having a diode structure. 3. The spatial light modulator according to claim 1, wherein the reflective layer is divided into pixel units on the photoconductor having a rectifying property. 4. After forming a thin film layer made of an amorphous silicon semiconductor having a diode structure, a part of the uppermost layer of the thin film layer is removed to form a photoconductor having a rectifying property for each pixel, A method for manufacturing a spatial light modulator, in which a reflective layer and an alignment film are sequentially formed on the surface thereof. 5. A reflective layer is formed after forming a thin film layer made of an amorphous silicon semiconductor having a diode structure, and then the reflective layer and a part of the uppermost layer of the thin film layer are removed to form the reflective layer. A method for manufacturing a spatial light modulator, in which a layer and a photoconductor having a rectifying property are formed in pixel units, and an alignment film is further formed on the surface thereof.