JPH05173173A - Production of spatial optical modulating element - Google Patents

Abstract

PURPOSE:To minimize the orientation energy of a ferroelectric liquid crystal and to form picture elements having high resolution and high density by separat ing an oriented film and a reflection layer on the lower side thereof by each picture element by using a resist. CONSTITUTION:Transparent electrodes 2, photoconductive layers (3 to 5) and the reflection layer 6 are formed on a glass substrate 1 and polyamic acid 6 is applied thereon. The adhesion to the reflection layer is previously increased by controlling the imidization rate at about 80 to 200 deg.C. the resist 14 is then applied in picture element units and the reflection layer 6 serving as a reflection surface is formed as micropicture elements by an etchant, etc., to constitute the structure having polyimide thin films 7 of high-polymer films for orienting the liquid crystal layer only on the micropicture elements of the reflection layer 6.

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 a holographic television or an optical arithmetic unit, and a manufacturing method thereof.

[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. In particular, the development of projection-type displays using liquid crystal technology has been active in place of the conventional CRT 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. Although a projection type display device using a liquid crystal element of a transistor drive system is a promising method, it is disadvantageous in that the aperture ratio does not increase and the element is expensive. On the other hand, C
The system in which an RT is used as an input device in combination with a liquid crystal light valve has been attracting attention as a device that has a simpler element shape and combines the advantages of a CRT and a liquid crystal element (JP-A-63-109422). In recent years, it has become possible to project moving images on a large screen of 100 inches or more by combining a highly sensitive light-receiving layer amorphous silicon material and liquid crystal. Moreover, liquid crystal light valves with higher resolution have become possible by using ferroelectric liquid crystals that can respond at high speed. This device is expected to be the core of the next-generation parallel computing device and optical computing device by utilizing the memory property and the binarization property of the ferroelectric liquid crystal.

A holographic television is attracting attention as a device that allows a user to view a three-dimensional stereoscopic moving image without glasses. In particular, a liquid crystal display element is expected as a rewritable hologram recording medium. Current transistor drive type liquid crystal devices have a resolution of 12-25 lp / m.
m, and it is hoped that 200 lp / mm will be realized in the future.

In a spatial light modulator comprising a liquid crystal layer and a photoconductive layer, an alignment film for aligning the liquid crystal is usually formed uniformly in a plane. On the other hand, in a spatial light modulator or a liquid crystal light valve including a liquid crystal layer and a photoconductive layer, there are JP-A-62-40430 and JP-A-62-169120 as conventional examples in which minute electrodes are provided at the interface between both layers. .. The microelectrodes are easy to manufacture with respect to the reflective layer of the multilayer dielectric thin film, have no dependency on the incident angle, and have high reflectivity.

When a display element or an optical operation element needs an element capable of handling a larger amount of information, it is important to display the information in high density. It has been reported that the resolution of a photo-writing type spatial light modulator consisting of a ferroelectric liquid crystal layer and a photoconductive layer can be several tens to one hundred and several tens of lp / mm (Proceedings of the Japan Society of Applied Physics, 1990, 26a-). H-9).

By the way, as an alignment film for a ferroelectric liquid crystal,
A polymer thin film formed by coating nylon, polyimide or the like, or a vapor deposited film of SiO ₂ is used. It has been reported that for the fine processing of the polyimide film, the reactive ion etching method using a metal shadow mask is suitable for the fine processing of the micron order.

[0007]

However, when the polyimide alignment film in the prior art is used, the resist material used for fine division processing is an organic substance similar to that of polyimide, and therefore the film thickness is extremely large with respect to the polyimide film thickness. There was an inconvenience that it had to be increased. Therefore, the film thickness is limited by the resolution of the resist, and as a result, it is difficult to finely process the polyimide alignment film by a simple process.

Further, it is difficult to suppress the increase in interface energy due to the increase in density and increase the limit resolution in the display element by extending the structure of the conventional spatial light modulator described above.

In order to solve the above-mentioned problems of the prior art, the present invention enables microfabrication even when a polyimide alignment film is used, and as a result, a spatial light modulator having excellent resolution and a method of manufacturing the same. The purpose is to provide.

[0010]

In order to achieve the above object, a method of manufacturing a spatial light modulator of the present invention comprises at least a transparent electrode, a photoconductive layer, a reflective layer and an alignment film on one substrate, and the other substrate. The substrate is provided with at least a transparent electrode and an alignment film,
A method for manufacturing a spatial light modulator in which a ferroelectric liquid crystal is sealed between the substrates, wherein a polyamic acid polymer that is a polyimide precursor is formed on a reflective layer that is uniformly formed on the one substrate side. After being uniformly applied to form a thin film, it is separated into pixel units, and then the reflection layer located thereunder is separated into pixel units having the same shape as the polyamic acid polymer film, and then heated to form the polyamic acid. The acid polymer thin film is a polyimide thin film.

In the above constitution, it is preferable that the polyamic acid polymer is applied, preheated at a predetermined temperature of 80 ° C. or higher and 200 ° C. or lower, and then divided into fine shapes.

[0012]

According to the structure of the method for manufacturing a spatial light modulator of the present invention described above, a polyamic acid polymer, which is a precursor of polyimide, is uniformly deposited on a reflective layer uniformly formed on one substrate side. After coating to form a thin film, it is divided into pixels divided into minute shapes, and then the reflection layer located thereunder is divided into minute pixels of the same shape as the polyamic acid polymer film, and then heated. Since the polyamic acid polymer thin film is formed as a polyimide thin film by removing the alignment film other than the micro-shaped portion corresponding to each pixel, the alignment energy of the ferroelectric liquid crystal is minimized to obtain a high density image. The formation can be realized.

Further, since the reflective layer is divided into pixels and the pixels of the reflective layer are formed in the same or narrower area than the pixels of the alignment film, light reflection from the inter-pixel area is reduced. To prevent blurring and blurring of pixels,
The contrast and resolution of the image can be improved.

Further, since the reflective layer divided into pixel units is a metal thin film, the light reflectance is high and the reflective layer can be easily formed, so that the manufacturing cost of the spatial light modulator is reduced. be able to.

Further, according to the method of manufacturing a spatial light modulator of the present invention, it is easy to realize that the pixel pattern of the alignment film and the pixel pattern of the reflective layer are substantially completely matched with each other, so that the manufacturing yield is improved. Therefore, the manufacturing cost can be reduced.

Further, a polyamic acid polymer is applied, and 8
According to the preferable configuration of the present invention in which the pretreatment is performed at a predetermined temperature of 0 ° C. or higher and 200 ° C. or lower and then divided into minute shapes, the imidization ratio can be easily controlled and the adhesion with the reflective layer can be changed. It is possible. That is, the film becomes dense and has high adhesion due to the increase in the imidization ratio. This can suppress the occurrence of film peeling in the resist removing step.

[0017]

The present invention will be described in more detail with reference to the following examples. In the present invention, the polyimide is a general term for polymers having an imide bond in the main chain. For example, a condensation type thermosetting polyimide of pyromellitic acid and diaminodiphenyl thioether (or diaminodiphenyl ether may be used), an addition type thermosetting polyimide, or a copolymer with an arbitrary monomer (for example, polyimide amide) can be used.

As an example, the polyimide represented by the general formula (Formula 2) shown below is synthesized by imidizing the precursor polyamic acid polymer of the general formula (Formula 1) by condensation dehydration reaction by heating or the like. It

[0019]

[Chemical 1]

(Wherein R ₁ and R ₂ are aromatic groups, alicyclic groups or aliphatic groups, and n represents the degree of polymerization).

[0021]

[Chemical 2]

(However, R ₁ and R ₂ are aromatic groups, alicyclic groups or aliphatic groups, and n is the degree of polymerization.) The polyamic acid polymer of this polyimide precursor is as shown in FIG. After coating on the surface of the photoconductive layer-reflection layer of the device structure, a normal resist is coated to form a pattern. Polyamic acid polymer has higher reactivity to oxygen plasma than polyimide. Therefore, it is easily decomposed and removed into small molecules in oxygen plasma. In particular, the reactivity can be increased by raising the substrate temperature. After that, by removing the reflective layer with the same remaining resist pattern, a reflective film and an alignment film having a minute shape can be obtained.

The degree of the imidization reaction of the polyamic acid polymer to the polyimide depends on the heating temperature and the reaction time. In particular, the imidization ratio is easily controlled in the temperature range of 80 ° C. or higher and 200 ° C. or lower. After coating the polyamic acid polymer film, it is possible to change the adhesion with the reflective layer by controlling the imidization ratio. That is, the film becomes dense and has high adhesion due to the increase in the imidization ratio. The occurrence of film peeling can be suppressed in the resist removing step. Therefore, the optimum temperature is determined by the etching conditions in oxygen plasma and the resist removal conditions.

Next, specific embodiments of the present invention will be described with reference to the drawings. Example 1 FIG. 1 is a sectional view of a spatial light modulator of this example. Figure 1
In the figure, 1 is one of the glass substrates, and the transparent electrode 2, the photoconductive layers (3 to 5), the reflective layer 6 and the polyimide alignment film 7 are formed on the glass substrate 1. The photoconductive layer is composed of a p-type amorphous silicon layer 3, an i-type amorphous silicon layer 4, and an i-type amorphous silicon layer 5. In addition, the transparent electrode 11 is provided on the other glass substrate 12.
And the alignment film 12 is formed. And both substrates 1, 1
A ferroelectric liquid crystal 8 is enclosed between the two. In addition, the alignment film 7
Are integrally divided into minute pixels together with the reflective layer 6.

The spatial light modulator of this embodiment shown in FIG. 1 was manufactured by the manufacturing method shown in FIG. That is, in step (a) of FIG. 2, a transparent conductive electrode 2 having a thickness of 0.05 μm to 0.5 μm, such as ITO, is formed on a 1.1 mm glass substrate 1 by a sputtering method. Form. Next, a hydrogenated amorphous silicon (hereinafter referred to as a-Si: H) film having a p / i / n diode structure is formed as a photoconductive layer,
P-type a-Si added with 400 ppm of boron:
The H film 3 is 1000 Å (100 nm), the i-type a-Si: H film 4 without addition is 1.7 μm, and the phosphorus is 50 μm.
The n-type a-Si: H film 5 added with ppm is formed by laminating using a plasma CVD method so as to have a thickness of 2000 angstrom (200 nm) and a total film thickness of about 2 μm.

The other materials used for the photoconductive layer are, for example,
For example, CdS, CdTe, CdSe, ZnS, ZnSe,
GaAs, GaN, GaP, GaAlAs, InP, etc.
Compound semiconductor, amorphous half such as Se, SeTe, AsSe
Conductor, Si, Ge, Si_1-xC_x, Si_1-xGe_x, G
e_1-xC_x(0 <x <1) polycrystalline or amorphous semiconductor
is there. Further, (1) phthalocyanine pigment (hereinafter abbreviated as Pc)
), For example, metal-free Pc, XPc (X = Cu, Ni, C
o, TiO, Mg, Si (OH)₂Etc.), AlClPc
Cl, TiOClPcCl, InClPcCl, InC
(2) monoazo dyes such as 1Pc and InBrPcBr,
Azo dyes such as disazo dyes, (3) Anhydrous penenylene acid
And penylene-based pigments such as penylene imide,
(4) indigoid dye, (5) quinacridone pigment,
(6) Polycyclic quinones such as anthraquinones and pyrenequinones
Non-type, (7) Cyanine dye, (8) Xanthene dye,
(9) Charge transfer complex such as PVK / TNF, (10) Bi
Formed from Lilium Salt Dye and Polycarbonate Resin
Eutectic complexes, (11) azurenium salt compounds and other organic semiconductors
Body, etc. In addition, 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) is used for the photoconductive layer.
If this is the case, it is also preferable to include hydrogen or a halogen element.
The purpose of decreasing the permittivity and increasing the resistivity.
It is preferable that oxygen or nitrogen be included. Control resistivity
In order to control p-type impurities such as B, Al and Ga,
Element, or n-type impurities such as P, As,
It is also preferable to add an element such as Sb. in this way
P / n type, p /
i-type, i / n-type, p / i / n-type, etc.
By forming a depletion layer in the conductive layer, the dielectric constant and
It is possible to control the dark resistance or the operating voltage polarity. Well
In addition to amorphous materials, products of two or more of the above materials
In the photoconductive layer by layering to form a heterojunction
A depletion layer may be formed in the.

Next, a reflection layer 6 made of aluminum or the like is formed on the surface of the photoconductive layer by electron beam evaporation or the like to a thickness of 500 to 100.
The film is formed with a film thickness of 0 angstrom. In step (b), a polyamic acid polymer film 13, which is a precursor of a polyimide polymer film for forming an alignment film, is applied on the reflective layer 6 by a spinner to a film thickness of about 200 angstroms, and in an atmosphere of about 120 ° C. Preheat for 30 minutes. This condition differs depending on the material of the reflective layer 6. As the polyamic acid polymer, for example, the compound disclosed in Japanese Patent Publication No. 3-1145 is suitable for the spatial light modulator of this embodiment. This polyamic acid polymer was synthesized by the following (chemical formula 3) 0.109 g (3.36 × 10 ⁻⁴ mo) of phenylene sulfide diamine.
1 g) was dissolved in 3 ml of N, N-dimethylacetamide (hereinafter referred to as DMAc), and 0.1 g (3.1 of benzophenone tetracarboxylic acid dianhydride of the following chemical formula 4)
1 × 10 ^-4 mol) was added little by little and dissolved by a stirrer etc., and after mixing for about 30 minutes, it became a highly viscous polyamic acid polymer, and 21 ml DMA
By diluting with c, a polyamic acid polymer solution for forming a thin film can be obtained.

[0028]

[Chemical 3]

[0029]

[Chemical 4]

In the step (c), for example, 1000 × 100 is formed on the polymer film 206 by using a photolithography technique.
A resist pattern 14 having 0 = 10 ⁶ pixels, a pixel size of 20 × 20 μm, and a pixel pitch of 25 μm is formed. Approximately 2.0 ~ by spin coating positive type resist
It is applied to 2.5 μm and heated in an atmosphere of about 90 ° C. for about 15 minutes. After that, exposure and development are performed and heating is performed at about 90 ° C. for about 15 minutes.

In the step (d), the inter-pixel portion is removed by an oxygen plasma asher, and the separation film 15 of the polyamic acid polymer thin film 13 separated into minute pixels is formed. The oxygen plasma asher was evacuated to 0.1 Torr, then oxygen was introduced to 1 Torr, high-frequency power of 40 W,
The substrate temperature is 100 to 120 ° C. and the time is 20 minutes.

In step (e), the reflective layer 6 made of an aluminum film is pixel-separated by the resist pattern formed in step (c). Etching is performed at room temperature for about 2 minutes with a mixed acid etchant containing phosphoric acid, nitric acid, acetic acid and the like. After etching, the resist is removed by acetone replacement. As a result, the reflective layer 6 serving as the reflective surface is formed by the minute pixels. Reference numeral 16 is a reflective layer 6, a polyamic acid polymer thin film 13 and a resist 14.
It is a unit separated into pixels.

In step (f), the glass substrate is placed in a constant temperature bath 23
Heat at 0 ° C. for 1 hour. After the dehydration reaction, the polyamic acid polymer film 13 becomes the polyimide film 6 having the structure shown below. Reference numeral 17 is a unit of the reflective layer 6 and the polyimide alignment film separated for each pixel.

[0034]

[Chemical 5]

After this step, a structure having a polymer film polyimide thin film for orienting the liquid crystal layer only on the minute pixels of the reflective layer 6 is formed. The polyimide polymer thin film is subjected to an alignment treatment so that the alignment of the ferroelectric liquid crystal molecules becomes parallel to the thickness direction of the device. For the orientation treatment, a rubbing treatment was performed using a nylon resin cloth. The film thickness of the polymer is preferably 1000 angstroms or less, and particularly preferably 200 angstroms or less.

To fabricate the spatial light modulator of FIG.
The ITO thin film 11 is formed on the other glass substrate 12, and the polyamic acid polymer thin film is applied and patterned by the same method as the above steps (a) to (c). Finally, a polyimide thin film 10 was formed by heat treatment. Resin beads 9 having a diameter of 2.6 μm are formed on the glass substrate 1 on which the photoconductive layer is laminated.
The thermosetting resin mixed with is printed by screen printing so as to surround the entire photoconductive layer except the liquid crystal injection opening. On the other glass substrate 12, a solution in which isopropyl alcohol is mixed with beads 9 made of resin or the like having a diameter of about 1.0 μm is sprayed to attach the beads to the entire surface. Next, the pair of glass substrates are attached to each other, placed in a vacuum bag, evacuated and hermetically sealed, and then heated in an atmosphere of about 90 ° C. for about 30 minutes while keeping the inside in a vacuum state.
The resin is cured by heating for about 2 hours in the atmosphere of ° C. Finally, while heating the ferroelectric liquid crystal at about 80 ° C. in a vacuum state, the liquid crystal is injected from the opening of the resin so as to be uniformly filled in the panel by utilizing the pressurization by the introduction of nitrogen gas and the capillary phenomenon. Since the liquid crystal molecules are uniformly aligned, this element is heated in a constant temperature bath to a temperature above the liquid crystal phase transition temperature, for example, about 90 ° C.
After gradually cooling to room temperature at a rate of about 0.2 ° C. per minute, the opening of the resin was sealed with the resin. The liquid crystal material of the liquid crystal layer is preferably a chiral smectic C liquid crystal which is a ferroelectric liquid crystal. In addition, in order to increase the contrast ratio of the output light, in the case of the reflective spatial light modulator of this embodiment, it is preferable that the thickness thereof be about 1 μm. In this way, the spatial light modulator of the present invention could be obtained.

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, the intensity of the output light with respect to the input light is very large, 80 to 90%, without considering the loss of the polarizer and the analyzer, and the rise of the output light is observed if the input light intensity is several μW / cm ² or more. As a result, it was confirmed that the operation was sufficient even when the incident light intensity was small.

Example 2 The spatial light modulator shown in FIG. 3 was produced in the same manner as in Example 1. The difference from FIG. 1 is that a light shielding layer 22 is provided on the incident side to prevent light leaking from between pixels. Shading layer 2
In No. 2, a chromium vapor deposition layer is formed on the glass substrate 21 with a thickness of 1000 angstroms to form a pattern. The subsequent steps are the same as in Example 1. That is, in FIG. 3, 21 is one of the glass substrates.
1, a transparent electrode 23, photoconductive layers (24 to 26), a reflective layer 27, and a polyimide alignment film 28 are formed. The photoconductive layer includes a p-type amorphous silicon layer 24, an i-type amorphous silicon layer 25, and an i-type amorphous silicon layer 26. A transparent electrode 32 and an alignment film 31 are formed on the other glass substrate 33. And
Ferroelectric liquid crystal 29 is enclosed between both substrates 21 and 33. Further, the alignment film 28 is integrally divided into minute pixels together with the reflective layer 27.

This spatial light modulator was evaluated as a projection display. FIG. 4 shows a schematic view of the projection display device. Optical writing is performed on the spatial light modulation element 19 of the present embodiment by the CRT display 43. The number of pixels of the element is 480 in height and 650 in width. Light source 40 for reading
A (metal halide lamp) is irradiated by a condenser lens 41 by a polarization beam splitter 42. The output image is enlarged by the lens 44 and displayed on the screen 45.
When each dot on the CRT screen is written in the separated pixel of the spatial light modulator, it is converted into a rectangular shape on the screen. Therefore, a large image with a large aperture ratio of 80% is obtained, and an image enlarged to a size of 100 inches has an illuminance of 2500 lumens on the screen. The image has a contrast of 250: 1 and a vertical resolution of 650 TV lines.
The number of rye was confirmed. When a moving image was output, a clear high-luminance image was obtained with no afterimage with respect to the movement of the video rate. In order to obtain a color image, a set of a CRT tube corresponding to each of RGB and a spatial light modulator is used.
A group was prepared and synthesized on the screen.

Embodiment 3 FIG. 5 is a schematic configuration diagram of a holographic television device used for evaluation of a spatial light modulator.

As means for performing optical writing in the spatial light modulator shown in the second embodiment, the coherent light from the He--Ne laser 51 is split by the half mirror 52, and one light flux passes through the lens 56 and the subject 50. Through CCD5
8 and the other light flux passes through a beam expander composed of lenses 54 and 55 and is applied to the CCD 58 as a reference light via the half mirror 57 to form an interference fringe pattern on the image pickup surface of the CCD 58. The image data of the interference fringe pattern is converted into an electric signal, transferred to the CRT 65 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 19 has a pixel pattern of 8 μm square pixels with 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.

[0045]

As described above, according to the present invention, it is possible to efficiently and rationally manufacture a spatial light modulation element most suitable for a projection type display device which displays a high-resolution, high-luminance, large-screen image. Further, an inexpensive element can be provided by a method capable of producing a simple constituent element with a small number of steps. Further, in the spatial light modulation element of the present invention, since the alignment film is divided into pixel units, the liquid crystal can be arranged at a higher density, so that high-resolution image display can be performed. Therefore, by using the spatial light modulator of the present invention, it is possible to realize a projection display device having high resolution, high brightness and a large screen. In addition, the holographic television device using the spatial light modulator of the present invention can observe a clear stereoscopic image in real time.

Further, according to the method of manufacturing a spatial light modulator of the present invention, since the deformation of the pixel pattern due to the alignment treatment can be prevented, the spatial light modulator can be reasonably manufactured by a simple process.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a spatial light modulator according to a manufacturing method of the present invention.

FIG. 2 is a process drawing showing a method for manufacturing a spatial light modulator of the present invention.

FIG. 3 is a sectional view of a spatial light modulator manufactured in Example 2 of the present invention.

FIG. 4 is a schematic diagram of a projection display device manufactured using the spatial light modulator of the present invention.

FIG. 5 is a schematic diagram of a holographic television device manufactured using the spatial light modulator of the present invention.

[Explanation of symbols]

 1 glass substrate 2 transparent conductive electrode 3 p-type amorphous silicon layer 4 i-type amorphous silicon layer 5 n-type amorphous silicon layer 6 reflective layer 7 alignment film 8 ferroelectric liquid crystal layer 9 beads 10 alignment film 11 transparent conductive electrode 12 glass substrate

Front page continuation (72) Inventor Yasuki Kuratomi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A space in which one substrate is provided with at least a transparent electrode, a photoconductive layer, a reflective layer, and an alignment film, and the other substrate is provided with at least a transparent electrode and an alignment film, and a ferroelectric liquid crystal is sealed between the substrates. A method for manufacturing a light modulation element, wherein a polyamic acid polymer, which is a precursor of polyimide, is uniformly applied on a reflective layer uniformly formed on the one substrate side to form a thin film, and then a pixel is formed. Separated into units, and then separating the reflection layer located below it into pixels having the same shape as the polyamic acid polymer film, and then heating to make the polyamic acid polymer thin film a polyimide thin film. Of manufacturing spatial light modulator. 2. A polyamic acid polymer is applied and the temperature is 80 ° C.
The method for manufacturing a spatial light modulator according to claim 2, wherein after the heating pretreatment is performed at a predetermined temperature of 200 ° C. or less, it is divided into minute shapes.