JPH0933942A - Spatial optical modulation element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a spatial optical modulation element capable of controlling the impedance of a photoconductor, well maintaining the performance of members including transparent electrodes and well operating an optical modulation member. SOLUTION: This spatial optical modulation element consists of two translucent electrodes 2 facing each other, an optical modulation member 12 and a photoconductive member 11, and writes information on the optical modulation member 12 by light signals. The photoconductive member 11 has at least a photoconductive layer 4 consisting of amorphous silicon hydride and an auxiliary layer 3 mainly composed of amorphous silicon hydride which contains nitrogen and in which the atomic ratio of the nitrogen and silicon is a non-stoichiometric ratio. This auxiliary layer 3 is formed by a plasma CVD method by using gaseous silicon hydride and/or gaseous silicon halide and >=1 kinds of gases contg. nitrogen. The writing of the light information is executed by impressing AC voltage between the translucent electrodes of this spatial optical modulation element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial light modulator for writing information on an optical modulator by an optical signal under application of a voltage, a method for manufacturing the same, and a method for writing optical information.

[0002]

2. Description of the Related Art Light input spatial light modulators used for image processing and display are shown in JP-A-49-21166, JP-A-58-199327 and JP-A-59-216126. As described above, the light modulator including the liquid crystal layer,
It is known to have a cell structure composed of a photoconductor formed uniformly in a plane. In such a spatial light modulator, a photoconductor is disclosed in JP-A-58-199332.
Hydrogenated amorphous silicon (a-Si: H) as disclosed in Japanese Patent Publication No. 7 has a high visible sensitivity, a high speed response,
It is advantageously used for reasons such as ambipolarity and ease of producing a homogeneous film. Such a spatial light modulator inputs information to the photoconductor by writing light and reads a change in voltage applied to the light modulator according to a change in impedance of the photoconductor as a change in the light modulator. is there.

In order to put the above spatial light modulator into practical use, it is important to have an element structure in which the degree of modulation is as large as possible. Therefore, the impedance of the photoconductor is higher than that of the light modulator when it is dark,
It is necessary that most of the applied voltage be distributed to the photoconductor, and that it be lower than the impedance of the light modulator during light so that most of the applied voltage is distributed to the photoconductor. The larger the impedance difference between the modulators, the better. When liquid crystal is used as the light modulator, the impedance is usually 10 ¹⁰ to 10 ¹¹ Ωcm. Further, the dark resistance of a-Si: H used as a photoconductor has a minimum value of 10 ¹¹ to 10 ^{12 due} to a slight doping of boron.
It is known that it can be set to {Ω.cm.
E. FIG. Spear and P.M. G. FIG. Le Combe
r: Phil. Mag. 33, 935 (1976)}.
Therefore, in JP-A-58-199327, 10-4
A-Si: H doped with 00 ppm of boron, and in Japanese Patent Application Laid-Open No. 6-67196, boron is added in an amount of 0.1-1.
It has been proposed to use 0 ppm doped a-Si: H. However, in such a structure, in an electric field of about 10 ⁵ V / cm ⁻¹ used as a light input element, dark resistance is lowered due to charge injection from the electrode, and space charge inside the photoconductive layer is reduced. As a result, the internal electric field is substantially reduced and the sensitivity is lowered. As a result, the bright resistance is increased, so that the voltage is distributed to the liquid crystal layer even in the dark, and the on / off voltage in the light / dark state in the liquid crystal layer is increased. Since the difference is small, there is a problem that a high contrast image cannot be obtained.

In order to solve the above problems, the photoconductive layer has a diode structure, and the fact that it has a high impedance at the time of reverse bias in the dark state is used so that almost no voltage is applied to the liquid crystal layer in the dark state. , A method of increasing the difference between the on / off voltages of the liquid crystal layer in the bright / dark state has been proposed (JP-A-5-19289). However, when an AC voltage is applied to such a diode structure, the characteristics are different in the forward direction and the reverse direction of the diode structure, so that the voltage applied to the liquid crystal layer has a polarity and the liquid crystal operates well. There was a problem not to do it.

Also proposed is a method of improving the dark resistance by sandwiching silicon oxide as an inorganic insulating film between an amorphous silicon photoconductive layer and an electrode (JP-A-4-261520). The resistivity of an inorganic insulating film such as silicon oxide and the resistivity of amorphous silicon are 4
There is a 6 digit difference. For this reason, in the structure in which the inorganic insulating film and the amorphous silicon photoconductive layer are laminated, the resistance is high in the dark, but most of the applied voltage is distributed to the inorganic insulating film even in the bright, resulting in a difference in on / off voltage. Becomes smaller. As a result, in order to increase the decrease in resistance during light, it is necessary to make the thicknesses of the inorganic insulating film and the amorphous silicon photoconductive layer different by 4 to 6 digits or more. It has been difficult to achieve both improvement of resistance and improvement of on / off voltage ratio. Further, there is a problem that the resolution is lowered due to accumulation of electric charges between the inorganic insulating films and the repetition characteristics become insufficient.

Further, under the condition that the inorganic insulating film is electrically selected, it is impossible to prevent lowering of sensitivity due to optical reflection at the interface between the substrate and the photoconductive layer. In the conventional spatial light modulator using the amorphous silicon photoconductive layer, the photoconductive layer is formed by plasma CV on a transparent electrode made of a metal oxide such as tin oxide or tin oxide doped with indium.
It is formed by the D method, but in that case, the transparent electrode is made of Si,
As a result of the metal oxide being reduced as a result of being exposed to the plasma state of H ₄ and H ₂ of the carrier gas, the deposition of metal causes a decrease in transparency and electrical conductivity, and the function as a transparent electrode also decreases. In addition, there is a problem that the spatial light modulator does not operate satisfactorily and uniformly due to the phenomenon that the metal element diffuses into the amorphous silicon photoconductive layer and the impedance lowers.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art. That is, an object of the present invention is to control the impedance of the photoconductor of the spatial light modulation element, keep the performance of the member including the transparent electrode good, and perform the spatial light modulation capable of operating the light modulation member well. It is to provide an element.

[0008]

The present inventor has succeeded in solving the above-mentioned problems by adopting the following constitution. That is, the spatial light modulation element according to the present invention for writing information in the light modulation member by an optical signal has two main translucent electrodes, a light modulation member and a photoconductive member facing each other as main constituent elements. The photoconductive member includes a photoconductive layer made of at least hydrogenated amorphous silicon, and an auxiliary layer containing nitrogen and having hydrogen atomized amorphous silicon as a main component in which the atomic ratio of nitrogen to silicon is non-stoichiometric. It is characterized by having.

In the above spatial light modulator of the present invention, it is preferable to have an auxiliary layer such that the light reflectance at the writing light incident side at the wavelength of the writing light is 1/2 or less of the maximum value of the reflection spectrum. The method for manufacturing the spatial light modulator of the present invention is performed by forming an auxiliary layer on the translucent electrode, in which case silicon hydride gas and / or silicon halide gas and nitrogen are used as source gases. It is characterized in that the auxiliary layer is formed by a plasma CVD method using one or more gases containing Further, the optical information writing method of the present invention is characterized in that an AC voltage is applied between the two translucent electrodes of the above spatial light modulator to write information.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The spatial light modulator of the present invention will be described in detail below with reference to the accompanying drawings. Figures 1-3
FIG. 3 is a schematic cross-sectional view of a spatial light modulation element that is one specific example of the present invention. FIG. 1 is a photoconductive member including a translucent electrode 2 provided on a translucent support 1, an auxiliary layer 3 formed thereon, and a photoconductive layer 4 mainly containing hydrogenated amorphous silicon, A space having a laminated structure of a light modulating member in which a light absorbing layer 5, a light reflecting layer 6 such as a dielectric mirror, and a light modulating element 7 are laminated, and a translucent electrode 8 provided on a translucent support 10. The light modulation element is shown. In the figure, the light-transmitting support 1 to the photoconductive layer 4 serve as a light input element portion. FIG.
3 has a structure in which an auxiliary layer 9 is provided on the photoconductive layer 4, and FIG. 3 shows that the auxiliary layer 3 of FIG. 9 shows a case where 9 is divided into 9a and 9b to form a layer region having different nitrogen concentrations.

Examples of the transparent support include transparent inorganic materials such as glass, quartz and sapphire, and transparent organic resins such as fluororesin, polyester, polycarbonate, polyethylene, polyethylene terephthalate, vinylon, epoxy resin and mylar. Films or plates, as well as optical fibers, SELFOC optical plates, etc. are used.

As the transparent electrode provided on the transparent support, a transparent conductive material such as ITO, zinc oxide, tin oxide, lead oxide, indium oxide or copper iodide is used, and vapor deposition or ion plating is performed. Those formed by a method such as sputtering, or those formed by forming a metal such as Al, Ni, Au, etc. thin by vapor deposition or sputtering so as to be semitransparent are used. Among these, tin oxide, indium oxide, and tin oxide doped with indium are preferable because they are excellent in transparency and conductivity. The film thickness is generally 10 to 50
It is set in the range of 0 nm.

In the present invention, the auxiliary layer provided on the translucent electrode is mainly composed of hydrogenated amorphous silicon containing nitrogen and having an atomic ratio of nitrogen to silicon of non-stoichiometry. It can be formed by reactive sputtering, electron beam evaporation, glow discharge, ECR, or the like. Among them, glow discharge method and EC using gas as raw material
The R method can be preferably used. In this case, in order to form the auxiliary layer, SiH ₄ and Si ₂ H are used as raw materials for silicon.
Silicon hydride gas such as ₆ and / or SiH ₃ Cl,
Using silicon halide gas such as SiH ₂ Cl ₂ and SiHCl ₃ and using NH ₃ or nitrogen gas as the nitrogen material,
Decomposes by glow discharge method to form hydrogenated amorphous silicon. Of these, nitrogen gas is preferably used. The substrate temperature is 100 to 350 ° C., preferably 150 to
A range of 300 ° C is suitable. When the substrate temperature is lower than the above range, the amount of hydrogen in the film increases and the translucent electrode is likely to deteriorate. When it is higher than the above range, the characteristics of the photoconductive member become unsuitable as a spatial light modulator. Frequency is 0-5GH
z and the internal pressure of the reactor are preferably 0.1 to 1333 Pa.

In the present invention, Si and N in the auxiliary layer are
The atomic ratio of is preferably in the range of 1: 0.3 to 1: 1.3, and particularly in the range of 1: 0.4 to 1: 1.3.
If the atomic ratio of Si and N is less than 1: 0.3, absorption in the visible region increases, and the sensitivity of the photoconductive member decreases, and at the same time, the effect of improving dark resistance cannot be obtained. The auxiliary layer may be composed of two or more layers having different nitrogen concentrations in order to prevent the deterioration of the resolution and the image unevenness due to the interference of the interfacial reflection, and to prevent the fluctuation of the operating voltage and the decrease of the contrast during the DC operation, or A concentration gradient may be added to the nitrogen concentration. In this case, the nitrogen concentration on the electrode side may be set high and the nitrogen concentration on the photoconductive layer side may be lowered.

The hydrogenated amorphous silicon in the auxiliary layer preferably has a hydrogen content in the range of 1 to 40 atomic%, preferably 2 to 30 atomic%, more preferably 2 to 20 atomic%. When the amount of hydrogen is less than 1 atomic%, the number of dangling bonds increases, so that the charge injection into the photoconductive layer increases, the impedance in the dark decreases, and the light-dark contrast decreases. When the amount of hydrogen in the auxiliary layer exceeds 40 atom%,
At the time of film formation, the metal oxide transparent electrode is reduced and deteriorated in plasma and does not function as a conductive substrate, so that normal and uniform operation as a spatial light modulator cannot be performed.

In the present invention, the auxiliary layer is provided with a first layer for improving charge injection blocking ability, for improving light-dark resistance contrast, for controlling electric resistance, and for preventing ghost and memory after light exposure. A group III or group V element may be included. In that case, a gas containing a Group III element and / or a Group V element may be mixed with the raw material. Diborane (B ₂ H ₆ ) is typically used as the source gas containing a Group III element, but other than that, B ₄ H
₁₀ , B ₅ H ₉ , B ₅ H _11, etc., and AlH ₃ etc. can also be used. Further, as the source gas containing the group V element gas,
Typically, PH ₃ , AsH ₃ , SbH ₃ , BiH ₃ or the like can be used. In the present invention, the auxiliary layer may be provided on both sides of the photoconductive layer.

The photoconductive layer is composed of at least hydrogenated amorphous silicon and can be formed by a glow discharge method, an ECR method or the like. At the time of the formation, it is preferable to contain an element for terminating dangling bonds, for example, hydrogen or halogen in addition to hydrogen. In particular, amorphous hydrogenated silicon (a-
(Si: H) layer. The content of hydrogen and halogen is preferably in the range of 3 to 40 atomic%. The photoconductive layer preferably contains a Group III element or a Group V element as an impurity element for controlling conductivity. The addition amount is determined by the polarity of the applied voltage of the spatial light modulator or the required spectral sensitivity, and is 0.00
Used in the range of 1 to 100 ppm. It is possible to further add elements such as nitrogen, carbon and oxygen to the photoconductive layer mainly composed of hydrogenated amorphous silicon for the purpose of improving dark resistance, reducing light resistance, improving sensitivity and the like. .
In this case, it is used in the range of 1 to 1000 ppm.
The photoconductive layer can also contain germanium and / or tin. The thickness of the photoconductive layer is 1 to 1
The range of 00 μm is preferable, and the range of 2 to 60 μm is particularly suitable. The photoconductive layer may be composed of two layers, a charge generation layer and a charge transport layer.

A charge trap layer may be provided between the photoconductive layer and the auxiliary layer in order to prevent image blur due to lateral flow of charges at the interface with the auxiliary layer. The charge trap layer can be made of amorphous silicon containing at least one element selected from Group III and Group V elements. The group III or group V element is selected according to the polarity of the applied voltage. When the positive voltage is applied to the auxiliary layer, the group III element is selected, or when the negative voltage is applied. May contain a Group V element. The content of the Group V element is in the range of 0.01 to 1000 ppm, and the content of the Group III element is in the range of 5 to 10000 ppm, which is appropriately set according to the film thickness. The thickness of the charge trap layer is preferably 0.01 to 10 μm,
Particularly, the range of 0.1 to 5 μm is suitable.

On the other hand, the light modulating member may use a liquid crystal film. As the liquid crystal film, a liquid crystal, a polymer-liquid crystal composite film in which liquid crystal is dispersed in a polymer film, or a polymer liquid crystal film in which liquid crystal is polymerized in a polymer film is used. As the liquid crystal, various ones used as a general display material such as a nematic type, a cholesteric type, a smectic type and a ferroelectric type can be used. Specifically, biphenyl, phenylbenzoate, cyclohexylbenzene, azoxybenzene, azobenzene, azomethine, terphenyl, biphenylbenzoate, cyclohexylbiphenyl, phenylpyrimidine, cyclohexylpyrimidine, cholesterol, etc. Of various liquid crystal compounds. These liquid crystals do not have to have a single structure and may be composed of a plurality of components. In the case of a polymer-liquid crystal composite film, a polymer material such as a polyester resin, a polycarbonate resin, a polyamide resin, or an acrylic resin is used as the polymer film that disperses liquid crystals, and a smectic type or nematic is used in these polymer materials. A polymer-liquid crystal composite film is obtained by dispersing a liquid crystal of a type or the like. The thickness of these liquid crystal layers is preferably in the range of 1 to 100 μm.

A light reflection layer may be provided between the liquid crystal layer and the light input element. As the light reflection layer, a dielectric multilayer film can be used. As the dielectric, a material having a high refractive index material of Si or Ge, SiO ₂ , TiO ₂ , ZnO ₂ or the like repeatedly and alternately laminated is used. A-Si: H, a-SiGe: H, a-SiCx: by plasma CVD method
H, a-SiNx: H, a-SiOx: H, etc. can also be used. In the spatial light modulator of the present invention, a light absorption layer may be provided between the liquid crystal layer and the amorphous silicon photoconductive layer. The light absorbing layer is coated with a paint in which a light absorbing pigment such as carbon black is dispersed in a photopolymerizable resin such as an acrylic resin, a polyimide resin or a polyamide resin, or a thermosetting resin such as an epoxy resin or a melamine resin. After that, the light absorption layer that can be formed by irradiation with light and / or heating changes the light transmittance and the specific resistance depending on the content of the light-absorbing pigment. The ratio is preferably 0.5% or less and the specific resistance is 10 ⁶ Ωcm or more at the input light wavelength used. Also, an amorphous carbon film formed by using glow discharge can be used. The thickness of these absorbing layers is adjusted depending on the wavelength used, but is generally preferably in the range of 0.1 to 100 μm. Further, an antireflection layer may be provided on the surface of the translucent support for the purpose of preventing reflection on the surface of the support. The anti-reflection layer can be formed by evaporating MgF ₂ or the like.

Next, the case where optical information is written and an image is reproduced by using the spatial light modulator of the present invention will be described.
FIG. 4 is for explaining writing and image reproduction, and the spatial light modulation element of the present invention comprises a photoconductive member 11, a light reflection layer 6, and a light modulation member, each of which includes an auxiliary layer 3 and a photoconductive layer 4. 12 has a structure provided between the translucent electrodes 2 and 8 arranged to face each other. Optical writing is performed by applying a predetermined AC voltage from an AC power supply 13 between the transparent electrodes 2 and 8 and causing an optical signal having an arbitrary spatial pattern to enter as writing light 14 from the left side of FIG. Be seen. When reproducing the written spatial light modulator, the read light 15 is read from the right side of FIG. 3 in a state where a predetermined AC voltage is applied between both transparent electrodes.
Can be read out by projecting the light 16 reflected by the light reflection layer 6 on the screen.

[0022]

When operating the spatial light modulator of the present invention, an AC voltage is applied between two opposing transparent electrodes. When laser light is incident from the photoconductive member side in that state, the impedance of the amorphous silicon-based photoconductive layer in the photoconductive member is lowered in the exposed region, and the supplied AC voltage is applied to the liquid crystal layer of the light modulation member. Applied, thereby changing the orientation of the liquid crystal molecules. On the other hand, the impedance of the amorphous silicon-based photoconductive layer does not change in a region where light is not exposed, and the liquid crystal molecules of the liquid crystal layer maintain the initial alignment state. As a result, an image corresponding to the incident light is formed on the liquid crystal layer.

In the spatial light modulator of the present invention, the photoconductive member comprises a photoconductive layer made of hydrogenated amorphous silicon, hydrogen containing hydrogen, and an atomic ratio of nitrogen to silicon being a non-stoichiometric ratio. Since the auxiliary layer is composed mainly of amorphous silicon, the optical input element part is manufactured while maintaining the performance of the transparent electrode made of a metal oxide containing tin and / or indium in an optically and electrically good condition. It is also possible to prevent deterioration of electrical characteristics due to diffusion of a trace amount of metal from the transparent electrode into the amorphous silicon-based photoconductive layer, and further to inject charge from the transparent electrode into the photoconductive layer by an auxiliary layer. To prevent this, the change in impedance of the photoconductive layer during bright and dark can be increased,
The light modulating member has a high contrast and can be operated favorably. In the present invention, since the auxiliary layer contains hydrogenated amorphous silicon containing nitrogen and the atomic ratio of the element and silicon is a non-stoichiometric ratio, the refractive index of the auxiliary layer is changed from the transparent substrate to the refractive index of the photoconductive layer. The sensitivity can be improved by freely changing it, and minimizing the reflection at the interface between the transparent electrode and the photoconductive layer with respect to the input wavelength, and increasing the light input efficiency. That is, the sensitivity can be improved by setting the light reflectance for the optical writing light to 1/2 or less of the maximum value of the light reflectance for all the incident light. Further, the auxiliary layer in the present invention has a function of improving the adhesiveness of the amorphous silicon photoconductive layer to the translucent electrode, and can improve the temporal stability of the spatial light modulator.

[0024]

Next, a method for manufacturing a spatial light modulator according to the present invention will be described with reference to FIG. Example 1 A transparent glass substrate was used as the transparent support 1, and an ITO film was formed on the surface of the transparent glass substrate to a thickness of 200 nm to form a transparent electrode 2. Then, after the interior of the apparatus was sufficiently evacuated using a capacitive plasma CVD apparatus, a mixed gas of silane gas and nitrogen gas was introduced and glow discharge decomposition was performed to form an auxiliary layer having a film thickness of 0.2 μm. Formed 3. In the obtained auxiliary layer, the atomic ratio of Si to N was 1: 0.
6, and the amount of hydrogen was 15 atomic%. The optical Gap was 2.0. The film forming conditions at that time were as follows. The atomic ratio is X-ray photoelectron spectroscopy (XPS).
Is used to measure the amount of hydrogen, infrared spectrophotometer (FT-I
R) was used to measure the stretching vibrations of NH and Si-H, and the amount of hydrogen was determined from the absorbance. Optical Gap was calculated from the absorbance. 100% silane gas flow rate: 20 cm ³ / min 100% nitrogen gas flow rate: 400 cm ³ / min Reactor internal pressure: 66.6 Pa Discharge power density: 0.1 W / cm ³ Discharge time: 30 min After forming the auxiliary layer, It was evacuated and a mixed gas of silane gas, hydrogen gas and diborane gas was introduced. The mixed gas was decomposed by glow discharge to form a photoconductive layer 4 having a film thickness of 10 μm on the auxiliary layer. The film forming conditions at that time were as follows. 100% silane gas: 180cm ³ / min 100% hydrogen gas flow rate: 162cm ³ / min 20ppm hydrogen dilution diborane flow rate: 18cm ³ /
min Reactor internal pressure: 133.3 Pa Discharge power density: 0.05 W / cm ³ Discharge time: 120 min When an Al electrode was vapor-deposited on another photoconductive layer formed at the same time and the resistance was measured, it was 5 × 10 ^{11 in the} dark. Ωcm, 5 at light
It was × 10 ⁵ Ωcm.

On the hydrogenated amorphous silicon photoconductor obtained as described above, a light absorption layer 5 was formed by a carbon dispersion type paint which is a kind of organic film. That is, a carbon-based paint in which carbon black is dispersed in an acrylic resin is applied using a spinner, photopolymerized by exposure, and then sintered at 220 ° C. for 1 hour to give a film thickness of about 1 μm and a ratio of A light absorption layer having a resistance of 10 ¹⁰ Ωcm and a transmittance in the visible region of about 0.1% was formed. further,
On the formed light absorption layer, a multi-layer film in which crystalline Si and SiO ₂ films were alternately laminated in 15 layers of 10 nm was formed as the light reflection layer 6 by an electron beam evaporation method. Further, as the light modulation element 7, a liquid crystal layer made of a scattering type liquid crystal composite film was formed. That is, n-butyl acrylate and 1,6-
Monomer of hexylene diacrylate mixed in a ratio of 3: 1 and nematic liquid crystal (Merck, trade name: E7) were mixed at 15:85, and 2 weight% of an ultraviolet polymerization initiator (Darocur 1173: Ciba Geigy) %, The coating liquid obtained was added onto the light absorbing layer and then irradiated with ultraviolet rays to form a scattering type liquid crystal composite film having a thickness of 10 μm. On the formed liquid crystal composite film, a laminated body of the translucent electrode 8 and the translucent support 10 was laminated. This laminate was obtained by forming an ITO film having a thickness of 100 nm on a second glass substrate by an evaporation method.

An alternating voltage of 1 KHz of 30 V is applied between the translucent electrodes 2 and 8 made of an ITO film facing each other of the photo-writing type spatial light modulator having the above structure, a wavelength of 660 nm and an exposure amount of 0. Image writing was performed under the condition of 4 μJ / cm ² . When the image was read out with the white light of the halogen lamp, the resolution was 50 lp / mm and an image with good contrast could be obtained.

Example 2 Using the same transparent glass electrode as in Example 1, a first auxiliary layer having a film thickness of 0.1 μm was formed in the same manner as in Example 1. The film forming conditions at that time were as follows. 100% Silane gas flow rate: 5 cm ³ / min 100% Nitrogen gas flow rate: 100 cm ³ / min Reactor internal pressure: 66.6 Pa Discharge power density: 0.2 W / cm ² Discharge time: 20 min The auxiliary layers obtained were Si and N. Had an atomic ratio of 1: 0.8 and a hydrogen content of 10 atomic%. Optical Gap is 2.5
Met. The same hydrogenated amorphous silicon photoconductive layer as in Example 1 was formed on this. Then, a second auxiliary layer which is the same as the first auxiliary layer was provided. When an Al electrode was vapor-deposited on another photoconductive layer formed at the same time and the resistance was measured, it was 1
It was × 10 ¹² Ωcm and 5 × 10 ⁶ Ωcm at bright time. A light absorption layer, a liquid crystal layer, an ITO film, and a glass substrate were laminated on the hydrogenated amorphous silicon-based photoconductive layer produced as described above in the same manner as in Example 1.

An alternating voltage of 30 V and 1 KHz is applied between the opposing ITO films of the obtained optical writing type spatial light modulator, and image writing is carried out under the conditions of a wavelength of 660 nm and an exposure amount of 0.4 μJ / cm ^2. It was When the image was read by the white light of the halogen lamp, the resolution was 50l.
An image of p / mm and good contrast could be obtained.

Example 3 Using the same transparent glass electrode as in Example 1, a first auxiliary layer having a film thickness of 0.1 μm was formed by the same method as in Example 1.
The film forming conditions at that time were as follows. 100% silane gas flow rate: 20 cm ³ / min 100% nitrogen gas flow rate: 400 cm ³ / min 200 ppm hydrogen diluted diborane gas flow rate: 50 cm ³
/ Min Reactor internal pressure: 66.6 Pa Discharge power density: 0.2 W / cm ² Discharge time: 10 min The same hydrogenated amorphous silicon photoconductive layer as in Example 1 was formed on the first auxiliary layer. Then, a second auxiliary layer which is the same as the first auxiliary layer was provided. When an Al electrode was vapor-deposited on another photoconductive layer formed at the same time and the resistance was measured, it was 4 × 10 ¹² Ωcm in the dark and 2 × 10 ⁶ Ωcm in the bright.

A light absorption layer, a liquid crystal layer, an ITO film and a glass substrate were laminated on the hydrogenated amorphous silicon photoconductive layer produced as described above in the same manner as in Example 1. Opposing I of the obtained optical writing type spatial light modulator
Apply an alternating voltage of 30 V and 1 KHz between the TO films,
Image writing was performed under the conditions of a wavelength of 660 nm and an exposure amount of 0.4 μJ / cm ² . When the image was read using the white light of the halogen lamp, the resolution was 50 lp / mm.
It was possible to obtain an image with good contrast.

Comparative Example 1 A hydrogenated amorphous silicon photoconductive layer and other constituent layers were formed under exactly the same conditions as in Example 1 except that the auxiliary layer was not provided. When an Al electrode was vapor-deposited on another photoconductor prepared at the same time and the resistance was measured, it was 2 × 10 ⁹ Ωcm in the dark and 1 × 10 ⁶ Ωcm in the light.
In the case of opposite polarities, there was no photoconductivity. When writing was performed on this spatial light modulator, the dark resistance was low and the light-dark resistance ratio was small, so that a voltage was also applied to the liquid crystal layer in the dark, and the device did not operate.

Comparative Examples 2 to 4 In forming the auxiliary layer in Example 2, hydrogenated amorphous silicon containing nitrogen and hydrogen containing carbon were similarly prepared except that a raw material for containing nitrogen, carbon or oxygen was used. A spatial light modulator was manufactured by forming an auxiliary layer made of hydrogenated amorphous silicon or hydrogenated amorphous silicon containing oxygen. When writing was performed on these spatial light modulators, the contrast was low and they did not operate.

With respect to the spatial light modulators of Examples 1 to 3 and Comparative Examples 1 to 4, Table 1 shows the preparation conditions and properties of the auxiliary layer, and the dark resistance and light-dark resistance ratio of the photoconductive member.

[Table 1]

[0034]

According to the present invention, the photoconductive member comprises a hydrogenated amorphous silicon photoconductive layer and an auxiliary layer containing at least nitrogen and containing hydrogenated amorphous silicon containing 40% or less of hydrogen. Therefore, the light input element section can be manufactured while maintaining the performance of the transparent electrode, for example, the transparent electrode made of a metal oxide containing tin and / or indium, in a good optical and electrical condition. It also prevents deterioration of electrical characteristics due to diffusion of a trace amount of metal from the transparent electrode into the hydrogenated amorphous silicon-based photoconductive layer, and further, by using an auxiliary layer to inject charge from the transparent electrode into the photoconductive layer. In order to prevent it, the impedance change between the bright and dark states of the photoconductive layer can be increased, and the light modulation member can have a high contrast and can operate favorably. Further, the sensitivity can be improved by changing the refractive index of the auxiliary layer to minimize the reflection at the interface between the transparent electrode and the photoconductive member with respect to the input wavelength and increasing the light input efficiency. Further, the auxiliary layer in the present invention has the effect of improving the adhesiveness of the hydrogenated amorphous silicon photoconductive layer to the translucent electrode, and has the effect of improving the temporal stability of the spatial light modulator.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a spatial light modulator according to an embodiment of the present invention.

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

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

FIG. 4 is an explanatory diagram for explaining an optical writing and reading method of the spatial light modulator of the present invention.

[Explanation of symbols]

1 ... Translucent support, 2 ... Translucent electrode, 3 ... Auxiliary layer, 4 ...
Photoconductive layer, 5 ... Light absorption layer, 6 ... Light reflection layer, 7 ... Light modulation element, 8 ... Translucent electrode, 9 ... Auxiliary layer, 10 ... Translucent support, 11 ... Photoconductive member, 12 ... Light modulation member, 13 ... AC power supply, 14 ... Writing light, 15 ... Read light, 16 ... Reflected light.

Claims (10)

[Claims] 1. A spatial light modulation element, which comprises two light-transmitting electrodes, a light modulation member, and a photoconductive member facing each other as main constituent elements and writes information to the light modulation member by an optical signal, wherein the photoconductive member is: A space characterized by having at least a photoconductive layer made of hydrogenated amorphous silicon and an auxiliary layer containing nitrogen and having hydrogen atomized amorphous silicon as a main component in which the atomic ratio of nitrogen and silicon is a non-stoichiometric ratio. Light modulator. 2. The spatial light according to claim 1, further comprising an auxiliary layer having a light reflectance on the writing light incident side at the wavelength of the writing light which is ½ or less of the maximum value of the reflection spectrum. Modulation element. 3. The spatial light modulator according to claim 1, wherein the auxiliary layer is provided on both surfaces of the photoconductive layer. 4. The spatial light modulator according to claim 1, wherein the auxiliary layer has regions having different nitrogen concentrations. 5. The spatial light modulator according to claim 1, wherein the auxiliary layer contains a Group III or Group V element. 6. The spatial light modulator according to claim 1, wherein the translucent electrode adjacent to the photoconductive member is made of a metal oxide containing tin and / or indium. 7. The auxiliary layer is mainly composed of hydrogenated amorphous silicon containing nitrogen and having an amount of hydrogen of 1 to 40 atomic%.
The spatial light modulator according to any one of 1. 8. The photoconductive layer contains 0.001 of a Group III element.
1 to 100 ppm is contained.
9. The spatial light modulator according to claim 7. 9. The method for producing a spatial light modulator according to claim 1, wherein a light modulating member and a photoconductive member including an auxiliary layer and a photoconductive layer are formed on the transparent electrode, and hydrogen is used as a source gas. A method of manufacturing a spatial light modulator, comprising forming an auxiliary layer by a plasma CVD method using a silicon dioxide gas and / or a silicon halide gas and one or more gases containing nitrogen. 10. A spatial light modulator in which two light-transmitting electrodes, a light modulating member, and a photoconductive member which face each other are used as main constituent elements, and information is written in the light modulating member by an optical signal. Of the spatial light modulator having at least a photoconductive layer made of hydrogenated amorphous silicon and an auxiliary layer containing nitrogen and having an atomic ratio of the nitrogen and silicon of non-stoichiometric ratio mainly consisting of hydrogenated amorphous silicon An optical information writing method, characterized in that an alternating voltage is applied between two transparent electrodes to write information.