JPH05173168A - Liquid crystal spatial optical modulating element - Google Patents

Abstract

PURPOSE:To omit a process for forming a transparent electrode and a reflection layer in a manufacture process and to eliminate the need for a driving device such as a power source for driving liquid crystal by employing a semiconductor layer which provides abnormal light photovoltanic effect for an optical address type liquid crystal spatial optical modulating element. CONSTITUTION:The semiconductor layer 3 of Sb2S3, etc., which provides the abnormal light photovoltanic effect and a liquid crystal layer 4 consisting of nematic liquid crystal, etc., are formed between transparent substrates 1 and 2 made of glass, etc. Write light 5 having wavelength for generating a large photoelectromotive voltage in the semiconductor layer 3 is made incident from the side of the semiconductor layer 3 for writing and the light part irradiated with the light generate the photoelectric motive voltage in the semiconductor layer 3 to apply the voltage to the liquid crystal. Consequently, a voltage pattern corresponding to the pattern of the write light 5 is applied to the liquid crystal and when read light 6a having wavelength which generates no photoelectromotive voltage is made incident from the side of the semiconductor layer 3, the light passes through the liquid crystal layer 4 to obtain read light 6b spatially modulated with the write light 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-addressable liquid crystal spatial light modulator using liquid crystal as a means for modulating light, and more specifically, it requires means for applying a voltage to drive the liquid crystal. It does not relate to a liquid crystal spatial light modulator.

[0002]

2. Description of the Related Art In recent years, liquid crystal spatial light modulators used as means for spatially modulating light in projection display devices applied to large-screen displays and optical information processing technologies have become popular. Came. This liquid crystal spatial light modulation element is classified into an optical address type in which two-dimensional information is directly written by light and an electrical address type in which two-dimensional information is written by a time series electric signal. Among them, the optical address type has an advantage that two-dimensional information can be input instantly, and the electric address type has a limitation of resolution associated with electrode wiring,
The optical address type has a possibility of realizing high resolution.

As shown in FIG. 3, a typical conventional photo-addressable liquid crystal spatial light modulator has a photoconductive layer 7, a reflective layer 8,
It has a structure in which the liquid crystal layer 9 is sandwiched between transparent substrates 11 such as glass on which two transparent electrodes 10 are formed. Usually photoconductive layer 7
Amorphous silicon (a-Si), single crystal silicon (Si), cadmium sulfide (CdS), or amorphous silicon photodiode is used as the reflective layer 8, and a reflective mirror having a dielectric multilayer structure, aluminum (A-Si) is used as the reflective layer 8.
l) or the like, a metal film or the like is used, a ferroelectric liquid crystal, a nematic liquid crystal, or the like is used for the liquid crystal layer 9, ITO or the like is used for the transparent electrode 10, and between the photoconductive layer 7 and the reflective layer 8. In some cases, a light-shielding layer may be formed.

Next, the operation principle of this conventional typical photo-address type liquid crystal spatial light modulator will be described. When an AC or DC voltage is applied to the transparent electrodes 10 at both ends and the writing light 12 having a bright and dark pattern is projected onto the photoconductive layer 7 from the photoconductive layer 7 side, as shown in FIG. In the area, the impedance of the photoconductive layer 7 is lowered, and a higher voltage is applied to the liquid crystal than in the dark area where the light is not irradiated. Therefore, when a voltage pattern corresponding to the pattern of the writing light 12 is applied to the liquid crystal and the reading light 13a is irradiated from the liquid crystal layer 9 side, the optical characteristics of the reading light 13a in the liquid crystal layer 9 change according to the voltage pattern. In this way, the read light 13b reflected by the reflective layer 8 via the liquid crystal layer 9 is spatially modulated by the write light 12.

[0005]

However, in the above-mentioned conventional liquid crystal spatial light modulator, in order to drive the liquid crystal, a transparent electrode for applying a voltage to the liquid crystal layer must be formed, and the external liquid crystal light modulator needs to be formed. It required a power supply and a driving device to supply the voltage from. Therefore, in the manufacturing process of the liquid crystal spatial light modulation element, the step of forming the transparent electrode on the transparent substrate is indispensable, and in the device using the liquid crystal spatial light modulation element, the liquid crystal is driven. However, it has a drawback in that a driving device such as a power source of the above must be incorporated.

Further, the above-mentioned conventional liquid crystal spatial light modulator is
Since it is a reflection type, a reflection layer had to be formed. In particular, when forming a reflecting mirror having a dielectric multilayer structure, a low-refractive index material such as magnesium fluoride (MgF ₂ ) and a high-refractive index material such as zinc sulfide (ZnS) are alternately controlled with high precision. However, many layers had to be laminated, which was a very difficult and economically expensive method.

The present invention can omit the step of forming the transparent electrode for driving the liquid crystal and the step of forming the reflective layer in the manufacturing process of the liquid crystal spatial light modulating element, and can also drive the liquid crystal. An object of the present invention is to provide an inexpensive photo-addressable liquid crystal spatial light modulator that does not require a driving device such as a power source.

[0008]

In order to solve the above problems, in an optically addressed liquid crystal spatial light modulator using liquid crystal as a means for modulating light, a liquid crystal layer and a semiconductor layer exhibiting an abnormal photovoltaic effect are provided. The semiconductor layer is Sb
₂ S ₃ , Sb ₂ Se ₃ , CdTe, Cd ₃ As ₂ , PbS, P
bI ₂ , GaAs, Ga ₂ Te ₃ , GaP, InP, In
It is made of a semiconductor material such as Te, AgInTe ₂ , ZnS, ZnSe, and HgTe, and the semiconductor layer is made of Sb.
₂ S ₃ , Sb ₂ Se ₃ , CdTe, Cd ₃ As ₂ , PbS, P
bI ₂ , GaAs, Ga ₂ Te ₃ , GaP, InP, In
A semiconductor material such as Te, AgInTe ₂ , ZnS, ZnSe, and HgTe is formed by oblique vapor deposition.

[0009]

[Operation] The abnormal photovoltaic effect used in the present invention is
alous Photovoltaic Effect. PANKOVE JI (RCA Laborat
(Articles): Physical Status Solidi A 61, 127 (1980) and others, and in some semiconductor materials formed by oblique evaporation, a photovoltage that is several times larger than the energy gap is obtained. It is an electromotive force effect. Further, the value of the photovoltage generated by the light irradiation shows the dependence on the wavelength of the irradiation light, a large photovoltage is generated at the wavelength of the specific irradiation light, and no photovoltage is generated at another specific wavelength.

Therefore, if the semiconductor layer having the extraordinary photovoltaic effect and the liquid crystal layer are combined, the writing light having the pattern of light and dark of the wavelength that produces a large photovoltaic voltage is irradiated from the semiconductor layer side to write the light. In the semiconductor layer, the bright portion irradiated with is generated a photovoltaic voltage by the photovoltaic effect, and this photovoltaic voltage is applied to the liquid crystal. Therefore, if a voltage pattern corresponding to the pattern of the writing light is applied to the liquid crystal and the reading light of a wavelength that does not generate the photovoltage is irradiated from the semiconductor layer side like the writing light, the photovoltage is not generated in the semiconductor layer. In the liquid crystal layer, the optical characteristics of the read light change according to the voltage pattern. In this way, the read light spatially modulated by the write light is obtained.

As described above, according to the present invention, by adopting the semiconductor layer exhibiting the above-mentioned extraordinary photovoltaic effect in the liquid crystal spatial light modulation element, the transparent electrode for driving the liquid crystal is formed in the manufacturing process. It is possible to omit the process for forming the reflective layer and the process for forming the reflective layer, and to configure an inexpensive optical address liquid crystal spatial light modulator that does not require a driving device such as a power source for driving the liquid crystal. become.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a liquid crystal spatial light modulator according to the present invention. As shown in FIG. 1, the transparent substrate 1
The semiconductor layer 3 exhibiting an extraordinary photovoltaic effect and the liquid crystal layer 4 are formed between the transparent substrate 2 and the transparent substrate 2. When writing is performed by irradiating writing light 5 having a pattern of light and dark of wavelengths that generate a large photovoltaic voltage in the semiconductor layer 3 from the side of the semiconductor layer 3 and writing, the bright portion irradiated with the light is caused by an abnormal photovoltaic effect in the semiconductor layer 3. A photovoltaic voltage is generated and this photovoltaic voltage is applied to the liquid crystal. Therefore, a voltage pattern corresponding to the pattern of the writing light 5 is applied to the liquid crystal, and if the reading light 6a having a wavelength that does not generate a photovoltaic voltage is irradiated from the semiconductor layer 3 side like the writing light 5, the semiconductor layer 3 emits light. The optical characteristics of the read light 6a change in the liquid crystal layer 4 according to the voltage pattern without generating a voltage. In this way, the read light 6b spatially modulated by the write light 5 is obtained.

In the examples, glass substrates were used as the transparent substrates 1 and 2. On one of the glass substrates, an Sb ₂ S ₃ film was formed as a semiconductor layer 3 exhibiting an abnormal photovoltaic effect to a film thickness of 1 μm by oblique vapor deposition under the conditions of a substrate temperature of 100 ° C. and a vapor deposition angle of 45 °. An alignment treatment was performed on the Sb ₂ S ₃ film so that the liquid crystal was vertically aligned. The other glass substrate was subjected to an alignment treatment so that the liquid crystal was vertically aligned.
Then, the surfaces of these glass substrates that had been subjected to the alignment treatment were adhered to each other through a spacer, and a nematic liquid crystal was sandwiched to form a liquid crystal layer 4.

The dependence of the photovoltaic voltage on the wavelength of the irradiation light in the Sb ₂ S ₃ film used as the semiconductor layer exhibiting the extraordinary photovoltaic effect is as shown in FIG. 2, and for 530 nm light, It can be seen that the largest photovoltaic voltage is generated and no photovoltaic voltage is generated for light of 590 nm.

Next, as described above, the spatial light modulation operation of the liquid crystal spatial light modulator manufactured by using the Sb ₂ S ₃ film as the semiconductor layer 3 exhibiting the extraordinary photovoltaic effect was tested. First, as the writing light 5, a light and dark pattern is written with light having a wavelength of 530 nm, and the reading light 6a
Was irradiated with light of 590 nm. Then, as a result of observing the read light 6b that has passed through the spatial light modulator, it was confirmed that the phase of only the bright portion was changed according to the pattern of the write light. This is because the writing light 5 having a wavelength of 530 nm, which is a wavelength at which a large photovoltaic voltage is generated in the Sb ₂ S ₃ film,
_{2 The} S ₃ film is irradiated to perform writing, and the photovoltaic voltage generated by the abnormal photovoltaic effect in the bright portion irradiated with light is applied to the liquid crystal layer 4 according to the voltage pattern corresponding to the pattern of the writing light 5. Then, since the alignment state of the nematic liquid crystal is changed, the read light 6a of 590 nm which does not generate a photovoltage in the Sb ₂ S ₃ film passes through the liquid crystal layer 4 and is read spatially phase-modulated by the pattern of the write light 5. The light 6b is obtained.

[0017] In the examples, it was used Sb ₂ S ₃ film as the semiconductor layer 3 exhibiting abnormal photovoltaic effect, Sb ₂
Se ₃ , CdTe, Cd ₃ As ₂ , PbS, PbI ₂ , Ga
As, Ga ₂ Te ₃ , GaP, InP, InTe, AgI
Anomalous photovoltaic effects have been confirmed in semiconductor materials such as nTe ₂ , ZnS, ZnSe, and HgTe, and even if these are used as the semiconductor layer 3 exhibiting the anomalous photovoltaic effect,
It is clear that the same effect can be obtained.

[0018]

As described above, according to the present invention, by adopting a semiconductor layer exhibiting an extraordinary photovoltaic effect in a liquid crystal spatial light modulator, a transparent electrode for driving a liquid crystal is formed in a manufacturing process. It is possible to omit the step of forming a reflective layer and the step of forming a reflection layer, and does not require a driving device such as a power source for driving the liquid crystal. It can be made. Further, such a highly productive liquid crystal spatial light modulator enables many applications.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a liquid crystal spatial light modulator according to the present invention.

FIG. 2 is a graph showing the dependence of the photovoltaic voltage on the wavelength of irradiation light in the Sb ₂ S ₃ film.

FIG. 3 is a sectional view showing a structure of a conventional liquid crystal spatial light modulator.

[Explanation of reference signs] 1,2,11 Transparent substrate 3 Semiconductor layer exhibiting extraordinary photovoltaic effect 4,9 Liquid crystal layer 5,12 Write light 6a, 6b, 13a, 13b Read light 7 Photoconductive layer 8 Reflective layer 10 Transparent electrode

Continued Front Page (72) Inventor Terutaka Tokumaru 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka

Claims (3)

[Claims] 1. A photo-addressable liquid crystal spatial light modulator using liquid crystal as a means for modulating light, comprising a liquid crystal layer and a semiconductor layer exhibiting an extraordinary photovoltaic effect. 2. The semiconductor layer comprises Sb ₂ S ₃ and Sb ₂ S
e ₃ , CdTe, Cd ₃ As ₂ , PbS, PbI ₂ , GaA
s, Ga ₂ Te ₃ , GaP, InP, InTe, AgIn
The liquid crystal spatial light modulator according to claim 1, which is made of a semiconductor material such as Te ₂ , ZnS, ZnSe, and HgTe. 3. The semiconductor layer comprises Sb ₂ S ₃ and Sb ₂ S
e ₃ , CdTe, Cd ₃ As ₂ , PbS, PbI ₂ , GaA
s, Ga ₂ Te ₃ , GaP, InP, InTe, AgIn
The liquid crystal spatial light modulator according to claim 1, wherein a semiconductor material such as Te ₂ , ZnS, ZnSe, and HgTe is formed by oblique vapor deposition.