JPH0822019A - Liquid crystal light valve - Google Patents

Abstract

PURPOSE:To provide a liquid crystal light valve having high reliability which shows no change in characteristics even when high intensity readout light is used. CONSTITUTION:A reflecting film for IR rays or a reflecting film for UV rays, or a reflecting films 17 for IR rays and UV rays are formed on the surface of a glass substrate 11b having neither photoconductive layer 15 nor mirror layer 16 on a transparent electrode. The reflection film is formed on the surface of the substrate where a transparent electrode 12b is not formed or the film is formed between the transparent electrode and the glass substrate or on the transparent electrode. By this method, even when readout light of high intensity is used, little changes in the characteristics due to the temp. increase of the element by IR rays or little deterioration due to decomposition or the like of the liquid crystal by UV rays is caused, and thereby, the obtd. liquid crystal light valve has as high reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal light valve used for an image projection device, a video projector and the like.

[0002]

2. Description of the Related Art A liquid crystal light valve is disclosed in US Pat.
527, etc., typically a photoconductive layer,
The device is a combination of a light reflection layer and a liquid crystal layer. In recent years, a high-brightness image projection device using a liquid crystal light valve for light amplification has been commercialized.

[0003]

In the case where the liquid crystal light valve is applied to a high-luminance image projector, it is necessary to irradiate the liquid crystal light valve with strong read light.
Therefore, the light source used is often a metal halide lamp, a xenon lamp, or the like that contains a large amount of infrared light or ultraviolet light. When strong infrared light is incident on the liquid crystal light valve, the temperature rises due to absorption in the element and the characteristics change. Further, when ultraviolet light is incident, problems such as decomposition of liquid crystal molecules occur and reliability is impaired.

[0004]

Therefore, the present invention is directed to a surface of a glass substrate on which a photoconductive layer and a mirror layer are not formed, on which the transparent electrode is not formed, between the transparent electrode and the glass substrate, or between the transparent electrodes. An infrared reflective film or an ultraviolet reflective film, or an infrared reflective film and an ultraviolet reflective film were formed on the top.

[0005]

By using the above method, the amount of light outside the visible range can be markedly reduced. As a result, even if a strong reading light is used, the characteristics change due to the temperature rise of the element due to infrared rays and the liquid crystal due to ultraviolet rays Provided is a liquid crystal light valve that is highly reliable and has little deterioration due to decomposition or the like.

When the reflective film is present in the element,
The film is not damaged during the device manufacturing process, and the yield is improved.

[0007]

The present invention will be described in detail below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic view showing the structure of a liquid crystal light valve according to the present invention.

Substrates 11a, 1 for sandwiching liquid crystal molecules
As 1b, a transparent glass substrate having a thickness of 5 mm was used, both surfaces of which were polished to a parallel flatness of λ / 5 or less at a He-Ne laser wavelength. The ITO transparent electrode layer 12 is formed on the surface of both substrates.
a and 12b are provided. A hydrogenated amorphous silicon (a-Si: H) photoconductive layer 15 having a thickness of 3.0 μm was formed on the transparent electrode layer 12a on the light writing side. A dielectric multilayer mirror 16 was formed as a mirror layer on the photoconductive layer. However, there is no problem even if the mirror layer has a structure in which mutually insulated metal films are arranged.

Further, a dielectric multilayer film was formed as the infrared and ultraviolet light reflecting film 17 on the surface of the glass substrate on which the photoconductive layer and the mirror layer were not formed on the transparent electrode, on which the transparent electrode was not formed. The dielectric multilayer film is made of TiO ₂ and Si.
An alternating laminated film of O ₂ was used. The reflection wavelength band was mainly set to near infrared, and the transmittance was set to 1% or less from 700 nm to 1500 nm. Although near-ultraviolet rays are reflected with respect to ultraviolet rays, since the TiO ₂ layer has a large absorption for ultraviolet rays, the number of layers is set smaller than that for infrared rays.

These substrates were formed by forming alignment films 13a and 13b on the transparent electrode 12a and the mirror layer 16 and then pasting them through a spacer to sandwich the liquid crystal layer 14 in the gap. As described above, in the liquid crystal light valve according to the present invention, due to the presence of the reflection film 17, the characteristic change due to the temperature rise of the element due to infrared rays and the deterioration due to the decomposition of liquid crystal due to ultraviolet rays are small, and the reliability is high. A liquid crystal light valve was provided.

(Embodiment 2) FIG. 2 is a schematic view showing the structure of a liquid crystal light valve according to the present invention. He-N on both sides is used as substrates 11a and 11b for holding liquid crystal molecules.
e A transparent glass substrate having a thickness of 5 mm and polished to have a parallel flatness of λ / 5 or less at a laser wavelength was used. ITO transparent electrode layers 12a and 12b were provided on the surfaces of both substrates. A hydrogenated amorphous silicon (a-Si: H) photoconductive layer 15 having a thickness of 3.0 μm was formed on the transparent electrode layer 12a on the light writing side. A dielectric multilayer mirror 16 was formed as a mirror layer on the photoconductive layer. However, there is no problem even if the mirror layer has a structure in which mutually insulated metal films are arranged.

Further, a dielectric multilayer film was formed as an infrared and ultraviolet light reflection film 17 between the transparent electrode of the glass substrate on which the photoconductive layer and the mirror layer are not formed on the transparent electrode and the glass substrate. As the dielectric multilayer film, an alternating laminated film of TiO ₂ and SiO ₂ was used. The reflection wavelength band was mainly set to near infrared, and the transmittance was set to 1% or less from 700 nm to 1500 nm. Although near-ultraviolet rays are reflected with respect to ultraviolet rays, since the TiO ₂ layer has a large absorption for ultraviolet rays, the number of layers is set smaller than that for infrared rays.

These substrates were formed by forming alignment films 13a and 13b on the transparent electrode 12a and the mirror layer 16 and then pasting them through a spacer to sandwich the liquid crystal layer 14 in the gap. As described above, in the liquid crystal light valve according to the present invention, due to the presence of the reflection film 17, the characteristic change due to the temperature rise of the element due to infrared rays and the deterioration due to the decomposition of liquid crystal due to ultraviolet rays are small, and the reliability is high. A liquid crystal light valve was provided.

Since the reflective film is present in the device, the film is not damaged during the device manufacturing process, and the yield is improved. (Embodiment 3) FIG. 3 is a schematic view showing the structure of a liquid crystal light valve according to the present invention.

Substrates 11a, 1 for sandwiching liquid crystal molecules
As 1b, a transparent glass substrate having a thickness of 5 mm was used, both surfaces of which were polished to a parallel flatness of λ / 5 or less at a He-Ne laser wavelength. The ITO transparent electrode layer 12 is formed on the surface of both substrates.
a and 12b are provided. A hydrogenated amorphous silicon (a-Si: H) photoconductive layer 15 having a thickness of 3.0 μm was formed on the transparent electrode layer 12a on the light writing side. A dielectric multilayer mirror 16 was formed as a mirror layer on the photoconductive layer. However, there is no problem even if the mirror layer has a structure in which mutually insulated metal films are arranged.

Further, a dielectric multilayer film was formed as the infrared and ultraviolet light reflecting film 17 on the transparent electrode of the glass substrate on which the photoconductive layer and the mirror layer were not formed on the transparent electrode. These substrates were formed by forming the alignment films 13a and 13b on the transparent electrode 12a and the mirror layer 16 and then bonding them via a spacer to sandwich the liquid crystal layer 14 in the gap.

As the dielectric multilayer film, an alternating laminated film of TiO ₂ and SiO ₂ is used. The reflection wavelength band was mainly set to near infrared, and the transmittance was set to 1% or less from 700 nm to 1500 nm. Although near-ultraviolet rays are reflected with respect to ultraviolet rays, since the TiO ₂ layer has a large absorption for ultraviolet rays, the number of layers is set smaller than that for infrared rays.

As described above, in the liquid crystal light valve according to the present invention, due to the presence of the reflection film 17, the characteristic change due to the temperature rise of the element due to infrared rays and the deterioration due to the decomposition of the liquid crystal due to ultraviolet rays are small, and the reliability is high. The liquid crystal light valve with high performance was provided. Further, since the reflective film is present in the element, the film is not damaged during the element manufacturing process,
Yield has also improved.

[0019]

By using the present invention, the range of application of the liquid crystal light valve to the high-brightness image projection device can be increased.

[Brief description of drawings]

FIG. 1 is a schematic view showing a structure of a liquid crystal light valve according to the present invention.

FIG. 2 is a schematic view showing a structure of a liquid crystal light valve according to the present invention.

FIG. 3 is a schematic view showing a structure of a liquid crystal light valve according to the present invention.

[Explanation of symbols]

 11a, 11b Transparent substrate 12a, 12b Transparent electrode 13a, 13b Alignment film layer 14 Liquid crystal layer 15 Photoconductive layer 16 Mirror layer 17 Infrared and / or ultraviolet reflection film

Claims (2)

[Claims] 1. A glass substrate having a writing means by light, a reading means by light and a voltage applying means, on which a photoconductive layer and a mirror layer are formed on a transparent electrode, and a glass substrate on which a transparent electrode is formed, respectively. A pair of glass substrates each having a liquid crystal alignment film formed on opposite surfaces of
In a liquid crystal light valve having a liquid crystal composition sealed in the gap, a surface of a glass substrate on which a photoconductive layer and a mirror layer are not formed, on which the transparent electrode is not formed, a transparent electrode and a glass substrate. A liquid crystal light valve comprising an infrared reflection film or an ultraviolet reflection film, or an infrared reflection film and an ultraviolet reflection film formed between or on a transparent electrode. 2. The liquid crystal light valve according to claim 1, wherein the reflective film is a dielectric multilayer film.