JPH0255762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a thermal write liquid crystal light valve.

Display devices used in computer terminal devices are required to have increasingly high resolution resolution due to the increased capacity and improved functionality of computers. Particularly in computer-based image processing, newspaper editing, and LSI design, displays with high precision and the ability to partially add information are desired. It is difficult to increase the resolution of conventional CRTs beyond 2,000 lines, and no equipment suitable for such displays has been obtained. In recent years, displays that thermally write on liquid crystals with a laser have been viewed as promising as such display devices, and thermally written liquid crystal displays have been featured in, for example, the magazine ``Proceeding of the S.I.D. SID)” 1978 1
The article “LASER-ADDRESSED LIQUID
CRYSTAL PROJECTION DISPLAYS)”. According to this paper, a laser beam 1 is applied to a liquid crystal light valve 10 as shown in FIG.
The image is recorded by scanning by, and the projection light 12 is incident,
The image can be displayed by reflection. The liquid crystal light valve 10 includes a glass substrate 2 on which a dielectric film 3, an aluminum reflective film 4, and a liquid crystal alignment film 8 are formed, and a glass substrate 7 on which a transparent electrode film 6 and a liquid crystal alignment film 8 are formed to form a liquid crystal material 5. It has a sandwiched structure. When the laser beam 1 enters the liquid crystal light valve 10, the laser beam 1 is absorbed by the dielectric film 3 and converted into heat, which propagates through the aluminum reflective film 4 and the liquid crystal alignment film 8 to increase the temperature of the liquid crystal material 5. Liquid crystal material 5
Smectic liquid crystal is used as a smectic liquid crystal, and smectic liquid crystal changes to a nematic phase by increasing the temperature.
It changes into a liquid layer and is rapidly cooled when the laser beam 1 is removed, thereby freezing the random orientation state of liquid crystal molecules in the liquid state and forming scattering nuclei. The scattering nuclei are read out by the projection light 12 and displayed as pixels on the screen.

The scattering nuclei can form a line with a width of about 10 μm, so it is difficult to use for a 2-inch square liquid crystal light valve.
5000 lines will be recorded, compared to the conventional
This enables displays with much higher resolution than CRTs (cathode ray tubes).

However, since the above-mentioned liquid crystal light valve displays an image by enlarging and projecting it using a Schilleren optical system, a negative type display is produced in which the portion recorded by the laser beam is displayed black due to the scattering effect. In order to display colors using a plurality of liquid crystal light valves, it is necessary to overlap the colors, but this requires a positive type display that can display the portion recorded by laser light in a single color. Therefore, in the past, aluminum reflective film 4
Alternatively, a positive type display can be performed by using a partial erase mode in which a current is applied to the transparent electrode film 6 and the entire surface of the liquid crystal light valve is written in a scattering state using the generated Joule heat, and then a voltage is applied and recording is performed with a laser beam. ing. The method of writing on the entire surface of the liquid crystal light valve by raising the temperature of the liquid crystal using resistance heating takes a long time, approximately one second, and has been problematic in terms of image display speed.

An object of the present invention is to provide a positive type liquid crystal light valve that can directly project and display a monochrome portion recorded by a laser beam.

According to this invention, at least a transparent substrate, a light absorption film, a light reflection film, a dielectric film having a lattice arrangement, a liquid crystal material, a liquid crystal alignment film, a transparent electrode film, and a transparent substrate are laminated in this order. By adopting this structure and further setting the film thickness of the dielectric film so that the phase difference of transmitted light is around 2.4 radians, a positive type liquid crystal light valve with a short recording time can be obtained.

Hereinafter, this invention will be explained in detail with reference to the drawings. FIG. 2 is a diagram showing a liquid crystal light valve according to the present invention. A light absorption film 3, a light reflection film 4, and a lattice-shaped dielectric film 9 are formed on the glass substrate 2, and a liquid crystal material 5 is disposed between the glass substrate 7 on which a liquid crystal alignment film 8 and a transparent electrode film 6 are provided. Encapsulate. The grid-shaped dielectric film 9 is set to have the effect of a liquid crystal alignment film and the effect of a phase grating on the projected light 12.
It is known that liquid crystal molecules align along the unevenness of the substrate surface they contact, and especially when there is a regular periodic structure in one dimension, the long axis direction of the liquid crystal molecules coincides with the groove direction of the periodic structure. Arrange as follows. This state is shown in FIG. 3a. Dielectric film 9
When the longitudinal direction of the one-dimensional lattice consisting of is perpendicular to the plane of the paper, the long axis direction of the liquid crystal molecules is also perpendicular to the plane of the paper. When arranged in this way, the liquid crystal is transparent, and the projected light 12 passes through the liquid crystal material 5 and the dielectric film 9, is reflected by the light reflecting film 3, and then passes through the dielectric film 9 and the liquid crystal material again. Transmits 5. At this time, the dielectric film 9 plays the role of a phase grating due to the difference in refractive index between the dielectric film 9 and the liquid crystal 5. Next, FIG. 3b shows a state in which the liquid crystal light valve is written with a laser beam. The reflective film 3 transfers the heat generated by the absorption of the laser beam to the liquid crystal material 5.
becomes scattered due to temperature changes. At this time, the liquid crystal material 5 in contact with the light reflecting film 3 enters a scattering state, but the liquid crystal material 5 in contact with the dielectric film 9 has low thermal conductivity of the dielectric film, so there is no light from the light reflecting film. The transparent state is maintained without heat propagation and scattering state. When the projected light 12 is incident, the incident light 12 is reflected from the place where the dielectric film 9 is present, but
Since the light is scattered where the dielectric film 9 is not present, the dielectric film 9 plays the role of an absorption type lattice.

FIG. 4 shows how the transmitted light is focused by the lens 13 when a grating with pitch P, thickness h, and refractive index n is installed in a liquid crystal with refractive index ne. The phase difference m of the phase grating in this case is obtained by the following formula, m = 2π (n - ne) h / λ (1) The phase grating with the phase difference expressed by formula (1) reduces the diffracted light to 0. ±1st order, ±2nd order, ..., ± on both sides of the next light
It is obtained by separating the P order,... Each diffracted light intensity Ip
It is well known that is expressed by Jp ² (m) (Jp is a Betzel function of order P). Phase difference m is 2.4
When the value is set to Jo(2.4)0, the diffracted light becomes only the ±1st order or higher order without the 0th order light.

In addition, in the case of an absorption type grating with a pitch P, the diffraction distribution at the focal point of the lens 13 is expressed by a Sinc function, and if the intensity of the 0th-order light is 1, the 1st-order light intensity has a value of 0.047. It is also well known. FIG. 5 compares the diffracted light distributions in the case of a phase type grating and an absorption type grating. In the case of a phase grating, the diffraction distribution (a) is a distribution in which the 0th-order light is zero and the ±1st-order light swells. In the case of an absorption type grating, the diffracted light distribution (b) is a distribution in which 0th-order light is the main component. At this time, if an aperture with the width W in FIG. 5 is placed at the condensing point of the lens 13 in FIG. can. That is, in FIG. 3, when writing is performed with a laser beam, an absorption type grating is formed and a projection light 12 is obtained, thereby realizing a positive type display. Here, the light absorption film 3 of the liquid crystal light valve includes CdTe,
An inorganic compound semiconductor such as Sb ₂ Te ₃ or a dielectric multilayer film can be formed by vapor deposition or sputtering, and the light reflecting film 4 can be made of a metal film such as aluminum or silver. The dielectric film 9 may be made of any material as long as it has a refractive index different from at least the refractive index of liquid crystal (n=1.5), is transparent, and allows formation of a lattice pattern by etching or the like. Such a dielectric film contains MgF ₂ ,
Examples include SiO, In ₂ O ₃ and ZrO ₂ . For example, when MgF ₂ is used, the thickness h at which the refractive index n = 1.38 and the modulation degree m = 2.4 means that the optical path in the reflective type is 2h.
When calculated from equation (1) keeping in mind that 0.8μm
(wavelength = 500 nm). Further, the lattice pattern of the dielectric film can be manufactured by a lift-off method in which a lattice pattern is created on the aluminum reflective film 4 using photoresist, a dielectric film is deposited thereon, and the resist is removed. The pitch of the grating pattern is set to 200 mm in consideration of the alignment performance of the liquid crystal and the separation of diffracted light.
It is sufficient to set the value to between 1000 lines/mm and 1000 lines/mm. Further, the liquid crystal alignment film 8 of the liquid crystal light valve may be subjected to a rubbing treatment or an SiO oblique evaporation film may be used, and the transparent electrode 6 may be formed using an In ₂ O ₃ or Sb ₂ O ₃ film.

As described in detail above, according to the present invention, a liquid crystal light valve can be obtained that can directly display a positive image of the area recorded by a laser beam by incorporating a dielectric film grating, and the image display time can be greatly reduced. This can be shortened to .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional liquid crystal light valve, FIG. 2 is a diagram showing a liquid crystal light valve according to the present invention,
3rd, 4th, 5th. The figure is a diagram explaining the function of the dielectric film in the present invention. In the figure, 1 is a laser beam, 2 and 7 are glass substrates, 3 is a light absorption film, 4 is a light reflection film, 5 is a liquid crystal material,
6 is a transparent electrode, 8 is a liquid crystal alignment film, 9 is a dielectric film,
12 is a projection light, and 13 is a lens.

Claims (1)

[Claims] 1 At least a transparent substrate, a light absorption film, a light reflection film, a dielectric film having a lattice arrangement, and a liquid crystal material,
It is characterized by having a structure in which a liquid crystal alignment film, a transparent electrode film, and a transparent substrate are laminated in this order, and further, the film thickness of the dielectric film is set so that the phase difference of transmitted light is around 2.4 radians. Positive type liquid crystal light bulb.