JPH01108529A - Driving method for optical write liquid crystal display element - Google Patents

Abstract

PURPOSE:To convert a negative image to a positive image by providing a means for putting a liquid crystal orientation into disorder in case there is no write information. CONSTITUTION:Projection light beams change the direction of light beams of a light source 500 by a refracting mirror 501, pass through a condenser lens 502 and go into a polarized light beam splitting prism 503. Subsequently, only a specific polarized light component goes into the projection light side of a light valve 200, reflected light beams go into the polarized light beam splitting prism 503 again, and the polarized light component being orthogonal to the incident polarized light direction of said light valve passes through and projected onto a screen by a projection lens 504. Also, the amplitude of an AC power source 9 applied to the light valve 200 is set larger than a conventional set value, so that an electric field of the AC power source 9 works on a liquid crystal layer 7 in the light valve 200 and puts a liquid crystal orientation into disorder, in a state that the write light intensity is '0'. In such a way, a positive image corresponding to an image of a negative film 505 can be projected onto a screen 600.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving an optically written liquid crystal display element, and more particularly to a method for reversing a negative-positive image of an optically written field effect liquid crystal display element.

[Prior Art] An optically written field effect liquid crystal display element called a light valve is an element used for image intensity conversion, etc., and has the feature of being simple and compact.

The operating principle of a conventional optically written field effect liquid crystal display element will be explained below.

A photoconductive film is provided on one of the two electrodes of a field-effect liquid crystal display element, an optical image is formed on this photoconductive film, and the resistance within the film plane is spatially modulated. Attempts have been made to transfer an image into a liquid crystal layer by applying an electric field between conductive films, and to use this for visible light modulation in projection devices. FIG. 4 shows an example of a cross section of a liquid crystal display element used in this projection type device.

In this device, a photoconductive film 2 and a liquid crystal layer 7 are laminated, and transparent electrodes 4 and 41 are attached to the outside of the photoconductive film 2 and the liquid crystal layer 7, sandwiching the two. Normally, an AC voltage of 9 is applied between these electrodes. In addition, a visible light blocking film 3 (CdTe film) and a dielectric light reflecting film (mirror N) 5 are inserted at the boundary between the photoconductive film 2 and the liquid crystal layer near. Forms a mirror surface for incident visible light.

Generally, a CdS film with a thickness of about 2 to 20 μm is used as the photoconductive film=2. When no image writing light is incident from the left side of the element, the electrical conductivity of this photoconductive film = 2 is sufficiently higher than that near the liquid crystal layer, and when light is incident, the electrical resistance of the photoconductive film = 2 is is adjusted so that it is sufficiently lower than that of the liquid crystal Nnear.

In this way, when an image is drawn on the photoconductive film 2 by the image writing light incident from the left side of the element, the internal resistance of the photoconductive film 2 changes locally according to the density of the image. For this purpose, the above-mentioned AC voltage: 9 is applied to the liquid crystal Nnear corresponding to these portions while being spatially modulated according to the density of the image.

In this liquid crystal layer 7, a smectic liquid crystal having positive dielectric anisotropy is oriented in an initial HFE (115° angle 1st). When an AC voltage of 9 is applied between the electrodes, the resistance of the photoconductive film 2 is high in places where there is no writing light, so the AC voltage of 9 is not applied to the liquid crystal and the alignment of the liquid crystal is not disturbed. Therefore, the polarization plane of the projection light incident through the polarizing plate is rotated by 45 degrees according to the twist of the liquid crystal, and reaches the dielectric light reflecting film (mirror layer) 5. The plane of polarization of the reflected light is rotated by 45 degrees and exits with the same polarization direction as when it was incident. Next, in the part where the image is drawn on the photoconductive film 2, an AC voltage of 9 is applied to the liquid crystal.
The liquid crystal molecules change orientation in the direction of the electric field (perpendicular to the electrodes). As a result, the above-mentioned conditions for rotation of the polarization plane change, and the reflected light of the projection light includes a polarization direction component perpendicular to the polarization direction of the projection light. Therefore, by detecting the component perpendicular to the polarization direction of this projection light, projection output light having the same pattern as the writing light can be obtained.

In this display element, the dielectric reflective film 5 is used to completely reflect the strong projected visible light that enters from the right side of the element, and is made of high and low dielectric constant dielectrics such as ZnS and Na5AIFe. It is made by stacking about 15 layers of membranes alternately. Furthermore, the light blocking film=3 is designed to block visible light for projection that enters from the right side of the element.

The above is an explanation of the structure and operation of a conventionally known optically written field effect liquid crystal display element called a light valve.

[Problems to be Solved by the Invention] The optically written field-effect liquid crystal display device described above projects a black and white gray pattern as it is, and has the problem that it is not possible to convert a negative image into a positive image. there were.

Therefore, the present invention considers the operation mode of this optically written field effect type liquid crystal display element and attempts to make it possible to convert a negative image into a positive image.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and the present invention has been made in order to solve the above-mentioned problems. , a method for driving an optically written liquid crystal display element configured to extract liquid crystal display information from a liquid crystal layer formed on the photoconductive film, including providing means for disturbing liquid crystal orientation when there is no written information. ,
The liquid crystal display is driven so that when written information is input, liquid crystal display information that is inversely proportional to the written information can be extracted.

As a means to disturb the liquid crystal alignment when there is no written information, there are two methods: Change to something with a higher price. ■Change the photoconductive film of conventional light valves to a thinner one made of the same material. ■For conventional light valves, the applied AC voltage value is set higher than before. A method in which a voltage applied from outside the photoconductive film and the liquid crystal layer is applied to the liquid crystal layer. and ■
In contrast to conventional light valves, a constant amount of light is always incident on the photoconductive film as bias light. Examples include a method using isoluminescence.

Among the above measures, (1) the applied AC voltage value is set higher than that of the conventional light valve;

■In contrast to conventional light valves, a constant amount of light is always incident on the photoconductive film as bias light.

These two methods are preferable because they can be used in conjunction with the conventional drive method by adding some additional means to the conventional light valve-based device.

The present invention uses the above means to change the operating mode of the liquid crystal, thereby making it possible to convert a negative image into a positive image.

[Operation] FIG. 1 shows the relationship between the writing light intensity: L of the light valve described as a conventional example and the projection light output intensity. The details of this relationship will be explained below.

When the writing light intensity L=O, as described in the conventional example, no AC voltage is applied to the liquid crystal layer, and the component perpendicular to the polarization direction of the projection light, ie, the projection light output, is zero. However, when the writing light intensity is gradually increased, a voltage is applied to the liquid crystal and a projection light output is generated. On the other hand, if the writing light intensity is made sufficiently large, the alignment of the liquid crystal will be completely destroyed.

Then, the optical rotation of the liquid crystal disappears, and the projected light is reflected by the dielectric mirror layer 5 without being affected by its polarization direction at all. That is, no projection light output occurs.

(C in the figure) Therefore, as shown in Figure 1, the relationship between the projection light output and the writing light intensity: L is as shown in Figure 1. There are a region A where the projection light output increases as the writing light intensity increases, and a region B where the projection light output decreases as the writing light intensity increases.

In the conventional light valve, the light valve is driven using the region A where the projection light output increases as the writing light intensity increases.

In the present invention, (1) the material of the photoconductive film of the conventional light valve is changed to a material with high conductivity in the dark; ■Change the photoconductive film of conventional light valves to a thinner one made of the same material.

Furthermore, ①The applied AC voltage value is set higher than that of conventional light valves. ■In contrast to conventional light valves, a certain amount of light is incident on the photoconductive film as bias light. By such means, the liquid crystal layer is made to be in a state where the liquid crystal alignment is disturbed even when the writing light intensity is 0, and the relationship between the writing light intensity and the projection light output is reversed, and the dark area is Bright, bright areas are getting dark projection output.

Therefore, according to the method for driving an optically written liquid crystal display element of the present invention, the optically written liquid crystal display element has a negative/positive image reversal function.

[Examples] Example 1 FIG. 2 shows a specific example in which the method for driving an optically written liquid crystal display element of the present invention is applied to a slide projector that uses an image of a normal negative film as the writing light.

The slide projection device includes an optical writing field effect liquid crystal display element (light valve): 200. Polarizing beam splitting prism +503. Light source +500. Projection lens two
Consists of 504 etc.

The operation is to take an image of negative film = 505 through the lens:
At 506, an image is formed on the light valve=200. On the other hand, the projection light changes the direction of light from a light source: 500 by a refracting mirror: 501 and enters a polarizing beam splitting prism: 503 through a condenser lens: 502. Then, only a specific polarized light component enters the projection light side of the light valve 200. The reflected light is then polarized again by a beam splitting prism: 50
3, the polarized light component perpendicular to the incident polarization direction of the light valve passes through and is projected onto a screen by a projection lens 504.

In this embodiment, the amplitude of the AC power supply 9 applied to the light valve 200 is set larger than the conventional setting value, and when the writing light intensity is 0, the light valve:
An electric field from the AC power supply 9 was applied to the liquid crystal N in the 200 to disturb the alignment of the liquid crystal.

As a result, a positive image corresponding to the image of the negative film 505 could be projected onto the screen 600.

Example-2 In the slide projection device of the previous example, lens = 506
A half mirror 400 as shown in Figure 3 is inserted between the light valve 200 and the light valve 200, and the photoconductive film is changed to a conductivity that disturbs the liquid crystal alignment of the smectic liquid crystal. The light (writing light intensity that gives the maximum output light intensity of the projection light: Lp), bias light: 3
03. (The setting width of the AC power source 9 was the same as the conventional setting value.) As a result, as in the previous embodiment, a positive image corresponding to the image of the negative film 505 could be projected onto the screen 800.

In this example, the half mirror: 400 is used as a lens:
If you do not fix it between the 506 and the light bulb = 200 and make it detachable, you can create a slide projection device that can selectively project negative-positive, negative-negative, positive-negative, positive-positive, etc. on the spot depending on the type of film image. can do.

[Effects of the Invention] As described above, according to the present invention, a new function of converting a negative image to a positive image of an optically written field effect liquid crystal display element (light valve), which was previously impossible, can be realized. .

[Brief explanation of the drawing]

Figure 1 shows a conventional optically written field effect liquid crystal display element.
A diagram showing the relationship between writing light intensity and projection output intensity, FIG. 2 is a side view schematically showing a slide projection device to which the optical writing liquid crystal display element driving method of the present invention is applied, and FIG. 3 is a diagram showing the relationship between the writing light intensity and the projection output intensity. FIG. 4 is a cross-sectional view schematically showing a conventional optically written field-effect liquid crystal display element. Patent Applicant Nippon Sheet Glass Co., Ltd. Agent Patent Attorney Takashi Ohno

Claims (3)

[Claims] (1) Optical writing configured such that written information irradiated as light onto a photoconductive film formed on a transparent substrate is extracted as liquid crystal display information on a liquid crystal layer formed on the photoconductive film. In a method for driving a liquid crystal display element, a means is provided to disturb the alignment of the liquid crystal when there is no written information, and when written information is incident, the liquid crystal display element is driven so that liquid crystal display information that is inversely proportional to the written information can be taken out. A method for driving an optically written liquid crystal display element, characterized in that: (2) Driving the optically written liquid crystal display element according to claim 1, wherein the means for disturbing the liquid crystal alignment when there is no written information is a voltage applied from outside the photoconductive film and the liquid crystal layer. Method. (3) The method for driving an optically written liquid crystal display element according to claim 1, wherein the means for disturbing the liquid crystal alignment when there is no written information is the incidence of a constant amount of light on the photoconductive film.