JPH083584B2 - Liquid crystal optical shutter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal shutter. More specifically, it relates to the structure of a liquid crystal optical shutter capable of high-speed response.

[Conventional technology]

A liquid crystal optical shutter is applied as a display device such as a calculator, a clock, a measuring instrument, and a computer that displays a pattern by controlling the transmittance or reflectance of external light or background light by applying a voltage to the liquid crystal layer. Has been done. The liquid crystal driven by two frequencies is also applied to printers and the like.

[Problems to be solved by the invention]

The liquid crystal shutter of TN type or guest-host type has a response of light transmittance to voltage of several tens ms to several hundreds ms, and is not suitable for applications requiring high-speed response. Also, the TN type liquid crystal shutter had a strong direction dependency, and its application range was narrowed. Further, although the TN type liquid crystal shutter driven by two frequencies has a quick response to a voltage, it has drawbacks such that the power consumption of the entire device is increased because a high frequency is used and a high voltage is required.

The response speed of the TN type liquid crystal shutter depends on the voltage when a voltage is applied, but it hardly depends on the voltage when the voltage is removed. As a method of speeding up the response of the TN type liquid crystal shutter, there is a method of reducing the thickness of the liquid crystal layer, but when the product of the thickness and the birefringence is set to 550 nm or less, the optical characteristics are rapidly deteriorated.

It is an object of the present invention to eliminate the above-mentioned drawbacks and provide a liquid crystal shutter which can be driven at low voltage and low power consumption and which has excellent optical characteristics and high-speed response.

[Means for solving problems]

The liquid crystal shutter of the present invention is a product of a thickness and a birefringence of a liquid crystal layer having a positive dielectric anisotropy that is substantially homogenously aligned is 180 nm or more and 400 nm or less, and a pair of polarizing plates sandwiching the liquid crystal layer. The angle between the polarization axis or absorption axis of the liquid crystal molecules on the surface of the liquid crystal layer adjacent to the polarizing plate is 30 ° or more 60
It is characterized by being less than °.

〔Example〕

 Hereinafter, description will be made using examples.

Example 1 The configuration of an example according to the present invention will be described with reference to FIG. In this example, the liquid crystal layer 1 has a birefringence of 0.12 and a thickness of 2 μm. Therefore the product is 240 nm. The liquid crystal layer 1 is sandwiched between two substrates 2 whose inner surfaces are rubbed in opposite directions to be homogeneously aligned, and a voltage can be applied by the transparent electrode 3. Further, it is held by the polarizing plate 4. The polarization axis of the polarizing plate is 45 ° with the rubbing axis, that is, the optical axis of the liquid crystal layer, and is parallel to each other. The polarizing plate has a transmittance of about 43%
96% was used. In the above structure, the spectral characteristics of the transmittance of the shutter when no voltage is applied to the transparent electrode 3 and when a rectangular wave of 480HZ8V is applied are shown in FIG. As is clear from FIG. 2, the contrast ratio is about 1:10, which shows almost black-and-white shutter characteristics.

FIG. 3 shows the response characteristic at that time. The response speed when applying voltage was about 0.4 ms, and the response speed when the voltage application was stopped was 2.5 ms, which was considerably faster than the TN type.

Example 2 In Example 1, as a polarizing plate, the transmittance was 38% and the polarization degree was 99.
%It was used. The response was the same as in Example 1, but the contrast ratio was improved to about 1:15 and the shutter characteristics were quite good.

Example 3 In Example 1, the polarizing axes of the polarizing plates were set to be 90 ° to each other. The spectral characteristics at this time are shown in FIG.
The contrast ratio was about 1:20, and the shutter characteristics were improved as compared with Example 1. The response characteristics at this time are shown in FIG.

Example 4 In Example 1, the transparent electrode 3 was patterned to obtain a negative type transmissive liquid crystal display device. It has a wider viewing angle range than the TN type, and it has become a nice-looking display. It is suitable for measuring instruments such as automobiles that require a high response speed.

Example 5 In Example 3, a transparent electrode was patterned, and a reflective plate was attached to the rear surface of the shutter to obtain a reflective liquid crystal display device. Wider viewing angle range than TN type.

〔The invention's effect〕

According to the present invention, the main wavelength range of visible light is 450 nm to 650
In nm, it has become possible to provide a liquid crystal shutter with a sufficient contrast ratio and a high-speed response. Further, according to the present invention, it is possible to provide a liquid crystal shutter which requires less directivity than the conventional TN system. A liquid crystal shutter according to the present invention or a measuring instrument such as an automobile display which requires a high response speed, a pair of conventional eyeglasses for stereoscopic image display by allowing the left and right eyes to see the high-speed response display at different times. We were able to exceed the limits of liquid crystal shutters and liquid crystal displays.

[Brief description of drawings]

FIG. 1 is a block diagram of a liquid crystal shutter showing an embodiment of the present invention. 1 ... Liquid crystal layer, 2 ... Substrate 3 ... Transparent electrode, 4 ... Polarizing plate FIG. 2 is a liquid crystal in Embodiment 1 of the present invention. FIG. 3 is a diagram showing the spectral characteristic of the shutter. FIG. 3 is a diagram showing the response in the first embodiment. FIG. 4 is a diagram showing the spectral characteristic of the liquid crystal shutter in the third embodiment. FIG. 5 is a diagram showing the response of the liquid crystal shutter in the third embodiment.

Claims (1)

[Claims] 1. The product of the thickness of a liquid crystal layer having a positive dielectric anisotropy substantially homogenously aligned between opposing electrode substrates and the birefringence of the liquid crystal layer is 180 nm or more and 400 nm or less, and at least The pair of polarizing plates sandwiching the liquid crystal layer has an absorption axis or a polarization axis that forms an angle of 30 ° or more and 60 ° or less with an optical axis of liquid crystal molecules on the surface of the liquid crystal layer adjacent to the polarizing plate. Liquid crystal light shutter.