JPH0525096B2 - - Google Patents

Description

Detailed Description of the Invention (1) Technical Field The present invention relates to a liquid crystal element suitable for various devices for optical recording, optical coupling, optical display, and optical communication.

(2) Prior Art Conventionally, in this type of liquid crystal element, rubbing treatment, oblique evaporation of SiO, MgF ₂ , etc., and the use of a coupling material have been used as means for aligning the liquid crystal. When liquid crystals are aligned using the above-mentioned alignment treatment method, the degree of alignment order of the liquid crystals is insufficient, and there are problems with stability against temperature changes and response characteristics when used in optical devices. Furthermore, although the contrast ratio was relatively excellent, the luminous flux utilization efficiency was low, and a practical device could not be obtained.

(3) Summary of the Invention An object of the present invention is to eliminate the drawbacks of the conventional device and to provide a liquid crystal device that is thin and simple in structure yet has advanced functions.

The liquid crystal element according to the present invention has a structure in which transparent insulators and liquid crystals are arranged alternately, and a set of two electrodes are provided substantially parallel to the arrangement direction. or,
In the narrow space formed by the transparent insulator and the electrode, the liquid crystal is oriented in the groove direction if it is a nematic liquid crystal with positive dielectricity, and the orientation direction is 90° perpendicular to the electrode surface by applying an electric field. °Change. or,
When a ferroelectric liquid crystal is used, the orientation direction of the liquid crystal changes in parallel to the electrode plane depending on the tilt angle. Therefore, by using the change in the alignment direction of the liquid crystal, the refractive index of the liquid crystal for the incident light beam can be determined as the ordinary refractive index n _p and the extraordinary refractive index.
By changing the refractive index between ne _{and e} , it is possible to control the change in the refractive index of the diffraction grating formed by the liquid crystal and the transparent insulator. Using this modifiable diffraction grating, it is possible to optically control incident light.

(4) Embodiment FIG. 1 shows an example of the basic configuration of a liquid crystal element according to the present invention. 1 is a transparent insulator, 2 is a liquid crystal, and 3 is a transparent electrode. The liquid crystal element shown in FIG. 1a has transparent electrodes 3 facing each other and close to each other, and rectangular transparent insulators 1 and liquid crystals 2 are alternately arranged in the space between them. This configuration is the most basic configuration of the present device, and in FIG. 1b, the transparent insulator 1 has a sawtooth shape, and in FIG. 1c, the transparent insulator 1 has a sine wave shape.

Next, the function of the liquid crystal element shown in FIG. 1a will be explained using the liquid crystal element shown in FIG. FIG. 2 illustrates the functions of the liquid crystal element according to the present invention. Reference numeral 4 indicates incident light, 5 indicates zero-order transmitted light, 5' indicates higher-order diffracted light, and 6 indicates a power source.
Also, the refractive index of the transparent insulator 1 is n _g , the refractive index of the liquid crystal 2 for ordinary light is n _p , the refractive index for extraordinary light is _ne , the thickness of the transparent insulator 1 - liquid crystal 2 layer is T, and the thickness of the incident light is Let the wavelength be λ.

Incident light 4 with wavelength λ polarized in the alignment direction of liquid crystal 3
feels the extraordinary refractive index n _e of the liquid crystal 3 in a static state. At this time, if the following equation (1) is satisfied, Figure 2 a
As shown in FIG. 2, all of the incident light 4 becomes higher-order diffracted light 5', and zero-order transmitted light 5 is not generated. Furthermore, if the formula (2) is satisfied, as shown in FIG. 2b, no higher-order diffracted light 5' is generated, and all of the incident light 4 is transmitted to become zero-order transmitted light 5.

(n _e − n _g )・T=λ/2 ...(1) n _e =n _g ...(2) Next, when an electric field is applied to the liquid crystal 2, even if the liquid crystal 2 is a positive dielectric nematic liquid crystal, If so, it is oriented in the direction of the electric field. At this time, the polarization direction of the incident light 4 and the alignment direction of the liquid crystal 2 are perpendicular to each other, and the refractive index of the liquid crystal 2 with respect to the incident light 4 becomes the ordinary refractive index n _p .

Here, if the following relationship is established between the parameters, the incident light 4 can be transmitted or blocked.

n _p = n _g ……(3) (n _g −n _p )・T=λ/2 ……(4) Under the above conditions, when formula (3) is satisfied, the incidence is as shown in Figure 2 b. All of the light 4 is transmitted and becomes 0th-order transmitted light 5, with no higher-order diffracted light 5' generated. Furthermore, when formula (4) is satisfied, all of the incident light 4 becomes higher-order diffracted light 5', and no zero-order transmitted light 5 is generated, as shown in FIG. 2a.

As described above, by appropriately selecting the materials of the liquid crystal 2 and the transparent insulator 1, it becomes possible to control the luminous flux of the zero-order transmitted light 5 and the higher-order diffracted light 5'.

Although the above conditional expressions (1) and (4) are different for the elements with the configurations shown in Figure 1 b and c, the condition under which zero-order transmitted light does not occur exists regardless of the shape of the transparent insulator. do. The pitch of the lattice formed by the transparent insulator and the liquid crystal and the thickness of the lattice usually need to be 10 μm or less and 0.5 μm or more, respectively. Note that glass, SiO ₂ ,
Transparent materials such as TiO ₂ and Al ₂ O ₃ , ITO for transparent electrodes,
Materials such as SnO ₂ and In ₂ O ₃ may be used.

The manufacturing process and performance evaluation results of this liquid crystal device are shown below.

FIG. 3 shows the manufacturing process of this liquid crystal element, 7 is a transparent substrate, and the other numbers in the figure have the same meanings as the numbers in FIGS. 1 and 2.

Corning 7059 glass (made by Corning, λ=
A refractive index of 1.544 for 6328 Å) was made into a shape of 25 x 25 mm ² and 1 mm thick. Both sides were polished to within a few Newton rings, ultrasonically cleaned with methanol, trichlene, acetone, and pure water, and then cleaned with nitrogen. It was dried using gas and further baked at 120°C for 20 minutes in nitrogen. An ITO film was formed to a thickness of 1000 Å by ion plating with a brass mask closely attached to the glass substrate so as to form stripes with a width of 5 mm. Furthermore, a MgF ₂ film with a thickness of 1146 Å was formed on the back surface by electron beam evaporation. At this time, the refractive index of the ITO film for He-Ne laser light (λ = 6328 Å) is 1.80, and the sheet resistance is
It was 18Ω/sq. Furthermore, when a He--Ne laser beam was vertically incident on the surface of the MgF ₂ film, almost no reflection occurred. Next, a 1.7 μm thick vapor deposition glass (#8329 made by Schott) was formed on the ITO film surface using the RF sputtering method, and then RD2000N (negative resist made by Hitachi, Ltd.) was applied with a spinner, and after prebaking, the film was coated. An RD2000N film with a thickness of 1.5 μm was formed.
Next, an exposure mask with a grid of 4 μm pitch was brought into close contact with the surface of the RD2000N film, and after exposure to far ultraviolet light, a development and rinsing process was performed.
A grid made of RD2000N was formed on the surface of the glass vapor deposited film. After etching the glass vapor deposited film into a lattice shape by Ar ion etching, the RD2000N mask was dissolved in a remover to form glass lattice grooves on the ITO film.

On the glass substrate with the glass lattice groove obtained in the above process, another glass substrate with an ITO film is closely attached with the electrode surfaces facing each other, and the positive dielectric liquid crystal RO-TN601 ( Made by Rossille n _p = 1.503, n _e =
1.699) was filled. After that, the lead wires were bonded and connected to the power supply.

When a He-Ne laser beam polarized in the groove direction of the glass lattice grooves was perpendicularly incident on the prepared liquid crystal element, the refractive index of the liquid crystal 3 with respect to the laser beam 4 became an extraordinary refractive index n _e , and the above formula (1) is obtained. Satisfying the following conditions, most of the incident light 4 becomes higher-order diffracted light 5'. next,
When an AC electric field of 10 V _pp and 1 KHz is applied, the liquid crystal 2 is oriented in the direction of the electric field, and the refractive index 2 of the liquid crystal 2 with respect to the laser beam 4 becomes the ordinary refractive index n _p , satisfying the above equation (3). Most of the light 4 turned into zero-order transmitted light 5 and passed through. At this time, the ratio of the zero-order transmitted light 5 to the incident light 4 in a static state was less than 1%, and when an electric field was applied, it was 90%. Therefore, the luminous flux utilization efficiency is 90
%, and the contrast ratio was 90:1 or more.

(5) Effects of the invention As explained above, the liquid crystal element according to the present invention has
It has high luminous flux utilization efficiency and excellent contrast ratio, and because the liquid crystal cell is thin, response time is fast and it can be driven at extremely low voltage. Furthermore, the element has a simple configuration and can be applied to many optical devices such as optical switches, optical polarizers, and optical distributors.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of a liquid crystal element according to the present invention. FIG. 2 is a diagram showing the functions of this liquid crystal element. FIG. 3 is a schematic diagram of the present liquid crystal device prepared in the example. 1... Transparent insulator, 2... Liquid crystal, 3... Transparent electrode, 4... Incident light, 5... Zero-order transmitted light, 5'...
Higher-order diffraction light, 6...power supply, 7...transparent substrate.

Claims (1)

[Claims] 1. A liquid crystal in which different orientation states are induced that produce an ordinary refractive index and an extraordinary refractive index in response to incident light;
Transparent insulators having a refractive index substantially equal to either the ordinary refractive index or the extraordinary refractive index of the liquid crystal are arranged alternately, and the film thickness of the liquid crystal and the transparent insulator is substantially reduced. The generation of zero-order diffracted light and the generation of higher-order diffracted light can be achieved by selecting the alignment state of the liquid crystal so that the liquid crystals are set equally and the liquid crystal selectively produces an ordinary refractive index or an extraordinary refractive index. A liquid crystal element characterized by having means for modulating.