JPS6186731A - liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain an element which has excellent utilizing efficiently of a luminous flux, response characteristic, etc. by filling a liquid crystal between substrates at least one of which has a grating structure, orienting preliminarily the liquid crystal by the grating structure and impressing an electric field between the substrates to change the orienting direction. CONSTITUTION:The liquid crystal element constituted by sealing the liquid crystal 2 between the substrates 1 and 1 of which at least one is transparent and has the grating structure (in the embodiment, both substrates are grated) is manufactured. The pitch of the grating is designated as P and the thickness thereof as T and the grating having a rectangular, triangular waveform sinusoidal or other shape is provided to the substrate. The liquid crystal having a positive dielectric property is put into the liquid crystal 2 and is oriented in the direction perpendicular to the groove direction of the grating, i.e., to the plane of the figure. The refractive index of the liquid crystal 2 is changed from the abnormal refractive index ne to normal refractive index by impressing the electric field between the substrates 1 and 1 and using the monochromatic light of the wavelength lambda polarized in the groove direction of the grating as the incident light, by which the modulation degree of the diffraction function is made controllable. The liquid crystal element which has the excellent contrast ratio and is suitable for an optical switch, etc. is thus obtd.

Description

[Detailed description of the invention] (1) Technical field The present invention is for optical display, optical coupling, and optical recording.

The present invention relates to a liquid crystal element suitable for various devices such as optical communication.

As means, rubbing treatment, oblique evaporation of Sin, MgF2, etc., and the use of a coupling agent have been used. When liquid crystals were aligned using the above-mentioned alignment treatment method, the degree of alignment order of the liquid crystals was insufficient and, therefore, the liquid crystals were unstable against temperature changes.

Furthermore, when used in devices such as optical switches, although the contrast ratio is relatively excellent, the utilization efficiency of the luminous flux is low and problems arise in terms of response characteristics and functional stability, making it impossible to obtain a practical device. Ta.

(3) Summary of the Invention An object of the present invention is to provide a liquid crystal element that eliminates the conventional drawbacks, has a simple structure, and has practical functions.

The liquid crystal element according to the present invention is one in which liquid crystal is filled between substrates, at least one of which has a grating structure, and the liquid crystal is oriented by the grating. By applying an electric field, a magnetic field, heat, etc. to the liquid crystal element, the refractive index of the liquid crystal is changed, and light control becomes possible by utilizing, for example, the diffraction effect of the grating. At least one of the substrates constituting the liquid crystal element must be transparent, and the cross-sectional shape, thickness, pitch size, etc. of the grating are determined by taking into account usage conditions, ease of manufacture, etc. In the study of the present invention, it is necessary that the pitch of the grating is 1107h or less, and under special conditions, for example, when it is desired to generate only 0th and 1st order diffracted light, 2I
There arises a need for it to be equal to or less than Lm. The thickness of the grating is determined by the difference between the ordinary refractive index and extraordinary refractive index of the liquid crystal (hereinafter Jn
) and the orientation of the liquid crystal, 0.5
pm or more is necessary, and the size of the common number Bm is appropriate.

Further, it is desirable that the liquid crystal has a large JH, and when the refractive index of the liquid crystal is controlled by an electric field or a magnetic field, a nematic liquid crystal having a positive dielectric property or a smectic liquid crystal having a ferroelectric property is suitable.

(4) Examples FIG. 1 shows an embodiment of a liquid crystal element according to the present invention.

1 is the substrate, 2 is the liquid crystal, P is the grating pitch, T
indicates the grating thickness.

In FIG. 1, both of the inner substrates 1 have a grating structure, but as mentioned earlier, it is sufficient that at least one of them has the grating structure, and the substrate 1 also has a grating structure. It does not matter as long as at least one of them is transparent.

FIG. 1(a) shows a rectangular grating, which is the most common shape for gratings used in this device. FIG. 1(b) shows a triangular wave grating, and FIG. 1(C) shows a sinusoidal grating. A case in which a nematic liquid crystal having positive dielectricity is used will be described below.

The liquid crystal 2 is aligned in the direction of the grooves of the grating (perpendicular to the plane of the paper) 1. For example, when an electric field is applied between the inner substrates l, the alignment direction of the liquid crystal 2 is tilted toward the electric field direction according to the strength of the electric field, and a predetermined direction is formed. When the amount of electric field reaches , the liquid crystal 2 is aligned in the direction of the electric field. At this time, a wavelength of light polarized in the grating groove direction enters as incident light. Therefore, the degree of modulation of the diffraction function by the grating can be controlled. This function can be obtained regardless of the shape of the grating,
Parameter T required when controlling diffracted light.

The only difference is the conditions that hold true during the j n r turn on. Note that the light source used in this device is not limited to monochromatic light, but may also be a light source with a wide range of wavelengths such as an LED. Further, a desirable wavelength width of the light source is usually 1000 Å or less.

Next, an application example using the liquid crystal element according to the present invention will be described.

FIG. 2 shows a schematic diagram of an electric field controlled optical switch using a liquid crystal element according to the present invention, 1' is a transparent insulator, 1'' is a transparent insulator with a grating structure, 2 is a liquid crystal, and 3 is a glass substrate. , 4 is a transparent electrode.

5 is a power source, 6 is a spacer, 7 is an extraction electrode, 8 is an adhesive layer, 9 is an incident light, 10 is a 0th-order diffracted light, and 10' is a higher-order diffracted light.

In the optical switch of this embodiment, a transparent electrode 4 is formed on the top of a glass substrate 3, and an extraction electrode 7 is provided at one end of the transparent electrode 4.
A transparent insulator 1 is provided on the entire surface except for the extraction electrode 7.
The inner substrate of the substrate is coated with a layer of transparent insulator 1' having a grating structure on a part of the substrate.
The transparent insulators 1.1' are placed close to each other so as to face each other, the gap between them is filled with liquid crystal 2, and the thickness between the substrates is reduced by a spacer 6.
After fixing and adhering, the power source 5 and the extraction electrode 7 were connected using lead wires.

The optical switch is supplied with H polarized in the direction of the grooves of the grating.
The e-Ne laser beam (λ=6328) 9 is vertically incident on the transparent electrode 4n by adjusting the power source 5.

The refractive index was changed from zero to ordinary refractive index. At this time, the ratio of the 0th-order transmitted light IO to the incident light 9 changed from 1% to 80%, and the contrast ratio of the 0th-order transmitted light IO became 80:1. Furthermore, the switching response time and stability against temperature were sufficient for use as an optical switch.

In this example, the liquid crystal element according to the present invention was used as an optical switch by focusing on the zero-order transmitted light lO, but the higher-order diffracted light
It is also possible to use 0' to create an optical switch or an optical distributor. Furthermore, it is believed that it is possible to create optical devices having a wide variety of other functions using the liquid crystal element of the present invention.

(5) As described in detail of the invention, the liquid crystal element according to the present invention has a simple structure, and when used in an optical device, it provides a device with high luminous flux utilization efficiency and an excellent contrast ratio, and can be used in a wide variety of applications. is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a grating shape of a liquid crystal element according to the present invention. FIG. 2 is a schematic diagram of an optical switch using the liquid crystal element of the present invention. ■---Substrate, 1'-m-transparent insulator. i''---Transparent insulator with grating structure. 2--M-liquid crystal, 3--1 glass substrate, 4-m-transparent electrode, 5--1 power source, 6--spacer, 7--drawer Electrode, ゛8--
-adhesive layer, 9-1 single incident light, 10--0th order diffracted light, 10'--higher order diffracted light. 20th

Claims (1)

[Claims] (1) A liquid crystal element characterized in that at least one of the substrates has a grating structure, and liquid crystal is filled between the substrates, and the grating structure has both the function of diffracting incident light and the function of aligning the liquid crystal. .