JPS597338A - Optical controller - Google Patents

Abstract

PURPOSE:To obtain an optical controller which shuts off thoroughly incident rays, losses less light and is suited for an optical shutter by the constitution wherein a prescribed liquid crystal is sandwiched between a pair of electrodes and linearly polarized light is made incident from a prescribed direction. CONSTITUTION:Electrodes 4, 5 and orientation films 7 are provided to transparent substrates 1, 2 and, for example, a positive nematic liquid crystal 3 is sandwhiched via a spacer 6. A polarization plate is disposed on an incident light 9 side, and the direction of the transmission axis thereof is made roughly equal to the direction of the uniform arrangement H of the liquid crystal 3. The refractive index ne of the liquid crystal 3 in the uniform state H under application of no voltage to incident polarized light 9' is smaller than the refractive index ng of the the substrate 1 and if an incident angle theta is smaller than a full reflection angle, the light 9' is transmitted light 11. The refractive index n0 of the liquid crystal 3 to the light 9' in the homeotropic state V when applied with voltage is smaller than ng and if the incident angle theta is made larger than the critical angle of total reflection, the light 9' is fully reflected and is thoroughly shut off. The optical shutter which losses less light is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical control device using a liquid crystal cell, and more particularly to a novel liquid crystal-optical shutter that can be applied to a camera shutter or a shutter array of a page printer using an electrophotographic method. It is.

, a liquid crystal optical filter is disclosed in, for example, Japanese Patent Application Laid-Open No. 47-1173.
No. 7, U.S. Patent No. 3,731,986, U.S. Patent No. 370
This is disclosed in Publication No. 0306 and the like.

This liquid crystal-optical shutter has a nematic liquid crystal with twisted orientation and positive dielectric anisotropy arranged between a pair of transparent electrode plates.
f#L has a configuration with a pair of single row or crossed polarizers on the outside of both transparent electrode plates17. Therefore, this liquid crystal-optical shutter can change the optical characteristics of the twisted nematic liquid crystal by applying a voltage to the pair of electrodes using a voltage applying means, and this change can be detected by a polarizing plate.

With such a conventional liquid crystal optical shutter, several rays of light pass through the polarizing plate when the rotation is ON or OFF! To do W,
Since it is not possible to create an optical shutter that completely blocks light, it is difficult to apply the above-mentioned liquid crystal optical shutter to a digital camera such as a camera.

Moreover, since two polarizing plates are used, there are drawbacks such as a large loss of light quantity.

A first object of the present invention is to provide a novel optical control device that can be used in a liquid crystal-optical shutter.

A second object of the present invention is to provide an optical control device that can completely block incident light.

A third object of the present invention is to provide an optical control device with less loss of light quantity.

A fourth object of the present invention is to provide a shutter array for a page printer using an electrophotographic method.

A fifth object of the present invention is to provide an electrophotographic printer using a liquid crystal-optical shutter array as an optical printer head.

Other objects of the invention will be readily apparent to those skilled in the art from the description.

An object of the present invention is to provide an optical control device in which a liquid crystal is sandwiched between a pair of electrodes, in which a liquid crystal is sandwiched between a pair of electrode bases, at least one of which is transparent. A liquid crystal cell sandwiching a liquid crystal having the relationship of <ng and ne <ng, 'controlling the molecular axis direction of the liquid crystal to either a homogeneous or homeotropic arrangement with respect to the surface of the substrate by applying a voltage. 5In-' (-) <θ
An optical control device having a means for making the light incident at an angle θ determined by
o is the ordinary ray refractive index of the liquid crystal molecules, and ne is the extraordinary ray refractive index of the liquid crystal molecules.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical control device and a printer using the same according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an optical control device of the present invention, and FIG. 2 is a sectional view of another embodiment of the optical control device. In the liquid crystal cell used in the present invention, a liquid crystal 3 is sandwiched between transparent substrates 1 and 2 having a refractive index of n2.

Electrodes 4 and 5 are formed on the transparent substrates 1 and 2, respectively, and the transparent substrates 1 and 2 are maintained at a constant distance (1/II, about 4 to 1511) by a seal spacer 6. There are still glass fibers and glass particles (
(not shown) may be mixed.

As the liquid crystal 3, a nematic liquid crystal or a smenoctic liquid crystal can be used, and in the case of a nematic liquid crystal, its dielectric anisotropy may be positive (hereinafter referred to as rNpi night crystal), or its dielectric anisotropy may be positive. (It may be one with negative anisotropy (hereinafter referred to as iNn?&crystal)).
.

For example, if the liquid crystal 3 is to be mixed with Np liquid crystals, the Np liquid crystals must be arranged homogeneously on the surface of the transparent substrate 1. At this time, such array shape j″
In order to further stabilize the flow, a method can be used in which an alignment film 7 is provided on each of the transparent substrates 1 and 2, and the alignment films 7 are rubbed in one direction. Examples of the orientation 1 and 7 include polyimide films, polyamide films, polyvinyl alcohol films, gelatin films, Sin films, and Ti0211 films.
4 or the like as the alignment film 7.

However, when forming a 5ift film, by using oblique evaporation, the entire alignment process can be performed simultaneously with film formation. However, according to the present invention, it is also possible to arrange the liquid crystals 3 in contact with the substrates 1 and 2 in different directions so that the molecules of the liquid crystal 3 in the middle thereof are arranged in a screw H structure. In this liquid crystal cell, a polarizing plate 8 is arranged on the incident light 9 side. The polarizing plate 8 is arranged so that its transmission axis direction 10 is the same or substantially the same as the direction of the homogeneous alignment H of the Np liquid crystal.

The refractive index of the Npr & crystal 3 arranged in the homogeneous state H is ne with respect to the incident linearly polarized light 9', and since ng and ne of the substrate l at this time are ne<ng, this incident linearly polarized light 9' When incident at an angle of incidence θ of 5in-'(')ng or more, this polarized light is totally reflected, but
If the angle is less than sin' (=), the liquid crystal 3 can be transmitted to n.

On the other hand, when the Np liquid crystal 3 is arranged in the homeotropic state ■, the refractive index of the Np liquid crystal 3 is n with respect to the incident linearly polarized light. Then, ng and n of the base 1 at this time. is n
Since o < ng, if the incident linearly polarized light 9' is incident at an angle of incidence θ of 5 in-1 (') or more, this polarized light will be totally reflected, but if the incident angle θ is less than 5 in-' (box) ng If it is at an angle, it will pass through the liquid crystal 30. Therefore, 5in-'(T'!2-)≦θ<5in-
' The incidence ng in the range of (ne-)
By directing the incident angle θ toward the liquid crystal 3 and at the same time selecting whether to apply a voltage between the electrodes 4 and 5 or to apply no voltage, that is, when no voltage is applied, the incident line Polarized light 9' becomes transmitted light 11 that has passed through the liquid crystal 3, while 711: In the pressure applied state, the incident linearly polarized light 9'
can be the totally reflected light 12. It should be noted that when a voltage is applied between electrodes 4 and 5, it is assumed that the Np liquid crystal remains in a homogeneous alignment at the boundary between substrates 1 and 2, but most of the other liquid crystal remains Since the liquid crystals are aligned in the field direction, the liquid crystal at this time can be substantially in the homeotropic state V0. Furthermore, as shown in FIGS. 1 and 2, the transparent substrates 1 and 2 have prisms. Preferably, a right angle prism is used, particularly as shown in FIG.

As mentioned above, the Np liquid crystal has an ordinary ray refractive index n. ,
n between the refractive index of the extraordinary ray and the refractive index of the transparent substrate.

Since it is necessary to have the relationships of <ng and ne <ng, the Npl crystal and the transparent substrate are selected so as to satisfy the above relationships. For example, Merck's [ZLI-15
In the case of 65J nematic liquid crystal, the number is 1.50, the number is 1.63, and at this time, ng is 1.80 as a transparent substrate.
5in-' (!!-!2) is 56
．． 50, 5in-'(') is 64.9° and ng
Because it becomes NG,
When incident linearly polarized light is directed toward the liquid crystal at an incident angle 'θ in the range of 56.5°〈θ (fi 4.90), the incident light can be controlled by applying or not applying a voltage. For example, When the angle of incidence of the incident linearly polarized light is set to 600, the incident linearly polarized light passes through the liquid crystal layer when no voltage is applied, but when a voltage is applied, the incident linearly polarized light is totally reflected and completely blocked. That will happen.

There are still LCDs and [7, for example n. is 1.52 and le is 1
．． In the case of using a pre-homeotropically aligned Nn liquid crystal of 70 (as a transparent substrate, n is set to be the same or approximately the same as the transmission axis direction 10, and when no voltage is applied, the liquid crystal refracts incident linearly polarized light. Since the rate is n.(1,52), I (no<ng), sin' (1 star -)
If 11-line polarized light is incident at an incident angle of -57.6° or more, it can be totally reflected. On the other hand, when a voltage is applied, the refractive index of the liquid crystal is ne ( 1,70), so (ne<ng), si
n ~ 1 (-L bar) = 1.80 linearly polarized light at an incident angle of 70.80 or more. When light is incident, it is totally reflected, but when it is incident at an incident angle of less than 70.8°, IK line polarized light is transmitted. be able to. Therefore, the incident angle 0 of linearly polarized light is 57, 60≦θ<7
By selecting from the range of 0.80, it is possible to control the transmission of linearly polarized light when a voltage is applied and the total reflection of linearly polarized light when no voltage is applied.

FIG. 3 shows a plan view when the optical control device of the present invention is applied to a liquid crystal-optical shutter array, and FIG. 4 is a sectional view taken along line A-A'. In FIGS. 3 and 4, the liquid crystal-optical/Yatsuta array 13 includes a plurality of shack sections 14, and this shutter section 14 has a pair of i
It has a structure in which a liquid crystal 17 is sandwiched between poles 15 and 16. The electrodes 15 and 16 are provided on opposing surfaces of the columnar rectangular prisms 19 and 20, respectively, and are arranged on the sides of the liquid crystal. and ne and right angle prismo ng have the above relationship (
The liquid crystal and right angle prism are selected so that no<ng and ne<ng. Furthermore, on the incident light side, a polarizing plate 18 having a transmission axis in the same or substantially the same direction as the direction when the liquid crystals are arranged in a homeotropic state is arranged.

By using the shutter array 13, either the light transmitted through the liquid crystal layer or the totally reflected light can be irradiated onto a photosensitive member such as a photosensitive drum. Then, by opening the shutter 1 (β14) to the photosensitive drum (7) in accordance with the digital signal, a desired latent image can be formed, and then image formation can be performed.

FIG. 5 is an explanatory diagram of a mode in which the optical control device 1 (liquid crystal-optical shutter array) of the present invention is utilized in an electrophotographic printer. In FIG. 5, the light source 21 is always on and always illuminates the liquid crystal optical/ray array 13. The shutter array 13 can transmit or totally reflect the light beam from the light source 21 by a liquid crystal drive circuit (not shown) to generate an optical signal, and can control the light beam irradiated onto the photosensitive drum 22. In addition, in order to obtain the focusing ability of the light beam from the light source 21 and the optical signal from the shutter array 13,
It is desirable to arrange lenses 23 and 24 in the optical path. The photosensitive drum 22 is charged with a positive or negative charge in advance at a charging station 25 equipped with a corona discharge device or the like before being irradiated with a light signal, and the charged charge disappears at the portion of the photosensitive drum that is irradiated with light, and the electrostatic latent is generated. An image is formed. The electrostatic latent image formed in this way is developed in the developing section 26 by applying a developing bias in the presence of a developer consisting of toner and carrier of opposite polarity to the polarity at the time of printing the strip, or of the same polarity when performing reversal development. After developing by magnetic brush development method etc., the image holding member 28 (for example,
The photoreceptor, which receives the optical signal generated from the shutter array 13, is used for electrophotography as described above. For example, the photoreceptor may be a photoreceptor using a silver salt photographic method (for example, monochrome paper, color beano (-1 "Dry Silver 1" by 3M, USA), etc.).

The optical control device of the present invention has the following advantages.

(1) Since incident light can be completely blocked by total reflection, high contrast control is possible.

(2) Since only one polarizing plate is used, there is less loss of light quantity and bright transmitted light can be obtained.

(3) When used in a camera shutter or an optical printer shutter array, there is no leakage of light from the slow closing shutter, and unnecessary information is not photographed or written.

In conventional twisted nematic mode shutters,
When the shutter is closed late, there is a leakage of several inches of light, but the present invention can completely block the incident light.

(4) Electronic control of the optical shutter is possible.

(5) A large optical shutter is possible.

(6) A high-speed optical shutter is possible.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the optical control device of the present invention. FIG. 3 is a plan view of the liquid crystal-optical shutter array of the present invention, and FIG. 4 is a sectional view taken along line A-A'. FIG. 5 is an explanatory diagram of a mode in which the optical control device of the present invention is utilized in an electrophotographic printer. 1.2.Transparent substrate 3...Liquid crystal 4.5...Electrode 6...Seal spacer 7...Alignment film 8 Polarizing plate 9 -Incoming light 9'...Incoming linearly polarized light 10 Transmission axis of polarizing plate Direction 11 - Transmitted light 12 - Totally reflected light θ Incident angle H - Homogeneous arrangement state V - Homeotropic arrangement state 13 - Liquid crystal - optical shutter array 14 Shutter section 15.16 - Electrode 17 - Liquid crystal layer 18 - Polarizing plate 19, 20, columnar right angle prism 21, light source 22, photosensitive drum 23, 24, lens 25, charging station 26, developing section 27, transfer section 28, image holding member 29, fixing section

Claims (5)

[Claims] (1) In an optical control device in which a liquid crystal is sandwiched between a pair of electrodes, n is formed between a pair of electrode bases, at least one of which is transparent. A liquid crystal cell sandwiching a liquid crystal having a relationship of <1 and <1, and controlling the molecular axis direction of the liquid crystal to either homogeneous or homeotropic alignment with respect to the surface of the substrate by applying a voltage. The formed linearly polarized light is made incident at an angle θ determined by 8 sin' through a linear polarizing plate having r2 transmission axes that are the same or substantially the same as the molecular axis direction of the homogeneously arranged liquid crystal. 1 means
g (where ng is the refractive index of the transparent substrate s and no is the refractive index of the ordinary rays of liquid crystal molecules in %)
ne is the refractive index of the extraordinary ray of the liquid crystal molecules). (2) The optical control device according to claim 1, wherein the electrode base is a prism having electrodes. (3) The optical control device according to claim 2, wherein the prism is a right-angled prism. (4) An optical control bag according to claim 1, wherein the electrode base has a group of a plurality of electrodes. (5) The optical control device according to claim 1, wherein the liquid crystal is a nematic liquid crystal.