JPS5915918A - Optical control device - Google Patents

Abstract

PURPOSE:To shut off thoroughly incident rays and to make a titled device usable as a shutter with little loss in the quantity of light by sandwiching a liquid crystal between a pair of substrates and making light incident at the angle larger than a specific angle to a liquid crystal cell having the refractive index of the liquid crystal selected smaller than the refractive index of the substrates. CONSTITUTION:Transparent substrates 1, 2 having a refractive index ng formed of transparent resistors 4, 5 sandwich a liquid crystal 3. A linearly polarizing plate 8 is arranged to have the direction 10 of the transmission axis thereof in the direction at a right angle to the homogeneous arrangement H of the liquid crystal, and the refractive index n0 of the liquid crystal 3 with respect to linearly polarized incident light 9' is selected smaller than the refractive index ng. If the polarized light 9' is made incident to the cell at the incident angle theta larger than the angle determined by Sin<-1>(n0/ng), total reflected light 12 is obtd. Now when the resistors 4, 5 are electrically heated, the liquid crystal 3 are transferred to the liquid phase I having isotropy, and the light passes through the liquid phase I irrespectively of the incident angle theta, by which transmitted light 11 is obtd. The incident light is thus totally reflected or transmitted by the heating with the resistors, whereby the titled device is made usable as a liquid crystal-optical shutter with little loss in the quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical control device using a liquid crystal cell.1-1 Specifically, the present invention relates to an optical control device using a liquid crystal cell. This concerns the shutter.

Liquid crystal optical shutters are disclosed in, for example, Japanese Patent Application Laid-Open No. 47-11737, US Pat. No. 3,731,986, and US Pat. No. 37
This is disclosed in JP 00306 and the like.

This liquid crystal-optical shutter has a twisted oriented nematic liquid crystal with positive dielectric anisotropy arranged between a pair of transparent electrode plates, and a pair of parallel or crossed polarizing plates on the outside of both transparent electrode plates. It has a structure.

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 m-poles using the voltage applying means, and this change can be detected by the polarizing plate.

In such a conventional liquid crystal optical shutter, several rays of light pass through the polarizing plate in the ON state or OFF state;
Since it is not possible to use an optical shutter that completely blocks light, the above-mentioned liquid crystal display is used for shutters such as cameras.
Applying optical shutters has difficult problems. Furthermore, since two biased 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.

The third object of the present invention is to provide an optical control device (
The goal is to provide σ.

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 following.

An object of the present invention is to provide an optical control device in which a liquid crystal is sandwiched between a pair of substrates. The linearly polarized light formed through a liquid crystal cell, a heating means for heating the liquid crystal to an isotropic liquid, and a linearly polarizing plate having a transmission axis perpendicular or substantially perpendicular to the molecular axis direction of the homogeneously aligned liquid crystal. An optical control device having a means for directing the incident light toward the liquid crystal in the liquid crystal cell at an angle of incidence greater than the angle determined by (n□9o is the refractive index when the liquid crystal molecules become an isotropic liquid).

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 ng. Transparent substrates 1 and 2 are coated with transparent resistors 4 and 5 (for example, indium oxide,
In addition, the transparent substrates 1 and 2 are maintained at a constant distance (for example, about 4 to 15 μm) by a seal spacer 6.

In addition, in order to stabilize the distance between the transparent substrates 1 and 2 in the liquid crystal 3, glass fins (-) and glass particles (not shown) are added.
can be mixed.

For the liquid crystals 3 and 7, a nematic liquid crystal can be used, and its dielectric anisotropy may be positive (hereinafter referred to as rNp liquid crystal), or its dielectric anisotropy may be negative (hereinafter referred to as rNp liquid crystal). (hereinafter referred to as "r Nn liquid crystal") may be teared off.

Furthermore, smectic liquid crystals can also be used.

The liquid crystals must be arranged homogeneously on the surface of the transparent substrate 1. At this time, in order to further stabilize the alignment state, alignment films 7 are formed on the transparent substrates 1 and 2, respectively.
A method can be used in which the alignment film 7 is rubbed in one direction. As the alignment film 7, for example, a polyimide film, a polyamide film, a polyvinyl alcohol film,
It is desirable to form the alignment film 7 using a gelatin film, a SiO2 film, a Ti, 02 film, or the like. Still S10. When forming a film, by using oblique vapor deposition, alignment treatment can be performed simultaneously with film formation. Further, in the present invention, the alignment directions of the liquid crystals 3 in contact with the substrates 1 and 2 can be made to be different from each other, and the molecules of the liquid crystal 3 in the middle thereof can be arranged in a twisted structure. In this liquid crystal cell, a linear polarizing plate 8 is arranged on the incident light 9 side. The linear polarizing plate 8 is arranged so that its transmission axis direction lO is perpendicular or substantially perpendicular to the homogeneous arrangement I of the liquid crystal. When the transparent resistors 4 and 5 are not energized, the liquid crystal The refractive index of 3 is no for the incident linearly polarized light, and at this time, ng and no of the substrate 1 are no (ng, so this incident linearly polarized light is larger than the ng angle determined by ml, -I(-) When the light is incident at an incident angle of 0, it is totally reflected and becomes totally reflected light 12. On the other hand, the linearly polarized light 9' that is incident at an angle 0g smaller than m-' (=-) is transmitted through the liquid crystal 3.

On the other hand, when the transparent resistors 4 and 5 are heated by energizing them, the liquid crystal 3 can undergo a phase transition to an isotropic liquid phase I. FIG. 6 shows the temperature dependence of the nematic phase-liquid phase of liquid crystal. In FIG. 6, C130 is the refractive index (net) of the extraordinary ray of the liquid crystal.

31 is the refractive index of ordinary rays (no), 32 is the refractive index of the liquid phase (n, lo), and it is understood that around 40°C is the nematic phase-liquid phase transition point (N-I point) 33. There is a C.

Since the refractive index n5° of the liquid phase I satisfies ng<nran, the incident linearly polarized light 9' can be transmitted through the liquid phase I to become the transmitted light 11, regardless of the angle thereof.

In addition, the transparent substrates 1 and 2 have prisms as shown in FIGS. 1 and 2. It is preferable to use a right-angled prism for hemorrhoids as shown in FIG.

As mentioned above, a liquid crystal has a refractive index of ordinary light +1'o, a refractive index of its isotropic liquid phase n,9°, and a refractive index of the transparent substrate ~. Since it is necessary to have a relationship, the liquid crystal and the transparent substrate are selected so as to satisfy the above relationship.For example, the refractive index no of ordinary rays is 1.
52 and the refractive index n□ of its liquid phase. is 1.60, and the refractive index of the glass substrate is ng75 (
1.58, the refractive index of the transparent resistor in an unheated state for incident linearly polarized light is 1.52 (no), so s! TI−+ (−E”) = = 1(
! ) The linearly polarized light is totally reflected at an angle determined by ng 1.58 = 74.2°, and then the transparent resistor is heated by electricity to undergo a phase transition from the nematic phase to the liquid phase. The refractive index for the liquid phase changes to l, 60 (nl, lo), and at this time ng (na.), so that the incident linearly polarized light passes through this liquid phase.

Sub-C1 In the device of the present invention, incident light can be totally reflected or transmitted by heating with a transparent resistor or without heating.

Further, as a method for heating the liquid crystal, in addition to the above-mentioned method of heating by energizing a transparent resistor, a method of heating with a laser or the like can also be used.

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 the line A-λ. In Figures 3 and 4,
The liquid crystal-optical shutter array 13 includes a plurality of shutter sections 1
4, this shutter section 14 is equipped with a transparent resistor 1.
It has a structure in which a liquid crystal 17 is sandwiched between 5 and 16.

The transparent resistors 15 and 16 are provided on the opposing surfaces of the columnar right-angle prisms 19 and 20, respectively, and are
o and its liquid phase n7. . The liquid crystal and the right-angle prism are selected so that ng of the right-angle prism and ng of the right-angle prism have the above-mentioned relationship (no < ng < nws.). Further, on the incident light side, a linear polarizing plate 18 having a transmission axis perpendicular or substantially perpendicular to the direction when the liquid crystals are arranged in a homeotropic state is arranged.

By using this shutter array 13, it is possible to irradiate a photosensitive member such as a photosensitive drum with either one of the liquid phase transmission yf and the total reflection light. Then, the shutter section 14
By opening the photosensitive drum with respect to the photosensitive drum, a desired latent image can be formed, and then image formation can be performed.

FIG. 5 is an explanatory diagram of a deaf person using the optical control device (liquid crystal-optical shutter array) of the present invention in an electrophotographic printer. In FIG. 5, the light source 21 is always on and constantly illuminates the liquid crystal-optical shutter array 13. The shutter array 13 transmits or totally reflects the light beam from the light source 21 using a liquid crystal drive circuit (not shown) to generate an optical signal, and can control the light beam irradiated onto the photosensitive drum 22. Further, in order to obtain a condensing property for 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 glass 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 in the area 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 has the opposite polarity to the polarity at the time of charging in the developing section 26, or the same polarity when reverse development is performed7).
After developing by a magnetic brush development method or the like while applying a developing bias in the presence of a developer consisting of toner and carrier, the image is transferred to an image holding member 28 (for example, paper) at a transfer section 27, and then at a fixing section 29. It is fixed using heat, pressure, etc., resulting in a completely fixed print.

The photoreceptor, which receives the optical signal generated from the shutter array 13, is not limited to the electrophotographic type described above, but also the photoreceptor of the silver salt photography type (for example, (such as 3M's "Dry Silver").

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, bright transmitted light can be obtained with less loss of light rays.

(3) When used in a camera shutter or a shutter array in a light-emitting printer, there is no leakage of light from the shielding shutter, and unnecessary information is not photographed or leaked. In conventional shutters using twisted nematic mode, a few beams of light leak when the shutter is closed and closed, but the present invention can completely block incident light.

(4) High-speed control of the optical shutter is possible.

(5) A large optical shutter is possible.

(6) High speed optical shutter is possible.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 1f 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 the line A-x. 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. FIG. 6 is an explanatory diagram showing the temperature dependence of the refractive index of nematic liquid crystal. 1.2...Transparent substrate 3...Liquid crystal 4.5...
Transparent resistor 6... Seal spacer 7... Orientation film 8... Polarizing plate 9... Incident light Re... Incident linearly polarized light 10... Transmission axis direction of polarizing plate 11... Transmitted Light 12... Totally reflected light θ...
Incident angle H: Homogeneous array state I.
...Liquid phase 13...Liquid crystal-optical strength 14...7 cross section 15, 16...Transparent resistor 17...Liquid crystal layer 18...Polarizing plate 19
, 20... Column-shaped 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...Fusing unit Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] In the optical side #device in which a liquid crystal is sandwiched between a pair of substrates,
Between the substrates, at least one of which is transparent"< ng <
nzs. a liquid crystal cell sandwiching a homogeneously aligned liquid crystal, a heating means for raising the temperature of the liquid crystal to an isotropic liquid, and a transmission axis direction perpendicular or approximately 100 angles to the molecular axis direction of the homogeneously aligned liquid crystal; An optical control device ( However, ng is the refractive index of the transparent substrate, n
o is the ordinary light refractive index of the liquid crystal molecules, and nfso is the refractive index when the liquid crystal molecules become an isotropic liquid).