JPS62153819A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To increase brightness and to enhance contrast without using a polariz ing plate by twisting the orientation of GH effect type liquid crystals filled in a space between substrates. CONSTITUTION:Liquid crystal 15 comprises a GH effect type one constituted of host liquid crystal molecules 15a and guest dichroic dye 15b. The axial direction of the liquid crystal molecules 15a is twisted by 180-450 deg. within a range between a signal electrode substrate 11 and a common electrode substrate 12 as the liquid crystals are filled between the substrate 11 and 12. When high frequency electric field is impressed to the liquid crystal 15 between the signal electrode 18 and the common electrode 22, the liquid crystal molecules 15a and the dye molecules 15b are oriented in the twisted state, and a shutter part S is turned OFF. Further, when low frequency electric field is impressed, the liquid crystal molecules 15a are oriented perpendicularly to the dye molecules 15b, and the shutter part S is turned ON.

Description

[Detailed description of the invention] [Technical field of invention] Concerning children.

[Technical background of the invention and its problems]

BACKGROUND ART Recently, liquid crystal elements in which a large number of minute shutter portions for controlling light transmission are arranged are used for optical writing in optical writing printers, image display in television receivers, and the like.

Among such liquid crystal elements, a liquid crystal element used for optical writing, that is, a liquid crystal shutter, is constructed by disposing a pair of transparent substrates facing each other with a liquid crystal layer made of a GH (dust-host) effect type liquid crystal sandwiched therebetween. , a large number of transparent signal electrodes are formed on the inner surface of one substrate, and a common electrode is formed on the inner surface of the other substrate so as to face each other, and a metal film is formed on the signal electrodes and the common electrode, leaving a shutter forming portion. Accordingly, a shutter section is formed by a signal electrode and a common electrode facing each other and a liquid crystal between the electrodes, and a large number of these shutter sections are arranged in some cases.

Since this liquid crystal shutter needs to be driven at high speed, a two-frequency drive method that utilizes the dielectric dispersion phenomenon of liquid crystal is adopted. In this driving method, when an electric field of the same high frequency is applied to the liquid crystal, the liquid crystal molecules are aligned perpendicular to the electric field, and when an electric field of a low frequency is applied, the liquid crystal molecules are aligned so as to be parallel to the electric field. In the case of GH-type liquid crystal elements using this drive method, the shutter closes (no light passes through) when high frequency is applied.
・Coloring), the shutter opens when low frequency is applied (light transmission...
・No coloring).

However, in the conventional liquid crystal shutter using the G-H effect liquid crystal, as shown in FIG.
In addition, a configuration in which a polarizing plate 4 is provided on the light incident side is adopted. In other words, by aligning the vibration plane of the incident light with the long sleeve direction of the dye molecules dissolved in the liquid crystal (the direction of the initial orientation of the liquid crystal molecules), light leakage in the closed state is prevented, and the liquid crystal shutter is High contrast in open and closed states.

However, in such a configuration, the light from the light source passes through the polarizing plate before entering the liquid crystal, so a portion of the light is absorbed by the polarizing plate. For this reason, the amount of light in the open state of the shutter section is less affected by the transmittance of the polarizing plate, and the open state becomes very dark and the contrast with the closed state is low. Furthermore, if the concentration of the dye added to the GH effect type liquid crystal is lowered in order to increase the brightness between the shutter parts and the shutter part, the contrast between the closed state and the open state of the shutter part will be reduced.

[Purpose of the invention]

The purpose is to provide ana.

GH effect practical use By aligning liquid crystal with a twist angle and regulating the light passing through the liquid crystal itself, a shutter can be constructed without using a polarizing plate.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings, taking as an example a liquid crystal element used for optical writing in an optical writing printer.

Optical writing printers control light from a light source using a liquid crystal element, and perform optical writing by irradiating the light beam transmitted through the liquid crystal element as a light spot on the surface of a photosensitive drum. This device develops an electrostatic latent image on the surface of a photosensitive drum using toner, transfers it onto recording paper, and then fixes the transferred toner image on the recording paper to perform printing.

The liquid crystal element has a horizontally elongated shape along the axial direction of the photosensitive drum, and has a large number of shutters formed at close intervals along its length to control the transmission of light.

1 to 5 show liquid crystal elements, and here a GH effect type liquid crystal element is shown.

The structure of this liquid crystal element will be explained with reference to FIGS. 4 and 5. In the figure, 11.12 is a pair of upper and lower substrates made of transparent glass plates, and this pair of substrates 11.1;! is bonded via an oblong frame-shaped outer sealing material 13a and a pair of mutually parallel inner sealing materials 1 jb and 13b formed inside both sides of this outer sealing material 131.

Both ends of the inner sealing materials 11b and 13b are connected to both sides of each can outer sealing material 13m, and the substrate 11
Inner sealing material 13b between e11.

The area surrounded by the outer seal member 13b and both sides of the outer seal member 13a is filled with air and has a total diameter of 14°14. The inner sealing material 13b.

Both ends of the narrow portion between the substrates 11 and 13b are communicated with wide portions at both ends of the outer sealing material 13, and a GH effect type liquid crystal 15 is filled in the narrow portion and the wide portion between the substrates 11 and 12. There is. This liquid crystal 15 is injected from a liquid crystal injection hole 16 provided in the outer sealing material 13a, and after injection, the liquid crystal injection hole 16 is sealed with a sealing material 17).

Among the substrates 11 and 12, one substrate 11 (hereinafter referred to as a signal electrode substrate) has inner sealing materials 13b and 1 on its inner surface.
A large number of signal electrodes 18 are formed side by side over the entire length within the narrow portion between the electrodes 3b. Further, on both sides of the inner surface of the signal electrode substrate 11, a large number of lead electrodes 19 are formed side by side, which are led out alternately on the left and right from the signal electrodes 18, and outside the outer sealing material 13m. The lead electrodes 19 are located on both edges of the inner surface of the substrate 11.
A large number of terminal electrodes 20 connected to... are formed side by side. Note that each of these electrodes 18..., 19...
... and 20... are integrally formed of a transparent electrode material such as indium oxide. The signal electrode 18...
・A metal film 21 made of a low resistance metal such as chromium or gold is deposited on a portion that does not correspond to the shutter portion to be described later and on the lead electrode 19.r. 21... Provided to reduce the electrical resistance of the signal electrodes 18... and lead electrodes 19... to which peelings are attached.

(9) On the inner surface of the other substrate 12 (hereinafter referred to as the common electrode substrate), two strip-shaped common electrodes 22° 22 are formed in parallel with a minute interval, facing the signal electrodes of the signal electrode substrate 11. .

The common electrodes 22.22 are the signal electrodes 18..., the lead electrodes 19... and the terminal electrodes 20 of the signal electrode substrate 11.
A signal electrode, a lead electrode, and a paneel electrode corresponding to the above are integrally formed, and are made of a transparent conductive material such as inzoum oxide. A metal film 23.23 made of a low-resistance metal is deposited on the common electrode 22.22, except for a shutter portion to be described later. This metal film 23
23 is provided to reduce the electrical resistance of the common electrodes 22 and 22 and to regulate the light transmission area of the shield portion.

Further, each signal electrode 1 is provided on the inner surface of the signal electrode substrate 11.
An alignment film 24 is formed on the inner surface of the common electrode substrate 12 to cover a region where the liquid crystal 15 is sealed, including the surface of the common electrode 18. The orientation of GILLS is formed. The alignment films 24 and 25 are each subjected to horizontal alignment treatment, and the surfaces thereof are subjected to rubbing treatment in a predetermined direction.

The direction of this rubbing process is set according to the twist angle of the liquid crystal 15, which will be described later.

Here, the liquid crystal 15 will be explained. The liquid crystal 15 has host liquid crystal molecules 1 as shown in FIGS. 1 and 2.
5h and dichroic dye 15b, which is dust, for the GH effect type.

Then, this liquid crystal 15 is filled between the two substrates 11 and 12, from the signal electrode substrate 1 to the common electrode substrate 1.
2, the axial direction of the liquid crystal molecules 15& is twisted at a predetermined angle. The twist angle of the liquid crystal molecules 15a is set within a range of 180 to 450°C. This is at least 180 degrees so that the long axes of liquid crystal molecules are oriented in all directions from one substrate to the other.
If the twist angle becomes large, uniform orientation cannot be obtained and the optical rotation dispersion becomes large.
Set to a range of

For this purpose, an optically active substance (Keitzl substance) which gives a twisting effect to the liquid crystal molecules 15& is mixed in the liquid crystal 15, and furthermore, as shown in FIG.
A according to the twist angle of 15m of liquid crystal molecules in tz4*xs
Two pinging processes are performed in the direction and B direction, and by rubbing the alignment films 24 and 25, an alignment regulating force is applied to the liquid crystal molecules 15* to twist them at the above-mentioned angle. FIG. 3 shows a state in which liquid crystal molecules are twisted clockwise. As a result, the liquid crystal 15 has the effect of regulating the light passing through the liquid crystal 15 depending on its twist angle. In other words, the incident light consists of light with vibration planes in all directions, but since the dye molecules are also oriented in all directions, all of this light is absorbed by the dye molecules, and the liquid crystal layer It does not pass through.

Therefore, the polarizing plate provided on the light incident side as in the past becomes unnecessary. Note that a dye having a maximum absorption wavelength band corresponding to the emission wavelength band of the light source is dissolved in the liquid crystal 15. This dye is, for example, an azo dye having a high dichroic ratio.

A large number of shutter portions S are formed by the shutter forming portions of each of the signal electrodes 18, the shutter forming portions of the common electrodes 22, 22, and the liquid crystal 15 located between these two shutter forming portions. It is composed of an array of...

In this way, a liquid crystal shutter is constructed, and this liquid crystal does not include a polarizing plate.

Then, when driving the shutter section S..., the first
As shown in the figure, when a high frequency electric field is applied to the liquid crystal 15 between the signal electrode 18 and the common electrode 22, the liquid crystal molecules 75m and the dye molecules 15b of the liquid crystal 15 are oriented in a twisted state. In this case, the dye molecules dissolved in the liquid crystal 15 absorb light rays with vibration planes in all directions of the incident light, so that the shutter section S becomes closed (no light is transmitted).
As shown in FIG. 2, when a low frequency electric field is applied to the liquid crystal 15, the liquid crystal molecules 15a and the dye molecules 15b are aligned perpendicularly (parallel to the direction of the electric field), and since the dye molecules do not absorb incident light, the shutter area The inside becomes open (light transmission).

In this way, when driving the shutter section S..., the liquid crystal 1
5 controls the transmitted light by itself. For this reason,
Since there is no need to provide a polarizing plate and the light from the light source is not blocked by the polarizing plate, the amount of light when the shutter section S is opened can be increased and the brightness can be improved.
The contrast with respect to the closed state of the shutter section S can be increased. Further, since there is no need to lower the concentration of the dye mixed into the liquid crystal, the contrast of the closed state of the shutter S does not deteriorate.

Here, a specific example will be explained.

The liquid crystal used was a liquid crystal material having the composition shown in Table 1 to which 1.5% by weight of the dichroic dye shown in Table 2 was added. As a chiral substance, 2% by weight of CB-15 manufactured by BDH was added. A liquid crystal shutter was manufactured by filling a cell with a thickness of 5.5 μm with this liquid crystal, and this liquid crystal shutter was driven at two frequencies at a high frequency of 200 kHz, a low frequency of 3.31 kHz, a voltage of 30 V, and an interval of 1 rn seconds. It was driven by a method.

Note that the twist angle of the liquid crystal was 2700. As a result,
This liquid crystal shutter has twice the brightness when the shutter is open and more than 1.5 times the contrast compared to conventional ones.

Note that the liquid crystal element of the present invention is not limited to optical writing printers, but can be widely applied to other liquid crystal display devices.

〔Effect of the invention〕

As explained above, according to the liquid crystal element of the present invention, since the alignment of the 90H effect type liquid crystal is twisted between the substrates, it is possible to increase the brightness and contrast without using a polarizing plate. Moreover, it is possible to reduce the thickness.

[Brief explanation of drawings]

1 to 5 show a liquid crystal shutter which is an embodiment of the liquid crystal element of the present invention, FIGS. 1 and 2 are explanatory views showing the open and closed states of the shutter section, and FIG. FIG. 4 is a plan view showing the inner surface of the signal electrode substrate, FIG. 5 is a cross-sectional view of a liquid crystal shutter, and FIG. 6 is a cross-sectional view of a conventional liquid crystal shutter. 11... Signal electrode substrate, 12... Common electrode substrate, 1
5...Liquid crystal, 18...Signal electrode, 22...Common electrode. Figure 3 Figure 6

Claims (3)

[Claims] (1) A liquid crystal for a guest-host effect type, a pair of substrates facing each other with this liquid crystal in between, a first electrode formed on one of the pair of substrates, and a first electrode formed on the other substrate. comprising a liquid crystal and a second electrode that together with the first electrode constitutes a light control section that controls transmission of light, and the liquid crystal is oriented such that the axial direction of the long axis of the liquid crystal molecules is twisted. A liquid crystal element featuring: (2) The liquid crystal element according to claim 1, wherein the twist angle of the long axis of the liquid crystal molecules is 180 to 450°C. (3) The liquid crystal element according to claim 1 or 2, wherein the liquid crystal composition has a maximum absorption wavelength band corresponding to the emission wavelength of the light source.