JPS63109419A - Liquid crystal panel - Google Patents

Abstract

PURPOSE:To simplify the production method of a liquid crystal panel and to strengthen the memory state of ferroelectric liquid crystal against vibration or shock by forming an optical modulating element as a liquid crystal film formed by a composite material consisting of a high molecular component and liquid crystal. CONSTITUTION:The liquid crystal is mixed with the high molecular component to form a composite film. Then, the orientation of the liquid crystal molecules is controlled by extending the composite film in one direction to form a liquid crystal film. Thereby, stages such as the spraying of spacer and the application and injection of an orientation film can be omitted and the whole stage can be simplified. Even if the cell thickness of a ferroelectric liquid crystal panel or the like consisting of upper and lower polarizing plates 1, upper and lower glass bases 2, a transparent electrode layer 3, and a composite film constituted of the ferroelectric liquid crystal and the high molecular component is thinly formed, the cell thickness can be easily formed because of the composite film consisting of the liquid crystal and the high molecular components and the memory state of the ferroelectric liquid crystal can be strengthened against vibration or shock.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device or a liquid crystal panel for optical shutter, and more particularly to a ferroelectric liquid crystal panel.

Conventional technology The conventional technology will be explained below with reference to the drawings.

Currently, T N (Twist) is the most popular liquid crystal display panel.
dNe＋＊atic: twisted nematic)
The type display method is the most widely used. However, since there is a limit to display capacity, improvements are desired.

Recently, display systems using ferroelectric liquid crystals have been announced, and are attracting much attention because of their fast response time and potential for high matrix properties.The present invention applies to these liquid crystal display systems. The aim is to develop suitable liquid crystal panels.

First, the configuration of a conventional liquid crystal panel will be described below with reference to the drawings.

FIG. 2 is a diagram showing the configuration of a conventional liquid crystal panel.

As shown in FIG. 2, a liquid crystal 23 sandwiched between glass substrates 21 having a transparent conductive film 22 on the surface thereof is oriented in a certain direction by an alignment film 24 that has been subjected to an alignment treatment. Further, a spacer 25 made of glass, plastic, etc. is used to make the cell thickness uniform. 26 is a polarizing plate.

In normal TN or GH (guest-host) type panels, the cell thickness is approximately 5 to 10μm, and in ferroelectric liquid crystals, the cell thickness is set to be as thin as approximately 2μm in order to utilize the surface memory effect. There is a need to.

In addition, the manufacturing process involves first applying an alignment film to a glass substrate with a transparent conductive film, and then rubbing as an alignment treatment.After that, glass fibers are usually uniformly distributed as spacers and the upper and lower substrates are bonded together. After providing a sealing portion and bonding, pressure is applied to create an empty panel with uniform cell thickness. Thereafter, it is necessary to inject liquid crystal into the empty panel by immersing the panel in liquid crystal in a vacuum and returning it to normal pressure.

Next, ferroelectric liquid crystal will be explained using drawings. First, let's explain about ferroelectric liquid crystals using diagrams.0 Ferroelectric liquid crystals are liquid crystals that exhibit ferroelectricity.From the theory of crystal symmetry, in order to exhibit ferroelectricity, liquid crystal molecules must first be It must have an asymmetric center. It also needs to have a layered structure and the molecules within the layers need to be tilted. As crystal phases that satisfy such symmetry, smectic C chiral phase,
Smectic 1 chiral phase, smectic C chiral phase, etc. have been discovered so far and are recognized as ferroelectric liquid crystal phases.

In this specification, the properties will be explained using the smectic C chiral phase, which has the highest symmetry among ferroelectric liquid crystal phases. FIG. 3 is a schematic diagram of ferroelectric liquid crystal molecules. Ferroelectric liquid crystal is usually a liquid crystal having a layered structure called smectic liquid crystal.

The molecules are tilted by θ with respect to the normal direction of the layer.

In addition, ferroelectric liquid crystals have an asymmetric center and are composed of optically active liquid crystal molecules that are not racemic.As shown in Figure 3, ferroelectric liquid crystal molecules are perpendicular to the long axis of the molecules. It has a permanent dipole moment that becomes spontaneously polarized in a direction such that it can move freely outside the conical shape (hereinafter referred to as a cone) in FIG. 3 in the chiral smectic C phase. Further, the vector directed from the center point O of the cone toward the liquid crystal molecules is called the C director.

In Figure 3, 31 is a liquid crystal molecule, 32 is a permanent dipole, 3
3 is a C director, 134 is a cone, 35 is a layered structure, 3
6 indicates the layer normal direction, and 37 indicates the inclination angle θ.

Ferroelectric liquid crystal molecules usually have a twisted structure because they contain asymmetric atoms. This twisted structure is shown in FIG. 4. From FIG. 4, it can be seen that the twisted structure exists in the normal direction of the layer.

In FIG. 4, 41 is a liquid crystal molecule, 42 is a permanent dipole moment, 43 is a pinch (L) representing the period of twist, and 44
represents the layer structure, 45 represents the normal direction of the layer, and 46 represents the angle θ.

Next, we will explain the operating principle of ferroelectric liquid crystal using a diagram.When cell P1(d) of a ferroelectric liquid crystal panel is thicker than the pitch (d>L), the influence of the cell substrate surface extends to the center of the cell. Therefore, it usually exists in a twisted structure. However, when the cell thickness is smaller than the pitch (d
) The twisted structure is unraveled by the force of the substrate surface, and two regions (domains) appear in which molecules such as (al) are parallel to the substrate surface. They are oriented in opposite directions, one from the back to the front of the paper and the other from the front to the back of the paper. This corresponds to the flJt angle of the molecule with respect to the layer normal, respectively. .

At this time, when an electric field is applied from the back to the front of the paper, all the permanent dipole moments are directed in the direction of the electric field, and all the molecules have an inclination angle of 10, as shown in Figure 5). In this state, if the polarization axis of the polarizer (P) of the polarizing plate is made parallel to the long axis of the molecule and the polarization axis of the analyzer (A) is made parallel to the short axis of the molecule (see Figure 5 (bl) ) Polarizer (P)
The linearly polarized light that has passed through passes through the analyzer (
A) and a dark state is obtained. Furthermore, when an electric field is applied in the opposite direction, the molecules all have a tilt of 10 as shown in Figure 5 (C), and the linearly polarized light that passes through the polarizer becomes bright when it passes through the analyzer due to the birefringence effect. It will be done.

Figure 5 + al, (bl, (In C1, 51 is the direction of the electric field, 52 is the permanent dipole moment of the molecule, 53 is the layer structure, 54 is the tilt angle θ, 55 is the polarizer (P), 56 is the analyzer (A ) respectively represent the polarization axes.

As described above, bright and dark states can be obtained depending on the positive and negative electric fields.

(Literature: width, confabulation, near sleep, high-speed display using diferroelectric liquid crystal, Optronics, No. 9, p. 64, 19
1983) Also, in this way, the cell thickness is smaller than the pitch (d<L
), the twisted structure is usually untwisted, so the molecules remain stable even after the electric field is removed, causing a so-called memory effect. This memory effect is an effect due to the surface, and therefore, in order to use this memory effect, the cell thickness must be approximately 2.0 μm.

Problems to be Solved by the Invention However, the above-mentioned panel configuration required many steps and took a long time for injection. In particular, with ferroelectric liquid crystals, the cell thickness is small, making it difficult to create a uniform panel, and there are also problems in that a large amount of injection time is required. In addition, ferroelectric liquid crystal panels have the problem of being susceptible to vibration or static since they use a surface memory effect. In particular, ferroelectric liquid crystal panels have the problem of having to have a cell thickness of about 2.0 μm.

Means for Solving the Problems In order to solve the various problems mentioned above, liquid crystal is mixed with polymer to create a composite film, and then the orientation of the liquid crystal molecules is controlled by stretching in one direction. It is characterized by creating liquid crystal film.

Function Liquid crystal is mixed with a polymer to create a composite film, and then stretched in one direction to control the orientation of the liquid crystal molecules.By creating a liquid crystal film, it is possible to spray spacers, apply an alignment film, inject, etc. Steps can be omitted and the process can be simplified. Furthermore, even in the case of a thin cell such as a ferroelectric liquid crystal panel, since it is a composite film with a polymer, it is easy to produce, and it also has the effect of being strong against vibrations and shocks.

EXAMPLE A composite material of a ferroelectric liquid crystal and a polymer will be described below as an example of the present invention with reference to the drawings.

First, the method for manufacturing the composite membrane used will be explained.

Polyvinyl chloride (PVC) was used as the polymer. As the ferroelectric liquid crystal, a mixed liquid crystal material C31015 manufactured by Chisso Corporation was used.

The preparation method is to add PvC and C51 to a cyclohexanone solution.
015 at a ratio of 5:2 to prepare a mixed solution.

After this, apply approximately 30μ on a Teflon plate using a roll coater.
It was applied to a film thickness of m, heated, and dried. After drying, it was stretched in one direction to a thickness of about 5 μm using a stretching machine.

The stretched composite film was heated to about 100° C. so that the ferroelectric liquid crystal C31015 became an isotropic liquid, and then slowly cooled to room temperature.

The orientation of the ferroelectric liquid crystal in the composite film thus prepared was observed using a polarized 8Ji microscope. By applying an electric field under crossed Nicol conditions, clear brightness and darkness could be observed depending on the positive and negative electric fields. Next, the optical properties of the composite film thus prepared were measured. The optical measurement system used will be explained using the drawings. In order to measure the characteristics of the composite film used here, a liquid crystal panel as shown in FIG. 1 was prepared. Here, 1 is the upper and lower polarizing plates, 2 is the upper and lower glass substrates, 3 is the transparent electrode layer, 4 is the composite film of ferroelectric liquid crystal and polymer, and the composite film of ferroelectric liquid crystal is placed between the opposing electrodes. A ferroelectric liquid crystal panel was created by encapsulating it.

Next, using this panel, a voltage-transmittance curve (hereinafter referred to as B-
V curve) was measured. The optical experimental system used for measuring the BV curve is shown in FIG. In FIG. 6, white light emitted from a light source 61 passes through a polarizer 62 and enters a liquid crystal cell 63 as linearly polarized light, passes through an analyzer 64, is focused by a condensing lens 65, and is sensed by a photomultiplier tube 66. , measured by the storage oscilloscope 67 as a BV curve. Note that an arbitrary waveform can be applied to the liquid crystal cell by a programmable pulse generator 68.

In such an experimental system, the BV curve of the ferroelectric liquid crystal panel having the above-mentioned configuration was measured. Further, the cell thickness of the ferroelectric liquid crystal panel used was approximately 5.0 μm.

The obtained BV curve is shown in Figure 7 (al, +bl).
Figure 7 181. lb), the horizontal axis is time < 1), and the vertical axis is voltage (V) or brightness (B).
FIG. 181 shows the applied voltage waveform, and the seventh peak) shows the corresponding brightness curve. From this drawing, firstly, in FIG. 7 181, a positive applied pulse (peak value +20V).

Width 1. Qmsec) was applied, and the corresponding luminance change in FIG. 7(b) was from a dark state to a bright state. Ov for 1.0 sec after the positive pulse is applied.
The situation continues.

Even in this Ov state, the brightness remains bright and a memory effect exists. After that, a negative applied pulse (peak value -20V
, width l, Qmsec), and the brightness changed from the bright state of the memory state to the dark state. This dark state also had memory properties and did not change until a positive pulse was applied 1.0 seconds later. Also, this memory state was not affected by shock or vibration because it was a composite membrane with polymers.

Effects of the Invention The liquid crystal film of the present invention makes the conventional liquid crystal panel manufacturing method a cylindrical one, and has the effect of making the memory state of ferroelectric liquid crystals more robust against vibrations and shocks. there were.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a panel using the liquid crystal film of the present invention, FIG. 2 is a schematic diagram showing the configuration of a conventional liquid crystal panel,
Figure 3 is a schematic diagram of ferroelectric liquid crystal molecules, Figure 4 is a schematic diagram showing the twisted structure of ferroelectric liquid crystal, Figure 5 +a+, (
bl, (el is a schematic diagram showing the display principle of ferroelectric liquid crystal, Figure 6 is a schematic diagram showing the optical experimental system for measuring the BV curve, Figure 7 (a) This is a graph showing the B-V curve of a liquid crystal panel with the following configurations: 1...Polarizing plate, 2...Glass substrate, 3
......Transparent electrode layer, 4...Composite film, Name of agent: Patent attorney Toshio Nakao and one other person
-Fu m anti 4 - η4 E erum? Figure 2 Figure 3 A Figure 4 Blood Figure 5 Figure 6 Figure 7 Weighing (also)

Claims (6)

[Claims] (1) A liquid crystal panel characterized in that the optical modulation element is a liquid crystal film made of a composite material consisting of a polymer and liquid crystal. (2) The liquid crystal panel according to claim (1), wherein the liquid crystal is a ferroelectric liquid crystal. (3) The liquid crystal panel according to claim (1), wherein the liquid crystal contains a pleochroic dye and is used in a guest-host mode. (4) The liquid crystal panel according to claim (1), which is a liquid crystal film in which alignment of liquid crystals is controlled by stretching a composite material made of a polymer and liquid crystals. (5) The liquid crystal panel according to claim (4), wherein the liquid crystal is a ferroelectric liquid crystal. (6) The liquid crystal panel according to claim (4), wherein the liquid crystal contains a pleochroic dye and is used in a guest-host mode.