JPH0245170B2 - SUMEKUTEITSUKUEKISHOSOCHINIOKERUEKISHOBUTSUSHITSUCHUNYUHOHO - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for injecting liquid crystal material suitable for chiral smect liquid crystal devices.

(Prior Art) In recent years, liquid crystal devices using chiral smectate C phase have attracted attention as display devices, optical shutters for cameras, and printers because of their high-speed response and memory retention properties.

As a ferroelectric liquid crystal compound having this chiral smectic C phase, for example, P-decyloxybenzylidene-P-amino-2-methybutylcinnamate is widely known, and its liquid crystal molecules are shown in Figure 7. As shown in the figure, each layer L ₁ , L ₂ , L ₃ , and L ₄ is arranged in a twisted spiral structure with a constant azimuth angle θ.

By the way, a liquid crystal cell is constructed by injecting a liquid crystal compound having this chiral smect C phase between two substrates A and B with a gap (for example, about 1 μm) smaller than the helical period (usually several μm). Then (Fig. 8A), the liquid crystal molecules lose their helical structure and their molecular axes are made parallel to substrates A and B, with domains tilted at an angle θ clockwise from the normal direction of the layers and domains tilted at an angle θ counterclockwise. In other words, it has a mixed state of -θ-inclined domains (FIG. 2B) and an electric dipole in a direction perpendicular to the molecular axis.

Therefore, if one domain has an electric dipole pointing upward with respect to substrates A and B, the other domain will have an electric dipole pointing downward, thus applying an electric field between substrates A and B. Then, all the liquid crystal molecules are aligned in positions tilted either +θ or -θ from the normal direction of the layer, and when an electric field in the opposite direction is applied, the liquid crystal molecules are also reversed and tilted -θ or +θ. Arrange them so that they are lined up all at once.

When polarizing plates are placed on both sides of this panel and an electric field is applied, a bright state and a dark state are generated due to the movement of liquid crystal molecules, allowing it to function as a display panel or light shutter (FIG. 9). The liquid crystal panel constructed in this manner has an extremely fast response speed of microseconds and an excellent property of retaining the displayed pattern even after the electric field is removed.

By the way, as mentioned above, since the gap length between the two substrates is extremely small, the slight gap length difference greatly affects the flow direction of the liquid crystal substance when it is injected, as shown in Figure 10. occurs.

However, in order to exhibit the above-mentioned excellent electrical properties, even if the orientation direction of the liquid crystal molecules on one substrate is regulated by uniaxial alignment, the orientation direction of the liquid crystal molecules on the other substrate is controlled by uniaxial alignment. Processes such as random orientation are performed to create a free surface that is easy to move. For this reason, the initial alignment state of the injected liquid crystal material on the substrate surface is controlled by the inflow direction of the injected liquid crystal, and a desirable random alignment state cannot be obtained, resulting in variations in opto-electrical characteristics. It was hot.

(Objective) In view of the above-mentioned problems, an object of the present invention is to propose a method for injecting a liquid crystal material that can obtain a uniform initial alignment.

(Means for Solving the Problem) That is, the present invention is characterized in that the temperature gradient in the inflow direction is changed in accordance with the inflow speed of the liquid crystal.

(Example) The details of the present invention will be described below based on illustrated examples.

FIG. 1 shows an example of an injection device used in the present invention, in which reference numeral 1 indicates a vacuum container 5 which selectively communicates with an atmosphere opening 3 and a vacuum pump 4 via a switching valve 2. With the liquid crystal cell gripper housed in the
A liquid crystal cell and a sheet-like heater, which will be described later, are alternately overlapped and held, and are configured to be moved up and down by a drive mechanism (not shown). Reference numeral 6 denotes a liquid crystal heating tank disposed below the gripping mechanism 1, which is configured to maintain a temperature at which the smectic liquid crystal substance maintains a liquid phase.

FIG. 2 shows an embodiment of the above-mentioned sheet-like heater, in which heating wires 8 are arranged in a meandering manner on a thin plate 7 that covers the surface of the panel into which the liquid crystal substance is to be injected, and at regular intervals. It is configured so that the power supply terminal can be pulled out and the heating wire 8 can be divided into five sections 8a to 8f for use.

FIG. 3 shows an embodiment of a cell constituting a smectic liquid crystal panel used in the present invention, and reference numeral 10 in the figure denotes one substrate constituting the liquid crystal display panel, which is made of a transparent conductive material. A thin film of polyimide is provided by printing or dipping on the surface of the electrically insulating transparent plate 10b made of glass or the like on which the segment electrodes 10a, 10a, 10a, . It is constructed by forming a random horizontal alignment film layer 10c having the following characteristics. 12 is the other substrate constituting the liquid crystal display panel, and segment electrodes 10a, 10
The common electrode 12 is perpendicular to a, 10a...
A uniaxially oriented film in which a thin film of polyimide is provided on the surface of the electrically insulating transparent plate 12b on which the elements a, 12a, 12a... are formed, and the surface of this thin film is rubbed in one direction to give orientation in only one direction. layer 12c
It is composed of the following. These two boards 1
0 and 12, the random horizontal alignment film layer 10c and the uniaxial alignment film layer 12c are arranged facing each other in parallel with a gap smaller than the helical pitch of the liquid crystal compound, and a liquid crystal injection port 14 is provided on one side. They are joined together using a sealant 16 to form a panel.

Next, the operation of the apparatus configured as described above will be explained.

The sheet-like heater 20 is stacked on the liquid crystal panel 22 and attached to the gripping mechanism so that the heating wire 8 is parallel to the lower end surface where the injection port 14 is formed (FIG. 4).
Further, the heating tank 6 is filled with a smectic liquid crystal material, and the vacuum container 5 is drawn to a predetermined vacuum pressure.

When these preparations are completed, power is supplied to the heating wire at the bottom end of the sheet heater to ensure that the area directly above the injection port of the liquid crystal panel 22 is horizontally uniform and the liquid phase is uniform as shown in FIG. Heat to a temperature that can be maintained (Figure 6).

In this state, when the gripping mechanism 1 is moved downward to immerse the inlet 14 of the liquid crystal panel 20 into the liquid crystal material in the heating tank 6, and then the switching valve 2 is communicated with the atmosphere opening 3, the heating tank The liquid crystal material in 6 gradually enters the panel 20 through the inlet 14 under atmospheric pressure.

By the way, as mentioned above, only the bottom edge of the panel is heated to a high temperature evenly in the horizontal direction, so
The liquid crystal flowing in from the injection port 14 has high fluidity and quickly spreads horizontally so that the tip becomes horizontal (), and then the tip of the liquid crystal substance is horizontally moved to the area heated to a high temperature by the heating wire 8a. Rise while held at (). At this point, when the next stage heating wire 8b is also energized, since the heating wire is arranged horizontally, the high temperature region of the panel is expanded parallel to and directly above the liquid crystal material that has flowed in. As a result, the liquid crystal inside the panel gradually moves upward while keeping its tip in a horizontal position ().

Thereafter, by energizing the heating wire placed directly above the tip in accordance with the inflow speed of the liquid crystal, the liquid crystal material rises inside the panel while keeping its tip horizontal. Fill inside panel(). As a result, the liquid crystal material in contact with the randomly horizontally aligned substrate side exhibits good random alignment, and the liquid crystal material injected into the panel as a whole forms a uniform initial alignment.

In the above-described embodiment, a plurality of liquid crystal panels are stacked and injected at the same time, but it goes without saying that the same effect can be obtained even if the injection is performed on a single panel. Furthermore, in the above embodiment, the panel is heated by placing the sheet-shaped heater in close contact with the panel, but the same effect can be obtained by using a heater in which a heating wire is wound around a body-shaped base that can accommodate the panel. To tank.

Furthermore, in the above examples, 2-methylbutyl-P (P-n-decyloxybenzylideamino) was explained, but the general formula A pyridine-based liquid crystal compound represented by S-4
-0(2-methyl)butyl-resolcylidene-4
-Alkyl n-tictylaniline and P-n-octylphenyl-P'-6-methyloctyloxybenzoate A similar effect can be obtained when using a ferroelectric chiral smectic liquid crystal compound formed by mixing equal proportions of the following.

Furthermore, in the above embodiment, a substrate having a uniaxially oriented film layer and a random horizontally oriented film layer formed of polyimide on the surface was used, but the uniaxially oriented film could be replaced by an organic film such as polyvinyl alcohol, fluororesin, silane, etc. A substrate formed by SiO ₂ oblique evaporation film, etc., and a random horizontal alignment film formed by epoxy, etc.
Organic films such as polyvinyl alcohol, fluororesin, polyurethane, silane, phenol, urea, etc.
It was confirmed that the same effect can be achieved when using a substrate made of an inorganic film formed by vapor-depositing SiO ₂ or MgF ₂ .

(Effects) As explained above, in the present invention, the area directly above the tip of the smectic liquid crystal that has flowed into the liquid crystal panel is heated so that the temperature is uniform in the horizontal direction. The inside of the panel can be raised with the affected inflow tip corrected to a horizontal state, and a smectic liquid crystal panel with uniform initial orientation can be constructed.

[Brief explanation of drawings]

FIG. 1 is a side view of an injection device used in the present invention, and FIG. 2 is a partial sectional view showing an example of a sheet heater used in the same device.
3A and 3B are a perspective sectional view and a side view of an apparatus showing one embodiment of the liquid crystal panel used in the present invention, respectively; FIG. 4 is a perspective view showing the relationship between the liquid crystal panel and the sheet-like heater; Figures 5A and 5B are explanatory diagrams showing the temperature distribution of the liquid crystal panel, Figures 6 to 5 are explanatory diagrams showing the inflow state of liquid crystal substances, and Figure 7 is a diagram showing the molecular arrangement of chiral smectate liquid crystal. The formula diagram, Figures 8A and 8B are schematic diagrams showing the arrangement of molecules when the panel gap is less than the helical pitch of the liquid crystal molecules, and Figure 9 is an explanation showing the relationship between the domains of the smectic liquid crystal and polarization. 1 and 10 are explanatory diagrams showing the state of inflow of liquid crystal material in the conventional method. DESCRIPTION OF SYMBOLS 1... Substrate, 1a... Electrically insulating transparent plate, 1c... Random horizontal alignment film layer, 2... Substrate, 2a... Electrically insulating transparent plate, 2c... Uniaxial alignment film layer, 3... Inlet, 4
...Sealing material.

Claims (1)

[Claims] 1. Reduce the pressure inside the panel structure in which the liquid crystal injection port is formed, and immerse the injection port side in the smectic liquid crystal material that has become a liquid phase, and at the same time, immerse the area directly above the tip of the liquid crystal material in the panel structure in the horizontal direction. 1. A method for injecting a liquid crystal material in a smectic liquid crystal device, characterized in that after uniformly heating the panel structure, the heating area of the panel structure is sequentially expanded according to the inflow speed of the liquid crystal material.