JPS63237027A - Injection into liquid crystal cell - Google Patents

Abstract

PURPOSE:To prevent degradation of quality for display of a liquid crystal cell without causing change of the cell thickness in an evacuating stage by applying force directing to the liquid crystal cell from two directions oppositely directing to each other and vertical to the substrate of the liquid crystal cell, wherein the application of the force is performed at least once during an injecting stage of the liquid crystal. CONSTITUTION:Force causing no expansion of cell thickness due to the pressure difference and being uniform within a range of the cell surface is applied from directions vertical to a substrate of a liquid crystal and oppositely directing to each other to the cell substrate in the initiating stage of evacuation in a process for injecting liquid crystals utilizing vacuum, to prevent thus the change of the cell thickness. For example, the liquid crystal cell 1 is set in the inside of a pressing jig 2, and fixed with plates 3, 4 having sufficient precision of plane from above and below using torque screws 5. A vacuum tank is evacuated with an externally installed vacuum pump, and the cell is heated uniformly with a heater 6. Then, ferroelectric liquid crystals are dropped from a dispenser 7 in such a manner that an injection port of the liquid crystal is closed by the liquid crystals. Thereafter, N2 is introduced into the vacuum tank and the pressure in the vacuum tank is elevated to atmospheric pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention proposes a method for preventing cell destruction due to pressure difference when injecting liquid crystal into a liquid crystal cell using a vacuum method.

``Prior Art J'' As a method for injecting liquid crystal into a liquid crystal cell, there are already known liquid crystal injection methods using a vacuum.

In particular, as an injection method for a liquid crystal cell using a liquid crystal material exhibiting ferroelectricity, there is a patent filed by the applicant (175192/1960).
No.). The outline of these methods is to place the entire liquid crystal cell in one vacuum chamber, evacuate the inside of the cell, fill the injection port of the cell with liquid crystal material, and gradually increase the pressure inside the chamber. This is a method in which the material is injected using a pressure difference.

``Problems to be solved by the invention'' The vacuum injection method is an effective means for uniformly injecting liquid crystal into the cell, but during the process, the cell is placed in a vacuum chamber and the entire chamber is vacuumed. To create a vacuum inside the cell when starting to draw, it must be evacuated through a narrow injection port, so it is impossible to create a vacuum inside the cell suddenly, and the cell expands due to the pressure difference between the inside of the cell and the vacuum chamber. However, there is a problem in that force is applied in a direction that increases the cell spacing.

In particular, when using a liquid crystal material that exhibits ferroelectricity, two or more types of spacers are used to keep the pair of substrates at a constant distance and to keep the relationship between the two substrates in order to prevent contraction and expansion of the cell thickness. It is often seen to be fixed. However, these fixing forces also have a limit, and cannot cope with the instantaneous force (approximately 1 kg/crl) that is applied at the start of evacuation, resulting in destruction of the cell.

In order to solve this problem, the present invention is designed to prevent the cell thickness from expanding due to the pressure difference in opposite directions perpendicular to the cell substrate when the vacuum starts to be drawn during liquid crystal injection using vacuum properties. It is characterized by applying a uniform force within the cell plane of a certain size to prevent changes in cell thickness.

The present invention will be explained below according to examples.

"Example" FIG. 1 shows an injection device for a liquid crystal cell embodying the present invention.

The liquid crystal cell [1] was installed inside the press jig [2], and force was applied from the top and bottom using the torque screw [5] using plates [3 and 4] with flatness accuracy. In this example,
The cell was fixed to the liquid crystal cell with a force of 1 kg/-.
After that, the vacuum chamber is heated to 1Xl using an external vacuum pump.
The cell was evacuated to 0-' (Torr), and at the same time the cell was uniformly heated to 150 DEG C. using a heater [6]. After that, liquid crystal exhibiting ferroelectricity is dripped from the dispenser [7] so as to block the injection port of the cell, and then the NZ
was put into a vacuum chamber at a rate of 20 cc/min to return it to atmospheric pressure.

As a comparative example, the distribution of cell thickness after vacuum injection in the case of a conventional method in which no pressure is applied [Figure 2(b)].

and Distribution of cell thickness after vacuum injection method according to the present invention [Second
Figure (C)] is shown.

``Effect'' In the case of liquid crystal cells that use liquid crystals that exhibit ferroelectric properties, non-uniformity in cell thickness leads to variations in driving conditions and deterioration of display quality, so the present invention, which can produce uniform cells, is extremely effective. Met.

When bonding cells, even cells with uniform gaps,
During subsequent steps (particularly during evacuation), the cell thickness becomes non-uniform, making repair difficult or impossible.

By using the method of the present invention, the cell thickness did not change even during the evacuation process during liquid crystal injection, and it was possible to prevent deterioration in display quality.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of an injection device used in the present invention. FIG. 2 shows the spacing of cells produced according to the present description.

Claims (1)

[Claims] When injecting liquid crystal into a liquid crystal display cell using a vacuum injection method, force is applied toward the liquid crystal cell from two opposing directions perpendicular to the liquid crystal cell substrate at least once during the liquid crystal injection process. How to inject liquid crystal cells.