JP2568574B2 - Liquid crystal cell manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal cell using a ferroelectric liquid crystal, and is particularly used for aligning a liquid crystal.

2. Description of the Related Art Liquid crystal display devices are used in watches, calculators, and the like because of their advantages such as thinness, weight reduction, and low voltage drive. However, the nematic liquid crystal currently used has a low response speed of several milliseconds to several tens of milliseconds, so that high-speed response is not possible, and the field of application is limited. On the other hand, ferroelectric liquid crystals can be applied to fields such as high-speed display elements, memory-type displays, and liquid crystal shutters because of their response speed and memory effect in units of microseconds. At present, a rubbing method, an oblique deposition method, a magnetic field application method, an electric field application method, a sharing method and the like have been devised as orientation methods, but the rubbing method is the most excellent in terms of mass productivity and practicality. As a conventional rubbing method, a method of directly rubbing on a substrate, a method of rubbing after providing an inorganic coating on a substrate, a method of rubbing after applying a surfactant, a coupling agent, etc. on a substrate, a method of rubbing on a substrate There is a method of rubbing after coating with a polymer such as polyimide, and the rubbing direction is one direction as shown in FIG. 3 (a) or an angle as shown in FIG. 3 (b). The attached multi-directional thing has been devised. In FIG. 3, 11 is a glass substrate, and 12 is a rubbing direction.

Problems to be Solved by the Invention In the conventional rubbing method as described above, there is no problem when the nematic liquid crystal is sealed, but when the ferroelectric liquid crystal is sealed, the liquid crystal molecule regulating force by rubbing is too strong. In many cases, bistability, which is an advantage of a ferroelectric liquid crystal, is lost and the liquid crystal becomes monostable. It is considered that if the force for regulating the liquid crystal molecules by rubbing is too strong, the molecular direction is regulated in the rubbing direction even when voltage is applied, and the liquid crystal molecules immediately return to the regulated direction. In other words, if the molecular direction of the ferroelectric liquid crystal is constant even before the voltage is applied, after the voltage is applied, the liquid crystal molecules are inclined in a fixed direction depending on the direction of the applied voltage, and are maintained for a long time even when the applied voltage is removed. Therefore, it is preferable that the rubbing force for regulating liquid crystal molecules is as weak as possible. However, it is difficult to weaken the regulating force by the conventional rubbing method, and there is a disadvantage that the contrast deteriorates when weak rubbing is performed by reducing the rubbing pressure and the number of times.

Means for Solving the Problems In order to solve the above problems, the present invention performs a rubbing treatment in at least one direction on at least one of the liquid crystal cell substrates sandwiching a pair of glass substrates with electrodes. A rubbing process is performed in the opposite direction, and a ferroelectric liquid crystal is sealed between the substrates.

According to this method, it is possible to create a ferroelectric liquid crystal cell having bistability by relaxing the molecular regulating force by rubbing in the opposite direction, instead of the strong molecular regulating force by the conventional one-way rubbing treatment. It becomes possible.

Examples Hereinafter, examples of the present invention will be described. First, the first
As shown in the figure, transparent electrodes I
The TO films 3 and 4 are formed, a polyimide resin is applied thereon as alignment films 5 and 6 by a spinner, and a rubbing treatment is performed on the alignment film 6 of one substrate 2 with a rubbing cloth using nylon as a material in one direction. After applying 10 times, this substrate 2
Invert 180 degrees and perform the rubbing process 0 times, 1 time, 5 times,
The test was performed 10 times, 15 times, and 20 times. 7 is a rubbing direction previously applied to the glass substrate 2 and 8 is a rubbing direction applied later to the glass substrate 2. Then, the substrate 2 subjected to the rubbing treatment and the substrate 1 not subjected to the rubbing treatment were bonded to each other so that the alignment film surfaces overlap each other. At this time, the thickness of the cell is set to 2 μm by a spacer (not shown) mixed in the sealing resin 10 as shown in FIG. A ferroelectric liquid crystal 9 was sealed in this cell.

Observation of this element using a polarizing microscope confirmed good orientation with few defects. Then, when there is no reverse rubbing, and when the reverse rubbing is performed once, five times, ten times, and 15 times.
The results for the response speed, contrast and bistability at 20 and 20 times are shown in the table below.

As shown in the above table, the cells subjected to reverse rubbing were able to obtain bistable characteristics compared to the cells not subjected to reverse rubbing. In these six examples, good characteristics were observed when the number of rubbings in the reverse direction was the same as that in the forward direction (10 rubbings in the reverse direction). In addition,
In the above embodiment, at least one of the substrates is only required to be transparent, and a polyimide resin has been described as an example of the alignment film. However, other materials may be used, and it is possible to perform no surface treatment with the alignment film. . That is, the effect of the reverse rubbing was observed regardless of the type of the alignment film. Also, the orientation film coating method is not limited to the spinner, but can be printing or the like. The rubbing cloth is not limited to nylon,
It is believed that other various materials such as rayon and polyester can be used.

As is clear from the above description, according to the present invention, after rubbing in one direction, rubbing in the opposite direction enables weak rubbing with a small molecular regulation force, and good alignment of ferroelectric liquid crystal. Was obtained, and the conventional rubbing provided only a monostable orientation, whereas a bistable orientation could be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a rubbing direction of a ferroelectric liquid crystal panel according to one embodiment of the present invention, FIG. 2 is a structural diagram of a ferroelectric liquid crystal panel according to one embodiment of the present invention, and FIGS.
(B) is a diagram showing a rubbing direction of a conventional ferroelectric liquid crystal panel. 1,2 ... Glass substrate, 3,4 ... ITO film (transparent electrode), 5,6 ...
Alignment film, 7 Rubbing direction applied to lower glass substrate first, 8 Rubbing direction applied to lower glass substrate later, 9
... ferroelectric liquid crystal, 10 ... seal resin.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroaki Mizuno 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-58-149022 (JP, A)

Claims (1)

(57) [Claims] 1. A rubbing process is performed in at least one direction on at least one of the liquid crystal cell substrates sandwiching a pair of electrode-attached glass substrates, and then a rubbing process is performed in the opposite direction. A method for manufacturing a liquid crystal cell, comprising sealing a liquid crystal.