JP3058780B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device using a ferroelectric liquid crystal, and more particularly, to a method for injecting the ferroelectric liquid crystal.

[0002]

2. Description of the Related Art Heretofore, there has been proposed a liquid crystal display device of a type in which a transmitted light is controlled by combining with a polarizer utilizing the refractive index anisotropy of a ferroelectric liquid crystal.
And Lagerwall (JP-A-56-107216, U.S. Pat. No. 4,367,924).

The ferroelectric liquid crystal generally has a chiral smectic C phase (SmC ^* ) or a chiral smectic H phase (SmH ^* ) in a specific temperature range, and responds to an applied electric field to obtain a first optical stability. It has a property of taking one of the state and the second optically stable state and maintaining the state (ie, bistability). Since the response to the electric field change is fast and the viewing angle is large, application to a large-sized liquid crystal display device capable of high-speed operation is expected.

[0004]

By the way, in order to use a ferroelectric liquid crystal as described above in a liquid crystal display device to exhibit high-speed response and storage characteristics, the gap between transparent electrodes in a liquid crystal cell must be increased. It is necessary to make the pitch smaller than the helical pitch developed in the Ch phase of the dielectric liquid crystal. However, there are the following problems in the manufacturing process.

[0005] That is, the ferroelectric liquid crystal transitions to each of the SmA phase, Ch phase or ISO phase according to the temperature thereof and each liquid crystal phase is injected into the liquid crystal cell. Generally, for example, when the injection is performed in the ISO phase, the viscosity of the ferroelectric liquid crystal is low in the ISO phase, and the liquid crystal molecules of the ferroelectric liquid crystal are injected again in random directions. For this reason, the injection is not performed smoothly, and for example, there is a case where the pixels on the back side are injected earlier than the injection wavefront while leaving the pixel part of the injection uncompleted except for the injection from the injection port gradually. . Then, in this pixel portion, an alignment defect occurs, and the alignment state of the ferroelectric liquid crystal becomes partially non-uniform, which causes a problem that the display quality as a liquid crystal display device is deteriorated.

On the other hand, when the implantation is performed in the Ch phase, the above-mentioned problem can be solved, but the orientation unevenness which is considered to be due to the helical structure peculiar to the Ch phase occurs. The reason is that the helical pitch peculiar to the Ch phase has a temperature dependency, and therefore, the unevenness in the temperature of the liquid crystal cell at the time of injection causes unevenness in the regulating force of the alignment film received from the upper and lower substrates, or the in-plane of the liquid crystal cell. It is considered that the unevenness of the cell thickness causes unevenness in the regulating force of the alignment film. Then, there is a problem that the overall display quality is deteriorated due to the alignment unevenness.

On the other hand, it was confirmed that when the ferroelectric liquid crystal was injected in the SmA phase, the viscosity of the liquid crystal was too high and the time required to complete the injection was enormous, which was not practical. .

The present invention solves the above-mentioned problems of the prior art, realizes uniform liquid crystal injection, eliminates in-plane alignment unevenness of a liquid crystal cell, improves display quality, and further shortens the injection time. And improve production efficiency.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a liquid crystal display device having a liquid crystal cell and a ferroelectric liquid crystal injected into the liquid crystal cell. The ferroelectric liquid crystal becomes SmA with increasing temperature.
Pyrimidine-based liquid that undergoes a phase transition with the phase, Ch phase, and ISO phase
In a temperature range where the Ch phase and the SmA phase are mixed
It is injected into the liquid crystal cell.

[0010]

[0011]

[0012]

According to the above construction, a pyrimidine-based mixed liquid crystal is injected into the liquid crystal cell in a temperature range where a Ch phase and an SmA phase are mixed.

[0013]

Embodiments of the present invention will be described below.

First, a general structure of a liquid crystal display device will be briefly described with reference to FIG.

The liquid crystal display device comprises a pair of glass substrates 11a, 11a, 11b,
11b, these glass substrates 11a, 11
On the inner surface of b, transparent electrodes 12a and 12b having a thickness of about 400 to 2000 ° are formed. Further, these transparent electrodes 12a and 12b are covered with alignment control films 13a and 13b. Note that these alignment control films 13a,
13b is formed of a high-molecular organic material such as polyimide, and has a thickness of about 10 to 1000 °. Although not formed in the present embodiment, between the transparent electrodes 12a and 12b and the orientation control films 13a and 13b,
An insulating film made of SiO ₂ or the like may be formed with a thickness of 100 to 2000 °.

Further, the alignment control films 13a, 13b
Mean particle size of about 1.5 μm (generally 0.1 to
A 3.5 μm) bead spacer 14 (silica beads, alumina beads, or the like) is interposed therebetween so as to keep the gap between the orientation control films 13a and 13b at a predetermined value. An epoxy-based particle adhesive 15 is disposed between the alignment control films 13a and 13b, so that the glass substrates 11a and 11b are bonded. As the particle adhesive 15, for example, trade name "Trepearl"
Toray's products are used. Although the particle adhesive 15 has an average particle size of about 5 μm, since the upper and lower glass substrates 11a and 11b are held in a gap defined by the bead spacer 14, the particle adhesive 15 is crushed. It has a columnar shape (see Fig. 1 (b)).

Further, the outer peripheral portions of the glass substrates 11a and 11b are adhered by an epoxy-based sealing adhesive 16 so as to form a closed space between the glass substrates 11a and 11b.

The liquid crystal cell 1 (effective display area 280 mm × 230 mm) is formed in such a configuration. In this embodiment, a pyrimidine-based mixed liquid is used as the ferroelectric liquid crystal 17 injected into the liquid crystal cell 1. Liquid crystal is used. Table 1
Shows the results of the present inventors experimentally determining the phase transition temperature of a pyrimidine-based mixed liquid crystal. Specifically, the phase transition process was observed by an optical microscope while changing the temperature of the liquid crystal 17. It is what I asked for. For example, 85 ±
In the temperature range of 1 ° C., the ISO phase and the Ch phase are mixed.

[0019]

[Outside 1]

[0020]

[Table 1] By the way, when injecting the ferroelectric liquid crystal 17 into the liquid crystal cell 1, a portion to which the seal adhesive 16 is not applied (hereinafter, referred to as “injection port 19”) is provided in advance between the glass substrates 11a and 11b. This is performed by injecting the ferroelectric liquid crystal 17 from the inlet 19 and closing the inlet 19 with the sealing adhesive 16. In the present embodiment, the temperature of the liquid crystal 17 at the time of injection is set to 85 ° C.
The test was performed in a state where the h phase was mixed.

As a result of injecting the ferroelectric liquid crystal 17 at the above-mentioned temperature, the present inventor has less alignment disorder and has uniform alignment characteristics as compared with the case where the ferroelectric liquid crystal 17 is completely injected at 100 ° C. That was confirmed. This is considered to be due to the fact that the viscosity is suppressed by the mixture of the Ch phase and the ferroelectric liquid crystal is gradually injected from the injection port 19 as compared with the case of only the ISO phase. Further, according to the present embodiment, a liquid crystal display device having a high display quality without alignment defects, which does not show alignment defects generated when implantation is performed in a temperature range where only the Ch phase is present (for example, 82 ° C.). Obtained.

Next, another embodiment of the present invention will be described.

In the present embodiment, the ferroelectric liquid crystal 17 was set at 80 ° C., and injection was performed in a temperature range where the Ch phase and the SmA phase were mixed. As a result, there is no alignment defect which is considered to be caused by a helical structure peculiar to the Ch phase, which is generated when implantation is performed at 82 ° C., which completely forms the Ch phase.
The viscosity was lower than in the case where the injection was performed at the phase temperature, so that the injection time could be significantly reduced.

As described above, the production efficiency can be improved by shortening the injection time, and a liquid crystal display device having high display quality without alignment unevenness can be obtained.

In the above embodiment, the case where a pyridine-based mixed liquid crystal is used has been described. However, the present invention is not limited to this, and another ferroelectric liquid crystal may be used. However, in this case, since the phase transition temperatures are different, it is necessary to newly observe the phase transition process with an optical microscope to obtain a temperature region where phases are mixed.

[0026]

As described above, according to the present invention,
Since the injection of the pyrimidine-based mixed liquid crystal into the liquid crystal cell is performed in a temperature range where the Ch phase and the SmA phase are mixed, a liquid crystal display device having uniform orientation can be obtained, and the display quality can be improved. It is now possible. In addition, since the injection is performed in a state having an appropriate viscosity, the injection time can be reduced and the production efficiency can be improved.

[Brief description of the drawings]

FIG. 1A is a plan view showing a general structure of a liquid crystal display device, and FIG. 1B is an enlarged cross-sectional view taken along a line BB of FIG.

[Explanation of symbols]

 11a, 11b Glass substrate (transparent substrate) 12a, 12b Transparent electrode 13a, 13b Alignment control film 14 Spacer 15 Particulate resin 16 Sealing adhesive 17 Liquid crystal (ferroelectric liquid crystal) 19 Filler

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-34819 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1341 G02F 1/1337 510

Claims (1)

(57) [Claims] 1. A liquid crystal cell and a liquid crystal cell injected into the liquid crystal cell.
A liquid crystal display device comprising: a ferroelectric liquid crystal;But the SmA phase, C with increasing temperature
a pyrimidine-based mixed liquid crystal that undergoes a phase transition with the h phase and the ISO phase
Thus, in a temperature range where the Ch phase and the SmA phase coexist,
Injected into the crystal cell,  A method for manufacturing a liquid crystal display device, comprising: