JPH03208020A - Liquid crystal display element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element using a smectic liquid crystal having ferroelectric properties, which prevents the occurrence of alignment defects.

[Prior Art] A type of display element that uses the refractive index anisotropy of liquid crystal molecules to control transmitted light in combination with a polarizing element was developed by Clark and Lagerwall.
(U.S. Patent No. 436,792)
Specification No. 4. (U.S. Pat. No. 4,639,089, etc.). The liquid crystal used in this display element generally exhibits a chiral smectic C phase (Sm"C) in a specific temperature range.
) or H phase (Sm”H), and in this state, it takes either the first optically stable state or the second optically stable state in response to the applied electric field, and in response to the applied electric field. It has the property of maintaining its state when it is not present, that is, it has bistability, and it also responds quickly to changes in electric field, so it is expected to be widely used in high-speed and memory-type display devices.

[Problem to be Solved by the Invention] However, according to experiments conducted by the present inventors, it was found that it was not possible to completely fill the isotropic phase ferroelectric liquid crystal compound in the above-mentioned cell in which the pair of substrates were sealed and fixed with a sealant. When a liquid crystal cell prepared by injection and subsequent cooling to a chiral smectic phase is supported by a pair of crossed Nicol polarizers and the cell surface is observed, a zigzag or wavy line that can be visually identified is generated. I understand.

This zigzag or wavy line causes a problem of deteriorating display quality.

Such zigzag or wavy lines are caused by volume contraction in the chiral smectic liquid crystal when the isotropic phase or cholesteric phase completely injected into the cell undergoes a phase transition to the smectic A phase or chiral smectic phase by cooling. This is due to the formation of zigzag or wavy void lines. This zigzag or wavy gap line is visually observed with a crossed Nicol polarizer.

The present inventors investigated the occurrence of the zigzag or wavy void lines and found that they often occur near the sealing material. Starting from the zigzag or wavy void lines, alignment defects occur along the alignment direction of the vertical molecular layers, and these alignment defects extend to the effective display area, resulting in a significant deterioration of display quality. There was a problem. Furthermore, the above-mentioned alignment defects also occur in the sealing member, resulting in a problem of deterioration of display quality.

An object of the present invention is to provide a ferroelectric liquid crystal element that solves the above-mentioned problems. That is, the object of the present invention is to provide a ferroelectric liquid crystal element that has improved durability against environmental temperature changes and improved display quality at the same time.

[Means and Effects for Solving the Problems] The inventors of the present invention repeatedly conducted experiments in accordance with the above-mentioned objectives, and found that the above-mentioned zigzag or wavy void lines often occurred near the sealing member. We discovered that alignment defects occur along the alignment direction of the vertical molecular layers, and that these alignment defects extend to the effective display area, significantly deteriorating the display quality.

By providing an area between the effective display area and the sealing member where the alignment control film exists only on one substrate, alignment defects that occur from zigzag or wavy gap lines and from the edge of the liquid crystal injection port can be avoided. The present invention was achieved by discovering that the alignment defects caused by the alignment control film are stopped in the area where the alignment control film is present only on one of the substrates, and do not reach the effective display area.

That is, the present invention provides a liquid crystal display element having a smectic liquid crystal having ferroelectricity and first and second substrates having electrodes and alignment control films facing each other with the liquid crystal interposed therebetween. It is characterized by providing an area outside the area where the alignment control film exists only on one substrate.

[Detailed Description of Aspects of the Invention] FIG. 1(A) is a cross-sectional view of a ferroelectric liquid crystal cell 101 illustrating a liquid crystal display element to which the present invention is applicable. A ferroelectric liquid crystal cell 101 includes a ferroelectric liquid crystal 104 between a pair of substrates 102 and 103 (glass, plastic), and a hard body 105 (glass fiber, plastic) that functions as a substrate.
silica beads, alumina beads) and substrates 102 and 10
3 is provided with an adhesive body for adhering the parts.

Transparent electrodes 10 are provided on the inner surfaces of the substrates 102 and 103, respectively.
7 and IOA, transparent ferroelectric films 109 and 110, and alignment control films 111 and 112 are provided. This orientation control film 1
It is also possible to omit either one of 11 and 112.

As the ferroelectric liquid crystal 104, for example, US Pat. No. 456
Publication No. 1726, Publication No. 4589996, Publication No. 45
The liquid crystal disclosed in US Pat. No. 92858, US Pat.
The suppressed or eliminated helical arrangement structure disclosed in Japanese Patent No. 73 can be used.

FIG. 2 shows the bistable alignment state of chiral smectic liquid crystal when the helical alignment structure inherent in the bulk state disappears.

This bistable alignment state is achieved by maintaining the distance between the pair of substrates 201 and 202 at a distance lIM (10 μm or less) that is sufficiently small to eliminate the helical alignment structure, and in the absence of an electric field, the liquid crystal molecules , are held as liquid crystal molecules 203A and 203B oriented in one of the stable states. Furthermore, in the present invention, in the absence of an electric field, the liquid crystal molecules 2
It is also possible to use an orientation state in which 03 is oriented at a pretilt angle with respect to the substrates 201 and 202. 204 in FIG. 2 represents a vertical molecular layer organized by a plurality of liquid crystal molecules, and the arrow in the figure represents the direction of the dipole moment.

Such a ferroelectric liquid crystal cell 101 includes a pair of polarizers ]13
and 114, the change in the orientation state is optically identified.

FIG. 1(B) is a plan view of the ferroelectric liquid crystal cell 101.
A sealing member 115 for sealing the pair of substrates 102 and 103 is arranged except for the injection port 116, and the inside of the sealing member 115 is used as an effective display area 117.

The alignment control films 111 and 112 include polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, area resin, etc. A film of an organic insulating material such as acrylic resin that has been subjected to a uniaxial alignment treatment (e.g., rubbing treatment) can be used, and the transparent dielectric films 109 and 110 can be made of silicon monoxide, silicon dioxide, aluminum oxide, or the like. nium,
A film of an inorganic insulating material such as zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, or borate nitride can be used.

The alignment control films 111 and 112 generally have 50 to 1,000 people.
Transparent dielectric materials 1i109 and 1
10 can generally contain 100 to 3,000 people.

Hereinafter, the present invention will be explained by giving specific examples and comparative examples.

Prepare two 1.1mm thick glass plates, and place ITO (indium nine oxide) on each glass plate.
A transparent stripe electrode was formed thereon, and a transparent dielectric film of SiO2 was formed thereon to a thickness of 1,000 ml by a sputtering method.

On this Si02, polyimide forming liquid S2710 (
A 4% by weight N-methylpyrrolidone/n-butylcelloring (2:1) solution was applied by a printing method, and
By firing at 0° C., a polyimide orientation control film with a thickness of 500 layers was formed. However, as shown in FIG. 3(A), the formation area 112 of the alignment control film formed on one glass substrate was formed to be wider than the formation area 111 of the alignment control film formed on the other glass substrate. .

This fired coating was subjected to a rubbing treatment with an acetate flocked cloth in the direction of arrow 118. After that, silica microbeads with an average particle size of 1.5 μm were distributed on one substrate using the Nordson electrostatic scattering method at a distribution density of 200 beads/mm.
Sprayed at 2. Next, a liquid adhesive (product name: Structbond; manufactured by Mitsui Toatsu Co., Ltd.) is used as the sealing member 115.
was applied by printing to a film thickness of 4 μm. Then, two glass plates were glued together and 4 kg/c at a temperature of 70°C.
crimping by applying a pressure of m 2 for 5 minutes,
Further, the adhesive was cured for 2 hours while applying a pressure of 1 kg/cm' at a temperature of 150° C. to produce a cell. At this time, the average bonding area per bonded body by the adhesive particles was 5×10-'mm2.

Thereafter, the pressure inside the liquid crystal cell was reduced to 10-4, and CS1014 (trade name) manufactured by Chisso Corporation was added as a ferroelectric liquid crystal to 90%
Injected at °C (isotropic phase). After that, Kai? It was cooled to 25° C. resulting in a smudge C phase. Then, the occurrence of zigzag or wavy void lines and alignment defects was investigated. As a result, as shown in FIG. 4(A), the injection port 116
Although an orientation defect 120 occurred from the corner of the seal, no visually observable orientation defect occurred within the effective display area 117.

Next, place the liquid crystal cell in a constant temperature bath under the following conditions: 25°C.
- 10℃ → 25℃ 1℃/min (left for 2 hours) A temperature change of 1℃/min was applied, and the occurrence of zigzag or wavy void lines and orientation defects was investigated, as shown in Figure 5 (A). As shown in FIG. 2, no visually observable alignment defects occurred within the effective display area 117.

Comparative Example 1 As shown in FIG. 3(B), the orientation control film shape area 11
A liquid crystal cell was prepared in the same manner as in Example 1, except that 1 and 112 were the same, and the occurrence of zigzag or wavy void lines and alignment defects was investigated.
℃, orientation defects 120' occur from the seal corners of the injection port 116, as shown in FIG. 4(B).
Unlike the case of the first embodiment, the effective display area 11
It reached within 7.

Furthermore, after applying the same temperature change as in Example 1, the length of the orientation defect 120° becomes longer, as shown in FIG. It extended beyond area 117 to sealing member 115.

After the rubbing process, epoxy resin adhesive particles (trade name: Trepearl; manufactured by Toray Industries, Inc.) with an average particle size of 5 μm were distributed at a distribution density of 130 on the other substrate on which the silica microbeads were not sprinkled using the Nordson electrostatic scattering method. A liquid crystal cell having a cross section as shown in FIG. 8 was prepared in the same manner as in Example 1, except that it was dispersed in an amount of 1000 g/m2 and cured in the same manner and at the same time as the sealing member 115. The occurrence of zigzag or wavy void lines and orientation defects was investigated.
In FIG. 8, 106 is an adhesive body of the epoxy resin adhesive particles. As a result, when the liquid crystal was cooled to 25° C. after being injected, alignment defects 620 occurred from the seal corners of the injection port 116, and zigzags appeared in the vicinity of the sealing member 115, as shown in FIG. 6(A). A void line 621 of the shape was generated, and an alignment defect 622 was also generated therefrom. However, within the effective display area 117, no visually observable alignment defects were observed. Even after the same temperature change as in Example 1 was applied, no visually observable alignment defects occurred within the effective display area 117, as shown in FIG. 7(A).

As shown in FIG. 3(B), the orientation control film forming area 111
A liquid crystal cell was prepared in the same manner as in Example 2, except that 112 and 112 were the same, and the occurrence of zigzag or wavy void lines and alignment defects was examined. As a result, when the liquid crystal was cooled to 25°C after injection, as shown in Figure 6 (B),
An alignment defect of 620° extending from the seal corner of the injection port 116 to the inside of the effective display area 117 occurred. In addition, a zigzag-shaped gap line 62 is provided near the sealing member 115.
1'' was generated, and an alignment defect 622' that extended into the effective display area 117 also occurred from there. After the temperature change was applied, the orientation defect 620' extended to reach the sealing member 115, and the orientation defect 622' also extended more than twice as long.

Comparative Example 3 Two types of liquid crystal cells were prepared in the same manner as in Examples 1 and 2, respectively, except that the alignment control film forming areas 111 and 112 were set to coincide with the entire inner surface of the sealing member 115, as shown in FIG. were fabricated, and the occurrence of zigzag or wavy void lines and orientation defects was investigated. The result is
The results were similar to those in Comparative Examples 1 and 2, respectively.

E1α41 As shown in FIG. 10, the alignment control film forming area 112 is divided into two parts near the outer periphery into inner and outer parts, and the inner alignment control film forming area 112 and the alignment control film forming area 11 of the other substrate are separated.
1 and 2 f! in the same manner as in Examples 1 and 2, respectively. A liquid crystal cell was prepared, and the occurrence of zigzag or wavy void lines and alignment defects was investigated.

As in the case of Examples 1 and 2, the results were as follows:
No alignment defects occurred within the effective display area 117.
Even when forming multiple alignment control film formation areas that exist only on one substrate as in Example 3 and examining alignment defects etc. in the same manner as in Example 3, the area within the effective display area No orientation defects were produced.

From the results of the above examples and comparative examples, Fig. 3(A)
By providing an area outside the effective display area where the alignment control film exists only on one substrate, as shown in FIG. It can be seen that the occurrence of alignment defects within the effective display area can be prevented even with sudden temperature changes, and therefore the image quality of the ferroelectric liquid crystal element can be significantly improved.

[Effects of the Invention] According to the present invention, in a liquid crystal display element, an area where an alignment control film is present is provided only on one substrate outside the effective display area, so that the alignment control film is generated from zigzag or wavy void lines. Orientation defects and orientation defects generated from the sealing member are prevented from extending to the effective display area, and even if the environmental temperature changes, orientation defects are prevented from occurring in the effective display area, thus improving durability and display quality. improve at the same time.

[Brief explanation of drawings]

1(A) and 8 are sectional views of a liquid crystal element to which the present invention is applied, FIG. 1(B) is a plan view of the liquid crystal element of FIG. 1(A), and FIG. 2 is a sectional view of a liquid crystal element to which the present invention is applied. , a perspective view schematically showing the alignment state of ferroelectric liquid crystal molecules used in the liquid crystal elements of FIGS. 1 and 8, FIG. 3(A), FIG. 4(A), FIG. 5(A), Figure 6'
(A), FIG. 7(A), and FIG. 10 are plan views of the liquid crystal elements of FIG. 1(A) and FIG. 8 having alignment control films according to the present invention, and FIG. 3(B). , FIG. 4(B), FIG. 5(B), FIG. 6(B), FIG. 7(B), and FIG. 9 are plan views of liquid crystal elements having conventional alignment control films. . 101: Ferroelectric liquid crystal cell, 102, 103, 201,
202: Substrate, 104: Ferroelectric liquid crystal, 107.108
: transparent electrode, 111, 112: alignment control film (formation area), 117: effective display area, 119: area where alignment control antinode exists only on one substrate, 120, 120
620, 622, 620', 622°: orientation defect, 621621': zigzag void line.

Claims (2)

[Claims] (1) In a liquid crystal display element comprising a smectic liquid crystal having ferroelectricity and first and second substrates having electrodes and alignment control films facing each other with the liquid crystal in between, the effective display area of the liquid crystal display element A liquid crystal display element characterized by having an outer area where an alignment control film exists only on one substrate. (2) The liquid crystal display element according to claim 1, wherein a plurality of areas are provided in which the alignment control film exists only on the one substrate.