JPH02197820A - 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 the Invention The present invention relates to a liquid crystal display element in a liquid crystal display.

A conventional liquid crystal display device generally includes two transparent substrates, a liquid crystal sandwiched between the transparent substrates, a transparent electrode or driving element formed on the transparent substrate, and a transparent electrode or driving element formed on the transparent electrode or driving element. The main component is an alignment film.

Nematic liquid crystal is used as a method that is often used as a liquid crystal display element, and TN (Tvfsted Nema
Some display images using the tfe) method. In this case, the average long axis direction of the molecules of the nematic liquid crystal is parallel to the substrate and regulated by the alignment film when no electric field is applied, and perpendicular to the substrate when an electric field is applied.

As the alignment film, polyvinyl alcohol or polyimide thin films rubbed in one direction or SlO obliquely deposited on the substrate surface have been mainly used.

In addition, recently, a ferroelectric liquid crystal display element has been proposed (US Pat. No. 4,387,924), which features high-speed response and memory properties that TNN liquid crystals do not have, but the orientation of this ferroelectric liquid crystal is similar to that of TN liquid crystal. It is more difficult than the case. In other words, in order to use ferroelectric liquid crystal as a display element, it is necessary to form uniform monodomains over the entire surface of the panel, but it is difficult to obtain uniform monodomains by rubbing or oblique evaporation, and currently there is no way to achieve uniform alignment. Much research and development is being carried out towards this goal.

Now, regarding the use of organosilicon compounds as alignment films, F-J, Kahn et al.
etters), Vat, 22. Nr
+, 3 (1973, 2, 1) p. 111-11
3, many researchers have investigated various organosilicon compounds. In early research, it was thought that the alignment of liquid crystals was determined by the balance between the surface tension of the liquid crystal and the critical surface tension of the substrate surface. According to the authors, it was found that when an organic silicon compound is used as an alignment film, the alignment is unrelated to the balance of surface tension between the substrate surface and the liquid crystal, and the liquid crystal tends to be aligned parallel to the substrate in most cases. Furthermore, when an organosilicon compound with a long alkyl chain (14 to 18 carbon atoms) is used for the alignment film, the alkyl groups are aligned perpendicular to the substrate, and the alkyl groups interact with the terminals of the liquid crystal molecules. The molecules are said to be aligned perpendicular to the substrate. (Matsumoto et al., “Latest Technology of Liquid Crystals” p., IG!,
(Published by Kogyo Kenkyukai Co., Ltd. in 1983) Organosilicon compounds that have been studied as alignment films are as follows. Moreover, these substances have almost never been used in practical applications.

Trimethyl-3-aminophylltrimethoxysilane, Tri(2-aminoethyl)-3-aminophylltrimethoxysilane, 3-aminophyltriethoxysilane, 3-aminophylltrimethoxysilane Methoxysilane, 3-monopropyltrimethoxysilane 3
- Nukuri zero-absorbing citrimethoxysilane, methoxytriethoxysilane, n-dimethyltriethoxysilane, phenyltriethoxysilane, tophenyl-3-aminophyllotrimethoxysilane, N,N-dimethyltriethoxysilane 3-aminophyltrimethoxysilyl chloride°.

Problem to be Solved by the Invention To make the alignment of liquid crystal uniform over the entire surface of a display panel in a liquid crystal display element.

Means for Solving the Problems In a liquid crystal display element in which a liquid crystal that exhibits an optical change due to an electric field is sealed between a pair of substrates on which a conductive film is provided facing each other, at least one of the substrates on which the conductive film is provided. A planarizing film having an organic silicon compound having the structure of a core portion of a liquid crystal material on its surface is applied onto the substrate.

Function: The organosilicon compound covering the surface of the flattening film of the present invention has the structure of a core portion of a liquid crystal material. In the liquid crystal display element of the present invention, the liquid crystal is in direct contact with the surface of the flattened film.

Since the interaction between the structure of the core portion of the liquid crystal substance and the liquid crystal is large, it is thought that the liquid crystal is oriented along the alignment direction of this core portion. Further, the planarization film fills in the irregularities of about 100A on the surface of the conductive film formed on the substrate to make it flat.

It is thought that the interaction between the liquid crystal on the surface of the flattened film and the organosilicon compound having the structure of the core portion of the liquid crystal substance is not disturbed by the alignment of the liquid crystal due to the unevenness of the surface.

Embodiment A liquid crystal display element of the present invention is a liquid crystal display element in which a liquid crystal that exhibits an optical change due to an electric field is sealed between a pair of opposing substrates each having a conductive film provided thereon. A flattening film having an organosilicon compound having a structure of the =ya portion of a liquid crystal material on its surface is provided on at least one of the substrates. Here, the structure of the core portion of the liquid crystal material will be explained. In the present invention, the liquid crystal substance is not limited to a substance that exhibits a liquid crystal phase in an appropriate temperature range when heated or cooled, or during both heating and cooling; It also includes substances that do not exhibit a liquid crystal phase, but can exhibit a liquid crystal phase when mixed with other appropriate substances. In theory, the core portion of the liquid crystal in the organosilicon compound formed on the surface of the flattening film may be different from the liquid crystal actually sealed in the liquid crystal display element. Further, the core portion refers to a portion having a considerable degree of rigidity in the molecular structure of a liquid crystal, such as a cyclic group excluding the terminal group consisting of an alkyl chain or an alkoxy chain, and a central group portion.

In the present invention, in a liquid crystal display element in which a liquid crystal that exhibits an optical change due to an electric field is sealed between a pair of substrates, an organic silicon having a structure of a core portion of a liquid crystal material is provided on at least one of the substrates. Any type of liquid crystal display element may be used as long as it is provided with a flattening film containing a compound on its surface.

The type of display element is T, which uses nematic liquid crystal.
N liquid crystal display element, GE liquid crystal display element using nematic liquid crystal or cholesteric liquid crystal and dye, SBE liquid crystal display element using nematic liquid crystal containing a chiral component, ferroelectric liquid crystal display element using chiral smectic C liquid crystal, etc. Any type of liquid crystal display element can be used as long as it is an element that aligns liquid crystal parallel to the substrate as an initial arrangement.

Note that the present invention is most effective for ferroelectric liquid crystal display elements in which uniform alignment control is difficult.

A liquid crystal display element basically consists of two substrates, a drive electrode or drive element formed on the substrates, an alignment film formed on the surface thereof, and a liquid crystal sandwiched between the two substrates. . Furthermore, the number of polarizing plates and the presence or absence of color filters are determined depending on the element type or whether or not colorization is used.

The figure shows a cross-sectional view of a ferroelectric liquid crystal display element as an embodiment of the present invention. Hereinafter, the present invention will be described in detail with reference to the drawings. In the figure, 1 is a transparent substrate, 2 is an electrode made of a transparent conductive film provided on the substrate, 3 is a flattening film whose surface has an organic silicon compound having the structure of the core part of a liquid crystal material, and 4 is a seal. 5 is a spacer member, and 6 is a chiral smectic C liquid crystal material. As the transparent substrate 1, known transparent materials such as glass, acrylic resin, polycarbonate resin, etc. can be used. Tin oxide or ITO (Ind.
A transparent conductive film 2 is formed using .ium tin oxide). A flat chloride film 3 having on its surface an organic silicon compound roughly having the structure of the core part of the liquid crystal part is formed. The method of forming the transparent conductive film 2 is not particularly limited.
The easiest method is to form a flattening film on the substrate 1 having a structure, and then to form an organosilicon compound thin film having the structure of the core of the liquid crystal portion on the surface of the flattening film. Regarding the material of the flattening film, any material may be used as long as it has the property of filling the unevenness of the surface and reacts with the alkoxy group of the organosilicon compound. Not only substances that inherently have polar groups in their molecules, such as polyvinyl alcohol, polyacrylic acid, starch, cellulose, water-soluble nylon, or copolymers of these and ethylene, but also substances such as polyethylene, polystyrene, and polyphenylene sulfide. Polar groups such as hydroxyl groups and carboxyl groups may be introduced onto the surface by plasma treatment. As for the method for forming the flattening film on the substrate, any method may be used as long as it can form a film that does not have irregularities on the order of 1 GOA. Examples include the spin code method and dip method. Note that printing methods and vapor deposition methods are not suitable because they result in unevenness of about 100A.

The thickness of the flattening film 8, which has an organosilicon compound on the surface that has the structure of the core part of the liquid crystal part, is not particularly limited, but if it is too thin, it will not be able to fill in the unevenness of about 100A, and if it is too thick, Since the effective voltage applied to the liquid crystal θ is extremely reduced, a thickness of about LOOOA is optimal. The thickness of the organosilicon compound layer having the structure of the core portion of the liquid crystal material is not limited.

Among organosilicon compounds, those having the following structure are superior in alignment ability.

m=0.1. n=1.2 (margin below C) m, n=0.1. However, m+n≠O m, m=o, 1j However, m+n≠0 m=1.2, n*1.2 n=1. Furthermore, m+n≠0 More preferably, organic silicon compounds having two or more benzene rings in one chain bonded to silicon have superior liquid crystal alignment ability.

The organosilicon compound used here has a hydrolyzable group bonded to a silicon atom and an organic functional group, but as a hydrolyzable group, an alkoxy group is superior to a halogen group9, and more preferably a methoxy group. The most preferred is one in which three or ethoxy groups are bonded to one silicon atom.

There are few organosilicon compounds that can be used in the present invention on the market, but for example, by anionizing a material obtained by halogenating the end of the core portion of a liquid crystal material with butyllithium and reacting it with tetraethoxysilane. Can be easily synthesized.

Also, the substrate 1 coated with the silicon compound in this way is! It is desirable to hold the film in a hot air dryer at about 50° C. for about 30 minutes to promote the bonding of the hydrolyzable groups in the organosilicon compound with the surface of the planarized film.

Furthermore, the flattening film 3 having an organic silicon compound having the structure of the core portion of the liquid crystal material on its surface is rubbed. Regarding the cloth used for rubbing and the strength of rubbing, optimal conditions differ depending on the type of film and the type of liquid crystal, but nylon nonwoven fabric is preferable as the rubbing cloth.

Next, the substrates 1 on which the planarizing film 3 has been formed in this manner are placed so that the planarizing film 3 faces each other, spacer members 5 are arranged between the substrates 1 at an appropriate density, and then the substrates 1 are bonded together using a sealing material 4. Here, as the spacer member, glass fibers or glass beads with a uniform diameter, which have been used in conventional TN liquid crystal display elements, may be used, or a spacer wall with a uniform thickness may be provided in the non-opening portion of the liquid crystal display element. . Further, the sealing material 4 covers the periphery of the substrate 1, but only a portion is left unsealed. Epoxy resins conventionally used in TN liquid crystal display elements can be used as the sealing material, but it is not limited to thermal epoxy resins; any material can be used as long as it has good adhesion to the substrate and does not dissolve in the liquid crystal. Various resins can be used. . Next, this cell is kept in a vacuum, and the chiral smectic C liquid crystal material 6 is heated from the unsealed portion to an isotropic phase and introduced into the cell. Finally, this injection port is sealed to produce a liquid crystal display element. As a method for introducing the liquid crystal material between the substrates, in addition to the vacuum liquid crystal injection method described here, a method of printing or vapor depositing the liquid crystal material on both sides and bonding them together can be used.

This will be explained below using specific examples. Although a ferroelectric liquid crystal display element was created in the following examples, the present invention is not limited thereto, and can be applied to any liquid crystal display element that is initially aligned parallel to the substrate, such as a conventional TN liquid crystal display element. It is possible.

Examples 1 to 10 Striped electrodes with a pitch of 100 μm and a width of 62.5 μm were obtained by sputtering ITO on a #7058 type glass substrate manufactured by Corning Inc. with a thickness of 1.1 mm. On this substrate, an aqueous solution containing polyvinyl alcohol (Poval 117 manufactured by Kuraray Co., Ltd.) dissolved at a concentration of 1% was applied as a coating liquid, and a planarized film of IGOOA was created by spin-coating and heating at 100°C for 1 hour. After that, using methyl cellosolve as a solvent, Example 1 in Table 1 was prepared.
A coating solution having a solution composition in which the organosilicon compound shown in ~1o is dissolved at a concentration of 0.1 wt% is spin coded to 15G
'G: After heating for 1 hour, it was rubbed in one direction under the suppression of % 100g/C1j, and the rubbed pair of glass bases were stacked so that the upper and lower rubbing directions were parallel, and the parts other than the injection port were After sealing, ferroelectric liquid crystal 0S-1014 manufactured by Chisso Corporation is heated to make it into an isotropic phase.
It was injected through the injection port under reduced pressure. Thereafter, the injection port was sealed to create a cell.

Examples 11 to 20 A pitch of 100 μm was applied to the surface of the same type of substrate as in Examples 1 to 10.
A striped electrode with a width of 62.5 μm was obtained by sputtering ITO. 2w of polystyrene (HRM-3 manufactured by Denka) was placed on this substrate using toluene as a solvent.
A solution fiber coating solution dissolved at a concentration of 1000O
After creating the planarization film A, use a plasma asher to introduce oxygen into the system at a flow rate of 100 SCCII, set the substrate temperature at 50°C in a vacuum of 0.8 torr, and process at an output of 600 W for 5 minutes. did. As a result of measuring the infrared spectrum of this film, the presence of hydroxyl groups, which were not present before plasma treatment, was confirmed. Next, using methyl cellosolve as a solvent, a coating solution having a solution composition in which the silicon compounds shown in Examples 11 to 20 in Table 1 were dissolved at a concentration of 0.1 wt% was spin-coded at 150°C for 1 hour. After heating for an hour, rubbing was performed in one direction under a pressure of 100 g/(!I', and the rubbed pair of glass substrates were stacked so that the upper and lower rubbing directions were parallel to each other, and the parts other than the injection port were sealed. Ferroelectric liquid crystal OS-10 later manufactured by Chisso Corporation
14 was heated to an isotropic phase and injected through the injection port under reduced pressure. Thereafter, the injection port was sealed to create a cell.

(Margin below) Table 1 (Continued) Comparative Examples 1 to 5 Using the same substrates as in Examples 1 to 20, liquid crystal display elements were created using the same liquid crystal. However, in this case, the second layer is used as the alignment film.
The materials shown in the table were applied, dried by heating, and then rubbed.

Table 2 Liquid crystal display element operation test Regarding the liquid crystal display elements prepared in the above examples and comparative examples, the difference between the upper and lower electrodes was
A 10 V square wave pulse was applied, and the contrast was measured from the change in the amount of transmitted light at that time. Regarding microscopic observation, cases where 90% or more uniform monodomains could be observed were ◎, 80% or more were Q, 80% or more were △, and BO% ungrooved ×. The results are shown in Table 3. The results show that the contrast of the liquid crystal display element of the example is higher than that of the liquid crystal display element of the comparative example, and from this it can be said that the liquid crystal alignment of the example is better than that of the comparative example.

(The following is a blank space) Effects of the Invention According to the present invention, by applying a flattening film having an organosilicon compound having the structure of the core portion of a liquid crystal material on the surface thereof, on the conductive film forming surface of the substrate, Unlike the conventional case where an organic silicon compound is used as an alignment film, alignment of liquid crystal becomes uniform over the entire panel surface.

[Brief explanation of the drawing]

The figure is a sectional view showing a liquid crystal display element in one embodiment of the present invention. 1... Transparent substrate 2... Electrode of transparent conductive film 3... Flattening film 4... Seal material 5... Spacer member θ... Chiral smectic C liquid crystal substance substitute Person's name Patent attorney Shigetaka Awano et al.18 Figure 1 Kazuhisa Shikinori

Claims (2)

[Claims] (1) In a liquid crystal display element in which a liquid crystal exhibiting an optical change due to an electric field is sealed between a pair of substrates having conductive films facing each other, a core of liquid crystal material is placed on at least one conductive film-forming surface of the substrates. 1. A liquid crystal display device characterized in that a flattening film is provided on the surface of an organosilicon compound having a structure as shown in FIG. (2) The liquid crystal display element according to claim 1, wherein the organosilicon compound having the structure of the core portion of the liquid crystal substance includes any one of the following structural formulas. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, m = 0, 1, n = 1, 2 ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
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2, 3, 4, 5 However, m + n ≠ 0, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, n = 1, 2, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
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1, 2, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼