JPH01178923A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To uniform the orientation of liquid crystal over the entire surface of a panel by using an organic silicon compound which has the structure of the part of the core of a liquid crystal material as an orienting film. CONSTITUTION:This is the liquid crystal display element formed by charging liquid crystal 6 which has optical variation with an electric field between a couple of substrates 1 and the orienting film 3 containing the organic silicon compound having the structure of the part of the core of the liquid crystal material 6 is provided on at least one surface of each substrate 1. Further, the part of the core shows the extremely stiff part of the parts of a cyclic group and a center group except a terminal group consisting of an alkyl chain and an alkoxyl chain in the molecular structure of the liquid crystal. Consequently, the mutual operation between the structure of the part of this core and the liquid crystal 6 is large, so the liquid crystal is oriented uniformly in the array direction of the part of the core.

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.

Conventional liquid crystal display elements mainly use nematic liquid crystal, and T
Image display is performed using the N (Twisted Nematic) method. In this case, the molecular long axis direction of the nematic liquid crystal is on average oriented in a direction parallel to the substrate and regulated by the alignment film when no electric field is applied. As the alignment film, polyvinyl alcohol or polyimide thin films rubbed in one direction or SiO obliquely deposited on the substrate surface have been mainly used.

In addition, recently, a ferroelectric liquid crystal display element has been proposed that features high-speed response and memory properties that are not found in TN liquid crystal (U.S. Pat. No. 4,367,924). It is also difficult to do so. 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 end.

Regarding the use of organosilicon compounds as alignment films, F., T., and Kahn have published Applied Physics Letters.
etters), Vol, 22. A3 (1973
, 2, 1) Since the publication on p. 111-113 of the magazine,
Various organosilicon compounds have been studied. 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.
7), 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. Ta. Also, alkyl long chain (14 to 1 carbon atoms)
When an organic silicon compound having 8) is used as an alignment film,
It is said that the alkyl groups are aligned perpendicular to the substrate, and the alkyl groups interact with the ends of the liquid crystal molecules, so that the liquid crystal molecules are aligned perpendicular to the substrate. (Matsumoto et al., "Liquid Crystal Latest Technology JP, 161. Published by Kogyo Chosenkai Co., Ltd., 1983)" The organic silicon compounds that have been conventionally studied as alignment films are as follows.

N-methyl-3-aminopropyltrimethoxysilane,
N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glyndoxypropyltrimethoxysilane, 3-morpholinopropyltrimethoxysilane, 3-methacryloxytrimethoxy Silane, methyltrimethoxysilane, n-pentyltriethoxysilane, phenyltriethoxysilane, N-pheny)v-3-aminopropyltrimethoxysilane, N,N-dimethy)v-N-octadecy)v-3-amino Propyltrimethoxysilyl chloride Problems to be Solved by the Invention In a conventional liquid crystal display device using an organic silicon compound as an alignment film, the alignment of the liquid crystal is uneven and not uniform over the entire surface.

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 in a pair of substrates on which conductive films are provided facing each other, at least one of the substrates on which conductive films are provided is sealed. An alignment film containing an organic silicon compound having the structure of a core portion of a liquid crystal material is used on one surface.

Function The organosilicon compound contained in the alignment film of the present invention has the structure of the core portion of a liquid crystal substance, so that the interaction between the structure of this core portion and the liquid crystal is large. It is thought that the liquid crystal is horizontally aligned along the horizontal axis.

Embodiment The 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 in a pair of substrates on which conductive films are disposed facing each other. At least one surface thereof has an alignment film containing an organic silicon compound having the structure of a core portion of a liquid crystal material. Here, the structure of the core portion of the liquid crystal material will be explained. The liquid crystal substance in the present invention is not limited to a substance that exhibits a liquid crystal phase in an appropriate temperature range when heated or cooled, or both during heating and cooling; The term also includes substances that do not exhibit a phase but come to exhibit a liquid crystal phase when mixed with other suitable substances. Thermally, the core portion of the liquid crystal in the organic silicon compound used as the alignment film may be different from the liquid crystal actually sealed in the liquid crystal display element. In addition, the core portion refers to a portion in the molecular structure of a liquid crystal that has rigidity to the extent of a cyclic group and a central group excluding the terminal group consisting of an alkyl chain or an alkoxy chain.

In the present invention, any display type of liquid crystal display element may be used as long as it has an alignment film containing an organic silicon compound having a structure of a core portion of an optical crystal material in a pair of substrates by applying an electric field to the liquid crystal display element. .

The type of display element is T, which uses nematic liquid crystal.
N liquid crystal display elements, GH liquid crystal display elements using nematic liquid crystals or cholesteric liquid crystals and dyes, SBE liquid crystal display elements using nematic liquid crystals containing chiral components, ferroelectric liquid crystal display elements using chiral smectic C liquid crystals, etc. Any type of liquid crystal display element can be used as long as it is an element in which the liquid crystal is aligned parallel to the substrate.

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 substrate, an alignment film formed on the surface of the substrate, and a liquid crystal sandwiched between the two substrates. Ru. 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 an alignment film, 4 is a sealing material, 5 is a spacer member, and 6 is a chiral smectic C.
Indicates a liquid crystal substance. As the transparent substrate 1, glass, Akira I
J) Known transparent materials such as carbon resin and polycarbonate resin can be used. Vapor deposition, sputtering, CV
Tin oxide or ITO (Indi
A transparent conductive film is formed using umTin Oxide. Further, an alignment film containing an organic silicon compound having the structure of the core portion of the liquid crystal portion is formed on the surface thereof. Among organosilicon compounds, those with the following structure have excellent alignment ability.

m=o, 1, n=1, 2 m, n=o, 1, but m+n'50m=1.2. n
=1.2 More preferably, organic silicon compounds having two or more benzene rings in one chain bonded to silicon have better 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 better than a halogen group, and more preferably a methoxy group. The most preferred is one in which three or nidoxy groups are bonded to one silicon atom.

Although there are few commercially available organosilicon compounds that can be used in the present invention, HBr is added to the vinyl moiety of commercially available vinyltriethoxysilane to obtain 2-bromoethyltriethoxysilane. It can be easily synthesized using the general Williamson ether synthesis method from ethyltriethoxysilane and an alcohol based on the core part of the liquid crystal.

When forming the alignment film 3 on the substrate 1 using this organosilicon compound, can various known coating methods such as a spin code method, a dip method, a printing method, and a vapor deposition method be used? °Non-coating method is the easiest. In the case of the spin code method, a cellosolve-based solvent such as ethyl cellosolve or ethyl cellosolve, or a substance with relatively high polarity and high viscosity such as NMP (N-methylpyrrolidone) or r-butyrolactone is used as a solvent, and approximately 1 wt% of the solvent is used. It is best to use a solution of a concentrated organosilicon compound as the coating solution. However, the thickness of the alignment film is not particularly limited, and even a monomolecular film can be used as the alignment film.

Further, it is preferable that the substrate 1 coated with the organosilicon compound in this manner be kept in a hot air dryer at about 150° C. for about 30 minutes to promote the bonding of the hydrolyzable groups in the organosilicon compound with the substrate 1. .

Further, this organic silicon compound coating film is rubbed to form an alignment film 3. Regarding the cloth used for rubbing and the strength of rubbing, optimal conditions vary depending on the type of membrane and the type of liquid crystal, but nylon nonwoven fabric is generally preferred.

Next, the substrates 1 on which the alignment films 3 have been formed in this manner are placed so that the alignment films 3 face each other, spacer members 6 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. It can also be used with other resins. Next, this cell is kept in a vacuum and chiral smectic C is removed from the unsealed part.
The liquid crystal substance 6 is heated to form an isotonic phase and introduced into the cell.

Finally, this injection port is sealed to produce a liquid crystal display element.

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 20 Striped electrodes with a pitch of 100 μm and a width of 62.5 μm were obtained by sputtering ITO on a #7069 type glass substrate manufactured by Corning Inc. with a thickness of 1.1 ym. On this substrate, using methyl cellosolve as a solvent, a coating solution having a solution composition in which the organosilicon compounds shown in Table 1 were dissolved at a concentration of 0.1 wt% was spin-coded to 150%.
After heating at ℃ for 1 hour, rubbing was performed in one direction under a pressure of 100 f/i, the rubbed pair of glass substrates were stacked on top of each other so that the upper and lower rubbing directions were parallel, and the parts other than the injection port were sealed. Thereafter, a ferroelectric liquid crystal C5-1014 manufactured by Chisso Corporation was heated to have a positive phase, and the liquid crystal was injected from the injection port under reduced pressure. Thereafter, the injection port was sealed to create a cell.

Table 1 Comparative Examples 1 to 8 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 homogeneous monodomains can be observed are ◎, 80% or more, 01eo% or more are △, and less than 60% are rated x. 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.

Table 3 Effects of the Invention The liquid crystal display element of the present invention uses an organosilicon compound having the structure of the core portion of a liquid crystal material as an alignment film. The alignment of the liquid crystal becomes uniform over the entire 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. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Electrode of transparent conductive film, 3... Orientation i, 4... Seal material, 5... Spacer member, 6... Chiral smectic C liquid crystal material.

Claims (5)

[Claims] (1) In a liquid crystal display element in which a liquid crystal that exhibits an optical change due to an electric field is sealed in a pair of substrates on which conductive films are disposed facing each other, a liquid crystal material is placed on the surface of at least one of the substrates on which conductive films are disposed. 1. A liquid crystal display element comprising an alignment film containing an organic silicon compound having a structure of a core portion. (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 is composed of at least one type selected from the following structures. ▲There are mathematical formulas, chemical formulas, tables, etc.▼▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼▲There are mathematical formulas, chemical formulas, tables, etc.▼ m, n = 0, 1, 2, 3, 4, 5, n=1, 2 but m
+n≠0 ▲ 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, tables, etc. etc. ▼ m, n = 0, 1, but m + n ≠ 0 ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ m + n = 0, 1, however, m + n ≠ 0 ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ Mathematical formulas, chemical formulas , tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼▲ There are mathematical formulas, chemical formulas, tables, etc. ▼▲ Numerical formulas, chemical formulas , tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ n = 1, 2▲Mathematical formula,
There are chemical formulas, tables, etc. ▼ m = 1, 2, n = 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. ▼ (3) An organosilicon compound having the structure of the core part of a liquid crystal material has two benzene rings in one chain bonded to silicon.
The liquid crystal display element according to claim 1 or 2, characterized in that the liquid crystal display element has at least one liquid crystal display element. (4) A patent claim characterized in that the organosilicon compound having the structure of the core portion of a liquid crystal substance is composed of three methoxy or ethoxy groups bonded to silicon and one group having the structure of the core of the liquid crystal substance. The liquid crystal display element according to any one of the ranges 1 to 3. (5) Claim 1, characterized in that the liquid crystal that exhibits optical changes due to an electric field is a ferroelectric liquid crystal.
The liquid crystal display element described in .