JPH0346623A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the tilt orientation approximate to a homeotropic orientation by depositing a metal oxide by oblique vapor deposition on at least either of 1st and 2nd substrates, then applying an orienting agent consisting of a mixture composed of a Ti compd. and Cr compd. thereon and subjecting the coating to an orientation treatment. CONSTITUTION:After the metal oxide 8 is deposited by oblique vapor deposition on at least either of the 1st and 2nd substrates 5, 6, the orienting agent 9 consisting of the mixture composed of the Ti compd. and the Cr compd. is applied thereon and the coating is subjected to the orientation treatment. MgF2, Al2O3, Sm2O3, SiO, CeF3, SiO2, etc., are preferably used as the metal oxide 8. The incident angle of the oblique vapor deposition is 70 to 89.9 deg., more prefer ably 83 to 89.5 deg. with the direction perpendicular to the substrate. The thickness of the vapor deposited film of the metal oxide 8 of this time is preferably 100 to 3,000Angstrom . The tilt orientation approximate to the homeotropic orientation which is heretofore difficult, i.e. the orientation of about 85 to 89.5 deg. pretilt angle is obtd. uniformly over a wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display element, and further relates to an alignment treatment thereof.

[Prior Art] A liquid crystal display element using the ECB mode consists of a liquid crystal cell in which a liquid crystal is sandwiched between two electrode substrates facing each other, and polarizing plates placed on both sides of the liquid crystal cell. In addition, an optically anisotropic body other than the above liquid crystal may be further provided especially for viewing angle compensation.

The orientation of the liquid crystal molecules in the liquid crystal cell is a tilted orientation close to the homeotropic orientation in both the first and second substrates, and the pretilt angle, which is the angle that the long axis of the liquid crystal molecules makes with the substrate surface, is , is set to about 85 to 89.5a with respect to the substrate surface. The purpose of this pretilt angle is to cause liquid crystal molecules to tilt in a certain direction when a voltage is applied to the liquid crystal cell. In order to achieve this pretilt angle, Si coupling agents, polyimides, aliphatic carboxylic acid Cr complexes, and the like have been used by coating them on the substrate surface.

[Problems and objects to be solved by the invention] When the above-mentioned alignment agent is used, there are problems such as the pretilt angle showing a predetermined pretilt angle immediately after alignment, but increasing over time, or the specific resistance of the cell being low. was there.

When the pretilt angle changes, the electro-optic characteristics of the liquid crystal optical element change accordingly, and there is a possibility that a reliable optical element cannot be obtained.

Furthermore, if the specific resistance of the cell is low, there is a possibility that the cell will not operate in extreme cases, especially if a TPT element is used.

Therefore, the present invention aims to develop an alignment agent that realizes tilt alignment close to homeotropic alignment, which has the characteristics of extremely little change in pretilt angle over time and high cell resistivity.

[Means for Solving the Problems] The present inventor has made earnest efforts to solve the above-mentioned problems and realize a stable pretilt angle, and as a result, has arrived at the present invention.

That is, the liquid crystal display element of the present invention includes at least a first substrate provided with a transparent electrode, a second substrate provided with a transparent electrode, a liquid crystal sandwiched between the two substrates, and a liquid crystal sandwiched between them. In a liquid crystal display element consisting of a pair of polarizing plates arranged on both sides, a metal oxide is obliquely vapor-deposited on at least one of the first and second substrates, and then a Ti
It is characterized in that an alignment agent made of a mixture of a compound and a Cr compound is applied and subjected to alignment treatment.

Examples of metal oxides include M g F 2, Al2O3, S
m2O3, SiO, CeF3, SiO2, etc. are preferably used. The large oblique angle of oblique vapor deposition is preferably 70 to 89.9 degrees, more preferably 83 to 89.5 degrees with respect to the direction perpendicular to the substrate. The thickness of the metal oxide vapor deposition film at this time is preferably 100 to 3000A.

The following mixture of Ti compound and Cr compound is used to coat the metal oxide vapor deposited film thus formed. That is, as a Ti compound, T i (0-C3H?) 41T i (0-C
4H9) a, Ti alkoxide compounds such as Ti (OC+7Has) a, and partial hydrolysates of the Ti alkoxide compounds, Ti(0-Cs Hv) α
(OCOC+vH3s)β, Ti(0-C3H7>α(
QC(CH3)CHCOCH*)β(α=1~3.β=
Ti acylate compounds such as 4-α> are preferably used.

Preferable Cr compounds include aliphatic carboxylic acid Cr complexes such as butyric acid, caproic acid, pelargonic acid, capric acid, undecanoic acid, stearic acid, and myristic acid, and fluorine-substituted carboxylic acid Cr complexes such as perfluorononanoic acid. used.

The mixing ratio of these Ti compounds and Cr compounds is 1:10.
~10:1 (weight ratio) is preferably used.

[Example] Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 shows a cross-sectional view of a liquid crystal display cell in an embodiment of the present invention. In the figure, 1 is an upper polarizing plate and 4 is a lower polarizing plate.

The two polarizing plates have a so-called crossed nicol relationship in which their absorption axes are orthogonal to each other. Further, the absorption axis direction of the upper polarizing plate forms an angle of 45'' with the rubbing direction of the first substrate of the adjacent liquid crystal cell.

SiO was obliquely vapor-deposited on the first substrate 5 and second substrate 6 of the liquid crystal cell at an incident angle of 88 degrees so that the film thickness was 2000 nm. A mixture of myristin HCrR and Ti (QC2Hs) 4 (mixing ratio 1:1 by weight) was applied as an alignment treatment agent onto this vapor-deposited film for alignment treatment.

The thus obtained substrate was assembled into a cell, and liquid crystal was sealed. Cell gap d was set to 6.0 μm. As the liquid crystal 10, ZLI-4318 manufactured by Merck & Co. (n-type liquid crystal Δε=-2,0Δn=0.1243) was used.

The pretilt angle of the obtained liquid crystal cell was 87 degrees (the pretilt angle was measured by the crystal rotation method in a magnetic field). Also, the specific resistance is 1.45xlO”Ω
・It was (1).

The contrast ratio of the liquid crystal display cell obtained in this way is
The contrast ratio is approximately 1:180 in the normal direction of the cell, and a uniform and good contrast ratio can be obtained throughout the cell. A close tilt orientation, that is, an orientation with a pretilt angle of about 85 to 89.5@ is obtained uniformly and over a wide range.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross-sectional view of a liquid crystal display cell in an example of the present invention, and FIG. 2 is a diagram showing an incident angle in oblique vapor deposition. Upper polarizing plate Optically anisotropic liquid crystal molecule pretilt angle Lower polarizing plate Second substrate Second substrate Transparent electrode Si○ Oblique vapor deposition film 9° 10° 11° 12° 13° 14° Aligning agent n-type nematic Incident angle deposition source for substrate deposition on which liquid crystal sealant is deposited

Claims (1)

[Claims] At least a first substrate provided with a transparent electrode, a second substrate provided with a transparent electrode, a liquid crystal sandwiched between the two substrates, and a pair of polarized lights disposed on both sides of the substrate. In a liquid crystal display element made of a plate, a metal oxide is obliquely vapor-deposited on at least one of the first and second substrates, and then an alignment agent made of a mixture of a Ti compound and a Cr compound is applied for alignment treatment. A liquid crystal display element characterized by: