Process for inducing alignment of liquid crystals and liquid crystal optical elements

• US 5,958,293 A
• Filed: 05/18/1998
• Issued: 09/28/1999
• Est. Priority Date: 03/29/1996
• Status: Expired due to Fees

• Current Assignee: Elsicon Incorporated
• Original Assignee: Elsicon Incorporated
• Inventors: Gibbons, Wayne M., Zheng, Hanxing, Shannon, Paul Joseph
• Primary Examiner(s): KELLY, CYNTHIA HARRIS
• Application Number:
  US09/080,639
• Time in Patent Office: 498 Days
• Field of Search: 428/1, 428/473.5, 252/299.4, 349/191
• US Class Current: 252/299.4
• CPC Class Codes: C08G 73/10 Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: C08G 73/1039 comprising halogen-containing substituents
• CPC Class Codes: C08G 73/1042 Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds
• CPC Class Codes: C08G 73/1085 Polyimides with diamino moieties or tetracarboxylic segments containing heterocyclic moieties
• CPC Class Codes: C09K 2323/02 Alignment layer characterised by chemical composition
• CPC Class Codes: C09K 2323/025 Polyamide
• CPC Class Codes: C09K 2323/027 Polyimide
• CPC Class Codes: G02F 1/133723 Polyimide, polyamide-imide
• CPC Class Codes: G02F 1/133742 for homeotropic alignment
• CPC Class Codes: G02F 1/133753 with different alignment orientations or pretilt angles on a same surface, e.g. for grey scale or improved viewing angle
• CPC Class Codes: G02F 1/133788 by light irradiation, e.g. linearly polarised light photo-polymerisation
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10T 428/31721 Of polyimide

Abstract

A process for inducing alignment of a liquid crystal medium adjacent to a surface of an optical alignment layer comprising: exposing at least one optical alignment layer to polarized light; the polarized light having a wavelength within the absorption band of said optical alignment layer; wherein the exposed alignment layer induces alignment of the liquid crystal medium at an angle + and -θ with respect to the direction of the polarization of the incident light beam and along the surface of the optical alignment layer; and applying a liquid crystal medium to the optical alignment layer, wherein the optical alignment layer is a polyimide comprising an an amine component having a 2-substituted 1,4-benzenediamine wherein the 2-substituent X₁ is an electron withdrawing group having a positive σ. Also claimed is a liquid crystal display element made by the process.

Claims

1. A process for inducing alignment of a liquid crystal medium adjacent to a surface of an optical alignment layer comprising:

(a) exposing at least one optical alignment layer to polarized light;

the polarized light having a wavelength within the absorption band of said optical alignment layer;

wherein the exposed alignment layer induces alignment of the liquid crystal medium at an angle + and -θ

with respect to the direction of the polarization of the incident light beam and along the surface of the optical alignment layer; and

(b) applying a liquid crystal medium to the optical alignment layer, wherein the optical alignment layer is a polyimide of structure I ##STR11## comprising the reaction product of at least one tetracarboxylic dianhydride and an amine component, wherein the amine component comprises a 2-substituted 1,4-benzenediamine wherein the 2-substituent X₁ is an electron withdrawing group having a positive σ

, and M is a tetravalent organic radical derived from said tetracarboxylic dianhydride containing at least two carbon atoms, no more than two carbonyl groups of the dianhydride being attached to any one carbon atom of the tetravalent radical.

2. A process of claim 1 wherein X₁ is selected from the group --CN, --CF₃, F, Cl, Br, I, --NO₂, --CO₂ R, and --CON(R)₂, wherein R is H or a C₁ -C₄ hydrocarbon.

3. A process of claim 2 wherein X₁ is selected from the group --CN and --CF₃.

4. A process of claim 1 wherein the tetracarboxylic dianhydride is selected from 3,3'"'"',4,4'"'"'-benzophenonetetracarboxylic dianhydride and 2,2'"'"'-dichloro-4,4'"'"',5,5'"'"'-benzophenone tetracarboxylic dianhydride.

5. A liquid crystal display element comprising a liquid crystal medium aligned by the process of claim 1.