Method for preparing photoalignment layer

Patent metadata

Field	Value
Publication number	US-10606128-B2
Application number	US-201615743958-A
Country	US
Kind code	B2
Filing date	Sep 6, 2016
Priority date	Oct 2, 2015
Publication date	Mar 31, 2020
Grant date	Mar 31, 2020

Abstract

The present invention relates to a method for preparing a photo-alignment layer. The photo-alignment layer prepared by the preparation method exhibits a high imidization ratio as well as an excellent aligning stability of liquid crystal, chemical resistance and strength, and has an excellent afterimage suppressing effect by an AC driving of a liquid crystal display element.

First claim

The invention claimed is:

1. A method for preparing a photo-alignment layer, comprising the steps of preparing a polymer by reacting a diamine represented by the following Chemical Formula 1 with at least one tetracarboxylic acid or its anhydride; preparing a liquid crystal alignment agent by dissolving or dispersing said polymer in an organic solvent; and coating said liquid crystal alignment agent onto a substrate, and then subjecting to i) a sintering after an irradiation with light, or ii) a sintering during an irradiation with light, or iii) an irradiation with light after a sintering,
wherein the photo-alignment layer exhibits a luminance variation rate of 41% or less represented by the following Equation 1:

in the Chemical Formula 1,
Y 1 is a tetravalent organic group derived from cyclic hydrocarbons having 4 to 8 carbon atoms, or a tetravalent organic group derived from compounds in which two or more of said cyclic hydrocarbons are linked by a single bond, —O—, —CR 1 R 2 —, —CO—, —CONH—, —COO—, —S—, —SO 2 — or a combination thereof, or a tetravalent organic group in which one or more hydrogens in said tetravalent organic group are substituted with an alkyl group having 1 to 3 carbon atoms, with a proviso that Y 1 is not a tetravalent organic group derived from unsubstituted cyclobutane,
wherein R 1 and R 2 is each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, or a fluoroalkyl group having 1 to 10 carbon atoms,
each of Z 1 is independently a divalent organic group represented by the following Chemical Formula 2,

in the Chemical Formula 2,
R 3 and R 4 are each independently a halogen, a cyano group, an alkenyl group having 2 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms,
p and q are each independently an integer between 0 and 4,
L 1 is a single bond, —O—, —CO—, —S—, —SO 2 —, —C(CH 3 ) 2 —, —C(CF 3 ) 2 —, —CONH—, —COO—, —(CH 2 ) a —, —O(CH 2 ) a O—, —OCH 2 —C(CH 3 ) 2 —CH 2 O— or —COO—(CH 2 ) a —OCO—, wherein a is an integer between 1 to 10, and
n is an integer between 0 and 3,
Luminance variation rate (%)=(| L 0− L 1|)/ L 0*100  [Equation 1]

in the Equation 1,
L0 is an initial luminance wherein luminance at the black state is measured using a luminance measurement apparatus, after arranging two liquid crystal alignment layers so as to face each other, sealing their edges excluding an inlet so as to be spaced 1-2 mm apart from each other, injecting a liquid crystal and sealing the inlet to produce a liquid crystal cell, then attaching a polarizing plate to both sides of the liquid crystal cell so as to be perpendicular to each other, and attaching the polarizing plate to a backlight of 7,000 cd/m 2 , and
L1 is a late luminance wherein luminance at the black state is measured in the same manner as in the method of measuring L0, after driving the liquid crystal cell at 60° C. for 24 hours by applying a voltage of 12V at 60 Hz, and then turning off the voltage of the liquid crystal cell.

2. The method for preparing a photo-alignment layer according to claim 1 , wherein Y 1 in Chemical Formula 1 is a tetravalent organic group derived from 1-methylcyclobutane, dimethylcyclobutane, 1,2,3,4-tetramethylcyclobutane, cyclopentane, 1-methylcyclopentane, cyclohexane, 1-methylcyclohexane, benzene, diphenyl ether, biphenyl, benzophenone, 2,2-diphenylpropane, diphenylsulfone or perfluoropropane-2,2-diyl dibenzene.

3. The method for preparing a photo-alignment layer according to claim 1 , wherein Y 1 in Chemical Formula 1 is a tetravalent organic group derived from dimethylcyclobutane or 1,2,3,4-tetramethylcyclobutane.

4. The method for preparing a photo-alignment layer according to claim 1 , wherein Z 1 in Chemical Formula 1 is a phenylene group or a biphenyldiyl group.

5. The method for preparing a photo-alignment layer according to claim 1 , wherein the diamine represented by Chemical Formula 1 is at least one compound selected from the following Chemical Formulae 1a to 1d:

6. The method for preparing a photo-alignment layer according to claim 1 , wherein a tetracarboxylic acid or its anhydride of the following Chemical Formula 3 is used as the tetracarboxylic acid or its anhydride:

in the Chemical Formula 3,
Y 2 is a tetravalent organic group derived from cyclic hydrocarbons having 4 to 8 carbon atoms, or a tetravalent organic group derived from compounds in which two or more of said cyclic hydrocarbons are linked by a single bond, —O—, —CR 1 R 2 —, —CO—, —CONH—, —COO—, —S—, —SO 2 — or a combination thereof, or a tetravalent organic group in which one or more hydrogens in the tetravalent organic group are substituted with an alkyl group having 1 to 3 carbon atoms,
wherein R 1 and R 2 is each independently hydrogen, an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms.

7. The method for preparing a photo-alignment layer according to claim 6 , wherein Y 2 in Chemical Formula 3 is a tetravalent organic group having the following structure:

wherein R 1 and R 2 are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms.

8. The method for preparing a photo-alignment layer according to claim 1 , wherein, through the step of preparing the polymer, a polymer containing a repeating unit of the following Chemical Formula 4 is prepared:

in the Chemical Formula 4,
Y 1 and Y 2 are each independently a tetravalent organic group derived from cyclic hydrocarbons having 4 to 8 carbon atoms, or a tetravalent organic group derived from compounds in which two or more of said cyclic hydrocarbons are linked by a single bond, —O—, —CR 1 R 2 —, —CO—, —CONH—, —COO—, —S—, —SO 2 — or a combination thereof, or a tetravalent organic group in which one or more hydrogens in the tetravalent organic group are substituted with an alkyl group having 1 to 3 carbon atoms, with a proviso that Y 1 is not a tetravalent organic group derived from unsubstituted cyclobutane,
wherein R 1 and R 2 is each independently hydrogen, an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms,
each of Z 1 is independently a divalent organic group represented by the following Chemical Formula 2,

in the Chemical Formula 2,
R 3 and R 4 are each independently a halogen, a cyano group, an alkenyl group having 2 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms or a fluoroalkyl group having 1 to 10 carbon atoms,
p and q are each independently an integer between 0 and 4,
L 1 is a single bond, —O—, —CO—, —S—, —SO 2 —, —C(CH 3 ) 2 —, —C(CF 3 ) 2 —, —CONH—, —COO—, —(CH 2 ) a —, —O(CH 2 ) a O—, —OCH 2 —C(CH 3 ) 2 —CH 2 O— or —COO—(CH 2 ) a —OCO—, wherein

Assignees

• Lg Chemical Ltd

Inventors

• Kwon Soon Ho
• Han Hee
• Jo Jung Ho
• Park Hang Ah
• Yoon Jun Young
• Yun Hyeong Seuk

Classifications

• G02F1/133788

  by light irradiation, e.g. linearly polarised light photo-polymerisation · CPC title

• G02F1/133723 Primary

  Polyimide, polyamide-imide · CPC title

• C09K19/56

  Aligning agents · CPC title

• C09K19/542

  Macromolecular compounds · CPC title

• C08G73/1007

  from tetracarboxylic acids or derivatives and diamines · CPC title