# US 2015/0146293 A1 · Method for producing optical film laminate, thin polarizing film, polarizing plate, and liquid crystal display device

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- Number: US 2015/0146293 A1
- Document ID: US20150146293A1
- Status: Published application
- Kind: A1
- Application number: 14/401,023
- Filed: 2013-06-14
- Published: 2015-05-28
- Earliest claimed: 2012-06-21
- Assignees: Konica Minolta, Inc.
- Applicants: Konica Minolta, Inc.
- Inventors: Tatsuya Sasaki
- Web page: https://patentgrep.com/patent/US20150146293A1

## CPC

- C08J 7/043: Improving the adhesiveness of the coatings per se, e.g. forming primers (adhesives in the form of films or foils characterised by the primer layers between the polymer carriers and the adhesives C09J7/50)
- B29D 11/00644: {polarizing}
- B29D 11/0073: {Optical laminates}
- B32B 33/00: Layered products characterised by particular properties or particular surface features, e.g. particular surface coatings; Layered products designed for particular purposes not covered by another single class
- B32B 37/24: with at least one layer not being coherent before laminating, e.g. made up from granular material sprinkled onto a substrate (B32B37/15 takes precedence)
- B32B 38/0012: {Mechanical treatment, e.g. roughening, deforming, stretching}
- B32B 38/10: Removing layers, or parts of layers, mechanically or chemically
- C08J 7/0427: {with only one layer of a composition containing a polymer binder (with more layers C08J7/042)}
- C08J 7/056: Forming hydrophilic coatings
- G02B 1/18: Coatings for keeping optical surfaces clean, e.g. hydrophobic or photo-catalytic films (G02B1/16 takes precedence)
- G02B 5/3025: {Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state (G02B5/3008, G02B5/3016 take precedence)}
- G02B 5/3033: {in the form of a thin sheet or foil, e.g. Polaroid}
- B32B 38/08: Impregnating
- B32B 2037/243: {Coating}
- B32B 2038/0028: {Stretching, elongating}
- B32B 2307/40: having particular optical properties
- B32B 2307/42: Polarizing, birefringent, filtering
- B32B 2307/728: Hydrophilic
- C08J 2367/02: Polyesters derived from dicarboxylic acids and dihydroxy compounds; (C08J2367/06 takes precedence)
- C08J 2429/04: Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

The present invention addresses the problem of providing: a method for producing an optical film laminate that has a thin polarizing film and is free from unevenness in the degree of polarization in the film width direction; a thin polarizing film which is free from unevenness in the degree of polarization; and a liquid crystal display device. A method for producing an optical film laminate according to the present invention comprises: (1) a lamination step wherein a hydrophilic polymer layer is laminated on a thermoplastic resin base, thereby forming a laminate; (2) a stretching step wherein the laminate is stretched in the air, thereby forming a stretched laminate that comprises an oriented hydrophilic polymer layer; and (3) a dyeing step wherein the hydrophilic polymer layer is caused to adsorb a dichroic dye. This method for producing an optical film laminate is characterized in that the temperature of the base in an end portion in the TD direction, on said portion the hydrophilic polymer layer being not laminated, is higher than the temperature of the base in the central portion in the TD direction by 1-40° C. during the stretching in the air.

## Claims

### Claim 1

A method for producing an optical film laminate, comprising:
(1) a laminating step of laminating a hydrophilic polymer layer on a thermoplastic resin base to form a laminate;
(2) a stretching step of stretching the laminate in the air to form a stretched laminate comprising the oriented hydrophilic polymer layer; and
(3) a staining step of allowing a dichroic substance to adsorb on the hydrophilic polymer layer,
wherein, in the stretching step in the air, a temperature of an edge part of the base in a transverse direction where the hydrophilic polymer layer is not laminated is 1° C. to 40° C. higher than a temperature of a center part of the base in the transverse direction.

### Claim 2 (depends on 1)

The method for producing the optical film laminate according to claim 1,
wherein the hydrophilic polymer layer of the optical film laminate has a thickness within a range from 2 to 10 μm,
wherein the base of the optical film laminate has a thickness within a range from 5 to 45 μm, and
wherein the base before the laminating step has a water absorption coefficient determined by the following Expression (1) according to JIS K 7209 (Method A) within a range from 0.3% to 4.3%,
Water absorption coefficient=(w2−w1)/w1×100(%), Expression (1):
where w1 is a dry mass (mg) of a test piece before being immersed in water, and w2 is a mass (mg) of the test piece after being immersed in water at 23.0±1.0° C. for 24±1 hours.

### Claim 3 (depends on 1)

The method for producing the optical film laminate according to claim 1, wherein a hydrophilic polymer of the hydrophilic polymer layer is a polyvinyl alcohol resin.

### Claim 4 (depends on 1)

The method for producing the optical film laminate according to claim 1, wherein the hydrophilic polymer layer is a thin polarizing film that is adjusted such that a polarization degree A at a center of the thin polarizing film in the transverse direction and a polarization degree B at 25 mm inward from an edge of the thin polarization film in the transverse direction satisfy the following Expression (2).
0.999≦A/B≦1.001 Expression (2):

### Claim 5 (depends on 1)

The method for producing the optical film laminate according to claim 1, further comprising, in addition to the steps (1) to (3), the steps of:
(4) a pasting step of pasting a second optical film on a surface of the hydrophilic polymer layer via an adhesive; and
(5) a peeling step of peeling off the base.

### Claim 6

A thin polarizing film that is a hydrophilic polymer layer having a thickness of 2 to 10 μm, wherein a polarization degree A at a center of the polarizing film in a transverse direction and a polarization degree B at 25 mm inward from an edge of the polarization film in the transverse direction satisfy the following Expression (2),
0.999≦A/B≦1.001. Expression (2):

### Claim 7 (depends on 1)

A polarizing plate comprising an optical film laminate that is produced by the method for producing the optical film laminate according to claim 1.

### Claim 8 (depends on 1)

A liquid display device comprising an optical film laminate that is produced by the method for producing the optical film laminate according to claim 1.