IP Library Granted Patent US 7,929,086
Granted Patent B2
US 7,929,086 · App. 12/090,307 · Granted Apr 19, 2011

Laminated film

Assignee: Nitto-Denko Corporation
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Quick Facts
Patent No.
US 7,929,086
App. No.
12/090,307
Granted
Apr 19, 2011
Kind
B2
Abstract

A laminated film includes a polarizing plate, a retardation film, and a first pressure-sensitive adhesive layer provided in this order, wherein the polarizing plate includes a polarizer, a first protective layer placed on a side of the polarizer where the retardation film is provided, and a second protective layer placed on another side of the polarizer which is opposite to the side where the retardation film is provided, the retardation film is a stretched film comprising a norbornene resin, the first pressure-sensitive adhesive layer includes a pressure-sensitive adhesive that may be produced by crosslinking a composition comprising a (meth)acrylate (co)polymer and a crosslinking agent comprising a peroxide as a main component. The laminated film has both good adhesion to a liquid crystal cell and easy peelability, and may improve the uniformity in a screen of liquid crystal display.

Claims (26)

1. A laminated film, comprising a polarizing plate, a retardation film, and a first pressure-sensitive adhesive layer provided in this order,

the polarizing plate comprising a polarizer, a first protective layer placed on a side of the polarizer where the retardation film is provided, and a second protective layer placed on another side of the polarizer which is opposite to the side where the retardation film is provided,

the retardation film being a stretched film comprising a norbornene resin,

the first pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive that may be produced by crosslinking a composition comprising a (meth)acrylate (co)polymer and a crosslinking agent comprising a peroxide as a main component, and

wherein the retardation film has an in-plane retardation (Re[590]) of 80 nm to 350 nm that is measured at 23° C. and a light wavelength of 590 nm.

2. The laminated film according to claim 1 , wherein the first protective layer and/or the second protective layer is a polymer film comprising a cellulose resin.

3. The laminated film according to claim 1 , wherein the first protective layer is substantially optically isotropic.

4. The laminated film according to claim 1 , wherein the first protective layer has a refractive index ellipsoid satisfying the relation nx≈nz>ny, wherein nx is a refractive index in a slow axis direction, ny is a refractive index in a fast axis direction, and nz is a refractive index in a thickness direction.

5. The laminated film according to claim 1 , wherein the retardation film has a refractive index ellipsoid satisfying the relation nx≧nz>ny, wherein nx is a refractive index in a slow axis direction, ny is a refractive index in a fast axis direction, and nz is a refractive index in a thickness direction.

6. The laminated film according to claim 1 , wherein the retardation film has an Nz coefficient of 0.1 to 0.7, wherein the Nz coefficient is calculated from the formula: Rth[590]/Re[590], wherein Re[590] is an in-plane retardation measured at 23° C. and a light wavelength of 590 nm, and Rth[590] is a retardation in a thickness direction that is measured at 23° C. and a light wavelength of 590 nm.

7. The laminated film according to claim 1 , wherein the retardation film has an absolute value of photoelastic coefficient of 1×10 −12 to 10×10 −12 that is measured at 23° C. and a light wavelength of 590 nm.

8. The laminated film according to claim 1 , wherein the first pressure-sensitive adhesive layer has an adhesive force (F A ) of 2 N/25 mm to 10 N/25 mm at 23° C. to a glass plate, wherein the adhesive force is measured by a process that comprises pressing the laminated film with a width of 25 mm against a glass plate by one reciprocation of a 2 kg roller to bond the laminate to the glass plate, aging the laminate at 23° C. for one hour, and then measuring an adhesive strength when the laminated film is peeled in a 90-degree direction at a rate of 300 mm/minute, wherein the adhesive strength is determined as the adhesive force.

9. The laminated film according to claim 1 , wherein the first pressure-sensitive adhesive layer has an anchoring force (F B ) of 10 N/25 mm to 40 N/25 mm at 23° C. to the retardation film, wherein the anchoring force is measured by a process that comprises pressing a laminate of the pressure-sensitive adhesive layer and the retardation film each with a width of 25 mm against a surface of an indium tin oxide vapor-deposited onto a polyethylene terephthalate film by one reciprocation of a 2 kg roller to bond the laminate to the polyethylene terephthalate film, aging the laminate at 23° C. for one hour, and then measuring an adhesive strength when the polyethylene terephthalate film is peeled together with the pressure-sensitive adhesive layer in a 180-degree direction at a rate of 300 mm/minute, wherein the adhesive strength is determined as the anchoring force.

10. The laminated film according to claim 1 , wherein there is a difference (F B −F A ) of at least 5 N/25 mm between the anchoring force (F B ) of the first pressure-sensitive adhesive layer at 23° C. to the retardation film and the adhesive force (F A ) of the first pressure-sensitive adhesive layer at 23° C. to a glass plate,

wherein the anchoring force is measured by a process that comprises pressing a laminate of the pressure-sensitive adhesive layer and the retardation film each with a width of 25 mm against a surface of an indium tin oxide vapor-deposited onto a polyethylene terephthalate film by one reciprocation of a 2 kg roller to bond the laminate to the polyethylene terephthalate film, aging the laminate at 23° C. for one hour, and then measuring an adhesive strength when the polyethylene terephthalate film is peeled together with the pressure-sensitive adhesive layer in a 180-degree direction at a rate of 300 mm/minute, wherein the adhesive strength is determined as the anchoring force, and

the adhesive force is measured by a process that comprises pressing the laminated film with a width of 25 mm against a glass plate by one reciprocation of a 2 kg roller to bond the laminate to the glass plate, aging the laminate at 23° C. for one hour, and then measuring an adhesive strength when the laminated film is peeled in a 90-degree direction at a rate of 300 mm/minute, wherein the adhesive strength is determined as the adhesive force.

11. The laminated film according to claim 1 , wherein the (meth)acrylate (co)polymer is a copolymer of a (meth)acrylate monomer having a straight or branched alkyl group of 1 to 8 carbon atoms and another (meth)acrylate monomer having a straight or branched alkyl group of 1 to 8 carbon atoms in which at least one hydrogen atom is replaced with a hydroxyl group.

12. The laminated film according to claim 1 , wherein the crosslinking agent comprising the peroxide as a main component has a content of 0.01 to 1.0 part by weight, based on 100 parts by weight of the (meth)acrylate (co)polymer.

13. The laminated film according to claim 1 , wherein the first pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive that may be produced by crosslinking a composition comprising a (meth)acrylate (co)polymer, an isocyanate group-containing compound, a silane coupling agent, and a crosslinking agent comprising a peroxide as a main component,

the isocyanate group-containing compound has a content of 0.005 to 1.0 part by weight, based on 100 parts by weight of the (meth)acrylate (co)polymer, and

the silane coupling agent has a content of 0.001 to 2.0 parts by weight, based on 100 parts by weight of the (meth)acrylate (co)polymer.

14. The laminated film according to claim 1 , wherein the pressure-sensitive adhesive has a glass transition temperature (Tg) of −70° C. to −10° C.

15. The laminated film according to claim 1 , wherein the pressure-sensitive adhesive has a moisture content of 1.0% or less.

16. The laminated film according to claim 1 , further comprising a second pressure-sensitive adhesive layer between the polarizing plate and the retardation film, wherein the second pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive that may be produced by crosslinking a composition comprising a (meth)acrylate (co)polymer, a silane coupling agent, and a crosslinking agent comprising an isocyanate group-containing compound as a main component.

17. A liquid crystal display panel, comprising the laminated film according to claim 1 , and a liquid crystal cell.

18. A liquid crystal display, comprising the liquid crystal panel according to claim 17 .

Assignments (1)
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Apr 16, 2008
From: TOYAMA, YUUSUKE; SATAKE, MASAYUKI; YODA, KENJI; TOMONAGA, MASATOSHI; YANO, SHUUJI
To: NITTO DENKO CORPORATION
Reel/Frame 020812/0489 →
Priority Claims (1)
JP 2005-305198 · Oct 20, 2005 · national
Continuity (1)
Related Publication 20090279030A1 · Nov 12, 2009