Optical film and liquid crystal display

• US 5,880,800 A
• Filed: 01/06/1997
• Issued: 03/09/1999
• Est. Priority Date: 01/09/1996
• Status: Expired due to Term

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Mikura, Chiemi, Yamaoka, Takashi, Wakabayashi, Akira
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/779,362
• Time in Patent Office: 792 Days
• Field of Search: 349/122, 349/96, 349/117, 427/208.4, 427/207.01, 428/343, 428/354
• US Class Current: 349/122
• CPC Class Codes: B32B 2307/40 having particular optical properties
• CPC Class Codes: B32B 2551/00 Optical elements
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: Y10T 428/28 Web or sheet containing structurally defined element or component and having an adhesive outermost layer
• CPC Class Codes: Y10T 428/2848 Three or more layers

Abstract

An optical film comprising an optical base film having one surface or both surface thereof multilayers of pressure-sensitive adhesive layers, wherein the multilayers comprise a combination of pressure-sensitive adhesive layers each having a different stress relaxation time, the pressure-sensitive adhesive layer having the longest stress relaxation time is disposed at the outermost side, and the thickness thereof is 80% or less of the total thickness of the pressure-sensitive layers. The optical film is excellent in heat resistance and moisture resistance, is not difficult to cause foaming and pealing at the interface between a liquid crystal cell and the film even in using at high temperature and high moisture atmosphere, and is suitable for providing a liquid crystal display.

Claims

1. An optical film comprising an optical base film having on one surface or both surfaces thereof multilayers of pressure-sensitive adhesive layers, wherein the multilayers comprise a combination of pressure-sensitive adhesive layers each having a different stress relaxation time, the pressure-sensitive adhesive layer having the longest stress relaxation time is disposed at the outermost position, and a thickness of said pressure-sensitive layer having the longest relaxation time is 80% or less of the total thickness of the pressure-sensitive adhesive layers.

2. The optical film of claim 1, wherein the stress relaxation time of the pressure-sensitive adhesive layers at 23°

C. is at least 100 seconds in the outermost pressure-sensitive adhesive layer and 300 seconds or less in the pressure-sensitive adhesive layer under the outermost layer, and the difference between the stress relaxation time of the outermost layer and that of the layer under the outermost layer is at least 50 seconds.

3. The optical film of claim 1, wherein the optical base film is a polarizing film, a reflection-type polarizing film, or a retardation film.

4. The optical film of claim 1, wherein the optical base film is an elliptically polarizing film obtained by laminating a polarizing film and a retardation film via a pressure-sensitive adhesive layer or a reflection-type elliptically polarizing film obtained by laminating a reflection-type polarizing film and a retardation film via a pressure-sensitive adhesive layer.

5. A liquid crystal display comprising a liquid crystal cell having adhered to one side or both sides thereof at least one of the optical film as claimed in claim 1.