Method for producing retardation film

Patent metadata

Field	Value
Publication number	US-9694550-B2
Application number	US-201514690563-A
Country	US
Kind code	B2
Filing date	Apr 20, 2015
Priority date	Feb 14, 2008
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A method for producing a retardation film comprising the steps of: (a) uniaxially stretching an original film for producing retardation film in one direction at either a temperature T 1 or T 2 ; and then (b) uniaxially stretching the film stretched in the step (a) in a direction perpendicular to the above-mentioned direction of stretching at a temperature T 2 or T 1 different from the above-mentioned temperature, in which the original film for producing retardation film has a characteristic that a phase of linearly polarized light entering vertically into the film plane and having an oscillating surface of an electric vector in an X-Z plane against linearly polarized light entering vertically into the film plane and having an oscillating surface of an electric vector in a Y-Z plane lags by uniaxially stretching in the direction of the X axis at a temperature T 1 , and leads by uniaxially stretching in the direction of the X axis at a temperature T 2 different from the above-mentioned temperature T 1 , in which the X axis is an uniaxially stretching direction, the Y axis is a direction perpendicular to the uniaxially stretching direction in the film plane, and the Z axis is a direction of a thickness of the film.

First claim

What is claimed is:

1. A method for producing a retardation film which satisfies a relation of n x >n z >n y , in which n x is a refractive index in a direction of a slow axis in a plane of the film, n y is a refractive index in a direction perpendicular to the direction of the slow axis in the plane, and n z is a refractive index in a thickness direction, the method comprising the steps of:
(a) uniaxially stretching an original film for producing retardation film in one direction at a temperature T 1 which is not less than (Ts B +5)° C. and not more than (Ts A +3)° C.; and then
(b) uniaxially stretching the film stretched in the step (a) in a direction perpendicular to the direction of stretching in the step (a) at a temperature T 2 which is not more than (Ts A +3)° C.,
wherein the original film for producing the retardation film is a laminate comprising
a layer comprising a thermoplastic resin A having a positive intrinsic birefringence and a deflection temperature under load (Ts A ), and
a layer comprising a thermoplastic resin B having a negative intrinsic birefringence and a deflection temperature under load (Ts B ), the deflection temperature under load (Ts A ) is higher than the deflection load temperature under (Ts B ),
and wherein if and when the original film is stretched at the temperature T 2 , an absolute value of a phase difference which appears in the resin A is small than an absolute value of the phase difference which appears in the resin B, and
if and when the original film is stretched at the temperature T 1 , an absolute value of the phase difference which appears in the resin B is smaller than an absolute value of the phase difference which appears in the resin A.

2. The method according to claim 1 , in which an absolute value of difference between the deflection temperature under load Ts A of the thermoplastic resin A and the deflection temperature under load Ts B of the thermoplastic resin B is 5° C. or more.

3. The method according to claim 1 , in which a rupture elongation of the thermoplastic resin A at the temperature TS B and a rupture elongation of the thermoplastic resin B at the temperature Ts A are both 50% or more.

4. The method according to claim 1 , in which the thermoplastic resin A is a polycarbonate resins and the thermoplastic resin B is a polystyrene resins.

5. The method according to claim 1 , in which a ratio of sum total thickness of layers composed of the thermoplastic resin A and sum total thickness of layers composed of the thermoplastic resin B is 1:5 to 1:10.

Assignees

• Zeon Corp

Inventors

• Hatano Taku

Classifications

• B32B2307/516

  mono-axially · CPC title

• B32B2307/42

  Polarizing, birefringent, filtering · CPC title

• C08J2369/00

  Characterised by the use of polycarbonates; Derivatives of polycarbonates · CPC title

• B32B27/36

  comprising polyesters · CPC title

• B32B27/365

  comprising polycarbonates · CPC title