Elongated film manufacturing method, long polarizing film, and liquid-crystal display device

Patent metadata

Field	Value
Publication number	US-10160157-B2
Application number	US-201415035792-A
Country	US
Kind code	B2
Filing date	Nov 13, 2014
Priority date	Nov 15, 2013
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

The present invention provides a method for producing a stretched film, the method including: (a) a first step of stretching a long-length pre-stretch film in a diagonal direction at a stretch ratio B1 to obtain a long-length intermediate film; and after the first step, (b) a second step of performing free uniaxial stretching of the intermediate film in a flow direction at a stretch ratio B2 while continuously conveying the intermediate film to obtain a long-length stretched film, wherein the stretch ratios satisfy B1>B2.

First claim

The invention claimed is:

1. A method for producing a stretched film, the method comprising:
(a) a first step of stretching a long-length pre-stretch film in a diagonal direction at a stretch ratio B1 to obtain a long-length intermediate film that has an average in-plane retardation Re1 of the long-length intermediate film is 300 nm or more; and
after the first step, (b) a second step of performing free uniaxial stretching of the long-length intermediate film that has an average in-plane retardation Re1 of the long-length intermediate film is 300 nm or more in a flow direction at a stretch ratio B2 while continuously conveying the long-length intermediate film to obtain a long-length stretched film, wherein
the stretch ratios satisfy B1>B2;
an average NZ coefficient of the stretched film is 2.0 to 3.0
the expression “long-length” means a shape in which the length is 5 times or more longer than a width thereof; and
the NZ coefficient is a value represented by (nx−nz)/(nx−ny), where nx represents a refractive index in a direction perpendicular to a thickness direction and in a direction providing the maximum refractive index, ny represents a refractive index in a direction perpendicular to the thickness direction and in a direction orthogonal to the direction of nx, and nz represents a refractive index in the thickness direction.

2. The method for producing a stretched film according to claim 1 , wherein
the stretch ratio B1 at the first step is 1.5 times to 4.0 times; and
the stretch ratio B2 at the second step is 1.1 times to 2.0 times.

3. The method for producing a stretched film according to claim 1 , wherein
the long-length intermediate film has a slow axis in a range of 10° to 35° on average with respect to a width direction of the long-length intermediate film; and
the stretched film has a slow axis in a range of 10° to 80° on average with respect to a width direction of the stretched film.

4. The method for producing a stretched film according to claim 1 , wherein a stretching temperature T1 at the first step and a stretching temperature T2 at the second step satisfy T1−5° C.<T2<T1+5° C.

5. The method for producing a stretched film according to claim 1 , wherein
an average in-plane retardation Re2 of the stretched film is 100 nm to 200 nm.

Assignees

• Zeon Corp

Inventors

• Kobayashi Takao

Classifications

• G02B5/30

  Polarising elements (light-modulating devices with active elements G02F1/00) · CPC title

• B29C55/16

  simultaneously · CPC title

• B29C55/065

  in several stretching steps · CPC title

• B29D11/00644

  polarizing · CPC title

• B29D11/00788

  Producing optical films · CPC title