Biaxially stretched film and method of manufacturing the same, polarizer protective film, decorative film, and layered film

Patent metadata

Field	Value
Publication number	US-10464253-B2
Application number	US-201515300527-A
Country	US
Kind code	B2
Filing date	Mar 26, 2015
Priority date	Mar 31, 2014
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

A method of manufacturing a biaxially stretched film according by: (I) preheating a thermoplastic resin film to a temperature in a rubbery plateau region in a storage elastic modulus curve; (II) biaxially stretching the thermoplastic resin film under a condition that a stretching speed is 500%/min or higher while heating the thermoplastic resin film to the temperature in the rubbery plateau region; (III) cooling the thermoplastic resin film after the biaxially stretching (II) to a temperature in a glass-to-rubber transition region or a glass region in the storage elastic modulus curve; and (IV) relaxing the thermoplastic resin film after the cooling (III) at a temperature in the glass-to-rubber transition region.

First claim

The invention claimed is:

1. A method of manufacturing a biaxially stretched film in which an unstretched thermoplastic resin film comprising at least one thermoplastic resin layer is biaxially stretched in a longitudinal direction and a width direction to manufacture the biaxially stretched film, the method comprising:
(I) preheating the thermoplastic resin film to a temperature in a rubbery plateau region in a storage elastic modulus curve;
(II) biaxially stretching the thermoplastic resin film under a condition that a stretching speed is 500%/min or higher while heating the thermoplastic resin film to the temperature in the rubbery plateau region;
(III) subsequently cooling the thermoplastic resin film to a temperature in a glass-to-rubber transition region or a glass region in the storage elastic modulus curve; and
(IV) subsequently relaxing the thermoplastic resin film at a temperature in the glass-to-rubber transition region,
wherein both a relaxation speed in the longitudinal direction and a relaxation speed in the width direction in said relaxing (IV) are 80%/min or higher, and
wherein both a stretching magnification of the thermoplastic resin film in the longitudinal direction and a stretching magnification of the thermoplastic resin film in the width direction after (II) to (IV) with respect to the thermoplastic resin film before said biaxially stretching (II) are 1.5 to 3 times,
wherein the at least one thermoplastic resin layer comprises a methacryl resin in which a triad syndiotacticity (rr) is 50% or larger.

2. The method according to claim 1 , wherein both a relaxation rate in the longitudinal direction and a relaxation rate in the width direction in said relaxing (IV) with respect to the thermoplastic resin film after said cooling (III) are 5 to 10.

3. The method according to claim 1 , wherein the biaxially stretched film has a deformation rate (%) expressed by the following Expression (1) of 0 to 0.5%:
Deformation rate (%)=Δ L (mm)/10 (mm)×100  (1)

wherein ΔL (mm)=L85 (mm)−L45 (mm), and
wherein the deformation rate (%) is measured by:
cutting a test piece with a length of 20 mm, a width of 5 mm, and a thickness of 45 μm out of the biaxially stretched film;
holding both end parts of the test piece in the longitudinal direction by a pair of film chucks,
setting a distance between the pair of film chucks to 10 mm;
applying a pulling load of 2 g to the biaxially stretched film;
attaching the test piece to a thermomechanical analyzer;
heating the the test piece from 25° C. to 85° C. at a heating speed of 2° C./min, holding the temperature of the test piece at 85° C. for 30 minutes, and measuring a length of the test piece at 85° C., to obtain L85 (mm); and
heating the test piece from 25° C. to 45° C. at a heating speed of 2° C./min and measuring a length of the test piece at 45° C., to obtain L45 (mm).

4. The method according to claim 1 , wherein the methacryl resin has a mass average molecular weight from 80,000 to 200,000, and a content of a monomer unit derived from methyl methacrylate of 92 mass % or more.

5. The method according to claim 1 , wherein the at least one thermoplastic resin layer comprises:
methacryl resin (X), which is the methacryl resin; and
carbonate resin (Y) in which a melt volume flow rate measured at 300° C., with a load of 1.2 kg, for 10 minutes is 130 to 250 cm3/10 min,
wherein a mass ratio of the methacryl resin (X) to the carbonate resin (Y) is 91/9 to 99/1, and
wherein a total amount of the methacryl resin (X) and the carbonate resin (Y) in the at least one thermoplastic resin layer is 80 to 100 mass %.

6. The method according to claim 1 , wherein the at least one thermoplastic resin layer comprises:
methacryl resin (X), which is the methacryl resin; and
phenoxy resin (Z),
wherein an amount of the phenoxy resin (Z) with respect to 100 parts by mass of the methacryl resin (X) is 0.1 to 8 parts by mass, and
wherein a total amount of the methacryl resin (X) and the phenoxy resin (Z) in the at least one thermoplastic resin layer is 80 to 100 mass %.

7. The method according to claim 1 , wherein the unstretched thermoplastic resin film is a layered film comprising a plurality of thermoplastic resin layers, and
wherein the thermoplastic resin layer exposed on at least one surface comprises a thermoplastic resin in which a melt mass flow rate measured at 230° C., with a load of 3.8 kg, for 10 minutes is 10 to 15 g/10 min.

8. The method according to claim 1 , wherein the unstretched thermoplastic resin film is a layered film comprising a plurality of thermoplastic resin layers, and
wherein the thermoplastic resin layer exposed on at least one surface comprises fine particles.

Assignees

• Kuraray Co

Inventors

• Zento Toshiyuki
• Fukuhara Naoto
• Nakamura Eiji
• Nanba Michiyuki

Classifications

• C08J5/18

  Manufacture of films or sheets · CPC title

• B29K2069/00

  Use of PC, i.e. polycarbonates {or derivatives thereof}, as moulding material · CPC title

• B32B27/365

  comprising polycarbonates · CPC title

• B32B27/30

  comprising vinyl {(co)polymers; comprising acrylic (co)polymers} · CPC title

• C08J2333/12

  Homopolymers or copolymers of methyl methacrylate · CPC title