Polyamic acid, varnish containing same, and polyimide film

Patent metadata

Field	Value
Publication number	US-9856399-B2
Application number	US-201414781931-A
Country	US
Kind code	B2
Filing date	Apr 1, 2014
Priority date	Apr 4, 2013
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

The present invention addresses the problem of providing a high-transparency polyimide film in which the thickness-direction phase difference Rth is kept within a predetermined range. The present invention also addresses the problem of providing a polyamic acid and a varnish used to obtain the polyimide film. In order to overcome the aforementioned problem, the present invention is a polyimide film containing a polyimide obtained by bringing about a reaction between a tetracarboxylic dianhydride and a diamine, the polyimide film having (a) a thickness-direction phase difference Rth of −5 to 100 nm per 10 μm of thickness, (b) a transmittance of 80% or more with respect to light having a wavelength of 400 nm, (c) a haze of 3% or less, and (d) a glass transition point of 250° C. or higher.

First claim

The invention claimed is:

1. A polyimide film comprising a polyimide obtained by reacting a tetracarboxylic dianhydride with a diamine,
wherein the polyimide contains a repeating unit represented by the following general formula (1):

wherein X is a group selected from the group consisting of:

 and
Y is a group selected from the group consisting of:

 and
wherein the polyimide film has the following characteristics:
(a) a thickness direction retardation Rth as calculated by the below equation of −5 nm or more and 100 nm or less per thickness of 10 μm;
(b) a light transmittance at 400 nm wavelength of 80% or more;
(c) a haze of 3% or less; and
(d) a glass transition temperature of 250° C. or higher,
Retardation Rth (nm)=[ nz −( nx+ny )/2]× d,

wherein nx, ny and nz are respective refractive indexes for x-, y- and z-axis directions of the polyimide film measured using light with a wavelength of 550 nm; and d is a thickness of the polyimide film.

2. A touch panel display comprising the polyimide film according to claim 1 .

3. A liquid crystal display comprising the polyimide film according to claim 1 .

4. An organic EL display comprising the polyimide film according to claim 1 .

5. A polyimide film comprising polyimide layer A comprising a polyimide and polyimide layer B comprising a polyimide wherein:
either one or both of the polyimide layer A and the polyimide layer B have properties (i) and (II) below:
(i) a thickness direction retardation Rth as calculated by the below equation of −5 nm or more and 100 nm or less per thickness of 10 μm; and
(ii) the polyimide contains a repeating unit represented by the following general formula (1):

wherein X is a group selected from the group consisting of:

 and
Y is a group selected from the group consisting of:

 and
wherein the polyimide film has a thickness direction retardation Rth as calculated by the below equation of −5 nm or more and 100 nm or less per thickness of 10 μm,
Retardation Rth (nm)=[ nz −( nx+ny )/2]× d,

wherein nx, ny and nz are respective refractive indexes for x-, y- and z-axis directions of an individual layer contained in the polyimide film or of the polyimide film measured using light with a wavelength of 550 nm; and d is a thickness of each layer in the polyimide film or of the polyimide film.

6. A polyamic acid comprising a repeating unit represented by the following general formula (1′):

wherein X is a group selected from the group consisting of:

 and
Y is a group selected from the group consisting of:

7. A dry film comprising the polyamic acid according to claim 6 .

8. A polyamic acid varnish comprising the polyamic acid according to claim 6 .

9. A polyimide obtained by curing the polyamic acid according to claim 6 .

10. A method for manufacturing a polyimide laminate in which a substrate and a polyimide layer are laminated, the method comprising:
coating a substrate with the polyamic acid varnish according to claim 8 ; and
heating a film of the coated polyamic acid varnish in an inert gas atmosphere.

11. A method for manufacturing a polyimide laminate in which a substrate and a polyimide layer are laminated, the method comprising:
coating a substrate with the polyamic acid varnish according to claim 8 ; and
heating a film of the coated polyamic acid varnish under an atmosphere of 15 kPa or less.

12. A method for manufacturing a polyimide laminate comprising a substrate and a polyimide layer,
wherein a thickness direction retardation Rth of the polyimide layer as calculated by the below equation is −5 nm or more and 100 nm or less per thickness of 10 μm,
the method comprising:
coating a substrate with a varnish containing polyamic acid a and polyamic acid b and heating the resultant coating to thereby obtain the polyimide layer, wherein
either one or both of polyamic acid a and polyamic acid b are the polyamic acid according to claim 6 ,
Retardation Rth (nm)=[ nz −( nx+ny )/2]× d,

wherein nx, ny and nz are respective refractive indexes for x-, y- and z-axis directions of the polyimide layer measured using light with a wavelength of 550 nm; and d is a thickness of the polyimide layer.

13. A method for manufacturing a polyimide laminate comprising a substrate, polyimide layer A and polyimide layer B,
wherein a thickness direction retardation Rth of a laminate, obtained by laminating polyimide layer A and polyimide layer B, as calculated by the below equation is −5 nm or more and 100 nm or less per thickness of 10 μm;
the method comprising:
coating a substrate with a varnish containing polyamic acid a and heating the resultant coating to thereby obtain the polyimide layer A, and
coating onto the polyimide layer A a varnish containing polyamic acid b and heating the resultant coating to thereby obtain the polyimide layer B, wherein
either one or both of polyamic acid a and polyamic acid b are the polyamic acid according to claim 6 ,
Retardation Rth (nm)=[ nz −( nx+ny )/2]× d,

wherein nx, ny and nz are respective refractive indexes for x-, y- and z-axis directions of an individual layer contained in the polyimide film or of the polyimide film measured using light with a wavelength of 550 nm; and d is a thickness of each layer of the polyimide film or of the polyimide film.

14. A method for manufacturing a display apparatus, the method comprising:
peeling off the substrate from the polyimide laminate obtained by the method according to claim 10 to thereby obtain a polyimide film; and
forming a device on the polyimide film.

15. The method for manufacturing a display apparatus according to claim 14 , wherein the step for forming a device includes forming a thin film by vapor-phase growth method.

16. A method for manufacturing a display apparatus, the method comprising:
forming a device on the polyimide layer of the polyimide laminate obtained by the method according to claim 10 ; and
peeling off the polyimide layer on which the device is formed from the substrate.

17. The method for manufacturing a display apparatus according to claim 16 , wherein the step for forming a device includes forming a thin film by vapor-phase growth method.

Assignees

• Mitsui Chemicals Inc

Inventors

• Fukukawa Kenichi
• Okazaki Masaki
• Sakata Yoshihiro
• Urakami Tatsuhiro
• Okubo Atsushi

Classifications

• B29C37/0025

  Applying surface layers, e.g. coatings, decorative layers, printed layers, to articles during shaping, e.g. in-mould printing (moulding on preformed layers as inserts B29C70/68; applying fluent material to surfaces in general B05) · CPC title

• C08G73/1078

  wholly aromatic in the diamino moiety · CPC title

• C09D179/08 Primary

  Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors · CPC title

• C08J2379/08

  Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors · CPC title

• B29C41/02

  for making articles of definite length, i.e. discrete articles · CPC title