Copolyesters plasticized with polymeric plasticizer

Patent metadata

Field	Value
Publication number	US-11427688-B2
Application number	US-201815866922-A
Country	US
Kind code	B2
Filing date	Jan 10, 2018
Priority date	Apr 17, 2017
Publication date	Aug 30, 2022
Grant date	Aug 30, 2022

Abstract

Polyester-based films contain certain copolyesters (A) and polyester plasticizers (B). The copolyesters (A) may be selected from those in which the force required to stretch a film of the copolyester (A) by itself, from 2× to 5×, increases by less than 200%. The polyester plasticizers (B) have a weight-average molecular weight of 900 to 12,000 g/mol, and contain (i) a diol component comprising residues of diols having 2 to 8 carbon atoms, and (ii) a diacid component comprising residues of dicarboxylic acids having 4 to 12 carbon atoms. These polyester-based films are particularly useful for preparing ultra-thin LCD or OLED polarizers, because they can be stretched very thin with a high stretch ratio at lower temperatures.

First claim

We claim:

1. A polyester-based film made from a blend comprising:
(A) a copolyester (A); and
(B) a polyester plasticizer (B) having a weight-average molecular weight (M w ) of 900 to 12,000 g/mol,
wherein the polyester-based film has been stretched underwater at least 6× its original length in the machine direction at a temperature of 60° C. or below without rupturing; and
wherein the underwater stretching is performed in one stage;
wherein the copolyester (A) comprises:
(a) a diacid component comprising at least 50 mole percent of residues of terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, or mixtures thereof; and
(b) a diol component comprising at least 80 mole percent of residues of a diol containing 2 to 10 carbon atoms,

wherein the diacid component is based on 100 mole percent of total diacid residues in the copolyester, and the diol component is based on 100 mole percent of total diol residues in the copolyester;
wherein the force required to stretch a film of the copolyester (A) alone from 2× to 5× increases by less than 200%, where the copolyester (A) film is stretched in the machine direction, in air, at 10 to 15° C. above the glass transition temperature of the copolyester (A); and
wherein the polyester plasticizer (B) comprises:
(a) a diol component comprising residues of a diol having 2 to 8 carbon atoms; and
(b) a diacid component comprising residues of a dicarboxylic acid having 4 to 12 carbon atoms; and

wherein the copolyester (A) has a T g of up to 70° C.; and wherein the copolyester (A) has a minimum crystallization half-time (t 1/2 min) of at least 8.6 minutes.

2. The polyester-based film according to claim 1 , wherein the copolyester (A) has a minimum crystallization half-time (t 1/2 min) of at least-12 minutes.

3. The polyester-based film according to claim 1 , which comprises from 0.2 to 0.3% by weight of moisture, based on the total weight of the polyester-based film.

4. The polyester-based film according to claim 1 , wherein the blend has a glass transition temperature (T g ) of less than 70° C.

5. The polyester-based film according to claim 1 , wherein the blend has a glass transition temperature (T g ) of 60° C. or less.

6. The polyester-based film according to claim 1 , which has been stretched in an aqueous solution comprising boric acid and optionally a dye.

7. The polyester-based film according to claim 1 , which has been stretched at least 7× in the machine direction at a temperature of 60° C. or below.

8. The polyester-based film according to claim 1 , wherein the blend comprises from 3 to 8% by weight of the polyester plasticizer (B), based on the total weight of the blend.

9. A laminate comprising:
(I) a polyvinyl alcohol-based film (I); and
(II) a polyester-based film (II),
wherein the laminate has been stretched under water at least 6× in the machine direction at a temperature of 60° C. or below without rupturing; and
wherein the underwater stretching is performed in one stage; and
wherein the polyester-based film (II) is made from a blend comprising:
(A) a copolyester (A); and
(B) a polyester plasticizer (B) having a weight-average molecular weight (M w ) of 900 to 12,000 g/mol,

wherein the copolyester (A) comprises:
(a) a diacid component comprising at least 50 mole percent of residues of terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, or mixtures thereof; and
(b) a diol component comprising at least 80 mole percent of residues of a diol containing 2 to 10 carbon atoms,

wherein the diacid component is based on 100 mole percent of total diacid residues in the copolyester, and the diol component is based on 100 mole percent of total diol residues in the copolyester;
wherein the force required to stretch a film of the copolyester (A) alone from 2× to 5× increases by less than 200% when the copolyester (A) film is stretched in the machine direction, in air, at 10 to 15° C. above the glass transition temperature of the copolyester (A); and
wherein the polyester plasticizer (B) comprises:
(a) a diol component comprising residues of a diol having 2 to 8 carbon atoms; and
(b) a diacid component comprising residues of a dicarboxylic acid having 4 to 12 carbon atoms; and

wherein the copolyester (A) has a T g of up to 70° C.; and
wherein the polyvinyl alcohol-based film, after stretching, has a single axis transmittance of at least 42%, a polarization degree of at least 99.95%, and a contrast ratio of at least 2000:1.

10. The laminate according to claim 9 , which has been stretched, in an aqueous solution comprising boric acid and optionally a dye, at least 6× in the machine direction at a temperature of 60° C. or below.

11. The laminate according to claim 9 , which has been stretched, in an aqueous solution comprising boric acid and optionally a dye, at least 7× in the machine direction at a temperature of 60° C. or below.

12. The laminate according to claim 9 , wherein the polyvinyl alcohol-based film (I) has a thickness of 10 μm or less after stretching.

13. The laminate according to claim 9 , wherein the polyvinyl alcohol-based film (I) has a thickness of 7 μm or less after stretching.

14. The laminate according to claim 9 , wherein the polyvinyl alcohol-based film (I) has a thickness of 5 μm or less after stretching.

15. The laminate according to claim 9 , which further comprises an adhesive layer between the polyvinyl alcohol-based film (I) and the polyester-based film (II).

16. A method of producing a thin-film polarizer, comprising:
(i) forming a polyvinyl alcohol-based film (I) on a substrate comprising a polyester-based film (II) to obtain a laminate;
(ii) contacting the laminate with a dyeing liquid to dye the polyvinyl alcohol-based film (I);
(iii) stretching the laminate so that the polyvinyl alcohol-based film (I) has a thickness of 10 μm or less after stretching; and
(iv) separating the polyvinyl alcohol-based film (I) from the substrate to obtain a thin-film polarizer,
wherein the polyester-based film (II) is made from a blend comprising:
(A) a copolyester (A); and
(B) a polyester plasticizer (B) having a weight-average molecular weight (M w ) of 900 to 12,000 g/mol,

wherein the polyester-based film has been stretched underwater at least 6× its original length in the machine direction at a temperature of 60° C. or below without rupturing; and
wherein the underwater stretching is performed in one stage;
wherein the copolyester (A) comprises:
(a) a diacid component comprising at least 50 mole percent of residues of terephthalic acid, naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, isophthalic acid, or mixtures thereof; and
(b) a diol component comprising at least 80 mole percent of residues of a diol containing 2 to 10 carbon atoms,

wherein the diacid component is based on 100 mole percent of total diacid residues in the copolyester, and the diol component is based on 100 mole percent of total diol residues in the copolyester;
wherein the force required to stretch a film of the copolyester (A) alone from 2× to 5× increases by less than 200% when the copolyester (A) film is stretched in the machine direction, in air, at 10 to 15° C. above the glass transition temperature of the copolyester (A); and
wherein the polyester plasticizer (B) comprises:
(a) a diol component comprising residues of a diol having 2 to 8 carbon atoms; and
(b) a diacid component comprising residues of a dicarboxylic acid having 4 to 12 carbon atoms; and

wherein the copolyester (A) has a T g

Assignees

• Eastman Chem Co

Inventors

• Shih Wayne Ken
• Carico Kimberley Carmenia

Classifications

• B29C48/919

  using a bath, e.g. extruding into an open bath to coagulate or cool the material · CPC title

• C08J2367/02

  Polyesters derived from dicarboxylic acids and dihydroxy compounds; (C08J2367/06 takes precedence) · CPC title

• C08K5/0016

  Plasticisers · CPC title

• C08K5/0008

  Organic ingredients according to more than one of the "one dot" groups of C08K5/01 - C08K5/59 · CPC title

• B32B27/306

  comprising vinyl acetate or vinyl alcohol (co)polymers · CPC title