US 11,891,483 B2
Polyimide film for display substrate
Jinyoung Park, Daejeon (KR); Cheolmin Yun, Daejeon (KR); Kyunghwan Kim, Daejeon (KR); and Danbi Choi, Daejeon (KR)
Assigned to LG CHEM, LTD., Seoul (KR)
Appl. No. 16/632,482
Filed by LG CHEM, LTD., Seoul (KR)
PCT Filed Jul. 20, 2018, PCT No. PCT/KR2018/008226
§ 371(c)(1), (2) Date Jan. 20, 2020,
PCT Pub. No. WO2019/103274, PCT Pub. Date May 31, 2019.
Claims priority of application No. 10-2017-0155408 (KR), filed on Nov. 21, 2017.
Prior Publication US 2020/0148826 A1, May 14, 2020
Int. Cl. C08G 73/10 (2006.01); C08J 5/18 (2006.01)
CPC C08G 73/1067 (2013.01) [C08G 73/1032 (2013.01); C08G 73/1039 (2013.01); C08G 73/1042 (2013.01); C08J 5/18 (2013.01); C08J 2379/08 (2013.01)] 7 Claims
 
1. A polyimide film for a flexible display substrate comprising a polyimide, which has a thickness of 5 to 20 μm, and has a stress variation of 0 to 5, wherein the stress variation is a difference in values of residual stress at a temperature of 350° C. and at a temperature of 500° C. while the film on a silicon wafer is subject to heating and cooling at a temperature ranging from 350 to 500° C.
wherein the polyimide comprises an end-capped polyimide including a polymerization product of a diamine, an acid dianhydride and an end-capping agent, and
the end capping agent is in an amount of 1 to 10 parts by weight based on 100 parts weight of the sum of the acid dianhydride and the diamine,
wherein the polyimide film comprises a heat-cured product of a polyimide precursor solution comprising a polyimide precursor and an organic solvent having a positive value of LogP, and the organic solvent having a positive value of Log P comprises diethylpropionamide (DEPA), and
wherein the polyimide has a repeat unit of formula 6 and a repeat unit of formula 6a:

OG Complex Work Unit Chemistry
wherein, R1, R2 and R3 are hydrogen atom;

OG Complex Work Unit Chemistry
wherein, R4 and R5 are hydrogen atom and R6 and R7 are each independently C1-10 fluoroalkyl, and
wherein the repeat unit of formula 6 is formed from p-phenylene diamine (p-PDA), the repeat unit of formula 6a is formed from bis(trifluoromethyl)benzidine (TFMB), and a ratio of p-PDA to TFMB is 90:10 to 95:5.