Method for fabricating flexible substrate
The present invention relates to a method for producing a flexible substrate. According to the method of the present invention, a flexible substrate layer can be easily separated from a carrier substrate even without the need for laser or light irradiation so that a device can be prevented from deterioration of reliability and occurrence of defects caused by laser or light irradiation. In addition, according to the method of the present invention, a flexible substrate can be continuously produced in an easier manner based on a roll-to-roll process.
1. A method for producing a flexible substrate, comprising feeding a carrier substrate comprising a polyimide resin, forming a flexible substrate layer comprising a polyimide resin on the carrier substrate, separating the flexible substrate layer from the carrier substrate layer by the application of a physical stimulus without causing chemical changes in the carrier substrate and the flexible substrate layer, and winding the flexible substrate layer separated from the carrier substrate layer to collect the flexible substrate layer in the form of a roll wherein the steps are performed by a roll-to-roll process, and wherein the carrier substrate layer has an adhesion strength of at least 1 N/cm to the flexible substrate layer before application of the physical stimulus.
2. The method according to claim 1 , wherein the flexible substrate layer is formed by casting a composition comprising a diamine and an excess of an acid dianhydride, followed by heating and curing.
3. The method according to claim 1 , further comprising forming metal patterns on the carrier substrate before formation of the flexible substrate layer to produce a flexible substrate with the metal patterns.
4. The method according to claim 3 , wherein at least a portion of the flexible substrate layer is in direct contact with the carrier substrate comprising a polyimide resin.
5. The method according to claim 3 , wherein the metal patterns are embedded in the flexible substrate layer.
6. The method according to claim 1 , further comprising winding the carrier substrate layer separated from the flexible substrate layer to collect the carrier substrate layer in the form of a roll.
7. The method according to claim 1 , wherein the physical stimulus is a tension applied during winding and collection of the carrier substrate and the flexible substrate layer.
8. The method according to claim 1 , wherein the carrier substrate layer has a peel strength not greater than 0.3 N/cm from the flexible substrate layer after application of the physical stimulus.
9. The method according to claim 1 , wherein the adhesion strength of the carrier substrate layer to the flexible substrate layer before application of the physical stimulus and the peel strength of the carrier substrate from the flexible substrate after application of the physical stimulus are defined as A1 and A2, respectively, wherein the ratio A2/A1 is from 0.001 to 0.5 and wherein the physical stimulus does not cause chemical changes in the carrier substrate and the flexible substrate layer.
10. The method according to claim 1 , wherein the polyimide resin is prepared by reacting an aromatic tetracarboxylic dianhydride of Formula 1:
wherein A is a tetravalent aromatic organic group of Formula 2a or 2b:
wherein R 11 is a C 1 -C 4 alkyl or C 1 -C 4 haloalkyl group, a is an integer from 0 to 3, and b is an integer from 0 to 2,
wherein R 12 to R 14 are each independently a C 1 -C 4 alkyl or C 1 -C 4 haloalkyl group, c and e are each independently an integer from 0 to 3, d is an integer from 0 to 4, and f is an integer from 0 to 3, with an aromatic diamine compound having a linear structure to give a polyamic acid, and curing the polyamic acid at a temperature of 200° C. or above.
11. The method according to claim 10 , wherein the diamine compound reacts with an excess of the dianhydride.
12. The method according to claim 11 , wherein the aromatic diamine compound is represented by Formula 4a or 4b:
wherein R 21 is a C 1 -C 10 alkyl or C 1 -C 10 haloalkyl group and 1 is an integer from 0 to 4,
wherein R 22 and R 23 are each independently a C 1 -C 10 alkyl or C 1 -C 10 haloalkyl group, X is selected from the group consisting of —O—, —CR 24 R 25 —, —C(═O)—, —C(═O)O—, —C(═O)NH—, —S—, —SO—, —SO 2 —, —O[CH 2 CH 2 O] q —, C 6 -C 18 monocyclic and polycyclic cycloalkylene groups, C 6 -C 18 monocyclic and polycyclic arylene groups, and combinations thereof, R 24 and R 25 are each independently selected from the group consisting of a hydrogen atom, C 1 -C 10 alkyl groups, and C 1 -C 10 haloalkyl groups, q is an integer of 1 or 2, m and n are each independently an integer from 0 to 4, and p is an integer of 0 or 1.