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CN-121975426-A - Folding screen-oriented dynamic self-repairing PI-based nano protective coating and preparation method thereof

CN121975426ACN 121975426 ACN121975426 ACN 121975426ACN-121975426-A

Abstract

The invention discloses a dynamic self-repairing PI-based nano protective coating for a crease-free folding screen, which is prepared from a polyimide matrix, a dynamic cross-linking agent, self-repairing microcapsules, surface-modified nano inorganic filler and a surface energy regulator, wherein the polyimide matrix is prepared by polymerizing aromatic dianhydride and diamine monomer containing a flexible chain segment, the flexible chain segment comprises ether bonds or methylene chain segments, the shell material of the self-repairing microcapsules is polyurea or polyurethane, the core material of the self-repairing microcapsules is polyimide repairing agent, and the surface-modified nano inorganic filler is SiO 2 or Al 2 O 3 nano particles grafted and modified on the surface of a silane coupling agent. The invention has the beneficial effects that the coating prepared by the invention simultaneously realizes the basic performances of high hardness, high toughness, high light transmittance and strong adhesion, and the high-efficiency grading self-repairing capability aiming at injuries of different scales, and finally passes the extreme bending fatigue test for more than 10 ten thousand times, thereby solving the problems of balanced multi-performance requirement, single repairing mechanism and low efficiency in the prior art.

Inventors

  • Zhong Yinzhou
  • YANG BIN

Assignees

  • 浙江恒嘉光电有限公司

Dates

Publication Date
20260505
Application Date
20260319

Claims (9)

  1. 1. The dynamic self-repairing PI-based nano protective coating for the crease-free folding screen is characterized by being prepared from the following raw materials of a polyimide matrix, a dynamic cross-linking agent, self-repairing microcapsules, a surface-modified nano inorganic filler and a surface energy regulator; The polyimide matrix is obtained by polymerizing aromatic dianhydride and diamine monomer containing a flexible chain segment, wherein the flexible chain segment comprises ether bond or methylene chain segment; The dynamic cross-linking agent is a chemical cross-linking agent which can be reversibly broken and recombined under the use condition, and comprises at least one of furan, maleimide groups and disulfide bonds (-S-S-); The shell material of the self-repairing microcapsule is polyurea or polyurethane, the core material is polyimide repairing agent, and the polyimide repairing agent is polyamide acid with the intrinsic viscosity of 0.1-0.5 dL/g or polyimide oligomer containing active groups; The surface modified nano inorganic filler is SiO 2 or Al 2 O 3 nano particles which are subjected to surface grafting modification by a silane coupling agent.
  2. 2. The coating of claim 1, wherein the self-healing microcapsules have a particle size of 5-20 μm.
  3. 3. The coating according to claim 1, wherein in the surface modified nano inorganic filler, the silane coupling agent is gamma-aminopropyl triethoxysilane (KH 550) or gamma- (2, 3-glycidoxy) propyl trimethoxysilane (KH 560), the particle size of the nano inorganic filler is 50-200nm, and the agglomerate size in the coating is less than or equal to 100nm.
  4. 4. A coating according to any one of claims 1 to 3, characterized in that the properties of the coating satisfy: the tensile strength is more than or equal to 50MPa, elongation at break is more than or equal to 300%; The hardness of the pencil is more than or equal to 3H; the light transmittance in the visible light wave band of 400-700nm is more than or equal to 92%; The adhesion to the plasma treated PI flexible substrate was 5B scale (cross-hatch).
  5. 5. The coating of claim 4, wherein the coating has graded self-healing properties: for microcracks with the diameter less than or equal to 50 mu m, the self-repairing efficiency in 24 hours at 25 ℃ is more than or equal to 90%; For mechanical scratch with depth less than or equal to 20 mu m, the self-repairing efficiency is more than or equal to 95 percent in 1 hour under the heat treatment condition of 60-80 ℃.
  6. 6. The coating according to claim 5, wherein the coating has a bending fatigue life of 10 or more and a hardness retention of 90 or more and a light transmittance reduction of 2 or less after bending at a bending angle of + -180 DEG, a bending radius of 1mm, a bending frequency of 1 time/second, and 25 ℃.
  7. 7. A method for preparing a dynamic self-healing PI-based nano-protective coating for a fold-free folding screen according to any one of claims 1 to 6, comprising the steps of: S1, synthesizing a high-toughness PI matrix, namely, reacting aromatic dianhydride with diamine monomer containing a flexible chain segment in a polar solvent, and imidizing to obtain a high-toughness polyimide resin solution; s2, constructing a composite self-repairing system, namely adding a dynamic cross-linking agent after the polymerization reaction of the S1 is completed, and independently preparing self-repairing microcapsules taking polyimide repairing agent as a core material and polyurea or polyurethane as a shell material; S3, dispersing nano-filler, namely dispersing nano SiO 2 or Al 2 O 3 in a solvent, adding a silane coupling agent for surface modification, and carrying out ultrasonic and high-speed shearing treatment to obtain nano-filler dispersion liquid; S4, preparing and coating slurry, namely mixing and homogenizing the resin solution obtained in the step S1, the self-repairing microcapsule obtained in the step S2, the nano filler dispersion liquid obtained in the step S3 and the surface energy regulator to obtain coating slurry; s5, drying and curing, namely performing step hot air drying on the coated wet film, and then curing for 30-60 minutes at 200-250 ℃ to form the protective coating.
  8. 8. The method according to claim 7, wherein the diamine monomer having a soft segment in S1 comprises 4,4' -diaminodiphenyl ether (ODA) or a diamine monomer having a fatty chain, and the polar solvent is N-methylpyrrolidone (NMP) or N, N-dimethylacetamide (DMAc).
  9. 9. The method according to claim 7, wherein the coating mode in S4 is slot extrusion coating or spin coating, the temperature range of the step hot air drying in S5 is 80-120 ℃, and the thickness of the finally formed coating is 5-20 μm.

Description

Folding screen-oriented dynamic self-repairing PI-based nano protective coating and preparation method thereof Technical Field The invention relates to the technical field of nano protective coatings, in particular to a dynamic self-repairing PI-based nano protective coating for a folding screen and a preparation method thereof. Background With the rapid development of flexible electronic technology, a foldable Organic Light Emitting Diode (OLED) display screen has become a core direction of next generation display technology. However, in the process of folding and bending for hundreds of thousands times, the surface protection layer of the folding screen is extremely easy to generate microcracks and scratches due to repeated stress, and the cracks are expanded to finally cause display failure, which is a key technical bottleneck for restricting the durability and the reliability of the folding screen. To solve this problem, it is common practice in the industry to prepare a protective coating of high hardness and high toughness on a flexible substrate such as Polyimide (PI). For example, the prior art has increased the hardness and scratch resistance of the coating by adding inorganic nanoparticles (e.g., siO 2) to the acrylic resin. However, such coatings are static in nature and are irreversible once damaged, and cannot cope with fatigue damage from long-term dynamic bending. Another category of research is the introduction of self-healing functions. The repairing agent microcapsules are embedded in the epoxy resin matrix, and when cracks are generated, the microcapsules are broken to release the repairing agent to realize repairing. However, the method has slow repairing response and is one-time repairing, the capability of repairing microcracks frequently generated in the use of the folding screen is limited, and the mechanical strength and the light transmittance of the coating are often damaged by the introduction of the microcapsules. In addition, in the prior art, the bulletin number is CN112608668B, the name is a hardened layer protection film of a transparent base film of a folding screen and a production process, the hardened layer protection film is obtained after the hardened layer is coated on the surface of the TPU base film, the bending property and the hardness are considered by coating the hardened layer on the TPU base film and the bending frequency and the wear resistance are limited by the scheme through adjusting the hardness of the TPU. Therefore, developing a protective coating which has excellent mechanical properties (high toughness and high hardness), long-term bending fatigue resistance and high-efficiency self-repairing capability and can be compatible with the OLED process is a key problem to be solved in the current folding screen technology development. The invention aims to provide a coating with excellent comprehensive performance and a preparation method thereof, so as to overcome the defects of the prior art. Disclosure of Invention The invention aims to solve the problems of insufficient toughness, single self-repairing mechanism, low efficiency, poor bending fatigue resistance, performance degradation caused by easy agglomeration of nano fillers and the like of a folding screen protective coating in the prior art, and provides a PI-based nano composite protective coating with high toughness, high hardness, excellent light transmittance and high-efficiency grading self-repairing capability and a preparation method thereof. In order to achieve the above purpose, the present invention provides the following technical solutions: a dynamic self-repairing PI-based nano protective coating for a crease-free folding screen is prepared from the following raw materials of a polyimide matrix, a dynamic cross-linking agent, self-repairing microcapsules, a surface-modified nano inorganic filler and a surface energy regulator; The polyimide matrix is obtained by polymerizing aromatic dianhydride and diamine monomer containing a flexible chain segment, the flexible chain segment comprises ether bond or methylene chain segment, the dynamic cross-linking agent is a chemical cross-linking agent which can be reversibly broken and recombined under the use condition, the dynamic cross-linking agent comprises at least one of furan, maleimide groups and disulfide bonds (-S-S-), the shell material of the self-repairing microcapsule is polyurea or polyurethane, the core material of the self-repairing microcapsule is polyimide repairing agent, the polyimide repairing agent is polyamide acid with the intrinsic viscosity of 0.1-0.5 dL/g or polyimide oligomer containing active groups, the polyamide acid has good fluidity and penetrability within the viscosity range, the repairing agent can be effectively filled and repaired into microcracks after the microcapsule is broken, and meanwhile, the self-repairing microcapsule has enough reactivity and is combined with the matrix, and the surface-modified