Modified Polyimide Film for Transparent Touch Panel Substrates
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Solution Overview
Problem
Current transparent polymer films for touch panels and display substrates face challenges in achieving a balance between heat resistance, optical properties, and mechanical properties, with existing materials either lacking in flexibility, scratch resistance, or exhibiting poor adhesion and brittleness, which limits their durability and processability.
Innovation Solution
A modified polyimide with terminal heat curable or photocurable functional groups is developed, incorporated into a curable resin composition, allowing for the production of a more colorless transparent polyimide film with improved mechanical and thermal properties, including enhanced scratch resistance and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If transparent polymer plastics are used for touch panel substrates, then ease of processing and mass productivity are improved, but heat resistance and surface hardness are insufficient
Solution Approach 1:
The patent uses a composite structure consisting of a polyimide base layer providing heat resistance and a transparent resin layer (PMMA or PC) providing optical properties and ease of processing. This composite approach allows the substrate to simultaneously achieve high heat resistance (polyimide can withstand deposition temperatures) and good optical properties (the transparent resin layer maintains high transmittance and low haze).
Solution Approach 2:
The patent modifies the polyimide structure by controlling the ratio of specific repeating units (Formula 1 and Formula 2) to optimize the balance between heat resistance, flexibility, and optical properties. By adjusting the compositional parameters of the polyimide and the thickness ratios of different layers, the substrate achieves both high heat resistance and good processability.
2Strength
If surface treatment with hard coating is applied to transparent polymer plastics, then surface hardness and scratch resistance are improved, but impact resistance and flex resistance deteriorate
Solution Approach 1:
The patent creates a multi-layer composite structure where the polyimide base layer provides flexibility and impact resistance, while the transparent resin layer provides surface hardness and scratch resistance. This eliminates the need for separate hard coating treatments that would compromise flexibility, as the hardness is inherently provided by the transparent resin layer in the composite structure.
3Strength
If multiple resin layers are laminated to produce flexible films with good heat resistance and high strength, then mechanical properties are improved, but processing efficiency deteriorates and adhesion problems arise
Solution Approach 1:
The patent combines the base layer and the hard/transparent layer into a single integrated substrate structure formed by extrusion or coextrusion processes. This merging of functions into one component eliminates the need for separate lamination steps, reducing processing complexity and improving adhesion between layers since they are formed as an integrated structure rather than bonded separately.
4Temperature
If fillers are added to maintain heat resistance of flexible substrates, then heat resistance is improved, but flexibility deteriorates and brittleness increases
Solution Approach 1:
The patent achieves heat resistance through compositional parameters of the polyimide structure itself (repeating unit ratios, molecular weight control) rather than adding fillers. This intrinsic approach to heat resistance maintains the flexibility and processability of the polymer matrix, avoiding the brittleness that would result from filler incorporation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified polyimide film exhibits improved yellowness index, heat resistance, and mechanical properties, enabling the production of durable and flexible transparent films suitable for high-temperature applications while maintaining transparency and low haze.
Implementation Method 1
A modified polyimide with terminal heat curable or photocurable functional groups is developed, incorporated into a curable resin composition
Implementation Method 2
allowing for the production of a more colorless transparent polyimide film with improved mechanical and thermal properties
Data Source
AI summary
A modified polyimide represented by Formula 4:wherein D is a heat curable or photocurable functional group, R is a divalent or higher polyvalent organic group, and n is an integer of 1 or greater, X1, X2, X3, and X4 are each independently a tetravalent organic group derived from a tetracarboxylic dianhydride, Y1, Y2, and Y3 are each independently a divalent organic group derived from a diamine, p, q, r, and v are each independently an integer of 0 or greater, with the proviso that p, q, r, and v are not simultaneously 0, and r+v is 1 or greater. Additionally, curable resin compositions including the modified polyimide, as well as polyimide films including a cured product of the curable resin composition, and methods for preparing the modified polyimide.