Hardcoat Multilayer Film Segmentation for Touch Panel Durability
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Solution Overview
Problem
Conventional hard coat laminated films for display devices lack sufficient resistance against stylus input, abrasion, and maintainance of antifouling properties, transparency, and surface hardness.
Innovation Solution
A hard coat laminated film structure comprising a first hard coat without inorganic particles and a second hard coat with inorganic particles, specifically formulated with polyfunctional (meth)acrylates, secondary thiol compounds, water-repellent agents, and silane coupling agents, enhancing resistance and surface properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coat is formed on a transparent resin film to improve surface hardness and abrasion resistance, then surface hardness is improved, but abrasion resistance remains insufficient
Solution Approach 1:
The hard coat is divided into two distinct layers: a first hard coat layer containing inorganic particles for providing surface hardness, and a second hard coat layer without inorganic particles for providing abrasion resistance and maintaining antifouling properties. This segmentation allows each layer to optimize its specific function rather than compromising one property for the other.
Solution Approach 2:
Different regions of the hard coat have different compositions tailored to local requirements: the first hard coat layer (closer to the resin film) contains inorganic particles for hardness, while the second hard coat layer (outer surface) is particle-free for smoothness and antifouling performance. This local differentiation resolves the contradiction between hardness and abrasion resistance.
2Strength
If inorganic particles are added to the coating material to improve surface hardness, then surface hardness is improved, but antifouling properties deteriorate
Solution Approach 1:
The coating is segmented into two layers with different compositions: the first hard coat layer contains inorganic particles for hardness, while the second hard coat layer is free of inorganic particles to maintain antifouling properties. This segmentation prevents inorganic particles from compromising the outer surface's antifouling performance.
Solution Approach 2:
Inorganic particles are localized to the first hard coat layer where they provide hardness without interfering with the outer surface's antifouling properties. The second hard coat layer maintains a particle-free composition to preserve smoothness and antifouling performance, resolving the contradiction between hardness and antifouling properties.
3Strength
If a single hard coat layer is used to provide surface hardness, then surface hardness is improved, but resistance against stylus input deteriorates
Solution Approach 1:
The hard coat is segmented into two functional layers: the first hard coat layer provides surface hardness through inorganic particles, while the second hard coat layer provides abrasion resistance and stylus input resistance through its particle-free composition and specific resin formulation. This segmentation enables the composite structure to achieve both hardness and stylus resistance simultaneously.
Solution Approach 2:
The hard coat is formulated as a composite structure with two distinct layers having different compositions and functions. The first layer combines inorganic particles with resin for hardness, while the second layer uses a particle-free resin formulation for abrasion and stylus resistance, creating a composite material system that achieves properties neither layer could achieve alone.
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 film exhibits excellent resistance against stylus input, maintains antifouling properties, and ensures high transparency and surface hardness, making it suitable for touch panel display devices.
Implementation Method 1
0.01 to 10 parts by mass of (D) a silane coupling agent
Implementation Method 2
100 parts by mass of (A1) a polyfunctional (meth)acrylate
Implementation Method 3
0.01 to 7 parts by mass of (C) a water-repellent agent
Data Source
Figure 1~2
Figure 3~4
AI summary
One embodiment of the present invention is a hardcoat multilayer film which comprises layers, namely, a first hardcoat, a second hardcoat and a transparent resin film sequentially from the surface layer side, and wherein: the first hardcoat is formed from a coating material that does not contain inorganic particles, while containing 100 parts by mass of (A) a polyfunctional (meth)acrylate, 0.5-20 parts by mass of (B) a compound having two or more secondary thiol groups in each molecule, 0.01-7 parts by mass of (C) a water repellent agent and 0.01-10 parts by mass of (D) a silane coupling agent; and the second hardcoat is formed from a coating material that contains 100 parts by mass of (A) a polyfunctional (meth)acrylate and 30-300 parts by mass of (F) inorganic fine particles having an average particle diameter of 1-300 nm. The polyfunctional (meth)acrylate (A) may contain 20% by mass or more of a tripentaerythritol acrylate. The coating material which forms the first hardcoat may additionally contain 0.1-5 parts by mass of (E) a thiophenyl-based photopolymerization initiator.