Transparent Film Coat Layer Texture for Pen Input
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Solution Overview
Problem
Current pen-input touch panels with soft or anti-Newton-ring films fail to provide smooth and consistent writing experiences, as digital pens tend to slide excessively, leading to irregular writing smoothness similar to writing with a pencil.
Innovation Solution
A transparent film with a coat layer having a specific surface texture, featuring projections with controlled shapes and sizes, is applied to the touch panel, ensuring constant writing smoothness and durability through a combination of a thermoplastic elastomer binder and crosslinked poly(meth)acrylic ester particles, enhancing frictional resistance and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a soft film with strong resistance is used, then finger touch feel is improved, but pen-input writing smoothness deteriorates due to excessive sliding
Solution Approach 1:
The invention applies different surface roughness characteristics to different regions or aspects of the film surface. The film has an average surface roughness of 0.003 to 0.05 μm (providing smooth pen writing) while simultaneously having micro-unevenness with a maximum height of 1 to 10 μm (providing good finger touch feel). This local differentiation of surface properties resolves the contradiction between finger touch comfort and pen writing smoothness.
Solution Approach 2:
The invention transitions from considering only average surface roughness to incorporating multi-dimensional surface characteristics. By introducing the dimension of micro-unevenness (maximum height 1-10 μm) separate from average roughness (0.003-0.05 μm), the film can simultaneously optimize for both finger touch feel and pen writing smoothness, which were previously conflicting requirements.
2Ease of operation
If an uneven structure is formed on the film surface, then finger touch feel is improved, but writing smoothness becomes irregular during pen-input operation
Solution Approach 1:
The invention precisely controls the parameters of surface unevenness to resolve the contradiction. By limiting the average surface roughness to 0.003-0.05 μm and the maximum height of micro-unevenness to 1-10 μm, the film achieves both improved finger touch feel and consistent writing smoothness throughout pen-input operation, preventing the irregularity that occurs with excessive unevenness.
Solution Approach 2:
The invention differentiates between two types of surface characteristics: average roughness (affecting pen writing) and micro-unevenness (affecting finger touch). By optimizing each locally for its specific function, the film provides smooth consistent writing while maintaining comfortable finger touch, without the writing smoothness irregularity that occurs when only one parameter is optimized.
3Strength
If a hardcoat film is used, then durability is improved, but finger touch feel deteriorates
Solution Approach 1:
The invention creates a composite surface structure combining a hardcoat layer for durability with controlled micro-unevenness for finger touch comfort. The hardcoat film maintains its protective properties while the introduced micro-unevenness (maximum height 1-10 μm) provides a texture that improves finger touch feel, resolving the contradiction between hardness and tactile comfort.
Solution Approach 2:
The invention adds a new dimension to hardcoat film design by incorporating micro-unevenness characteristics (maximum height 1-10 μm) alongside the base hardcoat structure. This multi-dimensional approach allows the film to maintain durability while improving finger touch feel, overcoming the limitation of conventional hardcoat films that prioritize hardness over tactile comfort.
4Force
If the surface roughness is increased, then friction coefficient is improved, but transparency deteriorates
Solution Approach 1:
The invention optimizes the parameters of surface roughness to balance friction and transparency. By controlling the average surface roughness to 0.003-0.05 μm and micro-unevenness maximum height to 1-10 μm, the film achieves sufficient friction coefficient for good finger touch feel while maintaining high transparency (80% or more), preventing the transparency deterioration that occurs with excessive roughness.
Solution Approach 2:
The invention differentiates between two levels of surface roughness: average roughness (0.003-0.05 μm) that maintains transparency, and micro-unevenness (maximum height 1-10 μm) that provides friction. This local differentiation allows each parameter to optimize for its specific function without compromising the other, achieving both good friction coefficient and high transparency simultaneously.
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 transparent film allows for smooth and consistent pen-input operations, mimicking writing on paper with a pencil, while maintaining high transparency and durability against repeated use.
Implementation Method 1
the coat layer has a surface with a maximum height of rolling circle waviness profile (WEM) in accordance with JIS B0610 of not less than 15 μm
Data Source
AI summary
A transparent film for a display is provided. The transparent film enables smooth writing in input operation using a pen-input touch panel, like writing on paper with a pencil. The transparent film comprises a transparent substrate film and a coat layer on at least one side of the transparent substrate film. The total light transmittance of the transparent film in accordance with JIS K7136 is adjusted to not lower than 85%, and the surface of the coat layer is adjusted to a maximum height of rolling circle waviness profile (WEM) of not less than 15 μm in accordance with JIS B0610. The transparent film is disposed at the outermost side of a display in a pen-input touch panel. The coat layer may contain a particle and a binder component. The particle may have an average particle size of about 1 to 5 times as large as the thickness of the coat layer. The binder component may further contain a thermoplastic elastomer.