Input Pen Cover Member Surface Texture Optimization
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Solution Overview
Problem
Conventional pen input devices with glass substrates as cover members result in an uncomfortable writing feel due to the nib catching excessively, making it difficult to achieve a good sliding operation.
Innovation Solution
A cover member with recesses and protrusions on its surface, specifically designed with a maximum roughness height of 3 to 1000 nm and a pitch of 50 to 1000 μm, and a three-dimensional arithmetic mean height of 1 to 50 nm, along with appropriate cutoff values for filters, to optimize the sliding of the input pen, ensuring neither too much nor too little friction, thereby enhancing the writing feel while maintaining transparency and visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resin layer with recesses and protrusions is formed on the cover member surface, then the writing feel is improved, but the nib catches too much and becomes difficult to slide
Solution Approach 1:
The patent applies parameter changes by precisely controlling the surface roughness parameters (Ra: 1-50 nm, Rz: 3-1000 nm) and pitch of recesses and protrusions. By optimizing these parameters within specific ranges, the invention achieves the desired writing feel while preventing excessive friction that would make sliding difficult.
Solution Approach 2:
The patent implements local quality by creating specific surface structures (recesses and protrusions) only on the contact surface of the cover member where the nib interacts with it. This localized modification provides improved writing feel without affecting other parts of the device.
2Ease of operation
If the surface of the glass substrate is made smooth, then the transparency and visibility are maintained, but the nib slides too easily causing uncomfortable writing
Solution Approach 1:
The patent changes the surface parameters from completely smooth to controlled roughness with specific Ra (1-50 nm) and Rz (3-1000 nm) values. This controlled modification provides sufficient friction for comfortable writing while maintaining overall transparency and visibility.
3Ease of operation
If the surface roughness is increased to improve writing feel, then friction is enhanced, but the transparency and visibility of the display device deteriorate
Solution Approach 1:
The patent optimizes the balance between roughness and transparency by controlling surface parameters within specific ranges (Ra: 1-50 nm, Rz: 3-1000 nm). These controlled roughness values provide sufficient writing feel while minimizing light scattering that would reduce transparency.
Solution Approach 2:
The surface modification is applied locally only where needed for writing interaction, with the overall surface structure maintained to preserve optical properties. The recesses and protrusions are designed to be subtle enough not to significantly impact light transmission.
Data Source
AI summary
A cover member for an input device is disposed on a front-surface side of a display device in the input device includes recesses and protrusions on at least one principal surface. In the principal surface having recesses and protrusions, when a cutoff value for a high-pass filter λc is set to 1.6 times the pitch of the recesses and protrusions of a measured cross-sectional curve and a cutoff value for a low-pass filter λs is set to 25 μm, the maximum roughness height Rz of the recesses and protrusions is 3-1000 nm and the pitch RSm of the recesses and protrusions is 50-1000 μm, and when the cutoff value of the high-pass filter λc is set to 25 μm, the three-dimensional arithmetic mean height Sa of the recesses and protrusions is 1-50 nm and the pitch RSm of the recesses and protrusions is 0.01-10 μm.