Spacerless Resistive Touch Panel Gap Filling for Optical Clarity
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Solution Overview
Problem
Multi-touch panels of the resistive film type face issues with light reflection and Newton's rings due to the interface between electrode plates, leading to poor visuality, and fail to detect pressure inputs from solid objects like stylus pens, causing operational errors and ineffective pressure-sensitive functions.
Innovation Solution
A spacerless design is implemented with a pressure-sensitive conductive layer and an intermediate layer filling the gap between the upper and lower transparent electrode base members, eliminating air layers and preventing light reflection, while a rigid upper electrode base member and adhesive paste with a hardened layer prevent warping and liquid leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If dot spacers are interposed between the conductive films to maintain gap distance, then the structural stability is improved, but light reflection and Newton's rings occur at the air layer interfaces, deteriorating visuality
Solution Approach 1:
The patent introduces a liquid intermediate layer filled between the upper and lower transparent electrode base members to replace the air layer. This liquid intermediary eliminates the refractive index mismatch at interfaces, thereby suppressing light reflection and Newton's rings while maintaining the necessary gap distance for pressure sensitivity
Solution Approach 2:
The patent fills the gap space with a liquid having appropriate optical properties (refractive index matching) to create an optically inert environment. This liquid filling acts as an inert medium that prevents harmful optical effects at the interfaces between electrode plates
2Reliability
If the upper transparent electrode base member is made flexible to enable pressure detection, then the pressure sensitivity is improved, but the member warps excessively, causing erroneous operation
Solution Approach 1:
The patent changes the physical parameters of the upper transparent electrode base member by controlling its thickness and material properties to achieve optimal balance between flexibility for pressure detection and rigidity to prevent excessive warping. The member is designed with specific thickness range to maintain both sensitivity and stability
Solution Approach 2:
The patent provides adhesive paste at the peripheral edges before assembly to prevent excessive warping of the upper transparent electrode base member. This pre-applied adhesive cushioning maintains the member's flatness while preserving its pressure-sensitive properties
3Object-affected harmful factors
If the gap between electrode plates is reduced to improve visuality, then light reflection is suppressed, but the pressure sensitivity decreases and multiple touch detection becomes difficult
Solution Approach 1:
The patent uses a liquid intermediate layer as a mediator that allows maintaining a sufficient gap distance for pressure sensitivity while eliminating light reflection issues. The liquid fills the gap space to provide both optical clarity and mechanical compliance for pressure detection
4Strength
If adhesive paste is applied at peripheral edges to bond electrode plates, then the bonding strength is improved, but the liquid intermediate layer may leak to FPC portions, causing operational failure
Solution Approach 1:
The patent applies different properties to different regions: the adhesive paste is applied only at the peripheral edges for bonding, while the liquid intermediate layer is contained in the central sensing area. This local differentiation ensures both strong bonding and prevention of liquid leakage to FPC portions
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
This design suppresses light reflection, prevents Newton's rings, enhances visuality, maintains operational integrity without spacers, and effectively detects pressure inputs from both soft and solid objects, improving the overall performance of the touch panel.
Implementation Method 1
the pressure-sensitive conductive layer and the intermediate layer are filled in the gap between the surface provided with the upper transparent electrode group of the upper transparent electrode base member and the surface provided with the lower transparent electrode group of the lower transparent electrode base member, thereby making it possible to suppress any reflection of light generated at two interfaces
Implementation Method 2
the upper transparent electrode base member is rigid and thick, thereby avoiding excessive warp of the upper transparent electrode base member and erroneous operation
Implementation Method 3
the adhesive paste that bonds the upper transparent electrode base member and the lower transparent electrode base member at peripheral edges
Data Source
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AI summary
There is provided a spacerless input device that suppresses reflection at an interface, prevents generation of Newton's rings, improves visuality, does not operate erroneously even with no provision of a dot spacer, and has a pressure sensitive function even responsive to input with a solid matter. In an input device of a resistive film type accepting multiple touches, a pressure-sensitive conductive layer and an intermediate layer are filled in a gap between a surface provided with an upper transparent electrode group of an upper transparent electrode base member and a surface provided with a lower transparent electrode group of a lower transparent electrode base member.