Capacitive Touch Panel Adhesive Dielectric Stability
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Solution Overview
Problem
Capacitive touch panels experience malfunctions when used for extended periods due to changes in the relative dielectric constants of pressure sensitive adhesive layers, leading to capacitance deviations and operational failures in normal temperature environments.
Innovation Solution
A capacitive touch panel configuration is developed with specific temperature dependence criteria for upper and lower pressure sensitive adhesive layers, ensuring their relative dielectric constants remain within predetermined ranges to minimize capacitance changes, comprising a display device, capacitive touch panel sensor, and protective substrate, where the upper layer's temperature dependence is 10.0% or less and the lower layer's is equal to or greater than the upper layer's, with a difference of 10.0% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pressure sensitive adhesive layers are used in capacitive touch panels, then the touch panel can be manufactured with standard materials, but the relative dielectric constant changes during prolonged use causing malfunction
Solution Approach 1:
The invention changes the material parameters of the pressure sensitive adhesive layers by selecting specific resin compositions (acrylic resin, vinyl resin, or polyolefin resin) with controlled glass transition temperatures and molecular weights. This ensures the relative dielectric constant remains stable within ±10% over the use period, preventing capacitance deviation and malfunction while maintaining manufacturability with standard adhesive materials
Solution Approach 2:
Instead of trying to prevent temperature changes or external influences on the adhesive layers, the invention inverts the approach by selecting materials whose dielectric properties are inherently insensitive to such changes. The pressure sensitive adhesive layers are chosen specifically for their stable relative dielectric constants, turning the potential weakness of polymer materials into a strength through careful material selection
2Manufacturing precision
If the upper pressure sensitive adhesive layer has low temperature dependence of relative dielectric constant, then capacitance stability is improved, but the lower layer must be carefully selected to maintain specific relationship
Solution Approach 1:
The invention applies different material specifications to the upper and lower pressure sensitive adhesive layers based on their specific functional requirements. The upper layer (closer to the touch surface) requires lower temperature dependence of relative dielectric constant to maintain capacitance stability during use, while the lower layer has slightly different requirements. This localized quality approach optimizes each layer's performance while maintaining overall system reliability
Solution Approach 2:
The invention defines specific parameter ranges for the pressure sensitive adhesive layers including resin type (acrylic, vinyl, or polyolefin), glass transition temperature (−50°C to 0°C), and molecular weight (10,000 to 1,000,000). These controlled parameter changes ensure the relative dielectric constant remains stable while providing clear manufacturing guidelines that balance precision requirements with ease of production
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 configuration significantly reduces the occurrence of malfunctions even after prolonged finger contact, maintaining reliable operation in normal temperature environments by stabilizing capacitance values.
Implementation Method 1
temperature dependence of a relative dielectric constant of an upper pressure sensitive adhesive layer which is obtained by a temperature dependency evaluation test described below is 10.0% or less
Implementation Method 2
temperature dependence of a relative dielectric constant of the lower pressure sensitive adhesive layer which is obtained by a temperature dependency evaluation test described below is equal to or greater than the temperature dependence of a relative dielectric constant of the upper pressure sensitive adhesive layer
Data Source
AI summary
The present invention provides a capacitive touch panel in which malfunction hardly occurs even when an operation is performed after a finger of an operator touches the capacitive touch panel for a long period of time in an ordinary temperature. The capacitive touch panel according to the invention is a capacitive touch panel comprising: a display device; a lower pressure sensitive adhesive layer; a capacitive touch panel sensor; an upper pressure sensitive adhesive layer; and a protective substrate, in this order, in which temperature dependence of a relative dielectric constant of the upper pressure sensitive adhesive layer which is obtained by a temperature dependency evaluation test described below is 10.0% or less.