Capacitance Touch Panel Adhesive Permittivity Control
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Solution Overview
Problem
Conventional capacitance touch panels experience malfunctions due to increased screen size, particularly because of the high temperature dependency of the relative permittivity of the adhesive layers, leading to parasitic capacitance changes and deviations in capacitance values.
Innovation Solution
A capacitance touch panel design where the relative permittivity of the upper adhesive layer is equal to or greater than that of the lower adhesive layer at various temperatures, with a controlled temperature dependency of the lower adhesive layer to minimize parasitic capacitance changes, ensuring stable capacitance detection over a range of temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the screen size of the capacitance touch panel is increased, then the display area is improved, but the reliability deteriorates due to malfunctions from temperature-dependent parasitic capacitance changes
Solution Approach 1:
The patent applies parameter changes by carefully selecting and controlling the relative permittivity values of the adhesive layers at different temperatures. Specifically, it sets the relative permittivity of the lower adhesive layer (B) to be less than or equal to that of the upper adhesive layer (A) across the temperature range of -40°C to 80°C, and limits the temperature dependency of the lower adhesive layer to 30% or less. This parameter control compensates for temperature-induced capacitance changes and prevents malfunctions in large-sized touch panels.
2Strength
If the temperature dependency of the adhesive layer's relative permittivity is high, then the adhesive performance is improved, but the measurement precision deteriorates due to capacitance value deviations
Solution Approach 1:
The patent controls the temperature dependency parameter of the adhesive layer's relative permittivity to be 30% or less across the temperature range from -40°C to 80°C. This parameter control ensures that the capacitance values remain stable and within acceptable ranges despite temperature variations, thereby maintaining both adhesive performance and measurement precision.
3Ease of manufacture
If the relative permittivity of the adhesive layers is not controlled, then the manufacturing process is simplified, but the device complexity increases due to malfunction-prone design
Solution Approach 1:
The patent establishes specific parameter ranges for the relative permittivity of the adhesive layers (A≥B at all temperatures from -40°C to 80°C, with B's temperature dependency ≤30%). These parameter specifications provide clear manufacturing guidelines that simplify the production process while ensuring reliable device performance, avoiding the complexity of troubleshooting malfunction-prone designs.
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 design significantly reduces the likelihood of malfunctions in capacitance touch panels, even after prolonged use, by maintaining consistent capacitance values and reducing the impact of temperature changes on the adhesive layers.
Implementation Method 1
relative permittivity A in the upper adhesive layer and relative permittivity B in the lower adhesive layer satisfy expression (1): Relative permittivity A≧relative permittivity B (1) at respective temperatures set in increments of 20° C. from −40° C. to 80° C., and wherein a temperature dependency of the relative permittivity B in the lower adhesive layer as determined by a temperature dependency evaluation test is up to 30%
Data Source
AI summary
A capacitance touch panel of the invention includes a display, a lower adhesive layer, a capacitance touch panel sensor, an upper adhesive layer and a protective substrate, which are formed in this order. Relative permittivity A in the upper adhesive layer and relative permittivity B in the lower adhesive layer satisfy expression (1): [relative permittivity A≧relative permittivity B . . . (1)] at respective temperatures set in increments of 20° C. from −40° C. to 80° C., and a temperature dependency of the relative permittivity B in the lower adhesive layer as determined by a temperature dependency evaluation test is up to 30%.