Curved Input Device Substrate Adhesion and Wiring
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Solution Overview
Problem
During the manufacturing of curved input devices, achieving full tight adhesion between the substrate and sensor film is challenging due to alignment issues and gaps, leading to potential detection errors and noise intrusion from wiring the lead from the detection area to the non-detection area.
Innovation Solution
A method involving lamination of a sensor film between two flat substrates, followed by bending to form a curved multilayer body, where the lead is extended through a non-lamination area to the back surface, avoiding wiring over the side surface and using an intermediate member to enhance adhesion and reduce tensile stress on the sensor film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the sensor film is attached to a substrate formed into an intended curved shape in advance, then the substrate can be bent to the desired curvature, but full tight adhesion between the substrate and sensor film cannot be achieved due to alignment issues and gaps
Solution Approach 1:
The substrate is formed into a curved shape in advance before attaching the sensor film. This preliminary shaping allows the substrate to be prepared with the desired curvature, and then the sensor film is attached to this pre-formed curved surface, solving the contradiction by performing the shaping action before the adhesion step.
Solution Approach 2:
An optically clear adhesive layer (OCA layer) is introduced as an intermediary between the substrate and sensor film. This adhesive layer fills gaps and ensures full tight adhesion while maintaining optical characteristics, resolving the alignment and gap issues that would otherwise prevent proper adhesion on curved surfaces.
2Measurement precision
If the sensor film is disposed as a layer near the panel surface to improve sensor responsivity, then detection accuracy improves, but wiring the lead from the detection area to the non-detection area causes detection errors and noise intrusion
Solution Approach 1:
The lead wiring is routed through the thickness dimension of the substrate rather than across the surface plane. The lead penetrates through the substrate from the front surface to the back surface, changing the wiring path from a two-dimensional surface route to a three-dimensional through-substrate route, thereby avoiding detection areas and eliminating noise intrusion.
Solution Approach 2:
The substrate is functionally segmented into detection areas and non-detection areas. By routing the lead through the substrate thickness rather than across the surface, the wiring path is separated from the detection areas, allowing the sensor film to remain in optimal positions for responsivity while the lead traverses through non-detection zones.
3Ease of manufacture
If a transparent resin plate is used as a bendable substrate, then ease of bending improves, but the smaller dielectric constant compared to glass results in lower sensor responsivity
Solution Approach 1:
The substrate material is changed from glass to transparent resin, altering the dielectric constant parameter. This material substitution provides improved bendability for curved input devices, accepting the trade-off in dielectric properties while achieving the desired mechanical flexibility through appropriate material selection.
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(c)
AI summary
An input device manufacturing method according to an aspect of the present invention includes a lamination step of preparing a first substrate formed from a flat plate of a translucent synthetic resin, a second substrate formed from a flat plate of a translucent synthetic resin, and a sensor film formed from a translucent resin film on which a translucent electrode is disposed, and holding the sensor film between the first substrate and the second substrate to form a flat multilayer body; and a bending step of bending the flat multilayer body into a curved multilayer body retaining a curved shape. Thus, the input device can secure sufficient adhesion between the substrates and the sensor film, and can retain high detection accuracy with the sensor film.