Flexible Wiring Substrate for Narrow Liquid Crystal Display Touch Panel
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Solution Overview
Problem
The existing liquid crystal display devices with built-in touch panels face challenges in minimizing the width of the flexible wiring substrate, which is necessary for efficient integration and protection of the integrated circuit, due to the wide width required for forming multiple lines and the protrusion of the flexible wiring substrate from the upper substrate shared with the touch panel.
Innovation Solution
A liquid crystal display device with a built-in touch panel is designed using a flexible wiring substrate formed as a multilayer substrate with conductive pattern layers, insulating layers, and contact portions that overlap with terminal portions, allowing for a narrower width by optimizing the arrangement and connection of terminal and contact portions, and avoiding overlap with the integrated circuit chip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flexible wiring substrate is made wide to form a large number of lines, then the electrical connection capability is improved, but the width of the flexible wiring substrate increases causing it to protrude from the upper substrate and preventing proper resin protection of the integrated circuit
Solution Approach 1:
The patent transitions from a planar arrangement of contact portions to a three-dimensional stacked configuration where multiple contact portions are arranged vertically across different layers of the flexible wiring substrate. This allows multiple signal lines to be connected through the same horizontal footprint area, reducing the substrate width while maintaining electrical connection capability.
Solution Approach 2:
The patent implements a multilayer structure where contact portions in upper layers are positioned directly above contact portions in lower layers, creating a nested vertical arrangement. This nesting allows the flexible wiring substrate to convey multiple signals through a compact width by stacking conductive paths vertically rather than spreading them horizontally.
2Length of moving object
If the flexible wiring substrate is made narrow to reduce protrusion, then the device thickness is reduced and resin protection is enabled, but the ability to form a large number of electrical lines is compromised
Solution Approach 1:
The patent resolves this contradiction by moving the electrical connection architecture from two-dimensional horizontal routing to three-dimensional vertical stacking. Multiple contact portions are arranged in the thickness direction of the flexible wiring substrate, allowing numerous signal lines to pass through a narrow width by utilizing the vertical dimension for signal routing.
Solution Approach 2:
The patent employs a multilayer composite structure of the flexible wiring substrate with alternating conductive and insulating layers. This composite architecture enables multiple independent electrical pathways to be integrated within a compact cross-sectional area, maintaining high electrical connection capability while minimizing the substrate width.
Data Source
AI summary
A liquid crystal display device equipped with a built-in touch panel includes a second substrate on which a wiring pattern for configuring a touch panel is formed, and a flexible wiring substrate joined to the second substrate with an overlap portion, and electrically connected to the wiring pattern. The flexible wiring substrate is formed of a multilayer substrate having a first conductive pattern layer having a plurality of terminal portions electrically connected onto the wiring pattern, a second conductive pattern layer, an insulating layer interposed between the first conductive pattern layer and the second conductive pattern layer, and a plurality of contact portions that penetrates through the insulating layer, and electrically connects the plurality of terminal portions to the second conductive pattern layer. The plurality of contact portions is arranged to overlap with the plurality of terminal portions.