LED Mounting on Touch Panel FPC for LCD Brightness Uniformity
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Solution Overview
Problem
Conventional small liquid crystal display apparatuses with touch panels experience brightness nonuniformity due to deformation of the backlight FPC substrate under pressure from the touch pen, leading to increased manufacturing costs and complexity.
Innovation Solution
Fixing the light sources to the touch panel instead of the light guide plate, allowing them to remain stationary under external pressure, and using a dual-use FPC substrate for both the touch panel and light sources to reduce component count and manufacturing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LEDs are mounted on the backlight I/F FPC substrate which is fixed to the light guide plate, then the liquid crystal display apparatus can be assembled with conventional components, but the FPC substrate is easily deformed by pressure from the touch pen causing brightness nonuniformity
Solution Approach 1:
The patent merges the backlight light source mounting function with the touch panel structure by fixing LEDs to the touch panel's FPC substrate rather than the light guide plate's FPC substrate. This integration ensures that the light source position remains stable relative to the touch panel, preventing brightness nonuniformity while reducing the number of separate component arrangements.
Solution Approach 2:
The touch panel's FPC substrate acts as an intermediary structure that simultaneously supports both the touch panel circuitry and the backlight light sources. This intermediary structure provides a stable mounting platform that is not affected by touch pen pressure, thereby maintaining brightness uniformity without increasing overall device complexity.
2Reliability
If LEDs are fixed to the light guide plate, then brightness uniformity can be improved, but the number of components and manufacturing steps increases
Solution Approach 1:
The patent combines multiple functions into a single FPC substrate structure. The touch panel's FPC substrate serves both as the circuit board for the touch panel and as the mounting substrate for the backlight LEDs, eliminating the need for separate LED mounting operations and reducing manufacturing complexity.
Solution Approach 2:
The FPC substrate of the touch panel is given multi-functionality by serving both as the electrical connection medium for the touch panel and as the mechanical support structure for the backlight light sources. This universal use of a single component reduces the total component count and simplifies manufacturing processes.
3Ease of manufacture
If the backlight I/F FPC substrate is used to mount LEDs, then conventional manufacturing processes can be used, but the substrate deforms under touch pen pressure causing display quality issues
Solution Approach 1:
Instead of mounting LEDs on the FPC substrate associated with the light guide plate (conventional approach), the patent inverts the mounting location to the FPC substrate of the touch panel. This inversion places the light sources on a structure that is not subjected to touch pen pressure, thereby maintaining manufacturing simplicity while achieving high position precision.
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 reduces brightness nonuniformity without increasing the number of components or manufacturing steps, while maintaining a compact design and protecting against electromagnetic noise.
Implementation Method 1
electromagnetic-induction touch panels that detect electromagnetic energy generated in the panel by a dedicated pen
Implementation Method 2
a backlight light guide plate which is disposed behind the liquid crystal panel and which supplies light to the liquid crystal panel
Data Source
AI summary
A plurality of LEDS used for a light source are mounted on the surface of an electromagnetic-induction touch panel in which coiled wiring is formed on a glass epoxy substrate. A dual-use touch-panel/backlight I/F FPC substrate is connected to the touch panel in order to feed power to the LEDs and to feed power and signals to the touch panel. A shield plate 7 is disposed on the reverse side of the touch panel, and a backlight light guide plate and a liquid crystal panel are disposed in the stated order on the side on which the LEDs are mounted. A liquid crystal panel I/F FPC substrate for feeding power to the liquid crystal panel is connected to the liquid crystal panel.