Flexible Substrate Folding for LCD Thinning
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Solution Overview
Problem
In compact liquid crystal display devices, such as mobile telephones, the mounting of LEDs on a flexible printed substrate (FPC) often results in interference with the reflection sheet of the backlight, hindering the thinning of the device due to the need for clearance to avoid superposition, which obstructs further miniaturization.
Innovation Solution
The FPC is folded around to the back surface of the backlight, with the LED mounting portion positioned to face the reflection sheet in the same plane, eliminating the need for clearance and allowing for thinner device designs by avoiding superposition with the reflection sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the LED mounting part of the FPC is disposed to be superposed on the reflection sheet of the backlight, then the device structure is simplified, but the superposed portion interferes with the mounting device and prevents further thinning
Solution Approach 1:
The FPC is folded back along the thickness direction (Z-axis) to position the LED mounting part in a different spatial dimension relative to the reflection sheet. This dimensional repositioning allows the LED mounting part to face the reflection sheet in the same plane without superposition, eliminating interference while maintaining structural simplicity.
Solution Approach 2:
Instead of extending the FPC linearly in the plane, the FPC is inverted by folding it back toward the backlight side. This inversion places the LED mounting part on the back surface side of the backlight, where it can face the reflection sheet without overlapping, thus resolving the interference issue.
2Reliability
If clearance is disposed to avoid interference between the LED mounting part and the reflection sheet, then interference is prevented, but the device thickness increases
Solution Approach 1:
The FPC is folded back along the thickness direction (Z-axis) to position the LED mounting part in a different spatial dimension relative to the reflection sheet. This dimensional repositioning allows the LED mounting part to face the reflection sheet in the same plane without superposition, eliminating interference while maintaining structural simplicity.
Solution Approach 2:
The FPC is folded back and nested within the space between the liquid crystal display panel and the reflection sheet. The LED mounting part is positioned to face the reflection sheet from the back surface side, effectively nesting the FPC within the existing device thickness without requiring additional clearance.
Data Source
AI summary
A liquid crystal display device includes: a liquid crystal display panel where a semiconductor chip driving pixel circuits is mounted on a main surface of a first substrate which is exposed by recession of a second substrate, wire terminals connect to the semiconductor chip; a backlight illuminating a back surface of the liquid crystal display panel with illumination light; a mold frame housing the liquid crystal display panel and the backlight; and a reflection sheet disposed on a back surface of the mold frame. The liquid crystal display device includes an FPC having one end portion connected to wire terminals on the main surface of the first substrate, and another end portion on which LEDs are mounted, the mold frame includes a housing portion for a light guide plate which has a light-exiting surface including a display region of the liquid crystal display panel and housing portions for the LEDs. When the FPC is folded around to the back surface side of the backlight and the LEDs mounted on the other end portion of the FPC are housed in the housing portions for the LEDs of the mold frame, an end surface of the other end portion of the FPC is disposed to face, in the same plane, an end surface of the reflection sheet.