Edge-Lit LCD Backlight Thermal Exhaustion via Conductive Sheet
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Solution Overview
Problem
Liquid crystal display devices face challenges in efficiently exhausting heat due to the concentration of light sources on edges in edge-lit types and increased cost and power consumption in direct-lit types, which hinder thickness reduction and image quality.
Innovation Solution
A liquid crystal display device with a backlight system featuring light-source units comprising LEDs, a wiring board, a light-guide plate, and a metal chassis, where a thermally conductive sheet connects the wiring board to the chassis, enhancing heat dissipation through a reduced thermal resistance path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light sources are concentratedly disposed on edges of the screen in edge-lit type backlight, then the structure is simplified and manufacturing is easier, but the heat from the light sources is not easily cooled or exhausted
Solution Approach 1:
A thermally conductive sheet is introduced as an intermediary component between the LED mounting board and the chassis. This sheet has high thermal conductivity to facilitate heat transfer from the LED to the chassis, while being electrically insulating to prevent electrical short circuits. The intermediary thermally conductive sheet resolves the contradiction by enabling effective heat exhaustion without compromising the simplified edge-lit structure.
2Illumination intensity
If direct-lit type backlight is used with larger number of light sources, then illumination is improved, but cost and power consumption increase
Solution Approach 1:
The patent changes the parameters of the light sources by using LEDs instead of traditional bulb-type light sources. LEDs have higher luminous efficiency and lower power consumption. The patent also optimizes the arrangement of LEDs on the edge, using a limited number of high-efficiency light sources to achieve adequate illumination, thereby reducing overall power consumption while maintaining image quality.
3Illumination intensity
If distance is put between light sources and liquid crystal panel, then luminance uniformity is improved, but thickness of the device increases
Solution Approach 1:
The patent uses a light guide plate to redirect light from the edge-mounted LEDs toward the liquid crystal panel in a controlled manner. By introducing this optical component that operates in the lateral dimension, the system achieves uniform luminance distribution across the display without requiring increased thickness in the vertical direction. The light guide plate guides light along the edge and distributes it uniformly across the panel surface.
4Length of stationary object
If thinner liquid crystal display device is made, then external shape is reduced, but airflow path for exhausting heat is compromised
Solution Approach 1:
The heat exhaustion function is extracted from the overall device thickness and implemented through a dedicated thermally conductive sheet that operates within the existing thin structure. The sheet is placed between the LED mounting board and the chassis, creating an efficient heat transfer path that does not require additional thickness. This extraction allows the device to maintain thin profile while achieving effective heat exhaustion.
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 improves thermal exhaustion properties while allowing for a thinner liquid crystal display device without compromising image quality, as demonstrated by temperature analysis showing reduced thermal resistance and improved cooling efficiency.
Implementation Method 1
a thermally conductive sheet making close contact with and inserted between the metal chassis and a reverse side of the wiring board which is opposite to a face on which the LED is mounted
Implementation Method 2
a light-guide plate having translucency for guiding the light of the LED toward the liquid crystal panel
Data Source
AI summary
A liquid crystal display device with improved thermal exhaustion property, enabling a thickness reduction, includes a backlight including light sources illuminating a liquid crystal panel from a back face, and a chassis holding the backlight. The backlight includes: plural light-source units each including a combination of a LED emitting light in a direction parallel to a display surface of the panel, a wiring board mounted with the LED, and a light-guide plate having translucency for guiding the LED light toward the panel; a metal chassis supporting the light-source units; and a thermally conductive sheet tightly inserted between the metal chassis and a reverse side of the wiring board opposite to the LED-mounted face. A wiring pattern is formed on the reverse side. The metal chassis and the wiring pattern located within a predetermined distance of the LED outer periphery are connected through the thermally conductive sheet.