Floating Reflection Films in LCD Backlight Efficiency
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Solution Overview
Problem
Medium/small-sized liquid crystal display devices face increased power consumption due to lower light use efficiency from backlights as screen resolution increases, and existing reflection layer structures adversely affect signal writing speed due to stray capacitance.
Innovation Solution
A liquid crystal display device with a TFT substrate featuring independently floating reflection films on the lower side of the base film, formed of high-reflectance Al alloy, specifically AlSi, which are divided for each pixel and line, reducing stray capacitance and enhancing light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a reflection layer is applied to the overall TFT substrate except for apertures to reutilize light from the backlight, then light use efficiency is improved, but signal writing speed deteriorates due to increased stray capacitance
Solution Approach 1:
The reflection layer is segmented into multiple independent reflection films, each corresponding to a specific pixel region. These reflection films are electrically isolated from each other and from signal lines, preventing capacitance formation while maintaining light reflection functionality. Each reflection film is formed only in the pixel area where it is needed, separating the optical function from the electrical interference.
Solution Approach 2:
The harmful capacitance effect is extracted and eliminated by removing the continuous reflection layer that caused the problem. Only the necessary reflection function is retained through discrete reflection films positioned precisely in pixel regions, extracting the harmful electrical coupling while preserving the useful optical reflection.
2Measurement precision
If screen resolution is increased to achieve high definition, then image quality is improved, but light use efficiency deteriorates due to lower aperture ratio
Solution Approach 1:
The reflection films continuously reflect light back toward the liquid crystal layer for multiple passes, maximizing the utilization of backlight light. This continuous reflection action compensates for the reduced aperture ratio by ensuring that light not immediately transmitted through the pixel aperture is systematically recovered and reused, maintaining effective light usage even at high resolutions.
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
The solution increases light use efficiency from backlights, preventing signal writing delays and maintaining brightness while reducing power consumption, even at higher screen resolutions.
Implementation Method 1
a reflection film is formed on a lower side of the base film at an area corresponding to the TFT... the reflection film has a reflectance of 70% or more at the lower side thereof
Data Source
AI summary
A provided is a liquid crystal display device for reducing power consumption by increasing efficiency of a backlight. The liquid crystal display includes, on a TFT substrate, a semiconductor layer and a gate electrode are laminated via a gate insulating film. A TFT is formed by the semiconductor layer and the gate electrode. A base film is formed of an insulating film and at a lower layer of the semiconductor layer. As seen in plan view, a reflection film is formed on a lower side of the base film at an area corresponding to the TFT. The reflection film is independently formed for each of the TFTs. Each of the reflection films is electrically floating. The reflection film has a reflectance of 70% or more at a lower side thereof. The use efficiency of the light from a backlight can be increased because of the existence of the reflection film.