Backlight Light Guide Plate Uniform Illuminance Thickness Trade-off
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in achieving uniform light distribution and high color temperature with thin, lightweight designs, while maintaining high color reproducibility and efficiency, particularly with the use of LED light sources and light guide plates.
Innovation Solution
A liquid crystal display device incorporating a planar lighting system with blue LEDs, a fluorescent member that converts blue light to white light, and a color filter with specific transmittance characteristics, along with a light guide plate that increases thickness towards the light exit plane, to enhance light use efficiency and adjust color temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a direct illumination type backlight unit is used to reduce thickness, then the thickness is reduced, but uniform light amount distribution cannot be achieved
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the light source and the liquid crystal display panel. The light guide plate receives light from the light source and distributes it uniformly across the display area through its optical properties, enabling thin design while maintaining uniform illumination.
Solution Approach 2:
The refractive index distribution within the light guide plate is optimized to control light propagation and extraction. By adjusting the refractive index gradient and incorporating specific optical particles, the light distribution uniformity is improved while maintaining a thin profile.
2Illumination intensity
If a light guide plate with scattering particles is used to achieve uniform light distribution, then uniform light emission is achieved, but color temperature control becomes difficult
Solution Approach 1:
Different regions of the light guide plate are designed with different optical properties. The light guide plate includes a light incident region with specific scattering characteristics and a light emitting region with optimized light extraction properties, allowing simultaneous achievement of uniform distribution and color temperature control.
Solution Approach 2:
The light guide plate is constructed using composite materials including transparent resin and specifically sized optical particles (0.01-10 μm diameter). This composite structure enables both uniform light distribution through scattering and controlled color temperature by selecting appropriate particle materials and size distributions.
3Illumination intensity
If optical particles are added to the light guide plate to improve light diffusion, then light distribution uniformity is improved, but light use efficiency decreases
Solution Approach 1:
The diameter of optical particles is precisely controlled within the range of 0.01-10 μm. This parameter optimization ensures sufficient light scattering for uniform distribution while minimizing excessive scattering that would cause light loss. The particle size is tuned to match the wavelength of LED light for efficient diffusion.
Solution Approach 2:
Optical particles are selectively positioned in the light incident region rather than uniformly throughout the entire light guide plate. This localized placement provides necessary diffusion at the entry point while reducing scattering losses in the light transmission and emission regions, thereby improving overall light use efficiency.
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 enables the display of high-quality images with uniform illuminance and high color temperature, while allowing for thinner and more efficient light emission, overcoming the limitations of previous technologies in terms of brightness and color reproducibility.
Implementation Method 1
a fluorescent member disposed between the light emission face of the at least one light source and the light entrance plane of the transparent light guide plate and comprising one or more fluorescent substance coated areas for emitting white light by converting the blue light emitted through the light emission face into the white light
Implementation Method 2
a transparent light guide plate comprising at least one light entrance plane for admitting light emitted by the light source and a light exit plane for emitting light admitted from the light entrance plane as planar light
Data Source
AI summary
The liquid crystal display device with a simple configuration is capable of emitting light with a desired color temperature, achieving high light use efficiency, and displaying high quality images. The liquid crystal display device includes a planar lighting device and a liquid crystal display panel. The planar lighting device includes a light source having LED chips for emitting blue light, a transparent light guide plate having a light entrance plane admitting light emitted by the light source and a light exit plane emitting planar light, and a fluorescent member disposed between the light emission plane and the light entrance plane and having one or more fluorescent substance coated areas for emitting white light by converting blue light from the light source into white light and one or more blue light passing areas passing blue light as blue light. The liquid crystal display panel essentially includes red, green and blue filters.