LCD Backlight Module and Color Filters for High Saturation
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Solution Overview
Problem
Current LCDs face challenges in achieving ideal color saturation, particularly in green and red color representations, as they often fall short of the Adobe specification in CIE1931 chromaticity coordinates, leading to suboptimal overall color saturation.
Innovation Solution
The LCD incorporates a backlight module with a white light source having specific relative maximum brightness peaks and fluorescent powder compositions, along with carefully designed color filter layers, to adjust and improve green and red saturation by controlling the emission spectrum and transmittance of the red and green filter layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional backlight modules with standard emission spectra are used, then the LCD structure remains simple and manufacturing is easy, but the color saturation NTSC ratio is limited to 70-75% with poor green and red color representation
Solution Approach 1:
The patent changes the spectral parameters of the backlight module by using a blue LED with specific wavelength (435-480nm) and controlling the emission spectrum characteristics (BL1/BL2 ratio ≥0.32). This parameter change in the light source enables achieving color saturation NTSC ratio of 83-88% without fundamentally changing the LCD structure
Solution Approach 2:
The patent employs composite fluorescent materials including green fluorescent powder (emission peak 500-560nm) and red fluorescent powder (emission peak 600-700nm) with specific luminance ratios. This composite fluorescent material system enables precise control over the emission spectrum to achieve superior color saturation while maintaining manufacturing feasibility
2Illumination intensity
If the green filter layer transmittance is increased to improve green color brightness, then the overall light output improves, but the green color saturation decreases and fails to meet Adobe specification
Solution Approach 1:
The patent applies local quality by making the green filter layer transmittance wavelength-dependent. The transmittance is specifically controlled at different wavelengths: at 530-560nm the transmittance is optimized for saturation, while at 500-525nm it allows sufficient brightness. This localized transmittance control enables the green filter layer to simultaneously achieve both brightness and saturation requirements
Solution Approach 2:
The patent changes the transmittance parameters of the green filter layer across different wavelength ranges. By controlling T1 (transmittance at 500-525nm) and T2 (transmittance at 530-560nm) with specific relationships, the system achieves optimal balance between green color saturation and brightness, meeting Adobe specification requirements
3Illumination intensity
If the red filter layer transmittance is increased to improve red color brightness, then the overall light output improves, but the red color saturation decreases and fails to meet Adobe specification
Solution Approach 1:
The patent applies local quality by making the red filter layer transmittance wavelength-dependent. The transmittance is specifically controlled at different wavelengths: at 615-665nm the transmittance is optimized for saturation, while at other wavelengths it allows sufficient brightness. This localized transmittance control enables the red filter layer to simultaneously achieve both brightness and saturation requirements
Solution Approach 2:
The patent changes the transmittance parameters of the red filter layer across different wavelength ranges. By controlling the transmittance at specific wavelength bands with specific relationships, the system achieves optimal balance between red color saturation and brightness, meeting Adobe specification requirements
4Ease of manufacture
If a CCFL with standard fluorescent powder is used as backlight, then the manufacturing process is simple and cost-effective, but the color saturation NTSC ratio is limited and cannot simultaneously achieve desirable green and red saturation
Solution Approach 1:
The patent changes the fundamental parameter of the light source from CCFL to blue LED, enabling precise control over the emission spectrum. The blue LED's narrow spectral width and adjustable wavelength allow for optimized BL1/BL2 ratio (≥0.32), which is critical for achieving color saturation NTSC ratio of 83-88% while maintaining manufacturing simplicity
Solution Approach 2:
The patent employs composite fluorescent materials converted by the blue LED, including green fluorescent powder (emission peak 500-560nm) and red fluorescent powder (emission peak 600-700nm) with specific luminance ratios. This composite material system enables precise spectral control to achieve superior color saturation while maintaining manufacturing feasibility and cost-effectiveness
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 approach effectively enhances the color saturation NTSC ratio from 70-75% to 83-88%, providing better representation of green and red colors, thus improving the overall color reproduction of the LCD.
Implementation Method 1
uses a blue LED together with a green fluorescent powder and a red fluorescent powder, in which an emission spectrum of the blue LED has a first relative maximum brightness peak BL1 at a wavelength between 435 nm and 480 nm, and has a second relative maximum brightness peak BL2 at a wavelength between 480 nm and 530 nm
Data Source
AI summary
A liquid crystal display (LCD) including a backlight module and a liquid crystal display panel is provided. The backlight module has at least one white light source. BL1 and BL2 respectively represent relative maximum brightness peaks of an emission spectrum of the backlight module at a wavelength between 500 nm and 525 nm and between 530 nm and 560 nm, in which BL1/BL2≧0.32. The liquid crystal display panel is disposed above the backlight module, and has two substrates and a liquid crystal layer sandwiched therebetween. One of the two substrates has a red filter layer, a green filter layer, and a blue filter layer, in which transmittances of the red filter layer and the green filter layer at wavelength of approximately 590 nm are both smaller than about 45%.