Backlight Optical Member Layout for Uniform LCD Edge Luminance
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Solution Overview
Problem
Conventional liquid crystal display devices face challenges in achieving uniform luminance across the entire screen, particularly at the outer peripheral portions, which affects visibility and display quality, especially in applications like vehicle instrument clusters where reliability is crucial.
Innovation Solution
A backlight device design featuring a substrate with light sources arranged in a specific pattern, an optical member with varying light transmittance regions, and a housing with a reflection sheet to ensure uniform luminance, incorporating a diffusion plate with an inclined surface and a polygonal optical unit to minimize absorption and enhance light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional optical sheets with geometric structures and hemispherical lenses are used, then light diffusion is improved, but luminance unevenness cannot be sufficiently reduced
Solution Approach 1:
The optical member is divided into multiple regions (first regions corresponding to light source positions, second regions surrounding the first regions, and third regions between light emitting elements) with different light transmittance characteristics. Each region has specifically designed transmittance values to compensate for luminance unevenness, with the outer peripheral portion having higher transmittance than the central portion to address the specific problem of luminance non-uniformity.
Solution Approach 2:
The light transmittance parameter is varied across different regions of the optical member. The transmittance is set to increase as distance from light emitting elements increases in first regions, and to increase from central to outer peripheral portions in second regions. This parameter variation allows precise control of luminance distribution to achieve uniform appearance across the display screen.
2Device complexity
If the number of LED light sources is reduced, then device complexity is decreased, but brightness uniformity control becomes difficult
Solution Approach 1:
The optical member features non-uniform light transmittance distribution with different transmittance values in first regions (above light sources), second regions (surrounding areas), and third regions (between elements). This local variation in optical properties compensates for the reduced number of light sources, enabling uniform brightness control without requiring numerous LEDs.
Solution Approach 2:
The optical member acts as an intermediary between the reduced number of LED light sources and the display screen. By incorporating regions with different light transmittance, it mediates the light distribution to achieve uniform brightness across the screen, effectively decoupling the relationship between light source quantity and brightness uniformity.
3Area of stationary object
If light sources are arranged adjacently to save space, then device compactness is improved, but luminance unevenness increases
Solution Approach 1:
The optical member is divided into first regions corresponding to each light source position, second regions surrounding these, and third regions between adjacent light emitting elements. Each region has specifically tailored light transmittance to compensate for the proximity of light sources, with third regions having lower transmittance than second regions to prevent excessive brightness in between closely spaced LEDs.
Solution Approach 2:
The light transmittance parameter is strategically varied across the optical member to address the challenges of closely spaced light sources. Transmittance increases with distance from light emitting elements in first regions and varies between central and outer peripheral portions, enabling uniform luminance distribution even when light sources are densely arranged for compactness.
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 achieves uniform luminance across the liquid crystal display device, even at the outer peripheral portions, enhancing visibility and power efficiency while accommodating the design constraints of limited spaces like vehicle instrument clusters.
Implementation Method 1
an optical member being plate-shaped which is disposed to face the surface of the substrate and through which a part of light emitted by the plurality of light sources is transmitted
Implementation Method 2
in each second region, in places in contact with another second region adjacent in the second direction, a light transmittance increases as approaching an outer peripheral portion from a central portion of the optical member
Implementation Method 3
a housing which houses the plurality of light sources, the substrate and the optical member, and the housing being not reflective, wherein a region of a surface of the substrate where the plurality of light sources are not mounted is covered with a reflection sheet
Data Source
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AI summary
A liquid crystal display device with high visibility and a backlight device for implementing the liquid crystal display device are provided. A backlight device (100) for irradiating light to a back surface of a liquid crystal panel (19) in a liquid crystal display device 101 includes: light sources (45); a substrate (51); and a plate-like optical member (29) through which a part of light emitted by the light sources (45) is transmitted. The optical member (29) includes: first region (A11) and two or more second regions (A21), wherein in the first region (A11), the light transmittance increases as separating from a mounting position of one light source (45), and in the second regions (A21), the light transmittance increases as approaching an outer peripheral portion from a central portion of the optical member (29) in a predetermined direction in places in contact with another adjacent second region (A21).