Prism Sheet Inclined Angles for LCD Light Distribution Control
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Solution Overview
Problem
Existing surface light source devices for liquid crystal display devices struggle to switch light distribution effectively in two steps while minimizing contrast issues, especially when achieving a wide outgoing angle, leading to potential dark-line portions on the display screen.
Innovation Solution
A surface light source device incorporating a prism sheet with specific prism shapes, featuring inclined surfaces with tailored inclination angles (35.5°≤A1≤39° and 23°≤A2≤30°) and ridge configurations, which allows for adjustable light directivity by switching the lighting state of the light sources, thereby controlling luminance distribution and reducing contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the first light source and the second light source are simultaneously turned on to obtain a light distribution having a wide outgoing angle, then the light distribution switches to wide-angle mode, but the light distribution forms three peaks with local minimum points (bottoms) that create dark-line portions on the display screen
Solution Approach 1:
The patent applies local quality by making each inclined surface have a specific inclination angle range (35.5°≤A1≤39° and 23°≤A2≤30°) to control the light distribution locally. This ensures that light is redirected at specific angles to fill in the dark-line portions while maintaining the overall wide outgoing angle distribution, thus resolving the contradiction between wide-angle capability and dark-line prevention
Solution Approach 2:
The patent changes the geometric parameters of the prism sheet, specifically the inclination angles of the inclined surfaces, to optimize light distribution. By setting the inclination angles within specific ranges, the patent achieves a balance between maintaining wide outgoing angle distribution and preventing the formation of dark-line portions caused by excessive luminance contrast between peaks and bottoms
2Adaptability or versatility
If a prism sheet with conventional prism shapes is used to achieve strong directivity in the normal direction, then narrow outgoing angle distribution is obtained, but only users positioned in the normal direction can visually recognize the display
Solution Approach 1:
The patent applies asymmetry by designing inclined surfaces with different inclination angles (A1 and A2 within different ranges) rather than using symmetric prisms with identical angles. This asymmetric configuration redistributes light more evenly across different viewing angles, expanding the effective viewing area while maintaining acceptable luminance uniformity
Solution Approach 2:
The patent introduces dynamic light distribution control by using the light guide plate to redirect light at various angles onto the inclined surfaces. This dynamic approach allows the system to adapt light distribution based on viewing conditions, ensuring both wide viewing angle coverage and acceptable luminance uniformity across different positions
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 seamless switching of light distribution in two steps, ensuring minimal contrast even at wide outgoing angles, preventing dark-line portions and maintaining visibility control for both narrow and wide-angle perspectives.
Implementation Method 1
a prism sheet which is arranged on the light-emitting surface of the light guide plate and through which light from the light guide plate is input
Implementation Method 2
the ridges include inclined surfaces extending from the top of each ridge to the sides of adjacent ridges
Data Source
AI summary
A surface light source device 100 comprises light sources 10 and 20, a light guide plate 30, and a prism sheet 40. A plurality of ridges 41 are formed on the incident surface of the prism sheet 40. Each ridge 41 includes first and second inclined surfaces 41a and 41b whose inclination angles with respect to a normal line 45a are A1 and A2, respectively, provided that 35.5°≤A1≤39° and 23°≤A2≤30°.