Light Guide Plate Directivity Control for LCD Uniformity
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Solution Overview
Problem
Existing liquid crystal display devices face challenges in achieving uniform luminance due to the warping of slimmed light guide plates, leading to light leakage and assembly difficulties, and existing solutions do not effectively address the issue of directivity spread and refractive index mismatches between the light guide plate and connection layers.
Innovation Solution
A surface light source device with a light guide plate featuring a directivity converting portion and light emitting means, where the light guide substrate is integrally configured with a light introducing portion, and a connection layer with a refractive index lower than the light guide plate, to narrow the directivity spread and prevent light leakage, ensuring uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the light guide plate is reduced to slim down the backlight, then the backlight thickness is reduced, but the light guide plate becomes warped and light leaks from warped portions
Solution Approach 1:
The patent uses a light guide plate with a specific thickness range (0.5mm to 2mm) that acts as a thin film structure, combining flexibility with structural integrity. The plate is designed to be thin enough for slimming while maintaining sufficient stiffness through material selection and structural design to prevent warping during assembly and operation.
2Reliability
If the refractive index of the connection layer is higher than that of the light guide plate to prevent light leakage, then light leakage is reduced, but total reflection does not occur and light is emitted from the panel near the light source causing luminance unevenness
Solution Approach 1:
The patent optimizes the refractive index of the connection layer to be lower than that of the light guide plate (ng > n1), reversing the conventional approach. This parameter change enables total internal reflection at the interface, improving light containment while maintaining luminance uniformity through proper index matching and optical path control.
Solution Approach 2:
The patent applies different refractive index requirements to different interfaces: the connection layer has a lower refractive index than the light guide plate for total reflection, while the outer surface may have protective coatings with appropriate refractive indices for light extraction. This local optimization of optical properties resolves the contradiction between light containment and uniform emission.
3Illumination intensity
If a thin film with lower refractive index is formed on the light guide plate surface to improve light guidance, then light guidance is improved, but the device complexity increases due to additional layers
Solution Approach 1:
The patent integrates the connection layer to serve dual functions: it provides mechanical bonding between the light guide plate and liquid crystal panel while simultaneously acting as the optical interface for total internal reflection. This merging of structural and optical functions eliminates the need for separate thin films, reducing device complexity while maintaining light guidance 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 effectively guides light inside the light guide plate, reducing leakage and enhancing luminance uniformity across the display surface, while maintaining a slim design and preventing warping, thus improving the assembly and performance of liquid crystal display devices.
Implementation Method 1
total reflection of light does not occur at an interface between the connection layer 13 and the light guide plate 12. Therefore, the light beam L entering the light guide plate 12 is not guided inside the light guide plate 12
Implementation Method 2
any of refractive indexes of the connection layers is lower than a refractive index of the light guide plate body... total reflection of light does not occur at an interface between the connection layer 13 and the light guide plate 12
Data Source
AI summary
A surface light source device includes a point source of light and a light guide plate causing light from the point source of light introduced from a light incident end face and emitted from a light emission surface to outside. The light guide plate is formed of a light introducing portion provided at an end of a light guide plate body. The point source of light is placed facing the light incident end face positioned at an end face of the light introducing portion. Along a region of the light introducing portion adjacent to the light guide plate body, a directivity converting portion is provided. The directivity converting portion is configured by arranging V-grooved directivity conversion patterns in an arc shape. A region of the light introducing portion has a thickness equal to that of the light guide plate body and has a surface positioned in the same plane.