Optical Sheet with Multi-Streak Diffraction Grating for LCD Backlight Luminance
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Solution Overview
Problem
Edge-lit backlight units for liquid crystal display devices fail to produce sufficient face luminance due to uneven distribution of light rays exiting from the light diffusion sheet, which does not align with the optical characteristics of the prism sheet, resulting in only a small proportion of light being directed upward.
Innovation Solution
An optical sheet with a multi-streak diffraction grating pattern oriented in a specific direction, including scratches or hairline stripes, is used to condense light in one direction and diffuse it in a perpendicular direction, enhancing the luminance by aligning with the prism sheet's orientation, thereby increasing the proportion of light directed upward.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light diffusion sheet is used, then light is diffused in all directions, but the distribution of light rays exiting the sheet is uneven and does not align with the prism sheet's optical characteristics, resulting in insufficient face luminance
Solution Approach 1:
The optical sheet is segmented into multiple functional layers: a light diffusion sheet for general diffusion, a light condensing sheet with microlens arrays for directional condensation, and a prism sheet for final light direction control. Each layer performs a specific function to progressively improve light distribution alignment with the prism sheet's optical characteristics, thereby enhancing face luminance.
Solution Approach 2:
The light condensing sheet introduces local quality variations through microlens arrays with specific focal lengths and orientations. These microlenses create localized regions of condensed light that are precisely directed toward the prism sheet's optical characteristics, rather than uniform diffusion across the entire sheet. This local optimization ensures better alignment between the diffused light and the prism sheet's refraction properties.
2Device complexity
If LED light sources are disposed along one end face of the light-guiding sheet, then the structure is compact, but the rays of light have strong directivity inclined toward the light emission direction, requiring additional diffusion components
Solution Approach 1:
The light condensing sheet performs preliminary action by pre-directing and condensing light rays from the LED sources before they reach the prism sheet. The microlens arrays are positioned and oriented to anticipate the directional bias of LED emission, pre-correcting the light distribution to align with the prism sheet's optical characteristics. This preliminary conditioning reduces the need for additional diffusion components and improves overall system 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 optical sheet effectively enhances face luminance by condensing and diffusing light in a manner that aligns with the prism sheet's orientation, improving the overall luminance of the backlight unit.
Implementation Method 1
An optical sheet with a multi-streak diffraction grating pattern oriented in a specific direction, including scratches or hairline stripes, is used to condense light in one direction
Implementation Method 2
diffuse it in a perpendicular direction, enhancing the luminance by aligning with the prism sheet's orientation
Implementation Method 3
prism sheet 106 which is disposed on the front face side of the light diffusion sheet 105 and has a function refracting rays of light toward a normal direction
Data Source
AI summary
An optical sheet for a liquid crystal display device has functions of condensing rays of light with respect to a specific direction in a plane of the optical sheet, and diffusing rays of light with respect to a direction perpendicular to the specific direction. A backlight unit for a liquid crystal display device includes: a light guide film for guiding rays of light incident on an end face of the light guide film toward a front face side; at least one LED light source disposed along the end face of the light guide film; the optical sheet disposed on the front face side; and a prism sheet disposed on a front face of the optical sheet, with the specific direction being parallel to a direction of rays of light emitted by the at least one LED light source and perpendicular to a direction of prism rows of the prism sheet.