Optical Sheet Laminate Recess Geometry for Thin Backlight Uniformity
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Solution Overview
Problem
The reduction in thickness of liquid crystal display device backlights leads to a decrease in in-plane luminance uniformity due to reduced thickness of diffusion sheets or number of layered diffusion sheets.
Innovation Solution
An optical sheet laminate comprising diffusion sheets with recesses having a substantially inverted quadrangular pyramid shape and prism sheets with perpendicular prism directions, where the recesses are arrayed in a two-dimensional matrix and intersect at an angular difference of 30° or less, maintaining in-plane luminance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the thickness of diffusion sheet is reduced to make the backlight unit thinner, then the thickness of the backlight unit is reduced, but the in-plane luminance uniformity decreases
Solution Approach 1:
The invention changes the geometric parameters of the recesses (apex angle of 95° or more, specific depth-to-pitch ratio) to optimize light diffusion characteristics. By precisely controlling these parameters, the diffusion sheet can achieve sufficient light uniformity with reduced thickness, resolving the contradiction between thinning the backlight unit and maintaining luminance uniformity.
Solution Approach 2:
The invention creates a composite optical structure by combining diffusion sheets with prism sheets in a specific layered configuration. The diffusion sheet with optimized recesses works synergistically with the prism sheet to achieve both thinness and luminance uniformity, as the combination compensates for the reduced diffusion capability of the thinner sheet.
2Length of moving object
If the number of layered diffusion sheets is reduced to make the backlight unit thinner, then the thickness of the backlight unit is reduced, but the in-plane luminance uniformity decreases
Solution Approach 1:
The invention optimizes the parameters of individual diffusion sheets (recess apex angle of 95° or more, specific array patterns) to compensate for having fewer layers. The enhanced per-sheet performance allows the system to achieve sufficient light diffusion and uniformity with reduced sheet count, resolving the contradiction between thinning and uniformity maintenance.
Solution Approach 2:
The invention replaces multiple diffusion sheets with a composite structure of optimized diffusion sheet plus prism sheet. The prism sheet complements the diffusion function, allowing the system to achieve equivalent or better luminance uniformity with fewer diffusion sheets, thus reducing overall thickness while maintaining performance.
3Length of moving object
If the distance between light sources and diffusion sheet is reduced to make the backlight unit thinner, then the thickness of the backlight unit is reduced, but the in-plane luminance uniformity decreases
Solution Approach 1:
The invention optimizes the recess parameters (apex angle of 95° or more, controlled depth) to enhance light diffusion efficiency at shorter distances. The optimized geometry ensures sufficient light scattering even when the diffusion sheet is positioned closer to the light sources, resolving the contradiction between reduced distance for thinning and maintained luminance uniformity.
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 configuration maintains or enhances in-plane luminance uniformity even when the backlight unit is made thinner, eliminating the need for additional optical sheets and reducing thickness.
Implementation Method 1
an optical sheet such as a diffusion sheet or a prism sheet is used to diffuse light emitted from a light source such as a light emitting diode (LED) to the improve uniformity of luminance and chromaticity over the entire screen
Implementation Method 2
two prism sheets whose respective prism ridges perpendicularly cross each other are arranged above a diffusion sheet
Data Source
AI summary
An optical sheet laminate 100 is built in a backlight unit 40. The optical sheet laminate 100 includes a plurality of diffusion sheets 43 each having a first surface 21a having a plurality of recesses 22 having a substantially inverted quadrangular pyramid shape, and a pair of prism sheets 44 and 45 arranged above the plurality of diffusion sheets 43 and having prism extending directions perpendicular to each other. The recesses 22 have an apex angle of 95° or more. The recesses 22 are arrayed in a two-dimensional matrix. The prism extending direction of a lower prism sheet 44 and the arrangement direction of the recesses 22 on an upper diffusion sheet 43A intersect with each other at an angular difference of 30° or less.