Optical Sheet Laminate for Backlight Luminance Uniformity
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Solution Overview
Problem
Conventional direct-type backlight units for liquid crystal displays suffer from insufficient light diffusion, leading to uneven luminance and chromaticity uniformity, particularly in portable devices where power consumption is a concern.
Innovation Solution
An optical sheet laminate comprising multiple diffusion sheets with recesses of a substantially inverted quadrangular pyramid shape and prism sheets with perpendicular extending directions is used, where the arrangement directions of the recesses on different diffusion sheets are varied to enhance light diffusion and luminance uniformity, and the distance between light sources and diffusion sheets is minimized to reduce thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the distance between light sources and diffusion sheet is made short to reduce thickness, then the backlight unit thickness is reduced, but light diffusion becomes insufficient leading to uneven luminance uniformity
Solution Approach 1:
The patent divides the diffusion function into multiple segments by using multiple diffusion sheets layered together. Each sheet has recesses with a specific arrangement direction, and collectively they provide comprehensive light diffusion over a short distance, achieving both thinness and uniformity.
Solution Approach 2:
The patent employs asymmetric arrangement of recesses on different diffusion sheets, where each sheet has recesses arranged in a different direction. This asymmetric configuration ensures that light is diffused from multiple angles simultaneously, improving luminance uniformity while maintaining a compact thickness.
2Manufacturing precision
If multiple diffusion sheets are layered to improve luminance uniformity, then uniformity is improved, but the backlight unit thickness increases
Solution Approach 1:
Each diffusion sheet is designed with specific local characteristics - recesses with particular arrangement directions optimized for diffusing light from specific directions. This localized optimization allows multiple sheets to work together efficiently without excessive thickness accumulation.
Solution Approach 2:
The patent addresses the thickness issue by optimizing the vertical stacking arrangement and the angular orientation of recesses in the horizontal plane. By utilizing directional arrangement in multiple dimensions, the system achieves superior diffusion without proportionally increasing thickness.
3Illumination intensity
If conventional diffusion sheets are used to improve overall luminance, then luminance is improved, but luminance uniformity decreases
Solution Approach 1:
The patent uses asymmetric arrangement of recesses on different diffusion sheets, where each sheet has recesses oriented in different directions. This asymmetric configuration prevents hotspots and ensures uniform light distribution across the entire screen while maintaining high overall luminance.
Solution Approach 2:
The diffusion function is segmented across multiple sheets with different recess arrangement directions. Each sheet handles a specific portion of the light distribution, and their combined effect achieves both high luminance and uniform distribution that cannot be achieved with a single sheet.
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 improves luminance uniformity while maintaining low power consumption, allowing for a high-luminance screen with reduced thickness in portable devices, and further enhances luminance uniformity through strategic arrangement of diffusion sheet recesses and prism sheet angles.
Implementation Method 1
an optical sheet laminate to be incorporated into a backlight unit includes a plurality of diffusion sheets each having surfaces, at least one of which has a plurality of recesses having a substantially inverted quadrangular pyramid shape
Implementation Method 2
light having traveled straight from the light sources 42 are repeatedly diffused
Implementation Method 3
a pair of prism sheets having prism extending directions perpendicular to each other
Data Source
AI summary
An optical sheet laminate 100 is incorporated into a backlight unit 40. The optical sheet laminate 100 includes a plurality of diffusion sheets 43 having a first surface 21a having a plurality of recesses 22 having a substantially inverted quadrangular pyramid shape and arranged in a two-dimensional matrix, and a pair of prism sheets 44 and 45 having prism extending directions perpendicular to each other. The plurality of diffusion sheets 43 include at least two diffusion sheets 43 where an arrangement direction of the recesses 22 of one of the at least two diffusion sheets 43 is different from that of the recesses of another one of the at least two diffusion sheets 43.