Light Diffusion Sheet Resin Bead Size Sparkle Reduction
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Solution Overview
Problem
Conventional light diffusion sheets for overlaying in liquid crystal display devices cause sparkle and lack in uniformity of luminance due to interference with the pixel pitch of the liquid crystal panel, particularly from the shape and protruding prism portions of the prism sheet.
Innovation Solution
A light diffusion sheet with a substrate layer and a light diffusion layer containing resin beads dispersed in a resin matrix, where the resin beads have a volume-weighted particle size distribution mode diameter between 2.5 μm and 5.5 μm, a density between 9,000 and 24,000 beads/mm², and an average thickness between 2 μm and 9 μm, forming fine and highly dense irregularities to diffuse light and inhibit sparkle generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional light diffusion sheets with larger resin beads are used, then light diffusion function is sufficient, but sparkle is generated due to interference with pixel pitch
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle size of resin beads to a specific range (mode diameter 2.0-5.0 μm, with 80% or more of beads within 1.5-6.0 μm). This parameter optimization ensures that the irregularities formed on the light diffusion layer are fine enough to avoid interference with the liquid crystal panel's pixel pitch, thereby eliminating sparkle while maintaining adequate light diffusion function.
Solution Approach 2:
The patent implements local quality by creating fine irregularities through controlled resin bead distribution on the light diffusion layer surface. These localized microscopic irregularities serve to diffuse light uniformly without creating the coarse patterns that cause sparkle, thus improving local optical quality at the interface with the liquid crystal panel.
2Object-affected harmful factors
If resin bead size is decreased to reduce sparkle, then interference with pixel pitch is reduced, but lack in uniformity of luminance from prism sheet becomes more prominent
Solution Approach 1:
The patent resolves this contradiction through optimized parameter selection: the mode diameter of resin beads is controlled at 2.0-5.0 μm with 80% or more of beads falling within 1.5-6.0 μm, and the light diffusion layer thickness is maintained at 2-9 μm. These parameters create fine irregularities that suppress sparkle while the controlled density and distribution ensure sufficient light diffusion to mask luminance non-uniformity from the prism sheet.
Solution Approach 2:
The patent uses a composite light diffusion layer comprising resin beads dispersed in a resin matrix. This composite structure allows the resin beads to form irregularities for sparkle suppression while the resin matrix provides a uniform background that diffuses light to compensate for prism sheet luminance non-uniformity, achieving both objectives simultaneously.
3Illumination intensity
If light diffusion layer thickness is increased to improve light diffusion, then luminance uniformity improves, but sparkle may be exacerbated by larger irregularities
Solution Approach 1:
The patent applies parameter changes by controlling the light diffusion layer thickness to 2-9 μm and the resin bead mode diameter to 2.0-5.0 μm. This parameter combination ensures that the layer is thick enough to provide sufficient light diffusion for luminance uniformity, while the thin layer and small bead size prevent the formation of large irregularities that would cause sparkle.
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 inhibits sparkle and lack in uniformity of luminance by diffusing light through the formation of fine irregularities on the light diffusion sheet, improving the display's visual quality by reducing interference with the pixel pitch and prism sheet shapes.
Implementation Method 1
a light diffusion layer overlaid on a front face side of the substrate layer, the light diffusion layer having a resin matrix, and resin beads dispersed in the resin matrix
Data Source
AI summary
A light diffusion sheet for overlaying is to be provided on a front face side of a prism sheet in a backlight unit of a liquid crystal display device, and has a substrate layer and a light diffusion layer overlaid on a front face side of the substrate layer, in which the light diffusion layer contains a resin matrix and resin beads dispersed in the resin matrix, wherein: a mode diameter in a volume-weighted particle size distribution of the resin beads is no less than 2.5 .mu.m and no greater than 5.5 .mu.m; a density of the resin beads per unit area is no less than 9,000 beads/mm.sup.2 and no greater than 24,000 beads/mm.sup.2; and an average thickness of the light diffusion layer is no less than 2 .mu.m and no greater than 9 .mu.m.