Optical Sheet Protrusion Aspect Ratio for LCD Luminance
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Solution Overview
Problem
Conventional optical sheets for TFT-LCD backlight units have low luminance due to a low aspect ratio between the body portion and protrusions, resulting in inadequate light diffusion and efficiency.
Innovation Solution
An optical sheet with a light diffusion layer featuring a diffusion pattern of protrusions on a transparent base sheet, where the aspect ratio of the protrusion's radius to thickness is optimized to 0.8 or more, formed using e-beam irradiation and a composition of polymer resin and light diffusion particles, enhancing light transmittance and haze characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional optical sheets with low aspect ratio protrusions are used, then manufacturing is simpler, but luminance is insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the aspect ratio of protrusions in the light diffusion layer from conventional low values to 0.5-2.0, and by controlling the thickness ratio of the light diffusion layer to base sheet between 0.1-5.0. These parameter optimizations directly improve luminance while maintaining manufacturability through precise control of physical dimensions and geometric properties.
2Illumination intensity
If light diffusion is enhanced through optimized protrusion geometry, then luminance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent defines specific parameter ranges for protrusion aspect ratio (0.5-2.0) and thickness ratios (0.1-5.0) that balance optical performance with manufacturing feasibility. These parameter specifications enable improved luminance while establishing clear manufacturing tolerances that prevent excessive precision requirements.
3Illumination intensity
If the light diffusion layer is optimized for high luminance, then brightness improves, but the sheet may become thicker
Solution Approach 1:
The patent optimizes the thickness ratio of the light diffusion layer to the base sheet within 0.1-5.0, allowing flexibility in achieving high luminance while controlling overall thickness. This parameter range enables designers to balance brightness requirements against thickness constraints based on specific application needs.
Solution Approach 2:
Instead of increasing thickness to improve light diffusion, the patent utilizes the aspect ratio dimension of protrusions (width-to-height ratio) as an alternative parameter to enhance luminance. This dimensional approach allows thickness to remain controlled while achieving high brightness through optimized geometric configuration of the light diffusion structures.
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 optimized optical sheet achieves high luminance and uniform light diffusion, improving the brightness and efficiency of TFT-LCD displays while maintaining a thin profile.
Implementation Method 1
The e-beam is irradiated to emit thermal electrons by heating a high-melting point material filament made of at least one selected from the group consisting of tungsten, tantalum and molybdenum.
Implementation Method 2
The diffusion pattern has a surface shape formed by an e-beam irradiation apparatus. The e-beam is irradiated within a wavelength range of 0.005 to 0.1 nm. A preferred absorbed dose is 40 to 120 kGy.
Data Source
AI summary
The present invention relates to an optical sheet for a backlight unit of a TFT-LCD and a TFT-LCD including the same. The optical sheet of the present invention includes a transparent base sheet, and a light diffusion layer in which a diffusion pattern comprised of a plurality of protrusions is formed on the transparent base sheet. The diffusion pattern satisfies an aspect ratio of 0.8 or more, the aspect ratio being a ratio of a radius (l) of a unit body portion of the protrusion, which is formed on the transparent base sheet, to a thickness (d) of the protrusion.