Light Diffusion Sheet Recess Geometry for Thin LCD Brightness Uniformity
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Solution Overview
Problem
As liquid crystal displays become thinner, the distance from the light source to the light diffusion sheet decreases, making it difficult to sufficiently diffuse light and resulting in deteriorated brightness uniformity on the display screen.
Innovation Solution
A light diffusion sheet with inverted polygonal pyramid-shaped recesses on its surface, composed of a resin with a refractive index of 1.55 to 1.7 and an absorption rate of 7.0% or less for light at 450 nm, is used to improve light diffusion and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the display is made thinner by reducing the distance from the light source to the light diffusion sheet and reducing the thickness of the light diffusion sheet, then the overall display thickness is reduced, but the light diffusion capability deteriorates and brightness uniformity worsens
Solution Approach 1:
The patent changes the optical parameters of the light diffusion sheet by specifying a refractive index of 1.55 or more (preferably 1.6 or more) and an absorption rate of 7.0% or less (preferably 6.0% or less) for light at 450 nm. These parameter changes enable the sheet to maintain effective light diffusion capability even when the display thickness is reduced, thereby resolving the contradiction between thinness and brightness uniformity
Solution Approach 2:
The patent employs composite material strategies by selecting resins with specific optical properties (high refractive index and low absorption rate) to construct the light diffusion sheet. This composite approach allows the sheet to achieve both thinness and effective light diffusion, simultaneously improving display thickness reduction while maintaining brightness uniformity
2Length of stationary object
If the thickness of the light diffusion sheet is reduced to achieve a thinner display, then the overall device thickness is decreased, but the light diffusion effectiveness deteriorates
Solution Approach 1:
The patent specifies critical parameter ranges for the light diffusion sheet material: refractive index of 1.55 or more (preferably 1.6 or more) and absorption rate of 7.0% or less (preferably 6.0% or less) at 450 nm wavelength. These parameter specifications ensure that even thin sheets maintain sufficient light diffusion effectiveness, resolving the contradiction between reduced thickness and manufacturing effectiveness
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 light diffusion sheet enhances brightness uniformity by uniformly diffusing light, even in thinner displays, reducing the thickness of the backlight unit and maintaining high refractive index and low absorption rates.
Implementation Method 1
a light diffusion sheet is used to erase an image of the light source, such as an LED (Light Emitting Diode), and increase brightness uniformity on the display screen
Implementation Method 2
a refractive index of the layer configuring the main body sheet for light having a wavelength of 450 nm is 1.55 or more and 1.7 or less
Implementation Method 3
an absorption rate of the main body sheet for light having the wavelength of 450 nm is 7.0% or less
Data Source
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AI summary
A light diffusion sheet capable of improving brightness uniformity is provided. The light diffusion sheet (43) has a plurality of recesses (22) having an inverted substantially polygonal pyramid shape on at least one surface of a main body sheet composed of a resin. A refractive index of at least one layer included in the main body sheet configuring the light diffusion sheet (43) for light having a wavelength of 450 nm is 1.55 or more and 1.7 or less. An absorption rate of the main body sheet configuring the light diffusion sheet (43) for light having the wavelength of 450 nm is 7.0% or less.