Multi-Layer Prism Optical Sheet for Backlight Luminance
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Solution Overview
Problem
Conventional backlight units in liquid crystal displays suffer from reduced luminance due to light loss as a result of light not interacting with the reflective surface of the prism sheet, leading to decreased overall display luminance.
Innovation Solution
An optical sheet comprising a base film, a high refractive index layer with prism portions, and a low refractive index layer, where the prism portions have an incidence surface and a reflective surface, optimized to refract and reflect light more effectively, reducing light loss and enhancing luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional prism sheet is used with a single refractive index layer, then the structure is simple and easy to manufacture, but light loss occurs when light does not touch the reflective surface, reducing luminance
Solution Approach 1:
The patent applies composite materials by creating a prism sheet with multiple refractive index layers (first refractive index layer with n1=1.50-1.65 and second refractive index layer with n2=1.70-1.85). This composite structure enables different layers to perform different optical functions: the first layer refracts light at a first angle while the second layer refracts light at a second angle greater than the first, ensuring that light not touching the reflective surface is still directed toward the display panel, thereby reducing light loss and improving luminance.
Solution Approach 2:
The patent applies local quality by creating regions with different refractive indices within the prism sheet structure. The first refractive index layer and second refractive index layer have distinct optical properties tailored to specific functions: the lower index layer handles initial light refraction while the higher index layer provides additional refraction and reflection control. This localized optimization of optical properties at different positions and layers resolves the contradiction between structural simplicity and light loss reduction.
2Illumination intensity
If the prism sheet structure is simplified for easy manufacture, then manufacturing cost is reduced, but luminance output is lowered due to light loss
Solution Approach 1:
The patent resolves the manufacturing complexity issue by using composite materials that can be manufactured as integrated multi-layer structures. The first and second refractive index layers are formed as part of the same prism sheet substrate, allowing simultaneous formation through coating or injection molding processes. This composite approach achieves complex optical functionality (dual refraction angles for improved luminance) without requiring multiple separate components, thus maintaining ease of manufacture while improving luminance output.
Solution Approach 2:
The patent applies universality by designing the multi-layer prism sheet to perform multiple optical functions within a single component. The first refractive index layer and second refractive index layer work together to provide both refraction and reflection control, replacing what would traditionally require separate optical elements. This multi-functional design improves luminance while maintaining manufacturing simplicity through integration.
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 optical sheet design significantly improves luminance by increasing the angle of refraction and reducing light loss, resulting in a higher luminance output for the backlight unit and display device.
Implementation Method 1
the light travels, and is refracted at a certain angle due to a refractive index difference between an air layer and the incidence plane of the prism 20
Implementation Method 2
The light touching the reflective surface is reflected upward or substantially vertically from the prism sheet and contributes to luminance
Data Source
AI summary
An optical sheet, a backlight unit having the optical sheet, and a display device having the backlight unit are discussed. According to an embodiment, the optical sheet includes a base film; a high refractive index layer having a plurality of prism portions on the base film; and a low refractive index layer positioned on the high refractive index layer, and covering the plurality of prism portions and having a surface parallel to the base film, each of the prism portions including an incidence surface on which incident light is refracted and a reflective surface on which the refracted light is reflected, the incidence surface including a bent for refracting the incident light towards the reflective surface.