Prism Sheet Micro Grooves Backlight Viewing Angle
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Solution Overview
Problem
Edge-lit backlight units using inverse prism sheets suffer from narrow viewing angles due to light condensing characteristics, which are difficult to improve without reducing luminance or increasing production costs, and diffusion layers can reduce front-direction luminance.
Innovation Solution
A prism sheet for backlight units with micro linear grooves on its surface, parallel or intersecting at an acute angle with the prism array, to diffuse light in the direction perpendicular to the array, enhancing viewing angles while maintaining luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an inverse prism sheet is used to direct light vertically, then luminance in the front direction is improved, but the viewing angle in the direction perpendicular to the prism array orientation becomes narrow
Solution Approach 1:
The inverse prism sheet is divided into multiple resin layers, with the outermost layer containing the prism array and inner layers containing micro linear grooves. This segmentation allows each layer to perform a specific optical function: the prism array directs light vertically for high front luminance, while the micro linear grooves diffuse light in the perpendicular direction to expand the viewing angle.
Solution Approach 2:
Different regions of the inverse prism sheet are given different optical properties. The prism array region provides light directing functionality for vertical orientation, while the micro linear grooves provide light diffusion functionality. This local differentiation allows the sheet to simultaneously achieve high front luminance and wide viewing angle without compromising either property.
2Adaptability or versatility
If a diffusion layer is added to expand the viewing angle, then the viewing angle is improved, but luminance in the front direction is reduced
Solution Approach 1:
Rather than using a single diffusion layer that affects all light uniformly, the invention segments the optical control into different layers: the prism array in the outermost layer maintains vertical light direction for high front luminance, while micro linear grooves in inner layers provide controlled diffusion. This segmentation prevents the luminance loss that would result from a uniform diffusion approach.
Solution Approach 2:
The micro linear grooves act as an intermediary between the prism array and the viewer. They receive the vertically directed light from the prism array and selectively diffuse it in the direction perpendicular to the prism array orientation, thereby expanding the viewing angle without significantly compromising the front luminance that the prism array produces.
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 prism sheet effectively diffuses light in the direction perpendicular to the prism array, expanding the viewing angle and maintaining desired luminance in the front direction, thereby addressing the limitations of existing inverse prism sheets.
Implementation Method 1
the prism array of the inverse prism sheet 104 provides an optical function of directing rays of light vertically, by refracting rays of light having exited from the optical waveguide sheet 102
Implementation Method 2
a large number of micro linear grooves are formed on a surface of at least one of the one or more resin layers... effectively diffuses light in the direction perpendicular to the prism array
Data Source
AI summary
Provided is a prism sheet for a backlight unit capable of attaining desired luminance in the front direction, and securing a sufficient viewing angle in the direction perpendicular to the orientation direction of the prism array. The prism sheet comprises one or more resin layers, an outermost resin layer of the one or more resin layers comprising a prism array, wherein on a surface of at least one of the one or more resin layers, micro linear grooves are formed to be parallel to, or to intersect at an acute angle with, an orientation direction of the prism array. An average number of existing micro linear grooves per unit length in a direction perpendicular to an average orientation direction of the micro linear grooves is preferably no less than 30/mm and no greater than 10,000/mm. The micro linear grooves are preferably irregular in length, width or pitch.