Prism Sheet Viewing Angle Control in LCD Backlights
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Solution Overview
Problem
Existing liquid crystal display devices with wide viewing angle capabilities face challenges in reducing thickness and manufacturing costs, and suffer from increased power consumption due to complex configurations and the use of guest-host liquid crystal cells.
Innovation Solution
The implementation of two prism sheets between a liquid crystal display panel and a light guide plate, where one prism sheet is adjustable to control light reflection and passage, allowing for simple adjustment of viewing angles without increasing device thickness or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a guest-host liquid crystal cell is used to adjust viewing angle, then viewing angle adjustment is achieved, but device thickness is largely increased
Solution Approach 1:
The patent divides the light control function into multiple prism sheets with different functions (first prism sheet for wide viewing angle, second prism sheet for narrow viewing angle) rather than using a single thick guest-host liquid crystal cell. This segmentation allows viewing angle adjustment without increasing overall device thickness.
Solution Approach 2:
The patent introduces prism sheets as intermediary optical elements between the backlight and liquid crystal display panel to achieve viewing angle control. These prism sheets act as mediators that redirect light paths without requiring the thick active layer needed for guest-host liquid crystal cells.
2Adaptability or versatility
If a guest-host liquid crystal cell is used to adjust viewing angle, then viewing angle adjustment is achieved, but manufacturing cost is pushed up
Solution Approach 1:
The patent replaces expensive guest-host liquid crystal cells with relatively inexpensive prism sheets that can be manufactured using standard optical film processes. The prism sheets are simpler in structure and can be produced at lower cost while achieving the same viewing angle adjustment function.
Solution Approach 2:
The patent changes the approach from using complex liquid crystal material properties (guest-host effect) to using geometric optical parameters (prism angles and orientations) to control viewing angle. This parameter change enables the use of simpler, cheaper materials and manufacturing processes.
3Adaptability or versatility
If voltage is applied to guest-host liquid crystal cell for viewing angle adjustment, then viewing angle control is achieved, but power consumption increases
Solution Approach 1:
The patent employs passive prism sheets that automatically control viewing angle based on their geometric structure without requiring external power input. The light redirection function is inherent to the prism sheet design, eliminating the need for electrical actuation and associated power consumption.
Solution Approach 2:
The patent replaces the electrical/field-based control mechanism of guest-host liquid crystal cells with a passive geometric optical system using prism sheets. This substitution eliminates the need for electrical energy input while maintaining viewing angle control capability.
4Adaptability or versatility
If guest-host liquid crystal cell with complicated configuration is used, then viewing angle adjustment is achieved, but device complexity increases
Solution Approach 1:
The patent segments the viewing angle control function into separate, simple prism sheets rather than using a single complex guest-host liquid crystal cell. Each prism sheet has a straightforward geometric structure and can be independently optimized and manufactured.
Solution Approach 2:
The patent extracts the viewing angle control function from the liquid crystal display panel itself and implements it separately using prism sheets in the optical path. This extraction simplifies the overall system by removing the need for complex liquid crystal material configurations.
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
This configuration enables flexible switching between wide and narrow viewing angles while maintaining a simple structure, reducing the need for thick guest-host liquid crystal cells and minimizing power consumption.
Implementation Method 1
control on whether light which is radiated from the light guide plate and is incident through the prism sheet on a light-guide-plate side (second prism sheet) is allowed to be reflected on the first prism sheet
Implementation Method 2
light which is emitted from the light source, enters the light guide plate through a side surface of the light guide plate, and is radiated from an upper surface of the light guide plate
Data Source
AI summary
A lighting device including a light source, a light guide plate, a first prism sheet which is arranged over the light guide plate, and a second prism sheet which is arranged between the first prism sheet and the light guide plate. The first prism sheet includes first prisms which are formed parallel to each other in the first direction on a first surface which is opposite to the second prism sheet, and the second prism sheet includes second prisms.