Multi-Angle Prism Optical Sheet for LCD Luminance Control
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Solution Overview
Problem
Existing backlight technologies for liquid crystal display devices suffer from luminance unevenness near light sources, color changes with viewing direction, and low luminance in the front direction due to wavelength dispersion in prism sheets, which affects the efficiency of reflective polarizers.
Innovation Solution
A lighting device with a light guide and optical sheets featuring columnar prisms where the distal surfaces have different inclination angles, optimizing the angle difference between 4° to 20° to minimize color changes and maximize luminance in the front direction, and incorporating a reflective polarizer to enhance luminance utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a prism sheet is used to guide light in the front direction, then luminance in the front direction is improved, but wavelength dispersion causes color changes with viewing direction
Solution Approach 1:
The patent changes the geometric parameters of the prism sheet by providing distal surfaces with at least two different inclination angles rather than a single uniform angle. This parameter variation optimizes light guidance in the front direction while minimizing wavelength dispersion effects, thereby maintaining color uniformity across different viewing angles.
Solution Approach 2:
Different portions of the distal surface are assigned different inclination angles to perform specialized functions. Specific local regions with particular angles are optimized for directing light in the front direction, while other regions are optimized for minimizing color changes, creating a functionally differentiated surface structure.
2Illumination intensity
If the inclination angle of distal surfaces is optimized for front direction luminance, then luminance in front direction is improved, but luminance unevenness near light sources increases
Solution Approach 1:
The patent employs multiple inclination angles on distal surfaces to balance two competing requirements: angles optimized for front direction luminance and angles optimized for reducing luminance unevenness near light sources. This multi-parameter approach allows simultaneous optimization of both performance metrics.
Solution Approach 2:
Different inclination angles are assigned to different local regions of the distal surface. Regions closer to light sources have angles optimized for uniformity, while other regions have angles optimized for front direction luminance, creating a spatially varying optical response that resolves the contradiction.
3Illumination intensity
If a reflective polarizer is added to enhance luminance utilization, then overall brightness is improved, but device complexity increases
Solution Approach 1:
The patent combines the light guiding function and the polarization reflection function into an integrated optical system. The prism sheet with multi-angle distal surfaces works in conjunction with a reflective polarizer, merging multiple optical functions into a coordinated structure that achieves high luminance without requiring separate independent components for each function.
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 solution achieves high luminance in the front direction while reducing luminance unevenness and color changes, effectively increasing the overall brightness and efficiency of the liquid crystal display device.
Implementation Method 1
the distal surfaces have different inclination angles, optimizing the angle difference between 4° to 20° to minimize color changes
Implementation Method 2
incorporating a reflective polarizer to enhance luminance utilization
Data Source
AI summary
A lighting device includes a light source 30, a light guide 20 provided adjacent to the light source 30 and including a light source light incident surface 21 on which light emitted by the light source 30 enters and a planar light emission surface 22 from which planar light is emitted, and an optical sheet 50 including a planar light incident surface 53 on which the planar light enters, and configured to change a traveling direction of the planar light because a light emission side of the optical sheet 50 has a shape in which plural columnar prisms 51 extending in parallel to the light source light incident surface 21 are arranged side by side. In each of the prisms 51, a distal surface has at least different two kinds of inclination angles.