Backlight Unit Reflective Polarizing Elements
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Solution Overview
Problem
Conventional backlight units for LCDs suffer from low light utilization efficiency due to the conversion of light to linearly polarized light by the backlight side polarizing plate and subsequent reflection or scattering by diffuser and prism elements, leading to reduced luminance and color reproducibility, especially in small and large-sized displays requiring high definition and power efficiency.
Innovation Solution
A backlight unit design incorporating a light guide plate with an optical film featuring reflective polarizing elements having curved or inclined surfaces, which reflect circularly polarized light to increase light utilization efficiency by minimizing absorption at the polarizing plate, and using a λ/4 plate to convert light to linear polarization, thereby enhancing light transmission to the liquid crystal panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a backlight side polarizing plate is used to convert light to linearly polarized light, then the LCD can function properly, but light utilization efficiency decreases to about 50% or less
Solution Approach 1:
Instead of converting light to linear polarization and accepting 50% loss, the patent inverts the approach by using circularly polarized light that can pass through the polarizing plate more efficiently. The optical film converts linearly polarized light from the light guide plate into circularly polarized light, which then interacts with the polarizing plate to achieve better light utilization while maintaining LCD functionality.
Solution Approach 2:
The patent changes the polarization state parameter from linear to circular. By introducing circularly polarized light through the optical film with reflective polarizing elements, the system achieves improved light utilization efficiency. The reflective polarizing elements with curved or inclined surfaces create the circular polarization effect, transforming the light parameter to overcome the 50% loss limitation.
2Illumination intensity
If diffuser and prism elements are added to the light guide plate, then light distribution is improved, but light is reflected or scattered reducing overall efficiency
Solution Approach 1:
The patent merges the functions of diffuser and prism elements into a single optical film layer. Instead of having separate diffuser and prism components that each cause reflection and scattering losses, the invention integrates both light distribution and directional control functions into one optical film with reflective polarizing elements, reducing the number of interfaces and associated losses.
Solution Approach 2:
The optical film is constructed as a composite structure containing reflective polarizing elements with curved or inclined surfaces. This composite design combines the light-diffusing function with the light-directing function in a single integrated component, achieving uniform illumination while minimizing reflection and scattering losses that would occur with separate diffuser and prism elements.
3Manufacturing precision
If the definition of LCD is increased, then image quality is improved, but pixel aperture ratios decrease and luminance decreases
Solution Approach 1:
The patent ensures continuous and efficient light transmission from the light guide plate through the optical film to the liquid crystal panel. By using circularly polarized light and reflective polarizing elements, the system maintains continuous light flow with minimal interruptions or losses, ensuring that even high-definition displays with smaller pixel apertures receive sufficient luminance for high-quality images.
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 proposed backlight unit significantly increases light utilization efficiency, reducing absorption at the polarizing plate and improving luminance and color reproducibility, particularly in high-definition displays like tablets and large TVs, while maintaining power efficiency.
Implementation Method 1
the optical film has at least one of a plurality of reflective polarizing elements having a curved surface, or a plurality of reflective polarizing elements having an inclined surface that is inclined with respect to the direction of light propagation of the light guide plate
Implementation Method 2
reflective polarizing elements having a curved surface, or a plurality of reflective polarizing elements having an inclined surface that is inclined with respect to the direction of light propagation
Implementation Method 3
using a λ/4 plate to convert light to linear polarization, thereby enhancing light transmission to the liquid crystal panel
Data Source
AI summary
Provided is a backlight unit capable of causing light that has exited from a light guide plate to be incident to a liquid crystal panel with high efficiency. The object is achieved by providing the backlight unit including a light source; a light guide plate that causes light to be incident to through an edge face and to exit through one of principal surfaces; and an optical film disposed on a surface of the light guide plate, the surface being on the opposite side of the light exiting surface, in which the optical film has a plurality of reflective polarizing elements each having a curved surface, and/or a plurality of reflective polarizing elements each having an inclined surface that is inclined with respect to the direction of light propagation of the light guide plate.