Chromaticity Correction Region in Backlight Optical Member
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Solution Overview
Problem
Liquid crystal display devices face challenges in maintaining uniform color emission due to light absorption by the light guide plate, leading to color variations as shorter wavelength light is absorbed more easily, causing chromaticity issues.
Innovation Solution
An illumination device with an optical member featuring a chromaticity correction region that progressively decreases in x and y chromaticity coordinates in the CIE 1931 color space from the light source, compensating for the light guide plate's absorption effects by suppressing longer wavelength light transmission, ensuring uniform chromaticity across the emission area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide plate is used to propagate light from the light source, then the light can be distributed across the display area, but shorter wavelength light is absorbed more easily by the light guide plate, causing color variation
Solution Approach 1:
The optical member is divided into multiple regions with different chromaticity characteristics. Specifically, the region closer to the light source has different chromaticity coordinates than regions farther away, allowing each region to compensate for the local color shift caused by light guide plate absorption. This local customization of optical properties corrects the non-uniform chromaticity without requiring a complete system redesign.
Solution Approach 2:
The patent changes the chromaticity parameters (x, y coordinates in CIE 1931 color space) of different regions of the optical member to counteract the absorption effects. By adjusting the chromaticity coordinates progressively across the optical member, the system compensates for the wavelength-dependent absorption in the light guide plate, maintaining uniform perceived color across the display area.
2Area of stationary object
If the display device is made larger to improve visibility, then the display area increases, but color variation becomes more pronounced due to longer light propagation paths
Solution Approach 1:
The optical member implements spatially varying chromaticity properties that are specifically designed for larger display areas. Each region of the optical member has tailored chromaticity coordinates that compensate for the cumulative absorption effects over longer propagation paths, enabling large displays to maintain color uniformity that would otherwise deteriorate with size.
3Stability of the object's composition
If a color correction unit is added to correct color errors, then chromaticity can be adjusted, but the device complexity increases
Solution Approach 1:
The chromaticity correction function is merged with the existing optical member (diffuser/reflector) in the backlight system. Instead of adding a separate color correction unit, the correction capability is integrated into the optical member's structure and material composition, maintaining chromaticity control while avoiding additional components and assembly complexity.
Data Source
AI summary
This backlight device (illumination device) is provided with (LEDs) light source; a light guide plate having a light-receiving face that opposes the LEDs and where light from the LEDs is incident, and a light-exiting surface where the incident light is emitted; and an optical sheet (optical member) arranged in opposition to the light-exiting surface of the light guide plate and imparting an optical effect to the light emitted from the light-exiting surface. Here, the optical sheet has, in at least one portion thereof, a chromaticity correction region for which x and y chromaticity coordinate values in a CIE 1931 color space both decrease with distance from the LEDs.