LCD Backlight Phosphor Mixing with Frame-Synchronized Afterglow Control
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Solution Overview
Problem
Existing liquid crystal display devices face issues with insufficient color reproducibility and brightness level for red light, and afterglows of phosphors are not effectively canceled out when using LEDs, leading to reduced display quality.
Innovation Solution
Incorporating a mixture of complex fluoride and nitride red phosphors in the LEDs, with specific content ratios, and controlling the driving of the LEDs in synchronization with the display panel to include turn-on and turn-off periods, thereby enhancing color reproducibility and brightness while minimizing afterglows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single type of red phosphor is used in LED, then the structure is simple, but color reproducibility and brightness level are insufficient
Solution Approach 1:
The patent applies composite materials by combining multiple types of red phosphors (e.g., KSF phosphor and CaAlSiN3 phosphor) in specific ratios within the LED light source. This composite phosphor system achieves superior color reproducibility and brightness level compared to single phosphor types, resolving the contradiction between performance improvement and structural complexity.
2Reliability
If phosphor afterglow is not canceled out, then the display structure remains simple, but display quality deteriorates due to insufficient color reproducibility and brightness
Solution Approach 1:
The patent implements periodic action by synchronizing the LED light source emission with the display panel's frame period, including turn-on and turn-off periods. This periodic control cancels out phosphor afterglow effects and maintains high display quality, resolving the contradiction between reliability improvement and control complexity.
3Productivity
If LED driving is not synchronized with display panel, then the control system is simple, but afterglow cancellation and display performance are insufficient
Solution Approach 1:
The patent applies feedback by synchronizing the LED light source driving signals with the display panel's scanning and refresh rates. This feedback-based synchronization ensures that light emission occurs only during active display periods, canceling afterglow and improving moving image display performance while maintaining manageable control complexity.
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 higher color reproducibility and brightness levels for red light, reduces afterglows, and improves moving image display performance, minimizing user discomfort such as 'VR sickness' in head-mounted displays.
Implementation Method 1
a blue light emitting element configured to emit blue light and a red phosphor configured to emit red light when excited by the blue light from the blue light emitting element
Data Source
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AI summary
A liquid crystal display device 10 includes: a liquid crystal panel 11; a backlight device 12; an LED 13 that includes at least a blue LED element 17 that emits blue light and a red phosphor configured to emit red light when excited by the blue light from the blue LED element 17; a backlight controller 21 configured to control the driving of the LED 13 in synchronization with a display of the liquid crystal panel 11 so that a one-frame display period in the liquid crystal panel 11 includes a turn-on period and a turn-off period; a complex fluoride red phosphor that constitutes the red phosphor and having a content ratio in a range from 50% to 85% inclusive; and a nitride red phosphor that constitutes the red phosphor and having a content ratio in a range from 15% to 50% inclusive.