Flat Lighting Device Using Dichroic Filters for LCD Color Reproducibility
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Solution Overview
Problem
Liquid crystal displays (LCDs) face challenges in achieving high color reproducibility without using quantum dot sheets, which increase manufacturing costs and can lead to the lens mura phenomenon in direct-type planar lighting devices.
Innovation Solution
A display device with a planar lighting system that includes a light source emitting white light using a light-emitting element and phosphors, combined with dichroic filter layers that reflect specific wavelength portions of light to reduce the full width at half maximum of blue, green, and red light, thereby enhancing color reproducibility without the need for quantum dot sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a quantum dot sheet is used to improve color reproducibility, then color quality is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the color conversion function into multiple independent layers: a quantum dot layer for primary color conversion and additional color conversion layers (red phosphor layer, green phosphor layer) for fine-tuning specific wavelength ranges. This segmentation allows each layer to be optimized independently and provides flexibility in achieving desired color reproduction without requiring a complete quantum dot sheet solution.
Solution Approach 2:
The patent applies local quality by using different materials with specific properties in different regions of the optical path. The quantum dot layer converts blue light to green, while red phosphor materials convert blue light to red, and green phosphor materials convert blue light to green. Each material is selected and positioned to address specific wavelength conversion needs, allowing precise control over the spectral distribution without uniformly applying expensive quantum dot materials throughout.
2Manufacturing precision
If a quantum dot sheet is used in a direct-type planar lighting device, then color reproducibility is improved, but the lens mura phenomenon occurs
Solution Approach 1:
The patent divides the color conversion function across multiple sequential layers rather than using a single quantum dot sheet. The light passes through the quantum dot layer first, then through additional color conversion layers, and finally through optical sheets. This segmentation distributes the color conversion task and prevents the concentration of optical path variations in a single layer, thereby reducing the lens mura phenomenon.
Solution Approach 2:
The patent introduces optical sheets as intermediary elements between the light source and the display panel. These optical sheets act as mediators that diffuse and uniformize the light before it reaches the panel, reducing the impact of non-uniformities introduced by the quantum dot layer and other components. This intermediary layer helps eliminate the lens mura phenomenon while preserving color reproduction quality.
3Use of energy by moving object
If a planar lighting device is used, then luminous efficiency is improved, but achieving high color reproducibility becomes difficult
Solution Approach 1:
The patent changes the spectral parameters of the light source by incorporating multiple phosphor materials with different emission characteristics. The quantum dot layer converts blue light to green, while red and green phosphor layers convert blue light to their respective wavelengths. By carefully selecting and combining phosphor materials with specific emission spectra, the patent achieves high color reproduction while maintaining the energy efficiency of LED-based planar lighting.
Solution Approach 2:
The patent uses composite materials comprising quantum dots combined with phosphor materials in a multi-layer structure. The quantum dot layer provides narrow-band green emission, while phosphor layers provide red and green emissions. This composite approach combines the advantages of quantum dots (narrow FWHM, high color purity) with phosphors (broad emission, efficient energy conversion) to achieve both high luminous efficiency and excellent color reproducibility in a planar lighting device.
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 allows for the emission of high-purity blue, green, and red lights with reduced full width at half maximum, improving color reproducibility in liquid crystal display devices without the use of quantum dot sheets, thus reducing manufacturing costs and avoiding the lens mura phenomenon.
Implementation Method 1
a light source configured to emit white light using a light-emitting element and a yellow phosphor
Implementation Method 2
a red phosphor layer located on the light source and configured to absorb a portion of the white light emitted from the light source and to emit red light
Implementation Method 3
a first dichroic filter layer located on the red phosphor layer and having a reflection pattern reflecting at least a part of the long-wavelength portion in the wavelength band of the red light
Implementation Method 4
a second dichroic filter layer, which is located between the light source and the red phosphor layer and has a reflection pattern reflecting at least a part of the long-wavelength portion in the wavelength band of the yellow light emitted from the yellow phosphor
Data Source
AI summary
The present invention can be applied to the technical field pertaining to display devices and, for example, relates to a flat lighting device using a light emitting diode (LED) and a display device including same. The present invention provides a display device including a flat lighting device, wherein the display device may comprise: a light source which emits white light by using a light emitting diode and a yellow phosphor; a red phosphor layer which is disposed on the light source and adsorbs a part of the white light emitted from the light source to emit red light; and a first dichroic filter layer which is disposed on the red phosphor layer and has a reflective pattern reflecting at least a part of the long-wavelength side of the wavelength region of the red light.