Display Device Color Filter Blue Light Absorption
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Solution Overview
Problem
The color reproducibility of display devices is compromised when transitioning from a cold cathode fluorescent lamp (CCFL) to a light emitting diode (LED) light source due to differences in light source spectra and coloring agents used in color filters.
Innovation Solution
Incorporating specific coloring agents in the color filters that absorb wavelengths between 420 nm to 470 nm, such as compounds represented by Chemical Formulas 1 and 2, to optimize color reproducibility when using a blue light emitting diode as the light source, which converts blue light into white light and emits it to the exterior, thereby preventing color mixture issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a blue light emitting diode (LED) is used as the light source to generate white light, then the brightness and energy efficiency are improved, but the color reproducibility deteriorates due to the blue light spectrum (420 nm to 470 nm) interfering with the color filters
Solution Approach 1:
A yellow phosphor material is introduced as an intermediary between the blue LED light source and the color filters. This phosphor absorbs excess blue light and converts it to yellow light, which then combines with the remaining blue light to produce white light with a more balanced spectrum. This mediator prevents the blue light from directly interfering with the color filters while maintaining the brightness advantages of LED illumination.
Solution Approach 2:
The spectral parameters of the light source are modified by combining blue LED emission with yellow phosphor conversion. This changes the wavelength distribution of the light, reducing the intensity in the 420-470 nm range that causes color filter interference, while maintaining overall brightness through the added yellow component. The color temperature and spectral power distribution are adjusted to achieve better color reproduction.
2Device complexity
If conventional color filters are used with LED light source, then the device complexity is reduced, but the color reproducibility deteriorates due to spectrum mismatch
Solution Approach 1:
A yellow phosphor layer is introduced as an intermediary optical element between the blue LED and the conventional color filters. This phosphor layer modifies the light spectrum in situ, converting harmful blue wavelengths to yellow wavelengths that do not interfere with the color filter performance. This approach maintains device simplicity while improving color reproduction by addressing the spectrum mismatch at the light source interface rather than requiring complex filter modifications.
Solution Approach 2:
The light providing assembly uses a composite light conversion system combining blue LED semiconductor material with yellow phosphor material. This composite approach creates a hybrid light source that leverages the high efficiency of LED technology while adding spectral conversion capabilities. The combination of blue light emission and yellow phosphor conversion produces a composite white light with improved spectral characteristics for color filter compatibility.
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 effectively maintains color reproducibility and brightness by absorbing unwanted wavelengths, minimizing color mixture problems and optimizing the performance of red and green color filters when using a blue light emitting diode as the light source.
Implementation Method 1
a light-converting part that converts the blue light into a white light and emits the white light to an exterior of the light emitting unit
Implementation Method 2
a first coloring agent that absorbs about 95% to about 100% of light having wavelengths of about 420 nm to about 470 nm in the white light
Data Source
AI summary
A display device includes a light emitting unit and a display panel including a first color filter. The light emitting unit includes a light source generating a blue light, and a light-converting part converting the blue light into a white light and emitting the white light to an exterior. The first color filter, through which the white light passes, includes a first coloring agent that absorbs about 95% to about 100% of light having wavelength of about 420 nm to about 470 nm in the white light. Thus, a color reproducibility of the display device may be improved.