Liquid Crystal Display Anisotropic Absorption Layer
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Solution Overview
Problem
Liquid crystal display devices using iodine-containing polarizing plates face challenges in achieving high contrast ratios due to low perpendicular transmittance, leading to bluishness in black displays and reduced white display luminance, and struggle with uniform alignment films on large screens, affecting image quality and productivity.
Innovation Solution
Incorporating an anisotropic absorption layer with dichromatic compounds like azobenzene derivatives or stilbene derivatives in alignment films and color filter layers, which are photoisomerized by linearly polarized light to improve polarization uniformity and reduce bluishness, and using photoisomerizable compounds with photoreactive polyimides or poly(amic acid) to enhance orientation control and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If iodine-containing polarizing plates are used to achieve high parallel transmittance for white display, then white display luminance is improved, but perpendicular transmittance becomes insufficient causing low contrast ratio and bluishness in black display
Solution Approach 1:
A compensation film with anisotropic absorption characteristics is introduced as an intermediary component between the polarizing plates and the liquid crystal layer. This compensation film specifically absorbs blue light in the shortwave region, mediating the harmful effect of blue leakage from the iodine-containing polarizing plates while preserving the high luminance benefit. The compensation film acts as a selective filter that corrects the spectral imbalance without compromising the overall light transmission.
2Illumination intensity
If iodine-containing polarizing plates are used to achieve high parallel transmittance, then white display quality is improved, but contrast ratio decreases due to insufficient perpendicular transmittance
Solution Approach 1:
The compensation film serves as a mediator that selectively enhances perpendicular transmittance in the blue wavelength region without affecting the parallel transmittance. By introducing this intermediate layer with specific anisotropic absorption properties, the system achieves improved contrast ratio while maintaining the high luminance characteristics provided by the iodine-containing polarizing plates.
3Manufacturing precision
If alignment films are used to control liquid crystal orientation, then display uniformity is improved, but formation on large screens is difficult affecting productivity
Solution Approach 1:
The patent replaces the conventional mechanical rubbing method with a photo-alignment method using optical fields. Alignment films containing photoreactive compounds are irradiated with polarized light to induce molecular orientation without mechanical contact. This substitution eliminates the complexity of large-scale rubbing operations, improves alignment uniformity across large screens, and significantly enhances manufacturing productivity.
Solution Approach 2:
The invention changes the alignment mechanism from mechanical force to optical field interaction. By using photoreactive compounds that undergo molecular reorientation upon light irradiation, the system transforms the alignment process into a parameter-controlled optical phenomenon, enabling precise and uniform alignment on large screens without mechanical constraints.
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
This solution reduces chromaticity differences between white and black displays, enhances contrast ratios, improves image quality, and increases productivity by stabilizing the orientation of liquid crystal molecules, thus addressing the limitations of existing technologies in liquid crystal display devices.
Implementation Method 1
at least one optical layer having anisotropic absorption (at least one anisotropic absorption layer) in a light path
Implementation Method 2
a dichromatic compound capable of undergoing photoisomerization, such as an azobenzene derivative or a stilbene derivative is added to the alignment films. The photoisomerization is caused by irradiating the dichromatic compound with substantially linearly polarized light
Implementation Method 3
the anisotropic absorption is effective in improving the contrast ratio by reducing the luminance at the time of black display
Data Source
AI summary
An object of the present invention is to provide a liquid crystal display device that has an excellent mass-productivity and gives an image improved by the reduction of the chromaticity difference between white display and black display, the reduction of coloring and luminance in black display, and the improvement of the contrast ratio. In the present invention, of a pair of alignment films 131 and 132 formed on a pair of substrates 101 and 102, respectively, the alignment film 132 formed on the glass substrate 102 on the observer side is made of a material obtained by adding a photoisomerized compound to a photosensitive polymer and has anisotropic absorption all over the visible light wavelength region (approximately 400 nm to 750 nm).