Resin Light Shielding Layer Adhesion in LCD Panels
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Solution Overview
Problem
The use of a resin-based light shielding layer in liquid crystal display panels leads to detachment issues with the seal material due to low adhesiveness, resulting in reduced transmittance and yellowish display, and increases manufacturing complexity compared to metal-based layers.
Innovation Solution
A protection film with openings is applied outside the display area to cover the resin light shielding layer, ensuring adhesiveness with the seal material and maintaining transmittance, while also serving as a transparent film for adjusting the cell gap in semi-transmissive panels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a resin-based light shielding layer is used instead of metal, then cost is reduced and light shielding property is improved, but adhesiveness with seal material deteriorates causing detachment
Solution Approach 1:
An adhesion promoter layer is introduced as an intermediary between the resin-based light shielding layer and the seal material. This intermediate layer has high adhesion to both the resin layer and the seal material, preventing detachment while maintaining the cost advantages of using resin instead of metal.
Solution Approach 2:
The light shielding structure uses a composite material system consisting of the resin-based light shielding layer combined with the adhesion promoter layer. This composite structure combines the cost and optical benefits of resin with the adhesion properties needed for reliable sealing.
2Reliability
If the light shielding layer is covered by a protection film, then adhesiveness with seal material is improved, but transmittance ratio is lowered causing yellowish display
Solution Approach 1:
The adhesion promoter layer is selectively applied only to the non-display area portions of the light shielding layer where the seal material contacts it. The display area portions are left uncovered, extracting the protection function only where needed for adhesion while preserving light transmission in the display area.
Solution Approach 2:
The light shielding layer has different surface properties in different areas: the non-display area has an adhesion promoter layer for high adhesion to seal material, while the display area has no coating to maintain high light transmittance. This local differentiation resolves the contradiction between adhesion and transmittance.
3Reliability
If a protection film is formed on the light shielding layer in semi-transmissive panels, then adhesiveness is improved, but the number of manufacturing processes is increased
Solution Approach 1:
The adhesion promoter layer is integrated into the existing light shielding layer formation process. The same coating and patterning steps used to create the light shielding layer are also used to apply the adhesion promoter layer, merging two functions into one process sequence and avoiding additional manufacturing steps.
Solution Approach 2:
The adhesion promoter layer serves multiple functions: it provides adhesion between the light shielding layer and seal material, and in semi-transmissive panels, it also serves as the transparent film for adjusting cell gap. This multi-functionality reduces the total number of processes needed.
Data Source
AI summary
There is provided a liquid crystal display panel that includes an array substrate having at least a pixel electrode and a switching element for every pixel area in a display area on a transparent substrate, a color filter substrate in which a light shielding layer made of a resin is formed on a transparent substrate at least outside the display area and a color filter layer is formed to oppose the pixel electrode, and liquid crystal enclosed between the array substrate and the color filter substrate that are bonded by a seal material. A protection film having an opening, the opening being opened in the display area, is formed on the color filter substrate in the outside of the display area to cover at least the portion of the light shielding layer on which the seal material is formed.