Liquid Crystal Display Columnar Spacer Recess Alignment
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Solution Overview
Problem
High-definition liquid crystal display devices face challenges with light transmittance and lateral displacement between the TFT substrate and the counter substrate, particularly at smaller pixel pitches, where traditional columnar spacers fail to suppress these issues effectively.
Innovation Solution
A liquid crystal display device design featuring a TFT substrate with an organic passivation film and through-hole configuration, where a columnar spacer on the counter substrate is in contact with a recess formed by a planarization film within the through-hole, allowing for controlled lateral displacement and reduced spacer height, thus maintaining the distance between substrates while minimizing light transmittance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a small pixel pitch is used to achieve high definition, then the display resolution is improved, but the light transmittance of the pixel decreases due to reduced light transmission region
Solution Approach 1:
The patent applies local quality by making the interconnection material transparent (using transparent oxide semiconductor) specifically in the pixel region where light transmittance is critical, while maintaining the necessary electrical connectivity function. This allows the interconnection to be present in the pixel area without significantly reducing light transmittance, thus resolving the contradiction between high resolution (small pixel pitch) and light transmittance.
2Length of stationary object
If a typical columnar spacer is used to maintain substrate distance, then the spacing between TFT substrate and counter substrate is controlled, but lateral displacement between substrates cannot be suppressed
Solution Approach 1:
The patent introduces asymmetry by forming a recess in the TFT substrate that corresponds to the columnar spacer position. This asymmetric feature (recess) combined with the columnar spacer creates a mechanical interlocking structure that prevents lateral displacement while maintaining the required substrate spacing. The recess acts as a positioning feature that guides and stabilizes the relative position of the two substrates.
3Area of stationary object
If conventional through-hole configuration is used without planarization film, then the pixel area is saved, but lateral displacement occurs and affects image quality at small pixel pitch
Solution Approach 1:
The patent applies preliminary action by forming the recess in the TFT substrate before assembling the display panel. This pre-formed recess serves as a positioning feature that will later receive and stabilize the columnar spacer, preventing lateral displacement. By preparing this structural feature in advance, the design ensures proper substrate alignment without requiring additional area in the pixel region.
Data Source
AI summary
A liquid crystal display device includes a thin film transistor (TFT) substrate and a counter substrate that are disposed opposite to each other with a liquid crystal layer in between. The TFT substrate has, an organic passivation film formed covering the TFT, and a pixel electrode and a common electrode formed on the organic passivation film, the organic passivation film having a through-hole to connect the pixel electrode and the TFT. A columnar spacer is formed on the counter substrate to define a distance between the TFT substrate and the counter substrate. A planarization film made of resin is formed in the through-hole. A recess is formed in the through-hole by a surface of the planarization film and a sidewall of the through-hole. A tip end of the columnar spacer exists in the recess.