Liquid Crystal Display Alignment Film Segmentation for Adhesion
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Solution Overview
Problem
Liquid crystal display devices face challenges in maintaining high alignment ability and adherence strength between the alignment film and the seal material, particularly due to the mechanical weakness of photo alignment films caused by ultraviolet ray decomposition, leading to issues with display performance and reliability.
Innovation Solution
A liquid crystal display device is designed with a two-layer alignment film structure, where the upper layer receiving photo alignment treatment is formed from polyimide with a precursor containing cyclobutane, and the lower layer not receiving photo alignment treatment is formed from polyamide acid without cyclobutane, with the polyimide existing 75-98 weight % at the surface and interface with the seal material, ensuring both high alignment ability and adherence strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photo alignment treatment is applied to the alignment film, then alignment ability is improved, but mechanical strength decreases
Solution Approach 1:
The alignment film is divided into two distinct layers: a first alignment film layer subjected to photo alignment treatment for high alignment ability, and a second alignment film layer not subjected to photo alignment treatment for high mechanical strength. This segmentation allows each layer to perform its specific function without compromising the other.
Solution Approach 2:
The alignment film uses a composite structure combining two different polyimide materials with distinct properties. The first polyimide layer provides photo-alignability while the second polyimide layer provides mechanical reinforcement, creating a composite film that achieves both alignment precision and structural strength.
2Manufacturing precision
If the alignment film surface is exposed to ultraviolet ray for photo alignment, then alignment effect is improved, but adherence strength with seal material decreases
Solution Approach 1:
The alignment film is segmented into two layers with distinct functions: the first layer receives photo alignment treatment to achieve precise liquid crystal alignment, while the second layer remains untreated to maintain strong adhesion with the seal material, thus preventing degradation of bonding strength.
Solution Approach 2:
Different regions of the alignment film structure are given different properties: the upper surface layer is optimized for photo alignment response, while the lower layer in contact with the seal material is optimized for adhesion, ensuring each region performs its specific function effectively.
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 configuration enhances the mechanical strength of the alignment film, maintains superior alignment ability, and secures sufficient adhesive strength between the alignment film and the seal material, thereby improving the reliability and display performance of the liquid crystal display device.
Implementation Method 1
the photo alignment method, in which the uniaxial anisotropy is generated by cutting the polymer chains in the alignment film in certain direction with polarized ultra violet ray
Data Source
AI summary
The purpose of the present invention is to realize the photo alignment film which has good alignment ability and good adhesive strength with the seal material. The structure of the invention is:A liquid crystal display device including a first substrate, having pixel electrodes and a first alignment film, and a second substrate adhere to each other by seal material, and the liquid crystal being sealed inside, in which the first alignment film is formed from a first polyimide, which receives a photo alignment treatment, and a second polyimide, which does not receive the photo alignment treatment, the first polyimide exists 75 to 98 weight % at a surface of the first alignment film on the pixel electrode and at an interface with the seal material, the second polyimide increases gradually in going to depth direction from the surface of the first alignment film in a cross sectional view.