Liquid Crystal Display Halftone Overlapping Masking Alignment
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Solution Overview
Problem
Conventional liquid crystal display devices suffer from insufficient viewing angle characteristics and the generation of joint lines on the display screen due to misalignment and differences in irradiation conditions during the alignment division process, especially in larger sizes like 60-inch models, which affects yield and display quality.
Innovation Solution
A production method for liquid crystal display devices that involves exposing the alignment film in a way that adjacent exposure regions partly overlap, using a photomask with a halftone part to ensure continuous change in the position and width of dark lines between domains, thereby minimizing joint line visibility and improving yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the substrate is subjected to alignment division through several exposures, then large liquid crystal display devices can be produced, but joint lines are generated on the display screen due to misalignment and differences in irradiation conditions
Solution Approach 1:
The substrate is divided into multiple exposure regions that are exposed in separate steps. By segmenting the exposure process into multiple regions, large substrates can be processed while allowing for overlap between regions to eliminate joint lines. The photomask is shifted between exposures to create overlapping exposure regions where dark lines from adjacent exposures meet and cancel each other out.
Solution Approach 2:
Adjacent exposure regions are merged through overlapping exposure. The patent intentionally creates overlap between adjacent exposure regions, and the dark lines generated at the boundaries of these regions combine to form continuous dark lines that are invisible on the display screen, effectively merging the separate exposures into a unified alignment pattern.
2Ease of manufacture
If a photomask without halftone part is used, then manufacturing is simpler, but joint lines are clearly observed on the display screen
Solution Approach 1:
The photomask is designed with different properties in different regions: the central region has full transparency for standard exposure, while the peripheral regions have halftone (reduced transparency) properties. This local differentiation ensures that overlapping exposure regions produce dark lines with appropriate intensity to blend seamlessly, eliminating visible joint lines while maintaining manufacturing feasibility.
3Area of stationary object
If multiple exposures are performed to cover the entire substrate, then complete alignment coverage is achieved, but differences in irradiation conditions cause misalignment
Solution Approach 1:
The photomask is designed in advance with halftone parts positioned at the periphery, anticipating the need for overlapping exposures. This preliminary design ensures that when multiple exposures are performed, the dark lines from adjacent regions will automatically blend without visible joints, compensating for variations in irradiation conditions before the actual exposure process begins.
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 method effectively suppresses joint line generation on the display screen, even with multiple exposures, allowing for stable production of large liquid crystal display devices like 60-inch models, and enhances viewing angle characteristics by ensuring continuous alignment and reduced misalignment issues.
Implementation Method 1
a photo alignment method is an alignment method in which a photo alignment film is used as a material for the alignment film, and the photo alignment film is irradiated with a light beam such as UV, thereby being provided with an alignment regulating force
Data Source
AI summary
To provide a production method of a liquid crystal display device and a liquid crystal display device, in which generation of a joint line on a display screen is suppressed and yield can be improved even if a substrate is subjected to an alignment treatment by completing exposure for the substrate through several exposures in a liquid crystal display device including pixels each having two or more domains. The present invention is a production method of a production method of a liquid crystal display device, the liquid crystal display device including: a pair of opposed substrates; a liquid crystal layer formed between the pair of opposed substrates; and an alignment film arranged on a liquid crystal layer side surface of at least one of the pair of opposed substrates, and the liquid crystal display device having two or more regions which differ in alignment azimuth in a pixel, wherein the production method comprises an exposure step of exposing the alignment film in such a way that a substrate plane is divided into two or more exposure regions through a photomask in each exposure region, and in the exposure step, exposure is performed in such a way that adjacent two exposure regions have an overlapping exposure region where the adjacent two exposure regions partly overlap with each other, and the photomask has a halftone part corresponding to the overlapping exposure region.