Liquid Crystal Display Alignment Film Rubbing Process
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Solution Overview
Problem
Liquid crystal display devices suffer from alignment defects caused by static electricity generated during the rubbing process, leading to optical holes that result in defective products with white or black dots in normally black or white displays.
Innovation Solution
A manufacturing method for liquid crystal display devices using a low duty ratio driving method with a duty ratio not smaller than 1/16, where only the alignment film on the substrate with fewer electrodes is subjected to the rubbing process, and an insulating film is formed between the electrodes to prevent static electricity discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a rubbing process is performed on alignment films to control liquid crystal molecule alignment directions, then image quality is improved, but static electricity is generated causing alignment defects and optical holes
Solution Approach 1:
The patent divides the alignment films into two groups: those requiring rubbing for alignment control and those requiring insulation to prevent static electricity. By segmenting the treatment approach based on electrode configuration, the patent achieves both alignment quality and static electricity prevention without compromising either function
Solution Approach 2:
An insulating film is introduced as an intermediary layer between the electrode and the alignment film on the common electrode substrate. This intermediary prevents static electricity discharge while allowing the alignment film to perform its alignment function, thereby resolving the contradiction between alignment quality and static electricity prevention
2Ease of operation
If alignment films are charged with static electricity during rubbing process, then alignment direction control is achieved, but discharge of static electricity damages liquid crystal alignment function and forms alignment holes
Solution Approach 1:
The patent applies preliminary anti-action by forming an insulating film on the common electrode before the rubbing process. This pre-established insulation prevents the harmful discharge effect before it can occur, allowing the rubbing process to be performed safely on the alignment film without risking static electricity damage to the liquid crystal alignment
3Reliability
If electrodes are externally connected to make them have the same potential to prevent alignment defects, then static electricity discharge is prevented, but device complexity increases
Solution Approach 1:
The patent extracts the electrostatic prevention function from the electrode connection system and transfers it to an insulating film layer. Instead of modifying the electrode connections, the harmful electrostatic discharge path is removed by introducing insulation between the electrode and alignment film, thereby preventing alignment defects without increasing device complexity
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 approach significantly reduces alignment hole formation rates and charge resident time, effectively preventing alignment defects and improving the quality of liquid crystal display devices by ensuring that only the alignment film on the substrate with fewer electrodes is rubbed.
Implementation Method 1
an insulating film having necessary insulation is formed between the first electrode and the first vertical alignment film and between the second electrode and the second vertical alignment film
Implementation Method 2
Alignment directions of liquid crystal molecules of a liquid crystal display device (particularly a vertical alignment type liquid crystal display device) are controlled by a rubbing process for alignment films
Implementation Method 3
disposing liquid crystal having a negative dielectric constant anisotropy between the first and second substrates
Data Source
AI summary
A liquid crystal display device using a low duty ratio driving method with a duty ratio not smaller than 1/16 is manufactured in the following manner. A first substrate is prepared having a first electrode of a predetermined shape. A second substrate is prepared having a second electrode of a shape different from said predetermined shape, the second electrode having signal line electrodes smaller in number than those of the first electrode. An insulating film having necessary insulation is formed on each of the first and second electrodes. First and second vertical alignment films are formed above the first and second substrates, respectively, the first and second vertical alignment films covering the first and second electrodes, respectively. A rubbing process is executed only for the second vertical alignment film. The first and second substrates are disposed facing each other, and liquid crystal having a negative dielectric constant anisotropy is disposed between the first and second substrates. It is possible to prevent alignment defects to be caused by static electricity generated by rubbing of a liquid crystal display device.