Polyvinyl Acetal Interlayer Filler for Touch Panel Lamination
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Solution Overview
Problem
Conventional interlayer filling materials for touch panels, such as acrylic adhesives, struggle with followability to steps and defoaming properties, leading to air bubbles and potential deterioration of ITO films under high-temperature and high-humidity conditions.
Innovation Solution
A polyvinyl acetal-based interlayer filling material incorporating specific plasticizers like triethylene glycol-di-2-ethylhexanoate and organic acids like 2-ethylhexanoic acid, adipic acid, or phthalic acid, which provides improved followability and defoaming properties while preventing whitening and ITO film deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If acrylic adhesives are used as interlayer filling material, then transparency and adhesiveness are improved, but air bubbles are entrapped during attachment leading to lower visibility and durability
Solution Approach 1:
The patent changes the chemical composition parameters of the filling material by using plasticized polyvinyl acetal with specific plasticizers (triethylene glycol-di-2-ethylhexanoate, tetraethylene glycol-di-2-ethylhexanoate, triethylene glycol-di-pivalate, or di-(2-butoxyethyl)adipate) and organic acids (2-ethylhexanoic acid, adipic acid, or phthalic acid) in controlled amounts. This compositional parameter change enables the material to release air bubbles during lamination while maintaining transparency and adhesion properties.
2Ease of manufacture
If conventional acrylic adhesives are used, then coating properties are improved, but followability to steps of printing portion or wiring is poor leading to residual air bubbles
Solution Approach 1:
The patent modifies the material parameters by selecting specific plasticizers and organic acids that adjust the viscosity and flow characteristics of the filling material. This allows the material to adequately follow the steps of printing portions and wiring patterns during lamination, eliminating residual air bubbles while maintaining ease of application.
3Length of moving object
If filling material is thinned for downsizing and thinning of personal digital assistant, then weight and thickness are reduced, but ability to follow steps and release air bubbles deteriorates
Solution Approach 1:
The patent achieves this by changing the chemical composition parameters - using plasticized polyvinyl acetal with specific plasticizers that provide adequate flow and defoaming properties even in thin layers. The organic acid components further enhance the material's ability to release air bubbles during lamination, ensuring that thin filling materials can still effectively eliminate air bubbles and follow steps.
4Strength
If acrylic adhesives are used under high-temperature and high-humidity environment, then initial adhesion is good, but whitening and ITO film deterioration occur
Solution Approach 1:
The patent changes the chemical composition by using plasticized polyvinyl acetal with specific plasticizers and organic acids that provide thermal and humidity stability. This compositional parameter change prevents whitening and ITO film deterioration under high-temperature and high-humidity conditions while maintaining adhesion strength.
Data Source
AI summary
An interlayer filling material for a touch panel which is used for filling an interlayer space between a touch panel and another component or an interlayer space between transparent conductive films included in the touch panel in production of a personal digital assistant, which is excellent in followability to steps of a decorative printing portion or wiring upon filling of an interlayer space (lamination) and also excellent in defoaming properties to release air bubbles entrapped during filling of an interlayer space (lamination) or air bubbles left near the steps, which is less likely to be whitened and less likely to deteriorate an ITO film even under a high-temperature and high-humidity environment. The present invention also aims to provide a laminate produced using the interlayer filling material for a touch panel. The interlayer filling material includes: a polyvinyl acetal; a plasticizer; and an organic acid.