Visible-Light Adhesive Composition for Low-Outgas OLED Bonding
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Solution Overview
Problem
Existing adhesive sheets for image display devices, particularly organic EL displays, face challenges in curing with low energy and long wavelength light due to photoinitiators generating harmful outgases and poor hydrogen abstraction ability, leading to potential device deterioration and insufficient curing sensitivity.
Innovation Solution
An adhesive composition comprising a (meth)acrylic polymer and a photoinitiator with a radically polymerizable functional group and radical generating group, having a molar absorption coefficient of 30 (L/mol·cm) at 405 nm, which includes hydrogen abstraction-type and intramolecular cleavage-type photoinitiators to cure with visible light, minimizing photodecomposition products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cleavage-type photoinitiators (α-aminoacetophenone-based or acylphosphine oxide-based) are used for visible light curing, then curing sensitivity is improved, but harmful outgases (benzaldehyde) are generated
Solution Approach 1:
The patent changes the chemical structure parameters of the photoinitiator from cleavage-type to hydrogen abstraction-type, specifically selecting thioxanthone derivatives which absorb visible light and generate radicals through hydrogen abstraction without producing harmful outgases. This parameter change maintains curing sensitivity while eliminating the harmful byproducts.
Solution Approach 2:
The patent uses a photoinitiator system where the thioxanthone derivative acts as a visible light-sensitive component that can be completely consumed in the curing reaction, converting the adhesive from a liquid state to a crosslinked gel state without leaving harmful residual decomposition products.
2Object-generated harmful factors
If hydrogen abstraction-type photoinitiators (thioxanthone-based or anthraquinone-based) are used for visible light curing, then harmful outgases are reduced, but curing sensitivity is insufficient
Solution Approach 1:
The patent creates a composite photoinitiator system combining thioxanthone derivative (visible light absorber) with a hydrogen donor compound. This composite system enhances the hydrogen abstraction ability and curing sensitivity while maintaining the advantage of not generating harmful outgases. The synergistic effect between the photoinitiator and hydrogen donor improves the overall curing performance.
Solution Approach 2:
The patent introduces a hydrogen donor compound as an intermediary substance that facilitates the hydrogen abstraction reaction. The thioxanthone derivative absorbs visible light and abstracts hydrogen from the donor compound, generating radicals that initiate polymerization. This intermediary mechanism enhances curing sensitivity while avoiding direct decomposition of the photoinitiator that would produce harmful outgases.
3Productivity
If ultraviolet rays are used for curing adhesive sheets, then curing efficiency is high, but device members are deteriorated
Solution Approach 1:
The patent changes the wavelength parameter of the curing light from ultraviolet range to visible light range (405 nm or longer wavelength). This parameter change allows curing to proceed efficiently while avoiding the harmful effects of ultraviolet radiation on organic EL display members, thus resolving the contradiction between curing efficiency and member protection.
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 adhesive composition effectively cures with visible light, reducing harmful outgases and enhancing curing sensitivity, suitable for bonding optical members in image display devices, including organic EL displays, with improved cohesive force and flexibility.
Implementation Method 1
a photoinitiator (B), in which the photoinitiator (B) contains a photoinitiator (b1), which is a compound having, in a molecule, a radically polymerizable functional group having a carbon-carbon double bond and a radical generating group and has a molar absorption coefficient of 30 (L/mol·cm) or more at 405 nm
Implementation Method 2
has a molar absorption coefficient of 30 (L/mol·cm) or more at 405 nm
Implementation Method 3
hydrogen abstraction-type and intramolecular cleavage-type photoinitiators to cure with visible light
Implementation Method 4
radical generating group and has a molar absorption coefficient of 30 (L/mol·cm) or more at 405 nm
Data Source
AI summary
An adhesive composition is used for bonding an optical member, the adhesive composition containing a (meth)acrylic polymer (A) and a photoinitiator (B), in which the photoinitiator (B) contains a photoinitiator (b1).