Block Copolymer Adhesive for Optical Displays
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Solution Overview
Problem
Existing pressure-sensitive adhesives for optical members in display devices face challenges in maintaining durability, reliability, and preventing light leakage, especially at high temperatures and humidity, while also requiring bending preventability and excellent interface adhesive strength.
Innovation Solution
A pressure-sensitive adhesive composition featuring a block copolymer with a high glass transition temperature first block and a low glass transition temperature second block, along with a multifunctional crosslinking agent, which forms a micro phase separation structure to enhance cohesive strength and stress relaxation, ensuring durability and reliability, and includes crosslinkable functional groups for controlled reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure-sensitive adhesive is designed for high durability and reliability at high temperature and humidity, then adhesive strength is improved, but bending preventability and cuttability deteriorate
Solution Approach 1:
The adhesive is segmented into two distinct blocks with different glass transition temperatures. The first block (Tg ≥ 50°C) provides high-temperature durability and reliability, while the second block (Tg ≤ -10°C) provides flexibility for bending preventability and cuttability. This segmentation allows each block to independently contribute its specialized properties without compromising the other.
Solution Approach 2:
The invention changes the parameter of glass transition temperature by creating a bimodal distribution with peaks at Tg ≥ 50°C and Tg ≤ -10°C. This parameter change enables the adhesive to exhibit both high-temperature stability (from the first block) and low-temperature flexibility (from the second block), resolving the contradiction between durability and processability.
2Reliability
If crosslinking density is increased to improve durability, then adhesive strength is improved, but stress relaxation capability deteriorates
Solution Approach 1:
The adhesive system is segmented into crosslinkable functional groups in the first block (for durability) and flexible segments in the second block (for stress relaxation). The first block forms a crosslinked network providing structural stability and durability, while the second block remains flexible to allow stress relaxation, preventing the contradiction between crosslinking density and stress relaxation capability.
Solution Approach 2:
The invention creates a composite structure within the block copolymer where the first block (with crosslinkable groups) and second block (with flexible chains) are combined at the molecular level. This composite material approach allows simultaneous achievement of high crosslinking density for durability and sufficient flexibility for stress relaxation.
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 solution provides a pressure-sensitive adhesive with excellent bending preventability, cuttability, and durability, maintaining physical properties under varying temperature and humidity conditions, suitable for optical members and display devices.
Implementation Method 1
a first block having a glass transition temperature of 50 °C or more and including a polymerization unit of 80 to 99.9 parts by weight of a (meth)acrylic acid ester monomer and a polymerization unit of 0.1 to 20 parts by weight of a monomer providing a crosslinkable functional group, and a second block having a glass transition temperature of -10°C or less
Implementation Method 2
a multifunctional crosslinking agent, and wherein the monomers providing a crosslinkable functional group included in the first and second blocks
Data Source
AI summary
Provided are a pressure-sensitive adhesive composition, an optical laminate, a pressure-sensitive adhesive polarizing plate and a display device. When a particular block copolymer forming a micro phase separation region in a crosslinking structure is used, and a cohesive strength of the block copolymer is controlled, a pressure-sensitive adhesive composition having excellent physical properties required for an optical member, and particularly having excellent bending preventability, cuttability and pressure-sensitive adhesive durability may be provided. Such a pressure-sensitive adhesive composition may be used for optical uses, for example, to laminate various optical members, or apply an optical member to a display device.