Pressure-Sensitive Adhesive for Optical Film Light Leakage and Static Control
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Solution Overview
Problem
Pressure-sensitive adhesives used for polarizing plates in liquid crystal displays face challenges in maintaining durability and preventing light leakage, especially under high temperature and humidity conditions, while also minimizing static electricity generation during peeling, which can disrupt display performance.
Innovation Solution
A pressure-sensitive adhesive comprising a resin and an antistatic agent, with specific storage elastic modulus and charged voltage characteristics, is developed to ensure durable adhesion and reduce static electricity, featuring a blend of acrylic copolymer and active energy beam-curable compounds, and incorporating a silane coupling agent for enhanced adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low molecular weight substance such as a plasticizer is added to the pressure-sensitive adhesive to provide stress relaxation property, then the light leakage problem is solved, but the holding power is lowered and lifting and peeling are liable to be caused
Solution Approach 1:
The patent changes the molecular weight parameter of the adhesive components. Specifically, it uses a pressure-sensitive adhesive with a weight-average molecular weight of 100,000 to 5,000,000 (higher than conventional low molecular weight plasticizers) to achieve stress relaxation without the negative effects of low molecular weight substances. This parameter change allows the adhesive to maintain both stress relaxation capability and holding power.
Solution Approach 2:
The patent employs a composite adhesive system consisting of multiple components: a pressure-sensitive adhesive (acrylic copolymer), a reactive diluent, and a photopolymerization initiator. This composite material approach allows the system to exhibit both stress relaxation properties (from the polymer chain flexibility) and maintained adhesion strength (from the crosslinked network structure), resolving the contradiction between light leakage prevention and holding power.
2Ease of manufacture
If plastic materials are used for optical films and release films, then manufacturing is simplified, but static electricity is generated during rubbing and peeling
Solution Approach 1:
The patent introduces an antistatic agent as an intermediary substance added to the pressure-sensitive adhesive composition. This antistatic agent (such as metal salts or organic compounds with specific functional groups) acts as a mediator that dissipates static electricity generated during peeling operations, while not interfering with the fundamental plastic material structure and manufacturing process of the optical films and release films.
Solution Approach 2:
The patent modifies the electrical properties of the adhesive system by incorporating substances that change the surface resistivity and charge dissipation characteristics. The addition of antistatic agents and selection of specific polymer materials with appropriate dielectric properties changes the electrostatic parameters of the system, reducing static electricity generation and accumulation during manufacturing operations.
3Duration of action of stationary object
If the pressure-sensitive adhesive is softened to provide stress relaxation, then adhesion durability is improved, but the adhesive strength is reduced
Solution Approach 1:
The patent implements preliminary crosslinking of the adhesive system before final application. The photopolymerization initiator and reactive diluent are incorporated in advance, creating a pre-conditioned adhesive that has both the flexibility for stress relaxation and the crosslinked structure for maintained strength. This preliminary preparation allows the adhesive to exhibit both softness for durability and strength for holding power when needed.
Solution Approach 2:
The patent creates a composite adhesive structure combining linear polymer chains (for flexibility and stress relaxation) with crosslinked network segments (for strength and durability). The acrylic copolymer provides the flexible matrix while the photopolymerization creates crosslinked regions that maintain adhesive strength, achieving both adhesion durability and holding power simultaneously.
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 provides excellent durability and light leakage prevention under high temperature and humidity, while minimizing static electricity issues, ensuring stable performance of liquid crystal displays.
Implementation Method 1
a pressure-sensitive adhesive which comprises a pressure-sensitive adhesive resin and an antistatic agent, wherein a storage elastic modulus (G′) at 23° C. is 0.3 MPa or more
Implementation Method 2
a charged voltage on the surface of a layer comprising the pressure-sensitive adhesive which is measured 5 seconds later since peeling off a release film attaching to the pressure-sensitive adhesive layer under the environment of 23° C. and a relative humidity of 50% is 1.0 kV or less
Implementation Method 3
a pressure-sensitive adhesive comprising a resin and an antistatic agent, with specific storage elastic modulus and charged voltage characteristics, is developed to ensure durable adhesion and reduce static electricity, featuring a blend of acrylic copolymer and active energy beam-curable compounds
Implementation Method 4
incorporating a silane coupling agent for enhanced adhesion
Data Source
AI summary
Provided is a pressure-sensitive adhesive for an optically functional film which can carry out adhesion with a good durability in adhesion of an optically functional film such as adhesion of a polarizing plate, particularly a polarizing plate integrated with a viewing angle expanding film and the like with a liquid crystal cell, adhesion of a polarizing plate with a retardation film, adhesion of a retardation film with a retardation film and adhesion of a retardation film with a liquid crystal cell and which has the characteristics that a liquid crystal display obtained therefrom is less liable to cause light leakage even under the environment of high temperature and high humidity and that static electricity is less liable to be produced when peeling off a release film from a pressure-sensitive adhesive layer.The pressure-sensitive adhesive for applying an optically functional film comprises a pressure-sensitive adhesive resin and an antistatic agent, wherein a storage elastic modulus (G′) at 23° C. is 0.3 MPa or more, and a charged voltage on the surface of a layer comprising the above pressure-sensitive adhesive which is measured 5 seconds later since peeling off a release film brought into contact with the above pressure-sensitive adhesive layer under the environment of 23° C. and a relative humidity of 50% is 1.0 kV or less.