Polarizing Plate Adhesive Layer Curling and Durability
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Solution Overview
Problem
Polarizing plates using polyethylene terephthalate films face issues with curling and inadequate optical properties due to low adhesive strength and water-based adhesives, leading to defects in image display devices.
Innovation Solution
A polarizing plate design incorporating a polyethylene terephthalate film with an active energy ray-curable adhesive layer and a primer layer, featuring a first epoxy compound with a glass transition temperature of 120°C or higher and a second epoxy compound with a glass transition temperature of 60°C or lower, along with a cationic photopolymerization initiator, and a primer composition including polyester or polyvinyl alcohol-based resins and cross-linking agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If water-based adhesive is used to bond polyethylene terephthalate film to polarizer, then adhesive layer can be formed, but adhesive strength is insufficient and durability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive from water-based to solvent-based adhesive, and specifies the glass transition temperature range (0°C to 100°C) to optimize adhesive strength and durability. This parameter change resolves the contradiction by providing both sufficient bonding strength and long-term reliability under various operating conditions.
Solution Approach 2:
The patent uses a composite adhesive system consisting of solvent-based adhesive with specific glass transition temperature characteristics, combined with polyethylene terephthalate film and polarizer. This composite material approach ensures both strong adhesion and durable performance, overcoming the limitations of simple water-based adhesives.
2Ease of manufacture
If polyethylene terephthalate film is used as protective film, then cost is reduced and transparency is improved, but curling occurs due to low permeability and optical properties
Solution Approach 1:
The patent controls the glass transition temperature of the adhesive within 0°C to 100°C to match the thermal properties of the polyethylene terephthalate film. This parameter matching prevents differential thermal expansion and contraction, thereby eliminating curling while maintaining the cost advantages of PET film.
Solution Approach 2:
The patent applies specific quality characteristics to the adhesive layer locally, including controlled glass transition temperature and solvent-based composition, to compensate for the low permeability and optical properties of the PET film in specific areas, preventing curling without compromising overall manufacturing efficiency.
3Illumination intensity
If different types of polymer films are used on both sides of polarizer, then optical properties are improved, but dry efficiency difference generates curling during drying process
Solution Approach 1:
The patent standardizes the glass transition temperature of the adhesive to a specific range (0°C to 100°C) that is compatible with different polymer films. This parameter control ensures uniform drying efficiency across different film types, preventing curling while allowing the use of diverse high-performance polymer films for optimal optical properties.
4Strength
If polyethylene terephthalate film is used, then adhesive strength is improved, but adhesive strength decreases under high temperature and humidity conditions
Solution Approach 1:
The patent optimizes the glass transition temperature of the adhesive to be within 0°C to 100°C, which provides a balance between room temperature adhesion and high temperature stability. This parameter optimization ensures that the adhesive maintains its bonding strength even under elevated temperature and humidity conditions, resolving the heat resistance issue.
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 minimizes curling and enhances optical properties and durability, maintaining adhesive strength even under high temperature and humidity conditions, reducing defects in image display devices.
Implementation Method 1
an active energy ray-curable adhesive including a first epoxy compound of which a homopolymer has a glass transition temperature of 120° C. or higher, a second epoxy compound of which a homopolymer has a glass transition temperature of 60° C. or lower, and a cationic photopolymerization initiator
Data Source
AI summary
The present disclosure relates to a polarizing plate including an adhesive layer, a primer layer and a polyethylene terephthalate film which are sequentially formed on at least one side of a polarizer, wherein the adhesive layer in the present disclosure is formed by an active energy ray-curable adhesive including a first epoxy compound of which a homopolymer has a glass transition temperature of 120° C. or higher, a second epoxy compound of which a homopolymer has a glass transition temperature of 60° C. or lower, and a cationic photopolymerization initiator, and wherein the primer layer is formed by a primer composition including one or more binder resins selected from the group consisting of polyester and polyvinyl alcohol-based resins, and one or more cross-linking agents selected from the group consisting of acrylic cross-linking agents, epoxy-based cross-linking agents and polyvinyl alcohol-based cross-linking agents.