PMMA Hard Coating Film Adhesion and Weatherability
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Solution Overview
Problem
Display devices such as LCDs and OLEDs face issues with scratch resistance due to poor weatherability and adhesion of traditional hard coating films, particularly triacetyl cellulose (TAC) and polymethyl methacrylate (PMMA) films, which affect image quality and durability.
Innovation Solution
A hard coating film with a polymethyl methacrylate (PMMA) base film and a (meth)acrylate composition comprising a polyurethane (meth)acrylate oligomer, (meth)acrylate monomers, and an initiator, along with optional silica nanoparticles and organic microparticles, to enhance adhesion, weatherability, and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If TAC film is used as base film, then good light transmittance is achieved, but high moisture absorption and high birefringence occur leading to poor weatherability
Solution Approach 1:
The patent changes the base film material from TAC to PMMA, fundamentally altering the material parameters to achieve both good light transmittance and excellent weatherability. PMMA has lower moisture absorption and birefringence compared to TAC, resolving the contradiction between optical performance and environmental stability.
Solution Approach 2:
The patent uses a composite structure combining PMMA base film with a specific (meth)acrylate coating composition containing polyurethane oligomer and monomers. This composite material approach allows optimization of both the base film properties (light transmittance, weatherability) and coating properties (adhesion, hardness).
2Reliability
If PMMA film is used as base film, then good light transmittance and weatherability are achieved, but adhesion of acrylate hard coating composition becomes poor
Solution Approach 1:
The patent modifies the coating composition parameters by incorporating polyurethane (meth)acrylate oligomer with specific functionality (6-15) and molecular weight (1000-4500), along with specific monomers. This changes the chemical parameters of the coating to improve adhesion to PMMA surface without compromising weatherability.
Solution Approach 2:
The polyurethane (meth)acrylate oligomer acts as an intermediary substance that bridges the PMMA base film and the hard coating layer. Its specific chemical structure provides both compatibility with PMMA surface and good adhesion for the coating, resolving the adhesion problem while maintaining weatherability.
3Strength
If surface modification treatments are applied to PMMA film, then adhesion is improved, but process complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the need for complex surface modification treatments (corona discharge, oxidation, anchoring agents, primer coatings) by incorporating adhesion-promoting functionality directly into the coating composition itself. The polyurethane (meth)acrylate oligomer provides adhesion in a single coating application, simplifying the manufacturing process.
Solution Approach 2:
The patent merges multiple functions (adhesion promotion, hard coating formation, weatherability protection) into a single coating layer using the (meth)acrylate composition. This eliminates the need for separate surface treatment steps and multiple coating layers, reducing process complexity while achieving good adhesion.
4Strength
If hard coating layer is applied to protect display surface, then scratch resistance is improved, but adhesion and weatherability become insufficient
Solution Approach 1:
The patent uses a composite coating system combining polyurethane (meth)acrylate oligomer with specific monomers to create a hard coating layer that simultaneously achieves scratch resistance, good adhesion to PMMA, and excellent weatherability. The composite chemistry allows optimization of all three properties without compromise.
Solution Approach 2:
The patent optimizes the coating composition parameters including the functionality (6-15) and molecular weight (1000-4500) of the polyurethane oligomer, and the ratios of different monomers. These parameter changes enable the coating to achieve balanced performance in hardness, adhesion, and weatherability.
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 excellent adhesion between the hard coating layer and the PMMA base film, improved weatherability, and enhanced abrasion resistance, maintaining high light transmittance and optical properties suitable for display devices.
Implementation Method 1
The hard coating layer comprises a (meth)acrylate composition and an initiator, wherein the (meth)acrylate composition comprises a polyurethane (meth)acrylate oligomer with a functionality of 6 to 15, at least one (meth)acrylate monomer with a functionality of 3 to 6, at least one (meth)acrylate monomer with functionality of less than 3
Data Source
AI summary
This invention is to provide a hard coating film, comprising a polymethyl methacrylate (PMMA) base film and an antiglare hard coating layer formed thereon, wherein the antiglare hard coating layer comprises a (meth)acrylate composition, an initiator, a plurality of silica nanoparticles, a plurality of organic microparticles and a leveling agent. The (meth)acrylate composition comprises a urethane (meth)acrylate oligomer with a functionality of 6 to 15 and a molecular weight ranging between 1,000 and 4,500, and at least one (meth)acrylate monomer with a functionality of 3 to 6, and at least one (meth)acrylate monomer with functionality of less than 3.