Laminated Polyester Film Coating for Backlight Adhesion
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Solution Overview
Problem
Conventional laminated polyester films used in micro-lens or prism sheets for backlight units in liquid crystal displays face challenges with adhesion properties, particularly when using solvent-free active energy ray-curable coating materials, leading to insufficient adhesion and increased processing costs due to higher energy irradiation requirements.
Innovation Solution
A laminated polyester film structure is developed with a coating layer comprising a urethane resin, epoxy compound, oxazoline compound, and melamine compound, which enhances adhesion properties even with reduced active energy ray exposure and provides wet heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solvent-free type active energy ray-curable coating material is used to form accurate prism pattern, then manufacturing precision is improved, but adhesion property deteriorates due to insufficient penetration into easy-bonding layer and swelling effect
Solution Approach 1:
The patent introduces a specific easy-bonding coating layer comprising polyester resin, acrylic resin, or urethane resin as an intermediary between the polyester film and the solvent-free coating material. This intermediate layer facilitates better penetration and adhesion, preventing the swelling effect while maintaining manufacturing precision of the prism pattern.
Solution Approach 2:
The patent modifies the composition and properties of the easy-bonding coating layer by selecting specific resin types (polyester, acrylic, or urethane) and controlling their physical and chemical parameters to optimize penetration into the solvent-free coating material while maintaining adhesion strength.
2Productivity
If processing speed is increased to reduce costs, then productivity is improved, but adhesion property deteriorates due to reduced amount of active energy rays irradiated
Solution Approach 1:
The patent changes the chemical composition parameters of the coating layer by incorporating specific resin components that enhance adhesion through chemical bonding, allowing sufficient adhesion even with reduced UV irradiation dosage at higher processing speeds.
Solution Approach 2:
The patent uses a composite coating layer structure combining multiple resin components (polyester resin, acrylic resin, urethane resin) with crosslinking agents to create a material that achieves adequate adhesion with lower energy input, enabling faster processing without sacrificing bond strength.
3Reliability
If amount of active energy rays is increased to improve adhesion, then adhesion property is improved, but costs increase due to introduction of lamps or increased electric power consumption
Solution Approach 1:
The patent modifies the photopolymerization parameters by using coating materials with lower curing thresholds and enhanced reactivity, allowing adequate adhesion to be achieved with reduced UV energy input, thereby lowering power consumption and equipment costs.
4Reliability
If amount of active energy rays is increased to improve adhesion, then adhesion property is improved, but polyester film suffers from curling due to heat generation
Solution Approach 1:
The patent changes the thermal properties of the coating system by selecting resins with lower exothermic heat during curing and improved thermal stability, reducing heat generation during UV curing and preventing polyester film curling while maintaining adequate adhesion.
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 achieves excellent adhesion and wet heat resistance for micro-lens and prism layers, reducing processing costs and maintaining high industrial value.
Implementation Method 1
an active energy ray-curable coating material is charged into a prism mold, and then a polyester film is placed on the coating material thus charged so as to interpose the coating material between the polyester film and the mold. Next, an active energy ray is irradiated to the active energy ray-curable coating material to cure the resin
Data Source
AI summary
The present invention provides a laminated polyester film which can be suitably used in the applications requiring good adhesion to a micro-lens layer, a prism layer or the like, for example, in a backlight unit for liquid crystal displays, etc. The laminated polyester film of the present invention comprises a polyester film, and a coating layer formed on at least one surface of the polyester film by applying a coating solution comprising a urethane resin, an epoxy compound, an oxazoline compound and a melamine compound thereonto.