Retardation Layer Adhesive Thermal Expansion for Thin Polarizer Rework
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Solution Overview
Problem
The challenge is to develop a thin polarizing plate with a retardation layer that can be satisfactorily peeled from a display cell during rework, especially at low temperatures using liquid nitrogen, as existing thin plates often break or fail to peel due to their low thickness and high fragility.
Innovation Solution
A polarizing plate with a retardation layer is designed, featuring a polarizer, a protective layer, a retardation layer, and adhesive layers with optimized linear expansion coefficients, where the second adhesive layer has a higher expansion coefficient than the first, ensuring better bonding and peeling properties, and the total thickness is kept at 140 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the polarizing plate thickness is reduced to meet thinning demands, then the overall thickness is improved, but the reworkability deteriorates due to breakage during manual peeling
Solution Approach 1:
The invention changes the physical parameter of the adhesive layer's linear expansion coefficient to resolve the contradiction. By selecting an adhesive layer with a linear expansion coefficient of 30×10⁻⁶/℃ or higher, the adhesive expands sufficiently at low temperatures to create gaps between the polarizing plate and display cell, enabling successful rework even with thin polarizing plates that would otherwise be too fragile for manual peeling.
2Ease of repair
If liquid nitrogen is used for rework to improve peeling capability, then the reworkability is improved, but the risk of breakage increases for thin polarizing plates
Solution Approach 1:
The invention utilizes thermal expansion of the adhesive layer to enable rework. The adhesive layer is specifically selected to have a high linear expansion coefficient (30×10⁻⁶/℃ or higher) so that when exposed to liquid nitrogen's low temperature, the adhesive contracts and creates separation between the polarizing plate and display cell, allowing easy peeling without the mechanical stress that causes breakage in thin plates.
3Length of stationary object
If the polarizing plate is made thinner to meet display demands, then the compactness is improved, but the structural strength deteriorates making manual rework difficult
Solution Approach 1:
The invention replaces mechanical rework methods with a thermal-based approach. Instead of relying on mechanical force to peel thin, fragile polarizing plates, the high linear expansion coefficient adhesive layer is utilized to create thermal separation when exposed to liquid nitrogen, substituting mechanical peeling with thermal expansion-driven separation that preserves the integrity of thin structures.
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
This configuration significantly reduces the occurrence of the retardation layer remaining on the display cell during rework, even at low temperatures, enhancing the reworkability and reliability of the polarizing plate.
Implementation Method 1
An average linear expansion coefficient of the second adhesive layer when an ambient temperature is changed from −150° C. to 20° C. is 38.0 (×10−5/° C.) or more, and is larger than an average linear expansion coefficient of the first adhesive layer
Data Source
AI summary
There is provided a thin polarizing plate with a retardation layer excellent in reworkability. A polarizing plate with a retardation layer according to the present invention includes: a polarizing plate including a polarizer and a protective layer on at least one side of the polarizer; a retardation layer; a first adhesive layer configured to bond the polarizing plate and the retardation layer; and a second adhesive layer arranged as an outermost layer on an opposite side of the retardation layer to the polarizing plate. An average linear expansion coefficient of the second adhesive layer when an ambient temperature is changed from −150° C. to 20° C. is 38.0(×10−5/° C.) or more, and is larger than an average linear expansion coefficient of the first adhesive layer when an ambient temperature is changed from −150° C. to 20° C.