UV-Curable Adhesive for Touch Sensors on Low-Transmittance Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing touch sensors face challenges with adhesion strength when bonded to UV poorly-permeating substrates, such as polarizing plates, leading to reduced durability and increased thickness, and poor folding characteristics due to the use of conventional adhesives.
Innovation Solution
A touch sensor with a substrate having 5% or less transmittance at 380 nm, a touch sensor layer of 2-10 μm thickness, and an adhesive layer comprising a cured product of an adhesive composition including an initiator and sensitizer with absorption wavelengths between 380-450 nm, providing an adhesion strength of 5 N/25 mm or more, which is enhanced by UV irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transparent pressure-sensitive adhesive is used to bond touch sensor to substrate, then bonding is achieved, but adhesion strength is weak and bonding particles and air bubbles are generated
Solution Approach 1:
The patent changes the adhesive type from pressure-sensitive adhesive to UV curable adhesive, which cures upon UV irradiation to form strong bonds without the defects of pressure-sensitive adhesives. This parameter change in adhesive chemistry resolves the adhesion strength and defect issues.
Solution Approach 2:
The patent replaces the mechanical bonding mechanism of pressure-sensitive adhesives with a photochemical curing mechanism using UV curable adhesives. The UV irradiation triggers polymerization, creating strong chemical bonds that eliminate bonding particles and air bubbles while improving adhesion strength.
2Reliability
If UV curable adhesive is used with UV poorly-permeating substrate, then bonding is achieved, but adhesion strength is lowered
Solution Approach 1:
The patent adjusts the UV wavelength parameter to match the absorption characteristics of the adhesive and substrate. By selecting specific UV wavelengths that can penetrate the UV poorly-permeating substrate while still curing the adhesive, the patent achieves strong adhesion despite the substrate's UV blocking properties.
Solution Approach 2:
The patent introduces an intermediary layer or modifies the adhesive composition to facilitate UV transmission through the UV poorly-permeating substrate. This intermediary approach allows UV light to reach the adhesive for curing while maintaining the substrate's protective functions.
3Reliability
If pressure-sensitive adhesive is used, then bonding is achieved, but overall thickness increases and folding characteristics deteriorate
Solution Approach 1:
The patent changes the adhesive from pressure-sensitive type to UV curable type, which enables thinner adhesive layers to achieve sufficient bond strength. This parameter change in adhesive chemistry allows reduced thickness while maintaining or improving folding characteristics.
Solution Approach 2:
The patent replaces mechanical pressure bonding with photochemical curing, allowing for thinner adhesive layers that maintain structural integrity during folding. The UV curable adhesive forms strong bonds at reduced thickness, improving flexibility and folding characteristics.
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 strength and improved folding characteristics by directly bonding the touch sensor to UV poorly-permeating substrates, eliminating the need for additional substrates and allowing for thinner, more durable touch sensors with enhanced reliability.
Implementation Method 1
an adhesive layer disposed between the substrate and the touch sensor layer, wherein the adhesive layer comprises a cured product of an adhesive composition comprising at least one selected from the group consisting of an initiator and a sensitizer having an absorption wavelength (λmax) in a range of 380 nm to 450 nm
Implementation Method 2
irradiating a surface of the substrate, which is not in contact with the adhesive composition, with a UV light having a wavelength of 390 nm to 460 nm
Data Source
AI summary
Provided herein is a touch sensor including: a substrate having a transmittance of 5% or less at a wavelength of 380 nm; a touch sensor layer configured to be opposite the substrate and having a thickness of 2 μm to 10 μm; and an adhesive layer disposed between the substrate and the touch sensor layer, wherein the adhesive layer includes a cured product of an adhesive composition including at least one selected from the group consisting of an initiator and a sensitizer having an absorption wavelength in the range of 380 nm to 450 nm and has an adhesion strength of 5 N/25 trim or more. There is an advantageous effect in that the provided film-type touch sensor represents excellent adhesion and folding characteristics even when the substrate has a relative low transmittance.