Optical Laminate Adhesive Hardness for Recess Intrusion Control
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Solution Overview
Problem
Adhesives or pressure-sensitive adhesives that are excessively hard fail to effectively attach to other members due to decreased adhesive force, while those with lowered hardness excessively intrude into the recessed portions of an uneven structure, affecting the function of optical sheets.
Innovation Solution
A laminate comprising a first optical sheet with an uneven structure and a pressure-sensitive adhesive layer made of a (meth)acrylic polymer with a nanoindentation hardness of 0.1 MPa to 2.0 MPa, ensuring minimal intrusion into recessed portions while maintaining strong adhesive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the adhesive layer is made excessively hard to suppress intrusion into recessed portions, then the intrusion into recessed portions is reduced, but the adhesive force decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hardness of the adhesive layer through selection of appropriate adhesive materials and adjustment of formulation parameters. The hardness is controlled to be within a specific range (Shore A 20-40 or equivalent Brinell hardness 10-30) to simultaneously achieve minimal intrusion into recessed portions and sufficient adhesive force. This parameter optimization resolves the contradiction between intrusion control and adhesive strength.
2Strength
If the adhesive layer is made softer to increase adhesive force, then the adhesive force improves, but the intrusion into recessed portions increases
Solution Approach 1:
The patent resolves this contradiction by changing the hardness parameter of the adhesive layer to an optimized range (Shore A 20-40 or Brinell hardness 10-30). This parameter selection ensures that the adhesive layer is soft enough to provide strong adhesive force but hard enough to suppress excessive intrusion into recessed portions, thereby achieving both goals simultaneously.
3Reliability
If the adhesive layer is made excessively hard to suppress intrusion, then the function of optical sheets is maintained, but the attachment to other members fails
Solution Approach 1:
The patent resolves this contradiction by optimizing the hardness parameter of the adhesive layer to fall within the specific range (Shore A 20-40 or Brinell hardness 10-30). This parameter control ensures that the adhesive layer maintains optical sheet functionality by suppressing excessive intrusion while simultaneously providing sufficient attachment force to other members, thus resolving the contradiction between reliability and strength.
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
Provided is a laminate including a pressure-sensitive adhesive/adhesive less liable to intrude into recessed portion of an uneven structure, and excellent in adhesive force or pressure-sensitive adhesive force to other member(s). In a laminate 100A, a first optical sheet 10a includes a first main surface 12s with an uneven structure, and a second main surface 18s opposite to the first main surface 12s, the pressure-sensitive adhesive/adhesive layer 20a is arranged on the first main surface side 12s of the first optical sheet 10a, the uneven structure of the first main surface 12s includes a plurality of recessed portions 14, and a flat portion 10s between each two adjacent recessed portions among the plurality of recessed portions 14, the flat portion 10s of the first main surface 12s is in contact with a surface of the pressure-sensitive adhesive/adhesive layer 20a, the pressure-sensitive adhesive/adhesive layer 20a includes a (meth)acrylic polymer, and a nanoindentation hardness, measured by pressing an indenter of a nanoindenter into the pressure-sensitive adhesive/adhesive layer 20a by 2000 nm, is 0.1 MPa or more and 2.0 MPa or less.