Double-Sided Adhesive Sheet for Display Devices with Stepped Surfaces
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Solution Overview
Problem
Existing adhesive sheets for image display devices face challenges in achieving close contact bonding over stepped surfaces without gaps, leading to issues like visibility deterioration, foaming, and peeling, especially under temperature and humidity changes.
Innovation Solution
A double-sided adhesive sheet is designed to match the surface shape of the adherend, allowing it to be bonded without spaces, even over stepped surfaces, through a shaping process that fits the adhesive sheet's bonding surface to the adherend's surface shape, preventing gaps and enhancing step followability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a planar adhesive sheet is used on a stepped surface, then the adhesive sheet can be easily manufactured and applied, but gaps occur between the adhesive sheet and the stepped surface leading to visibility deterioration, foaming, and peeling
Solution Approach 1:
The adhesive sheet is pre-shaped to match the stepped surface configuration before bonding. The shaping process creates protrusions and recessions that correspond to the steps on the surface, allowing the adhesive sheet to make close contact with the entire stepped surface without gaps when bonded.
Solution Approach 2:
The adhesive sheet is transformed from a planar shape to a curved three-dimensional shape that conforms to the stepped surface. The shaping process creates non-planar surfaces with varying elevations that match the stepped topology, enabling complete surface contact.
2Adaptability or versatility
If the adhesive sheet is made flexible to follow surface steps, then step followability improves, but foaming and peeling occur under temperature and humidity changes
Solution Approach 1:
The adhesive sheet is pre-shaped to exactly match the stepped surface configuration before bonding. This preliminary shaping eliminates the need for the adhesive sheet to flex or deform after bonding, maintaining dimensional stability under temperature and humidity changes while still achieving complete step followability.
Solution Approach 2:
The adhesive sheet is shaped to create a precise copy or replica of the stepped surface topology. By copying the exact geometry of the steps, the adhesive sheet achieves perfect fit without requiring flexibility, thereby maintaining bonding reliability under environmental variations.
3Object-generated harmful factors
If liquid adhesive is used to fill gaps, then resin sealing is achieved, but in-plane thickness accuracy is poor and uncured resin contaminates electrodes
Solution Approach 1:
The invention uses a disposable adhesive sheet that is pre-shaped to fit the stepped surface. This eliminates the need for liquid adhesive application and curing processes, avoiding thickness control issues and contamination risks while achieving complete gap filling through the pre-formed shape.
Solution Approach 2:
The invention replaces the chemical process of liquid adhesive flow and curing with a mechanical solution of pre-shaped adhesive sheet placement. The mechanical shaping achieves gap filling without the need for resin flow, eliminating thickness control problems and contamination risks associated with liquid adhesive.
4Ease of manufacture
If thermoplastic adhesive sheet material is heated to seal gaps, then bonding is achieved, but resin overflow and residual stress occur
Solution Approach 1:
The invention replaces the thermal process of heating and melting thermoplastic adhesive with a mechanical cold-bonding process. The pre-shaped adhesive sheet achieves gap sealing through its geometry without requiring heat, thereby eliminating resin overflow and thermal stress issues.
Solution Approach 2:
The invention uses a disposable pre-shaped adhesive sheet that achieves bonding without thermal processing. This eliminates the need for heating equipment and the associated problems of resin overflow and residual stress, simplifying the manufacturing process.
Data Source
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AI summary
Provided is a novel double-sided adhesive sheet for image display device which can be bonded to the adhesion surface in close contact without space therebetween although there is a step due to printing or the like on the adhesion surface to be bonded to the adhesive sheet. The double-sided adhesive sheet for image display device 1 of the invention is a sheet to bond any two adherends selected from a surface protective panel 2, a touch panel 3, and an image display panel, and the sheet is characterized in that at least one of the adherends (surface protective panel 2) has a stepped portion 2b on an adhesion surface 2a to adhere to the double-sided adhesive sheet 1 and the surface shape of the bonding surface 1a of the double-sided adhesive sheet 1 to be bonded to the adhesion surface 2a is shaped in accordance with the surface shape of the adhesion surface 2a.