US-12617985-B2 - Pressure-sensitive adhesive sheet and use thereof

US12617985B2US 12617985 B2US12617985 B2US 12617985B2US-12617985-B2

Abstract

Provided is a PSA sheet that can combine bonding reliability and peeling removability, and further can be peeled off without causing deformation or damage to the adherend in various peeling modes. The PSA sheet provided by this invention has a PSA layer. The PSA sheet has a water-peel strength of 2 N/10 mm or less. The PSA sheet further has a stress at 100% elongation of less than 30 MPa as well as a multiplication product (σf·εf) of fracture stress σf(MPa) and fracture strain εf (%) of 250 or greater.

Inventors

Yosuke Shimizu
Naofumi Kosaka
Ryoko Asai
Kenta KUMAKURA

Assignees

NITTO DENKO CORPORATION

Dates

Publication Date: 20260505
Application Date: 20210224
Priority Date: 20200228

Claims (7)

1 . A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet having a water-peel strength of 2 N/10 mm or less, determined after the adhesive face of the pressure-sensitive adhesive layer is applied to the surface of an alkaline float glass plate adherend having a contact angle of 5° to 10° with distilled water, the resultant is stored at room temperature for one day, 20 μL of distilled water is dropped onto the adherend and the distilled water is allowed to enter an interfacial edge between the adhesive face and the adherend; according to JIS Z0237: 2009 “10.4.1 Method 1: 180° Peel Strength to Test Plate”; specifically, at a test temperature of 23° C. at a tensile speed of 300 mm/min at a peel angle of 180° using a tensile tester; and further having a stress at 100% elongation of less than 30 MPa as well as a multiplication product (σf·εf) of fracture stress σf(MPa) and fracture strain εf (%) of 250 or greater, wherein the stress at 100% elongation, the fracture stress σf and the fracture strain εf are determined based on a tensile test carried out at a tensile speed of 100 mm/min.
2 . The pressure-sensitive adhesive sheet according to claim 1 , having a normal peel strength of 2.5 N/10 mm or greater and 15 N/10 mm or less, determined after the adhesive face of the pressure-sensitive adhesive layer is applied to the surface of an alkaline float glass plate adherend having a contact angle of 5° to 10° with distilled water, according to JIS Z0237: 2009 “10.4.1 Method 1:180° Peel Strength to Test Plate,” specifically, at a test temperature of 23° C. at a tensile speed of 300 mm/min at a peel angle of 180° using a tensile tester.
3 . The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive layer is formed from a water-dispersed pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, an active energy ray-curable pressure-sensitive adhesive composition or a hot-melt pressure-sensitive adhesive composition.
4 . The pressure-sensitive adhesive sheet according to claim 1 , wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer.
5 . The pressure-sensitive adhesive sheet according to claim 1 , that is formed as an adhesively double-faced pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer constitutes at least one adhesive face of the pressure-sensitive adhesive sheet.
6 . The pressure-sensitive adhesive sheet according to claim 5 , having first and second pressure-sensitive adhesive layers, each as the pressure-sensitive adhesive layer; and further having a middle layer placed between the first and second pressure-sensitive adhesive layers.
7 . The pressure-sensitive adhesive sheet according to claim 6 , wherein the middle layer is formed of a material comprising an acrylic resin, a polyurethane-based resin, a urethane (meth)acrylate-based polymer, a polyolefinic resin, a polyvinyl chloride-based resin, a silicone, a rubber or an elastomer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a National Stage of International Application No. PCT/JP2021/006816, filed on Feb. 24, 2021, which designates the United States and was published in Japan, and which claims priority to Japanese Patent Application No. 2020-034310, filed on Feb. 28, 2020 in the Japan Patent Office. All of the aforementioned applications are hereby incorporated by reference in their entireties. TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet, a method for peeling a pressure-sensitive adhesive sheet, and a method for separating two adherends joined with a pressure-sensitive adhesive sheet. The present application claims priority to Japanese Patent Application No. 2020-34310 filed on Feb. 28, 2020; and the entire content thereof is incorporated herein by reference. BACKGROUND ART In general, pressure-sensitive adhesive (PSA) exists as a soft solid (a viscoelastic material) in a room temperature range and has a property to adhere easily to an adherend with some pressure applied. For such a property, PSA has been widely used in various fields as an on-support PSA sheet having a PSA layer on a support or as a support-less PSA sheet free of a support. Technical documents about PSA sheets include Patent Documents 1 and 2. Patent Document 2 relates to a substrate-supported PSA sheet that can be removed by pulling. CITATION LIST Patent Literature [Patent Document 1] Japanese Patent Application Publication No. 2020-23656 [Patent Document 2] Japanese Patent Application Publication No. 2016-8288 SUMMARY OF INVENTION Technical Problem Various properties are required of PSA depending on the purposes. Among these properties, some are difficult to simultaneously achieve at a high level such that in improving a certain property, some other property has a tendency to decrease. One example of a set of properties in a trade-off relationship is adhesive strength to adherend and removability. For instance, after an adherend is fixed using a PSA sheet, for removal of the PSA sheet from the adherend, in order to prevent damage and deformation to the adherend, it may be necessary that, in contrast to when fixed, the PSA sheet's peel strength (adhesive strength) on the adherend) be lowered. For instance, when the adherend is fragile or thin, it is not easy to obtain a PSA sheet having both good removability and high adhesive strength. PSA sheets with good removability can be preferably used in various applications for their excellent reworkability, recyclability and repairability. The term rework here refers to, for instance, removal of PSA sheets from adherends when their applications to adherends result in failures (shifting, wrinkling, bubble formation, trapping of foreign material, etc.) and removal (or disassembly) of PSA sheets from adherends when defects are found after their applications, typically referring to reapplication of PSA sheets using the removed original PSA sheets or new PSA sheets. The term recycle refers to making adherends removed from PSA sheets available for reuse and encompasses reuse here. As for products that use PSA sheets to fix parts and the like, when they are in hands of users and reach the end of the product life cycle, in view of effective resource utilization, environmental impact reduction, etc., it would be significant if the respective parts can be disassembled for reuse without damage to the parts or leftover PSA sheets. The term repair refers to replacement, repair and examination of failed parts when there are problems such as parts failure. It would be beneficial if parts fixed with PSA sheets can be separated and subjected to replacement, repair and examination, for it leads to user-cost reduction and environmental impact reduction. With respect to such issues, in Patent Document 1, the present inventors have suggested a novel PSA sheet (water-peelable PSA sheet) that allows easy peeling with an aqueous liquid such as water and has highly reliable water resistance during bonding. This invention relates to an improvement in the water-peelable PSA sheet with an objective to provide a PSA sheet that can combine bonding reliability with removability and further that can be removed in various removal modes (e.g., after joining a low-strength rigid adherend such as a glass plate, removal from the adherend) without causing deformation or damage to the adherend. Other objectives of this invention are to provide novel methods for removal and adherend separation, using PSA sheets. Solution to Problem This description provides a PSA sheet having a PSA layer. The PSA sheet according to a first aspect has a water-peel adhesive strength of 2 N/10 mm or less, determined after the adhesive face of the PSA layer is applied to the surface of an alkaline float glass plate adherend having a contact angle of 5° to 10° with distilled water, the resultant is stored at room temperature for one day, 20 μL of distilled water is dropped ont