Laminate comprising multilayer adhesive layer, use of same, and production methods

Abstract

[Problem] The purpose of the present invention is to provide an easily releasable laminate, which has a low release strength and is not susceptible to problems of breakage and unevenness of an adhesive surface, without impairing the functions such as heat resistance derived from a silicone adhesive layer. [Solution] The present invention provides: a laminate having a structure in which a multilayer adhesive layer that comprises two or more adhesive layers is sandwiched between two release layers, wherein at least one layer of the multilayer adhesive layer is a silicone adhesive layer, and an adhesive layer that is in contact with at least one of the release layers is a non-silicone adhesive layer; a use of the multilayer adhesive layer as an elastic adhesive member; an electronic component or a display device comprising the same; and production methods of those.

Description

Laminates containing multiple pressure-sensitive adhesive layers, their use and manufacturing methods

[0001] The present invention relates to a peelable laminate that includes a multilayer pressure-sensitive adhesive layer composed of silicone-based and non-silicone-based pressure-sensitive adhesive layers, is easily peelable, can expose the pressure-sensitive adhesive layer with a low peel force, and provides a multilayer pressure-sensitive adhesive layer that has excellent electrical insulation, heat resistance, cold resistance, adhesion to various substrates, and, if necessary, transparency, without impairing the functionality of the pressure-sensitive adhesive layer, a method for producing the same, and uses thereof in electronic components or display devices (including flexible displays, touch panels, etc.). Note that the release layer in the present invention may be a release layer with reduced peel resistance without using a fluorine-containing compound, making it possible to realize a peelable laminate that does not contain PFAS (perfluoroalkyl substances).

[0002] Silicone-based pressure-sensitive adhesive compositions, compared to acrylic or rubber-based non-silicone pressure-sensitive adhesive compositions, are superior in electrical insulation, heat resistance, cold resistance, adhesion to various substrates, and transparency as needed, and therefore addition reaction curing pressure-sensitive adhesive compositions are widely used. In particular, in recent material development, there has been an increasing demand for silicone-based optically clear adhesives (hereinafter sometimes referred to as "OCA"). Silicone-based OCAs have sufficient adhesive strength for practical use, are flexible and highly deformable, and have excellent heat resistance, cold resistance, and light resistance. They are less likely to cause coloration or discoloration of the OCA layer, and show little change in the physical properties of the OCA layer, such as adhesive strength, storage modulus (e.g., shear storage modulus G'), and hardness. Therefore, they are expected to be used in applications such as bonding or sealing display devices that are expected to be folded or deformed to a certain extent, such as curved displays and flexible displays used over a wide temperature range, including as low as -20°C (e.g., Patent Documents 1 and 2). Furthermore, the present applicants have proposed several organopolysiloxane compositions capable of forming pressure-sensitive adhesive layers, which have different adhesive strengths for adhesive layers obtained by curing and different storage moduli at low to room temperature, to suit applications such as display devices (Patent Documents 3 to 10). It has also been proposed that silicone or non-silicone adhesive layers (single layer or multilayer) be sandwiched between film or sheet-like members (so-called release liners) with release surfaces, and used or distributed as release laminates, for use in bonding or assembling electronic components or display devices (Patent Document 11).

[0003] On the other hand, when forming a silicone-based adhesive layer to obtain a release laminate such as a double-sided pressure-sensitive adhesive sheet product, it is common to coat a liquid pressure-sensitive adhesive layer-forming organopolysiloxane composition on a first release liner, cure it, obtain a film- or sheet-like adhesive layer, and then laminate a second release liner to the cured adhesive layer. However, because silicone-based adhesive layers are formed by a curing reaction such as a hydrosilylation reaction, the interaction between the release surface of the first release liner (on which the liquid composition is coated) and the cured adhesive layer tends to be strong. This may require a strong peel force when peeling the release liner to expose the adhesive layer during the assembly process, or the surface of the adhesive layer may be damaged or uneven after peeling, thereby impairing its performance as an elastic adhesive member. For this reason, in the above-mentioned Patent Documents 3 to 10, the applicants have also proposed optimizing the release coating agent used on the release surface, but there is still room for improvement in terms of reducing peel resistance and achieving a low peel force. Furthermore, in recent years, organic fluorine compounds such as PFAS (perfluoroalkyl substances) have become subject to chemical substance regulations due to their persistence in the environment. Therefore, there is a demand in the market for the design of peelable laminates that do not use such fluorine-containing compounds and that do not impair the functionality and properties of the silicone-based adhesive layer.

[0004] On the other hand, while Patent Documents 12 to 14 propose a two-layered silicone or non-silicone adhesive layer, they do not describe or suggest a release laminate having a structure in which a multilayered adhesive layer consisting of two or more adhesive layers is sandwiched between two release layers. Furthermore, these documents do not describe or suggest the technical problem of designing a release laminate with the low release force necessary to expose a silicone-based adhesive layer formed by curing a liquid organopolysiloxane composition capable of forming a pressure-sensitive adhesive, thereby reducing the interaction between the silicone-based adhesive layer and the release layer during the curing reaction. Furthermore, these documents do not describe or suggest at all about providing a release laminate, particularly a PFAS-free release laminate, with low release force without significantly impairing the functional characteristics of a silicone-based adhesive layer that has electrical insulation, heat resistance, and cold resistance, and that exhibits strong adhesive strength as needed, and whose physical properties, such as storage modulus (e.g., shear storage modulus G') and hardness, are resistant to change at low temperatures.

[0005] Japanese Patent Publication No. 2019-528330 Japanese Patent Publication No. 2019-527745 International Patent Publication No. WO2017 / 188308 International Patent Publication No. WO2020 / 032285 International Patent Publication No. WO2020 / 032286 International Patent Publication No. WO2020 / 032287 International Patent Publication No. WO2021 / 029412 International Patent Publication No. WO2021 / 029413 International Patent Publication No. WO2021 / 029414 International Patent Publication No. WO2022 / 138913 Japanese Patent Application Laid-Open No. 2004-197089 Japanese Patent Application Laid-Open No. 05-17725 Japanese Patent Application Laid-Open No. 2004-231723 U.S. Patent Publication No. 6,521,309

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a release laminate that is easily peelable and has low peel strength, is less likely to cause problems such as damage or unevenness of the adhesive surface, and is less likely to occur due to reduced peel resistance between the silicone-based pressure-sensitive adhesive layer and the release layer, in particular, without impairing the functions inherent in the silicone-based pressure-sensitive adhesive layer, such as heat resistance. Another aim of the present invention is to provide a method for producing and use of the release laminate. The objectives of the present invention preferably include providing a PFAS-free release laminate.

[0007] The present inventors have intensively studied the above-mentioned problems and have arrived at the present invention. That is, one object of the present invention is achieved by a laminate having a structure in which a multilayer pressure-sensitive adhesive layer consisting of two or more pressure-sensitive adhesive layers is sandwiched between two release layers, at least one of the multilayer pressure-sensitive adhesive layers being a silicone-based pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer in contact with at least one of the release layers being a non-silicone-based pressure-sensitive adhesive layer, and at least one of the release layers may be a release layer that does not contain a fluorine atom-containing organic group. Similarly, the above-mentioned problem can be achieved by the use of the multilayer pressure-sensitive adhesive layer constituting the peelable laminate as an elastic pressure-sensitive adhesive member, or as a member for an electronic material or display device, or by an electronic component or display device including the same, or a method for producing the same.

[0008] The above-mentioned object is also achieved by a method for producing a laminate, which comprises the steps of forming a non-silicone pressure-sensitive adhesive layer on a film substrate having a first release layer, applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition to the non-silicone pressure-sensitive adhesive layer obtained in the above step and curing the composition to form a silicone pressure-sensitive adhesive layer, and laminating a film substrate having a second release layer onto the silicone pressure-sensitive adhesive layer or onto a pressure-sensitive adhesive layer further laminated thereon, so that the second release layer faces the pressure-sensitive adhesive layer. Note that another pressure-sensitive adhesive layer may be formed on the second release layer, and the peelable laminate of the present invention can also be obtained by the step of laminating the pressure-sensitive adhesive layers formed on the first and second release layers so that they face each other.

[0009] The present invention provides an easily peelable laminate and a method for producing the same, in which the peel resistance between the multilayer pressure-sensitive adhesive layer (preferably including a silicone-based pressure-sensitive adhesive layer formed by coating and curing a liquid organopolysiloxane composition capable of forming a pressure-sensitive adhesive layer) and the release layer is reduced without impairing the functionality inherent in the silicone-based pressure-sensitive adhesive layer that constitutes the multilayer pressure-sensitive adhesive layer, the laminate has a low peel force, and the performance as an elastic pressure-sensitive adhesive member is not impaired when the release layer is removed, and the multilayer pressure-sensitive adhesive layer obtained by removing the release layers from both sides of the multilayer pressure-sensitive adhesive layer can be used as an elastic pressure-sensitive adhesive member for electronic devices or electrical devices. Furthermore, since a release layer that does not contain a fluorine atom-containing organic group can be suitably used as the release layer according to the present invention, a PFAS-free peelable laminate can be provided.

[0010] Furthermore, by using the laminate according to the present invention, even elastic PSA members comprising a PSA layer, which, when used as a single silicone-based PSA layer, have been difficult to distribute as part of a peelable laminate due to their strong interaction with the release layer and excessively high peel resistance, can be incorporated into the peelable laminate according to the present invention in the form of a multilayer PSA layer. This makes it possible to design elastic PSA members with improved physical properties such as adhesive strength, storage modulus (e.g., shear storage modulus G'), and hardness, compared to conventional elastic PSA members comprising only a silicone-based PSA layer, without the problems of damage or non-uniformity of the adhesive surface or poor peeling during removal of the release layer, and these can be distributed on the market in the form of easily peelable laminates with low peel strength.

[0011] 1 to 4 are diagrams showing the structure of a peelable laminate having a multilayer pressure-sensitive adhesive layer according to the present invention.

[0012] [Configuration of Laminate] The laminate of the present invention is a peelable laminate having a structure in which a multilayer pressure-sensitive adhesive layer consisting of two or more pressure-sensitive adhesive layers is sandwiched between two release layers, at least one of the multilayer pressure-sensitive adhesive layers being a silicone-based pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer in contact with at least one of the release layers being a non-silicone-based pressure-sensitive adhesive layer. The configuration will be described in detail below.

[0013] The laminate of the present invention has a structure in which a multilayer pressure-sensitive adhesive layer consisting of two or more pressure-sensitive adhesive layers is sandwiched between two release layers. Here, the multilayer pressure-sensitive adhesive layer is configured so that it can be used as an elastic adhesive member, etc., by removing the release layers from both sides thereof. One object of the present invention is to provide an easily peelable laminate that reduces the peel resistance value for a specific multilayer pressure-sensitive adhesive layer, suppresses damage or unevenness of the pressure-sensitive adhesive surface during peeling, and allows the release layers to be removed with low peel force during an assembly process, etc. Here, the release layers in this laminate are positioned opposite both sides of the multilayer pressure-sensitive adhesive layer, and have a structure in which they sandwich the multilayer pressure-sensitive adhesive layer. The material and shape of the substrate having the release layer are not particularly limited, but a flat substrate having a release layer on its surface is preferred, and a film-like substrate selected from known materials such as paper, organic resin film, organic resin sheet, and metal foil is a suitable example. Hereinafter, in the present invention, when the term "film-like substrate" is used, it refers to a substantially flat substrate, excluding fine irregularities that function as a release layer, and a plate-like, sheet-like, or thin film-like substrate with an average thickness of 10,000 μm or less, regardless of the type of substrate. In addition, particularly suitable film-like substrates with a release layer include organic resin films, such as polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polypropylene and polymethylpentene; polycarbonate; and film-like substrates made of thermoplastic resins such as polyvinyl acetate, and the substrate may be continuous or discontinuous. The substrate may be a single layer, or may be a multilayer of two or more layers made of the same or different thermoplastic resins.

[0014] The release layer is preferably a release layer having release coating ability such as a silicone-based release agent, a fluorine-based release agent, an alkyd-based release agent, or a fluorosilicone-based release agent, or it may be a substrate itself that forms physically fine irregularities on the substrate surface or that is difficult to adhere to the multi-layer pressure-sensitive adhesive layer of the present invention. On the other hand, a fluorosilicone-based release agent containing one or more fluorine-containing groups selected from a fluoroalkyl group and a perfluoropolyether group may be used as the release layer to form a release layer that can easily releasably adhere to the multi-layer pressure-sensitive adhesive layer of the present invention, but it is not possible to achieve a PFAS-free release laminate.

[0015] Silicone-based release agents are suitable for use as the release layer in the present invention. Examples of silicone-based release agents include known silicone-based release agents such as addition reaction types including hydrosilylation reactions, condensation reaction types, cationic polymerization types, and radical polymerization types. Examples of commercially available products as addition reaction type silicone-based release agents include DOWSIL™ SRX211, SRX345, SRX357, SD7333, SD7220, SD7223, LTC 300B, LTC 350G, and LTC 310 (manufactured by Dow-Toray Industries, Inc.); KS-776A, KS-847T, KS-779H, KS-837, KS-778, and KS-830 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available products as condensation reaction type release agents include SRX290 and 23 Coating (manufactured by Dow-Toray Industries, Inc.). Examples of commercially available cationic polymerization type products include TPR6501, TPR6500, UV9300, UV9315, and UV9430 (manufactured by Momentive Performance Materials), and X62-7622 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of commercially available radical polymerization type products include X62-7205 (manufactured by Shin-Etsu Chemical Co., Ltd.). In addition, silicone resins (R ３ SiO 1 / 2 Units and SiO 4 / 2 Silicone resins consisting of units), silica, ethyl cellulose, etc. may also be added.

[0016] Among these, addition reaction type silicone release agents that cure via a hydrosilylation reaction are preferred, and solvent-based, solventless, or emulsion-type silicone release agents can be used without any particular restrictions. In addition to these commercially available silicone release agents, the laminate of the present invention can preferably use a specific hydrosilylation reaction curing silicone release agent, which will be described later. The applicants have specifically proposed the use of such silicone release agents and release layers in Japanese Patent Applications 2023-216168 and 2023-216170 and priority applications based thereon. (See Production Example 1 of the present application.)

[0017] [Multilayer Pressure-Sensitive Adhesive Layer] One of the features of the laminate of the present invention is that it comprises a multilayer pressure-sensitive adhesive layer consisting of two or more pressure-sensitive adhesive layers, at least one of which is a silicone-based pressure-sensitive adhesive layer. The multilayer pressure-sensitive adhesive layer can be used as an elastic pressure-sensitive adhesive member having adhesive surfaces exposed on both sides by removing the two release layers. The number of pressure-sensitive adhesive layers constituting the multilayer pressure-sensitive adhesive layer is not particularly limited as long as it is two or more layers, and may be three or more layers, or four or more layers. From an industrial standpoint, it may be 2 to 10 layers, 2 to 7 layers, or 2 to 6 layers.

[0018] At least one layer of the multilayer pressure-sensitive adhesive layer is a silicone-based pressure-sensitive adhesive layer. This is because the silicone-based pressure-sensitive adhesive layer can impart to the multilayer pressure-sensitive adhesive layer electrical insulation, heat resistance, cold resistance, adhesion to various adherends, and transparency as needed, and the multilayer pressure-sensitive adhesive layer as a whole can provide an elastic pressure-sensitive adhesive member with improved physical properties such as adhesive strength, storage modulus, and hardness. If the multilayer pressure-sensitive adhesive layer does not contain a silicone-based pressure-sensitive adhesive layer, the multilayer pressure-sensitive adhesive layer as a whole may not be able to fully achieve the functions and properties required of an elastic pressure-sensitive adhesive member.

[0019] Specifically, the multilayer pressure-sensitive adhesive layer is composed of a silicone-based pressure-sensitive adhesive layer (S) and a non-silicone-based pressure-sensitive adhesive layer (N).The silicone-based or non-silicone-based pressure-sensitive adhesive layers may be the same or different, and the same or different pressure-sensitive adhesive layers may be bonded together.Here, the pressure-sensitive adhesive layers constituting the multilayer pressure-sensitive adhesive layer preferably adhere firmly at their interfaces, and when attempting to peel the pressure-sensitive adhesive layers in contact with each other, it is preferable that the two layers are integrated to such an extent that the peeling mode is not interlayer delamination but cohesive failure.If the pressure-sensitive adhesive layers are not integrated and interlayer delamination is likely to occur between the pressure-sensitive adhesive layers constituting the multilayer pressure-sensitive adhesive layer, the multilayer pressure-sensitive adhesive layer as a whole will not be easily peelable, and the multilayer pressure-sensitive adhesive layer itself may delaminate when the release layer is removed, making it impossible to use as an elastic pressure-sensitive adhesive member.

[0020] The silicone-based pressure-sensitive adhesive layer (S) is a pressure-sensitive adhesive layer whose main constituent is a polysiloxane compound having a siloxane bond or a silicone-hybrid polymer compound. It may be a pressure-sensitive adhesive layer / pressure-sensitive adhesive layer that is a curing reaction product, or may be a pressure-sensitive adhesive layer / pressure-sensitive adhesive layer consisting of a silicone layer containing a polysiloxane bond obtained by drying with solvent removal, but a curing reaction product is particularly preferred. The curing reaction mechanism for obtaining the silicone-based pressure-sensitive adhesive layer is not limited, and examples include addition reaction, condensation reaction, radical reaction with organic peroxide, and radical reaction with UV irradiation. On the other hand, since it cures quickly, the silicone-based pressure-sensitive adhesive layer according to the present invention is preferably a curing reaction product obtained by curing via at least one curing reaction selected from a hydrosilylation curing reaction, a peroxide curing reaction, and a radical curing reaction. In particular, a polysiloxane component having two or more curing reactive groups containing a carbon-carbon double bond (C═C) in the molecule, SiO 4 / 2It is preferable to use a hydrosilylation-curing reactive silicone-based pressure-sensitive adhesive layer-forming composition containing a silicone resin component containing a Q or T unit represented by the following formula: (I) (II), two or more organohydrogenpolysiloxanes as crosslinkers, a hydrosilylation reaction catalyst (preferably containing a platinum-based metal), and other optional additives. The silicone resin component may also contain a condensation reaction product with the polysiloxane component.

[0021] In addition, when the multilayered pressure-sensitive adhesive layer of the present invention contains two or more silicone-based pressure-sensitive adhesive layers, the compositions and curing reaction mechanisms of these silicone-based pressure-sensitive adhesive layers may be the same or different from each other.Furthermore, the multilayered pressure-sensitive adhesive layer may contain two or more silicone-based pressure-sensitive adhesive layers with substantially the same physical properties such as adhesive strength, hardness, storage modulus, etc., or may contain silicone-based pressure-sensitive adhesive layers with different physical properties.Furthermore, the thickness of the two or more silicone-based pressure-sensitive adhesive layers in the multilayered pressure-sensitive adhesive layer is not particularly limited, and may be the same or different.

[0022] The adhesive used to form the silicone-based adhesive layer is not particularly limited in its formulation, and can be one or more curing-reactive silicone adhesive layer-forming compositions selected from the above-mentioned curing mechanisms, and can be any composition selected from solvent-based, solventless, emulsion-based, and hot-melt (heat-melting) types that are solid at room temperature, etc. When two or more silicone-based adhesive layers are formed, compositions of the same or different formulations may be used to form each silicone-based adhesive layer.

[0023] For forming each of these silicone-based pressure-sensitive adhesive layers, commercially available silicone-based pressure-sensitive adhesive products may be used. For example, examples of hydrosilylation curing reactive silicone pressure-sensitive adhesives include DOWSIL™ SD4580PSA, SD4584PSA, SD4585PSA, SD4587LPSA, SD4560PSA, SD4570PSA, SD4600FCA Adhesive, SD4593, SE1700, 2013 ADHESIVE, 2014 ADHESIVE, and 2015 manufactured by Dow-Toray Industries, Inc. Examples of ADHESIVE include those manufactured by Shin-Etsu Chemical Co., Ltd. under the trade names "KR-3700," "KR-3701," "X-40-3237-1," "X-40-3240," "X-40-3291-1," and "X-40-3306." In addition, peroxide-curable silicone-based adhesives (for example, those manufactured by Shin-Etsu Chemical Co., Ltd. under the trade names "KR-100," "KR-101-10," and "KR-130") may also be used. Preferably, those manufactured by Dow-Toray Industries, Inc. may be used under the trade names SD 4580 PSA, SD 4584 PSA, SD 4585 PSA, and SH 4280 PSA.

[0024] Particularly preferably, at least a portion of the silicone-based pressure-sensitive adhesive layer is formed by curing a hydrosilylation-curing reactive organopolysiloxane composition capable of forming a pressure-sensitive adhesive layer, the composition comprising: (A) a linear organopolysiloxane having, on average, more than one alkenyl group per molecule; (B) an organopolysiloxane resin having a sum of hydroxyl and hydrolyzable group contents relative to all silicon atoms per molecule of 9 mol % or less; (C) an organohydrogenpolysiloxane having at least two Si-H bonds per molecule; and (D) an effective amount of a hydrosilylation reaction catalyst. This composition rapidly cures via a curing reaction involving a hydrosilylation reaction to form a silicone-based pressure-sensitive adhesive layer with sufficient adhesive strength for practical use. Furthermore, the pressure-sensitive adhesive layer-forming organopolysiloxane composition may, and preferably does, contain (A') a linear organopolysiloxane having no alkenyl groups or silicon-bonded hydrogen atoms per molecule. Furthermore, the pressure-sensitive adhesive layer-forming organopolysiloxane composition may contain a curing retarder (E) as long as it does not impair the technical effects of the present invention, and may also contain an adhesion promoter and other additives described below as long as it does not contradict the object of the present invention. Patent Documents 3 to 9 propose various forms of such pressure-sensitive adhesive layer-forming organopolysiloxane compositions, each of which differs in the adhesive strength of the adhesive layer obtained by curing and in the storage modulus at low temperatures to room temperature. The hydrosilylation-curing reactive pressure-sensitive adhesive layer-forming organopolysiloxane composition used in the present invention may be heat-curable, or may be cured to form a silicone-based adhesive layer by irradiation with high-energy rays such as ultraviolet rays using a high-energy ray-activated catalyst (also called a photoactivated catalyst) that promotes the hydrosilylation reaction.

[0025] Furthermore, by using, as the main organopolysiloxane resin component in the pressure-sensitive adhesive layer-forming organopolysiloxane composition, an organopolysiloxane resin that contains almost no condensation-reactive functional groups and has a weight-average molecular weight (Mw) of less than 4,000 as measured in terms of standard polystyrene by GPC using toluene, when a specific resin component / polymer component ratio is selected, the pressure-sensitive adhesive layer will have both low-temperature properties, such as a low glass transition point (Tg), and adhesive properties, such as strong adhesive strength, compared to pressure-sensitive adhesive layers with the same glass transition point (Tg) but using other organopolysiloxane resins with a similar composition. As a result, it is easy to achieve a lower Tg and stronger adhesive strength than conventional silicone-based pressure-sensitive adhesive layers, and it is expected that, at a specific resin component / polymer component ratio, it will be possible to provide a silicone-based adhesive layer that has both a low Tg and strong adhesive strength, which was not possible with conventional compositions (see, for example, Patent Document 10).

[0026] In the laminate of the present invention, preferably, in the pressure-sensitive adhesive layer-forming organopolysiloxane composition, at least a portion of component (A) is a crude rubber-like alkenyl group-containing organopolysiloxane having a viscosity of 100,000 mPa·s or more at 25°C or a plasticity in the range of 50 to 200 as measured in accordance with the method specified in JIS K6249, and the content of the alkenyl groups, calculated as vinyl (CH2=CH), is in the range of 0.005 to 0.400 mass%, and component (B) is a linear organopolysiloxane containing R ３ SiO １／２ units (wherein R is a monovalent organic group, and 90 mol % or more of R are alkyl groups or phenyl groups having 1 to 6 carbon atoms; M units) and SiO ４／２Preferably, the organopolysiloxane resin or mixture thereof is essentially composed of units (Q units), and the amount of component (C) is such that the ratio (molar ratio) of the amount of SiH groups in component (C) to the sum of the amounts of alkenyl groups in components (A) and (B) is 0.1 to 100; the amount of component (D) is such that the platinum-based metal content in the solids of the composition is in the range of 0.1 to 200 ppm; and the composition optionally contains one or more members selected from (A') a linear organopolysiloxane that does not have alkenyl groups or silicon-bonded hydrogen atoms in the molecule, (E) a cure retarder, and an adhesion promoter. When such a silicone-based adhesive layer obtained by curing a pressure-sensitive adhesive layer-forming organopolysiloxane composition is used as the main component of the multilayer adhesive layer of the present invention, it is particularly useful in that it has the characteristic of easy peelability for the entire laminate and can provide an elastic adhesive member with improved physical properties such as adhesive strength, storage modulus, and hardness after removal of the release layer.

[0027] The multilayered pressure-sensitive adhesive layer further includes a non-silicone pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer in contact with at least one of the release layers must be a non-silicone pressure-sensitive adhesive layer. Here, the non-silicone pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer that does not contain a siloxane compound or a silicone-hybrid polymer as a main component, and more specifically, may be a non-silicone elastic pressure-sensitive adhesive layer obtained from at least one elastic pressure-sensitive adhesive composition selected from acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, vinyl acetate pressure-sensitive adhesives, styrene-butadiene rubber pressure-sensitive adhesives, and natural rubber pressure-sensitive adhesives, or a cured reaction product thereof, or obtained by drying and solidifying the composition, all of which have a silicon atom content of less than 1.0 mass%, less than 1.5 mass%, or less than 2.0 mass%.

[0028] In the multilayer adhesive layer of the present invention, the non-silicone adhesive layer is preferably at least one adhesive layer selected from acrylic adhesives, epoxy adhesives and urethane adhesives, each having a silicon atom content of less than 1.0 mass%.

[0029] In the laminate of the present invention, the non-silicone pressure-sensitive adhesive layer is a functional layer that, when disposed on the side of at least one release layer, makes the entire multilayer pressure-sensitive adhesive layer, including the silicone pressure-sensitive adhesive layer, easily peelable from the release layer. Silicone pressure-sensitive adhesive layers interact strongly with the surface of the release layer, particularly during their curing reaction, and even when the release layer is optimized, their peel resistance tends to be high. However, by disposing a non-silicone pressure-sensitive adhesive layer such as an acrylic pressure-sensitive adhesive on the side of the release layer and laminating a silicone pressure-sensitive adhesive layer on top of it, the multilayer pressure-sensitive adhesive layer as a whole exhibits easily peelable behavior from the release layer, while imparting to the multilayer pressure-sensitive adhesive layer the electrical insulation, heat resistance, cold resistance, adhesion to various adherends, and transparency as needed, inherent to the silicone pressure-sensitive adhesive layer. In addition, the multilayer pressure-sensitive adhesive layer as a whole can provide an elastic pressure-sensitive adhesive member with improved physical properties such as adhesive strength, storage modulus, and hardness. For this reason, it is preferable that the non-silicone pressure-sensitive adhesive layer in contact with at least one release layer be more easily peelable than the silicone pressure-sensitive adhesive layer. In addition, by optimizing the type and film thickness of the non-silicone pressure-sensitive adhesive layer, it may be possible to improve physical properties such as initial to long-term adhesive strength and adhesive characteristics to the substrate compared to when a silicone-based pressure-sensitive adhesive layer is used alone.

[0030] On the other hand, it is not essential in the present invention that the inner layer of the multilayer pressure-sensitive adhesive layer, i.e., the non-silicone pressure-sensitive adhesive layer that is not in contact with any release layer, be easily releasable, but if a step of temporarily laminating the pressure-sensitive adhesive layer with a film-like substrate having a release layer and removing the release layer when laminating to form a multilayer pressure-sensitive adhesive layer is selected during the manufacturing process, selecting an easily releasable non-silicone pressure-sensitive adhesive layer as the inner layer may enable uniform exposure of the adhesive surface and lamination. On the other hand, if the pressure-sensitive adhesive layer is formed by sequentially coating liquid non-silicone pressure-sensitive adhesives without laminating with a release layer, a non-silicone pressure-sensitive adhesive layer may be selected as the inner layer for the purpose of imparting functionality other than easy releasability.

[0031] One or more of the pressure-sensitive adhesive layers constituting the multilayer pressure-sensitive adhesive layer according to the present invention may optionally contain an tackifier. The type and amount of the tackifier are not limited, and it can be blended into a silicone-based or non-silicone-based pressure-sensitive adhesive layer. For example, it may be blended into a silicone-based pressure-sensitive adhesive layer to improve adhesion with an easily releasable non-silicone pressure-sensitive adhesive layer and achieve good releasability as a whole, or it may be blended into a desired pressure-sensitive adhesive layer to improve adhesion and integrity between pressure-sensitive adhesive layers.

[0032] Examples of adhesion promoters that can be used in the present invention include organosilanes having a trialkoxysiloxy group (e.g., trimethoxysiloxy group, triethoxysiloxy group) or a trialkoxysilylalkyl group (e.g., trimethoxysilylethyl group, triethoxysilylethyl group) and a hydrosilyl group or an alkenyl group (e.g., vinyl group, allyl group), or organosiloxane oligomers having a linear, branched or cyclic structure and about 4 to 20 silicon atoms; organosilanes having a trialkoxysiloxy group or a trialkoxysilylalkyl group and a methacryloxyalkyl group (e.g., 3-methacryloxypropyl group), Silanes or organosiloxane oligomers having a linear, branched, or cyclic structure and having about 4 to 20 silicon atoms; organosilanes or organosiloxane oligomers having a linear, branched, or cyclic structure and having about 4 to 20 silicon atoms, each having a trialkoxysiloxy group or trialkoxysilylalkyl group and an epoxy group-bonded alkyl group (e.g., 3-glycidoxypropyl group, 4-glycidoxybutyl group, 2-(3,4-epoxycyclohexyl)ethyl group, 3-(3,4-epoxycyclohexyl)propyl group); organic compounds having two or more trialkoxysilyl groups (e.g., trimethoxysilyl group, triethoxysilyl group);Examples thereof include reaction products of aminoalkyltrialkoxysilanes and epoxy group-bonded alkyltrialkoxysilanes, and epoxy group-containing ethyl polysilicates. Specific examples thereof include vinyltrimethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, hydrogentriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 1,6-bis(trimethoxysilane), silyl)hexane, 1,6-bis(triethoxysilyl)hexane, 1,3-bis[2-(trimethoxysilyl)ethyl]-1,1,3,3-tetramethyldisiloxane, a reaction product of 3-glycidoxypropyltriethoxysilane and 3-aminopropyltriethoxysilane, a condensation reaction product of a silanol group-blocked methylvinylsiloxane oligomer and 3-glycidoxypropyltrimethoxysilane, a condensation reaction product of a silanol group-blocked methylvinylsiloxane oligomer and 3-methacryloxypropyltriethoxysilane, and tris(3-trimethoxysilylpropyl)isocyanurate;

[0033] The thickness of each pressure-sensitive adhesive layer used in the multilayer pressure-sensitive adhesive layer after curing or drying is 0.1 to 3,000 μm, may be 0.5 to 900 μm, may be 0.5 to 800 μm, and more preferably 0.5 to 200 μm, but is not limited to these. Furthermore, the thickness of the entire multilayer pressure-sensitive adhesive layer obtained by laminating the individual pressure-sensitive adhesive layers depends on the total number of layers, but in the case of a multilayer pressure-sensitive adhesive layer having 2 to 10 layers, it may be 2 to 10,000 μm, 10 to 5,000 μm, or 10 to 2,500 μm. When the multilayer pressure-sensitive adhesive layer according to the present invention is used as an elastic pressure-sensitive adhesive member in the manufacture of an electronic device or electrical device, the thickness of the entire multilayer pressure-sensitive adhesive layer may be in the range of 25 to 1,000 μm.

[0034] The laminate of the present invention aims to achieve easy peelability as a whole multilayer pressure-sensitive adhesive layer while making the most of the functions and properties of the silicone-based pressure-sensitive adhesive layer, so it is generally preferred to adopt a design policy in which a thin, easily peelable non-silicone pressure-sensitive adhesive layer is disposed on the release surface where easy peelability is required, while the main constituent part of the multilayer pressure-sensitive adhesive layer is the silicone-based pressure-sensitive adhesive layer.In particular, a non-silicone pressure-sensitive adhesive layer is disposed on at least one of the release surfaces, preferably on the release layer on the side where the silicone-based pressure-sensitive adhesive layer is formed by applying and curing a precursor composition of the silicone-based pressure-sensitive adhesive layer (for example, the above-mentioned organopolysiloxane composition capable of forming a pressure-sensitive adhesive layer), and the silicone-based pressure-sensitive adhesive layer formed by curing and the release layer are laminated via at least one non-silicone pressure-sensitive adhesive layer.

[0035] As described above, in order to utilize the functions and properties of the silicone-based pressure-sensitive adhesive layer, it is preferable that the pressure-sensitive adhesive layers constituting the multilayer pressure-sensitive adhesive are primarily composed of one or more silicone-based pressure-sensitive adhesive layers. Specifically, the sum of the thicknesses (μm) of the silicone-based pressure-sensitive adhesive layers may be in the range of 50% or more, 55% or more, 60% or more, or 65% or more of the total thickness of the flat multilayer pressure-sensitive adhesive layer, and may be in the range of 99% or less, 95% or less, or 90% or less. This is because, when the thickness is within this range, the properties derived from the silicone-based pressure-sensitive adhesive layer are less likely to be impaired as a whole, and easy peelability can be suitably achieved. Particularly preferred is a pressure-sensitive adhesive layer in which the total thickness of the multilayer pressure-sensitive adhesive layer is in the range of 25 to 1,000 μm, and the sum of the thicknesses (μm) of the silicone-based pressure-sensitive adhesive layers is in the range of 60 to 99%, 60 to 95%, or 60 to 90% of the total thickness. On the other hand, the non-silicone pressure-sensitive adhesive layer may be, and preferably is, thinner than the silicone pressure-sensitive adhesive layer, as long as it can achieve easy releasability from the release layer and can be coated. Specifically, the sum of the thicknesses (μm) of the non-silicone pressure-sensitive adhesive layers may be in the range of 1 to 50% or 5 to 40% of the total thickness of the flat multilayer pressure-sensitive adhesive layer, assuming that the non-silicone pressure-sensitive adhesive layers have one layer in contact with the release layer. If the ratio of non-silicone layers in the entire multilayer pressure-sensitive adhesive layer (i.e., the sum of the thicknesses) exceeds the upper limit, the properties derived from the silicone pressure-sensitive adhesive layer as a whole may be insufficient, while if it is less than the lower limit, it may be impossible to achieve easy releasability, particularly from the release surface.

[0036] As described above, the overall structure of the multilayer adhesive layer includes at least one silicone-based adhesive layer, and as long as the adhesive layer in contact with the release layer (preferably the release layer on the side on which the silicone-based adhesive layer is formed upon curing) is a non-silicone-based adhesive layer, the number of adhesive layers and the thickness of each layer can be appropriately designed depending on the application and performance. To ensure thickness and performance, two or more silicone-based adhesive layers may be laminated directly or via a non-silicone layer. As an example, the following shows an example in which a silicone-based adhesive layer (S) and a non-silicone-based adhesive layer (N) are arranged relative to the release layers (R1, R2). However, the structure of the multilayer adhesive layer and laminate of the present invention is not limited to this. Note that SX... and NX... represent the Xth adhesive layer, based on the release layer R1 on the left, " / " represents the interface of the adhesive layers constituting the multilayer adhesive layer, and "|" represents the interface between the release layer and the multilayer adhesive layer. Furthermore, as described above, the release layers R1 and R2 are generally formed on the film-like substrate. [Examples of laminate and multi-layer pressure-sensitive adhesive layer configurations] R1|N1 / S1|R2 R1|N1 / S1 / N2|R2 R1|N1 / S1 / N2 / S2 / N2|R2 R1|N1 / S1 / S2 / N2|R2

[0037] [Embodiments of Figures 1 to 4] The drawings (Figures 1 to 4) according to the present invention are embodiments of laminates according to the present invention, and the structures of the laminates shown in each figure are as follows. Figure 1: Represents a laminate having a two-layer PSA layer structure in which a non-silicone PSA layer is formed between a silicone-based PSA layer and a release film on the coated side. Figure 2: Represents a laminate having a three-layer PSA layer structure in which a silicone-based PSA layer is positioned in the center and non-silicone PSA layers are positioned on both sides in contact with the release films. Figure 3: Represents a laminate having a five-layer PSA layer structure consisting of a non-silicone, silicone, non-silicone, silicone, and non-silicone PSA layer. Figure 4: Represents a laminate having a four-layer PSA layer structure consisting of a non-silicone, silicone, silicone, and non-silicone PSA layer. Here, in Figures 1 to 4, the release film in contact with the silicone-based pressure-sensitive adhesive layer may be selected from non-fluorine-based release films or fluorine-based release films, and the release film in contact with the non-silicone-based pressure-sensitive adhesive layer may also be selected from non-fluorine-based release films or fluorine-based release films.

[0038] [Use of a silicone-based release layer that does not contain a fluorine atom-containing organic group] In the present invention, when a PFAS-free release laminate is to be achieved, a silicone-based release layer that does not contain a fluorine atom-containing organic group can be selected as at least one layer of the release layer, and in particular, the release layer can be selected from (R-A) a linear organopolysiloxane having an alkenyl group having 2 to 12 carbon atoms, which has a viscosity at 25°C of 1,000,000 mPa·s or more or has a plasticity at 25°C, (R-B) a viscosity at 25°C of 500,000 mPa·s or more or a plasticity at 25°C, and optionally (R-C) an alkenyl-free linear organopolysiloxane having a viscosity of less than 500,000 mPa s at 25°C, (R-D) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (Si-H) per molecule, and (R-E) a cured product obtained by curing a hydrosilylation reaction catalyst. Such curable organopolysiloxane compositions capable of forming a release layer and laminates using the same as a release layer are proposed by the applicants in Japanese Patent Applications 2023-216168 and 2023-216170 and priority applications based thereon.

[0039] Specifically, the curable organopolysiloxane composition capable of forming the release layer of the present invention preferably consists only of components that do not contain fluorine atom-containing organic groups, and contains, relative to 100 parts by mass of the aforementioned component (R-A), 5 to 80 parts by mass of component (R-B), 0 to 20 parts by mass of component (R-C), an amount of component (R-D) such that the molar ratio of silicon-bonded hydrogen atoms in component (R-D) to alkenyl groups in component (R-A) is 0.5 to 10.0, and a catalytic amount of component (R-E) (= an amount such that the weight of platinum group metal atoms, relative to the total amount, is preferably 1.0 to 1,000 ppm by mass), and may optionally contain a cure retarder and an organic solvent, and may also contain other optional additives as long as they do not contradict the objectives of the present invention.

[0040] The curable organopolysiloxane composition can be used as the release layer of the present invention by curing it using a known method. Specifically, the composition is uniformly applied to the film-like substrate, and then heated, irradiated with high-energy radiation (e.g., ultraviolet light, electron beams, etc.), or a combination of these, under conditions sufficient to crosslink components (R-A) to (R-D) via a hydrosilylation reaction. This allows the formation of a release layer (cured release layer) on the surface of the substrate, consisting of a cured silicone coating (cured organopolysiloxane coating). This release layer has the advantage of having lower peel resistance than silicone-based or non-silicone pressure-sensitive adhesive layers, making it easier to design PFAS-free, easily peelable laminates.

[0041] In the laminate of the present invention, the thickness of the silicone-based release layer is not particularly limited, but is preferably 2.0 μm or less, 1.0 μm or less, 0.5 μm or less, 0.4 μm or less, or 0.3 μm or less. The thickness of the release layer is preferably 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. When the thickness of the release layer is within the above range, the peel resistance of the release layer from the pressure-sensitive adhesive layer can be reduced.

[0042] [Use of multilayer pressure-sensitive adhesive layer as elastic pressure-sensitive adhesive member] The laminate of the present invention is an easily peelable laminate having a structure in which the multilayer pressure-sensitive adhesive layer is sandwiched between two release layers. By removing the two release layers, the multilayer pressure-sensitive adhesive layer having pressure-sensitive adhesive layers on both sides is exposed, and the laminate can be suitably used as an elastic pressure-sensitive adhesive member for use in assembling, laminating, etc. electronic devices or electrical devices. In this case, at least one of the release layers constituting the laminate is in contact with a non-silicone pressure-sensitive adhesive layer, and therefore the pressure-sensitive adhesive layer on at least one side of the multilayer pressure-sensitive adhesive layer is a non-silicone pressure-sensitive adhesive layer. The multilayer pressure-sensitive adhesive layer of the present invention may have non-silicone pressure-sensitive adhesive layers on both sides, or one side may be a non-silicone pressure-sensitive adhesive layer while the other side is a silicone pressure-sensitive adhesive layer. As an example, a non-silicone adhesive layer can be placed only on the release layer on the side of the film substrate to which an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition is applied and cured, and a film substrate having a release layer can be directly laminated onto the cured silicone adhesive layer, thereby enabling the design of a two-layer adhesive layer having a non-silicone adhesive layer and a silicone adhesive layer on both sides.

[0043] The multilayer pressure-sensitive adhesive layer of the present invention is easily peelable from the release layer, has a uniform adhesive surface, and is resistant to damage during peeling. It can also be designed to combine the heat resistance, cold resistance, and other properties inherent in the silicone-based pressure-sensitive adhesive layer with viscoelastic properties and adhesive strength, making it useful as an elastic pressure-sensitive adhesive member for various electronic devices or electrical devices. It is particularly useful as an electronic material, a display device component, or a transducer component (including sensors, speakers, actuators, and generators), and the cured product is preferably used as a component for electronic components or display devices. The multilayer pressure-sensitive adhesive layer of the present invention may be transparent or opaque. A substantially transparent multilayer pressure-sensitive adhesive layer is particularly suitable as a display panel or display component, and is particularly useful for so-called touch panel applications in which devices, particularly electronic devices, can be operated by touching the screen with a fingertip or the like. Opaque multilayer pressure-sensitive adhesive layers are also particularly useful for film- or sheet-like components used in sensors, speakers, actuators, and the like, where transparency is not required and a certain degree of stretchability or flexibility is required for the pressure-sensitive adhesive layer itself.

[0044] The multilayer pressure-sensitive adhesive layer obtained by removing the two release layers from the easily peelable laminate of the present invention can achieve pressure-sensitive adhesive properties equivalent to those of conventional silicone pressure-sensitive adhesive layers, and can improve adhesion to substrates such as display devices without causing problems such as poor curing or reduced curing properties. For example, the multilayer pressure-sensitive adhesive layer can be used in the same applications as those described in Patent Documents 1 to 10, replacing part or all of the silicone-based pressure-sensitive adhesive or pressure-sensitive adhesive layer.

[0045] [Display Panel or Display Member] An elastic adhesive member comprising a multilayer adhesive layer obtained by removing two release layers from the laminate of the present invention can be used in the construction and use of a laminate touch screen or flat panel display, and its specific use method can be any known method for using a pressure-sensitive adhesive layer (especially a silicone PSA) without any particular restrictions. In particular, the multilayer adhesive layer obtained by removing two release layers from a laminate obtained or designed using the present invention can be designed to have both a low Tg and strong adhesive strength. Display devices having this multilayer adhesive layer between components can be widely used in flexible displays, specifically, curved displays used in car or airplane seats, foldable displays in which digital displays are folded in two or three, etc., deformable displays in which the entire display surface can be rolled or folded in any direction for storage, and deformable displays in which the entire display surface can be stretched (especially stretched) in any direction, and can improve their durability and reliability.

[0046] In addition, the multilayer pressure-sensitive adhesive layer obtained by removing the two release layers from the laminate of the present invention can be used in the manufacture of display devices such as touch panels, similar to the optically transparent silicone-based pressure-sensitive adhesive films or pressure-sensitive adhesive layers disclosed in the above-mentioned JP-T No. 2014-522436 or JP-T No. 2013-512326, etc. Specifically, the male adhesive member comprising the above-mentioned multilayer pressure-sensitive adhesive layer can be used, without particular limitation, as the pressure-sensitive adhesive layer or pressure-sensitive adhesive film described in JP-T No. 2013-512326.

[0047] As an example, the touch panel according to the present invention may be a touch panel including a substrate such as a conductive plastic film having a conductive layer formed on one surface thereof, and an elastic adhesive member made of the multilayer pressure-sensitive adhesive layer attached to the side on which the conductive layer is formed or the side opposite the conductive layer. The substrate is preferably a sheet-like or film-like substrate, and examples thereof include a resin film or a glass plate. The conductive plastic film may be a resin film or a glass plate, particularly a polyethylene terephthalate film, having an ITO layer formed on one surface thereof. These are disclosed in the aforementioned JP-A-2013-512326 and the like.

[0048] In addition, the elastic adhesive member comprising the multilayer pressure-sensitive adhesive layer may be used as an adhesive film for a polarizing plate used in the manufacture of a display device such as a touch panel, or may be used as a pressure-sensitive adhesive layer used for bonding between a touch panel and a display module as described in JP 2013-065009 A.

[0049] [Method for producing a laminate] The method for producing a laminate according to the present invention is not particularly limited, but from the viewpoint of suppressing the peel resistance resulting from the strong interaction between the silicone-based adhesive layer and the release layer, which comprises a step of applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition onto the release layer and curing it, a preferred method for producing a laminate comprises a step of forming a non-silicone-based adhesive layer on a film-like substrate having a first release layer (R1), a step of applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition onto the non-silicone-based adhesive layer obtained in this step and curing it to form a silicone-based adhesive layer, and a step of laminating a film-like substrate having a second release layer onto the silicone-based adhesive layer or an adhesive layer further laminated thereon so that the second release layer (R2) faces the adhesive layer. Note that another adhesive layer may be formed on the second release layer, and the peelable laminate according to the present invention can also be obtained by a step of laminating the adhesive layers formed on the first release layer and the second release layer so that they face each other.

[0050] More specifically, the laminate according to the present invention can be obtained by a production method comprising: step (I): forming a non-silicone pressure-sensitive adhesive layer on a film-like substrate having a first release layer (R1); step (II): applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition onto the non-silicone pressure-sensitive adhesive layer obtained in step (I) and curing it to form a silicone pressure-sensitive adhesive layer; and step (III): laminating a film-like substrate having a second release layer (R2) onto the silicone pressure-sensitive adhesive layer obtained in step (II) or onto one or more pressure-sensitive adhesive layers further laminated on the silicone pressure-sensitive adhesive layer obtained in step (II), so that the second release layer faces the pressure-sensitive adhesive layer.

[0051] As described above, when the structure of the laminate obtained by this manufacturing method is expressed using R1, R2, SX, NX, | and / , R1|N1 is formed in step (I), and in step (II) R1|N1 / S1 or, optionally, any other optional adhesive layer ([A1], any single-layer or multi-layer adhesive layer) is formed on S1 to form R1|N1 / S1 / [A1], and then a release film is attached in step (III) to obtain a laminate represented by R1|N1 / S1|R2 or R1|N1 / S1 / [A1]|R2.

[0052] Similarly, the laminate according to the present invention can be obtained by a production method comprising: step (I): a step of forming a non-silicone pressure-sensitive adhesive layer on a film-like substrate having a first release layer; step (II): a step of applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition on a film-like substrate having a second release layer and curing it to form a silicone pressure-sensitive adhesive layer; and step (III): a step of laminating the non-silicone pressure-sensitive adhesive layer obtained in step (I) or one or more pressure-sensitive adhesive layers further laminated thereon, and the silicone pressure-sensitive adhesive layer obtained in step (II) or one or more pressure-sensitive adhesive layers further laminated thereon, so as to face each other.

[0053] The laminate obtained by this manufacturing method, similarly to the above, when the laminate configuration is expressed using R1, R2, SX, NX, |, / , and any single-layer or multi-layer optional pressure-sensitive adhesive layer [AX], is obtained by forming R1|N1 in step (I), forming S1|R2 in step (II), and bonding the N1 and S1 surfaces together in step (III) to obtain a laminate represented by R1|N1 / S1|R2. Furthermore, after step (I) or step (II), an optional pressure-sensitive adhesive layer AX may be formed on N1 or S1 and then bonded together, in which case a laminate represented by R1|N1 / [A1] / S1|R2 or R1|N1 / [A1] / [A2] / S1|R2 is obtained.

[0054] Similarly, the laminate according to the present invention can be obtained by a production method comprising: step (I): a step of forming a non-silicone pressure-sensitive adhesive layer on a film-like substrate having a first release layer; step (II): a step of forming a non-silicone pressure-sensitive adhesive layer on a film-like substrate having a second release layer; step (III): a step of applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition onto the non-silicone pressure-sensitive adhesive layer obtained by at least one of step (I) or step (II) and curing it to form a silicone pressure-sensitive adhesive layer; and step (IV): a step of laminating, after step (III), one or more pressure-sensitive adhesive layers formed on the film-like substrate having the first release layer and one or more pressure-sensitive adhesive layers formed on the film-like substrate having the second release layer so that they face each other.

[0055] The laminate obtained by this manufacturing method, similarly to the above, when the laminate configuration is expressed using R1, R2, SX, NX, |, / , and any single or multiple adhesive layer [AX], forms R1|N1 in step (I), forms N2|R2 in step (II), forms at least one or both of R1|N1 / S1 and S1 / N2|R2 in step (III), and then bonds the adhesive surfaces of each layer together in step (IV) to obtain a laminate represented by R1|N1 / S1 / N2|R2 or R1|N1 / S1 / S2 / N2|R2. Furthermore, after step (III), an optional adhesive layer [AX] may be formed on each adhesive surface, and these adhesive layers may be bonded together in step (IV), in which case a laminate represented by any of R1|N1 / S1 / [A1] / N2|R2, R1|N1 / S1 / [A1] / [A2] / N2|R2, R1|N1 / S1 / [A1] / S2 / N2|R2 and R1|N1 / S1 / [A1] / [A2] / S2 / N2|R2 is obtained.

[0056] The single-layer or multi-layer optional pressure-sensitive adhesive layer [AX] may be a silicone-based pressure-sensitive adhesive layer or a non-silicone-based pressure-sensitive adhesive layer. For example, in a laminate represented by R1|N1 / S1 / [A1] / S2 / N2|R2, if [A1] is a single-layer silicone-based pressure-sensitive adhesive layer (S3), the laminate is a laminate represented by R1|N1 / S1 / S3 / S2 / N2|R2 having a partial structure in which three silicone-based pressure-sensitive adhesive layers are laminated. Similarly, if [A1] is a single-layer non-silicone pressure-sensitive adhesive layer (N3), the laminate is a laminate represented by R1|N1 / S1 / N3 / S2 / N2|R2 having a partial structure in which a non-silicone pressure-sensitive adhesive layer is laminated between two silicone-based pressure-sensitive adhesive layers.

[0057] The method for producing the laminate may include a step of laminating a film-like substrate having another release layer on the pressure-sensitive adhesive layer formed in the intermediate step. The film having the other release layer may be disposed for the purpose of curing the pressure-sensitive adhesive layer and protecting it during transportation or storage, and is peeled off and removed from the surface of the pressure-sensitive adhesive layer in a later step.

[0058] More specifically, the method for producing a laminate according to the present invention may include the steps of: after or during the formation of the pressure-sensitive adhesive layer in the above-mentioned step, laminating a film-like substrate having a release layer that does not fall under either a film-like substrate having a first release layer or a film-like substrate having a second release layer to the surface of the pressure-sensitive adhesive layer; and, after peeling the film-like substrate having the release layer from the surface of the pressure-sensitive adhesive layer, laminating the pressure-sensitive adhesive layer or a pressure-sensitive adhesive layer further laminated thereon to another pressure-sensitive adhesive layer or another release layer so that they face each other.

[0059] The laminate according to the present invention can be suitably produced by using any of the above-mentioned production methods. Here, the film-like substrate provided with a release layer is as already explained, and from the viewpoint of designing a PFAS-free peelable laminate, an organic resin film provided with a release layer that does not contain a fluorine atom-containing organic group is suitable.

[0060] The non-silicone pressure-sensitive adhesive layers can be formed by coating at least one elastic pressure-sensitive adhesive composition selected from acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, vinyl acetate pressure-sensitive adhesives, styrene-butadiene rubber pressure-sensitive adhesives, and natural rubber pressure-sensitive adhesives by a known method, and then proceeding with a curing reaction by heating or the like, or by drying to remove the solvent (dry-up). Suitable non-silicone pressure-sensitive adhesive layers for use in the present invention may be commercially available products, such as the acrylic pressure-sensitive adhesive Orivine® BPS-8170 manufactured by Toyochem, the acrylic pressure-sensitive adhesive SK-Dyne™ 2981H and its curing agent (Y2) manufactured by Soken Chemical & Engineering, and the acrylic optical pressure-sensitive adhesive POL-204 and its curing agent (NCO-14) manufactured by Fujimori Kogyo.

[0061] The silicone-based pressure-sensitive adhesive layers can be formed by independently applying the coating by a known method and then proceeding with a curing reaction accompanied by a crosslinking reaction at room temperature by heating or irradiation with high-energy rays. The curing reaction conditions can be appropriately designed depending on the type of curing mechanism, the thickness of the adhesive layer, and the like. When the silicone-based pressure-sensitive adhesive layer according to the present invention is an adhesive layer obtained by curing a hydrosilylation-curing reactive organopolysiloxane composition capable of forming a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is formed as a cured product by heating at a temperature of 80 to 200°C, preferably at a temperature of 90 to 190°C. When a photoactivatable hydrosilylation reaction catalyst is used, the coating film is irradiated with high-energy rays, followed by heating at room temperature or at an arbitrary temperature to form a cured pressure-sensitive adhesive layer. For example, in the case of ultraviolet irradiation, the cumulative exposure dose at a wavelength of 365 nm is 100 mJ / cm. ２ ~100 J / cm ２ It is preferable that the range is within the range of

[0062] Commercially available silicone-based pressure-sensitive adhesive layers can be used suitably in the present invention. For example, examples of hydrosilylation-curing reactive silicone pressure-sensitive adhesives that can be used include DOWSIL™ SD 4580 PSA, SD 4584 PSA, SD 4585 PSA, and SH 4280 PSA manufactured by Dow-Toray Industries, Inc. For assembly applications, particularly OCA applications, the pressure-sensitive adhesive layer-forming organopolysiloxane compositions proposed by the present applicant in Patent Documents 3 to 10 (claims, examples, and reference examples) may be appropriately selected and used depending on the desired properties.

[0063] In the production method according to the present invention, examples of the coating method for the composition that forms the adhesive layer include gravure coating, offset coating, offset gravure, roll coating, reverse roll coating, air knife coating, curtain coating, and comma coating. The coating amount can be designed to a desired thickness depending on the application, such as a display device, and the thickness of the adhesive layer after curing can be selected from the above-mentioned ranges, for example. In the case of a silicone-based adhesive layer, coating is preferably performed so that the thickness per layer after curing is 0.5 to 200 μm, and in the case of a non-silicone-based adhesive layer, coating is preferably performed so that the thickness per layer after curing is 0.1 to 50 μm. The pressure-sensitive adhesive layers constituting the multilayer pressure-sensitive adhesive of the present invention preferably comprise one or more silicone-based pressure-sensitive adhesive layers as the main component, and the sum of the thicknesses (μm) of the silicone-based pressure-sensitive adhesive layers preferably accounts for 50 to 99% of the total thickness of the flat multilayer pressure-sensitive adhesive layer. Assuming that there is one non-silicone-based pressure-sensitive adhesive layer in contact with the release layer, the sum of the thicknesses (μm) of the non-silicone pressure-sensitive adhesive layers preferably accounts for 1 to 50% of the total. Furthermore, since the multilayer pressure-sensitive adhesive is used as an elastic pressure-sensitive adhesive member, the total thickness of the multilayer pressure-sensitive adhesive layer may be in the range of 25 to 1,000 μm.

[0064] The easily peelable laminate of the present invention is preferably produced by the steps of coating a non-silicone adhesive on a film substrate having a first release layer, curing the non-silicone adhesive layer by curing or drying, and then coating a pressure-sensitive adhesive layer-forming organopolysiloxane composition in an uncured state onto the non-silicone adhesive layer to a desired thickness and curing the composition to form a silicone adhesive layer. Here, the step of sequentially forming adhesive layers on the first release layer or the second release layer comprises the coating step and the step of forming an adhesive layer by curing or drying. By repeating these steps, the same or different adhesive layers can be laminated. It is also possible to obtain a laminated adhesive layer by first laminating thin layers of multiple adhesive layer-forming compositions (the above-mentioned acrylic adhesives or pressure-sensitive adhesive layer-forming organopolysiloxane compositions) and then completely curing or drying the entire laminated adhesive layer-forming composition by means of heating or the like.

[0065] The easily peelable laminate of the present invention can be finally produced by a step of laminating a film substrate having a second release layer so that the second release layer faces the multilayer pressure-sensitive adhesive layer (= adhesive surface).Similarly, the easily peelable laminate of the present invention can also be produced by laminating one or more pressure-sensitive adhesive layers formed on a film substrate having a first release layer and one or more pressure-sensitive adhesive layers formed on a film substrate having a second release layer so that the pressure-sensitive adhesive layers face each other.The method of laminating the release layer or pressure-sensitive adhesive layer to the pressure-sensitive adhesive layer is not particularly limited, but it is common to arrange the functional layers to be laminated so that they face each other, and then laminate them from both sides of the film substrate using a pressure-bonding means such as a pressure roller or a press. The pressing pressure and the presence or absence of a heating operation at this time can be designed or selected appropriately depending on the type of functional layer and the purpose of lamination, and the release layer or adhesive layer may be pressed using a roller with a pressing pressure of 0.5 to 10 kg. During or after pressing, the entire laminate including the multilayer adhesive layer may be subjected to a heating step (post-treatment) at 60 to 180°C within a range that does not adversely affect the film-like substrate due to heat, thereby firmly adhering the adhesive layers constituting the multilayer adhesive layer to each other. Note that, while it is preferable that the release layer after lamination is easily peelable from the adhesive layer, it is particularly preferable that the adhesive layers constituting the multilayer adhesive layer are firmly adhered to each other and are integrated to the extent that the peel mode is cohesive failure.

[0066] The laminate according to the present invention is useful as an elastic pressure-sensitive adhesive material product having easily peelable layers on both sides, and can be used as a double-sided pressure-sensitive adhesive sheet product, double-sided tape, or double-sided adhesive film.

[0067] The multilayer pressure-sensitive adhesive layer obtained by removing the release layer from the laminate according to the present invention can be used as an elastic pressure-sensitive adhesive member in various display devices for displaying characters, symbols, and images, such as television sets, computer monitors, monitors for personal digital assistants, surveillance monitors, video cameras, digital cameras, mobile phones, personal digital assistants, dashboard displays for automobiles, etc., dashboard displays for various facilities, devices, and equipment, automatic ticket vending machines, automated teller machines, in-vehicle display devices, and in-vehicle transmission screens. The surface shape of such display devices may be curved rather than flat, and examples thereof include various flat panel displays (FPDs) as well as curved displays or curved transmission screens used in automobiles (including electric vehicles) and aircraft. Furthermore, these display devices can display on their screens or displays icons for executing functions or programs, notification displays for emails and programs, and operation buttons for various devices such as car navigation systems, audio systems, and air conditioners, and may be equipped with a touch panel function that allows input operations by touching these icons, notification displays, and operation buttons with a finger. The elastic pressure-sensitive adhesive member according to the present invention can be applied to display devices such as CRT displays, liquid crystal displays, plasma displays, organic EL displays, inorganic EL displays, LED displays, surface electrochemical displays (SEDs), and field emission displays (FEDs), as well as touch panels using these displays. Furthermore, the elastic pressure-sensitive adhesive member comprising the multilayer pressure-sensitive adhesive layer according to the present invention has excellent adhesiveness and viscoelastic properties, and can therefore be used as a film or sheet-like member that is a transducer member (including for sensors, speakers, actuators, and generators) such as a membrane for a speaker, and can also be used as a sealing layer or adhesive layer for a secondary battery, a fuel cell, or a solar cell module.

[0068] Examples and comparative examples of the present invention are described below. In each example, comparative example, and reference example, the term "cured" means that the composition was completely cured under the respective curing conditions. (Preparation of Pressure-Sensitive Adhesive Compositions) Curable organopolysiloxane compositions were prepared as shown in each example, comparative example, and reference example using components (A) to (E) shown in Table 1. Note that all percentages in Table 1 are by mass. Ac-1 in Table 1 was used as is for the acrylic pressure-sensitive adhesive, while Ac-2 and Ac-3 were prepared by adding crosslinkers G-1 and G-2, respectively, as shown in each example, comparative example, and reference example.

[0069] (Measurement of Molecular Weight of Organopolysiloxane Component) Using an Alliance gel permeation chromatograph (GPC) manufactured by Waters Corporation and toluene as a solvent, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the organopolysiloxane component of the organopolysiloxane resin, etc., were determined in terms of standard polystyrene.

[0070] (Measurement of hydroxyl (OH) content in organopolysiloxane resin) Bruker ACP-300 equipped with a glass-free probe ２９ Using a Si NMR spectrometer, Si(OH)O appears at -93 to -103.5 ppm, with the chemical shift of tetramethylsilane set at 0 ppm. 2 / 3 The molar content was calculated from the ratio of the units to the total silicon, and was then converted into the mass % of hydroxyl groups (OH) in the organopolysiloxane resin. Note that the organopolysiloxane resins in the following examples did not contain any hydrolyzable functional groups other than hydroxyl groups.

[0071] (Peel Force Measurement) As described in each Example and Comparative Example, a laminate having a multilayer or single-layer adhesive layer sandwiched between a first release film and a second release film was prepared, left for one day, and then cut into 20 mm widths. The heavy release side was attached to a 30 x 250 x 5 mm acrylic plate using double-sided tape with a roller, and the peel force of the light release side (measured at a 20 mm width and converted to gf / inch) was measured using an Orientec RTI-1220-HSS tensile tester at a 180° peeling speed of 300 mm / min according to JIS Z0237. The peeled adhesive side was attached to a 50 μm thick PET film with a roller, and the peel force of the heavy release side was measured in the same manner. (Adhesion Strength Measurement) Release film L-1 was coated with Ac-2 at a thickness of 10 μm and cured at 120°C for 3 minutes. Si-1 was then coated at a thickness of 40 μm and cured at 150°C for 3 minutes. A PET film (manufactured by Toray Industries, Inc., product name: Lumirror (registered trademark) S10, thickness: 50 μm) was then laminated onto the Si-1. After leaving the sample for 1 day, the sample was cut into a width of 20 mm, the release film L-1 was peeled off, and the sample was laminated to a glass plate (manufactured by Paltec, float glass, 50 x 120 x 2 mm) using a roller to prepare a test piece. Using an Orientec RTI-1220-HSS tensile tester, the adhesive strength (measured at a width of 20 mm and converted to gf / inch) was measured at a tensile speed of 300 mm / min using the 180° peel test method in accordance with JIS Z0237. (Adhesion Measurement at High Temperature and High Humidity) The release film L-1 was peeled off from a 25 mm wide test piece prepared in the same manner as in the adhesive strength measurement, and the acrylic adhesive surface was attached to a glass plate (Paltec, float glass, 75 x 150 x 2 mm) using a roller to prepare a test piece. After leaving it at room temperature for 3 days, a 50 g weight was attached to one end of the PET film with the adhesive layer, and the glass plate was attached horizontally so that the weight hung downward at a 90° angle. The test piece was then placed in an oven at 65 °C and 90% relative humidity. After 24 hours, if the adhesive layer was completely peeled from the glass plate, it was evaluated as ×, and if it remained peeled, it was evaluated as ◯.

[0072] Table 1 shows the raw materials of the curing-reactive organopolysiloxane composition: the acrylic adhesive (AC), the curing agent (G), and the additives (adhesion promoters). The viscosity or plasticity of each component was measured at room temperature using the following method. [Viscosity] Viscosity (mPa·s) was measured using a rotational viscometer in accordance with JIS K7117-1, and kinematic viscosity (mm ２ / s) is a value measured using an Ubbelohde viscometer in accordance with JIS Z 8803. [Plasticity] The plasticity is shown as a value measured in accordance with the method specified in JIS K 6249 (a 4.2 g spherical sample was subjected to a load of 1 kgf for 3 minutes at 25°C, the thickness was read to the nearest 1 / 100 mm, and this value was multiplied by 100).

[0073] Table 1. Components of adhesive layer

[0074] The film substrates having a release layer used in the examples are shown in Table 2 below. Table 2: Film substrates having a release layer (= release film)

[0075] [Production Example 1: Preparation of Release Film L1] The following components (RA1) to (RF) were mixed uniformly to prepare a curable organopolysiloxane composition (before dilution). Component (R-A1): 100 parts by mass of a gum-like polydimethylsiloxane whose molecular chain terminals are capped with hydroxyl groups and which has vinyl groups on the side chains (plasticity at 25°C = 1.50, vinyl group content = 0.85% by mass); Component (R-B1): 48.5 parts by mass of a gum-like organopolysiloxane whose molecular chain terminals are capped with hydroxyl groups and which has no alkenyl groups on the side chains (plasticity at 25°C = 1.60); Component (R-C1): 1.5 parts by mass of a liquid organopolysiloxane whose molecular chain terminals are capped with trimethylsilyl groups and which has phenyl groups on the side chains (viscosity at 25°C = 50,000 mPa s); Component (R-D): A mixture obtained by mixing the following components (R-D1) and (R-D2) in a mass ratio of 50:50 (amounts such that the SiH / Vi ratio in the composition is 1.3). Component (D1): methylhydrogenpolysiloxane terminally blocked with trimethylsilyl groups (viscosity at 25°C = 25 mPa·s) Component (D2): dimethylmethylhydrogenpolysiloxane terminally blocked with trimethylsilyl groups (viscosity at 25°C = 55 mPa·s) Component (R-E): toluene in an amount such that the total amount of components (R-A1) to (R-C1) was 30% by mass of the composition. Component (R-F): 1.5 parts by mass of 3-methyl-1-butyn-3-ol

[0076] The mixed composition was mixed with a toluene / heptane mixed solution (toluene:heptane=50:50) and diluted so that the total amount of components (R-A) to (R-D) was 5.3 mass% of the composition. Then, a chloroplatinic acid / 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex was added as component (RG) in an amount such that the platinum metal content was 260 ppm relative to the total amount of components (R-A) to (R-D), thereby preparing a diluted solution of the curable organopolysiloxane composition.

[0077] The diluted solution of the prepared curable organopolysiloxane composition was diluted to a concentration of 0.50 g / m2 in terms of solids excluding the solvent. ２The composition was applied to the surface of a biaxially oriented polyester film (Toray Industries, Inc., thickness 50 μm) using an A-bar manufactured by OSG System Products Co., Ltd. After coating, the substrate coated with each composition was heat-treated for 60 seconds in a hot air circulating oven set at 130°C, thereby forming a cured layer of organopolysiloxane on the polyester film substrate surface. The composition was then stored for 24 hours in a hot air circulating oven set at 70°C to produce release film L1. Note that this release film L1 is identical to the release films proposed by the applicants in Japanese Patent Applications 2023-216168 and 2023-216170 and priority applications based thereon, and is evaluated as not containing fluorine-containing organic groups, having low peel resistance, being releasable with a stable low peel force, and having good residual adhesive strength.

[0078] The structure of each layer of each laminate according to the Examples, Comparative Examples, and Reference Examples is summarized in Table 3, and the results of measuring the peel strength are summarized in Table 4. The preparation and evaluation of each laminate will be described in detail below.

[0079] Example 1: A one-component acrylic pressure-sensitive adhesive Ac-1 was applied to a fluorine-containing release film LF-1 to a cured film thickness of 10 μm and cured for 3 minutes in an oven at 120° C. 22.7 parts by weight of vinyl-functional polydimethylsiloxane (Component A), 22.7 parts by weight of non-functional polydimethylsiloxane (Component A'), 75.8 parts by weight of MQ silicone resin (Component B), 101 parts by weight of toluene, 0.483 parts by weight of dimethylsiloxane-methylhydrogensiloxane copolymer (Component C), and 0.409 parts by weight of a 20% solution of cure retarder (Component E) were thoroughly mixed at room temperature, and 0.483 parts by weight of platinum-based hydrosilylation catalyst (Component D) was added to the mixture to form curable organopolysiloxane composition Si-1. The molar ratio of SiH groups in Component C to the amount of alkenyl groups in Component A (SiH / Vi ratio) was 32.3, and the platinum metal content relative to the solid content was 22 ppm. Si-1 was coated onto the cured Ac-1 so that the film thickness after curing was 40 μm, and the coating was cured in an oven at 150°C for 3 minutes, followed by lamination with fluorine-based release film LF-2. The peel strength of this laminate was measured using the method described in (Peel Strength Measurement), and the results are shown in Table 4.

[0080] Example 2: 100 parts by weight of acrylic adhesive Ac-2 and 0.6 parts by weight of curing agent G-1 were added to fluorine-based release film LF-1 and mixed thoroughly. The mixture was coated to a thickness of 10 μm after curing and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated on top of this to a thickness of 40 μm after curing and cured in an oven at 150°C for 3 minutes, after which fluorine-based release film LF-2 was laminated. The peel strength of this laminate was measured using the method described in (Peel Strength Measurement), and the results are shown in Table 4.

[0081] Example 3 One-component acrylic adhesive Ac-1 was coated onto non-fluorine-containing release film L-1 to a thickness of 10 μm after curing, and cured in an oven at 120°C for 3 minutes. Organopolysiloxane composition Si-1 described in Example 1 was coated thereon to a thickness of 40 μm after curing, and cured in an oven at 150°C for 3 minutes, followed by lamination with fluorine-containing release film LF-2. The peel strength of this laminate was measured using the method described in (Peel Strength Measurement), and the results are shown in Table 4.

[0082] Example 4: 100 parts by weight of acrylic adhesive Ac-2 and 0.6 parts by weight of curing agent G-1 were added to non-fluorine-containing release film L-1 and mixed thoroughly. The mixture was coated to a thickness of 10 μm after curing and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated thereon to a thickness of 40 μm after curing and cured in an oven at 150°C for 3 minutes, after which a fluorine-containing release film LF-2 was laminated. The peel strength of this laminate was measured using the method described in (Peel Strength Measurement), and the results are shown in Table 4.

[0083] Example 5 Laminate (1) 100 parts by weight of acrylic adhesive Ac-3 and 0.1 parts by weight of curing agent G-2 were added to non-fluorine-based release film L-1, mixed thoroughly, and coated to a thickness of 10 μm after curing. Cured for 3 minutes in an oven at 120° C., and then non-fluorine-based release film L-1 was laminated on top. Laminate (2) 100 parts by weight of acrylic adhesive Ac-3 and 0.1 parts by weight of curing agent G-2 were added to non-fluorine-based release film L-2, mixed thoroughly, and then coated to a thickness of 10 μm after curing. Cured for 3 minutes in an oven at 120° C., and then non-fluorine-based release film L-1 was laminated on top. Laminate (3) The non-fluorine-containing release film L-1 of laminate (2) was peeled off, and the organopolysiloxane composition Si-1 described in Example 1 was coated onto the acrylic adhesive layer so that the film thickness after curing was 55 μm, and cured in an oven at 150 ° C. for 10 minutes. The non-fluorine-containing release film L-1 on one side of laminate (1) was peeled off and the laminate was attached to the organopolysiloxane adhesive surface, obtaining a laminate consisting of three adhesive layers sandwiched between non-fluorine-containing release films L-1 and L-2. The peel strength of this laminate was measured using the method shown in (Peel Strength Measurement), and the results are shown in Table 4.

[0084] Example 6 Laminate (1) 100 parts by weight of acrylic adhesive Ac-3 and 0.1 parts by weight of curing agent G-2 were added to fluorine-free release film L-1, mixed thoroughly, and coated to a thickness of 10 μm after curing. Cured for 3 minutes in an oven at 120° C., and then laminated to non-fluorine-free release film L-1. Laminate (2) 100 parts by weight of acrylic adhesive Ac-3 and 0.1 parts by weight of curing agent G-2 were added to non-fluorine-free release film L-2, mixed thoroughly, and then coated to a thickness of 10 μm after curing. Cured for 3 minutes in an oven at 120° C., and then laminated to non-fluorine-free release film L-1. Laminate (3) The non-fluorine-containing release film L-1 of laminate (2) was peeled off, and the organopolysiloxane composition Si-1 described in Example 1 was applied to the acrylic adhesive layer to a thickness of 55 μm after curing. This was then cured in an oven at 150°C for 10 minutes. The non-fluorine-containing release film L-1 on one side of laminate (1) was peeled off and the laminate was then bonded to the organopolysiloxane adhesive surface, resulting in a laminate consisting of three adhesive layers sandwiched between non-fluorine-containing release films L-1 and L-2. Laminate (4) A laminate identical to laminate (1) was separately prepared. Laminate (5) The non-fluorine-containing release film L-1 of laminate (4) was peeled off, and the organopolysiloxane composition Si-1 described in Example 1 was applied to the acrylic adhesive layer to a thickness of 65 μm after curing. This was then cured in an oven at 150°C for 10 minutes. The non-fluorine-containing release film L-1 of the laminate (3) was peeled off and the laminate was stuck to the surface of this organopolysiloxane adhesive, to obtain a laminate consisting of five adhesive layers sandwiched between the non-fluorine-containing release films L-1 and L-2. The peel strength of this laminate was measured by the method shown in (Peel Strength Measurement), and the results are shown in Table 4.

[0085] Comparative Example 1 The organopolysiloxane composition Si-1 described in Example 1 was applied to a non-fluorine-containing release film L-1 so that the film thickness after curing would be 50 μm, and the coating was cured for 3 minutes in an oven at 150° C., followed by lamination with a fluorine-containing release film LF-2. The peel strength of this laminate was measured by the method shown in (Peel Strength Measurement), and the results are shown in Table 4.

[0086] Comparative Example 2 The organopolysiloxane composition Si-1 described in Example 1 was applied to fluorine-based release film LF-1 so that the film thickness after curing would be 50 μm, and the coating was cured for 3 minutes in an oven at 150° C., followed by lamination of fluorine-based release film LF-1. The peel strength of this laminate was measured by the method shown in (Peel Strength Measurement), and the results are shown in Table 4.

[0087] Comparative Example 3 The organopolysiloxane composition Si-1 described in Example 1 was applied to fluorine-containing release film LF-3 so that the film thickness after curing would be 50 μm, and the coating was cured in an oven at 150° C. for 3 minutes, followed by lamination of fluorine-containing release film LF-3. The peel strength of this laminate was measured by the method shown in (Peel Strength Measurement), and the results are shown in Table 4.

[0088] The adhesiveness and adhesive strength of the laminate were evaluated in the following Reference Examples and Reference Examples, and the results are shown in Table 5.

[0089] Reference Example 1 The organopolysiloxane composition Si-1 described in Example 1 was applied to fluorine-based release film LF-2 so that the film thickness after curing would be 75 μm, and the coating was cured for 5 minutes in an oven at 150° C., followed by lamination of fluorine-based release film LF-2. LF-2 on the light release side of this laminate was peeled off, and the laminate was then laminated to a 50 μm-thick PET film, and LF-2 on the opposite side was peeled off and the laminate was then laminated to a glass plate. The adhesive strength was measured under high temperature and high humidity conditions using the method described in (Measurement of adhesive strength under high temperature and high humidity conditions), and the results are shown in Table 5.

[0090] Reference Example 1: 100 parts by weight of acrylic adhesive Ac-2 and 0.6 parts by weight of curing agent G-1 were added to fluorine-free release film L-1 and mixed thoroughly. The mixture was coated to a thickness of 10 μm after curing and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated thereon with 1 part by weight of additive H-1 added per 100 parts by weight of the solids content of Si-1, to a thickness of 40 μm after curing. The mixture was cured in an oven at 150°C for 3 minutes, and a 50 μm-thick PET film was then laminated. The adhesive strength of this laminate was measured using the method described in (Adhesion Strength Measurement), and the results are shown in Table 5.

[0091] Reference Example 2: 100 parts by weight of acrylic adhesive Ac-3, 1 part by weight of additive H-2, and 0.1 part by weight of curing agent G-2 were added to fluorine-free release film L-1, and the mixture was thoroughly mixed. The mixture was coated to a cured film thickness of 10 μm and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated thereon to a cured film thickness of 65 μm, cured in an oven at 150°C for 4 minutes, and a 50 μm-thick PET film was laminated. The adhesive properties of this laminate were measured under high temperature and high humidity conditions using the method described in (Measurement of adhesive properties under high temperature and high humidity conditions), and the results are shown in Table 5.

[0092] Reference Example 3: 100 parts by weight of acrylic adhesive Ac-3, 1 part by weight of additive H-3, and 0.1 part by weight of curing agent G-2 were added to fluorine-free release film L-1, and mixed thoroughly. The mixture was coated to a cured film thickness of 10 μm and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated thereon to a cured film thickness of 65 μm, cured in an oven at 150°C for 4 minutes, and then a 50 μm-thick PET film was laminated. The adhesive properties of this laminate were measured under high temperature and high humidity conditions using the method described in (Measurement of adhesive properties under high temperature and high humidity conditions), and the results are shown in Table 5.

[0093] (Reference Comparative Example 1) 100 parts by weight of acrylic adhesive Ac-2 and 0.6 parts by weight of curing agent G-1 were added to a non-fluorinated release film L-1 and mixed thoroughly. The mixture was coated to a thickness of 10 μm after curing and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated thereon to a thickness of 40 μm after curing and cured in an oven at 150°C for 3 minutes, and a 50 μm-thick PET film was laminated. The adhesive strength of this laminate was measured using the method described in (Adhesion Strength Measurement), and the results are shown in Table 5.

[0094] Comparative Example 2: 100 parts by weight of acrylic adhesive Ac-2 and 0.6 parts by weight of curing agent G-1 were added to a non-fluorinated release film L-1 and mixed thoroughly. The mixture was coated to a thickness of 10 μm after curing and cured in an oven at 120°C for 3 minutes. The organopolysiloxane composition Si-1 described in Example 1 was coated thereon to a thickness of 65 μm after curing and cured in an oven at 150°C for 4 minutes, followed by lamination with a 50 μm-thick PET film. The adhesive properties of this laminate were measured under high temperature and high humidity conditions using the method described in "Measurement of adhesive properties under high temperature and high humidity conditions." The results are shown in Table 5.

[0095] (Reference Comparative Example 3) 100 parts by weight of acrylic adhesive Ac-3 and 0.1 part by weight of curing agent G-2 were added to a 50 μm thick PET film and mixed well, and the resulting mixture was coated to a film thickness of 50 μm after curing, cured in an oven at 120° C. for 5 minutes, and then non-fluorinated release film L-1 was laminated. The adhesiveness of this laminate was measured under high temperature and high humidity conditions using the method described in (Measurement of adhesiveness under high temperature and high humidity conditions), and the results are shown in Table 5.

[0096] Table 3: Structure of each laminate *The type of adhesion promoter and the adhesive layer to which it was added are shown in parentheses.

[0097] Table 4. Evaluation results of peel strength of each laminate

[0098] Table 5. Evaluation results of adhesive strength and adhesion of each laminate

[0099] [Summary of Experimental Results] In Examples 1 and 2, which had a two-layer structure, fluorine-based release film LF-1 was used on both sides, and the release force of the first release film side, on which the liquid was applied, was a low value of 10 gf / inch or less, achieving easy releasability. In contrast, in Comparative Examples 2 and 3, which used a single layer of Si-1, fluorine-based LF-1 or LF-3 was used as the first release film, but the release force of the first release film side was 100 gf / inch or more, which was too strong for practical use.

[0100] In Examples 3 and 4, a two-layer structure was also used, and a non-fluorine-containing release film L-1 was used, but the release force on the first release film side was well below 100 gf / inch, achieving easy peelability. In Comparative Example 1, the same non-fluorine-containing release film L-1 was used as the first release film, but a single layer of Si-1 showed a weight of 400 g / inch or more.

[0101] Examples 5 and 6 show laminates with three and five pressure-sensitive adhesive layers, respectively. As shown in the examples, only a non-fluorinated release film was used, completely preventing contamination with fluorine compounds. The release film surfaces of the final laminate were the liquid-coated sides. Using the same release film would result in the same release strength on both sides, making it difficult to first peel off only one release film when laminating displays, etc. However, by using non-fluorinated release films L-1 and L-2, the release strengths on both sides were differentiated as shown in Table 4, achieving more favorable peelability. Using a multilayer structure like this not only reduced the release force for practical processes, but also reduced or completely prevented contamination with fluorine compounds. Additionally, Reference Example 1 demonstrates that, compared to Reference Comparative Example 1, adding additive H-1 to Si-1 increases adhesive strength.

[0102] As shown in Reference Example 1 and Reference Comparative Example 3, where the adhesive properties of single layers Si-1 and Ac-3 are shown under high temperature and high humidity, respectively, the acrylic adhesive results in poor adhesive properties under high temperature and high humidity. As shown in Reference Comparative Example 2, the same problem was observed with a multilayer structure. However, as shown in Reference Examples 2 and 3, by adding an additive to the acrylic adhesive, adhesive properties under high temperature and high humidity can be ensured, and adhesive strength comparable to that of a silicone-based adhesive layer can be achieved.

Claims

1. A laminate having a structure in which a multi-layer adhesive layer consisting of two or more adhesive layers is sandwiched between two release layers, at least one of the multi-layer adhesive layers being a silicone-based adhesive layer, and the adhesive layer in contact with at least one of the release layers being a non-silicone-based adhesive layer.

2. The laminate according to claim 1, wherein at least one of the release layers is a release layer that does not contain a fluorine atom-containing organic group.

3. The laminate according to claim 1, wherein the silicone-based pressure-sensitive adhesive layer is a cured reaction product obtained by curing through a curing reaction including at least one reaction selected from the group consisting of a hydrosilylation curing reaction, a peroxide curing reaction, and a radical curing reaction.

4. The laminate according to claim 1, wherein at least a portion of the silicone-based pressure-sensitive adhesive layer is an adhesive layer obtained by curing a hydrosilylation-curing reactive organopolysiloxane composition capable of forming a pressure-sensitive adhesive layer, the organopolysiloxane composition comprising: (A) a linear organopolysiloxane having an average of more than one alkenyl group per molecule; (B) an organopolysiloxane resin having a sum of 9 mol % or less of the hydroxyl and hydrolyzable groups relative to all silicon atoms per molecule; (C) an organohydrogenpolysiloxane having at least two Si-H bonds per molecule; and (D) an effective amount of a hydrosilylation reaction catalyst.

5. In the pressure-sensitive adhesive layer-forming organopolysiloxane composition, at least a portion of component (A) is a crude rubber-like alkenyl group-containing organopolysiloxane having a viscosity of 100,000 mPa·s or more at 25°C or a plasticity of 50 to 200 as measured in accordance with the method specified in JIS K6249, and the content of the alkenyl groups, calculated as vinyl (CH2=CH), is in the range of 0.005 to 0.400 mass%, and component (B) is a linear organopolysiloxane containing R ３ SiO １／２ units (wherein R is a monovalent organic group, and 90 mol % or more of R are alkyl groups or phenyl groups having 1 to 6 carbon atoms; M units) and SiO ４／２ 5. The laminate according to claim 4, wherein the organopolysiloxane resin or mixture thereof is comprised essentially of units (Q units), the amount of component (C) is such that the ratio (molar ratio) of the amount of SiH groups in component (C) to the sum of the amounts of alkenyl groups in components (A) and (B) is 0.1 to 100, and the amount of component (D) is such that the content of platinum-based metals in the solids of the composition is in the range of 0.1 to 200 ppm.

6. The laminate according to claim 4, wherein the pressure-sensitive adhesive layer-forming organopolysiloxane composition further contains (A') a linear organopolysiloxane having no alkenyl groups or silicon-bonded hydrogen atoms in the molecule.

7. The laminate according to claim 1, wherein the non-silicone adhesive layer is at least one adhesive layer selected from the group consisting of acrylic adhesives, epoxy adhesives, and urethane adhesives, and has a silicon atom content of less than 1.0% by mass.

8. At least one release layer comprises: (R-A) a linear organopolysiloxane having an alkenyl group and having 2 to 12 carbon atoms, which has a viscosity of 1,000,000 mPa·s or more at 25°C or has a plasticity at 25°C; (R-B) a linear organopolysiloxane having no alkenyl group, which has a viscosity of 500,000 mPa·s or more at 25°C or has a plasticity at 25°C; optionally, (R-C) a linear organopolysiloxane having no alkenyl group, which has a viscosity of less than 500,000 mPa·s at 25°C; (R-D) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (Si—H) per molecule; and (R-E) a hydrosilylation reaction catalyst.

2. The laminate according to claim 1, wherein the release layer is formed by curing a curable organopolysiloxane composition containing the formula (I) and not containing a fluorine atom-containing organic group.

9. The laminate according to claim 1, wherein one or more adhesive layers constituting the multi-layer adhesive layer contain one or more types of adhesion promoters.

10. A method for producing a laminate according to any one of claims 1 to 9, comprising: step (I): forming a non-silicone adhesive layer on a film-like substrate having a first release layer; step (II): applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition onto the non-silicone adhesive layer obtained in step (I) and curing it to form a silicone adhesive layer; and step (III): laminating a film-like substrate having a second release layer onto the silicone adhesive layer obtained in step (II) or onto one or more adhesive layers further laminated on the silicone adhesive layer obtained in step (II), so that the second release layer faces the adhesive layer.

11. A method for producing a laminate according to any one of claims 1 to 9, comprising: step (I): forming a non-silicone adhesive layer on a film substrate having a first release layer; step (II): applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition on a film substrate having a second release layer and curing it to form a silicone adhesive layer; and step (III): laminating the non-silicone adhesive layer obtained in step (I) or one or more adhesive layers further laminated thereon, and the silicone adhesive layer obtained in step (II) or one or more adhesive layers further laminated thereon, so as to face each other.

12. A method for producing a laminate according to any one of claims 1 to 9, comprising: step (I): forming a non-silicone pressure-sensitive adhesive layer on a film substrate having a first release layer; step (II): forming a non-silicone pressure-sensitive adhesive layer on a film substrate having a second release layer; step (III): applying an uncured pressure-sensitive adhesive layer-forming organopolysiloxane composition onto the non-silicone pressure-sensitive adhesive layer obtained by at least one of step (I) or step (II), and curing the composition to form a silicone pressure-sensitive adhesive layer; and step (IV): after step (III), laminating one or more pressure-sensitive adhesive layers formed on the film substrate having the first release layer and one or more pressure-sensitive adhesive layers formed on the film substrate having the second release layer so that they face each other.

13. A method for producing a laminate according to any one of claims 1 to 9, comprising the steps of: after or during the formation of a pressure-sensitive adhesive layer in any of the steps, laminating a film-like substrate with a release layer that does not fall under either a film-like substrate with a first release layer or a film-like substrate with a second release layer to the surface of the pressure-sensitive adhesive layer; and after peeling the film-like substrate with the release layer from the surface of the pressure-sensitive adhesive layer, laminating the pressure-sensitive adhesive layer or a pressure-sensitive adhesive layer further laminated thereon and another pressure-sensitive adhesive layer or another release layer so that they face each other.

14. The laminate according to any one of claims 1 to 9, wherein the multilayer adhesive layer is an elastic adhesive material.

15. An electronic device or electrical device comprising a multilayer adhesive layer obtained by removing two release layers from the laminate according to any one of claims 1 to 9.

16. A method for producing an electronic device or an electrical device, comprising the step of using the laminate according to any one of claims 1 to 9 as a peelable elastic pressure-sensitive adhesive member.

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