Method for separating conjugates

Abstract

A method for separating a bonded body that allows for peeling of an adhesive containing a hydrophilic agent even when the adhesive is firmly bonded to a component. A method for separating a bonded body comprising two components bonded by an adhesive is provided. The adhesive contains a hydrophilic agent. Furthermore, the method includes immersing the bonded body in a solvent and peeling the adhesive from the components.

Description

Technical Field

[0001] The present invention relates to a method for separating a conjugate.

[0002] This application claims priority based on Japanese Patent Application No. 2020-137978 filed on August 18, 2020, the entire contents of which are incorporated herein by reference. Background Art

[0003] Typically, adhesives (also referred to as pressure-sensitive adhesives. The same applies hereinafter) have the following properties: they are in the form of a soft solid (viscoelastic body) in a temperature range near room temperature and easily adhere to an adherend under pressure. By utilizing such properties, adhesives are widely used in various fields in the form of an adhesive sheet with an adhesive layer on a support, or in the form of an adhesive sheet without a support. In addition, the above-mentioned adhesive can be peeled off from the adherend by appropriate means after use if necessary. As technical documents related to adhesive sheets, Patent Document 1 can be cited. As technical documents for peeling an adhesive from an adherend, Patent Document 2 can be cited.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-23656

[0007] Patent Document 2: Japanese Patent Application Publication No. 2005-148638 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In recent years, from the perspectives of reducing environmental impact and conserving resources, there has been an increasing trend to separate components bonded with adhesives from products after use and reuse them (recycling, reusing, etc.). For example, display devices (LCDs), organic EL (electroluminescent) displays, and PDPs (plasma display panels) incorporated into products with display functions, such as smartphones, computers (desktop, notebook, tablet, etc.), and televisions, have multilayer structures containing multiple and diverse functional components, each composed of different materials. Therefore, recycling, reusing, and other methods are highly advantageous.

[0010] For the adhesive bonded to adherends such as parts, usually, the adhesive itself is peeled off from the adherend by the re-peelability. However, for the adhesive requiring high bonding reliability, generally speaking, its bonding strength relative to the adherend is high, and the peeling (re-peeling) from the adherend is often reduced. In addition, sometimes hard and brittle parts such as glass and thin-walled parts are included in the adherend. For such adherends, there is a situation in which the force borne when peeling off the adhesive is damaged. In view of this situation, as a technology that takes into account both the bonding strength relative to the adherend and the re-peeling, the inventor of the present application has proposed in patent document 1 an adhesive sheet (water-peelable adhesive sheet) that can be easily peeled off by aqueous liquids such as water, and the water-resistant reliability when joining is improved.

[0011] However, even such adhesives with excellent removability can sometimes experience increased adhesive strength over extended use due to environmental factors, making intended re-removal difficult. These adhesives are firmly bonded to adherends, sometimes preventing them from being removed even with hot water immersion, ultrasonic vibration, or other methods, hindering reuse. A method is needed to enable the adhesive to be removed from adherends and to separate components joined by the adhesive, even when the adhesive is firmly bonded to the components over extended periods of time.

[0012] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for separating a bonded body, which allows peeling of an adhesive containing a hydrophilic agent even when the adhesive is firmly adhered to a member.

[0013] Means for solving problems

[0014] According to this specification, a method for separating a joint body comprising two parts joined by an adhesive is provided. The adhesive comprises a water affinity agent. In addition, the above method comprises the step of immersing the joint body in a solvent so that the adhesive is peeled off from the parts. According to the above method, even if the adhesive is firmly bonded to the joint body of the parts, the adhesive can be peeled off from the parts, and the separation of the joint body can be achieved. For example, in the case where the water-peelable adhesive comprising a water affinity agent cannot be peeled off from the parts by water peeling using an aqueous liquid due to long-term bonding, the peeling of the adhesive can be achieved by applying the above method. In addition, since the peeling based on solvent immersion (solvent immersion peeling) does not require external force to be applied to the parts as adherends, the parts are not easily damaged when the adhesive is peeled off.

[0015] It should be noted that, in this specification, the term "two components joined by an adhesive" means that an adhesive is used in at least a portion of the joining of the two components, and is not limited to joining using a specific adhesive containing only a hydrophilic agent. For example, in a method of joining two components using a double-sided adhesive sheet with a substrate, if at least one of the adhesives provided on each side of the double-sided adhesive sheet is an adhesive containing a hydrophilic agent, the two components are interpreted as being "joined by an adhesive" as described above.

[0016] In some preferred embodiments, the HSP (Hansen Solubility Parameter) distance between the adhesive and the solvent is 4.0 or less. By ensuring that the adhesive to be stripped and the solvent used have this relationship (HSP distance), stripping by solvent immersion is performed effectively. The solvent preferably includes ethyl acetate. Ethyl acetate is suitable for solvent immersion stripping of acrylic adhesives, for example, but is not particularly limited.

[0017] In another preferred embodiment, the hydrogen bonding term (δH) of the solvent in HSP (Hansen Solubility Parameter) is 15.0 or greater. Solvents having such a hydrogen bonding term value act well on the adhesive containing the hydrophilic agent, and peeling by immersion in the solvent proceeds well.

[0018] In some embodiments, the adhesive is a solvent-based adhesive or an active energy ray-curable adhesive. Among the peeling methods of solvent-based adhesives and active energy ray-curable adhesives containing a hydrophilic agent, the solvent immersion peeling method disclosed herein is preferred.

[0019] In some ways, described 2 parts are joined by the two-sided adhesive adhesive sheet comprising described adhesive.In addition, the width of described adhesive sheet is more than 20mm. According to the solvent impregnation peeling of recording here, can make peeling well and carry out for the joined body joined by the adhesive sheet more than width 20mm, joined body can be separated.

[0020] In some preferred embodiments, the method for separating the bonded body is performed by immersing the bonded body in a solvent for 24 hours or longer. By setting the solvent immersion time to 24 hours or longer, the adhesive is effectively peeled from the components. For example, after 24 hours from the time the bonded body is immersed in the solvent, the distance the adhesive is peeled from one of the two components can be 20 mm or longer.

[0021] Some preferred embodiments involve a method comprising determining whether the adhesive can be water-peeled from at least one of the two components before immersing the assembly in a solvent. Water-peeling is performed in the presence of an aqueous liquid at the location where the adhesive is to be peeled from the surface of the component. In this method, after confirming that water-peeling is not possible, the assembly is immersed in a solvent. The method described herein is particularly suitable for peeling off water-peelable adhesives that could originally be peeled off from an adherend by water-peeling but have lost their water-peelability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] [ Figure 1 ] is a schematic cross-sectional view for illustrating a method for separating a conjugate according to one embodiment. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present invention are described below. It should be noted that matters necessary for implementing the present invention, except for those specifically mentioned in this specification, can be understood by those skilled in the art based on the teachings on the implementation of the invention recorded in this specification and the technical common sense at the time of application. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in this field. In addition, in the following drawings, parts and portions that play the same role are sometimes marked with the same symbols for description, and repeated descriptions are sometimes omitted or simplified. In addition, the embodiments described in the drawings are for the purpose of clearly illustrating the present invention and do not necessarily accurately represent the actual sizes or reduction ratios provided.

[0024] <Method for separating the conjugate>

[0025] The technology disclosed herein relates to a method for separating two components from a bonded body comprising two components bonded by an adhesive. Figure 1 While embodiments of the method disclosed herein are described, the method disclosed herein is not intended to be limited to these embodiments.

[0026] (joint)

[0027] The bonded body separated by the technology disclosed herein comprises two parts bonded by an adhesive. For example, Figure 1 The bonded body 100 according to one embodiment shown has a structure in which a first component 120 and a second component 140 are bonded together by an adhesive 1. It should be noted that the bonded body 100 is not particularly limited as long as it includes at least two components to be separated, and may be a bonded body composed of two or more components. For example, Figure 1As shown, it can be a multilayer structure formed by stacking more than two layered bodies. In the embodiment in which the joint body 100 is a multilayer structure, the first component 120 and the second component 140 can be in the form of a sheet or plate. In addition, the above two components can also be components that are continuous at a portion other than the portion joined by the adhesive. In this embodiment, a metal component can be used as the first component 120 and a glass component can be used as the second component 140, but it is not limited to this. The joint body 100 can be variously configured such as a configuration in which both the first component 120 and the second component 140 are transparent components (for example, at least one of them is a glass component).

[0028] Adhesive 1 is an adhesive containing a hydrophilic agent. In this embodiment, adhesive 1 has a sheet-like (adhesive sheet) form, specifically, a double-sided adhesive sheet without a substrate having adhesive properties on both sides. Adhesive 1 can also be called a layered (i.e., adhesive layer). As for adhesive 1, one surface (first adhesive surface) 1A is bonded to the first component 120, and the other surface (second adhesive surface) 1B is bonded to the second component 140. In this way, the first component 120 and the second component 140 are joined by the adhesive 1 which should be called a sheet-like or layered adhesive. The width of the adhesive sheet 1 of this embodiment is greater than 20 mm and has a thickness of greater than 100 μm.

[0029] As described above, adhesive 1 contains a hydrophilic agent. While it is originally a water-peelable adhesive capable of being peeled from an adherend by water peeling, it has become a water-depleted adhesive due to its use history, impairing its water-peelability. Consequently, adhesive 1 is firmly bonded to first component 120 and second component 140, becoming difficult to peel from, not only by normal peeling but also by water peeling. Furthermore, adhesive 1 remains firmly bonded to first component 120 and second component 140, becoming difficult to peel even by immersion in warm water, ultrasonic vibration, or the like. This situation may occur, for example, when adhesive 1 is used to join components for an extended period of time, causing the adhesive strength to increase excessively.

[0030] It should be noted that the so-called water peeling and water peelability in this specification refer to peeling using an aqueous liquid such as water and the ease of peeling (water peeling) (water peeling). The so-called water peeling refers to, for example, peeling an adhesive from an adherend in the presence of an aqueous liquid at the peeling front (the part where peeling (separation) starts from the bonding interface between the adhesive surface of the adhesive (which can be in the form of an adhesive layer or an adhesive sheet) and the surface of the adherend.

[0031] (Solvent immersion stripping)

[0032] As described above, the bonded body 100 including the adhesive 1 which is difficult to peel in the normal peeling or water peeling state is Figure 1The adhesive 1 is immersed in the solvent 200 as shown. Specifically, the bonded body 100 is placed in a suitable container 250 filled with the solvent 200 and immersed in the solvent 200. In this way, the adhesive 1 can be peeled off from the first component 120 and / or the second component 140. Specifically, the adhesive 1 immersed in the solvent 200 swells and peels off naturally. It should be noted that during the above-mentioned solvent immersion peeling, auxiliary peeling means such as manual peeling can be used, or the adhesive can be peeled off only by solvent immersion peeling. The above-mentioned auxiliary peeling can be performed in a state where the bonded body is immersed in the solvent, or it can be performed after the bonded body is taken out of the solvent.

[0033] As the solvent immersion time, the appropriate time for the adhesive 1 to be peeled off from either the first component 120 or the second component 140 varies depending on the type of adhesive, adherend, bonding state, bonding area, etc., and is therefore not limited to a specific range. The solvent immersion time is, for example, appropriate for more than 12 hours, preferably more than 24 hours, more than 48 hours, more than 72 hours, more than 100 hours, or more than 150 hours. By extending the solvent immersion time, the adhesive can be peeled off from the above-mentioned components. On the other hand, from the perspective of peeling operation efficiency, it is appropriate for the solvent immersion time to be within 1 week, preferably less than 120 hours, more preferably less than 90 hours, further preferably less than 60 hours, and particularly preferably less than 30 hours.

[0034] The temperature of the solvent is not particularly limited, and is usually in the room temperature range (eg, about 0°C to 40°C, typically about 10°C to 30°C). The solvent may be heated to an appropriate temperature before use.

[0035] (Solvent)

[0036] The solvent used can be selected from one or more appropriate solvents depending on the type of adhesive, the solvent resistance of the adherend, etc., and is not limited to a specific type. It should be noted that in this specification, a solvent refers to an organic compound (also referred to as an organic solvent) that is liquid at 23°C and can be used as a solvent or dispersion medium.

[0037] In some embodiments, as a solvent, it is preferred to use one or more solvents whose HSP (Hansen solubility parameter) distance relative to the adhesive to be peeled by the solvent is less than a specified value. The HSP distance between the adhesive and the solvent is, for example, less than 20, may be less than 15, or may be less than 10. The use of a solvent whose HSP distance relative to the above-mentioned adhesive is less than a specified value has a tendency for solvent immersion peeling to proceed well. It is appropriate for the above-mentioned HSP distance to be less than 8.0 (for example, less than 5.0), preferably less than 4.0 (for example, less than 3.0). The lower limit of the above-mentioned HSP distance is usually greater than 0, for example, it can be about 1 or more. In addition, the unit of the HSP distance is MPa 1 / 2 .

[0038] In this specification, the HSP distance (Ra) between the binder and the solvent is determined by the following method. That is, the HSP values (dispersion term (δD), polar term (δP), hydrogen bonding term (δH)) of the binder and the solvent are determined, and the HSP value of the binder (δD PSA ,δP PSA , δH PSA ) and the HSP value of the solvent (δD SOL ,δP SOL , δH SOL ) is the distance between vectors. It is taken as the HSP distance. Specifically, it is calculated by the following formula:

[0039] Ra=[4×(δD PSA -δD SOL ) 2 +(δP PSA -δP SOL ) 2 +(δH PSA -δH SOL ) 2 ] 1 / 2

[0040] In the above formula, δD PSA ,δP PSA and δH PSA They represent the dispersion term (δD), polar term (δP) and hydrogen bonding term (δH) of the binder, δD SOL ,δP SOL and δH SOLEach represents the dispersion term (δD), polar term (δP) and hydrogen bond term (δH) of the solvent. The HSP values of the adhesive and the solvent, more specifically the dispersion term (δD), polar term (δP) and hydrogen bond term (δH) can be calculated using the software "HSPiP, Hansen Solubility Parameters in Practice ver4". In the case where the adhesive and the solvent are composed of multiple components, the above software can be used to calculate them by the molecular group contribution method. Specifically, each constituent unit in the substance to be the object is input in SMILES notation, and the HSP value (δd, δp, δh) of each unit is calculated. For the adhesive, the HSP value (δd, δp, δh) of each constituent component of the adhesive is calculated based on the above method, and the HSP value (δD PSA ,δP PSA , δH PSA ). More specifically, it is obtained by the following formula:

[0041] (δD PSA ,δP PSA , δH PSA )=[(δd a ×a mole fraction)+(δd b × mole fraction of b)+…,(δp a ×a mole fraction)+(δp b × mole fraction of b)+…,(δh a ×a mole fraction)+(δh b × mole fraction of b) + ...).

[0042] Here, in the above formula, a and b represent the constituent components of the adhesive.

[0043] In some other embodiments, as a solvent, it is preferred to use one or more solvents whose hydrogen bond term (δH) in HSP is greater than a specified value. The solvent with a large hydrogen bond term value acts well on the adhesive containing the hydrophilic agent, and the peeling based on the immersion of the solvent is carried out well. The δH of the solvent is, for example, greater than 10.0, and greater than 12.0 is appropriate, preferably greater than 15.0, more preferably greater than 17.0, and may also be greater than 20.0. The solvent that meets the above δH can, for example, have an HSP distance greater than 5 or greater than 10, or even greater than 15, from the above adhesive. In addition, the unit of the above δH is MPa 1 / 2 The above-mentioned δH can be obtained according to the above-mentioned HSP value calculation method.

[0044] Examples of the solvent include any one solvent selected from alcohols such as methanol, ethanol, and isopropanol (e.g., monohydric alcohols having 1 to 4 carbon atoms); aliphatic or alicyclic hydrocarbons such as hexane, heptane, cyclohexane, and cycloheptane; aromatic compounds such as toluene and xylene (specifically, aromatic hydrocarbons); esters such as methyl acetate, ethyl acetate, and butyl acetate; ketones such as acetone and methyl ethyl ketone; ethers such as butyl methyl ether such as dimethyl ether and diethyl ether; and halogenated alkanes such as 1,2-dichloroethane, or a mixture of two or more. Of these, alcohols, esters, and aromatic hydrocarbons are preferred, with methanol, ethanol, and ethyl acetate being more preferred, and ethyl acetate being particularly preferred. Preferred examples of these solvents (particularly ethyl acetate) are suitable for solvent immersion stripping of acrylic adhesives.

[0045] By implementing the above-mentioned solvent impregnation, even if it is a joint body that is firmly adhered to the adhesive and is difficult to be peeled off by normal peeling or water peeling as described above, the adhesive can be peeled off from the parts, and the joint body can be separated (disintegrated). According to the above-mentioned method, the adhesive can be peeled off from the parts without damaging the adherend. In addition, in a process of solvent impregnation, and without the need for additional operation in the solvent impregnation, the adhesive can be peeled off only by placement, so it is practical.

[0046] It should be noted that, in some embodiments, solvent immersion peeling is not only applicable to adhesives that are difficult to peel by normal or water peeling, but can also be applied to adhesives containing water-affinity agents that are used to bond components in various states. The solvent immersion peeling disclosed herein allows the adhesive to be peeled from components without confirming whether it can be peeled by normal or water peeling.

[0047] (Determination of water-peelability)

[0048] Although not particularly limited, the above-mentioned solvent immersion stripping is effective and suitable for stripping the adhesive that will become difficult to strip by water stripping (in other words, water-stripping-loss adhesive) from the component as described above. From this point of view, the preferred embodiment involves a method for separating the bonded body including: before immersing the bonded body in a solvent, a process for judging whether the adhesive can be water-stripped from the two components (the first component and the second component) joined by the adhesive (a water-stripping determination process), and after confirming that water stripping cannot be performed, a method for immersing the bonded body in a solvent can be adopted. It is usually difficult to distinguish from the appearance whether the adhesive can be water-stripped from the component. Therefore, the above-mentioned determination of water strippability can typically be a process of actually attempting to strip the adhesive based on water stripping. Water stripping is the same as the above-mentioned definition, and the details are described later, so a detailed description is omitted here. The method for separating the bonded body disclosed herein is preferably implemented in a manner that includes a water-stripping determination process. According to the above-mentioned method, it is possible to efficiently and effectively strip the water-stripping-loss adhesive whose water stripping property has been damaged due to long-term bonding, etc. from the component.

[0049] (Adhesive bonding state)

[0050] It should be noted that, before the above-mentioned solvent immersion peeling, the adhesive (typically an adhesive sheet) firmly bonded to the component is difficult to be peeled off from the component by normal peeling. For example, the adhesive can be an adhesive bonded to the above-mentioned component with the following bonding strength, and the bonding strength is: under an environment of 23°C and 50% RH, a dynamometer is fixed to the end of the component joined with the adhesive, the dynamometer is held by hand, and the normal peeling force when hand peeling is performed at a peeling angle of 90 to 150 degrees and a peeling speed of 10 to 100 mm / minute is 10N / 20mm or more. The above-mentioned normal peeling force is, for example, 15N / 20mm or more, can be 20N / 20mm or more, and can further be 25N / 20mm or more (typically 28N / 20mm or more). The adhesive bonded to the component with the above-mentioned bonding strength is difficult to peel off from the component as the adherend by a usual peeling method, or the adherend is easily damaged, etc. It is difficult to peel smoothly. For such an adhesive, it is preferably applicable to the method disclosed herein. In the measurement of the normal peel force, a force gauge such as "Digital Force Gauge FG-5100" manufactured by SATOTECH Co., Ltd. or its substitute can be used. The same applies to the water peel force described below.

[0051] In addition, before the above-mentioned solvent immersion peeling, the adhesive (typically an adhesive sheet) firmly bonded to the component is difficult to peel off from the component by water peeling. For example, the adhesive can be an adhesive bonded to the above-mentioned component with the following bonding strength, and the bonding strength is: under an environment of 23°C and 50% RH, a dynamometer is fixed to the end of the component joined with the adhesive, the dynamometer is held by hand, 20 μL of distilled water is supplied to the position where the adhesive begins to leave the component as the adherend (peeling front), and the water peeling force when hand peeling is performed at a peeling angle of 90 to 150 degrees and a peeling speed of 10 to 100 mm / minute is 10N / 20mm or more. The above-mentioned water peeling force is, for example, 15N / 20mm or more, can be 20N / 20mm or more, and can further be 25N / 20mm or more (typically 28N / 20mm or more). The adhesive bonded to the component with the above-mentioned bonding strength is difficult to peel off from the component as the adherend by water peeling, or the adherend is easily damaged and is difficult to peel smoothly. The methods disclosed herein are particularly suitable for such adhesives.

[0052] <Water peeling>

[0053] Water stripping has the same definition as described above, and specifically refers to the following water stripping process, in which, at the peeling front of the adhesive from the component, in a state where an aqueous liquid is present at the interface between the component and the adhesive, the aqueous liquid is allowed to enter the interface as the peeling front moves, while the adhesive is peeled from the component.

[0054] As the aqueous liquid, a liquid containing a small amount of additives as needed in water or a mixed solvent with water as the main component can be used. As solvents other than water constituting the above-mentioned mixed solvent, lower alcohols (such as ethanol) and lower ketones (such as acetone) that can be uniformly mixed with water can be used. As the above-mentioned additives, known surfactants and the like can be used. In some embodiments, it is preferred to use an aqueous liquid that does not substantially contain additives. From the viewpoint of environmental hygiene, it is preferred to use water as the aqueous liquid. There are no particular restrictions on water. Considering the purity required for the application, ease of acquisition, etc., for example, distilled water, ion exchange water, tap water, etc. can be used. The temperature of the aqueous liquid is generally in the range of room temperature (10°C to 35°C), and warm water above 35°C and below 90°C (for example, above 40°C and below 60°C) can also be used.

[0055] In some embodiments, the water stripping process can be performed by supplying an aqueous liquid near the outer edge of the adhesive (layer) attached to the component. After the aqueous liquid enters the interface between the adhesive and the component from the outer edge of the adhesive, the adhesive is stripped without supplying new water (i.e., using only the aqueous liquid supplied to the component before the start of the stripping process). It should be noted that if the water that has entered the interface between the adhesive and the component due to the movement of the stripping front is exhausted during the water stripping process, additional water can be supplied intermittently or continuously after the water stripping process begins.

[0056] The amount of the aqueous liquid supplied before the peeling starts is not particularly limited as long as it can import the above-mentioned aqueous liquid from the adhesion range of the adhesive (layer) to the amount of the interface between the adhesive and the parts. The amount of the above-mentioned aqueous liquid can be, for example, more than 5 μL, and it is appropriate to be more than 10 μL, or more than 20 μL. In addition, the upper limit of the amount of the above-mentioned aqueous liquid is not particularly limited. In some ways, from the viewpoints of improving operability, the amount of the above-mentioned aqueous liquid can be, for example, less than 10 mL, less than 5 mL, less than 1 mL, less than 0.5 mL, less than 0.1 mL, or less than 0.05 mL.

[0057] The operation of allowing the aqueous liquid to enter the interface between the adhesive (layer) and the above-mentioned component from the outer edge of the above-mentioned adhesive at the beginning of peeling can be carried out in the following manner: for example, at the outer edge of the adhesive, the front end of an instrument such as a utility knife or a needle is inserted into the above-mentioned interface; the outer edge of the adhesive is hooked with a hook or the like and lifted upward; a highly adhesive adhesive tape, a suction cup, etc. is attached to the back side near the outer edge of the joint body to lift the end of the adhesive upward; and so on.

[0058] In addition, the water stripping process can be preferably implemented in a manner such that the above-mentioned peeling front moves at a speed of more than 10 mm / minute. In terms of moving the peeling front at a speed of more than 10 mm / minute, for example, under the condition that the peeling angle is 180 degrees, it is equivalent to peeling the adhesive (layer) at a tensile speed of more than 20 mm / minute. The speed at which the peeling front moves can be, for example, more than 50 mm / minute, more than 150 mm / minute, more than 300 mm / minute, or more than 500 mm / minute. There is no particular upper limit on the speed at which the peeling front moves. The speed at which the peeling front moves can be, for example, less than 1000 mm / minute.

[0059] For the aqueous peeling disclosed herein, for example, the adhesive (layer) can be peeled off with a volume of, for example, 50 cm per 10 μL of the aqueous liquid (eg, water) used in the method. 2 More than, preferably 100cm 2 The above method is implemented.

[0060] <Joint body and components>

[0061] The conjugate disclosed herein is not particularly limited as long as it comprises two parts joined by an adhesive (typically an adhesive layer) and can be composed of more than two parts. For example, it can be a multilayer structure stacked with more than two laminar bodies. Such a conjugate (typically a multilayer structure) can include optical components such as display components, transparent components, and other functional components. By implementing the conjugate separation method disclosed herein to such a conjugate of a multilayer structure comprising a plurality of different parts, the parts contained in the product after use can be effectively reused.

[0062] The bonded body disclosed in this article can be a structure used in various applications and products. The bonded body can be a structure for various applications that may need to be recycled or repaired. For example, in the structure constituting various portable devices, automobiles, household electrical appliances, etc., it can be a structure comprising two or more parts joined by an adhesive. Such joining can be used not only for fixing and joining, but also for forming, decoration, protection, support, etc. The material of the component constituting the bonded body joined by the adhesive, and the material constituting at least the surface of the component can be, for example, glass, metal, ceramic material, resin material, etc.

[0063] As the preferred example of the parts constituting the above-mentioned joint body, optical parts can be enumerated.So-called optical parts in this specification refer to parts with optical properties (for example, polarization, light refraction, light scattering, light reflectivity, light transmittance, light absorptivity, light diffraction, optical rotation, visual recognition, etc.).As the example of optical parts, polarizing plate, wavelength plate, phase difference plate, optical compensation film, brightness improvement film, light guide plate, reflective film, anti-reflection film, hard coating (HC) film, impact absorption film, antifouling film, photochromic film, dimming film, transparent conductive film (ITO film), design film, decorative film, surface protection plate, prism, lens, color filter, transparent substrate and parts stacked therewith (sometimes they are collectively referred to as " functional film ") etc. It should be noted that above-mentioned " plate " and " film " each include plate-like, membranous, sheet-like forms, for example, " polarizing film " includes " polarizing plate ", " polaroid " etc. The optical component may be, for example, a component (typically, a component constituting a display device) used in a display device (typically, an image display device).

[0064] The optical components are not particularly limited, and examples thereof include components formed from glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal thin films, etc. (e.g., sheet-shaped, film-shaped, or plate-shaped components). It should be noted that the term "optical component" as used herein may include components that serve a decorative or protective purpose while maintaining the visibility of the display device (e.g., design films, decorative films, surface protective films, etc.).

[0065] Furthermore, the material constituting at least the surface of the optical component may be, for example, glass such as alkali glass plate or alkali-free glass; metal materials such as stainless steel (SUS) or aluminum; ceramic materials such as alumina or silica; resin materials such as acrylic resin, ABS resin, polycarbonate resin, polystyrene resin, and transparent polyimide resin; and the like. Preferred examples of the component include components comprising inorganic materials such as the aforementioned glass, ceramic materials, and metal materials. The component may be an optical component in which at least a portion of the surface to which the adhesive is applied is composed of such a material.

[0066] The parts constituting the joint body can be painted surfaces of coatings such as acrylic, polyester, alkyd, melamine, polyurethane, acid-epoxy cross-linked, or their composites (such as acrylic melamine, alkyd resin melamine), or plated surfaces of galvanized steel plates.

[0067] In addition, in some preferred embodiments, the components constituting the joint body are glass components comprising brittle materials such as glass (typically hard and brittle materials). For example, for a joint body in which at least one of the two components joined by an adhesive is formed by a brittle material such as a glass material, the joint body separation method disclosed herein is preferably applicable. With regard to hard and brittle materials such as glass, sometimes it is unable to withstand the force of peeling off the adhesive attached thereto and is damaged. However, by adopting the method disclosed herein, the adhesive can be peeled off from the component without damaging an adherend such as glass. As a typical example of a glass component, a plate-shaped glass plate can be cited.

[0068] The size of the glass component is not limited to a specific range. The thickness of the glass component (e.g., a glass plate) can be, for example, 0.1 to 5 mm (e.g., 0.5 to 2 mm). The length of the glass component can be, for example, 5 mm to 1 m (e.g., 50 mm or more, further 100 mm or more and 500 mm or less). When peeling the adhesive from a glass component of such a size, the method disclosed herein can be preferably used. It should be noted that the length of the glass component (e.g., a glass plate) refers to the length of the portion having the maximum length in the surface direction of the glass component.

[0069] Furthermore, the components may have surfaces that have been hydrophilized. For example, the surfaces of the aforementioned optical components may have been subjected to a treatment that enhances hydrophilicity, such as corona treatment, plasma treatment, or hydrophilic coating treatment with a hydrophilic coating layer. Components with such hydrophilized surfaces have increased hydrophilicity and their water contact angles are limited to below a specified value, making them suitable for the removal of adhesives containing hydrophilic agents.

[0070] In embodiments where the components constituting the bonded body have a plate or sheet shape, their maximum thickness can be approximately 5 mm or less (e.g., 2 mm or less, preferably 1 mm or less). Components with such a maximum thickness are typically susceptible to deformation or breakage under external forces. However, by applying the method disclosed herein, the adhesive can be smoothly peeled from the component without damaging it. The thickness of the plate or sheet-shaped component can typically be, for example, 0.1 to 5 mm (e.g., 0.5 to 2 mm).

[0071] Some embodiments involve a bonded body for a display device. Examples of such display devices include liquid crystal displays, organic EL displays, PDPs, and electronic paper. In particular, when such display devices, such as foldable displays and in-vehicle displays, contain expensive components, the technology disclosed herein is preferably applied. Furthermore, such display devices include input-capable display devices such as touch panels. Given the strong demand for recycling and reuse of such display devices, the application of the technology disclosed herein is particularly significant.

[0072] In the above-mentioned display device, the display component joined by the adhesive is a component that assumes the display function of the display device. Other than this, there is no particular limitation, and it can be composed of, for example, various materials (including optical materials, light-emitting elements, etc.). The display component can be, for example, a liquid crystal display panel, an organic EL display panel, a PDP, a touch panel, etc., or their display parts (display units). It should be noted that the panel is sometimes also referred to as a sheet or a film. The shape of the display component is not particularly limited, for example, it has a sheet-like or plate-like shape. The display component can have a curved surface shape, and can also have deformability and flexibility. Such a display component is suitable, for example, as a display component of a foldable display device or a flexible display device.

[0073] In some preferred embodiments, one of the two components comprising the bonded body is a glass component and the other is a display component. According to the method disclosed herein, even when the components bonded by an adhesive include a hard and brittle glass component and a display component (e.g., a thin-walled component with a thickness of 2 mm or less), the two components can be separated by solvent immersion stripping without damaging (typically, cracking or splitting) the glass component and the display component.

[0074] The thickness of the display component is not limited to a specific range and can be, for example, 0.1 to 5 mm (e.g., 0.5 to 2 mm). For example, when peeling an adhesive from a display component having a thickness of 2 mm or less (e.g., 1 mm or less, further 300 μm or less, typically 100 μm or less), the technology disclosed herein can be applied to effectively separate the components without damaging the display component, which has low strength due to its thin wall. The thickness of the display component can be approximately 50 μm or less, and can be 30 μm or less.

[0075] The joint body that is joined with parts by adhesive can be the joint body of the time above certain since the joint based on adhesive.For example, the joint state based on adhesive of the goods that comprises joint body can be after use until being recycled for the purpose of recycling etc., further till the end of the product life of above-mentioned goods (for example, can be more than 6 months, further more than 1 year or more than 3 years, more than 5 years) always continue.Such adhesive sometimes due to use environment etc. excessively raises bonding force, the planned peeling off again becomes difficult.For example, even can realize the water peeling of having used aqueous liquid, comprise water affinity agent water peeling property adhesive, through a long time, desired water peeling property sometimes also can lose, and peeling off again becomes difficult.For the joint body that comprises the adhesive that is in such state, by being applicable to technology disclosed herein, can satisfactorily realize the separation of this joint body.

[0076] The display device comprising the above-mentioned junction body can be a component of an electronic device (suitably a portable electronic device) that requires high bonding reliability based on an adhesive when joining parts, and requires smooth removal of the components when repairing, replacing, inspecting, recycling, etc. For example, it can be a mobile phone, a smart phone, a tablet computer, a laptop computer, various wearable devices (for example, a wrist-worn type worn on the wrist like a watch, a module type worn on a part of the body with a clip, a strap, etc., a glasses-wearing type including a glasses type (monocular type, binocular type. Also including a head-worn type), a clothing type such as a shirt, socks, a hat, etc. installed in the form of an accessory, an ear-worn type worn on the ear like a headset, etc.), a digital camera, a digital video camera, an audio device (portable music player, IC recorder, etc.), a calculator (calculator, etc.), a mobile game device, an electronic dictionary, an electronic notebook, an electronic book, an in-vehicle information device, a mobile radio, a mobile TV, a mobile printer, a mobile scanner, a mobile modem, etc. The component of the portable electronic device. In addition, the above-mentioned display device can be a component of an electronic device such as a desktop computer, a display, a TV (liquid crystal, plasma, organic EL, etc.). It should be noted that the term "portable (or mobile)" in this specification not only means being able to be carried, but also means having portability at a level that an individual (a standard adult) can move relatively easily.

[0077] Adhesives

[0078] In the above-mentioned joint body, the form of the adhesive for joining the parts is not particularly limited, and for example, it can be a form in which the above-mentioned parts are joined in a regular or random pattern such as a dotted or striped shape, typically, a form of a continuously formed layered adhesive layer or adhesive sheet. For example, the adhesive can be constituted as a two-sided adhesive sheet without a support formed by an adhesive layer, or can also be constituted as an adhesive sheet (two-sided adhesive sheet) with two-sided adhesiveness of an intermediate layer such as a substrate layer. The adhesive sheet has a structure provided with a first adhesive layer and a second adhesive layer on each side (all non-peelable) of the intermediate layer.

[0079] The adhesive layer of the adhesive sheet is not limited to a single-layer structure and may include one or more adhesive layers having the same or different compositions. For example, in an adhesive sheet having an intermediate layer, the intermediate layer may be an adhesive layer. In this case, the adhesive sheet may have at least three adhesive layers, namely: a first adhesive layer constituting the surface of the adhesive sheet, a second adhesive layer, and an adhesive layer serving as the intermediate layer.

[0080] In the above-mentioned joint body, the adhesive used for joining the parts (which may be in the form of an adhesive layer or an adhesive sheet. The same shall apply hereinafter unless otherwise specified) may be one or more adhesives selected from various known adhesives such as acrylic adhesives, rubber adhesives (natural rubber adhesives, synthetic rubber adhesives, mixed systems thereof, etc.), silicone adhesives, polyester adhesives, polyurethane adhesives, polyether adhesives, polyamide adhesives, and fluorine adhesives. Here, the so-called acrylic adhesive refers to an adhesive with an acrylic polymer as the main component (base polymer). The same applies to rubber adhesives and other adhesives.

[0081] It should be noted that the term "base polymer" of an adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not intended to be limiting in any other way. The rubbery polymer mentioned above refers to a polymer that exhibits rubber elasticity in a temperature range near room temperature. Furthermore, in this specification, the term "main component" refers to the component comprising the largest proportion of the components present, based on weight. Therefore, for example, if an adhesive is composed of three or more components, the content of the main component in the adhesive may be 34% by weight or greater.

[0082] In this specification, the term "acrylic polymer" refers to a polymer derived from a monomer component containing an acrylic monomer in an amount exceeding 50% by weight, also referred to as an acrylic polymer. The aforementioned acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryloyl group per molecule. In this specification, the term "(meth)acryloyl" refers inclusively to both acryloyl and methacryloyl groups. Similarly, "(meth)acrylate" refers inclusively to both acrylate and methacrylate, and "(meth)acrylic-" refers inclusively to both acrylic- and methacrylic- groups.

[0083] (Acrylic adhesive)

[0084] In some embodiments, an acrylic adhesive may be preferably used as the adhesive material. Specifically, the adhesive disclosed herein may be an acrylic adhesive comprising an acrylic polymer. Acrylic adhesives tend to have excellent transparency, weather resistance, and design flexibility. Acrylic adhesives with high transparency are preferably used in optical applications and for bonding display devices.

[0085] As the adhesive disclosed herein, for example, it is preferable to contain, as a base polymer, an acrylic polymer composed of a monomer component containing 33% by weight or more of an alkyl (meth)acrylate having a linear or branched alkyl group with 1 to 20 carbon atoms at the ester terminal. Hereinafter, an alkyl (meth)acrylate having an alkyl group with X to Y carbon atoms at the ester terminal may be referred to as "alkyl (meth)acrylate C X-Y Alkyl ester". In order to easily obtain a balance of properties, in the entire monomer components of the acrylic polymer in some embodiments, (meth)acrylic acid C 1-20 The ratio of the alkyl ester is, for example, 35% by weight or more, preferably 50% by weight or more, and may be 55% by weight or more. 1-20 The proportion of the alkyl ester may be, for example, 99.9 wt % or less, 99 wt % or less, or 95 wt % or less. From the perspective of the cohesiveness of the adhesive layer, some embodiments of the acrylic polymer (meth) acrylic acid C 1-20 The proportion of the alkyl ester in the total monomer components may be, for example, 85% by weight or less, 75% by weight or less, or 65% by weight or less. 1-20 The alkyl esters may be used alone or in combination of two or more.

[0086] Among the above, it is preferred to use at least (meth)acrylic acid C 4-20 Alkyl esters, more preferably at least (meth) acrylic acid C4-18 Alkyl ester. For example, it is preferable to contain one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as the above-mentioned monomer components, and an acrylic adhesive containing at least BA is particularly preferable. (Meth)acrylic acid C 4-18 The alkyl esters may be used alone or in combination of two or more.

[0087] The monomer components constituting the acrylic polymer may include an alkyl (meth)acrylate and, if necessary, other monomers copolymerizable with the alkyl (meth)acrylate (comonomers). Preferred copolymerizable monomers include monomers having polar groups (e.g., carboxyl groups, hydroxyl groups, rings containing nitrogen atoms, etc.) and monomers having a relatively high homopolymer glass transition temperature (e.g., above 10°C). Monomers having polar groups can help introduce crosslinking points into the acrylic polymer or increase the cohesive strength of the adhesive. Coonomers may be used singly or in combination of two or more.

[0088] Non-limiting examples of copolymerizable monomers include carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, sulfonic acid group- or phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, amide group-containing monomers, amino group-containing monomers, monomers having a nitrogen atom-containing ring, monomers having a succinimide skeleton, maleimides, aminoalkyl (meth)acrylates, alkoxy group-containing monomers, alkoxysilyl group-containing monomers, vinyl esters, vinyl ethers, aromatic vinyl compounds, olefins, (meth)acrylates having an alicyclic hydrocarbon group, (meth)acrylates having an aromatic hydrocarbon group, heterocyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen-containing (meth)acrylates such as vinyl chloride and fluorine-containing (meth)acrylates, silicon-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylates derived from terpene compound derivative alcohols. Among them, a carboxyl group-containing monomer, a hydroxyl group-containing monomer, a monomer having a nitrogen atom-containing ring, and a (meth)acrylate having an alicyclic hydrocarbon group are preferred.

[0089] Preferred examples of the copolymerizable monomers, which are carboxyl group-containing monomers, include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0090] Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

[0091] Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and N-vinylpyridazine (for example, lactams such as N-vinyl-2-caprolactam).

[0092] Examples of the (meth)acrylate having an alicyclic hydrocarbon group include (meth)acrylates containing an alicyclic hydrocarbon group such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, and adamantyl (meth)acrylate.

[0093] When using the above-mentioned comonomer, its usage amount is not particularly limited, and for example, it is appropriate to set it to 0.01 weight % or more of the overall monomer component. From the viewpoint of better exerting the use effect of the comonomer, the usage amount of the comonomer can be 0.1 weight % or more of the overall monomer component, or 0.5 weight % or more. In addition, from the viewpoint of easily obtaining the balance of adhesive properties, it is appropriate to set the usage amount of the comonomer to 60 weight % or less of the overall monomer component, or 50 weight % or less, or 40 weight % or less.

[0094] In some embodiments, the monomer components constituting the acrylic polymer may include hydroxyl-containing monomers. By using hydroxyl-containing monomers, the cohesive force of the adhesive, the degree of crosslinking (for example, crosslinking based on isocyanate crosslinking agent) can be appropriately adjusted. As hydroxyl-containing monomers, the hydroxyl-containing monomers exemplified above can be used, for example, 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) can be preferably used. Hydroxyl-containing monomers can be used alone or in combination of two or more. There is no particular restriction on the amount used when using hydroxyl-containing monomers. In some preferred embodiments, the amount of hydroxyl-containing monomers is more than 15% by weight of the overall monomer component, more than 20% by weight is appropriate, and preferably more than 25% by weight. In addition, from the viewpoint of suppressing the water absorption of the adhesive, in some embodiments, it is appropriate to set the amount of hydroxyl-containing monomers to less than 50% by weight (for example, less than 45% by weight) of the overall monomer component, can be set to less than 40% by weight, can be set to less than 30% by weight, and can be set to less than 20% by weight.

[0095] In some embodiments, the monomer components constituting the acrylic polymer may include a (meth)acrylate containing an alicyclic hydrocarbon group. This can improve the cohesive force of the adhesive. As the (meth)acrylate containing an alicyclic hydrocarbon group, the (meth)acrylates exemplified above can be used, for example, cyclohexyl acrylate (CHA) and isobornyl acrylate can be preferably used. The (meth)acrylate containing an alicyclic hydrocarbon group can be used alone or in combination of two or more. There is no particular restriction on the amount of the (meth)acrylate containing an alicyclic hydrocarbon group used, for example, it can be set to more than 1% by weight of the total monomer component, or more than 5% by weight, or more than 10% by weight. It is appropriate to set the upper limit of the amount of the (meth)acrylate containing an alicyclic hydrocarbon group to be less than about 40% by weight, and it can be less than 25% by weight (for example, less than 15% by weight).

[0096] In some embodiments, the monomer components constituting the acrylic polymer may include monomers having nitrogen atoms. This can improve the cohesive force of the adhesive. As monomers having nitrogen atoms, the monomers exemplified above can be used. As preferred examples of monomers having nitrogen atoms, monomers having a ring containing nitrogen atoms can be mentioned. For example, N-vinyl cyclic amides can be mentioned, among which N-vinyl-2-pyrrolidone can be preferably used. Monomers having nitrogen atoms can be used alone or in combination of two or more. The amount of monomers having nitrogen atoms (preferably monomers having a ring containing nitrogen atoms) used is not particularly limited, for example, it can be more than 1% by weight of the entire monomer component, can be more than 5% by weight, and can further be set to more than 10% by weight. In addition, it is appropriate to set the amount of monomers having nitrogen atoms to, for example, less than 40% by weight of the entire monomer component, and can be set to less than 30% by weight, or can be set to less than 15% by weight.

[0097] In some embodiments, the proportion of carboxyl-containing monomers in the monomer components of the acrylic polymer can be, for example, less than 10% by weight, less than 3% by weight, or less than 1% by weight (e.g., less than 0.1% by weight). It is also possible to use substantially no carboxyl-containing monomers as monomer components of the acrylic polymer. Here, "substantially no carboxyl-containing monomers" means that carboxyl-containing monomers are at least not intentionally used. Acrylic polymers with such compositions can provide metal corrosion resistance to adherends containing metal.

[0098] The composition of the monomer components constituting the acrylic polymer can be set so that the glass transition temperature (Tg) calculated using the Fox equation based on the monomer component composition is between -75°C and 10°C. In some embodiments, from the perspective of adhesive strength, the Tg is suitably 0°C or lower, preferably -10°C or lower, and can be -20°C or lower, or -30°C or lower. Furthermore, from the perspective of cohesion, the Tg can be, for example, -60°C or higher, -50°C or higher, -45°C or higher, or -40°C or higher.

[0099] Here, the Fox equation is a relationship equation showing the relationship between Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each monomer constituting the copolymer, as shown below.

[0100] 1 / Tg=Σ(Wi / Tgi)

[0101] It should be noted that in the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). The glass transition temperature of the homopolymer used in the calculation of Tg is the value described in known literature, specifically, "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989). When multiple values are described in this document, the highest value is adopted.

[0102] When performing polymerization, known or customary thermal polymerization initiators and photopolymerization initiators can be used according to the polymerization method, polymerization mode, etc. As thermal polymerization initiators, there are no particular limitations, and for example, azo-based polymerization initiators, peroxide-based initiators, redox-based initiators based on a combination of peroxide and a reducing agent, substituted ethane-based initiators, etc. can be used. As photopolymerization initiators, there are no particular limitations, and for example, ketal-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin ether-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, etc. can be used. The polymerization initiator can be used alone or in appropriate combinations of two or more. The amount of such thermal polymerization initiator or photopolymerization initiator used can be the usual amount used according to the polymerization method, polymerization mode, etc., and is not particularly limited. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example, about 0.01 to 1 part by weight) of the polymerization initiator can be used per 100 parts by weight of the monomer to be polymerized.

[0103] In the above-mentioned polymerization, various chain transfer agents known in the past (which may also be considered as molecular weight regulators or polymerization degree regulators) may be used as needed. As chain transfer agents, thiols such as n-dodecyl mercaptan, tert-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol may be used. Alternatively, a chain transfer agent that does not contain a sulfur atom (non-sulfur chain transfer agent) may be used. Chain transfer agents may be used alone or in combination of two or more. When a chain transfer agent is used, its usage amount may be, for example, about 0.01 to 1 part by weight relative to 100 parts by weight of the monomer component. As far as the technology disclosed herein is concerned, it can be appropriately implemented even without using a chain transfer agent.

[0104] The molecular weight of the acrylic polymer obtained by appropriately adopting the above-mentioned various polymerization methods is not particularly limited and can be set within an appropriate range according to the required performance. The weight average molecular weight (Mw) of the acrylic polymer is, for example, approximately 10×10 4 From the perspective of achieving a good balance between cohesion and adhesion, more than 30 × 10 4 Some forms of acrylic polymer preferably have a 4 The upper limit of the Mw of the acrylic polymer may be about 500×10 4 Below (for example, about 150×10 4 The above Mw can be about 75×10 4Here, Mw refers to the value obtained by gel permeation chromatography (GPC) in terms of standard polystyrene. As a GPC apparatus, for example, the model "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used.

[0105] The adhesive disclosed herein can be formed using an adhesive composition containing monomer components of the composition described above in the form of a polymer, an unpolymer (i.e., a polymerizable functional group in an unreacted form), or a mixture thereof. The above-mentioned adhesive composition can be in the following various forms: a water-dispersible adhesive composition in the form of an adhesive (adhesive component) dispersed in water; a solvent-based adhesive composition in the form of an adhesive contained in an organic solvent; an active energy ray-curable adhesive composition prepared by curing with active energy rays such as ultraviolet rays and radiation to form an adhesive; a hot melt adhesive composition that forms an adhesive when applied in a heated molten state and cooled to near room temperature; and the like. Some forms of adhesive compositions are solvent-based adhesive compositions or solvent-free adhesive compositions. The solvent-free adhesive composition includes active energy ray-curable adhesive compositions and hot melt adhesive compositions. The solvent-immersion-based peeling disclosed herein is effective for solvent-based adhesives formed by solvent-based adhesive compositions and active energy ray-curable adhesives (typically ultraviolet-curable adhesives) formed by active energy ray (typically ultraviolet-curable) curable adhesive compositions.

[0106] The adhesive composition involved in some embodiments may be an active energy ray-curable adhesive composition. In this specification, the so-called "active energy ray" refers to an energy ray having energy that can cause chemical reactions such as polymerization reaction, cross-linking reaction, and decomposition of initiators. Examples of the active energy ray referred to herein include ultraviolet rays, visible rays, infrared rays, α rays, β rays, γ rays, electron rays, neutron rays, X-rays and other radiation. As a preferred example of an active energy ray-curable adhesive composition, a photocurable adhesive composition can be cited. The photocurable adhesive composition has the following advantages: even a thick adhesive layer can be easily formed. Among them, an ultraviolet ray-curable adhesive composition is preferred.

[0107] Typically, the photocurable adhesive composition contains at least a portion of the monomer components of the composition in the form of a polymer (which may be a portion of the monomer type or a portion of the amount). The polymerization method for forming the above-mentioned polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately adopted. For example, thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically, carried out in the presence of a thermal polymerization initiator); photopolymerization by irradiation with light such as ultraviolet rays (typically, carried out in the presence of a photopolymerization initiator); radiation polymerization by irradiation with radiation such as β rays and γ rays; and the like. Among them, photopolymerization is preferred.

[0108] Some preferred embodiments involve a photocurable adhesive composition comprising a partial polymer of a monomer component (e.g., an acrylic partial polymer). Such a partial polymer is typically a mixture of a polymer from a monomer component and an unreacted monomer, and is preferably in the form of a slurry (a viscous liquid). Hereinafter, a partial polymer of this nature is sometimes referred to as "monomer slurry" or simply "slurry". There is no particular limitation on the polymerization method for partially polymerizing the monomer component, and various polymerization methods such as those described above can be appropriately selected and used. From the viewpoint of efficiency and simplicity, photopolymerization can be preferably used. According to photopolymerization, the polymerization conversion rate (monomer conversion) of the monomer component can be easily controlled by polymerization conditions such as the amount of light irradiation (amount of light).

[0109] The polymerization conversion rate of the monomer mixture in the partially polymerized product is not particularly limited. For example, the polymerization conversion rate may be approximately 70% by weight or less. From the perspectives of ease of preparation and coating properties of the adhesive composition containing the partially polymerized product, a polymerization conversion rate of approximately 50% by weight or less is suitable, and preferably approximately 40% by weight or less is suitable. The lower limit of the polymerization conversion rate is not particularly limited, but is typically approximately 1% by weight or greater, with approximately 5% by weight or greater being suitable.

[0110] The adhesive composition containing the above-mentioned partially polymerized compound may be mixed with other components as needed (e.g., a photopolymerization initiator, a hydrophilic agent as described below, a crosslinking agent, a multifunctional monomer, an acrylic oligomer, a tackifying resin, a silane coupling agent, etc.). The method for mixing such other components is not particularly limited, and for example, they may be pre-mixed in the above-mentioned monomer mixture or added to the above-mentioned partially polymerized compound.

[0111] As emulsifiers for emulsion polymerization, there are no particular restrictions, and known anionic emulsifiers, nonionic emulsifiers, etc. can be used. Emulsifiers can be used alone or in combination of two or more. Non-limiting examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene lauryl sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkylphenyl ether ammonium sulfate, polyoxyethylene alkylphenyl ether sodium sulfate, polyoxyethylene alkyl sulfosuccinate sodium, etc. Non-limiting examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid esters, polyoxyethylene polyoxypropylene block polymers, etc. Emulsifiers with reactive functional groups (reactive emulsifiers) can be used. As examples of reactive emulsifiers, free radical polymerizable emulsifiers having a structure obtained by introducing free radical polymerizable functional groups such as propenyl and allyl ether groups into the above-mentioned anionic emulsifiers or nonionic emulsifiers can be mentioned.

[0112] The amount of the emulsifier used in the emulsion polymerization can be, for example, 0.2 parts by weight or more, 0.5 parts by weight or more, 1.0 parts by weight or more, or 1.5 parts by weight or more, relative to 100 parts by weight of the monomer components. Furthermore, from the perspective of improving water-resistant adhesion or enhancing the transparency of the adhesive, in some embodiments, it is appropriate to use an emulsifier in an amount of 10 parts by weight or less, preferably 5 parts by weight or less, or even 3 parts by weight or less, relative to 100 parts by weight of the monomer components. It should be noted that the emulsifier used in the emulsion polymerization herein can also function as a water affinity agent, which will be described later.

[0113] The adhesive composition involved in some aspects can be a solvent-based adhesive composition. The solvent-based adhesive composition typically contains a solution polymer of a monomer component and additives (such as a hydrophilic agent) used as needed. The solvent (polymerization solvent) used in the solution polymerization can be appropriately selected from conventionally known organic solvents (such as toluene, ethyl acetate, etc.). According to the solution polymerization, a polymerization reaction liquid in the form of a polymer of a monomer component dissolved in a polymerization solvent can be obtained. The solvent-based adhesive composition disclosed herein can be suitably manufactured using the above-mentioned polymerization reaction liquid.

[0114] (Hydrophilic Agent)

[0115] The above-mentioned adhesive contains a hydrophilic agent. By making the adhesive contain a hydrophilic agent, it is usually possible to effectively reduce the peeling force using aqueous liquids such as water, and improve the water peeling property. There is no special limiting explanation for the reason. It is believed that the hydrophilic agent usually has a hydrophilic region and is easily biased on the surface of the adhesive, thereby playing a role in efficiently improving the water affinity of the adhesive surface. When the adhesive comes into contact with water, the peeling force is effectively reduced and the water peeling property is improved. However, due to long-term use and other conditions, the adhesive that joins the parts in the above-mentioned bonded body sometimes fails to show the water peeling property it originally had, and becomes a water peeling-loss adhesive that is difficult to peel off by water peeling. Even such an adhesive containing a hydrophilic agent that has lost its water peeling property can be peeled off from the part to which the adhesive is joined by applying the technology disclosed in this article. The above-mentioned hydrophilic agent is typically contained in the adhesive composition (and then the adhesive) in a free form. As the hydrophilic agent, from the perspective of the ease of preparation of the adhesive composition, it is preferably used a hydrophilic agent that is liquid at room temperature (about 25°C). The hydrophilic agent can be used alone or in combination of two or more.

[0116] The HLB value of the hydrophilic agent (typically a surfactant) is not particularly limited, but is, for example, 3.0 or greater, with a value of approximately 5.0 or greater being suitable, preferably 8.0 or greater, more preferably 10 or greater, and even more preferably 13 or greater (e.g., 15 or greater). By incorporating a hydrophilic agent having an HLB within the above range into an adhesive (e.g., an adhesive containing an acrylic polymer), even if water-peelability is impaired, the adhesive can be peeled from a component by solvent immersion peeling. The upper limit of the HLB value is 20 or less, for example, 18 or less, or 16 or less (e.g., 15 or less).

[0117] It should be noted that the HLB value used in this specification is the hydrophile-lipophile balance (HLB) value proposed by Griffin. It indicates the affinity of a surfactant for water and oil, with a value between 0 and 20 representing the ratio of hydrophilicity to lipophilicity. The definition of HLB is described in W.C. Griffin, J. Soc. Cosmetic Chemists, 1, 311 (1949); and in Takahashi Kotomi, Namba Yoshiro, Koike Motoo, and Kobayashi Masao, "Surfactant Handbook," 3rd edition, published by Kogaku Book Co., Ltd., November 25, 1978, pp. 179-182. A hydrophilic agent having the above HLB value can be selected based on the technical knowledge of those skilled in the art, with reference to the above references, etc., as needed.

[0118] In some embodiments, at least one compound selected from surfactants and compounds having a polyoxyalkylene backbone can be used as a hydrophilic agent. As surfactants and compounds having a polyoxyalkylene backbone, one or more of known surfactants and compounds having a polyoxyalkylene backbone can be used without particular limitation. It should be noted that some of the above surfactants may contain compounds having a polyoxyalkylene backbone, and vice versa.

[0119] As surfactants that can be used as water affinity agents, known nonionic surfactants, anionic surfactants, cationic surfactants, etc. can be used. Among them, nonionic surfactants are preferred. Surfactants can be used alone or in combination of two or more.

[0120] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monooleate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate; polyoxyethylene glycerol ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; and the like. These nonionic surfactants can be used alone or in combination of two or more.

[0121] Examples of anionic surfactants include: alkyl sulfates such as lauryl sulfate and octadecyl sulfate; fatty acid salts; alkylbenzenesulfonates such as nonylbenzenesulfonate and dodecylbenzenesulfonate; naphthalenesulfonates such as dodecylnaphthalenesulfonate; alkyldiphenyletherdisulfonates such as dodecyldiphenyletherdisulfonate; polyoxyethylene alkylethersulfates such as polyoxyethylene octadecylethersulfate and polyoxyethylene laurylethersulfate; polyoxyethylene alkylphenylethersulfates such as polyoxyethylene laurylphenylethersulfate; polyoxyethylene styrenated phenylethersulfate; sulfosuccinates such as laurylsulfosuccinate and polyoxyethylene laurylsulfosuccinate; polyoxyethylene alkyletherphosphates; polyoxyethylene alkyletheracetates; and the like. When the anionic surfactant forms a salt, the salt may be, for example, a metal salt (preferably a monovalent metal salt) such as sodium, potassium, calcium, or magnesium salt, an ammonium salt, or an amine salt. These anionic surfactants may be used alone or in combination of two or more.

[0122] Examples of compounds having a polyoxyalkylene backbone that can be used as hydrophilic agents include polyalkylene glycols such as polyethylene glycol (PEG) and polypropylene glycol (PPG); polyethers containing polyoxyethylene units, polyethers containing polyoxypropylene units, and compounds containing oxyethylene and oxypropylene units (the arrangement of these units may be random or block-like); and derivatives thereof. Furthermore, compounds having a polyoxyalkylene backbone among the above-mentioned surfactants may also be used. These may be used alone or in combination of two or more. Among these, compounds containing a polyoxyethylene backbone (also referred to as a polyoxyethylene segment) are preferred, with PEG being more preferred.

[0123] The molecular weight (chemical formula weight) of the compound having a polyoxyalkylene skeleton (e.g., polyethylene glycol) is not particularly limited; for example, a molecular weight of less than 1000 is suitable, and from the perspective of the productivity of the adhesive composition, it is preferably about 600 or less (e.g., 500 or less). The lower limit of the molecular weight of the compound having a polyoxyalkylene skeleton (e.g., polyethylene glycol) is not particularly limited; however, compounds having a molecular weight of about 100 or greater (e.g., about 200 or greater, and further about 300 or greater) are preferably used.

[0124] The content of the hydrophilic agent in the adhesive is not particularly limited and can be set in a manner that appropriately brings into play the effect of the use of the hydrophilic agent. In some embodiments, relative to 100 parts by weight of the polymer (such as an acrylic polymer) contained in the adhesive, the content of the hydrophilic agent can be, for example, set to 0.001 parts by weight or more, and it is appropriate to set it to 0.01 parts by weight or more, preferably 0.05 parts by weight or more, and more preferably 0.1 parts by weight or more. In some other embodiments, relative to 100 parts by weight of the polymer contained in the adhesive, the content of the hydrophilic agent can be, for example, 1.0 parts by weight or more, and can be 1.5 parts by weight or more. In addition, in some embodiments, relative to 100 parts by weight of the above-mentioned polymer, the usage amount of the hydrophilic agent can be set to approximately 3 parts by weight or less, and it is appropriate to set it to approximately 2 parts by weight or less, preferably less than 1 part by weight, and more preferably less than 0.5 parts by weight. By limiting the usage amount of the hydrophilic agent, there is a tendency to be easy to maintain adhesive strength. In addition, in optical applications, there is a tendency to be less prone to losing the optical properties of the adhesive. An adhesive containing the hydrophilic agent in the amount defined above can achieve an ideal balance between adhesive strength and solvent immersion releasability. In optical applications, it can also provide an adhesive having excellent optical properties.

[0125] (Multifunctional monomer)

[0126] A multifunctional monomer can be used in the adhesive composition (and thus the adhesive) as needed. The multifunctional monomer helps to adjust the cohesive force and other purposes. When the adhesive layer is formed or after being attached to the adherend, the multifunctional monomer reacts with the above-mentioned ethylenically unsaturated group by light (such as ultraviolet light) irradiation, thereby forming a cross-linked structure with suitable flexibility. Therefore, in this specification, "multifunctional monomer" can be referred to as a cross-linking agent. For example, in the adhesive formed by the light-curing adhesive composition, a multifunctional monomer can be preferably used. As the multifunctional monomer, a compound having two or more ethylenically unsaturated groups can be used. One type of multifunctional monomer can be used alone or two or more types can be used in combination.

[0127] Examples of ethylenically unsaturated groups in polyfunctional monomers include, but are not limited to, acryloyl, methacryloyl, vinyl, and allyl groups. From the perspective of photoreactivity, preferred ethylenically unsaturated groups include acryloyl and methacryloyl. Of these, acryloyl is preferred.

[0128] Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol(meth)acrylate, and hexanediol di(meth)acrylate. Among them, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are suitable.

[0129] The amount of the multifunctional monomer used varies depending on its molecular weight, number of functional groups, etc. For example, it is appropriately in the range of about 0.01 to 3.0 parts by weight relative to 100 parts by weight of the monomer component forming the polymer contained in the adhesive (typically, an acrylic polymer or a monomer component of the polymer).

[0130] (cross-linking agent)

[0131] Adhesive composition disclosed herein can be mainly with the crosslinking in adhesive (layer) or the crosslinking of adhesive and its adjacent surface for purpose, contains crosslinking agent as required.The kind of crosslinking agent is not particularly limited, and can be from crosslinking agents known in the past, for example, according to the composition of adhesive composition, in the mode that this crosslinking agent brings into play suitable crosslinking function in adhesive, select.As spendable crosslinking agent, can exemplify isocyanate crosslinking agent, epoxy crosslinking agent, oxazoline crosslinking agent, aziridine crosslinking agent, carbodiimide crosslinking agent, melamine crosslinking agent, urea crosslinking agent, metal alkoxide crosslinking agent, metal chelate crosslinking agent, metal salt crosslinking agent, hydrazine crosslinking agent, amine crosslinking agent etc. These crosslinking agents can be used alone or in combination of two or more.

[0132] The content of the cross-linking agent (the total amount thereof when two or more cross-linking agents are included) is not particularly limited. From the perspective of achieving an adhesive that exhibits adhesive properties such as adhesion and cohesion in a well-balanced manner, it is appropriate that the content of the cross-linking agent is about 5 parts by weight or less, preferably about 0.001 to 5 parts by weight, more preferably about 0.001 to 4 parts by weight, and even more preferably about 0.001 to 3 parts by weight, relative to 100 parts by weight of the monomer component (e.g., an acrylic polymer or a monomer component of the polymer) of the polymer contained in the adhesive. Alternatively, it may be an adhesive composition that does not contain such a cross-linking agent. When a photocurable adhesive composition is used as the adhesive composition disclosed herein, the adhesive composition may substantially not contain a cross-linking agent such as an isocyanate cross-linking agent. Here, the so-called adhesive composition substantially does not contain a cross-linking agent (typically an isocyanate cross-linking agent) means that the amount of the cross-linking agent relative to 100 parts by weight of the above-mentioned monomer component is less than 0.05 parts by weight (e.g., less than 0.01 parts by weight).

[0133] In order to make the cross-linking reaction more effectively carry out, a cross-linking catalyst can also be used. In addition, in the adhesive composition used for the formation of adhesive, a cross-linking retarder (such as a compound producing keto-enol tautomerism) can be contained according to expectation. The usage amount of the cross-linking catalyst and the cross-linking retarder is not limited to a specific scope and can use an appropriate amount according to purpose etc.

[0134] (Tackifying resin)

[0135] The adhesive may contain a tackifying resin. Examples of the tackifying resin include rosin-based tackifying resins, rosin derivative tackifying resins, petroleum-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins. One of these tackifying resins may be used alone, or two or more may be used in combination. Among them, one or more selected from rosin-based tackifying resins, rosin derivative tackifying resins, and terpene-phenol resins may be preferably used. For example, a tackifying resin (preferably a rosin derivative tackifying resin) having a softening point of 80°C or higher (e.g., 120°C or higher and 180°C or lower) may be preferably used.

[0136] Consider from the viewpoint of suitably giving play to the use effect of tackifying resin, for the monomer component 100 weight parts of the polymer contained in the adhesive, the usage amount of tackifying resin is that more than 1 weight part is appropriate, can be more than 5 weight parts, can be more than 10 weight parts, can be more than 15 weight parts, can be more than 20 weight parts, can be more than 25 weight parts.In addition, consider from the viewpoint of well-balanced consideration with the adhesion and cohesiveness of adherend, for example, can be below 50 weight parts, can be below 30 weight parts relative to the usage amount of tackifying resin for monomer component 100 weight parts.Or, for example, the content of the above-mentioned tackifying resin in adhesive is less than 1 weight part, and above-mentioned adhesive can also not comprise tackifying resin in fact with respect to above-mentioned monomer component 100 weight parts.

[0137] (Acrylic oligomer)

[0138] The adhesive disclosed herein may contain an acrylic oligomer from the viewpoint of improving cohesive strength and adhesiveness. Preferably, a polymer having a Tg higher than that of the acrylic polymer described above is used. For example, when preparing the adhesive using ultraviolet irradiation, acrylic oligomers are suitable because they are less likely to cause polymerization inhibition.

[0139] Preferred examples of acrylic oligomers include homopolymers of dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA); copolymers of DCPMA and methyl methacrylate (MMA), copolymers of DCPMA and IBXMA, copolymers of ADA and MMA, copolymers of CHMA and isobutyl methacrylate (IBMA), copolymers of CHMA and IBXMA, copolymers of CHMA and acryloylmorpholine (ACMO), copolymers of CHMA and diethylacrylamide (DEAA), and copolymers of CHMA and AA. One acrylic oligomer may be used alone or in combination of two or more.

[0140] The Mw of the acrylic acid oligomer can typically be about 1000 or more and less than about 30000, preferably about 1500 or more and less than about 10000, and more preferably about 2000 or more and less than about 5000. When the Mw is within the above range, it is easy and appropriate to exert the effect of improving cohesion and adhesion to adjacent surfaces. With regard to the Mw of the acrylic acid oligomer, it can be measured by gel permeation chromatography (GPC) and obtained as a value converted by standard polystyrene. Specifically, in HPLC8020 manufactured by Tosoh Corporation, two TSKgel GMH-H (20) columns are used as columns, and tetrahydrofuran solvent is used to measure at a flow rate of about 0.5 mL / min.

[0141] When the adhesive contains an acrylic oligomer, its content can be, for example, 0.01 parts by weight or more, and to achieve higher effects, can be 0.05 parts by weight or more, or even 0.1 parts by weight or more, relative to 100 parts by weight of the base polymer (typically an acrylic polymer). Furthermore, from the perspective of compatibility with the base polymer, the content of the acrylic oligomer is preferably less than 30 parts by weight, and can be, for example, 10 parts by weight or less, or even 1 part by weight or less.

[0142] (Silane coupling agent)

[0143] The adhesive disclosed herein may also include a silane coupling agent. In the case of a silane coupling agent, the silane coupling agent is preferably included in the adhesive composition (and thus the adhesive) in a free form. By including a silane coupling agent, the adhesive tends to increase its adhesion to an adherend (e.g., a glass component), but on the other hand, due to its increased adhesion, the peelability from the adherend is easily reduced during peeling. Even such an adhesive (an adhesive that firmly adheres to a component) can be peeled from the component by including a hydrophilic agent. Even if the water peelability is impaired, it can be peeled from the component by implementing solvent immersion peeling.

[0144] Examples of silane coupling agents include silicon compounds having an epoxy structure such as 3-glycidylpropyltrimethoxysilane, 3-glycidylpropylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane; 3-chloropropyltrimethoxysilane; acetoacetyl-containing trimethoxysilane; (meth)acryloyl-containing silane coupling agents such as 3-acryloyloxypropyltrimethoxysilane and 3-methacryloyloxypropyltriethoxysilane; and isocyanate-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane. Preferred examples include 3-glycidylpropyltrimethoxysilane and acetoacetyl-containing trimethoxysilane. The silane coupling agents may be used alone or in combination of two or more.

[0145] The amount of silane coupling agent used can be set in a manner to obtain the desired effect, and is not particularly limited. In some embodiments, the amount of silane coupling agent used can be, for example, 0.001 parts by weight or more relative to 100 parts by weight of the monomer components of the polymer contained in the adhesive. From the perspective of obtaining a higher effect, it can be 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.015 parts by weight or more. In addition, in some embodiments, the amount of silane coupling agent used can be, for example, 3 parts by weight or less, 1 part by weight or less, or 0.5 parts by weight or less relative to 100 parts by weight of the monomer components constituting the adhesive. In addition, the technology disclosed herein can be implemented using an adhesive that does not substantially contain a silane coupling agent. By limiting the amount of silane coupling agent used, or not using a silane coupling agent, there is a tendency for the peelability from the adherend to be improved.

[0146] (Other ingredients)

[0147] The adhesive disclosed herein may contain, as other optional components, various additives commonly used in the adhesive field, such as viscosity modifiers (e.g., thickeners), pH modifiers, leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, and anti-aging agents. Conventionally known additives can be used, and detailed descriptions thereof will be omitted as they do not contribute to the characterization of the present invention.

[0148] In the technology disclosed herein, the amount of the components other than the base polymer (suitably an acrylic polymer) in the adhesive can be limited. In the technology disclosed herein, the amount of the components other than the base polymer in the adhesive is, for example, about 30% by weight or less, about 15% by weight or less is appropriate, and preferably about 12% by weight or less (for example, about 10% by weight or less). The adhesive of such a composition easily meets the specified optical properties (for example, transparency) and can be preferably used for optical purposes. In some ways, the amount of the components other than the base polymer in the adhesive can be about 5% by weight or less, about 3% by weight or less, or about 1.5% by weight or less (for example, about 1% by weight or less). The composition in which the amount of the components other than the base polymer (for example, an acrylic polymer) is limited in this way can be preferably used for light-curing adhesive compositions.

[0149] (Formation of Adhesive Layer)

[0150] When the adhesive has the form of an adhesive layer, the adhesive layer can be a cured layer of the adhesive composition. That is, the adhesive layer can be formed in the following manner: after the adhesive composition is imparted (for example, applied) to an appropriate surface, a curing treatment is appropriately implemented. When two or more curing treatments (drying, crosslinking, polymerization, etc.) are performed, they can be performed simultaneously or in multiple stages. In the adhesive composition using a partial polymer of a monomer component (acrylic polymer slurry), typically, as the above-mentioned curing treatment, a final copolymerization reaction is performed. That is, the partial polymer is supplied to a further copolymerization reaction to form a complete polymer. For example, if it is a photocurable adhesive composition, light irradiation is implemented. As needed, curing treatments such as crosslinking and drying can be implemented. For example, in the case where it is necessary to dry in the form of a photocurable adhesive composition (for example, in the case of a photocurable adhesive composition in which a partial polymer of a monomer component is dissolved in an organic solvent), light curing can be performed after the composition is dried. In the adhesive composition using a complete polymer, typically, as the above-mentioned curing treatment, drying (heat drying), crosslinking, etc. are implemented as needed. An adhesive layer with a multilayer structure of two or more layers can be made by laminating a preformed adhesive layer. Alternatively, the second adhesive layer may be formed by applying the adhesive composition on the pre-formed first adhesive layer and curing the adhesive composition.

[0151] The adhesive composition can be applied using a conventional coater such as a gravure coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater.

[0152] (Thickness of adhesive layer)

[0153] The thickness of the adhesive layer is not particularly limited, and can be, for example, about 3 μm to 2000 μm. From the perspective of step followability and adhesion to the adherend, in some embodiments, the thickness of the adhesive layer is, for example, more than 10 μm, preferably more than 50 μm, more than 70 μm, more than 100 μm, or more than 150 μm. Adhesives with large thickness often become difficult to peel off because of their high adhesive strength and the tendency of the adhesive strength to increase over time. On the other hand, when the adherend is solvent-impermeable, during solvent immersion, the solvent contacts the adhesive only at the end face of the adhesive layer. Therefore, the thicker the adhesive layer, the easier it is for the solvent to act on the adhesive. For such an adhesive layer, it is effective to apply the method disclosed in this article. In addition, from the perspective of preventing the occurrence of paste residue due to cohesive failure of the adhesive layer, in some embodiments, the thickness of the adhesive layer can be, for example, less than 1000 μm, less than 500 μm, less than 300 μm, or less than 200 μm.

[0154] (Haze value)

[0155] The adhesive is preferably an optical adhesive. The optical adhesive may be an optical adhesive that does not impair the optical properties. The haze value of the adhesive (layer), and further the adhesive sheet, is not particularly limited. In some embodiments, a haze value of about 10% or less is appropriate, and may be about 5% or less (for example, about 3% or less). The above haze value is preferably 1.0% or less. Thus, an adhesive with high transparency is suitable for optical applications requiring high light transmittance. The above haze value may be less than 1.0%. It may be less than 0.7%, and may be 0.5% or less (for example, 0 to 0.5%). The haze value can be adjusted, for example, by adjusting the composition and thickness of the adhesive.

[0156] The term "haze value" here refers to the ratio of diffuse transmitted light to total transmitted light when the object being measured is irradiated with visible light. It is also called the haze value. The haze value can be expressed by the following formula.

[0157] Th[%]=Td / Tt×100

[0158] In the above formula, Th is the haze value [%], Td is the scattered light transmittance, and Tt is the total light transmittance. The haze value can be measured by attaching the adhesive surface of the adhesive layer or adhesive sheet to a single surface of an alkaline glass having a haze value of 0.1% to form a laminate of the adhesive layer or adhesive sheet and the alkaline glass, and then using a haze meter (e.g., the product name "MR-100" manufactured by Murakami Color Research Laboratory). When performing the measurement, the alkaline glass to which the adhesive layer or adhesive sheet is attached is arranged so that the adhesive layer or adhesive sheet becomes the light source side. Since the haze value of alkaline glass is 0.1%, the value after subtracting 0.1% from the measured value is used as the haze value [%] of the adhesive layer or adhesive sheet.

[0159] (Base material layer)

[0160] In some embodiments, the adhesive sheet used for joining components in the assembly comprises a substrate layer. The substrate layer is a support (support layer) that supports the adhesive layer. The substrate layer can be an intermediate layer between a first adhesive layer and a second adhesive layer disposed on the surface of the adhesive sheet.

[0161] Examples of the substrate layer disclosed herein include various resin films such as polyolefin films, polyester films, and polyvinyl chloride films; foam sheets formed from foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and nonwoven fabrics made from various fibrous materials (which may include natural fibers such as linen and cotton, synthetic fibers such as polyester and vinylon, and semi-synthetic fibers such as acetate) either alone or in blends; paper such as Japanese paper, high-quality paper, kraft paper, and crepe paper; and metal foils such as aluminum foil, copper foil, and stainless steel (SUS). These may also be laminated structures. Examples of such composite substrate layers include laminated substrates (multilayered substrates) composed of metal foil and the aforementioned resin films, and resin sheets reinforced with inorganic fibers such as glass cloth.

[0162] As the material of the substrate layer, it is preferred to use a material comprising a resin film that can independently maintain its shape (self-supporting or non-dependent) as the base film. Here, the so-called "resin film" refers to a non-porous structure, typically a resin film that does not substantially contain bubbles (no voids). Therefore, the above-mentioned resin film is a concept that is different from foam film and non-woven fabric. The above-mentioned resin film can be a single-layer structure or a multi-layer structure (for example, a three-layer structure) of more than two layers. The above-mentioned resin film can be a transparent film. Transparent resin film is suitable for optical applications.

[0163] As a preferred example of the resin material constituting the resin film, polyester resin, polyphenylene sulfide (PPS) resin, polyolefin resin, polyimide resin can be mentioned. As a specific example of the resin film that can be preferably used as the substrate layer, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, PPS film, polyetheretherketone (PEEK) film, transparent polyimide (CPI) film, polypropylene (PP) film, triacetyl cellulose (TAC) film can be mentioned. As a preferred example considering strength, PET film, PEN film, PPS film, PEEK film, CPI film can be mentioned. As a preferred example considering ease of use, dimensional stability, optical properties, etc., PET film, CPI film, TAC film can be mentioned.

[0164] The resin film may be mixed with known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, lubricants, and anti-caking agents as needed. The amount of the additives is not particularly limited and can be appropriately set according to the application.

[0165] The method for producing the resin film is not particularly limited, and for example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately adopted.

[0166] The substrate layer may be a layer substantially consisting of such a resin film. Alternatively, the substrate layer may also include an auxiliary layer in addition to the resin film. Examples of the auxiliary layer include surface treatment layers such as a primer layer and a peeling layer. Additionally, the adhesive layer side surface of the substrate layer may be subjected to conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer (primer), antistatic treatment, and peeling treatment as needed.

[0167] The thickness of the substrate layer is not particularly limited, and may be, for example, approximately 1000 μm or less, or approximately 500 μm or less. From the perspective of lightweight and thin-walled construction, approximately 100 μm or less is suitable, and may be 70 μm or less. Furthermore, from the perspective of operability and processability, the thickness of the substrate layer may be, for example, 1 μm or more, approximately 20 μm or more is suitable, and preferably approximately 30 μm or more.

[0168] (Dimensions of adhesive sheet)

[0169] In the mode that two parts are joined by adhesive sheet, the length and width of this adhesive sheet (for example the length and width of tape-shaped adhesive sheet) are not particularly limited.For adhesive sheet, usually, adhesive sheet surface as a whole is bonded to adherend, so when adherend is solvent impermeable, in solvent impregnation, solvent is only in contact with adhesive at adhesive sheet end face. Therefore, the larger the size (length and width) of adhesive sheet becomes, the more time-consuming the tendency that solvent impregnation peeling needs. According to technology disclosed herein, even if relative size is relatively large adhesive sheet, for example at least one of length and width is more than 20mm (or even more than 40mm, for example more than 60mm), also can realize desired effect. In addition, for the width of the widest part of the adhesive sheet (specifically the bonding area of adhesive sheet) peeled off by technology disclosed herein, from the viewpoint of solvent impregnation peeling efficiency, for example, be less than 200mm, can also be less than 100mm.

[0170] Example

[0171] Hereinafter, some embodiments related to the present invention will be described, but it is not intended to limit the present invention to the contents shown in these embodiments. It should be noted that, unless otherwise specified, in the following description, "parts" and "%" are based on weight.

[0172] <Adhesive Sheet Production>

[0173] (Production Example A)

[0174] 100 parts of a monomer mixture containing n-butyl acrylate / cyclohexyl acrylate / 4-hydroxybutyl acrylate / hydroxyethyl acrylate in a weight ratio of 57 / 12 / 23 / 8, along with 0.1 parts of "IRGACURE 651" (manufactured by Ciba Specialty Chemicals Inc.) and 0.1 parts of "IRGACURE 184" (manufactured by Ciba Specialty Chemicals Inc.) as photopolymerization initiators were placed in a four-necked flask. The mixture was then irradiated with ultraviolet light under a nitrogen atmosphere for photopolymerization until the viscosity (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 15 Pa·s, thereby preparing a monomer syrup containing a partially polymerized product of the monomer mixture. To 100 parts of the monomer syrup were added 0.1 parts of dipentaerythritol hexaacrylate as a multifunctional monomer, 0.3 parts of a nonionic surfactant (polyoxyethylene sorbitan monolaurate, HLB 16.7, trade name "RHEODOL TW-L120", manufactured by Kao Corporation) as a hydrophilic agent, and 0.4 parts of a silane coupling agent (trade name "KBE403" (manufactured by Shin-Etsu Chemical Co., Ltd.), and the mixture was uniformly mixed to prepare a UV-curable adhesive composition.

[0175] The adhesive composition obtained above was applied to a release film R1 (Mitsubishi Plastics Corporation, product name "MRF#38") with a thickness of 38 μm, which was used as a release surface on one side of a polyester film. The film was then covered with a release film R2 (Mitsubishi Plastics Corporation, product name "MRE#38") with a thickness of 38 μm, which was used as a release surface on one side of a polyester film, to block air. The film was then cured by irradiation with ultraviolet light, thereby forming an adhesive layer with a thickness of 200 μm. The ultraviolet irradiation was performed using a black light lamp at an illumination of 4 mW / cm 2 (Measured using an industrial UV detector (manufactured by TOPCON, trade name "UVR-T1") with a peak sensitivity wavelength of approximately 350 nm) and irradiated for 180 seconds. In this manner, a PSA sheet A (consisting solely of the PSA layer) was obtained. The surface of PSA sheet A to be attached to the adherend was protected with release films R1 and R2.

[0176] (Production Example B>

[0177] A pressure-sensitive adhesive sheet B was obtained in the same manner as in Preparation Example A except that no hydrophilic agent was used.

[0178] <Evaluation of solvent immersion and peelability immediately after lamination>

[0179] For adhesive sheets A and B, the solvent immersion removability was evaluated using the following method. The peeling liner covering one surface of the adhesive layer (double-sided adhesive sheet without support) was peeled off from the adhesive sheet, and an aluminum foil (TOYO ALUMINIUM EKCO PRODUCTS CO., LTD., product name "sun foil") with a thickness of 11 μm was adhered to the exposed adhesive surface and cut into a size of 80 mm × 200 mm. Then, the peeling liner covering the other surface of the above-mentioned adhesive layer was peeled off, and the exposed adhesive surface was adhered to the entire surface (65 mm × 165 mm size) of an alkaline glass plate (Matsubo Glass Industry Co., Ltd., made by float method, thickness 1.35 mm, blue plate edge grinding product, contact angle of the surface to be adhered to the adhesive sheet with distilled water: 8 degrees) of the alkaline glass plate. A 2 kg rubber roller was moved back and forth 2 times to press the laminate of the aluminum foil / adhesive / alkaline glass plate. The aluminum foil and adhesive extending from the alkaline glass plate were cut off and removed to produce a laminate of aluminum foil / adhesive / alkaline glass plate as the evaluation object. A plurality of the above-mentioned laminates were prepared, each of which was immersed in each solvent shown in Table 1, and the peeling distance [mm] in the width direction of the adhesive sheet (65mm width) from the end (one end) was measured 5 hours after the start of the immersion and 24 hours after the start of the immersion. The solvent immersion was implemented under the condition of 23°C. The results are shown in Table 1. It should be noted that the "peeling" in the table means that the adhesive sheet is peeled off from the adherend as a whole (specifically, a state in which the adhesive sheet floats and peels off from the adherend due to swelling). It can be said that the peeling distance from one end is 32.5mm. In addition, "-" in the table means that it was not measured.

[0180] The contact angle of the alkaline glass plate was measured using the following method. Specifically, measurements were performed using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., trade name "DMo-501 model," control box "DMC-2," and control / analysis software "FAMAS (Version 5.0.30)") under a measurement atmosphere of 23°C and 50% RH, using the drop method. A 2 μL drop of distilled water was used, and the contact angle was calculated using the θ / 2 method (implemented with N5) based on an image taken 5 seconds after the addition.

[0181] <Peelability Evaluation after Accelerated Test>

[0182] (Solvent immersion stripping)

[0183] For adhesive sheets A and B, a laminate of aluminum foil / adhesive / alkali glass plate as the evaluation object was prepared in the same manner as in the case of the solvent immersion peeling evaluation just after the above-mentioned lamination. A plurality of the above-mentioned laminates were prepared, heated at 60°C for 4 days and stored (accelerated test equivalent to 25°C × 200 days based on the Arrhenius formula). Next, the above-mentioned laminate was immersed in each solvent shown in Table 1, and the peeling distance [mm] in the width direction of the adhesive sheet (65mm width) was measured 24 hours, 72 hours, 84 hours and 1 week after the start of immersion. The solvent immersion was implemented at 23°C. The results are shown in Table 2.

[0184] (Water peeling)

[0185] For PSA sheets A and B, an aluminum foil / adhesive / alkaline glass plate laminate was prepared as the evaluation target in the same manner as in the solvent immersion peelability evaluation after the accelerated test, and an accelerated test (stored at 60°C for 4 days) was performed. Next, in an environment of 23°C and 50% RH, a peeling starting point was created at the end using a knife or plastic spatula. 20 μL of distilled water was supplied to the area where the adhesive began to separate from the alkaline glass plate (peeling front). The aluminum foil / adhesive laminate was carefully peeled from the alkaline glass plate within 3 minutes without causing fragmentation or cracking. However, for both PSA sheets A and B, the aluminum foil cracked during peeling, and the adhesive could not be peeled smoothly without damaging the adherend.

[0186] (HSP value and HSP distance)

[0187] Furthermore, HSP values (dispersion term (δD), polar term (δP), and hydrogen bonding term (δH)) were calculated for the PSA and each solvent in PSA sheet A, and the HSP distances between the PSA and each solvent were determined. The results are shown in Table 3.

[0188] [Table 1]

[0189] Table 1: Evaluation of solvent immersion peelability immediately after lamination (peel distance [mm])

[0190]

[0191] [Table 2]

[0192]

[0193] [Table 3]

[0194] Table 3

[0195]

[0196] As shown in Table 1, after the adhesive sheet was attached to the adherend, the peelability based on solvent immersion was evaluated. No significant difference was observed in the peelability between the adhesive sheet A containing a water affinity agent and the adhesive sheet B without a water affinity agent. However, after an accelerated test at 60°C for 4 days, the adhesive sheet B without a water affinity agent was not peeled off from the adherend at all. In contrast, for the adhesive sheet A containing a water affinity agent, the longer the immersion time became, the more the peeling from the adherend was carried out. Specifically, the adhesive swelled by solvent immersion, and natural peeling was carried out. Among them, according to the solvent immersion using ethyl acetate, the adhesive can be peeled off with the shortest immersion time. It should be noted that after an accelerated test at 60°C for 4 days, it was confirmed that the adhesive sheet A containing a water affinity agent, which originally had water peelability, lost its water peelability.

[0197] Based on the HSP of the adhesive and the solvent, the solvent immersion peelability of the adhesive and the solvent was studied. As a result, in some test examples (specifically, examples using non-alcoholic solvents), as shown in Table 3, it was confirmed that the HSP distance between the adhesive and the solvent was correlated with the solvent immersion peelability shown in Table 2. Specifically, among the solvents, hexane, which had an HSP distance of 9.3 relative to the adhesive, failed to peel the adhesive during solvent immersion, but when toluene, with an HSP distance of 4.2, was used, solvent immersion peelability was confirmed. In addition, ethyl acetate, with an HSP distance of 4.0 or less, showed the best solvent immersion peelability relative to the evaluated adhesive. In addition, in other test examples (specifically, examples using alcoholic solvents), the experimental results and HSP values confirmed that the larger the hydrogen bonding term (δH), the better the solvent immersion peelability. Since the adhesive sheet A contains a hydrophilic agent, it is believed that the hydrogen bonding term promotes the improvement in peelability. Alcohols such as methanol and ethanol with a δH of 15.0 or more show good solvent immersion peelability.

[0198] From the above results, it is clear that by performing solvent immersion peeling on a bonded body of two members bonded by an adhesive containing a hydrophilic agent, the adhesive can be peeled from the members, thereby separating the two members.

[0199] While specific examples of the present invention have been described in detail above, the above description is for illustrative purposes only and does not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples described above.

[0200] Description of Reference Numerals

[0201] 1. Adhesive (adhesive sheet)

[0202] 1A surface (first adhesive surface)

[0203] 1B The other surface (second adhesive surface)

[0204] 100 joints

[0205] 120 Part 1

[0206] 140 Part 2

[0207] 200 solvent

[0208] 250 containers

Claims

1. A method for separating a joined body comprising two components joined by an adhesive, wherein: The adhesive comprises a hydrophilic agent, The method includes the step of immersing the bonded body in a solvent to peel the adhesive from the component. The hydrophilic agent is at least one compound selected from a surfactant and a compound having a polyoxyalkylene skeleton, and the solvent is at least one solvent selected from the group consisting of alcohols, aromatic hydrocarbons, and esters.

2. The method according to claim 1, wherein The HSP (Hansen Solubility Parameter) distance between the binder and the solvent is 4.0 or less.

3. The method according to claim 1, wherein The hydrogen bonding term (δH) in the HSP (Hansen solubility parameter) of the solvent is 15.0 or more.

4. The method according to claim 1 or 2, wherein The solvent comprises ethyl acetate.

5. The method according to claim 1 or 2, wherein: The adhesive is a solvent-based adhesive or an active energy ray-curable adhesive.

6. The method according to claim 1 or 2, wherein: The two components are joined via a double-sided adhesive sheet containing the adhesive, and the width of the adhesive sheet is 20 mm or more.

7. The method according to claim 1 or 2, wherein: The bonded structure is immersed in the solvent for 24 hours or more.

8. The method of claim 7, wherein: After 24 hours have passed since the bonded body was immersed in the solvent, the adhesive is peeled off from one of the two members by a distance of 20 mm or more.

9. The method according to claim 1 or 2, comprising the step of determining whether the adhesive can be water-peeled from at least one of the two components before immersing the bonded body in a solvent. Here, the water peeling is performed in a state where an aqueous liquid is present at the portion where the adhesive is peeled from the surface of the component. After confirming that the water peeling cannot proceed, the bonded body is immersed in a solvent.

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