Adhesive composition, recovery method, and reuse method

Abstract

The present invention provides an adhesive composition with excellent reusability, a recovery method for recovering components from the adhesive composition, and a reuse method for reusing components from the adhesive composition. [Solution] The monomer units that make up the polymer are given by the following formula (1) [Formula 1] TIFF2026136719000007.tif44153 An adhesive composition comprising a (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having the ethylene carbonate structure shown in [figure], and a cyclic carbonate compound (B) other than the (meth)acrylic acid ester polymer (A) having the ethylene carbonate structure.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, a recovery method for recovering components in the adhesive composition, and a reuse method for reusing components in the adhesive composition.

Background Art

[0002] In the manufacturing process of electronic components such as semiconductor chips and multilayer ceramic capacitors, an adhesive sheet may be used to temporarily fix a processing target such as a semiconductor wafer or a ceramic green sheet laminate. In such a manufacturing process, for example, a adherend such as a semiconductor wafer or a ceramic green sheet laminate is fixed to an adhesive sheet, cut into a predetermined size, and then the obtained cut pieces are separated from the adhesive sheet.

[0003] Here, as the above-described adhesive sheet, one that can reduce the adhesion between the adhesive sheet and the adherend at a desired timing is used. According to such an adhesive sheet, after obtaining the cut pieces, by reducing the adhesion between the adhesive sheet and the adherend, it becomes possible to easily separate the cut pieces from the adhesive sheet.

[0004] Patent Documents 1 and 2 disclose an adhesive composition containing an acrylic polymer containing a carboxyl precursor group-containing (meth)acrylate monomer as a monomer unit constituting the polymer, and an acid catalyst or an acid generator. In particular, an adhesive sheet provided with an adhesive layer formed from the adhesive composition generates a gas from the above-described carboxyl precursor group by the action of an acid generated from the acid catalyst or the acid generator due to external stimuli such as heating or exposure, and it is disclosed that the adhesive sheet can be easily separated from the adherend by the gas accumulating at the interface between the adhesive sheet and the adherend.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] Incidentally, in recent years, there has been a rapid development of technologies to reduce environmental impact by recovering and reusing the adhesive layer from used adhesive sheets.

[0007] This invention has been made in view of the above circumstances, and aims to provide an adhesive composition with excellent reusability, a recovery method for recovering components in the adhesive composition, and a reuse method for reusing components in the adhesive composition. [Means for solving the problem]

[0008] To achieve the above objective, firstly, the present invention provides the following formula (1) as the monomer unit constituting the polymer [ka] The present invention provides an adhesive composition characterized by containing an (meth)acrylic acid ester polymer (A) having an ethylene carbonate structure as shown in (1), and a cyclic carbonate compound (B) other than the (meth)acrylic acid ester polymer (A) having the ethylene carbonate structure (1).

[0009] In the above invention (Invention 1), the molecular weight of the cyclic carbonate compound (B) is preferably 88 or more and 400 or less (Invention 2).

[0010] In the above inventions (Inventions 1 and 2), the cyclic carbonate compound (B) is preferably at least one of ethylene carbonate, propylene carbonate, and butylene carbonate (Invention 3).

[0011] Secondly, the present invention provides a recovery method (Invention 4) characterized by dissolving at least a portion of the adhesive formed using the adhesive composition (Inventions 1 to 3) in a solvent to recover the (meth)acrylic acid ester polymer (A) and the cyclic carbonate compound (B).

[0012] Thirdly, the present invention provides a reuse method (Invention 5) characterized by comprising dissolving at least a portion of the adhesive formed using the adhesive composition (Inventions 1 to 3) in a solvent to recover the (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B), and forming an adhesive using the recovered (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B). [Effects of the Invention]

[0013] The adhesive composition according to the present invention has excellent reusability. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below. The adhesive composition according to this embodiment is The monomer units that make up the polymer are given by the following formula (1) [ka] A (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having the ethylene carbonate structure shown, A cyclic carbonate compound (B) other than the (meth)acrylic acid ester polymer (A) having the above-mentioned ethylene carbonate structure and It contains.

[0015] In the adhesive composition according to this embodiment, the (meth)acrylate polymer (A) can form a crosslinked structure via the ethylene carbonate structure within and between molecules because it has the ethylene carbonate structure within the molecule. More specifically, polarization occurs in the carbonyl group portion of the ethylene carbonate structure, and the carbonyl group portion of one ethylene carbonate structure and the carbonyl group portion of another ethylene carbonate structure are attracted to each other (dipole interaction). This dipole interaction occurs in a plurality of ethylene carbonate structures in the (meth)acrylate polymer (A), and as a result, a three-dimensional network is formed. Also, the ethylene carbonate structure possessed by the cyclic carbonate compound (B) can perform the above-described dipole interaction with the (meth)acrylate polymer (A) in the (meth)acrylate polymer (A). Therefore, the cyclic carbonate compound (B) is also incorporated into the above-described network. As a result of these, by using the adhesive composition according to this embodiment, an adhesive that is sufficiently aggregated and exhibits desired adhesive properties can be formed.

[0016] Furthermore, the adhesive formed using the adhesive composition according to this embodiment can be easily dissolved in a predetermined solvent because the ethylene carbonate structure is present. More specifically, when the adhesive and the solvent are brought into contact, an interaction between the carbonyl group in the above-described ethylene carbonate structure and the solvent occurs. At this time, the solvent also interacts with the two carbonyl groups that were attracted by the above-described dipole interaction, whereby the dipole interaction between the carbonyl groups is eliminated. As a result, the above-described network is eliminated, and the adhesive is dissolved in the solvent. In particular, since the adhesive composition according to this embodiment contains the cyclic carbonate compound (B), it is also possible to easily and quickly dissolve the adhesive. Therefore, the adhesive in this embodiment can be easily peeled off or removed by bringing a solvent into contact with the adhesive when, for example, it is desired to peel off the adhesive sheet from the adherend adhered in the form of an adhesive sheet, or when it is desired to remove the adhesive residue remaining on the adherend.

[0017] And the solution obtained by the above dissolution contains a (meth)acrylate polymer (A) and a cyclic carbonate compound (B), and these can be reused as materials for the adhesive composition according to the present embodiment. In particular, in the adhesive of the present embodiment, since the network is formed by the above-described dipole interaction without relying on physical crosslinking (such as covalent bonds), the (meth)acrylate polymer (A) and the cyclic carbonate compound (B) obtained by dissolution maintain their original structures. Therefore, these can be reused without any inferiority compared to the case before dissolution. Further, since the content ratio of the (meth)acrylate polymer (A) and the cyclic carbonate compound (B) basically does not change, for example, the solution obtained by dissolution can be used as it is as a coating solution for the adhesive composition to form an adhesive. From the above, the adhesive composition according to the present embodiment is very excellent in reusability.

[0018] 1. Composition of the adhesive composition (1) (Meth)acrylate polymer (A) The (meth)acrylate polymer (A) in the present embodiment is not particularly limited with respect to other monomer units and the like as long as it contains the ethylene carbonate-containing monomer described above as a monomer unit constituting the polymer.

[0019] Furthermore, the ethylene carbonate-containing monomer described above is not particularly limited as long as it contains the ethylene carbonate structure described above and can undergo a polymerization reaction with other monomers constituting the (meth)acrylate polymer (A).

[0020] Preferable examples of the ethylene carbonate-containing monomer include (meth)acrylates having a structure in which an organic group having an ethylene carbonate structure is bonded to a (meth)acryloyloxy group. Examples of such (meth)acrylates include the following formula (2)

Chemical formula

[0021] The (meth)acrylic acid ester polymer (A) preferably contains 0.5% by mass or more of the above-mentioned ethylene carbonate-containing monomer as monomer units constituting the polymer, more preferably 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more. This allows for effective dipole interactions between ethylene carbonate structures, making it easier to form a good network.

[0022] On the other hand, the (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or less of the above-mentioned ethylene carbonate-containing monomer as monomer units constituting the polymer, more preferably 30% by mass or less, particularly preferably 25% by mass or less, and even more preferably 20% by mass or less. By being within the above range, the adhesive is more likely to have the desired elasticity, and as a result, good tackiness is easily obtained.

[0023] In this embodiment, the (meth)acrylic acid ester polymer (A) preferably contains an alkyl (meth)acrylic acid ester as a monomer unit constituting the polymer. This allows the resulting adhesive to exhibit good tackiness. The alkyl group may be linear or branched.

[0024] From the viewpoint of adhesiveness, alkyl (meth)acrylate esters with 1 to 20 carbon atoms in the alkyl group are preferred. Examples of alkyl (meth)acrylate esters with 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0025] Among the above, alkyl (meth)acrylates with 2 to 12 C atoms in the alkyl group are more preferred, and alkyl (meth)acrylates with 4 to 10 C atoms in the alkyl group are particularly preferred, from the viewpoint of providing good tackiness. Specifically, 2-ethylhexyl (meth)acrylate is preferred, and 2-ethylhexyl acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0026] From the viewpoint of imparting good tackiness, the (meth)acrylic acid ester polymer (A) preferably contains 50% by mass or more of alkyl (meth)acrylic acid ester as monomer units constituting the polymer, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, from the viewpoint of ensuring the content of other monomers (especially ethylene carbonate-containing monomers), it is preferable that the polymer contains 99.6% by mass or less of alkyl (meth)acrylic acid ester, more preferably 99% by mass or less, particularly preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0027] The (meth)acrylic acid ester polymer (A) may also preferably contain a reactive functional group-containing monomer as a monomer constituting the polymer, which has a reactive functional group within its molecule. The inclusion of a reactive functional group-containing monomer facilitates dipole interactions in the ethylene carbonate structure, making it easier to form a good network.

[0028] Preferred examples of the above-mentioned reactive functional group-containing monomers include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers). Among these, hydroxyl group-containing monomers are preferred. These reactive functional group-containing monomers may be used individually or in combination of two or more.

[0029] Examples of hydroxyl group-containing monomers include hydroxyalkyl esters of (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred. These may be used individually or in combination of two or more.

[0030] Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually or in combination of two or more.

[0031] Examples of amino group-containing monomers include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used individually or in combination of two or more.

[0032] The (meth)acrylic acid ester polymer (A) preferably contains at least 0.1% by mass of reactive functional group-containing monomers as monomers constituting the polymer, more preferably at least 0.5% by mass, and particularly preferably at least 1% by mass. Furthermore, the (meth)acrylic acid ester polymer (A) preferably contains at least 30% by mass of reactive functional group-containing monomers as monomer units constituting the polymer, more preferably at least 25% by mass, particularly preferably at least 6% by mass, and even more preferably at least 20% by mass. By containing reactive functional group-containing monomers within the above ranges as monomer units constituting the polymer, the (meth)acrylic acid ester polymer (A) becomes more likely to form a good network and is more efficiently soluble in solvents.

[0033] The (meth)acrylic acid ester polymer (A) in this embodiment may further contain other monomers as monomers constituting the polymer. Examples of such other monomers include alicyclic structure-containing (meth)acrylic acid esters such as dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate; alkoxyalkyl (meth)acrylate esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; non-crosslinked acrylamides such as acrylamide and methacrylamide; non-crosslinked (meth)acrylic acid esters having a tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; and styrene. These may be used individually or in combination of two or more.

[0034] The polymerization method of the (meth)acrylic acid ester polymer (A) in this embodiment may be random polymerization or block polymerization. Furthermore, the (meth)acrylic acid ester polymer (A) can be obtained by polymerizing each of the above-mentioned monomers by conventional methods. For example, it can be prepared by polymerization using emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, aqueous solution polymerization, etc. Among these, from the viewpoint of stability during polymerization and ease of handling during use, it is preferable to prepare it by solution polymerization carried out in an organic solvent.

[0035] The weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 100,000 or more, more preferably 300,000 or more, particularly preferably 500,000 or more, and even more preferably 650,000 or more. Furthermore, the weight-average molecular weight is preferably 2,000,000 or less, more preferably 1,500,000 or less, particularly preferably 1,000,000 or less, and even more preferably 800,000 or less. When the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is within the above range, the adhesive composition is more likely to form a good network, and the formed adhesive is more likely to dissolve efficiently. Note that the weight-average molecular weight in this specification is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0036] The adhesive composition according to this embodiment may contain one of the above-described (meth)acrylic acid ester polymers (A), or it may contain two or more. Furthermore, the adhesive composition according to this embodiment may contain another (meth)acrylic acid ester polymer along with the above-described (meth)acrylic acid ester polymer (A).

[0037] (2) Cyclic carbonate compounds (B) The cyclic carbonate compound (B) in this embodiment is not particularly limited as long as it has the ethylene carbonate structure described above and is other than the (meth)acrylic acid ester polymer (A) described above.

[0038] The cyclic carbonate compound (B) is preferably a low molecular weight compound, from the viewpoint of easily improving the solubility of the formed adhesive. For example, the molecular weight of the cyclic carbonate compound (B) is preferably 400 or less, particularly preferably 300 or less, and even more preferably 200 or less. On the other hand, the lower limit of the molecular weight of the cyclic carbonate compound (B) is, for example, 88 or more.

[0039] The cyclic carbonate compound (B) is preferably at least one of alkylene carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, or a mixture thereof, and is particularly preferably propylene carbonate.

[0040] The content of the cyclic carbonate compound (B) in the adhesive composition is preferably 1 part by mass or more, particularly preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and may be even more than 15 parts by mass or more, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). Furthermore, the content of the cyclic carbonate compound (B) is preferably 50 parts by mass or less, particularly preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). When the content of the cyclic carbonate compound (B) is within the above range, the adhesive composition is more likely to form a good network and the formed adhesive is more likely to dissolve efficiently.

[0041] (3) Other ingredients The adhesive composition according to this embodiment may contain other components besides the (meth)acrylic acid ester polymer (A) and cyclic carbonate compound (B) described above. Examples of such other components include various additives commonly used in acrylic adhesives, such as silane coupling agents, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, fillers, and refractive index modifiers. The polymerization solvent and diluent solvent described later are not included in the additives constituting the adhesive composition.

[0042] As mentioned above, the adhesive composition according to this embodiment does not require a crosslinking agent because it can form the aforementioned network using only the (meth)acrylic acid ester polymer (A) and the cyclic carbonate compound (B). Furthermore, from the viewpoint of dissolving the formed adhesive in a solvent and recovering the (meth)acrylic acid ester polymer (A) and the cyclic carbonate compound (B), it is preferable that the adhesive composition according to this embodiment does not contain any components that form physical crosslinks with these components (i.e., a crosslinking agent).

[0043] However, the adhesive composition according to this embodiment does not exclude those containing a crosslinking agent. The crosslinking agent referred to herein is a crosslinking agent that forms a covalent bond with the (meth)acrylic acid ester polymer (A), such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, etc.

[0044] 2. Preparation of the adhesive composition The adhesive composition can be prepared by preparing a (meth)acrylic acid ester polymer (A), mixing the obtained (meth)acrylic acid ester polymer (A) with a cyclic carbonate compound (B), and optionally adding additives.

[0045] (Meth)acrylic acid ester polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer using a conventional radical polymerization method. Polymerization of (meth)acrylic acid ester polymer (A) is preferably carried out by solution polymerization using a polymerization initiator if desired. However, the present invention is not limited thereto, and polymerization may also be carried out without a solvent. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., and two or more types may be used in combination.

[0046] Examples of polymerization initiators include azo compounds and organic peroxides, and two or more may be used in combination. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane1-carbonitride), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0047] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, and diacetyl peroxide.

[0048] Furthermore, in the polymerization process described above, the weight-average molecular weight of the resulting polymer can be adjusted by incorporating a chain transfer agent such as 2-mercaptoethanol.

[0049] Once the (meth)acrylic acid ester polymer (A) is obtained, the cyclic carbonate compound (B), and optionally a diluent and additives, are added to the solution of the (meth)acrylic acid ester polymer (A), and thoroughly mixed to obtain a solvent-diluted adhesive composition (coating solution). If any of the above components are used in solid form, or if precipitation occurs when mixed with other components in an undiluted state, that component may be dissolved or diluted in the diluent beforehand before mixing with the other components.

[0050] Examples of the diluent solvents used include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

[0051] The concentration and viscosity of the coating solution prepared in this manner are not particularly limited, as long as they are within the range of coating, and can be appropriately selected depending on the situation. For example, the adhesive composition is diluted to a concentration of 10 to 60% by mass. Note that the addition of a diluent is not a necessary condition when obtaining the coating solution; if the adhesive composition has a viscosity suitable for coating, a diluent may not be added. In this case, the adhesive composition becomes a coating solution in which the polymerization solvent of the (meth)acrylic acid ester polymer (A) is used directly as the diluent.

[0052] 3. Adhesive An adhesive can be formed by using the adhesive composition according to this embodiment. As described above, this adhesive can be obtained by generating dipole interactions between ethylene carbonate structures in the adhesive composition according to this embodiment, thereby forming a network of (meth)acrylic acid polymer (A) and cyclic carbonate compound (B).

[0053] The formation of the network by the dipole interaction described above can usually be achieved by heat treatment. This heat treatment can also be combined with the drying process used to volatilize the diluent solvent from the adhesive composition coating applied to the desired object.

[0054] The heating temperature for the heat treatment is preferably 50 to 150°C, and more preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 5 minutes.

[0055] When an adhesive composition contains a crosslinking agent, it is desirable to allow a curing period after the heat treatment described above to complete the crosslinking reaction. However, the adhesive composition according to this embodiment does not need to contain a crosslinking agent, and in that case, a curing period is unnecessary. This makes it possible to improve the productivity of adhesive sheets.

[0056] 4. Adhesive sheet An adhesive sheet can also be formed using the adhesive composition according to this embodiment. The adhesive sheet comprises at least an adhesive layer formed using the adhesive composition according to this embodiment. Furthermore, the adhesive sheet in this embodiment may be an adhesive sheet formed by laminating a release sheet on one or both sides of the adhesive layer, or an adhesive sheet formed by laminating a substrate on one or both sides of the adhesive layer, or an adhesive sheet in which a release sheet is laminated on one side of the adhesive layer and a substrate is laminated on the other side. The adhesive sheet according to this embodiment can be used for the same purposes as conventional adhesive sheets.

[0057] (1) Adhesive layer The adhesive layer of the adhesive sheet in this embodiment is formed using the adhesive composition according to this embodiment.

[0058] The thickness of the adhesive layer in this embodiment (a value measured in accordance with JIS K7130) can be set appropriately depending on the application. For example, the thickness is preferably 1 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, and even more preferably 20 μm or more. Furthermore, the thickness of the adhesive layer is preferably 100 μm or less, more preferably 75 μm or less, particularly preferably 50 μm or less, and even more preferably 30 μm or less.

[0059] (2) Release sheet The release sheet protects the adhesive layer until the adhesive sheet (adhesive layer) is used, and is peeled off when the adhesive sheet is used. In the adhesive sheet according to this embodiment, one or both of the release sheets are not necessarily required.

[0060] Examples of release sheets include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylic acid polymer film, ethylene-(meth)acrylic acid ester polymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Crosslinked films of these materials can also be used. Furthermore, laminated films of these materials may also be used.

[0061] It is preferable that the release surface of the above-mentioned release sheet is subjected to a release treatment. Examples of release agents used in the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax-based release agents.

[0062] There are no specific restrictions on the thickness of the release liner, but it is usually around 20-150 μm.

[0063] (3) Base material As the above-mentioned substrates, known materials may be used depending on the purpose, such as resin films and paper, but it is particularly preferable to use resin films. An example of such resin film is the same as the film described above as the material for the release sheet.

[0064] (4) Method for manufacturing adhesive sheets The adhesive sheet can be manufactured in the same manner as conventional adhesive sheets. For example, in one example of manufacturing an adhesive sheet in which release sheets are laminated on both sides of an adhesive layer, the adhesive composition coating solution is applied to the release surface of one release sheet, and the adhesive composition is crosslinked by heat treatment to form an adhesive layer. Then, the release surface of the other release sheet is placed on top of this adhesive layer. This yields the adhesive sheet. The heat treatment conditions are as described above.

[0065] Methods for applying the coating solution of the above-mentioned adhesive composition include, for example, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0066] (5) Physical properties of adhesive sheets (1) Adhesive strength The adhesive strength of the adhesive sheet according to this embodiment to soda-lime glass is preferably 3N / 25mm or more, particularly preferably 8N / 25mm or more, and even more preferably 10N / 25mm or more. Being within this range makes it easier for the sheet to adhere well to the substrate. On the other hand, the upper limit of the adhesive strength is not particularly limited, but considering cases where reworkability is required, it is preferably 30N / 25mm or less, particularly preferably 20N / 25mm or less, and even more preferably 15N / 25mm or less. The above adhesive strength basically refers to the adhesive strength measured by the 180-degree peel method in accordance with JIS Z0237:2009, and the specific test method is as shown in the test examples described later.

[0067] (2) Total light transmittance The total light transmittance of the adhesive sheet according to this embodiment is set appropriately depending on the application, but is preferably 95% or higher, particularly preferably 97% or higher, and even more preferably 99% or higher. This makes it more suitable for applications where transparency is required, such as optical applications. The upper limit of the total light transmittance is not particularly limited and may be 100%, or it may be slightly higher than 100% due to measurement constraints. Details of the method for measuring the total light transmittance are described in the test examples below.

[0068] (3) Haze value The haze value of the adhesive sheet according to this embodiment is set appropriately depending on the application, but is preferably 3% or less, particularly preferably 2% or less, and even more preferably 1% or less. This makes it more suitable for applications where transparency is required, such as optical applications. The lower limit of the haze value is not particularly limited, and may be, for example, 0.1% or more, particularly 0.2% or more, and even more preferably 0.3% or more. Details of the method for measuring the haze value are described in the test examples below.

[0069] (4) Chromaticity b* In this embodiment, the adhesive layer of the adhesive sheet preferably has an absolute value of chromaticity b* defined by the CIE1976L*a*b* color system of 1 or less, more preferably 0.8 or less, and even more preferably 0.5 or less. This makes the adhesive layer in this embodiment suitable for optical applications (especially displays). Details of the method for measuring chromaticity b* are shown in the test examples described later.

[0070] (5) Storage modulus G' The storage modulus (G') of the adhesive constituting the adhesive layer of the adhesive sheet according to this embodiment is preferably 25 to 0.2 MPa, particularly preferably 23 to 0.5 MPa, and even more preferably 18 to 0.8 MPa.

[0071] Furthermore, the storage modulus (G') at 0°C of the adhesive constituting the adhesive layer of the adhesive sheet according to this embodiment is preferably 8 to 0.05 MPa, particularly preferably 7 to 0.10 MPa, and even more preferably 4 to 0.15 MPa.

[0072] Furthermore, the storage modulus (G') of the adhesive constituting the adhesive layer of the adhesive sheet according to this embodiment at 25°C is preferably 1 to 0.01 MPa, particularly preferably 0.6 to 0.02 MPa, and even more preferably 0.4 to 0.04 MPa.

[0073] Furthermore, the storage modulus (G') of the adhesive constituting the adhesive layer of the adhesive sheet according to this embodiment is preferably 0.050 to 0.001 MPa, particularly preferably 0.040 to 0.003 MPa, and even more preferably 0.030 to 0.005 MPa.

[0074] By having the storage modulus (G') at each temperature within the above range, the material is more likely to exhibit the desired adhesive properties in each temperature range. Details of the test method for determining the storage modulus (G') are shown in the test examples described later.

[0075] (6) Stress relaxation rate The relaxation modulus variation value ΔlogG(t) of the adhesive constituting the adhesive layer of the adhesive sheet according to this embodiment is preferably 1.8 to 1.0, particularly preferably 1.75 to 1.2, and even more preferably 1.6 to 1.4. Being within this range makes it easier to obtain the desired adhesive properties. Details of the test method for the relaxation modulus variation value ΔlogG(t) are shown in the test examples described later.

[0076] 5. Collection and Reuse Methods The adhesive composition according to this embodiment is also preferably used in the following recovery method. That is, it is preferable to use it in a recovery method that includes dissolving at least a portion of the adhesive formed using the adhesive composition according to this embodiment in a solvent to recover the aforementioned (meth)acrylic acid polymer (A) and the aforementioned cyclic carbonate compound (B).

[0077] The solvent mentioned above is not particularly limited as long as it can dissolve the adhesive, and examples include water and organic solvents. Examples of organic solvents include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve-type solvents such as ethyl cellosolve. These solvents may be used individually or in combination of two or more.

[0078] Furthermore, the method for dissolving the adhesive is not particularly limited and can be dissolved by known methods. For example, the adhesive can be dissolved by immersing it in a solvent and stirring as needed. The stirring method is not particularly limited, but examples include stirring with a stirrer or homomixer, or stirring by applying vibration. Specific examples of stirring by applying vibration include manual shaking or stirring by applying external vibration. In this case, the substrate or adherend may be immersed in the solvent together. Alternatively, the adhesive may be dissolved by applying the solvent to it.

[0079] The method for recovering the (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B) is not particularly limited, and known methods can be used. Recovery as used herein includes simply obtaining a solvent in which the (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B) are dissolved, and also includes separating both or each of the (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B) from the solvent. The method for separation in this case is also not particularly limited, and separation can be carried out by known methods.

[0080] The adhesive composition according to this embodiment may also be used in the following reuse method. Specifically, it is preferable to use it in a reuse method that includes dissolving at least a portion of the adhesive formed using the adhesive composition according to this embodiment in a solvent to recover the aforementioned (meth)acrylic acid polymer (A) and the aforementioned cyclic carbonate compound (B), and forming an adhesive using the recovered (meth)acrylic acid polymer (A) and cyclic carbonate compound (B).

[0081] The solvent, dissolution method, and recovery method used in the above reuse method can be the same as those used in the recovery method described above. Furthermore, the method for forming the adhesive is not particularly limited, and the same method as when forming an adhesive from the adhesive composition according to this embodiment can be used. For example, after dissolving the adhesive in a solvent, the resulting solution may be used as is as a coating liquid for the adhesive composition to re-form the adhesive.

[0082] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention. [Examples]

[0083] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0084] [Example 1] 1. Preparation of (meth)acrylic acid ester polymer (A) A (meth)acrylic acid ester polymer (A) was prepared by copolymerizing 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of (2-oxo-1,3-dioxolan-4-yl)methyl methacrylic acid as an ethylene carbonate-containing monomer, and 20 parts by mass of 2-hydroxyethyl acrylate by solution polymerization. The weight-average molecular weight (Mw) of this (meth)acrylic acid ester polymer (A) was measured by the method described later and was found to be 305,000.

[0085] 2. Preparation of the adhesive composition 100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth)acrylic acid ester polymer (A) obtained in step 1 above and 10.0 parts by mass of propylene carbonate as the cyclic carbonate compound (B) were mixed, stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0086] 3. Manufacturing of adhesive sheets The coating solution of the obtained adhesive composition was applied using a knife coater to the peeled surface of a heavy-peel type release sheet (Lintec Corporation, thickness: 75 μm) in which one side of a polyethylene terephthalate film had been peeled with a silicone-based release agent. The coated layer was then heated at 100°C for 1 minute to form a coating layer.

[0087] Next, the coating layer on the heavy-peel type release sheet obtained above and a light-peel type release sheet (Lintec Corporation, thickness: 38 μm) obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent were bonded together so that the peeled surface of the light-peel type release sheet was in contact with the coating layer, thereby producing an adhesive sheet with an adhesive layer of 25 μm thickness, i.e., an adhesive sheet consisting of a heavy-peel type release sheet / adhesive layer (thickness: 25 μm) / light-peel type release sheet. The thickness of the adhesive layer was measured in accordance with JIS K7130 using a constant-pressure thickness gauge (Teclock Corporation, product name "PG-02").

[0088] 4. GPC measurement The weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight in polystyrene terms, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> • GPC measuring device: Tosoh Corporation, HLC-8020 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Guard Column HXL-H TSK gel GMHXL (x2) TSK gel G2000HXL • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0089] [Example 2, Comparative Example 1] An adhesive sheet was prepared in the same manner as in Example 1, except that the amount of cyclic carbonate compound (B) was changed as shown in Table 1.

[0090] [Test Example 1] (Measurement of Adhesion) The light-peel release sheets were peeled off from the adhesive sheets prepared in the examples and comparative examples, and the exposed adhesive layer was laminated to the easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "PET TA063", thickness: 50 μm) having an easy-adhesion layer, to obtain a laminate of heavy-peel release sheet / adhesive layer / PET film. The obtained laminate was cut to a width of 25 mm and a length of 100 mm.

[0091] Under conditions of 23°C and 50%RH, a heavy-peel release sheet was peeled from the laminate, and the exposed adhesive layer was attached to a soda-lime glass plate (manufactured by Nippon Sheet Glass Co., Ltd., product name "Soda-lime Glass", thickness: 1.1 mm). After being left for 24 hours under conditions of 23°C and 50%RH, the adhesive strength (N / 25 mm) of the laminate of PET film and adhesive layer was measured when it was peeled from the substrate using a tensile testing machine (manufactured by Orientec, Tensilon) at a peeling speed of 300 mm / min and a peeling angle of 180 degrees. Measurements other than those described here were performed in accordance with JIS Z0237:2009. The results are shown in Table 1. In the table, "CF" indicates that cohesive failure occurred in the adhesive layer.

[0092] [Test Example 2] (Measurement of total light transmittance) The light-peel release sheet was peeled off from the adhesive sheets prepared in the examples and comparative examples, the exposed adhesive layer was bonded to one side of soda-lime glass, and then the heavy-peel release sheet was peeled off to obtain a laminate of the adhesive layer and soda-lime glass, which was used as a sample for measurement.

[0093] Then, after performing background measurements using soda-lime glass, the total light transmittance (%) of the above-mentioned sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH 5000") in accordance with JIS K7361-1:1997. The results are shown in Table 1.

[0094] [Test Example 3] (Measurement of haze value) A sample for measurement was obtained in the same manner as in Test Example 2. Then, after background measurement was performed using soda-lime glass, the haze value (%) of the above sample was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "NDH 5000") in accordance with JIS K7136:2000. The results are shown in Table 1.

[0095] [Test Example 4] (Measurement of L*a*b*) The lightness L*, chromaticity a*, and chromaticity b* of the adhesive layers of the adhesive sheets prepared in the examples and comparative examples were measured using a simultaneous photometric spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SQ2000") according to the CIE1976 L*a*b* color system. The results for chromaticity b* are shown in Table 1.

[0096] [Test Example 5] (Measurement of Storage Modulus G') Multiple adhesive layers from the adhesive sheets prepared in the examples and comparative examples were laminated to form a 0.8 mm thick laminate. From the resulting laminate of adhesive layers, a cylindrical object with a diameter of 8 mm (height 0.8 mm) was punched out and used as a sample.

[0097] For the above samples, the storage modulus G' was measured using the torsional shear method with a viscoelasticity measuring device (Anton Paar, product name "MCR302") in accordance with JIS K7244-1, under the following conditions, and the storage modulus G' (MPa) at -20°C, 0°C, 25°C, and 100°C was obtained, respectively. The results are shown in Table 1. Measurement frequency: 1Hz Measurement temperature: -20℃~100℃

[0098] [Test Example 6] (Measurement of Relaxation Modulus) Multiple layers of adhesive sheets prepared in the examples and comparative examples were laminated to form a laminate with a thickness of 0.8 mm. From the resulting laminate of adhesive layers, a cylindrical object with a diameter of 8 mm (height 0.5 mm) was punched out and used as a sample.

[0099] For the above sample, in accordance with JIS K7244-1, the relaxation modulus of elasticity G(t)(MPa) was measured by continuously straining the adhesive by 10% under the following conditions using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302"). From the measurement results, the maximum relaxation modulus of elasticity G(t) was determined. max (MPa) is derived, and the maximum relaxation modulus G(t) is also derived. max The minimum relaxing modulus of elasticity G(t) measured within 3757 seconds after the measurement was taken. min The value (MPa) was derived. Measurement temperature: 25℃ Measurement points: 1000 points (logarithmic plot)

[0100] The obtained maximum relaxation modulus G(t) max (MPa) and minimum relaxation modulus G(t) min The relaxation modulus variation value ΔlogG(t) was calculated from (MPa) based on the following equation (I). The results are shown in Table 1. ΔlogG(t)=logG(t) max -logG(t) min …(I)

[0101] [Test Example 7] Evaluation of dissolution and regeneration Multiple layers of adhesive from the adhesive sheets prepared in the examples and comparative examples were laminated to create a 0.25 g laminate with a thickness of 0.8 mm, which was used as the evaluation sample. After placing the evaluation sample in a vial, 0.73 g of methyl ethyl ketone was added. The mixture was then stirred by hand, and the time from the start of stirring until the dissolution of the adhesive was complete was measured. The results, as dissolution time, are shown in Table 1.

[0102] Furthermore, the solution obtained by the above dissolution was reused as the coating solution for the adhesive composition, and an adhesive sheet was prepared in the same manner as in Example 1. The adhesive strength of the obtained adhesive sheet was measured in the same manner as in Test Example 1. The results are shown in Table 1.

[0103] [Table 1]

[0104] Table 1 shows that by using the adhesive compositions prepared in the examples, it is possible to produce adhesives and adhesive sheets exhibiting good physical properties, such as optical properties and storage modulus. Furthermore, it was found that the adhesives and adhesive sheets according to the examples can be re-formed by dissolving them in a solvent. In particular, the adhesives and adhesive sheets according to the examples could be dissolved in the solvent in a shorter time than those in the comparative examples. Therefore, it was found that the adhesive compositions according to the examples have excellent reusability. [Industrial applicability]

[0105] The adhesive composition of the present invention can be suitably used in the manufacture of reusable adhesives and adhesive sheets.

Claims

1. The monomer units that make up the polymer are as follows: (1) 【Chemistry 1】 A (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having the ethylene carbonate structure shown, A cyclic carbonate compound (B) other than the (meth)acrylic acid ester polymer (A) having the ethylene carbonate structure, and An adhesive composition characterized by containing the following:

2. The adhesive composition according to claim 1, characterized in that the molecular weight of the cyclic carbonate compound (B) is 88 or more and 400 or less.

3. The adhesive composition according to claim 1, characterized in that the cyclic carbonate compound (B) is at least one of ethylene carbonate, propylene carbonate, and butylene carbonate.

4. A recovery method characterized by comprising dissolving at least a portion of an adhesive formed using the adhesive composition according to any one of claims 1 to 3 in a solvent to recover the (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B).

5. Dissolving at least a portion of the adhesive formed using the adhesive composition according to any one of claims 1 to 3 in a solvent to recover the (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B), and Forming an adhesive using the recovered (meth)acrylic acid polymer (A) and the cyclic carbonate compound (B). A reuse method characterized by including the following.

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