Adhesive sheet

Abstract

The present invention provides an adhesive sheet having a photocurable adhesive layer that exhibits a certain or more peel strength in an initial state, can be satisfactorily peeled off from an adherend by light irradiation, and is based on a polymer that does not use solution polymerization. Provided is an adhesive sheet having an adhesive layer cured by light irradiation. The total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator in the adhesive layer is 1.0 [mu] g / g or less. The adhesive sheet has an initial peel strength of 2.0 N / 20 mm or more as measured under conditions of a tensile rate of 300 mm / min and a peel angle of 180 degrees after being adhered to a silicon wafer, and the adhesive layer has a Young's modulus of 1.0 MPa or more as measured by a tensile test after being subjected to a curing treatment by irradiation with ultraviolet light having a cumulative light amount of 300 mJ / cm2.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet.

[0002] This application claims priority based on Japanese Patent Application No. 2022-185191 filed on November 18, 2022, and the entire contents of this application are incorporated herein by reference. Background Art

[0003] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter) is in a state of a soft solid (viscoelastic body) in a temperature region near room temperature and has a property of being easily adhered to an adherend by pressure. By exhibiting such a property, adhesives are widely used in various fields in the form of, for example, adhesive sheets having an adhesive layer. Among adhesive sheets, there are adhesive sheets having an adhesive layer (photo-curable adhesive layer) that is cured by light irradiation. As a prior art document related to such a technique, Patent Document 1 can be cited.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-059179 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] Among adhesives, there are adhesives that are temporarily adhered to an adherend and peeled off from the adherend after the adhesion purpose is completed. For such adhesives used in a manner of being peeled off from the adherend, it is required to have good adhesiveness during the adhesion to the adherend and be able to be peeled off well from the above-mentioned adherend when the adhesion purpose is completed and peeled off. As an adhesive having such a property, an adhesive that adheres with a peeling force of a certain level or more during bonding and fixing and can improve the peelability from the adherend during peeling can be used. For example, an adhesive sheet having a UV-curable adhesive layer that is cured by UV irradiation to improve peelability is known.

[0009] In the production of an ultraviolet curable adhesive layer, a liquid adhesive composition (solvent-based adhesive composition) containing a component having an ultraviolet reactive functional group (which imparts a decrease in peel force caused by ultraviolet irradiation) and a photoinitiator that promotes the reaction of the ultraviolet reactive functional group in an organic solvent is usually used. By applying the above solvent-based adhesive composition onto an appropriate surface and then drying it (removing the organic solvent), the above solvent-based adhesive composition cures to form an ultraviolet curable adhesive layer. A typical solvent-based adhesive composition contains a polymer or its modified product obtained by solution polymerization using an azo-based or peroxide-based polymerization initiator as the base polymer constituting the adhesive layer. Therefore, in the ultraviolet curable adhesive layer formed from the above solvent-based adhesive composition, the azo-based or peroxide-based polymerization initiator used in the solution polymerization usually exists in the form of decomposition products and residues of the polymerization initiator.

[0010] On the other hand, in recent years, due to considerations such as environmental hygiene, the requirement for reducing the amount of organic solvent used has become stronger. Therefore, an object of the present invention is to provide an adhesive sheet that exhibits a peel force of a certain level or more in an initial state, can be peeled well from an adherend by light irradiation, and has a photocurable adhesive layer based on a polymer that does not utilize solution polymerization.

[0011] Means for Solving the Problem

[0012] According to the present specification, there is provided an adhesive sheet having an adhesive layer (photocurable adhesive layer) that cures by light irradiation. In the above adhesive layer, the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator is 1.0 μg / g or less. By thus limiting the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator, it is possible to prevent or suppress the drawbacks caused by the above polymerization initiator (for example, the above polymerization initiator undergoes cleavage due to heat, thereby causing phenomena such as changes in the physical properties of the adhesive over time, deterioration, contamination, and generation of outgassing on the surface of the adherend to which the adhesive sheet is adhered). For example, the above adhesive layer may be an adhesive layer that does not contain any of the azo-based and peroxide-based polymerization initiators. The initial peel strength of the above adhesive sheet measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees after being adhered to a silicon wafer is 2.0 N / 20 mm or more. In addition, the Young's modulus (hereinafter, also referred to as "Young's modulus after curing treatment") of the above adhesive layer measured by a tensile test after curing treatment by irradiating ultraviolet rays (UV) with a cumulative light amount of 300 mJ / cm 2 is 1.0 MPa or more.

[0013] Since the above-mentioned adhesive layer does not rely on solution polymerization using azo-based or peroxide-based polymerization initiators, when using the adhesive sheet having such an adhesive layer, the amount of organic solvents used can be reduced. In addition, the above-mentioned adhesive sheet exhibits good adhesiveness with a peel strength in the initial state (state before curing treatment) of 2.0 N / 20 mm or more. Further, by making the Young's modulus (tensile elastic modulus) after the curing treatment of the adhesive layer 1.0 MPa or more, good peelability from the adherend is easily obtained after light irradiation.

[0014] In some embodiments, the above-mentioned adhesive layer contains a polymer having a carbon-carbon double bond. For the adhesive sheet having an adhesive layer with such a composition, the carbon-carbon double bond of the above-mentioned polymer can be reacted by light irradiation, and thus it is easy to simultaneously achieve the above-mentioned initial peel strength and the above-mentioned Young's modulus.

[0015] In some embodiments, the above-mentioned polymer having a carbon-carbon double bond is preferably crosslinked with a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule. For an adhesive layer in which the polymer having a carbon-carbon double bond has a crosslinked structure based on a polyfunctional monomer, the above-mentioned Young's modulus (Young's modulus after curing treatment) can be suitably achieved after the curing treatment.

[0016] Some embodiments relate to an adhesive layer containing an acrylic polymer as the above-mentioned polymer having a carbon-carbon double bond. The technology disclosed herein can be implemented in the form of an adhesive sheet having a photocurable adhesive layer containing an acrylic polymer having a carbon-carbon double bond.

[0017] In some embodiments, 50% by weight or more of all monomer components constituting the above-mentioned acrylic polymer (acrylic polymer having a carbon-carbon double bond) is a chain alkyl (meth)acrylate having 5 or more carbon atoms in the alkyl group. Thereby, there is a tendency to obtain an adhesive sheet that achieves good peelability from the adherend at a higher level.

[0018] In some embodiments, the above-mentioned adhesive layer contains 1.0×10 -4 mol / 100 g or more of carbon-carbon double bonds. According to an adhesive layer containing carbon-carbon double bonds in the above-mentioned content, it is easy to simultaneously achieve the above-mentioned initial peel strength and the above-mentioned Young's modulus after curing treatment.

[0019] In some embodiments, the gel fraction of the above-mentioned adhesive layer measured after curing treatment by irradiating ultraviolet rays with an accumulated light amount of 300 mJ / cm 2 is preferably 70% or more. According to the adhesive layer having a high gel fraction as described above, good peelability after light irradiation is easily obtained.

[0020] In some embodiments, the loss modulus G” of the above-mentioned adhesive layer at 25 °C is preferably 1.0×103 Pa or more. For the adhesive layer having the above loss modulus G", it can effectively dissipate the external force applied to the adhesive layer and easily maintain the adhesion to the adherend well.

[0021] In the above adhesive layer, the content of the organic solvent is preferably 1.0 μg / g or less. The adhesive layer with a small content of the organic solvent has a low odor and is ideal from the perspective of environmental hygiene. Considering the viewpoints of suppressing foaming caused by the volatilization of the organic solvent and low pollution, it is also beneficial that the content of the organic solvent in the adhesive layer is small.

[0022] It should be noted that the solutions obtained by appropriately combining the various elements described in this specification are also included in the scope of the invention claimed in this patent application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a cross-sectional view schematically showing the structure of the adhesive sheet according to one embodiment.

[0024] Figure 2 is a cross-sectional view schematically showing the structure of the adhesive sheet according to another embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] Hereinafter, suitable embodiments of the present invention will be described. It should be noted that for the matters necessary for the implementation of the present invention other than those specifically mentioned in this specification, they can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in this field.

[0026] It should be noted that in the following drawings, sometimes the same reference numerals are used to denote the components and parts that perform the same functions for description, and sometimes the repeated descriptions are omitted or simplified. In addition, the embodiments described in the drawings are schematized for clearly explaining the present invention and do not necessarily accurately represent the dimensions and scales of the adhesive sheet actually provided as a product.

[0027] In this specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight (preferably more than 70% by weight, for example more than 90% by weight) of acrylic monomers. The above acrylic monomers refer to monomers having at least one (meth)acryloyl group in one molecule. In addition, in this specification, "(meth)acryloyl group" comprehensively refers to acryloyl group and methacryloyl group. Similarly, respectively, "(meth)acrylate" comprehensively refers to acrylate and methacrylate, and "(meth)acrylic acid-" comprehensively refers to acrylic acid- and methacrylic acid-.

[0028] ​​In this specification, an "ethylenically unsaturated compound" refers to a compound having at least one ethylenically unsaturated group in the molecule. Examples of the ethylenically unsaturated group include (meth)acryloyl, vinyl, allyl, etc. Hereinafter, a compound having 1 ethylenically unsaturated group may sometimes be referred to as a "monofunctional monomer", and a compound having 2 or more ethylenically unsaturated groups may sometimes be referred to as a "polyfunctional monomer". In addition, a compound having X ethylenically unsaturated groups in the polyfunctional monomer may sometimes be expressed as an "X-functional monomer".

[0029] <Constitution example of the adhesive sheet>

[0030] The adhesive sheet disclosed herein includes an adhesive layer. Typically, this adhesive layer constitutes at least one surface of the adhesive sheet. The adhesive sheet may be a substrate-bearing adhesive sheet in which an adhesive layer is provided on one or both sides of a substrate (support), or may be a substrate-free adhesive sheet such as a form in which the above adhesive layer is held on a release liner (which may be regarded as a substrate having a release surface). In this case, the adhesive sheet may be formed only of the adhesive layer. The concept of the adhesive sheet referred to herein may include objects called adhesive tapes, adhesive labels, adhesive films, etc. In addition, the above adhesive layer is typically formed continuously, but is not limited to this form. For example, it may be an adhesive layer formed in a regular or irregular pattern such as a dot pattern or a strip pattern. In addition, the adhesive sheet provided by this specification may be in a roll form or a single sheet form. Alternatively, it may also be an adhesive sheet in a form further processed into various shapes.

[0031] One constitution example of the adhesive sheet having an adhesive layer disclosed herein is shown in Figure 1 . The adhesive sheet 1 is a substrate-free double-sided adhesive sheet formed of an adhesive layer 10. For example, as shown in Figure 1 , before use (before being adhered to an adherend), the adhesive sheet 1 may be in the form of an adhesive sheet 50 with release liners in which each surface 10A, 10B of the adhesive layer 10 is protected by release liners 31, 32 having at least the adhesive layer side as a peelable surface (release surface). Alternatively, it may also be in the following form: the back surface (the surface on the side opposite to the adhesive side) of the release liner 31 becomes a release surface, and the adhesive surface 10B is wound or laminated in contact with the back surface of the release liner 31, thereby protecting the adhesive surfaces 10A, 10B. The adhesive layer 10 may be a single layer or a laminated structure of 2 or more layers.

[0032] The adhesive layer 10 is configured to be cured by light irradiation. In some preferred forms, the adhesive layer 10 contains a polymer having a carbon-carbon double bond and a photoinitiator. The amount of the photoinitiator contained in the adhesive layer 10 is preferably 1.0×10 - 41.0 mol / 100 g or more. Based on this content, good curability based on light irradiation can be easily obtained. For the same reason, in some embodiments, the amount of carbon-carbon double bonds contained in the adhesive layer 10 is preferably 1.0×10 -4 mol / 100 g or more.

[0033] The content of the organic solvent in the adhesive layer 10 is preferably 1.0 μg / g or less. An adhesive layer containing a polymer having a carbon-carbon double bond and a photoinitiator and having the content of the organic solvent limited can be preferably formed, for example, by the following method: irradiating an active energy ray (such as ultraviolet ray) curable adhesive composition with an active energy ray to cure it, thereby forming a primary adhesive layer containing a primary polymer (typically, a polymer obtained by polymerizing with an active energy ray and not containing a carbon-carbon double bond), and then, by a method of not using an organic solvent or using only a small amount (to the extent that the content of the organic solvent can be achieved) of an organic solvent, adding a photoinitiator to the primary adhesive layer and introducing a carbon-carbon double bond into the primary polymer. In this forming method, since the primary adhesive layer formed in advance newly contains a photoinitiator and a carbon-carbon double bond, an active energy ray curable adhesive composition can be preferably used as the adhesive composition for forming the primary adhesive layer. As the active energy ray curable adhesive composition, a composition not containing an organic solvent or containing only a small amount (to the extent that the content of the organic solvent can be achieved) of an organic solvent is used.

[0034] In the adhesive layer 10, the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator is preferably 1.0 μg / g or less. Such an adhesive layer 10 can be preferably realized in the following configuration: as the polymer having a carbon-carbon double bond, a polymer obtained without solution polymerization using, for example, an azo-based or peroxide-based polymerization initiator (for example, a primary polymer obtained by polymerizing with an active energy ray and not containing a carbon-carbon double bond, and a polymer obtained by introducing a carbon-carbon double bond into the primary polymer) is included.

[0035] Another configuration example of the adhesive sheet having an adhesive layer disclosed herein is illustrated in Figure 2 . This adhesive sheet 2 is configured as a single-sided adhesive sheet (a single-sided adhesive sheet with a substrate), and this single-sided adhesive sheet includes: a photocurable adhesive layer 10 having one surface 10A as a sticking surface (adhesive surface) to an adherend; and a substrate (support) 20 laminated on the other surface 10B of the adhesive layer 10. The adhesive layer 10 is joined to one surface 20A of the substrate 20. As the substrate 20, a resin film such as a polyester film can be used, for example. As Figure 2As shown, before use, the adhesive sheet 1 can be in the form of an adhesive sheet 50 with a release liner, where the adhesive surface 10A is protected by a release liner 30 whose adhesive layer side at least forms a peelable surface (peel surface). Alternatively, it can also be in the following form: The second surface 20B of the substrate 20 (the surface on the side opposite to the first surface 20A, also referred to as the back surface) forms a peel surface, and the adhesive surface 10A is wound or laminated in contact with the second surface 20B of the substrate 20, thereby protecting the adhesive surface 10A.

[0036] In addition, the adhesive sheet disclosed herein can be in the form of a double-sided adhesive sheet with a substrate, where a first adhesive layer is laminated on one surface of the sheet-shaped substrate and a second adhesive layer is laminated on the other surface of the substrate. In the adhesive sheet of this form, either one or both of the first adhesive layer and the second adhesive layer can be constituted by the photocurable adhesive layer disclosed herein.

[0037] <Properties of the adhesive sheet>

[0038] The initial peel strength of the adhesive sheet disclosed herein with respect to a silicon wafer is 2.0 N / 20 mm or more. Regarding the above initial peel strength (initial adhesive force), based on JIS Z 0237:2000, in an environment of 23°C and 50% RH, with a silicon wafer as the adherend, it is measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. For the adhesive sheet disclosed herein, by having an initial peel strength of 2.0 N / 20 mm or more, it adheres well to the adherend in the initial state (before the curing treatment). From the viewpoint of, for example, having good peel resistance (peel resistance) against external forces in the initial state (before the curing treatment), an adhesive sheet with a high initial peel strength is preferred. From the viewpoint of improving the bonding reliability to the adherend, in some forms, the initial peel strength of the adhesive sheet is preferably more than 2.0 N / 20 mm, more preferably 2.5 N / 20 mm or more (for example, more than 2.5 N / 20 mm), can be 3.0 N / 20 mm or more, can be 3.5 N / 20 mm or more, can also be 4.0 N / 20 mm or more or 4.5 N / 20 mm or more. The upper limit of the above initial adhesive force is not particularly limited. For example, it can be less than 30 N / 20 mm. From the viewpoints of easily obtaining a balance with other properties, etc., it can be 25 N / 20 mm or less, can be 20 N / 20 mm or less, and can also be 15 N / 20 mm or less. It should be noted that the above initial adhesive force is the peel strength measured before the curing treatment. The initial adhesive force is specifically measured by the method described in the following examples.

[0039] For the adhesive layer provided in the adhesive sheet disclosed herein, when irradiating a cumulative light amount of 300 mJ / cm 2The Young's modulus (Young's modulus after curing) measured by a tensile test after the ultraviolet curing treatment is 1.0 MPa or more. By making the Young's modulus after the curing treatment of the adhesive layer 1.0 MPa or more, good peelability from the adherend is easily obtained after light irradiation. For example, when peeling from the adherend, the occurrence of a phenomenon (adhesive residue) in which a part of the adhesive layer tears and remains on the adherend can be prevented or suppressed. From the viewpoint of more easily exhibiting this effect, in some embodiments, the Young's modulus after the above-mentioned curing treatment is preferably 1.2 MPa or more, more preferably 1.5 MPa or more, may be 2.0 MPa or more, may be 2.5 MPa or more, may be 3.5 MPa or more, may be 4.0 MPa or more, or may be 4.5 MPa or more. In addition, the Young's modulus after the above-mentioned curing treatment can be, for example, 10 MPa or less, and from the viewpoint of easily achieving good adhesiveness before the curing treatment, it is preferably 7.0 MPa or less, more preferably 5.0 MPa or less. The Young's modulus after the curing treatment of the adhesive layer is specifically measured by the method described in the examples below.

[0040] For the adhesive sheet disclosed herein, the peel strength after curing (adhesive force after curing) measured by pasting the adhesive layer on a silicon wafer and performing a curing treatment by light irradiation is preferably 2.0 N / 20 mm or less, more preferably 1.0 N / 20 mm or less. For an adhesive sheet with such a limited peel force after curing, good peelability (easy peelability) can be exhibited in the usage mode of peeling from the adherend after the curing treatment. This is preferable from the viewpoint of, for example, reducing the load on the adherend during peeling. In some embodiments, the adhesive force after the above-mentioned curing is preferably less than 1.0 N / 20 mm (for example, less than 0.9 N / 20 mm), more preferably 0.7 N / 20 mm or less, further preferably 0.5 N / 20 mm or less, may be 0.3 N / 20 mm or less, may be 0.2 N / 20 mm or less, may be 0.1 N / 20 mm or less, or may be less than 0.1 N / 20 mm (for example, 0.08 N / 20 mm or less or 0.05 N / 20 mm or less). The lower limit of the adhesive force after curing is not particularly limited, and for example, it can be 0 N / 20 mm, or can exceed 0 N / 20 mm (for example, 0.005 N / 20 mm or more). The adhesive force after curing is specifically measured by the method described in the examples below.

[0041] In the adhesive sheet disclosed herein, the peel strength reduction rate calculated by the following formula can be, for example, 10% or more, 20% or more, or 30% or more.

[0042] Peel strength reduction rate [%] = (1 - B / A) × 100

[0043] Here, A in the formula is the above-mentioned initial peel strength [N / 20 mm], and B in the formula is the above-mentioned peel strength after the curing treatment [N / 20 mm]. In some embodiments, it is appropriate that the above-mentioned peel strength reduction rate is 50% or more. Thus, for the adhesive sheet whose peel force is significantly reduced by UV irradiation, after being adhered to the adherend, by irradiating light at a desired timing, the peel force (peel strength) from the adherend can be significantly reduced (easy peelability). Therefore, it is useful as an adhesive sheet having the property of showing good adhesiveness during the period of use (during the use period) when adhered to the adherend and being easily peeled from the adherend after the adhesion purpose is completed.

[0044] In some embodiments, the above-mentioned peel strength reduction rate is preferably 65% or more, more preferably 75% or more, further preferably 85% or more, may be 90% or more, may be 94% or more, may be 96% or more, may be 97% or more or 98% or more. By using an adhesive sheet with a higher peel strength reduction rate, good adhesiveness during the use period and easy peelability after light irradiation can be achieved at a higher level. The above-mentioned peel strength reduction rate is typically 100% or less, may be less than 100%, for example, may be 99.8% or less or 99.5% or less. From the viewpoint of, for example, preventing the adhesive sheet after the curing treatment from unexpectedly separating from the adherend, it is advantageous that the peel strength reduction rate is less than 100%.

[0045] In the adhesive sheet disclosed herein, the difference (peel strength difference) between the above-mentioned initial peel strength [N / 20 mm] and the above-mentioned peel strength after the curing treatment [N / 20 mm] can be, for example, 0 N / 20 mm or more, typically greater than 0 N / 20 mm, preferably 0.5 N / 20 mm or more, more preferably 1.0 N / 20 mm or more, further preferably 1.5 N / 20 mm or more or 2.0 N / 20 mm or more, can be 3.0 N / 20 mm or more, can be 4.0 N / 20 mm or more. Thus, the adhesive sheet whose peel force is significantly reduced by UV irradiation is useful as an adhesive sheet that can be easily peeled by irradiating light at a desired timing after being adhered to the adherend. The above-mentioned peel strength difference can be, for example, less than 30 N / 20 mm. From the viewpoint of easily obtaining the balance with other properties, etc., it can be less than 25 N / 20 mm, can be less than 20 N / 20 mm, can be less than 15 N / 20 mm or less than 10 N / 20 mm.

[0046] For the adhesive layer of the adhesive sheet disclosed herein (that is, the adhesive layer before the curing treatment based on light irradiation), the storage modulus G' (hereinafter, also referred to as "initial elastic modulus G'") at 25 °C measured by the method described in the following examples is not particularly limited. For example, it can be less than 5.0×10 6Pa, less than 3.0×10 6 Pa is appropriate, less than 1.0×10 6 Pa is advantageous, and can be less than 5.0×10 5 Pa, and can be less than 1.0×10 5 Pa, and can be less than 8.0×10 4 Pa, and can be less than 6.0×10 4 Pa, and can be less than 5.0×10 4 Pa. When the initial elastic modulus G' of the adhesive layer is low, since there is a tendency to easily obtain a large change in the elastic modulus by light irradiation, it is advantageous from the viewpoint of easy peeling, and is also preferable from the viewpoint of improving the followability to the surface shape of the adherend. The lower limit of the initial elastic modulus G' is not particularly limited, and for example, it can be 1.0×10 3 Pa or more. In some embodiments, from the viewpoints of moderate cohesiveness in the adhesive layer before the curing treatment, processability and operability of the adhesive sheet having the adhesive layer, etc., the initial elastic modulus G' of the adhesive layer is 5.0×10 3 Pa or more is appropriate, 8.0×10 3 Pa or more is advantageous, preferably 1.0×10 4 Pa or more, and can be 3.0×10 4 Pa or more, and can be 5.0×10 4 Pa or more.

[0047] For the adhesive layer of the adhesive sheet disclosed herein, the storage modulus G' (hereinafter, also referred to as "elastic modulus G' after curing treatment") at 25 °C measured after the curing treatment by the method described in the following examples is not particularly limited, and is preferably higher than the initial elastic modulus G' of the adhesive layer. The elastic modulus G' after the above curing treatment is a value higher than the initial elastic modulus G', and for example, it can be 1.0×10 4 Pa or more or greater than 1.0×10 4 Pa, and can be 3.0×10 4 Pa or more or greater than 3.0×10 4 Pa, and can be 5.0×10 4 Pa or more or greater than 5.0×10 4 Pa, and can be 1.0×10 5 Pa or more or greater than 1.0×10 5 Pa. In some embodiments, the elastic modulus G' after the curing treatment is a value higher than the initial elastic modulus G' and is 2.0×10 5 Pa or more is appropriate, preferably 4.0×10 5 Pa or more, and more preferably 6.0×105 Pa or more (for example, 8.0×10 5 Pa or more, 1.0×10 6 Pa or more, 1.3×10 6 Pa or more, or 1.5×10 6 Pa or more). From the viewpoint of easy peelability based on light irradiation, it is advantageous that the elastic modulus G' is high after the curing treatment. The upper limit of the elastic modulus G' after the curing treatment is not particularly limited. For example, it can be 1.0×10 8 Pa or less, it can be 1.0×10 7 Pa or less, it can be 5.0×10 6 Pa or less, or 3.0×10 6 Pa or less.

[0048] Based on the above initial elastic modulus G' and the elastic modulus G' after the curing treatment, the storage modulus increase rate of the adhesive layer is calculated by the following formula.

[0049] Storage modulus increase rate [%] = (R / Q - 1) × 100

[0050] Here, Q in the above formula is the initial elastic modulus G' [Pa], and R in the above formula is the elastic modulus G' [Pa] after the curing treatment. The storage modulus increase rate is typically greater than 0% (for example, greater than 2.5×10 2 %), preferably 3.0×10 2 % or more, more preferably 5.0×10 2 % or more (for example, 7.0×10 2 % or more), it can be 1.0×10 3 % or more, it can be 1.5×10 3 % or more, it can be 2.0×10 3 % or more, it can be 2.5×10 3 % or more, it can be 3.0×10 3 % or more. The upper limit of the storage modulus increase rate is not particularly limited. From the viewpoint of easily exhibiting appropriate cohesiveness in the adhesive layer before the curing treatment, in some embodiments, the above storage modulus increase rate can be, for example, 1.0×10 5 % or less, it can be 1.0×10 4 % or less, it can be 5.0×10 3 % or less.

[0051] For the adhesive layer of the adhesive sheet disclosed herein, the loss modulus G'' at 25°C measured by the method described in the examples below is not particularly limited. In some embodiments, for example, from the viewpoint of easily exhibiting appropriate adhesiveness in the adhesive layer before the curing treatment, the above loss modulus G'' is about 1.0×106 It is appropriate that the pressure is below 5.0×10 5 Pa (for example, below 3.0×10 5 Pa) is advantageous, and preferably below 1.5×10 5 Pa (for example, below 1.0×10 5 Pa), and can be below 5.0×10 4 Pa, can be below 1.0×10 4 Pa, can be below 7.0×10 3 Pa. In addition, the loss modulus G” of the adhesive layer can be, for example, 1.0×10 2 Pa or more. From the viewpoint of more favorably dissipating the external force that can be applied to the adhesive layer and thus easily maintaining the close adhesion to the adherend, it is advantageous that it is 5.0×10 2 Pa or more, and preferably 1.0×10 3 Pa or more. The adhesive layer having this loss modulus G” has a tendency not to peel off from the adherend easily even when an external force (for example, an external force in the shear direction) is applied. In some embodiments, the above loss modulus G” can be 3.0×10 3 Pa or more, can be 5.0×10 3 Pa or more, can be 7.0×10 3 Pa or more, can be 1.0×10 4 Pa or more.

[0052] For the adhesive layer of the adhesive sheet disclosed herein, the gel fraction after the curing treatment based on light irradiation measured by the method described in the examples below is not particularly limited. For example, it can be 50% or more, can be 60% or more, or 70% or more. From the viewpoints of easily and appropriately exerting the light irradiation-based peelability effect, low contamination of the adherend, etc., in some embodiments, the above gel fraction is preferably 80% or more, more preferably 82% or more, further preferably 84% or more, and can be 86% or more, can be 88% or more, can be 90% or more. In addition, from the viewpoint of easily achieving good softness and adhesiveness before the curing treatment, in some embodiments, the above gel fraction can be 99.5% or less, can be 99% or less, can be 97% or less, or 95% or less.

[0053] <Adhesive layer>

[0054] As the adhesive layer (photo-curable adhesive layer) in this technology, an adhesive layer is used which can achieve the above-mentioned initial peel strength of 2.0 N / 20 mm or more and the Young's modulus after the above-mentioned curing treatment of 1.0 MPa or less in the adhesive sheet provided with the adhesive layer. The type of the adhesive constituting the above-mentioned adhesive layer is not particularly limited. For example, it may contain one or more of various rubber-like polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, fluorine polymers, etc. as the base polymer. From the viewpoints of adhesion performance, cost, etc., an adhesive containing an acrylic polymer or a rubber polymer as the base polymer is preferably used. As an example of the values of the above-mentioned initial peel strength and the Young's modulus after the above-mentioned curing treatment, the acrylic adhesive containing an acrylic polymer as the base polymer will be mainly described below, but it is not intended to limit the adhesives disclosed herein to acrylic adhesives.

[0055] It should be noted that in this specification, the "base polymer" of the adhesive layer refers to the main component of the polymer contained in the adhesive layer. The above-mentioned polymer is preferably a rubber-like polymer that exhibits rubber elasticity in the temperature range near room temperature. In addition, in this specification, unless otherwise specified, the "main component" refers to a component contained in an amount greater than 50% by weight.

[0056] (Polymer having a carbon-carbon double bond)

[0057] In some preferred embodiments, the adhesive constituting the adhesive layer contains a polymer having a carbon-carbon double bond. The adhesive layer containing a polymer having a carbon-carbon double bond can be cured by a mechanism including reacting the carbon-carbon double bond in the above-mentioned polymer by light irradiation. By irradiating light on the adhesive layer adhered to the adherend, the carbon-carbon double bond in the above-mentioned polymer reacts, whereby the above-mentioned adhesive layer cures and shrinks, and the adhesive sheet provided with the adhesive layer can be effectively peeled off. Among them, an adhesive containing a polymer having a carbon-carbon double bond as the base polymer is preferred.

[0058] The mode of existence of the carbon-carbon double bonds in the above polymer is not particularly limited. The above polymer may be a polymer having a carbon-carbon double bond in the side chain or a polymer having a carbon-carbon double bond in the main chain. Here, having a carbon-carbon double bond in the main chain includes the presence of a carbon-carbon double bond in the main chain skeleton of the polymer and the presence of a carbon-carbon double bond at the end of the main chain. From the viewpoints of the reactivity of the carbon-carbon double bond and the improvement of the elastic modulus brought about by the reaction of the carbon-carbon double bond, etc., a polymer having a carbon-carbon double bond in the side chain is preferably used. Here, the main chain of the polymer refers to the chain-like structure that forms the backbone of the polymer. In addition, the side chain of the polymer refers to a group (side chain group, side group) bonded to the above main chain and a molecular chain that can be regarded as a side chain.

[0059] In some preferred embodiments, the above polymer having a carbon-carbon double bond has the carbon-carbon double bond in the form of an ethylenically unsaturated group. The above polymer having a carbon-carbon double bond can be, for example, a polymer having a carbon-carbon double bond in the form of a reactive group ((meth)acryloyl group) represented by the following formula (1).

[0060] [Chemical formula 1]

[0061]

[0062] (In the formula, R is a hydrogen atom or a methyl group.)

[0063] The polymer having a carbon-carbon double bond is not particularly limited, and an appropriate polymer can be selected and used in consideration of the characteristics of the adhesive layer, etc. The polymer having a carbon-carbon double bond can be, for example, a polymer (secondary polymer) obtained by introducing a carbon-carbon double bond into a primary polymer without a carbon-carbon double bond by methods such as chemical modification.

[0064] As a specific example of a method for introducing a carbon-carbon double bond into a primary polymer, the following method can be cited: Prepare a primary polymer copolymerized with a monomer having a functional group (hereinafter, also referred to as "functional group A"). React a compound having a functional group (hereinafter, also referred to as "functional group B") capable of reacting with the functional group A and a carbon-carbon double bond (for example, an ethylenically unsaturated compound having a functional group B) with the primary polymer in such a manner that the carbon-carbon double bond does not disappear, thereby obtaining a polymer (secondary polymer) into which a carbon-carbon double bond is introduced. The reaction between the functional group A and the functional group B is preferably a reaction that does not generate free radicals, such as a condensation reaction or an addition reaction. Examples of the combination of the functional group A and the functional group B include the combination of a carboxyl group and an epoxy group, the combination of a carboxyl group and an aziridinyl group, and the combination of a hydroxyl group and an isocyanate group. Among them, from the viewpoint of reaction traceability, the combination of a hydroxyl group and an isocyanate group is preferred. In addition, as long as the combination of the functional groups A and B can obtain a polymer having a carbon-carbon double bond, one of the functional groups in the above combination can be set as the functional group A and the other can be set as the functional group B, or one of the above functional groups can be set as the functional group B and the other can be set as the functional group A. For example, when explained by the combination of a hydroxyl group and an isocyanate group, the functional group A possessed by the primary polymer can be a hydroxyl group (in this case, the functional group B becomes an isocyanate group), or can be an isocyanate group (in this case, the functional group B becomes a hydroxyl group). Among them, a combination in which the primary polymer has a hydroxyl group and the functional group B-containing compound having a carbon-carbon double bond (preferably an ethylenically unsaturated compound having a functional group B) has an isocyanate group is preferred. When the above primary polymer is an acrylic polymer, this combination is particularly preferred.

[0065] When reacting the functional group A of the primary polymer with the functional group B of the compound having a carbon-carbon double bond, from the viewpoint of the reactivity of the two, the mole (M A ) of the above functional group A and the mole (M B ) of the above functional group B, the molar ratio (M A / M B ) is usually appropriately 0.2 or more, preferably 0.5 or more (for example, 0.7 or more, typically 1.0 or more), can be greater than 1.0 (for example, 1.1 or more), and can be 1.2 or more. The above molar ratio (M A / M B ) is usually appropriately 2000 or less (for example, 1500 or less or 1000 or less), advantageously 500 or less, can be 200 or less, can be 100 or less, and can be 50 or less. In some embodiments, the above molar ratio (M A / M B)Preferably, it is 30 or less, can be 20 or less, can be 10 or less, can be 5.0 or less, can be 3.0 or less, can be 2.5 or less, can be 2.0 or less, can be 1.5 or less. In addition, from the viewpoint of increasing the contact opportunity between functional group A and functional group B, a compound containing functional group B having a carbon-carbon double bond can be used in a larger amount. In this case, the molar ratio (M A / M B ) is preferably less than 1 (for example, less than 0.99, less than 0.95). In addition, in the case where, for example, the remaining functional group A is also used for other purposes (such as improving the adhesiveness of the photocurable adhesive layer before curing treatment, etc.), the molar ratio (M A / M B ) is preferably greater than 1.

[0066] The usage amount of the above-mentioned compound containing functional group B having a carbon-carbon double bond (preferably an ethylenically unsaturated compound having functional group B) relative to 100 parts by weight of the polymer having functional group A (typically, the polymer before introducing the carbon-carbon double bond) can be, for example, about 0.001 part by weight or more, about 0.01 part by weight or more, or about 0.1 part by weight or more, and it is appropriate to be about 0.5 part by weight or more (for example, about 1.0 part by weight or more), preferably about 3.0 part by weight or more, more preferably about 5.0 part by weight or more, can be about 7.0 part by weight or more, can be about 9.0 part by weight or more, can be about 10 part by weight or more, can be about 12 part by weight or more. In addition, the usage amount of the compound containing functional group B having a carbon-carbon double bond relative to 100 parts by weight of the polymer having functional group A (typically, the polymer before introducing the carbon-carbon double bond) is appropriately about 40 parts by weight or less, preferably about 35 parts by weight or less, more preferably about 30 parts by weight or less, can be about 25 parts by weight or less, can be about 20 parts by weight or less, can be about 17 parts by weight or less. The above usage amount is preferably set in a manner that satisfies the above-mentioned molar ratio (M A / M B ). For example, for the constitution using the following acrylic polymer as the polymer, the above-mentioned molar ratio (M A / M B ) and the usage amount of the compound containing functional group B having a carbon-carbon double bond can be preferably applied.

[0067] (Acrylic polymer having a carbon-carbon double bond)

[0068] From the viewpoint of ease of curing based on light irradiation and the like, the photocurable adhesive layer disclosed herein can be preferably implemented in such a manner that it contains an acrylic polymer (i.e., an acrylic polymer having a carbon-carbon double bond) as the polymer having a carbon-carbon double bond. The acrylic polymer is also advantageous in terms of high freedom in the selection of monomer raw materials and easy control of physical properties. From the viewpoint of being suitable for manufacturing by a method that does not rely on organic solvents as described later, an acrylic polymer having a carbon-carbon double bond and an adhesive layer containing the acrylic polymer are also preferred.

[0069] The acrylic polymer having a carbon-carbon double bond can be a polymer in which a carbon-carbon double bond is introduced by chemically modifying an acrylic polymer as a primary polymer (typically, an acrylic polymer without a carbon-carbon double bond). The method for introducing a carbon-carbon double bond into the acrylic polymer is not particularly limited. For example, the following method can be preferably adopted: reacting a functional group (functional group A) introduced into the acrylic polymer by copolymerization, with a compound having a functional group (functional group B) capable of reacting with the functional group A and a carbon-carbon double bond in such a manner that the carbon-carbon double bond does not disappear (typically, a condensation or addition reaction). Examples of the combination of functional group A and functional group B include the combination of a carboxyl group and an epoxy group, the combination of a carboxyl group and an aziridinyl group, the combination of a hydroxyl group and an isocyanate group, etc. Among them, from the viewpoint of reaction traceability, the combination of a hydroxyl group and an isocyanate group is preferred. From the viewpoint of polymer design and the like, the combination in which the acrylic polymer has a hydroxyl group and the above compound has an isocyanate group is particularly preferred. In addition, from the viewpoint of the photocurability of the photocurable adhesive layer and the like, the compound having the functional group B and a carbon-carbon double bond is preferably an ethylenically unsaturated compound having the functional group B.

[0070] As a suitable example of the ethylenically unsaturated compound having the functional group B, a monomer containing an isocyanate group (a compound containing an isocyanate group) can be cited. Specific examples of the monomer containing an isocyanate group include substances described later as comonomers that can be used in the polymerization of acrylic polymers. Among them, 2-(meth)acryloyloxyethyl isocyanate is more preferred. By reacting and bonding the isocyanate group (functional group B) of the monomer containing an isocyanate group with the hydroxyl group (functional group A) of the acrylic polymer (typically, a urethane bond), an acrylic polymer having a carbon-carbon double bond can be suitably achieved.

[0071] From the viewpoint of reactivity with the hydroxyl group as the above functional group A, the usage amount of the monomer containing an isocyanate group can satisfy the above molar ratio (M A / M B) is appropriately set within the range. For example, with respect to 100 parts by weight of the acrylic polymer (primary polymer) having a hydroxyl group, the amount of the isocyanate group-containing monomer used is preferably about 1 part by weight or more (e.g., 3 parts by weight or more), and from the viewpoint of more easily and better exhibiting the effect brought about by the curing treatment (e.g., the effect of reducing the peel strength), it is preferably 5 parts by weight or more (e.g., 7 parts by weight or more), and can be 8.5 parts by weight or more, can be 10 parts by weight or more, can be 12 parts by weight or more. The upper limit of the amount of the isocyanate group-containing monomer used is not particularly limited, and with respect to 100 parts by weight of the above-mentioned acrylic polymer having a hydroxyl group, it is appropriately about 40 parts by weight or less, preferably about 35 parts by weight or less, more preferably about 30 parts by weight or less, and can be, for example, about 25 parts by weight or less.

[0072] As another suitable example of the ethylenically unsaturated compound having a functional group B, a hydroxyl group-containing monomer can be cited. Specific examples of the hydroxyl group-containing monomer include the substances described later as comonomers that can be used in the polymerization of the acrylic polymer. For example, (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are preferred, and 4HBA is more preferred. By reacting and bonding the hydroxyl group (functional group B) of the hydroxyl group-containing monomer with the isocyanate group (functional group A) of the acrylic polymer (typically, a urethane bond), an acrylic polymer having a carbon-carbon double bond can be suitably achieved. From the viewpoint of the reactivity with the isocyanate group as the above-mentioned functional group A, the amount of the hydroxyl group-containing monomer as the ethylenically unsaturated compound having a functional group B can be appropriately set within the range that satisfies the above molar ratio (M A / M B ).

[0073] As other examples of the ethylenically unsaturated compound having a functional group B, an epoxy group-containing monomer can be cited. Specific examples of the epoxy group-containing monomer include the substances described later as comonomers that can be used in the polymerization of the acrylic polymer. For example, glycidyl acrylate and glycidyl methacrylate (GMA) are preferred. By reacting and bonding the epoxy group (functional group B) of the epoxy group-containing monomer with the carboxyl group (functional group A) of the acrylic polymer, an acrylic polymer having a carbon-carbon double bond can be suitably achieved. From the viewpoint of the reactivity with the carboxyl group as the above-mentioned functional group A, the amount of the epoxy group-containing monomer as the ethylenically unsaturated compound having a functional group B can be appropriately set within the range that satisfies the above molar ratio (M A / M B ). In some embodiments, by making the molar ratio (M A / M B)Greater than 1, capable of utilizing the effects brought by the remaining carboxyl groups (e.g., improvement in peel strength before curing treatment of the photocurable adhesive layer, improvement in cohesion and heat resistance before and / or after curing treatment, etc.). In this method, the molar ratio (M A / M B ) can be, for example, 1.1 or more, 1.5 or more, or 2.0 or more.

[0074] The acrylic polymer as the primary polymer can be, for example, a polymer of a monomer raw material containing (meth)acrylic acid alkyl ester as the main monomer and may further contain a comonomer copolymerizable with the main monomer. Here, the main monomer refers to a component accounting for more than 50% by weight in the monomer composition of the above monomer raw material.

[0075] As the (meth)acrylic acid alkyl ester, for example, a compound represented by the following formula (2) can be suitably used.

[0076] CH2=C(R 1 )COOR 2 (2)

[0077] Here, R 1 in the above formula (2) is a hydrogen atom or a methyl group. In addition, R 2 is a linear alkyl group having 1 to 20 carbon atoms (hereinafter, such a carbon atom number range may be expressed as “C 1-20 ”). From the viewpoint of the storage modulus of the adhesive layer, etc., it is preferably that R 2 is a linear alkyl group of C 1-14 (e.g., C 1-12 ) of the (meth)acrylic acid alkyl ester, and more preferably that R 1 is a hydrogen atom and R 2 is a linear alkyl group of C 1-20 (e.g., C 1-14 , typically C 1-12 ) of the acrylic acid alkyl ester.

[0078] As R 2 is C 1-20Alkyl (meth)acrylates having a chain-like alkyl group, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. These alkyl (meth)acrylates can be used alone or in combination of two or more. As preferred alkyl (meth)acrylates, ethyl acrylate (EA), n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and lauryl acrylate (LA) can be mentioned.

[0079] In some preferred embodiments, the above alkyl (meth)acrylate contains an alkyl (meth)acrylate A1 having 9 or less carbon atoms in the alkyl group (i.e., R 2 is C 1-9 alkyl (meth)acrylate). In this way, according to the structure in which the length of the side-chain alkyl group is restricted, it is easy to obtain a photocurable adhesive layer suitable for reducing the peeling force caused by light irradiation. For example, in a photocurable adhesive layer containing an acrylic polymer having a carbon-carbon double bond in the side chain (typically, at the end of the side chain) as the polymer having a carbon-carbon double bond, since the length of the side-chain alkyl group is restricted, the reaction of the carbon-carbon double bond can proceed smoothly during the curing treatment by light irradiation.

[0080] The blending ratio of the alkyl (meth)acrylate A1 in all monomer components constituting the acrylic polymer is preferably about 10% by weight or more, more preferably 20% by weight or more, still more preferably 40% by weight or more, further preferably 55% by weight or more, may be 65% by weight or more, may be 75% by weight or more, may be 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, may be 95% by weight or more, from the viewpoint of ideally presenting the function of the alkyl (meth)acrylate A1. The upper limit of the blending ratio of the alkyl (meth)acrylate A1 in all monomer components is not particularly limited. In some embodiments, considering the balance with the usage amount of the comonomer (for example, the monomer having the functional group A), the blending ratio of the alkyl (meth)acrylate A1 in all monomer components is preferably about 99.5% by weight or less (for example, 99% by weight or less), more preferably 95% by weight or less, may be 92% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, may be 75% by weight or less, may be 70% by weight or less.

[0081] The content ratio of the alkyl (meth)acrylate A1 in the whole alkyl (meth)acrylate as the main monomer is preferably about 50% by weight or more (for example, more than 50% by weight), more preferably 70% by weight or more, still more preferably 80% by weight or more, further preferably 90% by weight or more, may be 95% by weight or more, may be 99 to 100% by weight, from the viewpoint of ideally presenting the function of the alkyl (meth)acrylate A1.

[0082] In some preferred embodiments, the above-mentioned alkyl (meth)acrylate A1 includes an alkyl (meth)acrylate A3 having 7 or less carbon atoms in the alkyl group. The alkyl (meth)acrylate A3 can contribute to improving the adhesiveness to polar adherends such as metals, for example. The number of carbon atoms in the alkyl group of the alkyl (meth)acrylate A3 is typically 7 or less, preferably 6 or less, more preferably 4 or less, and may be 2 or less. In some embodiments, from the viewpoint of the flexibility of the photocurable adhesive layer before the curing treatment, etc., the number of carbon atoms in the alkyl group of the alkyl (meth)acrylate A3 is preferably 2 or more.

[0083] The blending ratio of the alkyl (meth)acrylate A3 in all monomer components is preferably about 10% by weight or more, more preferably 20% by weight or more, still more preferably 30% by weight or more, further more preferably 40% by weight or more, particularly preferably 50% by weight or more, and may be 60% by weight or more, may be 70% by weight or more, may be 80% by weight or more, may be 90% by weight or more, from the viewpoint of ideally presenting the function of the alkyl (meth)acrylate A3. The upper limit of the blending ratio of the alkyl (meth)acrylate A3 in all monomer components is not particularly limited. In some embodiments, considering the balance with the amount of the comonomer used, the blending ratio of the alkyl (meth)acrylate A3 in all monomer components is preferably about 99.5% by weight or less (for example, 99% by weight or less), more preferably 95% by weight or less, may be 90% by weight or less, 80% by weight or less, may be 70% by weight or less, may be 60% by weight or less, may be 50% by weight or less, may be 30% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less.

[0084] The content ratio of the alkyl (meth)acrylate A3 in the total alkyl (meth)acrylate as the main monomer is preferably about 5% by weight or more, more preferably 20% by weight or more, still more preferably 35% by weight or more, further more preferably 45% by weight or more, particularly preferably 55% by weight or more, and may be 65% by weight or more, may be 75% by weight or more, may be 85% by weight or more (for example, 90% by weight or more), from the viewpoint of ideally presenting the function of the alkyl (meth)acrylate A3. The upper limit of the content ratio of the alkyl (meth)acrylate A3 in the total alkyl (meth)acrylate is 100% by weight. In some embodiments, for example, in the case of containing the alkyl (meth)acrylate A2 described below, from the viewpoint of ideally presenting its function, the content ratio of the alkyl (meth)acrylate A3 in the total alkyl (meth)acrylate may be 90% by weight or less, may be 75% by weight or less, may be 60% by weight or less, may be 45% by weight or less, may be 30% by weight or less, or may be 15% by weight or less.

[0085] In some embodiments, the above-mentioned (meth)acrylic acid alkyl ester contains a (meth)acrylic acid alkyl ester A2 having 5 or more carbon atoms in the alkyl group as the above-mentioned (meth)acrylic acid alkyl ester A1 or A3, or as a monomer different from the (meth)acrylic acid alkyl ester A1 or A3. By using the (meth)acrylic acid alkyl ester A2, for example, it is easy to reduce the adhesion after the curing treatment, and it is easy to obtain more excellent peelability and low contamination. The number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester A2 is preferably 7 or more (for example, 8 or more), and can be 9 or more. From the viewpoint of adhesion characteristics such as adhesion, the number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester A2 is preferably 14 or less, more preferably 12 or less, and can be 10 or less or 9 or less.

[0086] The mixing ratio of the (meth)acrylic acid alkyl ester A2 in all monomer components constituting the acrylic polymer is preferably about 10% by weight or more. From the viewpoint of ideally exhibiting the function of the (meth)acrylic acid alkyl ester A2, it is preferably about 20% by weight or more, more preferably about 40% by weight or more, further preferably about 55% by weight or more, particularly preferably about 65% by weight or more. For example, it can be about 75% by weight or more, can be about 80% by weight or more, can be about 85% by weight or more, can be about 90% by weight or more, can be about 95% by weight or more. The mixing ratio of the (meth)acrylic acid alkyl ester A2 in all monomer components is not particularly limited. In some embodiments, considering the balance with the usage amount of the comonomer, the mixing ratio of the (meth)acrylic acid alkyl ester A2 in all monomer components is preferably about 99.5% by weight or less (for example, 99% by weight or less), preferably 95% by weight or less, can be 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 30% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less.

[0087] The content ratio of the alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate as the main monomer can be, for example, about 1% by weight or more. From the viewpoint of ideally presenting the function of the alkyl (meth)acrylate A2, it is preferably 5% by weight or more, more preferably 15% by weight or more, further preferably 25% by weight or more, particularly preferably 35% by weight or more, can be 45% by weight or more, can be 60% by weight or more, can be 80% by weight or more (for example, 90% by weight or more). The upper limit of the content ratio of the alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate is 100% by weight. In some embodiments, for example, when the alkyl (meth)acrylate A3 is included, from the viewpoint of ideally presenting its function, the content ratio of the alkyl (meth)acrylate A2 in the total alkyl (meth)acrylate can be, for example, 90% by weight or less, can be 75% by weight or less, can be 60% by weight or less, can be 45% by weight or less, can be 30% by weight or less, can be 15% by weight or less.

[0088] The compounding ratio of the main monomer in all monomer components constituting the acrylic polymer is preferably 55% by weight or more, more preferably 60% by weight or more (for example, 65% by weight or more). The upper limit of the compounding ratio of the main monomer is not particularly limited. In some embodiments, considering the balance with the usage amount of the comonomer, the compounding ratio of the main monomer is, for example, appropriately 99.5% by weight or less (for example, 99% by weight or less), can be 95% by weight or less, can be 90% by weight or less, 85% by weight or less, or about 75% by weight or less.

[0089] The comonomer copolymerizable with the alkyl (meth)acrylate as the main monomer can, for example, contribute to: improving the cohesion of the acrylic polymer as the primary polymer or the secondary polymer; or introducing crosslinking points into the polymer. It is preferable to use, as at least a part of the comonomer, a monomer having a functional group (functional group A) capable of reacting with a functional group (functional group B) of a compound having a carbon-carbon double bond as described below. As the comonomer, for example, the following functional group-containing monomer components can be used alone as only 1 kind or in combination of 2 kinds or more. A monomer having a functional group A and a monomer having other functional groups can also be used in combination.

[0090] Hydroxyl group-containing monomers: For example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol mono vinyl ether.

[0091] Isocyanate group-containing monomers: (meth)acryloyl isocyanate, 2-(meth)acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0092] Carboxyl group-containing monomers: For example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, citraconic acid and their anhydrides (maleic anhydride, itaconic anhydride, etc.).

[0093] Amide group-containing monomers: For example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethylpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide.

[0094] Amino group-containing monomers: For example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate.

[0095] Epoxy group-containing monomers: For example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.

[0096] Cyano group-containing monomers: For example, acrylonitrile, methacrylonitrile.

[0097] Keto group-containing monomers: For example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

[0098] Monomers having a nitrogen atom-containing ring: For example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine.

[0099] Alkoxysilyl group-containing monomers: For example, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane.

[0100] When using a comonomer having a functional group (functional group A) capable of reacting with a functional group (functional group B) of a compound having a carbon-carbon double bond, the type of the comonomer can be selected according to the type of functional group B. As the comonomer having functional group A, for example, a hydroxyl group-containing monomer, an isocyanate group-containing monomer, a carboxyl group-containing monomer, and an epoxy group-containing monomer are preferred.

[0101] In some embodiments, as the comonomer having functional group A, from the viewpoint of reactivity with the compound having functional group B, etc., a hydroxyl group-containing monomer is preferably used. By using a hydroxyl group-containing monomer as the comonomer, the resulting acrylic polymer (primary polymer) has a hydroxyl group. In contrast, by using a compound having an isocyanate group as the compound having a carbon-carbon double bond, the hydroxyl group of the above acrylic polymer reacts with the isocyanate group of the above compound, and the carbon-carbon double bond derived from the above compound is introduced into the above acrylic polymer to obtain an acrylic polymer having a carbon-carbon double bond (secondary polymer). Suitable examples of the hydroxyl group-containing monomer include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). Among them, 4HBA is preferred.

[0102] The amount of the above comonomer can be appropriately selected in a manner to achieve the desired purpose of use (introduction of reaction points with functional group B, adjustment of the cohesion and adhesion characteristics of the photocurable adhesive layer, etc.), and there is no particular limitation. Generally, from the viewpoint of easily and suitably exhibiting the effects brought about by irradiating (curing treatment) the photocurable adhesive layer with light (for example, the effect of reducing the peel force), the amount of the above comonomer is preferably 0.1% by weight or more in all monomer components of the acrylic polymer, more preferably 0.3% by weight or more (for example, 1% by weight or more). In addition, the amount of the comonomer is preferably 70% by weight or less (for example, 60% by weight or less) in all monomer components. In some embodiments, from the viewpoint of the flexibility of the photocurable adhesive layer, etc., it is preferably 50% by weight or less, more preferably 45% by weight or less, and can be 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, or 5% by weight or less.

[0103] When a comonomer having a functional group A is used for reaction with a compound having a carbon-carbon double bond (preferably an ethylenically unsaturated compound having a functional group B), from the viewpoint of easily obtaining a reduction in peel strength caused by a curing treatment (typically, a light irradiation treatment), etc., the amount of the comonomer having a functional group A (for example, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an isocyanate group-containing monomer, an epoxy group-containing monomer, etc. depending on the type of the functional group B) is preferably 1% by weight or more in all monomer components of the acrylic polymer, more preferably 5% by weight or more, still more preferably 10% by weight or more, and further preferably 12% by weight or more (for example, 14% by weight or more). Further, from the viewpoint of maintaining good adhesive properties such as adhesiveness in the adhesive layer (photocurable adhesive layer) before the curing treatment, the amount of the comonomer having a functional group A is preferably 50% by weight or less (for example, 40% by weight or less) in all monomer components, more preferably 30% by weight or less, still more preferably 25% by weight or less, and may be 20% by weight or less, and may be 15% by weight or less.

[0104] In some embodiments, as the comonomer, a monomer having a nitrogen atom-containing ring is preferably used. The monomer having a nitrogen atom-containing ring can contribute to an increase in the peel strength in the initial state (before the curing treatment) of the photocurable adhesive layer. Further, from the viewpoint of increasing the reduction in peel strength (peel strength difference) caused by light irradiation (curing treatment) of the photocurable adhesive layer, the use of the monomer having a nitrogen atom-containing ring is also advantageous. Further, by using the monomer having a nitrogen atom-containing ring as a comonomer, the loss modulus G" of the adhesive layer can be increased. Specific examples of the monomer having a nitrogen atom-containing ring are as described above, and as suitable examples, N-vinyl-2-pyrrolidone (NVP) and N-acryloylmorpholine (ACMO) can be mentioned. In all monomer components used as raw materials for the acrylic polymer (primary polymer), the amount of the monomer having a nitrogen atom-containing ring used can be, for example, 0.5% by weight or more or 1% by weight or more, and from the viewpoint of obtaining a higher use effect, it is preferably 3% by weight or more, advantageously 5% by weight or more, and can be 10% by weight or more, can be 12% by weight or more, can be 17% by weight or more, or 20% by weight or more. Further, in all monomer components used as raw materials for the acrylic polymer (primary polymer), the amount of the monomer having a nitrogen atom-containing ring used can be, for example, 40% by weight or less, and from the viewpoint of the flexibility of the photocurable adhesive layer, in some embodiments, it is preferably 35% by weight or less, more preferably 30% by weight or less (for example, 28% by weight or less).

[0105] In addition, in order to improve the cohesive force of the acrylic polymer, etc., other copolymerization components other than the above-mentioned comonomers can be used as needed. Examples of such copolymerization components include: vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, dicyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylates containing an aromatic ring such as (meth)acrylic acid aryl ester (e.g., phenyl (meth)acrylate), (meth)acrylic acid aryloxyalkyl ester (e.g., phenoxyethyl (meth)acrylate), and (meth)acrylic acid arylalkyl ester (e.g., benzyl (meth)acrylate); olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; alkoxy-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; etc. These copolymerization components other than the comonomers can be used alone or in combination of two or more. The amount of the other copolymerization components can be appropriately selected according to the purpose and use, and there is no particular limitation. For example, it is preferably 20% by weight or less (e.g., 2 to 20% by weight, typically 3 to 10% by weight) of all the monomer components constituting the acrylic polymer.

[0106] As the above other copolymerization components, polyfunctional monomers can also be used. Examples of polyfunctional monomers include various polyfunctional (meth)acrylates having two or more (meth)acryloyl groups in one molecule, polyfunctional vinyl monomers such as divinylbenzene, and polyfunctional monomers having a (meth)acryloyl group and other ethylenically unsaturated groups in combination, such as allyl (meth)acrylate and vinyl (meth)acrylate. The polyfunctional monomers can be used alone or in combination of two or more. Among them, polyfunctional (meth)acrylates are preferably used. Examples of polyfunctional (meth)acrylates include 1,6-hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, and vinyl (meth)acrylate. As the polyfunctional (meth)acrylate for the acrylic polymer, one kind of polyfunctional (meth)acrylate can be used alone, or two or more kinds of polyfunctional (meth)acrylates can be used in combination. In some embodiments, as the polyfunctional (meth)acrylate for the acrylic polymer, at least one selected from the group consisting of 1,6-hexanediol diacrylate, dipentaerythritol hexaacrylate, and trimethylolpropane triacrylate is preferably used.

[0107] By polymerizing the monomer component containing the polyfunctional monomer, typically, an acrylic polymer (primary polymer) having a structure crosslinked by the polyfunctional monomer can be obtained. That is, the above polyfunctional monomer can function as a copolymerization crosslinking agent. By introducing a carbon-carbon double bond into the acrylic polymer of this structure, an acrylic polymer (secondary polymer) having a carbon-carbon double bond and a structure crosslinked by the polyfunctional monomer can be obtained. From the viewpoint of imparting appropriate cohesiveness to the photocurable adhesive layer containing this polymer, it is advantageous for the acrylic polymer having a carbon-carbon double bond to have a crosslinked structure. In the photocurable adhesive layer containing an acrylic polymer having a carbon-carbon double bond as the base polymer, it is particularly meaningful that the above acrylic polymer is crosslinked.

[0108] The amount of the polyfunctional monomer (copolymerization crosslinking agent) used as the other copolymerization component described above can be appropriately selected according to the purpose and use, and is not particularly limited. For example, in all monomer components constituting the acrylic polymer (primary polymer), it can be 0.001% by weight or more. From the viewpoint of easily obtaining a higher usage effect, it is preferably 0.005% by weight or more, more preferably 0.007% by weight or more, can be 0.01% by weight or more, and can be 0.03% by weight or more. In addition, from the viewpoints of easily and appropriately exerting the effects brought about by curing the photocurable adhesive layer (for example, the effect of reducing the peel strength) and the flexibility of the photocurable adhesive layer, etc., in all monomer components constituting the acrylic polymer, the amount of the polyfunctional monomer used can be, for example, 10% by weight or less, and it is advantageous to be 5% by weight or less, preferably less than 5% by weight, can be 3% by weight or less, and can be 1% by weight or less. In some embodiments, in all monomer components constituting the acrylic polymer (typically, the acrylic polymer as the primary polymer), the amount of the polyfunctional monomer used is preferably less than 1% by weight (for example, 0.9% by weight or less), more preferably 0.5% by weight or less, can be 0.3% by weight or less, can be 0.2% by weight or less, can be 0.1% by weight or less (for example, less than 0.1% by weight), can be 0.09% by weight or less, 0.08% by weight or less, or 0.07% by weight or less. From the viewpoint of easily and appropriately exerting the effects (for example, the easy peelability effect) brought about by curing the photocurable adhesive layer (for example, ultraviolet irradiation treatment), it is advantageous that the amount of the polyfunctional monomer used as the copolymerization component of the primary polymer is not excessive.

[0109] The method for obtaining the acrylic polymer (primary polymer) from the monomer components as described above can be selected from various polymerization methods known as the synthesis methods of acrylic polymers. From the viewpoint of avoiding the use of organic solvents, a polymerization method other than solution polymerization (for example, solution polymerization using an azo-based polymerization initiator or a peroxide-based polymerization initiator) is preferred. In some embodiments, the above acrylic polymer (primary polymer) can be obtained by curing the following active energy ray-curable adhesive composition, which contains a part of the monomer components constituting the polymer in the form of a polymer and the remaining part in the form of unpolymerized (unreacted monomers). For example, by applying the above active energy ray-curable adhesive composition to an appropriate surface and irradiating it with active energy rays (such as ultraviolet rays) to cure it, an adhesive layer (primary adhesive layer) containing the acrylic polymer formed from the above monomer components is obtained. The above acrylic polymer is an active energy ray polymer of the above monomer components. Generally, the carbon-carbon double bonds (for example, ethylenically unsaturated bonds) contained in the active energy ray-curable adhesive composition react and disappear due to the irradiation of active energy rays when forming the adhesive layer by curing the adhesive composition. Therefore, according to the above method, typically, an adhesive layer (primary adhesive layer) without carbon-carbon double bonds is formed.

[0110] In some embodiments, for the primary adhesive layer, carbon-carbon double bonds are introduced into the acrylic polymer (acrylic polymer without carbon-carbon double bonds) in the adhesive layer, and an appropriate amount of a photoinitiator is added as needed. Thereby, photocurability can be imparted to the above primary adhesive layer, and a photocurable adhesive layer (secondary adhesive layer) containing the acrylic polymer having carbon-carbon double bonds and a specified amount or more of the photoinitiator is obtained. The above acrylic polymer having carbon-carbon double bonds is an acrylic polymer obtained by chemically modifying the active energy ray polymer of the above monomer components to introduce carbon-carbon double bonds, and belongs to the modified product of the above active energy ray polymer. Some suitable examples of the method for obtaining the secondary adhesive layer from the primary adhesive layer are described later.

[0111] In some preferred embodiments, the active energy ray-curable adhesive composition for forming the primary adhesive layer contains a partial polymer of a monomer mixture containing at least a part of the monomer components (raw material monomers) constituting the acrylic polymer. Such a partial polymer is a mixture of a polymer from the above monomer mixture and unreacted monomers, and typically has a paste-like liquid state (viscous liquid state). Hereinafter, the partial polymer having such a property may sometimes be referred to as "monomer paste" or simply "paste".

[0112] The polymerization method for obtaining the above-mentioned polymerized reactant is not particularly limited, and various known polymerization methods can be appropriately selected and used. From the perspective of avoiding the use of organic solvents, methods other than solution polymerization (for example, solution polymerization using an azo-based polymerization initiator or a peroxide-based polymerization initiator) are preferably adopted. Among them, from the perspectives of efficiency and simplicity, photopolymerization is preferably adopted. According to photopolymerization, the polymerization conversion rate of the above-mentioned monomer mixture can be easily controlled by polymerization conditions such as the irradiation amount (light amount) of light.

[0113] The polymerization conversion rate (monomer conversion rate) of the monomer mixture in the above-mentioned partial polymer is not particularly limited. The above-mentioned polymerization conversion rate can be, for example, about 70% by weight or less, preferably about 60% by weight or less. From the perspectives of the ease of preparation and coatability of the adhesive composition containing the above-mentioned partial polymer, generally, the above-mentioned polymerization conversion rate is appropriately about 50% by weight or less, preferably about 40% by weight or less (for example, about 35% by weight or less). The lower limit of the polymerization conversion rate is not particularly limited. Typically, it is about 1% by weight or more, and usually about 5% by weight or more is appropriate.

[0114] The adhesive composition containing the partial polymer of the above-mentioned monomer mixture can be obtained, for example, by partially polymerizing the monomer mixture containing a part or all of the monofunctional monomers in the raw material monomers using an appropriate polymerization method (for example, photopolymerization). In the adhesive composition containing the above-mentioned partial polymer, other components (for example, a photoinitiator, a polyfunctional monomer as a copolymerization crosslinking agent, etc.) can be incorporated as needed. The method of incorporating such other components is not particularly limited. For example, the above-mentioned monomer mixture can be pre-containing, or added to the above-mentioned partial polymer.

[0115] The adhesive composition disclosed herein can be in the following form: a partial polymer or a complete polymer of a monomer mixture containing a part of the types of monomers in the monomer component (raw material monomers) is dissolved in the remaining types of monomers or a partial polymer thereof. Such an adhesive composition also falls within the examples of the adhesive composition containing a polymer and an unpolymerized monomer component in the monomer component. It should be noted that in this specification, a "complete polymer" means that the polymerization conversion rate exceeds 95% by weight.

[0116] (First photoinitiator)

[0117] In the active energy ray-curable adhesive composition for forming the primary adhesive layer, a photoinitiator may be contained in order to promote curing and the like. In the case where light such as ultraviolet light is used as the active energy ray, it is particularly preferable to incorporate a photoinitiator in the adhesive composition. As the photoinitiator contained in the adhesive composition, one or more selected from the examples of the materials that can be used as the photoinitiator contained in the adhesive layer (photo-curable adhesive layer) of the adhesive sheet disclosed herein can be used. It should be noted that the above-mentioned photoinitiator incorporated in the adhesive composition functions as a catalyst for causing the polymerization and crosslinking reactions of the above-mentioned monomer components and crosslinking agent to form an acrylic polymer. Therefore, the above-mentioned photoinitiator is inactivated and decomposed by the irradiation of active energy rays (typically, ultraviolet irradiation) when the adhesive layer (primary adhesive layer) is formed from the above-mentioned adhesive composition, and thus does not remain in the adhesive layer of the adhesive sheet disclosed herein, or even if it remains, it is considered to be at a trace level. On the other hand, the photoinitiator contained in the adhesive layer (photo-curable adhesive layer) of the adhesive sheet disclosed herein is contained in the above-mentioned adhesive together with the polymer having a carbon-carbon double bond, and promotes the crosslinking reaction based on the above-mentioned carbon-carbon double bond. Hereinafter, the photoinitiator contained in the adhesive composition and used for forming the adhesive layer from the adhesive composition may sometimes be referred to as the "first photoinitiator". In addition, the photoinitiator contained in the adhesive layer (photo-curable adhesive layer) of the adhesive sheet disclosed herein and used for the photocuring of the adhesive layer may sometimes be referred to as the "second photoinitiator". The first photoinitiator and the second photoinitiator may be the same material or different materials.

[0118] (Catalyst)

[0119] In some embodiments, the primary adhesive layer may contain a catalyst that promotes the reaction between functional group A and functional group B. For example, as the catalyst that can be used to promote the addition reaction between an isocyanate group and a hydroxyl group, metal-based catalysts such as tetra-n-butyl titanate, tetra-isopropyl titanate, iron(III) acetylacetonate, butyltin oxide, and dioctyltin dilaurate can be exemplified. In addition, for example, as the catalyst that can be used to promote the addition reaction between a carboxyl group and an epoxy group, quaternary ammonium compounds such as tetrabutylammonium bromide (TBAB) and tetrabenzylammonium bromide, and their derivatives; phosphorus-based compounds such as triphenylphosphine (TPP) and their derivatives; amine-based compounds such as benzyldimethylamine and their derivatives; imidazole-based compounds such as 2-ethyl-4-methylimidazole and their derivatives; etc. can be exemplified. The amount of use of the above-mentioned catalyst is not particularly limited, and can be set in such a way that the reaction between functional group A and functional group B can be appropriately promoted. In some embodiments, in every 100 g of the primary adhesive layer, the amount of use of the above-mentioned catalyst can be, for example, about 0.05 to 15 g, can be about 0.1 to 10 g, and can be about 0.5 to 5 g.

[0120] By previously incorporating the above catalyst in an adhesive composition (e.g., an active energy ray-curable adhesive composition) used for forming a primary adhesive layer, a primary adhesive layer containing the catalyst can be easily obtained. For example, an ethylenically unsaturated compound having a functional group B is permeated into a primary adhesive layer containing a primary polymer having a functional group A (preferably an acrylic polymer) and the above catalyst, and then the functional group A and the functional group B are reacted in the presence of the above catalyst, whereby a polymer having a carbon-carbon double bond (a chemically modified product of the above primary polymer) can be efficiently obtained. As another method of reacting the functional group A and the functional group B in the presence of the above catalyst, for example, a method of making a post-coating liquid described later contain the above catalyst can be cited. From the viewpoint of controllability of the reaction between the functional group A and the functional group B, etc., a method of previously making the adhesive composition used in the formation of the primary adhesive layer contain the above catalyst is preferred.

[0121] (Second photoinitiator)

[0122] The adhesive layer (photo-curable adhesive layer) constituting the adhesive sheet disclosed herein preferably contains a photoinitiator. By containing a photoinitiator, free radicals are generated from the photoinitiator during the curing treatment, and the photocuring of the adhesive layer proceeds rapidly. Examples of photoinitiators include ketal-based photoinitiators, acetophenone-based photoinitiators, benzoin ether-based photoinitiators, acylphosphine oxide-based photoinitiators, α-ketol-based photoinitiators, aromatic sulfonyl chloride-based photoinitiators, photoactive oxime-based photoinitiators, benzoin-based photoinitiators, benzil-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, etc. The photoinitiator can be used alone or in appropriate combination of two or more.

[0123] Specific examples of ketal-based photoinitiators include 2,2-dimethoxy-1,2-diphenylethane-1-one (e.g., trade name “Omnirad 651”, manufactured by IGM Resins B.V.), etc.

[0124] Specific examples of acetophenone-based photoinitiators include 1-hydroxycyclohexyl-phenyl-ketone (e.g., trade name “Omnirad 184”, manufactured by IGM Resins B.V.), 4-phenoxydichloroacetophenone, 4-tert-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methoxyacetophenone, etc. Specific examples of benzoin ether-based photoinitiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether and other benzoin ethers and substituted benzoin ethers such as anisoin methyl ether. Specific examples of acylphosphine oxide-based photoinitiators include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-din-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, etc. Specific examples of α-ketol-based photoinitiators include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, etc. Specific examples of aromatic sulfonyl chloride-based photoinitiators include 2-naphthalenesulfonyl chloride, etc. Specific examples of photoactive oxime-based photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime, etc. Specific examples of benzoin-based photoinitiators include benzoin, etc. Specific examples of benzil-based photoinitiators include benzil, etc. Specific examples of benzophenone-based photoinitiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, etc. Specific examples of thioxanthone-based photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc.

[0125] The content of the photoinitiator in the photocurable adhesive layer disclosed herein is 1.0×10 -4 mol / 100 g or more (i.e., 1.0×10 -4 mol or more per 100 g of the adhesive layer) is appropriate. From the viewpoint of enabling the curing reaction to proceed with good precision, it is advantageous to be 3.0×10 -4 mol / 100 g or more, preferably 5.0×10 -4 mol / 100 g or more, can be 7.0×10 -4 mol / 100 g or more, can be 1.0×10 -3 mol / 100 g or more, can be 2.0×10 -3mol / 100 g or more, or 3.0×10 -3 mol / 100 g or more. There is no particular limitation on the upper limit of the content of the photoinitiator. In some embodiments, from the viewpoint of the storage stability of the adhesive sheet, for example, it may be 1.0×10 -1 mol / 100 g or less, it may be 5.0×10 -2 mol / 100 g or less, it may be 1.0×10 -2 mol / 100 g or less, it may be 5.0×10 -3 mol / 100 g or less.

[0126] The content of the photoinitiator in the photocurable adhesive layer can be calculated based on the total weight parts of the materials used as the raw materials for manufacturing the adhesive layer, the weight parts of the photoinitiator used in a manner that remains in the obtained adhesive layer, and the molecular weight of the photoinitiator. For example, in a photocurable adhesive layer obtained by post-coating an additional photoinitiator on a primary adhesive layer formed using an adhesive composition containing a photoinitiator and allowing it to penetrate, at least for the photoinitiator supplied by post-coating, in the case where a treatment (such as ultraviolet irradiation treatment) that actively decomposes the above photoinitiator is not performed thereafter, it can be said that the photoinitiator is used in a manner that remains in the obtained photocurable adhesive layer. Therefore, the content of the photoinitiator in the above photocurable adhesive layer can be regarded as being equal to or more than the content calculated based on the photoinitiator supplied by post-coating. In a photocurable adhesive layer obtained by post-coating a photoinitiator on a primary adhesive layer obtained by curing (primary curing) an adhesive composition containing a photoinitiator by light irradiation and allowing it to penetrate, the content of the photoinitiator in the photocurable adhesive layer can be regarded as being approximately the same as the content calculated based on the photoinitiator supplied by post-coating.

[0127] In the case where this information is unknown, as the content of the photoinitiator in the photocurable adhesive layer, a value obtained based on analysis by HPLC (high performance liquid chromatography) can be used. The above photoinitiator is identified by performing component analysis on the eluate corresponding to the photoinitiator peak among the peaks that appear in the chromatogram, and a standard curve is prepared using this identification substance or a compound having a molecular structure similar to the identification substance as a standard product, whereby the content of the above photoinitiator in the measurement sample can be determined. Based on its content and the molecular weight of the above photoinitiator, the content [mol / 100 g] of the above photoinitiator in the adhesive layer can be calculated.

[0128] The measurement sample for HPLC can be prepared in the following manner. That is, an appropriate amount (e.g., about 0.1 g) of the adhesive is collected from the adhesive layer, placed in a screw bottle, and weighed. 3 mL of chloroform is added to the above screw bottle, and it is shaken overnight (about 16 hours) in a cool and dark place, whereby the photoinitiator in the above sample is dissolved into the chloroform. Next, 10 mL of acetonitrile is added to precipitate the adhesive component again, and the supernatant liquid in which the photoinitiator is dissolved is filtered through a membrane filter (pore size 0.20 μm). This is used as the measurement sample for HPLC. As the analysis device, "UltiMate 3000" of Thermo Fisher Scientific Company or its equivalent can be used. As the measurement conditions, the following conditions can be adopted.

[0129] [Measurement Conditions]

[0130] Column: ZORBAX Eclipse Plus C18( Average particle size of the carrier 1.8 μm)

[0131] Column temperature: 40 °C

[0132] Column flow rate: 0.5 mL / min

[0133] Eluent composition: Gradient conditions of pure water / acetonitrile

[0134] Injection volume: 10 μL

[0135] Detector: DAD (extracting 190 nm - 800 nm, 210 nm, and 245 nm)

[0136] (Other polymers)

[0137] When the photocurable adhesive layer disclosed herein contains an acrylic polymer having a carbon-carbon double bond, the photocurable adhesive layer may further contain other polymers in addition to the acrylic polymer having a carbon-carbon double bond. The other polymers may be acrylic polymers without a carbon-carbon double bond or polymers other than acrylic polymers. As the polymers other than acrylic polymers, other substances among the various polymers exemplified as the polymers that can be contained in the adhesive layer, excluding acrylic polymers, can be cited as suitable examples. Such polymers may be polymers having a carbon-carbon double bond. As the acrylic polymer without a carbon-carbon double bond, the acrylic polymer as the primary polymer (i.e., the acrylic polymer that has not undergone chemical modification to introduce a carbon-carbon double bond) can be cited as a suitable example. When the adhesive layer disclosed herein contains the other polymers in addition to the acrylic polymer having a carbon-carbon double bond, it is appropriate that the content of the other polymer is 100 parts by weight or less, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 10 parts by weight or less, based on 100 parts by weight of the acrylic polymer having a carbon-carbon double bond. Based on 100 parts by weight of the acrylic polymer having a carbon-carbon double bond, the content of the other polymer may be 5 parts by weight or less, or may be 1 part by weight or less. The technology disclosed herein can be preferably implemented, for example, such that 99.5 to 100% by weight of the polymers contained in the adhesive layer is an acrylic polymer having a carbon-carbon double bond.

[0138] (Compound containing a carbon-carbon double bond other than a polymer)

[0139] The photocurable adhesive layer disclosed herein may contain a compound containing a carbon-carbon double bond other than a polymer containing a carbon-carbon double bond. Examples of such a compound containing a carbon-carbon double bond include polyfunctional monomers, monofunctional monomers, polyfunctional or polyfunctional oligomers having a carbon-carbon double bond, and the like. The fact that the photocurable adhesive layer contains the compound containing a carbon-carbon double bond means that the carbon-carbon double bond possessed by the compound containing a carbon-carbon double bond is contained in an unreacted manner.

[0140] In some embodiments, the photocurable adhesive layer may contain a polyfunctional monomer as the carbon-carbon double bond-containing compound described above. As the polyfunctional monomer contained in the photocurable adhesive layer, one or more may be selected from the same monomers as the polyfunctional monomers (copolymerizable crosslinking agents) that can be used as copolymerization components of the primary polymer. When the photocurable adhesive layer contains a polyfunctional monomer, the photocurable adhesive layer preferably contains, in combination, a polymer having a carbon-carbon bond (preferably an acrylic polymer having a carbon-carbon bond) and the above polyfunctional monomer. The polyfunctional monomer contained in the photocurable adhesive layer can contribute to improving the flexibility of the photocurable adhesive layer and the elastic modulus after curing treatment. For example, as a method of making the photocurable adhesive layer contain a polyfunctional monomer, for example, a method of coating a polyfunctional monomer on a primary adhesive layer (which can be a primary adhesive layer formed by irradiating an active energy ray-curable adhesive composition with active energy rays) and allowing it to penetrate can be adopted.

[0141] In the photocurable adhesive layer disclosed herein, the content of the carbon-carbon double bond-containing compound other than the polymer having a carbon-carbon double bond (for example, a polyfunctional monomer) can be set in a manner that appropriately exhibits the desired use effects. For example, it can be 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, based on 100 parts by weight of the base polymer of the photocurable adhesive layer (for example, an acrylic polymer having a carbon-carbon bond). Further, from the viewpoints of the cohesiveness of the photocurable adhesive layer, the peelability of the release liner, etc., in some embodiments, it is appropriate that the content of the carbon-carbon double bond-containing compound is 10 parts by weight or less, preferably 5 parts by weight or less, can be 1 part by weight or less, and can be less than 1 part by weight, based on 100 parts by weight of the base polymer of the photocurable adhesive layer. The technology disclosed herein can be preferably implemented in such a manner that the photocurable adhesive layer does not contain other carbon-carbon double bond-containing compounds other than the polymer having a carbon-carbon double bond.

[0142] (Other optional components)

[0143] In the adhesive layer disclosed herein, if necessary, various additives commonly used in the adhesive field, such as a leveling agent, a crosslinking aid, a plasticizer, a softening agent, a filler, a coloring agent (pigment, dye, etc.), an antistatic agent, an ultraviolet absorber, a light stabilizer, etc., can be contained as other optional components. For these various additives, conventionally known substances can be used by conventional methods, and since they do not particularly characterize the present invention, detailed description thereof is omitted.

[0144] In some preferred embodiments, the adhesive layer disclosed herein may have a composition in which the content of the polymer (typically a base polymer) accounts for more than about 90% by weight of the total weight of the adhesive (the solid components of the adhesive composition), i.e., the weight of the adhesive layer composed of the adhesive. Thus, it is possible to ideally achieve the easy peelability of the adhesive layer brought about by the curing treatment. From this perspective, the content of the above polymer is preferably more than about 95% by weight of the total weight of the adhesive layer, more preferably more than about 97% by weight, further preferably more than about 98% by weight, and may be more than about 99% by weight (e.g., 99 - 100% by weight). In other words, the content of components other than the polymer (additives, etc.) in the solid components (adhesive layer) of the above adhesive composition is suitably about 10% by weight or less, preferably about 5% by weight or less, more preferably about 3% by weight or less, further preferably about 2% by weight or less, and may be about 1% by weight or less.

[0145] The amount of carbon-carbon double bonds contained in the adhesive layer disclosed herein can be, for example, 1.0×10 -6 mol / 100g or more, and can be 1.0×10 -5 mol / 100g or more. In some embodiments, from the perspective of easily obtaining changes in properties and physical properties brought about by light irradiation, the amount of the above carbon-carbon double bonds being 5.0×10 -5 mol / 100g or more is suitable, being 1.0×10 - 4 mol / 100g or more is advantageous, preferably 5.0×10 -4 mol / 100g or more or 1.0×10 -3 mol / 100g or more, can be 5.0×10 -3 mol / 100g or more, can be 1.0×10 -2 mol / 100g or more, can be 3.0×10 -2 mol / 100g or more, can be 4.0×10 -2 mol / 100g or more, can be 5.0×10 -2 mol / 100g or more. Additionally, the amount of carbon-carbon double bonds contained in the adhesive layer can be, for example, 1.0 mol / 100g or less, can be 5.0×10 -1 mol / 100g or less, can be 1.0×10 -1 mol / 100g or less, can be 8.0×10 -2 mol / 100g or less, can be 7.0×10 -2less than 1 mol / 100 g. From the viewpoints of the storage stability of the adhesive layer or the adhesive sheet having the adhesive layer and the ease of obtaining a balance with other properties, it is advantageous that the content of carbon-carbon double bonds is not excessive. It should be noted that in this specification, the unit "mol / 100 g" of the amount of carbon-carbon double bonds contained in the adhesive layer refers to the molar amount of carbon-carbon double bonds per 100 g of the adhesive layer.

[0146] The carbon-carbon double bonds contained in the adhesive layer disclosed herein may be contained in the form of a polymer having carbon-carbon double bonds, or may be contained in a form other than a polymer having carbon-carbon double bonds (for example, in the form of a polyfunctional monomer, a monofunctional monomer, an oligomer, etc. having carbon-carbon double bonds). It is preferred that at least a part of the carbon-carbon double bonds contained in the adhesive layer is contained in the form of a polymer having carbon-carbon double bonds. In some embodiments, the amount of carbon-carbon double bonds contained in the adhesive layer in the form of a polymer having carbon-carbon double bonds can be, for example, 1.0×10 -6 mol / 100 g or 1.0×10 -5 mol / 100 g or more. From the viewpoint of easily obtaining changes in properties and physical properties brought about by light irradiation, it is appropriate that it is 5.0×10 -5 mol / 100 g or more, it is advantageous that it is 1.0×10 -4 mol / 100 g or more, preferably 5.0×10 -4 mol / 100 g or more or 1.0×10 -3 mol / 100 g or more, it can be 5.0×10 -3 mol / 100 g or more, it can be 1.0×10 -2 mol / 100 g or more, it can be 3.0×10 -2 mol / 100 g or more, it can be 4.0×10 -2 mol / 100 g or more, it can be 5.0×10 -2 mol / 100 g or more. Additionally, for example, it can be less than 1.0 mol / 100 g, it can be 5.0×10 -1 mol / 100 g or less, it can be 1.0×10 - 1 mol / 100 g or less, it can be 8.0×10 -2 mol / 100 g or less, it can be 7.0×10 -2 mol / 100 g or less.

[0147] The amount of carbon-carbon double bonds (typically, ethylenically unsaturated groups) contained in the adhesive layer can be calculated based on the total weight parts of the materials used as raw materials for manufacturing the adhesive layer, the weight parts of the materials used in such a way that the carbon-carbon double bonds remain in the adhesive layer, and the molecular weight.

[0148] In the case where such information is unknown, as the content of carbon-carbon double bonds in the adhesive layer, the measured value based on the NMR method can be used. Specifically, an appropriate amount of a sample is collected from the adhesive layer, and the substance obtained by dissolving the sample in a measurement solvent added with a specified amount of an internal standard substance is measured, whereby the amount of carbon-carbon double bonds present is determined. As an analytical device, a Fourier transform NMR device (manufactured by Bruker Biospin Corporation, "AVANCE III-600") or an equivalent product thereof can be used. As the measurement conditions, the following conditions can be adopted.

[0149] [Measurement Conditions]

[0150] Observation frequency: 1 H 600 MHz

[0151] Measurement solvent: CDCl3

[0152] Measurement temperature: 300 K

[0153] Chemical shift reference: Measurement solvent 1 H; 7.25 ppm

[0154] In some embodiments of the adhesive layer disclosed herein, in the adhesive layer, the content of the organic solvent is preferably 1.0 μg / g or less (that is, the content of the organic solvent per 1 g of the adhesive layer is 1.0 μg or less), for example, preferably less than 1.0 μg / g, more preferably less than 0.5 μg / g, may be less than 0.2 μg / g, and may be 0 μg / g. Specific examples of the above organic solvent include ethyl acetate and toluene. The adhesive layer with a small content of the organic solvent has a low odor and is desirable from the viewpoint of environmental hygiene. The content of the organic solvent in the adhesive layer is measured by the method described in the examples below.

[0155] In the adhesive layer disclosed herein, it is appropriate that the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator (the polymerization initiator that may be included in the form of decomposition products or residues) is limited to 1.0 μg / g or less. That is, the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator in 1 g of the above adhesive layer is 1.0 μg or less. Thereby, it is possible to prevent or suppress the drawbacks caused by the above polymerization initiator. As examples of the above drawbacks, the following can be cited: Since the azo-based polymerization initiator and the peroxide-based polymerization initiator, which are thermal polymerization initiators, are cracked by heat and cracked over time to generate free radicals, the physical properties of the adhesive are unexpectedly changed (for example, cured), or the surface of the adherend to which the adhesive sheet is adhered is modified (for example, oxidation accompanying the cracking of the peroxide-based polymerization initiator), contaminated (for example, contamination caused by low molecular weight decomposition products and reactants), or outgassing is generated (for example, N2 gas generated by the decomposition of the azo-based polymerization initiator), etc. From the viewpoint of better suppressing the above drawbacks, in some embodiments, in the adhesive layer, the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator is preferably less than 1.0 μg / g, more preferably less than 0.5 μg / g, may be less than 0.2 μg / g, and may be 0 μg / g (that is, not contained). The total content of the azo-based and peroxide-based polymerization initiators in the adhesive layer is measured by the method of the following examples.

[0156] (Thickness of the adhesive layer)

[0157] The thickness of the adhesive layer (photo-curable adhesive layer) of the adhesive sheet disclosed herein is not particularly limited and can be appropriately selected according to the purpose. The thickness of the above-mentioned adhesive layer can be selected, for example, from the range of 2 μm or more to about 2000 μm. In some embodiments, from the perspective of thinning the adhesive sheet, etc., the thickness of the above-mentioned adhesive layer can be 1000 μm or less, can be 500 μm or less, can be 200 μm or less, can be 150 μm or less, can be 100 μm or less. From the perspective of reducing the peel strength after light irradiation, in some embodiments, the thickness of the adhesive layer can be less than 100 μm, can be 80 μm or less, can be 60 μm or less, can be 40 μm or less, can be 30 μm or less. By making the thickness of the photo-curable adhesive layer not too large, there is a tendency to easily obtain the effect of easy peelability brought about by irradiating the adhesive layer with light. For example, in the case of forming a photo-curable adhesive layer by the following method, from the perspective of uniformly reacting functional group A and functional group B within the entire thickness range of the adhesive layer, it is also advantageous that the thickness of the photo-curable adhesive layer is not too large. The method here includes: forming a primary adhesive layer having functional group A, coating a post-coating liquid containing an ethylenically unsaturated compound having functional group B on the above-mentioned primary adhesive layer and allowing it to penetrate, and then reacting functional group A in the above-mentioned primary adhesive layer with the ethylenically unsaturated compound having functional group B. In addition, from the perspective of the adhesion to the adherend before the curing treatment, etc., the thickness of the adhesive layer is preferably 10 μm or more, more preferably 15 μm or more, and can be 20 μm or more. When the adhesive sheet disclosed herein is a double-sided adhesive sheet having adhesive layers on both sides of the substrate, the thicknesses of the respective adhesive layers can be the same or different.

[0158] <Fabrication of Adhesive Layer>

[0159] The adhesive layer disclosed herein can be suitably fabricated, for example, by a method including the following steps.

[0160] (a) Forming a primary adhesive layer containing a primary polymer having functional group A (primary adhesive layer forming step),

[0161] (b) Preparing a post-coating liquid containing a compound having a carbon-carbon double bond and containing functional group B (for example, an ethylenically unsaturated compound having functional group B) and a photoinitiator, and coating the post-coating liquid on at least one surface of the above-mentioned primary adhesive layer (post-coating liquid coating step),

[0162] (c) Allowing the compound having a carbon-carbon double bond and containing functional group B and the photoinitiator contained in the above-mentioned post-coating liquid to penetrate into the above-mentioned primary adhesive layer (post-coating liquid penetration step),

[0163] (d) The primary adhesive layer impregnated with the post-coating liquid is heated to allow the functional group A to react with the functional group B (reaction step).

[0164] The primary adhesive layer forming step may include: applying an adhesive composition for forming the primary adhesive layer on a support; and curing the applied adhesive composition to form a primary adhesive layer containing a primary polymer having a functional group A. As the support, a plastic film that can be used as a substrate layer described later and a release liner described later can be used. In the coating (application) of the adhesive composition, a known coating method can be used, for example, a coating machine such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a rod coater, a knife coater, a spray coater, a comma coater, a direct coater, etc. can be used.

[0165] In the above-mentioned primary adhesive layer forming process, there is no particular limitation on the method for curing the applied adhesive composition. For example, the coated adhesive composition can be heated and the adhesive composition can be irradiated with active energy rays to cure it. If necessary, it can be further heated and dried. In some embodiments, the following method can be preferably used: as the above-mentioned adhesive composition, an active energy ray-curable adhesive composition (preferably an active energy ray-curable adhesive composition without organic solvent) is used, and the composition is irradiated with active energy rays to cure it. As active energy rays, for example, ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron beams, ultraviolet rays, etc. can be cited, and ultraviolet rays are particularly preferred.

[0166] The applied adhesive composition can be directly irradiated with ultraviolet rays, and in order to block the oxygen that hinders the curing based on ultraviolet irradiation, it is preferably irradiated across a support (which can be a peeling film). For example, the surface of the adhesive composition applied to the support is covered with another support, and ultraviolet rays are irradiated across the other support. The illumination and time of ultraviolet irradiation are appropriately set according to the composition of the primary adhesive layer, the thickness of the adhesive layer, etc. Ultraviolet irradiation can use a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, etc.

[0167] Next, the support is peeled off from one surface of the primary adhesive layer, and a post-coating liquid containing a compound having a functional group B with a carbon-carbon double bond and a photoinitiator (second photoinitiator) is prepared, and this post-coating liquid is coated on one surface of the above primary adhesive layer (post-coating liquid coating step). The post-coating liquid is not particularly limited as long as it is a liquid that can be coated and penetrate into the adhesive layer. For example, when the compound having a functional group B with a carbon-carbon double bond and / or the photoinitiator is in a liquid state, they can be coated separately in any order, or it can be a mixed liquid of the compound having a functional group B with a carbon-carbon double bond and the photoinitiator. In addition, it can also be a post-coating liquid in which the photoinitiator is dissolved in the compound having a functional group B with a carbon-carbon double bond, and vice versa.

[0168] If the post-coating liquid is coated on the surface of the primary adhesive layer, the components contained in the post-coating liquid penetrate into the above adhesive layer. After the post-coating liquid is coated on the primary adhesive layer, before entering the next reaction step, if necessary, a standing time can be set to allow the above penetration to proceed sufficiently. The standing time is not particularly limited. For example, it can be appropriately selected within 15 minutes. In some embodiments, it can be selected from the range of 1 second to 10 minutes (e.g., 10 seconds to 10 minutes), preferably 5 seconds to 5 minutes (e.g., 10 seconds to 5 minutes). The standing temperature can be around room temperature (e.g., about 10 to 30 °C). By standing under the above conditions, the post-coating liquid can penetrate sufficiently into the primary adhesive layer.

[0169] Then, the primary adhesive layer penetrated with the above post-coating liquid is heated to cause the reaction between the functional group A and the functional group B (reaction step). The heating temperature in the reaction step is preferably 40 to 200 °C, more preferably 50 to 180 °C, and further preferably 60 to 170 °C (e.g., 100 to 150 °C). The heating time can be an appropriate and suitable time, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.

[0170] <Substrate layer>

[0171] In a single-sided adhesive type or double-sided adhesive type adhesive sheet with a substrate, various sheet-like substrates can be used as the substrate (layer) that supports (backs up) the adhesive layer. As the above-mentioned substrate, a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, a composite thereof, etc. can be used. Examples of the resin film include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyamide resin films; fluororesin films; cellophane; etc. Other examples of the resin film include resin films formed from one or more engineering plastics (which can be super engineering plastics) such as polyphenylene sulfide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyarylate resin, polyamideimide resin, and polyimide resin. From the viewpoint of heat resistance, it is preferable to use engineering plastics. Examples of the paper include Japanese paper, kraft paper, cellophane, high-quality paper, synthetic paper, painted paper, etc. Examples of the cloth include fabrics and non-woven fabrics formed by the single or blended use of various fibrous materials. Examples of the above-mentioned fibrous materials include cotton, staple fiber, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. Examples of the rubber sheet include natural rubber sheet, butyl rubber sheet, etc. Examples of the foam sheet include foamed polyurethane sheet, foamed chloroprene rubber sheet, etc. Examples of the metal foil include aluminum foil, copper foil, etc.

[0172] In a preferred embodiment, a resin film having a specified rigidity (strength) and excellent processability and operability is used as the substrate (layer). By using a resin film substrate with high rigidity, it is possible to appropriately prevent bending and damage of the adherend during conveyance, etc., when the thickness of the adherend is thin. From the same viewpoint, it is preferable to use a polyester film as the resin film substrate. It should be noted that in this specification, the so-called "resin film" typically refers to a non-porous film, which is a concept different from so-called non-woven fabrics and fabrics. The density of the resin film that can be used as the substrate can be about 0.85 to 1.50 g / cm 3 (for example, 0.90 g / cm 3 ~1.20 g / cm 3 , and typically, it is 0.92 g / cm 3 ~1.05 g / cm 3 ) or so.

[0173] It should be noted that in the above-mentioned substrate (such as a resin film substrate), various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.) can be blended as needed.

[0174] The surface of the above-mentioned base material layer (such as a resin film base material, a rubber sheet base material, a foam sheet base material, etc.) having the adhesive layer (the side surface of the adhesive layer) can be subjected to known or conventional surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, coating of a primer, etc. Such surface treatment can be a treatment for improving the adhesion between the base material and the adhesive layer, in other words, the anchoring property of the adhesive layer to the base material.

[0175] In some preferred embodiments, a primer layer is provided on the side surface of the base material layer on the adhesive layer side. In other words, a primer layer can be disposed between the base material layer and the adhesive layer. There is no particular limitation on the primer layer forming material, and one or more of urethane (polyisocyanate)-based resins, polyester-based resins, acrylic-based resins, polyamide-based resins, melamine-based resins, olefin-based resins, polystyrene-based resins, epoxy-based resins, phenolic-based resins, isocyanurate-based resins, polyvinyl acetate-based resins, etc. can be used. When an acrylic-based adhesive layer or the like is provided on a resin film base material, a polyester-based, urethane-based, or acrylic-based primer layer is preferred. When an acrylic-based adhesive layer is provided on a polyester-based base material layer such as a PET film, a polyester-based primer layer is particularly preferred. The thickness of the primer layer is not particularly limited and can generally be in the range of about 0.1 μm to 10 μm (for example, 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The primer layer can be formed using known or conventional coating machines such as a gravure roll coater or a reverse roll coater.

[0176] In addition, when the adhesive sheet disclosed herein is a single-sided adhesive sheet having an adhesive layer provided on one side of the base material layer, the non-adhesive layer forming surface (back surface) of the base material layer can be subjected to a peeling treatment using a peeling treatment agent (back surface treatment agent). There is no particular limitation on the back surface treatment agent that can be used for forming the back surface treatment layer, and silicone-based back surface treatment agents, fluorine-based back surface treatment agents, long-chain alkyl-based back surface treatment agents, and other known or conventional treatment agents can be used according to the purpose and application.

[0177] The thickness of the base material layer is not particularly limited and can be appropriately selected according to the purpose. Generally, it can be 1 to 800 μm. From the viewpoints of processability, operability, workability, etc., a thickness of the base material layer of 2 μm or more (for example, 3 μm or more, typically 5 μm or more) is appropriate, preferably about 10 μm or more, more preferably about 25 μm or more (for example, 30 μm or more). In addition, a thickness of about 700 μm or less (for example, 500 μm or less, typically 200 μm or less) is appropriate, preferably about 100 μm or less, more preferably about 80 μm or less (for example, about 70 μm or less).

[0178] <Release Liner>

[0179] As the release liner, conventional release paper or the like can be used, and there is no particular limitation. For example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a release liner formed from a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.), etc. can be used. The above-mentioned release treatment layer can be, for example, a layer formed by surface-treating the above-mentioned liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum disulfide-based agent.

[0180] The total thickness of the adhesive sheet (which may include an adhesive layer and a substrate layer, but does not include a release liner) disclosed herein is not particularly limited, and a range of about 5 to 1000 μm is appropriate. Considering the adhesion characteristics, etc., the total thickness of the adhesive sheet is preferably about 10 to 500 μm (for example, 15 to 300 μm, typically 20 to 200 μm). In addition, from the viewpoint of operability, etc., the total thickness of the adhesive sheet is more preferably 30 μm or more (for example, 50 μm or more, typically 70 μm or more).

[0181] <Use>

[0182] The use of the adhesive sheet disclosed herein is not particularly limited, and by virtue of the property of being highly capable of preventing residual glue when separated from the adherend after curing treatment, it can preferably be used for applications where it is adhered to an adherend and then peeled off. As such applications, a temporary fixing sheet and a protective sheet can be cited. In addition, for example, it can also preferably be used as a process material that is fixed to an adherend and then peeled off in the manufacturing process of electronic devices and electronic components.

[0183] As a suitable use of the adhesive sheet disclosed herein, semiconductor element manufacturing applications can be cited. For example, in semiconductor wafer processing (typically silicon wafer processing), it can preferably be used as a wafer fixing sheet (typically, a sheet for laser cutting) for fixing the wafer to a fixing plate (such as a hard substrate like a glass plate or an acrylic plate). In addition, the adhesive sheet disclosed herein can also preferably be used as a protective sheet for protecting the wafer (such as the circuit formation surface) in the above-mentioned wafer processing. For the above-mentioned sheet, the following can be required: an appropriate degree of adhesion such that it does not peel off from the adherend (typically, a semiconductor element or a hard substrate) during processing and transportation in the above-mentioned manufacturing; and the property of being well peeled off again from the adherend after the purpose is achieved. The adhesive sheet disclosed herein can preferably be used as a sheet that satisfies the performance required for the above-mentioned uses.

[0184] In addition, for example, the following uses can also be suitable uses of the adhesive sheet disclosed herein: fixing a plurality of miniaturized semiconductor chips (such as LED chips) on the adhesive surface of an adhesive sheet, performing processing such as sealing the semiconductor chips with resin on the adhesive sheet, and separating the semiconductor chips from the adhesive sheet after the processing is completed. The adhesive sheet disclosed herein can firmly fix the semiconductor chips during the above processing, and can be easily peeled off by light irradiation when peeling from the adherend (semiconductor chip). According to such an adhesive sheet, damage to the surface of the adherend during peeling can be prevented. The above adhesive sheet is suitable as an adhesive sheet used in FOWLP (Fan Out Wafer Level Package) and CSP (Chip Scale Package). By being used for the above uses, it can contribute to the high-volume and high-performance of various semiconductor products.

[0185] As described above, the adhesive sheet disclosed herein can preferably be applied to the manufacturing uses of semiconductor elements. Therefore, according to this specification, a method for manufacturing a semiconductor element using the adhesive sheet disclosed herein is provided. In a preferred embodiment, the manufacturing method includes: a step of fixing a semiconductor to the adhesive sheet (fixing step); a step of processing the semiconductor (processing step). The above processing step can be, for example, a back grinding step, a cutting step, a resin sealing step of a semiconductor chip, etc.

[0186] In addition, in the above manufacturing method, it can include a step of separating the adhesive sheet from the semiconductor (typically, a semiconductor chip) after the above processing step (removing step. Typically a peeling step). The above separation can be implemented by pasting a transfer tape on the surface of the semiconductor (the surface opposite to the adhesive surface of the adhesive sheet). In the above manufacturing method, typically, after the above processing step and before the above separation step, a curing treatment is performed on the adhesive sheet. The curing treatment can preferably be an active energy ray (such as UV) irradiation step. It should be noted that for other technical matters required for the manufacture of semiconductor elements, those skilled in the art can implement them based on the common technical knowledge in this field, so they are not specifically described here.

[0187] In addition, the adhesive sheet disclosed herein is suitable as a temporary fixing sheet used in the manufacture of substrates with a thin thickness, such as circuit boards (e.g., printed wiring boards (PCBs), flexible circuit boards (FPCs)), organic EL panels, color filters, electronic papers, flexible displays, etc. For example, in the chip fixing of a PCB, the adhesive sheet disclosed herein is used to bond and fix the adherend well, and a curing treatment is performed at a desired timing. Thereby, while highly preventing residual glue, the adhesive sheet can be separated from the adherend well. In addition, the adhesive sheet disclosed herein can preferably be used as a support tape for thin wafers. In this application, for example, in the printing of solder paste onto a thin wafer, the adhesive sheet disclosed herein is pasted onto the thin wafer as the adherend, and after being used as a support tape, a curing treatment is performed at an appropriate timing. Thereby, when separating from the adherend, residual glue can be highly prevented, and the adhesive sheet can be separated from the adherend well.

[0188] As described above, the adhesive sheet disclosed herein is preferably applied to the manufacturing use of substrates with a thin thickness, such as circuit boards (typically PCBs). Therefore, according to this specification, a manufacturing method of a substrate with a thin thickness (e.g., circuit board, organic EL panel, color filter, electronic paper, flexible display) using the above-mentioned adhesive sheet can be provided. In a preferred embodiment, the manufacturing method includes: a step of fixing a substrate with a thin thickness (typically, the back surface of the substrate) on the adhesive sheet (fixing step); a step of processing the substrate with a thin thickness.

[0189] Some embodiments of the processing step include a chip bonding step, a wire bonding step, and may further include a molding step and a package cutting step. The above-mentioned chip bonding typically refers to a step of disposing a plurality of chips on a substrate with a thin thickness, such as a PCB, and the above-mentioned wire bonding step refers to a step of bonding wires to the above-mentioned chips. The above-mentioned molding step can be, for example, a step of sealing the chips on the PCB with a resin such as epoxy resin. In addition, in the above-mentioned manufacturing method, after the above-mentioned processing step, a step of separating the adhesive sheet from the substrate with a thin thickness (removing step. Typically a peeling step) may be included. In the above-mentioned manufacturing method, typically, after the above-mentioned processing step and before the above-mentioned separating step, a curing treatment is performed on the adhesive sheet. The curing treatment can preferably be an active energy ray (e.g., UV) irradiation step. It should be noted that regarding other technical matters required for the manufacture of substrates with a thin thickness, such as PCBs, those skilled in the art can implement them based on the common technical knowledge in this field, so they are not specifically described herein.

[0190] Other methods involve manufacturing methods for a circuit board (typically, an FPC: Flexible Print Circuit), including: a step of attaching the adhesive sheet disclosed herein as a support tape to the back surface of a fixing tape to which a thin-layer wafer is fixed; and a step of processing the thin-layer wafer. The above manufacturing method may include a step of separating the adhesive sheet from the fixing tape (removing step. Typically, a peeling step) after the above processing step. In the above manufacturing method, typically, after the above processing step and before the above separating step, a curing treatment is performed on the adhesive sheet. The curing treatment is preferably an active energy ray (e.g., UV) irradiation step. It should be noted that regarding other technical matters required for manufacturing a thin substrate such as an FPC, those skilled in the art can implement them based on the common technical knowledge in this field, so no special description is provided here.

[0191] The matters disclosed in this specification include the following solutions.

[0192] 〔1〕An adhesive sheet which is an adhesive sheet having an adhesive layer cured by light irradiation,

[0193] In the above adhesive layer, the total content of an azo-based polymerization initiator and a peroxide-based polymerization initiator is 1.0 μg / g or less,

[0194] The initial peel strength measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees after being pasted on a silicon wafer is 2.0 N / 20 mm or more, and

[0195] The Young's modulus measured by a tensile test of the above adhesive layer after a curing treatment of irradiating ultraviolet rays with an accumulated light quantity of 300 mJ / cm 2 is 1.0 MPa or more.

[0196] 〔2〕The adhesive sheet as described in the above 〔1〕, wherein the above adhesive layer contains a polymer having a carbon-carbon double bond.

[0197] 〔3〕The adhesive sheet as described in the above 〔2〕, wherein the above polymer having a carbon-carbon double bond is crosslinked by a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule.

[0198] 〔4〕The adhesive sheet as described in the above 〔2〕 or 〔3〕, wherein an acrylic polymer is included as the above polymer having a carbon-carbon double bond.

[0199] 〔5〕The adhesive sheet as described in the above 〔4〕, wherein 50% by weight or more of all the monomer components constituting the above acrylic polymer is a chain alkyl (meth)acrylate having 5 or more carbon atoms in the alkyl group.

[0200] [[6]]The adhesive sheet according to any one of the above [1] to [5], wherein the adhesive layer contains carbon-carbon double bonds of 1.0×10 - 4 mol / 100g or more.

[0201] [[7]]The adhesive sheet according to any one of the above [1] to [6], wherein after being pasted on a silicon wafer and subjected to a curing treatment by irradiating ultraviolet rays with an accumulated light amount of 300 mJ / cm 2 the peel strength after the curing treatment measured under the conditions of a stretching speed of 300 mm / min and a peeling angle of 180 degrees is less than 1.0 N / 20 mm.

[0202] [[8]]The adhesive sheet according to any one of the above [1] to [7], wherein the gel fraction of the adhesive layer measured after being subjected to a curing treatment by irradiating ultraviolet rays with an accumulated light amount of 300 mJ / cm 2 is 70% or more.

[0203] [[9]]The adhesive sheet according to any one of the above [1] to [8], wherein the loss modulus G'' of the adhesive layer at 25°C is 1.0×10 3 Pa or more.

[0204] [

[10] ]The adhesive sheet according to any one of the above [1] to [9], wherein the content of the organic solvent in the adhesive layer is 1.0 μg / g or less.

[0205] In addition, the adhesive sheet disclosed in this specification includes a mode in which the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator is not limited for the adhesive layer of the adhesive sheet, and in this mode, the total content is not limited. For example, the following matters are also included in the matters disclosed in this specification.

[0206] [

[11] ]An adhesive sheet, which is an adhesive sheet having an adhesive layer that is cured by light irradiation,

[0207] the adhesive layer satisfies at least any one of the following conditions (A), (B), (C), and (D):

[0208] (A) The total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator is 1.0 μg / g or less;

[0209] (B) The content of the organic solvent is 1.0 μg / g or less;

[0210] (C) It is a photocured product of a photocurable adhesive composition or a modified product thereof;

[0211] (D) It contains a photopolymer or a polymer as a modified product thereof as a base polymer,

[0212] Moreover, the initial peel strength measured under the conditions of a stretching speed of 300 mm / min and a peel angle of 180 degrees after being pasted on a silicon wafer is 2.0 N / 20 mm or more, and

[0213] the Young's modulus measured by a tensile test of the adhesive layer after curing treatment by irradiating ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 is 1.0 MPa or more.

[0214] 〔12〕The adhesive sheet as described in the above 〔11〕, wherein the adhesive layer contains a polymer having a carbon-carbon double bond.

[0215] 〔13〕The adhesive sheet as described in the above 〔12〕, wherein the polymer having a carbon-carbon double bond is crosslinked by a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule.

[0216] 〔14〕The adhesive sheet as described in the above 〔12〕 or 〔13〕, wherein the polymer having a carbon-carbon double bond contains an acrylic polymer.

[0217] 〔15〕The adhesive sheet as described in the above 〔14〕, wherein 50% by weight or more of all monomer components constituting the acrylic polymer is a chain alkyl (meth) acrylate having 5 or more carbon atoms in the alkyl group.

[0218] 〔16〕The adhesive sheet as described in any one of the above 〔11〕 to 〔15〕, wherein the adhesive layer contains 1.0×10 -4 mol / 100 g or more of carbon-carbon double bonds.

[0219] 〔17〕The adhesive sheet as described in any one of the above 〔11〕 to 〔16〕, wherein after being pasted on a silicon wafer and cured by irradiating ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 the peel strength after curing treatment measured under the conditions of a stretching speed of 300 mm / min and a peel angle of 180 degrees is less than 1.0 N / 20 mm.

[0220] 〔18〕The adhesive sheet as described in any one of the above 〔11〕 to 〔17〕, wherein the gel fraction measured after curing treatment of the adhesive layer by irradiating ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 is 70% or more.

[0221] 〔19〕The adhesive sheet as described in any one of the above 〔11〕 to 〔18〕, wherein the loss modulus G'' of the adhesive layer at 25 °C is 1.0×10 3 Pa or more.

[0222] 〔20〕The adhesive sheet according to any one of 〔11〕to 〔19〕above, wherein the adhesive layer satisfies at least the above condition (B).

[0223] 〔21〕The adhesive sheet according to any one of 〔1〕to 〔20〕above, wherein the peel strength reduction rate calculated by the following formula is 50% or more,

[0224] Peel strength reduction rate [%] = (1 - B / A) × 100

[0225] (In the formula, A is the above initial peel strength (unit: [N / 20mm]), and B in the formula is the peel strength after the above curing treatment (unit: [N / 20mm])).

[0226] 〔22〕The adhesive sheet according to any one of 〔1〕to 〔21〕above, wherein the storage modulus increase rate calculated by the following formula is 300% or more,

[0227] Storage modulus increase rate [%] = (R / Q - 1) × 100

[0228] (In the formula, Q and R are the storage moduli G' (unit: [Pa]) at 25°C based on dynamic viscoelasticity measurement. Q is the storage modulus G' (initial elastic modulus G') measured using the measurement sample obtained from the above adhesive layer, and R is the storage modulus G' (elastic modulus G' after curing treatment) measured after irradiating the above measurement sample with ultraviolet rays for curing treatment).

[0229] 〔23〕The adhesive sheet according to any one of 〔1〕to 〔22〕above, wherein the storage modulus G' (initial elastic modulus G') of the adhesive layer measured using the measurement sample obtained from the adhesive layer is less than 1.0×10 6 Pa, and,

[0230] The storage modulus G' (modulus after curing treatment) measured after irradiating the above measurement sample with ultraviolet rays for curing treatment is 1.0×10 6 Pa or more.

[0231] 〔24〕The adhesive sheet according to any one of 〔1〕to 〔23〕above, wherein the thickness of the adhesive layer is 10 μm or more and less than 100 μm.

[0232] 〔25〕The adhesive sheet according to any one of 〔1〕to 〔24〕above, wherein the adhesive layer contains an acrylic polymer having a carbon-carbon double bond.

[0233]

[26] The adhesive sheet as described in

[25] above, wherein the acrylic polymer is crosslinked with a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule.

[0234]

[27] The adhesive sheet as described in

[26] or

[26] above, wherein the acrylic polymer is a photopolymer or a modified product thereof.

[0235]

[28] The adhesive sheet as described in any one of

[25] to

[27] above, wherein 50% by weight or more of all monomer components constituting the acrylic polymer is a chain alkyl (meth)acrylate having 5 or more carbon atoms in the alkyl group.

[0236]

[29] The adhesive sheet as described in any one of

[25] to

[27] above, wherein the adhesive layer contains the acrylic polymer as a base polymer.

[0237]

[30] A method for manufacturing an adhesive layer, which is a method for manufacturing an adhesive layer curable by light irradiation (photocurable adhesive layer), and the adhesive layer is produced by a method including the following steps:

[0238] Form a primary adhesive layer containing a primary polymer having a functional group A;

[0239] Prepare a post-coating liquid containing a compound having a carbon-carbon double bond and a functional group B and a photoinitiator, and coat the post-coating liquid on at least one surface of the primary adhesive layer;

[0240] Cause the compound having a carbon-carbon double bond and a functional group B and the photoinitiator contained in the post-coating liquid to penetrate into the primary adhesive layer; and,

[0241] Heat the primary adhesive layer into which the post-coating liquid has penetrated to cause the reaction between the functional group A and the functional group B to proceed.

[0242]

[31] The method for manufacturing an adhesive layer as described in

[30] above, which is applied to the manufacturing of the adhesive layer of the adhesive sheet as described in any one of [1] to

[29] above.

[0243]

[32] An adhesive sheet having an adhesive layer obtained by the method for manufacturing an adhesive layer as described in

[30] or

[31] above.

[0244] Examples

[0245] Hereinafter, some examples related to the present invention will be described, but the intention is not to limit the present invention to the embodiments shown in these examples. It should be noted that in the following description, "parts" and "%" are based on weight unless otherwise specified.

[0246] <Example 1>

[0247] (Preparation of prepolymer composition)

[0248] To a mixture of 100 parts of 2-ethylhexyl acrylate (2EHA) and 13 parts of 4-hydroxybutyl acrylate (4HBA) as monomer components, 0.05 part of a photoinitiator (trade name “Omnirad 184”, manufactured by IGM Resins B.V.; hereinafter referred to as “Omni.184”) was added. Then, ultraviolet rays were irradiated under a nitrogen atmosphere until the viscosity (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature 30°C) became about 20 Pa·s, to obtain a prepolymer composition in which a part of the above monomer components was polymerized.

[0249] (Preparation of ultraviolet curable adhesive composition)

[0250] To the above prepolymer composition, 0.05 part of a polyfunctional acrylate (hexanediol diacrylate (HDDA)) as a crosslinking agent, 0.05 part of a photoinitiator (Omni.184), and 1 part of dioctyltin dilaurate (trade name “Enbilizer OL-1”, manufactured by Tokyo Fine Chemical Co., Ltd.; hereinafter referred to as “OL-1”) were added and mixed to obtain an ultraviolet curable adhesive composition C1.

[0251] (Formation of primary adhesive layer)

[0252] The above adhesive composition C1 was coated on the surface of a release film (trade name “MRF#38”, manufactured by Mitsubishi Chemical Corporation) that had been subjected to a release treatment to form an adhesive composition layer. A release film (trade name “MRE#38”, manufactured by Mitsubishi Chemical Corporation) was covered on the surface of the above adhesive composition layer to block air, and ultraviolet rays were irradiated under the conditions of illuminance: 5 mW / cm 2 and cumulative light quantity: 2400 mJ / cm 2 to photocure the above adhesive composition layer and form a primary adhesive layer (unmodified adhesive layer) D1. This primary adhesive layer D1 contains a polymer of the above monomer components, i.e., an acrylic polymer crosslinked by the above polyfunctional acrylate, as a base polymer (primary polymer).

[0253] (Preparation and coating of post-coating liquid)

[0254] 11 parts of 2-methacryloyloxyethyl isocyanate (MOI) and 1 part of a photoinitiator (trade name “Omnirad 651”, manufactured by IGM Resins B.V.; hereinafter referred to as “Omni.651”) were mixed to prepare a post-coating liquid E1. The release film was peeled off from one surface of the above-mentioned primary adhesive layer D1, and the post-coating liquid E1 was applied onto the exposed surface using a wire wound rod coater manufactured by RD Specialties. After application, it was left standing for about 10 seconds to 10 minutes to allow the post-coating liquid E1 to penetrate into the primary adhesive layer D1.

[0255] (Introduction of carbon-carbon double bond)

[0256] Next, the primary adhesive layer D1 penetrated with the post-coating liquid E1 was heated in an oven at 130 °C for 3 minutes to cause an addition reaction of MOI, thereby introducing a carbon-carbon double bond into the side chain of the above-mentioned base polymer. Thus, a photocurable adhesive layer (substrate-free adhesive sheet) S1 containing a base polymer having a carbon-carbon double bond and a photoinitiator was obtained. The release-treated surface of a release film was bonded to the above-mentioned one surface of the obtained adhesive layer S1 for protection. It should be noted that the coating amount of the above-mentioned adhesive composition C1 and the coating amount of the above-mentioned post-coating liquid E1 were adjusted so that the content of each component in the above-mentioned adhesive layer S1 became as shown in the following table and the thickness of the adhesive layer S1 became 25 μm.

[0257] <Example 2>

[0258] 0.05 part of a photoinitiator (Omni.184) was added to 100 parts of 2-ethylhexyl acrylate as a monomer component, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which a part of the above-mentioned monomer component was polymerized.

[0259] 13 parts of 4-hydroxybutyl acrylate as a monomer component, 0.05 part of HDDA as a crosslinking agent, 0.05 part of a photoinitiator (Omni.184), and 1 part of OL-1 were added to the above-mentioned prepolymer composition and mixed to obtain an ultraviolet curable adhesive composition C2.

[0260] An adhesive layer (substrate-free adhesive sheet) S2 according to this example was produced in the same manner as in Example 1, except that the adhesive composition C2 was used instead of the adhesive composition C1.

[0261] <Example 3>

[0262] 0.05 part of a photoinitiator (Omni.184) was added to 100 parts of 2-ethylhexyl acrylate as a monomer component, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which a part of the above-mentioned monomer component was polymerized.

[0263] 12 parts of MOI as a monomer component, 0.05 parts of HDDA as a crosslinking agent, 0.05 parts of a photoinitiator (Omni.184), and 1 part of OL-1 were added to the above prepolymer composition and mixed to obtain an ultraviolet curable adhesive composition C3.

[0264] 11 parts of 4HBA and 1 part of a photoinitiator (Omni.651) were mixed to prepare a post-coating liquid E3. The adhesive composition C3 was used instead of the adhesive composition C1, and the post-coating liquid E3 was used instead of the post-coating liquid E1. Otherwise, the operation was the same as in Example 1 to produce the adhesive layer (substrate-free adhesive sheet) S3 related to this example.

[0265] <Example 4>

[0266] In a mixture of 100 parts of 2EHA as a monomer component and 13 parts of acrylic acid (AA), 0.05 parts of a photoinitiator (Omni.184) was incorporated, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which a part of the above monomer components was polymerized.

[0267] 0.05 parts of HDDA as a crosslinking agent, 0.05 parts of a photoinitiator (Omni.184), and 4 parts of tetrabutylammonium bromide (TBAB) were added to the above prepolymer composition and mixed to obtain an ultraviolet curable adhesive composition C4.

[0268] 11 parts of glycidyl methacrylate (GMA) and 1 part of a photoinitiator (Omni.651) were mixed to prepare a post-coating liquid E4. The adhesive composition C4 was used instead of the adhesive composition C1, and the post-coating liquid E4 was used instead of the post-coating liquid E1. Otherwise, the operation was the same as in Example 1 to produce the adhesive layer (substrate-free adhesive sheet) S4 related to this example.

[0269] <Examples 5 - 7>

[0270] Except that the composition of the post-coating liquid was changed as shown in Table 1, the operation was the same as in Example 2 to produce the adhesive layers (substrate-free adhesive sheets) S5 - S7 related to each example.

[0271] <Example 8>

[0272] In a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, etc., a monomer mixture was prepared at a mixing ratio of 85 parts of 2EHA and 15 parts of hydroxyethyl acrylate (HEA). For 100 parts of this monomer mixture, 0.2 parts of N,N'-azobisisobutyronitrile (AIBN) as an azo-based polymerization initiator and ethyl acetate as a polymerization solvent were added. Under a nitrogen gas stream, solution polymerization was carried out at about 60 °C to obtain an ethyl acetate solution of an acrylic polymer. 0.02 parts of OL-1 and 12 parts of MOI were added to this solution to carry out an addition reaction, and an acrylic polymer having a carbon-carbon double bond was prepared. To the ethyl acetate solution of the above acrylic polymer having a carbon-carbon double bond, 1 part (by solid content) of an isocyanate-based crosslinking agent (trade name "Takenate D-101E" manufactured by Mitsui Chemicals, Inc.) and 1 part of a photoinitiator (Omni.651) were added relative to 100 parts of the solid content of the acrylic polymer. In this way, a solvent-based adhesive composition C8 (solid content 50%) was prepared.

[0273] The above adhesive composition C8 was coated on the release-treated surface of a polyester film, dried at 120 °C for 3 minutes, and then cured at 50 °C for 24 hours, thereby producing the adhesive layer (substrate-free adhesive sheet) S8 related to this example.

[0274] <Example 9>

[0275] In the above solution polymerization, 0.2 parts of benzoyl peroxide (trade name "Nyper BMT-40SV" manufactured by NOF Corporation) as a peroxide-based polymerization initiator was used instead of 0.2 parts of AIBN. In other respects, the operation was the same as in Example 8, and the adhesive layer (substrate-free adhesive sheet) S9 related to this example was produced.

[0276] <Examples 10, 11>

[0277] The monomers of the types and amounts shown in Table 2 were further added to the prepolymer composition, and in other respects, the operation was the same as in Example 1, and the adhesive layers (substrate-free adhesive sheets) S10 and S11 related to each example were produced. It should be noted that in Table 2, "ACMO" represents N-acryloylmorpholine, and "NVP" represents N-vinyl-2-pyrrolidone.

[0278] <Example 12>

[0279] In a mixture of 100 parts of n-butyl acrylate (BA) as a monomer component and 22 parts of 4HBA, 0.05 parts of a photoinitiator (Omni.184) was mixed, and ultraviolet rays were irradiated in the same manner as in Example 1 to obtain a prepolymer composition in which a part of the above monomer components was polymerized.

[0280] To the above prepolymer composition, 0.05 part of HDDA as a crosslinking agent, 0.05 part of a photoinitiator (Omni.184), and 1 part of OL-1 were added and mixed to obtain an ultraviolet curable adhesive composition C12.

[0281] 18 parts of MOI was mixed with 1 part of a photoinitiator (Omni.651) to prepare a post-coating liquid E12. Except for using adhesive composition C12 instead of adhesive composition C1 and using post-coating liquid E12 instead of post-coating liquid E1, the same operations as in Example 1 were carried out to fabricate the adhesive layer (substrate-free adhesive sheet) S12 related to this example.

[0282] <Example 13>

[0283] Monomers of the types and amounts shown in Table 2 were further added to the prepolymer composition, and except for this, the same operations as in Example 12 were carried out to fabricate the adhesive layer (substrate-free adhesive sheet) S13 related to this example.

[0284] <Measurement and Evaluation>

[0285] [Amount of carbon-carbon double bonds]

[0286] The amount (unreacted double bond amount) of carbon-carbon double bonds contained in the adhesive layers (adhesive layers S1 to S13) obtained in each example was calculated by the following formula.

[0287] Carbon-carbon double bond content [mol / 100g] = ((number of parts of the carbon-carbon double bond-containing compound contained in the post-coating liquid [parts] × number of carbon-carbon double bonds contained in one molecule of this carbon-carbon double bond-containing compound) / total number of parts of the adhesive formulation [parts]) × 100 [g] / molecular weight of the carbon-carbon double bond-containing compound [g / mol]

[0288] [Amount of photoinitiator]

[0289] The amount (unreacted photoinitiator amount) of the photoinitiator contained in the adhesive layer obtained in each example was calculated by the following formula.

[0290] Photoinitiator amount [mol / 100g] = (number of parts of the photoinitiator contained in the post-coating liquid [parts] / total number of parts of the adhesive formulation [parts]) × 100 [g] / molecular weight of the photoinitiator [g / mol]

[0291] [Amount of azo-based and peroxide-based polymerization initiators]

[0292] Collect approximately 3 mg of the sample from the adhesive layer obtained from each example, and perform outgassing analysis at 180 °C for 1 hour using gas chromatography-mass spectrometry (GC / MS) method, and then conduct the measurement. The specific measurement conditions are as follows. Based on the measurement results, calculate the total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator in the above-mentioned adhesive layer (including the amounts contained in the form of decomposition products and residues).

[0293] (Analysis device)

[0294] Heating device: GERSTEL, TDU2

[0295] GC / MS: Agilent Technologies, 8890 / 5977B

[0296] (Measurement conditions)

[0297] TDU conditions (sample): 30 °C (1 min) → 720 °C / min → 180 °C (60 min)

[0298] TDU conditions (standard): 30 °C (1 min) → 720 °C / min → 300 °C (5 min)

[0299] CIS conditions: -150 °C (2.5 min) → 12 °C / sec → 300 °C (10 min)

[0300] GC / MS conditions

[0301] Column: HP-Ultra1( df = 0.33 μm)

[0302] Column temperature: 40 °C (5 min) → 10 °C / min → 100 °C → 20 °C / min → 300 °C (9 min)

[0303] Column pressure: Constant flow mode (113 kPa, Vac)

[0304] Column flow rate: 1 mL / min (He)

[0305] Injection method: CIS, Split (20:1)

[0306] Detector: MS

[0307] Ion source temperature: 230 °C

[0308] Ionization method: EI (70 eV)

[0309] Scan range: m / z10~800

[0310] [Content of organic solvent]

[0311] Collect about 3 mg of samples from the adhesive layers obtained in each example, and perform outgassing analysis at 180 °C for 1 hour using gas chromatography - mass spectrometry (GC / MS) to measure the content of organic solvents in the adhesive layer. The specific measurement conditions are as described above.

[0312] [Dynamic viscoelasticity measurement]

[0313] Stack the adhesive layers (adhesive sheets without substrates) obtained in each example to a thickness of about 2 mm, and use the products blanked into discs with a diameter of 7.9 mm as the measurement samples. Use the "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific Company, and perform dynamic viscoelasticity measurement under the following conditions to obtain the initial elastic modulus G' and loss modulus G" at 25 °C.

[0314] (Measurement conditions)

[0315] Deformation mode: Torsion

[0316] Measurement frequency: 1 Hz

[0317] Heating rate: 5 °C / minute

[0318] Shape: Parallel plates

[0319] Then, perform a curing treatment on the above - mentioned measurement samples with ultraviolet light having an irradiation intensity of 300 mW / cm² and an accumulated light quantity of 3000 mJ / cm². 2 Use the treated samples and perform dynamic viscoelasticity measurement using the above - mentioned method to obtain the elastic modulus G' after curing treatment at 25 °C.

[0320] Based on the obtained values of the initial elastic modulus G' [Pa] and the elastic modulus G' [Pa] after curing treatment, calculate the increase rate of the storage modulus G' using the following formula.

[0321] Increase rate of storage modulus G' [%]=(R / Q - 1)×100

[0322] (In the formula, Q is the initial storage modulus G', and R is the elastic modulus G' after curing treatment.)

[0323] [Young's modulus (Young's modulus after curing treatment)]

[0324] For the adhesive layer (substrate-free adhesive sheet) obtained from each example, ultraviolet curing treatment was performed under the following conditions with the adhesive layer sandwiched between two release films. Subsequently, the adhesive layer together with the release films was cut into a size of 80 mm in width and 30 mm in length. The width of 80 mm was set according to the thickness of the adhesive layer such that the cross-sectional area of the adhesive layer in the cross-section along the width direction was approximately 2 mm 2 Then, one of the release films was removed from the adhesive layer, and on the other release film, the adhesive layer was wound around its length axis without allowing air bubbles to enter, to produce a rod-shaped specimen with a length of 30 mm.

[0325] The rod-shaped specimen was set on a tensile testing machine (manufactured by ORIENTEC Co., Ltd., trade name “RTC-1150A”), and the SS curve was measured under the conditions of a measurement temperature of 23°C, a distance between chucks of 10 mm, and a tensile speed of 300 mm / min. The initial elastic modulus was obtained from the rising part of the SS curve, and this was set as the tensile elastic modulus (Young's modulus after curing treatment) of the adhesive layer after the curing treatment.

[0326] (UV irradiation conditions)

[0327] UV irradiator: manufactured by Nitto Seiki Co., Ltd., trade name “NEL SYSTEM UM810”, high-pressure mercury lamp light source (characteristic wavelength: 365 nm)

[0328] Irradiation dose: illuminance 60 mW / cm 2 , cumulative light quantity 300 mJ / cm 2

[0329] [Gel fraction]

[0330] For the adhesive layer (substrate-free adhesive sheet) obtained from each example, ultraviolet curing treatment was performed under the following conditions with the adhesive layer sandwiched between two release films. Subsequently, approximately 0.5 g of a measurement sample was collected from the adhesive layer and accurately weighed (weight W1). The measurement sample was wrapped in a porous PTFE (polytetrafluoroethylene) sheet, immersed in ethyl acetate at room temperature for one week, then dried, and the weight of the ethyl acetate-insoluble component was measured (weight W2). The above weights W1 and W2 were substituted into the following formula:

[0331] Gel fraction [%] = W2 / W1 × 100;

[0332] The gel fraction of the adhesive layer after the curing treatment was calculated. As the above porous PTFE sheet, “NITOFLON NTF1122” manufactured by Nitto Denko Corporation was used.

[0333] (UV irradiation conditions)

[0334] UV irradiator: manufactured by Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810", high-pressure mercury lamp light source (characteristic wavelength 365 nm)

[0335] Exposure dose: illuminance 60 mW / cm 2 , cumulative light quantity 300 mJ / cm 2

[0336] [180-degree peel strength]

[0337] One of the release liners was peeled off from the adhesive layer (substrate-free adhesive sheet) obtained from each example. After laminating a transparent PET film with a thickness of 50 μm as an inner liner, it was cut into strips with a width of 20 mm and a length of 80 mm to prepare test pieces. In an environment of 23°C and 50% RH, the other release liner was peeled off from the above test pieces, and it was adhered to the mirror surface of a silicon wafer (manufactured by Shin-Etsu Chemical Co., Ltd., 6-inch N<100>-100) as the adherend with a hand roller. After autoclave treatment (50°C, 5 atm, 15 minutes), in an environment of 23°C and 50% RH, using a tensile testing machine (manufactured by Minebea Co., Ltd., universal tensile-compression testing machine, device name "Tensile-Compression Testing Machine, TCM-1kNB"), the above test pieces were peeled off from the above silicon wafer under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees, and the peel strength at this time was measured. The measurement was carried out 3 times, and the arithmetic mean of them was used as the value of the initial peel strength.

[0338] In addition, after the above autoclave treatment, ultraviolet (UV) curing treatment was carried out from the PET film side under the following conditions, and then the above test pieces were peeled off from the above silicon wafer. Except for this, the operation was the same as that for the measurement of the above initial peel strength, and the peel strength after the curing treatment was measured.

[0339] (UV irradiation conditions)

[0340] UV irradiator: manufactured by Nitto Seiki Co., Ltd., product name "NEL SYSTEM UM810", high-pressure mercury lamp light source (characteristic wavelength 365 nm)

[0341] Exposure dose: illuminance 60 mW / cm 2 , cumulative light quantity 300 mJ / cm 2

[0342] Based on the values of the obtained initial peel strength [N / 20 mm] and the peel strength after the curing treatment [N / 20 mm], the peel force reduction rate (peel strength reduction rate) was calculated by the following formula.

[0343] Peel force reduction rate [%] = (1 - B / A) × 100

[0344] (In the formula, A is the initial peel strength and B is the peel strength after curing treatment.)

[0345] The results obtained are shown together with the outlines of the adhesive layers involved in each example in Tables 1 and 2. Example 1 in Table 2 shows Example 1 in Table 1 again.

[0346] [Table 1]

[0347]

[0348] [Table 2]

[0349]

[0350] As shown in Tables 1 and 2, the adhesive layers involved in Examples 1 to 6 and 10 to 13 satisfy an initial peel strength of 2.0 N / 20 mm or more and a Young's modulus after curing treatment of 1.0 MPa or more, and have both good initial peel strength and ease of peeling after curing treatment. In addition, for the adherend (silicon wafer) used in the measurement of the peel strength after curing treatment, the presence or absence of residual adhesive on the surface in the range where the adhesive sheet (test piece) was pasted was observed. As a result, no residual adhesive was observed in Examples 1 to 6 and 10 to 13. In this way, the adhesive layers of Examples 1 to 6 and 10 to 13 are adhesive layers having good initial peel strength and peelability, and can use a solvent-free adhesive composition obtained by a method that does not perform solution polymerization using an azo-based or peroxide-based polymerization initiator, and can be manufactured by a method that does not use an organic solvent also in the process of obtaining the adhesive layers involved in each example from the adhesive composition. Therefore, it is ideal from the viewpoint of environmental hygiene. It should be noted that in Examples 12 and 13, slight blurring was observed on the surface of the adherend used in the measurement of the peel strength after curing treatment. In contrast, in Examples 1 to 6, 10, and 11, no appearance change was observed on the surface of the above adherend, and the low contamination property was more excellent.

[0351] On the other hand, although the adhesive layer of Example 7 has a high initial peel strength, its Young's modulus is low after the curing treatment, and residual adhesive is generated on the surface of the adherend used in the measurement of the peel strength after the curing treatment. It should be noted that the adhesive layers of Examples 8 and 9 shown in Table 1 are obtained by coating and drying a solvent-based adhesive composition containing an acrylic polymer obtained by introducing a carbon-carbon double bond into an acrylic polymer obtained by solution polymerization (in Example 8, an azo-based polymerization initiator was used for this solution polymerization, and in Example 9, a peroxide-based polymerization initiator was used for this solution polymerization) through a reaction in solution (acrylic polymer having a carbon-carbon double bond) as a base polymer. For the adhesive layers of Examples 8 and 9, as a result of reflecting such a manufacturing process, the amounts of the azo-based and peroxide-based polymerization initiators are as high as 13 to 96 μg / 100 g, and it can be seen that the amount of residual solvent (organic solvent content) is also significantly larger.

[0352] The specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the claims. The technologies described in the claims include examples obtained by various deformations and changes of the specific examples illustrated above.

[0353] Explanation of reference numerals

[0354] 1, 2 Adhesive sheets

[0355] 10 Adhesive layer

[0356] 10A One surface (adhesive surface)

[0357] 10B Another surface

[0358] 20 Substrate

[0359] 20A First surface

[0360] 20B Second surface (back surface)

[0361] 30, 31, 32 Release liners

[0362] 50 Adhesive sheet with release liner

Claims

1. An adhesive sheet, which is an adhesive sheet having an adhesive layer cured by light irradiation, in the adhesive layer, the total content of an azo-based polymerization initiator and a peroxide-based polymerization initiator is 1.0 μg / g or less, the initial peel strength measured under the conditions of a peel rate of 300 mm / min and a peel angle of 180 degrees after being pasted on a silicon wafer is 2.0 N / 20 mm or more, and The Young's modulus of the adhesive layer measured by a tensile test after curing treatment with ultraviolet rays having an accumulated light amount of 300 mJ / cm 2 is 1.0 MPa or more.

2. The adhesive sheet according to claim 1, wherein, the adhesive layer contains a polymer having a carbon-carbon double bond.

3. The adhesive sheet according to claim 2, wherein, The polymer having a carbon-carbon double bond is crosslinked with a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule.

4. The adhesive sheet according to claim 2, wherein, The polymer having a carbon-carbon double bond includes an acrylic polymer.

5. The adhesive sheet according to claim 4, wherein, Among all the monomer components constituting the acrylic polymer, 50% by weight or more is a chain alkyl (meth)acrylate having 5 or more carbon atoms in the alkyl group.

6. The adhesive sheet according to any one of claims 1 to 5, wherein The adhesive layer contains carbon-carbon double bonds in an amount of 1.0×10 -4 mol / 100 g or more.

7. The adhesive sheet according to any one of claims 1 to 5, wherein After being pasted on a silicon wafer and irradiated with ultraviolet rays having an accumulated light amount of 300 mJ / cm 2 after the curing treatment, the post-curing peel strength measured under the conditions of a stretching speed of 300 mm / min and a peel angle of 180 degrees is less than 1.0 N / 20 mm.

8. The adhesive sheet according to any one of claims 1 to 5, wherein, The gel fraction of the adhesive layer measured after curing treatment with ultraviolet rays having an accumulated light amount of 300 mJ / cm 2 is 70% or more.

9. The adhesive sheet according to any one of claims 1 to 5, wherein The loss modulus G” of the adhesive layer at 25 °C is 1.0×10 3 Pa or more.

10. The adhesive sheet according to any one of claims 1 to 5, wherein, The content of the organic solvent in the adhesive layer is 1.0 μg / g or less.

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