Adhesive sheet

Abstract

The present invention provides an adhesive sheet having a photocurable adhesive layer, wherein the photocurable adhesive layer exhibits photocurability suitable for a reduction in peel strength due to light irradiation and is based on a polymer that does not utilize solution polymerization. [Solution] Provided is an adhesive sheet having an adhesive layer that is 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 a storage modulus increase rate of 300% or more as determined by the following formula. The storage modulus increase rate [%] = (R / Q-1) * 100 (wherein Q and R are storage modulus G '([Pa]) at 25 DEG C as determined by dynamic viscoelasticity measurement, Q is initial storage modulus G' measured using a measurement sample obtained from the adhesive layer, and R is post-curing storage modulus G 'measured after curing by irradiating the measurement sample with ultraviolet light).

Description

Technical Field

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

[0002] This application claims priority based on Japanese patent application No. 2022-185189 filed on November 18, 2022, the entire contents of which are incorporated herein by reference. Background Art

[0003] Generally, adhesives (also called pressure-sensitive adhesives. The same applies below.) are in a soft solid (viscoelastic) state in a temperature range near room temperature, and have the property of being easily bonded to an adherend by pressure. Taking advantage of such properties, adhesives are widely used in various fields in the form of adhesive sheets having an adhesive layer, for example. Among adhesive sheets, there are adhesive sheets having an adhesive layer (photocurable adhesive layer) that is cured by light irradiation. As a prior art document related to this technology, Patent Document 1 can be cited.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-059179 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Among adhesives, there are adhesives that are temporarily bonded to an adherend for use and are peeled off from the adherend after the purpose of bonding is completed. For adhesives that are used in such a way of being peeled off from an adherend, it is required to have good adhesion during bonding with the adherend and to be able to be easily peeled off from the adherend after the purpose of bonding is completed. As an adhesive with such performance, an adhesive that is bonded with a peeling force of more than a certain amount when bonding and fixing, and can reduce the peeling force when peeling is removed can be used. For example, it is known that there is an adhesive sheet with an ultraviolet curable adhesive layer that is cured by ultraviolet irradiation and thus reduces the peeling force.

[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 generally 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 a modified product thereof obtained by solution polymerization using an azo-based or peroxide-based polymerization initiator as a 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 generally 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 having a photocurable adhesive layer that exhibits photocurability suitable for a decrease in peel force (easy peelability) caused by light irradiation and is 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 disadvantages 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 of the surface of the adherend to which the adhesive sheet is adhered, contamination, and generation of outgassing). 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 storage modulus increase rate of the above adhesive sheet calculated by the following formula is 300% or more.

[0013] Storage modulus increase rate [%] = (R / Q - 1) × 100

[0014] Among them, Q and R in the formula are the storage moduli G’ (unit: [Pa]) at 25°C measured based on dynamic viscoelasticity. Q is the initial storage modulus G’ measured using the measurement sample obtained from the above adhesive layer, and R is the storage modulus G’ after curing treatment measured after subjecting the above measurement sample to ultraviolet (UV) irradiation curing treatment. Hereinafter, the initial storage modulus G’ may sometimes be abbreviated as “initial elastic modulus G’”, and the storage modulus G’ after curing treatment may be abbreviated as “elastic modulus G’ after curing treatment”.

[0015] Since the above adhesive layer does not rely on solution polymerization using azo-based or peroxide-based polymerization initiators, when using an adhesive sheet having such an adhesive layer, the amount of organic solvents used can be reduced. In addition, for an adhesive sheet having such an adhesive layer with a high storage modulus increase rate, there is a tendency for the peel strength to be significantly reduced easily by UV irradiation. Therefore, by performing light irradiation at a desired timing after pasting on an adherend, it can be an adhesive sheet that can be easily peeled off.

[0016] In some embodiments, the above adhesive layer contains a polymer having a carbon-carbon double bond. The adhesive layer of this composition can effectively increase the storage modulus by causing the carbon-carbon double bonds of the above polymer to react by using light irradiation, so it is easy to obtain the above storage modulus increase rate.

[0017] In some embodiments, the above polymer having a carbon-carbon double bond is preferably crosslinked with a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule. From the viewpoint of imparting appropriate cohesiveness to the photocurable adhesive layer containing this polymer, it is advantageous for the above polymer to have a crosslinked structure formed by a polyfunctional monomer.

[0018] In some embodiments, the above adhesive layer contains 1.0×10 -4 mol / 100 g or more of carbon-carbon double bonds. When the amount of carbon-carbon double bonds contained in the adhesive layer increases, there is a tendency for the characteristics and physical properties caused by light irradiation to be easily obtained. Therefore, by using an adhesive layer containing carbon-carbon double bonds in the above content, the peel strength after curing treatment can be reduced more effectively.

[0019] In some embodiments, the adhesive layer contains 1.0×10 -4 mol / 100 g or more of a photoinitiator. For an adhesive layer containing a photoinitiator in the above content, the photocurability of the adhesive layer is good, and it has a tendency to easily satisfy the above storage modulus increase rate.

[0020] In some embodiments, the above initial elastic modulus G’ is preferably less than 1.0×10 6Pa. The initial elastic modulus G' of the adhesive layer is low, which has a tendency to easily obtain a large change in elastic modulus by light irradiation, so 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.

[0021] In some embodiments, the gel fraction of the above-mentioned adhesive layer measured after curing treatment with ultraviolet rays having an accumulated light amount of 300 mJ / cm 2 is preferably 70% or more. By using the adhesive layer having a high gel fraction as described above, there is a tendency that the effect of easy peeling based on light irradiation can be suitably exhibited.

[0022] In the above-mentioned 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, which is ideal from the viewpoint of environmental hygiene. From the viewpoints of suppressing foaming caused by the volatilization of the organic solvent and low pollution, it is also advantageous that the content of the organic solvent in the adhesive layer is small.

[0023] 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

[0024] Figure 1 is a cross-sectional view schematically showing the configuration of the adhesive sheet according to an embodiment.

[0025] Figure 2 is a cross-sectional view schematically showing the configuration of the adhesive sheet according to another embodiment. Detailed Description of the Embodiments

[0026] Hereinafter, suitable embodiments of the present invention will be described. It should be noted that for 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.

[0027] It should be noted that in the following drawings, sometimes the same reference numerals are used to denote components and parts that perform the same function for description, and sometimes 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.

[0028] ​​In this specification, the "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight (preferably more than 70% by weight, such as 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, the "(meth)acryloyl group" comprehensively refers to the acryloyl group and the methacryloyl group. Similarly, respectively, "(meth)acrylate" comprehensively refers to acrylate and methacrylate, and "(meth)acrylic acid-" comprehensively refers to acrylic acid- and methacrylic acid-.

[0029] In this specification, the "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 group, vinyl group, allyl group, etc. Hereinafter, a compound having 1 ethylenically unsaturated group may be referred to as a "monofunctional monomer", and a compound having 2 or more ethylenically unsaturated groups may be referred to as a "polyfunctional monomer". In addition, a compound having X ethylenically unsaturated groups in the polyfunctional monomer may be expressed as an "X-functional monomer".

[0030] <Constitution example of the adhesive sheet>

[0031] The adhesive sheet disclosed herein has an adhesive layer. This adhesive layer typically constitutes at least one surface of the adhesive sheet. The adhesive sheet may be a substrate-bearing adhesive sheet in which the adhesive layer is provided on one or both sides of a substrate (support), or may be a substrate-free adhesive sheet such as a manner 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 manner. 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. Or, it may be an adhesive sheet in a manner further processed into various shapes.

[0032] One constitution example of the adhesive sheet having an adhesive layer disclosed herein is shown in Figure 1 . This adhesive sheet 1 is a substrate-free double-sided adhesive sheet formed of an adhesive layer 10. For example, as shown in Figure 1As shown, the adhesive sheet 1 before use (before being adhered to the adherend) may be in the form of an adhesive sheet 50 with release liners 31 and 32 that protect both surfaces 10A and 10B of the adhesive layer 10, where at least the adhesive layer side forms a peelable surface (peel surface). Alternatively, it may be in the following form: the back surface of the release liner 31 (the surface on the side opposite to the adhesive side) forms a peel 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 and 10B. The adhesive layer 10 may be a single layer or a laminated structure of two or more layers.

[0033] The adhesive layer 10 is configured to be cured by light irradiation. In some preferred embodiments, the adhesive layer 10 contains a polymer having carbon-carbon double bonds and a photoinitiator. The amount of the photoinitiator contained in the adhesive layer 10 is preferably 1.0×10 - 4 mol / 100g or more. With 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 / 100g or more.

[0034] 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 carbon-carbon double bonds and a photoinitiator and having a limited content of the above organic solvent can be preferably formed, for example, by 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 an active energy ray and not containing carbon-carbon double bonds), and then, by a method of not using an organic solvent or using only a small amount (within the limit that can achieve the above content of the organic solvent) of an organic solvent, adding a photoinitiator to the above primary adhesive layer and introducing carbon-carbon double bonds into the above primary polymer. In this forming method, since the pre-formed primary adhesive layer newly contains a photoinitiator and carbon-carbon double bonds, an active energy ray curable adhesive composition can be preferably used as the adhesive composition for forming the above primary adhesive layer. As the above active energy ray curable adhesive composition, a composition that does not contain an organic solvent or contains only a small amount (within the limit that can achieve the above content of the organic solvent) of an organic solvent is used.

[0035] 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 preferably be realized in the following constitution: as a polymer having a carbon-carbon double bond, it contains a polymer obtained without solution polymerization using, for example, an azo-based or peroxide-based polymerization initiator (for example, a primary polymer obtained by active energy ray polymerization and having no carbon-carbon double bond, and a polymer obtained by introducing a carbon-carbon double bond into the primary polymer).

[0036] Another constitution example of the adhesive sheet having an adhesive layer disclosed herein is illustrated in Figure 2 . The adhesive sheet 2 is configured as a single-sided adhesive sheet (a single-sided adhesive sheet with a substrate), and the single-sided adhesive sheet includes: a photocurable adhesive layer 10 whose one surface 10A becomes a paste 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. For example, as Figure 2 shown, before use, the adhesive sheet 1 can be in the form of an adhesive sheet 50 with a release liner in which the adhesive surface 10A is protected by a release liner 30 whose at least the adhesive layer side is a peelable surface (peel surface). Or, 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) becomes 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.

[0037] In addition, the adhesive sheet disclosed herein can be in the form of a double-sided adhesive sheet with a substrate in which a first adhesive layer is laminated on one surface of a sheet-like 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.

[0038] <Properties of the Adhesive Sheet>

[0039] The adhesive sheet disclosed herein is characterized in that the storage modulus increase rate calculated by the following formula is 300% or more (i.e., 3.0×10 2 % or more).

[0040] Storage modulus increase rate [%] = (R / Q - 1) × 100

[0041] Here, Q and R in the above formula represent the storage modulus G’ at 25°C (unit: [Pa]) based on dynamic viscoelasticity measurement. Q is the initial elastic modulus G’ measured using the measurement sample obtained from the above adhesive layer, and R is the elastic modulus G’ after curing treatment measured after subjecting the above measurement sample to ultraviolet irradiation curing treatment. An adhesive sheet satisfying the above storage modulus increase rate tends to have a large reduction in peel force easily by UV irradiation. Therefore, an adhesive sheet can be obtained that exhibits good adhesiveness during the period of use (during the use period) when bonded to an adherend and can be easily peeled from the adherend after the bonding purpose is completed. Specifically, the above initial elastic modulus G’ and the elastic modulus G’ after curing treatment are measured by the methods described in the following examples.

[0042] In some embodiments, the storage modulus increase rate is preferably 5.0×10 2 % or more, more preferably 7.0×10 2 % or more, can be 1.0×10 3 % or more, can be 1.5×10 3 % or more, can be 2.0×10 3 % or more, can be 2.5×10 3 % or more, 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 before curing treatment, in some embodiments, the above storage modulus increase rate can be, for example, 1.0×10 5 % or less, can also be 1.0×10 4 % or less, can also be 5.0×10 3 % or less.

[0043] The initial elastic modulus G’ of the adhesive sheet disclosed herein is set to satisfy any of the above storage modulus increase rates, and there is no particular limitation other than this. In some embodiments, the initial elastic modulus G’ can be, for example, less than 5.0×10 6 Pa, less than 3.0×10 6 Pa is appropriate, less than 1.0×10 6 Pa is advantageous, can be less than 5.0×10 5 Pa, can be less than 1.0×10 5 Pa, can be less than 8.0×10 4 Pa, can be less than 6.0×10 4 Pa, can be less than 5.0×10 4Pa. From the viewpoint of easily obtaining a large change in the elastic modulus by light irradiation, it is advantageous that the initial elastic modulus G' of the adhesive layer is low, and it 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 appropriately 5.0×10 3 Pa or more, advantageously 8.0×10 3 Pa or more, preferably 1.0×10 4 Pa or more, can be 3.0×10 4 Pa or more, and can also be 5.0×10 4 Pa or more.

[0044] The elastic modulus G' after the curing treatment of the adhesive sheet disclosed herein is set to be able to satisfy any one of the above-mentioned storage modulus increase rates, and there is no particular limitation other than this. In some embodiments, the elastic modulus G' after the curing treatment can be, for example, 1.0×10 4 Pa or more or greater than 1.0×10 4 Pa, can be 3.0×10 4 Pa or more or greater than 3.0×10 4 Pa, can be 5.0×10 4 Pa or more or greater than 5.0×10 4 Pa, 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 appropriately 2.0×10 5 Pa or more, preferably 4.0×10 5 Pa or more, more preferably 6.0×10 5 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' after the curing treatment is high. The upper limit of the elastic modulus G' after the curing treatment is not particularly limited, and for example, it can be 1.0×10 8 Pa or less, can be 1.0×10 7 Pa or less, can be 5.0×10 6 Pa or less or 3.0×10 6Below Pa.

[0045] For the adhesive sheet disclosed herein, based on JIS Z 0237:2000, in an environment of 23°C and 50% RH, with a silicon wafer as the adherend, the initial peel strength (initial adhesive force) measured under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min is not particularly limited and can be adjusted to an appropriate range according to the purpose and use. The above-mentioned initial adhesive force can be, for example, 0.5 N / 20 mm or more, and can be 0.8 N / 20 mm or more. An adhesive sheet showing an initial adhesive force of a specified value or more can adhere well to the adherend. From such a viewpoint, in some embodiments, the above-mentioned initial adhesive force is preferably 1.0 N / 20 mm or more (for example, greater than 1.0 N / 20 mm), more preferably 1.5 N / 20 mm or more, further preferably 2.0 N / 20 mm or more, can be 2.5 N / 20 mm or more, can be 3.0 N / 20 mm or more, can be 3.5 N / 20 mm or more, 4.0 N / 20 mm or more, or 4.5 N / 20 mm or more. The upper limit of the above-mentioned initial adhesive force is not particularly limited. For example, it can be less than 30 N / 20 mm. From the viewpoint of easily obtaining the balance with other properties, etc., it can be 25 N / 20 mm or less, can be 20 N / 20 mm or less, can be 15 N / 20 mm or less. It should be noted that the above-mentioned initial adhesive force is the peel strength measured before the curing treatment. Specifically, the initial adhesive force is measured by the method described in the examples below.

[0046] Regarding the adhesive sheet disclosed herein, the peel strength after the curing treatment (adhesive force after the curing treatment) measured after pasting the adhesive layer on a silicon wafer and performing the curing treatment based on light irradiation is preferably 2.0 N / 20 mm or less, more preferably 1.0 N / 20 mm or less. In this way, an adhesive sheet with a limited peel force after the curing treatment can exhibit good peelability (easy peelability) in the usage mode of peeling from the adherend after the curing treatment. From this viewpoint, in some embodiments, the above-mentioned adhesive force after the curing treatment 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, can be 0.3 N / 20 mm or less, can be 0.2 N / 20 mm or less, can be 0.1 N / 20 mm or less, can 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 the curing treatment is not particularly limited. For example, it can be 0 N / 20 mm, and can be greater than 0 N / 20 mm (for example, 0.005 N / 20 mm or more). Specifically, the adhesive force after the curing treatment is measured by the method described in the examples below.

[0047] In the adhesive sheet disclosed herein, the rate of reduction in peel strength calculated by the following formula can be, for example, 10% or more, 20% or more, or 30% or more.

[0048] Rate of reduction in peel strength [%] = (1 - B / A) × 100

[0049] Here, A in the formula is the above-mentioned initial peel strength [N / 20 mm], and B in the formula is the peel strength after the above-mentioned curing treatment [N / 20 mm]. In some embodiments, it is appropriate for the above-mentioned rate of reduction in peel strength to be 50% or more. In this way, for an adhesive sheet whose peel force is significantly reduced by UV irradiation, after being adhered to an 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 an adherend and being able to be easily peeled from the adherend after the adhesion purpose is completed.

[0050] In some embodiments, the above-mentioned rate of reduction in peel strength is preferably 65% or more, more preferably 75% or more, further preferably 85% or more, can also be 90% or more, can also be 94% or more, can also be 96% or more, can also be 97% or more, or 98% or more. By using an adhesive sheet with a higher rate of reduction in peel strength, good adhesiveness during the use period and easy peelability after light irradiation can be achieved at a higher level. The above-mentioned rate of reduction in peel strength is typically 100% or less, can be less than 100%, for example, can 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 being unexpectedly separated from the adherend, it is advantageous for the rate of reduction in peel strength to be less than 100%.

[0051] 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. In this way, an 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 an 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.

[0052] 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 1.0×10 6 Pa or less is appropriate, less than 5.0×10 5 Pa (for example, less than 3.0×10 5 Pa) is advantageous, preferably less than 1.5×10 5 Pa (for example, less than 1.0×10 5 Pa), may be less than 5.0×10 4 Pa, may be less than 1.0×10 4 Pa, may be less than 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 contact with the adherend, it is advantageous to be 5.0×10 2 Pa or more, 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 subjected to an external force (for example, an external force in the shear direction). 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.

[0053] Regarding the adhesive layer of the adhesive sheet disclosed herein, the Young's modulus after the curing treatment based on light irradiation (Young's modulus after curing treatment), which is measured by the method described in the examples below, is not particularly limited. For example, it can be greater than 0.05 MPa. In some embodiments, for example, from the perspective of low contamination in the usage mode where the adhesive sheet adhered to the adherend is peeled off after applying the curing treatment, the Young's modulus after the curing treatment is preferably greater than 0.1 MPa, advantageously greater than 0.5 MPa, and preferably 1.0 MPa or more. When the Young's modulus after the curing treatment of the adhesive layer increases, there is a tendency to easily obtain good peelability from the adherend after light irradiation. For example, when peeling from the adherend, it is easy to prevent or suppress the occurrence of the phenomenon (adhesive residue) where a part of the adhesive layer tears and remains on the adherend. From the perspective of more easily exerting this effect, in some embodiments, the Young's modulus after the curing treatment can be, for example, 1.2 MPa or more, 1.5 MPa or more, 2.0 MPa or more, 2.5 MPa or more, 3.5 MPa or more, 4.0 MPa or more, or 4.5 MPa or more. In addition, the Young's modulus after the curing treatment can be, for example, 10 MPa or less. From the perspective of easily achieving good flexibility before the curing treatment, it is preferably 7.0 MPa or less, and more preferably 5.0 MPa or less.

[0054] Regarding the adhesive layer of the adhesive sheet disclosed herein, the gel fraction after the curing treatment based on light irradiation, which is measured by the method described in the examples below, is not particularly limited. For example, it can be 50% or more, 60% or more, or 70% or more. From the perspective of easily and appropriately exerting the effect of easy peelability based on light irradiation, in some embodiments, the gel fraction is preferably 80% or more, more preferably 82% or more, further preferably 84% or more, and can be 86% or more, 88% or more, 90% or more. In addition, from the perspective of easily achieving good flexibility and adhesiveness before the curing treatment, in some embodiments, the gel fraction can be, for example, 99.5% or less, 99% or less, 97% or less, or 95% or less.

[0055] <Adhesive layer>

[0056] As the adhesive layer (photo-curable adhesive layer) in this technology, an adhesive layer capable of achieving a storage modulus increase rate of more than 300% is used. The type of the adhesive constituting the above 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, and fluorine polymers 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 adhesive capable of achieving the above storage modulus increase rate value, the acrylic adhesive containing an acrylic polymer as the base polymer will be mainly described below, but it is not intended to limit the adhesive disclosed herein to the acrylic adhesive.

[0057] 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 polymer is preferably a rubber-like polymer that exhibits rubber elasticity in the temperature region 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.

[0058] (Polymer having a carbon-carbon double bond)

[0059] 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 polymer by light irradiation. By irradiating light on the adhesive layer adhered to the adherend, the carbon-carbon double bond in the above polymer reacts, whereby the above adhesive layer cures and shrinks, and the adhesive sheet having the adhesive layer can be effectively peeled off. Among them, an adhesive preferably containing a polymer having a carbon-carbon double bond as the base polymer is used.

[0060] The existence mode of the carbon-carbon double bond 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, the so-called 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, a polymer having a carbon-carbon double bond in the side chain is preferably used. Here, the so-called main chain of the polymer refers to the chain-like structure that forms the skeleton 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.

[0061] In some preferred embodiments, the polymer having a carbon-carbon double bond has the carbon-carbon double bond in the form of an ethylenically unsaturated group. The 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).

[0062] [Chemical formula 1]

[0063]

[0064] (In the formula, R is a hydrogen atom or a methyl group.)

[0065] 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 that does not contain a carbon-carbon double bond by methods such as chemical modification.

[0066] As a specific example of the 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"), and react a compound having a functional group (hereinafter, also referred to as "functional group B") capable of reacting with the above functional group A and a carbon-carbon double bond (for example, an ethylenically unsaturated compound having 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 has been introduced. The reaction between functional group A and functional group B is preferably a reaction that does not generate free radicals, such as a condensation reaction or an addition reaction. As an example of the combination of functional group A and functional group B, 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. can be cited. 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 above functional groups A and B is a combination that can obtain a polymer having a carbon-carbon double bond, one of the functional groups in the above combination can be set as functional group A and the other can be set as functional group B, or one of the above functional groups can be set as functional group B and the other can be set as functional group A. For example, if the combination of a hydroxyl group and an isocyanate group is used for explanation, the functional group A possessed by the primary polymer can be a hydroxyl group (in this case, functional group B becomes an isocyanate group), or it can be an isocyanate group (in this case, functional group B becomes a hydroxyl group). Among them, the combination in which the primary polymer has a hydroxyl group and the above compound having a functional group B and a carbon-carbon double bond (preferably an ethylenically unsaturated compound having functional group B) has an isocyanate group is preferred. In the case where the above primary polymer is an acrylic polymer, this combination is particularly preferred.

[0067] 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 both, 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 suitably 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 suitably 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 ) is preferably 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, and can be 1.5 or less. Additionally, from the viewpoint of increasing the contact opportunity between the functional group A and the functional group B, a greater amount of the compound containing the functional group B having a carbon-carbon double bond can be used. 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). Further, in cases where, for example, the remaining functional group A is also utilized 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.

[0068] The amount of the compound having a functional group B and a carbon-carbon double bond (preferably an ethylenically unsaturated compound having a functional group B) used is, for example, about 0.001 parts by weight or more, about 0.01 parts by weight or more, or about 0.1 parts by weight or more, relative to 100 parts by weight of the polymer having a functional group A (typically, the polymer before the introduction of the carbon-carbon double bond). It is appropriate to be about 0.5 parts by weight or more (for example, about 1.0 parts by weight or more), preferably about 3.0 parts by weight or more, more preferably about 5.0 parts by weight or more, and can be about 7.0 parts by weight or more, can be about 9.0 parts by weight or more, can be about 10 parts by weight or more, can be about 12 parts by weight or more. In addition, the amount of the compound having a functional group B and a carbon-carbon double bond used is, for example, 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 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, relative to 100 parts by weight of the polymer having a functional group A (typically, the polymer before the introduction of the carbon-carbon double bond). The above-mentioned amount used is preferably set so as to satisfy the above-mentioned molar ratio (M A / M B ). For example, in the case of using the acrylic polymer described later as a component of the polymer, the above-mentioned molar ratio (M A / M B ) and the amount of the compound having a functional group B and a carbon-carbon double bond used can be preferably applied.

[0069] (Acrylic polymer having a carbon-carbon double bond)

[0070] From the viewpoint of ease of curing based on light irradiation, etc., 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, the acrylic polymer having a carbon-carbon double bond and the adhesive layer containing the acrylic polymer are also preferred.

[0071] The acrylic polymer having a carbon-carbon double bond can be a polymer into 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 the 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, condensation or 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, 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, etc., 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, etc., the compound having the functional group B and a carbon-carbon double bond is preferably an ethylenically unsaturated compound having the functional group B.

[0072] 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 the acrylic polymer, etc. 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 realized.

[0073] From the viewpoint of the reactivity with the hydroxyl group as the above functional group A, the amount of the monomer containing an isocyanate group used 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 effects brought about by the curing treatment (e.g., the effect of increasing the storage modulus and 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 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 about 25 parts by weight or less, for example.

[0074] As another suitable example of the ethylenically unsaturated compound having a functional group B, a hydroxyl group-containing monomer can be cited. As specific examples of the hydroxyl group-containing monomer, substances described later as comonomers that can be used in the polymerization of the acrylic polymer can be cited. For example, (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA) are preferred, and 4HBA is particularly 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 realized. From the viewpoint of the reactivity with the isocyanate group as the above functional group A, the amount of the hydroxyl group-containing monomer used 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 ).

[0075] As other examples of the ethylenically unsaturated compound having a functional group B, an epoxy group-containing monomer can be cited. As specific examples of the epoxy group-containing monomer, substances described later as comonomers that can be used in the polymerization of the acrylic polymer can be cited. 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 realized. From the viewpoint of the reactivity with the carboxyl group as the above functional group A, the amount of the epoxy group-containing monomer used 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, and can utilize the effects brought by the remaining carboxyl groups (for example, improvement of the peel strength before curing the photocurable adhesive layer, improvement of the cohesiveness and heat resistance before and / or after the 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.

[0076] 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.

[0077] As the (meth)acrylic acid alkyl ester, a compound represented by the following formula (2) can be suitably used, for example.

[0078] CH2=C(R 1 )COOR 2 (2)

[0079] 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 (for example, 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 (for example, C 1-14 , typically C 1-12 ) of the acrylic acid alkyl ester.

[0080] 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. Preferred alkyl (meth)acrylates include ethyl acrylate (EA), n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and lauryl acrylate (LA).

[0081] In some preferred embodiments, the above alkyl (meth)acrylate includes an alkyl (meth)acrylate A1 having 9 or less carbon atoms in the alkyl group (i.e., R 2 is an alkyl group of C 1-9 of the alkyl (meth)acrylate). In this way, according to the structure in which the length of the side-chain alkyl group is restricted, a photocurable adhesive layer suitable for enhancing the storage modulus by light irradiation can be easily obtained. 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.

[0082] The mixing 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. There is no particular limitation on the upper limit of the mixing ratio of the alkyl (meth)acrylate A1 in all monomer components. In some embodiments, in consideration of the balance with the amount of the comonomer (for example, the monomer having the functional group A), the mixing 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.

[0083] The content ratio of the alkyl (meth)acrylate A1 in the total 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 99-100% by weight, from the viewpoint of ideally presenting the function of the alkyl (meth)acrylate A1.

[0084] In some preferred embodiments, the above-mentioned alkyl (meth)acrylate A1 includes an alkyl (meth)acrylate A3 having less than 8 carbon atoms in the alkyl group. The alkyl (meth)acrylate A3 can contribute to, for example, improving the adhesiveness to polar adherends such as metals. 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 in 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.

[0085] 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 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 action 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, in consideration of 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 (e.g., 99% by weight or less), more preferably 95% by weight or less, may 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.

[0086] 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 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 (e.g., 90% by weight or more), from the viewpoint of ideally presenting the action 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 action, 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.

[0087] 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 adhesiveness 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 may be 9 or more. From the viewpoint of adhesive properties such as adhesiveness, 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 may be 10 or less or 9 or less.

[0088] 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 presenting 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 may be about 75% by weight or more, may be about 80% by weight or more, may be about 85% by weight or more, may be about 90% by weight or more, may 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), more preferably 95% by weight or less, and may 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.

[0089] 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 perspective 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 perspective 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.

[0090] 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.

[0091] 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 preferably 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 or in combination of two or more. A monomer having a functional group A and a monomer having other functional groups can also be used in combination.

[0092] Hydroxyl group-containing monomers: such as 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.

[0093] Isocyanate group-containing monomers: (meth)acryloyl isocyanate, 2-(meth)acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate.

[0094] 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.).

[0095] 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.

[0096] Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate.

[0097] Epoxy group-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.

[0098] Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile.

[0099] Keto group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

[0100] Monomers having a ring containing a nitrogen atom: 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.

[0101] Alkoxysilyl group-containing monomers: for example, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane.

[0102] 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 hydroxy group-containing monomer, an isocyanate group-containing monomer, a carboxyl group-containing monomer, and an epoxy group-containing monomer are preferred.

[0103] In some embodiments, as the comonomer having functional group A, a hydroxy group-containing monomer is preferably used from the viewpoint of reactivity with a compound having functional group B and the like. By using a hydroxy group-containing monomer as the comonomer, the resulting acrylic polymer (primary polymer) has a hydroxy group. In contrast, by using a compound having an isocyanate group as the compound having a carbon-carbon double bond, the hydroxy 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 hydroxy group-containing monomer include (meth)acrylic hydroxyalkyl esters such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA). Among them, 4HBA is preferred.

[0104] The amount of the above comonomer may be appropriately selected in a manner to achieve the desired use purpose (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 exerting 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 and the like, it is preferably 50% by weight or less, more preferably 45% by weight or less, and may 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.

[0105] When a comonomer having functional group A is used for reaction with a compound having a carbon-carbon double bond (preferably an ethylenically unsaturated compound having functional group B), from the viewpoint of easily obtaining an increase in storage modulus and the like brought about by a curing treatment (typically, a light irradiation treatment), it is appropriate that the amount of the comonomer having functional group A (depending on the type of functional group B, for example, a monomer containing a hydroxyl group, a monomer containing a carboxyl group, a monomer containing an isocyanate group, a monomer containing an epoxy group, etc.) is 1% by weight or more in all monomer components of the acrylic polymer, preferably 5% by weight or more, more preferably 10% by weight or more, and further preferably 12% by weight or more (for example, 14% by weight or more). In addition, from the viewpoint of maintaining good adhesive properties such as adhesiveness in the adhesive layer (photocurable adhesive layer) before the curing treatment, it is appropriate that the amount of the comonomer having functional group A is 50% by weight or less (for example, 40% by weight or less) in all monomer components, preferably 30% by weight or less, more preferably 25% by weight or less, can be 20% by weight or less, and can be 15% by weight or less.

[0106] In some embodiments, as the comonomer, a monomer having a nitrogen atom-containing ring can be 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. In addition, from the viewpoint of increasing the reduction amplitude of the peel strength (peel strength difference) brought about by light irradiation (curing treatment) of the photocurable adhesive layer, it is also advantageous. Specific examples of the monomer having a nitrogen atom-containing ring are as described above. As suitable examples, N-vinyl-2-pyrrolidone (NVP) and N-acryloylmorpholine (ACMO) can be cited. In all monomer components used as raw materials for the acrylic polymer (primary polymer), the usage amount of the monomer having a nitrogen atom-containing ring can be, for example, 0.5% by weight or more or 1% by weight or more. From the viewpoint of obtaining a higher usage effect, it is appropriate that it is 3% by weight or more, and it is advantageous that it is 5% by weight or more. It can be 10% by weight or more, can be 12% by weight or more, can be 17% by weight or more, or can be 20% by weight or more. In addition, in all monomer components used as raw materials for the acrylic polymer (primary polymer), the usage amount of the monomer having a nitrogen atom-containing ring can be, for example, 40% by weight or less. From the viewpoint of the flexibility of the photocurable adhesive layer, in some embodiments, it is appropriate that it is 35% by weight or less, and preferably 30% by weight or less (for example, 28% by weight or less).

[0107] In addition, in order to improve the cohesion 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 esters (e.g., phenyl (meth)acrylate), (meth)acrylic acid aryloxyalkyl esters (e.g., phenoxyethyl (meth)acrylate), and (meth)acrylic acid arylalkyl esters (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.

[0108] As the above-described 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.

[0109] By polymerizing a monomer component containing a 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 a 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 a base polymer, it is particularly meaningful that the above acrylic polymer is crosslinked.

[0110] 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 increasing the storage modulus and 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 brought about by curing the photocurable adhesive layer (for example, ultraviolet irradiation treatment) (for example, the easy peeling effect), it is advantageous that the amount of the polyfunctional monomer used as the copolymerization component of the primary polymer is not excessive.

[0111] The method for obtaining an acrylic polymer (primary polymer) from the above monomer components can be selected from various polymerization methods known as synthesis methods for acrylic polymers. From the viewpoint of avoiding the use of organic solvents, polymerization methods other than solution polymerization (for example, solution polymerization using an azo-based polymerization initiator or a peroxide-based polymerization initiator) are 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 an 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.

[0112] In some embodiments, for this 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 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 an acrylic polymer having carbon-carbon double bonds and a specified amount or more of 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 a 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.

[0113] In some preferred embodiments, the active energy ray-curable adhesive composition used to form the primary adhesive layer contains a partial polymer of a monomer mixture, and the monomer mixture contains 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 is sometimes referred to as "monomer slurry" or simply as "slurry".

[0114] The polymerization method for obtaining the above-mentioned aggregated reactant is not particularly limited, and various known polymerization methods can be appropriately selected and used. From the viewpoint 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 viewpoints 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.

[0115] 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 viewpoints 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 generally about 5% by weight or more is appropriate.

[0116] 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 made to contain them in advance, or they can be added to the above-mentioned partial polymer.

[0117] 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 is also included in the examples of the adhesive composition containing a polymer and an unpolymerized monomer component. It should be noted that in this specification, "complete polymer" means that the polymerization conversion rate exceeds 95% by weight.

[0118] (First photoinitiator)

[0119] In an active energy ray-curable adhesive composition for forming a 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 examples of 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 irradiation with active energy rays (typically, ultraviolet irradiation) when forming the adhesive layer (primary adhesive layer) 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 a 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 "first photoinitiator". In addition, the photoinitiator contained in the adhesive layer (photo-curable adhesive layer) of the adhesive sheet disclosed herein and used for photocuring of the adhesive layer may sometimes be referred to as "second photoinitiator". The first photoinitiator and the second photoinitiator may be the same material or different materials.

[0120] (Catalyst)

[0121] 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 a 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 a 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.

[0122] By previously including the above catalyst in an adhesive composition (e.g., a photoinitiator-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.

[0123] (Second photoinitiator)

[0124] The adhesive layer (photo-curable adhesive layer) constituting the adhesive sheet disclosed herein preferably contains a photoinitiator. By including a photoinitiator, free radicals are generated from the photoinitiator during the curing treatment, and the photocuring of the adhesive layer proceeds rapidly. Examples of the photoinitiator 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 combination of two or more as appropriate.

[0125] Specific examples of the ketal-based photoinitiator include 2,2-dimethoxy-1,2-diphenylethane-1-one (e.g., trade name “Omnirad 651”, manufactured by IGM Resins B.V.), etc.

[0126] 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-hydroxycyclohexyl phenyl 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.

[0127] 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. The upper limit of the content of the photoinitiator is not particularly limited. 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.

[0128] 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 such a manner as to remain 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 such a manner as to remain 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.

[0129] 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 appearing in the chromatogram, and a standard curve is prepared using the identified substance or a compound having a molecular structure similar to the identified 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.

[0130] 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, thereby dissolving the photoinitiator in the above sample into the chloroform. Then, 10 mL of acetonitrile is added to precipitate the adhesive component again, and the supernatant containing the dissolved photoinitiator is filtered through a membrane filter (pore size 0.20 μm). This is used as the measurement sample for HPLC. As the analytical device, "UltiMate 3000" of Thermo Fisher Scientific Company or its equivalent can be used. As the measurement conditions, the following conditions can be adopted.

[0131] [Measurement Conditions]

[0132] Column: ZORBAX Eclipse Plus C18( Average particle size of the carrier 1.8 μm)

[0133] Column temperature: 40 °C

[0134] Column flow rate: 0.5 mL / min

[0135] Eluent composition: Gradient conditions of pure water / acetonitrile

[0136] Injection volume: 10 μL

[0137] Detector: DAD (extracting 190 nm - 800 nm, 210 nm, and 245 nm)

[0138] (Other polymers)

[0139] 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 other than acrylic polymers among the various polymers exemplified as the polymers that can be contained in the adhesive layer can be preferably cited. Such polymers may be polymers having a carbon-carbon double bond. As the acrylic polymer without a carbon-carbon double bond, the above-mentioned acrylic polymer as a primary polymer (i.e., an acrylic polymer that has not been chemically modified to introduce a carbon-carbon double bond) can be preferably cited. When the adhesive layer disclosed herein contains the above-mentioned 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, in such a manner 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.

[0140] (Compound containing a carbon-carbon double bond other than a polymer)

[0141] 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, etc. The fact that the photocurable adhesive layer contains the above-mentioned 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.

[0142] 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 kinds can 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.

[0143] 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 effect. 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 with respect to 100 parts by weight of the base polymer of the photocurable adhesive layer (for example, an acrylic polymer having a carbon-carbon bond). In addition, from the viewpoints of the cohesiveness of the photocurable adhesive layer, the peelability of the self-peeling 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, 1 part by weight or less, and can be less than 1 part by weight with respect to 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.

[0144] (Other optional components)

[0145] 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 colorant (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.

[0146] 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, the peelability of the adhesive layer brought about by the curing treatment can be ideally achieved. 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, still more 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, still more preferably about 2% by weight or less, and may be about 1% by weight or less.

[0147] 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 1.0 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.

[0148] 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, and it is 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.

[0149] 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.

[0150] In the case where such information is unknown, as the content of the 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 the carbon-carbon double bonds present is determined. As the analytical device, a Fourier transform NMR device (manufactured by Bruker Biospin Corporation, "AVANCE III-600") or its equivalent can be used. As the measurement conditions, the following conditions can be adopted.

[0151] [Measurement Conditions]

[0152] Observation frequency: 1 H 600 MHz

[0153] Measurement solvent: CDCl3

[0154] Measurement temperature: 300 K

[0155] Chemical shift reference: Measurement solvent 1 H; 7.25 ppm

[0156] 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 ideal 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.

[0157] In the adhesive layer disclosed herein, preferably, the total content of an azo-based polymerization initiator and a peroxide-based polymerization initiator (which may be a polymerization initiator contained in the form of a decomposition product or a residue) 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 per 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. Examples of the above drawbacks include: since the azo-based polymerization initiator and the peroxide-based polymerization initiator as 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 more favorably 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.

[0158] (Thickness of the adhesive layer)

[0159] 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. For example, the thickness of the above-mentioned adhesive layer can be selected from the range of 2 μm or more and 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 peeling caused by light irradiation of the adhesive layer. 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. Here, the method 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.

[0160] <Manufacture of Adhesive Layer>

[0161] The adhesive layer disclosed herein can be suitably manufactured, for example, by a method including the following steps.

[0162] (a) Forming a primary adhesive layer containing a primary polymer having functional group A (primary adhesive layer forming step),

[0163] (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),

[0164] (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),

[0165] (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).

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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 (the second photoinitiator) is prepared, and this post-coating liquid is applied to one surface of the above primary adhesive layer (post-coating liquid application step). The post-coating liquid is not particularly limited as long as it is a liquid that can be applied 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 applied 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.

[0170] If the post-coating liquid is applied to 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 applied to 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 - 30°C). By standing under the above conditions, the post-coating liquid can penetrate sufficiently into the primary adhesive layer.

[0171] 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 - 200°C, more preferably 50 - 180°C, and further preferably 60 - 170°C (e.g., 100 - 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.

[0172] <Substrate layer>

[0173] 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-grade paper, synthetic paper, coated paper, etc. Examples of the cloth include fabrics, non-woven fabrics, etc. formed by the single or blended use of various fibrous substances. As the above-mentioned fibrous substances, cotton, staple fiber, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. can be exemplified. Examples of the rubber sheet include natural rubber sheets, butyl rubber sheets, etc. Examples of the foam sheet include foamed polyurethane sheets, foamed polychloroprene rubber sheets, etc. Examples of the metal foil include aluminum foil, copper foil, etc.

[0174] 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, when the thickness of the adherend is thin, bending and damage of the adherend during conveyance, etc. can be appropriately prevented. 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 (e.g., 0.90 g / cm 3 ~1.20 g / cm 3 , typically, 0.92 g / cm 3 ~1.05 g / cm 3 ) or so.

[0175] 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 incorporated as needed.

[0176] The surface of the above-mentioned substrate layer (such as a resin film substrate, a rubber sheet substrate, a foam sheet substrate, 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 substrate and the adhesive layer, in other words, the anchoring property of the adhesive layer to the substrate.

[0177] In some preferred embodiments, a primer layer is provided on the side surface of the substrate layer on the adhesive layer side. In other words, a primer layer can be disposed between the substrate 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 substrate, a polyester-based, urethane-based, or acrylic-based primer layer is preferred. When an acrylic-based adhesive layer is provided on a polyester-based substrate 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.

[0178] In addition, when the adhesive sheet disclosed herein is a single-sided adhesive sheet having an adhesive layer provided on one side of the substrate layer, the non-adhesive layer forming surface (back surface) of the substrate 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 a silicone-based back surface treatment agent, a fluorine-based back surface treatment agent, a long-chain alkyl-based back surface treatment agent, and other known or conventional treatment agents can be used according to the purpose and application.

[0179] The thickness of the substrate 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 substrate 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).

[0180] <Release Liner>

[0181] As the release liner, a 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.) 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.

[0182] 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 adhesive properties and the like, 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 and the like, 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).

[0183] <Use>

[0184] The use of the adhesive sheet disclosed herein is not particularly limited, and it can be preferably used for applications where it is peeled off from the adherend after curing and can highly prevent residual adhesive. As such applications, a temporary fixing sheet and a protective sheet can be cited. In addition, for example, it can also be preferably used as a process material that is fixed to the adherend and peeled off in the manufacturing process of electronic devices and electronic components.

[0185] 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 be preferably used as a wafer fixing sheet (typically, a laser cutting sheet) for fixing the wafer to a fixing plate (such as a hard substrate such as a glass plate or an acrylic plate). In addition, the adhesive sheet disclosed herein can also be preferably 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 a property of being peeled off well again from the adherend after the purpose is achieved. The adhesive sheet disclosed herein can be preferably used as a sheet that satisfies the performance required for the above-mentioned uses.

[0186] 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-capacity and high-performance of various semiconductor products.

[0187] 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 dicing step, a resin sealing step of a semiconductor chip, etc.

[0188] In addition, in the above manufacturing method, 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) can be included. 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 manufacturing of semiconductor elements, those skilled in the art can implement them based on the common technical knowledge in this field, so they are not particularly described here.

[0189] In addition, the adhesive sheet disclosed herein is suitable as a temporary fixing sheet used in the manufacture of substrates with a small 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 chip fixing of a PCB, the adhesive sheet disclosed herein is used to bond and fix the adherend well, and a curing process is performed at a desired timing. Thereby, while highly preventing residual adhesive, the adhesive sheet can be separated well from the adherend. In addition, the adhesive sheet disclosed herein is preferably used as a support tape for thin wafers. In this application, for example, in printing 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 process is performed at an appropriate timing. Thereby, while highly preventing residual adhesive when separating from the adherend, the adhesive sheet can be separated well from the adherend.

[0190] As described above, the adhesive sheet disclosed herein is preferably applied to the manufacturing use of substrates with a small thickness, such as circuit boards (typically PCBs). Therefore, according to this specification, a manufacturing method of a substrate with a small thickness (e.g., circuit board, organic EL panel, color filter, electronic paper, flexible display) using the above adhesive sheet can be provided. In a preferred embodiment, the manufacturing method includes: a step of fixing a substrate with a small thickness (typically, the back surface of the substrate) on the adhesive sheet (fixing step); a step of processing the substrate with a small thickness.

[0191] 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 chip bonding typically refers to a step of disposing a plurality of chips on a substrate with a small thickness, such as a PCB. The above wire bonding step refers to a step of bonding wires to the above chips. The above 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 manufacturing method, after the above processing step, a step of separating the adhesive sheet from the substrate with a small thickness (removing step. Typically a peeling step) may be included. In the above manufacturing method, typically, after the above processing step and before the above separating step, a curing process is performed on the adhesive sheet. The curing process is preferably 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 small thickness, such as PCBs, those skilled in the art can implement them based on the common technical knowledge in this field. Therefore, no special description is provided herein.

[0192] Other methods involve manufacturing methods for circuit boards (typically, 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 on 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, a curing treatment is performed on the adhesive sheet after the above processing step and before the above separating step. 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 substrates with a small thickness such as FPC, those skilled in the art can implement them based on the common technical knowledge in this field, so no special description is provided herein.

[0193] The matters disclosed in this specification include the following aspects.

[0194] 〔1〕An adhesive sheet which is an adhesive sheet having an adhesive layer cured by light irradiation,

[0195] 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,

[0196] The storage modulus increase rate of the above adhesive sheet obtained by the following formula is 300% or more,

[0197] Storage modulus increase rate [%] = (R / Q - 1) × 100

[0198] (In the formula, Q and R are the storage moduli G’ (unit: [Pa]) at 25°C based on dynamic viscoelasticity measurement, Q is the initial storage modulus G’ measured using a measurement sample obtained from the above adhesive layer, and R is the storage modulus G’ after curing treatment measured after subjecting the above measurement sample to ultraviolet irradiation curing treatment).

[0199] 〔2〕The adhesive sheet as described in the above 〔1〕, wherein the above adhesive layer contains a polymer having a carbon-carbon double bond.

[0200] 〔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.

[0201] 〔4〕The adhesive sheet as described in any one of the above 〔1〕 to 〔3〕, wherein the above adhesive layer contains 1.0×10 - 4 mol / 100g or more of carbon-carbon double bonds.

[0202] [5] The adhesive sheet according to any one of [1] to [4] above, wherein the adhesive layer contains a photoinitiator of 1.0×10 - 4 mol / 100 g or more.

[0203] [6] The adhesive sheet according to any one of [1] to [5] above, wherein the initial storage modulus G' is less than 1.0×10 6 Pa.

[0204] [7] The adhesive sheet according to any one of [1] to [6] above, wherein the gel fraction measured after the curing treatment of irradiating ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 is 70% or more.

[0205] [8] The adhesive sheet according to any one of [1] to [7] above, wherein the content of the organic solvent in the adhesive layer is 1.0 μg / g or less.

[0206] 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 in the adhesive layer possessed by the adhesive sheet is not limited. For example, the following matters are also included in the matters disclosed in this specification.

[0207] [9] An adhesive sheet having an adhesive layer that is cured by light irradiation,

[0208] the adhesive layer satisfies at least any one of the following conditions (A), (B), (C), and (D):

[0209] (A) The total content of the azo-based polymerization initiator and the peroxide-based polymerization initiator is 1.0 μg / g or less;

[0210] (B) The content of the organic solvent is 1.0 μg / g or less;

[0211] (C) It is a photocured product of a photocurable adhesive composition or a modified product thereof;

[0212] (D) It contains a photopolymer or a polymer as a modified product thereof as a base polymer,

[0213] and the storage modulus increase rate calculated by the following formula is 300% or more.

[0214] Storage modulus increase rate [%] = (R / Q - 1) × 100

[0215] (In the formula, Q and R are storage moduli G' at 25°C based on dynamic viscoelasticity measurement (unit: [Pa]), Q is the initial storage modulus G' measured using the measurement sample obtained from the above adhesive layer, and R is the storage modulus G' after curing treatment measured after subjecting the above measurement sample to ultraviolet irradiation curing treatment.)

[0216]

[10] The adhesive sheet as described in [9] above, wherein the above adhesive layer contains a polymer having a carbon-carbon double bond.

[0217]

[11] The adhesive sheet as described in

[10] above, 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.

[0218]

[12] The adhesive sheet as described in any one of [9] to

[11] above, wherein the above adhesive layer contains 1.0×10 - 4 mol / 100g or more of carbon-carbon double bonds.

[0219]

[13] The adhesive sheet as described in any one of [9] to

[12] above, wherein the above adhesive layer contains 1.0×10 - 4 mol / 100g or more of a photoinitiator.

[0220]

[14] The adhesive sheet as described in any one of [9] to

[13] above, wherein the above initial storage modulus G' is less than 1.0×10 6 Pa.

[0221]

[15] The adhesive sheet as described in any one of [9] to

[14] above, wherein the gel fraction of the above adhesive layer measured after curing treatment by irradiating ultraviolet rays with an accumulated light amount of 300 mJ / cm 2 is 70% or more.

[0222]

[16] The adhesive sheet as described in any one of [9] to

[15] above, wherein the above adhesive layer satisfies at least the above condition (B).

[0223]

[17] The adhesive sheet as described in any one of [1] to

[16] above, wherein the above initial elastic modulus G' is less than 1.0×10 6 Pa, and the elastic modulus G' after the above curing treatment is 1.0×10 6 Pa or more.

[0224]

[18] The adhesive sheet according to any one of [1] to

[17] above, wherein 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 1.0 N / 20 mm or more (for example, 2.0 N / 20 mm or more).

[0225]

[19] The adhesive sheet according to any one of [1] to

[18] above, wherein after being pasted on a silicon wafer and subjected to a curing treatment by irradiating ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 , the peel strength after the curing treatment measured under the conditions of a peel rate of 300 mm / min and a peel angle of 180 degrees is less than 1.0 N / 20 mm.

[0226]

[20] The adhesive sheet according to any one of [1] to

[19] above, wherein the peel strength reduction rate obtained by the following formula is 50% or more.

[0227] Peel strength reduction rate [%] = (1 - B / A) × 100

[0228] (In the formula, A is the initial peel strength (unit: [N / 20 mm]) 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, and B in the formula is the peel strength after the curing treatment (unit: [N / 20 mm]) 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 and subjected to a curing treatment by irradiating ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 ).)

[0229]

[21] The adhesive sheet according to any one of [1] to

[20] above, wherein the Young's modulus measured by a tensile test after the adhesive layer is irradiated with ultraviolet rays with a cumulative light amount of 300 mJ / cm 2 is 1.0 MPa or more.

[0230]

[22] The adhesive sheet according to any one of [1] to

[21] above, wherein the loss modulus of the adhesive layer at 25°C is 1.0 × 10 3 Pa or more and 1.0 × 10 6 Pa or less.

[0231]

[23] The adhesive sheet according to any one of [1] to

[22] above, wherein the thickness of the adhesive layer is 10 μm or more and less than 100 μm.

[0232]

[24] The adhesive sheet according to any one of [1] to

[23] above, wherein the adhesive layer contains an acrylic polymer having a carbon-carbon double bond.

[0233] 〔25〕The adhesive sheet as described in the above-mentioned 〔24〕, wherein the acrylic polymer is crosslinked with a polyfunctional monomer having two or more ethylenically unsaturated groups in one molecule.

[0234] 〔26〕The adhesive sheet as described in the above-mentioned 〔24〕 or 〔25〕, wherein the acrylic polymer is a photopolymer or a modified product thereof.

[0235] 〔27〕The adhesive sheet as described in any one of the above-mentioned 〔24〕 to 〔26〕, wherein 50% by weight or more of all monomer components constituting the acrylic polymer is a (meth)acrylic linear alkyl ester having 5 or more carbon atoms in the alkyl group.

[0236] 〔28〕The adhesive sheet as described in any one of the above-mentioned 〔24〕 to 〔27〕, wherein the adhesive layer contains the acrylic polymer as a base polymer.

[0237] 〔29〕A method for manufacturing an adhesive layer, which is a method for manufacturing an adhesive layer curable by light irradiation (a 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 having a functional group B and a photoinitiator, and coat the post-coating liquid on at least one surface of the primary adhesive layer;

[0240] Allow the compound having a carbon-carbon double bond and having 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] 〔30〕The method for manufacturing an adhesive layer as described in the above-mentioned 〔29〕, which is applied to the manufacturing of the adhesive layer of the adhesive sheet as described in any one of the above-mentioned 〔1〕 to 〔28〕.

[0243] 〔31〕An adhesive sheet having an adhesive layer obtained by the method for manufacturing an adhesive layer as described in the above-mentioned 〔29〕 or 〔30〕.

[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 solutions 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] In 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, and then ultraviolet rays were irradiated in 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 applied to 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 irradiation was performed 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, that is, an acrylic polymer crosslinked by the above polyfunctional acrylate, as a base polymer (primary polymer).

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

[0254] 11 parts of 2-(Methacryloyloxy)ethyl 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-described primary adhesive layer D1, and the post-coating liquid E1 was applied to the exposed surface using a wire-wound rod coater manufactured by RD Specialties. After application, it was allowed to stand 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-described 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 adhered to the above-described one surface of the obtained adhesive layer S1 for protection. It should be noted that the coating amount of the above-described adhesive composition C1 and the coating amount of the above-described post-coating liquid E1 were adjusted so that the content of each component in the above-described adhesive layer S1 was as shown in the following table and the thickness of the adhesive layer S1 was 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-described 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-described 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-described 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. Instead of using adhesive composition C1, adhesive composition C3 was used, and instead of using post-coating liquid E1, post-coating liquid E3 was used. Otherwise, the operation was the same as in Example 1 to produce an 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. Instead of using adhesive composition C1, adhesive composition C4 was used, and instead of using post-coating liquid E1, post-coating liquid E4 was used. Otherwise, the operation was the same as in Example 1 to produce an adhesive layer (substrate-free adhesive sheet) S4 related to this example.

[0269] <Examples 5 to 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 adhesive layers (substrate-free adhesive sheets) S5 to 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 with a mixing ratio of 85 parts of 2EHA and 15 parts of 2-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, and an addition reaction was carried out to prepare an acrylic polymer having a carbon-carbon double bond. 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 release-treated polyester film, dried at 120 °C for 3 minutes, and then cured at 50 °C for 24 hours to produce 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 to produce the adhesive layer (substrate-free adhesive sheet) S9 related to this example.

[0276] <Examples 10, 11>

[0277] The monomers of the types and amounts shown in Table 2 were further added to the prepolymer composition, and otherwise, the operation was the same as in Example 1 to produce the adhesive layers (substrate-free adhesive sheets) S10 and S11 related to each example. 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 added, 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 parts of HDDA as a crosslinking agent, 0.05 parts 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 and 1 part of a photoinitiator (Omni.651) were mixed to prepare a post-coating liquid E12. Instead of using adhesive composition C1, adhesive composition C12 was used, and instead of using post-coating liquid E1, post-coating liquid E12 was used. Otherwise, the operation was the same as in Example 1 to produce 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. Otherwise, the operation was the same as in Example 12 to produce the adhesive layer (substrate-free adhesive sheet) S13 related to this example.

[0284] <Measurement and Evaluation>

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

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

[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 adhesive formulation [parts]) × 100 [g] / molecular weight of this carbon-carbon double bond-containing compound [g / mol]

[0288] [Amount of photoinitiator]

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

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

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

[0292] Collect about 3 mg of a sample from the adhesive layer obtained from each case, and perform outgassing analysis at 180 °C for 1 hour using gas chromatography-mass spectrometry (GC / MS) to conduct the measurement. The specific measurement conditions are as described below. Based on the measurement results, determine 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] [Organic solvent content]

[0311] About 3 mg of a sample was collected from the adhesive layer obtained in each example, and outgassing analysis was performed at 180 °C for 1 hour using gas chromatography - mass spectrometry (GC / MS) to determine the content of organic solvents in the adhesive layer. The specific measurement conditions are as described above.

[0312] [Dynamic viscoelasticity measurement]

[0313] The adhesive layers (adhesive sheets without a substrate) obtained in each example were laminated to a thickness of about 2 mm, and a product cut into a disc shape with a diameter of 7.9 mm was used as a measurement sample. Using the "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific Company, dynamic viscoelasticity measurement was performed 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 / min

[0318] Shape: Parallel plates

[0319] Next, the above - mentioned measurement sample was subjected to a curing treatment with ultraviolet light having an irradiation intensity of 300 mW / cm and an accumulated light quantity of 3000 mJ / cm 2 . Using the treated sample, dynamic viscoelasticity measurement was performed by 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, the increase rate of the storage modulus G' was calculated by the following formula.

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

[0322] (In the formula, Q is the initial elastic 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 in 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 became approximately 2 mm 2 Next, one of the release films was removed from the adhesive layer, and on the other release film, the adhesive layer was wound around its longitudinal axis in a manner that no air bubbles entered, 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, 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 determined from the rising portion 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 in 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 piece, 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 piece was 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 taken 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 piece was peeled off from the above silicon wafer. Except for this, the same operations as the measurement of the above initial peel strength were performed to measure the peel strength after the curing treatment.

[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 the 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, for the adhesive layers of Examples 1 to 6 and 10 to 13 with a storage modulus increase rate of 300% or more, their peel strength is significantly reduced by the above-mentioned curing treatment, and the peelability based on light irradiation is excellent. The adhesive layers involved in Examples 1 to 6 and 10 to 13 are photocurable adhesive layers capable of obtaining such an effect, and a solvent-free adhesive composition obtained without performing solution polymerization using an azo-based or peroxide-based polymerization initiator can be used, and it can be manufactured by a method that also does not use an organic solvent in the process of obtaining the adhesive layers involved in each example from this adhesive composition. Therefore, it is ideal from the viewpoint of environmental hygiene.

[0351] On the other hand, the storage modulus increase rate of the adhesive layer of Example 7 is less than 300%, and the effect of peelability caused by light irradiation is not observed. It should be noted that the adhesive layers involved in 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 (an azo-based polymerization initiator is used in the solution polymerization of Example 8, and a peroxide-based polymerization initiator is used in the solution polymerization of Example 9) through a reaction in the solution as a base polymer. For the adhesive layers of Examples 8 and 9, reflecting the results of such a manufacturing process, the amounts of azo-based and peroxide-based polymerization initiators are as high as 13 to 96 μg / 100 g, and it can be seen that the residual solvent amount (organic solvent content) is also significantly large.

[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 technology described in the claims includes 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 side

[0360] 20B Second side (back side)

[0361] 30, 31, 32 Release liner

[0362] 50 Adhesive sheet with release liner

Claims

1. An adhesive sheet which is an adhesive sheet having an adhesive layer that is 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 storage modulus increase rate of the adhesive sheet, calculated by the following formula, is 300% or more. Storage modulus increase rate [%] = (R / Q - 1) × 100 (In the formula, Q and R are the storage moduli G’ (unit: [Pa]) at 25°C based on dynamic viscoelasticity measurement. Q is the initial storage modulus G’ measured using a measurement sample obtained from the adhesive layer, and R is the storage modulus G’ after curing treatment measured after subjecting the measurement sample to ultraviolet irradiation curing treatment.) 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 any one of claims 1 to 3, wherein The adhesive layer contains carbon-carbon double bonds in an amount of 1.0×10 -4 mol / 100 g or more.

5. The adhesive sheet according to any one of claims 1 to 3, wherein The adhesive layer contains a photoinitiator in an amount of 1.0×10 -4 mol / 100 g or more.

6. The adhesive sheet according to any one of claims 1 to 3, wherein, The initial storage modulus G’ is less than 1.0×10 6 Pa.

7. The adhesive sheet according to any one of claims 1 to 3, wherein The gel fraction of the adhesive layer measured after curing treatment with ultraviolet rays having an accumulated light quantity of 300 mJ / cm 2 is 70% or more.

8. The adhesive sheet according to any one of claims 1 to 3, wherein The content of the organic solvent in the adhesive layer is 1.0 μg / g or less.

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