JP6808817B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet.

The adhesive sheet may be used not only for semi-permanently fixing members, but also for temporary fixing for temporarily fixing building materials, interior materials, electronic parts, and the like when processing them. Such an adhesive sheet for temporary fixing is required to have both adhesiveness at the time of use and peelability after use.
Conventionally, as a pressure-sensitive adhesive sheet for temporary fixing that satisfies the above requirements, a heat-release type pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer containing heat-expandable particles is provided on a base material has been known. The heat-release type adhesive sheet has a feature that the adhesive force is reduced by foaming or expanding the heat-expandable particles by heating, and the adhesive sheet can be easily peeled off from the adherend. Therefore, it is used as a temporary fixing means, a label for recycling, etc. in the manufacturing process of electronic parts.

For example, Patent Document 1 describes a heat-release type pressure-sensitive adhesive sheet in which a heat-expandable pressure-sensitive adhesive layer containing heat-expandable microspheres is provided on at least one side of a base material, with respect to the thickness of the heat-expandable pressure-sensitive adhesive layer. By adjusting the maximum particle size of the heat-expandable microspheres added to the pressure-sensitive adhesive layer, the center line average roughness of the surface of the heat-expandable pressure-sensitive adhesive layer before heating is set to 0.4 μm or less. A heat-release type adhesive sheet for temporary fixing when cutting electronic parts is disclosed.
In recent years, as the miniaturization of electronic components has progressed, the adhesive area between the adhesive sheet and the adherend has become smaller, which may cause adhesion problems such as chip skipping. The heat-release type adhesive sheet described in Patent Document 1 can secure an effective contact area with the adhesive sheet by suppressing the surface roughness of the heat-expandable adhesive layer to be small, and prevent the occurrence of adhesive defects such as chip skipping. There is a statement that it can be done.

Japanese Patent No. 3594853

In the conventional heat-release type pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer containing the heat-expandable particles expands by foaming or expanding the heat-expandable particles by heating. Due to the expansion of the pressure-sensitive adhesive layer, the surface of the pressure-sensitive adhesive layer in contact with the adherend is deformed in an uneven shape, and the adhesive area between the pressure-sensitive adhesive layer and the adherend is reduced. As a result, the adhesive force of the pressure-sensitive adhesive layer is reduced, and the pressure-sensitive adhesive sheet can be easily peeled off from the adherend.
However, when the heat-expandable particles are foamed or expanded by heating, the pressure-sensitive adhesive layer containing the heat-expandable particles is likely to be destroyed inside, that is, the pressure-sensitive adhesive layer is likely to be aggregated and destroyed. As a result, there is a concern that the adhesive remains on the surface of the adherend after heat peeling (so-called adhesive residue).
In addition, if the adhesion between the base material and the pressure-sensitive adhesive layer is poor, when the heat-expandable pressure-sensitive adhesive layer is expanded by heating, it may cause unwanted peeling between the base material and the pressure-sensitive adhesive layer. There is also.

Further, the heat-removable pressure-sensitive adhesive sheet described in Patent Document 1 suppresses the surface roughness of the heat-expandable pressure-sensitive adhesive layer from the viewpoint of improving the adhesiveness at the time of temporary fixing. It is designed to reduce the particle size of the heat-expandable microspheres to be added. However, if the particle size of the heat-expandable microspheres is made too small, the surface roughness becomes small, resulting in poor interfacial adhesion, and there is a concern that adhesive residue on the surface of the adherend after heat peeling may occur.

The present invention has been made in view of the above problems, and there is little adhesive residue on the surface of the adherend after heat peeling, and the interfacial adhesion between the base material and the pressure-sensitive adhesive layer is good. An object of the present invention is to provide an adhesive sheet having excellent adhesiveness and heat peeling property at the time of temporary fixing.

The present inventors have found that the above-mentioned problems can be solved by impregnating a base material with heat-expandable particles and forming a laminate containing the base material and an adhesive layer by a specific method. , The present invention has been completed.

That is, the present invention provides the following [1] to [9].
[1] An adhesive sheet having a laminate in which an adhesive layer (X1) and a non-adhesive heat-expandable base material (Y) are directly laminated in this order.
The laminated body
A coating film (x1') composed of the composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1), and
A coating film (y') composed of a composition (y) containing a resin and heat-expandable particles, which is a material for forming the heat-expandable base material (Y),
The adhesive sheet is formed by directly laminating the coating film (x1') and the coating film (y') in this order and then irradiating the coating film (x1') with energy rays at the same time.
[2] The adhesive sheet according to the above [1], wherein the energy ray irradiation is ultraviolet irradiation.
[3] The adhesive sheet according to the above [1] or [2], wherein the heat-expandable base material (Y) satisfies the following requirement (1).
- Requirement (1): in the expansion starting temperature (t) of the heat expandable particles, thermally expandable base material (Y) the storage elastic modulus E of the '(t) is less than or equal to 1.0 × ¹⁰ 7 Pa.
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the heat-expandable base material (Y) satisfies the following requirement (2).
· Requirement (2): at 23 ° C., the storage modulus of the thermally expandable base material (Y) E '(23) is at 1.0 × ¹⁰ 6 Pa or more.
[5] The pressure-sensitive adhesive sheet according to any one of [1] to [4] above, wherein the heat-expandable base material (Y) has a thickness of 10 to 1000 μm.
[6] The pressure-sensitive adhesive sheet according to any one of [1] to [5] above, wherein the probe tack value on the surface of the heat-expandable base material (Y) is less than 50 mN / 5 mmφ.
[7] The laminate further contains an adhesive layer (X2), and the adhesive layer (X1), the heat-expandable base material (Y), and the adhesive layer (X2) are directly laminated in this order. The adhesive sheet according to any one of the above [1] to [6].
[8] The laminated body is
A coating film (x1') composed of the composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1), and
A coating film (y') composed of a composition (y) containing a resin and heat-expandable particles, which is a material for forming the heat-expandable base material (Y),
A coating film (x2') composed of the composition (x2) which is a material for forming the pressure-sensitive adhesive layer (X2), and
The adhesive sheet according to the above [7], which is formed by directly laminating in this order and then irradiating the coating films (x1'), (y') and (x2') with energy rays at the same time.
[9] The pressure-sensitive adhesive sheet according to any one of [1] to [8] above, wherein the average particle diameter of the heat-expandable particles before expansion at 23 ° C. is 3 to 100 μm.

The pressure-sensitive adhesive sheet of the present invention has little adhesive residue on the surface of the adherend after heat peeling, has good interfacial adhesion between the base material and the pressure-sensitive adhesive layer, and is excellent in adhesiveness and heat peelability during temporary fixing. ..

It is sectional drawing of the adhesive sheet which shows an example of the structure of the adhesive sheet of this invention. It is sectional drawing of the double-sided adhesive sheet which shows an example of the structure of the adhesive sheet of this invention.

In the present invention, the "active ingredient" refers to a component contained in the target composition excluding the diluting solvent.
The mass average molecular weight (Mw) is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method, and specifically, a value measured based on the method described in Examples.

In the present invention, for example, "(meth) acrylic acid" means both "acrylic acid" and "methacrylic acid", and other similar terms are the same.
Further, with respect to a preferable numerical range (for example, a range such as content), the lower limit value and the upper limit value described stepwise can be combined independently. For example, from the description of "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit value (10)" and the "more preferable upper limit value (60)" are combined to obtain "10 to 60". You can also do it.

≪Adhesive sheet≫
The adhesive sheet of the present invention will be described.
The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a laminate in which a pressure-sensitive adhesive layer (X1) and a non-adhesive heat-expandable base material (Y) are directly laminated in this order. Here, the laminate is a coating film (x1') composed of a composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1), a resin which is a material for forming a heat-expandable base material (Y), and a resin. The coating film (y') composed of the composition (y) containing the heat-expandable particles is directly laminated in this order, and then the coating film (x1') and the coating film (y') are simultaneously irradiated with energy rays. It is formed.
Here, the above-mentioned "direct lamination" refers to a configuration in which a layer and a layer are in direct contact with each other without interposing another layer between the two layers. That is, in the present invention, the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) are in direct contact with each other without interposing another layer.

When the adhesive sheet of the present invention is peeled off from the adherend, the heat-expandable particles in the heat-expandable base material (Y) expand due to heating, and irregularities are formed on the surface of the heat-expandable base material (Y). At the same time, the pressure-sensitive adhesive layer (X1) laminated on the unevenness is also pushed up, and unevenness is also formed on the surface of the pressure-sensitive adhesive layer (X1). By forming irregularities on the surface of the pressure-sensitive adhesive layer (X1), the contact area between the adherend and the surface of the pressure-sensitive adhesive layer (X1) is reduced, and the adherend and the pressure-sensitive adhesive layer (X1) are formed. A space is created between the surface and the surface of the. As a result, the adhesive sheet can be easily peeled off from the adherend attached to the surface of the adhesive layer (X1) with a slight force.
In the pressure-sensitive adhesive sheet of the present invention, by including the heat-expandable particles in the heat-expandable base material (Y) instead of in the pressure-sensitive adhesive layer (X1), aggregation destruction of the pressure-sensitive adhesive layer (X1) due to heating is suppressed. can do. As a result, it is possible to reduce the adhesive residue on the surface of the adherend after heat peeling.
Further, in the pressure-sensitive adhesive sheet of the present invention, since the laminate is formed by a specific method as described above, the interfacial adhesion between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) is to be improved. Can be done. As a result, even if the heat-expandable particles in the heat-expandable base material (Y) expand and irregularities are formed on the surface of the heat-expandable base material (Y), the pressure-sensitive adhesive layer (X1) and the heat-expandable particles are expandable. Unwanted peeling from the base material (Y) can be suppressed, and as described above, irregularities are also formed on the surface of the pressure-sensitive adhesive layer (X1).

1 and 2 are schematic cross-sectional views showing an example of the configuration of the pressure-sensitive adhesive sheet of the present invention.
As a specific configuration of the pressure-sensitive adhesive sheet according to one aspect of the present invention, for example, as shown in FIG. 1A, the pressure-sensitive adhesive layer (X1) 12 and the heat-expandable base material (Y) 11 are directly laminated in this order. An adhesive sheet 1a having the laminated body 10 which has been formed can be mentioned. Further, as in the pressure-sensitive adhesive sheet 1b shown in FIG. 1 (b), the release material 13 may be further provided on the surface of the pressure-sensitive adhesive layer (X1) 12.

As a specific configuration of the pressure-sensitive adhesive sheet of another aspect of the present invention, the pressure-sensitive adhesive layer (X1) 121, the heat-expandable base material (Y) 11, and the pressure-sensitive adhesive layer as shown in FIG. Examples thereof include a double-sided adhesive sheet 2a having a laminated body 10 in which (X2) 122 are directly laminated in this order. Further, as in the double-sided adhesive sheet 2b shown in FIG. 2B, the release material 131 is further provided on the surface of the adhesive layer (X1) 121, and the release material 131 is further released on the adhesive surface of the adhesive layer (X2) 122. It may be configured to have the material 132.
In the double-sided pressure-sensitive adhesive sheet 2b shown in FIG. 2B, the peeling force when the release material 131 is peeled from the pressure-sensitive adhesive layer (X1) 121 and the peeling force when the release material 132 is peeled off from the pressure-sensitive adhesive layer (X2) 122. When the forces are about the same, if both release materials are pulled outward to try to peel off, a phenomenon may occur in which the pressure-sensitive adhesive layer is separated and peeled off by the two release materials.
From the viewpoint of suppressing such a phenomenon, it is preferable to use two types of release materials designed so that the release forces from the pressure-sensitive adhesive layers attached to the two release materials 131 and 132 are different from each other.

As another adhesive sheet, in the double-sided adhesive sheet 2a shown in FIG. 2A, one surface of the adhesive layer (X1) 121 and the adhesive layer (X2) 122 is peeled off by performing peeling treatment on both sides. A double-sided adhesive sheet having a structure in which the laminated materials are wound in a roll shape may be used.

<Laminated body>
The laminate of the pressure-sensitive adhesive sheet of the present invention is a laminate in which the pressure-sensitive adhesive layer (X1) and the non-adhesive heat-expandable base material (Y) are directly laminated in this order, and the pressure-sensitive adhesive layer (X1) ) Consists of a coating film (x1') composed of the composition (x1), and a composition (y) containing a resin and heat-expandable particles, which is a material for forming the heat-expandable base material (Y). The coating film (y') is directly laminated in this order, and then the coating film (x1') and the coating film (y') are simultaneously irradiated with energy rays to form the coating film (y').
Examples of the energy ray irradiation include ultraviolet irradiation and electron beam irradiation, but from the viewpoint of not causing an unnecessary reaction, ultraviolet irradiation is preferable.
In the present invention, since the coating film (x1') and the coating film (y') form an energy ray-irradiated laminate "simultaneously", the coating film (x1') and the coating film (y') are "separate". Compared with the method of forming a laminate by irradiating with energy rays, the interfacial adhesion between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) can be improved.
A coating film (x1') composed of a composition (x1) that forms a pressure-sensitive adhesive layer (X1) and a coating film (y) composed of a composition (y) that forms a heat-expandable base material (Y). In the process of irradiating') with energy rays at the same time, a mixed layer of the coating film is formed near the interface, and the molecular chains of the resins contained in each composition are entangled with each other, so that the pressure-sensitive adhesive layer (X1) and the thermally expandable group are formed. It is considered that the interfacial adhesion with the material (Y) is improved.

Examples of a method of irradiating the coating film (x1') and the coating film (y') with energy rays "separately" to form a laminate include the following methods.
The composition (x1) is applied on the peeling surface of a release material such as a release film to form a coating film (x1'), and the coating film (x1') is irradiated with energy rays to form an adhesive layer (X1). To form. Further, the composition (y) containing the resin and the heat-expandable particles is applied on the peeling surface of the peeling material such as the peeling film prepared separately to form a coating film (y'), and the coating film (y) is formed. ') Is irradiated with energy rays to form a heat-expandable substrate (Y). After that, the surface of the pressure-sensitive adhesive layer (X1) that is not in contact with the release material and the surface of the heat-expandable base material (Y) that is not in contact with the release material are laminated to form a laminate.

In the method of irradiating the coating film (x1') and the coating film (y') with energy rays "separately" to form a laminate as described above, the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y') are formed. ) Are formed separately, so that the interfacial adhesion between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) is low.

The laminate of the pressure-sensitive adhesive sheet of one aspect of the present invention is preferably a composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1) and a composition which is a material for forming a heat-expandable base material (Y). (Y) is applied at the same time, the coating film (x1') and the coating film (y') are directly laminated in this order, and then the coating film (x1') and the coating film (y') are simultaneously energized. It was formed by irradiation. By applying the composition (x1) and the composition (y) at the same time, the entanglement of the molecular chains of the resins contained in each composition is promoted as compared with the case where each composition is applied sequentially. The interfacial adhesion between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) can be further enhanced.

The laminate of the pressure-sensitive adhesive sheet of one aspect of the present invention further includes a pressure-sensitive adhesive layer (X2), with the pressure-sensitive adhesive layer (X1), the heat-expandable base material (Y), and the pressure-sensitive adhesive layer (X2) in this order. It may be configured to be directly laminated with. The pressure-sensitive adhesive layer (X2) is a layer formed from the composition (x2).
As a method for forming a laminate further containing the above-mentioned pressure-sensitive adhesive layer (X2), for example, the composition (x2) is applied onto the expandable base material (Y) to form a coating film (x2'). A method of forming the coating film (x2') by irradiating it with energy rays can be mentioned. Further, for example, the pressure-sensitive adhesive layer (X2) prepared in advance by irradiating the coating film (x2') with energy rays may be directly attached onto the expandable base material (Y).

The laminate further containing the pressure-sensitive adhesive layer (X2) is preferably a coating film (x1') composed of a composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1), and a heat-expandable base material (x1'). A coating composed of a coating film (y') composed of a composition (y) containing a resin and heat-expandable particles, which is a material for forming Y), and a composition (x2), which is a material for forming an adhesive layer (X2). The film (x2') is directly laminated in this order, and then the coating film (x1'), (y') and (x2') are simultaneously irradiated with energy rays to form the film (x2').
By forming the laminate further containing the pressure-sensitive adhesive layer (X2) in this way, the interfacial adhesion between the heat-expandable base material (Y) and the pressure-sensitive adhesive layer (X2) can be enhanced for the reason described above. ..

The laminate further containing the above-mentioned pressure-sensitive adhesive layer (X2) is more preferably a composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1) and a material for forming a heat-expandable base material (Y). The composition (y) and the composition (x2), which is a material for forming the pressure-sensitive adhesive layer (X2), are simultaneously applied, and the coating films (x1'), (y') and (x2') are applied in this order. After being directly laminated, the coating film (x1'), (y') and (x2') are simultaneously irradiated with energy rays to form the coating film (x1').
By forming the laminate further containing the pressure-sensitive adhesive layer (X2) in this way, the interfacial adhesion between the heat-expandable base material (Y) and the pressure-sensitive adhesive layer (X2) can be further enhanced for the reason described above. it can.

In the present invention, the laminate of the pressure-sensitive adhesive sheet is specified by the manufacturing method as described above, but there is a circumstance that the laminate must be specified by such a manufacturing method.
Regarding the interface between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y), as an evaluation based on objective physical property values, for example, heat with the pressure-sensitive adhesive layer (X1) in a cross section cut in the thickness direction of the laminate. A method of measuring the roughness of the interface by observing the interface with the expandable base material (Y) using an electron microscope or the like can be considered. However, since the roughness of the interface is very small, it cannot be measured accurately, and the difference in roughness state depending on the observed region is very large. Therefore, it is extremely difficult to evaluate by a specific physical property value such as the roughness of the interface.
Further, depending on the type of the adhesive resin contained in the pressure-sensitive adhesive layer (X1) and the resin contained in the heat-expandable base material (Y), the pressure-sensitive adhesive layer (X1) and the heat-expandable property can be obtained by using an electron microscope or the like. Even if an attempt is made to observe the interface with the base material (Y), the interface may become unclear, making it difficult to measure the roughness itself in the first place.
Further, when the laminated body is cut in the thickness direction in order to obtain a cross section of the laminated body, since the laminated body is formed of a resin, the pressure-sensitive adhesive layer (X1) and the heat-expandable base material are used. There is also a situation in which the shape of the interface with (Y) collapses and the state of the interface cannot be evaluated accurately.
From such a situation, in the present invention, the laminated body of the pressure-sensitive adhesive sheet is specified by the manufacturing method as described above.
The laminate has a structure in which the pressure-sensitive adhesive layer (X1), the heat-expandable base material (Y), and the pressure-sensitive adhesive layer (X2) are directly laminated in this order, and is combined with the coating film (x1'). In the case where (y') and (x2') are directly laminated in this order, and then the coating film (x1'), (y') and (x2') are simultaneously irradiated with energy rays. However, the same circumstances as described above exist for the interface between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) and the interface between the heat-expandable base material (Y) and the pressure-sensitive adhesive layer (X2). There is no choice but to specify by such a manufacturing method.

The method for forming the coating film (x1'), (y') and (x2') and the energy ray irradiation conditions for the formed coating film are described in the items of "Adhesive sheet manufacturing method" described later. As described.

The thickness of the laminated body of the pressure-sensitive adhesive sheet of the present invention is preferably 10 to 1200 μm, more preferably 25 to 500 μm, still more preferably 40 to 300 μm, and even more preferably 55 to 200 μm.

The thickness of the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of the present invention is determined by the viewpoint of exhibiting excellent adhesive strength and the expansion of the heat-expandable particles in the heat-expandable base material (Y) by heat treatment. From the viewpoint of facilitating the formation of irregularities on the surface of the pressure-sensitive adhesive layer (X1), the thickness is preferably 1 to 100 μm, more preferably 2 to 70 μm, still more preferably 3 to 40 μm, and even more preferably 5 to 30 μm.

The thickness of the heat-expandable base material (Y) contained in the pressure-sensitive adhesive sheet of the present invention is preferably 10 to 1000 μm, more preferably 20 to 500 μm, still more preferably 25 to 400 μm, and even more preferably 30 to 300 μm.

When the laminate of the pressure-sensitive adhesive sheet of one aspect of the present invention further contains the pressure-sensitive adhesive layer (X2), from the viewpoint of exhibiting excellent adhesive strength and thermal expansion in the heat-expandable base material (Y) by heat treatment. From the viewpoint of facilitating the formation of irregularities on the surface of the pressure-sensitive adhesive layer (X2) due to the expansion of the sex particles, it is preferably 1 to 100 μm, more preferably 2 to 70 μm, still more preferably 3 to 40 μm, still more preferably 5 to 5 It is 30 μm.

In the present specification, the thickness of the laminate is a value measured using a constant pressure thickness measuring device conforming to JIS K6783, Z1702, Z1709, and specifically, it is measured based on the method described in Examples. Means the value given.
Further, the thickness of each layer constituting the laminate may be measured by the same method as the thickness of the laminate described above, and for example, a cross section obtained by cutting the laminate in the thickness direction is observed with a scanning electron microscope. Then, the ratio of the thickness of each layer may be measured and calculated from the thickness of the laminate measured by the above method.

In the laminate of the pressure-sensitive adhesive sheet of the present invention, the ratio of the thickness of the heat-expandable base material (Y) to the thickness of the pressure-sensitive adhesive layer (X1) at 23 ° C. (heat-expandable base material (Y) / pressure-sensitive adhesive layer). (X1)) is preferably 0.2 or more, more preferably 0.5 or more, still more preferably 1.0 or more, still more preferably 5.0 or more, from the viewpoint of preventing the displacement of the object. Also, from the viewpoint of making an adhesive sheet that can be easily peeled off with a slight force when peeling off, it is preferably 1000 or less, more preferably 200 or less, still more preferably 60 or less, still more preferably 30 or less. ..
When the laminate of the pressure-sensitive adhesive sheet of one aspect of the present invention further contains a pressure-sensitive adhesive layer (X2), the ratio of the thickness of the heat-expandable base material (Y) to the thickness of the pressure-sensitive adhesive layer (X2) at 23 ° C. (The heat-expandable base material (Y) / adhesive layer (X2)) is also preferably 0.2 or more, more preferably 0.5 or more, still more preferably 1.0 or more, still more, from the same viewpoint. It is preferably 5.0 or more, preferably 1000 or less, more preferably 200 or less, still more preferably 60 or less, and even more preferably 30 or less.

As described above, in the laminated body of the pressure-sensitive adhesive sheet of the present invention, a mixed layer is formed between the two coating films in the energy ray irradiation process of the coating film, and the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) are formed. ) And the interface between the heat-expandable base material (Y) and the pressure-sensitive adhesive layer (X2) may become so obscured that they disappear.
When a mixed layer is formed between the two coating films and between the formed layers, for example, as described above, the cross section of the laminated body cut in the thickness direction is observed with a scanning electron microscope, and the thickness of each layer is observed. In the case of measuring each of the ratios, if a mixed layer is formed between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y), the intermediate point in the thickness direction of the mixed layer. The thickness ratio of each layer may be measured on the assumption that an interface exists on a surface parallel to the surface of the pressure-sensitive adhesive layer (X1) opposite to the heat-expandable base material (Y). ..

[Thermal expandable base material (Y)]
The heat-expandable base material (Y) contained in the pressure-sensitive adhesive sheet of the present invention is a layer formed by irradiating a coating film (y') composed of a composition (y) containing a resin and heat-expandable particles with energy rays. , A non-adhesive substrate.
In the present invention, whether or not the substrate is a non-adhesive substrate is determined if the probe tack value measured in accordance with JIS Z0237: 1991 with respect to the surface of the substrate of interest is less than 50 mN / 5 mmφ. The base material is judged to be a "non-adhesive base material".
Here, the probe tack value on the surface of the thermally expandable base material (Y) is usually less than 50 mN / 5 mmφ, but preferably less than 30 mN / 5 mmφ, more preferably less than 10 mN / 5 mmφ, and further preferably 5 mN / 5 mmφ. Is less than.
The specific method for measuring the probe tack value on the surface of the heat-expandable base material (Y) is the method described in Examples.

The thermally expandable base material (Y) contained in the pressure-sensitive adhesive sheet of the present invention is preferably a non-adhesive base material that satisfies the following requirement (1).
- Requirement (1): in the expansion starting temperature (t) of the heat expandable particles, thermally expandable base material (Y) the storage elastic modulus E of the '(t) is less than or equal to 1.0 × ¹⁰ 7 Pa.
In the present specification, the storage elastic modulus E'of the heat-expandable base material (Y) at a predetermined temperature means a value measured by the method described in the examples.
The above requirement (1) defines the storage elastic modulus E'of the heat-expandable base material (Y) when the pressure-sensitive adhesive sheet is peeled off.
When the pressure-sensitive adhesive sheet of the present invention is peeled off from the adherend, the heat-expandable particles in the heat-expandable base material (Y) are heated to a temperature equal to or higher than the expansion start temperature (t) of the heat-expandable particles. Expands to form irregularities on the surface of the heat-expandable base material (Y), and the pressure-sensitive adhesive layer (X1) laminated on the irregularities is also pushed up to form irregularities on the adhesive surface.
By forming irregularities on the adhesive surface of the adhesive layer (X1), the contact area between the adherend and the adhesive surface is reduced, and a space is created between the adherend and the adhesive surface. The adhesive sheet can be easily peeled off from the adherend with a slight force.

By the way, in order to improve the peelability of the pressure-sensitive adhesive sheet, it is necessary to facilitate the formation of irregularities on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1) when heated to a temperature equal to or higher than the expansion start temperature (t). For that purpose, the heat-expandable particles contained in the heat-expandable base material (Y) need to be adjusted so as to be easily expanded.

The above requirement (1) defines the coefficient of thermal expansion E'(t) of the heat-expandable base material at the expansion start temperature (t) of the heat-expandable particles. It can also be said to be an index showing the rigidity of the heat-expandable base material immediately before expansion.
That is, according to the study by the present inventors, the coefficient of thermal expansion E'(t) of the heat-expandable base material (Y) at the expansion start temperature (t) of the heat-expandable particles is 1.0 × 10 ⁷ Pa. By doing the following, when the thermal expansion particles are attempted to expand by heating to a temperature equal to or higher than the expansion start temperature (t), the expansion is not suppressed and is placed on the surface of the thermal expansion base material (Y). The unevenness of the adhesive surface of the laminated adhesive layer (X1) can be sufficiently formed.

Thermally expandable base material used in one embodiment of the present invention (Y) of the requirement (1) storage modulus E defined in '(t), from the above viewpoint, preferably not more than 9.0 × 10 6 ^Pa, more preferably Is 8.0 × 10 ⁶ Pa or less, more preferably 6.0 × 10 ⁶ Pa or less, and even more preferably 4.0 × 10 ⁶ Pa or less.
Further, from the viewpoint of suppressing the flow of expanded heat-expandable particles, improving the shape-retaining property of the unevenness formed on the adhesive surface of the pressure-sensitive adhesive layer (X1), and further improving the peelability, the heat-expandable group. The storage elastic modulus E'(t) specified in the requirement (1) of the material (Y) is preferably 1.0 × 10 ³ Pa or more, more preferably 1.0 × 10 ⁴ Pa or more, and further preferably 1. It is 0 × 10 ⁵ Pa or more.

Further, the heat-expandable base material (Y) contained in the pressure-sensitive adhesive sheet according to one aspect of the present invention preferably further satisfies the following requirement (2).
· Requirement (2): at 23 ° C., the storage modulus of the thermally expandable base material (Y) E '(23) is at 1.0 × ¹⁰ 6 Pa or more.

By using the heat-expandable base material (Y) that satisfies the above requirement (2), it is possible to prevent misalignment when an object such as a semiconductor chip is attached. In addition, when the object is attached, it is possible to prevent excessive sinking into the adhesive layer.

From the above viewpoint, the storage elastic modulus E'(23) of the heat-expandable base material (Y) specified in the above requirement (2) is preferably 5.0 × 10 ^{6 to} 5.0 × 10 ¹² Pa, more preferably. Is 1.0 × 10 ^{7 to} 1.0 × 10 ¹² Pa, more preferably 5.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Pa, and even more preferably 1.0 × 10 ^{8 to} 1.0 × 10. It is ¹⁰ Pa.

The composition (y), which is a material for forming the heat-expandable base material (Y), contains a resin and heat-expandable particles. In one aspect of the present invention, an additive for a base material contained in a base material of a general pressure-sensitive adhesive sheet may be contained, if necessary, as long as the effects of the present invention are not impaired.

(Thermal expandable particles)
As the heat-expandable particles used in the present invention, known heat-expandable particles can be used, and are appropriately selected depending on the use of the pressure-sensitive adhesive sheet.
The heat-expandable particles are microencapsulated foaming agents composed of an outer shell made of a thermoplastic resin and an inner shell that is contained in the outer shell and vaporizes when heated to a predetermined temperature. Is preferable.
Examples of the thermoplastic resin constituting the outer shell of the microencapsulating foaming agent include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethylmethacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone and the like.

Examples of the contained components contained in the outer shell include propane, butane, pentane, hexane, heptane, octane, nonane, decane, isobutane, isopentane, isohexane, isoheptan, isooctane, isononan, isodecane, cyclopropane, cyclobutane, and cyclopentane. , Cyclohexane, cycloheptan, cyclooctane, neopentane, dodecane, isododecane, cyclotridecane, hexylcyclohexane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecan , isotridecane, 4-methyldodecane, isotetradecane, isopentadecane, iso Hexadecane, 2,2,4,4,6,8,8-heptamethylnonane, isoheptadecane, isooctadecane, isononadecane , 2,6,10,14-tetramethylpentadecane, cyclotridecane , heptylcyclohexane , n- octylcyclohexane , Cyclopentadecane, nonylcyclohexane, decylcyclohexane, pentadecylcyclohexane, hexadecylcyclohexane, heptadecylcyclohexane, octadecylcyclohexane and the like.
These inclusion components may be used alone or in combination of two or more.

The average particle size of the heat-expandable particles used in one embodiment of the present invention before expansion at 23 ° C. is preferably 3 to 100 μm, more preferably 4 to 70 μm, still more preferably 6 to 60 μm, still more preferably 10 to 10. It is 50 μm.
The average particle size of the heat-expandable particles before expansion is the volume medium particle size (D ₅₀ ), and is a laser diffraction type particle size distribution measuring device (for example, manufactured by Malvern, product name “Mastersizer 3000”). In the particle distribution of the heat-expandable particles before expansion, the cumulative volume frequency calculated from the smaller particle size of the heat-expandable particles before expansion means the particle size corresponding to 50%.

The 90% particle diameter (D ₉₀ ) of the heat-expandable particles before expansion at 23 ° C. used in one aspect of the present invention is preferably 10 to 150 μm, more preferably 20 to 100 μm, still more preferably 25 to ₉₀ μm. Even more preferably, it is 30 to 80 μm.
The 90% particle size (D ₉₀ ) of the thermally expandable particles before expansion is the expansion measured using a laser diffraction type particle size distribution measuring device (for example, manufactured by Malvern, product name “Mastersizer 3000”). In the particle distribution of the previous heat-expandable particles, it means a particle size in which the cumulative volume frequency calculated from the smaller particle size of the heat-expandable particles before expansion corresponds to 90%.

The thermally expandable particles used in the present invention are preferably particles whose expansion start temperature (t) is adjusted to 120 to 250 ° C. The expansion start temperature (t) of the thermally expandable particles can be adjusted by appropriately selecting the type of the inclusion component.
In addition, in this specification, the expansion start temperature (t) of a heat-expandable particle means a value measured based on the following method.
[Measurement method of expansion start temperature (t) of thermally expandable particles]
To an aluminum cup with a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm, 0.5 mg of the heat-expandable particles to be measured are added, and an aluminum lid (diameter 5.6 mm, thickness 0. Prepare a sample on which 1 mm) is placed.
Using a dynamic viscoelasticity measuring device, the height of the sample is measured with a force of 0.01 N applied by a pressurizer from the upper part of the aluminum lid to the sample. Then, with a force of 0.01 N applied by the pressurizer, it is heated from 20 ° C. to 300 ° C. at a heating rate of 10 ° C./min, the amount of displacement of the pressurizer in the vertical direction is measured, and the displacement in the positive direction is measured. Let the displacement start temperature be the expansion start temperature (t).

The maximum volume expansion rate of the heat-expandable particles used in one embodiment of the present invention by heating above the expansion start temperature (t) is preferably 1.5 to 100 times, more preferably 2 to 80 times, still more preferably 2. It is 5 to 60 times, more preferably 3 to 40 times.

The content of the heat-expandable particles is preferably 1 to 40% by mass, more preferably 5 to 35% by mass, still more preferably 10 to 10% by mass, based on the total amount (100% by mass) of the active ingredient of the composition (y). It is 30% by mass, more preferably 15 to 25% by mass.

(resin)
The resin contained in the composition (y) may be a polymer capable of forming a non-adhesive heat-expandable base material (Y).
The resin contained in the composition (y) may be a non-adhesive resin or an adhesive resin.
That is, even if the resin contained in the composition (y) is an adhesive resin, the adhesive resin polymerizes with the polymerizable compound in the process of forming the heat-expandable base material (Y) from the composition (y). It suffices that the resin obtained by the reaction becomes a non-adhesive resin, and the thermosetting base material (Y) containing the resin becomes non-adhesive.

(Solvent-free resin composition (y1))
As the composition (y) used in one embodiment of the present invention, an oligomer having an ethylenically unsaturated group having a mass average molecular weight (Mw) of 50,000 or less, an energy ray-polymerizable monomer, and the above-mentioned heat-expandable particles are blended. Therefore, a solvent-free resin composition (y1) that does not contain a solvent can be mentioned.
In the solvent-free resin composition (y1), no solvent is blended, but the energy ray-polymerizable monomer contributes to the improvement of the plasticity of the oligomer.

The types, shapes, and amounts (contents) of the heat-expandable particles to be blended in the solvent-free resin composition (y1) are as described above.
The mass average molecular weight (Mw) of the oligomer contained in the solvent-free resin composition (y1) is 50,000 or less, preferably 1000 to 50,000, more preferably 2000 to 40,000, still more preferably 3000 to 35,000, and more. More preferably, it is 4000 to 30000.
The oligomer may have an ethylenically unsaturated group having a mass average molecular weight of 50,000 or less, but a urethane prepolymer (UP) described later is preferable.
As the oligomer, a modified olefin resin having an ethylenically unsaturated group can also be used.

Examples of the urethane prepolymer (UP) include a reaction product of a polyol and a multivalent isocyanate.

Examples of the polyol which is a raw material of the urethane prepolymer (UP) include an alkylene type polyol, an ether type polyol, an ester type polyol, an ester amide type polyol, an ester ether type polyol, and a carbonate type polyol.
These polyols may be used alone or in combination of two or more.
As the polyol used in one aspect of the present invention, a diol is preferable, an ester type diol, an alkylene type diol and a carbonate type diol are more preferable, and an ester type diol and a carbonate type diol are further preferable.

Examples of the ester-type diol include alkanediols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol; ethylene glycol, propylene glycol, and the like. One or more selected from diols such as diethylene glycol, alkylene glycol such as dipropylene glycol; and phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenylmethane-4 , 4'-dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, hetic acid, maleic acid, fumaric acid, itaconic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexa Examples thereof include dicarboxylic acids such as hydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and methylhexahydrophthalic acid, and one or more selected from these anhydrides.
Specifically, polyethylene adipatediol, polybutylene adipatediol, polyhexamethylene adipatediol, polyhexamethyleneisophthalatediol, polyneopentyl adipatediol, polyethylenepropylene adipatediol, polyethylenebutylene adipatediol, polybutylenehexamethylene adipatediol, Polydiethylene adipate diol, poly (polytetramethylene ether) adipate diol, poly (3-methylpentylene adipate) diol, polyethylene azelate diol, polyethylene sebacate diol, polybutylene azelate diol, polybutylene sebacate diol and polyneo Examples thereof include pentyl terephthalate diol.

Examples of the alkylene-type diol include alkanediols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol; ethylene glycol, propylene glycol, and the like. Examples thereof include alkylene glycols such as diethylene glycol and dipropylene glycol; polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polybutylene glycol; and polyoxyalkylene glycols such as polytetramethylene glycol.

Examples of the carbonate type diol include 1,4-tetramethylene carbonate diol, 1,5-pentamethylene carbonate diol, 1,6-hexamethylene carbonate diol, 1,2-propylene carbonate diol, and 1,3-propylene carbonate diol. , 2,2-Dimethylpropylene carbonate diol, 1,7-heptamethylene carbonate diol, 1,8-octamethylene carbonate diol, 1,4-cyclohexane carbonate diol and the like.

Examples of the polyisocyanate used as a raw material for the urethane prepolymer (UP) include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.
These multivalent isocyanates may be used alone or in combination of two or more.
Further, these polyvalent isocyanates may be a trimethylolpropane adduct-type modified product, a biuret-type modified product reacted with water, or an isocyanurate-type modified product containing an isocyanurate ring.

Among these, as the polyvalent isocyanate used in one embodiment of the present invention, diisocyanate is preferable, 4,4'-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2,6. More preferably, one or more selected from −toluene diisocyanate (2,6-TDI), hexamethylene diisocyanate (HMDI), and alicyclic diisocyanate.

Examples of the alicyclic diisocyanate include 3-isocyanate methyl-3,5,5-trimethylcyclohexylisocyanate (isophorone diisocyanate, IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexanediisocyanate, and 1,4-cyclohexane. Examples thereof include diisocyanate, methyl-2,4-cyclohexanediisocyanate and methyl-2,6-cyclohexanediisocyanate, but isophorone diisocyanate (IPDI) is preferable.

In one aspect of the present invention, the urethane prepolymer (UP) is a reaction product of a diol and a diisocyanate, and a linear urethane prepolymer having ethylenically unsaturated groups at both ends is preferable.
As a method for introducing an ethylenically unsaturated group into both ends of the linear urethane prepolymer, an NCO group at the terminal of the linear urethane prepolymer formed by reacting a diol and a diisocyanate compound and a hydroxyalkyl (meth) acrylate are used. There is a method of reacting.

Examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxy. Examples thereof include butyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.

(Modified olefin resin having ethylenically unsaturated group)
A modified olefin resin having an ethylenically unsaturated group is one in which an ethylenically unsaturated group is introduced into a polymer having at least a structural unit derived from an olefin monomer.
The olefin monomer is preferably an α-olefin having 2 to 8 carbon atoms, and specific examples thereof include ethylene, propylene, butylene, isobutylene, and 1-hexene.
Among these, ethylene and propylene are preferable.

Examples of the modified olefin resin having an ethylenically unsaturated group include an acrylic modified olefin resin obtained by subjecting an olefin resin to acrylic modification.
The acrylic-modified olefin-based resin obtained by subjecting the olefin-based resin to acrylic modification is a modified polymer obtained by graft-polymerizing an alkyl (meth) acrylate as a side chain to an unmodified olefin-based resin which is a main chain. Can be mentioned.
Specific unmodified olefin resin, for example, ultra low density polyethylene (VLDPE, density: 880 kg / ^{m 3} or more 910 kg / ^m less than ^3), low density polyethylene (LDPE, density: 910 kg / ^{m 3} or more 915 kg / m ^3), medium density polyethylene (MDPE, density: 915 kg / ^{m 3} or more 942Kg / ^{m 3),} high density polyethylene (HDPE, density: 942kg / ^{m 3} or higher), polyethylene resins such as linear low density polyethylene Polypropylene resin (PP); Polybutene resin (PB); Ethylene-propylene copolymer; Olefin-based elastomer (TPO); Poly (4-methyl-1-pentene) (PMP); Ethylene-vinyl acetate copolymer (EVA) ); Ethylene-vinyl alcohol copolymer (EVOH); olefin-based ternary copolymer such as ethylene-propylene- (5-ethylidene-2-norbornene); and the like.
The alkyl group of the above alkyl (meth) acrylate has preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and further preferably 1 to 12 carbon atoms.
Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and lauryl (meth) acrylate. Examples thereof include tridecyl (meth) acrylate and stearyl (meth) acrylate.

The total content of the oligomer and the energy ray-polymerizable monomer in the solvent-free resin composition (y1) is preferably 50 to 50% by mass with respect to the total amount (100% by mass) of the solvent-free resin composition (y1). It is 99% by mass, more preferably 60 to 95% by mass, still more preferably 65 to 90% by mass, and even more preferably 70 to 85% by mass.

Examples of the energy ray-polymerizable monomer include isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxy (meth) acrylate, cyclohexyl (meth) acrylate, and adamantan (). Alicyclic polymerizable compounds such as meta) acrylates and tricyclodecane acrylates; aromatic polymerizable compounds such as phenylhydroxypropyl acrylates, benzyl acrylates and phenolethylene oxide modified acrylates; tetrahydrofurfuryl (meth) acrylates, morpholine acrylates, N- Examples thereof include heterocyclic polymerizable compounds such as vinylpyrrolidone and N-vinylcaprolactam.
These energy ray-polymerizable monomers may be used alone or in combination of two or more.

The content ratio of the oligomer to the energy ray-polymerizable monomer in the solvent-free resin composition (y1) [oligomer / energy ray-polymerizable monomer] is preferably 20/80 to 90 / by mass ratio. 10, more preferably 30/70 to 85/15, still more preferably 35/65 to 80/20.

In one aspect of the present invention, the solvent-free resin composition (y1) preferably further contains a photopolymerization initiator.
By containing the photopolymerization initiator, the curing reaction can be sufficiently advanced even by irradiation with relatively low energy energy rays.

Examples of the photopolymerization initiator include 1-hydroxy-cyclohexyl-phenyl-ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzylphenyl sulfate, tetramethylthium monosulfide, and azobisisobutyro. Examples thereof include nitrile , dibenzyl, diacetyl, 8-chloroanthraquinone and the like.
These photopolymerization initiators may be used alone or in combination of two or more.

The blending amount of the photopolymerization initiator is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 4 parts by mass, and further, based on the total amount (100 parts by mass) of the oligomer and the energy ray-polymerizable monomer. It is preferably 0.02 to 3 parts by mass.

(Additive for base material)
The composition (y) used in one aspect of the present invention may contain an additive for a base material contained in a base material of a general pressure-sensitive adhesive sheet as long as the effects of the present invention are not impaired.
Examples of such base material additives include ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, slip agents, antiblocking agents, colorants and the like.
In addition, these additives for a base material may be used individually or in combination of 2 or more types.
When these base material additives are contained, the content of each base material additive is preferably 0.0001 to 20 with respect to 100 parts by mass of the total amount of the resin contained in the composition (y). It is by mass, more preferably 0.001 to 10 parts by mass.
In one aspect of the present invention, the composition (y) may contain a small amount of a diluting solvent such as water or an organic solvent together with the above-mentioned various active ingredients, but it is preferable not to contain the composition (y).

[Adhesive layer (X1)]
The pressure-sensitive adhesive layer (X1) contained in the pressure-sensitive adhesive sheet of the present invention is a layer formed by irradiating a coating film (x1') composed of the composition (x1) with energy rays, and has adhesiveness.
In one aspect of the present invention, the adhesive force on the adhesive surface of the pressure-sensitive adhesive layer (X1) at 23 ° C. before expansion of the heat-expandable particles is preferably 0.1 to 10.0 N / 25 mm, more preferably 0. It is .2 to 8.0 N / 25 mm, more preferably 0.4 to 6.0 N / 25 mm, and even more preferably 0.5 to 4.0 N / 25 mm.
When the adhesive strength is 0.1 N / 25 mm or more, the semiconductor chip or the like can be sufficiently fixed to the extent that the adherend can be prevented from being displaced in the next step such as the sealing step.
On the other hand, if the adhesive strength is 10.0 N / 25 mm or less, the peeling can be easily performed with a slight force by heating to the expansion start temperature (t) at the time of peeling.
The above adhesive strength means a value measured by the method described in Examples.

(Composition (x1))
The composition (x1) may be any composition capable of forming the pressure-sensitive adhesive layer (X1) by irradiation with energy rays. That is, the resin obtained by irradiating the composition (x1) with energy rays may be an adhesive resin.
That is, the component itself contained in the composition (x1) may be non-adhesive or may be adhesive. Even if the component contained in the composition (x1) is non-adhesive, the resin obtained in the process of forming the pressure-sensitive adhesive layer (X1) from the composition (x1) may be an adhesive resin.

As the adhesive resin obtained from the composition (x1), it is preferable that the resin alone has adhesiveness.
Specific examples of the adhesive resin include rubber resins such as acrylic resins, urethane resins, acrylic urethane resins, and polyisobutylene resins, polyester resins, olefin resins, silicone resins, and polyvinyl ether resins. And so on.
These adhesive resins may be used alone or in combination of two or more.
When these adhesive resins are copolymers having two or more kinds of structural units, the form of the copolymer is not particularly limited, and block copolymers, random copolymers, and graft copolymers are used. It may be any of the polymers.

In one aspect of the present invention, the surface of the pressure-sensitive adhesive layer (X1) is uneven due to the viewpoint of exhibiting excellent adhesive strength and the expansion of the heat-expandable particles in the heat-expandable base material (Y) by heat treatment. From the viewpoint of facilitating formation, the adhesive resin preferably contains an acrylic urethane-based resin.
The content ratio of the acrylic urethane resin in the adhesive resin is preferably 30 to 100% by mass, more preferably 50, based on the total amount (100% by mass) of the adhesive resin contained in the adhesive layer (X1). It is ~ 100% by mass, more preferably 70 to 100% by mass, and even more preferably 85 to 100% by mass. Hereinafter, the composition (x1) for obtaining the acrylic urethane resin will be described.

The acrylic urethane resin can be produced by irradiating the composition (x1) containing the following (1) polymerization component with energy rays. The composition (x1) may contain (2) a polymerization initiator and (3) various additives, if necessary.
(1) Polymerization component The composition (x1) is at least one polymerization component selected from the group consisting of a polymerizable vinyl monomer, a polymerizable vinyl prepolymer, a polyfunctional (meth) acrylate monomer and a polyfunctional (meth) acrylate oligomer. Contains.

The composition (x1) preferably contains at least a polymerizable vinyl monomer and a polyfunctional (meth) acrylate oligomer among the above-mentioned four kinds of polymerization components. When the polymerization component contains these compounds, the cohesive force of the obtained pressure-sensitive adhesive can be improved, and the adhesive residue on the adherend can be suppressed.

(1-1) Polymerizable Vinyl Monomer The polymerizable vinyl monomer is not particularly limited as long as it has a vinyl group-containing group, and conventionally known ones can be appropriately used. The polymerizable vinyl monomer in the present embodiment means a polymerizable vinyl monomer having one vinyl group-containing group, and does not overlap with the polyfunctional (meth) acrylate monomer described later.

Specific examples of the polymerizable vinyl monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and cyclohexyl (meth). Acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) (Meta) acrylate having no functional group other than vinyl group in the molecule such as acrylate, isobornyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, polyoxyalkylene modified (meth) acrylate Can be mentioned. Among these, butyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, benzyl acrylate and cyclohexyl acrylate are preferably used, and 2-ethylhexyl acrylate or isobornyl acrylate is particularly preferable.

Further, the polymerizable vinyl monomer may further have a functional group other than the vinyl group-containing group in the molecule. Examples of the functional group include an amide group and the like in addition to the above-mentioned active hydrogen group, that is, a hydroxy group, a carboxy group, a thiol group, and a primary or secondary amino group. Examples of the amino group include a tertiary amino group. Specific examples of the polymerizable vinyl monomer having such a functional group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) butyl. ) Acrylate, hydroxyalkyl (meth) acrylates such as 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; acrylamide, methacrylicamide, N-methylacrylamide, N-methylmethacrylicamide, N-methylolacrylamide, Hydroxy group-containing acrylamides such as N-methylolmethacrylamide; NN-dimethyl (meth) acrylamide, NN-diethyl (meth) acrylamide, N- (meth) acryloylmorpholine, (meth) acrylic acid NN -Diethylaminoethyl; acrylate-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, it is preferable to use 2-hydroxyethyl acrylate.

In addition, as other polymerizable vinyl monomers, vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene and α-methylstyrene. Such as styrene-based monomers; diene-based monomers such as butadiene, isoprene, and chloroprene; nitrile-based monomers such as acryliconitrile and methacrylonitrile; acrylamide, methacrylicamide, N-methylacrylamide, and N-methylmethacrylicamide. , N-N-dimethyl (meth) acrylamide, N-N-diethyl (meth) acrylamide, N- (meth) acryloylmorpholine, N-vinylpyrrolidone and other amide-based monomers; (meth) acrylate NN Examples thereof include a tertiary amino group-containing monomer such as −diethylaminoethyl and N- (meth) acryloylmorpholine.

(1-2) Polymerizable Vinyl Prepolymer The polymerizable vinyl prepolymer is not particularly limited, and conventionally known ones can be appropriately used, but the above-mentioned polymerizable vinyl monomer is polymerized. It is preferable to use a polymerizable vinyl prepolymer.

When a polymerizable vinyl prepolymer is obtained by polymerizing the above-mentioned polymerizable vinyl monomer, one type of the monomer may be polymerized alone, or a plurality of types may be copolymerized.

Further, the polymerizable vinyl prepolymer may be obtained by free radical polymerization or by living polymerization, and in particular, the RAFT (Reversible Addition-Fragmentation Chain Transfer Polymerization) terminal is left. It may be a polymer.

The mass average molecular weight of the polymerizable vinyl prepolymer is preferably 6,000 or more, particularly preferably 7,500 or more, and further preferably 10,000 or more. The mass average molecular weight is preferably 1,500,000 or less, particularly preferably 1,000,000 or less, and further preferably 100,000 or less. When the mass average molecular weight is within the above range, the viscosity of the composition (x1) can be easily set within a desired range.

(1-3) Polyfunctional (meth) acrylate monomer The polyfunctional (meth) acrylate monomer is not particularly limited, and conventionally known ones can be appropriately used.

In particular, as the polyfunctional (meth) acrylate monomer, a monomer having two or more (meth) acryloyl groups in one molecule can be preferably mentioned. Examples of such monomers include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and the like. Neopentyl glycol adipate di (meth) acrylate, neopentyl glycol di (meth) acrylate of hydroxypivalate, dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide-modified di (meth) phosphate ) Acrylate, di (acryloxyethyl) isocyanurate, allylated cyclohexyldi (meth) acrylate, trimethylpropanthry (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate , pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth) acrylate, tris (acryloyloxyethyl) isocyanurate, bis (acryloxy ethyl) hydroxyethyl isocyanurate, isocyanuric acid ethylene oxide modified diacrylate, isocyanuric acid ethylene oxide-modified triacrylate, .epsilon.-caprolactone-modified tris (acryloyloxyethyl) isocyanurate, diglycerol tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipenta Examples thereof include erythritol hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate.

(1-4) Polyfunctional (meth) acrylate oligomer The polyfunctional (meth) acrylate oligomer is not particularly limited, and conventionally known ones can be appropriately used, but two or more in one molecule. It is preferable to use a polyfunctional (meth) acrylate oligomer having the (meth) acryloyl group of. Examples of such oligomers include oligomers such as urethane acrylate-based, polyester acrylate-based, epoxy acrylate-based, polyether acrylate-based, polybutadiene acrylate-based, and silicone acrylate-based oligomers.

The urethane acrylate-based oligomer is a polyurethane oligomer obtained by reacting a compound such as a polyalkylene polyol, a polyether polyol, a polyester polyol, a hydrogenated isoprene having a hydroxy group terminal, or a hydrogenated butadiene having a hydroxy group end with a polyisocyanate. Can be obtained by esterifying with (meth) acrylic acid or (meth) acrylic acid derivative.

Here, examples of the polyalkylene polyol used for producing the urethane acrylate-based oligomer include polypropylene glycol, polyethylene glycol, polybutylene glycol, polyhexylene glycol and the like, and it is particularly preferable to use polypropylene glycol. When the number of functional groups of the obtained urethane acrylate-based oligomer is 3 or more, glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, diethylenetriamine, sorbitol, sucrose and the like may be appropriately combined.

Examples of polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate and diphenyl diisocyanate; alicyclic diisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate. Among these, it is preferable to use an aliphatic diisocyanate, and it is particularly preferable to use hexamethylene diisocyanate. The polyisocyanate is not limited to bifunctional, and trifunctional or higher functional ones can also be used.

Examples of the (meth) acrylic acid derivative include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate, 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, and 1,1-bis (acrylate). Loxymethyl) ethyl isocyanate and the like can be mentioned, and 2-isocyanate ethyl acrylate is particularly preferable.

As another method for producing a urethane acrylate-based oligomer, a hydroxy group contained in a compound such as a polyalkylene polyol, a polyether polyol, a polyester polyol, a hydrogenated isoprene having a hydroxy group terminal, and a hydrogenated butadiene having a hydroxy group terminal, and an isocyanate alkyl ( Urethane acrylate-based oligomers can also be obtained by the reaction between the -N = C = O moiety of the meta) acrylate. In this case, as the isocyanate alkyl (meth) acrylate, the above-mentioned 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, 1,1-bis (acryloxymethyl) ethyl isocyanate and the like can be used.

The polyester acrylate-based oligomer can be obtained, for example, by esterifying the hydroxy group of a polyester oligomer having hydroxy groups at both ends obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid, or by polyvalent. It can be obtained by esterifying the hydroxy group at the end of the oligomer obtained by adding an alkylene oxide to a carboxylic acid with (meth) acrylic acid.

The epoxy acrylate-based oligomer can be obtained, for example, by reacting (meth) acrylic acid with the oxylan ring of a bisphenol type epoxy resin or a novolak type epoxy resin having a relatively low molecular weight to esterify it. It is also possible to use a carboxyl-modified epoxy acrylate-based oligomer in which the epoxy acrylate-based oligomer is partially modified with a dibasic carboxylic acid anhydride.

The polyether acrylate-based oligomer can be obtained, for example, by esterifying the hydroxy group of the polyether polyol with (meth) acrylic acid.

The mass average molecular weight of the polyfunctional (meth) acrylate oligomer is preferably 10,000 or more, and particularly preferably 20,000 or more. The mass average molecular weight is preferably 350,000 or less, and particularly preferably 200,000 or less.
(2) Polymerization Initiator The composition (x1) according to the present embodiment preferably further contains a polymerization initiator. By containing the polymerization initiator, the composition (x1) can be efficiently cured.

The polymerization initiator is not particularly limited, and conventionally known ones can be used, but it is preferable to select the polymerization initiator according to the mode of curing of the composition (x1). That is, when the composition (x1) is cured by irradiation with ultraviolet rays as active energy rays, it is preferable to use a photopolymerization initiator as the polymerization initiator. When the composition (x1) is cured by heating, it is preferable to use a thermal polymerization initiator. A photopolymerization initiator and a thermal polymerization initiator may be used in combination.

Examples of photopolymerization initiators include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-Diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (methylthio) phenyl]- 2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2 -Methylanthraquinone, 2-ethylanthraquinone, 2-tershary-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, Benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2,4,6-trimethylbenzoyl- Examples thereof include diphenyl-phosphine oxide . These may be used alone or in combination of two or more.

Examples of the thermal polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, peroxides such as benzoyl peroxide and laurium peroxide, and azo compounds such as azobisisobutyronitrile. These may be used alone or in combination of two or more.

The content of the polymerization initiator in the composition (x1) is preferably 0.1 part by mass or more, particularly preferably 0.3 part by mass or more, based on 100 parts by mass of the polymerization component. Is preferably 0.5 parts by mass or more. Further, the content is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 3 parts by mass or less with respect to 100 parts by mass of the polymerization component. When the content is 0.1 part by mass or more, the curing of the composition (x1) can be efficiently promoted. On the other hand, when the content is 10 parts by mass or less, it becomes possible to eliminate or reduce the polymerization initiator that remains unreacted in curing, and it becomes easy to set the obtained pressure-sensitive adhesive to desired physical properties.

(3) Various Additives The composition (x1) contains various additives such as a silane coupling agent, an ultraviolet absorber, an antistatic agent, a tackifier, an antioxidant, a light stabilizer, and a softening agent, if desired. Fillers, refractive index adjusters and the like can be added.
When these additives are contained, the content of each additive is independently, preferably 0.0001 to 20 parts by mass, and more preferably 0.001 to 10 parts by mass with respect to 100 parts by mass of the polymerization component. Is.
In one aspect of the present invention, the composition (x1) may contain a small amount of a diluting solvent such as water or an organic solvent together with the above-mentioned various active ingredients, but it is preferable not to contain the composition (x1).

In the pressure-sensitive adhesive sheet of the present invention, since the heat-expandable base material (Y) contains the heat-expandable particles, the pressure-removable material is exhibited, so that the composition (x1) which is the material for forming the pressure-sensitive adhesive layer (X1) It does not need to contain thermally expandable particles. However, for the purpose of assisting the heat peeling property, the composition (x1) may contain a small amount of heat-expandable particles as long as the effect of the present invention is not impaired, and the content of the heat-expandable particles is the composition (x1). ) Is preferably 0 to 50% by mass, more preferably 0 to 20% by mass, still more preferably 0 to 10% by mass, based on the total amount (100% by mass) of the active ingredient.

[Adhesive layer (X2)]
The pressure-sensitive adhesive layer (X2) contained in the pressure-sensitive adhesive sheet according to one aspect of the present invention is a layer formed from the composition (x2) and has adhesiveness.
The suitable physical properties of the pressure-sensitive adhesive layer (X2) are the same as those of the pressure-sensitive adhesive layer (X1).
Further, as the composition (x2) which is a material for forming the pressure-sensitive adhesive layer (X2), the same composition (x1) as which is a material for forming the pressure-sensitive adhesive layer (X1) can be used.

[Release material]
As the release materials 13, 131, and 132 of the pressure-sensitive adhesive sheet of one aspect of the present invention, a release sheet that has been subjected to double-sided release treatment, a release sheet that has been subjected to single-sided release treatment, or the like is used, and is used on a base material for the release material. Examples thereof include those coated with a release agent.
In the pressure-sensitive adhesive sheet of one aspect of the present invention, it is preferable that the two release materials 131 and the release material 132 that sandwich the laminate are adjusted so that the difference in release force is different.

Examples of the base material for the release material include papers such as high-quality paper, glassin paper, and kraft paper; polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin, and olefins such as polypropylene resin and polyethylene resin. Plastic films such as resin films; etc. may be mentioned.

Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins.

The thickness of the release material is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 170 μm, and even more preferably 35 to 80 μm.

≪Manufacturing method of adhesive sheet≫
The method for producing the pressure-sensitive adhesive sheet of the present invention is preferably a method including the following steps (1A) and (2A).
The method for producing an adhesive sheet of the present invention can reduce the number of steps for producing an adhesive sheet as compared with the conventional production method, so that productivity can be improved.
Step (1A): A step of directly laminating a coating film (x1') composed of the composition (x1) and a coating film (y') composed of the composition (y) in this order.
Step (2A): The coating film (x1') and the coating film (y') are simultaneously irradiated with energy rays, and the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) are directly laminated in this order. The process of forming a laminated body.
Hereinafter, steps (1A) and (2A) will be described.

In the step (1A), as a method of forming the coating film (x1') and the coating film (y'), for example, after forming the coating film (x1'), the coating film (y) is formed on the coating film (x1'). A method of sequentially forming the coating film (x1') may be used, but from the viewpoint of productivity and interfacial adhesion, the composition (x1) and the composition (y) are simultaneously applied to form the coating film (x1') and the coating film (x1'). A method of forming y') at the same time is preferable.
From the viewpoint of handleability, it is preferable that the coating film (x1') or the coating film (y') is formed on the peeling surface of the release material.

When the coating film (x1') and the coating film (y') are sequentially formed, examples of the coater used for coating the composition (x1) and the composition (y) include a spin coater, a spray coater, and a bar coater. Examples include knife coaters, roll coaters, knife roll coaters, blade coaters, gravure coaters, curtain coaters, and die coaters.

Examples of the coater used when the composition (x1) and the composition (y) are applied at the same time include a multi-layer coater, and specific examples thereof include a multi-layer curtain coater and a multi-layer die coater. Among these, a multi-layer die coater is preferable from the viewpoint of operability.

In the step (2A), the coating film (x1') and the coating film (y') are simultaneously irradiated with energy rays to form the laminate.
In this energy ray irradiation process, a mixed layer is formed at the interface between the coating film (x1') and the coating film (y'), and the adhesive resin in the coating film (x1') and the resin in the coating film (y') are formed. It is considered that the interfacial adhesion between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) is improved by irradiating with energy rays and curing in a state of being entangled with each other.

Examples of the energy ray irradiation of the coating film in the step (2A) include ultraviolet irradiation and electron beam irradiation, but from the viewpoint of not causing an unnecessary reaction, ultraviolet irradiation is preferable.
UV irradiation, high-pressure mercury lamp, a metal halide lamp, an electrodeless UV lamp, UV-LED, can be effected by a xenon lamp or the like, the dose of ultraviolet ray is illuminance 50 mW / cm ² or more, is 1000 mW / cm ² or less Is preferable. Amount is preferably at 50 mJ / cm ² or more, more preferably 80 mJ / cm ² or more, and particularly preferably 200 mJ / cm ² or more. Further, the light amount is preferably at 10000 mJ / cm ² or less, more preferably 5000 mJ / cm ² or less, particularly preferably 2000 mJ / cm ² or less. On the other hand, the electron beam irradiation can be performed by an electron beam accelerator or the like, and the electron beam irradiation amount is preferably 10 grad or more and 1000 grad or less.

When producing a pressure-sensitive adhesive sheet having a laminate further containing a pressure-sensitive adhesive layer (X2), which is a pressure-sensitive adhesive sheet according to one aspect of the present invention, the production method of the present invention is a pressure-sensitive adhesive for a heat-expandable base material (Y). The method is not particularly limited as long as the method further includes a step of forming the pressure-sensitive adhesive layer (X2) on the surface opposite to the layer (X1). For example, the following production method of the embodiment (A) and the production method of the embodiment (B) can be mentioned, from the viewpoint of productivity and interfacial adhesion between the heat-expandable base material (Y) and the pressure-sensitive adhesive layer (X2). Therefore, the production method of the embodiment (B) is preferable.

The production method of the embodiment (A) includes the following steps (3A-1) or (3A-2) in addition to the above-mentioned steps (1A) and (2A).
Step (3A-1): A coating film (x2') composed of the composition (x2) is formed on the surface of the heat-expandable base material (Y) obtained in the step (2A), and the coating film is formed. A process of irradiating (x2') with energy rays.
-Step (3A-2): The composition (x2) is applied on the peeling surface of the release material to form a coating film (x2'), and the coating film (x2') is irradiated with energy rays to adhere. A step of forming the agent layer (X2) in advance and directly attaching the pressure-sensitive adhesive layer (X2) formed on the release material onto the surface of the heat-expandable base material (Y) obtained in the step (2A). ..

The method for forming the coating film (x2') in the steps (3A-1) and (3A-2) is, for example, a spin coater, a spray coater, a bar coater, a knife coater, a roll coater, a knife roll coater, a blade coater, and a gravure coater. , Curtain coater, die coater and the like.

The energy ray irradiation conditions of the coating film (x2') in the steps (3A-1) and (3A-2) are the same as those of the energy ray irradiation of the coating film in the step (2A).

In the steps (3A-1) and (3A-2), the step (3A-1) is preferable from the viewpoint of productivity and interfacial adhesion between the heat-expandable base material (Y) and the pressure-sensitive adhesive layer (X2).

The production method of the embodiment (B) includes the following steps (1B) and (2B).
Step (1B): A coating film (x1') composed of the composition (x1), a coating film (y') composed of the composition (y), and a coating film (x2') composed of the composition (x2). The process of directly laminating and forming in this order.
Step (2B): The coating film (x1'), the coating film (y'), and the coating film (x2') are simultaneously irradiated with energy rays to obtain the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y). , And a step of forming a laminate in which the pressure-sensitive adhesive layer (X2) is directly laminated in this order.
Hereinafter, steps (1B) and (2B) will be described.

In the step (1B), as a method for forming the coating film (x1'), the coating film (y'), and the coating film (x2'), for example, after forming the coating film (x1'), the coating film (x1') is formed. A method of sequentially forming a coating film (y') on the coating film (y') and further forming a coating film (x2') on the coating film (y') may be used, but from the viewpoint of productivity, the composition ( A method in which the x1), the composition (y), and the composition (x2) are simultaneously applied to form the coating film (x1'), the coating film (y'), and the coating film (x2') at the same time is preferable.
From the viewpoint of handleability and productivity, it is preferable to form the coating film (x1') or (x2') on the peeling surface of the release material.

Examples of the coater used when sequentially forming each coating film include the above-mentioned coaters and the like.
Further, examples of the coater used when simultaneously applying the composition (x1), the composition (y), and the composition (x2) include a multilayer coater capable of simultaneously applying at least three or more layers. Specific examples thereof include a multi-layer curtain coater and a multi-layer die coater. Among these, a multi-layer die coater capable of applying three or more layers at the same time is preferable from the viewpoint of operability.

In the step (2B), the coating film (x1'), the coating film (y'), and the coating film (x2') are simultaneously irradiated with energy rays to form the laminate.
In this energy ray irradiation process, a mixed layer is formed at the interface between the coating film (x1') and the coating film (y'), and the adhesive resin in the coating film (x1') and the resin in the coating film (y') are formed. By irradiating with energy rays and curing in a state of being intertwined with each other, the interfacial adhesion between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y) is improved, and the coating film (y') and the coating film are also coated. A mixed layer is formed at the interface with (x2'), and the resin in the coating film (y') and the adhesive resin in the coating film (x2') are entangled with each other. It is considered that the interfacial adhesion between the expandable base material (Y) and the pressure-sensitive adhesive layer (X2) is improved.

The energy ray irradiation of the coating film in the step (2B) is the same as the energy ray irradiation of the coating film in the step (2A).

≪Use of adhesive sheet≫
The adhesive sheet of the present invention is useful as a means for temporarily fixing an object in the manufacturing process of building materials, interior materials, electronic parts, etc., and can be suitably used as a means for temporarily fixing a semiconductor chip in the manufacturing process of a semiconductor device. it can. In particular, a semiconductor package (FOWLP (Fan out Wafer)) in which a rewiring layer is provided on the surface of a semiconductor chip sealed with a sealing resin and the solder balls and the semiconductor chip are electrically connected via the rewiring layer. It can be suitably used as a temporary fixing means at the time of manufacturing) (called Level Package).

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples. The physical property values in the following production examples and examples are values measured by the following methods.

<Mass average molecular weight (Mw)>
It was measured under the following conditions using a gel permeation chromatograph device (manufactured by Tosoh Corporation, product name "HLC-8020"), and the value measured in terms of standard polystyrene was used.
(Measurement condition)
-Column: "TSK guard volume HXL-L""TSK gel G2500HXL""TSK gel G2000HXL""TSK gel G1000HXL" (all manufactured by Tosoh Corporation) are connected in sequence.-Column temperature: 40 ° C.
・ Developing solvent: tetrahydrofuran ・ Flow rate: 1.0 mL / min

<Thickness of laminate>
The measurement was performed using a constant pressure thickness measuring instrument (model number: "PG-02J", standard: JIS K6783, Z1702, Z1709) manufactured by Teclock Co., Ltd.
Specifically, after measuring the total thickness of the pressure-sensitive adhesive sheet to be measured, the value obtained by subtracting the thickness of the release material measured in advance was defined as the "thickness of the laminated body".

<Thickness of each layer>
Using a scanning electron microscope (manufactured by Hitachi, Ltd., product name "S-4700"), observe the cross section of the laminate in the thickness direction, and the pressure-sensitive adhesive layer (X1) and heat with respect to the thickness of the laminate. The thickness ratios of the expandable base material (Y) and the pressure-sensitive adhesive layer (X2) were measured.
Then, based on the thickness ratio of each layer, the thickness of each layer was calculated from the measured value of the "thickness of the laminated body" measured by the above method.

<Average particle size of thermally expandable particles (D ₅₀ ), 90% particle size (D ₉₀ )>
Using a laser diffraction type particle size distribution measuring device (for example, manufactured by Malvern, product name “Mastersizer 3000”), the particle distribution of the thermally expandable particles before expansion at 23 ° C. was measured.
Then, the particle diameters corresponding to the cumulative volume frequencies of 50% and 90% calculated from the smaller particle diameter of the particle distribution are set to "average particle diameter of thermally expandable particles (D ₅₀ )" and "thermally expandable particles", respectively. 90% particle size (D ₉₀ ).

<Probe tack value>
Laminated sample (heavy release film / heat expandable base material / light release film) so that the heat-expandable base material to be measured has a thickness of 20 μm while being sandwiched between the heavy release film and the light release film described later. It was created. The prepared sample was cut into squares having a side of 10 mm and then allowed to stand in an environment of 23 ° C. and 50% RH (relative humidity) for 24 hours to remove the light release film and the heavy release film, which was used as a test sample.
Then, in an environment of 23 ° C. and 50% RH (relative humidity), a tacking tester (manufactured by Japanese Industrial Standards Co., Ltd., product name "NTS-4800") is used to determine the probe tack value on the surface of the test sample. , JIS Z0237: 1991.
Specifically, a stainless steel probe having a diameter of 5 mm is brought into contact with the surface of the test sample for 1 second with a contact load of 0.98 N / cm ² , and then the probe is brought into contact with the surface of the test sample at a speed of 10 mm / sec. The force required to separate it from the surface was measured. Then, the measured value was used as the probe tack value of the test sample.

<Storage modulus of thermal expansion material E'>
The heat-expandable base material to be measured had a size of 5 mm in length × 30 mm in width × 200 μm in thickness, and the one from which the release material was removed was used as a test sample.
Using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, product name "DMAQ800"), test start temperature 0 ° C, test end temperature 300 ° C, temperature rise rate 3 ° C / min, frequency 1 Hz, amplitude 20 μm The storage elastic modulus E'of the test sample at a predetermined temperature was measured under the conditions of.

<Interfacial adhesion>
The adhesive sheets produced in Examples and Comparative Examples were cut into a size of 50 mm in length × 30 mm in width. Then, the evaluation was made in accordance with JIS K5600-5-6.
According to the following criteria, at two interfaces, the interface between the pressure-sensitive adhesive layer (X1) and the heat-expandable base material (Y), and the interface between the pressure-sensitive adhesive layer (X2) and the heat-expandable base material (Y). Adhesion was evaluated.
-A: The classification by JIS K5600-5-6 was "0 (best)" at both interfaces.
-B: At least one of the interfaces was classified as "1" to "4" according to JIS K5600-5-6.
-F: At least one of the interfaces was classified as "5 (worst)" according to JIS K5600-5-6.

<Measurement of adhesive strength of adhesive sheet before and after heating>
A 50 μm-thick polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name “Cosmo Shine A4100”) was placed on the adhesive surface of the exposed adhesive layer (X2) by removing the light release film of the produced adhesive sheet. ) Was laminated to form an adhesive sheet with a base material. Then, the heavy release film of the adhesive sheet was also removed, and the film was attached to a stainless steel plate (SUS304 No. 360 polished) as an adherend, and allowed to stand for 24 hours in an environment of 23 ° C. and 50% RH (relative humidity). The one was used as a test sample.
Then, using the above test sample, in an environment of 23 ° C. and 50% RH (relative humidity), at 23 ° C. at a tensile speed of 300 mm / min by a 180 ° peeling method based on JIS Z0237: 2000. Adhesive strength was measured.
Further, the above test sample is heated on a hot plate at 240 ° C., which is equal to or higher than the expansion start temperature (208 ° C.) of the thermally expandable particles, for 3 minutes in a standard environment (23 ° C., 50% RH (relative humidity)). Then, based on JIS Z0237: 2000, the adhesive strength after heating at a tensile speed of 300 mm / min and above the expansion start temperature was also measured by a 180 ° peeling method.
When it was difficult to measure the adhesive force so that it could not be attached to the stainless steel plate as the adherend, it was set as "unmeasurable" and the adhesive force was 0 (N / 25 mm).

The details of the heat-expandable particles and the release material used in the formation of each layer in the following production examples are as follows.

<Thermal expandable particles>
-Thermal expandable particles (i): manufactured by Kureha Co., Ltd., product name "S2640", expansion start temperature (t) = 208 ° C., average particle diameter (D ₅₀ ) = 24 μm, 90% particle diameter (D ₉₀ ) = 49 μm. ..
<Release material>
-Heavy release film: manufactured by Lintec Corporation, product name "SP-PET382150", polyethylene terephthalate (PET) film provided with a release agent layer formed from a silicone-based release agent on one side, thickness: 38 μm.
-Light release film: manufactured by Lintec Corporation, product name "SP-PET381031", PET film provided with a release agent layer formed from a silicone-based release agent on one side, thickness: 38 μm.

Production Example 1 (Preparation of composition (x1))
(1) Synthesis of urethane acrylate-based oligomer 100 parts by mass of polypropylene glycol having a mass average molecular weight of 3000 (solid content conversion value; the same applies hereinafter), 4 parts by mass of hexamethylene diisocyanate, and 0.02 parts by mass of dioctyltin dilaurate are mixed. , 80 ° C. for 6 hours to obtain a reaction product. When the IR spectrum of the obtained reactant was measured by infrared spectroscopy, it was confirmed that the isocyanate group had almost disappeared.
Then, 1 part by mass of 2-isocyanate ethyl acrylate was mixed with the total amount of the obtained reaction product, and the mixture was stirred at 80 ° C. for 3 hours to obtain a urethane acrylate-based oligomer. When the IR spectrum of the obtained urethane acrylate-based oligomer was measured by infrared spectroscopy, it was confirmed that the isocyanate groups had almost disappeared. Moreover, when the molecular weight of the obtained urethane acrylate-based oligomer was measured by the method described later, the mass average molecular weight (Mw) was 25,000.
(2) Preparation of liquid mixture As described above, 40 parts by mass of 2-ethylhexyl acrylate as a polymerizable vinyl monomer, 20 parts by mass of isobornyl acrylate as a polymerizable vinyl monomer, and a polyfunctional (meth) acrylate oligomer. A liquid mixture was obtained by mixing with 40 parts by mass of the prepared urethane acrylate-based oligomer and stirring.
(3) Preparation of Energy Ray Curable Acrylic Copolymer (i) 100 parts by mass of the liquid mixture prepared above (solid content conversion value; the same applies hereinafter) and 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator (Manufactured by BASF, product name "Irgacure 184") By mixing with 0.5 parts by mass, a solvent-free composition (x1) of an energy ray-curable acrylic pressure-sensitive adhesive was obtained.
As the composition (x2) as a material for forming the layer (X2) described later, the same composition as the composition (x1) described here was used.

Production Example 2 (Preparation of composition (y))
2-Hydroxyethyl acrylate is reacted with the terminal isocyanate urethane prepolymer obtained by reacting the ester-type diol with isophorone diisocyanate (IPDI) to obtain a bifunctional acrylic urethane-based oligomer having a mass average molecular weight (Mw) of 5000. Obtained.
Then, 40% by mass (solid content ratio) of the acrylic urethane-based oligomer synthesized above, 40% by mass (solid content ratio) of isobornyl acrylate (IBXA) and phenylhydroxypropyl acrylate (HPPA) as energy ray-polymerizable monomers. ) 20% by mass (solid content ratio) is blended, and 1-hydroxycyclohexylphenylketone (BASF) is further used as a photopolymerization initiator with respect to the total amount (100 parts by mass) of the acrylic urethane-based oligomer and the energy ray-polymerizable monomer. , Product name "Irgacure 184") 2.0 parts by mass (solid content ratio), and 0.2 parts by mass (solid content ratio) of phthalocyanine-based pigment as an additive to prepare an energy ray-curable composition. Prepared.
Then, the heat-expandable particles (i) were blended with the energy ray-curable composition to prepare a solvent-free composition (y) containing no solvent.
The content of the heat-expandable particles (i) was 20% by mass with respect to the total amount (100% by mass) of the composition (y).

Example 1
(1) Formation of coating film The composition (x1) prepared in Production Example 1, the composition (y) prepared in Production Example 2, and Production Example 1 are placed on the release agent layer of the heavy release film which is a release material. The composition (x2) prepared in the above was simultaneously applied in this order using a multilayer die coater (width: 250 mm) to obtain a coating film (x1'), a coating film (y') and a coating film (x2'). It was formed at the same time in this order.
(2) Energy ray irradiation treatment The formed coating film (x1'), coating film (y') and coating film (x2') have an illuminance of 160 mW / cm ² and a light amount of 1000 mJ / cm ² using an ultraviolet irradiation device. The coating film was cured by irradiating with ultraviolet rays under the conditions to form a laminated body in which the layer (X1), the layer (Y) and the layer (X2) were directly laminated in order from the release agent layer of the heavy release film. The above-mentioned illuminance and light intensity at the time of ultraviolet irradiation are values measured using an illuminance / light intensity meter (manufactured by EIT, product name "UV Power Pack II").
Then, the release agent layer of the light release film was laminated on the surface of the exposed layer (X2) to obtain the pressure-sensitive adhesive sheet of Example 1.

Example 2
Of the composition (x1), the composition (y) and the composition (x2) so that the thicknesses of the layer (X1), the layer (Y) and the layer (X2) are the thicknesses shown in Table 1, respectively. An adhesive sheet of Example 2 was obtained by using the same method as in Example 1 except that the coating amount was changed.

Comparative Example 1
A coating film (x1') composed of the composition (x1) prepared in Production Example 1 was formed on the release agent layer of the heavy release film which is a release material, and an illuminance of 160 mW / cm ² was used using an ultraviolet irradiation device. The coating film was cured by irradiating with ultraviolet rays under the condition of a light amount of 1000 mJ / cm ² , and a layer (X1) was formed.
Further, a coating film (y') composed of the composition (y) prepared in Production Example 2 is formed on the release agent layer of the light release film prepared separately from the release film on the layer (X1), and irradiated with ultraviolet rays. The layer (Y) was formed by irradiating with ultraviolet rays under the same irradiation conditions as described above using the apparatus.
Further, a coating film (x2') is formed on the release agent layer of the separately prepared light release film using the composition (x2) prepared in Production Example 1, and the above-mentioned irradiation is performed using an ultraviolet irradiation device. A layer (X2) was formed by irradiating with ultraviolet rays under the same conditions.
Then, the layer (Y) is laminated on the surface of the exposed layer (X1), the light release film on the layer (Y) is further removed, and the layer is placed on the surface of the exposed layer (Y). (X2) was laminated to obtain an adhesive sheet of Comparative Example 1 in which a heavy release film, a layer (X1), a layer (Y), a layer (X2), and a light release film were laminated in this order.
The thickness of the laminated body of the pressure-sensitive adhesive sheets produced in Examples and Comparative Examples, and the thicknesses of the layers (X1), layers (Y), and layers (X2) constituting the laminated body are used in the above-mentioned method. Measured according to. The measurement results are shown in Table 1.

1a, 1b Adhesive sheet 2a, 2b Double-sided adhesive sheet 10 Laminated body 11 Thermally expandable base material (Y)
12, 121 Adhesive layer (X1)
122 Adhesive layer (X2)
13, 131, 132 release material

Claims (9)

A pressure-sensitive adhesive sheet having a laminate in which a pressure-sensitive adhesive layer (X1) and a non-sticky heat-expandable base material (Y) are directly laminated in this order.
The laminated body
A coating film (x1') composed of the composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1), and
A coating film (y') composed of a composition (y) containing a resin and heat-expandable particles, which is a material for forming the heat-expandable base material (Y),
The adhesive sheet is formed by directly laminating the coating film (x1') and the coating film (y') in this order and then irradiating the coating film (x1') with energy rays at the same time. The adhesive sheet according to claim 1, wherein the energy ray irradiation is ultraviolet irradiation. The adhesive sheet according to claim 1 or 2, wherein the heat-expandable base material (Y) satisfies the following requirement (1).
- Requirement (1): in the expansion starting temperature (t) of the heat expandable particles, thermally expandable base material (Y) the storage elastic modulus E of the '(t) is less than or equal to 1.0 × ¹⁰ 7 Pa. The adhesive sheet according to any one of claims 1 to 3, wherein the heat-expandable base material (Y) satisfies the following requirement (2).
· Requirement (2): at 23 ° C., the storage modulus of the thermally expandable base material (Y) E '(23) is at 1.0 × ¹⁰ 6 Pa or more. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the heat-expandable base material (Y) has a thickness of 10 to 1000 μm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the probe tack value on the surface of the heat-expandable base material (Y) is less than 50 mN / 5 mmφ. Claim 1 in which the laminate further includes an adhesive layer (X2), and the adhesive layer (X1), the heat-expandable base material (Y), and the adhesive layer (X2) are directly laminated in this order. The adhesive sheet according to any one of 6 to 6. The laminated body
A coating film (x1') composed of the composition (x1) which is a material for forming the pressure-sensitive adhesive layer (X1), and
A coating film (y') composed of a composition (y) containing a resin and heat-expandable particles, which is a material for forming the heat-expandable base material (Y),
A coating film (x2') composed of the composition (x2) which is a material for forming the pressure-sensitive adhesive layer (X2), and
The adhesive sheet according to claim 7, wherein the coating films (x1'), (y') and (x2') are simultaneously irradiated with energy rays after being directly laminated in this order. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the average particle diameter of the heat-expandable particles before expansion at 23 ° C. is 3 to 100 μm.

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