JPWO2017159789A1 - Adhesive sheet and laminate - Google Patents

Abstract

An object of the present invention is to provide a pressure-sensitive adhesive sheet formed from a dual curable pressure-sensitive adhesive composition, which has a sufficiently low relative dielectric constant and excellent durability. The present invention relates to a pressure-sensitive adhesive sheet having active energy ray curability, and a pressure-sensitive adhesive sheet having a storage elastic modulus of 1.0 × 10 ⁶ Pa or more at 23 ° C. and a frequency of 1 Hz when irradiated with active energy rays.

Description

  The present invention relates to an adhesive sheet and a laminate.

  In recent years, a display device such as a liquid crystal display (LCD) and an input device such as a touch panel have been widely used in various fields. In the manufacture of these display devices and input devices, transparent adhesive sheets are used for the purpose of bonding optical members, and transparent adhesive sheets are also used for bonding between display devices and input devices. .

  When forming a pressure-sensitive adhesive sheet used for such applications, an active energy ray-curable pressure-sensitive adhesive composition or a thermosetting pressure-sensitive adhesive composition containing a base polymer is used. As the base polymer, acrylic monomers such as alkyl (meth) acrylates, urethane (meth) acrylates, epoxy (meth) acrylates, polyester (meth) acrylates, polyether (meth) acrylates, etc. because of their excellent transparency An acrylic base polymer containing units is used.

  Moreover, as a polymerization method of the base polymer which forms an adhesive sheet, it is known that there are several polymerization methods as described below. Specifically, (1) polymerization by heat, (2) polymerization by active energy, (3) two-stage polymerization in which polymerization is performed by active energy (or heat) after polymerization by heat (or active energy rays), (4) There is a method of two-stage polymerization in which polymerization is performed by active energy and then polymerization by active energy.

  In recent years, as a method of using a pressure-sensitive adhesive sheet used for the above-mentioned applications, (3) a method of curing by two-stage polymerization in which polymerization is performed by active energy (or heat) after polymerization by heat (or active energy rays) May be used. Since such a pressure-sensitive adhesive sheet is formed from a pressure-sensitive adhesive composition having both thermosetting and active energy ray-curing properties (hereinafter sometimes referred to as “dual curable pressure-sensitive adhesive composition”), it is heat-cured. And active energy ray curability. For this reason, before bonding with an adherend, it can be temporarily bonded, for example, by performing only thermosetting, and thereafter, it can be firmly bonded to the adherend by further curing with active energy rays. That is, it is said that such an adhesive sheet has both initial adhesive force and holding force.

For example, Patent Documents 1 to 3 disclose a dual curable pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition. Patent Document 1 discloses a pressure-sensitive adhesive sheet having a storage elastic modulus of 1 × 10 ⁴ Pa to 1 × 10 ⁶ Pa at a temperature of 20 ° C. and a frequency of 1 Hz after curing of active energy rays. Moreover, in patent document 2, the weight average molecular weight is 200,000 or more and 900,000 or less, (meth) acrylic acid ester copolymer containing predetermined amount of (meth) acrylic acid, and the adhesive containing an active energy ray hardening component A composition is disclosed. In the example of Patent Document 2, an adhesive sheet having a storage elastic modulus of 1 × 10 ⁵ Pa or less at a temperature of 23 ° C. and a frequency of 1 Hz after active energy ray curing is produced. Furthermore, Patent Document 3 discloses a pressure-sensitive adhesive composition containing a non-crosslinkable acrylic ester unit, a base polymer containing an acrylic monomer unit having a crosslinkable functional group, a crosslinking agent and an active energy ray curing component. It is disclosed. In Patent Document 3, butyl acrylate, 4-hydroxybutyl acrylate, and the like are used as constituent monomers of the base polymer.

Japanese Patent No. 5415658 JP 2014-196451 A Japanese Patent No. 5610085

  By using the pressure-sensitive adhesive sheet formed from the dual curable pressure-sensitive adhesive composition as described above, the pressure-sensitive adhesive can follow the unevenness of the adherend during temporary adhesion and can adhere firmly to the adherend after irradiation with active energy rays. A sheet is obtained. However, when the pressure-sensitive adhesive sheet described in Patent Documents 1 to 3 is used, the present inventor may generate bubbles between the pressure-sensitive adhesive sheet and the adherend in a wet heat environment after the active energy ray curing. It became clear by these examinations.

  In addition, in the pressure-sensitive adhesive sheet formed from the conventional dual curable pressure-sensitive adhesive composition, the relative dielectric constant before and after irradiation with active energy rays was high, and in particular, there was no sheet having a sufficiently low relative dielectric constant after irradiation with active energy rays. . For example, in a projected capacitive touch panel, when a finger is brought close to the surface, the capacitance between a plurality of electrodes changes simultaneously, and the position can be detected with high accuracy by measuring the ratio of the amount of current. . However, when this method is enlarged, the malfunction of the touch panel increases. In order to cope with such problems, it is conceivable to use a pressure-sensitive adhesive sheet having a low relative dielectric constant. However, the dual-curing pressure-sensitive adhesive sheet does not have a sufficiently low relative dielectric constant. It could not be used for a display device equipped with an integrated touch panel.

  Therefore, in order to solve such problems of the prior art, the present inventors provide a pressure-sensitive adhesive sheet formed from a dual curable pressure-sensitive adhesive composition, which does not generate bubbles and has excellent durability. We proceeded with the study for the purpose of providing. In addition, the present inventors have made studies for the purpose of providing a pressure-sensitive adhesive sheet having a sufficiently low relative dielectric constant.

As a result of intensive studies to solve the above problems, the present inventors, in the adhesive sheet having active energy ray curability, by setting the storage elastic modulus after irradiation of active energy rays to a predetermined value or more The present inventors have found that a pressure-sensitive adhesive sheet excellent in durability can be obtained by suppressing the generation of bubbles. In addition, the present inventors have found that such a pressure-sensitive adhesive sheet has a sufficiently low relative dielectric constant, and have completed the present invention.
Specifically, the present invention has the following configuration.

[1] A pressure-sensitive adhesive sheet having active energy ray curability, which has a storage elastic modulus of 1.0 × 10 ⁶ Pa or more at 23 ° C. and a frequency of 1 Hz when irradiated with active energy rays.
[2] The storage elastic modulus at any temperature of 0 ° C. to 45 ° C. before irradiating the adhesive sheet with active energy rays is S, and any of 0 ° C. to 45 ° C. after irradiating the adhesive sheet with active energy rays The adhesive sheet according to [1], wherein the T / S value at each temperature is 5 or more, where T is the storage elastic modulus at that temperature.
[3] The storage elastic modulus at any temperature from 3 ° C. to 35 ° C. before irradiating the adhesive sheet with active energy rays is S ′, and the temperature is from 3 ° C. to 35 ° C. after irradiating the adhesive sheet with active energy rays. The adhesive sheet according to [1] or [2], wherein the value of T ′ / S ′ at each temperature is 10 or more when the storage elastic modulus at any temperature is T ′.
[4] When the relative dielectric constant before irradiating the adhesive sheet with active energy rays is P and the relative dielectric constant after irradiating the adhesive sheet with active energy rays is Q, the value of PQ is 0.3. The pressure-sensitive adhesive sheet according to any one of [1] to [3].
[5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], which is a double-sided pressure-sensitive adhesive sheet.
[6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], which is for bonding an optical member constituting an image display device having a liquid crystal module.
[7] A laminate having an optical member constituting an image display device having a liquid crystal module on at least one surface of the pressure-sensitive adhesive sheet according to any one of [1] to [6].
[8] The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to [6] is brought into contact with the surface of an optical member constituting an image display device having a liquid crystal module, and active energy rays are irradiated in that state. And the manufacturing method of the laminated body including the process of hardening an adhesive layer completely.
[9] The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to [6] is brought into contact with the surface of an optical member constituting an image display device having a liquid crystal module, and active energy rays are irradiated in that state. And using the pressure-sensitive adhesive sheet to completely cure the pressure-sensitive adhesive layer.

ADVANTAGE OF THE INVENTION According to this invention, it is an adhesive sheet which has active energy ray curability, Comprising: Generation | occurrence | production of the bubble after irradiation of an active energy ray can be suppressed, and the adhesive sheet which can exhibit the outstanding durability can be obtained. Moreover, according to the present invention, an adhesive sheet having a sufficiently low relative dielectric constant can be obtained.
The pressure-sensitive adhesive sheet of the present invention has excellent unevenness followability, and after being irradiated with active energy rays, in addition to being firmly adhered to the adherend, it has a low relative dielectric constant and excellent durability, so it is equipped with a touch panel. It is preferably used for bonding optical members constituting the display device.

FIG. 1 is a cross-sectional view illustrating an example of the configuration of the pressure-sensitive adhesive sheet with a release sheet of the present invention. FIG. 2 is a cross-sectional view illustrating an example of the configuration of the laminate of the present invention.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

(Adhesive sheet)
The present invention relates to a pressure-sensitive adhesive sheet having active energy ray curability. The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having a storage elastic modulus of 1.0 × 10 ⁶ Pa or more at 23 ° C. and a frequency of 1 Hz by irradiation with active energy rays.

  Since the pressure-sensitive adhesive sheet of the present invention has the above-described configuration, durability after irradiation with active energy rays can be further increased. Specifically, the occurrence of floating / peeling from the adherend can be suppressed, and furthermore, the generation of bubbles between the adherend and the adhesive sheet can be suppressed. Moreover, the relative dielectric constant of the pressure-sensitive adhesive sheet of the present invention is sufficiently low, and the relative dielectric constant of the pressure-sensitive adhesive sheet after irradiation with active energy rays is sufficiently low. For this reason, the adhesive sheet of this invention is preferably used for bonding of the optical member which comprises the display apparatus which mounts a touchscreen, and the optical member which comprises the image display apparatus which has a liquid crystal module.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be a single-layer pressure-sensitive adhesive sheet composed only of a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet of the present invention may be a single-sided pressure-sensitive adhesive sheet or a double-sided pressure-sensitive adhesive sheet.
As a single-sided adhesive sheet, the multilayer sheet | seat which the adhesive layer laminated | stacked on the support body is mentioned. Moreover, another layer may be provided between the support and the pressure-sensitive adhesive layer.
Double-sided pressure-sensitive adhesive sheets include single-layer pressure-sensitive adhesive sheets composed of pressure-sensitive adhesive layers, multilayer pressure-sensitive adhesive sheets in which a plurality of pressure-sensitive adhesive layers are laminated, and multilayer pressure-sensitive adhesives in which another pressure-sensitive adhesive layer is laminated between pressure-sensitive adhesive layers. A multilayer pressure-sensitive adhesive sheet in which a support is laminated between the sheet, the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer can be used. When the double-sided pressure-sensitive adhesive sheet has a support, those using a transparent support as the support are preferred. Such a double-sided pressure-sensitive adhesive sheet is excellent in transparency as a whole pressure-sensitive adhesive sheet, and therefore can be suitably used for bonding optical members.
Among the above-mentioned, the pressure-sensitive adhesive sheet of the present invention is preferably a non-carrier type, preferably a single-layer pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer, or a multilayer pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated. A double-sided PSA sheet is particularly preferred.

  When the pressure-sensitive adhesive sheet of the present invention has a support, examples of the support include plastics such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyether ether ketone, and triacetyl cellulose. Film; optical films such as antireflection film and electromagnetic wave shielding film; and the like.

In the present invention, the storage elastic modulus at any temperature from 0 ° C. to 45 ° C. before irradiating the active energy ray to the pressure-sensitive adhesive sheet is S, and 0 ° C. to 45 ° C. after the active energy ray is irradiated to the pressure-sensitive adhesive sheet. When the storage elastic modulus at any temperature is T, the value of T / S at each temperature is preferably 5 or more. The value of T / S is calculated from the values of S and T at the same temperature at any temperature from 0 ° C to 45 ° C.
Further, the storage elastic modulus at any temperature from 3 ° C. to 35 ° C. before irradiating the adhesive sheet with active energy rays is S ′, and any of 3 ° C. to 35 ° C. after irradiating the adhesive sheet with active energy rays When the storage elastic modulus at such temperature is T ′, the value of T ′ / S ′ at each temperature is preferably 10 or more. The storage elastic modulus S ′ and the storage elastic modulus T ′ are preferably measured at 23 ° C. or 30 ° C., for example.
That is, the present invention is also characterized in that the storage elastic modulus increases after irradiation with active energy rays. Thereby, durability of the adhesive sheet after irradiation of an active energy ray can be improved more effectively. Moreover, the adhesive force with a to-be-adhered body can be strengthened by irradiation of an active energy ray.

  The storage elastic modulus of the pressure-sensitive adhesive sheet of the present invention is a value measured using a dynamic viscoelastic device (trade name: Rheogel-E4000) manufactured by UBM Co., Ltd. The measurement conditions are a frequency of 1 Hz, a temperature increase rate of 2 ° C./min, and measurement values at 0 ° C., 23 ° C., 30 ° C., and 45 ° C. in a range of −50 ° C. to 150 ° C. at a step temperature of 1 ° C.

  In the present invention, when the relative dielectric constant before irradiating active energy rays to the adhesive sheet is P and the relative dielectric constant after irradiating active energy rays to the adhesive sheet is Q, the value of PQ is 0. .3 or more is preferable. That is, in the present invention, the specific permittivity decreases by a predetermined amount or more after irradiation with active energy rays. As described above, the present invention is characterized in that the relative permittivity is low after irradiation with active energy rays.

  The relative dielectric constant is a relative dielectric constant at a specific frequency, and specifically, a relative dielectric constant at a specific frequency within a range of 1 KHz to 1 MHz. For example, it is a relative dielectric constant at a frequency of 100 KHz or 1 MHz, and is calculated by a method defined in JIS C 2138. When the relative dielectric constant P before irradiating the adhesive sheet with active energy rays is the relative dielectric constant at a frequency of 100 KHz, the relative dielectric constant Q after irradiating the adhesive sheet with active energy rays is also the relative dielectric constant at a frequency of 100 KHz. It is.

The adhesive strength of the pressure-sensitive adhesive sheet of the present invention is preferably 30 N / 25 mm or more, and more preferably 40 N / 25 mm or more. In addition, the said adhesive force is an adhesive force after irradiating an active energy ray to an adhesive sheet.
In this invention, even if it is a to-be-adhered body whose water contact angle is 0 degree or more and less than 90 degree | times, adhesive force is 40 N / 25mm or more. Further, even in an adherend having a water contact angle of 90 degrees or more and 100 degrees or less, the adhesive force is 30 N / 25 mm or more.
The surface-treated polarizing plate, the surface-treated PMMA (polymethylmethacrylate) resin plate, and the surface-treated PC (polycarbonate) resin plate are surface-treated with a hard coat film mainly composed of an acrylic resin. In many cases, the water contact angle is 90 degrees or more. On the other hand, the adhesive strength of general-purpose conventional pressure-sensitive adhesive sheets is often less than 30 N / 25 mm. Moreover, although the water contact angle of ITO film | membrane is 90 degree | times or more, the adhesive force of the general purpose conventional adhesive sheet with respect to it is often less than 20 N / 25mm, and improvement of adhesive force was a subject.
As described above, the adhesive strength of the pressure-sensitive adhesive sheet of the present invention can express an adhesive strength of 30 N / 25 mm or more even when the water contact angle is 90 ° or more and is difficult to wet. It is also characterized by good adhesion.

  In addition, the adhesive force of the adhesive sheet with respect to the adherend described above is a value obtained by measuring the adhesive force peeled off by 180 ° with respect to each adherend according to JIS Z0237.

  The thickness of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet can be appropriately set depending on the application and is not particularly limited, but is usually preferably in the range of 10 μm or more and 500 μm or less, more preferably 20 μm or more and 450 μm or less. 30 μm or more and 450 μm or less is more preferable, 40 μm or more and 400 μm or less is more preferable, 40 μm or more and 350 μm or less is even more preferable, and 40 μm or more and 300 μm or less is particularly preferable. By setting the thickness of the pressure-sensitive adhesive layer within the above range, it is possible to sufficiently ensure the uneven followability and further enhance the durability. Moreover, manufacture of a double-sided adhesive sheet becomes easy by making thickness of an adhesive layer into the said range.

  The pressure-sensitive adhesive sheet of the present invention preferably has a haze value of 2% or less in an environment of 23 ° C. and 50% relative humidity, more preferably 0% or more and 1.5% or less, and 0% or more and 1% or less. More preferably. If the haze value is within the above range, the transparency required for use in an adhesive sheet optical member can be satisfied. Moreover, if a haze value is 2% or less, it is suitable as an optical use.

  The pressure-sensitive adhesive sheet of the present invention has a haze value of less than 5% immediately after being stored in an environment of 85 ° C. and a relative humidity of 85% for 500 hours and taken out in an environment of 23 ° C. and a relative humidity of 50%. Preferably, it is less than 2%. The haze value after being placed in a high-temperature and high-humidity environment is preferably in the above range from the viewpoint of humidification cloudiness resistance.

  The pressure-sensitive adhesive sheet of the present invention preferably has a total light transmittance (a value based on JIS K 7361-1: 1997) in an environment of 23 ° C. and 50% relative humidity of 80% or more, particularly 90% or more. It is preferable. When the total light transmittance is within the above range, the transparency is high and it is suitable for optical applications.

The pressure-sensitive adhesive sheet of the present invention preferably has a b ^* value of less than 1 after 24 hours of storage at 85 ° C. in a dry environment for 500 hours and taken out in an environment of 23 ° C. and 50% relative humidity. More preferably, it is less than .5. If b ^* value is the said range, the transparency requested | required when an adhesive sheet is used for an optical member can be satisfied. The dry environment refers to a humidity environment in which the relative humidity is 3% or less, although it is affected by the humidity of the supplied outside air.

The surface of the pressure-sensitive adhesive layer of the present invention is preferably covered with a release sheet. That is, the present invention may be an adhesive sheet with a release sheet.
Drawing 1 is a sectional view showing an example of composition of an adhesive sheet with a release sheet. The pressure-sensitive adhesive sheet 11 shown in FIG. 1 has release sheets (12a, 12b). In addition, the adhesive sheet 11 of FIG. 1 is a non-carrier type single-layer adhesive sheet, and is a double-sided adhesive sheet.

As a release sheet, a peelable laminate sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low polarity substrate Is mentioned.
Papers and polymer films are used as the release sheet substrate in the peelable laminate sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition type or condensation type silicone release agent or a long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Is mentioned. Further, the silicone release agent may contain a silicone resin which is an organosilicon compound having a SiO ₂ unit and a (CH ₃ ) ₃ SiO _1/2 unit or CH ₂ ═CH (CH ₃ ) SiO _1/2 unit. preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone, KS-3800, X92-183, manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

  In the release sheet 12, in order to make it easy to peel, it is preferable that the release sheet 12a and the release sheet 12b have different peelability. That is, when the peelability from one side and the peelability from the other are different, it becomes easy to peel only the release sheet 12 having the higher peelability first. In that case, what is necessary is just to adjust the peelability of the peeling sheet 12 of the peeling sheet 12a and the peeling sheet 12b according to the bonding method and the bonding order.

  The present invention is preferably a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer obtained by semi-curing a pressure-sensitive adhesive composition to be described later by heating or active energy rays. The pressure-sensitive adhesive sheet of the present invention is a (meth) acrylic monomer having a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms and a crosslinkable functional group Polymerization of monomer (B) by irradiation with active energy ray, base polymer (A) containing unit (a2) derived from, monomer (B) containing at least one polymerizable unsaturated group A pressure-sensitive adhesive layer containing a polymerization initiator (D) for initiating the reaction is preferably provided.

(Adhesive composition)
The pressure-sensitive adhesive sheet of the present invention may be formed from a pressure-sensitive adhesive composition containing a base polymer (A), a monomer (B), a crosslinking agent (C), and a polymerization initiator (D). preferable. Here, the base polymer (A) is a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms, and a (meth) acryl having a crosslinkable functional group. The unit (a2) derived from a monomer is contained. The monomer (B) contains at least one polymerizable unsaturated group. The crosslinking agent (C) is a crosslinking agent that reacts with the base polymer (A) by heat. A polymerization initiator (D) is a polymerization initiator which starts the polymerization reaction of a monomer (B) by irradiation of an active energy ray.

  In the present invention, the base polymer (A) has a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms and a (meth) having a crosslinkable functional group. Since the unit (a2) derived from the acrylic monomer is contained, durability after irradiation with active energy rays can be further increased. Specifically, the occurrence of floating / peeling from the adherend can be suppressed, and furthermore, the generation of bubbles between the adherend and the adhesive sheet can be suppressed. In the present invention, a pressure-sensitive adhesive layer having a sufficiently low relative dielectric constant can be formed from a pressure-sensitive adhesive composition containing the base polymer (A). The relative dielectric constant of the pressure-sensitive adhesive layer is sufficiently low even after active energy ray curing, and a pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer is preferably used for bonding optical members constituting a display device equipped with a touch panel.

  The unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms contained in the base polymer (A) has an alkyl group having 5 or more carbon atoms, And since such an alkyl group is a branched structure, its molar volume is large and its density is low. For this reason, the molar volume of the base polymer (A) can be increased and the density can be decreased. In addition, since the unit (a1) has an alkyl group having 9 or less carbon atoms, the volume shrinkage when the polymer is used can be suppressed, and the molar volume of the base polymer (A) can be maintained large. Conceivable. As a result, an adhesive layer having a low relative dielectric constant can be formed.

(Base polymer (A))
The base polymer (A) is a (meth) acrylic monomer having a unit (a1) derived from a non-crosslinkable (meth) acrylic acid ester having a branched alkyl group having 5 to 9 carbon atoms and a crosslinkable functional group Contains the unit (a2) derived from. The base polymer (A) preferably has a transparency that does not deteriorate the visibility of the display device. In the present specification, the “unit” is a repeating unit (monomer unit) constituting the polymer.

<Unit derived from non-crosslinkable (meth) acrylic acid ester (a1)>
The unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester is a repeating unit derived from the (meth) acrylic acid alkyl ester having a branched alkyl group having 5 to 9 carbon atoms. Examples of such (meth) acrylic acid alkyl ester include isopentyl (meth) acrylate, isohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isoheptyl (meth) acrylate, isooctyl (meth) acrylate, Examples thereof include isononyl (meth) acrylate. These may be used individually by 1 type and may use 2 or more types together. Among these, it is preferable to use 2-ethylhexyl (meth) acrylate as the non-crosslinkable (meth) acrylic acid ester unit (a1).

  The number of carbon atoms of the branched alkyl group contained in the unit (a1) derived from the non-crosslinkable (meth) acrylic ester may be 5 or more and 9 or less, but is preferably 7 or more and 9 or less. By setting the number of carbon atoms of the branched alkyl group within the above range, a pressure-sensitive adhesive layer having a sufficiently low relative dielectric constant can be formed. Moreover, by setting the carbon number of the branched alkyl group within the above range, it is easy to control the degree of polymerization of the base polymer (A), and a pressure-sensitive adhesive composition excellent in processability can be obtained.

  The content of the unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester in the base polymer (A) is preferably 40% by mass or more based on the total mass of the base polymer (A), 50 The content is more preferably at least mass%, and further preferably at least 60 mass%. Moreover, it is preferable that content of a unit (a1) is 90 mass% or less, and it is more preferable that it is 85 mass% or less. When the content of the unit (a1) is within the above range, the relative dielectric constant of the pressure-sensitive adhesive layer can be sufficiently lowered, and the durability of the pressure-sensitive adhesive layer can be further increased.

<Unit (a2) derived from (meth) acrylic monomer having crosslinkable functional group>
As a unit (a2) derived from a (meth) acrylic monomer having a crosslinkable functional group, a hydroxy group-containing monomer unit, an amino group-containing monomer unit, a glycidyl group-containing monomer unit, a carboxy group-containing A monomer unit etc. are mentioned. These monomer units may be one kind or two or more kinds.
The hydroxy group-containing monomer unit is a repeating unit derived from the hydroxy group-containing monomer. Examples of the hydroxy group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate, (Meth) acrylic acid lactones such as (meth) acrylic acid mono (diethylene glycol) (meth) acrylic acid [(mono, di or poly) alkylene glycol] and (meth) acrylic acid monocaprolactone.
Examples of the amino group-containing monomer unit include repeating units derived from amino group-containing monomers such as (meth) acrylamide and allylamine.
Examples of the glycidyl group-containing monomer unit include repeating units derived from glycidyl group-containing monomers such as glycidyl (meth) acrylate.
Examples of the carboxy group-containing monomer unit include acrylic acid and methacrylic acid.

  The content of the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group in the base polymer (A) is 0.01% by mass or more with respect to the total mass of the base polymer (A). It is preferable that it is 0.5 mass% or more. Moreover, it is preferable that content of a unit (a2) is 40 mass% or less, and 35 mass% or less is more preferable. If the content of the unit (a2) is not less than the lower limit value of the above range, it has sufficient crosslinkability necessary to maintain a semi-cured state, and if it is not more than the upper limit value of the above range, it is necessary. The pressure-sensitive adhesive layer can be formed while maintaining the physical properties of the pressure-sensitive adhesive and having a sufficiently low relative dielectric constant.

<Other monomer units>
The base polymer (A) may contain other units other than the unit (a1) derived from the non-crosslinkable (meth) acrylic acid ester and the (meth) acrylic monomer unit (a2) having a crosslinkable functional group as necessary. It may have a monomer unit. Examples of other monomers include (meth) acrylic acid ester units having 4 or less carbon atoms or 10 or more carbon atoms. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-decyl (meth) acrylate, lauryl (meth) acrylate , Stearyl (meth) acrylate, and the like. Moreover, as another (meth) acrylic acid ester unit, the (meth) acrylic acid ester unit which has a C5-C9 linear alkyl group may be included. Specifically, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, etc. Can be mentioned. Furthermore, as other (meth) acrylic acid ester units, (meth) acrylic acid ester units having a cyclic group such as (meth) acrylic acid cyclohexyl, (meth) acrylic acid benzyl, (meth) acrylonitrile, vinyl acetate, Examples include styrene, vinyl chloride, vinyl pyrrolidone, vinyl pyridine and the like. The content of other monomer units in the base polymer (A) is preferably 20% by mass or less, and more preferably 15% by mass or less.

<Styrene polymer>
The base polymer (A) used in the present invention preferably further contains a styrene polymer. The base polymer (A) may contain one styrenic polymer alone, or may contain two or more different styrenic polymer compositions, weight average molecular weights, and the like.

  Styrenic polymers are hydrophobic. For this reason, when the base polymer (A) contains a styrene polymer, the styrene polymer is localized in the vicinity of the interface of the pressure-sensitive adhesive layer in a humid heat environment, and the inflow of moisture to the pressure-sensitive adhesive layer is suppressed. be able to. As a result, it is considered that the heat-and-moisture resistance of the pressure-sensitive adhesive layer can be improved.

  Styrene monomers that can constitute a styrene polymer include styrene, alkyl styrene (methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, octyl styrene. ) And monomers having a styrene skeleton such as halogenated styrene (chlorostyrene, promostyrene). Among these, styrene is preferably used as the styrene monomer from the viewpoint of having no functional group capable of reacting with a crosslinking agent and being easily available.

  The styrene polymer may be a polymer of one or more styrene monomers, or may be a copolymer of a styrene monomer and another monomer. The copolymer of the styrene monomer and the other monomer is not particularly limited. For example, a copolymer of the styrene monomer and n-butyl acrylate, methyl methacrylate, butadiene, acrylonitrile, or the like. Is mentioned.

  The styrene polymer may be a hydride (hereinafter also referred to as “hydrogenated styrene polymer”). When the styrene polymer is a hydrogenated styrene polymer, the hydrogenation rate (unit:%) of the hydrogenated styrene polymer is not particularly limited, and can be, for example, 10% or more and 99% or less. .

The hydrogenation rate of the hydrogenated styrenic polymer is determined by using ¹ H-NMR, the integrated value of the peak of the main chain styrenic polymer and hydrogenated aryl group at 0.5 ppm to 3.0 ppm, and 6 It is determined from the ratio with the integrated value of the peak of the non-hydrogenated aryl group of not less than 5 ppm and not more than 7.2 ppm.

  The weight average molecular weight of the styrenic polymer is preferably 1000 or less, and more preferably 700 or less. The weight average molecular weight of the styrene polymer is preferably 400 or more. By setting the weight average molecular weight of the styrenic polymer within the above range, the compatibility with the above-described (meth) acrylic polymer is improved, and an adhesive layer that is superior in heat and moisture resistance can be formed. Further, by setting the weight average molecular weight of the styrene polymer within the above range, it is possible to form a pressure-sensitive adhesive layer that is less likely to generate bubbles even in a moist heat environment and that is superior in durability.

The weight average molecular weight of the styrene polymer is a value measured according to the following (1) to (3) using gel permeation chromatography (GPC).
(1) A styrene polymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like styrene polymer.
(2) The film-like styrenic polymer obtained in the above (1) is dissolved in tetrahydrofuran so as to have a solid content of 0.2% by mass.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight of the styrene polymer is measured as a standard polystyrene equivalent value under the following conditions.
GPC: HLC-8220 GPC (manufactured by Tosoh Corporation)
Force ram: 4 TSK-GEL GMHXL used (manufactured by Tosoh Corporation)
Mobile phase solvent: Tetrahydrofuran Flow rate: 0.6 mL / min Power ram temperature: 40 ° C

  The content of the styrenic polymer is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more with respect to the total mass of the base polymer (A). The content of the styrene polymer is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less. By setting the content of the styrenic polymer within the above range, the specific dielectric constant of the pressure-sensitive adhesive layer can be more effectively lowered, and a pressure-sensitive adhesive layer having excellent durability can be formed.

  A commercially available product can be used as the styrene polymer. Examples of commercially available products include Piclastic A5 (trade name, styrene homopolymer, weight average molecular weight: 500), Regalrez 10l8 (trade name, hydrogenated styrene homopolymer, weight average molecular weight: 500) manufactured by EASTMAN CHEMICAL. , Piccolastic A75 (trade name, styrene homopolymer, weight average molecular weight: 1200), YS Resin SX100 (trade name, styrene homopolymer, weight average molecular weight: 2500) manufactured by Yashara Chemical Co., Ltd., and the like.

  When producing a styrene-type polymer by superposition | polymerization, the manufacturing method is not specifically limited, It can select suitably from the polymerization method used normally. Examples of the polymerization method include solution polymerization, emulsion polymerization, and suspension polymerization. Among these, a solution polymerization method is preferable as the polymerization method because the production can be performed relatively easily.

<Physical properties of base polymer (A)>
The weight average molecular weight of the base polymer (A) is preferably from 100,000 to 2,000,000, more preferably from 300,000 to 1,500,000. By making a weight average molecular weight into the said range, the semi-hardened state of an adhesive sheet can be maintained and sufficient uneven | corrugated followable | trackability can be ensured. In addition, the weight average molecular weight of a base polymer (A) is a value before bridge | crosslinking with a crosslinking agent (C). The weight average molecular weight is a value determined by gel permeation chromatography (GPC) and determined on the basis of polystyrene. As the base polymer (A), a commercially available product may be used, or a polymer synthesized by a known method may be used.

The measurement conditions of gel permeation chromatography (GPC) are as follows.
Solvent: Tetrahydrofuran Column: Shodex KF801, KF803L, KF800L, KF800D (used by connecting four Showa Denko Co., Ltd.)
Column temperature: 40 ° C
Sample concentration: 0.5% by mass
Detector: RI-2031plus (manufactured by JASCO)
Pump: RI-2080plus (manufactured by JASCO)
Flow rate (flow rate): 0.8 ml / min
Injection volume: 10 μl
Calibration curve: Standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko KK) Mw = 1320 to 2500,000 calibration curves with 10 samples were used.

  The glass transition temperature (Tg) of the base polymer (A) is preferably from −55 ° C. to −15 ° C., more preferably from −40 ° C. to −18 ° C., and from −35 ° C. to −18 ° C. More preferably, it is as follows. By setting the glass transition temperature (Tg) of the base polymer (A) within the above range, the cohesive force when used as an adhesive layer can be further increased. Thereby, the adhesive layer excellent in durability and excellent in adhesive force is obtained.

<Content of base polymer (A)>
The content of the base polymer (A) is preferably 75% by mass or more, more preferably 80% by mass or more, and further preferably 85% by mass or more with respect to the total mass of the pressure-sensitive adhesive composition. preferable. Further, the content of the base polymer (A) is preferably 98% by mass or less, more preferably 95% by mass or less, and further preferably 90% by mass or less.

(Monomer (B))
The monomer (B) is a monomer containing at least one polymerizable unsaturated group. The monomer (B) contains at least one of a monofunctional monomer (b1) having at least one polymerizable unsaturated group and a polyfunctional monomer (b2) having two or more polymerizable unsaturated groups. May be. Examples of the polymerizable unsaturated group include a group containing an ethylenic double bond, and examples thereof include a (meth) acryloyl group and a vinyl group. The monomer (B) may contain either the monofunctional monomer (b1) or the polyfunctional monomer (b2). The monofunctional monomer (b1) and the polyfunctional monomer Both of (b2) may be included.

  The pressure-sensitive adhesive composition of the present invention contains the monomer (B), so that when the pressure-sensitive adhesive composition is thermally cured in the first stage (semi-curing step), the thermosetting pressure-sensitive adhesive sheet is semi-cured. It is a state and can have active energy ray curability. When the pressure-sensitive adhesive composition is cured by irradiation with active energy rays in the first stage, the pressure-sensitive adhesive sheet is in a semi-cured state and has thermosetting properties. In addition, in this invention, after making it harden | cure in a 1st step and making it a semi-hardened state, it can also make it completely harden | cure by thermosetting again as a 2nd step.

As the monomer (B), one having a vapor pressure at 25 ° C. of 300 Pa or less may be used. This improves the coating suitability, and when the adhesive composition is applied and heat-cured, the adhesive layer has few coating defects such as the occurrence of thick edges and side walls while selectively evaporating the solvent. Can be formed.
The vapor pressure at 25 ° C. of the monomer (B) may be 200 Pa or less, or 100 Pa or less. The lower limit of the vapor pressure is not particularly limited in terms of the coating suitability of the pressure-sensitive adhesive composition. The vapor pressure of the monomer (B) can be measured according to JIS K 2258 “Crude oil and fuel oil—Vapor pressure test method—Lead method”, and the like, for example, http: // www. chemspider. The predicted value can be obtained by a website such as com / or software such as ACD / PhysChem Suite.

  Further, the melting point of the monomer (B) may be 25 ° C. or less. Thereby, transparency (haze etc.) etc. of the adhesive sheet formed improve. Further, the melting point of the monomer (B) may be 20 ° C. or less, or 15 ° C. or less. The lower limit of the melting point is not particularly limited. The melting point of the monomer (B) can be measured according to JIS K 0064: 1992 “Measuring method of melting point and melting range of chemical product”.

  Specific examples of the monofunctional monomer (b1) that can be used in the present invention include pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, and n-octyl (meth) acrylate. , Iso-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, ( Examples include lauryl methacrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Monofunctional monomers (b1) having a melting point of 25 ° C. or lower include pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, (meth ) Isooctyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) acrylic Examples include lauryl acid, isostearyl (meth) acrylate, isobornyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.

Examples of the polyfunctional monomer (b2) include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, and di (meth) acryl. 1,4-butylene glycol acid, 1,9-nonanediol di (meth) acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, Tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, tetra ( Many such as (meth) acrylic acid pentaerythritol (Meth) acrylic acid esters of alcohols, and vinyl methacrylate.
The monomer (B) may have no functional group that is reactive with the functional group of the (meth) acrylic monomer unit (a2). For example, the monomer (B) may have the same functional group (for example, a hydroxy group) as the (meth) acrylic monomer unit (a2) or may not have a functional group.

The molar volume of the monomer (B) is preferably 90 ml / mol or more, more preferably 180 ml / mol or more, further preferably 190 ml / mol or more, and 200 ml / mol or more. Even more preferred. The molar volume of the monomer (B) is preferably 500 ml / mol or less. Furthermore, the density of the monomer (B) is preferably 1.0 g / cm ³ or less, and more preferably 0.9 g / cm ³ or less. In the present invention, by using the monomer (B) having a large molar volume and a small density, a pressure-sensitive adhesive layer having a lower relative dielectric constant can be obtained, and the durability of the pressure-sensitive adhesive layer can be made more effective. Can be increased. Furthermore, by using a monomer (B) having a large molar volume and low density, an adhesive sheet having an adhesive layer is bonded to a display device such as a liquid crystal display (LCD) or an input device such as a touch panel. When used for the above, noise from the liquid crystal panel side can be suppressed.

The monomer (B) preferably has an alkyl group having 5 or more carbon atoms, and more preferably has an alkyl group having 10 or more carbon atoms. Further, the monomer (B) preferably has a branched alkyl group having 5 or more carbon atoms, and particularly preferably has a branched alkyl group having 10 or more carbon atoms. When the monomer (B) contains an alkyl group having a predetermined structure, a pressure-sensitive adhesive layer having a lower relative dielectric constant can be obtained, and the durability of the pressure-sensitive adhesive layer can be increased more effectively. . In addition, when the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer is used for bonding a display device such as a liquid crystal display (LCD) or an input device such as a touch panel, noise from the liquid crystal panel side can be suppressed.
Usually, in order to polymerize the monomer (B) as a higher molecular weight, the shorter the number of chain-length atoms, the easier the monomers are bonded to each other, and the more excellent curing occurs. However, in the present invention, by using the monomer (B) as described above, it is promoted that the monomer (B) and the base polymer (A) are intertwined. Thereby, it is thought that an adhesive composition is hardened | cured easily and can exhibit the outstanding holding power.

  Examples of the monomer (B) having an alkyl group having 5 or more carbon atoms include pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, and n-octyl (meth) acrylate. , Iso-octyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, ( Examples include lauryl methacrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, isobornyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. The monomer (B) is preferably at least one selected from the group described above.

  Moreover, the monomer (B) may have a polycyclic structure. Thereby, a further excellent holding force can be exhibited after complete curing. The monomer having a polycyclic structure may be a polycyclic aliphatic monomer or a polycyclic aromatic monomer. Examples of the polycyclic structure include a bicyclo structure and a tricyclo structure. A substituent such as an alkyl group may be bonded to these polycyclic structures. Specific examples of the polycyclic structure include a norbornene ring and an adamantane ring.

<Content of monomer (B)>
The content of the monomer (B) in the pressure-sensitive adhesive composition is appropriately selected according to the composition, molecular weight, crosslinking density, etc. of the base polymer (A), and is not particularly limited, but 100 parts by mass of the base polymer (A) On the other hand, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more. Further, the content of the monomer (B) is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and further preferably 90 parts by mass or less.
Further, the content of the monomer (B) is preferably 1% by mass or more, more preferably 2% by mass or more, and more preferably 5% by mass or more with respect to the total mass of the pressure-sensitive adhesive composition. More preferably. In addition, the content of the monomer (B) is preferably 60% by mass or less, more preferably 50% by mass or less, and further preferably 35% by mass or less.

  When the monomer (B) contains both the monofunctional monomer (b1) and the polyfunctional monomer (b2), it is appropriately selected according to the composition, molecular weight, crosslinking density, etc. of the polymer (A), Although it does not specifically limit, A monofunctional monomer (b1) can be 4 mass parts or more and 120 mass parts or less with respect to 100 mass parts of base polymer (A), and shall be 8 mass parts or more and 100 mass parts or less. And can be 12 parts by mass or more and 80 parts by mass or less. The polyfunctional monomer (b2) can be 1 part by mass or more and 30 parts by mass or less, can be 2 parts by mass or more and 20 parts by mass or less, and can be 3 parts by mass or more and 10 parts by mass or less. . The mass ratio of the monofunctional monomer (b1) and the polyfunctional monomer (b2) can be 2: 1, 3: 1, or 5: 1.

(Crosslinking agent (C))
The crosslinking agent (C) is a crosslinking agent that reacts with the base polymer (A) by heat. Examples of the cross-linking agent (C) include cross-linkable functional groups possessed by the base polymer (A) among known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, butylated melamine compounds. It can be appropriately selected in consideration of the reactivity with the group. For example, when a hydroxy group is included as a crosslinkable functional group, an isocyanate compound can be used from the reactivity of the hydroxy group. From the viewpoint that the unit (a2) derived from the (meth) acrylic monomer having a crosslinkable functional group can be easily crosslinked, it is preferable to use an isocyanate compound or an epoxy compound.

Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.
Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol diester. Glycidyl ether, tetraglycidyl xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. Can be mentioned.

As a crosslinking agent (C), 1 type may be used independently or 2 or more types may be used together. Although content of the crosslinking agent (C) in an adhesive composition is suitably selected according to the desired adhesive physical property etc., it is not specifically limited, 0.01 mass part with respect to 100 mass parts of base polymers (A) The amount can be 5 parts by mass or less, and can be 0.03 parts by mass or more and 3 parts by mass or less.
Moreover, content of a crosslinking agent (C) can be 0.01 mass% or more and 5.0 mass% or less with respect to the total mass of an adhesive composition, and is 0.02 mass% or more and 2.0 mass%. % Or less.

(Polymerization initiator (D))
A polymerization initiator (D) starts the polymerization reaction of a monomer (B) by irradiation of an active energy ray. As the polymerization initiator (D), any polymerization initiator may be used as long as it can initiate the polymerization reaction of the monomer (B) by irradiation with active energy rays.
Here, “active energy rays” mean those having energy quanta among electromagnetic waves or charged particle beams, and examples include ultraviolet rays, electron beams, visible rays, X-rays, ion rays and the like. Among these, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.

Examples of the polymerization initiator (D) include acetophenone-based initiators, benzoin ether-based initiators, benzophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, and amine-based initiators.
Specific examples of the acetophenone initiator include diethoxyacetophenone and benzyldimethyl ketal.
Specific examples of the benzoin ether initiator include benzoin and benzoin methyl ether.
Specific examples of the benzophenone-based initiator include benzophenone and methyl o-benzoylbenzoate.
Specific examples of the hydroxyalkylphenone-based initiator include 1-hydroxy-cyclohexyl-phenyl-ketone and the like.
Specific examples of the thioxanthone initiator include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone.
Specific examples of the amine initiator include triethanolamine and ethyl 4-dimethylbenzoate.

As the polymerization initiator (D), one type may be used alone, or two or more types may be used in combination. The content of the polymerization initiator (D) in the pressure-sensitive adhesive composition is appropriately selected according to the content of the monomer (B), the irradiation amount of active energy rays when semi-cured or completely cured, and the like. Although not limited, it can be 0.05 mass% or more and 10 mass% or less with respect to the total mass of a monomer (B), and can be 0.1 mass% or more and 5.0 mass% or less.
Moreover, content of a polymerization initiator (D) can be 0.1 to 10 mass parts with respect to 100 mass parts of base polymers (A), and is 1 to 5 mass parts. be able to.

(Solvent (E))
The pressure-sensitive adhesive composition of the present invention may further contain a solvent (E). The solvent (E) is used for improving the coating suitability of the pressure-sensitive adhesive composition.
Examples of such a solvent (E) include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane. Alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane and tetrahydrofuran; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone and cyclohexanone Ketones; methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate Esters; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, polyols and derivatives thereof such as propylene glycol monomethyl ether acetate.

  Examples of the solvent (E) include a solvent having no polymerizable unsaturated group and having a higher vapor pressure at 25 ° C. than that of the monomer (B). Since the larger the difference in vapor pressure between the monomer (B) and the solvent (E), the fewer the coating defects and the easier the production, the vapor pressure of the solvent (E) can be 2000 Pa or higher. This can be done. Although an upper limit is not specifically limited, It is 50000 Pa or less practically. The vapor pressure of the solvent (E) can be measured by JIS-K2258-2 “Crude oil and petroleum products—Method for obtaining vapor pressure—Part 2: Three-time expansion method”, and the like, for example, http: // www. chemspider. com / and software such as ACD / PhysChem Suite.

  Solvents that have no polymerizable unsaturated groups and have a higher vapor pressure at 25 ° C. than monomer (B) include hexane, heptane, cyclohexane, benzene, toluene, ethanol, isopropyl alcohol, diisopropyl ether, tetrahydrofuran, and acetone. , Methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and the like. The said solvent can be suitably selected according to the kind of monomer (B).

  Further, the solvent (E) may have a surface tension at 25 ° C. of 20 mN / m or more and less than 40 mN / m, or 22 mN / m or more and less than 36 mN / m. If the surface tension is not less than the above lower limit value, it is possible to suppress the formation of a yuzu skin (orange peel), and if it is less than the above upper limit value, coating defects such as occurrence of thick end portions (framing) are unlikely to occur.

The difference in solubility parameter between the solvent (E) and the monomer (B) may be within 2 [(cal / cm ³ ) ^1/2 ], or 1.5 [(cal / cm ³ ) ^{1 / 2} ]. As a result, coating defects such as the generation of yuzu skin (orange peel) due to abnormally accelerated evaporation of the solvent (E) are unlikely to occur. The solubility parameter serves as a guide for dissolution and has the meaning of the following formula.
δ = (ΔE / V) 1/2
Here, δ is a solubility parameter, ΔE is molar evaporation energy (cal / mol), and V is molar volume (ml / mol). Those having a similar solubility parameter δ dissolve well. It agrees with the rule of thumb that similar things melt well. The solubility parameter can be determined by various methods, but in the present specification, the solubility parameter is calculated from the chemical composition by the method of Fedors.

A solvent (E) may be used individually by 1 type, and may use 2 or more types together. In the pressure-sensitive adhesive composition, the content of the solvent (E) is not particularly limited, but can be 25 parts by mass or more and 500 parts by mass or less, and 30 parts by mass or more and 400 parts by mass with respect to 100 parts by mass of the base polymer (A). It can be below mass parts.
Moreover, content of a solvent (E) can be 10 to 90 mass% with respect to the total mass of an adhesive composition, and can be 20 to 80 mass%.

(Plasticizer)
The pressure-sensitive adhesive composition of the present invention may contain a plasticizer. When a plasticizer is included, the content of the plasticizer can be 50 parts by mass or less, 100 parts by mass or less, and 10 parts by mass or less with respect to 100 parts by mass of the base polymer (A). It can also be.

As the plasticizer, a non-functional acrylic polymer can be used. A non-functional acrylic polymer is a polymer consisting only of an acrylic monomer unit having no functional group other than an acrylate group, or an acrylic monomer unit having no functional group other than an acrylate group and no functional group. It means a polymer composed of non-acrylic monomer units.
As an acrylic monomer unit which does not have functional groups other than an acrylate group, the thing similar to a non-crosslinkable (meth) acrylic acid ester unit (a1) is mentioned, for example.
Non-acrylic monomer units having no functional group include, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, stearin. Examples thereof include carboxylic acid vinyl esters such as vinyl acid vinyl, vinyl cyclohexanecarboxylate, and vinyl benzoate, and styrene.

(Optional component)
The pressure-sensitive adhesive composition may contain components other than those described above as long as the effects of the present invention are not impaired. Other components include components known as additives for pressure-sensitive adhesives, such as antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, ultraviolet absorbers, light stabilizers such as hindered amine compounds, etc. You can select from among them as needed.
Examples of the antioxidant include phenolic antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. These antioxidants may be used alone or in combination of two or more.
Examples of the metal corrosion inhibitor include benzoriazol resins.
Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, coumarone indene resin, styrene resin, xylene resin, phenol resin, and petroleum resin.
Examples of the silane coupling agent include mercaptoalkoxysilane compounds (for example, mercapto group-substituted alkoxy oligomers).
Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds. However, when ultraviolet rays are used for the active energy rays during complete curing, it is necessary to add them in a range that does not inhibit the polymerization reaction.

(Method for producing adhesive sheet)
The pressure-sensitive adhesive sheet of the present invention is obtained by semi-curing the pressure-sensitive adhesive composition by heating or irradiation with active energy rays, containing at least a part of the monomer (B) in an unreacted state, and a crosslinking agent ( Among at least one selected from C) and the polymerization initiator (D), it is preferable to contain at least a part in an unreacted state. That is, it is preferable that the manufacturing method of the adhesive sheet of this invention includes the process of heating an adhesive composition or irradiating an active energy ray. Especially, it is preferable that the manufacturing method of the adhesive sheet of this invention includes the process of heating an adhesive composition.

  The pressure-sensitive adhesive sheet of the present invention may be composed of a pressure-sensitive adhesive layer and another layer, but is preferably composed of only a pressure-sensitive adhesive layer. Examples of other layers include a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition other than the above, a support, a release sheet, and the like. Examples of the support include plastic films such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyetheretherketone, and triacetyl cellulose; optical films such as antireflection films and electromagnetic wave shielding films; Is mentioned.

  The production process of the pressure-sensitive adhesive sheet of the present invention includes a step of applying a pressure-sensitive adhesive composition on a release sheet to form a coating film, a step of heating the coating film to a semi-cured product, or activating the coating film And a step of forming a semi-cured product by irradiation with energy rays.

Hereinafter, the step of coating the pressure-sensitive adhesive composition on the release sheet to form a coating film and the step of heating the coating film to make a semi-cured product will be described as a representative.
By heating the coating film, the reaction of the base polymer (A) and the crosslinking agent (C) proceeds to form a semi-cured product (adhesive sheet). That is, during heating, the polymerization reaction of the monomer (B) by the polymerization initiator (D) does not proceed or is slight in the coating film, so that in the resulting semi-cured product (adhesive sheet) The monomer (B) and polymerization initiator (D) contained in the pressure-sensitive adhesive composition remain. Therefore, the pressure-sensitive adhesive sheet of the present invention has active energy ray curability. In order to bring the pressure-sensitive adhesive composition into a semi-cured state, after removing the solvent after coating, an aging treatment may be performed in which the pressure-sensitive adhesive sheet is allowed to stand for a certain period at a certain temperature. The aging treatment can be performed, for example, by standing at 23 ° C. for 7 days.

Application of the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet can be carried out using a known coating apparatus. Examples of the coating apparatus include a blade coater, an air knife coater, a roll coater, a bar coater, a gravure coater, a micro gravure coater, a rod blade coater, a lip coater, a die coater, and a curtain coater.
The coating film can be heated using a known heating device such as a heating furnace or an infrared lamp.

(How to use the adhesive sheet)
In the method for using the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend, and the active energy ray is irradiated in that state to completely cure the pressure-sensitive adhesive layer. The adherend is preferably an optical member constituting an image display device having a liquid crystal module. That is, the method of using the pressure-sensitive adhesive sheet of the present invention is such that the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the surface of the optical member constituting the image display device having the liquid crystal module, and the active energy rays are irradiated in that state. A method of completely curing the layer is preferred.

  Before irradiating the active energy ray, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is in a semi-cured state. Therefore, even if the adherend has a stepped portion, the pressure-sensitive adhesive layer can follow the unevenness. In this way, after sticking the pressure-sensitive adhesive sheet and following the unevenness, the pressure-sensitive adhesive layer is completely cured with active energy rays, thereby increasing the cohesive force of the pressure-sensitive adhesive layer and improving the adhesion to the adherend. To do.

Examples of the active energy rays include ultraviolet rays, electron beams, visible rays, X-rays, ion rays and the like, and can be appropriately selected according to the polymerization initiator (D) contained in the pressure-sensitive adhesive layer. Among these, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.
As the ultraviolet light source, for example, a high pressure mercury lamp, a low pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a carbon arc, a xenon arc, an electrodeless ultraviolet lamp, or the like can be used.
As the electron beam, for example, an electron beam emitted from various electron beam accelerators such as a cockloftwald type, a bandecraft type, a resonant transformation type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type can be used.

(Laminate)
The present invention also relates to a laminate having an adherend on at least one surface of the pressure-sensitive adhesive sheet described above. The adherend is preferably an optical member constituting an image display device having a liquid crystal module. That is, the laminate of the present invention preferably has an optical member constituting an image display device having a liquid crystal module. The laminated body of this invention is obtained through the process of making the adhesive layer of an adhesive sheet contact the surface of a to-be-adhered body, and irradiating an active energy ray in that state, and hardening an adhesive layer completely.

  FIG. 2 is a cross-sectional view illustrating an example of the configuration of the laminate 20 in which the pressure-sensitive adhesive sheet 21 of the present invention is bonded to the adherend 22 and the adherend 24. As shown in FIG. 2, the adherends 22 and 24 may have stepped portions (27a, 27b, 27c, 27d). In FIG. 2, the adherend 22 has stepped portions (27a, 27b), and the adherend 24 has stepped portions (27c, 27d). The thickness of the stepped portions (27a, 27b, 27c, 27d) is usually 5 μm or more and 60 μm or less. Thus, the adhesive sheet 21 of this invention can be bonded also to the member which has a level difference part, and can follow the unevenness | corrugation which arises from a level difference part.

The adherend is preferably an optical member. As an optical member, each structural member in optical products, such as a touch panel and an image display apparatus, can be mentioned. As a constituent member of the touch panel, for example, an ITO film in which an ITO film is provided on a transparent resin film, an ITO glass in which an ITO film is provided on the surface of a glass plate, a transparent conductive film in which a transparent polymer film is coated with a conductive polymer, Examples thereof include a hard coat film and an anti-fingerprint film. Examples of the constituent member of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a brightness enhancement film used in a liquid crystal display device.
Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

  When the pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet, it can be used for bonding two adherends. In this case, the pressure-sensitive adhesive sheet of the present invention is formed by bonding between ITO films inside the touch panel, bonding between the ITO film and ITO glass, bonding between the ITO film of the touch panel and the liquid crystal panel, and the cover glass and the ITO film. Used for bonding, bonding between a cover glass and a decorative film.

(Laminate manufacturing method)
The present invention also relates to a method for producing a laminate. The manufacturing method of the laminated body of this invention includes the process which makes the adhesive sheet of the semi-hardened state mentioned above contact an adherend surface, and irradiates an active energy ray in the state, and hardens an adhesive layer completely. The adherend is preferably an optical member constituting an image display device having a liquid crystal module. That is, in the method for producing a laminate of the present invention, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is brought into contact with the surface of the optical member constituting the image display device having the liquid crystal module, and the active energy ray is irradiated in this state to pressure-sensitive adhesive. A method including a step of completely curing the layer is preferable.

Examples of the active energy rays include the energy rays described above, and ultraviolet rays or electron rays are preferable, and ultraviolet rays are particularly preferable.
Radiation output of the UV light, it is preferable that the integrated quantity of light is made to be a 100 mJ / cm ² or more 10000 mJ / cm ² or less, and more preferably made to be 500 mJ / cm ² or more 5000 mJ / cm ² or less.

  In the method for producing a laminate, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is in a semi-cured state before being irradiated with active energy rays, so even if the adherend has a stepped portion, the pressure-sensitive adhesive layer is uneven. Can follow. In this way, after sticking the pressure-sensitive adhesive sheet and following the unevenness, the pressure-sensitive adhesive layer is completely cured with active energy rays, thereby increasing the cohesive force of the pressure-sensitive adhesive layer and improving the adhesion to the adherend. To do.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

Example 1
Α was used as the base polymer (A). Base polymer α was prepared by solution polymerization in ethyl acetate. 2-ethylhexyl methacrylate (2-EHMA), 2-ethylhexyl acrylate (2-EHA), 2-hydroxyethyl acrylate (2-HEA) were blended in a mass ratio of 100: 28: 14, and a radical polymerization initiator. 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and random copolymerized to obtain a base polymer α. The solution viscosity at 23 ° C. of the 45% solution of the base polymer α was 5500 mPa · s.
15 parts by mass of isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) as monomer (B) and xylene diisocyanate compound (Mitsui Chemicals) as crosslinking agent (C) with respect to 100 parts by mass of base polymer α Co., Ltd., D-110N) 0.15 parts by mass, and 1 part by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan, IRGACURE 184) as a polymerization initiator (D), Ethyl acetate was added as a solvent (E) so that the solid content concentration was 40% by mass to obtain a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition was applied onto a first release sheet (manufactured by Teijin DuPont Films, Ltd., a polyethylene terephthalate film subjected to a release treatment). The coating was performed using a doctor blade YD type manufactured by Yoshimitsu Seiki Co., Ltd., and heated at 100 ° C. for 3 minutes with a hot air dryer. Then, it left still at 23 degreeC for 7 days, the aging process was performed, and the 200-micrometer-thick semi-hardened adhesive sheet (double-sided adhesive sheet) was formed.
A second release sheet (manufactured by Teijin DuPont Films Co., Ltd.), which was subjected to a release treatment having a higher releasability than the first release sheet, was bonded to one side of the pressure-sensitive adhesive sheet to obtain a pressure-sensitive adhesive sheet with a release sheet.

[Production of Laminate (1)]
On the surface of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm), ultraviolet curable ink was screen-printed in a frame shape (length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was 5 μm. Next, the ultraviolet curable ink printed by irradiating with ultraviolet rays was cured. This process was repeated 8 times to obtain a printed step glass having a step of 40 μm.
The obtained pressure-sensitive adhesive sheet was cut into a shape of 90 mm in length and 50 mm in width, the first release sheet was peeled off, and the pressure-sensitive adhesive layer was made of a printed step glass using a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT). Bonding was performed so as to cover the entire frame-shaped print. Thereafter, the second release sheet was peeled off, and a glass plate (90 mm long × 50 mm wide × 0.5 mm thick) was bonded to the exposed pressure-sensitive adhesive layer surface with the laminator, followed by autoclave treatment (40 ° C., 0.5 MPa, 30 min), and then the laminated body (1) was obtained by irradiating an integrated light amount of 1500 mJ / cm ² with an ultraviolet irradiator (ECS-301G1 manufactured by Eye Graphic).

[Production of Laminate (2)]
The obtained pressure-sensitive adhesive sheet was cut into a shape of 90 mm in length and 50 mm in width, the first release sheet was peeled off, and a laminate (1) was produced using a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT). The used printing step glass having a step of 40 μm used was bonded so as to cover the entire frame-like printed surface.
As an adherend, a polarizing plate (manufactured by Polatechno Co., Ltd., SKN-18243T) was cut in advance to the same dimensions as one side of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm), and the center particle diameter was placed on the polarizing plate surface. What sprinkled about 0.05 mg of 30 micrometer glass beads was produced.
The 2nd peeling sheet of the laminated body integrated with the printing level | step difference glass was peeled off, and it bonded with the polarizing plate surface of the said to-be-adhered body with the laminator. Thereafter, autoclave treatment (40 ° C., 0.5 MPa, 30 min) was carried out, and then a laminated body was obtained by irradiating with an integrated light amount of 1500 mJ / cm ² with an ultraviolet irradiator (ECS-301G1 manufactured by Eyegraphic). In addition, the ultraviolet rays were irradiated from the printed step glass.

(Example 2)
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a laminate were obtained in the same manner as in Example 1 except that lauryl acrylate (manufactured by Sartomer Japan Co., Ltd., SR335) was used as the monomer (B).

(Example 3)
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate are obtained in the same manner as in Example 1 except that isobornyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., Light Acrylate IB-XA) is used as the monomer (B). It was.

(Example 4)
[Production of adhesive sheet]
Β was used as the base polymer (A). β was prepared by solution polymerization in ethyl acetate. 2-Ethylhexyl acrylate (2-EHA), ethyl acrylate (EA), N, N-dimethylacrylamide (DMAA), 4-hydroxyacrylamide (4-HBA) so as to have a mass ratio of 100: 100: 45: 5 Then, 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution as a radical polymerization initiator. The solution was heated to 60 ° C. and randomly polymerized to obtain a base polymer β. The solution viscosity of the 35% solution of base polymer β at 23 ° C. was 6000 mPa · s. 30 parts by mass of trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., A-TMPT) as a monomer (B) and xylene diisocyanate as a crosslinking agent (C) with respect to 100 parts by mass of the base polymer β 0.10 parts by mass of a system compound (Mitsui Chemicals, D-110N) and 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan, IRGACURE 184) as a polymerization initiator (D). 0 parts by mass was added, and ethyl acetate was added as a solvent (E) so that the solid content concentration was 30% by mass to obtain a pressure-sensitive adhesive composition. Except having obtained this adhesive composition, it carried out similarly to Example 1, and obtained the adhesive sheet and the laminated body.

(Example 5)
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a laminate were obtained in the same manner as in Example 1 except that the base polymer σ was used as the base polymer (A). The base polymer σ was prepared by solution polymerization in ethyl acetate. 2-ethylhexyl methacrylate (2-EHMA), 2-ethylhexyl acrylate (2-EHA), 2-hydroxyethyl methacrylate (2-HEMA) are blended in a mass ratio of 100: 28: 14, and a radical polymerization initiator. 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and random copolymerized to obtain a base polymer σ. The solution viscosity at 23 ° C. of the 45% solution of the base polymer α was 5500 mPa · s.

(Comparative Example 1)
The pressure-sensitive adhesive composition, the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive composition were the same as in Example 1 except that the monomer (B) isostearyl acrylate and the polymerization initiator (D) were not used. A laminate was obtained.

(Comparative Example 2)
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a laminate were obtained in the same manner as in Comparative Example 1 except that base polymer β was used as the base polymer (A).

(Comparative Example 3)
A pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a laminate were obtained in the same manner as in Example 1 except that base polymer γ was used as the base polymer (A).
Base polymer γ was prepared by solution polymerization in ethyl acetate. n-Butyl acrylate (BA), acrylic acid (AAC), 2-hydroxyethyl acrylate (2-HEA) are blended in a mass ratio of 100: 12.5: 12.5, and 2 as a radical polymerization initiator. , 2'-azobis (2,4-dimethylvaleronitrile) was dissolved in the solution. The solution was heated to 60 ° C. and randomly polymerized to obtain a base polymer γ. The solution viscosity at 23 ° C. of a 37% solution of the base polymer γ was 6000 mPa · s.

(Evaluation)
(Evaluation 1: Storage elastic modulus)
The storage elastic modulus before irradiation with the active energy ray was determined by punching out 5 mm □ (5 mm length × 5 mm width) from the obtained laminate of the pressure-sensitive adhesive layer, and bonding it to a fixed shear jig. The measurement was performed using a mechanical viscoelastic device (trade name: Rheogel-E4000). The measurement conditions were a frequency of 1 Hz, a temperature increase rate of 2 ° C./min, and measurement was performed at 0 ° C., 23 ° C., 30 ° C., and 45 ° C. in a range of −50 ° C. to 150 ° C. at a step temperature of 1 ° C.
The storage elastic modulus after irradiation with active energy rays was measured in the same manner as in the above procedure except that the obtained pressure-sensitive adhesive layer laminate was irradiated with an integrated light amount of 1500 mJ / cm ² with an ultraviolet irradiator.

(Evaluation 2: Dielectric constant)
The relative dielectric constant before irradiation with the active energy ray was carried out by the following procedure. The pressure-sensitive adhesive layer (from which the first release sheet and the second release sheet were peeled from the pressure-sensitive adhesive sheet) was sandwiched between two copper foils and subjected to autoclave treatment (40 ° C., 0.5 MPa, 30 min). Then, it measured based on JISC2138 with the dielectric constant measuring system (Toyo Technica Co., Ltd. make, 1260 type | mold). The frequency and measurement environment were measured under the following conditions.
Frequency: 100KHz, 1MHz
Measurement environment: 23 ° C, relative humidity 55%
The relative dielectric constant after irradiation with active energy rays was carried out by the following procedure. The first release sheet of the pressure-sensitive adhesive sheet was peeled off and bonded to one copper foil with a laminator, and an autoclave treatment (40 ° C., 0.5 MPa, 30 min) was performed. Then, an integrated light quantity of 1500 mJ / cm ² is irradiated with an ultraviolet irradiator, the second release sheet is peeled off, the exposed adhesive layer is bonded to one copper foil with a laminator, and autoclaved (40 ° C., 0.5 MPa, 30 min). Thereafter, the relative dielectric constant was measured in the same manner as in the above procedure.

(Evaluation 3: Measurement of capacitance change rate)
<Assembly of capacitive touch panel>
A first transparent film (thickness of transparent film) on which a transparent conductive electrode pattern is formed using a laminator by peeling off a first release sheet of a commercially available adhesive sheet OC8173D (manufactured by LG, relative dielectric constant 5.7). The transparent conductive electrode pattern (200 μm, relative dielectric constant 3.1, receiving side ITO electrode) was bonded to the surface. Thereafter, the second release sheet was peeled off and bonded to a cover glass (thickness 1.0 mm, relative dielectric constant 7.4) using a laminator. This was designated as a laminate (3).
Next, the first release sheet of the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples is peeled off, and a transparent conductive material of a second transparent film (transmission side ITO electrode) on which a transparent conductive electrode pattern is formed using a laminator. It bonded on the surface in which the electrode pattern is formed. Thereafter, the second release sheet is peeled off, and using a laminator, the laminate (3) is bonded to the surface of the reception-side ITO electrode on which the transparent conductive electrode pattern is not formed to obtain a laminate (4). It was. The area size of each material used was 194 mm × 345 mm.
<Measurement of capacitance change rate>
The capacitance change rate, which is an index of touch sensor sensitivity, is determined based on C _ITO , which is the capacitance between the receiving-side ITO electrode and the transmitting-side ITO electrode before touching the touch panel, and the receiving-side ITO electrode after touching It measured as (DELTA) C (%) = _Cfinger / _CITO * 100 which is ratio with C _finger which is the electrostatic capacitance between transmission side ITO electrodes. The capacitance was measured using an Agilent LCR meter (4284A).

(Evaluation 4: Appearance durability)
<Floating / peeling>
The laminate (1) was treated in an environment of 85 ° C. for 240 hours, and the sample was observed with a microscope (magnification: 25 times) to see whether bubbles or peeling occurred in the entire sample, and evaluated according to the following criteria.
○: No bubble or peeling occurred.
Δ: There are some bubbles.
X: Many bubbles are generated.
The same evaluation was performed for the following two conditions.
・ Treatment for 240 hours in an environment of 85 ° C. and relative humidity 85% ・ Treatment for 240 cycles with an operation of standing at −40 ° C. for 30 minutes and then standing at 85 ° C. for 30 minutes

<Foreign matter embedding>
The laminate (2) was treated for 240 hours in an environment of 85 ° C., and the glass bead sprayed portion after the treatment was observed with a microscope (magnification: 25 times), and the foreign substance embedding property of the pressure-sensitive adhesive sheet was evaluated according to the following criteria. .
○: No new bubbles are generated around the glass beads.
X: New bubbles are generated around the glass beads.
The same evaluation was performed for the following two conditions.
・ Treatment for 240 hours in an environment of 85 ° C. and relative humidity 85% ・ Treatment for 240 cycles with an operation of standing at −40 ° C. for 30 minutes and then standing at 85 ° C. for 30 minutes as one cycle

(Evaluation 5: Step following ability)
The printed stepped portions of the laminate (1) and the laminate (2) were observed with a microscope (magnification: 25 times), and the step followability of the adhesive sheet was evaluated according to the following criteria.
○: The level difference is completely filled.
(Triangle | delta): Air remains in a part of level | step difference part.
X: Air remains in the entire step portion.

(Evaluation 6: Outgas resistance)
The 1st peeling sheet of the obtained adhesive sheet was peeled, and it bonded to PET film (The Toyobo make, Cosmo Shine A4300, thickness 100 micrometers) using the laminator. Then, the 2nd peeling sheet was peeled and it bonded to the PMMA resin board (Mitsubishi Rayon Co., Ltd. product, MR200) using the laminator. Thereafter, autoclave treatment (40 ° C., 0.5 MPa, 30 min) was carried out, and then an accumulated light amount of 1500 mJ / cm ² was irradiated with an ultraviolet irradiator to obtain a laminate (5). The laminate (5) was treated in an environment of 100 ° C. for 20 hours, and observed whether bubbles or peeling occurred in the entire sample, and evaluated according to the following criteria.
(Double-circle): A bubble and peeling do not generate | occur | produce at all. There are no bubbles less than 100 μm.
○: No bubble or peeling occurs. There are no bubbles larger than 100 μm.
Δ: Bubbles of 100 μm or more are generated.
×: Many bubbles and peeling occurred.

As can be seen from Table 1, the pressure-sensitive adhesive sheets obtained in the examples have a low relative dielectric constant, and the specific dielectric constant is further reduced after the active energy rays are irradiated to the pressure-sensitive adhesive sheet. Moreover, in the adhesive sheet obtained by the Example, the storage elastic modulus after irradiating an active energy ray is large, and it is excellent in durability. In the pressure-sensitive adhesive sheet after being irradiated with the active energy ray, it can be seen that there is no occurrence of floating / peeling, and in particular, the generation of bubbles is effectively suppressed.
In addition, in the liquid crystal panel using the pressure-sensitive adhesive sheet obtained in the example, since the relative dielectric constant is particularly low, generation of noise from the liquid crystal panel side is suppressed.

1 Adhesive sheet with release sheet 11 Adhesive sheet (adhesive layer)
12a, 12b Release sheet 20 Laminate 21 Adhesive sheet (adhesive layer)
22 adherend 24 adherend 27a, 27b, 27c, 27d stepped portion

Claims (9)

An adhesive sheet having active energy ray curability, wherein the storage elastic modulus at 23 ° C. and a frequency of 1 Hz becomes 1.0 × 10 ⁶ Pa or more by irradiation with active energy rays.   The storage elastic modulus at any temperature from 0 ° C. to 45 ° C. before irradiating the adhesive sheet with active energy rays is S, and any of 0 ° C. to 45 ° C. after irradiating the adhesive sheet with active energy rays 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the value of T / S at each temperature is 5 or more, where T is the storage elastic modulus at the temperature. The storage elastic modulus at any temperature of 3 ° C. to 35 ° C. before irradiating the adhesive sheet with active energy rays is S ′, and any of 3 ° C. to 35 ° C. after irradiating the adhesive sheet with active energy rays The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the value of T '/ S' at each temperature is 10 or more when the storage elastic modulus at temperature is T '.   When the relative dielectric constant before irradiating the adhesive sheet with active energy rays is P and the relative dielectric constant after irradiating the adhesive sheet with active energy rays is Q, the value of PQ is 0.3 or more. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3.   It is a double-sided adhesive sheet, The adhesive sheet of any one of Claims 1-4.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which is used for bonding an optical member constituting an image display device having a liquid crystal module.   The laminated body which has an optical member which comprises the image display apparatus which has a liquid crystal module in the at least one surface of the adhesive sheet of any one of Claims 1-6.   The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 is brought into contact with the surface of an optical member constituting an image display device having a liquid crystal module, and active energy rays are irradiated in that state to The manufacturing method of a laminated body including the process of fully hardening an adhesive layer.   The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 is brought into contact with the surface of an optical member constituting an image display device having a liquid crystal module, and active energy rays are irradiated in that state to A method for using a pressure-sensitive adhesive sheet for completely curing a pressure-sensitive adhesive layer.

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