JP7127260B2 - Double-sided pressure-sensitive adhesive sheet, method for producing laminate, and method for using double-sided pressure-sensitive adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a double-sided pressure-sensitive adhesive sheet, a method for producing a laminate, and a method for using the double-sided pressure-sensitive adhesive sheet.

In recent years, display devices such as liquid crystal displays (LCDs) and input devices such as touch panels have been widely used in various fields. In the manufacturing process of these display devices and input devices, transparent pressure-sensitive adhesive sheets are used for bonding optical members. Among them, portable terminals are used in various environments, and accordingly, high durability is required. For example, adhesive sheets used in portable terminals are required to exhibit high durability in various environments.

Further, when the optical member is a member having a step, the pressure-sensitive adhesive sheet is required to follow the step. For example, Patent Document 1 discloses a (meth)acrylic copolymer A having a weight average molecular weight of more than 50,000 and 600,000 or less and a (meth)acrylic copolymer A having a weight average molecular weight of 1,000 or more and 50,000 or less. A pressure-sensitive adhesive sheet is described which includes a pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition containing an acrylic copolymer B and which has a dynamic shear loss tangent tan δ satisfying a predetermined condition. Here, even when the pressure-sensitive adhesive sheet is used for bonding an adherend having a level difference, the pressure-sensitive adhesive sheet can exhibit excellent conformability to the level difference, so that air bubbles are not generated between the pressure-sensitive adhesive sheet and the adherend. can be suppressed, and the wet heat whitening resistance and delay bubble resistance can be further improved.

JP 2014-152198 A

By the way, a mobile terminal is configured by laminating a large number of modules such as an image display unit and a touch panel module, and each module is also configured by laminating various members. For this reason, slight warpage may occur in each module due to differences in the thermal expansion coefficients of the members used, and this warpage has become more pronounced as terminals have become lighter and thinner. Here, if the module warps, a force in the thickness direction (a force that causes the members to separate from each other) is applied to the edge of the adhesive sheet used for lamination, and air bubbles are mixed in due to cohesive failure. There is It is believed that such problems can be solved by increasing the cohesive strength of the pressure-sensitive adhesive sheet, that is, by increasing the durability of the pressure-sensitive adhesive sheet.

However, there is a trade-off between the adhesive sheet's ability to follow unevenness and its durability. there were.
Therefore, in order to solve such problems of the prior art, the present inventors conducted studies with the aim of providing a double-faced pressure-sensitive adhesive sheet having both step followability and durability.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that the floating length of the edge portion when the double-sided pressure-sensitive adhesive sheet is attached to a stainless steel pipe under predetermined conditions is set to a predetermined value or less. It was found that a double-sided pressure-sensitive adhesive sheet having both step followability and durability can be obtained.
Specifically, the present invention has the following configurations.

[1] A double-sided pressure-sensitive adhesive sheet for laminating an optical member having an edge floating length of 8 mm or less as measured by the following measurement method A;
(Measuring method A)
A laminate is obtained by bonding the double-sided pressure-sensitive adhesive sheet to a polarizing plate film having a rigidity of 21±1 mN; a test piece having a length of 30 mm and a width of 20 mm is cut out from the laminate; , and crimped by reciprocating a 2 kg roll; At that time, the length direction of the test piece is laminated along the arc of a stainless steel tube with a diameter of 50 mm; After leaving the tube in an environment of 85 ° C and a relative humidity of less than 10% for 24 hours, each peel length (B1, B2) of both edges of the test piece peeled from the stainless steel tube is measured in the short side of the test piece. It is determined by measuring the distance from the point (P1, P2) to the peel initiation point (Q1, Q2) on the center line (C) of the specimen, and the average value of the two peel lengths (B1, B2) is taken as the edge float length of the part.
[2] The double-sided pressure-sensitive adhesive sheet according to [1], wherein the value of the loss tangent tan δ of the dynamic shear viscoelastic modulus at a measurement temperature of 25°C and a frequency of 1 Hz is 0.56 or more and 0.75 or less.
[3] The double-sided pressure-sensitive adhesive sheet has a layer structure of two or more layers, and at least one layer of the layer structure of two or more layers contains a (meth)acrylic acid ester polymer according to [1] or [2]. double-sided adhesive sheet.
[4] The double-sided pressure-sensitive adhesive sheet has a layer structure of two or more layers, at least one layer of the layer structure of two or more layers contains a hydrogen abstraction type photopolymerization initiator, and has active energy ray-curing ability [1 ] to [3].
[5] A step of bringing at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of [1] to [4] into contact with the surface of an optical member and irradiating the double-sided pressure-sensitive adhesive sheet with active energy rays in this state to cure the double-sided pressure-sensitive adhesive sheet. A method of manufacturing a laminate comprising:
[6] A double-sided adhesive obtained by bringing at least one surface of the double-sided adhesive sheet according to any one of [1] to [4] into contact with the surface of an optical member and irradiating the double-sided adhesive sheet with an active energy ray in that state to cure the double-sided adhesive sheet. How to use the sheet.

According to the present invention, it is possible to obtain a double-sided pressure-sensitive adhesive sheet having both conformability and durability.

FIG. 1 is a diagram for explaining the floating length of the edge portion of a double-sided pressure-sensitive adhesive sheet in measurement method A. FIG. FIG. 2 is a cross-sectional view illustrating one embodiment of the double-sided pressure-sensitive adhesive sheet of the present invention. FIG. 3 is a cross-sectional view illustrating one embodiment of the double-sided pressure-sensitive adhesive sheet of the present invention.

The present invention will be described in detail below. Although the constituent elements described below may be described based on representative embodiments and specific examples, the present invention is not limited to such embodiments. In this specification, "(meth)acrylic acid" represents acrylic acid and methacrylic acid.

(Double-sided adhesive sheet)
TECHNICAL FIELD The present invention relates to a double-sided pressure-sensitive adhesive sheet for bonding an optical member, in which the floating length of the edge portion measured by the measuring method A is 8 mm or less. Here, the measuring method A is the following method.

Measurement method A
The double-sided pressure-sensitive adhesive sheet is attached to a polarizing plate film having a rigidity of 21±1 mN to obtain a laminate. A test piece having a length of 30 mm and a width of 20 mm is cut from the laminate. A test piece is attached to the outer peripheral surface of a stainless steel tube having a diameter of 50 mm, and crimped by reciprocating a 2 kg roll once. At that time, the longitudinal direction of the test piece is stuck along the circular arc of the stainless steel tube with a diameter of 50 mm. After leaving the stainless steel tube with the test piece bonded to it in an environment of 85 ° C and a relative humidity of less than 10% for 24 hours, each peel length (B1, B2 ) is determined by measuring the distance from the midpoint of the short side of the test piece (P1, P2) to the peel starting point (Q1, Q2) on the center line (C) of the test piece, and the two peel lengths ( The average value of B1, B2) is taken as the floating length of the edge.
In this specification, the diameter of the stainless steel tube means the outer diameter including the thickness of the stainless steel tube.

Here, the stiffness of the polarizing plate film used in measurement method A is 21±1 mN. When measuring the stiffness of the polarizing plate film, a Gurley Stiffness Tester (manufactured by Kumagai Riki Kogyo Co., Ltd., Gurley Stiffness Tester) was used as a measuring instrument, and Japan TAPPI No. 1 was used. 40, TAPPI 543. At this time, the size of the polarizing plate film is 25.4 mm×38.1 mm (1 inch×1.5 inch), the weight is 50 g, and the weight position is 4 inches. The thickness of the polarizing plate film used in the measurement method A is not particularly limited as long as the stiffness is 21±1 mN, but the thickness of the polarizing plate film is preferably 215 μm. As the polarizing plate film used in the measurement method A, for example, SKN-18243T-HC manufactured by Polatechno can be used.

When cutting out the laminate in which the double-sided adhesive sheet is bonded to the polarizing plate film, the test piece is cut so that the measurement direction of the rigidity of the polarizing plate film coincides with the length direction of the test piece.

FIG. 1 is a diagram for explaining the floating length of the edge portion in the measurement method A. FIG. In the upper diagram of FIG. 1(a), the entire surface of the test piece 200 is attached to the stainless steel tube 100 having a diameter of 50 mm. Here, the test piece 200 was obtained by bonding a double-sided pressure-sensitive adhesive sheet to a polarizing plate film having a rigidity of 21±1 mN, and cutting it into a length of 30 mm and a width of 20 mm. The lower diagram of FIG. 1(a) and FIG. 1(b) show the state after the stainless steel tube 100 to which the test piece 200 is bonded is left to stand in an environment of 85° C. and a relative humidity of less than 10% for 24 hours. It is a diagram. In the lower diagram of FIG. 1(a) and FIG. 1(b), the longitudinal end (edge) of the test piece 200 is separated from the stainless steel tube 100, and the edge is lifted. I understand.
The length of the test piece 200 peeled off from the stainless steel pipe 100 due to the floating of the edge portion (floating length of the edge portion) is the distance represented by B1 and B2 in FIG. 1(b). . In this specification, this distance is defined as the floating length of the edge portion.

The double-faced pressure-sensitive adhesive sheet of the present invention has an edge floating length of 8 mm or less as measured by the measurement method A described above, and thus has both excellent step followability and durability. Specifically, when the double-faced pressure-sensitive adhesive sheet of the present invention is attached to an adherend having steps, the surface pressure-sensitive adhesive layer follows the steps of the adherend without gaps. Therefore, problems such as the generation of air bubbles in the stepped portion are suppressed. In addition, the double-sided pressure-sensitive adhesive sheet of the present invention has excellent durability, and such durability is maintained even when placed in a high-temperature environment for a long time or when the edges of the double-sided pressure-sensitive adhesive sheet are distorted. can be demonstrated. Here, from the viewpoint of obtaining better step resistance and durability, the floating length of the edge portion is preferably 6 mm or less, more preferably 4 mm or less.

In addition, the present invention has succeeded in improving the conformability and durability of the double-sided pressure-sensitive adhesive sheet by setting the floating length of the edge portion measured by the above measuring method A within a predetermined range. It was also the first time to discover the relationship between the floating length of the edge portion measured by the measurement method A and the level difference conformability and durability of the double-sided PSA sheet.

Here, the step followability of the double-sided pressure-sensitive adhesive sheet of the present invention can be evaluated by the following method. First, one side of the double-sided pressure-sensitive adhesive sheet is attached to a glass plate having a printing step of 30 μm, and the other side of the double-sided pressure-sensitive adhesive sheet is attached to a glass plate having no printing step. The laminate thus obtained is autoclaved (40° C., 0.5 MPa, 30 minutes), and irradiated with ultraviolet rays from the glass plate side having printing steps so that the integrated light quantity becomes 2,000 mJ/cm ² . After that, the printing step portion is observed to evaluate whether or not bubbling or peeling occurs. When little or no foaming or peeling is observed, it can be judged that the step followability is good.

Moreover, the durability of the double-sided pressure-sensitive adhesive sheet of the present invention can be evaluated by the following method. First, one side of a double-sided pressure-sensitive adhesive sheet with a thickness of 175 μm is adhered to a glass plate having a 10 μm printing level difference, and the other side of the double-sided pressure-sensitive adhesive sheet is adhered to a glass plate having no printing level difference. The laminate thus obtained is autoclaved (40° C., 0.5 MPa, 30 minutes), and irradiated with ultraviolet rays from the glass plate side having printing steps so that the integrated light quantity becomes 2,000 mJ/cm ² . After that, a SUS plate having a thickness of 180 μm and a width of 12.7 mm was inserted between a glass plate with a printing step and a glass plate without a printing step to a position at a distance of 5 mm from the end of the adhesive layer, and strain was applied. °C and a relative humidity of less than 10% for 72 hours. Then, the degree of air bubble generation at the end of the adhesive layer near the SUS plate insertion portion is evaluated, and when little or no air bubble generation is observed, the durability is judged to be good. In this specification, excellent durability is also referred to as excellent cavitation aptitude.

The value of the loss tangent tan δ of the dynamic shear viscoelastic modulus at a measurement temperature of 25° C. and a frequency of 1 Hz of the double-sided pressure-sensitive adhesive sheet of the present invention is preferably 0.56 or more and 0.75 or less, more preferably 0.58 or more and 0.70. It is more preferably 0.59 or more and 0.68 or less. By setting the tan δ value of the double-sided pressure-sensitive adhesive sheet within the above range, it is possible to further enhance the step conformability of the double-sided pressure-sensitive adhesive sheet.

When measuring the loss tangent (tan δ) of the dynamic shear viscoelastic modulus of the double-sided PSA sheet, Rheogel-E4000 manufactured by UBM Co., Ltd. can be used as a measuring device. The following measurement conditions are adopted.
・Method: solid shear ・Strain: 2 μm
・Temperature increase rate: 2°C/min
・Frequency: 1Hz
・Thickness: 175 μm

The total thickness of the double-sided pressure-sensitive adhesive sheet of the present invention is preferably 10 µm or more, more preferably 30 µm or more, even more preferably 50 µm or more. The total thickness of the double-sided pressure-sensitive adhesive sheet is preferably 1000 μm or less, more preferably 700 μm or less, and even more preferably 500 μm or less.

The adhesive strength of the double-sided pressure-sensitive adhesive sheet of the present invention is preferably 20 N/25 mm or more, more preferably 25 N/25 mm or more. The above adhesive strength is the adhesive strength after the double-sided adhesive sheet is brought into contact with an adherend (after sticking) and after irradiation with 2000 mJ/cm ² of active energy rays (after complete curing). The adhesive strength of the double-sided PSA sheet to the adherend described above is a value obtained by measuring the 180° peeling adhesive strength to the adherend according to JIS Z 0237.

The double-sided pressure-sensitive adhesive sheet of the present invention preferably has a haze value (measured according to JIS K 7136:2000) of 2% or less, and 1.5% or less, in an environment of 23°C and 50% relative humidity. It is more preferably 1% or less. If the haze value is within the above range, the transparency required when the double-sided pressure-sensitive adhesive sheet is used for optical members can be satisfied.

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

Each surface of the double-sided pressure-sensitive adhesive sheet is preferably covered with a release sheet. That is, the present invention may relate to a double-sided pressure-sensitive adhesive sheet with a release sheet.

As the release sheet, a release laminated 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 base material for the release sheet in the release laminated sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone-based release agent or a compound containing a long-chain alkyl group is used. In particular, an addition-type silicone-based 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 Co., Ltd., and KS-3600, KS-774 and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. is mentioned. In addition, the silicone release agent may contain a silicone resin which is an organosilicon compound having _SiO2 units and ( _CH3 )3SiO1 _/2 units or _CH2 =CH( _CH3 ) _{SiO1 /2} units. preferable. Specific examples of silicone resins include BY24-843, SD-7292, SHR-1404, etc. manufactured by Dow Corning Toray Silicone Co., Ltd., and KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.

It is preferable that the release sheets laminated on the respective surfaces of the double-sided pressure-sensitive adhesive sheet have different release properties. If the releasability from one side is different from the releasability from the other, it is preferable because it becomes easy to peel off only the release sheet with higher releasability first.

The double-sided pressure-sensitive adhesive sheet of the present invention may have a single-layer structure or a multi-layer structure as long as it is a double-sided pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer. The double-sided pressure-sensitive adhesive sheet of the present invention may be a double-sided pressure-sensitive adhesive sheet 1 comprising a single pressure-sensitive adhesive layer 10 as shown in FIG. When the double-sided pressure-sensitive adhesive sheet has a multilayer structure, the double-sided pressure-sensitive adhesive sheet preferably has a layer structure of two or more layers. When the double-sided pressure-sensitive adhesive sheet has a layer structure of two layers, both layers are preferably pressure-sensitive adhesive layers. Also, as shown in FIG. 3, the double-sided pressure-sensitive adhesive sheet 1 has a structure in which a first surface pressure-sensitive adhesive layer 12a, an intermediate resin layer 11 and a second surface pressure-sensitive adhesive layer 12b are laminated in this order. may In this specification, the pressure-sensitive adhesive layer 10 as shown in FIG. 2 and the first surface pressure-sensitive adhesive layer 12a and the second surface pressure-sensitive adhesive layer 12b as shown in FIG. It is called "adhesive layer".

(Adhesive layer)
<(Meth)acrylic acid ester polymer (A)>
The pressure-sensitive adhesive layer preferably contains the (meth)acrylate polymer (A). The (meth)acrylic acid ester polymer (A) may be a polymer composed only of non-crosslinkable (meth)acrylic acid ester units (a1), but the non-crosslinkable (meth)acrylic acid ester units It is preferably a (meth)acrylic acid ester copolymer containing (a1) and a (meth)acrylic monomer unit (a2) having a crosslinkable functional group. As used herein, a "unit" is a repeating unit (monomer unit) that constitutes a polymer.
The (meth)acrylic acid ester polymer (A) preferably has a degree of transparency that does not impair the visibility of the display device.

The (meth)acrylic acid ester polymer (A) preferably has a weight average molecular weight of 100,000 or more, more preferably 200,000 or more. The weight average molecular weight of the (meth)acrylate polymer (A) is preferably 2,000,000 or less, more preferably 1,500,000 or less, and particularly preferably 1,000,000 or less. By setting the weight-average molecular weight within the above range, the pressure-sensitive adhesive layer can be in a semi-cured state, and sufficient adhesiveness and durability can be ensured. In addition, the durability of the pressure-sensitive adhesive layer can be enhanced by using a (meth)acrylic acid ester polymer (A) having a relatively large weight average molecular weight.

The weight average molecular weight of the (meth)acrylic acid ester polymer (A) is a value measured by gel permeation chromatography (GPC) and determined based on polystyrene standards. Measurement conditions for gel permeation chromatography (GPC) are as follows.
Solvent: tetrahydrofuran Columns: Shodex KF801, KF803L, KF800L, KF800D (4 columns manufactured by Showa Denko Co., Ltd. were connected and used)
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 2,500,000 A calibration curve of 10 samples was used.

The content of the (meth)acrylic acid ester polymer (A) is preferably 75% by mass or more, more preferably 80% by mass or more, relative to the total mass of the pressure-sensitive adhesive composition forming the surface pressure-sensitive adhesive layer. is more preferable, and 85% by mass or more is even more preferable. In addition, the "surface adhesive layer" referred to herein refers to an adhesive layer that constitutes the surface. In the double-sided pressure-sensitive adhesive sheet with a multilayer structure shown in FIG. 3, the "first pressure-sensitive adhesive layer 12a" and the "second pressure-sensitive adhesive layer 12b" correspond to the "surface pressure-sensitive adhesive layer".

<Non-crosslinkable (meth)acrylate unit (a1)>
The non-crosslinkable (meth)acrylate unit (a1) is preferably a repeating unit derived from a (meth)acrylic acid alkyl ester having an alkyl group, and is derived from a (meth)acrylic acid alkyl ester having a branched alkyl group. It is more preferable that it is a repeating unit that When the non-crosslinkable (meth)acrylate unit (a1) has an alkyl group, the number of carbon atoms in the alkyl group is preferably 1 or more and 20 or less, more preferably 1 or more and 10 or less, It is more preferably 3 or more and 10 or less, and even more preferably 3 or more and 9 or less.
Examples of such (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, Isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, (meth) ) 2-ethylhexyl acrylate, isoheptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, (meth)acrylic n-decyl acid, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, (meth)acrylic acid ethoxyethyl, cyclohexyl (meth)acrylate, benzyl (meth)acrylate and the like. These may be used individually by 1 type, and may use 2 or more types together. Among them, it is preferable to use n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate as the non-crosslinkable (meth)acrylic acid ester unit.

The content of the unit (a1) derived from the non-crosslinkable (meth)acrylate in the (meth)acrylate polymer (A) is based on the total mass of the (meth)acrylate polymer (A). , is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. Moreover, the content of the unit (a1) is preferably 99% by mass or less, more preferably 95% by mass or less.

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

The content of the (meth)acrylic monomer unit (a2) having a crosslinkable functional group in the (meth)acrylate polymer (A) is based on the total mass of the (meth)acrylate polymer (A). is preferably 0.01% by mass or more, more preferably 0.5% by mass or more, and even more preferably 2% by mass or more. Also, the content of the unit (a2) is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

<Other monomer units>
(Meth)acrylic acid ester polymer (A) is optionally a non-crosslinkable (meth)acrylic acid ester unit (a1) and a (meth)acrylic monomer unit having a crosslinkable functional group (a2) other than It may have other monomeric units. Other monomers may be those copolymerizable with non-crosslinkable (meth)acrylic acid esters and acrylic monomers having a crosslinkable functional group, such as (meth)acrylonitrile, vinyl acetate, styrene, vinyl chloride, vinylpyrrolidone, vinylpyridine and the like; The content of other monomer units is preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less.

<Hydrogen abstraction type photopolymerization initiator (B)>
The pressure-sensitive adhesive layer preferably further contains a hydrogen abstraction type photopolymerization initiator (B). The hydrogen abstraction type photopolymerization initiator (B) initiates the cross-linking reaction of the (meth)acrylic acid ester polymer (A) upon exposure to active energy rays. Hydrogen abstraction photopolymerization initiators include, for example, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 3,3′-dimethyl-4-methoxybenzophenone, 2,4,6-trimethyl Benzophenone, 4-methylbenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, camphorquinone, dibenzosuberone, 2-ethylanthraquinone, 3 ,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, benzyl, 9,10-phenanthrenequinone and the like. Among them, the hydrogen abstraction type photopolymerization initiator (B) preferably contains at least one selected from benzophenone, 4-methylbenzophenone and 2,4,6-trimethylbenzophenone.

The content of the hydrogen abstraction type photopolymerization initiator in the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer is 0.5 parts by mass or more per 100 parts by mass of the (meth)acrylic acid ester polymer (A)10. It is preferably 0 parts by mass or less, more preferably 1 part by mass or more and 7 parts by mass or less, and even more preferably 2 parts by mass or more and 5 parts by mass or less. By setting the content of the hydrogen abstraction type photopolymerization initiator in the pressure-sensitive adhesive composition within the above range, the cross-linking density of the pressure-sensitive adhesive layer can be increased, and the durability of the double-sided pressure-sensitive adhesive sheet can be increased more effectively. can be done.

Since the hydrogen abstraction type photopolymerization initiator can be repeatedly used as a reaction initiator by photoirradiation, it is possible to give the pressure-sensitive adhesive sheet of the present invention an after-curing property.

<Solvent (C)>
The pressure-sensitive adhesive layer is preferably formed by semi-curing a pressure-sensitive adhesive composition containing a solvent. That is, the surface pressure-sensitive adhesive layer is preferably a solvent-based pressure-sensitive adhesive layer, and the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer preferably further contains a solvent (C) in addition to the components described above. In this case, the pressure-sensitive adhesive layer is preferably formed by coating the solvent-based pressure-sensitive adhesive composition, volatilizing the solvent, and semi-curing the composition.
The pressure-sensitive adhesive layer is preferably formed by curing the pressure-sensitive adhesive composition into a sheet. As a method of forming a sheet, there is mainly a method of dissolving an adhesive composition in a solvent, applying an adhesive coating liquid, and drying to evaporate the solvent to form a sheet, but there is no particular limitation. do not have.

The solvent used in forming the solvent-type resin layer is used to improve the coatability of the pressure-sensitive adhesive composition. The solvent is preferably a solvent having no polymerizable unsaturated group. Moreover, when the adhesive layer contains a photopolymerization initiator, a solvent having a higher vapor pressure at 25° C. than the photopolymerization initiator is preferable. Since the larger the vapor pressure difference, the less the coating defects and the easier the production, the vapor pressure of the solvent is preferably 2000 Pa or more, particularly preferably 5000 Pa or more. Although the upper limit is not particularly limited, 50000 Pa or less is preferable for practical use.

Examples of the solvent (C) include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichlorethylene, tetrachloroethylene, and dichloropropane; , ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone Esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl Ethers, polyols such as propylene glycol monomethyl ether acetate, and derivatives thereof.

A solvent (C) may be used individually by 1 type, and may use 2 or more types together. The content of the solvent (C) in the adhesive coating liquid is not particularly limited, but can be 5% by mass or more and 95% by mass or less, and 10% by mass or more and 90% by mass with respect to the total mass of the adhesive composition. % or less.

<Other ingredients>
The pressure-sensitive adhesive composition may contain other cross-linking agents instead of the hydrogen abstraction photopolymerization initiator, or may contain both the hydrogen abstraction photopolymerization initiator and other cross-linking agents. good. Examples of cross-linking agents include known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds.
The content of the cross-linking agent in the adhesive composition is preferably 0.001 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A), It is more preferably 0.01 part by mass or more and 1 part by mass or less.

Moreover, the adhesive composition may contain a photopolymerization initiator other than the hydrogen abstraction type photopolymerization initiator. Examples of photopolymerization initiators include acetophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, and amine-based initiators.
Specific examples of acetophenone-based initiators include diethoxyacetophenone and benzyldimethylketal.
Specific examples of hydroxyalkylphenone-based initiators include 1-hydroxy-cyclohexyl-phenyl-ketone and the like.
Specific examples of thioxanthone-based initiators include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone.
Specific examples of amine-based initiators include triethanolamine and ethyl 4-dimethylbenzoate.

The pressure-sensitive adhesive composition may contain components other than the above as long as the effects of the present invention are not impaired. Other components can be selected from known additives for pressure-sensitive adhesives, such as antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, and UV absorbers, as required.
Examples of antioxidants include phenol antioxidants, amine antioxidants, lactone antioxidants, phosphorus antioxidants, sulfur antioxidants, and the like. These antioxidants may be used individually by 1 type, and may use 2 or more types together.
Examples of metal corrosion inhibitors include benzotriazole-based resins.
Examples of tackifiers include rosin-based resins, terpene-based resins, terpene-phenol-based resins, coumarone-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, and petroleum resins.
Silane coupling agents include, for example, mercaptoalkoxysilane compounds (eg, mercapto group-substituted alkoxy oligomers, etc.).
Examples of ultraviolet absorbers include benzotriazole-based compounds, benzophenone-based compounds, and hindered amine-based compounds. However, when ultraviolet light is used as the active energy ray for curing, it must be added within a range that does not inhibit the polymerization reaction.

Furthermore, the adhesive composition may contain a monomer containing at least one polymerizable unsaturated group. Examples of polymerizable unsaturated groups include groups containing ethylenic double bonds, such as (meth)acryloyl groups and vinyl groups. Oligomers of such monomers may be used as plasticizers.

Examples of monofunctional monomers having one polymerizable unsaturated group include pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, and (meth)acrylic acid. isooctyl, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, lauryl (meth)acrylate, Examples include stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and the like. Examples of the monofunctional monomer (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 Lauryl acid, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl (meth)acrylate can be mentioned.

Polyfunctional monomers containing two or more polymerizable unsaturated groups include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, di 1,4-butylene glycol (meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di(meth)acrylate, di(meth)acrylic acid Neopentyl glycol, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentatri(meth)acrylate (Meth)acrylic esters of polyhydric alcohols such as erythritol and pentaerythritol tetra(meth)acrylate; and vinyl methacrylate.

(Physical properties of adhesive layer)
In the present invention, the pressure-sensitive adhesive layer is preferably a pressure-sensitive adhesive layer before main curing. The pressure-sensitive adhesive layer before main curing is a pressure-sensitive adhesive layer that leaves room for curing by active energy rays or heat. Among them, the adhesive layer is preferably an adhesive layer that leaves room for curing by active energy rays, and it can be said that such an adhesive layer has active energy ray-curing ability. In addition, it can be said that the pressure-sensitive adhesive layer having active energy ray-curing ability has after-curability. When the pressure-sensitive adhesive layer has an after-curing property, the pressure-sensitive adhesive layer is in a semi-cured state, and the double-sided pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer is applied to an adherend and then irradiated with active energy rays. to fully cure the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer in a semi-cured state can follow the uneven structure of the adherend, and the pressure-sensitive adhesive layer is completely cured by the main curing, and can exhibit strong adhesive strength.
Here, "semi-cured state" means that the gel fraction increases by 0.5% or more after curing by irradiation with active energy rays or the like. The increase rate of the gel fraction is preferably 0.5% or more, more preferably 1% or more. "Main curing" means that the adhesive layer is completely cured by the active energy ray, and the main curing state means that the increase in the gel fraction when the active energy ray is irradiated is less than 0.5%. indicates In the present invention, the pressure-sensitive adhesive layer may be subjected to primary curing in order to obtain a semi-cured state, and secondary curing to obtain a fully cured state. In addition, multistage curing may be performed to obtain a semi-cured state, and multistage curing may be performed to obtain a fully cured state.
The gel fraction was determined by collecting about 0.1 g of the adhesive sheet in a sample bottle, adding 30 cm ³ of ethyl acetate and shaking for 24 hours. The above residue is dried at 100° C. for 1 hour, the dry weight W (g) is measured, and the obtained dry weight is calculated by the following formula (1).
Gel fraction (%) = (dry weight / collected weight of adhesive sheet) x 100

The pressure-sensitive adhesive layer is preferably a semi-cured pressure-sensitive adhesive layer, and preferably a pressure-sensitive adhesive layer before main curing. In the present invention, it is preferable to irradiate active energy rays in both the semi-curing step and the main curing step. As active energy rays, ultraviolet rays, electron beams, visible rays, X-rays, ion beams, and the like can be used. Among them, as the active energy ray, it is preferable to use ultraviolet rays or electron beams, and it is more preferable to use ultraviolet rays.

(Laminated adhesive sheet)
The double-sided pressure-sensitive adhesive sheet of the invention may have a layer structure of two or more layers. In this case, the double-sided pressure-sensitive adhesive sheet is sometimes called a laminated pressure-sensitive adhesive sheet. In the laminated pressure-sensitive adhesive sheet, it is preferable that at least one layer in the layer structure of two or more layers has the pressure-sensitive adhesive layer described above, and preferably contains a (meth)acrylic acid ester-based copolymer. Further, at least one layer of the layer structure of two or more layers more preferably further contains a hydrogen abstraction type photopolymerization initiator, and more preferably has active energy ray-curing ability.

When the laminated pressure-sensitive adhesive sheet has a structure in which the first surface pressure-sensitive adhesive layer 12a, the intermediate resin layer 11 and the second surface pressure-sensitive adhesive layer 12b are laminated in this order as shown in FIG. The one surface adhesive layer 12a and the second surface adhesive layer 12b are preferably the above-described adhesive layers. In this case, the compositions of the first surface adhesive layer 12a and the second surface adhesive layer 12b may be the same or different.

Examples of the intermediate resin layer include films of acrylic resin, urethane-acrylic copolymer, styrene-acrylic copolymer, polystyrene, polyethylene terephthalate, polycarbonate, polyetheretherketone, triacetylcellulose, and the like. Among them, it is preferable to use an adhesive containing an acrylic resin or a urethane-acrylic copolymer as the intermediate resin layer.

The intermediate resin layer may be a solvent type resin layer or a non-solvent type resin layer. The solvent-type resin layer is formed by coating a resin composition containing a solvent and volatilizing the solvent in a process such as heating and drying. The solventless resin layer is formed by applying a resin composition substantially free of solvent and curing the resin composition. The resin composition substantially free of solvent means that the solvent content is 1% by mass or less with respect to the total mass of the resin composition. Preferred ranges and specific examples of the solvent used for the intermediate resin layer are the same as those for the solvent used for the surface layer.

As shown in FIG. 3, the laminated pressure-sensitive adhesive sheet has a structure in which a first surface pressure-sensitive adhesive layer 12a, an intermediate resin layer 11 and a second surface pressure-sensitive adhesive layer 12b are laminated in this order. where A is the thickness of the first surface adhesive layer, B is the thickness of the intermediate resin layer, and C is the thickness of the second surface adhesive layer, the value of A/B is 0.23 or more. 0.46 or less, and the value of C/B is preferably 0.23 or more and 0.46 or less.
The value of A/B is more preferably 0.25 or more, and even more preferably 0.30 or more. The value of A/B is more preferably 0.43 or less, even more preferably 0.40 or less.
Also, the value of C/B is more preferably 0.25 or more, and even more preferably 0.30 or more. The value of C/B is more preferably 0.43 or less, even more preferably 0.40 or less.
In the present invention, by setting the relationship among the thickness of the first surface adhesive layer, the thickness of the intermediate resin layer, and the thickness of the second surface adhesive layer within the range of the above conditions, the step can be effectively achieved. Followability can be improved. Furthermore, the reworkability of the laminated pressure-sensitive adhesive sheet can be enhanced by setting the thickness relationship of each layer within the range of the above conditions. The high reworkability of the laminated pressure-sensitive adhesive sheet means that the laminated pressure-sensitive adhesive sheet can be peeled off from the adherend when necessary without leaving any adhesive residue, and the laminated pressure-sensitive adhesive sheet does not break during the peeling process.

Further, the value of A/C is preferably 0.25 or more and 4.0 or less, more preferably 0.65 or more and 1.5 or less, and 0.9 or more and 1.1 or less. More preferred. It is particularly preferable that the thickness (A) of the first surface pressure-sensitive adhesive layer and the thickness (C) of the second surface pressure-sensitive adhesive layer are equivalent.

The thickness (A) of the first surface pressure-sensitive adhesive layer is preferably 5 μm or more, more preferably 10 μm or more. The thickness (A) of the first surface pressure-sensitive adhesive layer is preferably 50 μm or less, more preferably 45 μm or less.
The thickness (C) of the second surface pressure-sensitive adhesive layer is preferably 5 μm or more, more preferably 10 μm or more. The thickness (C) of the second surface pressure-sensitive adhesive layer is preferably 50 μm or less, more preferably 45 μm or less.
The thickness (B) of the intermediate resin layer is preferably 10 µm or more, more preferably 30 µm or more, and even more preferably 50 µm or more. The thickness (B) of the intermediate resin layer is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less.

The dynamic storage elastic modulus G′ at a frequency of 1 Hz at 25° C. of the first surface pressure-sensitive adhesive layer and the second surface pressure-sensitive adhesive layer is preferably 3×10 ⁴ Pa or more and 3×10 ⁵ Pa or less, respectively. , 9×10 ⁴ Pa or more and 3×10 ⁵ Pa or less, and more preferably 1×10 ⁵ Pa or more and 2×10 ⁵ Pa or less. In addition, the dynamic storage elastic modulus G′ at a frequency of 1 Hz at 80° C. of the first surface pressure-sensitive adhesive layer and the second surface pressure-sensitive adhesive layer should be 5×10 ³ Pa or more and 5×10 ⁴ Pa or less, respectively. , more preferably 9×10 ³ Pa or more and 5×10 ⁴ Pa or less, and even more preferably 1×10 ⁴ Pa or more and 4×10 ⁴ Pa or less.
The dynamic storage modulus G′ of the intermediate resin layer at 25° C. at a frequency of 1 Hz is preferably 7×10 ⁴ Pa or more and 7×10 ⁵ Pa or less, and 1×10 ⁵ Pa or more and 7×10 ⁵ Pa or less. more preferably 1×10 ⁵ Pa or more and 4×10 ⁵ Pa or less. In addition, the dynamic storage modulus G′ of the intermediate resin layer at a frequency of 1 Hz at 80° C. is preferably 1×10 ⁴ Pa or more and 1×10 ⁵ Pa or less, more preferably 5×10 ⁴ Pa or more and 1×10 ⁵ Pa. It is more preferably 5×10 ⁴ Pa or more and 7×10 ⁴ Pa or less.

The dynamic storage elastic modulus G′ of the laminated adhesive sheet at a frequency of 1 Hz at 25° C. is preferably 3×10 ⁴ Pa or more and 3×10 ⁵ Pa or less, and is 9×10 ⁴ Pa or more and 3×10 ⁵ Pa or less. is more preferably 1×10 ⁵ Pa or more and 2×10 ⁵ Pa or less. In addition, the dynamic storage elastic modulus G′ at a frequency of 1 Hz at 80° C. is preferably 5×10 ³ Pa or more and 5×10 ⁴ Pa or less, more preferably 9×10 ³ Pa or more and 5×10 ⁴ Pa or less. It is preferably 1×10 ⁴ Pa or more and 4×10 ⁴ Pa or less, more preferably.
The dynamic storage elastic modulus of the laminated pressure-sensitive adhesive sheet is obtained by punching out a laminated pressure-sensitive adhesive sheet (first surface pressure-sensitive adhesive layer, intermediate resin layer, and second surface pressure-sensitive adhesive layer) of 10 mm × 8 mm, A dynamic viscoelasticity apparatus (trade name: Rheogel-E4000) is used for measurement using a jig for a solid shear method. The measurement conditions are a frequency of 1 Hz, a heating rate of 2°C/min, and measurements at 25°C and 80°C in the range of 0°C to 100°C when the temperature is raised at a step temperature of 1°C.

(Manufacturing method of double-sided pressure-sensitive adhesive sheet)
The method for producing a double-sided pressure-sensitive adhesive sheet of the present invention includes a step of applying a pressure-sensitive adhesive coating liquid and semi-curing (primary curing) by irradiation with active energy rays. The pressure-sensitive adhesive composition preferably contains a solvent (C), and in this case, after applying the pressure-sensitive adhesive composition, a heat drying step is preferably provided in order to volatilize the solvent (C). The coating film thus obtained is irradiated with active energy rays to form a semi-cured product (adhesive layer).

Coating of the pressure-sensitive adhesive composition can be carried out using a known coating device. Coating devices include, for example, blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, micro gravure coaters, rod blade coaters, lip coaters, die coaters and curtain coaters.

The heating and drying step of the coating film can be carried out using a known heating device such as a heating furnace and an infrared lamp. For example, the heating temperature can be 50° C. or higher and 150° C. or lower. In addition, the heating time may be set so that the solvent volatilizes and the residual solvent concentration in the adhesive layer is 1000 ppm or less. It is preferable to set the time for about 1 to 30 minutes.

In the step of irradiating the coating film with active energy rays, ultraviolet rays, electron beams, visible rays, X-rays, ion beams, etc. can be used as active energy rays. Among them, as the active energy ray, it is preferable to use ultraviolet rays or electron beams, and it is more preferable to use ultraviolet rays.
As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an extra-high 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 Cockroftwald accelerator, a Van de Clough accelerator, a resonance transformer accelerator, an insulating core transformer accelerator, a linear accelerator, a dynamitron accelerator, and a high frequency accelerator can be used.
The irradiation output of ultraviolet rays is preferably adjusted so that the integrated light intensity is 100 mJ/cm ² or more, more preferably 500 mJ/cm ² or more, and adjusted to 1000 mJ/cm ² or more. more preferably 2000 mJ/cm ² or more, more preferably 3000 mJ/cm ² or more, particularly preferably 5000 mJ/cm ² or more. is particularly preferred. Moreover, it is preferable to adjust the irradiation output of ultraviolet rays so that the integrated amount of light is 20000 mJ/cm ² or less. By setting the cumulative amount of light during irradiation of ultraviolet rays within the above range, the crosslink density of the pressure-sensitive adhesive layer can be increased, and the durability of the double-sided pressure-sensitive adhesive sheet can be more effectively increased.

When the double-sided pressure-sensitive adhesive sheet has a single-layer structure, it is preferable to apply the pressure-sensitive adhesive composition onto a release sheet and dry it. In this case, it is preferable to laminate a release sheet on the other side of the coating film after the heat-drying step, and irradiate the active energy ray in a state in which the release sheets are laminated on both sides of the coating film.

The double-sided pressure-sensitive adhesive sheet is a laminated pressure-sensitive adhesive sheet having a structure in which a first surface pressure-sensitive adhesive layer 12a, an intermediate resin layer 11 and a second surface pressure-sensitive adhesive layer 12b are laminated in this order, as shown in FIG. In this case, the method for producing the laminated pressure-sensitive adhesive sheet preferably includes a step of applying the pressure-sensitive adhesive composition on both sides of the intermediate resin layer and semi-curing (primary curing) by irradiation with active energy rays. Alternatively, the method for producing a laminated pressure-sensitive adhesive sheet includes a step of applying a pressure-sensitive adhesive composition for a first surface pressure-sensitive adhesive layer onto a first release sheet and semi-curing (primary curing) by irradiation with active energy rays. , coating the adhesive composition for the second surface adhesive layer on the second release sheet and semi-curing (primary curing) by irradiation with active energy rays, A step of bonding each surface pressure-sensitive adhesive layer to the intermediate resin layer may also be included.
In any method, it is preferable that a heat drying step is provided after coating the pressure-sensitive adhesive composition in order to volatilize the solvent (C). The coating film thus obtained is irradiated with an active energy ray to form a semi-cured product (surface pressure-sensitive adhesive layer).

(How to use the double-sided adhesive sheet)
In the method of using the double-sided pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend, and in this state, active energy rays are irradiated to cure the pressure-sensitive adhesive layer. This curing step is preferably a step of completely curing the surface pressure-sensitive adhesive layer. In the method of using the double-sided pressure-sensitive adhesive sheet, it is preferable to bring both sides of the double-sided pressure-sensitive adhesive sheet into contact with the surface of the adherend, and to cure the double-sided pressure-sensitive adhesive sheet by irradiating active energy rays in this state.

Since the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet is in a semi-cured state before being irradiated with an active energy ray, the surface pressure-sensitive adhesive layer can follow the irregularities even if the adherend has a stepped portion. can. In this way, after laminating the double-sided adhesive sheet and making it conform to the unevenness, the adhesive layer is completely cured with active energy rays, thereby increasing the cohesive force of the adhesive layer and increasing the adhesiveness to the adherend. improves.

Examples of active energy rays include ultraviolet rays, electron beams, visible rays, X-rays, and ion beams. Among them, 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 extra-high 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 Cockroftwald accelerator, a Van de Clough accelerator, a resonance transformer accelerator, an insulating core transformer accelerator, a linear accelerator, a dynamitron accelerator, and a high frequency accelerator can be used.

(Laminate)
The present invention also relates to a laminate having an optical member on at least one of the double-sided pressure-sensitive adhesive sheets described above. The laminate of the present invention preferably has an optical member on both sides of the double-sided pressure-sensitive adhesive sheet. The laminate of the present invention is obtained through a step of bringing a double-sided pressure-sensitive adhesive sheet into contact with the surface of an optical member and, in that state, irradiating an active energy ray to completely cure the double-sided pressure-sensitive adhesive sheet.

Examples of optical members include constituent members in optical products such as touch panels and image display devices. Examples of constituent members of the touch panel include 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 resin film is coated with a conductive polymer, Examples include hard coat films and anti-fingerprint films. Examples of constituent members of image display devices include antireflection films, oriented films, polarizer films, retardation films, and brightness enhancement films used in liquid crystal display devices.
Materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

The double-sided pressure-sensitive adhesive sheet of the present invention can be used for bonding two adherends. In this case, the double-sided pressure-sensitive adhesive sheet of the present invention can be used for lamination of ITO films inside the touch panel, lamination of the ITO film and ITO glass, lamination of the ITO film and the liquid crystal panel of the touch panel, lamination of the cover glass and the ITO film. It is used for lamination of glass, lamination of cover glass and decorative film, and the like.

The production of the laminate includes a step of bringing at least one of the double-sided pressure-sensitive adhesive sheets into contact with the surface of the optical member and irradiating active energy rays in this state to cure the double-sided pressure-sensitive adhesive sheet. This curing step is preferably a step of completely curing the double-sided pressure-sensitive adhesive sheet. Moreover, in the method for producing a laminate, it is preferable to bring both sides of the double-sided pressure-sensitive adhesive sheet into contact with the surface of the optical member, and to cure the double-sided pressure-sensitive adhesive sheet by irradiating active energy rays in this state.

In the method for producing a laminate, the double-sided pressure-sensitive adhesive sheet can contain a pressure-sensitive adhesive layer before the main curing, and can further contain a pressure-sensitive adhesive layer having active energy ray-curing ability. Even if there is a stepped portion, the double-sided pressure-sensitive adhesive sheet can follow the unevenness. In this way, after laminating the double-sided adhesive sheet and allowing it to conform to the unevenness, the adhesive layer is completely cured with active energy rays, thereby increasing the cohesive force of the adhesive layer and improving the adhesiveness to the optical member. do.

EXAMPLES The characteristics of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below. In the following, Example 4 shall be read as Reference Example 4.

(Example 1)
<Synthesis of polymer A>
90 parts by mass of ethyl acetate was added to a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a stirrer and a thermometer, and 65 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of vinyl acetate and 5 parts by mass of acrylic acid were added as monomers. did. After raising the temperature in the reaction vessel to 55° C., the whole amount of a solution of 0.06 parts by mass of azobisisobutyronitrile dissolved in 10 parts by mass of ethyl acetate was added. Then, after stirring for 12 hours while maintaining the temperature, the mixture was cooled to terminate the polymerization reaction. The obtained acrylic copolymer (polymer A) had a solid content concentration of 50% by mass and a polystyrene-equivalent weight average molecular weight Mw of 240,000 by GPC.

<Synthesis of polymer B>
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a stirrer and a thermometer was charged with 465.9 parts by mass of polytetramethylene glycol (weight average molecular weight: 1000), 9.6 parts by mass of 2-hydroxyethyl acrylate, 2,6-di 1.7 parts by mass of -tert-butyl-cresol and 0.3 parts by mass of p-methoxyphenol were added. After raising the temperature in the reaction vessel to 40° C., 101.5 parts by mass of isophorone diisocyanate was added. Then, 0.06 part by mass of dioctyltin dineodecanate was added, and the temperature was raised to 80° C. over 1 hour. Then, it was held at 80° C. for 12 hours, and after confirming that all the isocyanate groups had disappeared, it was cooled to obtain a urethane acrylate resin. The resulting urethane acrylate resin had an acrylic group equivalent weight of 7,000 and a polystyrene-equivalent weight average molecular weight Mw of 18,000 by GPC.
To 100 parts by mass of the obtained urethane acrylate resin, 30 parts by mass of 2-ethylhexyl acrylate and 30 parts by mass of acryloylmorpholine were added at an internal temperature of 80° C. and stirred until uniform. Then, it was cooled to room temperature and filtered through a 200-mesh wire mesh to obtain Polymer B.

[Preparation of adhesive coating liquid A]
To 100 parts by mass of polymer A obtained as described above, 4 parts by mass of a hydrogen abstraction type photopolymerization initiator (EsacureTZT, manufactured by Lamberti) was added, and ethyl acetate was added so that the solid content concentration became a solution of 40% by mass. The mixture was diluted and stirred to prepare an adhesive coating liquid A.

[Preparation of intermediate resin layer]
0.5 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE 184, manufactured by BASF Japan Ltd.) was further added to 100 parts by mass of the solid content of polymer B obtained as described above, and the intermediate resin layer solution was prepared. and The intermediate resin layer solution was applied onto one release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Ltd.) so that the thickness of the intermediate resin layer after curing was 105 μm. It was sandwiched between a release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Ltd.). After irradiating a chemical lamp with an illuminance of 4 mW/cm ² for 30 seconds from one side through the release-treated polyester film, an ultraviolet irradiator (manufactured by Eye Graphics Co., Ltd.) was applied so that the integrated light amount was 1,000 mJ/cm ² . , ECS-301G1) to produce an intermediate resin layer by irradiating ultraviolet rays having a wavelength of 365 nm. The integrated amount of light was measured using UVPF-A1 (manufactured by Eye Graphics Co., Ltd.).

[Production of double-sided adhesive sheet]
The pressure-sensitive adhesive coating liquid A obtained as described above was coated on a release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Ltd.) using a doctor blade YD type (manufactured by Yoshimitsu Seiki Co., Ltd.). and heated in a dryer at 80° C. for 3 minutes. Thus, a first surface pressure-sensitive adhesive layer having a thickness of 35 μm was produced. A second surface pressure-sensitive adhesive layer having a thickness of 35 μm was produced in the same manner. The adhesive surface of the first surface adhesive layer was laminated to one surface of the intermediate resin layer obtained as described above using a laminator. Also, the adhesive surface of the second surface adhesive layer was laminated to the other surface of the intermediate resin layer using a laminator.
Through the polyethylene terephthalate film laminated on the first surface pressure-sensitive adhesive layer, ultraviolet rays were applied using an ultraviolet irradiation device (manufactured by Eye Graphics Co., Ltd., ECS-301G1) so that the integrated light amount was 6,000 mJ/cm ² . to obtain a double-sided pressure-sensitive adhesive sheet of Example 1 (total thickness: 175 µm: first surface pressure-sensitive adhesive layer: intermediate resin layer: second surface pressure-sensitive adhesive layer = 35 µm: 105 µm: 35 µm).

(Example 2)
A double-sided pressure-sensitive adhesive sheet of Example 2 was prepared in the same manner as in Example 1, except that the ultraviolet irradiation time was changed so that the cumulative amount of ultraviolet light irradiated to the double-sided pressure-sensitive adhesive sheet was 10,000 mJ/cm ² . made.

(Example 3)
Except that the intermediate resin layer and the second surface pressure-sensitive adhesive layer were not formed in Example 1, and a single-layer structure pressure-sensitive adhesive layer having a thickness of 175 μm was formed in the same formation process as the first surface pressure-sensitive adhesive layer. A double-sided pressure-sensitive adhesive sheet of Example 3 was produced in the same manner as in Example 1. In addition, irradiation of ultraviolet rays to the adhesive layer is performed by laminating one exposed side of the adhesive layer formed on the release-treated polyethylene terephthalate film with another release-treated polyethylene terephthalate film, Ultraviolet rays with a wavelength of 365 nm were irradiated from one side through the release-treated polyethylene terephthalate film so that the integrated amount of light was 6,000 mJ/cm ² .

(Example 4)
Example 3 was the same as Example 3, except that a polymer C synthesized as described below was used in place of the polymer A in Example 3 to prepare a pressure-sensitive adhesive coating liquid C, and a pressure-sensitive adhesive layer having a single-layer structure was formed using this. A double-sided pressure-sensitive adhesive sheet of Example 4 was produced in the same manner.

<Synthesis of Polymer C>
90 parts by mass of ethyl acetate was added to a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a stirrer and a thermometer, and 70 parts by mass of 2-ethylhexyl methacrylate, 20 parts by mass of 2-ethylhexyl acrylate and 2-hydroxyethyl as monomers were added. 10 parts by weight of acrylate were added. After raising the internal temperature of the reaction vessel to 55° C., a solution of 0.06 parts by mass of 2,2′-azobis(2,4-dimethylvaleronitrile) dissolved in 10 parts by mass of ethyl acetate was added. Then, after stirring for 12 hours while maintaining the temperature, the mixture was cooled to terminate the polymerization reaction. The obtained acrylic copolymer had a solid content concentration of 50% by mass and a polystyrene-equivalent weight average molecular weight Mw of 450,000 by GPC.

[Preparation of adhesive coating liquid C]
Based on 100 parts by mass of polymer C, 0.15 parts by mass of xylene diisocyanate compound D-110N (manufactured by Mitsui Chemicals, Inc.), isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 7 parts by mass, 2 2 parts by mass of functional acrylate (manufactured by Toagosei Co., Ltd., M-321), 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan Co., Ltd., IRGACURE 184) was added 1.0 parts by mass, and the solid content concentration Adhesive coating liquid C was obtained by adding ethyl acetate so that the content was 40% by mass.

The pressure-sensitive adhesive coating liquid C obtained as described above was applied onto a release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Co., Ltd.) so that the thickness after drying was 175 μm. Co., Ltd.) and heated at 80° C. for 3 minutes in a dryer. One side of the exposed adhesive layer is laminated with another release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Co., Ltd.), and from one side through the release-treated polyester film, A double-faced pressure-sensitive adhesive sheet of Example 3 was prepared by irradiating ultraviolet rays with a wavelength of 365 nm using an ultraviolet irradiator (ECS-301G1, manufactured by Eyegraphics Co., Ltd.) so that the integrated amount of light was 1,000 mJ/cm ² .

(Comparative example 1)
A double-sided pressure-sensitive adhesive sheet of Comparative Example 1 was prepared in the same manner as in Example 1, except that the ultraviolet irradiation time was changed so that the cumulative amount of ultraviolet light irradiated to the double-sided pressure-sensitive adhesive sheet was 2,000 mJ/cm ² . made.

(Comparative example 2)
A double-sided pressure-sensitive adhesive sheet of Comparative Example 2 was prepared in the same manner as in Example 1, except that the ultraviolet irradiation time was changed so that the cumulative amount of ultraviolet light irradiated to the double-sided pressure-sensitive adhesive sheet was 4,000 mJ/cm ² . made.

(Comparative Example 3)
A double-sided pressure-sensitive adhesive sheet of Comparative Example 3 was prepared in the same manner as in Example 3, except that the ultraviolet irradiation time was changed so that the cumulative amount of ultraviolet light irradiated to the double-sided pressure-sensitive adhesive sheet was 2,000 mJ/cm ² . made.

(Comparative Example 4)
A double-sided pressure-sensitive adhesive sheet of Comparative Example 4 was prepared in the same manner as in Example 3, except that the ultraviolet irradiation time was changed so that the cumulative amount of ultraviolet light irradiated to the double-sided pressure-sensitive adhesive sheet was 4,000 mJ/cm ² . made.

(Comparative Example 5)
Example 4 was the same as Example 4, except that polymer D synthesized as described below was used in place of polymer C in Example 4 to prepare adhesive coating liquid D, and this was used to form an adhesive layer having a single-layer structure. A double-sided pressure-sensitive adhesive sheet of Comparative Example 5 was produced in the same manner. <Synthesis of polymer D>
90 parts by mass of ethyl acetate was added to a reactor equipped with a cooling tube, a nitrogen inlet tube, a stirrer and a thermometer, and 65 parts by mass of butyl acrylate, 25 parts by mass of 2-ethylhexyl acrylate, and 10 parts by mass of acrylic acid were added as monomers. did. After raising the internal temperature of the reaction vessel to 55° C., a solution of 0.06 parts by mass of 2,2′-azobis(2,4-dimethylvaleronitrile) dissolved in 10 parts by mass of ethyl acetate was added. Then, after stirring for 12 hours while maintaining the temperature, the mixture was cooled to terminate the polymerization reaction. The obtained acrylic copolymer had a solid content concentration of 50% by mass and a polystyrene-equivalent weight average molecular weight Mw of 300,000 by GPC.

[Preparation of adhesive coating liquid D]
Based on 100 parts by mass of polymer D, 0.15 parts by mass of xylene diisocyanate compound D-110N (manufactured by Mitsui Chemicals, Inc.) and 8.5 parts by mass of isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) , 1-Hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan Ltd., IRGACURE 184) was added to 1.0 parts by mass, and ethyl acetate was added so that the solid content concentration was 40% by mass. got a D.

The pressure-sensitive adhesive composition D obtained as described above was applied onto a release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Co., Ltd.) so that the thickness after drying was 175 μm. Co., Ltd.) and heated at 80° C. for 3 minutes in a dryer. One side of the exposed adhesive layer is laminated with another release-treated polyethylene terephthalate film (manufactured by Teijin DuPont Films Co., Ltd.), and from one side through the release-treated polyester film, A double-sided pressure-sensitive adhesive sheet of Comparative Example 5 was produced by irradiating ultraviolet rays with a wavelength of 365 nm using an ultraviolet irradiator (manufactured by igraphics Co., Ltd., ECS-301G1) so that the integrated amount of light at 365 nm was 1,000 mJ/cm ² . did.

(Evaluation and analysis)
(Followability to bumps)
On the surface of glass plate A (length 120 mm × width 70 mm × thickness 0.7 mm), UV-curable ink is screen-printed in a frame shape (inner frame size: length 90 mm × width 50 mm × width 5 mm) so that the thickness is 5 μm. did. Next, the UV curable ink printed by irradiating UV rays was cured. This process was repeated 6 times to obtain a printed stepped glass plate having a step of 30 μm.
The double-sided pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a shape of 94 mm long x 54 mm wide, the polyethylene terephthalate film laminated on one side of the double-sided pressure-sensitive adhesive sheet was peeled off, and a laminator (manufactured by Yubon Co., Ltd., IKO -650EMT), the pressure-sensitive adhesive layer was laminated so as to cover the entire surface of the printed stepped glass frame-like print. After that, the polyethylene terephthalate film laminated on the other side of the double-sided adhesive sheet is peeled off, and the exposed adhesive layer is laminated with glass plate B (length 115 mm × width 64 mm × thickness 0.7 mm) with the above laminator, followed by autoclaving. (40° C., 0.5 MPa, 30 minutes) was performed. Next, ultraviolet rays were irradiated from the glass plate A side with an ultraviolet ray irradiator (ECS-301G1, manufactured by Eyegraphics) so that the integrated quantity of light was 2,000 mJ/cm ² to obtain a laminate.
The print level difference portion of the laminate was visually observed, and the level difference followability of the double-sided pressure-sensitive adhesive sheet was evaluated according to the following criteria.
◯: No foaming, peeling, or the like is observed at all.
Δ: Occasionally, foaming, peeling, and the like are observed.
x: Foaming, peeling, and the like are observed in each experiment.

(durability)
A sample for evaluation (laminate) was prepared in the same manner as in the stepped printed glass plate used in the step followability test, except that the printed step was changed to 10 μm. Next, a SUS plate with a thickness of 180 μm and a width of 12.7 mm was placed at a position 5 mm from the end of the adhesive layer between the printed step on the glass plate A at the center of the short side of the evaluation sample and the glass plate B. After inserting and straining, it was allowed to stand in an environment of 85° C. and a relative humidity of less than 10% for 72 hours. After the treatment, the occurrence of air bubbles at the edge of the pressure-sensitive adhesive layer near the insertion portion of the SUS plate was visually evaluated.
Good: No air bubbles mixed in from the end of the pressure-sensitive adhesive layer.
Δ: Air bubbles mixed in from the wound edge of the adhesive are observed only on the printed steps of the adhesive layer.
x: Air bubbles mixed in from the end of the pressure-sensitive adhesive layer are observed up to the region inside the printing step.

(edge lift)
After performing corona treatment on the protective film side of a polarizing plate (manufactured by Polatechno Co., model number: SKN-18243T-HC, rigidity: 21.0 mN), a double-sided adhesive sheet was attached and cut into a length of 30 mm and a width of 20 mm. A test piece was produced. The surface of a stainless steel pipe (mirror-finished) with a diameter of 50 mm was washed with alcohol, and the test piece was laminated so that the longitudinal direction of the stainless steel pipe with a diameter of 50 mm was along the arc, and crimped by reciprocating a 2 kg roll once. . The stainless steel tube to which the test piece was bonded was left to stand in an environment of 85 ° C. and a relative humidity of less than 10% for 24 hours, and as shown in FIG. Measure the peel length (B1, B2) from the middle point (P1, P2) of the short side of the test piece (20 mm width) to the peel start point (Q1, Q2) on the center line (C) of the test piece. The average value of the two peel lengths (B1, B2) was recorded as the lift length of the edge.

(Measurement of tan δ)
The loss tangent (tan δ) of the dynamic shear viscoelastic modulus of the double-sided PSA sheet was measured using Rheogel-E4000 manufactured by UBM under the following conditions.
・Method: solid shear ・Strain: 2 μm
・Temperature increase rate: 2°C/min
・Frequency: 1Hz
・Thickness: 175 μm

In Examples, a double-sided pressure-sensitive adhesive sheet having excellent step followability and durability was obtained. On the other hand, the double-faced pressure-sensitive adhesive sheets obtained in the comparative examples did not have both step followability and durability.

REFERENCE SIGNS LIST 1 Double-sided adhesive sheet 10 Adhesive layer 11 Intermediate resin layer 12a First surface adhesive layer 12b Second surface adhesive layer 100 Stainless steel tube with a diameter of 50 mm 200 Test piece

Claims (5)

A double-sided pressure-sensitive adhesive sheet in a semi-cured state after irradiation with an active energy ray, comprising a (meth)acrylic acid ester polymer and a hydrogen abstraction type photopolymerization initiator ,
The (meth)acrylic acid ester polymer has a weight average molecular weight of 240,000 or less,
A double-sided pressure-sensitive adhesive sheet for laminating an optical member having an edge floating length of 8 mm or less as measured by the following measurement method A;
(Measuring method A)
The double-sided adhesive sheet is attached to a polarizing plate film having a rigidity of 21 ± 1 mN to obtain a laminate; a test piece having a length of 30 mm and a width of 20 mm is cut out from the laminate; Laminated on the surface and crimped by reciprocating a 2 kg roll once; At that time, the length direction of the test piece is laminated along the arc of a stainless steel tube with a diameter of 50 mm; The stainless steel to which the test piece is laminated After the tube was left to stand in an environment of 85°C and a relative humidity of less than 10% for 24 hours, each peel length (B1, B2) of both edges of the test piece peeled from the stainless steel tube was measured by the short side of the test piece. Determined by measuring the distance from the midpoint (P1, P2) to the peel initiation point (Q1, Q2) on the center line (C) of the test piece, and the average value of the two peel lengths (B1, B2) It is the floating length of the edge part. 2. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the loss tangent tan[delta] of the dynamic shear viscoelastic modulus at a measurement temperature of 25[deg.] C. and a frequency of 1 Hz is 0.56 or more and 0.75 or less. The double-sided pressure-sensitive adhesive sheet has a layer structure of two or more layers,
The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein at least one layer of the layer structure of two or more layers contains a (meth)acrylic acid ester polymer and a hydrogen abstraction type photopolymerization initiator. Lamination comprising the step of bringing at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3 into contact with the surface of an optical member, and irradiating the double-sided pressure-sensitive adhesive sheet in this state with active energy rays to cure the double-sided pressure-sensitive adhesive sheet. body manufacturing method. A double-sided pressure-sensitive adhesive sheet in which at least one surface of the double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3 is brought into contact with the surface of an optical member and irradiated with an active energy ray in this state to cure the double-sided pressure-sensitive adhesive sheet. how to use.

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