JP7287280B2 - Adhesive sheet and laminate manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an adhesive sheet and a laminate.

2. Description of the Related Art In recent years, display devices such as liquid crystal displays (LCDs) and input devices used in combination with display devices such as touch panels have been widely used in various fields. In the manufacture of these display devices and input devices, transparent double-sided adhesive sheets are used for bonding optical members, and transparent double-sided adhesive sheets are also used for bonding display devices and input devices. ing.

Some of the above-mentioned touch panels and liquid crystal displays include structural members having steps that occur due to printing or the like. For example, a mobile phone uses a touch panel having a frame-shaped printed member. In such applications, the pressure-sensitive adhesive sheet is required to have the performance (adhesiveness) of bonding and fixing members together and the performance of filling the printing step (step followability).

For example, in Patent Document 1, a hot-melt type adhesive sheet having a performance that makes it easier to follow a step by heating the adhesive sheet is irradiated with an active energy ray after following the step, and the adhesive sheet is post-cured. An after-curing adhesive sheet has been proposed in which adhesiveness is improved by curing. In this way, the development of adhesive sheets capable of achieving both adhesiveness and conformability to irregularities is underway.

JP 2016-222916 A

Touch panels and liquid crystal displays are sometimes exposed to harsh environments such as high temperature and high humidity. Therefore, there is a demand for a pressure-sensitive adhesive sheet that does not change its pressure-sensitive adhesive properties even under harsh environments such as high temperature and high humidity. In other words, pressure-sensitive adhesive sheets are now required to have durability in harsh environments. However, the conventional after-cure pressure-sensitive adhesive sheet has a problem that, when the durability is enhanced, the conformability to unevenness is not sufficient.

In addition, in conventional after-cure adhesive sheets, when trying to improve step conformability, the adhesive may spread unintentionally during lamination, and there is also the problem of poor handleability during lamination. .

In order to solve the problems of the prior art, the inventors of the present invention conducted studies aimed at providing a pressure-sensitive adhesive composition having step conformability, durability, and handleability.

As a result of intensive studies to solve the above problems, the present inventors have found that in a pressure-sensitive adhesive sheet having post-curing photocrosslinkability, the tensile stress and tensile modulus at a tensile elongation rate of 2000% before photocrosslinking is within a predetermined range, and the ratio of the tensile modulus before photocrosslinking and the tensile modulus after photocrosslinking is within a predetermined range, a pressure-sensitive adhesive sheet having both step followability, durability, and handleability can be obtained. I found
Specifically, the present invention has the following configurations.

[1] A pressure-sensitive adhesive sheet having photocrosslinkability,
The tensile stress at a tensile elongation rate of 2000% before photocrosslinking is 0.3 N / mm ² or less,
The tensile modulus before photocrosslinking is 150 kPa or more and 300 kPa or less,
A pressure-sensitive adhesive sheet in which b/a is less than 3.0, where a is the tensile modulus of elasticity before photocrosslinking and b is the tensile modulus of elasticity after photocrosslinking.
[2] The pressure-sensitive adhesive sheet according to [1], which contains a (meth)acrylic copolymer having a glass transition temperature (Tg) of −50° C. to −40° C. and a weight average molecular weight of 250,000 to 450,000.
[3] The pressure-sensitive adhesive sheet according to [1] or [2], which has a gel fraction of 5.0% or less before photocrosslinking and a gel fraction of 50% or more after photocrosslinking.
[4] Per 100 parts by mass of (meth)acrylic copolymer, 0.1 to 6 parts by mass of a polyfunctional monomer, and 0.1 to 0.1 part of a photopolymerization initiator that initiates the polymerization reaction of the polyfunctional monomer by light irradiation. The pressure-sensitive adhesive sheet according to [2] or [3] containing 10 parts by mass.
[5] The adhesive sheet according to any one of [1] to [4], which has a thickness of 50 to 200 μm.
[6] A double-sided pressure-sensitive adhesive sheet with a release sheet provided with release sheets on both sides of the pressure-sensitive adhesive sheet according to any one of [1] to [5].
[7] A method for producing a laminate, comprising a lamination step of bringing the pressure-sensitive adhesive sheet according to any one of [1] to [5] into contact with the surface of an adherend, and a light irradiation step.
[8] The method for producing a laminate according to [7], wherein the adherend is an optical member.

According to the present invention, it is possible to obtain a pressure-sensitive adhesive sheet having step followability, durability and handleability.

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

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, the numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits. Moreover, "(meth)acryl" means to include both acryl and methacryl.

(adhesive sheet)
TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet having photocrosslinkability. In the adhesive sheet of the present invention, the tensile stress at a tensile elongation rate of 2000% before photocrosslinking is 0.3 N/mm ² or less, the tensile elastic modulus before photocrosslinking is 150 kPa or more and 300 kPa or less, and the tensile stress before photocrosslinking is 300 kPa or less. When the tensile elastic modulus is a and the tensile elastic modulus after photocrosslinking is b, b/a is less than 3.0.

Since the pressure-sensitive adhesive sheet of the present invention has the above structure, it has step followability, durability, and handleability. The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having photocrosslinkability, and can follow the steps of an adherend without gaps before photocrosslinking. On the other hand, it exhibits sufficient durability after photocrosslinking. In the present invention, by optimizing the tensile stress and tensile modulus of the pressure-sensitive adhesive sheet, it is possible to achieve both step followability and durability, and also to improve the handleability of the pressure-sensitive adhesive sheet. In addition, the adhesive sheet of the present invention does not substantially contain a thermal cross-linking agent. When the pressure-sensitive adhesive sheet of the present invention does not contain a thermal cross-linking agent, the aging process can be omitted when forming the pressure-sensitive adhesive sheet, and the time required for the production of the pressure-sensitive adhesive sheet can be shortened.

The pressure-sensitive adhesive sheet of the present invention exhibits excellent step followability. The pressure-sensitive adhesive sheet of the present invention, for example, even if there is a step with a height of 35 μm or more in the adhered portion, it can follow the step without gaps. can be evaluated. Moreover, the pressure-sensitive adhesive sheet of the present invention is also excellent in durability. Specifically, even when the pressure-sensitive adhesive sheet of the present invention is attached to a stepped portion and repeatedly irradiated with ultraviolet light under the following conditions, no deterioration occurs and no air bubbles are observed. The ultraviolet irradiation conditions are, for example, 1 cycle of 0.8 W/m ² at 80° C. for 4 hours and 0.53 W/m ² at 50° C. for 4 hours×12 times.

The pressure-sensitive adhesive sheet of the present invention is also excellent in handleability. In the present specification, the handleability of the PSA sheet can be evaluated by the extrusion of the PSA (Woze value) during lamination. Specifically, when the temperature of the press section is set to 25° C. and the pressure is applied for 5 minutes at a pressure of 0.2 MPa, when the spread of the adhesive sheet (woze value) is small, the handling property is evaluated as good. can. The ooze value of the adhesive sheet is preferably 1.2 mm or less, more preferably 1.0 mm or less, and even more preferably 0.8 mm or less. The ooze value of the pressure-sensitive adhesive sheet is a value evaluated by the method described in Examples.

The tensile stress at a tensile elongation rate of 2000% before photocrosslinking of the adhesive sheet of the present invention may be 0.3 N/mm ² or less, preferably 0.25 N/mm ² or less, and 0.2 N/mm It is more preferably ² or less, still more preferably 0.15 N/mm ² or less, and particularly preferably 0.1 N/mm ² or less. By setting the tensile stress of the adhesive sheet within the above range, it becomes easier to obtain a pressure-sensitive adhesive sheet having step followability, durability, and handleability.

Here, the tensile stress at a tensile elongation of 2000% before photocrosslinking of the pressure-sensitive adhesive sheet is a value measured as follows. First, the pressure-sensitive adhesive sheet is cut into a length of 50 mm and a width (width direction) of A mm. At this time, the value of A in the horizontal direction (width direction) is determined so that the adhesive sheet thickness (mm)×A mm=6 mm ² . Next, the pressure-sensitive adhesive sheet was rolled in the width direction to form a cylindrical sample with a circle diameter of 2.8 mm and a height of 50 mm. Sandwiched between two 50 mm PET films (four in total). Then, this area is used as the chuck part of the tensile tester, fixed so that the distance between the chucks is 30 mm, and the tensile elongation rate is 300 mm / min under the conditions of a measurement temperature of 23 ° C. and a relative humidity of 50%. It pulls until it becomes 2000%, and let the stress value in this case be a tensile stress.
In addition, the tensile elongation rate in this specification is a rate calculated by the following formula.
Tensile elongation rate (%) = (distance between chucks after tension - distance between chucks before tension (30 mm)) / distance between chucks before tension (30 mm) x 100

As described above, when measuring the tensile stress at a tensile elongation of 2000% before photocrosslinking of the adhesive sheet, the maximum tensile elongation of the adhesive sheet before photocrosslinking must be 2000% or more. If the tensile elongation of the adhesive sheet before photocrosslinking is less than 2000%, the adhesive sheet breaks before the tensile elongation reaches 2000% when measuring the tensile stress. In this case, the stress value obtained by the above measurement is the breaking stress.

The breaking stress of the adhesive sheet after photocrosslinking is preferably 1.0 N/mm ² or less, more preferably 0.9 N/mm ² or less, and further preferably 0.8 N/mm ² or less. preferable. The post-photocrosslinking breaking stress of the adhesive sheet is a value obtained by irradiating the adhesive sheet with ultraviolet rays so that the integrated light quantity is 2000 mJ/cm ² and then measuring the tensile stress described above. In this specification, the pressure-sensitive adhesive sheet before photocrosslinking is, for example, a pressure-sensitive adhesive sheet before being irradiated with ultraviolet rays so that the integrated light amount is 2000 mJ/cm ² , and the pressure-sensitive adhesive sheet after photocrosslinking is, for example, This is the pressure-sensitive adhesive sheet after being irradiated with ultraviolet rays so that the integrated amount of light is 2000 mJ/cm ² . The cumulative light quantity of ultraviolet light can be appropriately set to a light quantity that can completely cure the adhesive sheet.

The tensile elastic modulus of the pressure-sensitive adhesive sheet of the present invention before photocrosslinking may be 150 kPa or more and 300 kPa or less, preferably 150 kPa or more and 250 kPa or less. Here, the tensile elastic modulus of the pressure-sensitive adhesive sheet before photocrosslinking is a value calculated from the stress-strain curve (SS curve) obtained in the measurement of the tensile stress described above. Specifically, the slope is calculated from the tensile elongation rate and stress value of 0% and 5%, and the tensile elastic modulus is obtained.

The tensile elastic modulus of the pressure-sensitive adhesive sheet of the present invention after photocrosslinking is preferably 200 kPa or more and 1000 kPa or less, more preferably 250 kPa or more and 800 kPa or less. The above-mentioned tensile elastic modulus is the tensile elastic modulus of the pressure-sensitive adhesive sheet after being irradiated with ultraviolet rays so that the cumulative amount of light is 2000 mJ/cm ² .

When the tensile elastic modulus of the pressure-sensitive adhesive sheet before photocrosslinking is a and the tensile elastic modulus of the pressure-sensitive adhesive sheet after photocrosslinking is b, b/a may be less than 3.0, and should be 2.8 or less. is preferred, and 2.5 or less is more preferred. By setting the tensile elastic modulus of the adhesive sheet before photo-crosslinking and the ratio of the tensile elastic modulus before and after photo-crosslinking within the above range, it becomes easier to obtain an adhesive sheet having step followability, durability, and handleability.

The gel fraction of the pressure-sensitive adhesive sheet of the present invention before photocrosslinking is preferably 5.0% or less, more preferably 4.5% or less, even more preferably 4.0% or less. It is more preferably 0.5% or less, and particularly preferably 2.5% or less. The lower limit of the gel fraction of the adhesive sheet is not particularly limited, and may be 0%, for example. By setting the gel fraction of the pressure-sensitive adhesive sheet before photocrosslinking within the above range, it is possible to obtain a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet having excellent conformability to irregularities.

The gel fraction of the adhesive sheet is a value measured by the following method.
First, about 0.1 g of the adhesive sheet (adhesive layer) is collected in a sample bottle, 30 ml of ethyl acetate is added, and shaken for 24 hours. Thereafter, the contents of the sample bottle are filtered through a 150-mesh stainless wire mesh, and the residue on the wire mesh is dried at 100° C. for 1 hour to measure the dry weight W (g). From the obtained dry weight, the gel fraction is determined by the following formula 1.
Gel fraction (% by mass) = (dry weight W/collected weight of adhesive sheet) x 100 Equation 1

The gel fraction of the pressure-sensitive adhesive sheet of the present invention is as described above, and it can be said that the pressure-sensitive adhesive sheet is in a semi-cured state when the gel fraction is within the above range. Here, being in a semi-cured state means that the pressure-sensitive adhesive sheet has photocrosslinkability (curability by light irradiation). That is, the adhesive sheet of the present invention is a sheet in a soft state before light irradiation (before photocrosslinking).

The gel fraction of the adhesive sheet after photocrosslinking of the present invention is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more. The gel fraction of the pressure-sensitive adhesive sheet after photocrosslinking is the gel fraction of the pressure-sensitive adhesive sheet after it has been irradiated with ultraviolet rays so that the integrated amount of light is 2000 mJ/cm ² or more.

The adhesive strength to glass of the adhesive sheet before photocrosslinking of the present invention is preferably 15.0 N/25 mm or more, more preferably 19.0 N/25 mm or more, and 20.0 N/25 mm or more. is more preferred. Further, the adhesive strength to glass of the adhesive sheet after photocrosslinking is preferably 20.0 N/25 mm or more, more preferably 24.0 N/25 mm or more, and 25.0 N/25 mm or more. More preferably, it is particularly preferably 27.0 N/25 mm or more. Here, the adhesive strength of the adhesive sheet to glass is the peel strength when the adhesive sheet is peeled from the glass by 180 degrees at a tensile speed of 300 mm/min according to JIS Z 0237.

The thickness of the pressure-sensitive adhesive sheet of the present invention is preferably 5-500 μm, more preferably 30-300 μm, even more preferably 50-200 μm. By setting the thickness of the pressure-sensitive adhesive sheet within the above range, it is possible to sufficiently improve the step followability and durability. In addition, it is possible to suppress the protrusion and stickiness of the adhesive, and to improve the handling property.

When using the pressure-sensitive adhesive sheet of the present invention, it is preferable to include a step of irradiating light after bringing the pressure-sensitive adhesive sheet into contact with the surface of the adherend. When using the pressure-sensitive adhesive sheet of the present invention, it is preferable to include a heat treatment step when and/or after the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend. Thus, the pressure-sensitive adhesive sheet of the present invention is preferably a hot-melt pressure-sensitive adhesive sheet and an after-cure pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet of the present invention is preferably a double-sided pressure-sensitive adhesive sheet. The double-sided pressure-sensitive adhesive sheet may be a single-layer double-sided pressure-sensitive adhesive sheet or a multilayer double-sided pressure-sensitive adhesive sheet obtained by laminating a plurality of pressure-sensitive adhesive layers. Also, the double-sided pressure-sensitive adhesive sheet may be a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a substrate (preferably a transparent substrate). In this case, the base material includes, for example, plastic films such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyether ether ketone, triacetyl cellulose; A film etc. are mentioned.

The present invention may also relate to a pressure-sensitive adhesive composition capable of forming the pressure-sensitive adhesive sheet. A pressure-sensitive adhesive sheet can be obtained by forming the pressure-sensitive adhesive composition into a sheet by a known method.

((Meth)acrylic copolymer)
The adhesive sheet of the present invention preferably contains a (meth)acrylic copolymer. A (meth)acrylic copolymer is the main polymer contained in the pressure-sensitive adhesive sheet, and such a polymer is sometimes called a base polymer.

The (meth)acrylic copolymer has a (meth)acrylic acid alkyl ester unit. As used herein, a "unit" is a repeating unit (monomer unit) that constitutes a polymer. A (meth)acrylic acid alkyl ester unit is derived from a (meth)acrylic acid alkyl ester. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylate. Isobutyl acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, ( Isooctyl meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, (meth)acrylate n-dodecyl acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, etc. is mentioned. These may be used individually by 1 type, and may use 2 or more types together.

The (meth)acrylic copolymer may also have acrylic monomer units other than the (meth)acrylic acid alkyl ester unit. Examples of other acrylic monomer units include acrylic monomer units having a crosslinkable functional group, such as hydroxyl group-containing acrylic monomer units and glycidyl group-containing acrylic monomer units. can be mentioned. One of these monomer units may be used, or two or more of them may be used.
A hydroxy group-containing acrylic monomer unit is derived from a hydroxy group-containing acrylic monomer. Examples of hydroxy group-containing acrylic monomers include hydroxy (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Examples include alkyl, (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 glycidyl group-containing acrylic monomer units include those derived from glycidyl group-containing acrylic monomers such as glycidyl (meth)acrylate.

When the (meth)acrylic copolymer has acrylic monomer units other than (meth)acrylic acid alkyl ester units, the content of the other acrylic monomer units is It is preferably 0.01 to 20% by mass, more preferably 0.5 to 10% by mass, based on the total mass of the polymer. Above all, it is preferable that the content of the acrylic monomer unit having a crosslinkable functional group is within the above range. If the content of the other acrylic monomer units is at least the above lower limit value, the cohesive force can be sufficiently increased, and if it is at most the above upper limit value, sufficient adhesive force can be easily ensured.

The glass transition temperature (Tg) of the (meth)acrylic copolymer may be -50°C or higher, preferably -49°C or higher, more preferably -48°C or higher. Further, the glass transition temperature (Tg) of the (meth)acrylic copolymer is preferably −10° C. or less, more preferably −20° C. or less, further preferably −30° C. or less, -40°C or lower is particularly preferred. By setting the glass transition temperature (Tg) of the (meth)acrylic copolymer within the above range, the handleability of the pressure-sensitive adhesive sheet can be improved, and the pressure-sensitive adhesive sheet can be easily processed. Furthermore, by setting the glass transition temperature (Tg) of the (meth)acrylic copolymer within the above range, the cohesive force of the pressure-sensitive adhesive sheet can be further increased, and a pressure-sensitive adhesive sheet having excellent durability and adhesiveness can be obtained. be able to.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer is preferably 250,000 or more, more preferably 260,000 or more, even more preferably 280,000 or more, and 300,000 or more. It is particularly preferred to have The weight average molecular weight (Mw) of the (meth)acrylic copolymer is preferably 450,000 or less, more preferably 430,000 or less. By setting the weight-average molecular weight (Mw) of the (meth)acrylic copolymer within the above range, it is possible to achieve both step followability and durability. Usually, there is a trade-off relationship between step conformability and durability in a pressure-sensitive adhesive sheet. It becomes easy to achieve both durability.

The weight average molecular weight of the (meth)acrylic copolymer is a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene.
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 2500000 A calibration curve of 10 samples was used.

The (meth)acrylic copolymer may be commercially available or may be produced by polymerizing acrylic monomers. As commercial products, for example, OP-9200-1, OP-9200-3, OP-9200-4, OP-9200-5, OP-9200-7 manufactured by Aica Kogyo Co., Ltd. can be used. Further, when the (meth)acrylic copolymer is produced by polymerization, the polymerization method can be appropriately selected from commonly used polymerization methods. Examples of the polymerization method include a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and the like.

(Polyfunctional monomer)
The adhesive sheet of the present invention preferably contains a polyfunctional monomer. A polyfunctional monomer is a monomer having two or more reactive double bonds in the molecule.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4- Butylene glycol, 1,9-nonanediol di(meth)acrylate, 1,6-hexanediol diacrylate, polybutylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, di(meth)acryl Tetraethylene glycol acid, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diacrylate of bisphenol A diglycidyl ether, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate , (meth)acrylic acid esters of polyhydric alcohols such as pentaerythritol tetra(meth)acrylate, and vinyl methacrylate.

A commercial item can be used for a polyfunctional monomer. Examples of commercially available products include ATM-4PL and A-TMM-3L manufactured by Shin-Nakamura Chemical Co., Ltd., and PET-30 manufactured by Nippon Kayaku Co., Ltd., and the like.

The pressure-sensitive adhesive sheet preferably contains 0.1 to 6 parts by mass, more preferably 0.5 to 4 parts by mass, of the polyfunctional monomer with respect to 100 parts by mass of the (meth)acrylic copolymer. The polyfunctional monomers may be used singly or in combination of two or more. When two or more are used in combination, the total mass is preferably within the above range.

(Photoinitiator)
The adhesive sheet of the present invention preferably contains a photopolymerization initiator. The photopolymerization initiator should be capable of initiating the polymerization reaction of the polyfunctional monomers described above by light irradiation, and preferably capable of initiating the polymerization reaction of the above polyfunctional monomers by ultraviolet irradiation.

Examples of photopolymerization initiators include acetophenone-based initiators, benzoin ether-based initiators, benzophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, and amine-based initiators. As the photopolymerization initiator, one type may be used alone, or two or more types may be used in combination.
Specific examples of acetophenone-based initiators include diethoxyacetophenone and benzyldimethylketal.
Specific examples of benzoin ether-based initiators include benzoin and benzoin methyl ether.
Specific examples of benzophenone-based initiators include benzophenone and methyl o-benzoylbenzoate.
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.

A commercial item can be used for a photoinitiator. Examples of commercially available products include TZT manufactured by IGM Resin and Irgacure 184 manufactured by BASF.

The adhesive sheet may contain a photopolymerization initiator in an amount of 0.1 to 10 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the (meth)acrylic copolymer. In addition, the said photoinitiator may be used individually by 1 type, or may use 2 or more types together, and when using 2 or more types together, it is preferable that a total mass is in the said range.

(solvent)
The adhesive sheet of the present invention may contain a solvent. In this case, the solvent is used to improve the coatability of the adhesive sheet.

Examples of such solvents 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.

As the solvent, one type may be used alone, or two or more types may be used in combination. The content of the solvent contained in the adhesive sheet is preferably 80% by mass or less, more preferably 50% by mass or less, relative to the total mass of the adhesive sheet.

(Optional component)
The pressure-sensitive adhesive sheet of the present invention may contain components other than the above as long as the effects of the present invention are not impaired. Other components include components known as additives for pressure-sensitive adhesives. For example, it can be selected from among plasticizers, antioxidants, metal corrosion inhibitors, tackifiers, silane coupling agents, ultraviolet absorbers, light stabilizers such as hindered amine compounds, and the like, as required.

A non-functional acrylic polymer can be used as a plasticizer. A non-functional acrylic polymer is a polymer consisting only of acrylic monomer units that do not have functional groups other than acrylate groups, or acrylic monomer units that do not have functional groups other than acrylate groups and functional groups. It means a polymer composed of non-acrylic monomer units having no
Examples of the acrylic monomer unit having no functional group other than an acrylate group include those similar to the non-crosslinkable (meth)acrylic acid ester unit.
Examples of non-acrylic monomer units having no functional group include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, Carboxylic acid vinyl esters such as vinyl stearate, vinyl cyclohexanecarboxylate, and vinyl benzoate, and styrene.

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 benzoriazole-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.
Examples of silane coupling agents include mercapto-based silane coupling agents, (meth)acrylic silane coupling agents, isocyanate-based silane coupling agents, epoxy-based silane coupling agents, and amino-based silane coupling agents. .
Examples of ultraviolet absorbers include benzotriazole-based compounds and benzophenone-based compounds.

The pressure-sensitive adhesive sheet of the present invention preferably contains substantially no thermal cross-linking agent. Here, the content of the thermal cross-linking agent in the adhesive sheet is preferably less than 0.5 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer, and is 0.3 parts by mass or less. is more preferably 0.2 parts by mass or less, even more preferably 0.1 parts by mass or less, and particularly preferably 0 parts by mass. By setting the content of the thermal cross-linking agent within the above range, it is possible to more effectively improve the conformability of the pressure-sensitive adhesive sheet to unevenness. Further, by setting the content of the thermal cross-linking agent within the above range, the aging process can be omitted when forming the pressure-sensitive adhesive sheet, and the time required for manufacturing the pressure-sensitive adhesive sheet can be shortened.

Examples of thermal cross-linking agents include known thermal cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds.

(Double-sided adhesive sheet with release sheet)
The present invention may also relate to a double-sided pressure-sensitive adhesive sheet with a release sheet provided with release sheets on both sides of the pressure-sensitive adhesive sheet described above.

FIG. 1 is a schematic diagram showing a cross section of an example of the double-sided pressure-sensitive adhesive sheet with a release sheet of the present invention. A double-sided pressure-sensitive adhesive sheet 1 with a release sheet includes a double-sided pressure-sensitive adhesive sheet 11 and release sheets 12a and 12b on both sides thereof. The double-sided pressure-sensitive adhesive sheet 11 may be a single-layer double-sided pressure-sensitive adhesive sheet as shown in FIG. 1, or may be a multilayer double-sided pressure-sensitive adhesive sheet obtained by laminating a plurality of pressure-sensitive adhesive layers. Also, the double-sided pressure-sensitive adhesive sheet 11 may be a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a substrate (preferably a transparent substrate).

As shown in FIG. 1, the surface of the double-sided pressure-sensitive adhesive sheet 11 is preferably covered with a release sheet 12a and a release sheet 12b. As the release sheet, a release laminated sheet having a release sheet base material and a release agent layer provided on one side of the release sheet base material, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity base material. 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. Further, the silicone release agent may contain a silicone resin which is an organosilicon compound having SiO ₂ units and (CH ₃ ) ₃ SiO _1/2 units or CH ₂ ═CH(CH ₃ ) SiO _1/2 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.
A commercially available product may be used as the peelable laminate sheet. Examples include a heavy separator film that is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films Limited, and a light separator film that is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Films Limited. can.

The pressure-sensitive adhesive sheet of the present invention preferably has a pair of release sheets with mutually different release forces. That is, it is preferable that the release sheet 12a and the release sheet 12b have different releasability so that they can be easily separated. When the releasability from one side and the releasability from the other are different, it becomes easy to peel off only the release sheet with higher releasability first. In that case, the releasability of the release sheets 12a and 12b may be adjusted according to the bonding method and the bonding order.

(Laminate manufacturing method)
When using the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend. Then, it is preferable to include a step of irradiating light after bringing the pressure-sensitive adhesive sheet into contact with the surface of the adherend. That is, the method for producing a laminate of the present invention preferably includes a lamination step of bringing the pressure-sensitive adhesive sheet into contact with the adherend surface, and a light irradiation step.

The method for producing a laminate of the present invention may include a heat treatment step when and/or after the pressure-sensitive adhesive sheet is brought into contact with the adherend surface. In this case, a step of light irradiation is included after the heat treatment step. That is, the method for producing a laminate of the present invention includes a lamination step of bringing the adhesive sheet into contact with the adherend surface, and a light irradiation step, and at least one of the following (a step) and (b step) may include.
(Step a) Heat treatment is performed in the bonding step.
(Step b) A step after the bonding step, which includes a defoaming step in the step before the light irradiation step, and heat treatment is performed in the defoaming step.

In the bonding step, the adhesive sheet is bonded to the adherend. Examples of the lamination method include a roll lamination method and a vacuum lamination method.

The heat treatment in the above (step a) and the above (step b) is preferably performed at 40 to 59°C. It is also preferable to set the heating temperature to 50 to 59°C. By providing such a heat treatment step in the manufacturing process of the laminate, the flexibility of the pressure-sensitive adhesive sheet or the double-sided pressure-sensitive adhesive sheet can be further increased, and the step can be easily followed.

Conventionally, when using a hot-melt adhesive sheet, it has been customary to perform heat treatment at 60° C. or higher, and such high-temperature heat treatment poses a risk of damaging the adherend. rice field. In the method for producing a laminate of the present invention, the treatment temperature during the heat treatment in the lamination step and/or the step after the lamination step can be kept lower than usual, and even in that case, sufficient step conformability can be obtained. can be obtained, the risk of damaging the adherend can be kept extremely low. In addition, it is possible to suppress the lighting and heating costs when manufacturing the laminate, and to more effectively increase the manufacturing efficiency of the laminate.

Note that the heat treatment at 40 to 59° C. is preferably performed in the bonding process or in the defoaming process. Note that heat treatment may be performed in both the bonding process and the defoaming process. Examples of the bonding process include a roll bonding process and a vacuum bonding process. Examples of the defoaming step include an autoclave treatment step. That is, the heat treatment at 40 to 59° C. is preferably carried out in at least one step selected from an autoclave treatment step, roll lamination step and vacuum lamination step. In this case, it is preferable to set the heating temperature in the autoclave treatment process, roll bonding process and vacuum bonding process to 40 to 59°C. In addition, it is also preferable that the heat treatment be performed in both the bonding step and the defoaming step.

In the light irradiation step, the adhesive sheet or the double-sided adhesive sheet and the adherend are irradiated with light. Thus, the light irradiation process can also be called a post-curing process. By post-curing the adhesive sheet with light, the cohesive force of the adhesive increases and the adhesiveness to the adherend improves.

The light irradiation step is preferably a step of irradiating 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.
Electron beams emitted from various types of electron beam accelerators, such as Cockroftwald type, Van de Clough type, resonance transformer type, insulated core transformer type, linear type, dynamitron type, and high frequency type, are used as electron beams. can.
The irradiation output of the ultraviolet rays is preferably such that the cumulative amount of light is 100 to 10000 mJ/cm ² , more preferably 500 to 5000 mJ/cm ² .

(Laminate)
A laminate manufactured by the manufacturing method described above includes a post-cured pressure-sensitive adhesive sheet and an adherend. The laminate of the present invention preferably comprises adherends on both sides of the post-cured pressure-sensitive adhesive sheet. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used for bonding adherends having stepped portions.

FIG. 2 is a cross-sectional view showing an example of the structure of a laminate 30 in which the double-faced pressure-sensitive adhesive sheet 11 of the present invention is adhered to an adherend 31 having a stepped portion 32. As shown in FIG. As shown in FIG. 2 , the adherend 31 has a stepped portion 32 . The thickness of the step portion 32 can be 5 to 60 μm. As described above, the double-sided pressure-sensitive adhesive sheet 11 of the present invention can be used for bonding adherends having stepped portions. In particular, the double-sided pressure-sensitive adhesive sheet 11 of the present invention can also be used for adhering an adherend having a stepped portion 32 with a thickness of 35 μm or more.

The adherend 31 is preferably an optical member. 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. The double-sided pressure-sensitive adhesive sheet of the present invention is preferably for sensor lamination of a touch panel, and more preferably for sensor lamination of a touch panel using a touch pen. From this point of view, the adherend of the double-sided pressure-sensitive adhesive sheet of the present invention includes 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, and a conductive transparent resin film. A transparent conductive film coated with a polymer is preferred.
Examples of constituent members of the image display device include antireflection films, oriented films, polarizing films, retardation films, brightness enhancement films and the like 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.

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.

[Example 1]
(Preparation of adhesive composition)
(Meth) acrylic copolymer (manufactured by Aica Kogyo Co., Ltd.: OP-9200-3) 100 parts by mass, pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: ATM-4PL) 2 parts by mass as a polyfunctional monomer, photopolymerization initiation 1.5 parts by mass of an agent (IGM Resin: TZT) was mixed and stirred under atmospheric pressure for 3 minutes using a stirrer (SHASHIN KAGAKU: SK-200TVS) to prepare an adhesive composition.

(Preparation of adhesive sheet)
A polyethylene terephthalate film (first release sheet) having a thickness of 38 μm and having a release layer treated with a silicone release agent (manufactured by Oji F-Tex Co., Ltd.: 38RL-07) was applied to the pressure-sensitive adhesive composition prepared as described above. The surface of (2)) was uniformly coated with an applicator so that the coating film thickness after drying was 100 μm. Then, it was dried in an air circulation type constant temperature oven at 100° C. for 3 minutes to form an adhesive layer on the surface of the first release sheet. Next, a second release sheet (manufactured by Oji F-Tex Co., Ltd.: 38RL-07(L)) with a thickness of 38 μm is attached to the surface of this adhesive layer, and the adhesive layer is a pair of adhesive layers with different peeling strengths. A double-sided pressure-sensitive adhesive sheet with a release sheet having a configuration of first release sheet/adhesive layer/second release sheet sandwiched between release sheets was obtained.

[Example 2]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that in Example 1 (Preparation of pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 3 parts by mass. .

[Example 3]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that in Example 1 (Preparation of pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 4 parts by mass. .

[Example 4]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were prepared in the same manner as in Example 1 except that in Example 1 (Preparation of the pressure-sensitive adhesive composition), the amount of the photopolymerization initiator was changed to 0.7 parts by mass. got

[Example 5]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1 except that the amount of the photopolymerization initiator was changed to 3 parts by mass in (Preparation of the pressure-sensitive adhesive composition) of Example 1. rice field.

[Example 6]
In Example 1 (Preparation of adhesive composition), the (meth)acrylic copolymer was changed to OP-9200-1 (manufactured by Aica Kogyo Co., Ltd.), and the amount of the polyfunctional monomer was 1 part by mass. A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except for changing to .

[Example 7]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 6, except that in Example 6 (Preparation of pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 2 parts by mass. .

[Example 8]
An adhesive composition was prepared in the same manner as in Example 1 except that the (meth)acrylic copolymer was changed to OP-9200-5 (manufactured by Aica Kogyo Co., Ltd.) in Example 1 (Preparation of the adhesive composition). A product and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained.

[Example 9]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 8, except that in Example 8 (Preparation of pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 4 parts by mass. .

[Example 10]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 9, except that in Example 9 (Preparation of pressure-sensitive adhesive composition), the amount of the photopolymerization initiator was changed to 3 parts by mass. rice field.

[Example 11]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 8, except that in Example 8 (Preparation of pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 3 parts by mass. .

[Example 12]
An adhesive composition was prepared in the same manner as in Example 1 except that the (meth)acrylic copolymer was changed to OP-9200-7 (manufactured by Aica Kogyo Co., Ltd.) in Example 1 (Preparation of the adhesive composition). A product and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained.

[Example 13]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 12, except that in Example 12 (Preparation of the pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 4 parts by mass. .

[Example 14]
An adhesive composition was prepared in the same manner as in Example 1 except that the (meth)acrylic copolymer was changed to OP-9200-4 (manufactured by Aica Kogyo Co., Ltd.) in Example 1 (Preparation of the adhesive composition). A product and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained.

[Example 15]
(Meth) acrylic copolymer (manufactured by Aika Kogyo Co.: OP-9200-3) 100 parts by mass, pentaerythritol triacrylate (manufactured by Nippon Kayaku Co.: PET-30) 1 part by mass as a polyfunctional monomer, photopolymerization initiation agent (manufactured by BASF: Irgacure 184) 1 part by mass, and stirred for 3 minutes under atmospheric pressure using a stirrer (manufactured by SHASHIN KAGAKU: SK-200TVS) Example 1 except that a pressure-sensitive adhesive composition was prepared. A double-sided pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as above.

[Example 16]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, and in (Preparation of pressure-sensitive adhesive sheet), the same as in Example 1 except that the composition was uniformly coated with an applicator so that the coating film thickness after drying was 150 μm. to obtain a double-sided pressure-sensitive adhesive sheet with a release sheet.

[Example 17]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 7, and in (Preparation of pressure-sensitive adhesive sheet), the same as in Example 1 except that the composition was uniformly coated with an applicator so that the coating film thickness after drying was 150 μm. to obtain a double-sided pressure-sensitive adhesive sheet with a release sheet.

[Example 18]
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 7, and in (Preparation of pressure-sensitive adhesive sheet), the same as in Example 1 except that the composition was uniformly coated with an applicator so that the coating film thickness after drying was 75 μm. to obtain a double-sided pressure-sensitive adhesive sheet with a release sheet.

[Comparative Example 1]
A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except that in Example 1 (Preparation of pressure-sensitive adhesive composition), the amount of the polyfunctional monomer was changed to 7 parts by mass. .

[Comparative Example 2]
An adhesive composition and a double-sided adhesive sheet with a release sheet were prepared in the same manner as in Comparative Example 1 except that in Comparative Example 1 (Preparation of the adhesive composition), the polyfunctional monomer was changed to PET-30 manufactured by Nippon Kayaku Co., Ltd. got

[Comparative Example 3]
An adhesive composition was prepared in the same manner as in Example 1 except that the (meth)acrylic copolymer was changed to OP-9200-6 (manufactured by Aica Kogyo Co., Ltd.) in Example 1 (Preparation of the adhesive composition). A product and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained.

[Comparative Example 4]
In Example 1 (Preparation of adhesive composition), the (meth)acrylic copolymer was changed to OP-9200-9 (manufactured by Aica Kogyo Co., Ltd.), and the amount of the polyfunctional monomer was 1 part by mass. A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except for changing to .

[Comparative Example 5]
An adhesive composition was prepared in the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-9 (manufactured by Aica Kogyo Co., Ltd.) in Example 1 (Preparation of the adhesive composition). A product and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained.

[Comparative Example 6]
In Example 1 (Preparation of adhesive composition), the (meth)acrylic copolymer was changed to OP-9200-9 (manufactured by Aica Kogyo Co., Ltd.), and the amount of the polyfunctional monomer was 4 parts by mass. A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except for changing to .

[Comparative Example 7]
An adhesive composition was prepared in the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-8 (manufactured by Aica Kogyo Co., Ltd.) in Example 1 (Preparation of the adhesive composition). A product and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained.

[Comparative Example 8]
In Example 1 (Preparation of adhesive composition), the (meth)acrylic copolymer was changed to OP-9200-8 (manufactured by Aica Kogyo Co., Ltd.), and the amount of the polyfunctional monomer was 4 parts by mass. A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except for changing to .

[Comparative Example 9]
In Example 1 (Preparation of adhesive composition), the (meth)acrylic copolymer was changed to OP-9200-5 (manufactured by Aica Kogyo Co., Ltd.), and the blending amount of the polyfunctional monomer was 1 part by mass. A pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet with a release sheet were obtained in the same manner as in Example 1, except for changing to .

(measurement)
<Tensile stress/maximum tensile elongation>
The tensile stress of the pressure-sensitive adhesive sheet before photocrosslinking was measured as follows. First, the double-sided pressure-sensitive adhesive sheets with a release sheet obtained in Examples and Comparative Examples were cut into pieces having a length of 50 mm and a width (width direction) of A mm. At this time, the value of A in the horizontal direction (width direction) was determined so that the adhesive sheet thickness (mm)×A mm=6 mm ² . Next, the first release sheet was peeled off, and only the pressure-sensitive adhesive sheet was rolled in the width direction to obtain a cylindrical sample with a circle diameter of 2.8 mm and a height of 50 mm. The area up to 10 mm at the top and bottom of the cylindrical sample is sandwiched between two PET films (4 sheets in total) with a thickness of 188 μm, a length of 25 mm, and a width of 50 mm. They were fixed so that the distance was 30 mm. After that, it was pulled until the tensile elongation percentage reached 2000% under conditions of a measurement temperature of 23° C. and a relative humidity of 50% at a tensile speed of 300 mm/min. The stress value at this time was taken as the tensile stress.
The tensile stress after photocrosslinking of the adhesive sheet was obtained by irradiating ultraviolet rays from the first release sheet side of the cut double-sided adhesive sheet with a release sheet so that the integrated light amount was 2000 mJ/cm ² , and then obtaining a cylindrical sample. , was measured in a similar manner.
In the table, the value marked with (*) is the value at which the cylindrical sample was broken before the tensile elongation percentage reached 2000%, and the stress at break was recorded. The maximum tensile elongation of cylindrical samples that broke before reaching 2000% in tensile elongation is shown in the table.

<Tensile modulus>
The tensile modulus of the pressure-sensitive adhesive sheet was calculated from the stress-strain curve (SS curve) obtained in the measurement of <tensile stress>. Specifically, the slope was calculated from the tensile elongation rate and stress value of 0% and 5%, and was taken as the tensile modulus.

<Gel fraction>
About 0.1 g of the pressure-sensitive adhesive sheet before and after photocrosslinking (before and after ultraviolet irradiation) was collected in a sample bottle, and 30 ml of ethyl acetate was added and shaken for 24 hours. Thereafter, the contents of the sample bottle were filtered through a 150-mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 100° C. for 1 hour to measure the dry weight W (g). From the obtained dry weight, the gel fraction was calculated by the following formula 1.
Gel fraction (% by mass) = (dry weight W/collected weight of adhesive sheet) x 100 Equation 1

<Adhesive strength>
The second release sheet of the double-sided pressure-sensitive adhesive sheet with a release sheet was peeled off, adhered to a PET film (manufactured by Toyobo Co., Ltd., Cosmoshine A4300, 100 μm), and cut into a size of 25 mm×150 mm. After that, the first release sheet was peeled off, and the glass plate was press-bonded with a 2 kg load roll and left at room temperature for 30 minutes. After that, using a tensile tester (model: Autograph AGS-J, manufactured by Shimadzu Corporation), the peel strength when peeled 180 degrees at a tensile speed of 300 mm / min according to JIS Z 0237 was measured and used as adhesive strength. .

(evaluation)
<Method for producing laminate>
On the surface of a glass plate (length 90 mm, width 50 mm, thickness 0.5 mm), UV 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 UV curable ink printed by irradiating UV rays was cured. This process was repeated a predetermined number of times to obtain printed stepped glass having a stepped portion with a thickness of 35 μm.
The double-sided pressure-sensitive adhesive sheet with a release sheet obtained in Examples and Comparative Examples was cut into a shape of 90 mm long × 50 mm wide, the first release sheet was peeled off, and a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT) was used. Then, the adhesive sheet (adhesive layer) was laminated so as to cover the entire surface of the printed stepped glass in the shape of a picture frame. After that, the second release sheet is peeled off, and the exposed adhesive sheet (adhesive layer) is applied to a glass plate (vertical 90 mm×50 mm in width×0.5 mm in thickness) were laminated. The bonding conditions at this time were 40° C., a weak pressure of 0.6 kN, a strong pressure of 1.2 kN, a vacuum pressure of 100 Pa, and a pressure holding time of 10 seconds. Next, a defoaming treatment (autoclave treatment: 40° C., 0.5 MPa, 10 minutes) is performed, and then an integrated light quantity is applied from the stepped glass side with an ultraviolet irradiator (manufactured by Eye Graphics Co., Ltd., ECS-301G1). was 2000 mJ/cm ² to obtain a laminate.

<Evaluation of step followability>
The printed stepped portion of the laminate was observed with a microscope (magnification: 25 times) and evaluated according to the following criteria.
○: No bubbles are seen on the stepped bonding surface, and the state is completely buried ×: Bubbles are seen on the stepped bonding surface, and the step is not filled

<Durability>
The laminate was placed in a QUV tester (manufactured by Q-LAB) and subjected to 12 cycles of 0.8 W/m ² at 80° C. for 4 hours and 0.53 W/m ² at 50° C. for 4 hours. was irradiated with ultraviolet rays (UV-A), and the entire sample was observed with a microscope (magnification: 25 times) to see if bubbles were generated, and evaluated according to the following criteria. In addition, irradiation of ultraviolet rays was performed from the printing stepped glass side.
◯: No bubbles were generated.
x: Air bubbles and peeling occur.

<Handleability>
A sheet piece having a size of 30 mm in length and 30 mm in width was cut out from the double-sided pressure-sensitive adhesive sheet with a release sheet. One side of the release sheet of the sheet piece was peeled off, and the exposed adhesive sheet (adhesive layer) was attached to the silicone-treated surface of a release sheet (A71, 100 μm: Teijin DuPont Films) that had been cut into 50 mm squares in advance. After that, the other release sheet remaining on the sheet piece was covered with a silicone-treated surface of a separate release sheet (A38#50: Teijin DuPont Films) cut into a 50 mm square. Then, using a press tester (manufactured by Toyo Seiki Co., Ltd.: MP-WNL), the temperature of the press section was set to 25° C., and pressure was applied at a pressure of 0.2 MPa for 5 minutes. After that, the distance by which the pressure-sensitive adhesive layer spread outward from each side of the release sheet was measured. Specifically, the distance (maximum distance) from the point where the pressure-sensitive adhesive layer spreads the most on each side of the release sheet was measured, and the average value of the four sides was taken as the ooze value.

It was found that the pressure-sensitive adhesive sheets obtained in Examples are excellent in conformability to irregularities and durability, and provide good handleability.

In Comparative Examples 4 to 8, air bubbles were generated on the step-bonded surface before the durability test, so the durability was not evaluated.

Reference Signs List 1 double-sided pressure-sensitive adhesive sheet with release sheet 11 double-sided pressure-sensitive adhesive sheet 12a release sheet 12b release sheet 30 laminate 31 adherend 32 stepped portion

Claims (6)

100 parts by mass of a (meth)acrylic copolymer having a glass transition temperature (Tg) of −50° C. to −40° C. and a weight average molecular weight of 250,000 to 450,000;
0.1 to 6 parts by mass of a polyfunctional monomer,
A pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing 0.1 to 10 parts by mass of a photopolymerization initiator that initiates the polymerization reaction of the polyfunctional monomer by irradiation with an active energy ray,
The pressure-sensitive adhesive sheet has photocrosslinkability,
The gel fraction before photocrosslinking is 5.0% or less,
The tensile stress at a tensile elongation rate of 2000% before photocrosslinking is 0.3 N / mm ² or less,
The tensile modulus before photocrosslinking is 150 kPa or more and 300 kPa or less,
A pressure-sensitive adhesive sheet in which b/a is less than 3.0, where a is the tensile modulus of elasticity before photocrosslinking and b is the tensile modulus of elasticity after photocrosslinking. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the gel fraction after photocrosslinking is 50% or more. 3. The pressure-sensitive adhesive sheet according to claim 1, which has a thickness of 50 to 200 μm. A double-sided pressure-sensitive adhesive sheet with a release sheet, comprising release sheets on both sides of the pressure-sensitive adhesive sheet according to any one of claims 1 to 3 . A method for producing a laminate, comprising a lamination step of bringing the pressure-sensitive adhesive sheet according to any one of claims 1 to 3 into contact with the surface of an adherend, and a light irradiation step. The method for producing a laminate according to claim 5 , wherein the adherend is an optical member.

Images