KR20200098533A - Manufacturing method of adhesive sheet and laminate - Google Patents

Abstract

An object of the present invention is to provide a pressure-sensitive adhesive sheet having both step followability, durability, and handling properties. The present invention is a pressure-sensitive adhesive sheet having photocrosslinking properties, wherein the tensile stress at a tensile elongation of 2000% before photocrosslinking is 0.3N/mm 2 or less, the tensile modulus before photocrosslinking is 150kPa or more and 300kPa or less, and the tensile modulus before photocrosslinking is a When the tensile modulus after light crosslinking is set to b, b/a relates to an adhesive sheet having less than 3.0.

Description

Manufacturing method of adhesive sheet and laminate

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

Recently, in various fields, an input device used in combination with a display device such as a liquid crystal display (LCD) or a display device such as a touch panel has been widely used. In the manufacture of these display devices and input devices, a transparent adhesive sheet is used for bonding an optical member, and a transparent adhesive sheet is also used for bonding a display device and an input device.

Some of the touch panels and liquid crystal displays include constituent members having a step difference caused by printing or the like. For example, in a mobile phone, a touch panel having a member subjected to frame-like printing is used. In such applications, the pressure-sensitive adhesive sheet is required to have the ability to bond and fix members (adhesiveness) and at the same time fill in a printing step (step followability).

For example, in Patent Document 1, as a hot-melt adhesive sheet having the ability to easily follow a step difference by heating the pressure-sensitive adhesive sheet, the adhesion is improved by post-curing the pressure-sensitive adhesive sheet by irradiating an active energy ray after following the step. An aftercure type pressure-sensitive adhesive sheet has been proposed. In this way, development of a pressure-sensitive adhesive sheet that can achieve both adhesion and step followability is in progress.

Japanese Unexamined Patent Publication No. 2016-222916

Touch panels or liquid crystal displays are sometimes exposed to harsh environments such as high temperature and high humidity. For this reason, there is a demand for an adhesive sheet in which the adhesive performance and the like do not change even in a harsh environment of high temperature and high humidity. That is, the pressure-sensitive adhesive sheet is also required to have durability under harsh environments. However, in the conventional aftercure type pressure-sensitive adhesive sheet, when the durability is increased, there is a problem that the level difference followability becomes insufficient.

In addition, in the conventional aftercure type pressure-sensitive adhesive sheet, in the case of attempting to increase the step followability, the pressure-sensitive adhesive may unintentionally spread during bonding, and there is a problem in that the handling property is poor during bonding.

Accordingly, the inventors of the present invention conducted a study for the purpose of providing an adhesive composition having both step followability, durability, and handling properties in order to solve the problems of the prior art.

As a result of intensive examination in order to solve the above problems, the inventors of the present invention set the tensile stress and tensile modulus at a tensile elongation of 2000% before light crosslinking in a predetermined range in a pressure-sensitive adhesive sheet having an aftercure photo-crosslinking property. It was found that by making the ratio of the tensile modulus before light crosslinking and the tensile modulus after light crosslinking in a predetermined range, a pressure-sensitive adhesive sheet having both step followability, durability, and handling properties can be obtained.

Specifically, the present invention has the following configuration.

[1] As a pressure-sensitive adhesive sheet having photocrosslinkability,

Tensile stress at 2000% of tensile elongation before light crosslinking is 0.3 N/mm 2 or less,

The tensile modulus of elasticity before light crosslinking is 150 kPa or more and 300 kPa or less,

When the tensile modulus before photocrosslinking is set to a and the tensile modulus after photocrosslinking is set to b, b/a is less than 3.0.

[2] The pressure-sensitive adhesive sheet according to [1], comprising 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], wherein the gel fraction before photo-crosslinking is 5.0% or less and the gel fraction after photo-crosslinking is 50% or more.

[4] With respect to 100 parts by mass of the (meth)acrylic copolymer, [2] containing 0.1 to 6 parts by mass of a polyfunctional monomer and 0.1 to 10 parts by mass of a photopolymerization initiator for initiating the polymerization reaction of the polyfunctional monomer by light irradiation. ] Or the adhesive sheet according to [3].

[5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the thickness is 50 to 200 µm.

[6] A double-sided adhesive sheet in which a release sheet provided with a release sheet was formed on both surfaces of the adhesive sheet according to any one of [1] to [5].

[7] A method for producing a laminate including a bonding step of bringing the pressure-sensitive adhesive sheet according to any one of [1] to [5] into contact with an adherend surface, and a light irradiation step.

[8] The method for producing a laminate according to [7], in which the adherend is an optical member.

ADVANTAGE OF THE INVENTION According to this invention, it is possible to obtain a pressure-sensitive adhesive sheet having both step-following properties, durability, and handling properties.

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

In the following, the present invention will be described in detail. The description of the configuration requirements described below may be made based on representative embodiments or specific examples, but the present invention is not limited to these embodiments. In addition, in this specification, the numerical range shown using "-" means a range including the numerical value described before and after "-" as a lower limit value and an upper limit value. In addition, "(meth)acryl" means containing both acrylic and methacryl.

(Adhesive sheet)

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

Since the pressure-sensitive adhesive sheet of the present invention has the above configuration, it has both step-following property, durability, and handling properties. The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having photo-crosslinking property, and before photo-crosslinking, it is possible to follow the step difference of the adherend without a gap. On the other hand, it exhibits sufficient durability after photocrosslinking. In the present invention, by optimizing the tensile stress and the tensile elastic modulus in the pressure-sensitive adhesive sheet, it has succeeded in achieving both step followability and durability, and further enhancing the handling properties of the pressure-sensitive adhesive sheet. On the other hand, the adhesive sheet of the present invention does not contain a thermal crosslinking agent substantially. When the pressure-sensitive adhesive sheet of the present invention does not contain a thermal crosslinking agent, the aging process can be omitted when forming the pressure-sensitive adhesive sheet, thereby reducing the time required for manufacturing the pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet of the present invention exhibits excellent step-following properties. The pressure-sensitive adhesive sheet of the present invention, for example, can follow the step without a gap even if there is a height difference of 35 µm or more in the adhered portion, and in this case, it can be evaluated as excellent in step followability. In addition, 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 bonded to a stepped portion and repeatedly irradiated with ultraviolet rays under the following conditions, it does not deteriorate, and generation of air bubbles or the like is not observed. On the other hand, the irradiation conditions of ultraviolet rays are, for example, 0.8 W/m 2, 4 hours at 80°C, 0.53 W/m 2, 4 hours at 50°C, 1 cycle×12 cycles.

The adhesive sheet of the present invention is also excellent in handling properties. In the present specification, the handling property of the pressure-sensitive adhesive sheet can be evaluated by the sticking out (wood value) of the pressure-sensitive adhesive at the time of bonding. Specifically, when the temperature of the press portion is set to 25°C and the pressure-sensitive adhesive sheet has a small spread (woods value) when it is pressed at a pressure of 0.2 MPa for 5 minutes, it can be evaluated as having good handling properties. The woods value of the pressure-sensitive 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. On the other hand, the Woods value of the adhesive sheet is a value evaluated by the method described in Examples.

The tensile stress in the tensile elongation of 2000% before photocrosslinking of the pressure-sensitive adhesive sheet of the present invention should be 0.3 N/mm 2 or less, preferably 0.25 N/mm 2 or less, more preferably 0.2 N/mm 2 or less, and 0.15 N/mm 2 It is more preferable that it is below, and it is especially preferable that it is 0.1 N/mm<2> or less. By making the tensile stress of the pressure-sensitive adhesive sheet within the above range, it becomes easy to obtain a pressure-sensitive adhesive sheet having both step-following property, durability, and handling properties.

Here, the tensile stress in the tensile elongation of 2000% before the photocrosslinking of the pressure-sensitive adhesive sheet is a value measured as follows. First, the pressure-sensitive adhesive sheet is cut out to be 50 mm in length and A mm in width (width direction). At this time, the A value in the horizontal (width direction) is determined so that the thickness (mm) of the pressure-sensitive adhesive sheet x Amm = 6 mm 2. Subsequently, the pressure-sensitive adhesive sheet was rolled in the width direction to obtain a columnar sample having a diameter of 2.8 mm and a height of 50 mm, and an area of the upper and lower ends of the columnar sample up to 10 mm each was 188 μm thick and 25 mm long. , Insert into two 50mm-wide PET films (4 sheets in total). Then, this region was used as the chuck portion of the tensile testing machine, and the chuck distance was fixed to be 30 mm, and the tensile elongation rate was 2000% under conditions of a tensile speed of 300 mm/min in an environment of a measurement temperature of 23°C and a relative humidity of 50%. Tension is carried out until it becomes, and the stress value at this time is taken as the tensile stress.

In addition, the tensile elongation rate in this specification is a ratio computed by the following formula.

Tensile elongation (%) = (Chuck distance after tension-Chuck distance before tension (30 mm)) / Chuck distance before tension (30 mm) × 100

As described above, when measuring the tensile stress at the tensile elongation of 2000% of the pressure-sensitive adhesive sheet before photo-crosslinking, it is necessary that the tensile maximum elongation of the pressure-sensitive adhesive sheet is 2000% or more. On the other hand, when the tensile elongation before photocrosslinking of the pressure-sensitive adhesive sheet is less than 2000%, when the above-described tensile stress is measured, the pressure-sensitive adhesive sheet is broken before the tensile elongation becomes 2000%. In this case, the stress value obtained by the above measurement becomes a breaking stress.

The breaking stress of the pressure-sensitive adhesive sheet after photocrosslinking is preferably 1.0 N/mm 2 or less, more preferably 0.9 N/mm 2 or less, and even more preferably 0.8 N/mm 2 or less. On the other hand, the breaking stress after photocrosslinking of the pressure-sensitive adhesive sheet is a value obtained by irradiating the pressure-sensitive adhesive sheet with ultraviolet rays so that the accumulated light amount becomes 2000 mJ/cm 2, and then measuring the tensile stress described above. On the other hand, in the present specification, the pressure-sensitive adhesive sheet before light-crosslinking is, for example, a pressure-sensitive adhesive sheet before irradiation with ultraviolet rays so that the accumulated light amount becomes 2000 mJ/cmm2, and the pressure-sensitive adhesive sheet after photo-crosslinking is, for example, the accumulated light amount of 2000 mJ/cm2. It is an adhesive sheet after irradiation of ultraviolet rays so that it may become cm 2. The accumulated light amount of ultraviolet rays can appropriately set the amount of light that the pressure-sensitive adhesive sheet can completely cure.

The tensile modulus of the pressure-sensitive adhesive sheet of the present invention before light crosslinking may be 150 kPa or more and 300 kPa or less, and preferably 150 kPa or more and 250 kPa or less. Here, the tensile modulus of the pressure-sensitive adhesive sheet before light crosslinking 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 and stress values of 0% and 5%, and it is set as the tensile modulus.

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

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

The gel fraction before photocrosslinking of the pressure-sensitive adhesive sheet of the present invention is preferably 5.0% or less, more preferably 4.5% or less, still more preferably 4.0% or less, even more preferably 3.5% or less, and particularly preferably 2.5% or less . In addition, the lower limit of the gel fraction of the pressure-sensitive adhesive sheet is not particularly limited, and may be, for example, 0%. By making 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 excellent in level difference followability.

The gel fraction of the pressure-sensitive adhesive sheet is a value measured by the following method.

First, about 0.1 g of the pressure-sensitive adhesive sheet (adhesive layer) was taken into a sample bottle, 30 ml of ethyl acetate was added, and the mixture was shaken for 24 hours. Thereafter, the contents of this sample bottle were filtered through a 150 mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 100 DEG C for 1 hour to measure the dry weight W (g). From the obtained dry weight, the gel fraction is calculated by the following formula 1.

Gel fraction (mass%) = (dry weight W/collection weight of adhesive sheet) x100... Equation 1

The gel fraction of the pressure-sensitive adhesive sheet of the present invention is as described above, and if the gel fraction is within the above range, the pressure-sensitive adhesive sheet can be said to be in a semi-cured state. Here, the term "a semi-cured state" means that the pressure-sensitive adhesive sheet has photocrosslinkability (hardenability by light irradiation). That is, the pressure-sensitive adhesive sheet of the present invention is a sheet in a flexible state before light irradiation (before light crosslinking).

The gel fraction of the pressure-sensitive 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. On the other hand, the gel fraction of the pressure-sensitive adhesive sheet after photocrosslinking is the gel fraction of the pressure-sensitive adhesive sheet after irradiation with ultraviolet rays so that the cumulative amount of light on the pressure-sensitive adhesive sheet is 2000 mJ/cm 2 or more.

It is preferable that it is 15.0 N/25 mm or more, and it is more preferable that it is 19.0 N/25 mm or more, and it is still more preferable that it is 20.0 N/25 mm or more as for the adhesive force to glass of the adhesive sheet before light crosslinking of this invention. In addition, the adhesive strength of the pressure-sensitive adhesive sheet after photocrosslinking is preferably 20.0 N/25 mm or more, more preferably 24.0 N/25 mm or more, even more preferably 25.0 N/25 mm or more, and 27.0 N/25 mm or more. It is particularly preferred. Here, the adhesive strength of the pressure-sensitive adhesive sheet to glass is the peel strength when the pressure-sensitive adhesive sheet is peeled 180 degrees from glass 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 to 500 µm, more preferably 30 to 300 µm, and even more preferably 50 to 200 µm. By setting the thickness of the pressure-sensitive adhesive sheet within the above range, it is possible to sufficiently increase the level difference followability and durability. In addition, it is possible to suppress the stickiness or push out of the pressure-sensitive adhesive, and thus handling property can be improved.

When using the pressure-sensitive adhesive sheet of the present invention, it is preferable to include a step of irradiating light after the pressure-sensitive adhesive sheet is brought into contact with the surface of an adherend. In addition, 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 adherend surface. As described above, the pressure-sensitive adhesive sheet of the present invention is a hot-melt-type pressure-sensitive adhesive sheet, and is preferably an aftercure-type pressure-sensitive adhesive sheet.

It is preferable that the adhesive sheet of this invention is a double-sided adhesive sheet. The double-sided pressure-sensitive adhesive sheet may be a single-layered double-sided pressure-sensitive adhesive sheet or a multi-layered double-sided pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated. Moreover, the double-sided adhesive sheet may be a double-sided adhesive sheet provided with an adhesive layer on both surfaces of a substrate (preferably, a transparent substrate). In this case, examples of the substrate include plastic films such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyether ether ketone, and triacetyl cellulose; Optical films, such as an antireflection film and an electromagnetic wave shielding film, etc. are mentioned.

On the other hand, the present invention may be directed to an adhesive composition capable of forming the adhesive sheet. A pressure-sensitive adhesive sheet is obtained by making the pressure-sensitive adhesive composition into a sheet by a known method.

((Meth)acrylic copolymer)

It is preferable that the adhesive sheet of this invention contains a (meth)acrylic-type copolymer. The (meth)acrylic copolymer is a main polymer included in the pressure-sensitive adhesive sheet, and such a polymer is also referred to as a base polymer.

The (meth)acrylic-based copolymer has an alkyl (meth)acrylate unit. In this specification, the "unit" is a repeating unit (monomer unit) constituting a polymer. The (meth)acrylate alkyl ester unit is derived from the (meth)acrylate alkyl ester. Examples of (meth)acrylate alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and ( Meth) 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 n-dodecyl, (meth) acrylic acid Stearyl, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, and the like. These may be used individually by 1 type, and may use 2 or more types together.

Further, the (meth)acrylic copolymer may have other acrylic monomer units other than the (meth)acrylate alkyl ester unit. Examples of the other acrylic monomer units include acrylic monomer units having a crosslinkable functional group, and examples thereof include a hydroxy group-containing acrylic monomer unit and a glycidyl group-containing acrylic monomer unit. These monomer units may be 1 type or 2 or more types.

The hydroxy group-containing acrylic monomer unit is derived from a hydroxy group-containing acrylic monomer. Examples of the hydroxy group-containing acrylic monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and ( (Meth)acrylic acid [(mono, di or poly)alkylene glycol], such as meth)acrylic acid mono (diethylene glycol), and (meth)acrylic acid lactone, such as (meth)acrylic acid monocaprolactone, are mentioned.

Examples of the glycidyl group-containing acrylic monomer unit include those derived from glycidyl group-containing acrylic monomers such as glycidyl (meth)acrylate.

When the (meth)acrylic copolymer has an acrylic monomer unit other than an alkyl (meth)acrylate unit, the content of the other acrylic monomer unit is preferably 0.01 to 20% by mass relative to the total mass of the (meth)acrylic copolymer. And it is more preferable that it is 0.5-10 mass %. Among them, it is preferable that the content of the acrylic monomer unit having a crosslinkable functional group is within the above range. When the content of the other acrylic monomer unit is more than the above lower limit, the cohesive strength can be sufficiently increased, and when it is less than the above upper limit, it becomes easy to secure sufficient adhesive strength.

The glass transition temperature (Tg) of the (meth)acrylic copolymer should just be -50°C or higher, preferably -49°C or higher, and 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, still more preferably -30°C or less, and particularly preferably -40°C or less . By setting the glass transition temperature (Tg) of the (meth)acrylic copolymer within the above range, the handling property of the pressure-sensitive adhesive sheet can be improved, and the processing of the pressure-sensitive adhesive sheet becomes easy. Further, 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.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer is preferably 250,000 or more, more preferably 260,000 or more, still more preferably 280,000 or more, and particularly preferably 300,000 or more. Further, the weight average molecular weight (Mw) of the (meth)acrylic copolymer is preferably 450,000 or less, and 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, in the pressure-sensitive adhesive sheet, step followability and durability are in a trade-off relationship, but in the present invention, by making the weight average molecular weight of the (meth)acrylic copolymer within the above range, it becomes easy to achieve both step followability and durability.

In addition, 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.

The measurement conditions of gel permeation chromatography (GPC) are as follows.

Solvent: Tetrahydrofuran

Column: Shodex KF801, KF803L, KF800L, KF800D (4 pieces manufactured by Showa Electric Works 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: 10μl

Calibration curve: Standard polystyrene Shodex standard polystyrene (manufactured by Showa Electric Co., Ltd.) A calibration curve by 10 samples up to Mw = 1320 to 250,000 was used.

A commercially available (meth)acrylic copolymer may be used or may be produced by polymerizing an acrylic monomer. As a commercial item, for example, OP-9200-1, OP-9200-3, OP-9200-4, OP-9200-5, OP-9200-7, etc. manufactured by Ica Industrial Co., Ltd. can be used. In addition, when producing a (meth)acrylic copolymer by polymerization, the polymerization method can be appropriately selected from polymerization methods commonly used. As a polymerization method, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, etc. are mentioned.

(Polyfunctional monomer)

It is preferable that the pressure-sensitive adhesive sheet of the present invention contains a polyfunctional monomer. The polyfunctional monomer is a monomer having two or more reactive double bonds in a molecule.

As a polyfunctional monomer, for example, di(meth)acrylate ethylene glycol, di(meth)acrylate triethylene glycol, di(meth)acrylate 1,3-butylene glycol, di(meth)acrylate 1,4-butylene Glycol, di(meth)acrylic acid 1,9-nonanediol, diacrylic acid 1,6-hexanediol, di(meth)acrylate polybutylene glycol, di(meth)acrylate neopentyl glycol, di(meth)acrylate tetraethylene glycol , Tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, diacrylate of bisphenol A diglycidyl ether, tri(meth)acrylate trimethylolpropane, tri(meth)acrylate pentaerythritol, tetra( (Meth)acrylic acid esters of polyhydric alcohols, such as meth)acrylate pentaerythritol, vinyl methacrylate, etc. are mentioned.

As the polyfunctional monomer, a commercial item can be used. Examples of commercially available products include ATM-4PL and A-TMM-3L manufactured by Shin-Nakamura Chemicals, and PET-30 manufactured by Nippon Explosives.

The pressure-sensitive adhesive sheet preferably contains 0.1 to 6 parts by mass, and more preferably 0.5 to 4 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer of the polyfunctional monomer. The polyfunctional monomer may be used alone or in combination of two or more, and when two or more types are used in combination, the total mass is preferably within the above range.

(Photopolymerization initiator)

It is preferable that the adhesive sheet of this invention contains a photoinitiator. The photoinitiator may be any one capable of initiating the polymerization reaction of the above-described polyfunctional monomer by irradiation with light, and it is preferable that the photoinitiator can initiate the polymerization reaction of the above-described polyfunctional monomer by irradiation with ultraviolet rays.

Examples of the photopolymerization initiator include an acetophenone initiator, a benzoin ether initiator, a benzophenone initiator, a hydroxyalkylphenone initiator, a thioxanthone initiator, and an amine initiator. As a photoinitiator, 1 type may be used individually, and 2 or more types may be used together.

Specific examples of the acetophenone initiator include diethoxyacetophenone and benzyl dimethyl ketal.

Specific examples of the benzoin ether initiator include benzoin and benzoin methyl ether.

Specific examples of the benzophenone initiator include benzophenone and methyl o-benzoylbenzoate.

Specific examples of the hydroxyalkylphenone initiator include 1-hydroxy-cyclohexyl-phenyl-ketone and the like.

Specific examples of the thioxanthone initiator include 2-isopropyl thioxanthone and 2,4-dimethyl thioxanthone.

Specific examples of the amine initiator include triethanolamine and ethyl 4-dimethylbenzoate.

The photoinitiator can use a commercial item. As an example of a commercial item, TZT by an IGM resin company, Irgacure184 by BASF, etc. are mentioned.

The pressure-sensitive adhesive sheet should just contain 0.1 to 10 parts by mass, and preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer. On the other hand, the photoinitiator may be used alone or in combination of two or more, and when two or more types are used in combination, the total mass is preferably within the above range.

(solvent)

A solvent may be contained in the adhesive sheet of this invention. In this case, the solvent is used to improve the coating aptitude of the pressure-sensitive adhesive sheet.

Examples of such a solvent include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; Halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; Alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; Ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone and cyclohexanone; Esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; Polyols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate, and derivatives thereof.

As a solvent, 1 type may be used individually, and 2 or more types may be used together. The content of the solvent contained in the PSA sheet is preferably 80% by mass or less, and more preferably 50% by mass or less with respect to the total mass of the PSA sheet.

(Optional ingredient)

The pressure-sensitive adhesive sheet of the present invention may contain other components other than the above within a range that does not impair the effects of the present invention. Other components include known components as additives for pressure-sensitive adhesives. For example, it can be selected from a plasticizer, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, and a light stabilizer such as a hindered amine compound as needed.

As the plasticizer, a non-functional acrylic polymer can be used. The non-functional acrylic polymer refers to a polymer composed of only acrylic monomer units having no functional groups other than an acrylate group, or a polymer composed of an acrylic monomer unit having no functional groups other than an acrylate group and a non-acrylic monomer unit having no functional group. .

As an acrylic monomer unit which does not have a functional group other than an acrylate group, the thing similar to the non-crosslinkable (meth)acrylic acid ester unit is mentioned, for example.

Non-acrylic monomer units having no functional group include, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristic acid, palmitic acid. Vinyl carboxylate esters such as vinyl, vinyl stearate, vinyl cyclohexanecarboxylic acid, vinyl benzoate, styrene, and the like.

Examples of antioxidants include phenolic antioxidants, amine antioxidants, lactone antioxidants, phosphorus antioxidants, and sulfur antioxidants. These antioxidants may be used alone or in combination of two or more.

As a metal corrosion inhibitor, a benzotriazole-type resin is mentioned.

Examples of the tackifier include rosin resins, terpene resins, terpenephenol resins, coumarone indene resins, styrene resins, xylene resins, phenol resins, and petroleum resins.

Examples of the silane coupling agent include a mercapto-based silane coupling agent, a (meth)acrylic silane coupling agent, an isocyanate-based silane coupling agent, an epoxy-based silane coupling agent, and an amino-based silane coupling agent.

Examples of the ultraviolet absorber include benzotriazole compounds and benzophenone compounds.

It is preferable that the adhesive sheet of this invention does not contain a thermal crosslinking agent substantially. Here, the content of the thermal crosslinking agent in the pressure-sensitive adhesive sheet is preferably less than 0.5 parts by mass, more preferably 0.3 parts by mass or less, still more preferably 0.2 parts by mass or less, and 0.1 based on 100 parts by mass of the (meth)acrylic copolymer. It is more preferable that it is less than a mass part, and it is especially preferable that it is 0 mass part. By setting the content of the thermal crosslinking agent within the above range, the step-following property of the pressure-sensitive adhesive sheet can be more effectively improved. Further, by making the content of the thermal crosslinking agent within the above range, when forming the pressure-sensitive adhesive sheet, the aging process can be omitted, and the time required for the production of the pressure-sensitive adhesive sheet can be shortened.

On the other hand, as a thermal crosslinking agent, a known thermal crosslinking agent, such as an isocyanate compound, an epoxy compound, an oxazoline compound, an aziridine compound, a metal chelate compound, and a butylated melamine compound, is mentioned, for example.

(Double-sided adhesive sheet with peeling sheet formed)

The present invention may also relate to a double-sided adhesive sheet in which a release sheet having a release sheet is formed on both sides of the above-described adhesive sheet.

1 is a schematic diagram showing a cross section of an example of a double-sided pressure-sensitive adhesive sheet on which a release sheet of the present invention is formed. The double-sided adhesive sheet 1 on which the release sheet is formed includes a double-sided adhesive sheet 11 and a release sheet 12a and a release sheet 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 multi-layered double-sided pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated. In addition, the double-sided adhesive sheet 11 may be a double-sided adhesive sheet provided with an adhesive layer on both sides of a substrate (preferably, a transparent substrate).

As shown in FIG. 1, it is preferable that the surface of the double-sided adhesive sheet 11 is covered with the release sheet 12a and the release sheet 12b. As a release sheet, a peelable laminated sheet having a release sheet base material and a release agent layer formed 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 may be mentioned.

Paper and a polymer film are used as a base material for a release sheet in a peelable laminated sheet. As the release agent constituting the release agent layer, a general-purpose addition-type or condensation-type silicone-based release agent or a long-chain alkyl group-containing compound is used, for example. In particular, a highly reactive addition type silicone-based release agent is preferably used.

Specific examples of the silicone release agent include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, and KS-3600, KS-774, X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. . In addition, it is preferable to 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 in the silicon-based release agent. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone, and KS-3800, X92-183 manufactured by Shin-Etsu Chemical Co., Ltd. .

A commercially available product may be used as the peelable laminated sheet. For example, there may be mentioned a middle separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Film Co., Ltd., and a light separator film, which is a release-treated polyethylene terephthalate film manufactured by Teijin DuPont Film Co., Ltd. .

It is preferable that the pressure-sensitive adhesive sheet of the present invention has a pair of peeling sheets different from each other in peeling force. That is, in order to make the release sheet easy to peel, it is preferable to make the peelability of the release sheet 12a and the release sheet 12b different. If the peelability on one side and the peelability on the other are different, it becomes easy to first peel only the release sheet on the side with high peelability. In that case, the peelability of the peeling sheet 12a and the peeling sheet 12b may be adjusted according to the bonding method and the bonding procedure.

(Method of manufacturing a laminate)

When using the adhesive sheet of the present invention, the adhesive sheet is brought into contact with the adherend surface. And it is preferable to include the step of performing light irradiation after making the adhesive sheet contact the surface of an adherend. That is, it is preferable that the manufacturing method of a laminated body of this invention includes the bonding process of making an adhesive sheet contact the surface of an adherend, and a light irradiation process.

On the other hand, the manufacturing method of the 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 irradiating light after the heat treatment step is included. That is, the manufacturing method of the laminated body of the present invention includes a bonding step of contacting the adhesive sheet to the adherend surface and a light irradiation step, and includes at least one of the following (step a) and (step b). You can do it.

(Step a) A heat treatment is performed in a bonding step.

(Step b) As a post-process of the bonding process, the degassing process is included in the pre-step of the light irradiation process, and heat treatment is performed in the said degassing process.

In the bonding step, the pressure-sensitive adhesive sheet is bonded to the adherend. As a bonding method, a roll bonding method, a vacuum bonding method, etc. are mentioned, for example.

In the heat treatment in the (a step) and the (b step), it is preferable to heat treatment at 40 to 59°C. It is also preferable that the heating temperature is 50 to 59°C. In the manufacturing process of the laminated body, by performing such a heat treatment process, the flexibility of the pressure-sensitive adhesive sheet or the double-sided pressure-sensitive adhesive sheet can be further increased, and thus the level difference can be easily followed.

Conventionally, when using a hot-melt pressure-sensitive adhesive sheet, heat treatment at 60°C or higher was considered a common method, and there was a risk of damaging the adherend in such a high-temperature heat treatment. In the manufacturing method of the laminate of the present invention, since the processing temperature when heat treatment is performed in the bonding step and/or the subsequent step of the bonding step can be suppressed lower than usual, and even in that case, sufficient step difference followability can be obtained. In addition, the risk of damaging the adherend can be suppressed to a very low level. In addition, it is possible to suppress the cost of light-heating when manufacturing the laminate, so that the production efficiency of the laminate can be more effectively increased.

On the other hand, the heat treatment at 40 to 59°C is preferably performed in a bonding step or a defoaming step. In addition, heat treatment may be performed in both the bonding process and the defoaming process. As a bonding process, a roll bonding process and a vacuum bonding process are mentioned, for example. As the defoaming process, an autoclave treatment process is mentioned, for example. That is, the heat treatment at 40 to 59°C is preferably performed in at least one step selected from an autoclave treatment step, a roll bonding step, and a vacuum bonding step. In this case, it is preferable to set the heating setting temperature in an autoclave processing process, a roll bonding process, and a vacuum bonding process to 40-59 degreeC. On the other hand, it is also preferable that the heat treatment is performed in both the bonding step and the defoaming step.

In the light irradiation step, light is irradiated to the adhesive sheet or the bonded product of the double-sided adhesive sheet and the adherend. In this way, the light irradiation process may be referred to as a post-curing process. By post-curing the pressure-sensitive adhesive sheet with light, the cohesive strength of the pressure-sensitive adhesive is increased, and the adhesion to the adherend is improved.

It is preferable that the light irradiation step is a step of irradiating ultraviolet rays.

As the ultraviolet light source, for example, a high-pressure mercury lamp, a low-pressure mercury lamp, an ultra-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 each type of electron beam accelerator, such as a Cockcroft Walton type, a Van Degraf type, a resonance transformer type, an insulating core transformer type, a straight type, a dynamitron type, and a high frequency type, can be used.

The ultraviolet irradiation output is preferably such that the accumulated light amount is 100 to 10000 mJ/cm 2, and more preferably 500 to 5000 mJ/cm 2.

(Laminate)

The laminate manufactured by the above-described manufacturing method includes a post-cured adhesive sheet and an adherend. It is preferable that the laminate of the present invention includes adherends on both sides of the post-cured adhesive sheet. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used for bonding of adherends having a stepped portion.

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

It is preferable that the adherend 31 is an optical member. As an optical member, each constituent member in an optical product, such as a touch panel and an image display device, is mentioned.

Components of the touch panel include, for example, an ITO film with an ITO film formed on a transparent resin film, an ITO glass with an ITO film formed on the surface of a glass plate, a transparent conductive film coated with a conductive polymer on a transparent resin film, a hard coat film, and a fingerprint resistant film. And the like. The double-sided 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 viewpoint, as the adherend of the double-sided adhesive sheet of the present invention, an ITO film having an ITO film formed on a transparent resin film, an ITO glass having an ITO film formed on the surface of a glass plate, and a transparent conductive film coated with a conductive polymer on a transparent resin film are preferable. .

As a constituent member of an image display device, an antireflection film, an alignment film, a polarizing film, a retardation film, a brightness improving film etc. used for a liquid crystal display device are mentioned, for example.

Examples of materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

Example

Hereinafter, the characteristics of the present invention will be described in more detail with reference to Examples and Comparative Examples. Materials, amounts used, ratios, treatment contents, treatment procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the specific examples shown below.

[Example 1]

(Preparation of adhesive composition)

100 parts by mass of (meth)acrylic copolymer (manufactured by Aika Industrial Co., Ltd.: OP-9200-3), 2 parts by mass of pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: ATM-4 PL) as a polyfunctional monomer, 2 parts by mass of a photoinitiator (IGM resin) Co., Ltd.: TZT) 1.5 parts by mass were mixed and stirred under atmospheric pressure for 3 minutes using a stirrer (SHASHIN KAGAKU: SK-200 TVS) to prepare a pressure-sensitive adhesive composition.

(Production of adhesive sheet)

The pressure-sensitive adhesive composition prepared as described above was applied to the surface of a 38 µm-thick polyethylene terephthalate film (first release sheet) (manufactured by Oji Ftex: 38RL-07(2)) having a release agent layer treated with a silicone-based release agent, The coating was uniformly applied with an applicator so that the thickness of the coated film after drying was 100 µm. Then, it dried for 3 minutes in a 100 degreeC air circulation type constant temperature oven, and the adhesive layer was formed on the surface of a 1st peeling sheet. Next, a second release sheet having a thickness of 38 μm (manufactured by Oji Ftex Co., Ltd.: 38RL-07 (L)) was bonded to the surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was sandwiched between a pair of release sheets having a difference in peeling force. A double-sided pressure-sensitive adhesive sheet with a release sheet having a configuration of 1 release sheet/adhesive layer/second release sheet was obtained.

[Example 2]

Except having changed the compounding amount of the polyfunctional monomer to 3 parts by mass in (Preparation of an adhesive composition) of Example 1, in the same manner as in Example 1, an adhesive composition and a double-sided adhesive sheet having a release sheet formed thereon were obtained.

[Example 3]

In the same manner as in Example 1, except that the blending amount of the polyfunctional monomer was changed to 4 parts by mass in (Preparation of an adhesive composition) of Example 1, a double-sided adhesive sheet having an adhesive composition and a release sheet was obtained.

[Example 4]

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

[Example 5]

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 adhesive composition) of Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Example 6]

Except for changing the (meth)acrylic copolymer to OP-9200-1 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, and further changing the blending amount of the polyfunctional monomer to 1 part by mass In the same manner as in Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Example 7]

In the same manner as in Example 6, except that the blending amount of the polyfunctional monomer was changed to 2 parts by mass in (Preparation of the adhesive composition) of Example 6, a double-sided adhesive sheet having an adhesive composition and a release sheet was obtained.

[Example 8]

In the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-5 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, both sides of the adhesive composition and the release sheet were formed. A pressure-sensitive adhesive sheet was obtained.

[Example 9]

In the same manner as in Example 8, except that the amount of the polyfunctional monomer was changed to 4 parts by mass in (Preparation of the adhesive composition) of Example 8, a double-sided adhesive sheet having an adhesive composition and a release sheet was obtained.

[Example 10]

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

[Example 11]

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

[Example 12]

In the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-7 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, the adhesive composition and the release sheet were formed on both sides. A pressure-sensitive adhesive sheet was obtained.

[Example 13]

In the same manner as in Example 12, except for changing the blending amount of the polyfunctional monomer to 4 parts by mass in (Preparation of the adhesive composition) of Example 12, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Example 14]

In the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-4 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, the adhesive composition and the release sheet were formed on both sides. A pressure-sensitive adhesive sheet was obtained.

[Example 15]

100 parts by mass of (meth)acrylic copolymer (manufactured by Aika Industrial Co., Ltd.: OP-9200-3), 1 part by mass of pentaerythritol triacrylate (manufactured by Nippon Explosives Co., Ltd.: PET-30), 1 part by mass of a photopolymerization initiator (manufactured by BASF) :Irgacure184) 1 part by mass of mixing and stirring under atmospheric pressure using a stirrer (SHASHIN KAGAKU: SK-200TVS) for 3 minutes to prepare a pressure-sensitive adhesive composition, in the same manner as in Example 1, the double-sided adhesive with a release sheet I got a sheet.

[Example 16]

A release sheet was formed in the same manner as in Example 1, except that an adhesive composition was obtained in the same manner as in Example 1, and in (Preparation of an adhesive sheet), a release sheet was formed in the same manner as in Example 1, except that uniform coating was performed with an applicator so that the thickness of the coated film after drying became 150 µm A double-sided adhesive sheet was obtained.

[Example 17]

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

[Example 18]

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

[Comparative Example 1]

In the same manner as in Example 1, except that the blending amount of the polyfunctional monomer was changed to 7 parts by mass in (Preparation of the adhesive composition) of Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Comparative Example 2]

In the same manner as in Comparative Example 1, except that the polyfunctional monomer was changed to PET-30 manufactured by Nippon Explosives in (Preparation of an adhesive composition) of Comparative Example 1, a double-sided adhesive sheet having an adhesive composition and a release sheet was obtained.

[Comparative Example 3]

In the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-6 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, the adhesive composition and the release sheet were formed on both sides. A pressure-sensitive adhesive sheet was obtained.

[Comparative Example 4]

Except for changing the (meth)acrylic copolymer to OP-9200-9 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, and further changing the blending amount of the polyfunctional monomer to 1 part by mass In the same manner as in Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Comparative Example 5]

In the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-9 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, the adhesive composition and the release sheet were formed on both sides. A pressure-sensitive adhesive sheet was obtained.

[Comparative Example 6]

Except for changing the (meth)acrylic copolymer to OP-9200-9 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, and further changing the blending amount of the polyfunctional monomer to 4 parts by mass. In the same manner as in Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Comparative Example 7]

In the same manner as in Example 1, except that the (meth)acrylic copolymer was changed to OP-9200-8 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, the adhesive composition and the release sheet were formed on both sides. A pressure-sensitive adhesive sheet was obtained.

[Comparative Example 8]

Except for changing the (meth)acrylic copolymer to OP-9200-8 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, and further changing the blending amount of the polyfunctional monomer to 4 parts by mass. In the same manner as in Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

[Comparative Example 9]

Except for changing the (meth)acrylic copolymer to OP-9200-5 (manufactured by Aika Industrial Co., Ltd.) in (Preparation of the adhesive composition) of Example 1, and further changing the blending amount of the polyfunctional monomer to 1 part by mass. In the same manner as in Example 1, a double-sided adhesive sheet with an adhesive composition and a release sheet was obtained.

(Measure)

＜Tensile stress·Tensile maximum elongation＞

The tensile stress before photocrosslinking of the pressure-sensitive adhesive sheet was measured as follows. First, the double-sided pressure-sensitive adhesive sheet on which the release sheet obtained in Examples and Comparative Examples was formed was cut to be 50 mm in length and A mm in width (width direction). At this time, the A value in the horizontal (width direction) was determined so that the thickness (mm) of the pressure-sensitive adhesive sheet x Amm = 6 mm 2. Next, the 1st peeling sheet was peeled, and only the adhesive sheet was rolled up in the width direction, and it was set as the columnar sample of 2.8 mm in diameter of a circle and 50 mm in height. The upper and lower regions of the columnar sample up to 10 mm each were inserted into two PET films (4 sheets in total) of 188 μm in thickness, 25 mm in length and 50 mm in width, and this area was used as the chuck of the tensile tester. And it fixed so that the distance between chuck might be 30 mm. Thereafter, in an environment at a measurement temperature of 23°C and a relative humidity of 50%, it was stretched under conditions of a tensile rate of 300 mm/min until the tensile elongation became 2000%. The stress value at this time was taken as the tensile stress.

The tensile stress after the photocrosslinking of the pressure-sensitive adhesive sheet was irradiated with ultraviolet rays so that the accumulated light amount became 2000 mJ/cm 2 from the side of the first release sheet of the double-sided pressure-sensitive adhesive sheet on which the cut-out release sheet was formed, and then a columnar sample was obtained and measured in the same manner.

On the other hand, the values marked with (*) in the table are those at break before the tensile elongation rate of the columnar sample reaches 2000%, and the stress at break is recorded. For the columnar sample fractured before reaching 2000%, the maximum tensile elongation is described in the table.

<Tensile elastic 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 and stress values of 0% and 5%, and it was set as the tensile modulus.

<Gel fraction>

About 0.1 g of the pressure-sensitive adhesive sheet before and after photocrosslinking (before and after irradiation with ultraviolet rays) was collected in each sample bottle, 30 ml of ethyl acetate was added, and the mixture was shaken for 24 hours. Thereafter, the contents of this sample bottle were separated by filtration 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). The gel fraction was calculated|required by following formula 1 from the obtained dry weight.

Gel fraction (mass%) = (dry weight W/collection weight of adhesive sheet) x100... Equation 1

<Adhesion>

The second release sheet of the double-sided pressure-sensitive adhesive sheet on which the release sheet was formed was peeled off, attached to a PET film (Cosmoshine A4300 100 µm, manufactured by Toyobo), and cut into 25 mm x 150 mm. Then, the 1st peeling sheet was peeled, it pressed-bonded with a 2 kg load roll to a glass plate, and it left for 30 minutes at normal temperature. Thereafter, using a tensile tester (model name: Autograph AGS-J, manufactured by Shimadzu Corporation), in accordance with JIS Z 0237, the peel strength at the time of peeling 180 degrees at a tensile speed of 300 mm/min was measured, and the adhesive strength was determined. did.

(evaluation)

<Method of manufacturing laminate>

UV-curable ink was applied on the surface of a glass plate (90 mm long x 50 mm wide x 0.5 mm thick) and screen-printed in a frame shape (90 mm long x 50 mm wide, 5 mm wide) so that the thickness was 5 m. Subsequently, the ultraviolet-curable ink printed by irradiation with ultraviolet rays was cured. This step was repeated a predetermined number of times to obtain a printed stepped glass having a stepped portion having a thickness of 35 μm.

The double-sided pressure-sensitive adhesive sheet on which the release sheet obtained in Examples and Comparative Examples was formed was cut into a shape of 90 mm in length x 50 mm in width, and the first release sheet was peeled off, using a laminator (manufactured by Yubon Co., Ltd., IKO-650EMT), The pressure-sensitive adhesive sheet (adhesive layer) was bonded to cover the entire printing surface of the frame-shaped print step glass. Thereafter, the second release sheet was peeled off, and a glass plate (90 mm in length x 50 mm in width) by using a vacuum bonding machine (manufactured by Joyo Engineering Co., Ltd.: vacuum polymerization device (JE2020B-MVH)) to the exposed adhesive sheet (adhesive layer). Thickness 0.5 mm) was bonded. At this time, the bonding conditions were 40°C, a weak pressing pressure of 0.6 kN, a strong pressing pressure of 1.2 kN, a vacuum pressure of 100 Pa, and a holding time of 10 seconds. Subsequently, degassing treatment (autoclave treatment: 40°C, 0.5 MPa, 10 minutes) was performed, and after that, the accumulated light amount was 2000 mJ by an ultraviolet irradiator (manufactured by Eye Graphics Co., Ltd., ECS-301G1) from the printing step glass side. It irradiated with ultraviolet rays so that it might become /cm<2>, and obtained the laminated body.

<Evaluation of level followability>

The printed step of the laminate was observed with a microscope (magnification: 25 times) and evaluated according to the following criteria.

(Circle): It is a state in which air bubbles are not visible on the step bonding surface, and is completely filled.

×: Bubbles are seen on the step-bonded surface, and the step is not filled.

<Durability>

Put the laminate in a QUV tester (manufactured by Q-LAB) and irradiate ultraviolet (UV-A) to 12 cycles of 0.8W/㎡, 4 hours at 80℃, 0.53W/㎡, 4 hours at 50℃. Then, it observed with a microscope (magnification: 25 times) whether bubbles were not generated in the whole sample, and evaluated according to the following criteria. On the other hand, ultraviolet irradiation was performed on the glass side of the printing step.

○: There is no generation of air bubbles.

X: Bubbles and peeling occurred.

<Handling property>

A sheet piece was cut out from the double-sided adhesive sheet on which the release sheet was formed into a size of 30 mm in length and 30 mm in width. One side of the release sheet of the sheet piece was peeled off, and the peeled adhesive sheet (adhesive layer) was affixed to the silicone-treated surface of a release sheet (A71 100 µm: Teijin DuPont film) cut into 50 mm in length in advance. Thereafter, the silicone-treated surface of a release sheet (A38#50: Teijin DuPont film) separately cut into 50 mm in width and length was covered on the other release sheet remaining on the sheet piece. Then, using a press tester (manufactured by Toyo Seiki Co., Ltd.: MP-WNL), the temperature of the press portion was set at 25° C., and pressurized for 5 minutes at a pressure of 0.2 MPa. Then, the distance that 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 on each side of the release sheet spreads most was measured, and the average value of the four sides was made into the Woods value.

It was found that the pressure-sensitive adhesive sheet obtained in Examples was excellent in step followability and durability, and good handling properties were obtained.

On the other hand, in Comparative Examples 4 to 8, the durability evaluation was not performed because bubbles were generated on the stepped bonding surface before performing the durability test.

1 Double-sided adhesive sheet with release sheet formed
11 double-sided adhesive sheet
12a release sheet
12b release sheet
30 laminate
31 adherend
32 step

Claims (8)

As an adhesive sheet having photocrosslinkability,
Tensile stress at 2000% of tensile elongation before light crosslinking is 0.3 N/mm 2 or less,
The tensile modulus of elasticity before light crosslinking is 150 kPa or more and 300 kPa or less,
When the tensile modulus before photocrosslinking is set to a and the tensile modulus after photocrosslinking is set to b, b/a is less than 3.0. The method of claim 1,
A pressure-sensitive adhesive sheet containing 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. The method according to claim 1 or 2,
A pressure-sensitive adhesive sheet in which the gel fraction before photocrosslinking is 5.0% or less and the gel fraction after photocrosslinking is 50% or more. The method according to claim 2 or 3,
An adhesive sheet containing 0.1 to 6 parts by mass of a polyfunctional monomer and 0.1 to 10 parts by mass of a photopolymerization initiator for initiating a polymerization reaction of the polyfunctional monomer by light irradiation with respect to 100 parts by mass of the (meth)acrylic copolymer. The method according to any one of claims 1 to 4,
An adhesive sheet having a thickness of 50 to 200 μm. A double-sided pressure-sensitive adhesive sheet having a release sheet provided on both surfaces of the pressure-sensitive adhesive sheet according to any one of claims 1 to 5. A method for producing a laminate comprising a bonding step of bringing the pressure-sensitive adhesive sheet according to any one of claims 1 to 5 into contact with the adherend surface, and a light irradiation step. The method of claim 7,
The method of manufacturing a laminate in which the adherend is an optical member.

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