JP6923053B1 - Adhesive sheet and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet which exhibits excellent step-following property even in a high-temperature environment or an ultraviolet irradiation environment and has excellent durability. The present invention is a pressure-sensitive adhesive sheet having photocrosslinkability, wherein the pressure-sensitive adhesive sheet has a glass transition temperature (Tg) of −50 ° C. to −40 ° C. and a weight average molecular weight of 330,000 to 400,000. It contains a (meth) acrylic copolymer, has a tensile stress of 0.3 N / mm2 or less at a tensile elongation of 2000% before photocrosslinking, a tensile elasticity before photocrosslinking of 50 kPa or more and 300 kPa or less, and photocrosslinking. When the previous tensile elasticity is a and the tensile elasticity after photocrosslinking is b, b / a is less than 3.0 and the integrated light amount is 2000 mJ / cm2 using a high-pressure mercury lamp with an illuminance of 80 mW / cm2. The present invention relates to an adhesive sheet in which the gel content of the photocrosslinked adhesive sheet after photocrosslinking by irradiating ultraviolet rays so as to be 20% or less. [Selection diagram] Fig. 1

Description

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

In recent years, in various fields, display devices such as liquid crystal displays (LCDs) and input devices used in combination with display devices such as touch panels have come to be widely used. 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 touch panels and liquid crystal displays include components having steps caused by printing or the like. For example, in a mobile phone, a touch panel having a frame-shaped printed member is used. In such applications, the adhesive sheet is required to have the ability to bond and fix the members (adhesiveness) as well as the ability to fill the printing step (step followability).

For example, in Patent Document 1, it is a hot-melt type adhesive sheet having a performance of easily following a step by heating the adhesive sheet, and after following the step, an active energy ray is irradiated to post-cure the adhesive sheet. An after-cure type adhesive sheet with improved adhesiveness has been proposed. In this way, the development of an adhesive sheet capable of achieving both adhesiveness and step followability is underway.

Japanese Unexamined Patent Publication No. 2016-22916

Touch panels and liquid crystal displays may be exposed to harsh environments. For example, a touch panel or a liquid crystal display may be used under high temperature conditions or low temperature conditions. In addition, when the touch panel or liquid crystal display is used outdoors, it may be exposed to ultraviolet rays. Therefore, there is a demand for an adhesive sheet whose adhesive performance and the like do not change even in a high-temperature environment or an ultraviolet irradiation environment. That is, the adhesive sheet is required to have durability in a harsh environment. However, in the conventional after-cure type adhesive sheet, there is a problem that the step followability becomes insufficient when the durability is improved.

Therefore, in order to solve the problems of the prior art, the present inventors provide an adhesive sheet that exhibits excellent step followability even in a high-temperature environment or an ultraviolet irradiation environment and has excellent durability. We proceeded with the study for the purpose.

As a result of diligent studies to solve the above problems, the present inventors have blended an acrylic copolymer satisfying a predetermined condition into the adhesive sheet in an aftercure type adhesive sheet having photocrosslinkability. Further, the ratio of the tensile stress and the tensile elastic coefficient at the tensile elongation rate of 2000% before photocrosslinking and the tensile elastic coefficient before photocrosslinking and the tensile elastic coefficient after photocrosslinking is set within a predetermined range, and in addition, the photocrosslinked photocrosslinking is performed. It has been found that by setting the gel content of the post-adhesive sheet to 20% or less, an adhesive sheet exhibiting excellent step followability even in a high-low temperature environment or an ultraviolet irradiation environment and having excellent durability can be obtained.
Specifically, the present invention has the following configuration.

[1] An adhesive sheet having photocrosslinkability, which is
The pressure-sensitive adhesive sheet contains a (meth) acrylic copolymer having a glass transition temperature (Tg) of −50 ° C. to −40 ° C. and a weight average molecular weight of 330,000 to 400,000.
The tensile stress at a tensile elongation of 2000% before photocrosslinking is 0.3 N / mm ² or less.
The tensile elastic modulus before photocrosslinking is 50 kPa or more and 300 kPa or less.
When the tensile elastic modulus before photocrosslinking is a and the tensile elastic modulus after photocrosslinking is b, b / a is less than 3.0.
Adhesive sheet with a gel content of 20% or less after photocrosslinking by irradiating ultraviolet rays so that the integrated light amount becomes 2000 mJ / cm ² using a high-pressure mercury lamp with an illuminance of 80 mW / cm ^2. ..
[2] The pressure-sensitive adhesive sheet according to [1], wherein the content of the polyfunctional monomer is less than 1 part by mass with respect to 100 parts by mass of the (meth) acrylic copolymer.
[3] The adhesive sheet contains a hydrogen abstraction type photopolymerization initiator and contains.
The pressure-sensitive adhesive sheet according to [1] or [2], wherein the content of the hydrogen abstraction type photopolymerization initiator with respect to 100 parts by mass of the (meth) acrylic copolymer is 0.1 to 10 parts by mass.
[4] The content of the hydroxy group-containing monomer unit in the (meth) acrylic copolymer is 5% by mass or less based on the total mass of the (meth) acrylic copolymer, [1] to The adhesive sheet according to any one of [3].
[5] Of [1] to [4], which are for bonding to a first adherend having a convex portion and a second adherend having at least one selected from the convex portion and the concave portion. Adhesive sheet described in any.
[6] The height of at least one convex portion of the first adherend is 30% or more of the thickness of the adhesive sheet.
The adhesive according to [5], wherein the height of at least one convex portion of the second adherend or the depth of at least one concave portion of the second adherend is 30% or more of the thickness of the adhesive sheet. Sheet.
[7] In the second adherend, the upper surface area of at least one convex portion or the bottom surface area of at least one concave portion is 10% or less with respect to the surface area of the second adherend, [5]. Or the adhesive sheet according to [6].
[8] Adhesive to the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive sheet according to any one of [1] to [7] and the first adherend having a convex portion laminated on one surface side of the pressure-sensitive adhesive layer. A laminated body having a second adherend having at least one selected from a convex portion and a concave portion laminated on the other surface side of the agent layer.
The height of at least one convex portion of the first adherend is 30% or more of the thickness of the pressure-sensitive adhesive layer.
The height of at least one convex portion of the second adherend or the depth of at least one concave portion of the second adherend is 30% or more of the thickness of the pressure-sensitive adhesive layer.
An extension virtual line extending in the thickness direction from the end of the convex portion of the first adherend, and an extension virtual line or a second adherend extending in the thickness direction from the end of the convex portion of the second adherend. A laminated body in which the shortest distance of an extension virtual line extending in the thickness direction from the end of the recess is 30 mm or less.
[9] The top surface area of at least one convex portion or the bottom surface area of at least one recess in the second adherend is 10% or less with respect to the surface area of the second adherend, [8]. The laminate described in.

According to the present invention, it is possible to obtain an adhesive sheet which exhibits excellent step followability even in a high-temperature environment or an ultraviolet irradiation environment and has excellent durability.

FIG. 1 is a cross-sectional view showing an example of the configuration of a 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 the laminated body.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value. Further, "(meth) acrylic" means that both acrylic and methacryl are contained.

(Adhesive sheet)
The present invention relates to a pressure-sensitive adhesive sheet having photocrosslinkability. The pressure-sensitive adhesive sheet of the present invention contains a (meth) acrylic copolymer having a glass transition temperature (Tg) of −50 ° C. to −40 ° C. and a weight average molecular weight of 330,000 to 400,000. Further, in the pressure-sensitive adhesive sheet of the present invention, the tensile stress at a tensile modulus of 2000% before photocrosslinking is 0.3 N / mm ² or less, the tensile elastic modulus before photocrosslinking is 50 kPa or more and 300 kPa or less, and photocrosslinking is performed. When the previous tensile elastic modulus is a and the tensile elastic modulus after photocrosslinking is b, b / a is less than 3.0. Further, when the adhesive sheet of the present invention is irradiated with ultraviolet rays so that the integrated light amount becomes 2000 mJ / cm ^{2 using a high-pressure mercury lamp having an illuminance of 80 mW / cm 2} , and photocrosslinking is performed, the adhesive sheet after photocrosslinking is subjected to photocrosslinking. The gel fraction is 20% or less.

Since the pressure-sensitive adhesive sheet of the present invention has the above-mentioned structure, it has both step-following property and durability. The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having photocrosslinkability, and can follow a step of an adherend without a gap before photocrosslinking. In particular, the adhesive sheet of the present invention can exhibit excellent step followability even when the distance between the steps of the adherend is narrow or when the height or depth of the uneven shape constituting the step is large. can. On the other hand, the pressure-sensitive adhesive sheet of the present invention exhibits sufficient durability after photocrosslinking. As described above, in the present invention, by optimizing the tensile stress, tensile elastic modulus, and gel fraction in the pressure-sensitive adhesive sheet, it has succeeded in achieving both step followability and durability.

The pressure-sensitive adhesive sheet of the present invention may not substantially contain a thermal cross-linking agent. When the pressure-sensitive adhesive sheet does not contain a heat-crosslinking agent, the aging step can be omitted when forming the pressure-sensitive adhesive sheet, and the time required for manufacturing the pressure-sensitive adhesive sheet can be shortened.

The adhesive sheet of the present invention is excellent for such an adherend even when the distance between the steps of the adherend is narrow or the height or depth of the uneven shape forming the step is large. Demonstrates the ability to follow steps. The adhesive sheet of the present invention can follow the step without a gap even if the sticking portion has a convex portion having a height of 30 μm or more and a concave portion having a depth of 70 μm or more. It can be evaluated that the step followability is excellent even when the height or depth of the uneven shape constituting the step is large.

In addition, the adhesive sheet of the present invention is also excellent in durability. Specifically, even when the adhesive sheet of the present invention is attached to the stepped portion and repeatedly irradiated with ultraviolet rays under the following conditions, the adhesive sheet does not deteriorate and bubbles or the like are observed in the stepped portion. I can't. The irradiation conditions of ultraviolet rays, for example, 4 hours and, 0.53W ^/ m 2, 50 1 cycle × 12 times 4 hours at ° C. at 0.8W ^/ m 2, 80 ℃.

Further, even when the adhesive sheet of the present invention is attached to the stepped portion and a thermal shock test is performed under the following conditions, the adhesive sheet does not deteriorate and no bubbles or the like are generated in the stepped portion. .. The conditions of the thermal shock test are, for example, a cycle of 80 ° C. for 30 minutes and -40 ° C. for 30 minutes x 200 times. The pressure-sensitive adhesive sheet of the present invention is particularly excellent in heat-resistant impact, and even when repeatedly exposed to high-temperature conditions and low-temperature conditions, the pressure-sensitive adhesive sheet does not deteriorate and can maintain its follow-up to the stepped portion.

As described above, the pressure-sensitive adhesive sheet of the present invention exhibits excellent step-following property even for stepped portions having various shapes. Therefore, the pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet for bonding an adherend having at least one selected from convex portions and concave portions. Among them, the pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet for being bonded to two adherends, and specifically, a first adherend having a convex portion, and a convex portion and a concave portion. It is preferably for bonding to a second adherend having at least one selected from the above. In this case, the height of at least one convex portion of the first adherend may be 30% or more of the thickness of the adhesive sheet, and the height of at least one convex portion of the second adherend or The depth of at least one recess of the second adherend may be 30% or more of the thickness of the pressure-sensitive adhesive sheet. The top surface area of at least one convex portion or the bottom surface area of at least one recess in the second adherend is preferably 10% or less with respect to the surface area of the second adherend. As described above, the adhesive sheet of the present invention can exhibit excellent step followability with respect to such an adherend even when the height or depth of the uneven shape forming the step is large. ..

Tensile stress at a tensile elongation 2000% before photocrosslinking of the pressure-sensitive adhesive sheet of the present invention may be any 0.3 N / mm ² or less, is preferably 0.25 N / mm ² or less, 0.2 N / mm It is more preferably ^{2 or less.} By setting 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 followability and durability.

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 adhesive sheet is cut out so as to have 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 thickness (mm) of the adhesive sheet x Amm = 6 mm 2.} Next, the adhesive sheet is rolled in the width direction to form a columnar sample having a circle diameter of 2.8 mm and a height of 50 mm. It is sandwiched between two 50 mm PET films (4 in total). Then, this region is used as the chuck portion of the tensile tester, and is fixed so that the distance between the chucks is 30 mm. It is pulled until it reaches 2000%, and the stress value at this time is taken as the tensile stress.
The tensile elongation rate in the present specification is a rate calculated by the following formula.
Tensile elongation (%) = (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 the tensile elongation of 2000% before photocrosslinking of the pressure-sensitive adhesive sheet, the maximum tensile elongation of the pressure-sensitive adhesive sheet before photocrosslinking needs to be 2000% or more. If the tensile elongation of the pressure-sensitive adhesive sheet before photocrosslinking is less than 2000%, the pressure-sensitive adhesive sheet breaks before the tensile elongation reaches 2000% when measuring the above-mentioned tensile stress. In this case, the stress value obtained by the above measurement is the breaking stress.

Breaking stress after photocrosslinking adhesive sheet is preferably 1.0 N / mm ² or less, more preferably 0.9N / mm ² or less, still be at 0.8N / mm ² or less preferable. The breaking stress of the pressure-sensitive adhesive sheet after photocrosslinking is a ^{value obtained by irradiating the pressure-sensitive adhesive sheet with ultraviolet rays so that the integrated light amount is 2000 mJ / cm 2,} and then measuring the tensile stress described above. In the present specification, the pressure-sensitive adhesive sheet before photocrosslinking is, for example, ^{a pressure-sensitive adhesive sheet before irradiating ultraviolet rays so that the integrated light amount becomes 2000 mJ / cm 2,} and the pressure-sensitive adhesive sheet after photocrosslinking has an illuminance of 80 mW. / accumulated light amount using a high-pressure mercury lamp cm ² is pressure-sensitive adhesive sheet after irradiation with ultraviolet rays so that the 2000 mJ / cm ^2. The integrated light amount of ultraviolet rays can be appropriately set to the amount of light 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 50 kPa or more, preferably 100 kPa or more, more preferably 120 kPa or more, and particularly preferably 150 kPa or more. The tensile elastic modulus of the pressure-sensitive adhesive sheet before photocrosslinking is preferably 300 kPa or less, more preferably 250 kPa or less, and even more preferably 200 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 above-mentioned measurement of tensile stress. Specifically, the slope is calculated from the tensile modulus and stress value of 0% and 5%, and is used as the tensile elastic modulus.

The tensile elastic modulus of the pressure-sensitive adhesive sheet of the present invention after photocrosslinking may be 100 kPa or more, and is particularly preferably 150 kPa or more. The tensile elastic modulus of the pressure-sensitive adhesive sheet before photocrosslinking is preferably 300 kPa or less, and more preferably 200 kPa or less. The tensile elastic modulus is the tensile elastic modulus of the pressure-sensitive adhesive sheet after being irradiated with ultraviolet rays so that the integrated light amount becomes 2000 mJ / cm ^{2 using a high-pressure mercury lamp having an illuminance of 80 mW / 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 2.8 or less. Is preferable, and 2.5 or less is more preferable. By setting the ratio of the tensile elastic modulus before photocrosslinking of the adhesive sheet to the tensile elastic modulus before and after photocrosslinking within the above range, it becomes easy to obtain an adhesive sheet having both step followability and durability.

The gel fraction of the pressure-sensitive adhesive sheet of the present invention before photocrosslinking is preferably 3.0% or less, more preferably 2.5% or less, still more preferably 2.0% or less, 1 It is more preferably 5.5% or less. The lower limit of the gel fraction of the pressure-sensitive adhesive sheet is not particularly limited, and may be, for example, 0%. By setting the gel fraction of the pressure-sensitive adhesive sheet before photocrosslinking within the above range, a pressure-sensitive adhesive sheet having excellent step followability can be obtained.

The gel fraction of the adhesive sheet is a value measured by the following method.
First, about 0.1 g of an adhesive sheet (adhesive layer) is collected in a sample bottle, 30 ml of ethyl acetate is added, and the mixture is shaken for 24 hours. Then, the contents of this sample bottle are filtered through a 150 mesh stainless steel 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 calculated by the following formula 1.
Gel fraction (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 if the gel fraction is within the above range, it can be said that the pressure-sensitive adhesive sheet is in a semi-cured state. Here, the semi-cured state means that the adhesive sheet has photocrosslinkability (curing ability 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 pressure-sensitive adhesive sheet after photocrosslinking of the present invention may be 20% or less, preferably 18% or less, and more preferably 16% or less. Further, the gel fraction of the pressure-sensitive adhesive sheet after photocrosslinking is preferably larger than 3.0%. Further, the gel fraction of the pressure-sensitive sheet after photocrosslinking, using a high pressure mercury lamp of the illuminance 80 mW / cm ^2, after photocrosslinking adhesive which photocrosslinked by irradiating ultraviolet rays so that the integrated light quantity is 2000 mJ / cm ² The gel fraction of the sheet. In the present specification, the pressure-sensitive adhesive sheet after photocrosslinking is a pressure-sensitive adhesive sheet after being irradiated with ultraviolet rays so that the integrated light amount becomes 2000 mJ / cm ^{2 using a high-pressure mercury lamp having an illuminance of 80 mW / cm 2.}

The adhesive strength of the pressure-sensitive adhesive sheet before photocrosslinking of the present invention to glass 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 even more preferable. The adhesive strength of the pressure-sensitive adhesive sheet after photocrosslinking to glass is preferably 20.0 N / 25 mm or more, more preferably 24.0 N / 25 mm or more, and more preferably 25.0 N / 25 mm or more. It is more preferably 27.0 N / 25 mm or more, and particularly preferably 27.0 N / 25 mm or more. Here, the adhesive strength of the adhesive sheet against glass is the peel strength when the adhesive sheet is peeled 180 degrees from the 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 adhesive sheet within the above range, the step followability and durability can be sufficiently improved.

When the pressure-sensitive adhesive sheet of the present invention is used, it is preferable to include a step of irradiating the pressure-sensitive adhesive sheet with light after bringing it into contact with the surface of the adherend. Further, when the pressure-sensitive adhesive sheet of the present invention is used, it is preferable to include a heat treatment step when the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend and / or after the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend. As described above, the pressure-sensitive adhesive sheet of the present invention is preferably a hot-melt type pressure-sensitive adhesive sheet and an after-cure type 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 may be a multi-layered double-sided pressure-sensitive adhesive sheet in which a plurality of pressure-sensitive adhesive layers are laminated. Further, 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 base material (preferably a transparent base material). In this case, the base material is, for example, a plastic film such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyether ether ketone, triacetyl cellulose; optical such as antireflection film and electromagnetic wave shielding film. Examples include films.

((Meta) acrylic copolymer)
The pressure-sensitive adhesive sheet of the present invention contains a (meth) acrylic copolymer having a glass transition temperature (Tg) of −50 ° C. to −40 ° C. and a weight average molecular weight of 330,000 to 400,000. The (meth) acrylic copolymer is a 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. In the present specification, the "unit" is a repeating unit (monomer unit) constituting the polymer. The (meth) acrylic acid alkyl ester unit is derived from the (meth) acrylic acid alkyl ester. Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, isopropyl (meth) acrylic acid, n-butyl (meth) acrylic acid, and (meth). Isobutyl acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, ( Isooctyl acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-undecyl (meth) acrylate, (meth) N-dodecyl acrylate, stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobolonyl (meth) acrylate, etc. Can be mentioned. One of these may be used alone, or two or more thereof may be used in combination.

Further, the (meth) acrylic copolymer may have an acrylic monomer unit other than the (meth) acrylic acid alkyl ester unit. Examples of other acrylic monomer units include acrylic monomer units having a crosslinkable functional group. For example, a hydroxy group-containing acrylic monomer unit and a glycidyl group-containing acrylic monomer unit. Can be mentioned. These monomer units may be one type or two or more types.
The hydroxy group-containing acrylic monomer unit is derived from the hydroxy group-containing acrylic monomer. Examples of the hydroxy group-containing acrylic monomer include hydroxy (meth) acrylate such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxypropyl (meth) acrylate. Examples thereof include (meth) acrylic acid [(mono, di or poly) alkylene glycol] such as alkyl and (meth) acrylic acid mono (diethylene glycol), and (meth) acrylic acid lactone such as (meth) acrylic acid monocaprolactone.
Examples of the glycidyl group-containing acrylic monomer unit include those derived from a glycidyl group-containing acrylic monomer such as glycidyl (meth) acrylate.

When the (meth) acrylic copolymer has other acrylic monomer units other than the (meth) acrylic acid alkyl ester unit, the content of the other acrylic monomer units is the same as the (meth) acrylic copolymer. 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, the content of the acrylic monomer unit having a crosslinkable functional group is preferably within the above range. When the content of the other acrylic monomer unit is at least the above lower limit value, the cohesive force can be sufficiently increased, and when it is at least the above upper limit value, it becomes easy to secure sufficient adhesive force.

However, when the (meth) acrylic copolymer has other acrylic monomer units other than the (meth) acrylic acid alkyl ester unit, the other acrylic monomer units contain hydroxy groups. In the case of a metric unit, the content of the hydroxy group-containing monomer unit is preferably 5% by mass or less with respect to the total mass of the (meth) acrylic copolymer. By setting the content of the hydroxy group-containing monomer unit within the above range, the durability of the pressure-sensitive adhesive sheet can be more effectively enhanced.

The glass transition temperature (Tg) of the (meth) acrylic copolymer may be −50 ° C. or higher, preferably −49 ° C. or higher, and more preferably −48 ° C. or higher. The glass transition temperature (Tg) of the (meth) acrylic copolymer may be −40 ° C. or lower, preferably −41 ° C. or lower, and more preferably −42 ° C. or lower. By setting the glass transition temperature (Tg) of the (meth) acrylic copolymer within the above range, the step followability of the pressure-sensitive adhesive sheet can be more effectively enhanced. 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 enhanced, and a pressure-sensitive adhesive sheet having excellent durability and adhesiveness can be obtained. be able to. In addition, 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 as a result, the pressure-sensitive adhesive sheet can be easily processed.

The weight average molecular weight (Mw) of the (meth) acrylic copolymer may be 330,000 or more, preferably 350,000 or more. The weight average molecular weight (Mw) of the (meth) acrylic copolymer may be 400,000 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. Normally, there is a trade-off relationship between step followability and durability in an adhesive sheet, but in the present invention, by setting the weight average molecular weight of the (meth) acrylic copolymer within the above range, step followability can be achieved. It is 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 obtained in terms of standard polystyrene.
The measurement conditions of gel permeation chromatography (GPC) are as follows.
Solvent: tetrahydrofuran
Columns: Shodex KF801, KF803L, KF800L, KF800D (4 made by Showa Denko KK 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 velocity): 0.8 ml / min
Injection volume: 10 μl
Calibration curve: Standard polystyrene Shodex standard polystyrene (manufactured by Showa Denko KK) A calibration curve of 10 samples from Mw = 1320 to 25000000 was used.

As the (meth) acrylic copolymer, a commercially available one may be used, or may be produced by polymerizing an acrylic monomer. As a commercially available product, for example, OP-9200-23 manufactured by Aica Kogyo Co., Ltd. can be used. When the (meth) acrylic copolymer is produced by polymerization, the polymerization method can be appropriately selected from the commonly used polymerization methods. Examples of the polymerization method include a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method.

(Polyfunctional monomer)
The pressure-sensitive adhesive sheet of the present invention may contain a polyfunctional monomer. A polyfunctional monomer is a monomer having two or more reactive double bonds in the molecule.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylic acid, triethylene glycol di (meth) acrylic acid, 1,3-butylene glycol di (meth) acrylic acid, and 1,4-di (meth) acrylic acid. Butylene glycol, di (meth) acrylic acid 1,9-nonanediol, diacrylic acid 1,6-hexanediol, di (meth) acrylic acid polybutylene glycol, di (meth) acrylic acid neopentyl glycol, di (meth) acrylic Tetraethylene glycol acid, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, diacrate of bisphenol A diglycidyl ether, trimethylol propane tri (meth) acrylate, pentaerythritol tri (meth) acrylate , (Meta) acrylic acid esters of polyhydric alcohols such as pentaerythritol tetra (meth) acrylate, vinyl methacrylate and the like.

Commercially available products can be used as the polyfunctional monomer. Examples of commercially available products include ATM-4PL manufactured by Shin-Nakamura Chemical Co., Ltd., A-TMM-3L, PET-30 manufactured by Nippon Kayaku Co., Ltd., Viscoat # 230 manufactured by Osaka Organic Chemical Industry Co., Ltd., and the like.

The content of the polyfunctional monomer is preferably less than 1 part by mass, more preferably 0.8 parts by mass or less, and 0.6 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. The following is more preferable. The content of the polyfunctional monomer may be 0 parts by mass. That is, the pressure-sensitive adhesive sheet may be substantially free of polyfunctional monomers.

(Monofunctional monomer)
The pressure-sensitive adhesive sheet of the present invention may contain a monofunctional monomer. A monofunctional monomer is a monomer having one reactive double bond in the molecule.

Examples of the monofunctional monomer include isobornyl acrylate, isostearyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, benzyl methacrylate, N-acryloyloxyethyl hexahydrophthalimide, acrylamide, N, N-dimethylacrylamide, N, N. -Diethylacrylamide, acryloylmorpholin, vinylpyrrolidone and the like can be mentioned. Among them, the monofunctional monomer is preferably an alkyl (meth) acrylate, preferably at least one selected from isobornyl acrylate and isostearyl acrylate, and more preferably isobornyl acrylate. Examples of commercially available monofunctional monomers include IBXA manufactured by Osaka Organic Chemical Industry Co., Ltd. and ISTA manufactured by Osaka Organic Chemical Industry Co., Ltd.

The content of the monofunctional monomer is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and 10 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer. Is even more preferable. The content of the monofunctional monomer may be 0 parts by mass. That is, the pressure-sensitive adhesive sheet may be substantially free of monofunctional monomers.

(Hydrogen abstraction type photopolymerization initiator)
The pressure-sensitive adhesive sheet of the present invention preferably contains a hydrogen abstraction type photopolymerization initiator. The hydrogen abstraction type photopolymerization initiator initiates the polymerization reaction of the above-mentioned (meth) acrylic copolymer or monomer by irradiation with active energy rays. The hydrogen abstraction type photopolymerization initiator is a photopolymerization initiator that promotes polymerization by forming an excitation complex between a photoexcited initiator and a hydrogen donor in the system and transferring hydrogen in the hydrogen donor.

Examples of the hydrogen abstraction type photopolymerization initiator include benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 2,4,6-trimethyl. Benzophenone, 4-methylbenzophenone, thioxanson, 2-chlorthioxanson, 2-methylthioxanson, 2,4-dimethylthioxanson, isopropylthioxanson, phenylquinone, dibenzosverone, 2-ethylanthraquinone, 3 , 3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, benzyl, 9,10-phenanthrene quinone and the like. Among them, the hydrogen abstraction type photopolymerization initiator is preferably a benzophenone-based photopolymerization initiator, and examples of the benzophenone-based photopolymerization initiator include benzophenone, 4-methylbenzophenone and 2,4,6-trimethyl. Benzophenone and the like can be mentioned.

As the hydrogen abstraction type photopolymerization initiator, a commercially available product can be used. Examples of commercially available products include TZT and MBF manufactured by IGM Resin Co., Ltd. and MBP manufactured by Lambson Co., Ltd.

The pressure-sensitive adhesive sheet preferably contains 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, with respect to 100 parts by mass of the (meth) acrylic copolymer. preferable. The hydrogen abstraction type photopolymerization initiator may be used alone or in combination of two or more, and when two or more of them are used in combination, the total mass is preferably within the above range.

(solvent)
The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive sheet of the present invention may contain a solvent. In this case, the solvent is used to improve the coating suitability of the pressure-sensitive adhesive composition.

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; methanol. , Ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol and other alcohols; ethers such as diethyl ether, diisopropyl ether, dioxane and tetrahydrofuran; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone and other ketones. Esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl butyrate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl Examples thereof include polyols such as ether and propylene glycol monomethyl ether acetate and derivatives thereof.

(Arbitrary ingredient)
The pressure-sensitive adhesive sheet of the present invention may contain other components other than the above as long as the effects of the present invention are not impaired. Examples of other components include components known as additives for adhesives. For example, a plasticizer, an antioxidant, a metal corrosion inhibitor, a tackifier, a silane coupling agent, an ultraviolet absorber, a light stabilizer such as a hindered amine compound, and the like can be selected as necessary.

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

Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, lactone-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. These antioxidants may be used alone or in combination of two or more.
Examples of the metal corrosion inhibitor include benzoliazole-based resins.
Examples of the tackifier include rosin resin, terpene resin, terpene phenol resin, Kumaron inden resin, styrene resin, xylene resin, phenol resin, petroleum resin and the like.
Examples of the silane coupling agent include a mercapto-based silane coupling agent, a (meth) acrylic-based 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-based compounds and benzophenone-based compounds.

The pressure-sensitive adhesive sheet of the present invention preferably contains substantially no heat-crosslinking agent. Here, the content of the thermal cross-linking agent in the pressure-sensitive adhesive sheet is preferably less than 0.5 parts by mass and 0.3 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic copolymer. Is more preferably 0.2 parts by mass or less, further 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, the step followability of the pressure-sensitive adhesive sheet can be more effectively enhanced. Further, by setting the content of the heat-crosslinking agent within the above range, the aging step 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 the thermal cross-linking agent 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 relate to a double-sided pressure-sensitive adhesive sheet with a release sheet provided with release sheets on both sides of the above-mentioned pressure-sensitive adhesive sheet.

FIG. 1 is a schematic view showing a cross section of an example of a double-sided pressure-sensitive adhesive sheet with a release sheet of the present invention. The double-sided adhesive sheet 1 with a release sheet 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. Further, 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 base material (preferably a transparent base material).

As shown in FIG. 1, the surface of the double-sided pressure-sensitive adhesive sheet 11 is preferably covered with the release sheet 12a and the release sheet 12b. The release sheet is a removable 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 polypropylene film as a low-polarity base material. Can be mentioned.

Papers and polymer films are used as the base material for the release sheet in the releaseable 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 long-chain alkyl group-containing compound is used. In particular, an addition type silicone release agent having high reactivity is preferably used.
Specific examples of the silicone-based release agent include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone, and KS-3600, KS-774, and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. Can be mentioned. Further, it contains a silicone resin which is an organic silicon compound having an SiO ₂ units and _{(CH 3) 3 SiO 1/2} units or _{CH 2 = CH (CH 3)} SiO 1/2 units in the silicone-based release agent preferable. Specific examples of the silicone resin include BY24-843, SD-7292, SHR-1404, etc. manufactured by Toray Dow Corning Silicone Co., Ltd., KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.
A commercially available product may be used as the peelable laminated sheet. Examples include a heavy 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. can.

The pressure-sensitive adhesive sheet of the present invention preferably has a pair of release sheets having different peeling forces. That is, it is preferable that the release sheet has different peelability between the release sheet 12a and the release sheet 12b in order to facilitate the release. When the peelability from one side and the peelability from the other side are different, it becomes easy to peel off only the release sheet having the higher peelability first. In that case, the peelability of the release sheet 12a and the release sheet 12b may be adjusted according to the bonding method and the bonding order.

(Manufacturing method of laminated body)
When using the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive sheet is brought into contact with the surface of an adherend having at least one selected from convex portions and concave portions. Then, after the pressure-sensitive adhesive sheet is brought into contact with the surface of the adherend, it is preferable to include a step of irradiating light. That is, the method for producing a laminated body of the present invention preferably includes a bonding step of bringing the pressure-sensitive adhesive sheet into contact with the surface of the adherend and a light irradiation step.

The method for producing a laminated body 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 surface of the adherend. In this case, a step of irradiating light is included after the heat treatment step. That is, the method for producing a laminated body of the present invention includes a bonding step of bringing the adhesive sheet into contact with the surface of the adherend and a light irradiation step, and at least one of the following (step a) and (b). May be included.
(Step a) Heat treatment is performed in the laminating step.
(Step b) A post-step of the laminating step, which includes a defoaming step in the pre-step of the light irradiation step, and a heat treatment is performed in the defoaming step.

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

In the heat treatment in the above (step a) and the above (b), it is preferable to perform the heat treatment at 40 to 59 ° C. The heating temperature is also preferably 50 to 59 ° C. By providing such a heat treatment step in the manufacturing process of the laminated body, the flexibility of the pressure-sensitive adhesive sheet or the double-sided pressure-sensitive adhesive sheet can be further increased, and it is possible to easily follow the step.

Conventionally, when using a hot melt type adhesive sheet, it is a common practice to perform heat treatment at 60 ° C. or higher, and such high temperature heat treatment may damage the adherend. rice field. In the method for producing a laminated body of the present invention, the treatment temperature at the time of performing the heat treatment in the bonding step and / or the post-process of the bonding step can be suppressed to be lower than usual, and even in that case, sufficient step followability can be suppressed. Therefore, the risk of damaging the adherend can be suppressed to an extremely low level. In addition, it is possible to suppress the utility cost when manufacturing the laminated body, and it is possible to more effectively increase the manufacturing efficiency of the laminated body.

The heat treatment at 40 to 59 ° C. is preferably performed in a laminating step or a defoaming step. The heat treatment may be performed in both the bonding step and the defoaming step. Examples of the bonding step include a roll bonding step and a vacuum bonding step. Examples of the defoaming step include an autoclave treatment step. That is, the heat treatment at 40 to 59 ° C. is preferably performed in at least one step selected from the autoclave treatment step, the roll bonding step and the vacuum bonding step. In this case, it is preferable to set the heating set temperature in the autoclave processing step, the roll bonding step, and the vacuum bonding step to 40 to 59 ° C. It is also preferable that the heat treatment is 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 bonded object having at least one selected from the convex portion and the concave portion are irradiated with light. As described above, the light irradiation step can also be called a post-curing step. By post-curing the adhesive sheet with light, the cohesive force of the adhesive is increased and the adhesiveness to the adherend is improved.

The light irradiation step is preferably a step of irradiating ultraviolet rays.
As the light source of ultraviolet rays, 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 and the like can be used.
As the electron beam, for example, an electron beam emitted from each type of electron beam accelerator such as Cockloft Wald type, Bandecliff type, Resonant transformer type, Insulated core transformer type, Linear type, Dynamitron type, High frequency type is used. can.
Radiation output of the UV, integrated light quantity is preferably to be a 100~10000mJ / cm ^2, and more preferably made to be 500~5000mJ / cm ^2.

(Laminated body)
The laminate produced by the above-mentioned production method includes an adhesive layer made of a post-cured pressure-sensitive adhesive sheet and an adherend having at least one selected from convex portions and concave portions. The laminate of the present invention preferably has an adherend on both surfaces of the pressure-sensitive adhesive layer made of a post-cured pressure-sensitive adhesive sheet. Among them, the laminated body of the present invention includes a pressure-sensitive adhesive layer made of a post-cured pressure-sensitive adhesive sheet, a first adherend having a convex portion laminated on one surface side of the pressure-sensitive adhesive layer, and the other side of the pressure-sensitive adhesive layer. It is preferable that the laminated body has a second adherend having at least one selected from the convex portion and the concave portion laminated on the surface side of the above.

In FIG. 2, a first adherend 31 having a convex portion 31a and a second adherend 32 having at least one selected from the convex portion and the concave portion are attached to both sides of the pressure-sensitive adhesive sheet 11 of the present invention. It is sectional drawing which shows an example of the structure of the laminated body 30 combined. Note that FIG. 2 depicts an example in which the second adherend 32 has a plurality of recesses 32b as an example of the present embodiment. As shown in FIG. 2, the first adherend 31 has a plurality of protrusions 31a. The height of at least one convex portion 31a may be 30% or more of the thickness of the pressure-sensitive adhesive layer 11. Further, the second adherend 32 has a recess 32b, and in this case, the depth of at least one recess 32b may be 30% or more of the thickness of the pressure-sensitive adhesive layer 11. When the second adherend 32 has a convex portion, the height of the convex portion may be 30% or more of the thickness of the pressure-sensitive adhesive layer 11. As described above, the adhesive sheet 11 can exhibit excellent step followability even when the height or depth of the uneven shape forming the step is large.

In the laminated body 30, an extension virtual line extending in the thickness direction from the end of the convex portion 31a of the first adherend 31 and an extension virtual line extending in the thickness direction from the end of the convex portion of the second adherend 32 in the thickness direction. The shortest distance of the line or the extension virtual line extending in the thickness direction from the end of the recess 32b of the second adherend 21 may be 30 mm or less. Here, in FIG. 2, the extension virtual line extending in the thickness direction from the end of the convex portion 31a of the first adherend 31 is a line shown as a dotted line A. Further, in FIG. 2, an extension virtual line extending in the thickness direction from the end of the recess 32b of the second adherend 21 is shown as a dotted line B. In this case, the end of the convex portion 31a is the end on the side close to the other target step portion for measuring the shortest distance, and the end of the concave portion 32b is another target for measuring the shortest distance. This is the end on the side close to the step. The distance between the extension virtual line A and the extension virtual line B is indicated by X, and this distance is the shortest distance between the extension virtual line A and the extension virtual line B. That is, the shortest distance X in the laminated body 30 may be 30 mm or less. In the prior art, when the distance between the steps is narrow, the amount of movement of the adhesive sheet per area (volume) required to fill the steps is large, so that it is difficult to exhibit the step followability. However, in the present invention, the adhesive sheet 11 can exhibit excellent step followability even when the distance between the steps in the two adherends is narrow.

The top surface area of at least one convex portion or the bottom surface area of at least one recess in the second adherend is preferably 10% or less with respect to the surface area of the second adherend. More preferably, it is less than%. Further, the upper surface area of at least one convex portion in the first adherend may be 10% or less or 5% or less with respect to the surface area of the first adherend. As described above, the adhesive sheet of the present invention can exhibit excellent step followability even in a small step portion.

In the present embodiment, when the first adherend has a plurality of convex portions, the shortest distance between the convex portions may be 30 mm or less. Further, when the second adherend has convex portions and concave portions, has a plurality of convex portions, or has a plurality of concave portions, the shortest distance between the convex portions and the concave portions, the shortest distance between the convex portions, and The shortest distance between the recesses may also be 30 mm or less. As described above, the adhesive sheet 11 can exhibit excellent step followability even when the distance between the steps in one adherend is narrow.

It is preferable that the first adherend and the second adherend are optical members, respectively. Examples of the optical member include each component in an optical product such as a touch panel and an image display device.
Examples of the 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, and a transparent conductive film in which a transparent resin film is coated with a conductive polymer. Examples include hard coat films and fingerprint resistant films. The adhesive sheet of the present invention is preferably for stacking touch panel sensors, and more preferably for stacking touch panel sensors using a touch pen. From this point of view, the adherend of the pressure-sensitive adhesive sheet of the present invention includes an ITO film having an ITO film provided on a transparent resin film, an ITO glass having an ITO film provided on the surface of a glass plate, and a conductive polymer on a transparent resin film. A transparent conductive film coated with is preferable.
Examples of the constituent members of the image display device include an antireflection film, an alignment film, a polarizing film, a retardation film, and a brightness improving film used in a liquid crystal display device.
Examples of the material used for these members include glass, polycarbonate, polyethylene terephthalate, polymethylmethacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.
Among them, it is preferable that the first adherend is a touch panel using glass, polycarbonate, or polymethylmethacrylate, and the second adherend is an image display device such as a polarizing plate or an organic EL display.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed in a limited manner by the specific examples shown below.

[Example 1]
(Preparation of adhesive composition)
(Meta) Acrylic copolymer (manufactured by Aika Kogyo Co., Ltd .: OP-9200-23) 100 parts by mass, pentaerythritol triacrylate as polyfunctional monomer (manufactured by Shin-Nakamura Chemical Co., Ltd .: ATM-4PL) 0.5 parts by mass, hydrogen 1.5 parts by mass of a draw-out type photopolymerization initiator (manufactured by IGM Resin Co., Ltd .: TZT) is mixed, and the pressure-sensitive adhesive composition is stirred for 3 minutes under atmospheric pressure using a stirrer (manufactured by SHASHIN KAGAKU Co., Ltd .: SK-200TVS). Made.

(Making an adhesive sheet)
A 38 μm-thick polyethylene terephthalate film (first release sheet) (manufactured by Oji F-Tex Co., Ltd .: 38RL-07) having a release agent layer treated with a silicone-based release agent on 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 150 μm. Then, it was dried in the air circulation type constant temperature oven of 100 degreeC for 3 minutes, and the pressure-sensitive adhesive layer was formed on the surface of the first release sheet. Next, a second release sheet having a thickness of 38 μm (manufactured by Oji F-Tex Co., Ltd .: 38RL-07 (L)) is attached to the surface of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is paired with a difference in peeling power. A double-sided pressure-sensitive adhesive sheet with a release sheet having a structure of a first release sheet / an adhesive layer / a second release sheet sandwiched between the release sheets was obtained.

[Example 2]
In Example 1 (Preparation of Adhesive Composition), 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 polyfunctional monomer was not blended.

[Example 3]
In Example 1 (Preparation of Adhesive Composition), the same as in Example 1 except that the polyfunctional monomer was not blended and the amount of the hydrogen abstraction type photopolymerization initiator added was changed to 3 parts by mass. A double-sided pressure-sensitive adhesive sheet with a pressure-sensitive adhesive composition and a release sheet was obtained.

[Example 4]
The pressure-sensitive adhesive composition and the double-sided pressure-sensitive adhesive sheet with a release sheet were prepared in the same manner as in Example 1 except that the blending amount of the polyfunctional monomer was changed to 0.3 parts by mass in Example 1 (Preparation of pressure-sensitive adhesive composition). Obtained.

[Example 5]
In Example 1 (Preparation of Adhesive Composition), the blending amount of the polyfunctional monomer was changed to 0.3 parts by mass, and 10 parts by mass of (Osaka Organic Chemical Industry Co., Ltd .: ISTA) was further added as a monofunctional monomer. 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.

[Example 6]
In Example 4 (Preparation of Adhesive Composition), a polyfunctional monomer (pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: ATM-4PL)) and a polyfunctional monomer (manufactured by Osaka Organic Chemical Industry Co., Ltd .: Viscoat # 230) were used. A double-sided pressure-sensitive adhesive sheet with a pressure-sensitive adhesive composition and a release sheet was obtained in the same manner as in Example 4 except that the pressure was changed to.

[Example 7]
In Example 4 (Preparation of Adhesive Composition), a polyfunctional monomer (pentaerythritol triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd .: ATM-4PL)) was converted into a polyfunctional monomer (manufactured by Shin-Nakamura Chemical Co., Ltd .: ATM-35E). 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 4 except for the modification.

[Comparative Example 1]
In Example 1 (Preparation of Adhesive Composition), 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 blending amount of the polyfunctional monomer was changed to 3 parts by mass. ..

[Comparative Example 2]
In Comparative Example 1 (Preparation of Adhesive Composition), the compounding amount of the polyfunctional monomer was changed to 1 part by mass, and the addition amount of the hydrogen abstraction type photopolymerization initiator was changed to 3 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.

[Comparative Example 3]
In Example 6 (Preparation of Adhesive Composition), 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 the blending amount of the polyfunctional monomer was changed to 1 part by mass. ..

[Comparative Example 4]
The pressure-sensitive adhesive composition is the same as in Example 4 except that the (meth) acrylic copolymer was changed to OP-9200-26 (manufactured by Aica Kogyo Co., Ltd.) in (Preparation of pressure-sensitive adhesive composition) of Example 4. A double-sided adhesive sheet with a material and a release sheet was obtained.

[Comparative Example 5]
The pressure-sensitive adhesive composition in the same manner as in Example 5 except that the (meth) acrylic copolymer was changed to OP-9200-25 (manufactured by Aica Kogyo Co., Ltd.) in (Preparation of pressure-sensitive adhesive composition) of Example 5. A double-sided adhesive sheet with a material and a release sheet was obtained.

[Comparative Example 6]
In Example 1 (Preparation of Adhesive Composition), the (meth) acrylic copolymer was changed to OP-9200-3 (manufactured by Aica Kogyo Co., Ltd.), and the amount of the polyfunctional monomer compounded was 7% 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 that the parts were changed.

[Comparative Example 7]
The pressure-sensitive adhesive composition is the same as in Example 4 except that the (meth) acrylic copolymer was changed to OP-9200-4 (manufactured by Aica Kogyo Co., Ltd.) in (Preparation of pressure-sensitive adhesive composition) of Example 4. A double-sided adhesive sheet with a material and a release sheet was obtained.

(measurement)
<2000% tensile stress / breaking stress>
The tensile stress of the adhesive sheet before photocrosslinking was measured as follows. First, the double-sided adhesive sheet with a release sheet obtained in Examples and Comparative Examples was cut out so as to have 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 thickness (mm) of the adhesive sheet x Amm = 6 mm 2.} Next, the first release sheet was peeled off, and only the adhesive sheet was rolled in the width direction to obtain a cylindrical sample having a circle diameter of 2.8 mm and a height of 50 mm. Areas up to 10 mm at the top and bottom of the columnar sample are sandwiched between two PET films (total of 4) with a thickness of 188 μm, a length of 25 mm, and a width of 50 mm. It was fixed so that the distance was 30 mm. Then, it was pulled under the conditions of a measurement temperature of 23 ° C. and a relative humidity of 50% at a tensile speed of 300 mm / min until the tensile elongation rate reached 2000%. The stress value at this time was taken as the tensile stress.
The breaking stress of the adhesive sheet after photocrosslinking was measured as follows. First, after irradiating ultraviolet rays from the first release sheet side of the double-sided adhesive sheet with a release sheet cut out ^{using a high-pressure mercury lamp having an illuminance of 80 mW / cm 2 so} that the integrated light intensity becomes 2000 mJ / cm ² , the diameter of the circle is 2. A columnar sample having a height of 0.8 mm and a height of 50 mm was obtained. Then, the tensile stress was measured by the same method as the above-mentioned measurement of the 2000% tensile stress, and when the columnar sample broke before the tensile elongation rate reached 2000%, the stress at the time of rupture was recorded. On the other hand, the values marked with (*) in the item of breaking stress in the table are those that did not break even when the tensile elongation of the columnar sample reached 2000%, which is the same as the above tensile stress. The stress value (2000% tensile stress) when pulled until the tensile elongation becomes 2000% by the method is shown.

<Tension modulus>
The tensile elastic modulus of the pressure-sensitive adhesive sheet was calculated from the stress-strain curve (SS curve) obtained in the measurement of <2000% tensile stress>. Specifically, the slope was calculated from the tensile modulus and stress value of 0% and 5%, and used as the tensile elastic modulus.

<Gel fraction>
Approximately 0.1 g of the pressure-sensitive adhesive sheet before and after photocrosslinking (before and after ultraviolet irradiation) was collected in a sample bottle, 30 ml of ethyl acetate was added, and the mixture was shaken for 24 hours. Then, 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 ° 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. The gel fraction of the adhesive sheet after photocrosslinking was measured after irradiating the adhesive sheet with ultraviolet rays so that the integrated light amount was 2000 mJ / cm ^{2 using a high-pressure mercury lamp having an illuminance of 80 mW / cm 2.}
Gel fraction (mass%) = (dry weight W / collected weight of adhesive sheet) x 100 ... Equation 1

(evaluation)
<Method of manufacturing laminate>
Ultraviolet curable ink was applied to the surface of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm) and screen-printed in a frame shape (length 90 mm × width 50 mm, width 5 mm) so that the coating thickness was 5 μm. Next, the ultraviolet curable ink printed by irradiating with ultraviolet rays was cured. This step was repeated a predetermined number of times to obtain a printed stepped glass (first adherend) having a stepped portion having a thickness of 50 μm.
Next, a second adherend was prepared by the following procedure. First, a polarizing plate with an adhesive layer (polarizing plate manufactured by Samsung SDI Co., Ltd .: “2144”) having a total thickness of 80 μm of the polarizing plate and the glue was cut into a length of 90 mm and a width of 50 mm. Next, after making a circular hole with a diameter of 4 mm at a position 15 mm from the upper end and 10 mm from the left end, a hole is made by pasting it on a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm) different from the above. A glass plate with a polarizing plate (second adherend) was obtained.
The double-sided adhesive sheet with a release sheet obtained in Examples and Comparative Examples was cut into a shape of 90 mm in length × 50 mm in width, 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 attached so as to cover the entire surface of the first adherend. After that, the second release sheet was peeled off, and the exposed pressure-sensitive adhesive sheet (adhesive layer) was provided with a perforated polarizing plate using a vacuum bonding machine (manufactured by Joyo Engineering Co., Ltd .: vacuum stacking device (JE2020B-MVH)). The polarizing plate side of a glass plate (length 90 mm × width 50 mm × thickness 0.5 mm) was bonded. The bonding conditions at this time 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 pressurizing holding time of 10 seconds. Then, defoaming treatment (autoclave treatment: 60 ° C., 0.5 MPa, 30 minutes) was carried out. Then, a high-pressure mercury lamp having an illuminance of 80 mW / cm ² was used to irradiate the printed step glass side with ultraviolet rays so that the integrated light intensity was 2000 mJ / cm ^2, and a laminate was obtained.

<Evaluation of step followability (before durability test)>
The printed step portion of the laminated body before the durability test, which will be described later, was observed with a microscope (magnification: 25 times) and evaluated according to the following criteria.
◯: No air bubbles are seen on the step bonding surface and the step is completely filled. ×: Bubbles are seen on the step bonding surface and the step is not filled.

<Durability (QUV)>
The presence or absence of air bubbles or the like in the laminate after the durability (QUV) test was evaluated according to the following criteria. Specifically, it was observed with a microscope (magnification: 25 times) whether or not bubbles were generated in the entire sample, and evaluated according to the following criteria.
Incidentally, the durability (QUV) tests, launch a laminate QUV tester (Q-LAB Inc.), and 4 hours at 0.8W ^/ m 2, 80 ℃, at 0.53W ^/ m 2, 50 ℃ This was done by irradiating with ultraviolet rays (UV-A) so as to have a 4-hour cycle × 12 times. The irradiation of ultraviolet rays was performed from the printing step glass side.
○: No bubbles or peeling occurred ×: Bubbles or peeling occurred

<Durability (thermal shock test)>
The presence or absence of air bubbles or the like in the laminate after the thermal shock test was evaluated according to the following criteria. Specifically, it was observed with a microscope (magnification: 25 times) whether or not air bubbles were generated in the holes of the second adherend, and evaluated according to the following criteria.
The thermal shock test was carried out by setting the laminate in a thermal shock tester and treating the laminate at 80 ° C. for 30 minutes and at −40 ° C. for 30 minutes × 200 times. The irradiation of ultraviolet rays was performed from the printing step glass side.
○: No bubbles or peeling occurred ×: Bubbles or peeling occurred

The adhesive sheet obtained in the examples was excellent in step followability and durability. The adhesive sheet obtained in the examples exhibited good step followability even in deep recesses.

1 Double-sided adhesive sheet with release sheet 11 Adhesive sheet (adhesive layer)
12a Peeling sheet 12b Peeling sheet 30 Laminated body 31 First adherend 32 Second adherend 31a Stepped portion (convex portion)
32b Step (recess)

Claims (9)

An adhesive sheet with photocrosslinkability
The pressure-sensitive adhesive sheet contains a (meth) acrylic copolymer having a glass transition temperature (Tg) of −50 ° C. to −40 ° C. and a weight average molecular weight of 330,000 to 400,000.
The tensile stress at a tensile elongation of 2000% before photocrosslinking is 0.3 N / mm ² or less.
The tensile elastic modulus before photocrosslinking is 50 kPa or more and 300 kPa or less.
When the tensile elastic modulus before photocrosslinking is a and the tensile elastic modulus after photocrosslinking is b, b / a is less than 3.0.
Adhesive sheet with a gel content of 20% or less after photocrosslinking by irradiating ultraviolet rays so that the integrated light amount becomes 2000 mJ / cm ² using a high-pressure mercury lamp with an illuminance of 80 mW / cm ^2. .. The pressure-sensitive adhesive sheet according to claim 1, wherein the content of the polyfunctional monomer is less than 1 part by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. The pressure-sensitive adhesive sheet contains a hydrogen-extracting photopolymerization initiator and contains.
The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the content of the hydrogen abstraction type photopolymerization initiator with respect to 100 parts by mass of the (meth) acrylic copolymer is 0.1 to 10 parts by mass. Claims 1 to 3 that the content of the hydroxy group-containing monomer unit in the (meth) acrylic copolymer is 5% by mass or less with respect to the total mass of the (meth) acrylic copolymer. The adhesive sheet according to any one of the above. The item according to any one of claims 1 to 4, which is for bonding to a first adherend having a convex portion and a second adherend having at least one selected from the convex portion and the concave portion. The described adhesive sheet. The height of at least one convex portion of the first adherend is 30% or more of the thickness of the adhesive sheet.
According to claim 5, the height of at least one convex portion of the second adherend or the depth of at least one concave portion of the second adherend is 30% or more of the thickness of the adhesive sheet. The adhesive sheet described. The fifth or claim 5 or that the surface area of at least one convex portion or the bottom surface area of at least one concave portion in the second adherend is 10% or less with respect to the surface area of the second adherend. The adhesive sheet according to 6. A pressure-sensitive adhesive layer made of the pressure-sensitive adhesive sheet according to any one of claims 1 to 7, a first adherend having a convex portion laminated on one surface side of the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive. A laminated body having a second adherend having at least one selected from a convex portion and a concave portion laminated on the other surface side of the layer.
The height of at least one convex portion of the first adherend is 30% or more of the thickness of the pressure-sensitive adhesive layer.
The height of at least one convex portion of the second adherend or the depth of at least one concave portion of the second adherend is 30% or more of the thickness of the pressure-sensitive adhesive layer.
An extension virtual line extending in the thickness direction from the end of the convex portion of the first adherend, and an extension virtual line extending in the thickness direction from the end of the convex portion of the second adherend, or the second cover. A laminated body in which the shortest distance of an extension virtual line extending in the thickness direction from the end of a concave portion of the body is 30 mm or less. The eighth aspect of the second adherend, wherein the upper surface area of at least one convex portion or the bottom surface area of at least one concave portion is 10% or less with respect to the surface area of the second adherend. The laminate described.

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