WO2019151192A1 - Method for peeling adhesive sheet - Google Patents

Abstract

Provided is a method for peeling an adhesive sheet adhered to a polarization plate. The adhesive sheet is provided with an adhesive layer, wherein the adhesive layer includes a layer A that constitutes at least one surface of the adhesive layer. The polarization plate has an adhesive sheet-attached surface which is corona-treated or plasma-treated. The peeling method includes a water peeling step wherein, in a state in which an aqueous liquid is present at the interface between the polarization plate and the adhesive sheet at a peeling frontal line of the adhesive sheet from the polarization plate, the adhesive sheet is peeled from the polarization plate while causing the aqueous liquid to enter the interface along the movement of the peeling frontal line.

Description

Adhesive sheet peeling method

The present invention relates to a method for peeling an adhesive sheet. This application is filed on Japanese Patent Application No. 2018-018621 filed on February 5, 2018, Japanese Patent Application No. 2018-109385 filed on June 7, 2018, and Jul. 3, 2018 application. And claims the priority based on Japanese Patent Application No. 2018-126577, the entire contents of which are incorporated herein by reference.

Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; hereinafter the same) is in a soft solid (viscoelastic body) state in the temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the adhesive is widely used in various fields in the form of a pressure-sensitive adhesive sheet with a support having a pressure-sensitive adhesive layer on the support, or in the form of a support-less pressure-sensitive adhesive sheet having no support. It's being used.

Japanese Patent Application Publication No. 2005-148638

Adhesives are required to have various properties depending on the application. Some of these characteristics are difficult to achieve at a high level, for example, when one characteristic tends to be improved, the other characteristic tends to decrease. As an example of the characteristics that are difficult to achieve both in this way, there are adhesive strength to the adherend and reworkability. The above-mentioned rework means that when the adhesive sheet is affixed to the adherend, it may fail to adhere (position misalignment, generation of wrinkles or bubbles, biting of foreign matter, etc.), or a problem with the adherend after application of the adhesive sheet. It means that the adhesive sheet is peeled off from the adherend and then reattached when the is found. Patent Document 1 relates to a method for peeling an adhesive optical film from a substrate with an optical film in which an adhesive optical film is attached to the surface of a substrate (adhered body) such as a glass substrate. A technique for peeling the pressure-sensitive adhesive optical film from the substrate in a state where a liquid exists at the peeling interface between the pressure-sensitive adhesive layer and the substrate is disclosed. On the other hand, in patent document 1, the peeling method of the adhesive sheet affixed on the polarizing plate, ie, the adhesive sheet peeling method in case an adherend is a polarizing plate, is not examined.

Therefore, an object of the present invention is to provide a pressure-sensitive adhesive sheet peeling method capable of easily peeling a pressure-sensitive adhesive sheet from a polarizing plate as an adherend using an aqueous liquid such as water.

According to this specification, a method for peeling the pressure-sensitive adhesive sheet attached to the polarizing plate as the adherend is provided. As for the said polarizing plate, the surface by which the said adhesive sheet is affixed is corona-treated or plasma-treated. The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer includes an A layer that constitutes at least the surface of the pressure-sensitive adhesive layer on the polarizing plate side. In the peeling front of the pressure-sensitive adhesive sheet from the polarizing plate, the peeling method follows the movement of the peeling front while the aqueous liquid is present at the interface between the polarizing plate and the pressure-sensitive adhesive sheet. A water peeling step of peeling the pressure-sensitive adhesive sheet from the polarizing plate while advancing to the interface may be included. Here, the peeling front refers to a position where the pressure-sensitive adhesive sheet starts to be separated from the polarizing plate when the pressure-sensitive adhesive sheet is peeled off from the polarizing plate. According to the water peeling step, the adhesive sheet can be peeled from the polarizing plate by effectively using the aqueous liquid. In some embodiments, the layer A is preferably composed of a pressure-sensitive adhesive containing a water affinity agent.

The peeling method can be preferably carried out in a mode in which the peeling front is moved at a speed of 10 mm / min or more in the water peeling step. According to this aspect, the pressure-sensitive adhesive sheet can be efficiently peeled from the polarizing plate.

FIG. 1 is a cross-sectional view schematically showing the configuration of the pressure-sensitive adhesive sheet. FIG. 2 is a cross-sectional view schematically showing the configuration of another pressure-sensitive adhesive sheet. FIG. 3 is a cross-sectional view schematically showing a member with an adhesive sheet in which another adhesive sheet is attached to the member.

Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings on the implementation of the invention described in the present specification and the common general technical knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Further, in the following drawings, members / parts having the same action may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and do not necessarily accurately represent the size and scale of a product actually provided.

In this specification, “acrylic polymer” refers to a polymer derived from a monomer component containing more than 50% by weight of an acrylic monomer. The acrylic monomer refers to a monomer derived from a monomer having at least one (meth) acryloyl group in one molecule. Further, in this specification, “(meth) acryloyl” means acryloyl and methacryloyl comprehensively. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acryl” generically means acrylic and methacryl.

<Configuration example of adhesive sheet>
One structural example of an adhesive sheet that can be used in the adhesive sheet peeling method disclosed herein is shown in FIG. The pressure-sensitive adhesive sheet 1 has a pressure-sensitive adhesive layer 10 having a surface 10A attached to a polarizing plate as an adherend (ie, a surface on the polarizing plate side) and the other surface 10B of the pressure-sensitive adhesive layer 10. It is comprised as a single-sided adhesive sheet containing the support body 20 laminated | stacked on. The pressure-sensitive adhesive layer 10 is fixedly bonded to one surface 20A of the support 20. As the support 20, for example, a plastic film such as a polyester film can be used. In the example shown in FIG. 1, the pressure-sensitive adhesive layer 10 has a single layer structure. That is, the entirety of the pressure-sensitive adhesive layer 10 is constituted by the A layer constituting one surface (pressure-sensitive adhesive surface) 10 </ b> A of the pressure-sensitive adhesive layer 10. The pressure-sensitive adhesive sheet 1 is used by attaching one surface 10A to a polarizing plate as an adherend. For example, as shown in FIG. 1, the pressure-sensitive adhesive sheet 1 before use (before sticking to an adherend) has a pressure-sensitive adhesive surface 10 </ b> A, and at least the pressure-sensitive adhesive layer side is a release surface (release surface). It can be in the form of an adhesive sheet 50 with a release liner protected with. Alternatively, the second surface 20B (the surface opposite to the first surface 20A and also referred to as the back surface) of the support 20 is a peeling surface, and the adhesive surface 10A is in contact with the second surface 20B. The adhesive surface 10A may be protected by being wound or laminated.

The release liner is not particularly limited. For example, a release liner whose surface of a liner base material such as a resin film or paper is subjected to a release treatment, a fluorine-based polymer (polytetrafluoroethylene, etc.), a polyolefin resin (polyethylene, polypropylene, etc.) And a release liner made of a low adhesion material. For the release treatment, for example, a release agent such as silicone or long chain alkyl may be used. In some embodiments, a release-treated resin film can be preferably used as a release liner.

FIG. 2 shows another configuration example of the pressure-sensitive adhesive sheet that can be used in the pressure-sensitive adhesive sheet peeling method disclosed herein. This pressure-sensitive adhesive sheet 2 has a single-sided adhesive property that includes a pressure-sensitive adhesive layer 110 whose one surface 110A is a surface to be adhered to an adherend, and a support 20 laminated on the other surface of the pressure-sensitive adhesive layer 110. It is comprised as an adhesive sheet. The pressure-sensitive adhesive layer 110 has a two-layer structure including an A layer 112 constituting one surface (adhesive surface) 110 </ b> A and a B layer 114 stacked on the back side of the A layer 112. The pressure-sensitive adhesive sheet 2 before use (before sticking to an adherend) is in the form of a pressure-sensitive adhesive sheet with a release liner in which the pressure-sensitive adhesive surface 110A is protected by a release liner (not shown), like the pressure-sensitive adhesive sheet 1 shown in FIG. obtain. Alternatively, the second surface 20B of the support 20 is a release surface, and the adhesive surface 110A is protected by being wound or laminated so that the adhesive surface 110A is in contact with the second surface 20B. Also good.

The pressure-sensitive adhesive sheet used in the pressure-sensitive adhesive sheet peeling method disclosed herein may be a support-less double-sided pressure-sensitive adhesive sheet composed of a pressure-sensitive adhesive layer. Such a support-less double-sided pressure-sensitive adhesive sheet can be used, for example, by bonding a support to the other surface of the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive sheet peeling method disclosed herein is a mode in which the pressure-sensitive adhesive sheet is peeled off from a member with a pressure-sensitive adhesive sheet in which one surface of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet (that is, the surface of layer A) is attached to the member Can be preferably implemented. Here, the member is a polarizing plate, and more specifically, a polarizing plate in which the surface on which the pressure-sensitive adhesive sheet is attached (surface to be attached) is subjected to corona treatment or plasma treatment. The polarizing plate generally has a configuration in which a polarizing film is sandwiched between two triacetyl cellulose (TAC) films. Of the two TAC films, it is preferable that at least the surface (surface to be attached) of the TAC film disposed on the side to which the adhesive sheet is attached is protected with a hard coat layer. The hard coat layer is preferably composed of a urethane acrylate material. A polarizing plate having a configuration in which an antireflection layer is further provided on the hard coat layer may be used.
For example, as shown in FIG. 3, the surface with the pressure-sensitive adhesive layer 110 of the pressure-sensitive adhesive layer 110 (surface on the polarizing plate side) 110 </ b> A is attached to the member (polarizing plate) 70. It may be the member 200 with the adhesive sheet attached. Instead of the pressure-sensitive adhesive sheet 2 shown in FIG. 2, a member with a pressure-sensitive adhesive sheet having a configuration in which one surface 10A of the pressure-sensitive adhesive sheet 1 shown in FIG.

<Characteristics of adhesive sheet>
The pressure-sensitive adhesive sheet used in the peeling method of the present invention preferably has a water-resistant adhesive strength reduction rate of 30% or less and a water-peeling adhesive strength reduction rate of 40% or more. The rate of decrease in water-resistant adhesive strength [%] is defined as a value calculated by (1− (N1 / N0)) × 100 from normal-state adhesive strength N0 [N / 10 mm] and water-resistant adhesive strength N1 [N / 10 mm]. . The water peeling adhesive strength reduction rate [%] is defined as a value calculated by (1− (N2 / N0)) × 100 from the normal state adhesive strength N0 [N / 10 mm] and the water peeling strength N2. Normal state adhesive strength N0, water-resistant adhesive strength N1, and water peeling strength N2 are measured by the following methods. The same measurement method is used in the examples described later.

[Measurement of normal adhesive strength N0]
A test piece is prepared by cutting the pressure-sensitive adhesive sheet to be measured into a rectangular shape having a width of 10 mm and a length of 120 mm. An evaluation sample in which the layer A side of the test piece is bonded to an adherend with a hand roller is put into an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50 ° C.
After holding the sample for evaluation taken out from the autoclave in an environment of 23 ° C. and 50% RH for one day, a cutter knife is inserted into the interface between the test piece and the adherend in the same environment, and the longitudinal direction of the test piece is measured. One end is peeled from the adherend, and the peel strength is measured using a tensile tester in accordance with JIS Z0237 under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees.

[Measurement of water-resistant adhesive strength N1]
A test piece is prepared by cutting the pressure-sensitive adhesive sheet to be measured into a rectangular shape having a width of 10 mm and a length of 120 mm. An evaluation sample in which the layer A side of the test piece is bonded to an adherend with a hand roller is put into an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50 ° C.
The sample for evaluation taken out from the autoclave is kept in an environment of 23 ° C. and 50% RH for 1 day, and then immersed in water at room temperature (23 ° C. to 25 ° C.) for 30 minutes. Ion exchange water or distilled water is used as water. In water, the sample for evaluation is held horizontally with the surface on which the test piece is attached facing upward. The distance (immersion depth) from the upper surface of the sample for evaluation to the water surface is 10 mm or more (for example, about 10 mm to 100 mm). Next, the sample for evaluation is pulled up from the water, and the water adhering to the sample for evaluation is gently wiped off. Then, a cutter knife is inserted into the interface between the test piece and the adherend, and one end in the longitudinal direction of the test piece is placed. Then, in an environment of 23 ° C. and 50% RH, the peel strength is measured under the conditions of a tensile rate of 300 mm / min and a peel angle of 180 degrees using a tensile tester according to JIS Z0237. The time from when the sample for evaluation is pulled up from the water until the peel strength is measured is within 10 minutes.

[Measurement of water peeling force N2]
A test piece is prepared by cutting the pressure-sensitive adhesive sheet to be measured into a rectangular shape having a width of 10 mm and a length of 120 mm. An evaluation sample in which the layer A side of the test piece is bonded to an adherend with a hand roller is put into an autoclave and treated for 15 minutes under conditions of a pressure of 5 atm and a temperature of 50 ° C.
After holding the sample for evaluation taken out from the autoclave in an environment of 23 ° C. and 50% RH for 1 day, one drop (on the surface of the adherend exposed from the one end in the vicinity of one end in the longitudinal direction of the test piece) About 10 μl to about 40 μl) of distilled water is added dropwise. And after inserting a cutter knife in the interface of a test piece and a to-be-adhered body, and making the said water approach into the said interface, using a tensile testing machine according to JISZ0237, without supplying new water. The peel strength is measured under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees. In addition, the water used in the measurement of the water peeling force N2 is only one drop of distilled water dropped on the adherend before the peeling starts.

In the measurement of the above-described normal adhesive strength N0, water-resistant adhesive strength N1, and water peeling strength N2, the adherend has a configuration in which a polarizing film is sandwiched between two TAC films, and the side to which the adhesive sheet is attached The surface (surface to be bonded) is a surface in which a hard coat layer and an antireflection layer as a protective layer are laminated in this order on the TAC film, and the surface (surface to be bonded) is subjected to corona treatment. Use a board. The corona treatment of the adherend surface is performed immediately before attaching the test piece to the adherend (typically within 30 minutes before the attachment). The adherend is subjected to KASUGA “AGF-012” (table surface corona treatment). It is performed by passing it once through the apparatus under the conditions of output setting 3 (display 0.17 kW) and table speed scale 20 (equivalent to a speed of 3 m / min). The test piece is attached to the adherend so that the distance from the outer peripheral end of the test piece to the outer peripheral end of the adherend is at least 10 mm or more, preferably 15 mm or more. As the tensile tester, a universal tensile / compression tester (device name “Tensile / Compression Tester, TCM-1kNB” manufactured by Minebea Co., Ltd.) or its equivalent can be used. The peel strength is measured so that the test piece attached to the adherend progresses upward from the bottom. In the measurement, a test piece can be reinforced by attaching an appropriate backing material to the back surface of the pressure-sensitive adhesive sheet (the surface opposite to the surface of the layer A) as necessary. As the backing material, for example, a polyethylene terephthalate film having a thickness of about 25 μm can be used. In addition, as an adherend, as a substitute for the polarizing plate having the above-described configuration, a TAC film imitating the configuration of the surface to be bonded of the polarizing plate, that is, a surface on which a hard coat layer and an antireflection layer are laminated in this order. And a TAC film having a corona treatment on the surface under the above conditions may be used. The hard coat layer and the antireflection layer can be formed by the method described in Examples described later.

(Water peeling adhesion reduction rate)
The peeling method of the present invention is preferably applied to a pressure-sensitive adhesive sheet having a water peeling pressure reduction rate of 40% or more. The pressure-sensitive adhesive sheet exhibiting such a water peeling pressure-sensitive adhesive strength reduction rate can be easily peeled from the polarizing plate by using an aqueous liquid such as water. For example, by supplying a small amount of aqueous liquid to the adherend (polarizing plate) to which the adhesive sheet is attached, and allowing the aqueous liquid to enter the interface between the adhesive sheet and the adherend from one end of the adhesive sheet. The peel strength of the pressure-sensitive adhesive sheet from the adherend can be greatly reduced by peeling the pressure-sensitive adhesive sheet after creating a trigger for peeling. Utilizing this property, both high adhesive strength during normal use and good reworkability can be achieved. In some embodiments, the rate of decrease in water peel adhesion may be, for example, 50% or more, 65% or more, 75% or more, 85% or more, 90% or more, 95% or more However, it may be 97% or more. The water peeling adhesion decreasing rate is 100% or less in principle, and typically less than 100%.

(Water adhesion resistance reduction rate)
The pressure-sensitive adhesive sheet to which the peeling method of the present invention is applied can be easily peeled off using an aqueous liquid such as water as described above, and the water-resistant adhesive strength reduction rate is preferably 30% or less. From the viewpoint of obtaining higher water-reliability, the water-resistant adhesive strength reduction rate is, for example, preferably 20% or less, more preferably 10% or less, and may be 7% or more. The rate of decrease in water-resistant adhesive strength is typically 0% or more. The pressure-sensitive adhesive sheet has a difference between the water peeling adhesive strength reduction rate [%] and the water-resistant adhesive strength reduction rate [%], for example, 45% or more, 55% or more, 70% or more, 80% or more, or 90 % Or more can be preferably implemented.

The pressure-sensitive adhesive sheet to which the peeling method disclosed herein is applied preferably has a normal pressure N0 of 2.0 N / 10 mm or more from the viewpoint of bonding reliability. In some embodiments, the normal adhesive strength N0 may be, for example, 2.5 N / 10 mm or more, 3.0 N / 10 mm or more, 3.5 N / 10 mm or more, or 4.0 N / 10 mm or more. . The upper limit of normal state adhesive force N0 is not specifically limited, For example, it may be 30 N / 10mm or less. In some embodiments, the normal adhesion N0 may be 20 N / 10 mm or less, or 15 N / 10 mm or less.

The water peeling force N2 is preferably 60% or less, more preferably 50% or less of the normal state adhesive force N0. Although not particularly limited, the water peeling force N2 may be, for example, 10 N / 10 mm or less, 3.5 N / 10 mm or less, 2.5 N / 10 mm or less, or 1.6 N / 10 mm or less. 1.2 N / 10 mm or less, or 1.0 N / 10 mm or less. According to the pressure-sensitive adhesive sheet having a low water peeling force N2, it is possible to reduce the load applied to the adherend when peeling the pressure-sensitive adhesive sheet. This is particularly significant in an embodiment in which the pressure-sensitive adhesive sheet is peeled from a polarizing plate having a thin film such as a hard coat layer or an antireflection layer on the surface. For example, the pressure-sensitive adhesive sheet is suitably implemented in an embodiment in which the water peeling force N2 is 0.75 N / 10 mm or less, or 0.50 N / 10 mm or less, or 0.25 N / 10 mm or less, or 0.15 N / 10 mm or less. obtain. The lower limit of the water peeling force N2 is not particularly limited, and may be substantially 0 N / 10 mm or more than 0 N / 10 mm.
From the viewpoint of improving reworkability, a pressure-sensitive adhesive sheet that peels from the adherend without leaving the pressure-sensitive adhesive on the adherend is preferable in the measurement of the water peeling force N2. That is, an adhesive sheet excellent in non-glue residue is preferable. The presence or absence of the adhesive remaining on the adherend can be grasped, for example, by visually observing the adherend after peeling off the adhesive sheet.

The ratio (N2 / N0) of the water peeling force N2 [N / 10 mm] to the normal state adhesive force N0 [N / 10 mm] may be, for example, 1 / 2.5 or less, 1/5 or less, and 1/10 It may be the following. A smaller ratio (N2 / N0) means that the water peeling force N2 is more significantly reduced with respect to the normal adhesive force N0. The peeling method disclosed here can be preferably implemented in a mode in which the pressure-sensitive adhesive sheet having a ratio (N2 / N0) of 1/15 or less, 1/25 or less, or 1/35 or less is peeled from the polarizing plate. The upper limit of the ratio (N2 / N0) is not particularly limited, and may be, for example, 1/200 or more, 1/150 or more, or 1/100 or more.

In the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive constituting the layer A constituting at least the surface on the polarizing plate side of the pressure-sensitive adhesive layer is preferably water-insoluble. According to the water-insoluble layer A, a pressure-sensitive adhesive sheet having a high water-resistant adhesive strength N1 and a low water-resistant adhesive strength reduction rate is easily obtained. It is preferable that the A layer is water-insoluble from the viewpoint of preventing a phenomenon in which the pressure-sensitive adhesive remains on the adherend in peeling using an aqueous liquid such as water. In addition, the water insolubility of the A layer can be advantageous from the viewpoint of preventing the phenomenon that the transparency of the pressure-sensitive adhesive sheet is lowered due to water immersion or humidity in the environment.

The pressure-sensitive adhesive constituting the A layer is preferably non-water swellable. According to the non-water-swellable layer A, a pressure-sensitive adhesive sheet having a high water-resistant adhesive strength N1 and a low water-resistant adhesive strength reduction rate is easily obtained. Further, in peeling using an aqueous liquid such as water, good peeling properties can be exhibited by effectively using a small amount of aqueous liquid. The non-water-swelling property of the A layer is also preferable from the viewpoint of preventing the phenomenon that the pressure-sensitive adhesive remains on the adherend during peeling using an aqueous liquid. In addition, the non-water-swelling property of the A layer can be advantageous from the viewpoint of preventing a phenomenon in which the transparency of the pressure-sensitive adhesive sheet is lowered due to water immersion or environmental moisture.

Here, in this specification, that the pressure-sensitive adhesive is water-insoluble means that the gel fraction measured by the following method is 75% or more. Moreover, that an adhesive is non-water-swellable means that the swelling degree measured by the following method is 2 or less.
That is, about 0.5 g of the pressure-sensitive adhesive to be measured is weighed, and its weight is defined as W1. The pressure-sensitive adhesive is immersed in 500 ml of distilled water for 48 hours at room temperature (about 23 ° C.), then filtered through a nylon mesh, and the weight W2 of the pressure-sensitive adhesive containing water is measured. Thereafter, the pressure-sensitive adhesive is dried at 130 ° C. for 5 hours, and the weight W3 of the nonvolatile content is measured. The gel fraction and the degree of swelling are calculated by the following equations.
Gel fraction [%] = (W3 / W1) × 100
Swelling degree = W2 / W1

In some embodiments, the gel fraction of the A layer may be, for example, 80% or more, 90% or more, 95% or more, or 98% or more. The gel fraction of the A layer is 100% or less in principle. In some embodiments, the swelling degree of the A layer may be, for example, 1.7 or less, 1.5 or less, or 1.2 or less. The swelling degree of the A layer is usually 1.0 or more, and typically exceeds 1.0.

In the pressure-sensitive adhesive sheet having a configuration in which the pressure-sensitive adhesive layer includes the layer A and the layer B disposed on the back side of the layer A, the gel fraction of the layer B is not particularly limited. In some embodiments, the gel fraction of the B layer is preferably equal to or higher than the gel fraction of the A layer, and may be higher than the gel fraction of the A layer. The gel fraction of the B layer may be, for example, 90% or more, 95% or more, 98% or more, or 99% or more. The gel fraction of the B layer is 100% or less in principle. Moreover, the gel fraction of the whole adhesive layer may be 85% or more, for example, 90% or more, 95% or more, 98% or more, or 99% or more. In addition, in the adhesive layer which consists only of A layers, the gel fraction of this whole adhesive layer means the gel fraction of A layer.

In the pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer includes the A layer and the B layer disposed on the back side of the A layer, the swelling degree of the B layer is not particularly limited. In some embodiments, the swelling degree of the B layer is preferably equal to or less than the swelling degree of the A layer, and may be lower than the swelling degree of the A layer. The swelling degree of the B layer may be, for example, 1.5 or less, 1.3 or less, or 1.1 or less. The swelling degree of the B layer is usually 1.0 or more, and typically exceeds 1.0. Moreover, the swelling degree of the whole adhesive layer may be 1.6 or less, for example, 1.4 or less, 1.2 or less, or 1.1 or less. In addition, in the adhesive layer which consists only of A layer, the swelling degree of this whole adhesive layer means the swelling degree of A layer.

The gel fraction and the degree of swelling of the pressure-sensitive adhesive with respect to water are generally used by those skilled in the art at the time of filing this application, such as the composition of the monomer component, the weight average molecular weight of the polymer, and the use of a crosslinking agent or a polyfunctional monomer. Can be adjusted by adopting as appropriate.

<Adhesive layer>
(1) A layer In the pressure-sensitive adhesive sheet peeled off by the peeling method disclosed herein, the A layer constituting at least the polarizing plate side surface of the pressure-sensitive adhesive layer is, for example, an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive (natural Rubber-based, synthetic rubber-based, mixed systems thereof), silicone-based adhesives, polyester-based adhesives, urethane-based adhesives, polyether-based adhesives, polyamide-based adhesives, fluorine-based adhesives, etc. It may be a pressure-sensitive adhesive layer composed of one or two or more pressure-sensitive adhesives selected from the agents. Here, the acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive mainly composed of an acrylic polymer. The same applies to rubber-based adhesives and other adhesives. In addition, the concept of a polymer here includes a polymer having a relatively low degree of polymerization, which is generally called an oligomer.

(Acrylic adhesive)
From the viewpoints of transparency, weather resistance, and the like, in some embodiments, an acrylic pressure-sensitive adhesive can be preferably employed as the constituent material of the A layer.

The acrylic pressure-sensitive adhesive is composed of, for example, a monomer component containing more than 50% by weight of (meth) acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal. Those containing an acrylic polymer are preferred. Hereinafter, a (meth) acrylic acid alkyl ester having an alkyl group having X or more and Y or less carbon atoms at the ester end may be referred to as a “(meth) acrylic acid C _XY alkyl ester”. Since it is easy to balance the characteristics, the proportion of the (meth) acrylic acid C _1-20 alkyl ester in the whole monomer component may be, for example, 55% by weight or more, 60% by weight or more, and 70% by weight or more. But you can. For the same reason, the proportion of the (meth) acrylic acid C _1-20 alkyl ester in the monomer component may be, for example, 99.9% by weight or less, 99.5% by weight or less, or 99% by weight or less. Good.

Non-limiting specific examples of (meth) acrylic acid C _1-20 alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, ( N-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) Hexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, (meth ) Decyl acrylate, isomethyl (meth) acrylate, undecyl (meth) acrylate, (meth ) Dodecyl acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, (meth) Examples include isostearyl acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and the like.

Of these, at least (meth) acrylic acid C _4-20 alkyl ester is preferably used, and at least (meth) acrylic acid C _4-18 alkyl ester is more preferably used. For example, an acrylic pressure-sensitive adhesive containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as the monomer component is preferable, and an acrylic pressure-sensitive adhesive containing at least 2EHA is particularly preferable. Other examples of (meth) acrylic acid C _4-20 alkyl esters that can be preferably used include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (ISTA) ) And the like.

In some embodiments, the monomer component constituting the acrylic polymer may contain (meth) acrylic acid C _4-18 alkyl ester in a proportion of 40% by weight or more. Thus, according to the monomer component containing a relatively large amount of (meth) acrylic acid alkyl ester having an alkyl group having 4 or more carbon atoms at the ester terminal, an acrylic polymer having a high lipophilicity tends to be formed. According to the highly lipophilic acrylic polymer, a pressure-sensitive adhesive layer having a low water-resistant adhesive strength reduction rate is likely to be formed. The proportion of the (meth) acrylic acid C _4-18 alkyl ester in the monomer component may be, for example, 60% by weight or more, 70% by weight or more, 75% by weight or more, or 80% by weight or more. It may be a monomer component containing (meth) acrylic acid C _6-18 alkyl ester at a ratio equal to or greater than any of the lower limit values described above.
Further, from the viewpoint of enhancing cohesiveness of the pressure-sensitive adhesive layer and preventing cohesive failure, the proportion of (meth) acrylic acid C _4-18 alkyl ester in the monomer component is usually 99.5% by weight or less. Appropriate and may be 99 weight% or less, 98 weight% or less, and 97 weight% or less. It may be a monomer component containing (meth) acrylic acid C _6-18 alkyl ester at a ratio equal to or lower than any of the above upper limit values.

The monomer component constituting the acrylic polymer contains (meth) acrylic acid alkyl ester and, if necessary, another monomer (copolymerizable monomer) copolymerizable with (meth) acrylic acid alkyl ester. Also good. As the copolymerizable monomer, a monomer having a polar group (for example, a carboxy group, a hydroxyl group, a nitrogen atom-containing ring, etc.) can be preferably used. A monomer having a polar group can be useful for introducing a crosslinking point into the acrylic polymer or increasing the cohesive strength of the pressure-sensitive adhesive. A copolymerizable monomer can be used individually by 1 type or in combination of 2 or more types.

Non-limiting specific examples of the copolymerizable monomer include the following.
Carboxy group-containing monomer: For example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and the like.
Acid anhydride group-containing monomer: for example, maleic anhydride, itaconic anhydride.
Hydroxyl group-containing monomers: for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acryl 4-hydroxybutyl acid, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxy Hydroxyalkyl (meth) acrylates such as methylcyclohexyl) methyl (meth) acrylate and the like.
Monomers containing sulfonic acid groups or phosphoric acid groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfo Propyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid, 2-hydroxyethyl acryloyl phosphate and the like.
Epoxy group-containing monomers: For example, epoxy group-containing acrylates such as glycidyl (meth) acrylate and (meth) acrylic acid-2-ethylglycidyl ether, allyl glycidyl ether, (meth) acrylic acid glycidyl ether, and the like.
Cyano group-containing monomer: For example, acrylonitrile, methacrylonitrile and the like.
Isocyanate group-containing monomer: for example, 2-isocyanatoethyl (meth) acrylate.
Amide group-containing monomer: for example, (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) N, N-dialkyl (meth) acrylamide, such as acrylamide, N, N-di (n-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide; N-ethyl (meth) N-alkyl (meth) acrylamides such as acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, Nn-butyl (meth) acrylamide; N-vinylcarboxylic amides such as N-vinylacetamide A monomer having a hydroxyl group and an amide group, for example, N- (2-hydro (Ciethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2 N-hydroxyalkyl (meth) acrylamides such as -hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) acrylamide; alkoxy groups and amides Monomers having a group, for example, N-alkoxyalkyl (meth) acrylamides such as N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide; N-dimethylaminopropi (Meth) acrylamide, N- (meth) acryloyl morpholine.
Amino group-containing monomer: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having an epoxy group: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N- Vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3 -Morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinyl Thiazole, N-vinylisothiazole, N-vinylpyridazine (E.g., lactams such as N- vinyl-2-caprolactam).
Monomers having a succinimide skeleton: for example, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyhexamethylene succinimide, and the like.
Maleimides: For example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide and the like.
Itaconic imides: for example, N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexylitaconimide, N-cyclohexyl leuconconimide, N-lauryl Itacone imide and the like.
Aminoalkyl (meth) acrylates: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, (meth) acrylic acid t -Butylaminoethyl.
Alkoxy group-containing monomer: for example, 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, (meth) acrylic acid (Meth) acrylic acid alkoxyalkylenes such as butoxyethyl and (meth) acrylic acid ethoxypropyl; (meth) acrylic acid alkoxyalkylene glycols such as (meth) acrylic acid methoxyethylene glycol and (meth) acrylic acid methoxypolypropylene glycol Kind.
Alkoxysilyl group-containing monomer: for example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy Propylmethyldiethoxysilane.
Vinyl esters: For example, vinyl acetate, vinyl propionate and the like.
Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene and the like.
Olefin: For example, ethylene, butadiene, isoprene, isobutylene and the like.
(Meth) acrylic acid ester having an alicyclic hydrocarbon group: for example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, etc. .
(Meth) acrylic acid ester having an aromatic hydrocarbon group: for example, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate and the like.
In addition, heterocycle-containing (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, halogen-containing (meth) acrylates such as vinyl chloride and fluorine-containing (meth) acrylate, silicon atoms such as silicone (meth) acrylate (Meth) acrylate, (meth) acrylic acid ester obtained from terpene compound derivative alcohol and the like.

When such a copolymerizable monomer is used, the amount used is not particularly limited, but it is usually appropriate to make it 0.01% by weight or more of the whole monomer component. From the viewpoint of more effectively using the copolymerizable monomer, the amount of the copolymerizable monomer used may be 0.1% by weight or more of the whole monomer component, or 0.5% by weight or more. Further, from the viewpoint of easily balancing the adhesive properties, the amount of the copolymerizable monomer used is usually suitably 50% by weight or less, preferably 40% by weight or less, based on the whole monomer component.

In some embodiments, the monomer component preferably includes a carboxy group-containing monomer. Preferable examples of the carboxy group-containing monomer include acrylic acid (AA) and methacrylic acid (MAA). AA and MAA may be used in combination. When AA and MAA are used in combination, their weight ratio (AA / MAA) is not particularly limited, and can be, for example, in the range of about 0.1 to 10. In some embodiments, the weight ratio (AA / MAA) may be, for example, approximately 0.3 or more, and may be approximately 0.5 or more. The weight ratio (AA / MAA) may be about 4 or less, for example, or about 3 or less.

By using a carboxyl group-containing monomer, an aqueous liquid such as water can be quickly adapted to the surface of the A layer. This can help reduce the water stripping force N2. The amount of the carboxy group-containing monomer used may be, for example, 0.05% by weight or more of the whole monomer component, 0.1% by weight or more, 0.3% by weight or more, 0.5% by weight or more. However, it may be 0.8% by weight or more. The proportion of the carboxy group-containing monomer may be, for example, 15% by weight or less, 10% by weight or less, 5% by weight or less, 4.5% by weight or less, or 3.5% by weight or less. Alternatively, it may be 3.0% by weight or less, or 2.5% by weight or less. It is preferable that the amount of the carboxy group-containing monomer used is not excessive from the viewpoint of suppressing the diffusion of water into the bulk of the A layer and suppressing the decrease in the water-resistant adhesive strength N1. Further, the fact that the amount of the carboxy group-containing monomer used is not too large can be advantageous from the viewpoint of preventing an event where water used for the measurement of the water peeling force N2 is absorbed by the A layer and the water is insufficient during the peeling. .

In some embodiments, the monomer component can include a hydroxyl group-containing monomer. By using the hydroxyl group-containing monomer, the cohesive force and crosslink density of the pressure-sensitive adhesive can be adjusted, and the normal pressure-sensitive adhesive force N0 can be improved. The amount used in the case of using a hydroxyl group-containing monomer is not particularly limited, and may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more of the entire monomer component. In addition, from the viewpoint of suppressing excessive water diffusion into the bulk of the A layer, in some embodiments, it is appropriate that the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer component. % Or less, 20% or less, 10% or less, 5% or less, or 3% or less. The peeling method disclosed here can also be suitably implemented in an embodiment in which the pressure-sensitive adhesive sheet peeled by the peeling method does not substantially use a hydroxyl group-containing monomer as the monomer component of the A layer.

In some embodiments, the monomer component can include an alkoxysilyl group-containing monomer. The alkoxysilyl group-containing monomer is typically an ethylenically unsaturated monomer having at least one (preferably two or more, for example, two or three) alkoxysilyl groups in one molecule, Specific examples are as described above. The said alkoxysilyl group containing monomer can be used individually by 1 type or in combination of 2 or more types. By using the alkoxysilyl group-containing monomer, a crosslinked structure by silanol group condensation reaction (silanol condensation) can be introduced into the pressure-sensitive adhesive layer. The alkoxysilyl group-containing monomer can also be understood as a silane coupling agent described later.

In the embodiment in which the monomer component includes an alkoxysilyl group-containing monomer, the proportion of the alkoxysilyl group-containing monomer in the entire monomer component can be, for example, 0.005% by weight or more, and usually 0.01% by weight or more. It is appropriate to do. Further, the proportion of the alkoxysilyl group-containing monomer may be, for example, 0.5% by weight or less, 0.1% by weight or less, or 0.05% by weight or less from the viewpoint of improving adhesion to an adherend. But you can.

The composition of the monomer component is such that the glass transition temperature (hereinafter also referred to as “glass transition temperature of acrylic polymer”) determined by the Fox formula based on the composition of the monomer component is −75 ° C. or higher and −10 ° C. or lower. Can be set to In some embodiments, the glass transition temperature (Tg) of the acrylic polymer is suitably −20 ° C. or lower, preferably −30 ° C. or lower, and preferably −40 ° C. or lower. More preferably, it is −50 ° C. or less, and for example, it may be −55 ° C. or less. When the Tg of the acrylic polymer is lowered, the adhesion of the A layer to the adherend generally tends to be improved. According to the A layer having high adhesion to the adherend, water intrusion to the interface between the adherend and the A layer can be easily suppressed in a situation where the adhesive sheet is not intended to be peeled off. This can be advantageous from the viewpoint of improving the water-resistant adhesive strength N1 and reducing the water-resistant adhesive strength reduction rate. The Tg of the acrylic polymer may be, for example, −70 ° C. or higher, or −65 ° C. or higher, from the viewpoint of easily increasing the normal state adhesive force N0.

Here, the Fox equation is a relational expression between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. .
1 / Tg = Σ (Wi / Tgi)
In the above Fox equation, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for the calculation of Tg, the values described in known materials are used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.
2-Ethylhexyl acrylate -70 ° C
n-Butyl acrylate -55 ° C
Methyl methacrylate 105 ° C
Methyl acrylate 8 ℃
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

For the glass transition temperature of homopolymers of monomers other than those exemplified above, the values described in “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple types of values are described in this document, the highest value is adopted.

For monomers whose homopolymer glass transition temperatures are not described in the Polymer Handbook, values obtained by the following measurement method are used (see Japanese Patent Application Publication No. 2007-51271). Specifically, a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser is charged with 100 parts by weight of monomer, 0.2 part by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent. Stir for 1 hour while flowing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape having a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to a shear strain with a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics), in a temperature range of −70 to 150 ° C. The viscoelasticity is measured by the shear mode at a heating rate of 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer.

The pressure-sensitive adhesive layer uses a pressure-sensitive adhesive composition containing the monomer component having the above composition in the form of a polymer, an unpolymerized product (that is, a form in which the polymerizable functional group is unreacted), or a mixture thereof. Can be formed. The pressure-sensitive adhesive composition includes a water-dispersed pressure-sensitive adhesive composition in which a pressure-sensitive adhesive (pressure-sensitive adhesive component) is dispersed in water, a solvent-type pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive in an organic solvent, ultraviolet light, radiation, and the like. Active energy ray-curable pressure-sensitive adhesive composition prepared to be cured by active energy rays to form a pressure-sensitive adhesive, a hot-melt type pressure-sensitive adhesive that is applied in a heated and melted state and forms a pressure-sensitive adhesive when cooled to near room temperature It can be in various forms such as a composition.

In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator can be used depending on the polymerization method, polymerization mode, and the like. Such polymerization initiators can be used singly or in appropriate combination of two or more.

The thermal polymerization initiator is not particularly limited. For example, an azo polymerization initiator, a peroxide initiator, a redox initiator by a combination of a peroxide and a reducing agent, a substituted ethane initiator. Etc. can be used. More specifically, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (2-amidinopropane) dihydrochloride 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (N, N′-dimethyleneisobutylamidine), 2,2 ′ -Azo initiators such as azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate; persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide Peroxide initiators such as hydrogen peroxide; substituted ethane initiators such as phenyl substituted ethane; persulfates and sulfites Combination of sodium hydrogen, redox initiators such as a combination of a peroxide and sodium ascorbate; but the like, without limitation. The thermal polymerization can be preferably carried out at a temperature of, for example, about 20 to 100 ° C. (typically 40 to 80 ° C.).

The photopolymerization initiator is not particularly limited. For example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acylphosphine oxide photopolymerization initiator, α- Ketol photoinitiator, aromatic sulfonyl chloride photoinitiator, photoactive oxime photoinitiator, benzoin photoinitiator, benzyl photoinitiator, benzophenone photoinitiator, thioxanthone light A polymerization initiator or the like can be used.

The amount of such a thermal polymerization initiator or photopolymerization initiator used can be a normal amount used according to the polymerization method, polymerization mode, etc., and is not particularly limited. For example, about 0.001 to 5 parts by weight of a polymerization initiator (typically about 0.01 to 2 parts by weight, for example, about 0.01 to 1 part by weight) is used with respect to 100 parts by weight of the monomer to be polymerized. Can do.

For the above polymerization, conventionally known various chain transfer agents (which can also be grasped as molecular weight regulators or polymerization degree regulators) can be used as necessary. As the chain transfer agent, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan and thioglycolic acid can be used. Or you may use the chain transfer agent (non-sulfur type chain transfer agent) which does not contain a sulfur atom. Specific examples of the non-sulfur chain transfer agent include anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methylstyrene, α-methylstyrene dimer Styrenes such as dibenzylideneacetone, cinnamyl alcohol, cinnamylaldehyde and other benzylidenyl groups; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; 2,3-dimethyl-2-butene Olefins such as 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene;
A chain transfer agent can be used individually by 1 type or in combination of 2 or more types. When a chain transfer agent is used, the amount used can be, for example, about 0.01 to 1 part by weight with respect to 100 parts by weight of the monomer component. The technique disclosed here can be preferably implemented even in an embodiment in which no chain transfer agent is used.

In some preferred embodiments of the peeling method disclosed herein, the pressure-sensitive adhesive sheet has an A layer formed from a water-dispersed pressure-sensitive adhesive composition. A typical example of the water-dispersed pressure-sensitive adhesive composition is an emulsion-type pressure-sensitive adhesive composition. The emulsion-type pressure-sensitive adhesive composition typically contains a polymer of monomer components and additives that are used as necessary.

The emulsion polymerization of the monomer component is usually performed in the presence of an emulsifier. The emulsifier for emulsion polymerization is not particularly limited, and known anionic emulsifiers, nonionic emulsifiers, and the like can be used. An emulsifier can be used individually by 1 type or in combination of 2 or more types.

Non-limiting examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene sodium lauryl sulfate, polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkyl phenyl ether ammonium sulfate, polyoxy Examples thereof include sodium ethylene alkylphenyl ether sulfate and sodium polyoxyethylene alkylsulfosuccinate. Non-limiting examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like. An emulsifier having a reactive functional group (reactive emulsifier) may be used. Examples of the reactive emulsifier include a radical polymerizable emulsifier having a structure in which a radical polymerizable functional group such as a propenyl group or an allyl ether group is introduced into the anionic emulsifier or the nonionic emulsifier described above.

The amount of the emulsifier used in the emulsion polymerization may be, for example, 0.2 parts by weight or more, 0.5 parts by weight or more, or 1.0 parts by weight or more with respect to 100 parts by weight of the monomer component. It may be 5 parts by weight or more. In some embodiments, the amount of emulsifier used is usually 100 parts by weight of the monomer component from the viewpoint of improving the water-resistant adhesive strength N1, reducing the water-resistant adhesive strength reduction rate, or improving the transparency of the pressure-sensitive adhesive layer. The amount is suitably 10 parts by weight or less, preferably 5 parts by weight or less, and may be 3 parts by weight or less. In addition, the emulsifier used here for emulsion polymerization can function also as a water affinity agent of A layer.

According to emulsion polymerization, a polymerization reaction liquid in the form of an emulsion in which a polymer of monomer components is dispersed in water is obtained. The water-dispersed pressure-sensitive adhesive composition used for forming the A layer can be preferably produced using the polymerization reaction solution.

In some embodiments, the pressure-sensitive adhesive sheet may have a layer A formed from a solvent-based pressure-sensitive adhesive composition. The solvent-type pressure-sensitive adhesive composition typically contains a solution polymer of monomer components and additives used as necessary. The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; Halogenated alkanes such as dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one kind of solvent or a mixed solvent of two or more kinds can be used. According to solution polymerization, a polymerization reaction liquid in a form in which a polymer of monomer components is dissolved in a polymerization solvent is obtained. The solvent-type pressure-sensitive adhesive composition used for forming the A layer can be preferably produced using the polymerization reaction solution.

In some embodiments, the pressure-sensitive adhesive sheet may have an A layer formed from an active energy ray-curable pressure-sensitive adhesive composition. Here, the “active energy ray” in the present specification refers to an energy ray having an energy that can cause a chemical reaction such as a polymerization reaction, a crosslinking reaction, and an initiator decomposition. Examples of active energy rays here include light such as ultraviolet rays, visible rays, and infrared rays, and radiation such as α rays, β rays, γ rays, electron beams, neutron rays, and X rays. A preferred example of the active energy ray-curable pressure-sensitive adhesive composition is a photocurable pressure-sensitive adhesive composition. The photocurable pressure-sensitive adhesive composition has an advantage that even a thick pressure-sensitive adhesive layer can be easily formed. Among these, an ultraviolet curable pressure-sensitive adhesive composition is preferable.

The photocurable pressure-sensitive adhesive composition typically contains at least a part of the monomer components of the composition (may be part of the monomer type or part of the quantity). In the form of a polymer. The polymerization method for forming the polymer is not particularly limited, and various conventionally known polymerization methods can be appropriately employed. For example, thermal polymerization such as solution polymerization, emulsion polymerization and bulk polymerization (typically performed in the presence of a thermal polymerization initiator); photopolymerization performed by irradiation with light such as ultraviolet rays (typically It is carried out in the presence of a photopolymerization initiator.); Radiation polymerization carried out by irradiation with radiation such as β-rays and γ-rays; Of these, photopolymerization is preferred.

The photocurable pressure-sensitive adhesive composition according to a preferred embodiment includes a partially polymerized monomer component. Such a partial polymer is typically a mixture of a polymer derived from a monomer component and an unreacted monomer, and preferably exhibits a syrup shape (viscous liquid). Hereinafter, such a partially polymerized product may be referred to as “monomer syrup” or simply “syrup”. The polymerization method used when the monomer component is partially polymerized is not particularly limited, and various polymerization methods as described above can be appropriately selected and used. From the viewpoints of efficiency and simplicity, a photopolymerization method can be preferably employed. According to the photopolymerization, the polymerization conversion rate (monomer conversion) of the monomer component can be easily controlled by the polymerization conditions such as the light irradiation amount (light quantity).

The polymerization conversion rate of the monomer mixture in the partial polymer is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, and preferably about 60% by weight or less. From the viewpoint of ease of preparation of the pressure-sensitive adhesive composition containing the partial polymer, coating properties, and the like, the polymerization conversion rate is usually suitably about 50% by weight or less, and about 40% by weight or less (eg, about 35%). % By weight or less) is preferred. The lower limit of the polymerization conversion is not particularly limited, but is typically about 1% by weight or more, and usually about 5% by weight or more is appropriate.

The pressure-sensitive adhesive composition containing a partially polymerized monomer component is obtained by, for example, partially polymerizing a monomer mixture containing the total amount of monomer components used for preparing the pressure-sensitive adhesive composition by an appropriate polymerization method (for example, photopolymerization method). Can be obtained. In addition, the pressure-sensitive adhesive composition containing the partial polymerization product of the monomer component includes a partial polymer or a complete polymerization product of the monomer mixture including a part of the monomer components used for the preparation of the pressure-sensitive adhesive composition, and the remaining monomer. The mixture with a component or its partial polymer may be sufficient. In the present specification, the “completely polymerized product” means that the polymerization conversion rate is more than 95% by weight.

The pressure-sensitive adhesive composition containing the partial polymer may contain other components (for example, a photopolymerization initiator, a polyfunctional monomer, a cross-linking agent, a water affinity agent, etc.) that are used as necessary. The method of blending such other components is not particularly limited, and for example, it may be previously contained in the monomer mixture or added to the partial polymer.

(Water affinity agent)
In the peeling method disclosed herein, in the pressure-sensitive adhesive sheet, the A layer constituting one surface of the pressure-sensitive adhesive layer preferably contains a water affinity agent in addition to the polymerization reaction product of the monomer component. For example, a pressure-sensitive adhesive sheet including an A-layer containing an acrylic polymer as the polymerization reaction product and further containing a water affinity agent is preferable.

As the water-affinity agent, various materials that can be used to enhance the water affinity of the surface of the A layer by being contained in the A layer can be appropriately selected and used. By increasing the water affinity of the A layer, an aqueous liquid such as water can be more quickly adapted to the surface of the A layer. Thereby, for example, at the time of measuring the water peeling force N2, the first drop of water can be spread over the surface of the layer A following the movement of the peeling front of the pressure-sensitive adhesive sheet from the adherend. The water peeling force N2 can be effectively reduced. In the pressure sensitive adhesive sheet peeling method including moving the peeling front while allowing an aqueous liquid such as water to enter the interface between the pressure sensitive adhesive sheet and the adherend by the same action, the peelability of the pressure sensitive adhesive sheet from the adherend is increased. Can be increased.

As the water-affinity agent, known anionic surfactants, nonionic surfactants, cationic surfactants, water-soluble plasticizers, water-soluble polymers, and the like can be used. A water affinity agent can be used individually or in combination of 2 or more types.

As the water-soluble plasticizer, various polyols (preferably polyether polyols) can be used. Specific examples include polyethylene glycol, polypropylene glycol, polyoxypropylene sorbitol ether, polyglycerin and the like. These can be used individually by 1 type or in combination of 2 or more types.
Examples of the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylic acid.

Examples of the anionic surfactant include alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate; alkyl sulfates such as sodium lauryl sulfate and ammonium lauryl sulfate; polyether amines such as polyoxyethylene lauryl amine and polyoxyethylene stearyl amine; Polyether sulfates such as sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate; polyoxyethylene stearyl ether phosphate, polyoxyethylene lauryl ether phosphate, etc. Polyoxyethylene alkyl ether phosphate; of the above polyoxyethylene alkyl ether phosphate Thorium salts, polyoxyethylene alkyl ether phosphoric acid ester salts such as potassium salts; polyoxyethylene alkyl sodium sulfosuccinate, and the like.

Nonionic surfactants include, for example, polyoxyalkylene ethers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene glyceryl ether, polyoxypropylene glyceryl ether, polyoxyethylene bisphenol A ether; polyoxyethylene Examples include fatty acid esters and polyoxyethylene / polyoxypropylene block polymers.

In some embodiments, for example, an anionic surfactant having at least one of a —POH group, a —COH group, and a —SOH group may be preferably used. Of these, surfactants having —POH groups are preferred. Such surfactants typically contain a phosphate ester structure, such as monoesters of phosphoric acid (ROP (= O) (OH) ₂ ; where R is a monovalent organic group), diesters ((RO) ₂ P (═O) OH; where R is the same or different monovalent organic group), a mixture containing both a monoester and a diester, and the like. A preferred example of the surfactant having a —POH group is polyoxyethylene alkyl ether phosphate. The number of carbon atoms of the alkyl group in the polyoxyethylene alkyl ether phosphate ester may be, for example, 6 to 20, 8 to 20, 10 to 20, 12 to 20, or 14 to 20.

The content of the water affinity agent in the A layer is not particularly limited. In some embodiments, the content of the water affinity agent may be, for example, 0.2 parts by weight or more per 100 parts by weight of the monomer component constituting the polymer contained in the layer A, from the viewpoint of obtaining a higher effect. It may be 0.5 parts by weight or more, 1.0 part by weight or more, or 1.5 parts by weight or more. Further, from the viewpoint of suppressing excessive water diffusion into the bulk of the layer A, in some embodiments, the amount of the water-affinity agent is suitably 10 parts by weight or less with respect to 100 parts by weight of the monomer component. Yes, preferably 5 parts by weight or less, and may be 3 parts by weight or less. It is preferable that the content of the water-affinity agent is not too large from the viewpoint of improving the water-resistant adhesive strength N1, reducing the water-resistant adhesive strength decreasing rate, or improving the transparency of the adhesive layer.

(Silane coupling agent)
In some embodiments, the A layer can contain a silane coupling agent. According to the A layer containing a silane coupling agent, a pressure-sensitive adhesive sheet having a low water-resistant adhesive strength reduction rate and a high water peeling adhesive strength reduction rate can be suitably realized.

Examples of the silane coupling agent include silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; Amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane; (Meth) acrylic group-containing silane coupling agents such as propyltrimethoxysilane; acetoacetyl group-containing trimethoxysilane, 3-acryloxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane; 3-isocyanatopropyltrie Kishishiran like isocyanate group-containing silane coupling agents such as. Among these, preferred examples include 3-glycidoxypropyltrimethoxysilane and acetoacetyl group-containing trimethoxysilane.

The amount of the silane coupling agent used can be set so as to obtain a desired use effect, and is not particularly limited. In some embodiments, the amount of the silane coupling agent used may be, for example, 0.001 part by weight or more with respect to 100 parts by weight of the monomer component constituting the polymer contained in the layer A. From the viewpoint of obtaining, it may be 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.015 parts by weight or more. Further, from the viewpoint of improving adhesion to the adherend, in some embodiments, the amount of the silane coupling agent used is, for example, 3 parts by weight or less with respect to 100 parts by weight of the monomer component constituting the A layer. It may be 1 part by weight or less, or 0.5 part by weight or less.

In the embodiment in which the monomer component includes an alkoxysilyl group-containing monomer, the alkoxysilyl group-containing monomer may be used as a part or all of the silane coupling agent included in the A layer.

(Crosslinking agent)
A layer can be made to contain a crosslinking agent as needed. The kind in particular of a crosslinking agent is not restrict | limited, For example, the crosslinking agent suitably selected from the conventionally well-known crosslinking agent can be used. Specific examples of the crosslinking agent include isocyanate crosslinking agent, epoxy crosslinking agent, oxazoline crosslinking agent, aziridine crosslinking agent, carbodiimide crosslinking agent, melamine crosslinking agent, urea crosslinking agent, metal alkoxide crosslinking agent, metal Examples include chelate-based crosslinking agents, metal salt-based crosslinking agents, hydrazine-based crosslinking agents, and amine-based crosslinking agents. These can be used individually by 1 type or in combination of 2 or more types.

As an example of the isocyanate-based crosslinking agent, a bifunctional or higher polyfunctional isocyanate compound can be used. For example, aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris (p-isocyanatophenyl) thiophosphate, diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatics such as hexamethylene diisocyanate Isocyanate; and the like. Commercially available products include trimethylolpropane / tolylene diisocyanate trimer adduct (trade name “Coronate L” manufactured by Tosoh Corporation), trimethylolpropane / hexamethylene diisocyanate trimer adduct (trade name “manufactured by Tosoh Corporation, trade name“ Coronate HL "), isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name" Coronate HX "), and the like. In the water-dispersed pressure-sensitive adhesive composition, it is preferable to use an isocyanate crosslinking agent that can be dissolved or dispersed in water. For example, a water-soluble, water-dispersible or self-emulsifying type isocyanate crosslinking agent can be preferably employed. A so-called blocked isocyanate type isocyanate crosslinking agent in which an isocyanate group is blocked can be preferably used.

As the epoxy-based crosslinking agent, those having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. Specific examples of the epoxy crosslinking agent include N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, 1,6-hexane. Examples include diol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy crosslinking agents include trade names “TETRAD-X” and “TETRAD-C” manufactured by Mitsubishi Gas Chemical Company, “Epicron CR-5L” manufactured by DIC, and products manufactured by Nagase ChemteX Corporation. Examples include the name “Denacol EX-512” and the trade name “TEPIC-G” manufactured by Nissan Chemical Industries, Ltd. In the water-dispersed pressure-sensitive adhesive composition, it is preferable to use an epoxy crosslinking agent that can be dissolved or dispersed in water.

As the oxazoline-based crosslinking agent, one having one or more oxazoline groups in one molecule can be used without any particular limitation. In the water-dispersed pressure-sensitive adhesive composition, it is preferable to use an oxazoline-based crosslinking agent that can be dissolved or dispersed in water.
Examples of the aziridine-based crosslinking agent include trimethylolpropane tris [3- (1-aziridinyl) propionate], trimethylolpropane tris [3- (1- (2-methyl) aziridinylpropionate)] and the like. It is done.
As the carbodiimide-based crosslinking agent, a low molecular compound or a high molecular compound having two or more carbodiimide groups can be used. In the water-dispersed pressure-sensitive adhesive composition, it is preferable to use a carbodiimide-based crosslinking agent that can be dissolved or dispersed in water.

In some embodiments, a peroxide may be used as a crosslinking agent. Examples of peroxides include di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, and t-butylperoxyneodecanoate. , T-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxyisobutyrate, di Examples thereof include benzoyl peroxide. Among these, as the peroxide having particularly excellent crosslinking reaction efficiency, di (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, dibenzoyl peroxide and the like can be mentioned. In addition, when a peroxide is used as the polymerization initiator, it is possible to use the remaining peroxide for the crosslinking reaction without being used for the polymerization reaction. In that case, the remaining amount of peroxide is quantified, and when the proportion of peroxide is less than a predetermined amount, it is preferable to add the peroxide so that it becomes a predetermined amount as necessary. Peroxide can be quantified by the method described in Japanese Patent No. 4971517.

The content of the crosslinking agent (when two or more crosslinking agents are included, the total amount thereof) is not particularly limited. From the viewpoint of realizing a pressure-sensitive adhesive that exhibits a good balance of adhesive properties such as adhesive strength and cohesive strength, the content of the crosslinking agent is usually about 5 weights per 100 parts by weight of the monomer component contained in the pressure-sensitive adhesive composition. The amount is suitably 0.001 to 5 parts by weight, more preferably about 0.001 to 4 parts by weight, and more preferably about 0.001 to 3 parts by weight. Is more preferable. Or the adhesive composition which does not contain the above crosslinking agents may be sufficient.

(Tackifying resin)
The A layer may contain a tackifying resin. Examples of the tackifying resin include petroleum-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, ketone-based tackifying resins, and the like including rosin-based tackifying resins and rosin derivative tackifying resins. . These can be used individually by 1 type or in combination of 2 or more types.

Examples of the rosin-based tackifying resin include a rosin such as gum rosin, wood rosin, tall oil rosin, a stabilized rosin (for example, a stabilized rosin obtained by disproportionating or hydrogenating the rosin), a polymerized rosin (for example, Rosin multimers, typically dimers), modified rosins (eg, unsaturated acid-modified rosin modified with an unsaturated acid such as maleic acid, fumaric acid, (meth) acrylic acid, etc.) Can be mentioned.
Examples of the rosin derivative tackifier resin include esterified products of the rosin-based tackifier resin (for example, rosin esters such as stabilized rosin ester and polymerized rosin ester), and phenol-modified products of the rosin-based resin (phenol-modified rosin). ) And esterified products thereof (phenol-modified rosin ester) and the like.
Examples of the petroleum-based tackifier resins include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and hydrides thereof.
Examples of the terpene tackifying resin include α-pinene resin, β-pinene resin, aromatic modified terpene resin, terpene phenol resin, and the like.
Examples of the ketone-based tackifying resin include ketone-based resins obtained by condensation of ketones (for example, aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone) and formaldehyde. And the like.

In some embodiments, as the tackifier resin, one or more selected from rosin-based tackifier resins, rosin derivative tackifier resins, and terpene phenol resins can be preferably used. Of these, rosin derivative tackifying resins are preferred, and preferred examples include rosin esters such as stabilized rosin esters and polymerized rosin esters.

In the water-dispersed pressure-sensitive adhesive composition, it is preferable to use a water-dispersed tackifying resin in a form in which the above-mentioned tackifying resin is dispersed in an aqueous solvent. For example, a pressure-sensitive adhesive composition containing these components in a desired ratio can be easily prepared by mixing an aqueous dispersion of an acrylic polymer and a water-dispersed tackifying resin. In some embodiments, as the water-dispersed tackifying resin, a resin substantially free of at least an aromatic hydrocarbon solvent can be preferably used from the viewpoint of consideration for environmental hygiene. It is more preferable to use a water-dispersed tackifying resin that does not substantially contain an aromatic hydrocarbon solvent or other organic solvent.

Examples of commercially available water-dispersed tackifying resins containing rosin esters include “Super Ester E-720”, “Super Ester E-730-55”, and “Super Ester E-” manufactured by Arakawa Chemical Co., Ltd. 865NT ”, trade names“ Hari Star SK-90D ”,“ Harri Star SK-70D ”,“ Harri Star SK-70E ”,“ Neotor 115E ”manufactured by Harima Kasei Co., Ltd., and the like. Commercially available terpene phenol resins (which may be in the form of water-dispersed terpene phenol resins) include trade names “Tamanol E-100”, “Tamanol E-200”, and “Tamanol” manufactured by Arakawa Chemical Industries, Ltd. E-200NT "and the like.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of suppressing a decrease in cohesive force of the pressure-sensitive adhesive layer, usually a tackifying resin having a softening point of 80 ° C. or higher can be preferably used. The softening point of the tackifying resin may be 90 ° C. or higher, 100 ° C. or higher, 110 ° C. or higher, or 120 ° C. or higher. A tackifying resin having a softening point of 130 ° C or higher or 140 ° C or higher may be used. Further, from the viewpoint of transparency and adhesion to an adherend, a tackifier resin having a softening point of 200 ° C. or lower or 180 ° C. or lower can be preferably used. In addition, as a softening point of tackifying resin here, the nominal value described in literature, a catalog, etc. is employable. When there is no nominal value, the softening point of the tackifier resin can be measured based on the softening point test method (ring ball method) defined in JIS K5902 or JIS K2207.

The amount of the tackifying resin used is usually suitably 1 part by weight or more with respect to 100 parts by weight of the monomer component constituting the polymer contained in the A layer from the viewpoint of suitably exhibiting the use effect. Yes, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or more. In addition, from the viewpoint of achieving a good balance between adhesion to the adherend and cohesion, the amount of the tackifier resin used relative to 100 parts by weight of the monomer component may be, for example, 70 parts by weight or less, or 50 parts by weight or less. 40 parts by weight or less. Or A layer which does not contain tackifying resin substantially may be sufficient.

In some embodiments of the peeling method disclosed herein, the pressure-sensitive adhesive sheet can further improve water resistance reliability by performing a treatment for increasing the water peeling force at a desired timing. Although the adhesive sheet which shows such a property can be implement | achieved in the structure in which A layer contains tackifying resin, for example, it is not limited to this structure. The process for increasing the water peeling force can be, for example, a process of applying a temperature higher than the room temperature range after the pressure-sensitive adhesive sheet is attached to the adherend. The temperature to be applied is not particularly limited, and can be selected in consideration of workability, economy, convenience, heat resistance of the pressure-sensitive adhesive sheet and the adherend, and the like. The said temperature may be 45 degreeC or more, for example, and 55 degreeC or more may be sufficient as it. Moreover, the said temperature may be less than 150 degreeC, for example, 120 degrees C or less, 100 degrees C or less, and 80 degrees C or less may be sufficient. The time for applying the temperature is not particularly limited, and may be, for example, 1 hour or longer, 3 hours or longer, or 1 day or longer. Alternatively, the above temperature may be applied for a longer period as long as no significant thermal deterioration occurs in the pressure-sensitive adhesive sheet or adherend. In some embodiments, from the viewpoint of improving processing efficiency, the time for applying the temperature may be, for example, within 14 days, or may be within 7 days. The above temperature may be applied at once, or may be applied in a plurality of times.

The water peeling force N3 of the pressure-sensitive adhesive sheet after the treatment for increasing the water peeling force may be, for example, twice or more than the water peeling force N2 measured by the method described above for the pressure-sensitive adhesive sheet, and may be 5 times The above may be sufficient, 10 times or more may be sufficient, 20 times or more may be sufficient, and 30 times or more may be sufficient. The water peeling force N3 may be, for example, 2.0 N / 10 mm or more, 3.0 N / 10 mm or more, or 4.0 N / 10 mm or more. The measurement of the water peeling force N3 is performed in the same manner as the measurement of the water peeling force N2 described above except that the evaluation sample taken out from the autoclave is subjected to a process for increasing the water peeling force.

The pressure-sensitive adhesive composition used for forming the A layer may contain an acid or a base (ammonia water or the like) used for the purpose of adjusting the pH, if necessary. Other optional components that can be contained in the composition include viscosity modifiers (eg, thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, and anti-aging agents. Examples of various additives that are common in the field of pressure-sensitive adhesive compositions. About such various additives, conventionally well-known things can be used by a conventional method, and since it does not characterize this invention in particular, detailed description is abbreviate | omitted.

(2) B layer The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet to be peeled off by the peeling method disclosed herein is on the back side of the layer A in addition to the layer A constituting at least the surface of the pressure-sensitive adhesive layer. It may further include a disposed B layer. As described above, according to the configuration including the A layer and the B layer, for example, the B layer provides the bulk properties of the pressure-sensitive adhesive layer (for example, water resistance, agglomeration property, heat resistance, etc. while giving good water peelability to the A layer. Etc.) can be adjusted. Therefore, according to the pressure-sensitive adhesive layer comprising the A layer and the B layer, it is easy to obtain a pressure-sensitive adhesive sheet having good water peelability and excellent water resistance reliability. For example, an adhesive sheet having a low water-resistant adhesive strength reduction rate and a high water peeling adhesive strength reduction rate can be suitably realized. In addition, for example, a pressure-sensitive adhesive sheet that achieves both high adhesiveness and good water peelability at a high level can be suitably realized.

The B layer may be disposed in direct contact with the back surface of the A layer, or may be disposed through another layer between the back surface of the A layer. The other layer (hereinafter also referred to as an intermediate layer) is typically a non-adhesive layer, for example, a plastic film, a foam sheet, a woven fabric or a woven fabric similar to a support described later, Paper, metal foil, etc. can be used. From the viewpoint of flexibility of the pressure-sensitive adhesive sheet and followability to the surface shape of the adherend, in some embodiments, the A layer and the B layer are in direct contact with each other (that is, not via an intermediate layer). An adhesive layer can be preferably employed.

The B layer is, for example, a known acrylic adhesive, rubber adhesive, silicone adhesive, polyester adhesive, urethane adhesive, polyether adhesive, polyamide adhesive, fluorine adhesive, and the like. It may be a pressure-sensitive adhesive layer composed of one or two or more pressure-sensitive adhesives selected from various pressure-sensitive adhesives. From the viewpoints of transparency, weather resistance, and the like, in some embodiments, an acrylic pressure-sensitive adhesive can be preferably employed as the constituent material of the B layer. The acrylic pressure-sensitive adhesive constituting the B layer can be selected from those exemplified as the acrylic pressure-sensitive adhesive that can be used for the A layer so that desired characteristics are exhibited in combination with the A layer. The B layer may have a single layer structure composed of one layer, or may have a multilayer structure including two or more layers having different compositions.

In some embodiments, the monomer component constituting the polymer (eg, acrylic polymer) contained in layer B is a C _1-20 alkyl (meth) acrylate in a proportion of 40% by weight or more of the total monomer component. Esters may be included. The proportion of the C _1-20 (meth) acrylic acid alkyl ester in the entire monomer component of the B layer may be, for example, 98% by weight or less, and may be 95% by weight or less from the viewpoint of improving the cohesiveness of the B layer. It may be 85% by weight or less, 70% by weight or less, or 60% by weight or less.
The monomer component constituting the B layer may contain a copolymerizable monomer together with the (meth) acrylic acid alkyl ester. The copolymerizable monomer can be appropriately selected from those exemplified as the copolymerizable monomer that can be used in the A layer. The amount of the copolymerizable monomer used may be, for example, 5% by weight or more, 15% by weight or more, 30% by weight or more, or 40% by weight or more of the entire monomer component constituting the B layer.

In some embodiments, the proportion of the carboxy group-containing monomer in the monomer component constituting the B layer may be, for example, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. A carboxy group-containing monomer may not be substantially used as the monomer component constituting the B layer. Here, substantially not using a carboxy group-containing monomer means that at least intentionally no carboxy group-containing monomer is used. The pressure-sensitive adhesive sheet having the B layer having such a composition is preferable because it tends to be highly reliable in water resistance.

As one preferred example of the pressure-sensitive adhesive sheet comprising the A layer and the B layer, one of the gel fraction of the B layer is higher than the gel fraction of the A layer, and the swelling degree of the B layer is lower than the swelling degree of the A layer. Or an adhesive sheet provided with the adhesive layer which satisfy | fills both is mentioned. According to such a configuration, it is easy to obtain an adhesive sheet having a low water-resistant adhesive strength reduction rate and a high water peeling adhesive strength reduction rate.

In some embodiments, the B layer may be a layer formed from a photocurable pressure-sensitive adhesive composition or a solvent-type pressure-sensitive adhesive composition. According to the B layer formed from such a composition, a pressure-sensitive adhesive sheet with good water resistance can be easily obtained. For example, a combination of a layer A formed from a water-dispersed pressure-sensitive adhesive composition and a layer B formed from a photocurable pressure-sensitive adhesive composition, or a layer A and a solvent formed from a water-dispersed pressure-sensitive adhesive composition In combination with the B layer formed from the mold pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet having a low water-resistant adhesive strength reduction rate and a high water-peeling adhesive strength reduction rate can be suitably realized. In some embodiments, from the viewpoint of improving water resistance, the B layer substantially not containing a water-affinity agent can be preferably employed.

<Support>
The pressure-sensitive adhesive sheet peeled off by the peeling method disclosed herein may be in the form of a pressure-sensitive adhesive sheet with a support including a support bonded to the other back surface of the pressure-sensitive adhesive layer. The material of the support is not particularly limited, and can be appropriately selected according to the purpose of use or usage of the pressure-sensitive adhesive sheet. Non-limiting examples of supports that can be used include polyolefin films based on polyolefins such as polypropylene and ethylene-propylene copolymers, polyester films based on polyesters such as polyethylene terephthalate and polybutylene terephthalate, Plastic films such as polyvinyl chloride films mainly composed of polyvinyl chloride; foam sheets made of foams such as polyurethane foam, polyethylene foam, polychloroprene foam; various fibrous materials (natural fibers such as hemp and cotton, Synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) Woven and non-woven fabrics of single or mixed spinning, etc .; paper such as Japanese paper, fine paper, kraft paper, crepe paper; aluminum foil, Metal foil such as copper foil; It is. A support having a structure in which these are combined may be used. Examples of such a composite structure support include a support having a structure in which a metal foil and the plastic film are laminated, a plastic sheet reinforced with inorganic fibers such as glass cloth, and the like.

As the support, various kinds of films (hereinafter also referred to as support films) can be preferably used. The support film may be a porous film such as a foam film or a non-woven sheet, or may be a non-porous film, and a porous layer and a non-porous layer are laminated. It may be a structured film. In some embodiments, as the support film, a film including a resin film that can be independently maintained in shape (self-supporting or independent) as a base film can be preferably used. Here, the “resin film” means a resin film having a non-porous structure and typically containing substantially no bubbles (voidless). Therefore, the said resin film is the concept distinguished from a foam film and a nonwoven fabric. The resin film may have a single-layer structure or a multilayer structure having two or more layers (for example, a three-layer structure).

Examples of the resin material constituting the resin film include polycycloolefin derived from a monomer having an aliphatic ring structure such as polyester, polyolefin, norbornene structure, polyamide (PA) such as nylon 6, nylon 66, and partially aromatic polyamide. , Polyimide (PI), polyamide imide (PAI), polyether ether ketone (PEEK), polyether sulfone (PES), polyphenylene sulfide (PPS), polycarbonate (PC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polystyrene, polyvinyl chloride, polyvinylidene chloride, polytetrafluoroethylene (PTFE) and other fluororesins, polymethyl methacrylate and other acrylic resins, diacetylcellulose and triacetylcellulose It cellulosic polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene-based polymer, the use of a resin such as an epoxy polymer. The resin film may be formed using a resin material containing one kind of such resin alone, or may be formed using a resin material in which two or more kinds are blended. Good. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched).

Preferable examples of the resin material constituting the resin film include polyester resins, PPS resins, and polyolefin resins. Here, the polyester-based resin refers to a resin containing polyester in a proportion exceeding 50% by weight. Similarly, a PPS resin refers to a resin containing PPS in a proportion exceeding 50% by weight, and a polyolefin-based resin refers to a resin containing a polyolefin in a proportion exceeding 50% by weight.

As the polyester resin, typically, a polyester resin containing as a main component a polyester obtained by polycondensation of a dicarboxylic acid and a diol is used. Specific examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate, and the like.

As the polyolefin resin, one kind of polyolefin can be used alone, or two or more kinds of polyolefins can be used in combination. The polyolefin may be, for example, an α-olefin homopolymer, a copolymer of two or more α-olefins, a copolymer of one or more α-olefins with another vinyl monomer, and the like. Specific examples include polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers such as ethylene propylene rubber (EPR), ethylene-propylene- Examples include butene copolymers, ethylene-butene copolymers, ethylene-vinyl alcohol copolymers, ethylene-ethyl acrylate copolymers, and the like. Both low density (LD) polyolefins and high density (HD) polyolefins can be used. Examples of polyolefin resin films include unstretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, and medium density polyethylene (MDPE). Examples thereof include a film, a high-density polyethylene (HDPE) film, a polyethylene (PE) film obtained by blending two or more kinds of polyethylene (PE), and a PP / PE blend film obtained by blending polypropylene (PP) and polyethylene (PE).

Specific examples of the resin film that can be preferably used as the support include PET film, PEN film, PPS film, PEEK film, CPP film, and OPP film. Preferable examples in terms of strength include PET film, PEN film, PPS film, and PEEK film. A PET film is a preferred example from the viewpoints of availability, dimensional stability, optical properties, and the like.

In the resin film, known additives such as a light stabilizer, an antioxidant, an antistatic agent, a colorant (dye, pigment, etc.), a filler, a slip agent, and an antiblocking agent are blended as necessary. Can do. The compounding quantity of an additive is not specifically limited, According to the use etc. of an adhesive sheet, it can set suitably.

The method for producing the resin film is not particularly limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately employed.

The support may be substantially composed of such a resin film. Alternatively, the support may include an auxiliary layer in addition to the resin film. Examples of the auxiliary layer include an optical property adjusting layer (for example, a colored layer or an antireflection layer), a printed layer or a laminate layer for imparting a desired appearance to a support or an adhesive sheet, an antistatic layer, an undercoat layer. And a surface treatment layer such as a release layer. Further, the support member may be an optical member described later.

The thickness of the support is not particularly limited, and can be selected according to the purpose of use or usage of the pressure-sensitive adhesive sheet. The thickness of the support may be, for example, 1000 μm or less, 500 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, or 5 μm or less. When the thickness of the support becomes small, the flexibility of the pressure-sensitive adhesive sheet and the followability to the surface shape of the adherend tend to be improved. Further, from the viewpoint of handleability, workability, etc., the thickness of the support may be, for example, 2 μm or more, and may be more than 5 μm or more than 10 μm. In some embodiments, the thickness of the support may be, for example, 20 μm or more, 35 μm or more, or 55 μm or more.

On the surface of the support that is to be bonded to the adhesive layer, corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, primer coating (primer) application, antistatic treatment, as necessary. A conventionally well-known surface treatment, such as these, may be given. Such a surface treatment may be a treatment for improving the adhesion between the support and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the support. The composition of the primer is not particularly limited and can be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, but is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm.

On the surface of the support opposite to the side to be bonded to the pressure-sensitive adhesive layer (hereinafter also referred to as the back surface), if necessary, such as peeling treatment, adhesion or tackiness improving treatment, antistatic treatment, etc. A conventionally known surface treatment may be applied. For example, the rewinding force of the pressure-sensitive adhesive sheet wound in a roll shape can be reduced by surface-treating the back surface of the support with a release treatment agent. As the release treatment agent, silicone release treatment agents, long-chain alkyl release treatment agents, olefin release treatment agents, fluorine release treatment agents, fatty acid amide release treatment agents, molybdenum sulfide, silica powder, and the like can be used. .

<Adhesive sheet>
The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet may be a cured layer of the pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer can be formed by applying (for example, applying) the pressure-sensitive adhesive composition to an appropriate surface and then appropriately performing a curing treatment. When performing 2 or more types of hardening processes (drying, bridge | crosslinking, superposition | polymerization, etc.), these can be performed simultaneously or over multiple steps. In an adhesive composition using a partially polymerized monomer component (acrylic polymer syrup), a final copolymerization reaction is typically performed as the curing treatment. That is, the partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, if it is a photocurable adhesive composition, light irradiation is implemented. If necessary, curing treatment such as cross-linking and drying may be performed. For example, when it is necessary to dry with a photocurable adhesive composition, it is good to perform photocuring after drying. In the pressure-sensitive adhesive composition using a completely polymerized product, typically, as the curing treatment, treatments such as drying (heat drying) and crosslinking are performed as necessary. The pressure-sensitive adhesive layer having a multilayer structure of two or more layers can be prepared by bonding together a pressure-sensitive adhesive layer formed in advance. Alternatively, the second pressure-sensitive adhesive layer may be formed by applying a pressure-sensitive adhesive composition onto a previously formed first pressure-sensitive adhesive layer and curing the pressure-sensitive adhesive composition.

Application of the pressure-sensitive adhesive composition can be carried out using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater and the like. In the pressure-sensitive adhesive sheet having a support, a direct method of directly forming the pressure-sensitive adhesive layer by directly applying the pressure-sensitive adhesive composition to the support may be used as a method for providing the pressure-sensitive adhesive layer on the support. You may use the transfer method which transcribe | transfers the adhesive layer formed on the surface to a support body.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be, for example, about 3 μm to 1000 μm. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 5 μm or more, may be 10 μm or more, or may be 20 μm or more from the viewpoint of increasing the water resistance reliability by closely attaching the pressure-sensitive adhesive layer to the adherend. 30 μm or more, 50 μm or more, more than 50 μm, 70 μm or more, 100 μm or more, or 120 μm or more. Further, from the viewpoint of preventing generation of adhesive residue due to cohesive failure of the pressure-sensitive adhesive layer, in some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 500 μm or less, 300 μm or less, or 200 μm or less. 170 μm or less may be used. The technique disclosed herein can be preferably applied to a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer has a thickness of 130 μm or less, 90 μm or less, 60 μm or less, or 40 μm or less. In addition, in the adhesive layer which consists of A layers, the thickness of an adhesive layer means the thickness of A layer.

When the pressure-sensitive adhesive layer is thick, it is generally difficult to achieve both water peelability and water resistance reliability. From such a viewpoint, in a mode in which the thickness of the pressure-sensitive adhesive layer is, for example, more than 50 μm, a configuration in which the pressure-sensitive adhesive layer includes an A layer and a B layer can be preferably employed. According to the pressure-sensitive adhesive layer having such a configuration, even if the pressure-sensitive adhesive layer becomes thick, it is easy to obtain a pressure-sensitive adhesive sheet having both a high level of water peelability and water resistance reliability.

In the embodiment in which the pressure-sensitive adhesive layer includes the A layer and the B layer, the thickness of the A layer may be, for example, 1 μm or more, 2 μm or more, 4 μm or more, 5 μm or more, or 10 μm or more, It may be 15 μm or more. Further, the thickness of the A layer may be, for example, 50 μm or less, 45 μm or less, 35 μm or less, or 25 μm or less. In particular, in the aspect including the A layer formed from the water-dispersed pressure-sensitive adhesive composition part and the aspect in which the A layer includes the water-affinity agent, the thickness of the A layer is not too large. It is preferable from the viewpoints of improvement and improvement of transparency of the pressure-sensitive adhesive layer.

In the embodiment in which the pressure-sensitive adhesive layer includes the A layer and the B layer, the thickness of the B layer may be, for example, 5 μm or more, or 10 μm or more. From the viewpoint of better exhibiting the effect of providing the B layer on the back side of the A layer, in some embodiments, the thickness of the B layer may be, for example, 20 μm or more, 30 μm or more, or 50 μm or more. It may be 70 μm or more, or 100 μm or more.

In the embodiment in which the pressure-sensitive adhesive layer includes the A layer and the B layer, the thickness of the A layer in the total thickness of the pressure-sensitive adhesive layer may be, for example, 90% or less, and is usually preferably 70% or less. 50% or less, 30% or less, 20% or less, or 15% or less. Moreover, from the viewpoint of easy formation of the A layer and water peelability of the pressure-sensitive adhesive sheet, in some embodiments, the thickness of the A layer in the total thickness of the pressure-sensitive adhesive layer may be, for example, 3% or more, It may be 5% or more, 7% or more, or 10% or more.

<Peeling method>
According to this specification, the peeling method of the adhesive sheet affixed on the polarizing plate which is a to-be-adhered body is provided. In the peeling method, the aqueous liquid follows the movement of the peeling front in the state where the aqueous liquid exists at the interface between the adherend and the pressure sensitive adhesive sheet at the peeling front of the pressure sensitive adhesive sheet from the adherend. The water peeling process of peeling the said adhesive sheet from the said to-be-adhered body is advanced, making the approach to the said interface progress. According to the water peeling step, the pressure-sensitive adhesive sheet can be peeled from the polarizing plate as an adherend by effectively using the aqueous liquid. As the aqueous liquid, water or a mixed solvent containing water as a main component and containing a small amount of additives as required can be used. As a solvent other than water constituting the mixed solvent, a lower alcohol (for example, ethyl alcohol) or a lower ketone (for example, acetone) that can be uniformly mixed with water can be used. A known surfactant or the like can be used as the additive. From the viewpoint of avoiding contamination of the adherend, in some embodiments, an aqueous liquid substantially free of additives may be preferably used. From the viewpoint of environmental hygiene, it is particularly preferable to use water as the aqueous liquid. The water is not particularly limited, and for example, distilled water, ion-exchanged water, tap water, or the like can be used in consideration of purity and availability required depending on the application.

In some embodiments, the peeling method includes supplying an aqueous liquid onto the adherend in the vicinity of the outer edge of the pressure-sensitive adhesive sheet attached to the adherend, for example, similarly to the measurement of the water peeling force N2. After the liquid has entered the interface between the pressure-sensitive adhesive sheet and the adherend from the outer edge of the pressure-sensitive adhesive sheet, the aqueous liquid is supplied onto the adherend without starting to supply new water. This is preferably performed in a mode in which the peeling of the pressure-sensitive adhesive sheet proceeds. In the middle of the water stripping step, if the water entering the interface between the pressure-sensitive adhesive sheet and the adherend follows the movement of the stripping front is exhausted in the middle, intermittently after the start of the water stripping step or Additional water may be continuously supplied. For example, when the adherend has water absorption, or when aqueous liquid tends to remain on the adherend surface or adhesive surface after peeling, an embodiment in which water is additionally supplied after the start of the water peeling step is preferably employed. obtain.

The amount of the aqueous liquid supplied before the start of peeling is not particularly limited as long as the aqueous liquid can be introduced into the interface between the pressure-sensitive adhesive sheet and the adherend from the outside of the adhesive sheet sticking range. The amount of the aqueous liquid may be, for example, 5 μl or more, usually 10 μl or more, and may be 20 μl or more. Moreover, there is no restriction | limiting in particular about the upper limit of the quantity of the said aqueous liquid. In some embodiments, from the viewpoint of improving workability, the amount of the aqueous liquid may be, for example, 10 ml or less, 5 ml or less, 1 ml or less, 0.5 ml or less, 0.1 ml or less. It may be 0.05 ml or less. By reducing the amount of the aqueous liquid, the operation of removing the aqueous liquid by drying, wiping, or the like after the pressure-sensitive adhesive sheet is peeled off can be omitted or simplified.

The operation of causing the aqueous liquid to enter the interface between the pressure-sensitive adhesive sheet and the adherend from the outer edge of the pressure-sensitive adhesive sheet at the start of peeling is performed by, for example, inserting a tip of a jig such as a cutter knife or a needle into the interface at the outer edge of the pressure-sensitive adhesive sheet. Inserting, scratching and lifting the outer edge of the adhesive sheet with scissors or nails, etc., sticking a strong adhesive tape or sucker to the back surface near the outer edge of the adhesive sheet and lifting the end of the adhesive sheet, etc. It can be carried out. Thus, by forcing the aqueous liquid to enter the interface from the outer edge of the pressure-sensitive adhesive sheet, it is possible to efficiently form a state in which the water-based liquid exists at the interface between the adherend and the pressure-sensitive adhesive sheet. In addition, it is preferable to achieve both good water releasability after an operation for forcibly entering an aqueous liquid into the interface and creating a trigger for separation, and high water resistance reliability when such operation is not performed. Can do.

The pressure-sensitive adhesive sheet to be peeled off by the peeling method includes a pressure-sensitive adhesive layer, and among the pressure-sensitive adhesive layers, at least the layer A constituting the surface on the polarizing plate side is preferably formed of a pressure-sensitive adhesive containing a water affinity agent. . The pressure-sensitive adhesive sheet is preferably, for example, any pressure-sensitive adhesive sheet disclosed herein. Therefore, the said peeling method is suitable as a peeling method of one of the adhesive sheets disclosed here.

The water stripping process according to some embodiments can be preferably performed in a mode in which the stripping front is moved at a speed of 10 mm / min or more. Moving the peeling front at a speed of 10 mm / min or more corresponds to peeling the pressure-sensitive adhesive sheet at a tensile speed of 20 mm / min or more under the condition of a peeling angle of 180 degrees, for example. The speed at which the peeling front is moved may be, for example, 50 mm / min or more, 150 mm / min or more, 300 mm / min or more, or 500 mm / min or more. According to the peeling method disclosed herein, the pressure-sensitive adhesive sheet is peeled off from the adherend while allowing the aqueous liquid to enter the interface. Water releasability can be exhibited. The upper limit of the speed at which the peeling front is moved is not particularly limited. The speed at which the peeling front is moved can be, for example, 1000 mm / min or less.

The peeling method disclosed here is carried out, for example, in such a manner that the peeling area of the pressure-sensitive adhesive sheet per 10 μl volume of the aqueous liquid (for example, water) used in the method is, for example, 50 cm ² or more, preferably 100 cm ² or more. be able to.

Hereinafter, some examples relating to the present invention will be described. However, the present invention is not intended to be limited to the examples shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

<Example 1>
(Preparation of adhesive composition U-1)
Monomer mixture comprising 2-ethylhexyl acrylate (2EHA), N-vinyl-2-pyrrolidone (NVP), 2-hydroxyethyl acrylate (HEA) and isobornyl acrylate (IBXA) in a weight ratio of 80/35/5/30 100 parts in a four-necked flask together with 0.05 part by trade name: Irgacure 651 (manufactured by Ciba Specialty Chemicals) and 0.05 part by trade name: Irgacure 184 (manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator The monomer mixture was partially polymerized by irradiating it with ultraviolet rays until the viscosity (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reached about 15 Pa · s under a nitrogen atmosphere. A monomer syrup containing the product was prepared.
To 100 parts of this monomer syrup, 0.13 part of 1,6-hexanediol diacrylate (HDDA) and 0.33 part of a photopolymerization initiator (trade name: Irgacure 651, manufactured by Ciba Specialty Chemicals) were added uniformly. By mixing, an ultraviolet curable pressure-sensitive adhesive composition U-1 was prepared.

(Preparation of adhesive composition E-1)
85 parts of 2EHA, 13 parts of methyl acrylate (MA), 1.2 parts of AA, 0.8 part of MAA, 0.02 part of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-503), as a chain transfer agent An aqueous emulsion of a monomer mixture (monomer emulsion) by mixing 0.048 parts of t-dodecyl mercaptan and 2.0 parts of an emulsifier (Latemul E-118B, manufactured by Kao Corporation) in 100 parts of ion-exchanged water and emulsifying. Was prepared.
The monomer emulsion was placed in a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer, and a stirring device, and stirred at room temperature for 1 hour or more while introducing nitrogen gas. Next, the temperature of the system was raised to 60 ° C., and 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (VA-057 manufactured by Wako Pure Chemical Industries, Ltd.) was used as a polymerization initiator. ) 0.1 part was added and reacted at 60 ° C. for 6 hours to obtain an aqueous dispersion of an acrylic polymer.
After cooling the system to room temperature, 30 parts of a tackifying resin emulsion (Superester E-865NT, manufactured by Arakawa Chemical Co., Ltd., having a softening point of 160 ° C. per 100 parts of the solid content of the acrylic polymer aqueous dispersion). Polymerized rosin ester aqueous dispersion) was added. Furthermore, by adjusting the pH to about 7.5 and the viscosity to about 9 Pa · s by using 10% aqueous ammonia as a pH adjusting agent and polyacrylic acid (an aqueous solution having a nonvolatile content of 36%) as a thickening agent, an emulsion Type pressure-sensitive adhesive composition E-1 was prepared.

(Preparation of adhesive sheet)
The pressure-sensitive adhesive composition U-1 was applied to a 38 μm-thick release film R1 (Mitsubishi Resin Co., Ltd., MRF # 38) with one side of the polyester film being the release surface, and one side of the polyester film was the release surface. An adhesive layer B1 having a thickness of 130 μm was formed by covering a release film R2 having a thickness of 38 μm (Mitsubishi Resin Co., Ltd., MRE # 38), blocking the air, and irradiating it with ultraviolet rays. Next, the peeling film R2 covering the pressure-sensitive adhesive layer B1 is peeled off, and a corona-treated polyethylene terephthalate (PET) film having a thickness of 75 μm is bonded to the PET film (support), the pressure-sensitive adhesive layer B1, and the peeling film R1. Obtained a laminated sheet laminated in this order.
The pressure-sensitive adhesive composition E-1 was applied to a release film R1 (Mitsubishi Resin Co., Ltd., MRF # 38) and dried at 120 ° C. for 3 minutes to form a pressure-sensitive adhesive layer A1 having a thickness of 20 μm. The release film R1 covering the pressure-sensitive adhesive layer B1 of the laminated sheet is peeled off, and the pressure-sensitive adhesive layer A1 is bonded thereto, whereby the pressure-sensitive adhesive layer B1 and the pressure-sensitive adhesive layer A1 are laminated in direct contact with each other. A pressure-sensitive adhesive sheet S1 having a structure in which a PET film (support) was bonded to the surface of the pressure-sensitive adhesive layer on the B1 layer side was obtained. The surface on the A1 layer side of this pressure-sensitive adhesive sheet is protected by the release film R1 used for forming the pressure-sensitive adhesive layer A1.

(Preparation of adherend)
The solution of the ultraviolet curable resin monomer or oligomer mainly composed of urethane acrylate dissolved in butyl acetate (made by DIC Corporation, trade name “Unidic 17-806”, solid content concentration 80%) was added to the solid solution. 5 parts of photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., product name “IRGACURE906”) and leveling agent (manufactured by DIC Corporation, product name “GRANDIC PC4100”) are added by 0.03 parts per 100 parts per minute. did. Thereafter, butyl acetate was added to the above solution to adjust the solid content concentration to 75%, and cyclopentanone (hereinafter referred to as “CPN”) was further added to adjust the solid content concentration to 50%. Thus, a hard coat layer forming material for forming a hard coat layer was produced. When the total amount of the hard coat layer forming material was 1, the content ratio (mass ratio) of the good solvent (CPN) in the hard coat layer forming material was 0.33. The ultraviolet curable resin monomer or oligomer contained in the hard coat layer forming material is a mixture of urethane acrylates having various molecular weights. When the total amount of the ultraviolet curable resin monomer or oligomer is 1, the low molecular weight component ( Here, the content ratio (mass ratio) of an ultraviolet curable resin monomer or oligomer having a molecular weight of 800 or less was 0.482.
The hard coat layer forming material is coated on a transparent TAC film (manufactured by Fuji Film Co., Ltd., product name “TD80UL”, thickness 80 μm, refractive index 1.49) using a die coater to form a coating film. did. The coating thickness of the hard coat layer forming material was 13.8 μm. That is, the hard coat layer-forming material was applied such that the thickness of the cured coating film (hard coat layer) was 7.5 μm, assuming that the solvent did not penetrate into the film. The coating film was dried at 80 ° C. for 2 minutes. Thereafter, the resin monomer was polymerized by irradiating the coating film with ultraviolet rays having an integrated light quantity of 300 mJ / cm ² using a high-pressure mercury lamp. In this way, a hard coat layer was produced on the TAC film. The intrinsic refractive index of this hard coat layer was 1.53.
Next, the antireflection layer forming material shown below was uniformly applied to the entire surface of the hard coat layer using a die coater. The coating film was heated at 90 ° C. for 2 minutes and irradiated with ultraviolet rays to be cured, thereby forming an antireflection layer having a thickness of 0.1 μm on the entire surface of the hard coat layer. The refractive index of this antireflection layer was 1.38. The material for forming the antireflection layer is a low refractive material (trade name “JUA204” manufactured by JSR Corporation, solid content concentration 9.5%), methyl isobutyl ketone (MIBK) and t-butyl alcohol (TBA). A mixed solvent (MIBK: TBA = 50: 50) was added and diluted to adjust the solid content concentration to 2.0%. The low refractive material is an ultraviolet curable resin containing a fluorine compound having an ethylenically unsaturated group, an acrylate, a polymerization initiator, and about 50% of hollow nanosilica with respect to an active ingredient.
Thus, a TAC film F1 having a surface on which a hard coat layer and an antireflection layer were laminated in this order was obtained. The adherend in Example 1 was obtained by subjecting the surface (surface to be bonded) of this TAC film F1 to corona treatment under the above-described conditions.

(Performance evaluation)
Using the adherend, the normal adhesive force N0, the water-resistant adhesive force N1, and the water peeling force N2 on the A layer side of the pressure-sensitive adhesive sheet S1 were measured by the methods described above. The time from the corona treatment of the surface to be pasted to the pasting of the adhesive sheet S1 was within 30 minutes. From the obtained measured value, the water-resistant adhesive strength reduction rate and the water peeling adhesive strength reduction rate were calculated. The results are shown in Table 1.

<Example 2>
In this example, the TAC film F1 was used as an adherend without performing corona treatment on the surface (surface to be bonded). The other points were the same as in Example 1, and the normal adhesive strength N0, water-resistant adhesive strength N1, and water peeling strength N2 on the A layer side of the adhesive sheet S1 were measured, and the water-resistant adhesive strength reduction rate and the water peeling adhesive strength reduction rate were determined. Calculated. The results are shown in Table 1.

As shown in Table 1, in Example 1 using the corona-treated adherend, the pressure-sensitive adhesive sheet S1 having a low water-resistant adhesive strength reduction rate was easily removed from the adherend using a small amount of water. It was possible to peel off. On the other hand, in Example 2 using the adherend not subjected to corona treatment, the water peeling adhesive force reduction rate of the pressure-sensitive adhesive sheet S1 was low, and peeling with water was difficult.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1, 2 Adhesive sheet 10 Adhesive layer (A layer)
10A One surface (adhesive surface, polarizing plate side surface)
10B Other surface 20 Support body 20A First surface 20B Second surface (back surface)
30 Release liner 50 Adhesive sheet with release liner 70 Member (polarizing plate)
110 Adhesive layer 110A One surface (adhesive surface, polarizing plate surface)
112 A layer 114 B layer 200 Member with adhesive sheet

Claims (4)

It is a method of peeling the pressure-sensitive adhesive sheet attached to the polarizing plate,
The pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer includes an A layer constituting the surface of at least the polarizing plate side of the pressure-sensitive adhesive layer,
The polarizing plate has a corona treatment or a plasma treatment on the surface on which the adhesive sheet is attached,
In the state where the aqueous liquid is present at the interface between the polarizing plate and the pressure-sensitive adhesive sheet at the peeling front of the pressure-sensitive adhesive sheet from the polarizing plate, the aqueous liquid enters the interface following the movement of the peeling front. A pressure-sensitive adhesive sheet peeling method comprising a water peeling step of peeling the pressure-sensitive adhesive sheet from the polarizing plate while proceeding. The pressure sensitive adhesive sheet peeling method according to claim 1, wherein in the water peeling step, the peeling front is moved at a speed of 10 mm / min or more. The pressure-sensitive adhesive sheet peeling method according to claim 1 or 2, wherein the layer A contains a water affinity agent. The pressure-sensitive adhesive sheet peeling method according to any one of claims 1 to 3, wherein the A layer is water-insoluble and water-swellable.

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