KR102434120B1 - Adhesive sheet - Google Patents

Abstract

Provided is a pressure-sensitive adhesive sheet in which there is little decrease in adhesive strength even in contact with oil, and in which the protrusion of the pressure-sensitive adhesive is suppressed. The adhesive sheet provided by this invention is equipped with the adhesive layer comprised with the adhesive which uses an acrylic polymer as a base polymer. The pressure-sensitive adhesive layer has a surface free energy γ of less than 40 mJ/m 2 and an oleic acid permeation amount of 1.5 g or more and 5.0 g or less per 1 g.

Description

Adhesive sheet {ADHESIVE SHEET}

The present invention relates to an adhesive sheet.

This application claims the priority based on the JP Patent application 2016-014180 for which it applied on January 28, 2016, The whole content of the application is taken in as a reference in this specification.

In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive, hereinafter the same) exhibits a state of a soft solid (viscoelastic body) in a temperature range around room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of these properties, the pressure-sensitive adhesive is, for example, in the form of a pressure-sensitive adhesive sheet provided with a base material having an pressure-sensitive adhesive layer on a supporting base material, and is widely used for bonding, fixing, and protection of members in mobile phones and other portable devices. is being used Patent documents 1 and 2 are mentioned as a technical document regarding the double-sided adhesive tape used for component fixing of a portable electronic device.

Japanese Patent Application Laid-Open No. 2009-215355 Japanese Patent Application Laid-Open No. 2013-100485

Since a mobile device is portable and used, the oil contained in secretions, such as sebum and hand grime, cosmetics, hair dressing, moisturizing cream, sunscreen, chemical products, or food, etc. adheres easily. In particular, since a touch panel type portable device, which has recently been widely spread, has a display unit/input unit that functions as an input unit as well as a display unit, and is operated by a user directly touching the surface of the display unit/input unit with a fingertip, oil is There are many opportunities to be attached. In addition, some so-called wearable devices are used while being in contact with the skin, and in such a use mode, there are many opportunities to be exposed to oils such as sebum or chemicals applied to the skin. When such oil comes into contact with the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet fixing the member, problems such as a decrease in adhesive strength and protrusion of the pressure-sensitive adhesive may occur.

In this regard, for example, in Patent Document 1, even if oil permeates, the pressure-sensitive adhesive is hardly softened and swelled, and when used for fixing parts, the double-sided pressure-sensitive adhesive sheet from which the pressure-sensitive adhesive does not protrude is examined. However, in patent document 1, suppressing the fall of the adhesive force resulting from the contact of an oil was not considered.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet in which there is little decrease in adhesive strength even if it comes into contact with oil, and in which the protrusion of the pressure-sensitive adhesive is suppressed.

According to this specification, the adhesive sheet provided with the adhesive layer comprised with the adhesive which uses an acrylic polymer as a base polymer is provided. The surface free energy γ of the pressure-sensitive adhesive layer is less than 40 mJ/m 2 . Further, the pressure-sensitive adhesive layer has an oleic acid permeation amount of 1.5 g or more and 5.0 g or less per 1 g.

Since the adhesive sheet of such a structure has the low surface energy (gamma) of an adhesive layer, there exists a tendency for the said adhesive layer to show favorable wettability with respect to a to-be-adhered body. Thereby, the pressure-sensitive adhesive layer and the adherend can be properly brought into close contact, and the penetration of oil from the outer edge of the pressure-sensitive adhesive sheet to the interface (adhesive interface) between the pressure-sensitive adhesive layer and the adherend can be suppressed. In addition, the pressure-sensitive adhesive layer has the ability to maintain 1.5 g or more of oleic acid per 1 g in the measurement of the amount of oleic acid permeation to be described later. By exhibiting such oil retention property, even if oil enters the adhesive interface from the outer edge of the pressure-sensitive adhesive sheet, the adhesive interface can be maintained in a low oil content state by absorbing (permeating) the oil into the layer of the pressure-sensitive adhesive layer. In this way, by suppressing the penetration of oil from the outer edge of the pressure-sensitive adhesive sheet to the adhesive interface, and making it easy to absorb the penetrating oil from the adhesive interface into the layer (bulk) of the pressure-sensitive adhesive layer, the adhesive force due to the contact of oil decrease can be effectively suppressed. In addition, by limiting the amount of oleic acid permeated per 1 g of the pressure-sensitive adhesive layer to 5.0 g or less, it is possible to prevent the pressure-sensitive adhesive layer from absorbing too much oil to prevent the pressure-sensitive adhesive from protruding.

In the adhesive sheet which concerns on one preferable aspect, the gel fraction of the said adhesive layer is 30 % or more and 70 % or less. By making the gel fraction into the above range, the pressure-sensitive adhesive layer in which the oleic acid permeation amount is in an appropriate range tends to be realized.

In another preferable aspect, the said adhesive layer is formed using the adhesive composition containing the said acrylic polymer and a crosslinking agent. This form has the advantage that the oleic acid penetration amount (or even the gel fraction) can be easily adjusted. As said crosslinking agent, the crosslinking agent containing at least an isocyanate type crosslinking agent can be used preferably.

The pressure-sensitive adhesive sheet disclosed herein may be preferably implemented in a form in which the pressure-sensitive adhesive layer includes a tackifying resin. By containing a tackifying resin in an adhesive layer, the adhesiveness of the adhesive layer with respect to a to-be-adhered body can be improved, and penetration of oil from the outer edge of an adhesive sheet to an adhesive interface can be suppressed better. Moreover, by selecting 50 weight% or more of the said tackifying resin from tackifying resins other than a rosin type tackifying resin, it exists in the tendency for an oleic acid penetration amount and surface free energy gamma to become easy to implement|achieve realization of the adhesive layer in appropriate ranges.

In one aspect of the pressure-sensitive adhesive sheet disclosed herein, the monomer component constituting the acrylic polymer has ₇ or more and 10 or less carbon atoms (hereinafter, the range of the number of carbon atoms may be expressed as “C _7-10 ”). It contains more than 50 weight% of the alkyl (meth)acrylate which has an alkyl group of the ester terminal at the ester terminal. According to the technology disclosed herein, even in the configuration in which the acrylic polymer having a monomer composition containing a large amount of C _7-10 alkyl (meth) acrylate is used as the base polymer of the pressure-sensitive adhesive layer, the reduction in adhesive strength due to oil and A pressure-sensitive adhesive sheet in which protrusion is suitably suppressed can be realized.

The pressure-sensitive adhesive sheet disclosed herein may be preferably implemented in a form in which the monomer component constituting the acrylic polymer contains more than 5% by weight of the carboxyl group-containing monomer. According to the acrylic polymer of such a monomer composition, oil content, such as an oleic acid, can be maintained favorably in the layer of an adhesive layer. Thereby, the oil content present at the bonding interface can be reduced, and a decrease in the adhesive force due to the oil content can be effectively suppressed. In the acrylic polymer having a monomer composition containing a large amount of C _7-10 alkyl (meth) acrylate, it is particularly effective to increase the content of the carboxyl group-containing monomer in the monomer component.

The pressure-sensitive adhesive sheet disclosed herein may be preferably implemented in a form in which the pressure-sensitive adhesive layer has a thickness of 25 μm or less. When the thickness of the pressure-sensitive adhesive layer is a relatively small pressure-sensitive adhesive sheet, since the amount of the pressure-sensitive adhesive per area of the pressure-sensitive adhesive sheet is small, it is particularly effective to set the oleic acid permeation amount of the pressure-sensitive adhesive layer to a predetermined value or more.

The pressure-sensitive adhesive sheet according to a preferred embodiment is configured as a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer on one surface and the other surface of a base material. Since the double-sided pressure-sensitive adhesive sheet is used by attaching one surface and the other surface of the pressure-sensitive adhesive sheet to an adherend, respectively, oil easily penetrates into the bonding interface with these adherends. Therefore, it is particularly meaningful to apply the technique disclosed herein to suppress a decrease in adhesive strength due to the oil content.

The pressure-sensitive adhesive sheet disclosed herein can be preferably used for, for example, a use for fixing a member in a portable device. As described above, since a mobile device has many opportunities to come into contact with oil, it is particularly meaningful to apply the technology disclosed herein to suppress a decrease in adhesive force due to oil and protrusion of the pressure-sensitive adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically one structural example of an adhesive sheet.
It is sectional drawing which shows typically the other structural example of an adhesive sheet.
It is sectional drawing which shows typically the other structural example of an adhesive sheet.
4 is a cross-sectional view schematically showing another structural example of the pressure-sensitive adhesive sheet.
5 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.
6 is a cross-sectional view schematically showing another configuration example of the pressure-sensitive adhesive sheet.

Hereinafter, preferred embodiments of the present invention will be described. In addition, matters necessary for the implementation of the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings related to the implementation of the invention described in the present specification and technical common sense at the time of filing. The present invention can be implemented based on the content disclosed in this specification and common technical knowledge in this field. In addition, in the following drawings, the same code|symbol may be attached|subjected to the member and site|part which exhibits the same action, and description may be given, and overlapping description may be abbreviate|omitted or simplified. In addition, embodiment described in drawing is schematic in order to demonstrate this invention clearly, and does not necessarily show exactly the size and scale of the adhesive sheet of this invention actually provided as a product.

As used herein, the term "adhesive" refers to a material that exhibits a state of a soft solid (viscoelastic body) in a temperature range around room temperature and has a property of easily adhering to an adherend by pressure. As defined in "CA Dahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) P.143", the adhesive referred to herein is generally complex tensile modulus E ^* (1 Hz) <10 ⁷ dyne/ It may be a material having a property satisfying cm 2 (typically, a material having the property at 25° C.).

In this specification, the term "(meth)acryloyl" refers to acryloyl and methacryloyl comprehensively. Similarly, "(meth)acrylate" refers to acrylate and methacrylate, and "(meth)acryl" refers to acryl and methacryl inclusively, respectively.

In this specification, the term "acrylic polymer" refers to a polymer comprising a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, the monomer which has at least 1 (meth)acryloyl group in 1 molecule is also called "acrylic monomer". The acryl-type polymer in this specification is defined as a polymer containing the monomeric unit derived from an acryl-type monomer.

The adhesive sheet disclosed here is equipped with the adhesive layer comprised with the adhesive which uses an acrylic polymer as a base polymer. Here, the base polymer refers to a main component of a rubbery polymer (a polymer exhibiting rubber elasticity in a temperature region near room temperature) contained in the pressure-sensitive adhesive layer. In addition, in this specification, a "main component" refers to a component contained in excess of 50 weight%, unless it mentions specially. The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet provided with a base material having the pressure-sensitive adhesive layer on one or both surfaces of a base material (support), and an inorganic pressure-sensitive adhesive sheet such as a form in which the pressure-sensitive adhesive layer is held by a release liner. may be The concept of the pressure-sensitive adhesive sheet referred to herein may include those referred to as pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films, and the like. In addition, roll shape may be sufficient as the adhesive sheet disclosed here, and sheet shape may be sufficient as it. Alternatively, the pressure-sensitive adhesive sheet in the form processed into more various shapes may be used.

The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIGS. 1 to 6 . Among these, FIG. 1 and FIG. 2 are structural examples of the adhesive sheet provided with the base material of a double-sided adhesive type. In the pressure-sensitive adhesive sheet 1 shown in FIG. 1 , pressure-sensitive adhesive layers 21 and 22 are respectively formed on each surface (both non-peelable) of the base material 10, and the pressure-sensitive adhesive layer is at least the pressure-sensitive adhesive layer side. It has a structure protected by the release liners 31 and 32 which are made of , respectively. In the pressure-sensitive adhesive sheet 2 shown in Fig. 2, pressure-sensitive adhesive layers 21 and 22 are respectively formed on each surface (both non-peelable) of the base material 10, and one of the pressure-sensitive adhesive layers 21 is a peelable surface on both surfaces. It has a structure protected by the release liner 31 which is made of In this type of pressure-sensitive adhesive sheet 2, the pressure-sensitive adhesive sheet 2 is wound so that the other pressure-sensitive adhesive layer 22 is brought into contact with the back surface of the release liner 31, so that the pressure-sensitive adhesive layer 22 is also protected by the release liner 31. configuration can be done.

3 and 4 are structural examples of an inorganic double-sided adhesive sheet. In the pressure-sensitive adhesive sheet 3 shown in Fig. 3, both surfaces 21A and 21B of the pressure-sensitive adhesive layer 21 made of an inorganic material are protected by release liners 31 and 32, respectively, in which at least the pressure-sensitive adhesive layer side serves as a release surface. has a configured configuration. The pressure-sensitive adhesive sheet 4 shown in Fig. 4 has a structure in which one surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 made of an inorganic material is protected by a release liner 31 on both surfaces of which is a release surface, , when this is wound, the other surface (adhesive surface) 21B of the pressure-sensitive adhesive layer 21 is brought into contact with the back surface of the release liner 31, so that the other surface 21B is also protected by the release liner 31. it is possible to do

5 and 6 are structural examples of an adhesive sheet provided with a single-sided adhesive type substrate. In the pressure-sensitive adhesive sheet 5 shown in Fig. 5, the pressure-sensitive adhesive layer 21 is formed on one surface 10A (non-peelable) of the substrate 10, and the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is , at least the pressure-sensitive adhesive layer side has a configuration protected by a release liner 31 serving as a release surface. The pressure-sensitive adhesive sheet 6 shown in FIG. 6 has a configuration in which the pressure-sensitive adhesive layer 21 is formed on one surface 10A (non-peelable) of the base material 10 . The other surface 10B of the base material 10 is a release surface, and when the pressure-sensitive adhesive sheet 6 is wound, the pressure-sensitive adhesive layer 21 comes into contact with the other surface 10B, and the surface of the pressure-sensitive adhesive layer (adhesive surface) 21B is protected by the other surface 10B of the base material.

<Adhesive layer>

The pressure-sensitive adhesive sheet disclosed herein is characterized by a surface free energy γ of the pressure-sensitive adhesive layer of less than 40 mJ/m 2 and an oleic acid permeation amount of the pressure-sensitive adhesive layer of 1.5 g/g or more and 5.0 g/g or less.

(surface free energy γ)

The surface free energy γ of the pressure-sensitive adhesive layer is a value represented by the following formula: γ=γ ^d +γ ^p +γ ^h ; Here, γ ^d , γ ^p and γ ^h in the above formula respectively represent a dispersion component of surface free energy, a polar component, and a hydrogen bonding component. The surface free energy γ of the pressure-sensitive adhesive layer was obtained by using water, diiodomethane and 1-bromonaphthalene as a probe solution, and from the contact angle of each probe solution, the Kitazaki-Hata formula (Journal of the Japan Adhesive Association, Vol.8, No.3, 1972, pp.131-141). The measurement of the contact angle can be performed using a commercially available contact angle meter. As a contact angle meter, the product name "CA-X" by Kyowa Chemical Co., Ltd. can be used. A droplet method is used for measurement, and a contact angle is measured from the droplet shape 1500 ms after deposition. A similar method is employed in the embodiments to be described later.

When the surface free energy γ of the pressure-sensitive adhesive layer is lowered, the wettability of the pressure-sensitive adhesive layer to the adherend is improved, and the adhesiveness of the interface between the pressure-sensitive adhesive layer and the adherend (adhesive interface) tends to increase. By improving the adhesiveness of the adhesive interface in this way, the penetration of oil from the outer edge of the adhesive sheet to the adhesive interface can be suppressed.

In relation to the surface free energy of the adherend, the lower the surface free energy of the pressure-sensitive adhesive layer, the higher the wettability to the adherend tends to be. Accordingly, by lowering the surface free energy γ of the pressure-sensitive adhesive layer, the adhesion to a predetermined adherend is further improved, and favorable adhesion to the adherend made of a variety of materials is possible. From such a viewpoint, the surface free energy γ of the pressure-sensitive adhesive layer is preferably about 35 mJ/m 2 or less, and more preferably about 30 mJ/m 2 or less. In one aspect, the surface free energy gamma of an adhesive layer may be 27 mJ/m<2> or less, 25 mJ/m<2> or less may be sufficient, and also 20 mJ/m<2> or less may be sufficient as it. Although the lower limit in particular of the surface free energy gamma of an adhesive layer is not restrict|limited, Usually, it is about 7 mJ/m<2> or more, Preferably it is about 10 mJ/m<2> or more. The surface free energy γ of the pressure-sensitive adhesive layer is, for example, the composition of the monomer component constituting the acrylic polymer (the type and amount of the sub-monomer to be described later and the sub-monomer used as necessary), the type and amount of the tackifying resin, etc. Can be adjusted.

(Oleic acid penetration)

In the technique disclosed herein, the oleic acid permeation amount of the pressure-sensitive adhesive layer is measured by the following method.

[Evaluation of oleic acid permeability]

The pressure-sensitive adhesive layer to be measured is prepared in the form of a single-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer having a thickness of 20 µm on the non-peelable surface of a polyethylene terephthalate (PET) film having a thickness of about 10 µm to 100 µm (eg, 50 µm) do. For example, the said single-sided adhesive sheet can be prepared by producing the said adhesive layer in the form of an inorganic material on a suitable peeling surface, and bonding this to the non-peelable surface of the said PET film. This single-sided pressure-sensitive adhesive sheet is cut into a square having a length of 25 mm and a width of 25 mm to prepare a test piece.

On the surface of the stainless steel plate (SUS304BA plate), two marked lines intersecting at an angle of 90 degrees in the central portion of the stainless steel plate are drawn with an oil pen. In the environment of 23 degreeC and 50 %RH, the adhesive surface of the said test piece is affixed to the stainless steel plate on which the said marked line was drawn, and the measurement sample is produced. At this time, the test piece is attached and aligned so that the vertical and horizontal center line of the test piece coincides with the above-mentioned marked line.

The said measurement sample is hold|maintained in 23 degreeC, 50%RH environment for 12 hours. Next, after measuring the weight (weight before immersion) of the measurement sample, the measurement sample is immersed in an oleic acid bath, and maintained for 2 weeks in an environment of 40°C and 90%RH. Thereafter, the measurement sample is removed from the oleic acid bath, and the oleic acid adhering thereto is lightly wiped off, and the weight (weight after immersion) of the measurement sample is measured. From the obtained measured value, the following formula:

Oleic acid penetration amount = (weight after immersion - weight before immersion)/weight of adhesive before penetration;

, the oleic acid permeation amount (g/g) per 1 g of the pressure-sensitive adhesive layer is calculated. The same evaluation method is adopted also in the Example mentioned later.

The pressure-sensitive adhesive layer having an oleic acid permeation amount of 1.5 g/g or more exhibits good oil retention properties as compared with the pressure-sensitive adhesive layer having a smaller oleic acid permeation amount. As a result, even if oil enters the adhesive interface from the outer edge of the pressure-sensitive adhesive sheet, the adhesive interface can be maintained in a state with little oil content by absorbing the oil into the layer (bulk) of the pressure-sensitive adhesive layer. Thereby, the fall of the adhesive force by the oil component which exists in an adhesive interface can be suppressed effectively. In addition, by absorbing the oil that has penetrated from the outer edge of the pressure-sensitive adhesive sheet to the adhesive interface into the bulk of the pressure-sensitive adhesive layer, it is possible to suppress the phenomenon that the oil proceeds along the adhesive interface to the inner portion of the adhesion range of the pressure-sensitive adhesive sheet. That is, the penetration distance of the oil from the outer edge of the adhesive sheet can be suppressed. Thereby, it is suppressed that the influence of an oil content reaches an inner part from the outer edge of an adhesive sheet, and the overall adhesive force of an adhesive sheet can be maintained better. Moreover, when the bulk of an adhesive layer absorbs oil appropriately, as a result of the said adhesive layer being softened, peeling strength can be ensured by the strain energy of the said adhesive layer. This can also advantageously contribute to suppression of a decrease in adhesive force due to oil. In this way, by suppressing the penetration of oil from the outer edge of the pressure-sensitive adhesive sheet to the adhesive interface, and making it easy to absorb the penetrating oil from the adhesive interface into the bulk of the pressure-sensitive adhesive layer, the decrease in adhesive strength due to the contact of oil can be effectively reduced can be suppressed

The oleic acid permeation amount of the pressure-sensitive adhesive layer is preferably about 1.6 g/g or more, and more preferably about 1.8 g/g or more from the viewpoint of better exhibiting the above-described effects. The technology disclosed herein may be preferably implemented in a form in which the oleic acid permeation amount of the pressure-sensitive adhesive layer is about 2.0 g/g or more (further, about 2.5 g/g or more, for example, about 3.0 g/g or more). The upper limit of the penetration amount of oleic acid in the pressure-sensitive adhesive layer is suitably set to about 5.0 g/g or less, and about 4.5 g/g or less (e.g. For example, it is preferable to set it as about 4.0 g/g or less). In the pressure-sensitive adhesive sheet according to a preferred embodiment, the oleic acid penetration amount of the pressure-sensitive adhesive layer is, for example, about 1.6 g/g or more and about 4.5 g/g or less, more preferably about 1.8 g/g or more and about 4.5 g/g or less can The amount of oleic acid permeated in the pressure-sensitive adhesive layer is, for example, the composition of the monomer components constituting the acrylic polymer (the type and amount of the main monomer to be described later and the sub-monomer used as necessary, etc.), the molecular weight of the acrylic polymer, the type and amount of the crosslinking agent, It can adjust according to the kind, usage-amount, etc. of tackifying resin.

Evaluation of the protrusion prevention property of an adhesive can also be performed by the said oleic acid permeability evaluation. Specifically, in the oleic acid permeability evaluation, immediately after the measurement sample is taken out of the oleic acid bath, the protrusion distance (protrusion width) of the adhesive from the outer edge of the PET film is visually measured. The same evaluation method is adopted also in the Example mentioned later.

In a preferred aspect, the protrusion width of the pressure-sensitive adhesive may be less than about 1.0 mm (more preferably about 0.5 mm or less, still more preferably about 0.3 mm or less). The adhesive sheet provided with the adhesive layer which has such protrusion prevention property is suitable for the use by which bonding in a limited space is calculated|required, for example, the use which fixes a member in a portable device. The protrusion width of an adhesive is so good that it is small, and it is about 0 mm ideally.

In addition, the permeation distance of oleic acid to the pressure-sensitive adhesive sheet can be measured by the oleic acid permeability evaluation. Specifically, the measurement sample is retrieved from the oleic acid bath, the oleic acid adhering to the surrounding is lightly wiped off, and then the length in which the marked line on the stainless steel disappears from the outer edge of the PET film toward the inside is measured, and the length is the penetration distance of oleic acid. A similar measurement method is also employed in the Examples to be described later.

In a preferred embodiment, the penetration distance of the oleic acid is suitably about 0.5 mm or more, more preferably about 0.8 mm or more, and still more preferably about 1.0 mm or more. The penetration distance of the oleic acid is preferably about 7.0 mm or less, more preferably about 5.0 mm or less, and still more preferably about 4.0 mm or less (for example, about 1.0 mm or more and about 4.0 mm or less). According to the pressure-sensitive adhesive layer in which the permeation distance of oleic acid is in the above range, the preferred permeation amount of oleic acid disclosed herein tends to be suitably realized.

(Acrylic polymer)

The pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is preferably a polymer of a monomer raw material that contains alkyl (meth)acrylate as a main monomer and may further contain a sub-monomer having copolymerizability with the main monomer. Here, the main monomer refers to a component contained in an amount exceeding 50 wt% in the monomer raw material.

As an alkyl (meth)acrylate, the compound represented by following formula (1) can be used suitably, for example.

CH ₂ =C(R ¹ )COOR ² (1)

Here, R ¹ in the formula (1) is a hydrogen atom or a methyl group. In addition, R ² is a chain alkyl group having ₁ to 20 carbon atoms (hereinafter, the range of the number of carbon atoms may be expressed as “C _1-20 ”). From the viewpoint of the storage modulus of the pressure-sensitive adhesive, etc., an alkyl (meth)acrylate in which R ² is a C _1-14 chain alkyl group is preferable, and an alkyl (meth) acrylate in which R ² is a C _1-10 chain alkyl group is more preferable. and R ² is a butyl group or a 2-ethylhexyl group, particularly preferably an alkyl (meth)acrylate.

As the alkyl (meth)acrylate in which R ² is a C _1-20 chain alkyl group, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate , n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) Acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate , hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate. These alkyl (meth)acrylates can be used individually by 1 type or in combination of 2 or more type. Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

In the technique disclosed herein, the monomer component constituting the acrylic polymer contains at least one of BA and 2EHA, and the total amount of BA and 2EHA in the alkyl (meth)acrylate contained in the monomer component is 75 wt% or more ( Usually, 85 weight% or more, for example, 90 weight% or more, further 95 weight% or more) can be implemented preferably in the form which occupies. The technology disclosed herein can be implemented, for example, in a form in which the alkyl (meth)acrylate contained in the monomer component is BA alone, 2EHA alone, BA and 2EHA, and the like.

When the monomer component includes BA and 2EHA, the weight ratio of BA to 2EHA (BA/2EHA) is not particularly limited, and may be, for example, 1/99 or more and 99/1 or less. In one preferred embodiment, BA/2EHA can be 40/60 or less (eg 1/99 or more and 40/60 or less), 20/80 or less, and 10/90 or less (eg 1/99 or less). 99 or more and 10/90 or less) may be sufficient.

The technology disclosed herein can be preferably implemented in a form in which the monomer component constituting the acrylic polymer contains more than 50% by weight of C _7-10 alkyl (meth)acrylate. As described above, the acrylic polymer having C _7-10 alkyl (meth) acrylate as the main monomer has a high affinity for oil. By taking advantage of this high affinity for oil, the oil that has penetrated from the outer edge of the pressure-sensitive adhesive sheet to the adhesive interface is appropriately absorbed into the layer of the pressure-sensitive adhesive layer, thereby effectively suppressing the decrease in adhesive strength due to the contact of oil. . The proportion of C _7-10 alkyl (meth)acrylate in the monomer component may be 60% by weight or more, or 70% by weight or more (eg 80% by weight or more, and further 85% by weight or more). The upper limit of the ratio of the C _7-10 alkyl (meth) acrylate in the monomer component is not particularly limited, and may be, for example, less than 98% by weight. Usually, from the viewpoint of facilitating compatibility with other properties, it is appropriate to set the ratio of C _7-10 alkyl (meth)acrylate in the monomer component to 97% by weight or less, and 95% by weight or less (usually 95% by weight). It is preferable to set it as less than weight%, for example, 93 weight% or less). C _7-10 alkyl (meth) acrylate can be used individually by 1 type or in combination of 2 or more types. Preferable examples of C _7-10 alkyl (meth)acrylate _{include C 7-10 alkyl} acrylates such as 2EHA, isooctyl acrylate, and isononyl acrylate. Among them, 2EHA is preferable.

The technology disclosed herein may also be preferably implemented in a form in which the monomer component constituting the acrylic polymer contains more than 50% by weight of C _1-6 alkyl (meth)acrylate. Even when the acrylic polymer having C _1-6 alkyl (meth) acrylate as the main monomer is used as the base polymer, for example, the type and amount of the sub-monomer, the type and amount of the cross-linking agent, the type and amount of the tackifying resin, etc. By appropriately setting the conditions of , a pressure-sensitive adhesive layer exhibiting a suitable oleic acid permeation amount disclosed herein can be obtained. The proportion of C _1-6 alkyl (meth)acrylate in the monomer component may be 60% by weight or more, or 70% by weight or more (for example, 85% by weight or more, further 90% by weight or more). The upper limit of the ratio of C _1-6 alkyl (meth)acrylate in the monomer component is not particularly limited, and may be, for example, 99.5% by weight or less. Usually, from the viewpoint of facilitating compatibility with other properties, it is appropriate to set the ratio of the C _1-6 alkyl (meth)acrylate in the monomer component to 99% by weight or less, and 98% by weight or less (for example, For example, it is preferable to set it as 97 weight% or less). C _{1-6 alkyl} (meth)acrylate can be used alone or in combination of two or more. BA is mentioned as a suitable example of C _{1-6 alkyl} (meth)acrylate.

The sub-monomer having copolymerizability with the alkyl (meth) acrylate, which is the main monomer, may be helpful in introducing a crosslinking point to the acrylic polymer or increasing the cohesive force of the acrylic polymer. As a submonomer, the following functional group containing monomers can be used individually by 1 type or in combination of 2 or more types, for example.

Carboxylic group-containing monomers: For example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, crotonic acid, and isocrotonic acid; Ethylenically unsaturated dicarboxylic acids, such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.).

Hydroxyl group-containing monomers: for example 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate hydroxyalkyl (meth)acrylates such as; unsaturated alcohols such as vinyl alcohol and allyl alcohol; Polypropylene glycol mono(meth)acrylate.

Amide group-containing monomers: for example (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane ( Meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide.

Amino group-containing monomers: 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.

Cyano group-containing monomers: for example acrylonitrile, methacrylonitrile.

Keto group-containing monomers: for example, diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

Monomers having a nitrogen atom-containing ring: for example N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperidone Razine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine.

Alkoxysilyl group-containing monomers: for example 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3- (meth)acryloxypropylmethyldiethoxysilane.

The functional group-containing monomer may be used alone or in combination of two or more. Among the functional group-containing monomers, carboxyl group-containing monomers and hydroxyl group-containing monomers can be preferably used from the viewpoint that introduction of a crosslinking point and improvement of cohesive force can be suitably realized as described above. Suitable examples of the carboxyl group-containing monomer include acrylic acid and methacrylic acid. These can be used individually by any 1 type or in combination of 2 types. As the hydroxyl group-containing monomer, a hydroxyalkyl (meth)acrylate having a hydroxyl group at the terminal of a straight-chain alkyl group having about 2 to 4 carbon atoms, such as 2-hydroxyethyl acrylate or 4-hydroxybutyl (meth)acrylate. can be heard A hydroxyl-containing monomer can be used individually by 1 type or in combination of 2 or more type. You may use combining a carboxy group containing monomer and a hydroxyl group containing monomer.

When the monomer component constituting the acrylic polymer contains a functional group-containing monomer, the proportion of the functional group-containing monomer in the monomer component is not particularly limited. Usually, from the viewpoint of obtaining appropriate cohesiveness in the preferable oleic acid permeation amount disclosed herein, the ratio of the functional group-containing monomer is 0.1 wt% or more and 40 wt% or less (for example, 0.5 wt% or more and 30 wt% or less, usually 1 wt% or more It is preferable to set it as about weight% or more and 20 weight% or less).

When the monomer component constituting the acrylic polymer contains a carboxyl group-containing monomer, the proportion of the carboxyl group-containing monomer in the monomer component is usually 0.5% by weight or more (preferably 1% by weight or more, e.g. For example, 2 wt% or more), 20 wt% or less (preferably 18 wt% or less, for example, 15 wt% or less) is suitable.

The technology disclosed herein may be preferably implemented in a form in which the monomer component contains about 3% by weight or more (preferably about 5% by weight or more) of the carboxyl group-containing monomer. According to the acrylic polymer having such a monomer composition, the absorbed oleic acid can be satisfactorily retained in the layer (bulk) of the pressure-sensitive adhesive layer due to the interaction between the carboxyl group and oleic acid that the polymer has. Thereby, the adhesive interface can be maintained in the state with little oleic acid, and the fall of the adhesive force by permeation of oleic acid can be suppressed effectively. From such a viewpoint, the content of the carboxyl group-containing monomer in the monomer component is preferably more than approximately 5% by weight, may be approximately 7% by weight or more, may be approximately 8% by weight or more, and further may be approximately 9% by weight. % or more. Although the upper limit in particular of content of a carboxyl group-containing monomer is not restrict|limited, Usually, it is suitable to set it as about 18 weight% or less, and it is good also as about 15 weight% or less (for example, about 12 weight% or less). In an acrylic polymer having a monomer composition containing a large amount of C _7-10 alkyl (meth) acrylate ( _{eg, an acrylic polymer having C 7-10 alkyl} (meth) acrylate as a main monomer), a carboxyl group in the monomer component It is particularly effective to increase the content of the containing monomer (eg, AA).

When the monomer component constituting the acrylic polymer contains a hydroxyl group-containing monomer, the content is usually about 0.001% by weight or more and about 10% by weight or less of the monomer component (for example, about 0.01% by weight or more and about 5% by weight or less) , preferably about 0.02% by weight or more and about 2% by weight or less).

As the monomer component constituting the acrylic polymer, for the purpose of increasing the cohesive force of the acrylic polymer, other copolymerization components other than the sub-monomer described above can be used. Examples of such a copolymerization component include vinyl ester-based monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; Aromatic vinyl compounds, such as styrene, substituted styrene ((alpha)-methylstyrene etc.), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; Aryl (meth) acrylates (such as phenyl (meth) acrylate), aryloxyalkyl (meth) acrylates (such as phenoxyethyl (meth) acrylate), arylalkyl (meth) acrylates (such as For example, aromatic ring containing (meth)acrylates, such as benzyl (meth)acrylate); olefinic monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; Alkoxy group-containing monomers, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; 2 or more (for example, 3 or more) polymerizable functional groups in 1 molecule (for example, (meth)acrylo polyfunctional monomers having a diary); and the like.

The amount of such other copolymerization components may be appropriately selected depending on the purpose and use, and is not particularly limited, but is usually preferably 10% by weight or less of the monomer component. For example, when a vinyl ester-based monomer (for example, vinyl acetate) is used as the other copolymerization component, the content thereof is, for example, about 0.1% by weight or more (usually about 0.5% by weight or more) of the monomer component. Moreover, it is suitable to set it as about 20 weight% or less (usually about 10 weight% or less).

The composition of the monomer component constituting the acrylic polymer is suitably designed so that the glass transition temperature (Tg) of the acrylic polymer is about -15°C or less (eg, about -70°C or more and -15°C or less). Here, Tg of an acrylic polymer means Tg calculated|required by Fox's formula based on the composition of the said monomer component. Fox's formula is a relational expression between Tg of the copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.

1/Tg=Σ(Wi/Tgi)

In addition, in the formula of Fox, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on weight), Tgi is the monomer i alone It represents the glass transition temperature (unit: K) of a polymer.

As the glass transition temperature of the homopolymer used for the calculation of Tg, the value described in known materials is used. For example, for the monomers enumerated below, the following values are used as the glass transition temperature of the homopolymer of the monomer.

2-ethylhexyl acrylate -70℃

n-Butyl acrylate -55℃

Ethyl acrylate -22℃

Methyl acrylate 8℃

Methyl methacrylate 105°C

2-hydroxyethyl acrylate -15℃

4-hydroxybutyl acrylate -40℃

Vinyl acetate 32℃

Styrene 100℃

Acrylic acid 106℃

methacrylic acid 228℃

For glass transition temperatures of homopolymers of monomers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd ed., John Wiley & Sons, Inc., 1989) shall be used. For monomers for which a plurality of types of values are described in this document, the highest value is adopted.

For monomers for which the glass transition temperature of the homopolymer is not described in the above literature, a value obtained by the following measurement method is used.

Specifically, 100 parts by weight of the monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were put into a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux cooling tube, and , and stirred 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 reacted for 10 hours. Then, it cools to room temperature and obtains the homopolymer solution of 33 weight% of solid content concentration. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and shear strain at a frequency of 1 Hz was applied using a viscoelasticity tester (manufactured by TAA Instruments Japan, model name "ARES"). While the viscoelasticity is measured in a shear mode at a temperature range of -70°C to 150°C and a temperature increase rate of 5°C/min, the temperature corresponding to the peak top temperature of tan δ is taken as Tg of the homopolymer.

Although not particularly limited, from the viewpoint of adhesion to an adherend or a base film, the Tg of the acrylic polymer is advantageously approximately -25°C or lower, preferably approximately -35°C or lower, more preferably approximately -40°C or lower. to be. Moreover, from a viewpoint of the cohesive force of an adhesive layer, Tg of an acrylic polymer is about -75 degreeC or more normally, Preferably it is about -70 degreeC or more. The technology disclosed herein may be preferably implemented in a form in which the acrylic polymer has a Tg of about -65°C or more and about -40°C or less (eg, about -65°C or more and about -45°C or less). In one preferable aspect, Tg of an acrylic polymer may be about -65 degreeC or more and about -55 degreeC or less. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and usage ratio of the monomer used for synthesis of the polymer).

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing the acrylic polymer, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, a solution polymerization method can be preferably employed. As a monomer supply method at the time of solution polymerization, the batch input method which supplies all the monomer raw materials at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. are employable suitably. Polymerization temperature can be suitably selected according to the kind of monomer and solvent used, kind of polymerization initiator, etc., For example, it can be set as about 20 degreeC - about 170 degreeC (usually about 40 degreeC - about 140 degreeC). In a preferable aspect, polymerization temperature can be made into about 75 degreeC or less (More preferably about 65 degrees C or less, for example, about 45 degreeC - about 65 degreeC).

The solvent (polymerization solvent) used for solution polymerization can be suitably selected from conventionally well-known organic solvent. For example, aromatic compounds, such as toluene and xylene (For example, aromatic hydrocarbons); acetate esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane and methylcyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (eg, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone and acetone; Any 1 type of solvent selected from etc., or 2 or more types of mixed solvent can be used.

The initiator used for polymerization can be suitably selected from the conventionally well-known polymerization initiator according to the kind of polymerization method. For example, the 1 type(s) or 2 or more types of azo polymerization initiators, such as 2,2'- azobisisobutyronitrile (AIBN), can be used preferably. As another suitable example of a polymerization initiator, peroxide type initiators, such as benzoyl peroxide (BPO) and hydrogen peroxide, are mentioned. Examples of other polymerization initiators include persulfates such as potassium persulfate; substituted ethane-based initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; a redox initiator by a combination of a peroxide and a reducing agent; and the like. These polymerization initiators can be used individually by 1 type or in combination of 2 or more type. The usage-amount of a polymerization initiator may just be a normal usage-amount, For example, it can select from about 0.005-1 weight part with respect to 100 weight part of monomer components (usually about 0.01-1 weight part).

According to the solution polymerization, a polymerization reaction solution in which the acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the technique disclosed herein may be formed of the above polymerization reaction solution or a pressure sensitive adhesive composition containing an acrylic polymer solution obtained by performing an appropriate post-treatment on the reaction solution. As said acrylic polymer solution, what prepared the said polymerization reaction liquid to suitable viscosity (concentration) as needed can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (eg, emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used.

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and may be, for example, about 10×10 ⁴ or more and 500×10 ⁴ or less. Here, Mw means the value of standard polystyrene conversion obtained by GPC (gel permeation chromatography). As a GPC apparatus, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), Tosoh Corporation make) can be used, for example. From the viewpoint of adhesive performance and oil resistance, Mw of the acrylic polymer is approximately 30×10 ⁴ or more and 200×10 ⁴ or less (more preferably about 45×10 ⁴ or more and 150×10 ⁴ or less, for example, about 65×10 ⁴ It is preferable to exist in the range of 150x10 ⁴ or less). In one preferred embodiment, the Mw of the acrylic polymer may be about 75×10 ⁴ or more and about 140×10 ⁴ or less (eg, about 90×10 ⁴ or more and about 140×10 ⁴ or less).

(crosslinking agent)

It is preferable that the adhesive composition (preferably solvent-type adhesive composition) used for formation of an adhesive layer contains a crosslinking agent as an arbitrary component. The pressure-sensitive adhesive layer in the technique disclosed herein may contain the crosslinking agent in the form after the crosslinking reaction, in the form before the crosslinking reaction, in a partially crosslinked form, an intermediate or complex form thereof, and the like. The crosslinking agent is usually contained in the pressure-sensitive adhesive layer only in the form after the crosslinking reaction.

The type of crosslinking agent is not particularly limited, and may be appropriately selected from conventionally known crosslinking agents. As such a crosslinking agent, for example, isocyanate type crosslinking agent, epoxy type crosslinking agent, oxazoline type crosslinking agent, aziridine type crosslinking agent, melamine type crosslinking agent, carbodiimide type crosslinking agent, hydrazine type crosslinking agent, amine type crosslinking agent, peroxide type crosslinking agent, metal chelate type crosslinking agent. , a metal alkoxide-based crosslinking agent, a metal salt-based crosslinking agent, and the like. A crosslinking agent can be used individually by 1 type or in combination of 2 or more type. The type and amount of the crosslinking agent to be used can be set, for example, so as to form a pressure-sensitive adhesive layer exhibiting the preferable oleic acid permeation amount disclosed herein. As a crosslinking agent which can be used preferably in the technique disclosed herein, an isocyanate type crosslinking agent and an epoxy type crosslinking agent are illustrated.

As the isocyanate-based crosslinking agent, polyfunctional isocyanate (referring to a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. An isocyanate type crosslinking agent can be used individually by 1 type or in combination of 2 or more type.

As an example of polyfunctional isocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, etc. are mentioned.

Specific examples of the aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanate such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexa hexamethylene diisocyanate such as methylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, etc. are mentioned.

Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; Cyclohexyl diisocyanate, such as 1,2-cyclohexyl diisocyanate, 1, 3- cyclohexyl diisocyanate, and 1, 4- cyclohexyl diisocyanate; cyclopentyl diisocyanate such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; Hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'- dicyclohexylmethane diisocyanate, etc. are mentioned.

Specific examples of the aromatic polyisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2' -diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3 , 3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, Naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, etc. can be heard

As a preferable polyfunctional isocyanate, the polyfunctional isocyanate which has 3 or more isocyanate groups on average per molecule is illustrated. Such trifunctional or more isocyanate is a multimer (for example, a dimer or trimer) of a bifunctional or trifunctional or more functional isocyanate, a derivative (for example, an addition reaction product of a polyhydric alcohol and a polyfunctional isocyanate of two or more molecules), a polymer or the like. For example, a dimer or trimer of diphenylmethane diisocyanate, an isocyanurate body of hexamethylene diisocyanate (trimer adduct of isocyanurate structure), a reaction product of trimethylolpropane and tolylene diisocyanate, trimethyl Polyfunctional isocyanate, such as a reaction product of allpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate, is mentioned. As a commercial item of such polyfunctional isocyanate, the brand name "Duranate TPA-100" by the Asahi Kasei Chemicals company, the brand name "Coronate L" by the Tosoh Corporation, the copper "Coronate HL", the copper "Coronate HK", the copper " Coronate HX", the copper "Coronate 2096", etc. are mentioned.

The form using an isocyanate type crosslinking agent WHEREIN: The usage-amount is not specifically limited. The usage-amount of an isocyanate type crosslinking agent can be made into about 0.5 weight part or more and about 10 weight part or less with respect to 100 weight part of acrylic polymers, for example. From the viewpoint of obtaining the preferable oleic acid permeation amount disclosed herein, the amount of the isocyanate-based crosslinking agent to be used relative to 100 parts by weight of the acrylic polymer is usually preferably about 1 part by weight or more, and preferably about 1.5 parts by weight or more. . In addition, the usage-amount of an isocyanate type crosslinking agent with respect to 100 weight part of acrylic polymers is normally set to about 8 weight part or less suitably, and it is preferable to set it as about 5 weight part or less (for example, less than about 4 weight part).

As the epoxy-based crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without any particular limitation. An epoxy-based crosslinking agent having 3 to 5 epoxy groups in one molecule is preferable. An epoxy-type crosslinking agent can be used individually by 1 type or in combination of 2 or more type.

Although not particularly limited, as specific examples of the epoxy-based crosslinking agent, for example, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycy dilaminomethyl) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. As a commercial item of an epoxy-type crosslinking agent, the brand name "TETRAD-C" and the brand name "TETRAD-X" by Mitsubishi Gas Chemical Company, the brand name "Epiclon CR-5L" by the DIC company, the brand name "Denacol" by the Nagase Chemtex company EX-512", the Nissan Chemical Industry Co., Ltd. brand name "TEPIC-G", etc. are mentioned.

The form of using an epoxy-type crosslinking agent WHEREIN: The usage-amount is not specifically limited. The amount of the epoxy-based crosslinking agent to be used may be, for example, more than 0 parts by weight and not more than about 1 part by weight (preferably about 0.001 to 0.5 parts by weight) with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of suitably exhibiting the effect of improving the cohesive force, usually, the amount of the epoxy-based crosslinking agent to be used is preferably about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, and about 0.008 parts by weight based on 100 parts by weight of the acrylic polymer. More preferably at least part by weight. In addition, from the viewpoint of avoiding the insufficient amount of oleic acid permeation due to excessive crosslinking, the amount of the epoxy-based crosslinking agent to be used is usually about 0.2 parts by weight or less based on 100 parts by weight of the acrylic polymer, and about 0.1 parts by weight or less. It is preferable, and it is more preferable to set it as about 0.05 weight part or less.

The technique disclosed herein can be preferably implemented in the form of using at least an isocyanate-based crosslinking agent as a crosslinking agent. Examples of such a form include a form in which an isocyanate-based crosslinking agent is used alone, and a form in which an isocyanate-based crosslinking agent is used in combination with another crosslinking agent. In the adhesive sheet of the form which has an adhesive layer on at least one surface among the base films mentioned later, it is especially meaningful to use an isocyanate type crosslinking agent from a viewpoint of the anchoring property improvement with respect to the said base film.

As one suitable example of a crosslinking agent used in combination with an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent is exemplified. By using the epoxy-based crosslinking agent and the isocyanate-based crosslinking agent in combination, the preferable oleic acid permeation amount disclosed herein can be suitably realized. Moreover, the cohesive force of an adhesive layer can further be improved, ensuring the adhesiveness with respect to a base film (support base material).

In the aspect containing an epoxy type crosslinking agent and an isocyanate type crosslinking agent, the relationship between content of an epoxy type crosslinking agent and content of an isocyanate type crosslinking agent is not specifically limited. Content of an epoxy-type crosslinking agent can be made into about 1/20 or less of content of an isocyanate type crosslinking agent, for example. From the viewpoint of more suitably cohesive force and adhesion to the adherend and the base film, the content of the epoxy-based crosslinking agent is preferably about 1/30 or less of the content of the isocyanate-based crosslinking agent, and about 1/40 or less (e.g. For example, 1/50 or less) is preferable. In addition, from the viewpoint of suitably exhibiting the effect of using the epoxy-based crosslinking agent in combination with the isocyanate-based crosslinking agent, the content of the epoxy-based crosslinking agent is usually about 1/1000 or more of the content of the isocyanate-based crosslinking agent, for example, approximately It is appropriate to set it to 1/500 or more.

(Tackifying resin)

Examples of the tackifying resin include phenol-based tackifying resin, terpene-based tackifying resin, modified terpene-based tackifying resin, rosin-based tackifying resin, hydrocarbon-based tackifying resin, epoxy-based tackifying resin, polyamide-based tackifying resin, The 1 type(s) or 2 or more types chosen from well-known various tackifying resins, such as an elastomer type tackifying resin and a ketone type tackifying resin, can be used. By use of a tackifying resin, the adhesiveness of the adhesive layer with respect to a to-be-adhered body can be improved, and oil penetration into the adhesive interface from the outer edge of an adhesive sheet can be suppressed effectively. For example, the permeation distance of oleic acid in the above-described oleic acid permeability evaluation can be shortened. The type and amount of the tackifying resin to be used can be set, for example, so as to form a pressure-sensitive adhesive layer satisfying the desired oleic acid permeation amount and surface free energy γ disclosed herein.

A terpene phenol resin, a hydrogenated terpene phenol resin, an alkylphenol resin, and a rosin phenol resin are contained in the example of a phenol type tackifying resin.

A terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, and a copolymer of terpenes and phenol compounds (terpene-phenol copolymer resin), terpenes or homopolymers or copolymers thereof are phenol-modified ( It is a concept including both phenol-modified terpene resins). Preferable examples of the terpenes constituting the terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-form, l-form and d/l-form (dipentene)). A hydrogenated terpene phenol resin means the hydrogenated terpene phenol resin which has a structure which hydrogenated such terpene phenol resin. It is sometimes called hydrogenated terpene phenol resin.

Alkylphenol resin is resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. As an example of an alkylphenol resin, the thing of a novolak type and a resol type is mentioned.

The rosin phenol resin is typically a phenol-modified product of rosin or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid modified rosins and unsaturated fatty acid modified rosin esters). Examples of the rosin phenol resin include rosin phenol resins obtained by thermal polymerization by adding phenol to rosins or the various rosin derivatives described above with an acid catalyst, and the like.

Among these phenolic tackifying resins, a terpene phenol resin, a hydrogenated terpene phenol resin, and an alkylphenol resin are preferable, a terpene phenol resin and a hydrogenated terpene phenol resin are more preferable, Especially, a terpene phenol resin is preferable.

Examples of the terpene-based tackifying resin include polymers of terpenes (eg, monoterpenes) such as α-pinene, β-pinene, d-limonene, 1-limonene and dipentene. A homopolymer of 1 type of terpenes may be sufficient, and the copolymer of 2 or more types of terpenes may be sufficient. As a homopolymer of 1 type of terpenes, alpha-pinene polymer, beta-pinene polymer, dipentene polymer, etc. are mentioned.

As an example of a modified terpene resin, what modified|denatured the said terpene resin is mentioned. Specifically, a styrene-modified terpene resin, a hydrogenated terpene resin, etc. are illustrated.

Both rosin and rosin derivative resin are contained in the concept of rosin-type tackifying resin here. Examples of the rosin include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc.);

The rosin derivative resin is typically a derivative of the above rosins. The concept of rosin-based resin herein includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin and polymerized rosin). For example, rosin esters, such as unmodified rosin ester which is ester of unmodified rosin and alcohol, and modified rosin ester which is ester of modified rosin and alcohol; For example, unsaturated fatty acid modified rosins which modified|denatured rosins with unsaturated fatty acids; For example, unsaturated fatty acid modified rosin esters which modified|denatured rosin esters with unsaturated fatty acids; For example, rosin alcohols obtained by reducing the carboxyl group of rosin or the various rosin derivatives (including rosin esters, unsaturated fatty acid modified rosins and unsaturated fatty acid modified rosin esters); For example, rosins or metal salts of the various rosin derivatives; and the like. Specific examples of the rosin esters include methyl esters, triethylene glycol esters, glycerin esters, and pentaerythritol esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

Examples of the hydrocarbon-based tackifying resin include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbons and various hydrocarbon-based resins such as resin, coumarone-based resin, and coumaron-indene-based resin.

The softening point of tackifying resin is not specifically limited. From a viewpoint of a cohesive force improvement, one aspect WHEREIN: Tackifying resin whose softening point (softening temperature) is about 80 degreeC or more (preferably about 100 degreeC or more) is employable preferably. The technique disclosed herein is the form in which the tackifying resin having the softening point is more than 50% by weight (more preferably more than 70% by weight, for example, more than 90% by weight) of the total tackifying resin contained in the pressure-sensitive adhesive layer. It can be carried out preferably. For example, a phenol-based tackifying resin (terpene phenol resin, etc.) having such a softening point can be preferably used. In one preferred embodiment, a terpene phenol resin having a softening point of approximately 135°C or higher (further, approximately 140°C or higher) can be used. The upper limit in particular of the softening point of tackifying resin is not restrict|limited. From a viewpoint of the adhesiveness to a to-be-adhered body or a base film, in one aspect, the softening point can use preferably tackifying resin whose softening point is about 200 degrees C or less (more preferably, about 180 degrees C or less). In addition, the softening point of tackifying resin can be measured based on the softening point test method (round-ball method) prescribed|regulated to JISK2207.

The aspect using tackifying resin WHEREIN: Content of the said tackifying resin is not specifically limited. Content of tackifying resin can be made into about 5 weight part or more with respect to 100 weight part of acrylic polymers, for example, and is good also as about 8 weight part or more (for example, about 10 weight part or more). The technique disclosed herein can also be preferably implemented in a form in which the content of the tackifying resin relative to 100 parts by weight of the acrylic polymer is approximately 15 parts by weight or more (for example, 25 parts by weight or more). The upper limit of content of tackifying resin is not specifically limited. From the viewpoint of compatibility with the acrylic polymer and initial adhesiveness, in one embodiment, the content of the tackifying resin with respect to 100 parts by weight of the acrylic polymer is preferably approximately 70 parts by weight or less, and is approximately 55 parts by weight or less. It is preferable to use it, and it is more preferable to set it as about 45 weight part or less (for example, about 40 weight part or less).

The aspect using tackifying resin WHEREIN: It is preferable to select 50 weight% or less of the total amount of tackifying resin from tackifying resins other than rosin-type tackifying resin. It is preferable to set it as 25 weight% or less, and, as for the ratio of rosin type tackifying resin to the total amount of tackifying resin, it is more preferable to set it as 10 weight% or less (for example, less than 5 weight%).

Moreover, it is preferable to set it as less than about 10 weight part with respect to 100 weight part of acrylic polymers, and, as for the usage-amount of rosin type tackifying resin, it is more preferable to set it as less than 5 weight part. Use of rosin-type tackifying resin tends to become a factor which raises oleic acid permeation amount excessively depending on the kind and usage-amount. Further, the surface free energy γ also tends to increase with the use of the rosin-based tackifying resin. By limiting the usage-amount of the rosin-type tackifying resin with respect to 100 weight part of acrylic polymers to less than 10 weight part, it becomes easy to obtain the adhesive layer which has an oleic acid penetration amount and surface free energy (gamma) in suitable ranges. The technique disclosed herein may be preferably implemented even in a form in which the pressure-sensitive adhesive layer does not substantially include a rosin-based tackifying resin.

As a preferable aspect, the aspect in which the said tackifying resin contains 1 type(s) or 2 or more types of phenol type tackifying resin (for example, terpene phenol resin) is mentioned. A phenolic tackifying resin tends to have low affinity with respect to oil compared with rosin-type tackifying resin, for example. Therefore, by using the phenolic tackifying resin, the effect of improving the adhesion of the pressure-sensitive adhesive layer to the adherend (for example, the effect of shortening the penetration distance) can be exhibited while suppressing an excessive increase in the amount of oleic acid permeation. . The technique disclosed herein can be preferably implemented, for example, in a form in which about 25% by weight or more (more preferably, about 30% by weight or more) of the total amount of the tackifying resin is a terpenephenol resin. About 50 weight% or more of the total amount of tackifying resin may be a terpene phenol resin, and about 80 weight% or more (for example, about 90 weight% or more) may be a terpene phenol resin. A terpene phenol resin may be sufficient as substantially all (for example, about 95 weight% or more and 100 weight% or less, Furthermore, about 99 weight% or more and 100 weight% or less) of tackifying resin substantially. Content of phenolic tackifying resin (for example, terpene phenol resin) is about 5 weight part or more and about 45 weight part or less with respect to 100 weight part of acrylic polymers (For example, about 5 weight part or more and about 40 weight part or less) ) is suitable, and it is preferable to set it as about 8 parts by weight or more and about 35 parts by weight or less.

Although it does not specifically limit, As tackifying resin in the technique disclosed herein, hydroxyl value can use less than 30 mgKOH/g (for example, less than 20 mgKOH/g) tackifying resin. Hereinafter, tackifying resin whose hydroxyl value is less than 30 mgKOH/g may be called "low hydroxyl value resin." About 15 mgKOH/g or less may be sufficient as the hydroxyl value of low-hydroxyl group resin, and about 10 mgKOH/g or less may be sufficient as it. The lower limit of the hydroxyl value of the low-hydroxyl group resin is not particularly limited, and may be substantially 0 mgKOH/g. Such a low-hydroxyl group resin (for example, a terpene phenol resin) is preferably used in combination with an acrylic polymer having, for example, C _7-10 alkyl (meth) acrylate as a main monomer, and the pressure-sensitive adhesive layer to the adherend The effect of improving the adhesion (for example, the effect of shortening the penetration distance) can be exhibited favorably.

Although it does not specifically limit, As tackifying resin in the technique disclosed here, hydroxyl value can use 30 mgKOH/g or more tackifying resin. Hereinafter, tackifying resin with a hydroxyl value of 30 mgKOH/g or more may be called "resin with a high hydroxyl value." The upper limit of the hydroxyl value of high hydroxyl value resin is not specifically limited. From the viewpoint of compatibility with the acrylic polymer, etc., the hydroxyl value of the high hydroxyl group resin is usually preferably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, more preferably about 160 mgKOH/g or less, More preferably, it is about 140 mgKOH/g or less. The tackifying resin containing such a high hydroxyl group resin (for example, a terpene phenol resin) is preferably used in combination with an acrylic polymer having, for example, C _1-6 alkyl (meth) acrylate as a main monomer, , the effect of improving the adhesion of the pressure-sensitive adhesive layer to the adherend (for example, the effect of shortening the penetration distance) can be favorably exhibited.

Here, as a value of the said hydroxyl value, the value measured by the potentiometric titration method prescribed|regulated to JISK0070:1992 is employable. A specific measuring method is as showing below.

[Method for measuring hydroxyl value]

1. Reagents

(1) As the acetylation reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, pyridine is added thereto, the total amount is made 50 mL, and the reagent is sufficiently stirred. Alternatively, about 25 g (about 23.5 mL) of acetic anhydride is taken, pyridine is added thereto, the total amount is made 100 mL, and the mixture sufficiently stirred is used.

(2) A 0.5 mol/L potassium hydroxide ethanol solution is used as the measurement reagent.

(3) Others, toluene, pyridine, ethanol and distilled water are prepared.

2. Manipulation

(1) About 2 g of a sample is precisely weighed and collected in a flat-bottom flask, 5 mL of an acetylation reagent and 10 mL of pyridine are added, and an air cooling tube is installed.

(2) The flask is heated in a bath at 100° C. for 70 minutes, allowed to cool, and then 35 mL of toluene as a solvent is added from the top of the cooling tube and stirred, and then 1 mL of distilled water is added and stirred to decompose acetic anhydride. In order to complete decomposition, it is heated again in a bath for 10 minutes, and is allowed to cool.

(3) Wash the cooling tube with 5mL of ethanol and remove. Next, 50 mL of pyridine as a solvent is added and stirred.

(4) 25 mL of 0.5 mol/L potassium hydroxide ethanol solution is added using a hole pipette.

(5) Potentiometric titration is performed with 0.5 mol/L potassium hydroxide ethanol solution. Let the inflection point of the obtained titration curve be an end point.

(6) In the blank test, the above (1) to (5) are performed without a sample.

3. Calculation

A hydroxyl value is computed by the following formula|equation.

Hydroxyl value (mgKOH/g)=[(B-C)×f×28.05]/S+D

here,

B: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the blank test,

C: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used for the sample,

f: factor of 0.5 mol/L potassium hydroxide ethanol solution,

S: the weight of the sample (g),

D: acid number,

28.05: 1/2 of the molecular weight 56.11 of potassium hydroxide,

to be.

As low-hydroxyl group resin and high-hydroxyl group resin, what has a corresponding hydroxyl value among the various tackifying resins mentioned above can be used. Low hydroxyl group resin and high hydroxyl group resin can be used individually by 1 type, respectively, or in combination of 2 or more type. For example, as low-hydroxyl group resin, phenolic tackifying resin whose hydroxyl value is less than 30 mgKOH/g can be employ|adopted preferably. Moreover, for example, a hydroxyl value is 30 mgKOH/g or more phenol type tackifying resin can employ|adopt preferably as resin with a high hydroxyl value. Especially, terpene phenol resin is preferable. A terpene phenol resin is preferable since it can control the hydroxyl value arbitrarily according to the copolymerization ratio of a phenol.

(Other additives)

In the pressure-sensitive adhesive composition, in addition to each component described above, if necessary, a leveling agent, a cross-linking aid, a plasticizer, a softener, an antistatic agent, an anti-aging agent, a UV absorber, an antioxidant, a light stabilizer, etc. In the field of the pressure-sensitive adhesive, it contains a variety of general additives. it may be As for these various additives, a conventionally known additive can be used by a conventional method, and since it does not specifically characterize this invention, detailed description is abbreviate|omitted.

The pressure-sensitive adhesive layer disclosed herein may be a pressure-sensitive adhesive layer formed of a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in the form of a pressure-sensitive adhesive (adhesive layer forming component) in a solvent (aqueous solvent) containing water as a main component, and typically, a water-dispersible pressure-sensitive adhesive composition (at least a part of the pressure-sensitive adhesive is dispersed in water) composition in the form of a product) and the like. In addition, a solvent-type adhesive composition means the adhesive composition of the form containing an adhesive in an organic solvent. The technology disclosed herein may be particularly preferably implemented in a form including a pressure-sensitive adhesive layer formed of a solvent-type pressure-sensitive adhesive composition from the viewpoint of adhesive properties and the like.

The adhesive layer disclosed here can be formed by a conventionally well-known method. For example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to a non-peelable substrate and drying it can be employed. Moreover, you may employ|adopt the method (transfer method) which forms an adhesive layer on the said surface by providing and drying the adhesive composition to the surface (peelable surface) which has peelability, and transcribe|transfers the adhesive layer to a non-peelable base material. From the viewpoint of productivity, the transfer method is preferable. As said release surface, the surface of a release liner, the back surface of the base material by which the release process was carried out, etc. can be used. In addition, the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a shape, and the pressure-sensitive adhesive layer formed in a regular or random pattern such as a dot shape or a stripe shape may be used.

Application|coating of an adhesive composition can be performed using conventionally well-known coaters, such as a gravure roll coater, a die coater, and a bar coater, for example. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, curtain coating, or the like.

It is preferable to perform drying of an adhesive composition under heating from viewpoints of acceleration|stimulation of a crosslinking reaction, improvement of manufacturing efficiency, etc. Drying temperature can be made into about 40-150 degreeC, for example, and it is preferable to set it as about 60-130 degreeC normally. After drying an adhesive composition, you may perform aging further for the purpose of adjustment of the component migration in an adhesive layer, advancing of a crosslinking reaction, alleviation of distortion which may exist in a base film or an adhesive layer, etc.

The thickness in particular of an adhesive layer is not restrict|limited. From the viewpoint of avoiding the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the pressure-sensitive adhesive layer is usually preferably about 100 µm or less, preferably about 70 µm or less, more preferably about 50 µm or less, still more preferably about 30 μm or less. In the adhesive sheet which concerns on one preferable aspect, the thickness of an adhesive layer is about 25 micrometers or less (usually less than 25 micrometers, More preferably, it is about 22 micrometers or less, for example, about 20 micrometers or less). In such a pressure-sensitive adhesive sheet having a relatively small thickness of the pressure-sensitive adhesive layer, since the amount of the pressure-sensitive adhesive per area of the pressure-sensitive adhesive sheet is small, it is particularly effective to set the oleic acid permeation amount of the pressure-sensitive adhesive layer to a predetermined level or more. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesion to an adherend, it is advantageous to set it to about 4 µm or more, preferably about 6 µm or more, more preferably about 10 µm or more (for example, For example, about 15 µm or more).

The technology disclosed herein can be suitably implemented, for example, in the form of a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of about 10 µm or more and about 25 µm or less (preferably about 15 µm or more and about 22 µm or less). . A pressure-sensitive adhesive sheet having such a thickness of the pressure-sensitive adhesive layer on both surfaces of the substrate is preferable.

(gel fraction)

Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein can be, on a weight basis, for example, 20% or more, and is usually preferably 30% or more, and preferably 35% or more. By making the gel fraction of an adhesive layer high in an appropriate range, there exists a tendency for the appropriate oleic acid permeation amount disclosed herein to become easy to implement|achieve. On the other hand, when the gel fraction is too high, there may be a case where the amount of oleic acid permeation tends to be insufficient. From such a viewpoint, 90 % or less is preferable, as for the gel fraction of an adhesive layer, 80 % or less is more preferable, and 70 % or less (for example, 65 % or less) is still more preferable.

Here, "the gel fraction of an adhesive layer" means the value measured by the following method. The said gel fraction can be grasped|ascertained as the weight ratio of the ethyl acetate insoluble content in an adhesive layer.

[Method for measuring gel fraction]

About 0.1 g of a pressure-sensitive adhesive sample (weight Wg ₁ ) is wrapped in a pouch shape with a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore diameter of 0.2 μm, and the inlet is tied with a smoke thread (weight Wg ₃ ). As said porous polytetrafluoroethylene (PTFE) film|membrane, the trade name "Nitoflon (trademark) NTF1122" (average pore diameter 0.2 µm, porosity 75%, thickness 85 µm) available from Nitto Denko Co., Ltd. or an equivalent thereof use

The package was immersed in 50 mL of ethyl acetate and maintained at room temperature (typically 23° C.) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer to the outside of the membrane. was wiped off, and the package was dried at 130° C. for 2 hours, and the weight (Wg ₄ ) of the package was measured. Gel fraction F _G of an adhesive layer is calculated|required by substituting each value into the following formula|equation. A similar method is employed in the embodiments to be described later.

Gel fraction F _G (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

<Reference>

In the aspect in which the pressure-sensitive adhesive sheet disclosed herein is in the form of a pressure-sensitive adhesive sheet provided with a single-sided or double-sided pressure-sensitive adhesive sheet, as a base material for supporting (overlaying) the pressure-sensitive adhesive layer, a resin film, paper, cloth, rubber sheet, foam A sheet, metal foil, a composite thereof, or the like can be used. Examples of the resin film include films made of polyolefins such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymer; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; Cellophane etc. are mentioned. Examples of the paper include Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, and top coated paper. Examples of the fabric include woven fabrics and nonwoven fabrics made of various fibrous materials alone or by blending or the like. Examples of the fibrous material include cotton, staple fiber, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber and the like. Examples of the rubber sheet include a natural rubber sheet and a butyl rubber sheet. As an example of a foam sheet, a foamed polyurethane sheet, a foamed polychloroprene rubber sheet, etc. are mentioned. Aluminum foil, copper foil, etc. are mentioned as an example of metal foil.

In addition, the nonwoven fabric used here is a concept which points out the nonwoven fabric for adhesive sheets mainly used in the field of adhesive tapes and other adhesive sheets, and the nonwoven fabric (so-called "paper") typically produced using a general paper machine. also) said. In addition, the resin film here is a non-porous resin sheet typically, and is a concept distinguished from a nonwoven fabric (that is, a nonwoven fabric is not included), for example. Any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film may be sufficient as the said resin film. In addition, the surface on which the adhesive layer of the said base material is formed may be surface-treated, such as application|coating of a primer, corona discharge treatment, and plasma treatment.

The technique disclosed herein can be preferably implemented in the form of a pressure-sensitive adhesive sheet having a base material having the pressure-sensitive adhesive layer on at least one surface of the base film (support). For example, it may be preferably implemented in the form of a double-sided pressure-sensitive adhesive sheet having a base material having the pressure-sensitive adhesive layer on one surface and the other surface of the base film.

As a base film, what contains a resin film as a base film can be used preferably. The base film is typically a member capable of maintaining a shape independently (independently). The base film in the technique disclosed herein may be substantially comprised from such a base film. Alternatively, the base film may include an auxiliary layer other than the base film. Examples of the auxiliary layer include an undercoat layer, an antistatic layer, and a colored layer formed on the surface of the base film.

The said resin film is a film which has a resin material as a main component (component contained more than 50 weight% in the said resin film). Examples of the resin film include polyolefin-based resin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymer; polyester-based resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride-based resin film; vinyl acetate-based resin film; polyimide-based resin film; polyamide-based resin film; fluororesin film; cellophane; and the like. The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Especially, from a viewpoint of handling property and workability, a polyester film is preferable, and PET film is especially preferable especially. In addition, in this specification, a "resin film" is typically a non-porous sheet, and is a concept (in other words, a concept excluding a nonwoven fabric and a woven fabric) different from what is called a nonwoven fabric and a woven fabric.

In the said resin film (for example, PET film), a filler (inorganic filler, organic filler, etc.), a colorant, a dispersing agent (surfactant etc.), antioxidant, antioxidant, ultraviolet absorber, antistatic agent, lubricating agent, a plasticizer as needed Various additives, such as these, may be mix|blended. The blending ratio of the various additives is usually less than about 30% by weight (for example, less than about 20% by weight, preferably less than about 10% by weight).

A single layer structure may be sufficient as the said resin film, and what has a two-layer, three-layer, or more multilayer structure may be sufficient as it. It is preferable that a resin film has a single-layer structure from a viewpoint of shape stability. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the resin (for example, a polyester-based resin). What is necessary is just to employ|adopt a conventionally well-known method suitably as for the manufacturing method of a resin film, and it is not specifically limited. For example, conventionally well-known general film forming methods, such as extrusion molding, inflation molding, T-die casting molding, and calender roll molding, can be employ|adopted suitably.

The thickness of the base film disclosed here is not specifically limited. From the viewpoint of avoiding the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the base film is, for example, about 200 µm or less, preferably about 150 µm or less, more preferably about 100 µm or less. The thickness of the base film may be approximately 70 µm or less, may be approximately 50 µm or less, or may be approximately 30 µm or less (eg, approximately 25 µm or less) according to the purpose or form of use of the pressure-sensitive adhesive sheet. One aspect WHEREIN: The thickness of a base film may just be about 20 micrometers or less, and may be about 15 micrometers or less, and may be about 10 micrometers or less (for example, about 5 micrometers or less). By making the thickness of a base film small, even if the total thickness of an adhesive sheet is the same, the thickness of an adhesive layer can be made larger. This can be advantageous from the viewpoint of improving the adhesion to the substrate. The lower limit in particular of the thickness of a base film is not restrict|limited. From viewpoints of handleability (handling property), workability, etc. of an adhesive sheet, the thickness of a base film is usually about 0.5 micrometer or more (for example, 1 micrometer or more), Preferably it is about 2 micrometers or more, for example, about 4 more than μm. One aspect WHEREIN: The thickness of a base film can be about 6 micrometers or more, and may be about 8 micrometers or more, and may be about 10 micrometers or more (for example, more than 10 micrometers).

Conventionally well-known surface treatment, such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application|coating of a primer, may be given to the surface of a base film. Such surface treatment may be a treatment for improving the adhesion between the base film and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the base film.

<Releasable Liner>

In the technique disclosed herein, a release liner can be used in the formation of the pressure-sensitive adhesive layer, preparation of the pressure-sensitive adhesive sheet, storage of the pressure-sensitive adhesive sheet before use, distribution, shape processing, and the like. The release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluorine-based polymer (polytetrafluoroethylene, etc.), or a polyolefin-based resin (polyethylene, poly A release liner or the like containing a low-adhesive material such as propylene or the like can be used. The release treatment layer may be formed by surface-treating the liner substrate with a release treatment agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide.

<Adhesive sheet>

The total thickness of the pressure-sensitive adhesive sheet (not including the release liner) disclosed herein is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet can be, for example, about 500 µm or less, usually about 350 µm or less is suitable, and about 250 µm or less (for example, about 200 µm or less) is preferable. The technique disclosed herein is a pressure-sensitive adhesive sheet (typically double-sided adhesive) having a total thickness of about 150 μm or less (more preferably about 100 μm or less, more preferably about 60 μm or less, for example about 55 μm or less). Sheet) may be preferably implemented in the form of. Although the lower limit in particular of the thickness of an adhesive sheet is not specifically limited, Usually, about 10 micrometers or more are suitable, about 20 micrometers or more are preferable, and about 30 micrometers or more are more preferable.

According to the technique disclosed herein, an adhesive sheet having an adhesive force retention rate exceeding 50% in the following oil-resistant adhesive evaluation can be provided. In the pressure-sensitive adhesive sheet according to a preferred embodiment, the adhesive force retention may be 60% or more (eg, 65% or more). Although the upper limit of adhesive force retention is not specifically limited, Usually, it is 150 % or less, Preferably it is 100 % or less.

[Evaluation of oil-resistance adhesion]

A sample piece is prepared by cutting the pressure-sensitive adhesive sheet to a size of 10 mm in width and 100 mm in length. Here, when the pressure-sensitive adhesive sheet of the measurement form is a double-sided pressure-sensitive adhesive sheet, a PET film having a thickness of 50 µm is attached to one side of the pressure-sensitive adhesive side, and then cut to the size described above.

In the environment of 23 degreeC and 50 %RH, the adhesive surface of the said sample piece is press-bonded to a stainless steel plate (SUS304BA plate), and a measurement sample is produced. The said crimping|compression-bonding is performed by making one reciprocating 2 kg roller. After leaving the measurement sample to stand in an environment of 23°C and 50%RH for 30 minutes, using a tensile tester, in accordance with JIS Z 0237:2000, peeling at a tensile rate of 150 mm/min and a peeling angle of 180 degrees The strength (N/10 mm) is measured. Let this value be the adhesive force before immersion.

On the other hand, the measurement sample prepared in the same manner as described above is left to stand for 30 minutes in an environment of 23°C and 50%RH, immersed in an oleic acid bath, and is maintained for 2 weeks in an environment of 40°C and 90%RH. Thereafter, the measurement sample is removed from the oleic acid bath, the surrounding oleic acid is lightly wiped off, and left for 30 minutes in an environment of 23° C. and 50% RH. mm) is measured. This value is called the adhesive force after immersion.

From the obtained measured value, the following formula:

Adhesive force retention (%) = (adhesive force after immersion/adhesive force before immersion) x 100;

to calculate the adhesive force retention rate.

In addition, as a tensile testing machine, "Precision Universal Testing Machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation can be used, for example. The same evaluation method is adopted also in the Example mentioned later.

In the adhesive sheet disclosed herein, the adhesive force before immersion is not particularly limited. The adhesive sheet which concerns on one preferable aspect is about 3.0 N/10 mm or more in adhesive force before immersion. The pressure-sensitive adhesive sheet exhibiting such adhesive strength before immersion has high adhesiveness to an adherend, and therefore has excellent performance for preventing oil from entering the adhesive interface from the outer edge of the pressure-sensitive adhesive sheet. The adhesive sheet whose adhesive force before immersion is about 5.0 N/10 mm or more (for example, about 6.0 N/10 mm or more) is more preferable. The higher the adhesiveness to the adherend, the better, so the upper limit of the adhesive force before immersion is not particularly limited, but usually about 30 N/10 mm or less (for example, about 20 N/10 mm or less) is suitable.

Although it does not specifically limit, It is preferable that the said adhesive force after immersion is 1.0 N/10mm or more from a viewpoint of suppressing the protrusion of an adhesive. The adhesive force after immersion is preferably about 2.0 N/10 mm or more, more preferably about 3.0 N/10 mm or more, still more preferably about 4.0 N/10 mm or more (for example, about 5.0 N/10 mm or more). or more, and further, about 6.0 N/10 mm or more). The pressure-sensitive adhesive sheet exhibiting adhesive strength after immersion is suitable for, for example, the use of fixing a member that can come into contact with oil.

<Use>

Even if the adhesive sheet disclosed herein comes into contact with oil, there is little fall in adhesive force, and the protrusion of an adhesive is suppressed. Taking advantage of these characteristics, the pressure-sensitive adhesive sheet can be preferably used for fixing various members that can come into contact with oil. As a representative example of such a use, the use for fixing a member in various portable apparatuses (portable apparatus) is mentioned. For example, it is suitable for the fixed use of the member in a portable electronic device. Non-limiting examples of the portable electronic device include a mobile phone, a smart phone, a tablet type personal computer, a notebook computer, and various wearable devices (eg, wrist wear type such as a wrist watch, a clip or strap, etc.). Modular type to be attached to a part of the body, eyewear type including glasses type (monocular type, binocular type, including head mounted type), clothing type for attaching to shirts, socks, hats, etc., for example, as accessories, such as earphones Ear wear type, etc.), digital camera, digital video camera, sound device (portable music player, IC recorder, etc.), calculator (electronic calculator, etc.), portable game device, electronic dictionary, electronic notebook, electronic book, in-vehicle use Information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, and the like are included. Non-limiting examples of portable devices other than portable electronic devices include mechanical wrist watches, pocket watches, flashlights, hand mirrors, commuter pass cases, and the like. In addition, in this specification, "portability" means that it is not enough to simply be able to carry it, and it means that it has a level of portability that an individual (a standard adult) can carry with relative ease.

The pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) disclosed herein is in the form of a bonding material processed into various shapes, and can be used for fixing members constituting a portable device. As a particularly preferable use, a use for fixing a member constituting a portable electronic device is exemplified. Among them, it can be preferably used for a portable electronic device having a liquid crystal display device. For example, in such a portable electronic device, the display unit (which may be a display unit of a liquid crystal display device) or a display unit protection member and a housing are suitable for bonding.

As a preferable aspect of such a bonding material, the aspect which has a narrow part of width 4.0 mm or less (for example, 2.0 mm or less, normally less than 2.0 mm) is mentioned. Since the pressure-sensitive adhesive sheet disclosed herein is excellent in cohesive force in addition to oil resistance, even if it is used as a bonding material having a shape including such a narrow portion (eg, a frame shape), the member can be satisfactorily fixed. In one aspect, 1.5 mm or less may be sufficient as the width of the said narrow part, and 1.0 mm or less may be sufficient as it, and about 0.5 mm or less may be sufficient as it. Although the lower limit in particular of the width|variety of a narrow part is not restrict|limited, Usually, 0.1 mm or more (for example, 0.2 mm or more) is suitable from a viewpoint of the handleability of an adhesive sheet.

The narrow portion is typically linear. Here, the term "linear" refers to a concept including not only a linear shape, a curved shape, a line shape (for example, an L shape), etc., but also an annular shape such as a frame shape or a circular shape, and a complex or intermediate shape thereof. The annular shape is not limited to being constituted by a curve, for example, a shape along the outer periphery of a rectangle (frame shape) or a shape along the periphery of a fan shape, a concept including an annular shape formed in a straight line in part or all to be. The length of the said narrow part is not specifically limited. For example, in the form in which the length of the narrow portion is 10 mm or more (more preferably 20 mm or more, for example 30 mm or more), the effect of applying the technique disclosed herein can be exhibited suitably. have.

Matters disclosed by this specification include the following.

(1) A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive having an acrylic polymer as a base polymer,

The pressure-sensitive adhesive layer has a surface free energy γ of less than about 40 mJ/m 2 and an oleic acid permeation amount of about 1.5 g or more and about 5.0 g or less.

(2) The adhesive sheet as described in said (1) whose gel fraction of the said adhesive layer is about 30 % or more and about 70 % or less.

(3) The adhesive sheet as described in said (1) or (2) in which the said adhesive layer is formed using the adhesive composition containing the said acrylic polymer and a crosslinking agent.

(4) The pressure-sensitive adhesive sheet according to (3), wherein the crosslinking agent contains an isocyanate-based crosslinking agent.

(5) The adhesive sheet according to any one of (1) to (4), wherein the pressure-sensitive adhesive layer contains a tackifying resin, and approximately 50% by weight or more of the tackifying resin is a tackifying resin other than a rosin-based resin. .

(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the monomer component constituting the acrylic polymer contains more than approximately 50% by weight of C _7-10 alkyl (meth)acrylate.

(7) The adhesive sheet according to the above (6), wherein the monomer component constituting the acrylic polymer contains a carboxyl group-containing monomer in an amount greater than approximately 5% by weight.

(8) The monomer component constituting the acrylic polymer comprises approximately 70% by weight or more of C _7-10 alkyl (meth)acrylate, and approximately 7% by weight or more and approximately 15% by weight or less of a carboxyl group-containing monomer. The pressure-sensitive adhesive sheet according to any one of 1) to (7).

(9) The C _7-10 alkyl (meth) acrylate is one or more selected from 2-ethylhexyl acrylate, isooctyl acrylate and isononyl acrylate, and the carboxyl group-containing monomer is acrylic acid, The adhesive sheet as described in said (8) which is methacrylic acid or a combination thereof.

(10) Any one of (6) to (9) above, wherein the pressure-sensitive adhesive layer contains a tackifying resin, and approximately 50% by weight or more of the tackifying resin is a phenolic tackifying resin (eg, terpenephenol resin). The adhesive sheet as described in one.

(11) The adhesive sheet as described in said (10) in which the said phenolic tackifying resin contains the terpene phenol resin whose hydroxyl value is less than about 30 mgKOH/g.

(12) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the monomer component constituting the acrylic polymer contains more than approximately 50% by weight of C _1-6 alkyl (meth)acrylate.

(13) The pressure-sensitive adhesive sheet according to (12), wherein the monomer component constituting the acrylic polymer contains more than approximately 3 wt% of a carboxyl group-containing monomer.

(14) The C _1-6 alkyl (meth) acrylate is one or more selected from n-butyl acrylate, ethyl acrylate and methyl acrylate, and the carboxyl group-containing monomer is acrylic acid, methacrylic acid The pressure-sensitive adhesive sheet according to the above (13), which is an acid or a combination thereof.

(15) Any one of (12) to (14) above, wherein the pressure-sensitive adhesive layer contains a tackifying resin, and approximately 50% by weight or more of the tackifying resin is a phenolic tackifying resin (eg, terpenephenol resin). The adhesive sheet as described in one.

(16) The adhesive sheet according to (15), wherein the phenolic tackifying resin contains a terpenephenol resin having a hydroxyl value of about 30 mgKOH/g or more.

(17) The pressure-sensitive adhesive sheet according to any one of (1) to (16), wherein the pressure-sensitive adhesive layer is formed using a solvent-type pressure-sensitive adhesive composition containing an pressure-sensitive adhesive in an organic solvent.

(18) The pressure-sensitive adhesive sheet according to (17), wherein the organic solvent contains at least one of toluene and ethyl acetate.

(19) The adhesive sheet in any one of said (1)-(18) whose thickness of the said adhesive layer is about 10 micrometers or more and about 25 micrometers or less.

(20) The pressure-sensitive adhesive sheet according to any one of (1) to (19), which is configured as a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer on one surface and the other surface of a base material.

(21) The adhesive sheet according to (20), wherein the substrate is a PET film having a single-layer structure.

(22) The pressure-sensitive adhesive sheet according to any one of (1) to (21), which is used for fixing a member in a mobile device.

(23) A mobile device having a member fixed using the pressure-sensitive adhesive sheet according to any one of (1) to (22).

(24) The mobile device according to (23), wherein the mobile device is a wearable device (eg, a list wear type wearable device).

[Example]

Hereinafter, some examples related to the present invention will be described, but it is not intended to limit the present invention to those shown in these examples. In addition, in the following description, "part" and "%" are based on weight unless otherwise indicated.

<Preparation of acrylic polymer solution>

(Acrylic polymer A)

In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel, 90 parts of 2EHA and 10 parts of AA as a monomer component and 199 parts of ethyl acetate as a polymerization solvent were charged, while introducing nitrogen gas for 2 hours stirred. After removing oxygen in the polymerization system in this way, 0.2 parts of benzoyl peroxide was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 6 hours to obtain a solution of the acrylic polymer A. The Mw of the acrylic polymer A was about 120×10 ⁴ .

(Acrylic polymer B)

100 parts of 2EHA as a monomer component, 2 parts of methyl methacrylate (MMA) and 2 parts of AA, and 190 parts of toluene as a polymerization solvent were put into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel Thus, the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.3 parts of 2,2'-azobisisobutyronitrile was added as a polymerization initiator, and solution polymerization was carried out at 60° C. for 6 hours to obtain a solution of acrylic polymer B. The Mw of the acrylic polymer B was about 100×10 ⁴ .

(Acrylic polymer C)

95 parts of BA and 5 parts of AA as a monomer component and 233 parts of ethyl acetate as a polymerization solvent were put into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel, and nitrogen gas was introduced for 2 hours stirred. After removing oxygen in the polymerization system in this way, 0.2 parts of 2,2'-azobisisobutyronitrile was added as a polymerization initiator, and solution polymerization was carried out at 60° C. for 8 hours to obtain an acrylic polymer solution. The Mw of this acrylic polymer was about 70×10 ⁴ .

<Preparation of adhesive composition>

(Example 1)

In the solution of the acrylic polymer A, 2 parts (based on non-volatile content; the same applies hereinafter) of an isocyanate-based crosslinking agent (trade name “Coronate L”, trimethylolpropane/tolylenedi) with respect to 100 parts of the acrylic polymer A contained in the solution. A 75% ethyl acetate solution of the isocyanate trimer adduct, manufactured by Tosoh Corporation; hereinafter referred to as "isocyanate-based crosslinking agent A") was added and stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

(Example 2)

In the solution of the acrylic polymer A, 2 parts of isocyanate-based crosslinking agent A and 0.01 parts of epoxy-based crosslinking agent (trade name "TETRAD-C", 1,3-bis(N, N-diglycidylaminomethyl) cyclohexane, manufactured by Mitsubishi Gas Chemical Co., Ltd.; hereinafter referred to as "epoxy crosslinking agent B") was added, stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

(Example 3)

To the solution of the acrylic polymer A, 2 parts of isocyanate-based cross-linking agent A, 0.035 parts of epoxy-based cross-linking agent B, and 10 parts of terpene phenol resin A (trade name "Tamanol 803L" with respect to 100 parts of acrylic polymer A contained in the solution) , manufactured by Arakawa Chemical Co., Ltd., a softening point of about 145 to 160° C., a hydroxyl value of 1 to 20 mgKOH/g) was added, stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

(Example 4)

To the solution of the acrylic polymer C, 2 parts of an isocyanate-based crosslinking agent A was added with respect to 100 parts of the acrylic polymer C contained in the solution, and stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

(Example 5)

With respect to 100 parts of acrylic polymer C, 30 parts of terpene phenol resin B (manufactured by Yasuhara Chemical, trade name "YS Polystar S-145", softening point of about 145° C., hydroxyl value of 70 to 110 mgKOH/g) was further added. It carried out similarly to Example 4, and prepared the adhesive composition which concerns on this example.

(Example 6)

Except having changed the usage-amount of the terpene phenol resin B with respect to 100 parts of acrylic polymer C into 40 parts, it carried out similarly to Example 5, and the adhesive composition which concerns on this example was prepared.

(Example 7)

To the solution of the acrylic polymer B, 2 parts of an isocyanate-based crosslinking agent A was added with respect to 100 parts of the acrylic polymer B contained in the solution, and stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

(Example 8)

Except having changed the usage-amount of the isocyanate type crosslinking agent A with respect to 100 parts of acrylic polymer C to 1 part, it carried out similarly to Example 4, and the adhesive composition which concerns on this example was prepared.

(Example 9)

As in Example 4, except that 10 parts of rosin-based tackifying resin A (trade name "Harrytag SE10", hydrogenated rosin glycerin ester, manufactured by Harima Kasei Co., Ltd., softening point about 80°C) was further added with respect to 100 parts of the acrylic polymer C Thus, the pressure-sensitive adhesive composition according to the present example was prepared.

(Example 10)

To the solution of the acrylic polymer C, 2 parts of isocyanate-based cross-linking agent A, 0.01 parts of epoxy-based cross-linking agent B, and 20 parts of rosin-based tackifying resin B (trade name "Pencel D125" with respect to 100 parts of acrylic polymer C contained in the solution) , manufactured by Arakawa Chemical Co., Ltd., pentaerythritol ester of polymerized rosin, softening point of about 125° C.) was added, stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example.

<Production of adhesive sheet>

As a release liner, two polyester release films (trade name "Diafoil MRF", 38 m thick, manufactured by Mitsubishi Polyester) having one side of the release surface subjected to a release treatment were prepared. The pressure-sensitive adhesive composition according to each example was applied to the release surface of these release liners, and dried at 100°C for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 19 µm. The pressure-sensitive adhesive layer formed on the two release liners was bonded to the first and second surfaces of a transparent base film having a thickness of 12 µm, respectively, to prepare a double-sided pressure-sensitive adhesive sheet having a total thickness of 50 µm. The release liner was left on the pressure-sensitive adhesive layer as it was, and was used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer. As the base film, a PET film (resin film) manufactured by Toray Corporation and a trade name "Lumiror" were used. In this way, the double-sided pressure-sensitive adhesive sheets of Examples 1 to 10 respectively corresponding to the pressure-sensitive adhesive compositions according to Examples 1 to 10 were produced.

<Evaluation Test>

After curing the double-sided pressure-sensitive adhesive sheets according to Examples 1 to 10 under an environment of 50° C. and 50% RH for 1 day, the surface free energy γ, the gel fraction, and the adhesive force retention were calculated by the method described above.

In addition, the pressure-sensitive adhesive composition according to Examples 1 to 10 was applied to the release surface of the polyester release film (trade name "Diafoil MRF", thickness 38 µm, manufactured by Mitsubishi Polyester Co., Ltd.), and dried at 120 ° C. for 2 minutes. , a pressure-sensitive adhesive layer (inorganic pressure-sensitive adhesive layer) having a thickness of 20 μm was formed on the release film. This pressure-sensitive adhesive layer was bonded to a 50 µm-thick PET film (trade name "Lumirer", manufactured by Toray Corporation), and cut into a square having a length of 25 mm and a width of 25 mm to prepare a test piece. By performing oleic acid permeability evaluation by the method mentioned above using this test piece, the oleic acid permeation amount and permeation distance were calculated|required, and the protrusion of an adhesive was evaluated.

The obtained results are shown in Tables 1 and 2.

As shown in Tables 1 and 2, the pressure-sensitive adhesive sheets of Examples 1 to 6 having a pressure-sensitive adhesive layer having a surface free energy γ of less than 40 mJ/m 2 and an oleic acid penetration in a range of 1.5 g/g or more and 5.0 g/g or less. All showed a favorable adhesive force retention, and there was also little protrusion of an adhesive. On the other hand, in Examples 7 and 8 in which the amount of oleic acid permeation was too small and Example 10 in which the surface free energy γ was too high, the adhesive force retention was low. In Example 9 with too much oleic acid permeation amount, the protrusion of an adhesive was large.

As mentioned above, although the specific example of this invention was demonstrated in detail, these are only an illustration and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

1, 2, 3, 4, 5, 6: adhesive sheet
10: description
21, 22: adhesive layer
31, 32: release liner

Claims (18)

It is a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive having an acrylic polymer as a base polymer,
The pressure-sensitive adhesive layer has a surface free energy γ of 7mJ/m2 or more and less than 40mJ/m2, and an oleic acid permeation amount of 1.5g or more and 5.0g or less per 1g,
The thickness of the pressure-sensitive adhesive layer is 25㎛ or less,
The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition comprising the acrylic polymer, a crosslinking agent, and a tackifying resin,
The crosslinking agent includes an isocyanate-based crosslinking agent,
The amount of the isocyanate-based crosslinking agent used is 0.5 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the acrylic polymer,
The said tackifying resin contains the phenolic tackifying resin, The adhesive sheet. According to claim 1,
The adhesive sheet whose gel fraction of the said adhesive layer is 30 % or more and 70 % or less. 3. The method of claim 1 or 2,
The adhesive sheet of which 50 weight% or more of the said tackifying resin is tackifying resin other than a rosin type tackifying resin. 3. The method of claim 1 or 2,
The monomer component constituting the acrylic polymer comprises more than 50% by weight of an alkyl (meth)acrylate having an alkyl group having 7 or more and 10 or less carbon atoms at the ester terminal thereof. 3. The method of claim 1 or 2,
The monomer component constituting the acrylic polymer comprises more than 5 wt% of a carboxyl group-containing monomer, the pressure-sensitive adhesive sheet. 3. The method of claim 1 or 2,
The adhesive sheet which is comprised as a double-sided adhesive sheet which has the said adhesive layer on one surface and the other surface of a base material. 3. The method of claim 1 or 2,
An adhesive sheet used for fixing a member in a mobile device. delete delete delete delete delete delete delete delete delete delete delete

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