JP2017057371A - Pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive sheet for fixing members of portable devices, the sheet having high retention capacity and resistant to oil infiltration.SOLUTION: The present invention provides a pressure-sensitive adhesive sheet 1 for fixing members of portable devices, the sheet including a pressure-sensitive adhesive layer 21, 22 formed from a pressure-sensitive adhesive composition which comprises: an acrylic polymer comprising Calkyl (meth)acrylate of more than 50 wt% as a monomer component; a crosslinking agent comprising an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent; and a tackifier resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adhesive sheet. In detail, it is related with the adhesive sheet suitable for fixation of the member which comprises a portable apparatus.

  In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same shall apply hereinafter) is in the form of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, the pressure-sensitive adhesive is typically used in the form of a pressure-sensitive adhesive sheet, and is widely used for the purpose of joining, fixing, and protecting members in mobile phones and other portable devices. Patent documents 1 and 2 are mentioned as technical literature about a double-sided adhesive tape used for component fixation of portable electronic equipment.

JP 2009-215355 A JP 2013-1000048 A1

  Since portable devices are used with carrying, oils contained in secretions such as sebum and dirt, cosmetics, hair styling agents, chemicals such as moisturizing creams, sunscreens, foods, etc. are likely to adhere. In particular, touch panel portable devices, which have been widely used in recent years, include a display unit / input unit whose display unit also functions as an input unit, and are operated when a user directly touches the surface of the display unit / input unit with a fingertip. Therefore, there are many opportunities for oil to adhere through the fingertips. Some so-called wearable devices are used while being in contact with the skin. In such usage, there are many opportunities to be exposed to oil such as sebum and chemicals applied to the skin. When such an oil component comes into contact with the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet fixing the member, the pressure-sensitive adhesive absorbs the oil and is softened, which may cause inconveniences such as expansion, deformation, and reduction in cohesive force. In this regard, for example, Patent Document 1 studies a double-sided pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive hardly swells even when the oil component penetrates, and the pressure-sensitive adhesive does not protrude when used for fixing components.

  On the other hand, as long as it is an adhesive sheet used for fixing a member, it goes without saying that the holding performance of the member, that is, the performance of keeping the member in a fixed state is important. Moreover, the holding performance is a performance that is continuously required after fixing the member using the adhesive sheet in the manufacturing process of the portable device, and the oil content that can be generated after the start of use of the manufactured portable device. This is the performance required before contact. However, the conventional technology for improving the oil resistance of the pressure-sensitive adhesive sheet for fixing members tends to be insufficient in holding performance of the pressure-sensitive adhesive sheet.

  With the diversification of forms of portable devices (particularly portable electronic devices) and the spread of usage scenes, higher holding performance has been required for pressure-sensitive adhesive sheets used for fixing members. This invention is made | formed in view of this situation, Comprising: It aims at providing the adhesive sheet with a high holding | maintenance performance, and an oil component being hard to osmose | permeate.

According to this specification, an adhesive sheet used for fixing a member in a portable device is provided. The said adhesive sheet contains the adhesive layer formed using the adhesive composition containing the acrylic polymer as a base polymer, tackifying resin, and a crosslinking agent. The monomer component constituting the acrylic polymer may be expressed as an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at the ester terminal (hereinafter referred to as “C _1-6 alkyl (meth) acrylate”). ) In excess of 50% by weight. The content of the tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer. And the said crosslinking agent contains an epoxy-type crosslinking agent and an isocyanate type crosslinking agent.

Since the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer contains an acrylic polymer having C _1-6 alkyl (meth) acrylate as a main constituent monomer component as a base polymer, it is difficult to absorb oil. Moreover, the cohesive force of the said adhesive layer can be raised and the holding | maintenance performance of an adhesive sheet can be improved by the combined use of an epoxy type crosslinking agent and an isocyanate type crosslinking agent. Furthermore, since the pressure-sensitive adhesive layer contains a predetermined amount or more of a tackifying resin, the adhesiveness to the adherend is good. Therefore, the infiltration of oil from the interface between the pressure-sensitive adhesive layer and the adherend can be effectively suppressed.

  As the tackifier resin, a phenol-based tackifier resin (for example, a terpene phenol resin) can be preferably used. By including a phenol-based tackifying resin in the pressure-sensitive adhesive layer, adhesion to the adherend can be improved, and oil penetration can be effectively suppressed. It is preferable that the content of the phenolic tackifying resin is more than 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.

  In the pressure-sensitive adhesive sheet according to a preferred embodiment, the tackifier resin contained in the pressure-sensitive adhesive layer contains a tackifier resin having a hydroxyl value of 30 mgKOH / g or more. By including a tackifier resin having a relatively high hydroxyl value in the pressure-sensitive adhesive layer as described above, the adhesion to the adherend can be improved and the infiltration of oil can be effectively suppressed. As the tackifier resin having a hydroxyl value of 30 mgKOH / g or more, for example, a phenol tackifier resin (typically a terpene phenol resin) can be preferably used.

  The monomer component constituting the acrylic polymer preferably contains a carboxy group-containing monomer. Thereby, the cohesive force of an adhesive layer improves and it exists in the tendency for the holding | maintenance performance of an adhesive sheet to improve by extension. When the monomer component contains a carboxy group-containing monomer, it can advantageously contribute to improving the adhesion between the pressure-sensitive adhesive layer and the adherend. In view of compatibility with other components, the content of the carboxy group-containing monomer in the monomer component is usually suitably about 0.5 wt% to 10 wt%.

  The content of the epoxy crosslinking agent is preferably less than about 0.05 parts by weight with respect to 100 parts by weight of the acrylic polymer. By using such an amount of the epoxy crosslinking agent in combination with the isocyanate crosslinking agent, a pressure-sensitive adhesive layer having high cohesive force and good adhesion to the adherend tends to be formed. Thereby, the adhesive sheet in which the oil infiltration from the interface was better suppressed can be realized.

  In one embodiment, the content of the epoxy crosslinking agent may be about 1/100 or less of the content of the isocyanate crosslinking agent. According to such an embodiment, the cohesive force and the adhesiveness of the pressure-sensitive adhesive layer can be compatible at a higher level, and better oil penetration prevention can be realized.

  The technique disclosed herein can be preferably applied to a pressure-sensitive adhesive sheet in which the thickness of the pressure-sensitive adhesive layer is about 30 μm or less (for example, about 25 μm or less). When the thickness of the pressure-sensitive adhesive layer is reduced, the amount of oil supplied per volume of the pressure-sensitive adhesive is increased even if the amount of oil attached is the same. In addition, when the thickness of the pressure-sensitive adhesive layer is reduced, generally the adhesiveness of the pressure-sensitive adhesive layer to the adherend tends to be reduced, and oil tends to enter from the interface between the pressure-sensitive adhesive layer and the adherend. is there. Therefore, it is particularly meaningful to apply the technology disclosed herein to suppress oil penetration.

  The pressure-sensitive adhesive sheet disclosed herein preferably has a 180-degree peel strength of about 17 N / 25 mm or more. According to the pressure-sensitive adhesive sheet exhibiting such pressure-sensitive adhesive strength, oil intrusion from the interface between the pressure-sensitive adhesive layer and the adherend tends to be suitably suppressed.

  A pressure-sensitive adhesive sheet according to a preferred embodiment includes any pressure-sensitive adhesive layer disclosed herein and a base film that supports the pressure-sensitive adhesive layer. Even when the cohesive force of the pressure-sensitive adhesive layer is increased by using a combination of an epoxy-based cross-linking agent and an isocyanate-based cross-linking agent, the pressure-sensitive adhesive layer is unlikely to deteriorate in adhesion to the base film. This can suppress oil intrusion from the interface between the pressure-sensitive adhesive layer and the base film.

  The technology disclosed herein can be preferably implemented in the form of a double-sided pressure-sensitive adhesive sheet (which can be a double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive on one surface and the other surface of the base film). Since the fixing part of the member by the double-sided pressure-sensitive adhesive sheet includes many interfaces as compared with the fixing part of the member by the single-sided pressure-sensitive adhesive sheet, oil easily enters from these interfaces. Therefore, it is particularly meaningful to apply the technique disclosed herein to suppress oil intrusion from the interface.

It is sectional drawing which shows one structural example of an adhesive sheet typically. It is sectional drawing which shows the other structural example of an adhesive sheet typically.

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

In the present specification, the “pressure-sensitive adhesive” refers to a material that exhibits a soft solid (viscoelastic body) state in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure as described above. . The adhesive here is generally defined as “CA Dahlquist,“ Adhesion: Fundamental and Practice ”, McLaren & Sons, (1966) P. 143”, and generally has a complex tensile modulus E ^* (1 Hz). It may be a material having a property satisfying <10 ⁷ dyne / cm ² (typically, a material having the above property at 25 ° C.).

  In this specification, “(meth) acryloyl” means acryloyl and methacryloyl comprehensively. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acryl” generically means acrylic and methacryl.

  In this specification, the “acrylic polymer” refers to a polymer containing monomer units derived from a monomer having at least one (meth) acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth) acryloyl group in one molecule is also referred to as an “acrylic monomer”. Accordingly, the acrylic polymer in this specification is defined as a polymer including monomer units derived from an acrylic monomer.

  The pressure-sensitive adhesive sheet disclosed herein includes a pressure-sensitive adhesive layer. A typical embodiment of the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on at least one surface of a substrate film (support). The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a single sheet. Or the adhesive sheet of the form processed into various shapes may be sufficient. Moreover, there may not be a base film.

  The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 1 includes a base film 10 and a first pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive layer 22 supported on the first surface 10A and the second surface 10B of the base film 10, respectively. The first surface 10A and the second surface 10B are both non-peelable surfaces (non-peel surfaces). The pressure-sensitive adhesive sheet 1 is used by attaching the surface (first pressure-sensitive adhesive surface) 21A of the first pressure-sensitive adhesive layer 21 and the surface (second pressure-sensitive adhesive surface) 22A of the second pressure-sensitive adhesive layer 22 to an adherend. That is, the pressure-sensitive adhesive sheet 1 is configured as a double-sided pressure-sensitive adhesive sheet (double-sided adhesive pressure-sensitive adhesive sheet). Prior to use, the pressure-sensitive adhesive sheet 1 was protected by release liners 31 and 32 on which the first pressure-sensitive adhesive surface 21A and the second pressure-sensitive adhesive surface 22A had at least a surface (peeling surface) having peelability on the pressure-sensitive adhesive surface side. It has a configuration. Alternatively, the release liner 32 may be omitted, and the release liner 31 having a release surface on both sides may be used, and the adhesive sheet 1 may be wound to bring the second adhesive surface 22A into contact with the back surface of the release liner 31. Accordingly, the second adhesive surface 22A may also be protected by the release liner 31.

  The technique disclosed here can also be implemented in the form of a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer only on one surface of the base film. An example of the single-sided pressure-sensitive adhesive sheet is shown in FIG. The pressure-sensitive adhesive sheet 2 has a base film 10 and a first pressure-sensitive adhesive layer 21 supported on the first surface 10A, and the surface (first pressure-sensitive adhesive surface) 21A of the first pressure-sensitive adhesive layer 21 is an adherend. Used to paste. The pressure-sensitive adhesive sheet 2 before use has a configuration in which the first pressure-sensitive adhesive surface 21A is protected by a release liner 31 having at least the pressure-sensitive adhesive surface side as a release surface. Alternatively, the release liner 31 is omitted, and the base film 10 having the second surface 10B as the release surface is used. The pressure-sensitive adhesive sheet 2 is wound around the first pressure-sensitive adhesive surface 21A of the base film 10. The first adhesive surface 21A may be protected by contacting the two surfaces 10B. Alternatively, the pressure-sensitive adhesive sheet disclosed herein is not particularly illustrated, but may be a baseless double-sided pressure-sensitive adhesive sheet composed of only a pressure-sensitive adhesive layer.

<Adhesive layer>
The pressure-sensitive adhesive sheet disclosed herein has a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer, a tackifier resin, and a crosslinking agent. The pressure-sensitive adhesive sheet can be, for example, a pressure-sensitive adhesive sheet with a substrate having the pressure-sensitive adhesive layer on at least one surface of the substrate film. Here, the base polymer refers to a main component of a rubber-like polymer (a polymer exhibiting rubber elasticity in a temperature range near room temperature) contained in the pressure-sensitive adhesive layer. Further, in this specification, “main component” refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

(Acrylic polymer)
The acrylic polymer is a polymer of a monomer component that contains C _1-6 alkyl (meth) acrylate as a main monomer and may further contain a submonomer copolymerizable with the main monomer. Here, the main monomer means a main component of the monomer component, that is, a component occupying more than 50% by weight.

Specific examples of the C _1-6 alkyl (meth) acrylate, but are not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n- butyl (meth) Examples include acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, and hexyl (meth) acrylate. These C _1-6 alkyl (meth) acrylates may be used alone or in combination of two or more.

Acrylic polymers having a C _1-6 alkyl (meth) acrylate as a main monomer are generally compared with acrylic polymers having an alkyl (meth) acrylate having an alkyl group having a larger number of carbon atoms at the ester terminal as a main monomer. Low affinity for oil. Therefore, the pressure-sensitive adhesive layer containing such an acrylic polymer as a base polymer tends to hardly absorb oil in the pressure-sensitive adhesive layer.

From the viewpoint of lowering the oil affinity of the pressure-sensitive adhesive layer, the acrylic polymer preferably has a main monomer of C _1-5 alkyl (meth) acrylate, and is C _1-4 alkyl (meth) acrylate. Is more preferable. In the acrylic polymer according to a preferred embodiment, the main monomer is C _2-6 alkyl (meth) acrylate from the viewpoint of improving the adhesion to the adherend and the adhesion to the substrate film in the configuration having the substrate film. Yes, more preferably C _4-6 alkyl (meth) acrylate. In the acrylic polymer according to another preferred embodiment, the main monomer is C _1-6 alkyl acrylate, more preferably C _1-4 alkyl acrylate (for example, C _2-4 alkyl acrylate), from the viewpoint of improving the adhesion. It is.

As the C _1-6 alkyl (meth) acrylate, from the viewpoint of improving adhesion to oil affinity reduction and the adherend and the substrate film of the adhesive layer, generally 20 ° C. The glass transition temperature of the homopolymer (Tg) of Preferably, C _1-6 alkyl (meth) acrylate is used (typically about 10 ° C. or lower, preferably about 0 ° C. or lower, more preferably about −10 ° C. or lower, more preferably about −15 ° C. or lower). Can do. The technique disclosed here can be preferably implemented, for example, in an embodiment in which the main monomer of the acrylic polymer is n-butyl acrylate (BA).

Further, from the viewpoint of reducing the oil affinity of the pressure-sensitive adhesive layer, among the monomer components constituting the acrylic polymer, C _1-6 alkyl (meth) acrylate (typically C _1-6 alkyl acrylate, such as BA). Is preferably about 60% by weight or more, more preferably about 75% by weight or more, and more preferably about 85% by weight or more. The technique disclosed herein is, for example, about 70% by weight or more of the monomer component (more preferably about 80% by weight or more, more preferably about 85% by weight or more, about 90% by weight or about 95% or more. May be preferably implemented in an embodiment wherein BA is BA.

  The acrylic polymer in the technique disclosed herein may be copolymerized with a monomer (other monomer) other than the above, if necessary, as long as the effects of the present invention are not significantly impaired. The above-mentioned other monomers can be used for the purpose of adjusting the Tg of the acrylic polymer, improving the cohesive force, adjusting the initial adhesiveness, and the like. Examples of monomers that can improve the cohesive strength and heat resistance of the pressure-sensitive adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, and aromatic vinyl compounds. Preferred examples of these include vinyl esters. Specific examples of vinyl esters include vinyl acetate (VAc), vinyl propionate, vinyl laurate, and the like. Of these, VAc is preferable.

  Other monomers that can introduce a functional group that can serve as a crosslinking base point into the acrylic polymer or contribute to an improvement in peel strength include a hydroxyl group (OH group) -containing monomer, a carboxy group-containing monomer, an acid anhydride group-containing monomer, an amide Examples thereof include a group-containing monomer, an amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, (meth) acryloylmorpholine, and vinyl ethers.

  As a preferable example of the acrylic polymer in the technology disclosed herein, an acrylic polymer obtained by copolymerizing a carboxy group-containing monomer as the other monomer may be mentioned. Thereby, it exists in the tendency which becomes easy to obtain an adhesive layer with high cohesion force. The fact that the monomer component contains a carboxy group-containing monomer can advantageously contribute to improving the adhesion between the pressure-sensitive adhesive layer and the adherend or substrate film. Examples of carboxy group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Is done. Among these, preferable carboxy group-containing monomers include AA and MAA. AA is particularly preferred.

  As another preferred example of the acrylic polymer in the technology disclosed herein, an acrylic polymer obtained by copolymerizing a hydroxyl group-containing monomer as the other monomer may be mentioned. The hydroxyl group-containing monomer may be copolymerized together with the carboxy group-containing monomer. Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meta ) Hydroxyalkyl (meth) acrylates such as acrylate; polypropylene glycol mono (meth) acrylate; N-hydroxyethyl (meth) acrylamide and the like. Among these, as preferred hydroxyl group-containing monomers, hydroxyalkyl (meth) having a hydroxyl group at the end of a linear alkyl group having about 2 to 4 carbon atoms, such as 2-hydroxyethyl acrylate and 4-hydroxybutyl (meth) acrylate. An acrylate is mentioned.

The acrylic polymer in the technology disclosed herein is copolymerized with hydrocarbyl (meth) acrylate other than C _1-6 alkyl (meth) acrylate as the above-mentioned other monomer as long as the effects of the present invention are not significantly impaired. It may be. Examples of such (meth) acrylates include alicyclic (meth) acrylates having an alicyclic group at the ester end, and alkyl groups having 7 or more carbon atoms (typically 7 to 20) at the ester end. Alkyl (meth) acrylates having are included. Examples of alicyclic (meth) acrylates include cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate , Isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and the like. Examples of C _7-20 alkyl (meth) acrylate include heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) Examples include acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tetradecyl (meth) acrylate, stearyl (meth) acrylate, and isostearyl (meth) acrylate.

  The “other monomers” may be used alone or in combination of two or more. The total content of other monomers can be, for example, less than about 50% by weight of the total monomer components (typically about 0.001 to 40% by weight), and is usually about 25% by weight or less (typical). Is suitably about 0.01 to 25% by weight, for example, about 0.1 to 20% by weight.

When a carboxy group-containing monomer is used as the other monomer, the amount used is usually about 0.1 to 20% by weight of the total monomer component (preferably about 0.1 to 15% by weight, typically 0.2%). ˜12% by weight, for example, about 0.5-10% by weight) is appropriate. When the amount of the carboxy group-containing monomer is increased, the cohesive force of the pressure-sensitive adhesive layer generally tends to be improved. By making the usage-amount of a carboxy-group containing monomer into the said range, the compounding effect of tackifying resin mentioned later is exhibited appropriately, and the adhesive layer which shows favorable adhesiveness with respect to a to-be-adhered body and a base film is suitable. Can be realized. In one embodiment, the content of the carboxy group-containing monomer can be about 1-8% by weight (eg, about 2-7% by weight) of the total monomer components.
In addition, when a hydroxyl group-containing monomer is used as the other monomer, the content thereof is usually about 0.001 to 10% by weight (for example, about 0.01 to 5% by weight, typically about 0. (02-2% by weight) is appropriate.

The copolymer composition of the acrylic polymer is suitably designed so that the Tg of the polymer is about −15 ° C. or lower (typically about −70 ° C. or higher and −15 ° C. or lower). Here, the Tg of the acrylic polymer refers to a Tg determined by the Fox formula based on the composition of the monomer component used for the synthesis of the polymer. The formula of Fox is a relational expression between Tg of a copolymer and 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 the above Fox equation, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for the calculation of Tg, the values described in known materials are used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.
2-Ethylhexyl acrylate -70 ° C
n-Butyl acrylate -55 ° C
Ethyl acrylate -22 ° C
Methyl acrylate 8 ℃
Methyl methacrylate 105 ° C
2-hydroxyethyl acrylate -15 ° C
4-hydroxybutyl acrylate -40 ° C
Vinyl acetate 32 ° C
Styrene 100 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

  Regarding the glass transition temperature of homopolymers of monomers other than those exemplified above, the values described in “Polymer Handbook” (3rd edition, John Wiley & Sons, Inc., 1989) are used. The highest value is adopted for the monomer whose values are described in this document.

For monomers for which the glass transition temperature of the homopolymer is not described in the above document, the value obtained by the following measurement method is used.
Specifically, a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser is charged with 100 parts by weight of monomer, 0.2 part by weight of 2,2′-azobisisobutyronitrile and acetic acid as a polymerization solvent. 200 parts by weight of ethyl is added 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 the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and shear strain with a frequency of 1 Hz using a viscoelasticity tester (model name “ARES” manufactured by TA Instruments Japan Co., Ltd.). The viscoelasticity is measured by a shear mode at a temperature increase rate of −70 ° C. to 150 ° C. and 5 ° C./min, and the peak top temperature of tan δ (loss tangent) is defined as Tg of the homopolymer.

  Although not particularly limited, from the viewpoint of adhesion to an adherend or a substrate film, the Tg of the acrylic polymer is advantageously about −25 ° C. or less, preferably about −35 ° C. or less. More preferably, it is about −40 ° C. or less. From the viewpoint of cohesive strength of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer is advantageously about −65 ° C. or higher, preferably about −60 ° C. or higher, more preferably about −55 ° C. or higher. . The technique disclosed herein can be preferably implemented in an embodiment in which the Tg of the acrylic polymer is about −65 ° C. or higher and −35 ° C. or lower (for example, about −55 ° C. or higher and −40 ° C. or lower). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of monomers used for the synthesis of the polymer).

  The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthetic methods for acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. Can be adopted as appropriate. For example, a solution polymerization method can be preferably employed. As a monomer supply method when performing solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided supply (dropping) method, or the like that supplies all monomer raw materials at once can be appropriately employed. The polymerization temperature can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, and the like, for example, about 20 ° C. to 170 ° C. (typically about 40 ° C. to 140 ° C.). Can do. In a preferred embodiment, the polymerization temperature can be about 75 ° C. or lower (more preferably about 65 ° C. or lower, for example, about 45 ° C. to 65 ° C.).

  The solvent (polymerization solvent) used for the solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane, etc. Halogenated alkanes; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; Any one kind of solvent or two or more kinds of mixed solvents can be used.

  The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of the polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of the polymerization initiator include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds And the like. Still another example of the polymerization initiator includes a redox initiator based on a combination of a peroxide and a reducing agent. Such a polymerization initiator can be used individually by 1 type or in combination of 2 or more types. The amount of the polymerization initiator used may be a normal amount, for example, about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight based on 100 parts by weight of all monomer components). Degree) range.

  According to the solution polymerization, a polymerization reaction liquid in a form in which an acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the technology disclosed herein may be formed from a pressure-sensitive adhesive composition containing the above-mentioned polymerization reaction liquid or an acrylic polymer solution obtained by subjecting the reaction liquid to an appropriate post-treatment. As said acrylic polymer solution, what prepared the said polymerization reaction liquid to the appropriate 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 (for example, emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used. Good.

The weight average molecular weight (Mw) of the base polymer (preferably an acrylic polymer) in the technique disclosed herein is not particularly limited, and may be, for example, in the range of about 10 × 10 ^{4 to} 500 × 10 ⁴ . From the viewpoint of adhesive performance, the Mw of the base polymer is about 30 × 10 ⁴ to 200 × 10 ⁴ (more preferably about 45 × 10 ^{4 to} 150 × 10 ⁴ , typically about 65 × 10 ^{4 to} 130 × 10 ^4. It is preferable that it exists in the range of ⁴ ). Here, Mw refers to a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used.

(Crosslinking agent)
The said crosslinking agent contains an epoxy-type crosslinking agent and an isocyanate type crosslinking agent. By using these two kinds of crosslinking agents in combination, the cohesive force of the pressure-sensitive adhesive layer can be sufficiently improved. Moreover, in the structure containing a base film (support base material), it is possible to ensure good adhesion to the base film. The pressure-sensitive adhesive layer in the technology disclosed herein contains the crosslinking agent in a form after the crosslinking reaction, a form before the crosslinking reaction, a partially crosslinked reaction, an intermediate or composite form thereof, and the like. obtain. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in the form after the crosslinking reaction.

  As the epoxy-based crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without 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 types.

  Although it does not specifically limit, As a specific example of an epoxy-type crosslinking agent, for example, N, N, N ', N'-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) ) Cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available epoxy crosslinking agents include trade names “TETRAD-C” and “TETRAD-X” manufactured by Mitsubishi Gas Chemical Company, “Epicron CR-5L” manufactured by DIC, and Nagase ChemteX Corp. Product name “Denacol EX-512”, product name “TEPIC-G” manufactured by Nissan Chemical Industries, Ltd., and the like.

  The amount of the epoxy crosslinking agent used is not particularly limited. The amount of the epoxy crosslinking agent used is, for example, more than 0 parts by weight and about 1 part by weight or less (typically about 0.001 to 0.5 parts by weight) with respect to 100 parts by weight of the acrylic polymer. be able to. From the viewpoint of suitably exhibiting the effect of improving the cohesive force, it is usually appropriate that the amount of the epoxy crosslinking agent used is about 0.002 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. 0.005 part by weight or more is preferable, and about 0.008 part by weight or more is more preferable. In addition, from the viewpoint of avoiding that the adhesion to the adherend and the substrate film is too low, the amount of the epoxy crosslinking agent used is usually about 0.2 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. It is appropriate that the amount is about 0.1 parts by weight or less, more preferably less than about 0.05 parts by weight, further less than about 0.03 parts by weight (for example, about 0.025 parts by weight or less). preferable.

  As the isocyanate-based crosslinking agent, a polyfunctional isocyanate (refers 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 types.

Examples of the polyfunctional isocyanate include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates and the like.
Specific examples of the aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanate such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, 1,4-tetramethylene diisocyanate; -Hexamethylene diisocyanate such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; Examples include 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

  Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate; 1,2-cyclopentyl diisocyanate, 1,3 -Cyclopentyl diisocyanate such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and the like.

  Specific examples of the aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and 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'-dimethoxy Diphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate.

  Preferable polyfunctional isocyanates include polyfunctional isocyanates having an average of 3 or more isocyanate groups per molecule. Such a trifunctional or higher functional isocyanate is a difunctional or trifunctional or higher polymer (typically a dimer or trimer), a derivative (for example, a polyhydric alcohol and two or more polyfunctional isocyanates). Addition reaction product), polymer and the like. For example, diphenylmethane diisocyanate dimer or trimer, hexamethylene diisocyanate isocyanurate (trimer adduct of isocyanurate structure), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexamer Examples of the reaction product with methylene diisocyanate include polyfunctional isocyanates such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. As commercial products of such polyfunctional isocyanates, trade names “Duranate TPA-100” manufactured by Asahi Kasei Chemicals, trade names “Coronate L”, “Coronate HL”, “Coronate HK” manufactured by Nippon Polyurethane Industry Co., Ltd. “Coronate HX”, “Coronate 2096” and the like.

  The amount of the isocyanate crosslinking agent used is not particularly limited. The amount of the isocyanate crosslinking agent used is, for example, more than 0 parts by weight and about 10 parts by weight or less (typically about 0.01 parts by weight to 10 parts by weight) with respect to 100 parts by weight of the acrylic polymer. can do. Usually, the amount of the isocyanate crosslinking agent used is suitably about 0.1 to 8 parts by weight, preferably about 0.3 to 5 parts by weight, preferably about 100 parts by weight of the acrylic polymer. More preferred is 0.5 to 4 parts by weight (for example, about 0.7 to 3.5 parts by weight). By using such an amount of the isocyanate-based crosslinking agent in combination with the epoxy-based crosslinking agent, the adhesion to the adherend and the substrate film and the cohesive force can be achieved at a high level. As a result, a pressure-sensitive adhesive sheet exhibiting good oil penetration prevention (oil resistance) and excellent holding performance (cohesive strength of the pressure-sensitive adhesive layer) can be realized.

  In the technology disclosed herein, the relationship between the content of the epoxy crosslinking agent and the content of the isocyanate crosslinking agent is not particularly limited. The content of the epoxy crosslinking agent can be, for example, about 1/50 or less of the content of the isocyanate crosslinking agent. From the viewpoint of more suitably achieving both adhesion to the adherend and substrate film and cohesion, the content of the epoxy crosslinking agent is suitably about 1/75 or less of the content of the isocyanate crosslinking agent. It is preferably about 1/100 or less (for example, 1/150 or less). Also, from the viewpoint of suitably exhibiting the effect of using an epoxy crosslinking agent and an isocyanate crosslinking agent in combination, the content of the epoxy crosslinking agent is usually about 1/1000 of the content of the isocyanate crosslinking agent. For example, it is appropriate to set it to about 1/500 or more.

  The pressure-sensitive adhesive composition in the technology disclosed herein contains other cross-linking agents as necessary in addition to the epoxy-based cross-linking agent and the isocyanate-based cross-linking agent as long as the effects of the present invention are not significantly impaired. Also good. Examples of such other crosslinking agents include oxazoline crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, aziridine crosslinking agents, metal chelate crosslinking agents, and the like. Or the adhesive composition which does not contain the said other crosslinking agent may be sufficient.

(Tackifying resin)
Examples of the tackifier resins include phenolic tackifier resins, terpene tackifier resins, modified terpene tackifier resins, rosin tackifier resins, hydrocarbon tackifier resins, epoxy tackifier resins, and polyamide tackifier resins. 1 type, or 2 or more types selected from well-known various tackifying resins, such as an elastomer type tackifying resin and a ketone type tackifying resin, can be used.

Examples of the phenolic tackifier resin include terpene phenol resin, hydrogenated terpene phenol resin, alkylphenol resin, and rosin phenol resin.
The terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue. A copolymer of a terpene and a phenol compound (terpene-phenol copolymer resin) and a terpene homopolymer or copolymer This is a concept that includes both phenol-modified products (phenol-modified terpene resins). Preferable examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene and limonene (including d-form, l-form and d / l-form (dipentene)). Is mentioned. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. Sometimes referred to as hydrogenated terpene phenol resin.
The alkylphenol resin is a resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include those of novolak type and resol type.
The rosin phenolic resin is typically a phenol-modified product of rosins or the above-mentioned various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosins and unsaturated fatty acid-modified rosin esters). Examples of the rosin phenol resin include a rosin phenol resin obtained by a method in which phenol is added to a rosin or the above-mentioned various rosin derivatives with an acid catalyst and thermally polymerized.

  Examples of terpene-based tackifier resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one terpene or a copolymer of two or more terpenes. Examples of the homopolymer of one kind of terpene include an α-pinene polymer, a β-pinene polymer, a dipentene polymer, and the like. Examples of the modified terpene resin include those obtained by modifying the terpene resin. Specific examples include styrene-modified terpene resins and hydrogenated terpene resins.

  The concept of rosin-based tackifying resin here includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins such as gum rosin, wood rosin, tall oil rosin (raw rosin); modified rosins modified with hydrogenation, disproportionation, polymerization, etc. Averaged rosin, polymerized rosin, other chemically modified rosins, etc.).

  The rosin derivative resin is typically a derivative of rosins as described above. The concept of the rosin resin here includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin and polymerized rosin). For example, rosin esters such as an unmodified rosin ester that is an ester of an unmodified rosin and an alcohol, and a modified rosin ester that is an ester of a modified rosin and an alcohol; for example, an rosin modified with an unsaturated fatty acid. Saturated fatty acid-modified rosins; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; for example, rosins or various rosin derivatives described above (rosin esters, unsaturated fatty acid-modified rosins and unsaturated Rosin alcohols obtained by reducing the carboxy group of fatty acid-modified rosin esters); for example, rosins or metal salts of the various rosin derivatives described above. Specific examples of rosin esters include unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) methyl ester, triethylene glycol ester, glycerin ester, pentaerythritol ester and the like.

  Examples of hydrocarbon tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc. ), Various hydrocarbon resins such as aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone indene resins, and the like.

  The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving the cohesive force, in one embodiment, a tackifier resin having a softening point (softening temperature) of about 80 ° C. or higher (preferably about 100 ° C. or higher) can be preferably used. In the technology disclosed herein, 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 entire tackifying resin contained in the pressure-sensitive adhesive layer. It can be preferably implemented in some embodiments. For example, a phenolic tackifier resin (terpene phenol resin or the like) having such a softening point can be preferably used. In a preferred embodiment, a terpene phenol resin having a softening point of about 135 ° C. or higher (or about 140 ° C. or higher) can be used. The upper limit of the softening point of the tackifier resin is not particularly limited. From the viewpoint of adhesion to an adherend or a substrate film, in one embodiment, a tackifying resin having a softening point of about 200 ° C. or lower (more preferably about 180 ° C. or lower) can be preferably used. In addition, the softening point of tackifying resin can be measured based on the softening point test method (ring ball method) prescribed | regulated to JISK2207.

  The content of the tackifying resin is preferably more than 10 parts by weight with respect to 100 parts by weight of the acrylic polymer. By this, the effect which improves the adhesiveness with respect to a to-be-adhered body is exhibited suitably, and the adhesive sheet which shows favorable oil penetration prevention property can be implement | achieved. From the viewpoint of obtaining higher adhesion, the content of the tackifier resin with respect to 100 parts by weight of the acrylic polymer is preferably about 15 parts by weight or more, and more preferably about 18 parts by weight (for example, about 20 parts by weight or more). The technique disclosed here can be preferably implemented in an embodiment in which the content of the tackifying resin with respect to 100 parts by weight of the acrylic polymer is about 25 parts by weight or more. The upper limit of the content of the tackifier resin is not particularly limited. In view of compatibility with the base polymer (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 usually about 70 parts by weight or less. It is preferably about 55 parts by weight or less, more preferably about 45 parts by weight or less (for example, about 40 parts by weight or less).

  A preferable embodiment includes an embodiment in which the tackifying resin contains one or more phenolic tackifying resins (typically terpene phenol resins). By using the phenol-based tackifying resin, the adhesiveness of the pressure-sensitive adhesive layer to the adherend can be improved, and the infiltration of oil from the interface with the adherend can be effectively suppressed. In addition, the phenol tackifier resin tends to have a lower affinity for oil than, for example, rosin tackifier resins. Therefore, the inclusion of the phenol tackifying resin can also help to suppress the infiltration (oil absorption) of oil into the pressure-sensitive adhesive layer. The technology disclosed herein can be preferably implemented in a mode in which, for example, about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of the tackifying resin is a terpene phenol resin. About 50% by weight or more of the total amount of the tackifying resin may be terpene phenol resin, and about 80% by weight or more (for example, about 90% by weight or more) may be terpene phenol resin. Substantially all of the tackifying resin (eg, about 95-100% by weight, or even about 99-100% by weight) may be a terpene phenol resin. The content of the phenolic tackifying resin (for example, terpene phenolic resin) is in the range of about 5 to 55 parts by weight (for example, more than about 10 parts by weight and 55 parts by weight or less) with respect to 100 parts by weight of the acrylic polymer. It is suitable that it is within the range of about 15 to 45 parts by weight (for example, about 20 to 40 parts by weight).

  Although not particularly limited, as the tackifier resin in the technology disclosed herein, a tackifier resin having a hydroxyl value higher than 20 mgKOH / g can be used, and in particular, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more is used. It can be preferably used. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more may be referred to as a “high hydroxyl value resin”. According to the tackifier resin containing such a high hydroxyl value resin, an adhesive layer having excellent adhesion to the adherend and high cohesion can be realized. The use of a high hydroxyl value resin can also help reduce the oil affinity of the pressure-sensitive adhesive layer. In a preferred embodiment, the tackifying resin may contain a high hydroxyl value resin having a hydroxyl value of 50 mgKOH / g or more (more preferably 70 mgKOH / g or more).

Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method defined in JIS K0070: 1992 can be adopted. The specific measurement method is as follows.
[Measurement method of hydroxyl value]
1. Reagent (1) As an acetylating reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, and pyridine is added thereto to make a total volume of 50 mL, and the mixture is sufficiently stirred. Alternatively, about 25 g (about 23.5 mL) of acetic anhydride is taken, and pyridine is added thereto to make a total volume of 100 mL, and the mixture is sufficiently stirred.
(2) As a measuring reagent, a 0.5 mol / L potassium hydroxide ethanol solution is used.
(3) Prepare toluene, pyridine, ethanol and distilled water.
2. Operation (1) About 2 g of a sample is accurately weighed in a flat bottom flask, 5 mL of an acetylating reagent and 10 mL of pyridine are added, and an air cooling tube is attached.
(2) The flask was heated in a bath at 100 ° C. for 70 minutes, allowed to cool, and 35 mL of toluene was added as a solvent from the top of the condenser and stirred, and then 1 mL of distilled water was added and stirred to acetic anhydride. Disassemble. Heat again in the bath for 10 minutes to complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Next, 50 mL of pyridine is added as a solvent and stirred.
(4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a whole pipette.
(5) Potentiometric titration with 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is the end point.
(6) In the blank test, the above (1) to (5) are performed without putting a sample.
3. Calculation The hydroxyl value is calculated by the following formula.
Hydroxyl value (mgKOH / g) = [(BC) × f × 28.05] / S + D
here,
B: Amount of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test (mL),
C: The amount of 0.5 mol / L potassium hydroxide ethanol solution used for the sample (mL),
f: factor of 0.5 mol / L potassium hydroxide ethanol solution,
S: weight of the sample (g),
D: Acid value,
28.05: 1/2 of the molecular weight of potassium hydroxide 56.11,
It is.

  As high hydroxyl value resin, what has the hydroxyl value more than predetermined value among the various tackifying resin mentioned above can be used. High hydroxyl value resin can be used individually by 1 type or in combination of 2 or more types. For example, a phenolic tackifier resin having a hydroxyl value of 30 mgKOH / g or more can be preferably employed as the high hydroxyl value resin. In a preferable embodiment, a terpene phenol resin having a hydroxyl value of 30 mgKOH / g or more is used as the tackifier resin. The terpene phenol resin is advantageous because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol.

  The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the base polymer, the hydroxyl value of the high hydroxyl value resin is usually appropriately about 200 mgKOH / g or less, preferably about 180 mgKOH / g or less, more preferably about 160 mgKOH / g or less, Preferably, it is about 140 mgKOH / g or less. The technology disclosed herein can be preferably implemented in an embodiment in which the tackifying resin contains a high hydroxyl value resin (for example, a phenolic tackifying resin, preferably a terpene phenol resin) having a hydroxyl value of 30 to 160 mgKOH / g.

  Although not particularly limited, when a high hydroxyl value resin is used, the proportion of the high hydroxyl value resin (for example, terpene phenol resin) in the entire tackifying resin contained in the pressure-sensitive adhesive layer is, for example, about 25% by weight or more. About 30% by weight or more is preferable, and about 50% by weight or more (eg, about 80% by weight or more, typically about 90% by weight or more) is more preferable. Substantially all of the tackifying resin (for example, about 95 to 100% by weight, and further about 99 to 100% by weight) may be a high hydroxyl value resin.

  As the high hydroxyl value resin, a resin R1 having a hydroxyl value of less than 70 mgKOH / g and a resin R2 having a hydroxyl value of 70 mgKOH / g or more may be used in combination. Although not particularly limited, the content of the resin R2 can be about 0.2 to 5 times the content of the resin R1, and usually about 0.3 to 3 times is appropriate. It is. The content of the resin R2 may be about 1 to 3 times the content of the resin R1.

(Other additives)
In addition to the above-described components, the pressure-sensitive adhesive composition includes a leveling agent, a crosslinking aid, a plasticizer, a softener, an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, and a light stabilizer as necessary. Various additives that are common in the field of pressure-sensitive adhesives may be included. About such various additives, conventionally well-known things can be used by a conventional method, and since it does not characterize this invention in particular, detailed description is abbreviate | omitted.

  The pressure-sensitive adhesive layer (layer made of pressure-sensitive adhesive) disclosed herein is formed from a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, and an active energy ray-curable pressure-sensitive adhesive composition. It can be an adhesive layer. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer forming component) in a water-based solvent (water-based solvent), and is typically dispersed in water. What is called a type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like are included. Moreover, a solvent-type adhesive composition means the adhesive composition of the form which contains an adhesive in an organic solvent. The technique disclosed here can be preferably implemented in an aspect including a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition from the viewpoint of pressure-sensitive adhesive properties and the like.

  The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method of forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition to a peelable surface (peeling surface) or a non-peelable surface and drying it can be employed. In the pressure-sensitive adhesive sheet having a base film, for example, a method (direct method) for forming a pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to the base film and drying it. Can be adopted. Also, a method (transfer method) in which a pressure-sensitive adhesive composition is applied to a peelable surface (peeling surface) and dried to form a pressure-sensitive adhesive layer on the surface, and the pressure-sensitive adhesive layer is transferred to a base film. ) May be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of the release liner, the back surface of the substrate film subjected to the release treatment, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, for example, a regular or random pattern such as a dot or stripe. The formed adhesive layer may be sufficient.

The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating.
From the viewpoint of promoting the crosslinking reaction and improving the production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. A drying temperature can be about 40-150 degreeC, for example, and it is preferable to usually be about 60-130 degreeC. After drying the pressure-sensitive adhesive composition, further aging is performed for the purpose of adjusting the component transfer in the pressure-sensitive adhesive layer, progress of the crosslinking reaction, alleviating the distortion that may exist in the base film or the pressure-sensitive adhesive layer, etc. Also good.

The thickness of the pressure-sensitive adhesive layer is not particularly limited. From the viewpoint of avoiding an excessively thick adhesive sheet, the thickness of the adhesive layer is usually about 100 μm or less, preferably about 70 μm or less, more preferably about 50 μm or less, more preferably about 30 μm or less. It is. In a preferred embodiment, the thickness of the pressure-sensitive adhesive layer may be about 28 μm or less, about 25 μm or less (for example, less than 25 μm), and further about 20 μm or less. Generally, when the thickness of the pressure-sensitive adhesive layer is reduced, the adhesion to the adherend is lowered, and oil intrusion from the interface with the adherend tends to occur. Therefore, it is particularly meaningful to apply the technique disclosed herein to prevent oil intrusion from the interface. It may be a pressure-sensitive adhesive sheet having such a thickness of the pressure-sensitive adhesive layer on one side or both sides of the base film.
The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesion to the adherend, it is advantageous to be about 4 μm or more, preferably about 6 μm or more, more preferably about 10 μm or more (for example, About 15 μm or more). It may be a pressure-sensitive adhesive sheet having such a thickness of the pressure-sensitive adhesive layer on one side or both sides of the base film.

<Base film>
In the pressure-sensitive adhesive sheet including the base film, those including a resin film as the base film can be preferably used as the base film. The base film is typically a member capable of maintaining its shape independently (independent). The base film in the technology disclosed herein can be substantially composed of such a base film. Alternatively, the base film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an undercoat layer, an antistatic layer, and a colored layer provided on the surface of the base film.

  The resin film is a film containing a resin material as a main component (a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene / propylene copolymers; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. Polyester resin film; vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; The resin film may be a rubber film such as a natural rubber film or a butyl rubber film. Of these, a polyester film is preferable from the viewpoint of handling properties and processability, and a PET film is particularly preferable. In the present specification, the “resin film” is typically a non-porous sheet and is a concept that is distinguished from a so-called nonwoven fabric or woven fabric (in other words, a concept that excludes nonwoven fabric or woven fabric). is there.

  For the resin film (for example, PET film), a filler (inorganic filler, organic filler, etc.), a colorant, a dispersant (surfactant, etc.), an anti-aging agent, an antioxidant, an ultraviolet ray, as necessary. Various additives such as an absorbent, an antistatic agent, a lubricant, and a plasticizer may be blended. The blending ratio of various additives is usually less than about 30% by weight (for example, less than about 20% by weight, typically less than about 10% by weight).

  The resin film may have a single layer structure or may have a multilayer structure of two layers, three layers or more. From the viewpoint of shape stability, the resin film preferably has a single layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (for example, polyester resin). The method for producing the resin film is not particularly limited as long as a conventionally known method is appropriately employed. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately employed.

  In the pressure-sensitive adhesive sheet including the base film, the thickness of the base film is not particularly limited. From the viewpoint of avoiding an excessively thick adhesive sheet, the thickness of the base film can be, for example, about 200 μm or less, preferably about 150 μm or less, more preferably about 100 μm or less. Depending on the purpose and mode of use of the pressure-sensitive adhesive sheet, the thickness of the base film may be about 70 μm or less, about 50 μm or less, or about 30 μm or less (for example, about 25 μm or less). In one embodiment, the thickness of the base film may be about 20 μm or less, about 15 μm or less, or about 10 μm or less (for example, about 5 μm or less). By reducing the thickness of the base film, the thickness of the pressure-sensitive adhesive layer can be increased even if the total thickness of the pressure-sensitive adhesive sheet is the same. This can be advantageous from the viewpoint of improving the adhesion to the substrate. The lower limit of the thickness of the base film is not particularly limited. From the viewpoint of handling property (handling property) and processability of the pressure-sensitive adhesive sheet, the thickness of the base film is usually about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example, about 4 μm or more. . In one embodiment, the thickness of the base film can be about 6 μm or more, about 8 μm or more, or about 10 μm or more (for example, more than 10 μm).

  The surface of the base film may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer. Such a 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.

<Release liner>
In the technology disclosed herein, a release liner can be used in forming the pressure-sensitive adhesive layer, preparing the pressure-sensitive adhesive sheet, storing the pressure-sensitive adhesive sheet before use, distributing it, and processing the shape. The release liner is not particularly limited. 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 fluoropolymer (polytetrafluoroethylene, etc.), a polyolefin resin (polyethylene, A release liner made of a low adhesion material such as polypropylene can be used. The release treatment layer may be formed, for example, by surface-treating the liner base material with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Adhesive sheet>
The total thickness of the pressure-sensitive adhesive sheet disclosed herein (including a pressure-sensitive adhesive layer and further including a base material film but not including a release liner is not particularly limited). The total thickness of the pressure-sensitive adhesive sheet can be, for example, about 500 μm or less. From the viewpoint of reducing the thickness of the portable device, it is usually about 350 μm or less, preferably about 250 μm or less (for example, about 200 μm or less). The technology disclosed herein is in the form of a pressure-sensitive adhesive sheet (typically a double-sided pressure-sensitive adhesive sheet) 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 50 μm or less). It can be preferably implemented. The lower limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, but is usually about 10 μm or more, preferably about 20 μm or more, and more preferably about 30 μm or more.

  The adhesive strength of the adhesive sheet disclosed here is not particularly limited. The pressure-sensitive adhesive sheet according to a preferred embodiment has a 180-degree peel strength of about 17 N / 25 mm or more. The pressure-sensitive adhesive sheet exhibiting such adhesive strength has high adhesion to the adherend, and therefore can be excellent in performance to prevent oil penetration. A pressure-sensitive adhesive sheet having a 180 degree peel strength of about 17.5 N / 25 mm or more (more preferably about 18 N / 25 mm or more, for example, about 18.5 N / 25 mm or more) is more preferable. From the standpoint that the higher the adhesion to the adherend, the better, the upper limit of the 180 degree peel strength is not particularly limited, but is usually about 80 N / 25 mm or less (typically about 70 N / 25 mm or less, for example, about 50 N / 25 mm or less) is appropriate.

  Here, the 180-degree peel strength refers to 180-degree peel strength (180-degree peeling adhesive strength) with respect to a stainless steel plate. The 180 degree peel strength can be measured as follows. Specifically, for the measurement sample obtained by cutting the pressure-sensitive adhesive sheet into a size of 25 mm in width and 100 mm in length, the pressure-sensitive adhesive surface of the measurement sample is the surface of a stainless steel plate (SUS304BA plate) in an environment of 23 ° C. and 50% RH. Then, a 2 kg roller is reciprocated once to be pressure-bonded. After leaving this in the same environment for 30 minutes, using a universal tensile compression tester, in accordance with JIS Z 0237: 2000, under conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees, the peel strength (N / 25 mm). As a universal tensile and compression tester, for example, “Tensile and compression tester, TG-1kN” manufactured by Minebea can be used. A similar measurement method is employed in the examples described later.

<Application>
The pressure-sensitive adhesive sheet disclosed herein has high retention performance and good oil resistance (oil content) in which oil infiltration from the interface between the pressure-sensitive adhesive layer and the adherend is suppressed in addition to oil absorption into the pressure-sensitive adhesive layer itself. Penetration resistance). Taking advantage of such characteristics, the pressure-sensitive adhesive sheet can be preferably used for fixing members in various portable devices (portable devices). For example, it is suitable for fixing members for portable electronic devices. Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear devices that are worn on the wrist like watches, clips, straps, etc. Modular type, eyeglass type (monocular type or binocular type, including head mount type), clothing type that attaches to shirts, socks, hats, etc. in the form of accessories, earphones, etc. Earphone type that attaches to the ear, etc.), digital camera, digital video camera, audio equipment (portable music player, IC recorder, etc.), calculator (calculator, etc.), portable game device, electronic dictionary, electronic notebook, electronic book, in-vehicle Information equipment, portable radio, portable television, portable printer, portable scanner, portable modem, and the like. Non-limiting examples of portable devices other than portable electronic devices include mechanical wristwatches, pocket watches, flashlights, hand mirrors, time slots and the like. In this specification, “carrying” means that it is not sufficient to be able to carry it alone, but that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. Shall mean.

  The pressure-sensitive adhesive sheet disclosed here (typically, a double-sided pressure-sensitive adhesive sheet) can be used for fixing members constituting a mobile device in the form of a bonding material processed into various external shapes. A particularly preferable application is an application of fixing a member constituting a portable electronic device. Especially, 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 use.

  As a preferable form of such a bonding material, a form having a narrow part having a width of 4.0 mm or less (for example, 2.0 mm or less, typically less than 2.0 mm) can be given. The pressure-sensitive adhesive sheet disclosed here is excellent in cohesive strength in addition to oil resistance, so even if it is used as a bonding material with such a narrow width part (for example, frame shape), the member can be fixed well. can do. In one embodiment, the width of the narrow portion may be 1.5 mm or less, 1.0 mm or less, or about 0.5 mm or less. Although the minimum of the width | variety of a narrow part is not restrict | limited in particular, Usually, 0.1 mm or more (typically 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” is a concept including a linear shape, a curved shape, a bent line shape (for example, an L shape), a ring shape such as a frame shape or a circular shape, or a composite or intermediate shape thereof. . The annular shape is not limited to a curved line, and a part or all of the shape is linearly formed, for example, a shape along the outer periphery of a square (frame shape) or a shape along a fan-shaped outer periphery. It is a concept that includes a ring. The length of the narrow portion is not particularly limited. For example, in the form in which the length of the narrow width portion is 10 mm or more (typically 20 mm or more, for example, 30 mm or more), the effect of applying the technique disclosed herein can be suitably exhibited.

The matters disclosed by this specification include the following.
(1) An adhesive sheet used for fixing a member in a portable device,
A base film, and an adhesive layer disposed on at least one surface of the base film,
The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer, a tackifier resin, and a crosslinking agent,
The monomer component constituting the acrylic polymer contains C _1-6 alkyl (meth) acrylate more than about 50% by weight,
The content of the tackifying resin is an amount exceeding about 10 parts by weight with respect to 100 parts by weight of the acrylic polymer (for example, more than about 10 parts by weight and 55 parts by weight or less),
The said crosslinking agent is an adhesive sheet containing an epoxy-type crosslinking agent and an isocyanate type crosslinking agent.
(2) The pressure-sensitive adhesive sheet according to (1), wherein the tackifying resin includes a phenol-based tackifying resin.
(3) The pressure-sensitive adhesive sheet according to (2), wherein the content of the phenolic tackifying resin is an amount exceeding about 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.
(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3), wherein the tackifier resin includes a tackifier resin having a hydroxyl value of about 30 mgKOH / g or more.
(5) The pressure-sensitive adhesive sheet according to any one of (1) to (4), wherein the monomer component contains about 0.5 wt% to about 10 wt% of a carboxy group-containing monomer.
(6) The pressure-sensitive adhesive sheet according to any one of (1) to (5), wherein the content of the epoxy crosslinking agent is less than about 0.05 parts by weight with respect to 100 parts by weight of the acrylic polymer.
(7) The pressure-sensitive adhesive sheet according to any one of (1) to (6), wherein the content of the epoxy crosslinking agent is about 1/100 or less of the content of the isocyanate crosslinking agent.
(8) The pressure-sensitive adhesive sheet according to any one of (1) to (7), wherein the pressure-sensitive adhesive layer has a thickness of about 25 μm or less.
(9) The pressure-sensitive adhesive sheet according to any one of (1) to (8), wherein the 180-degree peel strength is about 17 N / 25 mm or more.
(10) The pressure-sensitive adhesive sheet according to any one of (1) to (9), wherein the pressure-sensitive adhesive layer is configured as a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer on one surface and the other surface of the base film.

(11) About 80% by weight or more (for example, about 95% by weight or more) of the C _1-6 alkyl (meth) acrylate is an alkyl acrylate having a linear alkyl group having 3 to 6 carbon atoms at the ester end. The pressure-sensitive adhesive sheet according to any one of (1) to (10) above.
(12) The pressure-sensitive adhesive sheet according to any one of (1) to (11), wherein the monomer component contains more than about 50% by weight (preferably 80% by weight or more) of butyl acrylate.
(13) Any of (1) to (12) above, wherein the monomer component has a C _7-18 alkyl (meth) acrylate content of about 0 to 10% by weight (for example, about 0 to 5% by weight). The pressure-sensitive adhesive sheet described in 1.
(14) The pressure-sensitive adhesive sheet according to any one of (1) to (13), wherein the pressure-sensitive adhesive layer contains about 15 parts by weight or more of a terpene phenol resin with respect to 100 parts by weight of the acrylic polymer.
(15) The above pressure-sensitive adhesive layer contains about 15 parts by weight or more of a tackifier resin having a hydroxyl value of about 30 mgKOH / g or more (for example, about 50 mgKOH / g or more) with respect to 100 parts by weight of the acrylic polymer (1 ) To (14).
(16) The pressure-sensitive adhesive sheet according to any one of (1) to (15), wherein the base film is a single-layer PET film.
(17) The pressure-sensitive adhesive sheet according to any one of (1) to (16), wherein the pressure-sensitive adhesive sheet has a narrow portion, and the width of the narrow portion is about 0.2 mm or more and less than about 2.0 mm. Sheet.

(18) An adhesive sheet used for fixing a member in a portable device,
It is configured as a double-sided pressure-sensitive adhesive sheet comprising a base film, and a pressure-sensitive adhesive layer disposed on one surface and the other surface of the base film,
The pressure-sensitive adhesive layer has a thickness of about 10 μm to about 25 μm, and the double-sided pressure-sensitive adhesive sheet has a total thickness of about 30 μm to less than about 60 μm,
The base film is a PET film,
The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer, a terpene phenol resin as a tackifier resin, and a crosslinking agent,
The monomer component constituting the acrylic polymer contains butyl acrylate more than 80% by weight, and the content of C _7-18 alkyl (meth) acrylate is about 0 to 5% by weight,
The monomer component contains about 3 to 8% by weight of a carboxy group-containing monomer,
The content of the terpene phenol resin is about 15 to 45 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The crosslinking agent includes an epoxy crosslinking agent and an isocyanate crosslinking agent,
The content of the epoxy crosslinking agent is less than about 0.05 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The content of the isocyanate-based crosslinking agent is less than about 4 parts by weight with respect to 100 parts by weight of the acrylic polymer, and the content of the epoxy-based crosslinking agent is approximately 1 / of the content of the isocyanate-based crosslinking agent. The adhesive sheet which is 100 or less.

(19) A portable device having a member fixed using the pressure-sensitive adhesive sheet according to any one of (1) to (18).
(20) The mobile device according to (19), wherein the mobile device is a wearable device (for example, a wristwear type wearable device).

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

<Preparation of pressure-sensitive adhesive composition>
[Example 1]
A reactor equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel was charged with 95 parts of BA and 5 parts of AA as monomer components and 233 parts of ethyl acetate as a polymerization solvent, and nitrogen gas was introduced. The mixture was stirred for 2 hours. After removing oxygen in the polymerization system in this way, 0.2 part of 2,2′-azobisisobutyronitrile was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 8 hours to obtain an acrylic polymer. A solution was obtained. The acrylic polymer had an Mw of about 70 × 10 ⁴ .
In the acrylic polymer solution, terpene phenol resin (trade name “YS Polystar T-115”, softening point of about 115 ° C., hydroxyl value of 30 to 60 mg KOH as a tackifier resin with respect to 100 parts of the acrylic polymer contained in the solution. / G, manufactured by Yasuhara Chemical Co., Ltd .; hereinafter referred to as “tackifier resin A”) and 75 parts of an isocyanate-based crosslinking agent (trade name “Coronate L”, trimethylolpropane / tolylene diisocyanate trimer adduct as a crosslinking agent. % Ethyl acetate solution, manufactured by Nippon Polyurethane Industry Co., Ltd .; hereinafter referred to as “isocyanate-based crosslinking agent A” 2 parts and epoxy-based crosslinking agent (trade name “TETRAD-C”, 1,3-bis (N, N-diglycidyl) Aminomethyl) cyclohexane, manufactured by Mitsubishi Gas Chemical Company; hereinafter referred to as “epoxy-based crosslinking agent B”). And 1 part added to prepare a pressure-sensitive adhesive composition was stirred and mixed.

[Examples 2 to 10]
In the preparation of the pressure-sensitive adhesive composition according to Example 1, the types and amounts used of the tackifying resin used and the types and amounts used of the crosslinking agent used were set as shown in Tables 1 and 2. About the other point, it carried out similarly to Example 1, and prepared the adhesive composition which concerns on Examples 2-10, respectively. Here, tackifying resin B in Tables 1 and 2 is a trade name “YS Polystar S-145” (terpene phenol resin, softening point of about 145 ° C., hydroxyl value of 70 to 110 mg KOH / g) manufactured by Yasuhara Chemical Co., Ltd. The imparting resin C is a trade name “TAMANOL 803L” (terpene phenol resin, softening point of about 145 to 160 ° C., hydroxyl value of 1 to 20 mgKOH / g) manufactured by Arakawa Chemical Industries, Ltd. In Tables 1 and 2, “(part)” indicates the amount used relative to 100 parts of the acrylic polymer.

[Examples 11 and 12]
In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel, 90 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of AA as a monomer component, and 199 parts of ethyl acetate as a polymerization solvent And stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 part of benzoyl peroxide was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 6 hours to obtain an acrylic polymer solution. Mw of this acrylic polymer was about 120 × 10 ⁴ .
The pressure-sensitive adhesive composition according to Examples 11 and 12, using the above-mentioned acrylic polymer solution with 100 parts of the acrylic polymer contained in the solution using the types and amounts of tackifying resins and crosslinking agents shown in Table 2. Were prepared respectively.

[Examples 13 to 15]
In the preparation of the pressure-sensitive adhesive composition according to Example 1, only one of an isocyanate crosslinking agent and an epoxy crosslinking agent was used in the amount shown in Table 2. About the other point, it carried out similarly to Example 1, and prepared the adhesive composition which concerns on Examples 13-15, respectively.

<Production of adhesive sheet>
[Examples 1 to 15]
Two release films made of polyester (trade name “Diafoil MRF”, thickness 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) were prepared as release liners. 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 layers formed on the two release liners were bonded to the first and second surfaces of a transparent substrate 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 used for protecting the surface (adhesive surface) of the pressure-sensitive adhesive layer. As the base material film, a PET film (resin film) manufactured by Toray Industries, Inc. and a trade name “Lumirror” were used.

[Example 16]
The pressure-sensitive adhesive composition according to Example 4 was applied to the release surface of the above-mentioned 38 μm thick polyester release film (trade name “Diafoil MRF”, manufactured by Mitsubishi Polyester), and dried at 100 ° C. for 2 minutes to obtain a thickness. A 25 μm pressure-sensitive adhesive layer was formed. The release surface of a 25 μm thick polyester release film (trade name “Diafoil MRF”, 25 μm thick, manufactured by Mitsubishi Polyester) was bonded to this pressure-sensitive adhesive layer. In this way, a base-less double-sided pressure-sensitive adhesive sheet having a thickness of 25 μm and having both sides protected by the two polyester release films was obtained.

  After the obtained double-sided PSA sheet was cured for 1 day in an environment of 23 ° C. and 50% RH, the following evaluation test was performed on the double-sided PSA sheet.

<Evaluation test>
[180 degree peel strength]
In a measurement environment of 23 ° C. and 50% RH, a 50 μm-thick polyethylene terephthalate (PET) film is pasted on one adhesive surface of a double-sided adhesive sheet, and then cut into a size of 25 mm in width and 100 mm in length. A measurement sample was prepared. About the other adhesion surface of the measurement sample, 180 degree peel strength (N / 25mm) was measured by the method mentioned above.

[Retention force]
A holding power test was performed according to JIS Z 0237 (2004). That is, in an environment of 23 ° C. and 50% RH, a PET film having a thickness of 50 μm was attached to one adhesive surface of the double-sided pressure-sensitive adhesive sheet, lined, and cut into a width of 10 mm to prepare a measurement sample. The other adhesive surface of the measurement sample was attached to a bakelite plate as an adherend with an adhesive area of 10 mm width and 20 mm length. The measurement sample attached to the adherend in this manner was dropped in an environment of 80 ° C. and left for 30 minutes, and then a 1 kg load was applied to the free end of the measurement sample. With respect to the measurement sample after being left for 1 hour in an environment at 80 ° C. with the load applied, the displacement distance (mm) from the first application position was measured.

[Oil penetration distance]
Under an environment of 23 ° C. and 50% RH, a PET film having a thickness of 50 μm was attached to one adhesive surface of the double-sided pressure-sensitive adhesive sheet, lined, and cut into a 30 mm square to prepare a measurement sample. After the other adhesive surface of this measurement sample was attached to a stainless steel plate (SUS304BA plate) and left for 30 minutes, oleic acid was transferred from the entire back surface of the measurement sample (the surface of the PET film) to the stainless steel plate around the measurement sample. It was applied evenly and kept in an environment of 65 ° C. and 95% RH for 72 hours. Thereafter, the oleic acid was wiped off, and the distance (oil penetration distance) at which the oleic acid entered from the outer edge of the measurement sample to the inside of the measurement sample was measured. Specifically, for each of the four sides constituting the outer edge of the measurement sample, the distance at which the oleic acid penetrated most into that side was measured, and the average value thereof was calculated.

[Throwing property]
The double-sided pressure-sensitive adhesive sheets according to Examples 1 to 15 were cut into a size of 100 mm in length and 20 mm in width, and one of the pressure-sensitive adhesive surfaces was attached to a stainless steel plate and fixed. The other adhesive surface was exposed, and the tester rubbed the adhesive surface lightly in one direction with a finger. After repeating this operation 30 times in succession, the degree of removal of the adhesive layer from the base film is E (Excellent) when the adhesive layer is not removed, and the initial 70 area% or more G (Good) when the pressure-sensitive adhesive layer remains, A (Acceptable) when the pressure-sensitive adhesive layer of 50% by area or more and less than 70% by area remains, the pressure-sensitive adhesive layer remaining on the base film Was less than 50 area% at the beginning, it was evaluated as P (Poor).
The obtained results are shown in Tables 1 and 2 together with the schematic configuration of the pressure-sensitive adhesive sheet according to each example.

As shown in Tables 1 and 2, Example 1 in which an acrylic polymer containing more than 50% by weight of C _1-6 alkyl (meth) acrylate was used as a base polymer and an epoxy crosslinking agent and an isocyanate crosslinking agent were used in combination. Each of the adhesive sheets of -8 and Example 16 had an oil penetration distance of 5 mm or less, and exhibited good oil penetration prevention properties. Moreover, as for these adhesive sheets, the gap | deviation in holding power evaluation is 2.5 mm or less, and it was confirmed that the outstanding cohesive force (holding characteristic) is shown. Particularly good results were obtained with the pressure-sensitive adhesive sheets according to Examples 1 to 7.

In contrast, Examples 11 and 12 the main monomer usage 10 parts or less is Examples 9 and 10 and the acrylic polymer of the tackifier resin to 100 parts of the acrylic polymer is a C ₈ alkyl acrylates are all The oil penetration distance was long and the oil penetration prevention property was low. In Examples 13 and 14 in which the isocyanate crosslinking agent was used alone, the holding power was low. In Example 15 in which the epoxy-based crosslinking agent was used alone, the oil penetration distance was long and the anchoring property was low.

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

DESCRIPTION OF SYMBOLS 1, 2 Adhesive sheet 10 Base film 10A 1st surface 10B 2nd surface 21 1st adhesive layer 22 2nd adhesive layer 21A 1st adhesive surface 22A 2nd adhesive surface 31, 32 Release liner

Claims (11)

An adhesive sheet used for fixing a member in a portable device,
Including a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition including an acrylic polymer as a base polymer, a tackifier resin, and a crosslinking agent;
The monomer component constituting the acrylic polymer contains more than 50% by weight of an alkyl (meth) acrylate having an alkyl group having 1 to 6 carbon atoms at the ester end,
The content of the tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer,
The said crosslinking agent is an adhesive sheet containing an epoxy-type crosslinking agent and an isocyanate type crosslinking agent.   The pressure-sensitive adhesive sheet according to claim 1, wherein the tackifying resin includes a phenol-based tackifying resin.   The pressure-sensitive adhesive sheet according to claim 2, wherein the content of the phenolic tackifying resin is an amount exceeding 10 parts by weight with respect to 100 parts by weight of the acrylic polymer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the tackifier resin includes a tackifier resin having a hydroxyl value of 30 mgKOH / g or more.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the monomer component contains 0.5 wt% to 10 wt% of a carboxy group-containing monomer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the content of the epoxy-based crosslinking agent is less than 0.05 parts by weight with respect to 100 parts by weight of the acrylic polymer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the content of the epoxy-based crosslinking agent is 1/100 or less of the content of the isocyanate-based crosslinking agent.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive layer has a thickness of 30 µm or less.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the 180-degree peel strength is 17 N / 25 mm or more.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, further comprising a base film that supports the pressure-sensitive adhesive layer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 10, wherein the pressure-sensitive adhesive sheet 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 film.

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