JP5783768B2 - Acrylic diblock copolymer pellets and pressure-sensitive adhesive composition containing the same - Google Patents

Description

  The present invention relates to a pellet made of a specific acrylic diblock copolymer, a pressure-sensitive adhesive composition containing the pellet, and a pressure-sensitive adhesive product having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition.

  The pressure-sensitive adhesive is used for producing a pressure-sensitive adhesive product having a pressure-sensitive adhesive layer on at least a part of the surface of a base material such as a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive film, or a pressure-sensitive adhesive tape. As a method for forming this adhesive layer, conventionally, a method in which a base polymer such as natural rubber or synthetic rubber is dissolved in an organic solvent to produce a solution-type adhesive, which is applied to a substrate, and the organic solvent is evaporated is often used. It had been. In recent years, from the viewpoint of prevention of environmental pollution, safety, resource saving, etc., instead of solution type adhesives, in the state of hot melt type adhesives and aqueous emulsions that are used by applying to a substrate in a molten state Aqueous emulsion-type pressure-sensitive adhesives that are used by being applied to a substrate have been widely used.

  As a base polymer for a hot-melt pressure-sensitive adhesive, a styrene-based triblock copolymer composed of an aromatic vinyl compound polymer block, a conjugated diene polymer block, and an aromatic vinyl compound polymer block is known (for example, Patent Document 1). The pressure-sensitive adhesive produced using this styrene-based triblock copolymer has excellent adhesive properties at room temperature and low temperature, and has features such that it can easily flow when heated and can be easily applied to a substrate. . However, the pressure-sensitive adhesive using the styrene-based triblock copolymer has a carbon-carbon double bond derived from the conjugated diene polymer block or an aromatic ring derived from the aromatic vinyl compound polymer block in the molecule. Therefore, it is easily deteriorated by ultraviolet rays and heat, and is not suitable for applications that are exposed to high temperature or ultraviolet irradiation after use.

  In response to this problem, it has been proposed to use an acrylic block copolymer or an acrylic block copolymer composition as an adhesive. For example, a methacrylic acid alkyl ester polymer having a glass transition temperature of 110 ° C. or higher and a syndiotacticity of 70% or higher at both ends of a (meth) acrylic acid alkyl ester polymer block having a glass transition temperature of 30 ° C. or lower. A block copolymer composition containing a triblock copolymer having a block bonded thereto, a (meth) acrylic acid alkyl ester diblock copolymer, and a pressure-sensitive adhesive comprising the composition are disclosed (for example, patents). Reference 2). Also known is a pressure-sensitive adhesive composition containing a specific diblock copolymer composed of a methacrylic acid alkyl ester polymer block and an acrylic acid alkyl ester polymer block and a (meth) acrylic acid ester triblock copolymer. (For example, see Patent Document 3). Further, a (meth) acrylate triblock copolymer and a (meth) acrylate diblock copolymer having a weight average molecular weight of 120,000 or more and a molecular weight distribution (Mw / Mn) of less than 1.5, There is known a pressure-sensitive adhesive composition containing azobenzene (for example, see Patent Document 4).

  The pressure-sensitive adhesives and pressure-sensitive adhesive compositions described in Patent Documents 2, 3 and 4 have various pressure-sensitive adhesive properties such as holding power at high temperatures (for example, a creep test at 80 ° C.), heat resistance, weather resistance, It is superior to conventional pressure-sensitive adhesives and pressure-sensitive adhesive compositions in terms of bleed resistance and hot melt properties. However, these pressure-sensitive adhesive compositions are mainly composed of (meth) acrylic acid ester-based triblock copolymers, and are further (meth) acrylic acid ester-based diblocks in order to impart flexibility, tackiness, and adhesiveness. Copolymer is blended, but this diblock copolymer may be liquid and fluid, so when manufacturing an adhesive composition continuously using an extruder, etc. There was a problem in the supply method.

US Pat. No. 3,676,202 Japanese Patent Laid-Open No. 11-323072 Japanese Patent Laid-Open No. 2004-2736 JP 2005-307063 A JP-A-11-335432 Japanese Patent Publication No. 7-25859 JP-A-6-93060

Macromol. Chem. Phys. 2000, 201, p1108 to 1114

  The object of the present invention is a polymer suitable as an adhesive that is excellent in various adhesive properties such as holding power at high temperatures, has good heat resistance and weather resistance, and is excellent in hot melt coating and melt extrusion. It is to provide an adhesive product such as an adhesive film having a material, an adhesive composition having these features, and an adhesive layer having these features.

  As a result of intensive studies by the present inventors, a specific acrylic diblock copolymer can be pelletized and obtained from a mixture containing such a pellet and a specific acrylic triblock copolymer. The present inventors have found that the pressure-sensitive adhesive composition has the above-mentioned features and that a pressure-sensitive adhesive product suitable for the above-mentioned purpose can be obtained from this pressure-sensitive adhesive composition, thereby completing the present invention.

That is, the present invention
(1) General formula (1)
AB (1)
(In formula (1), A represents a methacrylic ester polymer block having no reactive group with a glass transition temperature of 25 ° C. or higher, and B represents an acrylate polymer block having no reactive group. .)
The polymer block B content is 10 to 75% by mass, the weight average molecular weight (Mw) is 10,000 to 300,000, and the molecular weight distribution (Mw / Mn) is 1.0 to 1. .5 pellets made of the acrylic diblock copolymer (a).

Furthermore, the present invention provides
(2) pellets made of the acrylic diblock copolymer (a) of (1);
Following formula (2)
C1-D-C2 (2)
(In the formula, C1 and C2 each independently represent a methacrylic ester polymer block, and D represents an acrylate polymer block.)
The polymer block D content is 40 to 90% by mass, the weight average molecular weight (Mw) is 50,000 to 300,000, and the molecular weight distribution (Mw / Mn) is 1.0 to 1. .5 acrylic triblock copolymer (b) as a mass ratio, pellet / acrylic triblock copolymer (b) comprising acrylic diblock copolymer (a) = 80 / 20-5 It is a pressure-sensitive adhesive composition obtained by mixing at 95 and melt kneading.

And this invention,
(3) The pressure-sensitive adhesive composition according to the above (2), wherein the acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 20,000 to 200,000;
(4) The pressure-sensitive adhesive composition according to any one of (2) and (3), wherein the content of the polymer block B constituting the acrylic diblock copolymer (a) is 18 to 49% by mass.

Furthermore, the present invention provides
(5) The pressure-sensitive adhesive according to any one of (2) to (4), wherein the polymer block A constituting the acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 2,500 to 150,000. Agent composition.

The present invention also provides:
(6) A pressure-sensitive adhesive product having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition according to any one of (2) to (5) above; and
(7) A pressure-sensitive adhesive optical film having a pressure-sensitive adhesive layer made of any one of the pressure-sensitive adhesive compositions of (2) to (5) above;
It is.
The present invention also provides
(1 ') General formula (1)
AB (1)
(In the formula (1), A represents a methacrylic acid ester polymer block having no reactive group having a glass transition temperature of 25 ° C. or higher, and B has a reactive group having a glass transition temperature of −20 ° C. or lower. No acrylic ester polymer block.)
The polymer block B content is 10 to 60.3% by mass, the weight average molecular weight (Mw) is 10,000 to 300,000, and the molecular weight distribution (Mw / Mn) is 1.0. Pellets consisting of an acrylic diblock copolymer (a) of ~ 1.5;
Following formula (2)
C1-D-C2 (2)
(In the formula, C1 and C2 each independently represent a methacrylic ester polymer block having a glass transition temperature of 50 ° C. or higher, and D represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower. .)
The polymer block D content is 40 to 90% by mass, the weight average molecular weight (Mw) is 50,000 to 300,000, and the molecular weight distribution (Mw / Mn) is 1.0 to Acrylic triblock copolymer (b) having a mass ratio of 1.5, pellets made of acrylic diblock copolymer (a) / acrylic triblock copolymer (b) = 80 / 20- It is a pressure-sensitive adhesive composition obtained by mixing at 5/95 and melt-kneading.
Furthermore, the present invention provides
(2 ′) The pressure-sensitive adhesive composition according to (1 ′), wherein the acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 20,000 to 200,000;
(3 ′) The pressure-sensitive adhesive composition according to (1 ′) or (2 ′), wherein the content of the polymer block B constituting the acrylic diblock copolymer (a) is 18 to 49% by mass. is there.
Furthermore, the present invention provides
(4 ′) Any of (1 ′) to (3 ′), wherein the polymer block A constituting the acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 2,500 to 150,000. It is a pressure-sensitive adhesive composition according to the above.
The present invention also provides
(5 ′) An adhesive product having an adhesive layer comprising the adhesive composition according to any one of (1 ′) to (4 ′); and
(6 ′) An adhesive optical film having an adhesive layer comprising the adhesive composition according to any one of (1 ′) to (4 ′);
It is.

  The pressure-sensitive adhesive composition obtained by the present invention has good heat resistance, weather resistance and bleed resistance, is excellent in adhesive properties such as adhesive strength, cohesive strength, and tack, and has a relatively low viscosity at the time of melting. Excellent coatability. One of the components constituting the pressure-sensitive adhesive composition is a pellet made of a specific acrylic diblock copolymer, and is a dry blend with another acrylic triblock copolymer, a meter feeder. Automatic weighing is possible. In addition, the pressure-sensitive adhesive composition can be easily prepared by a conventionally used hot melt facility or coextrusion facility.

  From the pressure-sensitive adhesive composition obtained in the present invention, for example, various pressure-sensitive adhesive products such as pressure-sensitive adhesive sheets, pressure-sensitive adhesive films, pressure-sensitive adhesive tapes, masking tapes, tapes for electrical insulation, and pressure-sensitive adhesive optical films, good melt coatability, excellent Can be manufactured smoothly with excellent workability.

  Hereinafter, the present invention will be described in detail. In this specification, methacryl and acryl may be collectively referred to as “(meth) acryl”. In the present specification, the “pressure-sensitive adhesive” means “pressure-sensitive adhesive”. The weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the acrylic triblock copolymer and acrylic diblock copolymer used in the present invention are described later. The value obtained by the method described in the example.

The pellet of this invention consists of a specific acrylic diblock copolymer (a).
The acrylic diblock copolymer (a) is represented by the following general formula (1).
AB (1)
In said formula (1), A shows the methacrylic ester polymer block (polymer block A) which does not have a reactive group whose glass transition temperature is 25 degreeC or more, B shows acrylic acid which does not have a reactive group An ester polymer block (polymer block B) is shown.

  Examples of the methacrylic acid ester constituting the polymer block A include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, methacrylic acid. Methacrylic acid alkyl esters such as 2-ethylhexyl acid, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate and isobornyl methacrylate; alkoxyalkyl esters of methacrylic acid such as methoxyethyl methacrylate and ethoxyethyl methacrylate Etc. Among the above methacrylic acid esters, methacrylic acid alkyl esters are preferable, and among them, methyl methacrylate, ethyl methacrylate, and propyl methacrylate are preferable. Among the above methacrylic acid esters, methyl methacrylate is most preferred because it is economically available and the resulting polymer block A is excellent in durability and weather resistance.

The polymer block A may be composed of only one kind of these methacrylic acid esters, or may be composed of two or more kinds.
The glass transition temperature of the polymer block A is 25 ° C. or higher, preferably 50 ° C. or higher, and more preferably 60 ° C. or higher. When the glass transition temperature of the polymer block A is within the above range, it is easy to process into pellets, and when stored as pellets, the stickiness at high temperatures (for example, 50 ° C.) tends to be reduced.

  Examples of the acrylate ester constituting the polymer block B include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, acrylic Examples include acrylic acid alkyl esters such as 2-ethylhexyl acid, n-octyl acrylate, lauryl acrylate, tridecyl acrylate, and stearyl acrylate; alkoxyalkyl esters such as methoxyethyl acrylate and ethoxyethyl acrylate. .

  When the alkyl group of the alkyl acrylate ester is a short chain alkyl group having 4 or less main chain carbon atoms (for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate) Etc.) tend to improve the fluidity and tensile strength of the acrylic diblock copolymer. When the alkyl group contained in the acrylic acid alkyl ester is a long chain alkyl group having 6 or more main chain carbon atoms (for example, acrylic acid alkyl ester includes n-hexyl acrylate, cyclohexyl acrylate, 2-acrylic acid 2- Ethyl hexyl, n-octyl acrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate, etc.) tend to improve the low-temperature properties of the acrylic diblock copolymer and compatibility with tackifying resins, etc. is there.

  When the acrylic acid ester is an acrylic acid alkoxyalkyl ester such as methoxyethyl acrylate and ethoxyethyl acrylate, the oil resistance is improved, and compatibility with polar tackifier resins, plasticizers, diluents, etc. is improved. Tend to.

  When copolymerizing these acrylic acid esters, they may be used in a desired combination and in combination of two or more. In the case of copolymerization, each component is preferably contained in an amount of 5 wt% or more in order to develop the characteristics of each acrylate ester.

The glass transition temperature of the polymer block B is preferably −20 ° C. or lower, and more preferably −30 ° C. or lower.
When the glass transition temperature of the polymer block B is within the above range, the adhesive composition at a low temperature (eg, −10 ° C.) and tack are good, and the adhesive strength is increased during high-speed peeling and the zipping phenomenon. Can be suppressed. Among the above acrylic esters, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and acrylic acid n are among the above acrylate esters because the glass transition temperature of the polymer block B is within the above preferred range and is easily available. -Octyl is preferred.

Further, the difference in glass transition temperature between the polymer block A and the polymer block B in the acrylic diblock copolymer (a) is preferably 70 ° C. or higher, and more preferably 100 ° C. or higher.
The content of the polymer block B in the acrylic diblock copolymer (a) is 10 to 75% by mass, preferably 15 to 65% by mass, and more preferably 18 to 49% by mass.

  When the content of the polymer block B in the acrylic diblock copolymer (a) is within the above range, for example, an acrylic diblock can be obtained by a device in which an underwater cutter or a center hot cutter is connected to a twin screw extruder. Block copolymer (a) pellets can be easily produced. Moreover, compatibility with the acryl-type triblock copolymer (b) mentioned later becomes high, and the adhesive composition obtained is excellent in transparency. Further, the cohesive force of the pressure-sensitive adhesive composition is increased, and the melt viscosity is excellent in melt coatability.

  When the content of the polymer block B exceeds 75% by mass, the acrylic diblock copolymer (a) has high fluidity and is liquid, or a pellet is produced from the acrylic diblock copolymer (a). At that time, for example, even if it is cut with an underwater cutter or the like, only pellets with high sticking property can be obtained, or even if an anti-sticking agent is used, the pellet shape cannot be maintained. In addition, the compatibility with the acrylic triblock copolymer (b) to be described later is lowered, the pressure-sensitive adhesive composition cannot be mixed uniformly, the resulting pressure-sensitive adhesive composition is opaque, Unevenness may occur. On the other hand, when the content of the polymer block B is less than 10% by mass, a desired tack may not be obtained when the pressure-sensitive adhesive composition is formed, or the initial adhesive force tends to be too low.

  Content of the polymer block A in an acrylic type diblock copolymer (a) is 90-25 mass%, Preferably it is 85-35 mass%, More preferably, it is 82-51 mass%.

  The acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 10,000 to 300,000, processability, adhesive performance, and compatibility with the acrylic triblock copolymer (b). In view of the above, the weight average molecular weight (Mw) of the acrylic diblock copolymer (a) is preferably 20,000 to 200,000, more preferably 25,000 to 170,000, still more preferably 30,000. 000 to 150,000. When the weight average molecular weight (Mw) of the acrylic diblock copolymer (a) is less than 10,000, the cohesive force of the pressure-sensitive adhesive composition containing the acrylic diblock copolymer (a) becomes insufficient, When the pressure-sensitive adhesive composition and the adherend are adhered, they are easily peeled off, resulting in poor durability or a desired tackiness. In addition, problems such as bleeding of the acrylic diblock copolymer (a) on the surface occur. On the other hand, if the weight average molecular weight (Mw) of the acrylic diblock copolymer (a) exceeds 300,000, the melt viscosity becomes too high and the productivity and workability are poor. Moreover, compatibility with the acryl-type triblock copolymer (b) mentioned later becomes low, and the obtained adhesive composition becomes opaque or unevenness occurs in the adhesive physical properties.

  When the content of the polymer block B in the acrylic diblock copolymer (a) is within the above range and the weight average molecular weight (Mw) is within the above range, the acrylic diblock copolymer ( The melt viscosity of a) is close to the melt viscosity of the acrylic triblock copolymer (b), which will be described later, and can be stably melt-extruded and mixed sufficiently even when a uniaxial mix screw is used. And a pressure-sensitive adhesive composition having excellent uniformity can be easily obtained. Further, even if the acrylic diblock copolymer (a) is blended in a large amount with respect to the acrylic triblock copolymer (b), the viscosity of the resulting pressure-sensitive adhesive composition is not greatly reduced. This increases the degree of freedom in blending design.

  The molecular weight distribution (Mw / Mn) of the acrylic diblock copolymer (a) is 1.0 to 1.5, improving the cohesive strength of the pressure-sensitive adhesive composition, and adherend contamination (adhesive residue, low From the point of reducing adhesion of molecular weight components, etc., it is preferably 1.0 to 1.4, more preferably 1.0 to 1.3, and still more preferably 1.0 to 1.2. When the molecular weight distribution (Mw / Mn) of the acrylic diblock copolymer (a) exceeds 1.5, the influence of low molecular weight components cannot be ignored, and there are problems such as a decrease in cohesive force and adhesive residue during rework. It tends to occur.

  The weight average molecular weight (Mw) of the polymer block A of the acrylic diblock copolymer (a) is preferably 2,500 to 150,000, more preferably 5,000 to 120,000, and further preferably. Is 8,000 to 100,000. When the weight average molecular weight of the polymer block A is in the above range, the acrylic diblock copolymer (a) can be easily formed into pellets, and the adhesive performance when the obtained pellets are heat resistant and an adhesive composition is obtained. It tends to be excellent.

  The weight average molecular weight (Mw) of the polymer block B of the acrylic diblock copolymer (a) is preferably 2,500 to 150,000, more preferably 5,000 to 120,000.

  The pellet of the present invention can be produced by, for example, melt-extruding the acrylic diblock copolymer (a) to form a strand, and cutting the pellet with an underwater cutter, a center hot cutter, a strand cutter, or the like to form a pellet. . The pellet is not particularly limited as long as it can be dry-blended with other pressure-sensitive adhesive components, for example, the acrylic triblock copolymer (b) described later. It has a substantially spherical shape and usually has a size of about 1 mm to 20 mm.

  The mass ratio of the acrylic diblock copolymer (a) contained in the pellet is preferably 80% by mass or more, more preferably 90% by mass or more, and 100% by mass in the pellet. It is particularly preferred.

  Furthermore, when producing the pellets, as long as the properties as pellets are not impaired, an additive to be added to the pressure-sensitive adhesive composition in addition to the acrylic diblock copolymer (a), For example, a tackifier resin, a plasticizer, a softener, and the like, which will be described later, may be blended to produce pellets from these mixtures.

  The pellet made of the acrylic diblock copolymer (a) of the present invention is premixed with other components by dry blending in advance, or melt blended and then re-pelletized after dry blending and stored. It may also be used by mixing with other components immediately before use.

  When sticking is observed in the pellet made of the acrylic diblock copolymer of the present invention, a general anti-sticking agent may be added in a small amount as necessary in order to reduce the sticking property. The anti-sticking agent can be used without particular limitation, for example, calcium carbonate, talc, kaolin, silica, clay, alumina, fatty acid amide, fatty acid ester, metal soap, acrylic polymer fine particles, aluminum hydroxide, Examples thereof include silicon dioxide. These anti-sticking agents may be used alone or in combination of two or more. The adhesion amount of the anti-sticking agent is preferably 0 to 999 ppm, more preferably 0 to 99 ppm, and more preferably 0 to 9 ppm with respect to the pellet made of the acrylic diblock copolymer. When the adhesion amount of the anti-sticking agent is within this range, the transparency of the pressure-sensitive adhesive product using the diblock copolymer as the pressure-sensitive adhesive composition is excellent.

  In the pressure-sensitive adhesive composition containing an acrylic block copolymer used for hot melt, melt extrusion, etc., in addition to the acrylic triblock copolymer, an acrylic diblock is added to impart softening, tackiness, adhesiveness, etc. Block copolymers may be used. However, the acrylic diblock copolymer is usually in a liquid state, and there is a problem in the raw material supply method when the pressure-sensitive adhesive composition is continuously produced using an extruder or the like. On the other hand, the acrylic diblock copolymer (a) used in the present invention can be pelletized. The pellets can be dry-blended with acrylic triblock copolymer pellets, and can be automatically weighed with a weighing feeder, thereby improving productivity. Moreover, since the melt viscosity of the acrylic diblock copolymer (a) is close to the melt viscosity of the acrylic triblock copolymer (b) described later, extrusion can be stably performed, and a uniaxial mix screw was used. Even in this case, it is possible to sufficiently mix these copolymers. In addition, equipment such as rotary blade type high speed mixer, screw type mixer, pressure type high speed kneader, kneader roll, kneader ruder, extruder, mixin gall, banbury mixer etc. that are usually used in manufacturing processes such as hot melt and coextrusion. Thus, the pellet of the present invention can be used.

  Conventionally well-known hot-melt pressure-sensitive adhesives made from styrene-based elastomers require tackifying resins and softening agents in order to exhibit adhesive performance. When tackifying resins and softeners are used, automatic metering with a metering feeder is difficult, so even if the styrenic diblock copolymer is pelletized, the metering feeder cannot be used to produce the adhesive.

  On the other hand, in the case of a pressure-sensitive adhesive using an acrylic block copolymer, the pressure-sensitive adhesive performance can be exhibited without containing a tackifying resin or a softening agent, and an acrylic for pressure-sensitive adhesives that could not be used as a conventional pellet. By making the system diblock copolymer into pellets, automatic weighing can be performed using a weighing feeder or the like when blending the pressure-sensitive adhesive.

  By blending the acrylic triblock copolymer (b) into the pellet made of the acrylic diblock copolymer (a) of the present invention, a pressure-sensitive adhesive composition having excellent characteristics can be obtained. The acrylic triblock copolymer (b) is represented by the following general formula (2).

C1-D-C2 (2)
In the above formula (2), C1 and C2 each independently represent a methacrylic ester polymer block, and D represents an acrylate polymer block. Since the acrylic triblock copolymer (b) has a melt viscosity close to that of the acrylic diblock copolymer (a), it can be easily melt kneaded even with a uniaxial mix screw, and the melt extrusion stability of these mixtures is It is high and an adhesive composition can be easily obtained.

  Examples of the methacrylic acid ester constituting the polymer block C1 and the polymer block C2 include, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, methacrylic acid. Methacrylic acid alkyl esters such as cyclohexyl acid, 2-ethylhexyl methacrylate, n-octyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate and isobornyl methacrylate, methacrylic acid such as methoxyethyl methacrylate and ethoxyethyl methacrylate Examples thereof include alkoxyalkyl esters. Among the above methacrylic acid esters, methacrylic acid alkyl esters are preferable, and among them, methyl methacrylate, ethyl methacrylate, and propyl methacrylate are preferable. Among the methacrylic acid esters, methyl methacrylate is particularly preferable because it is economically easily available and the resulting polymer block C1 and polymer block C2 are excellent in durability and weather resistance.

  The polymer block C1 and the polymer block C2 may be composed of only one kind of these methacrylic acid esters, or may be composed of two or more kinds. The molecular weights of the polymer block C1 and the polymer block C2 and the monomer composition forming the polymer block may be the same or different.

  The glass transition temperature of the polymer block C1 and the polymer block C2 is preferably 50 ° C. or higher, and more preferably 60 ° C. or higher. When the glass transition temperature of the polymer block C1 and the polymer block C2 is within the above range, it is easy to process into pellets, and when stored as pellets, the stickiness at high temperatures (for example, 50 ° C.) is reduced. There is a tendency, and the heat resistance of the resulting pressure-sensitive adhesive composition tends to be excellent.

  Examples of the acrylate ester constituting the polymer block D include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, acrylic Examples include acrylic acid alkyl esters such as 2-ethylhexyl acid, n-octyl acrylate, lauryl acrylate, tridecyl acrylate, and stearyl acrylate; alkoxyalkyl esters such as methoxyethyl acrylate and ethoxyethyl acrylate. .

  When the alkyl group of the alkyl acrylate ester is a short chain alkyl group having 4 or less main chain carbon atoms (for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate) Etc.) tend to improve the fluidity and tensile strength of the acrylic diblock copolymer. When the alkyl group contained in the acrylic acid alkyl ester is a long chain alkyl group having 6 or more main chain carbon atoms (for example, acrylic acid alkyl ester includes n-hexyl acrylate, cyclohexyl acrylate, 2-acrylic acid 2- Ethyl hexyl, n-octyl acrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate, etc.) tend to improve the low-temperature properties of the acrylic diblock copolymer and compatibility with tackifying resins, etc. is there.

  When the acrylic acid ester is an acrylic acid alkoxyalkyl ester such as methoxyethyl acrylate and ethoxyethyl acrylate, the oil resistance is improved, and compatibility with polar tackifier resins, plasticizers, diluents, etc. is improved. Tend to.

  When copolymerizing these acrylic acid esters, they may be used in a desired combination and in combination of two or more. In the case of copolymerization, each component is preferably contained in an amount of 5 wt% or more in order to develop the characteristics of each acrylate ester.

  The glass transition temperature of the polymer block D is preferably −20 ° C. or lower. When the glass transition temperature of the polymer block D is −20 ° C. or lower, the pressure-sensitive adhesive composition of the present invention containing the acrylic diblock copolymer (a) and the acrylic triblock copolymer (b) is usually used. In the pressure-sensitive adhesive composition, a microphase separation structure comprising at least one polymer block D is formed in the pressure-sensitive adhesive composition, and the pressure-sensitive adhesive composition is imparted with excellent flexibility and wettability. Appropriate adhesive strength and good reworkability are exhibited.

  The glass transition temperature of the polymer block D is preferably −30 ° C. or less, more preferably −40 ° C. to −80 ° C., from the viewpoint of excellent durability under low temperature (for example, −10 ° C.) conditions.

  Since the glass transition temperature of the polymer block D is in the above range, the resulting adhesive composition has good adhesive strength and tack at low temperature, and can suppress the increase in adhesive strength and zipping phenomenon during high-speed peeling. Among the acrylate esters constituting the combined block D, propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, and n-octyl acrylate are preferable.

The polymer block D may be composed of only one kind of these acrylate esters or may be composed of two or more kinds.
Content of the polymer block D in an acryl-type triblock copolymer (b) is 40-90 mass%, Preferably it is 50-85 mass%, More preferably, it is 60-80 mass%. When the content of the polymer block D is in the above range, a pressure-sensitive adhesive composition excellent in adhesive properties such as adhesive strength, cohesive strength, and tack can be obtained, and the phase with the acrylic diblock copolymer (a) can be obtained. Excellent tolerability. By using the acrylic triblock copolymer (b) having a relatively high content of the polymer block D in combination with the acrylic diblock copolymer (a), the adhesive force, cohesive force, tack and the like are higher. In terms of performance, a pressure-sensitive adhesive composition that is particularly excellent in processability can be obtained.

  The total content of the polymer block C1 and the polymer block C2 in the acrylic triblock copolymer (b) is 10 to 60% by mass, preferably 15 to 50% by mass, and 20 to 40% by mass. It is more preferable that

  The weight average molecular weight (Mw) of the acrylic triblock copolymer (b) is 50,000 to 300,000. From the viewpoint of achieving both durability and reworkability, the acrylic triblock copolymer (b) The weight average molecular weight (Mw) is preferably 60,000 to 250,000, more preferably 70,000 to 200,000. When the weight average molecular weight (Mw) of the acrylic triblock copolymer (b) is smaller than 50,000, the cohesive force of the pressure-sensitive adhesive composition becomes insufficient, and the adhesive composition is adhered to the adherend. In this case, it becomes easy to peel off and is inferior in durability. On the other hand, when larger than 300,000, melt viscosity becomes high and workability is inferior.

  The acrylic triblock copolymer (b) has a molecular weight distribution (Mw / Mn) of 1.0 to 1.5, which improves the cohesive force at high temperatures of the pressure-sensitive adhesive composition and is superior in durability. In view of the above, the molecular weight distribution (Mw / Mn) is preferably 1.0 to 1.4, more preferably 1.0 to 1.3, and still more preferably 1.0 to 1.2. When the molecular weight distribution (Mw / Mn) of the acrylic triblock copolymer (b) is larger than 1.5, the influence of low molecular weight components cannot be ignored, and there are problems such as a decrease in cohesive force and adhesive residue during rework. Is likely to occur.

The acrylic triblock copolymer (b) contained in the pressure-sensitive adhesive composition may be used alone or in a mixture of two or more.
The manufacturing method in particular of an acrylic diblock copolymer (a) and an acrylic triblock copolymer (b) is not restrict | limited, It can manufacture with the manufacturing method according to a well-known method. In general, as a method for obtaining a block copolymer having a narrow molecular weight distribution, a method of living polymerizing monomers as constituent units is employed. Examples of such living polymerization methods include a method of living polymerization using an organic rare earth metal complex as a polymerization initiator (see, for example, Patent Document 5), and an alkali metal or alkaline earth using an organic alkali metal compound as a polymerization initiator. A method of living anion polymerization in the presence of a mineral salt such as a metal salt (for example, see Patent Document 6), a method of living anion polymerization in the presence of an organoaluminum compound using an organic alkali metal compound as a polymerization initiator (for example, a patent) Reference 7), atom transfer radical polymerization method (ATRP) (for example, see Non-Patent Document 1), and the like.

  Among the above production methods, the method of living anion polymerization in the presence of an organoaluminum compound has little deactivation during polymerization, so that there is little mixing of homopolymer, and the resulting block copolymer has high transparency. Moreover, since the polymerization conversion rate of a monomer is high, there are few residual monomers in a block copolymer, and when using it as an adhesive composition, generation | occurrence | production of the bubble after bonding can be suppressed. Furthermore, the molecular structure of the methacrylic acid alkyl ester polymer block is highly syndiotactic and has the effect of enhancing durability when used in a pressure-sensitive adhesive composition. And because living anion polymerization is possible under relatively mild temperature conditions, it is possible to reduce the environmental load (mainly the electric power applied to the refrigerator for controlling the polymerization temperature) when producing industrially. There is. In view of the above, the acrylic diblock copolymer (a) and the acrylic triblock copolymer (b) are produced by living anion polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organic aluminum compound. Preferably manufactured.

Examples of the living anion polymerization method in the presence of the above-described organoaluminum compound include, for example, an organolithium compound and the following general formula (3)
AlR ¹ R ² R ³ (3)
(Wherein R ¹ , R ² and R ³ are each independently an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, or an aryl which may have a substituent) A group, an aralkyl group which may have a substituent, an alkoxy group which may have a substituent, an aryloxy group which may have a substituent or an N, N-disubstituted amino group, or R ¹ is any of the groups described above, and R ² and R ³ are combined to form an aryleneoxy group which may have a substituent.
In the presence of an organoaluminum compound represented by formula (2), an ether compound such as dimethyl ether, dimethoxyethane, diethoxyethane, or 12-crown-4; if necessary, in the reaction system; triethylamine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetramine, pyridine, 2,2 ′ A method of polymerizing a (meth) acrylic acid alkyl ester by further adding a nitrogen-containing compound such as dipyridyl can be employed.

  Examples of the organic lithium compound include alkyllithium or alkyldilithium such as n-butyllithium, sec-butyllithium and tetramethylenedilithium; aryllithium or aryldilithium such as phenyllithium and xylyllithium; benzyllithium And aralkyl lithium or aralkyl dilithium such as dilithium produced by the reaction of diisopropenylbenzene and butyllithium; lithium amide such as lithium diisopropylamide; lithium alkoxide such as methoxylithium.

  The organoaluminum compound represented by the general formula (3) is isobutyl bis (2,6-di-tert-butyl-4-yl) from the viewpoint of high living property of polymerization and easy handling. Methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum, isobutyl [2,2′-methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum and the like are preferable.

  The pressure-sensitive adhesive composition of the present invention is prepared by melt-kneading a pellet made of an acrylic diblock copolymer (a) and another polymer, for example, the above-mentioned acrylic triblock copolymer (b). can do.

  The mixing ratio of the pellet made of the acrylic diblock copolymer (a) and the acrylic triblock copolymer (b) is a mass ratio of the pellet / acrylic triblock copolymer made of the acrylic diblock copolymer (a). Polymer (b) = 80/20 to 5/95, preferably 70/30 to 10/90, more preferably 60/40 to 10/90. When the mass ratio exceeds 80/20, the cohesive force of the obtained pressure-sensitive adhesive composition is lowered, and the durability is lowered. On the other hand, when the mass ratio is less than 5/95, tack and wettability decrease.

The pressure-sensitive adhesive composition may contain a tackifier resin, a plasticizer, a softener, an anti-sticking agent, and other additives.
For example, when a tackifier resin is blended in the pressure-sensitive adhesive composition of the present invention, tack, adhesive strength, holding power, etc. can be improved, and the balance of these physical properties of pressure can be adjusted. As the tackifier resin, the hydrogenated terpene resin is highly compatible with the acrylic diblock copolymer (a) and the acrylic triblock copolymer (b), and exhibits stable adhesive force. Terpene resins such as terpene phenol; rosin resins such as hydrogenated rosin esters, disproportionated rosin esters and polymerized rosins; petroleum resins such as C5 / C9 petroleum resins and aromatic petroleum resins; α-methylstyrene polymers; Examples thereof include tackifying resins such as styrene resins such as styrene / α-methylstyrene copolymer.

From the point of expressing high adhesive strength, the softening point of the tackifying resin is preferably 50 ° C to 150 ° C.
When the tackifying resin is blended, the amount can be appropriately set according to the use of the pressure-sensitive adhesive composition, the type of adherend, etc., preferably 1 to 1 based on the solid content of the pressure-sensitive adhesive composition. The proportion is 35% by mass, more preferably 1 to 25% by mass, and still more preferably 1 to 15% by mass. When the blending amount exceeds the above range, the cohesive force is lowered, and inconveniences such as occurrence of adhesive residue at the time of peeling or reworking easily occur.

  Examples of the plasticizer include dibutyl phthalate, di-n-octyl phthalate, bis-2-ethylhexyl phthalate, di-n-decyl phthalate, diisodecyl phthalate and the like, bis-2-ethylhexyl. Fatty acid esters such as adipic acid esters such as adipate and di-n-octyl adipate; paraffins such as chlorinated paraffin; glycols such as polypropylene glycol; epoxidized soybean oil, epoxidized linseed Epoxy polymer plasticizers such as oil; Phosphate esters such as trioctyl phosphate and triphenyl phosphate; Sebacic acid esters such as bis-2-ethylhexyl sebacate and di-n-butyl sebacate Fatty acid esters such as azelaic acid esters such as bis-2-ethylhexyl azelate Phosphites such as totriphenyl phosphite; acrylic oligomers such as n-butyl poly (meth) acrylate and 2-ethylhexyl poly (meth) acrylate; polybutene; polyisobutylene; polyisoprene; process oil; A naphthenic oil etc. are mentioned, These may be used independently or may use 2 or more types together.

  When mix | blending a plasticizer, the quantity becomes like this. Preferably it is 1-25 mass% based on the total mass of solid content of an adhesive composition, More preferably, it is 1-10 mass%. When the blending amount of the plasticizer exceeds the above range, the cohesive force is lowered, and it is easy to cause inconveniences such as occurrence of adhesive residue at the time of peeling or reworking.

  In the pressure-sensitive adhesive composition of the present invention, when a large amount of tackifying resin, plasticizer, and softening agent is blended, the cohesive strength, weather resistance, heat stability, and substrate contamination tend to be poor. From this point of view, the amount of tackifier resin, plasticizer, and softener is preferably as small as possible, and it is more preferable not to mix these.

  The pressure-sensitive adhesive composition containing the acrylic diblock copolymer (a) and the acrylic triblock copolymer (b) of the present invention is, for example, a pellet made of an acrylic diblock copolymer (a), an acrylic It can prepare by mixing the pellet which consists of a system triblock copolymer (b), and other components, and melt-kneading in an extruder.

  In the pressure-sensitive adhesive composition of the present invention, physical crosslinking is formed in such a hard phase, so that cohesive force is expressed and excellent pressure-sensitive adhesive properties and durability are exhibited. Acrylic diblock copolymer (a) and acrylic triblock copolymer (b), specifically, polymer block A of acrylic diblock copolymer (a), and acrylic triblock copolymer (B) formed by polymer block C1 and C2 of hard block and polymer block B of acrylic diblock copolymer (a) and polymer block D of acrylic triblock copolymer (b) A microphase separation structure is formed by the soft phase.

Further, due to the presence of the soft phase, the pressure-sensitive adhesive composition has excellent flexibility and wettability.
The pressure-sensitive adhesive composition of the present invention can be used for producing pressure-sensitive adhesive products having various shapes such as a sheet shape, a film shape, and a tape shape, such as pressure-sensitive adhesive tapes and pressure-sensitive adhesive films. Further, as described in detail below, the pressure-sensitive adhesive composition of the present invention can be used by heating and melting, or it may be dissolved in a solvent such as toluene and used as a solution-type pressure-sensitive adhesive.

  The method for producing the pressure-sensitive adhesive product is not particularly limited. For example, the pressure-sensitive adhesive composition of the present invention is heated and melted, and the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition is obtained by coextrusion T-die method, inflation method, lamination method, etc. It can be manufactured by laminating and integrating on substrates such as paper, cellophane, plastic material, cloth, wood, and metal.

  Examples of the method of extruding the pressure-sensitive adhesive composition or the substrate heated and melted from the T die by the coextrusion T die method or the laminate method include a feed block method (single manifold method) and a multi manifold method.

  In the pressure-sensitive adhesive product of the present invention, surface treatment such as corona discharge treatment or plasma discharge treatment is applied to the surface of the base material layer in order to increase the adhesion between the base material and the pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition of the present invention. You may give it. Moreover, you may form an anchor layer in the surface of at least one of the said adhesion layer and the said base material layer using resin etc. which have adhesiveness.

  Examples of the resin used for the anchor layer include ethylene / vinyl acetate copolymers, ionomers, block copolymers (for example, styrenic triblock copolymers such as SIS and SBS, diblock copolymers, etc.), ethylene / Examples thereof include acrylic acid copolymers and ethylene / methacrylic acid copolymers. The anchor layer may be a single layer or two or more layers.

  In the case of forming the anchor layer, the method is not particularly limited. For example, a method of forming a anchor layer by applying a solution containing the resin to a base material, a composition containing the resin to be the anchor layer, etc. is heated. For example, a method of melting and forming an anchor layer on the surface of the substrate by using a T-die or the like can be used.

  When the anchor layer is formed, the anchor layer and the adhesive layer may be integrally laminated on the surface of the base material by co-extrusion of the resin serving as the anchor layer and the pressure-sensitive adhesive composition of the present invention. The resin that becomes the anchor layer and the pressure-sensitive adhesive composition may be sequentially laminated. Further, when the base material is a plastic material, the plastic material that becomes the base material, the resin that becomes the anchor layer, and the pressure-sensitive adhesive composition Articles may be coextruded at the same time.

A preferable application of the pressure-sensitive adhesive product includes a pressure-sensitive adhesive optical film including the base material and a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention.
The pressure-sensitive adhesive optical film of the present invention is used in optical applications, for example, a polarizing film, a polarizing plate, a retardation film, a viewing angle widening film, a brightness enhancement film, an antireflection film, an antiglare film, a color filter, a light guide plate, and diffusion. It is an optical film in which an adhesive layer is formed on at least a part or all of one surface or both surfaces of various films such as a film, a prism sheet, an electromagnetic wave shielding film, a near-infrared absorbing film, and a functional composite optical film in which a plurality of optical functions are combined. . Such an adhesive optical film includes a film in which an adhesive layer made of the adhesive composition of the present invention is formed on a protective film used for protecting the surface of the optical film.

The substrate for the adhesive optical film is preferably a plastic material because of its excellent transparency.
Examples of the plastic material used for the base material for the adhesive optical film include polyethylene terephthalate (PET), triacetyl cellulose (TAC), polyvinyl alcohol (PVA), cycloolefin resin, styrene-methyl methacrylate copolymer resin (MS Resin), and the like. Examples of the plastic material used for the protective film substrate for the optical film include polyethylene terephthalate (PET), polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), linear polyethylene (L-LDPE), etc. Polyethylene (PE), polyvinyl chloride (PVC), ethylene-vinyl acetate copolymer (EVA), copolymers of polyethylene and polypropylene, and various monomers, and two or more of these polymers A mixture etc. are mentioned.

  The said base material is properly used according to the function of an adhesive optical film. For example, when used as a polarizing plate, the film strength is improved on both sides of a film obtained by adsorbing and orienting a dichroic dye (mainly iodine) to PVA, and the expansion and contraction in a moist heat / thermal environment is suppressed. For the purpose, for example, a multilayer film obtained by laminating a TAC film having a role of a protective film is generally used.

  When used as a polarizing plate having a retardation function, a laminated film in which a multi-layer film in which a discotic liquid crystal is coated on TAC is bonded to a PVA film as a protective film is used.

  When used as a prism sheet, for example, a film in which a prism is formed on a PET film with a photocurable acrylic resin or the like is used. When used as a diffusion plate, a film manufactured from an MS resin or the like is used. Is done.

When used as a diffusion film, for example, a film having a surface processed on a PET film or a film containing an internal diffusion agent in the film is used.
When used as a light guide plate, for example, a special process is performed on the surface of a plate (film) manufactured from an acrylic resin, and in some cases, a reflective sheet made from a PET film is laminated below the plate. The film is used.

The base material layer made of these plastic materials may be a single layer or multiple layers.
The adhesive optical film is suitably used for various image display devices such as liquid crystal display devices, PDPs, organic EL display devices, and electronic paper.

  EXAMPLES Hereinafter, although an Example, a comparative example, etc. demonstrate this invention concretely, this invention is not limited to these Examples etc. at all.

First, acrylic diblock copolymers (a) [acrylic diblock copolymers (a-1) to (a-19)] and acrylic triblock copolymers used in the following Examples and Comparative Examples (B) Synthesis examples of [acrylic triblock copolymers (b-1) to (b-5)] will be described.
The molecular weight, molecular weight distribution, composition, glass transition temperature of each polymer block, and polymerization conversion rate of the block copolymer obtained in each synthesis example were measured by the following methods.

(1) Measurement of number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) of block copolymer: Gel permeation chromatography (GPC).
Apparatus: Gel permeation chromatograph (HLC-8020) manufactured by Tosoh Corporation
Column: “TSKgel GMHXL, G4000HXL” and “G5000HXL” manufactured by Tosoh Corporation are connected in series. Eluent: tetrahydrofuran Eluent flow rate: 1.0 ml / min Column temperature: 40 ° C.
・ Detection method: Differential refractive index (RI)
-Calibration curve: created using standard polystyrene

(2) Measurement of content of each copolymer component in block copolymer: Proton nuclear magnetic resonance ( ¹ H-NMR) spectroscopy was used.
・ Device: JEOL nuclear magnetic resonance apparatus (JNM-LA400)
-Solvent: deuterated chloroform-In ¹ H-NMR spectrum, signals near 3.6 ppm and 4.0 ppm are respectively the ester group of methyl methacrylate unit (-O-C H ₃ ) and n-butyl acrylate unit. is attributed to an ester group _{(-O-C H 2 -CH 2} -CH 2 -CH 3), was determined the content of the copolymerization component by the ratio of the integrated value.

(4) Measurement of glass transition temperature (Tg) of each block of the block copolymer:
In the curve obtained by the differential scanning calorimeter (DSC) measurement, the extrapolation start temperature (Tgi) was defined as the glass transition temperature (Tg).
・ Device: DSC-822 manufactured by METTLER
・ Conditions: 10 ° C / min

(5) Measurement of conversion rate of charged monomer (polymerization conversion rate): According to gas chromatography (GC).
・ Equipment: Gas chromatograph GC-14A manufactured by Shimadzu Corporation
Column: GL Sciences Inc. “INERT CAP 1” (df = 0.4 μm, 0.25 mm ID × 60 m)
Analysis conditions: injection 300 ° C., detector 300 ° C., 60 ° C. (0 minute hold) → heated at 5 ° C./minute→100° C. (0 minute hold) → 15 ° C./minute raised → 300 ° C. (2 minute hold)

  In the following synthesis examples, each block copolymer was produced by using a chemical dried and purified by a conventional method after degassing with nitrogen. Moreover, transfer and supply of monomers and other compounds to the reaction system were performed in a nitrogen atmosphere.

<< Synthesis Example a-5 >> [Synthesis of Acrylic Diblock Copolymer (a-5)]
(1) After attaching a three-way cock to a 2 L three-necked flask and replacing the inside with nitrogen, 950 g of toluene and 47.5 g of 1,2-dimethoxyethane were added at room temperature (25 ° C.), and then isobutyl bis (2,6 -Di-t-butyl-4-methylphenoxy) 23.8 g of toluene solution containing 16.0 mmol of aluminum was added, and 4.69 g of a mixed solution of cyclohexane and n-hexane containing 7.99 mmol of sec-butyllithium was further added. added. Subsequently, 275.4 g of methyl methacrylate was added to this mixed solution. The reaction mixture initially colored yellow, but became colorless after stirring at 30 ° C. for 30 minutes. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Subsequently, the internal temperature of the reaction mixture was cooled to −30 ° C., and 269.8 g of n-butyl acrylate was added dropwise over 1 hour. After completion of the addition, the mixture was stirred at −30 ° C. for 5 minutes, and then methanol. 15.0 g was added to stop the polymerization reaction. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. The obtained reaction mixture was poured into 15 kg of methanol to precipitate a white precipitate. Thereafter, the white precipitate is collected by filtration and dried to be referred to as a block copolymer [hereinafter referred to as “acrylic diblock copolymer (a-5)”]. ] 330 g was obtained.

(2) The acrylic diblock copolymer (a-5) obtained in (1) above was subjected to ¹ H-NMR measurement and GPC measurement. As a result, from polymethyl methacrylate-poly (n-butyl acrylate) The weight average molecular weight (Mw) was 53,000, the number average molecular weight (Mn) was 49,000, and the molecular weight distribution (Mw / Mn) was 1.08. In addition, the content of each polymer block in the acrylic diblock copolymer (a-5) is 80.5% by mass of the methyl methacrylate polymer block (polymer block A), and n-butyl acrylate The combined block (polymer block B) was 19.5% by mass. Moreover, the glass transition temperature (Tg) of each polymer block of the acrylic diblock copolymer (a-5) obtained above was a polymer block A109 ° C. and a polymer block B-45 ° C.

<< Synthesis Examples (a-1) to (a-4), (a-6) to (a-19) >>
In the same manner as in Synthesis Example a-5, diblock copolymers (a-1) to (a-4) and (a-6) to (a-19) shown in Table 1 were obtained. In addition, the mass ratio of the mixture of n-butyl acrylate and 2-ethylhexyl acrylate used in Synthesis Examples (a-12), (a-13) and (a-19) is (n-butyl acrylate) / (2 -Ethylhexyl acrylate) = 80/20.

  The weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn) of each of the obtained diblock copolymers, the content of the polymer block A in the diblock copolymer, and di Table 1 shows the content of the polymer block B in the block copolymer. The Tg of the polymer block A of (a-1) to (a-4) and (a-6) to (a-19) is 90 ° C. or higher, and the Tg of the polymer block B is −40 ° C. or lower. . Since Tg of the polymer block A of (a-14), (a-17), (a-18), and (a-19) is low, it could not be confirmed by DSC measurement.

<< Synthesis Example b-1 >> [Synthesis of Acrylic Triblock Copolymer (b-1)]
(1) After replacing the inside of the 2 L three-necked flask with nitrogen, 868 g of toluene and 43.4 g of 1,2-dimethoxyethane were added at room temperature (25 ° C.), and then isobutyl bis (2,6-di-t- 60.0 g of a toluene solution containing 40.2 mmol of (butyl-4-methylphenoxy) aluminum was added, and 2.07 g of a mixed solution of cyclohexane and n-hexane containing 3.54 mmol of sec-butyllithium was further added. Subsequently, 36.6 g of methyl methacrylate was added to the mixed solution. The reaction mixture initially colored yellow, but became colorless after stirring at room temperature for 60 minutes. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. Subsequently, the reaction mixture was cooled to −30 ° C., and 251.9 g of n-butyl acrylate was added dropwise over 2 hours. After completion of the addition, the mixture was stirred at −30 ° C. for 5 minutes. At this time, the polymerization conversion rate of n-butyl acrylate was 99.9% or more. Further, 36.6 g of methyl methacrylate was added to this and stirred at 25 ° C. for 8 hours, and then 3.50 g of methanol was added to terminate the polymerization reaction. At this time, the polymerization conversion rate of methyl methacrylate was 99.9% or more. The obtained reaction mixture was poured into 15 kg of methanol to precipitate a white precipitate. Thereafter, the white precipitate was collected by filtration and dried to obtain 320 g of a block copolymer [hereinafter referred to as acrylic triblock copolymer (b-1)].

(2) About the acrylic triblock copolymer (b-1) obtained in the above (1), ¹ H-NMR measurement and GPC measurement were conducted. As a result, polymethyl methacrylate-poly (n-butyl acrylate)- It is an acrylic triblock copolymer composed of polymethyl methacrylate, the weight average molecular weight (Mw) is 115,000, the number average molecular weight (Mn) is 105,000, and the molecular weight distribution (Mw / Mn) is 1. 10. The content of each polymer block in the acrylic triblock copolymer (b-1) is 22.5% by mass of the methyl methacrylate polymer block (the total of the polymer block C1 and the polymer block C2). The n-butyl acrylate polymer block (polymer block D) was 77.5% by mass. Moreover, as for the glass transition temperature of each polymer block of the acryl-type triblock copolymer (b-1) obtained above, the polymer block C1 and the polymer block C2 are both 104 degreeC, and the polymer block D is -46 ° C.

<< Synthesis Examples (b-2) to (b-5) >>
Triblock copolymers (b-2) to (b-5) shown in Table 2 were obtained in the same manner as in Synthesis Example (b-1). In addition, the mass ratio of the mixture of n-butyl acrylate and 2-ethylhexyl acrylate used in Synthesis Example (b-5) is (n-butyl acrylate) / (2-ethylhexyl acrylate) = 80/20. Weight average molecular weight (Mw), number average molecular weight (Mn), molecular weight distribution (Mw / Mn) of each of the obtained triblock copolymers, the total content of polymer blocks C1 and C2 in the triblock copolymer Table 2 shows the amount and the content of the polymer block D in the triblock copolymer. Moreover, Tg of each polymer block C1 and polymer block C2 of the triblock copolymers (b-2) to (b-5) is 90 ° C. or higher, and Tg of the polymer block D is −40 ° C. or lower. is there.

  In the following examples and comparative examples, the melt viscosity of the obtained pressure-sensitive adhesive composition, the adhesion durability and tack (ball tack) of the pressure-sensitive adhesive film prepared from the pressure-sensitive adhesive composition were measured as follows.

[Creep test (holding force test)]
The adhesive films prepared in the following examples and comparative examples were cut into a size of 25 mm (lateral direction: vertical direction with respect to the direction of load) × 10 mm (longitudinal direction: same direction as the direction of load), and a test piece was obtained. It produced and this test piece was affixed on the glass plate which is an adherend. A 1 kg weight was attached to the test piece, and a creep test was performed in accordance with JIS Z0237 under the condition of a temperature of 90 ° C.

  The test results are x when the drop time is less than 1000 minutes, and when the drop does not drop but there is a shift in the pasting position after 1000 minutes or more, and when the drop does not fall after 1000 minutes and there is no shift. It was.

[Tack Test (Initial Adhesion Test, Examples 14 to 31)]
The adhesive films prepared in the following examples and comparative examples were cut into a size of 200 mm × 200 mm to prepare test pieces.

  Using a ball (No. 3 to No. 10) conforming to the JIS Z0237 ball tack method under a temperature of 23 ° C. and passing through an inclined surface with an inclination angle of 5 ° by 7.5 cm, a horizontal adhesive surface The distance passing through was measured. This test is a test for examining the initial adhesive strength as a pressure-sensitive adhesive, and shows that the shorter the passing distance is, the higher the initial adhesive strength is.

<< Examples 1 to 11, 13, Reference Example 1, Comparative Example 1-6 >>
The acrylic diblock copolymers produced in the above synthesis examples a-1 to a-19 were melt-extruded with a single screw extruder to produce a strand, and processed into pellets using an underwater cutter. Whether or not pelletization was possible was determined according to the following criteria. The results are shown in Table 1.
○: Pelletization is possible and can be easily peeled even if partly agglomerated. Δ: Pelletization is possible, but when left at room temperature (25 ° C) for 1 week, agglutination occurs and the agglomerated parts coalesce. Can not be peeled off, or the pellets are torn off when peeled off, leaving traces on the pellets x: liquid and bowl-like at room temperature (25 ° C), cannot be pelletized

The triblock copolymers obtained in Synthesis Examples b-1 to b-5 were similarly melt extruded to produce strands, which were processed into pellets using an underwater cutter.
As shown in Table 1, pellets were obtained in Examples 1 to 13. All of the obtained pellets had a substantially elliptical shape, and the size corresponding to the major axis was in the range of 1 mm to 20 mm. On the other hand, even when the diblock copolymer of the comparative example can be formed into pellets, it is stuck when left at room temperature (25 ° C.) for 1 week, and the glued portions are united and cannot be peeled off or peeled off. Occasionally, the pellets were torn off, traces were left on the pellets, or were liquid and bowl-like at room temperature (25 ° C.) and could not be pelletized.
The pellets obtained in Examples 1 to 13 can be automatically weighed when the pressure-sensitive adhesive composition is produced, and can be dry blended with various pellets.

《実施例１４〜３０、比較例７〜１２》
（１） 上記実施例１〜１３で製造した、アクリル系ジブロック共重合体からなるペレット及びアクリル系トリブロック共重合体のペレットを、以下の表３に示す質量比でドライブレンドした後、溶融混練し、粘着剤組成物を得た。

<< Examples 14-30, Comparative Examples 7-12 >>
(1) The pellets made of the acrylic diblock copolymer and the acrylic triblock copolymer pellets produced in Examples 1 to 13 were dry blended at a mass ratio shown in Table 3 below, and then melted. The mixture was kneaded to obtain an adhesive composition.

  In Comparative Examples 7 to 12, the diblock copolymer was in a liquid state or strong in agglomeration, handling properties were poor, and it was not possible to dry blend with the acrylic triblock copolymer pellets. Moreover, since it cannot be supplied by automatic metering using a feeder to the melt extruder, the pressure-sensitive adhesive composition cannot be obtained by the same method as described above, which is industrially unsuitable.

  For Comparative Example 12, each component was separately weighed using an electronic balance at a mass ratio shown in Table 3, and then mixed into a solution using toluene, and then toluene was evaporated to prepare a pressure-sensitive adhesive composition. . In Comparative Example 12, mixing by dry blending or automatic weighing using a feeder cannot be performed, and therefore, many steps are required for mixing as compared to Examples, and the preparation of the pressure-sensitive adhesive composition It takes a lot of time. Moreover, when producing an adhesive composition using a solvent (toluene), more energy and cost are required, and the environmental load is also high.

(2) The adhesive compositions of Examples 14 to 30 and Comparative Example 12 obtained in the above (1) were used on a polyethylene terephthalate film (thickness 50 μm) at 220 ° C. using a hot melt coater. Hot melt coating was applied to a thickness of 25 μm to produce an adhesive film comprising an adhesive composition layer / polyethylene terephthalate film. Moreover, the adhesive composition layer of the obtained adhesive film was transparent.

(3) About the adhesive film obtained by said (2), the creep test and the tack test were done. The results are shown in Table 3. In addition, the handling property in the table indicates that the acrylic diblock copolymer of the present invention can be automatically metered into a melt extruder or a hot melt applicator using a feeder, or an acrylic triblock. The case where the copolymer pellets and dry blending were easily possible was marked as ◯, and the case where neither was possible was marked as x.

  In this example, polymer block A, polymer block C1, and polymer block C2 (hereinafter referred to as the total mass of the acrylic diblock copolymer and acrylic triblock copolymer in the pressure-sensitive adhesive composition). , These are collectively referred to as a hard block), and the test was conducted with the total mass ratio (hard content, mass%) unified. The amount of the total hard content directly affects the morphology of the pressure-sensitive adhesive composition. For example, if it is 10%, the hard block has a spherical morphology and the tackiness is excellent, but the durability is poor. Conversely, if it is 70%, a hard block will be a continuous phase (sea phase) and will hardly show tackiness. For this reason, in order to make the conditions uniform, the total hard content of the pressure-sensitive adhesive composition was tested.

実施例１４〜３０で得られた粘着剤組成物では、クリープ試験の結果が良好であり、タック性及び相溶性も良好であった。また、実施例１４〜２６では、実施例２７〜３０に比較して、よりタック性に優れる。比較例１２で得られた粘着剤組成物は、タック性は良好だが、クリープ試験結果が劣る。

In the pressure-sensitive adhesive compositions obtained in Examples 14 to 30, the results of the creep test were good, and the tackiness and compatibility were also good. Moreover, in Examples 14-26, compared with Examples 27-30, it is more excellent in tackiness. The pressure-sensitive adhesive composition obtained in Comparative Example 12 has good tackiness but poor creep test results.

  In the acrylic diblock copolymer (a), when the content of the polymer block A was increased, it was likely to be easily pelletized. Usually, when the content of the polymer block A is increased, the diblock copolymer becomes hard and the tack tends to decrease. However, even if the content of the polymer block A is increased, the acrylic diblock copolymer that satisfies the definition of the weight average molecular weight of the present invention maintains good tackiness. Although the reason is not necessarily clear, when the weight average molecular weight of the acrylic diblock copolymer satisfies the provisions of the present invention, the hard block such as the polymer block A and the polymer block C1, the polymer block B, the heavy block It is presumed that the microphase separation of the soft block such as the combined block D becomes clearer and the function of the soft block is easily developed.

<< Comparative Example 13 >>
Further, in the same manner as in Synthesis Example a-5, an acrylic made of polymethyl methacrylate-poly (n-butyl acrylate) having a weight average molecular weight (Mw) of 380,000 and a content of polymer block B of 55% by mass. A diblock copolymer (a-20) was produced. This acrylic diblock copolymer (a-20) had extremely low fluidity during melting, could not be melt-molded, and could not be hot-melt coated.

Example 31
In the same manner as in Synthesis Example a-5, an acrylic diester composed of polymethyl methacrylate-n-butyl polyacrylate having a weight average molecular weight (Mw) of 250,000 and a content of polymer block B of 55% by mass. A block copolymer (a-21) was produced. This acrylic diblock copolymer (a-21) was pelletized by the same operation as in Reference Example 1, and this pellet and the acrylic triblock copolymer (b-2) pellet were dry blended and then melt-kneaded. Then, when an adhesive composition was prepared and this adhesive composition was hot-melt coated on a polyethylene terephthalate film, an adhesive film excellent in durability and tack was obtained. However, since the fluidity of the pressure-sensitive adhesive composition is low, the surface smoothness of the pressure-sensitive adhesive film was slightly inferior.

<< Examples 32-35 >>
In the same manner as in Examples 14 to 30, pressure-sensitive adhesive compositions were prepared according to the formulations shown in Table 4. In any blending, it was confirmed that it could be dry blended and used as an adhesive as in Examples 14-30.

  Since the acrylic diblock copolymer (a) constituting the pellet of the present invention has a weight average molecular weight and a content of the polymer block B within predetermined ranges, it can be easily pelletized, and an adhesive composition It is possible to improve the tack. Moreover, since the said acrylic diblock copolymer becomes a pellet, when preparing an adhesive composition, dry blending is possible and automatic measurement with a measurement feeder is possible. Further, when preparing an adhesive composition by mixing with an acrylic triblock copolymer, the adhesive can be obtained only by melt-kneading using a conventionally used hot-melt equipment or co-extrusion equipment. A composition can be easily prepared. Moreover, various adhesive materials such as an adhesive film can be produced from the obtained adhesive composition by hot melt coating.

Claims (6)

General formula (1)
AB (1)
(In the formula (1), A represents a methacrylic acid ester polymer block having no reactive group having a glass transition temperature of 25 ° C. or higher, and B has a reactive group having a glass transition temperature of −20 ° C. or lower. No acrylic ester polymer block.)
The polymer block B content is 10 to 60.3 % by mass, the weight average molecular weight (Mw) is 10,000 to 300,000, and the molecular weight distribution (Mw / Mn) is 1.0. Pellets consisting of an acrylic diblock copolymer (a) of ~ 1.5;
Following formula (2)
C1-D-C2 (2)
(In the formula, C1 and C2 each independently represent a methacrylic ester polymer block having a glass transition temperature of 50 ° C. or higher, and D represents an acrylate polymer block having a glass transition temperature of −20 ° C. or lower. .)
The polymer block D content is 40 to 90% by mass, the weight average molecular weight (Mw) is 50,000 to 300,000, and the molecular weight distribution (Mw / Mn) is 1.0 to Acrylic triblock copolymer (b) having a mass ratio of 1.5, pellets made of acrylic diblock copolymer (a) / acrylic triblock copolymer (b) = 80 / 20- A pressure-sensitive adhesive composition obtained by mixing at 5/95 and melt-kneading.   The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 20,000 to 200,000.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the content of the polymer block B constituting the acrylic diblock copolymer (a) is 18 to 49% by mass.   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the polymer block A constituting the acrylic diblock copolymer (a) has a weight average molecular weight (Mw) of 2,500 to 150,000. Composition.   A pressure-sensitive adhesive product having a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to claim 1.   A pressure-sensitive adhesive optical film having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition according to claim 1.