JP2019089945A - Adhesive film - Google Patents

Abstract

To provide an adhesive film having excellent peelability and high adhesion under normal conditions.SOLUTION: The adhesive film comprises a substrate and an adhesive layer disposed on a surface of the substrate, where the adhesive layer is formed of an adhesive composition comprising a (meth)acrylic copolymer and a crosslinking agent, and an arithmetic average roughness Ra of a surface opposite to the substrate surface is 2 μm to 15 μm. The (meth)acrylic copolymer comprises a structural unit derived from a monomer having a carboxyl group and a structural unit derived from an alkyl (meth)acrylate monomer having a glass transition temperature as a homopolymer of -60°C or less in an amount of 8 mass% to 50 mass% relative to all constituent units, and has a glass transition temperature of -40°C or less.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive film.

  In vehicles, such as a motor vehicle and a two-wheeled motor vehicle, improving the designability is performed by sticking the adhesive film which provided decoration on the vehicle body. Such an adhesive film is stuck on a to-be-adhered body which has curved surfaces, such as a fuel tank, a front cover, a front fender.

For example, in Patent Document 1, as a marking film to be attached to an adherend having a curved surface, a base material having specific viscoelastic properties and butyl acrylate (n-butyl acrylate; n-BA) are main components. The marking film which has an adhesive layer whose glass transition temperature satisfies the range of -50--20 degreeC is disclosed.
Further, in Patent Document 2, a polyvinyl chloride film layer, an acrylic pressure-sensitive adhesive compound having a specific weight average molecular weight, and a specific weight average molecular weight as a wrapping film to be attached to an object having a curved surface shape, and Disclosed is a lapping film having a pressure-sensitive adhesive layer containing a methacrylic acid ester copolymer having a specific glass transition temperature, and a release film.

JP, 2009-234011, A JP 2017-52146 A

Generally, when sticking a pressure-sensitive adhesive film to an adherend having a curved surface, the pressure-sensitive adhesive film once bonded is peeled off halfway by hand in order to be neatly stuck at a precise position without causing bubble bite. Do paste again. In the work of peeling the laminated adhesive film halfway (so-called sticking operation), linear marks (so-called shock lines) may be formed in the direction perpendicular to the peeling direction at the peeled part of the adhesive film. , It could be a problem on the appearance.
Therefore, the pressure-sensitive adhesive film attached to an adherend having a curved surface may be required to have a property that a shock line is unlikely to occur during the sticking operation (hereinafter, appropriately referred to as "sticking ability").

With regard to the above-mentioned point, in the marking film described in Patent Document 1, the flexibility of the pressure-sensitive adhesive layer is insufficient, so that the occurrence of a shock line can not be sufficiently suppressed, and a satisfactory sticking property can not be obtained.
Further, in the film for wrapping described in Patent Document 2, by controlling the weight average molecular weight and the glass transition temperature of the methacrylic acid ester copolymer contained in the pressure-sensitive adhesive layer, the workability at the time of peeling is improved. However, it is not possible to sufficiently suppress the occurrence of a shock line and a satisfactory sticking property can not be obtained.

  In addition, the pressure-sensitive adhesive film to be attached to an adherend (particularly, a vehicle body) having a curved surface may be required not only to be excellent in the above-mentioned sticking property but also to have high normal adhesive strength satisfying the specifications. .

  The problem to be solved by the present invention is to provide a pressure-sensitive adhesive film which is excellent in sticking property and has high normal adhesion.

Specific means for solving the problems include the following aspects.
It has a <1> base material and the adhesive layer arrange | positioned on the surface of the said base material,
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and a crosslinking agent, and the arithmetic average roughness Ra of the surface opposite to the substrate is 2 μm to 15 μm. Yes,
The (meth) acrylic copolymer is composed of a structural unit derived from a monomer having a carboxy group, and a (meth) acrylic acid alkyl ester monomer having a glass transition temperature of -60 ° C. or less when used as a homopolymer. The adhesive film which contains the structural unit derived from a monomer with 8 mass%-50 mass% with respect to all the structural units, and whose glass transition temperature is -40 degrees C or less.
<2> The adhesive film as described in <1> which further has a peeling film in the surface on the opposite side to the base material of the said adhesive layer.
The adhesive film as described in <2> whose arithmetic mean roughness Ra of the surface of the side which contacts the said adhesive layer of the <3> said peeling film is 2 micrometers-15 micrometers.
The adhesive film as described in any one of <1>-<3> whose weight average molecular weight of the <4> above-mentioned (meth) acrylic-type copolymer is 400,000-1.5,000.
The adhesive film as described in any one of <1>-<4> whose <5> above-mentioned crosslinking agent is an isocyanate compound.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive film which is excellent in sticking property and has high normal-state adhesiveness is provided.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications within the scope of the object of the present invention.

The numerical range shown using "-" in this specification means the range which includes the numerical value described before and after "-" as minimum value and the maximum value, respectively.
The upper limit or the lower limit described in one numerical range may be replaced with the upper limit or the lower limit in the numerical range other stepwise described in the numerical range described stepwise in the present specification. . In addition, in the numerical range described in the present specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the example.
In the present specification, a combination of two or more preferred embodiments is a more preferred embodiment.
In the present specification, the amount of each component means the total amount of a plurality of substances unless a plurality of types of substances corresponding to each component are present.

  In the present specification, “(meth) acrylic copolymer” means that all structural units have a content of a structural unit derived from a monomer having a (meth) acryloyl group (that is, (meth) acrylic copolymer) The copolymer means 50% by mass or more of all the structural units constituting

  In the present specification, "(meth) acrylic" is a term including both "acrylic" and "methacrylic", and "(meth) acrylate" is a term including both "acrylate" and "methacrylate", "(Meth) acryloyl" is a term encompassing both "acryloyl" and "methacryloyl".

In the present specification, “pressure-sensitive adhesive composition” means a liquid or paste-like substance after the (meth) acrylic copolymer and the crosslinking agent are mixed and before the crosslinking reaction is completed.
In the present specification, the "pressure-sensitive adhesive layer" means a film made of a substance after the crosslinking reaction of the pressure-sensitive adhesive composition is completed.

[Adhesive film]
The adhesive film of the present invention has a substrate and an adhesive layer disposed on the surface of the substrate,
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and a crosslinking agent, and the arithmetic average roughness Ra of the surface opposite to the substrate is 2 μm to 15 μm. Yes,
The (meth) acrylic copolymer is composed of a structural unit derived from a monomer having a carboxy group, and a (meth) acrylic acid alkyl ester monomer having a glass transition temperature of -60 ° C. or less when used as a homopolymer. The constituent unit derived from a monomer is contained in an amount of 8% by mass to 50% by mass with respect to all the constituent units, and the glass transition temperature is −40 ° C. or less.
The pressure-sensitive adhesive film of the present invention is excellent in sticking property and has high normal adhesion.
Although the reason why the pressure-sensitive adhesive film of the present invention can exhibit such an effect is not clear, the present inventors speculate as follows. However, the following presumption does not limit interpretation of the effect of the pressure-sensitive adhesive film of the present invention, and is described as an example.
Hereinafter, the (meth) acrylic copolymer contained in the adhesive film of this invention is suitably called a "specific (meth) acrylic copolymer."

The pressure-sensitive adhesive layer in the present invention is a pressure-sensitive adhesive layer in which the surface on the opposite side to the substrate, that is, the surface in contact with the adherend has an arithmetic average roughness Ra of 2 μm to 15 μm and a relatively rough surface. .
In the pressure-sensitive adhesive layer according to the present invention, a single unit of (meth) acrylic acid alkyl ester having a structural unit derived from a monomer having a carboxy group and a glass transition temperature of −60 ° C. or less when used as a homopolymer A pressure-sensitive adhesive composition comprising a (meth) acrylic copolymer having a structural unit derived from a body of 8% by mass to 50% by mass with respect to all the constituent units, and having a glass transition temperature of -40 ° C or less It is a relatively soft adhesive layer because it is formed of
Since the adhesive film of the present invention has a relatively rough surface and the layer itself has a relatively soft adhesive layer, the effective adhesion area of the adhesive layer to the adherend is adjusted over time from the initial stage of bonding it can.
That is, in the pressure-sensitive adhesive film of the present invention, since the surface of the pressure-sensitive adhesive layer is relatively rough, the effective adhesion area to the adherend decreases at the initial stage of bonding. As the effective adhesion area to the adherend decreases, it becomes easy to peel off the adherend. Therefore, the adhesive film of the present invention is considered to be excellent in sticking property.
On the other hand, if the effective adhesion area of the pressure-sensitive adhesive layer to the adherend is small, sufficient adhesion can not be obtained. In the pressure-sensitive adhesive film of the present invention, since the pressure-sensitive adhesive layer is relatively soft and wet-spreads with time to the adherend, the effective adhesion area gradually increases. Therefore, the pressure-sensitive adhesive film of the present invention is considered to have high normal adhesion.

  In the pressure-sensitive adhesive film of the present invention, the pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition including a (meth) acrylic copolymer including a structural unit derived from a monomer having a carboxy group and a crosslinking agent. Since it has appropriate cohesion, it is also excellent in heat shrinkage resistance.

〔Base material〕
The pressure-sensitive adhesive film of the present invention has a substrate.
The material of the substrate is not particularly limited.
Materials for the substrate include resins such as polyvinyl chloride resin, polyester resin, acetate resin, polyether sulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, etc. It can be mentioned.
Among these, polyvinyl chloride resins are preferable as the material of the base material from the viewpoint of good processability.

  Although the thickness of the substrate is not particularly limited, for example, in view of good handleability, the range of 50 μm to 100 μm is preferable, and the range of 25 μm to 200 μm is more preferable.

[Adhesive layer]
The pressure-sensitive adhesive film of the present invention has a pressure-sensitive adhesive layer disposed on the surface of the substrate.
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a specific (meth) acrylic copolymer and a crosslinking agent, and the arithmetic average roughness Ra of the surface opposite to the substrate is 2 μm to 15 μm. is there.

(Adhesive composition)
The pressure-sensitive adhesive composition contains a specific (meth) acrylic copolymer and a crosslinking agent.
The pressure-sensitive adhesive composition contains components such as an organic solvent and an additive (hereinafter referred to as "other components") as necessary, in addition to the specific (meth) acrylic copolymer and the crosslinking agent. It is also good.
Hereinafter, each component of the pressure-sensitive adhesive composition will be described in detail.

-Specific (meth) acrylic copolymer-
The (meth) acrylic copolymer (that is, the specific (meth) acrylic copolymer) contained in the pressure-sensitive adhesive composition is a homopolymer having a structural unit derived from a monomer having a carboxy group Containing 8% by mass to 50% by mass of a constitutional unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature of -60.degree. C. or less, and a glass transition temperature Is −40 ° C. or less.

The specific (meth) acrylic copolymer includes a constituent unit derived from a monomer having a carboxy group.
In the present specification, the “structural unit derived from a monomer having a carboxy group” means a structural unit formed by addition polymerization of a monomer having a carboxy group.
When the specific (meth) acrylic copolymer includes a structural unit derived from a monomer having a carboxy group, the adhesive layer exhibits cohesive force, and the adhesive film has high normal adhesive strength and heat shrinkage resistance. It can.

The type of monomer having a carboxy group is not particularly limited.
As the monomer having a carboxy group, (meth) acrylic acid, 2-acryloyloxyethyl-succinic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone (N ≒ 2) Mono (meth) acrylate and the like can be mentioned.
Among these, as a monomer having a carboxy group, acrylic acid (AA) from the viewpoint of adhesion to an adherend, and adhesion to a substrate when the pressure-sensitive adhesive layer is applied to a pressure-sensitive adhesive film Is preferred.

  The specific (meth) acrylic copolymer may contain only one type of structural unit derived from a monomer having a carboxy group, or may contain two or more types.

The content (ratio) of the structural units derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is the total structural unit (that is, the entire configuration constituting the specific (meth) acrylic copolymer) The range of 1 mass%-11 mass% is preferable with respect to unit), the range of 2 mass%-8 mass% is more preferable, and the range of 4 mass%-7 mass% is still more preferable.
The cohesive force of the pressure-sensitive adhesive layer is too low when the content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is 1% by mass or more based on all the structural units. Since the adhesive film is more appropriate, the normal adhesion of the adhesive film can be further improved. In addition, the heat shrinkability of the adhesive film can be further improved.
If the content of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is 11% by mass or less with respect to all the structural units, the polarity of the pressure-sensitive adhesive layer becomes too high. Since the anchor effect to a to-be-adhered body is suppressed more, the sticking property of an adhesive film may be improved more.

The specific (meth) acrylic copolymer is a total of structural units derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or lower when it is a homopolymer. It contains 8% by mass to 50% by mass with respect to (that is, all the constituent units constituting the specific (meth) acrylic copolymer).
In the present specification, "a glass transition temperature when made into a homopolymer" means a glass transition temperature (Tg) represented by the absolute temperature (K) of a homopolymer produced by polymerizing the monomer alone. Say The glass transition temperature (Tg) of the homopolymer was measured using a differential scanning calorimeter (DSC) (model number: EXSTAR 6000, Seiko Instruments Inc.) in a nitrogen stream, with a measurement sample of 10 mg, a heating rate of 10 ° C./min. The inflection point of the obtained DSC curve is determined as the glass transition temperature (Tg) of the homopolymer.
Further, in the present specification, “a constituent unit derived from a (meth) acrylic acid alkyl ester monomer” means a constituent unit formed by addition polymerization of a (meth) acrylic acid alkyl ester monomer.

  The (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or less when it is a homopolymer has a glass transition temperature (Tg) of -90 ° C. or more when it is a homopolymer It is preferable that it is -60 degrees C or less, It is more preferable that it is -85 degrees C or more-65 degrees C or less, It is still more preferable that it is -80 degrees C or more-70 degrees C or less.

As the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or less when it is a homopolymer, an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable, and The type is not particularly limited.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic.
The carbon number of the alkyl group is preferably in the range of 1 to 18, and more preferably in the range of 1 to 12, from the viewpoint of the adhesion to the adherend and the adhesion to the substrate.

As a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60.degree. C. or less when it is a homopolymer, 2-ethylhexyl acrylate (2EHA, Tg when it is a homopolymer:- 76 ° C), i-octyl acrylate (i-OA, Tg as homopolymer: -75 ° C), n-octyl acrylate (n-OA, Tg as homopolymer: -80 ° C), A lauryl methacrylate (LMA, Tg when it is set as a homopolymer: -65 degreeC) etc. are mentioned.
Among these, at least one selected from 2-ethylhexyl acrylate (2EHA) and i-octyl acrylate (i-OA) is preferable from the viewpoint of achieving a pressure-sensitive adhesive film having higher normal adhesive strength, and sticking 2-Ethylhexyl acrylate (2EHA) is more preferable from the viewpoint of being able to realize a pressure-sensitive adhesive film which is more excellent in properties and has higher normal adhesion.

  The specific (meth) acrylic copolymer has only one structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or less when it is used as a homopolymer. It may be contained, and 2 or more types may be contained.

Content rate of constituent units derived from (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or lower when it is used as a homopolymer in a specific (meth) acrylic copolymer The ratio is in the range of 8% by mass to 50% by mass, and 15% by mass to 40% by mass, with respect to all the constituent units (that is, all constituent units constituting the specific (meth) acrylic copolymer). A range is preferable and the range of 20 mass%-40 mass% is more preferable.
In the specific (meth) acrylic copolymer, the content of a structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or lower when used as a homopolymer is If the amount is less than 8% by mass with respect to all the structural units, the pressure-sensitive adhesive layer becomes hard, and thus the sticking property of the pressure-sensitive adhesive film tends to be deteriorated.
In the specific (meth) acrylic copolymer, the content of a structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or lower when used as a homopolymer is If the content is more than 50% by mass with respect to all the structural units, the pressure-sensitive adhesive layer tends to be too soft, and the normal adhesion of the pressure-sensitive adhesive film tends to decrease.

The specific (meth) acrylic copolymer is a polymer other than a structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60.degree. C. or less when used as a homopolymer. ) Structural units derived from acrylic acid alkyl ester monomers (that is, structural units derived from (meth) acrylic acid alkyl ester monomers having a glass transition temperature (Tg) exceeding -60 ° C. as homopolymers It is preferable to further include
A structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C. as a homopolymer contributes to the adjustment of the adhesive strength of the pressure-sensitive adhesive layer.

  Although the upper limit of the said glass transition temperature (Tg) in the (meth) acrylic-acid alkylester monomer in which a glass transition temperature (Tg) when it is set as a homopolymer exceeds -60 degreeC is not restrict | limited, For example, 10 degreeC The following are preferred.

As the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C. as a homopolymer, a non-substituted (meth) acrylic acid alkyl ester monomer is preferable, and the type thereof Is not particularly limited.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic.
The carbon number of the alkyl group is preferably in the range of 1 to 18, and more preferably in the range of 1 to 12, from the viewpoint of the adhesion to the adherend and the adhesion to the substrate.

As a (meth) acrylic-acid alkylester monomer when the glass transition temperature (Tg) at the time of setting it as a homopolymer exceeds -60 degreeC, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) Acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl methacrylate, i-nonyl acrylate, stearyl acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and the like.
Among these, as a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C. as a homopolymer, for example, a glass transition of a specific (meth) acrylic copolymer From the viewpoint of easily adjusting the temperature (Tg) to −40 ° C. or less, n-butyl acrylate (n-BA, Tg as a homopolymer: −57 ° C.) is preferable.

  In the case where the specific (meth) acrylic copolymer further contains a structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C. as a homopolymer, The specific (meth) acrylic copolymer may contain only one type of structural unit derived from such a (meth) acrylic acid alkyl ester monomer, or may contain two or more types.

In the case where the specific (meth) acrylic copolymer further contains a structural unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C. as a homopolymer, The content (percentage) of the constituent unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer is, for example, from the viewpoint of easily adjusting the adhesive strength of the pressure-sensitive adhesive layer 39 mass% or more is preferable with respect to all the structural units (namely, all the structural units which comprise a specific (meth) acrylic-type copolymer), 45 mass% or more is more preferable, and 55 mass% or more is still more preferable.
The upper limit of the content (ratio) of the constituent unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer is not particularly limited, and for example, with respect to all the constituent units, 84 mass% or less is preferable.

  The specific (meth) acrylic copolymer has a glass transition temperature (Tg) which is a constituent unit derived from a monomer having a carboxy group and a homopolymer within the range where the effects of the present invention are exhibited. The glass transition temperature (Tg) at the time of setting it as the homopolymer which is a structural unit derived from the (meth) acrylic-acid alkylester monomer which is -60 degrees C or less, and is arbitrary structural units exceeds -60 degreeC (Meta) The structural unit (so-called, other structural unit) other than the structural unit derived from the acrylic acid alkyl ester monomer may be included.

There is no particular limitation on the types of monomers constituting the other constituent units.
Examples of the monomer constituting the other structural unit include (meth) acrylate having an aromatic ring represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, and ethoxy Alkoxyalkyl (meth) acrylates represented by ethyl (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyls represented by vinyltoluene, acrylonitrile and the like Examples thereof include vinyl cyanide represented by methacrylonitrile, and vinyl esters represented by vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate. In addition, various derivatives of these monomers may be mentioned.

<< Glass transition temperature of specific (meth) acrylic copolymer >>
The glass transition temperature (Tg) of the specific (meth) acrylic copolymer is −40 ° C. or less, preferably −60 ° C. or more and −40 ° C. or less, and more preferably −55 ° C. or more and −42 ° C. or less It is more preferably -50 ° C or more and -45 ° C or less.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer exceeds -40 ° C., the pressure-sensitive adhesive layer becomes hard, and thus the sticking property of the pressure-sensitive adhesive film tends to be deteriorated.

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer is a value obtained by converting the absolute temperature (K) obtained by calculation from the following formula 1 into the Celsius temperature (° C.).
1 / Tg = m1 / Tg1 + m2 / Tg2 +... + M (k-1) / Tg (k-1) + mk / Tgk (Formula 1)

In the formula 1, Tg1, Tg2, ..., Tg (k-1), and Tgk are absolute temperatures (when the respective monomers constituting the specific (meth) acrylic copolymer are homopolymers ( They each represent a glass transition temperature (Tg) represented by K). m1, m2, ..., m (k-1), and mk represent the mole fraction of each monomer constituting the specific (meth) acrylic copolymer, and m1 + m2 + ... + m (k -1) + mk = 1.
The absolute temperature (K) can be converted to the Celsius temperature (° C.) by subtracting 273 from the absolute temperature (K), and adding 273 to the Celsius temperature (° C.) makes the Celsius temperature (° C.) the absolute temperature (K) It can be converted to

  The “glass transition temperature (Tg) represented by the C. Cius temperature (.degree. C.) when it is made a homopolymer” of a typical monomer is 2-ethylhexyl acrylate (2EHA) at −76 ° C., 2-ethylhexyl methacrylate ( 2EHMA) at -10 ° C, n-butyl acrylate (n-BA) at -57 ° C, n-butyl methacrylate at 21 ° C, t-butyl acrylate (t-BA) at 41 ° C, t-butyl methacrylate at 107 ° C Methyl methacrylate (i-octyl acrylate (i-OA) at -75 ° C, n-octyl acrylate (n-OA) at -80 ° C, lauryl methacrylate (LMA) at -65 ° C, methyl acrylate (MA) at 5 ° C MMA) 103 ° C, isobonyl methacrylate (IBMX) 155 ° C, ethyl acrylate (EA)-2 ° C, methacrylic acid at 185 ° C, 4-hydroxybutyl acrylate (4HBA) at -39 ° C, 2-hydroxyethyl acrylate at -15 ° C, 2-hydroxyethyl methacrylate (2HEMA) at 55 ° C, acrylic acid (AA) 163 ° C, dimethylaminoethyl methacrylate (DM) at 18 ° C, 2-acryloyloxyethyl-succinic acid at -40 ° C.

  The glass transition temperature (Tg) of the specific (meth) acrylic copolymer can be appropriately adjusted, for example, by using a monomer having a different glass transition temperature (Tg) when it is a homopolymer.

<< weight average molecular weight of specific (meth) acrylic copolymer >>
The weight-average molecular weight (Mw) of the specific (meth) acrylic copolymer is not particularly limited, and for example, the range of 300,000 to 2,000,000 is preferable, and the range of 400,000 to 1,500,000 is more preferable, 600,000 to 120,000. A range of 10,000 is more preferred.
When the weight-average molecular weight (Mw) of the specific (meth) acrylic copolymer is 300,000 or more, the cohesion of the pressure-sensitive adhesive layer is not too low and is more appropriate, so the heat-shrinkability of the pressure-sensitive adhesive film is It can improve more.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 2,000,000 or less, the cohesion of the pressure-sensitive adhesive layer is not too high and becomes more appropriate, so the sticking property of the pressure-sensitive adhesive film is It can improve more.
The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer can be adjusted to a desired value by the temperature and time of the polymerization reaction, the amount of the organic solvent, the type and the amount of the polymerization initiator, and the like.

The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is a value measured by the following method. Specifically, it measures according to the following (1)-(3).
(1) A solution of a specific (meth) acrylic copolymer is applied to release paper and dried at 100 ° C. for 1 minute to obtain a film-like specific (meth) acrylic copolymer.
(2) A sample solution having a solid content concentration of 0.2% by mass is obtained using the film-like specific (meth) acrylic copolymer obtained in the above (1) and tetrahydrofuran.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is measured as a standard polystyrene conversion value under the following conditions.

~conditions~
Measuring device: High-speed GPC (Model number: HLC-8220 GPC, Tosoh Corporation)
Detector: Differential Refractometer (RI) (Incorporated in HLC-8220, Tosoh Corp.)
Column: Four TSK-GEL GMHXL (Tosoh Corp.) connected in series Column temperature: 40 ° C
Eluent: tetrahydrofuran Sample concentration: 0.2% by mass
Injection volume: 100 μL
Flow rate: 0.6 mL / min

<< Method for producing specific (meth) acrylic copolymer >>
The method for producing the specific (meth) acrylic copolymer is not particularly limited.
The specific (meth) acrylic copolymer can be produced by polymerizing monomers by a known polymerization method represented by, for example, solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization.
Among these, as the polymerization method, for example, solution polymerization is preferable in that the treatment process is relatively simple and can be performed in a short time when preparing the pressure-sensitive adhesive composition after production.

  In solution polymerization, generally, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are charged in a polymerization tank, and stirring is performed in a nitrogen stream or at the reflux temperature of the organic solvent. While making the reaction heat for several hours. In this case, at least a portion of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be added successively.

As an organic solvent used at the time of a polymerization reaction, an aromatic hydrocarbon compound, an aliphatic or alicyclic hydrocarbon compound, an ester compound, a ketone compound, a glycol ether compound, an alcohol compound etc. are mentioned.
At the time of the polymerization reaction, these organic solvents may be used alone or in combination of two or more.

  More specifically, examples of the organic solvent used in the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decaline, And aromatic hydrocarbons represented by aromatic naphtha, n-hexane, n-heptane, n-octane, i-octane, n-decane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and fats represented by turpentine oil Esters represented by aliphatic or alicyclic hydrocarbons, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate , Acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and Ketones typified by tyl cyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and glycol ethers typified by diethylene glycol monobutyl ether, and methyl alcohol Ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and alcohols represented by t-butyl alcohol.

  In the production of the specific (meth) acrylic copolymer, the use of an organic solvent which hardly causes chain transfer during polymerization reaction of esters, ketones and the like is preferable, and in particular, the dissolution of the specific (meth) acrylic copolymer From the viewpoint of properties, easiness of polymerization reaction, etc., use of ethyl acetate, toluene etc. is preferred.

Examples of the polymerization initiator include organic peroxides and azo compounds used in ordinary solution polymerization.
As the organic peroxide, for example, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonato, di-2-ethylhexylperoxydi Carbonato, t-butylperoxy bivalato, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,4 Di-t-butylperoxycyclohexyl) butane and 2,2 Bis (4,4-di -t- octyl peroxy cyclohexyl), and butane.
As the azo compound, for example, 2,2′-azobisisobutyl nitrile (AIBN), 2,2′-azobis (2,4-dimethylvaleronitrile) (ABVN), 2,2′-azobis (4-methoxy- 2,4-Dimethylvaleronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), and 2,2′-azobis (isobutyric acid) dimethyl.

  In the production of the specific (meth) acrylic copolymer, the use of a polymerization initiator which does not cause a grafting reaction during the polymerization reaction is preferable, and in particular, the use of an azobis polymerization initiator is preferable.

  The use amount of the polymerization initiator is not particularly limited, and is appropriately set according to the molecular weight of the target specific (meth) acrylic copolymer.

In the production of the specific (meth) acrylic copolymer, a chain transfer agent may be used as needed as long as the purpose and effect of the present invention are not impaired.
Examples of chain transfer agents include cyanoacetic acid, alkyl esters of 1 to 8 carbon atoms of cyanoacetic acid, bromoacetic acid, alkyl esters of 1 to 8 carbon atoms of bromoacetic acid, α-methylstyrene, anthracene, phenanthrene, fluorene And aromatic compounds represented by 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds represented by p-nitrotoluene, Benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2- Tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloro To halogenated hydrocarbons represented by tan, tribromomethane and 3-chloro-1-propene, aldehydes represented by chloral and furaldehyde, alkyl mercaptans having 1 to 18 carbon atoms, thiophenol and toluene mercaptan Typical examples include aromatic mercaptans, mercaptoacetic acid, alkyl esters of 1 to 10 carbon atoms of mercaptoacetic acid, hydroxyalkyl mercaptans of 1 to 12 carbon atoms, and terpenes represented by binene and terpinolene.

  When a chain transfer agent is used in the production of the specific (meth) acrylic copolymer, the amount of the chain transfer agent used is not particularly limited, depending on the molecular weight of the target specific (meth) acrylic copolymer , Is set appropriately.

  The polymerization temperature is not particularly limited, and is appropriately set depending on the molecular weight of the target specific (meth) acrylic copolymer.

-Crosslinking agent-
The pressure-sensitive adhesive composition contains a crosslinking agent.
The type of the crosslinking agent is not particularly limited as long as it can crosslink the specific (meth) acrylic copolymer.
As a crosslinking agent, crosslinking agents, such as an isocyanate compound, an epoxy compound, and a metal chelate compound, are mentioned.
Among these, as the crosslinking agent, for example, an isocyanate compound or an epoxy compound is preferable from the viewpoint that the normal adhesion of the adhesive film can be further improved, and from the viewpoint that the sticking property of the adhesive film can be further improved. And isocyanate compounds are more preferred.
In the present specification, the "isocyanate compound" means a compound having an isocyanate group, and the "epoxy compound" means a compound having an epoxy group.

  As the isocyanate compound, xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, aromatic polyisocyanate compound represented by tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate, the above-mentioned aroma Or cyclic aliphatic polyisocyanate compounds represented by the hydrogenated products of aromatic polyisocyanate compounds, biurets, dimers, trimers or pentamers of these polyisocyanate compounds, and these polyisocyanate compounds An adduct with a polyol compound such as trimethylolpropane and the like can be mentioned.

  Among these, as an isocyanate compound, from the viewpoint of maintaining the stability of adhesion over time, tolylene diisocyanate, a dimer of tolylene diisocyanate, an adduct of tolylene diisocyanate and a polyol, and three amounts of tolylene diisocyanate Preferred are tolylene diisocyanate compounds derived from various tolylene diisocyanates such as isocyanurate which is a body or pentamer and biuret of tolylene diisocyanate.

A commercial item can be used as an isocyanate compound.
As a commercial item of an isocyanate compound, the Tosoh Corp. "Coronato (trademark) HX", "Coronato (trademark) HL-S", "Coronato (trademark) L", "Coronato (trademark)" is mentioned, for example. L-45E, "Colonate (registered trademark) 2031,""Colonate (registered trademark) 2030,""Colonate (registered trademark) 2234", "Colonate (registered trademark) 2785", "Aquanate (registered trademark) 200" , And “Aquanate (registered trademark) 210”, “Sumidur (registered trademark) N 3300” of Sumika Kobe Soro Urethane Co., Ltd., “Desmodur (registered trademark) N 3400”, and “Sumidur (registered trademark) N” -75 "," Duranate (registered trademark) E-405-80T "of Asahi Kasei Co., Ltd.," Duranate (registered trademark) 24A- 00, "Duranate (registered trademark) TSE-100", and "Takenate (registered trademark) D-110N", "Takenate (registered trademark) D-120N", "Takenate (registered trademark)" of Mitsui Takeda Chemical Co., Ltd. Those commercially available under the trade names M-631N and MT-Olester (registered trademark) NP 1200 can be suitably used.

  As an epoxy compound, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcine diglycidyl ether, 2,2-dibromoneopentyl Glycol diglycidyl ether, Methylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1,3- Bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-1,3-benzenedi (methanamine) and the like can be mentioned.

A commercial item can be used as an epoxy compound.
As a commercial item of an epoxy compound, the thing marketed by the trade name of "TETRAD-X" and "TETRAD-C" of Mitsubishi Gas Chemical Co., Ltd. can be used conveniently, for example.

  The pressure-sensitive adhesive composition may contain only one type of crosslinking agent, or may contain two or more types.

The content of the crosslinking agent in the pressure-sensitive adhesive composition is not particularly limited, and can be appropriately set according to the type of the crosslinking agent.
For example, when the cross-linking agent is an isocyanate compound having an isocyanate group, the content of the cross-linking agent in the pressure-sensitive adhesive composition is superior to sticking property and can realize a pressure-sensitive adhesive film having higher normal adhesion. From the viewpoint, the range of 1.5 parts by mass to 8 parts by mass is preferable, and the range of 3 parts by mass to 7 parts by mass is more preferable with respect to 100 parts by mass of the specific (meth) acrylic copolymer described above.
For example, when the crosslinking agent is an epoxy compound having an epoxy group, the content of the crosslinking agent in the pressure-sensitive adhesive composition is 100 parts by mass of the specific (meth) acrylic copolymer described above from the same viewpoint as above. On the other hand, the range of 0.01 mass part-10 mass parts is preferable, and the range of 0.05 mass part-3 mass parts is more preferable.

-Organic solvent-
The pressure-sensitive adhesive composition preferably contains, for example, an organic solvent from the viewpoint of improving the coating property.
As an organic solvent, the thing similar to the organic solvent used at the time of the polymerization reaction of a specific (meth) acrylic-type copolymer as stated above is mentioned, for example.

The content of the organic solvent in the pressure-sensitive adhesive composition is not particularly limited.
When the pressure-sensitive adhesive composition contains an organic solvent, the content of the organic solvent in the pressure-sensitive adhesive composition is, for example, 100 parts by mass of the specific (meth) acrylic copolymer described above from the viewpoint of coatability. The range of 100 parts by mass to 900 parts by mass is preferable.

-Other ingredients-
The pressure-sensitive adhesive composition may contain components (so-called, other components) other than the components described above, as needed, as long as the effects of the present invention are not impaired.
Other components include polymers other than specific (meth) acrylic copolymers, antioxidants, colorants (eg, dyes and pigments), light stabilizers (eg, ultraviolet absorbers), antistatic agents, etc. Various additives can be mentioned.

(Arithmetic mean roughness)
The pressure-sensitive adhesive layer has an arithmetic average roughness Ra of 2 μm to 15 μm, preferably 3 μm to 13 μm, and more preferably 4 μm to 12 μm on the side opposite to the substrate.
If the arithmetic mean roughness Ra of the surface on the opposite side to the base material of the pressure-sensitive adhesive layer is less than 2 μm, the initial effective adhesion area is too large, and the sticking property of the pressure-sensitive adhesive film tends to be deteriorated.
When the arithmetic average roughness Ra of the surface on the opposite side to the substrate of the pressure-sensitive adhesive layer exceeds 15 μm, the effective adhesion area is too small, and the normal adhesion of the pressure-sensitive adhesive film tends to be reduced.

The arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to the substrate can be adjusted to a desired value, for example, by pressing a metal roll against the surface of the pressure-sensitive adhesive layer after curing.
Moreover, arithmetic mean roughness Ra of the surface on the opposite side to the base material of the pressure-sensitive adhesive layer is, for example, 2 μm to 15 μm on the surface opposite to the base material of the pressure-sensitive adhesive layer. By arranging a release film that is in the range, it can be adjusted to a desired value.
For example, from the viewpoint of usability (so-called ease of use) of the adhesive film, the adjustment of the arithmetic average roughness Ra is to place a release film having an arithmetic average roughness Ra of 2 μm to 15 μm on the surface. It is preferable to carry out.
Since the arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer gradually returns to the state before adjustment with the passage of time due to the elasticity of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer in which the arithmetic mean roughness Ra of the surface is adjusted is It is desirable to stick to the adherend as quickly as possible while being held. According to the method of using the release film, the release film can be immediately adhered to the adherend after releasing the release film from the surface of the pressure-sensitive adhesive layer, and therefore the usability of the pressure-sensitive adhesive film compared to the method using the metal roll Is better.

  Arithmetic mean roughness Ra of the surface on the opposite side to the substrate of the pressure-sensitive adhesive layer is a value measured using a laser microscope VK-X200 from Keyence Corporation and the observation application and analysis application attached to the laser microscope VK-X200. It is.

(Thickness of adhesive layer)
The thickness in particular of an adhesive layer is not restrict | limited, For example, according to the kind of to-be-adhered body, it can set suitably. The thickness of the pressure-sensitive adhesive layer is, for example, preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 60 μm, and still more preferably in the range of 20 μm to 40 μm.

[Peeling film]
The pressure-sensitive adhesive film of the present invention preferably further comprises a release film on the side opposite to the substrate of the pressure-sensitive adhesive layer.
In the pressure-sensitive adhesive film of the present invention, the release film contributes to the surface protection of the pressure-sensitive adhesive layer.

The release film is not particularly limited as long as it can be easily released from the pressure-sensitive adhesive layer, and examples thereof include resin films on which at least one surface is subjected to an easy release treatment with a release treatment agent. As a resin film, the polyester film represented by the polyethylene terephthalate film is mentioned, for example. Examples of the release agent include fluorine resins, paraffin wax, silicones, long chain alkyl group compounds and the like.
The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive film is put to practical use, and is peeled off at the time of use.

Arithmetic mean roughness Ra of the surface of the release film is not particularly limited.
For example, as described above, when the release film is used to adjust the arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to the substrate, the surface of the release film on the side in contact with the pressure-sensitive adhesive layer Arithmetic mean roughness Ra is preferably in the range of 2 μm to 15 μm, more preferably in the range of 3 μm to 13 μm, and in the range of 4 μm to 12 μm.

  Arithmetic mean roughness Ra of the surface of a peeling film is a value measured using the laser microscope VK-X200 of the Keyence Corporation, and the observation application and analysis application attached to the laser microscope VK-X200.

  The thickness of the release film is not particularly limited, and for example, the range of 100 μm to 300 μm is preferable.

[Production method of adhesive film]
The method for producing the pressure-sensitive adhesive film of the present invention is not particularly limited.
The pressure-sensitive adhesive film of the present invention can be produced, for example, by the following method.
The pressure-sensitive adhesive composition described above is applied onto the surface of the substrate, dried, and cured to form a pressure-sensitive adhesive layer. Then, laminating the substrate / pressure-sensitive adhesive layer by pressing a metal roll having an arithmetic average roughness Ra of the range of 2 μm to 15 μm on the exposed surface of the formed pressure-sensitive adhesive layer not in contact with the substrate. The pressure-sensitive adhesive film of the present invention having a structure can be produced.

Another method also includes, for example, the following method.
A pressure-sensitive adhesive layer is formed by applying the pressure-sensitive adhesive composition described above onto the surface of the release film having an arithmetic mean roughness Ra of the surface in the range of 2 μm to 15 μm, drying and curing. Then, the formed pressure-sensitive adhesive layer is transferred to the substrate, that is, the surface of the release film on which the pressure-sensitive adhesive layer is formed is attached to the substrate and pressed, and the substrate / pressure-sensitive adhesive layer / release film is After producing a laminate having a laminate structure, the pressure-sensitive adhesive film of the present invention having a laminate structure of a substrate / pressure-sensitive adhesive layer can be produced by peeling off the release film.

As another method, for example, the following method can also be mentioned.
The pressure-sensitive adhesive composition described above is applied on the surface of a release film having an arithmetic mean roughness Ra of the surface in the range of 2 μm to 15 μm, and then dried to prepare a film with a pressure-sensitive adhesive. Then, the substrate is attached to the adhesive surface of the pressure-sensitive adhesive film and cured, whereby the pressure-sensitive adhesive film of the present invention having a laminate structure of substrate / pressure-sensitive adhesive layer / release film can be produced.

There is no restriction | limiting in particular as a method to apply an adhesive composition on the surface of a base material or a peeling film, For example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a knife coater, a spray coater, A known method using a bar coater, an applicator or the like can be mentioned.
The application amount of the pressure-sensitive adhesive composition on the surface of the substrate or the release film is appropriately set according to the thickness of the pressure-sensitive adhesive layer to be formed.

There is no restriction | limiting in particular as a method to dry the adhesive composition apply | coated on the surface of a base material or a peeling film, Natural drying, heat drying, hot air drying, vacuum drying, etc. are mentioned.
The drying temperature and drying time of the pressure-sensitive adhesive composition coated on the surface of the substrate or the release film are not particularly limited, and it depends on the thickness of the applied pressure-sensitive adhesive composition, the amount of organic solvent in the pressure-sensitive adhesive composition, etc. Is set appropriately.

Curing is performed, for example, in an environment of 40 ° C. for 3 days to 7 days.
By curing, the crosslinking reaction of the pressure-sensitive adhesive composition is completed to form a pressure-sensitive adhesive layer.

  Hereinafter, the present invention will be more specifically described by way of examples. The present invention is not limited to the following examples, as long as the subject matter of the present invention is not exceeded.

  The glass transition temperature (Tg) and the weight average molecular weight (Mw) of the (meth) acrylic copolymer produced in this example were measured by the method described above.

Example 1
-Production of (meth) acrylic copolymer-
N-Butyl acrylate (n-BA; (meth) acrylic acid alkyl ester monomer, Tg as homopolymer in a reactor equipped with a stirrer, reflux condenser, sequential dropping device, and thermometer C .: 80.9 parts by mass at -57.degree. C., 2-ethylhexyl acrylate (2EHA; (meth) acrylic acid alkyl ester monomer, Tg as homopolymer): 34.7 parts by mass at -76.degree. C., acrylic acid (AA; monomer having a carboxy group) 7.4 parts by mass and ethyl acetate (EAc) 205 parts by mass are charged, and 2,2′-azobisisobutyronitrile (AIBN) 0.066 as a polymerization initiator Parts by weight were added. After addition of AIBN, the contents of the reactor were heated and held at reflux temperature (82 ° C.) for 20 minutes. Next, in the reactor, 104.1 parts by mass of 2EHA, 242.8 parts by mass of n-BA, 22.1 parts by mass of AA, 94.3 parts by mass of EAc, and 0.189 of AIBN Mixture A consisting of parts by mass was added dropwise over 120 minutes. After dropwise addition of mixture A, the temperature of the contents in the reactor is kept at 85 ° C. for 90 minutes, and then mixture B consisting of 61.5 parts by mass of EAc and 1.23 parts by mass of AIBN is applied for 60 minutes. It dripped one after another. After the mixture B is dropped, the temperature of the contents in the reactor is kept at 85 ° C. for 90 minutes, diluted to 35.1 mass% solid content using methyl ethyl ketone (MEK), and cooled (meth) A solution of acrylic copolymer was obtained. In addition, the "solid content" in the solution of a (meth) acrylic-type copolymer means the residual amount which removed volatile components, such as a solvent, from the solution of a (meth) acrylic-type copolymer (following, the same) .
The obtained (meth) acrylic copolymer had a glass transition temperature (Tg) of -48.8 ° C, and a weight average molecular weight (Mw) of 800,000.

-Preparation of adhesive composition-
100 parts by mass (solid content: 35.1 parts by mass) of the solution of the (meth) acrylic copolymer obtained above and Coronate L-45E (trade name; "Corronate") which is an isocyanate compound as a crosslinking agent Trademark, trimethylolpropane adduct of tolylene diisocyanate (TDI), solid content: 45% by mass, Tosoh Corp. 3.91 parts by mass (solid content: 1.76 parts by mass), and thoroughly mixed The pressure-sensitive adhesive composition was prepared.

-Preparation of adhesive film for evaluation test-
Using the doctor blade film applicator, apply the pressure-sensitive adhesive composition prepared above to a rough surface of a release film with an arithmetic average roughness Ra of 8.0 μm so that the minimum thickness after drying is 25 μm. Then, the film was dried for 1 minute under hot air at 100 ° C. and 5 m / sec to prepare a film with a pressure sensitive adhesive.
Next, a vinyl chloride film (trade name: 00178M7, thickness: 70 μm, Nippon Carbide Industrial Co., Ltd.) as a base material is attached to the adhesive surface of the film with adhesive and left to stand for 72 hours under an environment of 40 ° C. The adhesive film which has a laminated structure of a peeling film / adhesive layer / base material was obtained. Arithmetic mean roughness Ra of the surface at the side of the peeling film of the adhesive layer in the obtained adhesive film is 8.0 micrometers.
Then, after printing a screen ink (trade name: Hi-SSPINK, Nippon Carbide Industries Co., Ltd.) on a base (ie, vinyl chloride film) side of the produced adhesive film using a 250 mesh screen, a hot air It heat-dried for 10 minutes in a 60 degreeC environment using a drier. Then, screen clear (trade name: Hi-SSPCLEAR, Nippon Carbide Industries Co., Ltd.) is printed on the screen ink printing surface of the adhesive film using a 180 mesh screen, and 80 ° C. using a hot air dryer. Adhesiveness for evaluation test which has a laminated structure of release film / pressure-sensitive adhesive layer / substrate / screen ink layer / screen clear layer by heating and drying for 60 minutes under environment and standing for 72 hours under environment of 40 ° C. I got a film.

Example 2
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 3
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 4
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 5
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and an organic solvent and The weight average molecular weight was changed to 1.2 million by adjusting the amount of the polymerization initiator, and the solid content was 35.1% by mass except that a solution of (meth) acrylic copolymer was obtained. The same operation was performed to obtain a pressure-sensitive adhesive film for evaluation test.

Example 6
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 7
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 8
In “Production of pressure-sensitive adhesive film for evaluation test” in Example 1, peeling in which the surface arithmetic average roughness Ra is 3.0 μm instead of the peeling film in which the surface arithmetic average roughness Ra is 8.0 μm The same operation as in Example 1 was performed except that a film was used, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 9
In “Production of pressure-sensitive adhesive film for evaluation test” of Example 1, peeling in which the surface arithmetic average roughness Ra is 13.0 μm instead of the peeling film in which the surface arithmetic average roughness Ra is 8.0 μm The same operation as in Example 1 was performed except that a film was used, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 10
In “Preparation of (meth) acrylic copolymer of Example 1”, the weight average molecular weight is changed to 2,000,000 by adjusting the amount of the organic solvent and the polymerization initiator, and the solid content is 35.1 mass. The same operation as in Example 1 was carried out except that a solution of 50% (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 11
In “Preparation of (meth) acrylic copolymer of Example 1”, the weight average molecular weight is changed to 300,000 by adjusting the amount of the organic solvent and the polymerization initiator, and the solid content is 35.1 mass. The same operation as in Example 1 was carried out except that a solution of 50% (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 12
Instead of using 3.91 parts by mass (solid content: 1.76 parts by mass) of the isocyanate compound Coronate (registered trademark) L-45E as a crosslinking agent in “Preparation of pressure-sensitive adhesive composition” in Example 1 In addition, TETRAD-X (trade name; "TETRAD" is a registered trademark, 1,3-phenylene bis (N, N-diglycidylmethanamine) which is an epoxy compound, solid content: 100% by mass, Mitsubishi Gas Chemical Company, Ltd. The same operation as in Example 1 was carried out except using 0.1 parts by mass (solid content: 0.1 parts by mass) to obtain a pressure-sensitive adhesive film for evaluation test.

Example 13
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Example 14
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 1
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 2
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 3
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 4
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 5
In “Preparation of pressure-sensitive adhesive film for evaluation test” of Example 1, peeling in which the surface arithmetic average roughness Ra is 1.0 μm instead of the peeling film in which the surface arithmetic average roughness Ra is 8.0 μm The same operation as in Example 1 was performed except that a film was used, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 6
In “-Production of pressure-sensitive adhesive film for evaluation test-” in Example 1, peeling in which the surface arithmetic average roughness Ra is 18.0 μm instead of the peeling film in which the surface arithmetic average roughness Ra is 8.0 μm The same operation as in Example 1 was performed except that a film was used, to obtain a pressure-sensitive adhesive film for evaluation test.

Comparative Example 7
In “Preparation of (meth) acrylic copolymer of Example 1”, the composition of the monomer constituting the (meth) acrylic copolymer is changed to the composition shown in Table 1, and the solid content is 35 The same operation as in Example 1 was carried out except that a solution of 1% by mass of (meth) acrylic copolymer was obtained, to obtain a pressure-sensitive adhesive film for evaluation test.

The composition, the glass transition temperature (Tg), and the weight average molecular weight (Mw) of the monomer of the (meth) acrylic copolymer contained in the pressure-sensitive adhesive composition in each Example and each Comparative Example are shown in Table 1.
Further, the type and amount (unit: parts by mass) of the crosslinking agent contained in the pressure-sensitive adhesive composition in each example and each comparative example are shown in Table 1. In addition, the quantity of the crosslinking agent shown in Table 1 is dry part number (namely, solid content conversion value).
Moreover, arithmetic mean roughness Ra (unit: micrometer) of the surface at the side of the peeling film of the adhesive layer in the adhesive film for evaluation tests of each Example and each comparative example is shown in Table 1.

[Evaluation]
1. Sticking property The pressure-sensitive adhesive film for evaluation test prepared above was cut into a size of 5 cm × 20 cm to prepare a pressure-sensitive adhesive film piece for evaluation test.
A release film is peeled off from the prepared adhesive film for evaluation test, and the adhesive layer exposed by peeling is a white coated plate (trade name: melamine white coated plate, material: SPCC-SD, under room temperature (23 ° C.) environment. Specifications: Melamine coating, Paltec Co., Ltd., was attached using a squeegee. Then, the adhesive film piece for evaluation tests bonded together to the white paint board was peeled from the white paint board by hand so that a peeling angle might be 120 degrees in a long side (20 cm) direction. The operation from the bonding of the pressure-sensitive adhesive layer to the white-painted plate to peeling is taken as the first bonding operation.
Subsequently, the same sticking work was repeated 4 times using the adhesive film piece for evaluation tests which performed the 1st sticking work.
Every time when one sticking operation was completed, the peeled adhesive film piece for evaluation test was visually observed, and the sticking property was evaluated according to the following evaluation criteria. The results are shown in Table 1.
In the following evaluation criteria, "A" is the most excellent in sticking property. Moreover, when the evaluation result was "A", "B", or "C", it was judged that there was no problem in practical use.

-Evaluation criteria-
A: No shock line has occurred even after the 5th pasting work.
B: A shock line occurred after the 4th paste work.
C: A shockline occurred after the second or third bonding operation.
D: A shock line occurred after the first sticking work.

2. Normal Adhesion The pressure-sensitive adhesive film for evaluation test prepared above was cut into a size of 1 cm × 10.5 cm to prepare a pressure-sensitive adhesive film piece for evaluation test.
A release film is peeled off from the prepared adhesive film for evaluation test, and the adhesive layer exposed by peeling is a white coated plate (trade name: melamine white coated plate, material: SPCC-SD, under room temperature (23 ° C.) environment. Specifications: Melamine coating, Paltec Co., Ltd., after bonding using a squeegee, it was left at room temperature (23 ° C.) for 48 hours.
Next, the adhesive strength (unit: N / 10 mm) when the adhesive film piece for evaluation test was peeled 180 ° in the long side (10.5 cm) direction from the white painted plate, the universal material testing machine of ORIENTEC Co. (model number: It measured on conditions of 300 mm / min of peeling speeds using RTA-100). The measured adhesive strength was multiplied by 2.5, and the value converted to 25 mm width adhesive strength (unit: N / 25 mm) was regarded as normal adhesive strength and evaluated according to the following evaluation criteria. The results are shown in Table 1.
In the following evaluation criteria, "A" is the one with the best normal adhesion. Moreover, when the evaluation result was "A", "B", or "C", it was judged that there was no problem in practical use.

-Evaluation criteria-
A: Normal adhesion exceeds 12 N / 25 mm.
B: The ordinary adhesive strength is more than 8 N / 25 mm and less than 12 N / 25 mm.
C: The adhesive strength in the normal state is more than 5 N / 25 mm and not more than 8 N / 25 mm.
D: Normal adhesion is 5 N / 25 mm or less.

3. Heat-resistant Shrinkage The pressure-sensitive adhesive film for evaluation test prepared above was cut into a size of 5 cm × 5 cm to prepare a pressure-sensitive adhesive film piece for evaluation test.
A release film is peeled off from the prepared adhesive film for evaluation test, and the adhesive layer exposed by peeling is a white coated plate (trade name: melamine white coated plate, material: SPCC-SD, under room temperature (23 ° C.) environment. Specifications: Melamine coating, Paltec Co., Ltd., was attached using a squeegee, and after preparing a test body, it was left at room temperature (23 ° C.) for 48 hours. Subsequently, the test sample after being left to stand was further left to stand under an environment of 80 ° C. for 2 hours, and then left to stand at room temperature (23 ° C.) for 60 minutes to be cooled. After cooling, the shrinkage rate after heating of the adhesive film piece for evaluation test was measured using a measurement microscope (model number: STM6) of Olympus Corporation, and the heat resistant shrinkage was evaluated according to the following evaluation criteria. The results are shown in Table 1.
In the following evaluation criteria, the one with the highest heat shrinkage resistance is “A”. Moreover, when the evaluation result was "A", "B", or "C", it was judged that there was no problem in practical use.

-Evaluation criteria-
A: The contraction rate is 0.3% or less.
B: The contraction rate is more than 0.3% and not more than 0.5%.
C: The contraction rate is more than 0.5% and not more than 0.7%.
D: The contraction rate exceeds 0.7%.

  In Table 1, "-" described in the column of composition means that the corresponding component is not included.

The details of each monomer described in Table 1 are as follows.
<(Meth) acrylic acid alkyl ester monomer>
· "N-BA": n-butyl acrylate (Tg as homopolymer: -57 ° C)
・ "EA": Ethyl acrylate (Tg in homopolymer form: -27 ° C)
・ "2EHA": 2-ethylhexyl acrylate (Tg when considered as homopolymer: -76 ° C)
・ "I-OA": i-octyl acrylate (Tg as homopolymer: -75 ° C)
<Monomer having a carboxy group>
・ "AA": acrylic acid (Tg when it is set as a homopolymer: 163 ° C)
-"HOA-MS": 2-acryloyloxyethyl-succinic acid (Tg as homopolymer: -40 ° C)

  As shown in Table 1, the pressure-sensitive adhesive films of Examples 1 to 14 were excellent in sticking property and had high normal adhesive strength. Moreover, the adhesive films of Examples 1 to 14 were also excellent in heat shrinkage resistance.

  On the other hand, the pressure-sensitive adhesive films of Comparative Examples 1 and 2 having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer having a glass transition temperature (Tg) exceeding -40 ° C have a glass transition temperature Compared with the pressure-sensitive adhesive film of an example (for example, Example 1) having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer having a (Tg) of -40 ° C or less The sticking property was remarkably inferior.

The proportion of the structural unit derived from the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or less when used as a homopolymer is less than 8% by mass with respect to all the structural units The pressure-sensitive adhesive film of Comparative Example 3 having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a certain (meth) acrylic copolymer has a ratio of a constituent unit derived from the (meth) acrylic acid alkyl ester monomer Example having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer in the range of 8% by mass to 50% by mass with respect to all the structural units (for example, Example 1 As compared with the pressure-sensitive adhesive film, the sticking property was significantly inferior.
The proportion of a constituent unit derived from a (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or less as a homopolymer exceeds 50% by mass with respect to all constituent units The pressure-sensitive adhesive film of Comparative Example 4 having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer has a ratio of a constituent unit derived from the (meth) acrylic acid alkyl ester monomer Example having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer in a range of 8% by mass to 50% by mass with respect to all the structural units (for example, Example 1) Normal adhesion was significantly lower than that of the pressure-sensitive adhesive film.

The pressure-sensitive adhesive film of Comparative Example 5 in which the arithmetic average roughness Ra of the surface on the side opposite to the substrate of the pressure-sensitive adhesive layer (that is, the surface on the release film side) is less than 2 μm has the above-mentioned arithmetic average roughness Ra of 2 μm to 15 μm. As compared with the adhesive film of the example (for example, Example 1) which is in the range of (1), the sticking property was remarkably inferior.
The adhesive film of Comparative Example 6 in which the arithmetic average roughness Ra of the surface on the opposite side to the substrate of the pressure-sensitive adhesive layer (that is, the surface on the release film side) exceeds 15 μm has the above-mentioned arithmetic average roughness Ra of 2 μm to 15 μm. The ordinary adhesion was significantly lower than that of the pressure-sensitive adhesive film of the example (for example, Example 1) which is in the range.

  The pressure-sensitive adhesive film of Comparative Example 7 having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer not containing a constitutional unit derived from a monomer having a carboxy group has a carboxy group Compared with the pressure-sensitive adhesive film of the example (for example, Example 1) having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer containing a structural unit derived from a monomer, Normal adhesion was significantly lower. Moreover, compared with the adhesive film of Example 1, the adhesive film of Comparative Example 7 was also significantly inferior in heat shrinkage resistance.

Claims (5)

A substrate, and a pressure-sensitive adhesive layer disposed on the surface of the substrate,
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and a crosslinking agent, and the arithmetic average roughness Ra of the surface opposite to the substrate is 2 μm to 15 μm. Yes,
The (meth) acrylic copolymer is composed of a structural unit derived from a monomer having a carboxy group, and a (meth) acrylic acid alkyl ester monomer having a glass transition temperature of −60 ° C. or less when used as a homopolymer. The adhesive film which contains the structural unit derived from a monomer with 8 mass%-50 mass% with respect to all the structural units, and whose glass transition temperature is -40 degrees C or less.   The pressure-sensitive adhesive film according to claim 1, further comprising a release film on the side opposite to the substrate of the pressure-sensitive adhesive layer.   The pressure-sensitive adhesive film according to claim 2, wherein an arithmetic average roughness Ra of a surface of the release film on the side in contact with the pressure-sensitive adhesive layer is 2 μm to 15 μm.   The pressure-sensitive adhesive film according to any one of claims 1 to 3, wherein a weight average molecular weight of the (meth) acrylic copolymer is 400,000 to 1,500,000. The pressure-sensitive adhesive film according to any one of claims 1 to 4, wherein the crosslinking agent is an isocyanate compound.