JP6947610B2 - Adhesive film - Google Patents

Description

The present invention relates to an adhesive film.

In vehicles such as automobiles and motorcycles, the design is enhanced by attaching a decorated adhesive film on the vehicle body. Such an adhesive film is attached to an adherend having a curved surface such as a fuel tank, a front cover, and a front fender.

For example, Patent Document 1 describes a substrate having specific viscoelastic properties and butyl acrylate (n-butyl acrylate; n-BA) as main components as a marking film to be attached to an adherend having a curved surface. , A marking film having an adhesive layer satisfying a glass transition temperature in the range of −50 to −20 ° C. is disclosed.
Further, Patent Document 2 describes 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. A wrapping film having a pressure-sensitive adhesive layer containing a methacrylic acid-based ester copolymer having a specific glass transition temperature and a release film is disclosed.

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

Generally, when the adhesive film is attached to an adherend having a curved surface, the adhesive film once attached is peeled off by hand halfway in order to attach the adhesive film to a neat and accurate position without causing foam biting. Perform the work of pasting again. In the work of peeling off the bonded adhesive film halfway (so-called sticking work), a linear mark (so-called shock line) may be left on the peeled part of the adhesive film in the direction perpendicular to the peeling direction. , There was a problem in appearance.
Therefore, the adhesive film to be attached to the adherend having a curved surface may be required to have a property (hereinafter, appropriately referred to as "pasting property") in which a shock line is unlikely to occur during the raising operation.

Regarding the above points, in the marking film described in Patent Document 1, since the adhesive layer is insufficiently flexible, the occurrence of shock lines cannot be sufficiently suppressed, and a satisfactory sticking property cannot be obtained.
Further, in the wrapping film described in Patent Document 2, the workability at the time of peeling is improved 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. However, the occurrence of shock lines cannot be sufficiently suppressed, and satisfactory stickability cannot be obtained.

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

An object to be solved by the present invention is to provide an adhesive film having excellent sticking property and high normal adhesive strength.

Specific means for solving the problem include the following aspects.
<1> It has a base material and an adhesive layer arranged on the surface of the base material.
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and a cross-linking agent, and has an arithmetic mean roughness Ra of 2 μm to 15 μm on the surface opposite to the base material. can be,
The (meth) acrylic copolymer has a structural unit derived from a monomer having a carboxy group and a (meth) acrylic acid alkyl ester simple having a glass transition temperature of -60 ° C or lower when used as a homopolymer. An adhesive film containing 8% by mass to 50% by mass of constituent units derived from a polymer and having a glass transition temperature of −40 ° C. or lower.
<2> The pressure-sensitive adhesive film according to <1>, which further has a release film on the surface of the pressure-sensitive adhesive layer opposite to the base material.
<3> The pressure-sensitive adhesive film according to <2>, wherein the arithmetic average roughness Ra of the surface of the release film on the side in contact with the pressure-sensitive adhesive layer is 2 μm to 15 μm.
<4> The adhesive film according to any one of <1> to <3>, wherein the (meth) acrylic copolymer has a weight average molecular weight of 400,000 to 1,500,000.
<5> The pressure-sensitive adhesive film according to any one of <1> to <4>, wherein the cross-linking agent is an isocyanate compound.

According to the present invention, there is provided an adhesive film having excellent sticking property and high normal adhesive strength.

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

The numerical range indicated by using "~" in the present specification means a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, 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 examples.
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 kinds of substances when a plurality of kinds of substances corresponding to each component are present, unless otherwise specified.

As used herein, the term "(meth) acrylic copolymer" means that the content of structural units derived from a monomer having a (meth) acryloyl group is the total structural unit (that is, (meth) acrylic copolymer). It means a copolymer which is 50% by mass or more of all the constituent units constituting the above.

In the present specification, "(meth) acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth) acrylate" is a term that includes both "acrylate" and "methacrylate". "(Meta) acryloyl" is a term that includes both "acryloyl" and "methacrylic".

As used herein, the term "adhesive composition" means a liquid or paste-like substance after the (meth) acrylic copolymer and the cross-linking agent are mixed and before the cross-linking reaction is completed.
As used herein, the term "adhesive layer" means a film made of a substance after the cross-linking reaction of the pressure-sensitive adhesive composition is completed.

[Adhesive film]
The pressure-sensitive adhesive film of the present invention has a base material and a pressure-sensitive adhesive layer arranged on the surface of the base material.
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and a cross-linking agent, and has an arithmetic mean roughness Ra of 2 μm to 15 μm on the surface opposite to the base material. can be,
The (meth) acrylic copolymer has a structural unit derived from a monomer having a carboxy group and a (meth) acrylic acid alkyl ester simple having a glass transition temperature of -60 ° C or less when used as a homopolymer. The structural unit derived from the polymer is 8% by mass to 50% by mass with respect to all the structural units, and the glass transition temperature is −40 ° C. or lower.
The adhesive film of the present invention has excellent sticking property and high normal adhesive strength.
Although it is not clear why the adhesive film of the present invention can exert such an effect, the present inventors speculate as follows. However, the following speculation does not limitly interpret the effect of the adhesive film of the present invention, but is described as an example.
Hereinafter, the (meth) acrylic copolymer contained in the pressure-sensitive adhesive film of the present invention is appropriately referred to as a “specific (meth) acrylic copolymer”.

The pressure-sensitive adhesive layer in the present invention is a pressure-sensitive adhesive layer having an arithmetic average roughness Ra of 2 μm to 15 μm on the surface opposite to the base material, that is, the surface in contact with the adherend, and the surface is relatively rough. ..
Further, the pressure-sensitive adhesive layer in the present invention contains a structural unit derived from a monomer having a carboxy group and a (meth) acrylic acid alkyl ester single amount having a glass transition temperature of −60 ° C. or lower when used as a copolymer. Adhesive composition containing a (meth) acrylic copolymer containing a body-derived structural unit of 8% by mass to 50% by mass with respect to all the structural units and having a glass transition temperature of −40 ° C. or lower. It is a relatively soft pressure-sensitive adhesive layer because it is formed of an object.
Since the adhesive film of the present invention has an adhesive layer having a relatively rough surface and a relatively soft layer itself, the effective adhesive area of the adhesive layer on the adherend can be adjusted over time from the initial stage of bonding. 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 bonding area with respect to the adherend becomes small at the initial stage of bonding. When the effective adhesive area with respect to the adherend becomes small, it becomes easy to peel off from the adherend. Therefore, the adhesive film of the present invention is considered to have excellent stickability.
On the other hand, if the effective adhesive area of the pressure-sensitive adhesive layer on the adherend is small, sufficient adhesive strength cannot be obtained. In the pressure-sensitive adhesive film of the present invention, the pressure-sensitive adhesive layer is relatively soft and wets and spreads on the adherend over time, so that the effective adhesive area gradually increases. Therefore, the adhesive film of the present invention is considered to have a high normal adhesive strength.

Further, in the pressure-sensitive adhesive film of the present invention, the pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer containing a structural unit derived from a monomer having a carboxy group and a cross-linking agent. Since it has an appropriate cohesive force, it also has excellent heat shrinkage.

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

The thickness of the base material is not particularly limited, but for example, from the viewpoint 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 arranged on the surface of the base material.
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a specific (meth) acrylic copolymer and a cross-linking agent, and has an arithmetic average roughness Ra of 2 μm to 15 μm on the surface opposite to the base material. be.

(Adhesive composition)
The pressure-sensitive adhesive composition contains a specific (meth) acrylic copolymer and a cross-linking agent.
The pressure-sensitive adhesive composition contains components such as an organic solvent and additives (hereinafter, referred to as "other components"), if necessary, in addition to the specific (meth) acrylic copolymer and the cross-linking agent. May be 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 structural unit derived from a monomer having a carboxy group and a homopolymer. The glass transition temperature of the (meth) acrylic acid alkyl ester monomer having a glass transition temperature of -60 ° C. or lower is 8% by mass to 50% by mass with respect to all the structural units, and the glass transition temperature. Is -40 ° C or lower.

The specific (meth) acrylic copolymer contains a structural unit derived from a monomer having a carboxy group.
As used herein, the "constituent 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 contains a structural unit derived from a monomer having a carboxy group, cohesive force is developed in the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive film has high normal adhesive strength and heat-resistant shrinkage. Can be done.

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

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 constituent units derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is the total constituent units (that is, all the constituents constituting the specific (meth) acrylic copolymer). The unit) is preferably in the range of 1% by mass to 11% by mass, more preferably in the range of 2% by mass to 8% by mass, and further preferably in the range of 4% by mass to 7% by mass.
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 with respect to all the structural units, the cohesive force of the pressure-sensitive adhesive layer is too low. However, since it becomes more appropriate, the normal adhesive strength of the adhesive film can be further improved. In addition, the heat-resistant shrinkage of the adhesive film can be further improved.
When 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. However, since the anchor effect on the adherend is further suppressed, the stickability of the adhesive film can be further improved.

The specific (meth) acrylic copolymer contains all the structural units derived from the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C or lower when used as a homopolymer. (That is, 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, the "glass transition temperature when made into a homopolymer" is the glass transition temperature (Tg) represented by the absolute temperature (K) of the homopolymer produced by polymerizing the monomer alone. To say. The glass transition temperature (Tg) of the homopolymer was measured using a differential scanning calorimetry device (DSC) (model number: EXSTAR6000, Seiko Instruments Co., Ltd.) in a nitrogen stream, a measurement sample of 10 mg, and a temperature rise rate of 10 ° C./min. The turning point of the obtained DSC curve was taken as the glass transition temperature (Tg) of the homopolymer.
Further, in the present specification, the “constituent unit derived from the (meth) acrylic acid alkyl ester monomer” means a structural unit formed by addition polymerization of the (meth) acrylic acid alkyl ester monomer.

The (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of −60 ° C. or lower when used as a homopolymer has a glass transition temperature (Tg) of −90 ° C. or higher when used as a homopolymer. It is preferably −60 ° C. or lower, more preferably −85 ° C. or higher and −65 ° C. or lower, and further preferably −80 ° C. or higher and −70 ° C. or lower.

As the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of −60 ° C. or lower when used as a homopolymer, an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable. The type is not particularly limited.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic.
The number of carbon atoms 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 adhesive strength to the adherend and adhesion to the substrate.

As the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C. or lower when used as a homopolymer, 2-ethylhexyl acrylate (2EHA, Tg when used as a homopolymer:- 76 ° C.), i-octyl acrylate (i-OA, Tg when made into a homopolymer: −75 ° C.), n-octyl acrylate (n-OA, Tg when made into a homopolymer: −80 ° C.), Examples thereof include lauryl methacrylate (LMA, Tg when made into a homopolymer: -65 ° C.).
Among these, at least one selected from 2-ethylhexyl acrylate (2EHA) and i-octyl acrylate (i-OA) is preferable from the viewpoint that an adhesive film having higher normal adhesive strength can be realized, and the adhesive film is applied. 2-Ethylhexyl acrylate (2EHA) is more preferable from the viewpoint that an adhesive film having better properties and higher normal adhesive strength can be realized.

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

The content of structural units derived from the (meth) acrylic acid alkyl ester monomer, which has a glass transition temperature (Tg) of -60 ° C or lower when 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 the constituent units constituting the specific (meth) acrylic copolymer). The range is preferable, and the range of 20% by mass to 40% by mass is more preferable.
The content of structural units derived from the (meth) acrylic acid alkyl ester monomer, which has a glass transition temperature (Tg) of -60 ° C or lower when used as a homopolymer in a specific (meth) acrylic copolymer, is If it is less than 8% by mass with respect to all the constituent units, the pressure-sensitive adhesive layer becomes hard, and the stickability of the pressure-sensitive adhesive film tends to deteriorate.
The content of structural units derived from the (meth) acrylic acid alkyl ester monomer, which has a glass transition temperature (Tg) of -60 ° C or lower when used as a homopolymer in a specific (meth) acrylic copolymer, is If it exceeds 50% by mass with respect to all the constituent units, the pressure-sensitive adhesive layer becomes too soft, so that the normal adhesive strength of the pressure-sensitive adhesive film tends to decrease.

The specific (meth) acrylic copolymer has a glass transition temperature (Tg) of -60 ° C. or lower when used as a homopolymer, and is not a structural unit derived from the (meth) acrylic acid alkyl ester monomer (meth). ) Constituent unit derived from an acrylic acid alkyl ester monomer (that is, a structural unit derived from a (meth) acrylic acid alkyl ester monomer whose glass transition temperature (Tg) when made into a homopolymer exceeds -60 ° C. ) Is further included.
The structural unit derived from the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding −60 ° C. when made into a homopolymer contributes to the adjustment of the adhesive force of the pressure-sensitive adhesive layer.

The upper limit of the glass transition temperature (Tg) of the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C as a homopolymer is not particularly limited, but is, for example, 10 ° C. The following is preferable.

As the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding −60 ° C. as a homopolymer, an unsubstituted (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 number of carbon atoms 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 adhesive strength to the adherend and adhesion to the substrate.

Examples of the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) exceeding -60 ° C. as a homopolymer include methyl (meth) acrylate, ethyl (meth) acrylate, and n-butyl (meth). Examples thereof include acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl methacrylate, i-nonyl acrylate, stearyl acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate.
Among these, as the (meth) acrylic acid alkyl ester monomer whose glass transition temperature (Tg) exceeds -60 ° C when used as a homopolymer, for example, the glass transition of a specific (meth) acrylic copolymer From the viewpoint that the temperature (Tg) can be easily adjusted to −40 ° C. or lower, n-butyl acrylate (n-BA, Tg when homopolymerized: −57 ° C.) is preferable.

When 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. when made into 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.

When 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. when made into a homopolymer. The content (ratio) of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer is, for example, from the viewpoint that the adhesive strength of the pressure-sensitive adhesive layer can be easily adjusted. , 39% by mass or more is preferable, 45% by mass or more is more preferable, and 55% by mass or more is further preferable with respect to all the structural units (that is, all the structural units constituting the specific (meth) acrylic copolymer).
The upper limit of the content (ratio) of the structural 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 structural units, the upper limit is not particularly limited. It is preferably 84% by mass or less.

The specific (meth) acrylic copolymer has a structural unit derived from a monomer having a carboxy group and a glass transition temperature (Tg) when it is a homopolymer within the range in which the effect of the present invention is exhibited. The glass transition temperature (Tg) when a constituent unit derived from a (meth) acrylic acid alkyl ester monomer having a temperature of -60 ° C or lower and an arbitrary constituent unit as a copolymer is used exceeds -60 ° C (meth). ) A structural unit other than the structural unit derived from the acrylic acid alkyl ester monomer (so-called other structural unit) may be contained.

The type of monomer constituting the other structural unit is not particularly limited.
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) acrylate represented by ethyl (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl represented by vinyltoluene, acrylonitrile and Examples thereof include vinyl cyanide typified by acrylonitrile, and vinyl esters typified by vinyl acrylate, vinyl acetate, vinyl propionate, and vinyl versaticate. In addition, various derivatives of these monomers can 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 lower, preferably −60 ° C. or higher and −40 ° C. or lower, and more preferably −55 ° C. or higher and −42 ° C. or lower. Yes, more preferably −50 ° C. or higher and −45 ° C. or lower.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer exceeds −40 ° C., the pressure-sensitive adhesive layer becomes hard, so that the stickability of the pressure-sensitive adhesive film tends to deteriorate.

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

In the formula 1, Tg1, Tg2, ..., Tg (k-1), and Tgk are the absolute temperatures when each monomer constituting the specific (meth) acrylic copolymer is used as a homopolymer. Each represents the glass transition temperature (Tg) represented by K). m1, m2, ..., M (k-1), and mk represent the mole fractions 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 the Celsius temperature (° C) can be converted to the absolute temperature (K) by adding 273 to the Celsius temperature (° C). Can be converted to.

The "glass transition temperature (Tg) represented by the Celsius temperature (° C.) when made into a homopolymer" of a typical monomer is -76 ° C for 2-ethylhexyl acrylate (2EHA) and 2-ethylhexyl methacrylate (2-ethylhexyl methacrylate). 2EHMA) is -10 ° C, n-butyl acrylate (n-BA) is -57 ° C, n-butyl methacrylate is 21 ° C, t-butyl acrylate (t-BA) is 41 ° C, t-butyl methacrylate is 107 ° C, i-octyl acrylate (i-OA) is -75 ° C, n-octyl acrylate (n-OA) is -80 ° C, lauryl methacrylate (LMA) is -65 ° C, methyl acrylate (MA) is 5 ° C, methyl methacrylate ( MMA) at 103 ° C, isobonyl methacrylate (IBMX) at 155 ° C, ethyl acrylate (EA) at -27 ° 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) at 163 ° C, dimethylaminoethyl methacrylate (DM) at 18 ° C, and 2-acryloyloxyethyl-succinic acid at -40 ° C. be.

The glass transition temperature (Tg) of the specific (meth) acrylic copolymer can be appropriately adjusted by using, for example, monomers having different glass transition temperatures (Tg) when they are homopolymers.

<< 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 is preferably in the range of 300,000 to 2 million, more preferably in the range of 400,000 to 1.5 million, and more preferably 600,000 to 120. A range of 10,000 is even more preferred.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 300,000 or more, the cohesive force of the pressure-sensitive adhesive layer is not too low and becomes more appropriate, so that the heat-resistant shrinkage of the pressure-sensitive adhesive film becomes high. Can be improved.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 2 million or less, the cohesive force of the pressure-sensitive adhesive layer is not too high and becomes more appropriate, so that the adhesive film has a sticking property. Can be improved.
The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer can be adjusted to a desired value depending on the temperature and time of the polymerization reaction, the amount of the organic solvent, the type and 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, the measurement is performed according to the following (1) to (3).
(1) A solution of the specific (meth) acrylic copolymer is applied to a 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 by using the film-shaped specific (meth) acrylic copolymer obtained in (1) above 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-equivalent value under the following conditions.

~conditions~
Measuring device: High-speed GPC (Model number: HLC-8220 GPC, Tosoh Corporation)
Detector: Differential refractometer (RI) (embedded in HLC-8220, Tosoh Corporation)
Column: TSK-GEL GMHXL (Tosoh Corporation) connected in series 4 Column temperature: 40 ° C
Eluent: tetrahydrofuran Sample concentration: 0.2% by mass
Injection volume: 100 μL
Flow rate: 0.6 mL / min

<< Manufacturing method of 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 a monomer by a known polymerization method typified by, for example, solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization.
Among these, as a polymerization method, for example, in preparing a pressure-sensitive adhesive composition after production, solution polymerization is preferable because the treatment step is relatively simple and can be performed in a short time.

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 the mixture is stirred in a nitrogen stream or at the reflux temperature of the organic solvent. While heating for several hours. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be added sequentially.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, alcohol compounds and the like.
At the time of the polymerization reaction, only one of these organic solvents may be used, or two or more of these organic solvents may be mixed and used.

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, tetraline, and decalin. And aromatic hydrocarbons represented by aromatic naphtha, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and fat represented by terepine oil. Ethers typified by system or alicyclic hydrocarbons, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate. Classes, acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and ketones typified by methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether. , And glycol ethers typified by diethylene glycol monobutyl ether, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-. Examples thereof include alcohols typified by butyl alcohol.

In the production of the specific (meth) acrylic copolymer, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of esters, ketones, etc., and in particular, the dissolution of the specific (meth) acrylic copolymer. From the viewpoint of properties, ease of polymerization reaction and the like, it is preferable to use ethyl acetate, toluene or the like.

Examples of the polymerization initiator include organic peroxides and azo compounds used in ordinary solution polymerization.
Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonato, and di-2-ethylhexylperoxydi. Carbonato, t-butylperoxyvibalato, 2,2-bis (4,5-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,5-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,5-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,54-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,4) Examples include -di-t-butylperoxycyclohexyl) butane and 2,2-bis (4,5-di-t-octylperoxycyclohexyl) butane.
Examples of the azo compound include 2,2'-azobisisobutynitrile (AIBN), 2,2'-azobis (2,4-dimethylvaleronitrile) (ABVN), and 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, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and in particular, it is preferable to use an azobis-based polymerization initiator.

The amount of the polymerization initiator used 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, if necessary, as long as the object and effect of the present invention are not impaired.
Examples of the chain transfer agent include cyanoacetic acid, alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid, bromoacetic acid, alkyl esters having 1 to 8 carbon atoms of bromoacetic acid, α-methylstyrene, anthracene, phenanthrene, and fluorene. , And aromatic compounds typified by 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds typified by p-nitrotoluene, Benzoquinone and benzoquinone derivatives typified by 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives typified by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2- Tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, halogenated hydrocarbons typified by 3-chloro-1-propene, aldehydes typified by chloral and furaldehyde, carbon number 1 to 1 18 alkyl mercaptans, aromatic mercaptans typified by thiophenols and toluene mercaptans, mercaptoacetic acid, alkyl esters of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptans having 1 to 12 carbon atoms, and binen. And terpenes represented by turpinolene.

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, and depends on the molecular weight of the target specific (meth) acrylic copolymer. , Set as appropriate.

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

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

Examples of the isocyanate compound include xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, aromatic polyisocyanate compound typified by tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate, and the above-mentioned fragrance. With chain or cyclic aliphatic polyisocyanate compounds typified by hydrogenated additives of group polyisocyanate compounds, biuret, dimer, trimeric or pentamer of these polyisocyanate compounds, and these polyisocyanate compounds. Examples thereof include an adduct with a polyol compound such as trimethylol propane.

Among these, as the isocyanate compound, from the viewpoint of maintaining the stability of the adhesive force with time, a dimer of tolylene diisocyanate and tolylene diisocyanate, an adduct of tolylene diisocyanate and a polyol, and a triad of tolylene diisocyanate. A tolylene diisocyanate compound derived from various tolylene diisocyanates such as an isocyanurate form which is a body or a pentamer and a biuret form of a tolylene diisocyanate is preferable.

As the isocyanate compound, a commercially available product can be used.
Examples of commercially available isocyanate compounds include "Coronate (registered trademark) HX", "Coronate (registered trademark) HL-S", "Coronate (registered trademark) L", and "Coronate (registered trademark)" of Toso Co., Ltd. L-45E ”,“ Coronate® 2031 ”,“ Coronate® 2030 ”,“ Coronate® 2234 ”,“ Coronate® 2785 ”,“ Aquanate® 200 ” , And "Aquanate (registered trademark) 210", "Sumijuru (registered trademark) N3300", "Death Module (registered trademark) N3400", and "Sumijuru (registered trademark) N" of Sumika Cobestro Urethane Co., Ltd. -75 ", Asahi Kasei Co., Ltd.'s" Duranate (registered trademark) E-405-80T "," Duranate (registered trademark) 24A-100 "," Duranate (registered trademark) TSE-100 ", and Mitsui Takeda Chemical Products of "Takenate (registered trademark) D-110N", "Takenate (registered trademark) D-120N", "Takenate (registered trademark) M-631N" and "MT-Orester (registered trademark) NP1200" Those commercially available by name can be preferably used.

Examples of the epoxy compound include 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, resorcin diglycidyl ether, 2,2-dibromoneopentyl Glycoldiglycidyl ether, trimethylpropan triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocia Examples thereof include nurate, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-1,3-benzenedi (methaneamine) and the like.

As the epoxy compound, a commercially available product can be used.
As commercially available epoxy compounds, for example, those commercially available under the trade names of "TETRAD-X" and "TETRAD-C" of Mitsubishi Gas Chemical Company, Inc. can be preferably used.

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

The content of the cross-linking agent in the pressure-sensitive adhesive composition is not particularly limited and can be appropriately set according to the type of the cross-linking 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 can realize a pressure-sensitive adhesive film having better adhesiveness and higher normal adhesive strength. 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 above-mentioned specific (meth) acrylic copolymer.
For example, when the cross-linking agent is an epoxy compound having an epoxy group, the content of the cross-linking agent in the pressure-sensitive adhesive composition is 100 parts by mass of the above-mentioned specific (meth) acrylic copolymer from the same viewpoint as above. On the other hand, the range of 0.01 parts by mass to 10 parts by mass is preferable, and the range of 0.05 parts by mass to 3 parts by mass is more preferable.

-Organic solvent-
The pressure-sensitive adhesive composition preferably contains an organic solvent, for example, from the viewpoint of improving coatability.
Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the specific (meth) acrylic copolymer described above.

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, relative to 100 parts by mass of the above-mentioned specific (meth) acrylic copolymer 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 other than the components described above (so-called other components), if necessary, 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 UV absorbers), antistatic agents and the like. Various additives can be mentioned.

(Arithmetic mean roughness)
In the pressure-sensitive adhesive layer, the arithmetic mean roughness Ra of the surface opposite to the base material is in the range of 2 μm to 15 μm, preferably in the range of 3 μm to 13 μm, and more preferably in the range of 4 μm to 12 μm.
If the arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to that of the base material is less than 2 μm, the initial effective adhesive area is too large, and the adhesive film tends to be sticky.
When the arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to the base material exceeds 15 μm, the effective adhesive area is too small, and the normal adhesive strength of the pressure-sensitive adhesive film tends to decrease.

The arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to the base material can be adjusted to a desired value by, for example, pressing a metal roll against the surface of the pressure-sensitive adhesive layer after curing.
Further, the arithmetic average roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to the base material is, for example, an arithmetic average roughness Ra of the surface of the surface opposite to the base material of the pressure-sensitive adhesive layer of 2 μm to 15 μm. By arranging the release film in the range, it can be adjusted to a desired value.
For example, from the viewpoint of usability of the adhesive film (so-called ease of use), the adjustment of the arithmetic mean roughness Ra is to arrange a release film having an arithmetic average roughness Ra of the surface in the range of 2 μm to 15 μm. It is preferable to carry out by.
The arithmetic average roughness Ra of the surface of the pressure-sensitive adhesive layer gradually returns to the state before adjustment due to the elasticity of the pressure-sensitive adhesive layer. It is desirable to attach it to the adherend as soon as possible while it is being held. According to the method using the release film, the release film can be peeled off from the surface of the pressure-sensitive adhesive layer and then immediately attached to the adherend. Therefore, the usability of the pressure-sensitive adhesive film is compared with the method using the metal roll. Is better.

The arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer opposite to the substrate was measured using the Keyence laser microscope VK-X200 and the observation and analysis applications attached to the laser microscope VK-X200. Is.

(Thickness of adhesive layer)
The thickness of the pressure-sensitive adhesive layer is not particularly limited and can be appropriately set according to the type of adherend, for example. The thickness of the pressure-sensitive adhesive layer is preferably in the range of 5 μm to 100 μm, more preferably in the range of 10 μm to 60 μm, and even more preferably in the range of 20 μm to 40 μm.

[Release film]
The pressure-sensitive adhesive film of the present invention preferably further has a release film on the surface of the pressure-sensitive adhesive layer opposite to the base material.
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 peeled from the pressure-sensitive adhesive layer, and examples thereof include a resin film in which at least one surface is easily peeled with a release treatment agent. Examples of the resin film include a polyester film typified by a polyethylene terephthalate film. Examples of the stripping agent include fluororesins, paraffin waxes, 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 into practical use, and is peeled off during use.

The 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 for adjusting the arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer on the side opposite to the base material, the surface of the release film on the side in contact with the pressure-sensitive adhesive layer is used. The 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.

The arithmetic mean roughness Ra of the surface of the release film is a value measured using a laser microscope VK-X200 manufactured by KEYENCE and an observation application and an analysis application attached to the laser microscope VK-X200.

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

[Manufacturing method of adhesive film]
The method for producing the 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 base material, dried, and then cured to form a pressure-sensitive adhesive layer. Next, the base material / pressure-sensitive adhesive layer is laminated by pressing a metal roll having an arithmetic average roughness Ra of the surface in the range of 2 μm to 15 μm against the exposed surface of the formed pressure-sensitive adhesive layer that does not come into contact with the base material. The pressure-sensitive adhesive film of the present invention having a structure can be produced.

As another method, for example, the following method can be mentioned.
The pressure-sensitive adhesive layer is formed by applying the above-mentioned pressure-sensitive adhesive composition 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, drying the surface, and then curing the film. Next, the formed pressure-sensitive adhesive layer is transferred to the base material, that is, the surface of the release film on the side where the pressure-sensitive adhesive layer is formed is adhered to the base material and pressed to pressurize the base material / pressure-sensitive adhesive layer / release film. By peeling off the release film after producing the laminate having the laminated structure, the adhesive film of the present invention having the laminated structure of the base material / adhesive layer can be produced.

As yet another method, for example, the following method can be mentioned.
The above-mentioned pressure-sensitive adhesive composition is applied onto the surface of a release film having an arithmetic average 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. Next, the pressure-sensitive adhesive film of the present invention having a laminated structure of a base material / a pressure-sensitive adhesive layer / a release film can be produced by adhering a base material to the pressure-sensitive surface of a film with a pressure-sensitive adhesive and curing the base material.

The method of applying the pressure-sensitive adhesive composition on the surface of the base material or the release film is not particularly limited, and for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a knife coater, a spray coater, etc. A known method using a bar coater, an applicator, or the like can be mentioned.
The amount of the pressure-sensitive adhesive composition applied onto the surface of the base material or the release film is appropriately set according to the thickness of the pressure-sensitive adhesive layer to be formed.

The method for drying the pressure-sensitive adhesive composition applied on the surface of the base material or the release film is not particularly limited, and examples thereof include natural drying, heat drying, hot air drying, and vacuum drying.
The drying temperature and drying time of the pressure-sensitive adhesive composition applied on the surface of the base material or the release film are not particularly limited, and depend on the thickness of the applied pressure-sensitive adhesive composition, the amount of the organic solvent in the pressure-sensitive adhesive composition, and the like. Is set as appropriate.

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

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

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

<Example 1>
-Manufacture of (meth) acrylic copolymer-
N-butyl acrylate (n-BA; (meth) acrylic acid alkyl ester monomer, Tg as a homopolymer in a reactor equipped with a stirrer, a reflux cooler, a sequential dropping device, and a thermometer. : -57 ° C) 80.9 parts by mass, 2-ethylhexyl acrylate (2EHA; (meth) acrylic acid alkyl ester monomer, Tg when made into a homopolymer: -76 ° C) 34.7 parts by mass, acrylic acid (AA; monomer having a carboxy group) 7.4 parts by mass and ethyl acetate (EAc) 205 parts by mass were charged, and 2,2'-azobisisobutyronitrile (AIBN) 0.066 was charged as a polymerization initiator. Mass parts were added. After the addition of AIBN, the contents of the reactor were heated and kept at reflux temperature (82 ° C.) for 20 minutes. Then, in this 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 parts of AIBN. Mixture A consisting of parts by mass was sequentially added dropwise over 120 minutes. After dropping the mixture A, the temperature of the contents in the reactor was further maintained at 85 ° C. for 90 minutes, and then the mixture B consisting of 61.5 parts by mass of EAc and 1.23 parts by mass of AIBN was applied for 60 minutes. And dropped sequentially. After dropping the mixture B, the temperature of the contents in the reactor was further maintained at 85 ° C. for 90 minutes, diluted with methyl ethyl ketone (MEK) to a solid content of 35.1% by mass, cooled, and cooled (meth). A solution of the acrylic copolymer was obtained. The "solid content" in the solution of the (meth) acrylic copolymer means the amount of the residue obtained by removing volatile components such as a solvent from the solution of the (meth) acrylic copolymer (hereinafter, 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; "coronate") which is an isocyanate compound as a cross-linking agent are Thoroughly agitated and mixed with a registered trademark, trimethylolpropane adduct of tolylene diisocyanate (TDI), solid content: 45% by mass, and Toso Co., Ltd. 3.91 parts by mass (solid content: 1.76 parts by mass). To prepare a pressure-sensitive adhesive composition.

-Preparation of adhesive film for evaluation test-
The pressure-sensitive adhesive composition prepared above is applied to the uneven surface of the release film having an arithmetic average roughness Ra of 8.0 μm on the surface using a doctor blade film applicator so that the minimum thickness after drying is 25 μm. Then, it was dried for 1 minute under hot air at 100 ° C. and 5 m / sec to prepare a film with an adhesive.
Next, a vinyl chloride film (trade name: 00178M7, thickness: 70 μm, Nippon Carbide Industries, Ltd.) was attached to the adhesive surface of the film with an adhesive as a base material, and allowed to stand in an environment of 40 ° C. for 72 hours. , A pressure-sensitive adhesive film having a laminated structure of a release film / pressure-sensitive adhesive layer / base material was obtained. The arithmetic mean roughness Ra of the surface of the pressure-sensitive adhesive layer on the release film side of the obtained pressure-sensitive adhesive film is 8.0 μm.
Next, a screen ink (trade name: Hi-SSPINK, Nippon Carbide Industry Co., Ltd.) was printed on the base material (that is, vinyl chloride film) surface of the produced adhesive film using a 250 mesh screen, and then hot air was used. Using a dryer, it was heated and dried in an environment of 60 ° C. for 10 minutes. Next, a screen clear (trade name: Hi-SSPCLEAR, Nippon Carbide Industry Co., Ltd.) was printed on the screen ink printing surface of the adhesive film using a 180-mesh screen, and the temperature was 80 ° C. using a hot air dryer. Adhesion for evaluation test having a laminated structure of release film / adhesive layer / base material / screen ink layer / screen clear layer by heating and drying in an environment for 60 minutes and then allowing it to stand in an environment of 40 ° C for 72 hours. I got a film.

<Example 2>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Example 3>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Example 4>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Example 5>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the organic solvent and organic solvent were added. Example 1 and Example 1 except that the weight average molecular weight was changed to 1.2 million by adjusting the amount of the polymerization initiator to obtain a solution of the (meth) acrylic copolymer having a solid content of 35.1% by mass. The same operation was carried out to obtain an adhesive film for evaluation test.

<Example 6>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Example 7>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Example 8>
In "-Preparation of Adhesive Film for Evaluation Test-" of Example 1, the surface arithmetic mean roughness Ra is 3.0 μm instead of the release film having an arithmetic mean roughness Ra of 8.0 μm. The same operation as in Example 1 was performed except that the film was used, to obtain an adhesive film for evaluation test.

<Example 9>
In "-Preparation of Adhesive Film for Evaluation Test-" of Example 1, the surface arithmetic mean roughness Ra is 13.0 μm instead of the release film having an arithmetic mean roughness Ra of 8.0 μm. The same operation as in Example 1 was performed except that the film was used, to obtain an adhesive film for evaluation test.

<Example 10>
In Example 1 "Production of- (meth) acrylic copolymer-", the weight average molecular weight was changed to 2 million by adjusting the amounts of the organic solvent and the polymerization initiator, and the solid content was 35.1 mass. The same operation as in Example 1 was carried out except that a solution of% (meth) acrylic copolymer was obtained, and an adhesive film for evaluation test was obtained.

<Example 11>
In Example 1 "Production of- (meth) acrylic copolymer-", the weight average molecular weight was changed to 300,000 by adjusting the amounts of the organic solvent and the polymerization initiator, and the solid content was 35.1 mass. The same operation as in Example 1 was carried out except that a solution of% (meth) acrylic copolymer was obtained, and an adhesive film for evaluation test was obtained.

<Example 12>
In "-Preparation of Adhesive Composition-" of Example 1, instead of using 3.91 parts by mass (solid content: 1.76 parts by mass) of coronate (registered trademark) L-45E, which is an isocyanate compound, as a cross-linking agent. In addition, the epoxy compound TETRAD-X (trade name; "TETRAD" is a registered trademark, 1,3-phenylenebis (N, N-diglycidylmethaneamine), solid content: 100% by mass, Mitsubishi Gas Chemicals Co., Ltd. ) The same operation as in Example 1 was carried out except that 0.1 part by mass (solid content: 0.1 part by mass) was used to obtain an adhesive film for evaluation test.

<Example 13>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Example 14>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Comparative example 1>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Comparative example 2>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Comparative example 3>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Comparative example 4>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

<Comparative example 5>
In "-Preparation of Adhesive Film for Evaluation Test-" of Example 1, the surface arithmetic mean roughness Ra is 1.0 μm instead of the release film having an arithmetic mean roughness Ra of 8.0 μm. The same operation as in Example 1 was performed except that the film was used, to obtain an adhesive film for evaluation test.

<Comparative Example 6>
In "-Preparation of Adhesive Film for Evaluation Test-" of Example 1, the surface arithmetic mean roughness Ra is 18.0 μm instead of the release film having an arithmetic mean roughness Ra of 8.0 μm. The same operation as in Example 1 was performed except that the film was used, to obtain an adhesive film for evaluation test.

<Comparative Example 7>
In "-Producing a (meth) acrylic copolymer-" of Example 1, the composition of the monomers constituting the (meth) acrylic copolymer was changed to the composition shown in Table 1, and the solid content was 35. The same operation as in Example 1 was carried out except that a 1% by mass (meth) acrylic copolymer solution was obtained, and an adhesive film for evaluation test was obtained.

Table 1 shows the composition of the monomer of the (meth) acrylic copolymer contained in the pressure-sensitive adhesive composition in each Example and each Comparative Example, the glass transition temperature (Tg), and the weight average molecular weight (Mw).
Table 1 shows the types and amounts (unit: parts by mass) of the cross-linking agent contained in the pressure-sensitive adhesive composition in each Example and each Comparative Example. The amount of the cross-linking agent shown in Table 1 is the number of dry copies (that is, the solid content conversion value).
Table 1 shows the arithmetic mean roughness Ra (unit: μm) of the surface on the release film side of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive film for evaluation test of each Example and each comparative example.

[evaluation]
1. 1. Stickability The adhesive film for evaluation test prepared above was cut into a size of 5 cm × 20 cm, and a piece of adhesive film for evaluation test was prepared.
The release film is peeled off from the prepared adhesive film piece for evaluation test, and the pressure-sensitive adhesive layer exposed by the peeling is subjected to a white coating plate (trade name: melamine white coating plate, material: SPCC-SD,) in an environment of room temperature (23 ° C.). Specifications: Melamine-painted, Paltec Co., Ltd. was attached using a squeegee. Immediately after that, the evaluation test adhesive film piece attached to the white coated plate was manually peeled from the white coated plate so that the peeling angle was 120 ° in the long side (20 cm) direction. The work from sticking the adhesive layer to the white coated plate to peeling is the first sticking work.
Next, the same up-pasting work was repeated four more times using the evaluation test adhesive film piece on which the first up-pasting work was performed.
After each pasting operation was completed, the peeled adhesive film piece for evaluation test was visually observed, and the pasting property was evaluated according to the following evaluation criteria. The results are shown in Table 1.
In the following evaluation criteria, the one with the best stickability is "A". Further, if the evaluation result is "A", "B", or "C", it is judged that there is no practical problem.

-Evaluation criteria-
A: No shock line was generated even after the fifth pasting work.
B: A shock line occurred after the fourth pasting work.
C: A shock line occurred after the second or third pasting work.
D: A shock line occurred after the first pasting work.

2. Normal Adhesive Strength The adhesive film for evaluation test prepared above was cut into a size of 1 cm × 10.5 cm, and a piece of adhesive film for evaluation test was prepared.
The release film is peeled off from the prepared adhesive film piece for evaluation test, and the adhesive layer exposed by the peeling is subjected to a white coating plate (trade name: melamine white coating plate, material: SPCC-SD,) in an environment of room temperature (23 ° C.). Specifications: After sticking to melamine coating, Partec Co., Ltd. using a squeegee, it was left at room temperature (23 ° C.) for 48 hours.
Next, the adhesive force (unit: N / 10 mm) when the adhesive film piece for evaluation test is peeled 180 ° in the long side (10.5 cm) direction from the white coated plate is measured by Orientec's universal material testing machine (model number: model number: It was measured using RTA-100) under the condition of peeling speed of 300 mm / min. The measured adhesive strength was multiplied by 2.5, and the value converted into the adhesive strength of 25 mm width (unit: N / 25 mm) was defined as the normal adhesive strength, and the evaluation was performed according to the following evaluation criteria. The results are shown in Table 1.
In the following evaluation criteria, the one with the best normal adhesive strength is "A". Further, if the evaluation result is "A", "B", or "C", it is judged that there is no practical problem.

-Evaluation criteria-
A: The normal adhesive strength exceeds 12N / 25mm.
B: The normal adhesive strength exceeds 8N / 25mm and is 12N / 25mm or less.
C: The normal adhesive strength exceeds 5N / 25mm and is 8N / 25mm or less.
D: The normal adhesive strength is 5 N / 25 mm or less.

3. 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 piece of pressure-sensitive adhesive film for evaluation test.
The release film is peeled off from the prepared adhesive film piece for evaluation test, and the pressure-sensitive adhesive layer exposed by the peeling is subjected to a white coating plate (trade name: melamine white coating plate, material: SPCC-SD,) in an environment of room temperature (23 ° C.). Specifications: Melamine coating, Paltec Co., Ltd. was bonded to Paltec Co., Ltd. using a squeegee to prepare a test piece, and then left at room temperature (23 ° C.) for 48 hours. Then, the test piece after being left to stand was further left to stand in an environment of 80 ° C. for 2 hours, and then left to cool at room temperature (23 ° C.) for 60 minutes. After cooling, the shrinkage rate of the pressure-sensitive adhesive film piece for evaluation test after heating was measured using a measuring 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 best heat shrinkage is "A". Further, if the evaluation result is "A", "B", or "C", it is judged that there is no practical problem.

-Evaluation criteria-
A: The shrinkage rate is 0.3% or less.
B: The shrinkage rate exceeds 0.3% and is 0.5% or less.
C: The shrinkage rate exceeds 0.5% and is 0.7% or less.
D: The shrinkage rate exceeds 0.7%.

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

Details of each monomer shown in Table 1 are as shown below.
<(Meta) acrylic acid alkyl ester monomer>
-"N-BA": n-butyl acrylate (Tg when made into a homopolymer: -57 ° C.)
-"EA": Ethyl acrylate (Tg when made into a homopolymer: -27 ° C)
-"2EHA": 2-ethylhexyl acrylate (Tg when made into a homopolymer: -76 ° C)
-"I-OA": i-octyl acrylate (Tg when made into a homopolymer: -75 ° C.)
<Monomer having a carboxy group>
-"AA": Acrylic acid (Tg: 163 ° C. when made into a homopolymer)
-"HOA-MS": 2-acryloyloxyethyl-succinic acid (Tg when made into a homopolymer: -40 ° C)

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

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 Example (for example, Example 1) having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer having (Tg) of −40 ° C. or lower. The sticking property was remarkably inferior.

The proportion of structural units derived from the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C or lower 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 (meth) acrylic copolymer is a proportion of structural units derived from the above (meth) acrylic acid alkyl ester monomer. However, there is an Example (for example, Example 1) 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 constituent units. ), The stickability was significantly inferior to that of the adhesive film.
The proportion of structural units derived from the (meth) acrylic acid alkyl ester monomer having a glass transition temperature (Tg) of -60 ° C or lower when used as a homopolymer exceeds 50% by mass with respect to all the structural 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 proportion of structural units derived from the above (meth) acrylic acid alkyl ester monomer. Examples 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 based on all the constituent units (for example, Example 1). The normal adhesive strength was remarkably low as compared with the adhesive film of.

The adhesive film of Comparative Example 5 having an arithmetic average roughness Ra of less than 2 μm on the surface of the pressure-sensitive adhesive layer opposite to the substrate (that is, the surface on the release film side) has an arithmetic average roughness Ra of 2 μm to 15 μm. Compared with the adhesive film of Example (for example, Example 1) in the range of (1), the stickability was significantly inferior.
The adhesive film of Comparative Example 6 having an arithmetic average roughness Ra of more than 15 μm on the surface of the pressure-sensitive adhesive layer opposite to the substrate (that is, the surface on the release film side) has an arithmetic average roughness Ra of 2 μm to 15 μm. The normal adhesive strength was significantly lower than that of the pressure-sensitive adhesive film of Example (for example, Example 1), which was 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 containing no structural unit derived from a monomer having a carboxy group has a carboxy group. Compared to the pressure-sensitive adhesive film of Example (eg, Example 1) having a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer containing a monomer-derived structural unit. The normal adhesive strength was remarkably low. In addition, the pressure-resistant shrinkage of the pressure-sensitive adhesive film of Comparative Example 7 was significantly inferior to that of the pressure-sensitive adhesive film of Example 1.

Claims (4)

It has a base material and an adhesive layer arranged on the surface of the base material.
The pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and a cross-linking agent, and has an arithmetic average roughness Ra of 2 μm to 15 μm on the surface opposite to the base material. can be,
The (meth) acrylic copolymer has a glass transition temperature of 1% by mass to 11% by mass with respect to all the structural units derived from the monomer having a carboxy group, and the glass transition temperature when the homopolymer is used. The structural unit derived from the (meth) acrylic acid alkyl ester monomer having a temperature of -60 ° C or lower is 8% by mass to 50% by mass with respect to all the structural units, and the glass transition temperature when a copolymer is used is -60. Containing a constituent unit derived from a (meth) acrylic acid alkyl ester monomer exceeding ° C. of 39% by mass or more with respect to all the constituent units , and having a glass transition temperature of −40 ° C. or lower.
The cross-linking agent is an isocyanate compound.
A pressure-sensitive adhesive film in which the content of the isocyanate compound in the pressure-sensitive adhesive composition is 3 parts by mass to 7 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer. The pressure-sensitive adhesive film according to claim 1, further comprising a release film on the surface of the pressure-sensitive adhesive layer opposite to the base material. The pressure-sensitive adhesive film according to claim 2, wherein the arithmetic mean roughness Ra of the surface of the release film on the side in contact with the pressure-sensitive adhesive layer is 2 μm to 15 μm. The adhesive film according to any one of claims 1 to 3, wherein the (meth) acrylic copolymer has a weight average molecular weight of 400,000 to 1.5 million.