JP6905475B2 - Adhesive composition and adhesive film - Google Patents

Description

The present invention relates to pressure-sensitive adhesive compositions and pressure-sensitive adhesive films.

Various display boards such as signs, advertisements, and signboards are provided with, for example, a printing layer formed by an inkjet method. On a display board installed outdoors, the surface of the print layer is likely to be soiled to reduce visibility, and the print layer is likely to fade due to deterioration over time. Therefore, a protective film is provided on the surface of the printing layer of the display board installed outdoors. An acrylic adhesive is used to attach the protective film to the display board.
The protective film provided with the pressure-sensitive adhesive layer formed of the acrylic pressure-sensitive adhesive is, for example, a pressure-sensitive adhesive film having a base material made of a fluororesin film and a pressure-sensitive adhesive layer containing an acrylic-based pressure-sensitive adhesive. However, a fluororesin-based adhesive film containing a triazine-based ultraviolet absorber is known (see, for example, Patent Document 1).

In addition, a reflective sheet may be attached to the surface of the display board installed outdoors for the purpose of enhancing visibility. In this case, the print layer is often provided on the outermost surface of the reflective sheet.
As the reflective sheet provided with the protective film, for example, a fluororesin film having a total light transmittance of 80% or more is mainly acrylic on the surface layer of the retroreflective sheet having a smooth surface layer on the light incident side. A retroreflective sheet formed by being laminated via an adhesive layer made of a based resin is known (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2012-17407 International Publication No. 97/22098

By the way, the protective film used for the display board installed outdoors is required to have weather resistance. For example, the pressure-sensitive adhesive layer included in the protective film is formed by using a pressure-sensitive adhesive composition containing a light stabilizer in order to enhance its weather resistance. In particular, a hindered amine-based light stabilizer (so-called HALS) is often used as a light stabilizer capable of forming a pressure-sensitive adhesive layer having excellent weather resistance.
However, when a protective film having an adhesive layer containing a hindered amine light stabilizer is used in a high humidity environment (for example, in an area with a large amount of rainfall), the adhesive layer may be whitened. Whitening of the adhesive layer included in the protective film can reduce the visibility of the information displayed on the display board, which can be a serious problem especially for road signs. Therefore, the pressure-sensitive adhesive composition used for the protective film of the display board is required to be able to form a pressure-sensitive adhesive layer that is difficult to whiten even in a high humidity environment.
Further, the pressure-sensitive adhesive composition used for the protective film of the display board is required to be able to form a pressure-sensitive adhesive layer that is difficult to peel off from the display board.

The problem to be solved by the present invention is a pressure-sensitive adhesive composition containing a hindered amine-based light stabilizer, which is difficult to whiten in a high humidity environment and can form a pressure-sensitive adhesive layer capable of exhibiting high adhesive strength to an adherend. To provide things.
Further, the problem to be solved by the present invention is an adhesive film containing a hindered amine-based light stabilizer, which is difficult to whiten in a high humidity environment and has an adhesive layer capable of exhibiting high adhesive force to an adherend. Is to provide.

Specific means for solving the problem include the following aspects.
<1> Containing a structural unit A derived from at least one monomer selected from methyl acrylate and ethyl acrylate, and a structural unit B derived from a monomer having a carboxy group, and derived from the above-mentioned methyl acrylate. A (meth) acrylic copolymer having a total content of the structural unit A1 and the structural unit A2 derived from the ethyl acrylate of 5% by mass or more and 50% by mass or less with respect to all the structural units, and a cross-linking agent. A pressure-sensitive adhesive composition comprising a hindered amine-based photostabilizer having a molecular weight of 300 or more and 650 or less.
<2> The (meth) acrylic copolymer contains the structural unit A2 derived from the ethyl acrylate, and the content of the structural unit A2 derived from the ethyl acrylate is the same as the (meth) acrylic copolymer. The pressure-sensitive adhesive composition according to <1>, which is 5% by mass or more and 50% by mass or less based on all the constituent units of the coalescence.
<3> The (meth) acrylic copolymer contains the structural unit A1 derived from the methyl acrylate, and the content of the structural unit A1 derived from the methyl acrylate is the same as the (meth) acrylic copolymer. The pressure-sensitive adhesive composition according to <1>, which is 5% by mass or more and 45% by mass or less based on all the constituent units of the coalescence.
<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein the monomer having a carboxy group is acrylic acid.
<5> The content of the structural unit B derived from the monomer having a carboxy group is 5% by mass or more and 15% by mass or less with respect to all the structural units of the (meth) acrylic copolymer. The pressure-sensitive adhesive composition according to any one of 1> to <4>.
<6> The (meth) acrylic copolymer further contains a structural unit C derived from the methyl acrylate and the (meth) acrylic acid alkyl ester monomer other than the ethyl acrylate. The pressure-sensitive adhesive composition according to any one.
<7> A pressure-sensitive adhesive film comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the pressure-sensitive adhesive composition according to any one of <1> to <6>.
<8> The adhesive film according to <7>, which is used as a surface protective film for a reflective sheet.

According to the present invention, there is provided a pressure-sensitive adhesive composition containing a hindered amine-based light stabilizer, which is difficult to whiten in a high humidity environment and can form a pressure-sensitive adhesive layer capable of exhibiting high adhesive strength to an adherend. NS.
Further, according to the present invention, there is provided an adhesive film containing a hindered amine-based light stabilizer, which is difficult to whiten in a high humidity environment and has an adhesive layer capable of exhibiting high adhesive force to an adherend. ..

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 a certain 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 "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 layer made of a substance after the cross-linking reaction in the pressure-sensitive adhesive composition is completed. The pressure-sensitive adhesive layer is, for example, a solid or gel-like layer.

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".

In the present specification, "difficult to whiten in a high humidity environment" may be referred to as "excellent in moisture resistance".

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention has a structural unit A (hereinafter, also simply referred to as “constituent unit A”) derived from at least one monomer selected from methyl acrylate and ethyl acrylate, and a carboxy group. The total content of the structural unit A1 derived from the methyl acrylate and the structural unit A2 derived from the ethyl acrylate, which contains the structural unit B derived from the monomer (hereinafter, also simply referred to as “constituent unit B”). However, the (meth) acrylic copolymer (hereinafter, also referred to as “specific (meth) acrylic copolymer”) containing 5% by mass or more and 50% by mass or less with respect to all the constituent units, and the cross-linking agent , A hindered amine-based light stabilizer having a molecular weight of 300 or more and 650 or less (hereinafter, also referred to as “specific light stabilizer”).

Hindered amine-based light stabilizers are often used as light stabilizers capable of forming an adhesive layer having excellent weather resistance. However, when a protective film having an adhesive layer containing a hindered amine light stabilizer is used in a high humidity environment (for example, in an area with a large amount of rainfall), the adhesive layer may be whitened. Whitening of the adhesive layer included in the protective film can reduce the visibility of the information displayed on the display board, which can be a serious problem especially for road signs.
As a result of diligent studies by the present inventor, the pressure-sensitive adhesive layer is whitened by the action of water on the hindered amine-based light stabilizer, and the pressure-sensitive adhesive layer is whitened by using a hindered amine-based light stabilizer having a low molecular weight. We found that it could be suppressed. However, as a result of further studies by the inventor, in the pressure-sensitive adhesive layer containing a hindered amine-based light stabilizer having a low molecular weight, the hindered amine-based light stabilizer is located near the surface of the pressure-sensitive adhesive layer (so-called near the interface with the adherend). It was found that the adhesive strength to the adherend tended to decrease.

On the other hand, according to the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer containing a hindered amine-based light stabilizer, which is difficult to whiten in a high-humidity environment and exhibits high adhesive strength to an adherend. Can be formed.
Although it is not clear why the pressure-sensitive adhesive composition 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 pressure-sensitive adhesive composition of the present invention, but is described as an example.

The pressure-sensitive adhesive composition of the present invention contains a relatively low molecular weight hindered amine-based light stabilizer (that is, a specific light stabilizer) having a molecular weight of 300 or more and 650 or less, so that the pressure-sensitive adhesive is difficult to whiten in a high humidity environment. Layers can be formed.
In the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, the specific light stabilizer can be localized near the surface of the pressure-sensitive adhesive layer (near the interface with the adherend). The pressure-sensitive adhesive layer in which the specific light stabilizer is localized near the surface of the pressure-sensitive adhesive layer (near the interface with the adherend) has a low adhesive force to the adherend and is easily peeled off from the adherend. The pressure-sensitive adhesive composition of the present invention contains a structural unit A derived from at least one monomer selected from methyl acrylate and ethyl acrylate, and a structural unit B derived from a monomer having a carboxy group, and , A (meth) acrylic copolymer in which the total content of the structural unit A1 derived from methyl acrylate and the structural unit A2 derived from ethyl acrylate is 5% by mass or more and 50% by mass or less with respect to all the structural units. Since it is contained, it has excellent wettability to the adherend. As a result, it is considered that the pressure-sensitive adhesive composition of the present invention contains a hindered amine-based light stabilizer having a relatively low molecular weight, but the pressure-sensitive adhesive layer formed exhibits high adhesive strength.

With respect to the pressure-sensitive adhesive composition of the present invention, the acrylic pressure-sensitive adhesives described in Patent Document 1 (Japanese Patent Laid-Open No. 2012-17407) and Patent Document 2 (International Publication No. 97/22098) have a molecular weight of 650. It is believed that the pressure-sensitive adhesive layer formed is whitened in a high humidity environment because it contains more hindered amine light stabilizers.

Hereinafter, each component of the pressure-sensitive adhesive composition of the present invention will be described.

[Specific (meth) acrylic copolymer]
The (meth) acrylic copolymer (that is, the specific (meth) acrylic copolymer) contained in the pressure-sensitive adhesive composition of the present invention is derived from at least one monomer selected from methyl acrylate and ethyl acrylate. The total content of the structural unit A and the structural unit B derived from the monomer having a carboxy group, and the structural unit A1 derived from the methyl acrylate and the structural unit A2 derived from the ethyl acrylate is It is 5% by mass or more and 50% by mass or less with respect to all the constituent units.
In the present invention, the specific (meth) acrylic copolymer is coated on the pressure-sensitive adhesive layer due to the localization of the specific light stabilizer near the surface of the pressure-sensitive adhesive layer (near the interface with the adherend). Contributes to the improvement of the decrease in adhesive strength to the body.

<Structural unit A>
The specific (meth) acrylic copolymer contains a structural unit A derived from at least one monomer selected from methyl acrylate and ethyl acrylate.
The structural unit A contributes to the improvement of the wettability of the pressure-sensitive adhesive composition to an adherend (particularly, an adherend containing an acrylic resin).

In the present specification, the "constituent unit derived from at least one monomer selected from methyl acrylate and ethyl acrylate" is an addition polymerization of at least one monomer selected from methyl acrylate and ethyl acrylate. It means a structural unit to be formed.

The specific (meth) acrylic copolymer may contain only one of the structural unit A1 derived from methyl acrylate or the structural unit A2 derived from ethyl acrylate, and the structural unit A1 derived from methyl acrylate and ethyl may be contained. It may contain both of the structural units A2 derived from acrylate.
For example, the specific (meth) acrylic copolymer is derived from ethyl acrylate from the viewpoint that the wettability with the adherend is good even in a low temperature environment and the good wettability is easily maintained. It is preferable to include the structural unit A2.

The specific (meth) acrylic copolymer may contain only one type of structural unit A, or may contain two or more types of the constituent unit A.

The total content (total ratio) of the constituent unit A1 derived from methyl acrylate and the constituent unit A2 derived from ethyl acrylate in the specific (meth) acrylic copolymer is the total constituent unit of the specific (meth) acrylic copolymer. (That is, 5% by mass or more and 50% by mass or less, preferably 10% by mass or more and 50% by mass or less, based on all the constituent units constituting the specific (meth) acrylic copolymer; hereinafter the same). More preferably, it is by mass% or more and 45% by mass or less.
The total content of the constituent unit A1 derived from methyl acrylate and the constituent unit A2 derived from ethyl acrylate in the specific (meth) acrylic copolymer is 5 with respect to all the constituent units of the specific (meth) acrylic copolymer. Since it is by mass% or more, the wettability of the pressure-sensitive adhesive composition to the adherend is improved, and the pressure-sensitive adhesive layer can exhibit high adhesive strength to the adherend.
The total content of the structural unit A1 derived from methyl acrylate and the structural unit A2 derived from ethyl acrylate in the specific (meth) acrylic copolymer is 50 with respect to all the structural units of the specific (meth) acrylic copolymer. Since it is mass% or less, the cohesive force of the pressure-sensitive adhesive layer does not become excessively high, and the pressure-sensitive adhesive layer does not become too hard. Therefore, the pressure-sensitive adhesive layer can exhibit high adhesive strength to the adherend.

The specific (meth) acrylic copolymer is derived from ethyl acrylate, for example, from the viewpoint that it has good wettability with an adherend even in a low temperature environment and it is easier to maintain the good wettability. The content of the structural unit A2 containing the structural unit A2 and derived from ethyl acrylate is 5% by mass or more and 50% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer. It is preferable that it is 10% by mass or more and 45% by mass or less, and more preferably 20% by mass or more and 45% by mass or less.

The specific (meth) acrylic copolymer contains, for example, the structural unit A1 derived from methyl acrylate, and the content of the structural unit A1 derived from methyl acrylate is high, from the viewpoint that the adhesive strength is unlikely to decrease. It is preferably 5% by mass or more and 45% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and 10% by mass or more, based on all the constituent units of the specific (meth) acrylic copolymer. It is more preferably 35% by mass or less.

<Structural unit B>
The specific (meth) acrylic copolymer contains a structural unit B derived from a monomer having a carboxy group.
The structural unit B contributes to the improvement of the wettability of the pressure-sensitive adhesive composition to the adherend.

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.

The type of monomer having a carboxy group is not particularly limited.
Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, and ω-carboxy-polycaprolactone mono (meth) acrylate (for example, ω). -Carboxy-polycaprolactone (n≈2) monoacrylate), succinic acid ester (for example, 2-acryloyloxyethyl-succinic acid) and the like can be mentioned.
Among these, the monomer having a carboxy group is selected from the group consisting of acrylic acid, ω-carboxy-polycaprolactone mono (meth) acrylate, and succinic acid ester, for example, from the viewpoint of reactivity with a cross-linking agent. At least one monomer is preferable, and acrylic acid is more preferable from the viewpoint that the wettability of the pressure-sensitive adhesive composition to the adherend is improved and the pressure-sensitive adhesive layer can exhibit higher adhesive strength.

The specific (meth) acrylic copolymer may contain only one type of structural unit B, or may contain two or more types of the constituent unit B.

The content (ratio) of the constituent unit B in the specific (meth) acrylic copolymer is not particularly limited, but for example, it is 5% by mass or more 15 with respect to all the constituent units of the specific (meth) acrylic copolymer. It is preferably 6% by mass or more, more preferably 12% by mass or less, and further preferably 8% by mass or more and 12% by mass or less.
When the content of the structural unit B in the specific (meth) acrylic copolymer is 5% by mass or more with respect to all the structural units of the specific (meth) acrylic copolymer, the cohesive force of the pressure-sensitive adhesive layer becomes higher. To improve, the pressure-sensitive adhesive layer may exhibit higher adhesion to the adherend.
When the content of the structural unit B in the specific (meth) acrylic copolymer is 15% by mass or less with respect to all the structural units of the specific (meth) acrylic copolymer, the cohesive force of the pressure-sensitive adhesive layer is high. In the state, since it exhibits sufficient wettability to the adherend, it is possible to better suppress the decrease in the adhesive force of the pressure-sensitive adhesive layer to the adherend.

<Structural unit C>
The specific (meth) acrylic copolymer is a (meth) acrylic acid alkyl ester monomer (hereinafter, also referred to as “other (meth) acrylic acid alkyl ester monomer”) other than methyl acrylate and ethyl acrylate. It is preferable to further include the derived structural unit C.
The structural unit C contributes to the adjustment of the adhesive strength of the pressure-sensitive adhesive layer.

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.

As the other (meth) acrylic acid alkyl ester monomer, an unsubstituted (meth) acrylic acid alkyl ester monomer is preferable, and an unsubstituted acrylic acid alkyl ester monomer is more preferable.
The types of other (meth) acrylic acid alkyl ester monomers are not particularly limited.
The alkyl group of the other (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 3 to 18, more preferably in the range of 3 to 12, from the viewpoint of the adhesive force of the formed pressure-sensitive adhesive layer on the adherend and the adhesion to the substrate. ..

Other (meth) acrylic acid alkyl ester monomers include n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, and n-octyl. (Meta) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) ) Acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and the like can be mentioned.
Among these, other (meth) acrylic acid alkyl ester monomers include 2-ethylhexyl acrylate (2EHA) and n-butyl acrylate (n) from the viewpoint that the adhesive strength of the pressure-sensitive adhesive layer can be easily adjusted. At least one selected from −BA) is preferred.

When the specific (meth) acrylic copolymer further contains the structural unit C, it may contain only one type of the structural unit C, or may contain two or more types of the structural unit C.

When the specific (meth) acrylic copolymer contains the constituent unit C, the content (ratio) of the constituent unit C in the specific (meth) acrylic copolymer makes it easy to adjust the adhesive strength of the pressure-sensitive adhesive layer, for example. From the above viewpoint, 30% by mass or more is preferable, 40% by mass or more is more preferable, and 50% by mass or more is further preferable with respect to all the constituent units of the specific (meth) acrylic copolymer.
The upper limit of the content rate (ratio) of the constituent unit C in the specific (meth) acrylic copolymer is not particularly limited, and is, for example, 90% by mass with respect to all the constituent units of the specific (meth) acrylic copolymer. The following is preferable.

<Other building blocks>
The specific (meth) acrylic copolymer is a structural unit other than the structural unit A, the structural unit B, and the optional structural unit C (so-called other) within the range in which the effect of the present invention is exhibited. (Constituent unit of) may be included.

The type of monomer constituting the other structural unit is not particularly limited.
Examples of the monomer constituting the other structural unit include a monomer having a hydroxyl group.
Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (6-hydroxyhexyl). Meta) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-hydroxybutyl (meth) acrylate, 1,3-Dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, glycerin mono (meth) Examples thereof include acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, and poly (ethylene glycol-propylene glycol) mono (meth) acrylate.

Examples of the monomer constituting the other structural unit include (meth) acrylate having a cyclic group represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate and ethoxyethyl (meth). Acrylic alkyl (meth) acrylate represented by meta) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl represented by vinyltoluene, acrylonitrile and methacrylonitrile. Examples thereof include vinyl cyanate typified by nitrile, vinyl acrylate, vinyl acetate, vinyl propionate, vinyl esters typified by vinyl versaticate, and various derivatives of these monomers.

-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, but is preferably 300,000 or more and 2 million or less, more preferably 400,000 or more and 1.5 million or less, and 400,000 or more and 1.2 million or less. Is more preferable, and 500,000 or more and 1.2 million or less are particularly preferable.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 300,000 or more, the cohesive force is further improved and higher adhesive force can be exhibited.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 2 million or less, the wettability to the adherend can be further improved and higher adhesive strength can be exhibited.
The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is desired by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, and the like. Can be the value of.

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: 4 TSK-GEL GMHXL (Tosoh Corporation) 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

-Glass transition temperature of specific (meth) acrylic copolymer-
The glass transition temperature (Tg) of the specific (meth) acrylic copolymer is not particularly limited, but is preferably −50 ° C. or higher and −10 ° C. or lower, more preferably −45 ° C. or higher and −15 ° C. or lower, and −40 ° C. or lower. More preferably, it is ℃ or more and −20 ℃ or less.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer is −50 ° C. or higher, the cohesive force is further improved and higher adhesive force can be exhibited.
When the glass transition temperature (Tg) of the specific (meth) acrylic copolymer is −10 ° C. or lower, the wettability to the adherend can be further improved and higher adhesive strength can be exhibited.

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) when made into a homopolymer" refers to the glass transition temperature (Tg) represented by the absolute temperature (K) of the homopolymer produced by polymerizing the monomer alone. 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.

The "glass transition temperature (Tg) represented by the Celsius temperature (° C.) when made into a homopolymer" of a typical monomer is that 2-ethylhexyl acrylate (2EHA) is -76 ° C. 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, Methyl acrylate (MA) at 5 ° C, methyl methacrylate (MMA) at 103 ° C, isobonyl methacrylate (IBMX) at 155 ° C, ethyl acrylate (EA) at -27 ° C, 2-ethylhexyl acrylate (2EHA) at -76 ° C, Methacrylate is 185 ° C, 4-hydroxybutyl acrylate (4HBA) is -39 ° C, 2-hydroxyethyl acrylate (2HEA) is -15 ° C, 2-hydroxyethyl methacrylate (2HEMA) is 55 ° C, acrylic acid (AA) is 163 ° C, isooctyl acrylate (i-OA) -75 ° C, dimethylaminoethyl methacrylate (DM) 18 ° C, trifluoroethyl methacrylate 72 ° C, trifluoroethyl acrylate -5 ° C, ω-carboxy- Polycaprolactone (n≈2) monoacrylate is −30 ° C. and 2-acryloyloxyethyl-succinic acid is −40 ° C.

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.

-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, when preparing a pressure-sensitive adhesive composition after the production of a specific (meth) acrylic copolymer, a solution is relatively simple and can be carried out in a short time. Polymerization is preferred.

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 specific 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, decalin, and aroma. Aromatic hydrocarbons represented by group naphtha, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and fatty type represented by terepine oil or Alicyclic hydrocarbons, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and esters typified by methyl benzoate, Acenes such as acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and For 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-butyl alcohol. Typical examples are alcohols.

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, etc., it is preferable to use ethyl acetate.

Examples of the polymerization initiator include organic peroxides and azo compounds used in ordinary solution polymerization.
Organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, and di-2-ethylhexylperoxydicarbonate. , T-butylperoxypivalate, 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 (4,5-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,5-di) Examples thereof include -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), 2,2'-azobis (isobutyric acid) dimethyl and the like.

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, for example, 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 typified 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 is, for example, the molecular weight of the target specific (meth) acrylic copolymer. It is set as appropriate according to the situation.

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

[Crosslinking agent]
The pressure-sensitive adhesive composition of the present invention 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 isocyanate compounds, epoxy compounds, and metal chelate compounds. The "isocyanate compound" means a compound having an isocyanate group, and the "epoxy compound" means a compound having an epoxy group.
Among these, an isocyanate compound (so-called isocyanate-based cross-linking agent) is preferable as the cross-linking agent.
When the cross-linking agent is an isocyanate compound, the adhesive force of the pressure-sensitive adhesive layer to the adherend tends to be further improved.

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. Chain or cyclic aliphatic polyisocyanate compounds typified by hydrogenated additives of aromatic polyisocyanate compounds, biuret, dimer, trimeric or pentameric of these polyisocyanate compounds, these polyisocyanates. Examples thereof include an adduct of a compound and a polyol compound such as trimethylolpropane.

Among these, as the isocyanate compound, for example, when a pressure-sensitive adhesive film provided with a pressure-sensitive adhesive layer is used outdoors, hexaxamethylene is unlikely to cause coloring (so-called yellowing) of the pressure-sensitive adhesive layer due to the isocyanate compound. Various hexamethylene diisocyanates such as methylene diisocyanate, hexamethylene diisocyanate dimer, hexamethylene diisocyanate and polyol adduct, hexamethylene diisocyanate trimeric or pentameric isocyanurate, and hexamethylene diisocyanate biuret. Hexamethylene diisocyanate compound derived from 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 (registered trademark) -X" and "TETRAD (registered trademark) -C" of Mitsubishi Gas Chemical Company, Inc. can be preferably used. ..

Examples of the metal chelate compound include aluminum monoacetylacetonate bis (ethylacetoacetate), aluminumtris (ethylacetacetate), and aluminum chelate compounds typified by aluminumtris (acetylacetonate), titanium chelate compounds, and zirconium chelate compounds. Examples thereof include cobalt chelate compounds.

As the metal chelate compound, a commercially available product can be used.
As commercially available metal chelate compounds, for example, those commercially available under the trade names of "Aluminum Chelate A", "Aluminum Chelate D", and "ALCH-TR" of Kawaken Fine Chemicals Co., Ltd. can be preferably used. ..

The pressure-sensitive adhesive composition of the present invention 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 of the present invention is not particularly limited, and is appropriately set according to the type of the cross-linking agent, for example, from the viewpoint of the balance between wettability and cohesive force.
For example, when an isocyanate compound is used as the cross-linking agent, the content of the isocyanate compound in the pressure-sensitive adhesive composition of the present invention is 0.1 part by mass to 0 part by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer. 6 parts by mass is preferable, and 0.1 parts by mass to 0.4 parts by mass is more preferable.

[Specific light stabilizer]
The pressure-sensitive adhesive composition of the present invention contains a hindered amine-based light stabilizer (that is, a specific light stabilizer) having a molecular weight of 300 or more and 650 or less.
Since the molecular weight of the hindered amine light stabilizer is 300 or more and 650 or less, the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer that is difficult to whiten in a high humidity environment even though it contains the hindered amine-based light stabilizer.
Further, since the pressure-sensitive adhesive composition of the present invention contains a hindered amine-based light stabilizer, a pressure-sensitive adhesive layer having excellent weather resistance can be formed.

The molecular weight of the hindered amine light stabilizer is 300 or more and 650 or less, preferably 350 or more and 600 or less, and more preferably 400 or more and 600 or less.
When the molecular weight of the hindered amine light stabilizer is 300 or more, it is easy to obtain.
When the molecular weight of the hindered amine light stabilizer is 650 or less, an adhesive layer that is difficult to whiten can be formed in a high humidity environment.

Specific light stabilizers include bis sebacate (1,2,2,6,6-pentamethyl-4-piperidyl) [trade name: Tinuvin® 765, BASF], bis sebacate (2,2). 6,6-Tetramethyl-4-piperidyl) [trade name: Tinuvin (registered trademark) 770DF, BASF Corporation] and the like.

The pressure-sensitive adhesive composition of the present invention may contain only one type of specific light stabilizer, or may contain two or more types.

The content of the specific light stabilizer in the pressure-sensitive adhesive composition of the present invention is not particularly limited, and is appropriately set from the viewpoint of adhesive strength, for example.
The content of the specific light stabilizer in the pressure-sensitive adhesive composition of the present invention is preferably 0.5 parts by mass to 10 parts by mass, and 0.5 parts by mass with respect to 100 parts by mass of the specific (meth) acrylic copolymer. ~ 5 parts by mass is more preferable, and 1 part by mass to 4 parts by mass is further preferable.

[UV absorber]
The pressure-sensitive adhesive composition of the present invention preferably contains, for example, an ultraviolet absorber from the viewpoint of improving weather resistance.
The ultraviolet absorber is not particularly limited.
Examples of the ultraviolet absorber include a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a benzoate-based ultraviolet absorber, a hydroxyphenyltriazine-based ultraviolet absorber, and the like.
Among these, as the ultraviolet absorber, a benzotriazole-based ultraviolet absorber is preferable from the viewpoint of coloring the pressure-sensitive adhesive layer and weather resistance.

Examples of the benzotriazole-based ultraviolet absorber include 2- (3,5-di-tert-amyl-2-hydroxyphenyl) benzotriazole [trade name: Tinuvin (registered trademark) 328, BASF], 2- (2-hydroxy). -5-tert-octylphenyl) benzotriazole [trade name: Tinuvin® 329, BASF], 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H- Benzotriazole [trade name: Tinuvin (registered trademark) 234, BASF], 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole [trade name: Tinuvin (registered trademark) PS, BASF] , 2- (2H-benzotriazole-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol [trade name: tertwin® 900, BASF], 2- (2H-) Benzotriazole-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol [trade name: Tinuvin® 928, BASF, Inc. ], 2- [5-Chloro (2H) -benzotriazole-2-yl] -4-methyl-6- (tert-butyl) phenol [trade name: Tinuvin® 326, BASF], 2-2 '-Methylenebis [6- (2H-benzotriazole-2-yl) -4- (1, 1, 3, 3-tetramethylbutyl) phenol] [trade name: Tinuvin (registered trademark) 360, BASF], etc. Can be mentioned.

When the pressure-sensitive adhesive composition of the present invention contains an ultraviolet absorber, it may contain only one type of ultraviolet absorber, or may contain two or more types of the ultraviolet absorber.

The content of the ultraviolet absorber in the pressure-sensitive adhesive composition of the present invention is not particularly limited.
When the pressure-sensitive adhesive composition of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is, for example, 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer. preferable.

[Organic solvent]
The pressure-sensitive adhesive composition of the present invention may contain 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.

When the pressure-sensitive adhesive composition of the present invention contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvent.

The content of the organic solvent in the pressure-sensitive adhesive composition of the present invention is not particularly limited and can be appropriately set.

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than the above-mentioned components (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, cross-linking catalysts, tackifiers, antioxidants, colorants (eg dyes and pigments), and various additives such as antistatic agents. Can be mentioned.

[Gel fraction after cross-linking]
In the pressure-sensitive adhesive composition of the present invention, the gel content after cross-linking is preferably in the range of 5% by mass to 90% by mass, more preferably in the range of 10% by mass to 90% by mass, and 20% by mass. It is more preferably in the range of ~ 80% by mass.
When the gel fraction after cross-linking is within the above range, the permeation of water into the pressure-sensitive adhesive layer is further suppressed, so that the pressure-sensitive adhesive layer is more difficult to whiten.

In the present specification, the "gel fraction after cross-linking of the pressure-sensitive adhesive composition" is a value measured according to the following procedures (1) to (17).
(1) The pressure-sensitive adhesive composition is applied onto a polyethylene terephthalate (PET) film separator (release paper) having a thickness of 100 μm, air-dried at room temperature (23 ° C.) for 30 minutes, and then main-dried at an ambient temperature of 100 ° C. for 5 minutes. To form a pressure-sensitive adhesive layer to obtain a pressure-sensitive adhesive layer with a separator.
(2) The obtained pressure-sensitive adhesive layer with a separator is cured under the conditions of an atmospheric temperature of 23 ° C. and 65% RH for 10 days. Then, the pressure-sensitive adhesive layer with a separator is cut out to a size of 75 mm × 75 mm. The weight of the pressure-sensitive adhesive layer of the cut-out sample is about 0.2 g.

(3) Prepare a metal wire mesh of 250 mesh (wire diameter: 0.03 mm, opening: 72 μm, made of stainless steel), and cut the metal wire mesh into a size of 100 mm × 100 mm.
(4) The metal wire mesh is degreased with ethyl acetate and then dried. The metal wire mesh after degreasing and drying is stored in a desiccator. Further, the unraveling of the end portion of the metal wire mesh causes a measurement error, so it is removed in advance.
(5) Accurately measure the mass of the metal wire mesh. Let this mass be A.

(6) After attaching the pressure-sensitive adhesive layer with a separator of (2) cut out to a size of 75 mm × 75 mm to the center of the metal wire mesh, the PET film separator is peeled off from the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is attached to the metal wire mesh so that the pressure-sensitive adhesive layer is arranged in the plane after the metal wire mesh is folded by the steps (7) to (9) described later.
(7) The metal wire mesh is folded in half from the back side to the front side with the side to which the film-like adhesive layer is attached inside.
(8) Fold the front one-third of the metal wire mesh folded in half (there are two ends on the front side) to the back side, and further fold the back one-third to the front side (100 mm in the vertical direction). Folded to 1/6 of the above, not folded in the horizontal direction).
(9) Fold the wire mesh to the right at the one-third part from the left, and similarly fold it to the left at the one-third part from the right. This is referred to as sample 1. In sample 1, due to the size of the original metal wire mesh, the vertical direction is folded to 1/6 and the horizontal direction is folded to 1/3.
(10) Accurately measure the mass of the above sample 1. Let this mass be B.

(11) Stapler the sample 1 so that the creases do not open. This is referred to as sample 2. The mass of sample 2 is measured. Let this mass be C.
(12) For each type of pressure-sensitive adhesive composition, two samples 2 for measuring the gel fraction are prepared.

(13) Sample 2 is placed in a glass bottle containing 80 g of ethyl acetate and covered.
(14) The glass bottle containing the sample 2 is left to stand for 3 days under the conditions of an atmospheric temperature of 23 ° C. and 65% RH.
(15) Sample 2 is taken out from the glass bottle and easily washed with ethyl acetate.
(16) After drying the sample 2 at 120 ° C. for 24 hours, the mass is accurately measured. Let this be D.

(17) Calculate the gel fraction by the following formula.
Gel fraction [mass%] = (D- (A + (CB))) / (BA) x 100

[Adhesive film]
The pressure-sensitive adhesive film of the present invention includes a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the above-mentioned pressure-sensitive adhesive composition of the present invention. That is, in the pressure-sensitive adhesive film of the present invention, the base material and the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention are laminated.
In general, the pressure-sensitive adhesive layer containing a hindered amine-based light stabilizer has excellent weather resistance. However, when a pressure-sensitive adhesive film including a pressure-sensitive adhesive layer containing a hindered amine-based light stabilizer is used in a high-humidity environment, moisture may act on the hindered amine-based light stabilizer and the pressure-sensitive adhesive layer may be whitened. On the other hand, the pressure-sensitive adhesive layer included in the pressure-sensitive adhesive film of the present invention contains a hindered amine-based light stabilizer having a relatively low molecular weight, so that whitening of the pressure-sensitive adhesive layer is suppressed. Therefore, the adhesive film of the present invention is difficult to whiten even when used in a high humidity environment.
Further, in the pressure-sensitive adhesive layer containing a hindered amine-based light stabilizer having a low molecular weight, the hindered amine-based light stabilizer is localized near the surface of the pressure-sensitive adhesive layer (so-called near the interface with the adherend) and adheres to the adherend. The force tends to be low. On the other hand, the pressure-sensitive adhesive film of the present invention contains a specific (meth) acrylic copolymer and has a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition having excellent wettability to the adherend. On the other hand, it shows high adhesive strength.

The adhesive film of the present invention is suitably used as a surface protective film for a reflective sheet (also referred to as a "retroreflective sheet" or a "retroreflective sheet").
Reflective sheets are often attached to the surface of display boards such as signs (for example, road signs and public signs) and advertisements (for example, outdoor advertisements and indoor advertisements). The reflective sheet is used for the purpose of improving the visibility of signs, advertisements, etc. from the direction of the light source by a reflection phenomenon (so-called retroreflection) in which the incident light returns to the incident direction again. Further, in general, the outermost surface of the reflective sheet is a layer containing an acrylic resin.
Since the adhesive film of the present invention has an adhesive layer having high adhesive strength to an adherend (particularly an adherend containing an acrylic resin) and which is difficult to whiten in a high humidity environment, sunlight, snowfall, and rainfall Even if it is used as a surface protective film for a sign installed outdoors or a reflective sheet attached to an advertisement, etc., it may peel off during use, or the visibility of the sign or advertisement may decrease. Is unlikely to cause any problems.

The base material is not particularly limited as long as the pressure-sensitive adhesive layer can be formed on the base material.
Examples of the base material include vinyl chloride resin, acrylic resin, polyolefin resin, ABS resin, polycarbonate resin, polyimide resin, acetate resin, polyether sulfone resin, polyamide resin, and fluorine resin. Examples thereof include a base material containing a resin such as a polyester resin (for example, polyethylene terephthalate).
Among these, as the base material, a base material containing a vinyl chloride resin, an acrylic resin, a polyester resin, or a fluorine resin is preferable.
When the pressure-sensitive adhesive film of the present invention is used as a surface protective film for a reflective sheet, a base material containing an acrylic resin or a fluorine-based resin is preferable as the base material.

The substrate may contain various additives such as plasticizers, colorants (eg dyes and pigments), heat stabilizers, fillers, antistatic agents, flame retardants and the like.
Further, the base material may be partially or wholly patterned.

The thickness of the base material is generally 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less.
The lower limit of the thickness of the base material is, for example, preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of the strength of the adhesive film.

The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a commonly used method can be adopted.
As a method of forming the pressure-sensitive adhesive layer on the base material, for example, the following method can be adopted.
The pressure-sensitive adhesive composition of the present invention is applied as it is or, if necessary, diluted with a solvent on a release film to form a coating film on the release film. Next, the formed coating film is dried to remove the solvent, and then bonded to the base material and cured to form an adhesive layer on the base material.
The release film is not particularly limited as long as it can be easily peeled off from the surface of the pressure-sensitive adhesive layer. Can be mentioned. 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.

As another method for forming the pressure-sensitive adhesive layer on the base material, for example, the following method can be adopted.
The pressure-sensitive adhesive composition of the present invention is applied as it is or, if necessary, diluted with a solvent on a release film such as a paper or a resin film that has been easily peeled with a release agent. , A coating film is formed on the release film. Then, the formed coating film is dried to remove the solvent. Next, the surface of the release film on which the pressure-sensitive adhesive layer is formed is brought into contact with the base material and pressed, and the pressure-sensitive adhesive layer is transferred to the base material to form the pressure-sensitive adhesive layer on the base material. Then, curing is performed.

The method of applying the pressure-sensitive adhesive composition on the substrate 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, and a bar. A known method using a coater, an applicator, or the like can be mentioned.
The amount of the pressure-sensitive adhesive composition applied onto 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 coating film formed on 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 coating film are not particularly limited, and are appropriately set according to the thickness of the pressure-sensitive adhesive layer to be formed, the amount of the organic solvent in the pressure-sensitive adhesive composition, and the like.

The curing conditions are not particularly limited, and for example, the curing is carried out in an environment of 23 ° C. and 50% RH for 1 to 10 days.
Curing completes the cross-linking reaction of the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer.

The thickness of the pressure-sensitive adhesive layer is not particularly limited and can be appropriately set according to the application of the pressure-sensitive adhesive film, the required performance, and the like.
For example, when the pressure-sensitive adhesive film is used as the surface protective film of the reflective sheet, the thickness of the pressure-sensitive adhesive layer is preferably 10 μm or more and 100 μm or less, more preferably 20 μm or more and 100 μm or less, and further preferably 30 μm or more and 100 μm or less.

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.

[Manufacturing of (meth) acrylic copolymer]
[Manufacturing Example 1]
In a reactor equipped with a stirrer, a reflux cooler, a sequential dropping device, and a thermometer, 24 parts by mass of ethyl acrylate (EA), 10 parts by mass of acrylic acid (AA; monomer having a carboxy group), and 10 parts by mass. After charging 66 parts by mass of n-butyl acrylate (n-BA; other (meth) acrylic acid alkyl ester monomer) and 150 parts by mass of ethyl acetate (EAc), 2,2'as a polymerization initiator. -Azobisisobutyronitrile (AIBN; azo compound) was added in an amount of 0.05 parts by mass. After the addition of AIBN, the contents of the reactor were heated with stirring, raised until reflux occurred, and the temperature was maintained for 20 minutes. Hereinafter, the temperature at which reflux occurs is referred to as "reflux temperature".
Next, EA (75.6 parts by mass), AA (31 parts by mass), n-BA (206.3 parts by mass), and AIBN (0.5 parts by mass) were further added to the reactor in EAc (75.6 parts by mass). Solution A dissolved in 100 parts by mass) was sequentially added dropwise over 90 minutes. After the completion of the dropping of the solution A, the temperature of the contents in the reactor was further maintained at the reflux temperature for 60 minutes. Next, a solution B in which AIBN (1.0 part by mass) was dissolved in EAc (100 parts by mass) was sequentially added dropwise over 60 minutes, and then the temperature of the contents in the reactor was further maintained at the reflux temperature for 120 minutes. , Completed the reaction. After the reaction was completed, the mixture was diluted with EAc so that the solid content was 35% by mass, and then cooled to obtain a solution of the (meth) acrylic copolymer.
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). ..

(Meth) monomer composition of the acrylic copolymer (unit: mass%), weight average molecular weight (Mw, ten thousand (in Table 1, denoted as "× 10 ^4")), and glass transition temperature ( Tg, unit: ° C.) is shown in Table 1.
The weight average molecular weight (Mw) is measured by the method described above.
The glass transition temperature (Tg) is calculated by the method described above.

[Production Examples 2 to 13, and Production Examples 16 to 21]
In Production Examples 2 to 13 and Production Examples 16 to 21, the monomer composition in Production Example 1 is changed as shown in Table 1, and the amount of the solvent, the amount of the polymerization initiator, and the like are adjusted. As a result, the (meth) having a solid content of 35% by mass was adjusted by the same method as in Production Example 1 except that the weight average molecular weight (Mw) of the (meth) acrylic copolymer was adjusted to the values shown in Table 1. A solution of the acrylic copolymer was prepared.
(Meth) monomer composition of the acrylic copolymer (unit: mass%), weight average molecular weight (Mw, ten thousand (in Table 1, denoted as "× 10 ^4")), and glass transition temperature ( Tg, unit: ° C.) is shown in Table 1.
The weight average molecular weight (Mw) is measured by the method described above.
The glass transition temperature (Tg) is calculated by the method described above.

[Production Example 14 and Production Example 15]
In Production Example 14 and Production Example 15, the weight average molecular weight (Mw) of the (meth) acrylic copolymer is set to the value shown in Table 1 by adjusting the amount of the solvent, the amount of the polymerization initiator, etc. in Production Example 1. A solution of the (meth) acrylic copolymer having a solid content of 35% by mass was prepared by the same method as in Production Example 1 except that the solid content was adjusted to 35% by mass.
(Meth) monomer composition of the acrylic copolymer (unit: mass%), weight average molecular weight (Mw, ten thousand (in Table 1, denoted as "× 10 ^4")), and glass transition temperature ( Tg, unit: ° C.) is shown in Table 1.
The weight average molecular weight (Mw) is measured by the method described above.
The glass transition temperature (Tg) is calculated by the method described above.

Details of each monomer shown in Table 1 are as shown below.
"EA": Ethyl acrylate "MA": Methyl acrylate "AA": Acrylic acid "M-5300": Aronix (registered trademark) M-5300 [Product name: ω-carboxy-polycaprolactone (n≈2) monoacrylate, Toa Synthetic Co., Ltd.]
"HOA-MS": HOA-MS [trade name; 2-acryloyloxyethyl-succinic acid, succinic acid ester, Kyoeisha Chemical Co., Ltd.]
"2HEA": 2-hydroxyethyl acrylate "2EHA": 2-ethylhexyl acrylate "n-BA": n-butyl acrylate In Table 1, "-" means that the corresponding monomer is not used. ..

[Example 1]
-Preparation of adhesive composition-
100 parts by mass (solid content conversion value) of the solution of the (meth) acrylic copolymer [specific (meth) acrylic copolymer] prepared in Production Example 1 and the isocyanate compound as a cross-linking agent [trade name: coronate (trade name: coronate) Registered trademark) HX, isocyanurate compound of hexamethylene diisocyanate (HMDI), solid content: 100% by mass, Toso Co., Ltd.] 0.30 parts by mass, and light stabilizer [trade name: Tinuvin (registered trademark) 765, sebacin Bis acid acid (1,2,2,6,6-pentamethyl-4-piperidyl), hindered amine-based light stabilizer, molecular weight: 509, BASF; specified light stabilizer] 2.0 parts by mass, and UV absorber [commodity] Name: Tinuvin (registered trademark) 329, 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, benzotriazole-based ultraviolet absorber, BASF] 3.0 parts by mass, and thoroughly stirred. Then, a pressure-sensitive adhesive composition was obtained. Details of the composition of the pressure-sensitive adhesive composition are shown in Table 2.
The gel fraction after cross-linking of the pressure-sensitive adhesive composition was measured by the method described above and found to be 30% by mass.

-Making an adhesive film-
Using the pressure-sensitive adhesive composition obtained above, a pressure-sensitive adhesive film was prepared as follows.
The thickness after drying (that is, on the peeling surface of a release film (trade name: Film Vina (registered trademark) 100E, Fujimori Kogyo Co., Ltd.)) that has been easily peeled with a silicone-based release treatment agent using a gravure coater. , The thickness of the pressure-sensitive adhesive layer; hereinafter referred to as “film thickness”) was applied so that the pressure-sensitive adhesive composition was 40 μm to form a coating film. Next, the coating film formed on the release film was dried at 100 ° C. for 1 minute using a hot air circulation type dryer. Next, the exposed surface of the coating film after drying and the base material (trade name: HBS-006, thickness: 50 μm, acrylic resin film, Mitsubishi Chemical Corporation) are pressure-bonded and pasted with a pressure nip roll. I matched it. Then, it was cured for 168 hours in an environment of 23 ° C. and 50% RH to prepare an adhesive film (base material / adhesive layer / release film).

[Examples 2 to 13, Example 20, Example 21, and Example 26]
In Examples 2 to 13, Example 20, Example 21, and Example 26, the types of (meth) acrylic copolymers are shown in "-Preparation of Adhesive Composition-" of Example 1. An adhesive film was produced by performing the same operation as in Example 1 except that the film was changed to the one shown in 2.

[Examples 14 to 17]
In Examples 14 to 17, in "-Preparation of Adhesive Film-" of Example 1, the pressure-sensitive adhesive composition is applied onto the base material so as to have the film thickness shown in Table 2 to form a coating film. An adhesive film was produced by performing the same operation as in Example 1 except for the above.

[Example 18 and Example 19]
In Examples 18 and 19, the same operations as in Example 1 except that the blending amount of the cross-linking agent was changed to the amount shown in Table 2 in "-Preparation of Adhesive Composition-" of Example 1. To prepare an adhesive film.

[Example 22]
In Example 22, the same operation as in Example 1 was performed except that the type of the ultraviolet absorber was changed to that shown in Table 2 in "-Preparation of Adhesive Composition-" of Example 1 to obtain adhesive. A film was made.

[Example 23]
In Example 23, the same operation as in Example 1 was performed except that the type of the light stabilizer was changed to that shown in Table 2 in "-Preparation of Adhesive Composition-" of Example 1, and the adhesive was adhered. A film was made.

[Example 24]
In Example 24, the same operation as in Example 1 was carried out except that the ultraviolet absorber was not blended in "-Preparation of Adhesive Composition-" of Example 1 to prepare an adhesive film.

[Example 25]
In Example 25, the same operation as in Example 1 was performed except that the type of the cross-linking agent was changed to that shown in Table 2 in "-Preparation of Adhesive Composition-" of Example 1, and the adhesive film was formed. Was produced.

[Comparative Example 1]
In Comparative Example 1, in "-Preparation of Adhesive Composition-" of Example 1, the types of (meth) acrylic copolymers, the types of light stabilizers, and the types of ultraviolet absorbers are shown in Table 3. An adhesive film was produced by performing the same operation as in Example 1 except that it was changed to.
The gel fraction after cross-linking of the pressure-sensitive adhesive composition was measured by the method described above and found to be 44% by mass.

[Comparative Example 2]
In Comparative Example 2, except that the type of the (meth) acrylic copolymer and the type of the light stabilizer were changed to those shown in Table 3 in "-Preparation of Adhesive Composition-" of Example 1. The same operation as in Example 1 was carried out to prepare an adhesive film.

[Comparative Example 3, Comparative Example 4, and Comparative Example 9 to 11]
In Comparative Example 3, Comparative Example 4, and Comparative Examples 9 to 11, the types of (meth) acrylic copolymers in "-Preparation of Adhesive Composition-" of Example 1 are shown in Table 3. An adhesive film was produced by performing the same operation as in Example 1 except that it was changed to.

[Comparative Examples 5 to 8]
In Comparative Examples 5 to 8, the same operations as in Example 1 were performed except that the type of the light stabilizer was changed to that shown in Table 3 in "-Preparation of Adhesive Composition-" of Example 1. To prepare an adhesive film.

[evaluation]
1. 1. Moisture resistance A hot water test was conducted to evaluate the moisture resistance of the pressure-sensitive adhesive layer.
The adhesive film produced above was cut to a size of 40 mm × 50 mm using a cutter blade, and one adhesive film piece was prepared.
In an environment of an ambient temperature of 23 ° C. and 50% RH, the release film of the prepared adhesive film piece is peeled off, and the surface of the adhesive layer exposed by the peeling is a retroreflective sheet [trade name: Nikkalite ULS, capsule lens type height]. Bright retroreflective sheet, Nippon Carbide Industry Co., Ltd.] surface (acrylic resin) is overlaid and bonded, and then a 2 kg roller is reciprocated twice and crimped. Layer / base material) piece] was prepared.
First, the Y value (before the test) was measured using a spectrocolorimeter [model: SE 2000, Nippon Denshoku Kogyo Co., Ltd.] for the prepared evaluation sample. Next, the evaluation sample whose Y value (before the test) was measured was put into warm water at 50 ° C., left to stand for 7 days while maintaining the temperature, and then taken out. Then, the Y value (after the test) was measured using a spectrocolorimeter [model: SE 2000, Nippon Denshoku Kogyo Co., Ltd.] for the evaluation sample immediately after taking out.
The difference (ΔY) between the Y value (before the test) and the Y value (after the test) of the evaluation sample was calculated, and the moisture resistance was evaluated according to the following evaluation criteria.
When the evaluation result was "A", it was judged that the moisture resistance was excellent (that is, it was difficult to whiten in a high humidity environment).

-Evaluation criteria-
A: ΔY is less than 5.
B: ΔY is 5 or more.

2. Adhesive strength In order to evaluate the adhesive strength of the pressure-sensitive adhesive layer to the adherend, a 90 ° peel strength test, which is one of the constant load peeling tests, was performed.
The adhesive film produced above was cut to a size of 25 mm × 100 mm using a cutter blade, and one adhesive film piece was prepared.
The release film of the prepared adhesive film piece was peeled off to expose the surface of the adhesive layer by 25 mm × 50 mm. Next, the surface of the exposed adhesive layer was laminated on the surface (acrylic resin) of the retroreflective sheet [trade name: Nikkalite ULS, capsule lens type high-intensity retroreflective sheet, Nippon Carbide Industry Co., Ltd.]. After that, an evaluation sample in which the surface of the adhesive layer of the adhesive film piece was attached to the surface of the retroreflective sheet by reciprocating and crimping a 2 kg roller twice [retroreflective sheet / adhesive film (adhesive layer / base material) ) Piece, sticking area: 25 mm × 50 mm] was prepared. The operation from the exposure of the surface of the pressure-sensitive adhesive layer to the crimping was performed in an environment with an atmospheric temperature of 23 ° C. and 50% RH.
Next, the prepared evaluation sample was left for 24 hours in an environment of an atmospheric temperature of 23 ° C. and 50% RH, and then on one end side in the long side (100 mm) direction of the adhesive film piece attached to the retroreflective sheet. , The end portion on the side not attached to the retroreflective sheet was left for 10 minutes with a load of 800 g applied in the 90 ° direction. Then, after being left to stand, the peeling distance (unit: mm) in the long side (100 mm) direction of the adhesive film piece was measured.
The shorter the peeling distance of the adhesive film piece, the higher the adhesive force of the adhesive layer provided on the adhesive film piece to the adherend.

The composition, film thickness, measurement results, and evaluation results of the pressure-sensitive adhesive composition are shown in Tables 2 and 3.
In Table 2, "-" means that the corresponding component is not used.

Details of each component shown in Tables 2 and 3 are as shown below.
<Crosslinking agent>
"Coronate HX": Coronate (registered trademark) HX [trade name: isocyanurate of hexamethylene diisocyanate (HMDI), solid content: 100% by mass, Tosoh Corporation]
"TETRAD-C": TETRAD®-C [trade name; 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, solid content: 100% by mass, Mitsubishi Gas Chemical Company, Inc.]
<Light stabilizer>
-Specific light stabilizer-
"Tinuvin 765": Tinuvin® 765 [trade name: bissebacate (1,2,2,6,6-pentamethyl-4-piperidyl), molecular weight: 509, hindered amine light stabilizer, BASF]
"Tinuvin 770DF": Tinuvin® 770DF [trade name: bissebacate (2,2,6,6-tetramethyl-4-piperidyl), molecular weight: 481, hindered amine light stabilizer, BASF]
-Comparative specific light stabilizer-
"Tinuvin 622LD": Tinuvin® 622LD [trade name; dimethyl 1- (2 hydroxyethyl) succinate-4-hydroxy-2,2,6,6-tetramethyl-4-piperidin polycondensate, molecular weight : 3550, hindered amine light stabilizer, BASF]
"LA-52": ADEKA STAB® LA-52 [trade name; tetrakis butane-1,2,3,4-tetracarboxylic dian (1,2,2,6,6-pentamethyl-4-piperidinyl), Molecular weight: 847, hindered amine-based light stabilizer, ADEKA Corporation]
"Tinuvin 123": Tinuvin® 123 [trade name; bisdecanedioate [2,2,6,6-tetramethyl-1- (octyloxy) piperidine-4-yl], molecular weight: 737, hindered amine system Light stabilizer, BASF]
"Tinuvin 144": Tinuvin® 144 [trade name; 2-[[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] -2-butylpropanediate bis [1] , 2,2,6,6-pentamethyl-4-piperidinyl], molecular weight: 685, hindered amine light stabilizer, BASF]
<UV absorber>
"Tinuvin 328": Tinuvin® 328 [trade name; 2- (3,5-di-tert-amyl-2-hydroxyphenyl) benzotriazole, benzotriazole-based UV absorber, BASF]
"Tinuvin 329": Tinuvin® 329 [trade name; 2- (2-hydroxy-5-tert-octylphenyl) benzotriazole, benzotriazole-based UV absorber, BASF]

As shown in Table 2, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 26 contains a hindered amine-based light stabilizer, but is difficult to whiten in a high-humidity environment and has moisture resistance. It turned out to be excellent. Further, it was found that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Examples 1 to 26 exhibited high adhesive strength to the adherend.

On the other hand, as shown in Table 3, instead of the hindered amine-based light stabilizer (specific light stabilizer) having a molecular weight of 300 or more and 650 or less, a hindered amine-based light stabilizer having a molecular weight of more than 650 is contained, and methyl acrylate and methyl acrylate and A pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive compositions of Comparative Example 1 and Comparative Example 2 containing a (meth) acrylic copolymer not containing a structural unit A derived from at least one monomer selected from ethyl acrylate. Although it has high adhesive strength to the adherend, it whitens in a high humidity environment and is inferior in moisture resistance.
It was formed from the pressure-sensitive adhesive compositions of Comparative Example 3 and Comparative Example 4 containing a (meth) acrylic copolymer not containing the structural unit A derived from at least one monomer selected from methyl acrylate and ethyl acrylate. It was found that the pressure-sensitive adhesive layer had low adhesive strength to the adherend.
It is formed by the pressure-sensitive adhesive compositions of Comparative Examples 5 and 8 containing a hindered amine-based light stabilizer having a molecular weight of more than 650 instead of the hindered amine-based light stabilizer (specific light stabilizer) having a molecular weight of 300 or more and 650 or less. It was found that the adhesive layer whitened in a high humidity environment and was inferior in moisture resistance.
Adhesive of Comparative Example 9 containing a (meth) acrylic copolymer in which the total content of the structural unit A1 derived from methyl acrylate and the structural unit A2 derived from ethyl acrylate is less than 5% by mass with respect to all the structural units. It was found that the pressure-sensitive adhesive layer formed by the agent composition had low adhesive strength to the adherend.
The pressure-sensitive adhesive of Comparative Example 10 containing a (meth) acrylic copolymer in which the total content of the structural unit A1 derived from methyl acrylate and the structural unit A2 derived from ethyl acrylate exceeds 50% by mass with respect to all the structural units. It was found that the pressure-sensitive adhesive layer formed by the composition had a significantly low adhesive force to the adherend.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 11 containing a (meth) acrylic copolymer containing no structural unit B derived from a monomer having a carboxy group has adhesive strength to an adherend. It turned out to be significantly lower.

Claims (8)

A structural unit A derived from at least one monomer selected from methyl acrylate and ethyl acrylate, and a structural unit B derived from a monomer having a carboxy group, and a structural unit derived from the methyl acrylate. A (meth) acrylic copolymer having a total content of A1 and the structural unit A2 derived from the ethyl acrylate of 5% by mass or more and 50% by mass or less with respect to all the structural units.
With a cross-linking agent
A hindered amine-based light stabilizer having a molecular weight of 300 or more and 650 or less,
Adhesive composition containing. The (meth) acrylic copolymer contains the structural unit A2 derived from the ethyl acrylate, and the content of the structural unit A2 derived from the ethyl acrylate is the total of the (meth) acrylic copolymer. The pressure-sensitive adhesive composition according to claim 1, which is 5% by mass or more and 50% by mass or less with respect to the structural unit. The (meth) acrylic copolymer contains the structural unit A1 derived from the methyl acrylate, and the content of the structural unit A1 derived from the methyl acrylate is the total of the (meth) acrylic copolymer. The pressure-sensitive adhesive composition according to claim 1, wherein the content is 5% by mass or more and 45% by mass or less with respect to the structural unit. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the monomer having a carboxy group is acrylic acid. The content of the structural unit B derived from the monomer having a carboxy group is 5% by mass or more and 15% by mass or less with respect to all the structural units of the (meth) acrylic copolymer. The pressure-sensitive adhesive composition according to any one of claims 4. Any one of claims 1 to 5, wherein the (meth) acrylic copolymer further contains a structural unit C derived from the methyl acrylate and a (meth) acrylic acid alkyl ester monomer other than the ethyl acrylate. The pressure-sensitive adhesive composition according to the section. A pressure-sensitive adhesive film comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed by the pressure-sensitive adhesive composition according to any one of claims 1 to 6. The adhesive film according to claim 7, which is used as a surface protective film for a reflective sheet.