CN110564343A - Adhesive composition and adhesive sheet - Google Patents

Abstract

the invention provides an adhesive composition and an adhesive sheet. Provided is an adhesive composition which can form an adhesive layer having high adhesive strength even when the adhesive composition is thin. An adhesive composition is provided that includes a polymer of a monomeric component. The polymer satisfies the following conditions in peak separation analysis of molecular weight distribution by GPC measurement: (a) the area ratio of a peak H having a molecular weight peak top in the range of 100 to 2000 ten thousand is 3 to 30% of the entire peak area of the molecular weight distribution; and (b) the area ratio of the peak L having a molecular weight peak top in the range of 1000 to less than 100 ten thousand is 70 to 97% of the entire peak area of the molecular weight distribution.

Description

Adhesive composition and adhesive sheet

Technical Field

The invention relates to an adhesive composition and an adhesive sheet.

Background

The pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive hereinafter) is in a soft solid (viscoelastic body) state in a temperature region near room temperature, and has a property of being easily adhered to an adherend by pressure. Because of such convenience of use, the expectation for adhesives has been increasing, and replacement of adhesives has been studied in the field where adhesives have been used so far. Patent documents 1 to 3 are cited as technical documents relating to adhesives.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-75999

Patent document 2: japanese laid-open patent publication No. 2015-93981

Patent document 3: japanese laid-open patent publication No. 2017-160454

Disclosure of Invention

Problems to be solved by the invention

Generally, an adhesive has a weaker bonding strength to an adherend than an adhesive. Therefore, the adhesive is required to have strong adhesion. Generally, for further improving the adhesion, it is advantageous to further thicken the adhesive layer. However, in recent years, various devices tend to be small and lightweight, and therefore, it is desired to realize highly reliable bonding even with a thin adhesive layer.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an adhesive composition capable of forming an adhesive layer having high adhesive strength even when it is thin.

Means for solving the problems

According to this specification, an adhesive composition comprising a polymer of monomeric components is provided. The polymer satisfies the conditions (a) and (b) in peak separation analysis of molecular weight distribution by Gel Permeation Chromatography (GPC).

(a) The area ratio of the peak H having a molecular weight peak top in the range of 100 to 2000 ten thousand is 3 to 30% of the entire peak area of the molecular weight distribution.

(b) The area ratio of the peak L having a molecular weight peak top in the range of 1000 to less than 100 ten thousand is 70% to 97% of the entire peak area of the molecular weight distribution.

By containing the polymer satisfying the above (a) and (b), a high adhesive force can be achieved even if the thickness is small. Although not particularly limited, the weight average molecular weight of the peak H may be, for example, 200 to 800 ten thousand. The weight average molecular weight of the peak L may be, for example, 5 to 50 ten thousand. With such an adhesive composition, it is easy to achieve both adhesiveness and aggregability at a high level.

The monomer component preferably has a composition having a glass transition temperature (Tg) calculated from the composition of the monomer component in the range of-70 ℃ to-40 ℃. With the monomer component of the above composition, both adhesiveness and aggregability can be easily achieved at a high level.

The adhesive composition disclosed herein can be preferably implemented in such a manner that more than 50% by weight of the above monomer components is a (meth) acrylic monomer. The constitution in which the monomer component contains a (meth) acrylic monomer as a main component can particularly preferably exhibit the effects of satisfying the above (a) and (b). In some preferred embodiments, the monomer component may contain (meth) acrylic acid C_4-10Alkyl esters, acrylic acid, and hydroxyl-containing monomers.

The polymerization conversion rate of the monomer component is preferably 90% by weight or more. The pressure-sensitive adhesive composition having a high polymerization conversion ratio can suitably exhibit the effects (a) and (b) described above. The pressure-sensitive adhesive composition is preferably prepared as an organic solvent solution having a nonvolatile content of 20 wt% or more and 50 wt% or less from the viewpoint of coatability of the composition.

The adhesive composition disclosed herein may contain one or both of a crosslinking agent and a tackifier resin, if necessary. By using a crosslinking agent and/or a tackifying resin, both adhesiveness and aggregability can be achieved at a higher level.

according to the specification, there is provided an adhesive sheet having an adhesive layer formed from any of the adhesive compositions disclosed herein. The pressure-sensitive adhesive sheet having the above-described structure can exhibit high adhesive strength. The thickness of the pressure-sensitive adhesive layer may be, for example, 1 μm or more and 30 μm or less.

The gel fraction of the pressure-sensitive adhesive layer is preferably 70% or less, more preferably 50% or less. From the viewpoint of exerting higher adhesive force, it is advantageous that the gel fraction of the adhesive layer is not excessively high.

According to this specification, for example, there is provided a pressure-sensitive adhesive sheet in which the thickness of the pressure-sensitive adhesive layer is 3 μm or more and 8 μm or less, and the 180 ° peel adhesion strength after 30 minutes of attachment to a stainless steel plate is 8N/20mm or more. Such a pressure-sensitive adhesive sheet has a thin pressure-sensitive adhesive layer and high adhesive strength, and therefore is highly useful. The pressure-sensitive adhesive sheet is preferably used for various applications including portable electronic devices requiring reduction in size and weight, for example, for bonding and fixing.

It should be noted that the claims to be claimed in the present application may include an embodiment in which the above elements are appropriately combined.

Drawings

Fig. 1 is a sectional view schematically showing the structure of an adhesive sheet according to an embodiment.

Fig. 2 is a sectional view schematically showing the structure of a psa sheet according to yet another embodiment.

Fig. 3 is a sectional view schematically showing the structure of a psa sheet according to yet another embodiment.

Description of the reference numerals

1. 2, 3 pressure-sensitive adhesive sheet

10 support substrate

10A first side

10B second side (Back side)

21 adhesive layer (first adhesive layer)

21A adhesive surface (first adhesive surface)

21B second adhesive surface

22 adhesive layer (second adhesive layer)

22A adhesive surface (second adhesive surface)

31. 32 Release liner

100. 200, 300 Release liner-Equipped pressure-sensitive adhesive sheet

Detailed Description

Suitable embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in the present specification can be understood by those skilled in the art based on the teaching about the implementation of the invention described in the present specification and the common general knowledge at the time of application. The present invention can be implemented based on the contents disclosed in the present specification and the common general knowledge in the art.

In the following drawings, members and portions that exhibit the same function are sometimes denoted by the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematic for the purpose of clearly illustrating the present invention, and do not necessarily accurately show the size or scale of the pressure-sensitive adhesive sheet of the product actually provided.

< adhesive composition >

The adhesive compositions disclosed herein comprise a polymer of monomeric components. The composition of the monomer component is not particularly limited as long as a binder containing the above polymer as a base polymer can be formed. The adhesive composition disclosed herein may be an adhesive composition containing, as a base polymer (i.e., a component occupying 50% by weight or more of the polymer component), one or more kinds of polymers selected from, for example, acrylic polymers, rubber-based polymers, polyester-based polymers, urethane-based polymers, polyether-based polymers, silicone-based polymers, polyamide-based polymers, fluorine-based polymers, and the like, which exhibit rubber elasticity in a room temperature region. The form of the pressure-sensitive adhesive composition is not particularly limited, and may be, for example, various forms such as an aqueous dispersion type, a solvent type, a hot melt type, and an active energy ray-curable type (e.g., a photocurable type). In the present specification, the term "active energy ray" refers to an energy ray having energy capable of causing chemical reactions such as a polymerization reaction, a crosslinking reaction, and decomposition of an initiator. Examples of the active energy rays include ultraviolet rays (UV), visible rays, light such as infrared rays, radiation rays such as α rays, β rays, γ rays, electron rays, neutron rays, and X rays.

(molecular weight distribution)

The adhesive composition disclosed herein is characterized by containing a polymer satisfying the conditions (a) and (b) in peak separation analysis of molecular weight distribution measured by GPC.

(a) The area of the peak H having a molecular weight peak top in the range of 100 to 2000 ten thousand is 3 to 30% of the entire peak area of the molecular weight distribution.

(b) The area of the peak L having a molecular weight peak top in the range of 1000 to less than 100 ten thousand is 70% to 97% of the entire peak area of the molecular weight distribution.

Preferred are adhesive compositions comprising said polymers as base polymer. The adhesive composition having the base polymer satisfying the conditions (a) and (b) can achieve higher adhesive force than the adhesive composition not satisfying the conditions.

The GPC measurement is performed by the method described in the examples below. For the measurement results, peak separation analysis was performed using a commercially available peak separation software ORIGIN (LightStone corporation). More specifically, peak fitting is performed in a range of a molecular weight of 100 to 2000 ten thousand and a range of a molecular weight of 1000 to less than 100 ten thousand, and a component of a peak having a peak top in the former is separated from a component of a peak having a peak top in the latter, and the area ratio of each component is calculated. The same applies to the later-described embodiments.

In some embodiments, the area ratio of the peak H may be, for example, 5% or more and 25% or less, or 7% or more and 20% or less. From the viewpoint of improving the aggregation property of the binder, it is advantageous that the area ratio of the peak H is not excessively small. In addition, by making the area ratio of the peak H not excessively large, the elastic modulus of the pressure-sensitive adhesive can be reduced and the adhesion to the adherend can be improved.

The total of the area ratio of the peak L and the area ratio of the peak H is preferably 80% or more, more preferably 90% or more of the entire peak area. The sum of the area ratio of the peak L and the area ratio of the peak H is, in principle, 100 or less, and practically about 102 or less.

The weight average molecular weight (Mw) of the peak H is typically 100 to 2000 ten thousand, preferably 150 to 1000 ten thousand, and preferably 200 to 800 ten thousand. When the Mw of the peak H becomes high, the adhesive aggregation tends to be improved. When the Mw of the peak H is low, the elastic modulus of the pressure-sensitive adhesive tends to be low, and the adhesion to an adherend tends to be improved. In some embodiments of the adhesive composition disclosed herein, the Mw of the peak H may be, for example, 250 ten thousand or more, 350 ten thousand or more, or 450 ten thousand or more, or, for example, 700 ten thousand or less, 600 ten thousand or less, or 500 ten thousand or less. In this manner, a higher performance pressure-sensitive adhesive sheet can be formed.

The Mw of the peak L is typically 1000 or more and less than 100 ten thousand, and usually 1 ten thousand or more and 70 ten thousand or less is appropriate, and preferably 5 ten thousand or more and 50 ten thousand or less. In some embodiments of the adhesive compositions disclosed herein, the Mw of peak L may be, for example, 8 or more thousand or 10 or more thousand, or 35 or less thousand, 25 or less thousand or 20 or less thousand. In this manner, a higher performance pressure-sensitive adhesive sheet can be formed. The Mw of the peak H and the peak L are calculated from the measurement values of GPC. The same applies to the later-described embodiments.

(glass transition temperature (Tg))

The composition of the monomer component may be set so that the glass transition temperature (Tg) calculated based on the composition of the monomer component is less than 0 ℃. Herein, the Tg calculated based on the composition of the monomer component means the Tg obtained by the Fox equation based on the composition of the monomer component. The Fox formula is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing monomers constituting the copolymer.

1/Tg＝Σ(Wi/Tgi)

In the above Fox formula, Tg represents the glass transition temperature (unit: K) of a copolymer, Wi represents the weight fraction (copolymerization ratio on the weight basis) of the monomer i in the copolymer, and Tgi represents the glass transition temperature (unit: K) of a homopolymer of the monomer i.

The glass transition temperature of the homopolymer used for the calculation of Tg is the value described in the publicly known data. Specifically, numerical values are listed in "Polymer Handbook" (3 rd edition, John Wiley & Sons, Inc., 1989). The highest value was used for the monomers having various values described in the above Polymer Handbook. As the glass transition temperature of a homopolymer of a monomer not described in the above-mentioned PolymerHandbook, a value obtained by a measurement method described in Japanese patent laid-open No. 2007-51271 can be used.

The Tg calculated based on the composition of the monomer component can be grasped as the Tg of the polymer of the monomer component (typically, the base polymer in the adhesive composition disclosed herein). The Tg of the polymer is preferably-10 ℃ or lower, may be-20 ℃ or lower, may be-30 ℃ or lower, or may be-40 ℃ or lower. When the Tg is low, the adhesion to an adherend tends to be improved. In some embodiments, the Tg of the polymer may be-50 ℃ or lower, may be-55 ℃ or lower, or may be-60 ℃ or lower. The lower limit of the Tg of the polymer is not particularly limited, but is usually suitably at least-80 ℃ and preferably at least-70 ℃ from the viewpoints of ease of obtaining the material and improvement in the aggregation property of the pressure-sensitive adhesive layer.

(acrylic Polymer)

the adhesive composition disclosed herein may be preferably implemented in such a manner that more than 50% by weight of the above monomer components is a (meth) acrylic monomer. The pressure-sensitive adhesive composition disclosed herein is preferably a pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer, which is a polymer of the above monomer component, that is, an acrylic pressure-sensitive adhesive composition. For some preferred forms of the adhesive composition, more than 70 wt%, more than 80 wt%, or more than 90 wt% of the polymer components contained in the composition may be an acrylic polymer. The acrylic polymer may be contained in an amount of 95 wt% or more or 98 wt% or more of the polymer component.

In this specification, "acrylic polymer" refers to a polymer having a polymer structure containing a monomer unit derived from a (meth) acrylic monomer, and typically refers to a polymer containing a monomer unit derived from a (meth) acrylic monomer in a proportion of more than 50% by weight. In this specification, the (meth) acrylic monomer means a monomer having at least 1 (meth) acryloyl group in 1 molecule. Here, "(meth) acryloyl group" means that it includes both acryloyl and methacryloyl groups. Therefore, the concept of the (meth) acrylic monomer referred to herein may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer). Similarly, in this specification, "(meth) acrylic acid" means a meaning including acrylic acid and methacrylic acid, and "(meth) acrylate" means a meaning including acrylate and methacrylate.

The acrylic polymer may be, for example, a polymer containing 50% by weight or more of a monomer unit derived from an alkyl (meth) acrylate, that is, a polymer containing 50% by weight or more of an alkyl (meth) acrylate in the total amount of monomer components used for preparing the acrylic polymer. The alkyl (meth) acrylate preferably has 1 to 20 carbon atoms (i.e., C) at the ester end_1-20Of (b) a linear or branched alkyl (meth) acrylate. (meth) acrylic acid C in the total amount of monomer components from the viewpoint of easy availability of a balance of characteristics_1-20The proportion of the alkyl ester may be, for example, 50% by weight or more, preferably 60% by weight or more, and more preferably 70% by weight or more. (meth) acrylic acid C in the total amount of monomer components for the same reason_1-20the proportion of the alkyl ester may be, for example, 99.9% by weight or less, preferably 98% by weight or less, and more preferably 95% by weight or less. In some embodiments, (meth) acrylic acid C is contained in the total amount of the monomer components_1-20The proportion of the alkyl ester may be, for example, 80% by weight or more, or 85% by weight or more.

As (meth) acrylic acid C_1-20Non-limiting specific examples of the alkyl ester include methyl (meth) acrylate and methyl (meth) acrylate) Ethyl acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, dodecyl (meth) acrylate, and the like, Cetyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and the like.

Of these, it is preferable to use at least (meth) acrylic acid C_1-18Alkyl esters, more preferably at least (meth) acrylic acid C_1-14An alkyl ester. In some embodiments, the acrylic polymer may contain a monomer selected from (meth) acrylic acid C_4-12Alkyl esters (preferably acrylic acid C)_4-10Alkyl ester) as monomer units. For example, an acrylic polymer containing one or both of n-Butyl Acrylate (BA) and 2-ethylhexyl acrylate (2EHA) is preferable, and an acrylic polymer containing at least 2EHA is particularly preferable. Other (meth) acrylic acid C which can be preferably used_1-18Examples of the alkyl ester include methyl acrylate, Methyl Methacrylate (MMA), n-Butyl Methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (ISTA), and the like. Suitable examples of the acrylic polymer include acrylic acid C_4-8Acrylic polymer containing acrylic acid C as monomer unit of at least one of alkyl esters_4-6Acrylic polymer containing acrylic acid C as monomer unit of at least one of alkyl esters_6-10Acrylic polymers having at least one of the alkyl esters as a monomer unit, and the like.

The monomer unit constituting the acrylic polymer may contain, as a main component, an alkyl (meth) acrylate and, if necessary, another monomer (copolymerizable monomer) copolymerizable with the alkyl (meth) acrylate. As the copolymerizable monomer, a monomer having a polar group (for example, a carboxyl group, a hydroxyl group, an amide group, etc.) can be suitably used. The monomer having a polar group may contribute to introduction of a crosslinking point into the acrylic polymer or increase the cohesive force of the acrylic polymer. The copolymerizable monomers may be used singly or in combination of two or more.

Specific non-limiting examples of the copolymerizable monomer include the following monomers.

Carboxyl group-containing monomer: for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like.

Acid anhydride group-containing monomer: for example maleic anhydride, itaconic anhydride.

Hydroxyl group-containing monomer: for example, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate.

Sulfonic acid group-or phosphoric acid group-containing monomer: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloyl phosphate, and the like.

Epoxy group-containing monomer: examples of the epoxy group-containing acrylate include glycidyl (meth) acrylate, 2-ethyl glycidyl (meth) acrylate, allyl glycidyl ether, and glycidyl (meth) acrylate.

A cyano group-containing monomer: for example, acrylonitrile, methacrylonitrile, and the like.

Isocyanate group-containing monomer: for example, 2-isocyanatoethyl (meth) acrylate, and the like.

Amide group-containing monomer: for example, (meth) acrylamide; n, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-dipropyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, N-di (N-butyl) (meth) acrylamide, and N, N-di (tert-butyl) (meth) acrylamide; n-alkyl (meth) acrylamides such as N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, and N-N-butyl (meth) acrylamide; n-vinylcarboxylic acid amides such as N-vinylacetamide; a monomer having a hydroxyl group and an amide group, for example, N-hydroxyalkyl (meth) acrylamides such as N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, and N- (4-hydroxybutyl) (meth) acrylamide; a monomer having an alkoxy group and an amide group, for example, an N-alkoxyalkyl (meth) acrylamide such as N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, and N-butoxymethyl (meth) acrylamide; and N, N-dimethylaminopropyl (meth) acrylamide, N- (meth) acryloylmorpholine, and the like.

Monomer having nitrogen atom-containing ring: such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1, 3-oxazin-2-one, N-vinyl-3, 5-morpholinodione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, etc. (e.g., lactams such as N-vinyl-2-caprolactam).

Monomer having succinimide skeleton: for example, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxohexamethylene succinimide, N- (meth) acryloyl-8-oxohexamethylene succinimide, etc.

Maleimide group: such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, etc.

Itaconimides: such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-lauryl itaconimide, etc.

Aminoalkyl (meth) acrylates: for example, aminoethyl (meth) acrylate, N-dimethylaminoethyl (meth) acrylate, N-diethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.

Alkoxy group-containing monomers: alkoxyalkyl (meth) acrylate esters such as 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, and ethoxypropyl (meth) acrylate; alkoxyalkylene glycol (meth) acrylates such as methoxyethylene glycol (meth) acrylate and methoxypolypropylene glycol (meth) acrylate.

Vinyl esters: for example, vinyl acetate, vinyl propionate, and the like.

vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.

Aromatic vinyl compound: for example, styrene, alpha-methylstyrene, vinyltoluene, and the like.

olefins: for example, ethylene, butadiene, isoprene, isobutylene, and the like.

(meth) acrylate having alicyclic hydrocarbon group: for example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and the like.

(meth) acrylate having an aromatic hydrocarbon group: for example, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and the like.

And heterocyclic ring-containing (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, halogen atom-containing (meth) acrylates such as vinyl chloride-and/or fluorine atom-containing (meth) acrylates, silicon atom-containing (meth) acrylates such as silicone (meth) acrylates, and (meth) acrylates derived from terpene compound derivative alcohols.

When the copolymerizable monomer is used, the amount thereof is not particularly limited, and is usually preferably 0.01% by weight or more based on the total amount of the monomer components. From the viewpoint of more effectively exhibiting the effects of the use of the copolymerizable monomer, the amount of the copolymerizable monomer to be used may be 0.1% by weight or more, or may be 1% by weight or more, based on the total amount of the monomer components. The amount of the copolymerizable monomer used may be 50% by weight or less, preferably 40% by weight or less, based on the total amount of the monomer components. This prevents the cohesive force of the pressure-sensitive adhesive from becoming too high, and improves the adhesion to the adherend.

The adhesive composition disclosed herein may preferably contain (meth) acrylic acid C as the monomer component_4-10Alkyl esters, and one or both of acrylic acid and hydroxyl group-containing monomers. As the hydroxyl group-containing monomer, a hydroxyalkyl (meth) acrylate is preferably used. Particularly preferred is hydroxy C acrylate such as 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA)_1-4An alkyl ester.

The monomer component contains (meth) acrylic acid C_4-10In the embodiment where the alkyl ester further contains one or both of acrylic acid and a hydroxyl group-containing monomer, (meth) acrylic acid C in the monomer component_4-10The content of the alkyl ester is preferably 60% by weight or more, more preferably 70% by weight or more, and may be 80% by weight or more, and is preferably 99% by weight or less, more preferably 97% by weight or less, and may be 94% by weight or less, for example. In additionWhen the monomer component contains acrylic acid, the content thereof may be, for example, 0.5% by weight or more, preferably 2.5% by weight or more, more preferably 5% by weight or more, and may be, for example, 25% by weight or less, preferably 20% by weight or less, or may be 15% by weight or less. When the monomer component contains a hydroxyl group-containing monomer, the content thereof may be, for example, 0.01% by weight or more, preferably 0.05% by weight or more, and may be, for example, 15% by weight or less, preferably 10% by weight or less, and may be 5% by weight or less, 3% by weight or less, or 1% by weight or less. More preferably, the monomer component contains (meth) acrylic acid C_4-10Alkyl esters, and also both acrylic acid and hydroxyl group-containing monomers.

(crosslinking agent)

The adhesive composition disclosed herein may contain a crosslinking agent as needed for the purpose of adjustment of cohesive force and the like. As the crosslinking agent, a crosslinking agent known in the field of adhesives can be used, and examples thereof include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a silicone-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a silane-based crosslinking agent, an alkyl ether melamine-based crosslinking agent, and a metal chelate-based crosslinking agent. Among these, preferred crosslinking agents include isocyanate-based crosslinking agents and epoxy-based crosslinking agents. The crosslinking agent may be used singly or in combination of two or more.

Examples of the isocyanate-based crosslinking agent include toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and an adduct of these with a polyol such as trimethylolpropane. Or a compound having at least 1 or more isocyanate groups and 1 or more unsaturated bonds in 1 molecule, specifically 2-isocyanatoethyl (meth) acrylate, may be used as the isocyanate crosslinking agent. These may be used alone or in combination of two or more.

Examples of the epoxy-based crosslinking agent include bisphenol a, an epoxy-based resin of the epichlorohydrin type, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1, 6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidyl amine, N' -tetraglycidyl m-xylylenediamine, and 1, 3-bis (N, N-diglycidylaminomethyl) cyclohexane. These may be used alone or in combination of two or more.

The amount of the crosslinking agent used is not particularly limited, and may be, for example, more than 0 part by weight per 100 parts by weight of the base polymer. The amount of the crosslinking agent to be used may be, for example, 0.01 part by weight or more, preferably 0.05 part by weight or more, based on 100 parts by weight of the base polymer. By increasing the amount of the crosslinking agent, higher cohesive force tends to be obtained. In some embodiments, the crosslinking agent may be used in an amount of 1 part by weight or more, 2 parts by weight or more, or 3 parts by weight or more, relative to 100 parts by weight of the base polymer. On the other hand, from the viewpoint of avoiding a decrease in adhesive strength due to an excessive increase in cohesive strength, the amount of the crosslinking agent to be used is preferably 15 parts by weight or less, and may be 10 parts by weight or less, or may be 7 parts by weight or less, based on 100 parts by weight of the base polymer.

In order to more efficiently perform any of the above-mentioned crosslinking reactions, a crosslinking catalyst may be used. As the crosslinking catalyst, for example, a tin-based catalyst (in particular, dioctyltin dilaurate) can be preferably used. The amount of the crosslinking catalyst to be used is not particularly limited, and may be set to about 0.0001 to 1 part by weight, for example, relative to 100 parts by weight of the base polymer.

(polyfunctional monomer)

The adhesive compositions disclosed herein are prepared using polyfunctional monomers as needed. The use of a polyfunctional monomer in place of or in combination with the crosslinking agent as described above can contribute to the purpose of adjusting the cohesive force. Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 12-dodecanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, and vinyl (meth) acrylate, Butanediol (meth) acrylate, hexanediol di (meth) acrylate, and the like. Among them, preferable examples of the polyfunctional monomer include trimethylolpropane tri (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, and dipentaerythritol hexa (meth) acrylate. The polyfunctional monomer may be used alone or in combination of two or more. The amount of the polyfunctional monomer used varies depending on the molecular weight, the number of functional groups, and the like, and is usually suitably in the range of about 0.01 to 3.0 parts by weight based on 100 parts by weight of the base polymer. The adhesive composition disclosed herein may preferably be implemented in a manner substantially free of polyfunctional monomers.

(tackifying resin)

The adhesive composition may contain a tackifier resin as required. The tackifier resin is not particularly limited, and examples thereof include rosin-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, hydrocarbon-based tackifier resins, ketone-based tackifier resins, polyamide-based tackifier resins, epoxy-based tackifier resins, and elastic-based tackifier resins. The tackifier resins may be used singly or in combination of two or more.

Examples of the rosin-based tackifying resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin and tall oil rosin, modified rosins (polymerized rosins, stabilized rosins, disproportionated rosins, fully hydrogenated rosins, partially hydrogenated rosins, and other chemically modified rosins) obtained by modifying these unmodified rosins by polymerization, disproportionation, hydrogenation, and the like, and various rosin derivatives.

Examples of the rosin derivatives include rosin phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, and the like) with an acid catalyst and thermally polymerizing the resulting mixture;

Rosin ester resins such as ester compounds of rosin obtained by esterifying unmodified rosin with alcohols (unmodified rosin esters), ester compounds of modified rosin obtained by esterifying modified rosin such as polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, and partially hydrogenated rosin with alcohols (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, and partially hydrogenated rosin esters);

Unsaturated fatty acid-modified rosin resins obtained by modifying unmodified rosin or modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, or the like) with an unsaturated fatty acid;

Unsaturated fatty acid-modified rosin ester resin obtained by modifying rosin ester resin with unsaturated fatty acid;

Rosin alcohol resins obtained by reducing carboxyl groups in unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and the like), unsaturated fatty acid-modified rosin resin, and unsaturated fatty acid-modified rosin ester resin;

Metal salts of rosin-based resins (particularly rosin ester-based resins) such as unmodified rosin, modified rosin, and various rosin derivatives; and the like.

Examples of the terpene-based tackifier resin include terpene-based resins such as α -pinene polymer, β -pinene polymer, and dipentene polymer, and modified terpene-based resins (e.g., terpene-phenol-based resins, styrene-modified terpene-based resins, aromatic-modified terpene-based resins, and hydrogenated terpene-based resins) obtained by modifying (e.g., phenol modification, aromatic modification, hydrogenation modification, and hydrocarbon modification) these terpene-based resins.

Examples of the phenolic tackifier resin include condensates (for example, alkylphenol resin, xylene formaldehyde resin, and the like) of various phenols (for example, phenol, m-cresol, 3, 5-xylenol, p-alkylphenol, resorcinol, and the like) and formaldehyde, resol resins obtained by addition reaction of the above phenols and formaldehyde in the presence of an alkali catalyst, and novolacs obtained by condensation reaction of the above phenols and formaldehyde in the presence of an acid catalyst.

Examples of the hydrocarbon-based tackifier resin include various hydrocarbon-based resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers and the like), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

Commercially available products of polymerized rosin esters which can be preferably used include, but are not limited to, trade names "Pensel D-125", "Pensel D-135", "Pensel D-160", "Pensel KK" and "Pensel C" available from Seawa chemical industries, Ltd.

Examples of commercially available terpene-phenol resins that can be preferably used include, but are not limited to, yasura CHEMICAL co., ltd, trade name "YS POLYSTER S145", "YS POLYSTER G125", "YS POLYSTER N125", "YS POLYSTER U115", trade name "Tamanol 803L", "Tamanol 901", Sumitomo Bakelite co., ltd, trade name "sumitieren PR-12603", and the like.

As the tackifier resin, a tackifier resin having a softening point of about 80 ℃ or higher (more preferably about 100 ℃ or higher, for example, about 120 ℃ or higher) can be preferably used. The upper limit of the softening point is not particularly limited, and may be, for example, about 200 ℃ or lower (typically 180 ℃ or lower). The softening point of the tackifier resin can be measured according to a softening point test method (ring and ball method) specified in JIS K2207.

The amount of the tackifier resin used is not particularly limited, and may be set so as to exhibit an appropriate adhesive performance depending on the purpose and application. The content of the tackifier resin with respect to 100 parts by weight of the base polymer is, for example, 5 parts by weight or more, and may be 10 parts by weight or more or 15 parts by weight or more, and may be 50 parts by weight or less, 40 parts by weight or less or 30 parts by weight or less. Or no tackifying resin may be used.

further, the adhesive composition in the art disclosed herein may contain, as needed, known additives that can be used in adhesives such as leveling agents, plasticizers, softening agents, colorants (dyes, pigments, etc.), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, and the like, within a range that does not significantly hinder the effects of the present invention.

In some embodiments, the adhesive composition may be in the form of an organic solvent solution or emulsion having a nonvolatile content in a range of about 10 wt% or more and 70 wt% or less. The nonvolatile content may be 20% by weight or more or 30% by weight or more, and may be 60% by weight or less or 50% by weight or less. The pressure-sensitive adhesive composition disclosed herein is preferably prepared in the form of an organic solvent solution having a nonvolatile content of 20 wt% or more and 50 wt% or less from the viewpoint of coatability and the like. The pressure-sensitive adhesive composition usable for forming a pressure-sensitive adhesive layer having a thickness of 10 μm or less, and further 8 μm or less is particularly significant in the form of an organic solvent solution having a nonvolatile content in the above range.

The nonvolatile content of the adhesive composition was calculated as follows: the weight of the sample was measured by placing the sample in an aluminum pan having a known weight (W1) (W2), and the weight of the sample after heating at 130 ℃ for 2 hours (W3) was measured and substituted in the following formula to calculate the weight.

Nonvolatile content (%) - (W3-W1)/(W2-W1). times.100

The viscosity of the adhesive composition disclosed herein is not particularly limited. In some embodiments, the adhesive composition may have a viscosity of, for example, 5cP or more, 10cP or more, 20cP or more, or 25cP or more. The viscosity of the adhesive composition may be, for example, 150cP or less, 120cP or less, 90cP or less, or 75cP or less. If the viscosity of the pressure-sensitive adhesive composition is too high, the following problems tend to occur: the coating property is lowered to make it difficult to obtain a uniform adhesive surface, the line speed is limited to lower the productivity, and the like. When the viscosity of the pressure-sensitive adhesive composition is too low, coating defects such as shrinkage may be easily caused particularly when the composition is applied to the release surface of a release liner. The upper and lower viscosity limits can be suitably applied to, for example, an adhesive composition that can be used for forming an adhesive layer having a small thickness. The viscosity of the adhesive composition can be measured at room temperature (23 ℃) using a commercially available B-type viscometer at 10 rpm. The same method can be applied to the examples described later.

< production of adhesive composition >

The method for obtaining a polymer from the monomer component is not particularly limited, and various polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be suitably used. In some cases, solution polymerization or photopolymerization may be preferably used.

The initiator used for polymerization may be suitably selected from conventionally known thermal polymerization initiators, photopolymerization initiators and the like according to the polymerization method. The polymerization initiator may be used singly or in combination of two or more.

Examples of the thermal polymerization initiator include azo polymerization initiators (e.g., 2,2 ' -azobisisobutyronitrile, 2,2 ' -azobis (2-methylpropionamidine) disulfate, 2,2 ' -azobis (2-amidinopropane) dihydrochloride, 2,2 ' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2,2 ' -azobis (N, N ' -dimethyleneisobutylamidine), 2,2 ' -azobis [ N- (2-carboxyethyl) -2-methylpropionamidine ] hydrate, 2,2 ' -azobis (4-methoxy-2, 4-dimethylvaleronitrile), 2,2 ' -azobis (2, 4-dimethylvaleronitrile), 2,2 '-azobis (2-methylbutyronitrile), 1' -azobis (cyclohexane-1-carbonitrile), 2 '-azobis (2,4, 4-trimethylpentane), dimethyl-2, 2' -azobis (2-methylpropionate), and the like); persulfates such as potassium persulfate; peroxide-based polymerization initiators (e.g., dibenzoyl peroxide, t-butyl peroxymaleate, lauroyl peroxide, etc.); redox polymerization initiators, and the like. The amount of the thermal polymerization initiator to be used is not particularly limited, and may be, for example, in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the monomer component used for producing the acrylic polymer.

The photopolymerization initiator is not particularly limited, and for example, a benzoin ether type photopolymerization initiator, an acetophenone type photopolymerization initiator, an α -ketol type photopolymerization initiator, an aromatic sulfonyl chloride type photopolymerization initiator, a photoactive oxime type photopolymerization initiator, a benzoin type photopolymerization initiator, a benzil type photopolymerization initiator, a benzophenone type photopolymerization initiator, a ketal type photopolymerization initiator, a thioxanthone type photopolymerization initiator, an acylphosphine oxide type photopolymerization initiator, and the like can be used. The amount of the photopolymerization initiator used is not particularly limited, and may be, for example, in the range of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the monomer component.

The adhesive compositions disclosed herein can be made, for example, by a method comprising: the polymerization method comprises a first stage of polymerizing a part of monomer components used for the preparation of the composition to obtain a partial polymer, and a second stage of polymerizing the unreacted monomer components in the presence of the partial polymer and a polymerization solvent after the first stage. Such a production method including two-stage polymerization is preferable because the molecular weight distribution of the polymer can be easily adjusted to satisfy the above (a) and (b).

The polymerization in the first stage is preferably carried out by bulk polymerization without a polymerization solvent or in the presence of a smaller amount (low concentration) of a polymerization solvent than the polymerization in the second stage. By carrying out the first stage polymerization under a higher monomer concentration condition, a polymer having a higher molecular weight tends to be produced. If the monomer concentration in the first polymerization stage is too low, the molecular weight becomes low, and the polymerization of the target high molecular weight component becomes difficult. When the polymerization in the first stage is carried out in the presence of a small amount of the polymerization solvent, the amount of the polymerization solvent to be used may be, for example, 35% by weight or less, 30% by weight or less, or 25% by weight or less, where the total amount of the monomer component and the polymerization solvent used in the first stage is 100% by weight. In some embodiments, a small amount of the polymerization solvent, specifically, for example, 1% by weight or more, 5% by weight or more, 10% by weight or more, or 15% by weight or more of the total amount of the polymerization solvent may be used in the first-stage polymerization. For example, from the viewpoint of suppressing an increase in viscosity in the polymerization in the first stage to improve the operability and the reaction controllability, it is advantageous to use a small amount of the polymerization solvent in the polymerization in the first stage. The polymerization solvent is preferably an organic solvent, and for example, any one solvent selected from acetic acid esters such as ethyl acetate, aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane, lower alcohols such as ethanol and isopropanol, ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, ether solvents such as tetrahydrofuran and dimethoxyethanol, and mixed solvents of two or more kinds may be used. From the viewpoint of easily achieving a molecular weight distribution satisfying the above (a) and (b), it is preferable to use ethyl acetate alone or a mixed solvent of ethyl acetate and toluene as the polymerization solvent in the first stage. Particular preference is given to using ethyl acetate alone.

In some embodiments, the polymerization in the first stage may be carried out at a temperature of, for example, about 40 to 90 ℃ and preferably about 50 to 70 ℃ using the thermal polymerization initiator (for example, azo polymerization initiator) as described above. In another embodiment, the first-stage polymerization may be performed by irradiating light such as ultraviolet light using the above-mentioned photopolymerization initiator.

The monomer component used in the first-stage polymerization may be a part of the whole monomer component used in the production of the adhesive composition, or may be all of the monomer component. When a part of the whole monomer component is used in the first polymerization stage, the part may be the amount of the whole monomer component or the kind of a part of the plurality of monomers contained in the whole monomer component.

The polymerization in the first stage is preferably performed so that the polymerization conversion rate (monomer conversion) of the monomer components used for the preparation of the adhesive composition becomes about 3% by weight or more, assuming that the whole monomer components are 100% by weight. Hereinafter, the polymerization conversion of the monomer component at the end of the first stage may be referred to as "intermediate polymerization ratio". In some embodiments, the intermediate polymerization rate may be about 5% by weight or more, or may be about 8% by weight or more. The intermediate polymerization degree is usually preferably about 50% by weight or less, more preferably about 40% by weight or less, and may be about 30% by weight or less, or may be about 25% by weight or less. When the intermediate polymerization rate is high, the area ratio of the peak H after the second stage tends to be large. In addition, when the intermediate polymerization rate is low, the area ratio of the peak L after the second stage tends to be large.

The polymerization conversion of the monomer component used in the first stage was calculated as follows: the weight of a sample collected from the reaction solution at the end of the first stage was measured by placing it in an aluminum pan having a known weight (W1) (W2), and then the weight of the sample heated at 130 ℃ for 2 hours (W3) was measured and substituted into the following formula, thereby calculating the weight. Here, m1 in the following formula represents the ratio of the weight of the monomer used in the first stage to the weight of the reaction solution at the end of the first stage.

The polymerization conversion (%) of the monomer component used in the first stage was (W3-W1)/((W2-W1) × m1) × 100

The intermediate polymerization rate, which is the weight ratio of the monomer components polymerized in the first stage in the entire monomer components used for the production of the adhesive composition, can be calculated based on the polymerization conversion ratio of the monomer components used in the first stage and the amount of the monomer components used after the polymerization in the first stage is completed. When all the monomer components used for the preparation of the adhesive composition are charged into the reaction liquid at the end of the first stage, the polymerization conversion rate of the monomer components used in the first stage matches the intermediate polymerization rate. The intermediate polymerization rate was also determined in the same manner as in examples described later.

In the first stage, the polymerization of the monomer component is carried out to a desired extent (for example, until a desired intermediate polymerization rate is reached), and then the reaction is once terminated. For example, a polymerization solvent is added to the system, and the system is cooled in the case of thermal polymerization, and the light irradiation is stopped in the case of photopolymerization. As the polymerization solvent to be added at the end of the polymerization in the first stage, any one solvent or a mixed solvent of two or more kinds selected from the same organic solvents as the polymerization solvents exemplified as the polymerization solvents that can be used in the polymerization in the first stage can be preferably used. In the case where the polymerization in the first stage is carried out in the presence of a polymerization solvent, the polymerization solvent may be the same as or different from the polymerization solvent added at the time of completion of the polymerization in the first stage.

In the second stage, the polymerization reaction of the unreacted monomer components in the whole monomer components is carried out in the presence of the partial polymer obtained in the first stage and a polymerization solvent. The polymerization in the second stage is preferably carried out under conditions that contain more polymerization solvent than the polymerization in the first stage. This is preferably, for example, that the content (wt%) of the polymerization solvent in the polymerization in the second stage is higher by 5 wt% or more or 10 wt% or more than the content (wt%) of the polymerization solvent in the polymerization in the first stage. In some embodiments, the content of the polymerization solvent in the second stage may be, for example, more than 35% by weight, preferably 40% by weight or more, more preferably 45% by weight or more, and may be 50% by weight or 55% by weight or more, from the viewpoint of suppressing an increase in viscosity or the like. The content of the polymerization solvent in the second stage is usually preferably 90% by weight or less, and may be 80% by weight or less or 70% by weight or less.

The second-stage polymerization can be carried out at a temperature of, for example, about 35 to 90 ℃ and preferably about 35 to 70 ℃ by adding a thermal polymerization initiator (for example, an azo polymerization initiator) as described above. The thermal polymerization initiator used in the first stage may be the same as or different from the thermal polymerization initiator used in the second stage. In another embodiment, the first-stage polymerization may be carried out by adding a photopolymerization initiator as described above and irradiating with light such as ultraviolet light. The photopolymerization initiator used in the first stage may be the same as or different from the photopolymerization initiator used in the second stage. For example, a photopolymerization initiator may be used in the first stage and a thermal polymerization initiator may be used in the second stage, or a thermal polymerization initiator may be used in the first stage and a photopolymerization initiator may be used in the second stage. In the second stage polymerization, it is generally preferable to perform the first and second stages by using a thermal polymerization initiator or to perform the first and second stages by using a photopolymerization initiator, since the remaining portion (undecomposed portion) of the polymerization initiator used in the first stage can be used. The weight average molecular weight of the peak L can be adjusted by appropriately setting the kind and amount of the polymerization initiator, the polymerization temperature, the light irradiation intensity, and other polymerization conditions in the second stage polymerization.

The polymerization in the second stage is preferably performed so that the polymerization conversion of the monomer components used for the preparation of the adhesive composition is about 90% by weight or more, based on 100% by weight of the whole monomer components. Such a configuration with a high polymerization conversion ratio can suitably exhibit the effects of satisfying the above (a) and (b). Hereinafter, the polymerization conversion rate of the monomer component at the end of the second stage may be referred to as "final polymerization rate". The polymerization in the second stage is preferably carried out so that the final polymerization rate becomes about 95% by weight or more, and more preferably about 97% by weight or more. In one embodiment, the final polymerization rate may be 100% by weight, and may be 99.5% by weight or less or 99.0% by weight or less from the practical viewpoint of productivity, cost, and the like.

The final polymerization ratio was calculated as follows: the weight of the sample collected from the reaction solution at the end of the second stage was measured by placing it in an aluminum pan having a known weight (W1) (W2), and then the weight of the sample heated at 130 ℃ for 2 hours (W3) was measured and substituted into the following formula to calculate the weight. Here, m2 in the following formula represents the ratio of the weight of the entire monomer components to the weight of the reaction solution at the end of the second stage.

Final polymerization ratio (%) - (W3-W1)/((W2-W1) × m2) × 100

The final polymerization rate was also determined in the same manner as in examples described below.

When the adhesive composition disclosed herein contains a crosslinking agent and/or a tackifier resin, it is desirable to add and mix these components after the completion of the entire polymerization.

< pressure-sensitive adhesive sheet >

the pressure-sensitive adhesive sheet disclosed herein is configured to include a pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may be in the form of, for example, a substrate-free double-sided pressure-sensitive adhesive sheet including: the adhesive sheet comprises a first adhesive surface formed by one surface of an adhesive layer and a second adhesive surface formed by the other surface of the adhesive layer. Alternatively, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a substrate-attached pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is laminated on one or both sides of a support substrate. Hereinafter, the supporting substrate may be simply referred to as "substrate".

Fig. 1 schematically shows the structure of an adhesive sheet according to an embodiment. The adhesive sheet 1 is configured as a substrate-less double-sided adhesive sheet including an adhesive layer 21. The psa sheet 1 is used by attaching a first psa surface 21A, which is one surface (first surface) of the psa layer 21, and a second psa surface 21B, which is the other surface (second surface) of the psa layer 21, to different parts of an adherend. The portions to which the pressure-sensitive adhesive surfaces 21A and 21B are applied may be the respective portions of different members or may be the different portions in a single member. As shown in fig. 1, the psa sheet 1 before use (i.e., before application to an adherend) may be a release-lined psa sheet 100 in which the first psa surface 21A and the second psa surface 21B are protected by release liners 31 and 32, respectively, which are release surfaces on at least the sides facing the psa layer 21. As the release liners 31 and 32, for example, one configured such that a release layer formed by a release treatment agent is provided on one surface of a sheet-like base material (liner base material) and the one surface becomes a release surface can be preferably used. Alternatively, the following release-liner-attached adhesive sheet may be constituted: the release liner 32 is omitted, and a release liner 31 having both release surfaces is used, and the release liner is wound in a spiral shape while being overlapped with the psa sheet 1, so that the second adhesive surface 21B is protected by being in contact with the back surface of the release liner 31 (in a rolled form).

Fig. 2 schematically shows the structure of an adhesive sheet according to still another embodiment. The pressure-sensitive adhesive sheet 2 is configured as a single-sided pressure-sensitive adhesive sheet with a substrate, and includes: a sheet-like support base (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side thereof. The adhesive layer 21 is fixedly provided on the first surface 10A side of the support substrate 10, that is, on the first surface 10A side of the support substrate 10 without separating the adhesive layer 21 from the support substrate 10. As shown in fig. 2, the psa sheet 2 before use may be a release-lined psa sheet 200 in which the surface (psa surface) 21A of the psa layer 21 is protected by a release liner 31, which serves as a release surface at least on the side facing the psa layer 21. Alternatively, the following embodiments may be used: the release liner 31 is omitted, and the psa sheet 2 is wound around the support substrate 10 with the second surface 10B serving as the release surface, so that the adhesive surface 21A is protected by abutting against the second surface (back surface) 10B of the support substrate 10 (in a rolled form).

Fig. 3 schematically shows the structure of an adhesive sheet of another embodiment. The pressure-sensitive adhesive sheet 3 is configured as a double-sided pressure-sensitive adhesive sheet with a substrate, and includes: a sheet-like support base (for example, a resin film) 10 having a first surface 10A and a second surface 10B, a first pressure-sensitive adhesive layer 21 fixedly provided on the first surface 10A side thereof, and a second pressure-sensitive adhesive layer 22 fixedly provided on the second surface 10B side thereof. As shown in fig. 3, the psa sheet 3 before use may be a release-lined psa sheet 300 in which the surface (first psa surface) 21A of the first psa layer 21 and the surface (second psa surface) 22A of the second psa layer 22 are protected by release liners 31 and 32. Alternatively, the following release-liner-attached pressure-sensitive adhesive sheet may be constituted: the release liner 32 is omitted, and the release liner 31 having both release surfaces is used, and the release liner is overlaid on the pressure-sensitive adhesive sheet 3 and wound in a spiral shape, whereby the second pressure-sensitive adhesive surface 22A is in contact with the back surface of the release liner 31 to be protected (in a rolled form).

The term "pressure-sensitive adhesive sheet" as used herein includes articles such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive films, and pressure-sensitive adhesive labels. The pressure-sensitive adhesive sheet may be in a roll form, a sheet form, or a form which is cut or punched into an appropriate shape according to the application or use. The pressure-sensitive adhesive layer in the technique disclosed herein is typically formed continuously, but is not limited thereto, and may be formed in a regular or random pattern such as dots or stripes, for example.

(adhesive layer)

The adhesive layer constituting the adhesive sheet disclosed herein may be a cured layer of any of the adhesive compositions disclosed herein. The adhesive layer can be formed by applying (for example, coating) an adhesive composition to an appropriate surface and then appropriately performing curing treatment such as drying, polymerization, cooling, and crosslinking. The solvent-based or water-dispersed adhesive composition is usually at least dried as the curing treatment. The photocurable adhesive composition is irradiated with light. The hot melt type adhesive composition is solidified by cooling after coating. In the case where two or more curing treatments (e.g., drying and crosslinking) are performed, they may be performed simultaneously or in multiple stages.

The application of the adhesive composition can be carried out using a conventional coater such as a gravure roll coater, a reverse roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater.

As a method for providing an adhesive layer on a support substrate, a pressure-sensitive adhesive sheet having a form of a support substrate may be used such as a direct method in which an adhesive composition is directly applied to the support substrate to form an adhesive layer, a transfer method in which an adhesive layer formed on a surface having releasability (release surface) is transferred to a support substrate, or a combination of these methods. The release surface may be a surface of a release liner, a back surface of a support base material subjected to a release treatment, or the like.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and may be, for example, about 1 μm or more and 500 μm or less. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 200 μm or less, or 100 μm or less, or 50 μm or less, from the viewpoint of weight reduction and thickness reduction. When the adhesive composition disclosed herein is used, an adhesive layer exhibiting strong adhesive force even when it is thin can be formed. By utilizing the above feature, the thickness of the pressure-sensitive adhesive layer may be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 10 μm or less than 10 μm, or 8 μm or less or 7 μm or less. From the viewpoint of easily exhibiting strong adhesive force, the thickness of the adhesive layer is preferably 2 μm or more, and may be 3 μm or more. Preferred ranges of the thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet disclosed herein include a range of 1 μm to 30 μm, a range of 2 μm to 25 μm, a range of 3 μm to 20 μm, a range of 3 μm to less than 10 μm, a range of 3 μm to 8 μm, and the like. In the substrate-less pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer, the thickness of the pressure-sensitive adhesive layer is equal to the thickness of the pressure-sensitive adhesive sheet. In the case of a double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on both sides of a substrate, the thickness of the pressure-sensitive adhesive layer is the thickness of the pressure-sensitive adhesive layer on one side of the substrate. The pressure-sensitive adhesive layers constituting the pressure-sensitive adhesive sheet disclosed herein (each pressure-sensitive adhesive layer in the case of a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a substrate) may have a single-layer structure or a multilayer structure of two or more layers.

In the adhesive sheet disclosed herein, the gel fraction of the adhesive layer is preferably 70% or less, and more preferably 50% or less. The pressure-sensitive adhesive layer having an excessively high gel fraction tends to exhibit good adhesion to an adherend even when it is thin. This is advantageous from the viewpoint of improving the adhesive force. In some embodiments, the gel fraction of the pressure-sensitive adhesive layer may be 45% or less, or may be 40% or less. On the other hand, from the viewpoint of imparting appropriate aggregability to the pressure-sensitive adhesive layer, the gel fraction of the pressure-sensitive adhesive layer is usually appropriate to be 5% or more, and may be 10% or more, or 20% or more.

The gel fraction of the pressure-sensitive adhesive layer was calculated as follows: the weight (W1) of the sample collected from the pressure-sensitive adhesive layer was measured, and then the sample was immersed in ethyl acetate and kept at room temperature (typically 23 ℃) for 7 days, after which the insoluble matter of the sample was taken out, and the weight (W2) of the dried sample was measured and substituted into the following formula, thereby calculating the weight. The same method is used in the examples described later.

Gel fraction (%) (W2/W1) × 100

(supporting base Material)

The psa sheet of some embodiments may be a psa sheet with a substrate that includes a psa layer on one or both sides of a support substrate. The material of the support substrate is not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like of the adhesive sheet. Non-limiting examples of the usable substrate include plastic films such as polyolefin films mainly composed of polyolefins such as polypropylene and ethylene-propylene copolymers, polyester films mainly composed of polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polyvinyl chloride films mainly composed of polyvinyl chloride; foam sheets formed of foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and nonwoven fabrics obtained from various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semisynthetic fibers such as acetate) alone or by blending; paper such as japanese paper, fine paper, kraft paper, crepe paper, and the like; metal foils such as aluminum foil and copper foil; and the like. The substrate may be a composite substrate. Examples of such composite substrates include substrates having a structure in which a metal foil and the plastic film are laminated, and plastic substrates reinforced with inorganic fibers such as glass cloth.

As the substrate of the pressure-sensitive adhesive sheet disclosed herein, various film substrates can be preferably used. The film base may be a porous base such as a foamed film or a nonwoven fabric sheet, a non-porous base, or a base having a structure in which a porous layer and a non-porous layer are laminated. In some embodiments, it is preferable to use a film containing a resin film (self-supporting or independent) capable of independently maintaining its shape as a base film. Here, the "resin film" is a non-porous structure, and typically means a resin film substantially containing no bubbles (no bubbles). Therefore, the resin film is a concept different from a foamed film and a nonwoven fabric. The resin film may have a single-layer structure or a multilayer structure (for example, a three-layer structure) of two or more layers.

Examples of the resin material constituting the resin film include polyester, polyolefin, Polyamide (PA) such as nylon 6, nylon 66, and partially aromatic polyamide, Polyimide (PI), polyamide-imide (PAI), polyether ether ketone (PEEK), polyether sulfone (PES), polyphenylene sulfide (PPS), Polycarbonate (PC), Polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), fluorine resins such as Polytetrafluoroethylene (PTFE), acrylic resins, polyacrylates, polystyrene, polyvinyl chloride, and polyvinylidene chloride. The resin film may be formed using a resin material containing one kind of such resin alone, or may be formed using a resin material in which two or more kinds of resins are mixed. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched).

Suitable examples of the resin material constituting the resin film include a polyester resin, a polyolefin resin, and a polyurethane resin. The polyester resin is a resin containing a polyester in a proportion of more than 50% by weight. Similarly, the polyolefin-based resin refers to a resin containing polyolefin in a proportion of more than 50% by weight, and the polyurethane-based resin refers to a resin containing polyurethane in a proportion of more than 50% by weight.

The polyester resin typically contains a polyester obtained by polycondensation of a dicarboxylic acid and a diol as a main component. Specific examples of the polyester resin film include a polyethylene terephthalate (PET) film, a polybutylene terephthalate (PBT) film, a polyethylene naphthalate (PEN) film, and a polybutylene naphthalate film.

As the polyolefin-based resin, one kind of polyolefin may be used alone or two or more kinds of polyolefins may be used in combination. The polyolefin may be, for example, a homopolymer of an α -olefin, a copolymer of two or more α -olefins, a copolymer of one or two or more α -olefins with other vinyl monomers, or the like. Specific examples of the polyolefin-based resin include ethylene-propylene copolymers such as Polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene and Ethylene Propylene Rubber (EPR), ethylene-propylene-butene copolymers, ethylene-vinyl alcohol copolymers and ethylene-ethyl acrylate copolymers. Any of Low Density (LD) polyolefin and High Density (HD) polyolefin may be used. Examples of the polyolefin resin film include a non-oriented polypropylene (CPP) film, a biaxially oriented polypropylene (OPP) film, a Low Density Polyethylene (LDPE) film, a Linear Low Density Polyethylene (LLDPE) film, a Medium Density Polyethylene (MDPE) film, a High Density Polyethylene (HDPE) film, a Polyethylene (PE) film in which two or more kinds of Polyethylenes (PE) are mixed, and a PP/PE mixed film in which polypropylene (PP) and Polyethylene (PE) are mixed.

As the polyurethane constituting the polyurethane resin, any of ether polyurethane, ester polyurethane, carbonate polyurethane, and the like can be used. The polyurethane resin film may be composed of a polyurethane resin containing any of such polyurethanes, or may be composed of a polyurethane resin containing two or more polyurethanes at an arbitrary ratio.

The first surface of the substrate may be subjected to conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, coating with a primer (primer), antistatic treatment, or the like, as required. Such surface treatment may be treatment for improving adhesion between the base material and the adhesive layer, in other words, for improving anchoring properties of the adhesive layer to the base material. The composition of the primer is not particularly limited, and may be appropriately selected from known ones. The thickness of the undercoat layer is not particularly limited, and is usually preferably about 0.01 to 1 μm, more preferably about 0.1 to 1 μm.

The thickness of the substrate constituting the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like of the pressure-sensitive adhesive sheet. From the viewpoint of handling properties, processability, and the like, the thickness of the base material may be, for example, about 1 μm or more, or 2 μm or more, 5 μm or more, 10 μm or more, or 20 μm or more in some embodiments. In some embodiments, the thickness of the substrate may be, for example, 100 μm or less, 70 μm or less, 50 μm or less, or 40 μm or less, from the viewpoint of weight reduction and thickness reduction of the pressure-sensitive adhesive sheet.

The thickness of the pressure-sensitive adhesive sheet having a substrate is not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like of the pressure-sensitive adhesive sheet. From the viewpoint of handling properties, processability, and the like, the thickness of the pressure-sensitive adhesive sheet may be, for example, about 3 μm or more, 7 μm or more, 12 μm or more, or 22 μm or more in some embodiments. In some embodiments, the thickness of the pressure-sensitive adhesive sheet may be, for example, 150 μm or less, 130 μm or less, 100 μm or less, 75 μm or less, 50 μm or less, or 35 μm or less, from the viewpoint of weight reduction and thickness reduction of the pressure-sensitive adhesive sheet.

(Peel adhesion)

The adhesive sheet disclosed herein has an adhesive layer formed from the adhesive composition as described above, and thus the adhesive layer can exhibit strong adhesiveness even when it is relatively thin. According to the specification, for example, a pressure-sensitive adhesive sheet having a 180 DEG peel adhesion (hereinafter, also referred to as a peel adhesion to SUS) of 8N/20mm or more, 10N/20mm or more, or 12N/20mm or more after being attached to a stainless steel plate for 30 minutes can be provided. More preferably, the pressure-sensitive adhesive sheet satisfies the above peel adhesion and has a pressure-sensitive adhesive layer thickness of 3 μm or more and less than 10 μm, and still more preferably, the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer thickness of 3 μm or more and 8 μm or less (for example, about 4 to 6 μm, typically about 5 μm).

The peel adhesion to SUS was measured by the method described in the examples described later. When the 180 ° peel adhesion is measured for a psa sheet formed without a substrate on the psa layer, an appropriate liner (e.g., a PET film having a thickness of about 25 μm to 50 μm) may be attached to one side of the psa layer for reinforcement. The single-sided pressure-sensitive adhesive sheet with a substrate or the double-sided pressure-sensitive adhesive sheet with a substrate may be similarly reinforced as necessary.

Further, with respect to the adhesive composition disclosed herein, an adhesive sheet obtained by coating, drying and curing treatment using the adhesive composition by the same procedure as in the example described later (i.e., an adhesive sheet having an adhesive layer with a thickness of 5 μm on one side of a PET film with a thickness of 25 μm) can exhibit a peel adhesion to SUS of 8N/20mm or more, preferably 10N/20mm or more, or 12N/20mm or more, for example. The peel adhesion to SUS of the pressure-sensitive adhesive sheet may be, for example, 30N/20mm or less, or 20N/20mm or less. The adhesive sheet may have a gel fraction of the adhesive layer of preferably 70% or less, more preferably 50% or less, and may be 45% or less or 40% or less. The gel fraction of the pressure-sensitive adhesive layer is preferably 5% or more, and may be 10% or more, or 20% or more.

< use >

The adhesive composition and the adhesive sheet having an adhesive layer formed from the composition disclosed herein exhibit high adhesive strength, and therefore can be preferably used for applications such as fixing and bonding of members in various devices. In particular, since a high adhesive force is exhibited even when the thickness of the adhesive layer is small, the adhesive layer is suitable as an adhesive sheet to be attached to a member constituting a portable device (portable electronic device) which is strongly required to be small and light in size and weight, or an adhesive composition for forming the adhesive layer of the adhesive sheet. "portable" is herein interpreted as insufficient if it can only be carried, which means having a level of portability at which an individual (a standard adult) can be carried relatively easily. Examples of the portable devices include mobile phones, smart phones, tablet personal computers, notebook personal computers, various wearable devices, digital cameras, digital video cameras, audio devices (such as portable music players and IC recorders), calculators (such as desktop calculators), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, and other portable electronic devices, as well as mechanical watches, pocket watches, flashlights, and goggles. Examples of the member constituting the portable electronic device include an optical film, a display panel, and the like used in an image display device such as a liquid crystal display and an organic EL display. The pressure-sensitive adhesive sheet disclosed herein can be preferably used for fixing or bonding various members in automobiles, home electric appliances, and the like so as to be attached to the members.

The matters disclosed in this specification include the following matters.

(1)

An adhesive composition comprising a polymer of monomeric components,

The polymer satisfies the following conditions in peak separation analysis of molecular weight distribution by GPC measurement:

(a) The area ratio of the peak H having a molecular weight peak top in the range of 100 to 2000 ten thousand is 3 to 30% of the entire peak area of the molecular weight distribution; and

(b) The area ratio of the peak L having a molecular weight peak top in the range of 1000 to less than 100 ten thousand is 70% to 97% of the entire peak area of the molecular weight distribution.

(2)

The adhesive composition according to the item (1), wherein the Tg calculated based on the composition of the monomer component is in the range of-70 ℃ to-40 ℃.

(3)

The adhesive composition according to the above (1) or (2), wherein more than 50% by weight of the monomer component is a (meth) acrylic monomer.

(4)

The adhesive composition according to any one of the above (1) to (3), wherein the monomer component contains (meth) acrylic acid C_4-10Alkyl esters, acrylic acid, and hydroxyl-containing monomers.

(5)

The adhesive composition according to any one of the above (1) to (4), wherein the polymerization conversion rate of the monomer component is 90% by weight or more,

The adhesive composition is prepared as an organic solvent solution having a nonvolatile content of 20 wt% or more and 50 wt% or less.

(6)

The adhesive composition according to any one of the above (1) to (5), wherein the Mw of the peak H is 200 to 800 ten thousand.

(7)

The adhesive composition according to any one of the above (1) to (6), wherein the Mw of the peak L is 5 to 50 ten thousand.

(8)

The adhesive composition according to any one of the above (1) to (7), further comprising a crosslinking agent.

(9)

The adhesive composition according to any one of the above (1) to (8), further comprising a tackifier resin.

(10)

The adhesive composition according to any one of the above (1) to (9), wherein when a PET film (substrate) having a thickness of 25 μm is coated so that the thickness after drying becomes 5 μm, dried at 122 ℃ to form an adhesive layer, and subjected to aging treatment at 50 ℃ for 24 hours to form an adhesive sheet, the 180 DEG peel adhesion of the adhesive sheet after 30 minutes of attachment to a stainless steel plate is 8N/20mm or more.

(11)

The pressure-sensitive adhesive composition according to the item (10), wherein the gel fraction of the pressure-sensitive adhesive layer is 70% or less.

(12)

A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of (1) to (11) above.

(13)

The adhesive sheet according to the item (12), wherein the adhesive layer has a thickness of 1 μm or more and 30 μm or less.

(14)

The pressure-sensitive adhesive sheet according to the item (12) or (13), wherein the gel fraction of the pressure-sensitive adhesive layer is 70% or less.

(15)

The adhesive sheet according to any one of the above (12) to (14), wherein the adhesive layer has a thickness of 3 μm or more and 8 μm or less,

The 180 DEG peel adhesion strength after 30 minutes of the adhesion to a stainless steel plate was 8N/20mm or more.

(16)

A method for producing the adhesive composition according to any one of (1) to (11) above, comprising:

A first stage of polymerizing a part of the monomer component to obtain a partial polymer; and

A second stage of polymerizing the unreacted monomer components in the presence of the partial polymer and a polymerization solvent after the first stage.

(17)

the production method according to the above (16), wherein the polymerization in the first stage is carried out in the presence of a polymerization solvent,

The amount of the polymerization solvent used in the polymerization in the first stage is 1% by weight or more and 30% by weight or less, assuming that the total amount of the monomer component and the polymerization solvent used in the first stage is 100% by weight.

(18)

The production method according to the above (16) or (17), wherein the polymerization in the first stage is performed so that a polymerization conversion rate of the monomer component becomes 3 wt% or more and 30 wt% or less with respect to 100 wt% of the whole monomer component used in the production method.

(19)

The production method according to any one of the above (16) to (18), wherein the polymerization solvent is added to and diluted in the reaction solution obtained in the first stage, and the polymerization in the second stage is performed.

(20)

The production method according to any one of the above (16) to (19), wherein the monomer component contains a hydroxyl group-containing monomer,

At least in the initial stage of the first stage, a polymerization reaction is carried out using a monomer component containing no hydroxyl group-containing monomer out of the monomer components.

(21)

The production method according to any one of the above (16) to (20), further comprising adding a crosslinking agent and/or a tackifier resin to the reaction liquid obtained in the second stage.

Examples

The present invention will be described below with reference to some examples, but the present invention is not intended to be limited to the contents shown in the specific examples. In the following description, "part" and "%" are based on weight unless otherwise specified.

< Synthesis of base Polymer >

Production example 1

200 parts of 2-ethylhexyl acrylate (2EHA) and 10 parts of Acrylic Acid (AA) as monomer components, and 50 parts of ethyl acetate as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and stirred for 1 hour while introducing nitrogen (nitrogen substitution). The temperature in the reaction vessel was adjusted to 55 ℃ by means of a water bath, and 0.2 part of 2, 2' -Azoisobutyronitrile (AIBN) as a polymerization initiator was added to carry out a reaction at the same temperature. After 5 minutes from the start of the reaction, 0.1 part of 4-hydroxybutyl acrylate (4HBA) as a monomer component and 290 parts of ethyl acetate as a polymerization solvent were added thereto and diluted to once complete the reaction. At this time, a small amount of the reaction solution (containing about 19% of the polymerization solvent) was collected by a pipette, and the intermediate polymerization rate was determined in the same manner as described above.

After the reaction vessel containing the remaining reaction solution was again purged with nitrogen, the temperature was raised to 62 ℃ and 0.1 part of AIBN as an additional polymerization initiator was added thereto, and the reaction was carried out at the same temperature for 8 hours to obtain a solution of polymer A. This solution (containing about 38% of a polymerization solvent) was taken to measure the final polymerization rate. The viscosity of the above solution was measured at room temperature with a B-type viscometer (the same shall apply hereinafter), and found to be 54 cP.

production example 2

In production example 1, the amount of ethyl acetate charged into the reaction vessel together with 200 parts of 2EHA and 10 parts of AA as monomer components was changed from 50 parts to 90 parts, and the amount of ethyl acetate charged into the reaction vessel together with 0.1 part of 4HBA after the polymerization in the first stage was changed from 290 parts to 240 parts. Otherwise, a solution of polymer B was obtained by the same treatment as in production example 1. The viscosity of the solution was 36 cP.

(production example 3)

In production example 1, a mixture of 100 parts of 2EHA and 100 parts of n-butyl acrylate was used instead of 200 parts of 2 EHA. Otherwise, a solution of polymer C was obtained by the same treatment as in production example 1. The viscosity of the solution was 28 cP.

Production example 4

Using the same apparatus as in production example 1, 2 parts of EHA200 and AA10 as monomer components and 50 parts of ethyl acetate were charged into a reaction vessel, and nitrogen substitution was performed for 1 hour. The temperature in the reaction vessel was adjusted to 55 ℃ by means of a water bath, and 0.02 part of 2, 2' -azobis (2, 4-dimethylvaleronitrile) (Wako pure chemical industries, Ltd.) as a polymerization initiator was added thereto to carry out a reaction at the same temperature. After 5 hours from the start of the reaction, 0.1 part of 4HBA as monomer components and 290 parts of ethyl acetate were added to complete the reaction.

After nitrogen substitution was again performed, the temperature was raised to 62 ℃ and 0.18 part of V-65 and 0.1 part of AIBN were added to conduct a reaction at the same temperature for 3 hours to obtain a solution of polymer D. The viscosity of the solution was 48 cP.

Production example 5

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen inlet tube and an ultraviolet irradiation device (EXECURE4000, HOYA CANDEOOPTRONICS Co., Ltd.), 200 parts of 2EHA, 10 parts of AA, 90 parts of ethyl acetate and 0.02 part of IRGACURE819 (BASF Co., Ltd.) as a photopolymerization initiator were charged. The nitrogen gas was replaced for 1 hour, and the reaction was carried out for 5 minutes by irradiating with ultraviolet light. After the irradiation was stopped, 4 parts of HBA (0.1 parts), 240 parts of ethyl acetate, 0.4 parts of IRGACURE819 and 0.2 parts of IRGACURE184(BASF corporation) as a polymerization initiator were added. After the nitrogen substitution was performed again, the reaction was performed for 1 hour by irradiating ultraviolet light to obtain a solution of polymer E. The viscosity of the solution was 41 cP.

(production example 6)

Using the same apparatus as in production example 1, 200 parts of 2EHA and 10 parts of AA were charged into a reaction vessel, and nitrogen gas was replaced for 1 hour. The temperature in the reaction vessel was adjusted to 60 ℃ with a water bath, and 0.02 part of AIBN was added to conduct a reaction at the same temperature. After 15 minutes from the start of the reaction, 0.1 part of 4HBA and 330 parts of ethyl acetate were added to complete the reaction.

After the nitrogen substitution was performed again, the temperature was raised to 40 ℃ and 0.4 part of 2, 2' -azobis (4-methoxy-2, 4-dimethylvaleronitrile) (Wako pure chemical industries, Ltd.) as a polymerization initiator was added to carry out a reaction for 1 hour, and then the temperature was raised to 65 ℃ and 0.06 part of AIBN as an additional polymerization initiator was added to carry out a reaction at the same temperature for 6 hours, thereby obtaining a solution of a polymer F. The viscosity of the solution was 31 cP.

Production example 7

Using the same apparatus as in production example 1, 2 parts of EHA200, 10 parts of AA, 0.1 part of 4HBA, and 330 parts of ethyl acetate were charged into a reaction vessel, and nitrogen substitution was performed for 1 hour. The temperature in the reaction vessel was adjusted to 60 ℃ by means of a water bath, 0.2 part of AIBN was added thereto, and after 6 hours of reaction at the same temperature, the temperature was raised to 70 ℃ to further conduct reaction for 3 hours, thereby obtaining a solution of polymer G. The viscosity of the solution was 68 cP.

Production example 8

Using the same apparatus as in production example 1, 2 parts of EHA200, 10 parts of AA, and 0.1 part of 4HBA were charged into a reaction vessel, and nitrogen substitution was performed for 1 hour. The temperature in the reaction vessel was adjusted to 60 ℃ by means of a water bath, and 0.02 part of AIBN as a polymerization initiator was added to conduct a reaction at the same temperature. After 15 minutes from the start of the reaction, 330 parts of ethyl acetate in which 0.08 part of AIBN was dissolved was added over 8 hours, and the reaction was once terminated.

After nitrogen substitution was performed again, the temperature was raised to 40 ℃ and 0.4 part of V-70 was added to carry out a reaction for 1 hour, and then the temperature was raised to 65 ℃ and 0.06 part of AIBN was added to carry out a polymerization reaction at the same temperature for 6 hours, thereby obtaining a solution of a polymer H. The viscosity of the solution was 33 cP.

Production example 9

using the same apparatus as in production example 5, 2EHA200 parts, AA10 parts, 4HBA 0.1 part, ethyl acetate 90 parts, and IRGACURE819 as a photopolymerization initiator were charged into a reaction vessel. The reaction was carried out for 20 minutes by replacing nitrogen gas for 1 hour and irradiating ultraviolet rays. Subsequently, 240 parts of ethyl acetate substituted with nitrogen gas, in which 0.4 part of IRGACURE819 and 0.2 part of IRGACURE184 were dissolved, were added dropwise over 1 hour while irradiating with ultraviolet rays. After the completion of the dropwise addition, the reaction was further carried out by irradiation with ultraviolet light for 1 hour to obtain a solution of polymer I. The viscosity of the solution was 145 cP.

Production example 10

Using the same apparatus as in production example 5, 2EHA200 parts, AA10 parts, 4HBA 0.1 part, ethyl acetate 330 parts, and 0.2 parts IRGACURE819 and 0.1 parts IRGACURE184 as photopolymerization initiators were charged into a reaction vessel. The reaction mixture was subjected to nitrogen substitution for 1 hour, and irradiated with ultraviolet light for 1 hour to obtain a solution of polymer J. The viscosity of the solution was 14 cP.

< measurement of weight average molecular weight >

the molecular weight distribution of the polymer obtained in each production example was measured by GPC. As a sample for measurement, a solution of the polymer obtained in each production example was dried at room temperature, and the remaining solid content was dissolved in tetrahydrofuran to prepare a solution having a concentration of 0.1%, and the solution was left overnight and then filtered using a membrane filter having a pore size of 0.45 μm, and the obtained filtrate was used. GPC measurement was performed under the following apparatus and conditions, and the molecular weight distribution in terms of standard polystyrene was obtained.

[ GPC conditions ]

The using device comprises the following steps: HLC-8220GPC, manufactured by Tosoh corporation

Column: GMHHR-H (20), 7.8mm (inside diameter). times.30.0 cm (length)

Developing solvent: tetrahydrofuran (THF)

Flow rate: 0.8 mL/min

Sample injection amount: 100 μ L

Measuring temperature: 25 deg.C

A detector: differential refractometer

Standard sample: polystyrene

based on the GPC measurement, the area ratio of peak H and peak L and Mw of each peak were determined by the above method.

Production examples 1 to 10 are shown in table 1, together with the intermediate polymerization degree and the final polymerization degree obtained by the above methods, the area ratios and Mw of the peaks H and L obtained from GPC measurement results of the obtained polymers, and the Tg calculated based on the composition of the monomer component.

[ Table 1]

TABLE 1

< preparation of adhesive composition >

(example 1)

To 100 parts of the polymer a solution obtained in production example 1 were added 16 parts of a 50% ethyl acetate solution of YS polymer N125(YASUHARA chemcal co., ltd., terpene phenol resin having a softening point of 125 ℃), 84 parts of ethyl acetate, 2 parts of CORONATE L (trimethylolpropane adduct of toluene diisocyanate, manufactured by tokyo co., ltd.) and TAKENATE D140 (trimethylolpropane adduct of isophorone diisocyanate, manufactured by mitsui CHEMICAL corporation), 0.002 part of each crosslinking agent, and the mixture was stirred and mixed to obtain an adhesive composition.

(example 2)

An adhesive composition of the present example was obtained in the same manner as in example 1 except that the polymer B solution obtained in production example 2 was used instead of the polymer a solution, and YS polymer U115 (a terpene phenol resin having a softening point of 115 ℃ manufactured by YASUHARA chemcal co., ltd.) was used instead of yspolymer N125 as a tackifier resin.

(example 3)

An adhesive composition of this example was obtained in the same manner as in example 1 except that the solution of polymer C obtained in production example 3 was used in place of the solution of polymer A, and Pensel D125 (a rosin ester having a softening point of 125 ℃ C., manufactured by Seikagawa chemical Co., Ltd.) was used as a tackifier resin in place of YS POLYSTER N125.

(examples 4 to 10)

Adhesive compositions of the respective examples were obtained in the same manner as in example 1 except that the solutions of polymers D to I obtained in production examples 4 to 10 were used instead of the solution of polymer A.

< preparation of pressure-sensitive adhesive sheet >

The pressure-sensitive adhesive compositions of the examples were applied to a PET film (substrate) having a thickness of 25 μm so that the thickness thereof after drying became 5 μm, and dried at 122 ℃ to remove the solvent, thereby forming a pressure-sensitive adhesive layer on one surface of the PET film. A release liner was attached to the surface of the pressure-sensitive adhesive layer, and the resultant was cured at 50 ℃ for 24 hours to obtain the objective pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet with substrate). As the release liner, a 38 μm thick PET film (MRF-38, manufactured by Mitsubishi chemical) having one surface subjected to a release treatment with a silicone resin was used.

The adhesive compositions of the examples were applied to the release liner (MRF-38, manufactured by Mitsubishi chemical corporation) so that the thickness thereof after drying became 5 μm, and dried at 122 ℃ to form an adhesive layer on the release liner. A release liner (MRE-38, manufactured by Mitsubishi chemical) having a lighter peel strength was attached to the surface of the pressure-sensitive adhesive layer, and the resultant was cured at 50 ℃ for 24 hours. A substrate-free adhesive sheet was obtained. The first adhesive surface and the second adhesive surface of the adhesive sheet are protected by the release liner, respectively.

Samples were taken from the pressure-sensitive adhesive layer of the base-less pressure-sensitive adhesive sheet after the curing treatment, and the gel fraction was determined by the method described above. The pressure-sensitive adhesive sheet after the curing treatment was subjected to the following evaluation test. The results are shown in Table 2.

< evaluation test >

(180 ℃ peel adhesion)

The single-sided pressure-sensitive adhesive sheet with a substrate of each example was cut into a size of 20mm in width and 100mm in length together with a release liner to prepare a sample for measurement. The release liner was peeled off from the above measurement sample under a standard environment of 23 ℃ and 50% RH to expose the pressure-sensitive adhesive surface (surface of the pressure-sensitive adhesive layer), and a 2kg roller was reciprocated 1 time to pressure-bond the pressure-sensitive adhesive surface to the adherend. After being left to stand in the above-mentioned standard environment for 30 minutes, 180 ° peel adhesion was measured under the condition of a tensile speed of 300 mm/minute in accordance with JIS Z0237 using a peel TESTER manufactured by stester SANGYO CO. The results are shown in Table 2. In table 2, "counter SUS plate" in the column indicating the adhesive force is a measured value obtained by using a stainless steel plate (SUS304BA plate) as an adherend, and "counter PMMA plate" is a measured value obtained by using an acrylic resin plate (manufactured by mitsubishi chemical corporation, ACRYLITE) as an adherend.

(rebound resilience resistance)

the substrate-free adhesive sheets of the respective examples were cut into a size of 10mm in width and 90mm in length together with a release liner, and a clean aluminum plate having a thickness of 0.3mm, a width of 10mm and a length of 90mm was attached to one surface of the substrate-free adhesive sheets to prepare test pieces.

Next, the test piece was bent to have a curvature radius R of 50mm by winding the test piece along the outer periphery of the cylinder so that the aluminum plate side was inward. After the sheet was held in the bent state for 10 seconds, the release liner was peeled off from the test piece to expose the adhesive surface, and a 2kg roller was reciprocated 1 time to bond the adhesive surface to the surface of the acrylic resin plate (manufactured by mitsubishi chemical corporation, ACRYLITE). After the test piece was left to stand under the standard conditions for 24 hours, the height of the end portion of the test piece floating from the surface of the acrylic resin plate, that is, the distance (floating distance) from the surface of the acrylic resin plate to the adhesive surface was measured for one end and the other end in the longitudinal direction of the test piece. The average value (unit: mm) of the floating distances of the one end and the other end was obtained, and as a result, the value was evaluated as "G" (good repulsion resistance) when the value was 10mm or less, and as "P" (lack of repulsion resistance) when the value exceeded 10 mm.

(Retention characteristics)

the base material-less adhesive sheets of the respective examples were bonded to the back surface of the base material of the adhesive sheet of the respective examples, and a PET film (liner material) having a thickness of 50 μm was bonded via the base material-less adhesive sheets. The pressure-sensitive adhesive sheet was cut into a width of 10mm together with a liner material and a release liner to prepare a test piece. The release liner was peeled from the test piece to expose the adhesive surface, and a 2kg roller was reciprocated once with an adhesive area of 10mm in width and 20mm in length to be pressure-bonded to a bakelite plate cleaned with toluene. The bakelite plate with the test piece attached thereon was left standing at 60 ℃ for 30 minutes while hanging down, and then a weight was applied to the test piece so as to apply a load of 500g in the shear direction, and the test piece was left standing in a suspended state at 60 ℃ for 1 hour. The test piece was evaluated as "G" (good holding property) when it did not fall off the bakelite plate after 1 hour, and as "P" (poor holding property) when it fell off.

[ Table 2]

TABLE 2

As is clear from tables 1 and 2, the pressure-sensitive adhesive compositions of examples 1 to 6 containing the polymer having a molecular weight distribution satisfying the above (a) and (b) gave pressure-sensitive adhesive sheets exhibiting high peel adhesion even in a pressure-sensitive adhesive layer having a thickness of 5 μm. These pressure-sensitive adhesive sheets also have good repulsion resistance and holding properties.

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

Claims (12)

1. An adhesive composition comprising a polymer of monomeric components,

The polymer satisfies the following conditions in peak separation resolution of molecular weight distribution determined based on gel permeation chromatography:

(a) the area ratio of a peak H having a molecular weight peak top in the range of 100 to 2000 ten thousand is 3 to 30% of the entire peak area of the molecular weight distribution; and

(b) The area ratio of the peak L having a molecular weight peak top in the range of 1000 to less than 100 ten thousand is 70% to 97% of the entire peak area of the molecular weight distribution.

2. The adhesive composition according to claim 1, wherein the glass transition temperature calculated based on the composition of the monomer component is in a range of-70 ℃ or higher and-40 ℃ or lower.

3. The adhesive composition according to claim 1 or 2, wherein more than 50% by weight of the monomer component is a (meth) acrylic monomer.

4. The adhesive composition according to any one of claims 1 to 3, wherein the monomer component comprises: (meth) acrylic acid C_4-10Alkyl esters, acrylic acid, and hydroxyl-containing monomers.

5. The adhesive composition according to any one of claims 1 to 4, wherein the polymerization conversion rate of the monomer component is 90% by weight or more,

The adhesive composition is prepared as an organic solvent solution having a nonvolatile content of 20 wt% or more and 50 wt% or less.

6. The adhesive composition according to any one of claims 1 to 5, wherein the peak H has a weight average molecular weight of 200 to 800 ten thousand.

7. The adhesive composition according to any one of claims 1 to 6, wherein the peak L has a weight average molecular weight of 5 to 50 ten thousand.

8. The adhesive composition of any one of claims 1 to 7 further comprising a crosslinker.

9. The adhesive composition of any one of claims 1-8 further comprising a tackifying resin.

10. An adhesive sheet having an adhesive layer formed from the adhesive composition according to any one of claims 1 to 9,

The thickness of the adhesive layer is 1 [ mu ] m or more and 30 [ mu ] m or less.

11. The adhesive sheet according to claim 10, wherein the adhesive layer has a gel fraction of 70% or less.

12. The adhesive sheet according to claim 10 or 11, wherein the thickness of the adhesive layer is 3 μm or more and 8 μm or less,

The 180 DEG peel adhesion of the adhesive sheet to a stainless steel plate after 30 minutes of attachment is 8N/20mm or more.