JP6513347B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet.

  In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive, hereinafter the same) exhibits a soft solid (viscoelastic) state in a temperature range around room temperature, and has a property of easily adhering to an adherend by pressure. Among them, a pressure-sensitive adhesive containing an acrylic polymer is excellent in ease of polymer molecule design and excellent in various properties (light resistance, weather resistance, oil resistance, etc.), so bonding and fixing in various fields in the form of a pressure-sensitive adhesive sheet Widely used for the purpose of For example, it is preferably used also for portable electronic devices such as mobile phones and smartphones, which have become widespread in recent years. Patent documents 1 and 2 are mentioned as technical documents about this kind of adhesive sheet.

Patent No. 4825992 JP, 2014-51644, A

  For example, since the portable electronic device is used in a portable mode, it is required to have a characteristic that the main body is not damaged or malfunctioned when it is dropped. Demands for this characteristic are becoming more and more advanced yearly from the viewpoint of durability, long life, safety and the like. Therefore, the pressure-sensitive adhesive sheet applied to this type of application is also required to have a performance (drop-impact resistance) that does not cause a bonding defect such as peeling even under a drop impact under more severe conditions. However, in general, in order to further improve the drop impact resistance, it is necessary to sacrifice to some extent other properties required for the pressure-sensitive adhesive (specifically, one of the representative adhesion properties, repulsion resistance). Therefore, it has been difficult to achieve both drop impact resistance and repulsion resistance at a higher level.

  The present invention is created in view of the above-mentioned circumstances, and it aims at providing a pressure sensitive adhesive sheet further improved in fall impact resistance, maintaining good repulsion resistance.

  According to the present invention, a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer containing an acrylic polymer as a main component is provided. The acrylic polymer contains a polar group-containing monomer as a constituent monomer component. The polar group-containing monomer is contained in a proportion of 15% by weight or more based on all the monomer components constituting the acrylic polymer. Furthermore, the polar group-containing monomer contains a nitrogen atom-containing monomer in a proportion of 40% by weight or more. And the said adhesive layer is formed using the adhesive composition containing an acryl-type polymeric component and an acryl-type oligomer.

  According to this configuration, since the acrylic polymer that is the main component of the pressure-sensitive adhesive contains the polar group-containing monomer unit at a predetermined ratio or more, good repulsion resistance can be realized. Moreover, since the above-mentioned acrylic polymer contains a nitrogen atom-containing monomer unit at a predetermined ratio, and an acrylic oligomer is used for the adhesive, the drop impact resistance can be maintained while maintaining the repulsion resistance at a high level. It can be further improved.

  In a preferred aspect of the pressure-sensitive adhesive sheet disclosed herein, the polar group-containing monomer further includes at least one of a carboxy group-containing monomer and a hydroxyl group-containing monomer. By using the above-mentioned polar group-containing monomer, it is possible to preferably realize a configuration in which the drop impact resistance and the repulsion resistance are compatible at a high level. Among them, the polar group-containing monomer preferably contains a carboxy group-containing monomer. In a more preferable aspect, from the viewpoint of improving the drop impact resistance, the acrylic polymer contains, as a constituent monomer component thereof, the carboxyl group-containing monomer in a proportion of less than 5% by weight.

  In a preferable aspect of the pressure-sensitive adhesive sheet disclosed herein, the polar group-containing monomer includes a monomer having a nitrogen atom-containing ring as the nitrogen atom-containing monomer. By using a polar group-containing monomer containing a monomer having a nitrogen atom-containing ring, it is possible to preferably realize a configuration in which the drop impact resistance and the repulsion resistance are compatible at a high level.

In a preferable embodiment of the pressure-sensitive adhesive sheet disclosed herein, the content of the acrylic oligomer is 5 parts by weight or less with respect to 100 parts by weight of the acrylic polymerization component. By adding a somewhat limited amount of acrylic oligomer, it is possible to further improve the drop impact resistance and the repulsion resistance. The weight average molecular weight of the acrylic oligomer is preferably in the range of 0.1 × 10 ^{4 to} 3 × 10 ⁴ .

  According to the pressure-sensitive adhesive sheet disclosed herein, the drop impact resistance can be further improved while maintaining a good repulsion resistance. Therefore, the pressure-sensitive adhesive sheet disclosed herein is preferably used for portable electronic devices that require high levels of drop impact resistance and repulsion resistance.

It is sectional drawing which shows typically one structural example of an adhesive sheet. It is sectional drawing which shows typically another structural example of an adhesive sheet. It is explanatory drawing which shows the sample for evaluation used when evaluating drop impact resistance. It is a schematic diagram which shows the initial state of the test piece stuck on the to-be-adhered body in repulsion resistance evaluation. It is a schematic diagram which shows the state which the edge part of the test piece stuck on the to-be-adhered body lifted up from this to-be-adhered body in repulsion resistance evaluation.

Hereinafter, preferred embodiments of the present invention will be described. The matters other than the matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be understood as the design matters of those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in the present specification and common technical knowledge in the field.
In the following drawings, the same reference numerals may be given to members / parts having the same function, and overlapping descriptions may be omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly explain the present invention, and the sizes and scales of the pressure-sensitive adhesive sheet of the present invention actually provided as a product are not necessarily accurately represented. .

In the present specification, as described above, the term "adhesive" refers to a material which exhibits a soft solid (viscoelastic) state in a temperature range near room temperature and has a property of being easily adhered to an adherend by pressure. . The adhesive referred to here is generally a complex tensile modulus E ^* (1 Hz), as defined in “CA Dahlquist,“ Adhesion: Fundamental and Practice ”, McLaren & Sons, (1966) P. 143”. It is a material having a property satisfying <10 ⁷ dyne / cm ² (typically, a material having the above property at 25 ° C.).

  In the present specification, “(meth) acryloyl” is a meaning that generally refers to acryloyl and methacryloyl. Similarly, “(meth) acrylate” means acrylate and methacrylate, and “(meth) acrylic” generally means acrylic and methacrylic. In the present specification, the term "acrylic monomer" refers to a monomer having at least one (meth) acryloyl group in one molecule. Moreover, an "acrylic-type polymer" means the polymer which contains an acryl-type monomer as a monomer unit (component monomer component) which comprises this polymer. That is, it refers to a polymer containing monomer units derived from acrylic monomers.

  In the present specification, “main component” refers to the component contained in the largest proportion, unless otherwise specified, and typically refers to the component contained in excess of 50% by weight. For example, the “pressure-sensitive adhesive layer containing an acrylic polymer as a main component” means that the acrylic polymer is contained in the largest proportion among all the components contained in the pressure-sensitive adhesive layer, Typically, it refers to a pressure-sensitive adhesive layer containing an acrylic polymer in a proportion of 50% by weight or more. Similarly, “the main component of all the monomer components (typically, monomer mixture) is alkyl (meth) acrylate” means that the component contained in the largest proportion of all the monomer components (for example, more than 50% by weight) It is meant that the component contained in proportion is an alkyl (meth) acrylate.

  As used herein, "active energy ray" refers to an energy ray having energy capable of causing a chemical reaction such as polymerization reaction, crosslinking reaction, decomposition of an initiator, and the like. Examples of the active energy ray mentioned here include light such as ultraviolet (UV) light, visible light and infrared light, and radiation such as alpha ray, beta ray, gamma ray, electron beam, neutron ray, X ray and the like. Be

<Composition of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein comprises a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer typically constitutes at least one surface (for example, both surfaces) of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet with a substrate having the above-mentioned pressure-sensitive adhesive layer on one side or both sides of a substrate (support), and the pressure-sensitive adhesive layer may be a release liner (a substrate having a release surface). It may be a substrate-less pressure-sensitive adhesive sheet, such as in the form of being held by In this case, the pressure-sensitive adhesive sheet may consist of only the pressure-sensitive adhesive layer. The concept of the pressure-sensitive adhesive sheet herein includes those referred to as a pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film, and the like. The pressure-sensitive adhesive sheet provided by the present specification may be in roll form or in sheet form. Alternatively, it may be a pressure-sensitive adhesive sheet in a form further processed into various shapes.

  FIG. 1 and FIG. 2 show a configuration example of a substrate-less double-sided adhesive pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 has a configuration in which both surfaces 21A and 21B of the substrate-less pressure-sensitive adhesive layer 21 are protected by release liners 31 and 32 in which at least the pressure-sensitive adhesive layer side is a release surface. The pressure-sensitive adhesive sheet 2 shown in FIG. 2 has a configuration in which one surface (adhesion surface) 21A of the substrate-less pressure-sensitive adhesive layer 21 is protected by a release liner 31 whose both surfaces are release surfaces. When wound, the other surface (adhesion surface) 21 B of the pressure-sensitive adhesive layer 21 abuts on the back surface of the release liner 31 so that the other surface 21 B can also be protected by the release liner 31.

<Adhesive composition>
(Acrylic polymerization component)
The pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer disclosed herein contains an acrylic polymerization component. The acrylic polymerization component is a concept including unreacted matter (unpolymerized substance, ie, monomer component) of a monomer component containing an acrylic monomer and a reaction product (partially polymer and complete polymer), and , For example, by partial or complete polymerization.

As a monomer component which comprises an acryl-type polymerization component, chain | strand-shaped alkyl (meth) acrylate is mentioned. As a chain | strand-shaped alkyl (meth) acrylate, 1 type (s) or 2 or more types of chain | strand-shaped alkyl (meth) acrylate represented by following formula (1) can be used.
CH ₂ = CR ¹ COOR ² (1)
In the above formula (1), R ¹ is a hydrogen atom or a methyl group. R ² is a chain alkyl group, and is typically a chain alkyl group having 1 to 20 carbon atoms (hereinafter sometimes abbreviated as “C _1-20 ”). From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive and the like, a linear alkyl (meth) acrylate in which R ² is C _1-14 (eg, C _1-12 , typically C _1-10 ) can be preferably used. The alkyl group may be linear or branched. Specific examples of linear alkyl (meth) acrylates preferably used include methyl acrylate, methyl methacrylate (MMA), ethyl acrylate (EA), n-butyl acrylate (BA), isobutyl methacrylate (IBMA), t-butyl acrylate t-BA), 2-ethylhexyl acrylate (2EHA), isooctyl acrylate (IOA), nonyl acrylate (NA), isononyl acrylate (INA), lauryl acrylate (LA), lauryl methacrylate (LMA) and the like.

From the viewpoint of adhesive properties (in particular, compatibility between drop impact resistance and other adhesive properties), in the above formula (1), R ² is C _4-12 (for example, C _6-10 , typically C _6-8) And linear alkyl (meth) acrylates (typically alkyl acrylates) can be preferably used. Preferred examples of the linear alkyl (meth) acrylate include BA, IBMA, t-BA, 2EHA, IOA, LA, and LMA. Among them, 2EHA is particularly preferable.

The chain alkyl (meth) acrylate in which R ² is C _4-12 in the above formula (1) is 50% by weight of the total chain alkyl (meth) acrylate contained as a constituent monomer component of the acrylic polymerization component It is preferable to occupy more than (for example, 70% by weight or more, typically 80% by weight or more). Also, the upper limit thereof can be typically 100% by weight or less (e.g., 95% by weight or less) in the total chain alkyl (meth) acrylate.

  The chain alkyl (meth) acrylate contained in the acrylic polymerization component is suitably a main component of the monomer component constituting the acrylic polymerization component from the viewpoint of achieving good adhesive properties, and the above monomer component ( It is preferable to occupy about 50% by weight or more of the total monomer component), and more preferably about 60% by weight or more (eg 70% by weight or more, typically 75% by weight or more). The upper limit of the content of the linear alkyl (meth) acrylate is about 90% by weight or less (eg, 85% by weight or less, typically 80% by weight or less) from the viewpoint of sufficiently expressing the effect of the polar group-containing monomer described later It is appropriate to use

  In a preferred embodiment, the acrylic polymerization component contains a polar group-containing monomer as its constituent monomer component. In other words, a polar group-containing monomer may be copolymerized with the acrylic polymerization component. By including the polar group-containing monomer, the cohesion of the pressure-sensitive adhesive layer is improved. The polar group-containing monomer disclosed herein typically contains a nitrogen atom-containing monomer (hereinafter also referred to as "N-containing monomer").

Examples of the N-containing monomer include a monomer having a nitrogen atom (N) -containing ring, an amino group-containing monomer, an amide group-containing monomer, a cyano group-containing monomer, an imide group-containing monomer, and an isocyanate group-containing monomer.
Examples of the monomer having an N-containing ring (typically, an N-containing heterocycle) include N-vinyl-2-pyrrolidone (NVP), N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, and N-vinylpyrimidine N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl -2- oxazoline, N-vinyl morpholine, N-vinyl caprolactam, N- (meth) acryloyl morpholine etc. are mentioned.
As the amino group-containing monomer, N, N-dialkylaminoalkyl such as N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate and the like (Meth) acrylates; N-alkylaminoalkyl (meth) acrylates such as N-methylaminoethyl (meth) acrylate and N-ethylaminoethyl (meth) acrylate; N such as N, N-dimethylamino (meth) acrylate; N-dialkylamino (meth) acrylate; N-alkylamino (meth) acrylate such as N-methylamino (meth) acrylate; aminoalkyl (meth) acrylate such as aminomethyl (meth) acrylate; amino (meth) acrylate; etc Can be mentioned.
Examples of the amide group-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N -Methylolpropane (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, hydroxyethyl (meth) acrylamide and the like can be mentioned.
Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile.
Examples of imide group-containing monomers include maleimide-based monomers such as N-cyclohexyl maleimide, N-phenyl maleimide, etc .; itaconimide-based monomers such as N-methyl itaconimide; succinimide-based monomers such as N- (meth) acryloxy methylene succinimide; Can be mentioned.
As an isocyanate group containing monomer, (meth) acryloyl isocyanate and 2- (meth) acryloyl oxyethyl isocyanate are mentioned, for example.
These can be used singly or in combination of two or more. Among them, a monomer having an N-containing ring (typically, NVP, N-acryloyl morpholine (ACMO)), an amino group-containing monomer (typically, N, N-dimethylaminomethyl (meth) acrylate), an amide group-containing Monomers (typically N, N-diethylacrylamide (DEAA), N- (2-hydroxyethyl) acrylamide (HEAA)) are preferred.

The polar group-containing monomer may include one or more polar group-containing monomers (other polar group-containing monomers) other than the N-containing monomer. Examples of other polar group-containing monomers include the following.
Carboxy group-containing monomers: Ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid etc. Ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, citraconic acid and their anhydrides (Maleic anhydride, itaconic anhydride etc.).
Hydroxyl-containing monomers: for example, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. Unsaturated alcohols such as vinyl alcohol and allyl alcohol.
Sulfonic acid group-containing monomers: for example, styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, (meth) acrylamidopropane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene Sulfonic acid.
Phosphoric acid group-containing monomer: for example, 2-hydroxyethyl acryloyl phosphate.
Aziridine group-containing monomers: for example (meth) acryloyl aziridines, 2-aziridinyl ethyl (meth) acrylates.
Epoxy group-containing monomers: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Keto group-containing monomers: for example diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Alkoxy group-containing monomers: for example, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate.
Alkoxysilyl group-containing monomers: for example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxypropylmethyldimethoxysilane, 3- (meth) acryloxy Propylmethyldiethoxysilane.
The monomer which polymerized the vinyl group The macromonomer which has a radical polymerizable vinyl group at the terminal.

  When an N-containing monomer is used as the polar group-containing monomer constituting the acrylic polymerization component, the proportion of the N-containing monomer in all the monomer components constituting the acrylic polymerization component is about 5% by weight or more (eg 10% by weight or more, It is preferable that it is typically 15% by weight or more). As a result, the tendency of achieving both the impact resistance against falling and the repulsion resistance at a high level is enhanced. Further, the compatibility with the acrylic oligomer can be improved by selecting the type and the use ratio of the N-containing monomer (for example, a monomer having an N-containing ring) corresponding to the composition of the acrylic oligomer described later. From the same viewpoint, the upper limit of the ratio of the N-containing monomer to the total monomer component constituting the acrylic polymerization component is less than about 50% by weight (eg, 30% by weight or less, typically 25% by weight or less) Is appropriate.

  When another polar group-containing monomer is used as the polar group-containing monomer constituting the acrylic polymerization component, the ratio of the other polar group-containing monomer to the total monomer component constituting the acrylic polymerization component is the other polar group-containing monomer. It is preferable that the content is about 0.1% by weight or more (for example, 1% by weight or more, typically 2% by weight or more) from the viewpoint of achieving the effects of the group-containing monomer well. The upper limit of the proportion of the other polar group-containing monomer is suitably about 30% by weight or less (eg, 10% by weight or less, typically 5% by weight or less). As other polar group-containing monomers, carboxy group-containing monomers (for example, AA, MAA) and hydroxyl group-containing monomers (for example, 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4HBA)) are preferable.

  When a carboxyl group-containing monomer is copolymerized with an acrylic polymerization component, the proportion of the carboxy group-containing monomer in all the monomer components constituting the acrylic polymerization component is 5% by weight from the viewpoint of improvement in drop impact resistance. It is appropriate to use the following, preferably less than 5% by weight (eg less than 4% by weight, typically less than 3% by weight), more preferably 2.5% by weight or less (typically 2% by weight). % Or less). From the viewpoint of retention of repulsion resistance, the proportion of the carboxy group-containing monomer is preferably 0.5% by weight or more (eg, 1% by weight or more, typically 1.5% by weight or more).

  The acrylic polymerization component is, for the purpose of adjusting the glass transition temperature (Tg), improving cohesion, etc., as the constituent monomer component, other copolymerizations different from the above-mentioned linear acrylic (meth) acrylate and polar group-containing monomer May also contain a monomer. As such other copolymerizable monomers, for example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate and the like Alicyclic hydrocarbon group-containing (meth) acrylates; vinyl acetates such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl cyclohexanecarboxylate, vinyl benzoate and the like; styrene, substituted styrene (α-methylstyrene Etc.), aromatic vinyl compounds such as vinyl toluene; aromatic ring-containing (meth) acrylates such as aryl (meth) acrylates, aryloxyalkyl (meth) acrylates, arylalkyl (meth) acrylates; ethylene, May be used alone or two or more of the like; vinyl chloride, chlorine-containing monomers such as vinylidene chloride; propylene, isoprene, butadiene, olefin monomer isobutylene and methyl vinyl ether, vinyl ether monomers such as ethyl vinyl ether.

  When the acrylic polymerization component contains another copolymerizable monomer as its constituent monomer component, the content thereof is 20% by weight or less (eg, 10% by weight or less) of all the monomer components constituting the acrylic polymerization component. , Typically 5% by weight or less). The acrylic polymerization component disclosed herein may be substantially free of the above-mentioned other copolymerizable monomers as its constituent unit.

  In a preferred embodiment, the acrylic polymerization component can be prepared by at least partially polymerizing the above mentioned monomer components. The polymerization method of the said monomer component is not specifically limited, The conventionally well-known various polymerization method can be employ | adopted suitably. For example, thermal polymerization (typically performed in the presence of a thermal polymerization initiator) such as solution polymerization, emulsion polymerization, bulk polymerization, etc .; photopolymerization performed by irradiation with light such as UV (typically, Active energy ray irradiation polymerization such as radiation polymerization carried out by irradiation with radiation such as beta rays or gamma rays, which is carried out in the presence of a photopolymerization initiator, can be suitably employed. Among them, active energy ray irradiation polymerization (in particular, photopolymerization) is preferable.

  The mode of polymerization is not particularly limited, and conventionally known monomer supply methods, polymerization conditions (temperature, time, pressure, active energy ray irradiation amount, etc.), use materials other than monomers (polymerization initiator, surfactant, etc.), etc. It can be selected appropriately. For example, as a monomer supply method, all the monomer components may be supplied at once (batch supply) to the reaction vessel at one time, may be gradually dropped and supplied (continuous supply), or may be divided into a predetermined number of times. Each amount may be supplied (split supply) every hour. The monomer component may be supplied as a solution partially or entirely dissolved in a solvent or as a dispersion emulsified in water.

  In polymerization of the above-mentioned monomer component, according to a polymerization method, a polymerization mode, etc., 1 type, or 2 or more types of a well-known or usual polymerization initiator can be selected suitably, and can be used.

  The initiator for thermal polymerization is not particularly limited, and, for example, an azo polymerization initiator such as azobisisobutyronitrile (AIBN), a peroxide initiator, a peroxide and a reducing agent, and the like Redox initiators, substituted ethane initiators and the like according to combinations of the above can be used. Thermal polymerization can be preferably carried out, for example, at a temperature of about 20 to 100 ° C (typically 40 to 80 ° C).

  Various types of photopolymerization initiators can be used for active energy ray irradiation polymerization (typically, photopolymerization). The photopolymerization initiator is not particularly limited, but, for example, ketal photopolymerization initiators such as 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name "IRGACURE 651" etc.) 1-hydroxycyclohexyl-phenyl-ketone (trade name “IRGACURE 184” etc.), 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one ( Acetophenone photopolymerization initiators such as trade name "IRGACURE 2959" etc., 2-hydroxy-2-methyl-1-phenyl-propan-1-one (trade name "Darocure 1173 etc"); Benzoin such as benzoin methyl ether Benzoin ether photopolymerization initiators such as ethers, substituted benzoin ethers such as anisole methyl ether; bis (2, Acyl phosphine oxide type photopolymerization initiators such as 2, 6-trimethyl benzoyl) phenyl phosphine oxide (trade name "IRGACURE 819" etc.), 2,4, 6-trimethyl benzoyl diphenyl phosphine oxide (trade name "lucirin TPO" etc); Α-ketol photopolymerization initiators such as 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one; 2-naphthalenesulfonyl chloride and the like Aromatic sulfonyl chloride photopolymerization initiators; photoactive oxime photopolymerization initiators such as 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime; benzoin photopolymerizations such as benzoin Initiator; benzyl-based photoinitiators such as benzyl; benzophenone, benzoi Benzophenone photopolymerization initiators such as benzoic acid; thioxanthone, 2-chloro thioxanthone photopolymerization initiators such as thioxanthone; and the like (any of the above product is available from BASF).

  The use amount of such a thermal polymerization initiator or photopolymerization initiator can be used according to the polymerization method, polymerization mode, etc., and is not particularly limited. For example, the initiator may be 0.001 to 5 parts by weight (typically 0.01 to 2 parts by weight, for example 0.01 to 1 parts by weight) with respect to 100 parts by weight of the constituent monomer component of the acrylic polymerization component. be able to.

  The polymerization conversion (monomer conversion) of the monomer in the acrylic polymerization component is not particularly limited. Therefore, the above-mentioned acrylic polymerization component may or may not substantially contain an unreacted (unpolymerized) monomer. Here, "substantially free of unreacted monomers" means that the content of unreacted monomers is less than 1% by weight (typically less than 0.1% by weight) of the acrylic polymerization component. In addition, the above-mentioned acrylic polymerization component may contain materials (for example, a polymerization initiator, a solvent, a dispersion medium, etc.) other than the monomer used in the polymerization for obtaining the polymerization component.

  In a preferred embodiment, the acrylic polymerization component may be a partial polymer obtained by partially polymerizing the monomer component. Here, “partially polymerized product” refers to a polymerization reaction product in which the constituent monomer components are partially polymerized. Such a partially polymerized product typically exhibits a syrupy form (viscous liquid) in which a polymer formed from a part of the monomer components and an unreacted monomer are mixed. Hereinafter, such partially polymerized products of this nature may be referred to as "polymer syrup" or simply "syrup".

  The polymerization conversion ratio of the monomer component in such a partially polymerized product is suitably about 70% by weight or less, preferably 60% by weight or less. From the viewpoint of ease of preparation of the pressure-sensitive adhesive composition, coating properties, etc., the polymerization conversion ratio is more preferably 50% by weight or less (eg 40% by weight or less, typically 30% by weight or less). The lower limit of the polymerization conversion rate is not particularly limited, but is preferably 1% by weight or more, and preferably 5% by weight or more (eg, 10% by weight or more) from the viewpoint of adhesion performance and the like.

The polymerization conversion rate of the acrylic polymerization component (polymerization reaction product) can be determined by the following method.
[Measurement of polymerization conversion rate]
About 0.5 g of a sample is taken from the polymerization reaction and precisely weighed (weight Wp ₁ ). Then, the unreacted monomer is volatilized by heating the sample to 130 ° C. for 2 hours, and the weight of the sample left after the heating is precisely weighed (Wp ₂ ). The polymerization conversion rate can be obtained by substituting each value into the following equation.
Polymerization conversion [%] = (Wp ₂ / Wp ₁ ) × 100

  The polymerization method for partially polymerizing the monomer component is not particularly limited, but from the viewpoint of efficiency and simplicity, an active energy ray irradiation polymerization method (for example, a photopolymerization method) can be preferably adopted. For example, according to photopolymerization, the polymerization conversion ratio of the monomer component can be controlled by the polymerization conditions such as the irradiation amount (light amount) of light.

  The pressure-sensitive adhesive composition containing the above-mentioned partially polymerized material is in the form of containing the polymer formed from a part of the monomer component in the unreacted monomer (typically, the form in which the above polymer is dissolved in the unreacted monomer) As such, it may have a coatable viscosity at normal temperature without being diluted by a solvent or dispersion medium. Therefore, it is suitable as a pressure-sensitive adhesive composition substantially containing no solvent (solvent-free pressure-sensitive adhesive composition). Such a solventless pressure-sensitive adhesive composition can form a pressure-sensitive adhesive layer by applying an appropriate curing means (polymerization means) such as light irradiation and radiation irradiation. The solvent-free pressure-sensitive adhesive composition is preferable from the viewpoint of environmental hygiene because it contains substantially no organic solvent, and does not require drying equipment for the pressure-sensitive adhesive composition or recovery equipment for organic solvents, or the above equipment is miniaturized. It is also advantageous in that it can be simplified. The pressure-sensitive adhesive composition substantially does not contain a solvent if the content ratio of the solvent in the pressure-sensitive adhesive composition is 5% by weight or less (typically 2% by weight or less, preferably 1% by weight or less). It says that there is.

  In a preferred embodiment, the pressure-sensitive adhesive composition contains, as an acrylic polymerization component, an additional monomer component in addition to the above-mentioned polymer (for example, a partial polymer). An additional monomer component may be added to the polymer after obtaining the polymer.

  The additional monomer component may be any of the linear alkyl (meth) acrylates, polar group-containing monomers (N-containing monomers, carboxy group-containing monomers, hydroxyl-containing monomers, etc.) exemplified above, and other copolymerizable monomers. . As the additional monomer component, one or more of various monomers exemplified above can be used. Among them, polar group-containing monomers are preferable, and carboxy group-containing monomers (typically AA) are more preferable.

  When the additional monomer component is used, the content of the additional monomer component in the pressure-sensitive adhesive composition is determined in consideration of the action of the additional monomer component (e.g., aggregation in the case of a polar group-containing monomer), coatability, etc. Preferably, it is about 0.1 to 10% by weight (for example, 0.5 to 5% by weight, typically 1 to 3% by weight) of the total amount of the acrylic polymerization component.

  The pressure-sensitive adhesive composition preferably contains, as another copolymerizable monomer, a polyfunctional monomer for the purpose of crosslinking and the like. As such polyfunctional monomers, for example, 1,6-hexanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di ( Meta) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, Weight of 2 or more (typically 3 or more) in one molecule, such as dipentaerythritol penta (meth) acrylate or dipentaerythritol hexa (meth) acrylate (Typically (meth) acryloyl group) sexually functional group include monomers having a. These can be used singly or in combination of two or more.

  When the pressure-sensitive adhesive composition disclosed herein contains a polyfunctional monomer, the content thereof is 0.01 to 1% by weight (for example, 0.02 to 1%) of all the monomer components constituting the acrylic polymerization component. It is preferable to set it as weight%, typically 0.05-0.5 weight%.

  The polyfunctional monomer may be added to the pressure-sensitive adhesive composition prior to, for example, partial polymerization of the acrylic polymerization component, and may be added after the polymerization (at least after partial polymerization). When a polyfunctional monomer is added after the formation of an acrylic polymer (for example, a partial polymer), the pressure-sensitive adhesive composition is subjected to treatment such that it reacts (typically, a crosslinking reaction) after the addition. In one aspect using a polyfunctional monomer, a pressure-sensitive adhesive composition to which a polyfunctional monomer is added after formation of a partial polymer of an acrylic polymerization component is preferably used from the viewpoint of surely enhancing the cohesiveness.

  A pressure-sensitive adhesive composition (for example, a solvent-free pressure-sensitive adhesive composition) containing a partial polymer as an acrylic polymerization component is, for example, a partial polymer obtained by partially polymerizing the above-mentioned monomer component by a suitable polymerization method An acrylic oligomer described later, other components optionally used (for example, an unreacted monomer, the above-mentioned photopolymerization initiator, an additional monomer, a polyfunctional monomer, a tackifier described later, a crosslinking agent, etc.) It can be prepared by mixing.

In another aspect, the acrylic polymerization component may be a fully polymerized product with a polymerization conversion of greater than 95% by weight (typically greater than 99% by weight). It is preferable that the pressure-sensitive adhesive composition containing a completely polymerized product of such an acrylic polymerization component contains substantially no unreacted monomer. For example, it is preferable that the content rate of the unreacted monomer is less than 1% by weight (typically less than 0.5% by weight). When the acrylic polymerization component is a complete polymer, the weight average molecular weight (Mw) is 20 × 10 ⁴ to 200 × 10 ⁴ (eg, 30) from the viewpoint of the preparation easiness of the pressure-sensitive adhesive composition and the coatability. It may be about 10 ^{4 to} 150 10 ⁴ ). In the present specification, the Mw of a polymer (including partially and completely polymerized products) can be measured by gel permeation chromatography (GPC). More specifically, for example, using the trade name “HLC-8120GPC” (manufactured by Tosoh Corporation) as a GPC measurement device, the polymer can be used as a sample and calculated as a standard polystyrene conversion value. In addition, it is noted that the unreacted monomer which may be contained in the partially polymerized product hardly affects the value of Mw obtained from the above-mentioned GPC measurement.

  The fully polymerized product is prepared by, for example, diluting the adhesive component with a solvent to an appropriate viscosity, such as a solvent-type pressure-sensitive adhesive composition or a water-dispersed pressure-sensitive adhesive composition (typically, an emulsion-like pressure-sensitive adhesive composition). It can be preferably applied to the (dissolved or dispersed) form of the pressure-sensitive adhesive composition. The above-mentioned pressure-sensitive adhesive composition can form a high-performance pressure-sensitive adhesive layer by a simple curing process such as drying the composition by containing a completely polymerized product having a relatively high molecular weight.

  The solvent-type pressure-sensitive adhesive composition can be prepared, for example, by subjecting a monomer component having a composition corresponding to the constituent monomer component of the acrylic polymerization component to solution polymerization. As the polymerization solvent, various organic solvents conventionally known in the solution polymerization of acrylic polymers, such as ethyl acetate, toluene, hexane, and a mixed solvent thereof can be used. The mode of solution polymerization is not particularly limited, and conventionally known modes may be appropriately adopted. The type and amount of use of the polymerization initiator are generally as described above. Alternatively, the solvent-based pressure-sensitive adhesive composition may be prepared by dissolving a polymerization reaction product obtained by a polymerization method other than solution polymerization in a suitable organic solvent.

  The emulsion-like pressure-sensitive adhesive composition can be prepared, for example, by subjecting a monomer component having a composition corresponding to the constituent monomer component of the acrylic polymerization component to emulsion polymerization. The mode of the emulsion polymerization is not particularly limited, and conventionally known modes may be appropriately adopted. The type and amount of use of the polymerization initiator are generally as described above. In addition, the emulsion-like pressure-sensitive adhesive composition is obtained by emulsifying a polymerization reaction product obtained by a polymerization method other than emulsion polymerization in an aqueous solvent (typically water), typically in the presence of a suitable emulsifier. It may be prepared.

  The composition of all constituent monomer components of the acrylic polymerization component can be set such that the Tg of the completely polymerized product is -60 ° C or more and -10 ° C or less. The Tg calculated from the composition of all constituent monomer components of the acrylic polymerization component is -15 ° C. or less (for example, -20 ° C. or less, typically -25 ° C. or less) from the viewpoints of drop impact resistance and repulsion resistance Is preferred. Further, from the viewpoint of the cohesiveness of the pressure-sensitive adhesive, the above Tg is suitably set to −60 ° C. or more (eg, −55 ° C. or more). In a preferred embodiment, the Tg calculated from the composition of all the constituent monomer components may be -60 ° C to -30 ° C (typically -55 ° C to -35 ° C).

  Here, the above Tg means the Tg of the homopolymer (homopolymer) of each monomer constituting the acrylic polymerization component and the weight fraction of the monomer (the copolymerization ratio on a weight basis) of Fox. It means the value obtained from the formula. Therefore, the said Tg can be adjusted by changing the composition of the constituent monomer component suitably. As the Tg of the homopolymer, the value described in the known data is adopted.

In the technology disclosed herein, the following values are specifically used as the Tg of the homopolymer.
2-ethylhexyl acrylate -70 ° C
Methyl methacrylate 105 ° C
Dicyclopentanyl methacrylate 175 ° C
N-vinyl-2-pyrrolidone 54 ° C
2-hydroxyethyl acrylate -15 ° C
N- (2-hydroxyethyl) acrylamide 98 ° C
2-methoxyethyl acrylate-50 ° C
1,6-Hexanediol diacrylate 43 ° C
Acrylic acid 106 ° C
As for the Tg of homopolymers other than those exemplified above, the numerical values described in “Polymer Handbook” (Third Edition, John Wiley & Sons, Inc., 1989) are used. When not described in the above-mentioned Polymer Handbook, values obtained by the measurement method described in JP-A-2007-51271 are used.

(Acrylic oligomer)
The pressure-sensitive adhesive composition disclosed herein contains an acrylic oligomer. By adopting an acrylic oligomer, it is possible to improve the drop impact resistance and the repulsion in a well-balanced manner. In addition, when a pressure-sensitive adhesive composition is cured by active energy ray irradiation (for example, UV irradiation), an acrylic oligomer is a tackifying resin for general acrylic pressure-sensitive adhesives (for example, tackiness such as rosin type or terpene type) It has the advantage of being less likely to cause curing inhibition (e.g., polymerization inhibition of unreacted monomers) as compared to resins. In addition, an acryl-type oligomer is a polymer which contains an acryl-type monomer as the structure monomer component, and is defined as a polymer with smaller Mw than the acryl-type polymer formed from the said acryl-type polymerization component.

  The ratio of the acrylic monomer to the total monomer component constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (eg 80% by weight) The above, and further 90 wt% or more). In a preferred embodiment, the acrylic oligomer has a monomer composition consisting essentially of acrylic monomers.

  As a constituent monomer component of the acrylic oligomer, the chain alkyl (meth) acrylate exemplified as the monomer that can be used for the above acrylic polymerization component, a polar group-containing monomer, other copolymerizable monomers (for example, an alicyclic hydrocarbon group) Containing (meth) acrylates can be used. As a monomer component which comprises an acryl-type oligomer, 1 type, or 2 or more types of various monomers illustrated above can be used.

As a linear alkyl (meth) acrylate which can be used as a constituent monomer component of an acrylic oligomer, a linear alkyl (meth) acrylate in which R ² is C _1-12 (for example, C _1-8 ) in the above formula (1) Is preferably used. Preferred examples thereof include MMA, EA, BA, IBMA, t-BA and 2EHA. Among these, MMA is more preferable.

  Preferred examples of polar group-containing monomers that can be used as constituent monomer components of acrylic oligomers include monomers having an N-containing ring (typically, an N-containing heterocyclic ring) such as NVP, ACMO, etc .; N, N-dimethylaminoethyl ester Amino group-containing monomers such as (meth) acrylate; amide group-containing monomers such as N, N-diethyl (meth) acrylamide; carboxy group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as HEA;

  As a suitable example of the other copolymerizable monomer which can be used as a constituent monomer component of an acryl-type oligomer, 1 type, or 2 or more types of the alicyclic hydrocarbon group containing (meth) acrylate illustrated above is mentioned. The number of carbon atoms of the alicyclic hydrocarbon group of the alicyclic hydrocarbon group-containing (meth) acrylate is suitably 4 to 20. The number of carbon atoms is preferably 5 or more (eg, 6 or more, typically 8 or more), and preferably 16 or less (eg, 12 or less, typically 10 or less). Specifically, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate and dicyclopentanyl (meth) acrylate are more preferable, and dicyclopentanyl methacrylate (DCPMA) is particularly preferable.

  In a preferred embodiment, the acrylic oligomer contains, as its constituent monomer component, a linear alkyl (meth) acrylate and / or an alicyclic hydrocarbon group-containing (meth) acrylate. In this aspect, the proportion of the linear alkyl group-containing and alicyclic hydrocarbon group-containing (meth) acrylic acid ester in all the monomer components constituting the acrylic oligomer is about 80% by weight or more (for example, 90 to 100%). It is preferable to set it as wt%, typically 95 to 100 wt%). It is more preferable that the monomer component which comprises the said acryl-type oligomer consists essentially of chain | strand-shaped alkyl (meth) acrylate and / or alicyclic hydrocarbon group containing (meth) acrylate.

  The acrylic oligomer preferably contains an alicyclic hydrocarbon group-containing (meth) acrylate as a constituent monomer component. In this aspect, the ratio (that is, the copolymerization ratio) of the alicyclic hydrocarbon group-containing (meth) acrylate in all the monomer components constituting the acrylic oligomer is about 30 to about from the viewpoint of adhesiveness and cohesion. It is preferable to make it 90 weight% (for example, 50-80 weight%, typically 55-70 weight%). In addition, an acrylic oligomer using an alicyclic hydrocarbon group-containing (meth) acrylate as a constituent monomer component is a polar group-containing monomer (for example, an N-containing monomer, typically) by appropriately selecting the kind of the monomer. There is an advantage that the tendency to be compatible with the acrylic polymerization component having the N-containing ring as a constituent monomer component is enhanced.

When the acrylic oligomer is a copolymer of a monomer mixture containing a linear alkyl (meth) acrylate and an alicyclic hydrocarbon group-containing (meth) acrylate, the linear alkyl (meth) acrylate and the alicyclic hydrocarbon The ratio to the group-containing (meth) acrylate is not particularly limited. In one preferred embodiment, the weight ratio of the weight percentage of the chain alkyl (meth) weight ratio of acrylate (W _A) and the alicyclic hydrocarbon group-containing (meth) acrylate in the constituent monomer components of the acrylic oligomer (W _B) (W _A : W _B ) is 1: 9 to 9: 1, preferably 2: 8 to 7: 3 (eg, 3: 7 to 6: 4, typically 3: 7 to 5: 5) It is.

  Although not particularly limited, the composition (that is, the polymerization composition) of the constituent monomer component of the acrylic oligomer may be set such that the Tg of the acrylic oligomer is 10 ° C. or more and 300 ° C. or less. Here, the Tg of the acrylic oligomer refers to a value obtained in the same manner as the Tg based on the composition of the monomer constituting the above-mentioned acrylic polymerization component based on the composition of the component monomer of the acrylic oligomer. The Tg of the acrylic oligomer is preferably 180 ° C. or less (eg, 160 ° C. or less) from the viewpoint of initial adhesion. The Tg is preferably 60 ° C. or more (eg, 100 ° C. or more, typically 120 ° C. or more) from the viewpoint of the cohesiveness of the pressure-sensitive adhesive.

The Mw of the acrylic oligomer is not particularly limited, but is typically about 0.1 × 10 ^{4 to} 3 × 10 ⁴ . The Mw of the acrylic oligomer is preferably 1.5 × 10 ⁴ or less, more preferably 1 × 10 ⁴ or less, and 0.8 × 10 ⁴ or less, from the viewpoint of improving adhesion properties (for example, adhesion and repulsion resistance). (For example, 0.6 × 10 ⁴ or less) is more preferable. The Mw is preferably 0.2 × 10 ⁴ or more (eg, 0.3 × 10 ⁴ or more) from the viewpoint of the cohesiveness of the pressure-sensitive adhesive and the like.

  An acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and the polymerization mode are not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization and the like) can be adopted in appropriate modes. The types and amounts of polymerization initiators (for example, azo polymerization initiators such as AIBN) that can be used as necessary are generally as described above, and therefore the description will not be repeated here.

  A chain transfer agent can be used in the polymerization to adjust the molecular weight of the acrylic oligomer. Examples of chain transfer agents that can be used include compounds having a mercapto group, thioglycolic acid and derivatives thereof. Specific examples of the compound having a mercapto group include octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan and the like. Specific examples of thioglycolic acid and derivatives thereof include, in addition to thioglycolic acid, ethyl thioglycolate, propyl thioglycollate, butyl thioglycollate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, thioglycolic acid Thioglycolic acid esters such as octyl, decyl thioglycollate, dodecyl thioglycollate, thioglycolate of ethylene glycol, thioglycolate of neopentyl glycol, thioglycolate of pentaerythritol and the like can be mentioned. Thioglycolic acid is mentioned as an example of a preferable chain transfer agent among them.

  The use amount of the chain transfer agent is not particularly limited, and can be appropriately adjusted depending on the Mw and the like of the target acrylic oligomer. Usually, 0.1 to 20 parts by weight (preferably 0.2 to 15 parts by weight, more preferably 0.3 to 10 parts by weight) of a chain transfer agent per 100 parts by weight of the constituent monomer component of the acrylic oligomer It is preferable to use it to a certain extent.

  The content of the acrylic oligomer in the pressure-sensitive adhesive composition disclosed herein is suitably, for example, 0.5 parts by weight or more with respect to 100 parts by weight of the acrylic polymerization component. From the viewpoint of exhibiting the effect of the acrylic oligomer better, the content of the acrylic oligomer is preferably 1 part by weight or more (eg, 1.5 parts by weight or more, typically 2 parts by weight or more) . In addition, from the viewpoint of the curability of the pressure-sensitive adhesive composition and the compatibility with the acrylic polymerization component, the content of the above-mentioned acrylic oligomer is suitably less than 50 parts by weight (for example, less than 10 parts by weight) Preferably, the amount is less than 8 parts by weight (eg, less than 7 parts by weight, typically 5 parts by weight or less). Even with such a small amount addition, the repulsion resistance improvement effect by using the acrylic oligomer can be realized.

(Tackifier)
The pressure-sensitive adhesive composition disclosed herein can be a composition containing a tackifier. Although it does not restrict | limit especially as a tackifier, For example, various tackifying resin, such as rosin type, a terpene type, hydrocarbon type, a phenol type, can be used. Such tackifiers can be used alone or in combination of two or more.

  In a preferred embodiment, the pressure-sensitive adhesive composition contains a hydrocarbon-based tackifying resin as a tackifier. Examples of hydrocarbon-based tackifying resins include aliphatics such as olefins having about 4 to 5 carbon atoms (1-butene, isobutylene, 1-pentene, etc.) and dienes (butadiene, 1,3-pentadiene, isoprene, etc.) Aromatic hydrocarbon resins such as polymers of vinyl group-containing aromatic hydrocarbons having about 8 to 10 carbon atoms (styrene, vinyl toluene, α-methylstyrene, indene, methyl indene, etc.); Alicyclic hydrocarbon resins obtained by cyclizing and dimerizing so-called “C4 petroleum fractions” or “C5 petroleum fractions”, cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, etc. And the hydrogenated product thereof, an aromatic hydrocarbon resin, or a cycloaliphatic carbon obtained by hydrogenating the aromatic ring of an aliphatic / aromatic petroleum resin Aliphatic cyclic hydrocarbon resins such as hydrogen resins; aliphatic and aromatic petroleum resins (such as styrene-olefin copolymers); aliphatic and alicyclic petroleum resins; hydrogenated hydrocarbon resins; coumarone resins Resin; coumarone-indene resin; and the like. Among them, hydrogenated products of aliphatic cyclic hydrocarbon resins are preferable. This type of tackifying resin can be prepared by subjecting a petroleum-based resin to a hydrogenation treatment.

  In the art disclosed herein, a tackifier resin having a softening point (softening temperature) of about 60 ° C. or more (preferably, about 80 ° C. or more, typically 100 ° C. or more) can be preferably used. With the tackifying resin having the above-mentioned softening point, a higher performance (for example, highly adhesive) adhesive sheet can be realized. The upper limit of the softening point of the tackifying resin is not particularly limited, and can be about 180 ° C. or less (eg, about 140 ° C. or less). In addition, the softening point of tackifying resin here is defined as a value measured by the softening point test method (ring and ball method) prescribed in any of JIS K 5902: 2006 and JIS K 2207: 2006.

  The use amount of the tackifier is not particularly limited, but in consideration of the balance between the tackiness (for example, adhesion, resistance to repulsion) and the cohesion of the pressure-sensitive adhesive, generally 100 parts by weight of the acrylic polymer component About 0.5 to 50 parts by weight (more preferably 1 to 10 parts by weight, more preferably 1 to 3 parts by weight) is suitable. The method for causing the pressure-sensitive adhesive composition to contain a tackifier is not particularly limited. For example, the tackifier may be added after obtaining a polymer (for example, a partial polymer) of an acrylic polymerization component. In addition, the technique disclosed here can be implemented in the aspect using the adhesive which does not contain tackifying components (tackifiers) other than an acryl-type oligomer substantially.

(Other additive ingredients)
In addition to the acrylic polymerization component and the acrylic oligomer, various crosslinking agents can be contained in the solvent-type or water-dispersible pressure-sensitive adhesive composition as required. As a crosslinking agent, for example, an epoxy crosslinking agent, an isocyanate crosslinking agent, a silicone crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a silane crosslinking agent, an alkyl etherified melamine crosslinking agent, a metal chelate crosslinking agent, etc. One or two or more of these can be used. The crosslinking agent may be used in an appropriate amount based on the common knowledge of the person skilled in the art to obtain the desired adhesion properties. In addition, the technique disclosed here can be implemented in the aspect using the adhesive composition which does not contain substantially crosslinking components (crosslinking agent) other than the said polyfunctional monomer.

  The pressure-sensitive adhesive composition disclosed herein may contain various colorants (pigments, dyes, etc.) depending on the purpose and application site. For example, when the pressure-sensitive adhesive composition is cured by photopolymerization to form a pressure-sensitive adhesive layer, a pigment which does not separate photopolymerization may be used as a colorant in order to color the pressure-sensitive adhesive layer. it can. When black is desired as the color of the pressure-sensitive adhesive layer, for example, carbon black can be preferably used as a colorant. The amount of the colorant used is selected from the range of 10% by weight or less (eg 0.001 to 5% by weight), preferably 0.01 to 3% by weight, in the pressure-sensitive adhesive layer, in consideration of the degree of coloring and the like. Is desirable.

  The pressure-sensitive adhesive composition disclosed herein may contain various conventionally known fillers that can be included in the pressure-sensitive adhesive. As the filler, various particulate substances and fibrous substances can be used. The constituent material of the particulate matter may be, for example, metals, metal oxides, carbides such as calcium carbonate, hydroxides such as aluminum hydroxide, inorganic materials such as nitrides; organic materials such as polymers; Alternatively, natural raw material particles such as clay may be used. Furthermore, the pressure-sensitive adhesive composition may contain a hollow particulate material (for example, a hollow glass balloon) or various foaming agents (for example, thermally expandable microspheres). As the fibrous material, various synthetic fiber materials and natural fiber materials can be used. These can be used singly or in combination of two or more. The addition amount of such a filler is not particularly limited, and an appropriate amount may be added based on the purpose and technical common knowledge of the person skilled in the art.

  The pressure-sensitive adhesive composition disclosed herein is used in an acrylic pressure-sensitive adhesive such as a plasticizer, a softener, an antioxidant, a leveling agent, a stabilizer, a preservative, and the like, to the extent that the effects of the present invention are not significantly impaired. The composition may further contain known additives which can be added and various optional polymer components as required.

  The form of the pressure-sensitive adhesive composition disclosed herein is not particularly limited. For example, as described above, a composition prepared to cure by active energy rays such as UV and radiation to form a pressure-sensitive adhesive (active energy Line-curable pressure-sensitive adhesive composition), composition containing an adhesive (adhesive component) in an organic solvent (solvent-type adhesive composition), composition containing an adhesive dispersed in an aqueous solvent (water-dispersed type) It may be a pressure-sensitive adhesive composition), and may be a pressure-sensitive adhesive composition of various forms such as a hot-melt type pressure-sensitive adhesive composition which is applied in a heated and molten state and forms a pressure-sensitive adhesive when cooled to around room temperature.

<Pressure-sensitive adhesive layer>
The pressure-sensitive adhesive layer disclosed herein contains an acrylic polymer as a main component. Here, the acrylic polymer refers not only to a polymer derived from an acrylic polymer component (acrylic polymer) but also to a relatively low polymerization degree which may be generally referred to as an oligomer (including an acrylic oligomer). It is a concept that also includes polymers of

  Examples of the constituent monomer component of the acrylic polymer include various monomers exemplified as the constituent monomer component of the above-mentioned acrylic polymerization component and acrylic oligomer. Typically, a linear alkyl (meth) acrylate is used as the main component of the monomer component constituting the acrylic polymer. From the viewpoint of achieving good adhesion properties, the linear alkyl (meth) acrylate is 50% by weight or more (preferably 60% by weight or more, for example 70% by weight or more) of all the monomer components constituting the acrylic polymer. It is appropriate to include in proportions. As the chain alkyl (meth) acrylate, those exemplified as constituent monomer components of the above-mentioned acrylic polymerization component can be preferably used.

From the viewpoint of adhesive properties (in particular, compatibility between drop impact resistance and other adhesive properties), in the above formula (1), R ² is C _4-12 (for example, C _6-10 , typically C _6-8) And linear alkyl (meth) acrylates can be preferably used. The linear alkyl (meth) acrylate in which R ² is C _4-12 in the above formula (1) is 50% by weight of the total linear alkyl (meth) acrylate contained as a constituent monomer component of the acrylic polymer It is preferable to occupy more than (for example, 70% by weight or more, typically 80% by weight or more). In addition, the upper limit thereof may be 100% by weight or less (e.g., 95% by weight or less) in the total chain alkyl (meth) acrylate.

  The acrylic polymer contains a polar group-containing monomer as a constituent monomer component. By including the polar group-containing monomer, the cohesion of the pressure-sensitive adhesive layer is improved. The art disclosed herein is characterized in that the polar group-containing monomer contains an N-containing monomer.

  As the N-containing monomer, one or two or more kinds of monomers having an N-containing ring exemplified as constituent monomer components of the above-mentioned acrylic polymerization component, amino group-containing monomer, amide group-containing monomer and the like can be preferably used. Among them, NVP and ACMO are preferable as the monomer having an N-containing ring, N, N-dimethylaminomethyl (meth) acrylate is preferable as the amino group-containing monomer, and DEAA and HEAA are preferable as the amide group-containing monomer.

  The polar group-containing monomer may further include other polar group-containing monomers. As another polar group containing monomer, 1 type (s) or 2 or more types, such as a carboxy group containing monomer illustrated as a component monomer component of the said acryl-type polymerization component, a hydroxyl-containing monomer, etc. can be used.

  The art disclosed herein is characterized in that the ratio of the N-containing monomer to the total polar group-containing monomer component constituting the acrylic polymer is 40% by weight or more. By using the N-containing monomer in the above ratio, a configuration is realized in which both the drop impact resistance and the repulsion resistance are compatible at a high level. Moreover, the adhesiveness to resin-made adherends, such as a polycarbonate, improves by using N containing monomer as a polar group containing monomer. The proportion of the N-containing monomer in the total polar group-containing monomer component constituting the acrylic polymer is preferably about 50% by weight (eg, 60% by weight or more, typically 70% by weight or more). The upper limit of the ratio of the N-containing monomer to the total polar group-containing monomer component is not particularly limited, but may be, for example, 100% by weight or less, and from the viewpoint of favorably expressing the effects of other polar group-containing monomers. It may be 90% by weight or less (for example, 80% by weight or less).

  In a preferred embodiment, as the polar group-containing monomer, an N-containing monomer (for example, a monomer having an N-containing ring, typically NVP) and a carboxy group-containing monomer (for example, AA) are used in combination. As a result, the cohesiveness of the adhesive force tends to be stably expressed. When the N-containing monomer and the carboxy group-containing monomer are used in combination, the ratio of the content of the N-containing monomer to the total content of the N-containing monomer and the carboxy group-containing monomer is about 50% by weight or more (eg 70% by weight or more) And typically 80% by weight or more). In addition, it is preferable that the above ratio be less than about 100% by weight (for example, 95% by weight or less). This tends to balance the acid / base, and addition of a small amount of polar group-containing monomer can effectively improve aggregation.

  The proportion of the other polar group-containing monomer in the total polar group-containing monomer component constituting the acrylic polymer is 60% by weight or less, and less than 50% by weight (e.g. 40 It is suitable that the content is less than 10 wt%, typically less than 30 wt%, and may be about 10 wt% or less.

  It is preferable to include a carboxy group-containing monomer as the above-mentioned other polar group-containing monomer. Among them, AA and MAA are preferable, and AA is more preferable. From the viewpoint of falling impact resistance, the ratio of the carboxy group-containing monomer to the total polar group-containing monomer component constituting the acrylic polymer is preferably 15% by weight or less, more preferably 12% by weight or less. More preferably, it is 10% by weight or less. From the viewpoint of improving the repulsion resistance, the proportion of the carboxy group-containing monomer in the all polar group-containing monomer component is about 1 wt% or more (for example, 3 wt% or more, typically 6 wt% or more). Is preferred.

  When a carboxyl group-containing monomer (for example, AA) is copolymerized with the acrylic polymer as another polar group-containing monomer, the ratio of the carboxy group-containing monomer in all the monomer components constituting the acrylic polymer is From the viewpoint of improving the drop impact resistance, the content is suitably 5% by weight or less, preferably less than 5% by weight (eg, less than 4% by weight, typically less than 3% by weight), more preferably 2.5% by weight or less (typically 2% by weight or less). Also, from the viewpoint of improving the repulsion resistance, the proportion of the above-mentioned carboxy group-containing monomer is preferably 0.5% by weight or more (for example, 1% by weight or more, typically 1.5% by weight or more).

  Moreover, as another polar group containing monomer, it is preferable to contain a hydroxyl group containing monomer. Among them, HEA and 4HBA are preferable. From the viewpoint of the cohesiveness of the pressure-sensitive adhesive, the ratio of the hydroxyl group-containing monomer to the total polar group-containing monomer component constituting the acrylic polymer is about 1 to 40% by weight (eg 3 to 30% by weight, typically) It is suitable to set it as 5 to 20 weight%.

  The polar group-containing monomer is included in a proportion of 15% by weight or more based on all the monomer components constituting the acrylic polymer, because the polar group-containing monomer sufficiently contributes to the adhesive property by exerting its effect. The total amount of polar group-containing monomers in all monomer components constituting the acrylic polymer is preferably about 18% by weight or more (eg, 20% by weight or more, typically 22% by weight or more), and about 40% by weight. % Or less (eg, 30% by weight or less, typically 25% by weight or less) is preferred.

  The acrylic polymer may contain, as its constituent monomer component, the above-mentioned linear acrylic (meth) acrylate and other copolymerizable monomers different from the polar group-containing monomer for the purpose of adjusting Tg, improving cohesion, etc. Good. As such other copolymerizable monomers, alicyclic hydrocarbon group-containing (meth) acrylates, carboxylic acid vinyl esters, aromatic vinyl compounds, aromatic rings exemplified as constituent monomers of the above-mentioned acrylic polymerization component One or more kinds of contained (meth) acrylates and the like can be used. When the constituent monomer component of the acrylic polymer disclosed herein contains another copolymerizable monomer (for example, an alicyclic hydrocarbon group-containing (meth) acrylate), the content thereof is an acrylic polymer It is suitable that the content be 20% by weight or less (eg, 10% by weight or less, typically 5% by weight or less) of all the monomer components constituting the When the content is, for example, an alicyclic hydrocarbon group-containing (meth) acrylate as the other copolymerizable monomer, 0.5% by weight or more (eg, 1% by weight or more, typically 2% by weight) % Or more).

  Further, as the above-mentioned other copolymerizable monomers, polyfunctional monomers may be optionally contained for the purpose of crosslinking and the like. As such a polyfunctional monomer, two or more (typically, three or more) polymerizable functional groups (typically (meth) acryloyl) are exemplified in one molecule, as exemplified as the constituent monomer component of the above-mentioned acrylic polymerization component. 1 type, or 2 or more types of the monomer which has group can be used. When the constituent monomer component of the acrylic polymer disclosed herein contains a polyfunctional monomer, the content thereof is 0.01 to 1% by weight (for example, 0%) of all the monomer components constituting the acrylic polymer. It is preferable to set it to .02 to 1% by weight, typically 0.05 to 0.5% by weight).

The pressure-sensitive adhesive layer disclosed herein contains an acrylic polymer which is a completely polymerized product of an acrylic polymerization component. The monomer composition (type of monomer, ratio of use, etc.) of the acrylic polymer is the same as the description of the monomer composition of the acrylic polymerization component, and therefore the description will not be repeated here. The Mw of the acrylic polymer is preferably 20 × 10 ⁴ or more, more preferably 30 × 10 ⁴ or more, and may be, for example, 40 × 10 ⁴ or more. The upper limit of the Mw is not particularly limited, but from the viewpoint of ease of preparation of a pressure-sensitive adhesive composition, coating properties, etc., usually, the Mw is preferably 200 × 10 ⁴ or less, and 150 × 10 ⁴ or less Is more preferred.

  The pressure-sensitive adhesive layer disclosed herein contains an acrylic oligomer as in the above-described pressure-sensitive adhesive composition. The matters (monomer composition and the like) related to the acrylic oligomer are the same as the contents described in the pressure-sensitive adhesive composition, and therefore the description will not be repeated here.

  In addition, the pressure-sensitive adhesive layer disclosed herein may optionally include various additive components (tackifiers, colorants, and the like) exemplified as the additive components contained in the above-described pressure-sensitive adhesive composition. The details (compound name, blending ratio, etc.) are basically the same as the contents described in the pressure-sensitive adhesive composition, and therefore the description will not be repeated here.

  The pressure-sensitive adhesive in the art disclosed herein comprises all the component monomer components having the above-mentioned composition, such as a polymer (for example, an acrylic polymer or an acrylic oligomer), an unpolymerized substance (that is, a polymerizable functional group is unreacted). It can be formed using a pressure-sensitive adhesive composition contained in the form of a certain form) or a mixture of these. When the pressure-sensitive adhesive composition disclosed herein contains a partially polymerized product, the pressure-sensitive adhesive composition polymerizes unreacted monomers (for example, may contain additional monomers) contained in the composition by an appropriate means. It hardens by doing. In this embodiment, the polymerization method for curing the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive (pressure-sensitive adhesive layer) is not particularly limited, and the same method as the polymerization method used for partially polymerizing the above monomer component Alternatively, different methods can be adopted as appropriate.

  The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method of forming a pressure-sensitive adhesive layer by preferably applying (typically applying) a pressure-sensitive adhesive composition to a surface (peeling surface) having releasability and curing (curing reaction, drying, etc.) is preferably employed. be able to. Alternatively, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) a pressure-sensitive adhesive composition to a substrate and curing the composition (direct method), or applying a pressure-sensitive adhesive composition to a release surface A method may be employed in which a pressure-sensitive adhesive layer is formed on the surface by curing and the pressure-sensitive adhesive layer is transferred to a substrate (transfer method). As said peeling surface, the surface of a peeling liner, the base-material back surface etc. which were peel-treated can be utilized. The application may be performed using a known or conventional coater such as a gravure roll coater or a reverse roll coater. Although the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, it is not limited to such a form, and is formed, for example, in a regular or random pattern such as a dot shape, a stripe shape, etc. It may be a pressure-sensitive adhesive layer.

In a preferred embodiment, polymerization (typically photopolymerization) in forming a pressure-sensitive adhesive from a pressure-sensitive adhesive composition can be carried out by UV irradiation. As a UV lamp used for UV irradiation, a lamp having a spectral distribution in a wavelength range of 300 to 400 nm is suitably used. For example, a chemical lamp, a black light (for example, a black light manufactured by Toshiba Lighttech Co., Ltd.), a metal halide lamp or the like can be used as a light source. In particular, it is preferable to irradiate UV so that the illuminance at a wavelength of 300 to 400 nm is 1 to 50 mW / cm ² . Setting the illuminance of UV to 50 mW / cm ² or less (typically, 40 mW / cm ² or less, for example, 30 mW / cm ² or less) is advantageous from the viewpoint of obtaining better adhesion characteristics. The illuminance of the UV 1 mW / cm ² or more (more preferably 2 mW / cm ² or more, for example 3 mW / cm ² or higher) and that is advantageous from the viewpoint of productivity. The illuminance of the UV can be measured using an industrial UV checker with a peak sensitivity wavelength of about 350 nm (trade name “UVR-T1” manufactured by Topcon, light receiving unit model UD-T36). In addition, when formation of a pressure sensitive adhesive layer is performed using UV irradiation, from the viewpoint of suppressing reaction inhibition by oxygen in the atmosphere, curing is performed in a state where both surfaces of the pressure sensitive adhesive layer are covered with a release liner or a substrate It is preferred to carry out the reaction.

  The gel fraction of the pressure-sensitive adhesive layer disclosed herein is suitably about 10% by weight or more. From the viewpoint of cohesiveness, the gel fraction is preferably 30% by weight or more (eg, 50% by weight or more, typically 60% by weight or more). From the viewpoint of tackiness, the gel fraction is suitably 90% by weight or less (eg 85% by weight or less, typically 80% by weight or less). The gel fraction is adjusted by the monomer composition, the polymerization conversion ratio of the constituent monomer components, the Mw of the polymer, the forming conditions of the pressure-sensitive adhesive layer (curing conditions of the pressure-sensitive adhesive composition, for example, light irradiation conditions and drying conditions) Can.

The gel fraction can be measured by the following method. That is, about 0.1 g of a measurement sample is wrapped in a purse-like shape with a tetrafluoroethylene resin porous sheet having an average pore diameter of 0.2 μm, and the mouth is tied with a kite string. The total weight Wa (mg) of the tetrafluoroethylene resin porous sheet and the kite yarn is measured in advance. Then, the weight of the package (the total weight of the adhesive and the package) Wb (mg) is measured. The packet is placed in a 50 mL screw tube (one screw tube is used per packet) and the screw tube is filled with ethyl acetate. After leaving it to stand at room temperature (typically 23 ° C.) for 7 days, the packet is taken out and dried at 120 ° C. for 2 hours, and the weight Wc (mg) of the packet after drying is measured. The gel fraction (%) of the pressure-sensitive adhesive has the above-mentioned formulas Wa, Wb and Wc as follows:
Gel fraction [%] = (Wc-Wa) / (Wb-Wa) × 100;
It is obtained by substituting into. As the porous sheet made of tetrafluoroethylene resin, a trade name "Nitrophon NTF 1122" (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) manufactured by Nitto Denko Corporation, or an equivalent thereof can be used. The same applies to the gel fraction in the examples described later.

  The thickness of the pressure-sensitive adhesive layer disclosed herein is suitably 10 μm or more. The thickness is preferably 60 μm or more (eg, 90 μm or more, typically 140 μm or more) from the viewpoint of adhesive properties (particularly, drop impact resistance and repulsion resistance). The upper limit of the thickness is suitably about 5 mm or less. From the viewpoint of aggregation and the like, the thickness is preferably 1500 μm or less (eg, 600 μm or less, typically 400 μm or less). When the pressure-sensitive adhesive sheet disclosed herein is a double-sided pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on both sides of a substrate, the thickness of each pressure-sensitive adhesive layer may be the same or different. The pressure-sensitive adhesive sheet may also be provided with a pressure-sensitive adhesive layer having a multilayer structure. In that case, the plurality of pressure-sensitive adhesive layers may have a laminated structure of the pressure-sensitive adhesive layer disclosed herein and a conventionally known pressure-sensitive adhesive layer.

<Base material>
When the pressure-sensitive adhesive sheet disclosed herein is a pressure-sensitive adhesive sheet with a substrate, various sheet-like substrates can be used as a substrate for supporting (backing) the pressure-sensitive adhesive layer. As said base material, a resin film, paper, cloth, a rubber sheet, a foam sheet, metal foil, these composites etc. can be used, for example. The surface (pressure-sensitive adhesive layer side surface) on which the pressure-sensitive adhesive layer of the above-mentioned substrates (for example, resin film substrate, rubber sheet substrate, foam sheet substrate, etc.) is disposed is subjected to corona discharge treatment, plasma treatment, UV irradiation A known or conventional surface treatment such as treatment, acid treatment, alkali treatment, application of a primer may be applied. Alternatively, in the case of the single-sided adhesive pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive sheet disclosed herein is provided with a pressure-sensitive adhesive layer on one side of a substrate, a release treatment agent is formed The peeling process by (rear surface treatment agent) may be performed.

<Peeling liner>
As a release liner, a conventional release paper etc. can be used, It does not specifically limit. For example, it is composed of a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or a low adhesive material such as a fluorine-based polymer (polytetrafluoroethylene etc.) or a polyolefin resin (polyethylene, polypropylene etc.) A release liner or the like can be used. The release treatment layer may be formed, for example, by surface treatment of the liner base material with a release treatment agent such as silicone, long chain alkyl, fluorine, or molybdenum sulfide.

<Characteristics of adhesive sheet>
According to a preferred embodiment, the drop impact resistance is such a level that bonding defects such as peeling are not observed until it is dropped 25 times (preferably 40 times, more preferably 50 times) in the drop impact resistance evaluation in which 60 drops are performed. An adhesive sheet (typically, a double-sided adhesive sheet) can be realized. A pressure-sensitive adhesive sheet satisfying this characteristic is excellent in the ability to withstand an impact such as a drop and maintain bonding (that is, drop impact resistance), for example, in applications where dropping at the time of use such as portable electronic devices is expected. It is suitable as an adhesive sheet used for joining etc. of components. According to the pressure-sensitive adhesive sheet according to one particularly preferable embodiment, the drop impact resistance is realized at such a level that no bonding failure is recognized even when the adhesive sheet is dropped 60 times in the evaluation of the drop impact resistance. Drop impact resistance evaluation is performed by the method as described in the below-mentioned Example.

  According to a preferred embodiment, a pressure-sensitive adhesive sheet is provided that exhibits a level of repulsion resistance that satisfies the condition of 15 mm or less (preferably 10 mm or less, more preferably 5 mm or less) in the repulsion resistance test. The pressure-sensitive adhesive sheet exhibiting the above-mentioned characteristics can also be excellent in step followability. According to the pressure-sensitive adhesive sheet according to a particularly preferred embodiment, a level of repulsion resistance is realized at which the floating of the test piece in the repulsion resistance test can not be substantially recognized. Specifically, the repulsion resistance test is conducted by the method described in the examples below.

  The pressure-sensitive adhesive sheet disclosed herein preferably exhibits 180-degree peel strength (vs. polycarbonate (PC) adhesion) of 12 N / 20 mm or more. The pressure-sensitive adhesive sheet exhibiting the above-mentioned characteristics can firmly bond adherends (particularly, resin-made adherends such as PC), and can be preferably used for bonding, fixing and the like. For example, high adhesion reliability can be maintained in applications in which the adhesion area tends to be reduced, such as double-sided pressure-sensitive adhesive sheets used in portable electronic devices. The above-mentioned adhesion to PC is more preferably 15 N / 20 mm or more (for example, 18 N / 20 mm or more, typically 22 N / 20 mm or more). The adhesion to PC is measured by the method described in the examples below.

  The pressure-sensitive adhesive sheet disclosed herein may have desired optical properties (transmittance, reflectance, etc.). For example, the pressure-sensitive adhesive sheet used for light shielding applications preferably has a total light transmittance of 0% to 20% (more preferably 0% to 10%). The total light transmittance is measured by the method described in the examples below. The optical properties of the pressure-sensitive adhesive sheet can be adjusted, for example, by coloring the pressure-sensitive adhesive layer or the substrate.

  The total thickness of the pressure-sensitive adhesive sheet (which may include the pressure-sensitive adhesive layer and the substrate but does not include the release liner) disclosed herein is not particularly limited, and is preferably in the range of about 10 μm to 5 mm. The total thickness of the pressure-sensitive adhesive sheet is preferably about 60 to 1500 μm (eg, 90 to 800 μm, typically 140 to 500 μm) in consideration of adhesion properties such as drop impact resistance. When the total thickness of the pressure-sensitive adhesive sheet is equal to or less than a predetermined value, it can be advantageous in terms of thinning, downsizing, weight reduction, resource saving, and the like of a product to which the pressure-sensitive adhesive sheet is applied.

<Use>
The pressure-sensitive adhesive sheet disclosed herein is compatible with a high level of drop impact resistance and repulsion resistance. In a preferred embodiment, the adhesive strength is excellent. For this reason, it can be suitable as a pressure-sensitive adhesive sheet (typically, a double-sided pressure-sensitive adhesive sheet) used for the purpose of bonding, fixing, shock absorption, and the like in a portable device susceptible to impact due to falling or the like. In addition, for securing the protective panel (lens) that protects the display unit of electronic device applications, for example, portable electronic devices (for example, mobile phones, smartphones, tablet computers, notebook computers, cameras, etc.) using the above features. It can be preferably applied to applications such as fixing key module members of mobile phones, fixing decoration panels of TVs, fixing battery packs of personal computers, lens waterproofing of digital video cameras, and the like. Particularly preferred applications include portable electronics applications. In particular, it can be preferably used for a portable electronic device incorporating a liquid crystal display. For example, such a portable electronic device is suitable for use in bonding a protective panel (lens) for protecting a display portion and a housing. In the present specification, "portable" is not enough to be only portable, but it is relatively easy for an individual (standard adult) to have portability. Shall be meant. Moreover, the "lens" in this specification is a concept including both the transparent body which shows the refractive action of light, and the transparent body which does not have the refractive action of light. That is, the "lens" in the present specification also includes a protective panel that protects the display portion of a simple portable electronic device that does not have a refractive effect.

  The application target of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited. The pressure-sensitive adhesive sheet is, for example, metal materials such as stainless steel (SUS) and aluminum; inorganic materials such as glass and ceramics; resin materials such as PC, polymethyl methacrylate, polypropylene and polyethylene terephthalate (PET); natural rubber, butyl rubber and the like And a composite material having a surface made of these composite materials and the like.

  The following examples illustrate some of the embodiments of the present invention, but are not intended to limit the present invention to those shown. In the following description, "parts" and "%" are on a weight basis unless otherwise noted. Moreover, each evaluation item was measured or evaluated as follows, respectively.

[Evaluation method]
(1) Drop Impact Resistance A double-sided pressure-sensitive adhesive sheet as shown in FIG. 3 was cut into a 53 mm wide, 116 mm long, 1 mm wide window frame shape (frame shape) as shown in FIG. Using this window frame-like double-sided adhesive sheet, a 5 kg roller is reciprocated once between a PC plate (70 mm wide, 130 mm long, 2 mm thick) and a glass plate (53 mm wide, 116 mm long, 1 mm thick, 18 g weight) It bonded together by pressure-bonding on conditions, and obtained the sample for evaluation (refer FIG. 3 (a) (b)).
FIG. 3 is a schematic view of the evaluation sample, wherein (a) is a top view and (b) is a cross-sectional view taken along the line BB ′. In FIG. 3, reference numeral 50 denotes a window frame-shaped double-sided pressure-sensitive adhesive sheet, reference numeral 51 denotes a PC plate, and reference numeral 52 denotes a glass plate.
A 110 g weight was attached to the back surface (surface opposite to the surface bonded to the glass plate) of the PC plate of these evaluation samples. A drop test was conducted on the above-described evaluation sample with a weight, in which the free fall was made 60 times onto a concrete plate from a height of 1.2 m at normal temperature (about 23 ° C.). At this time, the falling direction was adjusted so that the six sides of the evaluation sample were sequentially downward. That is, 10 cycles of one drop pattern were performed for each of the six surfaces.
Then, each time it was dropped, it was visually confirmed whether or not peeling occurred between the PC plate and the glass plate, and the number of drops until peeling occurred was evaluated as drop impact resistance. When no peeling was observed even after dropping 60 times, "60 times or more" was displayed.

(2) Repulsion resistance 0.5 mm thick aluminum cut into a size of 20 mm wide and 180 mm long and peeled off the first release liner and cut into the same size on the first adhesive surface exposed The plate was attached and backed to make a test piece. The test piece was crimped to a 2 mm thick PC plate cut into a size of 30 mm × 200 mm using a laminator under an environment of 23 ° C. and RH 50%, and then held under the same environment for 24 hours. Next, as shown in FIG. 4, the bonded PC board of the test piece was warped into an arc shape with a chord length of 190 mm. This was held for 72 hours in an atmosphere of 70 ° C., and the distance h (mm) at which the end of the test piece was lifted from the surface of the PC plate was measured (FIG. 5). In addition, the code | symbol 100, 200, 300 shows the double-sided adhesive sheet except an 1st and 2nd peeling liner, an aluminum plate, and a PC board in FIGS. 4-5, respectively.

(3) Adhesion to Polycarbonate The release liner covering one adhesive surface of the double-sided adhesive sheet was peeled off, and a 50 μm-thick PET film was attached to the one adhesive surface. This was cut into a size of 20 mm in width and 100 mm in length to prepare a measurement sample.
Under the environment of 23 ° C. and 50% RH, the other adhesive surface of the measurement sample was exposed, and the other adhesive surface was crimped to the surface of the PC plate with one reciprocation of a 2 kg roller. After leaving this in the same environment for 30 minutes, using a universal tensile compression tester (product name "TG-1 kN", manufactured by Minebea Co., Ltd.), according to JIS Z 0237, tensile speed 300 mm / min, peeling angle The peel strength [N / 20 mm width] was measured under the condition of 180 degrees.

(4) Light transmittance The total light transmittance of the double-sided pressure-sensitive adhesive sheet after peeling off the release liner is used in accordance with JIS K 7361 using a haze meter (manufactured by Murakami Color Research Laboratory, trade name "HM-150") Measured. When the total light transmittance was 20% or less, it was evaluated as "absent", and when the total light transmittance exceeded 20%, it was evaluated as "present".

<Example 1>
[Preparation of pressure-sensitive adhesive composition]
Monomer mixture consisting of 78 parts of 2-ethylhexyl acrylate (2EHA), 18 parts of N-vinyl-2-pyrrolidone (NVP) and 4 parts of 2-hydroxyethyl acrylate (HEA) 0.05 parts of 1,2-diphenylethane-1-one (manufactured by BASF, trade name "IRGACURE 651") and 1-hydroxycyclohexyl-phenyl-ketone (manufactured by BASF, trade name "IRGACURE 184") 0. The resulting mixture was charged into a four-necked flask together with 05 parts, partially irradiated with UV under a nitrogen atmosphere, and partially polymerized to obtain syrup A containing a partially polymerized product. The polymerization conversion ratio of the above-mentioned monomer mixture in this syrup A was about 10%.
100 parts of this syrup A, 2 parts of acrylic acid (AA) as an additional monomer, 0.12 parts of 1,6-hexanediol diacrylate (HDDA), 3 parts of an acrylic oligomer, and a black coloring agent A pressure-sensitive adhesive composition according to this example was prepared by adding and mixing 0.8 parts of a product manufactured by Kagaku Kogyo Co., Ltd. (trade name "AT DN101 black").
As the acrylic oligomer, one prepared by the following method was used. 60 parts of dicyclopentanyl methacrylate (DCPMA: manufactured by Hitachi Chemical Co., Ltd., trade name "FA-513M") and 40 parts of methyl methacrylate (MMA), 3 parts of thioglycolic acid as a chain transfer agent, and toluene as a solvent And nitrogen gas was blown in to remove dissolved oxygen. Then, the mixture was heated to 70 ° C. and stirred at 70 ° C. for 1 hour, and then 0.2 parts of azobisisobutyronitrile as a polymerization initiator was added. This was reacted at 70 ° C. for 2 hours and then at 80 ° C. for 2 hours. Thereafter, the pressure was reduced under the condition of 130 ° C. and stirring was performed for 1 hour to remove the residual monomer, thereby obtaining an acrylic oligomer having a Mw of about 0.55 × 10 ⁴ and a Tg of about 144 ° C.

[Production of adhesive sheet]
Two PET films with a thickness of 38 μm, one surface of which was a release surface treated with a silicone release treatment agent, were prepared. The pressure-sensitive adhesive composition was applied onto the release surface of the first PET film. The release surface of the second PET film is covered on the coated pressure-sensitive adhesive composition, and the above-mentioned pressure-sensitive adhesive composition is cured by irradiating the UV, and the pressure-sensitive adhesive layer having a thickness of 230 μm is obtained. It formed. The UV irradiation was performed using a black light (15 W / cm) at an illuminance of 5 mW / cm ² (an industrial UV checker with a peak sensitivity wavelength of about 350 nm (trade name “UVR-T1” manufactured by Topcon Corporation, light receiving unit type UD− (T36)) and the light quantity of 1500 mJ / cm ² . Thus, a double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer was obtained. The first adhesive surface and the second adhesive surface of the adhesive sheet are each protected by the two PET films (release liners). The gel fraction of the pressure-sensitive adhesive layer according to this example was about 70% by weight.

<Examples 2 to 6>
The same as in Example 1 except that the amount of additional monomer used, the amount of acrylic oligomer used, the presence or absence of other additives (tackifier, black colorant) and the amount used were changed to the contents shown in Table 1. The pressure-sensitive adhesive composition according to each example was prepared. Using the pressure-sensitive adhesive composition, a double-sided pressure-sensitive adhesive sheet according to Examples 2 to 6 consisting of a pressure-sensitive adhesive layer having a thickness shown in Table 1 was produced in the same manner as Example 1.

<Example 7>
A monomer mixture consisting of 80 parts of 2EHA, 11.5 parts of 2-methoxyethyl acrylate (2MEA), 7 parts of NVP and 1.5 parts of N- (2-hydroxyethyl) acrylamide (HEAA) as a photopolymerization initiator, -Dimethoxy-1,2-diphenylethane-1-one (manufactured by BASF, trade name "IRGACURE 651") and 0.05 parts and 1-hydroxycyclohexyl-phenyl-ketone (manufactured by BASF, trade name "IRGACURE 184") It was charged into a four-necked flask together with 0.05 parts, irradiated with UV under a nitrogen atmosphere, and partially photopolymerized to obtain a syrup B containing a partially polymerized product. The polymerization conversion ratio of the above-mentioned monomer mixture in this syrup B was about 10%.
A pressure-sensitive adhesive composition according to this example was prepared by adding and mixing 3 parts of AA as an additional monomer, 0.12 parts of HDDA, and 5 parts of an acrylic oligomer to 100 parts of the syrup B. The same acrylic oligomer as that used in Example 1 was used. A double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1 except that this pressure-sensitive adhesive composition was used.

  The result of said measurement evaluation in the adhesive sheet which concerns on Examples 1-7 is shown in Table 1. Table 1 also shows a schematic configuration of the pressure-sensitive adhesive sheet according to each example. In addition, "-" shows no addition in a table | surface.

  As shown in Table 1, an example using an acrylic polymer containing N-containing monomer units as a polar group-containing monomer unit at a predetermined ratio or more and using an acrylic oligomer as one component of the acrylic polymer The pressure-sensitive adhesive sheets of Examples 1 to 4 were able to improve the drop impact resistance while maintaining the repulsion resistance at a high level. On the other hand, in Example 5 and Example 6, coexistence with drop impact resistance and repulsion resistance was not able to be realized. One of the reasons is that in these examples, acrylic oligomers were not used, and it is considered that the adhesive properties contributing to the drop impact resistance and the repulsion resistance were not obtained. In addition, in Example 7 in which the amount of the N-containing monomer used was small, the repulsion resistance tended to decrease. This suggests that a certain amount or more of N-containing monomer is required to maintain the repulsion resistance at a high level.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above.

1, 2 adhesive sheet 21 adhesive layer 31, 32 release liner

Claims (8)

A pressure-sensitive adhesive layer containing an acrylic polymer as a main component,
The acrylic polymer contains a polar group-containing monomer as its constituent monomer component,
The polar group-containing monomer is contained in a proportion of 15% by weight or more based on all monomer components constituting the acrylic polymer,
The polar group-containing monomer contains a nitrogen atom-containing monomer in a proportion of more than 50% by weight,
The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing an acrylic polymerization component and an acrylic oligomer.
The monomer component constituting the acrylic polymer contains 50% by weight or more of linear alkyl (meth) acrylate,
The linear alkyl (meth) acrylate is a group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl methacrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, nonyl acrylate and isononyl acrylate At least one selected from
The adhesive sheet whose ratio of polar group containing monomers other than the nitrogen atom containing monomer which occupies for all the monomer components which comprise the said acryl-type polymerization component is 10 weight% or less .   The pressure-sensitive adhesive sheet according to claim 1, wherein the polar group-containing monomer further comprises at least one of a carboxy group-containing monomer and a hydroxyl group-containing monomer.   The pressure-sensitive adhesive sheet according to claim 2, wherein the polar group-containing monomer comprises a carboxy group-containing monomer.   The pressure-sensitive adhesive sheet according to claim 3, wherein the acrylic polymer contains the carboxy group-containing monomer in a proportion of less than 5% by weight as a constituent monomer component.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the polar group-containing monomer contains a monomer having a nitrogen atom-containing ring as the nitrogen atom-containing monomer.   The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein a content of the acrylic oligomer is 5 parts by weight or less with respect to 100 parts by weight of the acrylic polymerization component. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the weight average molecular weight of the acrylic oligomer is in the range of 0.1 10 ^{4 to} 3 10 ⁴ . The adhesive sheet as described in any one of Claims 1-7 used for a portable electronic device.

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