JP5994445B2 - UV-curable adhesive resin composition and adhesive - Google Patents

Description

  The present invention relates to a resin composition for an ultraviolet curable adhesive and an adhesive that are excellent in adhesive strength and yellowing resistance.

  In optical related products such as touch panels and liquid crystal displays, a large number of optical members having various types of materials and shapes are used in accordance with their higher functions.

  For bonding optical members as described above, a pressure-sensitive adhesive has been conventionally used. However, a pressure-sensitive adhesive having an excellent adhesive force is required from the industry regardless of the material and shape of the part.

  Further, in the manufacturing scene of the optical related product, in recent years, improvement of productivity of the final product has become a big issue. This is because a conventionally used pressure-sensitive adhesive usually contains a solvent such as a solvent or water, so that the solvent contained in the pressure-sensitive adhesive is removed after the pressure-sensitive adhesive is applied to the surface of the substrate. The process took a lot of time and contributed to the reduction in production efficiency of the final product.

  As a pressure-sensitive adhesive capable of improving the production efficiency of the product, an ultraviolet curable pressure-sensitive adhesive is known. Since the ultraviolet curable pressure-sensitive adhesive usually does not contain a solvent such as a solvent or water, there is a feature that a step of removing the solvent is not required when forming the pressure-sensitive adhesive layer.

  Examples of the pressure-sensitive adhesive having a level of adhesive strength that can be used in the production of the product and the like and capable of improving the production efficiency of the final product as compared with the conventional product include, for example, 100 parts of a monomer having an unsaturated double bond On the other hand, it has a weight average molecular weight of 20,000 or more and has a urethane bond and an unsaturated double bond at the polymer terminal, and contains 5 to 200 parts by mass. An adhesive composition is known (for example, refer to Patent Document 1).

  However, the pressure-sensitive adhesive composition may not exhibit practically sufficient adhesive force depending on the material of the base material, etc., and depending on the material and shape of the base material, On the other hand, there have been problems such as causing displacement of the substrate with respect to a parallel lateral force, and yellowing over time.

JP 2006-104296 A

  The problem to be solved by the present invention is for an ultraviolet curable pressure-sensitive adhesive that has excellent adhesive strength at a level that does not cause peeling over time with respect to substrates made of various materials, and is excellent in yellowing resistance. It is to provide a resin composition.

  The inventors of the present invention have advanced their research while paying attention to the types of additives in the course of diligent research to solve the above problems.

  As a result, it was found that a pressure-sensitive adhesive having excellent adhesive strength and yellowing resistance can be obtained by containing a light stabilizer and an antioxidant in a specific ratio.

  That is, the present invention provides a urethane (meth) acrylate resin (A) obtained by reacting a polyol (a), a polyisocyanate (b) and a (meth) acrylic compound (c) having a hydroxyl group, and a (meth) acrylic monomer. A resin composition for an ultraviolet curable pressure-sensitive adhesive containing a body (B) and a photopolymerization initiator (C), further comprising a light stabilizer (D) and an antioxidant (E) in a mass ratio of 95 It provides in the range of / 5-5 / 95, and the resin composition for ultraviolet curable adhesives and adhesives characterized by the above-mentioned.

  The pressure-sensitive adhesive obtained by using the resin composition for an ultraviolet curable pressure-sensitive adhesive of the present invention is excellent in excellent adhesive force, holding power and yellowing resistance. In particular, it is excellent in yellowing resistance (light yellowing resistance, heat yellowing resistance) even after prolonged light exposure and heat exposure.

  The pressure-sensitive adhesive obtained by using the resin composition for an ultraviolet curable pressure-sensitive adhesive of the present invention can be suitably used as a pressure-sensitive adhesive used for an optical member. In particular, it can be suitably used for the production of touch panels, liquid crystal displays, plasma displays, organic EL, personal computers, mobile phones and the like.

  First, the urethane (meth) acrylate resin (A) used in the present invention will be described.

  Examples of the polyol (a) include polyester polyol, polyether polyol, polycarbonate polyol, polyacryl polyol, polybutadiene polyol, and the like. These may be used alone or in combination of two or more. Among these, polyether polyols and polycarbonate polyols are preferably used from the viewpoint of further improving the adhesive strength, holding power, step following ability, whitening resistance, and the like.

  Examples of the polyether polyol include products obtained by addition polymerization of one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, etc., to a compound having two or more active hydrogens, Examples include polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran, modified polytetramethylene glycol obtained by copolymerization of tetrahydrofuran and alkyl-substituted tetrahydrofuran, and modified polytetramethylene glycol obtained by copolymerization of neopentyl glycol and tetrahydrofuran. .

  Examples of the compound having two or more active hydrogens include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1 , 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2, 5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl -1,3-propanediol, neopentyl glycol 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2- Relatively low molecular weight dihydroxy compounds such as ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, hydroquinone, resorcin, bisphenol A, bisphenol F, 4,4′-bisphenol, -Cyclobutanediol, 1,3-cyclopentanediol, 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, 1,4-cyclohexanedimethanol, hydroxypropylcyclohexanol, tricyclo [5,2,1,0, 2,6] decane-dimethanol, bicyclo [4,3,0 Nonanediol, dicyclohexanediol, tricyclo [5,3,1,1] dodecanediol, bicyclo [4,3,0] nonanedimethanol, tricyclo [5,3,1,1] dodecane-diethanol, hydroxypropyltri Cyclo [5,3,1,1] dodecanol, spiro [3,4] octanediol, butylcyclohexanediol, 1,1′-bicyclohexylidenediol, cyclohexanetriol, hydrogenated bisphenol A, 1,3-adamantane Examples include alicyclic polyols such as diols, polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and polyester polyols such as polyhexamethylene adipate, polyhexamethylene succinate, and polycaprolactone. I can get lost.

  Among these, it is more preferable to use an aliphatic polyether polyol from the viewpoint of imparting good adhesive properties, and it is particularly preferable to use polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran.

  The number average molecular weight of the polyether polyol is preferably in the range of 500 to 3,000, more preferably in the range of 500 to 2,000, and still more preferably in the range of 500 to 1,500. In addition, the number average molecular weight of the said polyether polyol is the value calculated | required by polystyrene conversion using gel permeation chromatography (GPC).

  Examples of the polycarbonate polyol include those obtained by reacting a carbonate and / or phosgene with the compound having two or more active hydrogens.

  Examples of the carbonate ester include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, diphenyl carbonate, and the like.

  The hydroxyl value of the polycarbonate polyol is preferably 30 to 230 mgKOH / g, more preferably 50 to 230 mgKOH / g, from the viewpoint of adhesive strength and the like. In addition, the hydroxyl value of the said polycarbonate polyol shows the value which measured based on JISK0070.

  Examples of the polyisocyanate (b) include aromatic diisocyanates such as xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, 4,4. Examples include aliphatic or alicyclic diisocyanates such as' -dicyclohexylmethane diisocyanate, diisocyanate methylcyclohexane, and tetramethylxylylene diisocyanate. These may be used alone or in combination of two or more. Among these, the use of a diisocyanate having an alicyclic structure is preferable from the viewpoint of achieving both excellent adhesive strength and holding power and improving heat-resistant yellowing, and the like, 4,4′-dicyclohexylmethane diisocyanate, More preferably, isophorone diisocyanate, cyclohexane diisocyanate, or diisocyanate methylcyclohexane is used.

  The (meth) acrylic compound (c) having a hydroxyl group is used to introduce a (meth) acryloyl group into the urethane (meth) acrylate resin (A) and can react with an isocyanate group. It is what has.

  Examples of the (meth) acrylic compound having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxy. (Meth) acrylic acid alkyl ester having a hydroxyl group such as butyl (meth) acrylate, 6-hydroxyhexyl acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, etc. And polyfunctional (meth) acrylate having a hydroxyl group, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate and the like. Among these, from the viewpoint of curability by ultraviolet rays, it is more preferable to use an acrylic compound having a hydroxyl group. From the viewpoint of easy availability of raw materials, curability, and good adhesive properties, 2-hydroxyethyl can be used. Particularly preferred are acrylates and 4-hydroxybutyl acrylate.

  As a method for producing the urethane (meth) acrylate resin (A), for example, after the polyol (a) and the (meth) acrylic compound (c) are charged into a reaction system in the absence of a solvent, A method of producing by supplying isocyanate (b), mixing and reacting, or urethane having an isocyanate group at the molecular terminal by reacting the polyol (a) and the polyisocyanate (b) in the absence of a solvent. Examples thereof include a method in which a prepolymer is obtained, and then the (meth) acrylic compound (c) is supplied, mixed and reacted. In any case, the reaction is preferably carried out under a condition of 20 to 120 ° C. for about 30 minutes to 24 hours.

  The urethane (meth) acrylate resin (A) may be produced in the presence of an organic solvent or an aqueous medium. Furthermore, it may be produced in the presence of a (meth) acrylic monomer (B) described later, instead of an organic solvent or an aqueous medium. In particular, when manufacturing a laminate, it is not necessary to remove the organic solvent or aqueous medium and the manufacturing process can be simplified. From the viewpoint of suppressing viscosity in the absence of solvent or in the reaction system, (meth) acrylic It is preferable to carry out in the presence of the monomer (B).

  The reaction of the polyol (a), the polyisocyanate (b), and the (meth) acrylic compound (c) is the sum of the hydroxyl groups of the polyol (a) and the hydroxyl groups of the (meth) acrylic compound (c). The urethane (meth) acrylate resin (A) obtained by carrying out in an amount ratio [the total amount of isocyanate groups / hydroxyl groups] = 0.75 to 1.00 between the amount and the isocyanate group of the polyisocyanate (b) ) Is preferable in controlling the molecular weight, and more preferably in the range of 0.79 to 0.95. The reaction may be carried out when the equivalent ratio exceeds 1, but in that case, an alcohol such as methanol is used for the purpose of deactivating the terminal isocyanate group of the urethane (meth) acrylate resin (A). Is preferred. In that case, the total amount of the hydroxyl group of the polyol (a), the hydroxyl group of the (meth) acrylic compound (c) and the hydroxyl group of the alcohol, and the equivalent ratio of the polyisocyanate group [isocyanate group / hydroxyl group It is preferable to adjust so that [total amount] is within the above range.

  Moreover, as alcohol which can be used in order to inactivate the terminal isocyanate group of the said urethane (meth) acrylate resin (A), monofunctional alcohols, such as methanol, ethanol, a propanol, a butanol, 1, 2, for example, -Bifunctional alcohols composed of primary and secondary hydroxyl groups such as propylene glycol and 1,3-butylene glycol may be used.

  Moreover, when manufacturing urethane (meth) acrylate resin (A), you may use a polymerization inhibitor, a urethanization catalyst, etc. as needed.

  Examples of the polymerization inhibitor include 3,5-bismutual butyl-4-hydroxytoluene, hydroquinone, methyl hydroquinone, hydroquinone monomethyl ether (methoquinone), para-tertiary butyl catechol methoxyphenol, 2,6-ditertiary butyl cresol. Phenothiazine, tetramethylthiuram disulfide, diphenylamine, dinitrobenzene and the like can be used.

  Examples of the urethanization catalyst include nitrogen-containing compounds such as triethylamine, triethylenediamine and N-methylmorpholine, metal salts such as potassium acetate, zinc stearate and tin octylate, and organometallic compounds such as dibutyltin laurate. Can be used.

The urethane (meth) acrylate resin (A) has a (meth) acryloyl group that allows radical polymerization to proceed by light irradiation, heating, or the like. The equivalent of the (meth) acryloyl group is preferably in the range of 1,000 to 20,000, more preferably in the range of 5,000 to 17,000, from the viewpoints of pressure-sensitive physical properties and other physical properties. A range of 6,000 to 16,000 is more preferable. In addition, the equivalent of the (meth) acryloyl group is the total mass of the polyol (a), polyisocyanate (b), and (meth) acrylic compound (c) in the urethane (meth) acrylate resin (A). It shows the value divided by the equivalent of the (meth) acryl group present, and the unit is g / eq. It is.
In the present invention, “(meth) acrylic compound” refers to one or both of a methacrylic compound and an acrylic compound, and “(meth) acrylate” refers to one or both of methacrylate and acrylate. ") Acryloyl group" means one or both of methacryloyl group and acryloyl group, and "(meth) acrylic acid" means one or both of methacrylic acid and acrylic acid, and "(meth) acrylic monomer" Means one or both of a methacrylic monomer and an acrylic monomer.

  The weight average molecular weight of the urethane (meth) acrylate resin (A) is 5,000 to 50,000 from the viewpoint of achieving both excellent adhesive force and holding power and imparting good coating workability. Is preferable, the range of 7,000 to 45,000 is more preferable, the range of 10,000 to 40,000 is still more preferable, and the range of 12,000 to 35,000 is particularly preferable. In addition, the weight average molecular weight of the said urethane (meth) acrylate resin (A) is the value calculated | required by polystyrene conversion using the gel permeation chromatography (GPC).

  Next, the (meth) acrylic monomer (B) used in the present invention will be described.

  Examples of the (meth) acrylic monomer (B) include methyl acrylate (glass transition temperature (Tg): 10 ° C.), ethyl acrylate (−24 ° C.), propyl acrylate (−37 ° C.), acrylic Isopropyl (-6 ° C), butyl acrylate (-49 ° C), sec-butyl acrylate (-22 ° C), isobutyl acrylate (-24 ° C), 2-ethylbutyl acrylate (-50 ° C), acrylic acid n-pentyl (-57 ° C), hexyl acrylate (-57 ° C), 2-ethylhexyl acrylate (-50 ° C), heptyl acrylate (-60 ° C), octyl acrylate (-65 ° C), acrylic acid 2 -Octyl (-45 ° C), nonyl acrylate (-58 ° C), dodecyl acrylate (-3 ° C), 3-methoxybutyl acrylate (-56 ° C), 2-acrylic acid 2- Toxiethyl (-50 ° C), 3-methoxypropyl acrylate (-75 ° C), 2-methoxybutyl acrylate (-32 ° C), 3-methylbutyl acrylate (-45 ° C), benzyl acrylate (6 ° C), Pentyl methacrylate (−5 ° C.), hexyl methacrylate (−5 ° C.), 2-ethylhexyl methacrylate (−10 ° C.) (the Tg value is reprinted from Polmer Handbook (4th ed.)), 2-hydroxy acrylate Ethyl (HEA; -15 ° C), 2-hydroxypropyl acrylate (HPA; -7 ° C), 4-hydroxybutyl acrylate (4HBA; -32 ° C), isooctyl acrylate (IOAA; -58 ° C), acrylic acid Lauryl (LA; 15 ° C), stearyl acrylate (STA; -58 ° C), tetrahydrophrate acrylate Rufuryl (Biscoat # 150; -12 ° C), benzyl acrylate (Biscoat # 160; 6 ° C), ethyl carbitol acrylate (Biscoat # 190; -67 ° C), phenoxyethyl acrylate (Biscoat # 192; -22 ° C) (Osaka Organic Chemical Co., Ltd., Tg value reprinted from the company's HP), methoxypolyethylene glycol acrylate (EO 9 mol, AM-90G; -71 ° C.), phenoxypolyethylene glycol acrylate (AMP-20GY; -8) ° C) (Shin Nakamura Chemical Co., Ltd., Tg value reprinted from the company's HP), Isoamyl acrylate (IAA; -45 ° C), Ethoxyacrylate-diethylene glycol (EC-A; -70 ° C) (above , Kyoeisha Chemical Co., Ltd., Tg value reprinted from the company's HP), Neope Acrylate Chill (22 ° C), cyclohexyl acrylate (19 ° C), hexadecyl acrylate (35 ° C), isobornyl acrylate (94 ° C), phenyl acrylate (57 ° C), acrylamide (165 ° C), benzyl methacrylate (54 ° C ), Methyl methacrylate (105 ° C), ethyl methacrylate (65 ° C), propyl methacrylate (35 ° C), isopropyl methacrylate (81 ° C), butyl methacrylate (20 ° C), isobutyl methacrylate (53 ° C), Sec-butyl methacrylate (60 ° C), t-butyl methacrylate (118 ° C), cyclohexyl methacrylate (83 ° C) 2-hydroxyethyl methacrylate (85 ° C), isobornyl methacrylate (110 ° C) (above, Polymer Handbook) (Reproduced Tg value from 4th ed.) T-butyl acrylate (TBA; 41 ° C) (Osaka Organic Chemical Co., Ltd., Tg value reprinted from HP), 2-hydroxy-3-phenoxypropyl acrylate (M-600A; 17 ° C) (Reproduced from Kyoeisha Chemical Co., Ltd., Tg value reprinted from HP), dimethylacrylamide (DMAA; 119 ° C), acryloylmorpholine (ACMO; 145 ° C), dimethylaminopropylacrylamide (DMAPAA; 134 ° C), isopropylacrylamide (NIPAM; 134 ° C.), diethyl acrylamide (DEAA; 81 ° C.), hydroxyethyl acrylamide (HEAA; 98 ° C.) (manufactured by Kojin Co., Ltd., reprinted Tg value from HP). These monomers may be used alone or in combination of two or more. The Tg value represents the Tg of the homopolymer of the (meth) acrylic monomer, and Polymer Handbook (4th ed.) And (meth) acrylic monomer manufacturer homepage values were used. .

  As the (meth) acrylic monomer (B), from the viewpoints of adhesive strength, holding power, and other physical properties, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-acrylic acid 2- It is preferable to use methoxyethyl, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and particularly butyl acrylate, 2-ethylhexyl acrylate, dimethylacrylamide, acryloylmorpholine, dimethylaminopropylacrylamide, isopropylacrylamide, diethylacrylamide, It is preferable to use one or more selected from the group consisting of hydroxyethyl acrylamide and cyclohexyl acrylate.

  The amount of the (meth) acrylic monomer (B) used is the urethane (meth) acrylate resin (A) from the viewpoint that both excellent adhesive strength and holding power can be achieved, and coating properties such as viscosity can be imparted. ) It is preferably used in the range of 30 to 200 parts by mass, more preferably in the range of 50 to 150 parts by mass, and particularly preferably in the range of 70 to 130 parts by mass with respect to 100 parts by mass.

  Next, the photopolymerization initiator (C) used in the present invention will be described.

  The photopolymerization initiator (C) generates radicals by light irradiation, heating, or the like, and initiates radical polymerization of the urethane (meth) acrylate resin (A) or the (meth) acrylic monomer (B).

  Examples of the photopolymerization initiator include 4-phenoxydichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy- 2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 2-methyl- [4- (methylthio) phenyl]- Acetophenones such as 2-morpholino-1-propanone and 2,2-dimethoxy-2-phenylacetophenone; benzoins such as benzoin, benzoin methyl ether, benzoin isoethyl ether, benzoin isopropyl ether and benzoin isobutyl ether; benzopheno Benzophenones such as benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, 3,3′-dimethyl-4-methoxybenzophenone; thioxanthone, 2-chloro Thioxanthones such as thioxanthone, 2,4-dichlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone; 4,4′-dimethylaminothioxanthone (Also known as Minerals ketone), 4,4′-diethylaminobenzophenone, α-acyloxime ester, benzyl, methylbenzoylformate (“Biacure 55”), Anthraquinones such as 2-ethylanthraquinone; 2,4,6-trimethylbenzoyldiphenylphosphine oxide (“Lucirin TPO”), bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (“IRGACURE819”), etc. Acylphosphine oxides; 3,3 ′, 4,4′-tetra (tert-butylperoxycarbonyl) benzophenone [“BTTB” manufactured by NOF Corporation], acrylated benzophenone, and the like.

  As the photopolymerization initiator, 2-hydroxy-2-methyl- can be used from the viewpoints of achieving both excellent adhesive strength and holding power, preventing discoloration of the adhesive layer over time, and improving curability. It is preferable to use 1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide.

  The photopolymerization initiator (C) is preferably used in an amount of 0.1 to 20 parts by mass with respect to 100 parts by mass of the urethane (meth) acrylate resin (A). The range of parts by mass is more preferable, and the range of 1 to 5 parts by mass is particularly preferable.

    The amount of the photopolymerization initiator (C) used is, from the viewpoint of initial yellowing resistance (transparency) and the like, the mass ratio with the light stabilizer (D) described later [(C) / (D) ] Is preferably in the range of 95/5 to 20/80, more preferably in the range of 85/15 to 50/50.

  Next, the light stabilizer (D) used in the present invention will be described.

  The light stabilizer (D) captures radicals generated by photodegradation, for example, radical scavengers such as thiol, thioether, and hindered amine compounds, and ultraviolet light such as benzophenone and benzoate compounds. An absorbent etc. are mentioned, These may be used independently or may use 2 or more types together. Among these, it is preferable to use a hindered amine compound from the viewpoint of maintaining both excellent adhesive force and holding force and further improving yellowing resistance after exposure to light.

  Examples of the hindered amine compound include a reaction product of cyclohexane and N-butyl peroxide 2,2,6,6-tetramethyl-4-piperidineamine-2,4,6-trichloro-1,3,5-triazine. Product of 2-aminoethanol (trade name: Tinuvin (registered trademark) 152 (manufactured by BASF Japan Ltd.)), bis (2,2,6,6-tetramethyl-1- ( Octyloxy) -4-piperidinyl) ester (trade name: Tinuvin (registered trademark) 123 (manufactured by BASF Corp.)), 1,1-dimethylethyl hydroperoxide and a reaction product of octane, and other amino ether groups Hindered amine compound, N-acetyl-3-dodecyl-1- (2,2,6,6-tetramethyl-4-piperidinyl) pyrrolidi N-acetyl hindered amine compounds such as -2,5-dione (trade name: Hostavin (registered trademark) 3058 (manufactured by Clariant Japan)), bis (1,2,2,6,6-pentamethyl-4- Piperidyl) = decandioate (trade name: Tinuvin (registered trademark) 765 (manufactured by BASF Japan Ltd.)), bis (1,2,2,6,6, -pentamethyl-4-piperidyl) {[3,5 -Bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl} butyl malonate Trade name: Tinuvin (registered trademark) 144 (manufactured by BASF Japan Ltd.), dimethyl succinate 1- (2-hydroxy Ethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (trade name: Tinuvin (registered trademark) 622LD BASF Japan Ltd.)), Probandioic acid [{4-methoxyphenyl} methylene] -bis (1,2,2,6,6-pentamethyl-4-piperidyl) ester (trade name: Hostavin (registered trademark) ) PR-31 (manufactured by Clariant Japan Co., Ltd.)) and the like. Among these, it is preferable to use an N-alkyl hindered amine compound from the viewpoint of maintaining both excellent adhesive strength and holding power and further improving yellowing resistance after exposure to light. , 2,2,6,6-pentamethyl-4-piperidyl) = decandioate and dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensation It is preferable to use one or more light stabilizers selected from the group consisting of products.

  The light stabilizer (D) is used in an amount of 0.01 to 10 parts by mass with respect to 100 parts by mass of the urethane (meth) acrylate resin (A). It is preferable from a viewpoint which can provide, and the range of 0.1-5 mass parts is more preferable.

  Next, the antioxidant (E) used in the present invention will be described.

  Examples of the antioxidant (E) include hindered phenolic compounds (primary antioxidants) that capture radicals generated by thermal degradation, and phosphorus-based and sulfur-based compounds that decompose peroxides generated by thermal degradation ( Secondary antioxidants) and the like, and these may be used alone or in combination of two or more.

Examples of the hindered phenol compound include triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4hydroxyphenyl) propionate] (trade name: IRGANOX (registered trademark) 245 (BASF Japan). ), Pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name: IRGANOX (registered trademark) 1010 (manufactured by BASF Japan Ltd.)), Octadecyl [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name: IRGANOX (registered trademark) 1076 (manufactured by BASF Japan Ltd.)), thiodiethylene bis [3- (3 5-Di-tert-butyl-4-hydroxyphenyl) propionate (Trade name: IRGANOX (registered trade mark) 1035 (BASF Japan Ltd.), benzenepropanoic acid 3,5-bis (1,1-dimethylethyl) -4-hydroxy -C ₇ -C ₉ side chain alkyl Ester (trade name: IRGANOX (registered trademark) 1135 (manufactured by BASF Japan Ltd.)), 4,6-bis (dodecylthiomethyl) -o-cresol (trade name: IRGANOX (registered trademark) 1726 (BASF Japan Ltd.) )), Reaction product of N-phenylbenzenamine and 2,4,4-trimethylpentene (trade name: IRGANOX (registered trademark) 5057 (manufactured by BASF Japan Ltd.)), 2-t-butyl-6 -(3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate (trade name: Sumilizer ( Registered trademark) GM (manufactured by Sumitomo Chemical Co., Ltd.)), 3,9-bis [2- [3- (t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] 2,4,8,10-tetraoxaspiro [5.5] undecane (trade name: Sumilizer (registered trademark) GA-80 (manufactured by Sumitomo Chemical Co., Ltd.)), 2,6-di-tert-butyl-4 -Methylphenol (trade name: NOCRACK 200 (manufactured by Ouchi Shinsei Chemical Co., Ltd.)), 2,2'-methylenebis (4-methyl-6-tert-butylphenol) (trade name: NOCRACK NS-6 (Ouchi) Shinsei Chemical Industry Co., Ltd.)), 2,5-di-tert-amylhydroquinone (trade name: NOCRACK DAH (Ouchi Shinsei Chemical Industry Co., Ltd.)), and the like.

  Examples of the phosphorus compound include triphenylphosphine, bis (2,4-di-tert-butyl-6-methylphenyl) = ethyl phosphite, triphenyl phosphite, trisnonylphenyl phosphite, tris (2 , 4-Dibutylphenyl) phosphite, Tris (2,4-dibutyl-5-methylphenyl) phosphite, Tris [2-tert-butyl-4- (3-butyl-4-hydroxy-5-methylphenylthio) -5-methylphenyl] phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tridecylphosphite, octyldiphenylphosphite, di (decyl) monophenylphosphite, di (tridecyl) pentaerythritol Diphosphite, di (nonylphenyl) pentaerythritol Rudiphosphite, bis (2,4-dibutylphenyl) pentaerythritol diphosphite, bis (2,6-dibutyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,4,6-tributylphenyl) penta Erythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, tetra (tridecyl) isopropylidenediphenol diphosphite, tetra (tridecyl) -4,4′-n-butylidenebis (2-butyl) -5-methylphenol) diphosphite, hexa (tridecyl) -1,1,3-tris (2-methyl-4-hydroxy-5-butylphenyl) butanetriphosphite, tetrakis (2,4-dibutylphenyl) biphenylene diphospho Knight, 9,10- Hydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2,2′-methylenebis (4,6-butylphenyl) -2-ethylhexyl phosphite, 2,2′-methylenebis (4,6- Butylphenyl) -octadecylphosphite, 2,2′-ethylidenebis (4,6-dibutylphenyl) fluorophosphite, tris (2-[(2,4,8,10-tetrakisbutyldibenzo [d, f] [ 1,3,2] dioxaphosphin-6-yl) oxy] ethyl) amine, 2-ethyl-2-butylpropylene glycol and 2,4,6-tributylphenol phosphite.

  Examples of the sulfur compound include didodecyl-3,3′-thiopropionate, dilauryl-3,3′-thiodipropionate, laurylthiodithionate, ditridecyl-3,3′-thiodipropionate. , Dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, tetrakis-methylene-3-laurylthiopropionate methane, distearyl-3,3′-methyl-3 , 3′-thiodipropionate, laurylstearyl-3,3′-thiodipropionate, bis [2-methyl-4- (3-n-alkylthiopropionyloxy) -5-tert-butylphenyl] sulfide, β -Laurylthiopropionate, 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzoy Imidazole, dioctadecyl 3,3'-thiodipropionate isethionate, and the like.

  Among these, it is preferable to use a phosphorus compound from the viewpoints of maintaining both excellent adhesive strength and holding power and further improving the yellowing resistance after heat exposure. (2,4-di-tert-butyl-6-methylphenyl) = one or more antioxidants selected from the group consisting of ethyl phosphite and tris (2,4-di-tert-butylphenyl) phosphite It is more preferable to use triphenylphosphine and bis (2,4-di-tert-butyl-6-methylphenyl) = ethyl = phosphite.

  As the usage-amount of the said antioxidant (E), it is essential that mass ratio [(D) / (E)] with the said light stabilizer (D) is the range of 95 / 5-5 / 95. If it exceeds the above range, the desired yellowing resistance cannot be obtained. The mass ratio is more preferably in the range of 80/20 to 20/80, and still more preferably in the range of 70/30 to 30/70, from the viewpoint that heat yellowing resistance and light yellowing resistance can be further improved.

  Next, the ultraviolet curable adhesive resin composition of the present invention will be described.

  The resin composition for an ultraviolet curable pressure-sensitive adhesive according to the present invention is, for example, a urethane (meth) acrylate resin (A) produced alone, and then a (meth) acrylic monomer (B), a photopolymerization initiator (C). , A method of mixing the light stabilizer (D) and the antioxidant (E), or in the presence of a part or all of the (meth) acrylic monomer (B), the urethane (meth) acrylate resin (A) And a polymerization initiator (C), a light stabilizer (D) and an antioxidant (E) are mixed.

  The ultraviolet curable pressure-sensitive adhesive resin composition obtained by the above method is not particularly limited, but from the viewpoint of good coating properties and good handling of the pressure-sensitive adhesive solution during coating, 500 to 20,000 mPa · s. The range of 1,000 to 15,000 mPa · s is more preferable, and the range of 5,000 to 10,000 mPa · s is more preferable in order to further improve the step following ability. In addition, the said viscosity shows the value measured with the B-type viscometer at 25 degreeC.

  Moreover, the resin composition for ultraviolet curable adhesives of this invention may contain another additive other than what was mentioned above.

  Examples of the other additives include rust preventives, thixotropic agents, sensitizers, polymerization inhibitors, curing agents, curing accelerators, leveling agents, tackifiers, waxes, heat stabilizers, antistatic agents, Flame retardants, foam stabilizers, antifoaming agents, preservatives, antiblocking agents, silane coupling agents, and the like can be used.

  Moreover, the resin composition for ultraviolet curable adhesives of this invention is the said urethane (meth) acrylate resin (A), the said (meth) acryl monomer (B), the said photoinitiator (C), light stability. The agent (D), the antioxidant (E), and, if necessary, the other additives may be dissolved or dispersed in a solvent such as an organic solvent or an aqueous medium. A laminate is produced by laminating a base material that the urethane (meth) acrylate resin (A), the photopolymerization initiator (C), etc. are dissolved or dispersed in the acrylic monomer (B). In this case, a process for removing the solvent contained in the pressure-sensitive adhesive is not necessary, and the production efficiency of the laminate can be improved.

  The ultraviolet curable pressure-sensitive adhesive resin composition of the present invention can be cured by irradiation with energy rays such as ultraviolet rays.

  As a method for curing the ultraviolet curable adhesive resin composition of the present invention, for example, a known ultraviolet light irradiation device such as a xenon lamp, a xenon-mercury lamp, a metal halide lamp, a high pressure mercury lamp, a low pressure mercury lamp, or the like is used. It can be cured by irradiating with predetermined ultraviolet rays.

The ultraviolet irradiation is preferably in the range of 0.05 to 5 J / cm ² , more preferably 0.1 to 3 J / cm ² , and particularly preferably 0.3 to 1.5 J / cm ² . In addition, the ultraviolet irradiation amount was based on a value measured with an illuminance meter “UV Power Pack PP2000” (UV-A (320 to 390 nm)) manufactured by EIT.

  Moreover, when the resin composition for ultraviolet curable adhesives of this invention contains the said other additive, as needed, by heating at about 40-80 degreeC after the said ultraviolet irradiation, Curing may be further accelerated.

  As a base material which can apply the resin composition for UV curable pressure sensitive adhesive of the present invention to form a pressure sensitive adhesive layer, a plastic base material, a flexible printed base material, a glass base material, and ITO are deposited on these base materials. And the like.

As said plastic base material, the base material and PC which consist of generally used acrylic resin etc.
(Polycarbonate), PBT (polybutylene terephthalate), PPS (polyphenylene sulfide), modified PPE (polyphenylene ether), PET (polyethylene terephthalate), COP (cycloolefin polymer), TAC (triacetyl cellulose), antireflection film or sheet, Examples thereof include an antifouling film or sheet, and a film or sheet of a transparent conductive film constituting the touch panel.

  Hereinafter, the present invention will be specifically described by way of examples.

[Synthesis Example 1]
<Synthesis of urethane acrylate resin (A-1)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 706 parts by mass of polycarbonate polyol (“Duranate T5652”, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight; 2,000), 1,4-butane 8.0 parts by mass of diol, 13.6 parts by mass of 2-hydroxyethyl acrylate, 2 parts by mass of 2,6-di-tert-butyl-cresol, and 0.3 parts by mass of p-methoxyphenol were added. After raising the temperature in the reaction vessel to 40 ° C., 97 parts by mass of isophorone diisocyanate was added. Therefore, 0.1 part by mass of dioctyltin dineodecanate was added, and the temperature was raised to 80 ° C. over 1 hour. Then, after hold | maintaining at 80 degreeC for 12 hours and confirming that all the isocyanate groups have lose | disappeared, it cooled and obtained urethane acrylate resin (A-1). The obtained urethane acrylate resin (A-1) has an acryloyl group equivalent of 7039 (rounded off after the decimal point. The molecular weight of 2-hydroxyethyl acrylate is 116.1. The same applies hereinafter) and the weight average molecular weight is 22,000. there were.

[Synthesis Example 2]
<Synthesis of urethane acrylate resin (A-2)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 460 parts by mass of polytetramethylene glycol (number average molecular weight; 1,000), 6.5 parts by mass of 2-hydroxyethyl acrylate, 2, 2 parts by mass of 6-di-tert-butyl-cresol and 0.3 parts by mass of p-methoxyphenol were added. After raising the temperature in the reaction vessel to 40 ° C., 105 parts by mass of isophorone diisocyanate was added. Therefore, 0.1 part by mass of dioctyltin dineodecanate was added, and the temperature was raised to 80 ° C. over 1 hour. Then, after hold | maintaining at 80 degreeC for 12 hours and confirming that all the isocyanate groups have lose | disappeared, it cooled and obtained urethane acrylate resin (A-2). The obtained urethane acrylate resin (A-2) had an acryloyl group equivalent of 10,208 and a weight average molecular weight of 26,000.

[Synthesis Example 3]
<Synthesis of urethane acrylate resin (A-3)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 465 parts by mass of polycarbonate polyol (“DURANATE T5651”, manufactured by Asahi Kasei Chemicals Corporation, number average molecular weight; 1,000), 2-hydroxyethyl acrylate 9.5 parts by mass, 2 parts by mass of 2,6-ditertiarybutyl-cresol, and 0.3 parts by mass of p-methoxyphenol were added. After raising the temperature in the reaction vessel to 40 ° C., 102 parts by mass of isophorone diisocyanate was added. Therefore, 0.1 part by mass of dioctyltin dineodecanate was added, and the temperature was raised to 80 ° C. over 1 hour. Then, after hold | maintaining at 80 degreeC for 12 hours and confirming that all the isocyanate groups have lose | disappeared, it cooled and obtained urethane acrylate resin (A-3). The obtained urethane acrylate resin (A-3) had an acryloyl group equivalent of 7,045 and a weight average molecular weight of 20,000.

[Synthesis Example 4]
<Synthesis of urethane acrylate resin (A-4)>
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 470 parts by mass of polytetramethylene glycol (number average molecular weight; 1,000), 9.5 parts by mass of 2-hydroxyethyl acrylate, 2, 2 parts by mass of 6-di-tert-butyl-cresol and 0.3 parts by mass of p-methoxyphenol were added. After raising the temperature in the reaction vessel to 40 ° C., 102 parts by mass of isophorone diisocyanate was added. Therefore, 0.1 part by mass of dioctyltin dineodecanate was added, and the temperature was raised to 80 ° C. over 1 hour. Then, after hold | maintaining at 80 degreeC for 12 hours and confirming that all the isocyanate groups have lose | disappeared, it cooled and obtained urethane acrylate resin (A-4). The obtained urethane acrylate resin (A-4) had an acryloyl group equivalent of 7,107 and a weight average molecular weight of 19,000.

[Example 1]
In a container equipped with a stirrer, a reflux condenser, and a thermometer, 100 parts by mass of the urethane acrylate resin (A-1) synthesized by the above-described method, 70 parts by mass of butyl acrylate, and 35 parts by mass of cyclohexyl acrylate were heated to an internal temperature of 80. Added at 0 ° C. and stirred until uniform. Thereafter, the mixture was cooled to room temperature, and 4 parts by mass of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 0.5 mass of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate were stirred with stirring. And 1.5 parts by mass of triphenylphosphine were added and stirred until uniform. Thereafter, the mixture was filtered through a 200 mesh wire mesh to obtain an ultraviolet curable adhesive resin composition.

[Examples 2-4 , Reference Examples 1-2 , Comparative Examples 1-2]
Table 1 shows the types of urethane acrylate resins used, types and amounts of (meth) acrylic monomers, amounts of photopolymerization initiators, types and amounts of light stabilizers, and types and amounts of antioxidants. Except that, an ultraviolet curable adhesive resin composition was obtained in the same manner as in Example 1.

[Method for measuring weight average molecular weight]
The weight average molecular weights of the polyol and urethane acrylate resin used in Examples and / or Comparative Examples were measured by gel permeation chromatography (GPC) method under the following conditions.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series.
"TSKgel G5000" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection amount: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4 mass%)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

[Method for producing adhesive film]
For UV curable adhesives obtained in Examples and Comparative Examples so that the film thickness after the UV irradiation is 175 μm on the surface of a 50 μm-thick polyethylene terephthalate film (release PET 50) having a release treatment on the surface The resin composition was applied, and release PET50 was bonded. Thereafter, UV irradiation was performed with a UV irradiation apparatus so that the integrated light quantity of the wavelength in the UV-A region after passing through the release PET 50 was 1 J / cm ² , thereby producing an adhesive film.

[Measurement method of adhesive strength]
One side of the pressure-sensitive adhesive film prepared by the above-described method was bonded to a 75 μm-thick polyethylene terephthalate film (PET75), and a pressure-sensitive adhesive film having a PET75 substrate bonded to one side was prepared. What cut this into 25 mm width was made into the test piece. The test piece was attached to a glass plate and a polycarbonate (PC) plate, which are adherends, by 2 kg rolls × 2 reciprocations. One hour after pasting, the 180 ° peel strength was measured in an atmosphere of 23 ° C. and 50% RH to obtain adhesive strength.

[Method of measuring holding force]
A test piece prepared in the same manner as the test piece used in the method for measuring the adhesive strength was laminated on a mirror-finished stainless steel plate so that the adhesion area was 25 mm × 25 mm, and the atmosphere was 23 ° C. and 50% RH. They were pasted together by reciprocating 2 kg rolls twice.
Next, under an atmosphere of 70 ° C., a load of 500 g is applied to the test piece attached to the stainless steel plate in a 0 ° direction (shear direction) with respect to the stainless steel plate until the test piece slips off the stainless steel plate. Was measured and the holding time was defined as holding power.

[Measurement method of initial yellowing degree (b *)]
A test piece was prepared by sticking the pressure-sensitive adhesive film prepared by the above-described method to a glass plate and further peeling off another release PET50. The initial yellowing degree (B *) of the test piece was measured according to JIS K 7105 with a light source C, a visual field of 2 °, and a “spectral colorimeter” CM-5000d (manufactured by Konica Minolta Sensing).

[Measurement method of light yellowing resistance (b * (UV))]
A test piece was prepared by sticking the pressure-sensitive adhesive film prepared by the above-described method to a glass plate and further peeling off another release PET50. The test piece was allowed to stand for 250 hours and 500 hours in an ultraviolet carbon arc lamp, a black panel temperature of 63 ° C., and an ultraviolet fade meter “U48AU” (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS A 1415. Thereafter, the light yellowing resistance (b * (UV)) was measured according to JIS K 7105 in the same manner as described above.

[Heat resistant yellowing (b * (heat) measurement method)]
The pressure-sensitive adhesive film prepared by the method described above was attached to a glass plate and left in an atmosphere of 85 ° C. × 85% RH for 250 hours and 500 hours. Thereafter, another release PET 50 was peeled off, and the heat-resistant yellowing degree (b * (heat)) was measured according to JIS K 7105 in the same manner as described above.

The translated words in Table 1 will be described.
BA; butyl acrylate ACMO; acryloylmorpholine DMAA; dimethylacrylamide CHA; cyclohexyl C-1; 2,4,6-trimethylbenzoyldiphenylphosphine oxide C-2; 2-hydroxy-2-methyl-1-phenyl Propan-1-one Tinuvin765; bis (1,2,2,6,6-pentamethyl-4-piperidyl) = decandioate Tinuvin123; decandioic acid bis (2,2,6,6-tetramethyl-1- ( Octyloxy) -4-piperidinyl) ester Tinuvin 622LD; dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate TPP; triphenylphosphine Irgafos38; bis (2 4-di -tert- butyl-6-methylphenyl) = ethyl = phosphite Irganox 1035; 2,2'-thio-diethyl-bis [3- (3,5-di -tert- butyl-4-hydroxyphenyl) propionate]

  It was found that the pressure-sensitive adhesive obtained using the resin composition for ultraviolet curable pressure-sensitive adhesive of the present invention is excellent in adhesive strength, initial yellowing resistance, light yellowing resistance, and heat yellowing resistance.

  On the other hand, Comparative Example 1 was an embodiment containing no antioxidant, but it was found that light yellowing resistance and heat yellowing resistance were particularly poor.

  Moreover, although the comparative example 2 is an aspect which does not contain a light-resistant stabilizer, it turned out that especially light yellowing resistance and heat yellowing resistance are unsatisfactory.

Claims (3)

Urethane (meth) acrylate resin (A), (meth) acrylic monomer (B) obtained by reacting polyol (a), polyisocyanate (b) and (meth) acrylic compound (c) having a hydroxyl group, and an ultraviolet-curable pressure-sensitive adhesive resin composition containing a photopolymerization initiator (C), and further a light stabilizer (D) and bis (1,2,2,6,6-pentamethyl-4-piperidyl ) = decane Geo and art, with triphenylphosphine or bis as an antioxidant (E) (2,4-di -tert- butyl-6-methylphenyl) = ethyl = mass ratio and phosphite, 95 / It contains in 5-5 / 95, The resin composition for ultraviolet curable adhesives characterized by the above-mentioned. The resin composition for an ultraviolet curable adhesive according to claim 1, wherein a mass ratio of the light stabilizer (D) to the antioxidant (E) is in a range of 70/30 to 30/70. A pressure-sensitive adhesive obtained by using the resin composition for an ultraviolet curable pressure-sensitive adhesive according to claim 1 or 2 .