JP6024748B2 - UV-curable adhesive composition and adhesive layer - Google Patents

Description

  The present invention relates to an ultraviolet curable pressure-sensitive adhesive composition and an adhesive layer.

  In recent years, liquid crystal display devices have been widely used for display devices such as on-vehicle devices, outdoor instruments, displays such as personal computers, and televisions, and the demand for them has been increasing. It is increasing. Recently, in particular, there are ATMs of financial institutions such as banks, vending machines, mobile phones, personal digital assistants, digital audio players, portable game machines, electronic dictionaries, photocopiers, fax machines, car navigation systems and other digital information equipment. A touch panel using a liquid crystal display device is often used.

  The touch panel is an electronic component that combines a display device and a position input device, displays image information received from the outside on a liquid crystal display, senses touched screen position information, and outputs the information to the outside as an information signal. It has a function. The touch panel position input device mainly has a control method such as a resistance film method, a capacitance method, an electromagnetic induction method, an optical method, and an acoustic method, and in particular, a resistance film method and a capacitance method are generally controlled. It has become a method.

  The above resistive film type and capacitive type touch panel is a display device such as a front-surface protective film, a film provided with a transparent conductive layer such as glass and indium oxide (hereinafter referred to as “ITO”) film, glass, liquid crystal, etc. And other functional sheets. Among these, a film, glass, and a functional sheet are usually bonded together with an optical pressure-sensitive adhesive.

  As described above, the optical pressure-sensitive adhesive used for touch panel applications is a laminate of the frontmost protective film or glass and a film or glass provided with a transparent conductive layer, a film or glass provided with a transparent conductive layer, and liquid crystal. Since it is used for bonding with a display device, optical performance such as transparency and weather resistance is required.

  As such an optical pressure-sensitive adhesive, an optical pressure-sensitive adhesive composition comprising various high molecular weight acrylic polymers and various crosslinking agents has been proposed (see Patent Documents 1 and 2).

  On the other hand, recently, a thick adhesive layer of 100 μm or more has been demanded in order to improve the impact resistance of the touch panel, absorb the printing step of the frontmost protective film or glass, and the like. Such a thick film (having a thickness of 100 μm or more) can be obtained by forming a pressure-sensitive adhesive layer having a thickness of 25 μm or 50 μm from the optical pressure-sensitive adhesive composition and laminating them. However, this method has problems such as high cost due to the large number of steps and low transparency due to bonding. On the other hand, if an adhesive layer having a thickness of 100 μm or more is formed by a single coating, foaming occurs when the coating solvent dries, and bubbles are generated in the coating film, thus satisfying optical performance. There was no problem.

  As a method for obtaining a pressure-sensitive adhesive layer having a thickness of 100 μm or more by one coating without foaming, use of a solventless pressure-sensitive adhesive composition can be considered. As a solventless pressure-sensitive adhesive composition, an ultraviolet curable solventless pressure-sensitive adhesive composition containing various (meth) acrylate oligomers or (meth) acrylate monomers has been proposed (see Patent Document 3).

  However, with the above solvent-free pressure-sensitive adhesive composition, transparency, adhesive strength, durability under heating and humidification conditions, and adhesive performance such as adhesive remains at the time of peeling when misalignment occurs during bonding. There was a problem.

JP 2011-195651 A JP 2011-225835 A JP-T-2005-530024

  The present invention is a solvent-free optical pressure-sensitive adhesive composition used for touch panels and the like, and can form a thick-film pressure-sensitive adhesive layer by a single coating, and has transparency, adhesive strength, heating and humidification. The main object is to provide an ultraviolet curable optical pressure-sensitive adhesive composition that is excellent in durability under conditions and that can be peeled off after bonding without adhesive residue.

  As a result of intensive studies, the inventors of the present invention have adjusted the solvent content to less than 1% by weight, the viscosity at 25 ° C. to 100 to 10,000 mPa · s, and the color tone to Gardner color 1 or less in the ultraviolet curable pressure-sensitive adhesive composition. And (A) a polyfunctional urethane (meth) acrylate oligomer having a weight average molecular weight (polystyrene conversion value by gel permeation chromatography, the same applies hereinafter) of 10,000 to 100,000, (B) a tackifier, It has been found that the above problem can be solved by blending C) a monofunctional epoxy ester (meth) acrylate and (D) a photopolymerization initiator.

  Moreover, the present inventors have also found that an adhesive layer capable of solving the above problems can be provided by using the above-mentioned adhesive composition.

That is, the present invention relates to the following ultraviolet curable pressure-sensitive adhesive composition and pressure-sensitive adhesive layer.
1. Ultraviolet curable, having a solvent content of less than 1% by weight, a viscosity at 25 ° C. of 100 to 10,000 mPa · s, a color tone of Gardner color 1 or less, and the following (A) to (D) Adhesive composition.
(A) Polyfunctional urethane (meth) acrylate oligomer having a weight average molecular weight of 10,000 to 100,000 (B) Tackifier (C) Monofunctional epoxy ester (meth) acrylate (D) Photopolymerization initiator Item 2. The component (A) is a polyfunctional urethane (meth) acrylate oligomer obtained by reacting a polyether polyol, polyisocyanate, and a hydroxyl group-containing (meth) acrylate or isocyanato group-containing (meth) acrylate. UV curable adhesive composition.
3. Item 3. The ultraviolet curable pressure-sensitive adhesive composition according to Item 1 or 2, wherein the component (B) is a tackifier having a color tone of Gardner color 1 or less.
4). The components (A) to (D) are in the pressure-sensitive adhesive composition based on parts by weight, and (A) :( B) :( C) :( D) = 10 to 60: 0.5 to 15:15. Item 89.4: The ultraviolet curable pressure-sensitive adhesive composition according to any one of Items 1 to 3, which is blended at a ratio of 0.1 to 10.
5). 5. An adhesive layer obtained by curing the ultraviolet curable adhesive composition according to any one of items 1 to 4.
6). 6. The pressure-sensitive adhesive layer according to item 5, wherein the pressure-sensitive adhesive layer has a thickness of 10 to 1000 μm.

  The pressure-sensitive adhesive composition of the present invention can be used for touch panels, plasma display panels, and the like, and since it is solventless, it is not necessary to dry the solvent, and it is possible to form a thick film pressure-sensitive adhesive layer by a single coating. . Moreover, the pressure-sensitive adhesive composition of the present invention is excellent in transparency, adhesive strength, durability under heating and humidification conditions, and can be peeled off without any adhesive residue after being bonded together. Therefore, the pressure-sensitive adhesive layer of the present invention formed from the pressure-sensitive adhesive composition is excellent in pressure-sensitive adhesiveness, transparency and durability, and is suitable as a pressure-sensitive adhesive layer used for touch panels, plasma display panels and the like.

  The present invention has a solvent content of less than 1% by weight, a viscosity at 25 ° C. of 100 to 10,000 mPa · s, a color tone of Gardner color 1 or less, and (A) a weight average molecular weight of 10,000 to 100,000. Polyfunctional urethane (meth) acrylate oligomer (hereinafter also referred to as “component (A)”), (B) tackifier (hereinafter also referred to as “component (B)”), (C) monofunctional epoxy ester ( An ultraviolet curable pressure-sensitive adhesive composition containing a (meth) acrylate (hereinafter also referred to as “component (C)”) and (D) a photopolymerization initiator (hereinafter also referred to as “(D) component”).

  When the solvent content is 1% by weight or more, when a thick film (thickness of 100 μm or more) adhesive layer is formed, the coating solvent is dried and foamed when cured, and bubbles are generated in the coating film. There is a problem.

  When the viscosity is out of the range of 100 to 10,000 mPa · s, it is difficult to form a thick adhesive layer at a normal temperature and normal pressure by a single coating.

  By setting the color tone of the pressure-sensitive adhesive composition to 1 or less in Gardner color, an adhesive layer excellent in transparency and color tone can be formed.

  The adhesive force of an adhesion layer can be improved by making the weight average molecular weight of the said (A) component or more into 10,000. Moreover, the viscosity of a polyfunctional urethane (meth) acrylate oligomer can be made low because the weight average molecular weight of (A) component shall be 100,000 or less, and the handleability of an adhesive improves.

  The said (A) component is obtained by reaction of a polyol, polyisocyanate, and a hydroxyl-containing (meth) acrylate or isocyanato group containing (meth) acrylate.

  There is no restriction | limiting in particular as said polyol, Polyether polyols, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and these copolymers; Polycondensate of adipic acid and polyhydric alcohol, Sebacic acid and polyhydric acid Polyester polyols such as polycondensates of alcohols, polycondensates of phthalic acid and polyhydric alcohols, polyaddition products obtained by ring-opening reaction of lactones and polyhydric alcohols; 1,3-propanediol, 1 Polycarbonate polyols obtained by reaction of diols such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, cyclohexanedimethanol and phosgene; polyolefin polyols such as polybutadienediol and hydrogenated polybutadienepolyol Etc. It is. These may be used alone or in combination. Of these, the use of polyether polyols is preferred from the viewpoints of lowering the viscosity of the pressure-sensitive adhesive and increasing the adhesive strength of the pressure-sensitive adhesive layer.

  As the polyisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylene diisocyanate, diphenylmethane-4,4-diisocyanate, 3-methyl-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate Aromatic diisocyanate compounds such as dicyclohexylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate and the like; and dimer and hexamer thereof. These may be used alone or in combination. Among these, the use of aliphatic diisocyanates is preferable from the viewpoints of lowering the viscosity of the pressure-sensitive adhesive, high adhesive strength of the pressure-sensitive adhesive layer, and durability.

  A terminal hydroxyl group-containing urethane prepolymer obtained by reacting a hydroxyl group-containing (meth) acrylate with a terminal isocyanato group-containing urethane prepolymer obtained by reacting the polyol and polyisocyanate, or by reacting the polyol and polyisocyanate. A polyfunctional urethane (meth) acrylate oligomer is obtained by reacting an isocyanato group-containing (meth) acrylate with the polymer.

  Examples of the hydroxyl group-containing (meth) acrylate include monofunctional compounds such as 2-hydroxy (meth) acrylate, hydroxypropyl (meth) acrylate, 4-hydroxy (meth) acrylate, and 2-hydroxy-2-methylpropyl (meth) acrylate ( (Meth) acrylates; polyfunctional (meth) acrylates such as pentaerythritol triacrylate and dipentaerythritol pentaacrylate; and epoxy ester (meth) acrylates obtained by reacting an epoxy compound with (meth) acrylic acid. These may be used alone or in combination.

  Examples of the isocyanato group-containing (meth) acrylate include 2-isocyanatoethyl (meth) acrylate and 1,1- (bisacryloyloxymethyl) ethyl isocyanate. These may be used alone or in combination.

  The average functional group number of the polyfunctional urethane (meth) acrylate oligomer is at least 1.5, preferably 1.8 or more. The average number of functional groups of the urethane (meth) acrylate oligomer is a number indicating how many acryloyl groups exist on average in one molecule of the urethane (meth) acrylate oligomer. When synthesizing the urethane (meth) acrylate oligomer, the average functional group number of the urethane (meth) acrylate oligomer is controlled by controlling the reaction equivalent of the hydroxyl group-containing (meth) acrylate compound or the isocyanato group-containing (meth) acrylate compound. be able to. By using a urethane (meth) acrylate oligomer having an average functional group number of 1.5 or more, an optical pressure-sensitive adhesive having excellent durability can be obtained.

  The component (B) is a tackifier. Specific examples of the component (B) include petroleum resins, phenol resins, xylene resins, coumarone resins, rosin resins, terpene resins, hydrogenated petroleum resins, hydrogenated rosin resins, hydrogenated terpene resins, and the like. It is done. Among them, a color tone having a Gardner color of 1 or less is preferable. Examples of the color tone having a Gardner color of 1 or less include hydrogenated petroleum resins and hydrogenated rosin resins. These hydrogenated resins are usually tackifiers having excellent transparency because the color tone is Gardner color 1 or less, and improve the transparency of the optical pressure-sensitive adhesive and the pressure-sensitive adhesive layer. Furthermore, since these hydrogenated resins have little polymerization inhibition during polymerization due to ultraviolet irradiation, the use of these hydrogenated resins provides an optical pressure-sensitive adhesive having excellent curability.

  The hydrogenated rosin resin is not particularly limited as long as it is a hydrogenated rosin resin, and known resins can be used. As the rosin resin, for example, natural rosins such as gum rosin, tall oil rosin, and wood rosin, as well as natural rosins are processed by at least one method selected from polymerization, modification, disproportionation, and esterification. And rosin metal salts obtained by reacting natural rosins or processed rosins with metals such as calcium, magnesium, zinc, and the like.

  The manufacturing method of the rosins processed by the polymerization method among the processed rosins (hereinafter also referred to as “polymerized rosin”) is not particularly limited, and a known method can be employed. For example, there is a method in which the natural rosins or rosins obtained by processing natural rosins by at least one method selected from modification, disproportionation, and esterification is heated using a polymerization catalyst. It does not specifically limit as a polymerization catalyst, A well-known thing can be used. Specific examples of the polymerization catalyst include acids such as sulfuric acid, phosphoric acid, and hydrofluoric acid; and metal halides such as boron fluoride, aluminum chloride, and zinc chloride.

  A method for producing rosins processed by the above-described modification method (hereinafter also referred to as “modified rosin”) is not particularly limited, and a known method may be employed. Usually, a method in which natural rosins and phenols or unsaturated acids are mixed and heated is used. The phenols are not particularly limited, and specific examples include phenol and alkylphenol. The unsaturated acid is not particularly limited, and specific examples include fumaric acid, maleic acid, (meth) acrylic acid and the like.

  The production method of rosins processed by the above disproportionation method (hereinafter also referred to as “disproportionation rosin”) is not particularly limited, and a known method may be adopted. Usually, natural rosins or processed rosins are saponified by reacting them at 220 to 250 ° C. for 2 to 6 hours without adding hydrogen in the presence of a reduction catalyst such as nickel, platinum or palladium or a carbon catalyst. It is done.

  The production method of rosins processed by the above esterification method (hereinafter also referred to as “rosin ester”) is not particularly limited, and a known method can be adopted. Usually, natural rosins or processed rosins and alcohol are mixed and heated in the presence of an esterification catalyst as necessary. Examples of esterification catalysts include acid catalysts such as acetic acid and paratoluenesulfonic acid, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkaline earth such as calcium hydroxide and magnesium hydroxide. Metal oxides such as calcium oxide, magnesium oxide, zinc oxide, lead oxide and tin oxide can be used.

  Examples of the alcohol include aliphatic monovalent or polyhydric alcohols having 1 to 20 carbon atoms. Examples of such alcohols include monohydric alcohols such as methanol, ethanol, isopropyl alcohol, isoamyl alcohol, n-hexyl alcohol, 2-ethylhexyl alcohol, n-octyl alcohol, dodecyl alcohol, lauryl alcohol, stearyl alcohol, and dihydroabiethyl alcohol. Divalent alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and neopentyl glycol; trivalent alcohols such as glycerin, trimethylolethane, and trimethylolpropane; and tetrahydric alcohols such as pentaerythritol and diglycerin.

  One of these rosin resins may be used alone, or two or more thereof may be mixed and used. In addition, natural rosins and the like can be processed using two or more methods among polymerization, modification, disproportionation, and esterification. In the case of producing a rosin resin through two or more methods, the order of the methods is not particularly limited and can be a known method. For example, it may be polymerized after modifying natural rosins or processed rosins, or esterified after polymerization.

  The hydrogenated petroleum resin as the component (B) is not particularly limited as long as it is a hydrogenated petroleum resin, and known ones can be used. Petroleum resins are roughly classified into aliphatic petroleum resins, aromatic petroleum resins, and dicyclopentadiene petroleum resins, for example, depending on the type of raw material monomer (fraction). Examples of the aliphatic petroleum resins include C5 petroleum resins and C5-C9 petroleum resins. Aromatic petroleum resins include C9 petroleum resins. The C5 petroleum resin is obtained by cationic polymerization of a C5 petroleum fraction (for example, pentene, methylbutene, isoprene, cyclopentene, etc.). Although it does not specifically limit as C9 type | system | group petroleum resin, Generally, it obtained by cationic polymerization of C9 type | system | group petroleum fraction (for example, styrene, vinyl toluene, alpha-methyl styrene, indene etc.) obtained by cracking of naphtha. Things can be used. The C5-C9 petroleum resin is obtained by copolymerizing the C5 petroleum fraction and the C9 petroleum fraction in the same manner as in the production of the C5 petroleum resin. The dicyclopentadiene-based petroleum resin is obtained by thermal polymerization or cationic polymerization of dicyclopentadiene. These petroleum resins may be modified with polar groups such as hydroxyl groups and ester groups by a generally known method. The color tone of petroleum resin is usually about 5 to 15 Gardner.

  The component (C) is a monofunctional epoxy ester (meth) acrylate obtained by reacting a monofunctional epoxy compound with (meth) acrylic acid, and various known ones can be used without particular limitation. As the component (C), specifically, monofunctional epoxy ester (meth) acrylate obtained by reacting phenylglycidyl ether and (meth) acrylic acid, (methylphenyl) glycidyl ether and (meth) acrylic acid. It has an aromatic structure such as monofunctional epoxy ester (meth) acrylate obtained by reacting, (t-butylphenyl) glycidyl ether and monofunctional epoxy ester (meth) acrylate obtained by reacting (meth) acrylic acid. (Meth) acrylate; (ethylhexyl) glycidyl ether having an alkyl group having 1 to 30 carbon atoms such as monofunctional epoxy ester (meth) acrylate obtained by reacting methyl (meth) acrylate and (meth) acrylic acid ( And (meth) acrylate. Among these, the monofunctional epoxy ester (meth) acrylate having an aromatic structure is preferable from the viewpoint of compatibility with the urethane (meth) acrylate oligomer and the tackifier.

  As the component (D), various known ones can be used without particular limitation as long as they are photopolymerization initiators that decompose upon irradiation with ultraviolet rays to generate radicals. Examples of the component (D) include photopolymerization initiators such as benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, and oxime ester compounds; photosensitizers such as amines and quinones. Specific compounds include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1- [4- [4- (2-hydroxy-2) -Methyl-propionyl) -benzyl] phenyl] -2-methyl-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2- (dimethylamino) -2-[(4-Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone, 2,4,6-trimethylbenzoyl-diphenyl Phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H- Pyrrol-1-yl) -phenyl) titanium, 1,2-octanedione 1- [4- (phenylthio) -2- (O-benzoyloxime)], ethanone 1- [9-ethyl-6- (2-methyl) Benzoyl) -9H-carbazol-3-yl] -1- (0-acetyloxime) and the like. These may be used alone or in combination of two or more. Among these, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide are preferable because the curability of the pressure-sensitive adhesive composition is improved. It is.

  The above components (A) to (D) are (A) :( B) :( C) :( D) = 10-60: 0.5-15: 15 based on parts by weight in the pressure-sensitive adhesive composition. It is preferable to mix | blend in the ratio of 89.4: 0.1-10. A particularly preferable blending ratio is 20 to 35: 5 to 10:30 to 70: 0.2 to 5. By adjusting the blending ratio of the component (A) within the above range, the adhesive strength of the adhesive layer can be improved and the handling property of the adhesive can be improved. By adjusting the blending ratio of the component (B) within the above range, the adhesive strength of the adhesive layer can be improved and the adhesive residue of the adhesive layer can be eliminated. By adjusting the blending ratio of the component (C) within the above range, the handling property of the pressure-sensitive adhesive can be improved, and an appropriate viscosity can be obtained. A thick-film pressure-sensitive adhesive layer can be applied once. Can be formed. By making the blending ratio of the component (D) within the above range, it is possible to prevent variations in polymerization due to irradiation of active energy rays such as ultraviolet rays, and to prevent odor caused by decomposition products of the component (D) and further cure. Coloring of objects can be prevented.

  The ultraviolet curable adhesive composition of this invention can be manufactured by mixing the said (A)-(D) component. The mixing method is not particularly limited, and the addition order of the components (A) to (D) is not limited.

  Moreover, the pressure-sensitive adhesive composition of the present invention can contain various monofunctional or polyfunctional monomers as dilution monomers within the range not impairing the effects of the present invention, if necessary.

  Specific examples of the monofunctional monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, Decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate (Meth) acrylates having an alkyl group having 1 to 30 carbon atoms such as benzoate; isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meta ) (Meth) acrylates having an alicyclic structure such as acrylate and adamantane (meth) acrylate; (meth) acrylates having an aromatic structure such as phenoxyethyl (meth) acrylate and benzyl (meth) acrylate; tetrahydrofurfuryl (meth) ) (Meth) acrylates having a heterocyclic structure such as acrylate; vinyl compounds such as styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylformamide, N-vinylpyrrolidone, N-vinylcaprolactam And the like.

  Specific examples of the polyfunctional monomer include 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1.6-hexanediol (meth) acrylate, 1,9-nonanediol di ( Di (meth) acrylate having an aliphatic structure such as (meth) acrylate; Di (meth) acrylate having an alicyclic structure such as cyclohexanedimethanol di (meth) acrylate and tricyclodecane di (meth) acrylate; Bisphenol A ethylene Di (meth) acrylates having aromatic structures such as oxide-modified di (meth) acrylate and bisphenol F ethylene oxide-modified di (meth) acrylate; trimethylolpropane tri (meth) acrylate, isocyanuric acid ethylene oxide-modified tri (meth) acrylate Rate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and a polyfunctional (meth) acrylate having three or more functional such as dipentaerythritol hexaacrylate.

  Furthermore, the pressure-sensitive adhesive composition of the present invention can contain various additives as long as the effects of the present invention are not impaired. For example, additives such as a surface conditioner, a surfactant, an ultraviolet absorber, an inorganic filler, a silane coupling agent, colloidal silica, an antifoaming agent, a wetting agent, a rust inhibitor, and a stabilizer can be contained.

  In order to make the pressure-sensitive adhesive composition of the present invention into a pressure-sensitive adhesive layer, it is preferable to employ a technique called casting film formation (cast film formation). Specifically, the adhesive composition was cast into a thin film on a protective film such as a polyethylene terephthalate film (PET film) coated with a release agent such as a silicone resin, and then the coating film was irradiated with ultraviolet rays. The pressure-sensitive adhesive layer is obtained by polymerization and curing. According to such a manufacturing method, the stress applied to the pressure-sensitive adhesive composition during film formation is small, and the formation of defects is small. Moreover, the uniformity of the film thickness of the obtained coating film becomes high.

  Examples of the ultraviolet light source include an ultraviolet irradiation device having a xenon lamp, a high-pressure mercury lamp, a metal halide lamp, and the like. In addition, conditions such as the light amount, the light source, and the conveyance speed may be adjusted as appropriate. The amount of light is usually about 80 to 160 W / cm, and the conveyance speed is usually about 5 to 50 m / min.

  The thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is usually about 10 to 1000 μm, preferably about 25 to 500 μm. By making the film thickness within this range, the impact resistance of the touch panel can be improved and the printing step on the surface can be absorbed, so it can be used as the frontmost protective film, etc. It can be.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. In the examples, “parts” means “parts by weight” unless otherwise specified.

<Synthesis of component (A)>
Synthesis example 1
(A-1) Synthesis of Component To a reaction apparatus equipped with a stirrer and a condenser, 955 parts of polypropylene glycol having a weight average molecular weight of 4,000, 34 parts of hexamethylene diisocyanate and 0.2 part of tin octylate are added, and 80 ° C. The reaction was completed by NCO measurement and it was confirmed that a urethane oligomer was formed. Then, 11 parts of 2-isocyanatoethyl methacrylate was added and the mixture was heated at 80 ° C. for 2 hours. Keep warm. The NCO measurement confirmed that the reaction was complete, and a urethane methacrylate oligomer (hereinafter referred to as “component (A-1)”) having a weight average molecular weight of 30,000 and an average functional group number of 2.0 was obtained. In addition, the said weight average molecular weight is a commercially available molecular weight measuring machine (Body product name "HLC-8220GPC", the Tosoh Corporation make; column product name "TSKGel G1000H", "TSKGel G2000H", the Tosoh Corporation make; developing solvent) Tetrahydrofuran) (hereinafter the same)

Synthesis example 2
Synthesis of component (A-2) In the same reactor as in Synthesis Example 1, 915 parts of polypropylene glycol having a weight average molecular weight of 4,000, 68 parts of isophorone diisocyanate and 0.8 part of tin octylate were added, and the temperature was raised to 80 ° C. After incubating for 2 hours, 17 parts of 2-hydroxyethyl acrylate was added, and the mixture was kept at 80 ° C. for 2 hours. The NCO measurement confirmed that the reaction was complete, and a urethane acrylate oligomer (hereinafter referred to as “component (A-2)”) having a weight average molecular weight of 25,000 and an average functional group number of 2.0 was obtained.

<Synthesis of component (B)>
Synthesis example 3
Synthesis of component (B-1) Acid value 172, softening point (measured by ring and ball method specified in JIS K 5902, the same shall apply hereinafter) 75 ° C. and color tone Add 0.3 parts by weight carbon (hereinafter referred to as “5% palladium carbon”) (water content 50%), perform disproportionation reaction with stirring at 280 ° C. for 4 hours under a nitrogen seal, and acid value 157, a disproportionated rosin having a softening point of 77 ° C. and a color tone of Gardner 8 was obtained. The disproportionated rosin was purified by distillation under a nitrogen seal under reduced pressure of 3 mmHg to obtain a purified disproportionated rosin having an acid value of 178, a softening point of 78 ° C., and a color tone Gardner 2. 500 parts of this purified disproportionated rosin is placed in a 1 L four-necked flask, heated to 180 ° C. under a nitrogen seal, added with 60 parts of glycerin at 200 ° C. with melting and stirring, then heated to 280 ° C. The esterification reaction was carried out at a temperature for 12 hours to obtain a purified disproportionated rosin ester having an acid value of 3.4, a softening point of 99 ° C., and a color tone Gardner 3. 200 parts of this purified disproportionated rosin ester and 2 parts of 5% palladium carbon (water content 50%) were charged into a 2 L shaking autoclave to remove oxygen in the system, and then the system was filled with hydrogen at 100 kg / cm. ^The mixture was heated to 255 ° C. while being pressurized to ² , and subjected to a hydrogenation reaction at the same temperature for 3.5 hours. A hydrogenated rosin ester having an acid value of 12.5, a softening point of 89.5 ° C. and a color tone Gardner of 1 or less Agent (B-1)) (hereinafter referred to as “component (B-1)”).

Synthesis example 4
Synthesis of Component (B-2) 100 parts of dicyclopentadiene, 100 parts of allyl alcohol and 80 parts of xylene were charged into an autoclave and reacted in a nitrogen atmosphere at 270 ° C. for 2 hours to obtain a polymer oil. The polymer oil was distilled under reduced pressure at 200 ° C. and 2.7 kPa for 15 minutes to remove unreacted monomer solvent and low polymer, thereby obtaining a softening point of 97.5 ° C., a color tone Gardner 8, a hydroxyl value of 210 mg KOH / g and a weight. A hydroxyl group-containing petroleum resin having an average molecular weight of 540 (polystyrene equivalent value in GPC) was obtained. 100 parts of this hydroxyl group-containing petroleum resin, 100 parts of cyclohexane, and 2.0 parts of a stabilized nickel catalyst (trade name “N-113”, manufactured by JGC Chemical Co., Ltd.) were charged into an autoclave under a high-pressure hydrogen atmosphere at a hydrogen pressure of 18 MPa. And reacted at 240 ° C. for 5 hours. After the catalyst was filtered off, it was distilled at 220 ° C. and 0.27 kPa for 30 minutes under reduced pressure to obtain a softening point of 118 ° C., a color Gardner of 1 or less, a hydroxyl value of 180 mg KOH / g, and a weight average molecular weight of 600 (polystyrene equivalent value in GPC). A hydride of a hydroxyl group-containing petroleum resin (tackifier (B-2)) (hereinafter referred to as “component (B-2)”) was obtained.

Synthesis example 5
Synthesis of Component (E-1) In a reaction apparatus similar to Synthesis Example 1, 955 parts of polypropylene glycol having a weight average molecular weight of 4,000, 34 parts of hexamethylene diisocyanate and 0.2 part of tin octylate were added, and the temperature was raised to 80 ° C. After warming and incubating for 2 hours, the reaction was completed by NCO measurement and it was confirmed that a urethane oligomer was formed. Then, 6 parts of 2-isocyanatoethyl methacrylate was added, and the mixture was kept at 80 ° C. for 2 hours. . The NCO measurement confirmed that the reaction was complete, and a urethane methacrylate oligomer (hereinafter referred to as “component (E-1)”) having a weight average molecular weight of 30,000 and an average functional group number of 1.0 was obtained.

Synthesis Example 6
Synthesis of Component (E-2) In the same reactor as in Synthesis Example 1, 955 parts of polypropylene glycol having a weight average molecular weight of 4,000, 34 parts of hexamethylene diisocyanate and 0.2 part of tin octylate were added, and the temperature was raised to 80 ° C. After heating and incubating for 2 hours, it was confirmed by NCO measurement that the reaction was complete, and a urethane oligomer having a weight average molecular weight of 30,000 and an average number of functional groups of 0 (hereinafter referred to as “component (E-2)”) )

<Preparation of pressure-sensitive adhesive composition>
Example 1
3-hydroxypropyl, which is a monofunctional epoxy ester acrylate obtained by reacting 25 parts of (A-1) component, 5 parts of (B-1) component and reacting phenylglycidyl ether and acrylic acid as (C) component 45 parts of phenyl acrylate (HPPA) (trade name “epoxy ester M-600A” manufactured by Kyoeisha Chemical Co., Ltd.), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) (D) component ( 1 part of BASF Japan Co., Ltd., trade name “Lucirin TPO”), 25 parts of isostearyl acrylate (ISTA) (ISTA, manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a dilution monomer, Prepared (Table 1). In addition, all compounding quantities are the ratios of solid content. The color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated, and the results are shown in Table 2.

Examples 2-5
About each component, the adhesive composition was prepared using the raw material shown in Table 1 by each compounding quantity. Table 2 shows the results of evaluation of the color tone Gardner color, viscosity, solvent content and compatibility of each composition obtained.

Comparative Example 1
3-hydroxy, which is a monofunctional epoxy ester acrylate obtained by reacting phenylglycidyl ether and acrylic acid as a component (C-1) without using the component (A-1), 5 parts of the component (B-1) 45 parts of propylphenyl acrylate (HPPA) (trade name “epoxy ester M-600A” manufactured by Kyoeisha Chemical Co., Ltd.), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) as component (D) 1 part of BASF Japan (trade name “Lucirin TPO”) and 50 parts of isostearyl acrylate (ISTA) (ISTA, manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a diluting monomer Was prepared. In addition, all compounding quantities are the ratios of solid content. As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 2
3-hydroxy, which is a monofunctional epoxy ester acrylate obtained by reacting 25 parts of component (A-1), no component (B-1), and reacting phenylglycidyl ether and acrylic acid as component (C) 45 parts of propylphenyl acrylate (HPPA) (trade name “epoxy ester M-600A” manufactured by Kyoeisha Chemical Co., Ltd.), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) as component (D) 1 part of BASF Japan (trade name “Lucirin TPO”) and 30 parts of isostearyl acrylate (ISTA) (ISTA, manufactured by Osaka Organic Chemical Industry Co., Ltd.) as a dilution monomer Was prepared. In addition, all compounding quantities are the ratios of solid content. As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 3
(A-1) component 95 parts, (B-1) component 5 parts, (C) component not used, (D) component 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (TPO) ) (BASF Japan Co., Ltd., trade name “Lucirin TPO”) was blended in an amount to prepare an adhesive composition. In addition, all compounding quantities are the ratios of solid content. As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 4
A monofunctional epoxy ester acrylate obtained by reacting phenylglycidyl ether and acrylic acid with 25 parts of urethane methacrylate oligomer consisting of component (A-1), 5 parts of component (B-1), and component (C). , 45 parts of 3-hydroxypropylphenyl acrylate (HPPA) (trade name “Epoxyester M-600A” manufactured by Kyoeisha Chemical Co., Ltd.), isostearyl acrylate (ISTA) as a dilution monomer without using component (D) 25 parts of Osaka Organic Chemical Industry Co., Ltd. (ISTA) was blended to prepare an adhesive composition. In addition, all compounding quantities are the ratios of solid content. As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 5
(B-1) A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the component was changed to ZEON CORPORATION, trade name Quintone 1700 (softening point 100 ° C., color tone Gardner 4) (B-3). . As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 6
(B-1) A pressure-sensitive adhesive composition in the same manner as in Example 1 except that the component was changed to Arakawa Chemical Co., Ltd., trade name Superester A100 (softening point 95 to 105 ° C., color tone Gardner 7) (B-4) Was prepared. As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 7
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the component (A-1) was replaced with the component (E-1). As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

Comparative Example 8
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the component (A-1) was replaced with the component (E-2). As in Example 1, the color tone Gardner color, viscosity, solvent content and compatibility of the obtained composition were evaluated. The results are shown in Table 2.

(Color Gardner color)
The Gardner color number was measured according to JIS K5400.

(viscosity)
The viscosity (mPa · s) of the pressure-sensitive adhesive composition was measured with an E-type viscometer (Toki Sangyo Co., Ltd. TVE-10) at 25 ° C. for 5 minutes.

(Solvent content)
The solvent content of the coating liquid was measured using a gas chromatograph apparatus.
<Analyzer>
GC: Agilent, 6850
<GC measurement conditions>
GC column: HP-1
Column temperature: 50 ° C. (10 min) → 10 ° C./min→300 (10 min)
Column flow rate: 2.0 ml / min
Carrier gas: Helium injection method: Split (50: 1)
Detection temperature: 300 ° C

(Compatibility)
The compatibility was judged based on the following criteria by visually observing the obtained pressure-sensitive adhesive composition.
○: Uniform and completely transparent.
X: It is cloudy and is completely separated and there is an insoluble matter or liquid layer separation is confirmed.

<Preparation of adhesive layer>
Examples 6-10 and Comparative Examples 9-14
The composition of Example 1 was applied on a 38 μm-thick release polyester film (manufactured by Panac Corporation, trade name “SP-PET-01-38BU”) so as to have a film thickness of 150 μm. Pre-curing was performed by passing once under a high-pressure mercury lamp (35 mJ / cm ² ). The cured product coated surface and a 38 μm thick release-treated polyester film were bonded together so that the release-treated surface was in contact, and cured by passing 4 times under high pressure mercury lamp (300 mJ / cm ² ) in the air. Example 6 An adhesive layer was obtained. The adhesive layers of Examples 7 to 10 and Comparative Examples 9 to 14 were prepared in the same manner for the compositions of Examples 2 to 5 and Comparative Examples 1, 2, 4, 6, 7, and 8. Each of the obtained adhesive layers was subjected to the following test, and the results are shown in Table 3.

[Various tests on adhesive layer]
<Adhesion test>
The prepared polyester films on one side of the pressure-sensitive adhesive layers of Examples 6 to 10 and Comparative Examples 9 to 14 were peeled off, and a 50 μm thick polyester film (trade name “COSMO SHINE A-4300” manufactured by Toyobo Co., Ltd.) Were bonded with a 2 kg roller and left for 2 hours. The remaining release-treated polyester film was peeled off, and the glass was bonded with a 2 kg roller to prepare 50 μm PET / adhesive layer (150 μm) / glass test piece. After leaving it to stand at 25 ° C. and 50% RH for 24 hours, it was peeled at a speed of 300 mm / min in the 180 ° direction to measure the adhesive strength (N / 25 mm).

<Remaining glass test>
The glass residue evaluated whether the adhesion layer remained in glass after measuring said adhesive force. The evaluation criteria are as follows.
○: Adhesive layer does not remain on glass Δ: Partial adhesive layer remains on glass ×: Adhesive layer remains on glass

<Measurement of haze value>
For the adhesive layers of Examples 6 to 10 and Comparative Examples 9 to 14, 50 μm PET / adhesive layer (150 μm) / glass test piece was prepared in the same manner as the adhesive strength test, and the haze value was set to the color haze made by Murakami Color Research Laboratory. Measurement was performed using a meter in accordance with JIS K 5400. In addition, each haze value is a numerical value including the haze value of the polyester film which is a base material, and glass.

<Durability test>
About the adhesion layer of Examples 6-10 and Comparative Examples 9-14, 50 micrometers PET / adhesion layer (150 micrometers) / glass test piece was produced similarly to the adhesive force test, and the durability test was implemented. The durability test was a moisture and heat resistance test that was stored in a constant temperature and humidity chamber at 85 ° C. and 85% relative humidity for 500 hours. The haze value after the wet heat resistance test was measured according to JIS K 5400 using a color haze meter manufactured by Murakami Color Research Laboratory. In addition, each haze value is a numerical value including the haze value of the polyester film which is a base material, and glass. Moreover, the evaluation criteria of durability are as follows.
○: No peeling, no adhesion layer leaching, no coating whitening ×: Either peeling, adhesion layer leaching, or coating whitening

Claims (6)

Ultraviolet curable, having a solvent content of less than 1% by weight, a viscosity at 25 ° C. of 100 to 10,000 mPa · s, a color tone of Gardner color 1 or less, and the following (A) to (D) Adhesive composition.
(A) Polyfunctional urethane (meth) acrylate oligomer having a weight average molecular weight of 10,000 to 100,000 (B) Tackifier (C) Monofunctional epoxy ester (meth) acrylate (D) Photopolymerization initiator The said (A) component is a polyfunctional urethane (meth) acrylate oligomer obtained by making polyether polyol, polyisocyanate, and a hydroxyl-containing (meth) acrylate or isocyanato group containing (meth) acrylate react. UV curable adhesive composition. The ultraviolet curable adhesive composition according to claim 1 or 2, wherein the component (B) is a tackifier having a color tone of Gardner color 1 or less. The components (A) to (D) are in the pressure-sensitive adhesive composition based on parts by weight, and (A) :( B) :( C) :( D) = 10 to 60: 0.5 to 15:15. The ultraviolet curable adhesive composition in any one of Claims 1-3 mix | blended in the ratio of 89.4: 0.1-10. The adhesion layer obtained by hardening the ultraviolet curable adhesive composition in any one of Claims 1-4. The pressure-sensitive adhesive layer according to claim 5, wherein the pressure-sensitive adhesive layer has a thickness of 10 to 1000 μm.