JP6672794B2 - Active energy ray-curable pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet - Google Patents

Description

The present invention relates to pressure-sensitive adhesive and the adhesive sheet using an active energy ray-curable pressure-sensitive adhesive composition and pre-Symbol active energy ray-curable pressure-sensitive adhesive composition, more particularly, the active energy ray-curable pressure-sensitive adhesive The composition contains a urethane (meth) acrylate having a low dielectric constant and excellent compatibility.

  There are various types of adhesives, such as strong adhesives for the purpose of firmly bonding the adherend for a long period of time, and peel-type adhesives that are premised on peeling off from the adherend after pasting. There are types, and the optimal adhesive is designed and used for each field.

  Conventionally, pressure-sensitive adhesives for display members, electronic members, and optical materials include, for example, urethane (meth) acrylate obtained by reacting polyol, polyisocyanate, and hydroxyl group-containing (meth) acrylate, and are irradiated with active energy rays. Pressure sensitive adhesives are known. As the polyol, a polyester-based polyol obtained by condensing a polyhydric carboxylic acid and a polyhydric alcohol, among which polyols using adipic acid as the carboxylic acid, are well known (for example, see Patent Document 1).

  In recent years, in particular, in optical member applications, especially in touch panel applications, in addition to adhesiveness and wet heat resistance, the dielectric constant has been set to suppress malfunction of the touch panel caused by noise generated from the display member and other peripheral members. There is a need for low pressure sensitive adhesives.

  For example, as a pressure-sensitive adhesive having a low dielectric constant, a resin composition for an ultraviolet-curable pressure-sensitive adhesive containing a urethane (meth) acrylate obtained by reacting a hydrogenated polybutadiene polyol, a polyisocyanate, and a hydroxyl group-containing (meth) acrylate is disclosed. (For example, see Patent Document 2).

Japanese Patent Application Laid-Open No. 2011-162770 JP 2002-309185 A

  However, the urethane (meth) acrylate obtained by reacting a polyester-based polyol using adipic acid, a polyisocyanate, and a hydroxyl group-containing (meth) acrylate disclosed in Patent Document 1 has a dielectric constant of usually about 8.0. In terms of suppressing the malfunction of the touch panel when applied to an optical member, the required performance was not satisfied.

  Further, the urethane (meth) acrylate obtained by reacting a hydrogenated polybutadiene polyol, a polyisocyanate and a hydroxyl group-containing (meth) acrylate described in Patent Literature 2 has a low dielectric constant of usually about 3.0, but is a hydrogenated polybutadiene polyol. However, since urethane (meth) acrylate itself has low polarity because of its low polarity, and has insufficient compatibility with other monomers and resins, there are problems such as a low degree of freedom in material selection and difficulty in handling.

Under such circumstances, an object of the present invention is to provide an active energy ray-curable pressure-sensitive adhesive composition containing a urethane (meth) acrylate having a low dielectric constant and excellent compatibility in such a background. Things. Another object of the present invention is to provide the active energy ray-curable pressure-sensitive adhesive composition, a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet using the same.

However, the present inventors have conducted intensive studies in view of such circumstances, and as a result, in an active energy ray-curable pressure-sensitive adhesive composition containing a urethane (meth) acrylate obtained by reacting a polyester polyol, the urethane (meth) It has been found that by setting the dielectric constant of the acrylate to a specific value or less, a pressure-sensitive adhesive having a low dielectric constant and excellent compatibility can be obtained, thereby completing the present invention.

That is, the gist of the present invention is as follows.
[1] A urethane (meth) acrylate (A) which is a reaction product of a polyester polyol (a1), a polyisocyanate (a2) and a hydroxyl group-containing (meth) acrylate (a3) is contained, and the urethane (meth) acrylate ( A) has a dielectric constant of 7.0 or less , a weight average molecular weight of 30,000 to 100,000, and a content X of oxygen atoms in the repeating structural unit of the polyester-based polyol (a1) of 0.26 to 0. An active energy ray-curable pressure-sensitive adhesive composition having a pH of 0.35 . However, the content X is a value represented by the following formula (1).
X = 16c / (12a + b + 16c) (1)
a: Number of carbon atoms in repeating structural unit of polyester-based polyol (a1)
b: Number of hydrogen atoms in the repeating structural unit of the polyester-based polyol (a1)
c: the number of oxygen atoms in the repeating structural unit of the polyester-based polyol (a1) [ 2 ] The polyester-based polyol (a1) includes a polyvalent carboxylic acid containing a polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms. The active energy ray-curable pressure-sensitive adhesive composition according to the above [1 ], which is a polycondensate of the component and a polyhydric alcohol component.
[ 3 ] The active energy ray-curable pressure-sensitive adhesive composition according to [1] or [2] , wherein the polyester-based polyol (a1) has a number average molecular weight of 500 to 12,000.
[ 4 ] The active energy ray curing according to any one of [1] to [3] , further containing an ethylenically unsaturated monomer (B) (excluding the urethane (meth) acrylate (A)). Adhesive composition.
[ 5 ] An adhesive obtained by curing the active energy ray-curable adhesive composition according to any one of [1] to [4] .
[ 7 ] An adhesive sheet in which the adhesive according to [5] is laminated on a base sheet .

According to the active energy ray-curable pressure-sensitive adhesive composition of the present invention, low dielectric constant, also excellent in compatibility, the adhesive has cured it is useful as an optical member for a pressure-sensitive adhesive, especially touch panels, etc. It is preferably used.

Hereinafter, the present invention will be described in detail.
In the present invention, (meth) acrylic acid is acrylic acid and / or methacrylic acid, (meth) acryl is acryl and / or methacryl, (meth) acryloyl is acryloyl and / or methacryloyl, and ) Acrylate means acrylate and / or methacrylate, respectively. Further, the acrylic resin is a resin obtained by polymerizing at least one kind of (meth) acrylate-based monomer alone, or a resin obtained by polymerizing a polymerization component containing at least one kind of (meth) acrylate-based monomer. is there.
In this specification, “to” indicating a numerical range is used to mean that the numerical values described before and after the numerical value range are included as a lower limit value and an upper limit value.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention is a urethane (meth) which is a reaction product obtained by reacting a polyester polyol (a1), a polyisocyanate (a2) and a hydroxyl group-containing (meth) acrylate (a3). An active energy ray-curable pressure-sensitive adhesive composition containing an acrylate (A), wherein the urethane (meth) acrylate (A) has a dielectric constant of 7.0 or less.

Here, the dielectric constant is a value representing the degree of polarization of a substance when an electric field is applied.
In the present invention, the dielectric constant of urethane (meth) acrylate refers to an active energy ray-curable mixture of 4 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone and 100 parts by weight of urethane (meth) acrylate. It is a value obtained by measuring the dielectric constant of a cured film obtained by curing the pressure-sensitive adhesive composition, and is specifically measured by the following method.

(Measuring method)
An active energy ray-curable pressure-sensitive adhesive composition containing 4 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone as a photopolymerizable initiator and 100 parts by weight of a urethane (meth) acrylate, and a solvent, The film is applied on an untreated polyethylene terephthalate (PET) film (thickness: 50 μm) using an applicator so as to have a thickness of 150 μm, and placed in a dryer at 60 ° C. for 10 minutes to evaporate the solvent. Thereafter, the surface of the active energy ray-curable pressure-sensitive adhesive composition is laminated from above with an untreated polyethylene terephthalate (PET) film (thickness: 50 μm), and a tabletop UV irradiator (manufactured by Eye Graphics Co., Ltd., “Conveyor tabletop irradiator”) ), A cured film cured by irradiating ultraviolet rays from the laminate side under the conditions of 80 W / cm (high pressure mercury lamp) × 18 cmH × 2.04 m / min × 3 Pass (integrated irradiation amount 2,400 mJ / cm ² ) Is cut into 7 cm x 7 cm to obtain a test piece for dielectric constant measurement.
Using a HP4284A precision LCR meter (manufactured by Agilent), the test piece for permittivity measurement was sandwiched between the electrodes, an electric field was applied at a frequency of 1 MHz, and the electric capacity was measured. The dielectric constant of the active energy ray-curable pressure-sensitive adhesive composition is calculated.

  The urethane (meth) acrylate (A) used in the present invention is a reaction product obtained by reacting a polyester polyol (a1), a polyisocyanate (a2), and a hydroxyl group-containing (meth) acrylate (a3).

  Examples of the polyester polyol (a1) in the present invention include a condensation polymer (polycondensate) of a polyhydric alcohol component and a polycarboxylic acid component, a ring-opening polymer of a cyclic ester (lactone) component, and a polyhydric polyol. A reaction product of three kinds of components, such as an alcohol component, a polyvalent carboxylic acid component and a cyclic ester component, may be used.

Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylenediol, 1,3-tetramethylenediol, and 2-methyl-1,3- Trimethylene diol, 1,5-pentamethylene diol, neopentyl glycol, 1,6-hexamethylene diol, 3-methyl-1,5-pentamethylene diol, 2,4-diethyl-1,5-pentamethylene diol, Dihydric alcohols such as 1,9-nonanediol, cyclohexanediols (such as 1,4-cyclohexanediol) and bisphenols (such as bisphenol A); trihydric alcohols such as glycerin, trimethylolpropane, and trimethylolethane; and sugars Like alcohol compound (such as xylitol or sorbitol). Among them, dihydric alcohols are preferable in terms of excellent versatility, and ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylenediol, 2-methyl-1,3-trimethylene are preferable. Diols and neopentyl glycol are particularly preferred.
These can be used alone or in combination of two or more.

Examples of the polyvalent carboxylic acid component include aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecandioic acid; Alicyclic dicarboxylic acids such as 4-cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, and trimellitic acid; Among these, aliphatic dicarboxylic acids are preferable in terms of less yellowing, and succinic acid, adipic acid and sebacic acid are particularly preferable.
These can be used alone or in combination of two or more.

  Examples of the cyclic ester component include propiolactone, β-methyl-δ-valerolactone, ε-caprolactone, and the like.

In the present invention, the content X of oxygen atoms in the repeating structural unit of the polyester-based polyol (a1) is 0.26 to 0.35 as the polyester-based polyol (a1) from the viewpoint of low dielectric properties. Is required . However, the content X is a value represented by the following formula (1).
X = 16c / (12a + b + 16c) (1)
a: the number of carbon atoms in the repeating structural unit of the polyester polyol (a1) b: the number of hydrogen atoms in the repeating structural unit of the polyester polyol (a1) c: the number of carbon atoms in the repeating structural unit of the polyester polyol (a1) Number of oxygen atoms

  For example, when the polyester polyol (a1) is a copolymer of ethylene glycol and adipic acid, the repeating structural unit is represented by the following structural formula. In the structural formula, n represents the number of repeating structural units.

  In this case, since a = 8, b = 12 and c = 4 in the above formula (1), the oxygen atom content X in the repeating structural unit represented by the above formula (1) becomes X = 0.37. .

From the viewpoint of low dielectric properties, the polyester polyol (a1) may contain a polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms as a polyvalent carboxylic acid component. It is more preferable that it contains a polyvalent carboxylic acid having an alkylene group having 6 to 18 carbon atoms, particularly 7 to 16 carbon atoms. The polyester polyol (a1) is more preferably a polycondensate of a polyvalent carboxylic acid component containing a polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms and a polyhydric alcohol component.
If the carbon number of the alkylene group of the polyvalent carboxylic acid is too small, the dielectric constant tends to increase, and if the carbon number is too large, the crystallinity tends to be high and handling tends to be difficult.
Specific examples of the polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms include pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic acid, eicosanoic acid, and isoeicosanoic acid.

When such a polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms is used, it is preferably contained in an amount of 10 to 100 mol% based on the entire polyvalent carboxylic acid component from the viewpoint of low dielectric constant. More preferably, it is 20 to 100 mol%, particularly preferably 25 to 100 mol%, particularly preferably 30 to 100 mol%.
If the content of the polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms in the whole polyvalent carboxylic acid component is too small, the dielectric constant tends to increase.

  The number of hydroxyl groups contained in the polyester-based polyol (a1) is preferably 2 to 5, particularly preferably 2 to 3, and more preferably 2 per molecule. If the number of hydroxyl groups is too large, gelation tends to occur during the reaction.

The number average molecular weight of the polyester-based polyol (a1) is preferably from 500 to 12,000, more preferably from 600 to 10,000, and particularly preferably from 700 to 8,000.
If the number average molecular weight is too large, the viscosity tends to increase, and the workability tends to decrease.

  The above number average molecular weight is a value determined by the following equation.

  The number of functional groups (F) in the formula indicates the number of hydroxyl groups contained in one molecule.

  The hydroxyl value of the polyester-based polyol (a1) is preferably from 10 to 400 mgKOH / g, particularly preferably from 20 to 300 mgKOH / g, and further preferably from 30 to 250 mgKOH / g. If the hydroxyl value is too high, the urethane (meth) acrylate tends to have a low molecular weight and the tackiness tends to decrease. If the hydroxyl value is too low, the viscosity tends to increase and the workability tends to decrease.

  The hydroxyl value can be measured based on JIS K 0070-1992.

  Examples of the polyisocyanate (a2) include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate. Aliphatic polyisocyanates such as pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, 1,3 -Bi (Isocyanatomethyl) cyclohexane, alicyclic polyisocyanates, or trimers compound or multimeric compounds of these polyisocyanates, allophanate type polyisocyanate, buret type polyisocyanate, water dispersible polyisocyanate, and the like.

Among these, diisocyanates are preferred from the viewpoint of excellent reaction stability, and in particular, aliphatic diisocyanates such as pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; hydrogenated diphenylmethane diisocyanate; Alicyclic diisocyanates such as diisocyanate, isophorone diisocyanate, norbornene diisocyanate and 1,3-bis (isocyanatomethyl) cyclohexane are preferably used, and more preferably hydrogenated xylylene diisocyanate in terms of excellent reactivity and versatility. And isophorone diisocyanate.
The above polyisocyanates can be used alone or in combination of two or more.

  Examples of the hydroxyl group-containing (meth) acrylate (a3) include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate , 6-hydroxyhexyl (meth) acrylate and the like having 2 to 20 (preferably 2 to 18) carbon atoms in the alkyl group, such as hydroxyalkyl (meth) acrylate, 2-hydroxyethylacryloyl phosphate, and 2- (meth) acryloy Roxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth) acrylate, dipropylene glycol (meth) acrylate, fatty acid-modified glycidyl (meth) acrylate, polyethylene glycol mono (meth A) acrylate containing one ethylenically unsaturated group, such as acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate; glycerin di (meth) acrylate; ) (Meth) acrylates containing two ethylenically unsaturated groups such as acrylate and 2-hydroxy-3-acryloyl-oxypropyl methacrylate; pentaerythritol tri (meth) acrylate, caprolactone-modified pentaerythritol tri (meth) acrylate, ethylene Oxide-modified pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, caprolactone-modified dipentaerythritol penta (meth) acrylate, ethylene oxide The modified dipentaerythritol penta (meth) acrylate ethylenically unsaturated groups such as containing three or more (meth) acrylate. The hydroxyl group-containing (meth) acrylate (a3) can be used alone or in combination of two or more.

  Among these, a hydroxyl group-containing (meth) acrylate having one ethylenically unsaturated group is preferable in that the flexibility of the pressure-sensitive adhesive layer is excellent, and more preferably, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl And hydroxyalkyl (meth) acrylates such as (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. ) It is preferable to use acrylate and 4-hydroxybutyl (meth) acrylate since they are excellent in reactivity and versatility.

In the present invention, the urethane (meth) acrylate (A) can be produced as follows.
For example, a method in which the polyester polyol (a1), the polyisocyanate (a2), and the hydroxyl group-containing (meth) acrylate (a3) of (1) are charged into the reactor at once or separately and reacted, and (2) the polyester polyol (a1) ) And a polyisocyanate (a2) in advance to react with a reaction product obtained by reacting a hydroxyl group-containing (meth) acrylate (a3) with the reaction product. In view of the above, the method (2) is preferable.

  The urethane (meth) acrylate (A) is a polyester-based polyol (a1) which is a polycondensate of a polyvalent carboxylic acid component containing a polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms and a polyhydric alcohol component. ), A polyisocyanate (a2) and a reaction product of a hydroxyl group-containing (meth) acrylate (a3), and the reaction product, urethane (meth) acrylate, is a novel compound regardless of its dielectric constant. .

A method of reacting a hydroxyl group-containing (meth) acrylate (a3) with a reaction product obtained by previously reacting a polyester polyol (a1) and a polyisocyanate (a2) in the production of the urethane (meth) acrylate (A). Will be described.
Known reaction means can be used for the reaction between the polyester polyol (a1) and the polyisocyanate (a2). At that time, for example, the molar ratio of the isocyanate group in the polyisocyanate (a2) to the hydroxyl group in the polyester-based polyol (a1) is usually about 2n: (2n-2) (n is an integer of 2 or more). It is possible to obtain a terminal isocyanate group-containing urethane (meth) acrylate having an isocyanate group remaining, and after obtaining the compound, an addition reaction with a hydroxyl group-containing (meth) acrylate (a3) is enabled.

  Known reaction means may be used for the addition reaction between the reaction product obtained by previously reacting the polyester-based polyol (a1) and the polyisocyanate (a2) with the hydroxyl group-containing (meth) acrylate (a3). it can.

  The reaction molar ratio between the reaction product and the hydroxyl group-containing (meth) acrylate (a3) is, for example, such that the reaction product has two isocyanate groups and the hydroxyl group-containing (meth) acrylate (a3) has one hydroxyl group. In some cases, the reaction product: hydroxyl group-containing (meth) acrylate (a3) is about 1: 2, the reaction product has three isocyanate groups, and the hydroxyl group-containing (meth) acrylate (a3) has one hydroxyl group. When the number is about 1, the ratio of reaction product: hydroxyl group-containing (meth) acrylate (a3) is about 1: 3.

  In the addition reaction between the reaction product and the hydroxyl group-containing (meth) acrylate (a3), the reaction is terminated when the residual isocyanate group content of the reaction system becomes 0.3% by weight or less, whereby urethane ( A (meth) acrylate (A) is obtained.

  In the reaction between the polyester-based polyol (a1) and the polyisocyanate (a2), and further between the reaction product and the hydroxyl group-containing (meth) acrylate (a3), it is also preferable to use a catalyst for the purpose of accelerating the reaction. . Examples of such a catalyst include dibutyltin dilaurate, dibutyltin diacetate, trimethyltin hydroxide, tetra-n-butyltin, zinc bisacetylacetonate, zirconium tris (acetylacetonate) ethylacetoacetate, and zirconium tetraacetylacetonate. Metal salts such as organic metal compounds such as tin octenoate, zinc hexanoate, zinc octenoate, zinc stearate, zirconium 2-ethylhexanoate, cobalt naphthenate, stannous chloride, stannic chloride, and potassium acetate; Triethylamine, triethylenediamine, benzyldiethylamine, 1,4-diazabicyclo [2,2,2] octane, 1,8-diazabicyclo [5,4,0] undecene, N, N, N ′, N′-tetramethyl-1 , 3-butanediamine, N-meth Amine catalysts such as rumorpholine and N-ethylmorpholine, bismuth nitrate, bismuth bromide, bismuth iodide, bismuth sulfide, etc., organic bismuth compounds such as dibutyl bismuth dilaurate, dioctyl bismuth dilaurate, and bismuth 2-ethylhexanoate , Bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth livis neodecano Bismuth-based catalysts such as organic acid bismuth salts such as ate, bismuth disalicylate, bismuth digallate, and the like, among which dibutyltin dilaurate and 1,8-diazabicyclo [5,4,0] undecene are preferred. is there. These can be used alone or in combination of two or more.

  In addition, in the reaction between the polyester-based polyol (a1) and the polyisocyanate (a2), and further, the reaction between the reaction product and the hydroxyl group-containing (meth) acrylate (a3), the reaction with the isocyanate group is performed as necessary. Organic solvents having no functional group, for example, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, organic solvents such as aromatics such as toluene and xylene, and ethylenically unsaturated monomers ( For example, a compound such as the ethylenically unsaturated monomer (B) described below) may be used.

  The reaction temperature is usually 30 to 90 ° C, preferably 40 to 80 ° C, and the reaction time is usually 2 to 10 hours, preferably 3 to 8 hours.

The urethane (meth) acrylate (A) of the present invention thus obtained has a dielectric constant of 7.0 or less, and is preferably 6.5 or less, more preferably 6.0 or less in that malfunction of the touch panel can be suppressed. is there. The lower limit of the dielectric constant is usually 1.0.
If the dielectric constant is too high, the capacitance between the electrodes mounted on the touch panel tends to increase, causing a malfunction. If the dielectric constant is too low, the capacitance tends to decrease and the detection sensitivity tends to decrease.

The weight average molecular weight of the urethane (meth) acrylate (A) of the present invention is required to be 30,000 to 100,000, good Mashiku 30,000 ～90,000, more preferably 30,000 ~ 80,000. If the weight average molecular weight is too small, the adhesive strength tends to decrease, and if it is too large, the viscosity tends to be too high and coating tends to be difficult.

The above-mentioned weight average molecular weight is a weight average molecular weight in terms of standard polystyrene molecular weight, and the column: Shodex GPC KF-806L (excluded by high performance liquid chromatography (manufactured by Showa Denko KK, "Shodex GPC system-11 type")). limit molecular weight: 2 × 10 ^7, separation range: one hundred to two × 10 ^7, theoretical plate number: 10,000 plates / the filler material: styrene - divinylbenzene copolymer, filler particle size: 10 [mu] m) 3 present in This is the value measured by using the series.

The viscosity of the urethane (meth) acrylate (A) of the present invention is preferably from 1,000 to 1,000,000 mPa · s at 60 ° C, particularly preferably from 2,000 to 900, 000 mPa · s, more preferably 3,000 to 800,000 mPa · s. If the viscosity is too high, handling tends to be difficult, and if it is too low, control of the film thickness during coating tends to be difficult.
The viscosity was measured by an E-type viscometer.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention further includes, in addition to the urethane (meth) acrylate (A), an ethylenically unsaturated monomer (B) (excluding the urethane (meth) acrylate (A)). ) Is preferable.
Examples of the ethylenically unsaturated monomer (B) used in the present invention include a monofunctional monomer, a difunctional monomer, and a trifunctional or higher functional monomer.

  Such monofunctional monomers include, for example, styrene-based monomers such as styrene, vinyltoluene, chlorostyrene, α-methylstyrene, methyl (meth) acrylate, ethyl (meth) acrylate, acrylonitrile, 2-methoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-phenoxy-2-hydroxy Propyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, glycerin mono (meth) acrylate, glycidyl (Meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, Dicyclopentanyl (meth) acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl) -methyl (meth) acrylate, cyclohexanespiro-2- (1,3-dioxolan-4-yl) ) -Methyl (meth) acrylate, 3-ethyl-3-oxetanylmethyl (meth) acrylate, γ-butyrolactone (meth) acrylate, n-butyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (Meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, dodecyl (meth) acrylate, n-stearyl (meth) acrylate, benzyl (meth) acrylate, phenol ethylene oxide-modified (n = 2) Phthal such as (meth) acrylate, nonylphenol propylene oxide-modified (n = 2.5) (meth) acrylate, 2- (meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxy-2-hydroxypropyl phthalate Half (meth) acrylate, furfuryl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, carbitol (meth) acrylate, benzyl (meth) acrylate, butoxy of acid derivatives (Meth) acrylate monomers such as tyl (meth) acrylate, allyl (meth) acrylate, (meth) acryloylmorpholine, and polyoxyethylene secondary alkyl ether acrylate, 2-hydroxyethylacrylamide, N-methylol (meth) acrylamide , N-vinylpyrrolidone, 2-vinylpyridine, vinyl acetate and the like.

  Such bifunctional monomers include, for example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, Propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide-modified bisphenol A type di (meth) acrylate, propylene oxide-modified bisphenol A Di (meth) acrylate, cyclohexane dimethanol di (meth) acrylate, ethoxylated cyclohexane dimethanol A) acrylate, dimethylol dicyclopentanedi (meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) Acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, diglycidyl ester di (meth) acrylate phthalate, hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate, ethylene isocyanurate Oxide-modified diacrylate and the like.

  Examples of such trifunctional or higher-functional monomers include, for example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa ( (Meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified triacrylate, caprolactone modified dipentaerythritol penta (meth) acrylate, caprolactone modified dipentaerythritol hexa (Meth) acrylate, caprolactone-modified pentaerythritol tri (meth) acrylate, capro Cuton-modified pentaerythritol tetra (meth) acrylate, ethylene oxide-modified dipentaerythritol penta (meth) acrylate, ethylene oxide-modified dipentaerythritol hexa (meth) acrylate, ethylene oxide-modified pentaerythritol tri (meth) acrylate, ethylene oxide-modified pentaerythritol Examples thereof include tetra (meth) acrylate and ethoxylated glycerin triacrylate.

Further, a Michael addition product of acrylic acid or a 2-acryloyloxyethyl dicarboxylic acid monoester can also be used in combination. Examples of the Michael addition product of acrylic acid include acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, Acrylic acid tetramer, methacrylic acid tetramer and the like can be mentioned.
The 2-acryloyloxyethyl dicarboxylic acid monoester is a carboxylic acid having a specific substituent, for example, 2-acryloyloxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl Monoester of phthalic acid, monoester of 2-methacryloyloxyethyl phthalic acid, monoester of 2-acryloyloxyethyl hexahydrophthalic acid, monoester of 2-methacryloyloxyethyl hexahydrophthalic acid and the like can be mentioned. Furthermore, other oligoester acrylates can also be used.

  The content of the ethylenically unsaturated monomer (B) is preferably 5 to 900 parts by weight, particularly preferably 10 to 600 parts by weight, more preferably 100 parts by weight of the urethane (meth) acrylate (A). Is 15 to 400 parts by weight. If the content is too large, the viscosity tends to decrease, and the adhesive strength tends to decrease.

In the present invention, the active energy ray-curable pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator (C), and the photopolymerization initiator (C) generates a radical by the action of light. It is not particularly limited as long as it is one. For example, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1- Hydroxycyclohexyl phenyl ketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-2-morpholino (4-thiomethylphenyl) Propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone, 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomer and the like Acetophenones; benzoin, benzoin methyl ether, benzoin ethyl ether, Benzoins such as benzoin isopropyl ether and benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4′-methyl-diphenylsulfide, 3,3 ′, 4,4′- Tetra (t-butylperoxycarbonyl) benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethanami Benzophenones such as ammonium bromide and (4-benzoylbenzyl) trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxy Thioxanthones such as thioxanthone, 2- (3-dimethylamino-2-hydroxy) -3,4-dimethyl-9H-thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis Acylphosphone oxides such as (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; . These photopolymerization initiators (C) can be used alone or in combination of two or more.

  Further, as an auxiliary for the photopolymerization initiator (C), triethanolamine, triisopropanolamine, 4,4′-dimethylaminobenzophenone (Michler's ketone), 4,4′-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid Ethyl 4-dimethylaminobenzoate, (n-butoxy) ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, , 4-diisopropylthioxanthone and the like can be used in combination. These auxiliaries can be used alone or in combination of two or more.

  Regarding the content of the photopolymerization initiator (C), the urethane (meth) acrylate (A) (when the ethylenically unsaturated monomer (B) is further contained, the urethane (meth) acrylate (A) and the ethylenic The amount is preferably 1 to 10 parts by weight, particularly preferably 2 to 5 parts by weight, per 100 parts by weight of the saturated monomer (B). If the content is too small, the curing rate tends to decrease. If the content is too large, the curability does not improve and the economy tends to decrease.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention includes, in addition to the urethane (meth) acrylate (A), the ethylenically unsaturated monomer (B), and the photopolymerization initiator (C), an antioxidant, It is also possible to incorporate a fuel, an antistatic agent, a filler, a leveling agent, a stabilizer, a reinforcing agent, a matting agent, and the like. Further, as a crosslinking agent, a compound having the effect of causing crosslinking by heat, specifically epoxy compounds, aziridinyl di emissions compounds, melamine compounds, isocyanate compounds, chelating compounds can also be used. In addition, a carbodiimide compound can be used as a hydrolysis inhibitor.

Further, the active energy ray-curable pressure-sensitive adhesive composition of the present invention may be, if necessary, diluted with methanol, ethanol, propanol, n-butanol, i-butanol, etc. to adjust the viscosity at the time of coating. Alcohols, acetone, methyl isobutyl ketone, methyl ethyl ketone, ketones such as cyclohexanone, cellosolves such as ethyl cellosolve, aromatics such as toluene and xylene, glycol ethers such as propylene glycol monomethyl ether, methyl acetate, ethyl acetate, Acetates such as butyl acetate, and diluent solvents such as diacetone alcohol may be used. However, since the solvent may remain in the coating film and the cured component may be volatilized during drying, the solvent may be substantially used. Is preferably not contained.
In addition, the term "contains substantially no solvent" means that the content is generally 1% by weight or less, preferably 0.5% by weight or less, more preferably 0.1% by weight or less based on the entire active energy ray-curable pressure-sensitive adhesive composition. Refers to something.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention may be or used as an adhesive composition, such as laminating and the surface protective sheet of each species members.

Further, the active energy ray-curable pressure-sensitive adhesive composition of the present invention may contain a tackifier such as a polythiol compound from the viewpoint of suppressing unreacted components and improving the adhesive strength.
As the polythiol compound, a compound having 2 to 6 mercapto groups in the molecule is preferable. For example, aliphatic polythiols such as alkanedithiol having about 2 to 20 carbon atoms, aromatic polythiols such as xylylenedithiol, and alcohols Polythiols in which the halogen atom of the halohydrin adduct is substituted with a mercapto group, polythiols composed of hydrogen sulfide reaction products of polyepoxide compounds, polyhydric alcohols having 2 to 6 hydroxyl groups in the molecule, thioglycolic acid, β Polythiols comprising an esterified product with -mercaptopropionic acid or β-mercaptobutanoic acid; and one or more of these can be used.

  When the above-mentioned polythiol compound is contained, the content is defined as urethane (meth) acrylate (A) (and further containing ethylenically unsaturated monomer (B), urethane (meth) acrylate (A) and ethylenically unsaturated monomer It is preferably 10 parts by weight or less, more preferably 0.01 to 5 parts by weight, per 100 parts by weight of (B).

The active energy ray-curable pressure-sensitive adhesive composition of the present invention is preferably a cured pressure-sensitive adhesive. Specifically, it is usually applied to a base sheet or the like and is often used as a pressure-sensitive adhesive sheet or the like. After coating on the base sheet or the like, it is cross-linked by irradiation with active energy rays to become a pressure-sensitive adhesive. Is expressed.
Incidentally, the pressure-sensitive adhesive sheet, unless otherwise specified, is also meant to include a pressure-sensitive adhesive film, a pressure-sensitive adhesive tape, and is characterized in that a pressure-sensitive adhesive obtained by curing the active energy ray-curable pressure-sensitive adhesive composition of the present invention is laminated. I do.

  In the present invention, a separator can be laminated on the surface of the pressure-sensitive adhesive for the purpose of protecting the pressure-sensitive adhesive from contamination until the pressure-sensitive adhesive sheet is bonded to the adherend (member).

  As the base sheet, for example, polyethylene terephthalate, polyester resins such as polybutylene terephthalate, polyethylene, polypropylene, polyolefin resins such as ethylene-propylene copolymer, polycarbonate resins, polyurethane resins, acrylic resins, polystyrene A resin sheet such as a series resin, an ethylene-vinyl acetate copolymer, polyvinyl chloride, polybutene, polyester, polymethylpentene, acrylonitrile butadiene styrene copolymer (ABS), and a glass plate are exemplified. Various base sheets that have been subjected to surface treatment such as an anchor layer, corona treatment, or plasma treatment may be used.

  As the separator, a resin sheet as exemplified above as a base material sheet, or a material obtained by subjecting a base material such as paper, cloth, nonwoven fabric or the like to release treatment can be used.

  In forming the pressure-sensitive adhesive layer on the substrate sheet, a direct coating method in which the active energy ray-curable pressure-sensitive adhesive composition is directly applied to the substrate sheet, or an active energy ray-curable pressure-sensitive adhesive composition is coated on the separator. After coating, a transfer coating method of bonding the base sheet to the base sheet may be used.

  The active energy ray-curable pressure-sensitive adhesive composition is usually applied after being adjusted to a viscosity suitable for application with a solvent, if necessary. The method for applying the active energy ray-curable pressure-sensitive adhesive composition to a substrate sheet or a separator is not particularly limited, and examples thereof include spray, shower, dipping, roll, spin, curtain, flow, slit, and die. , Gravure, comma, screen printing, ink jet printing, and wet coating methods such as print coating with a dispenser.

Although the drying after coating in the case of the active energy ray-curable pressure-sensitive adhesive composition was applied is a solvent, the drying conditions, the active energy ray-curable pressure-sensitive adhesive composition was coated The drying temperature and the drying time sufficient to volatilize the solvent may be set. The drying temperature is usually from 40 to 100 ° C., particularly preferably from 50 to 90 ° C., and the drying time is preferably from 1 to 60 minutes in view of production adequacy.

  Incidentally, when the active energy ray-curable pressure-sensitive adhesive composition is a solid or a high-viscosity liquid, instead of adjusting the viscosity with a solvent, the active energy ray-curable composition is heated, and the viscosity is reduced. A hot melt method of coating by a method can also be used.

  The active energy ray-curable pressure-sensitive adhesive composition of the present invention is applied to a substrate sheet, dried, and then irradiated with active energy rays to be crosslinked to form a pressure-sensitive adhesive and further a pressure-sensitive adhesive sheet.

  Regarding the irradiation of active energy rays, in the direct coating method, after applying the active energy ray-curable pressure-sensitive adhesive composition to a base sheet and drying by heating, the active energy rays are irradiated, and then the separator is attached. Alternatively, the active energy ray-curable pressure-sensitive adhesive composition may be applied to a substrate sheet, dried by heating, bonded to a separator, and then irradiated with an active energy ray. On the other hand, in the transfer coating method, after applying the active energy ray-curable pressure-sensitive adhesive composition to the separator and heating and drying, the active energy ray is irradiated, and then the base sheet may be attached to the separator or the separator. After applying the active energy ray-curable pressure-sensitive adhesive composition and drying by heating, the base sheet may be adhered, and then the active energy ray may be irradiated.

  As the above-mentioned active energy rays, far-ultraviolet rays, ultraviolet rays, near-ultraviolet rays, infrared rays, and other electromagnetic waves such as X-rays and γ-rays, as well as electron rays, proton rays, neutron rays, etc., can be used. Curing by ultraviolet irradiation is advantageous from the standpoint of availability of the apparatus and cost. When electron beam irradiation is performed, curing can be performed without using a photopolymerization initiator (C).

As a method of curing by ultraviolet irradiation, using a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a chemical lamp, an electrodeless discharge lamp, an LED lamp, etc., which emit light in a wavelength range of 150 to 450 nm. , 30 to 5,000 mJ / cm ² .
After the ultraviolet irradiation, if necessary, heating can be performed to complete the curing.

  The thickness of the pressure-sensitive adhesive layer formed on the base sheet after irradiation with active energy rays is appropriately set depending on the application, but is usually 5 to 300 μm, and preferably 10 to 250 μm. . If the thickness of the pressure-sensitive adhesive layer is too small, the physical properties of the pressure-sensitive adhesive tend to be difficult to stabilize.

The pressure-sensitive adhesive of the present invention thus obtained has a dielectric constant of 7.0 or less, and is preferably 6.5 or less, and more preferably 6.0 or less, in that malfunction of the touch panel can be suppressed. The lower limit of the dielectric constant is usually 1.0.
If the dielectric constant is too high, the capacitance between the electrodes mounted on the touch panel tends to increase, which tends to cause malfunction. If the dielectric constant is too low, the capacitance tends to decrease and the detection sensitivity tends to decrease.

  The adhesive strength of the pressure-sensitive adhesive sheet of the present invention is usually 0.1 to 100 N / 25 mm, more preferably 0.5 to 75 N / 25 mm, further preferably 1 to 50 N / 25 mm, and particularly preferably 10 to 50 N. / 25 mm, particularly preferably 17.5 to 50 N / 25 mm.

Urethane (meth) acrylates of the present invention have low dielectric constants, dielectric constant of the active energy ray-curable pressure-sensitive adhesive composition of the present invention containing this is low, the active energy ray-curable pressure-sensitive adhesive composition and this The cured adhesive is useful as an adhesive for optical members, for example, optical devices such as touch panels and optical recording media, and is particularly suitable for use in laminating touch panel structural members and sealing organic EL displays. Used for

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In the examples, “parts” and “%” mean on a weight basis.

<Example 1>
[Synthesis of urethane acrylate (A-1)]
In a four-necked flask equipped with a thermometer, a stirrer, a water-cooled condenser, and a nitrogen gas inlet, 12.6 g (0.057 mol) of isophorone diisocyanate, a bifunctional polyester polyol (hydroxyl value 60.3 mgKOH / g, number average molecular weight) 2,000, oxygen atom content X in the repeating structural unit X = 0.26, polyvalent carboxylic acid component: containing 100 mol% of sebacic acid) 84.7 g (0.046 mol), and dibutyltin dilaurate 0. After charging 02 g and reacting at 80 ° C. for 6 hours, 2.7 g (0.023 mol) of 2-hydroxyethyl acrylate and 0.04 g of 2,6-di-tert-butylcresol as a polymerization inhibitor were charged, and C. for 3 hours. When the residual isocyanate groups became 0.3%, the reaction was terminated. Preparative (A-1) (weight average molecular weight (Mw); 30,000) was obtained.
The following evaluation was performed about the obtained urethane acrylate (A-1).

<Dielectric constant>
43 parts by weight of ethyl acetate and 4 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by BASF Japan; "Irgacure 184") as a photopolymerization initiator are uniformly added to 100 parts by weight of urethane acrylate (A-1). The mixture was mixed to obtain an active energy ray-curable pressure-sensitive adhesive composition.

(Preparation of test piece for dielectric constant measurement)
The active energy ray-curable pressure-sensitive adhesive composition obtained above is applied on an untreated polyethylene terephthalate (PET) film (thickness: 50 μm) using an applicator so that the cured film thickness is 150 μm. The solvent was volatilized by placing in a dryer at 10 ° C. for 10 minutes. Thereafter, the active energy ray-curable pressure-sensitive adhesive composition side is laminated from above with an untreated polyethylene terephthalate (PET) film (thickness: 50 μm), and a tabletop UV irradiation apparatus (manufactured by Eye Graphics Co., Ltd., “Conveyor tabletop irradiation apparatus”) ) At a temperature of 80 W / cm (high pressure mercury lamp) × 18 cmH × 2.04 m / min × 3 Pass (integrated irradiation amount 2,400 mJ / cm ² ). , 7 cm x 7 cm to obtain a dielectric constant measurement test piece.

(Measuring method)
Using an HP4284A Precision LCR meter (manufactured by Agilent), the obtained test piece was sandwiched between the electrodes, an electric field was applied at a frequency of 1 MHz, and the electric capacity was measured. The dielectric constant of the pressure-sensitive adhesive composition was calculated and evaluated as follows. The dielectric constant of the active energy ray-curable pressure-sensitive adhesive composition can be regarded as the dielectric constant of urethane (meth) acrylate contained in the active energy ray-curable pressure-sensitive adhesive composition.
(Evaluation criteria)
；: 7.0 or less ×: Greater than 7.0

<Compatibility>
The urethane acrylate (A-1) and the following ethylenically unsaturated monomer were blended in a weight ratio of 1: 1, respectively, and after mixing well, the appearance of the blended liquid was observed and evaluated as follows.
(B-1) Aliphatic monomer: butyl acrylate (B-2) Aromatic monomer: phenoxyethyl acrylate (B-3) Hydroxyl group-containing monomer: 4-hydroxybutyl acrylate (evaluation standard)
；: The mixed solution was uniform.
X: The compounded liquid was non-uniform.

  Next, the tackiness of the active energy ray-curable pressure-sensitive adhesive composition containing urethane acrylate (A-1) was evaluated.

<Tackiness>
For 100 parts of urethane (meth) acrylate (A-1), 81 parts of phenoxyethyl acrylate as an ethylenically unsaturated monomer (B) and 1-hydroxy-cyclohexyl-phenyl-ketone as a photopolymerization initiator (manufactured by BASF Japan Ltd.) ; Irgacure 184) was uniformly mixed to obtain an active energy ray-curable pressure-sensitive adhesive composition.

(Preparation of adhesive sheet for measuring adhesive strength)
The obtained active energy ray-curable pressure-sensitive adhesive composition is applied to an easily tackified polyethylene terephthalate (PET) film (125 μm thick) using an applicator so that the film thickness after curing becomes 175 μm, and is irradiated with desktop UV. 80 W / cm (high-pressure mercury lamp) x 18 cmH x 2.04 m / min x 3 Pass (integrated irradiation amount 2,400 mJ / cm ² ) using a device (manufactured by Eye Graphics Inc., “Conveyor tabletop irradiation device”) Irradiation with UV light was performed for curing to obtain an adhesive sheet for measuring adhesive strength.

(Test method)
The obtained pressure-sensitive adhesive sheet was cut into 25 mm × 100 mm, and then pressed against a glass plate as an adherend by two reciprocations using a 2 kg rubber roller in an atmosphere at 23 ° C. and a relative humidity of 50%. Was prepared. After leaving the test piece in the same atmosphere for 30 minutes, a 180 ° peel test was performed at a peel rate of 0.3 m / min, and the adhesive strength (N / 25 mm) was measured and evaluated according to the following criteria.
(Evaluation criteria)
；: 17.5 N / 25 mm or more △: 10 N / 25 mm or more and less than 17.5 N / 25 mm ×; less than 10 N / 25 mm

<Example 2>
[Synthesis of urethane acrylate (A-2)]
In a four-necked flask equipped with a thermometer, stirrer, water-cooled condenser, and nitrogen gas inlet, 11.9 g (0.054 mol) of isophorone diisocyanate, bifunctional polyester polyol (hydroxyl value 56.0 mgKOH / g, number average molecular weight) 2,000, 85.6 g (0.043 mol) of oxygen atom content X = 0.34 in the repeating structural unit, polyvalent carboxylic acid component: containing 35 mol% of sebacic acid, and 0.1 g of dibutyltin dilaurate as a reaction catalyst. After charging 2 g and reacting at 80 ° C. for 6 hours, 2.5 g (0.022 mol) of 2-hydroxyethyl acrylate and 0.04 g of 2,6-di-tert-butylcresol as a polymerization inhibitor were charged. C. for 3 hours. When the residual isocyanate groups became 0.3%, the reaction was terminated. (A-2) (weight average molecular weight (Mw); 38,000) was obtained.

  The obtained urethane acrylate (A-2) was evaluated for dielectric properties and compatibility in the same manner as in Example 1. The adhesiveness of the active energy ray-curable pressure-sensitive adhesive composition containing urethane acrylate (A-2) was evaluated in the same manner as in Example 1.

<Comparative Example 1>
[Synthesis of urethane acrylate (A'-1)]
In a four-necked flask equipped with a thermometer, a stirrer, a water-cooled condenser, and a nitrogen gas inlet, 11.8 g (0.053 mol) of isophorone diisocyanate, a bifunctional polyester polyol (hydroxyl value: 55.4 mgKOH / g, number-average molecular weight) 2,000, oxygen atom content X in the repeating structural unit X = 0.37, polycarboxylic acid component: adipic acid 100 mol%)) 85.7 g (0.042 mol), dibutyltin dilaurate 0 as a reaction catalyst After reacting at 80 ° C. for 6 hours, 2.5 g (0.022 mol) of 2-hydroxyethyl acrylate and 0.04 g of 2,6-di-tert-butylcresol as a polymerization inhibitor were charged. The reaction was carried out at 60 ° C. for 3 hours. When the remaining isocyanate groups became 0.3%, the reaction was terminated and urethane acrylate was added. Over preparative (A'-1) (weight average molecular weight (Mw); 26,000) was obtained.

  About the obtained urethane acrylate (A'-1), it carried out similarly to Example 1, and evaluated dielectricity and compatibility. Moreover, about the active-energy-ray-curable adhesive composition containing urethane acrylate (A'-1), adhesiveness was evaluated similarly to Example 1.

<Comparative Example 2> [Synthesis of urethane acrylate (A'-2)]
In a four-necked flask equipped with a thermometer, a stirrer, a water-cooled condenser, and a nitrogen gas inlet, 10.1 g (0.045 mol) of isophorone diisocyanate, a bifunctional hydrogenated polybutadiene polyol (having a hydroxyl value of 48.3 mgKOH / g, After charging 87.7 g (0.038 mol) of an average molecular weight of 2,000 and 0.02 g of dibutyltin dilaurate as a reaction catalyst and reacting at 80 ° C. for 6 hours, 2.2 g (0.015 mol) of 4-hydroxybutyl acrylate was added. ), 0.04 g of 2,6-di-tert-butylcresol as a polymerization inhibitor was charged and reacted at 60 ° C. for 3 hours. When the remaining isocyanate groups became 0.3%, the reaction was terminated. (A′-2) (weight average molecular weight (Mw); 49,000) was obtained.

About the obtained urethane acrylate (A'-2), it carried out similarly to Example 1, and evaluated dielectric property and compatibility.
Then, based on 100 parts by weight of urethane acrylate (A'-2), 69 parts by weight of isodecyl acrylate as an ethylenically unsaturated monomer (B), and 1-hydroxy-cyclohexyl-phenyl-ketone as a photopolymerization initiator (BASF Japan Ltd.) 6.8 parts of Irgacure 184) were uniformly mixed to obtain an active energy ray-curable pressure-sensitive adhesive composition, and the adhesion was evaluated in the same manner as in Example 1.

  The above evaluation results are shown in Table 1 below.

From the above evaluation results, it can be seen that the urethane acrylates of Examples 1 and 2 having a dielectric constant of 7.0 or less have good appearance of a liquid mixture with various ethylenically unsaturated monomers and are excellent in compatibility. In addition, it can be seen that the active energy ray-curable pressure-sensitive adhesive compositions of Examples 1 and 2 containing the urethane acrylate exhibit excellent tackiness.
On the other hand, the urethane (meth) acrylate of Comparative Example 1 having a dielectric constant exceeding 7.0 has excellent compatibility, but has a high dielectric constant and is difficult to be applied to an adhesive for optical members.
Further, the urethane acrylate of Comparative Example 2 obtained by reacting a polybutadiene-based polyol in place of the polyester-based polyol has a dielectric constant of 7.0 or less, but the urethane acrylate is inferior in compatibility to the examples. It can be seen that it is.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application (No. 2014-2333837) filed on November 18, 2014, the contents of which are incorporated herein by reference.

Since the active energy ray-curable pressure-sensitive adhesive composition of the present invention has a low dielectric constant, the active energy ray-curable pressure-sensitive adhesive composition of the present invention and a pressure-sensitive adhesive containing the same can be used for optical devices such as touch panels and optical recording. It is useful as a pressure-sensitive adhesive for optical members, such as a medium, and is particularly suitably used for laminating a touch panel structural member, sealing an organic EL display, and the like.

Claims (6)

It contains urethane (meth) acrylate (A) which is a reaction product of polyester-based polyol (a1), polyisocyanate (a2) and hydroxyl group-containing (meth) acrylate (a3). The dielectric constant is 7.0 or less , the weight average molecular weight is 30,000 to 100,000, and the content X of oxygen atoms in the repeating structural unit of the polyester-based polyol (a1) is 0.26 to 0.35 . An active energy ray-curable pressure-sensitive adhesive composition. However, the content X is a value represented by the following formula (1).
X = 16c / (12a + b + 16c) (1)
a: Number of carbon atoms in repeating structural unit of polyester-based polyol (a1)
b: Number of hydrogen atoms in the repeating structural unit of the polyester-based polyol (a1)
c: Number of oxygen atoms in repeating structural unit of polyester-based polyol (a1) The active energy according to claim 1, wherein the polyester-based polyol (a1) is a polycondensate of a polyvalent carboxylic acid component containing a polyvalent carboxylic acid having an alkylene group having 5 to 20 carbon atoms and a polyhydric alcohol component. A line-curable pressure-sensitive adhesive composition. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1 or 2 , wherein the polyester-based polyol (a1) has a number average molecular weight of 500 to 12,000. The active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 3 , further comprising an ethylenically unsaturated monomer (B) (however, excluding the urethane (meth) acrylate (A)). . Adhesive cured with an active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 4. An adhesive sheet in which the adhesive according to claim 5 is laminated on a base sheet.