JP2014196442A - Adhesive composition and adhesive sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition excellent in followability even if an adherend surface contains irregularity such as a level difference, and capable of maintaining elasticity even in a high temperature environment.SOLUTION: An adhesive composition at least includes: an acrylic adhesive; and an isocyanate compound as a crosslinking agent. The acrylic adhesive includes an acrylic resin whose mass average molecular weight is within a range of 50-300 thousand. The adhesive composition includes 0.3-0.8 pt.mass of the isocyanate compound in a solid form ratio to 100 pts.mass of the acrylic adhesive.

Description

  The present invention relates to a pressure-sensitive adhesive composition, and more specifically, a pressure-sensitive adhesive composition that has excellent followability even when there are irregularities such as steps on the surface of the adherend and can maintain elasticity even in a high-temperature environment. And an adhesive sheet using the same.

  In recent years, touch panels capable of intuitively operating electronic devices have been employed in so-called mobile products such as portable information terminals and electronic dictionaries. The touch panel is used by being incorporated into a liquid crystal display element, an organic EL element, or the like as a module substrate in which a transparent conductive film such as ITO is bonded to glass as a surface protective substrate via an adhesive. In such a touch sensor module substrate, one release sheet is peeled off from an adhesive sheet having a structure in which an adhesive is sandwiched between release sheets, the adhesive sheet is bonded to a transparent conductive film, and the other release sheet is peeled off. Then, it is general that the two are bonded together by bonding to a surface protective substrate, and then autoclaved under high temperature and high pressure.

  The touch sensor module substrate as described above is usually printed on the peripheral portion of the surface protection substrate for the purpose of imparting design properties to the surface to be bonded to the adhesive (that is, the inner surface of the surface protection substrate). May be decorated. For this reason, a step is formed at the boundary between the portion where the decoration such as printing is applied and the portion where the decoration such as printing is not provided on the surface of the surface protective substrate which is in contact with the adhesive. Therefore, it is necessary to prevent bubbles from being generated between the step and the adhesive by using a low-elasticity adhesive that can follow the step.

  However, if a low-elasticity adhesive that can follow unevenness such as steps is used, the adhesive will be deformed during autoclaving, and the position of the transparent conductive film and the surface protection substrate will shift, or the module substrate after autoclaving Due to slitting or punching when cutting the sheet into a predetermined size, the adhesive may protrude from the side of the end of the module substrate, and the protruding adhesive will adhere to the blade of the cutter or the operator's hand. As a result, workability is reduced. Therefore, there has been a demand for a pressure-sensitive adhesive that can follow unevenness such as a step, but has a certain degree of elasticity and does not deform under a high temperature environment.

Incidentally, JP 2010-229246 A (Patent Document 1) discloses that a printing step and an adhesive layer are prepared by adjusting the storage elastic modulus of the adhesive to 9.0 × 10 ^{4 to} 2.0 × 10 ⁵ Pa. A pressure-sensitive adhesive sheet in which no air bubbles are generated between the two is disclosed. JP 2012-193295 A (Patent Document 2) discloses an adhesive having a storage elastic modulus of 0.5 × 10 ^{6 to} 1.0 × 10 ⁸ Pa and a loss tangent of 0.1 or more. An adhesive tape for protecting the surface of a semiconductor wafer that can follow uneven steps on the surface of the wafer is disclosed.

JP 2010-229246 A JP 2012-193295 A

However, the pressure-sensitive adhesive proposed in Japanese Patent Application Laid-Open No. 2010-229246 has a high storage elastic modulus of 9.0 × 10 ^{4 to} 2.0 × 10 ⁵ Pa, and is intended to obtain a pressure-sensitive adhesive sheet that is smooth and has no unevenness. In other words, it is said that the pressure-sensitive adhesive layer must be composed of two or more layers, which increases the work load of the bonding process of the touch sensor module substrate. Moreover, the pressure-sensitive adhesive described in JP2012-193295A has an amorphous propylene- (1-butene) copolymer as a main component, and such an olefin-based pressure-sensitive adhesive has transparency and Optical characteristics such as haze are low, and it is not suitable for use as an adhesive for a touch panel module substrate used in the display device as described above.

  In the conventional acrylic pressure-sensitive adhesive, the present inventors have added a step difference to an adherend by adding an isocyanate compound in a specific blending amount as a crosslinking agent to an acrylic resin having a mass average molecular weight in a specific range. Can be tracked even in the presence of cracks, deforms even in high temperature environments, and the position of the transparent conductive film and the surface protection substrate shifts, or slit processing and punching processing when cutting the module substrate to a predetermined size after autoclaving As a result, it has been found that an adhesive that does not protrude from the side surface of the module substrate can be realized. The present invention is based on this finding.

  Therefore, the object of the present invention is to follow even if there is a step in the adherend, and even in a high temperature environment, the transparent conductive film and the surface protective substrate are displaced, and the module substrate is fixed after the autoclave process. It is to provide a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive does not protrude from the end side surface of the module substrate, and a pressure-sensitive adhesive sheet using the same.

The pressure-sensitive adhesive composition according to the present invention comprises at least an acrylic pressure-sensitive adhesive and an isocyanate compound as a crosslinking agent,
The acrylic pressure-sensitive adhesive comprises an acrylic resin having a mass average molecular weight in the range of 5 to 300,000,
The isocyanate compound is contained in an amount of 0.3 to 0.8 parts by mass in a solid ratio with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive.

  In an embodiment of the present invention, it is preferable that the acrylic pressure-sensitive adhesive comprises a copolymer of a (meth) acrylic acid ester monomer and a hydroxyl group-containing (meth) acrylate monomer.

In an embodiment of the present invention, the pressure-sensitive adhesive after crosslinking the pressure-sensitive adhesive composition has a storage elastic modulus at 25 ° C. of less than 1.1 × 10 ⁶ and a loss tangent of 0.7 or more. Preferably there is.

In an embodiment of the present invention, the pressure-sensitive adhesive after crosslinking the pressure-sensitive adhesive composition has a storage elastic modulus at 85 ° C. in the range of 1.5 × 10 ^{4 to} 5.0 × 10 ⁴ , and The loss tangent is preferably 0.7 to 1.5.

  In the embodiment of the present invention, it is preferable to further comprise a silane coupling agent.

  The pressure-sensitive adhesive sheet according to another aspect of the present invention is a pressure-sensitive adhesive sheet comprising a release paper and a pressure-sensitive adhesive layer provided on the release paper, wherein the pressure-sensitive adhesive layer is composed of the above-mentioned adhesive composition. It is.

Moreover, the manufacturing method of the bonding body by another aspect of this invention is a method of manufacturing a bonding body using the said adhesive sheet,
The adhesive sheet is bonded to an adherend so that the adhesive layer side of the adhesive sheet faces,
From the pressure-sensitive adhesive sheet bonded to the adherend, the release paper is peeled and removed to expose the pressure-sensitive adhesive layer,
Bonding the other adherend to the exposed pressure-sensitive adhesive layer, and bonding the adherend and the other adherend;
It is meant to include.

  According to the present invention, by adding an isocyanate compound at a specific blending amount as a crosslinking agent to an acrylic resin having a mass average molecular weight in a specific range, the adherend can follow even if there is a step, and high temperature Due to deformation even under the environment, the position of the transparent conductive film and the surface protection substrate is shifted, or from the side surface of the end of the module substrate by slitting or punching when cutting the module substrate to a predetermined size after autoclaving A pressure-sensitive adhesive composition in which the pressure-sensitive adhesive does not protrude can be realized.

<Adhesive composition>
The pressure-sensitive adhesive composition according to the present invention includes an acrylic pressure-sensitive adhesive and an isocyanate compound as a crosslinking agent as essential components. Hereinafter, each component which comprises an adhesive composition is demonstrated.

  As the acrylic pressure-sensitive adhesive contained in the pressure-sensitive adhesive composition according to the present invention, any conventionally known acrylic pressure-sensitive adhesive can be used without limitation as long as it can react with an isocyanate-based cross-linking agent described below to form a crosslink. For example, an acrylic pressure-sensitive adhesive mainly composed of (meth) acrylic acid ester can be preferably used. In the present specification, (meth) acrylic acid refers to acrylic acid and / or methacrylic acid, and (meth) acrylate refers to acrylate and / or methacrylate. Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, and n-octyl (meta ) Acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate Stearyl (meth) acrylate and the like can be used. These acrylic acid esters may contain 1 type (s) or 2 or more types.

  In this invention, it is preferable to use what copolymerized the hydroxyl-containing (meth) acrylate monomer in addition to above-mentioned (meth) acrylic acid ester.

  Examples of the hydroxyl group-containing (meth) acrylate monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-butyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl- 3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly (ethylene glycol) Lumpur - propylene glycol) mono (meth) acrylate, N- methylol acrylamide, allyl alcohol, methallyl alcohol and the like. One or more of these hydroxyl group-containing (meth) acrylate monomers may be contained. By including the hydroxyl group-containing (meth) acrylate monomer as described above, the reworkability of the acrylic pressure-sensitive adhesive can be improved.

  The hydroxyl group-containing (meth) acrylate monomer described above can be added to the (meth) acrylic acid ester in consideration of the adhesiveness and reworkability of the acrylic pressure-sensitive adhesive. It is preferable to add 0.1 to 20% of a hydroxyl group-containing (meth) acrylate monomer on a mass basis with respect to the (meth) acrylic acid ester monomer.

  In the present invention, in addition to the monomers described above, glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, glycidyl (meta ) Glycidyl group-containing (meth) acrylate monomers such as allyl ether and 3,4-epoxycyclohexyl (meth) allyl ether, acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-tert-butylacrylamide, N-o Chill acrylamide may be included containing amide groups of diacetone acrylamide (meth) acrylate monomer.

  The acrylic pressure-sensitive adhesive (copolymer) used in the present invention can be obtained by polymerizing the above monomers by a method such as ordinary solution polymerization, bulk polymerization, emulsion polymerization or suspension polymerization. However, it is preferable to manufacture by the solution polymerization from which the said acrylic adhesive is obtained as a solution. By obtaining the acrylic pressure-sensitive adhesive as a solution, it can be used as it is for the production of the pressure-sensitive adhesive composition of the present invention.

  Examples of the solvent used for the solution polymerization include organic solvents such as ethyl acetate, toluene, n-hexane, acetone, and methyl ethyl ketone. Examples of the polymerization initiator used in the polymerization include peroxides such as benzoyl peroxide and lauryl peroxide, azobis compounds such as azobisisobutyronitrile and azobisvaleronitrile, and polymer azo polymerization initiators. These can be used alone or in combination. Moreover, in the said superposition | polymerization, in order to adjust the molecular weight of an acrylic adhesive, a conventionally well-known chain transfer agent can be used.

  The above-mentioned acrylic copolymer has a mass average molecular weight in the range of 50,000 to 300,000, preferably in the range of 100,000 to 200,000. If the weight average molecular weight is less than 50,000, the hardness of the pressure-sensitive adhesive composition becomes too soft, and thus when the pressure-sensitive adhesive sheet is wound into a roll, such as when the pressure-sensitive adhesive sheet is wound into a roll, the sheet There is a risk of the adhesive sticking out of the end of the. On the other hand, when the mass average molecular weight exceeds 300,000, the hardness of the pressure-sensitive adhesive composition becomes too hard, and thus the followability of the pressure-sensitive adhesive composition is deteriorated, for example, when the adherend surface has irregularities. The mass average molecular weight can be measured by GPC (gel permeation chromatography) using a polystyrene standard sample.

  Next, the crosslinking agent will be described. The pressure-sensitive adhesive composition according to the present invention contains an isocyanate compound as a crosslinking agent in addition to the above-mentioned acrylic pressure-sensitive adhesive. As the isocyanate compound, a conventionally known crosslinking agent can be used. For example, a polyisocyanate compound, a trimer of a polyisocyanate compound, or an isocyanate group obtained by reacting a polyisocyanate compound with a polyol compound is terminated. And a urethane prepolymer, a trimer of the urethane prepolymer, and the like. Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate, 2,5-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3 -Methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like. These isocyanate crosslinking agents may be used alone or in combination of two or more.

In this invention, the above-mentioned isocyanate type compound is contained in the adhesive composition in the ratio of 0.3-0.8 mass part by solid ratio with respect to 100 mass parts of acrylic adhesives. When the content of the isocyanate compound is less than 0.3 parts by mass, the crosslinking density of the cured acrylic pressure-sensitive adhesive is low, and the acrylic pressure-sensitive adhesive having a mass average molecular weight in the range of 5 to 300,000 is at 85 ° C. Since the storage elastic modulus is higher than 5.0 × 10 ⁴ , the pressure-sensitive adhesive is easily deformed when placed in a high temperature environment such as autoclave treatment, and the position of the transparent conductive film and the surface protection substrate is shifted. In some cases, the adhesive protrudes from the side surface of the end of the module substrate due to slitting or punching when cutting. On the other hand, if the content of the isocyanate compound exceeds 0.8 parts by mass, the acrylic adhesive having a mass average molecular weight in the range of 5 to 300,000 is too hard to be cured, so that there is a step on the adherend. Even if there is, there is a case where the air bubbles generated between the printing step and the pressure-sensitive adhesive remain after the autoclave treatment. A preferred isocyanate compound is 0.35 to 0.65 parts by mass.

  Moreover, in this invention, in addition to the above-mentioned isocyanate type crosslinking agent, you may use an epoxy type crosslinking agent together as a crosslinking agent. Examples of the epoxy-based crosslinking agent include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diglycidyl ether. 1, 6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutadiene diglycidyl ether, and the like. These epoxy-based crosslinking agents may be used alone or in combination of two or more. When an epoxy crosslinking agent is used in combination, its content can be adjusted as appropriate, but as described above, it is necessary to add it in a range that does not impair the effects of the present invention.

  The pressure-sensitive adhesive composition according to the present invention may contain a silane coupling agent as an optional component. Although it depends on the material of the adherend, the adhesive strength is improved by including a silane coupling agent. Conventionally known silane coupling agents can be used, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, Epoxy group-containing silane coupling agents such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3 Amino group-containing silane coupling agents such as -triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, (meth) such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane Acrylic group-containing silane coupling agent Inshianeto group-containing silane coupling agents such as 3-isocyanate propyltriethoxysilane, and the like. These may be used alone or in combination of two or more.

  The pressure-sensitive adhesive composition according to the present invention may contain additives such as an ultraviolet absorber and an antioxidant. As the ultraviolet absorber, known compounds can be used, and examples thereof include organic ultraviolet absorbers such as benzotriazole, benzophenone, salicylate, and benzoate, and inorganic ultraviolet absorbers.

  In addition, by including an antioxidant in the pressure-sensitive adhesive composition, the color change in the visible light region and the color change in the near-infrared region can be further suppressed, and the transparency can be maintained. The pressure-sensitive adhesive composition (acrylic pressure-sensitive adhesive) may be deteriorated by ultraviolet rays or temperature, and the oxidation of the acrylic pressure-sensitive adhesive can be suppressed by the antioxidant, so that transparency can be maintained. . Examples of the antioxidant include phenol-based, amine-based, sulfur-based, and phosphorus-based antioxidants.

  In addition, the pressure-sensitive adhesive composition may include, for example, processability, heat resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slip properties, mold release properties, flame retardancy, antifungal properties. For the purpose of improving and modifying properties, electrical properties, strength, etc., for example, lubricants, plasticizers, fillers, fillers, antistatic agents, antiblocking agents, crosslinking agents, light stabilizers, dyes, pigments, etc. Other colorants, etc. may be added. Further, if necessary, a coupling agent such as silane, titanium, and aluminum can be further included.

  The pressure-sensitive adhesive composition according to the present invention can be prepared by mixing the above-described components and kneading and dispersing as necessary. The mixing or dispersing method is not particularly limited, and a usual kneading and dispersing machine such as a two-roll mill, a three-roll mill, a pebble mill, a tron mill, a Szegvari attritor, a high-speed impeller disperser, a high-speed stone mill, A high speed impact mill, a desper, a high speed mixer, a ribbon blender, a kneader, an intensive mixer, a tumbler, a blender, a desperser, a homogenizer, an ultrasonic disperser, and the like can be applied. In addition, in order to adjust the viscosity of the pressure-sensitive adhesive coating solution, a diluent solvent may be added to mix each component.

The pressure-sensitive adhesive composition obtained as described above undergoes a cross-linking reaction of the acrylic pressure-sensitive adhesive by carrying out autoclave treatment under high temperature and high pressure to become a pressure-sensitive adhesive. In the present invention, an acrylic resin having a mass average molecular weight in the range of 5 to 300,000 is a main agent, and an isocyanate compound is used as a crosslinking agent in a solid ratio of 0.3 to 0.8 with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive. Since it contains a mass part, the storage elastic modulus in 25 degreeC of the obtained adhesive can be less than 1.1 * 10 < ⁶ >, and loss tangent can be 0.7 or more. For this reason, even when a pressure-sensitive adhesive composition is applied to a transparent conductive film (glass or transparent resin film) in which there is a printed step at the peripheral edge at the time of pasting a module substrate, which is usually performed in a room temperature environment. The pressure-sensitive adhesive composition can follow the steps and suppress the generation of bubbles.

In the present invention, since the isocyanate compound is added at a specific blending amount as a crosslinking agent to the acrylic resin having a mass average molecular weight in a specific range as described above, the obtained adhesive has a temperature of 85 ° C. In the range of 1.5 × 10 ^{4 to} 5.0 × 10 ⁴ and the loss tangent can be in the range of 0.7 to 1.5. For this reason, the position of the transparent conductive film and the surface protection substrate is shifted due to deformation even in a high temperature environment, or the module substrate is cut or punched when the module substrate is cut into a predetermined size after the autoclave process. The adhesive does not protrude from the end side surface.

<Adhesive sheet>
The pressure-sensitive adhesive sheet according to the present invention comprises a release paper and a pressure-sensitive adhesive layer provided on the release paper, and the pressure-sensitive adhesive layer comprises the above-described pressure-sensitive adhesive composition. In this embodiment, it has a layer configuration in which the release paper is provided only on one side of the pressure-sensitive adhesive layer, but the layer configuration in which the first release paper and the second release paper are provided on both sides of the pressure-sensitive adhesive layer. It may be an embodiment. In the present specification, the first release paper and the second release paper are collectively referred to as release paper.

  The pressure-sensitive adhesive sheet can be obtained by applying the pressure-sensitive adhesive composition to a first release paper to be described later and drying it, and then bonding the second release paper to the coated surface. The thickness of the pressure-sensitive adhesive layer is preferably about 100 μm to 200 μm. If the thickness of the pressure-sensitive adhesive layer (the amount of the pressure-sensitive adhesive composition applied) is too thin, the pressure-sensitive adhesive composition may absorb unevenness of the adherend (for example, the step of frame printing provided on the periphery of the touch sensor member). There are cases where it is not possible. On the other hand, even if the thickness exceeds 200 μm, the adhesive strength and the like are not improved, and the cost is increased.

  The method for applying the pressure-sensitive adhesive composition to the release paper is not particularly limited. For example, roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coat, blade Coating, bar coating, wire bar coating, die coating, lip coating, dip coating, etc. can be applied. After the adhesive composition is applied to the release surface of the first release paper by the above-described coating method and dried, the second release paper may be bonded.

  The first release paper and the second release paper may be the same or different. As the release paper, conventionally known ones such as a release film, a separate paper, a separate film, a separate paper, a release film, a release paper and the like can be suitably used. Moreover, you may use what formed the release layer in the single side | surface or both surfaces of base materials for release paper, such as quality paper, a coated paper, an impregnation paper, and a plastic film. The release layer is not particularly limited as long as it is a material having releasability. For example, silicone resin, organic resin-modified silicone resin, fluororesin, aminoalkyd resin, melamine resin, acrylic resin, polyester resin, etc. There is. These resins can be used in any of emulsion type, solvent type and solventless type.

  The release layer is formed by applying a coating liquid in which a release layer component is dispersed and / or dissolved on one side of a release paper base film, followed by heat drying and / or curing. As a coating method of the coating liquid, a known and arbitrary coating method can be applied, for example, roll coating, gravure coating, spray coating and the like. Moreover, you may form a release layer in the whole surface or a part of at least single side | surface of a base film as needed.

  The peeling force of the first and second release papers is preferably about 1 to 2000 mN / cm, more preferably 100 to 1000 mN / cm, with respect to the pressure-sensitive adhesive sheet. When the release force of the release layer is less than 1 mN / cm, the release force from the pressure-sensitive adhesive sheet or the adherend is weak, and it peels off or partially floats. Moreover, when larger than 2000 mN / cm, the peeling force of a release layer is strong and it is hard to peel. From the viewpoint of stable releasability and processability, addition and / or polycondensation-type curable silicone resins for release paper, which are mainly composed of polydimethylsiloxane, are preferred.

  According to the present invention, an adherend can be bonded to another adherend via an adhesive layer using the above-described pressure-sensitive adhesive sheet to obtain a module substrate.

  Examples The present invention will be described in more detail with reference to examples, but the present invention is not limited to the contents of these examples.

Example 1
<Preparation of pressure-sensitive adhesive composition>
Nitrogen gas was introduced into a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, and the air in the reaction apparatus was replaced with nitrogen gas. Thereafter, 100 parts by mass of butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 10 parts by mass of N, N-diethylacrylamide, and 60 parts by mass of ethyl acetate were added to the reactor. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was allowed to react with stirring in a nitrogen gas stream at 50 ° C. for 3 hours to obtain a weight average molecular weight of 150,000 and a solid content of 64 % Acrylic copolymer was obtained.

  Further, K-341 (solid content: 75%, manufactured by Seiden Chemical Co., Ltd.), which is a polyisocyanate composed of an xylene diisocyanate adduct, was used as a crosslinking agent. A crosslinking agent was added to the acrylic copolymer obtained above so that the solid ratio was 0.4 parts by mass with respect to 100 parts by mass of the acrylic copolymer. Also. Silane coupling agent (S-1, solid content 6.3%, manufactured by Seiden Chemical Co., Ltd.) and ethyl acetate as solvent and 0.465 parts by mass and 0.1 parts by weight, respectively, with respect to 100 parts by mass of acrylic adhesive. It added so that it might become a mass part, and the adhesive composition was obtained by mixing with a stirrer.

Examples 2-3
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the addition amount of the crosslinking agent was changed as shown in Table 1.

Example 4
In the reactor used in Example 1, 100 parts by mass of butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 10 parts by mass of N, N-diethylacrylamide, and 60 parts by mass of ethyl acetate were added. It was. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was stirred and reacted in a nitrogen gas stream at 50 ° C. for 1.5 hours. An acrylic copolymer having a content of 66% was obtained (mass average molecular weight 60,000, solid content 66%). A pressure-sensitive adhesive composition was obtained in the same manner as in Example 3 except that the acrylic copolymer obtained above was used.

Example 5
In the reactor used in Example 1, 100 parts by mass of butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 10 parts by mass of N, N-diethylacrylamide, and 60 parts by mass of ethyl acetate were added. It was. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was stirred and reacted in a nitrogen gas stream at 50 ° C. for 5 hours to obtain a weight average molecular weight of 300,000 and a solid content of 52 % Acrylic copolymer was obtained (mass average molecular weight 300,000, solid content 52%). A pressure-sensitive adhesive composition was obtained in the same manner as in Example 3 except that the acrylic copolymer obtained above was used.

Comparative Examples 1 and 2
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the addition amount of the crosslinking agent was changed as shown in Table 1.

Comparative Example 3
In the reactor used in Example 1, 100 parts by mass of butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 10 parts by mass of N, N-diethylacrylamide, and 60 parts by mass of ethyl acetate were added. It was. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was stirred and reacted in a nitrogen gas stream at 50 ° C. for 0.5 hour. An acrylic copolymer having a content of 52% was obtained (mass average molecular weight 40,000, solid content 72%). A pressure-sensitive adhesive composition was obtained in the same manner as in Example 3 except that the acrylic copolymer obtained above was used.

Comparative Example 4
In the reactor used in Example 1, 100 parts by mass of butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 10 parts by mass of N, N-diethylacrylamide, and 60 parts by mass of ethyl acetate were added. It was. Thereafter, 0.1 part by mass of azobisisobutyronitrile was added as a polymerization initiator, and the mixture was stirred and reacted in a nitrogen gas stream at 50 ° C. for 6 hours to obtain a weight average molecular weight of 370,000 and a solid content of 52 % Acrylic copolymer was obtained (mass average molecular weight 370,000, solid content 52%). A pressure-sensitive adhesive composition was obtained in the same manner as in Example 3 except that the acrylic copolymer obtained above was used.

<Production of adhesive sheet>
Next, the obtained pressure-sensitive adhesive composition was applied to a PET carrier film (POL502150, manufactured by Lintec) having a thickness of 50 μm subjected to silicone peeling treatment with an applicator so that the thickness after drying was 175 μm. The adhesive layer was formed by drying for 4 minutes and further heating at 110 degreeC for 4 minute (s). Subsequently, a silicone carrier-treated PET carrier film (POL 501031, manufactured by Lintec) having a thickness of 50 μm was bonded to the adhesive layer surface, and an adhesive sheet was obtained by aging at room temperature, normal humidity and normal pressure for 1 week.

<Dynamic viscoelasticity measurement>
The obtained adhesive sheet was heat-treated in an autoclave apparatus under conditions of 0.5 MPa, 50 ° C. and 30 minutes, and then the carrier films on both sides were peeled off to obtain an adhesive. Measurement of storage elastic modulus E ′ and loss tangent tan δ of this pressure-sensitive adhesive at 25 ° C. and 85 ° C. was conducted in accordance with JIS K7244-1 using a solid viscoelasticity analyzer RSA-III manufactured by TA Instruments. The dynamic viscoelasticity measurement method (attachment mode: compression mode, frequency: 1 Hz, temperature: −50 to 150 ° C., temperature increase rate: 5 ° C./min) was performed. The results were as shown in Table 1 below.

<Evaluation of step following ability and glue shift>
A glass having a thickness of 1.0 mm and a size of 60 mm × 120 mm was prepared, and decorative printing was performed on the peripheral portion of one surface thereof so that the width was 5 mm and the thickness was 50 μm (hereinafter, a step-formed glass plate). Say). Further, a glass having a thickness of 1.0 mm and a size of 60 mm × 120 mm for bonding to the step-formed glass plate was prepared (hereinafter referred to as a flat glass plate). Furthermore, what cut | judged the adhesive sheet obtained above as a pressure-sensitive adhesive sheet for bonding these two glass plates so that a size might be set to 60 mm x 120 mm was prepared.

The carrier film on one side of the pressure-sensitive adhesive sheet is peeled to expose the pressure-sensitive adhesive layer, and after bonding to the flat glass plate, the other carrier film of the pressure-sensitive adhesive sheet is peeled off, and the pressure-sensitive adhesive layer exposed by an automatic laminator. Was bonded to the surface of the step-formed glass plate on which decorative printing was applied, thereby obtaining a bonded body of the flat glass plate and the step-formed glass plate. Subsequently, the obtained bonded body was heat-treated in an autoclave apparatus under conditions of 0.5 MPa, 50 ° C., and 30 minutes, and then the decorative print portion (peripheral edge of the bonded body) of the bonded body was visually observed. Then, it was confirmed whether or not the adhesive follows the step. The evaluation criteria were as follows.
○: No bubbles can be confirmed.
X: A bubble or air layer is observed in the step portion. The evaluation results are as shown in Table 1 below.

Next, after leaving the above-mentioned autoclave-treated bonded body in an atmosphere of 85 ° C. × 85% Rh for 100 hours, it is visually confirmed whether or not the position of the step-formed glass plate and the flat glass plate of the bonded body is shifted. did. The evaluation criteria were as follows.
○: No misalignment at all ×: Misalignment to the extent that visual discrimination is possible The evaluation results are as shown in Table 1 below.

Claims (7)

Comprising at least an acrylic pressure-sensitive adhesive and an isocyanate compound as a crosslinking agent,
The acrylic pressure-sensitive adhesive comprises an acrylic resin having a mass average molecular weight in the range of 5 to 300,000,
The pressure-sensitive adhesive composition comprising 0.3 to 0.8 parts by mass of the isocyanate compound in a solid ratio with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive.   The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic pressure-sensitive adhesive comprises a copolymer of a (meth) acrylic acid ester monomer and a hydroxyl group-containing (meth) acrylate monomer. The storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive after crosslinking the pressure-sensitive adhesive composition is less than 1.1 × 10 ⁶ , and the loss tangent is 0.7 or more. Adhesive composition. The pressure-sensitive adhesive after crosslinking the pressure-sensitive adhesive composition has a storage elastic modulus at 85 ° C. in the range of 1.5 × 10 ^{4 to} 5.0 × 10 ⁴ and a loss tangent of 0.7 to 1.5. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising a silane coupling agent.   It is an adhesive sheet provided with the release paper and the adhesive layer provided on the said release paper, Comprising: The said adhesive layer consists of an adhesive composition as described in any one of Claims 1-5. , Adhesive sheet. A method for producing a bonded body using the pressure-sensitive adhesive sheet according to claim 6,
The adhesive sheet is bonded to an adherend so that the adhesive layer side of the adhesive sheet faces,
From the pressure-sensitive adhesive sheet bonded to the adherend, the release paper is peeled and removed to expose the pressure-sensitive adhesive layer,
Bonding the other adherend to the exposed pressure-sensitive adhesive layer, and bonding the adherend and the other adherend;
Comprising a method.