JP6066390B1 - Adhesive composition, adhesive sheet, and touch panel and display device provided with adhesive sheet - Google Patents

Abstract

A pressure-sensitive adhesive composition that has excellent irregularity followability when bonded to an adherend and can suppress the occurrence of delayed bubbles, floating, and peeling after bonding, and a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition A pressure-sensitive adhesive sheet is provided. Moreover, the touch panel and display apparatus which are provided with the said adhesive sheet and can suppress effectively that a delay bubble etc. generate | occur | produce after joining are provided. Monomer having an acrylic ester copolymer having a crosslinkable functional group, an oligomer having two or more polymerizable unsaturated groups, a functional group that reacts with the acrylic ester copolymer, and a functional group that reacts with the oligomer And a crosslinking agent that reacts with the acrylate copolymer by heat, and a polymerization initiator that initiates a polymerization reaction by irradiation with active energy rays.

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, and a touch panel and a display device including the pressure-sensitive adhesive sheet.

  In recent years, display devices such as a liquid crystal display (LCD) and input devices used in combination with the display device such as a touch panel have been widely used in various fields. In the production of these display devices and input devices, for example, a transparent double-sided pressure-sensitive adhesive sheet is used for bonding optical members, and a transparent double-sided pressure-sensitive adhesive sheet is also used for bonding between a display device and an input device. It is used. Here, some of the touch panels, liquid crystal displays, and the like include a constituent member having a stepped portion (uneven portion) by printing or the like. For example, in a cellular phone, a member provided with a frame-like printed portion The touch panel which has is used. In such an application, the pressure-sensitive adhesive sheet is required to have a capability of filling a printing step at the same time as bonding and fixing a member, that is, an excellent uneven follow-up property (step absorption property) (for example, Patent Document 1). In addition, when uneven | corrugated followable | trackability is low, a bubble will remain easily in a level | step-difference part.

  As a double-sided pressure-sensitive adhesive sheet used for the above applications, a pressure-sensitive adhesive composition having both thermosetting and active energy ray-curing properties (hereinafter, sometimes referred to as “dual curable pressure-sensitive adhesive composition”). There has been proposed one provided with a pressure-sensitive adhesive layer which is applied onto a base material and semi-cured by heat curing or active energy ray curing. Such an adhesive layer has active energy ray curability in the case of a thermoset, and thermosetting properties in the case of an active energy ray cure. Therefore, it is possible to follow the unevenness by having flexibility at the time of bonding with the adherend, and then to adhere firmly to the adherend by further completely curing by active energy rays or heating, It is said that the holding power is compatible.

  Conventionally, as a dual curable pressure-sensitive adhesive composition used for such a pressure-sensitive adhesive sheet, a crosslinking agent is added as a component for imparting thermosetting properties, and a monomer and a photoinitiator are blended in a base polymer as components for imparting active energy ray curing. What has been proposed. As the monomer, a polyfunctional monomer is usually used.

  For example, Patent Document 2 discloses a pressure-sensitive adhesive that combines two types of crosslinking methods, ultraviolet crosslinking and heat crosslinking, by blending a base polymer with both a UV-crosslinkable photocrosslinking agent and a heat-curable latent curing agent. A pressure-sensitive adhesive and a pressure-sensitive adhesive to be cross-linked by either one of the crosslinking methods and pasting the adherend and then post-crosslinked by the remaining crosslinking method are disclosed. The thing containing an agent is used.

  Patent Document 3 discloses an active energy ray-curable adhesive composition containing a polymer having a maleimide group, the composition further comprising an organic solvent, one or more ethylene in the molecule. It describes that it may contain a compound having a polymerizable unsaturated group, a photopolymerization initiator, a thermosetting crosslinking agent, and the like.

JP 2010-90204 A JP 2006-335840 A JP 2010-261029 A

  The pressure-sensitive adhesive layer made of the dual-curing pressure-sensitive adhesive composition is soft and has excellent uneven surface followability because it is in a semi-cured state when bonded to an adherend (for example, a touch panel or a display device). It is certainly excellent in that it can effectively suppress the remaining of bubbles in the part and can be firmly adhered to the adherend by the subsequent active energy ray or complete curing by heating.

  However, the pressure-sensitive adhesive layer made of the dual-curing pressure-sensitive adhesive composition has a phenomenon that bubbles are restored with the passage of time after the complete curing (occurrence of delayed bubbles) and a phenomenon such as floating and peeling. It was difficult to suppress effectively, and appearance problems sometimes occurred.

  The present invention was made in order to solve such problems, and has excellent unevenness followability when bonded to an adherend, and delayed bubbles, floating and peeling occur after bonding. It is an object of the present invention to provide a pressure-sensitive adhesive composition capable of suppressing the above and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition. It is another object of the present invention to provide a touch panel and a display device that include the pressure-sensitive adhesive sheet and can effectively suppress the occurrence of delayed bubbles after bonding.

The object of the present invention is to provide an acrylic ester copolymer having a crosslinkable functional group, an oligomer having two or more polymerizable unsaturated groups, a functional group that reacts with the acrylic ester copolymer, and the oligomer. a monomer having a reactive functional group, contains a crosslinking agent that reacts with the acrylic acid ester copolymer by heat, a polymerization initiator to initiate the polymerization reaction by irradiation of active energy ray, wherein the monomer is a hydroxyl group It is achieved by a pressure-sensitive adhesive composition characterized by being a (meth) acryloyl group-containing monomer having an organic functional group that reacts with .

  Moreover, it is preferable that the said oligomer contains urethane (meth) acrylate.

  Moreover, it is preferable that the said acrylate copolymer does not contain a carboxyl group.

  The object of the present invention is achieved by a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer obtained by primary crosslinking of the pressure-sensitive adhesive composition described above by heating. Moreover, the said objective is achieved by a touchscreen and a display apparatus provided with such an adhesive sheet.

  According to the present invention, the pressure-sensitive adhesive composition has excellent unevenness followability at the time of bonding to an adherend, and can suppress the occurrence of delayed bubbles, floating, and peeling after bonding, and the pressure-sensitive adhesive composition. The adhesive sheet which has an adhesive layer which consists of a thing can be provided. In addition, it is possible to provide a touch panel and a display device that include the pressure-sensitive adhesive sheet and can effectively suppress the occurrence of delayed bubbles after bonding.

  Hereinafter, a pressure-sensitive adhesive composition according to an embodiment of the present invention and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition will be described. First, the pressure-sensitive adhesive composition according to the present invention is a dual-curing pressure-sensitive adhesive composition, which is first-cured (semi-cured) by heating and then second-cured (fully cured) by irradiation with active energy rays. It is a pressure-sensitive adhesive composition that can be applied.

  The pressure-sensitive adhesive composition according to the present invention includes an acrylic ester copolymer (A) having a crosslinkable functional group, an oligomer (B) having two or more polymerizable unsaturated groups, and the acrylic ester copolymer. A monomer (C) having a functional group that reacts with (A) and a functional group that reacts with the oligomer (B), a crosslinking agent (D) that reacts with the acrylate copolymer (A) by heat, and an activity A polymerization initiator (E) for initiating a polymerization reaction of the oligomer (B) and the monomer (C) by irradiation with energy rays;

  The acrylic ester copolymer (A) constitutes the main component of the pressure-sensitive adhesive composition according to the present invention, and can be preferably used as a pressure-sensitive adhesive composition because of its excellent transparency and durability. As the acrylic ester copolymer (A), a copolymer of (meth) acrylic acid alkyl ester and a monomer having a reactive functional group is preferable. The acrylic ester copolymer (A) may be used alone or in combination with other polymers.

  Examples of the (meth) acrylic acid alkyl ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and n-pentyl (meth) acrylate. , N-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate , Myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. These may be used alone or in combination of two or more. In the present invention, “(meth) acrylic acid” means containing both “acrylic acid” and “methacrylic acid”.

  In addition, examples of the monomer having a reactive functional group include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and an amino group-containing monomer, and a hydroxyl group-containing monomer that hardly corrodes a metal is preferable. Examples of the hydroxyl group-containing monomer of the present invention include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate. And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. These may be used alone or in combination of two or more. Moreover, you may have another monomer as needed. On the other hand, when the pressure-sensitive adhesive sheet according to the present invention is bonded to an adherend on which an electrode containing a metal or an alloy is formed, the acrylate copolymer is carboxylated because it may corrode the metal or the like. Preferably no groups are included. Here, “does not contain” means not contained in the material design of the pressure-sensitive adhesive composition, and is a concept that allows a minute amount to be contained as an impurity.

  The hydroxyl value in the acrylate copolymer (A) is preferably 50 to 200 mgKOH / g. If the hydroxyl value is smaller than the lower limit of the range, the wet heat durability is deteriorated, and if it is larger than the upper limit of the range, the compatibility with the oligomer (B) is deteriorated.

  The weight average molecular weight of the acrylate copolymer (A) is preferably 100,000 to 800,000, more preferably 200,000 to 600,000, and further preferably 300,000 to 500,000. If the weight average molecular weight is smaller than the lower limit, durability after curing is lowered, and if the weight average molecular weight is larger than the upper limit, the unevenness followability is lowered. In addition, the weight average molecular weight of an acrylate ester copolymer (A) is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method. As the acrylic ester copolymer, a commercially available one may be used, or one synthesized by a known method may be used.

  The oligomer (B) is a photocurable oligomer and has at least two polymerizable unsaturated groups. By including such an oligomer (B) in the pressure-sensitive adhesive composition, it is possible to obtain a flexible pressure-sensitive adhesive sheet having high unevenness followability by primary curing, and also increasing the cohesive force by irradiation with active energy rays to improve durability. Can be improved. In addition, since the oligomer (B) has less bleed out than the monomer, deterioration over time can be effectively suppressed.

  The polymerizable unsaturated group is preferably a group containing an ethylenic double bond, and examples thereof include a (meth) acryloyl group and a vinyl group. Of these, a (meth) acryloyl group is particularly preferable.

  As the oligomer (B), for example, oligomers such as alkyl (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and polyether (meth) acrylate can be preferably used. These may be used alone or in combination of two or more. In particular, those containing a urethane (meth) acrylate component are preferred because of compatibility with the acrylic ester copolymer (A) and ease of imparting properties such as flexibility and elongation. The oligomer (B) may contain other monomers and solvents as needed, for example, for the purpose of dilution.

  The urethane (meth) acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reaction of polyether polyol or polyester polyol with polyisocyanate by reaction with (meth) acrylic acid.

  In the pressure-sensitive adhesive composition according to the present invention, the content of the oligomer (B) is appropriately selected according to the composition, molecular weight, crosslinking density, etc. of the acrylate copolymer (A), and is not particularly limited. 0.3-30 weight part is preferable with respect to 100 weight part of ester copolymers (A), and 0.5-20 weight part is more preferable. 1 to 15 parts by weight is more preferable. If the content of the oligomer (B) is smaller than the lower limit value of the range, the cohesive force after photocuring is insufficient, and if it is larger than the upper limit value of the range, the adhesive force after photocuring is reduced.

  The monomer (C) is a monomer having a functional group (thermal crosslinking) that reacts with the acrylate copolymer (A) and a functional group (photocrosslinking) that reacts with the oligomer (B). Specifically, for example, a (meth) acryloyl group-containing monomer having an organic functional group that reacts with a hydroxyl group is preferred. As the (meth) acryloyl group-containing monomer having an organic functional group, the acrylate copolymer such as glycidyl group-containing (meth) acrylate monomer, hydroxy group-containing (meth) acrylate monomer, isocyanate group-containing (meth) acrylate monomer, etc. Although it will not specifically limit if it has a functional group which reacts with (A), An isocyanate group containing (meth) acrylate monomer is used suitably from the point that reaction is easy.

  In the pressure-sensitive adhesive composition according to the present invention, the content of the monomer (C) is appropriately selected according to the composition, molecular weight, crosslinking density, etc. of the acrylic ester copolymer (A), and is not particularly limited. 0.01-5.0 weight part is preferable with respect to 100 weight part of ester copolymer (A), and 0.05-1.0 weight part is more preferable. When the content of the monomer (C) is smaller than the lower limit value of the above range or larger than the upper limit value, there is a concern that the adhesive force is remarkably lowered.

  The crosslinking agent (D) is not particularly limited, and examples thereof include acrylic acid ester copolymers among known crosslinking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, butylated melamine compounds. It can be appropriately selected in consideration of the reactivity with the crosslinkable functional group possessed by (A). For example, when a hydroxy group is included as a crosslinkable functional group, it is preferable to use an isocyanate compound from the reactivity of the hydroxy group. In addition, as a crosslinking agent (D), 1 type of the said compound may be used independently, or 2 or more types may be used together.

  Of the above compounds exemplified as the crosslinking agent (D), an isocyanate compound and an epoxy compound are preferable because the acrylate copolymer (A) having a crosslinkable functional group can be easily crosslinked. Examples of the isocyanate compound include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of the epoxy compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexane. Diol diglycidyl ether, tetraglycidyl xylenediamine, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether Etc.

  In the pressure-sensitive adhesive composition, the content of the crosslinking agent (D) is appropriately selected according to the desired physical properties of the pressure-sensitive adhesive, and is not particularly limited, but is 0 with respect to 100 parts by weight of the acrylic ester copolymer (A). 0.01 to 5.0 parts by weight is preferable, and 0.01 to 3.0 parts by weight is more preferable. If the content of the crosslinking agent (D) is not less than the lower limit, the processability and durability are excellent, and if it is not more than the upper limit, the unevenness followability is excellent.

  The polymerization initiator (E) includes a polymerizable unsaturated group of the oligomer (B) and a functional group (polymerizable unsaturated group) that reacts with the oligomer (B) of the monomer (C) by irradiation with active energy rays. Any known photopolymerization initiator can be used as long as it can initiate the polymerization reaction. Here, “active energy rays” mean those having energy quanta among electromagnetic waves or charged particle beams, and examples include ultraviolet rays, electron beams, visible rays, X-rays, ion rays and the like. Among these, from the viewpoint of versatility, ultraviolet rays or electron beams are preferable, and ultraviolet rays are particularly preferable.

  Examples of the polymerization initiator (E) include acetophenone-based initiators, benzoin ether-based initiators, benzophenone-based initiators, hydroxyalkylphenone-based initiators, thioxanthone-based initiators, and amine-based initiators. Of these, specific examples of the acetophenone-based initiator include diethoxyacetophenone and benzyldimethyl ketal. Specific examples of the benzoin ether initiator include benzoin and benzoin methyl ether. Specific examples of the benzophenone-based initiator include benzophenone and methyl o-benzoylbenzoate. Specific examples of the hydroxyalkylphenone-based initiator include 1-hydroxy-cyclohexyl-phenyl-ketone and the like. Specific examples of the thioxanthone initiator include 2-isopropylthioxanthone and 2,4-dimethylthioxanthone. Specific examples of the amine initiator include triethanolamine and ethyl 4-dimethylbenzoate. In addition, as a polymerization initiator (E), 1 type of the said initiator may be used independently, or 2 or more types may be used together.

  In the pressure-sensitive adhesive composition according to the present invention, the content of the polymerization initiator (E) is appropriately determined according to the content of the oligomer (B) and the monomer (C), the irradiation amount of active energy rays when completely cured, and the like. Although selected and not particularly limited, it is preferably 0.05 to 10% by mass and more preferably 0.1 to 5.0% by mass with respect to the total mass of the oligomer (B) and the monomer (C). preferable. If it is not less than the lower limit value, the polymerization reaction at the time of complete curing can be easily started, and if it is not more than the upper limit value, damage to the substrate due to the heat of the polymerization reaction at the time of complete curing, or at the time of complete curing The occurrence of poor appearance such as yellowing and cloudiness due to the remaining polymerization initiator can be prevented.

  Moreover, the adhesive composition which concerns on this invention may contain other components other than the above arbitrarily in the range which does not impair the effect of invention. The other components include components known as additives for pressure-sensitive adhesives, such as antioxidants, metal corrosion inhibitors, tackifiers, UV absorbers, light stabilizers, softeners, refractive index adjusters, silane cups. A ring agent can be selected as necessary.

  Moreover, the adhesive sheet which concerns on this invention forms the adhesive layer by apply | coating the liquid mixture (coating liquid) of the above-mentioned adhesive composition and a solvent on a base material sheet, It forms by heating after that. be able to. By heating, the cross-linking agent (D) cross-links the acrylic ester copolymers (A) (primary cross-linking), and the pressure-sensitive adhesive layer can be brought into a semi-cured state. Here, the primary crosslinking means a state in which only the thermal crosslinking component of the acrylate copolymer (A) has reacted. Moreover, since the pressure-sensitive adhesive layer is in a semi-cured state by performing the primary crosslinking, the flexibility is high and it is easy to follow the uneven portion (step portion) of the adherend. The application method of the pressure-sensitive adhesive composition can be appropriately selected from known application methods such as knife coater, micro bar coater, air knife coater, reverse roll coater, reverse gravure coater, vario gravure coater, die coater and curtain coater. .

  Here, the solvent is used for improving the coating suitability of the pressure-sensitive adhesive composition. For example, hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; dichloromethane Halogenated hydrocarbons such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, diacetone alcohol; diethyl ether, diisopropyl ether, dioxane, tetrahydrofuran, etc. Ethers; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate, ethyl acetate, butyl acetate Esters such as ethylene, isobutyl acetate, amyl acetate, ethyl butyrate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether acetate And polyols and derivatives thereof. In addition, a solvent may be used individually by 1 type and may use 2 or more types together. In the pressure-sensitive adhesive composition, the content of the solvent can be arbitrarily determined in consideration of coating equipment.

  Further, the pressure-sensitive adhesive sheet may have either a single-sided adhesive type or a double-sided adhesive type. When forming as a double-sided adhesive type, for example, a first release sheet is adopted as the substrate sheet, and a mixed liquid of the adhesive composition and the solvent is applied and heated on the first release sheet. An agent layer can be formed and a 2nd peeling sheet can be laminated | stacked and formed on the said adhesive layer.

  The first and second release sheets are generally configured by forming a release agent layer on one surface of a substrate. As a base material, it can form using a conventionally well-known material as base material materials of a peeling sheet, such as a polyethylene film (PET), a polypropylene film (PP), a polybutene film, for example. Examples of the material of the release agent layer formed on the substrate include conventionally known release agents such as alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax. .

  As an example of bonding the adhesive sheet to the adherend, a case in which a protective cover or a touch panel is bonded to the display surface of the display device is shown below. First, the first release sheet is peeled off and bonded to a protective cover or a touch panel to create a protective cover or touch panel with an adhesive sheet. Thereafter, the second release sheet is peeled off and attached to the display surface of the display device. After confirming that there are no problems such as air bubble biting and sticking misalignment, ultraviolet rays and the like are irradiated, and by the action of the polymerization initiator (E) in the pressure-sensitive adhesive composition, the oligomer (B) and the monomer (C) The polymerization reaction (photocrosslinking component reacts: secondary crosslinking) is initiated. Thereby, the pressure-sensitive adhesive layer is completely cured, and the protective cover, the touch panel, and the display device are firmly bonded.

  According to the pressure-sensitive adhesive composition according to the present invention, the acrylic ester copolymers (A) are thermally cross-linked (primary cross-linked), and the holding power of the pressure-sensitive adhesive layer is 20000 [sec] or less, preferably 15000 [sec. ] A semi-cured state in the following range can be obtained. This makes it easier for the pressure-sensitive adhesive layer to follow the uneven part (step part) of the adherend in the stage of attaching the adhesive sheet to the adherend (protective cover, touch panel, display device, etc.). It is possible to effectively suppress the bubbles from remaining. Here, the holding force of an adhesive layer means the holding force prescribed | regulated in JISZ0237 (2000).

  Moreover, since the pressure-sensitive adhesive composition according to the present invention is configured to contain an oligomer (B) having two or more polymerizable unsaturated groups, the durability after the pressure-sensitive adhesive layer is completely cured is obtained. It becomes possible to improve.

  In addition, since the pressure-sensitive adhesive layer is completely cured by photocrosslinking of the oligomer (B) and the monomer (C), the retention strength of the pressure-sensitive adhesive layer after complete curing is less than 0.1 mm, Can be set to 5 N / 25 mm or more, preferably 7 N / 25 mm or more. In other words, after complete curing, the pressure-sensitive adhesive layer can be configured to have an appropriate adhesive force while having an extremely high holding force, and the phenomenon that bubbles are restored over time (lagging bubbles Occurrence), floating, and peeling phenomena can be effectively suppressed. Here, the holding force of an adhesive layer means the holding force prescribed | regulated in JISZ0237 (2000). Moreover, the adhesive force of an adhesive layer means the adhesive force measured by the 180 degree adhesive test prescribed | regulated in JISZ0237 (2000).

  In order to confirm the effects of the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet according to the present invention, the present inventors prepared four types of pressure-sensitive adhesive sheet samples (Examples 1 to 3 and Comparative Example 1), so-called A confirmation test was conducted as to whether or not delayed bubbles were generated. In addition, the adhesive sheet sample is created 6 pieces of the same kind.

Hereinafter, the structure of the produced adhesive sheet sample (Examples 1-3, Comparative Example 1) is demonstrated.
[Example 1]
(Creation of coating liquid)
First, with respect to 100 parts by weight of an acrylic acid ester copolymer (A) having a weight average molecular weight of 450,000 and a hydroxyl value of 90 to 100, it is diluted with 44 parts by weight of a solvent, and then oligomer (B), monomer (C), The coating liquid (adhesive solution) consisting of the adhesive composition and the solvent was prepared by adding the cross-linking agent (D) and the photopolymerization initiator (E) and stirring sufficiently. Here, ethyl acetate is employed as the solvent. Moreover, as an oligomer (B), Kyoeisha Chemical Co., Ltd. model number "UF-8001G" is employ | adopted and 2.2 weight part is added with respect to 100 weight part of acrylic ester copolymer (A). As the monomer (C), 2-isocyanatoethyl methacrylate is employed, and 0.11 part by weight is added to 100 parts by weight of the acrylate copolymer (A). Moreover, the model number "Coronate HX" by Tosoh Corporation is employ | adopted as a crosslinking agent (D), and 0.088 weight part is added with respect to 100 weight part of acrylic ester copolymer (A). As the photopolymerization initiator (E), model number “Irgacure 184” manufactured by BASF Japan Ltd. is adopted, and 1.0% of the total weight of the oligomer (B) and the monomer (C) is added.
(Creation of adhesive sheet)
An A4 size base sheet (corresponding to the first release sheet: manufactured by Nipper, model number: PET38X1-V0) is coated with the above coating solution (adhesive solution) using an applicator to form an adhesive layer After that, the pressure-sensitive adhesive layer was semi-cured by heating and drying at 90 ° C. for 5 minutes in a drying oven (model number: DRD620DA manufactured by Advantech). Then, the 2nd peeling sheet (Toyobo Co., Ltd. model number: E7006-38 micrometers) was bonded on the adhesive layer, and the adhesive sheet sample which concerns on Example 1 was formed. The thickness of the pressure-sensitive adhesive layer is configured to be 100 μm in a semi-cured state.

[Example 2]
The pressure-sensitive adhesive sheet sample according to Example 2 except that 6.6 parts by weight of the addition amount of the oligomer (B) in Example 1 is added to 100 parts by weight of the acrylate copolymer (A). This was prepared in the same manner as in Example 1 above.

[Example 3]
The pressure-sensitive adhesive sheet sample according to Example 3 is the above except that the amount of oligomer (B) added in Example 1 is 11 parts by weight with respect to 100 parts by weight of the acrylic ester copolymer (A). It was produced in the same manner as in Example 1.

[Comparative Example 1]
The pressure-sensitive adhesive sheet sample according to Comparative Example 1 was prepared by adding a monomer (MF-101, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., functional group number: 3) instead of the oligomer (B) in Example 1 to constitute a coating solution. It was created in the same manner as in Example 1 except for the above points. In addition, the addition amount of the monomer (Daiichi Kogyo Seiyaku MF-101, functional group number: 3) is 11 parts by weight with respect to 100 parts by weight of the acrylic ester copolymer (A). Here, a monomer (Daiichi Kogyo Seiyaku Co., Ltd. MF-101, functional group number: 3) is a photocurable monomer, and the pressure-sensitive adhesive layer composed of a coating solution containing the monomer is irradiated with active energy rays. The monomer (MF-101 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., functional group number: 3) and the monomer (C) are cured by polymerization reaction.

Next, a confirmation test (confirmation test as to whether delayed bubbles or the like are generated) performed using the four types of pressure-sensitive adhesive sheet samples (Examples 1 to 3 and Comparative Example 1) will be described below.
(Creation of test laminate)
First, after removing the first release sheet from each pressure-sensitive adhesive sheet sample, each pressure-sensitive adhesive sheet sample is laminated on a pseudo cover glass (base glass plate: thickness 0.7 mm, size 60 mm × 120 mm) and simulated using a hand roller. The cover glass and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet are bonded together to create a pseudo cover glass with a pressure-sensitive adhesive sheet. Next, after confirming that no air bubbles remain between the pseudo cover glass and the pressure-sensitive adhesive sheet, the second release sheet is removed from the pressure-sensitive adhesive layer and attached to the pseudo LCD. Produced. The pseudo LCD was prepared by bonding a polarizing plate (model number: HLC2-5610S, manufactured by Sanritz Co., Ltd.) to a 0.7 mm thick glass plate. In addition, a pseudo cover glass with an adhesive sheet is arranged so that an adhesive layer is laminated on a polarizing plate, and a laminate of a pseudo cover glass, an adhesive sheet sample, and a pseudo LCD is formed using a hand roller, and an autoclave is formed. After the treatment (temperature 45 ° C, pressure 0.6 MPa for 20 minutes), after confirming that no bubbles remain at the interface of the pseudo cover glass, adhesive sheet sample, and pseudo LCD, irradiate with ultraviolet rays. Then, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet was completely cured, and the pseudo cover glass, the pressure-sensitive adhesive sheet sample, and the pseudo LCD constituting the laminate were integrated. Further, the pseudo LCD is formed to have the same size as the pseudo cover glass. As the irradiation condition of the ultraviolet ray, integrated light quantity so that the 2000 mJ / cm ^2, was irradiated with 1PASS using a high pressure mercury lamp UV irradiation apparatus.

(Confirmation test contents)
Using an environmental test apparatus, a load of 80 ° C. × 240 hours was applied to three of the six adhesive sheet samples, and 60 ° C./90% R.D. H. After applying a load of × 240 hours, each pressure-sensitive adhesive sheet sample was taken out and confirmed by visual observation whether or not so-called delayed bubbles were generated. Visual confirmation was performed under a fluorescent lamp.

  The results of the confirmation test are shown in Table 1. In Table 1, if the occurrence of so-called delayed bubbles is not confirmed, ○ is indicated, and if it is determined that there is a slight delay bubble, etc., it is determined that there is no problem in performance, and Δ is clearly confirmed. What can be done is marked with x. In addition, six samples were prepared for each adhesive sheet sample, and a confirmation test was conducted for each sample. Three samples given a load of 80 ° C. × 240 hours were designated as “sample A”, “sample B”, and “sample C”. 60 ° C. and 90% R.S. H. The remaining three samples subjected to a load of × 240 hours are shown as “sample D”, “sample E”, and “sample F”, respectively, and the confirmation test results are shown in Table 1.

  In Table 1, the pressure-sensitive adhesive sheet characteristics (holding force, pressure-sensitive adhesive force) of each pressure-sensitive adhesive sheet sample (Examples 1 to 3 and Comparative Example 1) are also described. Here, the holding force is a value measured according to the holding force measurement method of JIS Z 0237 (2000). Each pressure-sensitive adhesive sheet sample is cut out with a width of 25 mm and a length of 60 mm after laminating a 25 μm thick polyethylene terephthalate (PET) film in order to maintain the form. This pressure sensitive adhesive sheet sample with a PET film is attached to a SUS plate fixed in the vertical direction in a range of 25 mm × 25 mm, a 1 kg load is applied in a 40 ° C. environment, and the amount of deviation after 50,000 seconds is determined. It is measured. In addition, about what fell before 50,000 second progress, the fall time is described as a measured value. Regarding the holding power, the holding power when the pressure-sensitive adhesive sheet sample is semi-cured by heating and the holding power when completely cured by irradiation with ultraviolet rays are described. The adhesive strength is a value obtained by measuring the strength in a 180 ° peeling mode using a peel strength tester in accordance with the 180 degree peeling adhesive strength measurement method of JIS Z 0237 (2000). The adhesive strength when semi-cured and the adhesive strength when completely cured by irradiating ultraviolet rays are described. The pressure-sensitive adhesive sheet sample has a PET film having a thickness of 25 μm bonded to maintain the form. As the adherend, a glass plate having a thickness of 1.1 mm was used.

  From Table 1 above, for Examples 1 to 3 in which the pressure-sensitive adhesive layer was formed with the pressure-sensitive adhesive composition according to the present invention, it was not possible to confirm delayed bubbles or the like that would cause problems in performance, Comparative Example 1 in which a monomer (MF-101 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., functional group number: 3) was added instead of the oligomer (B) to prepare a coating solution (adhesive solution) was used in all samples A to F. It can be seen that delayed bubbles are clearly confirmed. From this, according to the pressure-sensitive adhesive composition according to the present invention constituted by using a photocurable oligomer (oligomer (B)) instead of a photocurable monomer, it is confirmed that delayed bubbles are generated after complete curing. It turns out that it can suppress very effectively. Moreover, since the adhesive sheet which has the adhesive layer formed from the adhesive composition which concerns on this invention can suppress generation | occurrence | production of a delayed bubble etc., it can also be said that it is an adhesive sheet excellent in durability. Moreover, in Comparative Example 1, in the completely cured state after the ultraviolet irradiation, the holding power is increased to the same level as in Examples 1 to 3, but the adhesive strength is higher than in Examples 1 to 3. It has decreased significantly. It is inferred that this significant decrease in adhesive strength is one of the causes of delayed bubbles and the like.

  In addition, the pressure-sensitive adhesive sheet samples according to Examples 1 to 3 have a good followability with respect to unevenness because the holding power is about 7000 to 10500 [sec] in a semi-cured state before ultraviolet irradiation. I understand that. Moreover, since the retention strength in the semi-hardened state before ultraviolet irradiation is so low that the addition amount of an oligomer (B) is large (Example 1 <Example 2 <Example 3), of oligomer (B) It can be seen that a pressure-sensitive adhesive composition having better followability to unevenness can be obtained as the amount added is increased. In Comparative Example 1, since the holding power in the semi-cured state before the ultraviolet irradiation is as low as about 1700 [sec], it is recognized that the followability to the unevenness is extremely good, but the pressure-sensitive adhesive sheet according to Comparative Example 1 In such a case, there is a risk that problems may occur in storage stability and processability.

From the confirmation test results regarding Examples 1 to 3 described above, the pressure-sensitive adhesive composition according to the present invention can be configured so that the pressure-sensitive adhesive layer has excellent unevenness followability in a semi-cured state. It is recognized that bubbles can be effectively suppressed from remaining on the surface. In addition, since the pressure-sensitive adhesive layer can be configured to have an appropriate adhesive force while having an extremely high holding force in a completely cured state, for example, the touch panel is attached to the display surface of the display device via an adhesive sheet. It is recognized that it is possible to effectively suppress the generation of so-called delayed bubbles after being stuck and completely cured.

Claims (7)

An acrylate copolymer having a crosslinkable functional group;
An oligomer having two or more polymerizable unsaturated groups;
A monomer having a functional group that reacts with the acrylate copolymer and a functional group that reacts with the oligomer;
A crosslinking agent that reacts with the acrylic ester copolymer by heat;
A polymerization initiator that initiates a polymerization reaction by irradiation with active energy rays ,
The pressure-sensitive adhesive composition , wherein the monomer is a (meth) acryloyl group-containing monomer having an organic functional group that reacts with a hydroxyl group . The pressure-sensitive adhesive composition according to claim 1, wherein the monomer is contained in an amount of 0.001 to 5.0 parts by weight with respect to 100 parts by weight of the acrylate copolymer.   The pressure-sensitive adhesive composition according to claim 1, wherein the oligomer contains urethane (meth) acrylate.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the acrylic ester copolymer does not contain a carboxyl group.   An adhesive sheet provided with the adhesive layer which carried out the primary bridge | crosslinking of the adhesive composition in any one of Claim 1 to 4 by heating.   A touch panel provided with the adhesive sheet according to claim 5. A display apparatus provided with the adhesive sheet of Claim 5.