JP2018076456A - Adhesive composition and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition capable of forming an adhesive layer which exhibits excellent adhesive force even after being exposed to a high-temperature and high-humidity environment, and to provide an adhesive sheet.SOLUTION: The adhesive composition contains a urethane (meth)acrylate having no polymerizable unsaturated group other than a (meth)acryloyl group, a (meth)acrylic monomer, and a silane coupling agent having a mercapto group. The content of the silane coupling agent having a mercapto group is 0.01-5.0 pts.mass based on 100 pts.mass of the total of the urethane (meth)acrylate and the (meth)acrylic monomer.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

In general, an image display unit of a portable electronic device such as a mobile phone often includes at least a display device, a touch panel as an input device, and a cover glass. An adhesive sheet or a liquid adhesive is used for attaching the touch panel to the display device or the cover glass. Moreover, the adhesive sheet or the liquid adhesive agent is used also for sticking of the members which comprise a touch panel.
Since portable electronic devices may be impacted by dropping, etc., the adhesive sheet or liquid adhesive used to attach parts of portable electronic devices has strong adhesive strength that does not peel off due to impact such as dropping. Desired.

  An active energy ray-curable pressure-sensitive adhesive composition containing, for example, a urethane (meth) acrylate compound having a specific molecular weight and an ethylenically unsaturated monomer as a pressure-sensitive adhesive sheet having an excellent balance between adhesive strength and heat-and-moisture resistance An active energy ray-curable pressure-sensitive adhesive composition containing a heterocyclic ring-containing monomer and a hydroxyl group-containing monomer at a specific content ratio as an ethylenically unsaturated monomer is disclosed (for example, see Patent Document 1).

  Furthermore, as a liquid adhesive exhibiting high adhesion durability, for example, a group consisting of a specific (meth) acrylate oligomer, a (meth) acrylate having a specific range of homopolymer glass transition temperature, alkanethiol and carboxythiol A curable resin composition comprising a compound having one or more mercapto groups in a molecule selected from 1 and a photopolymerization initiator is disclosed (for example, see Patent Document 2).

International Publication No. 2016/13510 International Publication No. 2013/31678

By the way, with the miniaturization of portable electronic devices, for example, they may be carried in a high temperature and high humidity environment and exposed to a harsh environment.
As a result of investigations by the inventors, the pressure-sensitive adhesive sheet formed from the active energy ray-curable pressure-sensitive adhesive composition described in Patent Document 1 has low adhesive strength when exposed to a high temperature and high humidity environment and is easily peeled off. There was a problem of becoming.

  Since the curable resin composition described in Patent Document 2 is used as a liquid adhesive, when the adhesive is applied, the adhesive easily protrudes from the applied portion, and an unintended portion is pasted. There is a problem that. Moreover, when the part which applies an adhesive agent is a curved surface, there exists a malfunction that thickness becomes nonuniform. Generally, when a liquid adhesive is used as a pressure-sensitive adhesive sheet, it is known that the pressure-sensitive adhesive force is too low to be practically used as a pressure-sensitive adhesive sheet.

  The present invention has been made in view of the above, and a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet capable of forming a pressure-sensitive adhesive layer that exhibits excellent adhesive strength even after being exposed to a high-temperature and high-humidity environment. It is an issue to provide.

Specific means for solving the above problems include the following modes.
<1> A urethane (meth) acrylate having no polymerizable unsaturated group other than a (meth) acryloyl group, a (meth) acrylic monomer, and a silane coupling agent having a mercapto group, The adhesive composition whose content of the silane coupling agent which has the said mercapto group with respect to a total of 100 mass parts of a (meth) acrylate and the said (meth) acrylic-type monomer is 0.01 mass part-5.0 mass parts.

<2> The pressure-sensitive adhesive composition according to <1>, wherein the urethane (meth) acrylate has a structural unit derived from a polyether polyol.

<3> The (meth) acrylic monomer includes at least one kind of a (meth) acrylic monomer having a hydroxyl group, and the (meth) acrylic monomer having the hydroxyl group with respect to the total mass of the (meth) acrylic monomer. The content of is the pressure-sensitive adhesive composition according to <1> or <2>, which is 30% by mass to 90% by mass.

<4> The mixing ratio of the urethane (meth) acrylate and the (meth) acrylic monomer is 55:45 to 75:25 on a mass basis, and any one of <1> to <3>. 2. The pressure-sensitive adhesive composition according to 1.

<5> The (meth) acrylic monomer contains at least one alkyl methacrylate, and the content of the alkyl methacrylate with respect to the total mass of the (meth) acrylic monomer is 5% by mass to 50% by mass. <1>-<4> The adhesive composition according to any one of <4>.

<6> The pressure-sensitive adhesive composition according to any one of <1> to <5>, further including a photopolymerization initiator.

<7> The pressure-sensitive adhesive composition according to any one of <1> to <6>, which does not contain an organic solvent.

<8> A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition according to any one of <1> to <7>.

  According to the present invention, it is possible to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet that can form a pressure-sensitive adhesive layer that exhibits excellent adhesive strength even after being exposed to a high-temperature and high-humidity environment.

Hereinafter, the pressure-sensitive adhesive composition of the present invention will be described in detail. In the present invention, “to” in a numerical range means including numerical values before and after “to”.
In the present specification, the amount of each component in the composition and the ratio of the amount are determined in the case where a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. It means the total amount of substances and the proportion of the total amount.
In this specification, “(meth) acryl” means to include both “acryl” and “methacryl”, and “(meth) acrylate” includes both “acrylate” and “methacrylate”. And “(meth) acryloyl” is meant to encompass both “acryloyl” and “methacryloyl”.
In this specification, the pressure-sensitive adhesive means one that is used after being processed into a sheet and then stuck to an article to be bonded, and is distinguished from an adhesive that is applied to an article to be bonded in a liquid state. Is done.

≪Adhesive composition≫
The pressure-sensitive adhesive composition of the present invention comprises a urethane (meth) acrylate having no polymerizable unsaturated group other than a (meth) acryloyl group (hereinafter also referred to as “specific urethane (meth) acrylate”), and (meth). Containing an acrylic monomer and a silane coupling agent having a mercapto group, the content of the silane coupling agent having a mercapto group with respect to a total of 100 parts by mass of the urethane (meth) acrylate and the (meth) acrylic monomer The amount is 0.01 parts by mass to 5.0 parts by mass. The pressure-sensitive adhesive composition of the present invention may further contain other components than the components described above as necessary.

  By forming the pressure-sensitive adhesive composition of the present invention in the above-described configuration, a high pressure-sensitive adhesive force can be exhibited even after being exposed to a high-temperature and high-humidity environment when a pressure-sensitive adhesive sheet is formed. The reason for this is not clear, but is presumed as follows.

In the pressure-sensitive adhesive composition of the present invention, urethane (meth) acrylate having no polymerizable unsaturated group other than (meth) acryloyl group, (meth) acrylic monomer, and silane coupling agent having mercapto group are uniformly mixed. Is in a state. In this state, when the active energy rays such as ultraviolet rays and electron beams are irradiated to radically polymerize the specific urethane (meth) acrylate and (meth) acrylic monomer, the pressure-sensitive adhesive composition is cured and a pressure-sensitive adhesive layer is formed. Is done.
During radical polymerization, the mercapto group contained in the silane coupling agent undergoes a chain transfer reaction and is incorporated at the end of the main chain of the polymer formed from the specific urethane (meth) acrylate and (meth) acrylic monomer.
Here, the mercapto group, for example, tends to react with a vinylene group (—C═C—) preferentially and be added. Therefore, when a monomer having a polymerizable unsaturated group such as vinylene group is contained in the reaction system, the mercapto group cannot react as a chain transfer agent.
The specific urethane (meth) acrylate contained in the pressure-sensitive adhesive composition of the present invention does not have a polymerizable unsaturated group other than the (meth) acryloyl group, and therefore a mercapto group contained in the silane coupling agent during radical polymerization. Is prone to chain transfer reactions. Further, when the chain transfer reaction is completed, the mercapto group is bonded to the end of the main chain of the polymer formed from the specific urethane (meth) acrylate and (meth) acrylic monomer, and therefore the silane coupling agent is attached to the end of the polymer. Is easy to incorporate. Therefore, the degree of polymerization of the polymer can be reduced, that is, the number of polymer chains can be increased, the degree of crosslinking of the polymer can be reduced moderately, and a silane coupling agent can be incorporated at the end of the polymer. It becomes possible.
The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a moderate degree of cross-linking of the polymer as described above. It becomes possible to express force.

Moreover, generally, a silane coupling agent reacts with the functional group of the side chain of a (meth) acrylic-type polymer, alkoxysilane is incorporated in a side chain, and chemically modifies a (meth) acrylic-type polymer. Alkoxysilane is hydrolyzed to silanol by water, and further silanol is condensed to form a chemical bond with the interface of the adherend, so that adhesion to the adherend can be imparted. Due to the chemical bond with the interface of the adherend, a decrease in adhesive force can be suppressed even when exposed to a high temperature and high humidity environment.
However, in the case of a general silane coupling agent, when the (meth) acrylic monomer in the pressure-sensitive adhesive composition and the functional group of the side chain of the polymer react efficiently, the alkoxysilane is sufficiently incorporated into the side chain. Therefore, sufficient adhesion to the adherend can be obtained. On the other hand, when the reactivity between the silane coupling agent and the functional group of the side chain of the (meth) acrylic monomer and polymer is poor, the alkoxysilane is not sufficiently incorporated into the side chain, and the adhesion to the adherend Is difficult to fully express.
The silane coupling agent having a mercapto group contained in the pressure-sensitive adhesive composition of the present invention is excellent in chain transfer reactivity. Therefore, even if the (meth) acrylic monomer does not have a specific functional group, silane coupling is performed at the end of the main chain of the polymer formed from urethane (meth) acrylate and (meth) acrylic monomer. It is possible to reduce the amount of unreacted silane coupling agent that is not incorporated at the end of the main chain of the polymer. For this reason, it becomes possible to efficiently form the chemical bond with the interface of the adherend via the silane coupling agent.
From the above, when the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition in the present invention, it is presumed that excellent adhesive force is exhibited even after being exposed to a high temperature and high humidity environment.
In the present specification, the main chain of the polymer means a portion extended by a reaction between polymerizable unsaturated groups. Further, the side chain of the polymer means a chain bonded to the main chain of the polymer.
Hereinafter, the detail of each component of the adhesive composition of this invention is demonstrated.

<Specific urethane (meth) acrylate>
The pressure-sensitive adhesive composition of the present invention contains urethane (meth) acrylate (specific urethane (meth) acrylate) having no polymerizable unsaturated group other than (meth) acryloyl group. When the specific urethane (meth) acrylate is contained in the pressure-sensitive adhesive composition, the mercapto group contained in the silane coupling agent described later undergoes a chain transfer reaction during radical polymerization, and the specific urethane (meth) acrylate and the later described It becomes possible to incorporate a silane coupling agent at the end of the main chain of the polymer formed from the (meth) acrylic monomer.
When urethane (meth) acrylate having a polymerizable unsaturated group other than (meth) acryloyl group is contained in the pressure-sensitive adhesive composition, the mercapto group contained in the silane coupling agent is polymerized other than (meth) acryloyl group. The reaction as a chain transfer agent tends to be suppressed because it reacts preferentially with the unsaturated group, and in this case, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition becomes too hard, and has an appropriate elasticity and flexibility. Sex cannot get enough.

  Examples of the polymerizable unsaturated group other than the (meth) acryloyl group include polymerizable unsaturated groups such as vinylene group, phenyl vinylene group, vinylphenylene group, and arylene group.

  The specific urethane (meth) acrylate contained in the pressure-sensitive adhesive composition of the present invention has no polymerizable unsaturated group other than the (meth) acryloyl group, and has one molecule of the urethane structure and at least two (meth) acryloyl groups. It can be obtained by reacting a polyisocyanate compound, a polyol compound, and a hydroxyl group-containing (meth) acrylate.

  The method for synthesizing urethane (meth) acrylate is not particularly limited, and at least a polyisocyanate compound, a polyol compound, and a hydroxyl group-containing (meth) acrylate are used, and if necessary, heated in the presence of a known polymerization catalyst. It can synthesize | combine by mixing.

-Method for synthesizing urethane (meth) acrylate-
Urethane (meth) acrylate can be suitably synthesized by the following method. However, the method for synthesizing urethane (meth) acrylate in the present invention is not limited to the following method.
In a reaction vessel, a polyol compound, a polyisocyanate compound, and a polymerization catalyst such as dibutyltin dilaurate (DBTDL) are placed, and the temperature of the contents in the reaction vessel is raised to, for example, 60 ° C. to 80 ° C. The reaction is performed for 2 to 5 hours (prepolymer formation reaction). A polymerization catalyst and a hydroxyl group-containing (meth) acrylate are charged into the reaction vessel after the reaction, and further reacted for 1 to 3 hours to synthesize urethane (meth) acrylate. The completion of the reaction can be confirmed by the disappearance of the 2250 cm ⁻¹ peak derived from isocyanate in the infrared absorption spectrum (IR).
Hereinafter, the polyisocyanate compound, the polyol compound, and the hydroxyl group-containing (meth) acrylate will be described in detail.

-Polyisocyanate compound-
As the polyisocyanate compound used in the prepolymer formation reaction, known aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate, and the like can be used.

  Examples of the aromatic polyisocyanate compound include xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate.

  Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of the alicyclic polyisocyanate include isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane diisocyanate, methylenebis (4-cyclohexylisocyanate), hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, and the like. From the viewpoint of preventing yellowing of the layer, isophorone diisocyanate is preferable.

-Polyol compound-
The polyol compound used in the prepolymer formation reaction is a polyol compound having two or more hydroxy groups in the molecule, and examples thereof include polyester polyol, polycarbonate polyol, aliphatic diol, and polyether polyol.

  As the polyester polyol, a polycaprolactone polyol, a diol represented by 1,10-decanediol and 1,11-undecanediol, and a dicarboxylic acid represented by oxalic acid, malonic acid, and succinic acid are condensed. Etc.

  Polycarbonate polyols include those obtained by reacting diols with alkyl carbonates typified by ethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, glycol, diphenyl carbonate, 4-methyldiphenyl carbonate. And those obtained by reacting diaryl carbonate typified by phenyl naphthyl carbonate, and those obtained by reacting glycol with dialkyl carbonate typified by dimethyl carbonate and diethyl carbonate.

  Examples of the aliphatic diol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, and neopentyl glycol.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetraethylene glycol.

  From the viewpoint of imparting flexibility and excellent adhesive force to the pressure-sensitive adhesive layer, the polyol compound is preferably a polyether polyol, and from the viewpoint of suppressing whitening in a moist heat environment, the polyether polyol is polypropylene glycol. More preferred.

-Hydroxyl group-containing (meth) acrylate-
Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth) acrylate. , Glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate and pentaerythritol tri (meth) acrylate.

  The specific urethane (meth) acrylate preferably has at least a structural unit derived from a polyether polyol. When the specific urethane (meth) acrylate has a structural unit derived from a polyether polyol, the adhesive layer has flexibility and excellent adhesion as compared with a case where it has a structural unit derived from a polyester polyol, a polycarbonate polyol or an aliphatic diol. It tends to give power. Moreover, it becomes possible to effectively suppress whitening in a humid heat environment.

As a weight average molecular weight (Mw) of specific urethane (meth) acrylate, 10,000-100,000 are preferable. There exists a tendency for adhesive force to improve that the weight average molecular weight (Mw) of specific urethane (meth) acrylate is 10,000 or more. Moreover, when the weight average molecular weight (Mw) of specific urethane (meth) acrylate is 100,000 or less, it is possible to synthesize without gelation. From the above viewpoint, the weight average molecular weight (Mw) is more preferably 15,000 to 80,000, and still more preferably 20,000 to 40,000.
The weight average molecular weight (Mw) of the specific urethane (meth) acrylate is a value measured by the following method.

(Measurement method of weight average molecular weight (Mw))
It measures according to following (1)-(3).
(1) A specific urethane (meth) acrylate solution is applied to release paper and dried at 100 ° C. for 1 minute to obtain a film-like specific urethane (meth) acrylate.
(2) The film-like specific urethane (meth) acrylate obtained in the above (1) is dissolved in tetrahydrofuran so as to have a solid content of 0.5% by mass. Thereafter, the solution is filtered through a membrane filter (HPLC Millex-LH, pore size 0.45 μm, diameter 25 mm).
(3) The weight average molecular weight (Mw) of the specific urethane (meth) acrylate is measured as a standard polystyrene equivalent value using gel permeation chromatography (GPC) under the following conditions.
(conditions)
GPC: HLC-8220 GPC (manufactured by Tosoh Corporation)
Column: 4 TSK-GEL GMHXL used (manufactured by Tosoh Corporation)
Mobile phase solvent: Tetrahydrofuran Flow rate: 0.8 ml / min
Column temperature: 40 ° C

  The content of the specific urethane (meth) acrylate in the pressure-sensitive adhesive composition is preferably 50% by mass to 99% by mass and 55% by mass to 93% by mass with respect to the total mass of the pressure-sensitive adhesive composition. Is more preferable.

The content of urethane (meth) acrylate having a polymerizable unsaturated group other than (meth) acryloyl group was formed from a pressure-sensitive adhesive composition by reacting a mercapto group contained in a silane coupling agent described later as a chain transfer agent. From the viewpoint of imparting appropriate elasticity and flexibility to the pressure-sensitive adhesive layer, 0.5% by mass or less is preferable with respect to the total amount of the specific urethane (meth) acrylate and the (meth) acrylic monomer described later, 0.1 It is more preferable that the content is not more than mass%, and it is further preferable that the content is substantially not contained.
“Substantially free” means that the presence of a urethane (meth) acrylate having a polymerizable unsaturated group other than the (meth) acryloyl group inevitably mixed is allowed, but the (meth) acryloyl group added intentionally. The presence of a urethane (meth) acrylate having a polymerizable unsaturated group other than is implied.

<(Meth) acrylic monomer>
The pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic monomer. When the pressure-sensitive adhesive composition contains a (meth) acrylic monomer, the pressure-sensitive adhesive layer does not become too hard and good adhesive force tends to be obtained. (Meth) acrylic monomers may be used alone or in combination of two or more.
In the present specification, the (meth) acrylic monomer means a compound having a (meth) acryloyl group and means a compound other than urethane (meth) acrylate.

The pressure-sensitive adhesive composition of the present invention preferably contains a (meth) acrylic monomer having at least one hydroxyl group as the (meth) acrylic monomer. When a (meth) acrylic monomer having a hydroxyl group is included as the (meth) acrylic monomer, the adhesion to an adherend of an inorganic substance such as glass can be further improved due to the high polarity of the hydroxyl group. There is a tendency to further increase the adhesive strength of the adhesive and the adhesive strength after exposure to a high temperature and high humidity environment. Moreover, in a wet heat environment, compatibility with water is easily improved, and whitening of the pressure-sensitive adhesive layer can be suppressed.
When the pressure-sensitive adhesive layer is exposed to, for example, a high-temperature and high-humidity environment of 85 ° C. and 85% RH, it may be whitened by moisture in the environment and may be inferior in visibility. For this reason, it is preferable that the pressure-sensitive adhesive layer is not easily whitened even in a high-temperature and high-humidity environment.

Examples of the (meth) acrylic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate (2HEA), 4-hydroxybutyl (meth) acrylate (4HBA), 2-hydroxypropyl (meth) acrylate, and 3-hydroxy. Examples include propyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and 3-methyl-3-hydroxybutyl (meth) acrylate.
From the viewpoint of improving the adhesive strength at normal temperature and the adhesive strength after being exposed to a high temperature and high humidity environment, and suppressing whitening, 2-hydroxyethyl (meth) is a hydroxyl group-containing (meth) acrylic monomer. Acrylate and 4-hydroxybutyl (meth) acrylate are preferred, and 2-hydroxyethyl (meth) acrylate is more preferred.

When a (meth) acrylic monomer having a hydroxyl group is included as the (meth) acrylic monomer, the content of the (meth) acrylic monomer having a hydroxyl group with respect to the total mass of the (meth) acrylic monomer is 30% by mass to 90 mass% is preferable. When the content of the (meth) acrylic monomer having a hydroxyl group is 30% by mass to 90% by mass, after forming an adhesive sheet to be described later from the adhesive composition, after being exposed to a high temperature and high humidity environment Even so, the adhesive strength tends to be excellent.
From the above viewpoint, the content of the (meth) acrylic monomer having a hydroxyl group is more preferably 40% by mass to 80% by mass, and further preferably 45% by mass to 65% by mass.

The pressure-sensitive adhesive composition of the present invention preferably contains at least one alkyl methacrylate as a (meth) acrylic monomer. The alkyl methacrylate does not include alkyl methacrylate having a hydroxyl group.
In general, alkyl methacrylate has a slower reaction rate of the polymerization reaction because it has better radical stability than alkyl acrylate. When alkyl methacrylate and acrylate are included in the reaction system, a difference occurs in the reaction rate.
When the pressure-sensitive adhesive composition of the present invention contains alkyl methacrylate as a (meth) acrylic monomer, when the pressure-sensitive adhesive composition is cured with active energy rays, the polymer does not contain urethane (meth) acrylate, that is, is crosslinked. There is a tendency that no polymer (non-crosslinked polymer) is easily formed. When a non-crosslinked polymer is formed, it gives elasticity suitable for pressure-sensitive adhesives, improves adhesion, and improves adhesive strength at normal temperature and after exposure to high temperature and high humidity environments. It becomes possible.

  The alkyl group in the alkyl methacrylate may be linear or branched. As carbon number of an alkyl group, 6-20 are preferable, 8-16 are more preferable, and 8-12 are still more preferable from a viewpoint which suppresses generation | occurrence | production of the bubble in the adhesive sheet mentioned later and suppresses peeling.

  Examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate (2EHMA), n- Nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, lauryl methacrylate (LMA), stearyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, and 2-hexyldecyl methacrylate (2HDMA).

  From the viewpoint of imparting moderate adhesive strength at room temperature, maintaining adhesive strength after exposure to a high temperature and high humidity environment, improving adhesion, and suppressing peeling, 2-ethylhexyl methacrylate, Preferably, at least one of lauryl methacrylate and 2-hexyldecyl methacrylate is contained, more preferably at least one of 2-ethylhexyl methacrylate and lauryl methacrylate is contained, and lauryl methacrylate is further preferred.

  When the alkyl methacrylate is included as the (meth) acrylic monomer, the content of the alkyl methacrylate is preferably 5% by mass to 50% by mass with respect to the total mass of the (meth) acrylic monomer. When the content of the alkyl methacrylate is within the above range, there is a tendency to give an appropriate adhesive force to the pressure-sensitive adhesive layer and to further improve the adhesion to the adherend. From the above viewpoint, the content of the alkyl methacrylate is more preferably 10% by mass to 45% by mass, and further preferably 20% by mass to 40% by mass.

The pressure-sensitive adhesive composition of the present invention may contain an alkyl acrylate as a (meth) acrylic monomer. When the pressure-sensitive adhesive composition of the present invention contains an alkyl acrylate as a (meth) acrylic monomer, the alkyl acrylate is excellent in radical reactivity, so that it is difficult to cause curing failure when the pressure-sensitive adhesive composition is cured, and is excellent in adhesive strength. Tend.
The alkyl acrylate does not include an alkyl acrylate having a hydroxyl group.

  The alkyl group in the alkyl acrylate may be linear or branched. As carbon number of an alkyl group, 6-20 are preferable from a volatility and a compatible viewpoint, 8-16 are more preferable, and 8-12 are still more preferable.

Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, Examples include isononyl acrylate, n-decyl acrylate, lauryl acrylate (LA), stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, and 2-hexyl decyl acrylate.
Among these, lauryl acrylate is preferable as the alkyl acrylate from the viewpoint of volatility and compatibility.

  When the alkyl acrylate is included as the (meth) acrylic monomer, the content of the alkyl acrylate with respect to the total mass of the (meth) acrylic monomer is preferably 5% by mass to 45% by mass. When the content of the alkyl acrylate is within the above range, the elastic modulus of the pressure-sensitive adhesive layer is in a suitable range, and thus there is a tendency to be excellent in workability and followability to steps. From the above viewpoint, the content of the alkyl acrylate is more preferably 15% by mass to 45% by mass, and further preferably 25% by mass to 40% by mass.

The pressure-sensitive adhesive composition of the present invention may contain a (meth) acrylic monomer having a glycidyl group as the (meth) acrylic monomer.
When the pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic monomer having a glycidyl group as a (meth) acrylic monomer, the adhesion to the adherend tends to be improved and the adhesive strength tends to be excellent.

  Examples of the (meth) acrylic monomer having a glycidyl group include glycidyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate glycidyl ether.

  When a (meth) acrylic monomer having a glycidyl group is included as the (meth) acrylic monomer, the content of the (meth) acrylic monomer having a glycidyl group with respect to the total mass of the (meth) acrylic monomer is 0.8. 5 mass%-30 mass% are preferable. When the content of the (meth) acrylic monomer having a glycidyl group is within the above range, the adhesion to the adherend tends to be good. From the above viewpoint, the content of the (meth) acrylic monomer having a glycidyl group is more preferably 1% by mass to 25% by mass, and further preferably 2% by mass to 20% by mass.

The pressure-sensitive adhesive composition of the present invention may contain a polyfunctional (meth) acrylic monomer having two or more (meth) acryloyl groups in one molecule as a (meth) acrylic monomer.
When the pressure-sensitive adhesive composition of the present invention contains a polyfunctional (meth) acrylic monomer as a (meth) acrylic monomer, the cohesive force of the pressure-sensitive adhesive layer is improved and the processability tends to be excellent.

  Examples of the polyfunctional (meth) acrylic monomer include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) ) Acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri ( And (meth) acrylate and tetramethylolmethane tri (meth) acrylate.

  When the polyfunctional (meth) acrylic monomer is included as the (meth) acrylic monomer, the content of the polyfunctional (meth) acrylic monomer with respect to the total mass of the (meth) acrylic monomer is 0.01% by mass to 10 mass% is preferable. When the content of the polyfunctional (meth) acrylic monomer is within the above range, the workability tends to be improved while keeping the adhesive strength within a suitable range. From the above viewpoint, the content of the polyfunctional (meth) acrylic monomer is more preferably 0.05% by mass to 5% by mass, and further preferably 0.1% by mass to 3% by mass.

The pressure-sensitive adhesive composition of the present invention may contain a (meth) acrylic monomer having an acidic group as a (meth) acrylic monomer.
When the pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic monomer having an acidic group as a (meth) acrylic monomer, the adhesion to the adherend tends to be improved and the adhesive strength tends to be excellent.
In addition, when the adhesive composition of this invention does not contain the (meth) acrylic-type monomer which has an acidic group as a (meth) acrylic-type monomer, there exists a tendency which is hard to corrode metal members, such as a transparent conductive film, for example.

  Examples of the (meth) acrylic monomer having an acidic group include (meth) acrylic acid, polyalkylene glycol (meth) acrylate having a carboxy group, 2- (meth) acryloyloxyethyl succinic acid, monohydroxyethyl maleate ( (Meth) acrylate, monohydroxyethyl fumarate (meth) acrylate, monohydroxyethyl (meth) acrylate phthalate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate, (meth) acrylic acid dimer, ω-carboxy- (Meth) acrylic monomers having a carboxy group typified by polycaprolactone mono (meth) acrylate, acid phosphooxyethyl methacrylate, acid phosphooxyethyl acrylate, acid phosphooxy Typical examples are propyl methacrylate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol monomethacrylate, 2,2'-di (meth) acryloyloxydiethyl phosphate, EO (ethylene oxide) modified phosphoric dimethacrylate. (Meth) acrylic monomers having a phosphoric acid group.

  When a (meth) acrylic monomer having an acidic group is included as the (meth) acrylic monomer, the content of the (meth) acrylic monomer having an acidic group with respect to the total mass of the (meth) acrylic monomer is 0.8. 1 mass%-20 mass% are preferable. When the content of the (meth) acrylic monomer having an acidic group is within the above range, the adhesion to the adherend tends to be improved and the adhesive strength tends to be excellent. From the above viewpoint, the content of the (meth) acrylic monomer having an acidic group is more preferably 0.5% by mass to 10% by mass, and further preferably 1% by mass to 5% by mass.

The pressure-sensitive adhesive composition of the present invention may contain a (meth) acrylic monomer having a nitrogen atom as the (meth) acrylic monomer.
When the pressure-sensitive adhesive composition of the present invention contains a (meth) acrylic monomer having a nitrogen atom as a (meth) acrylic monomer, the radical reaction is hardly inhibited, so that curing failure hardly occurs and the adhesive strength tends to be excellent. .

  Examples of the (meth) acrylic monomer having a nitrogen atom include (meth) acryloylmorpholine, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl ( Examples include meth) acrylamide, N, N- (dimethylamino) propyl (meth) acrylamide, diacetone (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N-methylol (meth) acrylamide.

When a (meth) acrylic monomer having a nitrogen atom is included as a (meth) acrylic monomer, the content of the (meth) acrylic monomer having a nitrogen atom relative to the total mass of the (meth) acrylic monomer is 1 mass. % To 20% by mass is preferable. When the content of the (meth) acrylic monomer having a nitrogen atom is within the above range, the radical reaction is hardly inhibited, so that curing failure hardly occurs and the adhesive strength tends to be excellent. From the above viewpoint, the content of the (meth) acrylic monomer having a nitrogen atom is more preferably 2% by mass to 15% by mass, and further preferably 5% by mass to 10% by mass.
In addition, when the adhesive layer formed from the adhesive composition containing the (meth) acrylic-type monomer which has a nitrogen atom is exposed to a high-temperature, high-humidity environment, there exists a tendency for an adhesive layer to be yellowing more easily. From the viewpoint of the stability of the color tone of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition preferably does not contain a (meth) acrylic monomer having a nitrogen atom.

  The pressure-sensitive adhesive composition of the present invention may contain a (meth) acrylic monomer having an aromatic ring as the (meth) acrylic monomer.

  Examples of the (meth) acrylic monomer having an aromatic ring include phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and ethylene oxide-modified nonylphenol (meth) acrylate. , Hydroxyethylated β-naphthol acrylate and biphenyl (meth) acrylate.

  The pressure-sensitive adhesive composition of the present invention may contain other monomers other than urethane (meth) acrylate and (meth) acrylic monomers within the range in which the effects of the present invention are exhibited.

  Examples of other monomers include aromatic monovinyl monomers typified by styrene and α-methylstyrene, vinyl cyanide monomers typified by acrylonitrile and methacrylonitrile, N-vinyl-2-pyrrolidone, and methyl vinyl. Nitrogen atom-containing heterocyclic monomers represented by pyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinyl-ε-caprolactam, and N-vinyl Acetamide is mentioned.

When the pressure-sensitive adhesive composition of the present invention contains other monomers, the content of other monomers with respect to the total mass of the (meth) acrylic monomer is preferably 0.01% by mass to 5% by mass.
In addition, when the pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a nitrogen atom-containing heterocyclic monomer and other monomers containing nitrogen atoms such as N-vinylacetamide is exposed to a high-temperature and high-humidity environment, the pressure-sensitive adhesive layer is There is a tendency to yellow. From the viewpoint of the stability of the color tone of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition preferably does not contain other monomers containing nitrogen atoms.

  The blending ratio of urethane (meth) acrylate and (meth) acrylic monomer (urethane (meth) acrylate: (meth) acrylic monomer) is preferably 90:10 to 10:90 on a mass basis, 90 : 10 to 40:60 is more preferable. From the viewpoint of suitably maintaining the adhesive strength at normal temperature and the adhesive strength after exposure to a high temperature and high humidity environment as moderate elasticity and flexibility when the adhesive layer is used, the mixing ratio is 55:25. ~ 75: 25 is more preferred.

  Urethane (meth) acrylate and (meth) acrylic monomer from the viewpoint of maintaining appropriate elasticity and flexibility, adhesive strength at normal temperature, and adhesive strength after exposure to high temperature and high humidity As a content rate of the (meth) acrylic-type monomer with respect to the total amount of these, 25 mass%-45 mass% are preferable, and 30 mass%-40 mass% are more preferable.

  The content of the (meth) acrylic monomer in the pressure-sensitive adhesive composition is preferably 20% by mass to 50% by mass, and preferably 25% by mass to 45% by mass with respect to the total mass of the pressure-sensitive adhesive composition. Is more preferable.

<Silane coupling agent having a mercapto group>
The pressure-sensitive adhesive composition of the present invention contains at least one silane coupling agent having a mercapto group. When the pressure-sensitive adhesive composition contains a silane coupling agent having a mercapto group, the pressure-sensitive adhesive sheet described later formed from the pressure-sensitive adhesive composition has excellent adhesive strength even after being exposed to a high-temperature and high-humidity environment. It is easy to express. For this reason, peeling hardly occurs between the pressure-sensitive adhesive layer and the adherend. In addition, there exists a tendency which shows the outstanding adhesive force especially with respect to the adherend of inorganic substances, such as glass.

  As the number of mercapto groups in one molecule of a silane coupling agent having a mercapto group, the degree of crosslinking is controlled, and the adhesive strength at room temperature and the adhesive strength after being exposed to a high temperature and high humidity environment are as follows: From the viewpoint of keeping it suitable, two or less are preferable, and one is more preferable.

  Examples of the silane coupling agent having a mercapto group include a silane coupling agent having a mercapto group represented by 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, and the like. Can be mentioned. These may be used alone or in combination of two or more.

  As the silane coupling agent having a mercapto group, commercially available products may be used. Examples of commercially available products include trade names “KBM-803” and “KBM-802” manufactured by Shin-Etsu Chemical Co., Ltd. A silane coupling agent having a mercapto group such as “X-41-1810”, “X-41-1805”, “X-41-1818” and the like can be preferably used.

Among the silane coupling agents having a mercapto group, it is preferable to use at least one selected from oligomer-type silane coupling agents having a mercapto group from the viewpoint of durability and reworkability.
Here, the oligomer type silane coupling agent having a mercapto group is preferably a silane coupling agent comprising a silane coupling agent having a mercapto group and a silane coupling agent not having a mercapto group. Examples include trade names “X-41-1810”, “X-41-1805”, and “X-41-1818” manufactured by Chemical Industry Co., Ltd.

  Content of the silane coupling agent which has a mercapto group in an adhesive composition is 0.01 mass part-5.0 mass parts with respect to a total of 100 mass parts of urethane (meth) acrylate and a (meth) acrylic-type monomer. Range. When the content of the silane coupling agent is less than 0.01 parts by mass, the mercapto group of the silane coupling agent cannot sufficiently exhibit the effect as a chain transfer agent, the pressure-sensitive adhesive layer becomes too hard, There is a tendency that the adhesive strength at the time and the adhesive strength after exposure to a high temperature and high humidity environment are not sufficient. On the other hand, if the content of the silane coupling agent exceeds 5.0 parts by mass, the degree of polymerization of the polymer tends to be further reduced by the chain transfer reaction of the mercapto group, the pressure-sensitive adhesive layer becomes too soft, and the adhesive strength at room temperature. In addition, the adhesive strength after exposure to a high temperature and high humidity environment tends to be insufficient. From the above viewpoint, the content of the silane coupling agent is preferably in the range of 0.1 to 3.0 parts by mass, and more preferably in the range of 0.5 to 2.0 parts by mass.

<Photopolymerization initiator>
The pressure-sensitive adhesive composition of the present invention preferably contains a photopolymerization initiator. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the urethane (meth) acrylate and (meth) acrylic monomer are radically polymerized and cured by radicals generated from the photopolymerization initiator to form a pressure-sensitive adhesive layer. Is possible.
There is no restriction | limiting in particular as a photoinitiator, A well-known thing can be used.

Examples of the photopolymerization initiator include benzoin derivative compounds, benzyl ketal compounds, α-hydroxyacetophenone compounds, thioxanthone compounds, and acylphosphine oxide compounds.
Specific examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (trade name: Irgacure 184, BASF Japan Ltd.), 2-hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propanol. Oligomer (trade name: Esacure ONE, Lamberti Co., Ltd.), 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one (trade name: Irgacure 2959, BASF Japan Ltd.), 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one (trade name: Irgacure 127, BASF Japan Ltd.), 2,2-dimethoxy-2-phenylacetophenone (trade name: Gacure 651, BASF Japan Ltd.), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (trade name: Darocur 1173, BASF Japan Ltd.), 2-methyl-1-[(4 -Methylthio) phenyl] -2-morpholinopropan-1-one (trade name: Irgacure 907, BASF Japan Ltd.), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, isopropylthioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (trade name: Lucillin TPO, BASF Japan Ltd.), bis (2,4,6-Trimethylbenzoyl) phenylphos Examples include fin oxide (trade name: Irgacure 819, BASF Japan Ltd.), bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, and the like.

Among these, the α-hydroxyacetophenone compound is used as a photopolymerization initiator from the viewpoint that the compatibility with urethane (meth) acrylate is good, the yellowing of the pressure-sensitive adhesive composition hardly occurs, and there is little odor. 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propanol oligomer, 2-hydroxy-1- {4- [4- (2-hydroxy-2) More preferred is -methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one.
From the viewpoint of high reactivity, reduction in the amount of photopolymerization initiator, and prevention of yellowing in a high temperature and high humidity environment, the photopolymerization initiator may be bis (2,4, which is an acylphosphine oxide compound. , 6-Trimethylbenzoyl) phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are more preferable.

  When the pressure-sensitive adhesive composition of the present invention contains a photopolymerization initiator, the content of the photopolymerization initiator in the pressure-sensitive adhesive composition is 100 parts by mass in total of urethane (meth) acrylate and (meth) acrylic monomer. On the other hand, 0.1 mass part-5.0 mass parts are preferable, and 0.5 mass part-3.0 mass parts are more preferable.

<Other ingredients>
The pressure-sensitive adhesive composition of the present invention is optionally provided with a weather resistance stabilizer, a plasticizer, a softening agent, a peeling aid, a dye, a pigment, an inorganic filler, a surfactant, an antioxidant, a metal corrosion inhibitor, A light stabilizer or the like may be included.

  Although the adhesive composition of this invention may contain an organic solvent, it is preferable not to contain an organic solvent from a viewpoint which suppresses foaming at the time of setting it as the adhesive sheet mentioned later, and suppresses peeling. When the pressure-sensitive adhesive composition contains an organic solvent, the content of the organic solvent is preferably 5% by mass or less with respect to the total mass of the pressure-sensitive adhesive composition. “Not containing an organic solvent” means substantially not containing an organic solvent, and specifically indicates that the content of the organic solvent is 0.1% by mass or less.

  Examples of the organic solvent include alcohol-based organic solvents typified by methanol and propanol, aromatic hydrocarbon-based organic solvents typified by toluene and xylene, ester-based organic solvents typified by methyl acetate and ethyl acetate, , Ketone organic solvents typified by acetone and methyl ethyl ketone, aliphatic hydrocarbon organic solvents typified by n-hexane and cyclohexane, ether organic solvents typified by tetrahydrofuran, and chlorinated typified by dichloromethane An organic solvent is mentioned.

  The pressure-sensitive adhesive composition of the present invention may contain a chain transfer agent, but inhibits the reaction between a silane coupling agent having a mercapto group, a specific urethane acrylate and a (meth) acrylic monomer, and a silane having a mercapto group. Since the coupling agent is difficult to be incorporated into the polymer main chain, it is preferable not to include a chain transfer agent. When the pressure-sensitive adhesive composition contains a chain transfer agent, the content of the chain transfer agent is 0.05 parts by mass to 0.00 parts by mass with respect to 100 parts by mass in total of urethane (meth) acrylate and (meth) acrylic monomer. 5 mass parts is preferable and 0.1 mass part-0.3 mass part is more preferable.

In addition, a chain transfer agent shows the compound which has chain transfer effects other than the silane coupling agent which has the said mercapto group.
Examples of such chain transfer agents include mercaptans such as n-dodecyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, 2-ethylhexyl thioglycolate, and 2,3-dimethylcapto-1-propanol, allyl acetate, α -Allyl compounds such as methylstyrene dimer and allyl carbinol.

<Method for producing pressure-sensitive adhesive composition>
The production method of the pressure-sensitive adhesive composition of the present invention is not particularly limited, and known methods can be applied. For example, first, urethane (meth) acrylate is synthesized by the aforementioned urethane (meth) acrylate synthesis method, and the resulting urethane (meth) acrylate, (meth) acrylic monomer, and silane coupling having a mercapto group An agent and the other component contained as needed can be mixed and manufactured.
The method for adding the (meth) acrylate monomer is not particularly limited, and may be added at the time of synthesizing the urethane (meth) acrylate, or may be added after synthesizing the urethane (meth) acrylate.

≪Adhesive sheet≫
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer that is a cured product of the pressure-sensitive adhesive composition of the present invention.
The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet of a type having no base material (non-base material type).

As for the adhesive layer of the adhesive sheet of this invention, the exposed surface may be protected by the peeling film.
The release film is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer. For example, a resin film (for example, PET or the like) that has been subjected to easy release treatment on at least one side using a release treatment agent. Polyester film).
Examples of the release treatment agent include fluorine compounds, silicone compounds, and long-chain alkyl compounds.
The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is practically used, and is peeled off during use.

  From the viewpoint of the productivity of the pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is preferably 20 μm to 1200 μm, more preferably 25 μm to 800 μm, and still more preferably 80 μm to 500 μm.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention preferably has high transparency. Specifically, for example, the total light transmittance in the visible light wavelength region (JIS K 7361 (1997)) is 85% or more. It is preferably 90% or more.
The haze (JIS K 7136 (2000)) of the pressure-sensitive adhesive layer is preferably less than 2.0%, more preferably less than 1.0%, and still more preferably 0.5% or less.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is preferably not colored. Specifically, it is preferable that ^{b *} of 2.0 or less at a defined ^L * ^a * ^{b *} in CIE1976, more preferably 1.0 or less.
Moreover, it is preferable that there is little change in color tone when exposed to a high temperature and high humidity environment. Specifically, for example, the absolute value of the difference in b ^* before and after being left for 168 hours in an environment of 85 ° C. and 90% RH is preferably less than 2.0, and preferably less than 1.0. More preferred.

  The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by a method in which a pressure-sensitive adhesive composition is applied to a release film and irradiated with active energy rays to form a pressure-sensitive adhesive layer.

  The method of radically polymerizing the urethane (meth) acrylate and (meth) acrylic monomer contained in the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer that is a cured product of the pressure-sensitive adhesive composition is not particularly limited, It can be performed by a known method. For example, when the pressure-sensitive adhesive layer is formed in a sheet shape having a thickness of 80 μm to 200 μm, it can be formed by irradiating with active energy rays.

  The pressure-sensitive adhesive sheet of the present invention, for example, is obtained by applying a pressure-sensitive adhesive composition to the release treatment surface of a release film, and overlaying another release film on the application surface so that the release treatment surface is in contact with the active energy ray. Can be produced by a method of forming a pressure-sensitive adhesive layer by causing a curing reaction.

  Examples of the method for applying the pressure-sensitive adhesive composition to the release film include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater and the like.

  Examples of active energy rays include ultraviolet rays, infrared rays, visible rays, and electron beams. From the viewpoint of curing sensitivity and device availability, the active energy rays are preferably ultraviolet rays or electron beams, more preferably ultraviolet rays.

  Examples of light sources that can be irradiated with active energy rays include metal halide lamps, high-pressure mercury lamps, ultrahigh-pressure mercury lamps, ultraviolet lasers, xenon lamps, UV-LEDs, black lights, and chemical lamps.

The illuminance of the active energy ray to be irradiated, in accordance with the pressure-sensitive adhesive composition used may be appropriately ^{selected, 10mW / cm 2 ~300mW / cm} 2 are ^{preferred, 30mW / cm 2 ~150mW / cm} 2 Gayori preferable.

The irradiation condition of the active energy ray is not particularly limited and can be selected according to the composition of the pressure-sensitive adhesive composition, the thickness of the pressure-sensitive adhesive sheet, and the like. For example, when a high-pressure mercury lamp is used, the integrated light quantity is 100 mJ / cm ^{2 to} 2000 mJ / cm ² is preferable.

The adhesive sheet of this invention can be used suitably for bonding of the optical member in a touch panel, a display panel, etc. That is, the pressure-sensitive adhesive sheet of the present invention is represented by, for example, a polarizing plate, a retardation plate, an antireflection film, a viewing angle widening film, a brightness enhancement film, a transparent conductive film, a liquid crystal cell, a glass substrate, a protective film, and a plastic plate. It can use suitably for pasting of optical members, such as a protection board.
In particular, it is preferable to use it for pasting a transparent conductive film from the viewpoint of excellent adhesion and suppression of whitening in a wet and heat environment and excellent followability to steps.
Examples of the transparent conductive film include an ITO (Indium Tin Oxide) film, a silver nanowire film, a silver mesh film, a copper mesh film, and a carbon nanowire film.
Among these, the pressure-sensitive adhesive sheet of the present invention is preferably used for laminating a silver nanowire film from the viewpoint of easy adhesion to a curved surface, and is preferably used for laminating an ITO film because of its excellent adhesive strength. .

  As an optical member bonded using the adhesive sheet of this invention, a flat optical member may be sufficient and the optical member which has a curved surface may be sufficient. By using the pressure-sensitive adhesive sheet of the present invention, even a flat optical member or an optical member having a curved surface is excellent in adhesive force after being exposed to a high-temperature and high-humidity environment, and hardly peels off.

  For example, the touch panel using the pressure-sensitive adhesive composition or pressure-sensitive adhesive sheet of the present invention is excellent in the pressure-sensitive adhesive layer even after being exposed to a high-temperature and high-humidity environment. There is a tendency not to peel off.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

<Production Example A-1: Production of urethane acrylate UA-1>
In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 776.3 parts by mass of polypropylene glycol (trade name: Sannix PP2000, manufactured by Sanyo Chemical Industries, Ltd.), isophorone diisocyanate (trade name: Desmodur I, Covestro The product was 69.0 parts by mass (active ingredient 100%) and 0.225 parts by mass of dibutyltin dilaurate, heated to 70 ° C. and reacted for 180 minutes. Next, 34.5 parts by mass of isophorone diisocyanate (trade name: Desmodur I, manufactured by Covestro, active ingredient 100%) was added, and the mixture was reacted for 60 minutes while maintaining 70 ° C. Subsequently, 18.0 parts by mass of 2-hydroxyethyl acrylate was added and reacted for 120 minutes while maintaining at 70 ° C. In this way, urethane acrylate UA-1 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-1. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example A-2: Production of urethane acrylate UA-2>
In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 755.3 parts by mass of polypropylene glycol (trade name: Sannix PP2000, manufactured by Sanyo Chemical Industries), isophorone diisocyanate (trade name: Desmodur I, Covestro The product was 56.0 parts by mass, 100% active ingredient) and 0.225 parts by mass of dibutyltin dilaurate, and the temperature was raised to 70 ° C. and reacted for 180 minutes. Next, 56.0 parts by mass of isophorone diisocyanate (trade name: Desmodur I, manufactured by Covestro, 100% active ingredient) was added and reacted for 60 minutes while maintaining 70 ° C. Next, 30.0 parts by mass of 2-hydroxyethyl acrylate was added and reacted for 120 minutes while maintaining at 70 ° C. In this way, urethane acrylate UA-2 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-2. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example A-3: Production of urethane acrylate UA-3>
In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 798.4 parts by mass of polypropylene glycol (trade name: Sannix PP2000, manufactured by Sanyo Chemical Industries, Ltd.), isophorone diisocyanate (trade name: Desmodur I, Covestro 82.8 parts by mass of active ingredient 100%) and 0.225 parts by mass of dibutyltin dilaurate were charged, and the temperature was raised to 70 ° C. and reacted for 180 minutes. Next, 11.8 parts by mass of isophorone diisocyanate (trade name: Desmodur I, manufactured by Covestro, 100% active ingredient) was added and reacted for 60 minutes while maintaining 70 ° C. Subsequently, 7.0 mass parts of 2-hydroxyethyl acrylate was added, and it was made to react for 120 minutes, maintaining at 70 degreeC. In this way, urethane acrylate UA-3 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-3. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example A-4: Production of urethane acrylate UA-4>
Production Example A- except that the polypropylene glycol of Production Example A-1 (trade name: Sannix PP2000, manufactured by Sanyo Chemical Industries, Ltd.) was changed to polycaprolactone diol (trade name: Plaxel 220AL, manufactured by Daicel Corporation). 1 was synthesized under the same conditions as in 1. In this way, urethane acrylate UA-4 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-4. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example A-5: Production of urethane acrylate UA-5>
Polypropylene glycol (Product name: Sannix PP2000, manufactured by Sanyo Chemical Industries, Ltd.) of Production Example A-1 was changed to hydrogenated polybutadiene diol (Product name: NISSO-PB GI-2000, manufactured by Nippon Soda Co., Ltd.). The other conditions were the same as in Production Example A-1. In this way, urethane acrylate UA-5 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-5. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example A-6: Production of urethane acrylate UA-6>
In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 81.0 parts by mass of polyester polyol, isophorone diisocyanate (trade name: Desmodur I, manufactured by Covestro, 100% active ingredient) 14.0 parts by mass, dilauric acid 0.02 part by mass of dibutyltin was charged, and the temperature was raised to 60 ° C. and reacted for 240 minutes. Next, 5.0 parts by mass of 2-hydroxyethyl acrylate was added and reacted for 180 minutes while maintaining at 60 ° C. In this way, urethane acrylate UA-6 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-6. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example A-7: Production of urethane acrylate UA-7>
Production Example A-1 except that the polypropylene glycol of Production Example A-1 (trade name: Sannix PP2000, manufactured by Sanyo Chemical Industries, Ltd.) was changed to butadiene diol (trade name: G-2000, manufactured by Corporation). Were synthesized under the same conditions. In this way, urethane acrylate UA-7 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane acrylate UA-7. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example B-1: Production of urethane vinyl ether U-1>
The compound was synthesized under the same conditions as in Production Example A-1, except that 2-hydroxyethyl acrylate in Production Example A-1 was changed to 2-hydroxyethyl vinyl ether. In this way, urethane vinyl ether U-1 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane vinyl ether U-1. The weight average molecular weight (Mw) is determined by the method described above.

<Production Example B-2: Production of urethane resin U-2>
In a reaction vessel equipped with a stirrer, a reflux condenser, a sequential dropping device, and a thermometer, 786.0 parts by mass of polypropylene glycol (trade name: Sannix PP2000, manufactured by Sanyo Chemical Industries), isophorone diisocyanate (trade name: Death) Module I, manufactured by Covestro, active ingredient 100%) 75.0 parts by mass, dibutyltin dilaurate 0.225 parts by mass were charged and reacted at 70 ° C. for 200 minutes to complete the reaction. In this way, urethane resin U-2 was produced. Table 1 shows the weight average molecular weight (Mw) of the obtained urethane resin U-2. The weight average molecular weight (Mw) is determined by the method described above.

Example 1
<Preparation of pressure-sensitive adhesive composition>
62.5 parts by mass of urethane acrylate UA-1 as urethane (meth) acrylate, 22.5 parts by mass of 2-hydroxyethyl acrylate and 15.0 parts by mass of lauryl methacrylate as a (meth) acrylic monomer, and a mercapto group 1.25 parts by weight of KBM-803 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., 3-mercaptopropyltrimethoxysilane, 100% active ingredient) as a silane coupling agent having a silane coupling agent, Irgacure 184 as a photopolymerization initiator (Trade name, manufactured by BASF, 1-hydroxycyclohexyl phenyl ketone) was mixed with 3.0 parts by mass to prepare an adhesive composition.

[Evaluation]
<Preparation of test sample>
The prepared pressure-sensitive adhesive composition is subjected to active energy ray irradiation on the release-treated surface of a release film (trade name: Film Vina 100E, manufactured by Fujimori Kogyo Co., Ltd.) that has been easily released with a silicone-based release treatment agent. It applied so that the thickness of a layer might be set to 100 micrometers, and the application surface was bonded together to the peeling film (brand name: Film Bina 25E, Fujimori Kogyo Co., Ltd.) prepared separately. Thereafter, illuminance 120 mW / cm ² using a high pressure mercury lamp, under the conditions of integrated quantity of light 1500 mJ / cm ^2, was irradiated with an active energy ray. In this way, a base-free double-sided pressure-sensitive adhesive sheet (test sample) was produced.

(1) Evaluation of adhesive strength One release film of the produced test sample was peeled off, and the surface on which the pressure-sensitive adhesive layer was exposed was subjected to an easy adhesion treatment polyethylene terephthalate (hereinafter also referred to as “PET”) film (trade name). : A-4100, thickness 100 μm, manufactured by Toyobo Co., Ltd.). The test sample to which this PET film was bonded was cut into a size of 25 mm × 150 mm. Next, the other release film was peeled off, and the surface where the pressure-sensitive adhesive layer was exposed was superimposed on the glass plate. Using a rubber roller having a weight of 2 kg, the surface of the glass plate was pressure-bonded and bonded to prepare a sample for evaluating adhesive force. Using this adhesive strength evaluation sample, the adhesive strength was measured under the following conditions.

-Adhesive strength (1)-
This adhesive strength evaluation sample is left for 24 hours in an environment of 23 ° C. and 50% RH (hereinafter also referred to as “room temperature environment”), and then the adhesive strength (unit: N / 25 mm) at 180 ° peeling is peeled off. Measurement was performed at a speed of 300 mm / min. The adhesive strength after exposure to room temperature was evaluated according to the following evaluation criteria. The higher the adhesive strength, the better.

<Evaluation criteria>
A: The adhesive strength is 30 N / 25 mm or more, and the adhesive strength is very excellent.
B: The adhesive strength is 20 N / 25 mm or more and less than 30 N / 25 mm, and the adhesive strength is excellent.
C: The adhesive strength is 10 N / 25 mm or more and less than 20 N / 25 mm, and the adhesive strength is slightly superior.
D: Adhesive strength is less than 10 N / 25 mm, adhesive strength is inferior, and there are practical problems.

-Adhesive strength (2)-
Further, the adhesive strength evaluation sample prepared above was allowed to stand for 168 hours in an environment of 85 ° C. and 90% RH (hereinafter, also referred to as “high temperature and high humidity environment”), and then further 23 ° C. and 50% RH. After being left for 3 hours in this environment, the adhesive strength (unit: N / 25 mm) at 180 ° peeling was measured at a peeling speed of 300 mm / min. The adhesive strength after exposure to a high temperature and high humidity environment was evaluated according to the following evaluation criteria. The stronger the adhesive strength, the better.
<Evaluation criteria>
A: The adhesive strength is 20 N / 25 mm or more, and the adhesive strength is very excellent.
B: The adhesive strength is 15 N / 25 mm or more and less than 20 N / 25 mm, and the adhesive strength is excellent.
C: The adhesive strength is 10 N / 25 mm or more and less than 15 N / 25 mm, and the adhesive strength is slightly superior.
D: Adhesive strength is less than 10 N / 25 mm, adhesive strength is inferior, and there are practical problems.

(2) Evaluation of color tone One peeled film of the test sample prepared above was peeled off, and the surface on which the pressure-sensitive adhesive layer was exposed was subjected to an easy-adhesion-treated PET film (trade name: A-4100, thickness 100 μm, Toyobo The surface was subjected to easy adhesion treatment (manufactured by Co., Ltd.). The test sample to which this PET film was bonded was cut into a size of 85 mm × 55 mm. Next, the other release film was peeled off, and the surface where the pressure-sensitive adhesive layer was exposed was superimposed on the glass plate. Using a hand roller having a weight of 2 kg, the surface of the glass plate was pressed and bonded to prepare a sample for color tone evaluation. The sample for color tone evaluation was left in an environment of 85 ° C. and 90% RH for 168 hours (hereinafter also simply referred to as “left”), and the color change before and after being left was measured with a color difference meter (trade name: Spectrophotometer SE6000, Nippon Denki). B ^* (b ^* value is the value obtained by subtracting the measured value of the glass plate alone), respectively, and Δb ^* was calculated.
Δb ^* = after being left ^{b *} - before being left ^{b *}
The obtained Δb ^* was evaluated according to the following evaluation criteria. Note that Δb ^* is preferably as low as possible.

<Evaluation criteria>
A: Δb ^* is 0 or more and less than 1.0, yellowing is not observed in a high-temperature and high-humidity environment, and the color tone is excellent in stability.
B: Δb ^* is 1.0 or more and less than 2.0, and yellowing in a high-temperature and high-humidity environment is slightly observed, but the color tone stability is somewhat excellent, and there is no practical problem.
C: Δb ^* exceeds 2.0, yellowing is observed in a high-temperature and high-humidity environment, the color tone is poor in stability, and there is a practical problem.

(Examples 2 to 24 and Comparative Examples 1 to 10)
A pressure-sensitive adhesive composition as shown in Table 1 was prepared in the same manner as in Example 1 except that the composition was changed to the composition shown in Table 1 in Example 1. A test sample was prepared in the same manner as in Example 1 using the prepared pressure-sensitive adhesive composition. The obtained test samples were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Abbreviations in Table 1 are as follows. In addition, "-" in Table 1 indicates that the corresponding component is not included.
UA-1: Urethane acrylate having a polypropylene glycol skeleton (weight average molecular weight 30,000, bifunctional) (Production Example A-1)
UA-2: urethane acrylate having a polypropylene glycol skeleton (weight average molecular weight 18,000, bifunctional) (Production Example A-2)
UA-3: urethane acrylate having a polypropylene glycol skeleton (weight average molecular weight 75,000, bifunctional) (Production Example A-3)
UA-4: Urethane acrylate having a polyester skeleton (weight average molecular weight 30,000, bifunctional) (Production Example A-4)
UA-5: Urethane acrylate having a hydrogenated butadiene skeleton (weight average molecular weight 30,000, bifunctional) (Production Example A-5)
UA-6: Urethane acrylate having a polyester skeleton (weight average molecular weight 18,000, bifunctional) (Production Example A-6)
UA-7: Urethane acrylate having a butadiene skeleton (urethane acrylate having a polymerizable unsaturated group other than acryloyl group) (weight average molecular weight 30,000, bifunctional) (Production Example A-7)
U-1: Urethane vinyl ether having a polypropylene glycol skeleton (weight average molecular weight 30,000, bifunctional) (Production Example B-1)
U-2: Urethane resin (weight average molecular weight 30000, 0 functionality) (Production Example B-2)

2HEA: 2-hydroxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate LMA: lauryl methacrylate 2EHMA: 2-ethylhexyl methacrylate 2HDMA: 2-hexyldecyl methacrylate LA: lauryl acrylate AA: acrylic acid ACMO: acryloyl Morpholine

SC agent 1: silane coupling agent having a mercapto group (trade name: KBM-803, manufactured by Shin-Etsu Chemical Co., Ltd., 3-mercaptopropyltrimethoxysilane, the number of mercapto groups is 1)
SC agent 2: Silane coupling agent having a mercapto group (trade name: X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd., the number of mercapto groups is 2 or more)
SC agent 3: epoxy group-containing silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane)

M1: Compound having a mercapto group (trade name: Thiocalcol 20, manufactured by Kao Corporation, n-dodecyl mercaptan, number of mercapto groups is 1)
・ Irg184 (trade name: Irgacure 184, manufactured by BASF, 1-hydroxycyclohexyl phenyl ketone)

  Including urethane (meth) acrylate, (meth) acrylic monomer, and silane coupling agent having a mercapto group, and a total of 100 parts by mass of urethane (meth) acrylate and (meth) acrylic monomer The pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition of Examples 1 to 24 containing 0.01 parts by mass to 5.0 parts by mass of a silane coupling agent having a mercapto group is all evaluated for adhesive strength and color tone. In, it was favorable or was in tolerance level.

On the other hand, Comparative Examples 1 and 2 not containing urethane (meth) acrylate, Comparative Example 3 not containing (meth) acrylic monomer, Comparative Example 4 not containing a silane coupling agent having a mercapto group, Mercapto group Comparative Example 5 having a silane coupling agent content exceeding 5.0 parts by mass, Comparative Example 6 using a silane coupling agent not containing a mercapto group, and polymerizable unsaturated groups other than (meth) acryloyl groups In Comparative Example 10 containing urethane acrylate having a low adhesive strength after exposure to room temperature conditions or a high temperature and high humidity environment, the adhesive strength was inferior.
In Comparative Example 9 that does not include a silane coupling agent having a mercapto group, the adhesive strength after exposure to a high temperature and high humidity environment was low and the adhesive strength was poor. Moreover, in the comparative example 9, since the (meth) acrylic-type monomer containing a nitrogen atom was included as a (meth) acrylic-type monomer, yellowing in a high-temperature, high-humidity environment was seen, and the stability of the color tone was inferior.
In Comparative Example 7 including a compound containing a mercapto group that is not a silane coupling agent, and Comparative Example 8 combining a silane coupling agent not containing a mercapto group and a compound containing a mercapto group that is not a silane coupling agent In either case, the adhesive strength after exposure to a high temperature and high humidity environment was low and the adhesive strength was poor.

  From the above, it can be seen that the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition of the present invention has excellent adhesive force even after being exposed to a high temperature and high humidity environment. Moreover, it turns out that the adhesive sheet formed from the adhesive composition of this invention is also a favorable result also about transparency.

Claims (8)

Urethane (meth) acrylate having no polymerizable unsaturated group other than (meth) acryloyl group;
(Meth) acrylic monomers,
A silane coupling agent having a mercapto group;
Including
The pressure-sensitive adhesive composition in which the content of the silane coupling agent having a mercapto group is 0.01 parts by mass to 5.0 parts by mass with respect to a total of 100 parts by mass of the urethane (meth) acrylate and the (meth) acrylic monomer. object.   The pressure-sensitive adhesive composition according to claim 1, wherein the urethane (meth) acrylate has a structural unit derived from a polyether polyol. The (meth) acrylic monomer includes at least one (meth) acrylic monomer having a hydroxyl group,
The pressure-sensitive adhesive composition according to claim 1 or 2, wherein a content ratio of the (meth) acrylic monomer having a hydroxyl group with respect to a total mass of the (meth) acrylic monomer is 30% by mass to 90% by mass. .   The blending ratio of the urethane (meth) acrylate and the (meth) acrylic monomer is 55:45 to 75:25 on a mass basis, according to any one of claims 1 to 3. Adhesive composition.   The said (meth) acrylic-type monomer contains at least 1 sort (s) of alkyl methacrylate, The content rate of the said alkylmethacrylate with respect to the total mass of the said (meth) acrylic-type monomer is 5 mass%-50 mass%, The pressure-sensitive adhesive composition according to any one of claims 1 to 4.   Furthermore, the adhesive composition of any one of Claims 1-5 containing a photoinitiator.   The pressure-sensitive adhesive composition according to any one of claims 1 to 6, which does not contain an organic solvent.   The adhesive sheet which has an adhesive layer which is a hardened | cured material of the adhesive composition of any one of Claims 1-7.