JP5181498B2 - Active energy ray-curable pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet - Google Patents

Description

  The present invention relates to an active energy ray-curable pressure-sensitive adhesive composition containing a compound having two or more maleimide groups having a specific structure.

The pressure-sensitive adhesive is subjected to pressure-sensitive adhesive processing, and is used for various applications such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, and double-sided pressure-sensitive adhesive tapes. In particular, in applications such as adhesion of interior parts and exterior parts of automobiles, electrical equipment, houses, and adhesion between electronic parts, excellent water resistance and high adhesiveness, that is, it can be pasted with low pressure bonding at room temperature, In addition, there is a demand for performance that does not peel off even when left at high temperatures.
For applications that require heat resistance, adhesive products that use silicone adhesives are being studied, but there is no excellent release material corresponding to them, and the cost is high due to the use of expensive raw materials. It has not yet become widespread because it has the following problems.

On the other hand, as a widely used pressure-sensitive adhesive, a solvent-based pressure-sensitive adhesive prepared by dissolving an acrylic polymer or a rubber-based resin such as SIS or SEBS in an organic solvent is used. Therefore, various studies have been made to satisfy the above performance.
However, solvent-based adhesives use organic solvent agents because there are concerns about the environmental impact of organic solvents that diverge when processed into adhesive products and the safety of residual solvents in adhesive coatings. In recent years, non-adhesive adhesives have been required.

As an alternative to solvent-based adhesives, it cures with active energy rays such as ultraviolet rays and visible light because it is excellent in water resistance and heat resistance, low viscosity and easy to handle, and solvent-based coating equipment is easy to apply. Active energy ray-curable pressure-sensitive adhesives have been studied.
Active energy ray-curable adhesives and other active energy ray-curable pressure-sensitive adhesive compositions are not usually crosslinked or cured by the raw material components alone, so photopolymerization initiators or photosensitizers (hereinafter collectively referred to as photopolymerization). It is necessary to add an initiator).

The photo-initiator and the like tend to increase in amount because the curing proceeds faster when the amount added is increased. However, since photopolymerization initiators and the like use a compound having an aromatic ring to efficiently absorb light, this causes a problem that the resulting cured coating film turns yellow. It is.
As the photopolymerization initiator, a low molecular weight compound is usually used in order to efficiently initiate the polymerization reaction. However, when the composition is irradiated with active energy, the temperature rises due to the heat of polymerization.However, the low molecular weight photopolymerization initiator has a high vapor pressure, so that a bad odor is generated at the time of curing, resulting in a problem of working environment. It has the problem of generating or contaminating the resulting product. In addition, since a decomposition product such as an unreacted photopolymerization initiator remains in the cured coating film, when the cured coating film is subjected to light or heat, the cured coating film turns yellow or has a bad odor. There was a problem of generating.
Furthermore, if the cured coating is left in water, or if the cured coating is touched by sweat that radiates from the human body, a large amount of unreacted photopolymerization initiator bleeds, causing problems in terms of safety and health. It was.

In order to improve the drawbacks of the active energy ray-curable composition containing the above-described photopolymerization initiator and the like, a composition that does not contain a photopolymerization initiator and can be cured by irradiation with active energy rays has been studied. (For example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).
However, it is difficult for the compositions disclosed in the above-mentioned patent documents to achieve both adhesive strength and heat resistance at a high level, and further improvements in adhesive strength and active energy curability have been required depending on applications.

International publication pamphlet WO2004 / 108850 JP 2006-070060 International publication pamphlet WO2003 / 072674 JP 2006-2332739

  The invention of the present application is liquid at room temperature and has a practical crosslinkability or curability in the absence of a photopolymerization initiator when irradiated with active energy rays such as visible light or ultraviolet light. An object of the present invention is to provide an adhesive composition in which the film is not colored and is particularly excellent in adhesive strength and heat resistance.

In order to solve the above problems, the active energy ray-curable pressure-sensitive adhesive composition of the invention described in claim 1 includes a compound (A) having a specific polyether skeleton and two or more maleimide groups, and a specific polyester. The compound (B) having a skeleton and having two or more maleimide groups is contained at 5 to 19% by mass and 81 to 95% by mass, respectively, based on the total amount of (A) and (B), and is liquid at 25 ° C. what Monodea, maleimide groups compound (a) and the compound (B) is included in those having a specific structure.
The active energy ray-curable pressure-sensitive adhesive composition of the invention described in claim 2 is characterized in that, in the invention described in claim 1, the polyether skeleton is a polytetramethylene glycol skeleton.
In the pressure-sensitive adhesive sheet according to the third aspect , the pressure-sensitive adhesive composition according to any one of the first or second aspect is applied to a base material, and the coating film is irradiated with an active energy ray to develop a pressure-sensitive adhesive property. It is characterized by that.

  It is liquid at normal temperature, and has a practical crosslinkability or curability in the absence of a photopolymerization initiator when irradiated with visible light or ultraviolet light. An adhesive composition excellent in strength and heat resistance was obtained.

1. Maleimide compound (compound (A) and compound (B))
The compound (A) having a polyether skeleton and having two or more maleimide groups (also simply referred to as the compound (A)) is a main component for exhibiting active energy ray curability and basic performance as an adhesive. One.
Compound (B) having a polyester skeleton and having two or more maleimide groups (also referred to simply as compound (B)) is also a main component for exhibiting active energy ray curability and basic performance as an adhesive. One.

  In this specification, the compound (A) and the compound (B) are also simply referred to as a maleimide compound.

The maleimide compound is preferably the following compound (A) or mixture (A) when classified according to the type of maleimide group provided in the maleimide compound. The reason is that the curability of the composition is excellent (cured by irradiation with less active energy rays). In the case of a mixture as well, it is generically called a maleimide compound for convenience.
The compound (a) is a compound having two or more maleimide groups represented by the following formula (1).

[In Formula (1), R < ¹ > represents an alkyl group, an aryl group, an arylalkyl group, or a halogen atom. ]

  The compound (a) includes a compound (a) having two or more maleimide groups represented by the following formula (2) and two or more maleimide groups represented by the following formula (3) and / or formula (4). The compound (b) is a mixture containing 10 to 90% by mass and 10 to 90% by mass, respectively, based on the total amount of (a) and (b). 20-80 mass% and 20-80 mass% are respectively preferable, and 30-70 mass% and 30-70 mass% are respectively more preferable.

In [Equation (3), R ² and R ³ represents an alkyl group, an aryl group, an arylalkyl group or a halogen atom. ]

[In Formula (4), R < ⁴ > represents the propylene group or butylene group which may have an alkyl group as a substituent. ]

In the formula (1) and formula (3), the alkyl group of R ^{1 to} R ³ is preferably an alkyl group having 4 or less carbon atoms, particularly preferably a methyl group. A phenyl group etc. can be mentioned as an aryl group. Examples of the arylalkyl group include a benzyl group.
Among these, as R ^{1 to} R ³ , an alkyl group is preferable, an alkyl group having 4 or less carbon atoms is more preferable, and a methyl group is particularly preferable.
In the formula (4), as the propylene group or butylene group which may have an alkyl group as a substituent for R ⁴ , a butylene group is preferable because it is easily available and excellent in various adhesive performances. In the case of a propylene group or butylene group having a substituent, the substituent is preferably an alkyl group, and more preferably a methyl group. Specific examples of the propylene or butylene group having a _{substituent, -CH 2 CH (CH 3)} CH 2 CH 2 - and the like.

  In the maleimide compound, since the maleimide group is dimerized by irradiation with active energy rays, the molecules of the compound are combined to increase the molecular weight (curing). Even when the maleimide group is cured with ultraviolet rays or visible light, it can cause a dimerization reaction by irradiation with ultraviolet rays or visible light with or without a photopolymerization initiator.

The molecular weight of the maleimide compound (compound (A) and compound (B), respectively) is preferably 1000 to 30000 in terms of number average molecular weight, more preferably 2000 to 15000, and still more preferably 8000 to 12000. When the number average molecular weight is less than 1000, the adhesive strength and tack of the cured coating film may be reduced. On the other hand, when the number average molecular weight exceeds 30000, the viscosity of the composition becomes too high and the coatability may be reduced.
In the present invention, the number average molecular weight is a value obtained by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as GPC) using tetrahydrofuran as a solvent with reference to the molecular weight of polystyrene.
When the maleimide compound is a water-soluble compound, the number average molecular weight is a value obtained by converting a molecular weight measured by GPC using a phosphate buffer as a solvent based on the molecular weight of polyethylene oxide.

  The maleimide compound may be produced by a known method, but the following three maleimide compounds are preferable because they are easy to produce.

  An addition reaction product of a prepolymer having two or more isocyanate groups at the terminal and a compound having a maleimide group and an active hydrogen group (hereinafter referred to as compound [1]).

  An esterification reaction product of a prepolymer having two or more carboxyl groups at the terminal and a compound having a maleimide group and an active hydrogen group (hereinafter referred to as compound [2]).

An esterification reaction product of a prepolymer having two or more hydroxyl groups at its terminal and a carboxylic acid having a maleimide group (hereinafter referred to as compound [3]).
Hereinafter, the compounds [1] to [3] will be described.

1-1. Compound [1]
Compound [1] is an addition reaction product of a prepolymer having two or more isocyanate groups at the terminal (hereinafter simply referred to as a urethane prepolymer) and a compound having a maleimide group and an active hydrogen group (hereinafter simply referred to as a maleimide active hydrogen compound). It is produced by reacting 2 moles or more of maleimide active hydrogen compound with respect to 1 mole of urethane prepolymer.
Hereinafter, the urethane prepolymer and the maleimide active hydrogen compound will be described.

A) Urethane prepolymer As the urethane prepolymer, various compounds can be used as long as they have two or more isocyanate groups at the molecular ends.
Examples of the urethane prepolymer include a reaction product of a polyol having two or more hydroxyl groups (hereinafter simply referred to as polyol) and a polyisocyanate having two or more isocyanate groups (hereinafter simply referred to as polyisocyanate).

a1) As the polyol polyol, a polyether polyol is used when the compound (A) is produced, and a polyester polyol is used when the compound (B) is produced.
As a polyol, 2 or more types can be used together as needed.

a1-1) Polyether polyol As the polyether polyol, polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polybutylene glycol and polytetramethylene glycol; ethylene glycol, propanediol, propylene glycol, tetramethylene glycol, pentamethylene glycol, Ethylene oxide modified products, propylene oxide modified products, butylene oxide modified products and tetrahydrofuran modified products of alkylene glycols such as hexanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol, diglycerin, ditrimethylolpropane and dipentaerythritol; Copolymer of ethylene oxide and propylene oxide, propylene glycol Copolymers Lumpur and tetrahydrofuran, copolymers of ethylene glycol and tetrahydrofuran.
Among these, in the present invention, it is necessary to use one or more of polyethylene glycol, polypropylene glycol and polytetramethylene glycol.

As the polyether polyol, polytetramethylene glycol is preferable. Thereby, the obtained adhesive tends to be excellent in adhesive strength and heat resistance.

a1-2) Polyester polyol The polyester polyol is a random copolycondensation product of a polyvalent carboxylic acid and a polyhydric alcohol. Among these, it is necessary to be an aliphatic polyester polyol composed of an aliphatic dicarboxylic acid and an aliphatic diol, and this is preferable because the curability of the composition by active energy rays is excellent.

Here, various polycarboxylic acids can be used as long as they have two or more carboxyl groups in the molecule. Specifically, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicoic acid diacid, 2,6-naphthalenedicarboxylic acid, trimellitic acid, glutaric acid, 1,9 -Nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, malonic acid, fumaric acid, 2,2-dimethylglutaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid Examples include acids, itaconic acid, maleic acid, 2,5-norbornane dicarboxylic acid, 1,4-terephthalic acid, 1,3-terephthalic acid, dimer acid, and paraoxybenzoic acid.
Among these, it is necessary to be an aliphatic dicarboxylic acid , and adipic acid and sebacic acid are more preferable.
Two or more polycarboxylic acids can be used in combination as required.

Any polyhydric alcohol can be used as long as it has two or more hydroxyl groups in the molecule. Specifically, butylethylpropanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5-pentanediol and polyethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,2-octanediol, 1,8-octanediol, 1,9-nonanediol, 1,2, decanediol, 1,10-decanediol, 2 , 2-Dimethyl-1,3-propanediol, 2,2,4-trimethyl-1,6 Hexanediol, 1,3-cyclohexanedimethanol and 1,4-cyclohexane dimethanol, etc. diol dimer acid and 2-methyl-1,8-octanediol and the like.
Among these, it is necessary to be an aliphatic diol , and further, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 3-methyl-1,5- Pentanediol, dimer acid diol and 2-methyl-1,8-octanediol are more preferable because the resulting composition has low viscosity and excellent tackiness and water resistance.
Two or more polyhydric alcohols can be used in combination as required.

  As a method for producing the polyester polyol, a general esterification reaction may be followed, and examples thereof include a method in which a polyvalent carboxylic acid and a polyhydric alcohol are heated with stirring in the presence of a catalyst.

  As said catalyst, the catalyst normally used by esterification reaction can be used, A base catalyst, an acid catalyst, a metal alkoxide, etc. are mentioned. Examples of the base catalyst include metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as triethylamine, N, N-dimethylbenzylamine and triphenylamine. Examples of the acid catalyst include sulfuric acid and paratoluenesulfonic acid. As the metal alkoxide, an alkoxide of titanium, tin or zirconium is preferable. Specific examples of these metal alkoxides include tetraalkyl titanates such as tetrabutyl titanate; tin alkoxides such as dibutyltin oxide and monobutyltin oxide; and zirconium alkoxides such as zirconium tetrabutoxide and zirconium isopropoxide.

  What is necessary is just to set suitably as reaction temperature and time in esterification reaction according to the objective. As reaction temperature, 80-220 degreeC is preferable.

  As the aliphatic polyester polyol, commercially available products can be used. For example, “Kuraray polyol P-5010” and “Kuraray polyol P-5050” manufactured by Kuraray Co., Ltd., manufactured by Kyowa Hakko Kogyo Co., Ltd. “Kyowapol 5000PA”, “Kyowapol 3000PA”, “Dynacoll 7250” manufactured by Degussa Japan Co., Ltd., and the like.

a2) Various polyisocyanates can be used as long as they have two or more isocyanate groups in the molecule, and diisocyanates are preferred. Specifically, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate, 4,4′-diphenylene diisocyanate, 1,5-octylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexa Methylene diisocyanate, pentamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexane diisocyanate, diphenylmethane Diisocyanate, 1,4-bis (isocyanatemethyl) cyclohexane, 1,3-bis (isocyanatemethyl) cyclohexane, Examples include sophorone diisocyanate and carbodiimide-modified 4,4′-diphenylmethane diisocyanate.
Among these, alicyclic or aliphatic isocyanates are preferable in that they are excellent in curability by active energy rays of the composition and weather resistance of the cured product. As the alicyclic or aliphatic isocyanate, hexamethylene diisocyanate and isophorone diisocyanate are preferable.
Polyisocyanate can use 2 or more types together as needed.
In the present invention, the amount of the polyisocyanate with respect to the polyol in producing the urethane prepolymer is preferably in a range in which the equivalent ratio of group-NCO / group-OH is 1 to 3, more preferably 1.5 to 2.5. And particularly preferably 1.8 to 2.2.

a3) Method for Producing Urethane Prepolymer The urethane prepolymer may be produced by a conventional method. For example, a method of heating a polyol and a polyisocyanate in the presence of a catalyst can be mentioned. What is necessary is just to set suitably as reaction temperature and time in a urethanation reaction according to the objective. As reaction temperature, 20-140 degreeC is preferable.
As a catalyst, the catalyst used by a general urethanation reaction can be used, for example, a metal compound, an amine, etc. are mentioned. As metal compounds, tin-based catalysts such as dibutyltin dilaurate and dioctyltin dilaurate; lead-based catalysts such as lead dioctylate; zirconium-based compounds such as K-KAT XC-4025 and K-KAT XC-6212 (manufactured by KING INDUSTRIES, INC) Catalysts: Aluminum catalysts such as K-KAT XC-5217 (manufactured by KING INDUSTRIES, INC); and titanate catalysts such as tetra 2-ethylhexyl titanate. Examples of the amine include triethylamine, N, N-dimethylbenzylamine, triphenylamine, and triethylenediamine.
As a usage ratio of the urethanization reaction catalyst, it is preferable to use a small amount as much as possible so as not to adversely affect the skin.
In the production of the urethane prepolymer, a general radical polymerization inhibitor such as hydroquinone and triethylamine can be used as necessary for the purpose of preventing gelation during the reaction.

  Furthermore, a phosphorus compound can be blended during the production of the urethane prepolymer. By blending the phosphorus compound, the action of the catalyst used during esterification and ring-opening polyaddition can be stopped. If the activity of the catalyst is not deactivated, when the obtained urethane prepolymer is stored in the presence of moisture or heated in the presence of moisture in the next reaction, or the cured film of the resulting maleimide compound and composition, When stored in the presence of moisture, a transesterification reaction may occur and the physical properties of the composition may be significantly reduced.

  As a phosphorus compound, the inorganic or organic phosphorus compound etc. which are mentioned by following (D)-(H) are mentioned.

(D) Phosphoric acid and its alkyl esters Examples of phosphoric acid alkyl esters include trialkyl phosphates such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trinonyl phosphate, and triphenyl phosphate.

(E) Phosphonic acid organic esters Dibutylbutylphosphonate and the like can be mentioned.

(F) Phosphorous acid Used alone or in combination with other phosphorus compounds, it has the strongest hue stabilizing effect and oxidative degradation preventing effect.

(G) Organic esters of phosphorous acid Examples include dibutyl hydrogen phosphite and triphenyl phosphite. However, triphenyl phosphite may deteriorate the properties of the polyester skeleton in the maleimide compound, and it is necessary to pay attention to the amount of triphenyl phosphite added.

(H) Other inorganic phosphorus compounds Polyphosphoric acid etc. are mentioned.

  The amount of the phosphorus compound used may be appropriately set according to the molecular weight of the phosphorus compound (phosphorus atom content), and is generally preferably 0.001 to 3 parts by mass with respect to 100 parts by mass of the polyester polyol. More preferably, it is 0.01-1 mass part. When the amount of the phosphorus compound used is less than 0.001 part by mass, the effect of addition is not recognized, and when it is more than 3 parts by mass, the effect does not increase.

B) Maleimide active hydrogen compound As the maleimide active hydrogen compound, an alcohol having a maleimide group (hereinafter referred to as maleimide alcohol) is preferable. Examples of maleimide alcohols include maleimide alkyl alcohols represented by the following formulas (5-1) to (5-4).

In formulas (5-1) to (5-4), R ⁵ represents an alkylene group, preferably a linear or branched alkylene group having 1 to 6 carbon atoms. In formulas (5-1), (5-3) and (5-4), R ^{1 to} R ⁴ are the same groups as described above.

C) Method for producing maleimide compound, that is, compound (A) and compound (B) As a method for producing maleimide compound, that is, compound (A) and compound (B), urethane prepolymer and maleimide active hydrogen compound are generally urethanized. What is necessary is just to manufacture according to reaction. Specific examples of the urethanization reaction include the same methods as described above.
In the production of the maleimide compound, it is preferable to react in the presence of an antioxidant in order to prevent discoloration of the resulting maleimide compound.
Examples of antioxidants include phenolic, phosphite triester and amine antioxidants which are generally used. Examples of the antioxidant include JP-B 36-13738, JP-B 36-20041, and JP-B. Examples thereof include compounds described in Japanese Patent Publication No. 36-20042 and Japanese Patent Publication No. 36-20043.
Various phenolic antioxidants can be used, such as butylhydroxytoluene, pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate is particularly preferred.
The phenolic antioxidant can be used in combination with an acid value zinc in order to enhance the effect.
The mixing ratio of the antioxidant is preferably 0.01 to 2 parts by mass per 100 parts by mass of the urethane prepolymer. If this proportion is less than 0.01 parts by weight, the sufficient effect due to the blending of the antioxidant may not be exhibited, and even if blended more than 2 parts by weight, no further effect is expected and the cost is reduced. Disadvantageous.
Moreover, you may mix | blend the above-mentioned phosphorus compound at the time of maleimide compound manufacture.
(A) In manufacture of a component, in order to remove the trace amount impurity contained in the maleimide compound obtained and to improve safety | security further, it can refine | purify. There is no restriction | limiting in particular regarding a refinement | purification method, What is necessary is just to follow a well-known method. For example, a method of adding a washing solvent to the obtained maleimide compound, separating the impurities after extraction using the difference in solubility between the maleimide compound and the impurities to be removed, and then removing the solvent, and the like.

1-2. Compound [2]
Compound [2] is an esterification reaction product of a prepolymer having two or more carboxyl groups at its terminal (hereinafter simply referred to as carboxylic acid prepolymer) and a maleimide active hydrogen compound.
Examples of the carboxylic acid prepolymer include those produced using the same polycarboxylic acid and polyol or polyhydric alcohol as described above. In this case, when producing the compound (A), a polyether polyol is used, and when producing the compound (B), a polyester polyol is used.
Examples of the maleimide active hydrogen compound include those described above.
The esterification reaction method of the carboxylic acid prepolymer and the maleimide active hydrogen compound may follow the same method as described above.
Compound [2] can be preferably used when a lower viscosity is required as a maleimide compound.

1-3. Compound [3]
Compound [3] is an esterification reaction product of a prepolymer having two or more hydroxyl groups at its terminal (hereinafter simply referred to as polyol prepolymer) and a carboxylic acid having a maleimide group (hereinafter referred to as maleimide carboxylic acid).
Examples of the polyol prepolymer include the same polyols. In this case, when producing the compound (A), a polyether polyol is used, and when producing the compound (B), a polyester polyol is used.
As the maleimide carboxylic acid, various compounds can be used, and compounds represented by the following formulas (6-1) to (6-4) are preferable.

In formulas (6-1) to (6-4), R ⁶ represents an alkylene group and is preferably a linear or branched alkylene group having 1 to 6 carbon atoms. In formulas (6-1), (6-3) and (6-4), R ^{1 to} R ⁴ are the same groups as described above.
The esterification reaction method of the polyol prepolymer and maleimide carboxylic acid may follow the same method as described above.
Compound [3] can be preferably used when a lower viscosity is required as a maleimide compound.

1-4. Preferred maleimide compounds As the above-mentioned compounds [1] to [3], the compound [1] has a higher reaction rate than the compounds [2] and [3], a high yield, can be easily produced, and is cured. Most preferable in terms of excellent adhesive strength of the film. This is considered that the flexible polyol part and the hard polyisocyanate part have a micro phase separation structure, and the adhesiveness is improved by the difference in the cohesive force associated with van der Waals force and hydrogen bonding force in each micro domain. . For applications where a low viscosity maleimide compound is required, compounds [2] and [3] are preferred.
The maleimide compound can adjust the viscosity and fluidity of the composition, the adhesive strength, the holding power and the tack of the cured coating film by changing the copolymer composition according to the purpose.
As the maleimide compound, a compound having two maleimide groups is preferable because it is excellent in adhesive strength and tack of a cured coating film of the composition.

  The maleimide compound is preferably liquid at normal temperature (25 ° C.). Although the composition of the present invention is liquid at 25 ° C., the compound (A) and the compound (B) which are the main components of the composition are both liquid at 25 ° C. It is preferable because it is easy.

2. Active energy ray-curable pressure-sensitive adhesive composition The composition of the present invention contains a maleimide compound, that is, compound (A) and compound (B) as essential components. Based on the total amount of compound (A) and compound (B), the proportions of compound (A) and compound (B) are 5 to 19% by mass and 81 to 95% by mass, respectively. 5-17 mass% and 83-95 mass% are respectively preferable. If the proportion of the compound (A) is too small, the curability of the composition becomes insufficient. Therefore, the heat resistance of the pressure-sensitive adhesive tends to be insufficient unless the active energy ray irradiation is increased. If the proportion of the compound (A) is too large, the adhesive strength of the adhesive becomes insufficient.

  The composition of the present invention is liquid at ordinary temperature (25 ° C.). Thereby, handling of coating work etc. becomes easy. On the other hand, those that are solid at room temperature are difficult to handle, and the cured coating film has a high elastic modulus, resulting in insufficient adhesive performance.

The composition of the present invention may contain a component other than the compound (A) and the compound (B).

3-1. As described above, the composition of the present invention, such as a photopolymerization initiator , is easily cured by active energy rays, and further contains no photopolymerization initiator or a small amount of photopolymerization even when cured by ultraviolet rays or visible light. Although it has excellent curability by blending an initiator or the like, a photopolymerization initiator or the like can be blended as necessary.
In the case of blending a photopolymerization initiator, benzoin and its alkyl ethers, acetophenones, anthraquinones, thioxanthones, ketals, benzophenones, xanthones, acylphosphine oxides, α- And diketones.
Moreover, in order to improve the sensitivity by an active energy ray, a photosensitizer can also be used together.
Examples of the photosensitizer include benzoic acid and amine photosensitizers. These can also be used in combination of two or more. As these compounding ratios, 0.01-10 mass parts is preferable with respect to 100 mass parts of maleimide compounds.
As the photopolymerization initiator, benzophenones and thioxanthones are preferable because they have a high effect of improving the curing rate of the composition.

3-2. Compound having a reactive unsaturated group The composition of the present invention has a (meth) acrylic monomer, a (meth) acrylic oligomer, etc. in order to enhance the adhesive performance of the cured coating film or to adjust the sensitivity of the composition. You may mix | blend the compound which has these reactive unsaturated groups.
Examples of the (meth) acrylic monomer include alkyl acrylate or alkyl methacrylate (hereinafter, acrylate or methacrylate is referred to as (meth) acrylate), hydroxyalkyl (meth) acrylate, (meth) acrylate of phenol alkylene oxide adduct, mono or glycol Examples include di (meth) acrylate, polyol poly (meth) acrylate, and poly (meth) acrylate of a polyol alkylene oxide adduct.
Examples of (meth) acrylic oligomers include urethane (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and epoxy (meth) acrylate oligomers.
The compounding ratio of the compound having a reactive unsaturated group is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, with respect to 100 parts by mass of the maleimide compound.

3-3. Polymer A polymer may be added to the composition of the present invention in order to adjust the viscosity before curing and the adhesive performance after curing. Although it does not specifically limit as the said polymer, (meth) acrylate type polymer, polystyrene, polyolefin, etc. are mentioned. Among these, a (meth) acrylate polymer having a maleimide group is preferable because it crosslinks with the maleimide compound of the present invention in curing.

3-4. Other Maleimide Compound In the composition of the present invention, a compound having one maleimide group can be used in combination as long as the curability by active energy irradiation and the performance of the cured coating film are not impaired.
Examples of the compound include a compound having one maleimide group in the same skeleton as described above and a compound having a maleimide group and an ethylenically unsaturated group.
When the maleimide compound of the present invention is a polymer polyol produced from the radical polymerizable monomer described above, the polymer polyol has one having two or more hydroxyl groups in one molecule and one in one molecule. Mixtures with those having one hydroxyl group may be used. In this case, the resulting compound is a mixture of a compound having two or more maleimide groups and a compound having one maleimide group, which can be used as it is.
The blending ratio of the compound having one maleimide group is preferably 80 parts by mass or less, more preferably 50 parts by mass or less with respect to 100 parts by mass of the maleimide compound.

3-5. Tackifying agent In the composition of the present invention, a tackifying agent may be blended in order to lower the glass transition temperature (hereinafter abbreviated as Tg) of the cured coating film or to increase the adhesive performance.
Various tackifiers can be used, and examples thereof include natural resins such as rosin resins and terpene resins and derivatives thereof, and synthetic resins such as petroleum resins. Among these, those having no double bond or having a small ratio of double bonds are preferable because the inhibition of curing by active energy rays of the composition is small.
As a compounding ratio of the tackifier, the ratio of the tackifier is preferably 50 parts by mass or less, more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the total amount of the maleimide compound and the tackifier. is there. When the compounding amount of the tackifier exceeds 50 parts, the viscosity of the composition becomes too high, and the coating property is lowered.

3-6. Crosslinking agent In order to increase cohesion, the composition of the present invention may be used by adding a crosslinking agent that reacts quickly at normal temperature for the purpose of crosslinking between molecules of the polymer. Examples of the crosslinking agent include polyvalent isocyanate compounds, polyoxazoline compounds, epoxy resins, aziridine compounds, polycarbodiimide resins, and coupling agents.

3-7. Acid mask agent You may mix | blend an acid mask agent with the composition of this invention.
The ester bonds that are present in large numbers in the composition are not only hydrolyzed when the ester bonds are hydrolyzed by moisture when used over a long period of time under severe conditions such as high temperature and humidity. Since the acidic carboxyl group generated in the step further promotes hydrolysis of the ester bond, the pressure-sensitive adhesive strength is reduced, and further, the pressure-sensitive adhesive strength is reduced, whereby the pressure-sensitive adhesive layer is aggregated when the pressure-sensitive adhesive product is peeled off. It is known that there is a problem that an adhesive residue is generated on an article after being broken and peeled off.
If an acid mask agent is blended, a carboxyl group generated by hydrolysis can be trapped and further progress of hydrolysis can be prevented. Examples of the acid masking agent include carbodiimide compounds, oxazoline compounds, and epoxy compounds. As a compounding ratio of an acid mask agent, 0.01-2 mass parts is preferable per 100 mass parts of compounds (B).

3-8. Ultraviolet Absorber and Light Stabilizer The composition of the present invention may contain an ultraviolet absorber and a light stabilizer in order to improve light resistance.
Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, and include 2- (5-methyl-2-hydroxyphenyl) benzotriazole and 2- (3,5-di-t-amyl-2-hydroxyphenyl). Examples thereof include benzotriazole.
Examples of the light stabilizer include hindered amine light stabilizers and benzoate light stabilizers. Examples of hindered amine light stabilizers include bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n. -Butyl malonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. Examples of the benzoate light stabilizer include 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate.

3-9. In addition , a filler may be added to the composition of the present invention in order to enhance coloring and adhesion performance. Specific examples of the filler include various silicas, dyes, calcium carbonate, magnesium carbonate, titanium oxide, iron oxide, and glass fiber.
Moreover, you may mix | blend radical polymerization inhibitors, such as hydroquinone and hydroquinone monomethyl ether, according to a use.
In addition to these, antifoaming agents, dyes and pigments, thickeners, lubricants, film forming aids, fillers, plasticizers, antistatic agents, fiber auxiliaries, cleaning agents, antistatic agents, leveling agents, General additives used in adhesives and pressure-sensitive adhesives such as dispersion stabilizers, hydrophilic resins, latexes, wetting agents, and leveling improvers can be used in a commonly used proportion. In addition, antioxidants such as dibutylhydroxytoluene and butylhydroxyanisole; preservatives such as methyl paraoxybenzoate and propyl paraoxybenzoate; and general additives used in skin patches such as emulsifiers are usually used. Can be used in combination.
Moreover, in order to adjust a viscosity, an organic solvent can also be mix | blended as needed.
Furthermore, the above-mentioned phosphorus compound and antioxidant can also be mix | blended.

4). Production method of pressure-sensitive adhesive sheet The composition of the present invention can be used in various applications, and is usually used in the form of a pressure-sensitive adhesive sheet.
What is necessary is just to manufacture an adhesive sheet according to a conventional method. As a preferable method, for example, a method of applying the composition of the present invention to a base material and irradiating the coating film with an active energy ray and curing it may be mentioned.

  Examples of the substrate include metal, plastic, glass, ceramics, wood, paper, printing paper, and fiber. Examples of the metal include aluminum, iron, and copper. Examples of the plastic include vinyl chloride polymer, acrylate polymer, polycarbonate, polyethylene terephthalate, acrylonitrile butadiene styrene copolymer, polyethylene, and polypropylene.

Examples of the coating method of the composition include roll coating, gravure printing, screen printing, die coating and knife coating.
The coating amount of the composition with respect to the substrate may be appropriately selected according to the application to be used, but the preferable coating amount is 5 to 200 g / m ² , more preferably 10 to 100 g / m ² . If it is less than 5 g / m ² , the adhesive strength may be insufficient, and if it is 200 g or more, the target energy may not be obtained because the active energy ray hardly reaches the deep part.

After completion of the coating treatment, active energy rays are irradiated to crosslink the maleimide groups of the maleimide compound to increase the molecular weight, thereby improving the cohesive force and adhesive force of the resulting cured coating film.
The irradiation method of the active energy ray in this case may follow the method conventionally performed with the active energy ray-curable pressure-sensitive adhesive composition. Examples of active energy rays include visible light, ultraviolet rays, X-rays, and electron beams, and it is preferable to use ultraviolet rays because inexpensive devices can be used. Examples of the light source in the case of using ultraviolet light include ultrahigh pressure, high pressure, medium pressure or low pressure mercury lamp, metal halide lamp, xenon lamp, electrodeless discharge lamp, and carbon arc lamp, and the irradiation may be performed for several seconds to several minutes.

  Moreover, as Tg of the cured coating film of the composition of this invention, -10 degrees C or less is preferable, More preferably, it is -30 degrees C or less. In the present invention, Tg means the peak temperature of tan δ obtained by measuring temperature dependence using a dynamic viscoelasticity measuring apparatus.

5. Applications The pressure-sensitive adhesive composition of the present invention can be used for various applications.
For example, pressure-sensitive adhesive products such as pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, and pressure-sensitive adhesive sheets, such as pressure-sensitive adhesive sheets for confidential postcards, pressure-sensitive adhesive sheets for wallpaper, double-sided tape, seals, stickers, and masking films.
In particular, the adhesive-type cured coating film of the present invention is excellent in heat resistance, and is particularly useful for applications requiring heat resistance.
The effects of the present invention are summarized as follows. That is, according to the active energy ray-curable pressure-sensitive adhesive composition of the present invention, since it is liquid at room temperature, it is easy to handle and has excellent coatability. Further, even when irradiated with visible light or ultraviolet light, it has a practical crosslinkability or curability in the absence of a photopolymerization initiator, so that it is safe with little odor and toxicity. Further, the obtained cured coating film has a large adhesive force and excellent heat resistance.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
In the following, “%” means mass%.

○ Production Example 1
A flask equipped with a stirrer, a thermometer, and a condenser was charged with 100 g of polyether polyol PTMG-2000 [a compound having a polytetramethylene glycol ether average polymerization degree of 2000, manufactured by Mitsubishi Chemical Corporation, hereinafter referred to as PTMG2000]. The temperature was raised to 120 ° C. while dehydrating for 1 hour under reduced pressure.
After dehydration, the mixture was cooled to 80 ° C., and isophorone diisocyanate (hereinafter referred to as IPDI) 22.59 g and dilauric acid di-n-butyltin (hereinafter referred to as DBTL) 14 mg were charged and reacted for 2 hours. Then, after heating up to 100 degreeC and continuing reaction for 30 minutes, 70 mg of antioxidant Irganox1010 and 2-hydroxyethyl citracimide [compound of following formula (7). Hereinafter referred to as CM-ETA. 15.78 g was charged and reacted for 4 hours to obtain a maleimide compound.

○ Production Examples 2-6
In Production Example 1, a maleimide compound was produced under the same conditions as in Production Example 1, except that the components and amounts shown in the following table were used.

The abbreviations in Table 1 mean the following.
5000 PA: Polyester polyol comprising 2,4-diethyl-1,5-pentanediol and adipic acid, Kyowa Hakko Kogyo Kyowapol 5000PA
P-5010: polyester polyol comprising 3-methyl-1,5-pentanediol and adipic acid, Kuraray Kuraray Polyol P-5010
P-2000: Polypropylene glycol compound having an average polymerization degree of 2000, P-2000 manufactured by Asahi Denka Kogyo Co., Ltd.
PEG2000: Polyethylene glycol with an average degree of polymerization of 2000 PTMG1000: Polytetramethylene glycol ether with an average degree of polymerization of 1000, manufactured by Mitsubishi Chemical Corporation

○ Production Example 7
In production example 1, 5 g of PTMG-2000 as the polyether component, 95 g of P-5010 as the polyester component, the amount of IPDI was changed to 9.52 g, 12 mg of DBTL and 6.65 g of CM-ETA, and the antioxidant A maleimide compound was produced in the same manner as in Example 1 except that 60 mg of Irganox 1010 was added and then CM-ETA was added.

○ Production Example 8
In Example 1, 10 g of PTMG-2000 as the polyether component, 90 g of P-5010 as the polyester component, 10.21 g of IPDI, 12 mg of DBTL and 7.13 g of CM-ETA were used, and the antioxidant Irganox 1010 Was added in the same manner as in Example 1 except that CM-ETA was added, and then a maleimide compound was produced.

○ Examples 1-6, Comparative Examples 1-4
The compound (A) and the compound (B) obtained in Production Examples 1 to 6 were mixed at a mass ratio shown in Table 2 to prepare a composition, and later-described evaluation was performed.

○ Comparative Example 5
Compound (B) and Compound L (polyether skeleton bismaleimide obtained in Production Example 5 (LUMICURE MIA-200, manufactured by Dainippon Ink and Manufacturing Co., Ltd.) and the two maleimide groups are both represented by the formula (2). The composition was prepared by mixing at a mass ratio shown in Table 2 and evaluated below.

Examples 7 and 8
The maleimide compounds obtained in Production Example 7 and Production Example 8 were used as they were, and evaluations described later were conducted as Examples 7 and 8, respectively.

○ Evaluation of composition The surface of a polyester film having a thickness of 50 μm, which is a support sheet, was coated with the composition obtained so as to have a film thickness of 25 μm, and an ultraviolet irradiation device having a belt conveyor was used. The composition is cured by passing 4 passes under a concentrating high-pressure mercury lamp (1 light, height 10 cm) at a conveyor speed of 22 m / min and irradiating with ultraviolet rays from the coated surface side (integrated light amount = 400 mJ / cm ² ). An adhesive sheet was produced.
The obtained pressure-sensitive adhesive sheet was cut into a length direction of 200 mm and a width direction of 25 mm to obtain a test body.

The following evaluation was performed about the obtained test body. The results are shown in Table 3.
1) Adhesive strength The 180 degree peel strength of the test specimen was measured. Under the condition of 23 ° C. and 65% RH, the above test specimen was used, a length of 100 mm was attached to a stainless steel plate, and pressure-bonded with a roller with a load of 2 kg, and the peel strength after 24 hours was measured. Others were performed according to JIS Z-0237.
The unit of numerical values in Table 3 is N / inch.
2) Holding power Using the above test piece under the conditions of 23 ° C. and 65% RH, a test piece of 25 mm in length is attached to a stainless steel plate and pressure-bonded with a roller with a load of 2 kg. A weight of 1000 g was applied to the end of the wire, and the drop time until 24 hours later was measured to evaluate heat resistance. Others were performed according to JIS Z-0237.
In Table 3, NC means that there was no deviation, and the numerical value means the falling time (minutes).
3) SAFT (Shear Adhesion Failure Temperature)
Under the condition of 23 ° C. and 65% RH, the above test specimen was used, a length of 100 mm was pasted on a stainless steel plate, and it was pressure-bonded with a roller with a load of 2 kg, and left for 24 hours. A weight of 500 g was applied to the end of the test body, and the temperature at the time of dropping was evaluated while increasing the temperature from 40 ° C. to 200 ° C. at a temperature increase rate of 0.4 ° C./min.
In Table 3, ◯ means that it did not fall, and the numerical value means the drop temperature (° C.).
4) Tack It measured in 23 degreeC and 65% RH atmosphere according to the ball rolling method of JISZ-0237.

○ Evaluation when a large amount of active energy rays are irradiated The composition obtained so that the film thickness becomes 25 μm is applied to the surface of a 50 μm-thick polyester film as a support sheet, and ultraviolet irradiation having a belt conveyor is applied. Using an apparatus, 10 passes under a 80 W / cm condensing type high-pressure mercury lamp (1 light, height 10 cm) at a conveyor speed of 22 m / min and irradiated with ultraviolet rays from the coated surface side (integrated light quantity = 1000 mJ / cm ²⁾ And the composition was cured to produce an adhesive sheet.
The obtained patch was cut into a length direction of 200 mm and a width direction of 25 mm to obtain a test specimen.
The obtained test specimen was evaluated in the same manner as described above. The results are shown in Table 4. Comparative Examples 2, 3 and 5 which were inferior in heat resistance (retention force and SAFT) by ultraviolet irradiation of 400 mJ / cm ² due to poor curability were also irradiated with a large amount of ultraviolet light of 1000 mJ / cm ² . In the case, it was sufficiently cured and the heat resistance was improved as in the examples.

  The composition of the present invention is excellent in active energy curability, adhesive strength and heat resistance as an active energy ray-curable pressure-sensitive adhesive composition, and can be used for various adhesive applications.

Claims (3)

The compound (A) having a polyether skeleton and having two or more maleimide groups and the compound (B) having a polyester skeleton and having two or more maleimide groups are based on the total amount of (A) and (B). An active energy ray-curable pressure-sensitive adhesive composition containing 5 to 19% by mass and 81 to 95% by mass, respectively, which is liquid at 25 ° C. ,
The polyether skeleton of the compound (A) consists of one or more of polyethylene glycol, polypropylene glycol and polytetramethylene glycol,
The polyester skeleton of the compound (B) is composed of an aliphatic polyester polyol composed of an aliphatic dicarboxylic acid and an aliphatic diol,
The active energy ray-curable pressure-sensitive adhesive composition, wherein the compound (A) and the compound (B) are each independently the following compound (a) or mixture (b) .
(A): A compound having two or more maleimide groups represented by the following formula (1).

[In Formula (1), R < ¹ > represents an alkyl group, an aryl group, an arylalkyl group, or a halogen atom. ]
(A): Compound (a) having two or more maleimide groups represented by the following formula (2) and compound (2) having two or more maleimide groups represented by the following formula (3) and / or formula (4) ( A mixture containing 10 to 90% by weight and 10 to 90% by weight of b), respectively, based on the total amount of (a) and (b).

In [Equation (3), R ² and R ³ represents an alkyl group, an aryl group, an arylalkyl group or a halogen atom. ]

[In Formula (4), R < ⁴ > represents the propylene group or butylene group which may have an alkyl group as a substituent. ] 2. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the polyether skeleton of the compound (A) is a polytetramethylene glycol skeleton. A pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive composition according to claim 1 or 2 is applied to a substrate, and the coating film is irradiated with an active energy ray to exhibit adhesiveness.