JP2002322454A - Radiation-curing, peelable pressure-sensitive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation-curing, peelable pressure-sensitive adhesive having proper adhesion performances from the beginning of the adhesion of mutual by contacted two cured layers by appling a strong pressure, without deforming an adhesive layer non increasing or losing adhesive strength under the environment where the adhesive is allowed to stand at a high temperature or exposed to water or a high humidity for a long time. SOLUTION: This radiation-curing removable pressure-sensitive adhesive comprises a >=2-functional special urethane (meth)acrylate obtained by reacting (A) at least one polyol represented by the specific formulae with (B) a diisocyanate and (C) a hydroxy(meth)acrylate as an active ingredient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-curable removable pressure-sensitive adhesive, and more particularly to a radiation-curable pressure-sensitive adhesive capable of maintaining stable adhesive performance under environmental conditions such as high temperature and high humidity. Adhesive sheet such as a foldable sheet, the information carrying surface of which is a superimposed surface, a confidential information transmission sheet such as a superimposed sheet, an arrangable sheet that can be expanded in size, and an office sheet such as copy paper. The present invention relates to a radiation-curable removable pressure-sensitive adhesive applicable to printing sheets, easy-open packaging bags, labels, and the like.

[0002]

2. Description of the Related Art Conventionally, in a printing sheet that carries information on a superimposed surface, the superposed surfaces are usually arranged in a pattern such that the superimposed surfaces are in contact with each other so as to adhere to each other. A cured layer of a pressure-sensitive adhesive is provided on the entire surface, a specific portion, or linearly. This pressure-sensitive adhesive is also referred to as a self-adhesive pressure-sensitive adhesive, and is a type in which polymers are adhered to each other by self-diffusion by applying high pressure in a state where the cured layers are in contact with each other.
Depending on the type of the composition and the degree of the pressure, permanent adhesiveness and removable adhesiveness are realized.

Conventionally, the main component of the pressure-sensitive adhesive used in this type of printing sheet generally contains an aqueous medium such as an aqueous emulsion such as an acrylic emulsion, a natural rubber latex, or a synthetic rubber latex, or a rubber latex. When a pressure-sensitive adhesive containing such an aqueous medium is applied to the surface of a substrate such as paper and dried for the formation of a cured layer, a special dryer is required or the working time is increased. In addition, it has disadvantages such as deformation of a base material such as paper and loss of information carried.

In order to solve the problem of the conventional pressure-sensitive adhesive, the present inventors have proposed a solventless UV-curable pressure-sensitive adhesive which does not use an aqueous medium (Japanese Patent Laid-Open No. 10-26).
3466, JP-A-10-265742, etc.).

However, when a printing sheet using this ultraviolet-curable pressure-sensitive adhesive is brought into close contact by applying a high pressure in a state where the cured layers are in contact with each other, the printing sheet has a moderate adhesive strength at the beginning of the close contact. It is easy to peel off because it is, but as time goes on under high humidity, the adhesive strength becomes higher than necessary and peeling becomes difficult, and there is a problem that the base sheet is broken if it is forcibly peeled off .

A print sheet sample prepared with a UV curable varnish “Gorcelac UV2000B (manufactured by Nippon Synthetic Chemical Co., Ltd.)” described in Utility Model Registration No. 2540449 (laminated postcard) is left at room temperature for one week. Peel strength reaches 10 times of the initial adhesive strength, and there is no stability over time.
Even under the condition of high humidity of RH, the peeling force still increases, so that it cannot be used as it is.

[0007]

A printing sheet such as a postcard with a seal or an openable envelope can be lightly adhered to a degree of temporary fixing, and cannot be peeled off by a slight impact or abrasion during mailing, and can be broken at a mailing destination. A pressure-sensitive adhesive having an adhesive function that can be easily peeled off is required. The adhesive layer is deformed or absorbs moisture under high temperature conditions of about 50 ° C in the delivery vehicle during mailing, or in environments where water is leaked due to raindrops during delivery, or exposed to high humidity for a long period of time, and the adhesive strength is reduced due to moisture absorption. Promotion,
Alternatively, a function that does not decline is important. Also,
In addition to the environmental conditions described above, pressure-sensitive adhesives are desired to have a basic performance in which the adhesive force does not change with time at room temperature, and specifically, a long time after bonding. There is a strong demand for a pressure-sensitive adhesive having an adhesive property such that the adhesive strength after the bonding does not change from the adhesive strength immediately after the bonding, or even if it changes, it converges about 2-3 times.

An object of the present invention is to provide a proper adhesive performance from the beginning when the hardened layers are brought into close contact with each other by applying a high pressure in a state where the cured layers are in contact with each other, and for a long time at the above-mentioned high temperature, water leakage or high humidity. Radiation that can maintain a stable adhesive performance without deforming the adhesive layer or increasing or decreasing the adhesive strength in an environment such as exposure, and that can be peelably adhered to adherends such as glass and metal An object of the present invention is to provide a curable removable pressure-sensitive adhesive.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a radiation-curable re-stripping containing a special urethane acrylate synthesized using a specific polyol as an active ingredient. The present inventors have found that the object can be achieved by using a pressure-sensitive adhesive, and have completed the present invention.

That is, the radiation-curable pressure-sensitive adhesive according to claim 1 of the present invention for solving the above-mentioned problem is applied to a superposed surface of sheets, and forms a cured layer which is not adhered in a normal state by irradiation with radiation. By applying a predetermined pressure by bringing the superposed surfaces into contact with each other, the superposed surfaces can be releasably adhered to each other, or are applied to the sheet surface and do not adhere in a normal state by radiation irradiation. A radiation-curable removable pressure-sensitive adhesive capable of forming a cured layer and allowing the cured layer to come into contact with an adherend and to be releasably adhered, wherein (A) the following (1)
At least one polyol selected from the group consisting of
It is characterized by containing, as an active ingredient, a bifunctional or more functional special urethane (meth) acrylate obtained by reacting (B) diisocyanate and (C) hydroxy (meth) acrylate. Polyol: (1) Polydimethylsiloxane represented by formula (I) (2) Reactive silicone polyol represented by formula (II) (3) 1,4-polybutadiene polyol represented by formula (III) (4) ) Hydrogenated 1,4-polybutadiene polyol represented by formula (IV) (5) Polymethylene glycol represented by formula (V) (6) Fluoro / perfluoroalkylene polyol represented by formula (VI)

[0011]

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In the formula (I), n is an integer of 1 or more.

[0013]

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In the formula (II), R is usually -C ₃ H ₆
OC ₂ H ₄ — or another alkylene group.

[0015]

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In the formula (III), l, m and n are integers of 1 or more, and l >> m.

[0017]

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In the formula (IV), l, m and n are integers of 1 or more, and l >> m.

[0019]

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In the formula (V), n is an integer of 9 ≦ n ≦ 30.

[0021]

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In the formula (VI), l, m and n are integers of 1 or more.

The radiation-curable pressure-sensitive adhesive according to claim 2 of the present invention is the pressure-sensitive adhesive according to claim 1, wherein one or more kinds of monofunctional or polyfunctional (meth) acrylate monomers are selected. It is characterized by incorporating a monomer.

The radiation-curable pressure-sensitive adhesive according to claim 3 of the present invention is the pressure-sensitive adhesive according to claim 1 or 2, further comprising formula (VII) and / or formula (VII).
It is characterized by containing a urethane (meth) acrylate represented by I).

[0025]

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In the formula (VII), R is an average molecular weight of 1,
000 3,000 of _{-O - (- C 3 H 6} O-) n -, 1,2
Represents a polybutadiene polyol residue, a 1,2-hydrogenated polybutadiene polyol residue, or a poly-ε-caprolactone residue or a polytetramethylene glycol residue having an average molecular weight of 500 to 3,000, and R ′ is a diisocyanate residue. , R ″ represents a residue of hydroxy (meth) acrylate.

[0027]

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In the formula (VIII), R is an average molecular weight.
1,000 to 3,000 _{-O - (- C 3 H 6} O-) n -,
1,2-polybutadiene polyol residue, 1,2-hydrogenated polybutadiene polyol residue, or average molecular weight
500 to 3,000 poly-ε-caprolactone residues and polytetramethylene glycol residues are shown, R ′ is a diisocyanate residue, and R ″ is a hydroxy (meth) acrylate residue.

The radiation-curable pressure-sensitive adhesive according to claim 4 of the present invention is the pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the content of the special urethane (meth) acrylate is pressure-sensitive. It is characterized by being 1 to 80% by mass with respect to the whole adhesive.

The radiation-curable pressure-sensitive adhesive according to claim 5 of the present invention is the pressure-sensitive adhesive according to any one of claims 1 to 4, which is an ultraviolet-curable pressure-sensitive adhesive. And

The radiation-curable, removable pressure-sensitive adhesive of the present invention contains a special urethane acrylate as an active ingredient, so that the cured layers are brought into close contact with each other by applying high pressure in a state where the cured layers are in contact with each other. Adhesive performance and stable adhesive performance without deforming the adhesive layer or increasing or decreasing the adhesive strength under the environment of long exposure at high temperature, water leakage or high humidity as described above Is maintained. In addition, the radiation-curable removable pressure-sensitive adhesive of the present invention can be applied to the surface of a substrate sheet to produce a label or the like having a cured layer which does not adhere in a normal state by irradiation with radiation. The cured layer such as a label can be attached to an adherend such as glass or metal, and the label or the like can be stuck by hand or the like, and the label can be easily peeled whenever it is desired to peel it.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the radiation-curable removable pressure-sensitive adhesive of the present invention, (A) at least one polyol selected from the above (1) to (6), (B) diisocyanate, (C) hydroxy ( It is important to contain a bifunctional or higher functional special urethane (meth) acrylate obtained by reacting (meth) acrylate as an active ingredient.

When only a general urethane (meth) acrylate having a glass transition point of 50 ° C. or less is used for the compounding of the radiation-curable removable adhesive, the adhesive may be adhered when stored in an environment of about 50 ° C. for a long time. Great increase in power.

In the case where a hydrophilic polyol such as polyethylene glycol or polyethylene adipate is used for the polyol unit corresponding to the soft segment of urethane (meth) acrylate, the film absorbs and deforms under a high humidity environment of 80% RH or more. As a result, the adhesive strength increases or decreases.

However, conversely, the glass transition point is 50 ° C.
When the above urethane (meth) acrylate is used, the elastic modulus of the film increases, the initial adhesive strength at the time of crushing decreases, and the pressure-sensitive adhesive property is lost. Furthermore, at the time of peeling, zipping and cracking of the film are likely to occur.

Therefore, as the polyol unit corresponding to the soft segment of urethane (meth) acrylate, a structure having a low glass transition point, being flexible, hydrophobic or water-repellent, and having a peeling property is preferably used. Further, when the average number of functional groups per urethane (meth) acrylate molecule is 1 or less, the degree of freedom of molecular motion is large even after curing, and the release component tends to be unevenly distributed at the interface of the adhesive layer. ) Average number of functional groups of acrylate is 2
Must be at least

The polyol having a flexible structure which is hydrophobic or water-repellent and has a releasing property is, for example, polydimethylsiloxane represented by the above formula (I) or a polyether having a side chain or a molecular terminal of polyether. And a reactive silicone polyol represented by the formula (II) modified with alcohol, 1,4-polybutadiene polyol represented by the formula (III), hydrogenated 1,4 represented by the formula (IV)
Hydroxyl group-containing liquid butadiene rubber such as 4-polybutadiene polyol, non-methylene glycol or higher polymethylene glycol represented by the formula (V) or hydroxyl-terminated polyolefin represented by the formula (VI),
Examples thereof include fluoroalkylene polyols in which some or all of the hydrogens of the aliphatic alkylene polyol have been replaced with fluorine, and perfluoroalkylene polyols. The polydimethylsiloxane represented by the formula (I) preferably has an average molecular weight of 1,000 or more and 5,000 or less, more preferably 1,000 or more and 3,000 or less. If the average molecular weight is less than 1,000, adhesiveness and peelability may be adversely affected, and if it exceeds 5,000, applicability to the sheet surface and curability may be poor. Formula (II)
The reactive silicone polyol represented by the average molecular weight is preferably 1,000 or more and 5,000 or less, more preferably
It is between 1,000 and 3,000. The average molecular weight is 1,
If it is less than 000, adhesiveness and peelability may be adversely affected, and if it exceeds 5,000, applicability to the sheet surface and curability may be poor. 1,4- represented by the formula (III)
The polybutadiene polyol has an average molecular weight of 1,000 or more and preferably 3,000 or less, more preferably 1,000 or more.
Not more than 2,500. If the average molecular weight is less than 1,000, adhesiveness and peelability may be adversely affected, and if it exceeds 3,000, suitability for application to the sheet surface and curability may be poor. The average molecular weight of the hydrogenated 1,4-polybutadiene polyol represented by the formula (IV) is preferably from 1,000 to 3,000, more preferably from 1,000 to 2,500. If the average molecular weight is less than 1,000, adhesiveness and peelability may be adversely affected, and if it exceeds 3,000, suitability for application to the sheet surface and curability may be poor. In the polymethylene glycol represented by the formula (V), n is 9 ≦
It is an integer of n ≦ 30, preferably 9 or more and 20 or less. If n is less than 9, adhesiveness and peelability may be adversely affected, and if n exceeds 30, applicability to the sheet surface and curability may be poor.

These can be reacted with (B) various diisocyanates and (C) hydroxy (meth) acrylate to obtain the special urethane (meth) acrylate used in the present invention.

Of these, when transparency is desired for the adhesive layer of the diisocyanate (B), it is preferable to use an aliphatic type or an alicyclic type.

The aliphatic diisocyanate referred to here includes hexamethylene diisocyanate and the like.
Examples of the alicyclic diisocyanate include dicyclohexylmethane diisocyanate, isophorone diisocyanate, isopropylidene bis- (4-cyclohexyl isocyanate), hydrogenated xylene diisocyanate, and cyclohexyl diisocyanate.

The (C) hydroxy (meth) acrylate includes 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, glycidol di (meth) acrylate, pentaerythritol tri (meth) acrylate, -Hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth)
Acrylate and the like.

From these (A) polyol, (B) diisocyanate and (C) hydroxy (meth) acrylate, the special urethane (meth) acrylate used in the present invention can be synthesized by a known urethane synthesis method.

That is, first, in a dry nitrogen stream (B)
In a solvent such as toluene or MEK, or without using a solvent, a fixed amount of amines and tin compounds, which are known urethane synthesis catalysts, is added as a catalyst, and a polymerization inhibitor such as monoethylhydroquinone is further added. While dropping a predetermined amount of (A) polyol, 30 to 5
By reacting at a temperature of 0 ° C. for at least 40 minutes, a reaction intermediate having a terminal isocyanate group is obtained. At this time, the appropriate amount of the (B) diisocyanate to the (A) polyol needs to be equal to or more than the molar equivalent of the functional group equivalent calculated from the hydroxyl value of the (A) polyol. Next, (C) hydroxyl (meth) acrylate is added dropwise in an equimolar amount to (B) diisocyanate, and the mixture is further heated and reacted at a temperature of 60 to 90 ° C for 4 to 8 hours. After the completion of the reaction, the solvent and the reaction by-product are distilled off under reduced pressure or vacuum drying to purify, thereby obtaining the bifunctional or more functional urethane (meth) acrylate used in the present invention.

Solvents used in this reaction include benzene, toluene, xylene, ethylbenzene, trichloroethylene, ethylene chloride, dimethylformamide, dimethylsulfoxide (DMSO), methyl ethyl ketone (MEK), methyl isopropyl ketone, methyl isobutyl ketone (MIBK), Cyclohexanone, methyl acetate, ethyl acetate, isopropyl acetate, n-butyl acetate,
Examples include anisole and tetrahydrofuran (THF).

The urethane synthesis catalyst used in this reaction includes triethylenediamine, morpholine, N-ethylmorpholine, piperazine, triethanolamine,
Triethylamine, N, N, N ', N'-tetramethyl-butane-1,3-diamine, dibutyltin dilaurate, stannous octate, stannous laurate, dioctyltin diacetate, stannous oleate, stannous Examples thereof include tolate, dibutyltin oxide, and lead octate.

The special urethane (meth) acrylate synthesized as described above may be used as it is or diluted with various monofunctional (meth) acrylic monomers or polyfunctional (meth) acrylic monomers, and a photopolymerization initiator when cured with ultraviolet rays. Can be added to form a radiation-curable removable pressure-sensitive adhesive of the present invention.

The special urethane (meth) acrylate used in the present invention synthesized as described above has a higher compatibility with the (meth) acrylate monomer than the starting polyol. The radiation-curable removable pressure-sensitive adhesive of the present invention is cured by radiation such as ultraviolet rays, electron beams, X-rays, i-rays, and g-rays. Among these, the ultraviolet-curable type is preferably used.

The energy of ultraviolet light used for ultraviolet curing (free radical polymerization, cationic polymerization) is 3 to 6 eV
It is necessary to add a photoinitiator or sensitizer to accelerate the photochemical reaction because it takes only a few seconds or more to complete the curing, whereas it is generally used for electron beam curing (free radical polymerization) Even if the energy of the electron beam is low, the energy of the electron beam is as large as about 150 to 300 KeV, the reaction initiation mechanism is slightly different, and the polymerization and crosslinking reactions are started simultaneously with the irradiation. Therefore, these initiators and sensitizers are added. There is no need to complete the cure in a fraction of a second or less.

The content of the special urethane (meth) acrylate used in the present invention is not particularly limited, but is preferably 1 to 80% by mass, and more preferably 5 to 60% by mass based on the whole radiation-curable removable pressure-sensitive adhesive of the present invention. % Is more preferable, and
40% by weight is particularly preferred. If the amount is less than 1% by mass, the function and effect of the special urethane (meth) acrylate used in the present invention may not be exhibited, and if it exceeds 80% by mass, the adjustment of adhesive force and the curability may be impaired.

The (meth) acrylate monomer obtains viscosity according to the method of applying the radiation-curable removable pressure-sensitive adhesive of the present invention, adjusts the adhesive force to obtain a desired adhesive force, and improves the curability. It is preferable to mix them.
Preferred as such (meth) acrylate monomers are monofunctional monomers such as diethylene glycol-modified nonylphenol (meth) acrylate,
Isodecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, 2- (2
-Ethoxy) 2-ethylhexyl (meth) acrylate and the like, and polyfunctional monomers include 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate,
Tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, propylene oxide-modified trimethylolpropane tri (meth)
Examples of hydrophobic and water-resistant monomers such as acrylate, propylene oxide-modified glycerin tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and dipentaerythritol hexa (meth) acrylate Can be.

The radiation-curable removable pressure-sensitive adhesive of the present invention is preferably blended with a urethane (meth) acrylate represented by the above formula (VII) and / or (VIII) in order to adjust the adhesive strength. . As such a urethane (meth) acrylate, for example, 1,000 to
Urethane (meth) acrylate synthesized from polypropylene glycol having a molecular weight of about 5,000 as a polyol, 1,2-polybutadiene diol or hydrogenated 1,2-polybutadiene diol,
Urethane (meth) acrylate having (meth) acryloyl group introduced, or poly- obtained by ring-opening polymerization of ε-caprolactone with butanediol or hexanediol.
Urethane (meth) acrylate obtained by using ε-caprolactone diol as a polyol, or urethane (meth) obtained by using polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran as a polyol
Acrylate and the like can be mentioned.

Since these urethane (meth) acrylates are hydrophobic, have a low glass transition point, are flexible, and have a weak adhesive strength, they can be preferably used for adjusting the adhesive strength.

The content of these urethane (meth) acrylates is not particularly limited, but is preferably 1 to 80% by mass, more preferably 5 to 60% by mass, based on the whole radiation-curable removable pressure-sensitive adhesive of the present invention. Preferably, 10 to 40% by mass
Is particularly preferred. If the amount is less than 1% by mass, the effect of adjusting the adhesive strength may not be exhibited, and if it exceeds 80% by mass, the adhesive force may be impaired.

Specific examples of the photopolymerization initiator compounded for ultraviolet curing include, for example, 2,2-dimethoxy-1,2-diphenylethan-1-one (benzyldimethylketal: BDK), benzophenone (BP) and its derivatives, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether,
-Hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one and derivatives thereof, methylbenzoyl formate, 2-methyl-1 [4- (methylthio) phenyl] -2-monfoli Other thioxanthone derivatives such as nopropan-1-one, tetra (t-butylperoxycarbonyl) benzophenone, 2,4-diethylthioxanthone and isopropylthioxanthone, oligo [2-hydroxy-2
A polymer initiator such as -methyl-1- [4- (1-methyl-vinyl) phenyl] propanone]; an acylphosphine type such as trimethylbenzoyldiphenylphosphine oxide; or a mixture of two or more. be able to. In addition, a photopolymerization initiator such as 2-dimethylaminoethylbenzoate, N, N'-dimethylaminoethyl methacrylate, isoamyl p-dimethylaminobenzoate, or ethyl p-dimethylaminobenzoate is used in combination with the photopolymerization initiator. Can be given.

The amount of these photopolymerization initiators to be added is about 0.5 to the whole radiation-curable removable pressure-sensitive adhesive of the present invention.
It is 1 to 10% by weight, preferably about 0.5 to 7% by weight, and more preferably about 1 to 5% by weight.

The radiation-curable removable pressure-sensitive adhesive of the present invention may further contain, if desired, a photopolymerization accelerator, an additive component commonly used in general photosensitive resin compositions, such as a tackifier, Modifier, n-octadecyl-3 (3 ′,
Antioxidants such as 5'-di-t-butyl-4'-hydroxyphenyl) propionate; plasticizers and stabilizers which are difficult to bleed; pigments and dyes such as phthalocyanine blue and brilliant carmine B; dye lakes; A filler or the like can be contained in an amount of about 0.05 to 10% by mass based on the whole radiation-curable removable pressure-sensitive adhesive of the present invention. An antifoaming agent, a lubricant, a leveling agent, an antistatic agent, and the like can also be compounded, but the properties of the radiation-curable removable pressure-sensitive adhesive of the present invention may be impaired. .

An example of producing a pressure-sensitive adhesive printing sheet using the radiation-curable removable pressure-sensitive adhesive of the present invention will be described below. That is, a predetermined base material sheet is folded, tri-folded, cut and overlapped, or a portion opposed to each other by overlapping each other, such as a dry offset printing, flexo printing, gravure printing, a printing method such as screen printing, Alternatively, the adhesive layer is formed by applying the radiation-curable removable pressure-sensitive adhesive of the present invention using a general coating device such as a comma coater, a doctor coater, a gravure coater, or a rod coater. The application at this time is
It may be carried out over the entire surface of the substrate sheet, or may be carried out only on a part of the surface. Necessary information may be printed on the surface of the base sheet in advance,
After applying the adhesive layer, the information may be printed. At this time, when printing information using a commonly used printing machine using an ultraviolet curable ink for printing, this printing step and application of the radiation-curable removable pressure-sensitive adhesive of the present invention, This is advantageous because it can be performed simultaneously with fixing.

The base sheet used in the present invention includes, for example, high quality paper, medium paper, rough paper, and cotton paper which are uncoated papers; art paper, coated paper, lightweight coated paper which is coated paper; Other examples include plastic laminated paper, cloth, plastic laminated cloth, plastic film, and metal foil. The basis weight of the substrate is usually 50 to 160
g / m2. In the present invention, when a synthetic plastic film such as polyethylene, polypropylene, polyethylene terephthalate, or polyvinyl chloride is used as the base sheet, the surfaces of these base materials are subjected to a surface treatment such as a mat treatment or a corona treatment. Is preferred.

The thickness of the radiation-curable removable pressure-sensitive adhesive of the present invention applied to the surface of the substrate sheet is not particularly limited, but may be used to maintain the adhesiveness, peelability or transparency of the adhesive layer. , About 0.5 to 100 μm.

The pressure-sensitive adhesive printing sheet manufactured in this manner is irradiated with a radiation such as an ultraviolet lamp or an electron beam irradiation device to cleave the unsaturated double bond.
After the radicals are generated and polymerized to cure the adhesive layer appropriately, the superposed surfaces are brought into contact with each other and adhered under a predetermined pressure by, for example, a pressure roller.

Next, examples of the structure of a pressure-sensitive adhesive printing sheet made using the radiation-curable removable pressure-sensitive adhesive of the present invention will be described with reference to the accompanying drawings. However, the present invention is limited by these structural examples. It is not something to be done. Here, FIG. 1 is a front view of a three-fold postcard, FIG. 2 is a rear view of the postcard, FIG. 3 is a cross-sectional view taken along line XX of FIG. 1, and FIG. 4 is a state when the postcard of FIG. Explanatory drawing, FIG. 5 is a front development view of the two-fold postcard, FIG. 6 is a rear development view of this postcard, FIG. 7 is a state explanatory view when the postcard of FIG. 5 is folded,
FIG. 8 is a front view of a partially folded postcard, FIG. 9 is a rear view of the postcard, and FIG. 10 is a state explanatory view when the postcard of FIG. 8 is folded.

First, a three-fold postcard 1 shown in FIGS. 1 to 3 is composed of a base sheet 2 having a size three times the size of a standard postcard, and is divided into three regions by folding lines 3a and 3b. is there. On the front surface of the left section area A, print destination information such as a zip code, a destination name, and an address.
However, concealment information prints 5 are printed directly on the base sheet 2 on the front and back surfaces of the central partitioned area B and on the front face of the right partitioned area C. Further, the pressure-sensitive adhesive of the present invention is applied to the entire front surfaces of the divided regions B and C and the whole back surfaces of the divided regions A and B of the printed base sheet 2 to form the peelable adhesive layer 6. ing. As shown in FIG. 4, the three-fold postcard 1 configured as described above folds the overlapping surface of each section into a Z shape at folding lines 3a and 3b to bring the adhesive layers into contact with each other. By pressing with a sealer, the adhesive layer 6 is activated and adhered.

Next, the two-fold postcard 11 shown in FIGS. 5 and 6 is composed of a base sheet 2 having a size twice as large as the standard postcard size, and is divided into two regions D and E by a folding line 3 at the center. It is what is divided. A destination information print 4 such as a postal code, a destination name and an address is printed on the front surface of the left section area D, and a concealment information print 5 is printed directly on the base sheet 2 on the back sides of the section areas D and E. . further,
The pressure-sensitive adhesive of the present invention is applied to the entire back surface of the divided regions D and E of the printed base sheet 2 to form a peelable adhesive layer 6. As shown in FIG. 7, the two-fold postcard 11 configured as described above is folded and pressed at the fold line 3 so that the adhesive layers on the right and left rear surfaces are in contact with each other, similarly to the above-described three-fold postcard. The adhesive layer 6 is activated and adhered.

8 and 9 is composed of the base sheet 2 having a size 1.5 times the size of the standard postcard. And G. The postal code, address,
A destination information print 4 such as an address, and a concealment information print 5 is printed directly on the base sheet 2 on the back surface of the right side divided area G. Further, the pressure-sensitive adhesive of the present invention is applied to the entire back surface of the divided area G of the printed base sheet 2 and a part of the back surface of the divided area F which is overlapped when the divided area G is folded along the folding line 3. An adhesive layer 6 that is applied and peelable is formed. As shown in FIG. 10, the partially folded postcard 21 configured in this manner is folded and pressed at the folding line 3 so that the adhesive layers on the back surfaces of the left and right sections are in contact with each other, similarly to the above-described two-fold postcard. The adhesive layer 6
Are activated and adhered.

Further, since the peelable adhesive layer formed by the pressure-sensitive adhesive of the present invention itself has the receptivity of printing ink and toner, if necessary, the surface thereof may be further coated with a normal printing device or non-printing device. Additional information (not shown) can be printed by the impact printer.

Next, an example of an easy-open packaging bag made by using the radiation-curable removable pressure-sensitive adhesive of the present invention will be described. FIG. 11 is an illustration of an easy-open packaging bag. A normal easy-open packaging bag is provided with a chuck or a zipper at the opening and is mechanically locked, whereas the easy-open packaging bag 31 has a sealed bottom 32 as shown in FIG. An adhesive layer 35 is formed on the inner upper side of the opening 34 of the bag body 33 by using the radiation-curable re-peelable pressure-sensitive adhesive of which the adhesive force is adjusted according to the present invention, and which can be applied and peeled off. If the contents 36 are put in the easy-open packaging bag 31 configured as described above, and the adhesive layers 35 are adhered to each other with a finger pressure or a higher pressure so as to be in contact with each other, the package can be easily hermetically sealed. The easy-open packaging bag 31 can be opened when necessary.
Can be easily peeled off by hand, and the contents 36 can be easily taken out. The easy-open packaging bag 31 can be used repeatedly.

Next, examples of labels made using the radiation-curable removable pressure-sensitive adhesive of the present invention will be described. As described above, a monofunctional or polyfunctional (meth) acrylate monomer having a low glass transition point, or a urethane (meth) represented by the above formula (VII) and / or (VIII)
The radiation-curable removable pressure-sensitive adhesive of the present invention, in which the acrylate is blended and the adhesive strength is adjusted, can be used as the label adhesive. FIG. 12 is an explanatory diagram of a glass bottle to which a label is attached. On the surface of the main body 42 of the glass bottle 41,
Label 1a is attached. The label 1a is applied to a base material 43 such as paper using the radiation-curable re-peelable pressure-sensitive adhesive of the present invention, the adhesive force of which is adjusted and which can be peeled off.
4 are formed. The label 1a can be attached to an adherend having high smoothness such as the glass bottle 41 with light pressure such as a finger pressure. 45 indicates a lid, and 46 indicates the contents. Then, as shown in FIG. 13, when the label 1a is to be peeled, the label 1a can be easily peeled from the glass bottle 41, and the label 1a can be peeled cleanly without any adhesive residue on the surface of the adherend.

[0068]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. (Example 1) (Synthesis of special urethane (meth) acrylate) A stirrer, a dropping funnel, a Dimroth cooling tube, a nitrogen gas sealing tube, a thermometer, and a mantle heater were installed in a 2 liter four-necked flask, and 400 ml of a flask was prepared. Toluene, 185 g of hexamethylene diisocyanate (HDI), 0.7 g of dibutyltin dilaurate, 0.2 g of monoethylhydroquinone
Was charged. After heating to 50 ° C. with stirring, polyol [trade name: X-22-160AS] was added from a dropping funnel.
(Functional group equivalent: 112 mg KOH / g) (manufactured by Shin-Etsu Chemical Co., Ltd.)] was added dropwise over about 30 minutes, and the mixture was further stirred for 20 minutes. Next, hydroxypropyl acrylate (H
PA) (143 g) was added dropwise, the temperature was raised to 60 ° C., and the mixture was stirred and reacted for 6 hours. At the end of the reaction, add 5 ethanol
After 0 ml was added and washing was repeated with a separating funnel, toluene was distilled under reduced pressure to obtain 512 g of a viscous brown transparent liquid urethane-modified silicone acrylate (special urethane (meth) acrylate).

Using the urethane-modified silicone acrylate, a radiation-curable removable pressure-sensitive adhesive of the present invention was prepared in the following composition. Hereinafter,% indicates mass%. Special urethane (meth) acrylate (the above urethane-modified silicone acrylate) 11% Urethane acrylate 10% (synthesized using polypropylene glycol having a molecular weight of 1,000 and hexamethylene diisocyanate) Propylene oxide-modified trimethylol Propane triacrylate 48% 1,9-Nonanediol diacrylate 24% 2-Methyl-1 [4- (methylthio) phenyl] -2-monophorinopropan-1-one 7% Total 100%

The viscosity (20 ° C., Brookfield viscometer) of the radiation-curable removable pressure-sensitive adhesive of the present invention thus prepared was 79 mPa · s.

A pressure-sensitive adhesive label was prepared using the radiation-curable removable pressure-sensitive adhesive of the present invention thus prepared, and the adhesive performance was measured. The radiation-curable removable pressure-sensitive adhesive of the present invention is applied to 110 kg of gloss-coated paper with a wire bar having a wire diameter of 0.08 mm, and immediately applied to 120 wg.
/ Cm metal halide lamp [trade name; Aicurelight M06-L32 (manufactured by Eye Graphics)]
Curing was performed at a belt speed of 0 m / min. The cured samples are stuck together so that the adhesive layers overlap, about 500k
A high pressure of g / cm ² was applied for 0.1 second.

The T-shaped peeling force of the bonded sample was 17 gf / 2.
5 mm. The T-type peeling force is measured by a trade name;
Using an autograph AGS-50A (manufactured by Shimadzu Corporation), the measurement was performed at a peeling rate of 300 mm / min. When the bonded sample was peeled off one month later, the T-shaped peeling force was 24.
gf / 25 mm. When the adhered sample was peeled off after standing for one week in a 50 ° C oven, the T-shaped peeling force was 27.
gf / 25 mm. The bonded sample is kept at 20 ° C-90.
When the film was peeled after being left for 3 days in an environment of% RH, the T-shaped peel force was 30 gf / 25 mm. In each case, the surface of the coated paper was not broken, and the interface between the adhesive layers was separated, and the coated paper was separated cleanly.

(Example 2) (Synthesis of special urethane (meth) acrylate) A stirrer, a dropping funnel, a Dimroth cooling tube, a nitrogen gas sealed tube, a thermometer, and a mantle heater were installed in a two-liter four-necked flask. , 400 ml of toluene, 71.5 g of hydrogenated xylene diisocyanate, 0.25 g of dibutyltin dilaurate and 0.06 g of monoethylhydroquinone. After heating to 50 ° C. with stirring, a polyol [trade name: Poly-bd R-15] was added from a dropping funnel.
HT (functional group equivalent: 102.7 mg KOH / g) (manufactured by Idemitsu Petrochemical Co., Ltd.)], and 191.3 g was added dropwise over about 40 minutes.
Stir for another 15 minutes. Next, 47.9 g of hydroxypropyl acrylate (HPA) was added dropwise, the temperature was raised to 75 ° C., and the reaction was carried out for 8 hours. At the end of the reaction, 20 ml of ethanol was added, and washing with water was repeated with a separating funnel. Then, toluene was distilled off under reduced pressure and vacuum dried to obtain a high-viscosity transparent liquid urethane-modified 1,4-polybutadiene acrylate (special urethane ( 210 g of (meth) acrylate) were obtained.

Using the urethane-modified 1,4-polybutadiene acrylate, a radiation-curable removable pressure-sensitive adhesive of the present invention was prepared in the following composition. Below,% is mass%
Is shown. Special urethane (meth) acrylate (the above urethane-modified 1,4-polybutadiene acrylate) 31% Propylene oxide-modified trimethylolpropane triacrylate 33.5% 1,9-nonanediol diacrylate 20% 2-methyl-1 [4 -(Methylthio) phenyl] -2-monophorinopropan-1-one 6.5% Total 100%

The viscosity (20 ° C., Brookfield viscometer) of the radiation-curable removable pressure-sensitive adhesive thus prepared according to the present invention was 272 mPa · s.

Using the radiation-curable removable pressure-sensitive adhesive of the present invention thus prepared, a pressure-sensitive adhesive label was prepared in the same manner as in Example 1, and the adhesive performance was measured. The T-shaped peel force of the bonded sample was 12 gf / 25 mm.
When the bonded sample was peeled off one month later, the T-shaped peeling force was 16 gf / 25 mm. 50 ° C for the bonded sample
When peeled after standing for one week in an oven, the T-shaped peeling force was 15 gf / 25 mm. 20 ° C for bonded sample
When peeled after leaving for 3 days in an environment of -90% RH,
The T-shaped peel force was 15 gf / 25 mm. In each case, the surface of the coated paper was not broken, and the interface between the adhesive layers was separated, and the coated paper was separated cleanly.

Example 3 Using the special urethane (meth) acrylate (urethane-modified silicone acrylate) synthesized in Example 1, a radiation-curable removable pressure-sensitive adhesive of the present invention was prepared with the following composition. Below,% is mass%
Is shown. Special urethane (meth) acrylate (urethane-modified silicone acrylate of Example 1) 25% Urethane acrylate 37% (synthesized using polypropylene glycol having a molecular weight of 3,000, hexamethylene diisocyanate, and hydroxylpropyl acrylate) Tripropylene glycol diacrylate 24% Diethylene glycol-modified nonylphenol acrylate 9% 1-hydroxycyclohexyl phenyl ketone 5% Total 100%

The viscosity (20 ° C., Brookfield viscometer) of the radiation-curable removable pressure-sensitive adhesive of the present invention thus prepared was 3.5 Pa · s.

Using the radiation-curable removable pressure-sensitive adhesive of the present invention thus prepared, a pressure-sensitive adhesive label was prepared, and the adhesive performance was measured. The radiation-curable removable pressure-sensitive adhesive of the present invention is applied to 135 kg of one-side coated paper with a silk screen of 150 mesh and an emulsion layer thickness of 30 μm,
Immediately, it was cured at a belt speed of 10 m / min with a lamp having 120 w / cm high-pressure mercury ozone [trade name: iCurelight H06-L31 (manufactured by Eye Graphics)]. The cured samples were adhered to a glass plate and a stainless steel plate, respectively, and bonded with a 2 kg rubber roll (based on JIS-Z0237).

The 180 ° peeling force of the bonded sample was 415 gf / 25 mm on a glass plate and 221 gf / 25 mm on a stainless steel plate.
mm. The 180 ° peeling force was measured using a trade name: Autograph AGS-50A (manufactured by Shimadzu Corporation) at a peeling speed of 300 mm / min. When the bonded sample was peeled off after one week, 49
It was 0 gf / 25 mm and 255 gf / 25 mm. When the bonded sample was peeled off after being left in a 50 ° C. oven for 1 week, it was 516 gf / 25 mm and 342 gf /
It was 25 mm. 20 ° C-90% RH
42 days after peeling for 3 days
They were 1 gf / 25 mm and 210 gf / 25 mm. In each case, the surface of the adherend was peeled off without contamination and the interface was peeled off.

(Example 4) (Synthesis of special urethane (meth) acrylate) A stirrer, a dropping funnel, a Dimroth cooling tube, a nitrogen gas sealed tube, a thermometer, and a mantle heater were installed in a two-liter four-necked flask. 468. Isophorozin diisocyanate.
3 g, dibutyltin dilaurate 0.8 g, and monoethylhydroquinone 0.3 g were charged. After heating to 40 ° C. with stirring, 160 g of nonamethylene glycol was added dropwise from the dropping funnel over about 20 minutes, and the mixture was further stirred for 20 minutes. Next, hydroxypropyl acrylate (HPA)
273 g was added dropwise, the temperature was raised to 60 ° C., and the reaction was performed for 6 hours. At the time when the reaction was completed, 50 ml of ethanol was added, and washing with water was repeated with a separating funnel, followed by vacuum drying.
621 g of a high-viscosity transparent liquid urethane-modified olefin acrylate (special urethane (meth) acrylate) was obtained.

Using this urethane-modified olefin acrylate, the radiation-curable removable pressure-sensitive adhesive of the present invention was prepared with the following composition. Hereinafter,% indicates mass%. Special urethane (meth) acrylate (the above-mentioned urethane-modified olefin acrylate) 15.4% Propylene oxide-modified trimethylolpropane triacrylate 52% 1,9-nonanediol diacrylate 20% Diethylene glycol-modified nonylphenol acrylate 5% Methylbenzoyl olefin Mate 7.6% Total 100%

The viscosity (20 ° C., Brookfield viscometer) of the radiation-curable removable pressure-sensitive adhesive thus prepared according to the present invention was 60 mPa · s.

A pressure-sensitive adhesive label was prepared using the radiation-curable removable pressure-sensitive adhesive of the present invention thus prepared, and the adhesive performance was measured. The radiation-curable removable pressure-sensitive adhesive of the present invention is applied to 110 kg of gloss-coated paper with a wire bar having a wire diameter of 0.08 mm, and immediately applied to 120 wg.
/ Cm lamp with high-pressure mercury ozone [trade name: Aicurelight H06-L31 (manufactured by Eye Graphics Co., Ltd.)]
At a belt speed of 30 m / min. The cured samples are stuck together so that the adhesive layers overlap each other.
A high pressure of 00 kg / cm ² was applied for 0.1 second.

The T-shaped peeling force of the bonded sample was 5 gf / 25.
mm. The T-shaped peeling force was measured using a trade name; Autograph AGS-50A (manufactured by Shimadzu Corporation) at a peeling speed of 300 mm / min. When the bonded sample was peeled off one month later, the T-shaped peeling force was 6.
It was 5 gf / 25 mm. When the bonded sample was peeled off after being left in an oven at 50 ° C. for one week, the T-shaped peeling force was 9.6 gf / 25 mm. 20 ° C for bonded sample
When peeled after leaving for 3 days in an environment of -90% RH,
The T-shaped peel force was 5.2 gf / 25 mm. In each case, the surface of the coated paper was not broken, and the interface between the adhesive layers was separated, and the coated paper was separated cleanly.

[0086]

As described above, according to the first aspect of the present invention,
Since the radiation-curable removable pressure-sensitive adhesive described contains a special urethane acrylate as an active ingredient, it has a moderate adhesive performance from the beginning when the cured layers are brought into close contact with each other by applying high pressure in a state where the cured layers are in contact with each other. The adhesive layer is not deformed under the environment where it is left at high temperature or exposed for a long time due to water leakage or high humidity, and the adhesive strength does not increase or decrease. This has a remarkable effect that the adhesive force does not change with time and stable adhesive performance is maintained. In addition, the radiation-curable removable pressure-sensitive adhesive according to claim 1 of the present invention is applied to the surface of a base sheet, and a label or the like having a cured layer which does not adhere in a normal state by irradiation with radiation can be produced. It is possible to attach a label etc. by hand by bringing a cured layer such as a label into contact with an adherend such as glass or metal, and the remarkable effect that the label can be easily peeled off whenever you want to peel it off Play.

The radiation-curable pressure-sensitive adhesive according to claim 2 of the present invention is the pressure-sensitive adhesive according to claim 1, wherein one or two or more monofunctional or polyfunctional (meth) acrylate monomers are selected. Since the monomer is blended, the same effect as the pressure-sensitive adhesive according to claim 1 is obtained, and the viscosity is adjusted according to the application method, the adhesive force is adjusted to obtain a desired adhesive force, and the curability is improved. Has a further remarkable effect.

The radiation-curable pressure-sensitive adhesive according to claim 3 of the present invention is the pressure-sensitive adhesive according to claim 1 or 2, further comprising the formula (VII) and / or the formula (VI).
Since the urethane (meth) acrylate represented by I) is blended, the same effect as that of the pressure-sensitive adhesive according to claim 1 can be obtained, and the adhesive force can be adjusted so as to obtain a desired adhesive force. Play.

The radiation-curable pressure-sensitive adhesive according to claim 4 of the present invention is the pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the content of the special urethane (meth) acrylate is radiation-cured. 1 for the whole mold-removable pressure-sensitive adhesive
Since the content is set to about 80% by mass, the same effect as that of the pressure-sensitive adhesive according to claim 1 can be obtained, and the effect of the special urethane (meth) acrylate used in the present invention can be more effectively exhibited. Play.

The radiation-curable pressure-sensitive adhesive according to the fifth aspect of the present invention is the same as the pressure-sensitive adhesive according to any one of the first to fourth aspects, since it is an ultraviolet-curable type. It has the same effect as the pressure-sensitive adhesive, and has a further remarkable effect that the adhesive layer can be easily and economically cured.

[Brief description of the drawings]

FIG. 1 is a surface development view of a tri-fold postcard.

FIG. 2 is a developed rear view of the postcard of FIG. 1;

FIG. 3 is a sectional view taken along line XX of FIG. 1;

FIG. 4 is an explanatory diagram of a state when the postcard of FIG. 1 is folded.

FIG. 5 is a surface development view of a two-fold postcard.

FIG. 6 is a developed rear view of the postcard of FIG. 5;

FIG. 7 is an explanatory diagram of a state when the postcard of FIG. 5 is folded.

FIG. 8 is a surface development view of a partially folded postcard.

FIG. 9 is a developed rear view of the postcard of FIG. 8;

FIG. 10 is an explanatory view of the state when the postcard of FIG. 8 is folded.

FIG. 11 is an explanatory diagram of a state of an easy-open type package.

FIG. 12 is an explanatory diagram of a glass bottle to which a label is attached.

FIG. 13 is an explanatory diagram showing a situation in which the label shown in FIG. 12 is peeled off.

[Explanation of symbols]

 2, 12, 22 Base sheet 3, 3a, 3b Fold line 5 Concealed information printing 6 Peelable adhesive layer 31 Easy-open packaging bag 33 Bag body 34 Opening 35 Adhesive layer 41 Glass bottle 1a Label 43 Base material 44 Adhesive layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 3/10 G09F 3/10 B (72) Inventor Yasuhiro Fukuda 1-6-6 Kanda Surugadai, Chiyoda-ku, Tokyo Toppan・ Forms F-term (reference) 2C005 WA03 4J004 AA10 AA14 AB01 AB06 CA02 CB02 EA06 FA01 FA06 FA08 4J040 EF131 EF171 EF251 FA131 FA292 GA01 GA03 GA05 GA14 HB18 JA02 JB07 JB09 KA11 LA01 LA06 LA07 MA02 MA05 NA05 MB05 MB05

Claims (5)

[Claims] 1. A cured layer which is applied to a superposed surface of a sheet and which does not adhere in a normal state by irradiation with radiation is formed.
By applying a predetermined pressure by bringing the superposed surfaces into contact with each other, the superposed surfaces can be peelably adhered to each other, or applied to the sheet surface,
(A) a radiation-curable re-peelable pressure-sensitive adhesive capable of forming a cured layer that does not adhere in a normal state by irradiation with radiation, and adhering the cured layer to an adherend so that the cured layer can be peeled off; ) At least one polyol selected from the following (1) to (6), (B) diisocyanate,
(C) A radiation-curable, removable pressure-sensitive adhesive containing, as an active ingredient, a bifunctional or more functional urethane (meth) acrylate obtained by reacting hydroxy (meth) acrylate. Polyol: (1) Polydimethylsiloxane represented by formula (I) (2) Reactive silicone polyol represented by formula (II) (3) 1,4-polybutadiene polyol represented by formula (III) (4) ) Hydrogenated 1,4-polybutadiene polyol represented by the formula (IV) (5) Polymethylene glycol represented by the formula (V) (6) Fluoro / perfluoroalkylene polyol represented by the formula (VI) ] In the formula (I), n is an integer of 1 or more. Embedded image In formula (II), R is generally _{-C 3 H 6 OC 2 H 4} -
Or another alkylene group. Embedded image In the formula (III), l, m, and n are integers of 1 or more, and l >> m. Embedded image In the formula (IV), l, m, and n are integers of 1 or more, and l >> m. Embedded image In the formula (V), n is an integer of 9 ≦ n ≦ 30. [0008] In the formula (VI), l, m, and n are integers of 1 or more;
(L + m + n) ≧ 8. 2. The pressure-sensitive adhesive according to claim 1, wherein one or more monomers selected from monofunctional or polyfunctional (meth) acrylate monomers are blended. 3. A urethane (meth) acrylate represented by the formula (VII) and / or the formula (VIII) is further blended.
The pressure-sensitive adhesive as described. Embedded image In the formula (VII), R represents —O — (— C ₃ H ₆ O—)
_n- , 1,2-polybutadiene polyol residue, 1,2
-Hydrogenated polybutadiene polyol residue, poly-ε-
A caprolactone residue and a polytetramethylene glycol residue are shown, R ′ represents a diisocyanate residue, and R ″ represents a hydroxy (meth) acrylate residue. Embedded image In the formula (VIII), R represents an average molecular weight of 1,000 to 3,
000 _{-O - (- C 3 H 6} O-) n -, 1,2- polybutadiene polyol residue, 1,2-hydrogenated polybutadiene polyol residue or an average molecular weight from 500 to 3,000,
Represents a poly-ε-caprolactone residue and a polytetramethylene glycol residue, R ′ represents a diisocyanate residue, and R ″ represents a hydroxy (meth) acrylate residue. 4. The pressure-sensitive composition according to claim 1, wherein the content of the special urethane (meth) acrylate is 1 to 80% by mass based on the whole pressure-sensitive adhesive. adhesive. 5. The pressure-sensitive adhesive according to claim 1, which is a UV-curable pressure-sensitive adhesive.