JP2001011395A - Uv-hardening type pressure-sensitive adhesive and pressure-sensitive adhesive sheet by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pressure-sensitive adhesive sheet hardly adhering in a normal condition after hardening, stuck to each other when a prescribed pressure is applied by facing each adhesive face to each other, capable of being peeled off as necessary, and capable of having adequate adhesion and flexibility kept with time after the adherence. SOLUTION: This adhesive is a UV-hardenable pressure-sensitive adhesive comprising an acrylic oligomer, an acrylic photopolymerizable monomer and a photopolymerization initiator. An oligomer providing a UV-hardened product having a pressure-sensitive adhesion sufficiently smaller than that of the UV- hardened material of the acrylic photopolymerizable monomer is used as the acrylic oligomer. A hardened layer of the adhesive is formed on a prescribed position of a superposed surface of a substrate to a provide the objective pressure-sensitive adhesive sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a UV-curable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet using the same, and more particularly, to an information-carrying surface formed by folding or cutting a sheet. It has not been used in this type of printing sheet, such as a confidential information transmission sheet such as a folding sheet or 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 special UV-curable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet for bonding the superposed surfaces with the UV-curable pressure-sensitive adhesive.

[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 the pressure-sensitive adhesive is provided on the entire surface, partially or linearly. This pressure-sensitive adhesive is also referred to as a self-adhesive pressure-sensitive adhesive. When a high pressure is applied in a state where the cured layers are in contact with each other, the respective polymers adhere to each other by self-diffusion. Depending on the type of object and the degree of 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.

[0004]

In order to solve the problems of the conventional pressure-sensitive adhesives, the present inventors have proposed a solventless UV-curable pressure-sensitive adhesive which does not use an aqueous medium (Japanese Patent Application Laid-Open No. 10-1998). 263466, JP-A-10-26
No. 5742). However, when this UV-curable pressure-sensitive adhesive is adhered by applying a high pressure in a state where the cured layers are in contact with each other, it is easy to peel off because it has an appropriate adhesive strength at the beginning when adhered. However, as time goes on, the adhesive strength becomes higher than necessary and peeling becomes difficult (hereinafter, referred to as
In addition, there is a problem in that the flexibility is lowered along with the peeling, and the film is peeled without following when bent, or peeled during transportation.

[0005] A first object of the present invention is to solve the problems of such an increase in adhesive strength and a decrease in flexibility. Needless to say, it is an object of the present invention to provide a UV-curable pressure-sensitive adhesive in which appropriate adhesive strength and flexibility are maintained even after a long time. Is a pressure-sensitive adhesive sheet having a cured layer formed at a predetermined position on the superposed surface of the substrate, without the problem of increased adhesive strength and reduced flexibility, that is, moderate adhesive strength and flexibility The object of the present invention is to provide a pressure-sensitive adhesive sheet which can follow the bending well and does not peel off during transportation.

[0006]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that an acrylic oligomer having a specific pressure-sensitive adhesive strength, an acrylic photopolymerizable monomer, and a photopolymerization initiator. It has been found that the object can be achieved by using a UV-curable pressure-sensitive adhesive containing the following, and the present invention has been completed.

[0007] Claim 1 of the present invention relates to an acrylic oligomer and an acrylic resin which are not adhered in a normal state after curing, but are adhered to each other by applying a predetermined pressure to each other. A UV-curable pressure-sensitive adhesive containing a photopolymerizable monomer and a photopolymerization initiator, wherein the pressure-sensitive adhesive force of the UV-cured product as the acrylic oligomer is a UV-cured product of the acrylic photopolymerizable monomer. And a UV-curable pressure-sensitive adhesive characterized by using an oligomer sufficiently smaller than the pressure-sensitive adhesive force of the present invention.

[0008] The UV-curable pressure-sensitive adhesive of the present invention can be obtained by irradiating ultraviolet rays from a suitable ultraviolet light source such as a high-pressure mercury lamp or a metal halide lamp under appropriate conditions. The system-based photopolymerizable monomer itself is polymerized and cured, and the acrylic oligomer and the acrylic-based photopolymerizable monomer are copolymerized, whereby the entire adhesive is appropriately cured.

The UV-curable pressure-sensitive adhesive of the present invention is a specific oligomer, in which the pressure-sensitive adhesive strength of the UV-cured product itself as an acrylic oligomer is sufficiently smaller than the pressure-sensitive adhesive force of the UV-cured product of the acrylic photopolymerizable monomer itself. The use of oligomer eliminates the problem of increased adhesive strength and reduced flexibility,
Not only at the beginning when the cured layers of the UV-curable pressure-sensitive adhesive of the present invention are brought into close contact with each other by applying high pressure, but also over time, an appropriate adhesive force is maintained, and flexibility is maintained. Will be retained.

A conventional UV-curable pressure-sensitive adhesive containing an acrylic photopolymerizable monomer and a photopolymerization initiator has a large pressure-sensitive adhesive strength of a UV-cured product of the acrylic photopolymerizable monomer itself, and thus has an improved adhesion. It is easy to peel off because it has a moderate adhesive strength at the beginning when high pressure is applied and the cured layers of the conventional UV-curable pressure-sensitive adhesive are in contact with each other. However, there is a problem that as time passes, the adhesive force becomes unnecessarily high, and peeling becomes difficult, and flexibility is reduced. When the sheet is bent, it peels off without following or peels off during transportation.

[0011] The pressure-sensitive contact of the UV-cured product itself as an acrylic oligomer used in conventional UV-curable pressure-sensitive adhesives (JP-A-10-263466 and JP-A-10-265742). Even in the case of a conventional UV-curable pressure-sensitive adhesive in which an oligomer having a large adhesive force is used, and the oligomer, an acrylic photopolymerizable monomer, and a photopolymerization initiator are blended, there is a problem of increasing the adhesive strength. That is, it is easy to peel off since the cured layer of this conventional UV-curable pressure-sensitive adhesive has an appropriate adhesive strength at the beginning when it is brought into close contact with a high pressure in a state where the cured layers are in contact with each other. As time goes on, the adhesive force becomes unnecessarily high, and peeling becomes difficult, and the flexibility is reduced. When the sheet is bent, it peels off without following or peels off during transportation.

The pressure-sensitive adhesive strength of the UV-cured product of the acrylic oligomer itself used in the UV-curable pressure-sensitive adhesive of the present invention is as follows:
It is important that the acrylic photopolymerizable monomer itself used in the UV-curable pressure-sensitive adhesive of the present invention be sufficiently smaller than the pressure-sensitive adhesive strength of the UV-cured product. Specifically, the pressure-sensitive adhesive strength of the UV cured product of the acrylic oligomer itself is about 1/2 to the pressure-sensitive adhesive strength of the UV cured product of the acrylic photopolymerizable monomer itself.
1/10, preferably 1/3 to 1/8, more preferably 1/4 to 1/6, and particularly preferably about 1/5. If it exceeds １ ／, it cannot be said that it is small enough, so that there is a possibility that a problem of high adhesive strength may remain.
If it is less than 10, there is no problem of increasing the adhesive strength and lowering the flexibility, but there is a possibility that the adhesive strength after curing is reduced and the adhesive is peeled off.

According to a second aspect of the present invention, there is provided a laminating sheet to which a superposed surface is releasably adhered, wherein a UV-curable pressure-sensitive sheet according to the first aspect is provided on a predetermined portion of the superposed surface of the substrate. The present invention relates to a pressure-sensitive adhesive sheet provided with a cured layer of an adhesive. The pressure-sensitive adhesive sheet of the present invention, in which a cured layer of the UV-curable pressure-sensitive adhesive of the present invention is provided on a predetermined portion of the superposed surface of the base material, has problems of increasing adhesive strength and decreasing flexibility. No, moderate adhesive strength is maintained over time,
In addition, it follows the bending well, and does not peel off during transportation.

According to a third aspect of the present invention, in the pressure-sensitive adhesive sheet according to the second aspect, the cured layer comprises a UV cured product of the acrylic oligomer and a UV cured product of the acrylic photopolymerizable monomer. It is characterized by having a morphology (morphology, texture, structure) dispersed in a matrix.

The UV-curable pressure-sensitive adhesive of the present invention, when irradiated with ultraviolet light from a suitable ultraviolet light source, polymerizes and cures the acrylic oligomer itself, and simultaneously polymerizes the acrylic photopolymerizable monomer itself. And at the same time, the acrylic oligomer and the acrylic photopolymerizable monomer are copolymerized and cured.

The cured layer of the pressure-sensitive adhesive sheet of the present invention is formed in a matrix (for example, the sea) in which a UV cured product (for example, an island) of an acrylic oligomer itself is composed of a UV cured product of an acrylic photopolymerizable monomer itself. Having a morphology (for example, a sea-island structure) that is dispersed in a UV-cured product of the acrylic oligomer itself and the acrylic-based Since the UV-cured product of the photopolymerizable monomer itself is present in the copolymerized state at an appropriate ratio with each other, the problem of increased adhesive strength due to the UV-cured product of the acrylic photopolymerizable monomer itself is eliminated and improved. It is thought to be done.

In the cured layer of the pressure-sensitive adhesive sheet of the present invention,
UV cured product of acrylic oligomer itself (eg island)
Has a morphology (e.g., sea-island structure) dispersed in a matrix (e.g., sea) composed of a UV cured product of the acrylic photopolymerizable monomer itself, that is, the cured layer contains the acrylic oligomer itself. Since the UV cured product and the UV cured product of the acrylic photopolymerizable monomer itself are present in a copolymerized state at an appropriate ratio, the action and effect of the UV cured product of the flexible acrylic oligomer itself are present. Thus, the problem of a decrease in flexibility is eliminated and improved, and it follows that bending can be followed well, and it is considered that peeling does not occur during transportation.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The acrylic oligomer used in the present invention is an oligomer having an acryloyl group or a methacryloyl group at an end. Examples of such an oligomer include an epoxy acrylate, a polyester acrylate, a polyvinyl alcohol-based oligomer, a polyacrylic acid-based oligomer, and a urethane-based oligomer. And acrylates of epoxy resins, for example, diglycidyl ether diacrylate of bisphenol A, reaction products of epoxy resin with acrylic acid and methyltetrahydrophthalic anhydride, Epoxy acrylates such as reaction products with -hydroxyethyl acrylate,

Ring-opening copolymer esters of glycidyl diacrylate and phthalic anhydride, esters of methacrylic acid dimer and polyol, polyesters obtained from acrylic acid, phthalic anhydride and propylene oxide, polyethylene glycol and maleic anhydride. Polyester-based oligomers such as reaction products with glycidyl methacrylate,

A reaction product of polyvinyl alcohol and N-methylolacrylamide, a polyvinyl alcohol oligomer such as one obtained by esterifying polyvinyl alcohol with succinic anhydride and then adding glycidyl methacrylate, methyl vinyl ether-maleic anhydride Polyacrylic acid-based oligomers such as a reaction product of a copolymer and 2-hydroxyethyl acrylate or a product obtained by further reacting glycidyl methacrylate;

A urethane oligomer having a polyoxyalkylene segment and / or a saturated polyester segment linked via a urethane bond and having an acryloyl group or a methacryloyl group at both terminals can be given. These may be used alone or in combination of two or more. Further, it can be used in combination with an oligomer other than the acrylic oligomer.

Of these, epoxy-based acrylates, polyester-based acrylates, urethane-based acrylates, and oligomers combining two or more of these can be preferably used in the present invention. Further, it has a bifunctional or more preferably bifunctional functional group, does not have a side chain structure of an alkyl group or an alkylphenyl group of ethyl group or more in the main chain, and has a glass transition point of 0 ° C. or more of 60 ° C. or more of the cured film. Aliphatic epoxy acrylate, polyester acrylate, urethane acrylate (e.g., for example, Kurodamer UVU-300, UVU-310, UVE-150, manufactured by Nippon Crowda Co., Ltd.)
And the like, and an oligomer obtained by combining two or more of these can be more preferably used.

These acrylic oligomers preferably have a weight average molecular weight in the range of 2,000 to 30,000. If a material having a molecular weight smaller than this is used, it becomes difficult to handle because of the occurrence of blocking and the like, and if a material having a molecular weight larger than this is used, the pressure-sensitive adhesive property after curing is reduced. Since the adhesive strength is enhanced, it cannot be used for re-peelable adhesive.

The amount of the acrylic oligomer is about 1% to 50% by weight, preferably about 100% by weight based on the whole pressure-sensitive adhesive (acrylic oligomer + acrylic photopolymerizable monomer + photopolymerization initiator). 5% to 50% by weight, more preferably 10% to 50% by weight, particularly preferably 20% to 50% by weight is suitable. If the blending amount of the acrylic oligomer is less than 1% by weight, there is a possibility that the adhesive force enhancement property and the flexibility are not improved, and if it exceeds 50% by weight, the pressure-sensitive adhesive property after curing may be reduced. .

Next, specific examples of the acrylic photopolymerizable monomer used in combination with the acrylic oligomer in the present invention include unsaturated carboxylic acids such as acrylic acid and methacrylic acid and esters thereof, for example, alkyl- , Cycloalkyl-, halogenated alkyl-, alkoxyalkyl-, hydroxyalkyl-, aminoalkyl-, tetrahydrofurfuryl-, allyl-, glycidyl-, benzyl-, phenoxy-acrylate and methacrylate,

Lower alkylene glycol, acrylamide, methacrylamide or derivatives thereof, for example, acrylamide and methacrylamide mono- or di-substituted with an alkyl group or hydroxyalkyl group, diacetone acrylamide and methacrylamide, N, N'-alkylenebisacrylamide And methacrylamide.

These may be used alone or in combination of two or more. Further, it can be used in combination with a photopolymerizable monomer other than the acrylic photopolymerizable monomer.

The amount of these acrylic photopolymerizable monomers is based on the total pressure-sensitive adhesive (acrylic oligomer + acrylic photopolymerizable monomer + photopolymerization initiator = 1).
00% by weight) about 40% to 99% by weight, preferably 4% by weight.
5% to 95% by weight, more preferably 50% to 9% by weight
0% by weight, particularly preferably 55% to 85% by weight, is suitable. When the blending amount of the acrylic photopolymerizable monomer is 40
When the amount is less than 100% by weight, the pressure-sensitive adhesive property after curing may be reduced. When the amount is more than 99% by weight, there is a possibility that the adhesive force enhancement property and the flexibility are not improved.

As the photopolymerization initiator used together with the acrylic oligomer and the acrylic photopolymerizable monomer, any of known photopolymerization initiators can be selected and used. Specific examples of such a photopolymerization initiator include, for example, benzoin alkyl ethers such as benzoin, benzoin ethyl ether, benzoin-n-propyl ether, benzoin-isopropyl ether, and benzoin isobutyl-ether, and 2,2-dimethoxy. -Phenyl-2-acetophenone, benzophenone, benzyl, diacetyl, diphenyl sulfide, eosin, thionine, 9,10-anthraquinone, 2-ethyl-9,10-anthraquinone and the like.

These photopolymerization initiators may be used alone or in combination of two or more. The compounding amount is about 0.1% by weight to 10% by weight based on the entire pressure-sensitive adhesive (acrylic oligomer + acrylic photopolymerizable monomer + photopolymerization initiator = 100% by weight).
Is selected in the range.

The UV-curable pressure-sensitive adhesive of the present invention includes the acrylic oligomer, acrylic photopolymerizable monomer,
In addition to the three components of the photopolymerization initiator, if necessary, additional components commonly used in general photosensitive resin compositions such as a thermal polymerization inhibitor, a tackifier, a viscosity modifier, an antioxidant, and a stabilizer. Agents, coloring agents, fine particle fillers, and the like.

Examples of the thermal polymerization inhibitor include hydroquinone, mono-tert-butylhydroquinone, benzoquinone,
2,5-diphenyl-p-benzoquinone, picric acid,
Examples thereof include di-p-fluorophenylamine, di-p-methoxyphenol, and 2,6-ditert-butyl-p-cresol. These thermal polymerization inhibitors are for preventing a thermal polymerization reaction, and therefore, the content of the thermal polymerization inhibitor is usually set to 100% by the UV-curable pressure-sensitive adhesive.
It is selected in the range of 0.01 to 5 parts by weight per part by weight.

The pressure-sensitive adhesive sheet of the present invention can be produced, for example, as follows. That is, the present invention is applied to a portion where a predetermined base material sheet is folded, tri-folded, cut and overlapped, or overlapped with another body by a coating means such as a gravure coater, flexo, air knife coater, or bar coater. UV-curable pressure-sensitive adhesive is applied and then dried to form an adhesive layer. The application at this time may be performed over the entire surface of the substrate sheet, or may be performed only on a part of the surface. On the surface of the base sheet, necessary information may be printed in advance, or after applying an adhesive layer,
Information may be printed. At this time, when printing information with a commonly used printing machine using ultraviolet curable ink for printing, the printing process and the application and fixing of the UV curable pressure-sensitive adhesive of the present invention are performed. Advantageously, they can be performed simultaneously.

The base material 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, and the like. , Plastic laminated paper, cloth, plastic laminated cloth, plastic film, metal foil and the like. The basis weight of the substrate is usually 50 to 160 g / m
^{About 2} . In the present invention, as a substrate, polyethylene, polypropylene, polyethylene terephthalate,
When a synthetic plastic film such as polyvinyl chloride is used, it is preferable to apply a surface treatment such as a mat treatment or a corona treatment to the surface of the substrate.

The amount of the UV-curable pressure-sensitive adhesive of the present invention applied to the surface of the base material is 1 to 30 g / m ² for maintaining the adhesiveness, peelability or transparency of the adhesive layer. Preferably 3 to 20 g / m ² , more preferably 5 to 15 g / m ^2
It is chosen to be in the range of ² .

The pressure-sensitive adhesive sheet produced in this manner is irradiated with ultraviolet rays to cure the adhesive layer appropriately, and then the cured adhesive layers on the respective surfaces are overlaid. Under a pressure of about 1 to 100 kg / cm ² .

The permanent adhesion and removability of the cured layer of the UV-curable pressure-sensitive adhesive of the present invention are determined by the types of the acrylic oligomer and the acrylic photopolymerizable monomer,
It can be adjusted by changing the number of functional groups of the acrylic photopolymerizable monomer, the roller pressure at the time of bonding, and the like.
In general, as the number of functional groups of the acrylic photopolymerizable monomer increases, the bonding surface becomes harder and the bonding force decreases, and as the roller pressure during bonding increases, the bonding force increases.

The cured layer of the UV-curable pressure-sensitive adhesive in the present invention needs to have appropriate adhesiveness and removability. In this method, two samples of solid printed Kent paper cut to a width of 25 mm and a length of 100 mm are overlapped with each other at a length of 25 mm over a whole surface, applied with a load of 50 kg / cm ² and crimped, and then autograph AGS50 ( Peel strength measured using Shimadzu Corporation) is 50 to 150 g
/ 25 mm, preferably in the range of 80 to 120 g / 25 mm. If the adhesive strength is less than 50 g / 25 mm, the adhesiveness when crimped is low, and it is easy to peel off.
If it is larger than 5 mm, it will be difficult to peel off again, and it will not be possible to open it when necessary.

In the pressure-sensitive adhesive sheet of the present invention, U
It is preferable that the information on the cured layer of the V-curable pressure-sensitive adhesive is printed with an acrylic ultraviolet curable ink or an acrylic resin toner. First, the acrylic UV-curable ink is generally a vehicle comprising an acrylic oligomer, an acrylic photopolymerizable monomer, and a photopolymerization initiator, and a coloring agent, for example, a black pigment or carbon black and a dispersant, a stabilizer, a matting agent. , A fungicide, a viscosity modifier and the like. The acrylic oligomer, the acrylic photopolymerizable monomer and the photopolymerization initiator in this case are exemplified as the acrylic oligomer, the acrylic photopolymerizable monomer and the photopolymerization initiator in the UV-curable pressure-sensitive adhesive. Can be selected and used. When using this ink,
The application / fixing step of the UV-curable pressure-sensitive adhesive and the printing / drying step can be performed simultaneously with a normal printing machine.

When printing information on a cured layer of a UV-curable pressure-sensitive adhesive using a toner such as a laser printer or a digital press, an acrylic resin toner is most preferable. Currently, commonly used toners include, in addition to acrylic resins, which are currently the mainstream, epoxy resins, polystyrene resins, polyester resins, and polypropylene resins as main components. Each of the toners adheres to the cured layer of the UV-curable pressure-sensitive adhesive of the present invention, but, like the acrylic UV-curable ink, the toner is formed of an acrylic resin similar to the cured layer, thereby obtaining the toner. The adhesiveness between the layer and the cured layer is enhanced, and information can be provided very well.

In the present invention, it is advantageous that the UV-curable pressure-sensitive adhesive and the UV-curable ink have compositions as similar as possible. In this case, the adhesion between the two is improved, and the characters and patterns are not blurred or peeled off.

Next, constitutional examples of the pressure-sensitive adhesive sheet of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to these constitutional examples. FIG.
1 is a plan view of a two-fold pressure-sensitive adhesive sheet as a first configuration example of the present invention, FIG. 2 is a cross-sectional view taken along line XX of FIG. 1, and FIG.
FIG. 4 is a plan view of a three-fold pressure-sensitive adhesive sheet according to a second embodiment of the present invention, and FIG. 5 is a back view of the pressure-sensitive adhesive sheet of FIG. FIG. 6
FIG. 7 is an explanatory view of a state of superposition of the pressure-sensitive adhesive sheet of FIG. 4, and FIG. 7 is an explanatory view of various means for facilitating separation of the superposed surface after bonding.

A first embodiment of the present invention shown in FIGS. 1 to 3 is a superimposed surface 3 constructed as a "concealment postcard".
This is a two-fold pressure-sensitive adhesive sheet 1 in which a cured layer 4 of a UV-curable pressure-sensitive adhesive is applied to the entire surface. This is because the upper sheet A and the lower sheet C are folded by the folding perforation line Mf.
And concealed information in a state of being folded in two as shown in FIG. As shown in FIGS. 1 and 3, a general print 5 such as a postal code entry field, a purchase information entry field, a company name, etc. is provided on the front and back surfaces of the base sheet 2, and is also overlapped when folded. The entire surface of the mating surface 3, that is, the entire surface of one side of the upper sheet A and the lower sheet C
A cured layer 4 of a curable pressure sensitive adhesive is provided.

In this embodiment, cuts K are provided at the corners of the upper sheet piece A to form a step between the upper sheet piece A and the lower sheet piece B, thereby facilitating peeling of the superposed surface after bonding. And As such peeling facilitating means, as shown in FIG. 7, (a) a step is provided by making a cut K at the corner of the overlapping surface as in this configuration example, or (b) Make a notch K on the side to create a step,
(C) A method of extending the flap piece F on one of the overlapping surfaces to provide a step can be adopted.

A second embodiment of the present invention shown in FIGS. 4 to 6 is a superimposed surface 3 constructed as a "concealment postcard".
This is a three-fold pressure-sensitive adhesive sheet 1 in which a cured layer 4 of a UV-curable pressure-sensitive adhesive is applied to the entire surface. This is because the base sheet 2 is divided into an upper sheet piece A, a middle sheet piece B, and a lower sheet piece C by two folding perforation lines Mf, Mf, and as shown in FIG. It carries concealment information in a folded state. Then, as shown in FIGS. 4 and 5, on the front and back surfaces of the base sheet 2, a general print 5 such as a postal code entry field, a variable information entry field, an explanatory note, etc. is given, and the base sheet 2 is folded into a Z-shape. A cured layer 4 of a UV-curable pressure-sensitive adhesive is applied to the entire surface of the overlapping surface 3 in this case.

FIG. 8 is an explanatory view schematically showing a cross section of the cured layer 4 of the pressure-sensitive adhesive sheet 1 of the present invention shown in FIGS. The cured layer 4 of the upper paper strip A and the cured layer 4 of the lower paper strip C have a sea-island structure in which a UV cured product 6 of an acrylic oligomer itself is dispersed in a matrix composed of a UV cured product 7 of an acrylic photopolymerizable monomer itself. Have.

The cured layer 4 of the upper sheet A and the cured layer 4 of the lower sheet C
The UV cured product 6 of the acrylic oligomer itself and the UV cured product 7 of the acrylic photopolymerizable monomer are copolymerized with each other at an appropriate ratio on the surface 8 where the two are brought into close contact by applying high pressure. It is considered that the problem of high adhesive strength is eliminated because it exists in a state where it has been adhered.

The cured layer 4 also has a sea-island structure in which the UV cured product (island) 6 of the acrylic oligomer itself is dispersed in a matrix (sea) composed of the UV cured product 7 of the acrylic photopolymerizable monomer itself. In the layer of the cured layer 4, a UV cured product 6 of the acrylic oligomer itself and a UV cured product 7 of the acrylic photopolymerizable monomer itself are present in a state where they are copolymerized with each other at an appropriate ratio. Therefore, the problem of a decrease in flexibility is eliminated by the action and effect of the UV-cured product 6 of the acrylic oligomer itself having flexibility, the problem is improved, the film follows the bending well, and peeling may occur during transportation. It is thought to be gone.

[0049]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples without departing from the gist of the present invention. (Example 1) 25% by weight of monofunctional acrylate (M113, manufactured by Toagosei Co., Ltd.) as an acrylic photopolymerizable monomer 30% by weight of bifunctional acrylate (Viscoat 260, manufactured by Osaka Organic Chemical Industry Co., Ltd.) Trifunctional acrylate ( 35% by weight of Toa Gosei Co., Ltd., M310), 5% by weight of an urethane-based acrylate (manufactured by Nippon Crowda Co., Ltd., Crodamer UVU300) as an acrylic oligomer, and Irgacure 18 manufactured by Ciba-Geigy as a photopolymerization initiator.
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of No. 4 was prepared. The UV-curable pressure-sensitive adhesive thus obtained was applied to a 110 kg coated paper with a wire bar using a wire bar.
g / cm ² , and then exposed and cured using an ultraviolet irradiation device manufactured by Eye Graph Fix Co., Ltd. Thus, the pressure-sensitive adhesive sheet of the present invention having a colorless, transparent and glossy cured layer was produced. Next, the adhesive force enhancement property and flexibility of this pressure-sensitive adhesive sheet were evaluated by the following methods, and the results are shown in Table 1.

Adhesive force enhancing property: The obtained pressure-sensitive adhesive sheet is cut into a width of 25 mm and a length of 100 mm to prepare a sample.
After applying a load of kg / cm ² and crimping, the adhesive force (F1) was obtained using Autograph AGS50 (manufactured by Shimadzu Corporation).
Is measured. Next, after the pressure-bonded sample is left in the room for 7 days, the adhesive force (F2) is measured in the same manner, and the adhesive force increasing property (%) (adhesive force increase rate) is determined by the following equation (1). Adhesive force enhancement (%) = [(F2−F1) / F1] × 100 Equation (1)

Flexibility: The crimped sample was allowed to stand in a room for 7 days, and then bent 180 ^° and 10 times using a folding device manufactured by Toppan Forms, and the adhesive force (F3) was measured in the same manner. Flexibility (%) according to the following equation (2)
(Adhesive strength retention) is determined. Flexibility (%) = [(F3) / F1] × 100 Formula (2)

(Example 2) Monofunctional acrylate (manufactured by Toagosei Co., Ltd., M11) was used as the acrylic photopolymerizable monomer.
3) 20% by weight, 30% by weight of a bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat 260), 35% by weight of a trifunctional acrylate (M310, manufactured by Toagosei Co., Ltd.), and urethane acrylate (Nippon Crowda) as an acrylic oligomer 10% by weight of Kurodamer UVU300)
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

Example 3 Monofunctional acrylate (M11, manufactured by Toagosei Co., Ltd.) as an acrylic photopolymerizable monomer
3) 20% by weight, 25% by weight of bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Biscoat 260), 30% by weight of trifunctional acrylate (M310, manufactured by Toagosei Co., Ltd.), and urethane-based acrylate (Nippon Crowda) as an acrylic oligomer 20% by weight of Kurodamer UVU300)
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 Monofunctional acrylate (manufactured by Toagosei Co., Ltd., M11) was used as the acrylic photopolymerizable monomer.
3) 10% by weight, 15% by weight of a bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Biscoat 260), 20% by weight of a trifunctional acrylate (M310, manufactured by Toagosei Co., Ltd.), and urethane acrylate (Nippon Crowda) as an acrylic oligomer 50% by weight of Kurodamer UVU300)
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

(Example 5) Monofunctional acrylate (manufactured by Toagosei Co., Ltd., M11) was used as the acrylic photopolymerizable monomer.
3) 20% by weight, 30% by weight of a bifunctional acrylate (manufactured by Osaka Organic Chemical Industry, Biscoat 260), 35% by weight of a trifunctional acrylate (M310, manufactured by Toagosei Co., Ltd.) 10% by weight of Kurodamer UVE150)
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

Example 6 As an acrylic photopolymerizable monomer, a monofunctional acrylate (M11, manufactured by Toagosei Co., Ltd.)
3) 15% by weight, 20% by weight of a bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Biscoat 260), 30% by weight of a trifunctional acrylate (M310, manufactured by Toa Gosei Co., Ltd.), and an epoxy acrylate (Nippon Crowda) as an acrylic oligomer 30% by weight of Kurodamer UVE150),
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

(Example 7) Monofunctional acrylate (manufactured by Toagosei Co., Ltd., M11) was used as the acrylic photopolymerizable monomer.
3) 25% by weight, 30% by weight of a bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Biscoat 260), 35% by weight of a trifunctional acrylate (M310, manufactured by Toa Gosei Co.), and a polyester acrylate (Toa Gosei) as an acrylic oligomer M6100) 5% by weight, and as a photopolymerization initiator, Irgacure 18 manufactured by Ciba-Geigy
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of No. 4 was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

Example 8 As an acrylic photopolymerizable monomer, a monofunctional acrylate (M11, manufactured by Toagosei Co., Ltd.)
3) 15% by weight, 15% by weight of bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Biscoat 260) 25% by weight of trifunctional acrylate (M310, manufactured by Toa Gosei Co., Ltd.), and polyester acrylate (Toa Gosei Co., Ltd.) as an acrylic oligomer M6100) 40% by weight, and as a photopolymerization initiator, Irgacure 1 manufactured by Ciba-Geigy
A UV-curable pressure-sensitive adhesive of the present invention containing 5% by weight of No. 84 was prepared. A pressure-sensitive adhesive sheet of the present invention was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for an increase in adhesive strength and flexibility in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 Example 3 was repeated except that 20% by weight of a methacryl-modified polybutadiene-based oligomer (TEA1000, manufactured by Nippon Soda Co., Ltd.) was used instead of 20% by weight of a urethane-based acrylate (UVU300, Nippon Crowda).
A UV-curable pressure-sensitive adhesive for comparison was prepared in the same manner as described above. A pressure-sensitive adhesive sheet for comparison was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for the enhancement of adhesion and flexibility in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 2 Example 4 was repeated except that 50% by weight of a methacryl-modified polybutadiene-based oligomer (TEA1000, manufactured by Nippon Soda Co., Ltd.) was used instead of 50% by weight of a urethane acrylate (UVU300, Nippon Crowda).
A UV-curable pressure-sensitive adhesive for comparison was prepared in the same manner as described above. A pressure-sensitive adhesive sheet for comparison was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Next, the pressure-sensitive adhesive sheet was evaluated for the enhancement of adhesion and flexibility in the same manner as in Example 1, and the results are shown in Table 2.

(Comparative Example 3) Monofunctional acrylate (M113, manufactured by Toagosei Co., Ltd.) without blending an acrylic oligomer
30% by weight, 30% by weight of bifunctional acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., Viscoat 260) 35% by weight of trifunctional acrylate (manufactured by Toagosei Co., Ltd., M310), and Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator Was prepared for comparison as a UV-curable pressure-sensitive adhesive containing 5% by weight. A pressure-sensitive adhesive sheet for comparison was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained. Then, the pressure-sensitive adhesive sheet was evaluated for its adhesiveness enhancement and flexibility in the same manner as in Example 1,
Table 2 shows the results.

(Comparative Example 4) An urethane-based acrylate (manufactured by Nippon Crowda Co., Kurodamer UVU3) was used as an acrylic oligomer without blending an acrylic photopolymerizable monomer.
A UV-curable pressure-sensitive adhesive for comparison containing 95% by weight and 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet for comparison was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained.
Next, the pressure-sensitive adhesive sheet was evaluated for the enhancement of adhesion and flexibility in the same manner as in Example 1, and the results are shown in Table 2.

COMPARATIVE EXAMPLE 5 An acrylic oligomer was used as an acrylic oligomer without blending an acrylic photopolymerizable monomer.
50) A UV-curable pressure-sensitive adhesive for comparison containing 95% by weight and 5% by weight of Irgacure 184 manufactured by Ciba Geigy as a photopolymerization initiator was prepared. A pressure-sensitive adhesive sheet for comparison was produced in the same manner as in Example 1 using the UV-curable pressure-sensitive adhesive thus obtained.
Next, the pressure-sensitive adhesive sheet was evaluated for the enhancement of adhesion and flexibility in the same manner as in Example 1, and the results are shown in Table 2.

[0064]

[Table 1]

[0065]

[Table 2]

From Table 1, the pressure-sensitive adhesive sheet of the present invention using the UV-curable pressure-sensitive adhesive of the present invention of Examples 1 to 8 is as follows:
At the beginning, when the hardened layers are brought into close contact with each other by applying high pressure, the appropriate adhesive force is maintained even after a long time,
It can be seen that the flexibility is maintained.

On the other hand, from Table 2, the pressure-sensitive adhesive sheets using the UV-curable pressure-sensitive adhesives of Comparative Examples 1 to 3 were brought into close contact with each other by applying a high pressure while the cured layers were in contact with each other. Initially, it has moderate adhesive strength and flexibility, but over time, the adhesive strength becomes larger than necessary and peeling becomes difficult,
And it turns out that flexibility falls. Comparative Examples 4 and 5
The pressure-sensitive adhesive sheet using the UV-curable pressure-sensitive adhesive of
It can be seen that the adhesive strength is low 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. Also, when the results of Comparative Examples 4 and 5 in Table 2 are compared with the results of Comparative Example 3 in Table 1, the pressure-sensitive adhesive strength of the UV cured product of the acrylic oligomer used in the present invention is higher than the acrylic photopolymerization used in the present invention. It can be seen that it is sufficiently smaller than the pressure-sensitive adhesive force of the UV cured product of the hydrophilic monomer.

[0068]

The UV-curable pressure-sensitive adhesive according to claim 1 of the present invention is a non-aqueous type, so that it does not wrinkle when dried, and has a glossy appearance and a cured layer. It is also good, and it is possible to print on it, and furthermore, when the cured layers are brought into contact with each other, strong pressure is applied and they are adhered to each other so that they can be peeled off. Is maintained, and flexibility is also maintained.

The pressure-sensitive adhesive sheet according to the second aspect of the present invention is a sheet in which a cured layer of the UV-curable pressure-sensitive adhesive of the present invention is provided on a predetermined portion of a superposed surface of a substrate. There is no problem of increasing the force and lowering the flexibility, and a suitable adhesive force and flexibility are maintained even after a long time, and it follows the bending well, and does not peel off during transportation. The pressure-sensitive adhesive sheet of the present invention may be a folded sheet in which a surface superimposed by folding or cutting is used as an information carrying surface, a confidential information-transmitting sheet such as a superposed sheet, or a dimensionally expandable arrangement. It is useful as an office sheet such as a sheet or copy paper.

The pressure-sensitive adhesive sheet according to claim 3 of the present invention has a cured layer in which a UV cured product of an acrylic oligomer is dispersed in a matrix composed of a UV cured product of an acrylic photopolymerizable monomer. Since it has a morphology, the problem of enhancing the adhesive strength is eliminated and improved, and the problem of the decrease in flexibility due to the action and effect of the UV cured product of the acrylic oligomer itself is eliminated.

[Brief description of the drawings]

FIG. 1 is a plan view of a two-fold pressure-sensitive adhesive sheet that is a first configuration example of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is an explanatory view of a superposed state of the pressure-sensitive adhesive sheet of FIG. 1;

FIG. 4 is a plan view of a tri-fold pressure-sensitive adhesive sheet according to an example of the present invention.

FIG. 5 is a back view of the pressure-sensitive adhesive sheet of FIG.

FIG. 6 is an explanatory view of a superposed state of the pressure-sensitive adhesive sheet of FIG.

FIG. 7 is an explanatory view of various means for facilitating peeling of a superposed surface after bonding.

FIG. 8 is an explanatory view schematically showing a cross section of a cured layer of the pressure-sensitive adhesive sheet of the present invention in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pressure-sensitive adhesive sheet 2 Base sheet 3 Lamination surface 4 Cured layer of UV-curable pressure-sensitive adhesive 5 General printing part 6 UV-cured product (island) of acrylic oligomer itself 7 UV of acrylic photopolymerizable monomer itself Matrix consisting of cured product (sea) A Upper paper strip B Middle paper strip C Lower paper strip Mc Sewing machine line Mf Folding machine line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C005 WA03 4J004 AA01 AA17 AB01 CC02 FA08 4J040 FA101 FA102 FA141 FA142 FA151 FA152 FA161 FA162 FA171 FA172 FA231 FA232 FA261 FA262 FA271 FA272 FA291 FA292 HB19 JA09 JB08 JB09 KA13 LA01 LA06 MB14 NA21 PA33 PA42 4L055 AG71 AG93 AJ03 EA40 FA30 GA42 GA50

Claims (3)

[Claims] 1. An acrylic oligomer and an acrylic photopolymerizable monomer which are not adhered in a normal state after curing but are adhered to each other by applying a predetermined pressure to each other, but which can be peeled off if necessary. UV containing photopolymerization initiator
A curable pressure-sensitive adhesive, wherein the acrylic oligomer is an oligomer whose pressure-sensitive adhesive strength of a UV cured product is sufficiently smaller than the pressure-sensitive adhesive force of a UV cured product of the acrylic photopolymerizable monomer. UV curable pressure-sensitive adhesive. 2. A laminated sheet to which a superposed surface is releasably adhered, wherein a cured layer of the UV-curable pressure-sensitive adhesive according to claim 1 is applied to a predetermined portion of the superposed surface of a substrate. A pressure-sensitive adhesive sheet provided. 3. The cured layer according to claim 1, wherein the UV cured product of the acrylic oligomer is a UV cured product of the acrylic photopolymerizable monomer.
The pressure-sensitive adhesive sheet according to claim 2, having a morphology dispersed in a matrix composed of a V-cured product.