JP2805225B2 - How to bond plastic molded products - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for bonding a thermoplastic saturated norbornene-based polymer molded article particularly suitable as an optical material, and more specifically, it comprises a thermoplastic saturated norbornene-based polymer. The present invention relates to a method for firmly bonding plastic molded products or a material different from the molded product, for example, a material such as another plastic molded product or metal.

[Conventional technology]

Conventionally, for example, polycarbonate (PC) and polymethyl methacrylate (PMM) have been used as transparent plastic molding materials for optical disc substrates and plastic lenses.
A) has been mainly used. However, PC has a large birefringence, and PMMA has a large water absorption and insufficient heat resistance, and it has become difficult to meet increasingly sophisticated requirements.

Recently, thermoplastic saturated norbornene-based polymers such as hydrogenated ring-opening polymers of norbornene-based monomers and addition-type polymers of norbornene-based monomers and ethylene have attracted attention as optical plastic molding materials for optical disc substrates and the like. (Japanese Unexamined Patent Publication No. 60-26024, 6
4-24826, 60-168708, 61-115912, 61-1208
No. 16).

The thermoplastic saturated norbornene-based polymer has excellent transparency, small birefringence, and excellent heat resistance and water absorption resistance, and is a very useful material for optical use. Further, the polymer is excellent in strength, water resistance, electric insulation, solvent resistance, chemical resistance to acids and alkalis, etc., and in addition to optical applications, electric insulation materials, moisture resistance of containers and films, etc. It is also useful as a packaging material.

However, molded articles made of a thermoplastic saturated norbornene-based polymer have a problem that they are difficult to adhere to each other or to other materials.

In general, plastic molded articles may be used alone, but are often used after being adhered to each other or to other materials.

In optical molded products, for example, in the case of a large-sized optical disk having a diameter of 300 mm, two substrates made of the same material may be used together to correct the warpage of the substrate due to a change in temperature or humidity (adhesive bonding structure). Optical disk). In addition, a small metal disk called a hub may be bonded to the center of the optical disc. Further, the molded plastic lens is often used by being adhered to a holder.

Even in the case of an electric insulating material, a plastic molded product and another material are often used by bonding.

A conventional transparent plastic molded article for optical use can be bonded with a commonly used general solvent-based or emulsion-based adhesive.

For example, CP or metal such as CP and stainless steel, cyanoacrylate adhesive, epoxy adhesive,
Can be bonded with a polyurethane adhesive or the like.

Further, the PMMAs or the metal such as stainless steel can be bonded to each other with a cyanoacrylate adhesive, an epoxy adhesive, an acrylic adhesive, or the like.

However, a molded article made of a thermoplastic saturated norbornene-based polymer is a kind of olefin resin, so the surface of the molded article has poor wettability and is unlikely to adhere similarly to olefin resins such as polyethylene and polypropylene. However, the molded articles cannot be adhered to each other, and the molded articles have weak adhesion to the molded article and other materials and are easily peeled off.

[Problems to be solved by the invention]

An object of the present invention is to provide a bonding method in which a molded article made of a thermoplastic saturated norbornene-based polymer has improved adhesion.

Accordingly, the present inventors have conducted intensive studies to solve the above problems, and as a result, by using an ultraviolet-curable adhesive, plastic molded products made of a thermoplastic saturated norbornene-based polymer or between the molded products and other materials. Have been found to be able to be firmly bonded, and the present invention has been completed.

[Means for solving the problem]

Thus, according to the present invention, there is provided a method for bonding molded articles of a thermoplastic saturated norbornene-based polymer or a molded article and a different material, wherein the adhesive comprises a monofunctional acrylate monomer or a polyfunctional acrylate monomer. A polyester acrylate having an acryloyl group at the terminal, an epoxy acrylate having an epoxy group of an epoxy resin esterified with acrylic acid to form a functional group as an acryloyl group, a polyurethane acrylate, an unsaturated polyester having a double bond in a molecular chain, and 1, UV curable adhesive containing at least one selected from a reactive monomer and / or reactive oligomer selected from 2-polybutadiene, a photopolymerization initiator, a solvent, a thermoplastic polymer inert to ultraviolet light, and a filler. And applying the adhesive to the adherend. And a method for bonding plastic molded articles, characterized in that, after bonding the applied surfaces, the resin is irradiated with ultraviolet rays to perform radical polymerization with a photopolymerization initiator and to cure the same.

 Hereinafter, the present invention will be described in detail.

(Thermoplastic saturated norbornene-based polymer) The molding material targeted by the present invention is a thermoplastic saturated norbornene-based polymer, and specific examples thereof include structural units represented by the following general formulas [I] and / or [II]. Can be mentioned.

(Wherein, R ₁ and R ₂ represent hydrogen, a hydrocarbon residue,
Halogen, ester, a polar group such as a nitrile pyridyl may be the same or different, also, R ₁
And R ₂ may form a ring with each other. n is a positive integer. q is 0 or a positive integer. ] (Wherein, R ₃ and R ₄ are hydrogen, a hydrocarbon residue,
Halogen, ester, a polar group such as a nitrile pyridyl may be the same or different, and, R ₃
And R ₄ may form a ring with each other. l and m
Is a positive integer, and p is 0 or a positive integer. The polymer having the structural unit represented by the general formula (I) is
As monomers, for example, norbornene and its alkyl and / or alkylidene substituents, for example, 5-
Methyl-2-norbornene, 5,6-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc .: dicyclopentadiene, 2,3-dihydro Diclopentadiene, alkyl-substituted products thereof such as methyl, ethyl, propyl and butyl, and polar group-substituted products such as halogens: dimethanooctahydronaphthalene, alkyl- and / or alkylidene-substituted products thereof, and polar-substituted products such as halogens For example, 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-
Ethyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4, 4a, 5,6,7,8,8a-octahydronaphthalene,
6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-
Octahydronaphthalene, 6-cyano-1,4: 5,8-dimetano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene,
6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a
-Octahydronaphthalene, 6-methoxycarbonyl-
1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene and the like; cyclopentadiene trimer to tetramer, for example, 4,9: 5,8- Dimethano-3a, 4,4a, 5,8,8a, 9,9a-octahydro-1H-benzoindene, 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6 , 9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentaanthracene and the like, using a ring-opening polymer obtained by polymerization by a known ring-opening polymerization method,
It is a saturated polymer produced by hydrogenation by a usual hydrogenation method.

Further, the polymer having a structural unit represented by the general formula [II], as a monomer, a polymer obtained by addition copolymerization of a norbornene-based monomer as described above and ethylene by a known method and / or The hydrogenated product,
Each is a saturated polymer.

The molecular weight range is GPC using cyclohexane as a solvent.
(Gel Permeation Chromatography) A number average molecular weight of from 10,000 to 200,000 measured by analysis is appropriate.
When the unsaturated bonds remaining in the molecular chain are saturated by a hydrogenation reaction, the hydrogenation ratio is preferably 90% or more from the viewpoint of light resistance deterioration and weather resistance deterioration.

The thermoplastic saturated norbornene-based polymer may be a polymer obtained by copolymerizing other monomer components such as α-olefin and cycloolefin in the production process of the polymers [I] and [II].

The bonding method of the present invention is also effective when blended with another resin according to the purpose of use.

Furthermore, an antistatic agent, an antioxidant, a filler such as glass fiber, a dye,
The bonding method of the present invention is also effective for molded articles obtained by adding additives such as pigments.

The molding method of the molded article of the thermoplastic saturated norbornene-based polymer according to the present invention is not particularly limited, and examples thereof include those obtained by emission molding such as optical disks and lenses, those obtained by melt extrusion molding into tubes or rods, and those obtained by melting. Examples include a sheet or film extruded and wound by a roll, a sheet formed by hot pressing, a film obtained by casting a solvent solution, and a stretched film by stretching.

(Ultraviolet curing adhesive) An ultraviolet curing adhesive comprises a reactive monomer and / or a reactive oligomer and a photopolymerization initiator as essential components,
The composition contains a stabilizer, an antioxidant, a polymerization inhibitor and the like, if desired.

As the reactive monomer, acrylates are the main ones, and specifically, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
Monofunctional acrylate monomers such as phenoxyethyl acrylate, phenoxypropyl acrylate, and other higher alkyl acrylates; other monofunctional monomers such as vinylpyrrolidone; ethylene glycol, diethylene glycol, tripropylene glycol, butylene glycol, hexanediol, and trimethylolpropane And polyfunctional acrylate monomers in which two or more acrylates are bonded to a polyol such as pentaerythritol.

Reactive oligomers include polyester acrylate having an acryloyl group at the end, epoxy acrylate in which the epoxy group of an epoxy resin is esterified with acrylic acid and the functional group is an acryloyl group, polyurethane acrylate, unsaturated having a double bond in the molecular chain polyester,
Examples thereof include 1,2-polybutadiene.

As a photopolymerization initiator, benzophenone, benzyl,
Examples thereof include methyl orthobenzoyl benzoate, benzoin alkyl ether, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, chlorinated acetophenone, and α-acyloxime ester.

When irradiated with ultraviolet light, these reactive monomers and / or
Alternatively, radical polymerization is initiated or promoted by the photopolymerization initiator of the reactive oligomer, and the reactive oligomer is cured, whereby the adhesive performance is exhibited. Further, an appropriate solvent, a thermoplastic polymer, and various fillers may be added for the purpose of adjusting the viscosity or improving the adhesive strength.

When a solvent is added, aromatic solvents such as benzene, toluene, and xylene, which are good solvents for the thermoplastic saturated norbornene-based polymer, and alicyclic solvents such as cyclohexane, methylcyclohexane, and decalin are suitable. By adding an amount that does not affect the surface of the molded article, leakage between the adhesive and the adherend can be improved, and the adhesive strength can be improved.

Generally, polymers having similar structures have good compatibility and good wetting, and therefore, for the purpose of improving adhesion, a thermoplastic polymer which is inert to ultraviolet light can be added. If a polymer is added, it is effective to use a polymer having a structure similar to that of the adherend represented by the structural formula [I] or [II].
Specifically, norbornene-based polymer itself represented by the formula (I) or (II), dicyclopentadiene-based, diene-based, aliphatic-based, aromatic-based, petroleum resin such as water white-based or a resin thereof. Suitable are hydrogenated products and the like, and substituted or unsubstituted polystyrene resins.

Further, by adding various fillers, the development that the adhesive strength of the adhesive is improved is well known, for example, mica, glass fiber, silica, titanium white, alumina powder, calcium carbonate, goethite, Examples include inorganic fillers such as metal oxides and minerals such as talc, kaolin and zirconia, and organic fillers such as inert polymers such as polytetrafluoroethylene powder.

Among these, the addition of fine powder of silica or talc is particularly preferred. Since these fillers are nearly transparent and have fine particles, even if added, they do not strongly absorb ultraviolet light, so that they do not decrease sensitivity to ultraviolet light, and have an effective adhesive force. Can be improved.

The preferred range of the amount of the filler is usually 5 to 200 parts by weight based on 100 parts by weight of the total of the photoreactive monomer and the oligomer.
Parts by weight, preferably 10 to 100 parts by weight. If less than this range, the effect of improving the adhesive strength is not sufficient,
If the amount is larger than this range, the adhesive layer becomes brittle, and there is a disadvantage that the adhesive strength is reduced.

The above-mentioned solvents, thermoplastic polymers and fillers may be used alone or in combination of two or more, and further effects can be expected by using them in combination.

In addition, a thermal polymerization inhibitor, a photopolymerization inhibitor, a tackifier, and the like may be appropriately used.

UV-curable adhesive may be used commercially available,
For example, Nogawa Chemical's Diamond Bond DA855F, 855
G, 855GH, 855P, UV120B, 130, ThreeBond 300
0 series, Sanyuresin SUV200, 001, 300, 303,
NF series manufactured by Somar Industries, UBA-30 manufactured by Sanwa Chemical
1, Meisei Churchill photo bond series, Sony Chemical 17A, 19A, Toa Gosei Chemical Arontite
Examples include BU333V, BU246V, and Y-860 manufactured by Cemedine.

(Adhesion method) An adhesive is applied to both or one of the adherends, and the applied surfaces are immediately adhered and fixed so as not to move. When the adhesive contains a solvent, the solvent is sufficiently dried with a hot air dryer or the like. The drying temperature and time depend on the type of solvent included, the amount applied, and the shape of the adhesive surface, but so that there is no thermal deformation of the adherend,
Drying at 120 ° C. or lower is preferred.

Thereafter, by irradiating ultraviolet rays from a light source such as a high-pressure mercury lamp that efficiently generates ultraviolet rays, curing occurs in a short time, and a strong adhesive force is obtained. The irradiation amount varies depending on the reactivity of the reactive monomer, the reactive oligomer, and the photopolymerization initiator, but in the case of a high-pressure mercury lamp of 80 W / cm, curing can be performed in a short time of about 5 to 10 seconds.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples, Reference Examples, and Comparative Examples, but the present invention is not limited to Examples.

[Reference Example 1] 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a
-Injection molding of hydrogenated octahydronaphthalene (MTD) ring-opened polymer (number average molecular weight 28,000, hydrogenation rate almost 100%, glass transition temperature 152 ° C), width 25mm, length 100mm, thickness A 2 mm plate was prepared (test piece A).

Reference Example 2 100 g of dipentaerythrol hexaacrylate as a reactive monomer, a photopolymerization initiator (manufactured by Ciba-Geigy,
3 g of trade name Irgacure 184) and 40 g of toluene were mixed and stirred to prepare an ultraviolet curable adhesive.

[Example 1] Two test pieces A prepared in Reference Example 1 were used, and the ultraviolet-curable adhesive prepared in Reference Example 2 was applied to both of them. Immediately, the bonding surface was 25 mm long and 25 mm wide. And then press-clamp with cold press (clamping pressure: 1kg / cm ² )
did.

After drying with a hot air drier at 100 ° C for 30 minutes, and leaving it to stand at 20 ° C for 30 minutes, with an adhesive surface fixed, use an 80 W / cm high-pressure mercury lamp
UV light was applied for 5 seconds from a distance of cm to cure.

When one end of the two bonded test pieces was fixed, a 10 kg weight was hung on the other end, and allowed to stand for 10 minutes.
The adhesive surface did not peel off and showed good adhesive strength.

[Comparative Example 1] Two test pieces A prepared in Reference Example 1 were used, and a cyanoacrylate-based adhesive (manufactured by Sekisui Chemical Co., Ltd.,
Apply the product name Esdine 800) at room temperature, and immediately bond the applied surface so that the adhesive surface is 25 mm long and 25 mm wide.
Pressing was performed by a cold press (pressing pressure: 1 kg / cm ² ).

After curing at 20 ± 2 ° C. for 24 hours, one end of the two bonded test pieces was fixed, and a 10 kg weight was hung on the other end, and the bonded surface peeled off.

[Reference Example 3] 100 g of pentaerythritol triacrylate as a reactive monomer, 3 g of a photopolymerization initiator (trade name: Irgacure 184, manufactured by Ciba Geigy), and dicyclopentadiene-based hydrogenated petroleum resin (trade name: Escolets, manufactured by Tonex Corporation) 5300) was mixed and stirred to obtain an ultraviolet curable adhesive.

[Example 2] Two test pieces A prepared in Reference Example 1 were used, and the ultraviolet-curable adhesive prepared in Reference Example 3 was applied to both of them and irradiated with ultraviolet rays in the same manner as in Example 1 in a fixed state. And glued.

When the weight was suspended in the same manner as in Example 1, the adhesive surface did not peel off.

Reference Example 4 An adhesive composition was obtained by mixing 100 g of an ultraviolet curable adhesive (trade name: Diabond DA855P) manufactured by Nogawa Chemical Co., Ltd. and 70 g of toluene.

[Example 3] Two test pieces A prepared in Reference Example 1 were used, the adhesive prepared in Reference Example 4 was applied to both of them, dried and cooled in the same manner as in Example 1 in a fixed state. Ultraviolet rays were applied to bond.

When the weight was suspended in the same manner as in Example 1, the adhesive surface did not peel off.

Reference Example 5 A hydrogenated product of a copolymer obtained by ring-opening polymerization of a mixed monomer of MTD and dicyclopentadiene (DCP) (MTD / DCP = 70/30 molar ratio) (number-average molecular weight 27,000, water A plate similar to that of Reference Example 1 was prepared by injection molding with an addition ratio of almost 100% and a glass transition temperature of 133 ° C. (test piece B).

[Example 4] The ultraviolet-curable adhesive prepared in Reference Example 3 was applied to both the test piece A prepared in Reference Example 1 and the test piece B prepared in Reference Example 5, and the test piece A was fixed. In the same manner as in the above, adhesion was performed by irradiating ultraviolet rays.

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

[Reference Example 6] An addition copolymer of MTD and ethylene (ethylene content mol 6
(0%, number average molecular weight 32,000, glass transition temperature 130 ° C) was injection molded to prepare a plate similar to that of Reference Example 1 (test piece C).

Example 5 The adhesive prepared in Reference Example 3 was applied to both the test piece A prepared in Reference Example 1 and the test piece C prepared in Reference Example 6,
After drying and cooling in the same manner as in Example 1 in the fixed state, the substrate was bonded by irradiating ultraviolet rays.

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

[Comparative Example 2] Two test pieces A prepared in Reference Example 1 were used, and an epoxy-based adhesive (Cemedine Super 5 manufactured by Cemedine Co., Ltd.) was applied to both of them and immediately fixed.

After curing at 20 ± 2 ° C. for 24 hours, the weight was hung in the same manner as in Example 1 and the adhesive surface was peeled off.

[Comparative Example 3] Two test pieces A prepared in Reference Example 1 were used, and a polyurethane-based adhesive (Cemedine 700, trade name, manufactured by Cemedine Co., Ltd.) was applied to both of them and immediately fixed.

After curing at 20 ± 2 ° C. for 24 hours, the weight was hung in the same manner as in Example 1 and the adhesive surface was peeled off.

[Comparative Example 4] Two test pieces A prepared in Reference Example 1 were used, and an acrylic adhesive (manufactured by Konishi, trade name: Bond VP-
2000) and fixed immediately.

After curing at 20 ± 2 ° C. for 24 hours, the weight was hung in the same manner as in Example 1 and the adhesive surface was peeled off.

Example 6 Using the test piece A prepared in Reference Example 1 and an aluminum plate having a thickness of 2 mm, the ultraviolet-curable adhesive prepared in Reference Example 1 was applied to both of them, and the two were fixed to Example 1 in a state where they were fixed. After drying and cooling in the same manner, ultraviolet rays were applied to bond.

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

Example 7 Using the test piece A prepared in Reference Example 1 and a 5 mm-thick brass plate, the ultraviolet-curable adhesive prepared in Reference Example 1 was applied to both of them, and the test piece A and Example 1 were fixed. After drying and cooling in the same manner, ultraviolet rays were applied to bond.

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

[Example 8] The test piece A prepared in Reference Example 1 and a steel plate 1 mm thick (SUS31
6), the ultraviolet-curable adhesive prepared in Reference Example 1 was applied to both of them, dried and cooled in the same manner as in Example 1 in a fixed state, and then irradiated with ultraviolet rays for adhesion.

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

[Example 9] A test piece A prepared in Reference Example 1 and a polycarbonate plate having a thickness of 2 mm (trade name: Ubilon H-40 manufactured by Mitsubishi Gas Chemical Company, Inc.)
00), dried and cooled in the same manner as in Example 1 in a state in which both were coated with the ultraviolet-curable adhesive prepared in Reference Example 1 and fixed, and then bonded by irradiating ultraviolet rays. .

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

Example 10 The test piece A prepared in Reference Example 1 and a 2 mm-thick PMMA plate (molded by Mitsubishi Rayon Co., Ltd. under the trade name Acrypet VH) were used. After the curable adhesive was applied and fixed and dried and cooled in the same manner as in Example 1, the adhesive was applied by irradiating ultraviolet rays.

When the weight was hung in the same manner as in Example 1, the adhesive surface did not peel off.

[Reference Example 7] UV-curable adhesive (trade name: 300 manufactured by Three Bond Co., Ltd.)
6, Type without filler) For 100 parts by weight,
20 parts by weight of talc (a first-class product of Wako Pure Chemical Industries, Ltd.) was added to obtain an adhesive composition.

[Example 11] Two test pieces A prepared in Reference Example 1 were used, and the ultraviolet-curable adhesive prepared in Reference Example 7 was applied to both of them. And glued.

When the weight was suspended in the same manner as in Example 1,
The adhesive surface did not peel off.

[Reference Example 8] Urethane acrylate resin (trade name: XP, manufactured by Nippon Gosei Co., Ltd.)
-7000B) 20 parts by weight, trimethylolpropane triacrylate 50 parts by weight, polystyrene resin (manufactured by Idemitsu Petrochemical Co., trade name: Styrol HF10) 30 parts by weight, photopolymerization initiator (manufactured by Merck, trade name Darocur 1173) 2 parts by weight Were mixed to obtain an adhesive composition.

Example 12 Two test pieces A prepared in Reference Example 1 were used, and the ultraviolet-curable adhesive prepared in Reference Example 8 was applied to both of them and irradiated with ultraviolet rays in the same manner as in Example 1 in a fixed state. And glued.

When the weight was suspended in the same manner as in Example 1,
The adhesive surface did not peel off.

As is clear from the above Examples and Comparative Examples, molded articles made of thermoplastic saturated norbornene-based polymer, or when bonding a molded article and a different material,
It can be seen that when an ultraviolet curable adhesive is used as the adhesive, good adhesive strength can be obtained.

In the examples, a plate-like test piece obtained by injection molding of a thermoplastic saturated norbornene-based polymer was used as an adhesive. However, since the magnitude of the adhesive force is determined by the material, the molding method, the shape of the molded product, or the molecular weight of the material were used. It is clear that the present invention is not limited by the present invention.

The UV-curable adhesive, the UV-curable protective coating agent and the UV-curable hard coat agent have basically the same composition, although there are slight differences in the monomers and oligomers used and the viscosity of the materials. Therefore, as an application of this technology, a method of forming surface protection when a surface made of a thermoplastic saturated norbornene-based polymer and a surface made of another material such as a metal are continuous on the same surface, for example, a thermoplastic saturated It is also useful as a method for forming a protective film for a recording film on an optical information disk substrate made of a norbornene-based polymer.

〔The invention's effect〕

According to the present invention, there is provided a method for bonding molded articles made of a thermoplastic saturated norbornene-based polymer, or a molded article and a different material, wherein the adhesion is improved.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-150529 (JP, A) JP-A-63-121085 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C09J 5/00-5/10 C09J 133/00-133/26 C08J 5/00-5/24

Claims (1)

(57) [Claims] 1. A method for bonding molded articles of a thermoplastic saturated norbornene polymer or a molded article and a different material, wherein the adhesive is a monofunctional acrylate monomer, a polyfunctional acrylate monomer, Polyester acrylate with acryloyl group, epoxy acrylate with epoxy group of epoxy resin esterified with acrylic acid and functional group as acryloyl group, polyurethane acrylate, unsaturated polyester with double bond in molecular chain, and 1,2-polybutadiene Using a UV curable adhesive containing at least one selected from a reactive monomer and / or a reactive oligomer selected from the group consisting of a photopolymerization initiator, a solvent, a thermoplastic polymer inert to ultraviolet light, and a filler; Apply the adhesive to the adherend and paste the coated surface A method of bonding plastic molded articles, comprising irradiating ultraviolet rays, performing radical polymerization with a photopolymerization initiator, and curing the resulting mixture.