JP3352500B2 - Photopolymerizable composition and thermosetting adhesive sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylate-based photopolymerizable composition and a thermosetting adhesive sheet obtained by using the composition. The present invention relates to a thermosetting adhesive sheet that is cured by a heating operation after being attached.

[0002]

2. Description of the Related Art Adhesive sheets are utilized in various fields for fixing various members by utilizing the simplicity of the joining operation. However, since the pressure-sensitive adhesive sheet has conventionally realized the initial adhesiveness to the adherend by increasing the fluidity of the pressure-sensitive adhesive, the pressure-sensitive adhesive sheet cannot necessarily exhibit the same high adhesiveness as the adhesive. Had.

[0003] That is, there is a demand for an adhesive sheet having adhesiveness as a pressure-sensitive adhesive sheet at the initial stage of bonding to an adherend and having high adhesiveness after bonding after the bonding.

[0004] To meet such needs, so-called adhesives have been proposed in which a pressure-sensitive adhesive and an adhesive are combined. For example, Japanese Patent Publication No. 50-28970 discloses a technique in which a thermosetting resin such as an epoxy resin is combined with an acrylic rubber polymer to obtain tackiness and high adhesiveness after curing.

Further, Japanese Patent Application Laid-Open No. 2-272076 discloses a pressure-sensitive thermosetting adhesive made from a photopolymerizable composition comprising an acrylate monomer and an epoxy resin as raw materials. The publication describes that this pressure-sensitive thermosetting adhesive achieves quick tackiness and high adhesiveness.

[0006]

However, in the above-mentioned conventional pressure-sensitive thermosetting adhesive, the heat resistance was insufficient because the acrylic polymer and the epoxy compound were not crosslinked even after curing. For this reason, the range in which the pressure-sensitive thermosetting adhesive can be used has been considerably limited.

[0007] The object of the present invention against the above problems is as follows.
Providing a novel photopolymerizable composition, and using the composition, while having high adhesiveness, also has sufficient heat resistance, and also for joining metal members and the like where heat resistance is required It is to provide a thermosetting adhesive sheet that can be used.

[0008] The present inventors photopolymerize and mold a photopolymerizable composition in which an acrylate monomer selected from an ester of an epoxy group-containing alcohol and (meth) acrylic acid is mixed with an acrylate monomer. As a result, the above object has been achieved.

[0009]

That is, according to the present invention, (a) an alkyl group having 1 to 12 carbon atoms (meth)
30 to 95 parts by weight of at least one acrylate monomer selected from the group consisting of alkyl acrylates, and (b) a vinyl compound monomer having an unsaturated double bond copolymerizable with the acrylate monomer (a) Two
40 parts by weight, and (c) at least one acrylate-based monomer selected from the group consisting of an ester of an epoxy group-containing alcohol and (meth) acrylic acid.
Parts by weight and (d) epoxy resin 5 having no photopolymerizable group
To 100 parts by weight, (e) 0.01 to 5 parts by weight of a photopolymerization initiator, and (f) 0.1 to 10 parts by weight of a thermosetting agent for an epoxy resin. .

Further, according to the present invention, there is provided a thermosetting adhesive sheet having a pressure-sensitive adhesive layer containing an epoxy group in an unreacted state, obtained from the photopolymerizable composition.

Further, according to the present invention, there is provided a composite pressure-sensitive adhesive layer containing an epoxy group in an unreacted state, which is obtained from a composition obtained by blending the photopolymerizable composition with glass fiber. A thermosetting adhesive sheet is provided.

The components constituting the photopolymerizable composition according to the present invention and the method of photopolymerizing the composition will be described below.

(Acrylate Monomer (a)) The acrylate monomer (a) is the main monomer component of the composition of the present invention, and is used for producing a known photopolymerized acrylic viscoelastic product.

As the acrylate monomer, an alkyl acrylate or alkyl methacrylate having an alkyl group of 1 to 12, preferably 4 to 12, carbon atoms is used. Specific examples of these acrylate monomers include n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, and the like.

These monomers are used alone or in combination of two or more. From the balance of tackiness and cohesiveness, etc., the homopolymer generally has an alkyl acrylate having a glass transition temperature of −50 ° C. or lower as a main component, and as a comonomer, a lower alkyl group (meth).
It is preferable to use acrylic esters or the following vinyl monomers (b).

(Vinyl monomer (b)) The other vinyl monomer (b) copolymerizable with the acrylate monomer is
Those which are non-reactive with the epoxy group are preferred from the viewpoint of storage stability of the thermosetting adhesive sheet. For example, vinyl monomers such as acrylic acid and methacrylic acid may be cured with time after polymerization molding, and the tackiness of the adhesive sheet may be reduced. Therefore, in the present invention, for example, acrylonitrile, methacrylonitrile, N-vinylpyrrolidone, acrylamide, isobornyl (meth)
Acrylate, acryloyl morpholine, alkoxyalkyl acrylate and the like can be mentioned. Particularly preferred among these vinyl monomers are N-
It is vinylpyrrolidone.

These vinyl monomers are used alone or in combination of two or more.

(Epoxy group-containing acrylate monomer
(c)) Examples of the epoxy group-containing acrylate monomer (c) include glycidyl (meth) acrylate and alicyclic epoxy (meth) acrylate (Cyclomer, trade name, manufactured by Daicel Chemical Industries, Ltd.). The acrylate-based monomer containing an alicyclic epoxy group has a low glass transition temperature of the obtained copolymer even when blended in a high ratio,
A highly tacky adhesive is obtained.

Epoxy group-containing acrylate monomer
(c) is used in an amount of 0.5 to 50 parts by weight based on 100 parts by weight of the acrylate monomer (a). monomer
When the compounding ratio of (c) is less than 0.5 part by weight, the crosslinking reaction between the acrylic polymer and the epoxy resin is not sufficiently performed, and the heat resistance becomes insufficient. On the other hand, if the blending ratio of the monomer (c) exceeds 50 parts by weight, the cured product is excessively crosslinked, so that the interface is easily peeled at a high temperature.

(Epoxy resin (d)) Epoxy resin (d)
Does not have a photopolymerizable group, and examples thereof include a bisphenol epoxy resin, a phenolic epoxy resin, and a halogenated bisphenol epoxy resin.

Among these epoxy resins, those using a monomer having a high softening point as a raw material are preferable, and as this example, those having one epoxy group per molecule in the high softening point resin compound are preferable.

(Photopolymerization initiator (e)) Examples of the monofunctional photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [Darocur 2959: Ciba-Geigy]. 1-hydroxycyclohexyl phenyl ketone [Irgacure 184:
Ciba-Geigy], α-hydroxy-α, α-dimethylacetophenone [Darocur 1173: Ciba-Geigy]; acetophenone-based initiators such as methoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; benzoin ethyl ether, benzoin isopropyl Benzoin ether initiators such as ethers; ketal initiators such as benzyl dimethyl ketal; and other examples include halogenated ketones, acylphosphinoxides, and acylphosphonates.

(Thermosetting agent for epoxy resin (f)) In the present invention, a curing agent
(f) is blended.

The curing agent (f) may be any one capable of heating and curing an epoxy resin, and examples thereof include curing agents such as imidazole type, dicyandiamide, and polyamine salts.
CR hardener 3636 (trade name, manufactured by AC R).

The proportions of these components are 30 to 95 parts by weight of the acrylate monomer (a), 2 to 40 parts by weight of the vinyl compound monomer (b), and 0.5 to 50 parts by weight of the epoxy group-containing acrylate monomer (c). Parts by weight, epoxy resin (d)
5 to 100 parts by weight, 0.01 to 5 parts by weight of a photopolymerization initiator (e), 0.1 to 10 parts by weight of a thermosetting agent (f) for an epoxy resin, and preferably 40 to 100 parts by weight of an acrylate monomer (a). ~
60 parts by weight, 20 to 30 parts by weight of a vinyl compound monomer (b), 1 to 3 parts of an epoxy group-containing acrylate monomer (c)
10 parts by weight, 20 to 80 parts by weight of epoxy resin (d), 0.1 to 1 part by weight of photopolymerization initiator (e), and 0.5 to 5 parts by weight of thermosetting agent for epoxy resin (f).

(Crosslinking Agent) The photopolymerizable composition of the present invention contains a polyfunctional vinyl compound as a crosslinking agent together with the above photopolymerization initiator in order to increase heat resistance and cohesive strength at high temperatures. be able to.

Examples of such a crosslinking agent include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and neopentyl glycol di (meth) acrylate. Acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, other epoxy acrylates,
Examples thereof include polyester acrylate and urethane acrylate.

Such a crosslinking agent is generally added in an amount of 5 parts by weight or less based on 100 parts by weight of the total of the monomer components (a) to (c). By the incorporation of the cross-linking agent, cross-linking occurs between polymer molecules in the photopolymerization reaction, and the heat resistance of the pressure-sensitive adhesive is improved. In the adhesive state before curing, the cohesive force at a high temperature increases, and the holding force in the curing process improves.

(Tackifier) The photopolymerizable composition according to the present invention preferably contains a tackifier.

[0030] As tackifier fire to be used in the present invention, rosin resins, modified rosin resins, terpene resins, terpene phenol resins, aromatic modified terpene resins, C ₅ and C ₉ petroleum resins, and the like coumarone resin.

In the present invention, those having no reactivity with the epoxy group are preferable, and those having an effect of improving the initial tackiness are preferable. Examples thereof include alicyclic hydrocarbon resins, disproportionated rosin ester resins, hydrogenated terpene phenols, and the like.

(Other Additives) The photopolymerizable composition according to the present invention may contain commonly used additives such as a thickener, a thixotropic agent, a bulking agent and a filler.

As the thickener, acrylic rubber, epichlorohydrin rubber, isoprene rubber, butyl rubber and the like are used.

The photopolymerizable composition can be partially polymerized by irradiating light to increase the viscosity.

In the present invention, since the epoxy group is also grafted on the partial polymer, the partial polymer and the monomer are
It also has the property that it is co-crosslinked by heating and can further improve heat resistance.

As the thixotropic agent, colloidal silica, polyvinylpyrrolidone and the like are used.

As the extender, calcium carbonate, titanium oxide, clay and the like are used.

As the filler, inorganic hollow bodies such as glass balun, alumina balun and ceramic balun; organic spherical bodies such as nylon beads, acrylic beads and silicon beads; organic hollow bodies such as vinylidene chloride and acrylic balun; polyester and rayon Single fibers such as nylon, glass and the like are used.

In the present invention, when glass fiber is blended with the photopolymerizable composition, the epoxy group forms a chemical bond with the surface of the glass fiber, so that a strong reinforcing effect can be exhibited.

(Conditions of photopolymerization process) As a lamp used for light irradiation, a lamp having a light emission distribution at a wavelength of 400 nm or less is used. For example, a low-pressure mercury lamp, a medium-pressure mercury lamp,
A high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, and the like are used. Among these, the chemical lamp efficiently emits light in the active wavelength region of the initiator, and has low light absorption of the composition components other than the initiator, so that light is transmitted to the inside to produce a product with a thick film. Preferred for

The intensity of light irradiation on the photopolymerizable composition by the lamp is a factor that affects the degree of polymerization of the obtained polymer, and is appropriately controlled for each performance of the target product. When a cleavage type initiator having a normal acetophenone group is blended,
The light intensity in a wavelength region effective for photodecomposition of the initiator (light varying from 365 to 420 nm is usually used depending on the initiator) is preferably from 0.1 to 100 mW / cm ² .

Photopolymerization in the present invention is inhibited by oxygen in the air or oxygen dissolved in the photopolymerizable composition. Therefore, light irradiation must be performed using a method capable of eliminating the inhibition of oxygen reaction. As one of the methods, the photopolymerizable composition is covered with a film made of polyethylene terephthalate or Teflon to cut off contact with oxygen,
There is a method of irradiating the composition with light through this film. Further, the composition may be irradiated with light through a light-transmitting window in an inert atmosphere in which oxygen is replaced by an inert gas such as nitrogen gas or carbon dioxide gas. In order to sufficiently complete the polymerization of the photopolymerizable composition in the latter method until the conversion becomes 99.7% or more, the oxygen concentration in the irradiation atmosphere needs to be 5000 ppm or less.
The molecular weight of the polymer product obtained by light irradiation of the composition decreases with increasing atmospheric oxygen concentration. To achieve a molecular weight similar to the molecular weight of a product obtained by polymerization in a completely inert atmosphere, the oxygen concentration in the atmosphere should be 1000 pp.
m. Further, the extremely thin surface layer portion of the photopolymerizable composition is more susceptible to reaction inhibition by oxygen than the inside of the polymer, and the cohesive strength is reduced. In order for the surface layer to have the same cohesiveness as the inside, the oxygen concentration in the atmosphere should be 300
It is desirable to be below ppm.

When light irradiation is performed in the inert zone, a constant amount of an inert gas is always introduced into this zone in order to keep the atmospheric oxygen concentration at a low level. Due to this introduced gas, an air current is generated on the surface of the photopolymerizable composition, and monomer evaporation occurs. The air velocity required to keep this evaporation level low is preferably such that the relative velocity with the composition moved with the support in this zone is 1 m / sec or less, more preferably 0.1 m / sec. It is less than sec. If the airflow velocity is set to about 0.1 m / sec, evaporation by the airflow can be substantially suppressed.

The photopolymerization reaction is carried out at a low temperature, for example, at -5 to 30 ° C, preferably at -5 to 10 ° C in order to avoid a reaction between epoxy groups. The cause of the temperature rise is
These are radiation heat from the lamp and heat of polymerization of the monomer. Therefore, the photopolymerization reaction is carried out at a low temperature by using a light cut filter to suppress the radiation heat of the lamp, and by contacting the polymer with a cooling back plate or the like during the light irradiation to actively remove the polymerization heat. be able to.

By the above method, the thermosetting adhesive sheet of the present invention having the pressure-sensitive adhesive layer containing the epoxy group in an unreacted state can be obtained.

Further, according to the present invention, a steel sheet composite can be obtained by applying the above-mentioned thermosetting adhesive sheet to a steel sheet and heating the sheet. This steel sheet composite is easy to press-form. Further, a steel sheet composite material can also be obtained by forming and processing a steel sheet composite sheet in which the thermosetting adhesive sheet is attached to a steel sheet, and then heating the sheet.

The heating is generally performed at 100 to 150 ° C.
For 0.1 to 1 hour.

In the present invention, when the steel sheet is a damping steel sheet for a vehicle, a steel sheet composite material for a vehicle can be obtained. Etc. can also be obtained.

[0049]

In the thermosetting adhesive sheet according to the present invention, an epoxy group is grafted on an acrylic polymer, and the epoxy resin is cross-linked together through the epoxy group by a heat curing operation. It is thought that the property is improved.

Also, the acrylic polymer itself has an epoxy group capable of forming a strong chemical bond with an adherend such as a metal at the interface of the sheet, so that it is considered that the adhesiveness is improved.

[0051]

Next, in order to specifically explain the present invention,
An example showing an example of the present invention will be described.

Example 1 70 g of 2-ethylhexyl acrylate, 30 g of N-vinylpyrrolidone, 20 g of epoxy acrylate (Cyclomer, trade name, manufactured by Daicel Chemical Co., Ltd.), and Epicoat 828 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) Name) 50 g and epoxy curing agent (ACR hardener 3636, manufactured by AC R, Inc., trade name) 5 g
And 0.05 g of hexanediol diacrylate and 0.1 g of a photopolymerization initiator Irgacure 184 (trade name, manufactured by Ciba Geigy) are stirred and mixed in a separable flask until uniform, and the photopolymerizable composition is mixed. Obtained.

The composition is maintained at 10 ° C.
Coating was performed so as to have a thickness of 400 μm on a 38 μm-thick PET substrate having a surface release property, which was in close contact with a cooled stainless steel plate. Next, an oxygen concentration of 200 ppm was added to this composition.
In the inert zone, a chemical lamp is used as an ultraviolet ray source, and the lamp intensity on the irradiation surface is ² mW / cm ² (36
The lamp height was set so as to obtain a light intensity measuring device UVR-1 having a maximum sensitivity at 5 nm (as an intensity value measured by Tokyo Optical Machine Co., Ltd.), and UV irradiation was performed for 5 minutes to obtain a thermosetting resin. An adhesive sheet was made.

Each performance of the adhesive sheet thus obtained was measured as follows.

1) Room temperature T peeling force An adhesive sheet sample having a width of 10 mm and a length of 10 mm was sandwiched between two pieces of aluminum foil having a thickness of 300 μm, a length of 100 mm and a width of 20 mm, and reciprocating pressure bonding was performed with a 2 kg roller. did. The obtained sample was allowed to stand for 24 days in an atmosphere condition of 23 ° C. and a humidity of 65 RH%.
Peeling was performed in a direction of 180 degrees at a tensile speed of 50 mm / min, and the maximum strength was defined as a normal temperature T peeling force.

2) Room temperature shearing force An adhesive sheet sample having a width of 10 mm and a length of 10 mm was sandwiched between two stainless steel plates having a thickness of 500 μm, and was subjected to one reciprocating pressure bonding with a 5 kg roller. The obtained sample was
After standing for 24 days in an atmosphere condition of 3 ° C. and a humidity of 65 RH%, a tensile speed of 50 mm / min was applied in an atmosphere condition of 23 ° C.
, And the maximum strength was defined as a normal temperature shearing force.

3) 140 ° C. shearing force 2) Except that the ambient temperature in the shear fracture test is 140 ° C.
Under the same conditions as in the above, the maximum shear stress was measured and set as 140 ° C. shear force.

4) Gel Fraction A 100 mg sample of the adhesive sheet was taken, immersed in 50 cc of tetrahydrofuran, and left at 23 ° C. for 24 hours.
The obtained swollen gel solution was filtered through a 200 mesh stainless steel net, the residue was dried, and the dry weight of the residue was measured. The ratio of this weight to the weight of the collected sample was defined as the gel fraction.

Each performance of the adhesive sheet is such that the room temperature T peeling force is 0.3 kg / cm, and the room temperature shearing force is 3.7 kg / c.
m ² . After attaching the sample,
When subjected to heat curing treatment for 0 minutes, the room temperature T peeling force was 2.3.
kg / cm, and the room temperature shearing force was 60 kg / cm ² .

The 140 ° C. shear force of the cured sample is 3.5.
kg / cm ² and the gel fraction was 80%.

Comparative Example 1 The same photopolymerizable composition as in Example 1 was used, except that no epoxy acrylate was added.
A thermosetting adhesive sheet was prepared in the same manner as in Example 1.

Each performance of the adhesive sheet was measured in the same manner as in Example 1. The room temperature T peeling force was 0.3 kg / cm, and the room temperature shearing force was 4.5 kg / cm ² . After the sample was stuck and heat-cured at 120 ° C. for 30 minutes, the room temperature T peeling force was 0.9 kg / cm, and the room temperature shearing force was 30 kg / cm ² . The 140 ° C. shear force of the cured sample was 0.5 kg / cm ² , and the gel fraction was 50%.

As described above, the sample of Comparative Example 1 was significantly inferior to the sample of Example 1 in the shearing force at 140 ° C. of the cured sample.

Example 2 50 g of 2-ethylhexyl acrylate, 10 g of N-vinylpyrrolidone, 50 g of epoxy acrylate (Cyclomer, manufactured by Daicel Chemical Co., Ltd.), Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Ltd.) Name) 10 g and epoxy curing agent (ACR hardener 3636, manufactured by AC R Co., trade name) 5 g
And 0.1 g of a photopolymerization initiator Irgacure 184 (trade name, manufactured by Ciba Geigy) were stirred and mixed in a separable flask until uniform, to obtain a photopolymerizable composition.

From the photopolymerizable composition, a thermosetting adhesive sheet was prepared in the same manner as in Example 1.

Each performance of the adhesive sheet was measured in the same manner as in Example 1. The room temperature T peeling force was 1.0 kg / cm, and the room temperature shearing force was 10.0 kg / cm ² . After attaching the sample, the sample was subjected to a heat curing treatment at 120 ° C. for 30 minutes. As a result, the room temperature T peeling force was 3.5 kg / cm,
The room temperature shearing force was 40 kg / cm ² . The 140 ° C. shear force of the cured sample was 4.0 kg / cm ² , and the gel fraction was 85%.

Example 3 The same photopolymerizable composition as in Example 1 was used in the same manner as in Example 1 except that 30 g of glass fiber chip was further added in addition to the components of Example 1. A thermosetting adhesive sheet was prepared.

Each performance of this adhesive sheet was measured in the same manner as in Example 1. The room temperature T peeling force was 0.3 kg / cm, and the room temperature shearing force was 5.0 kg / cm ² . After the sample was applied, it was subjected to a heat curing treatment at 120 ° C. for 30 minutes. As a result, the room temperature T peeling force was 2.5 kg / cm, and the room temperature shearing force was 100 kg / cm ² . The 140 ° C. shear force of the sample after curing was 6.0 kg / cm ² .

As described above, the sample of Example 3 exhibited better performance than the sample of Example 1.

[0070]

According to the thermosetting adhesive sheet of the present invention,
It is extremely excellent in heat resistance after heat curing, and can achieve high bonding reliability in bonding where heat resistance is required.

According to the thermosetting adhesive sheet of the present invention, the adhesive sheet has a sufficient cohesive force so as not to be detached from the adherend even in the initial heating step. Therefore, a fixing jig or the like is not required in the curing step even if the load of the adherend is slightly large.

Further, the composite steel sheet composited with the thermosetting adhesive sheet of the present invention is excellent in press formability without causing peeling during forming and without causing dents or the like in the steel sheet. The steel sheet composite of the present invention obtained by heat-hardening this composite steel sheet has high vibration damping properties and strength. Therefore, the steel sheet composite material is very useful as a vibration damping material for vehicles, electric products, and vibrating mechanical products.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI G03F 7/032 501 G03F 7/032 501 (58) Investigated field (Int.Cl. ⁷ , DB name) C08G 59/20 C09J 4 / 02 C09J 7/00-7/04 C09J 163/00-163/10 G03F 7/027 G03F 7/032

Claims (5)

(57) [Claims] 1. (a) 30 to 95 parts by weight of at least one acrylate monomer selected from the group consisting of alkyl (meth) acrylates having an alkyl group having 1 to 12 carbon atoms, and (b) 2 to 40 parts by weight of a vinyl compound monomer having an unsaturated double bond copolymerizable with the acrylate monomer (a) and (c) an ester of an epoxy group-containing alcohol and (meth) acrylic acid. 0.5 to 50 parts by weight of at least one acrylate monomer to be obtained; (d) 5 to 100 parts by weight of an epoxy resin having no photopolymerizable group; and (e) 0.01 to 5 parts by weight of a photopolymerization initiator. And (f) 0.1 to 10 parts by weight of a thermosetting agent for an epoxy resin. 2. A thermosetting adhesive sheet obtained from the photopolymerizable composition according to claim 1 and having a pressure-sensitive adhesive layer containing an epoxy group in an unreacted state. 3. A thermosetting material having a composite pressure-sensitive adhesive layer containing an epoxy group in an unreacted state, obtained from a composition obtained by blending the photopolymerizable composition according to claim 1 and glass fiber. Adhesive sheet. 4. A steel sheet composite obtained by applying the thermosetting adhesive sheet according to claim 3 to a steel sheet and heating the sheet. 5. A steel sheet composite for a vehicle, wherein the steel sheet according to claim 4 is a damping steel sheet for a vehicle.