JPH07278500A - Ultraviolet-curable pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which brings about only a slight decrease in bonding strength to a bonded object even in long-term standing at a high temp. by using specific (meth)acrylic esters, a specific oligoacrylate, and a photopolymerization initiator. CONSTITUTION:This adhesive composition comprises 100 pts.wt. (meth)acrylic ester of a 4-14C alkyl alcohol (e.g. 2-ethylhexyl acrylate), 51-5 pts.wt. alkylphenoxypolyalkylene glycol (meth)acrylate (e.g. nonylphenoxydipropylene glycol acrylate), a polyfunctional oligoacrylate having a mol.wt. of 300 or higher (e.g. hydroxypivalic acid neopentyl glycol diacrylate), and a photopolymerization initiator (e.g. 2-hydroxy-2-methyl-1-phenylpropan-1-one).

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 composition and a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer obtained by curing the UV-curable pressure-sensitive adhesive composition by UV irradiation.

[0002]

2. Description of the Related Art Alkyl alcohols having 4 to 14 carbon atoms
Acrylic ester monomer, a monofunctional monomer that copolymerizes with it, a polyfunctional acrylate oligomer that serves as a cross-linking agent, and a UV-curable pressure-sensitive adhesive composition comprising a photopolymerization initiator are cured with UV light to produce an adhesive tape. Get Belgiu
m, 675,420, 5/1966 and U.S. Pat. No. 4,181,752 (January 1, 80).

Among the (meth) acrylic acid ester monomers of alkyl alcohol having 4 to 14 carbon atoms, the one generally used is butyl acrylate having 4 carbon atoms.
And 2-ethylhexyl acrylate and isooctyl acrylate having 8 carbon atoms. Adhesives containing these as the main components have a strong tack and a large initial adhesive force, and are therefore widely used in adhesive tapes and their applied products.

[0004]

A double-sided adhesive tape having a strong tack and a large initial adhesive strength adheres well to an object having an uneven surface or various polar or non-polar objects, and even when a low temperature is applied, an adhesive layer is added. It has the preferable feature that it is not necessary to bond it by heating. However, if the adhesive adhered with these double-sided adhesive tapes is left at a high temperature, the adhesive property is deteriorated and the adhesive strength is largely decreased, so that the temperature rating defined by UL standard (UL746C) cannot be satisfied.

The present invention is a temperature rating 1 required by the UL standard (UL746C evaluation of polymer materials used in electrical equipment).
1000 at a temperature of 153 ° C, which is a test condition satisfying 05 ° C.
The adhesive strength is 50% of the initial value after leaving for a long time and leaving the adhesive.
% Of the UV-curable adhesive composition, which does not deteriorate, and is used to produce a double-sided adhesive tape.

[0006]

The present inventors have found that the number of carbon atoms is 4
From 14 alkyl alcohol (meth) acrylic acid esters, alkylphenoxypolyalkyleneglycol (meth) acrylates, polyfunctional acrylate oligomers having a molecular weight of 300 or more, and a photoinitiator, It was found that the adhesive tape obtained by irradiating this with ultraviolet rays showed a small decrease in adhesive strength even when left at high temperature.

The photoinitiator is most preferably an acetophenone type or a benzoin type. After the above-mentioned pressure-sensitive adhesive composition is applied to a release-treated support, it is irradiated with ultraviolet rays by a plurality of insect trap fluorescent lamps having a main wavelength of 352 nm. At least 80% of the pressure-sensitive adhesive composition is polymerized with ultraviolet rays emitted from a fluorescent lamp for insect trapping, and then ultraviolet rays from a high-pressure mercury lamp having a main wavelength of 365 nm are irradiated to obtain a double-sided adhesive tape.

The present invention will be described in detail below. In the presence of a photoinitiator, a (meth) acrylic acid ester monomer having an alkyl alcohol having 4 to 14 carbon atoms, a monofunctional monomer copolymerizable therewith, and a polyfunctional acrylate oligomer serving as a crosslinking agent are used. To obtain an adhesive tape by irradiating with ultraviolet rays at Belgian Patent No. 675,420 (1966)
And U.S. Pat. No. 4,181,752 (1980
Year).

It is generally considered that a double-sided adhesive tape having a large tack and a good initial adhesive strength is excellent. However, when an adherend adhered with a double-sided pressure-sensitive adhesive tape manufactured by an ultraviolet curing method is left at a high temperature, the adhesive strength is reduced, and it is difficult to pass the temperature rating defined by UL standard (UL746C).

In the present invention, an adherend adhered by a double-sided adhesive tape is tested at a temperature rating of 105 ° C. and a test temperature of 153 ° C.
The present invention relates to a UV-curable pressure-sensitive adhesive composition in which a decrease in the adhesive strength thereof is suppressed even when left to stand and a double-sided pressure-sensitive adhesive tape comprising the UV-curable pressure-sensitive adhesive composition.

The temperature rating of 105 ° C. defined by UL746C (evaluation of polymer materials used in electric and electronic equipment) requires that the adhesive adhered with an adhesive is left in an air circulation oven at 153 ° C. for 1000 hours. It is that the adhesive strength does not deteriorate by 50% or more with respect to the initial value after standing.

The nonylphenoxypolyalkyleneglycol (meth) acrylate used in the present invention is a monofunctional acrylate and is well cured by ultraviolet rays. Further, since it has a nonyl group having 9 carbon atoms, it is also well compatible with the acrylate ester monomer of the alkyl alcohol having 4 to 14 carbon atoms as the main component.

The nonylphenoxypolyalkylene glycol (meth) acrylate is preferably selected from nonylphenoxypolyethylene glycol glycol acrylate and nonylphenoxypolypropylene glycol acrylate. The degree of polymerization n of polyethylene glycol and polypropylene glycol does not matter, and generally n is at least one selected from the group of compounds having a number of about 2 to 10.

The present invention has been made as a result of extensive studies on a method for suppressing a decrease in adhesive strength at high temperatures. The ether bond of polyalkyleneglycol in nonylphenoxypolyalkyleneglycol (meth) acrylate is oxidized. It can be estimated that it is effective against deterioration. Both monomers may be used alone or in combination. The amount used is preferably 5 to 15 parts by weight with respect to 100 parts by weight of a (meth) acrylic acid ester monomer of an alkyl alcohol having 4 to 14 carbon atoms as a main component.

[0015]

EFFECTS OF THE INVENTION Even if an adhesive is left at a high temperature, the adhesive strength is not significantly reduced. U
Satisfies the temperature rating of 105 ° C specified in L746C (evaluation of polymer materials used in electric and electronic devices). It satisfies the temperature rating required for electric and electronic devices, and is particularly suitable for bonding a reinforcing material to a flexible circuit board. Since the solvent-free UV-curable pressure-sensitive adhesive composition is used, the double-sided pressure-sensitive adhesive tape can be produced by a method having no environmental pollution and a high safety against fire and the like.

[Adhesive Composition of the Present Invention] (Meth) acrylic acid ester of alkyl alcohol having 4 to 14 carbon atoms in the alkyl group as the main component contains a few percent of a monomer having a functional group.
Therefore, it is preferable that the content is from several to 10%. Most preferred is about 10%.

The nonylphenoxypolyalkylene glycol is preferably selected from nonylphenoxypolyethylene glycol glycol acrylate and nonylphenoxypolypropylene glycol acrylate. Both monomers may be used alone or in combination. The amount used is 100 parts by weight of 100 parts by weight of a (meth) acrylic acid ester monomer of an alkyl alcohol having 4 to 14 carbon atoms as a main component.
It is preferable to add 5 to 15 parts by weight.

The present invention further relates to an ultraviolet-curable pressure-sensitive adhesive composition comprising 0.0001 to 0.02 mol of a polyfunctional oligoacrylate having a molecular weight of 300 or more and a photoinitiator which can be copolymerized therewith. .

The number of carbon atoms that can be used in the present invention is 4 to 1.
Examples of (meth) acrylic acid ester monomers of four alkyl alcohols include butyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, isononyl acrylate, isooctyl acrylate. A rate, a lauryl acrylate, etc. can be used.
In addition, tetrahydrofurfryl acrylate, isobonyl acrylate, ethoxy acrylate, butoxy acrylate, phenoxy acrylate, cyclohexyl acrylate and the like can be mentioned.

The (meth) acrylic acid ester monomer having an alkyl alcohol having 4 to 14 carbon atoms is a monomer having a functional group, such as acrylic acid, methacrylic acid or 2-hydroxyethyl acrylate. , 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl (meth) acrylate, glycidyl methacrylate from several% to several tens%.
It is preferably contained, and most preferably about 10%.

The polyfunctional oligoacrylate having a molecular weight of 300 or more has a carbon number between vinyl groups of 10 or more. For example, enene ethylene glycol diacrylate.
G (New Nakamura Chemical Co., Ltd., NK ester A-400
Etc.), tetradecaethylene glycol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK ester A-600, etc.), polyalkylene glycol diacrylate, ethylene oxide-modified bisphenol A diacrylate (Kyoeisha fat and oil). Chemical Industry Co., Ltd., BP-4EA, etc.), ethylene oxide modified bisphenol A diacrylate (Kyoeisha Oil & Fat Chemical Industry Co., BP4PA, etc.), ethylene oxide modified trimethylolpropane triacrylate (Kyoeisha Oil & Fat Chemical Industry). Company, TPM-6EO-3A, etc.), hydroxypivalic acid pentylglycol diacrylate (manufactured by Nippon Kayaku Kogyo Co., Ltd., KAYARD MANDAA, etc.) and its derivatives (Nippon Kayaku Kogyo Co., Ltd., KAYARAD H)
X-220, KAYARAD HX-620, etc.) and the like. Further, oligoester acrylate and oligourethane acrylate can also be used.

The amount of addition is 0.0001 to 0.02 mol based on 100 parts by weight of (meth) acrylic acid ester monomer of alkyl alcohol having 4 to 14 carbon atoms. Target. If it is less than 0.0001 mol, the heat-resistant holding power of the adhesive tape will be poor, and if it is added in excess of 0.02 mol, the tack of the adhesive tape will be reduced.

The photopolymerization initiator is most preferably an acetophenone-based or benzoin-based one, for example, generally commercially available 4-phenoxydicycloacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 2-hydroxy-. Examples thereof include 2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, benzoin, benzoin methyl ether, benzoin isobutyl-terl, benzyl dimethyl ketal, and mixtures thereof.

The amount of addition is such that a (meth) acrylic acid ester monomer of an alkyl alcohol having 4 to 14 carbon atoms, a nonylphenoxypolyalkylene glycol (meth) acrylic acid ester and a polyfunctional compound having a molecular weight of 300 or more. It is effective to add 0.005-0.1 parts by weight to the total 100 parts by weight of the oligoacrylate. If the addition amount is 0.005 parts by weight or less, the polymerization proceeds, and if it is 0.1 parts by weight or more, the heat resistance retention becomes poor.

On the other hand, since the viscosity of the liquid of the above-mentioned composition mainly composed of the monomer is as low as 0.002 to 0.02 Pa · s, it is difficult to apply it to the support, so that the polymer is dissolved or not. Prepolymerize the product to increase the viscosity of the composition from 1 to 10
It is necessary to raise it to about Pa · s.

The polymer is selected from polymers that dissolve or swell in monomers, such as acrylic rubber, styrene butadiene rubber, isoprene rubber, styrene isoprene block polymer, styrene butadiene block polymer, low molecular weight polyethylene, low molecular weight polyisoprene and the like. . The amount used is 1 to 15% by weight.

It is also effective to mix a filler to increase the viscosity of the monomer solution. Silica, aluminum hydroxide, barium sulfate, clay, talc, fine powder aerosil, glass bubbles, glass beads, plastic micro balloons, plastic fine powder, etc. can be used, but they block the transmission of ultraviolet rays. It is necessary to add in a range.

[Production of Double-sided Adhesive Tape of the Present Invention] An ultraviolet-curable pressure-sensitive adhesive composition is applied to one side of a transparent polyester film which has been subjected to a double-sided peeling treatment, to a predetermined thickness. Further, a transparent polyester film having a one-sided peeling treatment is superposed thereon, the thickness is adjusted by passing between rolls set at predetermined intervals, and then ultraviolet rays are irradiated to produce a double-sided adhesive tape.

Also, after applying the UV-curable pressure-sensitive adhesive composition to one surface of a transparent polyester film obtained by subjecting the pressure-sensitive adhesive composition to peeling treatment on both sides, a UV-permeable substrate is placed on the pressure-sensitive adhesive layer. Place it on a transparent polyester film that has been subjected to a peeling treatment on one side after impregnating the adhesive layer with the base material, and similarly adjusting the thickness to a predetermined value between rolls, and irradiating ultraviolet rays to produce an adhesive tape. You can also

[Ultraviolet Irradiation Method] In the present invention, a straight tubular fluorescent lamp for trapping insects that selectively emits light having a wavelength of 352 nm is used as an energy source for causing a polymerization reaction. Further, by arranging a plurality of the fluorescent lamps, it is possible to use lights having increased intensity by interfering with each other.

The light emitted by one fluorescent lamp for insect trapping is weak enough to be stared at by the naked eye with a light intensity of about 0.5 mw / cm ^2, but 1.5 mw /
Light with an intensity of cm ² or more is obtained, and the polymerization reaction time can be shortened, which is economical. In order for the light of the straight tube-shaped fluorescent lamp for insect trapping to interfere with each other, it is better to bring them closer to each other, and conversely, the light intensity does not increase if they are separated from each other. The interval is 0m
It is preferably from m to 100 mm.

At least 80% or more of the monomers are polymerized by irradiation with a fluorescent lamp for trapping insects. afterwards,
The polymerization is completed by irradiating it with ultraviolet rays from a high-pressure mercury lamp having a main wavelength of 365 nm. The polymerization progresses to nearly 100% even with the insect trap fluorescent lamp alone, but the tack of the obtained adhesive tape tends to be low. When a high-pressure mercury lamp is used together, a predetermined tack is exhibited and the polymerization time can be shortened, which is economical.

As the high pressure mercury lamp, it is preferable to use an ozoneless type which does not generate ultraviolet rays in the low wavelength region of 200 nm or less. That is, ultraviolet rays in the low wavelength region turn oxygen in the air into ozone, which is harmful and promotes deterioration of the adhesive tape. High pressure mercury lamp output 30w / c
Any type more than m can be used. The intensity of the irradiation ultraviolet rays is preferably 30 mw / cm ² or more.

[0034]

EXAMPLES The present invention will be described in detail below with reference to various examples.

Example 1 A solventless pressure-sensitive adhesive liquid was prepared by the following steps. 2-ethylhexyl acrylate 9
100g of mixed monomer liquid consisting of 0g and 10g of acrylic acid
5 g of acrylic rubber (Toacron PS220, manufactured by Toa Paint Co., Ltd.) was stirred and dissolved in a container equipped with a stirrer for 48 hours. This solution was a viscous liquid having a viscosity of 1.5 Pa · s. Furthermore, 10 g of nonylphenoxydipropylene glycol acrylate (M-117, manufactured by Toagosei Kagaku).
Hydroxyl pivalate neopentylglycol diacrylate having a molecular weight of 312 (KAYARAD MANDA)
Nippon Kayaku Co., Ltd.) 0.0005 mol (0.156 g),
Acetophenone photoinitiator 2-hydroxy-2-methyl-1-phenylpropan-1-one (Darocur 117
0.03 g (manufactured by Merck & Co., Inc.) was added to obtain an ultraviolet-curable pressure-sensitive adhesive composition. Next, a transfer type double-sided adhesive tape was manufactured by the following steps.

Thickness 5 of which both sides are peeled off with a silicone
The ultraviolet-curable pressure-sensitive adhesive composition was applied to one surface of a 0 μm transparent polyester film so that the thickness was about 0.06 mm. A transparent polyester film having a thickness of 50 μm, one surface of which was peeled off with silicone, was placed thereon, and the thickness was adjusted by passing between the rolls so that the pressure-sensitive adhesive layer had a thickness of 0.06 mm. Next, ultraviolet rays were irradiated in an irradiation furnace in which a plurality of insect trapping fluorescent lamps having a main wavelength of 352 nm were set until the polymerization rate of the ultraviolet curable adhesive composition reached at least about 80%.

Irradiated. The light intensity was 0.44 mw / cm ² with only one lamp, but it increased to 2.00 mw / cm ² by setting multiple lamps.

Next, irradiation with a high-pressure mercury lamp having a main wavelength of 365 nm is performed to complete the polymerization of the ultraviolet-curable adhesive composition. As the high pressure mercury lamp, a lamp having an output of 80 w / cm was used. The irradiation intensity of ultraviolet rays was 35.5 mw / cm ² .

The double-sided adhesive tape obtained in Example 1 was evaluated as follows. [Adhesive strength] As the adherend, a stainless steel plate having a thickness of 2 mm, a width of 30 mm and a length of 120 mm and a polyimide film having a thickness of 0.025 mm (Kapton 100H manufactured by DuPont), which is polished with No. 280 water-resistant abrasive paper are used. did.

A double-sided adhesive tape having a width of 20 mm and a length of 100
Cut into mm, peel off the polyester film that has been peeled off on one side, and temporarily attach it to a stainless steel plate. Next, the other polyester film was peeled off, the polyimide film was placed thereon, and pressure-bonded at 80 ° C. and 5 kgf / cm ² for 10 seconds.

The adhesion test piece was placed in an air circulation oven adjusted to 153 ° C., 250 hours, 500 hours, 750
After 1000 hours, remove at 18 ℃ at 23 ℃
It was peeled off at a speed of 300 mm / min in the 0 degree direction, and the adhesive strength was measured.

As a result, the initial adhesive strength was 1.9 kg.
f / 2 cm, 250 hours, 500 hours, 75
The adhesive strength after 0 hours and after 1000 hours is 2.1 k each.
gf / 2c, 1.8kgf / 2cm, 1.8kgf / 2
c, 1.8 kgf / 2 cm, there was no decrease in adhesive strength.

[Heat-resistant holding power] The heat-resistant holding power was measured according to the method of measuring the holding power of JIS Z 0237. As the adherend, 28
A stainless steel plate having a thickness of 2 mm and an aluminum foil having a thickness of 0.05 mm, which was polished with No. 0 water resistant polishing paper, were used. The adhesive area was 25 × 25 mm for the stainless steel plate and 25 mm wide and 50 mm long for the aluminum foil.

The bonding method was carried out according to the preparation of the test piece for measuring the adhesive strength. After adhesion, a load of 1 kgf was applied vertically from the aluminum foil side, and the size of the deviation of the adhesion part was measured after standing at 180 ° C. for 1 hour. It was a double-sided pressure-sensitive adhesive tape with almost no deviation and excellent heat resistance retention.

[Examples 2 to 5] The amount of nonylphenoxydipropyleneglycol acrylate (M-117, manufactured by Toagosei Kagaku Co., Ltd.) used in Example 1 was 5 each.
g, 7.5 g, 12.5 g and 15 g were prepared, and double-sided adhesive tape was prepared in the same manner as in Example 1.
Manufactured and evaluated. The evaluation results are shown in Table 1.

Example 6 The nonylphenoxydipropylene glycol acrylate (M) used in Example 1 was used.
-117, manufactured by Toagosei Kagaku Co., Ltd.) was used as nonylphenoxytetraethyleneglycol acrylate (M-
113, manufactured by Toagosei Kagaku Co., Ltd.) and evaluated in the same manner.

Example 7 The nonylphenoxydipropyleneglycol acrylate (M used in Example 1
-117, manufactured by Toagosei Kagaku Co., Ltd.), and a half amount of nonylphenoxytetraethyleneglycol acrylate (M-1
13, manufactured by Toagosei Kagaku Co., Ltd.) and evaluated in the same manner.

Example 8 Multifunctional oligoacrylate KAYA used in Example 1
The same as Example 1 except that 0.0005 mol (0.354 g) of tetradecaethylene glycol diacrylate (NK ester A-600 manufactured by Shin Nakamura Chemical Co., Ltd.) having a molecular weight of 708 was used instead of RAD MANDA. Then, a double-sided adhesive tape was manufactured and evaluated. As a result, the initial adhesive strength was 2.1 kgf / 2 cm, but when left at 153 ° C. for 500 hours, it was 2.0 kgf / cm.
At 2 cm for 1000 hours, 50% or more of the initial value could be maintained at 1.7 kgf / 2 cm. Further, in the heat resistance holding power test at 180 ° C., the deviation was 0.2 mm.

[0049]

[Table 1] Adhesive strength (Kgf / 20mm) Deviation (mm) Example M117: M113 Initial value 500H 1000H Heat resistance retention 1 10 − 1.9 1.8 1.8 0 2 5 − 1.8 1.6 1.4 0.5 3 7.5 − 2.0 1.8 1.6 0.1 4 12.5 − 1.8 1.8 1.8 0 5 15 − 1.8 1.7 1.7 0.2 6 − 10 2.1 1.9 1.9 0.2 7 5 5 1.9 1.9 1.7 0.5 500H is the adhesive strength after leaving the adhesive for 500 hours at 153 ° C. 1000H is the adhesive strength after leaving the adhesive for 1000 hours at 153 ° C.

Comparative Example 1 A UV-curable pressure-sensitive adhesive composition obtained by removing all nonylphenoxydipropylene glycol acrylate (M-117, manufactured by Toagosei Chemical Industry Co., Ltd.) from the pressure-sensitive adhesive composition of Example 1. A double-sided adhesive tape was prepared and evaluated in exactly the same manner as in Example 1. As a result, the adhesive strength was 1.9 kgf / 2 cm in the initial stage, but was 1.0 kgf / 2 cm, 100 after 500 hours.
It was 0.7 kgf / 2 cm after 0 hours, and could not maintain 50% of the initial value.

[Comparative Example 2] The amount of nonylphenoxydipropylene glycol acrylate (M-117, manufactured by Toagosei Kagaku Co., Ltd.) in the pressure-sensitive adhesive composition of Example 1 was adjusted to 3 parts by weight to prepare Example 1 and Double-sided adhesive tape was prepared and evaluated in the same manner. It was As a result, the initial adhesive strength was 1.9 kgf / 2 cm, but after 1000 hours, it was 0.60 kgf / 2 cm, which was not able to hold 50% of the initial value.

Comparative Example 3 Except for using 20 parts by weight of nonylphenoxydipropylene glycol acrylate (M-117, manufactured by Toasei Chemical Industry Co., Ltd.) in the pressure-sensitive adhesive composition of Example 1, 20 parts by weight was used. An ultraviolet-curable pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive tape were prepared and evaluated in the same manner as in Example 1. As a result, the initial adhesive strength was 1.1 kgf / 2cm, but after 1000 hours it became 0.50 kgf / 2cm,
50% of the initial value could not be retained.

Claims (4)

[Reference number] SCP930098 [Claims] 1. A polyfunctional oligoacrylate having a molecular weight of 300 or more and 100 parts by weight of a (meth) acrylic acid ester of an alkyl alcohol having 4 to 14 carbon atoms and 5 to 15 parts by weight of an alkylphenoxypolyalkylene glycol. An ultraviolet-curable pressure-sensitive adhesive composition comprising a photopolymerization initiator. 2. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1, wherein the alkylphenoxypolyalkyleneglycol (meth) acrylate is nonylphenoxydipropyleneglycol. 3. The alkylphenoxypolyalkyleneglycol (meth) acrylate is nonylphenoxydiethyleneglycol.
The ultraviolet-curable pressure-sensitive adhesive composition as described above. 4. The ultraviolet ray according to claim 1, wherein the (meth) acrylic acid ester of an alkyl alcohol having 4 to 14 carbon atoms contains 10% by weight of a monomer having at least one functional group. Curable adhesive composition.