JPH0455469B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pressure-sensitive adhesive that is cured by irradiation with active energy rays and has excellent physical properties. Conventionally, rubber-based or acrylic-based polymers have been used as pressure-sensitive adhesives, but mere thermoplastic polymers lack cohesive strength. Therefore, in the case of acrylic materials, functional groups have been introduced for crosslinking, a crosslinking agent has been added, and heat curing has been performed. However, it consumes a lot of time and energy. In order to improve these drawbacks, active energy ray-curable pressure-sensitive adhesives have recently been studied. This type of active energy ray-curable pressure-sensitive adhesive uses acrylic monomers or acrylic oligomers that have one or more unsaturated double bonds in the molecule that are reactive with active energy rays. It is known that it is blended with the combination. However, acrylic monomers or acrylic oligomers have problems of toxicity and rash when attached to the skin, and also have a unique odor, which causes odor pollution. Even when curing, the reaction is slow in air and requires long irradiation. Furthermore, physical properties as a pressure-sensitive adhesive after curing, such as adhesive strength, are not necessarily satisfactory. As a result of intensive research in view of the above-mentioned conventional problems, the present inventors have discovered that by using a polymer formed by polymerizing a unique (meth)acrylic monomer as an essential component, they can overcome the conventional problems. The inventors have now obtained an active energy ray-curable pressure-sensitive adhesive that cures rapidly and provides a pressure-sensitive adhesive with excellent performance without the use of acrylic monomers or acrylic oligomers. That is, the present invention provides an active polymer comprising a homopolymer of a (meth)acrylic monomer represented by the following general formula [A] or a copolymer of the monomer and a monomer copolymerizable therewith. It is an energy beam-curable pressure-sensitive adhesive. However, R ₁ is hydrogen or methyl group, R ₂ has 1 carbon number
-4 alkylene group, _R3 is an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4. In the (meth)acrylic monomer represented by the above general formula [A], R ₂ is an alkylene group having 1 to 4 carbon atoms, but it may be linear or branched, or
R ₃ is an alkyl group having 1 to 4 carbon atoms, which may also be linear or branched. Compared to conventional products, the composition of the present invention exhibits the unexpected effect of curing sufficiently even in an atmosphere containing oxygen and significantly improving the adhesive strength and/or cohesive strength of the resulting pressure-sensitive adhesive. It is. To explain each component constituting the composition of the present invention, the (meth)acrylic monomer represented by the above general formula [A] is an essential monomer, and examples of the monomer include, for example, methoxyethyl ( meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxyethoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, methyl triglycol (meth)acrylate, 1-butoxypropyl (meth)acrylate , 3-methoxybutyl (meth)acrylate, 1-ethoxybutyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, methoxymethyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, ethoxymethyl (meth)acrylate Examples include acrylate. Among these monomers, R ₁ is hydrogen,
R ₂ is a linear or branched alkylene group having 1 to 4 carbon atoms, R ₃ is an alkyl group having 1 to 4 carbon atoms, and n is 1
It is preferable from the viewpoint of ease of manufacture and availability. Examples of the monomer include methoxyethyl acrylate, ethoxyethyl acrylate,
Examples include 1-ethoxybutyl acrylate, 3-methoxypropyl acrylate, methoxymethyl acrylate, 3-ethoxypropyl acrylate, and ethoxymethyl acrylate. Examples of monomers copolymerizable with the (meth)acrylic monomer represented by general formula [A] include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. Acrylic or methacrylic alkyl ester monomers such as acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, butoxyethyl acrylate, (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl Vinyl monomers containing side chain functional groups such as (meth)acrylate, glycidyl (meth)acrylate, N-methylol (meth)acrylamide, N-ptoxymethyl (meth)acrylamide, vinyl acetate, acrylonitrile, styrene, maleic anhydride, etc. Can be mentioned. Among these monomers, alkyl acrylates having 2 to 8 carbon atoms are suitable for pressure-sensitive adhesives. In addition, adhesive strength,
When improving solvent resistance or curing using a crosslinking agent, and when using as a removable adhesive, it is preferable to use a monomer having a carboxyl group, hydroxyl group, amide group, or glycidyl group in combination. . The proportion of the monomer used is determined by the glass transition point (Tg point) of the polymer so as not to impair adhesiveness. Common as pressure sensitive adhesive
The Tg point is preferably -10°C or lower, more preferably -30°C or lower. Tg
If the point exceeds -10°C, the adhesive has poor tack and is not preferred as a pressure sensitive adhesive. Generally, to actually measure the Tg point of a polymer,
One example is a method of measuring thermal expansion at various temperatures and determining the Tg point as the intersection of two straight lines with different slopes on the specific volume-temperature curve. However, for convenience, the Tg of each single polymer is
Since the value of the Tg point is known, the Tg point of the copolymer can be calculated using the following formula (AVTobolsky; “Properties and Structure of
Polymers”John Wiley & Sons, Inc.New
York ('60)) 1/Tg=C ₁ /Tg ₁ +C ₂ /Tg ₂ +... _o 〓 ⁱ⁼¹ C _i /Tg _i C ₁ : Weight fraction of component 1 C ₂ : Weight fraction of component 2 Rate C _i : Weight fraction of component i Tg ₁ : Glass transition point of component 1 sole polymer (〓) Tg ₂ : Glass transition point of component 2 sole polymer (〓) Tg _i : Glass transition point of component i sole polymer (〓) 〓) Tg: Glass transition point of copolymer polymer of components 1, 2,...i (〓) Here, C ₁ +C ₂ +...= _o 〓 ⁱ⁼¹ C _i =1. Depending on the composition of the polymer, a crosslinking reaction may occur, but it is generally calculated on the assumption that no crosslinking reaction occurs. For typical monomers, the Tg points of their single polymers are as follows. <Solo polymer><Tgpoint> Polymethyl acrylate 8℃ Polymethyl methacrylate 105℃ Polyethyl acrylate -23℃ Poly n-butyl acrylate -54℃ Poly i-butyl acrylate -24℃ Poly 2-ethylhexyl acrylate -85℃ Polyacrylic Acid 106℃ Polymethacrylic acid 144℃ Polystyrene 100℃ Polyvinyl acetate 30℃ Polyacrylonitrile 96℃ Polyhydroxyethyl methacrylate 55℃ Polyacrylamide 165℃ 3-Methoxybutyl acrylate -56℃ 2-Methoxyethyl acrylate -50℃ 2-Ethoxyethyl Acrylate -50℃ 3-Methoxypropyl acrylate -75℃ 3-Ethoxypropyl acrylate -55℃ The amount of the monomer represented by general formula [A] used in the present invention in the monomer mixture is It is inseparably linked to the hardenability of
Preferably at least 3% or more, 10%
It is more preferable that it is above. If it is less than 3%, curing properties with active energy rays are poor and a good pressure-sensitive adhesive cannot be obtained. The copolymer or homopolymer of the present invention can be synthesized by conventional polymerization methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization. The polymer obtained as described above has active energy ray curability, but if necessary, a tackifier, filler, pigment, softener, etc. can be added to the polymer. In addition, isocyanate crosslinking using carboxyl groups and aquatic groups introduced into the copolymer,
A pressure-sensitive adhesive may be obtained by crosslinking by various methods such as melamine crosslinking, amine crosslinking using glycidyl groups, acid crosslinking, and metal crosslinking using carboxyl groups. Curing in the present invention is carried out by irradiation with active energy rays. The active energy rays used in the present invention refer to ionizing radiations such as ultraviolet rays, electron beams, and γ rays. Although the adhesive of the present invention is cured by the action of ultraviolet rays or ionizing radiation, it may contain a curing accelerator to further promote oxidation, and this is preferred in many cases. If the curing means is ultraviolet light, conventional photoinitiators are used. Suitable photoinitiators include benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isobutyl ether, benzoin octyl ether, benzyl, diacetyl, methylanthraquinone acetophenone, benzonephenone. carbonyl compounds such as 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, thioxanthone compounds, diphenyl disulfide,
Sulfur compounds such as dithiocarbamates, 2
Examples include naphthalene compounds such as chloromethylnaphthalene, metal salts such as anthracene, iron chloride, etc. Particularly suitable photoinitiators include benzophenone and 3,3'-dimethyl-4-methoxybenzophenone. and thioxanthone compounds such as 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4 diethylthioxanthone, and 2,4-dibropylthioxanthone. When the curing means is ionizing radiation such as electron beams or gamma rays, curing occurs quickly without the use of an initiator, so there is no particular need to use an initiator. The amount of the photoinitiator used is preferably 0.001 to 10 wt%, more preferably 0.01 to 5 wt%, based on the adhesive.
is within the range of The active energy ray-curable pressure-sensitive adhesive of the present invention is rapidly cured by active energy rays without consuming a large amount of time and energy,
Adhesive tapes with excellent properties such as adhesive strength, holding power, and tack can be easily obtained and are industrially useful. Furthermore, since it can be cured without using an acrylic oligomer, there is no problem of irritation and odor caused by it. EXAMPLES The present invention will be explained in more detail below with reference to Examples and Comparative Examples. In the examples, parts mean parts by weight, and the adhesive strength, holding power, and tack were measured by the following methods. (1) How to make an adhesive sheet After applying pressure-sensitive adhesive on one side of a 25μ polyester film to a thickness of approximately 30μ, active energy rays are irradiated from the pressure-sensitive adhesive surface, and release paper is applied. After combining them with a release paper, an adhesive sheet was prepared by irradiating active energy rays from the surface of the polyester film or without irradiating them. (2) Adhesive force Adhesive force measurement method of the adhesive sheet prepared as above 0JISZ0237 (Adhesive tape, adhesive sheet test method)
Paste it on a stainless steel plate and heat it to 180℃ after 30 minutes.
The peel-off adhesive strength was measured. (3) Holding force According to JISZ0237, the holding force was measured by pasting a 25 x 25 mm piece on a stainless steel plate, applying a load of 1 kg at 80℃ after 30 minutes, and measuring the time until the test piece falls from the stainless steel plate or up to 60 minutes. If the object did not fall, the distance traveled at that time was measured. (4) Tack Measurement of tack was also carried out using JISZ0237 to measure the maximum ball number of a steel ball that stops at an inclination angle of 30 degrees using the ball rolling method. Example 1 100 parts of a monomer mixture consisting of 55 parts of n-butyl acrylate, 40 parts of 3-methoxybutyl acrylate, and 5 parts of acrylic acid was placed in a four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a nitrogen gas blowing device. Add 20 parts and 80 parts of ethyl acetate,
The temperature was raised to 70°C with stirring in a nitrogen stream, and a solution of 0.3 parts of α, α′-azobisisobutyronitrile dissolved in 10 parts of ethyl acetate was added to start the reaction, and the remaining monomer mixture was added to this. 80 parts, 50 parts of ethyl acetate and 0.5 parts of α, α′-azobisisobutyronitrile.
10 parts of α, α'-azobisisobutyronitrile was added to 10 parts of ethyl acetate.
The solution dissolved in the solution was added dropwise, and stirring was continued for 2 hours at the same temperature to obtain a polymer solution, that is, an active energy ray-curable pressure-sensitive adhesive composition. Tg of the polymer
The temperature was -50℃. Regarding this composition, the adhesive strength of the adhesive sheet obtained by irradiating the polyester film surface with an electron beam at a dose of 2.4 megarads was 920gf/25mm, and the holding power was 60.
There was no difference in the minutes and the tack was 9. Comparative Example 1 An adhesive sheet obtained using the active energy ray-curable pressure-sensitive adhesive composition obtained in Example 1 without irradiation with electron beams had an adhesive strength of 1800 gf/25 mm and a holding power of 2
It fell in minutes. Example 2 A composition in which 0.2 wt% of benzophenone was added as a photoinitiator to the active energy ray-curable pressure-sensitive adhesive composition obtained in Example 1 had an output of 80 W/cm from the polyester film surface. High-pressure mercury lamp [Ushio Inc. Uniquiure System]
The adhesive strength of the adhesive sheet obtained by irradiating ultraviolet rays for 10 seconds at a distance of 15 cm using a single UV4000 ozone-less type semi-concentrating lamp was 980gf/25mm, and the retention strength remained unchanged even after 60 minutes. , Tatsuku was 9. Example 3 An adhesive sheet obtained in exactly the same manner as in Example 2 except that the pressure-sensitive adhesive surface was irradiated with ultraviolet rays in the air for 10 seconds had an adhesive strength of 890 gf/25 mm.
The holding force remained unchanged even after 60 minutes, and the tack was 8. Example 4 In Example 1, a monomer mixture was prepared in which the monomers were 40 parts of 2-ethoxyethyl acrylate, 20 parts of 3-ethoxypropyl acrylate, 20 parts of ethyl acrylate, 15 parts of vinyl acetate, and 5 parts of 2-hydroxyethyl methacrylate. Polymerization was performed to obtain an active energy ray-curable pressure-sensitive adhesive composition. of the polymer
Tg was -33°C. Further, the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 1 are shown in Table 1. Example 5 Each monomer body in Example 1 was prepared by polymerizing a monomer mixture consisting of 3 parts of 3-methoxypropyl acrylate, 92 parts of isobutyl acrylate, and 5 parts of glycidyl methacrylate to form an active energy ray-curable pressure-sensitive adhesive. A composition was obtained. Tg of polymer
The temperature was -24°C. In addition, Table 1 shows the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 1.
It was shown to. Example 6 Monomer is 2-methoxyethyl acrylate
An active energy ray-curable pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the amount was 100 parts. The Tg of the polymer was -50°C. Further, the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 1 are shown in Table 1. Example 7 An active energy ray-curable pressure-sensitive adhesive composition was obtained by polymerizing a monomer mixture in which the monomers in Example 1 were 35 parts of 2-ethoxyethyl acrylate and 65 parts of n-butyl methacrylate. Ta. Tg of polymer
The temperature was -12℃. Further, the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 1 are shown in Table 1. Example 8 A monomer mixture in which the monomers in Example 1 were 10 parts of 3-methoxybutyl acrylate, 80 parts of 2-ethylhexyl acrylate, 7 parts of acrylonitrile, and 3 parts of methacrylic acid was polymerized to produce active energy ray-curable sensitizers. A pressure sensitive adhesive composition was obtained. Tg of polymer
The temperature was -72℃. Further, the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 1 are shown in Table 1. Comparative Example 2 A pressure-sensitive adhesive composition was obtained by polymerizing a monomer mixture in which the monomers in Example 1 were 95 parts of n-butyl acrylate and 5 parts of acrylic acid. The Tg of the polymer was -49°C. Table 1 shows the adhesive strength, holding power, and tack of a pressure-sensitive adhesive sheet obtained by irradiating this composition with an electron beam in the same manner as in Example 1. Example 9 Table 1 shows the adhesive strength, holding power, and tack of a pressure-sensitive adhesive sheet obtained in the same manner as in Example 5 except that the electron beam irradiation dose was 5.0 megarads.
It was shown to. Example 10 Table 1 shows the adhesive strength, holding power, and tack of a pressure-sensitive adhesive sheet obtained in the same manner as in Example 6 except that the electron beam irradiation dose was 1.2 megarads.
It was shown to. Example 11 Adhesive strength and retention of a pressure-sensitive adhesive sheet obtained in the same manner as in Example 2 except that 2-chlorothioxanthone was used as the photoinitiator and the ultraviolet irradiation time was 5 seconds. Table 2 for force and tact
It was shown to

【table】

[Table] Example 12 In Example 2, benzyl dimethyl ketal was used as the photoinitiator, and the ultraviolet irradiation time was changed.
Table 2 shows the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 2, except that the time was changed to 15 seconds.
It was shown to. Example 13 Adhesive strength, holding power, Table 2
It was shown to. Example 14 The procedure was the same as in Example 2, except that the photoinitiator was 2,4-dimethylthioxanthone, the amount added was 0.05 wt%, and the ultraviolet irradiation time was 5 seconds. Table 2 shows the adhesive strength, holding power, and tack of the obtained adhesive sheet. Example 15 In Example 2, the amount of photoinitiator added was 0.05wt.
Table 2 shows the adhesive strength, holding power, and tack of the adhesive sheet obtained in the same manner as in Example 2, except that the UV irradiation time was 5 seconds. Example 16 0.5 wt% of Coronate L (polyisocyanate cross-linking agent manufactured by Nippon Polyurethane Industries, Ltd.) as a cross-linking agent and as a photoinitiator were added to the active energy ray-curable pressure-sensitive adhesive composition obtained in Example 1. , a composition containing 0.05wt% benzophenone was applied to one side of a 25μ polyester film so that the thickness of the pressure-sensitive adhesive was approximately 30μ, and then combined with release paper and not irradiated with active energy rays. Store it in the condition
After crosslinking the polyisocyanate, UV rays were irradiated from the polyester film surface for 55 minutes in the same manner as in Example 2.
The adhesive strength and holding power of the adhesive sheet obtained by irradiation for seconds,
The tactics are shown in Table 2. Comparative Example 3 In Example 16, the adhesive strength, holding power, and tack of the adhesive sheet before irradiation with ultraviolet rays are shown in Table 2. Comparative Example 4 100 parts of 3-methoxyethyl acrylate and 0.3 parts of benzophenone as a photoinitiator were applied to a polyester film to a coating thickness of approximately 30 μm.
It was applied so that The adhesive sheet obtained by irradiating ultraviolet rays for 20 seconds in the same manner as in Example 2 had an adhesive strength of 700gf/25mm,
The tack was 4, but the holding power fell in 5 minutes. Comparative Example 5 A monomer mixture consisting of 40 parts of 3-methoxybutyl acrylate, 55 parts of n-butyl acrylate, and 5 parts of acrylic acid, to which 0.3 parts of benzophenone was added as a photoinitiator, was applied to a polyester film to a coating thickness of approx. It was coated to a thickness of 30 μm. The adhesive sheet obtained by irradiating ultraviolet rays for 20 seconds in the same manner as in Example 2 had an adhesive strength of 950gf/25mm,
The tack was 5, but the holding power fell in 10 minutes. Example 17 In Comparative Example 3, the polyester surface of the adhesive sheet attached to a stainless steel plate was irradiated with ultraviolet rays for 5 seconds to measure adhesive strength and retention strength, and the adhesive strength and retention strength after 180 degree peeling are shown in Table 2. .

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1 From a homopolymer of a (meth)acrylic monomer represented by the following general formula [A] or a copolymer of the monomer and a monomer copolymerizable therewith. An active energy ray-curable pressure-sensitive adhesive. However, R ₁ is hydrogen or methyl group, R ₂ has 1 carbon number
-4 alkylene group, _R3 is an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4.