JPH04353582A - Pressure-sensitive adhesive - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photopolymerizable acrylic pressure-sensitive adhesive.

0002

[Prior Art] Acrylic pressure-sensitive adhesives are well known in the art, and generally have an alkyl group having 2 to 14 carbon atoms.
The main component is acrylic acid alkyl ester, and if necessary, a small amount of polar monomers such as acrylic acid and monomer components that give a high glass transition point such as styrene and vinyl acetate are copolymerized and peeled. I try to balance characteristics, tactics, etc. In addition, crosslinking may be applied for the purpose of improving heat resistance and cohesive force.

[0003] When producing such an acrylic pressure-sensitive adhesive, the monomer is usually solution polymerized in a solvent, and then a tackifying resin, a crosslinking agent, etc. are added to the solution to prepare an adhesive composition. After coating this on a base material, a large amount of the solvent is removed by heating to obtain a pressure-sensitive adhesive in the form of a sheet or tape. However, in recent years, the adoption of the above manufacturing method has come to be subject to considerable restrictions from the viewpoint of safety and environmental hygiene due to the use of solvents.

Therefore, US Pat. No. 4,181,752 discloses a method for obtaining a pressure-sensitive adhesive without using a solvent by photopolymerizing an acrylic acid alkyl ester and a modifying monomer on a base material. is disclosed. Transfer-type pressure-sensitive adhesives are also known in which a similar adhesive is obtained on a release liner and transferred onto a substrate. Furthermore, in the production of such photopolymerizable pressure-sensitive adhesives, chemically reactive isocyanates, epoxy, amino compounds, etc., which are added to conventional solution polymers, are used to crosslink the adhesive polymer. Attempts have also been made to add and copolymerize diacrylates, triacrylates, and the like as polyfunctional monomers, which are different from each other, to cause crosslinking to occur simultaneously with polymerization.

[0005]

[Problems to be Solved by the Invention] However, with the conventionally known photopolymerizable pressure-sensitive adhesives as described above, the bonding force (anchoring force) between the base material and the adhesive is insufficient, and the adhesive becomes unstable when used. It has the disadvantage that it peels off from the material and sticks to the adherend.

[0006] In order to overcome this drawback, it is necessary to undercoat the base material, but this increases the number of processing steps and
Because solvents must be used to apply a thin layer of primer,
The advantage of being a photopolymerizable type is halved. In addition, special public service 57-5
Publication No. 1700 discloses a method for producing a photopolymerizable pressure-sensitive adhesive in which a photosensitizer is used as an undercoat in order to improve the anchoring force with the base material, but this method also uses an undercoat. Since processing is required, problems similar to those described above arise. Furthermore, since the transfer-type pressure-sensitive adhesive described above does not produce any anchoring force to the base material, even if such an undercoating treatment is performed, it cannot be said that the anchoring force can be sufficiently improved. Ta.

SUMMARY OF THE INVENTION In view of the problems of the prior art, it is an object of the present invention to provide a photopolymerizable acrylic pressure-sensitive adhesive that has excellent anchoring power to a substrate.

[0008]

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventors added a small amount of isocyanate compound together with a photopolymerization initiator to the monomer mixture to be photopolymerized. The inventors have discovered that by adding the above, a photopolymerizable pressure-sensitive adhesive having a large anchoring force to a substrate can be obtained without the need for undercoating, and the present invention has been completed.

Specifically, the present invention comprises the following three components a to c; Ethylenically unsaturated monomer 30-0% by weight
100 parts by weight of a monomer mixture consisting of b) 0.01 to 4 parts by weight of a photopolymerization initiator c) A pressure-sensitive adhesive obtained by photopolymerizing a composition containing 0.1 to 5 parts by weight of an isocyanate compound. This is related to.

0010

Structure and operation of the invention The acrylic acid alkyl ester used in the present invention is the main component of the composition before photopolymerization, and is preferably a non-tertiary alkyl alcohol.
A monofunctional unsaturated acrylate having an alkyl group of 2 to 14 carbon atoms. Examples of such monomers include ethyl acrylate, butyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isononyl acrylate. Examples include acrylate, decyl acrylate, and dodecyl acrylate, and one or more of these may be used.

[0011] The monoethylenically unsaturated monomer copolymerizable with the acrylic acid alkyl ester can be copolymerized with the acrylic acid alkyl ester to improve adhesion by introducing a functional group or a polar group, or It is used to control the glass transition temperature of copolymers and improve their cohesive strength and heat resistance. Examples of such monomers include acrylic acid, itaconic acid, sulfopropyl acrylate, hydroxyalkyl acrylate, cyanoalkyl acrylate, acrylamide, substituted acrylamide, N-vinylcaprolactam, acrylonitrile, Examples include 2-methoxyethyl acrylate, glycidyl acrylate, and vinyl acetate, and one or more of them may be used depending on the purpose.

[0012] The proportion of the monomer mixture consisting of the above-mentioned acrylic acid alkyl ester and a monoethylenically unsaturated monomer copolymerizable with it is 70 to 100% by weight of the acrylic acid alkyl ester as the main component. %, preferably 85 to 100% by weight, and the monoethylenically unsaturated monomer copolymerizable with it is 30 to 0% by weight, preferably 15
It is preferable to set the amount to 0% by weight, and by using this range, a good balance of adhesiveness, cohesive force, etc. can be achieved.

Photopolymerization initiators used in the present invention include benzoin methyl ether and benzoin isopropyl ether.
benzoin ethers such as tel, substituted benzoin ethers such as anizoin methyl ether, substituted acetophenones such as 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenoneacetophenone, etc. Class, 2-
Substitutions such as methyl-2-hydroxypropiophenone
α-ketols, aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, and 1-phenone
There are photoactive oximes such as 1,1-propanedione-2-(o-ethoxycarbonyl)oxime. These photopolymerization initiators are used in an amount of 0.01 to 4 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the monomer mixture.
Used in parts by weight.

[0014] If necessary, a small amount of polyfunctional acrylate as a crosslinking agent may be added to the composition of the present invention in order to increase the shear strength of the adhesive. Examples of such polyfunctional acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, Examples include 1,6-hexanediol di(meth)acrylate, which can be used in an amount of usually 0.01 to 2 parts by weight per 100 parts by weight of the monomer mixture.

[0015] Examples of the isocyanate compound used in the present invention as an anchoring force improver for the substrate include trimethylsilyl isocyanate, dimethylsilyl diisocyanate, methylsilyl triisocyanate, and tetramethylsilyl isocyanate. Silicon isocyanate compounds such as isocyanate silane, phenylsilyl triisocyanate, and ethoxysilane triisocyanate; unsaturated isocyanates having a methacryloyl group such as isocyanate ethyl methacrylate; Diisocyanate compounds such as 2,4-tolylene diisocyanate, paraphenylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and block type isocyanate. [
Examples include Coronate 2507, Coronate 2513, and Coronate 2515 manufactured by Nippon Polyurethane Industries, Ltd.

The above isocyanate compound is used in an amount of 0.1 to 5 parts by weight, particularly preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the monomer mixture. When the amount is less than 0.1 part by weight, the effect of improving anchoring force is poor, and when it exceeds 5 parts by weight, problems such as solubility in the monomer mixture, pot life, polymerization inhibition, and adverse effects on adhesive properties occur. In some cases, it is desirable to add the minimum necessary amount. In particular, silicon isocyanate compounds are effective even in small amounts, and block-type isocyanates have advantages such as ease of handling and the ability to develop anchoring power through heat treatment in a post-process.

To prepare the composition of the present invention, the monomer mixture described above and a photoinitiator are first mixed together, and this premix is partially polymerized to a
Form into a coatable syrup with a viscosity in the centipoise range. Alternatively, a thixotropic agent such as fumed silica may be mixed into the premix of the above monomer mixture and photopolymerization initiator to form a coatable syrup. Next, a composition for photopolymerization is prepared by mixing an isocyanate compound into this syrup, and further mixing an additional photopolymerization initiator and, if necessary, a polyfunctional acrylate as a crosslinking agent. Ru.

In the present invention, this composition is coated on a substrate, and the monomer mixture is photopolymerized by irradiation with ultraviolet rays in an inert, ie, oxygen-free atmosphere. A pressure sensitive adhesive can be obtained. The pressure-sensitive adhesive of the present invention can also be obtained by coating the adhesive layer with an ultraviolet-transparent film and photopolymerizing it by irradiating it with ultraviolet rays in a state where air is cut off.

The base material used here includes synthetic resin films such as polyester film, polyethylene film, and polypropylene film, as well as kraft paper,
Various known base materials can be used, such as paper such as Japanese paper, and metal foil such as aluminum foil and SUS foil. The thickness of these base materials is generally about 12 to 150 μm.

Further, the ultraviolet rays used for photopolymerization are electromagnetic radiation having a wavelength range of about 180 to 460 μm, but electromagnetic radiation having longer or shorter wavelengths can also be used effectively. As a UV source, mercury arc, carbon arc
General irradiation equipment is used, such as a vacuum cleaner, low-pressure mercury lamp, medium- and high-pressure mercury lamp, and metal halide lamp.

The pressure-sensitive adhesive of the present invention obtained in this way has excellent adhesive strength and cohesive strength, and has excellent anchoring properties on substrates, comparable to conventional solution-type pressure-sensitive adhesives. It has power. This is based on the addition of an isocyanate compound to the composition before photopolymerization, and the reason for this is thought to be as follows.

[0022] With conventional photopolymerizable pressure-sensitive adhesives that do not contain isocyanate compounds, adhesive polymers are formed during the process of photopolymerizing monomers coated on a base material by irradiating them with ultraviolet rays. , changes such as volumetric contraction and expansion occur due to polymerization, and wettability with the substrate is impaired. In addition, in the process of photopolymerization, polymerization is completed instantaneously within a few seconds, so the produced polymer itself may not be able to ensure wettability with the base material, or the tape may not be formed without the application of heat. The fluidity of the polymer decreases.

[0023] Due to these factors, it is thought that the anchoring force of conventional photopolymerizable pressure-sensitive adhesives to the substrate is significantly reduced. On the other hand, when an isocyanate compound is added as in the present invention, this acts on the base material and creates some kind of chemical bond between the base material and the adhesive layer, and this bonding force improves the wettability. It is presumed that the lack of anchorage is compensated for and a good anchoring force to the base material is obtained.

[0024]

As described above, the present invention has excellent anchoring power with the substrate after photopolymerization by adding a small amount of isocyanate compound to the composition before photopolymerization, and also improves adhesive strength and Acrylic pressure-sensitive adhesives with excellent cohesive strength can be obtained.

[0025]

EXAMPLES Next, examples of the present invention will be described in more detail. In addition, in the following, parts mean parts by weight.

Example 1 98 parts of butyl acrylate, 2 parts of acrylic acid, 2.2-
A premix was prepared using 0.05 part of dimethoxy-2-phenylacetophenone (photopolymerization initiator). It was partially polymerized by exposure to ultraviolet light in a nitrogen atmosphere to give a coatable syrup with a viscosity of about 5000 centipoise.

To 100 parts of this partially polymerized syrup, 2.0 parts of an isocyanate compound as an anchoring force improver [Coronate L manufactured by Nippon Polyurethane Industries Co., Ltd.] and an additional 0.1 part of a photopolymerization initiator were added. 1 part and 0.1 part of trimethylolpropane triacrylate as a cross-linking agent were added and mixed, and this composition was coated on a polyethylene terephthalate film with a thickness of 25 μm, and the mixture was coated under a nitrogen atmosphere. A photopolymerizable pressure-sensitive adhesive having an adhesive layer thickness of 50 μm was obtained by irradiating ultraviolet rays of 900 mj/cm 2 from an ultraviolet lamp for photopolymerization.

Example 2 A composition comprising a partially polymerized syrup with an isocyanate compound, an additional photoinitiator, and a cross-linking agent was applied to a 25 μm thick film coated with a low-adhesion release coating. Except for coating it on a polyethylene terephthalate film and photopolymerizing it by irradiating it with ultraviolet rays.
In exactly the same manner as in Example 1, an easily transferable photopolymerizable pressure-sensitive adhesive was obtained.

Example 3 80 parts of 2-ethylhexyl acrylate, 15 parts of 2-methoxyethyl acrylate, 5 parts of vinyl acetate, 0 parts of 1-hydroxychlorohexyl phenyl ketone (photopolymerization initiator)
．． Using 05 parts, the same procedure as in Example 1 was carried out until the viscosity was 30.
A coatable syrup of 0.00 centipoise was prepared. To 100 parts of this partially polymerized syrup, 0.2 part of methylsilyl triisocyanate, which is an anchoring force improver,
0.1 part of 1,6-hexanediol diacrylate was added and mixed, and the same procedure as in Example 1 was repeated to obtain a photopolymerizable pressure-sensitive adhesive.

Example 4 60 parts of isononyl acrylate, 3 parts of butyl acrylate
A coatable syrup having a viscosity of 3000 centipoise was prepared in the same manner as in Example 1 using 5 parts of acrylic acid, 5 parts of acrylic acid, and 0.05 part of 2,2-dimethoxy-2-phenylacetophenone. did. To 100 parts of this partially polymerized syrup, a block type isocyanate (Coronate L manufactured by Nippon Polyurethane Industries, Ltd.) was added as an anchoring force improver.
2507], 0.1 part of an additional photopolymerization initiator, and 0.05 part of trimethylolpropane triacrylate as a cross-linking agent were added and mixed, and the following was carried out in exactly the same manner as in Example 1. A photopolymerizable pressure-sensitive adhesive was obtained.

EXAMPLE 5 A composition comprising partially polymerized syrup with blocked isocyanate, additional photoinitiator, and cross-linking agent was coated with a low-adhesion release coating 25 μm thick.
An easily transferable, photopolymerizable pressure-sensitive adhesive was prepared in the same manner as in Example 4, except that it was coated on a polyethylene terephthalate film of 100 m and photopolymerized by irradiating it with ultraviolet rays. Obtained.

Comparative Example 1 A photopolymerizable pressure-sensitive adhesive was obtained in exactly the same manner as in Example 1, except that no isocyanate compound as an anchoring force improver was added.

Comparative Example 2 An easily transferable photopolymerizable pressure-sensitive adhesive was obtained in exactly the same manner as in Example 2, except that no isocyanate compound as an anchoring force improver was added.

Comparative Example 3 A photopolymerizable pressure-sensitive adhesive was obtained in exactly the same manner as in Example 4, except that no block type isocyanate as an anchoring force improver was added.

Comparative Example 4 A composition before photopolymerization was obtained in exactly the same manner as in Example 1, except that the amount of isocyanate compound added to the partially polymerized syrup was changed to 10 parts. However, the viscosity of the liquid of this composition increased over time and became gel-like after about 1 hour, causing difficulties in handling in the subsequent step of producing a pressure-sensitive adhesive. In addition, after preparing this composition, it was immediately coated in the same manner as in Example 1 and photopolymerized by irradiating it with ultraviolet rays to obtain a photopolymerizable pressure-sensitive adhesive. The appearance was milky white, and poor compatibility was observed.

The adhesive force, holding force and anchoring force of each of the pressure-sensitive adhesives of Examples 1 to 5 and Comparative Examples 1 to 4 were examined in the following manner, and the results are shown in Table 1 below. That's right. The easily transferable photopolymerizable pressure-sensitive adhesives of Examples 2 and 5 and Comparative Example 2 were heat-laminated at 100°C on a polyethylene terephthalate film with a thickness of 25 μm. A pressure-sensitive adhesive for evaluation was obtained by transfer.

<Adhesive Strength> Measured according to JIS Z-1522 using a stainless steel plate as an adherend.

<Holding force> A stainless steel plate with a mirror-like surface (
An evaluation sample (width 10 mm) was attached to one end of the 30 mm x 120 mm x 3.0 mm in the longitudinal direction so that the adhesion area was 20 mm x 10 mm, and after being left for 30 minutes, 500 g of A load was applied and the time it took to fall due to displacement was measured.

<Anchoring Force> Method A: To determine the anchoring force on the substrate, the tape sample is immersed in a bath of ethyl acetate at room temperature and then visually inspected periodically. If evidence of delamination between the base material and the adhesive is confirmed within 4 hours, the anchoring force is deemed insufficient, and the
No delamination for more than an hour was evaluated as ○, delamination within 1 hour was evaluated as △, and delamination within 10 minutes was evaluated as ×. Method B: After preparing an evaluation sample in the same manner as in the case of adhesive strength measurement, it is heated and aged at 50° C. for 7 days. This was returned to room temperature, and at 23°C, the tensile speed was 500 mm/min.
A peel test was conducted to evaluate the presence or absence of transfer of the adhesive to the stainless steel plate. If there was transfer, it was determined that the anchoring force was insufficient, and no transfer was judged as ○, partial transfer was △, and full transfer was judged as ×.

[0040]

[Table 1]

As is clear from the results in Table 1 above, the pressure-sensitive adhesive of the present invention has a lower
Because it uses an isocyanate compound, it has a much better anchoring ability to the substrate, and it can be seen that it overcomes the drawbacks of conventional photopolymerizable pressure-sensitive adhesives.

Claims (1)

[Claims] Claim 1: The following three components a to c; a) 70 to 100% by weight of an acrylic acid alkyl ester whose alkyl group has an average of 2 to 14 carbon atoms, and a monoethylenically unsaturated monoethylenically unsaturated copolymerizable therewith. 100 parts by weight of a monomer mixture consisting of 30 to 0% by weight of a monomer b) 0.01 to 4 parts by weight of a photopolymerization initiator c) 0.1 to 5 parts by weight of an isocyanate compound A pressure-sensitive adhesive made by polymerization.