JPH073222A - Pressure sensitive adhesive tape or sheet - Google Patents

Abstract

(57) [Summary] [Structure] A low energy surface-treated microsphere is contained in the pressure-sensitive adhesive layer. [Effect] It is possible to obtain a pressure-sensitive adhesive tape or sheet that is excellent in conformability to the uneven surface.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a pressure sensitive adhesive tape or sheet having specially improved internal strength, excellent conformability and good adhesion.

[0002]

2. Description of the Prior Art U.S. Pat. No. 4,230,067 (Levens) states that "Tapes having pressure sensitive adhesive layers having a thickness greater than 0.1 to 0.2 mm tend to be difficult and costly to manufacture. Moreover, they tend to have low shear strength.For applications requiring greater thickness, foam back pressure sensitive adhesive tapes such as those disclosed in Canadian Patent 747341 are often used.
However, the porosity of the foam itself has a number of problems, such as the tendency to suck up liquids. The elastic memory of some foams tends to lift the foam from the bottom of rough or uneven surfaces. The production of foam layers less than about 1.0 mm is difficult and therefore expensive. ". The Levens patent addresses these problems with an acrylic-based adhesive where the adhesive layer is essentially formed from a polymer pressure sensitive adhesive matrix filled with glass microballoons that gives the tape the physical appearance and feel of a foam back tape. The solution is a pressure sensitive adhesive tape. The pressure sensitive adhesive tape is substantially void free and therefore does not exhibit water absorption.

Despite the drawbacks, foam back pressure sensitive adhesive tapes are widely used. Levens foam-like tapes are also widely used, but because glass microballoons are added to the polymerizable pressure-sensitive adhesive and coated and polymerized in a tape shape, the pressure-sensitive adhesive composition adheres to the glass microballoons. And the glass microballoons are fixed in the pressure-sensitive adhesive layer.
Therefore, there is a problem that sufficient fluidity does not occur with respect to stress and it does not follow unless very large pressure is applied, or there is a defect that elasticity rises with time even after following unevenness, or at low temperatures Then, this defect becomes more remarkable. For this reason, it was often necessary to provide an unfilled adhesive layer on each side of the Levens glass microballoon filled adhesive layer. Since these additional layers substantially increase the cost of foam-like tapes, relatively low cost foam back tapes are used in large quantities in the market despite poor performance.

As taught in the Levens patent, the glass microballoon-filled adhesive layer preferably disperses the glass microballoons in the partially polymerized monomer and then polymerizes the monomer by UV light. It is manufactured by This approach allows the formation of thicker unfilled pressure sensitive adhesive layers than can be economically coated from a solution or emulsion. Such thick unfilled pressure sensitive adhesive layers tend to exhibit lower cohesive strength than microvalve filled layers of the same thickness, especially at elevated temperatures. As described above, when a filler such as glass microballoons is added to improve the cohesive force of the pressure-sensitive adhesive tape, the adhesiveness is usually lowered.

[0005]

In order to solve the above problems, the present invention adds microspheres that have been subjected to a low-energy surface treatment to improve adhesion and friction between the microspheres and the pressure-sensitive adhesive matrix. As a result of the reduced resistance, the 500% modulus of tensile strength and elongation is significantly reduced, and the pressure-sensitive adhesive matrix and microspheres can move freely with respect to stress, improving shape followability and adhesion to uneven surfaces. And a pressure-sensitive adhesive tape or sheet exhibiting a cohesive strength superior to that of an unfilled pressure-sensitive adhesive tape even at high temperature. Since such a tape can improve the cohesive strength at high temperature without impairing the adhesive force and the shape-following property, it can be used in the fields where conventional adhesives, welding and rivets have been used for adhesion.

The low-energy surface treatment in the present invention is a treatment for reducing the tension at the interface between the microspheres and the pressure sensitive adhesive.

The pressure-sensitive adhesive layer in the present invention is, for example, 1
To 80 to 100% of a monofunctional unsaturated (meth) acrylic acid ester of a primary or secondary alkyl alcohol having about 14 carbon atoms, and 0 to 20% of at least one or more copolymerizable polar monomers. And a pressure-sensitive adhesive matrix containing microspheres surface-treated with a low energy substance.

The microspheres have an average diameter of 5 to 200 μm.
, Glass balloons (specific gravity 1.0 or less), inorganic hollow bodies such as alumina balloons and ceramic balloons, organic spherical bodies such as nylon beads, acrylic beads, and silicon beads, vinylidene chloride balloons, acrylic balloons, and other organic hollow bodies. There is.

As the low energy surface treatment, there are, for example, a silicon treatment with polyalkylsiloxane, a fluorine coating treatment with a fluorine-containing surfactant and a fluorine resin, and the like.

The content of the microspheres is preferably 5 vol% or more in the pressure sensitive adhesive layer.

Further, in order to provide the pressure-sensitive adhesive layer with thickness and flexibility, physical foaming such as mechanical foaming or chemical foaming in which a foaming agent is added to foam may be performed. At that time, a foaming agent or a stabilizer may be used.

Further, in order to enhance the cohesive force of the pressure sensitive adhesive, it is possible to formulate a crosslinking agent in the curable composition. For example, cross-linking agents such as 1,6-hexanediol diacrylate and polypropylene glycol diacrylate having vinyl groups having the same reactivity, glycerol methacrylate acrylate having unsaturated double bonds with different reactivity, and dicyclopentenyl. Crosslinking agents such as acrylates.

The curable composition prepared as above is
Polymerization is preferably carried out with active energy rays, and dissolved oxygen is removed by purging with an inert gas such as nitrogen gas. Also, phenyldiisodecyl phosphite,
A compound having a deoxidizing effect such as tridecyl phosphite and stannous octylate may be added.

It is also possible to add the surface-treated microspheres after the monomers are partially polymerized to have a viscosity capable of coating, or the viscosity is increased by adding a thickener.

The curable composition is applied or injected onto a film or paper having a low energy surface, or applied onto a substrate such as plastic film, paper, cellophane, cloth, non-woven fabric, metal foil or the like. Impregnated. Also,
A method of preventing oxygen damage by coating the surface of the release paper with a release-treated PET film is also desirable.

In the present invention, the active energy ray is α
Ionizing rays such as rays, β rays, γ rays, neutron rays, and accelerated electron rays, radiation, and ultraviolet rays. In the case of ionizing radiation, it can be used in the range of 0.5 to 50 Mrad, but 1 to 10
Mard is preferable. In the case of ultraviolet rays, 180
In the wavelength range of up to 480 nm, a high pressure mercury lamp, a fluorescent chemical lamp or the like is desirable as a generation source.

As a useful photopolymerization initiator which can be added in the case of photopolymerization, a photopolymerization initiator having an active site at 180 to 480 nm and having high initiation efficiency is preferable, and examples thereof include 4-phenoxydichloroacetophenone and 1-hydroxycyclohexylphenylketone. Such as acetophenone polymerization initiator, benzoin, benzoin methyl ether and other benzoin photopolymerization initiators, benzophenone, benzoylbenzoic acid and other benzophenone photopolymerization initiators, thioxanthone, 2-methylthioxanthone and other thioxanthone photopolymerization initiators Agents, and special ones other than those mentioned above include α-aloxime ester and acylphosphine oxide.

These photopolymerization initiators are used as the mixture 10 of the (meth) acrylic acid ester and the copolymerizable polar monomer.
It is desirable to add 0.001 to 10 parts by weight with respect to 0. When the amount added is less than 0.001 part by weight, the photopolymerization initiator is consumed at the initial stage of polymerization, so that the reaction does not proceed to the end point and a large amount of the monomer remains. On the other hand, when the amount added exceeds 10 parts by weight, the polymerization reaction becomes faster, but the molecular weight of the produced polymer is too low, so the peel strength and shear strength are reduced, and the balance as a pressure-sensitive adhesive tape becomes poor.

The pressure-sensitive adhesive tape or sheet according to the present invention may have a base material on at least one side of the pressure-sensitive adhesive layer, and the base material may be permanently adhered to the pressure-sensitive adhesive layer. However, it may be temporarily attached so that it can be peeled off. Furthermore, the base material may be impregnated with the pressure-sensitive adhesive layer. Substrates that can be used in the present invention include plastic film, paper, cellophane, cloth, non-woven fabric, metal foil and the like. In addition, when applied on a base material that has been subjected to a release treatment with silicon, fluorine or the like, or a base material having a low energy surface, a baseless pressure-sensitive adhesive tape or sheet can be obtained.

[0020]

EXAMPLES Examples of the present invention will be shown below. Example 1 90 parts of 2-ethylhexyl acrylate (parts by weight, the same applies hereinafter), 10 parts of acrylic acid, and Darocur 11 photoinitiator.
73 (manufactured by Merck) was added and irradiated with a fluorescent chemical lamp to obtain a syrup having a polymerization rate of 5%. Syrup 1
With respect to 00 parts, 0.3 part of polypropylene glycol diacrylate (APG700: manufactured by Shin Nakamura Chemical Co., Ltd.), 0.1 part of photoinitiator Lucillin TPO (manufactured by BASF), and a glass balloon surface-treated by coupling with polyalkylsiloxane. 8.55 parts (17.5 vol%) of (specific gravity 0.4, average diameter 50 μm, manufactured by Fuji Devison) were added and uniformly mixed, and then defoamed to prepare a curable composition.

PET obtained by subjecting this curable composition to a release treatment
P coated on the film to a thickness of 1.0 mm and peeled off
After coating with ET film, light intensity is 0.32 mW / c using fluorescent chemical lamp (wavelength 300-400 nm)
It was irradiated with m ² from both sides for 6 minutes to form a pressure-sensitive adhesive layer containing a low energy surface-treated glass balloon on the release-treated PET film.

Example 2 90 parts of 2-ethylhexyl acrylate, 1 acrylic acid
0 part, photoinitiator Darocur 1173 (manufactured by Merck)
0.3 part was added and irradiated with a fluorescent chemical lamp to obtain a syrup having a polymerization rate of 5%. For 100 parts of syrup, polypropylene glycol diacrylate (APG700:
Shin-Nakamura Chemical Co., Ltd.) 0.3 parts, photoinitiator Lucillin TPO
(BASF Corporation) 0.1 part, urethane beads coupled with polyalkylsiloxane and surface-treated (specific gravity 1.
1, average diameter 50 μm, manufactured by Dainippon Ink and Chemicals, Inc. 11
(10 vol%) and then uniformly mixed, and then defoamed to prepare a curable composition.

PET obtained by subjecting this curable composition to release treatment
P coated on the film to a thickness of 1.0 mm and peeled off
After coating with ET film, light intensity is 0.32 mW / c using fluorescent chemical lamp (wavelength 300-400 nm)
Irradiation with m ² from both sides was performed for 6 minutes to form a pressure-sensitive adhesive layer containing low energy surface-treated urethane beads on the release-treated PET film.

Example 3 90 parts of 2-ethylhexyl acrylate, 1 acrylic acid
0 part, photoinitiator Darocur 1173 (manufactured by Merck)
0.3 part was added and irradiated with a fluorescent chemical lamp to obtain a syrup having a polymerization rate of 5%. For 100 parts of syrup, polypropylene glycol diacrylate (APG700:
Shin-Nakamura Chemical Co., Ltd.) 0.3 parts, photoinitiator Lucillin TPO
(Manufactured by BASF) 0.1 part, fluorinated surfactant F-1
42D (manufactured by Dainippon Ink and Chemicals, Inc.) 8.55 parts (17.5 vol%) of glass balloon (specific gravity 0.4, average diameter 50 μm, manufactured by Fuji Devison) surface-treated with 1.0 part were added and mixed uniformly. After that, defoaming was performed to prepare a curable composition.

PET obtained by subjecting this curable composition to a release treatment
P coated on the film to a thickness of 1.0 mm and peeled off
After coating with ET film, light intensity is 0.32 mW / c using fluorescent chemical lamp (wavelength 300-400 nm)
Irradiation with m ² from both sides for 6 minutes was performed to form a pressure-sensitive adhesive layer containing a low energy surface-treated glass balloon on the PET film subjected to the release treatment.

Example 4 90 parts of 2-ethylhexyl acrylate, 1 acrylic acid
0 part, photoinitiator Darocur 1173 (manufactured by Merck)
0.3 part was added and irradiated with a fluorescent chemical lamp to obtain a syrup having a polymerization rate of 5%. For 100 parts of syrup, polypropylene glycol diacrylate (APG700:
Shin-Nakamura Chemical Co., Ltd.) 0.3 parts, photoinitiator Lucillin TPO
(Manufactured by BASF) 0.1 part, fluorinated surfactant F-1
42D (manufactured by Dainippon Ink and Chemicals, Inc.) and 11.0 parts (10 vol%) of urethane beads (specific gravity 1.1, average diameter 50 μm, manufactured by Dainippon Ink and Chemicals) surface-treated with 1.0 part were uniformly added. After mixing, defoaming was performed to prepare a curable composition.

PET obtained by subjecting this curable composition to release treatment
P coated on the film to a thickness of 1.0 mm and peeled off
After coating with ET film, light intensity is 0.32 mW / c using fluorescent chemical lamp (wavelength 300-400 nm)
Irradiation with m ² from both sides was performed for 6 minutes to form a pressure-sensitive adhesive layer containing low energy surface-treated urethane beads on the release-treated PET film.

Comparative Example 1 90 parts of 2-ethylhexyl acrylate, 1 acrylic acid
0 part, photoinitiator Darocur 1173 (manufactured by Merck)
0.3 part was added and irradiated with a fluorescent chemical lamp to obtain a syrup having a polymerization rate of 5%. For 100 parts of syrup, polypropylene glycol diacrylate (APG700:
Shin-Nakamura Chemical Co., Ltd.) 0.3 parts, photoinitiator Lucillin TPO
(BASF) 0.1 part, untreated glass balloon (specific gravity 0.4, average diameter 50 μm, manufactured by Fuji Devison) 8.55 parts (17.5 vol%) were added and uniformly mixed, and then degassed. Foamed to prepare a curable composition.

PET obtained by subjecting this curable composition to release treatment
P coated on the film to a thickness of 1.0 mm and peeled off
After coating with ET film, light intensity is 0.32 mW / c using fluorescent chemical lamp (wavelength 300-400 nm)
Irradiation with m ² from both sides was performed for 6 minutes to form a pressure-sensitive adhesive layer containing untreated glass balloons on the PET film subjected to the release treatment.

Comparative Example 2 2-Ethylhexyl acrylate 90 parts, acrylic acid 1
0 part, photoinitiator Darocur 1173 (manufactured by Merck)
0.3 part was added and irradiated with a fluorescent chemical lamp to obtain a syrup having a polymerization rate of 5%. For 100 parts of syrup, polypropylene glycol diacrylate (APG700:
Shin-Nakamura Chemical Co., Ltd.) 0.3 parts, photoinitiator Lucillin TPO
(BASF) 0.1 part, untreated urethane beads (specific gravity 1.1, average diameter 50 μm, Dainippon Ink and Chemicals) 11.0 parts (10 vol%) were added and mixed uniformly, After defoaming, a curable composition was prepared.

PET obtained by subjecting this curable composition to release treatment
P coated on the film to a thickness of 1.0 mm and peeled off
After coating with ET film, light intensity is 0.32 mW / c using fluorescent chemical lamp (wavelength 300-400 nm)
Irradiation was carried out for 6 minutes from both sides with m ² to form a pressure-sensitive adhesive layer containing untreated urethane beads on the release-treated PET film.

When various tests were conducted on the obtained pressure-sensitive adhesive tape or sheet, the results shown in Table 1 were obtained.

[0033]

[Table 1]

Test Method 180 ° Peel Adhesion (23 ° C., 65% RH) A sample of 25 mm width and 50 mm length was pressed on a 5.0 kg roller one way on an acrylic coated plate, and after 24 hours, pulled in the 180 ° direction at a speed of 50 mm / min. The adhesive strength when peeled off was measured.

Holding power at 150 ° C. 23 ° C. 65% RH Backed with aluminum foil 25
A sample with a width of mm is applied to a stainless steel plate that has been hairline-treated with sandpaper No. 240 for 0.5 hours after one-way pressure bonding of a 5.0 Kg roller, and a load of 1.0 Kg is applied in the shear direction at 150 ° C. The time until it dropped was measured. If it does not fall after 1440 minutes,
The displacement distance was measured.

500% modulus At 23 ° C. and 65% RH, a sample having a width of 10 mm and a marked line interval of 50 mm was pulled at a speed of 300 mm / min in the length direction, and the strength when stretched by 500% was measured.

Shape-following property (23 ° C., 65% RH) A 25 mm-width sample was affixed one-way with a 5.0 Kg roller to an acrylic plate having a 100 μm-thick spacer at intervals of 25 mm, and immediately afterward to a concave portion for 168 hours. The change in the followability of is expressed as a percentage.

[0038]

EFFECTS OF THE INVENTION According to the present invention, the addition of the microspheres subjected to the low energy surface treatment reduces the adhesion between the microspheres and the pressure-sensitive adhesive matrix and the frictional resistance. The 500% modulus of elongation is significantly reduced, and the pressure-sensitive adhesive matrix and microspheres can move freely against stress, improving shape followability and adhesion to uneven surfaces, and excellent even at high temperatures. A pressure sensitive adhesive tape or sheet can be provided that exhibits improved cohesive strength.

Claims (8)

[Claims] 1. A pressure-sensitive adhesive tape or sheet having a pressure-sensitive adhesive layer containing microspheres having a surface treated with a low energy surface. 2. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the low energy surface treatment of the surface of the microspheres is a silicon treatment. 3. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the low energy surface treatment of the surface of the microspheres is a fluorine coating treatment. 4. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the microspheres are glass balloons. 5. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the microspheres are plastic balloons. 6. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the microspheres are glass beads. 7. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the microspheres are plastic beads. 8. The pressure-sensitive adhesive tape or sheet according to claim 1, wherein the pressure-sensitive adhesive layer is formed of a curable composition containing a crosslinking agent.