JPH11140400A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive sheet which is free from undulation, shear, shrinkage, and discoloration even when stuck to a stainless steel sheet and used outdoors, does not undergo the change in color of an adhesive, and is easily applied by forming a pressure-sensitive adhesive layer comprising an acrylic adhesive and a chelating agent on one side of a synthetic resin sheet. SOLUTION: This adhesive sheet is prepd. by forming an 30-100 μm-thick adhesive layer comprising 100 pts.wt. acrylic base polymer formed mainly from an alkyl (meth)acrylate having a 4-12C alkyl group and 1.5-23 pts.wt. chelating agent on one side of a 50-200 μm-thick synthetic resin sheet made of a vinyl chloride resin, a fluororesin, etc. Phosphite-base antioxidants, such as represented by formulas I (wherein R is 12-14C alkyl), II and III are esp. pref. as the chelating agents, which retard the degradation of the adhesive caused by the catalytic action of the metal elements, Cr, Mn and Ni, contained in stainless steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet which is cut out into pictures and characters and used for decoration and marking indoors and outdoors, particularly when used as a stainless steel plate as an adherend, has excellent weather resistance. And a pressure-sensitive adhesive sheet which is also effective for protecting the pressure-sensitive adhesive sheet used for the marking.

[0002]

2. Description of the Related Art Conventionally, there has been known a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on one surface of a base material such as a vinyl chloride resin sheet containing a pigment, and laminated on a release sheet via the pressure-sensitive adhesive layer. ing. This adhesive sheet is cut out to a desired picture or character by a cutting machine, attached to a material to be displayed or decorated using an adhesive layer, and exerts a decorative effect by the color or pattern on the surface side of the film. It is. In recent years, it has been used in the field of display such as labels and stickers, signs and advertisements, and the field of fleet marking such as vehicle decoration, instead of painting.

When the conventional pressure-sensitive adhesive sheet described above is used outdoors with a stainless steel plate as an adherend, the soft vinyl chloride resin sheet may undulate or shift, causing discoloration of the pressure-sensitive adhesive, falling off of the pressure-sensitive adhesive sheet, and deterioration of the pressure-sensitive adhesive. There are problems such as the appearance being impaired due to contamination. The deterioration of the pressure-sensitive adhesive sheet adhered to a stainless steel plate for outdoor use is considered to be deterioration due to external factors such as light, heat, moisture, oxygen, and the action of metal ions derived from stainless steel. Attempts have been made to add an ultraviolet absorber or an antioxidant to one or both of them, or to select a material having essentially good weather resistance, but no satisfactory effect has been obtained.

As a method for solving the above-mentioned problem, for example, a method is known in which a non-chlorine-based resin barrier layer is first provided on a stainless steel plate, and a conventional pressure-sensitive adhesive sheet is adhered on the barrier layer (Japanese Patent Application Laid-Open No. 9-1997). 1722). However,
In the method described in the above publication, the appearance becomes poor unless the non-chlorine-based resin barrier layer is cut off at unnecessary portions other than the marking, and the construction time and cost are twice as much as those of the conventional method. Was not.

In order to protect the marking film from deterioration, a method of covering the marking film from above with a transparent film larger than the marking film is conceivable. In this case, too, an unnecessary portion sticking out of the marking film and affixed to the stainless steel plate is considered. In this case, there is a problem that the transparent film in this portion is yellowed over time, and there is a problem of swelling and shrinkage of the film due to deterioration of the pressure-sensitive adhesive.

Further, it is conceivable to use a composite sheet obtained by laminating two or more types of sheets. However, the number of steps for laminating is increased, and the modulus of the composite sheet is increased, so that the workability may be deteriorated.

[0007]

According to the present invention, the sheet does not undulate, shift, shrink, or fade even when it is adhered to a stainless steel plate as an adherend and used outdoors, and the discoloration of the pressure-sensitive adhesive does not occur. An object of the present invention is to provide a pressure-sensitive adhesive sheet which does not occur, has excellent weather resistance, and is easy to construct.

[0008]

Means for Solving the Problems When the pressure-sensitive adhesive sheet is adhered to a stainless steel plate and used outdoors, the undulation and deviation of the sheet are determined by the metal elements Cr, Mn,
It is considered that Ni caused a catalytic action and accelerated deterioration of the pressure-sensitive adhesive together with ultraviolet rays. Focusing on this point, the present invention and the like have found that the above problem can be solved by blending a phosphite-based antioxidant as a chelating agent in a pressure-sensitive adhesive, and reached the present invention.

That is, in the pressure-sensitive adhesive sheet of the present invention, an acrylic pressure-sensitive adhesive base polymer 10
An adhesive layer comprising 0 parts by weight and 1.5 to 23 parts by weight of a chelating agent is laminated.

In the present invention, as a base polymer of the acrylic pressure-sensitive adhesive, a (meth) acrylic acid ester, for example, a copolymer mainly containing an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms is used. . Specific examples of the alkyl (meth) acrylate include n-butyl (meth) acrylate and 2-ethylhexyl (meth).
Acrylate, isooctyl (meth) acrylate, n
-Octyl (meth) acrylate, isononyl (meth)
Acrylate, lauryl (meth) acrylate and the like can be mentioned. These can be used alone or in combination of two or more.

In terms of the balance between the adhesive strength and the cohesive strength, the homopolymer generally contains an alkyl (meth) acrylate having a glass transition temperature of -50 ° C. or less as a main component, and includes methyl (meth) acrylate, ethyl (meth) acrylate and the like. Carbon number 1
Alkyl (meth) acrylates having 3 to 3 alkyl groups may be used in combination.

In addition to the above-mentioned alkyl (meth) acrylate, a vinyl monomer copolymerizable therewith may be copolymerized. Examples of the copolymerizable vinyl monomer include carboxyl group-containing vinyl monomers such as (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid, and anhydrides thereof, 2-hydroxyethyl (meth) acrylate, -Hydroxybutyl (meth) acrylate, polyoxyethylene (meth) acrylate,
Examples include hydroxyl-containing vinyl monomers such as polyoxypropylene (meth) acrylate and caprolactone-modified (meth) acrylate.

The acrylic pressure-sensitive adhesive used in the present invention is:
A solvent-type pressure-sensitive adhesive polymerized in an organic solvent or an emulsion-type pressure-sensitive adhesive polymerized in water may be used. Alternatively, a block polymerization type pressure-sensitive adhesive obtained by irradiating the monomer mixture with ultraviolet light may be used.

In the present invention, an adhesive containing a chelating agent is used. As the chelating agent, various ones can be mentioned, and for example, those having a structure represented by the following formulas (1), (2), and (3) are particularly preferable.

Embedded image (Wherein, R represents an alkyl group of C ₁₂ -C ₁₄₎

[0015]

Embedded image

[0016]

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The above chelating agent is blended in an amount of 1.5 to 23 parts by weight based on 100 parts by weight of the base polymer of the pressure-sensitive adhesive.
If the amount of the chelating agent is less than 1.5 parts by weight, the desired level of weather resistance cannot be obtained, and if the amount exceeds 23 parts by weight, the amount of bleeding out to the surface of the adhesive becomes large, so that the adhesive strength is reduced,
The function as an adhesive sheet is not exhibited. Therefore, the compounding amount of the chelating agent is as described above.

The synthetic resin sheet used in the present invention includes:
Vinyl chloride resin; chlorinated vinyl chloride resin; vinylidene chloride resin; tetrafluoride resin, tetrahexafluoride resin (ethylene tetrafluoride-propylene hexafluoropropylene copolymer), PFA resin (ethylene tetrafluoride-perfluoro) Alkyl vinyl ether copolymers), fluorine-based resins such as ethylene trifluoride resin and vinylidene fluoride resin; ethylene-vinyl chloride copolymer; ethylene-vinyl acetate copolymer; ethylene-vinyl acetate-vinyl chloride graft polymer resin; Polyolefin resin; ABS resin (acrylonitrile-butadiene-styrene terpolymer); AAS resin (acrylonitrile-styrene-special rubber terpolymer); AES resin (acrylonitrile-EPDM-styrene terpolymer) Ternary copolymer resin; amide resin; imide resin; ether ether ketone tree ; Carbonate resins, ethylene terephthalate; polybutylene terephthalate resin; sulfone resins.

Among them, vinyl chloride resin and fluorine resin are particularly preferable in view of weather resistance and flexibility. A vinyl chloride resin sheet is a pigment, dye, stabilizer,
It can be obtained by casting or calendering a compound in which a plasticizer or the like is mixed. The thickness of the sheet is preferably in the range of 50 to 200 μm from the viewpoint of ease of handling.

The fluororesin sheet used to protect the marking adhesive sheet attached to the stainless steel plate is preferably transparent. As a protective pressure-sensitive adhesive sheet, an acrylic resin layer containing an ultraviolet absorber is laminated on one or both sides of a transparent fluororesin sheet by extrusion molding, and the pressure-sensitive adhesive layer is laminated on the acrylic resin layer surface. And it is sufficient.

The pressure-sensitive adhesive sheet of the present invention using a vinyl chloride resin sheet is attached to a stainless steel plate for marking, covered with the fluorine-based resin pressure-sensitive adhesive sheet larger than the pressure-sensitive adhesive sheet, and the periphery of the fluorine-based resin pressure-sensitive adhesive sheet is covered. Adhesion to a stainless steel plate prevents discoloration of the vinyl chloride resin sheet and generation of undulation.

Further, since the pressure-sensitive adhesive layer of the fluorine-based resin pressure-sensitive adhesive sheet does not deteriorate, unnecessary portions of the fluorine-based resin sheet do not need to be cut off, so that the construction is easy and a good appearance can be maintained for a long time.

In order to produce the pressure-sensitive adhesive sheet of the present invention, a predetermined compound such as the acrylic copolymer, an organic solvent, a chelating agent and an isocyanate-based crosslinking agent is applied to one surface of a synthetic resin sheet, and the organic solvent is volatilized. By drying, an adhesive layer is formed. In addition, apply adhesive to release paper
It is also possible to adopt a transfer method in which the pressure-sensitive adhesive layer formed by drying is attached to the sheet.

The coating machine that can be used for applying the pressure-sensitive adhesive is not particularly limited as long as it is used for applying a normal pressure-sensitive adhesive solution, but a knife coater that can adjust the thickness with high accuracy and can apply with high productivity. , A comma coater, a roll coater and the like are preferable. The thickness of the pressure-sensitive adhesive to be laminated is preferably from 30 to 100 μm because a sufficient adhesive strength cannot be obtained when the pressure-sensitive adhesive is thin, and the sticking operation becomes complicated when the pressure-sensitive adhesive is thick.

The pressure-sensitive adhesive sheet is usually stored as a laminate in which a release sheet is adhered to the surface of the pressure-sensitive adhesive layer, and the release sheet is peeled off when used. The release sheet is not particularly limited as long as it has a supportive force and has a release layer releasable from the acrylic pressure-sensitive adhesive layer on its surface. For example, a nonwoven fabric laminated with an ethylene resin, an olefin resin film and paper And a product obtained by coating an ethylene terephthalate resin film or the like with a releasable material such as silicone.

[0026]

Embodiments of the present invention will be described below.

Examples Polymerized n-butyl acrylate of acrylic pressure-sensitive adhesive 80 parts by weight 2-ethylhexyl acrylate 15 parts by weight Acrylic acid 5 parts by weight n-dodecanethiol 0.01 parts by weight Ethyl acetate 100 parts by weight The mixture was charged into a separable flask equipped with a thermometer and a stirrer, heated to reflux under a nitrogen gas atmosphere and maintained for 20 minutes, and then 0.5 parts by weight of benzyl peroxide as a polymerization initiator was added dropwise to start the reaction. did. After 1 hour, 0.5 part by weight of the initiator is added.
A part by weight was added dropwise and the reaction was continued for another 5 hours. After the reaction was completed, 57 parts by weight of ethyl acetate was mixed and stirred to obtain an 8700 cps solution-type adhesive. The weight average molecular weight was 590,000 and the solid content was 28%.

Production of Vinyl Chloride Resin Sheet In Examples 1 to 6 and Comparative Examples 1 to 6, a vinyl chloride resin sheet was used as a synthetic resin sheet. Vinyl chloride resin 10
0 parts by weight, 15 parts by weight of plasticizer (dioctyl phthalate), 4 parts by weight of heat stabilizer (epoxidized soybean oil), Ba-Z
A composition obtained by substantially uniformly mixing 5 parts by weight of an n-type heat stabilizer and 1 part by weight of an ultraviolet absorber is molded by a calender molding method,
A vinyl chloride resin sheet having a thickness of 50 μm was obtained.

(Examples 1 to 6 and Comparative Examples 1 to 6) 100 parts by weight of the acrylic pressure-sensitive adhesive was mixed with an isocyanate-based crosslinking agent (trade name "Coronate L-2" manufactured by Nippon Polyurethane Co., Ltd.).
8)) A mixture of 3 parts by weight and a chelating agent shown in Table 1 in a predetermined amount was dried on the above-mentioned vinyl chloride resin sheet, and then dried.
It was applied to a thickness of μm and dried to obtain an adhesive sheet.

(Examples 7 to 12 and Comparative Examples 7 to 12)
On one side of a transparent fluorine-based resin film (manufactured by Kureha Chemical Industry Co., Ltd., product number “FT-50Y”), 100 parts by weight of the acrylic pressure-sensitive adhesive was used. −28 ”) 2.5
A mixture prepared by mixing a predetermined amount of the chelating agent shown in Table 2 by weight with the chelating agent shown in Table 2 was dried and then applied and dried to a thickness of 40 μm to obtain an adhesive sheet.

Evaluation of Physical Properties The pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples were evaluated for physical properties as follows. (1) Weather resistance test on stainless steel plate (in the case of Examples 1 to 6 and Comparative Examples 1 to 6) The above adhesive sheet (size of 100 mm x 25 mm) was attached to a stainless steel plate (SUS304, size of 150 mm x 50 mm). This is a xenon weatherometer (Atlas,
Model number "Ci35"), and black panel temperature 63 ±
Irradiation was performed with a xenon lamp for 102 minutes at 2 ° C. and a relative humidity of 50%, followed by spraying warm water for 18 minutes for 120 minutes. This was repeated to conduct a weather resistance acceleration test, and the test specimen after 2,000 hours was visually evaluated according to the following criteria.

(Cases of Examples 7 to 12 and Comparative Examples 7 to 12) A stainless plate (SUS304, size 150 mm)
X 50 mm) except that the vinyl chloride resin sheet-based pressure-sensitive adhesive sheet (size 100 mm x 25 mm) used in Example 1 was adhered, and each of the fluororesin film-based pressure-sensitive adhesive sheets was further adhered so as to cover it. Was evaluated in the same manner as in Example 1 by conducting a weather resistance acceleration test.

Occurrence of sheet undulation ○: No undulation was observed Δ: Slight undulation was observed ×: Swell was remarkably observed Sheet deviation occurred ：: No deviation was observed at all Δ: Slight deviation X: The color shift of the vinyl chloride resin sheet was noticeable. ○: The same color tone and gloss as before the test were maintained. Δ: Some fading was observed. X: Fading was observed. Discoloration ○: No discoloration was observed at all △: Slight discoloration was observed ×: Discoloration was noticeably observed Deterioration of the fluorine resin sheet in the sheet directly adhered to the stainless steel plate ○: Transparency equivalent to that before the test Δ: Some fading is observed X: Fading is observed

(2) Adhesion to stainless steel plate The test piece used in the above-mentioned (1) accelerated weathering test was subjected to JIS.
The 180 ° peeling force when peeling at a peeling rate of 300 mm / min at 23 ° C. was measured according to Z0237. The above results are shown in Tables 1 and 2.

[0034]

[Table 1]

[0035]

[Table 2] [Note] Chelating agent (1): having the structure shown by formula (1) (Asahi Denka Co., Ltd., trade name "ADK STAB 1500") chelating agent (2): having the structure shown by formula (2) (Asahi Denka) Chelating agent (3): having a structure represented by formula (3) (manufactured by Asahi Denka Co., Ltd., trade name “Adeka stub 522A”) Chelating agent (4): EDTA (ethylenediamine Acetic acid)

[0036]

As described above, the pressure-sensitive adhesive sheet of the present invention employs a pressure-sensitive adhesive layer comprising 100 parts by weight of an acrylic pressure-sensitive adhesive base polymer and 1.5 to 23 parts by weight of a chelating agent. Even when the film is adhered to a stainless steel plate and used outdoors, the film does not undulate or displace, does not discolor the adhesive, and has excellent weather resistance. Further, a sheet using a transparent fluororesin sheet as a synthetic resin sheet is effective for protecting a decorative adhesive sheet attached to a stainless steel plate. Therefore, it can be suitably used in display fields such as labels and stickers, signs and advertisements, and fleet marking fields such as vehicle decoration.

Claims (1)

[Claims] 1. One side of a synthetic resin sheet is provided with 100 parts by weight of a base polymer of an acrylic pressure-sensitive adhesive and a chelating agent.
An adhesive sheet, wherein an adhesive layer comprising 5 to 23 parts by weight is laminated.