JP7702265B2 - Marking Film - Google Patents

Description

The present invention relates to a marking film.

Adhesive films called marking films are used for outdoor billboards, outdoor signs, outdoor advertisements, vehicle advertisements, etc. Marking films have a structure in which an adhesive layer is laminated on one side of a base film, and by attaching the adhesive layer surface to a signboard, building, vehicle, etc., the colors, letters, images, etc. applied to the base film can provide an advertising effect.

As mentioned above, marking films are sometimes used for advertising and promotional purposes, and it may become necessary to reapply a different marking film after a certain period of time has passed. In this case, the marking film needs to be peeled off from the substrate, but because the adhesive in the marking film has relatively strong adhesion, it is not easy to peel the marking film off the substrate. Furthermore, when peeling the marking film off the substrate, some of the adhesive may remain on the substrate surface.

Patent Document 1 states that by laminating an acrylic white adhesive containing a specific polymer onto a colored base film and improving the adhesion between the colored film layer and the adhesive layer, it is possible to peel the film off without leaving any adhesive components on the adherend. In this way, the issue of adhesive remaining on the adherend, or so-called adhesive residue, has been studied in the past.

JP 2009-203370 A

When attempting to peel off the marking film from the substrate, particularly after a long period of time has passed or after it has been exposed to high temperatures such as in direct sunlight, the adhesive may remain on the substrate surface. In such cases, it has been necessary to remove the adhesive from the substrate using an organic solvent, for example by wiping it off.

However, the use of organic solvents can cause the paint on the substrate, such as a sign or a vehicle, to peel off, making the use of organic solvents an issue that requires careful consideration.

Therefore, the present invention aims to provide a marking film that can be easily peeled off from an adherend without using an organic solvent. Another aim of the present invention is to provide a marking film that allows the adhesive to be easily removed from an adherend without using an organic solvent.

The present invention is a marking film having a substrate and an adhesive layer, the adhesive layer having a polar functional group selected from the group consisting of a hydroxyl group, an amino group, a carbonyl group, and a benzoyl group, and containing a water-soluble compound having a molecular weight of 1000 or less.

The marking film of the present invention can be easily peeled off from the substrate using an aqueous solvent. In addition, the marking film of the present invention can be easily removed from the substrate using an aqueous solvent.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a marking film.

This embodiment is described in detail below.

In this specification, the range "X-Y" means "X or more and Y or less." Furthermore, unless otherwise specified, operations and physical properties are measured at room temperature (20-25°C) and relative humidity of 45-55% RH. In this specification, "(meth)acrylate" refers to "acrylate or methacrylate," and "(meth)acrylic acid" refers to "acrylic acid or methacrylic acid."

The first embodiment of the present invention is a marking film having a substrate and an adhesive layer, the adhesive layer having a polar functional group selected from the group consisting of a hydroxyl group, an amino group, a carbonyl group, and a benzoyl group, and containing a water-soluble compound having a molecular weight of 1000 or less.

The water-soluble compound contained in the adhesive layer of the marking film of the first embodiment is thought to reduce the cohesive strength of the adhesive when it comes into contact with an aqueous solvent by wiping with water or spraying, making it easier for the adhesive to peel off from the substrate.

Therefore, the marking film of the first embodiment can be easily peeled off from the adherend using an aqueous solvent. Furthermore, even if the adhesive remains on the surface of the adherend after the marking film is peeled off from the adherend, it can be easily removed with an aqueous solvent (for example, by wiping). Hereinafter, the film characteristics that allow it to be easily peeled off from the adherend with an aqueous solvent are also referred to as water peeling characteristics. Hereinafter, the adhesive characteristics that allow it to be easily removed from the adherend with an aqueous solvent (for example, by wiping) are also referred to as water removal characteristics.

Figure 1 is a schematic cross-sectional view showing a marking film. In Figure 1, the marking film 10 is composed of a substrate 11, an adhesive layer 12, and a release liner 13. The substrate 11 is disposed adjacent to the adhesive layer 12. When applying, the release liner 13 is removed from the marking film 10, and the marking film is applied to the substrate by the exposed adhesive layer 12.

In FIG. 1, the laminate has a substrate 11, an adhesive layer 12, and a release liner 13 in that order, but other intermediate layers may be present on the substrate and/or between the substrate and the adhesive layer, as long as the adhesive layer is exposed when the laminate is attached to an adherend.

The adhesive strength of the marking film is preferably 2 N/25 mm or more, more preferably 4 N/25 mm or more, and even more preferably 5 N/25 mm or more. When the adhesive strength of the marking film is equal to or greater than the above lower limit, adhesion to the adherend is guaranteed. The marking film needs to be attached to the adherend for a long period of time, and therefore requires a certain degree of adhesiveness. There is no particular upper limit for the adhesive strength, but it is 15 N/25 mm or less. The adhesive strength is measured using the method described in the examples below.

The components that make up the marking film are explained below.

[Adhesive layer]
The adhesive layer contains an adhesive and a water-soluble compound having a polar functional group (hereinafter also simply referred to as a water-soluble compound). Here, water-soluble refers to a compound that dissolves in an amount of 1 g or more, preferably 3 g or more, and more preferably 10 g or more in 100 g of water (25° C.).

The polar functional groups in the water-soluble compound are hydroxyl, amino, carbonyl and benzoyl groups. Of these, the polar functional group is preferably a hydroxyl or amino group, and more preferably a hydroxyl group, since this improves the water removal properties of the adhesive remaining on the adherend.

Examples of compounds having an amino group include polyethyleneimine, propylene oxide-modified polyethyleneimine, and polyvinylamine.

Examples of compounds that have a carbonyl group include 2-pyrrolidone and triethyl citrate.

As the water-soluble compound having a hydroxyl group, a polyhydric alcohol or a polyhydric alcohol derivative is preferable, since this further improves the water peeling property from the adherend and/or the water removal property of the adhesive remaining on the adherend.

Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, 1,3-butylene glycol, polyethylene glycol, glycerin, diglycerin, polyglycerin, pentanediol, and hexamethylene glycol. These may be used alone or in combination of two or more. Of these, it is preferable that the polyhydric alcohol is at least one selected from the group consisting of ethylene glycol, triethylene glycol, polyethylene glycol, and glycerin.

Examples of polyhydric alcohol derivatives include polyhydric alcohol monoalkyl ethers (polyhydric alcohol ethers) having a hydroxyl group, such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, and ethylene glycol monoethyl ether.

The water-soluble compound is preferably at least one selected from the group consisting of polyhydric alcohols, polyhydric alcohol derivatives, and polyethyleneimines, as this further improves the water peeling properties from the adherend and/or the water removal properties of the adhesive remaining on the adherend. Furthermore, from the viewpoint of improving adhesion, it is more preferable that the water-soluble compound is a polyhydric alcohol.

The molecular weight of the water-soluble compound is 1000 or less. If the molecular weight of the water-soluble compound exceeds 1000, the solubility in water decreases, and the water stripping properties and/or water removal properties decrease. The molecular weight of the water-soluble compound is preferably 800 or less, and more preferably 500 or less. The lower limit of the molecular weight of the water-soluble compound is usually 30 or more, and may be 50 or more.

The water-soluble compounds may be used alone or in combination of two or more.

The amount of water-soluble compound added is appropriately set depending on the type of adhesive used, the type of water-soluble compound, etc. In order to further enhance the effects of water peeling properties and/or water wiping properties, the amount of water-soluble compound added is preferably 0.5% by mass or more relative to the adhesive (e.g., acrylic copolymer), more preferably 1% by mass or more, and even more preferably 3% by mass or more. In addition, from the viewpoint of adhesion, the amount of water-soluble compound added is preferably 30% by mass or less relative to the adhesive (e.g., acrylic copolymer), and more preferably 25% by mass or less.

There are no particular limitations on the adhesive, and for example, acrylic adhesives, rubber adhesives, silicone adhesives, polyurethane adhesives, and polyester adhesives can be used. From the viewpoint of adhesive reliability, acrylic adhesives are particularly suitable.

The acrylic copolymer constituting the acrylic adhesive is formed by using an alkyl (meth)acrylate ester as the main monomer component, and, if necessary, a monomer that can be copolymerized with the alkyl (meth)acrylate ester (copolymerizable monomer). Here, the main component refers to 50% by mass or more (up to 100% by mass) of the monomer, preferably 65% by mass or more, and more preferably 85% by mass or more.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. These may be used alone or in combination of two or more. Among these, in consideration of adhesiveness, it is preferable to use n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate as the alkyl (meth)acrylate, and it is more preferable to use 2-ethylhexyl (meth)acrylate, and it is even more preferable to use 2-ethylhexyl acrylate, because sufficient adhesive strength can be obtained even in a low-temperature environment. When n-butyl (meth)acrylate and/or 2-ethylhexyl (meth)acrylate are used, it is preferable that they are used in an amount of 70 to 97% by mass, and more preferably 80 to 95% by mass, based on the total amount of monomers.

In addition, from the viewpoint of adhesion, it is preferable to use methyl (meth)acrylate in combination with n-butyl (meth)acrylate and/or 2-ethylhexyl (meth)acrylate, and it is more preferable to combine it with methyl methacrylate. The content of methyl (meth)acrylate is preferably 0.5 to 25% by mass, more preferably 1 to 20% by mass, and even more preferably 5 to 20% by mass, based on the total amount of monomers.

Examples of copolymerizable monomers that can be copolymerized with (meth)acrylic acid alkyl esters include carboxyl group-containing monomers or anhydrides thereof, such as (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; hydroxyl group-containing monomers, such as (meth)acrylic acid 2-hydroxyethyl, (meth)acrylic acid 2-hydroxypropyl, and (meth)acrylic acid 4-hydroxybutyl; and glycerin dimethacrylate; amide group-containing monomers, such as acrylamide, methacrylamide, N-vinylpyrrolidone, and N,N-dimethylacrylamide; amino group-containing monomers, such as (meth)acrylic acid aminoethyl and (meth)acryloylmorpholine; aromatic vinyl compounds, such as styrene and substituted styrene; cyano group-containing monomers, such as acrylonitrile; and vinyl esters, such as vinyl acetate. These may be used alone or in combination of two or more.

Among them, it is preferable to use a carboxyl group-containing monomer or anhydride thereof as a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester, since this improves the dispersion stability in the emulsion polymer, which is the most suitable form. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, myristoleic acid, palmitoleic acid, and oleic acid. Examples of the anhydride of the carboxyl group-containing monomer include maleic acid anhydride and itaconic acid anhydride. Among them, it is more preferable to use (meth)acrylic acid as a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester, and even more preferable to use acrylic acid.

When a carboxyl group-containing monomer or its anhydride is used, its content in the total monomers is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass.

The content of the acrylic copolymer in the pressure-sensitive adhesive layer is preferably 50 to 99.5% by mass, more preferably 60 to 99% by mass, and even more preferably 80 to 97% by mass.

The method for producing the acrylic copolymer is not particularly limited, and conventionally known methods such as solution polymerization using a polymerization initiator, emulsion polymerization, suspension polymerization, reversed-phase suspension polymerization, thin film polymerization, and spray polymerization can be used. In addition to the method of initiating polymerization using a polymerization initiator, a method of initiating polymerization by irradiation with radiation, electron beams, ultraviolet rays, etc. is also available. Among these, it is preferable to use the emulsion polymerization method, since the effects of the present invention are more pronounced. That is, in a preferred embodiment of the present invention, the acrylic copolymer is an emulsion polymer.

When the acrylic copolymer is an emulsion polymer, it is preferable that the acrylic copolymer is not crosslinked by a crosslinking agent. In other words, the acrylic copolymer is preferably a non-crosslinked body.

An example of the emulsion polymerization method is a method in which an emulsifier and a polymerization initiator are added to a monomer mixture containing the above-mentioned monomers, and emulsion polymerization is carried out.

In emulsion polymerization, from the viewpoint of polymerization stability, it is preferable that the monomer mixture is prepared by dissolving the emulsifier (or a part of the emulsifier) in the monomer mixture or by preparing the monomer mixture in the form of an O/W type emulsion in advance.

The procedure for carrying out the emulsion polymerization may be, for example, the following methods (1) to (3).
(1) The entire amount of the monomer mixture, emulsifier, water, etc. is charged, the temperature is raised, and the polymerization initiator dissolved in water is added dropwise or in portions to carry out polymerization.
(2) Water, an emulsifier, and a portion of the monomer mixture are charged into a reaction vessel, the temperature is raised, and then a polymerization initiator dissolved in water is added dropwise or in portions to proceed with the polymerization reaction. The remaining monomer mixture is then added dropwise or in portions to continue the polymerization.
(3) A polymerization initiator dissolved in water is charged into a reaction vessel, and the vessel is heated. Then, an emulsion consisting of a monomer mixture, an emulsifier, and water is added dropwise or in portions to carry out polymerization.

There are no particular limitations on the emulsifier, but from the viewpoint of improving the dispersion stability of the emulsion polymer, anionic emulsifiers or nonionic emulsifiers are preferred, with anionic emulsifiers being more preferred.

Examples of anionic emulsifiers include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, allyl alkyl sulfosuccinate salt, etc. Examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, etc. These emulsifiers may be used alone or in combination of two or more.

The amount of emulsifier added is preferably 0.5 to 12 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 0.7 to 6 parts by mass, per 100 parts by mass of the monomer mixture, from the viewpoint of the stability of the emulsion polymerization reaction and of preventing a decrease in physical properties due to remaining unreacted emulsifier.

The emulsifier may be added directly to the solution of the monomer mixture and water, or may be added in advance to the polymerization vessel, or both may be used.

The polymerization initiator may be either water-soluble or oil-soluble, and examples thereof include azo compounds such as 2,2'-azobis(2-methylpropionamidine) dihydrochloride and 2,2'-azobis(2-amidinopropane) dihydrochloride, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, and peroxides such as benzoyl peroxide, t-butyl hydroperoxide and hydrogen peroxide. Redox initiators such as a combination of a persulfate and sodium hydrogen sulfite or a combination of a peracid and sodium ascorbate may also be used. The polymerization initiator may be used alone or in combination of two or more kinds. Among these, persulfates or redox initiators are preferred from the viewpoint of excellent polymerization stability.

The amount of polymerization initiator added is preferably 0.01 to 6 parts by mass, more preferably 0.03 to 4 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the monomer mixture, from the viewpoint of accelerating the polymerization rate.

The polymerization initiator may be added to the reaction vessel in advance, may be added immediately before the start of polymerization, may be added in multiple batches after the start of polymerization, may be added to the monomer mixture in advance, or may be added to an emulsion of the monomer mixture after the emulsion is prepared.

During emulsion polymerization, known chain transfer agents and pH buffers may also be added.

The water used in emulsion polymerization is preferably ion-exchanged water. The amount of water used is preferably 30 to 400 parts by mass, more preferably 35 to 200 parts by mass, and even more preferably 40 to 150 parts by mass, per 100 parts by mass of the monomer mixture.

It is preferable to further add an aqueous alkali solution such as aqueous ammonia, various water-soluble amines, an aqueous sodium hydroxide solution, or an aqueous potassium hydroxide solution to the emulsion polymer dispersion obtained by emulsion polymerization to adjust the pH to 5 to 9 (preferably 6 to 8.5).

The solids concentration of the emulsion polymer dispersion is preferably 10 to 80% by mass, more preferably 25 to 70% by mass, and even more preferably 45 to 65% by mass.

The viscosity of the emulsion polymer dispersion at 25°C is preferably 50 to 12,000 mPa·s, more preferably 100 to 10,000 mPa·s, and even more preferably 200 to 9,000 mPa·s. In this specification, the viscosity is a value measured using a B-type rotational viscometer.

The emulsion polymer has an emulsion shape (particle shape) in which the emulsion polymer is dispersed. In this case, the average particle size of the emulsion polymer is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. The average particle size of the emulsion polymer is usually 50 nm or more, and more preferably 100 nm or more. Here, the average particle size of the emulsion polymer is the volume-based median size measured by a laser diffraction dispersion method.

The adhesive layer may contain a tackifier. Examples of tackifiers include, but are not limited to, alicyclic petroleum resins, terpene resins, polymerized rosin ester resins, and styrene resins.

The adhesive layer may further contain other additives that are conventionally known. Examples of such additives include fillers, pigments, and ultraviolet absorbers. Examples of fillers include zinc oxide, silica, and calcium carbonate.

The method for forming the adhesive layer is not particularly limited, but the adhesive layer may be formed by directly applying an adhesive composition for forming an adhesive layer (hereinafter also simply referred to as an adhesive composition) onto the substrate, or the adhesive layer may be formed on a release liner, which is then attached to the substrate. Specifically, the adhesive composition may be applied onto a release liner, and the adhesive layer made of the adhesive composition may be transferred to the substrate.

The method for applying the adhesive composition to the substrate or release liner is not particularly limited, and the composition can be applied using a known application device such as a roll coater, knife coater, air knife coater, bar coater, blade coater, slot die coater, lip coater, or gravure coater.

The thickness of the adhesive layer (film thickness after drying) is usually 5 to 100 μm, preferably 10 to 50 μm.

<Base material>
The substrate is not particularly limited, but examples thereof include paper substrates such as kraft paper and Japanese paper, resin substrates, synthetic paper, etc. Among these, from the viewpoint of durability, the substrate is preferably a resin substrate.

Examples of resins constituting the resin substrate include olefin-based resins having α-olefins as monomer components, such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer (EVA); polyester-based resins, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); polyvinyl chloride (PVC); vinyl acetate-based resins; polycarbonate (PC); acrylic resins; and polyurethane. These resins may be used alone or in combination of two or more. Among these, from the viewpoints of weather resistance and flexibility, polyvinyl chloride, acrylic resins, and polyurethane are preferable as resins constituting the resin substrate.

Examples of synthetic paper include polyester film and polypropylene film with fine voids.

The thickness of the substrate is selected appropriately depending on the type of substrate used, but is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm.

The substrate may be transparent or opaque.

The substrate may be colored or colorless. If it is colored, any colorant can be used. The colored substrate can be manufactured by blending the colorant with the raw resin, melt-kneading the mixture, and forming it into a film, or by a cast film-forming method in which the mixture is cast onto a process film and dried to form the film.

The substrate may contain various additives such as ultraviolet absorbers, plasticizers, heat stabilizers, dispersion solvents, and diluted dispersion solvents. Examples of ultraviolet absorbers include salicylic acid-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazole-based ultraviolet absorbers. Examples of plasticizers include phosphoric acid-based plasticizers, phthalic acid-based plasticizers, adipic acid-based plasticizers, and polyester-based plasticizers. Examples of heat stabilizers include lead salt-based heat stabilizers, metal soap-based heat stabilizers, and organotin compound-based heat stabilizers. Examples of dispersion solvents include ketones such as diisobutyl ketone and methyl isobutyl ketone, esters such as butyl acetate, and glycol ethers such as butyl cellosolve. Examples of diluted dispersion solvents include paraffin-based hydrocarbons, naphthenic hydrocarbons, aromatic hydrocarbons, and terpenes.

When an adhesive layer is provided on one side of the substrate, one side of the substrate may be surface-treated to improve adhesion to the adhesive layer. Examples of surface treatments include corona discharge treatment, plasma treatment, and primer treatment.

<Release Liner>
The marking film may contain a release liner. The release liner is used before the adhesive film is attached to an adherend, and has the function of protecting the adhesive layer and preventing a decrease in adhesiveness before use.

Examples of release liners include, but are not limited to, plastic films such as polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene; and papers such as fine paper, glassine paper, kraft paper, and clay-coated paper.

There are no particular limitations on the thickness of the release liner, but it is usually 10 to 400 μm. In addition, a layer of a release agent composed of silicone or the like may be provided on the surface of the release liner to improve releasability from the adhesive layer.

<Uses of marking film>
The surface of the substrate 11 of the marking film 10 according to one embodiment of the present invention that is not in contact with the adhesive layer 12 may be colored or patterned by a method such as inkjet printing, if necessary, via an ink receiving layer or the like. By removing the release liner 13 from such a marking film and attaching the exposed adhesive layer 12 surface to the surface of an adherend, the color or pattern of the adherend can be concealed while the color or pattern applied to the substrate 11 can be presented on the adherend. Furthermore, even after the adherend to which this marking film is attached has been attached for a certain period of time in an outdoor environment, the marking film can be easily peeled off from the adherend with an aqueous medium, and even if the adhesive remains on the adherend after the marking film is peeled off from the adherend, the adhesive can be easily removed by wiping with water. Therefore, the marking film according to one embodiment of the present invention can be suitably used for the purpose of decorating an adherend (such as a signboard, advertisement, vehicle, building, or traffic sign) used outdoors for a certain period of time.

<Method of peeling off marking film from substrate>
The second embodiment of the present invention is a method for peeling a marking film from an adherend, in which the film is peeled off from the adherend using an aqueous solvent. In the marking film of the first embodiment, the adhesive layer contains a water-soluble compound having a polar functional group and a molecular weight of 1000 or less. Therefore, by using an aqueous solvent, the marking film can be easily and simply peeled off from the adherend (without using an organic solvent that affects coating, etc.).

An aqueous solvent refers to one that contains 60% or more by weight of water (up to 100% by weight), preferably 70% or more by weight, more preferably 85% or more by weight, and most preferably the aqueous solvent is water.

Components other than water contained in the aqueous solvent include organic solvents that dissolve in water; surfactants. Examples of organic solvents that dissolve in water include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, dimethylformamide, methyl cellosolve, and tetrahydrofuran.

Methods for peeling the marking film from the substrate include, for example, peeling the marking film slightly off the substrate and then peeling it off while spraying an aqueous solvent onto the interface between the marking film and the substrate. When spraying the aqueous solvent, the aqueous solvent may be sprayed at high pressure.

<Method of removing adhesive>
The third embodiment of the present invention is a method for removing the adhesive of the marking film of the first embodiment from an adherend using an aqueous solvent when the adhesive remains on the adherend. As described above, the marking film of the first embodiment can be easily peeled off from the adherend using an aqueous solvent, but even if the adhesive remains on the adherend surface, it has excellent water removal properties.

The aqueous solvent may be the same as that described in the second embodiment.

Specific methods for removing adhesive from an adherend using an aqueous solvent include wiping the adherend surface with a cloth or nonwoven fabric containing an aqueous solvent, or spraying the aqueous solvent at high pressure.

The effects of the present invention will be explained using the following examples and comparative examples. In the examples, the terms "parts" and "%" may be used, but unless otherwise specified, they represent "parts by mass" or "% by mass." Furthermore, unless otherwise specified, each operation is carried out at room temperature (25°C).

Example 1
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel was charged with 84 parts by mass of 2-ethylhexyl acrylate, 12.5 parts by mass of methyl methacrylate, and 3.5 parts by mass of acrylic acid as raw material monomers, 4 parts by mass (0.96 parts by mass in terms of solid content) of sodium lauryl sulfate ("EMAL AD-25R" manufactured by Kao Corporation) as an emulsifier, and 35 parts by mass of degassed ion-exchanged water, and the mixture was stirred to prepare an emulsion.

Separately, 40 parts by mass of degassed ion-exchanged water was added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel, and the temperature was raised to 80°C. Next, the emulsion was transferred to a dropping funnel and dropped over 4 hours. In parallel with this, 4 parts by mass of a 3% by mass aqueous potassium persulfate solution was dropped as a polymerization initiator solution, and emulsion polymerization was carried out at a reaction temperature of 80°C. After the dropping was completed, the mixture was aged at 80°C for 2 hours to obtain an emulsion polymerization composition. Then, it was cooled to room temperature, and the pH was adjusted to 7.0 with 25% by mass of ammonia water and 25% by mass of sodium hydroxide aqueous solution, to obtain an aqueous dispersion of an acrylic polymer.

1 part by mass of ethylene glycol was added to 100 parts by mass of the solid content of the obtained acrylic polymer aqueous solution to obtain a pressure-sensitive adhesive composition.

The obtained adhesive composition was applied to the release-coated surface of a release liner, which was a 38 μm-thick polyethylene terephthalate film coated with 0.1 μm of silicone-based release agent, using a knife coater to give a dry film thickness of 15 μm, and then dried at 90°C to obtain a laminate of the release liner and adhesive layer.

A 50 μm thick polyvinyl chloride film was used as a substrate and attached to the adhesive layer surface of the laminate to obtain a marking film.

Example 2
A marking film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol added was 10 parts by mass.

Example 3
A marking film was obtained in the same manner as in Example 1, except that the amount of ethylene glycol added was 20 parts by mass.

Example 4
A marking film was obtained in the same manner as in Example 2, except that ethylene glycol was changed to triethylene glycol.

(Example 5)
A marking film was obtained in the same manner as in Example 2, except that ethylene glycol was changed to polyethylene glycol (molecular weight 600).

Example 6
A marking film was obtained in the same manner as in Example 2, except that ethylene glycol was changed to glycerin.

(Example 7)
A marking film was obtained in the same manner as in Example 2, except that ethylene glycol was changed to polyethyleneimine (molecular weight 600, Epomin SP-006 manufactured by Nippon Shokubai Co., Ltd.).

(Comparative Example 1)
A marking film was obtained in the same manner as in Example 1, except that ethylene glycol was not added.

(Measurement method: adhesive strength)
The marking films obtained in the examples and comparative examples were left to stand for one day under standard conditions (23°C, 50% RH), the release liner was peeled off, and the adhesive layer surface was attached to a SUS plate (SUS304 steel plate), and then the adhesive strength was measured. Specifically, the sheet was peeled off in the 180° direction at a test speed of 300 mm/min using a tensile tester, and the adhesive strength was measured. The numerical value was converted to the peeling force per 25 mm of sheet width (N/25 mm). The results are shown in Table 1.

(Evaluation method: Wipe test)
In the examples and comparative examples, a release liner was attached instead of a polyvinyl chloride film. One release liner was peeled off, and an adhesive (15 μm) was attached to a melamine-coated plate and left to stand for 7 days in a 40° C. environment. After peeling off the other release liner, the adhesive surface was wiped back and forth 20 times with a water-soaked wiper (Bencotto (registered trademark), manufactured by Asahi Kasei Corporation), and then the appearance was evaluated.

○: completely wiped off
△: Partially wiped off,
×: Wiping was not possible.

(Evaluation method: Ease of peeling when sprayed with water)
The marking films obtained in the examples and comparative examples were left standing for one day in a standard environment (23°C, 50% RH), the release liner was peeled off, and the adhesive layer surface was attached to a melamine-coated plate, and then left standing for 7 days in a 40°C environment. After peeling off the edge of the marking film, the marking film was held at the edge and peeled off while spraying water at a water pressure of 10 MPa on the interface between the marking film and the adherend. The ease of peeling was evaluated.

◯: Easily peelable △: Peelable with great resistance ×: Cannot be peeled.

The results are shown in Table 1.

As can be seen from the above results, the marking films of Examples 1 to 7 could be easily peeled off from the substrate using water, and any adhesive residue remaining on the substrate could be removed by wiping with water.

10 marking film,
11 base material,
12 adhesive layer,
13 Release liner.

Claims (7)

A marking film having a substrate and a pressure-sensitive adhesive layer,
the pressure-sensitive adhesive layer comprises a water-soluble compound having a polar functional group selected from the group consisting of a hydroxyl group and an amino group and having a molecular weight of 1000 or less, and an acrylic copolymer;
The acrylic copolymer is formed by using 2-ethylhexyl (meth)acrylate in an amount of 80% by mass or more and 97% by mass or less based on the total amount of monomers,
The marking film, wherein the water-soluble compound is at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, 1,3-butylene glycol, glycerin, diglycerin, polyglycerin, pentanediol, hexamethylene glycol, and polyhydric alcohol alkyl ethers thereof, and compounds having an amino group, with the proviso that when the water-soluble compound is propylene glycol, the amount added is 3% by mass or more relative to the acrylic copolymer. A marking film having a substrate and a pressure-sensitive adhesive layer,
the pressure-sensitive adhesive layer comprises a water-soluble compound having a polar functional group selected from the group consisting of a hydroxyl group and an amino group and having a molecular weight of 1000 or less, and an acrylic copolymer;
The acrylic copolymer is formed by using 2-ethylhexyl (meth)acrylate in an amount of 80% by mass or more and 97% by mass or less based on the total amount of monomers,
the water-soluble compound is at least one selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, 1,3-butylene glycol, glycerin, diglycerin, polyglycerin, pentanediol, hexamethylene glycol, and polyhydric alcohol alkyl ethers thereof, and compounds having an amino group;
A marking film, wherein the amount of the water-soluble compound added is 3% by mass or more based on the acrylic copolymer. The water-soluble compound is ethylene glycol, diethylene glycol, triethylene glycol
The marking film according to claim 1 or 2, wherein the polyol is at least one selected from the group consisting of ethanol, tripropylene glycol, propylene glycol, 1,3-propanediol, dipropylene glycol, 1,3-butylene glycol, glycerin, diglycerin, polyglycerin, pentanediol, hexamethylene glycol, and polyhydric alcohol alkyl ethers thereof , and polyethyleneimine. The marking film according to any one of claims 1 to 3 , wherein the pressure-sensitive adhesive layer contains an emulsion-based acrylic copolymer. The marking film according to any one of claims 1 to 4 , wherein methyl (meth)acrylate is used in combination with the 2-ethylhexyl (meth)acrylate. The marking film according to any one of claims 1 to 5 , wherein the substrate is a resin substrate. The method for peeling a marking film from an adherend according to any one of claims 1 to 6 , wherein the marking film is peeled from the adherend by using an aqueous solvent.