JP2020185694A - Laminated sheet - Google Patents

Abstract

To provide a laminated sheet that prevents the occurrence of formaldehyde.SOLUTION: A laminated sheet has a foaming adhesive layer on one side of synthetic paper, where the foaming adhesive layer contains an acrylic resin having a hydroxy group and an epoxy crosslinker.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated sheet.

Conventionally, a laminated sheet having an adhesive layer has been used as a sheet to be temporarily attached to an adherend such as glass, resin, or metal. For example, a sheet provided with a foamed resin layer having a large number of pores as an adhesive layer has a high usability because the foamed resin layer adheres to an adherend like a suction cup, so that there is little adhesive residue when peeled off. (See, for example, Patent Documents 1 and 2).

Examples of applications of such laminated sheets include advertising materials such as labels, posters and stickers, stationery or toy materials such as table mats, mouse pads and stickers, and building materials such as wallpaper.

Japanese Unexamined Patent Publication No. 2004-174918 Japanese Unexamined Patent Publication No. 2006-176693

A cross-linking agent is often used in combination with the resin as the main agent for the purpose of increasing the cohesive force of the resin in the adhesive layer that temporarily adheres to the adherend, such as the foamed resin layer. The resin material is selected so as to obtain desired physical properties such as mechanical strength and water resistance of the laminated sheet, but formaldehyde may be generated depending on the selected material. In the past, the amount of formaldehyde generated was reduced by selecting a cross-linking agent, but for the production of laminated sheets at factories and indoor use, formaldehyde is generated from the time of manufacturing the laminated sheets to the time of use. It is required that it does not occur.

However, it is difficult to select a resin that does not generate formaldehyde, and although formaldehyde is not generated, the adhesive layer may become sticky and difficult to peel off, or the elasticity of the adhesive layer may become low and it may be difficult to attach the resin. Therefore, studies have been conducted on laminated sheets that do not generate formaldehyde while maintaining excellent physical properties.

An object of the present invention is to provide a laminated sheet that does not generate formaldehyde.

As a result of diligent studies by the present inventors to solve the above problems, if a specific acrylic resin and a specific cross-linking agent are used for the foamed pressure-sensitive adhesive layer, the physical properties such as elasticity of the foamed pressure-sensitive adhesive layer can be adjusted in a practically suitable range. The present invention was completed by finding that it can be maintained at a high level and does not generate formaldehyde.

That is, the present invention is as follows.
(1) A laminated sheet having a foamed adhesive layer on one surface of synthetic paper.
A laminated sheet in which the foamed adhesive layer contains an acrylic resin having a hydroxyl group and an epoxy-based cross-linking agent.

(2) The content of the epoxy-based cross-linking agent in the foamed pressure-sensitive adhesive layer is 0.5 to 20 parts by mass with respect to 100 parts by mass of the acrylic resin having a hydroxyl group.
The laminated sheet according to (1) above.

(3) The synthetic paper is a porous olefin resin sheet containing an inorganic filler.
The laminated sheet according to the above (1) or (2).

(4) A print receiving layer is provided on the surface of the synthetic paper opposite to the foamed adhesive layer.
The laminated sheet according to any one of (1) to (3) above.

According to the present invention, it is possible to provide a laminated sheet that does not generate formaldehyde.

It is sectional drawing which shows the structural example of the laminated sheet of one Embodiment of this invention. It is an enlarged cross-sectional view which illustrates the structure of the foam adhesive layer.

Hereinafter, the laminated sheet of the present invention will be described in detail, but the description of the constituent requirements described below is an example (typical example) as an embodiment of the present invention, and is not specified in these contents. ..
In the following description, the description of "(meth) acrylic" refers to both acrylic and methacrylic.

(Laminated sheet)
The laminated sheet of the present invention has a foamed adhesive layer on one surface of synthetic paper. The laminated sheet of the present invention can have a release sheet on the surface of the foamed adhesive layer, if necessary.
FIG. 1 shows a configuration example of a laminated sheet 1 as an embodiment of the present invention.
As shown in FIG. 1, the laminated sheet 1 has a synthetic paper 11 and a foam adhesive layer 12 provided on one surface of the synthetic paper 11. The foamed adhesive layer 12 is provided with a release sheet 13 as needed.

<Synthetic paper>
As the synthetic paper in the present invention, a porous resin sheet can be usually used, and examples of the porous resin sheet that can be used include an olefin resin sheet containing an inorganic filler.

When the synthetic paper is porous, the overall porosity of the synthetic paper is preferably 5% or more, more preferably 15% or more. The overall porosity is preferably 50% or less, more preferably 45% or less. If the total porosity is 5% or more, the opacity or flexibility of the synthetic paper can be easily increased, and if the total porosity is 50% or less, the mechanical strength such as the tensile elastic modulus of the synthetic paper is appropriate. Easy to control the range.
The overall pore ratio means a value obtained by cutting out a cross section of synthetic paper, observing it with an electron microscope, and measuring the area ratio (%) occupied by the pores in the entire region in the thickness direction.

<< Olefin resin >>
Examples of the olefin resin that can be used for synthetic paper include polyethylene resins such as low density polyethylene, linear low density polyethylene, medium density polyethylene, and high density polyethylene, polypropylene resins, polymethyl-1-pentene, and ethylene-cyclic olefins. Polyethylene-based resins such as polymers; polyamide resins such as nylon 6, nylon 6, 6, nylon 6, 10; polyethylene terephthalates and their copolymers, aromatic polyesters such as polyethylene naphthalate, and polylactic acid and polybutylene succinate. , Polyester-based resins such as aliphatic polyesters such as polybutylene adipate; examples thereof include polycarbonate, atactic polystyrene, syndiotactic polystyrene, polyphenylene sulfide and the like. These can also be used by mixing two or more kinds. Among these, polyolefin-based resins or polyester-based resins are preferable. Among the polyolefin-based resins, polypropylene-based resins are preferable. Examples of the polypropylene-based resin include a propylene homopolymer, a copolymer of propylene as a main component and an α-olefin such as ethylene, 1-butene, 1-hexene, 1-hexene, and 4-methyl-1-pentene. Can be mentioned. The stereoregularity is not particularly limited, and isotropic, syndiotactic, and polypropylene-based resins exhibiting various degrees of stereoregularity can be used. The copolymer may be a binary system, a ternary system, a quaternary system, a random copolymer, or a block copolymer.

<< Inorganic filler >>
Examples of the inorganic filler include heavy calcium carbonate, light calcium carbonate, calcined clay, silica, diatomaceous earth, talc, mica, synthetic mica, cericite, kaolinite, titanium oxide, barium sulfate, alumina and the like. Of these, heavy calcium carbonate is preferable. These may be used alone or in combination of two or more.

The content of the inorganic filler in the synthetic paper is preferably 8% by mass or more, more preferably 10% by mass or more, from the viewpoint of adjusting the synthetic paper to an appropriate whiteness. On the other hand, the content is preferably 65% by mass or less, more preferably 60% by mass or less, from the viewpoint of adjusting the synthetic paper to an appropriate strength.

The synthetic paper may contain other additives such as antioxidants, light stabilizers, dispersants of inorganic fillers, lubricants and the like, if desired. Examples of the antioxidant include steric hindrance phenol-based, phosphorus-based, amine-based and the like. The blending amount of the antioxidant in the synthetic paper is usually about 0.001 to 1% by mass. Examples of the light stabilizer include steric hindrance amines, benzotriazoles, benzophenones and the like. The blending amount of the light stabilizer in the synthetic paper is usually about 0.001 to 1% by mass. Examples of the dispersant include a silane coupling agent, higher fatty acids such as oleic acid and stearic acid, metal soap, polyacrylic acid, polymethacrylic acid, and salts thereof. The blending amount of the dispersant in the synthetic paper is usually about 0.01 to 4% by mass.

The synthetic paper may have a single-layer structure or a multi-layer structure. In the case of a single-layer structure, the synthetic paper may be any of a non-stretched sheet, a uniaxially stretched sheet and a biaxially stretched sheet. In the case of a multi-layer structure, it may be a two-layer structure or a structure having three or more layers. In the case of a two-layer structure, the number of stretching axes is any of non-stretching / uniaxial stretching, non-stretching / biaxial stretching, uniaxial stretching / uniaxial stretching, uniaxial stretching / biaxial stretching and biaxial stretching / biaxial stretching. It may be. In the case of a structure having three or more layers, the single-layer structure and the two-layer structure may be combined, and any combination may be used.

The whiteness of the synthetic paper is preferably 80% or more, more preferably 85% or more, from the viewpoint of facilitating the determination of the contents printed on the synthetic paper. The whiteness means the whiteness measured according to JIS-L1015.

The opacity of the synthetic paper can be adjusted to an appropriate opacity according to the application. Specifically, the opacity of the synthetic paper is preferably 40 to 100%, more preferably 70 to 100%, and even more preferably 80 to 100%. When the opacity is 40% or more, sufficient concealment as a printing paper can be easily obtained. The opacity means the opacity measured according to JIS-P8138.

<Foam adhesive layer>
The foamed adhesive layer is a foamed sheet of a resin composition containing an acrylic resin having a hydroxyl group and an epoxy-based cross-linking agent, and is temporarily attached to an adherend. The foamed adhesive layer has a suction cup structure formed on the surface by foaming, and has high adsorptivity to the adherend. In addition, the foamed adhesive layer has high elasticity and is easy to attach and peel off.

<< Acrylic resin with hydroxyl group >>
The acrylic resin having a hydroxyl group contains a hydroxyl group-containing monomer as an essential polymerization component, and if necessary, a polymerization component of an alkyl (meth) acrylate-based monomer, a polar group-containing monomer other than the hydroxyl group-containing monomer, and other polymerizable monomers. It is obtained by polymerizing as. A typical example of the acrylic resin having a hydroxyl group is a (meth) acrylic acid ester copolymer having a hydroxyl group.
Since such an acrylic resin having a hydroxyl group does not have a substituent such as an N-methylol group that causes formaldehyde generation, formaldehyde is not generated by a cross-linking reaction with an epoxy-based cross-linking agent.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, and 6-hydroxyhexyl (meth). ) Acrylate, hydroxyalkyl (meth) acrylate monomer such as 8-hydroxyoctyl (meth) acrylate, caprolactone-modified monomer such as caprolactone-modified 2-hydroxyethyl (meth) acrylate, diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, etc. Oxyalkylene-modified (meth) acrylate monomer, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid and other primary hydroxyl group-containing (meth) acrylate monomer; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) ) Secondary hydroxyl group-containing (meth) acrylate monomer such as acrylate and 3-chloro2-hydroxypropyl (meth) acrylate; Tertiary hydroxyl group-containing (meth) acrylate monomer such as 2,2-dimethyl2-hydroxyethyl (meth) acrylate. And so on. These may be used alone or in combination of two or more.

Among them, a primary hydroxyl group-containing (meth) acrylate monomer is preferable because it has excellent reactivity with a cross-linking agent described later and has improved moisture-heat whitening resistance. Among them, 4-hydroxybutyl (meth) acrylate or 2-hydroxyethyl (meth) acrylate makes it easy to appropriately adjust the physical properties such as adhesiveness and elasticity of the foamed adhesive layer, and impurities such as di (meth) acrylate are contained. It is more preferable because it is less and easy to manufacture.

The content ratio of the hydroxyl group-containing monomer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1% by mass or more, based on the total copolymerization component. The content ratio is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less. If the content is 0.1% by mass or more, the decrease in moisture-heat whitening resistance is likely to be suppressed, and if the content is 15% by mass or less, the storage stability or reworkability when used as an adhesive is deteriorated. Shortening of pot life is likely to be suppressed.

As the copolymerization component other than the hydroxyl group-containing monomer constituting the acrylic resin having a hydroxyl group, at least one of an alkyl (meth) acrylate-based monomer and an alkoxyalkyl (meth) acrylate-based monomer is preferable. Examples of the alkyl (meth) acrylate-based monomer that can be used include monomers having an alkyl group having usually 1 to 24 carbon atoms (preferably 1 to 18, more preferably 1 to 12, still more preferably 1 to 8). Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert- Butyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) Examples thereof include acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, and stearyl (meth) acrylate. Examples of the alkoxyalkyl (meth) acrylate-based monomer that can be used include 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, and ethoxymethyl (meth) acrylate. And so on. These may be used alone or in combination of two or more.

Among these, methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate, or methyl (meth) acrylate, ethyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate n-Butyl (meth) acrylate is preferred.

The content ratio of the alkyl (meth) acrylate-based monomer is usually preferably 99.9% by mass or less based on the total copolymerization component, and the change in the acrylic resin when the alkyl chain is hydrolyzed is large. From the viewpoint of suppressing deterioration, 99% by mass or less is more preferable, and 98% by mass or less is further preferable. From the viewpoint of facilitating the balance of adhesiveness, the content ratio is preferably 85% by mass or more, more preferably 88% by mass or more, and further preferably 90% by mass or more.

Further, as other polymerizable monomers such as polar group-containing monomers copolymerizable with the hydroxyl group-containing monomer, ethylene-based unsaturated monomers having a relatively low molecular weight such as acrylic acid, methacrylic acid, and acrylonitrile can be used. Can be mentioned. The content ratio of such an ethylene-based unsaturated monomer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and further preferably 1% by mass or more with respect to the entire copolymerization component. preferable. The content ratio is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less. When the content ratio is 0.1% by mass or more, it is easy to improve the stability at the time of polymerization and adjust the molecular weight, and it is easy to improve the water resistance of the obtained acrylic resin. When the content ratio is 10% by mass or less, it is easy to appropriately adjust the physical properties such as adhesiveness and elasticity of the obtained acrylic resin, and it is easy to suppress a decrease in moisture heat whitening resistance.

When a hydroxyl group-containing (meth) acrylic acid ester copolymer is used as the acrylic resin having a hydroxyl group, the glass transition temperature of the copolymer is preferably −10 ° C. or lower, and preferably −20 ° C. or lower. Is more preferable. When the glass transition temperature is -10 ° C or less, the gel fraction of the (meth) acrylic acid ester copolymer can be easily controlled to a predetermined value or less, and as a result, foam adhesion having excellent self-adhesiveness and surface smoothness is excellent. Layers are easy to obtain. There is no particular lower limit for the glass transition temperature, but it is usually −70 ° C. or higher. The self-adhesive force refers to the peel strength between the foamed adhesive layer and the adherend.

The hydroxyl group-containing (meth) acrylic acid ester copolymer forms a homopolymer having a glass transition temperature of -20 ° C or lower from the viewpoint of facilitating control of the glass transition temperature of -10 ° C or lower. It preferably contains a unit of acid ester monomer.

Examples of the (meth) acrylic acid ester monomer forming a homopolymer having a glass transition temperature of −20 ° C. or lower include ethyl acrylate (glass transition temperature of homopolymer (hereinafter, Tg): −24 ° C.). N-propyl acrylate (Tg: -37 ° C), n-butyl acrylate (Tg: -55 ° C), n-heptyl acrylate (Tg: -60 ° C), n-hexyl acrylate (Tg: -61 ° C) ° C.), n-octyl acrylate (Tg: -65 ° C.), 2-ethylhexyl acrylate (Tg: -70 ° C.), n-octyl methacrylate (Tg: -25 ° C.), n-decyl methacrylate (Tg:) (Meta) acrylic acid alkyl ester such as −49 ° C.; 2-methoxyethyl acrylate (Tg: -50 ° C.), 3-methoxypropyl acrylate (Tg: −75 ° C.), 3-methoxybutyl acrylate (Tg) : −56 ° C.), (meth) acrylic acid alkoxyalkyl ester such as ethoxymethyl acrylate (Tg: −50 ° C.) and the like can be mentioned.
Of these, a (meth) acrylic acid alkyl ester that forms a homopolymer having a glass transition temperature of −20 ° C. or lower is preferable.

If the glass transition temperature of the hydroxyl group-containing (meth) acrylic acid ester copolymer can be adjusted to -10 ° C or lower, methyl acrylate (glass transition of homopolymer) is used as another copolymerizable monomer. Temperature (hereinafter, Tg): 10 ° C.), Methyl methacrylate (Tg: 105 ° C.), Ethyl methacrylate (Tg: 63 ° C.), n-propyl methacrylate (Tg: 25 ° C.), n-butyl methacrylate (Tg) : 20 ° C.) or the like may be used.
Further, the above-mentioned (meth) acrylic acid ester monomer may be used alone or in combination of two or more.

<< Polymerization of acrylic resin containing hydroxyl groups >>
The polymerization method and conditions of the acrylic resin containing a hydroxyl group are not particularly limited, and an appropriately selected copolymerization component and polymerization initiator are mixed or dropped in an organic solvent under predetermined polymerization conditions. Solution for polymerization Radical polymerization, addition of a polymerization initiator and emulsifier in an aqueous solvent, and then mixing or dropping appropriately selected copolymerization components to polymerize under predetermined polymerization conditions, such as emulsion polymerization, suspension polymerization, and massive polymerization. Conventionally known methods and conditions can be used. Of these, solution radical polymerization or emulsion polymerization is preferable, and emulsion polymerization is particularly preferable in that an emulsion of an acrylic resin containing a hydroxyl group can be stably obtained.

Examples of the polymerization initiator include benzoyl peroxide, laurolyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxymaleic acid, succinic acid peroxide, and cumene hydroperoxide. , Diisopropyl peroxydicarbonate, cumyl peroxyneodecanoate, cumyl peroxyoctate, diisopropylbenzene hydroperoxide, paramentan hydroperoxide and 2,2-bis (4,5-di-t-butylperoxy). Organic peroxides such as cyclohexyl) propane; inorganic peroxides such as hydrogen peroxide, potassium peroxide and sodium peroxide; persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; 2,2'-azo Azo compounds such as bisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (methylpropionic acid) Etc., and can be appropriately selected and used according to the monomer to be used and the polymerization conditions. These polymerization initiators can be used alone or in combination of two or more.
The proportion of the polymerization initiator used is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, still more preferably 0.1, based on 100 parts by mass of the total amount of the copolymerization components. ~ 1 part by mass.

When the emulsion polymerization method is adopted as the polymerization method of the acrylic resin containing the hydroxyl group, organic peroxide and persulfate are preferable as the polymerization initiator.
Examples of emulsifiers used when the emulsion polymerization method is adopted include polyoxyethylene alkyl ether, polyoxyethylene alkyl sulfate, polyoxyethylene polycyclic phenyl ether sulfate, sodium polyoxyethylene alkyl succinate, and lauryl. Examples thereof include surfactants such as sodium sulfate and sodium dodecylbenzene sulfonate. Commercially available products can be used as the emulsifier, and examples of the commercially available products include "Latemuru S-180A" and "PD-104" manufactured by Kao Corporation; "Ereminol JS-2" manufactured by Sanyo Kasei Co., Ltd .; "Aqualon KH-10" and "KH-1025" manufactured by Pharmaceutical Co., Ltd .; "Adecaria Soap SE-10N" and "SR-10N" manufactured by Asahi Denka Kogyo Co., Ltd .; "Antox MS-60" manufactured by Nippon Emulsifier Co., Ltd .; Toho Examples thereof include "Surfmer FP-120" manufactured by Chemical Industry Co., Ltd.
The proportion of the emulsifier used is preferably 0.2 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, and further preferably 0.7 to 3 parts by mass with respect to 100 parts by mass of the total amount of the copolymerization components. It is a mass part.

Further, when the emulsion polymerization method is adopted, a molecular weight adjusting agent can be used in combination as an additive component at the time of the polymerization reaction in order to obtain a desired weight average molecular weight in addition to the copolymerization component, the polymerization initiator and the emulsifier. .. Examples of the molecular weight modifier include butyl mercaptan, dodecyl mercaptan, octyl thioglycolate, isopropyl alcohol, methanol, carbon tetrachloride and the like.
The ratio of the molecular weight adjusting agent used is preferably 0.001 to 0.50 parts by mass, more preferably 0.003 to 0.30 parts by mass, still more preferably 0.003 to 0.30 parts by mass, based on 100 parts by mass of the total amount of the copolymerization components. Is 0.005 to 0.20 parts by mass.

The weight average molecular weight of the acrylic resin containing a hydroxyl group is usually 20 to 2.5 million, preferably 600 to 1.8 million, and more preferably 800 to 1.6 million. The larger the weight average molecular weight, the higher the durability and reworkability, and the smaller the weight average molecular weight, the longer the pot life, and the less the need to dilute with a large amount of solvent during coating.

The dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, and even more preferably 6 or less. When the dispersity is 15 or less, the cohesive force, durability or reworkability tends to be difficult to decrease. The lower limit is usually 1.

<< Epoxy cross-linking agent >>
As the epoxy-based cross-linking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule can be used.
The present invention is characterized in that at least an epoxy-based cross-linking agent is used for the cross-linking reaction of the acrylic resin having a hydroxyl group. A cross-linking agent other than a cross-linking agent having a functional group capable of generating formaldehyde, such as an N-methylol group, can be used in combination with the above-mentioned epoxy-based cross-linking agent, but only the epoxy-based cross-linking agent is used. It is preferable to do so. If an epoxy-based cross-linking agent having no substituent or the like that generates formaldehyde is used alone, formaldehyde is not generated in the foamed adhesive layer. Even if the cross-linking reaction continues from the time of manufacturing the laminated sheet to the time of use, the generation of formaldehyde can be completely prevented. Furthermore, if it is an epoxy-based cross-linking agent, it can be sufficiently cross-linked even when used in combination with an acrylic resin having a hydroxyl group, so that the physical properties such as mechanical strength, viscosity, and elasticity of the foamed adhesive layer are the same as before, and they are laminated. It is possible to maintain the ease of peeling and attaching the sheet.

Examples of the epoxy-based cross-linking agent include diglycidyl aniline, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-Hexanediol diglycidyl ether, adipate diglycidyl ester, phthalic acid diglycidyl ester, resorcin diglycidyl ether, bisphenol A-diglycidyl ether, hydrogenated bisphenol A-diglycidyl ether, bisphenol F-diglycidyl ether, bisphenol S -Diglycidyl ether, bisphenol A / epichlorohydrin type epoxy resin, glycerin triglycidyl ether, trimethylolpropan triglycidyl ether, triglycidyl-tris (2-hydroxyethyl) isocyanurate, N, N, N', N'-tetraglycidyl -M-Xylylene diamine, N, N, N', N'-tetraglycidyl-4,4-diaminodiphenylmethane, 1,3-bis (N, N'-diamineglycidylaminomethyl) cyclohexane, 1,3-bis (N, N-diglycidyl aminomethyl) toluene, tetraglycidyl xylene diamine, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, sorbitan polyglycidyl ether, Trimethylol propanepolyglycidyl ether, phenol novolac type epoxy resin, cresol novolac type epoxy resin, cyclic aliphatic epoxy resin, glycidyl ester type epoxy resin, glycidyl diamine type epoxy resin, heterocyclic epoxy resin, having an epoxy group on the side chain Acrylic resin and the like can be mentioned.

Of these, glycidyl ether-based epoxy resins are preferable because they have high reactivity with acrylic resins having hydroxyl groups and the degree of cross-linking can be easily adjusted. Among glycidyl ether-based epoxy resins, ethylene glycol diglycidyl ether and glycerin More preferably, diglycidyl ether, glycerin triglycidyl ether or polyglycerol polyglycidyl ether. These epoxy-based cross-linking agents may be used alone or in combination of two or more.

The higher the content of the epoxy-based cross-linking agent in the foamed adhesive layer, the higher the cross-linking degree and cohesive force of the acrylic resin tend to be due to the cross-linking reaction. Further, as the number of functional groups in the acrylic resin decreases, the initial adhesiveness (tack force) of the foamed adhesive layer to the adherend tends to decrease, and the adhesiveness between the synthetic paper and the foamed adhesive layer tends to decrease. On the other hand, the smaller the content of the epoxy-based cross-linking agent, the weaker the cross-linking degree and cohesive force of the acrylic resin tend to be. In addition, it is difficult to maintain the position and shape of the bubbles when foamed, and the compression recovery rate of the foamed adhesive layer tends to decrease, making it difficult to maintain the adsorption function to the adherend. Therefore, the amount of the epoxy-based cross-linking agent used for the acrylic resin having a hydroxyl group has an appropriate range, and the content of the epoxy-based cross-linking agent in the foamed adhesive layer is the solid content with respect to 100 parts by mass of the acrylic resin having a hydroxyl group. Therefore, 0.5 parts by mass or more is preferable, 1 part by mass or more is more preferable, and 2 parts by mass or more is further preferable. When it is at least the above lower limit value, the degree of crosslinking and the cohesive force of the acrylic resin are increased by the crosslinking reaction, the bubbles in the foamed adhesive layer are maintained, the compression recovery rate is further improved, and a sufficient adsorption function can be easily obtained. On the other hand, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less. When it is less than the above upper limit, it is easy to suppress the decrease in the number of functional groups in the acrylic resin due to the cross-linking reaction, the initial adhesiveness (tack force) of the foamed adhesive layer to the adherend is decreased, and the synthetic paper and the foamed adhesive layer adhere to each other. It is easy to suppress the deterioration of sex. From the viewpoint of obtaining an appropriate degree of cross-linking, for example, the epoxy group (glycidyl group) of the epoxy-based cross-linking agent is in the range of 0.5 to 10 mol with respect to 1 mol of the hydroxyl group of the acrylic resin. A cross-linking agent can be used.

<< Additives >>
The foamed pressure-sensitive adhesive layer can contain various additives, if necessary, from the viewpoint of improving processability in the manufacturing process or improving the performance of the foamed pressure-sensitive adhesive layer.
Additives include, for example, defoamers, foaming aids, defoamers, thickeners, fillers, preservatives, fungicides, wetting agents, gelling agents, flame retardants, antioxidants, UV absorbers, etc. Examples include pigments, dyes, tackifiers, conductive compounds and the like.

Examples of the foam stabilizer include fatty acid ammonium such as ammonium stearate, sulfonic acid type anionic surfactant such as alkylsulfosuccinate, quaternary alkylammonium chloride, alkylbetaine amphoteric acid, and fatty acid alkanolamine.
Examples of the foaming aid include sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium polyoxyethylene alkylphenol ether sulfate, and the like.

Examples of the thickener include acrylic polymer particles such as a carboxylic acid-modified acrylic acid ester polymer, fine particles of an inorganic compound such as fine silica, and a reactive inorganic compound such as magnesium oxide.
Examples of the filler include calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, barium hydroxide, clay, kaolin, glass powder and the like.

Examples of preservatives or fungicides include dihydroxydichlorophenylmethane, sodium pentachlorophenate, 2,3,4,6-tetrachloro-4- (methylsulfonyl) pyridine, 2,3,5,6-tetrachloro-. Examples thereof include 4- (methylsulfonyl) pyridine, bis (tributyltin) oxide, hexahydro-1,3,5-triethyl-s-triazine, silver complex, zinc complex and the like.

Examples of the gelling agent include ammonium salts such as ammonium acetate, ammonium chloride and ammonium carbonate, alkylphenol alkylene oxide adducts, polyvinyl methyl ether, polypropylene glycol, polyether polyformal, methyl cellulose, hydroxyethyl cellulose and silica gel.

Examples of flame retardants include phosphate ester compounds, halogen phosphate compounds, ammonium polyphosphate, antimony trioxide, zinc borate, barium metaborate, ammonium hydroxide, magnesium hydroxide, tin compounds, and organophosphorus compounds. , Red phosphorus compounds, silicone flame retardants and the like.

Examples of the antioxidant include polyphenol-based, hydroquinone-based, and hindered amine-based antioxidants.
Examples of the pigment or dye include titanium oxide, carbon black, red iron oxide, quinacridone and the like.

Examples of the tackifier include gum rosin, tall oil rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, maleated rosin, rosin / glycerin ester, hydrogenated rosin / glycerin ester, hydrogenated rosin ester, and heterogeneous. Rosin-based resins such as rosin ester; turpen-based resins such as terpene resin, terpenphenol resin, and aromatic-modified terpene resin; petroleum-based resins such as aliphatic petroleum resin, aliphatic petroleum resin, and aromatic petroleum resin; Examples thereof include kumaron inden resin; phenol-based resin; xylene resin and the like.

<< Sucker structure >>
The foamed adhesive layer, which is a foamed sheet, has a large number of pores inside and a large number of depressed holes on the surface. FIG. 2 illustrates the structure of the foamed adhesive layer 12 having holes 121 inside and recessed holes 122 on the surface.
The depressed holes on the surface are formed by air bubbles generated on the surface when the resin composition containing the acrylic resin having a hydroxyl group and an epoxy-based cross-linking agent is foamed. The surface having such a recessed hole functions as a micro suction cup that adsorbs to the adherend.

The surface shape of the depression hole is spherical, and the diameter and depth of the depression hole are determined by the diameter of the bubble. Even if the diameter of the bubble is constant, the diameter of the recessed hole has a distribution because the diameter of the recessed hole differs depending on the position of the bubble from the surface of the foamed adhesive layer. The foamed adhesive layer used in the present invention preferably has a surface on which recessed holes having a diameter of 5 to 100 μm are formed. The number of recessed holes per unit area (1 mm ² ) is preferably 100 to 1000, more preferably 200 to 400, from the viewpoint of improving adsorptivity.

In particular, among the depression holes having a diameter of 5 to 100 μm, the distribution of the depression holes having a diameter of 10 to 50 μm is preferably 50% or more, more preferably 80% or more, and the distribution of the depression holes having a diameter of 20 to 30 μm. It is particularly preferable that it is 80% or more. If there are many recessed holes with a large diameter, the adsorptivity as a micro suction cup tends to improve, and conversely, if there are many depressed holes with a small diameter, the suction tends to be uniform. Further, the larger the number of recessed holes per unit area, the easier it is to improve the adsorptivity, and conversely, the smaller the number, the more uniformly the adsorptive tends to be. When the bubble is a closed cell, the distribution of the depth of the sinkhole is almost the same as the distribution of the diameter of the sinkhole.

<Print receiving layer>
The laminated sheet of the present invention is used by attaching a foam adhesive layer to an adherend, but usually, when used, characters, designs, etc. are printed on the side opposite to the foam adhesive layer. Therefore, from the viewpoint of improving the adhesion to the ink to improve the suitability for various printing methods, suppressing blocking and improving the handleability, the laminated sheet of the present invention has a surface opposite to the foamed adhesive layer of synthetic paper. It is preferable to have a print receiving layer on top.

The print receiving layer preferably contains 0.1 to 100% by mass of the antistatic agent, 0 to 99.9% by mass of the polymer binder, and 0 to 70% by mass of the pigment particles, and 0.5 to 70% by mass of the antistatic agent. %, 30 to 99.5% by mass of the polymer binder, and 0 to 69.5% by mass of the pigment particles, more preferably 1 to 50% by mass of the antistatic agent, 50 to 99% by mass of the polymer binder, and the pigment particles. It is more preferable to contain 0 to 49% by mass.
The print receiving layer can be formed by directly coating a coating liquid containing each component on synthetic paper, or by forming a print receiving layer on another film in advance and then laminating on synthetic paper.

<< Antistatic agent >>
The antistatic agent can impart antistatic performance to the print receiving layer. Examples of the antistatic agent include low molecular weight organic compound antistatic agents such as stearate monoglyceride, alkyldiethanolamine, sorbitan monolaurate, alkylbenzene sulfonate, and alkyldiphenyl ether sulfonate, and ITO (indium-doped oxidation). A so-called electron conductive polymer that exhibits conductivity by π electrons in the molecular chain such as conductive inorganic fillers such as tin), ATO (antimonized tin oxide), graphite whisker, and polythiophene, polypyroyl, and polyaniline. Non-ionic polymer antistatic agents such as polyethylene glycol and polyoxyethylene diamine, quaternary ammonium salt type copolymers such as polyvinylbenzyltrimethylammonium chloride and polydimethylaminoethylmethacrylate quaternized products, alkylene oxide groups and / or Examples thereof include a polymer having an antistatic function represented by an alkali metal salt-containing polymer such as an alkali metal ion additive to a hydroxyl group-containing polymer.

Among them, the polymer having an antistatic function is preferable in that it has little influence on the adhesion and transferability of the ink and has almost no coloring, and the quaternary ammonium salt type copolymer or the alkali metal salt-containing polymer is charged. It is more preferable because the prevention performance is good and the influence of environmental humidity on the antistatic performance is small.

<<< Quaternary Ammonium Salt Copolymer >>>
Examples of the quaternary ammonium salt type copolymer include a multication type water-soluble polymer. The quaternary ammonium salt-type copolymer is a quaternary ammonium salt-type monomer structural unit (a) represented by the following general formula (Chemical formula 1) and hydrophobic represented by the following general formula (Chemical formula 6). It is a copolymer of each monomer containing a sex monomer structural unit (b) and a structural unit (c) composed of a monomer copolymerizable therewith. The mass ratio (a): (b): (c) (unit is mass%) of each structural unit is in the range of 30 to 70:30 to 70: 0 to 40, preferably 35 to 65: 35 to 65 :. It is 0 to 20, more preferably 40 to 60:40 to 60: 0 to 10.

(A) Quaternary ammonium salt type monomer unit The quaternary ammonium salt type monomer forming the structural unit (a) is an ester of acrylic acid or methacrylic acid represented by the following general formula (Chemical formula 1). Or amide. The unit is a component that contributes to the antistatic function of the copolymer by two or more cations in the structure. When the same component in the copolymer is 30% by mass or more, it is easy to give a sufficient antistatic effect. Further, when it is 70% by mass or less, it becomes excessively water-soluble, and it is easy to suppress that it causes stickiness under high humidity conditions.

上記式中、Ａはオキソ基（−Ｏ−）又は第２級アミン基（−ＮＨ−）、Ｒ^１は水素原子又はメチル基、Ｒ^２は炭素数が２〜４のアルキレン基又は下記一般式（化２）で表される２−ヒドロキシプロピレン基であり、Ｒ^３、Ｒ^４、Ｒ^５及びＲ^６は炭素数が１〜３のアルキル基、Ｒ^７は炭素数が１〜１０のアルキル基又は炭素数が７〜１０のアラルキル基、Ｘは塩素原子、臭素原子又はヨウ素原子、ｍは１〜３の整数を表す。Ｒ^３、Ｒ^４、Ｒ^５及びＲ^６は同一であってもよく、異なっていてもよい。

In the above formula, A is an oxo group (-O-) or a secondary amine group (-NH-), R ¹ is a hydrogen atom or a methyl group, R ² is an alkylene group having 2 to 4 carbon atoms or the following general formula. It is a 2-hydroxypropylene group represented by (Chemical formula 2). R ³ , R ⁴ , R ⁵ and R ⁶ are alkyl groups having 1 to 3 carbon atoms, and R ⁷ is an alkyl group having 1 to 10 carbon atoms. Alternatively, an aralkyl group having 7 to 10 carbon atoms, X represents a chlorine atom, a bromine atom or an iodine atom, and m represents an integer of 1 to 3. R ³ , R ⁴ , R ⁵ and R ⁶ may be the same or different.

The quaternary ammonium salt-type monomer forming the structural unit (a) represented by the general formula (Chemical Formula 1) is a dimethylaminoethyl (meth) acrylate or diethylamino represented by the following general formula (Chemical Formula 3). Amine-containing monomers such as ethyl (meth) acrylate and dimethylaminopropyl (meth) acrylamide are modified with a modifier such as 3-chloro-2-hydroxypropyltrimethylammonium chloride represented by the following general formula (Chemical Formula 5). , Can be obtained by modification before or after polymerization.

上記式中、Ａはオキソ基（−Ｏ−）又は第２級アミン基（−ＮＨ−）、Ｒ^１は水素原子又はメチル基、Ｒ^２は炭素数が２〜４のアルキレン基又は下記一般式（化４）で表される２−ヒドロキシプロピレン基であり、Ｒ^３及びＲ^４は炭素数が１〜３のアルキル基を表す。Ｒ^３とＲ^４は同一であってもよく、異なっていてもよい。

In the above formula, A is an oxo group (-O-) or a secondary amine group (-NH-), R ¹ is a hydrogen atom or a methyl group, R ² is an alkylene group having 2 to 4 carbon atoms or the following general formula. It is a 2-hydroxypropylene group represented by (Chemical formula 4), and R ³ and R ⁴ represent an alkyl group having 1 to 3 carbon atoms. R ³ and R ⁴ may be the same or different.

上記式（化５）中、Ｒ^５及びＲ^６は炭素数が１〜３のアルキル基、Ｒ^７は炭素数が１〜１０のアルキル基又は炭素数が７〜１０のアラルキル基、Ｘは塩素原子、臭素原子又はヨウ素原子、ｍは１〜３の整数を表す。Ｒ^５とＲ^６は同一であってもよく、異なっていてもよい。

In the above formula (Chemical formula 5), R ⁵ and R ⁶ are alkyl groups having 1 to 3 carbon atoms, R ⁷ is an alkyl group having 1 to 10 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, and X is chlorine. Atom, bromine atom or iodine atom, m represents an integer of 1 to 3. R ⁵ and R ⁶ may be the same or different.

(B) Hydrophobic Monomer Unit The hydrophobic monomer forming the structural unit (b) is an ester of acrylic acid or methacrylic acid represented by the following general formula (Chemical formula 6). The unit imparts lipophilicity to the copolymer and is a component that contributes to water resistance and ink transfer property. Copolymerization with a hydrophobic monomer is required to achieve both printability and antistatic properties. When the same component in the polymer is 30% by mass or more, the above effect is likely to be obtained, and when it is 70% by mass or less, the antistatic effect is relatively increased.

上記式中、Ｒ^８は水素原子又はメチル基、Ｒ^９は炭素数が１〜３０のアルキル基、炭素数が７〜２２のアラルキル基、又は炭素数が５〜２２のシクロアルキル基を表す。
上記一般式（化６）で表される構造単位を形成する単量体としては、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ブチル（メタ）アクリレート、イソブチル（メタ）アクリレート、ターシャリーブチル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、２−エチルヘキシル（メタ）アクリレート、ラウリル（メタ）アクリレート、トリデシル（メタ）アクリレート、ステアリル（メタ）アクリレート等のアルキル（メタ）アクリレートが挙げられる。

In the above formula, R ⁸ represents a hydrogen atom or a methyl group, R ⁹ represents an alkyl group having 1 to 30 carbon atoms, an aralkyl group having 7 to 22 carbon atoms, or a cycloalkyl group having 5 to 22 carbon atoms.
Examples of the monomer forming the structural unit represented by the general formula (Chemical formula 6) include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and tertiary butyl (). Examples thereof include alkyl (meth) acrylates such as meta) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, and stearyl (meth) acrylate.

(C) Other monomer unit copolymerizable Other monomer unit copolymerizable with the above-mentioned monomer (a) component and monomer (b) component used for copolymerization as needed. As the above, hydrophobic monomers such as styrene, vinyltoluene and vinyl acetate represented by the following general formulas (Chemical formulas 7) to (Chemical formula 11) and hydrophilic monomers such as vinylpyrrolidone and (meth) acrylamide are used. Can be mentioned. These monomers can be suitably incorporated as the structural unit (c) in the quaternary ammonium salt type copolymer. The unit facilitates the copolymerization of the copolymer and adjusts the solubility in a solvent when adjusting the coating solution.

<<< Copolymerization >>>
As a copolymerization method for obtaining the above-mentioned copolymer, a known polymerization method such as bulk polymerization, solution polymerization, or emulsion polymerization using a radical initiator can be adopted. Of these, the preferred polymerization method is the solution polymerization method, which is carried out by dissolving each monomer in a solvent, adding a radical polymerization initiator to the solvent, and heating and stirring under a nitrogen stream. To. The solvent is preferably water or alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and cellosolob, and may be a mixed solvent thereof. As the polymerization initiator, peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile and azobisvaleronitrile are preferably used. The monomer solid content concentration at the time of polymerization is usually 10 to 60% by mass, and the concentration of the polymerization initiator is usually 0.1 to 10% by mass with respect to the monomer. The molecular weight of the quaternary ammonium salt-type copolymer can be set to any level depending on the polymerization conditions such as the polymerization temperature, the polymerization time, the type and amount of the polymerization initiator, the amount of the solvent used, and the chain transfer agent.
The molecular weight of the quaternary ammonium salt-type copolymer that can be used in the present invention is generally in the range of 10 to 1 million by weight average molecular weight measured by gel permeation chromatography (GPC). The range of 1,000 to 500,000 is preferable.

<< Polymer binder >>
The print receiving layer may contain a polymer binder, if necessary, from the viewpoint of improving adhesion to synthetic paper and ink.

Examples of the polymer binder include acrylic acid ester copolymers, methacrylic acid ester copolymers, acrylic acid amide-acrylic acid ester copolymers, acrylic acid amide-acrylic acid ester-methacrylic acid ester copolymers, and polyacrylamides. (Meta) acrylic acid ester-based polymers such as derivatives and oxazoline group-containing acrylic acid ester-based polymers; polyethyleneimine, alkyl-modified polyethyleneimine having 1 to 12 carbon atoms, poly (ethyleneimine-urea), poly (ethyleneimine). -Polymerimine-based polymers such as ethyleneimine adduct of (urea), polyamine polyamide, ethyleneimine adduct of polyamine polyamide, and epichlorohydrin adduct of polyamine polyamide; polyvinylpyrrolidone, polyethylene glycol, vinyl acetate resin, urethane resin, polyether. Resin, polyester resin, urea resin, terpene resin, petroleum resin, ethylene-vinyl acetate copolymer, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, vinylidene chloride resin, vinyl chloride-vinylidene chloride copolymer resin, Examples thereof include chlorinated ethylene resin, chlorinated propylene resin, butyral resin, silicone resin, nitrocellulose resin, styrene-acrylic copolymer resin, styrene-butadiene copolymer resin, acrylic nitrile-butadiene copolymer, and the like. It is not particularly limited to.

One of these polymer binders may be used alone, or two or more of them may be mixed and used. These polymer binders can be used in a form diluted or dispersed in an organic solvent or water. Among these, urethane resins such as polyether urethane, polyester polyurethane, and acrylic urethane, acrylic acid ester copolymers, and polyethyleneimine-based polymers are compatible with the above-mentioned ionic polymer-based polymer having an antistatic function (phase). It is preferable because it has good solubility), is stable when mixed to form a paint, and is easy to apply.

<< Pigment particles >>
The print receiving layer may contain pigment particles, if necessary. Pigment particles improve ink fixability due to their oil absorption, improve surface texture and luster as extender pigments, improve whiteness as white pigments, improve blocking prevention performance by adding surface irregularities, and light resistance and weather resistance as UV reflectors. It can be used as appropriate according to the performance to be given such as improvement.

As the pigment particles, for example, organic or inorganic fine powder can be used. Examples of the organic or inorganic fine powder include silicon oxide, calcium carbonate, calcined clay, titanium oxide, zinc oxide, barium sulfate, diatomaceous earth, acrylic particles, styrene particles, polyethylene particles, polypropylene particles and the like.
The particle size of the pigment particles is preferably 0.01 μm or more, more preferably 0.1 μm or more. When the particle size is at least the above lower limit value, undulations are formed on the layer surface, and it is easy to suppress blocking when laminated sheets are stacked and stored. The particle size of the pigment particles is preferably 20 μm or less, more preferably 15 μm or less, and further preferably 3 μm or less. When the particle size is not more than the above upper limit value, it is easy to suppress the falling off of the pigment particles and the powder blowing phenomenon due to the falling off.

The content of the pigment particles in the print receiving layer is preferably 0 to 70% by mass, more preferably 0 to 60% by mass, and further preferably 0 to 45% by mass. When the content of the pigment particles is less than the above range, a sufficient amount of the polymer binder can be blended, the cohesive force of the print receiving layer is improved, the adhesive force to the synthetic paper is likely to be enhanced, and the ink peeling is easily suppressed. ..

The surface resistivity of the print resistivity is usually 1 × 10 ^{-1 to} 9 × 10 ¹² Ω, preferably 1 × 10 ^{3 to} 9 × 10 ¹¹ Ω, and more preferably 1 × 10 ^{6 to} 9 × 10 ^10. It is Ω.
When the surface resistivity of the print receiving layer is 9 × 10 ¹² Ω or less, it is easy to reduce troubles such as sticking to the roll and blocking between sheets in the printing process. On the other hand, a highly conductive layer having a surface resistivity of less than 1 × 10 ^-1 Ω is technically difficult or, if possible, expensive, so that the surface resistivity is usually 1 × 10 ^-1. It is Ω or more.

<Peeling sheet>
The release sheet is a sheet that covers the foamed adhesive layer, and is provided as necessary in order to facilitate the handling of the laminated sheet during printing, use, and the like.
The release sheet is preferably a flexible resin film from the viewpoint of reducing wrinkles during winding. Examples of the resin film that can be used include polyethylene film, vinyl chloride film, polymethylpentene film and the like.

(Manufacturing method of laminated sheet)
The method for producing the laminated sheet of the present invention is not particularly limited, and the laminated sheet can be produced, for example, by forming a foamed adhesive layer on synthetic paper.

<Synthetic paper preparation process>
Although a commercially available product can be used as the synthetic paper, it may be produced by forming a resin composition containing an olefin resin, an inorganic filler, etc., which is a material of the synthetic paper, into a film. Examples of the film forming method include a cast molding method in which a molten resin is extruded into a film by a T die, an I die or the like connected to a screw type extruder, calender molding, rolling molding, inflation molding and the like. When the synthetic paper has a multi-layer structure, known methods such as a coextrusion method, a melt extrusion lamination method, and a combination thereof can be used.

Examples of the stretching method for stretching the film include a longitudinal stretching method using the peripheral speed difference of the roll group, a transverse stretching method using a tenter oven, a sequential biaxial stretching method combining these, a rolling method, and a tenter oven. Examples include a simultaneous biaxial stretching method using a combination of pantographs and a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor. Further, a simultaneous biaxial stretching (inflation molding) method in which the molten resin is extruded into a tube shape using a circular die connected to a screw type extruder and then air is blown into the molten resin can also be used.

The stretching temperature at the time of stretching is, for example, 152 to 164 ° C. when the resin is a propylene homopolymer (melting point 155 to 167 ° C.), and about 110 to 120 ° C. when the resin is high density polyethylene (melting point 121 to 134 ° C.). It is preferable that the temperature is 2 to 60 ° C. lower than the melting point of the thermoplastic resin used. When the resin is polyethylene terephthalate (melting point 246 to 260 ° C.), it is preferably about 70 to 120 ° C., which is 10 ° C. lower than the melting point of the resin and lower than the glass transition temperature + 50 ° C. of the resin. ..
The stretching speed is not particularly limited, but is preferably 20 to 350 m / min from the viewpoint of stable stretch molding.

<Foam process>
An acrylic resin having a hydroxyl group, which is a material of the foamed adhesive layer, and a predetermined amount of an epoxy-based cross-linking agent are mixed by an arbitrary method. It is preferable that the acrylic resin having a hydroxyl group is in the form of an aqueous emulsion or dispersion because a foamed adhesive layer is easily formed. The viscosity of the emulsion or dispersion is usually preferably 2,000 to 10,000 mPa · s, more preferably 3,500 to 5,500 mPa · s.

The obtained mixture is foamed to prepare a coating liquid for the foamed adhesive layer. The coating liquid is an unsolidified foam. Examples of the foaming treatment method include mechanical foaming. The foaming ratio may be adjusted as appropriate, but is usually 1.2 to 5 times, preferably 1.5 to 4 times. The method of mechanical foaming is not particularly limited, and examples thereof include a method of continuously or batch stirring with an oak mixer, a whipper, or the like that mixes a certain amount of air into the mixture. By such a foaming treatment, a creamy foam can be obtained as a coating liquid.

<Formation process of foamed adhesive layer>
A foamed adhesive layer can be formed by applying the above coating liquid onto synthetic paper. For coating, a known coating device such as a roll coater, a reverse roll coater, a screen coater, a doctor knife coater, and a comma knife coater can be used. Among them, the doctor knife coater is preferable because it can be applied uniformly.

By performing a heat treatment after the coating, the acrylic resin having a hydroxyl group can be sufficiently crosslinked and the coating film can be sufficiently dried, and a desired foamed adhesive layer can be formed. The method of heat treatment is not particularly limited as long as the foam coated on the synthetic paper can be crosslinked and dried. For example, a hot air circulation type oven, a hot oil circulation hot air chamber, a far infrared heater chamber, etc. A method of heating at 60 to 180 ° C. for 1 to 10 minutes using the above heating device can be mentioned. During the heat treatment, instead of heating at a constant temperature, it is preferable to perform multi-step heating in which the inside is dried at a low temperature in the initial stage and the whole is sufficiently dried at a high temperature in the later stage.

Properties such as adhesive strength, density, thickness, and hardness of the foamed adhesive layer can be adjusted by adjusting the mixing ratio of bubbles, the resin composition, the solid content concentration, the amount of the cross-linking agent used, the conditions for drying and solidifying by heat treatment, and the like.

<Laminating process of release sheet>
A laminated sheet can be obtained by laminating a release sheet on the foamed adhesive layer and then pressurizing with a pressure-bonding roll. The laminated sheet can be cut to a predetermined size by press cutting, slitter or the like.

<Process of forming the print receiving layer>
When the print receiving layer is provided, a coating liquid containing each component of the print receiving layer is prepared and coated on the surface opposite to the foamed adhesive layer of synthetic paper. A print receiving layer can be formed by drying and solidifying after coating. Conventionally known methods and devices can be used for coating.
The print receiving layer can also be provided by laminating. In this case, another film provided with a print receiving layer may be prepared in advance, and this may be laminated on synthetic paper. The laminating process can be performed by a method such as ordinary dry laminating or hot laminating.

(Characteristics of laminated sheet)
<Thickness>
The thickness of the synthetic paper is preferably 20 μm or more, more preferably 30 μm or more, from the viewpoint of improving the mechanical strength of the laminated sheet. The thickness is preferably 900 μm or less, more preferably 800 μm or less, from the viewpoint of obtaining an appropriate elasticity of the laminated sheet and preventing the laminated sheet from falling off from the adherend during use.

The thickness of the foamed pressure-sensitive adhesive layer is preferably 0.03 mm or more, and more preferably 0.05 mm or more, from the viewpoint of enhancing shock absorption when the laminated sheet is used as an article holding material or an article surface protecting material. From the viewpoint of improving the strength of the foamed adhesive layer, the same thickness is preferably 3 mm or less, more preferably 1 mm or less, and further preferably 0.5 mm or less.
The density of the foamed adhesive layer is not particularly limited, but is preferably 0.1 to 1.0 g / cm ³ from the viewpoint of shock absorption.

From the viewpoint of the uniformity of the print receiving layer, the thickness of the print receiving layer is preferably 0.01 μm or more, more preferably 0.05 μm or more, further preferably 0.1 μm or more, and particularly preferably 0.3 μm or more. The same thickness is preferably 50 μm or less, more preferably 30 μm or less, further preferably 10 μm or less, and particularly preferably 8 μm or less, from the viewpoint of suppressing peeling due to its own weight.

The thickness of the release sheet is preferably 10 μm or more, more preferably 12 μm or more, still more preferably 15 μm or more, from the viewpoint of reducing breakage during peeling. The same thickness is preferably 100 μm or less, more preferably 50 μm or less, still more preferably 35 μm or less, from the viewpoint of reducing wrinkles during winding.

<Printing>
Printing or writing is possible on the surface of the synthetic paper opposite to the foamed adhesive layer of the laminated sheet (on the print receiving layer when the printing receiving layer is provided). Examples of the printing method that can be used include electrophotographic method, sublimation heat transfer method, melt heat transfer method, direct thermal method, letterpress printing, gravure printing, flexographic printing, solvent type offset printing, and ultraviolet curable offset printing. Printing is possible with either a sheet-shaped or roll-shaped rotary press.

<Use>
The laminated sheet of the present invention can be used as a decorative material for construction, a sticking material for advertising, a stationery or a material for toys. For example, sales promotion cards, so-called POP cards (posters, stickers, displays, etc.), underlays (lunch mats, table mats, stationery, etc.), restaurant menus, catalogs, panels, plates (alternatives to metal plates), bromides, storefronts. Price list, information board (sales floor information, direction or destination information, etc.), POP for gardening (labels, etc.), road signs (road signs for funerals, housing exhibition places, etc.), display boards (no entry, forest road work, etc.) It can be used as a display sign), a calendar (with an image, etc.), a simple whiteboard, a mouse pad, a coaster, a printed matter as a substitute for a label writer, an adhesive label, a packaging material, a protective material, and the like.

The features of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Specific Examples. That is, the materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention.

(Manufacturing of synthetic paper)
Propylene homopolymer (manufactured by Japan Polychem Corporation, Novatec PP: MA4) 74%, high-density polyethylene (manufactured by Japan Polychem Corporation, Novatec HD: HJ360) 10% and calcium carbonate (manufactured by Bihoku Powder Industry Co., Ltd., Softon 1800) 16% Was melt-kneaded at 250 ° C., then supplied to a die set at 250 ° C., extruded into a sheet, and cooled with a cooling roll to obtain an unstretched sheet. The obtained unstretched sheet was heated to 135 ° C. and stretched in the longitudinal direction at a magnification of 4 times to obtain a uniaxially stretched film.

Next, propylene homopolymer (manufactured by Japan Polychem Corporation, Novatec PP: EA8) 52%, high-density polyethylene (manufactured by Japan Polychem Corporation, Novatec HD: HJ360) 3% and calcium carbonate (manufactured by Bihoku Powder Industry Co., Ltd., Softon 1800). ) 45% was melt-kneaded at 250 ° C. in separate extruders, then supplied to a die set at 250 ° C., extruded into a sheet, and laminated on both sides of the uniaxially stretched film. The film was cooled to 60 ° C. to obtain a two-layer structure laminated film (a / b / c). This three-layer structure laminated film was heated to 180 ° C. again and stretched laterally with a tenter at a magnification of 9 times. After the annealing treatment at 160 ° C., the paper was cooled to 60 ° C. and the ears were slit to obtain a synthetic paper having a thickness of 110 μm (a / b / c = 22 μm / 66 μm / 22 μm). The whiteness of the synthetic paper was 96%, the opacity was 94%, the thickness was 110 μm, and the porosity was 32%.

(Manufacturing of acrylic resin)
<Acrylic resin (a)>
Water and emulsifier (polyoxyethylene polycyclic phenyl ether sulfate ester salt, trade name "Newcol 707SF", Japan) in a 4-neck round-bottom flask equipped with a reflux condenser, agitator, a nitrogen gas inlet and a thermometer. (Manufactured by Emulsifier Co., Ltd.) 1.2 parts by mass was charged and stirred under a nitrogen stream to prepare an emulsifier solution. The temperature of the emulsifier solution was raised to 70 ° C., and then 3 parts by mass of 4-hydroxybutyl acrylate, 17 parts by mass of methyl methacrylate, 78 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of acrylic acid, and 25 parts by mass of water were added to the solution. Was added and stirred. Then, a 0.1% ammonium persulfate aqueous solution as a polymerization initiator was added dropwise to the same solution in an amount of 0.5 mass by mass, and stirring was continued at 80 ° C. for 3.25 hours. After the dropping was completed, the mixture was kept warm at 80 ° C. for 1 hour with stirring, and then cooled to obtain an emulsion solution of the acrylic resin (a). The glass transition temperature of the acrylic resin (a) was measured and found to be −49 ° C.

<Acrylic resin (b)>
The acrylic resin (a) is an emulsion of the acrylic resin (b) in the same manner as the acrylic resin (a) except that 3 parts by mass of 2-hydroxyethyl methacrylate is used instead of 3 parts by mass of 4-hydroxybutyl acrylate. I got the liquid. The glass transition temperature of the acrylic resin (b) was measured and found to be −48 ° C.

<Acrylic resin (c)>
1.4 parts by mass of N-methylolacrylamide, 46.9 parts by mass of ethyl acrylate, 45.8 parts by mass of butyl acrylate in a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer. , 5.9 parts by mass of acrylonitrile, 42 parts of acetone, 0.013 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator, and 3.25 at reflux temperature while dropping an azobisisobutyronitrile acetic acid solution. After a time reaction, it was diluted with ethyl acetate to obtain an acrylic resin (c). The glass transition temperature of the acrylic resin (c) was measured and found to be −26 ° C.

(Preparation of coating liquid)
<Coating liquid 1>
Add 100 parts by mass of acrylic resin (a) in terms of solid content and 3 parts by mass of epoxy-based cross-linking agent A (glycerin diglycidyl ether, trade name: Epolite 80MF, manufactured by Kyoei Chemical Co., Ltd.) to the mixing container. Then, the mixture was stirred with a high-speed disperser. While continuing stirring, 4.2 parts by mass of pigment (titanium dioxide aqueous dispersion, trade name: DISPERS WHITE EG-701, manufactured by DIC) and 2 parts by mass of thickener in terms of solid content (manufactured by DIC). Carboxylic acid-modified acrylic acid ester polymer, trade name: Aron B-300K, manufactured by Toa Synthetic Co., Ltd., and 4.1 parts by mass of foam stabilizer (alkylbetaine amphoteric / fatty acid alkanolamide mixture (trade name)) : DCNAL M-20, manufactured by DIC) and a sulfonic acid type anionic surfactant (trade name: DCNAL M-40, manufactured by DIC) in a 1: 1 mixture) were added in this order and mixed uniformly. .. After mixing, it was filtered through a 150 mesh stainless steel sieve. Finally, ammonia was added to adjust the viscosity to 4,500 mPa · s to obtain a coating liquid 1.

<Coating liquid 2>
In the coating liquid 1, the acrylic resin (b) is used instead of the acrylic resin (a), and the epoxy cross-linking agent B (polyglycerol polyglycidyl ether, trade name: Deconal EX-512,) is used instead of the epoxy cross-linking agent A. Coating liquid 2 was obtained in the same manner as coating liquid 1 except that (manufactured by Nagase ChemteX Corporation) was used.

<Coating liquid 3>
In the coating liquid 1, an acrylic resin (c) was used instead of the acrylic resin (a), and a melamine-based cross-linking agent (trade name: BECKMINE M3, manufactured by DIC Corporation) was used instead of the epoxy cross-linking agent A. A coating liquid 3 was obtained in the same manner as in the coating liquid 1 except for the above.

<Coating liquid 4>
In the coating liquid 1, an acrylic resin (c) was used instead of the acrylic resin (a), and a carbodiimide-based cross-linking agent (trade name: DICNAL HX, manufactured by DIC Corporation) was used instead of the epoxy cross-linking agent A. A coating liquid 4 was obtained in the same manner as in the coating liquid 1 except for the above.

Table 1 shows the composition of each coating liquid 1 to 4.

(Example 1)
The coating liquid 1 was stirred using a whisk, and air was blown during stirring to generate fine bubbles. After whipping until the foaming ratio became 2 times, the stirring speed was reduced and stirring was continued for another 5 minutes to obtain a foamed coating liquid 1.
Next, the foamed coating liquid 1 was applied to the entire surface of one side of the produced synthetic paper using an applicator so as to have a thickness of 300 μm. The coated synthetic paper is placed in a drying oven and heat-treated by holding it at 80 ° C. for 1.33 minutes, 120 ° C. for 1.33 minutes and 140 ° C. for 1.33 minutes, cross-linking it, and foaming it on the synthetic paper. An adhesive layer was formed.

A release sheet (biaxially stretched polypropylene film, trade name: pipe wrench film-OT P2261 60 μm, manufactured by Toyobo Co., Ltd.) was laminated on this foam adsorption layer. Crimping is performed by applying a load of 2 kg using a manual crimping device in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and then standing for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50% to carry out a crosslinking reaction. By accelerating, the laminated sheet of Example 1 was obtained.

(Example 2, Comparative Examples 1 and 2)
In Example 1, each laminated sheet of Example 2, Comparative Examples 1 and 2 was obtained in the same manner as in Example 1 except that the coating liquid 1 was replaced with the coating liquids 2 to 4, respectively.

(Evaluation)
<Measurement of formaldehyde concentration>
A test piece obtained by cutting out the laminated sheets of each Example and Comparative Example into a size of 200 mm × 200 mm was prepared. The test piece was placed in a Tedlar bag having a volume of 5 L, and the inside of the bag was degassed and sealed. Next, 2 L of air was sealed in the bag, and the bag was allowed to stand in a constant temperature bath set at a temperature of 23 ° C. and a relative humidity of 50% for 6 hours, and then the bag was placed in a gas detector tube (No. 91 L, manufactured by Gastec). The formaldehyde concentration in the bag was measured.

<Peeling adhesive strength>
The peeling adhesive strength (N / m) of the foamed adhesive layer in the laminated sheet is based on JIS K6854-3: 1999, when the laminated sheet and the PET film as an adherend are T-shaped peeled using a tensile tester. It was determined as the average peeling force (N / m) required for.
Specifically, the release sheet was peeled off from the laminated sheets obtained in the above Examples and Comparative Examples, and a PET film (biaxially stretched polyester film, trade name: ester film E5001 50 μm,) was formed on the surface of the laminated sheet on the foam adhesive layer side. Made by Toyobo Co., Ltd., both sides untreated) were pasted together. Using a manual crimping device (crimping roller for peeling test) of JIS Z0237: 2009, the rollers are reciprocated 20 times at a linear pressure of 0.3 kg / cm to crimp the two, and under an environment of temperature 23 ° C. and humidity 50% RH. A sample was obtained after adjusting for 16 hours. The prepared sample was cut into a size of 30 mm × 200 mm in each of the manufacturing direction (flow direction) of the laminated sheet and the width direction orthogonal to the manufacturing direction (flow direction) to obtain a test piece.

Next, the laminated sheet and the PET film were carefully peeled off from one short side of the test piece to create a portion peeled off by 50 mm, which was used as a gripping margin portion during the peeling test. Based on JIS K6854-3: 1999, a T-type peeling test was carried out using a tensile tester (manufactured by Shimadzu Corporation, Autograph AGS-5kNJ) under the condition of a peeling speed of 300 mm / min. After the start of peeling, the average value of the peeling force (N / m) required for peeling between 25 and 75 mm was measured at 6 points (3 points in the flow direction and 3 points in the width direction), and the measured values at the 6 points were averaged. The obtained value was taken as the peel-off adhesive strength (N / m). The peel-off adhesive strength when both were easily peeled off and could not be substantially measured was set to 0 N / m.

The peeling adhesive strength between the foamed adhesive layer and the PET film in the laminated sheet is preferably 5 to 20 N / m, more preferably 5 to 15 N / m, and 5 to 10 N / m. Is even more preferable. If the peeling adhesive strength is 5 N / m or more, the laminated sheet will not be easily peeled off from the adherend. Further, when the peeling adhesive strength is 20 N / m or less, the work of reattaching (peeling and reattaching) to the adherend is easy.

Table 2 shows the evaluation results.

As described above, the laminated sheet of Comparative Example 1 generated a small amount of formaldehyde, whereas Formaldehyde 1 and 2 did not generate formaldehyde. Further, in Examples 1 and 2, while it is difficult to peel off during processing, peeling adhesive strength that is easy to peel off by hand is obtained, and practical physical properties can be maintained.

1 ... Laminated sheet, 11 ... Synthetic paper, 12 ... Foam adhesive layer

Claims (4)

A laminated sheet having a foamed adhesive layer on one surface of synthetic paper.
A laminated sheet in which the foamed adhesive layer contains an acrylic resin having a hydroxyl group and an epoxy-based cross-linking agent. The content of the epoxy-based cross-linking agent in the foamed adhesive layer is 0.5 to 20 parts by mass with respect to 100 parts by mass of the acrylic resin having a hydroxyl group.
The laminated sheet according to claim 1. The synthetic paper is a porous olefin resin sheet containing an inorganic filler.
The laminated sheet according to claim 1 or 2. A print receiving layer is provided on the surface of the synthetic paper opposite to the foamed adhesive layer.
The laminated sheet according to any one of claims 1 to 3, wherein the laminated sheet is characterized in that.

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