Laminated resin film

Abstract

To provide a laminated resin film with excellent scratch resistance, water resistance, and film adhesion without the need for heating through baking treatment. [Solution] A laminated resin film comprising an overprint varnish layer, a plastic film, a printing layer, and an adhesive layer sequentially laminated, wherein the overprint varnish layer is formed from an overprint varnish composition (i) or an overprint varnish composition (ii), wherein composition (i) contains a specific amount of two types of polyester resins (A) and polyester resin (B) having different ranges of number average molecular weight and glass transition temperature (Tg), a block-type isocyanate (C) having a specific dissociation temperature range, and a silicone-modified acrylic resin (D), and composition (ii) contains a specific amount of two types of epoxy resins (E) and epoxy resin (F) having different ranges of epoxy equivalents, a silicone-modified acrylic resin (G), and an isophorone diisocyanate polymer (H).

Description

Technical Field

[0001] The present invention relates to a laminated resin film, and more particularly to a laminated resin film excellent in scratch resistance, water resistance and film adhesiveness.

Background Art

[0002] In film lamination of metal cans, first, an overprint varnish composition is applied to the outer surface of a base film and dried by heating; after performing printing and heating drying on the inner surface of the base film (the surface on the metal can side), an adhesive composition is applied thereon and dried by heating to obtain a laminated resin film. The obtained laminated resin film is wrapped around the surface of a metal can, subjected to lamination treatment, and then subjected to baking treatment in the final step, whereby a film-laminated can can be obtained. The main purposes of the baking treatment are two points: (1) to thermally cure the overprint varnish composition to form a coating with high scratch resistance and water resistance, and (2) to thermally cure the adhesive composition to increase cohesive force.

[0003] The baking treatment is usually carried out using a hot air oven at a heating temperature of 180 to 200°C for a heating time of 60 to 120 seconds. However, performing such a baking treatment complicates the production process and consumes a large amount of heat energy. Therefore, if the baking treatment can be omitted, it becomes possible to achieve a significant improvement in production capacity and a reduction in energy cost.

[0004] To omit the baking process, it is conceivable to obtain a film-laminated can by accelerating the hardening of the overprint varnish layer and adhesive layer by heat drying after applying the overprint varnish composition or after applying the adhesive composition, and then hardening the overprint varnish layer and adhesive layer by lamination after wrapping the laminated resin film around the metal can. However, the heating temperature and heating time for the heat drying after applying the overprint varnish composition, the heat drying after applying the adhesive composition, and the lamination process are lower and shorter than the baking process. Therefore, although several laminated resin films for use in film-laminated cans have been proposed (Patent Documents 1-7), if such a laminated resin film is used on a metal can and the baking process is omitted, there is a risk that the thermal energy required for hardening the overprint varnish layer and adhesive layer will be insufficient, resulting in insufficient hardening of the overprint varnish layer and adhesive layer. In other words, problems may arise in the resulting film-laminated can, such as poor scratch resistance and water resistance of the laminated resin film, and a tendency for delamination to occur between the surface of the metal can and the laminated resin film. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-254047 [Patent Document 2] Japanese Patent Publication No. 2001-107015 [Patent Document 3] Japanese Patent Publication No. 2001-123142 [Patent Document 4] Japanese Patent Publication No. 2003-183572 [Patent Document 5] Japanese Patent Publication No. 2003-277714 [Patent Document 6] Japanese Patent Publication No. 2003-260767 [Patent Document 7] Japanese Patent Publication No. 2003-206362 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to obtain a laminated resin film that, when used in metal cans, exhibits excellent scratch resistance, water resistance, and film adhesion without requiring heating by a baking process. [Means for solving the problem]

[0007] The inventors have found a solution to this problem by employing a low-temperature dissociation type blocked isocyanate in the overprint varnish composition that forms the overprint varnish layer and combining it with a specific polyester, or by employing a specific isocyanate polymer in the overprint varnish composition that forms the overprint varnish layer and combining it with an epoxy resin having a specific epoxy equivalent.

[0008] Furthermore, the inventors have found a solution to this problem by combining two types of block-type isocyanates, isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), in the adhesive composition that forms the adhesive layer, and by using a novolac-type epoxy resin in combination, thereby enabling adhesion through low-temperature heating.

[0009] That is, a laminated resin film comprising an overprint varnish layer, a plastic film, a printed layer, and an adhesive layer, in sequence, The overprint varnish layer is formed from overprint varnish composition (i) or overprint varnish composition (ii), The overprint varnish composition (i) contains 50 to 80 parts by mass of polyester resin (A) having a number average molecular weight of 8,000 or more and less than 30,000 and a glass transition temperature of 40°C or more and less than 65°C, 10 to 40 parts by mass of polyester resin (B) having a number average molecular weight of 10,000 or more and less than 35,000 and a glass transition temperature of 50°C or more and less than 80°C, 1 to 10 parts by mass of block-type isocyanate (C) having a dissociation temperature of 110 to 150°C, and 0.1 to 1.0 parts by mass of silicon-modified acrylic resin (D). The overprint varnish composition (ii) provides a laminated resin film characterized by containing 50 to 90 parts by mass of epoxy resin (E) having an epoxy equivalent of 1500 or more and less than 2500, 10 to 40 parts by mass of epoxy resin (F) having an epoxy equivalent of 2500 or more and less than 3500, 0.5 to 3.0 parts by mass of silicone-modified acrylic resin (G), and 1.0 to 10 parts by mass of isophorone diisocyanate polymer (H).

[0010] The present invention further relates to a laminated resin film in which the adhesive composition for forming the adhesive layer contains 10 to 40 parts by mass of polyester resin (I) having a number average molecular weight of 8,000 or more and less than 30,000 and a glass transition temperature of 40°C or more and less than 65°C, 1 to 10 parts by mass of polyester resin (J) having a number average molecular weight of 15,000 or more and less than 50,000 and a glass transition temperature of 5°C or more and less than 30°C, 40 to 60 parts by mass of titanium dioxide (K), 1 to 10 parts by mass of blocked isophorone diisocyanate (L), 1 to 10 parts by mass of blocked hexamethylene diisocyanate (M), and 1 to 5 parts by mass of novolac-type epoxy resin (N).

[0011] The present invention further relates to a laminated resin film in which the overprint varnish composition (i) contains a hexamethylene diisocyanate polymer (O).

[0012] The present invention further relates to a laminated resin film in which the overprint varnish composition (i) or the overprint varnish composition (ii) contains nylon resin beads (P) having an average particle size of 5 to 20 μm. [Effects of the Invention]

[0013] The present invention allows the curing of the overprint varnish layer to proceed even at low temperatures by employing a low-temperature dissociation type blocked isocyanate in the overprint varnish composition (i) and combining it with a specific polyester, or by employing a specific isocyanate polymer in the overprint varnish composition (ii) and combining it with an epoxy resin having a specific epoxy equivalent. Therefore, when the laminated resin film of the present invention is used in a metal can, a film-laminated can with a laminated resin film that has excellent scratch resistance and water resistance can be obtained without heating by baking treatment. Furthermore, since the laminated resin film of the present invention does not require heating by baking treatment, it is also excellent in terms of manufacturing efficiency and energy cost.

[0014] Furthermore, the present invention combines two types of block-type isocyanates, isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), in the adhesive composition, and also uses a novolac-type epoxy resin, thereby enabling the curing of the adhesive layer even at low temperatures. Therefore, when the laminated resin film of the present invention is used in a metal can, a film-laminated can with a laminated resin film exhibiting excellent film adhesion can be obtained without the need for heating by baking.

[0015] Furthermore, the present invention exhibits the effect that the curing of the overprint varnish layer can be advanced even at low temperatures, by including a hexamethylene diisocyanate polymer (O) in the overprint varnish composition (i) described above.

[0016] Furthermore, the present invention provides excellent scratch resistance by having the overprint varnish composition (i) or the overprint varnish composition (ii) contain nylon resin beads (P) of a specific average particle size. [Brief explanation of the drawing]

[0017] [Figure 1] A diagram showing an example of the layer structure of the laminated resin film of the present invention. Description of Embodiments

[0018] The present invention provides a laminated resin film formed by sequentially laminating an overprint varnish layer, a plastic film, a printing layer, and an adhesive layer, wherein the overprint varnish layer is formed from an overprint varnish composition (i) or an overprint varnish composition (ii), said overprint varnish composition (i) comprises 50 to 80 parts by mass of a polyester resin (A) having a number average molecular weight of not less than 8000 and less than 30000 and a glass transition temperature of not less than 40°C and less than 65°C, 10 to 40 parts by mass of a polyester resin (B) having a number average molecular weight of not less than 10000 and less than 35000 and a glass transition temperature of not less than 50°C and less than 80°C, 1 to 10 parts by mass of a blocked isocyanate (C) having a dissociation temperature of 110 to 150°C, and 0.1 to 1.0 part by mass of a silicone-modified acrylic resin (D), said overprint varnish composition (ii) comprises 50 to 90 parts by mass of an epoxy resin (E) having an epoxy equivalent of not less than 1500 and less than 2500, 10 to 40 parts by mass of an epoxy resin (F) having an epoxy equivalent of not less than 2500 and less than 3500, 0.5 to 3.0 parts by mass of a silicone-modified acrylic resin (G), and 1.0 to 10 parts by mass of an isophorone diisocyanate polymer (H). The object of the present invention is achieved by providing such a laminated resin film.

[0019] <Laminated Resin Film 1> The laminated resin film 1 of the present invention essentially comprises an overprint varnish layer 2, a plastic film 3, a printing layer 4, and an adhesive layer 5 that are sequentially laminated.

[0020] <Overprint Varnish Layer 2> The overprint varnish layer 2 of the laminated resin film 1 of the present invention is the outermost layer when the laminated resin film 1 is laminated to a metal can, and plays a role in protecting the plastic film 3 and the printed layer 4. The overprint varnish layer 2 must be formed from overprint varnish composition (i) or overprint varnish composition (ii).

[0021] [Overprint varnish composition (i)] The overprint varnish composition (i) for the laminated resin film 1 of the present invention must contain specific amounts of two types of polyester resins (A) and polyester resin (B) having different number-average molecular weight ranges and glass transition temperature (Tg) ranges, respectively, a block-type isocyanate (C) having a specific dissociation temperature range, and a silicon-modified acrylic resin (D).

[0022] The polyester resin (A) used in the overprint varnish composition (i) of the laminated resin film 1 of the present invention preferably has a number average molecular weight in the range of 8,000 or more and less than 30,000, and more preferably 12,000 or more and less than 24,000. If the number average molecular weight is less than 8,000, the reactivity with isocyanate tends to decrease, resulting in insufficient crosslinking, and depending on the heating conditions, there is a concern that the water resistance and scratch resistance may decrease. On the other hand, if the number average molecular weight is 30,000 or more, the viscosity of the solution when it is made into a paint becomes too high, which may adversely affect the coatability and workability.

[0023] The above polyester resin (A) is preferably one with a glass transition temperature of 40°C or higher and less than 65°C, and more preferably one with a glass transition temperature of 45°C or higher and less than 60°C. If the glass transition temperature is less than 40°C, blocking with the adhesive layer 5 on the back may occur when the coated film is wound up. On the other hand, if the glass transition temperature is 65°C or higher, when an overlap portion is formed, the adhesion with the adhesive layer 5 decreases, and overlap defects may occur.

[0024] The overprint varnish composition (i) for the laminated resin film 1 of the present invention preferably contains 50 to 80 parts by mass of polyester resin (A) per 100 parts by mass (on a solid content basis) of the overprint varnish composition (i), and more preferably 60 to 70 parts by mass. If the amount of polyester resin (A) is less than 50 parts by mass, the Tg of the overprint varnish layer 2 is too high, which tends to reduce the overlap suitability. On the other hand, if the amount of polyester resin (A) exceeds 80 parts by mass, the Tg of the overprint varnish layer 2 is too low, which may lead to a decrease in blocking properties.

[0025] The polyester resin (B) is preferably one with a number average molecular weight of 10,000 or more and less than 35,000, and more preferably one with a number average molecular weight of 15,000 or more and less than 25,000. If the number average molecular weight is less than 10,000, the molecular weight of the overprint varnish layer 2 when crosslinked may be insufficient, which may reduce processability. On the other hand, if the number average molecular weight is 35,000 or more, compatibility with other resins decreases, and scratch resistance and water resistance tend to decrease.

[0026] The polyester resin (B) described above preferably has a glass transition temperature of 50°C or higher and less than 80°C, and more preferably 55°C or higher and less than 75°C. If the glass transition temperature is below 50°C, the scratch resistance after curing of the overprint varnish layer 2 may decrease. On the other hand, if the glass transition temperature is 80°C or higher, the overlap suitability of the overprint varnish layer 2 tends to decrease.

[0027] The overprint varnish composition (i) for the laminated resin film 1 of the present invention preferably contains 10 to 40 parts by mass of polyester resin (B) per 100 parts by mass (on a solid content basis) of the overprint varnish composition (i), and more preferably 25 to 35 parts by mass. If the amount of polyester resin (B) is less than 10 parts by mass, the Tg of the overprint varnish layer 2 tends to be too high, resulting in reduced overlap suitability. On the other hand, if the amount of polyester resin (B) exceeds 40 parts by mass, the Tg of the overprint varnish layer 2 tends to be too low, resulting in reduced blocking properties.

[0028] Both polyester resins (A) and (B) can be those obtained by esterifying a polybasic acid component with a polyhydric alcohol component.

[0029] As polybasic acid components, one or more dibasic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, fumaric acid, adipic acid, azelaic acid, sebacic acid, and dimer acid, and lower alkyl esters of these acids are mainly used. If necessary, monobasic acids such as benzoic acid, crotonic acid, and pt-butylbenzoic acid, and polybasic acids of trivalent or higher valencies such as trimellitic anhydride, methylcyclohexentricarboxylic acid, and pyromellitic anhydride are used in combination.

[0030] As polyhydric alcohol components, dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, 1,6-hexanediol, and cyclohexanedimethanol are mainly used, and if necessary, trihydric or higher polyhydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol can be used in combination. These polyhydric alcohols can be used alone or in mixtures of two or more.

[0031] The block-type isocyanate (C) used in the laminated resin film 1 of the present invention preferably has a dissociation temperature of 110 to 150°C, and more preferably 120 to 140°C. As a result, the block-free isocyanate reacts with the hydroxyl groups of the polyester resin at room temperature, and the block-type isocyanate reacts during heating for film drying and lamination, causing the coating to harden in stages. This relieves the internal stress of the coating and makes it possible to maintain strong adhesion to the substrate.

[0032] The block-type isocyanate (C) can be any common type within the aforementioned dissociation temperature range. A polyfunctional organic polyisocyanate having a bonding form such as an adduct obtained by adding 3 moles of organic diisocyanate to 1 mole of trimethylolpropane, a burette obtained by reacting 3 moles of organic diisocyanate with 1 mole of water, or an isocyanurate obtained by polymerization of 3 moles of organic diisocyanate can be used. Alternatively, a polyurethane polyisocyanate compound obtained by reacting a polyisocyanate with a polyester polyol, a polyether polyol, or, if necessary, with a low molecular weight polyol can be used. Examples of these aromatic polyisocyanates include 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyle diisocyanate, tetraalkyldiphenylmethane diisocyanate, dialkyldiphenylmethane diisocyanate, 1,3-phenylenediisocyanate, polymeric diphenylmethane diisocyanate, tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or its compounds), 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 1,5-naphthylene diisocyanate, and naphthalene diisocyanate.

[0033] Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, trimethylene diisocyanate, trimethylhexamethylene diisocyanate (2,2,4- or 2,4,4-), lysine diisocyanate, xylylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and 1,5-pentamethylene diisocyanate.

[0034] Examples of alicyclic polyisocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,3- or 1,4-), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, methylcyclohexane diisocyanate (-2,4- or -2,6-), and norbornane diisocyanate.

[0035] Blocking agents that block the isocyanate group of the above polyisocyanate compound include phenols such as phenol, cresol (o,m,p), and xylenol; alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol; oximes such as acetooxime, methyl ethyl ketone oxime, acetaldehyde, formaldehyde, diacetylmonoxime, and cyclohexaneoxime; active methylene compounds such as methyl acetoacetate, ethyl acetoacetate, and acetylacetone; and lactams such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam.

[0036] The overprint varnish composition (i) for the laminated resin film 1 of the present invention preferably contains 1 to 10 parts by mass of block-type isocyanate (C) per 100 parts by mass (on a solid content basis) of the overprint varnish composition (i), and more preferably 3 to 7 parts by mass. If the amount of block-type isocyanate (C) is less than 1 part by mass, the degree of crosslinking of the overprint varnish layer 2 is low, and water resistance and scratch resistance tend to decrease. On the other hand, if the amount of block-type isocyanate (C) exceeds 10 parts by mass, the functional groups of the polyester resin and the formation of the allophanate skeleton after the urethane reaction result in a rigid structure, which tends to reduce processability.

[0037] The silicone-modified acrylic resin (D) used in the overprint varnish composition (i) of the laminated resin film 1 of the present invention is used to prevent scratches during the can manufacturing and conveying process and to impart slipperiness and abrasion resistance to the overprint varnish layer 2. This silicone-modified acrylic resin (D) exhibits slipperiness and abrasion resistance because the silicone groups are oriented on the coating surface, while the acrylic resin reacts with isocyanate groups and is stably arranged in the coating, resulting in less loss during retort processing and other processes. This silicone-modified acrylic resin (D) is a graft polymer synthesized by copolymerization of a silicone monomer and an acrylic monomer, and can be manufactured using known techniques.

[0038] The overprint varnish composition (i) for the laminated resin film 1 of the present invention preferably contains 0.1 to 1.0 parts by mass of silicone-modified acrylic resin (D) per 100 parts by mass (in terms of solid content) of the overprint varnish composition (i), and more preferably 0.3 to 0.7 parts by mass. If the amount of silicone-modified acrylic resin (D) is less than 0.1 parts by mass, the slipperiness and abrasion resistance of the overprint varnish layer 2 may be insufficient. On the other hand, if the amount of silicone-modified acrylic resin (D) exceeds 1.0 part by mass, there is a concern that it may impede adhesion with the adhesive layer 5 when overlapping.

[0039] Furthermore, it is preferable that the overprint varnish composition (i) of the laminated resin film 1 of the present invention contains a hexamethylene diisocyanate polymer (O). By containing the hexamethylene diisocyanate polymer (O), the curing reaction with the polyester resin proceeds more easily even at low temperatures, improving the scratch resistance of the overprint varnish layer 2 and the adhesion strength between the overprint varnish layer 2 and the plastic film 3.

[0040] [Overprint varnish composition (ii)] The overprint varnish composition (ii) for the laminated resin film 1 of the present invention must contain specific amounts of two epoxy resins (E) and epoxy resin (F) having different epoxy equivalent ranges, a silicone-modified acrylic resin (G), and an isophorone diisocyanate polymer (H).

[0041] The epoxy resin (E) used in the overprint varnish composition (ii) for the laminated resin film 1 of the present invention preferably has an epoxy equivalent of 1500 or more and less than 2500, and more preferably has an epoxy equivalent of 1800 or more and less than 2300. If the epoxy equivalent of the epoxy resin (E) is less than 1500, the reactivity with isocyanate tends to decrease, resulting in insufficient crosslinking, which may reduce water resistance and scratch resistance. On the other hand, if the epoxy equivalent of the epoxy resin (E) is 2500 or more, the viscosity of the solution when it is made into a paint may become too high, which may adversely affect the coatability and workability.

[0042] The overprint varnish composition (ii) for the laminated resin film 1 of the present invention preferably contains 50 to 90 parts by mass of epoxy resin (E) per 100 parts by mass (in terms of solid content) of the overprint varnish composition (ii), and more preferably 60 to 75 parts by mass. If the amount of epoxy resin (E) is less than 50 parts by mass, adhesion strength with the plastic film 3 may not be obtained. On the other hand, if the amount of epoxy resin (E) exceeds 90 parts by mass, the overprint varnish layer 2 will lack flexibility and have poor processability.

[0043] The epoxy resin (F) used in the overprint varnish composition (ii) for the laminated resin film 1 of the present invention preferably has an epoxy equivalent of 2500 or more and less than 3500, and more preferably has an epoxy equivalent of 2700 or more and less than 3300. If the epoxy equivalent of the epoxy resin (F) is less than 2500, the molecular weight of the coating film when crosslinked may be insufficient, which may reduce processability. On the other hand, if the epoxy equivalent of the epoxy resin (F) is 3500 or more, compatibility with other resins tends to decrease, and water resistance and scratch resistance tend to decrease.

[0044] The overprint varnish composition (ii) for the laminated resin film 1 of the present invention preferably contains 10 to 40 parts by mass of epoxy resin (F) per 100 parts by mass (in terms of solid content) of the overprint varnish composition (ii), and more preferably 25 to 35 parts by mass. If the amount of epoxy resin (F) is less than 10 parts by mass, the water resistance may decrease. On the other hand, if the amount of epoxy resin (F) exceeds 40 parts by mass, the viscosity of the solution when it is made into a paint may become too high, which may adversely affect the paintability and workability.

[0045] The epoxy resin (E) and epoxy resin (F) described above are preferably bisphenol A type epoxy resin or bisphenol F type epoxy resin, with bisphenol A type epoxy resin being particularly preferred.

[0046] The above-mentioned bisphenol A type epoxy resin may be, for example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of an acid or alkali catalyst (such as a phosphoric acid or ammonium salt catalyst) as needed, or a resin obtained by polyaddition reaction between epoxy resin and bisphenol.

[0047] The silicone-modified acrylic resin (G) used in the overprint varnish composition (ii) of the laminated resin film 1 of the present invention is used to prevent scratches during the can manufacturing and conveying process and to impart slipperiness and abrasion resistance to the coating film. The silicone-modified acrylic resin (G) can be the same as the silicone-modified acrylic resin (D) used in the overprint varnish composition (i).

[0048] The overprint varnish composition (ii) for the laminated resin film 1 of the present invention preferably contains 0.5 to 3.0 parts by mass of the silicone-modified acrylic resin (G) per 100 parts by mass (in terms of solid content) of the overprint varnish composition (ii), and more preferably 0.7 to 2.0 parts by mass. If the amount of silicone-modified acrylic resin (G) is less than 0.5 parts by mass, the slipperiness may be insufficient. On the other hand, if the amount of silicone-modified acrylic resin (G) exceeds 1.0 part by mass, there is a concern that it may impede adhesion with the adhesive layer 5 when overlapping.

[0049] The isophorone diisocyanate polymer (H) used in the overprint varnish composition (ii) of the laminated resin film 1 of the present invention is used for the purpose of imparting low-temperature curability.

[0050] The overprint varnish composition (ii) for the laminated resin film 1 of the present invention preferably contains 1.0 to 10 parts by mass of isophorone diisocyanate polymer (H) per 100 parts by mass of overprint varnish composition (ii), and more preferably 3.0 to 7.0 parts by mass. If the amount of isophorone diisocyanate polymer (H) is less than 1.0 part by mass per 100 parts by mass of overprint varnish composition (ii), the degree of crosslinking of the overprint varnish layer 2 is low, and the curing of the overprint varnish layer 2 at low temperatures becomes insufficient. On the other hand, if the amount of isophorone diisocyanate polymer (H) is more than 10 parts by mass, unreacted functional groups react with moisture in the air and tend to take on a rigid structure, resulting in reduced processability.

[0051] The overprint varnish composition (i) or overprint varnish composition (ii) of the laminated resin film 1 of the present invention preferably contains nylon resin beads (P) with an average particle size of 5 to 20 μm from the viewpoint of providing scratch resistance. If the average particle size is less than 5 μm, the scratch resistance of the overprint varnish layer 2 will be insufficient. On the other hand, if the average particle size is greater than 20 μm, there is a risk of transfer failure during gravure printing.

[0052] The overprint varnish compositions (i) and (ii) of the laminated resin film 1 of the present invention may contain lubricants, defoamers, leveling agents, pigments, etc., as needed. In addition, other curing agents such as urea resin, melamine resin, benzoguanamine resin, isocyanate resin, and polyamide resin may be used in combination as curing aids, and the appropriate one can be used depending on the drying conditions and lamination conditions.

[0053] The dry film thickness of the overprint varnish layer 2 of the laminated resin film 1 of the present invention is preferably 1.0 to 5.0 μm, and more preferably in the range of 2.0 to 4.0 μm. If the film thickness is less than 1.0 μm, scratches can easily reach the plastic film 3 when they occur, and the plastic film 3 cannot be adequately protected. On the other hand, if the film thickness is greater than 5.0 μm, the transparency of the overprint varnish layer 2 tends to decrease.

[0054] <Plastic film 3> The plastic film 3 of the laminated resin film 1 of the present invention is a film that serves as the base material for the laminated resin film 1. This plastic film 3 is generally a film formed from a thermoplastic resin, and its material is a known thermoplastic resin, for example, polyolefins such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, cyclic olefin resins such as cyclic olefin copolymers and cyclic olefin polymers, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-vinyl chloride copolymers, and other ethylene-vinyl compound copolymers, polystyrene, acrylonitrile-styrene copolymers, ABS, α-methyl-1-pentene Examples include styrene-based resins such as styrene-styrene copolymers, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymers, polymethyl polyacrylate, polymethyl methacrylate, and other polyvinyl compounds, polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12, polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polycarbonates, polyphenylene oxide, and other biodegradable resins such as fluororesins, allyl resins, polyurethane resins, cellulose resins, polysulfone resins, polyethersulfone resins, ketone resins, amino resins, or polylactic acid. Furthermore, blends of these resins and resins modified by copolymerization as appropriate (for example, acid-modified olefin resins) are also included. Among these, polyester resins such as polyethylene terephthalate are preferably used because they have good heat resistance and are insoluble in organic solvents.

[0055] The plastic film 3 may be uniaxially or biaxially stretched, and a biaxially stretched film is particularly suitable for use.

[0056] The thickness of the plastic film 3 in the laminated resin film 1 of the present invention cannot be specified in general terms as it varies depending on the size of the metal can, etc., but for a typical metal can for beverages, it is 8 to 20 μm. If it is excessively thick, when the laminated resin film is laminated to the metal can, the thickness of the overlapping portion will become thick, which may impair the appearance of the film-laminated can.

[0057] <Print layer 4> The type of ink used in the printing layer 4 of the laminated resin film 1 of the present invention can be any conventionally known ink. Specifically, from the viewpoint of water resistance, printability, and pigment dispersibility, it is preferable to use a thermosetting ink with a thermosetting resin such as acrylic, urethane, or polyester as the base resin.

[0058] The printed layer 4 of the laminated resin film 1 of the present invention may be a solid print, or the printed layer 4 may be partially formed.

[0059] <Adhesive layer 5> The adhesive layer 5 of the laminated resin film 1 of the present invention is a layer provided for laminating the laminated resin film 1 to a metal can. Preferably, the adhesive composition forming the adhesive layer 5 contains specific amounts of two types of polyester resin (I) and polyester resin (J) having different number-average molecular weight ranges and glass transition temperature (Tg) ranges, respectively, titanium dioxide (K), blocked isophorone diisocyanate (L), blocked hexamethylene diisocyanate (M), and novolac-type epoxy resin (N).

[0060] The polyester resin (I) used in the adhesive composition of the laminated resin film 1 of the present invention preferably has a number average molecular weight of 8,000 or more and less than 30,000, and more preferably 12,000 or more and less than 25,000. If the number average molecular weight is less than 8,000, the reactivity with isocyanate tends to decrease, resulting in insufficient crosslinking and a tendency for reduced water resistance. On the other hand, if the number average molecular weight is 30,000 or more, the viscosity of the solution when it is made into a paint may become too high, potentially adversely affecting the coatability and workability.

[0061] The polyester resin (I) used in the adhesive composition of the laminated resin film 1 of the present invention preferably has a glass transition temperature of 40°C or higher and less than 65°C, and more preferably 50°C or higher and less than 60°C. When the glass transition temperature is less than 40°C, blocking with the overprint varnish layer 2 tends to occur when the coated film is wound up. On the other hand, when the glass transition temperature is 65°C or higher, the adhesive layer 5 tends to melt and soften less easily during lamination, and the laminating properties tend to decrease.

[0062] In the laminated resin film 1 of the present invention, the polyester resin (I) is preferably 10 to 40 parts by mass, and more preferably 25 to 38 parts by mass, per 100 parts by mass (in terms of solid content) of the adhesive composition. If the amount of polyester resin (I) is less than 10 parts by mass, the Tg of the adhesive layer 5 is too high, which tends to reduce the laminating properties. On the other hand, if the amount of polyester resin (I) exceeds 40 parts by mass, the Tg of the adhesive layer 5 is too low, which tends to cause the adhesive layer 5 to soften too much when heated, making it prone to trapping bubbles and other impurities.

[0063] The polyester resin (J) used in the adhesive composition of the laminated resin film 1 of the present invention preferably has a number average molecular weight of 15,000 or more and less than 50,000, and more preferably 20,000 or more and less than 40,000. If the number average molecular weight is less than 15,000, the molecular weight of the adhesive layer 5 when crosslinked may be insufficient, which may reduce processability. On the other hand, if the number average molecular weight is 50,000 or more, the viscosity of the solution when it is made into a paint may become too high, which may adversely affect the coatability and workability.

[0064] The polyester resin (J) used in the adhesive composition of the laminated resin film 1 of the present invention preferably has a glass transition temperature of 5°C or higher and less than 30°C, and more preferably 10°C or higher and less than 25°C. When the glass transition temperature is less than 5°C, blocking with the overprint varnish layer 2 tends to occur when the coated film is wound up. On the other hand, when the glass transition temperature is 30°C or higher, the adhesive layer 5 tends to melt and soften less easily during lamination, and the laminating properties tend to decrease.

[0065] The adhesive composition for the laminated resin film 1 of the present invention preferably contains 1 to 10 parts by mass of polyester resin (J) per 100 parts by mass of the adhesive composition (on a solid content basis), and more preferably 3 to 8 parts by mass. If the amount of polyester resin (J) is less than 1 part by mass per 100 parts by mass of the adhesive composition (on a solid content basis), the Tg of the adhesive layer 5 tends to be too high, resulting in reduced laminating properties. If the amount of polyester resin (J) exceeds 10 parts by mass, the Tg of the adhesive layer 5 is too low, causing the adhesive layer 5 to soften too much when heated, and making it prone to trapping bubbles and other impurities.

[0066] The titanium dioxide (K) used in the adhesive composition of the laminated resin film 1 of the present invention can be suitably used as a white pigment to conceal the dull appearance color characteristic of steel plates. Generally, a thick plastic film 3 with titanium dioxide or the like kneaded into it is used as a means of imparting opacity to metal cans, but by incorporating titanium dioxide or the like into the adhesive, opacity can be achieved, enabling the plastic film 3 to be made thinner, and in some cases a transparent film can be used, leading to a significant cost reduction.

[0067] The titanium dioxide (K) used in the adhesive composition of the laminated resin film 1 of the present invention is preferably produced by the sulfuric acid method, has a particle size in the range of 0.1 to 0.4 μm, and is treated with silica or alumina as a surface treatment agent. Titanium dioxide produced by the chlorine method generally has a higher Mohs hardness than titanium dioxide produced by the sulfuric acid method, and tends to reduce workability by easily wearing down the doctor blade during printing. If the particle size of titanium dioxide is 0.1 μm or larger, the opacity tends not to decrease, and if it is 0.4 μm or smaller, it tends not to cause inhibition of the paste.

[0068] The adhesive composition for the laminated resin film 1 of the present invention preferably contains 40 to 60 parts by mass of titanium dioxide (K) per 100 parts by mass of the adhesive composition (based on solid content), and more preferably 42 to 50 parts by mass. If the amount of titanium dioxide (K) is less than 40 parts by mass per 100 parts by mass of the adhesive composition (based on solid content), the opacity may be insufficient. On the other hand, if the amount of titanium dioxide (K) is more than 60 parts by mass, it tends to easily cause inhibition of meat mixing.

[0069] The adhesive composition for the laminated resin film 1 of the present invention preferably contains block-type isophorone diisocyanate (L) for the purpose of promoting low-temperature curing of the adhesive layer 5.

[0070] The amount of block-type isophorone diisocyanate (L) used in the adhesive composition of the laminated resin film 1 of the present invention is preferably 1 to 10 parts by mass, and more preferably 3 to 8 parts by mass, per 100 parts by mass (solid content) of the adhesive composition. If the amount of block-type isophorone diisocyanate (L) is less than 1 part by mass per 100 parts by mass (solid content) of the adhesive composition, the curing of the adhesive layer 5 at low temperatures will be insufficient. On the other hand, if the amount of block-type isophorone diisocyanate (L) is more than 10 parts by mass, the processability tends to decrease because a rigid structure is formed due to the functional groups of the polyester resin and the formation of the allophanate skeleton after the urethane reaction.

[0071] The adhesive composition for the laminated resin film 1 of the present invention preferably contains block-type hexamethylene diisocyanate (M) for the purpose of promoting low-temperature curing of the adhesive layer 5.

[0072] The adhesive composition for the laminated resin film 1 of the present invention preferably contains 1 to 10 parts by mass of block-type hexamethylene diisocyanate (M) per 100 parts by mass of the adhesive composition (based on solid content), and more preferably 3 to 8 parts by mass. If the amount of block-type hexamethylene diisocyanate (M) is less than 1 part by mass per 100 parts by mass of the adhesive composition (based on solid content), the curing of the adhesive layer 5 at low temperatures will be insufficient. On the other hand, if the amount of block-type hexamethylene diisocyanate (M) is more than 10 parts by mass, the processability tends to decrease because a rigid structure is formed due to the functional groups of the polyester resin and the formation of the allophanate skeleton after the urethane reaction.

[0073] The adhesive composition of the laminated resin film 1 of the present invention preferably contains a novolac-type epoxy resin (N) for the purpose of promoting low-temperature curing of the adhesive layer 5.

[0074] The novolac-type epoxy resin (N) used in the adhesive composition of the laminated resin film 1 of the present invention is preferably 1 to 5 parts by mass, and more preferably 2 to 4 parts by mass, per 100 parts by mass (solid content) of the adhesive composition. If the amount of novolac-type epoxy resin (N) is less than 1 part by mass per 100 parts by mass (solid content) of the adhesive composition, the low-temperature softening properties of the adhesive film will be poor, and lamination defects may occur. On the other hand, if the amount of novolac-type epoxy resin (N) is more than 5 parts by mass, blocking with the overprint varnish layer 2 tends to occur when the coated film is wound up.

[0075] There are no particular limitations on the diluent solvents that can be used for the overprint varnish composition (i), overprint varnish composition (ii), and adhesive composition of the laminated resin film 1 of the present invention. Examples include aromatic hydrocarbons such as toluene, xylene, Solvesso #100, and Solvesso #150; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; and various ester-based organic solvents such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate. Furthermore, examples of water-miscible organic solvents include alcohol-based solvents such as methanol, ethanol, propanol, and butanol; ketone-based solvents such as acetone, methyl ethyl ketone, and cyclohexanone; and glycol ether-based solvents such as ethylene glycol (mono, di)methyl ether, ethylene glycol (mono, di)ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di)methyl ether, diethylene glycol (mono, di)ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di)methyl ether, propylene glycol (mono, di)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono, di)methyl ether. Of these, methyl ethyl ketone, ethyl acetate, or mixtures thereof are usually preferred.

[0076] The adhesive composition of the laminated resin film 1 of the present invention may contain lubricants, defoamers, leveling agents, pigments, etc., as needed. In addition, other curing agents such as urea resin, melamine resin, benzoguanamine resin, isocyanate resin, and polyamide resin may be used in combination as curing aids, and the appropriate one can be used depending on the heating and drying conditions and lamination conditions.

[0077] The dry film thickness of the adhesive layer 5 of the laminated resin film 1 of the present invention is 0.1 to 10 μm, preferably 2 to 6 μm. If the dry film thickness of the adhesive layer 5 is less than 0.1 μm, the adhesion between the laminated resin film 1 and the metal can may be insufficient. If the dry film thickness of the adhesive layer 5 is greater than 10 μm, interlayer adhesion can be ensured, but manufacturing costs will increase unnecessarily.

[0078] <Other layers> The laminated resin film 1 of the present invention may have other layers formed on it besides the overprint varnish layer 2, the plastic film 3, the printing layer 4, and the adhesive layer 5. For example, such other layers may include a surface printing layer, separate from the printing layer 4, placed between the overprint varnish layer 2 and the plastic film 3. The design of the laminated resin film 1 is improved by providing this surface printing layer.

[0079] <Manufacturing of Laminated Resin Film 1> In manufacturing the laminated resin film 1 of the present invention, the process includes at least the steps of forming an overprint varnish layer 2 on one side of a plastic film 3, forming a printed layer 4 on the other side of the plastic film 3, and forming an adhesive layer on the printed layer 4.

[0080] <Step to form overprint varnish layer 2> [Step of applying the overprint varnish composition] First, one side of the plastic film 3 is coated with either the overprint varnish composition (i) or the overprint varnish composition (ii). Methods of application include various spray coatings such as air spray, airless spray, or electrostatic spray, as well as known methods such as dip coating, roll coater coating, gravure coater coating, and electrodeposition coating.

[0081] [Step of heating and drying the overprint varnish composition] The applied overprint varnish composition (i) or overprint varnish composition (ii) is heated and dried to form a semi-cured overprint varnish layer 2. Drying methods include using an oven, dryer, UV curing, or electron beam curing. The heating temperature for drying the overprint varnish composition is preferably 80-140°C, and more preferably 100-120°C. If the drying temperature is below 80°C, curing may be insufficient, potentially causing blocking when the film is wound. On the other hand, if the temperature is higher than 140°C, the overprint varnish layer 2 may become over-cured, potentially reducing its overlap suitability. The heating time for drying the overprint varnish composition is preferably 5-20 seconds, and more preferably 6-12 seconds.

[0082] <Process for forming the printed layer 4> Next, printing is performed on the other side of the plastic film 3 (the side of the plastic film 3 opposite to the side on which the overprint varnish layer 2 is formed). Printing methods include known methods such as gravure printing or inkjet printing. After printing, heat drying is performed to form the printed layer 4. The drying method can be the same as the method described in the step of heat drying the overprint varnish composition.

[0083] <Step to form adhesive layer 5> [Step of applying the adhesive composition] The adhesive composition is applied to the dried printed layer 4. The application method can be the same as the method described in the step for applying the overprint varnish composition.

[0084] [Step of heating and drying the adhesive composition] The applied adhesive composition is heated and dried to form a semi-cured adhesive layer 5. The drying method can be the same as the method described in the step of heating and drying the overprint varnish composition. The heating temperature when heating and drying the adhesive composition is preferably 80 to 140°C, and more preferably 100 to 120°C. If the drying temperature is below 80°C, the curing will be insufficient, and blocking may occur when the film is wound up. On the other hand, if it is higher than 140°C, the adhesive layer 5 may become over-cured, and the overlap suitability may decrease. The heating time when heating and drying the overprint varnish composition is preferably 5 to 20 seconds, and more preferably 6 to 12 seconds.

[0085] The laminated resin film 1 of the present invention can be manufactured by following the procedure described above.

[0086] <Metal can> The laminated resin film 1 of the present invention is particularly suitable for use as a label for metal cans. The metal can may be a seamless can or a welded can, but a seamless can is particularly preferred. Such seamless cans are manufactured by subjecting various surface-treated steel sheets such as tin-free steel (TFS), various plated steel sheets such as tin-plated steel, light metal sheets such as aluminum, inorganic surface-treated light metal sheets that have undergone chemical conversion treatment such as chromium phosphate, or resin-coated metal sheets in which a coating of a thermoplastic resin such as polyester resin is formed on these metal sheets, to conventionally known methods such as drawing and redrawing, bending and stretching by drawing and redrawing (stretching), bending and stretching and ironing by drawing and redrawing, or drawing and ironing, or impact processing of light metal sheets.

[0087] When laminating the laminated resin film 1 of the present invention onto a metal can, the laminated resin film 1 is wrapped around the body of the metal can, and the film is heated with the ends of the laminated resin film 1 overlapping. This process allows for the production of a film-laminated can in which the laminated resin film 1 is laminated onto the surface of the metal can's body. In this invention, after lamination, the semi-cured overprint varnish layer 2 and adhesive layer 5 can be fully cured without the need for a conventional baking process. When laminating the laminated resin film 1 of the present invention onto a metal can, an oven is preferred as the heating method from the viewpoint of uniformly heating the entire can. Preferably, the heating temperature is 120-180°C and the oven passage speed is 100-200 m / min. The film-laminated can thus obtained has excellent design, corrosion resistance, processing adhesion, and retort resistance, and can be used for a wide variety of applications. [Examples]

[0088] The present invention will be specifically described below with reference to examples and comparative examples. In the examples, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0089] The following raw materials were weighed and mixed using an electronic balance according to the proportions of the adjustment examples shown in Tables 1-6 (the numbers in the table indicate the solid content mass ratio). The mixture was then stirred for 1 minute at 3000 rpm at a temperature of 25°C using a dispersion stirrer to prepare overprint varnish compositions (i), (ii), and adhesive composition. • Overprint varnish composition (i) Polyester resin (A): Elitel UE-3210, manufactured by Unitika Ltd. Polyester resin (B): Elitel UE-3600, manufactured by Unitika Ltd. Block-type isocyanate (C): Duranate 17B-60P, manufactured by Asahi Kasei Corporation. Silicone-modified acrylic resin (D): Cymac US-270, manufactured by Toagosei Co., Ltd. • Overprint varnish composition (ii) Epoxy resin (E): EPICLON7050, manufactured by DIC Corporation. Epoxy resin (F): EPICLON HM-091, manufactured by DIC Corporation. Silicone-modified acrylic resin (G): Cymac US-270, manufactured by Toagosei Co., Ltd. Isophorone diisocyanate polymer (H): Desmodule 4470BA, manufactured by Sumika Covestro Urethane Co., Ltd. • Adhesive composition Polyester resin (I): Elitel UE-3210, manufactured by Unitika Ltd. Polyester resin (J): Elitel UE-3500, manufactured by Unitika Ltd. Titanium Oxide (K): CR58-2, manufactured by Ishihara Sangyo Co., Ltd. Block-type IPDI (L): Desmodule BL2078 / 2, manufactured by Sumika Covestro Urethane Co., Ltd. Block-type HDI(M): Duranate 17B-60P, manufactured by Asahi Kasei Corporation. Novolac-type epoxy resin (N): YDCN-700-7, manufactured by Nippon Steel Chemical & Material Co., Ltd.

[0090] [Preparation of test panels] A. Toyobo Co., Ltd. PET film (thickness 12 μm) is coated with an overcoat layer having the composition shown in Tables 1 and 2, with a dry film thickness of 2.0 ± 0.3 g / m². 2 The material was coated using a bar coater and dried at 120°C for 8 seconds. A gravure ink of any type was applied to the back of a film created with BA using a bar coater to a dry film thickness of 1.0 μm. After drying with a dryer, the adhesive shown in Table 3 was applied using a bar coater to a dry film thickness of 6.0 μm and dried at 115°C for 8 seconds. Test pieces were obtained by laminating the adhesive-coated surfaces of the films prepared in CA and B onto a PET resin-coated metal can at 190°C and 150 m / min. Measurements were then taken according to the evaluation test method described below.

[0091] [Evaluation Test Method] 1. Coefficient of dynamic friction (overprint varnish only) The dynamic friction coefficient of the film treated using the method described in A above was measured using the three-point steel ball method with an Orientec RTA-100, in accordance with ASTM D1894-90. The load was 1 kg and the tensile speed was 100 mm / min. The dynamic friction coefficient values ​​were classified into the following four stages, with values ​​of ○ or higher being considered acceptable. (Rating) ◎: Less than 0.10 ○: 0.10 or higher, less than 0.15 △: 0.15 or higher, less than 0.30 ×: 0.30 or higher

[0092] 2. Overlap suitability (common) The peel strength of the film overlap portion of the laminated cans created using methods A, B, and C described above was measured, and the cans were deemed suitable for overlapping. The peeling speed was 100 mm / min. The cans were divided into the following four stages, with a score of ○ or higher being considered acceptable. ◎: 1.5N / 15mm or more ○: 1.0N / 15mm or more, less than 1.5N / 15mm △: 0.5N / 15mm or more, less than 1.0N / 15mm ×: 0.5N / less than 15mm

[0093] 3. Resistance to whitening in retort (common) Test pieces were molded into curved surfaces and placed in contact with each other. After retort treatment at 125°C for 30 minutes, the degree of whitening at the contact points was visually evaluated. The results were divided into the following four stages, with a score of ○ or higher considered acceptable. (Rating) ◎: No whitening at all ○: Slight whitening is visible in some areas. △: Widespread bleaching is observed. ×: Whitening is visible in most areas.

[0094] 4. Scratch resistance (overprint varnish only) Using the Norman Tool RCA Abrasion Wear Tester7-IBB, we evaluated the number of times the coating was removed by rubbing one spot with abrasion paper. The abrasion paper movement speed was 60 mm / s, and the load was 175 g. The results were divided into the following four categories, with a score of ○ or higher considered a pass. (Rating) ◎: Very high number of scrubbing cycles (41 times or more) ○: Too many scrubbings (40-21 times) △: Slightly insufficient number of scrubbing strokes (20-10 times) ×: Insufficient number of scrubbings (less than 10 times)

[0095] 5. Retort processing (adhesive only) The caps were molded to a height of 10 mm, and the film peeling after retort processing at 125°C for 30 minutes was visually evaluated on a 4-point scale. The following 4 levels were used, with a score of ○ or higher considered acceptable. (Rating) ◎: No peeling at all ○: Peeling area is less than 10% △: Peeling area is 10% or more but less than 50% ×: Peeling area is 50% or more

[0096] 6. Blocking properties (common) The adhesive-coated surfaces of 8cm x 8cm sample films were bonded together and held in a 40°C atmosphere under a pressure of 0.3 MPa for 72 hours. The bonded films were then peeled at a 180° angle at a peeling speed of 1000 mm / min, and the peel strength was measured. The results were classified into the following four stages, with a score of ○ or higher considered acceptable. (Rating) ◎: Less than 0.5 N / cm ○: 0.5 N / cm or more, less than 1.0 N / cm △: 1.0 N / cm or more, less than 1.5 N / cm ×:1.5N / cm or more

[0097] 7. Solvent rubbing (common) A cotton ball soaked in a mixed solvent of isopropyl alcohol / methyl ethyl ketone = 7 / 3 was attached to the contact area of ​​the rubbing tester, and the tester was moved back and forth across the coating surface with a load of 2 kg. The number of back-and-forth movements was measured when the substrate was exposed by 10% or more of the test area, which was set to 100%. A reading of 20 or more movements was considered a pass.

[0098] 8. Opacity (adhesives only) The L value of the adhesive surface coated on the PET film under the above conditions was measured using a Spectrophotometer SE7700 manufactured by Nippon Denshoku Co., Ltd., and this value was defined as the opacity. A value of 80 or higher was considered acceptable.

[0099] (Examples) Table 1 shows the composition of the prepared overprint varnish composition (i) and its evaluation results, as shown in adjustment example A. The numbers in the table represent the solid content mass ratio.

[0100] [Table 1]

[0101] Table 2 shows the composition of the prepared overprint varnish composition (ii) and its evaluation results, as shown in adjustment example B. The numbers in the table represent the solid content mass ratio.

[0102] [Table 2]

[0103] Table 3 shows the composition of the prepared adhesive composition, example C, and its evaluation results. The numbers in the table represent the solid content mass ratio.

[0104] [Table 3]

[0105] (Comparative example) Table 4 shows the composition of the prepared overprint varnish composition (i) and its evaluation results, as shown in adjustment example D. The numbers in the table represent the solid content mass ratio.

[0106] [Table 4]

[0107] Table 5 shows the composition of the prepared overprint varnish composition (ii) and its evaluation results, as shown in adjustment example E. The numbers in the table represent the solid content mass ratio.

[0108] [Table 5]

[0109] Table 6 shows the composition of the prepared adhesive composition, example F, and its evaluation results. The numbers in the table represent the solid content mass ratio.

[0110] [Table 6]

[0111] In the laminated resin film shown in the examples, a well-balanced, acceptable product (rated ○ or higher) was obtained in all evaluation items, including overlap suitability, retort whitening resistance, processing retortability, blocking properties, solvent rubbing resistance, and opacity (L value).

[0112] In contrast, the laminated resin film shown in the comparative example lacked at least one of the following: appropriate overlap, retort whitening resistance, retort processing resistance, blocking resistance, solvent rubbing resistance, and opacity (L value). [Industrial applicability]

[0113] The laminated resin film of the present invention, when used in metal cans, exhibits excellent scratch resistance, water resistance, and film adhesion without the need for heating by baking treatment. Therefore, it can be widely applied to a wide range of uses, including beverage cans for soft drinks, coffee, tea, beer, carbonated drinks, food cans, aerosol cans, tube cans, and more. [Explanation of symbols]

[0114] 1. Laminated resin film 2 Overprint varnish layers 3 Plastic film 4 Printed Layer 5. Next, peel off the top layer.

Claims

1. A laminated resin film comprising an overprint varnish layer, a plastic film, a printed layer, and an adhesive layer, in sequence, The overprint varnish layer is formed from overprint varnish composition (i) or overprint varnish composition (ii), The overprint varnish composition (i) contains 50 to 80 parts by mass of polyester resin (A) having a number average molecular weight of 8,000 or more and less than 30,000 and a glass transition temperature of 40°C or more and less than 65°C, 10 to 40 parts by mass of polyester resin (B) having a number average molecular weight of 10,000 or more and less than 35,000 and a glass transition temperature of 50°C or more and less than 80°C, 1 to 10 parts by mass of block-type isocyanate (C) having a dissociation temperature of 110 to 150°C, and 0.1 to 1.0 parts by mass of silicon-modified acrylic resin (D). The overprint varnish composition (ii) is characterized by containing 50 to 90 parts by mass of epoxy resin (E) having an epoxy equivalent of 1500 or more and less than 2500, 10 to 40 parts by mass of epoxy resin (F) having an epoxy equivalent of 2500 or more and less than 3500, 0.5 to 3.0 parts by mass of silicone-modified acrylic resin (G), and 1.0 to 10 parts by mass of isophorone diisocyanate polymer (H).

2. The laminated resin film according to claim 1, wherein the adhesive composition for forming the adhesive layer contains 10 to 40 parts by mass of polyester resin (I) having a number average molecular weight of 8,000 or more and less than 30,000 and a glass transition temperature of 40°C or more and less than 65°C, 1 to 10 parts by mass of polyester resin (J) having a number average molecular weight of 15,000 or more and less than 50,000 and a glass transition temperature of 5°C or more and less than 30°C, 40 to 60 parts by mass of titanium dioxide (K), 1 to 10 parts by mass of blocked isophorone diisocyanate (L), 1 to 10 parts by mass of blocked hexamethylene diisocyanate (M), and 1 to 5 parts by mass of novolac-type epoxy resin (N).

3. The laminated resin film according to claim 1 or 2, wherein the overprint varnish composition (i) contains a hexamethylene diisocyanate polymer (O).

4. The laminated resin film according to claim 1 or 2, wherein the overprint varnish composition (i) or the overprint varnish composition (ii) contains nylon resin beads (P) having an average particle size of 5 to 20 μm.

Images