Laminated Film

Abstract

To provide a laminate film with excellent antimicrobial and antiviral properties.SOLUTION: At least one side of a thermoplastic film comprises a resin layer containing cerium oxide particles of more than 20 weight percent and less than 90 weight percent, the surface zeta potential of the resin layer is more than -10 mV and less than +70 mV.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated film having antiviral properties. [Background technology]

[0002] Plastic films, including polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance, and are therefore widely used as substrate films in many applications, such as magnetic recording materials and packaging materials.

[0003] In particular, in recent years, with growing awareness of safety and hygiene management, antibacterial and antiviral films that decompose harmful substances and microorganisms have attracted attention, and various materials are being used to exhibit antibacterial and antiviral properties.

[0004] For example, titanium oxide particles have the photocatalytic properties of generating reactive oxygen species and oxidizing and decomposing organic matter. In addition to being used as an antibacterial agent, they are also expected to be used to decompose various harmful substances, including low-molecular-weight compounds such as acetaldehyde and ammonia, allergens, and viruses.

[0005] Cerium oxide particles (nanoceria) have various properties, including oxidizing, antioxidant, and antibacterial properties, and are known to have catalytic activity similar to that of enzymes such as catalase, oxidase, peroxidase, superoxide dismutase, and phosphatase. Cerium oxide particles are also expected to be used in applications different from those of titanium oxide, which has photocatalytic properties. Furthermore, nanoparticles can be optically transparent, making them suitable for use in displays and other optical applications.

[0006] Generally, nanoparticles tend to aggregate easily. Because cerium oxide nanoparticles also tend to aggregate easily, their surfaces are sometimes coated with polymers to improve their dispersibility, and they are then used as oxidizing agents, antibacterial agents, etc.

[0007] Patent Document 1 discloses a technology for an architectural coating liquid having a photocatalytic layer containing cerium oxide particles, and Patent Document 2 discloses a technology for a laminate using cerium oxide together with an antibacterial compound. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-63950 [Patent Document 2] Patent No. 6481619 Summary of the Invention [Problem to be solved by the invention]

[0009] However, Patent Document 1 discloses technology for antifungal and antialgal properties but not for antiviral properties, and the antifungal and antialgal properties are due to the photocatalytic oxidizing power resulting from the interaction between photocatalytic titanium oxide particles and copper compounds. Patent Document 2 discloses technology for antibacterial properties but, like Patent Document 1, does not disclose technology for antiviral properties, and the antibacterial properties are due to inorganic fine particles containing metal ions selected from the group consisting of gold, silver, copper, tin, zinc, and platinum.

[0010] An object of the present invention is to provide a laminated film that can efficiently inactivate viruses. [Means for solving the problem]

[0011] As a result of intensive research in light of the above-mentioned problems, the present inventors have found that a laminated film in which a resin layer containing cerium oxide particles is provided on a thermoplastic film has rapid and high virus inactivation performance due to the oxidizing power of the cerium oxide particles, and have thus completed the present invention.

[0012] The present invention comprises the following configurations: [I] A laminated film having a resin layer containing 20% by weight or more and 90% by weight or less of cerium oxide particles on at least one side of a thermoplastic film, wherein the surface zeta potential of the resin layer is -10 mV or more and +70 mV or less. [II] The laminate film according to [I], wherein the surface roughness Rz of the resin layer is 50 nm or more. [III] The laminate film according to [I] or [II], wherein the resin layer contains inorganic particles, and the particle diameter L(A) of the cerium oxide particles, the particle diameter L(B) of the inorganic particles, and the thickness L(X) of the resin layer satisfy the following formulas (1) and (2): L(B)>L(A) ··· Formula (1) L(B)≧L(X) ··· Formula (2) [IV] The laminate film according to any one of [I] to [III], wherein the resin layer contains one or more resins selected from polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins. [V] The laminate film according to any one of [I] to [IV], wherein the resin layer contains one or more resins selected from a melamine compound, an oxazoline compound, and a carbodiimide compound. [VI] A method for producing a laminated film, comprising the steps of applying a coating composition containing 20% by weight or more and 90% by weight or less of cerium oxide particles to at least one surface of a thermoplastic film, and heating and drying the coating composition to form a resin layer, wherein the surface zeta potential of the resin layer is -10 mV or more and +70 mV or less. [VII] The method for producing a laminated film according to [VI], wherein the resin plastic resin film is an unstretched thermoplastic resin film, a uniaxially stretched (uniaxially oriented) thermoplastic resin film, or a biaxially stretched (biaxially oriented) thermoplastic resin film before heat treatment, and the method includes a step of stretching the film in at least one direction after the step of applying a coating composition; [VIII] The method for producing a laminated film according to [VI] or [VII], wherein the resin composition further contains one or more resins selected from polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins. [IX] A method for producing a laminated film according to any one of [VI] to [VIII], wherein the resin composition further contains one or more resins selected from a melamine compound, an oxazoline compound, and a carbodiimide compound. is. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a laminated film that can efficiently inactivate viruses. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention is a laminated film having a resin layer containing 20% by weight or more and 90% by weight or less of cerium oxide particles on at least one side of a thermoplastic film.

[0015] (1) Cerium oxide particles The laminated film of the present invention is a film containing cerium oxide particles.

[0016] The cerium oxide particles must be contained in the resin layer at 20% by weight or more and 90% by weight or less. More preferably, it is contained at 50% by weight or more and 80% by weight or less. By containing 20% by weight or more of cerium oxide particles in the resin layer, the antiviral properties of the laminated film are exhibited. Furthermore, by containing 90% by weight or less of cerium oxide particles in the resin layer, the occurrence of cracks and defects can be suppressed, and a uniform resin layer can be produced.

[0017] The cerium oxide particles are preferably composed of a mixture of Ce2O3 and CeO2, and more preferably have a structure in which a mixture of Ce2O3 and CeO2 forms a central core with a polymer layer coated on the surface with various polymers or compounds. The particle size of the central core is preferably 1 nm or more and 100 nm or less. The particle size of the central core is determined by measuring two or more lengths of the major axis diameter, minor axis diameter, and unidirectional diameter using a transmission electron microscope, and calculating the average value as the particle size.

[0018] The ratio of Ce2O3 to CeO2 can be calculated as the ratio of cerium(III) to cerium(IV). To calculate this ratio, cerium oxide particles are dried and analyzed by X-ray photoelectron spectroscopy (XPS). The energy states of cerium(III) and cerium(IV) in Ce2O3 and CeO2 can be observed by X-ray absorption fine structure (XAFS) spectroscopy. In the XAFS spectrum, the structure approximately 20 eV from the absorption edge is called XANES (X-ray absorption near edge structure), and the extended X-ray absorption fine structure that appears approximately 100 eV or more higher than the absorption edge is called EXAFS (Extended X-ray Absorption Fine Structure). XANES provides information about the valence and structure of the target atom. EXAFS analysis, using the Fourier transform of the real spectrum (equivalent to the FT-EXAFS / radial distribution function), provides information about the local structure of the sample, the atomic species, valence, and distance around the target atom. The energy states of cerium(III) and cerium(IV) in the redox reaction of cerium oxide are reflected in the peak positions and peak intensity ratios of the absorption maxima in the XANES spectrum. The Ce L3 edge XANES spectrum obtained by X-ray absorption fine structure spectroscopy preferably has absorption maxima between 5726.0 and 5729.0 eV and between 5735.0 and 5739.0 eV.

[0019] The preferred particle size of the cerium oxide particles, including the surface polymer layer, is 1 nm or more and 200 nm or less in terms of hydrodynamic diameter. When cerium oxide particles are synthesized and manufactured, they are substantially 1 nm or more. By making the particle size 200 nm or less, they can be well dispersed in the resin layer without aggregation. Furthermore, films containing cerium oxide particles can be used to decompose nucleic acids and polypeptides. For example, viruses, which are primarily composed of nucleic acids and polypeptides, may be decomposed. Furthermore, allergens, which are primarily composed of polypeptides, may be decomposed.

[0020] As used herein, decomposing a nucleic acid means that the nucleotide chain constituting the nucleic acid is cleaved. When a nucleic acid is decomposed, the three-dimensional structure of the nucleic acid changes or the nucleic acid is fragmented. For example, in the case of a circular double-stranded nucleic acid such as a plasmid, when the nucleic acid is not cleaved, it has a closed circular structure, when one of the two strands is cleaved it has an open circular structure, and when both strands are cleaved it has a linear structure.

[0021] As used herein, decomposition of a polypeptide means that the polypeptide chain is cleaved, which may result in a change in the three-dimensional structure of the polypeptide or fragmentation of the polypeptide.

[0022] When nucleic acids or polypeptides are decomposed using cerium oxide particles, the cerium oxide particles may be contacted in a dried state with a sample containing nucleic acids or polypeptides, or the solution containing cerium oxide particles after the completion of the reaction may be contacted directly with the sample containing nucleic acids or polypeptides. As a contacting method, when the sample containing nucleic acids or polypeptides is liquid, cerium oxide nanoparticles or a solution containing cerium oxide particles may be added and mixed.

[0023] Nucleic acids that can be degraded by a film containing cerium oxide particles are not particularly limited as long as they are nucleic acids in which nucleotides are polymerized in a linear or circular form, and may also be artificial nucleic acids. Examples of nucleic acids include RNA, DNA, and RNA / DNA (chimeras). Examples of DNA include cDNA, microDNA (miDNA), plasmid DNA, genomic DNA, synthetic DNA, cell-free DNA (cfDNA), ctDNA, and mitochondrial DNA (mtDNA). Examples of RNA include total RNA, mRNA, rRNA, miRNA, siRNA, snoRNA, snRNA, non-coding RNA, their precursors, and synthetic RNA. Synthetic DNA and synthetic RNA are artificially prepared, for example, using an automated nucleic acid synthesizer, based on a predetermined base sequence (either a natural or non-natural sequence). Examples of artificial nucleic acids include LNA and BNA. Any sample containing these nucleic acids can be used for degradation.

[0024] Examples of polypeptides that can be decomposed by a film containing cerium oxide particles include proteins and artificially synthesized polypeptides based on a specific amino acid sequence (which may be either a natural sequence or a non-natural sequence).

[0025] In addition, polypeptide nucleic acids (PNAs), which have a nucleic acid-like structure with a polypeptide structure in the main chain, and viruses, which are mainly composed of proteins and nucleic acids, can also be used as samples containing nucleic acids or polypeptides.

[0026] Methods for confirming nucleic acid degradation include analyzing nucleic acids using electrophoresis (e.g., acrylamide gel electrophoresis, agarose gel electrophoresis, and capillary electrophoresis), size exclusion chromatography, mass spectrometry, and other methods. Nucleic acid degradation can be confirmed by a decrease in band concentration or peak intensity compared to before degradation, or by the disappearance of bands or peaks. Degradation can also be confirmed by the appearance of new bands or peaks indicating the presence of small fragments compared to before degradation. Specifically, when a circular double-stranded nucleic acid is degraded, the closed circular, open circular, and linear structures can be confirmed as separate bands in electrophoresis. Furthermore, if the three-dimensional structure of the nucleic acid changes due to degradation, the position of the bands may change compared to before degradation.

[0027] Degradation of the polypeptide can be confirmed by the same method as used to confirm the degradation of nucleic acids described above.

[0028] Cerium oxide particles can be used as an antifungal agent. Methods for evaluating their performance as an antifungal agent include, for example, mixing a mold spore suspension with a test solution, culturing the mixture on an inorganic salts agar medium or a glucose-containing inorganic salts agar medium, and observing the growth state; adding the test solution to an agar medium and observing growth inhibition; or measuring the growth inhibition zone. In the present invention, the antifungal performance is preferably evaluated by adding the test solution to an agar medium and observing growth inhibition or measuring the growth inhibition zone.

[0029] Examples of fungi that can be inactivated by cerium oxide particles include Penicillium, Aspergillus, Alternaria, Cladosporium, Trichoderma, and Chaetomium.

[0030] Cerium oxide particles can be used as an antiviral agent. The performance of the antiviral agent can be evaluated by contacting the surface-treated cerium oxide particles of the present invention with a virus and quantifying the amount of virus after contact. Methods for quantifying the virus include measuring the amount of virus antigens by ELISA, quantifying viral nucleic acids by PCR, measuring the infectivity titer by the plaque method, and measuring the infectivity titer by the 50% infectivity dose assay. In the present invention, the antiviral performance is preferably measured by measuring the infectivity titer by the plaque method or the 50% infectivity dose assay. The unit of the virus infectivity titer is TCID when tested on cultured cells in the 50% infectivity dose assay. 50 (Tissue culture infectious dose 50), EID 50 (Egg infectious dose 50), LD in animals 50 The infectivity titer is expressed as Lethal dose 50 (Lethal dose 50). Methods for calculating the infectivity titer from the data obtained in the 50% infectivity dose measurement method include the Reed-Muench method, the Behrens-Kaeber method, and the Spearman-Karber method, but the Reed-Muench method is used in the present invention. The standard for judging antiviral activity is generally that the antiviral activity is judged to be effective if the logarithmic reduction in infectivity titer is 2.0 or more compared to the infectivity titer before the cerium oxide particles are applied or to a control not containing the cerium oxide particles of the present invention.

[0031] Examples of viruses that can be inactivated by cerium oxide particles include rhinovirus, poliovirus, foot-and-mouth disease virus, rotavirus, norovirus, enterovirus, hepatovirus, astrovirus, sapovirus, hepatitis E virus, influenza A, B, and C viruses, parainfluenza virus, mumps virus, measles virus, human metapneumovirus, respiratory syncytial virus, Nipah virus, Hendra virus, yellow fever virus, dengue virus, Japanese encephalitis virus, West Nile virus, hepatitis B and C viruses, eastern and western equine encephalitis virus, Onyong-nyong virus, rubella virus, and Lassa virus. , Junin virus, Machupo virus, Guanarito virus, Sabia virus, Crimean-Congo hemorrhagic fever virus, sandfly fever, hantavirus, Sin Nombre virus, rabies virus, Ebola virus, Marburg virus, bat lyssavirus, human T-cell leukemia virus, human immunodeficiency virus, human coronavirus, SARS coronavirus, human porvovirus, polyomavirus, human papillomavirus, adenovirus, herpesvirus, varicella-zoster virus, Epstein-Barr virus, cytomegalovirus, smallpox virus, monkeypox virus, cowpox virus, molluscipox virus, and parapox virus.

[0032] When the laminated film containing the cerium oxide particles of the present invention is used as an antiviral agent, it can be used in a variety of fields, including medical caps, medical shoe covers, air conditioner filters, air purifier filters, vacuum cleaner filters, ventilation fan filters, vehicle filters, air conditioning filters, plastic parts such as air conditioner fins and air conditioner outlet louvers, as well as blower fans, car air conditioner fins and car air conditioner outlet louvers, as well as blower fans, clothing, bedding, nets for screen doors, chicken coop nets, mosquito nets, and other nets, wallpaper, windows, blinds, interior materials for buildings such as those in hospitals, interior materials for trains and automobiles, vehicle seats, blinds, chairs, sofas, virus-handling equipment, and building materials such as doors, ceiling boards, floor boards, and windows.

[0033] (2) Inorganic particles The laminate film of the present invention preferably contains inorganic particles in the resin layer. In the present invention, inorganic particles refer to particles of compounds other than organic compounds that have covalent bonds and whose smallest unit is a molecule consisting of two or more types of atoms. Therefore, in the present invention, metal oxide particles are included in the inorganic particles, but metal particles are not. Examples of inorganic particle compositions that can be used in the present invention include silica, colloidal silica, alumina, ceria, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, and fine particles made of various metal oxides. In particular, inorganic colloidal particles are preferred, and colloidal silica is particularly preferred, in terms of dispersibility in the resin (C) described below, particle hardness, heat resistance, and alkali-resistant adhesion. For example, the "Snowtex®" series manufactured by Nissan Chemical Industries, Ltd. and the "Cataloid®" series manufactured by JGC Catalysts and Chemicals Co., Ltd. are preferably used. When the above-mentioned colloidal silica is used as the inorganic particles, the inorganic particles can be well dispersed in the resin layer, and the surface roughness Rz of the resin layer can be made 50.0 nm or more. The surface roughness SRz can be specifically determined by the measurement method described in the Examples.

[0034] The average primary particle size of the inorganic particles is preferably 20 nm or more and 1000 nm or less. By setting the average primary particle size of the inorganic particles to 20 nm or more, the surface of the resin layer is provided with easy slippage, ensuring the handling properties of the film product, thereby preventing the resin layer containing cerium oxide particles from being scratched or scraped. Furthermore, by setting the average primary particle size of the inorganic particles to 1000 nm or less, coating unevenness and cracks in the resin layer are prevented, ensuring the transparency and coatability of the film. Note that the average primary particle size in the present invention refers to the particle size determined by the measurement method described below.

[0035] (3) One or more resins (C) selected from polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins The laminated film of the present invention can be produced by applying the coating composition described below to a thermoplastic resin film and drying the solvent as necessary. The coating composition can contain one or more resins (C) selected from polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins to an extent that does not deteriorate the properties of the resin layer.

[0036] The content of one or more resins (C) selected from polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins used in the present invention in the coating composition is preferably 5% by weight or more and 80% by weight or less, and more preferably 10% by weight or more and 30% by weight or less. By making it 5% by weight or more, it becomes possible to firmly fix the cerium oxide particles to the resin layer when the resin layer is formed. Furthermore, by making it 80% by weight or less, it becomes possible to incorporate the necessary amount of cerium oxide particles into the resin layer when the resin layer is formed.

[0037] The polyester resin usable in the present invention preferably has an ester bond in the main chain or side chain and is obtained by polycondensation of a dicarboxylic acid and a diol. Dicarboxylic acids used as raw materials for the polyester resin include aromatic, aliphatic, and alicyclic dicarboxylic acids. Examples of aromatic dicarboxylic acids that can be used include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 2,5-dimethylterephthalic acid, 1,4-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-bisphenoxyethane-p-p'-dicarboxylic acid, and phenylindanedicarboxylic acid. Examples of aliphatic and alicyclic dicarboxylic acids that can be used include succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid, as well as their ester-forming derivatives.

[0038] Diol components used as raw materials for polyester resins include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2,2,4-trimethyl- 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 4,4'-thiodiphenol, bisphenol A, 4,4'-methylenediphenol, 4,4'-(2-norbornylidene)diphenol, 4,4'-dihydroxybiphenol, o-, m-, and p-dihydroxybenzene, 4,4'-isopropylidenephenol, 4,4'-isopropylidenebindiol, cyclopentane-1,2-diol, cyclohexane-1,2'-diol, cyclohexane-1,2-diol, cyclohexane-1,4-diol, and the like can be used.

[0039] Furthermore, as the polyester resin, it is also possible to use modified polyester copolymers, for example, block copolymers and graft copolymers modified with acrylic, urethane, epoxy, or the like.

[0040] The acrylic resin that can be used in the present invention is not particularly limited, but is preferably composed of alkyl methacrylate and / or alkyl acrylate.

[0041] The alkyl methacrylate and / or alkyl acrylate preferably includes methacrylic acid, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, maleic acid, itaconic acid, acrylamide, N-methylolacrylamide, diacetone acrylamide, etc. These may be used alone or in combination of two or more.

[0042] The urethane resin that can be used in the present invention is preferably a resin obtained by reacting a polyhydroxy compound with a polyisocyanate compound by a known urethane resin polymerization method such as emulsion polymerization or suspension polymerization.

[0043] Examples of polyhydroxy compounds include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate diol, and glycerin.

[0044] Examples of polyisocyanate compounds that can be used include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate and trimethylenepropane, and an adduct of hexamethylene diisocyanate and trimethylolethane.

[0045] Furthermore, as the urethane resin, it is also possible to use a block copolymer or a graft copolymer modified with acrylic, such as an acrylic urethane copolymer.

[0046] The polyamide resin used in the present invention is preferably a polymer having a heterocyclic amine skeleton in its main chain. The polyamide resin may have a substituent at any position in its main chain or side chain, or may have a substituent at any position in its heterocyclic amine skeleton, such as piperazine, pyridine, imidazole, or carbazole. When the polyamide resin has a piperazine skeleton in its main chain, it is preferable that the piperazine skeleton be present between the carbonyl groups in the main chain, and that the nitrogen in the heterocyclic ring of the piperazine skeleton and the carbonyl group form an amide bond. When the polyamide resin has another heterocyclic amine skeleton, such as a pyridine, imidazole, or carbazole skeleton, having two or more primary or secondary amino groups in its main chain, it is also preferable that the heterocyclic amine skeleton be present between the carbonyl groups.

[0047] When the polyamide used in the present invention has a piperazine skeleton, the piperazine skeleton may be directly bonded to the carbon linking the amide group, or the piperazine skeleton may be bonded via an alkyl group or an amino group.When the polyamide used in the present invention has a heterocyclic amine skeleton other than the piperazine skeleton, such as a pyridine, imidazole, or carbazole skeleton, the heterocyclic amine skeleton such as a pyridine, imidazole, or carbazole skeleton may be directly bonded to the carbon linking the amide group, or the heterocyclic amine skeleton may be bonded via an alkyl group or an amino group.

[0048] The polyamide used in the present invention is preferably a polymer having a piperazine skeleton in the main chain or side chain, more preferably a polymer having a piperazine skeleton in the main chain. The polyamide having a piperazine skeleton in the main chain used in the present invention is preferably obtained by a polycondensation reaction between an amine having a piperazine skeleton and a dicarboxylic acid.

[0049] Preferred examples of amines having a piperazine skeleton include piperazine, aminomethylpiperazine, aminoethylpiperazine, aminopropylpiperazine, aminobutylpiperazine, 1,4-bis(aminomethyl)piperazine, 1,4-bis(2-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, and 1,4-bis(4-aminobutyl)piperazine. Among these, aminoethylpiperazine and 1,4-bis(3-aminopropyl)piperazine are more preferred. In addition, these amines may have a substituent at any position other than the nitrogen atom capable of forming an amide bond.

[0050] Preferred examples of dicarboxylic acids include 1H-imidazole-2,4-dicarboxylic acid, 1H-imidazole-2,5-dicarboxylic acid, 1H-imidazole-4,5-dicarboxylic acid, pyridine-2,3-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, pyridine-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-3,4-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, adipic acid, sebacic acid, dodecadicarboxylic acid, terephthalic acid, isophthalic acid, etc. Furthermore, these dicarboxylic acids may have a substituent at any position other than the carboxyl group capable of forming an amide bond.

[0051] The polyamide resin used in the present invention is preferably a polyamide obtained by combining the above-mentioned amine and dicarboxylic acid, and a polyamide obtained by combining aminoethylpiperazine and adipic acid is particularly preferred.

[0052] The polyamide resin used in the present invention may have a polyalkylene glycol structure in the main chain, specifically, polyamides having a skeleton of aminoethylpiperazine, adipic acid, and bisaminopropylpolyethylene glycol.

[0053] The polyamide resin used in the present invention may be a mixture or copolymer of a polyamide having a piperazine, pyridine, imidazole or carbazole skeleton with another polymer. In this case, specific examples of the other polymer include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polypentamethylene adipamide (nylon 56), polypentamethylene sebacamide (nylon 510), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), and polyhexamethylene adipamide. Examples include polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon 66 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), polyhexamethylene terephthalamide / polyhexamethylene isophthalamide copolymer (nylon 6T / 6I), and polyxylylene adipamide (nylon XD6).

[0054] (4) One or more resins (D) selected from melamine compounds, oxazoline compounds, and carbodiimide compounds The laminated film of the present invention can be produced by applying the coating composition described below to a thermoplastic resin film and drying the solvent as necessary. The coating composition can contain one or more resins (D) selected from melamine compounds, oxazoline compounds, carbodiimide compounds, and boric acid compounds to an extent that does not deteriorate the properties of the resin layer.

[0055] The content of one or more resins (D) selected from melamine compounds, oxazoline compounds, and carbodiimide compounds in the coating composition is preferably 3% by weight or more and 40% by weight or less. More preferably, it is 5% by weight or more and 20% by weight or less. By making it 3% by weight or more, when a resin layer is formed, it is possible to impart to the resin layer the solvent resistance, water resistance, abrasion resistance, and other properties required for various applications as a laminate film. Furthermore, by making it 40% by weight or less, when a resin layer is formed, it is possible not only to incorporate the necessary amount of cerium oxide particles into the resin layer, but also to impart good stretchability when the coating composition is applied and then stretched in the width direction in the in-line coating method described below.

[0056] The melamine compound that can be used in the present invention must have at least one triazine ring and at least one methylol group per molecule.Specific examples of the melamine compound include etherified compounds obtained by subjecting a methylolmelamine derivative obtained by condensing melamine with formaldehyde to a dehydration condensation reaction with a lower alcohol such as methyl alcohol, ethyl alcohol, or isopropyl alcohol.

[0057] Examples of the methylol melamine derivatives include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine.

[0058] The oxazoline compound is not particularly limited as long as it has at least one oxazoline group or oxazine group per molecule, but addition-polymerizable oxazoline group-containing monomers are preferred, and examples thereof include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0059] The carbodiimide compound is not particularly limited as long as it has at least one carbodiimide structure represented by the following formula (3) per molecule, but polycarbodiimide compounds having two or more per molecule are particularly preferred in terms of wet heat resistance, etc. In particular, polymeric isocyanate compounds having multiple carbodiimide groups at the end or side chain of a polymer such as a polyester resin or acrylic resin are preferably used because they improve the hardness of the resin layer and suppress oligomer precipitation. -N=C=N- Formula (3) Known techniques can be applied to the production of carbodiimide compounds, and carbodiimide compounds are generally obtained by polycondensation of diisocyanate compounds in the presence of a catalyst. Examples of diisocyanate compounds that can be used as starting materials for polycarbodiimide compounds include aromatic, aliphatic, and alicyclic diisocyanates, such as tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, and dicyclohexyl diisocyanate. Furthermore, to improve the water solubility or water dispersibility of the polycarbodiimide compound, surfactants or hydrophilic monomers such as polyalkylene oxides, quaternary ammonium salts of dialkylamino alcohols, and hydroxyalkyl sulfonates may be added within the scope of the present invention.

[0060] (5) Thermoplastic resin film The thermoplastic resin film used in the laminate film of the present invention is a film formed from a thermoplastic resin. It is a general term for films that melt or soften when heated, and is not particularly limited. Examples of thermoplastic resins include polyester resin, polypropylene resin, polyolefin resin such as polyethylene film, polylactic acid resin, polycarbonate resin, acrylic resin such as polymethacrylate resin and polystyrene resin, polyamide resin such as nylon resin, polyvinyl chloride resin, polyurethane resin, fluororesin, polyphenylene resin, etc. The thermoplastic resin used in the thermoplastic resin film may be a monopolymer or a copolymer. Furthermore, multiple resins may be used.

[0061] Representative examples of these thermoplastic resin films include polyester films, polyolefin films such as polypropylene films and polyethylene films, polylactic acid films, polycarbonate films, acrylic films such as polymethacrylate films and polystyrene films, polyamide films such as nylon, polyvinyl chloride films, polyurethane films, fluorine-based films, and polyphenylene sulfide films.

[0062] Among these, polyester film, polypropylene film, polyamide film, etc. are preferred in terms of mechanical properties, dimensional stability, transparency, etc., and polyester film is particularly preferred in terms of mechanical strength, versatility, etc.

[0063] Therefore, the polyester resin constituting the polyester film that is particularly preferably used as the thermoplastic resin film in the present invention will be described in detail below.

[0064] First, polyester is a general term for polymers whose main bond is an ester bond. Polyesters containing at least one component selected from the group consisting of ethylene terephthalate, propylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, propylene-2,6-naphthalate, and ethylene-α,β-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylate are preferred. These components may be used alone or in combination. However, considering overall quality and economic efficiency, ethylene terephthalate is particularly preferred. In other words, in the present invention, polyethylene terephthalate is preferred as the thermoplastic resin used in the thermoplastic resin film. Furthermore, when the thermoplastic resin film is subjected to heat or shrinkage stress, polyethylene-2,6-naphthalate, which has excellent heat resistance and rigidity, is particularly preferred. These polyesters may also contain other dicarboxylic acid components or diol components, preferably in an amount of up to 20 mol %.

[0065] The intrinsic viscosity (measured in o-chlorophenol at 25°C) of the polyester resin forming the thermoplastic resin film of the laminated film of the present invention is preferably 0.4 to 1.2 dL / g, more preferably 0.5 to 0.8 dL / g, which is suitable for implementing the present invention.

[0066] The polyester film using the above polyester is preferably biaxially oriented. A biaxially oriented polyester film is generally a film obtained by stretching an unstretched polyester sheet or film by about 2.5 to 5 times in both the longitudinal direction and the width direction perpendicular to the longitudinal direction, and then heat-treating the film to complete the crystal orientation, and the film exhibits a biaxially oriented pattern in wide-angle X-ray diffraction. If the thermoplastic resin film is not biaxially oriented, the resulting conductive film will have insufficient thermal stability, particularly dimensional stability and mechanical strength, and poor flatness, which is undesirable.

[0067] In addition, various additives such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, etc. may be added to the thermoplastic resin film to the extent that they do not deteriorate its properties.

[0068] The thickness of the thermoplastic resin film is not particularly limited and is appropriately selected depending on the application and type, but is usually preferably 10 to 500 μm, more preferably 30 to 250 μm, from the viewpoints of mechanical strength, handleability, etc. The thermoplastic resin film may be a composite film obtained by coextrusion, or may be a film obtained by laminating obtained films by various methods.

[0069] (6) Resin layer and laminated film The present invention is a laminated film having a resin layer containing 20% by weight or more and 90% by weight or less of cerium oxide particles on at least one side of a thermoplastic film, and the surface zeta potential of the resin layer must be -10 mV or more and +70 mV or less. By making the surface zeta potential of the resin layer -10 mV or more, various negatively charged viruses can be adsorbed to the surface of the resin layer, allowing for efficient inactivation by oxidation reaction.

[0070] The surface roughness Rz of the resin layer is preferably 50.0 nm or more. By making the surface roughness Rz 50.0 nm or more, the slipperiness and handling properties when laminated films come into contact with each other are improved, making the laminated film easier to handle and suitable for use in the various applications mentioned above. Furthermore, improving the slipperiness when laminated films come into contact with each other makes it possible to suppress scraping and scratches on the resin layer, and also makes it possible to maintain the antiviral properties and appearance quality of the laminated film.

[0071] The upper limit of the surface zeta potential of the resin layer is +70 mV, which is the upper limit for a resin layer formed from the cerium oxide particles and resin used. The surface zeta potential of the resin layer can be adjusted by the composition ratio of the cerium oxide particles in the resin layer and the composition ratio of the resin added. Specifically, the surface zeta potential of the resin layer can be determined by the measurement method described in the Examples.

[0072] Furthermore, when inorganic particles are contained in the resin layer, it is preferable that the particle diameter L(A) of the cerium oxide particles, the particle diameter L(B) of the inorganic particles, and the thickness L(X) of the resin layer satisfy the following formulas (1) and (2). L(B)>L(A) ··· Formula (1) L(B)≧L(X) ··· Formula (2) By satisfying formulas (1) and (2), the cerium oxide particles can be fixed within the resin layer and prevented from falling off. Furthermore, the inorganic particles are not embedded within the resin layer, but rather some of them protrude from the resin layer, imparting lubricity to the resin layer. This improves the handling and transportability of the laminated film of the present invention when used as a film product, making it suitable for use. Formulas (1) and (2) can be determined specifically by the measurement methods described in the Examples.

[0073] (7) Paint composition The coating composition used in the production of the laminated film of the present invention contains cerium oxide particles and a solvent, and can be prepared by mixing and stirring the inorganic particles, resin (C), and resin (D) in any order and at a desired weight ratio, as needed. It is preferable to use an aqueous solvent containing water as the solvent, from the viewpoints of producing the laminated film by the in-line coating method described below and reducing the environmental load.

[0074] In addition, various additives such as organic particles, surfactants, antioxidants, and thermal initiators can be mixed and stirred in any order into the coating composition so as not to deteriorate the properties of the resin layer. Methods for mixing and stirring include shaking the container by hand, using a magnetic stirrer or stirring blade, ultrasonic irradiation, vibration dispersion, etc.

[0075] (8) Manufacturing method of laminated film In the present invention, a resin layer can be formed on a thermoplastic resin film by applying a coating composition containing cerium oxide particles, and optionally inorganic particles, resin (C), resin (D), additives, and a solvent onto the thermoplastic resin film, and then drying the solvent as necessary.The method includes the steps of applying a coating composition containing 20% by weight or more and 90% by weight or less of cerium oxide particles to at least one surface of the thermoplastic film, and then heating and drying the coating composition to form a resin layer, thereby producing a laminated film in which the surface zeta potential of the resin layer is -10 mV or more and +70 mV or less.

[0076] In the present invention, it is preferable to use an aqueous solvent as the solvent, because the use of an aqueous solvent not only makes it possible to prevent the solvent from rapidly evaporating during the drying step and form a uniform resin layer, but also has an advantage in terms of environmental impact.

[0077] Here, aqueous solvent refers to water or a mixture of water and a water-soluble organic solvent, such as alcohols (e.g., methanol, ethanol, isopropyl alcohol, butanol), ketones (e.g., acetone, methyl ethyl ketone), or glycols (e.g., ethylene glycol, diethylene glycol, propylene glycol), in any ratio. The use of aqueous solvents not only makes it possible to prevent the solvent from rapidly evaporating during the drying process and form a uniform resin layer, but also has an advantage in terms of environmental impact.

[0078] In the step of applying the coating composition to the thermoplastic resin film, any known application method can be used, such as wire bar coating, reverse coating, gravure coating, die coating, blade coating, dip coating, air knife coating, curtain coating, and roller coating.

[0079] The coating composition can be applied to the thermoplastic resin film by either an in-line coating method or an off-coating method, but the in-line coating method is preferred.

[0080] The in-line coating method is a method in which coating is performed within the manufacturing process of thermoplastic resin films. Specifically, it refers to a method in which coating is performed at any stage from melt-extrusion of a thermoplastic resin to biaxially stretching, heat treatment, and winding up. Typically, coating is performed on either an unstretched (unoriented) thermoplastic resin film (A film) that is substantially amorphous and obtained by melt-extrusion and quenching, a uniaxially stretched (uniaxially oriented) thermoplastic resin film (B film) that has been subsequently stretched in the longitudinal direction, or a biaxially stretched (biaxially oriented) thermoplastic resin film (C film) that has been further stretched in the width direction and has not yet been heat-treated.

[0081] In the present invention, a step of stretching the resin film in at least one direction after applying a coating composition is preferably performed using an unstretched thermoplastic resin film before completion of crystalline orientation, a uniaxially stretched (uniaxially oriented) thermoplastic resin film, or a biaxially stretched (biaxially oriented) thermoplastic resin film before heat treatment. A step of subsequently performing heat treatment at a temperature higher than the boiling point of the solvent to complete the crystalline orientation of the thermoplastic resin film and provide a resin layer is preferably performed. This method has the advantage of reducing production costs because it allows the formation of a thermoplastic resin film and the application and drying of the coating composition (i.e., formation of a composition layer) to be performed simultaneously. Furthermore, the thickness of the resin layer can be easily reduced by performing stretching after application.

[0082] Among these, the method of applying the coating composition to a film (B film) that has been uniaxially stretched in the longitudinal direction, followed by stretching in the width direction and heat treatment is superior. This is because, compared to the method of applying the coating composition to an unstretched film and then biaxially stretching it, this method requires one less stretching step, making it less likely for defects or cracks to occur in the resin layer due to stretching, and allowing for the formation of a resin layer with excellent transparency and smoothness.

[0083] On the other hand, the offline coating method is a method in which the above-mentioned A film is stretched uniaxially or biaxially and heat-treated to complete the crystal orientation of the thermoplastic resin film, or the A film is coated with a coating composition in a process separate from the film-forming process.

[0084] In the present invention, the resin layer is preferably provided by an in-line coating method due to the various advantages described above.

[0085] Therefore, the best method for forming the resin layer in the present invention is to apply an aqueous coating composition using an aqueous solvent onto a thermoplastic resin film by in-line coating and then dry it. More preferably, the coating composition is applied in-line to the uniaxially stretched B film.

[0086] Next, the manufacturing method of the laminated film of the present invention will be described using a polyethylene terephthalate (PET) film as the thermoplastic resin film, but the method is not limited thereto. First, PET pellets are thoroughly vacuum-dried and then fed into an extruder. They are melt-extruded into a sheet at approximately 280°C and then cooled and solidified to produce an unstretched (unoriented) PET film (Film A). This film is stretched 2.5 to 5.0 times in the longitudinal direction using a roll heated to 80 to 120°C to obtain a uniaxially oriented PET film (Film B). A coating composition of the present invention, prepared to a predetermined concentration, is applied to one side of Film B. Before application, the surface of the PET film to be coated may be subjected to a surface treatment such as corona discharge treatment. Surface treatment such as corona discharge treatment improves the wettability of the coating composition to the PET film, prevents repellency of the coating composition, and achieves a uniform coating thickness.

[0087] After coating, the edges of the PET film are held with clips and guided to a heat treatment zone (preheating zone) at 80-130°C to dry out the solvent in the coating composition. After drying, the film is stretched 1.1-5.0 times in the width direction. The film is then guided to a heat treatment zone (thermal setting zone) at 160-240°C for 1-30 seconds, where it is heat-treated to complete the crystal orientation of the PET film, yielding a laminated film. [Example]

[0088] Methods for measuring characteristics and evaluating effects The methods for measuring the properties and evaluating the effects in the present invention are as follows.

[0089] <Measurement of the surface zeta potential of the resin layer> A 3 cm × 1 cm sample was taken from the laminate film obtained in the examples to fit the size of the cell for measuring solid surface zeta potential, and the sample was placed in a zeta potential meter (manufactured by Otsuka Electronics Co., Ltd., ELSZ-1000, using a flat surface cell) so that the measurement surface was the resin layer surface of the laminate film. Measurements were carried out three times using water (temperature: 25°C, refractive index: 1.3328, viscosity: 0.8878 (cP), dielectric constant: 78.3, pH: 7 ± 0.5) as the solvent, and the average of the three values calculated by the Smoluchowski equation was used as the surface zeta potential value.

[0090] <Measurement of surface roughness Rz (maximum height) of resin layer> The resin layer surface of the laminated film obtained in the examples was measured using a scanning probe microscope (Shimadzu, SPM9600). A non-contact mode high-resonance frequency type cantilever probe (NANOSENSORS, model number PPP-NCHR) was used, and measurements were taken over a 1 μm x 1 μm field of view, at a scanning speed of 0.5 Hz, with a pixel count of 512 x 512. The data obtained was then processed based on the JIS standard JIS B0601 (2001) to calculate the surface roughness Rz (maximum height).

[0091] <Oxidation activity evaluation (simple antiviral evaluation)> A 2cm x 2cm square sample was cut from the laminated film obtained in the example and placed in a plastic Petri dish. 130μL of a 10mg / mL aqueous solution of TMBZ·HCl (3,3',5,5'-tetramethylbenzidine dihydrochloride dihydrate) (pH = 2-3 using pH test paper) was added dropwise to the sample and allowed to stand for 10 minutes. Then, 100μL of the TMBZ·HCl solution added to the sample was collected and transferred to a 96-well plate. The plate was then placed in a plate reader and the absorbance at 655nm associated with the blue coloration of TMBZ was measured. A SpectraMaxiD3 plate reader from Molecular Devices was used to measure the absorbance. When the absorbance of TMBZ·HCl before evaluation was taken as the reference value of 0, an absorbance difference of less than 0.04 for the TMBZ·HCl added to the sample indicated no oxidizing activity and poor antiviral properties. When the absorbance of TMBZ·HCl before evaluation was taken as the reference value of 0, an absorbance difference of 0.04 or more for the TMBZ·HCl added to the sample indicated oxidizing activity and good antiviral properties.

[0092] <Measurement of particle size of cerium oxide particles, particle size of inorganic particles, and thickness of resin layer> The laminated film was stained with RuO4 staining solution. The laminated film was then frozen and cut in the film thickness direction to create 10 ultrathin section samples for resin layer cross-section observation. The cross-section of each sample was then observed at 10,000 to 1,000,000 magnifications using a TEM (transmission electron microscope: Hitachi, Ltd., Model H7100FA) and cross-sectional photographs were taken. The longest distances in the cross-sectional images of the cerium oxide particles and inorganic particles were measured from the cross-sectional photographs of the 10 samples, and the average values were calculated as the particle diameters of the cerium oxide particles and inorganic particles. The thickness of the resin layer was also calculated by averaging the measured values from the cross-sectional photographs of the 10 samples.

[0093] The laminated film of the present invention will be described in detail below based on specific examples, but the present invention is not limited to these examples. It should be noted that Examples 1 to 6, 8 and 9 should be read as Reference Examples 1 to 6, 8 and 9.

[0094] Example 1 Thermoplastic films: PET pellets (intrinsic viscosity 0.64 dl / g) containing two types of particles (4% by mass of silica particles with a primary particle size of 0.3 μm and 2% by mass of calcium carbonate particles with a primary particle size of 0.8 μm) were thoroughly vacuum dried, then fed into an extruder and melted at 280°C. The pellets were extruded into a sheet from a T-shaped die and wrapped around a mirror-finished casting drum with a surface temperature of 25°C using an electrostatic casting method, where they were cooled and solidified. This unstretched film was heated to 90°C and stretched 3.1 times in the longitudinal direction to obtain a uniaxially stretched polyester film (corresponding to Film B).

[0095] ·Paint composition: Cerium oxide particles with an average particle size of 25 nm were mixed with water as a solvent so that the solid content was 25 wt % and polyester resin (C-1) was 75 wt %. A fluorine-based surfactant (Plascoat (registered trademark) RY-2, manufactured by GOO Chemical Co., Ltd.) was added to the mixture at 0.03 wt % relative to the total weight of the cerium oxide particles, polyester resin, and solvent (100 wt %) to prepare a coating composition.

[0096] Polyester resin (C-1) was prepared as follows. First, 50 parts by weight of terephthalic acid, 50 parts by weight of isophthalic acid, 50 parts by weight of ethylene glycol, and 30 parts by weight of neopentyl glycol were charged into a nitrogen-purged reactor together with 0.3 parts by weight of antimony trioxide and 0.3 parts by weight of zinc acetate as polymerization catalysts. The polymerization reaction was carried out at 190 to 220 °C under normal pressure for 12 hours while removing water, to obtain polyester glycol. Next, 5 parts by weight of 5-sodium sulfoisophthalic acid and xylene as a solvent were charged into the reactor, and the resulting polyester glycol was polymerized for 3 hours at 260 °C under a reduced pressure of 0.2 mmHg while distilling off the xylene, to obtain polyester resin (C-1) having hydrophilic functional groups.

[0097] Laminated film After subjecting the uniaxially stretched polyester film to a corona discharge treatment in air, the coating composition was applied to a thickness of approximately 6 μm using a wire bar coater. The coated polyester film was then held at both widthwise ends with clips and guided into a preheating zone. The ambient temperature in the preheating zone was set to 90-100°C, allowing the solvent in the coating composition to dry. The film was then continuously stretched 3.6 times in the widthwise direction in a 100°C stretching zone, followed by heat treatment for 20 seconds in a 240°C heat treatment zone to form a resin layer. A 5% relaxation treatment in the widthwise direction at the same temperature was then performed, resulting in a laminated film in which the polyester film had completed its crystalline orientation. The resulting laminated film had a resin layer thickness of 40 nm.

[0098] The properties of the obtained laminated film are shown in Table 2. The absorbance was 0.04 or more, which indicated that the film had oxidizing activity.

[0099] Examples 2 to 4 A laminated film was obtained in the same manner as in Example 1, except that the ratio of the components contained in the coating composition was changed as shown in Table 1. The properties of the obtained laminated film are shown in Table 2. The absorbance was 0.04 or more, which indicated the presence of oxidation activity.

[0100] Example 5 A laminated film was obtained in the same manner as in Example 1, except that the solids weight ratio of cerium oxide particles with an average particle size of 25 nm was set to 70 wt % and a melamine compound (D-1 / "Nicalac" "MX-035", manufactured by Sanwa Chemical Co., Ltd.) was added to the coating composition. The properties of the obtained laminated film are shown in Table 2. The absorbance was 0.04 or more, indicating the presence of oxidation activity.

[0101] Example 6 A laminated film was obtained in the same manner as in Example 1, except that the solids weight ratio of cerium oxide particles with an average particle size of 25 nm was set to 70 wt % and a carbodiimide compound (D-2 / "Carbodilite" V-04, manufactured by Nisshinbo Chemical Inc.) was added to the coating composition. The properties of the obtained laminated film are shown in Table 2. The absorbance was 0.04 or more, indicating the presence of oxidation activity.

[0102] Example 7 A laminated film was obtained in the same manner as in Example 5, except that the polyester resin (C-1) was changed to a water-based urethane resin (C-2 / "Superflex 620" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and inorganic particles (B-1 / colloidal silica "Cataloid SI-80P" (average primary particle size 80 nm, manufactured by JGC Catalysts and Chemicals Co., Ltd.)) were added. The properties of the obtained laminated film are shown in Table 2. The absorbance was 0.04 or more, which indicated the presence of oxidation activity.

[0103] Example 8 A laminated film was obtained in the same manner as in Example 7, except that the inorganic particles (B-1) were replaced with inorganic particles (B-2 / colloidal silica "Snowtex MP-1040" (average primary particle size 100 nm, manufactured by Nissan Chemical Industries, Ltd.)). The thickness of the resin layer of the obtained laminated film was 150 nm. The properties of the obtained laminated film are shown in Table 2. The absorbance was 0.04 or more, which indicated the presence of oxidation activity.

[0104] Example 9 The coating composition of Example 3 was applied using a wire bar to a PET film "Lumirror" (registered trademark) T60 (50 μm thick) manufactured by Toray Industries, Inc., and the solvent in the coating composition was then dried in a hot air oven at 120°C for 2 minutes. In the resulting laminated polyester film, the PET film had a thickness of 50 μm and the resin layer had a thickness of 140 nm. The properties of the resulting laminated film are shown in Table 2. The absorbance was 0.04 or higher, indicating the presence of oxidative activity.

[0105] (Comparative Example 1) A laminated film was obtained in the same manner as in Example 1, except that the solid weight ratio of cerium oxide particles with an average particle size of 25 nm was changed to 15 wt %. The properties of the obtained laminated film are shown in Table 2. In Comparative Example 1, the composition ratio of cerium oxide particles was small, and both the surface zeta potential and absorbance were poor.

[0106] (Comparative Example 2) A laminated film was obtained in the same manner as in Example 1, except that the solids weight ratio of cerium oxide particles with an average particle size of 25 nm was changed to 95 wt %. The properties of the obtained laminated film are shown in Table 2. In Comparative Example 2, the composition ratio of cerium oxide particles was extremely high, causing cracks in the resin layer and preventing the resin layer from being formed uniformly. As a result, it was impossible to measure both the surface zeta potential and absorbance.

[0107] (Comparative Example 3) A laminated film was obtained in the same manner as in Example 1, except that the solid weight ratio of cerium oxide particles having an average particle size of 25 nm was changed to 10 wt %. The properties of the obtained laminated film are shown in Table 2. In Comparative Example 3, the surface zeta potential was low and the absorbance was poor.

[0108] [Table 1]

[0109] [Table 2]

Claims

1. A laminated film comprising a thermoplastic film and a resin layer on at least one surface thereof, the resin layer containing 20% by weight or more and 90% by weight or less of cerium oxide particles, the resin layer having a surface zeta potential of -10 mV or more and +70 mV or less, the resin layer containing inorganic particles made of any of silica, colloidal silica, alumina, ceria, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, and various metal oxides in addition to the cerium oxide particles, the particle diameter L(A) of the cerium oxide particles being 1 nm or more and 100 nm or less as measured by the following method, and the average primary particle diameter L(B) of the inorganic particles and the thickness L(X) of the resin layer satisfying the following formulas (1) and (2). L(B)>L(A)... Formula (1) L(B)≧L(X)... Formula (2) <Method for measuring particle size of cerium oxide particles> The laminated film was stained with RuO4 staining solution. Next, the laminated film was frozen and cut in the film thickness direction to prepare 10 ultrathin section samples for observing the cross section of the resin layer. Next, the cross section of each sample was observed at 10,000 to 1,000,000 magnifications using a TEM (transmission electron microscope: H7100FA model, manufactured by Hitachi, Ltd.), and cross-sectional photographs were taken. From the cross-sectional photographs of the 10 samples, the longest distance in the cross-sectional image of the cerium oxide particles was measured, and the average value was calculated as the particle diameter of the cerium oxide particles.

2. 2. The laminated film according to claim 1, wherein the resin layer has a surface roughness Rz of 50 nm or more.

3. 3. The laminated film according to claim 1, wherein the resin layer contains one or more resins selected from the group consisting of polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins.

4. 4. The laminated film according to claim 3, wherein the resin layer contains one or more compounds selected from the group consisting of melamine compounds, oxazoline compounds, and carbodiimide compounds.

5. A method for producing a laminated film, comprising the steps of applying a coating composition containing 20% by weight or more and 90% by weight or less of cerium oxide particles to at least one surface of a thermoplastic resin film, and heating and drying the coating composition to form a resin layer, wherein the resin layer has a surface zeta potential of -10 mV or more and +70 mV or less, and the resin layer contains, in addition to the cerium oxide particles, inorganic particles made of any of silica, colloidal silica, alumina, ceria, kaolin, talc, mica, calcium carbonate, barium sulfate, carbon black, zeolite, titanium oxide, and various metal oxides, and the particle diameter L(A) of the cerium oxide particles measured by the following method is 1 nm or more and 100 nm or less, and the average primary particle diameter L(B) of the inorganic particles and the thickness L(X) of the resin layer satisfy the following formulas (1) and (2). L(B)>L(A)... Formula (1) L(B)≧L(X)... Formula (2) <Method for measuring particle size of cerium oxide particles> The laminated film was stained with RuO4 staining solution. Next, the laminated film was frozen and cut in the film thickness direction to prepare 10 ultrathin section samples for observing the cross section of the resin layer. Next, the cross section of each sample was observed at 10,000 to 1,000,000 magnifications using a TEM (transmission electron microscope: H7100FA model, manufactured by Hitachi, Ltd.), and cross-sectional photographs were taken. From the cross-sectional photographs of the 10 samples, the longest distance in the cross-sectional image of the cerium oxide particles was measured, and the average value was calculated as the particle diameter of the cerium oxide particles.

6. 6. The method for producing a laminated film according to claim 5, wherein the thermoplastic resin film is an unstretched thermoplastic resin film, a uniaxially stretched (uniaxially oriented) thermoplastic resin film, or a biaxially stretched (biaxially oriented) thermoplastic resin film before heat treatment, and the method further comprises a step of stretching the film in at least one direction after the step of applying the coating composition.

7. 7. The method for producing a laminated film according to claim 5, wherein the coating composition contains one or more resins selected from polyester resins, acrylic resins, nylon resins, urethane resins, and polyamide resins.

8. The method for producing a laminated film according to claim 7, wherein the coating composition contains one or more compounds selected from the group consisting of melamine compounds, oxazoline compounds, and carbodiimide compounds.

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