JP2022127243A - Metal base material to be printed and method for manufacturing the same, and coated metal material - Google Patents

Abstract

To provide a metal base material to be printed which has a layer to be printed that can strongly adhere a cured product of an active ray energy ray-curable composition, and is excellent in workability and scratch resistance.SOLUTION: A metal base material to be printed has a metal plate, and a layer to be printed which is arranged on the metal plate, and contains a cured product of a coating material containing a polyester resin having a number average molecular weight of 12,000-30,000 and a melamine resin. When a composition of a region to a depth of 10 mm from the surface of the layer to be printed is analyzed in a depth direction by an X-ray electron spectroscopy analysis method using an AlKα rays as an X-ray source, a maximum value of N atoms to the total amount of the N atoms, C atoms and O atoms is 5-30 atom%.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a metal substrate for printing, a method for producing the same, and a coated metal material.

BACKGROUND ART In recent years, there has been a demand for coated metal materials with a high degree of designability, such as forming coating films of various colors on a metal plate or providing a fine pattern on the surface of the metal plate. Therefore, applying an active energy ray-curable composition onto a metal plate has been studied.

The active energy ray-curable composition is cured by irradiation with an active energy ray. Therefore, it is possible to form an image even on a substrate that does not absorb solvents. However, active energy ray-curable compositions have relatively large shrinkage during curing. Therefore, when the active energy ray-curable composition is used for image formation, there is a problem that the ink layer, which is a cured product, is easily peeled off from various substrates.

In order to solve such problems, several methods have been proposed to improve the adhesion of the ink layer to the base material. For example, Patent Literature 1 describes a method in which an active energy ray-curable composition is applied onto a substrate, irradiated with an active energy ray, and then heated with a heater. According to this method, it is thought that the adhesiveness between the ink layer and the substrate is enhanced by increasing the curability of the ink layer. Further, Patent Document 2 describes a method of applying an active energy ray-curable composition onto a preheated base material. According to this method, the active energy ray-curable composition can be sufficiently wetted and spread on the substrate, and it is believed that the adhesion between the ink layer and the substrate increases.

Furthermore, prior to coating the active energy ray-curable composition on the resin film, the resin film is subjected to corona discharge treatment to increase the adhesion between the resin film and the ink layer, which is described in Patent Documents 3 and 4. It is

Japanese Patent Application Laid-Open No. 2001-009367 JP 2008-087242 A WO2018/163941 JP-A-9-300477

However, when applying an active energy ray-curable composition to a metal plate, it is difficult to sufficiently improve the adhesion between the metal plate and the ink layer, regardless of which method described in Patent Documents 1 to 4 is performed. rice field. In particular, when the thickness of the application of the active energy ray-curable composition was increased, the amount of curing shrinkage during curing increased, and the ink layer was more likely to peel off.

Accordingly, the present invention provides a metal substrate for printing, which has a layer to be printed on which a cured product of an actinic ray energy ray-curable composition can be strongly adhered and which is excellent in workability and scratch resistance, and its production. The object is to provide a method, as well as a painted metal material.

The present invention provides the following metal substrate for printing.
a metal plate, and a printed layer containing a cured product of a paint containing a polyester resin and a melamine resin having a number average molecular weight of 12000 to 30000, disposed on the metal plate, and from the surface of the printed layer When analyzing the composition in the depth direction by X-ray electron spectroscopy using AlKα rays as an X-ray source for a region up to a depth of 10 nm, the ratio of N atoms to the total amount of N atoms, C atoms, and O atoms A metal substrate to be printed, having a maximum value of 5 to 30 atom %.

The present invention provides the following coated metal material.
A coated metal material comprising: the metal base material to be printed; and an ink layer, which is a cured product of an active energy ray-curable composition, disposed on the layer to be printed of the metal base material to be printed. .

The present invention provides the following method for producing a metal substrate for printing.
In the above method for producing a metal substrate for printing, the step of applying a paint containing a polyester resin and a melamine resin having a number average molecular weight of 12,000 to 30,000 on a metal plate and curing the coating to form a printing layer is performed. A method for producing a printed metal substrate, comprising:

According to the metal substrate for printing of the present invention, when an ink layer is formed using an active energy ray-curable composition, the ink layer is less likely to peel off. In addition, the printable layer of the printable metal substrate has good workability and scratch resistance. Therefore, it is possible to form various coated metal materials with high designability.

FIG. 1 shows the total number of N atoms, C atoms, and O atoms when the composition of the printed layer of the metal substrate for printing of Example 8 was analyzed in the depth direction by X-ray electron spectroscopy. 2 is a graph showing the relationship between the ratio of each element to , and the depth from the surface. FIG. 2 shows the total number of N atoms, C atoms, and O atoms when the composition of the printed layer of the metal substrate for printing of Example 5 was analyzed in the depth direction by X-ray electron spectroscopy. 2 is a graph showing the relationship between the ratio of each element to , and the depth from the surface. FIG. 3 shows the sum of N atoms, C atoms, and O atoms when the composition of the printed layer of the printed metal substrate of Example 2 is analyzed in the depth direction by X-ray electron spectroscopy. 2 is a graph showing the relationship between the ratio of each element to , and the depth from the surface. FIG. 4 shows the total number of N atoms, C atoms, and O atoms when the composition of the printed layer of the printed metal substrate of Comparative Example 8 was analyzed in the depth direction by X-ray electron spectroscopy. 2 is a graph showing the relationship between the ratio of each element to , and the depth from the surface. FIG. 5 shows the total number of N atoms, C atoms, and O atoms when the composition of the printed layer of the printed metal substrate of Comparative Example 2 was analyzed in the depth direction by X-ray electron spectroscopy. 2 is a graph showing the relationship between the ratio of each element to , and the depth from the surface.

1. Metal base material for printing The metal base material for printing of the present invention only needs to have at least a metal plate and a layer to be printed disposed on the metal plate, and other layers may be added as necessary. It may contain further. The metal base material for printing is used as a base material for forming an ink layer by applying an active energy ray-curable composition or the like, for example, which will be described later. The substrate to be printed may be a precoated metal plate or a postcoated metal plate.

As described above, it has been conventionally studied to apply an active energy ray-curable composition onto a metal plate, but it is difficult to improve the adhesion of the ink layer, which is a cured product of the active energy ray-curable composition. In particular, when the thickness of the ink layer is thick, peeling tends to occur at these interfaces. The reason for this is that the active energy ray-curable composition shrinks greatly when cured, and residual stress is generated in the ink layer after curing, and stress is generated at the interface between the metal plate and the ink layer during curing. , the ink layer peels off.

In contrast, the printable metal base material of the present invention has a printable layer on a metal plate. The printed layer contains a cured product of a coating containing a polyester resin having a number average molecular weight of 12,000 to 30,000 and a melamine resin. In addition, when the composition is analyzed in the depth direction from the surface to a depth of 10 nm by X-ray electron spectroscopy (hereinafter also referred to as “XPS method”), N The maximum value of atoms is 5 to 30 atom %. According to the intensive study of the present inventors, the maximum value of N atoms with respect to the total amount of N atoms, C atoms, and O atoms in a region from the surface of the printed layer to a depth of 10 nm is the peeling of the ink layer. It has become clear that the adhesion to the ink layer is enhanced by setting the maximum value to 5 to 30 atom %. Further, by setting the maximum value in the above range, the workability, scratch resistance, etc. of the metal base material to be printed are improved. The reason for this is considered as follows.

The N atoms observed when the layer to be printed is analyzed by XPS are mainly N atoms derived from the melamine resin, and the above maximum value is an index representing the degree of concentration of the melamine resin on the surface. It can be said that a layer to be printed having a large maximum value of N atoms has a high crosslinking density of the polyester resin in the vicinity of the surface of the layer to be printed, and has a high hardness on the surface of the layer to be printed. When such a printed layer is provided, the scratch resistance of the printed metal substrate is improved, but the printed layer having a high hardness tends to have low adhesion to the ink layer described above, and the workability is also poor. easy to decline.

On the other hand, the printed layer having a small maximum value of N atoms has a low crosslinking density of the polyester resin in the vicinity of the surface of the printed layer, and the surface is flexible. When such a printable layer is provided, the adhesion between the ink layer and the printable layer tends to be good, and workability is improved, but the scratch resistance of the metal substrate for printing is lowered. , difficult to use for various purposes.

On the other hand, when the maximum value of the N atoms is 5 atom% or more and 30 atom% or less, the crosslink density of the polyester resin becomes moderate, and even if the active energy ray-curable composition shrinks during curing, it is possible to print. Layers can relieve stress. That is, residual stress is less likely to occur in the ink layer. In addition, the layer to be printed can be deformed following the curing shrinkage of the active energy ray-curable composition. Therefore, stress is less likely to act between the layer to be printed and the ink layer, and the adhesion between them can be enhanced. In addition, since the cross-linking density of the polyester resin is within an appropriate range, the workability and scratch resistance of the printed layer are also improved.

It is difficult to satisfy such a concentration of N atoms in a coating film obtained from a conventional paint containing a polyester resin and a melamine resin. For example, conventionally, methylated melamine resin, butylated melamine resin, etc. are known as melamine resins. It tends to be less than 5 atom %. On the other hand, butylated melamine resin tends to concentrate on the surface, and when used in a general blending amount, the maximum value of the N atoms tends to exceed 30 atom %. Therefore, in the present application, by adjusting the amount of the melamine resin or combining a plurality of melamine resins, the maximum value of the N atoms is adjusted to fall within the desired range. The metal substrate for printing according to the present invention will be described in detail below.

- Metal plate The metal plate should just have the structure which can form the below-mentioned to-be-printed layer, and the shape in particular is not restrict|limited. For example, it may be tabular or have a three-dimensional structure. Also, the metal plate may be strip-shaped or the like. The thickness of the metal plate is not particularly limited, and is appropriately selected according to the application of the coated metal material.

In addition, the material of the metal plate is not particularly limited, hot-dip Zn-plated steel plate, hot-dip Zn-55% Al alloy-plated steel plate, hot-dip Zn-Al-Mg alloy-plated steel plate, hot-dip Al-plated steel plate, electric Zn-plated steel plate, electric Cu-plated plated steel sheets such as steel sheets; steel sheets such as ordinary steel sheets and stainless steel sheets; aluminum sheets; The metal plate may have a chemical conversion treatment film, an undercoat film, or the like formed on its surface as long as the effects of the present invention are not impaired. Further, the metal plate may be subjected to uneven processing such as embossing or drawing within a range that does not impair the effects of the present invention.

The type of chemical conversion treatment for forming the chemical conversion film is not particularly limited. Examples of chemical conversion treatments include chromate treatments, chromium-free treatments, phosphate treatments, and the like. The amount of the chemical conversion coating applied is not particularly limited as long as it is within a range effective for improving corrosion resistance.

Further, the undercoat film is a layer that is formed directly on the metal plate or on the chemical conversion film to improve the adhesion of the printed layer or improve the corrosion resistance of the metal plate.

The undercoat film is formed, for example, by applying an undercoat paint containing a resin to the surface of a metal plate or a chemical conversion coating and drying (or curing) the paint. The type of resin contained in the undercoat is not particularly limited. Examples of resins include polyesters, epoxy resins, acrylic resins, and the like. Epoxy resins are particularly preferred because they have high polarity and good adhesion to metal plates. The thickness of the undercoat film is appropriately selected according to the intended use and type of the final coated metal material, and is, for example, about 5 μm.

- To-be-printed layer The to-be-printed layer is a layer containing a cured product of a paint containing a polyester resin and a melamine resin having a number average molecular weight of 12,000 to 30,000. The printed layer is formed by applying a printed layer-forming coating composition containing a polyester resin and a melamine resin having a number average molecular weight of 12,000 to 30,000 on the metal plate and curing the coating.

A layer composed of a cured product of the coating material for forming the printed layer may be used as the printed layer as it is, but it is more preferable to use a layer obtained by subjecting the layer to flame treatment or corona discharge treatment as the printed layer. By performing the flame treatment or the corona discharge treatment, the adhesion of the ink layer to the layer to be printed, which will be described later, is remarkably improved, and even if a thick ink layer is formed, it becomes difficult to peel off. Among these, a layer to be printed that has undergone frame treatment is particularly preferable from the viewpoint of adhesion of the ink layer and the like.

The method of applying the coating for forming the printed layer onto the metal plate is not particularly limited, and is appropriately selected according to the shape of the metal plate, the pattern of the printed layer to be formed, the area of the printed layer to be formed, etc. . Examples of coating methods include inkjet printing, gravure printing, offset printing, screen printing, roll coating, bar coating, spin coating, air spraying, airless spraying, immersion and lifting, and the like. included. Two or more of these methods may be combined when applying the coating material for forming the printed layer.

The coating material for forming the printed layer may contain a polyester resin having a number average molecular weight of 12,000 to 30,000 and a melamine resin. Polyester resins and melamine resins have a ratio of N atoms to the amount of N atoms, C atoms, and O atoms in a region 10 nm from the surface when the cured product (printed layer) of the coating for forming the printed layer is measured by the XPS method. are appropriately combined so that the amount of is 5 to 30 atom %. For example, depending on the number average molecular weight of the polyester resin, the degree of concentration of the melamine resin on the coating film surface side differs. When the polyester resin has a large number average molecular weight, it becomes difficult for the melamine resin to concentrate on the surface of the coating film. Therefore, it is preferable to increase the amount of the butylated melamine resin, which tends to concentrate on the surface. On the other hand, when the number average molecular weight of the polyester resin is small, the butylated melamine resin tends to concentrate on the coating film surface, so the amount of the butylated melamine resin is reduced and the amount of the melamine resin other than the butylated melamine resin is increased. Therefore, the amount of N atoms described above is adjusted to fall within the desired range. The coating material for forming the layer to be printed may contain other components such as catalysts, amines, extender pigments and color pigments, if necessary.

The polyester resin may be any resin having a plurality of ester structures in its molecular chain, and can be usually prepared by polymerizing a polyhydric carboxylic acid and a polyhydric alcohol.

Here, examples of polyvalent carboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid, and their anhydrides; succinic acid; , adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and other aliphatic dicarboxylic acids and their anhydrides; γ-butyrolactone, ε-caprolactone and other lactones; trimellitic acid, trimedine trivalent or higher polyvalent carboxylic acids such as acids and pyromellitic acid; The polyester resin may contain only one type of carboxylic acid structural unit derived from the polyvalent carboxylic acid, or may contain two or more types thereof.

In the polyester resin, the ratio of the amount of structural units derived from trivalent or higher polyvalent carboxylic acid to the total amount of alcohol structural units derived from polyhydric alcohol and carboxylic acid structural units derived from polyvalent carboxylic acid is It is preferably 20 mol % or less, more preferably 10 mol % or less, so as not to excessively increase the crosslink density of the film.

On the other hand, examples of polyhydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, 2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 1,4-hexanediol, 2,5-hexanediol, 1,5-hexanediol, 1,6 -hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, diethylene glycol, triethylene glycol, 1,2-dodecanediol, 1,2-octadecanediol, neopentyl glycol, Glycols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A alkylene oxide adduct, bisphenol S alkylene oxide adduct; Trimethylolpropane, glycerin, trihydric or higher polyhydric alcohols such as pentaerythritol etc. are included. The polyester resin may contain only one type of alcohol structural unit derived from the polyhydric alcohol, or may contain two or more types thereof.

The polyester resin may have a number average molecular weight of 12,000 to 30,000, preferably 12,000 to 25,000, more preferably 14,000 to 23,000. The number average molecular weight of the polyester resin is a styrene conversion value specified by gel permeation chromatography (GPC). If the number average molecular weight of the polyester resin is too small, the strength of the printed layer tends to be low and the hardness of the printed layer tends to be low. On the other hand, when the polyester resin has a number average molecular weight of 12,000 or more, a printed layer having sufficient strength (scratch resistance) can be obtained. On the other hand, when the number average molecular weight is 30,000 or less, the viscosity of the paint containing the polyester resin does not excessively increase, and it becomes easy to form a coating film using the paint for forming a printed layer containing the polyester resin. Furthermore, the workability of the printed layer is also enhanced.

Moreover, the hydroxyl value of the polyester resin is preferably 3 to 40 mgKOH/g, more preferably 5 to 20 mgKOH/g. A hydroxyl value is specified by a potentiometric titration method defined in JIS K0070 using a 0.5 mol/L KOH alcohol solution. When the hydroxyl value of the polyester resin is within this range, the OH groups on the surface of the metal plate and the OH groups in the polyester resin (printed layer) are likely to form hydrogen bonds, etc., and the adhesion between the metal plate and the printed layer is improved. increase. Similarly, the OH groups in the polyester resin (printing layer) are more likely to form hydrogen bonds with the hydrophilic groups in the ink layer, further increasing their adhesion.

The glass transition temperature of the polyester resin is preferably -10 to 80°C, more preferably 0 to 50°C. When the glass transition temperature of the polyester resin is within the above range, the processability of the resulting printed layer is improved.

On the other hand, the melamine resin contained in the coating material for forming the printed layer is a thermosetting resin obtained by reacting melamine and aldehyde. The melamine resin is appropriately selected so as to realize the above-described maximum N atom value when the layer to be printed is analyzed by the XPS method. Melamine resin has three reactive functional groups —NX ¹ X ² per triazine nucleus molecule. X ¹ and X ² usually represent CH ₂ OR (R is an alkyl group), CH ₂ OH, or a hydrogen atom. However, it is not limited to this structure.

Specific examples of melamine resins include fully alkyl melamine resins in which all three reactive functional groups are -N-(CH ₂ OR) ₂ ; at least one reactive functional group is -N-( a methylol group-type melamine resin that is CH ₂ OR)(CH ₂ OH); an imino group-type melamine resin in which at least one reactive functional group is —N—(CH ₂ OR)(H); a methylol/imino group-type melamine resin containing -N-(CH2OR) _{( CH2OH} ) and -N-( _CH2OR )(H), or containing -N-( _CH2OH )(H); 4 types are included. The melamine resin may also be a polymer of melamine in which reactive functional groups are condensed. Moreover, the coating material for forming a layer to be printed may contain only one kind of melamine resin, or may contain two or more kinds thereof.

The R, that is, the alkyl group of the reactive group of the melamine resin is preferably an alkyl group having 1 to 4 carbon atoms, and the alkyl group may be linear or branched. Among these, a methyl group or a butyl group is particularly preferred.

Melamine resins may be commercially available resins. Examples of commercially available melamine resins include fully alkyl methyl/butyl mixed ethers such as Cymel 232, Cymel 232S, Cymel 235, Cymel 236, Cymel 238, Cymel 266, Cymel 267, and Cymel 285 manufactured by Allnex Japan. melamine resin; methylol group type methyl/butyl mixed etherified melamine resin such as Cymel 272 manufactured by Allnex Japan; imino group such as Cymel 202, Cymel 207, Cymel 212, Cymel 253, and Cymel 254 manufactured by Allnex Japan type methyl/butyl mixed etherified melamine resin; completely alkyl type methylated melamine resin such as Cymel 300, Cymel 301, Cymel 303, Cymel 350 manufactured by Allnex Japan (referred to as "completely alkyl type methyl etherified melamine resin") Cymel 325, Cymel 327, Cymel 703, Cymel 712, Cymel 253, Cymel 212, Cymel 1128, etc. of Allnex Japan Co., Ltd.; Cymel 370, etc. of Allnex Japan Co., Ltd. Methylol group type methylated melamine resins; butylated melamine resins such as Uban 20SE60 manufactured by Mitsui Chemicals, Super Beckamine J830 manufactured by DIC (sometimes referred to as "butyl etherified melamine resin"); .

The term "methylated melamine resin" as used herein refers to a completely alkyl-type methyl-etherified melamine resin, an imino group-type methyl-etherified melamine resin, a methylol-group type methyl-etherified melamine resin, or a mixed resin thereof. The term "butylated melamine resin" refers to a butyl-etherified melamine resin having a complete alkyl-type butyl-etherified melamine, an imino group-type butyl-etherified melamine as a main structure, or a mixed resin thereof. We also offer melamine resins with both methyl and butyl groups, such as complete alkyl type methyl/butyl mixed etherified melamine resin, methylol group type methyl/butyl mixed etherified melamine resin, and imino group type methyl/butyl mixed etherified melamine resin. Also referred to as "methyl/butyl mixed melamine resin".

The melamine resin may contain only one type of melamine resin selected from the above. It preferably contains two or more melamine resins, more preferably a mixture of a butylated melamine resin and other melamine resins such as a methylated melamine resin and a methyl/butyl mixed melamine resin. A mixture of a butylated melamine resin and a methylated melamine resin is particularly preferred. In this case, the mass ratio of the butylated melamine resin and the methylated melamine resin is preferably 1:1 to 1:8, more preferably 2:3 to 1:6. In addition, the melamine resin may contain three or more kinds of melamine resins.

The ratio (mass ratio) of the polyester resin and the melamine resin contained in the coating material for forming the printed layer is preferably 90:10 to 60:40, more preferably about 85:15 to 70:30. When the mass ratio of the polyester resin and the melamine resin is within this range, a printed layer having excellent weather resistance and impact resistance can be obtained.

The total amount of the polyester resin and the melamine resin is preferably 30 to 80 parts by mass, more preferably 50 to 70 parts by mass, based on 100 parts by mass of the solid content of the coating material for forming the printed layer. When the total amount of the polyester resin and the melamine resin is within this range, the strength of the printed layer obtained from the printed layer-forming paint tends to be sufficiently increased. Furthermore, the adhesion between the layer to be printed and the ink layer tends to be good.

The coating material for forming a layer to be printed may further contain a catalyst. Examples of catalysts include dodecylbenzenesulfonic acid, paratoluenesulfonic acid, benzenesulfonic acid, and the like. The amount of the catalyst to be used is preferably 0.1 to 8% by mass with respect to the total solid content of the coating material for forming the printed layer.

Furthermore, the coating material for forming the printed layer may further contain an amine. Amines are compounds for neutralizing catalysts, examples of which include triethylamine, dimethylethanolamine, dimethylaminoethanol, monoethanolamine, isopropanolamine, and the like. The amount of amine to be used is not particularly limited, but is preferably 50 mol % or more of the acid (catalyst) equivalent.

In addition, the coating material for forming the printed layer may further contain an extender pigment (including beads), a color pigment, and the like. Examples of extender pigments include silica, calcium carbonate, barium sulfate, aluminum hydroxide, talc, mica, resin beads, glass beads, and the like. Examples of resin beads include acrylic resin beads, polyacrylonitrile beads, polyethylene beads, polypropylene beads, polyester beads, urethane resin beads, epoxy resin beads and the like.

These resin beads may be produced using a known method, or may be commercially available. Examples of commercially available acrylic resin beads include “Toughtic AR650S (average particle size 18 μm)”, “Tufftic AR650M (average particle size 30 μm)”, “Tufftic AR650MX (average particle size 40 μm)”, “Tufftic AR650MZ” manufactured by Toyobo Co., Ltd. (average particle size 60 μm)”, “TUFTIC AR650ML (average particle size 80 μm)”, “TUFTIC AR650L (average particle size 100 μm)” and “TUFTIC AR650LL (average particle size 150 μm)”. Examples of commercially available polyacrylonitrile beads include Toyobo Co., Ltd. "Toughtic A-20 (average particle size 24 μm)", "Toughtic YK-30 (average particle size 33 μm)", "Toughtic YK-50 (average particle size diameter 50 μm)” and “Tuftic YK-80 (average particle diameter 80 μm)”. The coating material for forming a layer to be printed may contain only one of these, or may contain two or more thereof.

On the other hand, examples of coloring pigments include carbon black, titanium oxide, iron oxide, yellow iron oxide, phthalocyanine blue, cobalt blue and the like. The amount of pigment is appropriately selected according to the type of pigment, particle size, and the like. The coating material for forming a layer to be printed may contain only one of these, or may contain two or more thereof.

The coating material for forming a layer to be printed may further contain a solvent, if necessary. The solvent is not particularly limited as long as it can sufficiently dissolve the polyester resin and melamine resin and can uniformly disperse the extender pigment and coloring pigment. Examples of solvents include toluene, xylene, Solvesso® 100 (trade name, manufactured by ExxonMobil), Solvesso® 150 (trade name, manufactured by ExxonMobil), Solvesso® 200 (trade name). name, manufactured by Exxon Mobil); ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as ethyl acetate, butyl acetate, and ethylene glycol monoethyl ether acetate; methanol, isopropyl Alcohol solvents such as alcohol and n-butyl alcohol; ether alcohol solvents such as ethylene glycol monoethyl ether and diethylene glycol monobutyl ether; n-methylpyrrolidone; ethyl-3-ethoxy-propionate and the like. The coating material for forming a layer to be printed may contain only one of these, or may contain two or more thereof. Among these, xylene, Solvesso (registered trademark) 100, Solvesso (registered trademark) 150, cyclohexanone, and n-butyl alcohol are preferred from the viewpoint of compatibility with polyester resins and melamine resins.

The method for preparing the coating material for forming the printed layer is not particularly limited, and the polyester resin, the melamine resin, and, if necessary, other components may be mixed by a known method.

After the coating for forming the layer to be printed is applied onto the metal plate, the coating for forming the layer to be printed is heated (hereinafter also referred to as “baking”) to cure. The baking method is not particularly limited, but it is preferable to heat the metal plate so that the plate temperature reached is within the range of 150 to 250°C.

After baking the coating material for forming the printed layer, if the printed layer is to be subjected to flame treatment, the metal plate on which the printed layer is formed is placed on a conveyor such as a belt conveyor. Then, while moving in a fixed direction, a flame treatment burner is used to radiate a flame onto the layer to be printed.

Here, the frame processing amount is preferably 100 to 600 kJ/m ² . As used herein, the term "flame throughput" refers to the amount of heat per unit area of the metal base calculated on the basis of the amount of combustion gas such as LP gas supplied. The amount of flame treatment can be adjusted by adjusting the distance between the burner head of the flame treatment burner and the surface of the layer to be printed, the transport speed of the layer to be printed, and the like. When the flame treatment amount is 100 kJ/m ² or more, the entire surface of the layer to be printed is likely to be uniformly treated. On the other hand, when the flame treatment amount is 600 kJ/m ² or less, the printed layer is less likely to turn yellow.

In addition, preheating may be performed by heating the surface of the layer to be printed to 40° C. or higher before the flame treatment. When the print layer formed on the surface of a metal substrate having a high thermal conductivity (for example, a metal substrate having a thermal conductivity of 10 W/mK or more) is irradiated with a flame, water vapor generated by combustion of the combustible gas is cooled. becomes water and temporarily accumulates on the surface of the printed layer. Then, the water absorbs the energy during the flame treatment and becomes water vapor, which may hinder the flame treatment. In contrast, by preheating the surface of the layer to be printed, the generation of water during flame irradiation can be suppressed.

The means for preheating the layer to be printed is not particularly limited, and is appropriately selected according to the shape of the metal plate. For example, a heating device commonly called a drying oven can be used. For example, a batch-type drying furnace (also referred to as a "safe furnace") can be used, and specific examples include a low-temperature thermostat manufactured by Isuzu Manufacturing Co., Ltd. (model Mini Catarina MRLV-11), an automatic drying furnace manufactured by Tojo Thermal Engineering Co., Ltd. It includes a discharge type dryer (model ATO-101) and a simple explosion-proof specification dryer manufactured by Tojo Thermal Engineering (model TNAT-1000).

On the other hand, when the corona discharge treatment is applied to the printed layer, the metal plate on which the printed layer is formed is placed between the insulated electrode and the grounded counter electrode dielectric roll. A high frequency and high voltage of 1 to 600 KHz and 5 to 30 KV are applied between them to generate corona discharge. As a corona discharge treatment apparatus, there are a spark gap system, a vacuum tube system, a solid state system, etc., and any of them can be used. The corona discharge treatment conditions are preferably 200 w/m ² /min or more, more preferably 200 to 800 w/m ² /min. If it is less than 200 w/m ² /min, the corona discharge treatment amount may be insufficient, and if it exceeds 800 w/m ² /min, the treatment will be excessive, which is not economically preferable.

Here, the thickness of the layer to be printed is not particularly limited, but is preferably 10 to 40 μm, more preferably 12 to 25 μm. When the thickness of the layer to be printed is 10 μm or more, the durability of the layer to be printed tends to be good. In addition, the layer to be printed tends to become flexible, and the adhesiveness of the ink layer, which will be described later, tends to increase. On the other hand, when the thickness is 40 μm or less, popping is less likely to occur during the heating, and the surface condition tends to be good. Furthermore, when the surface condition of the layer to be printed is good, the active energy ray-curable composition to be described later tends to spread evenly, and the adhesion between the resulting ink layer and the layer to be printed tends to increase.

As described above, for a region from the surface of the layer to be printed to a depth of 10 nm, using AlKα rays as an X-ray source, when the composition was analyzed in the depth direction by the XPS method, N atoms, C atoms, and O atoms The maximum value of N atoms with respect to the total amount of is preferably 5 to 30 atom %, more preferably 12 to 28 atom %, and still more preferably 15 to 25 atom %. The concentration of each atom from the surface of the printed layer to a depth of 10 nm is measured by an XPS analyzer under the following conditions while etching the printed layer from the surface to a depth of 10 nm.
(Measurement condition)
Measuring device: Versaprobe II scanning X-ray photoelectron spectrometer manufactured by ULVAC-PHI X-ray source: AlKα (monochrome: 50 W, 15 kV) 1486.6 eV
Analysis area: 1.0 x 1.0 ^mm2
Pass Energy: 5.85 eV (C1s, O1s), 187.85 eV (N1s)
Charge neutralization use (electron neutralization + ion gun)
Analysis room vacuum: 1.0 × 10 ^-7 Pa
(Etching conditions)
Etching conditions: Ar-gas cluster ion beam Accelerating voltage: 5 kV
Etching rate: about 1 nm/min (converted to polymethyl methacrylate resin (PMMA))

Here, in order to sufficiently wet and spread the active energy ray-curable ink described later on the surface of the layer to be printed, it is preferable that the surface of the layer to be printed is uniformly hydrophilized. Whether or not the surface of the layer to be printed is uniformly hydrophilized can be evaluated by the following methylene iodide sliding angle. For example, when the methylene iodide sliding angle of the layer to be printed is 10° or more and 40° or less, it can be said that the surface is uniformly hydrophilized. Note that the falling angle of methylene iodide is more preferably 35° or less.

The methylene iodide sliding angle tends to fall within the above range when the surface of the layer to be printed is sufficiently hydrophilic or when the surface of the layer to be printed is rough. However, if the hydrophilicity of the layer to be printed is non-uniform, the methylene iodide sliding angle will be higher than 40°. For example, when the surface is treated by corona treatment, the methylene iodide sliding angle tends to exceed 40°. On the other hand, when flame treatment is performed, the surface is uniformly hydrophilized, and the methylene iodide sliding angle is 40° or less.

The reason why the falling angle of methylene iodide exceeds 40° when the hydrophilicity of the surface of the layer to be printed becomes non-uniform due to corona discharge treatment or the like is considered as follows. It is assumed that there are two types of coating films each having the same number of hydrophilic groups and hydrophobic groups on the surface, one has no bias in the distribution of the hydrophilic groups and hydrophobic groups, and the other has a bias in the distribution of the hydrophilic groups and the hydrophobic groups. Assume. At this time, the static contact angles of both are hardly influenced by the distribution of the hydrophilic group and the hydrophobic group, and are substantially the same. On the other hand, the dynamic contact angles (methylene iodide sliding angles) of the two are influenced by the distribution of hydrophilic groups and hydrophobic groups and have different values. When the methylene iodide slid angle is measured, if the distribution of the hydrophilic groups and the hydrophobic groups is non-uniform, the methylene iodide droplets will be adsorbed to the portion with high density of the hydrophilic groups. In other words, if the distribution of the hydrophilic groups and the hydrophobic groups is biased, the methylene iodide droplets are more difficult to move than when there is no uneven distribution, resulting in a large falling angle. Therefore, when a large number of hydrophilic groups are introduced to the surface of the printing layer as in corona discharge treatment, but the distribution thereof is uneven, the falling angle of methylene iodide becomes a high value exceeding 40°.

The methylene iodide slid angle is a value measured as follows. First, 2 μl of methylene iodide is dropped onto the layer to be printed. After that, using a contact angle measuring device, the inclination angle of the printed layer (the angle between the plane perpendicular to gravity and the printed layer) is increased at a speed of 2 degrees/second. At this time, the droplet of methylene iodide is observed with a camera attached to the contact angle measuring device. Then, the inclination angle at the moment when the droplet of methylene iodide falls is specified, and the average value of five times is taken as the methylene iodide sliding angle of the layer to be printed. The moment when the methylene iodide droplet falls is the moment when both the end point of the methylene iodide (droplet) in the downward direction of gravity and the end point in the upward direction of gravity start to move.

2. Coated metal material The coated metal material includes the above-described metal base material to be printed and an active energy ray-curable composition (hereinafter referred to as "curable composition and an ink layer that is a cured product of (also referred to as ""). The ink layer may be arranged on the entire region where the layer to be printed is formed, or may be arranged on only a part of the region where the layer to be printed is formed.

The ink layer may be a cured product of only one type (for example, one color) of curable composition, or may be a cured product of two or more types (for example, two or more colors) of curable composition. The composition of the curable composition will be described later. The type of curable composition, the area of arrangement, the pattern of arrangement, etc. are appropriately selected according to the application of the coated metal material. Examples of active energy rays in this specification include electron beams, ultraviolet rays, α-rays, γ-rays, X-rays, and the like.

The method of applying the curable composition is not particularly limited, and is appropriately selected from known methods. Examples of methods for applying the curable composition include inkjet printing, gravure printing, offset printing, screen printing, roll coating, bar coating, and the like. Among these, the inkjet method is preferable from the viewpoint that multicolor patterns and complicated patterns can be easily formed in a short time. These may be combined when applying the curable composition.

Furthermore, the coating amount of the curable composition is not particularly limited, and it is preferably applied so that the thickness after curing is about 5 to 150 μm, more preferably about 10 to 100 μm. The above thickness may be achieved by applying the curable composition to the same location multiple times. As described above, in general, when the coating amount of the curable composition increases, curing shrinkage during curing increases, and the resulting ink layer tends to peel off. However, the metal substrate for printing (especially when it has a printing layer subjected to frame treatment) has high adhesion between the printing layer and the formed ink layer, and the ink layer has a thickness of, for example, 40 μm or more. is formed, peeling is unlikely to occur.

The curable composition may be applied such that the thickness of the cured ink layer changes continuously or intermittently. When printing layers with different thicknesses are formed on a general printing layer, the adhesion changes between the areas where the ink layer is thick and the areas where the ink layer is thin. Sometimes. On the other hand, in the metal base material for printing (especially when it has a layer to be printed that has undergone frame treatment), the ink layer and high adhesion to the printed layer. Therefore, even if an ink layer with a varying thickness is formed, peeling is unlikely to occur.

After applying the curable composition, the coating film is irradiated with an active energy ray to be cured. The activation energy can be any of electron beams, ultraviolet rays, alpha rays, gamma rays, and x-rays. Among these, electron beams or ultraviolet rays are preferred, and ultraviolet rays are particularly preferred, from the viewpoint of energy efficiency and the need for no large-scale apparatus.

The amount of active energy rays to be irradiated is appropriately selected according to the type and amount of the photopolymerization initiator and photoacid generator in the curable composition described later. The dominant wavelength of the active energy ray to be irradiated is also appropriately selected according to the type of the photopolymerization initiator and the photoacid generator, and can be, for example, a wavelength of 360 to 425 nm.

In the case of applying multiple types of curable compositions, each time one type of curable composition is applied, irradiation with an active energy ray may be performed. After applying multiple types of curable compositions, the active energy Line irradiation may be performed.

- Curable composition The curable composition to be applied onto the layer to be printed may be a known composition conventionally used for printing on a metal plate. Curable compositions include radical polymerizable compositions and cationic polymerizable compositions, and both of them can be used in the present invention.

A radically polymerizable composition can be, for example, a composition containing a photopolymerizable compound, a photoinitiator, and a colorant. The photopolymerizable compound may be a compound having at least one photopolymerizable group that exhibits reactivity when irradiated with an active energy ray. Examples of photopolymerizable compounds include known (meth)acrylic monomers or (meth)acrylic oligomers having 1 to 6 (meth)acryloyloxy groups. In this specification, the term "(meth)acryloyl" refers to either or both of methacryloyl and acryloyl, and the term "(meth)acryl" refers to either or both of methacryl and acryl. The radically polymerizable composition may contain only one type of photopolymerizable compound, or may contain two or more types.

The radically polymerizable composition preferably contains 50 to 90% by mass of the photopolymerizable compound in solid content. When the amount of the photopolymerizable compound in the radically polymerizable composition is within the above range, the radically polymerizable composition easily wets and spreads on the above-described layer to be printed, and the ink layer easily adheres to the layer to be printed. .

On the other hand, the photopolymerization initiator may be any compound capable of generating radicals upon irradiation with active energy rays, and is preferably a compound having an absorption wavelength corresponding to the wavelength of the active energy rays. Examples of photopolymerization initiators include benzophenone-based compounds, acetophenone-based compounds, thioxanthone-based compounds, phosphine oxide-based compounds, and the like. In particular, since the phosphine oxide compound has an absorption wavelength of 370 nm or more, it is more preferable to add it in order to promote deep curing of the ink layer. The radically polymerizable composition may contain only one type of photopolymerization initiator, or may contain two or more types.

The radically polymerizable composition preferably contains 1 to 25% by mass of the photopolymerization initiator in solid content. When the amount of the photopolymerization initiator in the radically polymerizable composition is within this range, the photopolymerizable compound can be cured.

Also, the type of coloring agent is not particularly limited, and known pigments or dyes can be used. The radically polymerizable composition preferably contains 0.1 to 10% by mass of the colorant in the solid content. The radically polymerizable composition may contain only one colorant, or may contain two or more colorants.

On the other hand, the cationic polymerizable composition can be a composition containing a photopolymerizable compound, a photoacid generator, and a colorant.

The photopolymerizable compound may be a compound having at least one photopolymerizable group that exhibits reactivity when irradiated with an active energy ray. Examples of photopolymerizable compounds include epoxy compounds having oxirane groups. Examples of epoxy compounds include aromatic epoxides, cycloaliphatic epoxides, and aliphatic epoxides.

Further, the photopolymerizable compound may be a fatty acid ester, an epoxidized fatty acid ester obtained by introducing an epoxy group into a fatty acid glyceride, an epoxidized fatty acid glyceride, or the like. Furthermore, the photopolymerizable compound may be an oxetane ring-containing compound or a vinyl ether compound. The cationic polymerizable composition may contain only one type of photopolymerizable compound, or may contain two or more types.

Further, the cationic polymerizable composition preferably contains 60 to 95% by mass of the photopolymerizable compound in solid content. When the amount of the photopolymerizable compound in the cationically polymerizable composition is within the above range, the cationically polymerizable composition easily spreads over the above-described layer to be printed, and the ink layer easily adheres to the layer to be printed. .

Examples of photoacid generators include salts of aromatic onium compounds; sulfonates that generate sulfonic acid; halides that generate hydrogen halide, and the like. The cationic polymerizable composition preferably contains 3 to 20% by mass of the photoacid generator based on the solid content. When the amount of the photoacid generator in the cationic polymerizable composition is within this range, the photopolymerizable compound can be sufficiently cured.

Further, the colorant contained in the cationic polymerizable composition is the same as the colorant contained in the radical polymerizable composition.

The curable composition may contain other components as necessary. Examples of other ingredients include polymerization inhibitors, antioxidants, silane coupling agents, plasticizers, rust inhibitors, solvents, non-reactive polymers, fillers, pH adjusters, antifoaming agents, charge control agents, Includes stress relievers, surface conditioners, and the like.

- Application of coated metal material The application of the above-described coated metal material is not particularly limited, and it can be used for a wide variety of members and applications that use a metal base material. Examples of applications include home appliances such as refrigerator outer panels, microwave oven outer panels, PC housings, air conditioner housings; interior decorative building materials such as partitions, doors, ceiling materials, flooring materials, elevator doors, elevator interior panels, etc. housing equipment such as range hoods and bathroom interior materials; furniture such as desks, chairs, lockers and shelves; vehicle materials such as passenger car interiors and railway vehicle interiors. However, the application of the coated metal material is not limited to these.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited by these examples.

1. Preparation of metal plate A hot-dip Zn-plated steel plate of A4 size with a plate thickness of 0.3 mm and a coating weight per side of 45 g/m ² was used. After the plated steel sheet is degreased with alkali, a coating type chromate (NRC300NS: manufactured by Nippon Paint Industrial Coatings Co., Ltd.) is applied so that the amount of Cr is 50 mg / m ² , and a primer composition (Nippon Paint FL641EU primer manufactured by Industrial Coatings Co., Ltd.) was applied by a roll coater so that the dry film thickness was 5 μm. After that, it was baked to obtain a metal plate at a maximum plate temperature of 215°C.

2. Preparation of Paint for Forming Layer to be Printed A polyester resin and a melamine resin shown below were mixed at a mass ratio shown in Table 1. Furthermore, the following catalyst and color pigment were also mixed to prepare a paint for forming a printed layer.

(1) Polyester resins The following four types of polyester resins were used. Also, the polyester resin was dissolved in a solvent and then mixed with other components. The solvent is one of n-methylpyrrolidone, cyclohexanone, an aromatic solvent (Solvesso (registered trademark) 150, surface tension 30 mN/m), and ethyl-3-ethoxy-propionate (surface tension 25 mN/m), or A mixture of multiple species was used.

- Polyester resin A (prepared by the following method, number average molecular weight: 10,000)
· Polyester resin B (manufactured by Toyobo Co., Ltd., Vylon (registered trademark) GK140, Tg: 20 ° C., number average molecular weight: 14,000, amorphous)
· Polyester resin C (manufactured by Toyobo Co., Ltd., Vylon (registered trademark) 630, Tg: 7 ° C., number average molecular weight: 23,000, amorphous)
- Polyester resin D (prepared by the following method, number average molecular weight: 31,000)

(Method for preparing polyester resins A and D)
Dimethylterephthalic acid, dimethylisophthalic acid, trimellitic anhydride, ethylene glycol, neopentyl glycol, 1,6-hexanediol, and 2-methyl-1,3-propanediol were added to a reaction vessel equipped with a stirrer, condenser, and thermometer. was charged in an appropriate amount, and the transesterification reaction was carried out from 160° C. to 240° C. over 4 hours. Then, the mixture was cooled to 200°C, adipic acid was charged, and the mixture was gradually heated to 240°C to carry out an esterification reaction. Then, the pressure in the system was gradually reduced to 5 mmHg over 50 minutes, and the polycondensation reaction was carried out at 260° C. for 60 minutes under a vacuum of 0.3 mmHg or less. Polyester resins A and D were obtained by changing the composition ratio during polymerization.

(2) About melamine resin The following two types of melamine resins were used: Methylated melamine (Cymel 303, manufactured by Ornex Japan Co., Ltd., completely alkyl-type methylated melamine resin)
・Butyl melamine (manufactured by DIC, Super Beccamine (registered trademark) J830, butyl melamine resin)

(3) Catalyst Dodecylbenzenesulfonic acid was used as the catalyst. More specifically, neutralized with triethylamine so that the amine equivalent is 1.25 times the acid equivalent was added in an amount of 1% by mass based on the resin solid content of the paint for forming the printed layer.

(4) Color Pigment Titanium oxide (Tipake (registered trademark) CR-95 manufactured by Ishihara Sangyo Co., Ltd.) was used as the color pigment. Moreover, the amount added was set to 50% by mass with respect to the total amount of the amorphous polyester resin and the melamine resin.

3. Formation of To-be-Printed Layer On one side of the metal plate having the above primer layer, each of the to-be-printed layer forming paints P1 to P16 was applied by a roll coater so that the dry film thickness was 18 μm. After that, baking was performed for 60 seconds so that the maximum plate temperature reached 225° C. to form a layer to be printed on the metal plate.

4. Flame treatment and corona discharge treatment 4-1. Frame Treatment The metal base material for printing on which the above-mentioned to-be-printed layer was formed was placed on a carrier, and the to-be-printed layer was subjected to frame treatment. F-3000 manufactured by Flynn Burner (USA) was used as a flame treatment burner. As the combustible gas, a mixed gas (LP gas:clean dry air (volume ratio)=1:25) obtained by mixing LP gas (combustion gas) and clean dry air with a gas mixer was used. The flow rate of each gas was adjusted to 1.67 L/min for LP gas (combustion gas) and 41.7 L/min for clean dry air per 1 cm ² of the flame port of the burner. The length of the flame port of the burner head in the conveying direction of the layer to be printed was set to 4 mm. On the other hand, the length of the flame port of the burner head in the direction perpendicular to the conveying direction was 450 mm. Furthermore, the distance between the flame port of the burner head and the surface of the layer to be printed was set to 50 mm according to the desired flame throughput. Furthermore, the frame throughput was adjusted to 212 kJ/m ² by setting the transport speed of the layer to be printed to 30 m/min.

4-2. Corona Discharge Treatment The printed layer of the printed metal substrate having the printed layer formed thereon was subjected to a corona discharge treatment. A corona discharge treatment apparatus manufactured by Kasuga Denki Co., Ltd. was used for the corona discharge treatment.
(specification)
・Electrode ceramic electrode ・Electrode length 430mm
・Output 310W
In addition, the number of times of corona discharge treatment for the layer to be printed was set to one in each case. The amount of corona discharge treatment was adjusted by the treatment speed. Specifically, the treatment was performed at 2.8 m/min, and the amount of corona discharge treatment was 250 W/m ² /min.

5. Preparation of active energy ray-curable composition An active energy ray-curable composition (hereinafter A radically polymerizable composition or a cationic polymerizable composition) was applied under the conditions described later.

5-1. Preparation of radically polymerizable black composition Composition The following components were mixed to prepare a radically polymerizable black composition.
Pigment dispersion (pigment: 10% by mass) 10 parts by mass Photopolymerizable compound A 25 parts by mass Photopolymerizable compound B 57 parts by mass Photopolymerization initiator a 5 parts by mass Photopolymerization initiator b 3 parts by mass

- Materials The following compounds were used as the materials for the radically polymerizable black composition.
Pigment dispersion: a mixture of carbon black (manufactured by Degussa Japan, NIPex 35) and a dispersion medium (manufactured by Sartomer Japan, SR9003, PO-modified neopentyl glycol diacrylate) Photopolymerizable compound A: manufactured by Sartomer Japan, CN985B88 (mixture of 88% by weight of bifunctional aliphatic urethane acrylate and 12% by weight of 1,6-hexanediol diacrylate)
Photopolymerizable compound B: 1,6-hexanediol diacrylate Photopolymerization initiator a: Ciba Japan Co., Ltd., Irgacure 184 (hydroxyketones)
Photopolymerization initiator b: Ciba Japan Co., Ltd., Irgacure 819 (acylphosphine oxides)

5-2. Preparation of Cationic Polymerization Black Composition A cationic polymerization black composition was prepared by first preparing a pigment dispersion and then mixing the pigment dispersion with other components.

Preparation of pigment dispersion 9 parts by mass of a polymer dispersant (manufactured by Ajinomoto Fine-Techno Co., Ltd., PB821), 71 parts by mass of an oxetane compound (manufactured by Toagosei Co., Ltd., OXT211), and 20 parts by mass of a black pigment (Pigment Black 7) were mixed. Then, the mixture was placed in a glass bottle together with 200 g of zirconia beads having a diameter of 1 mm, and the glass bottle was sealed and subjected to dispersion treatment in a paint shaker for 4 hours. After that, the zirconia beads were removed to obtain a pigment dispersion.

- Composition A cationic polymerizable black composition was prepared by mixing the following components.
Pigment dispersion 14 parts by mass Photopolymerizable compound C 4 parts by mass Photopolymerizable compound D 34 parts by mass Photopolymerizable compound E 24 parts by mass Photopolymerizable compound F 8.9 parts by mass Basic compound 0.05 parts by mass Surfactant Agent a 0.025 parts by mass Surfactant b 0.025 parts by mass Compatibilizer 10 parts by mass Photoacid generator 5 parts by mass

光重合性化合物Ｅ：オキセタン化合物（東亜合成社製、ＯＸＴ－２２１）
光重合性化合物Ｆ：オキセタン化合物（東亜合成社製、ＯＸＴ－２１１）
塩基性硬化型組成物：Ｎ－エチルジエタノールアミン
界面活性剤ａ：ＤＩＣ社製、メガファックＦ１７８ｋ（パーフルオロアルキル基含有アクリルオリゴマー）
界面活性剤ｂ：ＤＩＣ社製、メガファックＦ１４０５(パーフルオロアルキル基含有エチレンオキサイド付加物）
相溶化剤：東邦化学社製、ハイゾルブＢＤＢ（グリコールエーテル）
光酸発生剤：ダウケミカル社製、ＵＶ１６９９２ - Materials The following compounds were used as materials for the cationic polymerizable black composition.
Photopolymerizable compound C: epoxidized linseed oil (manufactured by ATOFINA, Vikoflex 9040)
Photopolymerizable compound D: a compound represented by the following formula

Photopolymerizable compound E: oxetane compound (manufactured by Toagosei Co., Ltd., OXT-221)
Photopolymerizable compound F: oxetane compound (manufactured by Toagosei Co., Ltd., OXT-211)
Basic curable composition: N-ethyldiethanolamine Surfactant a: DIC Corporation, Megafac F178k (perfluoroalkyl group-containing acrylic oligomer)
Surfactant b: Megafac F1405 (perfluoroalkyl group-containing ethylene oxide adduct) manufactured by DIC Corporation
Compatibilizer: Hi-solve BDB (glycol ether) manufactured by Toho Chemical Co., Ltd.
Photoacid generator: Dow Chemical Company, UV16992

5-3. Printing Conditions for Active Energy Ray-Curable Composition The printing conditions for the above-described radically polymerizable black composition and cationic polymerizable black composition are as follows.

(Inkjet printing conditions for radically polymerizable composition)
(a) Nozzle diameter: 35 μm
(b) Applied voltage: 11.5V
(c) Pulse width: 10.0 μs
(d) Drive frequency: 3,483Hz
(e) Resolution: 360dpi
(f) Droplet volume: 42pl
(g) Head heating temperature: 45°C
(h) Application amount: 8.4 g/m ²
(i) Distance between head and recording surface: 5.0 mm
(j) Droplet initial velocity: 5.9 m/sec

(Inkjet printing conditions for cationic polymerizable composition)
(a) Nozzle diameter: 35 μm
(b) Applied voltage: 13.2V
(c) Pulse width: 10.0 μs
(d) Drive frequency: 3,483Hz
(e) Resolution: 360dpi
(f) Droplet volume: 42pl
(g) Head heating temperature: 45°C
(h) Application amount: 8.4 g/m ²
(i) Distance between head and recording surface: 5.0 mm
(j) Droplet initial velocity: 6.1 m/sec

6. Evaluation For each printed layer, analysis by the following XPS method, measurement of methylene iodide falling angle, pencil hardness (untreated only), coating workability test (untreated only), solvent rubbing test (untreated only), And wetting spread evaluation (dot diameter evaluation) was performed. Furthermore, the adhesiveness of the ink layer was evaluated with respect to the coated metal material after forming the ink layer by applying the active energy ray-curable composition. Each result is shown in Table 2, Table 3, and Table 4.

6-1. Analysis by XPS method (identification of the amount of N atoms, C atoms, and O atoms in the printed layer)
Using an XPS analyzer, under the following conditions, while etching from the surface of the printed layer to a depth of 10 nm, the concentrations of N atoms, C atoms, and O atoms in the depth direction (N atoms, C atoms, and O atoms The total amount of 100 atom %) was measured. Then, the maximum amount of N atoms with respect to the total amount of N atoms, C atoms, and O atoms was specified. 1, Example 5 in FIG. 2, Example 2 in FIG. 3, Comparative Example 8 in FIG. 4, and Comparative Example 2 in FIG. 5 were analyzed by the XPS method. A relation between atomic concentration and depth is shown.
(Measurement condition)
Measuring device: Versaprobe II scanning X-ray photoelectron spectrometer manufactured by ULVAC-PHI X-ray source: AlKα (monochrome: 50 W, 15 kV) 1486.6 eV
Analysis area: 1.0 x 1.0 ^mm2
Pass Energy: 5.85 eV (C1s, O1s), 187.85 eV (N1s)
Charge neutralization use (electron neutralization + ion gun)
Analysis room vacuum: 1.0 × 10 ^-7 Pa
(Etching conditions)
Etching conditions: Ar-gas cluster ion beam Accelerating voltage: 5 kV
Etching rate: about 1 nm/min (converted to polymethyl methacrylate resin (PMMA))

6-2. Measurement of Methylene Iodide Sliding Angle 2 μl of methylene iodide was dropped onto the printed layer held horizontally. Then, using a contact angle measuring device (Kyowa Interface Science Co., Ltd. DM901), the inclination angle of the printed layer (the angle formed by the horizontal plane and the printed layer) was increased at a rate of 2 degrees/second. Then, the droplets of methylene iodide were observed with a camera attached to the contact angle measuring device. The tilt angle of the layer to be printed at the moment when the droplet of methylene iodide falls was specified, and the average value of five times was taken as the falling angle of methylene iodide of the layer to be printed. The moment when the methylene iodide droplet falls is the moment when both the end point of the methylene iodide droplet in the downward direction of gravity and the end point in the upward direction of gravity start to move.

6-3. Pencil Hardness The pencil hardness of the printed layer was measured according to the measuring method specified in JIS K5600-5-4. ○ or more was defined as a pass.
◎: H or more ○: HB to F
×: B or less

6-4. Coating workability test The prepared coated steel plate for printing is bent 180° (adhesion bending) according to the bending test of JIS G3322, and the state of the coating film in the processed part is visually observed to determine whether there is cracking in the coating film. examined. When the 180° bending was performed, the printed surface of the painted steel sheet to be printed was on the outside of the bending, and contact bending was performed (generally known as 0T bending). Further, when observing the processed portion, the processed portion was observed with a magnifying glass of 10x magnification, and a processed portion adhesion test was also conducted in which a tape was adhered to the processed portion and peeled off. Then, the adhesion after peeling off the tape was visually observed. Evaluation was based on the following criteria, and an evaluation of Δ or higher was regarded as acceptable.
◎: No peeling, no cracks (cracks in the coating film) ○: No peeling, cracks (cracks in the coating film) △: Very slight peeling ×: Slight peeling ××: Peeling

6-5. Solvent Rubbing Test A load of 1 kg was pressed against the surface of the layer to be printed through gauze impregnated with xylol, and rubbed back and forth 100 times. Then, the appearance of the printed layer was observed and evaluated as follows. The length of rubbing gauze impregnated with xylol against the surface of the layer to be printed was set to 70 mm one way. In addition, only ○ was regarded as a pass.
〇: The printed layer was not mechanically abraded or the printed layer was peeled off by the solvent, and a good appearance was maintained. △: The printed layer was mechanically abraded or the printed layer by the solvent. When the primer layer is exposed due to peeling ×: When all layers including the primer layer are mechanically worn, or the printed layer is peeled off by the solvent, exposing the metal plate which is the original plate

6-6. Evaluation of wetting and spreadability of active energy ray-curable composition (evaluation of dot diameter)
The active energy ray-curable composition (radical polymerizable black composition and cationic polymerizable black composition) was applied in dots on the above-mentioned layer to be printed. Specifically, dots were printed using an inkjet printer (patterning jet manufactured by Tritec) so that the volume of each droplet was 42 pl. The distance between dots was set to 500 μm so that the dots would not overlap each other. Then, the diameter of each dot was measured using a scanning confocal laser microscope LEXT OLS3000 manufactured by Olympus Corporation. More specifically, the dot diameter of 8 dots was measured by enlarging the range in which only one dot was visible (200 times), and the average value was evaluated as the dot diameter. When the spread of the dots was close to an ellipse, the average value of the major and minor diameters was taken as the dot diameter and evaluated as follows. If the dot diameter is less than 100 μm, the active energy ray-curable composition is difficult to wet and spread, and even if 100% printing is performed, the surface of the layer to be printed cannot be completely covered with the active energy ray-curable composition. Therefore, the smaller the dot diameter, the lower the evaluation. However, if it is Δ or more, there is no practical problem.
◎: Dot diameter 130 µm or more ○: Dot diameter 100 µm or more and less than 130 µm △: Dot diameter 80 µm or more and less than 100 µm ×: Dot diameter less than 80 µm

6-7. Evaluation of adhesion of ink layer On the above-mentioned layer to be printed, apply the active energy ray-curable composition to a resolution of 360 dpi under the above conditions, 100 to 1000% (ink coating amount: 8.4 to 84.0 g /m ² ). Then, using a high-pressure mercury lamp (manufactured by Fusion UV Systems Japan, H bulb), lamp output: 200 W / cm, integrated light intensity: 600 mJ / cm ² (manufactured by Oak Manufacturing Co., ultraviolet light meter UV-351-25 was irradiated with ultraviolet rays at the time of measurement using ) to form an ink layer. A cross-cut test according to JIS K5600-5-6 G330 was performed on the obtained coated metal material. Specifically, the surface of the ink layer was cut in a grid pattern so that 25 squares were formed at intervals of 2 mm. Then, an adhesive tape was attached to the portion and peeled off. After peeling off the adhesive tape, the ink layer remaining rate was observed. The evaluation was performed according to the following criteria, and △ or more was regarded as a pass.
○: The peeling area of the ink layer is 0%
△: The peeled area of the ink layer is more than 0% and within 20% ×: The peeled area of the ink layer is more than 20%

6-8. Adhesion test On the above-mentioned layer to be printed, the active energy ray-curable composition was printed at 100% (ink coating amount: 8.4 g / m ² ) so that the resolution was 360 dpi under the above conditions. Similarly, the ink layer was formed by irradiating ultraviolet rays to cure the ink. A 4T bending test was performed on the obtained coated metal material according to the bending test of JIS G3322. After that, an adhesive tape was adhered to the surface of the ink layer at the bent portion and peeled off. The appearance of the coated metal material was observed before the adhesive tape was attached and after the adhesive tape was peeled off, and evaluated as follows. Likewise, the coated metal materials printed at 500% and 1000% were also evaluated in the same manner. An evaluation of △ or more was regarded as a pass.
○: No peeling of the ink layer or the printed layer △: Punctate peeling of 1 mmφ or less on the ink layer or printed layer ×: Peeling of the ink layer or printed layer

As shown in FIGS. 1 to 5 and Tables 2 to 4, when the composition was analyzed by the XPS method in the depth direction of the printed layer, depending on the amount, type, and combination of melamine resin, the area from the surface to 10 nm , it became clear that the ratio of N atoms changes greatly.

Also, at this time, if the maximum value of N atoms with respect to the total amount of N atoms, C atoms, and O atoms in the region from the surface of the printed layer to a depth of 10 nm is 5 to 30 atom%, pencil hardness and coating Both the film workability test and the rubbing test were good. In addition, when an ink layer was formed on the layer to be printed, the adhesion was also good. 18).

Also, untreated printed layers (Examples 1, 4, 7, 10, 13, and 16), flame-treated printed layers (Examples 2, 5, 8, 11, 14, and 17), and corona Comparing the discharge-treated printed layers (Examples 3, 6, 9, 12, 15, and 18), the flame-treated printed layer gave the best results in dot diameter evaluation, and further Adhesion of the ink was also good.

On the other hand, when the maximum value of N atoms with respect to the total amount of N atoms, C atoms, and O atoms exceeds 30 atom %, the evaluation result of pencil hardness is good, but the adhesion of the ink layer is low. showed poor results in coating processability tests and rubbing tests (Comparative Examples 1 to 18). It is believed that when the maximum value of N atoms was large, the layer to be printed became hard and the adhesiveness of the ink layer decreased.

On the other hand, when the maximum amount of N atoms to the total amount of N atoms, C atoms and O atoms was less than 5 atom %, the pencil hardness was low and the rubbing test results were also poor (Comparative Examples 19 to 24).

Moreover, when the number average molecular weight of the polyester resin was less than 12,000, sufficient workability was not obtained (Comparative Examples 25 to 27). On the other hand, when the number average molecular weight of the polyester resin exceeded 30,000, sufficient coating film hardness was not obtained (Comparative Examples 28 to 30).

According to the metal substrate for printing of the present invention, when an ink layer is formed using an active energy ray-curable composition, the ink layer is less likely to peel off. In addition, the printable layer of the printable metal substrate has good workability and scratch resistance. Therefore, it is possible to form various coated metal materials with high designability.

Claims (6)

a metal plate;
A printed layer containing a cured product of a paint containing a polyester resin and a melamine resin having a number average molecular weight of 12,000 to 30,000, disposed on the metal plate;
has
When analyzing the composition in the depth direction by X-ray electron spectroscopy using AlKα rays as an X-ray source for a region from the surface of the printed layer to a depth of 10 nm, N atoms, C atoms, and O atoms The maximum value of N atoms with respect to the total amount of is 5 to 30 atom%,
A metal substrate for printing. 2. The metal substrate for printing according to claim 1, wherein the melamine resin is a mixture of at least a butylated melamine resin and a melamine resin other than the butylated melamine resin. The surface of the layer to be printed has a methylene iodide falling angle of 10° or more and 40° or less.
The metal substrate for printing according to claim 1 or 2. A metal substrate for printing according to any one of claims 1 to 3;
an ink layer, which is a cured product of an active energy ray-curable composition, disposed on the printed layer of the printed metal substrate;
having
Painted metal material. A method for producing a metal substrate for printing according to any one of claims 1 to 3,
A step of applying a paint containing a polyester resin and a melamine resin having a number average molecular weight of 12,000 to 30,000 on a metal plate and curing it to form a printed layer,
A method for producing a metal substrate for printing. further comprising subjecting the printed layer to flame treatment or corona discharge treatment;
The method for producing a metal substrate for printing according to claim 5.

Images