JPH0924334A - Formation of multicolor pattern coating film excellent in workability and its steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a multicolor pattern coating film industrially, excellent in decorativeness and workability. SOLUTION: An electron beam-curing coating material consisting essentially of a colored grain, a low electron beam-sensitive polymer having >=10,000mol.wt. and an oligo(meth)acryloyl including >=2 (meth)acnyloyl group in one molecule is applied on a substrate in one layer and irradiated with an electron beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a surface of metal or the like to form a multicolored pattern with good workability, and a steel sheet thereof.

[0002]

2. Description of the Related Art Paints that give a multicolored pattern on the surface of a substrate are JI
S. For details, see JIS-K-5667.
According to the regulations, liquid or gel-like particles of two or more colors are suspended in a dispersion medium, and the respective color particles are not mixed to form an intermediate color.
It is a finishing material that can produce a variety of design effects with one coating. As a method of applying a multicolored pattern, an internal pressure type spray method was generally used, but this method has a limit in designability (roughness due to unevenness of colored particles on the coating surface, soft feeling There are drawbacks such as poor touch feeling, strong contrast feeling due to colorant particles, and hard feeling), a lot of paint loss, bad environment, and difficulty in obtaining high productivity.
Further, the drying method of the coating used is room temperature drying or heat drying, which usually takes several tens of minutes to several days until curing, and the productivity is not good either. Further, when the multi-colored steel sheet is used for doors, partitions, etc., it is often subjected to processing such as bending, but this workability is not always good.

[0003]

Therefore, as a coating method for correcting the above-mentioned drawbacks, other methods such as a curtain flow coater, a roll coater, a gravure offset printing, a screen printing and the like are conceivable. Since high shearing force and mechanical external force are applied at the time of application, there is a principle problem that the colorant particles are likely to be non-uniform. On the other hand, as the coating material, a conventional room temperature or thermosetting coating material is also conceivable, but there is a limit in improving the designability such as colorant particles protruding on the surface of the coating film to give a rough feeling and a soft touch feeling.

The reason for this is considered to be that the non-volatile content during coating and printing is low (the amount of solvent is large). The low non-volatile content of the coating agent means that the surface of the colorant particles is thickly coated in the wet state, but the coating layer becomes thin due to the scattering of the solvent, when viewed microscopically.
Then, it is presumed that the colorant particles are projected on the surface of the coating film to cause a feeling of roughness, poor soft touch feeling, and the like. Therefore, as a method for solving the above-mentioned drawbacks, a coating / ink having a high non-volatile content, a low heat applied after coating and curing in a short time, and a technique having a curing method thereof are desired. Under such circumstances, in recent years, technologies have been developed to cope with social needs such as pollution-free (high non-volatile content paint, low furnace exhaust gas), high-speed production (hardening in a short time), and resource saving. As an example thereof, an ultraviolet ray curing method or an electron beam curing method has been put into practical use as a method for curing a coating film.

However, in the method by ultraviolet irradiation of the above-mentioned publication, since the colorant particles have a basic characteristic of absorbing or blocking ultraviolet rays, it is difficult to reach the inside of the coating film by ultraviolet irradiation. Is time consuming, and involves the problem of heating the coating surface by both radiant heat from a UV lamp and convective heat to fluidize the resin and cause a "thinning" phenomenon. But there are some areas for improvement.

Therefore, the present invention is more excellent in design than the above-mentioned conventional methods, and in particular, has beauty (three-dimensional appearance / shape / color tone, multicolored appearance), curtain flow coater, roll coater, gravure offset printing, It is possible to form a multicolor pattern coating film by a coating method such as screen printing that applies shear force or mechanical external force, and further it can be cured in a shorter time than before to form a multicolor pattern coating film with good processability. A method and its steel sheet are provided.

[0007]

According to the present invention, one or more electron beam-curable coatings containing colorant particles dispersed therein are coated on the surface of a substrate and irradiated with an electron beam to form a coating film. A method for forming a multicolored pattern coating film characterized by the above, and a multicolored pattern coated steel sheet having a coating film formed by coating an electron beam curable coating material containing dispersed colorant particles on the surface thereof, wherein the electron beam is The cured coating composition includes a low electron beam sensitive polymer having a molecular weight of 10,000 or more, one or more oligo (meth) acrylates containing two or more (meth) acryloyl groups in one molecule, and two or more in one molecule. At least one polyhydric alcohol (meth) acrylate containing a (meth) acryloyl group is an essential component.

Hereinafter, the present invention will be described in detail. Electron beam curable paint: The paint for various coating films used in the present invention is an electron beam curable paint having good processability. If the accelerating voltage of electron beam is properly selected, its penetration depth and penetration force are overwhelmingly stronger than that of ultraviolet rays, and the surrounding heat does not occur due to electron beam irradiation. As a result, the design is superior to the conventional one and it is possible to combine the aesthetics. Further, it can be sufficiently cured by electron beam irradiation for a very short time.

The electron beam-curable coating material is specifically one or more low electron beam sensitive polymers having a molecular weight of 10,000 or more and oligo (meth) containing two or more (meth) acryloyl groups in one molecule. It is preferable to contain one or more acrylates. The above-mentioned molecular weight of 10,000
Examples of the above low electron beam sensitive polymers include polyester, acryl and urethane type resins. Here, the term "low electron beam sensitive polymer" in the present invention is defined. The low electron beam-sensitive polymer has a (meth) acryloyl group having a high sensitivity to an electron beam per molecular weight of 1,000 in the range of 0 to 0.5, and it is preferably close to 0. The reason is that the product obtained by the present invention emphasizes processability, and when the electron beam sensitivity of the polymer is high, the crosslinking reaction proceeds to a high degree and the coating film becomes too hard, resulting in a significant decrease in processability. , Because it does not meet the purpose.

These will be described in more detail below. The low electron beam sensitive polyester uses a polyester skeleton in the main chain, and contains (meth) acrylic acid in an amount of 0 to 0.
The product obtained by the esterification reaction in the range of 5 / 1,000 molecular weight. The main chain polyester skeleton refers to a synthetic raw material which is composed of a polyhydric alcohol and a polycarboxylic acid.

That is, as the dihydric alcohol, alkylene glycol type ethylene glycol, propylene glycol, chloropropylene glycol, butanediol (1,3- or 1,4- or 2,3-), 3
-Methylpentanediol, 2,2-diethylpropanediol, pentamethylene glycol, 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol, hexamethylenediol, etc., alicyclic glycol type As 1,4-cyclohexanediol, cyclohexane-1,4-dimethanol, hydrogenated bisphenol A, etc., as a polyalkylene glycol type, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol , Polybutadiene diol, etc., and 2,2'-bis (4-hydroxyphenyl) propane (also known as bis Phenol A), bis (4-hydroxyphenyl) methane (also known as bisphenol F), 4,
Examples thereof include glycols obtained by adding alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as 4′-dihydroxyphenyl, hydroquinone, resorcin and the like.

Examples of the trihydric alcohol include alkanetriol type glycerin, trimethylolmethane, trimethylolethane, trimethylolpropane,
1,2,6-hexanetriol, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-
2,3,4-butanetriol, 2-methyl-1,2,
As alkanetetraols such as 3-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-hexanetriol, and pentamethylene glycol, erythritol, pentaerythritol, toilet, 1,2,3,3. 4-pentane tetrol, 2,3
4,5-hexanetetrol, 2,5-dimethyl-2,
3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, 3-hexene-1,2,5,6-tetrol, 3-hexyne-1,2,5,6-tetrol, etc. , An ether group-containing aliphatic triol, a triol obtained by adding alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) to glycerin, trimethylolpropane, etc., and an ether group-containing aliphatic tetraol, erythritol and pentaerythritol. Tetraol and the like obtained by adding alkylene oxide to, and the like, and aromatic triols include triol obtained by adding alkylene oxide to pyrogallol.

Next, as the carboxylic acid, a linear or branched divalent carboxylic acid such as oxalic acid, malonic acid, succinic acid, glutaric acid, itaconic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, dotecan Acids, methylene glutaric acid, methyl maleic acid, methyl succinic acid, dodecenyl succinic acid, etc. as aliphatic dicarboxylic acids such as tetrahydrophthalic acid, hexahydrophthalic acid, 6-methyltetrahydrophthalic acid, 6-methylhexahydrophthalic acid, endomethylenetetrahydro Phthalic acid, endo isopropylidene tetrahydrophthalic acid, 1, 4, 5, 6,
7,7-Hexachloro-endo-5-norbornene-
2,3-dicarboxylic acid (also called het acid), 1,4,5,
6,7,7-Hexabromo-endo-5-norbornene-2,3-dicarboxylic acid, cyclohexane, 1,4-dicarboxylic acid and the like, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid and tetrachlorophthal Examples thereof include acid, tetrabromophthalic acid, and their anhydrides.

The low electron beam sensitive acrylic means that an acrylic skeleton is used for the main chain, and (meth) acrylic acid is added to the acrylic skeleton.
It refers to one obtained by an esterification reaction in the range of 0.5 / 1,000 molecular weight. The synthetic raw material of this component will be described in more detail. The main chain is acrylic acid such as
Alternatively, it is composed of a monomer such as α-substituted acrylate.

Acrylic acid, methyl acrylate, ethyl acrylate, -n-propyl acrylate, isopropyl acrylate, -n-butyl acrylate, isobutyl acrylate, -n-amyl acrylate, -n-hexyl acrylate, Acrylic acid alkyl esters such as n-octyl, 2-chloroethyl acrylate, alkyl halides such as 3-chloropropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate OH group-containing acrylic acid ester having OH group such as, methyl methacrylate, ethyl methacrylate, -n-propyl methacrylate, isopropyl methacrylate, -n-butyl methacrylate, isobutyl methacrylate, -n-amyl methacrylate, Methacrylic acid-n-octane Le, α, such as lauryl methacrylate
-Alkyl acrylate alkyl ester, α-methyl chloroacrylate, α-ethyl chloroacrylate and other α
-Α-alkyl acrylic acid halogenated alkyl ester such as halogen acrylic acid ester, 2-chloroethyl methacrylate, and 3-chloropropyl methacrylate,
Methacrylic acid-2-hydroxyethyl, methacrylic acid-
2-hydroxypropyl, methacrylic acid-1-chloro-
Included are α-alkyl acrylates having an OH group such as 2-hydroxyethyl, and acrylic monomers such as glycidyl methacrylate.

The low electron beam-sensitive urethane has a urethane skeleton in its main chain, to which (meth) acrylic acid is added.
It refers to one obtained by an esterification reaction in the range of 0.5 / 1,000 molecular weight. The urethane resin referred to in the present invention may be any of polyether type urethane acrylate, polyester type urethane acrylate, and polyether / polyester type urethane acrylate in a mixed form of these. More specifically, as the polyether type urethane acrylate, for example, the one represented by the following general formula (1) is used. _{(CH 2 = CH-COO)} n R-OOC-NH-R 1 -NH-COO- (A-OOC-NH-R 1 -COO) x R 2 (OOC-CH = CH 2) m ‥‥ (1 )

As the polyester / urethane acrylate, for example, the one represented by the general formula (2) is used. _{(CH 2 = CH-COO)} n R-OOC-NH-R 1 -NH-COO- [(A-B) y A-OOC-NH-R 1 -NH-COO] z R 2 - (OOC-CH = CH ₂ ) m ・ ・ ・ (2)

[0018] Polyether-polyester type mixing forms, in the polyether urethane acrylate was the elements - (A-OOC-NH- R 1 -NH-COO) - ‥‥ (3) and a polyester type urethane acrylate elements in - [(a-B) y -A-OOC-NH-R 1 -NH-COO] - ‥ (4) is in the form of coexistence is employed.

The symbols in the above general formulas (1), (2), etc. have the following meanings. n and m are n ≧ 1, m ≧ 1, n
+ M = an integer satisfying the conditions of 2 to 6 R is an n + 1-valent polyhydric alcohol residue, R ¹ is a diisocyanate residue, R ² is an m + 1-valent polyhydric alcohol residue A is an ether-type diol Diol residues, including

B is a dibasic acid residue, x is 1 to 20, y is 1 to 18, and z is 1 to 18, and a number giving a molecular weight of 1500 to 7000 as a whole urethane acrylate,
A and B are each one molecule of urethane acrylate,
There may be one kind or two or more kinds. However, at least a part of A in the general formula (1) is an ether type diol residue.

Specific examples of A include ether type diol residues such as diethylene glycol, tripropylene glycol, tetrapropylene glycol, hexaethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol and hexa. Residues such as propylene glycol, polypropylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, polymethylene glycol, polytetramethylene glycol, poly 1,4-oxybutylene glycol, etc. Examples of the diol residue include ethylene glycol, propylene glycol, 1,4 butane diol, 1,5 pentane diol, 1,6 hexanediene. Lumpur, hexylene glycol,
It is a residue such as neopentyl glycol.

B is, for example, a residue of maleic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid or the like. R and R ² are each independently, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, trimethylolmethane, trimethyl It is a polyhydric alcohol residue such as methylolethane, trimethylolpropane, glycerin, hexanetriol, pentaerythritol, and dipentaerythritol.

R ¹ is, for example, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, xylylene-1,3-diisocyanate, xylylene-1,4-diisocyanate, 1,5 ethylene diisocyanate, diphenylmethane-4. , 4 diisocyanate, diphenylmethane-2,4 'diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and the like. This R ¹ is usually one type in the urethane acrylate molecule, but two or more types may be used. From the viewpoint of corrosion resistance, the urethane / acrylate resin is preferably a non-yellowing type rather than a yellowing type. The diisocyanate used is isophorone diisocyanate, hexamethylene diisocyanate, tetramethalene isocyanate, etc. It is desirable to use the resin that has been used.

Further, the oligo (meth) acrylate is
Containing two or more (meth) acrylate groups in one molecule,
Also, it means a polyester (meth) acrylate having a (meth) acryloyl group equivalent of 400 or less. Polyester (meth) cleats are those obtained by using a polyester skeleton in the main chain and esterifying two or more (meth) acrylic acids in one molecule. The polyester skeleton of the main chain refers to a synthetic raw material which comprises a polyhydric alcohol and a polycarboxylic acid and forms them.

That is, as described above, as the dihydric alcohol, alkylene glycol type ethylene glycol, propylene glycol, chloropropylene glycol, butanediol (1,3- or 1,4- or 2,3-), 3 -Methylpentanediol, 2,2-diethylpropanediol, pentamethylene glycol,
1,6-Cyclohexanediol, cyclohexane-1,4-dimethanol as an alicyclic glycol type such as 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol and hexamethylene diol. , Hydrogenated bisphenol A, polyalkylene glycol type, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol, polybutadiene diol, etc., and aromatic glycol type, 2,2 '. -Bis (4-hydroxyphenyl) propane (also known as bisphenol A),
Glycol obtained by adding alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as bis (4-hydroxyphenyl) methane (also known as bisphenol F), 4,4′-dihydroxyphenyl, hydroquinone, resorcin, etc. Kind and the like.

The trihydric alcohol is an alkanetriol type glycerin, trimethylolmethane, trimethylolethane, trimethylolpropane,
1,2,6-hexanetriol, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-
2,3,4-butanetriol, 2-methyl-1,2,
As alkanetetraols such as 3-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-hexanetriol, and pentamethylene glycol, erythritol, pentaerythritol, toilet, 1,2,3,3. 4-pentane tetrol, 2,3
4,5-hexanetetrol, 2,5-dimethyl-2,
3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, 3-hexene-1,2,5,6-tetrol, 3-hexyne-1,2,5,6-tetrol, etc. , An ether group-containing aliphatic triol, a triol obtained by adding alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) to glycerin, trimethylolpropane, etc., and an ether group-containing aliphatic tetraol, erythritol and pentaerythritol. Tetraol and the like obtained by adding alkylene oxide to, and the like, and aromatic triols include triol obtained by adding alkylene oxide to pyrogallol.

Next, as the carboxylic acid, as a chain or branched divalent carboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, itaconic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, dotecan Acids, methylene glutaric acid, methyl maleic acid, methyl succinic acid, dodecenyl succinic acid, etc. as aliphatic dicarboxylic acids such as tetrahydrophthalic acid, hexahydrophthalic acid, 6-methyltetrahydrophthalic acid, 6-methylhexahydrophthalic acid, endomethylenetetrahydro Phthalic acid, endo isopropylidene tetrahydrophthalic acid, 1, 4, 5, 6,
7,7-Hexachloro-endo-5-norbornene-
2,3-dicarboxylic acid (also called het acid), 1,4,5,
6,7,7-Hexabromo-endo-5-norbornene-2,3-dicarboxylic acid, cyclohexane, 1,4-dicarboxylic acid and the like, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid and tetrachlorophthal Examples thereof include acid, tetrabromophthalic acid, and their anhydrides. As the C component, polyhydric alcohol (meth) acrylate and polyester (meth) acrylate may be used in combination.

[0028]

EXAMPLES Next, the present invention will be specifically described with reference to Examples. In the examples, “parts” are based on weight unless otherwise specified. The performance of the multi-colored steel sheet was evaluated by the following method. (1) Appearance Visual judgment was performed according to JIS K-5400 (6.1). ◯: Good Δ: Slightly bad ×: Poor (2) Pencil hardness Judged according to JIS K-5400 (6.1). (3) Bending process Judgment was performed according to JIS K-5400 (6.1).
The smaller the number, the better the workability.

Embodiment 1

[Component composition of colorant coating] A: Yellow colorant particles (lead chromate) 10 parts B: Acrylic resin (acrylic acid / ethyl acrylate / methyl methacrylate / dihydroxyethyl acrylate / copolymer: molecular weight 15 5,000, (Meth) Aquilo group 0/1000 molecular weight) 55 parts C: Trifunctional alcohol acrylate (condensation molar ratio of trimethylolpropane / acrylic acid 1: 3 acryloyl group equivalent 111) 10 parts or more It is an essential component. D: Pigment (calcium carbonate) 15 parts E: Solvent (xylene) 10 parts

[0030]

[Coating of colorant paint] Electrogalvanized steel sheet coated with an epoxy primer to a dry film thickness of 2 μm (plating adhesion amount 20
g / m ² ), the above colorant coating material is applied by a bar coater so that the dry film thickness becomes 50 μm,
Hold for a minute to disperse the solvent. After this, the electron beam was
It was irradiated with ad (nitrogen atmosphere: O ₂ amount 100 ppm).
The performance was as shown in Table 1. The surface appearance is good and the workability is excellent.

[0031]

[Table 1]

Comparative Example 1 To the component B of Example 1, glycidyl methacrylate was simultaneously added and polymerized (without changing the molecular weight) so that the metaquino group had 2/1000 molecular weight. The performance was as shown in Table 1. The surface appearance is good, but the workability is poor.

Comparative Example 2

The composition of the colorant coating was the same as in Comparative Example 1 except that 5 parts of the photosensitizer 2,4,6-trimethylbenzoyldiphenylphosphine ococide was added.

[Coating with colorant paint] Electrogalvanized steel sheet coated with an epoxy primer to a dry film thickness of 2 μm
0 g / m ² ) of the colorant paint was applied by a bar coater so that the dry film thickness was 50 μm, and the solvent was scattered in the atmosphere at 80 ° C. for 1 minute. Then, at a position 100 mm below the metal halide lamp (input: 120 W / cm), the colorant-painted steel sheet was passed through the steel sheet and cured at a conveyor speed of 6 m / min. The performance was as shown in Table 1. There is also a rough feeling and the workability is not good.

Comparative Example 3

[Ingredient composition of colorant paint] is the same as that of Example 1 except that the acryloyl group equivalent of the component C of Example 1 was set to 170.

[Coating of colorant paint] is the same as in Example 1. The performance was as shown in Table 1. Hardness is low.

Example 2 The component B of Example 1 was used as a polyester resin (phthalic acid / adipic acid / neopentyl glycol / ethylene glycol condensate: molecular weight 20,000, (meth) cryloyl group).
The component composition of the colorant paint and the coating of the colorant paint were the same as in Example 1 except that the number was 0/1000 molecular weight).
The performance was as shown in Table 1. The performance similar to that of Example 1 was exhibited.

[0036]

The steel sheet obtained by the (electron beam curing method) method of forming a multicolored coating film of the present invention has the advantages of the conventional technology (UV curing method) such as no pollution, resource saving and high speed productivity. Because it is utilized and the coating film is formed in a non-heated atmosphere, it has a good design (texture and soft touch).
Is better than the conventional method. In addition, in the case of electron beam curing, since the penetrating ability and the quality of the rays are different from ultraviolet rays, by appropriately selecting the accelerating voltage, colored particles, which are an essential component of the multicolored paint, can be used without restriction, and the film thickness There is no limit. Furthermore, the workability is also good.

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Claims (8)

[Claims] 1. A. First Embodiment Colorant particles, B.I. Molecular weight 10,000
0 or more low electron beam sensitive polymers, C.I. Coating by coating one or more layers of electron beam curable coating containing, as an essential component, oligo (meth) acrylate containing two or more (meth) acryloyl groups in one molecule on a substrate and irradiating with an electron beam A method for forming a multicolored coating film having excellent processability, which comprises curing and forming a film. 2. C. As a component, one or more polyhydric alcohol (meth) acrylate containing two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 150 or less is added. The method for forming a multicolor pattern coating film having excellent processability according to claim 1. 3. C.I. As a component, one or more polyester (meth) acrylates containing two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 400 or less are added. The method for forming a multicolored coating film having excellent processability according to claim 1. 4. The method for forming a multicolored paint film having excellent processability according to claim 1, wherein the nonvolatile content of the electron beam curable coating material is 65% or more. 5. A. Colorant particles, B.I. Molecular weight 10,000
0 or more low electron beam sensitive polymers, C.I. One or more electron beam curable coatings containing, as an essential component, oligo (meth) acrylate containing two or more (meth) acryloyl groups in one molecule are applied to a substrate to form a cured coating film by electron beam irradiation. A multi-layer coated steel sheet with excellent workability that is formed. 6. C.I. As a component, one or more polyhydric alcohol (meth) acrylate containing two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 150 or less is added. A multi-color coated steel sheet having excellent workability according to claim 5. 7. C.I. As a component, one or more polyester (meth) acrylates containing two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 400 or less are added. A multi-color coated steel sheet having excellent workability according to claim 5. 8. The multi-pattern coated steel sheet with excellent workability according to claim 6, 7 or 8, wherein the electron beam curable coating material has a nonvolatile content of 65% or more.