JP5380983B2 - Decorative sheet for steel plate and decorative steel plate using the same - Google Patents

Description

  The present invention relates to a decorative sheet for steel plate and a decorative steel plate using the same.

  In order to impart a design to a steel plate, a sheet decorated with a polyester resin film such as a vinyl chloride resin film, an olefin resin film, or PET is laminated on the steel plate. In particular, a PET film laminated steel sheet has been proposed as having stain resistance, molding processability and high hardness (see Patent Document 1 and Claims). In addition, a decorative sheet for a steel sheet is proposed in which a pattern layer, a transparent adhesive layer, and a transparent polyester resin layer are sequentially laminated on a base material sheet made of polyolefin resin or polyester resin ( Patent Document 2).

The decorative sheet has high contamination resistance and high hardness, but has a problem that cracks are generated on the surface of the curved surface portion when the steel sheet is bent. When a polyester film such as PET is used, cracks hardly occur and a certain degree of workability is ensured, but there is a problem that resistance to scratches is low. In order to impart scratch resistance to PET or the like, there is a method of hard-coating the surface, but there is also a problem that cracks occur in the hard coat at the curved surface portion. When such a crack occurs, dirt accumulates in the crack portion, and the stain resistance decreases. In addition, when used around water, problems such as the occurrence of mold in the cracks occur, and when used in whiteboards, markers remain on the cracks and the marker erasability is significantly reduced. Problem arises.
In order to solve the above-mentioned problems, the present inventors do not crack in the curved surface part even when laminated and bent on a steel sheet, and have high formability and have stain resistance and scratch resistance. As a decorative sheet for a steel sheet, on a base material made of a biaxially stretched polyester film, a primer layer made of a urethane resin composition and a surface protective layer obtained by crosslinking and curing an ionizing radiation curable resin composition are laminated in this order. A decorative sheet was proposed (see Patent Document 3).

  By the way, as demand for steel sheet whiteboards using steel sheet decorative sheets increases, more stringent marker erasability is required, and at the same time, whiteboards are used in combination as projector reflective screens such as OHP and slides. Projectivity is required as a new performance. However, the decorative sheets for steel sheets described in Patent Documents 1 to 3 may not be able to sufficiently meet these performance requirements, and further improvements are required.

JP 2000-43192 A JP 2005-238498 A JP 2007-290382 A

  The present invention is a further improvement of the decorative sheet for steel sheet described in Patent Document 3, and has a good projectability and has excellent marker erasability even after bending, and a decorative sheet for steel sheet and makeup An object is to provide a steel sheet.

  As a result of intensive studies to achieve the above object, the present inventors have found that a colored layer composed of a specific material, a concavo-convex layer containing specific concavo-convex particles and an ionizing radiation curable resin on a substrate. It has been found that a decorative sheet for a steel sheet obtained by laminating a surface protective layer obtained by crosslinking and curing the composition in this order can solve the above problems. The present invention has been completed based on such findings.

That is, the present invention
(1) A decorative sheet for a steel sheet in which a colored layer, an unevenness imparting layer, and a surface protective layer are laminated in this order on a substrate, wherein the colored layer is made of a urethane-based resin composition containing an inorganic pigment. A decorative sheet for steel sheet, wherein the imparting layer is made of a urethane-based resin composition containing irregularities imparting fine particles having an average particle diameter of 1 to 7 μm, and the surface protective layer is obtained by crosslinking and curing the ionizing radiation curable resin composition;
(2) The surface protective layer includes irregularities-providing fine particles, and the content ratio of the irregularity-providing fine particles is 6 parts by mass or less with respect to 100 parts by mass of the resin solid content of the surface protective layer. Decorative sheet for steel sheet,
(3) The content ratio of the irregularity-providing fine particles contained in the irregularity-imparting layer is 5 to 60 parts by mass with respect to 100 parts by mass of the resin solid content of the irregularity-imparting layer, as described in (1) or (2) above. Decorative sheet for steel sheet,
(4) The decorative sheet for steel sheet according to any one of (1) to (3), wherein the inorganic pigment is titanium oxide,
(5) The decorative sheet for steel sheet according to any one of (1) to (4), wherein the ionizing radiation curable resin composition is an electron beam curable resin composition, and (5) the above (1) to ( 5) a decorative steel sheet obtained by attaching the decorative sheet according to any one of the above to a steel sheet;
Is to provide.

  According to the present invention, it is possible to provide a decorative sheet for steel sheet and a decorative steel sheet having excellent marker erasability even when bending is performed while having excellent projectability.

[Base material]
A typical structure of the decorative sheet for steel sheet according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic view showing a cross section of a decorative sheet 1 for steel sheet according to the present invention. In the example shown in FIG. 1, a colored layer 3, an unevenness imparting layer 4, and a surface protective layer 5 are laminated on a base material 2 in this order.
In the decorative sheet for steel sheet of the present invention, the substrate 2 is preferably made of a resin film, more preferably a polyester film from the viewpoint of suppressing the occurrence of cracks in the surface protective layer 4, and a biaxially stretched polyester film. More preferably it is. It does not specifically limit as a polyester resin used for a polyester film, What is normally used in the field | area of a decorative sheet can be used. Examples thereof include polyethylene terephthalate (hereinafter sometimes referred to as “PET”), polybutylene terephthalate, polyethylene naphthalate, polyarylate, polycarbonate, ethylene terephthalate-isophthalate copolymer, polyarylate, and the like. Of these, polyethylene terephthalate, polybutylene terephthalate, and the like are preferable, and polyethylene terephthalate is particularly preferable.

  In addition to various homopolymers, polyester resins such as copolymer polyester resins and polyester thermoplastic elastomers to which various copolymer components or modifying components are added may be used for the purpose of softening the resin. For example, in the case of PET, in the condensation polymerization reaction between terephthalic acid and ethylene glycol, as the dicarboxylic acid component, for example, long-chain aliphatic dicarboxylic acids such as sebacic acid, eicoic acid, dodecanedioic acid, dimer acid, cyclohexanedicarboxylic acid, and the like / Or an alicyclic dicarboxylic acid can be introduced. In addition, polyether diols having hydroxyl groups at both ends, such as polyethylene glycol and polytetramethylene glycol, can be introduced as the diol component.

  In the present invention, the polyester film preferably used as the substrate 2 is formed into a film by, for example, a calendar method, an inflation method, a T-die extrusion method, or the like, and more preferably prepared by biaxial stretching. By using the biaxially stretched polyester resin film as the base material 2, it is possible to suppress the elongation of the surface protective layer 4, which will be described in detail later, and to suppress the occurrence of cracks in the surface protective layer 4.

The thickness of the base material 2 is not particularly limited, and can be appropriately set according to product characteristics, but a range of 25 to 100 μm is preferable. When the thickness of the substrate 2 is in the range of 25 to 100 μm, the tension applied to the surface protective layer 4 can be sufficiently relaxed.
Moreover, when the polyester resin film by which biaxial stretching was used for the base material 2, it is preferable that the tensile strength measured based on JISC2151 of this film is 150 Mpa or more. When the tensile strength is 150 MPa or more, since it is highly rigid, local elongation generated in the bent portion can be suppressed, and extension of the upper surface protective layer can also be suppressed.

  The resin film used for the substrate 2 may contain an additive as necessary. Examples of the additive include a filler, a flame retardant, an antioxidant, a lubricant, a foaming agent, a colorant, an ultraviolet absorber, and a light stabilizer.

Among the above additives, in particular, from the viewpoint of improving the elasticity and elongation rate of the base material 2, imparting impact resistance, and not causing cracks or cracks in the surface protective layer when subjected to bending, It is preferable to contain inorganic fillers such as calcium, barium sulfate, clay and talc.
The content of these inorganic fillers is preferably in the range of 5 to 60% by mass with respect to the substrate 2.

Moreover, it does not specifically limit as said coloring agent, Well-known coloring agents, such as a pigment and dye, can be used. Examples of the colorant include inorganic pigments such as titanium white, zinc white, petal, vermilion, ultramarine, cobalt blue, titanium yellow, yellow lead, and carbon black; isoindolinone, Hansa yellow A, quinacridone, permanent red 4R, Organic pigments (including dyes) such as phthalocyanine blue, indanthrene blue RS, and aniline black; metal pigments such as aluminum and brass; pearlescent pigments made of foil powder such as titanium dioxide-coated mica and basic lead carbonate Is mentioned.
The coloring of the substrate 2 includes transparent coloring and opaque coloring (hiding coloring), and these can be arbitrarily selected. For example, when the ground color of the adherend (steel plate to which the decorative sheet is bonded) is concealed, opaque coloring may be selected. On the other hand, in order to make the ground pattern of the adherend visible, transparent coloring may be selected.
Moreover, about a ultraviolet absorber and a light stabilizer, the thing similar to what can be added to the resin composition which comprises the surface protective layer 4 of this invention explained in full detail later can be used.

The base material 2 can be subjected to physical or chemical surface treatment such as an oxidation method or a concavo-convex method on one side or both sides as desired in order to improve the adhesion with other layers.
Examples of the oxidation method include corona discharge treatment, chromium oxidation treatment, flame treatment, hot air treatment, ozone / ultraviolet treatment method, and examples of the unevenness method include a sand blast method and a solvent treatment method. These surface treatments are appropriately selected according to the type of the substrate 2, but generally, a corona discharge treatment method is preferably used from the viewpoints of effects and operability.

[Colored layer]
The decorative sheet of the present invention has a configuration in which a colored layer 3, an unevenness imparting layer 4, and a surface protective layer 5 are sequentially laminated on a substrate 2. By taking such a configuration, the decorative sheet of the present invention can have excellent projectability and excellent marker erasability even when bending is performed. More specifically, for example, an inorganic pigment such as titanium oxide absorbs water due to moisture in the air over time, causing cracks and the like, and the marker erasability is significantly reduced. These effects can be suppressed and the projection performance can be secured.

  The colored layer may be provided on the entire surface, may be provided on a part, or may form a pattern. In the case of having a pattern, there is no particular limitation on the type of pattern, for example, wood grain pattern, stone pattern, sand pattern, tiled pattern, brickwork pattern, cloth pattern, leather pattern, geometric figure, character , Symbols, abstract patterns, etc.

<< Urethane resin composition >>
The colored layer 3 is made of a urethane resin composition containing an inorganic pigment. The urethane-based resin composition has flexibility, toughness, and elasticity. By providing such a specific colored layer 3, the impact, tensile force, or shearing force applied to the surface protective layer 5 during bending is reduced. And the occurrence of cracks in the surface protective layer 5 can be suppressed.
The urethane resin used here preferably has an elongation at room temperature of 300% or more measured according to JIS K6732. When the elongation is 300% or more, the impact, tensile force or shear force applied to the surface protective layer 4 during bending can be sufficiently relaxed. From the above viewpoint, the elongation is more preferably 400% or more, and further preferably 500% or more. Further, the glass transition point (Tg) is −20 ° C. or less from the viewpoint of imparting bending workability at low temperatures in addition to the necessary and sufficient flexibility, toughness and elasticity of the decorative sheet for steel plate. Is preferred.

As urethane-type resin, what satisfies said elongation rate and Tg is preferable, and it can select from a conventionally well-known thermoplastic urethane resin. For example, thermoplastic urethane resins such as polyester, polyether, acrylic and polycarbonate are used alone or in combination.
As the thermoplastic urethane resin, for example, a urethane resin having no cross-linked structure and having a structure in which the skeleton structure is linear or branched is preferably exemplified. A saturated thermoplastic urethane resin having no isocyanate group is also preferred in that it is not cured by moisture or the like and has good stability over time.
On the other hand, when water resistance is particularly required, a urethane resin having a crosslinked structure to some extent while satisfying the above-described elongation rate and Tg is suitable. When particularly toughness is required, polyester urethane or polycarbonate Urethane is preferred.

As a specific example of such a thermoplastic urethane resin, a urethane resin composed of a linear polymer obtained by reacting a polyol having a hydroxyl group at a terminal and a polyisocyanate can be exemplified.
Examples of the polyol include polyester polyol, polyether polyol, polycarbonate polyol, and the like. More specifically, examples of the polyester polyol include poly (ethylene adipate), poly (butylene adipate), poly (neopentyl adipate), Examples include polyester diols such as poly (hexamethylene adipate), poly (butylene azelate), poly (butylene sebacate), polycaprolactone, and the polyether polyol includes polyethylene oxide, polypropylene oxide, poly (tetramethylene ether) Examples of the polycarbonate polyol include poly (butylene carbonate) and poly (hexamethylene carbonate). It is. Other examples include acrylic polyol, urethane polyol, fluorine-based polyol, acrylic silicone-based polyol, polyethylene glycol, and polypropylene glycol. These are used alone or in combination of two or more.

  Examples of the diisocyanate component include various aliphatic (or alicyclic) or aromatic diisocyanates conventionally known in the polyurethane field. For example, aliphatic (or alicyclic) systems include aliphatic isocyanates such as 1,6-hexamethylene diisocyanate, alicyclic isocyanates such as isophorone diisocyanate and hydrogenated tolylene diisocyanate, 2,4-tolylene diisocyanate, Aromatic isocyanates such as 2,6-tolylene diisocyanate, xylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and the like. These can be used alone or in combination of two or more.

<Inorganic pigment>
The urethane resin composition used in the colored layer in the present invention contains an inorganic pigment. Examples of inorganic pigments include titanium white, zinc white, petal, vermilion, ultramarine, cobalt blue, titanium yellow, yellow lead, and carbon black. These may be used alone or in combination depending on the application. Although selected and used, titanium white (titanium oxide) is preferably used. These inorganic pigments have a high effect of concealing the base, and also have an effect of cutting off ultraviolet rays. Furthermore, there is an effect of preventing blocking in the production process of the decorative sheet.

The content ratio of the inorganic pigment is preferably in the range of 5 to 300 parts by mass with respect to 100 parts by mass of the urethane resin. The effect as an inorganic pigment can fully be exhibited as it is 5 mass parts or more. On the other hand, when the content ratio of the inorganic pigment is too large, the elongation rate of the urethane resin composition is reduced. However, if it is 300 parts by mass or less, sufficient toughness is maintained even if the elongation rate is reduced.
The particle size of the inorganic pigment is preferably 5 μm or less. If it is 5 μm or less, there is no problem that cracks are generated starting from the inorganic particles. From the above points, the particle size is preferably 2 μm or less.

When the thickness of the colored layer is 1 μm or more, the impact, tensile force or shearing force applied to the surface protective layer 4 during bending can be relaxed, and the occurrence of cracks in the surface protective layer 5 can be suppressed. . Further, when it is 10 μm or less, blocking can be suppressed in the production process of the decorative sheet, and when the printing surface comes into contact with the guide roll that leads the printing paper, the printing ink is transferred to the guide roll. There is no inconvenience. From the above points, the thickness of the colored 3 is more preferably in the range of 1 to 6 μm, and further preferably in the range of 1 to 4 μm.
Moreover, the coating amount of the urethane resin composition forming the colored layer is usually in the range of 0.5 to 10 g / m ² , more preferably in the range of 0.5 to 6 g / m ² , still more preferably. in the range of 0.5 to 5 g / m ^2.

[Roughness imparting layer]
Next, the unevenness imparting layer 4 is made of a urethane-based resin composition containing unevenness imparting fine particles having an average particle diameter of 1 to 7 μm. By adopting a urethane-based resin, the irregularity-imparting layer contributes to the suppression of the occurrence of cracks in the surface protective layer 5 by a synergistic effect with the above-described colored layer, and includes irregularity-imparting fine particles, so that it is projected on the decorative sheet. Gives sex. The urethane resin used for the unevenness imparting layer can be used without particular limitation as long as it is a urethane resin usually used for decorative sheets, and a two-component curable urethane resin is particularly preferable.

<Roughness imparting fine particles>
Various fine particles are used as the fine particles to be used in the uneven layer, and inorganic fine powders, organic fillers, and the like are used. Examples of the inorganic fine powder include silica, clay, heavy calcium carbonate, light calcium carbonate, precipitated barium sulfate, calcium silicate, synthetic silicate, and fine silicate powder. Organic fillers include acrylic, urethane, Examples include fillers made of nylon, polypropylene, urea resins, styrene crosslinked fillers, benzoguanamine crosslinked fillers, and the like. Here, the filler also contains beads.

  The average particle diameter of the unevenness-imparting fine particles needs to be 1 to 7 μm. If the average particle diameter of the unevenness-imparting fine particles is within the above range, excellent marker erasability can be obtained, and sufficient glossiness can be obtained. Since it is possible to obtain an erasing effect, it is possible to obtain excellent projectability. Here, the average particle diameter of the unevenness imparting fine particles is measured by a Coulter counter method or a laser diffraction method.

The content of the unevenness-imparting fine particles contained in the unevenness-imparting layer is the same as the content of the unevenness-providing fine particles contained in the surface protective layer, which will be described later, in consideration of the coatability of the urethane-based resin composition containing the unevenness-providing fine particles. If it chooses according to it, since the decorative sheet excellent in projection property and marker erasability is obtained, it is preferable.
Specifically, the content of the unevenness imparting fine particles contained in the unevenness providing layer is such that the content of the unevenness imparting fine particles contained in the surface protective layer is less than 1 part by mass with respect to 100 parts by mass of the resin solid content of the surface protective layer. In this case, the range of 20 to 60 parts by mass is preferable with respect to 100 parts by mass of the resin solid content of the irregularity imparting layer. In this case, the average particle diameter of the irregularity imparting fine particles used in the irregularity imparting layer is 4 to 7 μm. It is particularly preferred. Further, when the content of the irregularity-providing fine particles contained in the surface protective layer is 1 part by mass or more and less than 4.5 parts by mass with respect to 100 parts by mass of the resin solid content of the surface protective layer, the irregularity-providing fine particles contained in the irregularity-providing layer The content of is preferably in the range of 5 to 60 parts by mass with respect to 100 parts by mass of the resin solid content of the irregularity-imparting layer, and the content of the irregularity-providing fine particles contained in the surface protective layer is the resin solid content of the surface protective layer. In the case of 4.5 parts by mass or more and 6 parts by mass or less with respect to 100 parts by mass, the content of the irregularity imparting fine particles contained in the irregularity imparting layer is 1 to 100 parts by mass of the resin solid content of the irregularity imparting layer. A range of 15 parts by weight is preferred. Thus, in the present invention, in order to obtain a decorative sheet having excellent projectability and marker erasability, the average particle diameter and content of the irregularity-providing fine particles contained in the irregularity-providing layer and the irregularity-providing fine particles contained in the surface protective layer It is important to adjust the content of.

The thickness of the unevenness providing layer is preferably in the range of 0.5 to 10 μm, more preferably in the range of 0.5 to 5 μm, and still more preferably in the range of 0.5 to 3 μm. If the thickness of the unevenness providing layer is within the above range, the impact, tensile force or shearing force applied to the surface protective layer 5 during bending can be reduced while imparting excellent projectability to the decorative sheet of the present invention. It is possible not only to suppress the occurrence of cracks in the surface protective layer 5, but also to suppress blocking in the production process of the decorative sheet, and when the printing surface comes into contact with the guide roll that leads the printing paper In addition, there is no inconvenience that the printing ink is transferred to the guide roll.
Further, the coating weight of the urethane resin composition for forming irregularities imparting layer is generally in the range of 0.2 to 10 g / m ^2, more preferably in the range of 0.2-5 g / m ^2, more preferably Is in the range of 0.2-3 g / m ² .

[Hidden layer]
Next, as shown in FIG. 2, the decorative sheet of the present invention can be further laminated with a concealing layer 6 via an adhesive layer 7 on the opposite side of the colored layer. Even when the base material 2 is transparent and when the base material 2 is concealed and colored, it can be formed in order to stabilize the concealability.
It does not specifically limit as a material which comprises the concealment layer 6, A vinyl chloride resin film, an olefin film, a polyester film etc. can be used. Among these, from the viewpoint of suppressing the occurrence of cracks in the surface protective layer 5, it is preferable to use a resin film similar to the substrate 2, more preferably a PET film, and more preferably a polyester film such as a biaxially stretched PET film. is there. In consideration of concealability, design properties, cushioning properties, and environment, an olefin film, particularly a polypropylene film is preferable.

The film constituting the masking layer 6 usually contains a colorant in order to exhibit the function as the masking layer. The kind of the colorant is not particularly limited, and the same colorant as that which can be used for coloring the base material 2 can be used.
Although there is no restriction | limiting in particular as the thickness of the film which comprises the concealing layer 6, The range of 25-100 micrometers is preferable. When the thickness is 25 μm or more, a sufficient hiding effect is obtained, and when the thickness is 100 μm or less, the surface protective layer 5 is not extended more than necessary due to the curvature, and the generation of cracks can be further suppressed.
Although the formation method of the concealing layer 6 is not particularly limited, a method that can be formed so as to cover the entire base material 2 (entire solid surface) is preferable. For example, a roll coating method, a knife coating method, an air knife coating method, a die coating method, a lip coating method, a comma coating method, a kiss coating method, a flow coating method, a dip coating method and the like are preferable.

[Adhesive layer]
There is no restriction | limiting in particular as a material used for the adhesive bond layer 7, A well-known adhesive can be used in the field of a decorative sheet. Specific examples include thermoplastic resins such as polyamide resin, acrylic resin and vinyl acetate resin, and curable resins such as thermosetting urethane resin. Further, a two-component curable polyurethane resin or polyester resin using isocyanate as a curing agent can also be applied. Among these, a thermoplastic resin is preferable because it functions as a cushion layer and has an effect of suppressing cracks in the surface protective layer 5 during processing of the decorative steel sheet.
Although there is no restriction | limiting in particular in the thickness of the adhesive bond layer 7, Usually, the thickness after drying is the range of 3-50 micrometers.

[Pattern pattern layer]
The decorative sheet of the present invention may be provided with a pattern layer (not shown) between the base 2 and the colored layer 3 or on the back side of the base 2 (opposite side of the colored layer 3). The design pattern layer imparts design properties with a desired design to the decorative sheet and the decorative steel plate, and the type of the design is not particularly limited. For example, a wood grain pattern, a stone pattern, a grain pattern, a tiled pattern, a brickwork pattern, a cloth pattern, a leather pattern, a geometric figure, a character, a symbol, an abstract pattern, and the like.

The method for forming the pattern layer is not particularly limited. For example, a colored ink or coating obtained by dissolving (or dispersing) a known colorant (dye or pigment) in a solvent (or dispersion medium) together with a binder resin. What is necessary is just to form by the printing method etc. which used the agent.
Examples of colorants include inorganic pigments such as carbon black, titanium white, zinc white, petal, bitumen, cadmium red; azo pigments, lake pigments, anthraquinone pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, dioxazine pigments. Organic pigments such as: metal powder pigments such as aluminum powder and bronze powder; pearlescent pigments such as titanium oxide-coated mica and bismuth oxide chloride; fluorescent pigments; These colorants can be used alone or in admixture of two or more. These colorants may further contain fillers such as silica, extender pigments such as organic beads, neutralizing agents, surfactants and the like.

Examples of the binder resin include acrylic resins, styrene resins, polyester resins, urethane resins, chlorinated polyolefin resins, vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, alkyd resins, petroleum Resin, ketone resin, epoxy resin, melamine resin, fluorine resin, silicone resin, fiber derivative, rubber resin and the like. These resins can be used alone or in admixture of two or more.
Examples of the solvent (or dispersion medium) include petroleum-based organic solvents such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; ethyl acetate, butyl acetate, 2-methoxyethyl acetate, acetic acid -2-Ethoxyethyl and other ester organic solvents; methyl alcohol, ethyl alcohol, normal propyl alcohol, isopropyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol and other alcohol organic solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketone organic solvents; diethyl ether, dioxane, tetrahydrofuran, etc. organic solvents; dichloromethane, carbon tetrachloride, trichloroethylene, tetra Chlorinated organic solvents such as Roroechiren; and inorganic solvents such as water. These solvents (or dispersion media) can be used alone or in admixture of two or more.

Examples of the printing method used for forming the pattern layer include a gravure printing method, an offset printing method, a screen printing method, a flexographic printing method, an electrostatic printing method, and an inkjet printing method. When forming a solid pattern pattern layer, for example, roll coating method, knife coating method, air knife coating method, die coating method, lip coating method, comma coating method, kiss coating method, flow coating method, dip coating Various coating methods such as a coating method may be mentioned. In addition, a hand-drawn method, an ink sink method, a photographic method, a transfer method, a laser beam drawing method, an electron beam drawing method, a partial vapor deposition method such as a metal, an etching method, or the like may be used.
The thickness of the pattern layer is not particularly limited, and can be set as appropriate according to product characteristics, but the layer thickness after drying is about 0.1 to 10 μm.

[Surface protective layer]
<Ionizing radiation curable resin composition>
The surface protective layer 5 is composed of a material obtained by crosslinking and curing the ionizing radiation curable resin composition. Here, the ionizing radiation curable resin composition has an energy quantum capable of crosslinking and polymerizing molecules in an electromagnetic wave or charged particle beam, that is, crosslinked and cured by irradiation with ultraviolet rays or electron beams. A resin composition is shown. Specifically, it can be appropriately selected from polymerizable monomers, polymerizable oligomers or prepolymers conventionally used as ionizing radiation curable resin compositions.
Typically, as the polymerizable monomer, a (meth) acrylate monomer having a radical polymerizable unsaturated group in the molecule is preferable, and among them, a polyfunctional (meth) acrylate is preferable. Here, “(meth) acrylate” means “acrylate or methacrylate”. The polyfunctional (meth) acrylate is not particularly limited as long as it is a (meth) acrylate having two or more ethylenically unsaturated bonds in the molecule. Specifically, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, polyethylene glycol di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified diphosphate ( (Meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylo Propane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris ( Acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, etc. Is mentioned. These polyfunctional (meth) acrylates may be used singly or in combination of two or more.

  In the present invention, a monofunctional (meth) acrylate can be used in combination with the polyfunctional (meth) acrylate as long as the object of the present invention is not impaired, for the purpose of lowering the viscosity. Examples of monofunctional (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl ( Examples include meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and isobornyl (meth) acrylate. These monofunctional (meth) acrylates may be used alone or in combination of two or more.

  Next, as the polymerizable oligomer, an oligomer having a radical polymerizable unsaturated group in the molecule, for example, epoxy (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, polyether (meth) acrylate The system etc. are mentioned. Here, the epoxy (meth) acrylate oligomer can be obtained, for example, by reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolak type epoxy resin and esterifying it. . Further, a carboxyl-modified epoxy (meth) acrylate oligomer obtained by partially modifying this epoxy (meth) acrylate oligomer with a dibasic carboxylic acid anhydride can also be used. The urethane (meth) acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reaction of polyether polyol or polyester polyol and polyisocyanate with (meth) acrylic acid. Examples of polyester (meth) acrylate oligomers include esterification of hydroxyl groups of polyester oligomers having hydroxyl groups at both ends obtained by condensation of polycarboxylic acid and polyhydric alcohol with (meth) acrylic acid, It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding an alkylene oxide to a carboxylic acid with (meth) acrylic acid. The polyether (meth) acrylate oligomer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid.

  Furthermore, other polymerizable oligomers include polybutadiene (meth) acrylate oligomers with high hydrophobicity that have (meth) acrylate groups in the side chain of polybutadiene oligomers, and silicone (meth) acrylate oligomers that have polysiloxane bonds in the main chain. In a molecule such as an aminoplast resin (meth) acrylate oligomer modified with an aminoplast resin having many reactive groups in a small molecule, or a novolak type epoxy resin, bisphenol type epoxy resin, aliphatic vinyl ether, aromatic vinyl ether, etc. There are oligomers having a cationic polymerizable functional group.

When an ultraviolet curable resin composition is used as the ionizing radiation curable resin composition, it is desirable to add about 0.1 to 5 parts by mass of the photopolymerization initiator with respect to 100 parts by mass of the resin composition. The initiator for photopolymerization can be appropriately selected from those conventionally used and is not particularly limited. For example, for a polymerizable monomer or polymerizable oligomer having a radically polymerizable unsaturated group in the molecule. Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2 -Phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propane-1 - 4- (2-hydroxyethoxy) phenyl-2 (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4′-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2 -Tertiary butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal It is done.
Examples of polymerizable oligomers having a cationic polymerizable functional group in the molecule include aromatic sulfonium salts, aromatic diazonium salts, aromatic iodonium salts, metallocene compounds, and benzoin sulfonic acid esters.
Moreover, as a photosensitizer, p-dimethylbenzoic acid ester, tertiary amines, a thiol type sensitizer, etc. can be used, for example.
In the present invention, it is preferable to use an electron beam curable resin composition as the ionizing radiation curable resin composition. This is because the electron beam curable resin composition can be made solvent-free, is more preferable from the viewpoint of environment and health, and does not require a photopolymerization initiator and can provide stable curing characteristics.

(Concavity and convexity imparting fine particles)
In the decorative sheet of the present invention, it is preferable that the surface protective layer 5 includes irregularities-providing fine particles from the viewpoint of obtaining excellent projectability, and the content ratio of the ionizing radiation curable resin composition is excellent. From the viewpoint of obtaining coatability and the like, 6 parts by mass or less is preferable with respect to 100 parts by mass of the resin solid content of the surface protective layer. In addition, as described above, the content ratio can be adjusted in a preferable range in relation to the average particle diameter of the unevenness-providing fine particles contained in the unevenness-imparting layer and the content thereof, from the viewpoint of facilitating this adjustment. Is preferably 1 part by mass or more and less than 4.5 parts by mass.

As the unevenness-imparting fine particles used in the surface protective layer, the unevenness-imparting fine particles used in the unevenness-imparting layer can be preferably mentioned, and organic fillers are more preferable than generally used inorganic fillers such as silica. This is because when the irregularity imparting fine particles are added, cracks may occur from the interface between the resin constituting the surface protective layer and the irregularity imparting fine particles, but the organic filler is more familiar with the ionizing radiation curable resin, and the interface This is because the occurrence of cracks due to the occurrence of cracks is difficult. Among organic fillers, a filler made of urea resin is particularly preferable.
The average particle diameter of the unevenness imparting fine particles is preferably 1 to 7 μm, and more preferably 1 to 5 μm. If the average particle size of the irregularity-providing fine particles is within the above range, cracks generated from the interface between the resin constituting the surface protective layer and the irregularity-providing fine particles can be suppressed, so that excellent marker erasability can be obtained. In addition, since a sufficient matte effect can be obtained, excellent projectability can also be obtained.

(Isocyanate curing agent)
In the steel sheet decorative sheet of the present invention, the ionizing radiation curable resin composition preferably contains an isocyanate curing agent. By containing an isocyanate-based curing agent, the adhesion with the irregularity-imparting layer is improved, and further, the adhesion between the ionizing radiation curable resins is improved, so that the occurrence of cracks in the surface protective layer is suppressed, which is excellent. The marker erasability can be obtained, and even when time elapses, it is possible to suppress deterioration in performance such as bending workability, excellent stain resistance and scratch resistance.
As an isocyanate type hardening | curing agent used here, a terminal isocyanate prepolymer is preferable, and also urethane polycarbonate or polyester urethane is preferable. By using these, the adhesiveness with the unevenness imparting layer becomes higher.

(Various additives)
Moreover, various additives can be mix | blended with the ionizing radiation-curable resin composition in this invention according to the desired physical property of the cured resin layer obtained. Examples of the additive include a weather resistance improver, an abrasion resistance improver, a polymerization inhibitor, a crosslinking agent, an infrared absorber, an antistatic agent, an adhesion improver, a leveling agent, a thixotropic agent, and a coupling agent. , Plasticizers, antifoaming agents, fillers, solvents, colorants and the like.

  Here, as the weather resistance improving agent, an ultraviolet absorber or a light stabilizer can be used. The ultraviolet absorber may be either inorganic or organic, and as the inorganic ultraviolet absorber, titanium dioxide, cerium oxide, zinc oxide or the like having an average particle diameter of about 5 to 120 nm can be preferably used. Examples of the organic ultraviolet absorber include benzotriazole-based compounds, specifically 2- (2-hydroxy-5-methylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-). Amylphenyl) benzotriazole, 3- [3- (benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl] propionic acid ester of polyethylene glycol, and the like. On the other hand, examples of the light stabilizer include hindered amines, specifically 2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2′-n-butylmalonate bis (1,2,2). , 6,6-pentamethyl-4-piperidyl), bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl)- 1,2,3,4-butanetetracarboxylate and the like. Further, as the ultraviolet absorber or light stabilizer, a reactive ultraviolet absorber or light stabilizer having a polymerizable group such as a (meth) acryloyl group in the molecule can be used.

Examples of the wear resistance improver include spherical particles such as α-alumina, silica, kaolinite, iron oxide, diamond, and silicon carbide. Examples of the particle shape include a sphere, an ellipsoid, a polyhedron, a scale shape, and the like. Although there is no particular limitation, a spherical shape is preferable. Organic materials include synthetic resin beads such as cross-linked acrylic resin and polycarbonate resin. The particle size is usually about 30 to 200% of the film thickness. Among these, spherical α-alumina is particularly preferable because it has high hardness and a large effect on improving wear resistance, and it is relatively easy to obtain spherical particles.
Examples of the polymerization inhibitor include hydroquinone, p-benzoquinone, hydroquinone monomethyl ether, pyrogallol, and t-butylcatechol.
As the crosslinking agent, for example, fluorinated acrylate, silicone acrylate, polyisocyanate compound, epoxy compound, metal chelate compound, aziridine compound, oxazoline compound and the like are used. Of these, fluorinated acrylate and silicone acrylate are particularly preferable.
As the filler, for example, barium sulfate, talc, clay, calcium carbonate, aluminum hydroxide and the like are used.
Examples of the colorant include known coloring pigments such as quinacridone red, isoindolinone yellow, phthalocyanine blue, phthalocyanine green, titanium oxide, and carbon black.
As the infrared absorber, for example, a dithiol metal complex, a phthalocyanine compound, a diimmonium compound, or the like is used.

(Formation of surface protective layer)
In the present invention, the polymerizable monomer and polymerizable oligomer, which are the electron beam curing components, and various additives are homogeneously mixed at predetermined ratios to prepare a coating liquid comprising an electron beam curable resin composition. To do. The viscosity of the coating solution is not particularly limited as long as it is a viscosity capable of forming an uncured resin layer on the surface of the substrate by a coating method described later.
In the present invention, the coating liquid prepared in this way is applied to the surface of the substrate so that the thickness after curing is 1 to 20 μm, gravure coating, bar coating, roll coating, reverse roll coating, Coating is performed by a known method such as comma coating, preferably gravure coating, to form an uncured resin layer.
The preferable film thickness after curing is appropriately determined according to the type of resin used in the range of 1 to 20 μm. When the resin composition is composed of a hard system, the relatively thin film thickness is less likely to cause cracks in the surface protective layer. Conversely, when the resin composition is a soft system, the film thickness is relatively thick. Cracks in the surface protective layer are unlikely to occur.

The uncured resin layer formed as described above is irradiated with an electron beam to cure the uncured resin layer. The acceleration voltage can be appropriately selected according to the resin to be used and the thickness of the layer, but it is preferable to cure the uncured resin layer at an acceleration voltage of about 70 to 300 kV.
In electron beam irradiation, the transmission capability increases as the acceleration voltage increases. Therefore, when using a base material that deteriorates due to the electron beam as the base material, the transmission depth of the electron beam and the thickness of the resin layer are substantially equal. By selecting the accelerating voltage so as to be equal to each other, it is possible to suppress the irradiation of the electron beam to the base material, and to minimize the deterioration of the base material due to the excessive electron beam.
The irradiation dose is preferably an amount that saturates the crosslink density of the resin layer, and is usually selected in the range of 5 to 300 kGy.

  The electron beam source is not particularly limited, and for example, various electron beam accelerators such as a Cockloft Walton type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type are used. be able to.

  The surface protective layer thus formed has various functions by adding various additives, for example, a so-called hard coat function, anti-fogging coat function, and anti-fouling coat having high hardness and scratch resistance. A function, an antiglare coating function, an antireflection coating function, an ultraviolet shielding coating function, an infrared shielding coating function, and the like can also be imparted.

[Decorative steel plate]
The decorative sheet of the present invention is used as a decorative steel sheet by sticking to a steel sheet. Examples of the steel plate to be adhered include metal materials such as iron, aluminum, and copper, and these may be subjected to surface treatment such as hot dip galvanizing or electrogalvanizing. Moreover, the shape of a to-be-adhered body is not specifically limited, For example, shapes, such as a flat plate, a curved surface board, a polygonal column, can be employ | adopted arbitrarily.
Moreover, there is no restriction | limiting in particular about the thickness of a steel plate, Usually, it is about 0.2-1 mm. In addition, in order to provide the concealability, the steel plate which is a to-be-adhered body may be directly colored on the steel plate and provided with a coating layer.

The adhesive or pressure-sensitive adhesive used for laminating the steel sheet as the adherend and the decorative sheet is not particularly limited, and any adhesive or pressure-sensitive adhesive known in the field of decorative sheets can be used. As the adhesive, the same adhesive as that used in the adhesive layer 7 for adhering the hiding layer 6 can be used. Further, as the pressure-sensitive adhesive, an acrylic, urethane-based, silicone-based, rubber-based or the like can be appropriately selected and used. Among these, from the viewpoint of weather resistance and the like, an acrylic pressure-sensitive adhesive mainly composed of a polymer or copolymer of an acrylic monomer such as acrylic acid ester or methacrylic acid ester is preferable, and in particular, n-butyl acrylate, 2- Ethylhexyl acrylate and the like are suitable.
Moreover, a crosslinking agent can also be added and specifically, an isocyanate type, a metal chelate, an epoxy type, and a melamine type are mentioned.
Although there is no restriction | limiting in particular about the thickness of this adhesive agent or an adhesive, Usually, it is the range of 1-100 micrometers.

  The steel sheet to which the decorative sheet of the present invention is attached is suitably used for, for example, a whiteboard that requires marker erasure and projection properties, and a wall surface of a unit bath that is easily contaminated, and effectively utilizes the features of the decorative sheet of the present invention. From the viewpoint, it is particularly preferably used for a whiteboard. In addition, for building interior materials such as walls and ceilings, surface materials for fittings such as doors, door frames and window frames, surface materials for construction parts such as skirts and skirting boards, surface materials for furniture such as fences and cabinets, etc. Can also be used. Further, the decorative sheet itself can be used as a laminate material, a wrapping material, or the like for a building material member without using a steel plate as an adherend. For example, the decorative sheet of the present invention may be attached to the surface of a steel plate substrate used in a bathroom or the like for decoration.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by this example.
(Evaluation method)
1. Evaluation of marker erasability The decorative steel sheet produced in each Example and Comparative Example was written with a marker ("Knockle (trade name)" manufactured by Pentel Co., Ltd.) and the wiped state was evaluated according to the following evaluation criteria. .
A: The marker was easily wiped off without being contaminated with the marker.
○: The marker could be wiped off carefully.
X: The marker could not be completely wiped off.
2. Evaluation of Projectivity For the decorative steel sheets produced in each of the examples and comparative examples, the gloss value was measured under the condition of an incident angle of 60 degrees using a gloss meter (“micro-TRI-gloss” manufactured by Gardner). The lower the number, the lower the gloss (low gloss), and the better the projection.
A: The gloss value of the surface protective layer was less than 30.
○: The gloss value of the surface protective layer was 30 or more and less than 40.
Δ: The gloss value of the surface protective layer was 40 or more and less than 50.
X: The gloss value of the surface protective layer was 50 or more.

Example 1
As the base material 2, a polyester urethane resin (E-Nissei Kogyo Co., Ltd.) “E-made by Daiichi Seika Kogyo Co., Ltd.” on the back side of a biaxially stretched transparent PET film (“Cosmo Shine A4300” manufactured by Toyobo Co., Ltd.) having a thickness of 50 μm 295 L) ”(trade name)), a base material on which a 60 μm-thick polypropylene film (“ PB-013 ”(trade name) manufactured by Mitsubishi Chemical MKV Co., Ltd.) was attached was prepared. A soft urethane resin (elongation rate: 780%, Tg: −41 ° C.) is used as a binder on the surface side of the base material, and titanium white (titanium oxide, particle size: 0.2 to 0.3 μm) is contained by 50 mass%. Ink was applied at a coating amount of 2.8 g / m ² to form a colored layer 3. After drying, a filler-containing ink in which a soft urethane resin is used as a binder and a silica filler (average particle size: 1.3 μm) is contained in a proportion of 53 parts by mass with respect to 100 parts by mass of the soft urethane resin solid content. On the colored layer, the unevenness imparting layer 4 was formed by coating at a coating amount of 1 g / m ² .
Next, 60 parts by mass of ethylene oxide-modified trimethylolpropane ethylene oxide triacrylate, which is a trifunctional acrylate monomer, and 40 parts by mass of dipentaerythritol hexaacrylate, which is a hexafunctional acrylate monomer, are formed on the concavo-convex layer 4. 2 g / m ^{2 of} the electron beam curable resin composition to which 1.5 parts by mass of the polymer was added was applied by a gravure direct coater method. After the coating, an electron beam with an acceleration voltage of 165 kV and an irradiation dose of 50 kGy (5 Mrad) was irradiated to cure the electron beam curable resin composition, whereby the surface protective layer 5 was obtained. Next, curing was performed at 70 ° C. for 24 hours to obtain a decorative sheet 1. The thickness of the surface protective layer 5 was 1.5 μm.
The decorative sheet 1 was attached to a galvanized steel sheet having a thickness of 0.4 mm using a urethane-based adhesive to obtain a decorative steel sheet of the present invention.
The decorative steel sheet was evaluated by the above method. The evaluation results are shown in Table 1.

Examples 2 to 10 and Comparative Examples 1 and 2
In Example 1, the particle size of the filler forming the unevenness imparting layer 4 is shown in Table 1, and the filler (average particle size: 5 μm) made of urea resin is added to the electron beam curable resin composition. A decorative steel sheet was obtained in the same manner as in Example 1 except that the amount shown in Table 1 was added. The results of evaluation of the obtained decorative steel sheet in the same manner as in Example 1 are shown in Table 1. In addition, the content rate of the filler which consists of urea-type resin shown in Table 1 is a mass part with respect to 100 mass parts of resin solid content of the said resin composition.

Examples 11 to 20 and Comparative Examples 3 and 4
In Example 1, the particle size and the content ratio of the filler forming the unevenness imparting layer 4 are shown in Table 2, and the filler made of urea resin to be contained in the electron beam curable resin composition is shown in Table 2. A decorative steel sheet was obtained in the same manner as in Example 1 except that the amount shown in (1) was added. The results of evaluation of the obtained decorative steel sheet in the same manner as in Example 1 are shown in Table 2.

Examples 21 to 30 and Comparative Examples 5 and 6
In Example 1, the particle size and content ratio of the filler forming the unevenness imparting layer 4 are shown in Table 3, and the filler made of urea-based resin to be contained in the electron beam curable resin composition is shown in Table 3. A decorative steel sheet was obtained in the same manner as in Example 1 except that the amount shown in (1) was added. Table 3 shows the results of evaluating the decorative steel sheet obtained in the same manner as in Example 1.

  The steel sheet decorative sheet and the steel sheet using the decorative sheet of the present invention have excellent marker erasability even when subjected to bending while having excellent projectability. The decorative sheet and decorative steel sheet according to the present invention include a building interior material such as a wall and a ceiling, a surface material of a fitting such as a door, a door frame, and a window frame, a surface material of a construction member such as a curb and a baseboard, a fence, and a cabinet. It can also be used for furniture surface materials. In particular, it is suitably used for whiteboards that require marker erasure and projectability, and wall surfaces of unit baths that are easily soiled.

It is a schematic diagram which shows the cross section of the decorative sheet of this invention. It is a schematic diagram which shows the cross section of the decorative sheet of this invention.

Explanation of symbols

1. Cosmetic sheet Base material 3. 3. Colored layer 4. Concavity and convexity imparting layer Surface protective layer 6. 6. Hiding layer Adhesive layer

Claims (6)

A decorative sheet for a steel sheet in which a colored layer, an unevenness imparting layer, and a surface protective layer are laminated in this order on a substrate, the colored layer is made of a urethane-based resin composition containing an inorganic pigment, and the unevenness imparting layer is It consists of a urethane-based resin composition containing unevenness-imparting fine particles that are matting agents having an average particle diameter of 1 to 7 μm, and is a layer provided over the entire surface, and the surface protective layer contains organic filler as unevenness-imparting fine particles that are matting agents. A decorative sheet for a steel sheet obtained by crosslinking and curing an ionizing radiation curable resin composition.   The makeup for steel sheet according to claim 1, wherein the surface protective layer includes irregularities-providing fine particles, and the content ratio of the irregularities-providing fine particles is 6 parts by mass or less with respect to 100 parts by mass of the resin solid content of the surface protective layer. Sheet.   The decorative sheet for steel sheet according to claim 1 or 2, wherein the content ratio of the unevenness-imparting fine particles contained in the unevenness-imparting layer is 5 to 60 parts by mass with respect to 100 parts by mass of the resin solid content of the unevenness-imparting layer.   The said inorganic pigment is a titanium oxide, The decorative sheet for steel plates in any one of Claims 1-3.   The decorative sheet for steel sheet according to any one of claims 1 to 4, wherein the ionizing radiation curable resin composition is an electron beam curable resin composition.   A decorative steel sheet obtained by attaching the decorative sheet according to any one of claims 1 to 5 to a steel sheet.

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