Decorative sheet, decorative board, and inkjet ink for decorative sheet

Abstract

Provided are a decorative sheet and a decorative plate that are provided with both a highly bright feel and high design properties, and an inkjet ink for decorative sheets that is used in order to manufacture the decorative sheet and the decorative plate. The decorative sheet (10) according to an embodiment of the present invention comprises at least a brilliance layer (K1), which is a inkjet printing layer formed using an inkjet ink, provided on a base material sheet (1). The inkjet ink contains silver nanoparticles. The decorative plate (100) according to an embodiment of the present invention comprises a decorative sheet (10) and a substrate (5) positioned on the base-material-sheet (1) side of the decorative sheet (10). The inkjet ink for decorative sheets according to an embodiment of the present invention is an ink for forming a brilliance layer (K1) on a base material sheet (1) by inkjet printing, and contains silver nanoparticles.

Description

[Technical field]

[0001] The present invention relates to a decorative sheet, a decorative board, and an ink-jet ink for decorative sheets for use in interior materials and fittings such as wall materials, ceiling materials, floor materials, and fittings in buildings such as houses, furniture and fixtures, the exteriors of housing equipment and home appliances, and the interiors of vehicles such as automobiles. [Background technology]

[0002] Conventionally, for the purpose of obtaining a special design effect that reflects illumination light and exhibits brilliance, brilliant printed matter has been widely used for various applications in which brilliant patterns or the like are printed on a substrate using brilliant ink made by kneading brilliant pigments, such as metal powders such as scaly aluminum powder (aluminum flakes) and pearlescent pigments (pearl pigments) such as titanium dioxide-coated mica, into an appropriate binder resin (for example, Patent Documents 1 and 2).

[0003] For example, in the surface decoration of building materials, furniture, housings of home appliances, etc., a glittering layer is added to a wood grain pattern for the purpose of reproducing the shine, depth, and wood grain feel that are unique to natural wood by printing technology. In addition to wood grain patterns, various glittering decorative sheets and decorative boards (hereinafter simply referred to as "decorative sheets") that express glittering designs such as silk, pearl, and metallic tones in stone and abstract patterns are used in a wide range of fields.

[0004] By the way, various types of glittering pigments are commercially available with particle sizes ranging from a few μm to over 100 μm. For glittering decorative sheets that use printing techniques, metallic inks such as silver inks (sometimes called mirror inks, regel inks, hologram inks, or stellar inks depending on the powder shape) that contain glittering pigments, and pearl inks, are used, so glittering pigments with an average particle size of approximately 30 μm or less are usually used due to restrictions on the printability of these inks.

[0005] On the other hand, inkjet printing has been put to practical use in various fields and applications and has become familiar to us. For example, inkjet printing is often used in homes as an output device for personal computers or as a printer for New Year's cards and photos, and in industry, it is often used for commercial printing such as barcode printers, signs, POP, and advertising media.

[0006] The main advantage of inkjet printing is that the printers are relatively inexpensive and high image quality can be obtained. Also, even though it is called printing, it does not require printing plates, and the desired printed matter can be obtained using data from a computer or dedicated equipment. This does not just mean that the cost of printing plates can be saved, but also has many other advantages, such as shortening the time required for printing and simplifying the process of making prototypes and test prints, known as proofs.

[0007] However, in conventional decorative sheets, patterns were printed by gravure printing. Gravure printing has the advantage of being able to print large quantities at high speed. However, gravure printing is not economical when only a small amount of printing is required, and may not be suitable in terms of print quality when the pattern is complex. For this reason, the technology described in Patent Document 3 proposes using inkjet printing for printing on decorative sheets. In this case, for example, in order to improve the design of the decorative sheet, it is possible to mix a glittering pigment into the inkjet ink to impart glitter to the inkjet-printed layer.

[0008] However, as seen in Patent Documents 4 and 5, a problem with inkjet printing is that the nozzle inner diameter needs to be reduced to the order of 10 μm to eject minute droplets. On the other hand, since most photoluminescent pigments have a large particle size, inks in which photoluminescent pigments are dispersed can have problems with clogging in the nozzle, making stable ejection difficult. For this reason, it is generally difficult to print with inkjet inks containing photoluminescent pigments, and as in Patent Documents 1 and 2, the only way to print a photoluminescent layer is to use a solid film by coating or to print it by another method such as gravure printing, which often results in poor design and a complicated printing process. In other words, there was a problem that there were few conventional decorative sheets that had both high brightness and high design. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 4725226 [Patent Document 2] Patent No. 6107180 [Patent Document 3] JP 2001-71447 A [Patent Document 4] JP 2004-299378 A [Patent Document 5] Patent No. 4834981 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been devised in consideration of the above problems and circumstances, and has an object to provide a decorative sheet and decorative board having both high brightness and high designability, and an inkjet ink for decorative sheets used to manufacture the decorative sheet and decorative board. Specifically, the object of the present invention is to provide a decorative sheet and decorative board having a high brightness, and an inkjet ink for decorative sheets, which can be printed with a glittering picture print layer by inkjet printing using an ink containing silver nanoparticles. [Means for solving the problem]

[0011] In order to solve the above problems, a decorative sheet according to one embodiment of the present invention comprises at least an inkjet printed layer formed on a base sheet using an inkjet ink, the inkjet ink containing silver nanoparticles. A decorative board according to one aspect of the present invention includes the decorative sheet described above, and a substrate disposed on the base sheet side of the decorative sheet. Furthermore, an inkjet ink for decorative sheets according to one embodiment of the present invention is an inkjet ink for decorative sheets for forming a picture printed layer on a base sheet by inkjet printing, and contains silver nanoparticles. Effect of the Invention

[0012] According to the present invention, a decorative sheet and decorative plate having both high brightness and high designability, and an inkjet ink for decorative sheet used to manufacture the decorative sheet and decorative plate can be obtained. Specifically, according to the present invention, since an inkjet ink for decorative sheet containing silver nanoparticles is used, a glittering picture print layer can be printed using an inkjet printing method, and a decorative sheet and decorative plate having high brightness can be obtained without requiring a printing plate. [Brief description of the drawings]

[0013] [Figure 1]1 is a schematic cross-sectional view illustrating the configuration of a decorative sheet according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a schematic cross-sectional view illustrating the configuration of a decorative sheet according to a second embodiment of the present invention. [Diagram 3] FIG. 4 is a schematic cross-sectional view illustrating the configuration of a decorative sheet according to a third embodiment of the present invention. [Figure 4] FIG. 11 is a schematic cross-sectional view illustrating the configuration of a decorative sheet according to a fourth embodiment of the present invention. [Diagram 5] FIG. 11 is a schematic cross-sectional view illustrating the configuration of a decorative sheet according to a fifth embodiment of the present invention. [Figure 6] 1 is a schematic cross-sectional view illustrating the configuration of a decorative board provided with a decorative sheet according to a first embodiment of the present invention. [Figure 7] FIG. 2 is a diagram showing a scanning electron microscope image of silver nanoparticles observed after a toluene dispersion of silver nanoparticles obtained in Example 1 of the present invention was applied to a substrate and dried. [Figure 8] FIG. 2 is a diagram showing the particle size distribution and cumulative frequency (%) of the silver nanoparticles obtained in Example 1 of the present invention. [Figure 9] FIG. 2 is a diagram showing a scanning electron microscope image of silver nanoparticles observed after a n-butanol dispersion of silver nanoparticles obtained in Example 2 of the present invention was applied to a substrate and dried. [Figure 10] FIG. 13 is a diagram showing a scanning electron microscope image of silver nanoparticles observed after a n-butanol dispersion of the silver nanoparticles obtained in Example 3 of the present invention was applied to a substrate and dried. [Figure 11] FIG. 13 is a diagram showing a scanning electron microscope image of silver nanoparticles observed after a n-butanol dispersion of the silver nanoparticles obtained in Example 4 of the present invention was applied to a substrate and dried. [Figure 12] FIG. 13 is a diagram showing a scanning electron microscope image of silver nanoparticles observed after a n-butanol dispersion of silver nanoparticles obtained in Example 5 of the present invention was applied to a substrate and dried. [Figure 13] FIG. 13 is a diagram showing a scanning electron microscope image of silver nanoparticles observed after the aqueous dispersion of silver nanoparticles obtained in Example 6 of the present invention was applied to a substrate and dried. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the configurations of the decorative sheet and decorative board according to the embodiment of the present invention will be described with reference to the drawings. The same components are given the same reference numerals unless there is a reason for convenience. In each drawing, the thickness and ratio of the components may be exaggerated for ease of viewing, and the number of components may be reduced. In addition, the present invention is not limited to the following embodiments as they are, and can be embodied by appropriate combinations and modifications without departing from the spirit of the invention.

[0015] All of the decorative sheets according to the embodiments of the present invention have a common feature that they include at least an inkjet printed layer formed on a base sheet using an inkjet ink, and the inkjet ink contains silver nanoparticles. Whether the glossy layer, which is a printed layer that is given glossiness by including silver nanoparticles, is produced by an inkjet printing method can be easily determined by observing, for example, a wood grain pattern or other pattern expressed in the printed layer with a magnifying glass or the like, whether it is printed in brown or multiple colors such as red, blue, yellow, and black.

[0016] Traditionally, it has been difficult to make inkjet ink from photoluminescent pigments, and although there are devices capable of discharging them, they are limited in number. In addition, the brightness is often insufficient or excessive, making it difficult to print with the desired design. The inventors of the present application have discovered that by using an inkjet ink containing silver nanoparticles (hereinafter simply referred to as "silver nanoparticle ink") to print a photoluminescent layer and suitably selecting the particle size and concentration of the silver nanoparticles, it is possible to adjust the sense of brightness and enhance both the design and photoluminescence, making it possible to print and reproduce, for example, the fine lines and gradations that are characteristic of building materials, and pearl-like designs characterized by a pale luster that is difficult to express using ink that uses aluminum. The composition of the silver nanoparticle ink used in this embodiment will be described in detail below.

[0017] The surface of the silver nanoparticles used in this embodiment is covered with protective molecules containing an amine compound as a main component. The "main component" here refers to the component (molecule) that is most abundant among the multiple protective molecules covering the surface of the silver nanoparticles. The silver nanoparticles according to this embodiment have a median diameter (D50) in the range of 1 nm to 250 nm, and can be dispersed in a dispersion medium such as an organic solvent or water. If the median diameter (D50) of the silver nanoparticles is smaller than 1 nm, the visibility (brilliance) may decrease, and if the median diameter (D50) of the silver nanoparticles is larger than 250 nm, the dispersibility may decrease. The average primary particle diameter was determined from the particle size distribution measured in a 0.1% by mass dispersion using a Nanotrac UPA-EX150 particle size distribution analyzer (dynamic light scattering method, Nikkiso Co., Ltd.).

[0018] There is no limitation on the shape of the silver nanoparticles, but it is preferable that the silver nanoparticles include any one or more of spherical, flat, polygonal, etc. Flat silver nanoparticles have a large surface area, and are expected to have good visibility (brilliance) even in small amounts of particles. In addition, if the silver nanoparticles are spherical in shape, the size tends to be uniform, and it is expected that the silver nanoparticles will be arranged without gaps. For this reason, spherical silver nanoparticles are also expected to have good visibility (brilliance).

[0019] As the source of silver constituting the silver nanoparticles, among silver-containing compounds, a silver compound that is easily decomposed by heating to generate metallic silver is preferably used. Examples of such silver compounds include silver carboxylates, which are compounds of silver with carboxylic acids such as formic acid, acetic acid, oxalic acid, malonic acid, benzoic acid, and phthalic acid, as well as silver chloride, silver nitrate, and silver carbonate. Among these silver compounds, silver oxalate is preferably used because it easily produces metal by decomposition and is less likely to produce impurities other than silver. Silver oxalate has a high silver content, and when heated, the oxalate ions are decomposed and removed as carbon dioxide. This means that no reducing agent is required, and metallic silver can be obtained by thermal decomposition without leaving any impurities behind, which is an advantage.

[0020] When the silver compound is thermally decomposed, alcohol, fatty acid, polymer, etc. may be added. The addition of these is expected to adjust the particle size, change the dispersion medium, and improve the dispersion stability. Examples of alcohol include methanol, ethanol, 1-propanol, etc., fatty acids include oleic acid, linoleic acid, etc., and polymers include polyvinylpyrrolidone, gelatin, etc.

[0021] The amine compound that protects the surface of the silver nanoparticles is not particularly limited in structure, but a primary amino group, RNH, is preferred because of its ease of coordination with silver atoms. 2 (R is a hydrocarbon group). Secondary amino groups can also be coordinated, but their reactivity is lower than that of primary amino groups. A diamine compound having multiple amino groups may also be used. In the case of a diamine compound, if the compound has a primary amino group and a tertiary amino group, the primary amino group is selectively coordinated to the silver atom, and the bulky tertiary amino group faces outward, so that the surface of the silver nanoparticles is easily protected.

[0022] Examples of the amine include ethylamine, n-propylamine, isopropylamine, 1,2-dimethylpropylamine, n-butylamine, isobutylamine, n-nonylamine, n-aminodecane, n-aminoundecane, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, and n-oleylamine. Further, examples of diamines include, but are not limited to, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dimethyl-1,5-diamino-2-methylpentane, N,N-dimethyl-1,6-hexanediamine, N,N-dibutylaminopropane, N,N-diisobutyl-1,3-diaminopropane, etc. Also, a plurality of different amines may be used simultaneously.

[0023] Thus, the silver nanoparticles used in this embodiment may be silver nanoparticles produced, for example, by mixing silver oxalate and amine and thermally decomposing them to form a silver oxalate amine complex. Techniques for producing silver nanoparticles by thermally decomposing silver oxalate and amine are described, for example, in JP 2012-162767 A and JP 5574761 A. The above-mentioned method does not require mixing a reducing agent for reducing silver ions, and it is possible to produce silver nanoparticles by a simple method. In addition, the silver nanoparticles obtained by the above-mentioned method have amino groups of amine molecules mainly coordinated to the silver particle surface, and have high dispersibility in a dispersion medium. In addition, since the particle size and dispersibility can be changed depending on the manufacturing conditions, the silver nanoparticle ink using these can express a design in which the brilliance is adjusted depending on the silver nanoparticles used and their concentration.

[0024] There is also a method for producing silver nanoparticles by using polyvinylpyrrolidone as a molecule that coordinates to the surface of the particles when silver oxalate is thermally decomposed (see Reference 1 below). The silver nanoparticles synthesized by this method include plate-shaped ones, which are expected to have a high sense of brightness when printed. [Reference 1] T. Togashi, S. Ojima, I. Sato, K. Kanaizuka, and M. Kurihara, Chem. Lett., 2016, 45, 646-648

[0025] The amount of silver nanoparticles added to the coating liquid is preferably, for example, in the range of 1% by mass to 50% by mass relative to the dispersion medium. In addition, since the metallic luster is enhanced, the amount of silver nanoparticles added is particularly preferably 15% by mass or more. If the amount of silver nanoparticles added is less than 1% by mass, the visibility (brilliance) of the printed matter decreases, and if it exceeds 50% by mass, the dispersibility may decrease.

[0026] A dispersant may be used when dispersing the silver nanoparticles according to this embodiment in a solvent or the like used as a dispersion medium. Dispersants can be broadly classified into anionic, cationic, and nonionic, and are appropriately selected according to the electric potential of the particle surface and the dispersion medium. Anionic types are typically sulfate ester type, phosphate ester type, carboxylic acid type, and sulfonic acid type, and many of them have an ethylene oxide (EO)-added molecular structure. Cationic types are quaternary ammonium salt types, and can be classified into Cl salt type, non-Cl salt type, and EO-added type. Nonionic types can be broadly classified into alkylene oxide-added type and carcanolamide type. Since the surface modification of the silver nanoparticles according to this embodiment is an amine complex, anionic types are particularly preferred. Specifically, polyoxyethylene alkyl ether phosphoric acid (salt), polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether succinate, etc. are preferred, and polyoxyethylene alkyl ether phosphoric acid (salt) is particularly preferred. Specific examples include, but are not limited to, Phosphanol RB-40, RD-510Y, RD720N, RL-210, RS-410 (Toho Chemical Industry Co., Ltd.), NIKKOL DDP-8NV, DDP-2, DDP-4, DDP-6, DDP-8, DDP-10 (Nikko Chemicals Co., Ltd.), Plysurf A212C, A215C, A208F, M208F, A208A, A208B, A210B, A219B, DB-01, AL, DBS (Dai-ichi Kogyo Seiyaku Co., Ltd.), and the like.

[0027] The silver nanoparticle ink according to this embodiment may contain additives such as a pigment, a defoaming agent, a leveling agent, and a curing agent in addition to the dispersant described above. Examples of the dispersion medium contained in the silver nanoparticle ink according to this embodiment include water, ethanol, 2-propanol, 1-butanol, methyl ethyl ketone, ethyl acetate, toluene, cyclohexanone, terpenes such as terpineol, etc. The dispersion medium may be a suitable mixture of the above-mentioned components according to the desired physical properties of the coating liquid.

[0028] The blending ratio of the above components in the coating liquid is not particularly limited, but when it is necessary to prevent the coating liquid from drying in the nozzle, such as in the inkjet printing method, it is more preferable that the inkjet coating liquid (silver nanoparticle ink) contains at least one organic solvent with a boiling point of 110°C or higher, such as glycerin, propylene glycol, 1-butanol, cyclohexanone, and terpineol, in total at 1% by mass or more. If the content of the above components in the coating liquid is less than 1% by mass, the coating liquid is more likely to dry, which may cause clogging of the nozzle. There is no upper limit to the content of the above components, but if the content is too high, the time required for drying the coating liquid may be extended.

[0029] The color of the layer printed with the silver nanoparticle ink according to this embodiment (inkjet printing layer) can be expressed not only in silver derived from silver, but also in blue, green, yellow, red, and other colors derived from localized surface plasmon resonance of silver nanoparticles, but is not limited to these. The size and shape of the silver nanoparticles, surface modification, ink concentration, particle density on the substrate, etc. affect the color.

[0030] The configuration of the decorative sheet according to each embodiment of the present invention will be described below. (First embodiment) FIG. 1 is a schematic cross-sectional view illustrating the configuration of a decorative sheet 10 according to a first embodiment of the present invention. In the decorative sheet 10 according to the first embodiment, a silver pattern printed layer (glossy pattern printed layer) 2 is formed on a substrate sheet 1 by an inkjet printing method using silver nanoparticle ink. The silver pattern printed layer 2 formed using the silver nanoparticle ink simultaneously becomes a glossy layer K1, and has the function of imparting a sense of brilliance to the decorative sheet 10 and enhancing the design. Here, the color of the "silver pattern printed layer 2" according to this embodiment is not limited to silver (silver color). This is because, as described above, the color changes depending on the size and shape of the silver nanoparticles contained, surface modification, ink concentration, particle density on the substrate, etc. In this embodiment, in order to distinguish it from the "color pattern printed layer" described later, the glossy pattern printed layer formed containing silver nanoparticles is conveniently referred to as a "silver pattern printed layer".

[0031] The silver pattern printed layer 2 preferably contains 90% by mass or more of silver nanoparticles, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the total mass of the silver pattern printed layer 2. If the content of silver nanoparticles is 90% by mass or more, a sense of brightness can be effectively imparted to the silver pattern printed layer 2. The thickness of the silver pattern printed layer 2 is preferably in the range of 5 nm to 500 nm, and more preferably in the range of 10 nm to 400 nm. If the thickness of the silver pattern printed layer 2 is within the above numerical range, it can be printed by the inkjet printing method and effectively impart brilliance to the inkjet printed layer.

[0032] As shown in FIG. 1, the silver pattern printed layer 2 may be formed so as to cover at least a portion of the surface of the base sheet 1, or may be formed so as to cover the entire surface of the base sheet 1. Materials for the base sheet 1 include sheet-shaped polyvinyl chloride (PVC) resin, acrylic resin, polyolefin-based polypropylene resin, polyethylene resin, polycarbonate resin, and other materials that are flexible, thermoplastic, moldable, and suitable for printing, as well as sheet-shaped paper, steel plate, wood, etc. These can be appropriately selected depending on the application and specifications of the base sheet 1.

[0033] Second embodiment 2 is a schematic cross-sectional view illustrating the configuration of a decorative sheet 20 according to a second embodiment of the present invention. In the decorative sheet 20 according to the second embodiment, a pattern formed with colored ink is used as a color picture printed layer 2', and a silver picture printed layer 2 (glossy layer K2) using silver nanoparticle ink is formed thereon by inkjet printing. Therefore, the decorative sheet 20 according to the second embodiment is a highly designed decorative sheet 20 in which the glittering layer K2 shows a sense of brilliance colored with any color. The color picture printed layer 2' can be formed by a printing method such as gravure printing or inkjet printing.

[0034] The thickness of the color pattern printed layer 2' is not particularly limited and can be set appropriately. The color pattern printed layer 2' is a layer that does not contain silver nanoparticles. Since the color pattern printed layer 2' does not contain silver nanoparticles, the brightness of the silver pattern printed layer 2 formed on the color pattern printed layer 2' tends to be more prominent. In addition, the silver pattern printed layer 2 (lustrous layer K2) may be formed so as to cover the entire surface of the color pattern printed layer 2', as shown in Figure 2, or may be formed so as to cover only a portion of the surface of the color pattern printed layer 2'.

[0035] Third embodiment FIG. 3 is a schematic cross-sectional view illustrating the configuration of a decorative sheet 30 according to a third embodiment of the present invention. In the decorative sheet 30 according to the third embodiment, the silver pattern printed layer 2 formed using the silver nanoparticle ink included in the decorative sheet 10 according to the first embodiment shown in FIG. 1 and the color pattern printed layer 2' formed using the color ink included in the decorative sheet 20 according to the second embodiment shown in FIG. 2 are formed on the same plane of the base sheet 1. Therefore, only the silver pattern printed layer 2 becomes the glittering layer K1, and a highly designed decorative sheet 30 is obtained in which only that part shows a sense of brilliance. It is not important to note that the order of forming the silver pattern printed layer 2 formed using the silver nanoparticle ink and the color pattern printed layer 2' formed using the color ink may be either first. In other words, the silver pattern printed layer 2 may be formed on the base sheet 1 by inkjet printing using silver nanoparticle ink, and then the color pattern printed layer 2' may be formed using color ink, or the color pattern printed layer 2' may be formed using color ink, and then the silver pattern printed layer 2 may be formed by inkjet printing using silver nanoparticle ink.

[0036] In addition, the silver pattern printed layer 2 (photoluminescent layer K1) and the color pattern printed layer 2' may be formed so that a portion of the surface of the base sheet 1 is exposed, as shown in Figure 3, or the silver pattern printed layer 2 (photoluminescent layer K1) and the color pattern printed layer 2' may be formed so as to cover the entire surface of the base sheet 1.

[0037] (Fourth embodiment) FIG. 4 is a schematic cross-sectional view illustrating the configuration of a decorative sheet 40 according to a fourth embodiment of the present invention. In the decorative sheet 40 according to the fourth embodiment, a colored pattern printed layer 2' formed on a base sheet 1 using a colored ink, a glittering layer K2 which is a silver pattern printed layer 2 formed on the colored pattern printed layer 2' using a silver nanoparticle ink, and a glittering layer K3 which is a silver pattern printed layer 2 formed on the base sheet 1 using a silver nanoparticle ink are formed. In other words, in the decorative sheet 40 according to the fourth embodiment, in addition to the form of the decorative sheet 20 according to the second embodiment shown in FIG. 2, a glittering layer K3 is formed. As a result, the decorative sheet 40 according to the fourth embodiment is a decorative sheet 40 that is partially colored and has a high designability that shows a sense of brilliance overall.

[0038] Although not shown, the side surfaces of the color pattern printed layer 2' may also be covered with a glittering layer (silver pattern printed layer 2). In addition, the silver pattern printed layer 2 (lustrous layer K2 and lustrous layer K3) may be formed so as to cover the entire surface of the base sheet 1 and the color pattern printed layer 2', as shown in Figure 4, or may be formed so as to cover at least a portion of the surface of the base sheet 1 and the color pattern printed layer 2'.

[0039] Fifth embodiment Fig. 5 is a schematic cross-sectional view illustrating the configuration of a decorative sheet 50 according to a fifth embodiment of the present invention. In the decorative sheet 50 according to the fifth embodiment, the surface of the decorative sheet 10 according to the first embodiment shown in Fig. 1 is covered with a surface protective layer 3. In other words, the decorative sheet 50 is a decorative sheet having a surface protective layer 3 on the outermost layer.

[0040] The material of the surface protection layer 3 may be, for example, a thermosetting resin, an ionizing radiation curing resin, or a mixture of these resins. The thermosetting resin may be, for example, a thermosetting resin having a urethane bond, such as a two-component curing urethane resin. The ionizing radiation curing resin may be, for example, an ultraviolet curing resin. The ultraviolet curing resin may be, for example, a (meth)acrylic resin, a silicone resin, a polyester resin, a urethane resin, an amide resin, or an epoxy resin. By using these materials, the hardness of the surface protection layer 3 may be improved, and the surface physical properties such as abrasion resistance, scratch resistance, and solvent resistance may be improved.

[0041] In addition, functional additives such as antibacterial agents and antifungal agents may be added to the surface protective layer 3 in order to impart various functions. In addition, if necessary, an ultraviolet absorber or a light stabilizer may be added to the surface protective layer 3. For example, benzotriazole-based, benzoate-based, benzophenone-based, and triazine-based ultraviolet absorbers can be used. For example, hindered amine-based light stabilizers can be used. Furthermore, when anti-staining performance and Cellotape (registered trademark) releasability are required, a release agent having a silicone skeleton can be added. In this case, the type of release agent is not particularly limited, but by using a silicone release agent having a terminal functional group that is reactive to the resin composition, the durability of anti-staining performance and Cellotape (registered trademark) releasability can be improved.

[0042] The decorative sheet 50 of the fifth embodiment has a surface protective layer 3 covering the surface of the decorative sheet 10 of the first embodiment shown in Figure 1, but may also have a form in which a surface protective layer 3 covers each surface of the decorative sheet 20 of the second embodiment and the decorative sheet 30 of the third embodiment shown in Figures 2 and 3, respectively. The thickness of the surface protective layer 3 is not particularly limited as long as it can cover the entire silver pattern printed layer 2 (lustrous layer K1), but is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 10 μm to 80 μm. If the thickness of the surface protective layer 3 is within the above numerical range, the silver pattern printed layer 2 can be effectively protected and the flexibility of the decorative sheet 50 can be maintained.

[0043] Fig. 6 is a schematic cross-sectional view illustrating the configuration of a decorative board 100 including a decorative sheet 10 according to the first embodiment of the present invention. As shown in Fig. 6, the decorative board 100 according to this embodiment has a laminated structure in which the decorative sheet 50 shown in Fig. 5 is laminated on one surface of a substrate 5. An adhesive layer 4 is provided between the substrate 5 and the decorative sheet 50, and the substrate 5 and the decorative sheet 50 are bonded together by the adhesive layer 4.

[0044] For example, a wood board such as plywood, particle board, medium density fiberboard (MDF), hardboard, or a metal board can be used as the substrate 5. Furthermore, for example, a thermoplastic resin, a thermosetting resin, or the like can be used as the adhesive layer 4. The decorative board 100 shown in Figure 6 has a laminated structure in which the decorative sheet 50 shown in Figure 5 is laminated on one side of the substrate 5, but it may also have a laminated structure in which decorative sheets, each surface of which is covered with a surface protective layer 3, are laminated together, as in the second embodiment of the decorative sheet 20 and the third embodiment of the decorative sheet 30 shown in Figures 2 and 3, respectively.

[0045] [Example] <Example 1> The decorative sheet 30 according to the third embodiment shown in FIG. 3 was produced using the materials and steps described below, but the present invention is not limited to these. [Synthesis of silver oxalate] 9.92g of oxalic acid dihydrate (Kanto Chemical Co., Ltd.) was dissolved in 60mL of distilled water while heating, and 26.7g of silver nitrate (Kanto Chemical Co., Ltd.) was dissolved in 20mL of distilled water while heating while stirring in a 110℃ oil bath, and the mixture was added and heated and stirred for 1 hour. The precipitated silver oxalate was collected by natural filtration, and then filtered and washed with 200mL of hot water and 50mL of methanol (Kanto Chemical Co., Ltd.), and then dried at room temperature under reduced pressure in a light-shielding desiccator. The yield of silver oxalate thus obtained was 21.6g (yield 90.4%).

[0046] [Synthesis of silver nanoparticles] 3.26g of N,N-diethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.) was added to 0.13g of oleic acid (Kanto Chemical Co., Ltd.), and 1.90g of the silver oxalate obtained in the above process was added and heated and stirred in a 110°C oil bath. Carbon dioxide bubbles began to form within one minute, and after a few minutes the mixture turned into a brown suspension. After heating for 5 minutes, the mixture was cooled, and 30mL of methanol was added. The precipitate obtained by centrifugation was naturally dried to obtain 1.48g of silver nanoparticles as a blue solid (yield based on silver: 97.0%).

[0047] The obtained silver nanoparticles were observed in S-TEM mode (accelerating voltage 30 kV) using a scanning electron microscope (Hitachi High-Technologies Corporation, SEM S-4800), and spherical particles with a particle diameter of about 5 to 20 nm were observed. The results are shown in Figure 7. More specifically, Figure 7 is a scanning electron microscope image of silver nanoparticles observed after the toluene dispersion of the silver nanoparticles obtained in Example 1 was dropped onto a substrate (copper mesh microgrid) and dried. Next, since the obtained silver nanoparticles were dispersed in toluene, the toluene dispersion was subjected to dynamic light scattering particle size measurement (Nikkiso Co., Ltd., Nanotrac UPA-EX150). As a result, it was found that the silver nanoparticles were well dispersed with an average particle diameter of 15 nm. The results are shown in Figure 8. The solid line in Figure 8 indicates the cumulative frequency (%).

[0048] [Ink preparation] 0.20 g of the silver nanoparticles obtained in the above process was added to 1.8 g of toluene (Kanto Chemical Co., Ltd.) and 0.2 g of terpineol (mixture of isomers, Fujifilm Wako Pure Chemical Industries, Ltd.), and stirred to make a dispersion. In this case, since there were 0.2 g of silver nanoparticles per 2.0 g of dispersion solvent, the mass % of silver nanoparticles was 10%. The dispersion was passed through a syringe filter (Whatman, 25 mm GD / X syringe filter (GF / B 1.0 μm)) to make a silver nanoparticle ink for inkjet printing.

[0049] [Preparation of decorative sheet 30] A PVC film (FZ manufactured by Riken Technos Corporation) was used as the base sheet 1. Next, as the color pattern printing layer 2', inkjet inks (yellow, magenta, cyan) not containing glittering pigment were used to print wood grain with an inkjet printer. Next, on the same plane of the base sheet 1 on which the color pattern printing layer 2' was formed, a middle-color wood grain pattern was printed as the glittering pattern printing layer 2 with the above-mentioned silver nanoparticle ink by an inkjet printer. Furthermore, as the surface protection layer 3, Acrydic (manufactured by DIC Graphics Corporation) containing thermosetting multifunctional acrylic urethane resin and silica was applied to a thickness of 1 μm after drying. In this manner, the decorative sheet of Example 1 was produced.

[0050] <Example 2> In the synthesis of silver nanoparticles, a mixture of 1.43 g of n-hexylamine (Tokyo Chemical Industry Co., Ltd.) and 1.21 g of N,N-diethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.) was used instead of 3.26 g of N,N-diethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.), and silver nanoparticles were obtained in the same manner as in Example 1. A scanning electron microscope image of the obtained silver nanoparticles is shown in FIG. 9. The obtained silver nanoparticles were used in the same manner as in Example 1, except that n-butanol (Kanto Chemical Co., Ltd.) was used as a dispersion medium instead of toluene and terpineol, and Plysurf A208F (Dai-ichi Kogyo Seiyaku Co., Ltd.) was used as a dispersant, and a decorative sheet of Example 2 was produced.

[0051] <Example 3> The synthesis of silver nanoparticles was changed as follows. 6.51 g of N,N-diethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.), 0.25 g of oleic acid (Kanto Chemical Co., Ltd.), and 9.60 g of n-butanol (Kanto Chemical Co., Ltd.) were added, and 1.92 g of silver oxalate was added and heated and stirred in an oil bath at 95 ° C. After heating, the color began to change after a few minutes, and after 18 minutes, carbon dioxide foaming occurred and the suspension turned brown. After heating for 5 minutes, the mixture was cooled, and 30 mL of methanol was added. The precipitate obtained by centrifugation was naturally dried to obtain 1.29 g of silver nanoparticles (silver-based yield 95.0%), which is a blue solid. A scanning electron microscope image of the obtained silver nanoparticles is shown in FIG. 10. The obtained silver nanoparticles were used in the same manner as in Example 2 to produce the decorative sheet of Example 3.

[0052] <Example 4> In the synthesis of silver nanoparticles, a mixture of 1.47 g of n-hexylamine (Tokyo Chemical Industry Co., Ltd.) and 1.24 g of N,N-diethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.) was used instead of 6.51 g of N,N-diethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.), and the same procedure was followed to obtain silver nanoparticles. A scanning electron microscope image of the obtained silver nanoparticles is shown in Figure 11. The obtained silver nanoparticles were used in the same procedure as in Example 2 to produce the decorative sheet of Example 4.

[0053] <Example 5> In the synthesis of silver nanoparticles, the procedure was the same as in Example 3, except that n-hexanol (Kanto Chemical Co., Ltd.) was used instead of n-butanol (Kanto Chemical Co., Ltd.), to obtain silver nanoparticles. A scanning electron microscope image of the obtained silver nanoparticles is shown in Figure 12. The decorative sheet of Example 5 was produced using the obtained silver nanoparticles in the same manner as in Example 2.

[0054] <Example 6> The synthesis of silver nanoparticles was changed as follows. 0.32 g of gelatin (Kanto Chemical Co., Ltd.) and 2.56 g of N,N-dimethyl-1,3-diaminopropane (Tokyo Chemical Industry Co., Ltd.) were dissolved in 8.00 g of distilled water, and 0.96 g of silver oxalate was added and heated and stirred in an oil bath at 100 ° C. for 3 hours. After cooling the reaction solution, it was diluted with 50 mL of distilled water and centrifuged to obtain a precipitate, which was then naturally dried to obtain 0.61 g of silver nanoparticles (silver-based yield 90.0%). A scanning electron microscope image of the obtained silver nanoparticles is shown in FIG. 13. The obtained silver nanoparticles were treated in the same manner as in Example 1, except that water was used as a dispersion medium and Plysurf AL (Dai-ichi Kogyo Seiyaku Co., Ltd.) was used as a dispersant, to produce a decorative sheet of Example 6.

[0055] <Example 7> The synthesis of silver nanoparticles was changed as follows to produce silver nanoparticles whose surfaces were modified with polyvinylpyrrolidone. 2.4 g of polyvinylpyrrolidone K30 (Wako Fujifilm) was added to 4.0 g of water to prepare an aqueous solution, and 0.48 g of silver oxalate was added to the dispersion medium and heated and stirred in an oil bath at 80 ° C. The heating and stirring was carried out for 5 hours to obtain a dispersion liquid that turned gray. The dispersion liquid was cooled, and 40 mL of water was added, and the mixture was separated by centrifugation (Beckman Coulter, AvantiHP-26XP, 15,000 rpm for 30 minutes) to obtain 0.35 g of gray solid matter. The decorative sheet of Example 7 was produced by the same operation as in Example 1, except that water was used as the dispersion medium and Plysurf AL (Dai-ichi Kogyo Seiyaku Co., Ltd.) was used as the dispersant.

[0056] <Example 8> The decorative sheet of Example 8 was produced in the same manner as in Example 1, except that silver nanoparticles manufactured by Osaka Soda Co., Ltd. were used as the silver nanoparticles, cyclohexanone was used as the dispersion medium, and Plysurf AL (Dai-ichi Kogyo Seiyaku Co., Ltd.) was used as the dispersant. The D50 of silver nanoparticles manufactured by Osaka Soda was measured and found to be 265 nm.

[0057] <Comparative Example 1> The decorative sheet of Comparative Example 1 was produced in the same manner as Example 1, except that a wood grain pattern was printed with a gravure printing machine using a gravure ink containing a glittering pigment (Lamistar (registered trademark) manufactured by Toyo Ink Co., Ltd.) as the glittering picture printed layer. <Comparative Example 2> A decorative sheet of Comparative Example 2 was produced in the same manner as in Example 1, except that a wood grain pattern was printed with an inkjet printer using a UV ink (manufactured by Konica Minolta) that did not contain a glittering pigment as the picture printed layer. <Comparative Example 3> The decorative sheet of Comparative Example 3 was produced in the same manner as in Example 1, except that a wood grain pattern was printed with an inkjet printer using UV silver ink (manufactured by Mimaki Engineering Co., Ltd.) that did not contain silver nanoparticles as the picture printed layer.

[0058] [Evaluation method] Regarding the sense of brilliance, if more than 50 out of 100 test subjects rated it as natural as the shine of the wood grain and as reproducing the natural luster of natural wood, they were judged as "○", and if they rated it as not reproducing the natural luster of natural wood because the shine of the wood grain was unnaturally too strong, or the shine of the wood grain was too weak, they were judged as "×". If the evaluation was "○", there was no problem in using it, so it was judged as "passed". In terms of design, products that 50 or more of the 100 test subjects felt were properly reproduced without blurring the outlines of the fine lines (a few microns wide) of the wood grain pattern were judged as "○", products that they felt were not reproduced properly due to blurring the outlines of the fine lines (a few microns wide) of the wood grain pattern were judged as "×", and products with partial printing unevenness were judged as "△". A microscope with a magnification of 100x was used to check the outlines of the fine lines of the wood grain pattern. If the evaluation was "○" or "△", there was no problem with use and it was judged as "passed".

[0059] [Evaluation Results] The evaluation results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0060] [Table 1]

[0061] As shown in Table 1, the decorative sheets of Examples 1 to 6, which satisfy the conditions of the present invention, were good in both brilliance and design. Examples 7 and 8 had sufficient brilliance, but some unevenness was observed in the print. On the other hand, in Comparative Example 1, which used a gravure printing machine, thin lines were blurred and design was insufficient. In Comparative Example 2, in which a UV ink not containing a glittering pigment was inkjet printed, the brilliance was insufficient. In Comparative Example 3, in which a UV silver ink not containing silver nanoparticles was inkjet printed, the brilliance was excessive. [Explanation of symbols]

[0062] 1. Base sheet 2. Silver pattern printed layer (shiny pattern printed layer) 2' Color pattern printing layer K1, K2, K3...Glitter layer 3...Surface protective layer 4...Adhesive layer 5. Circuit Board 10, 20, 30, 40, 50...decorative sheet 100·········Decorative board

Claims

1. The ink jet printing apparatus includes at least an ink jet printing layer formed on a base sheet using an ink jet ink, The inkjet ink comprises silver nanoparticles, The silver nanoparticles are silver nanoparticles whose surfaces are protected by protective molecules mainly containing an amine compound, The decorative sheet is characterized in that the amine compound is at least one of ethylamine, n-propylamine, isopropylamine, 1,2-dimethylpropylamine, isobutylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-oleylamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dimethyl-1,5-diamino-2-methylpentane, N,N-dimethyl-1,6-hexanediamine, N,N-dibutylaminopropane, N,N-diisobutyl-1,3-diaminopropane, and polyvinylpyrrolidone.

2. 2. The decorative sheet according to claim 1, wherein the median diameter (D50) of the silver nanoparticles is within the range of 1 nm or more and 250 nm or less.

3. 3. The decorative sheet according to claim 1, wherein the inkjet printed layer is a glittering picture printed layer containing the silver nanoparticles.

4. 4. The decorative sheet according to claim 1, further comprising a colored picture printed layer formed on the base sheet using colored inks.

5. The decorative sheet according to any one of claims 1 to 4, characterized in that it has a glossy pattern printed layer, which is an inkjet printing layer formed using the inkjet ink containing the silver nanoparticles, and a color pattern printed layer formed using a colored ink, on the same plane of the base sheet.

6. 6. The decorative sheet according to claim 4, wherein the inkjet printed layer is formed on at least one of the base sheet and the color picture printed layer.

7. 7. The decorative sheet according to claim 1, further comprising a surface protective layer as an outermost layer.

8. A decorative sheet described in any one of claims 1 to 7, characterized in that the amine compound is a diamine compound having a primary amino group and a tertiary amino group.

9. A decorative sheet described in any one of claims 1 to 7, characterized in that the amine compound is only N,N-diisobutyl-1,3-diaminopropane, only n-hexylamine and N,N-diethyl-1,3-diaminopropane, or only polyvinylpyrrolidone.

10. A decorative board comprising: the decorative sheet according to claim 1 ; and a substrate disposed on the base sheet side of the decorative sheet.

11. An inkjet ink for decorative sheets for forming a picture print layer on a base sheet by using an inkjet printing method, Contains silver nanoparticles, The silver nanoparticles are silver nanoparticles whose surfaces are protected by protective molecules mainly containing an amine compound, The inkjet ink for decorative sheets is characterized in that the amine compound is at least one of ethylamine, n-propylamine, isopropylamine, 1,2-dimethylpropylamine, isobutylamine, n-hexadecylamine, n-heptadecylamine, n-octadecylamine, n-oleylamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, N,N-dimethyl-1,5-diamino-2-methylpentane, N,N-dimethyl-1,6-hexanediamine, N,N-dibutylaminopropane, N,N-diisobutyl-1,3-diaminopropane, and polyvinylpyrrolidone.

12. 12. The inkjet ink for decorative sheets according to claim 11, wherein the median diameter (D50) of the silver nanoparticles is within the range of 1 nm or more and 250 nm or less.

13. An inkjet ink for decorative sheets as described in claim 11 or claim 12, characterized in that the amine compound is a diamine compound having a primary amino group and a tertiary amino group.

14. An inkjet ink for decorative sheets as described in claim 11 or claim 12, characterized in that the amine compound is only N,N-diisobutyl-1,3-diaminopropane, only n-hexylamine and N,N-diethyl-1,3-diaminopropane, or only polyvinylpyrrolidone.

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