JP2019077070A - Inkjet printing method for leather with synthetic resin-made surface, and aqueous inkjet ink for leather with synthetic resin-made surface - Google Patents

Abstract

An inkjet printing method is provided that can form a high-quality image on a leather made of a synthetic resin, the surface of which is difficult to peel off, excellent in bending resistance, and high quality. SOLUTION: The step of heating the surface of the leather whose surface is made of synthetic resin to 40 ° C. or higher, the step of discharging the ink contained in the water-based ink set onto the surface of the leather by an inkjet method, and the surface of the leather of 60 ° C. or higher. The ink of the water-based ink set contains water, a pigment, a water-soluble organic solvent, a surfactant, and resin fine particles, and the glass transition temperature of the resin fine particles is 0 ° C. or less. , Containing 3-methoxy-1-butanol and / or 3-methoxy-3-methyl-1-butanol as a water-soluble organic solvent in an amount of 8% by mass to 23% by mass, and the aqueous ink set contains a white pigment as a pigment And a colored ink containing a pigment other than white as a pigment, and the surface is a synthetic resin-made leather inkjet printing method. [Selection figure] None

Description

  The present invention relates to an ink jet printing method of leather made of synthetic resin on the surface. The present invention also relates to an aqueous inkjet ink for leather whose surface is made of synthetic resin.

  Conventionally, ink jet decoration for natural leather is performed by applying a top coat after printing using a solvent ink or an aqueous ink on a water absorbing surface such as Nume leather. However, in the case of ink-jet printing on top-coated natural leather and artificial leather, since these surfaces are made of synthetic resin, the ink is difficult to be absorbed by the surface. On the other hand, UV curable inks (so-called UV inks) are suitable for ink jet printing on low absorbing non-absorbing substrates. Therefore, a UV ink is generally used for inkjet printing on top coats of natural leather and artificial leather (see, for example, Patent Document 1).

  When inkjet printing is performed on leather whose surface is made of synthetic resin using UV ink, the ink is cured by UV irradiation during image formation to form a coating film. However, since this coating film is poor in flexibility, there is a problem that the image tends to be cracked when the post-process or the leather is repeatedly bent.

  On the other hand, printing can also be performed on leather whose surface is made of synthetic resin using textile ink (see, for example, Patent Document 2). However, printing inks are most suitable for fabrics having high ink absorbability. Therefore, when ink jet printing is performed on leather made of synthetic resin on the surface using textile ink, there is a problem that bleeding easily occurs in the formed image, and it is difficult to form a high quality image.

  In addition, an aqueous inkjet ink (so-called latex ink) containing water, a pigment, a water-soluble organic solvent, a surfactant, and resin fine particles is used for inkjet printing on a non-absorbing substrate (for example, Patent Document 3) reference). However, in inkjet printing using an aqueous inkjet ink, the printing target is a hard base such as an outdoor sign board, coated paper, and the like. Therefore, when ink jet printing is performed on a leather made of synthetic resin on the surface using a conventional aqueous ink jet ink, there is a problem that the fixing property is bad and the image to be formed is easily peeled off.

JP, 2017-080805, A JP, 2015-218191, A JP 2014-205766 A

  The present invention has been made in view of such a point, and the present invention is an ink jet printing method capable of forming a high quality image with excellent resistance to peeling on a surface of leather made of synthetic resin and excellent in bending resistance. Intended to provide.

  The inkjet printing method of a leather made of a synthetic resin surface according to the present invention comprises the steps of heating the surface of the synthetic resin leather to at least 40 ° C., the ink contained in the aqueous inkjet ink set by the inkjet method And the step of heating the surface of the leather from which the ink has been discharged to 60 ° C. or higher. The ink contained in the aqueous inkjet ink set contains at least water (A), pigment (B), water-soluble organic solvent component (C), surfactant (D), and resin fine particles (E). The glass transition temperature of the resin fine particles (E) is 0 ° C. or less. The ink comprises, as a water-soluble organic solvent component (C), 8 mass% of at least one substituted butanol selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol % Or more and 23 mass% or less. The aqueous inkjet ink set includes a white ink containing a white pigment as the pigment (B), and a colored ink containing a pigment other than white as the pigment (B).

  The aqueous inkjet ink for leather according to the present invention whose surface is a synthetic resin is at least water (A), pigment (B), water-soluble organic solvent component (C), surfactant (D), and resin fine particles (E). Containing). The glass transition temperature of the resin fine particles (E) is 0 ° C. or less. The aqueous inkjet ink comprises, as a water-soluble organic solvent component (C), at least one substituted butanol selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol; 8 mass% or more and 23 mass% or less are contained.

  According to the present invention, it is possible to form a high quality image with excellent resistance to peeling, excellent bending resistance, and leather having a surface made of synthetic resin.

  The inkjet printing method of leather made of a synthetic resin surface according to the present invention is included in the step of heating the surface of the synthetic resin leather to at least 40 ° C. (first heating step), an aqueous inkjet ink set It includes a step of discharging the ink onto the surface of the leather by an inkjet method (discharge step), and a step of heating the surface of the leather from which the ink has been discharged to 60 ° C. or higher (second heating step). The ink contained in the aqueous inkjet ink set contains at least water (A), pigment (B), water-soluble organic solvent component (C), surfactant (D), and resin fine particles (E). The glass transition temperature of the said resin fine particle (E) is 0 degrees C or less. The ink contains, as a water-soluble organic solvent component (C), 8 mass% of at least one substituted butanol selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol % Or more and 23 mass% or less. The aqueous inkjet ink set includes a white ink containing a white pigment as the pigment (B), and a colored ink containing a pigment other than white as the pigment (B).

  First, the first heating step will be described. In the first heating step, the surface of the leather made of synthetic resin is heated to 40 ° C. or higher. The heating can be performed according to a known method. For example, the surface of the above-mentioned leather made of synthetic resin is heated using a contact heating type sheet heater, a radiation heater emitting infrared rays or microwaves, a warm air heater or the like. The heating temperature is preferably 40 ° C. or more and 60 ° C. or less.

  Examples of the leather at least the surface of which is made of synthetic resin include natural leather provided with a synthetic resin layer such as a top coat layer on the surface, and artificial leather provided with a synthetic resin layer on the surface of a substrate. Examples of artificial leather include synthetic leather having a synthetic resin layer provided on the surface of a fabric base made of natural fibers, nylon fibers, polyester fibers, etc., and a non-woven fabric made of micro fibers such as nylon, polyester, etc. The artificial leather etc. in which the synthetic resin layer was provided on the surface of the material are mentioned. As an example of a synthetic resin, a urethane resin, a vinyl chloride resin, etc. are mentioned, Preferably it is a urethane resin. At least the surface is preferably artificial leather as leather made of a synthetic resin, and more preferably artificial leather made of a urethane resin.

  Next, the discharge process will be described. First, the aqueous inkjet ink set used in the ejection step will be described. The aqueous inkjet ink of the aqueous inkjet ink set contains at least water (A), pigment (B), water-soluble organic solvent component (C), surfactant (D), and resin fine particles (E).

[Water (A)]
The aqueous inkjet ink used here contains water (A). By containing water (A), the aqueous inkjet ink has the advantage of low environmental impact. The water (A) to be used is not particularly limited, but ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water or ultrapure water is preferable from the viewpoint of preventing mixing of impurities, and ion-exchanged water Is more preferred.

  40 mass% or more is preferable, as for content of the water (A) in aqueous | water-based inkjet ink, 45 mass% or more is more preferable, and 50 mass% or more is more preferable. On the other hand, 80 mass% or less is preferable, 75 mass% or less is more preferable, and 70 mass% or less is more preferable.

[Pigment (B)]
Both inorganic and organic pigments can be used as the pigment (B). The pigment (B) can be used singly or in combination of two or more in any ratio. In the present invention, the pigment (B) is divided into a white pigment (B-1) and a colored pigment (B-2) (pigments other than white) for the sake of convenience.

  As the white pigment (B-1), inorganic pigments are preferable, and examples thereof include titanium oxide, zinc white, zinc sulfide, lead white, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, Bentonite etc. are mentioned. The white pigment (B-1) is preferably titanium oxide because it has high whiteness and excellent hiding power. An organic pigment may be used as the white pigment (B-1).

  When the colored pigment (B-2) is an inorganic pigment, examples thereof include black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chromium vermillion, yellow lead, cadmium yellow, yellow iron oxide, titanium Yellow, chromium oxide, bilizian, titanium cobalt green, cobalt green, cobalt chromium green, Victoria green, ultramarine blue, bitumen, cobalt blue, cerulian blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, cobalt violet and the like can be mentioned.

  When the colored pigment (B-2) is an organic pigment, examples thereof include azo pigments (eg, azo lake, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (eg, phthalocyanine pigments, Rylene pigments, perrinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofurarone pigments, etc., dye chelates (eg, basic dye type chelates, acid dye type chelates, etc.), Nitro pigments, nitroso pigments, aniline black and the like can be mentioned.

  More specifically, as black pigments, for example, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, etc .; copper, iron (CI pigment black) 11) Metals such as 11); metal oxides such as titanium oxide; and organic pigments such as aniline black (CI pigment black 1).

  Examples of cyan pigments include C.I. I. Pigment blue 1, 2, 3, 15: 1, 15: 3, 15: 4, 15: 6, 16, 21, 22, 60, 64 and the like.

  As a magenta pigment, for example, C.I. I. Pigment red 5, 9, 9, 12, 31, 48, 49, 52, 53, 57, 97, 112, 120, 122, 146, 149, 150, 168, 170, 177, 178, 179, 184, 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282; I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50, and the like.

  As a yellow pigment, for example, C.I. I. Pigment yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like.

  As other colored pigments, for example, C.I. I. Pigment green 7, 10, 36; C.I. I. Pigment brown 3, 5, 25, 26; C.I. I. Pigment orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71, and the like.

  In addition, pigments having a hydrophilic group such as a carboxyl group, a sulfonic acid group, a phosphonic acid group and a hydroxyl group on the surface (so-called "self-dispersion pigment") can be used. As a carbon black type self-dispersion pigment, CAB-O-JET200, 300, 352K, 400 (above, Cabot company make) etc. are mentioned, for example. Examples of the cyan-based self-dispersion pigment include CAB-O-JET 250C, 260C, 450C, 554B (above, manufactured by Cabot Corporation). As a magenta type self-dispersion pigment, CAB-O-JET260M, 265M, 465M (above, Cabot company make) etc. are mentioned, for example. As a yellow type self-dispersion pigment, CAB-O-JET270, 470Y, 740Y (above, Cabot company make) etc. are mentioned, for example. A self-dispersible pigment is preferable as the colored pigment (B-2) because it can be dispersed in water (A) without using a dispersant.

  The content of the pigment (B) in the aqueous inkjet ink is preferably 0.1 mass% or more as solid content (solid content concentration), more preferably 0.5 mass% or more, and still more preferably 1 mass% or more. On the other hand, 15 mass% or less is preferable, and 12.5 mass% or less is more preferable.

[Water-soluble organic solvent component (C)]
In the present specification, the “water-soluble organic solvent” constituting the water-soluble organic solvent component (C) refers to an organic solvent having a solubility of at least 500 g / L at 20 ° C. in water. The water-soluble organic solvent is preferably an organic solvent which is uniformly mixed with water at an arbitrary ratio at 20 ° C.

  The aqueous inkjet ink used here is at least one kind of substitution selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol as the water-soluble organic solvent component (C). It contains 8% by mass or more and 23% by mass or less of butanol. The substituted butanol is a component that improves the initial drying speed of the aqueous inkjet ink. If the content of substituted butanol is less than 8% by mass, the initial drying speed is slowed and image bleeding occurs. In addition, the fixability also decreases, and the formed image is likely to be peeled off. 10 mass% or more is preferable, and, as for content of substituted butanol, 12 mass% or more is more preferable. On the other hand, when the content of substituted butanol exceeds 23% by mass, the initial drying speed becomes too fast, the ink coating film (particularly, white ink) is easily formed unevenly, and image bleeding occurs. 21 mass% or less is preferable, and, as for content of substituted butanol, 20 mass% or less is more preferable.

  The aqueous inkjet ink may contain, as the water-soluble organic solvent component (C), a water-soluble organic solvent other than the above-mentioned substituted butanol. As water-soluble organic solvents other than the said substituted butanol, a well-known thing can be especially used as a water-soluble organic solvent of water-based inkjet ink, without restriction.

  From the fact that the water retention property of the aqueous inkjet ink is improved, diols are suitably used as water-soluble organic solvents other than the above-mentioned substituted butanol. Examples of diols include ethylene glycol (boiling point: about 196 ° C.), diethylene glycol (boiling point: about 244 ° C.), triethylene glycol (boiling point: about 287 ° C.), propylene glycol (boiling point: about 188 ° C.), dipropylene glycol (Boiling point: about 230 ° C.), 1,3-propanediol (boiling point: about 213 ° C.), 1,2-butanediol (boiling point: about 194 ° C.), 2,3-butanediol (boiling point: about 183 ° C.), 1,3-butanediol (boiling point: about 208 ° C), 2,2-dimethyl-1,3-propanediol (boiling point: about 208 ° C), 2-methyl-1,3-propanediol (boiling point: about 213 ° C) 1, 2-pentanediol (boiling point: about 206 ° C), 2,4-pentanediol (boiling point: about 201 ° C), 2-methyl-2,4-pentanediol ( Point: about 198 ° C., 1,5-pentanediol (boiling point: about 242 ° C.), 1,2-hexanediol (boiling point: about 224 ° C.), 1,6-hexane diol (boiling point: about 250 ° C.), 2 Ethyl, 1,3-hexanediol (boiling point: about 243 ° C.) and the like. These can be used alone or in combination of two or more at any ratio. As the diols, diols having a linear or branched alkylene chain having 3 to 6 carbon atoms (particularly 4 to 5 carbon atoms) are preferable. The content of the diols in the aqueous inkjet ink is preferably 1.5% by mass or more, and more preferably 3% by mass or more. On the other hand, 20 mass% or less is preferable, and 15 mass% or less is more preferable.

  From the viewpoint of particularly high image quality, glycol monoethers are preferably used as water-soluble organic solvents other than the above substituted butanol. Examples of glycol monoethers include triethylene glycol monobutyl ether (boiling point: about 278 ° C.), dipropylene glycol monomethyl ether (boiling point: about 190 ° C.), tripropylene glycol monomethyl ether (boiling point: about 242 ° C.), propylene glycol N-Butyl ether (boiling point: about 171 ° C), propylene glycol t-butyl ether (boiling point: about 153 ° C), diethylene glycol monobutyl ether (boiling point: about 230 ° C), diethylene glycol monoethyl ether (boiling point: about 202 ° C), diethylene glycol Glycol groups such as monomethyl ether (boiling point: about 194 ° C.), ethylene glycol n-propyl ether (boiling point: about 150 ° C.), ethylene glycol n-butyl ether (boiling point: about 171 ° C.) Such as ethers, and the like. These can be used alone or in combination of two or more at any ratio. As glycol monoethers, methyl ether, ethyl ether, propyl ether or butyl ether of diethylene glycol, triethylene glycol, dipropylene glycol or tripropylene glycol is preferred. The content of the glycol monoethers in the aqueous inkjet ink is preferably 1.5% by mass or more, and more preferably 3% by mass or more. On the other hand, 20 mass% or less is preferable, and 15 mass% or less is more preferable.

  The aqueous inkjet ink preferably contains both the above diols and glycol monoethers as the water-soluble organic solvent component (C).

  If the content of the water-soluble organic solvent component (C) in the aqueous inkjet ink is too low, the drying property tends to be reduced, and the wettability to the above-mentioned leather is reduced, and the fixing property is reduced and the image quality is reduced. There is a risk of Therefore, the content of the water-soluble organic solvent component (C) in the aqueous inkjet ink is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more. On the other hand, when the content of the water-soluble organic solvent component (C) is too large, the ink viscosity tends to increase. Therefore, 55 mass% or less is preferable, as for content of the water-soluble organic solvent component (C) in aqueous inkjet ink, 45 mass% or less is more preferable, and 40 mass% or less is more preferable.

[Surfactant (D)]
The surfactant (D) is a component that optimizes the surface tension and interfacial tension of the ink. As the surfactant (D), known ones usable for an aqueous inkjet ink can be used without particular limitation, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants And amphoteric surfactants. Among them, anionic surfactants and nonionic surfactants are preferable, and nonionic surfactants are more preferable.

  Examples of nonionic surfactants include Sorbit surfactants, acetylene glycol surfactants, sorbitan surfactants, silicone surfactants, polyoxyethylene alkyl ether surfactants, fluorine surfactants. Etc. Among them, silicone surfactants are preferable because the static surface tension can be adjusted with a small amount.

  As a silicone type surfactant, a well-known silicone type surfactant can be used without a restriction | limiting especially, It is available as a commercial item. Examples of commercial products include BYK-306, BYK-307, BYK-333, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (above, manufactured by Big Chemie Japan), KF- 351A, KF-352A, KF-353, KF- 354L, KF- 615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF- 6011, KF-6012 (all manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG 002, SAG 005, SAG 503 A, SAG 008 (all manufactured by Nisshin Chemical Co., Ltd.), and the like. As a silicone type surfactant, a polyether modified silicone type surfactant is preferable.

  The content of the surfactant (D) in the inkjet ink of the present invention may be appropriately determined so as to optimize the surface tension and the interfacial tension of the ink according to the type of surfactant used. The content of the surfactant (D) is preferably 0.05% by mass or more, more preferably 0.2% by mass or more. On the other hand, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2.5% by mass or less.

[Resin fine particles (E)]
The fine resin particle (E) is a binder component that improves the fixing property of the leather to the surface made of synthetic resin and the coating film resistance.

  The glass transition temperature (Tg) of the resin fine particles (E) is 0 ° C. or less. When the glass transition temperature of the resin fine particles exceeds 0 ° C., the flexibility of the formed ink coating film is lost and the bending resistance is deteriorated. The kind of the resin fine particles (E) is not particularly limited as long as Tg is 0 ° C. or less. As a suitable example of resin which comprises resin fine particle (E), a urethane resin, an acrylic resin, polyethylene, a polypropylene, a butadiene resin, a styrene butadiene resin etc. are mentioned, Especially, a urethane resin is more suitable. The glass transition temperature of the resin fine particles (E) is preferably -65 ° C to 0 ° C, more preferably -55 ° C to -5 ° C, and still more preferably -45 ° C to -10 ° C. . The glass transition temperature can be measured according to a known method, and can be measured, for example, using a thermal analyzer such as a differential scanning calorimeter (DSC).

  The resin fine particles (E) do not have to be composed of one kind of resin, and may be composed of two or more kinds of resins. For example, core-shell type resin fine particles having different resin compositions in the core portion and the shell portion, and hybrid type resin fine particles in which resin fine particles made of different resins are chemically bonded can be used.

  The resin fine particles (E) preferably contain a urethane resin because the fixability and the ink stability are particularly excellent.

  The volume average particle size of the resin fine particles (E) is not particularly limited, but is preferably 10 to 1000 nm, more preferably 10 to 200 nm, and still more preferably 10 to 50 nm. In addition, a volume average particle diameter can be calculated | required, for example using a particle size distribution measuring apparatus.

  3 mass% or more is preferable as solid content (solid content concentration), and, as for content of the resin fine particle (E) in aqueous inkjet ink, 5 mass% or more is more preferable. On the other hand, 15 mass% or less is preferable, and 12 mass% or less is more preferable.

  In the ejection step, a white aqueous inkjet ink containing a white pigment (B-1) as a pigment (B), and a colored inkjet ink containing a colored pigment (B-2) which is a pigment other than white as a pigment (B) And an aqueous ink jet ink set comprising The colored ink may use only one colored ink or may be a combination of a plurality of colored inks. Examples of combinations of multiple colored inks include combinations of cyan ink, magenta ink, and yellow ink, combinations of cyan ink, magenta ink, yellow ink, and black ink, and the like.

  In the ejection step, the ink contained in the aqueous inkjet ink set is ejected onto the heated surface of the leather by an inkjet method, whereby the ink is adhered to the surface of the leather. Specifically, for example, ink is ejected in the form of fine droplets from the nozzle of an inkjet head of a piezo system, a bubble system, a thermal system or the like, and the ink is attached to the surface of the leather.

  In the ejection step, the white ink and the colored ink may be ejected simultaneously or almost simultaneously, but after the white ink is ejected and adhered to the surface of the leather, the above (ie, the ejection of the white ink Preferably, the colored ink is discharged onto the surface of the above-mentioned leather. In this way, the color of the surface of the leather can be concealed by the white ink, and a clear color layer can be formed even for dark leather such as black leather. The white ink is discharged to adhere to the surface of the leather, and then the colored ink is discharged thereon to adhere to the surface of the leather. For example, the white ink is discharged from an ink jet head to After adhering to the surface, the substrate is pulled back in the direction opposite to the transport direction, and the same ink jet head ejects colored ink thereon to adhere to the surface of the leather, or the first method of ejecting white ink An ink jet head and a second ink jet which discharges colored ink separately from this are prepared, and white ink is discharged from the first ink jet head to adhere to the surface of the leather, and then the second ink is formed thereon. And a method of discharging colored ink from the ink jet head of the present invention to adhere to the surface of the leather.

  Next, the second heating step will be described. In the second heating step, the surface of the leather from which the ink has been discharged is heated to 60 ° C. or higher to dry the aqueous inkjet ink. By this heating, the inkjet ink is coated to form an image. The heating can be performed according to a known method. For example, the surface of the above-mentioned leather made of synthetic resin is heated using a contact heating type sheet heater, a radiation heater emitting infrared rays or microwaves, a warm air heater or the like. When the heating temperature is 60 ° C. or more, a film based on resin fine particles having a glass transition temperature of 0 ° C. or less can be formed on the surface of the synthetic resin of the leather with high fixability. In addition, even in the case of using a solvent having a relatively high boiling point such as diols and glycol monoethers, drying can be sufficiently promoted. The heating temperature is preferably 60 ° C. or more and 90 ° C. or less.

  According to the ink jet recording method of the present invention, a leather having a non-absorbent and flexible surface, which is a substrate made of synthetic resin, is hardly peeled off, is excellent in bending resistance, and forms a high quality image. be able to.

  EXAMPLES Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

[Preparation and printing of inkjet ink]
Each component described in Tables 1 to 3 was uniformly mixed at a mass ratio shown in each table to obtain an inkjet ink set of each example and each comparative example. Each inkjet ink set is composed of cyan (C), magenta (M), yellow (Y), and black (K) colored inks and white (Wh) ink. The obtained ink jet ink set was printed on an artificial leather ("CORD LE BLACK Gloss normal" manufactured by Teijin Ltd.) using an ink jet printer, and the scratch resistance, image blur, and flex resistance were evaluated by the following method. . The printing was performed as follows. The artificial leather was conveyed by a roller of an ink jet printer, and the surface of the artificial leather was heated to 40 to 45 ° C. before printing by a heater. Next, printing was performed on the surface of the artificial leather with each ink set. At this time, first, the white ink was discharged onto the surface of the artificial leather, the transport roller was reversely rotated to pull back the artificial leather, and then the colored ink was discharged. In the case of a white ink, a solid image was formed under the conditions of 22 pl per drop and a resolution of 600 dpi × 600 dpi. In the case of colored ink, a full-solid image and white letters of 5 pt were printed under the conditions of 22 pl per drop and a resolution of 600 dpi × 600 dpi. Subsequently, the printing surface was heated to 60 ° C. or higher by a heater and held for 3 minutes. The evaluation results of the image formed in this manner are shown in Tables 1 to 3.

[Abrasion resistance evaluation]
A dry cotton cloth was attached to a Gakushin tester, and under a weight of 500 g, the state of the ink coating was observed after reciprocating 100 times on the ink coating immediately after forming an image. From the observation results, the scratch resistance was evaluated based on the following criteria. "○" and "△" were accepted.
○: The ink film can not be taken out Δ: Only a part of the ink film can be taken out ×: More than half of the ink film can be taken

[Image blur evaluation]
The degree of the blur of the image of the white characters was visually observed. From the observation results, the degree of bleeding was evaluated according to the following criteria. "○" and "△" were accepted.
○: excellent in the visibility of white characters 文字: white characters are slightly blurred, but visible ×: white characters are not visible

[Flexibility]
The printed leather was flexed 10000 times by the flex resistance test method according to JIS K6545: 1994. Flexibility was determined according to the determination standard described in JIS K6545: 1994. From the determination result, the following criteria evaluated bending resistance. Passed "○".
○: 4 or higher ×: 3 or lower

(The numerical values for each component in each table indicate the mass ratio.)
CAB-O-JET 260C (manufactured by Cabot Co., Ltd.): Cyan-based self-dispersing pigment (water-based emulsion with solid content of 10% by mass)
CAB-O-JET 260M (manufactured by Cabot Co., Ltd.): Magenta-based self-dispersing pigment (water-based emulsion with solid content of 10% by mass)
CAB-O-JET 270 (manufactured by Cabot Co., Ltd.): Yellow-based self-dispersing pigment (water-based emulsion with 10% by weight of solid content)
CAB-O-JET 300 (manufactured by Cabot Co., Ltd.): Black-based self-dispersible pigment (15% by mass solids aqueous emulsion)
WD-0024 (manufactured by Tayca Corporation): titanium oxide (45% solids aqueous emulsion)
SAG 503A (made by Nisshin Chemical Industry Co., Ltd.): silicone surfactant "Silface SAG 503A"
SAG 002 (manufactured by Nisshin Chemical Industries, Ltd.): silicone surfactant "Silface SAG 002"
Superflex 460 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.): aqueous emulsion of urethane resin (resin Tg: -21 ° C, solid content 38% by mass)
Superflex 470 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.): aqueous emulsion of urethane resin (resin Tg: -31 ° C, solid content 38% by mass)
Viniblanc 700 (manufactured by Nisshin Chemical Industry Co., Ltd.): aqueous emulsion of polyvinyl chloride-acrylic resin core-shell particles (resin Tg: 70 ° C., solid content: 30% by mass)

  As shown in Tables 1 to 3, by the printing method using the aqueous inkjet ink set of Examples 1 to 7 within the scope of the present invention, the bleeding on the leather made of a synthetic resin is small and the abrasion resistance is reduced. It was possible to form an image excellent in flexibility and flex resistance.

  On the other hand, in Comparative Example 1 in which resin fine particles having a Tg of more than 0 ° C. were used, the bending resistance was poor. This is because when the Tg of the resin fine particles exceeds 0 ° C., the flexibility of the formed ink coating film is lost. In Comparative Example 2 in which the content of 3-methoxy-1-butanol which is substituted butanol was 5% by mass, image bleeding occurred and image peeling also occurred. This is because the initial drying rate is slow. In order to compensate for the initial drying speed, other water-soluble organic solvents are required, but when the other water-soluble organic solvents are contained in a large amount, the fixing property tends to be deteriorated. In Comparative Example 3 in which the content of 3-methoxy-1-butanol which is substituted butanol was 25% by mass, image blur occurred. This is because the initial drying speed becomes too high, and the dispersion state of the pigment in the ink coating film (particularly in the white ink coating film) becomes uneven.

  The present invention is extremely useful for decorating leathers of which top coats are applied, such as natural leathers and artificial leathers.

Claims (9)

Heating at least the surface of the synthetic resin leather surface to 40 ° C. or higher;
A leather made of a synthetic resin, including a step of discharging the ink contained in the aqueous inkjet ink set onto the surface of the leather by an ink jet method, and a step of heating the surface of the leather from which the ink is discharged to 60 ° C. or higher Ink jet printing method of
The ink contained in the aqueous inkjet ink set contains at least water (A), pigment (B), water-soluble organic solvent component (C), surfactant (D), and resin fine particles (E).
The glass transition temperature of the resin fine particles (E) is 0 ° C. or less,
The ink comprises, as a water-soluble organic solvent component (C), 8 mass% of at least one substituted butanol selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol % To 23% by mass,
The aqueous inkjet ink set includes a white ink containing a white pigment as the pigment (B), and a colored ink containing a pigment other than white as the pigment (B).
An inkjet printing method characterized in that.   The inkjet printing method of Claim 1 in which the said resin fine particle (E) contains a urethane resin.   The inkjet printing method according to claim 1, wherein the water-soluble organic solvent component further contains a diol solvent and a glycol monoether solvent.   The inkjet printing method according to any one of claims 1 to 3, wherein the leather is an artificial leather.   The step of discharging the ink on the surface of the leather, the white ink is discharged to adhere to the surface of the leather, and then the colored ink is discharged to adhere to the surface of the leather. The inkjet printing method according to any one of the above. An aqueous inkjet ink for leather, the surface of which is made of synthetic resin, containing at least water (A), pigment (B), water-soluble organic solvent component (C), surfactant (D), and resin fine particles (E) There,
The glass transition temperature of the resin fine particles (E) is 0 ° C. or less,
The aqueous inkjet ink comprises, as a water-soluble organic solvent component (C), at least one substituted butanol selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol; Aqueous inkjet ink containing 8 mass% or more and 23 mass% or less.   The aqueous inkjet ink according to claim 6, wherein the resin fine particles (E) contain a urethane resin.   The aqueous inkjet ink according to claim 6, wherein the water-soluble organic solvent component further contains a diol solvent and a glycol monoether solvent.   The aqueous inkjet ink according to any one of claims 6 to 8, wherein the leather is an artificial leather.