JP2021046515A - Ink, ink set, printed matter, printing method, and printing apparatus - Google Patents

Abstract

To provide an ink wherein: even when used for leather as a matter to be printed, the ink has excellent fixability and beading resistance and can form an image of good quality.SOLUTION: An ink is used for leather as a matter to be printed, the ink including: a coloring material; an organic solvent; a resin; and a surfactant, wherein a contact angle of the ink to the leather is 45° or less.SELECTED DRAWING: None

Description

The present invention relates to inks, ink sets, printing methods, and printing devices.

Conventionally, there are a screen method, an inkjet method, and the like as decorations on leather. Among these, the process is simple, full color is easy, and high-resolution images can be obtained even with a device with a simple configuration, compared to the decorative demand of various designs and other recording methods. Therefore, the use of the inkjet method is increasing.

As the inkjet method, water-based ink and solvent ink are used for permeable leather such as Nume leather. Further, the ultraviolet curable ink (UV ink) is used for a wide variety of leathers (see, for example, Patent Documents 1 and 2).
Further, latex ink has been proposed as one that can decorate a wide range of leather and can form an ink film that is more flexible and safer than the UV ink (see, for example, Patent Document 3).

An object of the present invention is to provide an ink having excellent fixability and beading resistance and capable of forming an image of good image quality even when leather is used as a printed matter.

The ink of the present invention as a means for solving the above-mentioned problems is an ink that uses leather as a printed matter, contains a coloring material, an organic solvent, a resin, and a surfactant, and contacts the ink with the leather. The angle is 45 ° or less.

An object of the present invention is to provide an ink capable of forming an image having excellent fixability and good image quality with less beading even when leather is used as a printed matter.

FIG. 1 is a perspective explanatory view showing an example of a printing apparatus. FIG. 2 is a perspective explanatory view showing an example of a main tank in a printing apparatus.

(ink)
The ink of the present invention is an ink that uses leather as a printed matter, contains a coloring material, an organic solvent, a resin, and a surfactant, and the contact angle of the ink with respect to the leather is 45 ° or less, which is further required. Contains other ingredients depending on the condition.

Conventional water-based inks and solvent inks have a problem that abnormal images such as color bleeding and beading occur on non-permeable or non-permeable leather coated with a resin or the like on the surface.
Since a hard ink film is formed in the conventional UV ink, the softness of the leather and the texture such as the touch feeling may be impaired, and there is also a problem in safety.
The conventional latex ink has a problem that the fixability and scratch resistance of the ink film formed on the leather are inferior to those of the UV ink.
Therefore, in the prior art, when leather is used as the printed matter, there is a problem that the fixability is lowered, beading occurs, and the texture such as softness and touch feeling of the original leather is impaired.

In the present invention, a coloring material, an organic solvent, a resin, and a surfactant are contained, and the contact angle of the ink with respect to the leather is 45 ° or less, so that the ink adheres to various leathers and has bead resistance. It has excellent properties and can form an image with good image quality without impairing the soft texture of the original leather.

The contact angle of the ink with respect to the leather is 45 ° or less, preferably 40 ° or less. The lower limit of the contact angle of the ink is preferably 0 ° or more.
For the contact angle of the ink with respect to the leather, for example, the contact angle of the ink can be measured by dropping the ink on the surface of the leather as the printed matter under the following conditions using the following contact angle meter.
Contact angle meter: Kyowa Interface Science Co., Ltd. Model: Dmo-501
[conditions]
・ Drop size: 2 μL
・ Time from landing to measurement: 100ms
・ Analysis: θ / 2 method

In one aspect of the present invention, the surface free energy of the leather is preferably 30 mJ / ^{m 2} or more 50 mJ / ^{m 2} or less. When the surface free energy of the leather is 30 mJ / ^{m 2} or more 50 mJ / ^{m 2} or less, high adhesion between the ink layer and the leather is obtained.

In an inkjet recording type image forming apparatus (printing apparatus), when a pattern having a high density is formed on leather, which is a printed matter having low ink absorbency, adjacent inks land before the inks are fixed. In such a case, the ink droplets that have not been completely dried attract each other and aggregate, and the color of the aggregated portion becomes darker, and this portion is visually recognized as color unevenness. Such a phenomenon is called "beading". The beading phenomenon can be controlled by the surface free energy of the leather as the printed matter and the contact angle of the ink with respect to the leather.

<Contact angle and surface free energy>
Surface tension (mN / m) is involved in the magnitude of the intermolecular interaction that occurs between two substances. The surface tension of a liquid can be quantified by, for example, the Wilhelmy method, the suspension method, or the ring method, but since it cannot be directly measured when the substance is a solid, the surface free energy (mJ) having the same dimension is obtained. / M ² ) is calculated.
Solids with similar surface free energies are prone to intermolecular interactions and exhibit high adhesion.

In the present invention, when the surface free energy of leather is γ _A and the surface free energy of an ink film formed by using ink is γ _B , γ represented by the formula: (γ = γ _A −γ _{B) is} The closer it is to 0, the better the adhesion. Particularly preferred because of its excellent adhesion leather and the ink film is -10mJ / ^{m 2} or more 15 mJ / ^{m 2} or less in the range, gamma and more preferably at -2mJ / ^{m 2} or more 10 mJ / ^{m 2} or less.

The surface free energy (surface tension) of a solid can be calculated by the following method.
A small amount of solvent is dropped on the surface of the test piece, and the contact angle in the θ / 2 method is measured.
At this time, a known surface tension of the solvent is used.
It is known that the surface free energy can be calculated by using the extended Fowkes equation based on the measured contact angle of the solvent.
Assuming that the surface tension of the liquid is γ ^L , the surface free energy of the solid is γ ^S , and the contact angle is θ, the extended Fowkes equation is expressed by the following equation.
γ ^L (1 + cos θ) = 2 (γ ^L γ ^S ) ^1/2

Here, in "Journal of the Japan Adhesion Association, 1972, Vol. 8, No. 3, pp. 131-141", Kitazaki-Hata et al. Extend the Fowkes equation and set the surface free energy by the type of intermolecular force. It is decomposed into two components.
It has been clarified that it can be applied not only to general non-polar intermolecular forces but also to systems having polar or hydrogen-bonding intermolecular forces.

Each component of the surface tension (mN / m) of the solvent for measuring the contact angle and the surface free energy (mJ / m ² ) of the solid are related, and the non-polar component of the non-polar intermolecular force of the solvent γ _d , The surface free energy of a solid can be calculated by knowing the contact angles with each component _{of the polar component γ p} of the intermolecular force due to the dipole and the _{hydrogen bond component γ h} due to the hydroxy group.

If the total value of the surface free energy is γ _total , then γ _total = γ _d + γ _p + γ _h .
The extended Fokes expression is
It is represented by γ ^L (1 + cos θ) = 2 [(γ ^L _d γ ^S _d ) ^1/2 + (γ ^L _p γ ^S _p ) ^1/2 + (γ ^L _h γ ^S _h ) ^1/2 ].
The contact angle can be measured with three kinds of solvents whose components are known, and the surface free energy and the total value of the solid can be calculated by using the above formula.

Furthermore, in order to improve the measurement accuracy of the surface free energy, four or more kinds of solvents are used, and each component is obtained by linear regression.
By further transforming the extended Fowkes formula,
1 + cosθ = [(2 / γ ^L ) (γ ^L _d ) ^1/2 ] (γ ^S _d ) ^1/2 + [(2 / γ ^L ) (γ ^L _p ) ^1/2 ] (γ ^S _p ) ^{1 / 2 + [(2 / γ L} ) (γ L h) 1/2] (γ S h) 1/2
And to simplify the formula
y = 1 + cosθ
d = (γ ^S _d ) ^1/2
_p = (γ ^S p) ^1/2
_h = (γ ^S h) ^1/2
x ₁ = [(2 / γ ^L ) (γ ^L _d ) ^1/2 ]
x ₂ = [(2 / γ ^L ) (γ ^L _p ) ^1/2 ]
x ₃ = [(2 / γ ^L ) (γ ^L _h ) ^1/2 ]
By the way, the extended Fokes expression is
y = dx ₁ + px ₂ + hx ₃
It can be expressed as.

Here, assuming that n kinds of solvents are used, n of the above equations hold.
y _i = dx _i1 + px _i2 + hx _i3 (i = 1 to n)

Assuming that the error that occurs when n = 4 or more is ε, it can be expressed as follows.
ε _i = y _i − (dx _i1 + px _i2 + hx _i3

The sum S (d, p, h) of the squares of this error can be expressed as follows.
S (d, p, h) = Σ (ε _i ) ² = Σ [y _i − (dx _i1 + px _i2 + hx _i3 )] ²

Since S (d, p, h) is minimized when ∂S / ∂d = 0, ∂S / ∂p = 0, and ∂S / ∂h = 0, the following three equations It holds.
Σ x _i1 ² d + Σ _{x i1 x i2} p + _Σ x _{i1 x i3} h = _{Σ x i1} y i
Σ x _{i2 x i1} d + _Σ x _i2 ² p + _{Σ x i2 x i3} h = _{Σ x i2} y i
Σ x _{i3 x i1} d + Σ x _{i3 x i2} p + _{Σ x i3} ² h = _{Σ x i3} y i

By solving this three-dimensional simultaneous equation, d, p, and h are obtained, and the surface free energy (γ _d , γ _p , γ _h ) of the solid is calculated.
However, when any of d, p, and h has a negative value, γ ^1/2 <0, which is unsuitable.
In that case, the approximate value is obtained by calculating the inappropriate component value as 0.

The solvent used for measuring the contact angle is not particularly limited except that the component value of the surface tension is known, and examples thereof include the following solvents.
Group A: Hexadecane, Tetradecane, Dodecane, Undecane, Decane, Nonane, Octane, Heptane, Hexane Group B: Diiodomethane, 1,1,2,2-Tetrabromoethane, 1-Bromonaphthalene, Trichlorobiphenyl, Tetrachloroethane Group C: β-thiodiglycol, glycerin, formamide, diethylene glycol, ethylene glycol, dipropylene glycol, water

It is preferable to select four or more kinds of solvents from the above because the calculation accuracy of the surface free energy is improved, and it is more preferable to select from two or more groups. It is particularly preferable to select the above.

<Printed matter>
Leather is used as the printed matter. There are various types of leather. Natural leather manufactured from animal skin, synthetic leather coated with synthetic resin based on woven cloth or knitted cloth, artificial leather coated with synthetic resin based on non-woven fabric impregnated with synthetic resin, natural Examples thereof include recycled leather in which cut pieces generated in the leather manufacturing process are crushed and hardened into a sheet to be surface-coated. Further, leather is generally provided with various functions such as water resistance and heat resistance by various finishing methods, and the surface composition is diverse.
Examples of the leather include permeable natural leather such as Nume leather, artificial leather, synthetic leather, recycled leather, natural leather whose surface is surface-treated with resin or the like, and artificial leather whose surface is surface-treated with resin or the like. Examples thereof include synthetic leather whose surface is surface-treated with resin or the like, and recycled leather whose surface is surface-treated with resin or the like.
Examples of the resin include acrylic resin, urethane resin, vinyl chloride resin and the like.

The natural leather is not particularly limited, and leather made from various animal skins such as cowhide, pig leather, sheep leather, and horse leather can be used.
The artificial leather is not particularly limited, and a non-woven fabric made of microfibers such as nylon and polyester may be used as a base material impregnated with a synthetic resin or a surface thereof coated with a synthetic resin.
The synthetic leather is not particularly limited, and a woven or knitted fabric base material composed of natural fibers, nylon fibers, polyester fibers, or the like coated with a synthetic resin can be used.
The leather products made of leather are used in a wide range of fields such as clothing, bags, shoes, interior materials, and vehicle interior materials because of their unique soft texture and luxury.

The printed matter is not particularly limited, and plain paper, glossy paper, special paper, cloth, or the like can also be used.

In one aspect of the present invention, the difference (AB) between the friction coefficient A on the surface of the leather and the friction coefficient B on the surface of the ink film is preferably 0.5 or less, more preferably 0.3 or less. When the difference in friction coefficient is 0.5 or less, a printed matter having good fixability and texture can be obtained.

Here, the coefficient of friction can be measured using, for example, a portable tactile meter (HEIDON model: TRIBOGEAR Type: 33, manufactured by Shinto Kagaku Co., Ltd.). A leather or ink film is cut into a size of 25 mm × 10 mm with a cutter, placed on the device, and rubbed with the pad of the index finger under the following conditions to measure the coefficient of friction.
[Measurement condition]
・ Analog voltage output: 2.5V
・ Maximum frictional force: 2000gf (= 5V)
・ Scraping speed: 7 cm / sec ・ Threshold: 4 gf
・ Minimum width: 0.2s

The ink of the present invention contains a coloring material, an organic solvent, a resin, and a surfactant, and further contains other components as required.

<Color material>
The coloring material is not particularly limited, and pigments and dyes can be used.
As the pigment, an inorganic pigment or an organic pigment can be used. These may be used alone or in combination of two or more. Moreover, you may use a mixed crystal.
As the pigment, for example, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, a glossy color pigment such as gold or silver, a metallic pigment, or the like can be used.
As inorganic pigments, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, carbon black produced by known methods such as contact method, furnace method, and thermal method. Can be used.
Examples of organic pigments include azo pigments and polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.). , Dye chelate (for example, basic dye type chelate, acidic dye type chelate, etc.), nitro pigment, nitroso pigment, aniline black and the like can be used. Among these pigments, those having a good affinity with a solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
As a specific example of the pigment, for black, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper, iron (CI pigment black 11) , Metals such as titanium oxide, and organic pigments such as aniline black (CI pigment black 1).
Further, for color, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmin 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. I. Pigment Violet 1 (Rhodamine Lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3, 15: 4 (phthalocyanine blue), 16, 17: 1, 56, 60, 63, C.I. I. Pigment Greens 1, 4, 7, 8, 10, 17, 18, 36 and the like.

The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type may be used alone or two or more types may be used in combination.
As the dye, for example, C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52,80,82,249,254,289, C.I. I. Acid Blue 9,45,249, C.I. I. Acid Black 1,2,24,94, C.I. I. Hood Black 1, 2, C.I. I. Direct Yellow 1,12,24,33,50,55,58,86,132,142,144,173, C.I. I. Direct Red 1,4,9,80,81,225,227, C.I. I. Direct Blue 1,2,15,71,86,87,98,165,199,202, C.I. I. Dilekdo Black 19,38,51,71,154,168,171,195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive Black 3, 4, 35 and the like can be mentioned.

The content of the coloring material in the ink is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less from the viewpoint of improving image density, good fixability and ejection stability. preferable.

In order to disperse the pigment to obtain an ink, a method of introducing a hydrophilic functional group into the pigment to obtain a self-dispersing pigment, a method of coating the surface of the pigment with a resin and dispersing it, and a method of dispersing using a dispersant are used. The method, etc. can be mentioned.
As a method of introducing a hydrophilic functional group into a pigment to obtain a self-dispersing pigment, for example, by adding a functional group such as a sulfone group or a carboxyl group to the pigment (for example, carbon), the pigment can be dispersed in water. The method can be mentioned.
Examples of the method of coating the surface of the pigment with a resin and dispersing the pigment include a method of encapsulating the pigment in microcapsules so that the pigment can be dispersed in water. This can be rephrased as a resin-coated pigment. In this case, it is not necessary that all the pigments blended in the ink are coated with the resin, and the uncoated pigments and the partially coated pigments are dispersed in the ink as long as the effects of the present invention are not impaired. May be. Among these, resin-coated pigments are preferable from the viewpoints of ink fixability, storage stability, and ejection reliability.
Examples of the method of dispersing using a dispersant include a method of dispersing using a known low molecular weight dispersant and a high molecular weight dispersant represented by a surfactant.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant and the like can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Oil & Fat Co., Ltd. and a naphthalene sulfonate Na formalin condensate can also be suitably used as a dispersant.
The dispersant may be used alone or in combination of two or more.

<Pigment dispersion>
It is possible to obtain an ink by mixing a material such as water or an organic solvent with a pigment. It is also possible to produce an ink by mixing a material such as water or an organic solvent with a pigment dispersion obtained by mixing a pigment and other water or a dispersant.
The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. A disperser may be used for dispersion.
The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency is 20 nm in terms of the maximum number because the dispersion stability of the pigment is good and the image quality such as ejection stability and image density is also high. More than 500 nm is preferable, and more preferably 20 nm or more and 150 nm or less. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good ejection stability and increasing the image density, 0.1 mass is used. % Or more and 50% by mass or less are preferable, and 0.1% by mass or more and 30% by mass or less are more preferable.
If necessary, the pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifuge, or the like.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and a water-soluble organic solvent can be used. Examples thereof include ethers such as polyhydric alcohols, polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amide compounds, amines and sulfur-containing compounds. Among these, it is preferable to contain an amide compound from the viewpoint of fixability to non-permeable or non-permeable leather surface-treated with a resin or the like.
Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2 , 3-Butandiol, 3-Methyl-1,3-Butandiol, Triethylene Glycol, Polyethylene Glycol, Polypropylene Glycol, 1,2-Pentanediol, 1,3-Pentanediol, 1,4-Pentanediol, 2, 4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1 , 2,6-Hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3 -Polyhydric alcohols such as pentanediol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, etc. Polyhydric alcohol aryl ethers such as polyhydric alcohol alkyl ethers, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1, Nitrogen-containing heterocyclic compounds such as 3-dimethyl-2-imidazolidinone, ε-caprolactam and γ-butyrolactone, amide compounds represented by the following general formula (1), amines such as monoethanolamine, diethanolamine and triethylamine, Examples thereof include sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate, ethylene carbonate, and alkoxy group-substituted butanol. Among these, the amide compound represented by the general formula (1) and the alkoxy group-substituted butanol are preferable from the viewpoint of fixability to leather.
It is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because it not only functions as a wetting agent but also has good drying properties.

ただし、前記一般式（１）中、Ｒ_１、Ｒ_２、及びＲ_３は、それぞれ独立に、炭素数１以上８以下の炭化水素基を表す。
前記炭化水素基としては、炭素数が１以上８以下であれば特に制限はなく、例えば、直鎖又は分岐鎖、或いは環状のアルキル基などが挙げられる。
前記アルキル基としては、メチル基、エチル基、プロピル基、ブチル基、イソプロピル基、イソブチル基、ペンチル基、ヘキシル基、ヘプチル基、エチルヘキシル基、オクチル基、シクロプロピル基、シクロブチル基、シクロペンチル基、シクロヘキシル基などが挙げられる。
前記一般式（１）で表されるアミド化合物としては、例えば、３−メトキシ−Ｎ，Ｎ−ジメチルプロピオンアミド、３−ブトキシ−Ｎ，Ｎ−ジメチルプロピオンアミドなどが挙げられる。

However, in the general formula (1), R ₁ , R ₂ , and R ₃ independently represent hydrocarbon groups having 1 or more and 8 or less carbon atoms.
The hydrocarbon group is not particularly limited as long as it has 1 or more and 8 or less carbon atoms, and examples thereof include a linear or branched chain or a cyclic alkyl group.
Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, isopropyl group, isobutyl group, pentyl group, hexyl group, heptyl group, ethylhexyl group, octyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group and cyclohexyl. Group etc. can be mentioned.
Examples of the amide compound represented by the general formula (1) include 3-methoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide and the like.

As the alkoxy group-substituted butanol, butanol having a methoxy group is preferable, and examples thereof include 3-methoxy-3-methyl-1-butanol and 3-methoxy-1-butanol.

Polyol compounds having 5 or more carbon atoms and glycol ether compounds are also preferably used.
Examples of the polyol compound having 5 or more carbon atoms include 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, and 2,2,4-trimethyl-1,3-pentanediol. Can be mentioned.
Examples of the glycol ether compound include polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Kind: Polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

<Resin>
The type of resin contained in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, etc. Examples thereof include resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, and acrylic-silicone resins. These may be used individually by 1 type, may be used in combination of 2 or more type, and resin particles made of these resins may be used. It is possible to obtain ink by mixing resin particles with a material such as a coloring material or an organic solvent in the state of a resin emulsion in which water is dispersed as a dispersion medium. As the resin particles, those synthesized as appropriate may be used, or commercially available products may be used. Among these resins, urethane resin or acrylic resin is preferable from the viewpoint of scratch resistance and fixability to leather.

The content of the resin is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of fixability and storage stability of the ink, 1% by mass or more and 30% by mass with respect to the total amount of the ink. The following is preferable, and from the viewpoint of fixability and texture, 3% by mass or more and 15% by mass or less is more preferable.

The particle size of the solid content in the ink is not particularly limited and can be appropriately selected according to the purpose, but from the viewpoint of improving image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number of inks. Is preferably 20 nm or more and 1000 nm or less, and more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

<Surfactant>
As the surfactant, any of a silicone-based surfactant, a fluorine-based surfactant, an amphoteric surfactant, a nonionic surfactant, and an anionic surfactant can be used.
The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Among these, those that do not decompose even at high pH are preferable, and examples thereof include side chain modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, one-ended modified polydimethylsiloxane, and side chain double-ended modified polydimethylsiloxane. Those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a group are particularly preferable because they exhibit good properties as an aqueous surfactant. Further, as the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include a compound in which a polyalkylene oxide structure is introduced into the Si portion side chain of dimethylsiloxane.

Examples of the fluorine-based surfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. A polyoxyalkylene ether polymer compound is particularly preferable because it has a low foaming property. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonic acid salt. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylic acid salt. The polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain includes a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain and a perfluoroalkyl ether group in the side chain. Examples thereof include salts of polyoxyalkylene ether polymers. The counterions of the salts in these fluorine-based surfactants are Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH). _{3 and the} like can be mentioned.

Examples of the amphoteric tenside include laurylaminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of the nonionic surfactant include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, and polyoxyethylene sorbitan. Examples thereof include fatty acid esters and ethylene oxide adducts of acetylene alcohols.
Examples of the anionic surfactant include salts of polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, and polyoxyethylene alkyl ether sulfate.
These may be used alone or in combination of two or more.

The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, side chain-modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, one-ended modified polydimethylsiloxane, side. Examples thereof include polydimethylsiloxane modified at both ends of the chain, and a polyether-modified silicone-based surfactant having a polyoxyethylene group and a polyoxyethylene polyoxypropylene group as modifying groups exhibits good properties as an aqueous surfactant, and is particularly effective. preferable.
As such a surfactant, an appropriately synthesized one may be used, or a commercially available product may be used. As commercially available products, for example, they can be obtained from Big Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like.

The polyether-modified silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the polyalkylene oxide structure represented by the following general formula (S-1) is dimethyl. Examples thereof include those introduced into the Si part side chain of polysiloxane.

（ただし、前記一般式（Ｓ−１）式中、ｍ、ｎ、ａ、及びｂは、それぞれ独立に、整数を表し、Ｒは、アルキレン基を表し、Ｒ’は、アルキル基を表す。）

(However, in the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R'represents an alkyl group.)

Commercially available products can be used as the polyether-modified silicone-based surfactant, for example, KF-618, KF-642, KF-643 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), EMALEX-SS-5602, SS- 1906EX (manufactured by Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (manufactured by Toray Dow Corning Silicone Co., Ltd.), BYK- 33, BYK-387 (manufactured by Big Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (manufactured by Toshiba Silicon Co., Ltd.) and the like.

As the fluorine-based surfactant, a compound having 2 to 16 carbon atoms substituted with fluorine is preferable, and a compound having 4 to 16 carbon atoms substituted with fluorine is more preferable.
Examples of the fluorine-based surfactant include a perfluoroalkyl phosphate ester compound, a perfluoroalkyl ethylene oxide adduct, and a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain.
Among these, the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain is preferable because it has low foaming property, and is represented by the following general formula (F-1) and the following general formula (F-2). Fluorosurfactants are particularly preferred.

上記一般式（Ｆ−１）で表される化合物において、水溶性を付与するためにｍは０〜１０の整数が好ましく、ｎは０〜４０の整数が好ましい。 [General formula (F-1)]

In the compound represented by the general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility.

[General formula (F-2)]
C _n F _{2n + 1-} CH ₂ CH (OH) CH _2- O- (CH ₂ CH ₂ O) _a- Y
In the compound represented by the above general formula (F-2), Y is H or C _n F _{2n + 1} , and n is an integer of 1 to 6 or CH ₂ CH (OH) CH _2- C _n F _{2n + 1} . Yes, n is an integer of 4 to 6, and in C _p H _{2p + 1} , p is an integer of 1 to 19. a is an integer of 4 to 14.

A commercially available product may be used as the fluorine-based surfactant.
Examples of the commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.). Full Lard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Co., Ltd.); Megafuck F-470, F -1405, F-474 (all manufactured by DIC Corporation); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by The Chemours Company); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Chemours). , Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omniova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.) and the like. Among these, FS-3100, FS-34, FS-300, Neos Co., Ltd. manufactured by The Chemours Company, from the viewpoint of remarkably improving good print quality, especially color development, penetrability to paper, wettability, and leveling property. FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW, Polyfox PF-151N manufactured by Omniova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferable.

The content of the surfactant in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of excellent wettability and ejection stability and improvement in image quality, 0.001 mass is used. % Or more and 5% by mass or less is preferable, and 0.8% by mass or more and 4% by mass or less is more preferable.

<Additives>
If necessary, water, an antifoaming agent, an antiseptic / antifungal agent, a rust preventive, a pH adjuster, or the like may be added to the ink.

-Water-
As the water, pure water such as ion-exchanged water, ultra-filtered water, reverse osmosis water, distilled water, or ultrapure water can be used.
The content of water in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but from the viewpoint of ink drying property and ejection reliability, it is preferably 10% by mass or more and 90% by mass or less, and 20% by mass. % Or more and 60% by mass or less are more preferable.

-Defoamer-
The defoaming agent is not particularly limited, and examples thereof include a silicone-based defoaming agent, a polyether-based defoaming agent, and a fatty acid ester-based defoaming agent. These may be used alone or in combination of two or more. Among these, a silicone-based defoaming agent is preferable because it has an excellent defoaming effect.

-Preservatives and fungicides-
The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

-Rust inhibitor-
The rust preventive is not particularly limited, and examples thereof include acidic sulfites and sodium thiosulfate.

-PH regulator-
The pH adjusting agent is not particularly limited as long as the pH can be adjusted to 7 or more, and examples thereof include amines such as diethanolamine and triethanolamine.

The physical characteristics of the ink are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity, surface tension, pH and the like are preferably in the following ranges.
The viscosity of the ink at 25 ° C. is preferably 5 mPa · s or more and 30 mPa · s or less, preferably 5 mPa · s or more and 25 mPa · s or less, from the viewpoint of improving the print density and character quality and obtaining good ejection properties. More preferred. Here, for the viscosity, for example, a rotary viscometer (manufactured by Toki Sangyo Co., Ltd., RE-80L) can be used. As the measurement conditions, it is possible to measure at 25 ° C. with a standard cone rotor (1 ° 34'x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes.
The surface tension of the ink is preferably 35 mN / m or less, more preferably 32 mN / m or less at 25 ° C. from the viewpoint that the ink is preferably leveled on the printed matter and the drying time of the ink is shortened.
The pH of the ink is preferably 7 to 12, more preferably 8 to 11, from the viewpoint of preventing corrosion of the metal member in contact with the liquid.

The coloring of the ink of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose, and examples thereof include yellow, magenta, cyan, black, and white.

(Ink set)
The ink set of the present invention is an ink set that uses leather as a printed matter.
An ink set consisting of at least two types selected from cyan ink, magenta ink, yellow ink, black ink, and white ink.
At least two inks selected from the cyan ink, magenta ink, yellow ink, black ink, and white ink all contain a coloring material, a resin, an organic solvent, and a surfactant.
The contact angle of the ink with respect to the leather is 45 ° or less.
It is preferable that the surface free energy of the leather is 30 mJ / ^{m 2} or more 50 mJ / ^{m 2} or less.

When recording is performed using an ink set in which two or more types are used in combination, a multicolor image can be recorded, and when recording is performed using an ink set in which all colors are used in combination, a full-color image can be recorded. White ink is suitable as a base for color images.

The method of applying ink is not particularly limited and may be appropriately selected depending on the intended purpose. For example, an inkjet method, a blade coating method, a gravure coating method, a bar coating method, a roll coating method, a dip coating method, and a curtain. Examples include a coating method, a slide coating method, a die coating method, and a spray coating method. Among these, the inkjet method is preferable.

(Printing device and printing method)
The ink of the present invention can be suitably used for various recording devices by an inkjet recording method, for example, a printer, a facsimile device, a copying device, a printer / fax / copier multifunction device, a three-dimensional modeling device, and the like.
In the present invention, the printing apparatus and the printing method are an apparatus capable of ejecting ink, various processing liquids, and the like onto a printed matter, and a method for recording using the apparatus. The printed matter means a material to which ink and various treatment liquids can be attached even temporarily, and leather is suitable in the present invention.
The printing device may include not only a head portion for ejecting ink, but also means for feeding, transporting, and discharging printed matter, and other devices called pretreatment devices and posttreatment devices. ..
The printing apparatus and printing method may include a heating means used in the heating step and a drying means used in the drying step. The heating means and the drying means include, for example, means for heating and drying the printed surface and the back surface of the printed matter. The heating means and the drying means are not particularly limited, but for example, a hot air heater and an infrared heater can be used. Heating and drying can be performed before printing, during printing, after printing, and the like. The heating temperature is preferably 40 ° C. or higher and 120 ° C. or lower, more preferably 60 ° C. or higher and 120 ° C. or lower from the viewpoint of fixability, and 60 ° C. or higher and 90 ° C. or lower from the viewpoint of preventing the texture such as the flexibility of leather from being impaired. More preferred.
Further, the printing apparatus and printing method are not limited to those in which significant images such as characters and figures are visualized by ink. For example, those that form patterns such as geometric patterns and those that form a three-dimensional image are also included.
Further, the printing apparatus includes both a serial type apparatus that moves the ejection head and a line type apparatus that does not move the ejection head, unless otherwise specified.
Further, as the printing device, not only a desktop type but also a wide printing device capable of printing on an A0 size printed matter, or, for example, continuous paper wound in a roll shape can be used as the printed matter. A continuous line printer is also included.

An example of the printing apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective explanatory view of the device. FIG. 2 is a perspective explanatory view of the main tank. The image forming apparatus 400 as an example of the printing apparatus is a serial type image forming apparatus. A mechanical unit 420 is provided in the exterior 401 of the image forming apparatus 400. Each ink container 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is, for example, an aluminum laminate film or the like. It is made of packaging members. The ink container 411 is housed in, for example, a plastic container case 414. As a result, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 is provided behind the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404. As a result, each ink discharge port 413 of the main tank 410 and the discharge head 434 for each color communicate with each other via the supply tube 436 for each color, and ink can be discharged from the discharge head 434 to the printed matter.

In addition, image formation, recording, printing, printing, etc. in the terms of the present invention are all synonymous terms.
Recording media, media, and printed matter are all synonymous.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.

(Preparation Example 1 of Pigment Dispersion Solution)
<Preparation of black pigment dispersion A>
After premixing the following raw materials, a black pigment dispersion liquid A was obtained by circulating and dispersing for 7 hours with a disc type bead mill (manufactured by Simmal Enterprises, KDL type, media: using zirconia balls having a diameter of 0.3 mm).
[composition]
-Carbon black pigment (trade name: Monarch800, manufactured by Cabot Corporation): 15 parts by mass-Anionic surfactant (Pionin A-51-B, manufactured by Takemoto Oil & Fat Co., Ltd.): 2 parts by mass-Ion-exchanged water: 83 parts by mass

(Preparation Example 2 of Pigment Dispersion Solution)
<Preparation of cyan pigment dispersion A>
Same as Preparation Example 1 of Pigment Dispersion Liquid, except that the carbon black pigment was changed to Pigment Blue 15: 3 (trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.) in Preparation Example 1 of the pigment dispersion liquid. A cyan pigment dispersion liquid A was obtained.

(Preparation Example 3 of Pigment Dispersion Solution)
<Preparation of magenta pigment dispersion A>
Magenta in the same manner as in Preparation Example 1 of the pigment dispersion, except that the carbon black pigment was changed to Pigment Red 122 (trade name: Toner Magenta EO02, manufactured by Clariant Japan Co., Ltd.) in Preparation Example 1 of the pigment dispersion. A pigment dispersion A was obtained.

(Preparation Example 4 of Pigment Dispersion Solution)
<Preparation of yellow pigment dispersion A>
In Preparation Example 1 of the pigment dispersion liquid, the carbon black pigment was changed to Pigment Yellow 74 (trade name: First Yellow 531; manufactured by Dainichiseika Kogyo Co., Ltd.) in the same manner as in Preparation Example 1 of the pigment dispersion liquid. , Yellow pigment dispersion A was obtained.

(Preparation Example 5 of Pigment Dispersion Solution)
-Synthesis of Polymer A-
11.2 g of styrene, 2.8 g of acrylic acid, 12 g of lauryl methacrylate, 4 g of polyethylene glycol methacrylate, 4 g of styrene macromer, and 0.4 g of mercaptoethanol were mixed and heated to 65 ° C.
Next, styrene 100.8 g, acrylic acid 25.2 g, lauryl methacrylate 108 g, polyethylene glycol methacrylate 36 g, hydroxyl ethyl methacrylate 60 g, styrene macromer 36 g, mercaptoethanol 3.6 g, azobismethylvaleronitrile 2.4 g, and methyl ethyl ketone 18 g. The mixed solution of was added dropwise into the flask over 2.5 hours.
After the dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours.
After aging at 65 ° C. for 1 hour, 0.8 g of azobismethylvaleronitrile was added, and the mixture was further aged for 1 hour.
After completion of the reaction, 364 g of methyl ethyl ketone was added into the flask to obtain 800 g of a polymer solution A having a solid content concentration of 50% by mass.

-Preparation of black pigment dispersion B-
Next, 28 g of the polymer solution A, 42 g of carbon black (Black Pearls 1000 manufactured by Cabot Corporation), 13.6 g of a 1 mol / L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of water were sufficiently stirred. Kneaded with a roll mill.
The obtained paste is put into 200 g of pure water and sufficiently stirred, then methyl ethyl ketone is removed by an evaporator, and pressure filtration is performed with a polyvinylidene fluoride membrane filter having an average pore size of 5 μm, and then the solid content concentration becomes 20% by mass. The water content was adjusted in this manner to obtain a styrene-acrylic resin-coated black pigment dispersion B having a solid content concentration of 20% by mass.

(Preparation Example 6 of Pigment Dispersion Solution)
<Preparation of cyan pigment dispersion B>
In Preparation Example 5 of the pigment dispersion liquid, the solid content concentration was 20 in the same manner as in Preparation Example 5 of the pigment dispersion liquid, except that Pigment Blue 15: 4 (SMART Cyan 3154BA manufactured by SENSIENT) was used instead of carbon black. A mass% styrene-acrylic resin-coated cyan pigment dispersion B was obtained.

(Preparation Example 7 of Pigment Dispersion Solution)
<Preparation of magenta pigment dispersion B>
In Preparation Example 5 of the pigment dispersion liquid, the solid content concentration was 20 mass in the same manner as in Preparation Example 5 of the pigment dispersion liquid, except that Pigment Red 122 (Pigment Red 122 manufactured by Sun Chemical Co., Ltd.) was used instead of carbon black. % Styrene-acrylic resin-coated magenta pigment dispersion B was obtained.

(Preparation Example 8 of Pigment Dispersion Solution)
<Preparation of yellow pigment dispersion B>
In Preparation Example 5 of the pigment dispersion liquid, the solid content concentration was 20% by mass in the same manner as in Preparation Example 5 of the pigment dispersion liquid, except that Pigment Yellow 74 (SMART Yellow 3074BA manufactured by SENSIENT) was used instead of carbon black. A styrene-acrylic resin-coated yellow pigment dispersion B was obtained.

(Preparation Example 1 of Polyurethane Resin Emulsion)
<Preparation of polyester urethane resin emulsion>
Double the amount of polyester polyol (trade name: Polylite OD-X-2251, manufactured by DIC Co., Ltd., average molecular weight 2,000) in a nitrogen-substituted container equipped with a thermometer, a nitrogen gas introduction tube, and a stirrer. The reaction was carried out using 200.4 g, 15.7 g of 2,2-dimethylolpropionic acid, 48.0 g of isophorone diisocyanate, 77.1 g of methyl ethyl ketone as an organic solvent, and 0.06 g of DMTDL (dibutyltin dilaurate) as a catalyst. After continuing the reaction for 4 hours, 30.7 g of methyl ethyl ketone was supplied as a diluting solvent, and the reaction was further continued. When the average molecular weight of the reaction product reached the range of 20,000 to 60,000, 1.4 g of methanol was added to terminate the reaction to obtain an organic solvent solution of urethane resin.
Next, 13.4 g of a 48 mass% potassium hydroxide aqueous solution was added to the organic solvent solution of the urethane resin to neutralize the carboxyl group of the urethane resin, and then 715.3 g of water was added and the mixture was sufficiently stirred. , Aging and solvent removal to obtain a polyester-based urethane resin emulsion having a solid content concentration of 30% by mass.
With respect to the obtained polyester-based urethane emulsion, the minimum film-forming temperature (MFT) measured by a "film-forming temperature tester" (manufactured by Imoto Seisakusho Co., Ltd.) was 74 ° C.

(Example 1)
<Manufacturing of ink A>
Ink A was prepared by adding ion-exchanged water so that the total amount of the following ink formulation was 100 parts by mass, mixing, stirring, and filtering with a filter (Sartorius, Minisalt) having an average pore size of 5 μm. ..
[Ink prescription]
-Magenta pigment dispersion B (resin coating type): 20 parts by mass-Polyurethane resin emulsion obtained in Preparation Example 1 (solid content concentration: 30% by mass, minimum film forming temperature (MFT) 74 ℃): 7.0 parts by mass ・ Triton HW1000 (manufactured by Dow Chemical Co., Ltd.): 1.8 parts by mass ・ BYK348 (manufactured by BYK, silicone surfactant): 0.2 parts by mass ・ 1,3-propanediol ( (Manufactured by Dupont): 4 parts by mass ・ 1,3-Butandiol (trade name: 1,3-Butandiol, manufactured by Daicel Chemical Co., Ltd.): 2 parts by mass ・ 3-Methyl-1,5-pentanediol (trade name) : MPD, manufactured by Kuraray Co., Ltd.): 3 parts by mass ・ 3-methoxy-1-butanol (trade name: MB, manufactured by Daicel Chemical Co., Ltd.): 3 parts by mass ・ 3-methoxy-N, N-dimethylpropionamide (product) Name: Equamid M100, manufactured by Idemitsu Kosan Co., Ltd.): 8 parts by mass ・ Proxel LV (manufactured by Abyssia, antiseptic and antifungal agent): 0.1 parts by mass ・ Ion exchanged water: remaining amount (total: 100 parts by mass)

(Examples 2 to 9 and Comparative Examples 1 to 4)
<Manufacturing of inks B to M>
Inks B to M were produced in the same manner as in Example 1 except that the ink formulations shown in Tables 1 to 3 were changed in Example 1. The resin content in Tables 1 to 3 is the solid content.

The detailed contents of each component in Tables 1 to 3 are as follows.
-Resin-
-Polyurethane resin (1): Superflex 300 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., solid content concentration: 30% by mass)
-Polyurethane resin (2): Polyester-based urethane resin emulsion obtained in Preparation Example 1 of polyurethane resin emulsion (solid content concentration: 30% by mass, minimum film-forming temperature (MFT) 74 ° C.)
・ Acrylic resin: Movinyl 6969D (manufactured by Japan Coating Resin Co., Ltd., solid ・ Fluororesin: AF1600 (manufactured by Mitsui DuPont Fluorochemical Co., Ltd.)

-Organic solvent-
・ 1,2-Propylene diol (trade name: propylene glycol, manufactured by ADEKA Corporation)
・ 1,3-Propanediol (manufactured by DuPont)
・ 1,3-Butanediol (trade name: 1,3-butanediol, manufactured by Daicel Chemical Co., Ltd.)
-2-Ethyl-1,3-hexanediol (trade name: octanediol, manufactured by KH Neochem Co., Ltd.)
・ 3-Methyl-1,5-pentanediol (trade name: MPD, manufactured by Kuraray Co., Ltd.)
・ 3-Methoxy-1-butanol (trade name: MB, manufactured by Daicel Corporation)
・ 3-Methoxy-3-methyl-1-butanol (trade name: Solfit, manufactured by Kuraray Co., Ltd.)
-3-Methoxy-N, N-dimethylpropionamide (trade name: Equamid M100, manufactured by Idemitsu Kosan Co., Ltd.)
-3-Butoxy-N, N-dimethylpropionamide (trade name: Equamid B100, manufactured by Idemitsu Kosan Co., Ltd.)

-Surfactant-
-Surfactant (1): Triton HW1000, manufactured by Dow Chemical Co., Ltd.-Surfactant (2): Wet270, manufactured by Ebony Co., Ltd.-Surfactant (3): SAG503A, manufactured by Shin-Etsu Chemical Industry Co., Ltd.-Surfactant ( 4): DSN403, manufactured by Daikin Industries, Ltd. ・ Surfactant (5): BYK348, manufactured by BYK, silicone surfactant

-Preservatives and fungicides-
・ Proxel LV, manufactured by Abyssia

<Image formation>
Each ink is filled in an inkjet printer (device name: IPSiO GXe5500 modified machine, manufactured by Ricoh Co., Ltd.), and for each leather as a printed matter shown below, the volume of one drop of ink is 21 pL and the resolution is 600 x 600 dpi. After printing the solid image of the tone, the printed matter was passed through a hot air drying unit at 70 ° C., dried, and fixed.

-Printed matter-
The following leathers a to e were used as the printed matter.
-Leather a: Natural leather, cowhide, thickness 2 mm
-Leather b: Natural leather, cowhide, thickness 2 mm
-Leather c: Synthetic leather, polyvinyl chloride resin (PVC), thickness 1.5 mm
-Leather d: Synthetic leather, polyvinyl chloride resin (PVC), thickness 1.5 mm
-Leather e: Synthetic leather, polyurethane resin (PU), thickness 1.2 mm

<Surface free energy>
The surface free energy of each leather was measured as follows. The results are shown in Table 4.
For the measurement, a contact angle meter (Kyowa Interface Science Co., Ltd., model: Dmo-501) was used, and 0.05 mL of the following five kinds of solvents was dropped onto each leather surface at 25 ° C. in an environment of 50% RH. The contact angle was measured 5.0 seconds after contact with the liquid.

(1) Methylene iodide [γ _d = 46.8, γ _p = 4.0, γ _h = 0, (mN / m)]
(2) 1-Bromonaphthalene [γ _d = 44.4, γ _p = 0.2, γ _h = 0, (mN / m)]
(3) Ethylene glycol [γ _d = 30.1, γ _p = 0, γ _h = 17.6, (mN / m)]
(4) Formamide [γ _d = 35.1, γ _p = 1.6, γ _h = 21.5, (mN / m)]
(5) Water (ultrapure water) [γ _d = 29.1, γ _p = 1.3, γ _h = 42.4, (mN / m)]

Known values were used for the surface tension component of each solvent.
Assuming that the surface free energy of each leather calculated from the contact angle is γ _A and the surface free energy of the ink film is γ _B , the surface free energy γ represented by the formula (γ = γ _{A −} γ _{B) was calculated.}

Next, for each ink and printed matter, "ink contact angle", "dot diameter", "beading resistance", and "fixability" were evaluated as follows. The results are shown in Tables 5 and 6.

<Ink contact angle>
For the combinations of ink and leather shown in Tables 5 and 6, ink was dropped on the surface of each leather under the following conditions using the following contact angle meter, and the contact angle of the ink was measured.
・ Contact angle meter: Kyowa Interface Science Co., Ltd. Model: Dmo-501
[conditions]
・ Drop size: 2 μL
・ Time from landing to measurement: 100ms
・ Analysis: θ / 2 method

<Dot diameter>
For each printed matter obtained by the above image formation, an image was measured with a digital microscope: VHX-200 manufactured by KEYENCE CORPORATION, and then an average value of dot diameters of N (= number of samples) = 20 was measured by dot diameter analysis software. (Μm) was calculated. The larger the dot diameter, the better the image quality, and B or higher is a level that can be actually used.
[Evaluation criteria]
AA: 80 μm or more A: 65 μm or more and less than 80 μm B: 50 μm or more and less than 65 μm C: less than 50 μm

<Beading resistance evaluation>
A solid image was printed under the same printing conditions as the measurement of the dot diameter, the density unevenness (beading) of the solid image was visually observed, and the beading resistance was evaluated according to the following evaluation criteria. In addition, B or more is a level that can be actually used.
[Evaluation criteria]
AA: None A: Slightly B: Quite Yes C: Violent

<Fixability (adhesion)>
A solid image is printed under the same printing conditions as the above dot diameter measurement, and the obtained solid image is used for a cross-cut test (1.5 mm interval, 100-mass test) in accordance with JIS K5600-5-6. Was done. "Fixability" was evaluated based on the following evaluation criteria based on the degree of mass peeling. In addition, B or more is a level that can be actually used.
[Evaluation criteria]
AA: 100 squares out of 100 squares that did not peel off A: 80 squares or more and 99 squares or less out of 100 squares that did not peel off B: 40 squares or more and 79 squares or less out of 100 squares that did not peel off C: Peeled The number of squares that did not come off is 10 or more and 39 or less out of 100. D: The number of squares that did not come off is 9 or less out of 100.

Examples of aspects of the present invention are as follows.
<1> An ink that uses leather as the printed matter.
Contains colorants, organic solvents, resins, and surfactants,
The ink is characterized in that the contact angle of the ink with respect to the leather is 45 ° or less.
<2> surface free energy of the leather is an ink according to 30 mJ / ^{m 2} or more 50 mJ / ^{m 2} or less is the <1>.
<3> The ink according to any one of <1> to <2>, wherein the organic solvent contains a diol compound having 5 or more carbon atoms.
<4> The ink according to any one of <1> to <3>, wherein the organic solvent contains at least one of an amide compound and an alkoxy group-substituted butanol.
<5> The ink according to any one of <1> to <4>, wherein the resin contains at least one of a urethane resin and an acrylic resin.
<6> The ink according to any one of <1> to <5>, wherein the content of the surfactant is 0.8% by mass or more and 4.0% by mass or less.
<7> The ink according to any one of <1> to <6>, wherein the coloring material contains a resin-coated pigment.
<8> The leather is natural leather, artificial leather, synthetic leather, recycled leather, natural leather whose surface is surface-treated with resin or the like, artificial leather whose surface is surface-treated with resin or the like, and surface treatment with resin or the like. The ink according to any one of <1> to <7>, which is at least one selected from the synthetic leather made and the recycled leather whose surface is surface-treated with a resin or the like.
<9> An ink applying step of applying the ink according to any one of <1> to <8> on leather, and an ink applying step.
The printing method comprises a drying step of drying the leather to which the ink is applied.
<10> Leather and
An ink applying means for applying the ink according to any one of <1> to <8> onto the leather, and an ink applying means.
The printing apparatus is characterized by having a drying means for drying the leather to which the ink is applied.
<11> An ink set that uses leather as the printed matter.
An ink set consisting of at least two types selected from cyan ink, magenta ink, yellow ink, black ink, and white ink.
At least two inks selected from the cyan ink, magenta ink, yellow ink, black ink, and white ink all contain a coloring material, an organic solvent, a resin, and a surfactant.
The ink set is characterized in that the contact angle of the ink with respect to the leather is 45 ° or less.

According to the ink according to any one of <1> to <8>, the printing method according to <9>, the printing apparatus according to <10>, and the ink set according to <11>. The object of the present invention can be achieved by solving various problems in the above.

400 Image forming device 401 Image forming device exterior 401c Device body cover 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y For each color of black (K), cyan (C), magenta (M), yellow (Y) Main tank 411 Ink storage unit 413 Ink discharge port 414 Storage container case 420 Mechanical unit 434 Discharge head 436 Supply tube

Japanese Unexamined Patent Publication No. 2014-55210 International Publication No. 2017/10431 JP-A-2019-77070

Claims (11)

An ink that uses leather as the printed matter.
Contains colorants, organic solvents, resins, and surfactants,
An ink characterized in that the contact angle of the ink with respect to the leather is 45 ° or less. The ink according to claim 1, wherein the surface free energy of the leather is 30 mJ / ^{m 2} or more 50 mJ / ^{m 2} or less. The ink according to any one of claims 1 to 2, wherein the organic solvent contains a diol compound having 5 or more carbon atoms. The ink according to any one of claims 1 to 3, wherein the organic solvent contains at least one of an amide compound and an alkoxy group-substituted butanol. The ink according to any one of claims 1 to 4, wherein the resin contains at least one of a urethane resin and an acrylic resin. The ink according to any one of claims 1 to 5, wherein the content of the surfactant is 0.8% by mass or more and 4.0% by mass or less. The ink according to any one of claims 1 to 6, wherein the coloring material contains a resin-coated pigment. The leather is natural leather, artificial leather, synthetic leather, recycled leather, natural leather whose surface is surface-treated with resin or the like, artificial leather whose surface is surface-treated with resin or the like, or synthetic whose surface is surface-treated with resin or the like. The ink according to any one of claims 1 to 7, which is at least one selected from leather and recycled leather whose surface is surface-treated with resin or the like. An ink applying step of applying the ink according to any one of claims 1 to 8 onto leather, and an ink applying step.
A printing method comprising a drying step of drying the leather to which the ink has been applied. With leather
An ink applying means for applying the ink according to any one of claims 1 to 8 onto the leather, and an ink applying means.
A printing apparatus comprising: a drying means for drying the leather to which the ink is applied. An ink set that uses leather as the printed matter.
An ink set consisting of at least two types selected from cyan ink, magenta ink, yellow ink, black ink, and white ink.
At least two inks selected from the cyan ink, magenta ink, yellow ink, black ink, and white ink all contain a coloring material, an organic solvent, a resin, and a surfactant.
An ink set characterized in that the contact angle of the ink with respect to the leather is 45 ° or less.

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