JP6717054B2 - Ink, ink container, inkjet method, and inkjet apparatus - Google Patents

Description

The present invention relates to an ink, an ink container, an inkjet method, and an inkjet device.

Conventionally, metallic coloring has been performed using pigment particles that perform metallic coloring. However, since the pigment particles have a small particle diameter, the brightness is lowered, and thus the miniaturization has not progressed. In recent years, finely-divided aluminum having high brightness has been developed by crushing vapor-deposited aluminum showing high brightness.
It is known that aluminum used for such a metallic pigment has reactivity with water and generates hydrogen gas when mixed with water. Further, there is a problem that the surface area of the pigment is increased by reducing the particle size and the reactivity is increased by increasing the frequency of contact with water. Aluminum reacts with water to generate not only hydrogen gas, but also to be oxidized and converted into alumina, so that the color changes to white and loses metallic luster, and there is a problem that the metallic pigment disappears.
Therefore, in order to solve the above-mentioned problems, for example, a water-based ink composition containing water, silver particles, and a humectant, wherein the average primary particle diameter of the silver particles is 10 nm or more and 100 nm or less, There has been proposed a method of forming a metal coating by fusing silver particles to each other to develop metallicity (for example, refer to Patent Document 1).

An object of the present invention is to provide an ink that can be colored metallic even on a poorly water-absorbent recording medium, and that is excellent in storage stability without changing the metallic color over a long period of time.

The ink of the present invention as a means for solving the problems is an ink containing water, silver particles, and an organic solvent,
The cumulative 10% particle diameter (D ₁₀ ) of the silver particles by the dynamic light scattering method is 100 nm or more, and the cumulative 90% particle diameter (D ₉₀ ) is 5,000 nm or less,
The organic solvent does not include an organic solvent having a boiling point of higher than 250°C.

According to the present invention, a metallic color can be colored even on a poorly water-absorbent recording medium, and an ink excellent in storage stability can be provided without changing the metallic color for a long period of time.

FIG. 1 is a diagram showing an example of a recording apparatus using the ink of the present invention. FIG. 2 is a perspective view of a main tank that stores the ink of the present invention.

(ink)
The ink of the present invention contains water, silver particles, and an organic solvent,
The cumulative 10% particle diameter (D ₁₀ ) of the silver particles by the dynamic light scattering method is 100 nm or more, and the cumulative 90% particle diameter (D ₉₀ ) is 5,000 nm or less,
The organic solvent does not contain an organic solvent having a boiling point of higher than 250° C., and further contains other components as necessary.

In the ink of the present invention, in the prior art, metal particles having a particle size of less than 100 nm are colored by plasmons, and silver particles are colored brown or the like. If such metal particles cannot be completely fused, plasmon coloration remains and shows a colored metallic luster, and if the metal particles are not adjacent to each other at a high concentration, the fusion phenomenon does not occur. In a recording medium having a coarse mesh like that, the ink is absorbed and spread in the recording medium, it is difficult for metal particles to be adjacent to each other, and sufficient fusion to show metallic is not generated. In a poorly water-absorbent recording medium such as a film or coated paper having poor absorbency, it is not possible to release the dispersant for silver particles from the surface of the silver particles to promote fusion of the silver particles with each other, and to not exhibit metallic. Furthermore, the present invention is based on the finding that metal particles having a particle size of less than 20 nm are easily taken up by cells of a living organism, so that the metal particles may be taken up into cells and exhibit toxicity.

Therefore, it is required that the silver particles do not develop color due to surface plasmon resonance on the particle surface so that the ink dry film is not colored during dry fixing. The smaller the particle size is, the narrower the absorption wavelength region becomes and the larger the maximum absorption becomes, so that the coloring due to surface plasmon resonance becomes stronger.
Therefore, the ink of the present invention has a cumulative 10% particle diameter (D ₁₀ ) of the silver particles of 100 nm or more and a cumulative 90% particle diameter (D ₉₀ ) of 5,000 nm or less according to the dynamic light scattering method.
When the cumulative 10% particle diameter (D ₁₀ ) of the silver particles is 100 nm or more, the absorption wavelength range spreads over the entire visible region and the maximum absorption also decreases, so that the color of the dry film becomes bluish like metallic silver. It becomes gray. Further, in order to be ejected from the nozzle as inkjet ink, the nozzle will be clogged unless the size is sufficiently small with respect to the nozzle. Further, when the cumulative 90% particle diameter (D ₉₀ ) is 5,000 nm or less, stable ink ejection can be performed.
Further, when performing inkjet printing with a water-based ink even on a poorly water-absorbent recording medium such as a film or a coated paper for printing, if a high-boiling organic solvent is contained, the drying of the ink is hindered, It significantly reduces the durability of the dry ink film. Therefore, it is necessary that the organic solvent does not include an organic solvent having a boiling point of higher than 250°C.
By using the ink-jet ink having such a composition, the metallic ink can be expressed in the water-based ink even on the poorly water-absorbent recording medium, and the metallic color does not change over a long period of time.

<Silver particles>
The silver particles are powders that exhibit a metallic color, and are not particularly limited as long as they exhibit a silver color.
The shape of the silver particles is not particularly limited and may be appropriately selected depending on the intended purpose, and may be, for example, a scaly shape, a spherical shape, a flake shape, an irregular shape, or a mixture thereof.
The cumulative 10% particle diameter (D ₁₀ ) of the silver particles by the dynamic light scattering method is 100 nm or more from the viewpoint of exhibiting metallic luster. When the cumulative 10% particle diameter (D ₁₀ ) is 100 nm or more, coloring due to surface plasmon resonance does not occur on the surface of silver particles, and coloring due to plasmon does not occur. As a result, when the cumulative 10% particle diameter (D ₁₀ ) is 100 nm or more, the absorption wavelength range spreads over the entire visible region and the maximum absorption also decreases, so that the dry film made of silver particles is not colored by plasmons, Can be a typical silver metallic silver. Furthermore, it is preferable that the cumulative 10% particle diameter (D ₁₀ ) is 300 nm or more, because most of the silver particles can absorb visible wavelengths and a stronger metallic luster can be exhibited.

The cumulative 90% particle diameter (D ₉₀ ) of the silver particles by the dynamic light scattering method is 5,000 nm or less. It is preferable that the cumulative 90% particle diameter (D ₉₀ ) is 5,000 nm or less, because the silver particles are sufficiently small with respect to the nozzle of the inkjet head and can be stably ejected. Further, when the cumulative 90% particle diameter (D ₉₀ ) of the silver particles is 2,000 nm or less, it is difficult to affect the ink ejection even if the primary aggregation of the silver particles occurs, and from the viewpoint of continuous ejection stability. preferable.

The cumulative 50% particle diameter (D ₅₀ ) of the silver particles is preferably 300 nm or more from the viewpoint of exhibiting metallic luster with a single particle, and preferably 1,000 nm or less from the viewpoint of reducing sedimentation.

The cumulative 10% particle diameter (D ₁₀ ), cumulative 50% particle diameter (D ₅₀ ), and cumulative 90% particle diameter (D ₉₀ ) of the silver particles were measured by determining the diameter and the number of silver particles, From the particle size accumulating curve obtained by statistically processing, the diameter of particles at 10% of the total mass is 10% of the cumulative particle diameter (D ₁₀ ) and 50% of the total mass is The diameter is the cumulative 50% particle diameter (D ₅₀ ), and the diameter of the particles at 90% of the total mass is the cumulative 90% particle diameter (D ₉₀ ). The diameter of the silver particles may be the diameter of the silver particles themselves, or may be the diameter of the particle colloid when the silver particles are dispersed in a colloidal form.
The diameter of the silver particles can be determined, for example, by using a particle size distribution measuring device based on the dynamic light scattering method, if it is in a dispersed state in water. Examples of the particle size distribution measuring device by the dynamic light scattering method include Nanotrac Wave-UT151 (manufactured by Microtrac Bell Co., Ltd.), Nanotrac Wave-EX150 (manufactured by Nikkiso Co., Ltd.), ELSZ-2, DLS-8000. (Above, manufactured by Otsuka Electronics Co., Ltd.), LB-550 (manufactured by Horiba Ltd.) and the like.
In addition to these, it is possible to measure by electron microscopy. The diameter of the silver particles can be determined by obtaining a photograph of the silver particles with the electron microscope and subjecting the photograph to image processing for measurement. As an example, the area of 50 or more silver particles in the photograph is randomly obtained from the photograph, and the diameters of equivalent circles are calculated to obtain the particle diameter. Then, a particle size accumulation curve can be obtained from the obtained particle size.

-Method for producing silver particles-
The method for producing the silver particles is not particularly limited and may be appropriately selected depending on the purpose.For example, a pulverizing method of pulverizing a coarse powder obtained by pulverizing an ingot or the like to a desired particle size, A method of peeling and crushing a metal film formed on a film by vapor deposition such as vapor deposition from the film (particularly, a method of peeling and crushing in a liquid and dispersing in a liquid), a wet reduction method. Examples of such methods include chemical granulation methods and various atomizing methods.

Examples of the wet reduction method include a method of adding ammonia water to an aqueous solution of silver nitrate to form a silver ammine complex, and then adding a reducing agent such as formalin or hydrazine to reduce to silver to obtain silver powder or an aqueous solution of silver nitrate. A method may be mentioned in which sodium hydroxide is added to produce silver oxide particles, and then a reducing agent such as formalin or hydrazine is added to reduce the silver to obtain silver powder. Then, if necessary, the solution containing silver particles is subjected to solid-liquid separation to separate the silver particles and the solution as solid content, and the silver powder is washed with an appropriate cleaning agent to remove the liquid adhering to the silver powder. Further, the silver powder is further dried to remove water and subjected to treatments such as crushing and classification to obtain silver particles having a desired particle size.

The atomizing method is, for example, a method in which a molten metal (molten metal) is made to collide with a coolant such as water or gas and finely pulverized to produce it. According to the atomizing method, metal particles having a uniform particle size can be obtained.

-Method for producing silver particle dispersion-
In order to obtain the silver particle dispersion liquid by dispersing the silver particles in water, a method of introducing a hydrophilic functional group into the surface of the silver particles to obtain a self-dispersing pigment, and a method of coating the surfaces of the silver particles with a resin to disperse them And a method of dispersing with a dispersant.
As a method of coating the surface of the silver particles with a resin to disperse the silver particles, a method in which the silver particles are contained in microcapsules and can be dispersed in water can be used. In this case, it is not necessary that all the silver particles blended in the ink be coated with the resin, and as long as the effect of the present invention is not impaired, uncoated silver particles or partially coated silver particles are submerged in water. It may be dispersed.
Examples of the method of dispersing using the dispersant include a method of dispersing using a known low molecular type dispersant or polymer type dispersant represented by a surfactant.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or the like can be used depending on the system of silver particles or the ink used.
Among these, as the dispersant, either an anionic surfactant or a nonionic surfactant having an HLB value of 10 to 20 is suitable.

Examples of the anionic surfactants include polyoxyethylene alkyl ether acetate, alkylbenzene sulfonate (eg, NH ₄ , Na, Ca, etc.), alkyldiphenyl ether disulfonate (eg, NH ₄ , Na, Ca, etc.). , Dialkyl succinate sulfonic acid Na salt, naphthalene sulfonic acid formalin condensate Na salt, polyoxyethylene polycyclic phenyl ether sulfate ester salt (eg, NH ₄ , Na, etc.), lauric acid salt, polyoxyethylene alkyl ether sulfate salt, Examples thereof include oleate. These may be used alone or in combination of two or more.
Among these, dioctyl sulfosuccinic acid Na salt, naphthalene sulfonic acid formalin condensate Na salt, and polyoxyethylene styrene phenyl ether sulfonic acid NH ₄ salt are particularly preferable.

Examples of the nonionic surfactant having an HLB value of 10 to 20 include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene polycyclic phenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene. Examples thereof include alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, acetylene glycol and the like. These may be used alone or in combination of two or more.
Among these, polyoxyethylene lauryl ether, polyoxyethylene-β-naphthyl ether, polyoxyethylene sorbitan monooleate, and polyoxyethylene styrene phenyl ether are particularly preferable.

Examples of the polymer dispersant include an α-olefin-maleic anhydride copolymer represented by the following general formula (A), a styrene-(meth)acrylic copolymer, a water-soluble polyurethane resin, and a water-soluble polyester resin. There is at least one selected from

In the general formula (A), R represents an alkyl group having 6 to 30 carbon atoms, preferably 12 to 22 carbon atoms, and more preferably 18 to 22 carbon atoms. n represents an integer of 1 or more, and an integer of 20 to 100 is preferable.

The α-olefin-maleic anhydride copolymer represented by the general formula (A) can also be synthesized by using, as a raw material, a mixture of olefins containing olefins having different carbon numbers.
In that case, the R part is a copolymer in which alkyl groups having different carbon numbers are randomly introduced into the polymer chain.
In the present invention, not only an α-olefin-maleic anhydride copolymer in which an alkyl group having a uniform carbon number of R is introduced into a polymer chain, but also an alkyl group having a different carbon number of R as described above. An α-olefin-maleic anhydride copolymer in which groups are randomly introduced into the polymer chain can be used as the α-olefin-maleic anhydride copolymer represented by the general formula (A). is there.

The weight average molecular weight of the α-olefin-maleic anhydride copolymer represented by the general formula (A) is preferably 5,000 or more and 20,000 or less.
The α-olefin-maleic anhydride copolymer, the styrene-(meth)acrylic copolymer, the water-soluble polyurethane resin and the water-soluble polyester resin represented by the general formula (A) are solid at room temperature and cold water. Is almost insoluble in. However, when used as a dispersant when dissolved in an alkaline solution or an alkaline aqueous solution having an acid value equal to or more than the acid value of the copolymer and the resin (preferably 1.0 to 1.5 times the acid value) The effect will appear. Further, in order to dissolve the copolymer and the resin in an alkaline solution or an alkaline aqueous solution, they can be easily dissolved by heating and stirring. When the olefin chain in the α-olefin-maleic anhydride copolymer is long, it is relatively difficult to dissolve, and insoluble matter may remain, but when the insoluble matter is removed with an appropriate filter or the like, it is used as a dispersion stabilizer. The effect of is not impaired.

Examples of the base in the alkaline solution or the alkaline aqueous solution include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide; basic substances such as ammonia, triethylamine and morpholine; triethanolamine and diethanolamine, Examples thereof include N-methyldiethanolamine, 2-amino-2-ethyl-1,3-propanediol, alcohol amines such as choline, and the like. These may be used alone or in combination of two or more.

As the α-olefin-maleic anhydride copolymer represented by the general formula (A), those appropriately synthesized may be used, or commercially available products may be used.
Examples of the commercially available products include T-YP112, T-YP115, T-YP114, T-YP116 (all manufactured by Seikou PMC Co., Ltd.).

As the styrene-(meth)acrylic copolymer, those synthesized appropriately may be used, or commercially available products may be used.
Examples of the commercially available products include JC-05 (manufactured by Seikou PMC Co., Ltd.), ARUFON UC-3900, ARUFON UC-3910, and ARUFON UC-3920 (all manufactured by Toagosei Co., Ltd.).

As the water-soluble polyurethane resin, a properly synthesized product may be used, or a commercially available product may be used.
Examples of the commercially available products include Takelac W-5025, Takelac W-6010, Takelac W-5661 (all manufactured by Mitsui Takeda Chemical Co., Ltd.).

As the water-soluble polyester resin, those synthesized appropriately may be used, or commercially available products may be used.
Examples of the commercially available product include Nichigo Polyester W-0030, Nichigo Polyester W-0005S30WO, Nichigo Polyester WR-961 (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), PESRESIN A-210, PESRESIN A-520. (All manufactured by Takamatsu Yushi Co., Ltd.) and the like.

The acid value of the polymeric dispersant is preferably 40 mgKOH/g or more and 400 mgKOH/g or less, and more preferably 60 mgKOH/g or more and 350 mgKOH/g or less.
When the acid value is 40 mgKOH/g or more, the solubility of the alkaline solution is high, and when the acid value is 400 mgKOH/g or less, the viscosity of the dispersion can be suppressed and the increase in the ink viscosity can be suppressed, so that the ejection is suppressed. It can be kept good, or the dispersion stability of the dispersion can be kept high.
The weight average molecular weight of the polymeric dispersant is appropriately selected depending on the intended purpose without any limitation, but it is preferably 20,000 or less, more preferably 5,000 or more and 20,000 or less. When the weight average molecular weight is 5,000 or more, the dispersion stability of the pigment dispersion is likely to be improved, and when the weight average molecular weight is 20,000 or less, the solubility of the alkali solution is high and the viscosity is low, so that the dispersion viscosity is lowered. Can be made.
The above dispersants may be used alone or in combination of two or more, and a plurality of high molecular dispersants and low molecular dispersants may be used in combination. By using a combination of plural kinds of dispersants, it is possible to make a dispersion that takes advantage of the characteristics of the dispersants, and it is possible to enhance the dispersibility of silver particles and the stability over time.

The content of the dispersant is preferably 1 part by mass or more and 100 parts by mass or less, and more preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the silver particles. When the content of the dispersant is 1 part by mass or more, the silver particles can be dispersed, and even the primary particles can be dispersed depending on the dispersion conditions. Further, when the content of the dispersant is 100 parts by mass or less, there is no excess component not adsorbed on the silver particles, which does not affect the physical properties of the ink. Therefore, it is possible to suppress image bleeding, deterioration of water resistance and abrasion resistance, deterioration of ejection property from a nozzle, and deterioration of economic efficiency.

In the silver particle dispersion, water, silver particles, a dispersant, and, if necessary, other components are combined and dispersed. It is preferable to use a disperser for the dispersion, and after the dispersant is dissolved in water and then the silver particles are sufficiently wetted, high-speed stirring with a homogenizer, a ball such as a bead mill or a ball mill is used. It is possible to prepare a silver particle dispersion liquid by dispersing using a dispersing machine, a kneading dispersing machine using a shearing force such as a roll mill, an ultrasonic dispersing machine or the like.

Observation with a transmission electron microscope or a reflection electron microscope is effective for observing the state of such silver particles. Further, in order to confirm the silver particles, it is effective to embed the pigment in a resin and cut it to expose a cross section and observe it. To understand the dispersion state of silver particle dispersion liquid, to observe individual particles, freeze the dispersion liquid using the frozen replica method at the time of preparing the observation sample, and fix the split surface by vapor deposition etc. It becomes possible to confirm the state of dispersion of particles.

The composition of the silver particles can be macroscopically analyzed by fluorescent X-ray analysis, and the composition can be analyzed even for a minute portion by an electron beam microanalyzer (EPMA). Furthermore, by using energy dispersive X-ray spectroscopy (EDX) in combination with a reflection electron microscope (SEM), the composition of each silver particle can be grasped.
In addition to these, X-ray photoelectron spectroscopy (XPS) can be used to understand the elemental analysis of the outermost layer of the composition and the chemical state of the elements, and to grasp the detailed film state. Furthermore, by performing surface etching by the sputtering method, it is possible to grasp the three-dimensional composition distribution.

The content of silver particles in the silver particle dispersion is not particularly limited and can be appropriately selected according to the purpose, but good dispersibility is obtained, and the degree of freedom in ink formulation is increased, 1 mass% or more and 50 mass% or less are preferable, and 1 mass% or more and 30 mass% or less are more preferable.
When the content of the silver particles is 1% by mass or more, the silver particle concentration can be adjusted as the ink formulation. Further, when the content of the silver particles is 50% by mass or less, the viscosity of the dispersion liquid can be lowered, so that the handling at the time of producing the ink becomes easy. Further, when the content of the silver particles is 30% by mass or less, it is easy to stir during the production of the dispersion liquid, and the dispersion efficiency can be increased.
It is preferable that coarse particles are removed from the silver particle dispersion liquid by a filter, a centrifugal separator or the like, if necessary.

The content of the silver particles in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of enhancing good ejection stability and image density, it is 0.1% by mass or more and 30% by mass or more. The following is preferable, and 0.5% by mass or more and 10% by mass or less is more preferable. When the content is 0.1% by mass or more, metallic properties can be exhibited on the hardly water-absorbent recording medium. Further, when the content is 30% by mass or less, the viscosity of the ink can be lowered, and printing can be performed with various inkjet heads. When the content is 10% by mass or less, the specific gravity of the ink can be reduced and continuous ejection can be stabilized.

<Ink>
Hereinafter, the organic solvent, water, coloring material, resin, additive and the like used in the ink will be described.

-Organic solvent-
It is necessary that the organic solvent does not include an organic solvent having a boiling point of higher than 250°C. As a result, the metallic ink can be expressed in the water-based ink even on the hardly water-absorbent recording medium.
That is, when ink-jet printing is performed with a water-based ink even on a poorly water-absorbent recording medium such as a film or a coated paper for printing, a solvent having a high boiling point prevents the ink from drying, and thus the dry ink It significantly reduces the durability of the film. Therefore, it is necessary that the organic solvent added to the ink does not include a solvent having a boiling point of higher than 250°C.
The fact that the organic solvent does not contain an organic solvent having a boiling point higher than 250° C. means the amount from the state of not containing it at all to the presence of less than 1 mass% in view of mixing from impurities.
Examples of the organic solvent having a boiling point of higher than 250° C. include glycerin.

The organic solvent includes an organic solvent having a boiling point of 200° C. or lower, and the content of the organic solvent having a boiling point of 200° C. or lower is preferably 50% by mass or more based on the total amount of the organic solvent. Achieving a practical drying property even on a hardly water-absorptive recording medium by using 50% by mass or more of the organic solvent having a boiling point of 200° C. or less based on the total amount of the organic solvent contained in the ink. It is possible to improve coating film characteristics and reduce the amount of energy required for drying due to a decrease in heater temperature.
Examples of the organic solvent having a boiling point of 200° C. or lower include 3-methoxy-3-methyl-1-butanol, 1,2-propanediol, 2,3-butanediol, 1,2-butanediol, and 2-methyl. Examples include 2,4,4-pentanediol and the like. These may be used alone or in combination of two or more.
Among these, the affinity of the ink with water and the moisturizing power are improved, the drying of the ink in the inkjet head is suppressed, and nozzle defects such as ejection bending and ejection failure are suppressed, while the ink is hardly absorbed on a recording medium. At least one selected from 3-methoxy-3-methyl-1-butanol, 1,2-propanediol, and 2,3-butanediol is particularly preferable from the viewpoint of improving the drying property in.

The ink of the present invention does not contain the organic solvent having a boiling point of more than 250° C., and may contain a water-soluble organic solvent, if necessary, in addition to the organic solvent having a boiling point of 200° C. or less.

Specific examples of the water-soluble organic solvent include, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butane. Diol, 2,3-butanediol, 3-methyl-1,3-butanediol, 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, Polyhydric alcohols such as 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Polyhydric alcohol alkyl ethers such as ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether and propylene glycol monoethyl ether, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, 2-pyrrolidone, Nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone and γ-butyrolactone, formamide, N-methylformamide, 3-methoxy-N,N-dimethylpropionamide, 3-butoxy-N,N-dimethylpropionamide, etc. Amides, amines such as monoethanolamine, diethanolamine and triethylamine, and propylene carbonate.

A polyol compound having 8 or more carbon atoms and a glycol ether compound are also preferably used. Specific examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Specific examples of glycol ether compounds include polyhydric alcohol alkyls 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. Ethers; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether and the like.

The polyol compound having 8 or more carbon atoms and the glycol ether compound can improve the ink permeability when paper is used as the recording medium.

The content of the organic solvent in the ink is not particularly limited and may be appropriately selected depending on the purpose. However, from the viewpoint of ink drying properties and ejection reliability, 10% by mass or more and 60% by mass or less is preferable, 20 mass% or more and 60 mass% or less are more preferable.

-Resin-
The type of resin contained in the ink is not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, and butadiene resin. Examples thereof include resins, styrene-butadiene resins, vinyl chloride resins, acrylic styrene resins, acrylic silicone resins and the like.
You may use the resin particle which consists of these resins. 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 used as a dispersion medium. As the resin particles, those synthesized appropriately may be used, or commercially available products may be used. These may be used alone or in combination of two or more kinds of resin particles.

The volume average particle diameter of the resin particles is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10 nm or more and 1,000 nm or less from the viewpoint of obtaining good fixability and high image hardness. It is more preferably 200 nm or less and more preferably 10 nm or more and 100 nm or less.
The volume average particle diameter can be measured using, for example, a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

The content of the resin is not particularly limited and may be appropriately selected depending on the intended purpose, but from the viewpoint of fixability and storage stability of the ink, 1% by mass or more and 30% by mass or less based on the total amount of the ink. Is preferable and 5 mass% or more and 20 mass% or less are more preferable.

The solid content of the resin particles is preferably smaller than the solid content of the silver particles. This makes it possible to achieve both glossiness and fixability of the ink.
That is, since the hardly water-absorbent recording medium has few pores for absorbing ink and the surface is smooth, the ink on the hardly water-absorbent recording medium is very easily detached. Therefore, it is necessary to fix the ink on the hardly water-absorbent recording medium. In the ink of the present invention, the fixing property can be improved by containing the resin particles. However, when the amount of resin particles is large relative to the amount of silver particles, the fixability is improved, but the arrangement of silver particles is disturbed and gloss development is suppressed. Therefore, it is possible to achieve both glossiness and fixability by adding so that the solid content of the resin particles is smaller than the solid content of the silver particles.

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

<Additive>
If necessary, a surfactant, a defoaming agent, a rust preventive, a pH adjuster, etc. may be added to the ink.

<Surfactant>
As the surfactant, any of silicone-based surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used.
The silicone-based surfactant is not particularly limited and can be appropriately selected according to the purpose. Among them, those that do not decompose even at high pH are preferable, and examples thereof include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and side-chain both-end modified polydimethylsiloxane. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene 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 having a polyalkylene oxide structure introduced into the side chain of the Si moiety of dimethylsiloxane.
Examples of the fluorinated surfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate ester 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 sulfonate. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylic acid salts. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in its side chain include a sulfuric acid ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in its side chain and a perfluoroalkyl ether group in its side chain. Examples thereof include salts of polyoxyalkylene ether polymers. The counterions of the salts in these fluorine-based surfactants include Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ and NH(CH ₂ CH ₂ OH). ₃ etc. are mentioned.
Examples of the amphoteric surfactant include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan. Examples thereof include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, and salt of polyoxyethylene alkyl ether sulfate.
These may be used alone or in combination of two or more.

The fluorine-based surfactant is preferably a fluorine-substituted compound having 2 to 16 carbon atoms, and more preferably a fluorine-substituted compound having 4 to 16 carbon atoms.
Examples of the fluorine-based surfactant include a perfluoroalkyl phosphate ester compound, a perfluoroalkylethylene oxide adduct, and a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in its side chain.
Among these, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain are preferable because they have a low foaming property, and the fluorine-based compounds represented by the general formula (F-1) and the general formula (F-2) are particularly preferable. Surfactants are preferred.
[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 general formula (F-2), Y is H, or CnF _2n+1 and n is an integer of 1 to 6, or CH ₂ CH(OH)CH ₂ -CnF _2n+1 and n is 4 to 6. An integer, or CpH _2p+1 and p is an integer of 1 to 19. a is an integer of 4-14.
A commercially available product may be used as the above-mentioned fluorine-based surfactant.
Examples of the commercially available product include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullrad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Limited); Megafac 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 Chemours); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all). , Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by OMNOVA), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.) and the like. Among these, good printing quality, especially color developability, penetrability to paper, wettability, and even dyeability are remarkably improved, and therefore FS-3100, FS-34, FS-300 manufactured by Chemours Co., Ltd. FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos, Polyfox PF-151N manufactured by Omnova Co., 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, but is 0.001 mass from the viewpoint of excellent wettability and ejection stability and improving image quality. % Or more and 5 mass% or less is preferable, and 0.05 mass% or more and 5 mass% or less is more preferable.

<Antifoam>
The defoaming agent is not particularly limited, and examples thereof include a silicone defoaming agent, a polyether defoaming agent, and a fatty acid ester defoaming agent. These may be used alone or in combination of two or more. Among these, a silicone-based defoaming agent is preferable because of its excellent foam breaking effect.

<Rust preventive>
The rust preventive agent is not particularly limited, and examples thereof include acid sulfite and sodium thiosulfate.

<pH adjuster>
The pH adjuster is not particularly limited as long as the pH can be adjusted to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

The physical properties of the ink are not particularly limited and may be appropriately selected depending on the 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, from the viewpoint that the printing density and character quality are improved and good ejection properties are obtained, and the viscosity is preferably 5 mPa·s or more and 25 mPa·s or less. More preferable. Here, as the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. The measurement conditions are 25° C., standard cone rotor (1°34′×R24), sample liquid volume 1.2 mL, rotation speed 50 rpm, and 3 minutes.
The surface tension of the ink is preferably 35 mN/m or less, and more preferably 32 mN/m or less at 25° C., from the viewpoint that the ink is preferably leveled on the recording medium and the drying time of the ink is shortened.
The pH of the ink is preferably 7 to 12, and more preferably 8 to 11 from the viewpoint of preventing corrosion of the metal member that comes into contact with the liquid.

<Pretreatment liquid>
The pretreatment liquid contains a flocculant, an organic solvent, and water, and may contain a surfactant, an antifoaming agent, a pH adjusting agent, an antiseptic/antifungal agent, an antirust agent, etc., if necessary.
As the organic solvent, the surfactant, the defoaming agent, the pH adjuster, the antiseptic/antifungal agent and the rust preventive agent, the same materials as those used for the ink can be used, and other materials used for the known treatment liquid can be used. ..
The type of aggregating agent is not particularly limited, and examples thereof include water-soluble cationic polymers, acids, polyvalent metal salts and the like.

<Post-treatment liquid>
The post-treatment liquid is not particularly limited as long as it can form a transparent layer. The post-treatment liquid is obtained by selecting and mixing an organic solvent, water, a resin, a surfactant, an antifoaming agent, a pH adjusting agent, an antiseptic/antifungal agent, an anticorrosive agent, etc., if necessary. Further, the post-treatment liquid may be applied to the entire recording area formed on the recording medium, or may be applied only to the area where the ink image is formed.

<Recording medium>
The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, and the like can be used, but excellent image formation can be performed even with a hardly water-absorbent recording medium.
The hardly water-absorbent recording medium is a recording medium having a surface having low water permeability and absorptivity, and includes a material that does not open to the outside even if there are many cavities inside, and more quantitatively. Is the standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000 Edition”. 51, in the Bristow method described in “Paper and board-Liquid absorbency test method-Bristow method”, a recording medium having a water absorption amount of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 is used. Say.
Examples of the hardly water-absorbent recording medium include vinyl chloride resin film, polyethylene terephthalate (PET) film, plastic film such as polypropylene film, polyethylene film, polycarbonate film, coated paper for printing, art paper and the like. These may be used alone or in combination of two or more. Among these, vinyl chloride resin film and coated paper for printing are preferable.
INDUSTRIAL APPLICABILITY The ink of the present invention has sufficient performance not only for a hardly water-absorptive recording medium but also for a conventionally used porous medium such as a porous medium such as plain paper or inkjet paper and an inorganic-coated porous medium. Show.
The ink of the present invention can perform printing with high image quality on the hardly water-absorptive recording medium, but forms an image with higher image quality and high abrasion resistance and adhesiveness, and can also support high-speed printing conditions. Therefore, it is more preferable to heat the recording medium after printing.

<Recorded matter>
The ink recorded matter of the invention has an image formed by using the ink of the invention on a recording medium.
A recorded matter can be obtained by recording with an inkjet recording apparatus and an inkjet recording method.

<Recording device, recording method>
The ink of the present invention can be suitably used for various recording devices using an inkjet recording method, such as a printer, a facsimile device, a copying device, a printer/fax/copier compound machine, and a three-dimensional modeling device.
In the present invention, the recording device and the recording method are a device capable of ejecting ink, various treatment liquids, and the like onto a recording medium, and a method of performing recording using the device. The recording medium means a medium to which ink or various treatment liquids can be attached even temporarily.
This recording device can include not only a head portion for ejecting ink, but also means for feeding, conveying, and discharging a recording medium, and other devices such as a pre-processing device and a post-processing device. ..
The recording device and the recording method may have 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 printing surface or the back surface of the recording medium. The heating means and the drying means are not particularly limited, but, for example, a warm air heater or an infrared heater can be used. Heating and drying can be performed before printing, during printing, after printing, and the like.
Further, the recording device and the recording method are not limited to those in which a significant image such as a character or a figure is visualized by ink. For example, it also includes one that forms a pattern such as a geometric pattern and one that models a three-dimensional image.
Further, the recording 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 limited.
Further, this recording device is not limited to a desktop type, and can be used as a wide recording device capable of printing on an A0 size recording medium, or for example, a continuous paper rolled into a roll as a recording medium. It also includes a continuous printer.
An example of the recording device will be described with reference to FIGS. FIG. 1 is a perspective explanatory view of the device. FIG. 2 is a perspective view of the main tank. The image forming apparatus 400 as an example of the recording apparatus is a serial type image forming apparatus. A mechanism section 420 is provided inside the exterior 401 of the image forming apparatus 400. Each ink storage portion 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is packed with, for example, an aluminum laminate film. It is formed of a member. The ink container 411 is housed in a container case 414 made of plastics, for example. 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 on the inner side of the opening when the cover 401c of the apparatus body is opened. The 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 ejection head 434 for each color communicate with each other via the supply tube 436 for each color, and ink can be ejected from the ejection head 434 to the recording medium.

This recording device can include not only a portion for ejecting ink, but also a device called a pre-processing device, a post-processing device, or the like.
As one mode of the pretreatment device and the posttreatment device, as in the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y), a pretreatment liquid and a posttreatment liquid are included. There is a mode in which a liquid container and a liquid discharge head are added and a pretreatment liquid and a posttreatment liquid are discharged by an inkjet recording method.
As another aspect of the pretreatment device and the posttreatment device, there is an aspect in which a pretreatment device and a posttreatment device other than the ink jet recording method are provided, for example, by a blade coating method, a roll coating method, a spray coating method.

The use of the ink of the present invention is not particularly limited and can be appropriately selected according to the purpose. For example, it can be applied to printed matter, paints, coating materials, bases and the like. Furthermore, it can be used not only as a two-dimensional character or image by using as ink, but also as a three-dimensional modeling material for forming a three-dimensional three-dimensional image (three-dimensional model).
A known three-dimensional modeling device can be used as a three-dimensional modeling device for modeling a three-dimensional molded object, and is not particularly limited, but for example, a device including an ink containing means, a supply means, a discharging means, a drying means, etc. is used. be able to. The three-dimensional molded item includes a three-dimensional molded item obtained by overcoating with ink. Further, it also includes a molded product obtained by processing a structure to which ink is applied on a substrate such as a recording medium. The molded product is, for example, a recording product or structure formed in a sheet shape or a film shape, which has been subjected to molding processing such as heat drawing and punching processing. -It is suitable for use in applications such as electronic devices, meters for cameras, panels for operation parts, etc., after the surface is decorated.

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

(Preparation example 1 of silver particle dispersion liquid)
-Preparation of silver particle 1 dispersion-
In a reaction vessel, 340 g of silver nitrate (manufactured by Kanto Kagaku Co., Ltd.) was added to 700 g of pure water and completely dissolved to prepare a silver nitrate aqueous solution. To this, 700 g of ammonia water (manufactured by Kanto Chemical Co., Inc., special grade) adjusted to have an ammonia concentration of 25% by mass was added and stirred to prepare an ammine silver complex aqueous solution, and the temperature was adjusted to 23°C.
Hydroquinone (manufactured by Kanto Chemical Co., Ltd.) 111 g and anhydrous potassium sulfite (manufactured by Kanto Chemical Co., Ltd.) 50 g were dissolved in 1,260 g of pure water in different containers to prepare a reducing agent aqueous solution, and the temperature was adjusted to 23° C., To the reducing agent aqueous solution, the above-mentioned ammine silver complex aqueous solution whose temperature was similarly adjusted to 23° C. was added all at once, and the reduction precipitation of silver particles was completed by stirring for 10 minutes.
Then, the silver particles were collected by filtration with a Buchner funnel, and washing with 1 L of water was repeated 3 times and dried to obtain silver particles.
30 parts by mass of the obtained silver particles, 3 parts by mass of Leodol TW-O120V (manufactured by Kao Corporation), and 67 parts by mass of pure water were added to a beaker, thoroughly stirred with a stirrer, and then ultrasonically homogenized while cooling with water (Japan. Seiki Seisakusho, US-300T (chip diameter 26 mm)) was treated with 200 μA for 1 hour for dispersion treatment to obtain a silver particle 1 dispersion liquid.
The particle size distribution of the obtained silver particle 1 dispersion was measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and a cumulative 10% particle diameter (D ₁₀ ) was 950 nm and a cumulative 50% particle. The diameter (D ₅₀ ) was 1,540 nm, and the cumulative 90% particle diameter (D ₉₀ ) was 3,020 nm.

(Preparation example 2 of silver particle dispersion liquid)
-Preparation of silver particle 2 dispersion-
A polyethylene terephthalate (PET) film (E-5100, manufactured by Toyobo Co., Ltd., average thickness 100 μm) was subjected to corona treatment, and 5% by mass of polyvinylpyrrolidone K15 (manufactured by Kanto Kagaku Co., Ltd.) and a fluorosurfactant (Capstone) on the surface thereof. FS-3100, manufactured by DuPont) 0.1% by mass, diethylene glycol-n butyl ether (manufactured by Kanto Kagaku Co., Ltd.) 10% by mass, and ion-exchanged water 84.9% by mass are mixed and applied by a bar coater. Then, by drying at 70° C. for 15 minutes, a PET film having a release resin layer coated on the PET film was produced.
A silver vapor deposition layer having an average thickness of 100 nm was formed on the PET film by using a vacuum vapor deposition device to prepare a thin film PET film.
The obtained thin-layer PET film was immersed in high-purity water, and peeled off by an ultrasonic cleaner (VS-150 manufactured by As One Co., Ltd.). After peeling off the thin silver film together with the peeling resin layer from the PET film in a treatment for 2 hours, the PET film is removed and the thin silver film is separated as a precipitation component by applying 1,000 G for 1 hour in a centrifuge. did. The supernatant was discarded, pure water was added and dispersed again, and the precipitation and separation operations were carried out three times by centrifugation to wash the silver thin layer film.
The solid content of the precipitated component was determined by thermogravimetric measurement by thermal analysis, and 10 parts by mass of Rheodor TW-O120V (manufactured by Kao Corporation) was added to 100 parts by mass of the silver solid content to give a silver solid content of 5% by mass. Thus, pure water was added, and while being cooled with water, an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho Ltd., chip diameter 26 mm) was used to perform a dispersion treatment at 200 μA for 1 hour.
The obtained silver thin layer film dispersion liquid was subjected to pressure filtration with a SUS mesh filter having a pore diameter of 18 μm (LCF-241 manufactured by Pall Ltd.), and subsequently, pressure filtration with a cellulose acetate membrane filter having a pore diameter of 5 μm. Coarse particles were removed by using the above method to obtain a dispersion of silver particles 2.
The particle size distribution of the obtained silver particle 2 dispersion was measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and a cumulative 10% particle diameter (D ₁₀ ) was 1,370 nm and a cumulative 50. The% particle size (D ₅₀ ) was 1,610 nm, and the cumulative 90% particle size (D ₉₀ ) was 1,990 nm.

(Preparation example 3 of silver particle dispersion liquid)
-Preparation of silver particle 3 dispersion-
1,000 g of polyvinylpyrrolidone (PVP) (K15, manufactured by Kanto Chemical Co., Inc.) was dissolved in 500 g of propylene glycol (manufactured by Kanto Chemical Co., Ltd.) to obtain a PVP solution. Further, 128 g of silver nitrate (manufactured by Kanto Chemical Co., Inc.) was dissolved in 500 mL of propylene glycol (manufactured by Kanto Chemical Co., Ltd.) to obtain a silver nitrate solution.
The PVP solution and the silver nitrate solution were mixed and stirred at 120° C. for 90 minutes, and the silver nitrate was thermally reduced to generate silver particles.
The obtained silver particles were separated by using a centrifugal separator at 1,000 G for 1 hour to use the silver particles as a precipitation component. The supernatant was discarded, pure water was added, the dispersion was carried out again, and the precipitation and separation operations were carried out three times by centrifugation to wash the silver particles. The solid content of the precipitated component was determined by thermogravimetric measurement by thermal analysis, and 10 parts by mass of Rheodor TW-O120V (manufactured by Kao Corporation) was added to 100 parts by mass of the silver solid content to give a silver solid content of 20% by mass. Pure water was added as described above, and while being cooled with water, an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho Ltd., chip diameter 26 mm) was applied for 1 hour at 200 μA for dispersion treatment to obtain a silver particle 3 dispersion liquid.
The particle size distribution of the obtained silver particle 3 dispersion was measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and a cumulative 10% particle diameter (D ₁₀ ) 6 nm and a cumulative 50% particle diameter were obtained. (D ₅₀ ) 8 nm and cumulative 90% particle size (D ₉₀ ) 15 nm.

(Preparation Example 4 of silver particle dispersion liquid)
-Preparation of silver particle 4 dispersion-
In a reaction vessel, 340 g of silver nitrate (manufactured by Kanto Chemical Co., Inc.) was added to 500 g of pure water and completely dissolved to prepare an aqueous silver nitrate solution. Ammonia water (manufactured by Kanto Chemical Co., Inc., special grade) was added with 464 g of ammonia water adjusted to have an ammonia concentration of 25% by mass and stirred to prepare an ammine silver complex aqueous solution, and the temperature was adjusted to 20°C.
70 g of hydroquinone (Kanto Chemical Co., Inc.) and 500 g of anhydrous potassium sulfite (Kanto Chemical Co., Inc.) were dissolved in 7,000 g of pure water in different containers to prepare a reducing agent aqueous solution, and the temperature was adjusted to 20° C., To the reducing agent aqueous solution, the above-mentioned ammine silver complex aqueous solution whose temperature was adjusted to 20° C. was added all at once, and the reduction precipitation of silver particles was completed by stirring for 10 minutes.
Then, the silver particles were collected by filtration with a Buchner funnel, and washing with 1 L of water was repeated 3 times and dried to obtain silver particles.
30 parts by mass of the obtained silver particles, 3 parts by mass of Leodol TW-O120V (manufactured by Kao Corporation), and 67 parts by mass of pure water were added to a beaker, thoroughly stirred with a stirrer, and then ultrasonically homogenized while cooling with water (Japan. Seiki Seisakusho, US-300T (chip diameter 26 mm) treated for 1 hour at 200 μA for dispersion treatment to obtain a silver particle 4 dispersion liquid.
The particle size distribution of the obtained silver particle 4 dispersion liquid was measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and a cumulative 10% particle diameter (D ₁₀ ) 3,520 nm and a cumulative 50% were obtained. The particle diameter (D ₅₀ ) was 7,560 nm, and the cumulative 90% particle diameter (D ₉₀ ) was 18,480 nm.

(Preparation example 1 of aluminum particle dispersion liquid)
-Preparation of aluminum particle dispersion-
A polyethylene terephthalate (PET) film (E-5100, manufactured by Toyobo Co., Ltd., average thickness 100 μm) was subjected to corona treatment, and 5% by mass of polyvinylpyrrolidone K15 (manufactured by Kanto Kagaku Co., Ltd.) and a fluorosurfactant (Capstone) on the surface thereof. FS-3100, manufactured by DuPont) 0.1% by mass, diethylene glycol-n-butyl ether (manufactured by Kanto Chemical Co., Inc.) 10% by mass, and ion-exchanged water 84.9% by mass were mixed and dissolved with a bar coater. A PET film coated with a release resin layer was prepared by coating and drying at 70° C. for 15 minutes.
An aluminum vapor deposition layer having an average thickness of 20 nm was attached on the PET film by using a vacuum vapor deposition device to prepare a thin film PET film.
This thin film PET film was attached to high-purity water and subjected to a peeling treatment with an ultrasonic cleaner (VS-150 manufactured by As One Co., Ltd.). After peeling the aluminum thin layer film together with the peeling resin layer from the PET film in the treatment for 2 hours, the PET film is removed, and 1,000 G is applied for 1 hour in a centrifuge to separate the aluminum thin layer film as a precipitation component. did. The supernatant was discarded, pure water was added and dispersed again, and the precipitation and separation operations were performed three times by centrifugation to wash the aluminum thin film. The solid content of the precipitated component was determined by thermogravimetric measurement of thermal analysis, and 10 parts by mass of Rheodor TW-O120V (manufactured by Kao Corporation) was added to 100 parts by mass of the aluminum solid content to give an aluminum solid content of 5% by mass. Pure water was added as described above, and while being cooled with water, an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300T, tip diameter 26 mm) was used to perform a dispersion treatment at 200 μA for 1 hour.
The obtained aluminum thin film dispersion liquid was subjected to pressure filtration with a SUS mesh filter (LCF-241, manufactured by Pall Ltd.) having a pore diameter of 18 μm, and subsequently, pressure filtration using a cellulose acetate membrane filter having a pore diameter of 5 μm. Coarse particles were removed to obtain an aluminum particle dispersion liquid.
The particle size distribution of the obtained aluminum particle dispersion was measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and a cumulative 10% particle diameter (D ₁₀ ) 0.43 μm and a cumulative 50% particle were obtained. The diameter (D ₅₀ ) was 0.82 μm, and the cumulative 90% particle size (D ₉₀ ) was 2.2 μm.

(Example of preparation of polycarbonate urethane resin emulsion)
1,500 g of polycarbonate diol (reaction product of 1,6-hexanediol and dimethyl carbonate) and 220 g of 2,2-dimethylolpropionic acid (DMPA) were placed in a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer. , And N-methyl-2-pyrrolidone (NMP) (1,347 g) were charged under a nitrogen stream and heated to 60° C. to dissolve DMPA.
Next, 1,445 g of 4,4′-dicyclohexylmethane diisocyanate and 2.6 g of dibutyltin dilaurylate (catalyst) were added and heated to 90° C. to carry out a urethanization reaction for 5 hours to give an isocyanate-terminated urethane prepolymer. Obtained.
The reaction mixture was cooled to 80° C., 149 g of triethylamine was added thereto, 4,340 g of the mixture was taken out, and added under strong stirring to a mixed solution of 5,400 g of water and 15 g of triethylamine. ..
Then, 1,500 g of ice was added, 626 g of a 35 mass% 2-methyl-1,5-pentanediamine aqueous solution was added to carry out a chain extension reaction, and the solvent was distilled off so that the solid content concentration became 30 mass %. Then, a polycarbonate-based urethane resin emulsion was obtained.
The volume average particle size of the obtained polycarbonate-based urethane resin emulsion was measured with a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and it was 35 nm.

(Preparation example of polyether urethane resin emulsion)
In the preparation example of the polycarbonate-based urethane resin emulsion, the same procedure as in the preparation example of the polycarbonate-based urethane resin emulsion was carried out except that polyether polyol (Daiichi Kogyo Seiyaku Co., Ltd., Hiflex D2000) was used in place of the polycarbonate diol. Thus, a polyether urethane resin emulsion was obtained.
The volume average particle size of the obtained polyether urethane resin emulsion was measured by using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and it was 13 nm.

(Preparation example of polyester-based urethane resin emulsion)
In the preparation example of the polycarbonate-based urethane resin emulsion, the same procedure as in the preparation example of the polycarbonate-based urethane resin emulsion was performed except that polyester polyol (Polylite OD-X-2420 manufactured by DIC Corporation) was used instead of the polycarbonate diol. A polyester-based urethane resin emulsion was obtained.
The volume average particle size of the obtained polyester-based urethane resin emulsion was measured with a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.), and it was 54 nm.

(Preparation example of acrylic resin emulsion)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion-exchanged water and 1 g of sodium lauryl sulfate, and the temperature was raised to 70° C. while substituting nitrogen with stirring.
Keeping the internal temperature at 70° C., adding 4 g of potassium persulfate as a polymerization initiator and dissolving it, 450 g of ion-exchanged water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 365 g of styrene, 545 g of butyl acrylate, and 10 g of methacrylic acid were stirred in advance. The emulsion prepared by adding below was continuously added dropwise to the reaction solution over 4 hours. After completion of dropping, aging was carried out for 3 hours.
After the obtained acrylic resin emulsion was cooled to room temperature, ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 30% by mass and the pH to 8.
The volume average particle size of the obtained acrylic resin emulsion was 88 nm when measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.).

(Examples 1 to 7 and Comparative Examples 1 to 4)
-Preparation of ink-
Based on the compositions and contents shown in Tables 1 to 3 below, organic solvents 1 to 3, a surfactant, an antifoaming agent, an antibacterial agent, and high-purity water were added to a beaker and stirred with a stirrer for 15 minutes to homogenize them. Mixed. The prepared resin emulsion was added to this mixed solution, and after stirring for 15 minutes, the bright pigment dispersion was added and stirred for 30 minutes to prepare inks of Examples 1 to 7 and Comparative Examples 1 to 4. did.

Details of each material of the used ink are as follows.
-Bright pigment-
Silver particle 1 dispersion: Solids content 30 wt%, the cumulative 10% particle diameter _(D 10) = 950nm, cumulative 50% particle size _(D 50) = _1,540nm, cumulative 90% particle diameter _(D 90) = 3 , 020nm
Silver particles 2 dispersion: solid content of 5 wt%, the cumulative 10% particle diameter _(D 10) = _1,370nm, cumulative 50% particle size _(D 50) = _1,610nm, cumulative 90% particle diameter _{(D 90)} = 1,990 nm
Silver particles 3 Dispersion: solid content 20 wt%, the cumulative 10% particle diameter _(D 10) = 6nm, cumulative 50% particle size _(D 50) = 8nm, cumulative 90% particle diameter _(D 90) = 15nm
Silver particles 4 Dispersion: solid content 30 wt%, the cumulative 10% particle diameter _(D 10) _3,520nm, cumulative 50% particle size _(D 50) _7,560nm, and the cumulative 90% particle diameter _(D 90) 18 , 480 nm.
Aluminum particle dispersion: solid content of 5 wt%, the cumulative 10% particle diameter _(D 10) = 430nm, cumulative 50% particle size _(D 50) = 820nm, 90% cumulative particle diameter _(D 90) = _2,200nm

-Resin emulsion-
・Polycarbonate urethane resin emulsion (solid content 30% by mass, NMP (boiling point 202°C, corresponding to organic solvent 2) content 11% by mass)
-Polyether urethane resin emulsion (solid content 30% by mass, NMP (boiling point 202°C, corresponding to organic solvent 2) content 11% by mass)
-Polyester urethane resin emulsion (solid content 30% by mass, NMP (boiling point 202°C, corresponding to organic solvent 2) content 11% by mass)
Acrylic resin emulsion (solid content 30% by mass, NMP (boiling point 202°C, corresponding to organic solvent 2) content 11% by mass)

-Organic solvent 1 (organic solvent having a boiling point of 200°C or lower)-
・2,3-Butanediol (boiling point 183°C, manufactured by Kanto Chemical Co., Inc.)
・3-Methoxy-3-methyl-1-butanol (boiling point 174° C., manufactured by Kanto Chemical Co., Inc.)
・1,2-Propanediol (boiling point 188°C, manufactured by Kanto Chemical Co., Inc.)
・1,2-Butanediol (boiling point 194°C, manufactured by Kanto Chemical Co., Inc.)
・2-Methyl-2,4-pentanediol (boiling point 197°C, manufactured by Kanto Chemical Co., Inc.)

-Organic solvent 2 (organic solvent having a boiling point higher than 200°C and lower than 250°C)-
・1,3-Propanediol (boiling point 211°C, manufactured by Kanto Chemical Co., Inc.)
・1,3-Butanediol (boiling point: 203°C, manufactured by Kanto Chemical Co., Inc.)
・2-Ethyl-1,3-hexanediol (boiling point 244°C, manufactured by Tokyo Chemical Industry Co., Ltd.)
・Diethylene glycol monobutyl ether (boiling point 230°C, Kanto Chemical Co., Ltd.)

-Organic solvent 3 (organic solvent having a boiling point higher than 250°C)-
・Glycerin (boiling point 290°C, manufactured by Kanto Chemical Co., Inc.)

-Surfactant-
・Capstone FS-34 (Chemours)
・BYK-348 (manufactured by BYK)

-Antifoam-
・Surfynol AD01 (manufactured by Nissin Chemical Industry Co., Ltd.)

-Antibacterial agent-
・Proxel GXL (manufactured by Lonza)

Next, various characteristics of each produced ink were evaluated as follows. The results are shown in Tables 1 to 3.

<Particle size distribution of solid content in ink>
The cumulative 10% particle diameter (D ₁₀ ), the cumulative 50% particle diameter (D ₅₀ ) and the cumulative 90% particle diameter (D ₉₀ ) of the solid content (bright pigment and resin particles) in each of the obtained inks are calculated as The measurement was performed by a dynamic light scattering method using an analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.).

<Ink filterability>
After stirring each produced ink for 10 minutes with a stirrer, 50 g of the ink was pressure filtered with a syringe filter unit (trade name: Minisart 17594K, manufactured by Sartorius) of a cellulose acetate membrane filter having an average pore size of 5.0 μm, and the filter unit was used. The amount of liquid passing through each piece was determined, and the ink filterability was evaluated according to the following criteria.
[Evaluation rank]
A: Liquid flow rate is 45 g or more B: Liquid flow rate is 35 g or more and less than 45 g C: Liquid flow rate is 25 g or more and less than 35 g D: Liquid flow rate is less than 25 g

<Print evaluation>
-Printing conditions-
A recording head (MH5420, manufactured by Ricoh Co., Ltd., 4 rows of ejection ports, 320 nozzles each, ink amount 35 pL, resolution 600 dpi (horizontal)×600 dpi (vertical)) is used for an expansion type coating device (EV2500, manufactured by Ricoh Co., Ltd.). The printing was evaluated.
First, the ink in the ink was degassed by stirring the ink for 30 minutes under a reduced pressure condition of 5 Pa to 10 Pa, and the ink bag was filled with the ink to make an ink cartridge.
Next, the head difference between the ink and the head nozzle surface is changed so that the ink in the ink cartridge has a positive pressure with respect to the head, so that the head is filled with the ink.
Next, the inside of the head was heated to 40° C., and it was confirmed that all the nozzles of the head were filled with the ink by an ejection confirmation chart (nozzle check chart) of all channels.
Next, when a solid image is printed on an inkjet matte coated paper (Super Fine Paper manufactured by Seiko Epson Corporation) at a resolution of 1,200 dpi×1,200 dpi, the amount of ink adhered to the paper is 20 g/m ^2. Thus, the ejection amount was adjusted by changing the drive voltage of the head. Further, the output image was 1,200 dpi×1,200 dpi, the printing frequency was adjusted by changing the drive frequency of the head so that the printing speed was 0.15 mm/sec.
The heating and drying temperature was measured by bringing the temperature of the paper surface as a set temperature and contacting a mold type surface sensor MF-OK (manufactured by Toa Denki Co., Ltd.). Similarly, the temperature of the hot air at the hot air outlet was measured. Further, the hot air temperature was set to 70° C., and the platen during hot air drying was set to be heated to the same temperature as the hot air temperature. The hot air volume was set to be 10 m ³ /m ² /sec. The heat drying was performed for 15 minutes including the heating time during printing, and the warm air time was 15 minutes.
The printed image was a solid image of 50 mm×50 mm.

-Recording medium-
As a recording medium, PVC film (Roland Dizzy, DGS-210-WH), PP film (Toyobo Co., Ltd., P2161), PET film (Toyobo Co., E5100), offset coated paper (Oji Paper Co., Ltd.) Manufactured, product name: OK top coat+), and glossy paper for inkjet (Fuji Film Co., Ltd., Picture Paint Photo Finish Pro) were used.
Regarding the recording medium, the standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000 Edition” is used. The water absorption amount from the start of contact to 30 msec ^1/2 was measured by the Bristow method described in 51 "Paper and paperboard-Liquid absorption test method-Bristow method". The results are shown in Table A. In addition, when the water absorption amount is 10 mL/m ² or less, it corresponds to a poor water-absorption recording medium.

<Fixed state of coating film>
The peeled state was confirmed by rubbing the coated surface of the printed coating film prepared under the above-mentioned printing conditions with a finger pad, and the fixing state of the coated film was evaluated. In addition, the worst state was set as the evaluation result from the evaluation results of the respective recording media.
[Evaluation criteria]
A: The coating film cannot be peeled off B: Traces of rubbing on the coating film are visible C: Part of the coating film is peeled off and the ink spreads D: The coating film is completely peeled off and disappears

<Hue evaluation>
The hue evaluation of each print film dried by printing was measured by laying my paper (manufactured by Ricoh Co., Ltd.) under the evaluation sample and using a spectrophotometric densitometer X-Rite 939 (manufactured by X-Rite) on the printed portion. .. Saturation C ^* =((a ^* ) ² +(b ^* ) ² ) ^0.5 was calculated from the measurement results, and evaluated based on the following evaluation criteria. In addition, the worst state was set as the evaluation result from the evaluation results of the respective recording media.
[Evaluation criteria]
A: Saturation C ^* is less than 10 B: Saturation C ^* is 10 or more and less than 20 C: Saturation C ^* is 20 or more and less than 30 D: Saturation C ^* is 30 or more

<Glossiness>
The 60 degree glossiness was measured with BYK Gardner Micro Trigloss for each coating film, and the average value of the measured values at three points was taken as the measured value of the coating film, and the glossiness was evaluated according to the following criteria. In addition, the worst state was set as the evaluation result from the evaluation results of the respective recording media.
[Evaluation criteria]
A: Gloss is 160 or more B: Gloss is 120 or more and less than 160 C: Gloss is 80 or more and less than 120 D: Gloss is less than 80

<Storage stability>
Each ink was filled in an ink container and stored at 50° C. for 1 week, and then each ink was stirred with a stirrer for 30 minutes, and then a syringe filter unit of cellulose acetate membrane filter having an average pore diameter of 5.0 μm (trade name: Pressure filtration was carried out with a Mini Sarto 17594K (manufactured by Sartorius), and the gloss of the coating film was evaluated with the ink after filtration to evaluate the storage stability. The evaluation standard is based on the gloss evaluation.

*In Comparative Example 2, the ink filterability is poor, and the silver particles are removed by the filter, so the silver particle content in the filtrate cannot be determined. Moreover, the non-ejection nozzle was not eliminated by the ink filling operation to the inkjet head, and the printing evaluation could not be performed. Therefore, it is not evaluated as an inkjet ink.

From the results of Tables 1 to 3, in Examples 1 to 7, compared to Comparative Examples 1 to 3, it is possible to color the hardly water-absorbent recording medium with a metallic color, and the metallic color deteriorates over a long period of time. It was found that the storage stability was excellent.
Further, when the cumulative 10% particle diameter (D ₁₀ ) of silver particles is less than 100 nm as in Comparative Example 1, silver coloring is not obtained in a hardly water-absorbent recording medium such as PVC or PP, and it becomes ocher. It is a colored coating film and cannot be used as metallic.
Further, when the cumulative 90% particle diameter (D ₉₀ ) of silver particles exceeds 5,000 nm as in Comparative Example 2, there is a problem in ink filterability, and the ink cannot be used as an ink.
In addition, when aluminum particles are used as in Comparative Example 3, it changes to white upon storage and loses metallic luster, and is lost as a metallic pigment.
Further, when an organic solvent having a boiling point of higher than 250° C. is contained as in Comparative Example 4, the ink cannot be dried on a hardly water-absorbent recording medium such as PVC or PP, and the ink becomes damp and is fixed. Not done.

Aspects of the present invention are as follows, for example.
<1> An ink containing water, silver particles, and an organic solvent,
The cumulative 10% particle diameter (D ₁₀ ) of the silver particles by the dynamic light scattering method is 100 nm or more, and the cumulative 90% particle diameter (D ₉₀ ) is 5,000 nm or less,
The ink is characterized in that the organic solvent does not include an organic solvent having a boiling point of higher than 250°C.
<2> In <1>, the volume-based cumulative 10% particle diameter (D ₁₀ ) of the silver particles by dynamic light scattering method is 300 nm or more, and the cumulative 90% particle diameter (D ₉₀ ) is 2,000 nm or less. It is the described ink.
<3> The organic solvent includes an organic solvent having a boiling point of 200° C. or lower,
The ink according to any one of <1> to <2>, wherein the content of the organic solvent having a boiling point of 200° C. or less is 50% by mass or more based on the total amount of the organic solvent.
<4> The organic solvent having a boiling point of 200° C. or lower is at least one selected from 3-methoxy-3-methyl-1-butanol, 1,2-propanediol, and 2,3-butanediol. The ink according to <3>.
<5> The ink according to any one of <1> to <4>, further containing resin particles.
<6> The ink according to <5>, wherein the resin particles are at least one selected from polycarbonate-based urethane resin particles, polyether-based urethane resin particles, polyester-based urethane resin particles, and acrylic resin particles. ..
<7> The ink according to any one of <5> to <6>, in which the solid content of the resin particles is smaller than the solid content of the silver particles.
<8> The ink according to any one of <1> to <7>, in which the solid content of the silver particles is 0.1% by mass or more and 30% by mass or less.
<9> An ink container, characterized in that the ink according to any one of <1> to <8> is contained in a container.
<10> A step of applying a stimulus to the ink according to any one of <1> to <8> and discharging the ink onto a recording medium,
And a step of heating and drying the ink on the recording medium, the inkjet method.
<11> The inkjet method according to <10>, wherein the stimulus is at least one selected from heat, pressure, vibration, and light.
<12> The inkjet method according to any one of <10> to <11>, wherein the recording medium is a poorly water-absorbent recording medium.
<13> A unit for applying a stimulus to the ink according to any one of <1> to <8> and discharging the ink onto a recording medium,
And a unit for heating and drying the ink on the recording medium.
<14> The inkjet device according to <13>, wherein the stimulus is at least one selected from heat, pressure, vibration, and light.
<15> The inkjet device according to any one of <13> to <14>, wherein the recording medium is a poorly water-absorbent recording medium.
<16> An image-formed product, which comprises an image formed using the ink according to any one of <1> to <8> on a recording medium.
<17> The recording medium is the image-formed product according to <16>, which is a hardly water-absorbent recording medium.

The ink according to any one of the items <1> to <8>, the ink container according to the item <9>, the inkjet method according to any one of the items <10> to <12>, and the item <13> to < The inkjet device according to any one of 15> and the image-formed product according to any of <16> to <17> solves the above problems in the related art and achieves the object of the present invention. You can

400 image forming apparatus 401 exterior of image forming apparatus 401c cover of apparatus body 404 cartridge holder 410 main tank 410k, 410c, 410m, 410y for each color of black (K), cyan (C), magenta (M), and yellow (Y) Main tank 411 Ink storage section 413 Ink discharge port 414 Storage container case 420 Mechanism section 434 Ejection head 436 Supply tube

JP, 2005-134935, A

Claims (10)

An ink containing water, silver particles, an organic solvent , and resin particles ,
The cumulative 10% particle diameter (D ₁₀ ) of the silver particles by the dynamic light scattering method is 100 nm or more, and the cumulative 90% particle diameter (D ₉₀ ) is 5,000 nm or less,
An ink characterized in that the organic solvent does not include an organic solvent having a boiling point of higher than 250°C. The organic solvent includes an organic solvent having a boiling point of 200° C. or lower,
The ink according to claim 1, wherein the content of the organic solvent having a boiling point of 200° C. or lower is 50% by mass or more based on the total amount of the organic solvent. The organic solvent having a boiling point of 200° C. or lower is at least one selected from 3-methoxy-3-methyl-1-butanol, 1,2-propanediol, and 2,3-butanediol. Ink described. The ink according to any one of claims 1 to 3, wherein the resin particles are at least one selected from polycarbonate-based urethane resin particles, polyether-based urethane resin particles, polyester-based urethane resin particles, and acrylic resin particles. The ink according to claim 1, wherein the solid content of the resin particles is lower than the solid content of the silver particles. An ink container comprising the ink according to claim 1 contained in a container. Applying a stimulus to the ink according to any one of claims 1 to 5 and discharging the ink onto a recording medium;
And a step of heating and drying the ink on the recording medium. Means for applying a stimulus to the ink according to any one of claims 1 to 5 and ejecting the ink onto a recording medium;
An ink jet device comprising: a unit configured to heat and dry the ink on the recording medium. The inkjet device according to claim 8, wherein the recording medium is a water-absorptive recording medium. Cumulative 50% particle diameter (D _Fifty ) Is 300 nm or more, The ink according to any one of claims 1 to 5.