JP2018109118A - Ink, ink set, ink cartridge, printing method and printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink having excellent hiding property and solvent resistance in an ink used for printing in which the brightness of an image is changed by applying a liquid. SOLUTION: In an ink used for printing in which an image is changed by applying a liquid, the ink contains a solvent and hollow inorganic particles, and the change in the image is a change in the brightness of the image. [Selection diagram] Fig. 6

Description

The present invention relates to an ink, an ink set, an ink cartridge, a printing method, and a printing apparatus.

In recent years, image recording in which an image changes in response to an external stimulus has been used in recent years for ballpoint pens that disappear with frictional heat using ink having hysteresis characteristics in the color density-temperature curve, and mercury (II) iodide metal that changes color reversibly with temperature. Temperature-recorded materials using complex salts have been developed.
Moisture indicator inks that are colored or decolored by moisture have also been developed. In the past, discoloration of hydrated complexes of cobalt salts has been used. In recent years, inks using pH-sensitive dyes have been developed. These have a mechanism for detecting moisture by combining a colored dye with an acidic component eluted under the influence of moisture to make it colorless.

On the other hand, there is a demand for inks that change the light transmission upon receiving a stimulus from a white state, instead of the presence or absence of such coloring, and change to a transparent state from the variety of image representation.
In general, titanium dioxide, which is a white pigment excellent in hiding power, coloring power, and the like, is widely used as a pigment for white ink. Similarly, ink using hollow particles has been reported. The hiding property of the hollow particles can be obtained by utilizing the refractive index difference between the hollow shell after drying the coating film and the pores from which the liquid component of the ink has been removed.

In the following Patent Document 1, a white hollow having a porosity of 40% or more and 80% or less, a number average particle diameter of 50 nm or more and 200 nm or less, and a ratio of particles having a particle diameter of 1 μm or more is 1000 ppm or less. Ink jet inks containing particles have been proposed. White hollow particles described in Patent Document 1 are resins having styrene or the like as a skeleton.
Patent Document 2 discloses a white ink composition comprising a base material and an image recording layer recorded on the base material, the image recording layer including hollow resin particles as a white color material. A white color material layer recorded by a product and a color color material layer recorded by a process color ink composition, and the white color material layer is heated or a solvent is removed. A sticking member that is made transparent by permeation is disclosed.

  In the prior art, since hollow resin particles are used, there is a problem that solvent resistance and heat resistance are low, and if repeated transparency is performed, the hollow shape cannot be maintained and the initial concealability cannot be maintained.

  Accordingly, an object of the present invention is to provide an ink excellent in concealing property and solvent resistance in an ink used for printing in which the brightness of an image changes by application of a liquid.

The above problem is solved by the configuration 1) below.
1) Ink used for printing in which an image changes due to application of a liquid, the ink contains a solvent and hollow inorganic particles, and the change in the image is a change in brightness of the image.

  ADVANTAGE OF THE INVENTION According to this invention, the ink which is excellent in concealment property and solvent resistance can be provided in the ink used for the printing from which the brightness of an image changes with provision of a liquid.

It is a perspective explanatory view of an ink jet recording apparatus. It is a perspective view of a main tank. It is a figure for demonstrating the cartridge of this invention. It is a figure for demonstrating the cartridge of this invention. It is a figure for demonstrating the printing method of this invention. It is a figure for demonstrating the printing method of this invention. It is a figure for demonstrating the printing method of this invention. It is a figure for demonstrating the printing method of this invention. It is a figure for demonstrating the printing pattern used in the Example.

Hereinafter, embodiments of the present invention will be described in more detail.
The present invention is characterized in that, in an ink used for printing in which the brightness of an image is changed by applying a liquid, the ink contains a solvent and hollow inorganic particles. In the ink of the present invention, when water or a volatile solvent is applied to the formed image, the image emerges, and is white when dry and transparent when wet.

<Hollow inorganic particles>
Although it does not specifically limit as a hollow inorganic particle used for this invention, For example, oxides, nitrides, oxynitrides, etc., such as titanium, silicon, aluminum, zirconium, and strontium, can be utilized. Titanium oxide is preferable from the viewpoint of the white hiding property of the coating film because of its lack of coloring and high refractive index. However, in the case of hollow inorganic particles, in addition to scattering of the particle surface, the shell corresponding to the outer shell of the hollow inorganic particles and the internal pores Other materials such as silica (silicon dioxide) can also be used. From the standpoint of settling in the ink, it is preferable to use silica having a small specific gravity as the hollow inorganic particles, and the silica is also compared with controlling the shell thickness (shell thickness) and pore diameter of the hollow inorganic particles. Easy. Silica can be freely designed with organic silicon compounds such as tetraethoxysilane and tetramethoxysilane and inorganic silicon compounds such as silicate as starting materials.

  The hollow inorganic particles preferably have a specific gravity close to the specific gravity of the ink liquid in order to suppress precipitation, floating, and separation in the ink. Therefore, the shell thickness of the hollow inorganic particles is preferably 4 nm or more and 20 nm or less, and 6 nm. More preferably, it is 18 nm or less. When the shell thickness is 4 nm or more, collapse of the hollow structure due to energy loaded in the dispersion process is prevented, high concealability is obtained, and sedimentation in the ink is also prevented. When the shell thickness is 20 nm or less, the specific gravity as hollow inorganic particles can be kept small, and settling in the ink is prevented. The ratio (inner diameter / outer diameter) of the inner diameter (hole diameter) and the outer diameter (primary particle diameter) of the hollow inorganic particles is preferably 0.75 or more and 0.95 or less. When the ratio is 0.75 or more, sufficient scattering of the hollow shell and the internal vacancies can be obtained, high concealing property can be obtained, and further, the internal vacancies make it difficult to settle, and 0.95 or less The strength of the hollow shell can be obtained, the structure can be maintained even under the energy load at the time of dispersion, and high concealability and high dispersion stability that is difficult to settle are obtained.

  The number average primary particle diameter of the hollow inorganic particles is preferably 20 nm or more and less than 200 nm. When the number average primary particle is 20 nm or more, the concealing property of the coating film can be ensured by scattering of the hollow shell and the internal pores. When the number average primary particle is less than 200 nm, it is difficult to settle in the ink and high dispersion stability. Can be expected. The number primary average particle diameter and the shell thickness are primary particles of 200 to 500 primary particles in a 30,000-fold field of view using a transmission electron microscope (manufactured by JEOL, "JEM-2100F"). The diameter in a certain direction at the interval between two parallel lines in a certain direction sandwiching the particles can be measured and obtained from the average value of the cumulative distribution.

  The 50% cumulative volume particle size (D50) of the hollow inorganic particles in the ink is preferably 200 nm or more and 500 nm or less. When the 50% cumulative volume particle diameter (D50) is 200 nm or more, the concealability of the coating film can be improved, and when it is 500 nm or less, the apparent specific gravity increases due to the constraining solvent between the particles due to secondary aggregation. It can be suppressed, and it is difficult to settle and high dispersion stability can be obtained. The 50% cumulative volume particle size (D50) of the ink composition described here is the secondary particle size in the ink.

Cumulative 10% particle diameter (D10), cumulative 50% particle diameter (D50), and cumulative 90% particle diameter (D90) of the hollow inorganic particles are obtained by measuring the diameter and number of hollow inorganic particles. From the particle size accumulation curve obtained by statistical processing, the particle diameter when it becomes 10% of the total mass is 10% cumulative (D10), and the particle diameter when it becomes 50% of the total mass. The cumulative 50% particle diameter (D50) is the value when the diameter of the particle when it becomes 90% of the total mass is the cumulative 90% particle diameter (D90). The diameter of the hollow inorganic particles may be the diameter of the hollow inorganic particles themselves, or may be the diameter of the particle colloid when the hollow inorganic particles are colloidally dispersed.
The diameter of the hollow inorganic particles can be determined by using, for example, a particle size distribution measuring apparatus based on a dynamic light scattering method, if the hollow inorganic particles are in a dispersed state in a solvent. Examples of the particle size distribution measuring apparatus using the dynamic light scattering method include Nanotrack Wave-UT151 (manufactured by Microtrack Bell Co., Ltd.), Nanotrack Wave-EX150 (manufactured by Nikkiso Co., Ltd.), ELSZ-2, and DLS-8000. (Above, manufactured by Otsuka Electronics Co., Ltd.), LB-550 (manufactured by Horiba, Ltd.), and the like.
In addition to these, it can be measured by electron microscopy. The diameter of a hollow inorganic particle can be calculated | required by obtaining the photograph of a hollow inorganic particle with the said electron microscope, image-processing and measuring this photograph. As an example, the area of 50 or more hollow inorganic particles in the photograph is randomly obtained from the photograph, and the diameter of the equivalent circle is calculated to obtain the particle diameter. And a particle size accumulation curve can be calculated | required from the obtained particle diameter.

  The 90% cumulative volume particle diameter (D90) of the hollow inorganic particles in the ink is preferably 1 μm or less. Furthermore, it is more preferable that it is 600 nm or less. When the 90% cumulative volume particle diameter (D90) is 1 μm or less, even if the particles are agglomerated due to drying of the ink or foreign matter in the ink, the agglomeration exceeding the nozzle diameter does not occur and nozzle clogging does not occur. Further, when D90 is 600 nm or less, the size of the aggregate is sufficiently small with respect to the in-head flow path and the nozzle, so that stable ejection can be performed. Note that the 90% cumulative volume particle size (D90) of the ink described here is the secondary particle size in the ink.

  The content of the hollow inorganic particles in the ink is preferably 3% by mass or more and 12% by mass or less, and more preferably 4.5% by mass or more and 10% by mass or less. When it is 3% by mass or more, sufficient concealing property and scratch resistance are obtained, and when it is 12% by mass or less, a sufficient coating film concentration can be obtained and good ejection stability can be obtained.

When the hollow inorganic particles are made of silica (hereinafter sometimes referred to as hollow silica particles), the production method is not particularly limited, but may be a known production method. For example, as described in Japanese Patent No. 4654428 and Japanese Patent No. 5810362, silica is obtained by forming an alkoxysilane on the surface of calcium carbonate in the presence of a basic catalyst using calcium carbonate as a core material. Thereafter, hollow silica particles can be obtained by a method of dissolving calcium carbonate by acid addition.

  When hollow silica particles are used in the ink of the present invention, it is preferable to use a dispersion of hollow silica particles produced in the process of producing hollow silica particles, rather than powder-dried hollow silica particles. By using a dispersion of hollow silica particles, it is possible to prevent strong interparticle aggregation during drying, and it is possible to disperse in ink while maintaining a hollow structure.

When dispersing the hollow inorganic particles in the ink, it is desirable to add a dispersant polymer. Examples of the dispersant polymer include an α-olefin-maleic anhydride copolymer, a styrene- (meth) acrylic copolymer, a water-soluble polyurethane resin, and a water-soluble polyester resin. These may be used alone or in combination of two or more. When the dispersant polymer is used, the steric repulsion effect accompanying the adsorption of the dispersant can be improved, and high dispersion stability can be obtained. The dispersant polymer means a polymer having a weight average molecular weight of 1,000 or more.
As content of the said dispersing agent polymer, 10 mass% or more and 60 mass% or less are preferable with respect to a hollow inorganic particle, and 15 mass% or more and 50 mass% or less are more preferable. When the content is 10% by mass or more, dispersibility can be secured by the steric repulsion effect of the dispersant polymer adsorbed on the hollow inorganic particles, and when the content is 60% by mass or less, the dispersion is not adsorbed on the hollow inorganic particles. The amount of the agent polymer is small, and the viscosity of the ink can be reduced. Further, since the amount of the dispersant polymer that is not adsorbed is small, an increase in the thixotropy of the ink is suppressed, and the filtration liquid permeability and the discharge performance are improved.

<Solvent>
The ink of the present invention contains a solvent, and typically contains a volatile solvent. The volatile solvent is preferably a non-polymerizable solvent having no polymerizable functional group, and more preferably not remaining in the hollow inorganic particles when the coating film is dried. When the volatile solvent is water or a water-soluble organic solvent, it can be used as a water-based ink, and when the volatile solvent is an organic solvent, it can be used as a solvent ink. However, in recent years, many VOC (volatile organic compound) problems have been taken up, and water-based inks capable of reducing the amount of VOC generation are widely desired. VOC is a general term for organic compounds that easily volatilize in the atmosphere at normal temperature and pressure. The volatile solvent described in the present invention is required to volatilize when heated on a recording medium, and has a boiling point of 300 It means the one below ℃.
As described above, the ink of the present invention provides concealability by utilizing the scattering of the shell of the hollow inorganic particles and the internal pores in addition to the scattering of the particle surface. Therefore, if the ink component remains in the hollow inorganic particles after the coating film is dried, the concealability of the coating film is lowered. From the above points, the volatile solvent preferably has a boiling point of 260 ° C. or lower.

<< Water-soluble organic solvent for water-based ink >>
Examples of water-soluble organic solvents for water-based inks include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, and propylene carbonate. And ethylene carbonate.
The content of the water-soluble organic solvent is preferably 20% by mass or more, and more preferably 30% by mass to 70% by mass with respect to the total amount of the ink.
When the content is less than 20% by mass, the ink moisturizing power is reduced, so that it is easy to dry, causing precipitation of dissolved components in the ink due to drying and aggregation of the dispersed components at the head meniscus, causing ejection. May be defective.
Examples of such water-soluble organic solvents include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, cyclic ethers, amines, amides, sulfur-containing compounds, propylene carbonate, and carbonic acid. Examples include ethylene.

Examples of the polyhydric alcohols include 1,2-propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, 1,5- Pentanediol, 2-methyl-2,4-pentanediol, hexylene glycol, 1,6-hexanediol, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, 3-methyl-1,3- Examples include hexanediol and propylpropylene diglycol.
Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol mono-2-ethylhexyl ether, propylene glycol monoethyl ether. , Triethylene glycol dimethyl ether, and the like.
Examples of the polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.
Examples of the cyclic ethers include epoxies, oxetanes, tetrahydrofurans, tetrahydropyrans, and crown ethers. Among these, oxetanes and tetrahydrofurans are preferable, and oxetanes are more preferable from the viewpoint of water solubility.
Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiglycol, and the like.
Examples of the amines include monoethanolamine, diethanolamine, triethanolamine, N, N-dimethylmonoethanolamine, N-methyldiethanolamine, N-methylethanolamine, N-phenylethanolamine, and 3-aminopropyldiethylamine. Is mentioned.
Examples of the amide compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone, β-methoxy-N, N-dimethyl. Examples include propionamide and β-butoxy-N, N-dimethylpropionamide. Among these, water-soluble amide compounds described below are preferable.
The water-soluble amide compound is a polar solvent capable of dissolving many organic compounds and inorganic salts, and can be widely mixed from water to an organic solvent. Therefore, the effect of improving the wettability and solubility with respect to the recording medium and the mixing stability of other components can be obtained.

  Moreover, the amide compound shown with the following structural formula which is 1 type of an acyclic amide compound is also contained.

  The amide compound of the above structural formula has different hydrophilicity depending on the length of the alkyl group, and the miscibility with water or an organic solvent differs.

<Water>
The water content in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10% by mass or more and 90% by mass or less, and 20% by mass from the viewpoint of ink drying property and ejection reliability. % To 60% by mass is more preferable.

<< Organic solvent for solvent-based ink >>
As the organic solvent for the solvent-based ink, a volatile organic solvent used for a normal solvent-based ink can be used.
Examples of the organic solvent include alcohols, glycols, glycol ethers, esters, ketones, aromatic compounds, nitrogen-containing compounds, and the like.
Examples of the alcohols include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, tridecyl alcohol, cyclohexyl alcohol, 2-methylcyclohexyl alcohol and the like.
Examples of the glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, and dipropylene glycol.
Examples of the esters include ethyl acetate, isopropyl acetate, n-butyl acetate, methyl lactate, ethyl lactate, and butyl lactate.
Examples of the ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, diacetone alcohol, and the like.
Examples of the aromatic compound include toluene and xylene.
Examples of the nitrogen-containing compound include acetonitrile, γ-butyrolactone, γ-valerolactone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and the like.
From these, various solvents are selected from the viewpoints of compatibility with the characteristics of the head nozzle during printing, safety, and drying properties, and a plurality of solvents can be mixed and used as necessary.

The solvent-based ink preferably contains glycol ethers as an organic solvent from the viewpoints of wettability to recording media, permeability, and moderate drying properties.
Examples of the glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, Diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol Such as Bruno butyl ether acetate, and the like.

  In the solvent-based ink, the content of the organic solvent is preferably 85% by mass or more, and more preferably 85% by mass to 95% by mass with respect to the total amount of the ink.

The ink of the present invention is used for spectroscopic measurement of an image printed on a polyethylene terephthalate film before dipping in pure water and after dipping for 1 minute, with a black paper laid under the polyethylene terephthalate film. When the lightness is measured using a color densitometer, the lightness difference | ΔL * | determined by the following formula 1 is preferably 13 or more. When the brightness difference | ΔL * | is 13 or more, a change in brightness can be confirmed well.
Formula 1 | ΔL * | = (L * initial stage) − (after L * immersion)
(In Formula 1, L * initial is L * before immersing the image in pure water, and L * after immersing is L * after immersing the image in pure water for 1 minute)
The brightness difference | ΔL * | can be measured by a known method, for example, using a spectrocolorimetric densitometer X-Rite 939.

In addition, the ink of the present invention is an image printed on a polyethylene terephthalate film before being dipped in an organic solvent and after being dipped for 1 minute and dried, and then printed with a black paper under the polyethylene terephthalate film. When the lightness is measured using a spectrocolorimetric densitometer, it is preferable that the lightness difference | ΔL * | When the brightness difference | ΔL * | is 13 or less, the solvent resistance is excellent.
Formula 2 | ΔL * | = (L * initial stage) − (after L * organic solvent immersion drying)
(In Formula 2, L * initial is L * before immersing the image in an organic solvent, and L * after immersing and drying the organic solvent is after immersing and drying the image in an organic solvent for 1 minute. L *)

<Ink set>
The ink set of the present invention includes a first ink containing hollow inorganic particles and a second ink containing solid inorganic particles. The second ink is preferably one in which the image does not change due to application of liquid. The ink set of the present invention preferably includes the first ink which is the above ink containing a solvent and hollow inorganic particles, and more preferably the first ink and the second ink. The ink is a white ink, and particularly preferably, the first ink, which is the above-mentioned ink containing a solvent and hollow inorganic particles, and the second ink containing solid inorganic particles and the image is not changed by application of a liquid. Ink.
When forming a printed matter in which the image changes due to the application of liquid, for example, the image floats, the hollow inorganic particles in the first ink become white when dried and become transparent when wet, causing the image to appear. Since the solid inorganic particles in the second ink do not change in lightness due to the application of the liquid, the contrast of the image can be increased by using both inks. Also, by including hollow inorganic particles and solid inorganic particles respectively in the ink set, the heat resistance and solvent resistance are excellent, and the coating film can be used even if the coating film is repeatedly exposed to the solvent because it uses the hollow inorganic particles. Since the hollow shape inside is not broken, the white hiding property can be restored every time the coating film is dried.

  The ink set of the present invention can contain a known ink in addition to the first ink and the second ink. For example, process color inks such as black ink, cyan ink, magenta ink, yellow ink, special color inks such as red ink, orange ink, blue ink, green ink, metallic ink, gray ink, light cyan ink, light magenta ink, etc. Light color ink or the like can be used in combination.

The second ink or the ink that can be used in combination can be a photocurable ink, a thermosetting ink, or a hot melt ink that does not contain a volatile solvent. Are preferably aligned with ink containing a volatile solvent. Further, since the apparatus can be miniaturized by using a single dry fixing process, it is preferable to perform dry fixing with an ink containing a volatile solvent.
In order to suppress feathering and bleeding between the inks, it is desirable to control the ink additive component to suppress the difference in surface tension between the inks to 5 mN / m or less, preferably 2 mN / m.

<Solid inorganic particles>
Unlike the hollow particles, the solid inorganic particles are filled with solid components, and the particles themselves are composed of a single component or a plurality of components. Since solids occupy the interior of the particles, when the ink dries, the solids inside the particles do not change and no gas cavities are generated inside the particles.
Such solid inorganic particles are not particularly limited. For example, oxides such as titanium, silicon, aluminum, zirconium, and strontium, nitrides, oxynitrides, and the like can be used. It is preferable to include an inorganic white pigment from the viewpoint of matching the color with the hollow inorganic particles, weather resistance, and heat resistance. Such solid inorganic pigments are barium sulfate, lead white, zinc oxide, titanium oxide, etc. because of their lack of color and high refractive index. To adjust the whiteness, silica, aluminum oxide, zirconium oxide, carbonate It is also possible to use calcium and the like together. Of these, titanium dioxide is preferably used for the solid inorganic particles from the viewpoint of white hiding.

The crystal system of the titanium dioxide particles is preferably a rutile type having a high refractive index and easily increasing whiteness among amorphous, rutile, and anatase types. Further, when the average primary particle size of the titanium dioxide particles is 100 to 400 nm, the whiteness is high, and from the visible light scattering property, the whiteness increases when it is 200 to 300 nm, particularly 210 to 250 nm. Examples of the method for producing such titanium oxide particles include a sulfuric acid method and a chlorine method, but are not particularly limited.
Further, the surface treatment of the titanium dioxide particles is not particularly limited, but in order to suppress the high photocatalytic activity of the titanium dioxide particles and to suppress the decomposition of the additive attached to the particle surface, the surface of the particles is made of aluminum, silicon, zirconia or the like. Those treated with an oxide are preferred.
In the above, a white pigment is exemplified as the solid inorganic particles, but other inorganic pigments can also be used. Examples of other inorganic pigments include iron oxide, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, titanium yellow, and carbon black.

The 50% cumulative volume particle size (D50) of the solid inorganic particles in the second ink is preferably 50 nm to 350 nm, and more preferably 150 nm to 302 nm. When the 50% cumulative volume particle size (D50) is 50 nm or more, it is possible to obtain a concealing property of the coating film, and when it is 350 nm or less, an increase in apparent specific gravity due to the constraining solvent between the particles due to secondary aggregation. It can be suppressed, and it is difficult to settle and high dispersion stability can be obtained. Note that the 50% cumulative volume particle size (D50) of the ink described here is the secondary particle size in the ink.
The accumulated 10% particle diameter (D10), accumulated 50% particle diameter (D50), and accumulated 90% particle diameter (D90) of the solid inorganic particles can be calculated by measuring in the same manner as the hollow inorganic particles. . The diameter of the solid inorganic particles may be the diameter of the solid inorganic particles themselves, or may be the diameter of the particle colloid when the solid inorganic particles are colloidally dispersed.
If the diameter of the said solid inorganic particle is a dispersion state in a solvent, it can be calculated | required by using the particle size distribution measuring apparatus based on a dynamic light scattering method, for example. Moreover, it can also measure by an electron microscope like a hollow inorganic particle.

  The 90% cumulative volume particle size (D90) of the solid inorganic particles in the second ink is preferably 1 μm or less. Furthermore, it is more preferable that it is 600 nm or less. When the 90% cumulative volume particle diameter (D90) is 1 μm or less, even if the particles are agglomerated due to drying of the ink or foreign matter in the ink, the agglomeration exceeding the nozzle diameter does not occur and nozzle clogging does not occur. Further, when D90 is 600 nm or less, the size of the aggregate is sufficiently small with respect to the in-head flow path and the nozzle, so that stable ejection can be performed.

  The content of the solid inorganic particles in the second ink is preferably 3% by mass or more and 12% by mass or less, and more preferably 4.5% by mass or more and 10% by mass or less. When it is 3% by mass or more, sufficient concealing property and scratch resistance are obtained, and when it is 12% by mass or less, a sufficient coating film concentration can be obtained and good ejection stability can be obtained.

<Color material>
In the present invention, the first ink and the second ink are preferably white inks, but these inks can also be used as colored inks. As the coloring material, both pigments and dyes can be used. However, since titanium dioxide has a high photoactivity and a high decomposability, a pigment is preferable from the viewpoint of light fading.

Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable.
Examples of the azo pigments include azo lakes, hardly soluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples of the dye chelate include basic dye chelate and acid dye chelate.
There is no restriction | limiting in particular in the color of the said color material, According to the objective, it can select suitably, For example, the color material for black, the color material for colors, etc. are mentioned.
These may be used individually by 1 type and may use 2 or more types together.

Examples of the black color material include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black, copper, iron (CI pigment black 11), and the like. And organic pigments such as aniline black (CI Pigment Black 1).
Examples of the color material for the color include 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, 128, 138, 150, 151, 153, 155, 183, 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, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 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, 185, 190, 193, 209, 219, 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 (phthalocyanine blue), 15: 4 (phthalocyanine blue), 16, 17: 1, 56, 60, 63; I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like.
Other suitable colored pigments include those described in The Color Index, Third Edition (The Society of Dyer's and Colorists, 1982).
Such a pigment is preferably added as necessary for the toning of the ink, and the color becomes transparent without being affected by the hiding power of the inorganic particles.

  The content of the color material in the ink is preferably 0.1% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass from the viewpoints of improvement in image density, good fixability and ejection stability. It is as follows.

<Distribution method>
As a method for dispersing the hollow inorganic particles and the solid inorganic particles, a dispersion device using a recording medium such as a ball mill, a sand mill, or a bead mill, or a recording medium-less dispersion device may be used. The hollow inorganic particles destroy the hollow structure when a strong force is applied to the particles at the time of dispersion. Therefore, it is preferable to use a recording medium-less dispersion apparatus in order to maintain the hollow structure.
The recording medium-less device can disperse the hollow inorganic particles while maintaining the hollow structure by avoiding the collision of the recording medium with the particles. Further, since no contamination derived from the recording medium is generated, generation of fine powder and coarse powder in the system can be suppressed. Furthermore, since the uniformity of the particle size distribution can be improved, good ink discharge properties can be obtained. Examples of the recording medium-less disperser include a disperser that uses a high-speed shearing force such as a collision dispersive type or an ultrasonic dispersive type, a disperser that uses high-speed stirring, or an ultrasonic disperser. Examples of the dispersing device that uses high-speed shearing force include device name: Nanovaita series laboratory machine C-ES008 (manufactured by Yoshida Kikai Kogyo Co., Ltd.). Examples of the ultrasonic dispersing apparatus include apparatus name: ultrasonic homogenizer US-150E (manufactured by Nippon Seiki Seisakusho Co., Ltd.).
The temperature of the dispersion during dispersion is preferably 5 ° C. or higher and 60 ° C. or lower, and more preferably 5 ° C. or higher and 50 ° C. or lower.
The dispersion recording medium in the dispersion apparatus using the recording medium needs to have mild conditions by appropriately selecting the recording medium specific gravity and the recording medium diameter so that the hollow structure of the hollow inorganic particles can be maintained.

  Hereinafter, other components that can be used for the first ink and / or the second ink (hereinafter, simply referred to as ink) will be described.

<Resin>
The type of resin contained in the ink is not particularly limited and can be appropriately selected according to the purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene type Examples thereof include resins, styrene-butadiene resins, vinyl chloride resins, acrylic styrene resins, and acrylic silicone resins.
Resin particles made of these resins may be used. An ink can be obtained by mixing resin particles with a material such as a colorant or an organic solvent in a resin emulsion state in which water is dispersed as a dispersion medium. As said resin particle, what was synthesize | combined suitably may be used and a commercial item may be used. Moreover, these may be used individually by 1 type, or may be used in combination of 2 or more types 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 particularly 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 Microtrack Bell Co., Ltd.).

  The resin content is not particularly limited and may be appropriately selected according to the purpose. However, from the viewpoint of fixability and ink storage stability, the content of the resin is 1% by mass or more and 30% by mass or less. Is preferable, and 5 mass% or more and 20 mass% or less are 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. From the viewpoint of improving the image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number Is preferably 20 nm to 1000 nm, and more preferably 20 nm to 150 nm. 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.).

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

<Surfactant>
As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants and anionic surfactants can be used.
There is no restriction | limiting in particular in silicone type surfactant, According to the objective, it can select suitably. Among them, those that do not decompose even at high pH are preferable, and examples thereof include side chain modified polydimethylsiloxane, both terminal modified polydimethylsiloxane, one terminal modified polydimethylsiloxane, and side chain both terminal modified polydimethylsiloxane. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferred because they exhibit good properties as an aqueous surfactant. In addition, as the silicone surfactant, a polyether-modified silicone surfactant can be used, and examples thereof include a compound in which a polyalkylene oxide structure is introduced into the side chain of the Si portion of dimethylsiloxane.
Examples of the fluorosurfactant 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. Polyoxyalkylene ether polymer compounds are particularly preferred because of their low foaming properties. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, and the like. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylate. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include 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. As counter ions of salts in these fluorosurfactants, 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 etc. are mentioned.
Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkylamide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate salt, and the like.
These may be used alone or in combination of two or more.

The silicone surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, side chain modified polydimethylsiloxane, both terminal modified polydimethylsiloxane, one terminal modified polydimethylsiloxane, side Since both ends of the chain are modified with polydimethylsiloxane, a polyether-modified silicone surfactant having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group exhibits good properties as an aqueous surfactant. preferable.
As such a surfactant, an appropriately synthesized product or a commercially available product may be used. Commercially available products can be obtained from, for example, Big Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.
The polyether-modified silicone surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a polyalkylene oxide structure represented by the general formula (S-1) is represented by dimethylpolysiloxane. Examples thereof include those introduced into the side chain of Si part of siloxane.

Formula (S-1)
(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.)
A commercial item can be used as said polyether modified silicone type surfactant, For example, KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS- 1906EX (Japan Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Dow Corning Silicone Co., Ltd.), BYK-33, BYK-387 (Bic Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.), etc. are mentioned.

As the fluorine-based surfactant, a fluorine-substituted compound having 2 to 16 carbon atoms is preferable, and a fluorine-substituted compound having 4 to 16 carbon atoms is more preferable.
Examples of the fluorosurfactant include perfluoroalkyl phosphate compounds, perfluoroalkylethylene oxide adducts, and polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain. Among these, polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain are preferred because of their low foaming properties, and are particularly fluorine-based compounds represented by the general formulas (F-1) and (F-2). A surfactant is preferred.

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} , n is an integer of 1 to 6, or CH ₂ CH (OH) CH ₂ —CnF _{2n + 1,} where n is 4 to 6. An integer, or CpH _{2p + 1} , p is an integer of 1-19. a is an integer of 4-14.
A commercial item may be used as said fluorosurfactant. As this commercial item, for example, 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 Dainippon Ink & Chemicals, Inc.); 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 manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (Omnova) Manufactured), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.) and the like. Among these, good print quality, particularly color developability, penetrability to paper, wettability, and leveling are significantly improved. FS-3100, FS-34, FS-300 manufactured by Chemours, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Co., Ltd. Particularly preferred are Fox PF-151N and Unidyne DSN-403N manufactured by Daikin Industries, Ltd.

  There is no restriction | limiting in particular as content of surfactant in an ink, Although it can select suitably according to the objective, From the point which is excellent in wettability and discharge stability, and image quality improves, it is 0.001 mass. % To 5% by mass is preferable, and 0.05% to 5% by mass is more preferable.

<Antifoaming agent>
There is no restriction | limiting in particular as an antifoamer, For example, a silicone type antifoamer, a polyether type | system | group antifoamer, a fatty-acid ester type | system | group antifoamer etc. are mentioned. These may be used alone or in combination of two or more. Among these, a silicone type antifoaming agent is preferable from the viewpoint of excellent foam breaking effect.

<Antiseptic and antifungal agent>
The antiseptic / antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

<Rust preventive>
There is no restriction | limiting in particular as a rust preventive agent, For example, acidic sulfite, sodium thiosulfate, etc. are mentioned.

<PH adjuster>
The pH adjuster 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.

There is no restriction | limiting in particular as a physical property of an ink, According to the objective, it can select suitably, For example, it is preferable that a viscosity, surface tension, pH, etc. are the following ranges.
The viscosity at 25 ° C. of the ink 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 printing density and character quality and obtaining good discharge properties. More preferred. Here, for the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. Measurement conditions are 25 ° C., standard cone rotor (1 ° 34 ′ × R24), sample liquid amount 1.2 mL, rotation speed 50 rpm, and measurement is possible for 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 suitably 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 in 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 adjuster, an antiseptic / antifungal agent, an antirust agent, and the like as necessary.
For organic solvents, surfactants, antifoaming agents, pH adjusters, antiseptic / antifungal agents, and rust preventive agents, the same materials as those used for ink can be used, and other materials used for known processing liquids can be used. .
The type of the flocculant is not particularly limited, and examples thereof include water-soluble cationic polymers, acids, and polyvalent metal salts.

<Post-treatment liquid>
The post-treatment liquid is not particularly limited as long as a transparent layer can be formed. The post-treatment liquid is obtained by selecting and mixing an organic solvent, water, resin, surfactant, antifoaming agent, pH adjuster, antiseptic / antifungal agent, rust inhibitor, and the like as 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.

<Ink cartridge>
The ink cartridge of the present invention contains the first ink and / or the second ink in the ink set in each container, and further includes other members and the like appropriately selected as necessary.
The container is not particularly limited, and its shape, structure, size, material and the like can be appropriately selected according to the purpose. For example, at least an ink bag formed of an aluminum laminate film, a resin film, or the like Preferred examples include those possessed.
Next, the ink cartridge will be described with reference to FIGS.
Here, FIG. 3 is a schematic view showing the ink cartridge, and FIG. 4 is a schematic view showing a modification of the ink cartridge of FIG.
As shown in FIG. 3, in the ink cartridge 201, the ink bag 241 is filled with the ink of the present invention from the ink inlet 242 and exhausted, and then the ink inlet 242 is closed by fusion. In use, for example, a needle of an ink jet recording apparatus is pierced into an ink discharge port 243 made of a rubber member and supplied to the ink jet recording apparatus.
The ink bag 241 is formed of a packaging member such as an aluminum laminate film having low air permeability. As shown in FIG. 4, the ink bag 241 is usually housed in a plastic cartridge case 244, and is used, for example, by being detachably attached to various ink jet recording apparatuses.
The ink cartridge 201 contains the ink of the present invention and can be used by being detachably attached to, for example, various ink jet recording apparatuses, and is particularly preferably used by being detachably attached to an ink jet recording apparatus described later. .

<Recording medium>
The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, etc. can be used. However, according to the ink of the present invention, good image formation is possible even with a hardly water-absorbing recording medium. It is. Such a recording medium may be a transparent medium without concealment, and the recording medium may be colored and may be formed with an image made up of photographs, illustrations, patterns, characters, and the like. .
The hardly water-absorbing recording medium is a recording medium having a surface with low water permeability and low absorbency, including a material that does not open to the outside even if there are many cavities inside, and more quantitatively. Is a standard no. Of “JAPAN TAPPI Paper Pulp Test Method 2000”. In the Bristow method described in 51 “Paper and paperboard—Liquid absorbability test method—Bristow method”, a recording medium having a water absorption of 10 mL / m ² or less from the start of contact until 30 msec ^1/2 is obtained. Say.
Examples of the hardly water-absorbing recording medium include plastic films such as vinyl chloride resin film, polyethylene terephthalate (PET) film, polypropylene film, polyethylene film, and polycarbonate film, coated paper for printing, and art paper. These may be used alone or in combination of two or more. Among these, a vinyl chloride resin film and a coated paper for printing are preferable.
The ink of the present invention has sufficient performance not only for hardly water-absorbing recording media but also for conventionally used porous media such as porous media such as plain paper and inkjet paper and inorganic coated porous media. Show.
The ink of the present invention can perform high-image quality printing on the hardly water-absorbing recording medium, but can form images with higher image quality and higher abrasion resistance and adhesion, and can cope with high-speed printing conditions. Therefore, it is more preferable to heat the recording medium after printing.

The printing method of the present invention includes an ink application step of applying the ink (first ink) of the present invention to a printing material and a drying step of drying the printing material to which the ink has been applied.
According to another printing method of the present invention, the ink set of the present invention is used, and a first ink application step of applying the first ink to a printing material and a second ink of applying the second ink. An ink applying step and a drying step of drying the printed material to which the first ink and the second ink have been applied.
A new image can be formed by applying water or a volatile solvent to an image printed by these printing methods.
Moreover, the printing apparatus of this invention has a means to discharge ink, and the ink (1st ink) of this invention.
Another printing apparatus of the present invention includes means for ejecting ink and the ink set of the present invention.
Further, the terms “image formation”, “recording”, “printing”, “printing”, etc. in the terms of the present invention are all synonymous.

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

<Recording apparatus and recording method>
The ink of the present invention can be suitably used for various recording apparatuses using an ink jet recording method, such as a printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier complex machine, and a three-dimensional modeling apparatus.
In the present invention, the recording apparatus and the recording method are an apparatus capable of ejecting ink, various treatment liquids, and the like to a recording medium, and a method of performing recording using the apparatus. The recording medium means a medium on which ink or various processing liquids can be temporarily attached.
The recording apparatus can include not only a head portion that ejects ink but also means for feeding, transporting, and discharging a recording medium, and other devices called pre-processing devices and post-processing devices. .
The recording apparatus and the recording method may include a heating unit used in the heating step and a drying unit used in the drying step. The heating means and the drying means include, for example, a means for heating and drying the printing surface and the back surface of the recording medium. Although it does not specifically limit as a heating means and a drying means, For example, a warm air heater and an infrared heater can be used. Heating and drying can be performed before printing, during printing, after printing, and the like.
Further, the recording apparatus and the recording method are not limited to those in which significant images such as characters and figures are visualized by ink. For example, what forms patterns, such as a geometric pattern, etc. includes what forms 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 specified.
Furthermore, this recording apparatus can use not only a desktop type but also a wide recording apparatus that can print on an A0 size recording medium, for example, a continuous paper wound up in a roll shape as a recording medium. Also included are continuous paper printers.
An example of the recording apparatus will be described with reference to FIGS. FIG. 1 is a perspective view of the apparatus. FIG. 2 is an explanatory perspective view of the main tank. An image forming apparatus 400 as an example of a recording apparatus is a serial type image forming apparatus. A mechanism unit 420 is provided in 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), yellow (Y) is packaged, for example, an aluminum laminate film It is formed by a member. The ink storage unit 411 is stored 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 on the inner side of 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. Thus, the ink discharge ports 413 of the main tank 410 and the discharge heads 434 for the respective colors communicate with each other via the supply tubes 436 for the respective colors, and ink can be discharged from the discharge heads 434 to the recording medium.

  The general ink jet recording apparatus has been described above, but the main tank 410 contains the ink or ink set of the present invention.

The recording apparatus can include not only a portion that ejects ink but also a device called a pre-processing device or a post-processing device.
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 ink jet recording method.
As another aspect of the pretreatment apparatus and the posttreatment apparatus, there is an aspect in which, for example, a pretreatment apparatus or a posttreatment apparatus other than the ink jet recording method is provided by a blade coating method, a roll coating method, or a spray coating method.

In the recording method using the ink set of the present invention, a first ink coating portion made of hollow inorganic particles and a second ink coating portion made of solid inorganic particles are formed as an image pattern on a recording medium. To do. The ink coating method is not particularly limited, but in addition to the above-described ink jet recording method, plate printing such as stencil printing, letterpress printing, intaglio printing, and lithographic printing, and plateless printing such as electrophotography. Either printing can be used. Among them, the ink jet recording method is preferable because the ink can be adhered in an arbitrary pattern without depending on the shape of the recording medium.
When both the first ink and the second ink are dried, they show concealment by light scattering derived from the hollow inorganic particles. The first ink contains hollow inorganic particles, and the coating film has fine pores derived from the hollow inorganic particles, so a liquid such as water or a solvent is sucked into the coating film, and the fine pores change from air to liquid. Can be replaced. As a result of substituting the liquid, the liquid having a refractive index higher than that of air fills the hole, so that the refractive index difference is reduced, and the light scattering of the coating film is reduced, so that the concealability is lowered.
Since the second ink contains a solid inorganic pigment, no minute holes are formed in the coating film, and no liquid is sucked into the coating film. Therefore, the difference in the concealability between the two types of ink is greater when the coating film is wet than when it is dried, so that the concealing power of the first ink coating portion is reduced and the image pattern becomes conspicuous.

If the recording medium being printed is a colored medium, the concealing power of the first ink coating film wetted with the liquid is reduced, so that the color of the recording medium becomes visible and the pattern becomes conspicuous. When the recording medium is a transparent medium, the light transmitted through the recording medium can be seen when the hiding power is reduced. Therefore, when the recording medium is wet, the scenery beyond the recording medium can be shown.
Also, when the coating film is wetted with a liquid colored with a dye or the like, the colored liquid in the coating film of the first ink penetrates into the micropores together with the dye, so the coating film of the second ink is colored. Is not colored because it does not penetrate. The image pattern can be revealed with ease of coloring.

The order in which the first ink and the second ink are printed is not particularly limited as long as images can be formed simultaneously or images can be formed in order. In addition, the first ink and the second ink may not be clearly separated from each other, but may be changed continuously from the first ink to the second ink by forming a gradation.
When the gradation part is wet with liquid, the part with more hollow inorganic particles becomes transparent, and the part with more solid inorganic particles has less change, so the transparency can also show gradation.

The temperature of the drying step after recording the ink of the present invention on a recording medium by an ink jet method is preferably 50 ° C. or higher and 200 ° C. or lower. According to this temperature range, the influence of heat on the recording medium hardly occurs.
As described above, the ink of the present invention provides concealability by utilizing the scattering of the shell of the hollow inorganic particles and the internal pores in addition to the scattering of the particle surface. Therefore, when components such as a water-soluble organic solvent remain in the hollow inorganic particles after the coating film is dried, the concealability of the coating film is deteriorated. Compared to the hollow resin particles, it has higher solvent resistance even during high-temperature drying, so that it can be dried at high speed in a high-temperature environment.

In addition, the ink of the present invention has a lightness of 50 mm × 50 mm solid image formed on a polyethylene terephthalate (PET) film in a 50 ° C. constant temperature bath for 1 hour in a L * 50 ° C., 100 ° C. constant temperature bath for 1 hour. When the lightness when dried is L * 100 ° C., the absolute value of the lightness difference ΔL * represented by the following formula 3 can be 10 or less. That is, the ink of the present invention is excellent in the stability of an image (for example, whiteness).
| ΔL * | = (L * 50 ° C.) − (L * 100 ° C.) Equation 3

The recording method (printing method) of the present invention will be exemplified below with reference to FIGS.
A first ink 51 containing a solvent and hollow inorganic particles, a second ink 52 containing solid inorganic particles, and a discharge device capable of printing these inks are used. First, a recording medium 54 such as a transparent PET film is conveyed to the printing area, and the first ink 51 is ejected onto the recording medium 54 to form an image (FIG. 5A). Thereafter, the second ink 52 is printed (FIG. 5B), the recording medium 54 is conveyed, the recording medium 54 is heated by the heater 55, and the first ink 51 and the second ink 52 are dried. To fix (FIG. 5C).
When water or a solvent is applied to the image thus recorded, the water or solvent penetrates into the hollow inorganic particles, and the scattering property of the ink coating film changes.
In the dry state, the hollow inorganic particles have small pores made of air, and the refractive index difference between the air portion and the shell portion of the hollow inorganic particles and other solid portions of the ink, such as binder resin, increases and scatters. Increases and appears white (FIG. 6A). In a wet state, water or a solvent enters the air portion and the refractive index difference becomes small, so that scattering is reduced and transmitted light increases (FIG. 6 (b) wet state).
In the dry state (FIG. 7A), since the printing unit 511 made of the first ink 51 and the printing unit 521 made of the second ink 52 both show white on the recording medium 54, the paper 56 with an image. Even if they are stacked, the recording medium 54 does not change (FIG. 7C).
In the wet state (FIG. 7 (b)), the printing unit 511 made of the first ink 51 becomes transparent on the recording medium 54, so that a difference from the printing unit 521 made of the second ink 52 occurs, and the paper with the image is printed. When superimposed, the image drawn on the paper can be seen through the transparent printing portion 511 (FIG. 7D).
Similarly, for example, when the recording medium 54 having the colored layer 57 on transparent PET is used, even if the colored layer 57 is on the printing unit 511 side made of the first ink 51 (FIG. 8A), the colored layer 57 is Even on the opposite side of the printing unit 511 made of the first ink 51 (FIG. 8B), the printing unit 511 becomes transparent in the wet state, and the colored layer 57 shows through, and an image appears (FIG. 8C). )).

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

<< Preparation of dispersion >>
The hollow inorganic particles in the present invention can be produced by a known method as described above.
<Preparation Example 1: Preparation of hollow inorganic particle dispersion 1>
In a beaker, 18.15 parts by mass of calcium carbonate (manufactured by Shiroishi Kogyo, product name “Homocal-D”, particle shape: cubic, surface treatment agent: rosin acid, primary particle size: 80 nm) 181.54 parts by mass of methanol (Kishida) The product was sufficiently dispersed using a homogenizer (manufactured by Hitachi Koki, HG30, C20 cutter, 8000 rpm, 30 minutes). Thereafter, while sufficiently stirring to maintain the dispersed state of calcium carbonate, 14.52 parts by mass of tetraethoxysilane (TEOS, manufactured by Shin-Etsu Chemical Co., Ltd., product name “KBE-04”), 14.61 mass of 28% aqueous ammonia Parts (NH ₄ OH, manufactured by Wako Pure Chemical Industries) and 71.17 parts by mass of water are reacted at 25 ° C. for 2 hours, and a silica shell is formed on the surface of calcium carbonate using a sol-gel reaction. A silica-coated particle dispersion was obtained.
Next, the obtained silica-coated particles were precipitated with a centrifugal separator at 4000 rpm × 1 hour, the supernatant was discarded, and pure water was added and dispersed in water. Further, acetic acid diluted 10 times was added to dissolve the calcium carbonate of the core particles. The pH after addition of acetic acid was 4.0. Thereafter, in order to desalinate the generated calcium acetate out of the system, the generated hollow particles are precipitated in a centrifugal separator at 4000 rpm × 1 hour, the supernatant is discarded, and a washing operation is performed in which pure water is added and dispersed in water. By carrying out 3 times and concentrating, the 18 mass% solid hollow inorganic particle liquid was obtained.
To 100 parts by mass of the hollow inorganic particle liquid, an amine group-containing acrylic block copolymer (dispersant, manufactured by Big Chemie Japan, product name “BYKJET-9151”, acid value: 8 mgKOH / g, amine value: 18 mgKOH / g, effective (100% by mass of component) 6 parts by mass and 14 parts by mass of water were added and stirred sufficiently, and then a recording medium-less dispersion device (manufactured by Yoshida Kikai Kogyo, NVC-ES008, 150 μm collision type nozzle, discharge pressure 50 MPa, number of passes, 10 times) Dispersion was performed at The obtained dispersion was filtered through a 5 μm cellulose acetate membrane filter (trade name: Minisart 17594K, manufactured by Sartorius) to obtain hollow inorganic particle dispersion 1 having a particle concentration of 15% by mass. The volume average particle diameter (D50) is 310 nm.

<Adjustment Example 2: Production of hollow inorganic particle dispersion 2>
The dispersion was obtained by changing the calcium carbonate used in Preparation Example 1 to “Hakujyuka DD” (manufactured by Shiroishi Kogyo, particle shape: cubic, surface treatment agent: rosin acid, primary particle diameter: 50 nm). The volume average particle diameter (D50) is measured while centrifuging the dispersion liquid and sampling the supernatant in a timely manner. A hollow inorganic particle dispersion liquid 2 having a volume average particle diameter (D50) of 200 nm and a particle concentration of 15% by mass is obtained. It was.

<Adjustment Example 3: Preparation of hollow inorganic particle dispersion 3>
In a beaker, 18.15 parts by mass of calcium carbonate (manufactured by Shiraishi Kogyo Co., Ltd., product name “Shiraka Hana DD”, particle shape: cubic, surface treatment agent: rosin acid, primary particle size: 50 nm) 181.54 parts by mass of methanol (Kishida Chemical) Manufactured by Hitachi Koki Co., Ltd., HG30, C20 cutter, 8000 rpm, 30 minutes). ) To 200 μA for 1 hour and sufficiently dispersed. Thereafter, while sufficiently stirring to maintain the dispersed state of calcium carbonate, 14.52 parts by mass of tetraethoxysilane (TEOS, manufactured by Shin-Etsu Chemical Co., Ltd., product name “KBE-04”), 14.61 mass of 28% aqueous ammonia Parts (NH ₄ OH, manufactured by Wako Pure Chemical Industries) and 71.17 parts by mass of water are reacted at 25 ° C. for 2 hours, and a silica shell is formed on the surface of calcium carbonate using a sol-gel reaction. A silica-coated particle dispersion was obtained.
In the same manner, hollow inorganic particle dispersion 3 having a particle concentration of 15% by mass was obtained by carrying out hollowing treatment and dispersion. The volume average particle diameter (D50) is 94 nm.

<Adjustment Example 4: Production of hollow inorganic particle dispersion 4>
The calcium carbonate used in Preparation Example 1 was changed to “Brillant 1500” (manufactured by Shiraishi Kogyo Co., Ltd., particle shape: cubic, surface treatment agent: none, primary particle diameter: 150 nm), and a hollow inorganic particle dispersion liquid having a particle concentration of 15% by mass 4 was obtained. The volume average particle diameter (D50) was 690 nm.

<Adjustment Example 5: Production of hollow inorganic particle dispersion 5>
The hollow inorganic particle dispersion 4 obtained in Preparation Example 4 is centrifuged, and the volume average particle diameter (D50) is measured while sampling the supernatant in a timely manner. The volume average particle diameter (D50) is 500 nm, and the particle concentration is 15 mass. % Hollow inorganic particle dispersion 5 was obtained.

<Adjustment Example 6: Production of hollow inorganic particle dispersion 6>
Titanium isopropoxide (0.1 mol) and orthophthalic acid (0.5 mol) were mixed with 10 L of methanol and stirred overnight. 3.5 mL of this mixture was transferred to a SUS316 reaction tube having a volume of 10 mL, and the temperature was increased to 300 ° C. at a temperature increase rate of 6.0 ° C./min to form supercritical methanol, which was reacted for 10 minutes to obtain anatase-type titanium oxide hollow particles.
Next, the produced hollow particles are precipitated with a centrifuge at 4000 rpm × 1 hour, the supernatant is discarded, and then a washing operation of adding pure water to disperse in water is performed three times and concentrated to obtain a solid 18% by mass. The hollow inorganic particle liquid was obtained.
In a dispersion container, 66.7 parts by mass of a hollow inorganic particle liquid and 1.2 parts by mass of a dispersant (trade name: DISPERBYK-190, manufactured by Big Chemie Japan Co., Ltd.) are added, and the mixture is lightly stirred to be uniform, and then cooled with water. However, it was treated with an ultrasonic homogenizer (trade name: US-300T, manufactured by Nippon Seiki Seisakusho Co., Ltd., chip: φ26) for 1 hour at 200 μA and filtered through a 5 μm cellulose acetate membrane filter (trade name: Mini-Salto 17594K, manufactured by Sartorius). The solid content was adjusted to obtain a solid inorganic particle dispersion 6 having a solid content of 15% by mass. The volume average particle diameter (D50) was 630 nm.

<Adjustment Example 7: Production of solid inorganic particle dispersion 1>
In a dispersion vessel, 30.8 parts by mass of high-purity water and 1.2 parts by mass of a dispersant (trade name: DISPERBYK-190, manufactured by Big Chemie Japan Co., Ltd.) are placed, and after lightly stirring and uniforming, titanium dioxide (trade name) : JR-405, manufactured by Teika Co., Ltd., primary particle size: 210 nm, crystal form: rutile type, Al surface treatment product) 12.0 parts by mass, and ultrasonic cooling homogenizer (trade name: US-300T, stock) Disperse solid inorganic particles at a solid content of 30% by mass by treating with 200 μA for 1 hour using a chip manufactured by Nihon Seiki Seisakusho, chip: φ26), filtering through a 5 μm cellulose acetate membrane filter (trade name: Mini-Salto 17594K, manufactured by Sartorius) Liquid 1 was obtained. The volume average particle diameter (D50) was 302 nm.

<Adjustment Example 8: Production of solid inorganic particle dispersion 2>
The titanium dioxide used in Preparation Example 7 was changed to “MT-900HD” (manufactured by Teika Co., Ltd., primary particle size: 110 nm, crystal form: rutile type, Al, Zr surface-treated product), and the particle concentration was 15 mass%. A solid inorganic particle dispersion 2 was obtained. The volume average particle diameter (D50) was 150 nm.

<Adjustment Example 9: Production of solid inorganic particle dispersion 3>
The titanium dioxide used in Preparation Example 7 was changed to “MT-700HD” (manufactured by Teika Co., Ltd., primary particle size: 50 nm, crystal form: rutile type, Al, Zr surface treatment product), and the particle concentration was 15% by mass. A solid inorganic particle dispersion 3 was obtained. The volume average particle diameter (D50) was 92 nm.

<Adjustment Example 10: Preparation of solid inorganic particle dispersion 4>
Zirconium oxide dispersion “Nanouse ZR-40BL” (manufactured by Nissan Chemical Industries, Ltd., solid 40 mass%, primary particle size: 90 nm, pH 9.6) was used as solid inorganic particle dispersion 4.

<Adjustment Example 11: Preparation of solid inorganic particle dispersion 5>
Silica dispersion “Snowtex MP-4540M” (manufactured by Nissan Chemical Industries, Ltd., solid 40% by mass, primary particle size: 440 nm, pH 8.5) was used as solid inorganic particle dispersion 5.

<Adjustment Example 12: Production of urethane resin fine particles>
1,500 parts by mass of polycarbonate diol, 2,2-dimethylol, which is a reaction product obtained by reacting 1,6-hexanediol and dimethyl carbonate in a reaction vessel in which a stirrer, a reflux condenser, and a thermometer are inserted. 220 parts by mass of propionic acid (DMPA) and 1,347 parts by mass of N-methylpyrrolidone (NMP) were charged under a nitrogen stream and heated to 60 ° C. to dissolve 2,2-dimethylolpropionic acid.
Next, 1,445 parts by mass of 4,4′-dicyclohexylmethane diisocyanate and 2.6 parts by mass of dibutyltin dilaurate (catalyst) were added and heated to 90 ° C., followed by a urethanization reaction over 5 hours. A urethane prepolymer solution 1 was obtained.
Next, the isocyanate-terminated urethane prepolymer solution 1 is cooled to 80 ° C., 149 parts by mass of triethylamine is added, 4,340 parts by mass is extracted from the mixed mixture, and 5,400 parts by mass of water with vigorous stirring. And triethylamine in a mixed solution of 15 parts by mass.
Next, 1,500 parts by mass of ice is added, and 626 parts by mass of a 35% by mass 2-methyl-1,5-pentanediamine aqueous solution is added to carry out a chain extension reaction so that the solid content concentration becomes 30% by mass. The solvent was distilled off to obtain a urethane resin emulsion (resin dispersion).

<Preparation Example 13: Preparation of water-insoluble polymer solution>
In a reaction vessel equipped with two dropping funnels 1 and 2, 17.6 parts by mass of styrene, 12.0 parts by mass of AS-6 (S) (manufactured by Toagosei Co., Ltd., styrene macromer, effective concentration 50% by mass, Number average molecular weight 6000), NK ester M-40G 10.0 parts by mass (manufactured by Shin-Nakamura Chemical Co., Ltd., methoxypolyethylene glycol monomethacrylate, ethylene oxide average added mole number: 4, terminal: methoxy group), methyl ethyl ketone 6.0 mass Part and 0.08 part by mass of 2-mercaptoethanol were added, and the temperature was raised to 77 ° C. while stirring while performing nitrogen gas replacement.
Further, 51.2 parts by mass of methacrylic acid, 140.8 parts by mass of styrene, 108.0 parts by mass of AS-6 (S) (manufactured by Toagosei Co., Ltd., styrene macromer, effective component concentration 50% by mass, number average molecular weight 6000), NK ester M-40G 80.0 parts by mass (manufactured by Shin-Nakamura Chemical Co., Ltd., methoxypolyethylene glycol monomethacrylate, average number of moles of ethylene oxide added: 4, terminal: methoxy group), methyl ethyl ketone 66.0 parts by mass, V65 3.2 In a dropping funnel 1, a mass part (manufactured by Wako Pure Chemical Industries, Ltd., 2,2′-azobis (2,4-dimethylvaleronitrile)) and 0.56 parts by mass of 2-mercaptoethanol were added and stirred. And nitrogen gas replacement was performed.
Similarly, 12.8 parts by mass of methacrylic acid, 17.6 parts by mass of styrene, 10.0 parts by mass of NK ester M-40G (manufactured by Shin-Nakamura Chemical Co., Ltd., methoxypolyethylene glycol monomethacrylate, average added mole number of ethylene oxide: 4 , Terminal: methoxy group), methyl ethyl ketone 48.0 parts by mass, V65 0.8 parts by mass (manufactured by Wako Pure Chemical Industries, Ltd., 2,2′-azobis (2,4-dimethylvaleronitrile)), 2-mercaptoethanol A solution prepared by adding 0.16 parts by mass was placed in the dropping funnel 2 and replaced with nitrogen gas.
While stirring at 80 ° C. under a nitrogen atmosphere, the dropping monomer solution 1 in the dropping funnel 1 was gradually dropped into the reaction vessel over 3 hours. Subsequently, the dropping monomer solution 2 in the dropping funnel 2 was gradually dropped into the reaction vessel over 2 hours. After completion of dropping, the mixed solution in the reaction vessel was stirred at 80 ° C. for 0.5 hour.
Next, 0.6 mass parts of V-65 and 27.0 mass parts of methyl ethyl ketone were stirred and dissolved in a reaction vessel, and the mixture was stirred at 80 ° C. for 1 hour for aging reaction. The same ripening reaction operation was repeated 5 times, and the reaction was continued for 5 hours. Thereafter, the reaction solution in the reaction vessel was maintained at 85 ° C. for 1 hour, and methyl ethyl ketone was added to obtain a water-insoluble polymer solution (solid content concentration: 40% )

<Preparation Example 14: Preparation of black pigment dispersion>
While mixing 160.8 parts by mass of a water-insoluble polymer solution (solid content concentration 40%) with 60.4 parts by mass of methyl ethyl ketone, stirring at 1400 rpm with a disper, 448.3 parts by mass of pure water, 5N sodium hydroxide 19.5 mass parts of aqueous solution was added, and it stirred at 1400 rpm for 15 minutes, cooling with a 0 degreeC water bath.
Next, 150 parts by mass of carbon black pigment (trade name: Monarch 800, manufactured by Cabot) was added, and the mixture was stirred at 7000 rpm for 3 hours. The obtained pigment mixture was subjected to dispersion treatment with a recording medium-less dispersion device (manufactured by Nanomizer, tabletop ultrafine atomization tester NM2-2000AR, 100 μm collision type nozzle, discharge pressure 200 MPa, number of passes, 20 times), and obtained dispersion treatment I got a thing. After adding 400 g of ion-exchanged water to this dispersion-treated product and removing the organic solvent with a rotary evaporator, the concentration was further advanced to a solid content concentration of 25.0% by mass. The concentrate was treated with a centrifuge at 4000 rpm for 60 minutes, and the liquid layer portion was filtered with a 5 μm membrane filter “Minisart” (manufactured by Sartorius).
Ion exchange water was added to the filtrate so that the solid content concentration was 15.0% by mass to obtain a black content dispersion.

<Adjustment Example 15: Preparation of cyan pigment dispersion>
A cyan pigment dispersion having a solid concentration of 15% by mass was obtained in the same manner as the black pigment dispersion except that the carbon black pigment was changed to Pigment Blue 15: 4 in the preparation of the black pigment dispersion. .

<Adjustment Example 16: Preparation of magenta pigment dispersion>
A magenta pigment dispersion having a solid content concentration of 15% by mass was obtained in the same manner as in the preparation of the black pigment dispersion except that the carbon black pigment was changed to Pigment Red 122 in the preparation of the black pigment dispersion.

<Adjustment Example 17: Preparation of yellow pigment dispersion>
A yellow pigment dispersion having a solid content of 15% by mass was obtained in the same manner as the black pigment dispersion except that the carbon black pigment was changed to Pigment Yellow 74 in the preparation of the black pigment dispersion.

<< Preparation of ink >>
To prepare the ink, add an organic solvent, surfactant, antifoaming agent, antiseptic / antifungal agent, and high purity water to a beaker according to the mass ratio shown in Table 1 below, and stir for 30 minutes with a stirrer to mix evenly. did. To this mixed solution, the resin dispersion liquid produced in the above preparation example was added and stirred for 15 minutes, then a coloring material was added and stirred for 30 minutes, and a syringe filter unit of a cellulose acetate membrane filter having an average pore size of 5.0 μm (product) (Name: Mini-Salto 17594K, manufactured by Sartorius Co., Ltd.) and subjected to pressure filtration to obtain an evaluation ink. The volume average particle size of the obtained ink was measured using a particle size analyzer (Nanotrac Wave-EX150, manufactured by Nikkiso Co., Ltd.) to evaluate the particle size.

The following evaluation was performed about each obtained ink.
<Printing conditions>
Remove the exterior of the inkjet printer (Ricoh's IPSiO GXe5500), attach the rear multi-manual feeder, and wash it by passing pure water through the ink supply path including the print head. Then, the cleaning liquid was completely removed from the apparatus to obtain an evaluation printing apparatus.
Further, the prepared ink was stirred for 30 minutes under a reduced pressure condition of 5 to 10 Pa, thereby degassing the gas in the evaluation ink and filling the ink cartridge to obtain an evaluation ink cartridge. A filling operation was performed, and it was confirmed that all nozzles were filled with evaluation ink and no abnormal image appeared. After selecting the glossy paper clean mode with the driver attached to the printer, the color matching off was set to the print mode by the user setting. In this mode, the ejection amount was adjusted by changing the driving voltage of the head so that the amount of ink adhering to the recording medium of the solid image was 20 g / m ² .

<< Brightness evaluation of printed image >>
The prepared ink was filled in an ink jet printer (Ricoh: IPSiO GXe5500) in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester Film E5100) fixed with double-sided tape on My Paper (Ricoh PPC plain paper). On the other hand, a solid image of 50 cm × 50 cm created by Microsoft Word 2013 was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.
The printed portion was measured for lightness using a spectrocolorimetric densitometer X-Rite 939 to measure L *.
[Evaluation criteria]
A: L * value is 70 or more B: L * value is 60 or more and less than 70 C: L * value is less than 60

<< Discharge stability evaluation >>
The prepared ink was filled in an ink jet printer (covered by Ricoh: IPSiO GXe5500) having cover means in the same manner as the above printing conditions. A nozzle check pattern was printed on the black paper, and the presence or absence of ejection failure or ejection disturbance was evaluated by visual observation based on the following criteria.
〔Evaluation criteria〕
A: No ejection, no injection disturbance
B: Some injection disturbance is recognized.
C: There is a nozzle where non-ejection is recognized.

<< Evaluation of whiteness of printed image when wet >>
The prepared ink was filled in an ink jet printer (Ricoh: IPSiO GXe5500) in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester Film E5100) fixed with double-sided tape on My Paper (Ricoh PPC plain paper). On the other hand, a solid image of 50 cm × 50 cm created by Microsoft Word 2013 was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.
The printed portion is measured for lightness using a spectrocolorimetric densitometer X-Rite 939 to make it the L ^* initial stage, the printed recording medium is immersed in pure water for 1 minute, removed from the liquid, and the surface water is removed with a filter paper. After that, the printed portion was measured for brightness using a spectrocolorimetric densitometer X-Rite 939 to obtain L ^* immersion. Lightness difference | ΔL ^* | = (L ^* initial stage) − (L ^* dipping) was calculated and evaluated.
The brightness was measured with a commercially available black paper placed under the printed PET film, and the printed portion was measured using a spectrocolorimetric densitometer X-Rite 939, and evaluated according to the following criteria.
[Evaluation criteria]
A: | ΔL * | value is 30 or more B: | ΔL * | value is 13 or more and less than 30 C: | ΔL * | value is less than 13

<< Evaluation of solvent resistance recovery of printed images >>
The prepared ink was filled in an ink jet printer (Ricoh: IPSiO GXe5500) in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester Film E5100) fixed with double-sided tape on My Paper (Ricoh PPC plain paper). On the other hand, a solid image of 50 cm × 50 cm created by Microsoft Word 2013 was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour. With the commercially available black paper laid under the PET film on which the obtained solid image was printed, the printed portion was measured for lightness using a spectrocolorimetric densitometer X-Rite 939 to make L ^* initial.
The printed recording medium is soaked in acetone for 1 minute, taken out from the liquid, the surface solvent is removed with filter paper, and the printed portion is dried until there is no tack on the surface. -Brightness was measured using Rite 939 to determine L ^* immersion. Thereafter, the recording medium was put in a thermostatic bath at 50 ° C. and dried for 1 hour, and the printed portion was measured for brightness using a spectrocolorimetric densitometer X-Rite 939 as described above to obtain L ^* drying. Based on the measured brightness, the following brightness difference was determined.
Evaluation was performed by calculating a lightness difference | ΔL * wet | = (L * dry) − (L * dipping).
Lightness difference | ΔL * drying | = (L * initial) − (L * drying) was calculated and evaluated.
From the measured values, the following criteria were evaluated.
[Evaluation criteria]
A: | ΔL * wetting | value is 30 or more and | ΔL * drying | value is 13 or less B: | ΔL * wetting | value is 13 or more and less than 30 and | ΔL * drying | value is 13 or less C: | ΔL * Wet | value is less than 13 or | ΔL * dry | value is greater than 13

<< Durability Evaluation of Printed Images >>
The prepared ink was filled in an ink jet printer (Ricoh: IPSiO GXe5500) in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester Film E5100) fixed with double-sided tape on My Paper (Ricoh PPC plain paper). On the other hand, a solid image of 50 cm × 50 cm created by Microsoft Word 2013 was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.
The printed portion is measured for lightness using a spectrocolorimetric densitometer X-Rite 939 to make L * initial, the printed recording medium is immersed in pure water for 1 minute, removed from the liquid, and the surface water is removed with a filter paper. After that, it is placed in a constant temperature bath at 60 ° C. and dried for 1 hour. After this operation was repeated 20 times, the printed portion was measured for brightness using a spectrocolorimetric densitometer X-Rite 939, and L * durability was obtained.
Lightness difference | ΔL * | = (L * initial stage) − (L * durability) was calculated and evaluated.
The brightness was measured with a commercially available black paper placed under the printed PET film, and the printed portion was measured using a spectrocolorimetric densitometer X-Rite 939, and evaluated according to the following criteria.
[Evaluation criteria]
A: | ΔL * | value is 13 or less B: | ΔL * | value is greater than 13 and 30 or less C: | ΔL * | value is greater than 30

<Ink set evaluation>
The prepared inks were combined as shown in Table 3 to prepare ink sets for each example, and filled in a cartridge of an ink jet printer (manufactured by Ricoh: IPSiO GXe5500).

<Printing conditions>
Remove the exterior of the inkjet printer (Ricoh's IPSiO GXe5500), attach the rear multi-manual feeder, and wash it by passing pure water through the ink supply path including the print head. Then, the cleaning liquid was completely removed from the apparatus to obtain an evaluation printing apparatus.
Further, the prepared ink was stirred for 30 minutes under a reduced pressure condition of 5 to 10 Pa, thereby degassing the gas in the evaluation ink and filling the ink cartridge to obtain an evaluation ink cartridge. A filling operation was performed, and it was confirmed that all nozzles were filled with evaluation ink and no abnormal image appeared. After selecting the glossy paper clean mode with the driver attached to the printer, the color matching off was set to the print mode by the user setting. In this mode, the ejection amount was adjusted by changing the driving voltage of the head so that the amount of ink adhering to the recording medium of the solid image was 20 g / m ² .

<< Discharge stability evaluation >>
The prepared ink was filled in an ink jet printer (covered by Ricoh: IPSiO GXe5500) having cover means in the same manner as the above printing conditions. A nozzle check pattern was printed on the black paper, and the presence or absence of ejection failure or ejection disturbance was evaluated by visual observation based on the following criteria.
〔Evaluation criteria〕
A: No ejection, no injection disturbance
B: Some injection disturbance is recognized.
C: There is a nozzle where non-ejection is recognized.

<< Pattern confirmation evaluation when the printed image is wet >>
Using this cartridge, an ink jet printer (Ricoh: IPSiO GXe5500) was filled with ink in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester made by Toyobo) fixed on My Paper (Ricoh PPC plain paper) with double-sided tape. On the film E5100), a checkerboard pattern image (FIG. 9A) made of ink 1 and ink 2 having a square of 4 cm × 4 cm, which is created by Microsoft Word 2013, is printed, and the recording medium is placed in a thermostatic chamber at 50 ° C. Placed and dried for 1 hour.
For the image formed on the printed recording medium, immerse the printed recording medium in water for 1 minute, remove it from the liquid, remove the surface solvent with filter paper, and place a commercially available black paper under the PET film. The checkerboard pattern was observed and evaluated in the laid state.
[Evaluation criteria]
A: The checkerboard pattern can be clearly seen (Fig. 9 (d)).
B: The checkerboard pattern cannot be understood without staring.

<< Pattern Confirmation Evaluation for Solvent Recovery of Printed Images >>
Using this cartridge, an ink jet printer (Ricoh: IPSiO GXe5500) was filled with ink in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester made by Toyobo) fixed on My Paper (Ricoh PPC plain paper) with double-sided tape. On the film E5100), a checkerboard image made of ink 1 and ink 2 each having a size of 4 cm × 4 cm, which was created by Microsoft Word 2013, was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.
For the white checkered pattern formed on the printed recording medium, immerse the printed recording medium in acetone for 1 minute, remove it from the liquid, remove the solvent on the surface with filter paper, and dry until there is no tack on the surface. Then, a checkerboard pattern was observed and evaluated with a commercially available black paper laid under the PET film.
[Evaluation criteria]
A: The checkerboard pattern cannot be understood without staring. B: The checkerboard pattern can be clearly seen.

<< Pattern confirmation evaluation during repeated use of printed images >>
Using this cartridge, an ink jet printer (Ricoh: IPSiO GXe5500) was filled with ink in the same manner as the above printing conditions, and a transparent PET film (Toyobo Ester made by Toyobo) fixed on My Paper (Ricoh PPC plain paper) with double-sided tape. On the film E5100), a checkerboard image made of ink 1 and ink 2 each having a size of 4 cm × 4 cm, which was created by Microsoft Word 2013, was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.
For the white checkered pattern formed on the printed recording medium, immerse the printed recording medium in pure water for 1 minute, remove it from the liquid, remove the surface water with filter paper, and then a thermostat at 60 ° C And let dry for 1 hour. After repeating this operation 20 times, a checkerboard pattern was observed and evaluated with a commercially available black paper laid under the PET film.
[Evaluation criteria]
A: The checkerboard pattern cannot be understood without staring. B: The checkerboard pattern can be clearly seen.

<< Pattern evaluation when wet when white ink is printed on the image surface >>
The process color inks of black, cyan, magenta, and yellow shown in Preparation Examples 30 to 33 are filled in each color cartridge of an ink jet printer (manufactured by Ricoh: IPSiO GXe5500), and the ink jet printer (manufactured by Ricoh) is used in the same manner as the above printing conditions. : IPSiO GXe5500) was filled with ink, and a transparent PET film (Toyobo ester film E5100) fixed on MyPaper (Ricoh PPC plain paper) with a double-sided tape was tested with Microsoft Word 2013 using Test Pattern 1 (FIG. 9). (B)) was printed in glossy paper-clean mode, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour. After drying, the test pattern 1 was formed on a transparent PET film by cooling to room temperature.

  In addition, as shown in Table 3, the prepared ink is filled into each color cartridge of an ink jet printer (Ricoh: IPSiO GXe5500), and using this cartridge, an ink jet printer (Ricoh: IPSiO GXe5500) is used in the same manner as the above printing conditions. ) Is filled with ink, and on the transparent PET film (fixed with double-sided tape on My Paper) on which the test pattern 1 prepared above is printed, one square created by Microsoft Word 2013 is 4 cm × 4 cm. A checkered pattern image of Ink 1 and Ink 2 was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.

(Image concealment)
The printed recording medium was observed from the printing surface, and the concealed state of the J6 image was observed and evaluated with respect to the white checkered pattern formed on the medium surface.
[Evaluation criteria]
AA: Test pattern 1 is sufficiently concealed A: Test pattern 1 is slightly transparent B: Test pattern 1 is transparent (FIG. 9C)

(Pattern expression)
The printed recording medium was immersed in water for 1 minute, taken out from the liquid, the surface solvent was removed with filter paper, and the PET film was observed from the printed surface for evaluation.
[Evaluation criteria]
A: Test pattern 1 can be clearly seen from part of the checkered pattern when wet (Fig. 9 (c))
B: The appearance of test pattern 1 does not change when wet

≪Pattern evaluation when wet when white ink is printed on the back of the image≫
The process color inks of black, cyan, magenta, and yellow shown in Preparation Examples 30 to 33 are filled in each color cartridge of an ink jet printer (manufactured by Ricoh: IPSiO GXe5500), and the ink jet printer (manufactured by Ricoh) is used in the same manner as the above printing conditions. : IPSiO GXe5500) is filled with ink, and a transparent PET film (Toyobo Ester Film E5100) fixed on My Paper (Ricoh PPC plain paper) with double-sided tape is glossy paper with Test Pattern 1 using Microsoft Word2013. Printing was performed in a clean mode, and the recording medium was placed in a constant temperature bath at 50 ° C. and dried for 1 hour. After drying, the test pattern 1 was formed on a transparent PET film by cooling to room temperature.

  In addition, as shown in Table 3, the prepared ink is filled into each color cartridge of an ink jet printer (Ricoh: IPSiO GXe5500), and using this cartridge, an ink jet printer (Ricoh: IPSiO GXe5500) is used in the same manner as the above printing conditions. ) Is filled with ink, and Microsoft Word 2013 is applied to the back side of the transparent PET film on which the test pattern 1 produced above is printed (the printed side is reversed and fixed on the double-sided tape on My Paper). A checkerboard pattern image made of ink 1 and ink 2 each having a size of 4 cm × 4 cm was printed, and the recording medium was placed in a thermostat at 50 ° C. and dried for 1 hour.

(Image clarity)
The printed recording medium was observed from the test pattern 1 printing surface with a commercially available black paper laid, and the sharpness of the test pattern 1 formed on the medium surface was observed and evaluated.
[Evaluation criteria]
AA: The back side of the test pattern 1 is white and looks very clear A: The white side of the back side is slightly transparent, but it looks clear B: The white side of the back side is transparent and black paper is visible, Slightly inferior

(Pattern expression)
The printed recording medium was immersed in water for 1 minute, removed from the liquid, the surface solvent was removed with filter paper, and the PET film was observed from the test pattern 1 printed surface for evaluation.
[Evaluation criteria]
A: A part of the back surface becomes transparent when wet, and the test pattern 1 becomes translucent. B: The appearance of the test pattern 1 does not change even when wet. Table 4 shows the evaluation results of the above water-based ink set.

As in Examples 1 to 7, in an ink set comprising a first ink containing a solvent and hollow inorganic particles, and a second ink containing solid inorganic particles and whose image does not change by application of a liquid Thus, it is possible to obtain an image that is excellent in pattern expression when the image is wet and excellent in durability when used repeatedly with a solvent.
On the other hand, as in Comparative Example 1, the ink set including the ink containing the hollow resin particles has pattern developability at the time of image wetting, but is not practical due to lack of durability at the time of repeated use. It became.
In addition, as in Comparative Examples 2 and 3, an ink set composed of only the second ink or only the first ink does not exhibit a function when the image is wet and does not exhibit a function.

51 First Ink 52 Second Ink 53 Discharge Device 54 Recording Medium 55 Heater 56 Paper with Image 57 Colored Layer 201 Ink Cartridge 241 Ink Bag 242 Ink Inlet 243 Ink Outlet 244 Cartridge Case 400 Image Forming Device 401 Image Exterior of forming apparatus 401c Cover of apparatus main body 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y Main tank 411 for each color of black (K), cyan (C), magenta (M), yellow (Y) Section 413 Ink discharge port 414 Storage container case 420 Mechanism section 434 Discharge head 436 Supply tube 511 Printing section made of first ink 51 521 Printing section made of second ink 52

JP 2014-122310 A JP 2011-170064 A

Claims (13)

In an ink used for printing in which an image changes due to application of liquid,
The ink contains a solvent and hollow inorganic particles,
The ink according to claim 1, wherein the change in the image is a change in brightness of the image.   The ink according to claim 1, wherein the hollow inorganic particles are silica. Before dipping the image printed on the polyethylene terephthalate film in pure water and after dipping for 1 minute, using a spectral colorimetric densitometer of the image printed with black paper laid under the polyethylene terephthalate film 3. The ink according to claim 1, wherein the brightness difference | ΔL * | calculated by the following formula 1 is 13 or more when the brightness is measured.
Formula 1 | ΔL * | = (L * initial stage) − (after L * immersion)
(In Formula 1, L * initial is L * before immersing the image in pure water, and L * after immersing is L * after immersing the image in pure water for 1 minute) Before dipping an image printed on a polyethylene terephthalate film in an organic solvent and after dipping for 1 minute and drying, a spectrophotometric densitometer of the image printed with black paper laid under the polyethylene terephthalate film 4. The ink according to claim 1, wherein the brightness difference | ΔL * | determined by the following formula 2 is 13 or less when the brightness is measured using the ink.
Formula 2 | ΔL * | = (L * initial stage) − (after L * organic solvent immersion drying)
(In Formula 2, L * initial is L * before immersing the image in an organic solvent, and L * after immersing and drying the organic solvent is after immersing and drying the image in an organic solvent for 1 minute. L *) A first ink containing hollow inorganic particles;
An ink set comprising: a second ink containing solid inorganic particles.   The ink set according to claim 5, wherein the first ink is the ink according to claim 1.   The ink set according to claim 5 or 6, wherein the first ink and the second ink are white inks.   An ink cartridge comprising the first ink and / or the second ink in the ink set according to claim 5 in a container.   5. A printing method comprising: an ink applying step for applying the ink according to claim 1 to a printing material; and a drying step for drying the printing material to which the ink has been applied.   A first ink application step for applying the first ink to a printing material using the ink set according to claim 5 and a second ink application for applying the second ink. A printing method comprising: a step, and a drying step of drying the substrate to which the first ink and the second ink are applied.   A printing method, wherein a new image is formed by applying water or a volatile solvent to an image printed by the printing method according to claim 9.   A printing apparatus comprising: means for ejecting ink; and the ink according to claim 1. A printing apparatus comprising: means for ejecting ink; and the ink set according to claim 5.