JP2018172568A - Inkjet recording method, and inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method excellent in luster of an obtained image.SOLUTION: An inkjet recording method includes: a treatment step of imparting a first ink to a recording medium, and a recording step of imparting a second ink to the recording medium so as to at least partially overlap with a region on which the first ink was imparted, in which the first ink is an aqueous ink containing a nonionic surfactant containing fluorine atoms or silicon, and the second ink is an aqueous ink containing metal particles constituted of transition metal or its oxide.SELECTED DRAWING: None

Description

  The present invention relates to an ink jet recording method and an ink jet recording apparatus.

  Conventional ink jet recording methods use ink containing metal particles. Such inks have been mainly used for forming electric circuits, but in recent years, inks containing metal particles have also been used for applications that express metallic feeling such as Christmas cards. . Therefore, an ink capable of recording an image having a metallic feeling is demanded. Inks containing metal particles for recording an image with a metallic feeling have been proposed (see Patent Documents 1 and 2).

JP 2013-52654 A Japanese Patent Laid-Open No. 2006-02729

  When recording images on various recording media, the present inventors studied using inks or clear inks containing metal particles described in Patent Documents 1 and 2. As a result, it was found that when the image described in Patent Document 1 is used to record an image on a certain type of recording medium, the glossiness of the image cannot be obtained. Furthermore, in the inkjet recording method described in Patent Document 2, after applying the ink containing metal particles to the recording medium, the clear ink is applied to the same region as the region to which the ink has been applied. It was found that sex could not be obtained.

  Accordingly, an object of the present invention is to provide an ink jet recording method which is excellent in glossiness of an image regardless of a recording medium. Another object of the present invention is to provide an ink jet recording apparatus using the ink jet recording method.

  The above object is achieved by the present invention described below. That is, the present invention includes a processing step of applying the first ink to the recording medium, and a recording step of applying the second ink to the recording medium so as to at least partially overlap the region to which the first ink has been applied. The first ink is a water-based ink containing a nonionic surfactant having fluorine atoms or silicon, and the second ink is a metal composed of a transition metal or an oxide thereof. The present invention relates to an ink jet recording method, which is a water-based ink containing particles.

  The present invention is also an ink jet recording apparatus provided with a means for applying a second ink after applying the first ink, wherein the first ink contains a nonionic surfactant having fluorine atoms or silicon. The present invention relates to an ink jet recording apparatus, wherein the second ink is an aqueous ink containing metal particles composed of a transition metal or an oxide thereof.

  According to the present invention, it is possible to provide an ink jet recording method and an ink jet recording apparatus that are excellent in glossiness of an image regardless of a recording medium.

4 is an electron micrograph showing a state in which metal particles are fused in a recording medium. It is an electron micrograph in which the metal particles remain in the state of particles in the recording medium without being fused. FIG. 2 is a diagram schematically illustrating an example of an ink jet recording apparatus used in the ink jet recording method of the present invention, in which (a) is a perspective view of a main part of the ink jet recording apparatus, and (b) is a perspective view of a head cartridge.

  Hereinafter, embodiments of the present invention will be described in detail. In the present invention, the water-based ink is hereinafter sometimes referred to as “ink”. Various physical property values are values at a temperature of 25 ° C. unless otherwise specified.

  The present inventors have found that the glossiness of an image cannot be obtained when the ink described in Patent Document 1 is used when an image is recorded on matte paper among recording media. Matte paper is a recording medium provided with an ink receiving layer having pores of several μm. Therefore, the mat paper has larger pores than the glossy paper which is the same coated paper, so that the metal particles easily enter the pores together with the liquid component in the ink. Thereby, it is considered that the metal film constituting the image becomes non-uniform and the glossiness of the image cannot be obtained. Even with the same coated paper, glossy paper is a recording medium provided with an ink receiving layer having very fine pores of about 10 to 20 nm, so that the metal particles hardly enter the pores together with the liquid components in the ink. Since the metal film constituting the image is likely to be uniform, it has been found that although the glossiness of the image can be obtained to some extent, there is room for further improvement.

  Furthermore, the present inventors used the inkjet recording method described in Patent Document 2 in which clear ink is applied to the same region as the region to which the ink containing metal particles is applied. Since the image recorded in this manner is covered with an oil film and looks like a color different from the original silver color, the glossiness of the image cannot be obtained.

  Accordingly, the present inventors have considered a configuration of an ink jet recording method for obtaining glossiness of an image regardless of a recording medium. The ink jet recording method of the present invention includes a processing step of applying a first ink to a recording medium, and a recording step of applying a second ink to the recording medium so as to at least partially overlap a region where the first ink is applied. And have. The first ink is a water-based ink containing a nonionic surfactant having fluorine atoms or silicon. The second ink is a water-based ink containing metal particles composed of a transition metal or an oxide thereof. The mechanism by which the glossiness of the image can be obtained by the ink jet recording method having such a configuration will be described in detail.

  A metal particle is comprised by many metal atoms. In general, compared with a non-metal atom, a nucleus of a metal atom has a weak force for attracting electrons and easily emits an electron, so that a metal atom is easily charged positively. When many metal atoms gather, the electron orbit (electron shell) of the metal atom overlaps the electron shell of the adjacent metal atom, so that the electron emitted from the metal atom is the electron of the adjacent metal atom. It becomes possible to move to the shell. In this way, the electrons move through the overlapping electron shells and can freely move between a large number of metal atoms. Since electrons can move freely in the metal particles, the electrons can move on the surface of the metal particles.

  When ink adheres to the recording medium, water in the ink penetrates into the recording medium, so that water is reduced from around the metal particles. Thereby, the distance between the metal particles in the ink is reduced. As the distance between the metal particles becomes closer, the electrons moving on the surface of the metal particles attract the positively charged metal atoms of the nearby metal particles. When metal atoms having a positive charge are attracted to the metal particles, the metal particles and the metal particles are fused, and a continuous metal film can be formed.

  However, it has been found that an image recorded using a conventional ink containing metal particles is not glossy. “Improving gloss” means that the proportion of light reflected in a certain direction among the light incident on the metal film constituting the image increases. When the present inventors examined, since the metal film which comprises an image is non-uniform | heterogenous, the light which injected into the image reflected in various directions, and the ratio of the light which reflects in a fixed direction among the incident light is It was found that the glossiness of the image could not be obtained due to the decrease. That is, in order to improve the glossiness of the image, it is necessary to form a uniform metal film.

  Therefore, in order to form a uniform metal film, before applying an ink containing metal particles (hereinafter referred to as “second ink”), an ink containing a nonionic surfactant (hereinafter referred to as “first ink”). Ink ”) was applied to the recording medium. The nonionic surfactant has a fluorine atom or silicon. Compared with a surfactant obtained by adding ethylene oxide to acetylene glycol, which has neither a general-purpose fluorine atom nor silicon in an inkjet ink, the surfactant having a fluorine atom or silicon has a strong hydrophobic property. Therefore, the nonionic surfactant is easily oriented at the interface in the region where the first ink is applied.

  When the first ink is applied to the recording medium, the nonionic surfactant is oriented at the interface of the first ink, so that the region where the first ink is applied to the recording medium has a low surface energy. “Low surface energy” means that it is difficult to wet and has a low affinity for water. As a result, even if the second ink is applied so that at least part of it overlaps the region where the first ink is applied, the water in the second ink does not easily permeate, and the second ink tends to stay on the surface of the recording medium. . While the second ink stays on the surface of the recording medium, the metal particles in the ink spread to the recording medium, so that even if water in the ink permeates the recording medium, the metal particles remain on the recording medium. Can adhere uniformly. By fusing the attached metal particles in this way, a uniform metal film can be formed, and the glossiness of the image is improved.

<Inkjet recording method>
The inkjet recording method of the present invention includes a processing step of applying the first ink to the recording medium, and a recording step of applying the second ink to the recording medium so as to at least partially overlap the region to which the first ink has been applied. An inkjet recording method. This method may further include a heating step after the recording step.

[Processing process]
In the processing step, the first ink is applied to the recording medium. Thereby, the recording medium can be impregnated with the first ink. The amount of the first ink applied to the recording medium is preferably an amount that does not deform the recording medium. Specifically, the application amount (μg) of the first ink per unit area (inch ² ) of the recording medium is preferably 1 μg or more and 17 μg or less, and more preferably 3 μg or more and 14 μg or less.

  The treatment process may be a process in which the first ink is ejected from an ink jet recording head and applied to the recording medium, or a process in which the first ink is applied with a roller or the like and applied to the recording medium. May be. When applying the first ink with a roller or the like, an amount equivalent to a predetermined recording duty is applied. Especially, it is preferable that a process process is a process of discharging a 1st ink from the inkjet recording head, and providing to a recording medium. Since the second ink is ejected from the ink jet recording head, both the first ink and the second ink are ejected from the ink jet recording head, which is preferable in that a complicated apparatus is not required.

  Examples of the method for ejecting ink include a method for imparting mechanical energy to the ink and a method for imparting thermal energy to the ink. In the present invention, it is preferable to employ a method in which thermal energy is applied to the ink and the ink is ejected.

[Recording process]
In the recording step, the second ink is ejected from an ink jet recording head so as to be at least partially overlapped with the region where the first ink is applied, and is applied to the recording medium. Examples of the method for ejecting ink include a method for imparting mechanical energy to the ink and a method for imparting thermal energy to the ink. In the present invention, it is preferable to employ a method in which thermal energy is applied to the ink and the ink is ejected. The application amount (μg) of the second ink per unit area (inch ² ) of the recording medium is preferably 25 μg or more and 45 μg or less, and more preferably 30 μg or more and 40 μg or less. Note that after the second ink is applied to the recording medium, it is not necessary to apply the first ink to the recording medium so as to at least partially overlap the area where the second ink is applied.

[Heating process]
A heating step may be performed after the recording step in order to promote fusion of the metal particles. Examples of the means for heating the recording medium include heating means such as an infrared heater, air blowing means using air blown by a dryer, or a combination of these. In the heating step, it is preferable to heat the recording medium so that the surface temperature is 50 ° C. or less. When the surface temperature of the recording medium exceeds 50 ° C., the metal particles in the second ink are fused by heat before the metal particles spread, so that the metal particles adhere unevenly to the recording medium. End up. As a result, a non-uniform metal film is formed, so that sufficient glossiness of the image may not be obtained.

  The surface temperature of the recording medium can be measured using a general non-contact infrared thermometer. Examples of such a non-contact infrared thermometer include a digital radiation temperature sensor (FT-H20, manufactured by Keyence). Further, a drying step may be provided between the processing step and the recording step. This is because even if the drying process is performed, the nonionic surfactant is likely to be present in the region to which the first ink has been applied, so it is unlikely that the surface energy is lost.

  3A and 3B are diagrams schematically showing an example of an ink jet recording apparatus used in the ink jet recording method of the present invention. FIG. 3A is a perspective view of a main part of the ink jet recording apparatus, and FIG. 3B is a perspective view of a head cartridge. It is. The ink jet recording apparatus is provided with a conveying means (not shown) for conveying the recording medium 32 and a carriage shaft 34. A head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 includes recording heads 38 and 40, and is configured such that an ink cartridge 42 is set. While the head cartridge 36 is conveyed along the carriage shaft 34 in the main scanning direction, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32. Then, the recording medium 32 is conveyed in the sub-scanning direction by a conveying unit (not shown), whereby an image is recorded on the recording medium 32.

(recoding media)
As the recording medium, it is preferable to use an absorptive recording medium rather than a non-absorbing recording medium. Whether the recording medium is “absorbing or non-absorbing” can be determined by the Bristow method shown below. First, J.H. TAPPI paper pulp test method no. The liquid absorptivity measurement by the Bristow method based on 51-87 is performed, and the Ka value for water is calculated. A recording medium having a Ka value with respect to water of 0.35 mL · m ⁻² · msec ^−1/2 or more can be determined as an “absorbent recording medium”. A “non-absorbable recording medium” is a recording medium that does not absorb water. For this reason, when liquid absorptivity measurement is performed by the above method, the Ka value is naturally smaller than 0.35 mL · m ⁻² · msec ^−1/2 . Examples of non-absorbable recording media include plastic films such as vinyl chloride sheets, polyethylene terephthalate films, and acrylic resin films. It is not preferable to use the above non-absorbing recording medium.

  Examples of the absorbent recording medium include uncoated paper such as plain paper that does not have a coating layer, and coated paper that has a coating layer such as matte paper and glossy paper. Among these, the absorbent recording medium is preferably coated paper, and more preferably glossy paper having high surface smoothness. In glossy paper, the inorganic pigment constituting the ink receiving layer has a small particle size and is tightly packed, so that the smoothness of the glossy paper surface is high. When a metal film is formed on a recording medium with high smoothness, the light incident on the metal film is easily reflected in a certain direction, so that the glossiness of the image can be further improved.

<Ink>
The ink jet recording method of the present invention uses the first ink and the second ink. Hereinafter, “(meth) acrylic acid” and “(meth) acrylate” represent “acrylic acid, methacrylic acid” and “acrylate, methacrylate”. The water-soluble organic solvent includes a water-soluble organic solvent that is solid at a temperature of 25 ° C. Even a water-soluble organic solvent that is solid at a temperature of 25 ° C. is dissolved in the ink.

[First ink]
The first ink contains a nonionic surfactant. When an anionic surfactant is used, the reaction with the cationic component of the recording medium (alumina, alumina hydrate, cationic resin, etc.) is more dominant than the orientation at the interface of the region to which the first ink is applied. It becomes the target. As a result, the anionic surfactant is difficult to orient at the interface in the region where the first ink is applied, so even if the second ink is applied so as to overlap the region where the first ink is applied, Difficult to suppress water penetration. For this reason, the second ink is less likely to stay on the surface of the recording medium, and the metal particles are less likely to adhere uniformly to the recording medium, so that the glossiness of the image cannot be obtained. The first ink preferably does not contain a coloring material such as a dye or a pigment. Hereinafter, components constituting the first ink will be described.

(Nonionic surfactant)
The nonionic surfactant has a fluorine atom or silicon. Examples of the nonionic surfactant having a fluorine atom include a surfactant having a perfluoroalkyl group. A perfluoroalkyl group is represented by C _x F _{2x + 1} . X defining the number of carbon atoms and the number of fluorine atoms in the perfluoroalkyl group is preferably 1 or more and 6 or less. Examples of the surfactant having a perfluoroalkyl group include an amine oxide adduct of a perfluoroalkyl group and an ethylene oxide adduct of a perfluoroalkyl group. The perfluoroalkyl group is hydrophobic, and the amine oxide group and the ethylene oxide group are hydrophilic. Examples of the amine oxide adduct of a perfluoroalkyl group include Surflon S-141 and S-241 (both manufactured by AGC Seimi Chemical). Examples of the ethylene oxide adduct having a perfluoroalkyl group include Surflon S-242, S-243, and S-420 (all manufactured by AGC Seimi Chemical). Of these, the surfactant having a perfluoroalkyl group is preferably an ethylene oxide adduct of a perfluoroalkyl group. The number of ethylene oxide structures in the perfluoroalkyl group ethylene oxide adduct is preferably 1 or more and 50 or less, more preferably 1 or more and 20 or less, and particularly preferably 1 or more and 10 or less.

Examples of the nonionic surfactant having silicon include surfactants having a siloxane (—Si—O—) structure. Examples of the surfactant having a siloxane structure include polyether-modified siloxane compounds. The polyether-modified siloxane compound has a hydrophilic siloxane (—Si—O—) unit having a polyether chain and a hydrophobic siloxane unit having no polyether chain. Some polyether-modified siloxane compounds have a polyether chain bonded to the main chain, and some have a polyether chain bonded to the side chain. The structure of the polyether chain is represented by —O— (C ₂ H ₄ O) _a — (C ₃ H ₆ O) _b —R). Here, a is an integer of 1 to 100, b is an integer of 0 to 100, and R is a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. C ₂ H ₄ O is an ethylene oxide group, and C ₃ H ₆ O is a propylene oxide group. The siloxane structure is hydrophobic, and the ethylene oxide group and the propylene oxide group are hydrophilic. In the polyether-modified siloxane compound, the state in which the ethylene oxide unit and the propylene oxide unit exist in the structure may exist in any state such as a random form or a block form. Here, that each unit exists in a random state means that ethylene oxide units and propylene oxide units are irregularly arranged. In addition, the presence of each unit in a block state means that each block is composed of several units as described above, and the blocks configured in this way are regularly arranged. Yes. Examples of the polyether-modified siloxane compound include BYK-307, BYK-346, BYK-3455 (all manufactured by BYK Chemie). Of these, the polyether-modified siloxane compound preferably has a polyether chain as a side chain. Specifically, BYK-307 (manufactured by Big Chemie) is available.

  Especially, it is preferable that the nonionic surfactant has an HLB value by Griffin method of 6.0 or more. When the HLB value is smaller than 6.0, the hydrophobicity is high, so that it is difficult to dissolve in the first ink. Here, the HLB value according to the Griffin method is calculated based on the formula weight of the hydrophilic group of the surfactant and the molecular weight of the surfactant. HLB value = 20 × (formula weight of the ethylene oxide group or amine oxide group of the surfactant) / It is calculated from the formula (molecular weight of surfactant). The HLB value indicates the degree of hydrophilicity or lipophilicity of the surfactant (compound) in the range of 0.0 to 20.0. The lower the HLB value, the higher the lipophilicity (hydrophobicity) of the compound. On the other hand, the higher the HLB value, the higher the hydrophilicity of the compound.

The content (% by mass) of the nonionic surfactant is preferably 5.0% by mass or less, and more preferably 1.0% by mass or less, based on the total mass of the first ink. The content is more preferably 0.5% by mass or more. Further, the total application amount (μg) of the surfactant per unit area of the recording medium is a ratio (times) to the application amount (μg) of the second ink per unit area of the recording medium, and is 0.004 times or more. It is preferable that it is 0.020 times or less. When the ratio is less than 0.004 times, the total amount of the surfactant applied per unit area of the recording medium is small, so that the second ink hardly stays on the surface of the recording medium. Therefore, since the water in the ink permeates before the metal particles spread in the second ink, the metal particles cannot uniformly adhere to the recording medium, and the image glossiness may not be sufficiently obtained. When the ratio exceeds 0.020 times, the amount of surfactant applied per unit area of the recording medium is large, and the hydrophobicity of the interface becomes strong. Thereby, even if the metal particles spread in the second ink, the water in the ink does not easily permeate, so the metal particles and the metal particles do not approach each other, and the metal particles are difficult to fuse. Therefore, since it becomes difficult to form a uniform metal film on the recording medium, there are cases where the glossiness of the image cannot be sufficiently obtained.
(Aqueous medium)
The first ink contains an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water (ion exchange water) as water. The water-soluble organic solvent is not particularly limited. As the water-soluble organic solvent, any of those usable for water-based inks such as alcohols, glycols, glycol ethers, and nitrogen-containing compounds can be used. Of these, the water-soluble organic solvent is preferably a polyhydric phenol having two or more hydroxy groups in the same molecule. Examples of the polyhydric phenol include tannin and catechin. The polyhydric phenol is preferably catechin. Further, one or more of these water-soluble organic solvents can be contained in the ink.

  The content (% by mass) of water in the first ink is preferably 80.0% by mass or more and 98.00% by mass or less based on the total mass of the ink. The content (% by mass) of the water-soluble organic solvent in the first ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. When the content of the water-soluble organic solvent is less than 3.0% by mass, reliability such as anti-sticking property may not be sufficiently obtained when the ink is used in an ink jet recording apparatus. Further, when the content of the water-soluble organic solvent is more than 50.0% by mass, the viscosity of the ink is increased and ink supply failure may occur.

(Physical properties of the first ink)
The viscosity (mPa · s) at 25 ° C. of the ink is preferably 1.0 mPa · s to 10.0 mPa · s, and more preferably 1.0 mPa · s to 5.0 mPa · s. .

[Second ink]
The second ink contains metal particles. Hereinafter, components constituting the second ink will be described.

(Metal particles)
The metal particles are composed of a transition metal or an oxide thereof. Examples of the transition metal include nickel, copper, silver, gold, chromium, and titanium. Especially, it is preferable that a metal particle is comprised with silver and gold | metal | money. Among transition metals, silver and gold have a small energy (ionization energy) necessary for a metal atom to release an electron to become a positively charged metal atom. Therefore, even with a small amount of energy, electrons are easily released from the metal atom, and the metal atom having a positive charge in the metal particle is easily attracted. Thereby, the metal particles and the metal particles are fused, a metal film is easily formed on the recording medium, and the glossiness of the image is particularly improved.

  The content (% by mass) of the metal particles in the second ink is preferably 2.0% by mass or more and 6.0% by mass or less, and preferably 2.0% by mass or more and 4.0% by mass or less. Further preferred.

  Examples of the method for dispersing the metal particles include surfactant-dispersed metal particles using a surfactant as a dispersant, and resin-dispersed metal particles using a resin as a dispersant. Of course, in the second ink, metal particles having different dispersion methods can be used in combination.

  As the surfactant used as the dispersant in the surfactant-dispersed metal particles, an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, and the like can be used.

  The resin used as the dispersant in the resin dispersion type metal particles preferably has a hydrophilic unit and a hydrophobic unit. The hydrophilic unit is a unit derived from a monomer having a hydrophilic group. The hydrophobic unit is a unit derived from a monomer having a hydrophobic group. The proportion (% by mass) of the hydrophilic unit in the resin is preferably 10.0% by mass or more and 30.0% by mass or less based on the total mass of the resin. The proportion (mass%) of the hydrophobic unit in the resin is preferably 70.0 mass% or more and 90.0 mass% or less based on the total mass of the resin.

  The monomer having a hydrophilic group is selected from the group consisting of a monomer having a carboxylic acid group, a monomer having a phosphonic acid group, a monomer having a hydroxy group, and a monomer having an ethylene oxide structure It is preferable that it is at least one kind. Examples of the monomer having a carboxylic acid group include monomers having an α, β-ethylenically unsaturated bond such as (meth) acrylic acid, maleic acid, itaconic acid, and fumaric acid. Examples of the monomer having a phosphonic acid group include monomers having an α, β-ethylenically unsaturated bond such as 2-phosphonic acid ethyl (meth) acrylate. Carboxylic acid and phosphonic acid may be anhydrides and salts thereof. Examples of the salt include alkali metal salts such as lithium, sodium and potassium, ammonium salts, and organic ammonium salts. Examples of the monomer having a hydroxy group include alkyl (meth) acrylates having a hydroxy group such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Furthermore, examples of the monomer having an ethylene oxide structure include alkoxy polyethylene glycol (meth) acrylates having 1 to 3 ethylene oxide structures such as methoxyethylene glycol (meth) acrylate and methoxypolyethylene glycol (meth) acrylate. Can be mentioned. These may be used alone or in combination of two or more as required. Among these, the monomer having a hydrophilic group is preferably (meth) acrylic acid.

  Examples of the monomer having a hydrophobic group include monomers having an aromatic group and alkyl (meth) acrylates. Examples of the monomer having an aromatic group include styrene, α-methylstyrene, benzyl (meth) acrylate, and 2-phenoxyethyl (meth) acrylate. Among them, the monomer having an aromatic group is preferably styrene. Examples of the alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth) acrylate. Examples thereof include alkyl (meth) acrylates having 1 to 4 carbon atoms. These may be used alone or in combination of two or more as required. Especially, it is preferable that alkyl (meth) acrylates are butyl (meth) acrylate.

  The polystyrene-converted weight average molecular weight (Mw) obtained by gel permeation chromatography (GPC) of the resin is preferably 1,000 or more and 100,000 or less, and preferably 3,000 or more and 50,000 or less. Further preferred.

  The content (% by mass) of the dispersant in the second ink is preferably 0.1% by mass to 10.0% by mass, and more preferably 0.2% by mass to 5.0% by mass. Further preferred. Moreover, it is preferable that content (mass%) of a dispersing agent is 0.1 time or more and 1.0 time or less by mass ratio with respect to content (mass%) of a metal particle.

[Volume-based cumulative 50% particle size (D ₅₀ )]
The volume-based cumulative 50% particle size (nm) of the metal particles is preferably 50 nm or less. When D50 exceeds ₅₀ nm, the range in which electrons can move in the metal particles becomes wide, and thus electrons hardly move on the surface of the metal particles. This makes it difficult for metal atoms having positive charges in the metal particles to be attracted, so that the metal particles and the metal particles do not fuse and it is difficult to form a metal film on the recording medium, and the glossiness of the image cannot be sufficiently obtained. There is a case. D ₅₀ is more preferably 15 nm or less, and further preferably 1 nm or more.

When the present inventors use metal particles having D ₅₀ of 15 nm and 50 nm, the ratio of the number of metal atoms fused in one metal particle to the total number of metal atoms of one metal particle (%) Was calculated. If D ₅₀ is used the metal particles is 15 nm, the ratio was 25%. However, when metal particles having a D50 of ₅₀ nm are used, the ratio is 5% or less. By D ₅₀ is used the metal particles is 15 nm, since the number of metal atoms that are fused in one metal particle is increased, the metal particles and the metal particles are efficiently fused to form a metal film . Thereby, the glossiness of the image is improved. D ₅₀ is measured by a dynamic light scattering method.

[Production method of metal particles]
Any conventionally known method can be used as a method for producing metal particles. Examples of the method for producing metal particles include a method of pulverizing a lump of metal with a pulverizer such as a ball mill or a jet mill (pulverization method), a method of reducing metal ions or metal complexes with a reducing agent and aggregating them (reduction method). Etc. In the present invention, the metal particles are preferably produced by a reduction method.

(resin)
The second ink preferably further contains a resin in order to improve the scratch resistance of the image. The resin used as the additive may be the same as or different from the resin used as the dispersant. Specifically, the resin unit that can be used as the dispersant may be appropriately selected from the units listed above. The content (% by mass) of the additive in the second ink is preferably 1.0% by mass or less based on the total mass of the ink. When the content of the resin in the second ink exceeds 1.0% by mass, the resin that has entered between the many metal atoms in the second ink makes it difficult to fuse the metal particles to the metal particles. As a result, it is difficult to form a metal film on the recording medium, and the glossiness of the image may not be sufficiently obtained. The content (% by mass) of the resin in the second ink is more preferably from 0.1% by mass to 1.0% by mass.

(Aqueous medium)
The second ink contains an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water (ion exchange water) as water. The water-soluble organic solvent is not particularly limited. As the water-soluble organic solvent, any of those usable for water-based inks such as alcohols, glycols, glycol ethers, and nitrogen-containing compounds can be used. Of these, the water-soluble organic solvent is preferably a polyhydric phenol, and more preferably catechin. Further, one or more of these water-soluble organic solvents can be contained in the ink.

  The content (% by mass) of water in the second ink is preferably 50.0% by mass or more and 90.00% by mass or less based on the total mass of the ink. In addition, the content (% by mass) of the water-soluble organic solvent in the second ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. When the content of the water-soluble organic solvent is less than 3.0% by mass, reliability such as anti-sticking property may not be sufficiently obtained when the ink is used in an ink jet recording apparatus. Further, when the content of the water-soluble organic solvent is more than 50.0% by mass, the viscosity of the ink is increased and ink supply failure may occur. The content (% by mass) of the water-soluble organic solvent in the second ink is more preferably 3.0% by mass or more and 10.0% by mass or less based on the total mass of the ink.

(Other ingredients)
In addition to the above components, the second ink may contain a water-soluble organic compound that is solid at a temperature of 25 ° C., such as urea and its derivatives, trimethylolpropane, and trimethylolethane. In addition, the ink of the present invention includes a surfactant, a pH adjuster, an antifoaming agent, a rust preventive, an antiseptic, an antifungal agent, an antioxidant, an anti-reducing agent, and a chelating agent as necessary. Various additives may be contained.

(Method for producing second ink)
The second ink is produced by dispersing metal particles in an aqueous liquid medium. Examples of the method for dispersing the metal particles in an aqueous liquid medium include a method in which a surfactant is added to an aqueous liquid medium and dispersed, and a method in which a water-soluble resin is added to an aqueous liquid medium and dispersed.

(Physical properties of the second ink)
The viscosity (mPa · s) at 25 ° C. of the ink is preferably 1.0 mPa · s to 10.0 mPa · s, and more preferably 1.0 mPa · s to 5.0 mPa · s. . The surface tension (mN / m) of the ink at 25 ° C. is preferably 30.0 mN / m or more and 35.0 mN / m or less.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited at all by the following Example, unless the summary is exceeded. In addition, what is described as “parts” and “%” with respect to the component amounts is based on mass unless otherwise specified.

<Preparation of first ink>
The first inks 1 to 5 were prepared by mixing the components shown in Table 1. In Table 1, Surflon S-241 is an amine oxide adduct of a perfluoroalkyl group manufactured by AGC Seimi Chemical. Surflon S-242 is an ethylene oxide adduct of a perfluoroalkyl group manufactured by AGC Seimi Chemical. BYK-307 is a polyether-modified siloxane compound manufactured by Big Chemie. Acetylenol E100 is an ethylene oxide adduct of acetylene glycol manufactured by Kawaken Fine Chemicals. The lower part of Table 1 describes the content (%) of the surfactant in the first ink. The HLB values of the surfactants listed in Table 1 are shown in parentheses.

<Preparation of the second ink>
(Preparation of silver particle 1 colloidal solution)
To 500 mL of an aqueous solution containing 0.25 mol / L iron (II) sulfate heptahydrate (manufactured by Wako Pure Chemical Industries) and 0.50 mol / L trisodium citrate dihydrate (manufactured by Wako Pure Chemical Industries) 100 mL of 0.83 mol / L silver nitrate aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added over 3 seconds. The solution was stirred at 300 rpm for 30 seconds at a temperature of 20 ° C. The obtained solution was centrifuged at 3,000 rpm, and the collected solid content was dispersed in water to obtain a colloidal solution of silver particles 1 (the content of silver particles 1 was 10.0%). The D ₅₀ of the silver particles 1 in the colloidal liquid was measured using a particle size distribution meter (DLS-6500, manufactured by Otsuka Electronics Co., Ltd.) by a dynamic light scattering method. The measurement conditions are Setzero: 30 s, number of measurements: 3, measurement time: 180 seconds, shape: true sphere, and refractive index: 1.59. The D ₅₀ of the silver particles 1 in the colloidal liquid was 12 nm.

(Preparation of silver particle 2 colloidal solution)
In the preparation of the silver particle 1 colloidal solution, the stirring speed during centrifugation was changed to 1,200 rpm. Otherwise, a colloidal solution of silver particles 2 (the content of silver particles 2 was 10.0%) was obtained in the same procedure as the preparation of the colloidal solution of silver particles 1. The D ₅₀ of the silver particles 2 in the colloidal liquid was 15 nm.

(Preparation of colloidal solution of silver particles 3)
In the preparation of the colloidal solution of silver particles 1, the stirring speed during centrifugation was changed to 800 rpm. Otherwise, a colloidal solution of silver particles 3 (the content of silver particles 3 was 10.0%) was obtained in the same procedure as the preparation of the colloidal solution of silver particles 1. The D ₅₀ of the silver particles 3 in the colloidal liquid was 50 nm.

(Preparation of colloidal solution of silver particles 4)
In the preparation of the colloidal solution of silver particles 1, the stirring speed during centrifugation was changed to 500 rpm. Otherwise, a colloidal solution of silver particles 4 (the content of silver particles 4 was 10.0%) was obtained in the same procedure as the preparation of the colloidal solution of silver particles 1. The D ₅₀ of the silver particles 4 in the dispersion was 60 nm.

(Preparation of gold particle dispersion)
Add 1.00 mmol / L of tetrachloroauric (III) acid tetrahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) to 1 L of water and bring to a boil. By adding 1.00 mmol / L and heating for 30 minutes, a colloidal solution of gold particles (content of gold particles is 20.0%) was obtained. The D ₅₀ of the gold particles in the colloidal liquid was measured by the same method as that for the silver particles in the colloidal liquid. The D ₅₀ of the colloidal gold particles was 12 nm.

(Preparation of the second ink)
[Second ink 1-7]
Components other than the styrene-acrylic acid-n-butyl acrylate copolymer shown in Table 2 were mixed to prepare second inks 1 to 9. The metal particles in the second ink are dispersed with acetylenol E100 or a styrene-acrylic acid copolymer. Except for the second inks 8 and 9, a styrene-acrylic acid-n-butyl acrylate copolymer in an amount shown in Table 2 was further added to the second ink. In Table 2, acetylenol E100 is an ethylene oxide adduct of acetylene glycol manufactured by Kawaken Fine Chemicals. The styrene-acrylic acid copolymer produced by a conventional method has an acid value of 120 mgKOH / g and a weight average molecular weight of 8,000. The styrene-acrylic acid-n-butyl acrylate copolymer produced by a conventional method has an acid value of 120 mgKOH / g and a weight average molecular weight of 5,000.

<Evaluation>
Each of the first ink and the second ink listed in Table 3 was filled in an ink cartridge, and set in an ink jet recording apparatus (PIXUS MG5730, manufactured by Canon Inc.) equipped with a recording head that ejects ink by thermal energy. An image recorded under the condition of applying 20 pL of ink to a unit area of 1 / 1,200 inch × 1 / 1,200 inch is defined as having a recording duty of 100%. Using the inkjet recording apparatus, two types of recording media ((1) matte paper: matte photo paper MP-101, manufactured by Canon, (2) glossy paper: Canon photographic paper / glossy gold GL-101, manufactured by Canon) A predetermined ink was first applied in a circular pattern having a diameter of 10 mm at the recording duty shown in Table 3. Thereafter, the ink was allowed to stand for 1 minute, and a predetermined ink was applied so as to overlap with the previously applied ink area at the recording duty shown in Table 3. The surface temperature of the recording medium was measured using a digital radiation temperature sensor (FT-H20, manufactured by Keyence). In the present invention, according to the evaluation criteria for the following items, A or B is an acceptable level and C is an unacceptable level. The evaluation results are shown in Table 3. In Table 3, “total applied amount of surfactant / applied amount of second ink (times)” is the amount per unit area of the recording medium relative to the applied amount (μg) of the second ink per unit area of the recording medium. It is the ratio (times) of the total application amount (μg) of the surfactant.

(Glossy)
After the obtained image was naturally dried for 24 hours, the 20-degree specular gloss based on JIS Z 8741 was measured using a gloss meter (VG 7000, manufactured by Nippon Denshoku Industries Co., Ltd.).

A: Among the two types of recording media, the glossiness of the recording medium having a relatively low glossiness was 550 or more. B: Among the two types of recording media, the glossiness of the recording medium having a relatively low glossiness was It was 500 or more and less than 550 C: Among the two types of recording media, the glossiness of the recording medium having a relatively low glossiness was less than 500500

(Abrasion resistance)
After naturally drying the obtained image for 24 hours, the wear resistance tester (manufactured by Imoto Seisakusho), which is a Gakushin type testing machine according to JIS L 0849, is used to determine the value of the load that does not cause any scratch marks on the image. By obtaining, the scratch resistance was evaluated.

A: Among the two types of recording media, the load on the recording medium having a relatively low load was 700 g or more. B: Among the two types of recording media, the load on the recording medium having a relatively low load was less than 700 g.

Example 1 In the image the field emission scanning electron microscope obtained (FE-SEM) (S- 8000, manufactured by Hitachi High Technologies) was observed with _the silver particles _{D 50} is 12nm is not observed, the silver particles The continuous film 1 was formed by fusing. Meanwhile, observation of the image obtained in Comparative Example 1 in the same way, the silver particles 2 D ₅₀ is 12nm is observed, the silver particles are not fused, did not form a continuous film .

In Example 2, the recording medium was heated using an infrared heater after the second ink was applied. At that time, the temperature of the surface of the recording medium was prevented from exceeding 50 ° C. By heating the recording medium, a uniform metal film could be quickly formed on the recording medium. In Comparative Example 3, the first ink was applied to the same area as the area where the second ink was applied. The image recorded in this manner was covered with an oil film, the color looked different from the original silver color, and the glossiness of the image was at an unacceptable level D.

Claims (7)

A process of applying the first ink to the recording medium;
A recording step of applying a second ink to the recording medium so that the second ink is at least partially overlapped with the region to which the first ink has been applied,
The first ink is a water-based ink containing a nonionic surfactant having fluorine atoms or silicon,
An ink jet recording method, wherein the second ink is an aqueous ink containing metal particles composed of a transition metal or an oxide thereof.   The inkjet recording method according to claim 1, wherein the nonionic surfactant is a surfactant having a perfluoroalkyl group or a surfactant having a siloxane structure.   The inkjet recording method according to claim 1, wherein a volume-based cumulative 50% particle size (nm) of the metal particles is 50 nm or less.   4. The ink jet recording method according to claim 1, wherein, in the processing step, the first ink is ejected from an ink jet recording head and applied to the recording medium. 5.   The total application amount (μg) of the surfactant per unit area of the recording medium is 0.004 as a ratio (times) to the application amount (μg) of the second ink per unit area of the recording medium. 5. The inkjet recording method according to claim 1, wherein the inkjet recording method is at least twice and at most 0.020 times.   The inkjet recording method according to claim 1, wherein the second ink further contains a resin. An ink jet recording apparatus comprising means for applying a second ink after applying the first ink,
The first ink is a water-based ink containing a nonionic surfactant having fluorine atoms or silicon,
An ink jet recording apparatus, wherein the second ink is an aqueous ink containing metal particles composed of a transition metal or an oxide thereof.