JP2021091218A - Inkjet recording method, and inkjet recorder - Google Patents

Abstract

To provide an inkjet recording method and an inkjet recorder capable of suppressing thin film interference and capable of recording a color metallic image having excellent fine line quality.SOLUTION: An ink jet recording method in which ink is ejected from an ink jet recording head to record an image on a recording medium includes: a step of imparting first ink to a recording medium; a step of imparting second ink on the recording medium so as to overlap with at least part of a region where the first ink is imparted; and a step of imparting third ink on the recording medium so as to overlap with at least a part of a region where the first ink and the second ink are imparted, in which the first ink is ink containing silver particles, the second ink is ink that contains a resin and a predetermined additive and does not contain a colorant, the third ink is ink that contains a colorant.SELECTED DRAWING: None

Description

The present invention relates to an inkjet recording method and an inkjet recording device.

Inks containing metal particles have been used to form electric circuits by utilizing the conductivity of the metal particles used, but in recent years, they have also been used for expressing a metallic feeling such as Christmas cards. It has become to. In particular, there is a need to give a metallic image a color tone, that is, to record a "color metallic image". In order to record a color metallic image, an inkjet recording method has been proposed in which an ink containing silver particles and an ink containing a pigment are sequentially applied to a recording medium (see Patent Document 1). Further, an inkjet recording method has been proposed in which an ink containing silver particles, a clear ink, and an ink containing a coloring material are sequentially applied to a recording medium (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2012-12179 Japanese Unexamined Patent Publication No. 2012-206481

The present inventors recorded a color metallic image by the inkjet recording method described in Patent Document 1, and examined the obtained image. As a result, it was found that thin film interference occurs in the region where the silver layer formed of silver particles and the coloring material layer formed of the coloring material overlap, and the color may be different from that of the coloring material. Further, the images recorded by applying three kinds of inks to the recording medium in the order described in Patent Document 2 were examined. As a result, it was found that thin film interference tended to be less likely to occur, but when an image such as a thin line was recorded with an ink containing a coloring material, the ink bleeded and the image quality was impaired. Ink bleeding can occur not only in fine lines, but in an image such as thin lines, deterioration of image quality due to bleeding is particularly easy to recognize. Therefore, in the present invention, this problem is referred to as "thin line quality" for convenience. ..

Therefore, an object of the present invention is to provide an inkjet recording method and an inkjet recording apparatus capable of recording a color metallic image having good fine wire quality while suppressing thin film interference.

The above object is achieved by the following invention. That is, the inkjet recording method according to the present invention is an inkjet recording method in which ink is ejected from an inkjet recording head to record an image on a recording medium, and the step of applying the first ink to the recording medium, the first step. The step of applying the second ink to the recording medium so as to overlap at least a part of the area to which one ink is applied, and so as to overlap at least a part of the area to which the first ink and the second ink are applied. , The third ink has a step of applying the third ink to the recording medium, the first ink is an ink containing silver particles, the second ink contains a resin and an additive, and a coloring material is used. It is an ink that does not contain, and the additive is (1) a compound having an ethylene oxide group, a hydroxy group, or an anionic group and a siloxane structure, and (2) an ethylene oxide group, a hydroxy group, or an anionic group. It is selected from the group consisting of a compound having a perfluoroalkyl structure and the third ink, and is characterized in that the third ink is an ink containing a coloring material.

According to the present invention, it is possible to provide an inkjet recording method and an inkjet recording apparatus capable of recording a color metallic image having good fine wire quality while suppressing thin film interference.

It is a figure which shows typically an example of the inkjet recording apparatus used in the inkjet recording method of this invention, (a) is the perspective view of the main part of the inkjet recording apparatus, (b) is the perspective view of the head cartridge.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions and exists in the ink, but for convenience, it is expressed as "containing a salt". The physical characteristic value is a value at room temperature (25 ° C.) unless otherwise specified.

As described in Patent Document 1, a color metallic image can be recorded by applying an ink containing silver particles and an ink containing a coloring material in order to a recording medium. The color metallic image recorded in this way has a layer structure in which a silver layer having no saturation and a color material layer are formed in this order on a recording medium. The silver layer formed by the silver particles exhibits a metallic luster, resulting in a glossy metallic image. Further, the light incident on the color metallic image passes through the color material layer, is reflected by the silver layer, passes through the color material layer again, and expresses the color tone of the color material contained in the ink. That is, when the silver layer reflects light, a metallic feeling, that is, glossiness is exhibited, and when light is transmitted through the coloring material layer, color development is exhibited. As described above, the image having "color development property" in the present invention refers to an image in which the specularly reflected light from the image exhibits the color tone of the color material of the third ink instead of the colorless silver color. The specularly reflected light is light that is reflected by the incident light on the image at the same angle (reflection angle) as the angle (incident angle) formed by the normal direction of the image and the incident direction of the light.

Thin-film interference means that the light reflected from the surface of the film and the light reflected from the lower layer of the film interfere with each other, and the light of a specific wavelength strengthens or weakens each other, so that the reflected light is colored. It is a visible phenomenon. The wavelengths that strengthen each other and the wavelengths that weaken each other change depending on the optical path difference between the light reflected from the surface of the film and the light reflected from the lower layer. The optical path difference depends on the thickness of the film and the refractive index of the substance forming the film. When there are many irregularities on the surface of the film, interference light corresponding to various optical path differences is generated, and the colors of the interference light are mixed and whitened, so that the coloring of the reflected light tends to be reduced. .. On the contrary, when the surface of the film has few irregularities and is smooth, light of a specific wavelength is significantly reflected, and the coloring of the reflected light is remarkably recognized.

In the inkjet recording method, ink droplets ejected from a recording head adhere to a recording medium while maintaining the shape of dots, and an image is recorded. When the image is recorded in this way, the surface becomes uneven and uneven due to the step due to the overlapping of dots and the step due to the presence or absence of dots. When the ink containing the coloring material is applied to the silver layer previously formed on the recording medium by the ink containing silver, the same phenomenon as described above is considered to occur. It is presumed that the surface of the color material layer formed on the surface also has irregularities.

When, for example, an ink containing a yellow pigment is ejected from a recording head and applied onto the silver layer formed on the recording medium, a color material layer composed of the yellow pigment is formed on the silver layer. Since there are many irregularities on the surface of this color material layer, the reflected light is whitened and becomes colorless, and the positively reflected light from the color metallic image is transmitted through the color material layer composed of the yellow pigment. , Was expected to appear colored yellow.

However, as a result of examination by the present inventors, it was found that the specularly reflected light from the color metallic image recorded as described above has a color tone different from that of the color material. A detailed observation of the color metallic image in which such a phenomenon occurred revealed that the dots of the ink containing the color material were connected on the silver layer to form a color material layer having a smooth surface with few irregularities. Was there. It was found that thin film interference occurs in the region where the color material layer having a smooth surface is formed, and the reflected light colored in a color tone different from that of the color material is recognized.

The reason why there are few irregularities on the surface of the color material layer formed on the silver layer is that the surface energy of silver is high. When an ink containing a coloring material is applied on the silver layer, the dots quickly adapt to the silver layer and spread widely, so that they are easily connected to adjacent dots. As a result, a color material layer having a smooth surface with few irregularities is formed, and it is considered that thin film interference occurs.

The present inventors have studied the provision of a resin layer between the silver layer and the color material layer in order to suppress the occurrence of thin film interference in a color metallic image. If the resin layer is interposed, the silver layer and the coloring material layer will not come into direct contact with each other. As a result, it was found that the dots of the ink containing the coloring material applied on the silver layer are less likely to get wet and spread, the coloring material layer having a surface having many irregularities is formed, and the thin film interference is suppressed. ..

As described above, a first ink containing silver particles, a second ink containing a resin and not containing a coloring material, and a third ink containing a coloring material are applied to a recording medium in this order to obtain a color metallic image. If the above is recorded, thin film interference can be suppressed due to the presence of the resin layer. However, as a result of the studies by the present inventors, it has been found that when a second ink containing a resin is used for recording a color metallic image, another problem arises. Specifically, it has been found that when a third ink is applied on the resin layer and an image such as a thin line is recorded, ink bleeding occurs and the image quality is impaired. Such deterioration of fine wire quality is a problem peculiar to the case of using a third ink containing a resin and not containing a coloring material when recording a color metallic image.

The silver particles used in the ink for inkjet have a particle size of several tens to several hundreds of nm in consideration of ejection stability. The silver layer formed on the recording medium by fusing silver particles having such a particle size does not mean that the silver particles are completely fused to form a uniform layer, and the shape of the particles is changed to some extent. Is fused in a maintained state, so that pores are present in the silver layer. If the third ink is applied onto the silver layer without applying the second ink, the liquid component of the third ink penetrates into the recording medium through the pores in the silver layer, so that the ink bleeds. Although it is unlikely that the fine wire quality will be deteriorated due to this, thin film interference will occur. On the other hand, if the second ink containing the resin is applied onto the silver layer and then the third ink is applied, the thin film interference can be suppressed. However, in this case, since the resin of the second ink enters the pores of the silver layer and the pores are clogged, it becomes difficult for the third ink to penetrate into the recording medium, and the third ink is formed on the silver layer. It overflows, ink bleeds, and the fine wire quality deteriorates.

The present inventors have studied the composition of the second ink in consideration of the cause of the above-mentioned deterioration of the fine wire quality caused by the second ink for forming the resin layer. As a result, it has been found that the second ink may contain a predetermined additive. This additive includes (1) a compound having an ethylene oxide group, a hydroxy group, or an anionic group and a siloxane structure, or (2) an ethylene oxide group, a hydroxy group, or an anionic group and a perfluoroalkyl structure. It is a compound having and. These compounds may be hereinafter referred to as "predetermined additives".

By using the second ink containing a predetermined additive and the first ink and the third ink, it is possible to suppress thin film interference and record a color metallic image having good fine line quality. The above-mentioned additive has a hydrophilic group (ethylene oxide group, hydroxy group, anionic group) and a hydrophobic group (siloxane structure, perfluoroalkyl structure) in its molecule, and has a property of being easily oriented to an interface. Have. After the dots of the second ink adhere to the silver layer, the predetermined additive is oriented near the surface of the dots. The siloxane structure and the perfluoroalkyl structure have weaker intermolecular forces than the hydrocarbon structure which is a hydrophobic group in a hydrocarbon-based surfactant which is a general-purpose additive for water-based ink for inkjet. Therefore, the surface energy of the dots of the second ink in which the predetermined additive is oriented near the surface is remarkably lowered, and the dots of the second ink to be subsequently adhered are difficult to be connected, and the dots of the second ink to be adhered to the dots are less likely to be connected to some extent. The ink is fixed in the presence of a distance. The resin layer formed in this way has a gap corresponding to the distance between the dots, and the liquid component of the third ink to be applied later permeates smoothly through the gap, so that bleeding due to ink overflow occurs. It is less likely to occur, and deterioration of fine wire quality can be suppressed.

It is known that thin film interference is a phenomenon that tends to occur when a resin layer is present even if the silver layer is not present. For example, if an ink containing a coloring material is applied to a recording medium and then an ink containing a resin and not containing a coloring material is applied, an image having a resin layer on the surface is formed, so that thin film interference occurs. .. On the other hand, if the image has a color material layer on the surface, thin film interference does not occur. On the other hand, when the silver layer is present, unlike the previous case, thin film interference occurs even in the image in which the coloring material layer is present on the surface. This is because a silver layer having a high surface energy exists between the color material layer and the recording medium.

<Inkjet recording method, inkjet recording device>
The inkjet recording method of the present invention is a method of ejecting ink from an inkjet recording head to record an image on a recording medium. Specifically, a step of applying a first ink containing silver particles to a recording medium, a step of applying a second ink containing a resin and a predetermined additive and not containing a coloring material to the recording medium, and a step of applying the second ink to the recording medium. It has a step of applying a third ink containing a coloring material to a recording medium. Further, the inkjet recording apparatus of the present invention is used to carry out the above-mentioned inkjet recording method, and first ink, second ink, and third ink are applied to the recording medium in this order to be applied to the recording medium. A means for recording an image is provided. The first ink, the second ink, and the third ink are applied to the recording medium so that at least a part of the areas to which they are applied overlap with each other.

Examples of the method of ejecting ink from the inkjet recording head include a method of applying mechanical energy to the ink and a method of applying thermal energy to the ink. In the present invention, it is preferable to adopt a method of applying thermal energy to the ink to eject the ink. In the recording method of the present invention, it is not necessary to carry out a step of applying a reaction liquid that reacts with each ink or a step of irradiating with active energy rays such as ultraviolet rays and electron beams. Further, it is preferable that each ink is directly applied to a recording medium (preferably, a recording medium having permeability).

FIG. 1 is a diagram schematically showing an example of an inkjet recording device used in the inkjet recording method of the present invention, (a) is a perspective view of a main part of the inkjet recording device, and (b) is a perspective view of a head cartridge. Is. The inkjet recording apparatus is provided with a transport means (not shown) for transporting the recording medium 32 and a carriage shaft 34. The head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 includes recording heads 38 and 40, and is configured so that the 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 the conveying means (not shown), so that the image is recorded on the recording medium 32.

The time difference between the step of applying the first ink to the recording medium and the step of applying the second ink to the recording medium is preferably 1 second or more. It can be said that this time difference is the time from when the first ink is applied to the recording medium until the second ink applied on top of the first ink comes into contact with the first ink. If the time difference is less than 1 second, the time difference between the first ink and the second ink being applied in layers is short, so that the ink containing the resin is applied in a state where the silver particles are not fused. .. Then, since the resin enters between the plurality of silver particles, it becomes difficult for the silver particles to fuse. In the silver layer formed in this way, there are silver particles that are not fused with other silver particles and have a particle size of several tens to several hundreds of nm and thus have a property of causing surface plasmon resonance. .. Therefore, when the image is exposed to light, the reflectance of the light from the silver layer is low, and a high level of glossiness may not be sufficiently obtained. If the time difference is too long, the productivity at the time of recording an image may decrease, so it is preferably 600 seconds or less. The time difference is more preferably 3 seconds or more and 300 seconds or less, and particularly preferably 3 seconds or more and 90 seconds or less.

The time difference between the step of applying the first ink to the recording medium and the step of applying the second ink to the recording medium is within a predetermined range, that is, a predetermined time difference between the first ink and the second ink on the recording medium. The method of granting in will be described. For example, in the case of unidirectional recording in a serial system in which an image is recorded while moving the recording head in the main scanning direction, the following methods (1) to (3) can be used. The unit area can be set as an arbitrary area such as one pixel or one band.

(1) A recording head having a discharge port row of each of the first ink and the second ink arranged in a direction orthogonal to the main scanning direction is used. After applying the first ink to the unit area of the recording medium, the second ink is applied to the unit area without transporting the recording medium.

(2) A recording head having a discharge port row of each of the first ink and the second ink arranged in a direction orthogonal to the main scanning direction is used. The first ink uses a discharge port that is a part of the discharge port row on the upstream side in the sub-scanning direction, and the second ink uses a discharge port that is a part of the discharge port row on the downstream side in the sub-scanning direction. Then, while transporting the recording medium, the first ink and the second ink are applied to the unit area of the recording medium.

(3) A recording head having a first ink ejection port row on the upstream side and a second ink ejection port row on the downstream side in the sub-scanning direction is used. The first ink uses a discharge port that corresponds to a part of the discharge port row on the upstream side, and the second ink uses a discharge port that corresponds to a part of the discharge port row on the downstream side. Then, while transporting the recording medium, the first ink and the second ink are applied with a time difference of at least the transport time of the recording medium.

In the above, the case of performing one-way recording has been described as an example. Of course, in the present invention, even in the case of bidirectional recording, any method may be used as long as the two types of ink can be applied to the recording medium with a predetermined time difference. The time difference between the step of applying the second ink to the recording medium and the step of applying the third ink to the recording medium is not particularly limited, but is preferably 0.1 seconds or more and 600 seconds or less, for example.

In the case of clear ink containing a resin, the application of the ink to the unit area of the recording medium is performed in a batch rather than in a plurality of times because a resin layer having a flatter surface is formed. It is advantageous from the viewpoint of image quality and the like. However, in the present invention, it is preferable that the second ink is applied to the unit area of the recording medium in a plurality of times. When dividing into a plurality of times, the number of main scans of the recording head (number of recording passes) can be adjusted. In the present invention, the third ink is applied following the second ink. When the second ink is applied to the unit area of the recording medium at one time, the second ink is further applied to the adjacent unit area before the dots of the second ink applied earlier are dried and a stable film is formed. Granted. Therefore, it becomes easy to come into contact with the subsequent dots before the surface energy of the earlier dots is sufficiently lowered. Then, the action of the predetermined additive to make it difficult to connect a plurality of dots is not sufficiently exhibited, the resin layer having a gap is hard to be formed, bleeding due to the overflow of ink is likely to occur, and the deterioration of fine wire quality is suppressed. It may be less likely to be done. It is more preferable that the third ink is applied to the unit area of the recording medium in four or more times. From the viewpoint of productivity, it is preferable that the third ink is applied to the unit area of the recording medium in 12 or less steps.

The step of applying the first ink, the second ink, and the third ink to the recording medium, recording the color metallic image, and then laminating the laminating material may be performed. By laminating, it is possible to maintain a high level of robustness such as glossiness, color development, and ozone resistance of a color metallic image for a long period of time. Examples of the laminating material include sheet-shaped or film-shaped resins. Examples of the resin include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, polystyrene, vinyl chloride, and polyamides. Further, a laminating material having an adhesive layer provided on one surface of a sheet or film made of resin can also be used. The thickness of the laminating material is preferably 10 μm or more and 300 μm or less. The laminating step may be carried out by a laminator incorporated in the recording device, may be carried out by a device different from the recording device, or may be carried out by applying heat or pressure.

<First ink>
The first ink is an ink containing silver particles, and is preferably a water-based ink containing at least water as the water-based medium. Since the first ink does not need to be an active energy ray-curable type, it does not need to contain a monomer having a polymerizable group or the like. Hereinafter, the components constituting the first ink will be described.

(Silver particles)
The coloring material of the first ink is silver particles. Silver particles are composed of silver atoms. The silver particles may be composed of other metal atoms, oxygen atoms, sulfur atoms, carbon atoms and the like in addition to the silver atoms. However, the proportion (%) of silver atoms in the silver particles is preferably 50.0% by mass or more and 100.0% by mass or less. The content (mass%) of silver particles in the first ink is preferably 2.00% by mass or more and 15.00% by mass or less, and 2.00% by mass or more and 8.00, based on the total mass of the ink. It is more preferably mass% or less. The first ink may or may not further contain a color material other than silver particles (described as "another color material"). The content (mass%) of the other coloring material is preferably 0.00 times or more and 5.00 times or less, and 0.00 times or more and 3. It is more preferably 00 times or less. The mass ratio is more preferably 0.00 times or more and 0.10 times or less.

Examples of the method for producing silver particles include a method of crushing a silver mass with a crusher such as a ball mill or a jet mill (crushing method), and a method of reducing silver ions or silver complexes with a reducing agent to agglomerate them (reduction method). And so on. In the present invention, it is preferable to use silver particles produced by the reduction method from the viewpoint of ease of controlling the particle size of the silver particles and the dispersion stability of the silver particles.

The silver particles are preferably dispersed using a dispersant such as a surfactant or a resin, and a resin is more preferable as the dispersant. The content (mass%) of the dispersant in the first ink is preferably 0.10% by mass or more and 5.00% by mass or less based on the total mass of the ink.

As the dispersant for silver particles, various surfactants such as anionic surfactant, nonionic surfactant, cationic surfactant, and amphoteric surfactant can be used. Anionic surfactants include fatty acid salts, alkyl sulfates, alkylaryl sulfonates, alkyldiaryl ether disulfonates, dialkyl sulfosuccinates, alkyl phosphates, naphthalene sulfonate formalin condensates, and polyoxyethylene alkyl. Examples thereof include ether sulfate, polyoxyethylene alkyl phosphate ester, and glycerol borate fatty acid ester. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene block copolymers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, fluorine compounds, and silicone compounds. And so on. Examples of the cationic surfactant include an alkylamine salt, a quaternary ammonium salt, an alkylpyridinium salt, an alkylimidazolium salt and the like. Examples of the amphoteric surfactant include alkylamine oxide and phosphatidylcholine. Among them, it is preferable to use at least one surfactant selected from the group consisting of anionic surfactants and nonionic surfactants as the dispersant. As the anionic surfactant, it is preferable to use polyoxyethylene alkyl ether sulfate. Moreover, it is preferable to use polyoxyethylene alkyl ether as a nonionic surfactant. When a surfactant is used as the dispersant, the content (mass%) of the dispersant in the first ink is 0.02 times or more and 1.00 times or less in terms of the mass ratio to the content (mass%) of silver particles. Is preferable.

Further, as the dispersant for silver particles, a resin having a unit having an anionic group and a unit having no anionic group can be used. As the skeleton of the resin, vinyl-based resin, ester-based resin, amino-based resin, acrylic-based resin, epoxy-based resin, urethane-based resin, ether-based resin, amide-based resin, phenol-based resin, silicone-based resin, fluorine-based resin, etc. Can be mentioned. When a resin is used as the dispersant, the content (mass%) of the dispersant in the first ink is 0.05 times or more and 1.00 times or less in terms of the mass ratio with respect to the content (mass%) of silver particles. Is preferable.

The cumulative 50% particle size (d50 _S ) based on the volume of silver particles is preferably 100 nm or less, and more preferably 50 nm or less. The volume-based cumulative 50% particle size refers to the diameter of particles that are integrated from the small particle size side to 50% based on the total volume of the measured particles in the particle size integration curve. When the cumulative 50% particle size is small, the ratio of silver atoms present on the surface of the silver particles to the number of silver atoms per unit mass is large. By increasing the proportion of silver atoms that are easy to move in the silver particles, the silver atoms existing on the surface of a certain silver particle are likely to form a metal bond with the silver atoms existing on the surface of the surrounding silver particles. The particles are easily fused. Therefore, when d50 _S is 50 nm or less, the glossiness tends to be improved. The cumulative 50% particle size is preferably 1 nm or more, and more preferably 10 nm or more.

The cumulative 50% particle size based on the volume of silver particles can be measured as follows, using the first ink or the dispersion liquid of silver particles diluted with water as a sample. After applying the sample to the silicon substrate, water is removed to prepare the sample. Using the obtained sample, 3,000 or more silver particles are observed with a scanning electron microscope (SEM), a transmission electron microscope (TEM), etc., and image processing is performed to obtain the particles defined above. Calculate the diameter. In the examples described later, after observing the silver particles, the particle size was calculated using image analysis / measurement software (trade name “WinROOF2015”, manufactured by Mitani Corporation). The particle size of the silver particles can also be measured by a dynamic light scattering method for the ink or the dispersion liquid. However, since the measured value is likely to fluctuate due to the influence of aggregation and the like, when measuring by the dynamic light scattering method, it is preferable to sufficiently dilute it with water.

[Amount of silver particles added]
^{The amount of silver particles (g / m 2} ) applied to the first ink per unit area of the recording medium is preferably 0.30 g / m ² or more and 1.00 g / m ² or less. The amount of the silver particles applied can be adjusted by adjusting the content of the silver particles in the first ink, the amount of the first ink applied, and the like.

(Surfactant)
The first ink preferably further contains a surfactant in addition to the surfactant that can be used as a dispersant for silver particles. The content (mass%) of the surfactant in the first ink other than the surfactant used as the dispersant for silver particles is 0.10% by mass or more and 2.00% by mass or less based on the total mass of the ink. Is preferable.

Examples of the surfactant include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants and the like. Of these, nonionic surfactants such as ethylene oxide adducts of acetylene glycol and polyoxyethylene alkyl ethers are preferable.

(Multivalent alcohols)
The first ink preferably contains polyhydric alcohols. Polyhydric alcohols are compounds in which one or more carbon atoms constituting a saturated hydrocarbon chain are substituted with a plurality of hydroxy groups. Examples of polyhydric alcohols include 1,2-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, and 1, , 2-Hexanediol, 1,2,6-hexanetriol, 1,2-heptanediol and other dihydric alcohols with 3 to 7 carbon atoms; polyhydric alcohols such as glycerin and trimethylolpropane; -Sugar alcohols such as glucose and sorbitol can be mentioned. Among them, trihydric to hexavalent polyhydric alcohols or sugar alcohols are preferable, and pentavalent or hexavalent polyhydric alcohols or sugar alcohols are more preferable. The content (mass%) of polyhydric alcohols in the first ink is preferably 1.00% by mass or more and 20.00% by mass or less, and 3.00% by mass or more and 10 by mass, based on the total mass of the ink. It is more preferably 0.00% by mass or less.

(Aqueous medium)
The first ink preferably contains water or an aqueous medium which is a mixed solvent of water and a water-soluble organic solvent. The first ink is preferably an ink containing water as a water-based medium (water-based ink). As the water, it is preferable to use deionized water or ion-exchanged water. The water content (mass%) in the first ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and alcohols, (poly) alkylene glycols, glycol ethers, nitrogen-containing polar solvents, sulfur-containing polar solvents and the like can be used. The content (mass%) of the water-soluble organic solvent in the first ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink. When applied to the inkjet recording method, if the content of the water-soluble organic solvent is out of the above range, reliability such as sticking resistance and ejection stability may be slightly lowered.

(Other ingredients)
In addition to the above components, the first ink may contain a water-soluble organic compound that is solid at 25 ° C., such as urea or a derivative thereof. In addition to the above components, the first ink contains, if necessary, a defoaming agent, a pH adjuster, a rust preventive, a preservative, a fungicide, an antioxidant, an antioxidant, a chelating agent, and the like. Various additives may be contained.

(Physical characteristics of the first ink)
The viscosity of the first ink at 25 ° C. is preferably 1 mPa · s or more and 6 mPa · s or less, and more preferably 1 mPa · s or more and 4 mPa · s or less. The surface tension of the first ink at 25 ° C. is preferably 10 mN / m or more and 60 mN / m or less, more preferably 20 mN / m or more and 50 mN / m or less, and 25 mN / m or more and 40 mN / m or less. Is particularly preferable.

<Second ink>
The second ink is an ink that contains a resin and a predetermined additive and does not contain a coloring material, and is preferably a water-based ink that contains at least water as an aqueous medium. Since the second ink does not need to be an active energy ray-curable type, it does not need to contain a monomer having a polymerizable group or the like. Hereinafter, the components constituting the second ink will be described.

(resin)
The second ink contains a resin. The resin may be either a water-soluble resin or resin particles. The term "water-soluble resin" as used herein means that when the resin is neutralized with a base 1.0 times (molar ratio) or more with respect to the acid value, particles whose particle size can be measured are not formed. It means a resin present in a liquid medium. Further, "resin particles" are contained in a liquid medium in a state where particles having a measurable particle size are formed when the resin is neutralized with a base 1.0 times (molar ratio) or more with respect to the acid value. Means the resin present in. The particle size of the resin is measured by the dynamic light scattering method.

Whether a certain resin is a water-soluble resin or resin particles (water-dispersible resin) can be determined according to the method shown below. First, a liquid (resin content: about 10% by mass) containing a resin neutralized with a base (sodium hydroxide, potassium hydroxide, etc.) equal to or more than the acid value is prepared. Next, the prepared liquid is diluted 10-fold (volume basis) with pure water to prepare a sample. Then, the particle size of the resin in the sample is measured by a dynamic light scattering method. If the particles having a particle size are not measured, the resin is determined to be a water-soluble resin, and if the particles having a particle size are measured, the resin is determined to be resin particles. The measurement conditions at this time can be set, for example, SetZero: 30 seconds, the number of measurements: 3 times, and the measurement time: 180 seconds. As the particle size distribution measuring device, a particle size analyzer (for example, UPA-EX150, manufactured by Nikkiso Co., Ltd.) by a dynamic light scattering method can be used. Of course, the particle size distribution measuring device and the measuring conditions to be used are not limited to the above.

The units constituting the resin ^{can be analyzed by nuclear magnetic resonance spectrum (1} H-NMR), pyrolysis gas chromatography and the like. The form of the acrylic resin (random copolymer, block copolymer) can be analyzed by thermal decomposition gas chromatography (EGA-GC / MS) or the like by multivariate analysis.

Examples of the resin include an acrylic resin, a urethane resin, an olefin resin, and the like, and an acrylic resin and a urethane resin are preferable, and an acrylic resin is more preferable. Examples of the olefin resin include polyethylene and polypropylene. The water-soluble resin and the resin particles, which are resins that can be contained in the second ink, can have the same configuration except that the state of existence in the ink is different mainly due to the dissolved state. The water-soluble resin exists in a state of being dissolved in the ink, and the resin particles are present in a state of being dispersed in the ink, that is, as a resin emulsion.

Hereinafter, the details of the resin (water-soluble resin, resin particles) of the acrylic resin and the urethane resin will be described. The description of "(meth) acrylic acid" means "acrylic acid, methacrylic acid", and the description of "(meth) acrylate" means "acrylate, methacrylate".

[Polypoly resin component unit]
The acrylic resin is a resin obtained by (co) polymerizing an acrylic monomer such as (meth) acrylic acid or (meth) acrylic ester. Preferably, a resin composed of a unit having an acid group and a unit having no acid group, which is obtained by copolymerizing a monomer having an acid group and a monomer having no acid group, is used.

Examples of the acid group-containing monomer that becomes a unit having an acid group by polymerization include a monomer having a carboxylic acid group such as (meth) acrylic acid, maleic acid, itaconic acid, and fumaric acid; and a sulfonic acid group such as styrene sulfonic acid. Monomer having a phosphonic acid group such as ethyl 2-phosphonate (meth) acrylate; An anhydride or salt of these monomers can be mentioned. Examples of the salt include alkali metal salts such as lithium, sodium, and potassium, ammonium salts, and organic ammonium salts. As the monomer having an acid group, a monomer having a carboxylic acid group is preferable, and (meth) acrylic acid is more preferable.

Examples of the acid group-free monomer that becomes an acid group-free unit by polymerization are 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 3-methyl-5-hydroxypentyl (meth) acrylate. Monomer having a hydroxy group such as; monomer having an aromatic group such as styrene, α-methylstyrene, benzyl (meth) acrylate; methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl Examples thereof include alkyl (meth) acrylates such as (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. As the monomer having no acid group, a monomer having an aromatic group and alkyl (meth) acrylates are preferable, and a monomer having an aromatic group is more preferable.

[Constituent unit of urethane resin]
The urethane-based resin is a resin synthesized by using at least a polyisocyanate and a component (polyol or polyamine) that reacts with the polyisocyanate, and if necessary, a cross-linking agent or a chain extender. Preferably, a urethane resin obtained by polymerizing a polyisocyanate, a polyol having no acid group, and a polyol having an acid group is used.

Polyisocyanate is a compound having two or more isocyanate groups in its molecular structure. Examples of the polyisocyanate include aliphatic polyisocyanates and aromatic polyisocyanates.

Examples of the aliphatic polyisocyanate include polyisocyanates having a chain structure such as tetramethylene diisocyanate and hexamethylene diisocyanate; and polyisocyanates having a cyclic structure such as isophorone diisocyanate and hydrogenated xylylene diisocyanate. Examples of the aromatic polyisocyanate include tolylene diisocyanate and 1,5-naphthylene diisocyanate. Among them, the polyisocyanate is preferably isophorone diisocyanate.

A polyol is a compound having two or more hydroxy groups in its molecular structure. Examples of the polyol include polyols having no acid group such as polyether polyols, polyester polyols, and polycarbonate polyols; and polyols having an acid group. Further, a polyamine is a compound having two or more "amino groups and imino groups" in its molecular structure.

Examples of the polyether polyol include addition polymers of alkylene oxides and polyols; glycols such as (poly) alkylene glycol and the like. Examples of the polyester polyol include acid esters and the like. Examples of the polycarbonate polyol include alkanediol-based polycarbonate diols. The number average molecular weight of the polyol having no acid group is preferably 400 or more and 4,500 or less.

Examples of the polyol having an acid group include those having an acid group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. The acid group may form a salt, and examples of the salt include alkali metal salts such as lithium, sodium, and potassium, ammonium salts, and organic ammonium salts. As the monomer having an acid group, a polyol having a carboxylic acid group such as dimethylol acetic acid, dimethylol propionic acid, dimethylol butyric acid, and dimethylol butyric acid is preferable, and dimethylol propionic acid and dimethylol butyric acid are more preferable.

Examples of the polyamine include monoamines having a plurality of hydroxy groups such as dimethylolethylamine and diethanolmethylamine; bifunctional polyamines such as ethylenediamine and propylenediamine; and trifunctional or higher functional polyamines such as diethylenetriamine and triethylenetetramine. For convenience, compounds having a plurality of hydroxy groups and one "amino group, imino group" are also listed as "polyamines".

When synthesizing a urethane resin, a cross-linking agent or a chain extender can be used. Usually, the cross-linking agent is used in the synthesis of the prepolymer, and the chain extender is used in carrying out the chain extension reaction with the pre-synthesized prepolymer. Basically, as the cross-linking agent or chain extender, water, polyisocyanate, polyol, polyamine, or the like can be appropriately selected and used depending on the purpose such as cross-linking or chain extension.

[Physical characteristics of resin]
The acid value of the acrylic resin is preferably 0 mgKOH / g or more and 300 mgKOH / g or less, and more preferably 100 mgKOH / g or more and 300 mgKOH / g or less. The acid value of the urethane resin is preferably 45 mgKOH / g or more and 70 mgKOH / g or less. The acid value of the resin can be measured by potentiometric titration. The weight average molecular weight of the acrylic resin is preferably 1,000 or more and 30,000 or less, and more preferably 3,000 or more and 15,000 or less. The weight average molecular weight of the urethane resin is preferably 8,000 or more and 22,000 or less. The weight average molecular weight of the resin can be measured as a polystyrene-equivalent value by gel permeation chromatography.

[Resin content]
The content (mass%) of the resin in the second ink is preferably 0.10% by mass or more and 20.00% by mass or less, and 1.00% by mass or more and 10.00% by mass, based on the total mass of the ink. It is more preferably less than or equal to%. When a water-soluble resin is used, the content (mass%) of the water-soluble resin in the second ink is preferably 0.10% by mass or more and 10.00% by mass or less based on the total mass of the ink, and is 0. . More preferably, it is 10% by mass or more and 5.00% by mass or less. When resin particles are used, the content (mass%) of the resin particles in the second ink is preferably 0.10% by mass or more and 10.00% by mass or less based on the total mass of the ink, and is 0. . More preferably, it is 10% by mass or more and 5.00% by mass or less. The resin content (mass%) in the second ink is preferably the same as or higher than the resin content (mass%) in the third ink.

[Form of water-soluble resin]
The water-soluble resin is preferably an acrylic random copolymer containing a unit having an acid group and a unit having no acid group.

[Form and physical properties of resin particles]
The resin particles are preferably composed of an acrylic resin because thin film interference can be suppressed at a higher level. In particular, the resin particles are preferably composed of a core containing a unit having no acid group and a shell containing a unit having an acid group. In the resin particles having a core-shell structure, the resins constituting the core and the shell have different refractive indexes. When light hits the resin layer containing the resin particles having a core-shell structure, the light is reflected by each of the resin constituting the shell and the resin constituting the core, and interference light corresponding to a plurality of optical path differences is generated. The colors of these interference lights are mixed and whitened more easily, so that thin film interference can be suppressed at a higher level. In addition, when the third ink is applied onto the resin layer, the hydrophilicity of the shell containing the unit having an acid group draws in the water of the third ink, which makes it easier for the liquid component to permeate, which is more excellent. Fine wire quality can be obtained. Further, the core containing the unit having no acid group contributes to maintaining the shape of the resin particles after the second ink containing the resin particles adheres to the silver layer, and provides a resin layer having voids derived between the resin particles. Can be formed. Since the liquid component of the third ink to be added later smoothly permeates through the voids, better fine wire quality can be obtained.

The cumulative 50% particle size (d50) of the resin particles based on the volume is preferably 50 nm or more and 300 nm or less. The volume-based cumulative 50% particle size refers to the diameter of particles that are integrated from the small particle size side to 50% based on the total volume of the measured particles in the particle size integration curve.

[Combined use of water-soluble resin and resin particles]
When a second ink containing a water-soluble resin is applied onto the silver layer without containing resin particles, the resin layer is formed by the water-soluble resin. When the third ink is applied onto the resin layer, a coloring material layer is formed while a part of the water-soluble resin constituting the resin layer is dissolved again in the liquid component of the third ink. In this case, a portion where the interface between the resin layer and the coloring material layer is mixed and a portion which is clearly separated are generated, and unevenness is present at the interface. The light transmitted through the color material layer is scattered by the unevenness of the interface, and interference light corresponding to various optical path differences is generated, and the colors of the interference light are mixed and whitened, so that the thin film interference is suppressed. Will be higher. However, since it is difficult for the liquid component of the third ink to permeate into the resin layer formed of the water-soluble resin, the degree to which deterioration of fine wire quality is suppressed may be low.

On the other hand, when a second ink containing resin particles is applied onto the silver layer without containing the water-soluble resin, the resin particles form a resin layer. When the third ink is applied onto the resin layer, the liquid component of the third ink rapidly permeates through the voids derived between the resin particles existing in the resin layer, so that better fine wire quality can be obtained. Can be done. However, in the third ink applied to the resin layer formed by the resin particles, the liquid component rapidly permeates as described above, and more coloring material remains on the resin layer to form the coloring material layer. .. In this case, the interface between the resin layer and the coloring material layer tends to be clearly separated. When light is incident on an image having such a layer structure, the degree of suppressing thin film interference may be reduced when a situation occurs in which the light reflected from each layer is intensified.

When the second ink containing both the water-soluble resin and the resin particles is used, it is possible to achieve both the effect of suppressing the thin film interference by the water-soluble resin and the expression of excellent fine wire quality by the resin particles at a high level. When a water-soluble resin and resin particles are used, the content (mass%) of the resin particles in the second ink is 0.30 times or more and 0.70 times or less in terms of the mass ratio to the resin content (mass%). Is preferable. When the mass ratio is less than 0.30 times, the resin particles occupying the resin forming the resin layer are too small, and the voids in the resin layer tend to be reduced, so that bleeding due to ink overflow is likely to occur, and the fine wire quality. The degree to which the decrease in the amount of plastic is suppressed may be low. On the other hand, when the mass ratio is more than 0.70 times, the number of resin particles in the resin forming the resin layer is too large, and the number of voids in the resin layer tends to increase. It tends to be in a clearly separated state, and the degree of suppressing thin film interference may be low.

[Amount of resin applied]
The amount of the resin applied to the second ink (g / m ² ) per unit area of the recording medium is preferably 0.01 g / m ² or more and 1.00 g / m ² or less. The amount of the resin applied can be adjusted by adjusting the content of the resin in the second ink, the amount of the second ink applied, and the like. The amount of resin applied to the second ink (g / m ² ) per unit area of the recording medium is 0.15 times or more as a ratio to the amount of silver particles applied to the first ink (g / m ^2). It is preferably 00 times or less. If the ratio is less than 0.15 times, the amount of resin in the second ink is too small with respect to the silver particles, so that the third ink applied to the resin layer after that tends to come into direct contact with the silver layer, resulting in a thin film. The degree of suppression of interference may be low. On the other hand, when the ratio is more than 2.00 times, the resin of the second ink is too much for the silver particles, so that not only the pores of the silver layer but also the voids of the resin layer are likely to be clogged. The degree to which deterioration of fine wire quality is suppressed may be reduced. The ratio is more preferably 1.00 times or less.

(Additive)
The second ink contains a predetermined additive. Additives include (1) a compound having an ethylene oxide group, a hydroxy group, or an anionic group and a siloxane structure, or (2) an ethylene oxide group, a hydroxy group, or an anionic group, and a perfluoroalkyl structure. It is a compound having. Hereinafter, (1) may be referred to as a “siloxane compound” and (2) may be referred to as a “perfluoroalkyl compound”. The content (mass%) of the predetermined additive in the second ink is preferably 0.05% by mass or more and 5.00% by mass or less, and 0.10% by mass or more 1 based on the total mass of the ink. It is more preferably 0.00% by mass or less.

The siloxane compound is a compound having an ethylene oxide group, a hydroxy group, or an anionic group and a siloxane structure (a repeating unit of Si—O). The ethylene oxide group, anionic group, and hydroxy group are hydrophilic groups, and the siloxane structure is a hydrophobic group. The siloxane compound is classified into a side chain type, a single-ended type, a double-ended type, an ABN type, etc. according to the bonding position of the hydrophilic group to the siloxane structure, and it is preferable to use the side chain type siloxane compound.

The compound having a perfluoroalkyl group is a compound having an ethylene oxide group, a hydroxy group, or an anionic group and a perfluoroalkyl structure. The ethylene oxide group, anionic group, and hydroxy group are hydrophilic groups, and the perfluoroalkyl structure is a hydrophobic group. Examples of the perfluoroalkyl compound include those having a linear perfluoroalkyl group structure and those having a branched chain structure.

As the additive, it is preferable to use a siloxane compound because more excellent fine wire grade can be obtained. Compared to the perfluoroalkyl structure containing a carbon-carbon bond, the siloxane structure containing a carbon-silicon bond is more likely to be oriented toward the interface because the hydrophobic group has a flexible three-dimensional structure. Therefore, when the siloxane compound is used, the additive is more likely to be oriented on the dot surface more quickly after the dots of the second ink are attached to the silver layer, and more excellent fine wire quality can be obtained. In particular, it is preferable to use a siloxane compound having a siloxane structure repeating number of 20 or more. By the hydrophobic interaction of the siloxane structure, which is the hydrophobic group of the siloxane compound, with the resin in the second ink, the permeation of the siloxane compound into the recording medium is effectively suppressed, and the siloxane compound is efficiently oriented on the dot surface. When the number of repetitions of the siloxane structure is small, the hydrophobic interaction is weakened, the number of siloxane compounds that can be oriented on the dot surface is reduced, and the degree of suppression of the deterioration of fine wire quality may be reduced. The number of repetitions of the siloxane structure in the siloxane compound is preferably 100 or less.

Moreover, as a predetermined additive, one having an ethylene oxide group is preferable. As described above, by utilizing the hydrophobic interaction with the resin by the hydrophobic group of the additive, the penetration of the additive is suppressed and the additive can be oriented on the dot surface. On the other hand, if the hydrophobic group of the additive is lengthened in order to strongly generate the hydrophobic interaction, the hydrophobicity of the additive as a whole becomes too high, and it becomes easy to aggregate in the ink. Therefore, it is preferable to use an additive having an ethylene oxide group whose hydrophilicity can be easily adjusted by the number of repetitions as compared with the case of a hydroxy group or an anionic group.

Further, it is preferable that the HLB value obtained by the Griffin method of a predetermined additive is 8 or more and 16 or less. The HLB value by the Griffin method can be calculated from the formula of "HLB value = 20 x formula amount of ethylene oxide group of additive / molecular weight of additive". The HLB value obtained by the Griffin method is a physical property value indicating the degree of hydrophilicity or lipophilicity of the additive (compound), and takes a value of 0 to 20. The smaller the HLB value, the higher the lipophilicity, and the larger the HLB value, the higher the hydrophilicity. When the HLB value is less than 8, the hydrophobicity of the additive is too high, the additive tends to aggregate, and the additive is less likely to be oriented on the dot surface, so that the deterioration of fine wire quality is suppressed to a low degree. May become. On the other hand, when the HLB value is more than 16, the hydrophilicity of the additive is too high, and the additive is also difficult to be oriented on the dot surface, so that the degree of suppressing the deterioration of the fine wire quality may be low. The HLB value obtained by the Griffin method is a physical property value applied to a compound having no ionic group (nonionic compound).

[Amount of additive added]
^{The amount (g / m 2} ) of the predetermined additive applied to the second ink per unit area of the recording medium is preferably 0.01 g / m ² or more and 1.00 g / m ² or less. The amount of the predetermined additive applied can be adjusted by adjusting the content of the predetermined additive in the second ink, the amount of the second ink applied, and the like. The amount of the additive applied to the second ink (g / m ² ) per unit area of the recording medium is 0.05 times or more as a ratio to the amount of silver particles applied to the first ink (g / m ^2). It is preferable to have. When the ratio is less than 0.05 times, the amount of the additive oriented to the dot surface of the second ink is too small with respect to the silver particles, so that the surface energy of the dots is not sufficiently lowered and the deterioration of the fine wire quality is suppressed. The degree of being done may be low. The ratio is preferably 7.00 times or less, more preferably 1.00 times or less, and particularly preferably 0.50 times or less.

(Aqueous medium)
The second ink preferably contains water or an aqueous medium which is a mixed medium of water and a water-soluble organic solvent. The second ink is preferably an ink containing water as a water-based medium (water-based ink). As the water, it is preferable to use deionized water or ion-exchanged water. The water content (mass%) in the second ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and alcohols, (poly) alkylene glycols, glycol ethers, nitrogen-containing polar solvents, sulfur-containing polar solvents and the like can be used. The content (mass%) of the water-soluble organic solvent in the second ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink. When applied to the inkjet recording method, if the content of the water-soluble organic solvent is out of the above range, reliability such as sticking resistance and ejection stability may be slightly lowered.

(Other ingredients)
In addition to the above components, the second ink may contain a water-soluble organic compound solid at 25 ° C. such as urea or a derivative thereof, trimethylolpropane, and trimethylolethane. In addition to the above components, the second ink contains a surfactant, an antifoaming agent, a pH adjuster, a rust preventive, a preservative, a fungicide, an antioxidant, an antioxidant, and an antioxidant, if necessary. Various components such as a chelating agent may be contained.

(Physical characteristics of the second ink)
The viscosity of the second ink at 25 ° C. is preferably 1 mPa · s or more and 6 mPa · s or less, and more preferably 1 mPa · s or more and 4 mPa · s or less. The surface tension of the second ink at 25 ° C. is preferably 10 mN / m or more and 60 mN / m or less, more preferably 20 mN / m or more and 50 mN / m or less, and 25 mN / m or more and 40 mN / m or less. Is particularly preferable.

<Third ink>
The third ink is an ink containing a coloring material, and is preferably a water-based ink containing at least water as the water-based medium. Since the third ink does not need to be an active energy ray-curable type, it does not need to contain a monomer having a polymerizable group or the like. Hereinafter, the components constituting the third ink will be described.

(Color material)
Examples of the coloring material include dyes and pigments. The content (mass%) of the coloring material in the third ink is preferably 0.05% by mass or more and 15.00% by mass or less, and 0.10% by mass or more and 10.00% by mass, based on the total mass of the ink. It is more preferably mass% or less.

The dye is preferably an anionic dye. The dye is preferably a compound having at least one selected from the group consisting of an azo skeleton, a phthalocyanine skeleton, an anthrapyridone skeleton, and a xanthene skeleton. Among them, a dye having a stable dissolved state in the ink and a property of easily agglomerating in the recording medium is preferable because both the storage stability of the ink and the color development property of the color metallic image can be achieved at the same time. .. Such properties can be adjusted by the skeleton of the dye and the number of anionic groups.

Examples of the pigment include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindoleone, imidazolone, diketopyrrolopyrrole, and dioxazine. As a pigment dispersion method, a resin-dispersed pigment using a resin as a dispersant, a self-dispersing pigment in which a hydrophilic group is bonded to the particle surface of the pigment, or the like can be used. Further, a resin-bonded pigment in which a resin is chemically bonded to the particle surface of the pigment, a microcapsule pigment in which the particle surface of the pigment is coated with a resin or the like can be used.

From the viewpoint of glossiness of a color metallic image, it is preferable to use a dye or a resin dispersion pigment using a resin dispersant as a coloring material. Further, from the viewpoint of color development of a color metallic image, it is preferable to use a pigment as a coloring material. In order to record a color metallic image having color-developing property, it is important that the interfaces of the silver layer and the color material layer are not mixed and exist separately from each other in the recording medium. In the case of dye ink, it is difficult to form a color material layer separated from the silver layer. This is because the dye having no particle shape does not easily stay on the silver layer and sinks into the inside of the silver layer or the recording medium. On the other hand, in the case of pigment ink, a color material layer separated from the silver layer is likely to be formed. This is because the pigment has the shape of particles and tends to stay on the silver layer.

The cumulative 50% particle size (d50) based on the volume of the pigment is preferably 10 nm or more and 300 nm or less. The volume-based cumulative 50% particle size refers to the diameter of particles that are integrated from the small particle size side to 50% based on the total volume of the measured particles in the particle size integration curve. When the mass of the particles is constant, the total surface area is large when the particle size is small, and the total surface area is small when the particle size is large. When d50 is less than 10 nm, the total surface area of the particles tends to be large, the hydrophobic interaction between the pigment particles tends to be strong, and a high level of storage stability of the third ink may not be sufficiently obtained. .. On the other hand, when d50 is more than 300 nm, the particle size of the pigment is large, so that a high level of color development and glossiness may not be sufficiently obtained.

(Aqueous medium)
The third ink preferably contains water or an aqueous medium which is a mixed medium of water and a water-soluble organic solvent. The third ink is preferably an ink containing water as a water-based medium (water-based ink). As the water, it is preferable to use deionized water or ion-exchanged water. The water content (mass%) in the third ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink. The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and alcohols, (poly) alkylene glycols, glycol ethers, nitrogen-containing polar solvents, sulfur-containing polar solvents and the like can be used. The content (mass%) of the water-soluble organic solvent in the third ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink. When applied to the inkjet recording method, if the content of the water-soluble organic solvent is out of the above range, reliability such as sticking resistance and ejection stability may be slightly lowered.

(Other ingredients)
In addition to the above components, the third ink may contain a water-soluble organic compound solid at 25 ° C. such as urea or a derivative thereof, trimethylolpropane, and trimethylolethane. In addition to the above components, the third ink contains a surfactant, a resin, an antifoaming agent, a pH adjuster, a rust preventive, a preservative, a fungicide, an antioxidant, and a reduction inhibitor, if necessary. , And various additives such as chelating agents may be contained.

The third ink may contain a resin. The resin is added to the ink for (i) stabilizing the dispersed state of the pigment, that is, as a resin dispersant or an auxiliary thereof, and (ii) improving various characteristics of the recorded image. be able to. When the third ink contains a resin, the content (mass%) of the resin in the third ink is 1.20 times or less as a mass ratio to the content (mass%) of the coloring material in the third ink. It is preferable to have. When the mass ratio exceeds 1.20 times, not only the color development efficiency of the color material layer constituting the image tends to decrease, but also light scattering by the resin occurs, and a high level of glossiness is sufficiently obtained. It may not be possible. The mass ratio is preferably 0.10 times or more.

(Physical characteristics of the third ink)
The viscosity of the third ink at 25 ° C. is preferably 1 mPa · s or more and 6 mPa · s or less, and more preferably 1 mPa · s or more and 4 mPa · s or less. The surface tension of the third ink at 25 ° C. is preferably 10 mN / m or more and 60 mN / m or less, more preferably 20 mN / m or more and 50 mN / m or less, and 25 mN / m or more and 40 mN / m or less. Is particularly preferable.

<Recording medium>
Any recording medium may be used, but it is preferable to use a permeable recording medium such as plain paper or a recording medium having an ink receiving layer (glossy paper or art paper). Among them, it is preferable to use a recording medium having an ink receiving layer such as glossy paper because the recorded image has an excellent metallic feeling. A recording medium such as glossy paper used in an inkjet recording method usually includes an ink receiving layer containing a halide ion such as a chloride ion. Chloride ions are contained in cationic compounds such as polydiallyldimethylammonium chloride and polyaluminum chloride.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded. In addition, regarding the amount of components, those described as "part" and "%" are based on mass unless otherwise specified.

<Preparation of dispersion of silver particles>
A dispersion liquid of silver particles having a silver particle content of 10.0% and a resin content of 3.0% was prepared with reference to the description of Example 2 of JP-A-2010-507727. did. The cumulative 50% particle size based on the volume of silver particles was 42 nm. The cumulative 50% particle size based on the volume of silver particles was measured by the following procedure. First, a dispersion liquid diluted about 2,000 times (mass basis) with ion-exchanged water was applied to a substrate made of a silicon material, and the water was removed by drying to prepare a sample. Next, using the obtained sample, observe 3,000 or more silver particles with a scanning electron microscope, and use image analysis / measurement software (trade name "WinROOF2015", manufactured by Mitani Shoji) to create an image. It was calculated by processing.

<Synthesis of siloxane compound>
(Analytical method of siloxane compound)
The characteristics of each of the synthesized siloxane compounds having the structures represented by the general formulas (1) and (2) were specified from the weight average molecular weight calculated by the method described later.

The weight average molecular weight of the siloxane compound was determined by gel permeation chromatography as a polystyrene-equivalent value. A siloxane compound was added to tetrahydrofuran to dissolve it and filtered through a membrane filter to prepare a sample. The sample was adjusted so that the content of the siloxane compound was about 0.1%. For this sample, the weight average molecular weight of the siloxane compound was measured under the following conditions.
-Measuring device: Product name "Waters 2695 Separations Model", manufactured by Waters-RI (refractive index) detector: Product name "2414 detector", manufactured by Waters-Column: 4-column column with product name "Shodex KF-806M", manufactured by Showa Denko・ Eluent: tetrahydrofuran ・ Flow velocity: 1.0 mL / min
・ Oven temperature: 40 ℃
-Sample injection amount: 100 μL
-Detector: RI (refractive index).

In calculating the weight average molecular weight of the siloxane compound, standard polystyrene samples (trade names "PS-1" and "PS-2", manufactured by Polymer Laboratories, molecular weights: 7500000, 2560000, 841700, 377400, 320,000, 210500, 148000, 96000) , 59500, 50400, 28500, 20650, 10850, 5460, 2930, 1300, 580).

(Siloxane compounds 1, 3-12)
By a conventional method, siloxane compounds 1 and 3 to 12 having a structure (side chain type) represented by the following general formula (1) were synthesized, respectively. Table 1 shows the characteristics of siloxane compounds 1, 3 to 12.

(Siloxane compound 2)
A siloxane compound 2 having a structure (single-ended type) represented by the following general formula (2) was synthesized by a conventional method. Table 1 shows the characteristics of the siloxane compound 2.

<Preparation of the first ink>
Each component (unit:%) shown in the upper part of Table 2 was mixed, sufficiently stirred, and then pressure-filtered with a cellulose acetate filter (manufactured by Advantech) having a pore size of 0.8 μm to obtain a first ink. Acetyleneol E100 is a nonionic surfactant manufactured by Kawaken Fine Chemicals.

<Preparation of water-soluble resin>
(Water-soluble resin 1)
After putting 100.0 parts of ethylene glycol monobutyl ether in a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux tube, nitrogen gas is introduced into the flask and the temperature rises to 110 ° C. with stirring. It was warm. Ethylene glycol monobutyl ether in which a mixture of monomers (40.0 parts of styrene, 40.0 parts of methyl methacrylate, and 20.0 parts of acrylic acid) and 1.3 parts of a polymerization initiator (t-butyl peroxide) are dissolved. Was dropped into the flask over 3 hours. After aging for 2 hours, ethylene glycol monobutyl ether was removed under reduced pressure to obtain a water-soluble resin 1 as a solid. The obtained water-soluble resin 1 is neutralized with potassium hydroxide having an acid value of 1.0 times (molar ratio), an appropriate amount of ion-exchanged water is added, and the solution is dissolved at 80 ° C. to increase the resin content. A liquid containing 10.0% of the water-soluble resin 1 was obtained.

(Water-soluble resin 2)
The type of monomer was changed to 40.0 parts of benzyl methacrylate, 40.0 parts of n-butyl acrylate, and 20.0 parts of p-styrene sulfonic acid. Except for this, a liquid containing the water-soluble resin 2 having a resin content of 8.0% was obtained by the same procedure as that of the water-soluble resin 1.

(Water-soluble resin 3)
A "fluorene resin" was synthesized with reference to the description in Patent Document 2. This resin is a water-soluble urethane-based resin having a weight average molecular weight of 3,300. The obtained resin is neutralized with potassium hydroxide having an acid value of 1.0 times (molar ratio), an appropriate amount of ion-exchanged water is added, and the mixture is dissolved at 80 ° C., and the resin content is 10.0. %, A liquid containing the water-soluble resin 3 was obtained.

<Preparation of resin particles>
(Resin particles 1 to 6)
2.0 parts of n-hexadecane, 1.0 part of polymerization initiator (2,2'-azobis- (2-methylbutyronitrile)), and monomer (unit: part) of the core part shown in Table 3 are mixed. , Stirred for 30 minutes to give a mixture. The abbreviations of the monomers indicate St: styrene, nBA: n-butyl acrylate, AA: acrylic acid. The obtained mixture was added dropwise to 229.5 parts of water in which 0.27 parts of sodium dodecyl sulfate was dissolved, and then the mixture was stirred for 30 minutes to obtain a monomer mixture in the core part. Then, using an ultrasonic homogenizer (trade name "S-150D Digital Sonifier", manufactured by Branson), the monomer mixture in the core is irradiated with ultrasonic waves under the conditions of output: 400 W, frequency: 20 kHz, and 3 hours. , The components were dispersed. Then, the resin was synthesized by polymerizing at 80 ° C. for 4 hours in a nitrogen atmosphere to obtain a dispersion liquid containing an acrylic resin serving as a core portion of the resin particles.

Next, 200.0 parts of ion-exchanged water, 0.1 part of potassium persulfate, 8.0 parts of sodium dodecyl sulfate, and the monomer (unit: part) of the shell part shown in Table 3 were emulsified, and the monomer for the shell part was emulsified. I got something. Monomer abbreviations indicate MMA: methyl methacrylate, nBA: n-butyl acrylate, AA: acrylic acid, StSA: styrene sulfonic acid. 0.1 part of potassium persulfate and 600.0 parts of ion-exchanged water were added to 240.0 parts of the dispersion liquid containing the resin serving as the core part obtained above, and the temperature was raised to 75 ° C. under a nitrogen atmosphere. To this dispersion, 350.0 parts of an emulsion of the monomer for the shell part was added dropwise over 3 hours. Then, the temperature was raised to 85 ° C., and the mixture was stirred for 2 hours to polymerize to synthesize an acrylic resin to be a shell portion of the resin particles. Then, the mixture is cooled to 25 ° C., an appropriate amount of ion-exchanged water and an aqueous potassium hydroxide solution are added, and each resin particle having a pH of 8.5 and a resin content of 10.0% is contained. Obtained liquid. All of the resin particles 1 to 6 were resin particles composed of a core and a shell.

(Resin particles 7)
9.0 parts of styrene, 1.5 parts of acrylic acid, 0.1 part of sodium dodecyl sulfate, in a 4-necked flask with a capacity of 300 mL equipped with a stirring seal, a stirring rod, a reflux condenser, a septum rubber, and a nitrogen introduction tube. And 100.0 parts of distilled water were added and mixed. The flask was placed in a constant temperature bath at 70 ° C., nitrogen gas was introduced into the flask while stirring the contents at 300 rpm, and nitrogen substitution was performed for 1 hour. Then, potassium persulfate dissolved in 100.0 parts of distilled water was injected into the flask using a syringe to initiate polymerization. The completion of polymerization was confirmed by monitoring the molecular weight by gel permeation chromatography. After purification by ultrafiltration, an appropriate amount of ion-exchanged water and an aqueous solution of potassium hydroxide are added to a liquid containing resin particles 7 having a pH of 8.5 and a resin content of 10.0%. Got The resin particles 7 were single-layer resin particles composed of an acrylic resin.

(Resin particles 8)
An appropriate amount of ion-exchanged water is added to a commercially available aqueous dispersion (trade name "Takelac W-6061", manufactured by Mitsui Chemicals, Inc.) containing resin particles composed of urethane-based resin to adjust the concentration, and the resin particles 8 are contained. Obtained liquid.

<Preparation of second ink>
Each component (unit:%) shown in the upper part of Tables 4 and 5 is mixed, sufficiently stirred, and then pressure-filtered with a cellulose acetate filter (manufactured by Advantech) having a pore size of 0.8 μm to obtain a second ink. It was. Acetyleneol E100 is a nonionic surfactant manufactured by Kawaken Fine Chemicals. As the perfluoroalkyl compounds 1 to 3, those shown below were used.
-Perfluoroalkyl compound 1 (trade name "Zonil FS-3100", manufactured by DuPont, perfluoroalkylethylene oxide adduct)
-Perfluoroalkyl compound 2 (trade name "Zonil FSO-100", manufactured by DuPont, perfluoroalkylethylene oxide adduct)
-Perfluoroalkyl compound 3 (trade name "Megafuck F-410", manufactured by DIC, perfluoroalkylcarboxylic acid salt)

<Preparation of pigment dispersion liquid>
(Pigment dispersion liquid 1)
C. I. A mixture was obtained by mixing 24.0 parts of Pigment Yellow 74, 48.0 parts of an aqueous solution of a resin dispersant, and 28.0 parts of ion-exchanged water. As the aqueous solution of the resin dispersant, a styrene-acrylic acid copolymer (trade name "John Krill 680", manufactured by BASF) is neutralized with potassium hydroxide having an acid value of 0.85 times (molar ratio), and an appropriate amount is used. An aqueous solution having a water-soluble resin content of 20.0%, which was obtained by adding the ion-exchanged water of the above, was used. The obtained mixture and 85 parts of zirconia beads having a diameter of 0.3 mm were placed in a batch type vertical sand mill (manufactured by Imex) and dispersed for 3 hours while cooling with water. Then, it was centrifuged to remove coarse particles. A pigment dispersion 1 having a pigment content of 20.0% and a resin content of 8.0% was prepared by pressure filtration through a cellulose acetate filter (manufactured by Advantech) having a pore size of 3.0 μm.

(Pigment dispersion liquid 2)
Pigment C.I. I. A pigment dispersion liquid 2 having a pigment content of 20.0% and a resin content of 8.0% was prepared by the same procedure as that of the pigment dispersion liquid 1 except that the pigment blue was changed to 15: 3. ..

(Pigment dispersion liquid 3)
A pigment dispersion liquid 3 having a pigment content of 20.0% and a resin content of 8.0% was prepared by the same procedure as that of the pigment dispersion liquid 1 except that the pigment was changed to carbon black.

<Preparation of third ink>
Each component (unit:%) shown in Table 6 was mixed, sufficiently stirred, and then pressure-filtered with a cellulose acetate filter (manufactured by Advantech) having a pore size of 0.8 μm to obtain a third ink. Acetyleneol E100 is a trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals.

<Evaluation>
Each ink prepared above was filled in an ink cartridge and set in an inkjet recording device (PIXUS PRO 10-S, manufactured by Canon) equipped with a recording head that ejects ink by the action of thermal energy. In this recording head, the ejection port rows of the first ink, the second ink, and the third ink are arranged along the direction orthogonal to the main scanning direction. In this embodiment, an image recorded under the condition that eight drops of about 3.8 ng of ink are applied to a unit area (1 pixel) of 1/600 inch × 1/600 inch is assumed to have a recording duty of 100%. Define.

The first ink was set to be ejected from the ejection port corresponding to 1/3 of the ejection port row on the upstream side in the sub-scanning direction. The second ink was set to be ejected from the ejection port corresponding to 1/3 of the ejection port row at the center in the sub-scanning direction. Further, the third ink is set to be ejected from the ejection port corresponding to 1/3 of the ejection port row on the downstream side in the sub-scanning direction.

In order to keep the application time difference between the first ink, the second ink, and the third ink constant, for convenience, each ink was ejected only in one direction of the main scan of the recording head to record an image. The first ink was ejected from the ejection port row on the upstream side and applied to the recording medium. After that, while the carriage on which the recording head was mounted was returned to the home position, the recording medium was conveyed in the sub-scanning direction with a width corresponding to the area to which the ink was applied. The second ink and the third ink were also applied to the recording medium in the same procedure as in the case of the first ink. The application time difference between the first ink and the second ink was 10 seconds.

The left side of Table 7 shows the type of each ink, the order of application, the recording duty, and the number of main scans (number of recording passes) when the second ink is applied to the unit area. Further, the application amount of silver in the first ink _{A S,} the application amount of the resin of the second ink _{A R,} the applied amount of the second ink additive _{A A,} the value of A A / _{A S,} the A R / _{A S} Indicates a value. As the recording medium, glossy paper (trade name "Canon Photo Paper / Glossy Pro [Platinum Grade] PT-201", manufactured by Canon) was used. The ink receiving layer of this recording medium contains chloride ions.

In the present invention, A and B are set to an acceptable level, and C is set to an unacceptable level in the evaluation criteria of each of the following items. The evaluation results are shown on the right side of Table 7.

(Thin film interference suppression)
Under the conditions shown on the left side of Table 7, the first ink and the second ink are overlaid on the entire surface of the A4 size recording medium, and further, the third ink is overlaid with a predetermined recording duty to apply 2 cm ×. A pattern containing 6 types of 2 cm solid images was recorded. Separately from this, a pattern including 6 types of solid images of 2 cm × 2 cm was recorded with a predetermined recording duty using only the third ink. In any of the above cases, the recording duty of the third ink was set to 6 types of 50%, 60%, 70%, 80%, 90%, and 100%. For solid images (6 types of recording duty) recorded using 3 types of ink, the hue angle h in ^{the L *} a ^* b ^{* display system specified by the CIE (Commission Internationale de l'Eclairage) was measured.} Further, the hue angle h was measured in the same manner for the solid image (6 types of recording duty) recorded using only the third ink. The hue angle h is SCI mode (conditions including specular reflected light), measurement diameter: 3 mm, viewing angle: 2 using an integrating sphere type spectrophotometer (trade name "CM-2600d", manufactured by Konica Minolta). °, light source: Measured under the condition of D50.

The difference in hue angle is calculated for the combination of solid images with the same recording duty, and the difference Δh between the maximum value and the minimum value of the difference in hue angle for six types of solid images is calculated. The suppression of thin film interference was evaluated according to the above.
A: Δh was less than 10.
B: Δh was 10 or more and less than 20.
C: Δh was 20 or more.

(Thin wire quality)
The first ink and the second ink were superposed on the recording medium under the conditions shown on the left side of Table 7, and further, using the third ink, under the conditions of font: MS Mincho and font size: 24 points, "Den. "Is recorded. The part including "electricity" of the image was saved as image data by an optical microscope (trade name "ZEISS SteREO Discovery V8", manufactured by ZEISS, magnification: 8 times, with scale). This image data was read by image processing software (trade name "Adobe Photoshop CC", manufactured by Adobe System), and the line width of the vertical line of the fourth stroke of "Den" was measured by the ruler tool of the software. The line width of the vertical line of the actual image was calculated from the scale of the image data, and the fine line quality was evaluated from the average value of the three places according to the evaluation criteria shown below. For Reference Examples 3 and 4 in which the third ink was not used, the fine wire quality was not evaluated.
A: The line width was less than 400 μm.
B: The line width was 400 μm or more and less than 500 μm.
C: The line width was 500 μm or more.

Further, the color metallic image recorded in Example 1 was laminated using a laminator (trade name "Arctic Titan 165", manufactured by Japan GBC). As the laminating material, a polyethylene terephthalate film having an adhesive layer (trade name "G-030EV50", manufactured by Lintec, thickness 50 μm) was used. By laminating a color metallic image, it was possible to maintain a high level without impairing glossiness, color development, and ozone resistance.

Claims (9)

An inkjet recording method in which ink is ejected from an inkjet recording head to record an image on a recording medium.
A step of applying the first ink to the recording medium, a step of applying the second ink to the recording medium so as to overlap at least a part of the region to which the first ink is applied, and the first ink and the first ink. The step of applying the third ink to the recording medium so as to overlap at least a part of the area to which the ink is applied is provided.
The first ink is an ink containing silver particles.
The second ink is an ink containing a resin and an additive and does not contain a coloring material, and the additive comprises (1) an ethylene oxide group, a hydroxy group, or an anionic group and a siloxane structure. It is selected from the group consisting of a compound having a compound and (2) a compound having an ethylene oxide group, a hydroxy group, or an anionic group and a perfluoroalkyl structure.
An inkjet recording method, wherein the third ink is an ink containing a coloring material. The inkjet recording method according to claim 1, wherein the HLB value obtained by the Griffin method of the additive is 8 or more and 16 or less. The inkjet recording method according to claim 1 or 2, wherein the additive contains the compound having the siloxane structure, and the number of repetitions of the siloxane structure in the compound having the siloxane structure is 20 or more. The inkjet recording method according to any one of claims 1 to 3, wherein the resin of the second ink contains a water-soluble resin and resin particles. The inkjet recording method according to claim 4, wherein the resin particles are composed of a core including a unit having no acid group and a shell containing a unit having an acid group. The amount of the additive applied to the second ink (g / m ² ) per unit area of the recording medium is 0 as a ratio to the amount of the silver particles applied to the first ink (g / m ^2). The inkjet recording method according to any one of claims 1 to 5, which is 0.05 times or more. The amount of the resin applied to the second ink (g / m ² ) per unit area of the recording medium is the ratio of the amount of the silver particles applied to the first ink (g / m ² ) to 0. The inkjet recording method according to any one of claims 1 to 6, wherein the ink jet recording method is 15 times or more and 2.00 times or less. The inkjet recording method according to any one of claims 1 to 7, wherein the second ink is applied to a unit area of the recording medium in a plurality of times. An inkjet recording device used to eject ink from an inkjet recording head and record an image on a recording medium.
Means for applying the first ink to the recording medium, means for applying the second ink to the recording medium so as to overlap at least a part of the area to which the first ink is applied, and the first ink and the second ink. A means for applying the third ink to the recording medium is provided so as to overlap at least a part of the area to which the ink is applied.
The first ink is an ink containing silver particles.
The second ink is an ink containing a resin and an additive and does not contain a coloring material, and the additive contains (1) an ethylene oxide group, a hydroxy group, or an anionic group and has a siloxane structure. It is selected from the group consisting of a compound having a perfluoroalkyl structure and (2) a compound having a perfluoroalkyl structure.
An inkjet recording apparatus, wherein the third ink is an ink containing a coloring material.

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