JP2019202420A - Inkjet recording method and inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording method capable of recording an image having excellent image clarity and excellent in scratch resistance on an ink absorbing recording medium such as glossy paper even immediately after recording. An ink jet recording method for ejecting a plurality of ink jet inks from a recording head to record an image on an ink absorbing recording medium. A plurality of water-based inks include a combination of a first ink containing a pigment and a second ink not containing a coloring material, and the second ink is a wax particle formed of a water-soluble acrylic resin and a hydrocarbon wax. , And a second ink containing a water-soluble organic solvent having an SP value calculated by the Fedors method of 11.5 or more and 13.5 or less and overlapping at least a part of a region of the recording medium to which the first ink is applied. Is discharged and applied to the recording medium. [Selection diagram] None

Description

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

  In recent years, ink for inkjet recording containing a pigment as a color material has been widely used. Such ink for ink-jet recording is required to be able to record a high-quality image comparable to a silver salt photograph. When an inkjet recording apparatus capable of recording a large image is used, an image immediately after recording may touch a basket (a member made of cloth or the like that receives a recorded matter). In addition, since an image immediately after recording may be moved manually by a plurality of hands, it is required to have scratch resistance even for an image immediately after recording. Furthermore, in the case of an ink using a pigment that exists in the state of particles as a color material, it is one of important issues to improve the image clarity of the recorded image.

  In order to improve the scratch resistance and image clarity of an image immediately after recording, for example, laminating immediately after recording has been studied. However, a large-scale apparatus is required for laminating, which tends to increase the cost of image recording.

  Various proposals have been made so far to solve the above problems. For example, in order to record an image having excellent glossiness, a set of a water-based ink and a post-treatment liquid in which the solubility parameters of the water-soluble organic solvent used for each is controlled in a predetermined relationship has been proposed (Patent Document 1). In addition, it uses an ink set including ink containing resin particles and wax particles, and color ink, and has a drying process at the time of recording or after recording, and has excellent image quality and scratch resistance on a low-absorbency recording medium. A method for recording a recorded image has been proposed (Patent Document 2).

Japanese Patent Laid-Open No. 2006-117872 JP 2010-105187 A

  The present inventors examined a set of a water-based ink and a post-treatment liquid proposed in Patent Document 1. As a result, it was found that when the drying process is not performed after recording, the glossiness of the image is slightly improved, but the image clarity is not so much improved. It was also found that when the image immediately after recording was rubbed with a nail, the image was easily peeled off and the scratch resistance was insufficient. In the case of the method proposed in Patent Document 2, it has been found that if the drying process is performed, the scratch resistance of the image is improved, but if the drying process is not performed, the scratch resistance of the image is not improved so much. Furthermore, since the method proposed in Patent Document 2 uses resin ink containing resin particles, it has also been found that the unevenness generated on the surface of the recorded image tends to increase and the image clarity tends to decrease.

  Therefore, an object of the present invention is an inkjet recording method capable of recording an image having excellent image clarity and excellent scratch resistance even immediately after recording on an ink-absorbing recording medium such as glossy paper. Is to provide. Another object of the present invention is to provide an ink jet recording apparatus used in the above ink jet recording method.

  The above object is achieved by the present invention described below. That is, according to the present invention, there is provided an ink jet recording method for recording an image on an ink-absorbing recording medium by discharging a plurality of ink jet inks from a recording head, wherein the plurality of water-based inks contain a pigment. The second ink is calculated by a Fedors method including a combination of a first ink and a second ink that does not contain a color material, and the second ink is a water-soluble acrylic resin, a wax particle formed of a hydrocarbon wax, and the like. A water-soluble organic solvent having an SP value of 11.5 or more and 13.5 or less is contained, and the second ink is ejected so as to overlap at least part of the region to which the first ink is applied of the recording medium. An ink jet recording method is provided which is applied to a recording medium.

  According to the present invention, there is provided an inkjet recording method capable of recording an image having excellent image clarity and excellent scratch resistance even immediately after recording on an ink-absorbing recording medium such as glossy paper. can do. Moreover, according to this invention, the inkjet recording device used for the said inkjet recording method can be provided.

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, 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 in the ink, but for convenience, it is expressed as “contains a salt”. In addition, water-based ink for inkjet may be simply referred to as “ink”. The physical property values are values at normal temperature (25 ° C.) unless otherwise specified.

  According to the study by the present inventors, the pigment ink is combined with an ink that does not contain a color material, and the ink that does not contain a color material is applied so as to overlap at least part of the region to which the pigment ink is applied. It has been found that the above problem can be solved by performing the recording method. Specifically, the ink containing no coloring material contains a water-soluble acrylic resin, a hydrocarbon wax, and a specific water-soluble organic solvent. The present inventors consider the mechanism for obtaining such an effect as follows.

  The inventors of the present invention have studied the composition of an ink that does not contain a coloring material in order to improve the scratch resistance of an image immediately after recording with pigment ink. Specifically, in order to reduce the dynamic friction coefficient of the image surface, an ink containing no coloring material added with wax particles was examined. As a result, it was found that the scratch resistance of the image after a lapse of a certain time after recording was slightly improved, but the image clarity was lowered. When the recorded image was analyzed, the presence of wax particles reduced the surface energy of the image and reduced the ink dot wettability, and the unevenness of the image surface increased as the ink dot wettability decreased. It was found that the image clarity decreased. In addition, the addition of a water-soluble acrylic resin that hardly deteriorates in image clarity was examined, but the scratch resistance of an image immediately after recording could not be improved.

  Furthermore, in order to improve the image clarity and scratch resistance immediately after recording, an ink containing no coloring material and containing wax particles and a water-soluble acrylic resin was studied. However, since the water-soluble acrylic resin has high affinity with the aqueous medium in the ink, it is difficult to remain on the surface of the recording medium, and the scratch resistance of the image immediately after recording cannot be improved.

The present inventors effectively develop the film-forming property of a water-soluble acrylic resin while effectively leaving the wax on the surface of the image (pigment layer), thereby improving the image clarity and scratch resistance immediately after recording. We estimated that it would be possible to record excellent images, and further studied. As a result, by satisfying the requirements (i) to (iii) shown below, an image having excellent image clarity and scratch resistance even immediately after recording can be obtained with an ink-absorbing property such as glossy paper. It has been found that recording on a recording medium is possible.
(I) A plurality of aqueous inks including a combination of a first ink containing a pigment and a second ink not containing a coloring material are ejected from a recording head to record an image on an ink-absorbing recording medium.
(Ii) The second ink contains a water-soluble acrylic resin, wax particles formed of a hydrocarbon wax, and a water-soluble organic solvent having an SP value of 11.5 or more and 13.5 or less calculated by the Fedors method. To do.
(Iii) The second ink is ejected and applied to the recording medium so as to overlap at least part of the area to which the first ink of the recording medium is applied.

  Hydrocarbon waxes are formed of long-chain hydrocarbon compounds such as alkanes, and have a very high surface hydrophobicity. A water-soluble organic solvent having an SP value calculated by the Fedors method of 11.5 or more and 13.5 or less (hereinafter also referred to as “first water-soluble organic solvent”) is wax particles formed of hydrocarbon wax. Has high affinity. For this reason, it is presumed that the first water-soluble organic solvent is present in the second ink so as to surround the wax particles. The wax particles in the second ink discharged from the recording head and applied to the recording medium have a low affinity with water-soluble organic solvents (other water-soluble organic solvents) other than the first water-soluble organic solvent. Become. As a result, solid-liquid separation between the wax particles and the other water-soluble organic solvent proceeds, and the wax is considered to remain efficiently on the surface of the image.

  Furthermore, since the first water-soluble organic solvent has a high affinity with the wax particles, it is considered that a part of the wax particles is eluted in the first water-soluble organic solvent. The wax particles from which a part of the particles are eluted become unstable, and function as a film forming aid as the first water-soluble organic solvent in the ink applied to the recording medium decreases. For this reason, it is considered that the binding property between the wax particles and the water-soluble acrylic resin is improved, and the scratch resistance of the image immediately after recording is improved.

  The surface energy of an image in which wax remains efficiently on the surface is unlikely to decrease, and surface irregularities due to overlapping dots are unlikely to increase. Furthermore, the wax particles that are partly eluted and become unstable function as a thickening aid. And since a water-soluble acrylic resin has the hydrophilic unit derived from (meth) acrylic acid, even if the water | moisture content in an ink evaporates, a viscosity does not raise easily. Thereby, it is considered that the film-forming property of the water-soluble acrylic resin is improved and the image clarity of the recorded image is improved.

  Further, when the image immediately after recording is analyzed at the dot level, the image transferability and the image are improved by ejecting the second ink and applying it to the recording medium so as to overlap at least a part of the region to which the first ink is applied. It was found that the scratch resistance of the image immediately after recording was significantly improved.

<Ink>
In the inkjet recording method of the present invention, a plurality of water-based inks for inkjet are used. The plurality of water-based inks include a combination of a first ink containing a pigment and a second ink not containing a coloring material. The second ink contains water-soluble acrylic resin, wax particles formed of hydrocarbon wax, and a water-soluble organic solvent having an SP value calculated by the Fedors method of 11.5 or more and 13.5 or less. To do. Hereinafter, each component constituting the ink will be described in detail.

(Pigment)
The color material used for the first ink is a pigment such as an inorganic pigment or an organic pigment. Examples of the pigment include carbon black, azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole and dioxazine. These pigments can be used alone or in combination of two or more.

  The pigments used in the first ink are classified according to different dispersion methods. Resin dispersion type pigments using a resin as a dispersing agent, or self having hydrophilic groups bonded directly or via other atomic groups to the pigment particle surface. Examples thereof include a dispersed pigment. Examples of the resin-dispersed pigment include a resin-dispersed pigment using a resin dispersant; a microcapsule pigment in which the pigment particle surface is coated with a resin; and a resin-bonded pigment in which an organic group containing a resin is chemically bonded to the pigment particle surface. is there. Pigments with different dispersion methods may be used in combination with the ink.

  The pigment used for the first ink is preferably a resin dispersion type pigment because the scratch resistance of an image to be recorded can be further improved. Among these, a resin dispersed pigment using a resin dispersant is preferable. As the resin dispersant, any resin conventionally used in ink jet inks can be preferably used. Of these, acrylic resins are preferred. When an acrylic resin is contained in the first ink, the compatibility with the second ink is improved, and the scratch resistance of the recorded image can be further improved.

  The weight average molecular weight of the resin used as the resin dispersant is preferably 1,000 or more and 30,000 or less, and more preferably 3,000 or more and 15,000 or less. The acid value of the resin used as the resin dispersant is preferably 50 mgKOH / g or more and 300 mgKOH / g or less, and more preferably 120 mgKOH / g or more and 250 mgKOH / g or less. The content (% by mass) of the pigment in the ink is preferably 0.05% by mass or more and 15.00% by mass or less, and 0.10% by mass or more and 11.50% by mass or less based on the total mass of the ink. More preferably.

(Water-soluble acrylic resin)
The second ink contains a water-soluble acrylic resin (hereinafter also simply referred to as “acrylic resin”). Any acrylic resin may be used as long as it has an acrylic component such as a unit derived from (meth) acrylic acid or a unit derived from an acrylate ester. The acrylic resin is preferably a water-soluble resin having a hydrophilic unit and a hydrophobic unit as constituent units.

  The hydrophilic unit is a unit having a hydrophilic group such as an acid group or a hydroxy group, and can be formed by polymerizing a monomer having a hydrophilic group. Examples of the monomer having a hydrophilic group include a monomer having a carboxy group such as (meth) acrylic acid, itaconic acid, maleic acid and fumaric acid; a monomer having a sulfonic acid group such as styrenesulfonic acid; Monomers having a phosphonic acid group such as (meth) acrylic acid-2-ethyl phosphonate; anionic monomers such as anhydrides and salts of these acidic monomers; 2-hydroxyethyl (meth) acrylate; Mention may be made of monomers having a hydroxy group such as (meth) acrylic acid 3-hydroxypropyl. Examples of the cation constituting the salt of the anionic monomer include ions such as lithium, sodium, potassium, ammonium, and organic ammonium.

  The hydrophobic unit is a unit having no hydrophilic group such as an acid group or a hydroxy group, and can be formed by polymerizing a monomer having a hydrophobic group. Monomers having a hydrophobic group include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth) acrylate; ethyl (meth) acrylate, methyl (meth) acrylate, (iso) propyl ( Examples thereof include a monomer having an aliphatic group such as (meth) acrylate, (n-, iso-, t-) butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate.

  The content (% by mass) of the water-soluble acrylic resin in the second ink is preferably 0.10% by mass or more and 4.00% by mass or less based on the total mass of the ink.

  The weight average molecular weight of the water-soluble 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 acrylic resin can be measured by a size exclusion chromatography method (GPC method) in accordance with JIS Handbook Chemical Analysis K0124. Moreover, it is preferable that the acid value of an acrylic resin is 160 mgKOH / g or more. When the acid value of the acrylic resin is less than 160 mgKOH / g, the stability at the time of water evaporation tends to be lowered, and the cohesive force between the acrylic resins tends to increase. For this reason, the binding action with the wax particles is reduced, and the effect of improving the scratch resistance may be slightly reduced. The acid value of the acrylic resin can be determined by potentiometric titration.

  The “water-soluble resin” in the present invention is dissolved in water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent, and has a particle size when measured by a dynamic light scattering method. Alternatively, it means a resin that can be present in an aqueous medium. Whether or not the resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10% by mass) containing a resin neutralized with an alkali corresponding to an acid value (sodium hydroxide, potassium hydroxide, etc.) is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. And when the particle diameter of resin in a sample solution is measured by a dynamic light scattering method, if the particle | grains which have a particle diameter are not measured, it can be judged that the resin is water-soluble. The measurement conditions at this time can be as follows, for example.

[Measurement condition]
SetZero: 30 seconds Number of measurements: 3 times Measurement time: 180 seconds

  As the particle size distribution measuring apparatus, a particle size analyzer (for example, trade name “UPA-EX150”, manufactured by Nikkiso) using a dynamic light scattering method can be used. Of course, the particle size distribution measuring apparatus and measurement conditions to be used are not limited to the above.

(Wax particles)
The second ink contains wax particles formed of hydrocarbon wax. The wax particles are present in a state of being dispersed in the ink. The hydrocarbon wax is a wax whose main chain is composed of hydrocarbons. Examples of the hydrocarbon wax include paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene wax, and polypropylene wax. These waxes can be used alone or in combination of two or more. Among these, it is preferable to use polyethylene wax because a pigment layer having higher flexibility can be formed and the image clarity and scratch resistance of the recorded image are further improved.

  The wax particles are preferably dispersed in the second ink by a dispersant. Examples of the dispersant include a surfactant; a resin having a hydrophilic group such as a sulfonic acid group or a carboxylic acid group; Examples of the resin having a hydrophilic group include a resin having a hydrophilic group graft-bonded; a resin having a unit derived from a hydrophilic monomer and a monomer having a hydrophobic portion; Can do.

  The volume average particle diameter of the wax particles is preferably 180 nm or less. When the volume average particle diameter of the wax particles is more than 180 nm, the smoothness of the image surface tends to be lowered, and the effect of improving the image clarity may be slightly lowered. The volume average particle diameter of the wax particles is preferably 50 nm or more. The volume average particle diameter can be measured in the same manner as described above for determining whether or not a resin is water-soluble.

  The content (% by mass) of the wax particles in the second ink is preferably 0.05% by mass or more and 3.00% by mass or less based on the total mass of the ink. When the content of the wax particles is less than 0.05% by mass, the effect of improving the scratch resistance of the image may be slightly lowered. On the other hand, if the content of the wax particles is more than 3.00% by mass, the effect of improving the image clarity may be slightly lowered.

(Water-soluble organic solvent)
The second ink contains a water-soluble organic solvent (first water-soluble organic solvent) having an SP value calculated by the Fedors method of 11.5 to 13.5. A water-soluble organic solvent having an SP value of less than 11.5 has too high affinity with wax, so that the wax particles cannot maintain the particle state, and the effect of improving the scratch resistance cannot be obtained. Moreover, since the thickening action is insufficient, the effect of improving the image clarity cannot be obtained. On the other hand, a water-soluble organic solvent having an SP value of more than 13.5 has too low affinity with wax, so that solid-liquid separation is not promoted and the effect of improving scratch resistance cannot be obtained. Further, since the affinity with the water-soluble acrylic resin is too high, the water-soluble acrylic resin easily penetrates into the recording medium, and the effect of improving the image clarity cannot be obtained.

In the present invention, the SP value (δ) [unit: (cal / cm ³ ) ^1/2 ] used for defining the water-soluble organic solvent is a value determined by the Fedors method. The SP value is also called a “solubility parameter”, and the smaller the difference between the SP value of the solute and the SP value of the solvent, the greater the affinity of the solute to the solvent. Specifically, the SP value (δ) of the water-soluble organic solvent can be calculated by the following formula (1). In the following formula (1), ΔE _vap represents the heat of molar evaporation (cal / mol) of the water-soluble organic solvent, and V represents the molar volume (cm ³ / mol) of the water-soluble organic solvent at 25 ° C. Note that the molar heat of vaporization (ΔE _vap ) of the water-soluble organic solvent and the molar volume (V) of the water-soluble organic solvent at 25 ° C. are both obtained by adding together certain values attributed to atoms and groups in the molecule. . In general, cal is used as the unit of the SP value, but when converted to the SI unit system, (cal / cm ³ ) ^1/2 = 2.046 × 10 ³ (J / m ³ ) Use the ^1/2 relationship. In the following description, the unit of the SP value may be omitted, but the SP value is a value expressed in units of (cal / cm ³ ) ^1/2 .

  As specific examples of the first water-soluble organic solvent, when SP value is shown in parentheses, N-methyl-2-pyrrolidone (11.5), ethylene glycol monoethyl ether (11.5), isopropanol (11.6) ), 2-methyl-2-hydroxypentan-4-one (11.7), n-propanol (11.8), 1,2-hexanediol (11.8), ethylene glycol monomethyl ether (12.0) 1,2-pentanediol (12.2), 2-pyrrolidone (12.6), ethanol (12.6), tetraethylene glycol (12.8), 3-methyl-1,5-pentanediol (13 .4), 1,6-hexanediol (13.5) and the like. As a 1st water-soluble organic solvent, the thing whose vapor pressure in 25 degreeC is lower than water is preferable, and 2-pyrrolidone is more preferable. 2-Pyrrolidone is particularly high in polarity and has a higher affinity with wax particles formed from hydrocarbon waxes. For this reason, solid-liquid separation is further promoted, and the scratch resistance of the image can be further improved.

  In addition to the first water-soluble organic solvent, a water-soluble organic solvent having an SP value of less than 11.5 or a water-soluble organic solvent having an SP value of more than 13.5 may be used in combination. As the water-soluble organic solvent having an SP value of less than 11.5, the SP value shown in parentheses is ethylene glycol dimethyl ether (7.6), tetrahydrofuran (8.3), dimethyl sulfoxide (8.4), triethylene. Glycol butyl methyl ether (8.4), tetraethylene glycol dimethyl ether (8.5), N-methylmorpholine (8.5), dioxane (8.6), ethyl acetate (8.7), butyl acetate (8. 7), methyl ethyl ketone (9.0), acetone (9.1), trimethylglycine (9.1), polyethylene glycol (10.1) having a number average molecular weight of 1,000, tetraethylene glycol monobutyl ether (10.2) , Triethylene glycol monobutyl ether (10.3), acetic acid (10.4), number average molecular weight 60 Polyethylene glycol (10.5), diethylene glycol monobutyl ether (10.5), N, N-dimethylformamide (10.6), triethylene glycol monoethyl ether (10.6), N, N-dimethylacetamide (10 .6), diethylene glycol monoethyl ether (10.9), tert-butanol (10.9), 2-butanol (11.1), isobutanol (11.1), diethylene glycol monomethyl ether (11.2), n -Butanol (11.3), 1,3-dimethyl-2-imidazolidinone (11.4), etc. can be mentioned.

  As the water-soluble organic solvent having an SP value of more than 13.5, when the SP value is shown in parentheses, triethylene glycol (13.6), methanol (13.8), formamide (14.0), ethylene urea ( 14.2), 1,5-pentanediol (14.2), urea (14.4), 1,2,6-hexanetriol (14.5), ethylene glycol (14.8), 1,3- Butanediol (14.8), 2-methyl-1,3-propanediol (14.8), 1,4-butanediol (15.0), diethylene glycol (15.0), trimethylolpropane (15.9) ), 1,3-propanediol (16.1), glycerin (16.4) and the like.

  The content (% by mass) of the first water-soluble organic solvent in the second ink is preferably 1.00% by mass or more and 15.00% by mass or less based on the total mass of the ink, and is 1.00% by mass. More preferably, it is 10.00 mass% or less.

  The content (mass%) of the wax particles in the second ink is a mass ratio with respect to the content (mass%) of the first water-soluble organic solvent, and is preferably 0.003 times or more and 1.00 times or less. If the mass ratio is less than 0.003 times, the wax particles are likely to be excessively eluted in the first water-soluble organic solvent, and the scratch resistance may be slightly lowered. On the other hand, when the above-mentioned mass ratio is more than 1.00 times, the thickening action is slightly reduced, and thus the effect of improving the scratch resistance and the effect of improving the image clarity may be slightly reduced.

  The content (mass%) of the water-soluble acrylic resin in the second ink is a mass ratio with respect to the content (mass%) of the first water-soluble organic solvent, and is 0.03 times or more and 2.50 times or less. Is preferred. If the above mass ratio is less than 0.03 times, the thickening action becomes too large, and the smoothness of the image surface is lowered, and the image clarity may be slightly lowered. On the other hand, when the mass ratio is more than 2.50 times, the film-forming action of the water-soluble acrylic resin tends to be lowered, and the effect of improving the scratch resistance may be slightly lowered.

(Aqueous medium)
Both the first ink and the second ink used in the ink jet recording method of the present invention are aqueous inks containing at least water as an aqueous medium. As water, it is preferable to use deionized water (ion exchange water). The content (% by mass) of water in the ink is preferably 10.00% by mass or more and 90.00% by mass or less, preferably 50.00% by mass or more and 90.00% by mass or less, based on the total mass of the ink. More preferably.

  The aqueous medium used for the first ink may further contain a water-soluble organic solvent. The aqueous medium used for the second ink may further contain a water-soluble organic solvent other than the first water-soluble organic solvent. Further, the water-soluble organic solvent that can be contained is not particularly limited as long as it is water-soluble, and includes monohydric alcohol, polyhydric alcohol, (poly) alkylene glycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent, and the like. Can be used.

(Other additives)
The first ink and the second ink may contain a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, a chelating agent, Various additives such as other resins may be contained. Among these, it is preferable to include an acetylenol surfactant because the stability of the ink can be improved. These additives generally have a considerably low content in the ink and have little influence on the effect of the present invention. For this reason, in the present invention, these additives are not included in the “water-soluble organic solvent” and are not subject to calculation of the SP value.

<Inkjet recording method and inkjet recording apparatus>
The inkjet recording method of the present invention is a method for recording an image on an ink-absorbing recording medium by discharging a plurality of water-based inks from a recording head. The plurality of water-based inks include a combination of the first ink and the second ink described above. In the ink jet recording method of the present invention, the second ink is ejected and applied to the recording medium so as to overlap at least a part of the region to which the first ink of the recording medium is applied. Other than using a plurality of water-based inks including a combination of the first ink and the second ink described above, the steps of the inkjet recording method may be known. In addition, an ink jet recording apparatus according to the present invention includes a recording head that discharges a plurality of water-based inks that are filled with a plurality of water-based inks and a plurality of water-based inks including a combination of the first ink and the second ink. With. The configuration of the ink jet recording apparatus may be a known one except that the plurality of inks described above are filled in the recording head.

  Examples of a method for ejecting ink from the recording head include a method for imparting mechanical energy to the ink and a method for imparting thermal energy to the ink. In particular, it is particularly preferable to employ a method in which thermal energy is applied to the ink and the ink is ejected.

  An ink-absorbing recording medium is used as the recording medium. Specific examples of the ink-absorbing recording medium include a paper-based recording medium such as glossy paper and plain paper.

  1A and 1B are diagrams schematically showing an example of an ink jet recording apparatus used in the ink jet recording method of the present invention. FIG. 1A is a perspective view of a main part of the ink jet recording apparatus, and FIG. 1B 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.

  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. What is described as “parts” and “%” with respect to the component amounts is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Pigment dispersion 1)
C. I. Pigment Blue 15: 3 (trade name “Hostaperm Blue B2G” manufactured by Clariant) 12.0 parts, an aqueous resin dispersant solution 24.0 parts, and ion-exchanged water 64.0 parts were mixed to obtain a mixture. The aqueous solution of the resin dispersant was obtained by neutralizing a styrene-acrylic acid copolymer having an acid value of 250 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution (solid %) Is an aqueous solution having a content of 20.0%. The obtained mixture was charged into a batch type vertical sand mill (manufactured by IMEX), filled with 85 parts of 0.3 mm zirconia beads, and dispersed for 3 hours while cooling with water. Thereafter, the non-dispersed material containing coarse particles was removed by centrifugation. Furthermore, it is filtered under pressure through a 3.0 μm cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm, and the pigment content (solid content) is 10.0% and the resin content is 4.0%. A pigment dispersion 1 was prepared.

(Pigment dispersion 2)
The type of pigment is C.I. I. A pigment dispersion 2 was prepared in the same manner as in the case of the pigment dispersion 1 except that the pigment was changed to CI Pigment Yellow 74 (trade name “Hansa Yellow 5GXB”, manufactured by Clariant). The pigment content in Pigment Dispersion Liquid 2 was 10.0%, and the resin content was 4.0%.

(Pigment dispersion 3)
The type of pigment is C.I. I. Pigment red 202 and C.I. I. Pigment Violet 19 solid solution (trade name “CROMOPHTAL JET MAGENTA 2BC”, manufactured by Ciba Specialty Chemicals). Except for this, a pigment dispersion 3 was prepared in the same manner as in the case of the pigment dispersion 1. The pigment content in Pigment Dispersion Liquid 3 was 10.0%, and the resin content was 4.0%.

(Pigment dispersion 4)
A pigment dispersion 4 was prepared in the same manner as in the case of the pigment dispersion 1 except that the type of pigment was changed to carbon black (trade name “Black Pearls 880”, manufactured by Cabot). The pigment content in the pigment dispersion 4 was 10.0%, and the resin content was 4.0%.

<Preparation of liquid containing acrylic resin>
(Acrylic resin 1-5)
200.0 parts of methyl ethyl ketone was placed in a four-necked flask equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a cooling tube, and the reaction system was replaced with nitrogen. After heating up to 80 degreeC, the mixture of the monomer of the kind and usage-amount shown on the left side of Table 1, and 2.0 parts of t-butyl peroxide (polymerization initiator) was dripped over 2 hours. Reaction was performed at 80 ° C. for 12 hours to obtain acrylic resins 1 to 5. After neutralizing all acidic groups of the obtained acrylic resin with 10.0% potassium hydroxide aqueous solution, ion-exchanged water is added, and the acrylic resin 1 having a resin (solid content) content of 20.0% A liquid containing ˜5 was obtained.

  The acid value of the acrylic resin was measured by potentiometric titration with a potassium hydroxide / ethanol titrant using an automatic potentiometric titrator. The polystyrene-reduced weight average molecular weight of the acrylic resin was determined by gel permeation chromatography. The acrylic resins 1 to 4 were water-soluble, and the acrylic resin 5 was water-dispersible.

(Acrylic resin 6)
After putting 100 parts of water into a four-necked flask equipped with a stirrer, thermometer, reflux cooling device, and nitrogen gas inlet tube, nitrogen gas was introduced and the temperature was raised to 80 ° C. with stirring. A monomer emulsion was prepared by mixing 100 parts of water, 1.0 part of sodium lauryl sulfate, 20 parts of styrene, 30 parts of 2-ethylhexyl acrylate, 30 parts of methyl methacrylate, and 18 parts of acrylic acid. The prepared monomer emulsion and 10 parts of a 5% aqueous potassium persulfate solution were dropped into the flask over 3 hours. After aging for 2 hours, an appropriate amount of ion-exchanged water was added to obtain a liquid containing acrylic resin 6 having an acid value of 130 mgKOH / g, a minimum film forming temperature of 20 ° C., and a volume average particle diameter of 101 nm. Content of the liquid resin (solid content) containing the obtained acrylic resin 6 was 10.0%.

<Preparation of liquid containing nonionic resin>
The concentration of a commercially available aqueous dispersion containing a nonionic resin (trade name “BYK-190”, weight average molecular weight 2,000, acid value 10 mgKOH / g) was adjusted, and the resin (solid content) content was 20.0. % Of a nonionic resin-containing liquid was obtained.

<Preparation of aqueous dispersion of wax particles>
The concentration of the aqueous dispersion of commercially available wax particles shown below was adjusted to obtain an aqueous dispersion of wax particles 1 to 3 having a wax particle content of 10.0%.
Wax particles 1: Trade name “AQUACER 539” (by Big Chemie Japan)
Wax particles 2: Trade name “Trasol PF60” (manufactured by Chukyo Yushi)
Wax particles 3: Trade name “Cerosol 524” (manufactured by Chukyo Yushi)

<Preparation of ink>
(Inks I-1 to I-4, Inks II-1 to II-24)
After mixing each component (unit:%) shown in the upper part of Table 2 and 3-1 to 3-3 and stirring sufficiently, pressure filtration is performed with a pore size 0.8 μm cellulose acetate filter (manufactured by Advantech). An ink was prepared. In Tables 2 and 3-1 to 3-3, the numerical value in parentheses attached to the water-soluble organic solvent is the SP value of the water-soluble organic solvent. In Tables 2 and 3-1 to 3-3, “acetylenol E100” is a trade name of a nonionic surfactant (ethylene oxide adduct of acetylene glycol) manufactured by Kawaken Fine Chemicals, and “Proxel GXL” is Arch. It is a trade name of a chemicals antifungal agent. In Tables 3-1 to 3-3, “content A (%) of acrylic resin” means “content of water-soluble acrylic resin”.

(Ink II-25)
Ink II-25 containing wax particles and an ether-based urethane resin was prepared in accordance with the preparation of “Post-treatment liquid” in “Example 1” described in JP-A-2006-117872 (Patent Document 1).

(Ink II-26)
Ink II-26 containing a styrene acrylic acid copolymer and wax particles was prepared according to the preparation of “resin ink B13” in “Examples” described in JP 2010-105187 A (Patent Document 2).

<Evaluation>
An ink jet recording apparatus (product name “PIXUS PRO-6000S” (manufactured by Canon) modified) equipped with a recording head for discharging ink by thermal energy was prepared. The first ink was set at the cyan ink position of the prepared ink jet recording apparatus, and the second ink was set at the matte black ink position. In the present embodiment, an image recorded under the condition that eight droplets of 4.0 ng are applied to a unit area of 1/600 inch × 1/600 inch is defined as a recording duty of 100%. First, a solid image was recorded by applying the first ink in 8 passes to glossy paper (trade name “Canon Premium Glossy Paper 2 (Thick))” manufactured by Canon so that the recording duty was 100%. Next, a second ink was applied on the recorded solid image so as to have a recording duty of 20% to form a pattern, thereby obtaining a recorded matter. At this time, the dots of the second ink were arranged so as to overlap the dots of the first ink. In the present invention, “A” and “B” are acceptable levels and “C” is unacceptable levels in the evaluation criteria for each item shown below.

(Abrasion resistance)
A jig capable of performing an image abrasion test at an angle of 30 °, a load of 0.7 kgf, and a speed of 3 cm / second was prepared using a card made of polycarbonate having a thickness of 0.76 mm. 5 minutes after recording the image portion of the recorded matter obtained above, the image was scraped by dragging a 3 cm card using a prepared jig. Thereafter, the state of the image was visually confirmed, and the scratch resistance of the image was evaluated according to the following evaluation criteria.
A: Even when the image was viewed from the front, scars could hardly be confirmed, and when the recorded matter was tilted, it could be slightly confirmed.
B: Although the shaved trace could be confirmed visually, the color of the image did not change, and the change in glossiness could be confirmed when the recorded material was tilted.
C: The shaved trace could be confirmed visually, and the color of the image was changed, and the white background of the recording medium was visible.

(Image clarity)
Two fluorescent lamps arranged at intervals of 10 cm were used as observation light sources, and the fluorescent lamps were projected onto the image from a position 2 m away. The shape of the fluorescent lamp projected onto the image was visually confirmed under the conditions of an illumination angle of 45 degrees and an observation angle of 45 degrees, and the image clarity was evaluated according to the following evaluation criteria.
A: Two fluorescent lamps were clearly projected on the image.
B: Edge portions of the two projected fluorescent lamps were slightly blurred.
C: The boundary between the two projected fluorescent lamps was not known.

Claims (6)

An inkjet recording method for recording an image on an ink-absorbing recording medium by discharging a plurality of water-based inks for inkjet from a recording head,
The plurality of water-based inks include a combination of a first ink containing a pigment and a second ink not containing a coloring material,
The second ink contains water-soluble acrylic resin, wax particles formed of hydrocarbon wax, and a water-soluble organic solvent having an SP value calculated by the Fedors method of 11.5 to 13.5. ,
An ink jet recording method, wherein the second ink is ejected and applied to the recording medium so as to overlap at least a part of the region to which the first ink is applied of the recording medium.   The content (mass%) of the wax particles in the second ink is 0.003 times or more and 1.00 times or less as a mass ratio with respect to the content (mass%) of the water-soluble organic solvent. 2. An ink jet recording method according to 1.   The content (% by mass) of the acrylic resin in the second ink is a mass ratio with respect to the content (% by mass) of the water-soluble organic solvent and is 0.03 to 2.50 times. Or the inkjet recording method of 2.   The inkjet recording method according to any one of claims 1 to 3, wherein an acid value of the acrylic resin is 160 mgKOH / g or more.   The inkjet recording method according to any one of claims 1 to 4, wherein the water-soluble organic solvent is 2-pyrrolidone. An ink jet recording apparatus comprising: a plurality of water-based inks for ink jet; and a recording head for discharging the plurality of water-based inks filled with the plurality of water-based inks therein.
The plurality of water-based inks include a combination of a first ink containing a pigment and a second ink not containing a coloring material,
The second ink contains a water-soluble acrylic resin, wax particles formed of a hydrocarbon wax, and a water-soluble organic solvent having an SP value calculated by the Fedors method of 11.5 to 13.5. An ink jet recording apparatus.

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