JP2019155679A - Inkjet recording method, and inkjet recording device - Google Patents

Abstract

To provide an inkjet recording method which has good ink discharge stability when discharging ink containing a pigment having a perinone skeleton from a recording head by action of thermal energy, and can record an image with good color development property.SOLUTION: An inkjet recording method discharges aqueous ink from a recording head by action of thermal energy, and records an image onto a recording medium. The aqueous ink containing a pigment having a perinone skeleton, calcium and resin having an anionic group is used as the aqueous ink.SELECTED DRAWING: None

Description

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

  In recent years, pigment inks containing pigments have been used as coloring materials in order to improve fastness such as light resistance, gas resistance, and water resistance of images obtained by inkjet recording methods. ing. However, compared to a dye ink containing a dye used as a coloring material in the same manner as a pigment, there is a problem that the color developability of an image obtained may be inferior when a pigment ink is used.

  Ink for ink jet recording is generally based on four colors obtained by adding black to three basic colors of yellow, magenta, and cyan. In recent years, in order to compensate for the low color developability of pigment inks, a method of expanding the color gamut by using intermediate colors such as red, orange, green, and blue together with basic colors has been used. .

  The pigment ink having an orange hue includes C.I. I. A pigment having a perinone skeleton such as CI Pigment Orange 43 is used. Various proposals have been made for inks using pigments having a perinone skeleton. For example, in Patent Document 1, C.I. I. Pigment orange 43 and C.I. I. There has been proposed an ink capable of recording an image having good bronze resistance, glossiness, and color developability by using together with Pigment Yellow 128. Patent Document 2 also proposes an ink that defines a cation content in order to achieve both the discharge stability and storage stability of orange ink.

JP-A-2015-199849 JP 2004-0743433 A

  The present inventors have studied to record an image on a recording medium by ejecting an ink containing a pigment having a perinone skeleton from a recording head using thermal energy. As a result, it has been found that when a resin having an anionic group is added to the ink in order to improve the color developability, the ejection stability of the ink is lowered.

  Accordingly, an object of the present invention is to record an image having good ink ejection stability and good color development when ink containing a pigment having a perinone skeleton is ejected from a recording head by the action of thermal energy. An object of the present invention is to provide a possible 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 inkjet recording method for recording an image on a recording medium by discharging aqueous ink from a recording head by the action of thermal energy, wherein the aqueous ink comprises a pigment having a perinone skeleton, calcium, and An inkjet recording method comprising a resin having an anionic group is provided.

  According to the present invention, when an ink containing a pigment having a perinone skeleton is ejected from a recording head by the action of thermal energy, an ink jet recording method capable of recording an image having good ejection stability and good color development 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 it is expressed as “contains a salt” for convenience. 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.

  First, the present inventors analyzed a cause of a decrease in ejection stability that occurs when an ink containing a pigment having a perinone skeleton as a coloring material is ejected from a recording head by the action of thermal energy. As a result, it was found that foreign matter adhered to the heater of the recording head, which caused the ink ejection stability to deteriorate. The pigment ink having an orange hue is a high saturation region, and is expected to increase the color development of the image while reducing the pigment content. A solution is strongly desired.

  As a result of studying the above problems, the present inventors have found that ink ejection stability is good by using an ink containing a pigment having a perinone skeleton, calcium, and a resin having an anionic group. In addition, it has been found that an image having good color developability can be obtained. The present inventors consider the mechanism for obtaining such an effect as follows.

When an ink containing a pigment having a perinone skeleton is used as the ink ejected from the recording head by the action of thermal energy, the ink decomposed by heat adheres to the heater, thereby lowering the ink ejection stability. The thermal decomposition temperature of a pigment having a perinone skeleton is 500 ° C. or higher. However, in a water-based ink containing a highly polar substance such as water or a water-soluble organic solvent, the heat resistance of the pigment is apt to decrease, and the ink is discharged. It is considered that decomposition occurs even at a temperature of about 200 ° C. When calcium is allowed to coexist in this water-based ink, calcium ions are oriented at sites polarized in δ ⁻ of the molecular structure constituting the pigment. Thereby, it is considered that the attack to the pigment by the highly polar substance in the ink is inhibited, and the decomposition of the pigment is suppressed. Thereby, it is considered that a decrease in ink ejection stability can be suppressed.

  In addition, in the recording medium to which the ink is applied, the liquid component in the ink evaporates, and the resin having calcium and an anionic group causes an ionic reaction, and the pigment having the perinone skeleton can be rapidly aggregated. For this reason, since a large amount of pigment can be present on the surface of the recording medium, an image with good color developability can be obtained.

<Inkjet recording method>
The inkjet recording method of the present invention includes a step of recording an image on a recording medium by discharging aqueous ink from a recording head by the action of thermal energy. For image recording, a water-based ink containing a pigment having a perinone skeleton, calcium, and a resin having an anionic group is used. Except for using the ink having such a configuration, the steps of the ink jet recording method may be known ones.

  In the ink jet recording method of the present invention, an ink jet recording apparatus including a recording head that discharges aqueous ink by the action of thermal energy can be used. This ink jet recording apparatus can include the water-based ink used in the ink jet recording method of the present invention.

  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.

  The components constituting the ink used in the ink jet recording method of the present invention and the physical properties of the ink will be described below.

(Pigment)
As the ink coloring material (pigment), a pigment having a perinone skeleton is used. Examples of the pigment having a perinone skeleton include C.I. I. Pigment orange 43, and C.I. I. And CI Pigment Red 194. The ink may contain one or more pigments having a perinone skeleton. Among these pigments, C.I. I. Pigment Orange 43 is preferable. The content (% by mass) of the pigment having a perinone skeleton in the ink is preferably 0.1% by mass or more and 10.0% by mass or less based on the total mass of the ink.

  The pigment dispersion method includes a resin dispersion type pigment using a resin as a dispersant (a resin dispersed pigment using a resin dispersant, a microcapsule pigment in which the surface of pigment particles is coated with a resin, and a resin on the surface of pigment particles. Resin bonded pigments). In addition, self-dispersion type pigments (self-dispersing pigments) in which hydrophilic groups are bonded directly or via other atomic groups to the surface of the pigment particles are exemplified. Of course, it is possible to use pigments having different dispersion methods in combination. In the present invention, it is preferable to use a resin dispersion type pigment.

  In a resin dispersion type pigment, it is preferable to use a resin having a hydrophilic part and a hydrophobic part as a pigment dispersant. Specifically, acrylic resins polymerized using hydrophilic monomers having a carboxylic acid group such as (meth) acrylic acid and hydrophobic monomers such as styrene and alkyl (meth) acrylate; anionic properties such as dimethylolpropionic acid Examples thereof include a urethane resin polymerized using a diol having a group and a polyisocyanate. The acid value of the resin used as the dispersant is preferably 50 mgKOH / g or more and 300 mgKOH / g or less. Moreover, it is preferable that the polystyrene conversion weight average molecular weight (Mw) obtained by GPC of resin used as a dispersing agent is 1,000 or more and 15,000 or less. The content (% by mass) of the resin used as the dispersant in the ink is preferably 0.1% by mass or more and 10.0% by mass or less, and 0.2% by mass or more based on the total mass of the ink. More preferably, it is 4.0 mass% or less. The content of the resin used as the dispersant is preferably 0.1 times or more and 1.0 times or less in terms of mass ratio with respect to the pigment content.

  In self-dispersion type pigments, anionic groups such as carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, and phosphonic acid groups are bonded to the pigment particle surface directly or via other atomic groups (-R-). It is what you are doing. The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either partially dissociated or completely dissociated. Examples of the cation serving as a counter ion when the anionic group is a salt type include alkali metal cations; ammonium; organic ammonium. Examples of the alkali metal cation include lithium, sodium, and potassium. Examples of the organic ammonium include cations such as alkylamines having 1 to 3 carbon atoms; alkanolamines having 1 to 4 carbon atoms. Specific examples of the other atomic group (-R-) include linear or branched alkylene groups having 1 to 12 carbon atoms, arylene groups such as phenylene groups and naphthylene groups, amide groups, sulfonyl groups, amino groups. , A carbonyl group, an ester group, and an ether group. Moreover, it is good also as a group which combined at least 2 group among these.

(Resin having an anionic group)
Examples of the resin having an anionic group include resins having an anionic group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. This resin may have one kind or two or more kinds of anionic groups. In addition, the ink may contain one or more kinds of resins having an anionic group. Among the resins having an anionic group, it is preferable to use a resin having a carboxylic acid group.

  The resin having an anionic group may be used as a resin dispersant for dispersing the pigment, or may be used as a resin added to the ink instead of as a resin dispersant. Specifically, acrylic resins polymerized using hydrophilic monomers having a carboxylic acid group such as (meth) acrylic acid and hydrophobic monomers such as styrene and alkyl (meth) acrylate; anionic properties such as dimethylolpropionic acid Examples thereof include a urethane resin polymerized using a diol having a group and a polyisocyanate.

  The acid value of the resin having an anionic group is preferably 70 mgKOH / g or more and 180 mgKOH / g or less. If the acid value is less than 70 mgKOH / g, the ink ejection stability may be slightly lowered. On the other hand, if the acid value exceeds 180 mgKOH / g, the color developability of the image may be slightly lowered. Moreover, it is preferable that the polystyrene equivalent weight average molecular weight (Mw) obtained by GPC of the resin which has anionic group is 1,000 or more and 30,000 or less. The content (% by mass) of the resin having an anionic group in the ink is preferably from 0.1% by mass to 10.0% by mass based on the total mass of the ink, and from 0.2% by mass to 4% by mass. More preferably, it is 0.0 mass% or less.

(calcium)
The ink needs to contain calcium. Calcium may be in the form of metal or ion, but is preferably calcium ion. In order to contain calcium ions in the water-based ink, a calcium salt such as calcium chloride which is at least partially dissolved in water may be added to the ink.

  The calcium content (ppm) in the ink is preferably from 1 ppm to 100 ppm, more preferably from 4 ppm to 50 ppm, based on the total mass of the ink. If the calcium content is less than 1 ppm or more than 100 ppm, ink ejection stability and image colorability may not be compatible at a high level. When the calcium content is 4 ppm or more and 50 ppm or less, both the ink ejection stability and the color development of the image can be achieved at a high level.

(Aqueous medium)
The ink used in the present invention is an aqueous ink containing at least water as an aqueous medium. The ink can contain an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As water, deionized water or ion exchange water is preferably used. The content (% by mass) of water in the water-based ink is preferably 45.0% by mass or more and 95.0% by mass or less, based on the total mass of the ink, and 50.0% by mass or more and 95.0% by mass. More preferably, it is as follows.

  The water-soluble organic solvent is not particularly limited as long as it is water-soluble. Examples of the water-soluble organic solvent include alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, and sulfur-containing polar solvent. These 1 type (s) or 2 or more types can be used. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, and 3.0% by mass or more and 45.0% by mass based on the total mass of the ink. More preferably, it is at most mass%.

(Other additives)
In the ink used in the present invention, 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, and the like are included as necessary. Various additives may be contained.

  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)
A mixture was obtained by mixing 15.0 parts of a pigment (CI Pigment Orange 43), 7.5 parts of a resin dispersant, and 77.5 parts of ion-exchanged water. As the resin dispersant, a styrene-acrylic acid copolymer having an acid value of 250 mgKOH / g and a weight average molecular weight of 8,000 neutralized with sodium hydroxide in an equimolar amount with respect to the acid value was used. The obtained mixture was put into a batch type vertical sand mill (manufactured by IMEX), filled with 85.0 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. Further, by applying pressure filtration through a cellulose acetate filter having a pore size of 3.0 μm (manufactured by Advantech), a pigment dispersion 1 having a pigment content of 10.0% and a resin dispersant content of 5.0% is obtained. Prepared.

(Pigment dispersion 2)
15.0 parts of pigment (CI Pigment Orange 43), 7.5 parts of nonionic surfactant (polyoxyethylene cetyl ether, HLB value 15.7 by Griffin method), and 77.5 parts of ion-exchanged water Mix to obtain a mixture. Thereafter, a pigment dispersion 2 having a pigment content of 10.0% and a nonionic surfactant content of 5.0% was prepared in the same manner as the preparation method of the pigment dispersion 1.

(Pigment dispersion 3)
The type of pigment is C.I. I. A pigment dispersion 3 having a pigment content of 10.0% and a resin dispersant content of 5.0% was prepared in the same manner as the preparation method of the pigment dispersion 1, except that the pigment red 194 was changed. did.

<Preparation of resin having an anionic group>
After putting 200.0 parts of isopropanol in a flask equipped with a stirrer, a nitrogen inlet tube, a reflux cooling device, and a thermometer, the system was purged with nitrogen and heated to 85 ° C. with stirring. A mixture of monomers shown in Table 1, a liquid containing a polymerization initiator, and a chain transfer agent were dropped into the flask while maintaining the temperature at 80 ° C. for 2 hours. As a liquid containing a polymerization initiator, a solution obtained by dissolving 5.0 parts of a trade name “Parkadox L-W75 (LS)” (manufactured by Kayaku Akzo, dibenzoyl peroxide, purity 75%) in 10.0 parts of isopropanol. Using. As the liquid containing the chain transfer agent, a solution in which 1.9 parts of 1-thioglycerol was dissolved in 10.0 parts of isopropanol was used. The temperature of the reaction system was maintained at 80 ° C. and stirred for 4 hours to synthesize a resin. After adding 0.9 moles of potassium hydroxide and an appropriate amount of ion-exchanged water based on the acid value of the resin, isopropanol was removed under reduced pressure. Thus, an aqueous solution of each resin having a weight average molecular weight of 7,000 and a resin (solid content) content of 20.0% was obtained.

<Preparation of ink>
After mixing the components (unit:%) shown in the upper part of Table 2-1 and Table 2-2 and stirring sufficiently, each ink was filtered under pressure with a cellulose acetate filter (manufactured by Advantech) having a pore size of 0.8 μm. Prepared. The amount of ion-exchanged water used was the remaining amount in which the total of the components was 100.0%. “Zonyl FS3100” (trade name) shown in the table is a DuPont fluorosurfactant, and “Proxel GXL (S)” (trade name) is an antifungal agent manufactured by Arch Chemicals. Further, the lower part of Table 2-1 and Table 2-2 shows the calcium (Ca) content (ppm) in the ink as the ink characteristics.

<Evaluation>
Using the inks shown in Table 3, the following items were evaluated. In the present invention, “A” and “B” are acceptable levels and “C” is an unacceptable level in the evaluation criteria for the following items. The evaluation results are shown in Table 3.

(Discharge stability)
Using an ink jet recording apparatus (trade name “PIXUS PRO-10”, manufactured by Canon Inc.) equipped with a recording head (recording head “1” in Table 3) that fills the ink cartridge with ink and ejects the ink by thermal energy. The following evaluation was performed. In the above-described ink jet recording apparatus, an image recorded under the condition of applying 8 drops of 3.8 ng ink to a unit area of 1/600 inch × 1/600 inch is defined as having a recording duty of 100%. However, in Reference Examples 1 and 2, the resolution conditions were not changed, except that the recording head using a piezo element and ejecting ink by mechanical energy (recording head “2” in Table 3) was changed. Evaluation was performed in the same manner. Using the above inkjet recording apparatus, 200 sheets of A4 size solid images having a recording duty of 50% were continuously recorded on a recording medium (plain paper, trade name “PB PAPER”, manufactured by Canon) for 200 sheets. Then, the disordered state of the first and 200th images was visually confirmed, and ejection stability was evaluated according to the following evaluation criteria.
A: Recording for 200 sheets was possible, and there was no disorder in the 200th image.
B: Recording for 200 sheets was possible and the image on the 200th sheet was disordered, but there were no white spots.
C: Recording for 200 sheets was possible, but the 200th image had irregularities and white spots.

(Color development)
The following evaluation was performed using an ink jet recording apparatus (trade name “PIXUS MG5230”) equipped with a recording head (recording head “1” in Table 3) that fills an ink cartridge with ink and ejects ink by thermal energy. went. In the above-described ink jet recording apparatus, an image recorded under the condition that 28 ng of ink is applied to a unit area of 1/600 inch × 1/600 inch is defined as having a recording duty of 100%. However, in Reference Examples 1 and 2, the resolution conditions were not changed, except that the recording head using a piezo element and ejecting ink by mechanical energy (recording head “2” in Table 3) was changed. Evaluation was performed in the same manner. Using the ink jet recording apparatus, solid images having a recording duty of 100% were recorded on four types of recording media (plain paper). As the recording medium, trade names “PB PAPER”, “SW-101” and “Canon Office” (manufactured by Canon Inc.) and trade names “Steinbeis Classic White” (manufactured by Steinbeis) were used. Then, using a spectrophotometer (trade name “Spectrolino”, manufactured by Gretag Macbeth), the optical density of the solid image is measured under the conditions of the light source: D50 and the field of view: 2 °, and the color developability according to the evaluation criteria shown below. Evaluated.
A: The minimum value of the optical density in the four types of recording media was 1.2 or more.
B: The minimum value of the optical density in the four types of recording media was 1.1 or more and less than 1.2.
C: The minimum value of the optical density in the four types of recording media was less than 1.1.

Claims (5)

An inkjet recording method for recording an image on a recording medium by discharging aqueous ink from a recording head by the action of thermal energy,
The inkjet recording method, wherein the water-based ink contains a pigment having a perinone skeleton, calcium, and a resin having an anionic group.   The pigment having the perinone skeleton is C.I. I. The inkjet recording method according to claim 1, which is CI Pigment Orange 43.   3. The inkjet recording method according to claim 1, wherein a content (ppm) of the calcium in the water-based ink is 4 ppm or more and 50 ppm or less based on the total mass of the ink.   The inkjet recording method according to any one of claims 1 to 3, wherein an acid value of the resin having an anionic group is 70 mgKOH / g or more and 180 mgKOH / g or less. An inkjet recording apparatus including a recording head that discharges aqueous ink by the action of thermal energy,
The ink jet recording apparatus, wherein the water-based ink contains a pigment having a perinone skeleton, calcium, and a resin having an anionic group.

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