JP2019131644A - Ink set and inkjet recording method - Google Patents

Abstract

To provide an ink set excellent in suppression of aggregates in a cap and black color development.SOLUTION: A color material of a cyan ink is represented by general formula (1), and a color material of a black ink is a self-dispersible pigment. (R, R, Rand Reach independently represent an alkyl group or the like; and at least one of R, R, Rand Ris substituted with an anionic group.)SELECTED DRAWING: None

Description

  The present invention relates to an ink set and an ink jet recording method using the ink set.

  According to the ink jet recording method, images can be recorded on various recording media. In order to obtain a better image, for example, ink suitable for recording photographic image quality on glossy paper, ink suitable for recording a document on plain paper, etc. Inks have been proposed.

  In recent years, the inkjet recording method has been used even when business texts including characters and charts are recorded on a recording medium such as plain paper, and the frequency of use for such applications has increased remarkably. In addition, with the development of the ink jet recording method, it is required to improve the color developability of the obtained image and to improve durability and reliability for long-term use. Furthermore, increasing the number of recordable sheets is required to achieve high productivity.

  Incidentally, it is known that it is advantageous to use a self-dispersing pigment instead of a resin-dispersed pigment from the viewpoint of improving the color developability of an image recorded with black ink. Further, in order to improve the ozone resistance of an image recorded with cyan ink, cyan ink containing a phthalocyanine dye having a specific substituent at the β-position has been proposed (see Patent Document 1). Furthermore, a cyan ink containing a phthalocyanine dye having a specific substituent at the α-position has been proposed in order to improve the color developability and ozone resistance of an image recorded with cyan ink (see Patent Document 2).

JP 2003-231834 A Japanese Patent Laid-Open No. 2002-249677

  The present inventors evaluated a combination of a black ink containing a self-dispersing pigment and a cyan ink proposed in Patent Documents 1 and 2 assuming long-term use. As a result, it has been found that there may be a new problem that ink aggregates (deposits) accumulate inside the cap for suppressing the drying of the recording head of the ink jet recording apparatus. If aggregates excessively accumulate inside the cap, unnecessary ink adheres to the recording head, and a phenomenon that an image to be recorded thereafter becomes dirty is likely to occur.

  Therefore, the object of the present invention is to have a combination of a cyan ink and a black ink containing a self-dispersing pigment, which can suppress the accumulation of aggregates in the cap and can record a black image with excellent color development. Is to provide a simple ink set. Another object of the present invention is to provide an ink jet recording method using the ink set.

  That is, according to the present invention, a water-based ink set having a combination of a cyan ink and a black ink, wherein the color material of the cyan ink is a compound represented by the following general formula (1), and the black ink The coloring material is a self-dispersing pigment, the cyan ink contains a first water-soluble organic solvent having a relative dielectric constant of 18.0 or more, and the cyan ink contains the first water-soluble organic solvent. An ink set is provided in which the amount (mass%) is 4.5 times or more in terms of mass ratio to the content (mass%) of the colorant.

（前記一般式（１）中、Ｒ₁、Ｒ₂、Ｒ₃、及びＲ₄は、それぞれ独立に、アルキル基、シクロアルキル基、アルケニル基、アラルキル基、アリール基、又はヘテロ環基を表し、Ｒ₁、Ｒ₂、Ｒ₃、及びＲ₄の少なくとも１つにはアニオン性基が置換している。ａ、ｂ、ｃ、及びｄは、それぞれ独立に、１又は２を表す）

(In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ each independently represents an alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group, At least one of R ₁ , R ₂ , R ₃ , and R ₄ is substituted with an anionic group. A, b, c, and d each independently represent 1 or 2)

  According to the present invention, an ink having a combination of a cyan ink and a black ink containing a self-dispersing pigment, which can suppress accumulation of aggregates in the cap and can record a black image with excellent color developability. Set can be offered. Moreover, according to the present invention, an ink jet recording method using this ink set 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”. Various physical property values in the present invention are values at room temperature (25 ° C.) unless otherwise specified.

  The inventors of the present invention have examined the accumulation mechanism of aggregates generated in the cap when the cyan ink containing the compound represented by the general formula (1) and the black ink containing the self-dispersing pigment are used. did. Since the compound represented by the general formula (1) has a substituent at the α-position of the phthalocyanine skeleton, it is considered that the steric hindrance is small and the molecules are close to each other and easily form an aggregate. Furthermore, the compound represented by the general formula (1) is considered to easily form an aggregate even when mixed with other colorants.

  When the combination of the black ink containing the self-dispersing pigment and the cyan ink containing the compound represented by the general formula (1) was examined, the aggregate of the ink was significantly deposited on the cap in the ink jet recording apparatus. As described above, the compound represented by the general formula (1) has a property of being easily accessible to other materials. In addition, the self-dispersed pigment has an anionic group bonded to the pigment particle surface directly or via another atomic group, and therefore, the occupied volume of the pigment in the dispersed state is small compared to the resin-dispersed pigment. . That is, it can be said that the compound represented by the general formula (1) that is easily accessible to other materials and the self-dispersing pigment having a relatively small occupied volume are a combination that easily interacts. When an image is recorded using inks each containing a combination of color materials that are likely to interact with each other, each ink discharged into a cap in the inkjet recording apparatus is mixed in the process, and each color material is evaporated by moisture evaporation. Agglomerates that are strongly agglomerated are formed. And since this agglomerate is strongly agglomerated, it is difficult to remove by a normal suction operation for cleaning, and it is considered that it gradually accumulates.

  On the other hand, when a black ink containing a resin dispersion pigment was used instead of the self-dispersion pigment, it was confirmed that although some deposits were generated, the deposits could be removed by a normal suction operation for cleaning. This is presumably because the compound represented by the general formula (1) and the resin-dispersed pigment hardly interact with each other because steric hindrance due to the resin dispersant exists.

  From the above, it is possible to control the generation of aggregates by mixing black ink containing a self-dispersing pigment and cyan ink containing a compound represented by the general formula (1). It can be said that it is essential for suppression. As a result of further studies, the present inventors have met the following requirements, in the case where a black ink containing a self-dispersing pigment and a cyan ink containing a compound represented by the general formula (1) are used in combination. Even if it exists, it discovered that accumulation of the aggregate in a cap could be suppressed. That is, the cyan ink needs to contain a first water-soluble organic solvent having a relative dielectric constant of 18.0 or more. Further, the content (% by mass) of the first water-soluble organic solvent in the cyan ink is required to be 4.5 times or more as a mass ratio with respect to the content (% by mass) of the color material.

  As the moisture evaporates from the ink, ink aggregates accumulate on the cap in the ink jet recording apparatus. Due to the progress of water evaporation, that is, the relative concentration of the water-soluble organic solvent increases, the color materials, the water-soluble organic solvent around the color material and the interaction with other color materials, and the formation of aggregates It is thought that it will affect. Since the compound represented by the general formula (1) has high ozone resistance, it is easy to form an aggregate which is an aggregate due to the interaction of the compound itself or the interaction with other colorants. Is difficult to remove by normal suction operation.

  Among water-soluble organic solvents generally used for ink-jet inks, a relatively high relative polarity, that is, a water-soluble organic solvent having a high polarity is contained in the above-mentioned mass ratio, so that cyan ink can be used even after evaporation of moisture. The color material inside is solvated. For this reason, it is considered that the formation of aggregates between the color materials in the cyan ink or with other color materials is effectively suppressed. Further, even when aggregates are deposited on the cap, it is considered that the aggregates contain a water-soluble organic solvent having a high relative dielectric constant. That is, the coloring material of the cyan ink in the aggregate is less aggregated than the case where the water-soluble organic solvent having a high relative dielectric constant is not present. Can be removed.

<Ink set>
The ink set of the present invention is an aqueous ink set having a combination of cyan ink and black ink. The cyan ink contains a compound represented by the general formula (1) as a color material. The black ink contains a self-dispersing pigment as a color material. The ink set of the present invention is particularly suitable as an ink set for inkjet. The ink set according to the present invention is integrally configured by combining a plurality of ink cartridge sets each independently containing the above inks and a plurality of ink containing portions each containing a plurality of inks. The state of the ink cartridge that has been used. The ink set of the present invention is not limited to the above-described form as long as it is configured so that cyan ink and black ink can be used in combination. Hereinafter, the components contained in each ink constituting the ink set of the present invention will be described.

(Color material)
[Color material of cyan ink: compound represented by general formula (1)]
The color material (dye) of the cyan ink constituting the ink set of the present invention is a compound represented by the following general formula (1), which is an α-position-substituted phthalocyanine dye. The content (% by mass) of the compound represented by the general formula (1) 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. More preferably, the content is not less than mass% and not more than 6.0 mass%.

（前記一般式（１）中、Ｒ₁、Ｒ₂、Ｒ₃、及びＲ₄は、それぞれ独立に、アルキル基、シクロアルキル基、アルケニル基、アラルキル基、アリール基、又はヘテロ環基を表し、Ｒ₁、Ｒ₂、Ｒ₃、及びＲ₄の少なくとも１つにはアニオン性基が置換している。ａ、ｂ、ｃ、及びｄは、それぞれ独立に、１又は２を表す）

(In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ each independently represents an alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group, At least one of R ₁ , R ₂ , R ₃ , and R ₄ is substituted with an anionic group. A, b, c, and d each independently represent 1 or 2)

  Examples of the alkyl group include a substituted or unsubstituted alkyl group and a linear or branched alkyl group. The alkyl group has preferably 1 to 12 carbon atoms (excluding substituents), more preferably 1 to 8, and particularly preferably 1 to 5. Examples of the substituent include a hydroxy group, an alkoxy group, a cyano group, an alkylamino group, a carbamoyl group, a sulfamoyl group, a sulfonylamino group, a halogen atom, and an anionic group. Examples of the alkyl group include unsubstituted alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and a t-butyl group; a hydroxyethyl group, a methoxyethyl group, a cyanoethyl group, and a trifluoromethyl group. , Substituted alkyl groups such as 3-sulfopropyl group and 4-sulfobutyl group;

  Examples of the cycloalkyl group include a substituted or unsubstituted cycloalkyl group. The cycloalkyl group preferably has 5 to 12 carbon atoms (excluding substituents). Examples of the substituent include an anionic group. Examples of the cycloalkyl group include a cyclopentyl group, a cyclohexyl group, and a cyclodecyl group.

  Examples of the alkenyl group include a substituted or unsubstituted alkenyl group. The alkenyl group preferably has 2 to 12 carbon atoms (excluding substituents). Examples of the substituent include an anionic group. Examples of the alkenyl group include a vinyl group and a 1-propenyl group.

  Examples of the aralkyl group include a substituted or unsubstituted aralkyl group. The aralkyl group preferably has 7 to 12 carbon atoms (excluding substituents). Examples of the substituent include an anionic group. Examples of the aralkyl group include a benzyl group and a 2-phenethyl group.

  As the aryl group, a substituted or unsubstituted aryl group can be exemplified. The aryl group preferably has 6 to 12 carbon atoms (excluding substituents). Examples of the substituent include an alkyl group, an alkoxy group, an alkylamino group, a carbamoyl group, a sulfamoyl group, a sulfonylamino group, a halogen atom, and an anionic group. Examples of the aryl group include unsubstituted aryl groups such as a phenyl group and a naphthyl group; p-tolyl group, p-methoxyphenyl group, o-chlorophenyl group, m- (3-sulfopropylamino) phenyl group, and m-sulfophenyl group. And substituted aryl groups such as Of these, a phenyl group is particularly preferable.

  Examples of the heterocyclic group include a substituted or unsubstituted heterocyclic group and a 5-membered or 6-membered heterocyclic group. The heterocyclic group may form a condensed ring with other rings. Examples of the substituent include an alkyl group, an aryl group, an alkoxy group, an alkylamino group, a carbamoyl group, a sulfamoyl group, a sulfonylamino group, a sulfonyl group, an acylamino group, a halogen atom, and an anionic group. The ring structure constituting the heterocyclic group is not limited to the position of the heterocyclic ring, and imidazole, benzimidazole, pyrazole, benzopyrazole, triazole, thiazole, benzothiazole, isothiazole, benzoisothiazole, oxazole, benzo Oxazole, thiadiazole, oxadiazole, pyrrole, benzopyrrole, indole, isoxazole, benzisoxazole, thiophene, benzothiophene, furan, benzofuran, pyridine, quinoline, isoquinoline, pyridazine, pyrimidine, pyrazine, cinnoline, phthalazine, quinazoline, quinoxaline And triazine.

  As described above, any of the alkyl group, cycloalkyl group, alkenyl group, aralkyl group, aryl group, and heterocyclic group may have a substituent. Further, preferred examples of each group that can be substituted are as follows. As the anionic group, a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phosphonic acid group are preferable. The group having an alkyl moiety preferably has 1 to 10 carbon atoms. The aryl group is preferably a phenyl group. As a halogen atom, a fluorine atom, a chlorine atom, and a bromine atom are preferable. A carbamoyl group, a sulfamoyl group, or the like may form a ring structure. Further, the substituent may further have these groups as a substituent.

R ₁ , R ₂ , R ₃ , and R ₄ are preferably an alkyl group, an aryl group, or a heterocyclic group, more preferably an alkyl group or an aryl group, particularly preferably an alkyl group, or a substituent. preferable.

At least one of R ₁ , R ₂ , R ₃ , and R ₄ is substituted with an anionic group. Examples of the anionic group include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phosphonic acid group. Of these, a carboxylic acid group and a sulfonic acid group are preferable, and a sulfonic acid group is more preferable. The anionic group may be a free acid type (H type) or a salt type. Examples of the counter ion when the anionic group is in a salt form (when a salt is formed) include alkali metal, ammonium, and organic ammonium cations. Examples of the alkali metal include lithium, sodium, and potassium. Examples of the organic ammonium include 1 to 3 alkylamines such as methylamine and ethylamine; 1 to 4 monomonoyl such as monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, and triisopropanolamine; Di- or trialkanolamines can be mentioned.

  In general formula (1), a, b, c, and d each independently represent 1 or 2. Therefore, a + b + c + d is 4 or more and 8 or less. a + b + c + d is preferably 4 to 6, and more preferably each of a, b, c, and d is 1.

R ₁ , R ₂ , R ₃ , and R ₄ are each independently preferably an alkyl group, and more preferably an alkyl group substituted with an anionic group such as a sulfonic acid group. The alkyl group is preferably linear and the carbon number is preferably 1 to 5.

[Black ink colorant: self-dispersing pigment]
The color material (pigment) of the black ink constituting the ink set of the present invention is a self-dispersing pigment. The content (% by mass) of the self-dispersing pigment in the ink is preferably 0.1% by mass or more and 10.0% by mass or less, and 1.0% by mass or more and 6.0% by mass based on the total mass of the ink. More preferably, it is% or less.

  As the self-dispersing pigment, it is preferable to use a self-dispersing pigment in which an anionic group is bonded to the pigment particle surface directly or through another atomic group. Specific examples of the pigment include inorganic pigments such as carbon black and titanium oxide; organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole and dioxazine. Since it is used as a coloring material for black ink, the pigment type is preferably carbon black.

Examples of the anionic group include _{-COOM, -SO 3 M, -OPO 3} M 2, and -PO ₃ M _2. M represents each independently a hydrogen atom; alkali metal; ammonium (NH ₄ ); organic ammonium. Examples of the other atomic group (—R—) include an alkylene group; an arylene group; an amide group; a sulfonyl group; an imino group; a carbonyl group; an ester group; an ether group; Among these, self-dispersing pigments in which —COOM and —C ₆ H ₃ — (COOM) ₂ are bonded to the pigment particle surface are preferable. In particular, a self-dispersing pigment in which a carboxylic acid group is directly bonded to the pigment particle surface is preferable. The steric hindrance due to the functional group bonded to the pigment particle surface is less than that of the self-dispersing pigment in which the anionic group is bonded through another atomic group. For this reason, the interaction between the pigments tends to be strong, and the interaction between the self-dispersing pigment and the cyan ink color material tends to be weak, so that the generation of deposits during evaporation of the mixed ink is reduced and normal suction is performed. The deposit can be removed more efficiently by the operation.

(Aqueous medium)
Each ink constituting the ink set of the present invention is an aqueous ink containing an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water (ion exchange water) as the water. The content (% by mass) of water in the ink is preferably 50.00% by mass or more and 95.00% by mass or less, and 70.00% by mass or more and 90.00% by mass or less based on the total mass of the ink. More preferably.

  The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent and the like can be used. The content (% by mass) of the water-soluble organic solvent in the ink is preferably from 3.00% by mass to 50.00% by mass based on the total mass of the ink, and from 15.00% by mass to 40.00%. More preferably, it is at most mass%. If the content of the water-soluble organic solvent is out of the above range, a high level of ink ejection stability may not be obtained sufficiently.

  The cyan ink contains a first water-soluble organic solvent having a relative dielectric constant of 18.0 or more. The content (% by mass) of the first water-soluble organic solvent in the cyan ink is a mass ratio with respect to the content (% by mass) of the color material (the compound represented by the general formula (1)). It is 5 times or more, preferably 8.5 times or more, and more preferably 16.0 times or more. When the mass ratio is less than 4.5, the amount of the first water-soluble organic solvent relative to the color material of the cyan ink is relatively small. It cannot be suppressed.

  The black ink also preferably contains a first water-soluble organic solvent having a relative dielectric constant of 18.0 or more. The content (% by mass) of the first water-soluble organic solvent in the black ink is a mass ratio with respect to the content (% by mass) of the color material (self-dispersing pigment), and is 1.0 to 10.0 times. The following is preferable. When the mass ratio is within the above range, it is possible to achieve both higher levels of suppressing the accumulation of aggregates on the cap and improving the color developability of a monochrome image recorded with black ink.

The relative dielectric constant of the water-soluble organic solvent can be measured under the condition of a frequency of 10 kHz using a dielectric constant meter (for example, trade name “BI-870” (manufactured by BROOKHAVEN INSTRUMENTS CORPORATION)). The relative dielectric constant of a solid water-soluble organic solvent at a temperature of 25 ° C. is a value calculated from the following formula (1) by measuring the relative dielectric constant of a 50 mass% aqueous solution. Usually, the “water-soluble organic solvent” means a liquid, but in the present invention, those which are solid at 25 ° C. (room temperature) are also included in the water-soluble organic solvent.
ε _sol = 2ε _50% −ε _water (1)
ε _sol : relative permittivity of water-soluble organic solvent solid at 25 ° C. ε _50% : relative permittivity of _{50% by} weight aqueous solution of water-soluble organic solvent solid at 25 ° C. ε _water : relative permittivity of _water

  Specific examples of water-soluble organic solvents that are general to water-based inks and are solid at 25 ° C. include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, polyethylene glycol having a number average molecular weight of 1,000, and the like. Can be mentioned.

The reason why the relative dielectric constant of the water-soluble organic solvent that is solid at 25 ° C. is calculated from the relative dielectric constant of the 50 mass% aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25 ° C., there are those that can be constituents of water-based inks, and it is difficult to prepare a high-concentration aqueous solution exceeding 50 mass%. On the other hand, in a low-concentration aqueous solution of 10% by mass or less, the relative permittivity of water is dominant, and it is difficult to obtain a certain (effective) relative permittivity value of the water-soluble organic solvent. Therefore, the present inventors have studied that most of the water-soluble organic solvents that are solid at 25 ° C. used in the ink can prepare an aqueous solution to be measured, and the calculated dielectric constant is also shown in this figure. It was found to be consistent with the effect of the invention. For the above reasons, in the present invention, the relative dielectric constant of a water-soluble organic solvent that is solid at 25 ° C. is calculated and used from the relative dielectric constant of a 50 mass% aqueous solution. Be a solid water-soluble organic solvent at 25 ° C., low solubility in water, that could not be prepared 50 wt% aqueous solution, according to the case of using an aqueous solution of saturated concentration, it calculates the above epsilon _sol The relative dielectric constant value calculated in the above is used for convenience.

  Specific examples of the first water-soluble organic solvent having a relative dielectric constant of 18.0 or more include ethylene urea (49.7), glycerin (42.3), ethylene glycol (40.4), 1- (2-hydroxy Ethyl) -2-pyrrolidone (37.6), trimethylolpropane (33.7), N-methyl-2-pyrrolidone (32.0), triethanolamine (31.9), diethylene glycol (31.7), 1,4-butanediol (31.1), 1,3-butanediol (30.0), 3-methylsulfolane (29.0), 1,2-propanediol (28.8), 1,2, 6-hexanetriol (28.5), 2-methyl-1,3-propanediol (28.3), 2-pyrrolidone (28.0), 1,5-pentanediol (27.0), 3-methyl -1,3 Butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), ethanol (23.8), triethylene glycol (22.7), tetraethylene glycol (20.8), number Examples include polyethylene glycol (18.9) having an average molecular weight of 200, 2-ethyl-1,3-hexanediol (18.5), isopropanol (18.3), and the like. Dielectric constant). The relative dielectric constant of the first water-soluble organic solvent is preferably 120.0 or less. The vapor pressure of the first water-soluble organic solvent at 25 ° C. is preferably lower than that of water.

  In addition, a water-soluble organic solvent having a relative dielectric constant of less than 18.0 may be used. Specific examples of the water-soluble organic solvent having a relative dielectric constant of less than 18.0 include the following. 1,2-hexanediol (14.8), n-propanol (12.0), polyethylene glycol (11.4) having a number average molecular weight of 600, triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), tripropylene glycol monomethyl ether (8.5), 1,6-hexanediol (7.1), polyethylene glycol (4.6) having a number average molecular weight of 1,000, etc. ( (The numerical value in parentheses is the relative dielectric constant at 25 ° C.). The relative dielectric constant is preferably 3.0 or more. These water-soluble organic solvents preferably have a vapor pressure at 25 ° C. lower than that of water.

(Other additives)
Each ink constituting the ink set of the present invention includes a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, and a chelating agent as necessary. Various additives such as an agent and other water-soluble resins may be contained. These additives generally have a considerably low content in the ink, and have little influence on the effects 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 targeted for calculating the relative dielectric constant.

<Inkjet recording method>
The ink jet recording method of the present invention is a method of recording an image on a recording medium by ejecting each ink contained in the ink set of the present invention described above from an ink jet recording head. Examples of the method for ejecting ink include a method for imparting mechanical energy to the ink and a method for imparting thermal energy to the ink. In the present invention, it is particularly preferable to employ a method in which thermal energy is applied to the ink and the ink is ejected. Other than using each ink included in the ink set of the present invention, the steps of the ink jet recording method may be known.

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

<Synthesis of coloring materials>
(Compound A)
A compound represented by the following formula (a) as a free acid form was synthesized with reference to the description in JP-A-2002-249677. Thereafter, ion exchange was performed according to a conventional method to obtain a sodium salt type compound (this compound is referred to as “compound A”).

(Compound B)
A compound represented by the following formula (b) was synthesized as a free acid type with reference to the description of JP-A-2002-249677. Thereafter, ion exchange was performed according to a conventional method to obtain a sodium salt type compound (this compound is referred to as “compound B”).

<Preparation of pigment dispersion>
(Pigment dispersion 1)
With reference to the description in International Publication No. 2000/058411, the surface of the pigment was oxidized using an oxidizing agent to prepare a self-dispersing pigment in which carboxylic acid groups were directly bonded to the pigment particle surface. After 14.0 parts of the pigment was dispersed in 65.0 parts of ion-exchanged water, 21.0 parts of an aqueous sodium hypochlorite solution (effective chlorine concentration: 4%) was added dropwise and stirred at a temperature of 100 ° C. for 10 hours. As the pigment, carbon black (trade name “FW-18”, manufactured by Orion Engineered Carbon) was used. Next, after purification by ultrafiltration, an appropriate amount of ion-exchanged water was added to adjust the pigment content, and a pigment dispersion 1 having a self-dispersing pigment content of 10.0% was obtained.

(Pigment dispersion 2)
500 g of ion-exchanged water and 15.0 g of a pigment (carbon black, trade name “FW-18”, manufactured by Orion Engineered Carbon) were mixed and stirred at a rotational speed of 15,000 rpm for 30 minutes to pre-wet the pigment. Further, 4,485 g of ion exchange water was added and dispersed with a high pressure homogenizer to obtain a dispersion. The obtained dispersion was transferred to a high-pressure vessel, and ozone water having an ozone concentration of 100 ppm was introduced into the high-pressure vessel while pressurizing at a pressure of 3.0 MPa to oxidize the pigment. Remove the mixture from the high-pressure vessel, add aqueous sodium hydroxide to adjust the pH of the liquid to 10.0, add an appropriate amount of ion-exchanged water to adjust the pigment content, Obtained. The pigment dispersion 2 contained a self-dispersing pigment in which a carboxylic acid group whose counter ion is sodium was directly bonded to the particle surface, and the pigment content was 10.0%.

(Pigment dispersion 3)
A solution obtained by dissolving 70.6 mmol of concentrated hydrochloric acid in 5.5 g of water was cooled to a temperature of 5 ° C., and 9.8 mmol of 4-aminophthalic acid was added. The container containing the solution was placed in an ice bath and the liquid was stirred, so that the solution was always kept at 10 ° C. or lower. To this was added a solution of 24.9 mmol of sodium nitrite in 9.0 g of water at 5 ° C. After stirring for an additional 15 minutes, 6.0 g of pigment was added with stirring. Carbon black (trade name “Black Pearls 880”, manufactured by Cabot) was used as the pigment. Thereafter, the mixture was further stirred for 15 minutes to obtain a slurry. The obtained slurry was filtered with a filter paper (trade name “filter paper for standard No. 2”, manufactured by Advantech), washed thoroughly with water, and dried in an oven at a temperature of 110 ° C. to obtain a self-dispersing pigment. The pigment dispersion 3 was obtained by adjusting the pigment content using ion-exchanged water. Pigment dispersion 3 contained a self-dispersed pigment in which a phthalic acid group whose counter ion is sodium was bonded to the particle surface, and the pigment content was 10.0%.

(Pigment dispersion 4)
10.0 parts of pigment, 20.0 parts of an aqueous solution of a resin dispersant, and 70.0 parts of ion-exchanged water were mixed to obtain a mixture. Carbon black (trade name “Black Pearls 880”, manufactured by Cabot) was used as the pigment. In addition, as an aqueous solution of the resin dispersant, a water-soluble resin styrene-acrylic acid copolymer (weight average molecular weight 10,000, acid value 200 mgKOH / g) is water having a neutralization equivalent 1 with respect to the acid value. What was dissolved in ion exchange water using sodium oxide was used. The obtained mixture was dispersed for 3 hours using a batch type vertical sand mill, and then pressure filtered through a microfilter (Fuji Film) having a pore size of 1.2 μm. Next, ion-exchanged water was added to adjust the pigment content, and a pigment dispersion 4 was obtained. The pigment dispersion 4 contains a pigment dispersed with a water-soluble resin (resin dispersant). The pigment content was 10.0% and the water-soluble resin content was 4.0%. .

<Preparation of ink>
Each component (unit:%) shown in the upper part of Tables 1-1, 1-2, and 2 is mixed and sufficiently stirred, and then filtered under pressure with a microfilter (manufactured by Fuji Film) having a pore size of 0.2 μm. Thus, each ink was prepared. In the lower part of Tables 1-1, 1-2, and 2, ink characteristics are shown. “Acetylenol E100” in Tables 1-1, 1-2, and 2 are trade names of nonionic surfactants manufactured by Kawaken Fine Chemicals, and “Proxel GXL (S)” is a preservative manufactured by Arch Chemicals. Product name.

<Evaluation>
The inks shown in Table 3 were combined to form an ink set, and the following evaluation was performed. The ink cartridge filled with each ink was set in an ink jet recording apparatus (trade name “MAXIFY MB5330”, manufactured by Canon Inc.) equipped with a recording head that ejects ink by thermal energy. The cyan ink was set at the cyan ink position, and the black ink was set at the black ink position. In this embodiment, a solid image recorded by applying 20 ng of ink to a unit area of 1/600 inch × 1/600 inch is defined as “recording duty is 100%”. In the present invention, “AA”, “A ⁺ ”, “A”, “A ⁻ ”, and “B” are acceptable levels, and “C” is an unacceptable level in the evaluation criteria of the following items. The evaluation results are shown in Table 3.

(Deposition suppression)
Using the above-described ink jet recording apparatus, a solid image of 2.5 cm × 2.5 cm in which the recording duty of cyan ink and black ink is 25% (total 50%), respectively, at a temperature of 30 ° C. and a relative humidity of 15 A total of 5,000 sheets were recorded in a% environment. The interval after recording one solid image was 3 minutes. Each time ten solid images were recorded, 1.5 mg cyan ink and 1.5 mg black ink were preliminarily ejected to the same position in the cap. After recording the predetermined number of sheets, the state of the deposit in the cap was visually confirmed, the situation in which the deposit was removed by the suction operation was confirmed, and deposition suppression was evaluated according to the following evaluation criteria.
AA: After recording 5,000 sheets, no deposit was generated in the cap.
A ⁺ : After recording 5,000 sheets, a small amount of deposit was generated in the cap, but it could be removed by one suction operation.
A: After recording 4,000 sheets, a small amount of deposit was generated in the cap, but it could be removed by one suction operation.
A ⁻ : After recording 3,000 sheets, a small amount of deposit was generated in the cap, but it could be removed by one suction operation.
B: A small amount of deposit was generated in the cap after 2,500 sheets were recorded, but it could be removed by one suction operation.
C: After 2,500 sheets were recorded, many deposits were present in the cap and could not be removed even after two suction operations.

(Color development (black))
Using a black ink mounted on the above-described ink jet recording apparatus, a solid image with a recording duty of 100% is printed on a recording medium (plain paper, trade name “PB PAPER”, manufactured by Canon) at a temperature of 23 ° C. and a relative humidity of 55. Recorded in a% environment. Using a spectrophotometer (trade name “Spectorolino”, manufactured by Gretag Macbeth), the optical density of a solid image obtained under the conditions of a light source: D50 and a field of view: 2 ° was measured. (Black) was evaluated.
A: The optical density was 1.2 or more.
C: The optical density was less than 1.2.

Claims (5)

A water-based ink set having a combination of cyan ink and black ink,
The color material of the cyan ink is a compound represented by the following general formula (1):
The color material of the black ink is a self-dispersing pigment,
The cyan ink contains a first water-soluble organic solvent having a relative dielectric constant of 18.0 or more,
The ink characterized in that the content (mass%) of the first water-soluble organic solvent in the cyan ink is 4.5 times or more in terms of the mass ratio with respect to the content (mass%) of the color material. set.

(In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ each independently represents an alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group, At least one of R ₁ , R ₂ , R ₃ , and R ₄ is substituted with an anionic group. A, b, c, and d each independently represent 1 or 2)   The ink set according to claim 1, wherein the self-dispersing pigment has a carboxylic acid group directly bonded to the surface of the pigment particle.   The content (mass%) of the first water-soluble organic solvent in the cyan ink is 8.5 times or more in terms of a mass ratio with respect to the content (mass%) of the color material. The ink set described.   The content (% by mass) of the first water-soluble organic solvent in the cyan ink is 16.0 times or more in terms of a mass ratio with respect to the content (% by mass) of the color material. The ink set described. An inkjet recording method for recording an image on a recording medium by discharging ink from an inkjet recording head,
An ink jet recording method, wherein the ink is each ink constituting the ink set according to any one of claims 1 to 4.

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