JP2010018764A - Ink set, method for inkjet-recording, recording unit, and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set in which especially in a regular paper recording, sufficient image concentration can be achieved, uniformity of image concentration is high, especially bleed in color image is prevented, and high toughness image showing high character grade, excellent water resistance and light resistance can be achieved. <P>SOLUTION: The ink set independently includes a first ink, and a second ink which is different in color or colorless, and is applied to a recording medium of a regular paper or the like to be used to form an image on a recording medium. The first ink is an aqueous ink having pH from 3 to 10 which includes: a compound of formula (I), a pigment in which an anion functional group chemically bonds to the surface of a pigment particle; and an aqueous medium. The second ink is an aqueous ink which includes a reactive compound making the dispersion of a pigment in the first ink be unstable when mixed with the first ink. The method for inkjet-recording, recording unit, and inkjet recording apparatus using the same are disclosed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink set, an ink jet recording method, a recording unit, and an ink jet recording apparatus which are used for forming an image by applying to a recording medium containing cellulose. In particular, when an image is formed on plain paper, a clear and high-quality image having a sufficient image density is provided, and the printed image is excellent in fastness such as water resistance and light resistance. Regarding technology. In addition to the effects described above, the present invention provides an ink set that gives a color image in which bleeding in the boundary region is sufficiently relaxed even when different color ink images are adjacent to each other, an ink jet recording method using the ink set, and recording The present invention relates to a unit and an ink jet recording apparatus.

  Inkjet recording is a method in which droplets of ink are generated by various ink ejection methods, and the droplets are ejected and adhered to a recording medium such as paper, and recording is performed by forming an inkjet. There is an advantage that high-speed printing and multicolor printing can be performed. As an ink jet recording method, there are various methods such as an electrostatic attraction method by applying a high voltage, a method of applying mechanical vibration or displacement to colored ink using a piezoelectric element, and a method of using pressure to heat and foam the ink. is there.

  In the case of forming a color image by the above-described ink jet recording method, generally three primary colors of water-based inks of cyan (C), magenta (M), and yellow (Y) are used. Furthermore, since many images are provided, such as text images, black (Bk) images are frequently recorded. Therefore, in addition to the above three primary color inks of C, M, and Y, Bk aqueous ink is added. More commonly, four color inks are used.

  In order to form a high-definition image on a recording medium containing cellulose such as plain paper by the ink jet recording method, the following performance is required for the water-based ink used for ink jet recording. That is, there is no feathering or bleeding, there is no color mixing (bleeding) between different colors in color images, and the fastness of the resulting image has good water resistance, light resistance, etc. Etc. are required.

  In particular, Bk ink, which is often used when forming an image mainly composed of characters, is required to have good character quality, high image density and black reproducibility. However, a water-based ink using a water-soluble dye as a coloring material has a problem that the water resistance of an image is not sufficient, and a pigment has been used as a coloring material. In order to use a pigment as a coloring material for aqueous ink, it is necessary to stably disperse the pigment in an aqueous medium. Patent Document 1 discloses a method of using a water-soluble resin as a dispersant in order to improve the dispersibility of a pigment.

  As a method for dispersing a pigment without using a dispersant, the pigment is modified to be self-dispersible by introducing a hydrophilic group on the surface of the pigment particles, and the pigment is dispersed in an aqueous medium without using a dispersant. A method has been proposed (see Patent Documents 2 and 3). These self-dispersing pigments are cationically or anionicly charged by the hydrophilic group on the pigment particle surface, have water dispersibility by repulsion of the ions, and have improved hydrophilicity by the hydrophilic group. It is a thing. Therefore, even when the ink is stored for a long time, a pigment ink in which the pigment is stably dispersed in the aqueous medium can be obtained. By forming an image with an aqueous ink using such a pigment as a color material, it is possible to obtain an image with good character quality and high image density. Also, the water resistance of the formed image is much better than that of the image formed with the dye ink. However, even when such a pigment ink is used, the problem of bleeding is not improved.

  Here, bleed means that when four color inks of C, M, Y, and Bk are used and an image is formed by applying different color inks to adjacent areas of the recording medium, the ink is not fixed at the boundary. This is a phenomenon in which they are partially mixed and as a result, boundary blur between different colors occurs. In particular, this bleed phenomenon becomes significant when two inks of Bk and color are adjacent to each other.

  As a means for solving the problem of bleeding, an ink in which a compound that enhances permeability such as a surfactant is added to an ink having a specific configuration is used (see Patent Document 4), and a volatile solvent is mainly used. It has been proposed to use the prepared ink (see Patent Document 5). However, in the former method, the permeability of the ink to the recording paper is improved and bleeding is suppressed to some extent, but the ink penetrates deep into the recording paper together with the colorant. There was a problem such as a decrease in the sharpness of the image. In addition, because the ink wettability with respect to the recording paper surface is improved, the ink is easy to spread, resolution is deteriorated, blurring occurs, and particularly when black characters are expressed, the quality is lowered. It was hard to say. On the other hand, in the latter case, in addition to the former problem, clogging due to evaporation of the solvent at the nozzle portion of the recording head is likely to occur, and this is a problem.

  Various other proposals have been made as means for solving the bleeding problem. For example, there is a proposal for a method of forming a color image with an ink set in which water-soluble dyes precipitated by a chemical reaction are combined (see Patent Documents 6 to 8). These techniques prevent bleeding by using a pH-sensitive dye as a coloring material or using a precipitating agent to deposit the dye after applying ink to the recording medium.

  There is also a proposal for a method of preventing mixing at the boundary between different colors of ink by changing the polarity of different colors of ink (see Patent Documents 9 and 10). In the method described in Patent Document 9, bleed is reduced by bringing an anionic ink or a cationic ink containing a polymer into contact with one of two or more colors. In the method described in Patent Document 10, bleed reduction is attempted by a combination of an anionic dye and a cationic dye, or a combination of one water-soluble dye and the other water-insoluble dye and a polymer substance.

  The ink sets disclosed therein reduce bleed by salting and agglomerating at the boundary of different color inks by reaction between inks of different polarities, anionic and cationic. The ink polarity is derived from a water-soluble dye or a water-soluble polymer, but these substances that influence the polarity of the ink are uniformly dissolved in the aqueous medium. For this reason, salt formation and aggregation reactions at the boundary between different color inks occur at a small molecular level of water-soluble dye molecules and water-soluble polymer molecules, which prevents sudden agglomeration and completely prevents bleeding. It has not yet reached. In addition, when the dye causes a salt-forming reaction, there is a problem that a change in color tone also occurs. Further, in these techniques, since the ink using a water-soluble dye as a color material is used for at least one of the inks constituting the ink set, the water resistance of the obtained recorded image becomes a problem.

JP-A-3-210373 JP-A-5-186704 JP-A-8-3498 JP 55-65269 A JP-A-55-66976 Japanese Patent Laid-Open No. 5-208548 JP-A-6-57192 JP-A-6-106841 JP-A-7-145336 JP-A-9-109547

  The present invention has been made in view of the above circumstances, and the object thereof is as follows. An object of the present invention is to obtain a sufficient image density, particularly in ordinary paper recording, to have high uniformity of image density, to prevent bleeding particularly in color images, and to achieve high character quality, excellent water resistance and light resistance. It is an object of the present invention to provide an ink set capable of obtaining a fast image having high properties. Another object of the present invention is to provide an ink jet recording method, a recording unit, and an ink jet recording apparatus capable of forming a color image having high quality and excellent fastness by using such an ink set. is there.

（式中、Ｍ₁及びＭ₂は、独立して、水素原子、アルカリ金属、有機アミンを示し、Ｒは、アルキル基又はアリール基、アルキルアリール基を表す。ｎは、０≦ｎ≦７のいずれかの整数を表す。） The above object is achieved by the present invention described below. That is, the present invention independently comprises at least a first ink and a second ink that is different in color or colorless from the first ink, and these inks contain a cellulose-containing recording medium. An ink set for use in a recording method for forming an image by applying to the compound, wherein the first ink comprises a compound of the following general formula (I) and a coloring material, either directly on the surface or via other atomic groups An aqueous ink having a pH of 3 to 10 comprising a pigment having an anionic functional group chemically bonded thereto, and an aqueous medium as a dispersion medium for the pigment, and the second ink comprises An ink set comprising: a reactive compound that destabilizes dispersion of a pigment in the first ink when mixed with the first ink, and an aqueous medium.

(In the formula, M ₁ and M ₂ independently represent a hydrogen atom, an alkali metal, or an organic amine, R represents an alkyl group, an aryl group, or an alkylaryl group. N represents 0 ≦ n ≦ 7. Represents any integer.)

  Another embodiment of the present invention is an ink jet recording method in which a color image is formed by an ink jet method on a recording medium containing cellulose using the ink set having the above structure, and the ink set is configured. A step of applying a first ink to a recording medium by an ink jet recording method, and a step of applying a second ink constituting the ink set to the recording medium, wherein the first ink and the second ink An ink-jet recording method comprising contacting ink.

  In another embodiment of the present invention, a first ink storage portion that stores the first ink that constitutes the ink set, and a second storage portion that stores the second ink. And an inkjet head group for ejecting each ink independently.

  Another embodiment of the present invention is an ink jet recording apparatus comprising the above recording unit.

  According to the present invention, a sufficient image density is obtained, particularly in plain paper recording, the uniformity of the image density is high, bleeding is prevented particularly in color images, high character quality, and excellent water resistance and light resistance. Provided is an ink set capable of obtaining a high-strength image exhibiting the property. In addition, according to the present invention, it is possible to provide an ink jet recording method, a recording unit, and an ink jet recording apparatus capable of forming a color image having high quality and excellent fastness.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.
As a result of intensive studies on the above-described problems of the prior art, the present inventors have found that the first ink containing a specific compound and a specific color material is different in color or colorless from the first ink. It has been found that the above-mentioned object can be achieved by combining an ink of the above and making an ink set. The components constituting each of the first ink characterizing the ink set of the present invention and the second ink used together with the first ink will be described.

（式中、Ｍ₁及びＭ₂は、独立して、水素原子、アルカリ金属、有機アミンを示し、Ｒは、アルキル基又はアリール基、アルキルアリール基を表す。ｎは、０≦ｎ≦７のいずれかの整数を表す。） The first ink constituting the ink set of the present invention needs to be a water-based ink containing the following three components and having a pH adjusted from 3 to 10. That is, the first ink includes a compound represented by the following general formula (I), a pigment having an anionic functional group chemically bonded to the surface directly or through another atomic group as a coloring material, and the pigment And an aqueous medium as a dispersion medium.

(In the formula, M ₁ and M ₂ independently represent a hydrogen atom, an alkali metal, or an organic amine, R represents an alkyl group, an aryl group, or an alkylaryl group. N represents 0 ≦ n ≦ 7. Represents any integer.)

  The second ink constituting the ink set of the present invention is an aqueous ink comprising a reactive compound that destabilizes dispersion of the pigment in the first ink when mixed with the first ink. It is necessary to be.

  A more preferable form of the ink set of the present invention is that the first or second ink is a water-based ink (hereinafter simply referred to as ink) that satisfies the following requirements. First, the following is mentioned as a more preferable configuration of the first ink. The compound of the general formula (I) in the first ink does not contain an ethylene oxide chain [that is, n = 0 in the formula (I)]. The average particle diameter of the pigment in the first ink is in the range of 60 nm to 180 nm. The anionic functional group chemically bonded to the surface of the pigment particles in the first ink directly or through another atomic group is a carboxylic acid or a sulfonic acid. The number of anionic functional groups bonded to the pigment in the first ink is 100 μmol / g or more and 5,000 μmol / g or less with respect to 1 g of the pigment. Furthermore, the anionic functional group bonded to the pigment particles in the first ink is 300 μmol / g or more and 2,500 μmol / g or less as the amount applied to 1 g of the pigment. The first ink contains polyvalent metal ions, and the polyvalent metal ion concentration is 300 ppm or less. The first ink is black ink.

  Moreover, as a more preferable configuration of the second ink, it is mentioned that the second ink contains any of a polyvalent metal salt, a low molecular weight cationic compound, and a cationic polymer.

[First ink]
(Compound represented by formula (I))
The first ink constituting the ink set of the present invention is required to contain a compound represented by the following general formula (I), but when an image is formed with the ink set of the present invention, An excellent bleed suppression effect is exhibited by the reaction with the second ink. According to the study by the present inventors, a stronger bleed suppression effect is exhibited, particularly when a compound that does not contain an ethylene oxide chain (n = 0) among the compounds of general formula (I) is used. A high image density can be obtained.

（式中、Ｍ₁、Ｍ₂は、独立して水素原子、アルカリ金属、有機アミンを示し、Ｒは、アルキル基又はアリール基、アルキルアリール基を表す。ｎは、０≦ｎ≦７の整数を表す。）

(In the formula, M ₁ and M ₂ independently represent a hydrogen atom, an alkali metal, or an organic amine, R represents an alkyl group, an aryl group, or an alkylaryl group. N represents an integer of 0 ≦ n ≦ 7. Represents.)

  The reason why the excellent bleed suppression effect is recognized by using the compound of the general formula (I) is not clear, but the present inventors consider as follows. In the first ink, the compound of the general formula (I) having the above structure adsorbs the hydrophobic part of the compound on the hydrophobic part present on the pigment surface, and the hydrophilic part is compatible with the aqueous medium and serves as a dispersion aid. work. On the other hand, when it contacts the second ink when forming an image, it functions as follows. Since the compound of the above general formula (I) has two acid groups bonded to phosphorus in the structure, the dispersion of the pigment in the first ink contained in the second ink is destabilized. It is considered that the hydrophilicity of the pigment is lowered by reacting strongly with the reaction components for making it hydrophobic. For this reason, it is presumed that the outflow of the pigment to the different color ink when the different color ink is driven adjacently is suppressed, and as a result, a high quality image in which the bleeding phenomenon is suppressed is obtained.

  In the above, in order to further promote the hydrophobization of the pigment, it is preferable that the hydrophobicity of the compound of the general formula (I) is higher. Therefore, it is preferable that the ethylene oxide chain number (number of n in the general formula (I)) exhibiting hydrophilicity is smaller. However, since the solubility of the compound represented by the general formula (I) in the aqueous solution decreases accordingly, it is necessary to set n and R within a range where the compound is dissolved or dispersed in the aqueous solution. The content of the compound represented by the general formula (I) in the ink is not particularly limited, but is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.8% by mass with respect to the total amount of the ink. It is 05 mass% or more and 5 mass% or less.

Preferred specific examples of the compound of the general formula (I) are shown below.

(Pigment)
The pigment contained in the first ink constituting the ink set of the present invention needs to be a pigment in which an anionic functional group is chemically bonded to the surface of the pigment particle directly or through another atomic group. . The content of the pigment in the ink is not particularly limited, but is preferably configured as follows. The amount added to the ink is not limited to this range, but it is preferable to add it in the following range. The content is preferably 0.1% by mass or more and 15% by mass or less with respect to the total amount of the ink, particularly 0.2% by mass or more and 12% by mass or less, and more preferably 0.3% by mass or more and 10% by mass or less. preferable.

Hereinafter, pigment particles (hereinafter simply referred to as a pigment) constituting the pigment contained in the first ink will be described. First, as a pigment used for black ink, for example, carbon black such as furnace black, lamp black, acetylene black, and channel black is preferable. Among carbon blacks, those having the following characteristics are preferably used. That is, the primary particle size is 15 nm to 40 nm, the specific surface area by BET method is 50 m ² / g to 300 m ² / g, DBP oil absorption is 40 ml / 100 g to 150 ml / 100 g, and the volatile content is 0.5% by mass or more. It has the characteristic of 10 mass% or less.

  As the pigment used in the color ink, organic pigments as listed below are preferably used. Specifically, the following pigments can be exemplified. Insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, and Pyrazolone Red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon. Phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green. Quinacridone pigments such as quinacridone red and quinacridone magenta. Perylene pigments such as perylene red and perylene scarlet. Isoindolinone pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Indigo pigment. Condensed azo pigments and thioindigo pigments. Diketopyrrolopyrrole pigment. Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet, etc.

  Moreover, when an organic pigment is shown by a color index (CI) number, the following are mentioned. C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 55, 74, 83, 86, 93, 97, 98, 109, 110, 117, 120, 125, and 128. C. I. Pigment Yellow 137, 138, 139, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, and 185. C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71. C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192. C. I. Pigment Red 202, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272. C. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50. C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 22 and 60, 64. C. I. Pigment Green 7 and 36. C. I. Examples thereof include CI Pigment Brown 23, 25, and 26. Although pigments other than those described above can be used, among these pigments, those listed below are particularly preferable. C. I. Pigment Yellow 13, 17, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154, 155, 180, the same 185. C. I. Pigment Red 122, 202 and 209. C. I. Pigment Blue 15: 3 and 15: 4 are preferable.

  Furthermore, the pigment to be contained in the ink used for ink jet recording is preferably one in which primary particles are finely divided. As the fine particle method used in this case, the following methods can be used. For example, a method of applying strong grinding with a bead mill or the like, a mechanical method using a jet mill or the like, or a method of synthesizing a pigment having a primary particle size as small as possible and low surface activity at the time of pigment synthesis. . In addition, fine particle formation by an evaporation method in an inert gas, that is, a method such as a gas phase method may be mentioned. In order to obtain a preferable adsorptive power of pigment to plain paper when an image is formed, the average particle size of the pigment contained in the ink is 60 nm or more and 180 nm or less, preferably 80 nm or more and 170 nm or less, more preferably 100 nm or more and 160 nm. The following.

(Anionic functional group chemically bonded to the surface of pigment particles)
As described above, the pigment constituting the first ink used in the present invention has an anionic functional group in which an anionic functional group is chemically bonded to the surface of the pigment particle directly or through another atomic group. The functional group will be described below. Examples of the functional group include those in which a hydrophilic group such as —COO (M2), —SO ₃ (M2) ₂ , —PO ₃ H (M2), —PO ₃ (M2) ₂ is bonded. . However, M2 in a formula represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium.

  Among those expressed as “M2” in the hydrophilic group, specific examples of the alkali metal include Li, Na, K, Rb and Cs. Moreover, as a specific example of organic ammonium, the following are mentioned, for example. That is, methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, monohydroxymethylamine, dihydroxymethylamine, trihydroxymethylamine and the like.

  Specific examples of a method for producing a pigment having an anionic functional group in which an anionic functional group is chemically bonded to the surface of the pigment particle used in the present invention directly or through another atomic group include carbon black. The method of oxidizing with sodium hypochlorite is mentioned. According to this method, a —COONa group, which is a hydrophilic group, can be chemically bonded to the carbon black surface.

By the way, the various hydrophilic groups as described above may be directly bonded to the surface of the pigment, or other atomic groups may be interposed between the pigment surface and the hydrophilic group as described above, The functional group may be indirectly bonded to the pigment surface. Specific examples of the other atomic groups include, for example, a linear or branched alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group. . Here, as a substituent of a phenylene group and a naphthylene group, a C1-C6 linear or branched alkyl group is mentioned, for example. Specific examples of combinations of other atomic groups and hydrophilic groups include, for example, —C ₂ H ₄ —COO (M2), —Ph—SO ₃ (M2) ₂ , —Ph—COO (M2), and the like. Can be mentioned. However, said Ph represents a phenyl group.

  Here, the number of anionic functional groups (hydrophilic treatment amount) bonded to the pigment particles is preferably 100 μmol / g or more and 5,000 μmol / g or less, more preferably 300 μmol with respect to 1 g of the pigment. / G to 2,500 μmol / g. When the hydrophilization treatment amount is less than 100 μmol / g, the pigment is not stably dispersed in the aqueous solution, and the pigment may settle, resulting in lack of reliability as an ink. On the other hand, if the amount of hydrophilic treatment exceeds 5,000 μmol / g, bleeding of printed matter may not be sufficiently suppressed, which is not preferable. Even if the hydrophobicity of the pigment is increased by the reaction of the pigment in the first ink and the compound of the general formula (I) with the reactive compound in the second ink, the hydrophilicity of the pigment is sufficiently high, so that the dispersion Is not destabilized, and as a result, bleed of printed matter may not be sufficiently suppressed.

(Aqueous medium)
The first ink used in the present invention contains an aqueous medium as an essential component, but preferably contains water. The content of water in the ink is preferably 30% by mass or more and preferably 95% by mass or less with respect to the total mass of the ink. In many cases, an aqueous medium in which water and a water-soluble solvent are used in combination is used as the aqueous medium. Examples of the water-soluble solvent used in combination with water include the following, but are not limited thereto. For example, alkyl alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and n-pentanol. Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane. Oxyethylene or oxypropylene polymers such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol. Alkylene glycols in which an alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol; Triols such as 1,2,6-hexanetriol, glycerin and trimethylolpropane. Lower alkyl ethers of glycols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl, butyl) ether. Lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether. Alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. Examples include sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, urea, ethylene urea, bishydroxyethyl sulfone, diglycerin, and triglycerin. The type and content of the water-soluble solvent used in combination with water are not particularly limited, but it is preferably 3% by mass or more and preferably 60% by mass or less with respect to the total amount of the ink.

(Surfactant)
In the first ink used in the present invention, in order to obtain a more balanced ejection stability, it is preferable to further contain a surfactant in the ink. Among them, it is preferable to use a nonionic surfactant in combination at a mass ratio of 1/10 to 10/1 with respect to the compound of the general formula (I). The surfactant used here is particularly preferably an ethylene oxide adduct of acetylene glycol. The HLB (Hydrophile-Lipophile Balance) value is preferably 10 or more. The content of the surfactant used in this manner is preferably 0.01% by mass or more and 5% by mass or less, particularly 0.05% by mass or more and 4% by mass or less, and more preferably 0.00% by mass or less with respect to the total amount of the ink. It is preferable that they are 1 mass% or more and 3 mass% or less.

(Other additives)
The first ink used in the present invention is an ink having a desired physical property value. In addition to the above-described components, the first ink, as necessary, includes a viscosity modifier, an antifoaming agent, a preservative, Anti-fungal agents, antioxidants and the like can be added. The additive is preferably selected so that the surface tension of the ink is 25 mN / m or more, preferably 28 mN / m or more.

(PH)
The pH of the first ink used in the present invention needs to be adjusted to a range of 3 to 10. When the pH is less than 3, the solubility of the compound of the general formula (I) described above or the pigment used in the present invention is lowered, and precipitates may be generated in the ink. On the other hand, if the pH is higher than 10, even if the first ink and the second ink come into contact with each other, the dispersion is not destabilized and the technical problem of the present invention may not be solved. In addition, although it is preferable to use lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. for pH adjustment of the 1st ink, it is not limited to these.

(Polyvalent metal)
Furthermore, the first ink used in the present invention may additionally contain a metal. However, considering that the compound of the general formula (I) described above reacts with the polyvalent metal, it is preferable to reduce the ion concentration of the polyvalent metal contained in the first ink as much as possible. Specifically, it is preferably 300 ppm or less. This is because if the polyvalent metal ion concentration in the first ink used in the present invention exceeds 300 ppm, the effect of using the compound may not be sufficiently exhibited.

[Second ink]
(Reactive compounds)
The second ink constituting the ink set of the present invention is a water-based ink having a color different from that of the first ink or colorless. Here, “colorless” means that no color material is positively contained as a component of the ink, and the color tone of the first ink is not changed when mixed with the first ink. It may be colored. Furthermore, the second ink constituting the ink set of the present invention contains a reactive compound that destabilizes dispersion of the pigment in the first ink when mixed with the first ink described above. It is necessary to be a water-based ink consisting of Here, “destabilize pigment dispersion” means that insoluble matter is generated when the first ink and the second ink are mixed. Most of the insolubles are aggregates that can be visually judged. For example, the insolubles are aggregates that can be confirmed by the presence of precipitates when filtered with a filter having a pore diameter of about 1 μm.

  The reactive compound contained in the second ink of the present invention that destabilizes the dispersion of the pigment when mixed with the first ink includes the pigment in the first ink, and the general formula (I) Any of the compounds that cause a chemical reaction with the above compound and destabilize the dispersion of the pigment may be used. For example, a polyvalent metal salt, a low molecular weight cationic compound, a cationic polymer and the like can be cited as representative examples, and specifically, the following can be used, but are not limited thereto. Absent.

  Specific examples of the polyvalent metal salt include the following. Examples of the polyvalent metal salt include alkaline earth metal salts and transition metal salts. Examples of the alkaline earth metal salt include magnesium chloride, calcium chloride, strontium chloride, magnesium acetate, calcium acetate, magnesium nitrate, and calcium nitrate. Examples of the transition metal salt include zinc chloride, zinc acetate, copper (II) chloride, yttrium nitrate, and zirconium chloride. Moreover, as a typical thing of a low molecular cation compound, an amine type compound is mentioned, A quaternary ammonium salt is especially preferable. Specifically, tetramethylammonium chloride, tetramethylammonium bromide, tetraethylammonium bromide, tetrabutylammonium bromide. Moreover, dodecyl trimethyl ammonium chloride, benzyl trimethyl ammonium chloride, cetyl pyridinium chloride, etc. are mentioned. Furthermore, the cationic polymer may be any as long as it has a cationic group in the polymer molecule such as a homopolymer or copolymer of a cationic monomer. Specific examples include polymer hydrolysates containing polyvinylamine, polyallylamine, polydiallyldimethylammonium chloride, and N-vinylformamide as a copolymerization component.

  These reactive compounds may be used alone or in combination. The addition amount may be any as long as it is sufficient to cause a chemical reaction when the first ink and the second ink are mixed. Usually, it is preferably 0.1% by mass or more and 20% by mass or less, and particularly preferably 0.5% by mass or more and 10% by mass or less with respect to the total amount of the second ink. Also, the second ink may contain a water-soluble solvent, water, a surfactant, and various additives in the same manner as the first ink. Further, the second ink may or may not contain a color material. When the second ink contains a color material, a color material having a color different from that of the first ink is used. Of course, the coloring material contained in the second ink does not react with the reactive compound as described above constituting the second ink, or is dissolved or dissolved stably in the aqueous solution even in the presence of the reactive compound. It is necessary to select one that can be dispersed.

  The ink set of the present invention is suitably used for recording by an ink jet recording method. That is, when a color image is formed on a recording medium containing cellulose by an ink jet method using the ink set of the present invention, a color image having high quality and excellent fastness can be formed. The ink jet recording method of the present invention includes a step of applying the first ink constituting the ink set of the present invention to the recording medium by the ink jet recording method, and the second ink constituting the ink set described above. And applying to the recording medium. Furthermore, the first ink and the second ink constituting the ink set of the present invention are brought into contact with each other.

  As an ink jet recording method, there are a recording method in which mechanical energy is applied to ink to eject the ink, and a recording method in which thermal energy is applied to the ink and ink is ejected by foaming of the ink. A recording method can also be used. In the ink jet recording method of the present invention, it is preferable to use a thermal jet method utilizing thermal energy. The contact method for bringing the first ink and the second ink into contact with each other is not particularly limited. For example, the following method may be used. It is preferable to apply one of the inks to the recording medium by the ink jet recording method first, and then apply the other to the recording medium by the ink jet recording method so as to overlap or adjoin. It is also effective to apply the first ink by an ink jet recording method after applying the second ink to the recording medium with a roller or the like.

  Next, a preferred example of the ink jet recording apparatus of the present invention, which performs recording using the above-described ink set of the present invention, will be described below. The ink jet recording apparatus of the present invention includes a recording unit having the following configuration. The recording unit includes a first ink storage portion that stores the first ink constituting the ink set of the present invention, a second storage portion that stores the second ink, and each ink. And an inkjet head group for independently discharging.

FIG. 1 and FIG. 2 show an example of a head configuration which is a main part of an ink jet recording apparatus using thermal energy. FIG. 1 is a cross-sectional view of the head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along line AB in FIG. The head 13 is obtained by bonding a heating element substrate 15 and a glass, ceramic, silicon, or plastic plate having a flow path (nozzle) 14 through which ink passes. The heating element substrate 15 includes a protective layer 16, electrodes 17-1 and 17-2, a heating resistor layer 18, a heat storage layer 19, and a substrate 20. The protective layer 16 is made of silicon oxide, silicon nitride, silicon carbide, or the like. The electrodes 17-1 and 17-2 are made of aluminum, gold, aluminum-copper alloy, or the like. The heating resistor layer 18 is formed of a high melting point material such as HfB ₂ , TaN, TaAl. The heat storage layer 19 is formed of thermally oxidized silicon, aluminum oxide, or the like, and the substrate 20 and the substrate 20 are formed of a material with good heat dissipation such as silicon, aluminum, or aluminum nitride.

  In an ink jet recording apparatus using thermal energy, ink is ejected from the recording head having the above-described configuration as follows. First, when a pulsed electric signal is applied to the electrodes 17-1 and 17-2 of the head 13, the region indicated by n of the heating element substrate 15 rapidly generates heat, and the ink 21 in contact with this surface Bubbles are generated. Then, the meniscus 23 protrudes by the pressure of the bubbles, the ink 21 is ejected through the nozzle 14 of the head, becomes an ink droplet 24 from the ejection orifice 22, and flies toward the recording medium 25. FIG. 3 shows an external view of an example of a multi-head in which a large number of heads shown in FIG. 1 are arranged. This multi-head is made by adhering a glass plate 27 having multi-nozzles 26 and a heat-generating head 28 having the same configuration as that described in FIG.

  FIG. 4 shows an example of an ink jet recording apparatus incorporating this head. In FIG. 4, reference numeral 61 denotes a blade as a wiping member, one end of which is held and fixed by a blade holding member, and forms a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head 65, and in this example, is held in a form protruding in the moving path of the recording head 65.

  Reference numeral 62 denotes a cap on the protruding port surface of the recording head 65, which is disposed at the home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, contacts the ink discharge port surface, and capping. The structure which performs is provided. Further, 63 is an ink absorber provided adjacent to the blade 61, and is held in a form protruding in the moving path of the recording head 65, similar to the blade 61. The blade 61, the cap 62, and the ink absorber 63 constitute a discharge recovery portion 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the discharge port surface.

  Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording medium facing the discharge port surface where the discharge port is arranged. Reference numeral 66 denotes a movement of the recording head 65 by mounting the recording head 65. It is a carriage for performing. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording area and its adjacent area can be moved by the recording head 65.

  51 is a paper feeding unit for inserting a recording medium, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording medium is fed to a position facing the 65 discharge port surface of the recording head, and is discharged to a discharge portion provided with a discharge roller 53 as recording progresses. In the above configuration, when the recording head 65 finishes recording and returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port of the recording head 65 is wiped.

  When the cap 62 is in contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as that at the time of wiping described above. As a result, the ejection port surface of the recording head 65 is wiped even during this movement. The above-mentioned movement of the recording head to the home position is not only at the end of recording or at the time of ejection recovery, but also to the home position adjacent to the recording area at a predetermined interval while the recording head moves the recording area for recording. Then, the wiping is performed with this movement.

  FIG. 5 is a diagram illustrating an example of an ink cartridge that contains ink supplied to the recording head via an ink supply member, for example, a tube. Reference numeral 40 denotes an ink container, for example, an ink bag, which stores ink for supply, and a rubber plug 42 is provided at the tip of the ink container. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives waste ink. The ink container preferably has a liquid contact surface made of polyolefin, particularly polyethylene.

  The ink jet recording apparatus of the present invention is suitably used not only for the recording head and the ink cartridge as described above, but also for those in which they are integrated as shown in FIG. . In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage portion that stores ink, for example, an ink absorber is stored, and the ink in the ink absorber from the head portion 71 having a plurality of orifices. It is configured to be ejected as ink droplets. As the material of the ink absorber, polyurethane is preferably used in the present invention. Alternatively, a structure in which the ink container is an ink bag with a spring or the like inside without using an ink absorber may be used. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere. The recording unit 70 is used in place of the recording head 65 shown in FIG. 4 and is detachable from the carriage 66.

  Next, a preferred example of an ink jet recording apparatus configured to eject ink using mechanical energy will be described. As the recording head constituting such an apparatus, the following on-demand ink jet recording head can be exemplified. The recording head includes a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed to face the nozzles, and ink filling the periphery of the pressure generating element. The pressure generating element is displaced by the applied voltage, and a small droplet of ink is ejected from the nozzle. FIG. 7 shows an example of the configuration of a recording head that is a main part of a recording apparatus that ejects ink using mechanical energy.

  The recording head includes an ink flow path 80 communicating with an ink chamber (not shown), an orifice plate 81 for ejecting ink droplets of a desired volume, a vibration plate 82, a piezoelectric element 83, an orifice plate 81, vibrations. And a substrate 84 that supports and fixes the plate 82 and the like. The vibration plate 82 applies pressure directly to the ink, and the piezoelectric element 83 is joined to the vibration plate 82 and is configured to be displaced by an electric signal.

  Each member constituting the recording head shown in FIG. 7 is made of the following materials. The ink flow path 80 is formed of a photosensitive resin or the like, and the orifice plate 81 is made of a metal such as stainless steel or nickel, but an ink discharge port 85 is formed by electroforming or punching by pressing. The diaphragm 82 is made of a metal film such as stainless steel, nickel, or titanium and a highly elastic resin film, and the piezoelectric element 83 is made of a dielectric material such as barium titanate or PZT.

  In an ink jet recording apparatus that ejects ink using mechanical energy, recording is performed by ejecting ink as follows from the recording head having the above-described configuration. First, a strain stress is generated by applying a pulsed voltage to the piezoelectric element 83. Then, the energy deforms the vibration plate 82 bonded to the piezoelectric element 83, pressurizes the ink in the ink flow path 80 vertically, and discharges ink droplets (not shown) from the discharge port 85 of the orifice plate 81. Operates to record. The recording head of the above system is also used by being incorporated in an ink jet recording apparatus similar to that shown in FIG. The detailed operation of the ink jet recording apparatus at this time may be performed in the same manner as the recording apparatus that ejects ink using the thermal energy described above.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, “parts” and “%” are based on mass unless otherwise specified. In the embodiment, the first ink and the second ink defined in the present invention are used. However, since two types of ink are used in the comparative example, these inks are also referred to as the first ink and the second ink for convenience. Called ink.

<Example of production of black pigment A>
100 g of carbon black having a specific surface area of 220 m ² / g and a DBP oil absorption of 105 ml / 100 g and 25 g of p-aminobenzoic acid were mixed well with 750 g of water, and then 16.2 g of nitric acid was added dropwise thereto at 70 ° C. Stir. A few minutes later, a solution prepared by dissolving 10.7 g of sodium nitrite in 50 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry was filtered with a filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis), and the pigment particles collected by filtration were sufficiently washed with water and dried in an oven at 90 ° C. By the above method, the black pigment A in which the p-benzoic acid group which is an anionic functional group was introduce | transduced on the surface of carbon black was produced.

  The surface functional group density of the black pigment prepared above was subjected to neutralization titration with sodium hydroxide, and the density of the anionic functional group on the particle surface (amount of anionic functional group added to 1 g of pigment) was converted from the value. However, it was 700 μmol / g. Moreover, when the average particle diameter of the black pigment produced above was measured with a concentrated particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics), the average particle diameter was 110 nm.

<Preparation example of first inks 1-5>
The first inks 1 to 5 were prepared by using the black pigment A, adding each component according to the following formulation to a predetermined concentration (100 parts in total), thoroughly mixing and stirring these, and adjusting the pH with potassium hydroxide. Was adjusted to 8.5. Thereafter, the first inks 1 to 5 were prepared by pressure filtration with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm. In addition, acetylenol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) was used as an acetylene glycol ethylene oxide adduct which is a nonionic surfactant contained in each ink.

[First ink 1]
・ Black pigment A 4 parts ・ Glycerin 10 parts ・ Triethylene glycol 5 parts ・ Trimethylolpropane 5 parts ・ The following compound (a) 0.5 part ・ Acetylene glycol ethylene oxide adduct 0.5 part ・ Water balance

[First ink 2]
・ Black pigment A 4 parts ・ Diglycerin 12 parts ・ Diethylene glycol 4 parts ・ Trimethylolpropane 4 parts ・ The following compound (b) 0.5 part ・ Acetylene glycol ethylene oxide adduct 0.5 part ・ Water remainder

[First ink 3]
・ Black pigment A 4 parts ・ Glycerin 10 parts ・ Ethylene glycol 6 parts ・ 2-Pyrrolidone 4 parts ・ The following compound (c) 0.5 part ・ Acetylene glycol ethylene oxide adduct 0.5 part ・ Water balance

[First ink 4]
・ Black pigment A 4 parts ・ Glycerin 10 parts ・ Triethylene glycol 5 parts ・ Trimethylolpropane 5 parts ・ The following compound (z) 0.5 part ・ Acetylene glycol ethylene oxide adduct 0.5 part ・ Water balance

[First ink 5]
A first ink 5 was produced in exactly the same manner except that the compound (a) of the first ink 1 was removed.

<Examples of preparing second inks 1 to 3>
With the following formulation, the pH was adjusted to 5.0 with a 1N-hydrochloric acid aqueous solution, and pressure filtered through a 1 μm filter to prepare second colorless inks 1 to 3. In addition, acetylenol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) was used as an acetylene glycol ethylene oxide adduct which is a nonionic surfactant contained in each ink.

[Second ink 1]
・ C. I. Acid Blue 9 1 part ・ Magnesium nitrate 2 parts ・ Diglycerin 7 parts ・ Ethylene glycol 7 parts ・ Diethylene glycol 5 parts ・ Acetylene glycol ethylene oxide adduct 1 part ・ Water balance

[Second ink 2]
-Polyallylamine (average molecular weight 1,300) 1.5 parts-Benzalkonium chloride 0.5 parts-Glycerol 8 parts-Polyethylene glycol (average molecular weight 200) 5 parts-Ethylene glycol 5 parts-Acetylene glycol ethylene oxide adduct 1 Department / Water balance

[Second ink 3]
A poly (diallylamine hydrochloride / sulfur dioxide) having the average molecular weight of 5,000 in the following composition was used.
・ Calcium acetate 2 parts ・ Poly (diallylamine hydrochloride / sulfur dioxide) 1 part ・ Glycerin 10 parts ・ Diethylene glycol 4 parts ・ 1,2-hexanediol 4 parts ・ Acetylene glycol ethylene oxide adduct 0.5 part ・ Water balance

<Preparation example of yellow ink>
Acetylene glycol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) was used as an acetylene glycol ethylene oxide adduct which is a nonionic surfactant in the following composition.
・ C. I. Acid Yellow 23 3.5 parts, Glycerol 8 parts, Diethylene glycol 8 parts, Ethylene urea 4 parts, Acetylene glycol ethylene oxide adduct 1 part, Water balance

[Examples and Comparative Examples]
<Configuration of each ink set>
The first inks 1 to 5 and the second inks 1 to 3 were combined as shown in Table 1, respectively, to obtain ink sets of Examples 1 to 9 and Comparative Examples 1 to 6.

<Evaluation>
Each ink set was evaluated by the following evaluation methods and evaluation criteria. As the evaluation 1, the reactivity when the first ink and the second ink were mixed was evaluated. In addition, an image was formed using each of the ink sets described above and the yellow ink prepared above, and the bleed of the formed image was evaluated. Further, an image was formed using each of the above ink sets, and the image density was measured and evaluated. The obtained evaluation results are summarized in Table 1.

[Evaluation 1: Reactivity (dispersion of pigment dispersion)]
50 g each of the first ink and the second ink were mixed and stirred for about 1 hour, and then the mixed solution was filtered under pressure through a 1 μm filter. The state of the filtrate (precipitate) remaining on the filter was observed, and the reactivity (pigment dispersion instability) was evaluated according to the following evaluation criteria.
A: Deposits are deposited on the filter.
B: Some precipitates are present on the filter.
C: There is almost no precipitate on the filter.

[Evaluation 2: Bleed]
The first ink and the second ink were respectively filled in an ink tank, and the second ink was printed on a Canon PPC paper with a print density of 50% using an ink jet printer (BJF8500) equipped with an ink overstrike mechanism. . Thereafter, the first ink was solid-printed at a print density of 100%, and immediately thereafter, the yellow ink was solid-printed at a print density of 100% so as to be adjacent thereto. The boundary portion of the obtained solid print portion was visually observed to evaluate bleeding between the black ink and the yellow ink. The evaluation criteria at that time were as follows.
A: Bleed is hardly recognized at all the boundaries.
B: Some bleeding is recognized.
C: Bleed is terrible at almost all boundaries.

[Evaluation 3: Image density]
Using an ink jet printer (BJF8500) equipped with an ink overprinting mechanism, the first ink and the second ink are respectively filled in an ink tank, and the second ink is printed on a Canon PPC paper with a print density of 50%. did. Thereafter, the first ink was solid printed at a printing density of 100%. This was repeated three times to obtain three paper prints. The printed matter thus obtained was allowed to stand for 3 days, and then the reflection density of the solid printing portion was measured with a reflection densitometer Macbeth RD915 (manufactured by Macbeth), and this value was used as the image density of each ink. The average value of the three papers was evaluated according to the following evaluation criteria as the print density.
A: 1.30 or more B: 1.25 or more, less than 1.30 C: less than 1.25

  From the evaluation results in Table 1 above, it was confirmed that all of the ink sets of Examples 1 to 9 of the present invention were those that suppressed bleeding of printed matter and had higher image density.

It is a longitudinal cross-sectional view which shows an example of the head of an inkjet recording device. It is a cross-sectional view showing an example of the head of the ink jet recording apparatus. FIG. 2 is an external perspective view of a head in which the head shown in FIG. It is a schematic perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view which shows an example of an ink cartridge. It is a perspective view which shows an example of a recording unit. It is a schematic sectional drawing which shows another structural example of an inkjet recording head.

Claims (12)

At least the first ink and the second ink, which are different in color or colorless, are independently provided, and these inks are applied to a recording medium containing cellulose to form an image. An ink set used for a recording method to be formed,
The first ink includes a compound represented by the following general formula (I), a pigment having an anionic functional group chemically bonded to the surface directly or through another atomic group as a coloring material, A water-based ink having a pH of 3 to 10 comprising an aqueous medium as a dispersion medium,
The second ink is an aqueous ink comprising a reactive compound that destabilizes dispersion of the pigment in the first ink when mixed with the first ink, and an aqueous medium. An ink set characterized by

(In the formula, M ₁ and M ₂ independently represent a hydrogen atom, an alkali metal, or an organic amine, R represents an alkyl group, an aryl group, or an alkylaryl group. N represents 0 ≦ n ≦ 7. Represents any integer.)   The ink set according to claim 1, wherein the compound of the general formula (I) does not contain an ethylene oxide chain (n = 0 in the formula (I)).   The ink set according to claim 1 or 2, wherein an average particle diameter of the pigment in the first ink is in a range of 60 nm to 180 nm.   The ink set according to any one of claims 1 to 3, wherein the anionic functional group bonded to the pigment in the first ink is a carboxylic acid or a sulfonic acid.   5. The ink set according to claim 1, wherein the anionic functional group bonded to the pigment is 100 μmol / g or more and 5,000 μmol / g or less as an amount applied to 1 g of the pigment.   The ink set according to any one of claims 1 to 5, wherein the number of anionic functional groups bonded to the pigment is 300 µmol / g or more and 2500 µmol / g or less with respect to 1 g of the pigment.   The ink set according to any one of claims 1 to 6, wherein the first ink contains a polyvalent metal ion, and the polyvalent metal ion concentration is 300 ppm or less.   The ink set according to claim 1, wherein the first ink is a black ink.   The ink set according to claim 1, wherein the reactive compound in the second ink is any one of a polyvalent metal salt, a low molecular weight cationic compound, and a cationic polymer.   An ink jet recording method for forming a color image by an ink jet method on a cellulose-containing recording medium using the ink set according to any one of claims 1 to 9, wherein the ink set constitutes the ink set. A step of applying one ink to a recording medium by an ink-jet recording method, and a step of applying a second ink constituting the ink set to the recording medium, the first ink and the second ink, An ink jet recording method, comprising: bringing the ink into contact with each other.   A first ink storage unit that stores the first ink that constitutes the ink set according to any one of claims 1 to 9, and a second storage that stores the second ink. A recording unit, and an inkjet head for ejecting each ink independently.   An ink jet recording apparatus comprising the recording unit according to claim 11.

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