JP2009091492A - Ink set, method for inkjet-recording, ink cartridge, recording unit, and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set suppressing the occurrence of a misaligning phenomenon in forming an image by mounting an ink set consisting of a combination of first ink and second ink, on the inkjet recording apparatus, and to provide a method for inkjet-recording using this. <P>SOLUTION: The ink set is composed of a combination of first ink and second ink, the first ink containing a self-dispersible pigment having at least one hydrophilic group directly or through another atomic group bonding to the pigment, and ammonium ions, the second ink containing a pigment, a polymer having an acid value of 160 mg KOH/g or less, and alkali metal ions, wherein the concentration of the ammonium ion in the first ink A [mol/L] and the concentration of the alkali metal ion in the second ink B [mol/L] satisfy the relationship of 0.03≤A/B≤0.32. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink set, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus.

  Ink for ink jet recording is generally used as a dye ink in which a water-soluble dye is dissolved in an aqueous medium. However, in recent years, a pigment having excellent water resistance and light resistance of an image formed compared to a dye is aqueous. There is also provided a pigment ink dispersed in a medium. For pigment inks, self-dispersing pigments, in which pigments are dispersed in an aqueous medium with a dispersing agent, or self-dispersing pigments that disperse pigments by bonding hydrophilic groups to the pigment surface, are used as coloring materials. Some are dispersed in a medium. For example, because of its high image density and excellent character quality such as bleeding, it is proposed to select a self-dispersing pigment as the color material for black ink used when recording characters and figures on plain paper. (See Patent Documents 1 and 2).

  In addition, the pigment ink used when forming images on special recording media such as glossy paper with a coated surface is a type in which pigments are dispersed using a resin as a dispersant in consideration of scratch resistance and glossiness. It is said that it is effective to use the above resin dispersion type pigment as a coloring material. Furthermore, in recent years, there is also a proposal for using a plurality of different types of pigment inks together in order to obtain good image quality regardless of the type of recording medium. For example, two types of resin-dispersed pigment ink using a resin-dispersed pigment as a coloring material and self-dispersing pigment ink using a self-dispersing pigment as a coloring material can be mounted on an inkjet recording apparatus to form an image. It has been proposed (see Patent Document 3).

JP 2000-198955 A JP 2001-089688 A JP 2003-213180 A

Among the above-mentioned technical trends, the present inventors have also proposed two types of inks, a self-dispersed pigment ink and a resin-dispersed pigment ink, for the purpose of obtaining good image quality regardless of the type of recording medium. Various investigations were made using an ink jet recording apparatus equipped with. Specifically, the image quality of the formed image, examination of water resistance and scratch resistance, and recording durability in the recording apparatus were examined. During the examination, a self-dispersing pigment in which —COONH ₄ having excellent water resistance as a hydrophilic group was bonded to the pigment surface was used as a coloring material of the self-dispersing pigment ink. Further, a pigment dispersion in which a pigment was dispersed with an acrylic resin having an acid value of 160 mgKOH / g or less neutralized with potassium hydroxide to 1 equivalent was used for the color material of the resin-dispersed pigment ink.

  The present inventors performed the following tests in the course of various studies using the above two types of inks. As a result, it was newly confirmed that the following phenomenon occurred. That is, a recording durability test was performed in which hundreds of specific images were recorded using each ink. Then, the degree of deterioration of the image before and after the recording durability test was investigated by observing the nozzle check pattern recorded for confirming the state of each nozzle every time a predetermined number of the specific images were recorded. . The specific image in the above is specifically a solid image having a duty of 15% with respect to an image having a recording density of 1200 dpi × 1200 dpi formed on A4 size plain paper.

  As a result, when recording was performed with each ink alone mounted on an ink jet recording apparatus, the phenomenon that the image deteriorated was not confirmed even when several hundred images were recorded. However, when two types of ink, the self-dispersed pigment ink and the resin-dispersed pigment ink, are both mounted on an ink jet recording apparatus and the recording durability test is performed as described above, the following phenomenon occurs. It was confirmed. That is, in this case, it was confirmed that the nozzle check pattern recorded by using the self-dispersing pigment ink caused a twist and the image quality was lowered. This misalignment is a phenomenon that occurs when the position where ink is applied to the recording medium is deviated (hereinafter referred to as the “delay phenomenon”). In addition, depending on the type of ink studied, this twisting phenomenon may occur even if the suction recovery operation is performed immediately after both of the two types of ink are mounted on the ink jet recording apparatus.

  Therefore, the present inventors have made a detailed study in order to clarify the factor causing the above-mentioned twist phenomenon. As a result, it has been found that the above-mentioned twist phenomenon occurs when the acid value of the resin contained in the resin-dispersed pigment ink is 160 mgKOH / g or less. Furthermore, it has been found that this twist phenomenon occurs more prominently when the following three conditions are satisfied. In addition, when the ink components are adjusted to solve the above-described problem, the storage stability of the first ink may be impaired, and the occurrence of the twist phenomenon is suppressed and the first ink is suppressed. Recognizing that both storage stability is an important issue.

  The first condition is when the distance between each of the ejection port arrays for ejecting the self-dispersing pigment ink and the resin-dispersed pigment ink is short in the recording apparatus. Specifically, the twist phenomenon was confirmed by discharging the self-dispersing pigment ink and the resin-dispersed pigment ink from the adjacent discharge port arrays, performing the suction recovery operation after that, and further recording the nozzle check pattern. .

  The second condition is that the recording apparatus has a structure in which the ejection port area including each ejection port array that ejects the self-dispersion pigment ink and the resin dispersion pigment ink is capped with one cap. is there.

  The third condition is a case where, among the inks used, there are many resins (hereinafter referred to as “free resins”) present in the resin-dispersed pigment ink that are not adsorbed to the pigments. Specifically, when the ink was prepared, when the resin was added more than 2% by mass in addition to the pigment dispersant, the above twist phenomenon was confirmed.

  Therefore, the object of the present invention occurs when an inkjet image is formed by using an ink containing a self-dispersing pigment and ammonium ions together with an ink containing a pigment, a resin having a specific acid value, and an alkali metal ion. It is to elucidate the substance of the twist phenomenon. Furthermore, an object of the present invention is to provide an ink set that can suppress the occurrence of the twist phenomenon without impairing the storage stability of an ink containing a self-dispersing pigment and ammonium ions, and an ink jet recording method using the ink set. Is to provide. Another object of the present invention is to provide an ink cartridge, a recording unit, and an ink jet recording apparatus using the ink set, which can obtain the effects described above.

  The above object is achieved by the present invention described below. That is, the present invention relates to a first ink containing a self-dispersing pigment in which a hydrophilic group is bonded directly or through another atomic group and an ammonium ion, a pigment, and an acid value of 160 mgKOH / g or less. An ink set having at least a combination of a resin and a second ink containing alkali metal ions, wherein the concentration of ammonium ions in the first ink is A [mol / L] and the second ink contains The alkali metal ion concentration B [mol / L] satisfies the relationship of 0.03 ≦ A / B ≦ 0.32.

  In another embodiment of the present invention, in an ink jet recording method for recording on a recording medium by ejecting ink by an ink jet method, the ink used is at least an ink constituting the ink set. It is a recording method.

  Another embodiment of the present invention is characterized in that, in an ink cartridge including an ink storage portion for storing ink, the ink stored in the ink storage portion is at least ink constituting the ink set. An ink cartridge.

  In another embodiment of the present invention, in a recording unit including an ink storage portion that stores ink and a recording head for ejecting ink, the ink stored in the ink storage portion is at least the ink set. Is a recording unit.

  In another embodiment of the present invention, in an ink jet recording apparatus including an ink containing portion for containing ink and a recording head for ejecting ink, the ink contained in the ink containing portion is at least the above ink. An ink jet recording apparatus characterized in that it is an ink constituting a set.

  According to the present invention, there is provided an ink set, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus capable of suppressing the occurrence of a twist phenomenon that occurs when an image is formed using a plurality of inks as a subject of the present invention. Provided. In particular, according to the present invention, the twist phenomenon that occurs during image formation, which is the subject of the present invention, is suppressed, and the storage stability of the ink containing the self-dispersing pigment and the ammonium ions that constitute the ink set is improved. An unbroken ink set is provided.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments. The first ink used in the following description means an ink containing a self-dispersing pigment in which at least one hydrophilic group is bonded directly or through another atomic group, and an ammonium ion. . The second ink contains a pigment, a resin having an acid value of 160 mgKOH / g or less, and alkali metal ions, and the ammonium ion concentration in the first ink and the alkali metal ion concentration in the second ink. Means an ink with a specified ratio. In the second ink containing a resin and a pigment, the pigment is dispersed by at least a part of the resin. In the following description, it is described that the second ink contains a resin-dispersed pigment. There is a case.

  First, the present inventors have found that these two kinds of twisting phenomena, which are not confirmed even when the recording durability test is carried out by mounting the first ink and the ink containing alkali metal ions individually in the ink jet recording apparatus, The cause that occurred when recording with ink mounted together was investigated. The twist phenomenon referred to in the present invention is a phenomenon that occurs when two types of inks having the above-described configuration are both mounted on a recording apparatus and recording is performed. In the combination described above, the first of the two types of inks. This is a phenomenon in which an image formed with one ink is distorted. The present inventors have made various studies on the twist phenomenon in order to pursue the cause. As a result, the following was found.

  For example, when the ink containing an alkali metal ion contains an acrylic resin, the resin usually contains a carboxylate ion as a solubilizing group, and further contains an alkali metal ion as a counter ion of the solubilizing group. Present in ink. When the first ink and the ink containing alkali metal ions are mixed on the face surface (surface having the discharge port) by the suction recovery operation of the recording head, the following phenomenon occurs. First, a part of resin counter ions present in the ink containing alkali metal ions is exchanged from alkali metal ions to ammonium ions contained in the first ink. Here, the suction recovery operation of the recording head refers to an operation for forcibly sucking and discharging ink from the nozzles. After the exchange from the alkali metal ion to the ammonium ion, ammonia is desorbed from the ammonium ion along with the evaporation of moisture and the like, and a part of the carboxylate ion becomes the carboxylic acid type. This means that the number of carboxylic acid-type sites in the resin in the ink increases, and therefore, the solubility of the resin decreases and the resin tends to precipitate. Furthermore, the re-solubility is significantly reduced as compared with a resin in which ammonium ions or alkali metal ions are bound as counter ions. Therefore, if a resin having a relatively large number of carboxylic acid types adheres to the vicinity of the discharge port and solidifies, it is very difficult to remove the resin by a normal cleaning operation. The normal cleaning operation is an operation of sweeping the head surface of the recording head with a wiping member (wiper) made of an elastic material such as rubber at a predetermined timing to remove the adhered matter. The main ink droplets ejected from the ejection ports are pulled by the resin that has adhered and solidified in the vicinity of the ejection ports, which may impede the straightness of the main ink droplets. It has been found that the twist phenomenon as described above occurs as a result of the above occurrence.

  As described above, the greatest cause of the twist phenomenon is the first ink containing a self-dispersing pigment and ammonium ions, and the ink containing a pigment and an acid value of 160 mgKOH / g or less and an alkali metal ion. Is in contact. That is, a phenomenon that has not been predicted in the past, such as ion exchange occurs when these two types of ink come into contact with each other, and the solubility of the resin contained in the ink containing alkali metal ions is significantly reduced. It was because it happened.

  In the course of the study, the inventors have confirmed that the twist phenomenon that occurs when the recording durability test is performed is not confirmed in the image formed with the ink containing alkali metal ions, but the first ink. I noticed that it was confirmed only by the formed image. Therefore, the present inventors conducted further detailed studies. As a result, it was concluded that the relationship between the absolute amount of alkali metal ions and the absolute amount of ammonium ions when these two types of ink contact each other greatly affects the problem of the present invention. That is, there is a difference in the balance of these ion amounts in the vicinity of each ink ejection port as described below.

  Near the discharge port of the ink containing alkali metal ions, the first ink containing ammonium ions attached during the suction recovery operation exists. However, the total amount of ammonium ions present in the vicinity of the ejection port of the ink containing alkali metal ions is very small because it is only the ammonium ions contained in the attached first ink. Therefore, in the vicinity of the discharge port of the ink containing alkali metal ions, only a small part of the counter ion of the resin is exchanged for ammonium ions, so the solubility of the resin in the ink containing alkali metal ions is almost not. Has no effect.

  On the other hand, there is ink containing alkali metal ions attached in the vicinity of the first ink ejection port during the suction recovery operation. The total amount of alkali metal ions in the ink containing the deposited alkali metal ions is very small. As a result, when the first ink is ejected, it is exposed to an amount of ammonium ions far exceeding the amount of alkali metal ions, so that most of the counter ions of the resin in the ink containing alkali metal ions are converted to ammonium ions. It becomes easy to be replaced. Accordingly, ammonia is desorbed with the evaporation of moisture and the like, and the resin in which the number of the carboxylic acid type is increased rapidly increases and the resin is precipitated. In the vicinity of the ejection opening of the first ink, the above-mentioned twist phenomenon occurs. It turns out that happens.

  Therefore, the present inventors pay attention to the relationship between the amounts of ions in these inks when forming an image using an ink set having a combination of the first ink and an ink containing alkali metal ions. Therefore, we studied to find a method that can prevent the twist phenomenon.

  As a result, when preparing an ink containing the first ink and alkali metal ions, the relationship between the amount of ammonium ions in the first ink and the amount of alkali metal ions in the latter ink is as follows. By doing so, it discovered that the subject of this invention could be solved. Specifically, the concentration A [mol / L] of ammonium ions in the first ink and the concentration B [mol / L] of alkali metal ions in the second ink are 0.03 ≦ A Each ink is prepared so as to satisfy the relationship of /B≦0.32.

  As described above, the reason why the twist phenomenon of the present invention can be solved by specifying the relationship between the amounts of ions in the first ink and the second ink used for image formation is not clear. About this, the present inventors guess as follows.

  As described above, the twist phenomenon of the subject of the present invention is caused not by the vicinity of the second ink discharge port but by the vicinity of the first ink discharge port due to the relationship between the alkali metal ion amount and the ammonium ion amount. This is a phenomenon that occurs specifically. More specifically, the twist phenomenon of the subject of the present invention is when the amount of ammonium ions contained in the first ink is relatively large compared to the amount of alkali metal ions contained in the second ink. In addition, it is a phenomenon that occurs when these ions come into contact with each other.

  For these reasons, the present inventors suppress the resin deposition by defining the relative relationship between the amount of alkali metal ions in the second ink and the amount of ammonium ions in the first ink. I thought it was possible. That is, if the amount of ammonium ions in the first ink is a certain amount or less, even if the second ink adheres to the vicinity of the ejection opening of the first ink, the resin contained in the second ink is removed. It does not reach the amount of ammonium ions that can be actively deposited. As a result, the idea is that the deposition of the resin in the vicinity of the first ink ejection port can be suppressed.

  Therefore, the present inventors changed the density of the hydrophilic group bonded to the pigment contained in the first ink, thereby changing the amount of ammonium ions that are counter ions of the hydrophilic group in various ways. A first ink was prepared. Then, a recording durability test was performed by combining the first ink and the second ink.

  As a result, first, the concentration A [mol / L] of ammonium ions in the first ink and the concentration B [mol / L] of alkali metal ions in the second ink are A / B ≦ 0. It was found that the twist phenomenon can be suppressed by satisfying the relationship of 32. That is, it was found that the twist phenomenon can be suppressed when the ammonium ion concentration in the first ink is 0.32 times or less than the alkali metal ion concentration in the second ink. In other words, it is necessary to reduce the concentration A of ammonium ions in the first ink.

  If attention is paid only to the suppression of the twist phenomenon, the ammonium ion concentration in the first ink is preferably close to zero. However, reducing the ammonium ion concentration in the first ink leads to a decrease in the density of hydrophilic groups of the self-dispersing pigment. For this reason, if the ammonium ion concentration in the first ink is too low, the dispersion stability of the pigment in the first ink, that is, the storage stability of the first ink may be affected. Therefore, in consideration of this, it has been concluded that the above A / B needs to be as follows in order to achieve both suppression of the twist phenomenon and storage stability of the first ink. That is, in order to achieve the object of the present invention, the concentration A [mol / L] of ammonium ions in the first ink and the concentration B [mol / L] of alkali metal ions in the second ink are: It is necessary to satisfy the relationship of 0.03 ≦ A / B ≦ 0.32.

  As described above, the twist phenomenon that is the subject of the present invention is governed by the ratio between the amount of ammonium ions in the first ink and the amount of alkali metal ions in the second ink. It is a phenomenon that occurs. However, if the amount of ammonium ions in the first ink is too large, the effect of suppressing the twist phenomenon may not be sufficiently obtained even if the relationship of A / B ≦ 0.32 is satisfied. Further, if the ammonium ion concentration in the first ink is too low, the storage stability of the first ink may not be sufficiently obtained. For this reason, it is particularly preferable that the ammonium ion concentration [mol / L] in the first ink is 0.0035 mol / L or more and 0.034 mol / L or less.

  As a result of the study by the present inventors, the acid value of the resin contained in the second ink is preferably 80 mgKOH / g or more, more preferably 90 mgKOH / g or more, considering the solubility of the resin. On the other hand, the twist phenomenon that is a problem to be solved by the present invention is a phenomenon that occurs when the acid value of the resin contained in the second ink is 160 mgKOH / g or less. From the above, the particularly problematic range in the present invention is the twist phenomenon that occurs in the first ink that occurs in relation to the second ink that contains a resin having an acid value of 80 mgKOH / g or more and 160 mgKOH / g or less. It is.

<Each component constituting the first ink and the second ink>
Next, each component constituting the first ink and the second ink will be described.

(Resin used for the second ink)
The second ink contains a resin having an acid value of 160 mgKOH / g or less, and any resin can be used as long as it is such. As described above, a resin having an acid value of 80 mgKOH / g or more, more preferably 90 mgKOH / g or more is preferable. The monomer component constituting the resin used in the second ink and the ratio of each monomer component are not particularly limited except that the acid value of the resin is as described above.

  The following are mentioned as a monomer component which forms resin used by this invention. For example, aromatic monomers, acrylic acid ester monomers, methacrylic acid ester monomers, anionic group-containing monomers, polyethylene oxide group-containing monomers, hydrocarbon monomers and the like can be mentioned. Specific examples of preferable monomers include the following. For example, styrene, benzyl methacrylate, methyl acrylate, butyl acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol acrylate, methoxypolyethylene glycol methacrylate, and the like. Moreover, acrylic acid, methacrylic acid, etc. are mentioned.

  The resin in the second ink used in the present invention preferably has a weight average molecular weight of 3,000 to 10,000. If the weight average molecular weight is less than 3,000, sufficient scratch resistance may not be obtained in the formed image. On the other hand, when the weight average molecular weight exceeds 10,000, the solubility of the resin in an aqueous medium is lowered, so that even if only a part of the counter ion of the resin is exchanged with ammonium ion, the resin is likely to be precipitated. May be more likely to occur.

  The resin content (% by mass) in the second ink is 0.5% by mass or more and 5.0% by mass or less, and further 1.0% by mass or more and 4.0% by mass or less based on the total mass of the ink. It is preferable that By setting the resin content in the above-described range, it is possible to leave a sufficient amount of resin on the surface of the recording medium so that the effect of improving the scratch resistance in the formed image can be obtained.

(Alkali metal ions used for the second ink)
The second ink used in the present invention needs to contain an alkali metal ion in the ink. The present invention suppresses occurrence of a twist phenomenon that is considered to be caused by ammonium ions of the first ink and alkali metal ions of the second ink of the ink set used for ink jet recording. Because it is aimed. Alkali metal ions are contained in the ink due to, for example, the base used as the neutralizing agent for the resin described above, or due to the pH adjusting agent or salt used as necessary. . As the resin neutralizing agent, inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide and potassium hydroxide are used. Examples of the salt include sulfates such as sodium sulfate, lithium sulfate, and potassium sulfate, and benzoates such as sodium benzoate, lithium benzoate, and potassium benzoate. Note that if the alkali metal ion concentration in the second ink is too low or too high, the storage stability of the second ink may not be sufficiently obtained. For this reason, it is preferable to adjust so that the alkali metal ion concentration [mol / L] in the second ink is in the range of 0.0076 mol / L to 0.15 mol / L. In particular, when the alkali metal ions present in the second ink are caused by a base used as a neutralizing agent for the resin, the alkali metal ion concentration in the second ink is more preferably within the above range. preferable.

(Color material)
The color material used for the first ink and the second ink constituting the ink set of the present invention is a pigment. As the pigment, for example, carbon black, organic pigments and the like as listed below can be used.

〔Carbon black〕
The carbon black is, for example, a carbon black pigment such as furnace black, lamp black, acetylene black, or channel black. For example, the following commercially available products can be used. The carbon black that can be used in the present invention is not limited to these, and a known carbon black can be used. Further, magnetic fine particles such as magnetite and ferrite, titanium black and the like may be used.
Ray Van: 7000, 5750, 5250, 5000, 3500, 2000, 1500, 1250, 1200, 1190 ULTRA-II, 1170, 1255 (above Colombia). Black Pearls: L, Legal: 400R, 330R, 660R, Mougl: L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, Vulcan: XC-72R (above Cabot). Color black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 6, 5, 4A, 4 (manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical).

[Organic pigments]
As the organic pigment, for example, the following can be used.
Water-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 pigment. Thioindigo 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 can be used, for example.
C. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 151, 153, 154, 166 168. C. I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61. C. I. Pigment Red: 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 170, 192, 215, 216, 217, 220, 223, 224, 226, 227 228, 238, 240. C. I. Pigment Violet: 19, 23, 29, 30, 37, 40, 50. C. I. Pigment Blue: 15, 15: 3, 15: 1, 15: 4, 15: 6, 22, 60, 64. C. I. Pigment Green: 7, 36. C. I. Pigment Brown: 23, 25, 26, etc. can be exemplified. Of course, other than the above, known organic pigments can be used.

(Pigment used for the first ink)
The pigment used for the first ink is a self-dispersing pigment in which at least one hydrophilic group is bonded to the pigment as mentioned above directly or through another atomic group. An example of such a pigment is self-dispersing carbon black. Furthermore, as an example of the self-dispersing carbon black, an anionic carbon black in which an anionic group is bonded to the surface of the carbon black can be exemplified. The first ink used in the present invention is required to contain ammonium ions in the ink. The present invention suppresses occurrence of a twist phenomenon that is considered to be caused by ammonium ions of the first ink and alkali metal ions of the second ink of the ink set used for ink jet recording. Because it is aimed. As will be described later, ammonium ions may be contained in the ink due to an anionic group bonded to the pigment surface.

(Anionic carbon black)
Examples of the anionic carbon black include those in which at least one anionic group such as —COOM, —SO ₃ M, —PO ₃ HM, and —PO ₃ M ₂ is bonded to the surface of the carbon black. In the above formula, M is a hydrogen atom, ammonium, or organic ammonium. In particular, carbon black in which —COOM or —SO ₃ M is bonded to the surface of carbon black via another atomic group as necessary and charged anionicly has good dispersibility in ink. Particularly preferred. In addition, the following are mentioned as a specific example of organic ammonium among what was represented as "M" above. For example, methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methanolammonium, dimethanolammonium, trimethanolammonium and the like.

  In the present invention, it is particularly preferable to use ammonium or organic ammonium as the counter ion (shown as “M” above) of the anionic group. As described above, the first ink used in the present invention needs to contain ammonium ions. Here, by using a self-dispersing pigment containing ammonium as the counter ion of the anionic group, the counter ion bonded to the anionic group can be dissociated in the ink to become an ammonium ion. Therefore, if the counter ion of the anionic group is ammonium or organic ammonium, the constitution that the ink contains ammonium ions, which is necessary for the first ink, can be easily satisfied without adding other components. It is because it can do.

  Specific examples of the other atomic groups described above include, for example, an alkylene group and an aromatic ring. Specific examples of the alkylene group include a methylene group, an ethylene group, and a propylene group. Specific examples of the aromatic ring include, for example, a benzene ring and a naphthalene ring.

  As described above, if the ammonium ion concentration in the first ink is too low, the storage stability of the first ink may not be sufficiently obtained. For this reason, it is preferable to adjust the ammonium ion concentration [mol / L] in the first ink to be in the range of 0.0035 mol / L to 0.034 mol / L.

[Pigment used for second ink]
The pigment used for the second ink is a resin-dispersed pigment in which the pigment is dispersed with a resin. As described above, in the present invention, a resin-dispersed pigment ink is an ink that contains a pigment and a resin and in which the pigment is dispersed by at least a part of the resin. The resin used as the dispersant is not particularly limited, and water-soluble resins having an acid value of 160 mgKOH / g or less can be used. Moreover, the neutralizing agent containing an alkali metal as mentioned above as a neutralizing agent of this resin can be used.

(Aqueous medium)
Both the first ink and the second ink constituting the ink set of the present invention preferably contain an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent, in addition to the above-described components. . It is preferable to use deionized water (ion exchange water) as the water. The content (% by mass) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink.

  As the water-soluble organic solvent, for example, the following can be used. Alkanediols such as 1,3-butanediol, 1,5-pentanediol, 1,2-hexanediol and 1,6-hexanediol. Glycol ethers such as diethylene glycol monomethyl (or ethyl) ether and triethylene glycol monoethyl (or butyl) ether. Alkyl alcohols having 1 to 4 carbon atoms such as ethanol, isopropanol, n-butanol, isobutanol, secondary butanol and tertiary butanol; Carboxylic acid amides such as N, N-dimethylformamide and N, N-dimethylacetamide. Ketones such as acetone, methyl ethyl ketone, 2-methyl-2-hydroxypentan-4-one, or keto alcohol. Cyclic ethers such as tetrahydrofuran and dioxane. Glycerin. Alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- or 1,3-propylene glycol, 1,2- or 1,4-butylene glycol, polyethylene glycol; Polyhydric alcohols such as thiodiglycol, 1,2,6-hexanetriol, and acetylene glycol derivatives; Heterocycles such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine, and sulfur-containing compounds such as dimethyl sulfoxide.

(Other ingredients)
The first ink and the second ink constituting the ink set of the present invention are both moisturizing agents such as urea, urea derivatives, trimethylolpropane, trimethylolethane, etc. in addition to the above-described components in order to maintain the moisturizing property. May contain a soluble solid. The content of moisturizing solids such as urea, urea derivatives, and trimethylolpropane in the ink is generally 0.10% by mass or more and 20.0% by mass or less based on the total mass of the ink. The range is preferably 0% by mass or more and 10.0% by mass or less.

  In addition to the above components, the first ink and the second ink constituting the ink set of the present invention may be a pH adjuster, a rust inhibitor, a preservative, an antifungal agent, and an antioxidant as necessary. Various additives such as an agent, a reduction inhibitor, a water-soluble resin neutralizer, and a salt may be contained. For example, a base may be used as the neutralizing agent for the water-soluble resin, and in that case, as described above, inorganic substances such as hydrates of alkali metal salts such as sodium hydroxide, lithium hydroxide, and potassium hydroxide are used. An alkali agent or the like can be used. Examples of the salt include sulfates (for example, potassium sulfate and ammonium sulfate) and benzoates (for example, ammonium benzoate).

<Ink set>
The ink set of the present invention having the above-described configuration is particularly preferably used for inkjet recording, that is, an inkjet ink set. As a result, when the ink set of the present invention is used for ink jet recording, a high-quality image can be obtained without causing the above-mentioned twist phenomenon. Of course, the ink set of the present invention only needs to have a combination of the first ink and the second ink. In addition to these, the ink set may be a combination of other inks.

<Ink cartridge>
An ink cartridge suitable for performing ink jet recording using the ink set of the present invention is characterized in that it includes an ink containing portion that contains at least each ink constituting the ink set described above. The ink cartridge that stores each ink constituting the ink set includes not only an ink cartridge in which a plurality of ink storage portions of each ink are integrated but also a case where a plurality of individual ink cartridges are used in combination. Further, an ink cartridge and a recording head integrated are also included. That is, in the present invention, the use of a plurality of ink cartridges or an ink cartridge that integrally contains a plurality of inks so as to be detachable from the ink jet recording apparatus is substantially an ink set.

(Ink set form)
In the present invention, the ink cartridge can be used as an example of an ink set even when used in combination as follows. When using an ink cartridge that integrally contains cyan ink, magenta ink, yellow ink, and black ink. Alternatively, an ink cartridge that integrally contains cyan ink, magenta ink, and yellow ink is used in combination with an ink cartridge that contains another black ink. Further, specific examples in the case where a plurality of single ink cartridges are used in combination in the ink set include the following forms. When an independent ink cartridge that contains cyan ink, magenta ink, and yellow ink is used in combination with an ink cartridge that contains another black ink. When using a combination of ink cartridges each containing black ink, light cyan ink, and light magenta ink. When adding a single ink cartridge that contains red ink. When a single ink cartridge containing green ink is additionally used. In any case, the present invention relatively defines the characteristics of one ink relative to other inks used together in an ink jet recording apparatus that uses an ink cartridge and an ink cartridge that integrally stores a plurality of inks. . Therefore, the present invention is not limited to the above-described form, and any form may be used.

<Inkjet recording method>
The ink jet recording method of the present invention is characterized in that in the ink jet recording method of recording on a recording medium by ejecting ink by an ink jet method, the ink used includes at least a combination of inks constituting the ink set of the present invention. To do. Examples of the ink jet system used in the ink jet recording method of the present invention include a recording method in which ink is ejected by applying mechanical energy to the ink, and a recording method in which ink is ejected by applying thermal energy to the ink. . In particular, in the present invention, an ink jet recording method using thermal energy can be preferably used.

<Recording unit>
The recording unit of the present invention includes an ink storage portion for storing ink and a recording head for ejecting ink, and the ink stored in the ink storage portion constitutes at least the ink set of the present invention. It is characterized by being each ink.

<Inkjet recording apparatus>
The ink jet recording apparatus of the present invention includes an ink storage portion that stores ink and a recording head for discharging ink, and the ink stored in the ink storage portion constitutes at least the ink set of the present invention. It is characterized by being an ink to be used. In particular, when the recording head is an ink jet recording apparatus that discharges ink by applying thermal energy to ink, a more remarkable effect can be obtained.

  Below, the schematic structure of the mechanism part of an inkjet recording device is demonstrated. The ink jet recording apparatus includes a paper feeding unit, a transport unit, a carriage unit, a paper discharging unit, a cleaning unit, and an exterior unit that protects these parts and provides design properties from the role of each mechanism. Hereinafter, an outline of these will be described.

  FIG. 1 is a perspective view of the ink jet recording apparatus. 2 and 3 are diagrams for explaining the internal mechanism of the ink jet recording apparatus. FIG. 2 is a perspective view from the upper right portion, and FIG. 3 is a side sectional view of the ink jet recording apparatus. is there.

  When performing paper feeding, first, a predetermined number of recording media are sent to a nip portion including a paper feeding roller M2080 and a separation roller M2041 in a paper feeding unit including a paper feeding tray M2060 (FIGS. 1 and 3). reference). The recording medium is separated at the nip portion, and only the uppermost recording medium is conveyed. The recording medium sent to the conveyance unit is guided by the pinch roller holder M3000 and the paper guide flapper M3030, and is sent to the roller pair of the conveyance roller M3060 and the pinch roller M3070. A pair of rollers including a conveyance roller M3060 and a pinch roller M3070 is rotated by driving of the LF motor E0002, and the recording medium is conveyed on the platen M3040 by this rotation (see FIGS. 2 and 3 above).

  When forming an image, the carriage unit places the recording head H1001 (see FIG. 4) at a target image forming position, and ink is ejected onto the recording medium in accordance with a signal from the electric substrate E0014 (see FIG. 2). The The detailed configuration of the recording head H1001 will be described later. The main scanning in which the carriage M4000 (see FIG. 2) scans in the column direction while recording is performed by the recording head H1001, and the sub-scan in which the transport roller M3060 (see FIGS. 2 and 3) transports the recording medium in the row direction alternately. By repeating the above, an image is formed on the recording medium. Finally, the recording medium is sandwiched by the nip between the first paper discharge roller M3110 and the spur M3120 at the paper discharge unit (see FIG. 3), conveyed, and discharged to the paper discharge tray M3160 (see FIG. 1).

  The cleaning unit cleans the recording head H1001. When the pump M5000 (see FIG. 2) is operated in a state where the cap M5010 (see FIG. 2) is in close contact with the ejection port of the recording head H1001, the cleaning unit sucks ink or the like from the recording head H1001. Further, if the ink remaining in the cap M5010 is sucked with the cap M5010 opened, ink sticking and other harmful effects do not occur.

(Configuration of recording head)
The configuration of the head cartridge H1000 will be described (see FIG. 4). The head cartridge H1000 has a recording head H1001, means for mounting the ink cartridge H1900, and means for supplying ink from the ink cartridge H1900 to the recording head. The head cartridge H1000 is detachably mounted on the carriage M4000 (see FIG. 2).

  FIG. 4 is a diagram showing how the ink cartridge H1900 is mounted on the head cartridge H1000. The ink jet recording apparatus forms an image with, for example, seven types of ink. Therefore, the ink cartridge H1900 is also prepared for seven colors independently. As shown in FIG. 4, each ink cartridge is attachable to and detachable from the head cartridge H1000. The ink cartridge H1900 can be attached and detached while the head cartridge H1000 is mounted on the carriage M4000 (see FIG. 2).

  FIG. 5 is an exploded perspective view of the head cartridge H1000. The head cartridge H1000 includes a recording element substrate, a plate, an electric wiring substrate H1300, a tank holder H1500, a flow path forming member H1600, a filter H1700, a seal rubber H1800, and the like. The recording element substrate is composed of a first recording element substrate H1100 and a second recording element substrate H1101, and the plate is composed of a first plate H1200 and a second plate H1400.

  The first recording element substrate H1100 and the second recording element substrate H1101 are Si substrates, and a plurality of recording elements (nozzles) for ejecting ink are formed on one side thereof by a photolithography technique. An electric wiring such as Al for supplying electric power to each recording element is formed by a film forming technique, and a plurality of ink flow paths corresponding to individual recording elements are also formed by a photolithography technique. Further, an ink supply port for supplying ink to the plurality of ink flow paths is formed to open on the back surface.

FIG. 6 is an enlarged front view illustrating the configuration of the first recording element substrate H1100 and the second recording element substrate H1101. H2000 to H2600 are recording element arrays (hereinafter also referred to as ejection port arrays) for supplying different inks. On the first recording element substrate H1100, ejection port arrays H2000 to H2200 for three colors are formed. On the second recording element substrate H1101, ejection port arrays H2300 to H2600 for four colors are formed. Each ejection port array is composed of 768 nozzles arranged at an interval of 1,200 dpi (dot / inch; reference value) in the conveyance direction of the recording medium, and ejects about 2 picoliters of ink. The opening area at each discharge port is set to about 100 μm ² .

  Hereinafter, a description will be given with reference to FIGS. The first recording element substrate H1100 and the second recording element substrate H1101 are bonded and fixed to the first plate H1200. Here, an ink supply port H1201 for supplying ink to the first recording element substrate H1100 and the second recording element substrate H1101 is formed. Further, a second plate H1400 having an opening is bonded and fixed to the first plate H1200. The second plate H1400 holds the electrical wiring substrate H1300 so that the electrical wiring substrate H1300 is electrically connected to the first recording element substrate H1100 and the second recording element substrate H1101.

  The electrical wiring substrate H1300 applies an electrical signal for ejecting ink from each nozzle formed on the first recording element substrate H1100 and the second recording element substrate H1101. The electric wiring board H1300 is arranged on the electric wiring corresponding to the first recording element substrate H1100 and the second recording element substrate H1101, and an external part for receiving an electric signal from the ink jet recording apparatus. And a signal input terminal H1301. The external signal input terminal H1301 is positioned and fixed on the back side of the tank holder H1500.

  In the tank holder H1500 that holds the ink cartridge H1900, a flow path forming member H1600 is fixed by, for example, ultrasonic welding to form an ink flow path H1501 that communicates from the ink cartridge H1900 to the first plate H1200. A filter H1700 is provided at the ink cartridge side end of the ink flow path H1501 that engages with the ink cartridge H1900, and can prevent dust from entering from the outside. Further, a seal rubber H1800 is attached to the engaging portion with the ink cartridge H1900 so that the ink can be prevented from evaporating from the engaging portion.

  Further, as described above, the head cartridge H1000 is configured by joining the tank holder portion and the recording head H1001 by bonding or the like. The tank holder portion includes a tank holder H1500, a flow path forming member H1600, a filter H1700, and a seal rubber H1800. The recording head H1001 includes a first recording element substrate H1100 and a second recording element substrate H1101, a first plate H1200, an electric wiring substrate H1300, and a second plate H1400.

  Here, as an embodiment of the recording head, a thermal ink jet recording head that performs recording using an electrothermal transducer (recording element) that generates thermal energy for causing ink to cause film boiling in accordance with an electrical signal. Said. About this typical structure and principle, for example, what is performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is preferable. . This method can be applied to both a so-called on-demand type and a continuous type.

  The thermal ink jet method is particularly effective when applied to an on-demand type. In the case of the on-demand type, at least one drive that applies a rapid temperature rise exceeding nucleate boiling corresponding to the recording information to the electrothermal transducer disposed corresponding to the liquid flow path holding the ink Apply a signal. As a result, thermal energy is generated in the electrothermal transducer, and film boiling occurs in the ink. As a result, bubbles in the ink corresponding to the drive signal on a one-to-one basis can be formed. At least one droplet is formed by ejecting ink through the ejection port by the growth and contraction of the bubbles. It is more preferable that the driving signal has a pulse shape, since the bubble grows and contracts immediately and appropriately, so that ink discharge with particularly excellent response can be achieved.

  Further, not only the thermal ink jet method described above but also an ink jet recording apparatus using mechanical energy as described below can be preferably used. An ink jet recording apparatus having such a configuration 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. Become. Then, the pressure generating element is displaced by the applied voltage, and ink is ejected from the nozzle.

  As described above, the ink jet recording apparatus is not limited to one in which the recording head and the ink cartridge are separated from each other. Further, the ink cartridge is integrated with the recording head so as to be separable or non-separable and mounted on the carriage, and is provided at a fixed portion of the ink jet recording apparatus, and recording is performed via an ink supply member such as a tube. An ink may be supplied to the head. Further, when the ink cartridge is provided with a configuration for applying a preferable negative pressure to the recording head, the following configuration can be adopted. That is, a mode in which an absorber is disposed in the ink storage portion of the ink cartridge, or a mode in which a flexible ink storage bag and a spring portion that applies a biasing force in the direction of expanding the inner volume of the flexible ink storage bag It can be. The ink jet recording apparatus may take the form of a line printer in which recording elements are aligned over a range corresponding to the entire width of the recording medium, in addition to the serial type recording method described above.

  Hereinafter, although it demonstrates more concretely using an Example and a comparative example, this invention is not limited to these, unless the summary is exceeded. In the following description, “part” or “%” is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Preparation of pigment dispersion A)
To a solution of 5 g of concentrated hydrochloric acid dissolved in 5.5 g of water, 1.5 g of 4-aminophthalic acid is added while being cooled to 5 ° C. Next, the solution containing the solution is placed in an ice bath and the solution is stirred to keep the solution at 10 ° C. or lower, and 1.8 g of sodium nitrite is dissolved in 9 g of water at 5 ° C. Solution was added. After stirring this solution for another 15 minutes, 6 g of carbon black having a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g was added with stirring. Thereafter, the mixture was further stirred for 15 minutes. The obtained slurry was filtered with a filter paper (trade name: Standard filter paper No. 2; manufactured by Advantech), and then the particles were sufficiently washed with water and dried in an oven at 110 ° C. to prepare self-dispersing carbon black. Further, the self-dispersing carbon black A obtained above was treated with hydrochloric acid and then neutralized with aqueous ammonia to prepare self-dispersing carbon black A. Thereafter, water was added to the self-dispersing carbon black A obtained above to disperse the pigment so that the pigment concentration became 10.0% by mass to prepare a pigment dispersion. By the above method, a pigment dispersion A was obtained in which self-dispersing carbon black A having —C ₆ H ₃ — (COONH ₄ ) ₂ groups introduced on the surface of carbon black particles was dispersed in water. The amount of ammonium ions in the pigment dispersion A was measured by using an ion meter (Orion 290A +; manufactured by Thermo Electron) connected with an ammonium ion electrode, and it was 1,500 ppm.

(Preparation of pigment dispersion B)
Pigment dispersion B was prepared in the same manner as in the preparation of pigment dispersion A, except that the amount of 4-aminophthalic acid was changed to 1.4 g. When the amount of ammonium ion in the pigment dispersion B was measured in the same manner as described above, it was 1,450 ppm.

(Preparation of pigment dispersion C)
A pigment dispersion C was prepared in the same manner as the production method of the pigment dispersion A except that 1.5 g of 4-aminophthalic acid was changed to 1.1 g. When the amount of ammonium ion in the pigment dispersion C was measured in the same manner as described above, it was 1,000 ppm.

(Preparation of pigment dispersion D)
A pigment dispersion D was prepared in the same manner as the production method of the pigment dispersion A except that 1.5 g of 4-aminophthalic acid was changed to 0.25 g. When the amount of ammonium ion in the pigment dispersion D was measured in the same manner as described above, it was 150 ppm.

(Preparation of pigment dispersion E)
A pigment dispersion E was prepared in the same manner as the production method of the pigment dispersion A except that 1.5 g of 4-aminophthalic acid was changed to 0.21 g. When the amount of ammonium ion in the pigment dispersion E was measured in the same manner as described above, it was 100 ppm.

(Preparation of pigment dispersion F)
A pigment dispersion F was prepared in the same manner as the production method of the pigment dispersion A except that 1.5 g of 4-aminophthalic acid was changed to 1.7 g. When the amount of ammonium ion in the pigment dispersion F was measured in the same manner as described above, it was 1,600 ppm.

(Preparation of pigment dispersion G)
10 parts of carbon black similar to that used in the preparation of the pigment dispersion, 2.5 parts of the following block copolymer as a dispersant, and 87.5 parts of ion-exchanged water are mixed, and 3 hours using a paint shaker. Dispersed. The block copolymer used above is a block copolymer of styrene / methoxytriethylene glycol methacrylate / acrylic acid, and has a weight average molecular weight of 10,000 neutralized with an acid value of 160 mgKOH / g and 1 equivalent of potassium hydroxide. belongs to. After the dispersion treatment, coarse particles were removed by centrifugal separation treatment, and further filtered under pressure with a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare a resin dispersion type carbon black. Then, it adjusted with water so that a pigment concentration might be 10.0 mass%, and the pigment dispersion G with a pigment concentration of 10.0 mass% and a resin concentration of 2.5 mass% was obtained.

<Preparation of aqueous resin solution>
A random copolymer of styrene / n-butyl acrylate / acrylic acid having an acid value of 160 mgKOH / g and a weight average molecular weight of 7,500 was neutralized to 1 equivalent with potassium hydroxide. Then, it adjusted with water so that solid content might be 10.0 mass%, and resin aqueous solution was obtained.

<Preparation of ink>
Each component shown in the upper part of Table 1 was mixed and sufficiently stirred, and then pressure filtered through a micro filter (manufactured by Pole) having a pore size of 2.5 μm to prepare each ink. Inks BK1-1 to BK1-6 are inks containing self-dispersing pigments. The inks BK2-1 and BK2-2 are inks containing a resin as a dispersant. A concentration A [mol / L] of ammonium ions contained in the ink composition containing the self-dispersing pigment and an alkali metal ion concentration B [mol / L] contained in the ink composition containing the resin as a dispersant, It measured by the following method.

(Quantification of ammonium ion concentration in ink containing self-dispersing pigment)
The ammonium ion concentration in the inks BK1-1 to BK1-6 containing the self-dispersing pigment obtained above was quantified. First, the specific gravity of each ink was measured at 25 ° C. using a floating type specific gravity meter (trade name: standard specific gravity meter; manufactured by Tech Jam). The specific gravity of each ink is shown in the lower part of Table 1. Then, the ammonium ion concentration A [mol / L] in each ink was determined from the amount of ammonium ions in the pigment dispersion used for the preparation of each ink and the specific gravity of the ink. The obtained results are shown in the lower part of Table 1.

(Quantification of alkali metal ion concentration in resin-containing ink)
The alkali metal ion concentration, that is, the potassium ion concentration in the inks BK2-1 and BK2-2 containing the resin obtained above was quantified. First, the specific gravity of each ink was measured at 25 ° C. using a floating type specific gravity meter (trade name: standard specific gravity meter; manufactured by Tech Jam). The specific gravity of each ink is shown in the lower part of Table 1. Then, the amount of potassium ions [ppm] in each ink was measured using an ion meter (Orion 290A +; manufactured by Thermo Electron) connected with a potassium ion electrode. Then, the potassium ion concentration B [mol / L] in each ink was determined from the amount of potassium ions in each ink and the specific gravity of the ink. The obtained results are shown in the lower part of Table 1.

<Evaluation>
As shown in Table 2, using the inks BK1-1 to 1-6 containing the self-dispersing pigment and the inks BK2-1 to 2-2 containing the resin, The ink sets of Examples and Comparative Examples were combined. Using these ink sets, an image was formed as follows in a PPC paper office planner (manufactured by Canon) using the following recording apparatus, and each ink set was evaluated. At this time, an ink jet recording apparatus PIXUS PRO9000 (manufactured by Canon Inc.) having an on-demand recording head that ejects ink by applying thermal energy corresponding to the recording signal to the ink was used as the recording apparatus. Then, an ink containing a self-dispersing pigment was attached to the green position of the apparatus, and an ink containing a resin was attached to the red position, and evaluation was performed as follows. In the ink jet recording apparatus used for the test, the ejection port array that ejects green ink and the ejection port array that ejects red ink are configured to simultaneously perform the suction recovery operation with the same suction cap.

  After the ink containing the self-dispersing pigment and the ink containing the resin constituting each ink set were mounted at the above-described positions of the ink jet recording apparatus, the suction recovery operation was performed once. Then, the nozzle check pattern of PIXUS PRO9000 was recorded, the obtained nozzle check pattern was visually confirmed, and the occurrence of the twist phenomenon was evaluated according to the evaluation criteria for the twist phenomenon shown below. If the evaluation result of the twist phenomenon is A at this time, using the ink set, a solid image with a recording density of 1200 dpi × 1200 dpi and a recording duty of 15% is recorded in the default mode on the above-described recording medium. Ten sheets were recorded continuously. Thereafter, a nozzle check pattern of PIXUS PRO9000 was recorded, and the twist phenomenon was evaluated in the same manner as described above. When the evaluation result of the twist phenomenon at this time was A, 90 images were continuously recorded on the recording medium using the ink set in the same manner as described above. After recording, a nozzle check pattern of PIXUS PRO9000 was recorded, and the twist phenomenon was evaluated in the same manner as described above. At this time, if the evaluation result of the twist phenomenon was A, 100 images were continuously recorded on the recording medium using the ink set in the same manner as described above. After recording, a nozzle check pattern of PIXUS PRO9000 was recorded, and the twist phenomenon was evaluated in the same manner as described above.

  As described above, recording was repeated continuously in units of 100 sheets until the evaluation result according to the evaluation standard of the twist phenomenon shown below became B, and evaluation was performed in the same manner as described above. Table 2 shows the number of images formed until the evaluation result of the twist phenomenon becomes B. Therefore, the ink set having a larger number of obtained results suppresses the occurrence of the twist phenomenon, and it is possible to stably form a good image.

  Further, when the evaluation result of the twist phenomenon was B, the recording head was removed from the ink jet recording apparatus, and the state around the discharge port was observed with an optical microscope. And it evaluated by the following evaluation criteria with the state of the deposit produced around the discharge outlet. Table 2 shows the evaluation results of the state around the obtained discharge port.

(Evaluation criteria for twist phenomenon)
A: The check pattern is not disturbed and can be recorded normally.
B: There is a slight disturbance in the check pattern.

(Evaluation criteria for the condition around the discharge port)
A: Resin lump was confirmed in a part around the discharge port.
B: A lump of resin was confirmed as a whole around the discharge port.

(Evaluation of ink storage stability)
The storage stability of the ink containing the self-dispersing pigment constituting each ink set of Examples and Comparative Examples was evaluated. First, the viscosity of the ink and the average particle diameter of the pigment in the ink were measured. Thereafter, the ink containing the self-dispersing pigment constituting each ink set was put in a Teflon (registered trademark) container, sealed, and stored in an oven at 60 ° C. for 4 weeks. Thereafter, the Teflon (registered trademark) container was taken out of the oven, and after the ink returned to room temperature, the viscosity of the ink after storage at 60 ° C. and the average particle diameter of the pigment in the ink were measured. From the viscosity and average particle size values thus obtained, the change rate of the viscosity of the ink and the change rate of the average particle size of the pigment before and after storage at 60 ° C. for 4 weeks were determined. As a result, as compared with the other inks, the ink BK1-4 containing the self-dispersing pigment of Comparative Example 2 had a large change rate of 15% in the average particle diameter of the pigment. The viscosity of the ink was measured at 25 ° C. using a RE80L viscometer (manufactured by Toki Sangyo). The average particle diameter of the pigment in the ink was measured at 25 ° C. using ELS-8000 (manufactured by Otsuka Electronics).

It is a perspective view of an inkjet recording device. It is a perspective view of the mechanism part of an inkjet recording device. It is sectional drawing of an inkjet recording device. FIG. 6 is a perspective view illustrating a state where an ink cartridge is mounted on the head cartridge. It is a disassembled perspective view of a head cartridge. FIG. 6 is a front view showing a recording element substrate in the head cartridge.

Explanation of symbols

M2041: Separation roller M2060: Paper feed tray M2080: Paper feed roller M3000: Pinch roller holder M3030: Paper guide flapper M3040: Platen M3060: Transport roller M3070: Pinch roller M3110: Paper discharge roller M3120: Spur M3160: Paper discharge tray M4000: Carriage M5000: Pump M5010: Cap E0002: LF motor E0014: Electric substrate H1000: Head cartridge H1001: Recording head H1100: First recording element substrate H1101: Second recording element substrate H1200: First plate H1201: Ink supply port H1300: Electric wiring board H1301: External signal input terminal H1400: Second plate H1500: Tank holder H1501: Ink channel H1600: Channel type Member H1700: Filter H1800: seal rubber H1900: ink cartridge H2000～H2600: outlet row

Claims (6)

A first ink containing a self-dispersing pigment having a hydrophilic group bonded directly or through another atomic group and an ammonium ion; a pigment; a resin having an acid value of 160 mgKOH / g or less; and an alkali metal ion An ink set having at least a combination with a second ink containing
The concentration A [mol / L] of ammonium ions in the first ink and the concentration B [mol / L] of alkali metal ions in the second ink are 0.03 ≦ A / B ≦ 0. An ink set characterized by satisfying 32 relationships.   2. The ink set according to claim 1, wherein the concentration of ammonium ions in the first ink is 0.0035 mol / L or more and 0.034 mol / L or less.   3. An ink jet recording method for recording on a recording medium by ejecting ink by an ink jet method, wherein the ink used is at least the ink constituting the ink set according to claim 1 or 2. .   An ink cartridge comprising an ink containing portion for containing ink, wherein the ink contained in the ink containing portion is at least the ink constituting the ink set according to claim 1 or 2. .   3. An ink set according to claim 1, wherein at least an ink stored in the ink storage portion includes an ink storage portion that stores ink and a recording head that discharges ink. A recording unit characterized in that the recording unit is ink.   3. An ink jet recording apparatus comprising an ink containing part for containing ink and a recording head for ejecting ink, wherein the ink contained in the ink containing part comprises at least the ink set according to claim 1 or 2. An ink jet recording apparatus, characterized in that the ink is a constituent ink.

Images