JP2015203095A - Ink, inkjet recording method and ink cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink which can record an image having high optical density and excellent marker resistance, suppresses the elution of silicon from a constituent member of a recording head and has excellent storage stability.SOLUTION: There is provided an ink used for an inkjet recording method using a recording head in which a member in contact with an ink is composed of silicon. The ink comprises a pigment, an urethane resin and a silicone resin. The pigment is a self-dispersible pigment in which a phosphonic acid group is bonded directly or through another atomic group to the particle surface, the urethane resin has a unit derived from a polyether polyol and an acid value of 40 mgKOH/g or more and 140 mgKOH/g or less and the silicone resin has at least a unit having a siloxane structure and a unit having an acidic group and an acid value of 80 mgKOH/g or more and 150 mgKOH/g or less.

Description

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

  Conventionally, ink jet recording apparatuses have been used to output photographic images and web pages at home. However, in recent years, with improvement in image quality and recording speed, opportunities for use in outputting business documents in the business field, particularly in offices, have increased. Ink-jet inks used for outputting such business documents are required to have recorded images having high optical density and various fastness properties. For example, robustness is required such that an image is not soiled (marker resistance) when the image is traced with a marker pen.

  Therefore, in order to improve the optical density, development of pigment ink using a pigment as a coloring material and adding a resin to improve the fastness of an image has been vigorously advanced. Particularly recently, attempts have been made to add a urethane resin to the pigment ink (see Patent Documents 1 and 2).

  On the other hand, in the business field, it is necessary to improve the recordable number of ink jet recording apparatuses by extending the life of the recording head. For example, in a recording head in which a recording element substrate is made of silicon, silicon or a silicon compound in the recording element substrate elutes due to contact with ink, so that it may be assumed that ink ejection becomes difficult. Accordingly, there is a demand for ink that makes it difficult for silicon to elute from the constituent members of the recording head. In response to such a demand, a method for suppressing elution of silicon from the constituent members of the recording head by incorporating an inorganic silicate compound in the ink has been proposed (see Patent Document 3).

JP 2009-062519 A JP 2009-0119198 A JP 2011-062998 A

  However, as described in Patent Documents 1 and 2, by simply adding a urethane resin to the pigment ink, it is possible to achieve high optical density and excellent marker resistance required for outputting business documents. There wasn't.

  Therefore, the present inventors examined adding an inorganic silicate compound, which is described in Patent Document 3 as having an effect of suppressing elution of silicon, to the ink. However, it has been found that the inorganic silicic acid compound significantly reduces the storage stability of the ink, although the effect of suppressing the elution of silicon from the constituent members of the recording head has been recognized.

  That is, as far as existing knowledge is concerned, it is possible to record an image having a high optical density and excellent marker resistance, and it is difficult to suppress the elution of silicon from the constituent members of the recording head. Is the current situation.

  Therefore, an object of the present invention is to record an image having a high optical density and excellent marker resistance, and further, it is possible to suppress elution of silicon from the constituent members of the recording head, and storage stability. It is another object of the present invention to provide an excellent ink. Another object of the present invention is to provide an ink cartridge and an ink jet recording method using the ink.

  The object is achieved by the present invention described below. That is, according to the present invention, an ink jet recording which uses a recording head in which at least a part of a member in contact with ink is made of silicon or a silicon compound and discharges ink from the recording head to record an image on a recording medium. Ink used in the method, comprising a pigment, a urethane resin, and a silicone resin, the pigment being a self-dispersing pigment having a phosphonic acid group bonded to the particle surface directly or via other atomic groups The urethane resin has a unit derived from a polyether polyol and has an acid value of 40 mgKOH / g or more and 140 mgKOH / g or less, and the silicone resin has a siloxane structure having a siloxane structure. At least a unit having an acidic group and an acid value of 80 mgK Ink equal to or less than H / g or more 150 mgKOH / g is provided.

  According to the present invention, it is possible to record an image having a high optical density and excellent marker resistance, and further, it is possible to suppress elution of silicon from the constituent members of the recording head and to have excellent storage stability. Can be provided. Another object of the present invention is to provide an ink cartridge and an ink jet recording method using the ink.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Hereinafter, silicon or silicon compounds may be collectively referred to as “silicon”. Further, a self-dispersing pigment in which a phosphonic acid group is bonded to the particle surface directly or through another atomic group may be referred to as a “phosphonic acid-type self-dispersing pigment”. In addition, when “unit” is described as a constituent component of the resin, the unit is a single repeating unit.

  The present inventors have studied in order to provide an ink capable of recording an image having a high optical density and excellent marker resistance. As a result, it has been found that it is optimal to use a phosphonic acid type self-dispersing pigment as a coloring material in order to record a high optical density image. Further, it has been found that in order to record an image having excellent marker resistance, it is optimal to add a urethane resin using a polyether polyol to the ink.

The present inventors presume the reason why a high optical density can be realized by using a phosphonic acid type self-dispersing pigment as a coloring material. Here, according to the study by the present inventors, it is particularly important to satisfy the following two conditions in order to record a high optical density image using a recording medium such as plain paper.
i) The pigment is effectively present on the surface of the recording medium.
ii) To capture a large amount of light by roughening the surface of the pigment layer and reduce the reflected light.

  Self-dispersed pigment reacts with an inorganic metal contained as a filler in the recording medium when ink is applied to the recording medium, so that electrostatic repulsion between the pigment particles is released, and the pigment quickly aggregates. Many pigment aggregates remain on the surface of the recording medium. In contrast, resin-dispersed pigments that disperse pigments with resin dispersants cause the resin to become insoluble when ink is applied to the recording medium, thereby reducing the electrostatic repulsion and steric hindrance of the resin and causing the pigments to aggregate To do. However, a part of the resin is present between the pigment particles and inhibits the aggregation of the pigment due to the electrostatic repulsion and steric hindrance of the resin, so that the aggregation of the pigment is estimated to be slower than that of the self-dispersing pigment. When a recording medium such as plain paper is used, if the aggregation of the pigment is delayed, the pigment is likely to sink into the recording medium, so that it is difficult for the pigment to remain on the surface of the recording medium. Further, since the insolubilized resin dispersant partially remains on the surface of the pigment layer, it is considered that the surface roughness of the pigment layer is reduced and the reflected light is further increased. That is, the self-dispersing pigment is more likely to satisfy the above conditions i) and ii) than the resin-dispersed pigment, and is considered to be a color material suitable for recording an image having a high optical density. Furthermore, since the phosphonic acid group is highly reactive with inorganic metals, particularly calcium, contained as a filler in the recording medium, the ink containing the phosphonic acid type self-dispersing pigment is applied to the recording medium. The pigment aggregates quickly. As a result, a large amount of pigment aggregate remains on the surface of the recording medium, so that an image with a high optical density can be recorded.

  Further, as a result of studies by the present inventors, it has been found that excellent marker resistance can be realized by using a urethane resin using a polyether polyol as a polyol component. Details are described below. The urethane resin has a crystalline hard segment (urethane bond portion) and an amorphous soft segment (polyol portion), and the hard segment and the soft segment have a micro phase separation structure (sea-island structure). The reason why the scratch resistance / marker resistance of the image is improved by adding the urethane resin is that the urethane resin has a micro phase separation structure, so that the resin film can exhibit high elasticity with both strength and flexibility. It is considered. And, by selecting polyether polyol as the polyol component, it is considered that the balance between strength and flexibility of the resin film is further optimized, and as a result, an image having excellent marker resistance can be recorded. . For the above reasons, an ink containing a phosphonic acid type self-dispersing pigment and a urethane resin using a polyether polyol can record an image having a high optical density and excellent marker resistance.

  However, according to studies by the present inventors, it has been found that the ink remarkably elutes silicon from the constituent members of the recording head. About this reason, it estimates as follows. In general, in an inkjet ink, particularly an aqueous ink, a resin having a certain acid value is often used in order to stabilize the dispersion state of the pigment in the ink as the resin having higher hydrophilicity. Also in the ink of the present invention, the acid value of the urethane resin is limited to 40 mgKOH / g or more for the same reason. In the case of water-based inks, the acid groups of the resin are usually neutralized with an alkali when the resin is made hydrophilic. And the higher the acid value of the resin to increase the hydrophilicity of the resin, the greater the amount of alkali required for neutralization. That is, the ink containing a resin having a certain degree of hydrophilicity necessarily contains a certain amount of alkali for neutralization. The hydroxide ions derived from the alkali attack the silicon crystal in the constituent member of the recording head (such as a silicon substrate constituting the recording element substrate), thereby breaking the Si-Si bond. Is considered to cause a phenomenon of elution into the ink. Actually, according to the study by the present inventors, it was confirmed that when the silicon film was immersed in an aqueous solution containing a resin having a certain acid value and stored at a high temperature, the thickness of the silicon film decreased. Yes. When the silicon substrate is further melted, the ink enters the electrical wiring of the recording head, so that it becomes difficult to eject the ink from the recording head.

  However, when an immersion test of a silicon film was similarly conducted on an aqueous solution containing a water-soluble organic solvent (details will be described later) widely used in ink jet ink, the film thickness of the silicon film was hardly reduced. I understood. This is because the water-soluble organic solvent contains a Lewis acid containing a polyvalent metal as a trace component, and the Lewis acid traps hydroxide ions derived from the alkali for neutralization of the resin, thereby This is considered to be because the elution of silicon from the constituent members is suppressed. Therefore, even when an ink jet ink containing a resin having a high acid value is used, the elution of silicon from the constituent members of the recording head is suppressed by the presence of the water-soluble organic solvent. We can predict that it was.

  However, even when the water-soluble organic solvent was used, it was found that when a phosphonic acid-type self-dispersing pigment was used as the color material, the elution of silicon from the constituent members of the recording head was not suppressed. . The reason is that the Lewis acid derived from the water-soluble organic solvent is chelated by the phosphonic acid group of the self-dispersing pigment, so that the hydroxide ions trapped in the Lewis acid are not trapped. It is possible that they are attacking. Actually, the present inventors conducted a silicon film immersion test on an ink containing a phosphonic acid type self-dispersing pigment, the urethane resin having an acid value of 40 mgKOH / g or more, and a water-soluble organic solvent. As a result, it was confirmed that the thickness of the silicon film was reduced.

  Further, as described above, when an inorganic silicate compound as described in Patent Document 3 is added to an ink containing a phosphonic acid type self-dispersing pigment and the urethane resin, the effect of suppressing the elution of silicon is as follows. Admitted. However, when an inorganic silicate compound is added to the ink in an amount that can suppress the elution of silicon, the dispersion state of the self-dispersing pigment in the ink becomes unstable and the storage stability of the ink is reduced. Was confirmed. The decrease in the storage stability was confirmed in all kinds of inorganic silicate compounds subjected to the reliability test.

  Furthermore, the present inventors have also studied a method of adding a resin that easily forms a film on the metal surface to the ink to coat the surface of the constituent member of the recording head. However, the resin rather promotes the elution of silicon or lowers the optical density of the image, and does not exhibit either the effect of suppressing the elution of silicon or the improvement of the optical density of the image. It was confirmed.

  Therefore, the present inventors can record an image having a high optical density and excellent marker resistance, and can further suppress the elution of silicon from the constituent members of the recording head, and also have storage stability. The ink excellent in the above was examined. As a result, the desired performance can be achieved by including in the ink at least a silicone resin having a unit having a siloxane structure and a unit having an acidic group and having an acid value within a predetermined range. As a result, they have reached the present invention.

  Regarding the mechanism in which the ink containing the silicone resin can record an image having a high optical density and excellent marker resistance, and suppresses the elution of silicon from the constituent members of the recording head, the present inventors have described the following. I guess that. According to the study by the present inventors, it was found that the silicone resin having an acid value of 80 mgKOH / g or more and 150 mgKOH / g or less is excellent in compatibility with the urethane resin. Therefore, the silicone resin can be uniformly distributed with the urethane resin in the ink. On the other hand, in the case of a silicone resin having an acid value of less than 80 mgKOH / g, the hydrophilicity of the silicone resin is lowered, so that the silicone resin is unilaterally adsorbed to the pigment, and the dispersion state of the pigment is stabilized more than necessary. I found out. As a result, it was found that the aggregation of the pigment in the recording medium is inhibited, and the image quality, particularly the optical density of the image is lowered. In addition, when the acid value of the silicone resin is larger than 150 mgKOH / g, the water resistance of the silicone resin decreases due to the hydrophilicity of the silicone resin, and as a result, the marker resistance of the image may be insufficient. I understood. For these reasons, the use of the silicone resin having an acid value of 80 mgKOH / g or more and 150 mgKOH / g or less is a necessary condition for recording an image having high optical density and excellent marker resistance. The inventors are thinking.

  Furthermore, the silicone resin has a unit having a siloxane structure, and the Si—O bond in the unit has an effect of mitigating the attack of hydroxide ions on the constituent members of the recording head. It is thought that there is. That is, the Si—O bond in the siloxane structure receives an attack of hydroxide ions instead of silicon constituting the recording head component, thereby suppressing the elution of silicon from the recording head component. it is conceivable that.

<Ink>
Hereinafter, each component constituting the ink of the present invention will be described in detail.

(Urethane resin)
Details of the urethane resin, which is a component of the ink of the present invention, will be described below. The urethane resin is a urethane resin having units derived from polyether polyol and having an acid value of 40 mgKOH / g or more and 140 mgKOH / g or less. Such a urethane resin can be obtained, for example, by reacting polyisocyanate, polyether polyol, and acid group-containing diol. If necessary, a chain extender may be further reacted. The urethane resin is preferably water-soluble. In the present invention, “the resin is water-soluble” means that when the resin is neutralized with an alkali equivalent to the acid value, particles that can measure the particle diameter are not formed. To do. A resin that satisfies such conditions is described as a water-soluble resin in the present invention.

[Polyisocyanate]
Examples of the polyisocyanate include aliphatic polyisocyanates and aromatic polyisocyanates. As said polyisocyanate, the following polyisocyanate can be used individually or in combination.

  Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and 2-methylpentane. -1,5-diisocyanate, aliphatic polyisocyanate having a chain structure such as 3-methylpentane-1,5-diisocyanate; isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1,4 -Cyclic structures such as cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane An aliphatic polyisocyanate having; a. Examples of the aromatic polyisocyanate include tolylene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-dibenzyldiisocyanate, 1,5- These include naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α, α, α, α-tetramethylxylylene diisocyanate. Among these polyisocyanates, aliphatic polyisocyanates having a cyclic structure are preferable, and isophorone diisocyanate or dicyclohexylmethane-4,4'-diisocyanate is more preferable.

[Polyether polyol]
Examples of the polyether polyol include glycols such as (poly) alkylene glycol, or addition polymerization products of a polyhydric alcohol and an alkylene oxide. Examples of the glycols include tetramethylene glycol, hexamethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and (poly) tetra. Methylene glycol, ethylene glycol-propylene glycol copolymer and the like. Examples of the polyhydric alcohol include 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1, 5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-cyclohexanediol, 4,4′-dihydroxyphenylpropane, 4,4′-dihydroxyphenylmethane, hydrogenated bisphenol A, Dihydric alcohols such as di-n-methylol urea and derivatives thereof; glycerin, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, pentaerythritol, trimethylolmelamine and derivatives thereof, polyoxy Trihydric or higher alcohols such as propylene triol; That. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, α-olefin oxide, and the like. These polyether polyols can use 1 type (s) or 2 or more types as needed.

  Among the polyether polyols, polyethylene glycol, poly (1,2-butylene glycol), poly (1,3-butylene glycol), and polypropylene glycol are preferable. In particular, polypropylene glycol is preferable. The four kinds of polyether polyols can impart appropriate toughness and flexibility to the urethane resin, and also have high hydrophilicity, so that the recorded images have scratch and marker resistance and ink ejection. Can be improved. Moreover, when using the said 4 types of polyether polyol, it is preferable that the ratio of the total number of moles of the said 4 types of polyether polyol to the total number of moles of a polyether polyol is 80% or more.

  The number average molecular weight of the polyether polyol is preferably 450 or more and 4,000 or less. If it is set to 450 or more, the flexibility of the formed resin film can be increased, so that the scratch resistance and marker resistance of the image can be improved. On the other hand, if it is 4,000 or less, the flexibility of the formed resin film does not become excessively high, so that the image scratch resistance and marker resistance can be improved.

[Acid group-containing diol]
The “acid group-containing diol” refers to a diol having an acid group such as a carboxy group, a sulfonic acid group, a phosphoric acid group, or a phosphonic acid group in the molecule. The acid group-containing diol is used to increase the hydrophilicity of the urethane resin by increasing the acid value of the urethane resin. As the acid group-containing diol, those having a carboxy group are preferable, and among them, dimethylolpropionic acid and dimethylolbutanoic acid are particularly preferable.

  The acid group-containing diol exists as a salt form. However, the form is not particularly limited. For example, alkali metal salts such as lithium salts, sodium salts, and potassium salts; ammonium salts; organic amine salts such as dimethylamine salts; and the like are preferable.

(Chain extender)
The “chain extender” refers to a compound that is used when a chain extension reaction is performed after the synthesis of a urethane prepolymer and has a plurality of functional groups capable of reacting with an isocyanate group of a polyisocyanate. Examples of the functional group include a hydroxy group and an amino group. Examples of the compound used as a chain extender include polyols and polyamines. Of these, neopentyl glycol, ethylenediamine and the like are preferable. The molecular weight of the chain extender is preferably 200 or less. Moreover, what can bridge | crosslink a urethane resin can also be used as a chain extension agent.

  The urethane resin has an acid value of 40 mgKOH / g or more and 140 mgKOH / g or less. If it is 40 mgKOH / g or more, hydrophilicity is imparted to the urethane resin, and reliability such as ink ejection can be improved. However, by setting it to 40 mgKOH / g or more, the elution of silicon from the constituent members of the recording head is promoted, so that it is necessary to add a silicone resin to be described later to the ink. On the other hand, if it is 140 mgKOH / g or less, the ratio of the urethane bond part (hard segment) of the urethane resin does not increase excessively, and a urethane resin having a polyol part (soft segment) at a certain ratio or more is obtained. As a result, the flexibility of the formed urethane resin film is improved, and the marker resistance of the image is improved.

  The method for producing the urethane resin is not particularly limited. It may be produced by a usual method for producing a urethane resin (one-shot method or multistage method), or may be obtained by any other production method.

  The content (% by mass) of the urethane resin in the ink is preferably 0.1% by mass or more and 10.0% by mass or less based on the total mass of the ink. When the content is 0.1% by mass or more, the scratch resistance and marker resistance of the image can be sufficiently improved. Moreover, if it is 10.0 mass% or less, the raise of the viscosity of an ink can be suppressed and reliability, such as the discharge property of an ink, can be improved.

  The urethane resin content (mass%) based on the total mass of the ink is preferably 0.05 times or more and 2.0 times or less as a mass ratio with respect to the pigment content (mass%). When the mass ratio is 0.05 times or more, the scratch resistance and marker resistance of the image can be further improved. Further, when the mass ratio is 2.0 times or less, it is possible to further improve reliability such as ink discharge performance.

  The weight average molecular weight of the urethane resin is preferably 30,000 to 150,000, more preferably more than 30,000 to 150,000, and more preferably 40,000 to 100,000. Particularly preferred. If it is 30,000 or more, elasticity can be imparted to the formed urethane resin film, and the scratch resistance and marker resistance of the image can be further improved. When the viscosity is 150,000 or less, the viscosity of the ink does not increase excessively, the dispersion state of the pigment can be stabilized, and the reliability such as the ink ejection property can be further improved. The weight average molecular weight of the urethane resin is a polystyrene equivalent weight average molecular weight obtained by gel permeation chromatography (GPC).

〔Method of verification〕
The (1) composition and (2) acid value of the urethane resin can be analyzed by the following methods. First, a method for extracting the urethane resin from the ink containing the urethane resin will be described. Specifically, the urethane resin can be extracted by adding an excess acid (hydrochloric acid or the like) to the supernatant obtained by centrifuging the ink at 80,000 rpm and precipitating the urethane resin. it can. The following analysis can also be performed using ink without performing the extraction. However, a more accurate analysis can be performed by using the urethane resin (solid content) extracted by the above method.

(1) Composition of urethane resin From the position of the peak obtained by dissolving the urethane resin in deuterated dimethyl sulfoxide and analyzing by proton nuclear magnetic resonance ( ¹ H-NMR), polyisocyanate, polyether The type of polyol or the like can be confirmed. Furthermore, the composition ratio can also be calculated from the ratio of the integrated values of the chemical shift peaks of the respective components. Moreover, it analyzes by carbon nuclear magnetic resonance spectroscopy (< ¹³ > C-NMR), calculates | requires the repeating number of the unit unit of polyether polyol, and can calculate the number average molecular weight of polyether polyol.

(2) Acid value of urethane resin The acid value of the urethane resin can be measured by a titration method. In the examples described later, a potentiometric automatic titration apparatus (trade name “AT-510”, manufactured by Kyoto Electronics Industry) equipped with a streaming potential titration unit (trade name “PCD-500”, manufactured by Kyoto Electronics Industry Co., Ltd.) is used. The acid value was measured by the colloid titration used. At this time, the measurement was performed in a state where the urethane resin was dissolved in tetrahydrofuran. As a titration reagent, an ethanol solution of potassium hydroxide was used.

(Silicone resin)
The silicone resin that is a constituent component of the ink of the present invention has at least a unit having a siloxane structure and a unit having an acidic group, and has an acid value of 80 mgKOH / g or more and 150 mgKOH / g or less.

[Units having a siloxane structure]
The unit having a siloxane structure has a siloxane structure represented by -Si-O-Si-. The structure is not particularly limited as long as it is a unit having a siloxane structure, and the main chain may have a siloxane structure or the side chain may have a siloxane structure.

As the unit having a siloxane structure, a unit represented by the following general formula (I) is particularly preferable. The unit represented by the following general formula (I) is a unit derived from a monomer represented by the following general formula (II) having a polymerizable functional group at one end. Furthermore, the silicone resin preferably has a siloxane structure in the side chain, that is, a silicone graft resin. That is, in the resin, the C—C bond derived from the vinyl group or vinylidene group of the monomer represented by the following general formula (II) becomes a part of the main chain of the resin, and the part from the ester bond to R ₄ is branched. Thus, it is preferable that the structure be a side chain of the resin. Further, the resin may have only one type of unit having a siloxane structure, or may have two or more types.

Formula (I)

(In general formula (I), R ₁ is a hydrogen atom or a methyl group. R ₂ is an alkylene group. R ₃ is each independently a methyl group or a phenyl group. R ₄ is an alkyl group having 1 to 6 carbon atoms. An alkyl group or a phenyl group, and n is 1 to 150.)

Formula (II)

(In general formula (II), R ₁ is a hydrogen atom or a methyl group. R ₂ is an alkylene group having 1 to 6 carbon atoms. R ₃ is independently a methyl group or a phenyl group. R ₄ is An alkyl group having 1 to 6 carbon atoms or a phenyl group, and n is 1 to 150.)

In the general formula (I) or the general formula (II), examples of the alkylene group having 1 to 6 carbon atoms of R ₂ include a methylene group, an ethylene group, a propylene group, and a butylene group. In general formula (I) or general formula (II), examples of the alkyl group having 1 to 6 carbon atoms of R ₄ include a methyl group, an ethyl group, a propyl group, and a butyl group. In general formula (I) or general formula (II), R ₁ is preferably a methyl group, R ₂ is preferably a propylene group, all R ₃ are preferably methyl groups, and R ₄ is A butyl group is preferred. n is preferably 10 to 150, and more preferably 12 to 130.

Examples of the monomer represented by the general formula (II) include commercially available silicone macromers (trade names “Silaplane FM-0711”, “FM-0721”, “FM-0725” (above, manufactured by JNC). Etc.) can be used. “Silaplane FM-0711” is a compound in which R ₁ is a methyl group, R ₂ is a propylene group, R ₃ is all a methyl group, R ₄ is a butyl group, and n is 12. “FM-0721” is a compound in which R ₁ is a methyl group, R ₂ is a propylene group, R ₃ is all a methyl group, R ₄ is a butyl group, and n is 66. “FM-0725” is a compound in which R ₁ is a methyl group, R ₂ is a propylene group, R ₃ is all a methyl group, R ₄ is a butyl group, and n is 131.

  The proportion (% by mass) of the unit having the siloxane structure in the silicone resin is preferably 10.0% by mass or more and 40.0% by mass or less based on the total mass of the silicone resin. When the ratio is 10.0% by mass or more, the effect of suppressing the elution of silicon from the constituent members of the recording head is easily exhibited regardless of the content of the silicone resin in the ink. On the other hand, when the ratio is 40.0% by mass or less, the optical density of the image is further improved. When the ratio of the unit having the siloxane structure in the silicone resin is kept below a certain level, the hydrophobicity of the silicone resin does not become too high and the adsorption effect on the pigment is not exhibited more than necessary. As a result, the dispersion state of the pigment is not excessively stabilized, and the aggregation of the pigment in the recording medium is hardly inhibited. Therefore, it is considered that the optical density of the image can be further improved.

[Units having acidic groups]
The unit increases the hydrophilicity of the silicone resin by increasing the acid value of the silicone resin. Examples of the unit having an acidic group include a unit derived from a monomer having an acidic group and a unit derived from an anhydride or salt of these monomers. Examples of the monomer having an acidic group include monomers having a carboxy group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. In addition, a monomer having a sulfonic acid group such as styrenesulfonic acid; a monomer having a phosphonic acid group such as vinylphosphonic acid;

  The silicone resin has an acid value of 80 mgKOH / g or more and 150 mgKOH / g or less. The acid value of the silicone resin can be adjusted by appropriately setting the structure of the unit having the acidic group and the proportion of the resin in the resin.

  When the acid value of the silicone resin is 150 mgKOH / g or less, the hydrophilicity of the silicone resin does not become excessively high. Therefore, the water resistance of the silicone resin can be maintained, and the marker resistance of the image can be sufficiently improved. On the other hand, when the acid value is 80 mgKOH / g or more, moderate hydrophilicity can be imparted to the silicone resin, and the adsorption action of the silicone resin on the pigment can be suppressed. Therefore, the dispersion state of the pigment is not stabilized more than necessary. As a result, the aggregation of the pigment in the recording medium is hardly inhibited, and the image quality, particularly the optical density of the image can be improved.

[Other units]
The silicone resin has at least a unit having the siloxane structure and a unit having the acidic group. That is, the resin may further include other units in addition to the unit having the siloxane structure and the unit having the acidic group. Examples of other units include units derived from nonionic monomers such as (meth) acrylic ester compounds and aromatic compounds.

  Examples of other units include units derived from acrylic esters such as methyl acrylate, ethyl acrylate, and butyl acrylate; units derived from methacrylic esters such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate; In addition, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl- Units derived from monomers such as 2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate; styrene and its derivatives Body, benzyl acrylate, aromatic compounds such as meta benzyl acrylate; and the like. Among these, units derived from methyl acrylate, butyl acrylate, methyl methacrylate, or butyl methacrylate are preferable. The self-dispersing pigment used as the coloring material of the ink of the present invention has an anionic phosphonic acid group. In consideration of the stability of the ink containing such a pigment, the silicone resin preferably does not contain a unit derived from a cationic monomer that can react with the anionic group of the self-dispersing pigment.

  The content (% by mass) of the silicone resin in the ink is preferably 0.1% by mass or more and 10.0% by mass or less, more preferably 0.1% by mass or more and 5.% by mass or less based on the total mass of the ink. It is preferable that it is 0 mass% or less. When the content is 0.1% by mass or more, desired marker resistance can be obtained, and it becomes easy to obtain an effect of suppressing elution of silicon from the constituent members of the recording head. Moreover, if it is 10.0 mass% or less, reliability, such as the discharge property of an ink, can further be improved.

  Moreover, it is preferable that the weight average molecular weights of the said silicone resin are 5,000 or more and 50,000 or less. When the weight average molecular weight is 50,000 or less, the viscosity of the ink hardly increases even when the silicone resin is added, so that the reliability such as the ink ejection property can be improved. Further, since the ink can be sufficiently applied to the recording medium by suppressing the ink ejection failure, the optical density of the image can be improved. When the weight average molecular weight is 5,000 or more, the marker resistance of the image can be sufficiently improved.

  The pigment content (mass%) based on the total mass of the ink is preferably 0.2 times or more and 10.0 times or less as a mass ratio with respect to the content (mass%) of the silicone resin. That is, (content of the pigment / content of the silicone resin) = 0.2 times or more and 10.0 times or less is preferable. When the mass ratio is 0.2 times or more, the amount of the silicone resin is relatively small with respect to the pigment, so that the aggregation of the pigment on the recording medium is hardly inhibited and the optical density of the image is improved. On the other hand, when the mass ratio is 10.0 times or less, the marker resistance of the image can be sufficiently improved.

  The content (mass%) of the urethane resin based on the total mass of the ink is preferably 1.0 times or more and 10.0 times or less as a mass ratio with respect to the content (mass%) of the silicone resin. . That is, (the urethane resin / the silicone resin) is preferably 1.0 times or more and 10.0 times or less. When the mass ratio is 1.0 times or more, the ratio of the urethane resin in the total mass of the resin increases, so that the marker resistance of the image can be improved. On the other hand, if the mass ratio is 10.0 times or less, the ratio of the silicone resin to the total mass of the resin increases, so that the effect of suppressing the elution of silicon from the constituent members of the recording head is sufficiently exerted. .

(Pigment)
The pigment which is a constituent component of the ink of the present invention is a self-dispersing pigment in which a phosphonic acid group is bonded to the particle surface directly or via another atomic group.

The phosphonic acid group is a hydrophilic group represented by a general formula, —PO (OM) ₂ . However, the phosphonic acid groups include those in which a part or all of them are dissociated. That is, a phosphonic acid group, -PO ₃ H ₂ (acid ^{_{form), - PO 3 H - M}} + ( monobasic salt), and any form of ^{_{-PO 3 2- (M +) 2}} ( dibasic salt) It may be. M in the formula represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. Examples of the alkali metal include lithium, sodium, potassium, and the like, and potassium is particularly preferable from the viewpoint of color development of recorded images and ink storage stability. Other atomic groups (—R—) include, for example, linear or branched alkylene groups having 1 to 12 carbon atoms; arylene groups such as phenylene groups and naphthylene groups; other amide groups, sulfonyl groups, amino groups Group, imino group, carbonyl group, ester group, ether group and the like. Or the group which combined these groups.

  As the pigment species, inorganic pigments such as carbon black, calcium carbonate, and titanium oxide; organic pigments such as azo, phthalocyanine, and quinacdrine; and the like can be used. In addition to pigments, dyes and the like may be used in combination for purposes such as toning. The content (% by mass) of the pigment in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass or less based on the total mass of the ink. More preferably.

  The surface charge amount of the pigment is preferably 0.20 mmol / g or more and 0.50 mmol / g or less, and more preferably 0.25 mmol / g or more and 0.42 mmol / g or less. The surface charge amount is an index of the amount of phosphonic acid groups introduced to the particle surface, and represents the amount of phosphonic acid groups per gram of pigment. In the present invention, the surface charge amount of the self-dispersing pigment is determined by colloid titration. In the examples described later, a potentiometric automatic titration apparatus (trade name “AT-510”, manufactured by Kyoto Electronics Industry) equipped with a streaming potential titration unit (trade name “PCD-500”, manufactured by Kyoto Electronics Industry Co., Ltd.) is used. The surface charge amount of the self-dispersing pigment was measured by colloid titration. Methyl glycol chitosan was used as a titration reagent.

〔Method of verification〕
In general, as a coloring material for inkjet ink, in addition to the self-dispersing pigment having a hydrophilic group bonded to the particle surface, the resin dispersant or the like does not have the hydrophilic group and the particle surface is physically adsorbed. Resin dispersed pigments are also used. According to the study by the present inventors, it has been found that it is effective to use the following method in order to determine the dispersion form of the pigment in the ink. That is, after the pigment in the ink is precipitated with an acid, the pigment that can be redispersed is a self-dispersed pigment, and the pigment that is not redispersed can be identified as a resin-dispersed pigment.

  In addition, as for the type of hydrophilic group bonded to the particle surface of the self-dispersing pigment, it is possible to determine whether or not it is a phosphonic acid group by quantifying phosphorus using an ICP emission analyzer. . In the first place, when a phosphonic acid group is not bonded as a hydrophilic group, phosphorus is detected only in the same amount as other metal elements. When phosphorus is obviously abundantly contained as compared with other metal elements, it can be determined that a phosphonic acid group is bonded as a hydrophilic group. More specifically, the presence or absence of a phosphonic acid group can be confirmed by using NMR or the like.

(Aqueous medium)
The ink of the present invention is preferably an aqueous ink containing at least water as an aqueous medium. As the aqueous medium, water or a mixed solvent of water and a water-soluble organic solvent can be used. It is preferable to use deionized water (ion exchange water) as the water. The content (% by mass) of water in the ink is preferably 10.0% by mass or more and 90.0% by mass or less, preferably 50.0% by mass or more and 90.0% by mass or less, based on the total mass of the ink. More preferably.

  The water-soluble organic solvent is not particularly limited as long as it is water-soluble. For example, monohydric or polyhydric alcohol, (poly) alkylene glycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent and the like can be used. The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink.

(Other additives)
The ink of the present invention may contain a water-soluble organic compound that is solid at room temperature, if necessary, in addition to the above components. For example, polyhydric alcohols such as trimethylolpropane and trimethylolethane; urea derivatives such as urea and ethyleneurea; Furthermore, the ink of the present invention contains a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, an evaporation accelerator, a chelating agent, and a water-soluble agent as necessary. Various additives such as a functional resin may be contained.

<Ink cartridge>
The ink cartridge of the present invention includes ink and an ink storage unit that stores the ink. And the ink accommodated in the ink accommodating part is the ink of the present invention. Examples of the ink storage unit include a negative pressure generating member storage chamber and an ink storage chamber. The negative pressure generating member storage chamber contains a negative pressure generating member, and is configured to hold ink in a state where the negative pressure generating member is impregnated with ink. Examples of the negative pressure generating member include a fiber assembly (sponge etc.) having a capillary force. On the other hand, the negative pressure generating member is not stored in the ink storage chamber, and the ink is stored in the ink storage chamber in a state where the negative pressure generation member is not impregnated. However, the ink storage portion may be one in which either the negative pressure generating member storage chamber or the ink storage chamber is not formed. In the case where only the negative pressure generating member storage chamber is formed, the entire amount of ink is held in a state where the negative pressure generating member is impregnated. On the other hand, when the negative pressure generating member storage chamber is not formed but only the ink storage chamber is formed, the entire amount of ink is stored in the ink storage chamber in a state where the negative pressure generating member is not impregnated. Further, the ink cartridge of the present invention includes a structure having a recording head in addition to the ink containing portion.

<Inkjet recording method>
The ink jet recording method of the present invention is a method of recording an image on a recording medium by ejecting ink from a recording head, wherein the ink is the ink of the present invention. As a method for ejecting ink, a piezo method for ejecting ink from a recording head by the action of mechanical energy and a thermal method for ejecting ink from a recording head by the action of thermal energy are known. However, in the present invention, it is particularly preferable to employ a thermal method in which ink is ejected from the recording head by the action of thermal energy. Other than using the ink of the present invention, the steps of the ink jet recording method may be known.

  As the recording head, a recording head in which at least a part of a member in contact with ink is made of silicon or a silicon compound is used. Examples of the silicon compound include silicon nitride, oxide, and carbide. Examples of the constituent member of the recording head made of silicon or a silicon compound include a recording element substrate, an ink flow path, an orifice plate, and a diaphragm that is a discharge pressure generating element. The recording element substrate is a member in which an ink supply port which is a through hole is formed in a silicon substrate. The ink supply port can be formed on the silicon substrate using, for example, sand blasting, laser processing, dry etching, crystal anisotropic wet etching, or a combination of these processing methods. The present invention is also applicable to a recording head in which a silicon compound film (for example, a silicon nitride film, a silicon oxide film, or a silicon carbide film) is formed on these members. Furthermore, the present invention can be applied to a recording head or the like on which a silicon or silicon compound film is formed as a protective film for protecting an element formed on a substrate.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, this invention is not limited at all by the following example, unless the summary is exceeded. In addition, what is described as “parts” and “%” with respect to the component amounts is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Pigment dispersion 1)
20.0 g of pigment, 5.3 mmol of a treating agent (phosphonic acid group introducing agent), 15.1 mmol of nitric acid, and 200.0 mL of pure water were mixed. Carbon black (specific surface area 220 m ² / g) was used as the pigment, and ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid monosodium salt was used as the treating agent. The mixing was performed using a Silverson mixer at a room temperature of 6,000 rpm. After 30 minutes, an aqueous solution in which 15.1 mmol of sodium nitrite was dissolved in a small amount of water was slowly added to the obtained mixture. The temperature of the mixture reached 60 ° C. by the addition of the aqueous solution. The mixture was reacted at this temperature for 1 hour to obtain the product. Thereafter, the pH of the product was adjusted to 10 using an aqueous sodium hydroxide solution. After 30 minutes, 20.0 mL of pure water was added to the product, and diafiltration (removal and desalting of low molecular weight substances) was performed using a spectrum membrane to obtain a concentrated solution. Furthermore, the concentrated liquid was diluted, and the pigment dispersion 1 was obtained by adjusting the solid content of the pigment. The pigment dispersion 1 contained a self-dispersing pigment having ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid groups bonded to the particle surface. The counter ion of the phosphonic acid group was sodium ion. The surface charge amount of the pigment was 0.34 mmol / g. The content of the self-dispersing pigment in the pigment dispersion 1 was 10.0%.

(Pigment dispersion 2)
In the preparation of pigment dispersion 1, the amount of treating agent was changed to 3.9 mmol, the amount of nitric acid was changed to 11.1 mmol, and the amount of sodium nitrite was changed to 11.1 mmol. Other than that, the pigment dispersion 2 was obtained in the same procedure as the preparation of the pigment dispersion 1. Pigment dispersion 2 contained a self-dispersed pigment having ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid groups bonded to the particle surface. The counter ion of the phosphonic acid group was sodium ion. The surface charge amount of the pigment was 0.25 mmol / g. The content of the self-dispersing pigment in the pigment dispersion 2 was 10.0%.

(Pigment dispersion 3)
In the preparation of the pigment dispersion 1, the pigment type is C.I. I. Pigment Blue 15: 3 (specific surface area 90 m ² / g), pigment amount 7.0 g, treating agent amount 14.0 mmol, nitric acid amount 40.0 mmol, sodium nitrite amount Changed to 40.0 mmol. Other than that, the pigment dispersion 3 was obtained in the same procedure as the preparation of the pigment dispersion 1. The pigment dispersion 3 contained a self-dispersed pigment having ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid groups bonded to the particle surface. The counter ion of the phosphonic acid group was sodium ion. The surface charge amount of the pigment was 0.34 mmol / g. The content of the self-dispersing pigment in the pigment dispersion 3 was 10.0%.

(Pigment dispersion 4)
In the preparation of the pigment dispersion 1, the pigment type is C.I. Pigment Red 122 (specific surface area 130 m ² / g), pigment amount 7.0 g, treating agent amount 18.0 mmol, nitric acid amount 51.0 mmol, sodium nitrite amount 51. Changed to 0 mmol. Other than that, the pigment dispersion 4 was obtained in the same procedure as the preparation of the pigment dispersion 1. The pigment dispersion 4 contained a self-dispersed pigment having ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid groups bonded to the particle surface. The counter ion of the phosphonic acid group was sodium ion. The surface charge amount of the pigment was 0.34 mmol / g. In the pigment dispersion liquid 4, the content of self-dispersion therein was 10.0%.

(Pigment dispersion 5)
To a solution obtained by dissolving 60 mmol of concentrated hydrochloric acid in 5.5 g of water, 8.28 mmol of 4-aminophthalic acid, which is a treatment agent (carboxylic acid group introducing agent), was added while being cooled to 5 ° C. Next, the container containing the solution was placed in an ice bath, and the solution was stirred so that the solution was always kept at 10 ° C. or lower. In this state, a solution in which 21.2 mmol of sodium nitrite was dissolved in 9.0 g of water at 5 ° C. was added to the solution, and the resulting solution was stirred for 15 minutes. Thereafter, 6.0 g of carbon black (specific surface area 220 m ^{2 /} g) was added to the solution under stirring, and the mixture was further stirred for 15 minutes to obtain a pigment slurry. By using a filter paper (trade name “standard filter paper No. 2”, manufactured by Advantech), the obtained slurry is filtered, and the filtered pigment is sufficiently washed with water and dried in an oven at a temperature of 110 ° C. A self-dispersing pigment was prepared. By adding water to this self-dispersing pigment, the pigment dispersion 5 was obtained by adjusting the solid content of the pigment. The pigment dispersion 5 contained a self-dispersed pigment having a phthalic acid group (an acidic group is a carboxylic acid group) bonded to the particle surface. The counter ion of the carboxylic acid group was sodium ion. The surface charge amount of the pigment was 0.34 mmol / g. The content of the self-dispersing pigment in the pigment dispersion 5 was 10.0%.

<Synthesis of urethane resin>
A four-necked flask equipped with a thermometer, a stirrer, a nitrogen gas inlet tube, and a reflux tube was prepared. The amount of polyisocyanate, polyol, and acid group-containing diol shown in Table 1 and 300.0 parts of methyl ethyl ketone were added to the flask, and reacted at a temperature of 80 ° C. for 6 hours in a nitrogen gas atmosphere to synthesize a prepolymer. . Subsequently, the used amount of chain extender shown in Table 1 was added, and further reacted at a temperature of 80 ° C. At this time, the residual ratio of the isocyanate group was confirmed by FT-IR, and the reaction was continued until the desired residual ratio was obtained, whereby a reaction liquid was obtained. After cooling the obtained reaction liquid to a temperature of 40 ° C., ion-exchanged water was added, and an aqueous potassium hydroxide solution was added while stirring at high speed with a homomixer to obtain a liquid containing a urethane resin. Methyl ethyl ketone is distilled off under reduced pressure from the obtained liquid under heating, thereby obtaining aqueous solutions containing water-soluble urethane resins 1 to 9 each having a urethane resin (solid content) content of 20.0%. It was. Table 1 also shows the acid value and weight average molecular weight of the urethane resin. The acid value was measured by potentiometric titration using a methanol solution of potassium hydroxide. Moreover, the weight average molecular weight was measured as a value in terms of polystyrene by gel permeation chromatography (GPC).

  Abbreviations in Table 1 are as follows. IPDI: isophorone diisocyanate, H12MDI: dicyclohexylmethane-4,4′-diisocyanate, PPG: polypropylene glycol (number average molecular weight: 2000), PES: polyester polyol (number average molecular weight: 2000), PC: polycarbonate polyol (number average molecular weight: 2000), DMPA: dimethylolpropionic acid, EDA: ethylenediamine, NPG: neopentyl glycol.

<Synthesis of silicone resin>
A flask equipped with a thermometer, a stirrer, and a nitrogen gas inlet tube was prepared. The flask is charged with each of the monomers used in Table 2 below and a polymerization initiator (azobisisobutyronitrile) and 500.0 parts of 1-methoxy-2-propanol. Reaction was performed for 4 hours to obtain a reaction solution. The obtained reaction liquid was dried under reduced pressure to obtain a silicone resin as a copolymer. After 25.0 parts of methyl ethyl ketone was added and dissolved in the obtained silicone resin, 2.0 parts of a 30.0% aqueous potassium hydroxide solution was added to neutralize some of the acidic groups of the silicone resin. Thereafter, 300.0 parts of ion exchange water was further added and stirred to obtain a liquid containing a silicone resin. At a temperature of 60 ° C., methyl ethyl ketone is distilled off from the obtained liquid under reduced pressure, and further, a part of the water is concentrated by distillation under reduced pressure, and the content of the silicone resin (solid content) is 20.0%. Liquids containing silicone resins 1 to 14 were obtained. Table 2 also shows the acid value of the silicone resin, the weight average molecular weight, and the proportion of units having a siloxane structure in the silicone resin (denoted as “Si unit proportion (%)”). The acid value was measured by potentiometric titration using a methanol solution of potassium hydroxide. Moreover, the weight average molecular weight was measured as a value in terms of polystyrene by gel permeation chromatography (GPC).

  Abbreviations in Table 2 are as follows. Si monomer: Monomer having a siloxane structure (monomer represented by general formula (II)), trade name “Silaplane FM-0711”, manufactured by JNC, number average molecular weight of about 1,000), AA: acrylic acid, MMA: Methyl methacrylate, BMA: butyl methacrylate, PME: methoxypolyethylene glycol monomethacrylate (trade name “Blenmer PME-200”, manufactured by NOF, number of ethylene oxide groups: about 4), AIBN: azobisisobutyronitrile.

<Preparation of ink>
Each component shown in Tables 3-1 to 3-4 was mixed and sufficiently stirred, and then pressure filtration was performed with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare each ink. “Acetyleneol E100” is a trade name of a nonionic surfactant (acetylene glycol ethylene oxide adduct) manufactured by Kawaken Fine Chemicals.

  Further, inks of Comparative Examples 9 to 11 were prepared by the following method.

(Comparative Example 9)
Ink 1 described in Patent Document 1 was prepared and used as the ink of Comparative Example 9. This ink differs from the present invention in that it contains a resin-dispersed pigment, a polyether-type urethane resin emulsion, and an acrylic silicone resin, and at least the pigment is not a self-dispersed pigment.

(Comparative Example 10)
The ink of Example 9 described in Patent Document 2 was prepared and used as the ink of Comparative Example 10. This ink differs from the present invention in that it contains a carboxylic acid type self-dispersing pigment, a urethane resin emulsion, and an acrylic silicone resin, and at least the pigment is not a phosphonic acid type self-dispersing pigment.

(Comparative Example 11)
A cyan ink described in Patent Document 3 was prepared and used as the ink of Comparative Example 11. This ink is different from the present invention in that it contains a resin-dispersed pigment, colloidal silica (inorganic silicic acid compound), and at least the pigment is not a self-dispersing pigment and does not contain a urethane resin or a silicone resin.

<Evaluation>
Each ink was filled in an ink cartridge and mounted on an ink jet recording apparatus (trade name “PIXUS MX7600”, manufactured by Canon Inc.) that discharges ink from the recording head by the action of thermal energy. The ink jet recording apparatus has a mechanism for applying the reaction liquid to the recording medium, but was modified so that it does not operate. The recording head of this ink jet recording apparatus is a member that comes into contact with ink, the recording element substrate is made of silicon, and silicon nitride and silicon oxide are used as part of the ink flow path. . In this embodiment, in the case of black ink, the recording duty of a solid image recorded under the condition of applying one droplet of about 28 ng to a unit area of 600 dpi × 600 dpi is defined as 100%. In the case of color ink, the recording duty of a solid image recorded under the condition that four drops of about 5.8 ng of ink are applied to a unit area of 600 dpi × 600 dpi is defined as 100%. The recording conditions were temperature: 23 ° C., relative humidity: 55%, ejection amount per ink drop: 28 ng ± 10% (black ink), and within 5.8 ng ± 10% (color ink). In the present invention, in the evaluation criteria of the following evaluation items, AA, A and B are acceptable levels, and C is an unacceptable level. The evaluation results are shown in Table 4.

(Optical density)
Using the ink jet recording apparatus, solid images each having a recording duty of 2 cm × 2 cm and a recording duty of 100% were recorded on the following three types of recording media (plain paper) to obtain three recorded materials.
PPC paper (trade name "GF-500", manufactured by Canon)
PPC paper (trade name “Xerox Business”, made by Xerox)
PPC paper (trade name “Bright White Inkjet Paper”, manufactured by Hured Packard)
One day after recording, the optical density of the solid images recorded on the three recorded materials was measured using a spectrophotometer (trade name “Spectrolino”, manufactured by Gretag Macbeth). From these average values, the optical density was evaluated according to the evaluation criteria shown below.

[Black ink]
A: Average value of optical density was 1.4 or more B: Average value of optical density was 1.2 or more and less than 1.4 C: Average value of optical density was less than 1.2

[Color ink]
A: The average value of optical density was 0.9 or more B: The average value of optical density was 0.8 or more and less than 0.9 C: The average value of optical density was less than 0.8

(Marker resistance)
Using the ink jet recording apparatus, a vertical ruled line having a thickness of 1/10 inch was recorded on a recording medium (trade name “PPC paper Everyday Printing” manufactured by DataCopy) to obtain a recorded matter. After 5 minutes of recording, the vertical ruled line was marked using a yellow line marker (trade name “OPTEX2”, manufactured by Zebra), and the state of the vertical ruled line was visually confirmed, and in accordance with the evaluation criteria shown below. The marker resistance was evaluated.

AA: Dirt was not generated at all. A: Dirt was hardly generated. B: Dirt was not noticeable. C: Conspicuous dirt was generated.

(Silicon elution suppression)
First, the silicon concentration in the ink was measured using an ICP emission analyzer (trade name “SPS5100”, manufactured by SII Nano Technology). Then, the ink flow path of the recording head of the ink jet recording apparatus is filled with each ink, and the discharge port surface of the recording head is capped (covered with a cap for preventing ink evaporation), and the temperature It was left in an environment of 60 ° C. for 3 months. Thereafter, the ink filled in the ink flow path of the recording head was extracted using a rotary pump. The silicon concentration in the extracted ink was measured in the same manner. Based on the ratio of the silicon concentration in the ink before and after the test (after the test / before the test), the elution suppression of silicon was evaluated according to the evaluation criteria shown below.

A: Ratio of silicon concentration was 1.2 times or less B: Ratio of silicon concentration was more than 1.2 times and 2.0 times or less C: Ratio of silicon concentration was more than 2.0 times

(Storage stability)
First, the viscosity of the ink obtained above and the average particle diameter of the pigment in the ink were measured. The viscosity of the ink was measured using an E-type viscometer (trade name “RE-80L”, manufactured by TOKI) at a temperature of 25 ° C. and 50 rpm. The particle diameter of the pigment was measured with a concentrated particle size analyzer (trade name “FPAR-1000”, manufactured by Otsuka Electronics Co., Ltd.). Each ink was then sealed in a container made of polytetrafluoroethylene. This was stored in an oven at a temperature of 60 ° C. for 2 months. Thereafter, the ink was returned to room temperature, and the viscosity of the ink and the average particle diameter of the pigment in the ink were measured again. From the viscosity of the ink before and after the test and the increase rate of the average particle diameter of the pigment in the ink, the storage stability was evaluated according to the evaluation criteria shown below.

A: The increase rate of the viscosity of the ink and the average particle size of the pigment was 1% or less B: The increase rate of the viscosity of the ink and the average particle size of the pigment was more than 1% and 5% or less C: The viscosity of the ink And the average particle diameter increase rate of the pigment was more than 5%.

Claims (7)

An ink used for an ink jet recording method in which at least a part of a member in contact with ink is made of silicon or a silicon compound, and an image is recorded on a recording medium by ejecting the ink from the recording head. ,
Contains pigments, urethane resins, and silicone resins,
The pigment is a self-dispersing pigment in which a phosphonic acid group is bonded to the particle surface directly or through another atomic group,
The urethane resin is a urethane resin having a unit derived from a polyether polyol and having an acid value of 40 mgKOH / g or more and 140 mgKOH / g or less,
The ink, wherein the silicone resin has at least a unit having a siloxane structure and a unit having an acidic group, and has an acid value of 80 mgKOH / g or more and 150 mgKOH / g or less. The silicone resin has a siloxane structure in its side chain;
The ink according to claim 1, wherein the unit having a siloxane structure is a unit represented by the following general formula (I).
Formula (I)

(In general formula (I), R ₁ is a hydrogen atom or a methyl group, R ₂ is an alkylene group having 1 to 6 carbon atoms, R ₃ is independently a methyl group or a phenyl group, and R ₄ is (It is a C1-C6 alkyl group or a phenyl group, and n is 1-150.)   The ink according to claim 1 or 2, wherein the silicone resin has a weight average molecular weight of 5,000 or more and 50,000 or less.   The ink according to any one of claims 1 to 3, wherein a ratio (mass%) of the unit having the siloxane structure in the silicone resin is 10.0 mass% or more and 40.0 mass% or less.   2. The content (mass%) of the urethane resin based on the total mass of the ink is 1.0 to 10.0 times as a mass ratio with respect to the content (mass%) of the silicone resin. 5. The ink according to any one of items 4 to 4. An ink jet recording method for recording an image on a recording medium by using a recording head in which at least a part of a member in contact with ink is composed of silicon or a silicon compound, and discharging ink from the recording head,
An ink jet recording method, wherein the ink is the ink according to any one of claims 1 to 5. An ink cartridge comprising ink and an ink containing portion for containing the ink,
The ink cartridge according to claim 1, wherein the ink is an ink according to claim 1.