JP2006097017A - Ink set for ink jet recording, ink jet recording method, ink cartridge, recording unit, and recording apparatus - Google Patents

Abstract

To provide an ink set excellent in uniformity and an ink jet recording method capable of stably forming a high-quality image. Furthermore, an ink cartridge, a recording unit, and a recording apparatus applicable to the ink jet recording method are provided.
In an ink composition containing at least water, a pigment, and a dispersant for dispersing the pigment, the ink set has (hydrophobic segment)-(oxyethylene structure-containing nonionic hydrophilic) as the dispersant. Using a block copolymer having (segment)-(ionic hydrophilic segment), the ratio of the number of unit structures of the hydrophobic segment to the number of oxyethylene structures is adjusted according to the solid content concentration of the ink composition.
[Selection] Figure 1

Description

  The present invention relates to an ink set, an ink jet recording method, an ink cartridge, a recording unit, and a recording apparatus that are particularly suitable for use in ink jet recording.

  The ink jet recording method is a method in which energy is applied to ink, ink droplets are ejected from nozzles, and ink is attached to a recording medium such as paper to perform recording.

  In recent years, the size of ink droplets ejected from a single nozzle has been reduced in order to cope with an extremely high-quality ink-jet recording image at the silver salt photographic level for ink-jet recording images. At present, an ink jet printer having an ink droplet amount of about 10 pl (picoliter) or less is commercially available. Further, with respect to the recording speed, further higher speed has been demanded, and accordingly, it is an urgent need to cope with a higher driving frequency.

By the way, recently, ink jet recording images are required to have not only high definition but also excellent fastness (light resistance, etc.). Therefore, the transition from dyes to pigments is progressing as a color material. For example, Patent Document 1 proposes a recording liquid including an aqueous medium containing at least a pigment, a polymer dispersant, and a nonionic surfactant. Patent Documents 2 and 3 propose using a block copolymer having a hydrophilic segment and a hydrophobic segment as a pigment dispersant.
Japanese Patent Laid-Open No. 56-147871 US Pat. No. 5,221,334 US Pat. No. 5,085,698

  The present inventors have confirmed that the use of a block copolymer having a specific structure as a pigment dispersant is effective in preventing so-called solvent shock in which pigment particles increase when the water content decreases. is doing. Specifically, it is a block copolymer having an ionic hydrophilic segment and a nonionic hydrophilic segment containing an oxyethylene structure in the middle of the hydrophobic segment.

  However, when ink is not ejected for a certain period of time and the nozzle recovery operation is not performed, the ink viscosity at the nozzle tip increases due to a relative increase in the pigment concentration due to water evaporation from the nozzle tip. There was a thing. As a result, when the next first drop of ink is ejected from the nozzle, the ink may not be ejected, or stable ejection may not be performed, and printing may be disturbed. Even if the time during which ink is not ejected is short and the ink can be ejected normally, the pigment concentration of the first few drops is concentrated and high, which may cause problems in image formation. It was. In order to obtain higher quality images, many improvements are still desired.

  Hereinafter, the discharge of the first drop after the discharge is stopped for a certain time is referred to as firing, and if any inconvenience occurs in the first drop and several discharges thereafter, it is referred to as poor firing.

  SUMMARY An advantage of some aspects of the invention is that it provides an ink set that is excellent in lightness. Another object of the present invention is to provide an ink jet recording method capable of stably forming a high-quality image. Furthermore, an object of the present invention is to provide an ink cartridge, a recording unit, and a recording apparatus that can be applied to the ink jet recording method.

  Under such circumstances, the present inventors have conducted intensive research on the use of a block polymer having an ionic hydrophilic segment and a nonionic hydrophilic segment containing an oxyethylene structure in the middle of a hydrophobic segment as a pigment dispersant. Piled up. As a result, it was found that the larger the ratio of the number of unit structures of the hydrophobic segment to the number of oxyethylene structures, the less the pigment concentration at the nozzle tip is relatively increased and the better the uniformity. Invented.

That is, the present invention is an ink set for ink jet recording having a combination of two ink compositions having a solid content concentration difference of more than 2% by mass,
Each of the two types of ink compositions contains at least an aqueous medium, a pigment, and a dispersant for dispersing the pigment, and the dispersant is a hydrophobic segment, an A segment, and an oxyethylene structure-containing nonion Ink set for inkjet recording, which is a block copolymer having a B segment which is a hydrophilic hydrophilic segment and a C segment which is an ionic hydrophilic segment,
The ratio of the number of unit structures of the A segment to the number of oxyethylene structures contained in the B segment of the block copolymer contained in each of the two ink compositions (number of unit structures of the A segment / B The block copolymer contained in the ink composition having a relatively higher solid content concentration than the block copolymer contained in the ink composition having a relatively low solid content concentration) The ink set for ink jet recording is characterized in that is larger.

  An ink jet recording method capable of achieving the above object is characterized in that recording is performed using the above ink set for ink jet recording.

  In addition, an ink cartridge that can achieve the above object is characterized by including an ink containing portion for containing the ink set for ink jet recording.

  In addition, a recording unit that can achieve the above object includes the above ink cartridge that contains the above ink set for ink jet recording, and an ink jet recording head for discharging ink. It is characterized by.

  Further, a recording apparatus that can achieve the above object is characterized by comprising the above recording unit.

  According to the present invention, it is possible to provide an ink set that can achieve a very high level of uniformity while maintaining the effect of the nonionic hydrophilic segment. Further, it is possible to provide an ink jet recording method capable of stably forming a high-quality image. Furthermore, an ink cartridge, a recording unit, and a recording apparatus that can be applied to the inkjet recording method can be provided.

  The present invention is described in detail below.

  In the block copolymer used in the present invention, the A segment is a hydrophobic segment, the B segment is an oxyethylene structure-containing nonionic hydrophilic segment, and the C segment is an ionic hydrophilic segment. If it is a block copolymer having such a so-called ABC structure, each segment may be a copolymer segment. The form of the copolymerization is not limited. For example, it may be a random copolymer or a gradient copolymer whose composition ratio gradually changes.

  In the present invention, the amphiphilic block copolymer has the B segment, so that after the ink has landed on the recording paper, the viscosity increases instantly with the penetration of water. For this reason, when two or more colors of ink are overlapped, a phenomenon (color bleeding) in which the inks are mixed with each other and the boundary is not clear is reduced. Also, by having the B segment, even after the landing, the organic solvent agglomerates rapidly, and the particles are uniformly fixed without forming coarse particles. It is. It is also excellent in scratching and water resistance.

  However, when ink containing a conventional dispersion resin is used, if ink is ejected from a predetermined nozzle of the inkjet recording head, and then the ejection is stopped for a certain period of time, the ink is re-emitted from the nozzle again. In some cases, it was difficult to discharge stably. For this reason, problems such as streak-like unevenness have occurred during image formation. As a result of intensive studies, the present inventors have found that this re-ejectability is greatly influenced by two factors: the solid content concentration of the ink and the number of unit structures of the A segment / the number of oxyethylene structures contained in the B segment. It was. That is, when ink is not ejected from the nozzle tip of the inkjet head for a certain period of time, moisture evaporates from the nozzle tip opening, the solid content concentration increases, and the viscosity increases, which may affect the next ejection. Are known. The effect appears remarkably in the ink having a high solid content concentration. However, it has been found that by increasing the number of unit structures of the A segment / the number of oxyethylene structures contained in the B segment, the influence on the next discharge can be suppressed to a small extent without causing thickening due to an increase in the solid content concentration. It was. This is considered to be because the dispersed pigment particles move to a region with a higher proportion of water when the ratio of water and organic solvent at the nozzle tip due to moisture evaporation changes.

  For this reason, according to the present invention, it is possible to achieve both a good image with high fastness and a good discharge stability by the ink jet head.

  In the present invention, the solid content concentration of the ink composition refers to the ratio of non-volatile components (for example, ink and dispersant) in the ink composition to the total mass of the ink composition. Further, the technical problem of the present invention is particularly noticeable when the solid content concentration of the ink composition is 4% by mass or more.

  FIG. 3 is a graph showing the relationship between the number of unit structures of the A segment / the number of oxyethylene structures contained in the B segment and the re-ejection interval time. Specifically, with respect to cyan ink dispersed using various polymers having different structures, after a certain interval after stopping the discharge, the discharge speed is measured, and the interval time during which the discharge speed can be discharged at 5 m / s or more. Is plotted as shown in FIG. As a result, it can be seen that the greater the number of unit structures of the A segment / the number of oxyethylene structures contained in the B segment, the better the uniformity. More preferably, the number of unit structures of the A segment / the number of oxyethylene structures contained in the B segment is 0.5 or more.

  In general, color image formation in ink jet recording is performed with a minimum of three colors of a yellow ink composition, a magenta ink composition, and a cyan ink composition, and is therefore suitable for an ink set having these three color ink compositions. Applies to In these three-color ink sets, the optimum solid content concentration is set for each ink composition from the viewpoint of color reproduction. In the present invention, at this time, by selecting the amphiphilic block copolymer of the dispersant as described above, since the ejection stability becomes good, a color image having no defect can be formed.

  It is also possible to use ink compositions other than the above three colors for the purpose of expanding the color reproduction range and improving the image quality. Specifically, color ink compositions such as light magenta, light cyan, black, light black, red, green, blue, orange, violet, and the like can be used.

  Note that the light magenta and light cyan ink compositions described here are generally those in which the color material concentrations of the magenta and cyan ink compositions are lowered for the purpose of improving the image quality of a printed image by density modulation. At this time, a color image having good color reproduction can be formed by using an ink set having an ink composition satisfying the configuration of the present invention between the same colors.

  The red, orange, green, blue and violet ink compositions are ink compositions used as elements constituting intermediate colors of yellow, magenta and cyan in order to improve the color reproduction range. In addition, the light black ink composition is one in which the color material concentration of the black ink composition is lowered for the purpose of improving color reproducibility and gradation with respect to dark colors such as shadow portions and lowering graininess.

  The block copolymer is a copolymer in which polymer segments having a different unit structure are bonded by a covalent bond, and is also called a block copolymer or a block polymer.

  Specific examples of the block copolymer used as a dispersant in the ink composition according to the present invention are as follows. In other words, acrylic, methacrylic block copolymers, polystyrene and other addition polymerization or condensation polymerization block copolymers, block copolymers having polyoxyethylene and polyoxyalkylene blocks, and the like have been conventionally known. It is a block copolymer. In the present invention, the block copolymer may be bound to a copolymer chain in a T shape to form a graft copolymer. The block copolymer of the present invention preferably contains a polyvinyl ether structure as a unit structure.

  A preferred specific unit structure of the ionic hydrophilic segment (C segment) includes a repeating unit represented by the following general formula (1).

(In the general formula (1), R ⁰ represents —X— (COOH) _r , —X— (COO—M) _r , or —X— (COO) ₂ M ² , where X represents 1 to 20 carbon atoms. linear, branched or cyclic alkanediyl or alkanetriyl group ^{or,, - (CH (R 5} ) -CH (R 6) -O) p - (CH 2) m -CH 3-r - or _{- (CH 2) m - (} O) n - (CH 2) q -CH 3-r -, or at least one is substituted with a carbonyl group or an aromatic ring structure group thereof methylene group, or their A group in which at least one methine group is substituted with an aromatic ring structure is represented, r represents 1 or 2, p represents an integer of 1 to 18, m represents an integer of 0 to 35, and n represents 1. Or represents 0, q represents an integer of 0 to 17, M represents a monovalent cation, and M ² represents a divalent group. R ⁵ and R ⁶ represent an alkyl group, and R ⁵ and R ⁶ may be the same or different, and when there are a plurality of them, they may be the same or different.)
Furthermore, as a preferable specific unit structure of the hydrophobic segment (A segment) or the oxyethylene structure-containing nonionic hydrophilic segment (B segment), a repeating unit represented by the following general formula (2) may be mentioned.

(In the general formula (2), R ¹ is a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, -Ph, -Pyr, -Ph-Ph, -Ph-Pyr,-(CH ( R ⁵ ) —CH (R ⁵ ) —O) _p —R ⁷ and — (CH ₂ ) _m — (O) _n —R ^7, and the hydrogen atom bonded to the carbon atom in the aromatic ring is carbon. The linear or branched alkyl group represented by formulas 1 to 4 and a carbon atom in the aromatic ring each independently represent a nitrogen atom, p is an integer of 1 to 18, and m is 1 to 1. An integer of 36, n represents 0 or 1. R ⁵ and R ⁶ each independently represents a hydrogen atom or —CH ₃ , and when there are a plurality of R ⁵ and R ⁶ , they may be the same or different. R ⁷ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, —Ph, —Pyr, — When Ph 7 -Ph, —Ph—Pyr, —CHO, —CH ₂ CHO, —CO—CH═CH ₂ , and —CO—C (CH ₃ ) ═CH ₂ are selected, and R ⁷ is other than a hydrogen atom , A hydrogen atom bonded to a carbon atom in R ⁷ is a linear or branched alkyl group having 1 to 4 carbon atoms or —F, —Cl, —Br, and a carbon atom in an aromatic ring is a nitrogen atom A group which may be substituted with an atom, Ph represents a phenyl group or a phenylene group, and Pyr represents a pyridyl group.
Specific examples of preferred unit structures represented by the general formula (1) constituting the C segment are given below.

(Ph represents a substituted benzene ring.)
Specific examples of the preferable unit structure represented by the general formula (2) constituting the A segment include those described below.

(Ph represents a phenyl group or a phenylene group.)
Specific examples of the preferred unit structure represented by the general formula (2) constituting the B segment include those described below.

A number of methods for synthesizing a polymer containing a polyvinyl ether structure have been reported (Japanese Patent Laid-Open No. 11-080221, etc.), but a method using cationic living polymerization by Aoshima et al. Publications, etc.) are typical. By conducting polymer synthesis using cationic living polymerization, various polymers such as homopolymers, copolymers of two or more monomers, block polymers, graft polymers, and gradient polymers can be accurately measured in length (molecular weight). Can be combined and synthesized. In addition, various functional groups can be introduced into the side chain of polyvinyl ether. The cationic polymerization method can also be carried out in the HI / I ₂ system, HCl / SnCl ₄ system, or the like.

  As described above, the block copolymer used in the present invention has an A segment that is a hydrophobic segment, a B segment that is an oxyethylene structure-containing nonionic hydrophilic segment, and a C segment that is an ionic hydrophilic segment. The proportion of the A segment with respect to the entire block copolymer is preferably 25 to 80 mol%, and more preferably 30 to 80 mol%. The proportion of the B segment is preferably 5 to 70 mol%, and more preferably 5 to 40 mol%. The proportion of the C segment is preferably 5 to 30 mol%.

  Moreover, the preferable polymerization degree of each segment in this invention is 3 or more and 10000 or less each independently. More preferably, they are each independently 5 or more and 5000 or less. Further, the number of unit structures of the A segment is preferably 30 to 120, the number of unit structures of the B segment is preferably 5 to 160, and the number of unit structures of the C segment is 5 to 160. 20 is preferable.

  On the other hand, the number of oxyethylene structures contained in the unit structure of the B segment is preferably 1 to 4, and more preferably 1 to 2.

  Furthermore, the ratio of the number of unit structures of the A segment to the number of oxyethylene structures contained in the B segment of the block copolymer (number of unit structures of A segment / number of oxyethylene structures contained in the B segment) Is preferably 0.5 or more. Moreover, it is more preferable that it is 2 or less.

  The number of unit structures of the A segment contained in the ink composition having a relatively high solid content concentration / the number of oxyethylene structures contained in the B segment of the block copolymer is relatively low in solid content concentration. The number of unit structures of the A segment contained in the composition / the number of oxyethylene structures contained in the B segment of the block copolymer is preferably 1.1 times or more, particularly 1.5 times or more. Is preferred. Further, it is preferably 5 times or less, and particularly preferably 3 times or less.

  In the present invention, in any combination of two kinds of ink compositions selected from a plurality of ink compositions constituting the ink set, if the difference in solid content concentration exceeds 2% by mass, the relative In the ink composition having a relatively low solid content concentration, the number of unit structures of the A segment of the block copolymer / the number of oxyethylene structures contained in the B segment contained in the ink composition having a high solid content concentration It is necessary that the number of unit structures of the A segment of the block copolymer contained is larger than the number of oxyethylene structures contained in the B segment. In the present invention, even in the case of a combination of ink compositions in which the solid content concentration difference is 2% by mass or less, as long as the solid content concentration is different, the number of unit structures of the A segment / oxyethylene structure contained in the B segment More preferably, the number satisfies the same configuration as the present invention.

  In the present invention, the content of the unit structure represented by the general formula (1) or the general formula (2) contained in the block copolymer is 0.01 to 99 mol% with respect to the entire block copolymer. It is preferable that it is 1 to 90 mol%. If it is less than 0.01 mol%, the polymer interaction to be caused by the functional group of each segment may be insufficient, and if it exceeds 99 mol%, the interaction may be excessively performed and the function may be insufficient.

  The number average molecular weight (Mn) of the block copolymer used in the present invention is preferably 200 or more and 10000000 or less, particularly preferably 1000 or more and 1000000 or less. If it exceeds 10,000,000, the entanglement between the polymer chains and between the polymer chains becomes excessive, and it is difficult to disperse in the solvent. If it is less than 200, the steric effect as a polymer may be difficult to obtain due to the low molecular weight.

  Further, in order to improve the dispersion stability of the pigment and the inclusion property (inclusive property), it is preferable that the molecular mobility of the block copolymer is more flexible. This is because the molecular mobility of the block copolymer is flexible, so that the block copolymer is likely to physically entangle with the surface of the functional substance and to have an affinity. Furthermore, as described later in detail, it is preferable that the coating layer is flexible in that a coating layer can be easily formed on a recording medium. For this purpose, the glass transition temperature Tg of the block copolymer is preferably 20 ° C. or lower, more preferably 0 ° C. or lower, and further preferably −20 ° C. or lower. Also in this respect, a block copolymer having a polyvinyl ether structure is preferably used because it generally has a low glass transition point and flexible properties. In the case of the above unit structure example, the glass transition temperature is often about −20 ° C. or lower.

  The block copolymer as a dispersant contained in the ink composition of the present invention can be used alone or in combination of two or more. Further, a known dispersant can be used in combination. The content of the dispersant contained in the ink composition of the present invention is preferably 0.1 to 30% by mass, more preferably 0.5 to 10% by mass, and more preferably 0 to 0% by mass with respect to the total mass of the ink. It is the range of 5-6 mass%. If the content of the dispersant is higher than this range, it may be difficult to maintain a desired ink viscosity. Moreover, when content of a dispersing agent is lower than this range, it may become difficult to implement | achieve desired dispersibility. The ratio of the pigment and the block copolymer as a dispersant (pigment / block copolymer) is preferably 0.05 or more and 5 or less, and particularly preferably 1 or more and 3 or less, based on mass.

  As the aqueous medium contained in the ink composition of the present invention, one containing at least water can be used. Furthermore, a solvent and a dispersion medium are contained, and a binder resin can be used as the dispersion medium. As the solvent or dispersion medium, a water-soluble organic solvent, a water-insoluble organic solvent, or the like can be used. Of course, a mixture thereof can also be used.

Preferred examples of the constituent material used in combination with water include the following.
Alkyl alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-pentanol;
Amides such as dimethylformamide and dimethylacetamide;
Ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane;
Copolymers of oxyethylene or oxypropylene such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol;
Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, trimethylene glycol, 1,4 butanediol, 1,5 pentanediol;
Triols such as 1,2,6-hexanetriol, glycerin, trimethylolpropane;
Lower alkyl ethers of glycols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl, butyl) ether;
Lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether, tetraethylene glycol dimethyl (or ethyl) ether;
Alkanolamines such as monoethanolamine, diethanolamine, triethanolamine;
Sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, urea, ethylene urea, bishydroxyethyl sulfone and the like.
Of these, the following materials are preferably used.
Ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (average molecular weight 200 to 1000), 2-pyrrolidone, glycerin, 1,2,6-hexanetriol, ethylene urea, trimethylolpropane.
In particular, glycerin is most preferred.

  The content of the above-described constituent materials used in combination with water is not particularly limited, but is preferably 3% by mass or more, and preferably 60% by mass or less with respect to the total mass of the ink.

  Examples of the binder resin include styrene acrylic copolymer and polyester.

  The content of the aqueous medium contained in the ink composition of the present invention is preferably 30% by mass or more and preferably 95% by mass or less with respect to the total mass of the ink.

  In addition to the above-described components, the ink composition of the present invention may have, as necessary, additives such as various surfactants, ultraviolet absorbers, and stabilizers in order to obtain ink having desired physical property values. Etc., viscosity modifiers, antifoaming agents, antiseptics, fungicides, antioxidants, etc. can be added. The additive is preferably selected so that the surface tension of the ink is 25 mN / m or more, preferably 28 mN / m or more.

Next, as an example of the pigment which is an essential component in the present invention, carbon black is preferably used as the pigment used in the black ink. Examples thereof include carbon black pigments such as furnace black, lamp black, acetylene black and channel black. In particular, the primary particle size is 15 to 40 nm, the specific surface area by the BET method is 50 to 300 m ² / g, the DBP oil absorption is 40 to 150 ml / 100 g, and the volatile content is 0.5 to 10% by mass. Preferably used.

As the pigment used in the color ink, an organic pigment is preferably used. Specific examples include the following.
Insoluble azo pigments such as Toluidine Red, Toluidine Maroon, Hansa Yellow, Benzidine Yellow, Pyrazolone Red;
Soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, Permanent Red 2B;
Derivatives from vat dyes such as alizarin, indanthrone, 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;
Pyranthrone pigments such as pyranthrone red and pyranthrone orange;
Thioindigo pigments;
Condensed azo pigments;
Thioindigo pigments;
Diketopyrrolopyrrole pigments;
Flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and other pigments.
However, the present invention is not limited to these.

The organic pigment is represented by the color index (CI) number as follows.
C. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 55, 74, 83, 86, 93, 97, 98, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185;
C. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71;
C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 202, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272;
C. I. Pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64,
C. I. Pigment green 7, 36;
C. I. Pigment brown 23, 25, 26, and the like.
However, the present invention is not limited to these. Among these pigments, the following are more preferable.
C. I. Pigment Yellow 13, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154, 155, 180, 185;
C. I. Pigment red 122, 202, 209;
C. I. Pigment Blue 15: 3, 15: 4.

  The amount of these pigments added to the ink composition is not limited, but is preferably in the range of 0.1 to 50% by mass, more preferably in the range of 0.5 to 30% by mass.

  The above is the description of the material constituting the ink of the present application, but the average particle size of the pigment dispersion of the present application is preferably in the range of 50 to 200 nm. As a measuring method of the average particle diameter, FPAR-1000 (trade name, manufactured by Otsuka Electronics Co., Ltd.) using laser light scattering can be used.

  The inkjet ink set of the present invention has an ink composition in the above combination. It is preferable to have at least a cyan ink composition, a magenta ink composition, and a yellow ink composition.

  Further, the present invention is an ink jet recording method for performing recording using the ink jet ink set as described above. In particular, the method is suitably applied to a method in which thermal energy is ignited in ink. Further, the present invention can be suitably applied to a method in which the ink discharge amount per discharge operation is 20 pl (picoliter) or less.

  Next, an ink jet printer will be described as a specific example for the recording apparatus of the present invention.

  FIG. 1 is a schematic perspective view showing a main part of an example of a liquid discharge head as a liquid discharge head of a discharge method for communicating bubbles with the atmosphere during discharge and an ink jet printer as a liquid discharge apparatus using the head.

  In FIG. 1, the ink jet printer includes a conveyance device 1030 that intermittently conveys a sheet 1028 as a recording medium provided in the casing 1008 along the longitudinal direction in a direction indicated by an arrow P in the drawing. Also included is a recording unit 1010 that can reciprocate substantially in parallel with the guide shaft 1014 in an arrow S direction substantially orthogonal to the conveyance direction P of the paper 1028 by the conveyance device 1030. Furthermore, a moving drive unit 1006 as a driving means for reciprocating the recording unit 1010 is included.

  The conveying device 1030 includes a pair of roller units 1022a and 1022b that are arranged to face each other substantially in parallel, a pair of roller units 1024a and 1024b, and a drive unit 1020 for driving each of these roller units. Yes. With this configuration, when the driving unit 1020 of the transport device 1030 is activated, the paper 1028 is sandwiched between the roller units 1022a and 1022b and the roller units 1024a and 1024b, and is intermittently fed in the direction of the arrow P. It will be transported. The movement drive unit 1006 includes a pulley 1026a disposed on a rotation shaft opposed to the pulley 1026a at a predetermined interval, a belt 1016 wound around the pulley 1026b, a roller unit 1022a, and a roller unit 1022b. Further, it includes a roller unit 1022a and a motor 1018 that is arranged substantially in parallel to the roller unit 1022b and drives the belt 1016 connected to the carriage member 1010a of the recording unit 1010 in the forward and reverse directions.

  When the motor 1018 is activated and the belt 1016 rotates in the arrow R direction, the carriage member 1010a of the recording unit 1010 is moved in the arrow S direction by a predetermined movement amount. When the motor 1018 is activated and the belt 1016 rotates in the direction opposite to the arrow R direction shown in the drawing, the carriage member 1010a of the recording unit 1010 moves in a predetermined direction in the direction opposite to the arrow S direction. It will be moved by the amount. Further, a recovery unit 1026 for performing an ejection recovery process of the recording unit 1010 is opposed to the ink ejection port array of the recording unit 1010 at one end of the movement driving unit 1006 at a position that becomes the home position of the carriage member 1010a. Is provided.

  The recording unit 1010 is provided with ink jet cartridges (hereinafter simply referred to as cartridges) 1012Y, 1012M, 1012C, and 1012B detachably with respect to the carriage member 1010a for each color. For example, each of yellow, magenta, cyan, and black is detachably attached to the carriage member 1010a.

  FIG. 2 shows an example of an ink jet cartridge that can be mounted on the above ink jet recording apparatus. The cartridge 1012 in this example is of a serial type, and the main part is composed of an ink jet recording head 100 and a liquid tank 1001 as an ink containing part for containing a liquid such as ink.

  The ink jet recording head 100 is formed with a large number of ejection ports 832 for ejecting liquid, and liquid such as ink flows from the liquid tank 1001 through a liquid supply passage (not shown). (Shown). The ink jet recording head preferably includes a heater for applying thermal energy. In the cartridge 1012 shown in FIG. 2, the ink jet recording head 100 and the liquid tank 1001 are integrally formed so that liquid can be supplied into the liquid tank 1001 as necessary. The cartridge 1012 may adopt a structure in which the liquid tank 1001 is connected to the liquid discharge head 100 in a replaceable manner.

  An ink jet cartridge equipped with an ink jet recording head is a recording unit.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples.

<Synthesis of block copolymer>
The following were used as the A segment.
Random copolymer of biphenyl ethyl vinyl ether and isobutyl vinyl ether (A1; copolymer unit ratio 46/45), isobutyl vinyl ether polymer (A2), or 4-methylphenoxyethyl vinyl ether polymer (A3)
The following were used as the B segment.
2- (2-methoxyethyloxy) ethyl vinyl ether (B1) polymer or 2- (2- (2-methoxyethyloxy) ethyloxy) ethyl vinyl ether polymer (B2)
The following were used as the C segment.
4- (2-vinyloxy) ethoxybenzoic acid polymer (C1) or 5- (2-vinyloxy) ethoxy-1,3-phthalic acid polymer (C2)
A total of 12 types of triblock copolymers having different combinations of segments and the number of unit structures in each segment were synthesized by living cationic polymerization using an aluminum catalyst to obtain the following block copolymers (Table 1). ).

  Specifically, after the inside of the glass container provided with the three-way cock was replaced with nitrogen, the adsorbed water was removed by heating to 250 ° C. in a nitrogen gas atmosphere. After returning the system to room temperature, a monomer having an A segment unit structure was added to 16 mmol of ethyl acetate, 0.05 mmol of 1-isobutoxyethyl acetate, and 11 ml of toluene, and the reaction system was cooled. When the system temperature reached 0 ° C., 0.2 mmol of ethylaluminum sesquichloride (an equimolar mixture of diethylaluminum chloride and ethylaluminum dichloride) was added to initiate polymerization. The molecular weight was monitored in a time-sharing manner using molecular sieving column chromatography (GPC) to confirm the completion of the polymerization of the monomer that became the unit structure of the A segment.

  Subsequently, the monomer used as the unit structure of B segment was added, and superposition | polymerization was continued. Monitoring using GPC confirmed the completion of the polymerization of the monomer that becomes the unit structure of the B segment. Then, the toluene solution of the monomer used as the unit structure in which the carboxylic acid part in the unit structure of C segment was esterified was added, and superposition | polymerization was continued. After 20 hours, the polymerization reaction was stopped. The polymerization reaction was stopped by adding a 0.3% by mass ammonia / methanol aqueous solution to the system. The reaction mixture solution was diluted with dichloromethane and washed 3 times with 0.6M hydrochloric acid and then 3 times with distilled water. The organic phase obtained was concentrated and dried with an evaporator, and then vacuum-dried, and then repeatedly dialyzed in a methanol solvent using a cellulose semipermeable membrane to remove the monomeric compound, and the target product, tri A block polymer was obtained. The compound was identified using NMR and GPC.

  Furthermore, the block polymer obtained here was hydrolyzed in a mixed solution of dimethylformamide and aqueous sodium hydroxide to hydrolyze the ester part of the C segment to obtain a sodium triblock polymer. The compound was identified using NMR and GPC.

  Furthermore, the triblock polymer in which the sodium salt portion of the C segment was a free carboxylic acid was obtained by neutralization with 0.1N hydrochloric acid in an aqueous dispersion. The compound was identified using NMR and GPC.

  The ratio of the number of unit structures of the A segment to the number of oxyethylene structures contained in the B segment is expressed as A / EO.

<Example 1>
10 parts by mass of the block copolymer P9 and 10 parts by mass of C.I. I. Pigment Blue 15: 3 was co-dissolved in 90 parts by mass of dimethylformamide and converted into an aqueous phase using 100 parts by mass of distilled water to obtain a pigment dispersion. Next, coarse particles of the pigment dispersion were removed with a 2 micron membrane filter. Then, water, glycerin, ethylene urea, 2-pyrrolidone, 1,2,6-hexanetriol, acetylenol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) are used so that the solid content concentration is finally 5.0% by mass. In addition, a cyan ink was produced. The ratios of glycerin, ethylene urea, 2-pyrrolidone, 1,2,6-hexanetriol, and acetylenol EH in the ink are 7% by mass, 2% by mass, 3% by mass, 5% by mass, and 0.3% by mass, respectively. did.

  Next, the block copolymer P8 and C.I. I. Pigment Red 122, the block copolymer P5 and C.I. I. Pigment yellow 128, and the block copolymers P6 and C.I. I. Using Pigment Black 7, a pigment dispersion was prepared by the above-described method. The coarse particles were then removed with a 2 micron membrane filter. Then, water, glycerin, ethylene urea, 2-pyrrolidone, 1,2,6-hexanetriol, acetylenol EH so that the solid content concentration becomes 7.0% by mass, 9.0% by mass and 8.0% by mass, respectively. Was added. The ratios of glycerin, ethylene urea, 2-pyrrolidone, 1,2,6-hexanetriol, and acetylenol EH in the ink are 7% by mass, 2% by mass, 3% by mass, 5% by mass, and 0.3% by mass, respectively. did. The ink set composed of these four types of ink was designated as ink set 1 (Table 2).

<Example 2>
The block copolymer P1 and C.I. I. Pigment Blue 15: 4 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P7 and C.I. I. Pigment Red 122 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P4 and C.I. I. Pigment Yellow 128 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P3 and C.I. I. Pigment black 7 was used to prepare a pigment dispersion by the same method as described above. The coarse particles were then removed with a 2 micron membrane filter. Thereafter, water, glycerin, trimethylolpropane, ethylene urea, acetylenol EH (commodity) so that the solid content concentrations are 5.0% by mass, 7.0% by mass, 9.0% by mass, and 8.0% by mass, respectively. Name, manufactured by Kawaken Fine Chemicals). The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively. The ink set composed of these four types of inks was designated as ink set 2 (Table 3).

<Example 3>
Using the block copolymer P6, C.I. I. Pigment blue 15: 3, C.I. I. A pigment dispersion containing Pigment Red 122 was produced by the above-described method. Further, using the block copolymer P3, C.I. I. Pigment yellow 128, and C.I. I. A pigment dispersion containing Pigment Black 7 was prepared by the above-described method. For each pigment dispersion, coarse particles were removed with a 2 micron membrane filter. Thereafter, water, glycerin, trimethylolpropane, ethyleneurea, acetylenol so that the solid content concentrations are finally 5.0% by mass, 7.0% by mass, 9.0% by mass and 8.0% by mass, respectively. EH (trade name, manufactured by Kawaken Fine Chemicals) was added. The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively.

  Next, using the block polymer P10, C.I. I. Pigment blue 15: 3 and C.I. I. A pigment dispersion containing Pigment Red 122 was prepared by the above-described method. The coarse particles were then removed with a 2 micron membrane filter. Thereafter, water, glycerin, trimethylolpropane, ethylene urea, and acetylenol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) were added so that the solid content concentrations were 1.0 mass% and 1.4 mass%, respectively. The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively. By combining these light inks and the four types of inks, an ink set 3 composed of six types of inks was produced (Table 4).

<Example 4>
Using the block copolymer P7, C.I. I. Pigment blue 15: 3 and C.I. I. A pigment dispersion containing Pigment Red 122 was produced by the above-described method. Further, by using the block copolymer P4, C.I. I. Pigment yellow 74, and C.I. I. A pigment dispersion containing Pigment Black 7 was similarly prepared. Further, using the block copolymer P1, C.I. I. Pigment blue 15: 3 and C.I. I. A pigment dispersion containing Pigment Red 122 was similarly prepared. Coarse particles of the prepared pigment dispersion were removed with a 2 micron membrane filter. Thereafter, water and glycerin were adjusted so that the solid content concentrations were 5.0% by mass, 7.0% by mass, 9.0% by mass, 8.0% by mass, 1.0% by mass, and 1.4% by mass, respectively. Trimethylolpropane, ethylene urea, and acetylenol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) were added. The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively. The ink set composed of these six types of ink was designated as ink set 4 (Table 5).

<Example 5>
The block copolymer P8 and C.I. I. Pigment Blue 15: 3 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P7 and C.I. I. Pigment Red 122 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P3 and C.I. I. Pigment Yellow 128 was used to prepare a pigment dispersion by the same method as described above. Further, the block copolymer P5 and C.I. I. Pigment black 7 was used to prepare a pigment dispersion by the same method as described above. Further, the block copolymer P11 and C.I. I. Pigment Blue 15: 3 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P2 and C.I. I. Pigment Red 122 was used to prepare a pigment dispersion by the same method as described above. In the prepared pigment dispersion, coarse particles were removed with a 2 micron membrane filter. Thereafter, water, glycerin, so that the solid content concentration is 5.0% by mass, 7.0% by mass, 9.0% by mass, 8.0% by mass, 1.0% by mass, and 1.4% by mass, respectively. Trimethylolpropane, ethylene urea, and acetylenol EH (trade name, manufactured by Kawaken Fine Chemical) were added. The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively. An ink set consisting of these six types of ink was designated as ink set 5 (Table 6).

<Comparative Example 1>
Using the above block copolymer P12, C.I. I. Pigment blue 15: 3, C.I. I. Pigment red 122, C.I. I. Pigment yellow 128, and C.I. I. A pigment dispersion containing Pigment Black 7 pigment was prepared. The coarse particles were then removed with a 2 micron membrane filter. Thereafter, water, glycerin, trimethylolpropane, ethylene urea, acetylenol EH (commodity) so that the solid content concentrations are 5.0% by mass, 7.0% by mass, 9.0% by mass, and 8.0% by mass, respectively. Name, manufactured by Kawaken Fine Chemicals). The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively. The ink set consisting of these four types of ink was designated as ink set 6 (Table 7).

<Comparative example 2>
The block copolymer P4 and C.I. I. Pigment Blue 15: 3 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P3 and C.I. I. Pigment Red 122 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P2 and C.I. I. Pigment Yellow 128 was used to prepare a pigment dispersion by the same method as described above. The block copolymers P1 and C.I. I. Pigment black 7 pigment was used to prepare a pigment dispersion by the same method as described above. The coarse particles were then removed with a 2 micron membrane filter. Thereafter, water, glycerin, ethylene urea, 2-pyrrolidone, 1, 2, and so that the solid content concentrations are 5.0% by mass, 7.0% by mass, 9.0% by mass, and 8.0% by mass, respectively. 6-hexanetriol and acetylenol EH (trade name, manufactured by Kawaken Fine Chemical Co., Ltd.) were added. The ratios of glycerin, ethylene urea, 2-pyrrolidone, 1,2,6-hexanetriol, and acetylenol EH in the ink are 7% by mass, 2% by mass, 3% by mass, 5% by mass, and 0.3% by mass, respectively. did. The ink set consisting of these four types of ink was designated as ink set 7 (Table 8).

<Comparative Example 3>
The block copolymer P11 and C.I. I. Pigment Blue 15: 3 was used to prepare a pigment dispersion by the same method as described above. The block copolymers P1 and C.I. I. Pigment Red 122 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P9 and C.I. I. Pigment Yellow 128 was used to prepare a pigment dispersion by the same method as described above. Further, the block copolymer P5 and C.I. I. Pigment black 7 was used to prepare a pigment dispersion by the same method as described above. Further, the block copolymer P11 and C.I. I. Pigment Blue 15: 3 was used to prepare a pigment dispersion by the same method as described above. The block copolymer P2 and C.I. I. Pigment Red 122 was used to prepare a pigment dispersion by the same method as described above. In the prepared pigment dispersion, coarse particles were removed with a 2 micron membrane filter. Thereafter, water, glycerin, so that the solid content concentration is 5.0% by mass, 7.0% by mass, 9.0% by mass, 8.0% by mass, 1.0% by mass, and 1.4% by mass, respectively. Trimethylolpropane, ethylene urea, and acetylenol EH (trade name, manufactured by Kawaken Fine Chemical) were added. The ratios of glycerin, trimethylolpropane, ethylene urea, and acetylenol EH in the ink were 7% by mass, 8% by mass, 2% by mass, and 0.5% by mass, respectively. The ink set consisting of these six types of ink was designated as ink set 8 (Table 9).

(Image evaluation)
Each ink set produced was evaluated for color unevenness, scratching, water resistance, and glossiness as follows. For evaluation, each ink set was mounted on an inkjet printer BJF-930 (trade name, manufactured by Canon Inc.), and printing was performed on professional photo paper PR101 (trade name, manufactured by Canon Inc.) under predetermined conditions. The obtained image was conducted.

[Color unevenness evaluation]
Using each ink of black, cyan, magenta, yellow, light magenta (Examples 3, 4 and 5 and Comparative Example 3 only) and light cyan (Examples 3, 4 and 5 and Comparative Example 3 only), 100 A solid patch (5 × 5 cm) of% duty was printed. About the obtained image, the presence or absence of color unevenness was confirmed visually.
Evaluation A: Color unevenness is not visible.
Evaluation B: Some color unevenness occurs.
Evaluation C: Color unevenness occurs remarkably.

  In the print samples of evaluations B and C, streaky color unevenness was observed on the writing start side. Table 10 shows the obtained results.

[Abrasion evaluation]
Solid printing was performed in the same manner as the color unevenness evaluation, and the rubbing property was evaluated by rubbing with a finger immediately after completion of printing. When the image is not disturbed even if the finger is rubbed with each color, “A” is set. When the image is disturbed after the finger is rubbed with at least one color, “C” is set. The obtained results are shown in Table 11.

[Water resistance evaluation]
The solid printing was performed in the same manner as the color unevenness evaluation, and immediately after the printing was completed, water was poured into the print sample to evaluate the water resistance. When the image did not bleed for each color, “A” was set, and when the image bleeded with at least one color, “C” was set. The obtained results are shown in Table 11.

[Glossiness evaluation]
A photo image for gloss evaluation was printed in 4 passes, and the 20 ° glossiness of the obtained image was measured with a specular gloss meter (manufactured by Murakami Color Research Laboratory) and judged according to the following criteria. The obtained results are shown in Table 11.
AA: 50 or more A: 40 or more and less than 50 B: 30 or more and less than 40 C: less than 30

It is a schematic perspective view which shows the principal part of an example of the inkjet printer which can mount a liquid discharge head. It is a schematic perspective view showing an example of an ink jet cartridge provided with a liquid discharge head. It is a graph which shows the relationship between the number of the unit structure of A segment / the number of the oxyethylene structures contained in B segment, and the interval time which can be re-discharged.

Explanation of symbols

100: inkjet recording head 832: discharge port 1001: liquid tank 1006: moving drive unit 1008: casing 1010: recording unit 1010a: carriage member 1012: cartridge 1012Y, M, C, B: inkjet cartridge 1014: guide shaft 1016: belt 1018 : Motor 1020: Drive unit 1022a, 1022b: Roller unit 1024a, 1024b: Roller unit 1026: Recovery unit 1026a, 1026b: Pulley 1028: Paper 1030: Transport device P: Paper transport direction R: Belt rotation direction S: Paper Direction approximately perpendicular to the transport direction

Claims (13)

An ink set for inkjet recording having a combination of two kinds of ink compositions having a difference in solid content concentration exceeding 2% by mass,
Each of the two types of ink compositions contains at least an aqueous medium, a pigment, and a dispersant for dispersing the pigment, and the dispersant is a hydrophobic segment, an A segment, and an oxyethylene structure-containing nonion Ink set for inkjet recording, which is a block copolymer having a B segment which is a hydrophilic hydrophilic segment and a C segment which is an ionic hydrophilic segment,
The ratio of the number of unit structures of the A segment to the number of oxyethylene structures contained in the B segment of the block copolymer contained in each of the two ink compositions (number of unit structures of the A segment / B The block copolymer contained in the ink composition having a relatively higher solid content concentration than the block copolymer contained in the ink composition having a relatively low solid content concentration) An ink set for ink-jet recording, characterized in that is larger.   The ink set for inkjet recording according to claim 1, wherein the two kinds of ink compositions are ink compositions of the same color.   The ink set for inkjet recording according to claim 1 or 2, comprising at least a cyan ink composition, a magenta ink composition, and a yellow ink composition.   The ink set for inkjet recording according to any one of claims 1 to 3, wherein the block copolymer has a polyvinyl ether structure as a unit structure. The ink set for inkjet recording according to claim 4, wherein the C segment has a unit structure represented by the following general formula (1).

(In the general formula (1), R ⁰ represents —X— (COOH) _r , —X— (COO—M) _r , or —X— (COO) ₂ M ² , where X represents 1 to 20 carbon atoms. linear, branched or cyclic alkanediyl or alkanetriyl group ^{or,, - (CH (R 5} ) -CH (R 6) -O) p - (CH 2) m -CH 3-r - or _{- (CH 2) m - (} O) n - (CH 2) q -CH 3-r -, or at least one is substituted with a carbonyl group or an aromatic ring structure group thereof methylene group, or their A group in which at least one methine group is substituted with an aromatic ring structure is represented, r represents 1 or 2, p represents an integer of 1 to 18, m represents an integer of 0 to 35, and n represents 1. Or represents 0, q represents an integer of 0 to 17, M represents a monovalent cation, and M ² represents a divalent group. R ⁵ and R ⁶ represent an alkyl group, and R ⁵ and R ⁶ may be the same or different, and when there are a plurality of them, they may be the same or different.) The ink set for inkjet recording according to claim 4 or 5, wherein at least one of the A segment and the B segment has a unit structure represented by the following general formula (2).

(In the general formula (2), R ¹ is a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, -Ph, -Pyr, -Ph-Ph, -Ph-Pyr,-(CH ( R ⁵ ) —CH (R ⁵ ) —O) _p —R ⁷ and — (CH ₂ ) _m — (O) _n —R ^7, and the hydrogen atom bonded to the carbon atom in the aromatic ring is carbon. The linear or branched alkyl group represented by formulas 1 to 4 and a carbon atom in the aromatic ring each independently represent a nitrogen atom, p is an integer of 1 to 18, and m is 1 to 1. An integer of 36, n represents 0 or 1. R ⁵ and R ⁶ each independently represents a hydrogen atom or —CH ₃ , and when there are a plurality of R ⁵ and R ⁶ , they may be the same or different. R ⁷ is a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, —Ph, —Pyr, — When Ph 7 -Ph, —Ph—Pyr, —CHO, —CH ₂ CHO, —CO—CH═CH ₂ , and —CO—C (CH ₃ ) ═CH ₂ are selected, and R ⁷ is other than a hydrogen atom , A hydrogen atom bonded to a carbon atom in R ⁷ is a linear or branched alkyl group having 1 to 4 carbon atoms or —F, —Cl, —Br, and a carbon atom in an aromatic ring is a nitrogen atom A group which may be substituted with an atom, Ph represents a phenyl group or a phenylene group, and Pyr represents a pyridyl group.   7. An ink jet recording method, wherein recording is performed using the ink set for ink jet recording according to claim 1.   The inkjet recording method according to claim 7, further comprising a step of applying thermal energy to the ink.   The ink jet recording method according to claim 7 or 8, wherein an ink discharge amount per discharge operation is 20 pl (picoliter) or less.   An ink cartridge comprising an ink containing portion for containing the ink set for ink jet recording according to claim 1.   An ink cartridge according to claim 10 containing the ink set for ink jet recording according to any one of claims 1 to 6, and an ink jet recording head for discharging ink. To record unit.   The recording unit according to claim 11, wherein the ink jet recording head includes a heater for applying heat energy.   A recording apparatus comprising the recording unit according to claim 11.

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