JP2006348304A - Ink, ink set, ink cartridge, recording unit, image recording apparatus and image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink capable of mitigating the dependency on image quality of recording media and giving a high quality image stably. <P>SOLUTION: The ink for inkjet recording contains carbon black and a salt. The carbon black is a self dispersible carbon black having a hydrophilic group: -COO(M2) (wherein, M2 is a hydrogen atom, an alkali metal, ammonium or an organic ammonium) bonded to the surface of the carbon black through a substituted or nonsubstituted phenylene group. The salt is represented by Ph-COO(M1) (wherein, M1 is ammonium; and Ph is a phenyl group). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink, an ink set, an ink cartridge, a recording unit, an image recording apparatus, an image recording method, a color image forming method, and a color image bleeding reducing method.

  Conventionally, as black ink for writing instruments (fountain pens, sign pens, water-based ballpoint pens, etc.) and black ink for inkjet, inks using carbon black, which is a black colorant with high print density and excellent fastness, etc. Proposed.

In particular, in recent years, the ink composition and the ink composition have been improved so that good recording can be performed even on plain paper such as copy paper, report paper, notebook, notepaper, bond paper, and continuous slip paper that are commonly used in offices in recent years. Detailed research and development has been done from various aspects such as physical properties. For example, Patent Document 1 and Patent Document 2 disclose aqueous pigment inks containing carbon black and a dispersant. Further, Patent Document 3 gives a technical problem that, when an ink containing carbon black together with a dispersant is used as an ink for an ink jet printer, ejection becomes unstable or sufficient print density cannot be obtained. As an ink that can solve the problem, an aqueous pigment ink using self-dispersing carbon black that does not use a dispersant is disclosed.
JP-A 61-283875 JP-A 64-6074 JP-A-8-3498

  The present inventors have made various studies on the case where the black ink containing the self-dispersing carbon black as a black pigment is used for ink jet recording. As a result, it has been found that such inks do not always provide sufficient character quality and print density depending on the type of recording medium (for example, paper).

  In addition, when a color image is printed using the black ink as described above together with an ink of another color (for example, at least one selected from magenta, cyan, yellow, red, green, and blue), the black color is printed on the recording medium. In some cases, a phenomenon (hereinafter referred to as “bleeding”) in which the color is blurred at the boundary between the image portion and the color image portion, the ink is mixed nonuniformly, and the quality of the image is degraded.

  For such bleeding, the idea of improving the penetrability of the ink into the recording medium by adding a so-called surfactant (for example, JP-A-55-65269), and a volatile solvent as a main solvent are used. Ideas (for example, JP-A-55-66976) have been proposed. However, these prior arts may also cause a decrease in image density and a decrease in ejection stability. In view of such a conventional technique, the present inventors have considered that an ink containing self-dispersing carbon black as a black pigment, when used alone or in combination with other color inks, even if the type of recording medium changes. It was found that it was necessary to develop a black ink with little change in quality.

  One of the objects of the present invention is to provide a black ink that can alleviate the influence of a recording medium on image quality and can stably provide a high-quality image.

  One of the objects of the present invention is to provide a black ink that can alleviate the influence of a recording medium on image quality, can stably provide a high-quality image, and has excellent ink jet ejection characteristics. is there.

  Another object of the present invention is to provide an ink set capable of effectively suppressing bleeding. In particular, since black ink is often used for output of characters and the like, a high OD and sharpness difference between characters is strongly required. For this reason, as described above, a technique for preventing bleeding using highly penetrating inks. It has not yet been achieved to satisfy both the character quality and the OD at a high level, and it is also an object of the present invention to satisfy the character quality and the OD at a higher level.

  Another object of the present invention is to provide an image forming apparatus, an image forming method, an ink cartridge used for them, and a recording unit that can reduce the influence of a recording medium on image quality and can stably form a high quality image. It is in.

Ink as one embodiment of the present invention includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, (M1) Br, It contains at least one salt selected from (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black. Here, M1 represents an alkali metal, ammonium or organic ammonium, or Ph represents a phenyl group.

  According to this embodiment, it is possible to form a high-quality image even when printing is performed on highly penetrating paper that may impair the image quality, for example, the sharpness of characters or cause the image density to decrease. is there. Although the reason why such an effect can be obtained by this embodiment is not clear, for example, when the ink is ejected onto the paper surface by the inkjet method and adhered, the pigment is stably dispersed in the ink, but the ink adheres to the paper surface. This is probably because the subsequent solid-liquid separation occurs promptly. That is, if the solid-liquid separation is slow, the ink diffuses into the paper when the paper has high permeability. As a result, the sharpness (character quality) of characters is impaired, and at the same time, the ink penetrates deep into the paper, so that the image density naturally decreases. However, since the solid-liquid separation occurs quickly in the ink of this embodiment, the above-described phenomenon is unlikely to occur even on paper having relatively high permeability. That is, it is thought that it becomes difficult to receive the factor by paper types, such as a permeability. Such an effect is considered to be best obtained when the salt is 0.05 to 10 wt% with respect to the total weight of the ink. Further, among the above-mentioned salts, sulfates (for example, potassium sulfate) and benzoates (for example, ammonium benzoate) have a slight effect on the characteristics of the ink, for example, characteristics when the ink is used for inkjet. .

As another example of ink according to this _{embodiment, -COO (M2), - SO} 3 (M2) 2, carbon at least one selected from -PO 3 H (M2) and _-PO 3 (M2) Examples thereof include self-dispersing carbon black bonded to the black surface directly or through other atomic groups and an ink containing a salt in which M1 is the same as M2. This ink is one of the particularly preferred embodiments because its stability is further improved. For example, if M2 is ammonium (NH ₄ ), the addition of an ammonium salt such as ammonium benzoate as a salt can further improve the water resistance and the like of an ink jet recorded image obtained using this ink.

  As another embodiment of the ink, an ink prepared by adjusting the pH of the ink to 9 to 12 can be mentioned. Such an ink is also preferably used for stably obtaining a high-quality image. That is, it has been found that the pH of the ink described above shifts in an acidic direction by long-term storage, and the ink characteristics such as viscosity tend to increase accordingly. As a result of further studies on this point, when the pH of the ink is adjusted within the above range, the change in the ink characteristics is extremely gradual, and the change in the ink characteristics accompanying the pH change during storage is substantially reduced. I got new knowledge that it would be negligible. And said invention is based on this knowledge.

  Further, as another embodiment of the ink, there may be mentioned, for example, a coexisting stabilizer selected from an anionic surfactant and a cationic surfactant. According to such a configuration, it is possible to moderate a change in ink characteristics accompanying a change in ink pH. The reason why such an effect is obtained is not clear, but it is considered that the pH region in which the stabilizer can stably exist is widened because the stabilizer inhibits the contact (collision) between the carbon black particles. The effects described above are particularly remarkable when alkylbenzene sulfonate is used as a stabilizer. In addition, as one of preferred embodiments, an ink prepared by adding a stabilizer and adjusting the pH to be in the range of 9 to 12 can be mentioned. This aspect has both effects of suppressing pH change during ink storage and preventing sudden change in characteristics when the pH changes. Furthermore, the addition amount of the stabilizer can be suppressed, and the possibility of changing the ink characteristics can be almost eliminated.

  As still another embodiment of the present invention, there may be mentioned an embodiment in which an antioxidant is added to the ink according to the various embodiments described above. As a result, it is possible to suppress chemical changes and ink jet discharge characteristics when the ink is stored for a long period of time.

  Furthermore, as another embodiment of the present invention, there is an embodiment in which a water-soluble polymer compound is added to the ink according to the various embodiments described above. This is effective in improving the scratch resistance of the recording medium when the ink is attached to the surface of the recording medium such as paper.

An ink according to another embodiment of the present invention is an ink for forming a print having a predetermined optical density on a recording medium by an inkjet method, and includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph. _{-COO (M1), (M1)} NO 3, (M1) Cl, (M1) Br, (M1) I, (M1) 2 SO 3 and _(M1) at least one salt selected from 2 CO ₃ and a self dispersible Type carbon black, and the concentration of the carbon black is such a density that an image having the predetermined optical density cannot be obtained when the salt is not contained. M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group.

Next, an ink set according to an embodiment of the present invention includes an aqueous ink containing at least one colorant selected from cyan, magenta, yellow, red, green, and blue colorants; _{M1) 2 SO 4, CH 3} COO (M1), Ph-COO (M1), (M1) NO 3, (M1) Cl, (M1) Br, (M1) I, (M1) 2 SO 3 and (M1 ) A combination of at least one salt selected from ₂ CO ₃ and a water-based ink containing self-dispersing carbon black. Here, M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group.

  When a color image is formed using such an ink set, it is possible to effectively suppress bleeding in a boundary region between an image formed using an ink containing carbon black and an image formed using an ink containing another color material. it can. The reason why the effects as described above are obtained by this embodiment is not clear, but it is considered that the speed of solid-liquid separation on the surface of the recording medium is involved.

The ink cartridge according to one embodiment of the present invention includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, (M1) Br, ( And an ink tank containing an aqueous ink containing at least one salt selected from M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black. To do.

The recording unit according to an embodiment of the present invention includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, (M1) Br, ( M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and at least one salt selected from water-based inkjet recording ink containing self-dispersing carbon black and self-dispersing carbon black, and ejecting the ink It is characterized by having a head part for making it happen.

The image recording apparatus according to one embodiment of the present invention includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph—COO (M1), (M1) NO ₃ , (M1) Cl, and (M1) Br. , (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO _3, and an ink tank containing an aqueous ink jet recording ink containing at least one salt selected from self-dispersing carbon black. An ink cartridge, a recording head for ejecting ink, and a means for supplying ink from the ink cartridge to the recording head.

The image recording apparatus according to another embodiment of the present invention includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, and (M1). An ink containing portion containing a water-based inkjet recording ink containing at least one salt selected from Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black; and A recording unit including a head unit for ejecting ink is provided.

An image recording apparatus according to another embodiment of the present invention contains an aqueous ink containing at least one color material selected from cyan, magenta, yellow, red, green and blue color materials. (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph—COO (M1), (M1) NO ₃ , (M1) Cl, (M1) Br, (M1) I, (M1) An ink containing portion containing water-based inkjet recording ink containing at least one salt selected from ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black, and ink contained in each ink containing portion It is characterized by having a head part for discharging each.

According to still another embodiment of the present invention, an image recording apparatus includes an aqueous ink containing at least one color material selected from cyan, magenta, yellow, red, green, and blue color materials. accommodating ink accommodating portion an ink cartridge equipped _{with, (M1) 2 SO 4,} CH 3 COO (M1), Ph-COO (M1), (M1) NO 3, (M1) Cl, (M1) Br, (M1 Ink cartridges each including an ink containing portion containing an aqueous inkjet recording ink containing at least one salt selected from I), (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black A head portion for ejecting each of the ink contained in each ink containing portion, and each ink from each ink cartridge to each head. Characterized in that it comprises means for supplying to the de section.

The image recording method according to an embodiment of the present invention includes (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph—COO (M1), (M1) NO ₃ , (M1) Cl, and (M1) Br. , (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ at least one salt selected from water-based inkjet recording ink containing self-dispersing carbon black and flying toward the recording medium surface; An image is recorded by being attached to the surface.

The color image forming method according to an embodiment of the present invention is a water-based first method including at least one color material selected from cyan, magenta, yellow, red, green, and blue color materials. And a step of causing the ink to be ejected toward the surface of the recording medium and adhering to the surface, and (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , ( An aqueous second ink containing at least one salt selected from M1) Cl, (M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black; And a step of discharging the ink toward the surface of the recording medium and attaching to the surface.

In addition, the color image bleed mitigation method according to one embodiment of the present invention is formed of a black image formed of an aqueous inkjet black ink and an aqueous inkjet color ink which are adjacent to each other on a recording medium. A method for reducing bleeding between color images,
As the black ink for inkjet, (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, (M1) Br, (M1) I, ( It is characterized by using an ink containing at least one salt selected from M1) ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersing carbon black. Here, M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group.

According to each embodiment of the present invention, for example, the following effects can be obtained.
(1) It is possible to obtain an ink that can alleviate the influence of a recording medium on image quality and can stably provide a high-quality image.
(2) It is possible to obtain an ink that maintains a stable characteristic with very little change in quality due to a change in pH.
(3) Even when stored for a long period of time, there is little change in quality, and for example, an ink with little change in ink jet ejection characteristics can be obtained.
(4) It is possible to obtain an ink that is excellent in scratch resistance of printed matter and that is hardly dependent on the type of recording medium.
(5) An ink set that can effectively suppress bleeding can be obtained.
(6) It is possible to obtain an image forming apparatus, an image forming method, an ink cartridge used for them, and a recording unit that can alleviate the influence of the recording medium on the image quality and stably form a high-quality image.

(First embodiment)
The ink according to an embodiment of the present invention is characterized in that it contains self-dispersing carbon black as one of coloring materials and further contains a salt. These are dispersed and dissolved in, for example, an aqueous medium to form an ink.

(About self-dispersing carbon black / salt)
Examples of the self-dispersing carbon black that is the coloring material of the ink include carbon black in which at least one hydrophilic group is bonded to the surface of the carbon black directly or through another atomic group. By using this, it becomes unnecessary to add a dispersant to disperse the carbon black as in the prior art.

The salt _{(M1) 2 SO 4, CH} 3 COO (M1), Ph-COO (M1), (M1) NO 3, (M1) Cl, (M1) Br, (M1) I, (M1) 2 SO It is preferable to use at least one selected from ₃ and (M1) ₂ CO ₃ . Here, M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group. Specific examples of the alkali metal include Li, Na, K, Rb, and Cs. Specific examples of the organic ammonium include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, Examples include trimethanol ammonium, dimethanol ammonium, trimethanol ammonium, ethanol ammonium, diethanol ammonium, and triethanol ammonium.

  By coexisting the salt as described above in the ink containing self-dispersing carbon black in this way, it is possible to stably form a high-quality image without greatly changing the image quality depending on the type of the recording medium. Can be obtained. The detailed mechanism by which the ink according to this embodiment exhibits the above-described characteristics is not clear at present. However, with respect to the Ka value obtained by the Bristow method, which is known as a measure representing the penetrability of the ink into the recording medium, the ink of this embodiment is larger than the ink having the same composition except that no salt is added. The present inventors have obtained the knowledge that a Ka value is exhibited. An increase in the Ka value indicates that the permeability of the ink into the recording medium has been improved, and as a common sense of those skilled in the art, an improvement in the permeability of the ink means a decrease in the image density. It was.

  That is, it has been recognized by those skilled in the art that the image density is lowered as a result of the penetration of the color material into the recording medium as the ink penetrates. And judging comprehensively from various findings relating to the ink of this embodiment, the salt in the ink of this embodiment is separated from the solvent and solids in the ink after being applied on the paper (solid-liquid separation). It is thought that it produces a specific action that causes urine to occur very quickly. That is, if solid-liquid separation is slow when the ink is applied to the recording medium, the ink isotropically diffuses into the paper together with the color material on the ink having a large Ka value or on the paper having a high ink permeability. As a result, the sharpness (character quality) of the character is impaired, and at the same time, the color material penetrates to the back of the paper, so that it is predicted that the image density also decreases. However, since such a phenomenon is not observed in the ink of this embodiment, solid-liquid separation occurs quickly when applied to a recording medium. As a result, a high-quality image is obtained despite an increase in the Ka value of the ink. It is presumed that In addition, even in the case of paper having a relatively high permeability, in the case of the ink of this aspect, the reason why it is difficult for the phenomenon such as the deterioration of the character quality and the reduction of the image density to occur is considered to be the same. Hereinafter, this point will be further described with reference to FIGS.

  11 (A) to (C) and FIGS. 12 (A) to (C) respectively show a highly permeable recording medium in which each of an ink containing a salt and an ink containing no salt is ejected from an orifice by an ink jet recording method. It is explanatory drawing which showed typically the mode of the solid-liquid separation which arises there when giving to. That is, immediately after ink landing, both inks are in a state where the pigment ink 1101 or 1201 is on the paper surface regardless of whether or not salt is added, as shown in FIGS. 11 (A) and 12 (A). . As shown in FIG. 11B, the pigment ink to which salt is added after the time T1 has passed, so that solid-liquid separation occurs quickly, and the region 1105 in which most of the solid components in the ink are abundant and the solvent in the ink. , And the permeation tip 1107 of the separated solvent advances into the paper 1103. On the other hand, as shown in FIG. 12B, the pigment ink not added with salt does not cause solid-liquid separation as quickly as the ink added with salt. It penetrates into. After the time T2 has elapsed: As shown in FIG. 11C, the pigment ink to which salt has been added penetrates further into the interior of the paper, but the region 1105 remains at and near the surface of the paper. Maintained. On the other hand, as shown in FIG. 12C, the pigment ink to which no salt is added gradually starts solid-liquid separation at this point in time, and the solid content penetration tip 1207 and the solvent penetration tip 1209 in the ink. Although there is a difference between them, the solid content-containing region 1211 in the ink reaches the deep part of the recording medium. The times T1 and T2 in the above description are reference times for conceptually grasping the difference in solid-liquid separation depending on the presence or absence of salt. As is clear from the above description, the addition of salt causes solid-liquid separation to occur quickly, so that after the landing, the solid-liquid separation at a relatively fast stage and permeate into the inside of the paper. I guess it will be effective. In other words, it is considered that the image quality is hardly affected by the addition of salt due to the permeability of the recording medium. Among the above-mentioned salts, sulfates (for example, potassium sulfate) and benzoates (for example, ammonium benzoate) are compatible with self-dispersing carbon black, and specifically, solid-liquid separation when applied to a recording medium. Because the effect is particularly excellent, it is possible to form inkjet recording images of particularly excellent quality on various recording media.

  The content of the self-dispersing carbon black in the ink is preferably 0.1 to 15% by weight, particularly 1 to 10% by weight, based on the total weight of the ink. The salt content is preferably 0.05 to 10% by weight, particularly 0.1 to 5% by weight, based on the total weight of the ink. By setting the content of the self-dispersing carbon black and the salt in the ink within the above range, a more excellent effect can be obtained.

(Self-dispersing carbon black)
Next, the self-dispersing carbon black in the ink will be described in detail.

  As the self-dispersing carbon black, those having ionicity are preferable. For example, carbon black charged anionic or cationic can be suitably used.

(Anionic charge CB)
Examples of the anionically charged carbon black include those in which a hydrophilic group as shown below is bonded to the surface of the carbon black.
_{-COO (M2), - SO 3} (M2) 2, -PO 3 H (M2), - PO 3 (M2) 2
In the above formula, M2 represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. R represents an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group. Among these, carbon black in which —COO (M2) or —SO ₃ (M2) ₂ is bonded to the surface of carbon black to be anionic charged is particularly suitable for this embodiment because of its excellent dispersibility in ink. It can be used for. By the way, among those expressed as “M2” in the hydrophilic group, specific examples of the alkali metal include Li, Na, K, Rb and Cs, and specific examples of the organic ammonium include, for example, methylammonium, dimethyl Examples include ammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methanolammonium, dimethanolammonium, and trimethanolammonium. The ink of this embodiment containing self-dispersing carbon black in which M2 is ammonium or organic ammonium can further improve the water resistance of the recorded image, and can be used particularly suitably in this respect. This is considered to be due to the fact that when the ink is applied onto the recording medium, ammonium is decomposed and ammonia is evaporated. Here, the self-dispersing carbon black in which M2 is ammonium is obtained by, for example, substituting the self-dispersing carbon black in which M2 is an alkali metal by using an ion exchange method to replace M2 with ammonium or by adding an acid to form H-type. Examples include a method of adding ammonium hydroxide to make M2 ammonium.

  An example of a method for producing an anionically charged self-dispersing carbon black is a method in which carbon black is oxidized with sodium hypochlorite. By this method, a —COONa group is chemically bonded to the carbon black surface. be able to.

(Cationically charged CB)
Examples of the cationically charged carbon black include those in which at least one selected from the following quaternary ammonium groups is bonded to the surface of the carbon black.

  In the above formula, R represents an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group.

Note The above cationic such as NO as a counter ion based ₃ ^- and _CH 3 COO ^- is present.

  An example of a method for producing a cationically charged self-dispersing carbon black having a hydrophilic group bonded thereto as described above will be described with reference to, for example, a method of bonding an N-ethylpyridyl group having the structure shown below. Then

  A method of treating carbon black with 3-amino-N-ethylpyridinium bromide is mentioned. In this way, carbon black charged anionic or cationic by introducing a hydrophilic group to the surface of carbon black has excellent water dispersibility due to repulsion of ions, so even when it is contained in aqueous ink. A stable dispersion state is maintained without adding a dispersant or the like.

By the way, various hydrophilic groups as described above may be directly bonded to the surface of carbon black. Alternatively, other atomic groups may be interposed between the carbon black surface and the hydrophilic group, and the hydrophilic group may be indirectly bonded to the carbon black surface. Here, specific examples of the other atomic groups include, for example, a linear or branched alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group. Here, examples of the substituent for the phenylene group and the naphthylene group include linear or branched alkyl groups having 1 to 6 carbon atoms. The specific examples of the combination of another atomic group and the hydrophilic group, for example, _{-C 2 H 4 COOM, -Ph-} SO 3 M, -Ph-COOM , etc. (where, Ph is a phenyl group) include .

  Incidentally, in the present embodiment, two or more of the above-described self-dispersing carbon blacks may be used as the ink color material appropriately selected. The addition amount of the self-dispersing carbon black in the ink is preferably 0.1 to 15% by weight, particularly 1 to 10% by weight, based on the total weight of the ink. By setting this range, the self-dispersing carbon black can maintain a sufficiently dispersed state in the ink. Furthermore, for the purpose of adjusting the color tone of the ink, a dye may be added as a coloring material in addition to the self-dispersing carbon black.

(Compatibility between self-dispersing CB and salt)
Of the various self-dispersion carbon black as described above, for example, -COO _(M2) as the hydrophilic groups on the surface of carbon _{black, - SO 3 (M2) 2} , -PO 3 H (M2), - PO 3 (M2) _As described above, when ₂ is used, ammonium or organic ammonium can be preferably used as M2, but the salt to be combined at this time is preferably matched with M1 and M2. That is, the present inventors made M2 (counter ion) and M1 of the hydrophilic group of the self-dispersing carbon black the same in the examination process of the effect of adding salt to the ink containing the self-dispersing carbon black. Occasionally, we have found that the stability of the ink is particularly improved. The reason why such an effect can be obtained by aligning M1 and M2 is not clear, but salt exchange does not occur between the counter ion of the hydrophilic group of the self-dispersing carbon black and the salt in the ink. It is presumed that the dispersion stability of the self-dispersing carbon black is stably maintained.

  If both M1 and M2 are ammonium or organic ammonium, in addition to the effect of stabilizing ink characteristics, the water resistance of the recorded image can be further improved. At this time, if Ph—COO (NH 4) (ammonium benzoate) is used as the salt in the ink, extremely excellent results can be obtained in the re-ejection property of the ink from the head nozzle after the ink jet recording is temporarily stopped. Can do.

(Aqueous medium)
Examples of the aqueous medium used in the ink according to this embodiment include water or a mixed solvent of water and a water-soluble organic solvent. As the water-soluble organic solvent, those having an ink drying preventing effect are particularly preferable. Specifically, for example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; dimethylformamide, dimethyl Amides such as acetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, and triethylene 2 to 6 alkylene groups such as glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol Alkylene glycols containing carbon atoms; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; glycerin; ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether Lower alkyl ethers of polyhydric alcohols such as; polyhydric alcohols such as trimethylolpropane and trimethylolethane; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, etc. It is done. The water-soluble organic solvents as described above can be used alone or as a mixture.

  Moreover, it is desirable to use deionized water as water.

  The content of the water-soluble organic solvent contained in the ink according to this embodiment is not particularly limited, but is preferably in the range of 3 to 50 wt% with respect to the total weight of the ink. The content of water contained in the ink is preferably in the range of 50 to 95% by weight with respect to the total weight of the ink.

  The ink according to the first aspect described above has an excellent effect that the dependency of the print quality on the recording medium characteristics can be extremely reduced. And the excellent point of the ink of this aspect is not only this. That is, the graph plotting the relationship between the pigment concentration and the optical density of the image of each ink for the ink (a) according to this embodiment and the ink (b) having the same composition except that it does not contain salt as a control. As shown in FIG. As can be seen from FIG. 13, the optical density of the image by any ink eventually reaches a similar value, but the ink of this embodiment reaches the saturation value at a pigment concentration lower than that of the control ink. Obtained knowledge. In other words, the addition of salt makes it possible to reduce the pigment concentration in the ink without changing the optical density of the image. Specifically, for example, when about 1 wt% of ammonium benzoate is included as a salt, the optical density of printing on plain paper is up to about 1.4, for example, by setting the concentration of self-dispersing carbon black to about 4 wt%. The optical density does not change much even if the carbon black density is increased further. On the other hand, the optical density of printing on plain paper is about 1.32 when the self-dispersion type carbon black concentration is 4 wt%, and the optical density is 1 when the carbon black concentration is 7 wt%. .35, and even when 8 wt%, it is about 1.35, and this value is almost saturated. Even if the difference between the saturation values of optical density (1.4 and 1.35) is only 0.05 on the numerical value, the difference is clearly recognized visually by comparing each printed matter. It is something that can be done. Ink added with salt in this way can produce a high optical density print even at a low carbon black density compared to an ink containing no salt, and provides a favorable result that the saturation value of the optical density itself is high. It is.

  This also brings the following benefits: That is, the ink containing salt has a characteristic that the carbon black density margin with respect to the optical density of the printed matter is wide as described above. Therefore, for example, an ink tank having an absorber is filled with this ink, and the ink tank is left in the same posture for a long time (for example, left for 6 months with the nozzle up), and then printing is performed using the ink tank. It is extremely effective to prevent the difference in optical density that can be visually confirmed between the printed matter obtained at the initial stage of printing and the print obtained immediately before the ink in the ink tank is used up. it can.

  The ink according to the first aspect is further excellent in intermittent ejection property as another effect of adding salt. Intermittent discharge refers to a predetermined nozzle of the recording head, discharges ink from the nozzle, and then leaves it for a predetermined time without performing preliminary ink discharge or ink suction in the nozzle, and again from the nozzle. When ink is ejected, it is evaluated whether ink is ejected normally from the beginning of re-ejection.

(Second Embodiment)
As a second embodiment of the ink according to the present invention, for example, a mode in which a stabilizer is further added to the ink described as the first embodiment can be given. Here, examples of the stabilizer include a surfactant. As the surfactant, one selected from an anionic surfactant, a nonionic surfactant, and a cationic surfactant can be used. Further, when the content of the stabilizer in the ink is, for example, 0.005 to 0.4 wt%, particularly 0.0 to 0.2 wt% based on the total weight of the ink, the storage stability of the ink is further improved. In addition, the ink ejection characteristics and the like are hardly affected, and this technique can be obtained by aligning both the ink according to the first embodiment, in particular, M1 and M2 with, for example, ammonium. There is little effect on the effect.

(Anionic surfactant)
Examples of the anionic surfactant include higher fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, and naphthalene sulfonate salts (Na, K). , Li, Ca, etc.), formalin polycondensates, condensates of higher fatty acids and amino acids, dialkylsulfosuccinates, alkylsulfosuccinates, naphthenates, alkyl ether carboxylates, acylated peptides, α-olefin sulfones Acid salt, N-acylmethyl taurine, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl pheny ether sulfate, monoglyculate, alkyl ether phosphate ester salt, alkyl phosphate ester Salts and the like.

(Cationic surfactant)
Examples of the cationic surfactant include aliphatic amines, quaternary ammonium salts, sulfonium salts, phosphonium salts and the like.

(Nonionic surfactant)
Nonionic surfactants include, for example, fluorine-based, silicon-based, acrylic acid copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene sterol ether, polyoxyethylene. Lanolin derivative, ethylene oxide derivative of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene block polymer, aliphatic ester type of polyoxyethylene polyoxypropylene alkyl ether polyoxyethylene compound, polyethylene oxide condensed type polyethylene glycol fatty acid ester, fatty acid monoglyceride , Polyglycerin fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid al Noruamido, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines and alkylamine oxides. Of the various surfactants described above, those having an ionic group are preferably used. These surfactants preferably use an anion or nonion type when the hydrophilic group on the carbon surface is an anion, and a cation or nonion type when the hydrophilic group is a cation.

(About dodecylbenzenesulfonate)
Incidentally in this embodiment, directly or indirectly to the surface as a self-dispersing carbon _{black, -COO (M2), - SO} 3 (M2) 2, -PO 3 H (M2), - PO 3 (M2) 2, (However, M2 in the formula represents a hydrogen atom, an alkali metal, an ammonium or an organic ammonium.) When dodecyl benzene sulfonate (sodium salt, potassium salt, ammonium salt, etc.) is added as a surfactant, surprisingly, the change in ink characteristics accompanying the change in pH of the ink can be made very gradual. That is, the schematic relationship of the change in the viscosity of the ink accompanying the change in pH of the ink in which the self-dispersing carbon black charged in an anionic manner coexisting with the salt included in the first embodiment is shown in FIG. ). As described above, the ink according to the first embodiment tends to have a slightly large change in ink characteristics with respect to a change in pH. However, when dodecylbenzenesulfonate is added to such an ink, the change in ink characteristics with respect to a change in pH can be made very gradual as shown in FIG. Here, the content of dodecylbenzenesulfonate in the ink is preferably 0.02 to 0.2 wt% based on the total weight of the ink.

(Third embodiment)
Next, as a third embodiment of the present invention, an ink prepared by adjusting the pH of the ink according to the first or second embodiment to 9 to 12, particularly 9 to 11 can be mentioned. That is, the knowledge that the ink according to the first embodiment of the present invention has a slightly large variation in ink characteristics with respect to pH change, and that the pH may slightly change when the ink is stored for a long period of time. As described above, the present inventors have obtained the above. However, if the pH of the ink is within the above-described range, the change with time in the ink characteristics is almost negligible.

  The pH of the ink described in Embodiments 1 and 2 is usually about 7 to 8 unless particularly adjusted. The pH of such an ink can be adjusted to a desired pH using, for example, hydroxide, specifically potassium hydroxide, aqueous ammonia, lithium hydroxide, or the like. By the way, when the ink is stored for a long time, the pH may change by about 1, specifically, although it varies depending on the composition and storage conditions of the ink, the pH of the ink after such long-term storage falls within the above range. In order to keep it, it is preferable to adjust the initial ink pH to be slightly higher, for example, within the range of pH 9-12.

  The ink according to the second embodiment described above, that is, the ink prepared by adjusting the pH of the ink containing dodecylbenzenesulfonate as a stabilizer within the above range, is particularly preferably used as an ink for ink jet recording. Can do. This is because the change in the ink characteristics becomes smaller and smaller within the above pH range due to the effect of mitigating the fluctuation of the ink characteristics with respect to the pH fluctuation of the ink obtained by including dodecylbenzenesulfonate. Further, since dodecylbenzene sulfonate may be added so as to suppress fluctuations in ink characteristics within the above pH range, an effect of suppressing the amount of dodecyl benzene sulfonate added can also be achieved.

(Fourth embodiment)
Examples of the ink according to the fourth embodiment of the present invention include an ink obtained by adding an antioxidant to any of the inks according to the first to third embodiments. By adding such an antioxidant, the storage stability of the ink can be further improved.

  Examples of the antioxidant include sodium sulfite, sodium bisulfite, ascorbic acid, gallic acid, 2-naphthol tannic acid, catechol, o-phenylenediamine, oxalic acid, and the like. From this, one or more compounds can be added to the ink. It ’s fine.

  Although the action when these compounds are added to the ink is not clear, for example, the time-dependent oxidation of a water-soluble organic solvent (for example, ethylene glycol) is considered to affect the dispersion state of the pigment. Since the compound can effectively prevent oxidation of the compound, it is presumed that the long-term storage stability of the ink is stabilized.

  Here, when the addition amount of the antioxidant is 0.02 to 10 wt%, particularly 0.1 to 2 wt% with respect to the total weight of the ink, the storage stability is improved without substantially changing the ink characteristics. Can be achieved.

(Fifth embodiment)
Examples of the ink according to the fifth embodiment of the present invention include an ink obtained by adding a water-soluble polymer compound to any of the inks according to the first to fourth embodiments. By adding such a water-soluble polymer compound, it is possible to improve the scratch resistance of the image after the ink is adhered to the surface of the recording medium and the image is recorded.

(Water-soluble polymer compound)
Examples of the water-soluble polymer compound include a styrene-acrylic acid copolymer, a styrene-acrylic acid-alkyl acrylate copolymer, a styrene-maleic acid copolymer, and a styrene-maleic acid-acrylic acid alkyl ester copolymer. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic acid copolymer, alginic acid, polyacrylic acid or salts thereof And derivatives thereof.

  The water-soluble polymer compound used here preferably has a weight average molecular weight of, for example, about 1000 to 5000, and the content of these water-soluble polymer compounds is, for example, 0.02 to 2 wt with respect to the total weight of the ink. %, Particularly 0.05 to 1 wt%. That is, when the molecular weight of the water-soluble polymer compound and the content in the ink are within such ranges, the water-soluble polymer compound is secured while ensuring the effects of the water-soluble polymer compound (improved scratch resistance of the recorded image). Changes in ink viscosity, changes in ink ejection characteristics, and the like due to the addition of the compound can be suppressed to a level that can be substantially ignored.

(Ink characteristics; ink jet ejection characteristics, permeability to recording media)
The ink according to each of the above embodiments can be used for writing instrument ink and ink jet recording ink. As an ink jet recording method, there are a recording method in which mechanical energy is applied to ink to eject droplets, and a recording method in which thermal energy is applied to ink and ink droplets are ejected by foaming of the ink. The ink of the present invention is particularly suitable. By the way, when the ink according to each of the above embodiments is used for inkjet recording, it is preferable that the ink has a characteristic that it can be ejected from an inkjet head. From the viewpoint of dischargeability from an inkjet head, the liquid has, for example, a viscosity of 1 to 15 cps, a surface tension of 25 dyn / cm or more, particularly a viscosity of 1 to 5 cps, and a surface tension of 25 to 50 dyn / cm. It is preferable that

A Ka value obtained by the Bristow method is a measure representing the penetrability of ink into a recording medium. That is, when the ink permeability is expressed as an ink amount V per 1 m ² , the ink penetration amount V (ml / m ² = μm) after a predetermined time t has elapsed since the ink droplet was ejected. Is shown by the Bristow equation shown below.
V = Vr + Ka (t−tw) ^1/2
Here, immediately after the ink droplets adhere to the surface of the recording medium, the ink is mostly absorbed in the uneven portion of the surface of the recording medium (the rough portion of the surface of the recording medium) and almost penetrates into the inside of the recording medium. Not. The time between them is the contact time (tw), and the amount of ink absorbed by the uneven portions of the recording medium at the contact time is Vr. Then, when the contact time is exceeded after the ink is deposited, the amount of penetration into the recording medium increases by an amount proportional to the time that exceeds the contact time, that is, (t-tw) to the power of 1/2. Ka is a proportional coefficient of this increase, and shows a value corresponding to the penetration rate. The Ka value can be measured using a liquid dynamic permeability tester (eg, trade name: dynamic permeability tester S; manufactured by Toyo Seiki Seisakusho, etc.) according to the Bristow method. In the ink according to each embodiment of the present invention, the Ka value is preferably less than 1.5 in order to further improve the recorded image quality, and more preferably 0.2 or more and less than 1.5. is there. For example, as described above, the ink containing self-dispersing carbon black and salt according to the first embodiment promotes solid-liquid separation on the recording medium and greatly contributes to improvement in image quality. When the Ka value is less than 1.5, solid-liquid separation occurs at an earlier stage of the ink penetration into the recording medium. It appears that high quality images with very few rings can be formed on various recording media. The Ka value according to the Bristow method in the present invention is PB used for plain paper (for example, a copying machine using an electrophotographic method, a page printer (laser beam printer) manufactured by Canon Inc., or a printer using an ink jet recording method). This is a value measured by using a recording medium such as paper or a PPC paper which is a paper for an electrophotographic copying machine. As a measurement environment, a normal office environment, for example, a temperature of 20 to 25 ° C. and a humidity of 40 to 60% is assumed.

  The composition of the preferable aqueous medium in which the above-described characteristics are carried on the ink according to each embodiment includes, for example, glycerin, trimethylolpropane, thiodiglycol, ethylene glycol, diethylene glycol, isopropyl alcohol, and acetylene alcohol. It is preferable. Examples of acetylene alcohol include acetylene alcohol represented by the following chemical formula.

  In particular, when the Ka value is less than 1.5 as described above, it can be achieved by adding a predetermined amount of a surfactant such as acetylenol or a permeable solvent.

  In addition to the above components, surfactants, antifoaming agents, antiseptics, antifungal agents, and the like can be added to obtain inks having desired physical properties as required. May also be added.

(Inkjet recording technology)
Next, an ink jet recording technique that can suitably use each ink of this embodiment will be described.

  FIG. 1 and FIG. 2 show an example of a head structure that is a main part of an apparatus that uses thermal energy for ink ejection as an ink jet recording apparatus.

  FIG. 1 is a cross-sectional view of the head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along line AB in FIG. The head 13 is obtained by bonding a heating element substrate 15 and a glass, ceramic, silicon or plastic plate having a flow path (nozzle) 14 through which ink passes. The heating element substrate 15 includes a protective layer 16 formed of silicon oxide, silicon nitride, silicon carbide, etc., electrodes 17-1, 17-2 formed of aluminum, gold, aluminum-copper alloy, etc., HfB2, TaN, TaAl, etc. A heating resistor layer 18 formed of a high melting point material, a heat storage layer 19 formed of thermal silicon oxide, aluminum oxide, and the like, and a substrate 20 formed of a material having good heat dissipation such as silicon, aluminum, aluminum nitride. ing.

  When a pulsed electric signal is applied to the electrodes 17-1 and 17-2 of the head, the region indicated by n of the heating element substrate 15 rapidly generates heat, and bubbles are generated in the ink in contact with the surface. Then, the meniscus 23 protrudes due to the generated pressure, and ink is ejected through the nozzle 14 of the head, becomes an ink droplet 24 from the ejection orifice 22, and flies toward the recording material 25.

  FIG. 3 shows an external view of a multi-head in which a large number of heads shown in FIG. 1 are arranged. This multi-head is made by adhering a glass plate 27 having multi-nozzles 26 and a heating head 28 similar to that described in FIG.

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

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

  Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording material facing the discharge port surface on which the discharge port is arranged. Reference numeral 66 denotes a recording head mounted with the recording head 65. It is a carriage for moving. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording area by the recording head 65 and its adjacent area can be moved. 51 is a paper feeding unit for inserting a recording material, and 52 is a paper feed roller driven by a motor (not shown).

  With these configurations, the recording material is fed to a position opposite to the 65 discharge port surface of the recording head, and is discharged to a paper discharge unit provided with a paper discharge roller 53 as recording progresses. In the above configuration, when the recording head 65 finishes recording and returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port of the recording head 65 is wiped. When the cap 62 is in contact with the ejection surface of the recording head 65 and is capped, the cap 62 moves so as to protrude into the moving path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as that at the time of wiping described above. As a result, the ejection port surface of the recording head 65 is wiped even during this movement.

  The above-mentioned movement of the recording head to the home position is not only at the end of recording or at the time of ejection recovery, but also to the home position adjacent to the recording area at a predetermined interval while the recording head moves the recording area for recording. Then, the wiping is performed with this movement.

(ink cartridge)
FIG. 5 is a diagram illustrating an example of an ink cartridge 45 that contains ink supplied to the recording head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink container, for example, an ink bag, in which supply ink is stored, and a rubber plug 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives waste ink. The ink container preferably has a liquid contact surface made of polyolefin, particularly polyethylene.

(Recording unit)
The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separated as described above, and is preferably used in an apparatus in which they are integrated as shown in FIG. It is done. In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage portion that stores ink, for example, an ink absorber is stored, and the ink in the ink absorber from the head portion 71 having a plurality of orifices. It is configured to be ejected as ink droplets. It is preferable for the present invention to use polyurethane as the material of the ink absorber.

  Alternatively, a structure in which the ink container is an ink bag with a spring or the like inside without using an ink absorber may be used. Reference numeral 72 denotes an air communication port for connecting the inside of the cartridge to the air. The recording unit 70 is used in place of the recording head 65 shown in FIG. 4 and is detachable from the carriage 66.

  Next, as a form of the ink jet recording apparatus using the second mechanical energy, a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed facing the nozzles, and this An on-demand ink jet recording head that includes ink that fills the periphery of the pressure generating element, displaces the pressure generating element by an applied voltage, and discharges a small droplet of ink from a nozzle can be exemplified. FIG. 7 shows a configuration example of a recording head which is a main part of the recording apparatus.

  The head includes an ink flow path 80 communicating with an ink chamber (not shown), an orifice plate 81 for ejecting ink droplets of a desired volume, a vibration plate 82 that directly applies pressure to ink, and the vibration plate 82. And a substrate 84 for supporting and fixing the orifice plate 81, the vibration plate, and the like.

  In FIG. 7, an ink flow path 80 is formed of a photosensitive resin or the like, an orifice plate 81 has a discharge port 85 formed by electroforming or punching a metal such as stainless steel or nickel, and the vibration plate 82 is The piezoelectric element 83 is formed of a dielectric material such as barium titanate or PZT. The piezoelectric element 83 is formed of a metal film such as stainless steel, nickel, or titanium and a highly elastic resin film. The recording head configured as described above applies a pulsed voltage to the piezoelectric element 83 to generate a strain stress, and the energy deforms the vibration plate bonded to the piezoelectric element 83, so that the ink in the ink flow path 80 is obtained. The ink is vertically pressed and ink droplets (not shown) are discharged from the discharge port 85 of the orifice plate to perform recording. Such a recording head is used by being incorporated in a recording apparatus similar to that shown in FIG. The detailed operation of the recording apparatus can be performed in the same manner as described above.

(Ink set)
By the way, the ink according to each of the first to fifth embodiments described above constitutes a black ink. This ink is a color ink containing a yellow color material, a color ink containing a magenta color material, and a cyan color ink. Color by combining with at least one color ink selected from a color ink containing a color material, a color ink containing a color material for red, a color ink containing a color material for blue, and a color ink containing a color material for green An ink set that can be suitably used for forming an image can be provided. When recording is performed using such an ink set so as to be adjacent to the black image portion and the color image portion, the occurrence of bleeding can be suppressed extremely effectively. The reason why such an ink set can effectively suppress bleeding is not clear, but as an effect of coexistence of self-dispersing carbon black and salt in black ink, the ink after the black ink adheres to the recording medium. This is presumably because solid-liquid separation and subsequent solidification of the colorant occur rapidly, and as a result, the black ink is less likely to bleed to the color ink side at the boundary of the color image.

(About color ink)
Here, as the color material of the color ink that can be used in the ink set, known dyes and pigments can be used. As the dye, for example, an acid dye or a direct dye can be used. For example, existing anionic dyes, newly synthesized ones, and any one having an appropriate color tone and concentration can be used, and any of these can be used in combination. It is also possible. Specific examples of the anionic dye are listed below.

(Coloring material for yellow)
CI Direct Yellow 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 100, 110
CI Acid Yellow 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99
CI Reactive Yellow 2, 3, 17, 25, 37, 42,
CI Food Yellow 3
(Coloring material for red)
CI Direct Red 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 229
CI Acid Red 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134, 145 158, 198, 249, 265, 289
CI Reactive Red 7, 12, 13, 15, 17, 20, 23, 24, 31, 42, 45, 46, 59
CI Food Red 87, 92, 94
(Coloring material for blue)
CI Direct Blue 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226
CI Acid Blue 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 117, 127, 138, 158, 161
CI Reactive Blue 4, 5, 7, 13, 14, 15, 18, 19, 21, 26, 27, 29, 32, 38, 40, 44, 100
(Coloring material for black)
CI Acid Black 2, 4, 8, 51, 52, 110, 115, 156
CI food black 1, 2

(solvent)
Examples of the ink solvent or dispersion medium containing the color material for color ink as described above include water or a mixed solvent of water and a water-soluble organic solvent. And as a water-soluble organic solvent, the thing similar to what was described in the said 1st embodiment is mentioned. In addition, when the color ink is adhered to a recording medium by an ink jet method (for example, bubble jet (registered trademark) method), the ink has a desired viscosity and surface tension so as to have excellent ink jet discharge characteristics as described above. It is preferable to prepare so that it may have.

(Coloring material content)
Here, the content of the color material in each color ink may be appropriately selected so that, for example, when used for inkjet recording, the ink has excellent inkjet ejection characteristics and has a desired color tone and density. As a guide, for example, a range of 3 to 50 wt% with respect to the total weight of the ink is preferable. The amount of water contained in the ink is preferably in the range of 50 to 95 wt% with respect to the total weight of the ink.

(Color ink penetration)
Regarding the color ink as described above, it is preferable that the Ka value is, for example, 5 or more because a high-quality color image can be formed on the recording medium. That is, since ink having such a Ka value has high penetrability into a recording medium, for example, even when images of at least two colors selected from yellow, magenta, and cyan are recorded adjacently, between adjacent images. Color bleeding (bleeding) can be suppressed, and even when these inks are overlaid to form a secondary color image, each ink has high penetrability, so it is possible to prevent an image between adjacent different color images. Can effectively suppress bleeding. As a method for adjusting the Ka value of the color ink to such a value, for example, a conventionally known method such as addition of a surfactant or addition of a permeable solvent such as glycol ether can be applied. Of course, the addition amount is appropriately selected. That's fine.

(Recording apparatus and recording method using ink set)
Next, when recording a color image using the ink set described above, for example, a recording apparatus in which four recording heads shown in FIG. 3 are arranged on a carriage can be used. FIG. 9 shows an embodiment thereof. Reference numerals 91, 92, 93 and 94 denote recording units for ejecting black, cyan, magenta and yellow inks, respectively. The recording unit is disposed on the carriage of the above-described recording apparatus and ejects ink of each color according to a recording signal. FIG. 9 shows an example in which four recording units are used. However, the present invention is not limited to this. For example, as shown in FIG. 8, from one of the ink cartridges 86 to 89 containing each of the four color inks as shown in FIG. There may be mentioned a mode in which recording is performed by attaching to a recording head 95 configured by dividing ink flow paths so that the supplied ink of each color can be individually ejected.

  Hereinafter, although it demonstrates more concretely using an Example and a comparative example, this invention is not limited by the following Example, unless the summary is exceeded. In the following description, parts and% are based on weight unless otherwise specified.

Experimental Example I- (1) (Evaluation of ink according to first embodiment)
First, pigment dispersions 1 to 4 were prepared.

Pigment dispersion 1
10 g of carbon black having a surface area of 230 m ² / g and DBP oil absorption of 70 ml / 100 g and 3.41 g of p-amino-N-benzoic acid were mixed well with 72 g of water, and 1.62 g of nitric acid was added dropwise thereto. And stirred at 70 ° C. A few minutes later, a solution prepared by dissolving 1.07 g of sodium nitrite in 5 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry was filtered with a filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis Co., Ltd.), and the pigment particles collected by filtration were thoroughly washed with water and dried in an oven at 90 ° C. Was added to prepare an aqueous pigment solution having a pigment concentration of 10% by weight. By the above method, a group represented by the following chemical formula was introduced on the surface of carbon black.

Pigment dispersion 2
1.58 g of anthranilic acid was added at 5 ° C. in a solution of 5 g of concentrated hydrochloric acid in 5.3 g of water. A solution obtained by adding 1.78 g of sodium nitrite to 8.7 g of water at 5 ° C. was added in a state where the temperature was constantly kept at 10 ° C. or lower by stirring with an ice bath. After further stirring for 15 minutes, 20 g of carbon black having a surface area of 320 m ² / g and a DBP oil absorption of 120 ml / 100 g was added in a mixed state and further stirred for 15 minutes. The obtained slurry is filtered with a filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis), and the pigment particles filtered are sufficiently washed with water, dried in an oven at 110 ° C., and water is added to the pigment. Thus, an aqueous pigment solution having a pigment concentration of 10% by weight was prepared. By the above method, groups represented by the following chemical formula were introduced on the surface of carbon black.

Pigment dispersion 3
Sulfuric acid was added to the pigment dispersion 2 prepared above so that the pH was about 4.5, and the carboxyl group bonded to the surface of the carbon black was changed to the H type. Thereafter, the mixture was centrifuged (5000 rpm, 5 minutes), and the precipitated portion was taken out and dispersed again in pure water. Carbon was washed with water by repeating this centrifugation process three times. Further, NH ₄ OH was added to this dispersion to adjust the pH to about 8. Through the above treatment, the counter ion of the carboxyl group bonded to the carbon surface was substituted from Na ⁺ to NH ₄ ⁺ . The pigment dispersion containing the self-dispersing carbon black was designated as pigment dispersion 3.

Pigment dispersion 4
Carbon black having a -COONa group introduced on the surface was prepared by the following method.

  After mixing 300 g of acidic carbon black (trade name: MA-77 (pH 3.0); manufactured by Mitsubishi Kasei Co., Ltd.) with 1000 ml of water, 450 g of sodium hypochlorite (effective chlorine concentration 12%) was added thereto. The solution was added dropwise and stirred at 100 to 105 ° C. for 10 hours. The obtained slurry was filtered using filter paper (trade name: Toyo Filter Paper No. 2: manufactured by Advantis), and the pigment particles collected by filtration were sufficiently washed with water. This pigment wet cake was redispersed in 3000 ml of water and desalted with a reverse osmosis membrane until the conductivity reached 0.2 μs. Further, the pigment dispersion (pH = 8 to 10) was concentrated to a pigment concentration of 10% by weight to obtain carbon black having a —COONa group introduced on the surface.

  Next, black inks 1 to 4 were prepared by the following method using the above pigment dispersions.

(Black ink 1)
The following components were mixed, sufficiently stirred and dissolved, and then pressure filtered through a microfilter (manufactured by Fuji Film) having a pore size of 3 μm to prepare a black ink.
Pigment dispersion: 1 part 30 parts Potassium sulfate: 1 part Trimethylolpropane: 6 parts Glycerin: 6 parts Diethylene glycol: 6 parts Acetylene glycol ethylene oxide adduct: 0.2 parts (trade name: acetylenol EH; Kawaken Fine Chemicals Co., Ltd.)
Water: 50.8 parts (Black ink 2)
A black ink was prepared in the same manner as the black ink 1 using the following components.
Pigment dispersion 2: 30 parts Potassium chloride: 0.5 parts Trimethylolpropane: 6 parts Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.) )
・ Glycerin: 5 parts ・ Ethylene glycol: 5 parts ・ Water: 53.35 parts (Black ink 3)
A black ink was prepared in the same manner as the black ink 1 using the following components.
Pigment dispersion 3: 30 parts Ammonium benzoate: 1 part Trimethylolpropane: 6 parts Acetylene glycol oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
・ Glycerin: 5 parts ・ Diethylene glycol: 5 parts ・ Water: 52.85 parts (Black ink 4)
The following components were mixed, sufficiently stirred and dissolved, and then pressure filtered through a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare a black ink.
Pigment dispersion 4: 30 parts Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Glycerin: 5 parts-Diethylene glycol: 5 parts-Trimethylolpropane: 6 parts-Water: 53.85 parts The main characteristics of the black inks 1 to 4 thus obtained are shown in Table 1 below.

  Each of the black inks 1 to 4 is an ink jet recording apparatus having an on-demand type multi-recording head (trade name: BJC-4000; Canon) that discharges ink by applying thermal energy corresponding to a recording signal to the ink. The following evaluation was performed using a product manufactured by Co., Ltd. The results are shown in Table 2 below.

1) Character quality Characters are printed on the following five types of plain papers A, B, C, D, and E having different ink penetrability for each of the above inks using the above ink jet recording apparatus. Was evaluated according to the following criteria.
A: PPC paper NSK manufactured by Canon Inc.
B: PPC paper NDK manufactured by Canon Inc.
C: PPC paper 4024 manufactured by Xerox Co., Ltd.
D: Fox River PPC paper prober bond E: Neuzidola Canon PPC paper ○: There is almost no bleeding on all five papers.
Δ: Some blur paper is seen.
X: All 5 papers bleed.

2) Print density Using the above inkjet recording apparatus, the above inks are printed on plain copy papers A, B, C, D, and E. The print density at that time is measured using a Macbeth print density measuring instrument. Evaluation based on the criteria.
○: The difference in printing density between plain papers A, B, C, D, and E for copying is maximum and minimum is less than 0.1.
×: Difference in printing density between plain papers A, B, C, D and E for copying is 0.1 or more at the highest and the lowest.

3) Water resistance Using the above ink jet recording apparatus, each ink is printed on each of the plain papers A, B, C, D, and E in the same manner as in 1) above, and after a predetermined time has elapsed since printing. The printed recording medium was immersed in running water, and the state of soiling was visually observed. The results were evaluated according to the following criteria.
A: Background smudges become inconspicuous within 1 hour after printing on all the plain papers A, B, C, D and E for copying.
○: Background smudges become inconspicuous within one day after printing on all the plain papers A, B, C, D and E for copying.
X: There is paper with a noticeable background stain even after 1 day or more has passed since printing.

4) Intermittent ejection property Using the above ink jet recording apparatus, the above ink is printed on the plain paper A for copying, and then the vertical line is again printed after 30 seconds without performing preliminary ink ejection or suction from the nozzle. The difference between the two vertical lines obtained by printing was determined according to the following criteria.
A: The difference between the two cannot be seen with a loupe.
○: The difference between the two is not visually recognized.
(Triangle | delta): Although the difference of both is understood visually, it is not a problem practically.

  As can be seen from the results in Table 2 above, the ink according to the first embodiment of the present invention has high character quality and print density when recording is performed, for example, by the ink jet recording method, and these results depend on the paper type. There is little nature.

  Further, the black ink 3 in which the counter ion of the hydrophilic group of the self-dispersing carbon black is an ammonium salt and ammonium benzoate is used as a salt in the ink has a particularly excellent effect on water resistance.

Experimental Example I- (2)
Evaluation of ink set using ink according to first embodiment (Black ink 1)
A black ink prepared in the same manner as the black ink 1 of Experimental Example I- (1) was prepared.

(Black ink 2)
A black ink prepared in the same manner as the black ink 2 of Experimental Example I- (1) was prepared.

(Black ink 3)
A black ink prepared in the same manner as the black ink 3 of Experimental Example I- (1) was prepared.

(Black ink 5)
Black ink 5 was prepared in the same manner as black ink 1 using the following components.
Pigment dispersion 3: 30 parts prepared in Experimental Example I- (1) Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH: manufactured by Kawaken Fine Chemical Co., Ltd.)
-Trimethylolpropane: 6 parts-Glycerin: 5 parts-Diethylene glycol: 5 parts-Water: 53.85 parts (Black ink 6)
Preparation of Pigment Dispersion 5 Pigment Dispersion 5 was prepared by the following method.

First, the following components were mixed and heated to 70 ° C. in a water bath to completely dissolve the resin component.
Styrene-acrylic acid-butyl acrylate copolymer: 3 parts (acid value 60, weight average molecular weight 13000)
1,3-bis- (β-hydrooxyethyl) urea: 0.5
・ Ion-exchanged water: 72.5 parts ・ Diethylene glycol: 5 parts Next, 14 parts of carbon black (trade name: Color Black S170; manufactured by Tegusa) and 5 parts of isopropyl alcohol are added to the above mixture, and pre-treated for 30 minutes. After mixing, dispersion treatment was performed under the following conditions.
Dispersing machine Sand grinder (Igarashi Machine Co., Ltd.)
Grinding media Filling rate of 1 mm diameter zirconium bead grinding media 50% (volume)
Grinding time 3 hours After the dispersion treatment, further centrifugal separation treatment (12000 rpm, 20 minutes) was carried out to remove coarse particles, whereby a pigment dispersion 5 was obtained.

Next, a black ink 6 was prepared in the same manner as the black ink 1 using the following components.
Pigment dispersion 5:30 parts Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Ethyl alcohol: 6 parts-2-methylpyrrolidone: 6 parts-Water: 57.85 parts (Yellow ink 1)
The following components were mixed, sufficiently stirred and dissolved, followed by pressure filtration with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare yellow ink 1.
-Acetylene glycol ethylene oxide adduct: 1 part (trade name: acetylenol EH manufactured by Kawaken Fine Chemicals Co., Ltd.)
・ Diethylene glycol: 10 parts ・ Glycerin: 5 parts ・ CI Direct Yellow 86: 3 parts ・ Water: 81 parts (Magenta ink 1)
Magenta ink 1 was prepared in the same manner as yellow ink 1 using the following components.
-Acetylene glycol ethylene oxide adduct: 1 part (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Thiodiglycol: 20 parts-CI Acid Red 35: 3 parts-Water: 76 parts (Cyan Ink 1)
Cyan ink 1 was prepared in the same manner as yellow ink 1 using the following components.
-Acetylene glycol ethylene oxide adduct: 1 part (trade name: acetylenol EH manufactured by Kawaken Fine Chemicals Co., Ltd.)
・ Diethylene glycol: 35 parts ・ CI acid blue 9: 3 parts ・ Water: 61 parts

Example 1
An ink set was prepared by combining the inks prepared above as follows.
・ Black ink 1
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 2
An ink set was prepared by combining the inks prepared above as follows.
・ Black ink 2
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 3
An ink set was prepared by combining the inks prepared above as follows.
・ Black ink 3
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Comparative Example 1
An ink set was prepared by combining the inks prepared above as follows.
・ Black ink 5
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Comparative Example 2
An ink set was prepared by combining the inks prepared above as follows.
・ Black ink 6
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

  Table 3 below shows the main configuration of each black ink constituting the ink sets of Examples 1 to 3 and Comparative Examples 1 and 2.

  An ink jet recording apparatus having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to a recording signal to the ink using the ink sets of Examples 1 to 3 and Comparative Examples 1 and 2 (commodity) (Name: BJC4000; manufactured by Canon Inc.), recording was performed on the same five types of plain papers A to E as described above. The recording results were evaluated as follows. The results are shown in Table 4 below.

1) Bleeding The printed image is divided into 5 x 5 squares (1 square size: 2 cm x 2 cm) within a 10 cm square, and the black print area is printed with black ink and each color ink alternately. Bleeding at the boundary between the image and the color printing portion was evaluated according to the following criteria.
○: The boundary line between the two colors is clear, and no blur or color mixture is seen at the boundary part.
Δ: It is clear that there is a boundary line between two colors, but some of the paper has some blurring or color mixing at the boundary.
X: The boundary line between two colors cannot be identified.

  As is clear from the above results, a color image with no or little bleeding can be recorded by the ink set using the ink according to the first embodiment.

Pigment dispersion 6
After 10 g of carbon black having a surface area of 230 m ² / g and DBP oil absorption of 70 ml / 100 g and 3.06 g of 3-amino-N-ethylpyridinium bromide were mixed well with 72 g of water, 1.62 g of nitric acid was added dropwise thereto. Stir to 70 ° C. A few minutes later, a solution prepared by dissolving 1.07 g of sodium nitrite in 5 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry is filtered with a filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis), the pigment particles are sufficiently washed with water, dried in an oven at 110 ° C., and water is added to the pigment. An aqueous pigment solution having a concentration of 10% by weight was prepared. By the above method, groups represented by the following chemical formula were introduced on the surface of carbon black.

(Black ink 7)
Next, the pigment dispersion 6 and the following components were mixed, sufficiently stirred and dissolved, and then pressure filtered through a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to prepare a black ink 7.
-Pigment dispersion 6: 30 parts-Ammonium sulfate: 2 parts-Trimethylolpropane: 6 parts-Sodium tetradecyl sulfate: 0.1 parts-Glycerin: 6 parts-Thiodiglycol: 6 parts-Water: 49.9 parts The main characteristics of the black ink 7 obtained as described above are shown below.

  The character quality, print density, and water resistance of the black ink 7 were evaluated by the same method and the same standard as those of the black inks 1 to 4, and all were good.

Experimental Example II- (1) (Evaluation of Ink According to Second Embodiment)
(Black ink 8)
The following components were mixed, sufficiently stirred and dissolved, and then pressure filtered through a microfilter (manufactured by Fuji Film) having a pore size of 3 μm to prepare a black ink.
Pigment dispersion: 1 part 30 parts Potassium sulfate: 1 part Sodium dodecylbenzenesulfonate: 0.1 part Trimethylolpropane: 6 parts Glycerin: 6 parts Diethylene glycol: 6 parts Acetylene glycol ethylene oxide adduct: 0.2 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
Water: 50.7 parts (Black ink 9)
A black ink was prepared in the same manner as the black ink 8 using the following components.
Pigment dispersion 2: 30 parts Potassium chloride: 0.5 parts Sodium dodecylbenzenesulfonate: 0.15 parts Trimethylolpropane: 6 parts Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: Acetylenol EH; Kawaken Fine Chemicals Co., Ltd.)
・ Glycerin: 5 parts ・ Ethylene glycol: 5 parts ・ Water: 53.2 parts (Black ink 10)
A black ink was prepared in the same manner as the black ink 8 using the following components.
-Pigment dispersion 2: 30 parts-Ammonium sulfate: 2 parts-Sodium dodecylbenzenesulfonate: 0.1 part-Trimethylolpropane: 6 parts-Sodium tetradecyl sulfate: 0.1 part-Glycerin: 6 parts-Thiodiglycol: 6 parts / water: 49.8 parts (black ink 11)
A black ink was prepared in the same manner as the black ink 8 using the following components.
-Pigment dispersion 3: 30 parts-Ammonium benzoate: 1 part-Sodium dodecylbenzenesulfonate: 0.15 parts-Trimethylolpropane: 6 parts-Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol) EH; Kawaken Fine Chemical Co., Ltd.)
-Glycerin: 5 parts-Ethylene glycol: 5 parts-Water: 52.7 parts The main characteristics of the black inks 8 to 11 are shown in Table 5 below.

The storage stability of each of the above black inks 8 to 11 was evaluated. That is, four 100 ml glass containers (manufactured by Schott) are prepared, and 100 ml of the black ink 8 to 11 is put in each glass container, and left at 60 ° C. for one month. Observed. The results are shown in Table 6 below. The evaluation criteria are as follows.
○: Almost no change in ink viscosity before and after standing.
X: Change in ink viscosity is observed before and after standing.

Experimental Example II- (2) (Evaluation of Ink Set Using Ink According to Second Embodiment)
(Black ink 8)
A black ink prepared in the same manner as the black ink 8 of Experimental Example II- (1) was prepared.

(Black ink 9)
A black ink prepared in the same manner as the black ink 9 of Experimental Example II- (1) was prepared.

(Black ink 10)
A black ink prepared in the same manner as the black ink 10 of Experimental Example II- (1) was prepared.

(Black ink 11)
A black ink prepared in the same manner as the black ink 11 of Experimental Example II- (1) was prepared.

(Yellow ink 1)
A yellow ink 1 prepared in the same manner as the yellow ink 1 of Experimental Example I- (2) was prepared.

(Magenta ink 1)
A magenta ink 1 prepared in the same manner as the magenta ink 1 of Experimental Example I- (2) was prepared.

(Cyan ink 1)
Cyan ink 1 prepared in the same manner as cyan ink 1 of Experimental Example I- (2) was prepared.

Example 4
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 8
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 5
・ Black ink 9
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 6
・ Black ink 10
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 7
・ Black ink 11
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

  The ink sets of Examples 4 to 7 were evaluated for bleeding in the same manner as in Experimental Example I- (2). The results are shown in Table 7 below.

Experimental Example III- (1) (Evaluation of Ink According to Third Embodiment)
(Black ink 12)
The following components were mixed, sufficiently stirred and dissolved, and then adjusted to pH 10.5 with potassium hydroxide. Thereafter, the mixture was filtered under pressure through a micro filter (manufactured by Fuji Film) having a pore size of 3 μm to prepare a black ink.
Pigment dispersion prepared in Experimental Example I- (1) 1:30 parts Potassium sulfate: 1 part Trimethylolpropane: 6 parts Glycerin: 6 parts Diethylene glycol: 6 parts Acetylene glycol ethylene oxide adduct: 0 .2 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
Water: 50.8 parts (Black ink 13)
A black ink was prepared in the same manner as the black ink 12 using the following components. The pH was adjusted to 11 using ammonia.
Pigment dispersion 2 prepared in Experimental Example I- (1): 30 parts Potassium chloride: 0.5 part Trimethylolpropane: 6 parts Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol) EH; Kawaken Fine Chemical Co., Ltd.)
・ Glycerin: 5 parts ・ Ethylene glycol: 5 parts ・ Water: 53.35 parts (Black ink 14)
A black ink was prepared in the same manner as the black ink 12 using the following components. The pH was adjusted to 11 using lithium hydroxide.
Pigment dispersion prepared in Experimental Example I- (1) 2:30 parts Ammonium sulfate: 2 parts Trimethylolpropane: 6 parts Sodium tetradecyl sulfate: 0.1 parts Glycerin: 6 parts Thiodiglycol: 6 Parts / water: 49.9 parts (black ink 15)
A black ink was prepared in the same manner as the black ink 12 using the following components. The pH was adjusted to 11 using ammonia.
Pigment dispersion 3 prepared in Experimental Example I- (1): 30 parts Ammonium benzoate: 1 part Trimethylolpropane: 6 parts Acetylene glycol ethylene oxide adduct: 0.15 part (trade name: acetylenol EH ; Kawaken Fine Chemical Co., Ltd.)
-Glycerin: 5 parts-Ethylene glycol: 5 parts-Water: 52.85 parts The main characteristics of the black inks 12 to 15 thus obtained are shown in Table 8 below.

The storage stability of each of the above black inks 12 to 15 was evaluated. That is, four 100 ml glass containers (manufactured by Schott) were prepared, and 100 ml of the black ink 11 to 13 was put in each of them, and the presence or absence of ink viscosity change before and after being left was observed. The results are shown in Table 9 below. The evaluation criteria are as follows.
○: Almost no change in ink viscosity before and after standing.
X: The change in ink viscosity is large before and after being left.

Experimental Example III- (2)
(Black ink 12)
A black ink prepared in the same manner as the black ink 12 of Experimental Example III- (1) was prepared.

(Black ink 13)
A black ink prepared in the same manner as the black ink 13 of Experimental Example III- (1) was prepared.

(Black ink 14)
A black ink prepared in the same manner as the black ink 14 of Experimental Example III- (1) was prepared.

(Black ink 15)
A black ink prepared in the same manner as the black ink 15 of Experimental Example III- (1) was prepared.

(Black ink 16)
The following components were mixed and the pH was adjusted to 11 with potassium hydroxide, followed by pressure filtration with a micro filter (manufactured by Fuji Film) having a pore size of 3 μm to prepare a black ink.
-Pigment dispersion 5 of Experimental Example I- (2)-30 parts of acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Ethyl alcohol: 6 parts-2-methylpyrrolidone: 6 parts-Water: 57.85 parts (Yellow ink 1)
A yellow ink 1 prepared in the same manner as the yellow ink 1 of Experimental Example I- (2) was prepared.

(Magenta ink 1)
A magenta ink 1 prepared in the same manner as the magenta ink 1 of Experimental Example I- (2) was prepared.

(Cyan ink 1)
Cyan ink 1 prepared in the same manner as cyan ink 1 of Experimental Example I- (2) was prepared.

Example 8
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 12
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 9
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 13
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 10
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 14
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 11
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 15
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Comparative Example 3
・ Black ink 16
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Table 10 below shows the main characteristics of the black ink constituting the ink sets of Examples 8 to 11 and Comparative Example 3.

  For the ink sets of Examples 8 to 11 and Comparative Example 3, bleeding was evaluated in the same manner as in Experimental Example I- (2). The results are shown in Table 11 below.

Experimental Example IV- (1) (Evaluation of Ink According to Fourth Embodiment)
(Black ink 17)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion of Experimental Example I- (1): 1 part-Potassium sulfate: 1 part-Sodium sulfite: 0.3 part-Trimethylolpropane: 6 parts-Glycerin: 6 parts-Diethylene glycol: 6 parts-Acetylene glycol Ethylene oxide adduct: 0.2 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
Water: 50.5 parts (Black ink 18)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 2 of Experimental Example I- (1): 30 parts-Potassium chloride: 0.5 parts-Sodium ascorbate: 0.15 parts-Trimethylolpropane: 6 parts-Glycerin: 5 parts-Ethylene glycol: 5 Part / acetylene glycol ethylene oxide adduct: 0.15 part (trade name: acetylenol EH; manufactured by Kawaken Fine Chemicals Co., Ltd.)
Water: 53.2 parts (Black ink 19)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 2 of Experimental Example I- (1): 30 parts-Ammonium sulfate: 2 parts-Sodium sulfite: 0.1 part-Trimethylolpropane: 6 parts-Sodium tetradecyl sulfate: 0.1 part-Glycerin: 6 parts -Thiodiglycol: 6 parts-Water: 49.8 parts (Black ink 20)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 3 of Experimental Example I- (1)-30 parts-Ammonium benzoate: 1 part-Sodium ascorbate: 0.15 part-Trimethylolpropane: 6 parts-Glycerin: 5 parts-Ethylene glycol: 5 parts -Acetylene glycol ethylene oxide adduct: 0.15 part (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
・ Water: 52.7 parts

  The characteristics of each of the black inks 17 to 20 thus obtained are shown in Table 12 below.

  The storage stability of the black inks 17 to 20 was evaluated in the same manner as in Experimental Example II- (1). The results are shown in Table 13 below.

Experimental Example IV- (2) (Evaluation of Ink Set Using Ink of Fourth Embodiment)
(Black ink 17)
A black ink prepared in the same manner as the black ink 17 of Experimental Example IV- (1) was prepared.

(Black ink 18)
A black ink prepared in the same manner as the black ink 18 of Experimental Example IV- (1) was prepared.

(Black ink 19)
A black ink prepared in the same manner as the black ink 19 of Experimental Example IV- (1) was prepared.

(Black ink 20)
A black ink prepared in the same manner as the black ink 20 of Experimental Example IV- (1) was prepared.

(Yellow ink 1)
A yellow ink 1 prepared in the same manner as the yellow ink 1 of Experimental Example I- (2) was prepared.

(Magenta ink 1)
A magenta ink 1 prepared in the same manner as the magenta ink 1 of Experimental Example I- (2) was prepared.

(Cyan ink 1)
Cyan ink 1 prepared in the same manner as cyan ink 1 of Experimental Example I- (2) was prepared.

Example 12
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 17
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 13
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 18
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 14
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 19
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 15
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 20
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

  The ink sets of Examples 12 to 15 were evaluated for bleeding in the same manner as in Experimental Example I- (2). The results are shown in Table 14 below.

Experimental Example V- (1) (Evaluation of Ink of Fifth Embodiment)
(Black ink 21)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion of Experimental Example I- (1): 1 part-Potassium sulfate: 1 part-Trimethylolpropane: 6 parts-Glycerin: 6 parts-Diethylene glycol: 6 parts-Acetylene glycol ethylene oxide adduct: 0.2 (Product name: Acetylenol EH; Kawaken Fine Chemical Co., Ltd.)
・ Sodium alginate: 0.1 part ・ Water: 50.7 parts (Black ink 22)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 2 of Experimental Example I- (1): 30 parts-Potassium chloride: 0.5 parts-Trimethylolpropane: 6 parts-Glycerin: 5 parts-Ethylene glycol: 5 parts-Acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Sodium polyacrylate: 0.1 part-Water: 53.25 parts (Black ink 23)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 3 of Experimental Example I- (1): 30 parts-Ammonium benzoate: 1 part-Trimethylolpropane: 6 parts-Glycerin: 5 parts-Ethylene glycol: 5 parts-Acetylene glycol ethylene oxide adduct: 0 .15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Sodium polyacrylate: 0.1 part-Water: 52.75 parts (Black ink 24)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 6 of Experimental Example I- (2)-Ammonium sulfate: 2 parts-Trimethylolpropane: 6 parts-Sodium alginate: 0.1 part-Glycerin: 6 parts-Thiodiglycol: 6 parts-Water : 49.9 parts Main characteristics of the black inks 21 to 24 thus obtained are shown in Table 15 below.

  Ink jet recording apparatus (trade name: BJC-4000; Canon Inc.) having an on-demand type multi-recording head that discharges each of the black inks 21 to 24 by applying thermal energy corresponding to a recording signal to the ink. The following evaluation was performed using The results are shown in Table 16 below.

1) Character quality Each of the above inks was printed on the five types of plain papers A, B, C, D, and E using the ink jet recording apparatus, and the bleeding of the characters was evaluated according to the following criteria. .
○: There is almost no bleeding on all five papers.
Δ: Some blur paper is seen.
X: All 5 papers bleed.

2) Print density Using the above ink jet recording apparatus, the above-mentioned inks are printed on the five types of plain papers A, B, C, D, and E, and the print density at that time is measured using a Macbeth print density measuring device. Measured and evaluated according to the following criteria.
○: The difference in printing density between plain papers A, B, C, D, and E for copying is maximum and minimum is less than 0.1.
×: Difference in printing density between plain papers A, B, C, D and E for copying is 0.1 or more at the highest and the lowest.

3) Scratch resistance Each of the above inks was printed on the above five types of plain papers A, B, C, D, and E using the above-described ink jet recording apparatus and left for one day, and then a weight of 40 g / cm 2 was loaded. Using this, a scratch test was conducted, and the following criteria were evaluated.
○: Dirt is not noticeable on all papers.
Δ: Contamination is noticeable on some paper.
X: Dirt is noticeable on all papers.

4) Water resistance Each of the above inks is printed on the above five types of plain papers A, B, C, D and E using the ink jet recording apparatus in the same manner as in the above 1), and a predetermined time has elapsed since the printing. After that, the printed recording medium was put on running water and the state of soiling was visually observed, and the result was evaluated according to the following criteria.
A: Background smudges become inconspicuous within 1 hour after printing on all the plain papers A, B, C, D and E for copying.
○: Background smudges become inconspicuous within one day after printing on all the plain papers A, B, C, D and E for copying.
X: There is paper with a noticeable background stain even after 1 day or more has passed since printing.

Experimental Example V- (2) (Evaluation of Ink Set Using Ink of Fifth Embodiment)
(Black ink 21)
A black ink prepared in the same manner as the black ink 21 of Experimental Example V- (1) was prepared.

(Black ink 22)
A black ink prepared in the same manner as the black ink 22 of Experimental Example V- (1) was prepared.

(Black ink 23)
A black ink prepared in the same manner as the black ink 18 of Experimental Example V- (1) was prepared.

  A black ink prepared in the same manner as the black ink 23 of Experimental Example V- (1) was prepared.

(Black ink 25)
A black ink was prepared using the following components in accordance with the same method as that for the previously prepared black ink.
-Pigment dispersion 2 of Experimental Example I- (1): 30 parts-Ammonium sulfate: 2 parts-Trimethylolpropane: 6 parts-Sodium alginate: 0.1 part-Glycerin: 6 parts-Thiodiglycol: 6 parts-Water : 49.9 parts (Yellow ink 1)
A yellow ink prepared in the same manner as the yellow ink 1 of Experimental Example I- (2) above (Magenta ink 1)
A magenta ink prepared in the same manner as the magenta ink 1 of Experimental Example I- (2) was prepared.

(Cyan ink 1)
A cyan ink prepared in the same manner as the cyan ink 1 of Experimental Example I- (2) was prepared.

Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 21
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 17
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 22
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 18
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 23
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Example 19
Each ink prepared above was combined as follows to prepare an ink set.
・ Black ink 25
・ Yellow ink 1
・ Magenta ink 1
・ Cyan ink 1

Comparative Example 4
An ink set similar to that used in Comparative Example 2 of Experimental Example I- (2) was prepared.

The main characteristics of the black ink used in the ink sets of Examples 16 to 19 and Comparative Example 4 are shown in Table 17 below.

  For the ink sets of Examples 16 to 19 and Comparative Example 4, bleeding was evaluated in the same manner as described in Experimental Example I- (2). The scratching property was also evaluated in the same manner as in Experimental Example V- (1). The results are shown in Table 18 below.

It is a longitudinal cross-sectional view which shows one embodiment of the head of an inkjet recording device. FIG. 2 is a cross-sectional view taken along line AB in FIG. 1. It is a schematic explanatory drawing of a multihead. It is a schematic perspective view which shows one embodiment of an inkjet recording device. It is a longitudinal cross-sectional view which shows one embodiment of an ink cartridge. It is a perspective view which shows an example of a recording unit. It is a schematic perspective view which shows another structural example of an inkjet recording head. FIG. 4 is a schematic explanatory diagram of a recording head to which four ink cartridges are attached. FIG. 4 is a schematic explanatory diagram illustrating a configuration in which four recording heads are arranged on a carriage. It is the schematic which shows the correlation of pH and the viscosity of the ink concerning one embodiment of this invention. It is a schematic diagram showing a process of solid-liquid separation when a pigment ink containing salt is applied to a recording medium. It is a schematic diagram showing a solid-liquid separation process when a pigment ink not containing salt is applied to a recording medium. It is a graph which shows the relationship between the pigment density | concentration in ink and the optical density of printing by each ink in the ink containing salt and the ink which does not contain salt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 13 Head 14 Ink groove 15 Heat generating head 16 Protective film 17-1, 17-2 Electrode 18 Heating resistor tank 19 Heat storage layer 20 Substrate 21 Ink 22 Discharge orifice 23 Meniscus 24 Ink droplet 25 Recording material 26 Multi groove 27 Glass plate 40 Ink bag 42 Plug 44 Ink absorber 45 Ink cartridge 51 Paper feed portion 52 Paper feed roller 53 Paper discharge roller 61 Blade 62 Cap 63 Ink absorber 64 Discharge recovery portion 65 Recording head 66 Carriage 67 Guide shaft 68 Motor 69 Belt 70 Recording unit 71 Head part 72 Atmospheric communication port 80 Ink flow path 81 Orifice plate 82 Vibration plate 83 Piezoelectric element 84 Substrate 85 Discharge port 86, 87, 88, 89 Ink cartridge 90, 91, 92, 93 Recording unit 1101 Salt Pigment ink containing 1103, 1203 recording medium

Claims (9)

An ink for inkjet recording containing carbon black and a salt,
The carbon black bonds a hydrophilic group —COO (M2) (wherein M2 represents a hydrogen atom, an alkali metal, ammonium, or organic ammonium) to the surface of the carbon black through a substituted or unsubstituted phenylene group. Self-dispersing carbon black
An ink for ink jet recording, wherein the salt is a salt represented by Ph-COO (M1) (wherein M1 represents ammonium and Ph represents a phenyl group).   The ink for inkjet recording according to claim 1, wherein the content of the carbon black is 0.1 wt% or more and 15 wt% or less with respect to the total weight of the ink.   The ink for inkjet recording according to claim 1 or 2, wherein the content of the salt is 0.05% by weight or more and 10% by weight or less based on the total weight of the ink.   The ink for inkjet recording according to claim 3, wherein the content of the salt is 0.5 wt% or more and 2 wt% or less with respect to the total weight of the ink.   5. An aqueous ink containing at least one colorant selected from cyan, magenta, yellow, red, green and blue colorants, and the ink jet recording ink according to claim 1. An ink set characterized by combining.   An ink cartridge comprising an ink tank containing the ink for ink jet recording according to any one of claims 1 to 4.   A recording unit, comprising: an ink storage unit storing the ink according to claim 1; and a head unit for discharging the ink.   An ink cartridge comprising an ink tank containing the ink for ink jet recording according to any one of claims 1 to 4, a recording head for ejecting ink, and supplying ink from the ink cartridge to the recording head An image recording apparatus comprising: means for performing the operation. An image recording method for recording an image by causing the ink for inkjet recording according to any one of claims 1 to 4 to fly toward a surface of a recording medium and adhere to the surface.

Images