JP2004352996A - Method for mitigating bleed of color image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for mitigating bleed capable of effectively preventing bleeding from occurring. <P>SOLUTION: The method for mitigating bleed is a method for mitigating bleed between a black image formed with an aqueous black ink for inkjet and a color image formed with an aqueous color ink for inkjet, wherein the method is characterized by using, as the aqueous black ink for inkjet, an ink comprising at least one salt chosen from (M1)<SB>2</SB>SO<SB>4</SB>, CH<SB>3</SB>COO(M1), Ph-COO(M1), (M1)NO<SB>3</SB>, (M1)Cl, (M1)Br, (M1)I, (M1)<SB>2</SB>SO<SB>3</SB>and (M1)<SB>2</SB>CO<SB>3</SB>, and a self-dispersion type carbon black (wherein M1 represents an alkali metal, ammonium or an organic ammonium, and Ph represents a phenyl group). <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 bleed mitigation method.

  Conventionally, as black ink for writing instruments (fountain pens, felt-tip pens, water-based ballpoint pens, etc.) and black ink for inkjet, there has been an ink using carbon black which is a black colorant having a high density of printed matter and excellent in fastness and the like. Proposed.

In particular, in recent years, the composition of the ink and the composition of the ink have been set so that good recording can be performed on plain paper such as copy paper, report paper, notebooks, stationery, bond paper, and continuous slip paper commonly used in offices. Detailed research and development are being conducted from various aspects such as physical properties. For example, Patent Documents 1 and 2 disclose aqueous pigment inks containing carbon black and a dispersant. Patent Document 3 discloses a technical problem that when ink containing carbon black together with a dispersant is used as an ink for an ink jet printer, ejection becomes unstable or a sufficient print density cannot be obtained. An aqueous pigment ink using self-dispersion type carbon black without using a dispersant is disclosed as an ink that can solve the problem.
JP-A-61-283875 JP-A-64-6074 JP-A-8-3498

  The present inventors have conducted various studies on a case where a black ink containing the self-dispersion type carbon black as a black pigment is used for inkjet recording. As a result, they have found that such inks may not always provide sufficient character quality and print density depending on the type of recording medium (for example, paper or the like).

  When a color image is printed using the above-described black ink together with another color ink (for example, at least one selected from magenta, cyan, yellow, red, green, and blue), a black image is printed on the recording medium. At the boundary between the image portion and the color image portion, a phenomenon (hereinafter, referred to as “bleeding”) in which the color blurs or the ink is mixed unevenly and the image quality deteriorates may be observed.

  Regarding such bleeding, there is an idea to improve the permeability of the ink into the recording medium by adding a so-called surfactant (for example, JP-A-55-65269), or a volatile solvent is mainly used as a solvent for the ink. An idea (for example, JP-A-55-66976) has been proposed. However, these prior arts may cause a decrease in image density and a decrease in ejection stability. In view of such prior art, the present inventors have considered that an ink containing self-dispersion type carbon black as a black pigment, when used alone or in combination with other color inks, can be used even when the type of recording medium changes. It has been found that it is necessary to develop a black ink with little change in quality.

  An object of the present invention is to provide a black ink capable of reducing the influence of a recording medium on image quality and stably giving a high quality image.

  An object of the present invention is to provide a black ink which can reduce the influence of a recording medium on image quality, stably provide a high-quality image, and also has excellent inkjet discharge characteristics. is there.

  It is another object of the present invention to provide an ink set that can effectively suppress bleeding. In particular, black ink is often used for outputting characters and the like, and therefore, high OD and sharpness difference of characters are strongly required. Therefore, as described above, in the method of preventing bleeding using ink having high permeability, 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.

  It is another object of the present invention to provide an image forming apparatus, an image forming method, an ink cartridge used for the image forming apparatus, an ink cartridge, and a recording unit capable of reducing the influence of a recording medium on image quality and stably forming a high-quality image. It is in.

Ink as one embodiment of the present _{invention, (M1) 2 SO 4,} CH 3 COO (M1), Ph-COO (M1), (M1) NO 3, (M1) Cl, (M1) Br, It is characterized by containing at least one salt selected from (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and a self-dispersible 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 a highly permeable paper that may impair the image quality, for example, the sharpness of characters or cause a decrease in image density. is there. It is not clear why such an effect can be obtained by this embodiment, but, for example, when the ink is caused to fly on the paper surface by an ink-jet method and adheres, the pigment is stably dispersed in the ink, but the ink adheres to the paper surface. It is considered that the later solid-liquid separation occurs promptly. In other words, if the solid-liquid separation is slow, the ink will diffuse into the paper on paper having high permeability. As a result, the sharpness (character quality) of the characters is impaired, and at the same time, the image density naturally decreases because the ink penetrates deep into the paper. However, since the solid-liquid separation occurs quickly in the ink of the present embodiment, it is considered that the above-described phenomenon is unlikely to occur even on paper having relatively high permeability. In other words, it is considered that factors such as the size of the permeability and the like are less likely to be affected. It is considered that such an effect is best obtained when the salt is 0.05 to 10% by weight based on the total weight of the ink. Further, among the above salts, sulfates (for example, potassium sulfate and the like) and benzoates (for example, ammonium benzoate) have a negligible effect on the characteristics of the ink, for example, the 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) An ink containing a self-dispersible carbon black bonded directly to the black surface or through another atomic group, 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, there is an ink in which the pH of the ink is adjusted to 9 to 12. Such an ink is also suitably used for stably obtaining a high-quality image. That is, it has been found that the pH of the above-mentioned ink is shifted to the acidic direction due to long-term storage, and the ink properties, for example, the viscosity tend to increase with the shift. As a result of further study on this point, when the pH of the ink is adjusted to 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. We have gained new knowledge that it will be negligible. And the above invention is based on such knowledge.

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

  Further, as still another embodiment of the present invention, there is 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 a chemical change and a change in ink jet ejection characteristics when the ink is stored for a long period of time.

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

The ink of another embodiment of the present invention is an ink for forming a print of a predetermined optical density on a recording medium by an ink-jet 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 at least one salt selected from (M1) ₂ CO ₃ and self-dispersing. And carbon black, wherein the concentration of the carbon black is such 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 as one embodiment of the present invention includes 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) 2 SO 3 and (M1 ₂ ) A combination of at least one salt selected from ₂ CO ₃ and an aqueous ink containing self-dispersible 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 by ink containing carbon black and an image formed by ink containing another color material. it can. Although the reason why the above-described effects are obtained by this embodiment is not clear, it is considered that the speed of solid-liquid separation on the recording medium surface is involved.

The ink cartridge 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, M1) An ink tank containing an aqueous ink containing at least one salt selected from I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and a self-dispersible carbon black. I do.

Recording unit as one embodiment of the _{invention, (M1) 2 SO 4,} CH 3 COO (M1), Ph-COO (M1), (M1) NO 3, (M1) Cl, (M1) Br, ( M1) an ink container containing an aqueous inkjet recording ink containing self-dispersible carbon black and at least one salt selected from I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ , and discharging the ink A head portion for causing the head portion to be provided.

The image recording apparatus as 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 provided with an ink tank containing an aqueous inkjet recording ink containing a self-dispersible carbon black and at least one salt selected from the group consisting of: An ink cartridge, a recording head for discharging ink, and a unit for supplying ink from the ink cartridge to the recording head.

An image recording apparatus as 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 section containing an aqueous inkjet recording ink containing at least one salt selected from Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and a self-dispersible carbon black; A recording unit having a head unit for discharging 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. the ink container _{portion, (M1) 2 SO 4,} CH 3 COO (M1), Ph-COO (M1), (M1) NO 3, (M1) Cl, (M1) Br, (M1) I, (M1) Ink containing section containing aqueous inkjet recording ink containing at least one salt selected from ₂ SO ₃ and (M1) ₂ CO ₃ and self-dispersible carbon black, and ink contained in each ink containing section Is provided with a head section for causing each of them to be ejected.

An image recording apparatus according to still another embodiment of the present invention includes an aqueous ink containing at least one color material selected from cyan, magenta, yellow, red, green, and blue color materials. An ink cartridge having an ink containing section, (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , (M1) Cl, (M1) Br, (M1 A) an ink cartridge provided with an ink containing section containing an aqueous inkjet recording ink containing at least one salt selected from I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ and a self-dispersible carbon black; And a head unit for ejecting the ink contained in each of the ink containing units, and each ink from the ink cartridge to each of the ink cartridges. Characterized in that it comprises means for supplying to the de section.

The image recording method 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, an aqueous ink jet recording ink containing self-dispersible carbon black and at least one salt selected from (M1) ₂ SO ₃ and (M1) ₂ CO ₃ , flying toward the surface of the recording medium; An image is recorded by being attached to the surface.

Further, the method of forming a color image according to one embodiment of the present invention is a method for forming a color image including at least one color material selected from cyan, magenta, yellow, red, green, and blue color materials. Is ejected toward the surface of the recording medium and adheres to the surface, and (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) NO ₃ , An aqueous second ink containing self-dispersible carbon black and at least one salt selected from M1) Cl, (M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ is prepared. Discharging to the surface of the recording medium and adhering to the surface.

Further, the method for alleviating bleeding of a color image according to an embodiment of the present invention includes a method of forming 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 of mitigating bleed 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, (M1) 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-dispersible 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) The effect of the recording medium on the image quality can be reduced, and an ink that can stably provide a high-quality image can be obtained.
(2) It is possible to obtain an ink that has a very small change in quality due to a change in pH and maintains characteristics stably.
(3) Even when stored for a long period of time, there is little change in quality, and for example, an ink in which the ink jet ejection characteristics hardly change can be obtained.
(4) It is possible to obtain an ink which is excellent in scratch resistance of a printed matter and hardly depends on the type of the 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 stably form high-quality images by alleviating the influence of the recording medium on image quality.

(First embodiment)
The ink according to one embodiment of the present invention has one of the features in that the ink further includes a salt using carbon black of self-dispersion type as one of coloring materials. These are dispersed and dissolved in, for example, an aqueous medium to form an ink.

(About self-dispersion type carbon black / salt)
Examples of the self-dispersion type carbon black as a coloring material of the ink include a carbon black in which at least one hydrophilic group is bonded to the surface of the carbon black directly or via another atomic group. By using this, it is not necessary to add a dispersant to disperse carbon black as in the related 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, for example, Li, Na, K, Rb, and Cs. Specific examples of the organic ammonium include, for example, methyl ammonium, dimethyl ammonium, trimethyl ammonium, ethyl ammonium, diethyl ammonium, triethyl ammonium, Examples include trimethanol ammonium, dimethanol ammonium, trimethanol ammonium, ethanol ammonium, diethanol ammonium, and triethanol ammonium.

By coexisting the above-described salt in the ink containing the self-dispersible carbon black, 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 of 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 they show a Ka value. An increase in the Ka value indicates that the permeability of the ink to the recording medium has been improved. As a common knowledge of those skilled in the art, the improvement in the permeability of the ink means a decrease in image density. Was.
That is, it has been recognized by those skilled in the art that the image density is reduced as a result of the permeation of the color material into the recording medium along with the permeation of the ink. Comprehensively judging from such various findings on the ink of the present embodiment, the salt in the ink of the present embodiment is separated from the solvent and the solid content in the ink after being applied on the paper (solid-liquid separation). Is caused very quickly. That is, if the solid-liquid separation is slow when the ink is applied to the recording medium, the ink is isotropically diffused into the paper together with the coloring material on the ink having a large Ka value or on the paper having a large ink permeability, As a result, it is expected that the sharpness (character quality) of the character is impaired, and at the same time, the color density penetrates deep into the paper, so that the image density also decreases. However, since such a phenomenon is not observed in the ink of the present embodiment, solid-liquid separation occurs quickly when applied to a recording medium, and as a result, high-quality images are obtained despite an increase in the Ka value of the ink. It is presumed to give. In addition, even if the paper has relatively high permeability, in the case of the ink of the present embodiment, it is considered that the reason why it is difficult to cause a phenomenon such as a decrease in character quality and a decrease in image density is the same. Hereinafter, this point will be further described with reference to FIGS.

  FIGS. 11A to 11C and FIGS. 12A to 12C show a recording medium having high permeability, in which an ink containing a salt and an ink containing no salt are respectively ejected from an orifice by an ink jet recording method. FIG. 4 is an explanatory diagram schematically and conceptually showing a state of solid-liquid separation that occurs when the liquid crystal is applied. That is, immediately after the ink has landed, the pigment ink 1101 or 1201 is on the paper surface regardless of the presence or absence of the salt as shown in FIGS. 11A and 12A for both inks. . After the lapse of the time T1, the pigment ink to which the salt is added quickly undergoes solid-liquid separation as shown in FIG. 11B, and the region 1105 where the solid components in the ink are abundantly contained and the solvent in the ink. Are separated, and the separated permeation tip 1107 of the solvent proceeds into the paper 1103. On the other hand, as shown in FIG. 12 (B), the solid-liquid separation of the pigment ink to which no salt is added does not occur as quickly as the ink to which the salt is added. To penetrate After a lapse of time T2: as shown in FIG. 11C, the pigment ink to which the salt is added further penetrates into the inside of the paper at the penetrating tip 1107 of the solvent, but the region 1105 remains on the surface of the paper and in the vicinity thereof. Will be maintained as is. On the other hand, in the pigment ink to which no salt is added, as shown in FIG. 12 (C), solid-liquid separation starts gradually at this point, and the permeation tip 1207 of the solid content in the ink and the permeation tip 1209 of the solvent are separated. Although there is a difference between them, the solid content region 1211 in the ink has reached the deep portion of the recording medium. The times T1 and T2 in the above description are reference times for conceptually understanding the difference in solid-liquid separation due to the presence or absence of a salt. As is clear from the above description, by adding the salt, the solid-liquid separation occurs quickly, and after landing, the solid-liquid separation occurs at a relatively fast stage, and the liquid permeates into the paper. We speculate that this will produce an effect. That is, it is considered that the addition of the salt makes it difficult for the image quality to be influenced by the degree of permeability of the recording medium. Among the above-mentioned salts, sulfates (for example, potassium sulfate) and benzoates (for example, ammonium benzoate) have good compatibility with self-dispersion type carbon black, and specifically, solid-liquid separation when applied to a recording medium. Because of the particularly excellent effect, it is possible to form an ink jet recorded image of particularly excellent quality on various recording media.

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

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

  The self-dispersion type carbon black is preferably ionic, and for example, anionic or cationic carbon black can be suitably used.

(Anionic charged CB)
Examples of the anionic charged carbon black include carbon black having the following hydrophilic groups 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 -COO (M2) or -SO 3 _(M2) is carbon black was allowed charging ₂ to bind to anionic carbon black surface particularly suitable for the present embodiment because the dispersibility is good in ink It can be used for: Among the hydrophilic groups represented by “M2”, specific examples of the alkali metal include, for example, Li, Na, K, Rb, and Cs, and specific examples of the organic ammonium include, for example, methylammonium and dimethyl. Examples include ammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methanolammonium, dimethanolammonium, and trimethanolammonium. The ink of the present embodiment including the self-dispersion type carbon black in which M2 is ammonium or organic ammonium can further improve the water resistance of a recorded image, and can be particularly preferably used in this regard. It is considered that this is because when the ink is applied on the recording medium, ammonium is decomposed and ammonia evaporates. Here, the self-dispersion type carbon black in which M2 is ammonium is prepared by, for example, replacing the self-dispersion type carbon black in which M2 is an alkali metal with M2 by ammonium using an ion exchange method, or adding an acid to form H-type. A method of adding M2 to ammonium by adding ammonium hydroxide may, for example, be mentioned.

  Examples of a method for producing a self-dispersible carbon black charged anionic include a method of oxidizing carbon black with sodium hypochlorite, and chemically bonding a -COONa group to the carbon black surface by this method. 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 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.

The above cationic group includes, for example, NO ₃ ⁻ and CH ₃ COO ⁻ as counter ions.

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

  A method in which carbon black is treated with 3-amino-N-ethylpyridinium bromide. Since carbon black charged anionic or cationic by the introduction of a hydrophilic group to the surface of carbon black in this way has excellent water dispersibility due to repulsion of ions, it can be contained even in an aqueous ink. A stable dispersion state is maintained without adding a dispersant or the like.

Incidentally, various hydrophilic groups as described above may be directly bonded to the surface of carbon black. Alternatively, another atomic group 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 of the phenylene group and the naphthylene group include a linear or branched alkyl group 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-dispersion type carbon blacks may be used as a color material of an ink appropriately selected. The amount of the self-dispersible carbon black in the ink is preferably 0.1 to 15% by weight, particularly preferably 1 to 10% by weight based on the total weight of the ink. Within this range, the self-dispersion type carbon black can maintain a sufficiently dispersed state in the ink. Further, a dye may be added as a coloring material in addition to the self-dispersion type carbon black for the purpose of adjusting the color tone of the ink.

(Compatibility between self-dispersed 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) _{In the} case of using 2, as described above, ammonium or organic ammonium can be suitably used as M2, but it is preferable that the salt to be combined at this time is the same as M1 and M2. That is, in the process of studying the effect of adding a salt to the ink containing the self-dispersible carbon black, the present inventors made the hydrophilic group M2 (counter ion) and M1 of the self-dispersible carbon black the same. At times, it was found that the stability of the ink was 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-dispersible carbon black and the salt in the ink. It is assumed that the dispersion stability of the self-dispersion type carbon black is stably maintained.

  When both M1 and M2 are ammonium or organic ammonium, the water resistance of the recorded image can be further improved in addition to the effect of stabilizing the ink characteristics. Also, when Ph-COO (NH4) (ammonium benzoate) is used as the salt in the ink at this time, an extremely excellent result can be obtained in terms of the re-ejectability of the ink from the head nozzles after the inkjet recording is temporarily stopped. Can be.

(Aqueous medium)
Examples of the aqueous medium used in the ink according to the present embodiment include, for example, water or a mixed solvent of water and a water-soluble organic solvent. As the water-soluble organic solvent, those having an effect of preventing drying of the ink 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 and tert-butyl alcohol; dimethylformamide, dimethyl Amides such as acetamide; ketones or keto alcohols 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 trimethylolpropane and trimethylolethane; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. Can be The water-soluble organic solvents as described above can be used alone or as a mixture.

  It is desirable to use deionized water as the 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% by weight based on 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 based on the total weight of the ink.

  The ink according to the first aspect described above has an excellent effect that the dependence of print quality on recording medium characteristics can be extremely reduced. And the excellent point of the ink of this embodiment is not only this. That is, for the ink (a) according to the present embodiment and the ink (b) having the same composition except that no salt is contained as a control, a graph plotting the relationship between the pigment density and the optical density of an image using each ink is shown. As shown in FIG. As can be seen from FIG. 13, although the optical densities of the images with any of the inks eventually reach similar values, the ink of this embodiment reaches the saturation value at a lower pigment concentration than the control ink. Obtained knowledge. That is, the addition of the 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 contained as a salt, the optical density of printing on plain paper is reduced to, for example, about 1.4 by setting the concentration of the self-dispersible carbon black to about 4 wt%. The optical density does not change much even if the carbon black concentration is further increased. On the other hand, the ink containing no salt has an optical density of about 1.32 for printing on plain paper when the self-dispersion type carbon black concentration is 4 wt%, and an optical density of 1% when the carbon black concentration is 7 wt%. It is about 0.35, and even when it is 8 wt%, it is about 1.35, which is almost a saturation value. Even if the difference between the saturation values of optical density (1.4 and 1.35) is only 0.05 in numerical value, the difference is clearly recognized visually when comparing each printed matter. Can be done. Such a salt-added ink can provide high optical density printing even at a low carbon black concentration as compared to a salt-free ink, and has a favorable result that the optical density saturation value itself is also high. It is.

  This also has the following advantages. That is, the ink containing the salt has a characteristic that the margin of the carbon black concentration with respect to the optical density of the printed matter is wide as described above. For this reason, 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, the nozzle is up for 6 months), and then printing is performed using the ink tank. When performed, it is possible to extremely effectively prevent a difference in optical density that can be visually confirmed between a printed matter obtained at the beginning of printing and a print obtained immediately before the ink in the ink tank is used up. it can.

  Another advantage of the ink of the first embodiment is that the ink is excellent in intermittent ejection. The intermittent ejection property focuses on a predetermined nozzle of the print head, discharges ink from that nozzle, then leaves it for a predetermined time without performing preliminary ejection of ink or suction of ink in the nozzle, and again from that nozzle This is to evaluate whether or not ink is normally ejected from the beginning of re-ejection when ink is ejected.

(Second embodiment)
As a second embodiment of the ink according to the present invention, there can be mentioned, for example, an embodiment in which a stabilizer is further added to the ink described above as the first embodiment. Here, examples of the stabilizer include a surfactant. Further, as the surfactant, one selected from an anionic surfactant, a nonionic surfactant and a cationic surfactant can be used. 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. And has almost no effect on the ejection characteristics of the ink, and can be obtained by aligning the ink according to the first embodiment, particularly both M1 and M2, with ammonium, for example. It hardly affects 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 salts of naphthalene sulfonic acids (Na, K , Li, Ca etc.), formalin polycondensate, condensate of higher fatty acid and amino acid, dialkyl sulfosuccinate, alkyl sulfosuccinate, naphthenate, etc., alkyl ether carboxylate, acylated peptide, α-olefin sulfone Acid salt, N-acylmethyl taurine, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglycol sulfate, alkyl ether phosphate, alkyl phosphate Salts and the like.

(Cationic surfactant)
Examples of the cationic surfactant include an aliphatic amine, a quaternary ammonium salt, a sulfonium salt, a phosphonium salt and the like.

(Nonionic surfactant)
Nonionic surfactants include, for example, fluorine-based, silicon-based, acrylic acid copolymer, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene sterol ether, polyoxyethylene Lanolin derivatives, ethylene oxide derivatives of alkylphenol formalin condensates, polyoxyethylene polyoxypropylene block polymers, aliphatic ester types of polyoxyethylene polyoxypropylene alkyl ether polyoxyethylene compounds, polyethylene oxide condensed polyethylene glycol fatty acid esters, fatty acid monoglycerides , Polyglycerin fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alcohol Noruamido, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines and alkylamine oxides. Among the various surfactants described above, those having an ionic group are preferably used. In addition, it is preferable to use an anion or a nonionic type of those surfactants having an anionic hydrophilic group on the surface of carbon, and a cation or a nonionic type of a surfactant having a cationic hydrophilic group on the surface of carbon.

(About dodecylbenzene sulfonate)
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, ammonium or organic ammonium.) An ink charged with an anionic property by introducing a hydrophilic group, and further, an ink further containing a salt, When dodecylbenzenesulfonate (a sodium salt, a potassium salt, an ammonium salt, etc.) is added as a surfactant, surprisingly, the change in the ink characteristics accompanying the pH change of the ink can be extremely moderated. That is, FIG. 10 (a) shows a schematic relationship of the change in the viscosity of the ink accompanying the pH change of the ink in which the self-dispersible carbon black charged to the anionic property and the salt included in the first embodiment coexist with the salt. ). As described above, the ink according to the first embodiment tends to have a relatively large change in the ink characteristics with respect to the pH change. However, when dodecylbenzenesulfonate is added to such an ink, the change in the ink characteristics with respect to the pH change can be made very gentle 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, there may be mentioned an ink according to the first or second embodiment, wherein the pH of the ink is adjusted to 9 to 12, particularly 9 to 11. That is, the knowledge that the ink according to the first embodiment of the present invention has a slightly large variation in the ink characteristics with respect to the pH change, and that the pH may slightly change in the direction of decreasing the pH when the ink is stored for a long period of time. Is obtained by the present inventors as described above. However, if the pH of the ink is within the above-mentioned range, the variation with time of the ink characteristics is almost negligible.

  The pH of the ink described in the first and second embodiments is usually about 7 to 8 when not particularly adjusted. The pH of such an ink can be adjusted to a desired pH using, for example, a hydroxide, specifically, potassium hydroxide, aqueous ammonia, lithium hydroxide, or the like. By the way, when the ink is stored for a long period of time, although the pH varies depending on the composition and storage conditions of the ink, the pH may be changed by about 1 or specifically, may be lowered. In order to keep it, it is preferable to adjust the initial pH of the ink slightly higher, for example, in the range of pH 9 to 12.

  Here, the ink according to the second embodiment, that is, the ink containing dodecylbenzenesulfonate as a stabilizing agent whose pH is adjusted within the above-mentioned range, is preferably used particularly as an ink for inkjet recording. Can be. This is because the change in the ink characteristics becomes even smaller within the above-mentioned pH range due to the effect of reducing the fluctuation in the ink characteristics with respect to the fluctuation in the pH of the ink obtained by including the dodecylbenzenesulfonate. Also, dodecylbenzenesulfonate may be added so as to suppress the fluctuation of the ink characteristics within the above-mentioned pH range, so that the effect of suppressing the addition amount of dodecylbenzenesulfonate is also exhibited.

(Fourth embodiment)
As an ink according to the fourth embodiment of the present invention, an ink obtained by adding an antioxidant to any of the inks according to the first to third embodiments can be exemplified. 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-naphtholtannic acid, catechol, o-phenylenediamine, oxalic acid, and the like. From this, one or more compounds are added to the ink. Good.

  Although the action when these compounds are added to the ink is not clear, for example, the oxidization of a water-soluble organic solvent (eg, ethylene glycol or the like) over time may affect the dispersion state of the pigment. Since the compound can effectively prevent the oxidation of the above 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% by weight, particularly 0.1 to 2% by weight based on the total weight of the ink, the storage stability is improved without substantially changing the ink characteristics. It is possible to achieve.

(Fifth embodiment)
As the ink according to the fifth embodiment of the present invention, there may be mentioned 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 abrasion resistance of the image after the image is recorded by attaching the ink to the surface of the recording medium.

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

  The weight average molecular weight of the water-soluble polymer compound used here is preferably, for example, about 1,000 to 5,000, and the content of these water-soluble polymer compounds is, for example, 0.02 to 2 wt. %, Particularly preferably 0.05 to 1 wt%. That is, when the molecular weight of the water-soluble polymer compound or the content in the ink is in such a range, the effect of the water-soluble polymer compound (improvement of abrasion resistance of a recorded image, etc.) is ensured while the water-soluble polymer compound is maintained. A change in ink viscosity and a change in ink ejection characteristics due to the addition of the compound can be suppressed to a substantially negligible level.

(Ink properties; inkjet ejection properties, permeability to recording media)
The ink according to each of the above embodiments can be used for writing implement ink and ink jet recording ink. Ink jet recording methods include a recording method in which mechanical energy is applied to ink to discharge droplets, and a recording method in which thermal energy is applied to ink to discharge droplets by bubbling 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 ink jet recording, it is preferable that the ink has characteristics capable of being ejected from an ink jet head. From the viewpoint of the ejection property from the inkjet head, the properties of the liquid include, for example, a viscosity of 1 to 15 cps and 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

As a measure of the permeability of the ink into the recording medium, there is a Ka value obtained by the Bristow method. That is, when the ink permeability is represented by the ink amount V per m ² , the ink penetrates into the recording medium V (ml / m ² = μm) after a predetermined time t has elapsed from the ejection of the ink droplet. Is represented by Bristow's equation shown below.
V = Vr + Ka (t-tw) ^1/2
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 (a portion of the surface of the recording medium having a roughness), and almost penetrates into the inside of the recording medium. Not. The time during that time is the contact time (tw), and the amount of ink absorbed by the concave and convex portions of the recording medium during the contact time is Vr. If the contact time exceeds the contact time after the ink is attached, the amount of permeation into the recording medium increases by the time exceeding the contact time, that is, by an amount proportional to a half power of (t-tw). Ka is a proportional coefficient of this increase, and shows a value corresponding to the permeation rate. The Ka value can be measured using a liquid dynamic permeability tester (for example, trade name: Dynamic Permeability Tester S; manufactured by Toyo Seiki Seisakusho, etc.) by the Bristow method. In the ink according to each of the embodiments of the present invention described above, it is preferable that the Ka value is less than 1.5 in order to further improve the quality of a recorded image, and more preferably, 0.2 to less than 1.5. is there. For example, as described above, the ink including the self-dispersion type carbon black and the salt according to the first embodiment promotes solid-liquid separation on a recording medium and greatly contributes to improvement of image quality. If the Ka value is less than 1.5, the solid-liquid separation occurs at an earlier stage in the process of penetrating the ink into the recording medium. It is believed 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 a value of PB used for plain paper (for example, a copier or page printer (laser beam printer) using an electrophotographic method, or a printer using an ink jet recording method, manufactured by Canon Inc.). This is a value measured using a recording medium such as paper or PPC paper which is a paper for a copying machine using an electrophotographic method. 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 preferred aqueous medium composition capable of carrying the above-described properties in the ink according to each of the above embodiments includes, for example, glycerin, trimethylolpropane, thiodiglycol, ethylene glycol, diethylene glycol, isopropyl alcohol, and acetylene alcohol. Is preferred. The acetylene alcohol includes, for example, 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 appropriately adding a predetermined amount of a surfactant such as acetylenol or a permeable solvent.

  In addition to the above components, a surfactant, an antifoaming agent, an antiseptic, an antifungal agent, etc. can be added in order to obtain an ink having desired physical properties as required. Sex dyes and the like may be added.

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

  FIGS. 1 and 2 show examples of the configuration of a head, which is a main part of an ink jet recording apparatus that uses thermal energy for discharging ink.

  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 to 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, or the like, electrodes 17-1, 17-2 formed of aluminum, gold, an aluminum-copper alloy, or the like, HfB2, TaN, TaAl, or the like. A heat-resisting layer 18 formed of a material having a high melting point, a heat storage layer 19 formed of thermally oxidized silicon, aluminum oxide, or the like, and a substrate 20 formed of a material having good heat dissipation properties such as silicon, aluminum, or aluminum nitride. ing.

  When a pulse-like electric signal is applied to the electrodes 17-1 and 17-2 of the head, a 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 by the generated pressure, and the 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 many heads shown in FIG. 1 are arranged. This multi-head is formed by bonding a glass plate 27 having a multi-nozzle 26 and a heating head 28 similar to that described with reference to 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 arranged at a position adjacent to a recording area of the recording head 65, and in this example, is held in a form protruding into the movement path of the recording head 65.

  A cap 62 is provided at a home position adjacent to the blade 61 and moves in a direction perpendicular to the moving direction of the recording head 65 so as to abut on the ink outlet face to perform capping. It has a configuration to perform. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61, and is held in a form protruding into the movement path of the recording head 65, similarly to the blade 61. The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery section 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the ejection port surface.

  Reference numeral 65 denotes a recording head which has ejection energy generating means and performs recording by discharging ink on a recording material opposed to a discharge port surface provided with discharge ports, and 66 denotes a recording head 65 on which the recording head 65 is mounted. This is a carriage for performing movement. The carriage 66 is slidably connected to a guide shaft 67, and a part of the carriage 66 is connected to a belt 69 driven by a motor 68 (not shown). As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and the adjacent area. Reference numeral 51 denotes a paper feed unit for inserting a recording material, and reference numeral 52 denotes a paper feed roller driven by a motor (not shown).

  With such a configuration, the recording material is fed to a position facing the discharge port surface 65 of the recording head, and is discharged to a discharge section provided with a discharge roller 53 as recording proceeds. 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 openings of the recording head 65 are wiped. When capping is performed with the cap 62 in contact with the ejection surface of the recording head 65, the cap 62 moves so as to protrude into the movement 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 the position at the time of the wiping described above. As a result, the ejection port surface of the recording head 65 is also wiped during this movement.

  The above-described movement of the print head to the home position is performed not only at the end of printing and at the time of ejection recovery, but also at a predetermined interval while the print head moves through the printing area for printing to the home position adjacent to the printing area. Then, the wiping is performed along with this movement.

(ink cartridge)
FIG. 5 is a diagram illustrating an example of an ink cartridge 45 that stores ink supplied to a recording head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink storage unit storing the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the end 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 the waste ink. It is preferable that the ink container has a surface in contact with the ink 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, but is also suitably used in an integrated one as shown in FIG. Can be In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage unit storing ink, for example, an ink absorber is stored, and the ink in the ink absorber is transferred from a head unit 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.

  Further, a structure may be used in which the ink storage unit is an ink bag in which a spring or the like is provided inside without using an ink absorber. Reference numeral 72 denotes an air communication port for connecting the inside of the cartridge to the atmosphere. This 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 an 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 to face the nozzles, An on-demand inkjet recording head that includes ink filling around 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 given. 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 discharging ink droplets of a desired volume, a vibrating plate 82 for directly applying pressure to ink, and a vibrating plate 82 And a substrate 84 for supporting and fixing an orifice plate 81, a vibration plate, and the like.

  In FIG. 7, an ink channel 80 is formed of a photosensitive resin or the like, an orifice plate 81 is formed with a discharge port 85 by drilling a metal such as stainless steel or nickel by electroforming or pressing, and a diaphragm 82 is formed. The piezoelectric element 83 is formed of a metal film such as stainless steel, nickel, titanium and the like and a high elastic resin film, and the piezoelectric element 83 is formed of a dielectric material such as barium titanate and PZT. The recording head having the above-described configuration applies a pulse-like voltage to the piezoelectric element 83 to generate a strain stress, and the energy of the energy deforms the diaphragm joined to the piezoelectric element 83, causing the ink in the ink flow path 80 to deform. Is pressed vertically, and an ink droplet (not shown) is ejected from the ejection port 85 of the orifice plate to perform printing. 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 may be performed in the same manner as described above.

(Ink set)
The inks according to the first to fifth embodiments constitute a black ink. The ink includes a color ink including a color material for yellow, a color ink including a color material for magenta, and a color ink including a color material for cyan. Color by combining with at least one color ink selected from a color ink containing a color material, a color ink containing a red color material, a color ink containing a blue color material, and a color ink containing a green color material An ink set that can be suitably used for forming an image can be provided. When printing is performed so as to be adjacent to a black image portion and a color image portion using such an ink set, occurrence of bleeding can be extremely effectively suppressed. It is not clear why such an ink set can effectively suppress bleeding.However, as a result of coexistence of the self-dispersible carbon black and the salt in the black ink, the ink after the black ink adheres to the recording medium is used. It is considered that as a result of the solid-liquid separation and the subsequent solidification of the coloring material occurring promptly, the black ink is less likely to bleed to the color ink side at the boundary of the color image.

(About color ink)
Here, a known dye or pigment can be used as a color material of the color ink that can be used in the ink set. As the dye, for example, an acid dye or a direct dye can be used. For example, as the anionic dye, any of the existing dyes or newly synthesized ones can be used as long as they have an appropriate color tone and density, or any of these can be used as a mixture. It is also possible. Specific examples of the anionic dye are described below.

(Color 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
(Color 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
(Color 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
(Color 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 a color ink as described above include water or a mixed solvent of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include the same ones as described in the first embodiment. When the color ink is applied to a recording medium by an ink jet method (for example, a 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 to have.

(Color material content)
Here, the content of the coloring material in each color ink, for example, when used for inkjet recording, the ink may have excellent inkjet ejection characteristics, and may be appropriately selected so as to have a desired color tone and density, As a guide, for example, a range of 3 to 50% by weight based on 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% by weight based on the total weight of the ink.

(Permeability of color ink)
With respect to the above-described color ink, it is preferable to use an ink having a Ka value of, for example, 5 or more because a high-quality color image can be formed on a recording medium. That is, since the ink having such a Ka value has a high permeability to the recording medium, even if images of at least two colors selected from, for example, yellow, magenta and cyan are to be recorded adjacent to each other, the distance between the adjacent images is low. Bleeding of colors can be suppressed, and even when these inks are overprinted to form a secondary color image, the permeability of each ink is high. Bleeding can be effectively suppressed. As a method for adjusting the Ka value of the color ink to such a value, a conventionally known method such as addition of a surfactant and addition of a penetrating solvent such as glycol ether can be applied. Of course, the addition amount can be appropriately selected. Just fine.

(Recording device and recording method using ink set)
Next, when a color image is printed using the above-described ink set, for example, a printing apparatus in which four print heads shown in FIG. 3 are arranged on a carriage can be used. FIG. 9 shows an embodiment of the present invention. Reference numerals 91, 92, 93 and 94 denote recording units for discharging black, cyan, magenta and yellow inks, respectively. The recording unit is disposed on the carriage of the above-described recording apparatus, and discharges 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. There is also a mode in which recording is performed by attaching to a recording head 95 having ink channels separated so that the supplied inks of the respective colors can be ejected individually.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples as long as the gist is not exceeded. In the following description, parts and percentages are by weight unless otherwise specified.

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

Pigment dispersion 1
After thoroughly mixing 10 g of carbon black having a surface area of 230 m ² / g and a DBP oil absorption of 70 ml / 100 g with 3.41 g of p-amino-N-benzoic acid in 72 g of water, 1.62 g of nitric acid was added dropwise thereto. And stirred at 70 ° C. After a few more minutes, a solution of 1.07 g of sodium nitrite dissolved in 5 g of water was added, and the mixture was further stirred for 1 hour. The obtained slurry was filtered through filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis Co., Ltd.), and the filtered pigment particles were sufficiently washed with water, dried in a 90 ° C. oven, and further added to the pigment with water. Was added to prepare a pigment aqueous solution having a pigment concentration of 10% by weight. By the above method, a group represented by the following chemical formula was introduced into 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 to the mixture while stirring was constantly maintained at 10 ° C. or lower by an ice bath. After stirring for further 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 was filtered with filter paper (trade name: Toyo Filter Paper No. 2; manufactured by Advantis Co., Ltd.), and the pigment particles filtered were thoroughly washed with water, dried in an oven at 110 ° C., and water was added to the pigment. Thus, an aqueous pigment solution having a pigment concentration of 10% by weight was prepared. According to the above method, a group represented by the following chemical formula was introduced into the surface of carbon black.

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

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

  300 g of acidic carbon black (trade name: MA-77 (pH 3.0); manufactured by Mitsubishi Kasei Co., Ltd.) is thoroughly mixed with 1000 ml of water, and 450 g of sodium hypochlorite (effective chlorine concentration 12%) is added thereto. The mixture 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 electric conductivity was 0.2 μs. Further, this pigment dispersion (pH = 8 to 10) was concentrated until the pigment concentration became 10% by weight to obtain carbon black having a surface-introduced -COONa group.

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

(Black ink 1)
The following components were mixed, sufficiently stirred and dissolved, and then subjected to pressure filtration with a micro filter having a pore size of 3 μm (manufactured by Fuji Film) to prepare a black ink.
Pigment dispersion 1: 30 parts Potassium sulfate: 1 part Trimethylolpropane: 6 parts Glycerin: 6 parts Diethylene glycol: 6 parts Acetylene glycol ethylene oxide adduct: 0.2 part (trade name: acetylenol EH; (Kawaken Fine Chemical Co., Ltd.)
・ Water: 50.8 parts (black ink 2)
A black ink was prepared in the same manner as in 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 in 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 part (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 filtered under pressure through a micro filter (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.

  An ink jet recording apparatus having an on-demand type multi-recording head that discharges ink by applying thermal energy according to a recording signal to each of the above black inks 1 to 4 (trade name: BJC-4000; Canon ( The following evaluation was carried out using the following method. The results are shown in Table 2 below.

1) Character quality The above inks are printed on the following five types of plain paper for copying A, B, C, D, and E using the above-described ink jet recording apparatus and having different ink permeability. Was evaluated according to the following criteria.
A: PSK paper NSK manufactured by Canon Inc.
B: PPC paper NDK manufactured by Canon Inc.
C: PPC paper 4024 manufactured by Xerox Corporation
D: PPC paper prober bond manufactured by Fox River Co. E: PPC paper for Canon manufactured by Noizidora Co .;
Δ: Some blurred paper is observed.
×: Bleed on all five papers.

2) Print density The above inks were printed on plain paper for copying A, B, C, D and E using the above-mentioned ink jet recording apparatus, and the print density at that time was measured using a Macbeth print density meter. The evaluation was based on the following criteria.
；: The difference between the print densities of the plain papers A, B, C, D, and E for copying is maximum and minimum and less than 0.1.
×: The difference between the print densities of the plain papers A, B, C, D, and E for copying is 0.1 or more at the maximum and minimum.

3) Water resistance Each of the above inks is printed on each of the plain papers A, B, C, D, and E for copying in the same manner as in 1) above using the ink jet recording apparatus, and after a predetermined time has elapsed from the printing. Then, the printed recording medium was immersed in running water to visually observe the state of background staining, and the results were evaluated according to the following criteria.
：: The background stain becomes inconspicuous within 1 hour after printing for all of the plain papers A, B, C, D and E for copying.
：: Background dirt is not noticeable within one day after printing on all of the plain papers A, B, C, D and E for copying.
X: There is paper with conspicuous background stain even after one day or more from printing.

4) Intermittent ejection property Each ink is printed with a vertical line on plain paper for copying A using the above-mentioned ink jet recording apparatus, and then the vertical line is again formed after 30 seconds without performing preliminary ejection and suction of the ink from the nozzle. After printing, the difference between the two obtained vertical lines was determined based on the following criteria.
：: The difference between the two is not apparent even when viewed with a loupe.
：: The difference between the two is not visible.
Δ: Although the difference between the two can be seen visually, there is no problem in practical use.

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

  Further, the black ink 3 in which the counter ion of the hydrophilic group of the self-dispersion type carbon black was an ammonium salt and ammonium benzoate was used as the salt in the ink showed 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.
-3:30 parts of the pigment dispersion prepared in Experimental Example I- (1) above-0.15 part of acetylene glycol ethylene oxide adduct (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-hydroethoxyethyl) urea: 0.5
-Ion-exchanged water: 72.5 parts-Diethylene glycol: 5 parts Then, 14 parts of carbon black (trade name: Color Black (Color Black) S170; manufactured by Texa) and 5 parts of isopropyl alcohol are added to the above mixture, and the mixture is pre-pressed for 30 minutes. After mixing, dispersion treatment was performed under the following conditions.
Dispersing machine Sand grinder (Igarashi Kikai Co., Ltd.)
Grinding media Filling rate of 1mm diameter zirconium bead grinding media 50% (volume)
Pulverization time: 3 hours After the dispersion treatment, a centrifugal separation treatment (12000 rpm, 20 minutes) was further performed to remove coarse particles to obtain a pigment dispersion 5.

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, and then pressure-filtered with a micro filter having a pore size of 3.0 μm (manufactured by Fuji Film) to prepare Yellow Ink 1.
Acetylene glycol ethylene oxide adduct: 1 part (trade name: acetylenol EH manufactured by Kawaken Fine Chemical Co., Ltd.)
・ Diethylene glycol: 10 parts ・ Glycerin: 5 parts ・ CI Direct Yellow 86: 3 parts ・ Water: 81 parts (Magenta Ink 1)
A magenta ink 1 was prepared in the same manner as the 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 in 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.)
・ Diethylene glycol: 35 parts ・ CI Acid Blue 9: 3 parts ・ Water: 61 parts
An ink set was prepared by combining the inks prepared above in the following manner.
・ 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 in the following manner.
・ 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 in the following manner.
・ 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 in the following manner.
・ 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 in the following manner.
・ 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.

  Using 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 for discharging ink by applying thermal energy according to a recording signal to the ink (product Using BJC4000 (manufactured by Canon Inc.), recording was performed on the same five types of plain paper for copying A to E as described above. This recording result was evaluated as follows. The results are shown in Table 4 below.

1) Bleeding The printed image is a black printed area, which is obtained by partitioning a 10 cm square into 5 x 5 squares (the size of one square: 2 cm x 2 cm) and alternately printing solid with black ink and each color ink. The bleeding at the boundary between the image and the color printing portion was evaluated according to the following criteria.
：: The boundary between the two colors is clear, and no bleeding or color mixing is observed at the boundary.
Δ: It is clear that there is a boundary between the two colors, but some paper shows some bleeding and color mixing at the boundary.
X: Borderline between two colors cannot be identified.

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

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

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

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

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 subjected to pressure filtration with a micro filter having a pore size of 3 μm (manufactured by Fuji Film) to prepare a black ink.
-Pigment dispersion 1: 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 in the above 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: Acetyleneol EH; manufactured by Kawaken Fine Chemical 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 in the above black ink 8 using the following components.
-Pigment dispersion 2: 30 parts-Ammonium sulfate: 2 parts-Sodium dodecylbenzenesulfonate: 0.1 parts-Trimethylolpropane: 6 parts-Sodium tetradecyl sulfate: 0.1 parts-Glycerin: 6 parts-Thiodiglycol: 6 parts, water: 49.8 parts (black ink 11)
A black ink was prepared in the same manner as in the above 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; manufactured by Kawaken Fine Chemical Co., Ltd.)
Glycerin: 5 parts Ethylene glycol: 5 parts Water: 52.7 parts The main characteristics of the above 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 Shot Co., Ltd.) were prepared, and 100 ml of each of the black inks 8 to 11 was placed in each of them, and left at 60 ° C. for one month. Observed. The results are shown in Table 6 below. The evaluation criteria are as follows.
：: There is almost no change in ink viscosity before and after standing.
×: Changes in ink viscosity before and after standing are observed.

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

(Cyan ink 1)
A cyan ink 1 prepared in the same manner as the 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
With respect to the ink sets of Examples 4 to 7, bleeding was evaluated 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)
After mixing and dissolving the following components with sufficient stirring, the pH was adjusted to 10.5 with potassium hydroxide. Thereafter, the solution was filtered under pressure through a micro filter (manufactured by Fuji Film) having a pore size of 3 μm to prepare a black ink.
-30 parts of the pigment dispersion prepared in Experimental Example I- (1)-1 part of potassium sulfate-6 parts of trimethylolpropane-6 parts of glycerin-6 parts of diethylene glycol-6 parts of 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.
-2:30 parts of the pigment dispersion prepared in Experimental Example I- (1)-0.5 parts of potassium chloride-6 parts of trimethylolpropane-0.15 parts of acetylene glycol ethylene oxide adduct (trade name: acetylenol) EH; manufactured by 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.
2:30 parts of the pigment dispersion prepared in Experimental Example I- (1) Ammonium sulfate: 2 parts Trimethylolpropane: 6 parts Sodium tetradecyl sulfate: 0.1 part 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.
3:30 parts of pigment dispersion prepared in Experimental Example I- (1) 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 Shot Co., Ltd.) were prepared, and 100 ml of each of the black inks 11 to 13 was placed in each of the four containers, and the presence or absence of a change in ink viscosity before and after standing was observed. The results are shown in Table 9 below. The evaluation criteria are as follows.
：: There is almost no change in ink viscosity before and after standing.
X: The change in ink viscosity before and after standing is large.

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, the pH was adjusted to 11 with potassium hydroxide, and the mixture was filtered under pressure with a micro filter having a pore size of 3 μm (manufactured by Fuji Film) to prepare a black ink.
-5:30 parts of the pigment dispersion of Experimental Example I- (2)-0.15 parts of acetylene glycol ethylene oxide adduct (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)
Magenta ink 1 prepared in the same manner as magenta ink 1 of Experimental Example I- (2) was prepared.

(Cyan ink 1)
A cyan ink 1 prepared in the same manner as the 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
The main characteristics of the black inks constituting the ink sets of Examples 8 to 11 and Comparative Example 3 are shown in Table 10 below.

  The bleeding of the ink sets of Examples 8 to 11 and Comparative Example 3 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)
Using the following components, a black ink was prepared according to a method similar to that of the previously prepared black ink.
-30 parts of the pigment dispersion of Experimental Example I- (1)-1 part of potassium sulfate-0.3 parts of sodium sulfite-6 parts of trimethylolpropane-6 parts of glycerin-6 parts of diethylene glycol: 6 parts of acetylene glycol Ethylene oxide adduct: 0.2 part (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
・ Water: 50.5 parts (black ink 18)
Using the following components, a black ink was prepared according to a method similar to that of 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 Parts: acetylene glycol ethylene oxide adduct: 0.15 parts (trade name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
・ Water: 53.2 parts (black ink 19)
Using the following components, a black ink was prepared according to a method similar to that of 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)
Using the following components, a black ink was prepared according to a method similar to that of the previously prepared black ink.
-Pigment dispersion 3 of Experimental Example I- (1): 3:30 parts-Ammonium benzoate: 1 part-Sodium ascorbate: 0.15 parts-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)
Magenta ink 1 prepared in the same manner as magenta ink 1 of Experimental Example I- (2) was prepared.

(Cyan ink 1)
A cyan ink 1 prepared in the same manner as the 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)
Using the following components, a black ink was prepared according to a method similar to that of the previously prepared black ink.
-30 parts of the pigment dispersion of Experimental Example I- (1)-1 part of potassium sulfate-6 parts of trimethylolpropane-6 parts of glycerin-6 parts-6 parts of diethylene glycol-0.2 parts of acetylene glycol ethylene oxide adduct (Product name: acetylenol EH; manufactured by Kawaken Fine Chemical Co., Ltd.)
-Sodium alginate: 0.1 part-Water: 50.7 parts (black ink 22)
Using the following components, a black ink was prepared according to a method similar to that of 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)
Using the following components, a black ink was prepared according to a method similar to that of the previously prepared black ink.
3:30 parts of the pigment dispersion of Experimental Example I- (1) 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)
Using the following components, a black ink was prepared according to a method similar to that of the previously prepared black ink.
-6:30 parts of the pigment dispersion of Experimental Example I- (2)-2 parts of ammonium sulfate-6 parts of trimethylolpropane-0.1 part of sodium alginate-6 parts of glycerin-6 parts of thiodiglycol-6 parts of water : 49.9 parts The main characteristics of the black inks 21 to 24 thus obtained are shown in Table 15 below.

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

1) Character quality The above inks were printed on the five types of plain paper for copying A, B, C, D and E using the above-mentioned ink jet recording apparatus, and the bleeding of the characters was evaluated according to the following criteria. .
；: Almost no bleeding on all five papers.
Δ: Some blurred paper is observed.
×: Bleed on all five papers.

2) Print density The above inks were printed on the five types of plain paper for copying A, B, C, D, and E using the ink jet recording apparatus, and the print density at that time was measured using a Macbeth print density meter. It was measured and evaluated according to the following criteria.
；: The difference between the print densities of the plain papers A, B, C, D, and E for copying is maximum and minimum and less than 0.1.
×: The difference between the print densities of the plain papers A, B, C, D, and E for copying is 0.1 or more at the maximum and minimum.

3) Scratch resistance After printing each of the above inks on the above five types of plain paper for copying A, B, C, D, and E using the above-mentioned ink jet recording apparatus and leaving it to stand for one day, a weight having a load of 40 g / cm2 was applied. A rubbing test was carried out using the same and evaluated according to the following criteria.
：: Dirt is not noticeable on all papers.
Δ: Soil is noticeable on some papers.
X: Stain is conspicuous on all papers.

4) Water resistance The above inks were printed on the five types of plain paper for copying A, B, C, D, and E in the same manner as in 1) above using the ink jet recording apparatus, and a predetermined time elapsed from printing. After that, the printed recording medium was immersed in running water, and the state of background contamination was visually observed, and the results were evaluated according to the following criteria.
A: The background stain becomes inconspicuous within 1 hour after printing for all of the plain papers A, B, C, D and E for copying.
：: Background dirt is not noticeable within one day after printing on all of the plain papers A, B, C, D and E for copying.
X: There is paper with conspicuous background stain even after one day or more from 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)
Using the following components, a black ink was prepared according to a method similar to that of 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) was used (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.

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

FIG. 2 is a longitudinal sectional view showing one embodiment of a head of the ink jet recording apparatus. FIG. 2 is a sectional view taken along line AB in FIG. 1. FIG. 3 is a schematic explanatory diagram of a multi-head. FIG. 1 is a schematic perspective view illustrating one embodiment of an ink jet recording apparatus. FIG. 3 is a longitudinal sectional view illustrating one embodiment of an ink cartridge. FIG. 3 is a perspective view illustrating an example of a recording unit. FIG. 7 is a schematic perspective view illustrating another example of the configuration of the inkjet recording head. FIG. 4 is a schematic explanatory view of a recording head to which four ink cartridges are attached. FIG. 3 is a schematic explanatory diagram illustrating a configuration in which four recording heads are arranged on a carriage. FIG. 3 is a schematic diagram illustrating a correlation between pH and viscosity of an ink according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a process of solid-liquid separation when a pigment ink containing a salt is applied to a recording medium. FIG. 3 is a schematic diagram illustrating a process of solid-liquid separation when a pigment ink containing no salt is applied to a recording medium. 4 is a graph showing a relationship between a pigment concentration in an ink and an optical density of printing by each ink in an ink containing a salt and an ink containing no salt.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 13 Head 14 Ink groove 15 Heating 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 feeder 52 Paper feed roller 53 Paper discharge roller 61 Blade 62 Cap 63 Ink absorber 64 Discharge recovery unit 65 Recording head 66 Carriage 67 Guide shaft 68 Motor 69 Belt 70 Recording unit 71 head part 72 atmosphere communication port 80 ink flow path 81 orifice plate 82 diaphragm 83 piezoelectric element 84 substrate 85 discharge port 86, 87, 88, 89 ink cartridge 90, 91, 92, 93 recording unit 1101 salt Ink containing 1103, 1203 recording medium

Claims (13)

Adjacent to each other on the recording medium, a method for alleviating bleed between a black image formed with the aqueous inkjet black ink and a color image formed with the aqueous inkjet color ink,
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, (M1) A bleed mitigation method characterized by using an ink containing at least one salt selected from M1) ₂ SO ₃ and (M1) ₂ CO ₃ and a self-dispersion type carbon black (where M1 is an alkali metal, ammonium or Represents an organic ammonium, and Ph represents a phenyl group). Bleed alleviating method of claim 1 wherein the salt is _(M1) 2 SO _4, or Ph-COO (M1).   The bleed mitigation method according to claim 1, wherein the salt is contained in an amount of 0.05 to 10 wt% or less based on the total weight of the ink.   The bleed mitigation method according to claim 3, wherein the salt is contained in an amount of 0.1 to 5 wt% based on the total weight of the ink.   The bleed mitigation method according to any one of claims 1 to 4, wherein the carbon black has at least one hydrophilic group bonded to the surface thereof directly or via another atomic group. The bleed mitigation method according to claim 5, wherein the hydrophilic group is at least one selected from the following group.
_{-COO (M2), - SO 3} (M2) 2, -PO 3 H (M2), - PO 3 (M2) 2,

(Wherein M2 represents a hydrogen atom, an alkali metal, ammonium or organic ammonium, and R represents an alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted naphthyl group. )   The bleed mitigation method according to claim 5 or 6, wherein the other atomic group is an alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, or a substituted or unsubstituted naphthylene group. Hydrophilic group _{-COO (M2), - SO 3} (M2) 2, is at least one selected from -PO 3 H (M2) and _-PO 3 _{(M2) 2,} and, the M2 is the M1 The bleed mitigation method according to any one of claims 5 to 7, which is the same as described above.   9. The bleed mitigation method according to claim 5, wherein M2 is ammonium or organic ammonium.   The bleed mitigation method according to any one of claims 1 to 9, wherein the pH of the ink is 9 to 12.   The bleed mitigation method according to claim 10, wherein the pH of the ink is 9 to 11.   The bleed mitigation method according to any one of claims 1 to 11, wherein a Ka value of the ink by a Bristow method is less than 1.5. The bleed mitigation method according to claim 12, wherein a Ka value of the ink by a Bristow method is 0.2 or more and less than 1.5.

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