JP2006037010A - Inkjet ink, method for inkjet recording using the same and inkjet recorded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a black inkjet ink improved in weatherability and optical density, a method for inkjet recording using the same and an inkjet recorded product. <P>SOLUTION: In the black inkjet ink used for recording on a recording medium having a porous member for accepting the ink on a substrate and 3.0-5.0 surface pH, the ink contains at least a dye having a carboxy group and a dye solely having a sulfone group as an acidic solubilizing group except a hydroxy group and has a pH higher than that of the recording medium. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inkjet ink, an inkjet recording method using the same, and an inkjet recording.

  The ink jet recording method is a method in which micro droplets of ink are ejected by various operating principles and adhered to a recording medium such as paper to record images, characters and the like. In recent years, it has rapidly become widespread in various applications including information equipment as a recording apparatus for various images. Furthermore, images formed by the multi-color ink jet method can obtain a recording that is comparable to multi-color printing by the plate-making method and printing by the color photographic method. Since it is cheaper than multi-color printing or printing, it is being widely applied to the field of full-color image recording.

  In recent years, a recording medium using a porous material such as alumina or silica as an ink receiving material has been used as an ink jet recording medium in order to obtain an image quality comparable to or exceeding that of a silver salt photograph.

  In particular, a recording medium using alumina hydrate has a positive charge, so when an anionic ink dye is used as a color material, fixing is good and an image with good color development is obtained. In particular, it has advantages such as being preferable to conventional recording media in terms of image quality and gloss in a full-color image.

  In addition to the reliability of ink used in the ink jet recording method, the recorded matter gives sufficient optical density (OD), the drying property is good, the recorded image does not bleed, the water Further, it is required that the recorded image does not flow out even when contacted with alcohol or the like, and that the recorded image has good weather resistance. In particular, it is strongly required that the recorded images have good weather resistance. Weather resistance means that the color of the thigh is not caused by sunlight or various illumination lights (light resistance), and the thigh is changed with respect to oxidizing gas (ozone, NOx, SOx, etc.) contained in a minute amount in the atmosphere. Image fastness such as no color (gas resistance).

  Conventionally, the image fastness has been mainly regarded as a problem of fading due to sunlight or various illumination lights, and these problems of fading have been solved by selecting a dye having excellent light resistance. However, as the image quality has been improved, the opportunity for indoor exhibitions has increased, so that fading or discoloration caused by oxidizing gas in the atmosphere as well as light resistance has become a problem.

  In particular, in a black ink, when a dye having poor gas resistance is used, not only the color fading but also black tends to turn brown, which causes a sharp deterioration in image quality for a full-color image.

  In addition, recording materials that are used to increase the sharpness, color tone reproducibility, and optical density of the ink, and on which the ink receiving layer containing a pigment and a binder is formed on the base material, may exhibit significantly discoloration. Also in this respect, improvement in gas resistance is desired.

  For this technical problem, for example, the color tone and the discoloration of ozone gas have been improved (Patent Document 1, Patent Document 2), but a high-quality recorded image comparable to a silver salt photograph can be obtained. In recent inkjet recording systems, it has been recognized that further improvement in gas resistance is still necessary.

  In addition to image fastness, with regard to black ink, when forming a photographic image on a recording medium using a porous material such as alumina or silica as an ink receiving material, sufficient gradation and depth of a shadow portion are obtained. High O. D. Is particularly required to be expressed.

Up to now, as a technique for improving the image density of black, for example, a technique using two specific types of dyes has been shown (Patent Document 3). In addition, in an inkjet recording method in which an ink containing a color material, a water-soluble organic solvent and water is attached to a recording medium containing a polymer material, a technique is disclosed in which the polymer material aggregates the color material. (Patent Document 4). Furthermore, high O.D. D. Inks using novel disazo and trisazo dyes are disclosed as dyes that exhibit the above (Patent Documents 5 and 6).
Japanese Patent Registration No. 0219615 Japanese Patent Publication No. 8-26263 JP 2000-290552 A JP 2000-318300 A JP 2002-275380 A JP 2003-292808 A

  As described above, an ink having excellent weather resistance and high optical density is demanded, but usually ink having excellent weather resistance tends to have low optical density, and ink having high optical density is It tends to be inferior in weather resistance. Therefore, the present inventors conducted a technical analysis in order to satisfy these conflicting performances. As a result, ink with a high optical density tends to have a shallow penetration of the color material into the recording medium, and ink with excellent weather resistance tends to have a deep penetration of the color material into the recording medium. For this reason, we have found that these have contradictory performance.

  Therefore, as a result of further investigation, the surface pH of the recording medium provided with a porous body for receiving ink on a support for an ink containing a carboxyl group-containing dye is 3.0 to 5.0. Ink containing a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group is obtained when printing on a recording medium results in shallow penetration of the coloring material in the ink into the recording medium and a high image density is obtained. Even if printing is performed on a recording medium having a surface pH of 3.0 or more and 5.0 or less of a recording medium provided with a porous body for receiving ink on the support, the recording medium of the coloring material in the ink It has been found that the penetration of water does not become shallow.

  Therefore, ink containing a carboxyl group-containing dye is printed on a recording medium having a porous medium for receiving ink on the support and having a surface pH of 3.0 to 5.0. Then, after that, it was studied that inks containing only a sulfone group as an acidic solubilizing group excluding a hydroxyl group and containing a dye having excellent weather resistance were printed on top of each other. As a result, it was possible to obtain a printed image having high optical density and excellent weather resistance. On the contrary, the surface pH of a recording medium having a porous material for receiving ink on a support containing an ink containing only a sulfone group as an acidic solubilizing group excluding a hydroxyl group and having excellent weather resistance. Was printed on a recording medium having a viscosity of 3.0 or more and 5.0 or less, and thereafter, the same result was obtained by printing the ink containing a carboxyl group-containing dye on top of each other.

  Based on the above-described findings, the present invention provides an inkjet black ink capable of obtaining a printed image having a higher optical density and excellent weather resistance, an inkjet recording method using the same, and an inkjet recorded matter. For the purpose.

  The above object is achieved by the present invention described below. That is, the first invention of the present invention is a black ink for ink jet recording on a recording medium having a porous body for receiving ink on a support and having a pH of 3.0 to 5.0. Black ink for ink-jet, comprising at least a dye having a carboxyl group and a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group, wherein the pH is higher than the pH of the recording medium It is. By using this ink, improvement in weather resistance and optical density can be achieved.

  In particular, the dyes represented by the general formulas I and II, which will be described later, not only contribute to the solubility of the sulfone group but also serve to protect the molecular bond contributing to the color development. It has very good weather resistance.

  In the second invention using these, an excellent optical density is realized by a dye having a carboxyl group, and an excellent weather resistance is realized by a dye having only a sulfone group, particularly dyes represented by the general formulas I and II. Conceivable.

  Although the detailed mechanism of the present invention is not clear, in the case of adopting the configuration of the present invention, the dye having a carboxyl group strongly aggregates on the surface of the recording medium, and the sulfone as an acidic solubilizing group excluding the hydroxyl group. It can be considered that a dye having only a group penetrates deeply into a recording medium, and thus a synergistic effect of both dyes is clearly achieved.

  In general, it is known that a compound having a carboxyl group has a large pH dependency. Accordingly, the dye having a carboxyl group also has pH dependency and is likely to cause aggregation in a low pH region. Therefore, in the region where the surface pH of the recording medium is 3.0 or more and 5.0 or less, aggregation occurs rapidly on the recording medium, so that a recorded matter having a high optical density can be obtained. It was also found that this is particularly remarkable when the pH of the ink is higher than the pH of the recording medium. When the pH of the ink exceeds the pH of the recording medium, even if the surface pH of the recording medium is 3.0 or more and 5.0 or less, the pH of the ink does not decrease during fixing, and the dye on the surface of the recording medium This is thought to be due to the fact that the effect of agglomerating is reduced.

  In contrast, an ink containing a carboxyl group-containing dye is printed on a recording medium having a porous body for receiving ink on a support and having a surface pH of 3.0 to 5.0, and then When an ink containing only a sulfone group as an acidic solubilizing group excluding a hydroxyl group and having excellent weather resistance is printed repeatedly, the dye having a carboxyl group is strong on the surface of the recording medium. Although agglomeration is performed, it is influenced by an ink containing a dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group printed later, and the dye having a carboxyl group also penetrates deep into the recording medium. It is conceivable that the functional separation of the two dyes is not sufficient as in the case of.

  Furthermore, the surface pH of a recording medium provided with a porous material for receiving ink on a support containing an ink containing only a sulfone group as an acidic solubilizing group excluding a hydroxyl group and having excellent weather resistance. When printing on a recording medium of 3.0 or more and 5.0 or less, and then printing with an ink containing a carboxyl group-containing dye on top of it, it is possible to remove the hydroxyl group printed earlier. The surface pH of the recording medium rises due to the influence of an ink containing a dye having only a sulfone group as a solubilizing group and excellent in weather resistance, and the dye having a carboxyl group also penetrates deeply into the recording medium. It is conceivable that the functional separation of the two dyes is not sufficient.

  The reason for using a recording medium having porosity as the recording medium is as follows. In recent years, as an ink jet recording medium, a recording medium using a porous material such as alumina or silica as an ink receiving material has been used in order to obtain an image quality comparable to or exceeding that of a silver salt photograph. In particular, a recording medium using alumina hydrate has a positive charge, and therefore, when an anionic ink dye is used as a coloring material, fixing is good and an image with good color development is obtained. High O.D. for black ink D. It is effective to express.

  In view of the above, a black ink for ink jet recording intended to be recorded on a recording medium having a surface pH of 3.0 or more and 5.0 or less of the recording medium provided with a porous body for receiving ink on the support. An ink jet black ink comprising: a dye having at least a carboxyl group; a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group; water; and a water-soluble organic solvent. By using it, the weather resistance and the optical density can be improved.

  According to the present invention, at least a dye having a carboxyl group and a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group have a pH higher than that of the recording medium. By using a black ink, the surface pH of a recording medium provided with a porous body for receiving ink on a support simply containing a dye having a carboxyl group is 3.0 to 5.0. When printing is performed on a recording medium, and then printing is repeated with an ink containing a dye having excellent weather resistance having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group. Ink containing a dye having excellent weather resistance having only a sulfone group as an acidic solubilizing group is provided on a support with a porous body for receiving the ink. Even when printing is performed on a recording medium having a surface pH of 3.0 or more and 5.0 or less, and the ink containing a dye having a carboxyl group is further printed, the optical density is higher. It was possible to provide an ink that was high and excellent in weather resistance.

  According to the present invention, ink having sufficient weather resistance and high optical density can be provided. Further, by using the ink, it is possible to provide a recorded matter having excellent weather resistance and a recorded matter having a high printing density.

  The present invention relates to a black ink for ink jet recording intended for recording on a recording medium having a surface pH of 3.0 or more and 5.0 or less of a recording medium provided with a porous body for receiving ink on a support. A black ink for ink jet, wherein the black ink comprises a dye having at least a carboxyl group, a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group, water, a water-soluble organic solvent, and An ink jet recording method and an ink jet recorded product using this ink.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

  In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but is expressed as “contains a salt” for convenience.

(recoding media)
First, the inkjet black ink used in the present invention is recorded on a recording medium having a surface pH of 3.0 or more and 5.0 or less of a recording medium provided with a porous body for receiving ink on a support. With the goal. Therefore, this specific recording medium will be described in detail.

  The recording medium that can be used in the present invention is a recording medium that has a porous ink-receiving layer and performs recording by adhering ink, and the pH of the surface of the recording medium is 3.0 or more and 5.0 or less. Any one can be used. By printing the ink of the present invention on a recording medium having a pH of 3.0 or more and 5.0 or less on the surface of the recording medium, the dye used in the ink of the present invention quickly aggregates on the surface of the recording medium. A recorded matter having a high optical density can be obtained.

  The pH of the surface of the recording medium is set to 3.0 or more and 5.0 or less when the ink of the present invention is used, and the recording medium having a pH of less than 3.0 has a too strong dye aggregating effect. This is because the adverse effect of causing bronzing is caused, and in a recording medium having a pH of more than 5.0, the effect of the present invention cannot be obtained because the dye aggregation effect is too weak.

A particularly suitable recording medium according to the present invention is preferably a recording medium having an ink receiving layer mainly composed of fine particles having an average particle diameter of 1 μm or less as the fine particles described above. Particularly preferable examples of the fine particles include silica or aluminum oxide fine particles. A preferable silica fine particle is a silica fine particle typified by colloidal silica. Colloidal silica itself is also available from the market, and particularly preferable examples include those described in Japanese Patent Nos. 2803134 and 2881847. Preferable examples of the aluminum oxide fine particles include alumina hydrate fine particles. As one of such alumina-based pigments, preferred is an alumina hydrate represented by the following formula.
Al ₂ O _3-n (OH) _2n · mH ₂ O
In the above formula, n represents an integer of 1, 2 or 3, and m represents a value of 0 to 10, preferably 0 to 5. However, m and n are not 0 at the same time. Since mH ₂ O also represents a detachable aqueous phase that is not involved in the formation of the mH ₂ O crystal lattice in many cases, m can take an integer or a non-integer value. Also, when this type of material is heated, m can reach a value of zero.

  Alumina hydrate is generally used for hydrolysis of aluminum alkoxide and sodium aluminate as described in US Pat. No. 4,242,271 and US Pat. No. 4,202,870. In addition, use is made of a known method such as a method of neutralizing by adding an aqueous solution of sodium sulfate, aluminum chloride or the like to an aqueous solution of sodium aluminate or the like described in JP-B-57-44605. That is suitable.

  Furthermore, the ink jet recording medium using these alumina hydrates is excellent in affinity, absorbability and fixability with the image fastness improving agent according to the present invention, and also realizes the above-mentioned photographic image quality. Further, it is more suitable for applying the present invention because it has excellent gloss, transparency and fixing property of coloring materials in recording liquids such as dyes.

  Examples of suitable binders include water-soluble polymers and latex. For example, polyvinyl alcohol or a modified product thereof, starch or a modified product thereof, gelatin or a modified product thereof, gum arabic, cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, SBR latex, NBR latex, methyl methacrylate-butadiene copolymer Polymer latex, functional group-modified polymer latex, vinyl copolymer latex such as ethylene vinyl acetate copolymer, polyvinyl pyrrolidone, maleic anhydride or copolymer thereof, acrylic ester copolymer, etc. are used. One selected or a combination of two or more can be used as necessary.

The mixing ratio of the fine particles of the ink jet recording medium used in the present invention and the binder is preferably in the range of 1: 1 to 100: 1 by weight. By setting the amount of the binder within the above range, it is possible to maintain a pore volume suitable for impregnation of the image fastness improving agent into the ink receiving layer. The preferable content of aluminum oxide fine particles or silica fine particles in the ink receiving layer is 50% by weight or more, more preferably 70% by weight or more, still more preferably 80% by weight or more, and 99% by weight or less. Most preferred. The coating amount of the ink receiving layer, is preferably 10 g / m ² or more on a dry solid basis for the impregnation of image fastness enhancing agent good, 10 to 60 g / m ² is most preferred is there.

  The recording medium used in the present invention preferably has a support for supporting the above-described ink receiving layer, but the support is not particularly limited, and the above-described porous structure ink receiving layer can be formed. Any material can be used as long as it provides rigidity that can be transported by a transport mechanism such as an ink jet printer. For example, one having a porous layer formed by coating an inorganic pigment such as barium sulfate, titanium oxide, zinc oxide or the like with a binder between the support and the ink receiving layer, or using a resin-coated paper for the support Also good.

  Furthermore, other additives can also be used in the ink receiving layer, for example, a dispersant, a thickener, a pH adjuster, a lubricant, a fluidity modifier, a surfactant, and an antifoaming agent as necessary. , Release agents, fluorescent brighteners, and the like.

(Dye having carboxyl group)
The dye having a specific carboxyl group used in the present invention will be described in detail. The carboxyl group dye used in the present invention is not particularly limited as long as it has at least one carboxyl group in the dye molecule.

  The reason why the dye is contained is that the dye has a carboxyl group, and thus has a large pH dependency and is likely to cause aggregation in a low pH region. Therefore, when the surface pH of the recording medium is in the range of 3.0 or more and 5.0 or less, the dye quickly aggregates on the recording medium, and a recorded matter having a high optical density can be produced.

  Particularly suitable carboxyl group dyes include dyes represented by the following general formula (I).

  Formula (I)

（上記一般式（I）中、Ｒ_１、Ｒ_２は各々独立に置換もしくは未置換の炭素数１〜４のアルキル基を表し、少なくともＲ_１、Ｒ_２のうちいずれかは１つの水酸基を有する。Ｒ_３は水素原子もしくは、置換もしくは未置換のフェニル基を表す。ｍは０〜１の整数を表し、ｎは１〜２の整数を表す。Ｍは対イオンであり、アルカリ金属、アンモニウム或いは有機アンモニウムのいずれかを表す。）

(In the general formula (I), R ₁ and R ₂ each independently represents a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, and at least _one of R ₁ and R ₂ has one hydroxyl group. R ₃ represents a hydrogen atom or a substituted or unsubstituted phenyl group, m represents an integer of 0 to 1, n represents an integer of 1 to 2, M represents a counter ion, an alkali metal, ammonium, or Represents either organic ammonium.)

  Although the exemplary compounds 1 to 3 are shown below as specific examples of the first color material represented by the general formula (I), the color material used in the present invention is not limited thereto. Further, two or more kinds of color materials as listed below may be used at the same time.

  The content of the carboxyl group dye represented by the general formula I contained in the ink according to this embodiment in the ink is in the range of 0.5% by weight or more and 8.0% by weight or less with respect to the total amount of the ink. Is preferred. If it is less than 0.5% by weight, a sufficient optical density, which is one of the effects of the present invention, cannot be obtained, and if it exceeds 8.0% by weight, the dye aggregates on the recording medium and has a metallic gloss. This is because it causes a phenomenon (bronze) that emits light. In order to sufficiently exhibit the effects of the present invention, the content of the dye in the ink is more preferably in the range of 1.0% by weight to 4.0% by weight with respect to the total amount of the ink.

(Dye having only sulfone group as acidic solubilizing group excluding hydroxyl group)
Next, the dye which has only a sulfone group as an acidic solubilizing group except the specific hydroxyl group used by this invention is explained in full detail. The dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group used in the present invention has at least one sulfone group in the dye molecule, and the sulfone group as an acidic solubilizing group excluding the hydroxyl group. It does not specifically limit if it does not have solubilizing groups other than. However, those having a molecular weight of 1000 to 2000 in the form of free acid are preferred.

  The reason for including the dye is that the sulfone group has a property of being easily dissolved in an aqueous solution, so that a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group is compared with a dye having a carboxyl group, etc. It is easier to dive deeper into the paper. By dive deep in the paper, it becomes difficult to receive external stimuli such as gas and light. For this reason, it is because the recorded matter which has the outstanding weather resistance can be created.

  Particularly preferred dyes having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group include a dye that is a pentakisazo compound represented by the following general formula (II) or a salt thereof, and the following general formula (III): The dye which is the tetrakisazo compound represented by these, or its salt is mentioned.

  Formula (II)

(In the general formula _{(II), R 1, R} 2 is a hydrogen atom; a hydroxyl group; an amino group; a sulfo group; an alkyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 4 carbon _{atoms, R} 3, R ₄ is a hydrogen atom; an alkyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 4 carbon atoms; a hydroxyl group; a carbon group having 1 to 4 carbon atoms that may be substituted with a hydroxyl group or an alkoxy group having 1 to 4 carbon atoms. An alkyl group, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms which may be substituted with a sulfo group; an amino group substituted with an alkyl group or an acyl group, and n is 0 or 1)

  Formula (III)

(In the general formula (III), R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms; hydroxyl groups; amino groups; sulfo groups; alkyl groups having 1 to 4 carbon atoms; alkoxy groups having 1 to 4 carbon atoms. A hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkoxy group substituted with a sulfo group; an alkoxy group having 1 to 4 carbon atoms that may be further substituted with a sulfo group; a phenyl group, an alkyl group, or an acyl group; And n is 0 or 1).
Hereinafter, exemplary compounds 4 to 6 are shown as specific examples of the first coloring material represented by the general formula (II), but the coloring material used in the present invention is not limited thereto. Further, two or more kinds of color materials as listed below may be used at the same time.

  Although the exemplary compounds 7 to 9 are shown below as specific examples of the first color material represented by the general formula (III), the color material used in the present invention is not limited to these. Further, two or more kinds of color materials as listed below may be used at the same time.

  The content of the dye having only the sulfone group as an acidic solubilizing group excluding the hydroxyl group contained in the ink according to this embodiment in the ink is 0.5% by weight or more and 10.0% by weight with respect to the total amount of the ink. The following is preferred. If it is less than 0.5% by weight, the light resistance and gas resistance, which are one of the effects of the present invention, cannot be obtained sufficiently, and if it exceeds 10.0% by weight, the dye aggregates on the recording medium. This is to cause a phenomenon of metallic luster (bronze). In order to sufficiently exhibit the effects of the present invention, the content of the dye in the ink is more preferably in the range of 1.0% by weight to 6.0% by weight with respect to the total amount of the ink.

  The weight ratio of the above-mentioned dye having a carboxyl group and the dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group in the ink is preferably 1:10 to 5: 1. . When the ratio of the carboxyl group dye is high outside the above range, the aggregation density of the carboxyl group dye on the recording medium becomes very high, causing bronze, or insufficient weather resistance due to insufficient sulfone group dye. . Also, if the ratio of the sulfone group dye is high outside the above range, the density of the sulfone group dye in the recording medium becomes very high, causing bronze, or a sufficient optical density can be obtained due to the lack of carboxyl group dye. This is because it disappears.

In addition, although it is the verification method of this dye used by this invention, it was measured with the following analytical methods about whether this dye contained in an ink.
(1) Peak retention time by high performance liquid chromatography,
(2) Maximum absorption wavelength of the same peak,
(3) M / Z (posi, nega) in the mass spectrum of the same peak
Verification is possible by using.

(1) (2) Analytical conditions for high performance liquid chromatography are as follows.
The ink solution diluted about 1000 times with pure water is analyzed by high performance liquid chromatography under the following conditions, and the retention time of the peak and the maximum absorption wavelength of the peak are measured.
Column: Symmetry C18 2.1 mm x 150 mm
Mobile phase gradient conditions

Flow rate: 0.2 ml / min
Column temperature: 40 ° C
PDA: 210 nm to 700 nm

(3) Mass spectrum analysis conditions are as follows.
With respect to the obtained peak, a mass spectrum is measured under the following conditions, and the most strongly detected M / Z is measured for each of posi and negative.
Ionization method ESI
Capillary voltage 3.5 kV
Desolvent gas 300 ℃
Ion source temperature 120 ° C
Detector posi 40V 200-1500amu / 0.9sec
nega 40V 200-1500amu / 0.9sec
The retention time, maximum absorption wavelength, M / Z (posi), and M / Z (negative) values of Example Compound (1) and Example Compound (4) with respect to the dye are shown below.

  When it corresponds to this value, it can be judged that it corresponds to the dye of the present invention.

(Ink pH)
The ink of the present invention is characterized in that the pH is higher than the pH of the recording medium. When the pH exceeds 10, when the ink is printed on the recording medium, the aggregation of the dye having a carboxyl group on the surface of the recording medium becomes insufficient, and the effect of the present invention is not sufficiently exhibited.

  Further, the pH of the ink is preferably 7 or more in consideration of the storage stability of the ink.

(Water-soluble organic solvent)
The ink used in the ink jet recording apparatus according to the present invention contains water and a water-soluble organic solvent.

  The water-soluble organic solvent is not particularly limited as long as it shows water solubility, and alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent, ureas, saccharides, etc. Any solvent that is used as a solvent for inkjet ink can be used without any problem. These solvents are used for maintaining the moisture retention of the ink, improving the solubility of the dye, and penetrating the ink into the recording paper. These solvents can be used alone or in combination.

  The upper limit of the content of the water-soluble organic solvent is preferably 50% by weight or less, more preferably 40% by weight or less of the entire ink. Further, the lower limit is preferably 1% by weight or more, more preferably 3% by weight or more of the whole ink. The water content in the ink is preferably in the range of 30% by weight to 95% by weight in order to maintain good dye solubility and ink ejection stability.

(Additives, etc.)
Further, in addition to the above components, the ink of the present invention contains a surfactant, a pH adjuster, a rust inhibitor, a preservative, an antifungal agent, an antioxidant, a reduction inhibitor, an evaporation accelerator, a chelating agent as necessary. Various additives such as a water-soluble polymer may be contained.

  For example, as surfactants, fatty acid salts, higher alcohol sulfate esters, liquid fatty oil sulfate esters, alkylallyl sulfonates and other anionic surfactants, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, There are nonionic surfactants such as polyoxyethylene sorbitan alkyl esters, acetylene alcohol, and acetylene glycol, and one or more of these can be appropriately selected and used. Among the above-mentioned, acetylene alcohols and acetylene glycols can be preferably used in order to exhibit an effect excellent in permeability to plain paper. The amount used varies depending on the amount of dispersant added, but is preferably 0.01 to 5% by mass relative to the total amount of ink.

  At this time, the surface tension of the ink at 25 ° C. is 10 mN / in order to effectively suppress the occurrence of printing deviation (deviation of the landing point of ink droplets) due to the wetness of the nozzle tip of the ink jet head, and to provide ejection characteristics. m (dyn / cm) or more is preferable, more preferably 20 mN / m or more, and it is preferable to determine the amount of the activator added so that the surface tension is 60 mN / m or less.

  The ink is preferably adjusted to have a desired viscosity and pH in order to obtain good ejection characteristics in the ink jet recording apparatus.

(Inkjet recording method)
An ink jet recording method in which ink is ejected from an orifice in accordance with a recording signal and recording is performed on a recording medium can be preferably used. In particular, recording is performed by applying thermal energy to the ink. An ink jet recording method for recording on a medium can be more preferably used.

(Recording unit)
As a recording unit suitable for performing recording using the ink of the present invention, a recording unit having a recording head having an ink storage part for storing these inks can be cited, and the head part is used for recording signals. Examples thereof include a recording unit that applies corresponding thermal energy and generates ink droplets by the energy.

(ink cartridge)
As an ink cartridge suitable for performing recording using the ink of the present invention, an ink cartridge having an ink containing portion for containing these inks may be mentioned.

(Inkjet recording device)
As a recording apparatus suitable for recording using the ink of the present invention, thermal energy corresponding to a recording signal is given to the ink in the chamber of the recording head having an ink storage part in which these inks are stored. An apparatus that generates ink droplets by energy is used.

  Below, the schematic structure of the mechanism part of the inkjet recording device used by this embodiment is demonstrated. The main body of the recording apparatus according to the present embodiment includes a paper feed unit, a paper transport unit, a carriage unit, a paper discharge unit, a cleaning unit, and an exterior unit that protects these parts and has a design from the role of each mechanism. The outline of these will be described below.

  FIG. 1 is a perspective view of a recording apparatus applied in this embodiment. 2 and 3 are diagrams for explaining the internal mechanism of the recording apparatus main body. FIG. 2 is a perspective view from the upper right part, and FIG. 3 is a side sectional view of the recording apparatus main body. is there.

  When paper feeding is performed in the recording apparatus applied in the present embodiment, first, only a predetermined number of recording media in the paper feeding unit including the paper feeding tray M2060 is transferred to the nip part constituted by the paper feeding roller M2080 and the separation roller M2041. Sent. The sent recording medium is separated at the nip portion, and only the uppermost recording medium is conveyed. The recording medium sent to the paper transport unit is guided by the pinch roller holder M3000 and the paper guide flapper M3030, and is sent to the roller pair of the transport roller M3060 and the pinch roller M3070. A roller pair composed of a conveyance roller M3060 and a pinch roller M3070 is rotated by driving of the LF motor E0002, and the recording medium is conveyed on the platen M3040 by this rotation.

  When an image is formed on a recording medium in the carriage unit, the recording head H1001 (FIG. 4) is disposed at a target image forming position, and ink is ejected onto the recording medium in accordance with a signal from the electric substrate E0014. Although the detailed configuration of the recording head H1001 will be described later, in the recording apparatus of the present embodiment, a recording medium is scanned by the carriage M4000 in the column direction while recording is performed by the recording head H1001, and a recording medium is detected by the conveyance roller M3060. An image is formed on the recording medium by alternately repeating the sub-scan transported in the row direction.

  The recording medium on which the image has been finally formed is sandwiched between nips of the first paper discharge roller M3110 and the spur M3120 at the paper discharge unit, conveyed, and discharged to the paper discharge tray M3160.

  For the purpose of cleaning the recording head H1001 before and after image recording in the cleaning unit, if the pump M5000 is operated in a state where the cap M5010 is in close contact with the ink discharge port of the recording head H1001, the recording head H1001 does not need to operate. Ink or the like is sucked. Further, by sucking the ink remaining in the cap M5010 with the cap M5010 opened, consideration is given to preventing the remaining ink from adhering and the subsequent adverse effects.

(Recording head configuration)
The configuration of the head cartridge H1000 applied in the present embodiment will be described below. The head cartridge H1000 in this embodiment has a recording head H1001, a means for mounting the ink tank H1900, and a means for supplying ink from the ink tank H1900 to the recording head, and is detachable from the carriage M4000. Mounted on.

  FIG. 4 is a diagram illustrating a state in which the ink tank H1900 is attached to the head cartridge H1000 applied in the present embodiment. The recording apparatus of the present embodiment forms an image with yellow, magenta, cyan, black, light magenta, light cyan, and green ink, and therefore, ink tanks H1900 are also prepared for seven colors independently. In the above, the ink according to the present invention is used as at least one kind of ink. As shown in the figure, each is detachable from the head cartridge H1000. The ink tank H1900 can be attached and detached while the head cartridge H1000 is mounted on the carriage M4000.

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

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

  FIG. 6 is an enlarged front view for explaining the configuration of the first recording element substrate H1100 and the second recording element substrate H1101. H2000 to H2600 are printing element rows (hereinafter also referred to as nozzle rows) corresponding to different ink colors, and the first printing element substrate H1100 has a nozzle row H2000 supplied with yellow ink and a supply of magenta ink. The nozzle row for three colors is configured, that is, the nozzle row H2100 to be supplied and the nozzle row H2200 to which cyan ink is supplied. The second recording element substrate H1101 includes a nozzle row H2300 supplied with light cyan ink, a nozzle row H2400 supplied with black ink, a nozzle row H2500 supplied with orange ink, and a nozzle supplied with light magenta ink. Nozzle rows for four colors of the row H2600 are configured.

  Each nozzle row is composed of 768 nozzles arranged at an interval of 1200 dpi (dot / inch; reference value) in the conveyance direction of the recording medium, and ejects approximately 2 picoliters of ink droplets. The opening area at each nozzle outlet is set to about 100 square μm 2. Further, the first recording element substrate H1100 and the second recording element substrate H1101 are bonded and fixed to the first plate H1200. Here, the first recording element substrate H1100 and the second recording element substrate H1101 are attached. An ink supply port H1201 for supplying ink is formed.

  Further, a second plate H1400 having an opening is bonded and fixed to the first plate H1200, and the second plate H1400 includes the electric wiring substrate H1300, the first recording element substrate H1100, and the second recording element substrate H1100. The electric wiring substrate H1300 is held so that the recording element substrate H1101 is electrically connected.

  The electrical wiring substrate H1300 applies an electrical signal for ejecting ink from each nozzle formed on the first recording element substrate H1100 and the second recording element substrate H1101, and the first recording element substrate Electrical wiring corresponding to the H1100 and the second recording element substrate H1101, and an external signal input terminal H1301 for receiving an electrical signal from the recording apparatus main body located at the end of the electrical wiring. The external signal input terminal H1301 is positioned and fixed on the back side of the tank holder H1500.

  On the other hand, in a tank holder H1500 that holds the ink tank H1900, a flow path forming member H1600 is fixed by, for example, ultrasonic welding to form an ink flow path H1501 that communicates from the ink tank H1900 to the first plate H1200.

  A filter H1700 is provided at the ink tank side end of the ink flow path H1501 that engages with the ink tank H1900, and can prevent dust from entering from the outside. Further, a seal rubber H1800 is attached to the engaging portion with the ink tank H1900 so that ink can be prevented from evaporating from the engaging portion.

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

  Here, as an embodiment of the recording head, a bubble jet (registration) that performs recording using an electrothermal transducer (recording element) that generates thermal energy for causing film boiling to the ink in response to an electrical signal. A trademark type recording head has been described with an example.

  About this typical structure and principle, for example, what is performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is preferable. . This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it corresponds to a sheet or liquid flow path in which liquid (ink) is held. By applying at least one drive signal that corresponds to the recorded information and gives a rapid temperature rise exceeding the nucleate boiling to the electrothermal transducer arranged in a manner, heat energy is generated in the electrothermal transducer, This is effective because film boiling occurs on the heat acting surface of the recording head, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. When this drive signal is in a pulse shape, bubbles are grown and contracted immediately and appropriately, so that it is possible to achieve the discharge of liquid (ink) with particularly excellent responsiveness, which is more preferable.

  Further, as a form of the ink jet recording apparatus using the second mechanical energy, a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed opposite to the nozzles, and this pressure An on-demand ink jet recording head that includes ink that fills the periphery of the generating element, displaces the pressure generating element by an applied voltage, and discharges a small droplet of ink from a nozzle can be exemplified.

  Further, the ink jet recording apparatus is not limited to the one in which the head and the ink tank are separated as described above, but may be one in which they are integrated so as not to be separated. The ink tank is integrated with the head so as to be separable or inseparable from the head and mounted on the carriage, and is provided at a fixed portion of the apparatus so that ink is supplied to the recording head via an ink supply member, for example, a tube. The thing of the form to supply may be sufficient. Further, when the ink tank is provided with a configuration for applying a preferable negative pressure to the recording head, a configuration in which an absorber is disposed in the ink storage portion of the ink tank, or a flexible ink storage bag and the same A form having a spring portion that applies a biasing force in the direction of expanding the internal volume can be employed. In addition to the serial recording method as described above, the recording apparatus may take the form of a line printer in which recording elements are aligned over a range corresponding to the entire width of the recording medium.

  Next, the present invention will be described in more detail with reference to examples and comparative examples. Unless otherwise specified, the ink components in Examples and Comparative Examples mean “parts by weight”.

  Each component shown in Table 3 was mixed, sufficiently stirred and dissolved, and then pressure filtered through a 0.20 μm filter to prepare inks of Examples 1 to 6 and Comparative Examples 1 to 6, respectively.

  The pH of the recording medium was adjusted as follows. A 0.5N nitric acid aqueous solution was applied onto glossy paper (PR-101; manufactured by Canon) with a wire bar, and then dried in an oven at 120 ° C. for 2 minutes. When this recording medium was measured for paper surface pH using a paper surface pH measurement set (manufactured by Kyoritsu Riken), the pH was adjusted to 4.0. By adjusting the concentration of the aqueous nitric acid solution in the same manner as this method, a recording medium was prepared so as to have a pH of 2.5, 3.0, 5.0, and 5.5.

  The pH of the glossy paper without pH adjustment was 6.0.

<Evaluation of ink>
The inks of Examples 1 to 12 and Comparative Examples 1 to 6 of the present invention obtained above were respectively mounted on an ink jet printer (trade name: PIXUS950i; manufactured by Canon), and the following (1), (2), (3) and (4) were evaluated according to the following methods and criteria. Table 4 shows the evaluation results obtained using these inks.

(1) Optical density The ink of each of the above examples or comparative examples was set, and printed matter was obtained in which a solid part of 100% DUTY was printed on the recording medium. Each obtained printed matter was naturally dried for 24 hours, and the optical density of the patch was measured by Gretag Spectrolino (manufactured by Gretag Macbeth) and evaluated according to the following criteria.
○: Optical density is 2.40 or more Δ: Optical density is 2.30 to 2.39
X: Optical density is 2.29 or less

(2) Gas resistance The ink of each of the above examples or comparative examples was set to obtain a printed matter in which a solid portion of 100% DUTY was printed on the recording medium. Using a fade meter, the printed matter was loaded for 2 hours under the conditions of an ozone atmosphere of a bath temperature of 40 ° C., a relative humidity of 55%, and 3 ppm. From the L * a * b * calculated by measuring the solid part of the printed matter before and after the test with Gretag Spectrolino (manufactured by Gretag Macbeth), the color difference ΔE before and after the test is obtained, and the gas resistance is evaluated according to the following criteria. It was.
○: ΔE is less than 5.0 Δ: ΔE is 5.0 or more and less than 10.0 x: ΔE is 10.0 or more

(3) Light resistance The ink of each of the above examples or comparative examples was set to obtain a printed matter in which a solid portion of 100% DUTY was printed on the recording medium. Thereafter, the printed matter was naturally dried for 24 hours, and exposed and irradiated with an Atlas Fade Meter Ci35 (manufactured by Atlas) for 30 hours at an illuminance of 0.39 W / m 2 under conditions of a tank temperature of 50 ° C. and a relative humidity of 70%. From L * a * b * calculated by measuring the solid part of the printed matter before and after the test with Gretag Spectrolino (manufactured by Gretag Macbeth), the color difference ΔE before and after the test is obtained, and the light resistance is evaluated according to the following criteria. did.
○: ΔE is less than 1.0 Δ: ΔE is 1.0 or more and less than 5.0 ×: ΔE is 5.0 or more

(4) Bronze property The inks of the above examples or comparative examples were set, and printed matter was obtained in which a solid part of 100% DUTY was printed on the recording medium. About this solid part, bronze property was visually evaluated on the following reference | standard. In the following criteria, ○, ○ ', and Δ were judged to be practically usable levels.
○: Bronze is not generated ○ ': Minute bronze is generated △: Some bronze is generated ×: Bronze is severely generated

1 is a perspective view of a recording apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of a mechanism unit of the recording apparatus according to the embodiment of the invention. 1 is a cross-sectional view of a recording apparatus according to an embodiment of the present invention. FIG. 5 is a perspective view showing a state where an ink tank is mounted on the head cartridge applied in the embodiment of the present invention. It is a disassembled perspective view of the head cartridge applied in the embodiment of the present invention. FIG. 3 is a front view showing a recording element substrate in a head cartridge applied in an embodiment of the present invention.

Explanation of symbols

M2041 Separation roller M2060 Paper feed tray M2080 Paper feed roller M3000 Pinch roller holder M3030 Paper guide flapper M3040 Platen M3060 Transport roller M3070 Pinch roller M3110 Paper discharge roller M3120 Spur M3160 Paper discharge tray M4000F Carriage M5000 Pump M500P Head cartridge H1001 Recording head H1100 First recording element substrate H1101 Second recording element substrate H1200 First plate H1201 Ink supply port H1300 Electrical wiring substrate H1301 External signal input terminal H1400 Second plate H1500 Tank holder H1501 Ink channel H1600 Flow path forming member H1700 Luther H1800 seal rubber H1900 ink tank H2000 yellow nozzle row H2100 magenta nozzle row H2200 cyan nozzle row H2300 light cyan nozzle row H2400 black nozzle row H2500 green nozzle row H2600 light magenta nozzle row

Claims (10)

  In the black ink for ink jet recording on a recording medium having a surface pH of 3.0 or more and 5.0 or less provided with a porous body for receiving ink on a support, the ink contains at least a dye having a carboxyl group and An ink-jet black ink comprising a dye having only a sulfone group as an acidic solubilizing group excluding a hydroxyl group and having a pH higher than that of the recording medium. The black ink for inkjet according to claim 1, wherein the dye having a carboxyl group is a dye represented by the following general formula (I).
Formula (I)

(In the above general formula I, R ₁ and R ₂ each independently represents any substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, and at least _one of R ₁ and R ₂ represents one hydroxyl group. R ₃ represents a hydrogen atom or a substituted or unsubstituted phenyl group, m represents 0 or 1, n represents 1 or 2, M represents a counter ion, and represents an alkali metal, ammonium or organic ammonium. Represents either one.) The dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group is a pentakisazo compound represented by the following general formula (II) or a salt thereof, or a tetrakis represented by the general formula (III) The inkjet black ink according to claim 1, which is a dye which is an azo compound or a salt thereof.
Formula (II)

(In the general formula (II), R ₁ and R ₂ are a hydrogen atom; a hydroxyl group; an amino group; a sulfo group; an alkyl group having 1 to 4 carbon atoms; R ₃ and R ₄ are each a hydrogen atom; an alkyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 4 carbon atoms; a hydroxyl group; a hydroxyl group or having 1 to 4 carbon atoms Any alkyl group having 1 to 4 carbon atoms that may be substituted with any alkoxy group; one to 1 carbon atoms that may be substituted with a hydroxyl group, any alkoxy group having 1 to 4 carbon atoms, or a sulfo group Any one of 4 alkoxy groups; an amino group substituted by an alkyl group or an acyl group, and n is 0 or 1)
Formula (III)

(In the general formula (III), R ₁ , R ₂ , R ₃ , and R ₄ are a hydrogen atom; a hydroxyl group; an amino group; a sulfo group; an alkyl group having 1 to 4 carbon atoms; Any one of 4 alkoxy groups; a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkoxy group substituted with a sulfo group; any alkoxy group having 1 to 4 carbon atoms that may be further substituted with a sulfo group An amino group substituted by a phenyl group, an alkyl group, or an acyl group, and n is 0 or 1.)   4. The black ink for ink jet according to claim 1, comprising a dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group in an amount of 0.5 wt% to 10.0 wt%.   The black ink for inkjet according to claim 4, comprising 1.0% by weight or more of a dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group.   The black ink for inkjet according to claim 4 or 5, comprising 6.0% by weight or less of a dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group.   7. The dye according to claim 1, wherein the dye having a carboxyl group and the dye having only a sulfone group as an acidic solubilizing group excluding the hydroxyl group are contained in a weight ratio of 1:10 to 5: 1. The black ink for inkjet described in 2.   An ink jet recording method using the black ink for ink jet according to claim 1.   An ink jet recorded matter obtained by the ink jet recording method according to claim 8. An ink cartridge using the inkjet black ink according to any one of claims 1 to 7.

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