JP2001106946A - Black ink for inkjet-recording, and ink-jet recording and full-color ink jet recording by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a black ink for an ink jet-recording, excellent in color reproducibility and light resistance, especially in hue after its light discoloration, and showing an excellent image quality close to a photography and reliability, and to provide an inkjet recording method and a full-color inkjet-recording method by using the same ink. SOLUTION: This ink jet-recording liquid contains at least water, an organic solvent and a water-soluble dyestuff, which contains (A) at least 1 kind selected from a group consisting of black color dyestuffs having a disazo structure, (B) at least 1 kind selected from a group consisting of blue color-based dyestuffs having a phthalocyanin structure and (C) at least 1 kind selected from a group consisting of red colored dyestuffs, and satisfies that the weight mixing ratios of the above (A) to (B) and (C) are (A):[(B)+(C)]=(50:1)-(4:1) and (B):(C)=(2:3)-(3:2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black ink for ink jet recording which has excellent color reproducibility and light fastness, and particularly excellent hue after photobleaching, an ink jet recording method using the same, and a full color ink jet recording method.

[0002]

2. Description of the Related Art The principle of an ink jet recording method is to discharge a liquid ink or a molten solid ink from a nozzle, a slit, a porous film, or the like, and perform recording on paper, cloth, film, or the like. As for the method of ejecting ink, a so-called charge control method in which ink is ejected using electrostatic attraction, and a so-called drop-on-demand method (pressure pulse method) in which ink is ejected using vibration pressure of a piezo element. Various methods have been proposed, such as a so-called thermal ink jet method, in which ink is ejected using pressure generated by forming and growing bubbles by high heat, and an extremely high-definition image is obtained by these methods. Can be.

The inks used in the ink jet recording system include aqueous dye inks in which various water-soluble dyes are dissolved in a liquid medium composed of water and a water-soluble organic solvent, and various pigments formed from water and a water-soluble organic solvent. An aqueous pigment ink dispersed in a liquid medium, an oil-based dye ink in which an oil-soluble dye is dissolved in an organic solvent, and the like are known. Among these inks, aqueous inks in which a water-soluble dye is dissolved are excellent in safety because the main solvent is water, and furthermore, since dyes are used, the color image of a color image has good color development and high quality printed image. Is obtained, and the storage stability of the ink is excellent, so that it has become a mainstream ink jet recording ink.

On the other hand, in recent years, a printed image of a quality close to a photograph using an ink jet printing technique has been required, and a better color reproducibility has been demanded. In addition, since the resolution of a printed image has been increased by a high-resolution small-drop inkjet recording method, the nozzles of an inkjet recording head have become finer, and it is important to prevent nozzle clogging of ink. Furthermore,
In order to preserve the quality of the obtained printed image without losing the quality for a long period of time, it is important that the fastness such as water resistance and light resistance is excellent.

As for black ink for ink-jet recording, examples using pigment-dispersed inks such as carbon black have been increasing in recent years. However, the pigment-dispersed ink is superior in terms of fastness to the water-soluble dye ink, but has a drawback that the printed image is not glossy and a good image is hardly obtained in combination with the water-soluble color dye ink. . Therefore, a water-soluble black dye ink is generally used for a photographic quality inkjet image. However, the water-soluble black dye is difficult to obtain a pure black color compared to the pigment-dispersed ink, and is inferior in light resistance, so that improvement is required.

[0006] In order to improve the color reproducibility and light resistance of the black ink, some researches and developments have been already made on a method of obtaining a pure black by mixing a color dye with an existing black dye. For example,
No. 6, JP-A-5-13997 discloses a method in which food black 2 and one or more yellow dyes are used in combination, and JP-B-5-13997 discloses a method in which food black 2 is used in combination with one or more yellow dyes. JP-A-5-13998 proposes a method in which food black 2 is used in combination with one or more red dyes and one or more yellow dyes, whereby the color reproducibility is improved, and the image density is also printed on light fastness. Articles are reported to have improved to an acceptable level.

In these methods, however, pure black can be obtained for the ink and its printed image, but for the printed image after photobleaching, the hood black 2 can be obtained.
Even in the case of an ink containing only a color, there is a property of fading in the direction of reddish, and further, since a red dye or a yellow dye is mixed, redness / yellowness further increases and a large change in hue becomes a problem. Japanese Patent Application Laid-Open No. 60-86178 proposes a method in which food black 2 and one or more blue dyes are used in combination. Not suitable as a color tone.

As described above, the water-soluble black dye ink for ink-jet recording has excellent color reproducibility and light fastness, particularly excellent hue after photobleaching, excellent image quality close to a photograph, and high reliability. At present, there is no ink jet recording ink that has been obtained.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention is excellent in color reproducibility and light fastness,
In particular, it is an object of the present invention to provide a black ink for inkjet recording which has excellent hue after photobleaching, excellent image quality close to a photograph, and high reliability, an inkjet recording method using the same, and a full-color inkjet recording method.

[0010]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that in a black ink for ink jet recording comprising at least water, a water-soluble organic solvent and a water-soluble dye, the water-soluble dye has a disazo structure. It has been found that the above object can be achieved by adjusting the weight mixing ratio of the black dye, the blue dye having a phthalocyanine structure, and the red dye having the phthalocyanine structure, thereby completing the present invention.

The means for solving the above-mentioned problems are as follows. That is, <1> at least a black ink for inkjet recording comprising water, a water-soluble organic solvent, and a water-soluble dye,
The water-soluble dye is (A) at least one selected from the group consisting of black dyes having a disazo structure, (B) at least one selected from the group consisting of blue dyes having a phthalocyanine structure, and (C) red. (A) comprising at least one selected from the group consisting of system dyes,
The weight mixing ratio of (B) and (C) is (A): [(B)
+ (C)] = 50: 1 to 4: 1, and (B) :( C)
= 2: 3 to 3: 2. <2> In an ink jet recording method for performing recording on a recording material by discharging ink droplets from an orifice according to a recording signal, the ink is the black ink for inkjet recording according to <1>. This is an inkjet recording method. <3> Black ink, cyan ink, magenta ink,
And a full-color inkjet recording method in which a yellow ink is ejected from an orifice in accordance with a recording signal to perform recording on a recording material, wherein the black ink is the black ink for inkjet recording according to <1>. This is a full-color inkjet recording method.

[0012] Further, as means for solving the above-mentioned problems, the following aspects are preferable. <4> The group consisting of the black dye having a disazo structure includes C.I. I. Food black 2 and C.I. The black ink for inkjet recording according to <1>, wherein the black ink is I Direct Black 195. <5> The group consisting of the blue dye having a phthalocyanine structure includes C.I. I. Direct Blue 86, C.I. I.
Direct Blue 199 and C.I. I. The black ink for inkjet recording according to <1> or <4>, which is Direct Blue 307. <6> The group consisting of the red dyes includes C.I. I. Direct Red 75, C.I. I. Acid Red 289, C.I.
I. Reactive Red 24, C.I. I. Reactive red 120, and C.I. I. The black ink for inkjet recording according to any one of <1>, <4>, and <5>, which is Reactive Red 180. <7> The water-soluble organic solvent comprises two or more different water-soluble organic solvents, at least one of which is an organic solvent having a cyclic structure having a boiling point of 200 ° C. or more at normal pressure. >, <4> to <6>. <8> The content of the above <1>, <4> to <7, wherein the content of the water-soluble organic solvent is 3 to 40% by weight based on the total amount of the ink.
The black ink for inkjet recording according to any one of <1> to <3>. <9> The content of the above <1>, <4> to <8, wherein the content of the water-soluble dye is 0.1 to 10% by weight based on the total amount of the ink.
The black ink for inkjet recording according to any one of <1> to <3>. <10> The four-color inks each include at least water, a water-soluble organic solvent, and a water-soluble dye, and the content of the water-soluble dye is at least one of the four-color inks. , 2.0 to 10.
<3> using the high-concentration ink of 0% by weight and the low-concentration ink whose content of the water-soluble dye is 0.1 to 2.0% by weight based on the total amount of the ink. Is a full-color inkjet recording method. <11> The amount of ink ejected per droplet is set to 20
The full-color inkjet recording method according to <3> or <10>, wherein the recording is performed at ng or less. <12> The above-mentioned <3>, wherein the recording material is an inkjet recording sheet having a printing surface having a 75-degree specular glossiness of 40% or more defined by JIS-Z-8741.
The full-color inkjet recording method according to any one of <10> and <11>.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. [Black Ink for Inkjet Recording] The black ink for inkjet recording of the present invention (hereinafter, may be simply referred to as “black ink”) comprises at least water, a water-soluble organic solvent, and a water-soluble dye. Depending on the other components.

(Water-soluble dye) The water-soluble dye is (A)
At least one selected from the group consisting of black dyes having a disazo structure, (B) at least one selected from the group consisting of blue dyes having a phthalocyanine structure, and (C) at least one selected from the group consisting of red dyes 1
Seeds.

A printed image of an ink containing only a black dye having a disazo structure tends to have a hue shift more than that of pure black, but the black ink of the present invention contains a red dye, so that the printed image is pure. Black can be toned, and color reproducibility of black can be improved.

On the other hand, in the case of an ink containing only a black dye, there is a property of fading in the direction of red tint in addition to an ink containing only a black dye. In addition, since a red dye is added, the red tint further increases. Become. However, in the black ink of the present invention, since a blue dye having a phthalocyanine structure, which is more excellent in light resistance, is added, it can be toned to pure black. That is, the black ink of the present invention, in addition to the red dye,
By including a blue dye having a phthalocyanine structure having excellent light fastness, an image after photobleaching can be kept pure black without a large change in hue.

Since the black dye used in the present invention has a disazo structure, it has better dissolution stability in ink than other black dyes having a polyazo structure. In this case, deposition on the heater surface hardly occurs, and the ink ejection stability is excellent. The black dye used in the present invention can be used without particular limitation as long as it has a disazo structure. Specifically, for example, C.I. I. Food black 2, C.I. I. Direct Black 195, C.I. I. Direct Black 17, C.I. I. Direct Black 51, C.I. I. Direct Black 112, C.I. I. Direct Black 1
13 and the like. Among them, C.I. I. Food black 2, and C.I. I. Direct black 195 is preferred.

The blue dye used in the present invention has a phthalocyanine structure and is therefore excellent in light resistance. The blue dye used in the present invention can be used without particular limitation as long as it has a phthalocyanine structure. Specifically, for example, C.I. I. Direct Blue 8
6, C.I. I. Direct Blue 199, C.I. I. Direct Blue 307, C.I. I. Direct Blue 262,
C. I. Direct Blue 264 and the like. Among them, C.I.
I. Direct Blue 86, C.I. I. Direct Blue 199 and C.I. I. Direct Blue 307 is preferred.

The red dye used in the present invention is not particularly limited, and a conventionally known red dye can be used.
Specifically, for example, C.I. I. Direct Red 75,
C. I. Acid Red 289, C.I. I. Reactive Red 24, C.I. I. Reactive Red 120, C.I.
I. Reactive Red 180, C.I. I. Direct Red 23, C.I. I. Direct Red 227, C.I. I.
Direct Red 23, C.I. I. Direct Red 22
7, C.I. I. Acid Red 52, C.I. I. Acid Red 317 and the like. Among them, C.I. I. Direct Red 7
5, C.I. I. Acid Red 289, C.I. I. Reactive Red 24, C.I. I. Reactive Red 120,
And C.I. I. Reactive Red 180 is preferred, and C.I. I. Direct Red 75 is more preferred.

In the black ink of the present invention, the black dye, the blue dye and the red dye (hereinafter, referred to as “dye”)
Called "color dyes". ) Is 50: 1.
４4: 1. When the weight mixing ratio of the color dye is lower than 50: 1, the image after photobleaching becomes reddish, and the hue changes. On the other hand, when the weight ratio of the color dyes is higher than 4: 1, the printed image cannot be said to be pure black, the image after photobleaching becomes reddish, and the hue change of the printed image becomes large. In order to maintain pure black without hue change of the printed image and the image after photobleaching,
The weight mixing ratio of the black dye and the color dye is 3
The ratio is more preferably 0: 1 to 7: 1.

Further, the weight mixing ratio of the blue dye and the red dye must be 2: 3 to 3: 2. If the weight ratio of the blue dye is more than 3: 2, the printed image becomes bluish black and cannot be said to be pure black. On the other hand, the weight mixing ratio of the blue dye is 2:
If it is less than 3, the hue after photobleaching becomes reddish and the hue changes significantly.

In the black ink of the present invention, the content of the water-soluble dye (mixed dye) is 0.1 to the total amount of the ink.
1-10% by weight is preferred. When the content of the water-soluble dye is less than 0.1% by weight, the image density may be low. On the other hand, when the content of the water-soluble dye exceeds 10% by weight, the dye is easily precipitated. . From the viewpoint of dissolution stability of the dye, the content of the water-soluble dye is more preferably 0.3 to 9% by weight.

(Water-soluble organic solvent) The water-soluble organic solvent used for the black ink of the present invention is not particularly limited, and a conventionally known water-soluble organic solvent can be used.
It is preferable that at least one of them is an organic solvent having a cyclic structure having a boiling point of 200 ° C. or more at normal pressure. Examples of the organic solvent having a cyclic structure whose boiling point at normal pressure is 200 ° C. or higher include, for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, sulfolane, ethylene carbonate, propylene carbonate, and the like, but are not limited thereto. Not something. Sulfolane is particularly preferred from the viewpoints of solubility of the dye, moisture retention of the ink, ejection stability of the ink and prevention of clogging.

The water-soluble organic solvent other than the above is preferably at least one selected from polyhydric alcohols, polyalkylene glycols and glycol ethers. When these water-soluble organic solvents are used, even when a high-resolution fine nozzle head is used in order to obtain an image quality close to a photograph, clogging of the ink does not occur and ink ejection stability is maintained. Aggregation and precipitation of the coloring material can be prevented even for long-term storage. Among them, from the viewpoint of the dissolution stability of the coloring material, and from the viewpoint of the permeability of the ink to paper, and the solubility of the coloring material, glycol ether is preferably exemplified, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and Triethylene glycol monobutyl ether is particularly preferred.

The polyhydric alcohol and polyalkylene glycol include, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, 1,5-pentanediol, glycerin, 2,2'-thiodiethanol, triethanol Amines and the like are preferred. Preferred examples of the glycol ether include ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and propylene glycol monomethyl ether.

In addition to these water-soluble organic solvents, alcohols such as ethanol, isopropanol, butanol and benzyl alcohol, and alkanolamines such as monoethanolamine, diethanolamine and triethanolamine may be added. Among the above water-soluble organic solvents, a combination of sulfolane and glycerin, and a combination of sulfolane and diethylene glycol are particularly preferable from the balance of solubility and clogging of the coloring material and stability of ink ejection.

In the black ink of the present invention, the content of the water-soluble organic solvent is preferably 3 to 40% by weight based on the total amount of the ink. When the content of the water-soluble organic solvent is less than 3% by weight, the black ink is liable to dry and precipitate, and ejection failure such as nozzle clogging is liable to occur.
On the other hand, if it exceeds 40% by weight, the fixing property of the ink to the paper is poor, and the viscosity of the ink becomes high, so that the ejection failure is likely to occur. From the balance between nozzle clogging prevention and ejection stability, the content of the water-soluble organic solvent is more preferably from 10 to 35% by weight based on the total ink amount. Furthermore, the content of the organic solvent having a cyclic structure having a boiling point of 200 ° C. or more at normal pressure is preferably 5 to 15% by weight based on the total amount of the ink.

(Other components) The black ink of the present invention comprises:
A so-called surfactant may be added as the other component in order to further stabilize the dye dissolution state. The surfactant may be any of nonionic, anionic, cationic and amphoteric surfactants.

Examples of the nonionic surfactant include polyoxyethylene nonylphenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene alkyl phenyl ether such as polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene alkyl ether. Ethylene fatty acid esters,
Examples include sorbitan fatty acid esters, polyoxyethylene-polyoxypropylene block copolymers, ethylene oxide adducts of acetylene glycol, ethylene oxide adducts of glycerin, polyoxyethylene sorbitan fatty acid esters, and fatty acid alkylolamides.

Examples of the anionic surfactant include alkyl benzene sulfonate, alkyl naphthalene sulfonate, formalin condensate of alkyl naphthalene sulfonate, higher fatty acid salt, higher fatty acid ester sulfate and higher fatty acid ester. Sulfonate,
Sulfate esters and sulfonates of higher alcohol ethers, alkyl carboxylate salts of higher alkyl sulfonamides, sulfosuccinates, and ester salts thereof. As the cationic surfactant, for example, first,
Secondary and tertiary amine salts, quaternary ammonium salts and the like, and as the amphoteric surfactant, for example,
Betaine, sulfobetaine, sulfate betaine, imidazolyl betaine and the like.

Further, a fluorine-based surfactant such as polyoxyethylene perfluoroalkyl ether, perfluoroalkylbenzenesulfonate, perfluoroalkyl quaternary ammonium salt, or a silicon-based surfactant may be added.

Among these surfactants, nonionic surfactants that do not easily interact with dye ions and additive ions are preferable, and from the viewpoint of thermal stability and purity,
Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene
Polyoxypropylene block copolymers are preferred.

The amount of the surfactant added is preferably 0.005 to 5% by weight based on the total ink amount, and 0.01 to 2% by weight.
% Is more preferred.

[Inkjet Recording Method / Full-Color Inkjet Recording Method] The inkjet recording method of the present invention is an inkjet recording method in which ink droplets are ejected from an orifice in accordance with a recording signal to perform recording on a recording material. The ink is the black ink for inkjet recording of the present invention. Further, the full-color inkjet recording method of the present invention is a full-color inkjet recording method for recording on a recording material by discharging black ink, cyan ink, magenta ink, and yellow ink from an orifice according to a recording signal,
The black ink is the black ink for inkjet recording of the present invention.

In the ink-jet recording method and the full-color ink-jet recording method of the present invention (hereinafter simply referred to as "ink-jet recording method"), it is preferable to use inks having at least two dye concentrations (high and low). . Specifically, a high-concentration ink having a water-soluble dye concentration of 2.0 to 10.0% by weight based on the total ink amount, and a water-soluble dye concentration of 0.1 to 2.0% by weight based on the total ink amount. It is preferred to use inks having at least two density levels of low density inks, by weight. If the concentration of the water-soluble dye is higher than 10.0% by weight, the granularity of the image may be noticeable. On the other hand, when the concentration of the water-soluble dye is lower than 0.1% by weight, the image density becomes low, and the printing speed and the absorption speed to the medium may become slow due to the necessity of overprinting for deep printing. is there. The recording method using the high-density ink and the low-density ink as described above is particularly preferably applied to a full-color inkjet recording method. Thereby, an excellent image close to a photograph can be obtained. In this case, it is preferable to use a high density ink and a low density ink for the black ink, the cyan ink, and the magenta ink, respectively.

In the above-mentioned ink jet recording method, it is preferable that an ink ejection amount per one droplet (one drop) is 20 ng or less. The ink ejection amount can be used for an ink jet recording method of a large drop exceeding 20 ng. However, in order to obtain an image of excellent quality close to a photograph, the ink ejection amount per drop is 20 ng.
A small-drop inkjet recording method for high resolution in the following range is preferred. By using the black ink of the present invention, a high-quality printed image can be obtained without causing nozzle clogging. In addition, in order to obtain a higher quality print image, the amount of ink ejected per droplet should be 10
ng or less, more preferably 5 ng or less.

In the present invention, one droplet (one drop)
In an environment of 20 ° C. and 50% RH, the ink ejection amount per head is 、 of 662 × 80 dots using a head.
The toned image was ejected five times, the ejected ink was received by an ink absorber, and its weight was measured to determine the ejection amount per droplet.

Further, in the above-mentioned ink jet recording method, the surface to be printed has a surface defined by JIS-Z-8741.
It is preferable to print on an inkjet recording sheet having a 5 degree specular gloss of 40% or more. By printing the black ink of the present invention on the inkjet recording sheet, it is possible to obtain a printed image having excellent color developability and color reproducibility. The ink jet recording sheet has at least one coating layer on the surface to be printed, and the coating layer may contain at least one of inorganic fine particles and a cationic substance.

The inorganic fine particles preferably have a large specific surface area and a low refractive index. For example, synthetic fine particles of silica, calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium oxide, zinc oxide, Zinc carbonate, aluminum silicate, aluminum hydroxide, aluminum oxide, calcium silicate, magnesium silicate, polyaluminum hydroxide compound, alumina hydrate, colloidal silica, cereal starch particles, processed starch particles, plastic pigment, urea resin pigment, crystal Cellulose cellulose particles, inorganic, such as non-crystallized cellulose particles, organic pigments and particles and the like, among these pigments and particles, from the viewpoint of ink absorption and the color of the printed image,
Synthetic particulate silica, magnesium carbonate, barium sulfate,
Aluminum hydroxide, polyaluminum hydroxide compound,
Alumina hydrate, cereal starch particles, and modified starch particles are preferred.

Examples of the cationic substance include a conventionally known cationic resin which is a monomer, an oligomer or a polymer which dissociates when dissolved in water to exhibit a cationic property, and a cationic surfactant. Examples of the cationic resin include polyalkylene polyamines such as polyethylene amine and polypropylene polyamine, and derivatives thereof, acrylic resins having a tertiary amino group and a quaternary ammonium group, and diacrylamine. Examples of the cationic surfactant include primary, secondary and tertiary amine salts and quaternary ammonium salts.

The ink jet recording sheet may contain U
The light resistance can be further improved by adding a V absorber or an antioxidant, or by laminating a printed image with a UV film. In this case, a UV absorber or an antioxidant may be added to the ink as well as the ink jet recording sheet.

As the recording method used in the ink jet recording method, a so-called charge control method for discharging ink using electrostatic attraction, and a so-called drop-on-demand method for discharging ink using vibration pressure of a piezo element are used. (Pressure pulse method), and a so-called thermal ink-jet method in which ink droplets are formed using pressure generated by heating and forming bubbles by heating ink, and the like, and a thermal ink-jet method is preferable.

[0043]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples. [Preparation of Black Ink] A water-soluble dye, a water-soluble organic solvent, a surfactant, and water were mixed and dissolved sufficiently in the proportions shown in Table 1 below, and the pH was adjusted.
Filtered under pressure with a filter, Examples 1 to 6 and Comparative Example 1
To 12 were prepared (the numbers in the table indicate parts by weight).

[0044]

[Table 1]

For the 12 kinds of black inks prepared,
The following evaluation was performed. The evaluation was performed using a prototype inkjet recording head (constituting material is made of silicon, polyimide, epoxy, etc.) and a thermal inkjet printer on which the inkjet recording head was mounted. The driving conditions of the recording head are as follows: a driving voltage of 35 V, a resistance value of the heating resistor of 18;
The drive pulse for print ejection and the drive pulse for preliminary ejection for a recording signal at 0 Ω, frequency 7 kHz were performed under the following conditions. Preliminary ejection was performed at 1 × 10 ⁵ pulses when printing ejection exceeded 1 × 10 ⁷ pulses.

<Evaluation of Lightfastness> Using the black inks of Examples 1 to 6 and Comparative Examples 1 to 6, glossy paper A for ink-jet printer (75-degree specular gloss: 82%) by a thermal ink-jet printer produced as a trial. A solid image was printed on glossy paper B (75 ° specular gloss: 64%) for a commercially available inkjet printer. The image density (D1) was measured, and the light resistance tester (XF-180;
The image density (D2) after irradiation with light for 100 hours was measured using a Shimadzu Corporation (made by Shimadzu Corporation), and the density remaining rate (D = D2 / D)
1) was calculated. The higher the concentration residual ratio, the more excellent the light resistance. Further, the hue immediately after printing the solid image and the hue after light fading were visually compared and subjected to sensory evaluation, and the change in hue (color difference) was calculated using the following equation. The smaller the hue change, the better the light resistance. The results are shown in Table 2 below. (ΔE ^* ab = ｛(ΔL ^* ) ² + (Δa ^* ) ² + (Δ
b ^* ) ² ｝ ^1/2 )

The evaluation criteria are as follows. About hue (visual comparison sensory evaluation) ○: Black. ×: Reddish, not black.

Hue change (ΔE ^* ) ○: 0 ≦ ΔE ^* <10 Δ: 10 ≦ ΔE ^* <20 ×: 20 ≦ ΔE ^*

Concentration residual ratio D (%) ：: D ≧ 95 Δ: 90 ≦ D <95 ×: D <90

<Evaluation of Nozzle Clogging Resistance>
Using the black inks of Comparative Example 6 and Comparative Examples 1 to 6, a thermal inkjet printer with a resolution of 800 dpi was prototyped and left open for a predetermined time in an environment of 20 ° C. and 50% RH. Was done.
The ink drop amount at this time is 8 to 10
ng. The results are shown in Table 2 below. ：: A state in which ejection is possible after leaving for 300 seconds. Δ: State in which discharge is possible after standing for 180 seconds. ×: A state in which ejection is impossible after standing for 180 seconds.

[0051]

[Table 2]

From the results shown in Table 2, it can be seen that the use of the black inks of Examples 1 to 6 of the present invention is excellent in color reproducibility and light fastness, particularly in hue after light fading. Further, it can be seen that even when a fine nozzle for high resolution is used, the nozzle clogging resistance is excellent. On the other hand, it can be seen that these characteristics are inferior in the black inks of Comparative Examples 1 to 6 in which the components and the composition of the water-soluble dye are out of the range of the present invention.

[Preparation of Full Color Ink] A water-soluble dye, a water-soluble organic solvent, a surfactant, and water were sufficiently mixed and dissolved at the ratios shown in Table 3 below, and the pH was adjusted. The mixture was filtered under pressure with a 45 μm filter to prepare a black ink, a cyan ink, a magenta ink, and a yellow ink. Except for the yellow ink, inks of two types of dye concentrations, high density and low density, were prepared, respectively, to prepare a total of seven types of inks (the numbers in the table indicate parts by weight).

[0054]

[Table 3]

When a photographic image was printed on glossy paper using a prototype thermal ink jet printer with a resolution of 800 dpi using the seven types of inks thus produced, a printed image having no graininess and excellent color reproducibility was obtained. did it. Also, good image quality could be obtained even after light fading without changing from the hue immediately after printing.

[0056]

According to the present invention, a black ink for ink jet recording having excellent color reproducibility and light fastness, particularly excellent hue after photobleaching, excellent image quality close to photographs and high reliability, and The ink jet recording method and the full color ink jet recording method used can be provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eisuke Hiraoka 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. ) Inventor Hiromi Nagai 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Kaoru Watanabe 1600 Takematsu Minami Ashigara City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. 1600 Fuji Xerox Co., Ltd. (72) Inventor Takeshi Hashimoto 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.F-term (reference) 2C056 EA13 FC01 2H086 BA02 BA04 BA53 BA56 BA62 4J039 BC07 BC09 BC13 BC31 BC35 BC36 BC41 BC50 BC54 BC55 BC60 BE03 BE04 BE06 BE12 CA03 EA15 EA16 EA17 E A19 EA35 EA41 EA44 GA24

Claims (3)

[Claims] 1. A black ink for inkjet recording comprising at least water, a water-soluble organic solvent and a water-soluble dye, wherein the water-soluble dye is at least one selected from the group consisting of (A) a black dye having a disazo structure. Seed, (B)
(A) containing at least one selected from the group consisting of blue dyes having a phthalocyanine structure and (C) at least one selected from the group consisting of red dyes; )
(A): black for inkjet recording, satisfying [(B) + (C)] = 50: 1 to 4: 1, and (B) :( C) = 2: 3 to 3: 2. ink. 2. An ink jet recording method in which ink droplets are ejected from an orifice according to a recording signal to record on a recording material, wherein the ink is the black ink for inkjet recording according to claim 1. Inkjet recording method. 3. A full-color ink jet recording method in which a black ink, a cyan ink, a magenta ink, and a yellow ink are ejected from an orifice according to a recording signal to perform recording on a recording material, wherein the black ink is described in claim 1. A full-color ink jet recording method, characterized in that it is a black ink for ink jet recording.