JP2001106950A - Color ink set for ink jet recording and method for carrying out ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain color ink set for ink jet recording, excellent in reproducibility of color without depending on a material to be recorded, not causing clogging to ultrafine nozzle head and having following property to further sufficient printing frequency and provide a method for carrying out ink jet recording by using the ink set. SOLUTION: This color ink set for ink jet recording has Magenta ink, cyan ink and yellow ink. Each ink comprises at least water, a coloring material and a water-soluble organic solvent. In the ink, an absorption coefficient A in wavelength λA (nm) in which visible absorption spectrum of ink at pH 4-5 exhibits maximum absorption and an absorption coefficient B in wavelength λB (nm) in which visible absorption spectrum of ink at pH 7-9 satisfy (a) the formula 0.85<=A/B<=1.20 and (b) -10<=(λB-λA) <=10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color ink set for ink jet recording, and more particularly, to a color ink set for ink jet recording which provides excellent color reproducibility without depending on the properties of a recording material. The present invention relates to an ink jet recording method using the ink.

[0002]

2. Description of the Related Art The principle of an ink jet recording system is to discharge a liquid 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. A method of discharging ink includes a so-called charge control method in which ink is discharged using electrostatic attraction, a so-called drop-on-demand method (pressure pulse method) in which ink is discharged 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 by these methods, an extremely high-definition image can be obtained. it can.

As inks used in such an ink jet recording system, 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 types of liquid media composed of water and a water-soluble organic solvent are used. An aqueous pigment ink in which a pigment is dispersed, 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, an aqueous ink in which a water-soluble dye is dissolved has excellent safety because the main solvent is water. In addition, since a dye is used, a high-quality printed image is obtained with good color developability of a color image, the storage stability of the ink is excellent, and it has become a mainstream ink jet recording ink.

[0004] In recent years, there has been an increasing need for printed images of near-photo quality using ink-jet printing technology. To meet this need, magenta, cyan, and yellow inks themselves have excellent color reproducibility in forming color images, and the secondary colors obtained by printing these inks in layers It is important that the color reproducibility of the RGB colors is excellent.
Also, considering that printing is performed by overlaying inks of multiple color material density levels to obtain a print image of a quality close to a photograph, the occurrence of color bleeding and color mixing when printing multiple times, and It is important to prevent a delay in the drying properties.

Further, in order to increase the resolution of a printed image by a high-resolution small-drop ink jet recording method, the nozzles of an ink jet recording head become finer and it is important to prevent nozzle clogging. On the other hand, with the widespread use of inkjet printing technology, the variety of inkjet recording papers has also increased, and plain paper, coated paper, glossy paper, postcards, conventional copy paper, acidic paper, and OHP paper developed specifically for inkjet printing have been developed. Good recording quality has been required for each recording material such as a light-transmitting substrate such as a film.

However, in this case, the color tone of the printed image may change depending on the surface condition of the recording material, for example, pH. This is presumed that the chromophore of the dye molecule undergoes a structural change in the acidic region, resulting in a color change. In addition, since the dye rapidly aggregates and precipitates due to the change in pH, the form of aggregation and precipitation is not uniform unlike the conventional method, and since they are relatively large lumps, the printed matter becomes uneven. As a result, the light may be partially absorbed differently from the original selective absorption of the light, and may exhibit a color different from the original color tone of the coloring material separately from the above-described color change. Further, the irradiation light may cause irregular reflection on the surface of the coloring material, and white light may be added to the color spectrum, so that the sharpness may be deteriorated.

[0007] In particular, when the above phenomenon occurs in an OHP film or the like that requires transparency, not only the color tone of the dye is deviated from the original but also the printed portion does not transmit light. become.

Japanese Patent Application Laid-Open No. 9-3380 discloses that CI Direct Red 227 is used for magenta ink, and C.I.
I. Direct Blue 86 or CI Direct Blue 199
Discloses a color ink set for ink jet recording using CI Direct Yellow 86 and CI Direct Yellow 132 as color materials for at least one of the yellow inks. Japanese Patent Application Laid-Open No. Hei 9-100427 discloses that CI Direct Red 227 is used for magenta ink.
And CI Direct Blue 199 as the cyan ink and CI Direct Yellow 142 as the yellow ink, respectively, as a color material for inkjet recording. Further, JP-A-5-194889 discloses that CI Reactive Red 180 is used for magenta ink.
And CI Acid Red 52, CI Acid Blue Dye for cyan ink, CI Acid Yellow 23 for Yellow Ink, and a specific ink-jet recording color ink set.

Each of the ink sets described in these publications proposes to improve color reproducibility by using these ink sets. However, these ink jet recording color ink sets have not been able to obtain satisfactory color reproducibility for various recording materials. For example, when printing is performed on a recording material having an acidic surface, there has been a problem that the color tone of the dye is shifted from the original color tone. Further, when printing is performed using a fine nozzle head, there are problems that ejection is unstable and nozzle clogging occurs.

[0010]

As described above, there is a demand for a color ink set for ink jet recording, which is excellent in color reproducibility regardless of a recording material, does not clog even a fine nozzle head. No color ink set for inkjet recording satisfying various performances has been obtained.

Therefore, an object of the present invention is to provide an ink jet recording system which has excellent color reproducibility regardless of a recording material, does not cause clogging even in a fine nozzle head, and has sufficient followability to a printing frequency. It is an object of the present invention to provide a color ink set for use and an ink jet recording method using this ink set.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies, and as a result, have completed the following inventions <1> to <12>. <1> A color ink set for inkjet recording having a magenta ink, a cyan ink, and a yellow ink, wherein each of the magenta ink, the cyan ink, and the yellow ink contains at least water, a coloring material, and a water-soluble organic solvent. And an ink jet recording color ink set that satisfies the following conditions (a) and (b) at the same time. ( _A ) Absorbance A (abs.) At wavelength λ _A (nm) at which the visible absorption spectrum of the ink at pH 4 to 5 shows the maximum absorption
And the absorbance B (abs.) At a wavelength λ _B (nm) at which the visible absorption spectrum of the ink at pH 7 to 9 shows the maximum absorption, in the relationship of 0.85 ≦ A / B ≦ 1.20; and (b) −
10 ≦ (λ _B −λ _A ) ≦ 10.

<2> In the ink set of <1>,
A nitrogen-containing compound having a carboxylic acid and / or sulfonic acid structure (each of which may be a salt) having a pKa in the range of 6.0 to 10.0 at 20 ° C., and an alkali metal hydroxide (Represented by MOH, M is Li, Na
Or selected from K). <3> In the ink set of <2>, the nitrogen-containing compound is aminoethanesulfonic acid, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, acetamidoglycine, N-carbamoylmethyliminodiacetic acid , N-tris (hydroxymethyl) methyl-3-aminopropanesulfonic acid, and N, N-bis (2-hydroxyethyl) glycine. <4> In the ink set of <1> to <3>, the coloring material is preferably an anionic water-soluble dye.

<5> In the ink set of <4>,
The anionic water-soluble dye is preferably at least one selected from the following groups. I Magenta: CI Reactive Red 180, CI Acid Red 289 and CI Direct Red 75; II Cyan: CI Direct Blue 86, CI Direct Blue 199 and CI Acid Blue 9; and III Yellow: CI Direct Yellow 132 and CI Direct Yellow 144 .

<6> In the ink set of <1> to <5>, the water-soluble organic solvent contains two or more water-soluble organic solvents, and at least one of the water-soluble organic solvents has a boiling point of 200 at normal pressure. It is preferable that the temperature is not less than ° C. and that it has a cyclic structure. <7> In the ink set of <1> to <6>, the total content of the water-soluble organic solvent in each ink is preferably 3 to 40% by weight.

<8> In the ink set of <1> to <7>, the content of the water-soluble dye in each ink is 0.5.
It is preferably from 1 to 10.0% by weight. <9> In the ink sets of <1> to <8>, it is preferable that the cyan ink and / or the magenta ink have at least two color material density levels.

<10> An ink jet recording method in which ink is ejected using the color ink set for ink jet recording of <1> to <9> to perform recording on a recording material is preferable. <11> In the recording method of <10>, it is preferable that the amount of ink ejected per one droplet of the liquid droplet is 20 ng or less. <12> In the recording method of <10> to <11>, the recording material is an ink jet recording sheet, and the surface of the sheet preferably has a 75-degree specular glossiness specified by JIS Z8741 of 40% or more. .

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The color ink set for inkjet recording of the present invention,
It has a magenta ink, a cyan ink, and a yellow ink, and each of the inks contains at least water, a coloring material, and a water-soluble organic solvent.

Each of the inks has a wavelength λ at which the visible absorption spectrum of the ink at pH 4 to 5 shows the maximum absorption.
_A and absorbance at (nm) A (abs.) And the absorbance at a wavelength of the visible light absorption spectrum shows a maximum absorption λ _B (nm) of the ink in pH7~9 B (abs.) But, (a) 0.
85 ≦ A / B ≦ 1.20; and (b) −10 ≦ (λ _B −
Preferably, λ _A ) ≦ 10. Here, the absorbance at a certain wavelength, which shows the maximum absorption, differs for each ink. Therefore, the absorbances A and B are values when each ink is measured, that is, measured values. The absorbance at the wavelength showing the maximum absorption may be based on a single absorption band or a composite absorption band in which two or more absorption bands overlap.

If the A / B ratio is too small, aggregation and precipitation of the coloring material or a structural change occurs in the acidic region. For example, when printing is performed on acidic paper, the density of the printed image is reduced and the color tone is likely to change. Become. In addition, when printing is performed on an OHP film, the density of a printed image is reduced, the color tone is changed, and the transparency of a printed portion is further reduced. On the other hand, A
If the ratio / B is too large, the structural change of the coloring material occurs in the acidic region, and similarly, the color tone tends to change when printing on acidic paper. Also, when printing on an OHP film, a change in color tone occurs.

Further, the difference (λ _B -λ _A ) between the wavelengths showing the maximum absorption exceeds 10, that is, (λ _B -λ _A ) is -1.
If it is smaller than 0 or larger than 10, the change in the color tone due to the pH is large, and for example, the structural change of the coloring material occurs. For this reason, for example, when printing on acidic paper, the color tone is likely to change. Further, even when printing is performed on an OHP film, a change in color tone occurs, and a color different from the original color tone of the color material is exhibited. From the viewpoint of the stability of the color material and the color reproducibility, the condition of the above (a) is 0.900 ≦ A / B ≦ 1.
10, and the condition (b) is preferably −5 ≦
(Λ _B −λ _A ) ≦ 5 is preferred, and a combination of these is more preferred.

As the coloring material used in the color ink set for ink jet recording of the present invention, dyes and pigments are used for magenta ink, cyan ink and yellow ink, respectively. From the viewpoint of solubility and solubility stability, an anionic water-soluble dye is more preferable. Acid dyes, direct dyes, reactive dyes, food dyes and the like can be used as the anionic water-soluble dye.

The anionic water-soluble dye is not particularly limited as long as it satisfies the above conditions, but the magenta ink is at least one selected from the group consisting of CI Reactive Red 180, CI Acid Red 289 and CI Direct Red 75. One type, cyan ink is CI Direct Blue 86, CI Direct Blue 199 and CI Direct Blue 199
At least one selected from the group consisting of Acid Blue 9
It is preferable that the yellow ink contains at least one selected from the group consisting of CI Direct Yellow 132 and CI Direct Yellow 144.

By using the ink set for ink jet recording of such a combination, the color reproducibility of each color is excellent without being affected by the paper quality, and the secondary color obtained by superposing and printing these inks is obtained. Are also excellent in color reproducibility in RGB colors (red, green, blue), and black obtained by printing three colors in a superimposed manner is particularly preferable in that excellent color reproducibility can be obtained. When the recording material is an OHP film,
In addition to excellent color reproducibility, a printed image excellent in light transmittance of a printed portion can be obtained.

The magenta ink is CI Direct Red 75, and the cyan ink is CI Direct Blue 86
And a color ink set for inkjet recording containing at least one selected from the group consisting of CI Direct Blue 199 and at least one selected from the group consisting of CI Direct Yellow 132 and CI Direct Yellow 144. The obtained printed image shows excellent light fastness, and thus can be stored for a long period of time without impairing the quality of the printed image, which is a particularly preferable combination.

The color ink set of the present invention may optionally further comprise a black ink. As the coloring material of the black ink, either a dye or a pigment may be used, but a dye is preferable, and an anionic water-soluble dye is more preferable. As the anionic water-soluble dye, an acid dye, a direct dye, a reactive dye, an edible dye, and the like can be used, but the dye is not particularly limited as long as it satisfies the above conditions. Note that the black ink may be a black ink composed of a composite color of the cyan ink, the magenta ink, and the yellow ink.

Although the content of these dyes depends on the coloring properties of the dyes, it is 0.1 to 10.0% by weight based on the total amount of the ink.
Is preferably within the range. If the content of the dye is too small, the image density is low, and if the content of the dye is too large, the dye tends to precipitate. From the viewpoint of dissolution stability of the dye, the content of the dye is more preferably 0.3 to 8% by weight.

The water used in the present invention is preferably distilled water, ion-exchanged water, pure water, or ultrapure water. The ultrapure water is free from polyvalent cations, microorganisms, etc., and has high storage stability and clogging. Is particularly preferably used. The water content is 1
The content is preferably 30% to 98% by weight, more preferably 50% to 98% by weight, of the 00% by weight.

The water-soluble organic solvent used in the present invention contains two or more water-soluble organic solvents, and at least one of the water-soluble organic solvents has a boiling point of 200 ° C. or more at normal pressure (about 1 atm). And those having a cyclic structure are preferred. When the water-soluble organic solvent having a boiling point of 200 ° C. or more at normal pressure and having a cyclic structure is contained, the nozzle clogging resistance particularly when a fine nozzle head is used is improved. Further, since the ejection stability is also improved, excellent image quality can be obtained. Boiling point at normal pressure is 200
Examples of the water-soluble organic solvent having a cyclic structure at a temperature of not lower than 2 ° C. include, but are not limited to, 2-pyrrolidone, N-methyl-2-pyrrolidone, sulfolane, ethylene carbonate, and propylene carbonate. Sulfolane is particularly preferred from the viewpoint of the ejection stability of the ink for inkjet recording.

The water-soluble organic solvent other than the water-soluble organic solvent having a boiling point of 200 ° C. or more at normal pressure and having a cyclic structure is at least one selected from the group consisting of polyhydric alcohols, polyalkylene glycols and glycol ethers. Preferably it is a seed. When these water-soluble organic solvents are contained in the ink for inkjet recording, the moisturizing property of the ink and the solubility of the coloring material are improved, the clogging is suppressed, the ejection stability of the inkjet recording ink is maintained, and Aggregation and precipitation of the coloring material can be prevented even during storage.

Of these, glycerin, diethylene glycol, and 2,2'-thiodiethanol are particularly preferable from the viewpoint of the dissolution stability of the coloring material. Further, from the viewpoint of the permeability of the ink for inkjet recording into paper and the solubility of the coloring material, glycol ether is preferred, and diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether are particularly preferred.

Examples of the above-mentioned polyhydric alcohols and polyalkylene glycols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, 1,5-pentanediol, glycerin, 2,2'-thiodiethanol, and triethanolamine. Etc. can be suitably used.

As the above-mentioned glycol ether, for example, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether and the like can be suitably used.

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

In the present invention, the total content of the water-soluble organic solvent is 3% in 100% by weight of the ink for ink jet recording.
Preferably, it is about 40% by weight. If the total content of the water-soluble organic solvent is too small, the ink jet recording ink is liable to dry and precipitate, and ejection failure such as nozzle clogging is likely to occur. On the other hand, if the total content is too large,
The fixing property of the ink to paper is poor, and the viscosity of the ink is increased, which tends to cause ejection failure. From the balance of prevention of nozzle clogging and ejection stability, the content is more preferably 10.0 to 35.0% by weight. Further, the content of the water-soluble organic solvent having a boiling point of 200 ° C. or more at normal pressure and having a cyclic structure is determined by the ink for inkjet recording 100
It is preferable that it is 5 to 15% by weight of the weight%.

The color ink set for ink jet recording of the present invention may contain components other than those described above. For example,
The color ink set for inkjet recording of the present invention,
A nitrogen-containing compound having a carboxylic acid and / or sulfonic acid structure having a pKa in the range of 6.0 to 10.0 at 20 ° C. or a salt structure thereof, and an alkali metal hydroxide (MOH represented by MOH; Is selected from the group consisting of Li, Na and K). By containing these nitrogen-containing compounds and hydroxides of alkali metals, the pH change when the ink droplets land on the surface of the recording material is reduced by the buffering action. A change in color tone can be suppressed.

Examples of the above-mentioned nitrogen-containing compounds include nitrogen-containing compounds containing an alkyl group substituted with a carboxyl group and an alkyl group substituted with a sulfonic acid group. Further, in addition to a carboxyl group and a sulfonic acid group, compounds further containing an alkyl group substituted with a hydroxyl group, an alkyl group substituted with a carbamoyl group, and the like can be given.

Examples of the alkyl group substituted with a carboxyl group include a carboxymethyl group, a 1-carboxyethyl group, a 2-carboxyethyl group, a 1-carboxy-n-propyl group, a 2-carboxy-n-propyl group, -Carboxypropyl group, 2-carboxy-I-propyl group, 1-carboxy-n-
Butyl group 4-carboxybutyl group, 3-carboxy-I-butyl group, 2-methyl-4-carboxyl group, carboxy-t-butyl group, 5-carboxypentyl group and the like.

Examples of the alkyl group substituted with a sulfonic acid group include the above-mentioned alkyl group substituted with a carboxyl group, wherein the carboxyl group is replaced with a sulfonic acid group.

These acidic groups may be substituted with an alkyl group in the form of a lithium, sodium, potassium or ammonium salt. Preferred examples of these acidic groups include a carboxymethyl group, a 1-carboxyethyl group,
Examples thereof include a carboxy-n-propyl group, a sulfomethyl group, a 1-sulfoethyl group, and a 1-sulfo-n-propyl group.

Examples of the alkyl group substituted with a hydroxyl group include a methylol group, a 2-hydroxyethyl group, a methylolmethyl group, a trimethylolmethyl group, and a 1-hydroxy-n-
Propyl, 2-hydroxy-n-propyl, 3-hydroxypropyl, 2-hydroxy-I-propyl, 1-hydroxy-n-butyl, 4-hydroxybutyl, 3-hydroxy-I-butyl , 2-methyl-4-hydroxyl group, hydroxy-t-butyl group, 5-hydroxypentyl group and the like.

Examples of the alkyl group substituted with a carbamoyl group include the above-mentioned alkyl group substituted with a carboxyl group, in which the carboxyl group is replaced with carbamoyl. Preferred specific examples thereof include a methylol group, a 2-hydroxyethyl group, a trimethylolmethyl group, a carbamoylmethyl group and the like.

Examples of nitrogen-containing compounds containing these groups include acetamidoglycine, N-2-hydroxyethylglycine, N-carbamoylmethyl-β-alanine,
Hydroxyethyl-N-carbamoylmethylglycine, N-
Hydroxymethyl-N-carbamoylmethyl-γ-aminobutyric acid, N-carboxymethyliminodiacetamide, N-carbamoylmethyliminodiacetic acid, N-hydroxypropyliminodipropionic acid, N, N-bis (2-hydroxyethyl) glycine Or aminoethanesulfonic acid, N-2-hydroxyethyl-2-aminoethanesulfonic acid, N-3-hydroxypropyl-2-aminoethanesulfonic acid, N-carbamoylmethyl-2-aminoethanesulfonic acid, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, N-2-hydroxyethyl-N-carbamoylmethylaminoethanesulfonic acid, N-2-hydroxyethyl-N-carbamoylmethyl-
2-aminoethanesulfonic acid, N, N-bis-carbamoylmethyl-2-aminoethanesulfonic acid, N-2-hydroxyethyliminodiethanesulfonic acid, N-tris (hydroxymethyl) methyl-3-aminopropanesulfonic acid Or lithium, sodium, potassium or ammonium salts thereof.

In the present invention, among these nitrogen-containing compounds, aminoethanesulfonic acid and N, N-bis (2-hydroxyethyl) -2 are preferred in terms of solubility in an ink vehicle.
-Aminoethanesulfonic acid, acetamidoglycine, N-
Carbamoylmethyliminodiacetic acid, N-tris (hydroxymethyl) methyl-3-aminopropanesulfonic acid, N, N-
Bis (2-hydroxyethyl) glycine is preferred. In view of thermal stability, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid is more preferable.
In addition, since they do not absorb light in the visible portion, they do not affect the color tone and transparency of the printed image. These nitrogen-containing compounds may be used alone or in combination of two or more.

The content of the nitrogen-containing compound in the color ink set for ink-jet recording is appropriately determined depending on the solubility of the coloring material itself and the stability of color development with respect to pH.
An appropriate amount is selected. In order to exhibit sufficient coloring material dissolution stabilizing ability and pH stability, and also to sufficiently dissolve and stabilize the nitrogen-containing compound itself, 0.03 to 8% by weight is preferable. From the viewpoint of the balance with the dissolution stability, the content is more preferably 0.05 to 3% by weight.

The alkali metal hydroxide used in the present invention is selected from the group consisting of lithium hydroxide, sodium hydroxide and potassium hydroxide. Among these, lithium hydroxide or sodium hydroxide is preferred from the viewpoint of water retention when ionized.

In the present invention, the content of the alkali metal hydroxide in the color ink set for ink jet recording depends on the content of the nitrogen-containing compound and cannot be specified unconditionally. However, in order to stably dissolve each color material in the color ink set for inkjet recording, the pH of each ink is adjusted to 6.0 to 12.
It is preferable to keep it at zero. Therefore, the content of the alkali metal hydroxide is preferably 0.003% by weight or more. In order to sufficiently suppress deterioration such as corrosion, dissolution, and peeling of a material that is always in contact with the ink in the ink jet recording apparatus including the head material, the content is preferably 5.0% by weight or less. Thing is 0.00
It is preferably added in an amount within the range of 3 to 5.0% by weight and adjusting the pH of the color ink set for ink jet recording to the range of 6.0 to 12.0.

The ink-jet recording ink of the present invention comprises:
Other components may be contained, and those components can be appropriately selected according to the purpose without any particular limitation. For example, the inkjet recording ink of the present invention may contain a surfactant. Surfactants not only promote the penetration of the ink for inkjet recording into paper, but also interact with the colorant molecules to improve the wettability of the colorant with the paper fibers, resulting in color unevenness. This can prevent deterioration of image quality and color tone due to the image.

The surfactant that can be used in the present invention is at least one selected from nonionic surfactants, anionic surfactants and amphoteric surfactants.

As the nonionic surfactant, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene such as polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, etc. Fatty acid esters, sorbitan fatty acid esters, polyoxyethylene-polyoxypropylene block copolymers, ethylene oxide adducts of acetylene glycol, ethylene oxide adducts of glycerin, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylolamide and the like can be used. it can.

Examples of the anionic surfactant include alkyl benzene sulfonate, alkyl naphthalene sulfonate, formalin condensate of alkyl naphthalene sulfonate, higher fatty acid salt, sulfate salt of higher fatty acid ester, and sulfonic acid of higher fatty acid ester Salts, sulfates and sulfonates of higher alcohol ethers, and alkylcarboxylates, sulfosuccinates and ester salts of higher alkylsulfonamides, and the like can be used.

As the amphoteric surfactant, for example, betaine,
Sulfobetaine, sulfate betaine, imidazolidone betaine and the like can be used.

In the present invention, among these surfactants, nonionic surfactants that hardly interact with ions of the coloring material and ions of other components are preferable. Particularly, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene-polyoxypropylene block copolymer are more preferable in terms of thermal stability and purity.

In the present invention, the content of these surfactants in the inkjet recording ink is 0.00
It is preferably from 5 to 5% by weight, more preferably from 0.01 to 2% by weight.

The ink in the ink set for ink jet recording of the present invention may contain other components as necessary. As other components, for example, fungicides such as sodium dehydroacetate and sodium benzoate; PR
Fungicides such as OXEL (manufactured by ICI) and DOWICIL (manufactured by Dow Chemical Company); clathrates such as cyclodextrin, polycyclodextocin, and macrocyclic amines; urea;
Solubilizing agents such as thiourea; viscosity modifiers; conductive agents and the like.

The color material density level of each color of the color ink set of the present invention is preferably set to an appropriate level depending on the type of the color material used. Among them, it is preferable to set at least two types of color material density levels for the magenta and cyan inks of the color ink set of the present invention. Assuming that the color material density level of the ink having the highest color material density level is 1, the color material density level of the ink whose color material is lower than that of the ink is the granularity in the low density portion of the image. From the viewpoint of reduction, a color material density level selected from the range of 2/3 to 1/20 is preferable. When a level darker than 2/3 is used, the dot density is reduced in the low density portion of the image, so that individual dots are relatively easily recognized and the graininess tends to be noticeable. Using a level thinner than 1/20,
When image density is required to a certain extent, excessive overprinting is required.As a result, the printing speed is delayed, the drying time of the printed image is delayed, and the medium such as paper cannot absorb the ink droplets and the printing surface is not sufficiently absorbed. Tend to remain as unevenness. A color material density level selected from a range of 1/2 to 1/10 is more preferable as a balance that reduces the graininess and does not cause unevenness of a printed image.

The color ink set for ink jet recording according to the present invention is preferably applied to an ink jet recording method in which each ink is ejected to perform recording on a recording medium. A known technique can be used as a recording method of the inkjet recording method. For example, a so-called charge control method in which ink is ejected using electrostatic attraction, a so-called drop-on-demand method (pressure pulse method) in which ink is ejected using the oscillating pressure of a piezo element, and formation of bubbles by high heat A so-called thermal ink jet method in which ink is ejected using pressure generated by growth.

When the ink is ejected, it is preferable to use the method for a high-resolution small-drop ink jet recording method in which the ink ejection amount per one droplet (one drop) is within 20 ng or less. It is possible to use the ink jet recording method having a drop larger than 20 ng. However, in order to obtain a high-resolution excellent image, the ink discharge amount per drop is in the range of 20 ng or less. Small drop inkjet recording is preferred. As described above, by using the color ink set for inkjet recording of the present invention, a high-quality printed image can be obtained without causing nozzle clogging.
In order to obtain a higher quality printed image, the amount is preferably 10 ng or less, more preferably 5 ng or less.

The color ink set for ink jet recording of the present invention is not limited to the type of recording material, but the ink jet recording sheet whose surface to be printed has a 75 ° specular glossiness specified by JIS Z8741 of 40% or more. It is particularly preferable to print on the paper. By printing on the ink jet recording sheet using the color ink set for ink jet recording of the present invention, it is possible to obtain a printed image having particularly excellent color developing properties and color reproducibility. The ink jet recording sheet preferably has at least one coating layer on the surface to be printed, and the coating layer contains at least one inorganic or organic pigment or particle and / or cationic substance. Is good.

As the inorganic or organic pigments or particles, those having a large specific surface area and a low refractive index are preferred. For example, synthetic fine particle 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,
Inorganic or organic pigments or particles such as crystallized cellulose particles and non-crystallized cellulose particles can be used. Among these pigments and particles, synthetic fine particles of silica, magnesium carbonate, barium sulfate, aluminum hydroxide, a polyaluminum hydroxide compound, alumina hydrate, and cereal starch particles are used in terms of ink absorption and color of printed images. Preferred are processed starch particles.

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

[0062]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. (Examples 1 to 7 and Comparative Examples 1 to 6) Twelve kinds of ink composition sets of Examples 1 to 7 and Comparative Examples 1 to 6 were prepared using the components shown in Tables 1 and 2. Table 1 and Table 2
All numerical values in% are% by weight. After sufficiently mixing and dissolving each of the constituents shown in Tables 1 and 2, the pH of the ink was adjusted to about 7.5 with the pH adjusters shown in Tables 1 and 2, and the ink was applied with a 0.45 μm filter. Pressure filtration was performed to obtain an ink composition.

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[Table 1]

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[Table 2]

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[Table 3]

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[Table 4]

(Measurement of Characteristic Values) <Absorbance> Each of the inks of Examples 1 to 7 and Comparative Examples 1 to 6 was diluted with pure water, and the standard buffer pH4.
01 (manufactured by Wako Pure Chemical Industries, Ltd.) to adjust the pH of the diluent to about 4.5.
The pH of the diluent was adjusted to about 8.5 with a standard buffer pH 9.18 (manufactured by Wako Pure Chemical Industries, Ltd.).
Diluted 000-fold. These diluents were 10 m thick using a self-recording spectrophotometer (UV-2500PC: manufactured by Shimadzu Corporation).
The absorbance of the spectral characteristics was measured with a quartz cell of m. Table 3 shows the results.

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[Table 5]

<Ink Drop Amount> In a 20 ° C., 50% RH environment, a 662 × 80 dot 1/4 tone image was ejected five times using an ink head, and the ejected ink was ejected. The ejection amount per droplet was determined by measuring the weight of a small piece of the ink absorber.

(Evaluation of Ink Performance) <Saturation> For each of the ink sets of Examples 1 to 7 and Comparative Examples 1 to 6, a commercially available glossy paper for ink jet printer A (75
Degree specular gloss: 82%, manufactured by Fuji Xerox Co., Ltd .; commercially available glossy paper B for ink jet printer (75 degree specular gloss: 64%, manufactured by Seiko Epson); FX-L
Paper (neutral paper, Fuji Xerox Co., Ltd.) and 4024 paper (acid paper, Xerox Co., Ltd.), (i) cyan, magenta and yellow as primary colors; (ii) R as secondary colors
A solid image of GB color; and (iii) a black solid image in which cyan, magenta, and yellow were overprinted were printed, and a visual comparison sensory evaluation of chroma was performed. The results are shown in Tables 4 and 5.

The evaluation criteria are as follows. ：: There is almost no dullness of the color solid image. Δ: The color solid image is slightly dull. X: The dullness of the color solid image is sharp.

The evaluation criteria for (ii) red, green and blue secondary colors and (iii) black are as follows. (Red) ：: Bright red color. ×: Vermilion. (Green) ○: Vivid green color. X: A dull green color.

(Blue) ：: Vivid blue color. X: A dull blue color. (Black) ：: Pure black. ×: Reddish or bluish black.

<Light Transmittance> Examples 1 to 7 and Comparative Examples 1 to
For each ink set of No. 6, using a prototype inkjet printer, a solid image of primary colors of cyan, magenta, yellow, and a secondary color of RGB was formed on a commercially available OHP film (manufactured by Fuji Xerox Co., Ltd.). Print,
The image was projected by a transmission type overhead projector (manufactured by Fuji Xerox Co., Ltd.), and the color tone of each printed portion was visually evaluated. The results are shown in Tables 4 and 5.

The evaluation criteria are as follows. ：: There is no problem in the color tone of the color solid image. Δ: The color tone of the color solid image is slightly changed, or the projected image is slightly dark. X: The color tone of the color solid image is clearly changed, or the projected image is dark.

<Light resistance> Examples 1 to 7 and Comparative examples 1 to 6
For each ink set, a commercially available glossy paper A for ink jet printer (75% specular gloss: 82%, manufactured by Fuji Xerox Co., Ltd.) and a commercially available glossy paper B for ink jet printer (75 ° specular Gloss: 64%, Seiko Epson Corporation), FX-L paper (Fuji Xerox Corporation) and 4024
On paper (manufactured by Xerox Corporation), (i) cyan as a primary color,
Magenta and yellow; (ii) an RGB solid image as a secondary color; and (iii) a black solid image in which cyan, magenta and yellow were overprinted. After measuring the image density with a Macbeth densitometer, a light fastness tester (XF
-180: Shimadzu Corporation), irradiate light for 100 hours, and color difference before and after the test (ΔE ^* ab = ｛(ΔL ^* ) ² + (Δa ^* ) ²
+ (Δb ^* )｝ ^1/2 ) was calculated. The results are shown in Tables 4 and 5.

The evaluation criteria are as follows. ：: ΔE ^* is 25 or less, Δ: ΔE ^* is greater than 25 and 40 or less ×: ΔE ^* is greater than 40.

<Evaluation of Clogging Resistance> Each of the ink sets of Examples 1 to 7 and Comparative Examples 1 to 6 was tested to obtain a resolution of 800.
Using a dpi inkjet printer, 20 ° C,
After being left open for a predetermined time under an environment of 50% RH, a discharge test was performed. The results are shown in Tables 6 and 7. The evaluation was performed according to the following criteria. ：: A state in which ejection is possible after leaving for 300 seconds. Δ: State in which ejection is possible after standing for 180 seconds. ×: A state in which ejection is impossible after leaving for 180 seconds.

<Evaluation of Image White Area (Evaluation of Followability to Printing Frequency)> Each of the ink sets of Examples 1 to 7 and Comparative Examples 1 to 6 was subjected to FX using a prototype inkjet printer.
-A solid image was printed on L paper (manufactured by Fuji Xerox Co., Ltd.), and image white spots were visually evaluated. Tables 6 and 7 show the results.
Shown in The evaluation criteria are as follows. ：: A uniform image without white spots in a solid image. Δ: There are some white portions in the solid image. ×: There are large white portions in the solid image.

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[Table 6]

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[Table 7]

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[Table 8]

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[Table 9]

From the results shown in Tables 3 to 7, from Example 1,
-The color ink set for ink jet recording according to Example 7 is not limited to each ink, regardless of the paper quality, as well as the color reproducibility of the secondary color when printed in a superimposed manner, the light transmittance when printed on an OHP film, and the light fastness. It was found to be excellent in performance, nozzle clogging resistance and frequency response. On the other hand, in the color ink sets for ink jet recording of Comparative Examples 1 to 6 including inks in which the relationship of A / B or (λ _B −λ _A ) is out of the range of the present invention, those characteristics are inferior. It became.

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According to the present invention, excellent color reproducibility of secondary colors when printed in an overlapped manner and light transmittance when printed on an OHP film, regardless of paper quality, regardless of the paper quality, An ink jet recording color ink set having excellent light fastness and high reliability without causing nozzle clogging even in a fine nozzle head, and an ink jet recording method using this ink are provided.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiko Nakajo 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Hiromi Nagai 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72 ) Inventor Mihoko Tani 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 F Xerox Co., Ltd. F-term (reference) 2C056 EA09 EA13 FC02 4J039 BC06 BC07 BC09 BC24 BC35 BC36 BC50 BC54 BC55 BE03 BE04 BE06 BE12 CA03 EA15 EA16 EA17 EA33 EA35 EA41 EA42 EA44 FA02 GA24

Claims (2)

[Claims] 1. Magenta ink, cyan ink and yellow ink
Color ink for inkjet recording with low ink
A set, wherein said magenta ink, cyan ink and
Each of the yellow inks is at least water, colorant and water soluble
Containing an organic solvent and simultaneously carrying out the following (a) and (b)
Color for inkjet recording characterized by satisfying
Ink set; (a) Visible absorption spectrum of ink at pH 4-5
Is the wavelength λ at which _AAbsorbance A (abs.) In (nm)
And the maximum of the visible absorption spectrum of the ink at pH 7-9.
Λ showing large absorption_BThe absorbance B (abs.) At (nm) is
0.85 ≦ A / B ≦ 1.20, and (b) −10 ≦ (λ_B−λ_A) ≦ 10. 2. An ink jet recording method for recording on a recording material by discharging ink using the color ink set for ink jet recording according to claim 1.