JP2000345079A - Black ink excellent in black color reproducibility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide substantially achromatic black ink compositions excellent in black color reproducibility. SOLUTION: Upon carefully observing prints by a black ink composition containing carbon black at a very low concentration, a slightly yellowish black color has been observed. By improving this very slight color by addition of a magenta organic pigment, a cyan organic pigment, and a yellow organic pigment, the printing quality of prints could be improved beyond expectations. Accordingly, a black ink composition comprising carbon black, a magenta organic pigment, a cyan organic pigment, and a yellow organic pigment at a weight ratio of 1:0.01-0.5:0.01-0.5:0.01-0.5 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a black ink composition containing carbon black as a colorant, and more particularly to an ink composition preferably used in an ink jet recording method.

2. Description of the Related Art An ink jet recording method is a printing method in which small droplets of an ink composition fly and adhere to a recording medium such as paper to perform printing. This method has a feature that high-resolution and high-quality images can be printed at a high speed with a relatively inexpensive device.

[0003] Ink compositions used for ink-jet recording generally contain water as a main component, and further contain a coloring component and a wetting agent such as glycerin for the purpose of preventing clogging. As the colorant used in the ink composition for ink jet recording, a large number of water-soluble dyes are used because of high chroma of the colorant, a wide variety of available colorants, and solubility in water. I have. However, on the other hand, since the dye is essentially water-soluble, it may be inferior in various properties such as water resistance.

[0004] Pigments are more excellent in water resistance than dyes, and in recent years, their use as colorants in ink compositions for ink jet recording has been studied for the purpose of improving water resistance.
In a black ink composition, carbon black is generally used as a coloring agent.

[0005]

SUMMARY OF THE INVENTION When the present inventors carefully observed the printed matter using the black ink composition containing a very low concentration of carbon black, a slightly colored black was observed. Pure black is achromatic (a ^* = 0, b ^* =
0) but deviated from it.

The present inventor has found that by improving the above-mentioned slight coloring, the printing quality of the printed matter can be improved more than expected, and in improving the coloring, it is necessary to add an organic pigment instead of a dye. Was found to be desirable. The present invention is based on such findings.

Therefore, an object of the present invention is to provide a black ink composition having excellent black reproducibility.

[0008] The black ink composition according to the present invention comprises carbon black, a magenta organic pigment, a cyan organic pigment, and a yellow organic pigment.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The black ink composition according to the present invention is used in a recording system using the ink composition. Examples of the recording method using the ink composition include an ink jet recording method, a recording method using a writing instrument such as a pen, and various other printing methods. In particular, the ink composition according to the present invention is preferably used for an ink jet recording method.

[0010] The black ink composition according to the present invention basically comprises carbon black, a magenta organic pigment, a cyan organic pigment, and a yellow organic pigment.

As the carbon black, carbon black produced by a known method such as a contact method, a furnace method, and a thermal method can be used.

In the present invention, magenta organic pigment, cyan organic pigment, and yellow organic pigment are added in order to cancel the slight coloring of the carbon black used. As described above, although the coloring is negligible, a substantial improvement in print image quality can be obtained by substantially eliminating the coloring. Furthermore, this slight coloring is noticeably observed when the concentration of carbon black is low. However, according to the present invention, even in the ink composition having a low carbon black concentration, a good black color and a good print image can be formed. In particular, it is possible to realize an achromatic color under a low duty, and as a result, it is possible to stabilize the hue. Since carbon black is present as particles in the ink composition, if its concentration is high, it may not be desirable in terms of nozzle clogging or the like in an ink jet recording method. If the present invention is viewed from another viewpoint, the carbon black concentration can be reduced. Therefore, it is possible to obtain an advantage that a disadvantage that may be caused by a high carbon black concentration can be avoided.

The unit “duty” used in the present specification is defined by the following equation (I) and indicates the unit of the calculated value D.

(Equation 1)

The magenta organic pigment, cyan organic pigment, and yellow organic pigment used in the present invention are not particularly limited as long as the coloring can be substantially eliminated. According to a preferred embodiment of the present invention, As magenta organic pigments, C.I. I. Pigment Red 122,
In addition, C.I. I. Pigment Blue 1
5: 3 as C.I. I. Pigment yellow 74, C.I. I. Pigment Yellow 109,
C. I. Pigment yellow 110, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 13
8, C.I. I. Pigment Yellow 150 or C.I.
I. Pigment Yellow 154 is preferably used. The use of these three organic pigments, especially the simultaneous use, is most preferred.

The amounts of carbon black, magenta organic pigment, cyan organic pigment and yellow organic pigment to be added may be appropriately determined. According to a preferred embodiment of the present invention, the addition amount of carbon black is preferably about 1 to 5% by weight,
More preferably about 1.5 to 4% by weight,
The addition amount of the magenta organic pigment is preferably about 0.1 to 1.5% by weight, more preferably about 0.2 to 1% by weight, and the addition amount of the cyan organic pigment is 0.1 to 1.5% by weight. % By weight, more preferably about 0.2 to 1% by weight, and the addition amount of the yellow organic pigment is 0.1 to 1.
It is preferably about 5% by weight, more preferably about 0.2 to 1% by weight. Further, according to a preferred embodiment of the present invention, the black ink composition according to the present invention comprises carbon black, a magenta organic pigment, a cyan organic pigment, and a yellow organic pigment in a ratio of 1: 0.01 to 0.5: 0.01
０．５0.5: 0.01 to 0.5 by weight.

In the present invention, carbon black, magenta organic pigment, cyan organic pigment, and yellow organic pigment are added to an ink as a pigment dispersion obtained by dispersing in an aqueous medium with a dispersant or a surfactant. Is preferred. The average particle size of the pigment fine particles is preferably 200 nm or less, more preferably 150 nm or less.

According to a preferred embodiment of the present invention, the pigment is preferably added to the ink composition as a pigment dispersion obtained by dispersing the pigment in a solvent with a dispersant.
As a preferable dispersant, a known dispersant used for preparing a conventionally known pigment dispersion, for example, a polymer dispersant or a surfactant can be used.

Preferred examples of the polymer dispersant include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein and albumin; natural rubbers such as gum arabic and tragacanth; and savonin and the like. Glucosides; alginic acid and alginic acid derivatives such as alginic acid propylene glycol ester, alginic acid triethanolamine and ammonium alginate; methylcellulose, carboxymethylcellulose,
Examples include cellulose derivatives such as hydroxyethyl cellulose and ethyl hydroxyethyl cellulose.

Preferred examples of the polymer dispersant include synthetic polymers, such as polyvinyl alcohols; polyvinyl pyrrolidones; polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, and vinyl acetate. Acrylic resins such as acrylic ester copolymers and acrylic acid-alkyl acrylate copolymers; styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, and styrene-methacrylic acid-alkyl acrylate copolymers Styrene-acrylic acid resin such as polymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-alkyl acrylate copolymer; styrene-maleic acid; styrene-maleic anhydride Acid; vinyl naphthale -Acrylic acid copolymer; Vinyl naphthalene-maleic acid copolymer; Vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate maleate ester copolymer, vinyl acetate crotonic acid copolymer And vinyl acetate copolymers such as vinyl acetate acrylic acid copolymer and salts thereof. Among them, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer of a monomer having both a hydrophobic group and a hydrophilic group are preferable. Examples of the salt include salts with diethylamine, ammonia, ethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, triethanolamine, diethanolamine, aminomethylpropanol, morpholine, and the like. These copolymers preferably have a weight average molecular weight of 3,000 to 30,000, more preferably 5,000 to 15,000.

Examples of surfactants which are preferred as dispersants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, and sulfosuccinates. Anionic surfactants such as salts, naphthenates, liquid fatty oil sulfates, and alkyl allyl sulfonates; cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts, and phosphonium; polyoxyethylene Examples include nonionic surfactants such as alkyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, and polyoxyethylene sorbitan alkyl esters.

The amount of the dispersant added is preferably in the range of 0.1 to 1, more preferably 0.2 to 1, based on the total amount of the pigment in the ink composition.

The ink composition according to the present invention is preferably formed using a mixture of water and a water-soluble organic solvent as a basic solvent.

The water-soluble organic solvent added in the present invention is preferably a low-boiling organic solvent, and preferred examples thereof include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec- Butanol, tert-butanol, is
o-butanol, n-pentanol and the like.
Particularly, a monohydric alcohol is preferable. The low-boiling organic solvent has the effect of shortening the drying time of the ink composition.

According to a preferred embodiment of the present invention, the ink composition according to the present invention preferably further contains a high-boiling organic solvent in order to prevent nozzle clogging. Preferred examples of the high boiling organic solvent agent,
Polyvalents such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane Polyvalents such as alcohols, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and triethylene glycol monobutyl ether Alkyl ethers of alcohol S, urea, 2-pyrrolidone, N- methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, monoethanolamine, diethanolamine, triethanolamine.

The amount of the low boiling organic solvent to be added is preferably 0.5 to 10% by weight of the ink composition, more preferably 1.5 to 10% by weight.
-6% by weight. The amount of the high-boiling organic solvent to be added is preferably 0.5 to 40% by weight of the ink composition.
More preferably, it is in the range of 2 to 20% by weight.

According to a preferred embodiment of the present invention, the ink composition according to the present invention may contain a surfactant.
Examples of preferred surfactants include anionic surfactants (for example, sodium dodecylbenzenesulfonate, sodium laurate, ammonium salts of polyoxyethylene alkyl ether sulfate, etc.), nonionic surfactants (for example, Ethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkyl amide, etc., and these may be used alone or in combination of two or more. Can be used. In addition, acetylene glycol (olefin Y, surfynol 82, 10
4, 440, 465, 485, and TG (all Ai
r Products and Chemicals Inc.)) can also be used.

According to a preferred embodiment of the present invention, the ink composition according to the present invention may contain sugar. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucosyl Sorbitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a sugar in a broad sense, and is used to include a substance widely existing in nature such as alginic acid, α-cyclodextrin, and cellulose.

As the derivatives of these saccharides, reducing sugars of the above-mentioned saccharides (for example, sugar alcohols (formula H
OCH ₂ (CHOH) n CH ₂ OH (where n = 2
Represented by an integer of 5), oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thiosugars and the like. In particular, sugar alcohols are preferred, and specific examples include maltitol and sorbitol.

The content of these saccharides is suitably in the range of 0.1 to 40% by weight, preferably 0.5 to 30% by weight of the ink composition.

In addition, if necessary, a pH adjuster, a preservative, a fungicide, and the like may be added.

[0031]

EXAMPLES Preparation of ink An ink composition having the following composition was prepared as follows. First, a pigment and a dispersant resin were mixed and dispersed in a sand mill (manufactured by Yasukawa Seisakusho) together with glass beads (diameter 1.7 mm, 1.5 times the weight (weight) of the mixture) for 2 hours. Thereafter, the glass beads were removed, other additives were added, and the mixture was stirred at room temperature for 20 minutes. The mixture was filtered through a 5 μm membrane filter to obtain an ink composition. In the following,% is% by weight
Represents

Example 1 Carbon black 3.0% C.I. I. Pigment Blue 15: 3 0.3% C.I. I. Pigment Red 122 0.5% C.I. I. Pigment Yellow 74 0.4% Dispersant (styrene-acrylic acid copolymer) 0.9% (solid content) Glycerin 13% Diethylene glycol 5% Surfynol 465 1% Pure water Remaining amount

Example 2 Carbon black 2.1% C.I. I. Pigment Blue 15: 3 0.3% C.I. I. Pigment Red 122 0.5% C.I. I. Pigment Yellow 128 0.3% Dispersant (styrene-acrylic acid copolymer) 0.9% (solid content) Glycerin 15% Ethylene glycol 5% Triethanolamine 0.7% Surfynol 465 1% Diethylene glycol monobutyl ether 8% Pure water remaining

Example 3 Carbon black 3.5% C.I. I. Pigment Blue 15: 3 0.4% C.I. I. Pigment Red 122 0.7% C.I. I. Pigment Yellow 110 0.4% Dispersant (styrene-acrylic acid copolymer) 1.5% (solid content) Glycerin 10% Ethylene glycol 5% Triethanolamine 0.8% Surfynol 465 1% Triethylene glycol monobutyl ether 3% pure water remaining

Example 4 Carbon black 2.2% C.I. I. Pigment Blue 15: 3 0.3% C.I. I. Pigment Red 122 0.4% C.I. I. Pigment Yellow 154 0.3% Dispersant (styrene-acrylic acid copolymer) 0.7% (solid content) Glycerin 15% Ethylene glycol 7% Triethanolamine 0.7% Surfynol 465 0.8% Triethylene glycol Monobutyl ether 5% pure water

Comparative Example 1 1.0% carbon black I. Pigment Blue 15: 3 1.1% C.I. I. Pigment Red 122 3.0% C.I. I. Pigment Yellow 74 0.9% Dispersant (styrene-acrylic acid copolymer) 1.5% (solid content) Glycerin 11% Diethylene glycol 8% Triethanolamine 0.5% Surfynol 465 0.9% Pure water Remaining amount

Printing evaluation test Using an ink jet printer MJ-930C (manufactured by Seiko Epson Corporation), the solid ink image prepared above was used to print a solid image on a recording medium dedicated for ink jet (manufactured by Seiko Epson Corporation, exclusive glossy film). To 40
Printed at% duty and 100% duty. The weight of the ejected ink per dot was 0.040 μg, and the resolution was 360 dpi × 360 dpi.

The hue of the obtained image is expressed by Macbeth C
Using an E-7000 spectrophotometer (manufactured by Macbeth), L ^* a ^* b ^{* of the} color difference display method specified by CIE ^.
The coordinates of the color system were determined, and the image was evaluated based on the value of the saturation C ^* defined by the following equation (II).

(Equation 2) Criteria Evaluation A: C ^* <3 Evaluation B: 3 <C ^* <7 Evaluation NG: C ^* ≧ 7

[0039]

Claims (9)

[Claims] A carbon black, a magenta organic pigment, a cyan organic pigment, and a yellow organic pigment are:
0.01-0.5: 0.01-0.5: 0.01-0.
A black ink composition comprising the composition in a weight ratio of 5. 2. The method according to claim 1, wherein the magenta organic pigment is C.I. I. The black ink composition according to claim 1, which is Pigment Red 122. 3. The method according to claim 1, wherein the cyan organic pigment is C.I. I. The black ink composition according to claim 1, wherein the composition is Pigment Blue 15: 3. 4. The method according to claim 1, wherein the yellow organic pigment is C.I. I. Pigment yellow 74, C.I. I. Pigment Yellow 109,
C. I. Pigment yellow 110, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 13
8, C.I. I. Pigment Yellow 150 or C.I.
I. The black ink composition according to any one of claims 1 to 3, which is Pigment Yellow 154. 5. The black ink composition according to claim 1, comprising 1 to 5% by weight of said carbon black. 6. The black ink composition according to claim 1, which is used in an ink jet recording method. 7. A recording method for printing on a recording medium by adhering an ink composition, wherein the ink composition is an ink composition.
A recording method using the ink composition according to any one of claims 1 to 5. 8. An ink jet recording method for ejecting droplets of an ink composition and attaching the droplets to a recording medium to perform printing, wherein the ink composition is an ink composition according to any one of claims 1 to 5. A recording method using the ink composition described above. 9. A recorded matter printed by the method according to claim 7. Description: