JP2001288390A - Ink set for inkjet recording and method of inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set for inkjet recording and a method of inkjet recording having short drying time and capable of quickly attaining high density and high image-quality in recording regardless the kinds of a printing mode (printing speed and printing image) and a recording medium. SOLUTION: The inkjet set comprises at least one kind of color ink selected from a cyan ink, a magenta ink and a yellow ink, a black ink (a) having a surface tension (γa) of <=40 mN/m and a drying time of <=5 sec, and a black ink (b) having a surface tension (γb) of >=35 mN/m and a drying time of >=15 sec, and satisfying the surface tension (γa)<the surface tension (γb). In the method of inkjet recording using the ink set, the recording is carried out at a dropping amount (Vdrop(a)) per 1 drop of <=20 ng in the black ink (a) and at a dropping amount (Vdrop(b)) per 1 drop of >=1 ng and <=40 ng in the black ink (b), at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink set for ink jet recording and an ink jet recording method.

[0002]

2. Description of the Related Art Liquid or molten solid ink is ejected from a nozzle, a slit, a porous film, or the like.
Ink jet recording methods for recording on recording materials such as paper, cloth, film, etc. are commercially available because they have various advantages such as small size, low cost, excellent quietness, and high quality printing of photo quality. I have. Among them, the so-called piezo inkjet method using a piezoelectric element and the so-called thermal inkjet method in which droplets are formed by applying thermal energy to perform recording have many advantages such as high-speed printing and high resolution. I have.

The inks used in the ink jet recording method include (1) a high-resolution, high-density, uniform image without bleeding and fogging on paper, and (2) clogging due to ink drying at the nozzle tip. No discharge occurs, always good ejection responsiveness and ejection stability, (3) good ink drying properties on paper, (4) good image robustness, (5) long-term storage stability Are required.

[0004] In recent years, the printing speed in the ink jet recording method has been increasing more and more. with this,
The demand for ink having a short drying time on a recording medium has been increasing.

[0005] As a method of accelerating the penetration of the ink, various methods have been proposed in which a surfactant such as a surfactant is added to the ink. Regarding the amount of the surfactant,
No. 88048 discloses a recording method using an ink in which the surfactant concentration in the ink is between the CMC of the ink and the CMC in pure water. Regarding the HLB of a surfactant, Japanese Patent Application Laid-Open No. Hei 4-239067 discloses a method of improving the ejection characteristics with an ink containing a surfactant having an HLB of 10 to 20 used for a head having a specific configuration.
No. 7713 discloses an ink containing a nonionic surfactant having an HLB of 10 or more and a lipophilic group having a molecular weight of 400 or less for the purpose of improving image quality and jetting stability. JP-A-6-116522 discloses an ink containing a pigment, a water-soluble resin, and an acetylene glycol-based surfactant, and JP-A-10-287837 discloses an ink containing a self-dispersed pigment and an acetylene glycol-based surfactant. An ink containing an activator is disclosed.

[0006] However, in these methods, although the ink drying time is shortened, the optical density is reduced, the characters are blurred, and the like, and the compatibility with the image quality is not sufficient.

As a method for achieving both the image quality and the ink drying time, for example, Japanese Patent Application Laid-Open No. 6-122208 discloses a method in which the surface tension of black ink is 40 dyn / cm.
As described above, the surface tension of the other color ink is 40 dyn / c.
An ink jet recording method is disclosed in which a recording ink having a length of less than m is used, a color ink is printed on a black recording portion, and the black ink is overlaid and printed. JP-A-6-106735 discloses a surfactant or a penetrative solvent for imparting permeability to a color recording ink and a salt, and a black recording ink containing a component which causes thickening or aggregation by the action of the salt. And a method of contacting both on paper is disclosed.

However, these methods are inadequate in terms of high-speed printing adaptability because the color ink and the black ink are overprinted.

[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, an object of the present invention is to provide an ink jet recording system capable of quickly realizing a high density and high image quality without causing a drying time, regardless of a printing speed, an image to be printed, and a type of a recording medium. It is an object of the present invention to provide an ink set for printing and an ink jet recording method.

[0010]

The above object is achieved by the following means. That is, the present invention relates to <1> at least one type of color ink selected from cyan ink, magenta ink and yellow ink, and black ink (a)
And at least two kinds of black inks selected from black ink (b), wherein the black ink (a) has a surface tension (γa) of 40 mN / m or less, a drying time of 5 seconds or less, and a black ink (b) of Surface tension (γb)
35 mN / m or more, the drying time is 15 seconds or more, and the surface tension (γa) <the surface tension (γb), and the colorants in the black ink (a) and the black ink (b) are both pigments. It is an ink set for ink jet recording, which is a feature.

<2> The black ink comprises at least one kind of color ink selected from cyan, magenta and yellow, and at least two kinds of black inks selected from black ink (a) and black ink (b). (A) has a surface tension (γa) of 40 mN / m or less,
Using an ink set having a drying time of 5 seconds or less, a black ink (b) having a surface tension (γb) of 35 mN / m or more, a drying time of 15 seconds or more, and a surface tension (γa) <surface tension (γb), The drop amount per drop ( _{Vdrop (a)} ) in the ink (a) is 20 ng or less,
An ink-jet recording method wherein simultaneous recording is performed with a drop amount per drop (V _{drop (b)} ) in the black ink (b) of 1 ng to 40 ng.

[0012]

DETAILED DESCRIPTION OF THE INVENTION

[Ink set for inkjet recording] The ink set of the present invention comprises at least one kind of color ink selected from cyan ink, magenta ink and yellow ink;
And at least two kinds of black inks selected from black ink (a) and black ink (b).

[0013] The ink set of the present invention comprises a black ink (a) and a black ink (b) as black ink.
The black ink (a) has a surface tension (γa) of 40 mN / m or less, the drying time is 5 seconds or less, and the black ink (b) has a surface tension (γ) of
b) 35 mN / m or more, drying time 15 seconds or more, and surface tension (γa) <surface tension (γb), and the colorants in the black ink (a) and the black ink (b) are both pigments. By using at least two types of the black ink (a) and the black ink (b),
Regardless of the printing speed, the image to be printed, and the type of recording medium,
The drying time is short, and high density and high image quality can be realized quickly, that is, both high quality printing and high speed printing can be realized. In particular, by containing a pigment as a coloring agent in the black ink (a) and the black ink (b), high density and high image quality excellent in water resistance and light resistance can be realized.

Here, the drying time means that 100% black solid pattern is formed on FX-L paper (manufactured by Fuji Xerox Co., Ltd.).
And immediately after printing, another blank FX-L
This is the time during which the paper is pressed with a load of 100 N / m ² and is not stained. In addition, this printing is performed at a temperature of 23 ° C. ± 0.5 ° C.
Humidity 55 ± 5% R. H. It was done in an environment. The surface tension is a value measured using CPVP-A3 type (manufactured by Kyowa Interface Science Co., Ltd.). This device uses the Wilhelmy method in principle and is performed in an environment of 23 ° C.

The surface tension (γa) of the black ink (a) is 40 mN / m or less, but is preferably 4 mN / m.
0 to 20 mN / m, more preferably 35 to 25 m
N / m. This surface tension (γa) is 40 mN / m
When the black ink (a) is printed alone, the drying property on paper is deteriorated, and the paper is easily stained. Further, even when the black inks (a) and (b) are simultaneously printed, the drying property on the paper deteriorates, the paper is easily stained, and the boundary between the black ink and the color ink is easily blurred. .

The surface tension (γb) of the black ink (b) is not less than 35 mN / m, preferably 3 mN / m.
5 to 60 mN / m, more preferably 40 to 55 mN / m
N / m. This surface tension (γb) is 35 mN / m
If it is less than 3, when printing the black inks (a) and (b) simultaneously, blurring of the boundary between the black ink and the color ink easily occurs, and the image density also decreases.
Also, when black ink (b) is printed alone in the low-speed printing mode, image bleeding is likely to occur, and density reduction and image unevenness are likely to occur.

The relationship between the surface tension (γa) and the surface tension (γb) is as follows: surface tension (γa) <surface tension (γb), but when surface tension (γa) ≧ surface tension (γb), black ink is used. When (a) and (b) are simultaneously printed, image bleeding becomes conspicuous, and boundary bleeding between black ink and color ink also easily occurs.

The drying time of the black ink (a) is 5 seconds or less, preferably 1 to 5 seconds, and more preferably 1 to 4 seconds. If the drying time exceeds 5 seconds, when black inks (a) and (b) are printed at the same time, the permeability to paper is deteriorated, and drying is difficult.

The drying time of the black ink (b) is 15 seconds or more, preferably 15 to 150 seconds, more preferably 15 to 100 seconds. If the drying time is less than 15 seconds, the image density tends to decrease when the black inks (a) and (b) are simultaneously printed.

As the color ink, conventionally known color inks can be used, and each color has a surface tension of 40 mN /
m or less, more preferably 35 mN / m or less. If the surface tension exceeds 40 mN / m, the drying property in the secondary color portion may be deteriorated and the bleeding between adjacent colors may become conspicuous. Further, as the colorant in each color, any of pigments and dyes can be used, and it is also possible to combine the pigment and the dye for each color, but it is particularly preferable to use the dye from the viewpoint of the color developing property. .

The details of the black ink and color ink materials and the manufacturing method in the ink set of the present invention will be described later.

[Ink-jet recording method] The ink-jet recording method of the present invention comprises at least one color ink selected from cyan, magenta and yellow, and at least two types selected from black ink (a) and black ink (b). A black ink (a) having a surface tension (γa) of 40 mN / m or less and a drying time of 5 seconds or less, and a black ink (b) having a surface tension (γb) of 35 mN / m or more and a drying time of 15 seconds. Above,
This is a recording method using an ink set in which surface tension (γa) <surface tension (γb). The details are as described above.

In the ink jet recording method of the present invention, the drop amount per drop (V _{drop (a)} ) in the black ink ( _a ) is 20 ng or less, and the drop amount per drop (V) in the black ink (b) is
_{drop (b)} ) is 1 ng or more and 40 ng or less, and recording is performed simultaneously. By using the above specific ink set, and controlling the drop amount per drop in the black ink (a) and the black ink (b) and recording simultaneously, the printing speed, the image to be printed, and the type of the recording medium are reduced. Regardless, the drying time is short, and high density and high image quality can be realized quickly, that is, both high quality printing and high speed printing can be realized.

The drop amount per drop (V _{drop (a)} ) in the black ink (a) is 20 ng or less, preferably 15 ng or less, more preferably 7 ng or less.
ng or less. If the drop amount (V _{drop (a)} ) exceeds 20 ng, uneven bleeding of print dots tends to occur,
Bleeding of a character portion, a solid edge portion, a line portion and the like increases.

The drop amount per drop ( _{Vdrop (a)} ) in the black ink ( _a ) is the drop amount ( _Vdrop) per drop in the black ink (b).
_{drop (b)} ) is preferably smaller. Drop amount (V
_{If drop (a)} ) is larger than the drop amount ( _{Vdrop (b)} ), the bleeding of the image may easily increase.

The drop amount per drop (V _{drop (b)} ) in the black ink (b) is 1 ng or more and 40
ng or less, preferably 3 ng or more and 35 ng or less, more preferably 5 ng or more and 35 ng or less. If the drop amount ( _{Vdrop (b)} ) is less than 1 ng, the print dots will not spread sufficiently, making it difficult to obtain a sufficient image density. On the other hand, when it exceeds 40 ng, when black inks (a) and (b) are simultaneously printed, the drying property is apt to deteriorate, and the boundary blur between the black ink and the color ink is liable to occur.

Simultaneous recording of the black ink (a) and the black ink (b) means that these black inks are applied on a recording medium in such a manner as to be superimposed on a black print portion (dot). Either of the black inks (a) and (b) may be applied to the recording medium first.
Further, other color inks may be applied simultaneously (overlapping).

The ink weight ratio applied per unit area in the black inks (a) and (b) is black ink (a): black ink (b) = 0.1:
It is preferably in the range of 1-2: 1. When the ink weight applied per unit area of the black ink (a) is smaller than 1/10 times the ink weight applied per unit area of the black ink (b), the drying time becomes longer, The effect according to the present invention may not be sufficiently obtained. Further, the weight of the ink applied per unit area of the black ink (a) is equal to the weight of the black ink (b).
If the weight is more than twice the weight of the ink applied per unit area, the density may decrease and the bleeding may increase.

According to the ink jet recording method of the present invention, it is possible to quickly obtain high density and high image quality without causing any paper stain at any printing speed and type of print image (print mode). Print modes include, for example, high-speed print mode, low-speed print mode, photographic / high-gradation image print mode depending on the type of data image to be printed, high-coverage image print mode, low-coverage image print mode, and combinations thereof. And the like. Among these, in the high-speed print mode, it is possible to print effectively and quickly with high density and high image quality. In the present invention, the high-speed print mode refers to FX-L paper.
(Manufactured by Fuji Xerox Co., Ltd.) means an image forming apparatus such as a printer capable of printing eight or more sheets per minute.

The ink jet recording method of the present invention can quickly obtain high density and high image quality without causing paper stains, regardless of the type of recording medium. For example, a plain paper, a recording medium having a gloss layer and / or an ink absorbing layer, and the like can be mentioned. Plain paper refers to commercially available paper, mainly used for electrophotography, and not manufactured with the intention of having a structure, composition, and characteristics optimized for the application of the inkjet recording method. Specific examples of plain paper include high-quality paper and PPC paper. Further, a recording medium having a gloss layer and / or an ink absorbing layer means that the recording medium is provided with gloss and / or absorbs the ink composition,
Paper that has the function of fixing. Specific examples of such a recording medium include so-called coated paper and glossy paper.

In the ink jet recording method of the present invention, at least two kinds of black inks can be selectively used depending on the printing speed, the image to be printed, and the type of paper. In other words, by printing two or more types simultaneously or separately in the same device and printing, it is possible to obtain a printed image according to the application, reduce ink consumption per unit number, and reduce cost per sheet become. In particular,

In the high-speed printing mode, the black ink (a) can be used alone, and the drying time is short, and an image can be obtained. When it is desired to obtain a good image, it is preferable to use both the black inks (a) and (b).

In the low-speed printing mode, the black ink (a) can be used alone or the black ink (b) can be used alone, and a good image having no problem in drying property can be obtained. When it is desired to obtain a good image more quickly, it is preferable to use both the black inks (a) and (b).

In the photographic / high gradation image printing mode, black ink (a) is used alone for the light color portion,
By using the black ink (a) alone or the black ink (b) alone in the dark color portion, an image having excellent gradation can be obtained. If you want to obtain a good image more quickly, add black ink (a)
Preferably, both (b) and (b) are used.

In the high coverage image printing mode, the black ink (a) can be used alone, and the drying time is short, and a good image can be obtained. When it is desired to obtain a better image, it is preferable to use both the black inks (a) and (b).

In the low coverage image printing mode, the black ink (a) can be used alone or the black ink (b) can be used alone, and a good image can be obtained without any problem in drying property. When it is desired to obtain a good image more quickly, it is preferable to use both the black inks (a) and (b).

When a recording medium having a gloss layer and / or an ink absorbing layer is used, the black ink (a) can be used alone or the black ink (b) can be used alone. Can be obtained. To obtain better image quality, it is preferable to use both black inks (a) and (b).

The use examples of the black inks (a) and (b) according to the printing speed, the image to be printed, and the type of the recording medium are not particularly limited. It is determined as appropriate from the combination of the image to be printed and the type of recording medium.

In the ink jet recording method of the present invention, the drop amount per drop of the color ink is:
Each color is preferably 20 ng or less, more preferably 0.5 ng or more and 10 ng or less. By printing the color ink in this manner, it is possible to obtain an image quality with less blur and excellent gradation.

The details of the materials of the black ink and the color ink in the ink jet recording method of the present invention and the production method thereof will be described later.

[Others] With respect to the black ink and the color ink in the ink set of the present invention and the ink jet recording method (hereinafter, simply referred to as “the present invention”),
explain in detail.

As the coloring agent in the black ink,
Dyes and pigments are mentioned, and two or more kinds may be mixed. However, in the ink set of the present invention, only the pigment is used.

As the pigment, carbon black is preferably used. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Specific examples include the following, but are not limited thereto.

"Rave" manufactured by Columbian Carbon Co., Ltd.
n7000 "," Raven 5750 "," Raven
5250 ”,“ Raven5000 ULTRAI ”
I "," Raven 3500 "," Raven 200
0 "," Raven 1500 "," Raven 125
0 "," Raven 1200 "," Raven 1190 "
ULTRA II "," Raven 1170 "," Ra
ven 1255 "," Raven 1080, Raven
1060 ":" Regal400 "manufactured by Cabot Corporation
R "," Regal330R "," Regal660 "
R "," Mogul L "," Black Pearl "
s L "," Monarch 700 "," Monar
ch 800 "," Monarch 880 "," Mon
arch 900 "," Monarch 1000 ",
"Monarch 1100", "Monarch 1
300 "," Monarch 1400 ":" Color Black FW1 "," Colo "manufactured by Degussa
r Black FW2 "," Color Black
FW2V "," Color Black 18 ",
"Color Black FW200", "Colo
r Black S150 "," Color Black "
k S160 ”,“ ColorBlack S17 ”
0 "," Pritex35, PritexU "," P
ritex Vritex140U ”,“ Print
ex140V "," Special Black "
6 "," Special Black 5 "," Spe
Cial Black 4A "," Special B
rack4 ": Mitsubishi Chemical's" No. 25 "," N
o. No. 33, No. 40, No. 47, N
o. 52 "," No. 900 "," No. 2300 ",
"MCF-88", "MA600", "MA7", "M
A8 "," MA100 "

Although it is difficult to uniformly discuss the preferable structure of carbon black, it is difficult for carbon black to have a particle diameter of 15 to 30 n.
m, BET specific surface area is 70 to 300 m ² / g, DBP lubrication amount is 0.5 to 1.0 × 10 ⁻³ liter / g, volatile matter is 0.5 to 10 wt%, ash is 0.01 to 1.0 wt% It is preferred that When carbon black outside the above range is used, the dispersed particle diameter in the ink may be large.

The pigment is usually preferably used in a state of being dispersed by a pigment dispersant. As the pigment dispersant, a polymer dispersant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant and the like can be used.

As the polymer dispersant, any polymer having a hydrophilic structure portion and a hydrophobic structure portion can be effectively used.
As a polymer having a hydrophilic structure and a hydrophobic structure,
Condensed polymers and addition polymers can be used. Examples of the condensation polymer include known polyester dispersants.
Examples of the addition polymer include an addition polymer of a monomer having an α, β-ethylenically unsaturated group. The desired polymer dispersant can be obtained by appropriately combining and copolymerizing a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group and a monomer having an α, β-ethylenically unsaturated group having a hydrophobic group. Can be Further, a homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic group can also be used.

Examples of the monomer having an α, β-ethylenically unsaturated group having a hydrophilic group include monomers having a carboxyl group, a sulfonic acid group, a hydroxyl group, a phosphate group, etc., for example, acrylic acid, methacrylic acid, crotonic acid, Itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinylsulfonic acid, styrenesulfonic acid, sulfonated vinylnaphthalene, vinyl alcohol, vinylacetamide,
Acrylamide, methacryloxyethyl phosphate,
Bismethacryloxyethyl phosphate, methacryloxyethylphenylacid phosphate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate and the like can be mentioned.

The monomers having an α, β-ethylenically unsaturated group having a hydrophobic group include styrene derivatives such as styrene, α-methylstyrene and vinyltoluene, vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, and alkyl acrylates. And alkyl methacrylate, phenyl methacrylate, cycloalkyl methacrylate, alkyl crotonate, dialkyl itaconate, and dialkyl maleate.

A preferred example of the copolymer is styrene-
Styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-
Acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, alkyl acrylate-acrylic acid copolymer, alkyl methacrylate-methacrylic acid Acid, styrene-alkyl methacrylate-methacrylic acid copolymer, styrene-
Examples include alkyl acrylate-acrylic acid copolymer, styrene-phenyl methacrylate-methacrylic acid copolymer, and styrene-cyclohexyl methacrylate-methacrylic acid copolymer. Further, a monomer having a polyoxyethylene group or a hydroxyl group may be appropriately copolymerized with these polymers.

The copolymer may have any structure such as random, block and graft copolymers. Also, polystyrenesulfonic acid, polyacrylic acid, polymethacrylic acid, polyvinylsulfonic acid, polyalginic acid, polyoxyethylene-polyoxypropylene-polyoxyethylene block resin, formalin condensate of naphthalenesulfonic acid, polyvinylpyrrolidone, polyethyleneimine, polyamine , Polyamides, polyvinylimidazoline,
Aminoalkyl acrylate / acrylamide copolymer, chitosan, polyoxyethylene fatty acid amide, polyvinyl alcohol, polyacrylamide, cellulose derivatives such as carboxymethylcellulose, carboxyethylcellulose, and polysaccharides and derivatives thereof can also be used.

The pigment dispersants may be used alone or in combination of two or more. The amount of the pigment dispersing agent varies greatly depending on the pigment, but cannot be specified unconditionally. In general, however, the total amount is about 0.1 to 100% by weight, preferably 1 to 70% by weight, more preferably 3 to 50% by weight based on the pigment. weight%
Is added.

Preferred examples of the pigment include a pigment which can be self-dispersed in water. When a pigment that can be self-dispersed in water is used, a pigment dispersant is not required, so that a pigment dispersion having a low viscosity can be obtained, and the degree of freedom in designing additives and the like is widened, which is very suitable. The pigment that is self-dispersible in water is a pigment that has many water-solubilizing groups on the surface of the pigment and is stably dispersed without the presence of a polymer dispersant. Specifically, acid / base treatment, coupling agent treatment, polymer graft treatment,
By performing a surface modification treatment such as a plasma treatment or an oxidation / reduction treatment, a pigment that can be self-dispersed in water can be obtained. The criterion for self-dispersibility in water in the present invention is water 9
At a concentration of 5% by weight / 5% by weight of pigment, it is dispersed without a dispersant using an ultrasonic homogenizer, a nanomizer, a microfluidizer, a ball mill, etc., the initial pigment concentration is measured, and the dispersion is left in a glass bottle for one day. The pigment concentration of the supernatant was measured, and it was 98% or more of the initial concentration.

As pigments which can be self-dispersed in water, pigments obtained by subjecting the above-mentioned pigments such as carbon black to a surface modification treatment, and “Cab-o-jet-2” manufactured by Cabot Corporation
00 "," Cab-o-jet-300 "," IJX-
55 ":" Microjet B manufactured by Orient Chemical Co., Ltd. "
and commercially available pigments such as pigments sold by Nippon Shokubai Co., Ltd.

The solubilizing group present on the surface of the water-dispersible pigment can be any of nonionic, cationic and anionic. In the case of sulfonic acid, carboxylic acid and phosphoric acid, it can be used in the form of a free acid as it is, but it is preferable to use it in the form of a salt with a basic compound in order to enhance water solubility. Compounds that form salts with these polymers include alkali metals such as sodium, potassium and lithium, aliphatic amines such as monomethylamine, dimethylamine and triethylamine, monomethanolamine, monoethanolamine, diethanolamine and triethanol. Examples include amines, alcoholamines such as diisopropanolamine, and ammonia. Among these, basic compounds of alkali metals such as sodium, potassium and lithium are preferred. This is because basic compounds of alkali metals are strong electrolytes,
This is probably because the effect of promoting the dissociation of the acidic group is large.

The particle size of the pigment is preferably from 10 nm to 50 nm in number average particle size. When the number average particle diameter is in this range, when two or more kinds of black inks are mixed on a recording medium, an image having good ink fixability and high optical density can be obtained. This is because, when two or more kinds of black inks are mixed, when aggregation occurs due to particle interaction due to evaporation on paper and pH change, if the number average particle diameter of the carbon black is within the above range, the aggregation will occur. It is presumed that since the particle size becomes an appropriate size, it is possible to obtain an image which is balanced with penetration and has a high optical density and excellent fixability.

Here, the measuring device for the number average particle size is a Microtrac UPA particle size analyzer 9340 (Leeds
& Northrup). Specifically, 4 ml of the ink is placed in a measurement cell, and the measurement is performed according to a predetermined measurement method.
As parameters to be input at the time of measurement, the viscosity of the ink is input for the viscosity, and the density of the pigment is input for the density of the dispersed particles. This device measures the particle size using the Brownian motion of a dispersoid, and irradiates a solution with laser light and detects the scattered light to measure the particle size.

The pigment is used in an amount of 0.5 to 20% based on the weight of the ink.
It is preferred that it be used in a weight percent, preferably in the range of 2 to 10 weight percent.

Dyes include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes,
Any of a soluble vat dye, a reactive disperse dye, and an oil dye can be used. Among these, water-soluble dyes are preferred.

Among the water-soluble dyes, acidic dyes and direct dyes include, for example, C.I. I. Direct Black-2,-
4, -9, -11, -17, -19, -22, -32,
-80, -151, -154, -168, -171,-
194: C.I. I. Food Black-1, -2: C.I. I.
Acid Black-1, -2, -7, -16, -24,
-26, -28, -31, -48, -52, -63,-
107, -112, -118, -119, -121,-
156, -172, -194, -208: and the like, but are not limited thereto.

The dyes may be used alone or in combination of two or more. Furthermore, you may mix and use with a pigment. The dye is used in an amount of 0.1 to the total weight of the ink.
Preferably 10 to 10% by weight, more preferably 1 to 8% by weight
Is preferably used.

In the present invention, the colorants in the black inks (a) and (b) may be both pigments or dyes, or may be a combination in which one is a dye and the other is a pigment. In the case of the ink set of (1), only the pigment is used), and as the colorant in the black ink (b), a pigment is preferable in terms of water resistance and light resistance. Among them, carbon black which has been subjected to hydrophilic treatment by surface treatment is more preferable, and carbon black whose solubilizing group present on the surface is a carboxylic acid is more preferable. Also,
As the colorant in the black ink (a), pigments,
Any dye can be used, but in the case of a pigment, carbon black similarly hydrophilically treated by a surface treatment is preferable.

In the present invention, the black ink (a) and the black ink (b) are mixed (overlap) with each other.
Therefore, it is preferable to increase the viscosity or agglomerate. Thus, when applied over the recording medium, the density can be increased and the bleeding can be reduced.

When the black inks (a) and (b) are mixed with each other, the ink composition for thickening or aggregating one of the black inks (a) and (b) is a cationic ink. Carbon treated with a hydrophilic dye or a cationic dispersant or cationic carbon hydrophilically treated with a surface treatment, and the other colorant is carbon dispersed with an anionic dispersant or anion hydrophilic treated with a surface treatment And a composition for forming the conductive carbon. Further, a composition containing an electrolyte or a cationic substance in one or both of the black inks (a) and (b) may also be used.

As the electrolyte, alkali metal ions such as lithium ions, sodium ions, and potassium ions:
Polyvalent metal ions such as aluminum ion, barium ion, calcium ion, copper ion, iron ion, magnesium ion, manganese ion, nickel ion, tin ion, titanium ion and zinc ion: hydrochloric acid, bromic acid, hydroiodic acid, sulfuric acid , Nitric acid, phosphoric acid, thiocyanic acid: organic carboxylic acids such as acetic acid, oxalic acid, lactic acid, fumaric acid, fumaric acid, citric acid, salicylic acid, and benzoic acid, and salts of organic sulfonic acids. It is also possible to use a cationic substance which becomes an organic cation by dissociation in water, and specific examples thereof include primary, secondary, tertiary and quaternary amines and salts thereof. Can be

Specific examples of the electrolyte include lithium chloride, sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, sodium sulfate, potassium nitrate, sodium acetate, and the like.
Salts of alkali metals such as potassium oxalate, sodium citrate, potassium benzoate, and aluminum chloride;
Aluminum bromide, aluminum sulfate, aluminum nitrate, sodium aluminum sulfate, potassium aluminum sulfate, aluminum acetate, barium chloride, barium bromide, barium iodide, barium oxide, barium nitrate, barium thionate, calcium chloride, calcium bromide,
Calcium iodide, calcium nitrite, calcium nitrate, calcium dihydrogen phosphate, calcium thiocyanate, calcium benzoate, calcium acetate, calcium salicylate, calcium tartrate, calcium lactate, calcium fumarate, calcium citrate, copper chloride, bromide Copper, copper sulfate, copper nitrate, copper acetate, iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, iron oxalate, iron lactate, iron fumarate, iron citrate, magnesium chloride, magnesium bromide, iodine Magnesium iodide, magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium lactate, manganese chloride, manganese sulfate, manganese nitrate, manganese dihydrogen phosphate, manganese acetate, manganese salicylate, manganese benzoate, manganese lactate, nickel chloride, nickel bromide, Nickel sulfate, nickel nitrate Nickel acetate, tin sulfate,
Examples include salts of polyvalent metals such as titanium chloride, zinc chloride, zinc bromide, zinc sulfate, zinc nitrate, zinc thiocyanate, and zinc acetate.

Specific examples of the cationic substance include a tetraalkylammonium salt, an alkylamine salt, a benzalkonium salt, an alkylpyridium salt, an imidazolium salt, and a polyamine. -Butylamine, 2-ethylhexylamine, nonylamine, dipropylamine,
Diethylamine, trimethylamine, triethylamine, dimethylpropylamine, ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, tetraethylenepentamine, diethanolamine, diethylethanolamine, triethanolamine, tetramethylammonium chloride, tetraethylammonium bromide, dihydroxyethylstearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, stearamidomethylpyridium chloride, diallyldimethylammonium chloride polymer, diallylamine polymer,
Monoallylamine polymers and the like can be mentioned.

Examples of electrolytes and cationic substances include aluminum sulfate, calcium chloride, calcium nitrate, calcium acetate, magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium acetate, tin sulfate, zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, Aluminum nitrate, monoallylamine polymer, diallylamine polymer,
A diallyldimethylammonium chloride polymer or the like is preferred. Also, a cationic surfactant can be used.

The electrolyte and the cationic substance may be used alone or in combination of two or more. The content of the electrolyte is 0.1 to 15% by weight, preferably 0.1 to 15% by weight.
Used at 5-10% by weight. When an electrolyte or a cationic substance is added to the black ink, it is preferable to use a dye or carbon black which can be self-dispersed in water as a coloring agent from the viewpoint of storage stability of the ink.

As the colorant for the color ink, any of dyes and pigments can be used, and a dye having excellent color developing properties is preferably used.

The dyes include direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes,
Any of a soluble vat dye, a reactive disperse dye, and an oil dye can be used. The dye is preferably a water-soluble anionic dye. C. I. Direct Blue-1, -2, -6,
-8, -22, -34, -70, -71, -76, -7
8, -86, -112, -142, -165, -19
9, -200, -201, -202, -203, -20
7, -218, -236, -287, -307 ,: C.I.
I. Direct Red-1, -2, -4, -8, -9,
-11, -13, -15, -20, -28, -31,-
33, -37, -39, -51, -59, -62, -6
3, -73, -75, -80, -81, -83, -8
7, -90, -94, -95, -99, -101, -1
10, -189, -227: C.I. I. Direct Violet-2, -5, -9, -12, -18, -25,-
37, -43, -66, -72, -76, -84, -9
2, -107: C.I. I. Direct Yellow-1,-
2, -4, -8, -11, -12, -26, -27,-
28, -33, -34, -41, -44, -48, -5
8, -86, -87, -88, -132, -135,-
142, -144, -173: C.I. I. Acid Red-1, -4, -8, -13, -14, -15, -18,
−21, −26, −35, −37, −52, −110,
-144. -180, -249, -257: C.I. I. Acid Yellow-1, -3, -4, -7, -11, -1
2, -13, -14, -18, -19, -23, -2
5, -34, -38, -41, -42, -44, -5
3, -55, -61, -71, -76, -78, -7
And dyes having the following general formulas (I) and (II), such as 9, -122.

[0072]

Embedded image

(In the general formula (I), R ¹ and R ² each independently represent a group represented by the following formula (1) or (2), and Y and Z each independently represent a hydrogen atom or -SO ₃ M
Represents M represents a counter ion, and is an ion selected from the group consisting of an alkali metal ion, an ammonium ion, and a substituted ammonium ion. (In the general formula (II), Y represents a hydrogen atom, a methyl group, a methoxy group, an acetylamino group, or a nitro group, and may further form a benzene ring together with the 3-position carbon atom of the benzene ring A.) X represents an acetyl group, a benzoyl group, a paratoluenesulfonyl group, or a 4-chloro-6-hydroxy-1,3,5-triazin-2-yl group.
⁴ , M ⁵ and M ⁶ each represent a counter ion, and each is a base selected from among alkali metals, ammonium and amines. )

[0074]

Embedded image

(In the formulas (1) and (2), A, E, and G each independently represent a hydrogen atom, an alkyl group, —OH, and —
Represents a group selected from the group consisting of COOM. J, L,
Q, W are each independently hydrogen, -OH, -NH _2,
And it represents a group selected from the group consisting of -SO ₃ M.
M represents a counter ion, and is an ion selected from the group consisting of an alkali metal ion, an ammonium ion, and a substituted ammonium ion. )

The dyes may be used alone or in combination. The dye is used in an amount of 0.1 to 10 with respect to the total weight of the ink.
% By weight, more preferably 1 to 8% by weight.

In the present invention, water and a water-soluble organic solvent are usually added to the black ink and the color ink in addition to the components described above. Examples of the water-soluble organic solvent include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol and glycerin, and ethylene glycol monomethyl ether. , Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether,
Polyhydric alcohol derivatives such as diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and ethylene oxide adduct of diglycerin, pyrrolidone, N-methyl-
Nitrogen-containing solvents such as 2-pyrrolidone, cyclohexylpyrrolidone, and triethanolamine; alcohols such as ethanol, isopropyl alcohol, butyl alcohol, and benzyl alcohol; and sulfur-containing solvents such as thiodiethanol, thiodiglycerol, sulfolane, and dimethyl sulfoxide; Propylene carbonate, ethylene carbonate and the like can be used.

The water-soluble organic solvents may be used alone or in combination of two or more. The content of the water-soluble organic solvent is 1 to 60% by weight, preferably 5 to 40% by weight. If the amount of the water-soluble organic solvent is 1% by weight or less, clogging of the ink at the nozzle tip is likely to occur, and if the amount of the water-soluble organic solvent is 60% by weight or more, the ink ejection properties deteriorate.

In the present invention, a surfactant may be added to the black ink and the color ink in order to adjust the surface tension in addition to the components described above. As surfactants, anionic surfactants, cationic surfactants,
Examples include amphoteric surfactants and nonionic surfactants.

Examples of the anionic surfactant include, for example,
Alkyl benzene sulfonate, alkyl phenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, higher fatty acid ester sulfate, higher fatty acid ester sulfonate, higher alcohol ether sulfate and sulfonate, higher Alkyl sulfosuccinates, higher alkyl phosphate esters, phosphate esters of higher alcohol ethylene oxide adducts and the like can be mentioned. Also, for example, dodecylbenzenesulfonate, kerylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, monobutylbiphenylsulfonate, dibutylphenylphenoldisulfone Acid salts and the like can also be used effectively.

Examples of the nonionic surfactant include, for example,
Polypropylene glycol ethylene oxide adduct,
Polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester,
Examples include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, aliphatic alkanolamides, glycerin esters, sorbitan esters, and the like.

Examples of the cationic surfactant include:
Tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts and the like, for example, dihydroxyethylstearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium Chloride, stearamidomethylpyridium chloride and the like.

Other surfactants include silicone-based surfactants such as polysiloxane oxyethylene adducts and fluorine-based surfactants such as perfluoroalkyl carboxylate, perfluoroalkyl sulfonate and oxyethylene perfluoroalkyl ether. Surfactants, biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin can also be used.

In the present invention, in addition to the above-mentioned components, the black ink and the color ink include cellulose derivatives such as polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethyleneglycol, ethylcellulose and carboxyethylcellulose for the purpose of controlling ink properties. Sugars and their derivatives, other water-soluble polymers and polymer emulsions, cyclodextrins, macrocyclic amines, dendrimers, crown ethers, urea and its derivatives, acetamide, trimethylolethane, trimethylolpropane, and the like may be added. If necessary, an antioxidant, a fungicide, a conductive agent, an antioxidant, an ultraviolet absorber, a chelating agent, and the like can be added.

As the chelating agent, ethylenediaminetetraacetic acid (EDTA), iminodiacetic acid (IDA), ethylenediaminedi (o-hydroxyphenylacetic acid)
(EDDHA), nitrilotriacetic acid (NTA), dihydroxyethylglycine (DHEG), trans-1,2-
Cyclohexanediaminetetraacetic acid (CyDTA), diethylenetriamine-N, N, N ′, N ″, N ″ -pentaacetic acid (DTPA), glycol etherdiamine-N,
N, N ′, N ″ -tetraacetic acid (GEDTA) and the like.

As a viscosity modifier, it is also useful to add polysaccharides and derivatives thereof in addition to methylcellulose, ethylcellulose and derivatives thereof, glycerin and polyglycerin and adducts of polyethylene oxide and polypropylene oxide. For example, glucose, fructose, mannitol, D-sorbitol, dextran,
Xanthan gum, curdlan, cycloamylose, maltitol and derivatives thereof.

In the present invention, the pH of the black ink and the color ink can be adjusted as required. For adjusting the pH, for example, potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, triethanolamine, diethanolamine,
Ethanolamine, 2-amino-2-methyl-1-propanol, ammonia, ammonium phosphate, potassium phosphate, sodium phosphate, lithium phosphate, sodium sulfate, acetate, lactate, benzoate, acetic acid, hydrochloric acid, nitric acid, Sulfuric acid, phosphoric acid, propionic acid, P-toluenesulfonic acid and the like can be mentioned. It is also possible to use a general pH buffer.

In the present invention, the black ink and the color ink have the same viscosity for both inks.
It is preferably 1.5 to 5.0 mPas at 20 ° C., more preferably 1.6 to 4.0 mPas. If the viscosity is less than 1.5 mPas, it may be difficult to obtain ejection stability. On the other hand, if the viscosity exceeds 5.0 mPas, clogging may be easily caused, which is not preferable.

The present invention can be applied to a normal ink jet recording apparatus, and is supplied with energy according to an image signal, whereby ink is ejected as droplets and landed at a predetermined position on a recording medium. Images can be recorded. The present invention is particularly preferably applied to a thermal inkjet system. The thermal ink jet system heats ink to form bubbles, and utilizes the pressure generated by growing the bubbles to cause ink droplets to fly from a nozzle to a predetermined position on a recording medium, This is a method that can record images.

The present invention can be applied not only to a general ink jet recording apparatus but also to a recording apparatus equipped with a heater or the like for controlling the drying of ink, or to a recording material provided with an intermediate transfer mechanism, Can also be used in a recording device or the like that prints and transfers it to a recording medium such as paper.

[0091]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these embodiments do not limit the present invention.

[Carbon Black Dispersion Method 1] Pigment 30
3 parts by weight of a water-soluble resin and ion-exchanged water were added to parts by weight to make the total amount 300 parts by weight. This liquid was dispersed using an ultrasonic homogenizer. This liquid is subjected to a centrifugal separation treatment (8000 rpm × 30 minutes) by a centrifugal separator,
100 parts by weight of the residue portion was removed. This liquid was passed through a 1 μm filter to obtain a dispersion.

[Carbon Black Dispersion Method 2] With respect to the pigment dispersion liquid which can be self-dispersed in water, the dispersion liquid is subjected to a centrifugal separation treatment (8000 rpm ×
30 minutes), and the residue portion (20% by weight based on the total amount)
Was used.

(Dispersion liquid 1) According to the above carbon black dispersion method 1, a dispersion liquid having the following composition was obtained. —Composition— Carbon black: 20 parts by weight (Black Pearls L / Cabot) Styrene-methacrylic acid-sodium methacrylate copolymer: 5 parts by weight (St: MAA = 33: 67 / weight molecular weight: about 6200) /HLB=17.8) Ion-exchanged water: 75 parts by weight

(Dispersion liquid 2) According to the above carbon black dispersion method 2, a dispersion liquid having the following composition was obtained. —Composition— Anionic surface-treated pigment: 10 parts by weight (Cab-o-jet-300 / Cabot) Ion-exchanged water: 90 parts by weight

(Dispersion liquid 3) According to the above carbon black dispersion method 2, a dispersion liquid having the following composition was obtained. —Composition— Anionic surface-treated pigment: 10 parts by weight (Cab-o-jet-200 / Cabot) Ion-exchanged water: 90 parts by weight

(Dispersion liquid 4) According to the above carbon black dispersion method 2, a dispersion liquid having the following composition was obtained. -Composition- Cationic surface-treated pigment: 10 parts by weight (Surface functional group: quaternary ammonium salt) Ion-exchanged water: 90 parts by weight

<Ink Set 1> An ink set 1 comprising the following black ink, cyan ink, magenta ink, and yellow ink was prepared.

(Black Ink A-1) The following components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink A-1. -Components- Dispersion liquid 2 50 parts by weight Thiodiethanol 15 parts by weight Isopropyl alcohol 5 parts by weight Surfactant (Nonion E-215 / Nippon Oil & Fats Co., Ltd.) 0.05 parts by weight Ion exchange water: 29.95 parts by weight

(Black Ink A-2) The following components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink A-2. -Components- Dispersion liquid 2 ... 30 parts by weight Diethylene glycol ... 10 parts by weight Thiodiethanol ... 10 parts by weight Surfactant (Surfinol 440, manufactured by Nissin Chemical Co.) ... 0.4 parts by weight ion Replacement water: 49.6 parts by weight

(Cyan ink) The following components were thoroughly mixed,
The target cyan ink was obtained by stirring and passing through a 0.45 μm filter. The cyan ink had a surface tension of 34.1 mN / m. -Components- C. I. Direct Blue-199: 3 parts by weight Glycerin: 20 parts by weight Butyl carbitol: 5 parts by weight Ion exchange water: 72 parts by weight

(Magenta Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a desired magenta ink. The surface tension of this ink was 34.8 mN / m. -Components- C. I. Acid Red-75 2.5 parts by weight Diethylene glycol 15 parts by weight 2-pyrrolidone 5 parts by weight Butyl carbitol 4 parts by weight Ion-exchanged water 73.5 parts by weight

(Yellow Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a target yellow ink. The surface tension of this yellow ink was 33.1 mN / m. -Components- C. I. Direct Yellow-142 2 parts by weight Diethylene glycol 10 parts by weight Sulfolane 10 parts by weight Butyl carbitol 4 parts by weight Ion exchange water 76 parts by weight

<Ink Set 2> An ink set 2 comprising the following black ink, cyan ink, magenta ink, and yellow ink was prepared.

(Black Ink B-1) The following components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink B-1. -Components- Dispersion liquid 2 ... 40 parts by weight Diethylene glycol ... 5 parts by weight Glycerin ... 10 parts by weight Urea ... 3 parts by weight Surfactant (Nonion E-206 / manufactured by NOF Corporation) ... 0.02 parts by weight Ion exchange water ・ ・ ・ 41.98 parts by weight

(Black Ink B-2) The following components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink B-2. -Components- Dispersion 2 ... 5 parts by weight Dispersion 3 ... 20 parts by weight Glycerin ... 20 parts by weight Surfactant (Surfinol 465, manufactured by Nissin Chemical Co.) ... 1.5 parts by weight Calcium nitrate tetrahydrate: 0.5 parts by weight Ion-exchanged water: 63 parts by weight

(Cyan ink) The following components were sufficiently mixed,
The target cyan ink was obtained by stirring and passing through a 0.45 μm filter. The surface tension of this cyan ink was 31.2 mN / m. -Components- C. I. Direct Blue-199: 2.5 parts by weight C.I. I. Acid Blue-9: 0.5 parts by weight Ethylene glycol: 12 parts by weight Butyl carbitol: 3 parts by weight Surfactant (Surfinol 440, manufactured by Nissin Chemical Co., Ltd.): 0.4 parts by weight Part Ion exchange water ・ ・ ・ 81.6 parts by weight

(Magenta Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a desired magenta ink. The surface tension of this magenta ink was 35.2 mN / m. -Components- C. I. Acid Red-37 2.0 parts by weight C.I. I. Direct Violet-107: 0.5 parts by weight Propylene glycol: 20 parts by weight Butyl carbitol: 4 parts by weight Deionized water: 73.5 parts by weight

(Yellow Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a target yellow ink. The surface tension of this yellow ink was 35.0 mN / m. -Components- C. I. Direct Yellow-132: 2.0 parts by weight Diethylene glycol: 10 parts by weight Thiodiethanol: 5 parts by weight Hexyl carbitol: 3 parts by weight Deionized water: 80 parts by weight

<Ink Set 3> An ink set 3 comprising the following black ink, cyan ink, magenta ink, and yellow ink was prepared.

(Black Ink C-1) The above-mentioned components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink C-1. -Components- Dispersion 1 25 parts by weight Glycerin 10 parts by weight 2-pyrrolidone 6 parts by weight Diglycerin ethylene ethylene oxide adduct 3 parts by weight Urea 5 parts by weight Ion exchange Water: 51 parts by weight

(Black Ink C-2) The above-mentioned components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink C-2. -Components- Dispersion liquid 2 ... 30 parts by weight Diethylene glycol ... 15 parts by weight 2-Pyrrolidone ... 5 parts by weight Surfactant (Surfinol 485, manufactured by Nissin Chemical Co.) ... 1 part by weight Surface activity Agent (Surfinol 104, manufactured by Nissin Chemical Co., Ltd.) ... 0.2 parts by weight Sodium chloride ... 0.25 parts by weight N, N-Bis (2-hydroxyethyl) -2-aminoethane sulfonic acid ... 1.2 parts by weight Ion-exchanged water 47.35 parts by weight

(Cyan ink) The following components were thoroughly mixed,
The target cyan ink was obtained by stirring and passing through a 0.45 μm filter. The surface tension of this cyan ink was 31.6 mN / m. -Components- C. I. Direct Blue-86 3.0 parts by weight Glycerin 10 parts by weight 2-pyrrolidone 10 parts by weight Surfactant (Surfinol 440 / Nissin Chemical Co., Ltd.) 0.5 part by weight Ion exchange water: 76.5 parts by weight

(Magenta Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a desired magenta ink. The surface tension of this magenta ink was 29.1 mN / m. C. I. Direct Red-75 2.0 parts by weight Glycerin 10 parts by weight Sulfolane 10 parts by weight Surfactant (Surfinol 465, manufactured by Nissin Chemical Co.) 2.0 parts by weight Ion exchange Water: 76 parts by weight

(Yellow Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a target yellow ink. The surface tension of this yellow ink was 30.2 mN / m. C. I. Direct Yellow-86 2.5 parts by weight Glycerin 10 parts by weight Sulfolane 10 parts by weight Surfactant (Surfinol 485 / Nissin Chemical Co., Ltd.) 1.0 part by weight Surfactant Agent (Surfinol 465 / Nissin Chemical Co., Ltd.) 1.0 parts by weight Ion-exchanged water 75.5 parts

<Ink Set 4> An ink set 4 composed of a black ink, a cyan ink, a magenta ink, and a yellow ink shown below was prepared.

(Black Ink D-1) The following components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink D-1. -Components- Dispersion liquid 2 ... 50 parts by weight Diethylene glycol ... 15 parts by weight Thiodiethanol ... 5 parts by weight Urea ... 1 part by weight Surfactant (Pluronic PE6400, manufactured by BASF) ... 0. 03 parts by weight Ion exchange water… 28.97 parts by weight

(Black Ink D-2) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a desired black ink D-2. -Components- C. I. Direct Black-168 ... 3 parts by weight Glycerin ... 20 parts by weight Butyl carbitol ... 5 parts by weight Magnesium nitrate hexahydrate ... 1.0 parts by weight Ion exchange water ... 71 parts by weight

(Cyan ink) The following components were thoroughly mixed,
The target cyan ink was obtained by stirring and passing through a 0.45 μm filter. The surface tension of this cyan ink was 33.2 mN / m. -Components- C. I. Direct Blue-307: 3 parts by weight Diethylene glycol: 20 parts by weight Butyl carbitol: 6 parts by weight Ion exchange water: 71 parts by weight

(Magenta Ink) The following components were thoroughly mixed and stirred, and passed through a 0.45 μm filter to obtain a desired magenta ink. The surface tension of this magenta ink was 31.8 mN / m. -Components- C. I. Acid Red-37: 3 parts by weight Glycerin: 20 parts by weight Surfactant (SFN465, manufactured by Nissin Chemical Co., Ltd.): 1.2 parts by weight Ion exchange water: 75 parts by weight

(Yellow Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a target yellow ink. The surface tension of this yellow ink was 36.2 mN / m. -Components- C. I. Direct Yellow-142 2 parts by weight Thiodiglycol 5 parts by weight Ethylene glycol 15 parts by weight Triethylene glycol monobutyl ether 5 parts by weight Oxyethylene oleyl ether 0.5 parts by weight Ion exchange water: 72.5 parts by weight

<Ink Set 5> An ink set 5 comprising the following black ink, cyan ink, magenta ink, and yellow ink was prepared.

(Black Ink E-1) The following components were sufficiently mixed and stirred, and passed through a 2 μm filter to obtain a desired black ink E-1. -Components- Dispersion liquid 4 ... 40 parts by weight Diethylene glycol ... 10 parts by weight Propylene glycol ... 5 parts by weight Isopropyl alcohol ... 3 parts by weight Surfactant (Nonion E-230 / manufactured by NOF Corporation) ..0.05 parts by weight ion-exchange water 41.95 parts by weight

(Black Ink E-2) The following components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink E-2. -Components- Dispersion liquid 2 40 weight parts Glycerin 20 weight parts Urea 4 weight parts Surfactant (Surfinol 104, manufactured by Nissin Chemical Co., Ltd.) 0.25 weight parts Water: 35.75 parts by weight

(Cyan ink) The following components were thoroughly mixed,
The target cyan ink was obtained by stirring and passing through a 0.45 μm filter. The surface tension of this cyan ink was 33.1 mN / m. -Components- C. I. Direct Blue-86: 3.0 parts by weight Propylene glycol: 20 parts by weight Butyl carbitol: 5 parts by weight Urea: 3 parts by weight Ion exchange water: 69 parts by weight

(Magenta Ink) The following components were thoroughly mixed and stirred, and passed through a 0.45 μm filter to obtain a desired magenta ink. The surface tension of this magenta ink was 34.2 mN / m. -Components- C. I. Acid Red-37 1.5 parts by weight C.I. I. Direct Violet-107: 1.0 part by weight Thiodiglycol: 15 parts by weight Butyl carbitol: 5 parts by weight Deionized water: 77.5 parts by weight

(Yellow Ink) The following components were sufficiently mixed and stirred, and passed through a 0.45 μm filter to obtain a target yellow ink. The surface tension of this yellow ink was 32.9 mN / m. -Components- C. I. Direct Yellow-142: 2.0 parts by weight Thiodiglycol: 15 parts by weight Ethylene glycol: 5 parts by weight Butyl carbitol: 5 parts by weight Ion exchange water: 73 parts by weight

<Ink Set 6> An ink set 6 comprising the following black ink, cyan ink, magenta ink, and yellow ink was prepared.

(Black Ink F-1) The following components were sufficiently mixed and stirred, and passed through a 2 μm filter to obtain a desired black ink F-1. -Components- Dispersion liquid 1 ... 50 parts by weight Propylene glycol ... 15 parts by weight Isopropyl alcohol ... 3 parts by weight Surfactant (Nonion E-215 / Nippon Yushi Co., Ltd.) ... 0.05 parts by weight Ion exchange water: 31.95 parts by weight

(Black Ink F-2) The following components were sufficiently mixed and stirred, and passed through a 2 μm filter to obtain a desired black ink F-2. -Components- Dispersion liquid 2 ... 30 parts by weight Diethylene glycol ... 10 parts by weight Thiodiethanol ... 10 parts by weight Surfactant (Pluronic BE6400, manufactured by BASF) ... 0.03 parts by weight Ion exchange water ..49.7 parts by weight

(Cyan Ink, Magenta Ink, Yellow Ink) The same color inks as those in the ink set 1 were used as the cyan, magenta, and yellow inks.

<Ink Set 7> An ink set 7 comprising the following black ink, cyan ink, magenta ink, and yellow ink was prepared.

(Black Ink G-1) The following components were sufficiently mixed and stirred, and passed through a 2 μm filter to obtain a desired black ink G-1. -Components- Dispersion liquid 2 ... 40 parts by weight Thiodiethanol ... 10 parts by weight Sulfolane ... 5 parts by weight Urea ... 6 parts by weight Surfactant (Surfinol 440, manufactured by Nissin Chemical Co., Ltd.)・ 0.4 parts by weight

(Black Ink G-2) The above components were sufficiently mixed, stirred, and passed through a 2 μm filter to obtain a desired black ink G-2. -Components- Dispersion 2 ... 30 parts by weight Dispersion 3 ... 10 parts by weight Glycerin ... 15 parts by weight Surfactant (Surfinol 440, manufactured by Nissin Chemical Co.) ... 0.4 parts by weight

(Cyan Ink, Magenta Ink, and Yellow Ink) The same color inks as the ink set 2 were used for the cyan, magenta, and yellow inks.

<Ink Set 1a, 1b to Ink Set 5a, 5b> Except that the ink set 1 uses only one of the two types of black ink,
Ink set 1a similar to ink set 1 (black ink uses only A-1), 2b (black ink
A-1). Similarly, the configurations other than the black ink are the same as the ink sets 2a and 2a, respectively.
b to ink sets 5a and 5b were obtained.

[Examples 1 to 5, Comparative Examples 1-1 and 1-2]
Comparative Examples 5-1 and 5-2 and Comparative Examples 6 to 9] Each of the ink sets shown in Table 1 was applied to Fuji Xerox 800 dp.
i, placed in a thermal-type full-color inkjet printer prototype, the black ink shown in Table 1 was ejected at a specific drop amount, and a black solid pattern for evaluation and a color black adjacent pattern were printed. Printing was performed in both a high-speed printing mode of 15 ppm (15 sheets / min) and a high-quality (low-speed) printing mode of 5 ppm (5 sheets / min). FX-L paper (manufactured by Fuji Xerox Co., Ltd.) was used as a recording medium. Unless otherwise specified, printing and evaluation were performed in a general environment (temperature: 23 ° C. ± 0.5 ° C., humidity: 55 ° C.).
± 5% R. H). Table 1 shows the surface tension of each black ink measured as described above.

(Evaluation) Evaluation was made on the drying time of the black solid part, the optical density of the black solid part, the paper stain when the paper was overlapped immediately after printing, the bleeding of the black character part, the bleeding of the black color boundary, the water resistance of the black solid part. Went about. Table 1 shows the results.

-Drying time- The drying time was as follows: a 100% black solid pattern was applied, and immediately after printing, another blank FX-L paper
/ M ² was measured by measuring the time when it was pressed to remove stains.

—Optical Density— The optical density was measured by measuring the black solid pattern portion using X-Rite 404 (manufactured by X-Rite Co.). 、, those of 1.1 or more and less than 1.3 were evaluated as Δ, and those of less than 1.1 were evaluated as x.

—Paper Stain— Paper stain is immediately after printing on the black solid pattern portion.
X-L paper was overlapped, and the degree of dirt transferred to the paper was organoleptically evaluated. A sample that was not dirty at all was rated as ○, a slightly dirty one was rated △, and one that was very dirty was rated X.

-Bleeding of the black character part-The bleeding of the black character part was visually evaluated by the sensory evaluation of Mincho and Gothic 11-point characters, and those without bleeding were evaluated as ○, slightly blurred 滲, and severely blurred as ×. Did.

-Black color boundary bleed-The black color boundary bleed was visually evaluated by sensory evaluation of the printed black-color adjacent pattern. .

-Water resistance of black solit part-Water resistance of the black solit part was determined by immersing a black solit part after printing for 24 hours in pure water for 1 minute, and visually evaluating the discoloration after pulling up. ○, little discoloration, Δ, slight discoloration, and x, severe discoloration.

[0145]

[Table 1]

From Table 1, it can be seen that by using the two kinds of black inks (a) and (b) in the present invention for printing, regardless of the high-speed printing mode and the high-quality (low-speed) printing mode.
It can be seen that printing is possible at a high density, with little character bleeding or color bleeding between colors, and without paper stains due to the slow drying property of printed matter even when paper is superimposed immediately after printing. It can be seen that an image having good water resistance can be obtained by using a pigment as a coloring agent in the two types of black inks (a) and (b).

In the high quality (low speed) printing mode,
Depending on the type of ink, two types of black ink (a)
Alternatively, it can be seen that a good image can be obtained to some extent even when (b) is printed alone. On the other hand, in the case of the high-speed printing mode, when the black ink (a) was printed alone, a good image was not obtained, but the drying time was extremely fast.
It can be seen that quick printing can be performed. From these results, it can be seen that the running cost can be reduced by performing printing in combination or alone according to the application.

[0148]

As described above, according to the present invention, regardless of the printing speed, the image to be printed, and the type of the recording medium, the drying time is fast, the paper is not stained, and the high density and high image quality are quickly obtained. It is possible to provide an ink jet recording ink set and an ink jet recording method that can realize the above.

Continued on the front page (72) Inventor Nobuyuki Ichizawa 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Takeshi Hashimoto 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. F-term (reference) 2C056 EA01 EA05 EA13 EA24 EA25 EC15 EC65 EC80 FA03 FC02 2H086 BA03 BA53 BA55 BA60 4J039 BA04 BE01 BE03 BE04 BE05 BE06 EA10 EA15 EA16 EA17 EA19 EA42 EA47 GA24

Claims (2)

[Claims] 1. A color ink comprising at least one kind of color ink selected from cyan ink, magenta ink and yellow ink, and at least two kinds of black ink selected from black ink (a) and black ink (b), Black ink (a) has a surface tension (γa) of 40 mN /
m, the drying time is 5 seconds or less, the black ink (b) has a surface tension (γb) of 35 mN / m or more, the drying time is 15 seconds or more, and the surface tension (γa) <the surface tension (γb). An ink set for inkjet recording, wherein the colorant in the ink (a) and the colorant in the black ink (b) are both pigments. 2. A color ink comprising at least one kind of color ink selected from cyan, magenta and yellow, and at least two kinds of black inks selected from black ink (a) and black ink (b). a) is a surface tension (γa) of 40 mN /
m or less, a drying time of 5 seconds or less, an ink set in which the black ink (b) has a surface tension (γb) of 35 mN / m or more, a drying time of 15 seconds or more, and a surface tension (γa) <surface tension (γb). The drop amount per drop (V _{drop (a)} ) in the black ink ( _a ) is 20 ng or less, and the drop amount per drop (V
An ink jet recording method characterized in that simultaneous recording is carried out at a _{drop (b)} of 1 ng to 40 ng.