JP2002121438A - Ink set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink set for ink-jet recording, having high drying characteristics of ink, slight blurring between different colors especially in forming a color image and no unevenness of secondary color. SOLUTION: This ink set is an aqueous ink provided with a colorless or light-colored solution and an ink material containing one or more kinds of inks. The colorless or the light-colored solution contains at least a water-soluble organic solvent and water, has <=5 seconds drying time on plain paper and a surface tension γa of >=20 mN/m and <=40 mN/m. Each ink contained in the ink material comprises a colorant, a water-soluble organic solvent and water, has <=20 seconds drying time on plain paper and a surface tension γb of >=25 mN/m and <=40 mN/m and a relation of γa<=γb is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording apparatus (printer, copier, facsimile,
Ink set used in a word processor or the like).

[0002]

2. Description of the Related Art The principle of the ink jet recording method 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 a recording medium such as paper, cloth, or film. The method of discharging ink is a method of discharging ink using electrostatic attraction, a so-called charge control method, a method of discharging ink using vibration pressure of a piezoelectric element, and forming and growing bubbles by heat. Ejecting ink using the generated pressure,
Various systems such as a so-called thermal inkjet system have been proposed.

A recording apparatus of the ink jet recording system has been energetically studied because of its advantages such as small size, low cost, quietness, etc., and recently, excellent printing on so-called plain paper such as report paper and copy paper. Many color printers capable of full-color printing as well as black single-color printers capable of obtaining high quality are commercially available, and occupy a large position in the field of printing apparatuses.

[0004] Ink used in an ink jet recording apparatus is required to have various excellent properties such as fixability on a recording medium. In order to satisfy such demands, various additives have been conventionally added to ink to improve the characteristics, but there is a limit to improving the characteristics by using the ink alone. Therefore, various ink sets have been proposed in which a liquid and ink are set as a set for improving the characteristics of the ink.
For example, JP-A-6-228478 discloses an ink set comprising a colorless liquid and an ink, which causes a thickening / aggregation or precipitation when the colorless liquid and the ink are mixed, and a colorless liquid. It is disclosed that the ink and the ink are adjusted so that the penetration speed into the paper is different.

[0005]

However, in the above-described conventional ink set, since the drying property of the ink is not yet sufficient, it takes a long time to complete printing, or stains on the recording medium due to the undried ink. May have occurred. In addition, when a color image is formed using two or more colors of ink, there is a problem that bleeding occurs between different colors and that secondary colors become uneven.

[0006] Therefore, the present invention provides a high ink drying property,
In particular, it is an object of the present invention to provide an ink set for ink jet recording that has little bleeding between different colors when forming a color image and has no unevenness of secondary colors.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, by adjusting the drying time and surface tension to desired values as characteristics of a colorless or pale solution and ink, It has been found that the drying property of the ink can be improved, and the bleeding between different colors and the unevenness of the secondary colors can be reduced, and the present invention has been completed.

That is, the ink set according to the present invention comprises:
An aqueous ink set comprising a colorless or pale solution and an ink material containing one or more inks, wherein the colorless or pale solution contains at least a water-soluble organic solvent and water, and has a drying time on plain paper. Less than 5 seconds and surface tension γa
20 mN / m or more and 40 mN / m or less, each ink contained in the ink material contains at least a colorant, a water-soluble organic solvent, and water, and the drying time on plain paper is 20 seconds or less. Tension γb is 25mN / m or more and 50m
N / m or less and satisfying a relationship of γa ≦ γb.

This ink set has a high drying property, especially when forming a color image, has little bleeding between different colors, and has little secondary color unevenness. This is because the colorless or light-colored solution adhering to the recording medium surface quickly permeates the recording medium and reduces the surface energy of the adhering portion because the drying time and surface tension are adjusted to the desired values as described above. Let it. It is presumed that the ink whose drying time and surface tension have been adjusted to desired values as described above lands on the relevant portion, whereby the landed ink quickly penetrates into the inside of the recording medium to enhance the drying property. You. Also, the penetration of the ink coloring material into the inside of the recording medium, the spread of the recording medium in the lateral direction,
Further, it is assumed that the trapping state of the coloring material in the space inside the recording medium is appropriately balanced, the drying property is high, the bleeding between different colors is reduced, and the unevenness of the secondary color is reduced.

In the ink set according to the present invention, when the colorless or light-colored solution and each ink contained in the ink material are mixed, it is preferable that the colorant contained in each ink is aggregated or thickened. With this configuration, the permeation of the ink into the recording medium and the trap due to the aggregation or thickening of the colorant contained in the ink are more appropriately balanced, so that the character and the line due to the improvement of the color development and the reduction of the dot blur are improved. Is further improved.

In the ink set according to the present invention, it is preferable that the colorant contained in each ink contained in the ink material contains a pigment. By doing so, the water resistance and light resistance of the image recorded on the recording medium can be improved.

In the ink set according to the present invention, when the colorless or light-colored solution is mixed with each ink contained in the ink material, the particle diameter of the mixed solution of the colorless or light-colored solution and each ink is 0.5 μm The number of the above particles is preferably 20 times or more the number of particles having a particle diameter of 0.5 μm or more contained in each ink before mixing. In this way, the color development of the image recorded on the recording medium can be improved.

In the ink set according to the present invention, the volume average particle diameter of the dispersed particles in each ink contained in the ink material is preferably 20 nm or more and 200 nm or less, and the number average particle diameter is preferably 10 nm or more and 100 nm or less. When the volume average particle diameter of the dispersed particles is larger than 200 nm or when the number average particle diameter is larger than 100 nm, particularly when a secondary color is formed, the sharpness of color development tends to decrease and the transparency tends to deteriorate. is there. This is presumably because the larger the dispersed particle size, the larger the pigment aggregation particle size and the worse the light transmittance. Further, when the volume average particle diameter is smaller than 20 nm or when the number average particle diameter is smaller than 10 nm, the viscosity of the ink is increased, and the nozzle tends to be easily clogged.

Further, in the ink set according to the present invention, the ink material includes at least three color inks of cyan, magenta and yellow and a black ink, and both the color ink and the colorant contained in the black ink are used. It is preferable to include a pigment. This makes it possible to form a color image having excellent water resistance and light resistance on a recording medium such as paper.

In the ink set according to the present invention, it is preferable that the colorant contained in the black ink contains carbon black which is self-dispersible in water. In the ink set according to the present invention, it is preferable that the colorants contained in the color ink and the black ink both include a self-dispersible pigment which can be self-dispersed in water. By doing so, the dot directivity during continuous printing is improved. This is presumed to be due to the improvement in the cleaning performance of the ink adhered to the head nozzle surface during continuous printing.

In the ink set according to the present invention, it is preferable that the hydrophilic functional group of the self-dispersing pigment contains at least one of a carboxylic acid or a salt thereof and a sulfonic acid or a salt thereof. By doing so, the dispersion stability over time is improved.

In the ink set according to the present invention, it is preferable that the colorless or pale solution contains one or more cationic substances. By doing so, it is possible to further enhance the color developability of the printed matter and to further reduce bleeding of characters and line portions.

In the ink set according to the present invention, the colorless or pale solution preferably contains at least one of a resin emulsion, an inorganic oxide, a water-soluble polymer, and a water-soluble oligomer. By doing so, it is possible to improve the abrasion resistance of the printed matter.

In the ink set according to the present invention, the colorless or light-colored solution contains 1,1,1-tris (hydroxylmethyl) propane and monosaccharide as water-soluble organic solvents in a total amount of 100% by weight of the colorless or light-colored solution. , Oligosaccharides and sugar alcohols in the range of 10 to 50% by weight. Also, each ink contained in the ink material is contained in 100% by weight of the total amount of each ink.
It is preferable that at least one of 1,1,1-tris (hydroxylmethyl) propane, xylitol, monosaccharides, oligosaccharides, and sugar alcohols is contained as a water-soluble organic solvent in a range of 10% or less. In this way, curling and cuckling of the recording medium in a high-density image can be suppressed.

In the above-described ink jet recording method using the ink set, a colorless or pale color solution is applied to the recording medium, and then each ink contained in the ink material is applied to the recording medium, or each ink contained in the ink material is applied. After the ink has been applied to the recording medium, it is preferable to apply a colorless or pale solution to the recording medium. As the above-described ink jet recording method, it is preferable that the ink jet recording method is a thermal ink jet recording method.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the ink set according to the present invention will be described below.

The ink set according to the present embodiment is an aqueous ink set including a colorless or pale-colored solution and an ink material containing one or more inks. Here, the “colorless or light-colored solution” refers to the absorbance using a spectrophotometer.
A solution having an average value of 2 or less in the range of 400 to 750 nm. The absorbance can be measured using a U-3210 type self-recording spectrophotometer (manufactured by Hitachi, Ltd.) or the like. Also,
"Ink material" includes at least one type of ink, for example, black ink only, cyan,
In some cases, a plurality of inks such as yellow and magenta may be referred to as one.

The colorless or pale solution contains at least a water-soluble organic solvent and water, and each ink contained in the ink material contains at least a colorant, a water-soluble organic solvent, and water.

The water-soluble organic solvent contained in the colorless or pale solution and each ink includes ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2, Polyhydric alcohols such as 6-hexanetriol, trimethylolpropane, glycerin and polyethylene glycol, lower alcohols such as ethanol, isopropyl alcohol and 1-propanol, pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, triethanolamine Nitrogen-containing solvents such as thiodiethanol, thiodiglycerol, sulfolane, dimethylsulfoxide, etc .; propylene carbonate, ethylene carbonate, glucose, fructose, galacto Scan, mannose, sugars and derivatives thereof and sugar alcohols such as xylose, and the like.

These water-soluble organic solvents may be used alone or in combination of two or more. At this time, as the water-soluble organic solvent contained in each ink, it is preferable to select a more suitable one from a combination with a pigment, a dispersant, and the like described below.

The water-soluble organic solvent is preferably contained in an amount of 1 to 60% by weight, more preferably 5 to 40% by weight, based on 100% by weight of the total colorless or pale solution.
If the proportion of the water-soluble organic solvent exceeds 60% by weight, the ejection stability tends to deteriorate. If the proportion of the water-soluble organic solvent is less than 1% by weight, the colorless or pale-colored solution tends to be easily clogged at the head nozzle tip.

The above-mentioned water-soluble organic solvent is preferably contained in an amount of 1 to 60% by weight, more preferably 5 to 40% by weight, based on 100% by weight of each ink. If the proportion of the water-soluble organic solvent exceeds 60% by weight, the ejection stability tends to deteriorate. If the proportion of the water-soluble organic solvent is less than 1% by weight, the colorless or pale-colored solution tends to be easily clogged at the head nozzle tip.

It is preferable to use ion-exchanged water, ultrapure water, distilled water, ultrafiltration water, etc. for the water contained in the colorless or pale-colored solution and each ink, particularly in order to prevent impurities from being mixed.

The coloring agent contained in each ink preferably contains a pigment. By doing so, the water resistance and light resistance of an image recorded on a recording medium such as paper can be improved.

As the pigment contained in the coloring agent, any of an organic pigment and an inorganic pigment can be used. CIigment Blue 1, CIigment Blue 2, CI
Pigmet Blue 3, CI Pigment Blue 15, CI Pigment Bl
ue 15: 1, CI Pigment Blue 15: 3, CI Pigment Blue 1
5: 4, CI Pigment Blue 16, CI Pigment Blue 22, C.
Pigment such as I. Pigment Blue 60, but not limited thereto.

In the magenta color, CI Pigment Red
5, CI Pigment Red 7, CI Pigment Red 12, CI Pigme
nt Red 48, CI Pigment Red 48: 1, CI Pigment Red 5
7, CI Pigment Red 112, CI Pigment Red 122, CIP
igment Red 123, CI Pigment Red 146, CI Pigment Re
d 168, CI Pigment Red 184, CI Pigment Red 202,
Examples include, but are not limited to, pigments such as CI Pigment Violet 19.

Further, CIigment Yellow is used for the yellow color.
1, CI Pigment Yellow 2, CI Pigment Yellow 3, C.
I. Pigment Yellow 12, CI Pigment Yellow 13, CIPI
gment Yellow 14, CI Pigment Yellow 16, CI Pigmen
t Yellow 17, CI Pigment Yellow 55, CI Pigment Ye
llow 73, CI Pigment Yellow 74, CI Pigment Yellow
75, CI Pigment Yellow 83, CI Pigment Yellow 9
3, CI Pigment Yellow 95, CI Pigment Yellow 97, C.
I. Pigment Yellow 98, CI Pigment Yellow 114, CIP
igment Yellow 128, CIPigment Yellow 129, CIPig
ment Yellow 150, CI Pigment Yellow 151, CI Pigme
nt Yellow 154, CI Pigment Yellow 180, CI Pigment
Pigment such as Yellow 185, but not limited thereto.

The black is preferably a carbon black pigment such as furnace black, lamp black, acetylene black and channel black.
Raven5750, Raven5250, Raven5000ULTRA II, Raven350
0, Raven2500ULTRA, Raven2000, Raven1500, Raven125
5, Raven1250, Raven1200, Raven1190ULTRA II, Raven1
170, Raven1080ULTRA, Raven1060ULTRA, Raven790ULTR
A, Raven780 ULTRA, Raven760 ULTRA (Colombian
Carbon Co.), Regal400R, Regal330R, Regal660R, Mog
ul L, Monarch 700, Monarch 800, Monarch 880, Monar
ch 900, Monarch 1000, Monarch 1100, Monarch 1300,
Monarch 1400 (all made by Cabot), Color Black FW1,
Color Black FW2, Color Black FW2V, Color Black 1
8, Color Black FW200, Color Black S150, Color Blac
k S160, Color Black S170, Printex 35, Printex U, P
rintex V, Printex 140U, Printex 140V, SpecialBlack
6, Special Black 5, Special Black 4A, Special Bla
ck4 (all made by Degussa), No.25, No.33, No.40, No.47,
No.52, No.900, No.2300, MCF-88, MA600, MA7, MA8, M
A100 (all manufactured by Mitsubishi Chemical Corporation) and the like.

Further, magnetic fine particles such as magnetite and ferrite, titanium black and the like may be used as a black pigment. In addition to the three primary color pigments of black, cyan, magenta, and yellow,
Specific color pigments such as red, green, blue, brown, and white, metallic luster pigments such as gold and silver, colorless extender pigments, and plastic pigments may be used. Further, a pigment newly synthesized for the present embodiment may be used.

In the present embodiment, it is preferable to use a dispersant for dispersing the pigment. As the dispersant, a surfactant and a water-soluble resin can be used, and it is particularly preferable to use a water-soluble resin to disperse the pigment.

As the water-soluble resin, a known resin used as a dispersant can be used, and a (co) polymer can be particularly preferably used. As the copolymer,
A monomer having at least one α, β-ethylenically unsaturated group constituting a hydrophilic part and a monomer having at least one α, β-ethylenically unsaturated group constituting a hydrophobic part; Can be suitably used. Further, a homopolymer of a monomer having an α, β-ethylenically unsaturated group having a hydrophilic functional group can also be used.

At least the hydrophilic portion of the copolymer
The monomer having one α, β-ethylenically unsaturated group is
It is preferable to use it at 40 to 80 mol%. The monomer having at least one α, β-ethylenically unsaturated group constituting the hydrophobic part is preferably used in an amount of 20 to 60 mol%. If the monomer composition ratio of the copolymer is out of this range on the hydrophobic side, the solubility in an aqueous medium tends to be low and the stability tends to be poor. Also, when the monomer composition ratio of the copolymer is out of this range on the hydrophilic side, the water solubility is too high, the water resistance tends to deteriorate, and the image density tends to decrease.

As the monomer having an α, β-ethylenically unsaturated group constituting the hydrophilic portion, a monomer having a carboxyl group, a sulfonic acid group, a hydroxyl group, polyoxyethylene, or the like can be used. Preferably a carboxyl group, a sulfonic acid group-containing monomer such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene Sulfonic acid, sulfonated vinyl naphthalene, and the like can be used. Among these, a carboxyl group-containing monomer is particularly preferred, and acrylic acid, methacrylic acid, maleic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid,
Fumaric acid monoesters can be used.

Examples of the monomer having an α, β-ethylenically unsaturated group constituting the hydrophobic part include styrene derivatives such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, vinylnaphthalene derivatives, and alkyl acrylate. Ester, alkyl methacrylate, alkyl crotonate, dialkyl itaconate, and dialkyl maleate can be suitably used.

Further, a monomer having an α, β-ethylenically unsaturated group constituting the hydrophilic portion is selected from at least one of acrylic acid, methacrylic acid, and maleic anhydride, and constitutes the hydrophobic portion. The monomer having an α, β-ethylenically unsaturated group is at least one selected from the group consisting of styrene, alkyl, aryl and alkylaryl esters of (meth) acrylic acid.
It is more preferable to select the species.

When copolymerizing these monomers, various polymerization initiators can be used. In addition to known polymerization initiators, newly prepared polymerization initiators may be used. Among them, it is preferable to use a polymerization initiator having a hydrophilic functional group. As the hydrophilic functional group, a carboxyl group, a hydroxyl group, a sulfonic acid group, a sulfate group and the like are preferable, and among them, the carboxyl group is particularly preferable.

Examples of the polymerization initiator include azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, azobisisobutylamidine hydrochloride,
Azo initiators such as 4,4'-azobis-4-cyanopentanol, 4,4'-azobis-4-cyanovaleric acid, benzoyl peroxide, di-t-butyl peroxide, potassium persulfate, and ammonium persulfate Peroxide initiators such as, among them,
4,4'-Azobis-4-cyanovaleric acid, potassium persulfate and ammonium persulfate are preferred.

Various methods are known for measuring the average molecular weight of the copolymer. In this embodiment, GPC is used.
(Gel permeation chromatography) is defined as the value measured by the method. The weight average molecular weight of the polymer that can be used in the ink set according to this embodiment is 3000 to 15
000, more preferably 4,000 to 7000. If the weight average molecular weight of the copolymer is less than 3,000, the molecular weight is too low and the dispersion stability tends to be poor. When the weight average molecular weight of the copolymer exceeds 15,000, the viscosity of the ink increases,
This is because the ink ejection property tends to be deteriorated.

The ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn of the copolymer used in the ink set according to this embodiment is preferably 1 to 2.5, and 1 to 2.5.
2.2 is more preferable. If the ratio Mw / Mn exceeds 2.5, the viscosity tends to increase and the dispersion tends to be unstable.

The molecular weight of the copolymer can be adjusted by a method based on known polymerization conditions such as selection of a polymerization solvent, adjustment of a polymerization temperature, concentration of a monomer and an initiator, and combined use of a chain transfer agent and the like.

The acid value of the copolymer used in the ink set according to the present embodiment is preferably 200 to 500 mgKOH / g, more preferably 250 to 450 mgKOH / g, and more preferably 300 to 400 mgKOH / g. More preferred. If the acid value of the copolymer is less than 200 mgKOH / g, the solubility in an aqueous medium tends to be low and the stability tends to be poor. If the acid value of the copolymer exceeds 500 mg KOH / g, the water solubility is too high and the water resistance is deteriorated,
This is because the image density tends to decrease.

The dispersant used in the ink set according to this embodiment is preferably a dispersant obtained by neutralizing the above copolymer by at least 50% with respect to the acid value. Neutralization is carried out by various basic substances, but it is preferable that the neutralization is carried out by a basic substance containing at least one kind of alkali metal hydroxide. As the alkali metal hydroxide,
NaOH, KOH, LiOH can be used, but NaO
H can be suitably used.

The pigment dispersants described above may be used alone or as a mixture of two or more. The amount of dispersant added
Although it cannot be said unconditionally because it greatly varies depending on the pigment, it is generally preferably 0.1 to 100% by weight, more preferably 1 to 70% by weight, and more preferably 3 to 50% by weight based on 100% by weight of the total amount of the pigment. Is more preferable.

It is preferable that the hydrophilic functional group contained in the dispersant contains at least one of carboxylic acid or a salt thereof and sulfonic acid or a salt thereof. By doing so, the dispersion stability over time is improved.

As described above, the pigment can be dispersed in the ink by using the dispersant. In the present embodiment, however, the self-dispersion pigment having a hydrophilic functional group introduced into the surface of the pigment is used in the ink. Pigments may be dispersed therein. As a method for introducing a hydrophilic functional group, any of known methods and newly invented methods can be used. For example, oxidation treatment with an oxidizing agent such as nitric acid, permanganate, dichromate, hypochlorite, ammonium persulfate, hydrogen peroxide, ozone, treatment with a coupling agent such as a silane compound, polymer grafting treatment In addition to known methods such as plasma treatment and the like, newly developed methods can be used, and these methods may be used in combination. The amount of the hydrophilic functional group can be adjusted by controlling the treatment concentration or the time, and the surface functional group of the commercially available self-dispersible pigment can be adjusted to the range of the present embodiment by modification such as esterification. .

Commercially available hydrophilic treated pigments which can be suitably used in the present embodiment and which can be self-dispersed in water include, for example, MICROJET (BONJET) BLACK CW-1 (manufactured by Orient Chemical Industries) and CAB- O-JET200 (Cabot)
And CAB-O-JET300 (manufactured by Cabot).

In the present embodiment, the criteria for self-dispersibility in water are as follows: 95% by weight of water / 5% by weight of pigment dispersed without a dispersant using an ultrasonic homogenizer, a nanomizer, a microfluidizer, a ball mill or the like. Let
After measuring the initial pigment concentration and leaving the dispersion liquid in a glass bottle for one day, the pigment concentration of the supernatant was measured to be 98% or more of the initial concentration.

The ratio of the above pigment contained in each ink is 0.1 to 20 per 100% by weight of the total amount of each ink.
%, More preferably 1 to 10% by weight, even more preferably 1 to 7% by weight.
If the proportion of the pigment exceeds 20% by weight, the clogging property when water evaporates at the nozzle tip tends to deteriorate. On the other hand, if the proportion of the pigment is less than 0.1% by weight, sufficient image density tends to be naturally not obtained.

These pigments are preferably purified by removing impurities mixed in the production process, such as impurities such as residual oxidizing agents, and other inorganic and organic impurities. In particular, the content of calcium, iron and silicon in the ink is preferably 10 ppm or less, and more preferably 5 ppm or less. The content of these impurities can be measured by, for example, high frequency inductively coupled plasma emission spectrometry.

The removal of these impurities includes, for example, washing with water,
Reverse osmosis membranes, ultrafiltration membranes, methods such as ion exchange, and methods of adsorption with activated carbon, zeolite and the like can be used alone or in combination.

In the ink set according to the present embodiment, the ink material includes at least three color inks of cyan, magenta, and yellow and a black ink, and both the color ink and the colorant contained in the black ink are used. It is preferable to include a pigment. This makes it possible to form a color image having excellent water resistance and light resistance on a recording medium such as paper.

Here, it is preferable that the colorant contained in the black ink contains carbon black which is self-dispersible in water. Further, it is preferable that each of the colorants contained in the black ink and the color ink contains a self-dispersible pigment which can be self-dispersed in water. By doing so, the dot directivity during continuous printing is improved. This is presumed to be due to the improvement in the cleaning performance of the ink adhered to the head nozzle surface during continuous printing.

The hydrophilic functional group of the self-dispersible pigment self-dispersible in water subjected to surface hydrophilic treatment as described above preferably contains at least one of carboxylic acid or a salt thereof, and sulfonic acid or a salt thereof. By doing so, the dispersion stability over time is improved.

In the ink set according to this embodiment,
The colorless or pale solution and each ink can include a surfactant. Examples of the type of surfactant include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. The surfactant contained in each ink is preferably an anionic surfactant or a nonionic surfactant among these surfactants.

Examples of usable anionic surfactants include alkyl benzene sulfonates, alkyl phenyl sulfonates, alkyl naphthalene sulfonates, higher fatty acid salts, higher fatty acid ester sulfates, and higher fatty acid ester sulfonates. , Sulfates and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylate, polyoxyethylene alkyl ether sulfate, alkyl phosphate, polyoxyethylene alkyl ether phosphate, etc. And preferably, dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, monobutylbiphenylsulfonate Salt, dibutyl phenyl phenol disulfonic acid salts.

Examples of usable nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene sorbitol. Fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, alkylalkanolamides, polyethylene glycol polypropylene glycol block copolymers and the like. , Preferably polyoxyethylene nonylphenyl ether, polyoxyethylene octyl Ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylol amides, polyethylene glycol polypropylene glycol block copolymers.

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

These surfactants may be used alone or in combination of two or more. HLB (Hydrophilic-Lipophilic Balan) of surfactant contained in each ink
ce) is preferably from 7 to 20 in consideration of dissolution stability and the like.

The proportion of the surfactant contained in the colorless or pale solution is preferably 10% by weight or less, more preferably 0.1 to 5% by weight, based on 100% by weight of the colorless or pale solution. . If the proportion of the surfactant exceeds 10% by weight, the optical density of the printed matter tends to decrease.

On the other hand, the ratio of the surfactant contained in each ink is preferably 0.001 to 5% by weight, more preferably 0.01 to 3% by weight, based on 100% by weight of each ink. If the proportion of the surfactant exceeds 5% by weight, a problem tends to occur in the storage stability of the ink.

In the ink set according to the present embodiment, the colorless or light-colored solution preferably contains one or more cationic substances. In this way, the color development of printed matter and the bleeding of characters and lines can be further improved.

Examples of the cationic substance include a cationic surfactant, a cationic polymer, and a polyvalent metal salt. Specific examples of the cationic surfactant include:
For example, tetraalkylammonium salt, alkylamine salt, benzalkonium salt, alkylpyridinium salt,
Imidazolium salts and derivatives thereof, and the like,
For example, dihydroxyethylstearylamine, 2-heptadecenyl-hydroxyethylimidazoline, lauryldimethylbenzylammonium chloride, cetylpyridinium chloride, stearamidomethylpyridium chloride, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyldimethylamine hydrochloride , Hexadecylpyridinium chloride, stearylamine EO adduct hydrochloride, distearyldimethylammonium chloride and the like.

Examples of the cationic polymer include polyallylamine, polyamine sulfone, polyethyleneimine,
Polyvinylamine, polyalkylenepolyamine, polyvinylimidazoline, chitosan, and their neutralized or partially neutralized products with acids such as hydrochloric acid and acetic acid, diethylenetriamine polycondensate, N, N-bisaminopropylethylenediamine, diallyldimethylammonium chloride dioxide Sulfur copolymer, perfluoroalkylammonium chloride and the like can be mentioned.

The polyvalent metal salt is composed of polyvalent metal ions having two or more valences and an anion bonded to these polyvalent metal ions, and can be used if it is soluble in water.
For example, polyvalent metal ions include calcium ions,
Examples thereof include copper ions, nickel ions, magnesium ions, zinc ions, barium ions, iron ions, aluminum ions, and chromium ions. As the anion,
Examples include chloride ion, iodide ion, bromide ion, nitrate ion, sulfate ion, sulfite ion, phosphate ion, chlorate ion, acetate ion and the like. Specifically, aluminum chloride, aluminum bromide, aluminum sulfate, aluminum nitrate, aluminum acetate, barium chloride, barium bromide, barium iodide, barium nitrate, calcium chloride, calcium bromide, calcium iodide, calcium nitrate, acetic acid Calcium, copper chloride, copper bromide, copper sulfate, copper nitrate, copper acetate, iron chloride, iron bromide, iron iodide, iron sulfate, iron nitrate, magnesium chloride, magnesium bromide, magnesium iodide, magnesium sulfate, nitric acid Magnesium, magnesium acetate, nickel chloride, nickel bromide,
Examples thereof include nickel sulfate, nickel nitrate, nickel acetate, zinc chloride, zinc bromide, zinc sulfate, zinc nitrate, and zinc acetate. These polyvalent metal salts may be used alone or as a mixture of two or more as needed.

The above-mentioned cationic substances may be used alone or in combination of two or more. The content of the cationic substance is preferably 0.1 to 15% by weight, and more preferably 0.5 to 1% by weight based on 100% by weight of the total colorless or pale solution.
More preferably, it is 0% by weight. When the content of the cationic substance exceeds 15% by weight, clogging of the head end portion and discharge directionality at the time of continuous printing tend to be deteriorated. This is because the effects described above tend to be difficult to sufficiently exert.

In the ink set according to the present embodiment, the colorless or pale solution preferably contains at least one of a resin emulsion, an inorganic oxide, a water-soluble polymer, and a water-soluble oligomer. By doing so, the abrasion resistance of the printed matter can be improved.

Examples of usable resin emulsions include acrylic resin, vinyl acetate resin, styrene-butadiene resin, acryl-styrene resin, butadiene resin, styrene resin, polyurethane resin, polyolefin resin, and polyester resin. Resin, polyamide resin,
Melamine resins, urea resins, silicone resins, fluorine resins, polybutene resins, various waxes and the like can be mentioned. As commercially available emulsions, for example, Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.) Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), J-74J, J-734 (manufactured by John Krill) and the like, but are not limited thereto.

The resin emulsion is used for mechanically pulverizing and dispersing resins and waxes in an aqueous medium, and for emulsifying and polymerizing resins and waxes.
Fine particles may be directly polymerized by dispersion polymerization, suspension polymerization, or the like.

These resins are preferably polymers having both a hydrophilic part and a hydrophobic part. The particle shape may be spherical or any other shape. Further, when the product is produced by emulsion polymerization, any of a product using an emulsifier and a soap-free product may be used.

Examples of usable inorganic oxides include, but are not limited to, high molecular weight silicic anhydride (SiO ₂ ) and alumina (Al ₂ O ₃ ).

The volume average particle diameter of the resin emulsion or the inorganic oxide colloid is preferably from 10 nm to 2 μm, more preferably from 50 to 500 nm. If the volume average particle size is larger than 2 μm, the ejection stability of the liquid composition and the stability during standing tend to decrease. Further, when the volume average particle diameter is smaller than 10 nm, the recovery property of the nozzle from standing tends to decrease.

The addition amount of the resin emulsion or the colloid of the inorganic oxide is preferably 0.1% by weight or more and 10% by weight or less in terms of solids based on 100% by weight of the total colorless or pale color solution. If the amount is less than 0.1% by weight, there is no effect of improving the fixability of the printed matter, and the image density tends to decrease. On the other hand, if the addition amount exceeds 10% by weight, the ejection stability tends to decrease and the image drying property tends to deteriorate.

In this embodiment, a Microtrac UPA particle size analyzer 9340 (manufactured by Leeds & Northrup) was used as a device for measuring the number average particle diameter and the volume average particle diameter. The measurement was performed according to a predetermined measurement method without diluting the sample by placing 4 ml of the measurement sample in the measurement cell. As parameters to be input at the time of measurement, the viscosity of the measurement sample was input as the viscosity, and the density of the pigment or emulsion or the inorganic oxide colloid particles of the measurement sample was input as the density of the dispersed particles. This device measures the particle size using Brownian motion of the dispersoid,
The particle diameter is measured by irradiating the solution with laser light and detecting the scattered light.

Examples of the water-soluble polymer include acrylic resins, vinyl acetate resins, urethane resins, acryl-styrene resins, butadiene resins, styrene resins, polyester resins, silicone resins, fluorine resins, Acrylic silicone resin and the like can be mentioned.

In the ink set according to the present embodiment,
The colorless or pale solution has at least one of 1,1,1-tris (hydroxylmethyl) propane, a monosaccharide, an oligosaccharide, and a sugar alcohol as a water-soluble organic solvent,
10 to 50 in 100% by weight of the total colorless or pale solution
It is preferable to contain it in the range of weight%. Further, each ink, as a water-soluble organic solvent, 1,1,1-tris (hydroxylmethyl) propane, xylitol, monosaccharides, oligosaccharides, and at least one of sugar alcohols,
It is preferable that the content of each ink is 10% by weight or less based on 100% by weight of the total amount. By doing so, it is possible to suppress curling and cuckling of a recording medium such as paper in a high-density image.

In addition, in the ink set according to this embodiment, cellulose derivatives such as polyethyleneimine, polyamines, polyvinylpyrrolidone, polyethyleneglycol, ethylcellulose, carboxymethylcellulose, polysaccharides, and the like are used to control the properties of the colorless or pale solution and the ink. Its derivatives, cyclodextrin, macrocyclic amines, dendrimers, crown ethers, urea and its derivatives, acetamide and the like can be used. Further, in order to adjust conductivity and pH, compounds of alkali metals such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, triethanolamine, diethanolamine, ethanolamine, 2-amino-2- Methyl-
Nitrogen-containing compounds such as 1-propanol, compounds of alkaline earth metals such as calcium hydroxide, acids such as sulfuric acid, hydrochloric acid and nitric acid, and salts of strong acids and weak alkalis such as ammonium sulfate can be used.

Further, if necessary, a pH buffer, an antioxidant, a fungicide, a viscosity modifier, a conductive agent, an ultraviolet absorber, a chelating agent, a water-soluble dye, a disperse dye, an oil-soluble dye and the like are added. be able to.

In the present embodiment, as a method for preparing each ink contained in the ink material, for example, a predetermined amount of the above-described pigment is added to an aqueous solution containing a predetermined amount of the above-mentioned pigment dispersant, and the mixture is sufficiently stirred. . Then, dispersion is performed using a disperser, and coarse particles are removed by centrifugation or the like. Thereafter, a predetermined solvent, an additive and the like are added, and the mixture is stirred, mixed and filtered to obtain an ink. At this time, a method of preparing a concentrated dispersion of the pigment and diluting it at the time of preparing the ink may be adopted. Further, a pigment pulverizing step may be provided before the dispersing step. The disperser is
Any of commercially available products may be used. For example, colloid mill, flow jet mill, slasher mill, high speed disperser, ball mill, attritor, sand mill, sand grinder, ultra fine mill, Eiger motor mill, dyno mill, pearl mill, agitator mill, kobol mill, 3 rolls, 2 rolls There are a roll, an extruder, a kneader, a microfluidizer, a laboratory homogenizer, an ultrasonic homogenizer, and the like, and these may be used alone or in combination. Or
After mixing a predetermined solvent, water and a pigment dispersant, a pigment may be added and dispersed using a disperser. Further, in order to prevent mixing of inorganic impurities, it is preferable to use a dispersion method that does not use a dispersion medium, and it is preferable to use a microfluidizer, an ultrasonic homogenizer, or the like. In the present embodiment, dispersion was performed with an ultrasonic homogenizer.

On the other hand, as a method for preparing an ink using a pigment that is self-dispersible in water, for example, a surface modification treatment is performed on the pigment, and the obtained pigment is added to water and sufficiently stirred. Then, if necessary, dispersion is performed by a disperser, and coarse particles are removed by centrifugation or the like. Thereafter, a predetermined solvent, an additive, and the like are added, and the mixture is stirred, mixed, and filtered to obtain an ink.

In the ink set according to this embodiment, the volume average particle diameter of the dispersed particles of the pigment in each ink prepared as described above is 20 nm or more and 200 nm or less, preferably 20 nm or more and 170 nm or less. Preferably it is 25 to 150 nm, and the number average particle size is 10 nm or more and 10
0 nm or less, preferably 10 to 80 nm, and more preferably 15 to 70 nm. When the volume average particle diameter of the dispersed particles is larger than 200 nm or when the number average particle diameter is larger than 100 nm, particularly when a color secondary color is formed, the color sharpness tends to decrease and the transparency tends to deteriorate. It is. This is presumably because the larger the dispersed particle size, the larger the pigment aggregation particle size and the worse the light transmittance. Further, when the volume average particle diameter is smaller than 20 nm or when the number average particle diameter is smaller than 10 nm, the viscosity of the ink is increased, and the nozzle tends to be easily clogged. If the dispersed particle size is in the above-mentioned desired range, the fixability of the image and the color development can be improved.

Although not particularly limited, the pH range of each ink in the present embodiment is 3 to 11, preferably
It is preferable to use 44.5 to 9.5. The pH of the ink having an anionic free radical on the surface of the pigment is preferably 6 to 11, preferably 6 to 9.5, and more preferably 7.5 to 9.0. On the other hand, for an ink having a cationic free radical on the surface of a pigment, it is suitable to use the ink at a pH of 4.5 to 8.0, preferably 4.5 to 7.0.

In this embodiment, the viscosity of each ink is 1.
It is preferably from 5 to 6.0 mPa · s, and from 1.5 to 4.0 mP
More preferably, it is a · s. This is because, when the viscosity of the ink is larger than 6.0 and smaller than 1.5, the ink ejection property from the nozzle tends to deteriorate.

Here, in the ink set according to the present embodiment, the drying time of the colorless or light-colored solution on plain paper is 5 seconds or less, and the surface tension γa is 20 mN / m or more and 40 mN / m or less. The drying time of each ink contained in the ink material on plain paper is 20 seconds or less, and the surface tension γb is 25 mN / m to 50 mN / m.
It is characterized in that it satisfies the relationship of γa ≦ γb. Here, “plain paper” refers to paper mainly used in the electrophotographic system, and is not optimized for the inkjet recording system. The measurement of the actual drying time is
For example, plain paper manufactured by Fuji Xerox Co., Ltd. (trade name: F
LX paper). By having such properties, the drying property of the ink is increased, and when forming a color image, bleeding between different colors is reduced,
Secondary color unevenness is reduced. This is because the colorless or light-colored solution adhering to the recording medium surface such as plain paper has the drying time and surface tension adjusted to desired values as described above.
Immediately penetrates the recording medium and lowers the surface energy of the attached portion. It is presumed that the ink whose drying time and surface tension have been adjusted to desired values as described above lands on the relevant portion, whereby the landed ink quickly penetrates into the inside of the recording medium to enhance the drying property. You. In addition, since the spread of the landed ink in the horizontal direction is suppressed, it is estimated that the bleeding between different colors is reduced and the unevenness of the secondary colors is reduced.

The surface tension γa of the above colorless or pale solution is preferably 20 mN / m to 35 mN / m.
It is as follows. The drying time of each ink contained in the ink material on plain paper is preferably 18 seconds or less, and the surface tension γb is preferably 28 mN / m or more.
5 mN / m or less.

In the ink set according to the present embodiment, when the colorless or light-colored solution and each ink contained in the ink material are mixed, it is preferable that the coloring agent contained in each ink is aggregated or thickened. In this way, the permeation of the ink into the recording medium and the trap due to the aggregation or thickening of the coloring agent contained in the ink are appropriately balanced, so that the coloring property is improved, and the characters and lines associated with the reduction of dot blur are reduced. The bleeding is reduced and the drying property is further improved.

When a colorless or pale solution and each ink contained in the ink material are mixed, the number of particles having a particle size of 0.5 μm or more contained in the mixture of the colorless or pale solution and each ink is reduced. Preferably, the number of particles having a particle size of 0.5 μm or more contained in each ink before mixing is 20 times or more. By doing so, the color development of the image is improved.

The ink set according to the present embodiment is suitably used for ink jet recording using an ink jet recording method. In this case, after the colorless or light-colored solution is attached to the recording medium, each ink contained in the ink material may be attached to the recording medium, or after each ink contained in the ink material is attached to the recording medium. Alternatively, a colorless or pale solution may be applied to the recording medium.

At this time, the ratio of the applied amount of the colorless or pale color solution to the applied amount of the ink as the whole ink material is 2: 1.
１ ： 1: 10 is preferred. This is because if the amount of the colorless or light-colored solution applied is larger than twice the amount of the ink applied, the paper tends to curl and cuckle.
Also, if the amount of the colorless or pale solution is less than 1/10 of the amount of the ink, the desired effect tends not to be sufficiently obtained.

The most preferable recording medium for ink-jet recording using the ink set according to the present embodiment is plain paper, but other recording media include medium-sized paper, Japanese paper, glossy paper, coated paper, surface-treated paper, and the like. Needless to say, recording may be performed using the ink set according to the present embodiment.

As the ink jet recording method, any method such as a piezo ink jet recording method and a thermal ink jet recording method can be used. The ink set according to this embodiment is particularly suitable for the thermal ink jet recording method. Further, the ink set according to the present embodiment is not limited to a normal inkjet recording apparatus, but also a recording apparatus equipped with a heater or the like for controlling the drying of the ink, or an intermediate body transfer mechanism is mounted, and the recording material is provided on the intermediate body. Can also be used in a recording device or the like that prints and transfers it to a recording medium such as paper. Hereinafter, the ink set according to the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0096]

EXAMPLES [Method of preparing colorless or light-colored solution] The following components were mixed and dissolved, and then filtered through a 0.45 μm filter to obtain a colorless or light-colored solution. (A) Colorless or pale color solution-A Diethylene glycol 10 parts by weight Surfactant (Surfinol 465 / Nissin Chemical Co., Ltd.) 1.5 parts by weight Calcium nitrate tetrahydrate 3 parts by weight Ion-exchanged water balance 100 parts by weight in total (B) Colorless or pale-colored solution-B Glycerin 10 parts by weight Polydiallyldimethylammonium chloride 3 parts by weight Surfactant (Surfinol 440 / Nissin Chemical Co., Ltd.) 0.4 part by weight Ion-exchanged water balance 100 parts by weight in total (C ) Colorless or pale solution-C diglycerin ethylene oxide adduct 10 parts by weight Acrylic resin emulsion aqueous dispersion (solid content 50% by weight) 10 parts by weight Surfactant (Pluronic PE63 / BASF) 0.5 part by weight Ion Exchanged water balance Total 100 parts by weight (D) Colorless or pale-colored solution-D 1,1,1-tris (hydroxylmethyl) propane 30 parts by weight Benzalkonium chloride 2 parts by weight Polyallylamine (PAA-HCl-10L / manufactured by Nitto Boseki) 2 parts by weight Ion-exchanged water balance 100 parts by weight in total (E) Colorless or pale color solution-E propylene glycol 10 parts by weight 2-ethylhexyl methacrylate / sodium methacrylate Combined (monomer ratio 50/50, molecular weight 5400) 2 parts by weight Surfactant (Olfin E1010) 2.0 parts by weight Ion-exchanged water balance 100 parts by weight in total (F) Colorless or pale color solution-F Diethylene glycol 10 parts by weight butyl carbitol 10 parts by weight Calcium nitrate tetrahydrate 3 parts by weight Ion-exchanged water balance 100 parts by weight in total (G) Colorless or pale-colored solution-G glycerin 15 parts by weight Styrene-sulfonic acid sodium salt copolymer (monomer ratio 33/67, (Molecular weight 4500) 1 part by weight Surfactant (Nonion E230 / Nippon Yushi) 1.0 part by weight Ion-exchanged water balance 100 parts by weight in total (I) colorless Or light-colored solution-I diethylene glycol 10 parts by weight thiodiglycol 5 parts by weight surfactant (Pulronic P123 / BASF) 0.3 part by weight ion-exchanged water balance 100 parts by weight (J) colorless or light-colored solution-J diethylene glycol 10 parts by weight Butyl carbitol 3.0 parts by weight Calcium nitrate tetrahydrate 3 parts by weight Ion-exchanged water balance 100 parts by weight in total (L) Colorless or pale solution -L N-methyl-2-pyrroline 20 parts by weight Surfactant Agent (Fluorard FC-170 / 3M) 0.07 parts by weight Urea 3 parts by weight Polyallylamine (PAA-HCl-10L / Nitto Boseki Co., Ltd.) 2 parts by weight Ion exchange water balance 100 parts by weight [Pigment dispersion method] (Pigment dispersion method 1) Carbon black (Black Pearls
L, manufactured by Cabot Corporation) 30 parts by weight of a sodium neutralized salt of a styrene-methacrylic acid copolymer, 3 parts by weight, and further,
Deionized water was added to make the total amount 300 parts by weight. This liquid was dispersed using an ultrasonic homogenizer. This liquid is centrifuged by a centrifuge (8000 rpm x 30 minutes).
To remove 100 parts by weight of a residue portion. 1
Filtration through a μm filter gave a dispersion.

(Pigment Dispersion Method 2) With respect to a dispersion liquid (Cab-o-jet-300 / manufactured by Cabot Corporation) which can be self-dispersed in water, the dispersion liquid is subjected to a centrifugal separation treatment (800
0 rpm × 30 minutes), and the residue (20% of the total amount)
Was used.

(Pigment dispersion method 3) Cyan pigment (CI.
Pigment Blue 15: 3) to treatment with sulfanilic acid and sodium nitrite, the surface C ₆ H ₄ SO ₃ ^- N
A treated color pigment with an a ⁺ group was obtained. The self-dispersibility index of this cyan pigment was 100%. The treated color pigment was purified and converted into an aqueous dispersion having a pigment concentration of 10% by weight, and then centrifuged at 8,000 rpm for 30 minutes. A portion of this pigment dispersion was sampled and dried to dry up to calculate the pigment content. From the obtained results, pure water was added so that the pigment concentration became 8% by weight, and the cyan pigment dispersion was obtained. Prepared.

(Pigment dispersion method 4) Cyan pigment (CI.
Pigment Blue 15: 3) is treated with anthranilic acid and sodium nitrite, and the surface is treated with C ₆ H ₄ COO ^- N
A treated color pigment with an a ⁺ group was obtained. The self-dispersibility index of this cyan pigment was 100%. The treated color pigment was purified and converted into an aqueous dispersion having a pigment concentration of 10% by weight, and then centrifuged at 8,000 rpm for 30 minutes. A portion of this pigment dispersion was sampled and dried to dry up to calculate the pigment content. From the obtained results, pure water was added so that the pigment concentration became 8% by weight, and the cyan pigment dispersion was obtained. Prepared.

[Ink Preparation Method] To a proper amount of the above-mentioned dispersion liquid, a proper amount of a solvent, ion-exchanged water and the like were added, and the total amount was adjusted to 100 parts by weight based on the composition described later. This was mixed, stirred, and passed through a 2 μm filter to obtain the desired ink.

(Black Ink 1) Pigment Dispersion Method 1
In addition, an ink having the following composition was obtained according to the ink preparation method.

Carbon black (Black Pearls L / Cabot) 4 parts by weight Styrene-methacrylic acid-sodium methacrylate copolymer 0.4 parts by weight Glycerin 15 parts by weight Surfactant (Nonion E230 / Nippon Oil & Fats Co., Ltd.) 0.1 parts by weight Urea 3 parts by weight Ion-exchanged water balance 100 parts by weight in total (black ink 2) According to the above-mentioned pigment dispersion method 2 and ink preparation method, an ink having the following composition was obtained.

Surface-treated pigment (Cab-o-jet-300 / Cabot) 5 parts by weight Propylene glycol 10 parts by weight Diglycerin ethylene oxide adduct 5 parts by weight Isopropyl alcohol 3 parts by weight Surfactant (Surfinol 104 / day) 0.2 parts by weight ion-exchanged water balance 100 parts by weight in total (black ink 3) According to the above-mentioned pigment dispersion method 2 and ink preparation method, an ink having the following composition was obtained.

Surface-treated pigment (Microjet Black CW-1 / manufactured by Orient) 5 parts by weight Glycerin 10 parts by weight 2-pyrrolidone 5 parts by weight Urea 4 parts by weight Surfactant (Surfinol 440 / Nissin Chemical Co., Ltd.) 3 parts by weight ion-exchanged water balance 100 parts by weight in total (black ink 4) In accordance with the above-mentioned pigment dispersion method 2 and ink preparation method, an ink having the following composition was obtained.

Surface-treated pigment (Cab-o-jet-300 / Cabot) 5 parts by weight Glycerin 20 parts by weight Isopropyl alcohol 3 parts by weight Surfactant (Nonion E230 / Nippon Oil & Fats) 0.02 parts by weight Ion exchange Water Remainder Total 100 parts by weight (Cyan Ink 1) An ink having the following composition was obtained according to the above-described pigment dispersion method 1 and ink preparation method.

Cyan Pigment (CIPigment Blue 15: 3) 3 parts by weight Styrene-maleic acid-sodium maleate copolymer 1.0 part by weight Glycerin 10 parts by weight Sulfolane 3 parts by weight Surfactant (NONION E230 / Nissin Chemical Co., Ltd.) 0.03 parts by weight ion-exchanged water balance 100 parts by weight in total (cyan ink 2) According to the above-mentioned pigment dispersion method 3 and ink preparation method, an ink having the following composition was obtained.

Self-dispersed surface-treated pigment (CI Pigment Blue 15: 3) 3 parts by weight Diethylene glycol 10 parts by weight Thiodiethanol 5 parts by weight Surfactant (Nonion E215 / Nissin Chemical Co., Ltd.) 0.03 parts by weight Ion-exchanged water balance 100 parts by weight in total (cyan ink 3) In accordance with the above-mentioned pigment dispersion method 4 and ink preparation method, an ink having the following composition was obtained.

Self-dispersed surface-treated pigment (CI Pigment Blue 15: 3) 3 parts by weight Diethylene glycol 10 parts by weight Urea 5 parts by weight Surfactant (Pulronic PE63 / BASF) 0.4 part by weight Ion-exchanged water balance 100 parts in total Part (cyan ink 4) An ink having the following composition was obtained according to the above-mentioned pigment dispersion method 1 and ink preparation method.

Cyan pigment (CIPigment Blue 15: 3) 3 parts by weight Styrene-maleic acid-sodium maleate copolymer 1.0 part by weight Glycerin 10 parts by weight Diglycerin ethylene oxide adduct 5 parts by weight Surfactant (Nonion E230) (Manufactured by Nissin Chemical Co., Ltd.) 0.02 parts by weight Ion-exchanged water balance 100 parts by weight in total (cyan ink 5) An ink having the following composition was obtained according to the above-mentioned pigment dispersion method 4 and ink preparation method.

Self-dispersed surface-treated pigment (CI Pigment Blue 15: 3) 3 parts by weight Propylene glycol 10 parts by weight Urea 5 parts by weight Surfactant (Pulronic P123 / BASF) 0.03 parts by weight Ion-exchanged water balance 100 in total Part by weight (Cyan ink 6) In accordance with the above-mentioned pigment dispersion method 3 and ink preparation method, an ink having the following composition was obtained.

Self-dispersed surface-treated pigment (CI Pigment Blue 15: 3) 3 parts by weight Diethylene glycol 10 parts by weight Thiodiethanol 5 parts by weight Surfactant (Surfinol 104 / Nissin Chemical Co., Ltd.) 0.25 parts by weight ion-exchanged water Residual Total 100 parts by weight (Cyan Ink 7) An ink having the following composition was obtained according to the above-mentioned pigment dispersion method 3 and ink preparation method.

Self-dispersed surface-treated pigment (CI Pigment Blue 15: 3) 3 parts by weight Sulfolane 10 parts by weight Glycerin 5 parts by weight Surfactant (Fluorard FC-170 / 3M) 0.1 part by weight Urea 2 parts by weight Ion Exchanged water balance 100 parts by weight in total (cyan ink 8) According to the above-mentioned pigment dispersion method 3 and ink preparation method, an ink having the following composition was obtained.

Self-dispersed surface-treated pigment (CI Pigment Blue 15: 3) 3 parts by weight Glycerin 20 parts by weight Isopropyl alcohol 5 parts by weight Surfactant (Pulronic PE6400 / BASF) 0.02 parts by weight Ion-exchanged water Balance 100 Parts by weight (magenta ink 1) magenta pigment instead of cyan pigment
A magenta ink was obtained in the same manner as for the cyan ink 1 except that (CIPigment Red 122) was used.

(Magenta Ink 2) Instead of cyan pigment,
A magenta ink was obtained in the same manner as for cyan ink 2, except that a magenta pigment (CIPigment Red 122) was used.

(Magenta Ink 3) Instead of cyan pigment,
A magenta ink was obtained in the same manner as for the cyan ink 3, except that a magenta pigment (CIPigment Red 122) was used.

(Magenta Ink 4) Instead of cyan pigment,
A magenta ink was obtained in the same manner as the cyan ink 4, except that a magenta pigment (CIPigment Red 122) was used.

(Magenta Ink 5) Instead of cyan pigment,
A magenta ink was obtained in the same manner as for the cyan ink 5, except that a magenta pigment (CIPigment Red 122) was used.

(Magenta Ink 6) Instead of cyan pigment,
A magenta ink was obtained in the same manner as for the cyan ink 6, except that a magenta pigment (CIPigment Red 122) was used.

(Magenta Ink 7) Instead of cyan pigment,
A magenta ink was obtained in the same manner as for the cyan ink 7, except that a magenta pigment (CIPigment Red 122) was used.

(Magenta Ink 8) Instead of cyan pigment,
A magenta ink was obtained in the same manner as for the cyan ink 8, except that the magenta pigment (CIPigment Red 122) was used.

(Yellow Ink 1) A yellow ink was obtained in the same manner as for cyan ink 1, except that magenta pigment (CIPigment Yellow 55) was used instead of cyan pigment.

(Yellow Ink 2) A yellow ink was obtained in the same manner as for the cyan ink 2, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

(Yellow Ink 3) A yellow ink was obtained in the same manner as for the cyan ink 3, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

(Yellow Ink 4) A yellow ink was obtained in the same manner as the cyan ink 4, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

(Yellow Ink 5) A yellow ink was obtained in the same manner as for the cyan ink 5, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

(Yellow Ink 6) A yellow ink was obtained in the same manner as for the cyan ink 6, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

(Yellow Ink 7) A yellow ink was obtained in the same manner as for the cyan ink 7, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

(Yellow Ink 8) A yellow ink was obtained in the same manner as for the cyan ink 8, except that a magenta pigment (CIPigment Yellow 55) was used instead of the cyan pigment.

[Characteristic Evaluation and Print Evaluation] The colorless or light-colored solution and the ink were evaluated for the following characteristics. Unless otherwise stated below, characteristic evaluation and print evaluation were performed under general environment (temperature 23 ± 0.5 ° C, humidity 55 ±
5% RH). (A) Characteristic Evaluation (1) Surface Tension In an environment of 23 ° C. and 55% RH, measurement was performed using a Wilhelmy type surface tension type.

(2) Drying Time Using a printing device (prototype print head of 400 dpi, 160 nozzles), a colorless or light-colored solution and ink were jetted with a 100% coverage pattern to print. FX-L paper (manufactured by Fuji Xerox Co., Ltd.) was used as the recording medium, and the time until the ink permeated from the surface of the recording medium visually and disappeared after printing was measured.

(3) Ink number average particle diameter and volume average particle diameter The particle diameter of the dispersed particles was measured using a Microtrac UPA particle size analyzer.
The measurement was performed without dilution of the above ink using 9340 (manufactured by Leeds & Northrup). As the parameters to be input at the time of measurement, the viscosity of the ink to be measured was used for the viscosity, and the density of the coloring material was used for the density of the dispersed particles.

(4) State of mixed solution of ink and colorless or pale color solution Ink and colorless or pale color solution are mixed in a petri dish at a weight ratio of 1:
1 and the state of the mixed solution was visually observed. In the evaluation, ○ indicates that aggregation / thickening was observed, Δ indicates slight aggregation / thickening, and X indicates no aggregation / thickening.

(5) Increasing magnification of the number of particles of the ink-colorless or pale solution mixture of 0.5 μm or more with respect to the number of particles of the ink 0.5 μm or more The weight ratio of the colorless or pale solution to the ink is 1: 1 2 μl of this mixture was weighed, and
^{usizer TM 770 Optical Particle Sizer (Particle} Sizi
ng Systems) was used as a measuring device to measure the number of particles. Further, the same measurement was performed on 4 μl of the ink before mixing, and the number of particles having a particle diameter of 0.5 μm or more of the mixed liquid was calculated as many times as that of the ink before mixing. As a parameter to be input when measuring the Accusizer ^™ 770 Optical Particle Sizer, the density of the pigment was input as the density of the dispersed particles.

(B) Print Evaluation Print evaluation was performed under the following conditions. The printing device has 40
Using a prototype print head of 0 dpi and 160 nozzles, printing was performed by ejecting a colorless or pale solution and ink. FX-L paper (manufactured by Fuji Xerox) was used as a recording medium.

A test ink cartridge was filled with the evaluation ink set, and the following items were evaluated.

(1) Evaluation of Chromogenicity In the evaluation of chromaticity, a 100% coverage pattern was printed in a single color, and the chromaticity of each color was sensory evaluated. A sample with a vivid color was evaluated as ○, a model with a slightly poor color was evaluated as Δ, and a sample with low density and poor definition was evaluated as ×.

(2) Character / line bleed Character / line bleed was obtained by printing a single color 12-point Mincho character in each color, and comparing it with a separately prepared bleed limit sample for sensory evaluation.も の: less bleeding, Δ: acceptable but bleeding, x: severely bleeding.

(3) Secondary color development The secondary color development consists of one yellow ink and one cyan ink.
Printing was performed with 00% coverage to form a green solid image. Similarly, a secondary color image was formed using magenta ink and yellow ink, and magenta ink and cyan ink. These secondary color images were visually evaluated for sensory evaluation.も の indicates uniform and good color development, △ indicates acceptable but uneven color development, and × indicates uneven and severe color unevenness.
And

(4) Drying property The drying property was measured by printing a color pattern with a 100% coverage pattern, and measuring the time until the ink permeated from the paper surface after printing and disappeared. Less than 3 seconds until completion of permeation was evaluated as ○, 3 seconds or more and 5 seconds or less, Δ as 10 seconds or more.

(5) Injection stability A total of 1 × 10 ⁷ pulses were printed per nozzle, and the deviation of the dot landing position was examined.も の indicates that no positional deviation was observed, Δ indicates that the positional deviation was recognized but was acceptable, and X indicates that the positional deviation was severe.

(6) Intercolor bleed A 100% coverage pattern was printed so that black ink and yellow ink, cyan ink and yellow ink, and magenta ink and yellow ink were adjacent to each other. .も の: less bleeding, Δ: acceptable but bleeding, x: severely bleeding.

Example 1 In Example 1, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution A, black ink 2, cyan ink 3, magenta ink 3, and yellow ink 3. . The evaluation results are as shown in Table 1.

Example 2 In Example 2, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution B, black ink 3, cyan ink 1, magenta ink 1, and yellow ink 1. . The evaluation results are as shown in Table 1.

Example 3 In Example 3, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution C, black ink 3, cyan ink 2, magenta ink 3, and yellow ink 2. . The evaluation results are as shown in Table 1.

Example 4 In Example 4, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution D, black ink 1, cyan ink 2, magenta ink 2, and yellow ink 2. . The evaluation results are as shown in Table 1.

Example 5 In Example 5, the above-described property evaluation and printing evaluation were performed using the above colorless or pale color solution E, black ink 2, cyan ink 3, magenta ink 3, and yellow ink 1. . The evaluation results are as shown in Table 1. The test results are as shown in Table 1.

Example 6 In Example 6, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution F, black ink 1, cyan ink 1, magenta ink 1, and yellow ink 1. . The evaluation results are as shown in Table 1.

[Example 7] In Example 7, the above-described property evaluation and print evaluation were performed using the above colorless or pale solution G, black ink 3, cyan ink 2, magenta ink 2, and yellow ink 2. . The evaluation results are as shown in Table 1.

Comparative Example 1 In Comparative Example 1, the above-described property evaluation and print evaluation were performed using the above colorless or pale solution I, black ink 3, cyan ink 1, magenta ink 1, and yellow ink 1. . The evaluation results are as shown in Table 2.

[Comparative Example 2] In Comparative Example 2, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution J, black ink 4, cyan ink 1, magenta ink 1, and yellow ink 1. . The evaluation results are as shown in Table 2.

Comparative Example 3 In Comparative Example 3, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution L, black ink 3, cyan ink 3, magenta ink 3, and yellow ink 3. . The evaluation results are as shown in Table 2.

[Comparative Example 4] In Comparative Example 4, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution B, black ink 3, cyan ink 5, magenta ink 5, and yellow ink 5. . The evaluation results are as shown in Table 2.

[Comparative Example 5] In Comparative Example 5, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution B, black ink 2, cyan ink 8, magenta ink 8, and yellow ink 8. . The evaluation results are as shown in Table 2.

Comparative Example 6 In Comparative Example 6, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution F, black ink 2, cyan ink 7, magenta ink 7, and yellow ink 7. . The evaluation results are as shown in Table 2.

Comparative Example 7 In Comparative Example 7, the above-described property evaluation and print evaluation were performed using the above colorless or pale color solution B, black ink 2, cyan ink 6, magenta ink 6, and yellow ink 6. . The evaluation results are as shown in Table 2.

Comparative Example 8 In Comparative Example 8, the black ink 5 and the black ink 5 were used without using the above colorless or pale solution.
The characteristic evaluation and the printing evaluation described above were performed using only the cyan ink 6, the magenta ink 6, and the yellow ink 6. The evaluation results are as shown in Table 2.

[Comparative Example 9] In Comparative Example 9, the black ink 3 and the black ink 3 were used without using the above colorless or pale solution.
Using the cyan ink 2, the magenta ink 3, and the yellow ink 2, the above-described property evaluation and printing evaluation were performed.
The evaluation results are as shown in Table 2.

[0158]

[Table 1]

[0159]

[Table 2]

In Tables 1 and 2, “<1” indicates that the drying time is shorter than 1 second, and “≧ 100” indicates that the magnification is 100 times or more.

As shown in Table 1, according to the ink sets of Examples 1 to 7, the drying time and the surface tension of the colorless or light-colored solution and the ink contained in the ink material were adjusted to desired values. Therefore, excellent evaluation results were obtained for all of intercolor bleeding, secondary color development, drying property, and jetting stability. In particular, when a colorless or light-colored solution and ink are mixed, when the colorant is observed to aggregate or thicken,
The number of particles having a particle diameter of 0.5 μm or more contained in the mixture of the colorless or pale solution and the ink is at least 20 times the number of particles having a particle diameter of 0.5 μm or more contained in the ink before mixing. In the case of, the color developability was improved and blurring of characters and lines was reduced. On the other hand, as shown in Table 2, according to the ink sets according to Comparative Examples 1 to 9, the drying time and the surface tension of each of the inks contained in the colorless or pale solution and the ink material were out of the desired ranges. Therefore, excellent evaluation results could not be obtained for all of the evaluation items.

[0162]

According to the present invention, there is provided an ink set having high drying property, in particular, when a color image is formed, bleeding between different colors is small, and unevenness of a secondary color is small.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Hashimoto 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.F-term (reference) BC35 BC50 BC54 BE01 BE12 BE28 CA06 EA10 EA14 EA15 EA16 EA17 EA19 EA47 GA24

Claims (4)

[Claims] 1. An aqueous ink set comprising a colorless or light-colored solution and an ink material containing one or more inks, wherein the colorless or light-colored solution contains at least a water-soluble organic solvent and water. The drying time on paper is 5 seconds or less, the surface tension γa is 20 mN / m or more and 40 mN / m or less, and each ink contained in the ink material is at least a colorant;
It contains a water-soluble organic solvent and water, the drying time on plain paper is 20 seconds or less, and the surface tension γb is 25 mN /
m and not more than 50 mN / m, and satisfying a relationship of γa ≦ γb. 2. The colorant according to claim 1, wherein when the colorless or light-colored solution and each ink contained in the ink material are mixed, the colorant contained in each ink aggregates or thickens. Ink set. 3. The ink set according to claim 1, wherein the colorant contained in each of the inks contains a pigment. 4. When the colorless or light-colored solution and each ink contained in the ink material are mixed, the particle size of the mixed solution of the colorless or light-colored solution and each ink is 0.5 μm.
4. The ink set according to claim 3, wherein the number of particles having a particle size of m or more is 20 times or more the number of particles having a particle size of 0.5 μm or more contained in each ink before mixing. 5.