JP3538660B2 - INK JET RECORDING INK AND INK JET RECORDING METHOD USING THE INK JET RECORDING INK - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording ink and an ink jet recording method using the ink.

[0002]

2. Description of the Related Art In an ink jet recording method for recording information by ejecting ink onto a recording medium, the recording head is not brought into contact with the recording medium, so that there is no noise and high-speed recording is possible.

[0003] In the ink jet recording method, the stability of ink ejection is important. If the ejection of the ink is unstable, the image density of the formed image is reduced, and streak-like unevenness occurs, thereby deteriorating the image quality.

Normally, a gas is dissolved in ink. However, if a sudden change in pressure occurs in the ink during ink jet recording, the dissolved gas is generated as bubbles and the ink is ejected. Stability decreases.

[0005] As a method of removing gas dissolved in ink, there is known a method of removing gas in ink by performing film deaeration using a gas-permeable membrane.

[0006]

However, film degassing of the ink jet recording ink has a problem that the effective processing amount of the gas permeable film is limited and the processing takes a long time, so that the cost is increased. Have. Accordingly, there has been a demand for an ink jet recording ink which is low in cost and has high emission stability.

Further, it is necessary to avoid a situation in which the ink performance is reduced by improving the ejection stability of the ink, and the quality of the ink jet image is reduced.

Further, in ink jet recording,
Further high-speed printing is required. The present invention has been made in view of such problems, and an object of the present invention is to provide an ink jet recording ink having improved emission stability at low cost and high image quality at high speed by using the ink jet recording ink. An object of the present invention is to provide an ink jet recording method for forming an ink jet image.

[0009]

The object of the present invention has been attained by the following constitutions.

(1) The content of free sulfur is 0.002 to 0.002.
Ink jet recording ink of 10 ppm.

(2) The content of free sulfur is 0.006 to
1 ppm of an inkjet recording ink.

(3) The ink jet recording ink according to (1) or (2), wherein the ink contains carbon black as a coloring material.

(4) The ink for inkjet recording according to (3), further comprising a dye as a coloring material.

(5) In an ink jet recording method for ejecting ink from a recording head as fine droplets, the ink is the ink for ink jet recording described in any one of (1) to (4). Inkjet recording method.

(6) The driving frequency of the recording head is 1
The inkjet recording method according to (5), wherein the frequency is 0 kHz or more.

(7) The driving frequency of the recording head is 2
The inkjet recording method according to (5), wherein the frequency is 0 kHz or more.

(8) The driving frequency of the recording head is 3
The inkjet recording method according to (5), wherein the frequency is 0 kHz or more.

Hereinafter, the present invention will be described in detail. The present inventors have conducted intensive studies and found that free sulfur in the ink was 0.0%
It has been found that the addition of from 02 to 10 ppm improves the ejection stability of the ink. This works as a quencher for oxygen dissolved in the ink when the free sulfur present in the ink is 0.002 to 10 ppm, thereby suppressing the generation of bubbles in the ink head and improving the emission stability. Is presumed to be improved. Further, according to the present invention, since it is not necessary to perform the film degassing for a long time, the emission stability can be improved at a very low cost.

In the present invention, the content of free sulfur is set at 0.1.
When the content is 006 to 1 ppm, the emission stability can be further improved.

In the present invention, free sulfur refers to sulfur not chemically bonded to other elements.

Further, the ink jet recording ink of the present invention contains water, an ink solvent, and a coloring material.

The ink solvent that can be used in the present invention is preferably a water-soluble organic solvent. Specifically, alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pen) Polyhydric alcohols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, and the like). Glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (for example, ethylene glycol mono Tyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate , Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol dimethyl ether Etc.),
Amines (e.g., ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine,
N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.),
Amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, 2 -Oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (for example, dimethylsulfoxide), sulfones (for example, sulfolane) and the like.

Here, it is more preferable to use a compound represented by the following general formula (1) as the ink solvent.

In the general formula (1) AB, A represents a group containing a hydrophilic substituent, and B represents a hydrophobic group.

The hydrophilic substituent represented by A includes a hydroxy group, a carboxyl group, a sulfoxide group, a sulfone group, a sulfonic acid group, a 2-keto-1-pyrrolidinyl group and the like. Among them, a hydroxy group is preferred.

B represents a hydrophobic group, preferably an aliphatic or aromatic hydrocarbon group having 3 to 10 carbon atoms. Further, B is preferably an aliphatic group having 4 to 8 carbon atoms.

The compound represented by the general formula (1) has a structure similar to that of a general surfactant, but preferably does not have a strong surfactant action such as a surfactant. . General surfactants have the characteristic of forming micelles at low concentrations in aqueous solutions. It is preferable that the compound represented by the general formula (1) does not have such micelle-forming ability. This is because when the surfactant has a strong surface activity, the interaction between the molecules is strong, and when the concentration exceeds 1%, there is a disadvantage that the viscosity of the ink is significantly increased.

Among the compounds represented by the above general formula (1), preferable examples include polyhydric alcohol ether derivatives and aliphatic 1,2-diols having 4 to 8 carbon atoms, and ethylene glycol monobutyl ether ( (Butyl cellosolve), diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, 1,2-hexanediol, or 1,2-pentanediol. More preferably, triethylene glycol monobutyl ether or 1,
2-hexanediol.

In the ink solvent used in the present invention, it is preferable to use the compound represented by the general formula (1) in an amount of 5 to 50% or more of the ink solvent in order to improve various properties. The various performances referred to here include, for example, decap resistance (resistance to a phenomenon in which the ink solvent evaporates on the head surface during output and the ink ejection speed fluctuates), dot diameter (recording dot on the recording medium surface). Diameter), boundary blur, and the like.

The ink solvent used in the present invention is:
The compound represented by the above general formula (1)
It is preferable to use 50% or more in order to improve the image quality by expanding the decap resistance and the dot diameter. The decap resistance can be improved by increasing the amount of the ink solvent, and practical problems can be reduced by increasing the composition ratio of the ink solvent in the ink to more than 45%. However, in order to improve the image quality by increasing the dot diameter, it is preferable to include the ink solvent represented by the general formula (1). These ink solvents may be used alone or in combination.

The coloring materials usable in the present invention include:
Examples include water-soluble dyes, disperse dyes, oil-based dyes and pigments.

Examples of the water-soluble dye which can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes and the like. Specific compounds are shown below.
However, the compounds are not limited to these exemplified compounds.

[C. I. Acid Yellow] 1, 3, 1
1, 17, 18, 19, 23, 25, 36, 38, 4
0, 42, 44, 49, 59, 61, 65, 67, 7
2, 73, 79, 99, 104, 110, 114, 11
6, 118, 121, 127, 129, 135, 13
7, 141, 143, 151, 155, 158, 15
9, 169, 176, 184, 193, 200, 20
4, 207, 215, 219, 220, 230, 23
2, 235, 241, 242, 246 [C. I. Acid Orange] 3, 7, 8, 10, 1
9, 24, 51, 56, 67, 74, 80, 86, 8
7, 88, 89, 94, 95, 107, 108, 11
6, 122, 127, 140, 142, 144, 14
9, 152, 156, 162, 166, 168 [C. I. Acid Red] 1, 6, 8, 9, 13, 1
8, 27, 35, 37, 52, 54, 57, 73, 8
2, 88, 97, 106, 111, 114, 118, 1
19, 127, 131, 138, 143, 145, 15
1, 183, 195, 198, 211, 215, 21
7, 225, 226, 249, 251, 254, 25
6, 257, 260, 261, 265, 266, 27
4, 276, 277, 289, 296, 299, 31
5, 318, 336, 337, 357, 359, 36
1, 362, 364, 366, 399, 407, 415 [C. I. Acid Violet] 17, 19, 21,
42, 43, 47, 48, 49, 54, 66, 78, 9
0, 97, 102, 109, 126 [C. I. Acid Blue] 1, 7, 9, 15, 23,
25, 40, 62, 72, 74, 80, 83, 90, 9
2, 103, 104, 112, 113, 114, 12
0, 127, 128, 129, 138, 140, 14
2, 156, 158, 171, 182, 185, 19
3, 199, 201, 203, 204, 205, 20
7, 209, 220, 221, 224, 225, 22
9, 230, 239, 249, 258, 260, 26
4, 278, 279, 280, 284, 290, 29
6, 298, 300, 317, 324, 333, 33
5, 338, 342, 350 [C. I. Acid Green] 9, 12, 16, 19,
20, 25, 27, 28, 40, 43, 56, 73, 8
1, 84, 104, 108, 109 [C. I. Acid Brown] 2, 4, 13, 14, 1
9, 28, 44, 123, 224, 226, 227, 2
48, 282, 283, 289, 294, 297, 29
8, 301, 355, 357, 413 [C. I. Acid Black] 1, 2, 3, 24, 2
6, 31, 50, 52, 58, 60, 63, 107, 1
09, 112, 119, 132, 140, 155, 17
2, 187, 188, 194, 207, 222 [C. I. Direct Yellow] 8, 9, 10, 11,
12, 22, 27, 28, 39, 44, 50, 58, 7
9,86,87,98,105,106,130,13
2, 137, 142, 147, 153 [C. I. Direct orange] 6, 26, 27, 3
4, 39, 40, 46, 102, 105, 107, 11
8 [C. I. Direct Red] 2, 4, 9, 23, 2
4, 31, 54, 62, 69, 79, 80, 81, 8
3, 84, 89, 95, 212, 224, 225, 22
6, 227, 239, 242, 243, 254 [C. I. Direct violet] 9, 35, 51,
66, 94, 95 [C. I. Direct Blue] 1, 15, 71, 76,
77, 78, 80, 86, 87, 90, 98, 106,
108, 160, 168, 189, 192, 193, 1
99, 200, 201, 202, 203, 218, 22
5,229,237,244,248,251,27
0, 273, 274, 290, 291 [C. I. Direct Green] 26, 28, 59, 8
0, 85 [C. I. Direct Brown] 44, 106, 11
5, 195, 209, 210, 222, 223 [C. I. Direct Black] 17, 19, 22, 3
2, 51, 62, 108, 112, 113, 117, 1,
18, 132, 146, 154, 159, 169 [C. I. Basic Yellow] 1, 2, 11, 13,
15, 19, 21, 28, 29, 32, 36, 40, 4
1, 45, 51, 63, 67, 70, 73, 91 [C. I. Basic Orange] 2, 21, 22 [C. I. Basic Red] 1, 2, 12, 13, 1
4, 15, 18, 23, 24, 27, 29, 35, 3,
6, 39, 46, 51, 52, 69, 70, 73, 8
2, 109 [C. I. Basic Violet] 1, 3, 7, 1
0, 11, 15, 16, 21, 27, 39 [C. I. Basic Blue] 1, 3, 7, 9, 21,
22, 26, 41, 45, 47, 52, 54, 65, 6
9, 75, 77, 92, 100, 105, 117, 12
4, 129, 147, 151 [C. I. Basic Green] 1, 4 [C. I. Basic Brown] 1 [C. I. Reactive Yellow] 2, 3, 7, 15,
17, 18, 22, 23, 24, 25, 27, 37, 3,
9, 42, 57, 69, 76, 81, 84, 85, 8
6, 87, 92, 95, 102, 105, 111, 12
5, 135, 136, 137, 142, 143, 14
5, 151, 160, 161, 165, 167, 16
8, 175, 176 [C. I. Reactive Orange] 1, 4, 5, 7, 1
1, 12, 13, 15, 16, 20, 30, 35, 5
6, 64, 67, 69, 70, 72, 74, 82, 8
4, 86, 87, 91, 92, 93, 95, 107 [C. I. Reactive Red] 2, 3, 5, 8, 1
1, 21, 22, 23, 24, 28, 29, 31, 3
3, 35, 43, 45, 49, 55, 56, 58, 6
5, 66, 78, 83, 84, 106, 111, 11
2, 113, 114, 116, 120, 123, 12
4, 128, 130, 136, 141, 147, 15
8, 159, 171, 174, 180, 183, 18
4, 187, 190, 193, 194, 195, 19
8, 218, 220, 222, 223, 228, 235 [C. I. Reactive Violet] 1, 2, 4,
5, 6, 22, 23, 33, 36, 38 [C. I. Reactive Blue] 2, 3, 4, 5, 7,
13, 14, 15, 19, 21, 25, 27, 28, 2
9, 38, 39, 41, 49, 50, 52, 63, 6
9, 71, 72, 77, 79, 89, 104, 109,
112, 113, 114, 116, 119, 120, 1
22, 137, 140, 143, 147, 160, 16
1,162,163,168,171,176,18
2, 184, 191, 194, 195, 198, 20
3, 204, 207, 209, 211, 214, 22
0, 221, 222, 231, 235, 236 [C. I. Reactive Green] 8, 12, 15, 1
9, 21 [C. I. Reactive Brown] 2, 7, 9, 10,
11, 17, 18, 19, 21, 23, 31, 37, 4
3, 46 [C. I. Reactive Black] 5, 8, 13, 1
4, 31, 34, 39, etc., and the dyes listed above are described in "Dyeing Notebook 21st Edition" (published by Shisensensha) and the like.

Of these water-soluble dyes, phthalocyanine dyes are preferred. Examples of the phthalocyanine dye include unsubstituted dyes and dyes having a central element, and examples of the central element include metal and non-metallic dyes, preferably copper, and more preferably C.I. I. Direct blue 19
9 is mentioned.

Particularly preferred specific examples of the above disperse dye are shown below. Particularly preferred specific examples include C.I. I.
Disperse Yellow 5, 42, 54, 64, 79, 8
2, 83, 93, 99, 100, 119, 122, 12
4, 126, 160, 184: 1, 186, 198, 1
C. 99, 204, 224 and 237; I. Disperse Orange 13, 29, 31: 1, 33, 49, 54,
55, 66, 73, 118, 119 and 163;
I. Disperse Red 54, 60, 72, 73, 8
6, 88, 91, 92, 93, 111, 126, 12
7, 134, 135, 143, 145, 152, 15
3, 154, 159, 164, 167: 1, 177, 1
81, 204, 206, 207, 221, 239, 24
0, 258, 277, 278, 283, 311, 32
3, 343, 348, 356 and 362; I. Disperse Bio Red 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143,
148, 154, 158, 165, 165: 1, 16
5: 2, 176, 183, 185, 197, 198, 2
01, 214, 224, 225, 257, 266, 26
7, 287, 354, 358, 365 and 368; and C.I. I. Disperse Green 6: 1 and 9 and the like. On the other hand, the oily dye is not limited to the following, but particularly preferred specific examples include, for example, C.I. I. Solvent Black 3, 7, 27, 29
And 34; I. Solvent Yellow 14, 16,
19, 29, 56 and 82; I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 51, 72,
73, 132 and 218; I. Solvent Violet 3; I. Solvent Blue 2, 11 and 7
0; I. Solvent Green 3 and 7; and C.I. I. Solvent Orange 2 and the like.

The ink-jet recording ink of the present invention comprises:
Since the content of free sulfur is 10 ppm or less, even if the ink is stored for a long time using these dyes, deterioration in the quality of the ink due to decomposition of the dyes is suppressed. When the content of free sulfur is 1 ppm or less, the deterioration of the ink quality can be further suppressed.

As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo lakes, insoluble azo pigments, condensed azo pigments, azo pigments such as chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments,
Polycyclic pigments such as dioxazine pigment, thioindigo pigment, isoindolinone pigment, quinophthaloni pigment, dye lakes such as basic dye lake and acid dye lake, nitro pigment, nitroso pigment, aniline black, daylight fluorescent Organic pigments such as pigments and inorganic pigments such as carbon black are exemplified.

Specific examples of the organic pigment are shown below. Pigments for magenta or red include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I.
I. Pigment Red 7, C.I. I. Pigment Red 1
5, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 53:
1, C.I. I. Pigment Red 57: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 12
3, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149,
C. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I.
I. Pigment Red 222 and the like.

As pigments for orange or yellow,
C. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I.
I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I.
Pigment Yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 12
8, C.I. I. Pigment Yellow 138 and the like.

The pigments for green or cyan include:
C. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 2, C.I. I. Pigment Blue 15: 3,
C. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.

Examples of black pigments include carbon black (CI Pigment Black 7, Ketjen Black EC, Denka Black HS-100, acetylene black, etc.).

The ink-jet recording ink of the present invention comprises:
Particularly when carbon black is contained as a coloring material,
Since many bubbles are included in many cases, the effects of the present invention can be further obtained.

The content of the pigment used in the aqueous ink is as follows:
It is preferably from 1 to 10% by mass based on the total mass of the ink.

In the present invention, a pigment dispersant may be used if necessary. Examples of the pigment dispersant that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, and sulfosuccinic acids. Salt, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide Activators such as styrene, styrene derivatives, vinylnaphthalene derivatives, acrylic acid,
Block copolymers, random copolymers and salts thereof composed of two or more monomers selected from acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives Can be mentioned.

As a method for dispersing the pigment, various methods such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used.

Using the pigment and the pigment dispersant, a centrifugal separator or a filter is preferably used for the purpose of removing coarse particles of the pigment dispersion obtained by the dispersion method.

The average particle size of the pigment dispersion used in the aqueous ink is preferably from 10 to 200 nm.
50 nm is more preferred, and 10-100 nm is even more preferred. When the average particle size of the pigment dispersion is 200 nm or less, the glossiness of an image recorded on a glossy medium increases, and the image recorded on a transparency medium has a remarkable transparency. When the average particle size of the pigment dispersion is 10 nm or more, the stability of the pigment dispersion is improved, and the storage stability of the ink is improved.

The particle size of the pigment dispersion can be measured by a commercially available particle size measuring device using a laser Doppler method.

The ink-jet recording ink of the present invention comprises:
The viscosity is preferably 3.5 to 6.0 mPa · s. By setting the viscosity within this range, clogging of the ink nozzle hardly occurs, and the ink can be stably ejected for a long period of time.

The viscosity of the ink for ink jet recording can be measured using a commercially available viscosity meter.

The ink-jet recording ink of the present invention comprises:
Latex may be contained. In the present invention, the latex refers to polymer particles dispersed in a medium. Examples of the type of polymer include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylate copolymer, polyurethane, silicon-acryl copolymer, and acrylic-modified fluororesin. Acid esters, polyurethanes and silicone-acrylic copolymers are preferred.

As the emulsifier used in the production of the latex, a low molecular weight surfactant is generally used. Among them, a high molecular weight surfactant (for example, a surfactant having a solubilizing group grafted to the polymer) is used. Type or a block polymer type in which a portion having a solubilizing group and an insoluble portion are linked) as an emulsifier, or by directly bonding a solubilizing group to a central polymer of a latex without using an emulsifier. Some latex is also dispersed. The latex using a high molecular weight surfactant as the emulsifier and the latex not using the emulsifier are called soap-free latex. The latex used in the present invention is not limited to the type and form of the emulsifier, but it is more preferable to use a soap-free latex having excellent storage stability of the ink.

In addition, recently, besides latex having a uniform central polymer, a core / shell type latex having a different composition at the center and the outer edge of polymer particles also exists.
This type of latex can also be preferably used.

The average particle size of the latex in the present invention is 1
50 nm or less is preferable, and 50 nm or less is more preferable.

The average particle size of the latex can be easily measured using a commercially available measuring device using a light scattering method or a laser Doppler method.

The solid content of the latex in the present invention is from 0.1 to 10% by mass based on the total mass of the ink.
It is particularly preferred that the content is 0.3 to 5% by mass or less. If the addition amount is less than 0.1% by mass, it is difficult to exert a sufficient effect on water resistance, and if it exceeds 10% by mass, the ink viscosity tends to increase and the pigment dispersion particle size tends to increase over time. Problems often arise in terms of points.

The ink jet recording ink of the present invention may further contain a preservative, a fungicide, a viscosity modifier and the like, if necessary.

The recording medium used in the ink jet recording method of the present invention may be any recording medium which is usually used for ink jet recording, but is preferably a recording medium having an ink absorbing layer on a support. The ink absorbing layer is preferably formed by applying a water-soluble coating solution containing a hydrophilic binder and fine particles on a support to form a layer having voids.

As the fine particles that can be used in the present invention, inorganic fine particles and organic fine particles can be used.
In particular, inorganic fine particles are preferred because high color density can be obtained and fine particles can be easily obtained. Examples of such inorganic fine particles include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide,
Zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, Examples include white inorganic pigments such as lithopone, zeolite, and magnesium hydroxide. The inorganic fine particles can be used as they are as primary particles or in a state where secondary aggregated particles are formed.

In the present invention, from the viewpoint of obtaining high-quality prints on a recording medium, alumina,
Pseudo-boehmite, colloidal silica or particulate silica synthesized by a gas phase method is preferred, and particulate silica synthesized by a gas phase method is particularly preferred. The silica synthesized by this gas phase method may be one whose surface is modified with Al. The Al content of the fumed silica whose surface is modified with Al is preferably 0.05 to 5% by mass relative to silica.

The inorganic fine particles may have any size, but preferably have an average particle size of 1 μm or less. If it exceeds 1 μm, the glossiness and the color developability tend to decrease, and therefore, the thickness is particularly preferably 0.2 μm or less, and most preferably 0.1 μm or less. The lower limit of the particle size is not particularly limited, but is preferably about 0.003 μm or more, particularly preferably 0.005 μm or more from the viewpoint of production of the inorganic fine particles.

The average particle size of the inorganic fine particles can be obtained as a simple average value (number average) by observing the cross section and surface of the porous layer with an electron microscope, obtaining the particle size of 100 arbitrary particles. . Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

The degree of dispersion of the fine particles is preferably 0.5 or less from the viewpoint of glossiness and coloring. If it exceeds 0.5, the gloss and the coloring property at the time of printing tend to be reduced. In particular, 0.3
The following is preferred. Here, the degree of dispersion of the fine particles refers to the value obtained by observing the fine particles in the ink absorbing layer with an electron microscope in the same manner as for obtaining the average particle diameter, and dividing the standard deviation by the average particle diameter.

The fine particles may be present in the ink absorbing layer as primary particles or as secondary particles or higher aggregated particles. The above average particle size is determined by an electron microscope. It refers to the particle size of what forms independent particles in the ink absorbing layer when observed.

The content of the fine particles in the water-soluble coating solution is 5 to 40% by mass, particularly preferably 7 to 30% by mass.

The hydrophilic binder contained in the ink absorbing layer is not particularly limited, and a conventionally known hydrophilic binder can be used. Examples thereof include gelatin, polyvinylpyrrolidone, polyethylene oxide, polyacrylamide, and polyvinyl alcohol. Although polyvinyl alcohol can be used, polyvinyl alcohol is particularly preferred.

Polyvinyl alcohol has an interaction with inorganic fine particles, has a particularly high holding power for inorganic fine particles, and is a polymer having a relatively small humidity dependency of hygroscopicity. Is relatively small, so that suitability for cracking during coating and drying is excellent. Polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol having a cationically modified terminal or anionic modified polyvinyl alcohol having an anionic group. Polyvinyl alcohol is also included.

The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 300 or more, and particularly preferably has an average degree of polymerization of 1,000 to 5,000.
Is preferably used. Degree of saponification is 70-10
0% is preferable, and 80 to 99.5% is particularly preferable.

As the cation-modified polyvinyl alcohol, for example, as described in JP-A-61-10483, a primary to tertiary amino group or a quaternary ammonium group is added to the main chain or side chain of the polyvinyl alcohol. The polyvinyl alcohol contained therein is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

Two or more types of polyvinyl alcohols having different degrees of polymerization and different types of modification can be used in combination. In particular, when a polyvinyl alcohol having a polymerization degree of 2,000 or more is used, the polymerization degree of the inorganic fine particle dispersion is 1 in advance.
000 or less polyvinyl alcohol based on inorganic fine particles in an amount of 0.05 to 10% by mass, preferably 0.1 to 5% by mass.
It is preferable to add polyvinyl alcohol having a degree of polymerization of 2,000 or more after the addition, since there is no remarkable increase in viscosity.

The ratio of the fine particles to the hydrophilic binder in the ink absorbing layer is preferably 2 to 20 times by mass. When the mass ratio is less than twice, the porosity of the porous layer is reduced, and not only is it difficult to obtain a sufficient void volume, but also an excess hydrophilic binder swells at the time of inkjet recording to close the voids, This causes a reduction in the ink absorption speed. On the other hand, if this ratio exceeds 20 times, cracks are likely to occur when the ink absorbing layer is applied as a thick film, which is not preferable. A particularly preferred ratio of the fine particles to the hydrophilic binder is 2.5 to 12 times, most preferably 3 to 10 times.

Various additives can be added to the water-soluble coating solution for forming the ink absorbing layer. Such additives include, for example, a crosslinking agent, a surfactant (cation, nonionic, anionic, amphoteric), a white color tone adjusting agent, a fluorescent whitening agent, a fungicide, a viscosity adjusting agent, a low boiling organic solvent, Examples include a boiling point organic solvent, a latex emulsion, an anti-fading agent, an ultraviolet absorber, a polyvalent metal compound (water-soluble or water-insoluble), a matting agent, and silicone oil. Preferred for improving moisture resistance.

As the crosslinking agent, conventionally known crosslinking agents can be used, and inorganic crosslinking agents (for example, chromium compounds, aluminum compounds, zirconium compounds, boric acids, etc.) and organic crosslinking agents (for example, epoxy-based crosslinking agents) Crosslinking agent,
Use of isocyanate-based crosslinking agents, aldehyde-based crosslinking agents, N-methylol-based crosslinking agents, acryloyl-based crosslinking agents, vinylsulfone-based crosslinking agents, active halogen-based crosslinking agents, carbodiimide-based crosslinking agents, ethyleneimino-based crosslinking agents, and the like. be able to.

These crosslinking agents are used in an amount of about 1 to 50% by mass, preferably 2 to 40% by mass, based on the hydrophilic binder.
% By mass.

When the hydrophilic binder is polyvinyl alcohols and the fine particles are silica, inorganic crosslinking agents such as boric acids and zirconium compounds and epoxy crosslinking agents are particularly preferred as the crosslinking agent.

As a particularly preferred embodiment, when polyvinyl alcohol and silica fine particles are used, by using boric acid or a salt thereof, when the temperature of the water-soluble coating solution is lowered, the viscosity of the coating solution greatly increases, and Even when a strong wind is blown on the film surface, the turbulence of the coating film is greatly suppressed and high-speed coating is facilitated, which is preferable. The boric acid or a salt thereof refers to an oxyacid having a boron atom as a central atom and a salt thereof. Specifically, orthoboric acid, metaboric acid, hypoboric acid, tetraboric acid, pentaboric acid and salts thereof (for example, Sodium salts, potassium salts, ammonium salts and the like).

The amount of boric acid or a salt thereof may vary widely depending on the concentration, pH, etc. of the inorganic fine particles and polyvinyl alcohol in the coating solution, but is generally about 5 to 60% by mass, preferably 10 to 40% by mass based on polyvinyl alcohol. % By mass.

As a support that can be used for the recording medium used in the ink jet recording method of the present invention, a water-absorbing support (for example, paper) or a non-water-absorbing support can be used. A non-water-absorbing support is preferable from the viewpoint of obtaining a good print.

Examples of the non-water-absorbing support preferably used include polyester films, diacetate films, triatethate films, polyolefin films, acrylic films, polycarbonate films, polyvinyl chloride films, and polyimide films. , A transparent or opaque film made of a material such as cellophane or celluloid, or a resin coated paper in which both surfaces of a base paper are coated with a polyolefin resin coating layer, so-called RC
Paper or the like is used.

The ink jet head of the ink jet printer which can be used in the ink jet recording method of the present invention is preferably a piezo type head.

The piezo type head shown in FIGS. 1 and 2 will be described. FIG. 1 is a schematic perspective view having a partially broken cross section of the head, and FIG. 2 is a schematic cross section showing an example of an ink chamber portion of the head.

A lower substrate 1b and an upper substrate 1c made of lead zirconate titanate, which is a piezoelectric material, are bonded to each other with an adhesive 6. The lower substrate 1b and the upper substrate 1c are polarized in opposite directions as shown by arrows in FIG. A plurality of elongated grooves 2 are formed over the upper substrate and the lower substrate. Thereby, a plurality of parallel partition walls 4 and grooves 2 are formed.

The electrode film 3 is provided on the inner surface of the plurality of grooves by vapor deposition. After the electrode film 3 is attached to the groove 2, a part of the upper surface of the substrate 1 is stepped to form a step 35. The lid 8 is adhered to the upper surface of the partition 4 with the adhesive 6, and the groove 25 is attached to the end surface of the partition 4 with the adhesive. The surface of the electrode film 3 formed on the inner surface of the plurality of grooves is coated with an insulating film 17 such as parylene, and the surface of the insulating film 17 is hydrophilized by oxygen plasma processing. This hydrophilic treatment makes it difficult for bubbles due to carbon dioxide gas to remain in the head, and improves emission stability. A nozzle plate 10 having a nozzle hole 11 is bonded to the open end face of the groove 2 with the same adhesive 6 to form an ink chamber 9 for every other groove 2. The nozzle holes are provided corresponding to each ink chamber, that is, provided every other nozzle corresponding to the groove 2. A common groove 5 is carved in the upper part of the lid 8, and a hole 12 for communicating with each ink chamber is provided. Every other groove 2 has both a nozzle hole 11 and a communication hole 12. An upper plate 14 having an ink supply hole 15 is provided above the lid 8 with a common groove 5.
Is adhered by an adhesive 6 so as to cover the upper part of.

The electrode films are connected to the lead wires 7 exposed at the step portions 35 of the lid 8, respectively.

Ink is supplied from the ink supply holes 15 to fill the ink chambers 9 formed in every other one of the parallel grooves 2 in FIGS. No ink is supplied to the adjacent dummy grooves 9 '.

When an electric signal is sent to the lead line 7 and a driving voltage is applied between the electrode film of the ink chamber 2a and the electrode films of the dummy grooves on both sides thereof so that the potential of the electrode film of the ink chamber becomes high, the ink is applied. The partition walls on both sides of the chamber 2a are deformed inward, the ink chamber contracts, and the ink is emitted as small droplets. Subsequently, when the ink chamber electrode film is grounded, the ink is sucked into the ink chamber without deformation.

The ink-jet recording ink of the present invention comprises:
Even if the driving frequency of the inkjet head is increased, the emission stability is maintained, so that high-speed printing can be performed. In the present invention, the driving frequency of the head is set to 10
It is preferable to perform printing at a frequency of kHz or higher, whereby higher-speed printing can be performed. The driving frequency of the head is preferably 20 kHz or more, and more preferably 30 kHz or more.

[0088]

Hereinafter, the present invention will be described with reference to examples.
The present invention is not limited to these examples. In addition,
In Examples, "%" represents% by mass unless otherwise specified.

Example 1 <Preparation of Pigment Ink 1> Carbon black 20 mass% Styrene-acrylic acid copolymer (molecular weight 7,000, acid value 150) 10 mass% glycerin 10 mass% ion-exchanged water 60 mass% The additives were mixed and dispersed using a horizontal bead mill filled with 0.3 mm glass beads at a volume ratio of 60%,
Pigment dispersion 1 was obtained. The average particle size of the pigment of the obtained pigment dispersion 1 was 75 nm.

Pigment Dispersion 1 10% by mass Ethylene glycol 10% by mass Diethylene glycol 10% by mass Triethylene glycol monobutyl ether 6% by mass Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass Deionized water 63. 9% by mass or more of each composition was mixed, stirred, filtered with a 1 μm filter, and further adjusted to pH 9.5 with an aqueous sodium hydroxide solution to prepare Ink 1 as an aqueous pigment ink. The average particle size of the pigment in the ink was 85 nm.

The amount of free sulfur contained in the pigment ink 1 was measured by the following method. [Quantitative Determination of Free Sulfur in Ink] After adding hydrochloric acid to the pigment ink 1, centrifugation (16000 rpm: 20 minutes) was performed, and the precipitate was washed with methanol, and the precipitate was dried. 5 g of the dried precipitate was dissolved in 100 ml of toluene, refluxed for 5 hours, filtered, dried again, dissolved in 3 ml of toluene / methanol (= 1/3), and subjected to high performance liquid chromatography ( Hitachi, column: GL Sciences Inertsil ODS-2
(Inner diameter 4.6 mm, length 250 mm), eluent: methanol / water = 9/1) to determine free sulfur.

Further, after the supernatant liquid after centrifugation was extracted with toluene, the oil phase was dried and dissolved with 3 ml of toluene / methanol (= 1/3). Sulfur was determined. The sum of the quantitative values of free sulfur determined by the above two high performance liquid chromatography measurements was defined as the content of free sulfur. <Preparation of Pigment Ink 2> SulfurPowder (manufactured by Kanto Chemical Co., Ltd.) was ground in a mortar and 1% in toluene.
The pigment ink 1 was dissolved at a concentration to form a solution, and the content was 0.1%.
Pigment ink 2 was prepared by adding so as to be 0.01 ppm. The final confirmation of the content of free sulfur contained in the pigment ink 2 was performed using the quantitative method for the pigment ink 1. <Preparation of pigment ink 3> In the preparation of pigment ink 2,
Pigment ink 3 was prepared in the same manner as pigment ink 2 except that the content of free sulfur was 0.02 ppm. The final confirmation of the content of free sulfur contained in the pigment ink 3 was performed using the quantitative method for the pigment ink 1. <Preparation of pigment ink 4> In the preparation of pigment ink 2,
Pigment ink 4 was prepared in the same manner as pigment ink 2 except that the content of free sulfur was 0.1 ppm. The final confirmation of the content of free sulfur contained in the pigment ink 4 was performed using the quantitative method for the pigment ink 1. <Preparation of pigment ink 5> In the preparation of pigment ink 2,
Pigment ink 2 except that the content of free sulfur was 3 ppm
Pigment ink 5 was prepared in the same manner as described above. The final confirmation of the content of free sulfur contained in the pigment ink 5 is as follows.
This was performed using the quantification method described above. <Preparation of pigment ink 6> In the preparation of pigment ink 2,
Pigment ink 6 was prepared in the same manner as pigment ink 2 except that the content of free sulfur was 20 ppm. Pigment ink 6
The final confirmation of the content of free sulfur contained in the pigment ink 1 was performed using the quantitative method for the pigment ink 1. [Evaluation of Emission Stability of Pigment Inks 1 to 6] As an inkjet recording method, a nozzle hole diameter of 20 μm shown in FIGS.
m, drive frequency 30 kHz, ink drops 6 pl, number of nozzles per color 128, nozzle density 180 dpi between the same colors
(Dpi indicates the number of dots per 2.54 cm) and a maximum recording density of 720 × 72
Continuous printing was performed on each of the pigment inks 1 to 6 using an on-demand type inkjet printer of 0 dpi. <Evaluation of Emission Stability> The number of missing dots generated when continuous printing was performed for each pigment ink was totaled, and the total number of printing lines was divided by the number of missing dots to calculate the average number of printing lines. ：: 150,000 lines or more ：: 50,000 lines or more and less than 150,000 lines ×: less than 50,000 lines The results are shown in Table 1.

[0093]

[Table 1]

As shown in Table 1, the ink jet recording ink of the present invention was able to print at a high speed with little dot omission. It was found that the use of the ink jet recording ink of the present invention stably emitted ink droplets.

Example 2 <Dye-Pigment Inks 1 to 6> Dye-Pigment Inks 1 to 6 were prepared by adding Direct Blue 199 to each of the pigment inks 1 to 6 at a concentration of 1.0% by mass. [Evaluation of Storage Stability of Dye / Pigment Inks 1 to 6] The following residual ratios of the dye / pigment inks 1 to 6 were determined. The absorbance was measured using a spectrophotometer (U-3200 Spectrop).
wavelength using a photometer (Hitachi, Ltd.).
The absorbance at 0 nm was measured. The measurement was performed after dilution with water so that the absorbance at a wavelength of 620 nm of each ink was 0.5 to 1.0. Residual rate = (A _CD80 −A _C80 ) / (A _CD −A _C ) A _CD : Absorbance of dye pigment ink A _C : Absorbance of pigment ink A _CD80 : Absorbance A after storing dye pigment ink at 80 ° C. for 2 weeks _C80 : Table 2 shows the absorbance results after the pigment ink was stored at 80 ° C. for 2 weeks.

[0096]

[Table 2]

From the results shown in Table 2, if the content of free sulfur is within the range of the present invention, the decomposition of the dye can be suppressed even during long-term storage, and the ink can be stored for a long time. The emission stability of the dye pigment inks 1 to 6 was similar to the emission stability of the pigment ink of Example 1.

[0098]

According to the present invention, there is provided an ink jet recording ink which has improved emission stability at a low cost, and an ink jet recording method for forming an ink jet image with high image quality at high speed by using the ink. I was able to.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view having a partially broken surface of a head that can be used in the present invention.

FIG. 2 is a schematic sectional view showing an example of an ink chamber portion of a head that can be used in the present invention.

[Explanation of symbols]

1 substrate 2 groove 2a Ink chamber 3 Electrode film 6 adhesive 8 Lid 9 Ink chamber 9 'dummy groove 14 Upper plate 15 Ink supply hole

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Saori Nishio Sakuracho, Hino-shi, Tokyo 1 Konica Corporation (72) Inventor Yasuhiro Oka 1 Sakura-cho, Hino-shi, Tokyo Konica Co., Ltd. (56) References JP-A-52-74406 (JP, A) JP-A-53-61412 (JP, A) JP-A-56-41275 (JP, A) JP-A-57-102970 (JP, A) JP-A-9-48937 (JP, A) JP-A-2000-226544 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (8)

(57) [Claims] 1. The content of free sulfur is 0.002 to 10 p
pm, an inkjet recording ink. 2. A free sulfur content of 0.006-1 pp.
m, the ink for inkjet recording. 3. The ink jet recording ink according to claim 1, wherein carbon black is contained as a coloring material. 4. The ink for ink jet recording according to claim 3, further comprising a dye as a coloring material. 5. An ink jet recording method for ejecting ink as fine droplets from a recording head, wherein the ink is the ink for ink jet recording according to any one of claims 1 to 4. Method. 6. A driving frequency of the recording head is 10 kHz.
The ink jet recording method according to claim 5, wherein z is not less than z. 7. A driving frequency of the recording head is 20 kHz.
The ink jet recording method according to claim 5, wherein z is not less than z. 8. A driving frequency of the recording head is 30 kHz.
The ink jet recording method according to claim 5, wherein z is not less than z.