JP2011079952A - Ink set, ink cartridge, inkjet recording device and ink recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set or the like comprising a black ink and color inks and capable of suppressing bleeding not only in plain paper but in paper with inferior ink permeability. <P>SOLUTION: The ink set is a set of a plurality of aqueous inks each comprising water, a water-soluble organic solvent, a colorant and a surfactant, wherein the inks are at least a black ink and color inks of cyan, magenta and yellow. The ink set satisfies the following requirements (1) and (2): (1) in a surface lifetime region of <100 ms after impact, the dynamic surface tension of each of the color inks is not less than that of the black ink, and (2) in a surface lifetime region of 100-3,000 ms after impact, there is a point at which the dynamic surface tension of the black ink and that of each of the color inks are equal to each other, and in a surface lifetime region subsequent to the point, the dynamic surface tension of the black ink is larger than that of each of the color inks. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ink set comprising at least black ink and cyan, magenta and yellow color inks, an ink cartridge containing the ink set in a container, an ink jet recording apparatus equipped with the ink cartridge, and printing using the ink set To the recorded ink.

Ink jet printers are required to print high-quality recorded materials at high speed, and one of the most problematic problems in aiming for high image quality is color boundary bleeding (bleed) between different inks. On the other hand, it is already known that bleeding can be suppressed by controlling the difference in dynamic surface tension between black ink and color ink.
However, the conventional control method has no reference to the behavior of the dynamic surface tension in the long life region, and there is a problem that it does not lead to suppression of bleeding on a paper surface having poor ink permeability.
Patent Document 1 discloses an ink set in which the dynamic surface tension difference between inks and the difference in dynamic surface tension are controlled within the range of a surface life of 30 to 1000 ms for the purpose of reducing color bleeding between inks. ing. However, this ink set is similar to the present invention in that it suppresses bleed by controlling the dynamic surface tension, but at a color boundary, such as a coated paper for printing, which has a lower ink absorption than plain paper. No measures have been taken for recording media in which bleeding is particularly noticeable. For this reason, the problem that intense color bleeding occurs on paper with poor ink permeability cannot be solved.

  The present invention relates to an ink set composed of black ink and color ink that can reduce bleeding not only on plain paper but also on paper with poor ink permeability, an ink cartridge containing the ink set in a container, and the ink cartridge The present invention aims to provide an ink-jet recording apparatus on which the ink set is mounted and an ink record printed using the ink set.

The above problems are solved by the following inventions 1) to 4).
1) An ink set comprising a plurality of water-based inks containing water, a water-soluble organic solvent, a colorant, and a surfactant, comprising at least a black ink and cyan, magenta, and yellow color inks. ) An ink set that satisfies the requirement (2).
(1) The dynamic surface tension of each color ink is greater than or equal to the dynamic surface tension of the black ink in a surface lifetime region of less than 100 ms after landing.
(2) There is a point where the dynamic surface tension of the black ink is equal to the dynamic surface tension of each color ink in the surface life region of 100 to 3000 ms after landing, and the black ink dynamic in the surface life region after that point. The surface tension is larger than the dynamic surface tension of each color ink.
2) An ink cartridge containing the ink set according to 1) in a container.
3) An ink jet recording apparatus equipped with the ink cartridge described in 2).
4) An ink record printed using the ink set described in 1).

  According to the present invention, an ink set composed of black ink and color ink capable of reducing bleeding on not only plain paper but also paper with poor ink permeability, an ink cartridge containing the ink set in a container, An ink jet recording apparatus equipped with the ink cartridge and an ink recorded matter printed using the ink set can be provided.

FIG. 3 is a diagram illustrating an example of an ink cartridge. 1 is a diagram illustrating an example of an ink jet recording apparatus. FIG. 3 is a graph showing the relationship between the dynamic surface tension of ink used in Example 1 and the surface life. FIG. 6 is a graph showing the relationship between the dynamic surface tension of ink used in Example 4 and the surface life. FIG. 5 is a graph showing the relationship between the dynamic surface tension of ink used in Comparative Example 1 and the surface life. FIG. 6 is a diagram showing the relationship between the dynamic surface tension of ink used in Comparative Example 2 and the surface life. FIG. 10 is a diagram showing the relationship between the dynamic surface tension of ink used in Comparative Example 3 and the surface life. FIG. 6 is a diagram showing the relationship between the dynamic surface tension of ink used in Comparative Example 4 and the surface life. FIG. 10 is a graph showing the relationship between the dynamic surface tension of ink used in Comparative Example 5 and the surface life. FIG. 10 is a graph showing the relationship between the dynamic surface tension of ink used in Comparative Example 6 and the surface life. FIG. 10 is a graph showing the relationship between the dynamic surface tension of ink used in Comparative Example 7 and the surface life.

Hereinafter, the present invention will be described in detail.
In the present invention, the following requirements (1) and (2) are satisfied in an ink set composed of black ink and color inks such as cyan, magenta, and yellow. That is, the dynamic surface tensions of the black ink and the color ink are defined for a wide range of surface lifetime regions including a surface lifetime region that has not been mentioned heretofore.
(1) The dynamic surface tension of each color ink is greater than or equal to the dynamic surface tension of the black ink in a surface lifetime region of less than 100 ms after landing.
(2) There is a point where the dynamic surface tension of the black ink is equal to the dynamic surface tension of each color ink in the surface life region of 100 to 3000 ms after landing, and the black ink movement in the surface life region after that point. The surface tension is larger than the dynamic surface tension of each color ink.
By satisfying the above requirements, with regard to the dynamic surface tension of the black ink and each color ink, each color ink is more than the black ink in the surface life region (low life region) of less than 100 ms after landing, and the long life region ( On the contrary, the black ink is larger than each color ink at 3000 ms or more).
When the dynamic surface tension of the black ink and each color ink overlaps in the low life region as shown in FIG. 4 of Example 4 described later, the “equal point” in the above (2) In addition, it means that the dynamic surface tension of the black ink and each color ink branches.

Immediately after the ink has landed on the recording medium, the permeation speed of the ink into the recording medium is faster than the speed at which expansion wetting between the inks occurs, so it is considered that the permeation into the recording medium is dominant.
If the dynamic surface tension of each color ink is equal to or higher than the dynamic surface tension of the black ink at this surface life stage, the penetration speed of the black ink is equal to or higher than the penetration speed of each color ink. Then, since each color ink is pulled by the penetration of the black ink, it is possible to prevent the black ink from entering the color ink side.
However, since the penetration speed into the recording medium decreases with the passage of time (as the surface life becomes longer), the expansion work (expansion wetting) for inks of different hues gradually becomes dominant.
Therefore, at this surface life stage, the dynamic surface tension of the black ink is made larger than the dynamic surface tension of each color ink, so that the force that the black ink draws each color ink when the inks come into contact with each other becomes stronger. Further, it is possible to prevent the black ink from entering each color ink side.

Each ink constituting the ink set of the present invention contains water, a water-soluble organic solvent, a colorant, and a surfactant. Of particular importance is the surfactant. In addition, penetrants and other various additives (fixing agents, dispersants, stabilizers, antifoaming agents, pH adjusters, antiseptic / antifungal agents, rust preventives, antioxidants, etc.) are contained as necessary. You may let them.
<Surfactant>
The surfactant is used to lower the surface tension of the ink so as to easily penetrate into the recording medium, and to control the behavior of the dynamic surface tension of the black ink and the color ink.
The addition amount of the surfactant is preferably 0.5 to 5.0% by weight with respect to the total amount of the ink. If it is 0.5% by weight or more, sufficient permeability to the recording medium can be secured, and the image density does not decrease. Moreover, if it is 5.0 weight% or less, a viscosity will become high too much and it will not have a bad influence on discharge stability.

In the present invention, it is preferable to use the following two types of surfactants together, and it is particularly preferable to add both (a) and (b) to the color ink and only (a) to the black ink.
(A) Surfactant having a structure in which a hydrophilic group is bonded to the end of a hydrophobic chain (b) Oligomeric surfactant having a hydrophilic side chain bonded to a hydrophobic main chain (a) Examples thereof include those represented by structural formulas (I) and (II). Examples of (b) include those represented by the following structural formulas (III) and (IV).
The reason why the dynamic surface tension can be controlled by the combination of (a) and (b) is considered as follows.
(A) and (b) differ in the form of micelle formation in solution, (a) forms relatively small micelles, while (b) forms large micelles. Therefore, regardless of the molecular weight of the surfactant itself, (a) moves to the interface relatively quickly and contributes to the reduction of the surface tension in the low life region, whereas (b) has a long life because of the slow movement. This contributes to the reduction of the surface tension of the region.

式中、Ｒ^３、Ｒ^４は水素又は炭素数１〜１０のアルキル基、ｒ、ｓ、ｔ、ｕは１〜９の整数を表す。

式中、ｍは０〜１０の整数、ｎは０〜４０の整数を表す。

式中、Ｒ^１は炭素数１〜１０のアルキレン基、Ｒ^２は水素又は炭素数１〜５のアルキル基であり、ｍは０〜１０の整数、ｎは０〜４０の整数、ａ、ｂはともに１〜２０の整数を表す。

式中、Ｒ^５は水素原子又はメチル基、Ｒ^６は炭素数１〜１０の直鎖状又は分岐状アルキル基、Ｒ^７は炭素数１〜１０のハロゲン化アルキル基、Ｒ^８はポリエステル基、又はポリエーテル基、ｘ、ｙ、ｚはそれぞれ１〜２０の整数を表す。

^Wherein, R 3, ^{R 4} is hydrogen or an alkyl group having 1 to 10 carbon atoms, r, s, t, u is an integer of 1-9.

In the formula, m represents an integer of 0 to 10, and n represents an integer of 0 to 40.

In the formula, R ¹ is an alkylene group having 1 to 10 carbon atoms, R ² is hydrogen or an alkyl group having 1 to 5 carbon atoms, m is an integer of 0 to 10, n is an integer of 0 to 40, a, b Both represent an integer of 1-20.

In the formula, R ⁵ is a hydrogen atom or a methyl group, R ⁶ is a linear or branched alkyl group having 1 to 10 carbon atoms, R ⁷ is a halogenated alkyl group having 1 to 10 carbon atoms, R ⁸ is a polyester group, Or a polyether group, x, y, z represents the integer of 1-20, respectively.

<Water-soluble organic solvent>
The water-soluble organic solvent is used for improving ejection stability by providing a moisturizing effect.
The addition amount is preferably 30 to 40% by weight based on the total amount of ink. If the addition amount is within this range, ink thickening due to water evaporation in the ink jet recording apparatus is suppressed, and when ink lands on the recording medium, ink thickening due to water evaporation is suppressed and image bleeding is suppressed, resulting in a high quality recorded matter. Obtainable. If the amount added is more than 40% by weight, it may be necessary to reduce the amount of solids such as pigments and resins in order to make the ink have a desired viscosity. In this case, the image density of the recorded matter may be lowered. Further, the thickened ink clogging is less likely to occur in the ink jet recording apparatus, but on the other hand, the ink is less likely to thicken upon landing on the recording medium, and bleeding may occur.

Although it does not specifically limit as a water-soluble organic solvent, For example, the following are mentioned.
Ethylene glycol, diethylene glycol, 1,3-butyl glycol, 3-methyl-1,3-butyl glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerin, 1 Polyhydric alcohols such as 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, and petriol; ethylene glycol Monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene Polyhydric alcohol alkyl ethers such as recall monoethyl ether; Polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl- Nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; amides such as formamide, N-methylformamide, N, N-dimethylformamide; monoethanolamine, Amines such as diethanolamine and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol; propylene carbonate and ethylene carbonate. These water-soluble organic solvents can be used alone or in admixture of two or more.
Among these, inclusion of 1,3-butyl glycol, diethylene glycol, triethylene glycol and / or glycerin provides an excellent effect in preventing discharge failure due to moisture evaporation.

<Colorant>
The colorant is used for coloring the ink and improving the image density, and can be appropriately selected from known pigments and dyes according to the purpose, but the pigment is preferred.
The pigment content is preferably 0.1 to 50.0% by weight, more preferably 0.1 to 20.0% by weight, based on the total amount of ink.
The 50% average particle diameter (D50) of the pigment is preferably 150 nm or less, and more preferably 100 nm or less. Here, the value of “D50” is measured by a dynamic light scattering method using a Microtrac UPA manufactured by Nikkiso Co., Ltd. in an environment of 23 ° C. and 55% RH.
The pigment may be either an inorganic pigment or an organic pigment, and may be used alone or in combination of two or more.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, metal powder, and carbon black. Among these, carbon black is preferable, and examples thereof include those produced by known methods such as a contact method, a furnace method, and a thermal method.

Examples of organic pigments include azo pigments, azomethine pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable.
Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments.
Examples of polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, rhodamine B lake pigments, and the like. Can be mentioned.
Examples of dye chelates include basic dye chelates and acid dye chelates.

Examples of pigments for black ink include carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black, copper, iron (CI pigment black 11), and oxidation. Examples thereof include metals such as titanium, organic pigments such as aniline black (CI pigment black 1), and the like.
As the carbon black, carbon black produced by the furnace method and the channel method, the primary particle size is 15 to 40 nm, the specific surface area by the BET method is 50 to 300 m ² / g, the DBP oil absorption is 40 to 150 ml / 100 g, Those having a volatile content of 0.5 to 10% and a pH value of 2 to 9 are preferred.
Examples of commercially available carbon black include No. 2300, no. 900, MCF-88, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B (all manufactured by Mitsubishi Chemical Corporation); Raven700, 5750, 5250, 5000, 3500, 1255 (all manufactured by Columbia); Regal400R, 330R, 660R, Mulg L, Monarch700, 800, 880, 900, 1000, 1100, 1300, Monarch 1400 (all manufactured by Cabot Corporation); Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, 140V, Special Black 6, 5, 4A, and 4 (all manufactured by Degussa).

  Examples of commercially available color ink pigments include yellow inks such as C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 2, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 174, C.I. I. Pigment yellow 180, and the like.

  For magenta ink, for example, C.I. I. Pigment red 5, C.I. I. Pigment red 7, C.I. I. Pigment red 12, C.I. I. Pigment red 48 (Ca), C.I. I. Pigment red 48 (Mn), C.I. I. Pigment red 57 (Ca), C.I. I. Pigment red 57: 1, C.I. I. Pigment red 112, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 146, C.I. I. Pigment red 168, C.I. I. Pigment red 176, C.I. I. Pigment red 184, C.I. I. Pigment red 185, C.I. I. Pigment red 202, pigment violet 19, and the like.

For cyan ink, for example, C.I. I. Pigment blue 1, C.I. I. Pigment blue 2, C.I. I. Pigment blue 3, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15:34, C.I. I. Pigment blue 16, C.I. I. Pigment blue 22, C.I. I. Pigment blue 60, C.I. I. Pigment blue 63, C.I. I. Pigment blue 66; C.I. I. Bat Blue 4, C.I. I. Bat Blue 60 and the like.
In addition to the above-mentioned commercially available products, those newly produced for the present invention can also be used.
If Pigment Yellow 74 is used as the yellow pigment, Pigment Red 122, Pigment Bio Red 19 as the magenta pigment, and Pigment Blue 15: 3 as the cyan pigment, an ink having excellent color tone and light resistance and well-balanced can be obtained. .

As the dye, those having excellent water resistance and light resistance among dyes classified in the color index into acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes are used. These dyes may be used as a mixture of plural kinds, or may be used as a mixture with other colorants such as pigments as necessary. However, it is necessary to add other colorants as long as the effects of the present invention are not inhibited.
Specific examples of the dye include those shown in the following (a) to (d).

(A) Acid dyes and food dyes C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142
・ C. I. Acid Red 1,8,13,14,18,26,27,35,37,
42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115,
134,186,249,254,289
・ C. I. Acid Blue 9, 29, 45, 92, 249
・ C. I. Acid Black 1, 2, 7, 24, 26, 94
・ C. I. Food Yellow 3, 4
・ C. I. Food Red 7, 9, 14
・ C. I. Food Black 1, 2

(B) Direct dye, C.I. I. Direct yellow 1,12,24,26,33,44,50,86,
120, 132, 142, 144
・ C. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39,
80, 81, 83, 89, 225, 227
・ C. I. Direct orange 26, 29, 62, 102
・ C. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79,
86, 87, 90, 98, 163, 165, 199, 202
・ C. I. Direct black 19, 22, 32, 38, 51, 56, 71,
74, 75, 77, 154, 168, 171

(C) Basic dye, C.I. I. Basic yellow 1, 2, 11, 13, 14, 15, 19, 21,
23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51,
53, 63, 64, 65, 67, 70, 73, 77, 87, 91
・ C. I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23,
24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54,
59, 68, 69, 70, 73, 78, 82, 102, 104, 109, 112
・ C. I. Basic blue 1,3,5,7,9,21,22,26,35,
41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78,
89, 92, 93, 105, 117, 120, 122, 124, 129, 137,
141, 147, 155
・ C. I. Basic Black 2,8

(D) Reactive dyes, C.I. I. Reactive Black 3, 4, 7, 11, 12, 17
・ C. I. Reactive Yellow 1,5,11,13,14,20,21,22
25, 40, 47, 51, 55, 65, 67
・ C. I. Reactive Red 1,14,17,25,26,32,37,44,
46, 55, 60, 66, 74, 79, 96, 97
・ C. I. Reactive Blue 1, 2, 7, 14, 15, 23, 32, 35,
38, 41, 63, 80, 95

<Penetration agent>
The penetrant is used to reduce bleeding and improve image density by improving penetrability.
The addition amount is preferably 0.2 to 4.5% by weight with respect to the total amount of ink. If it is 0.2 weight or more, high permeability is obtained. Moreover, if it is 4.5 weight% or less, storage stability will not fall.
Preferred penetrants include 2,2,4-trimethyl-1,3-pentanediol and 2-ethyl-1,3-hexanediol.

Each ink constituting the ink set of the present invention can be accommodated in a container and used as an ink cartridge, and other members appropriately selected as necessary may be attached.
The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. For example, the container has an ink bag formed of an aluminum laminate film, a resin film, etc. Etc. are preferable.
FIG. 1 shows an example of the ink cartridge. This figure is a schematic view showing an ink cartridge 200 in which an ink bag 241 is accommodated in a cartridge case 244.
First, ink is filled into the ink bag 241 from the ink inlet 242, the air remaining in the ink bag 241 is exhausted, and then the ink inlet 242 is closed by fusion. In use, the needle of the apparatus main body is pierced into the ink discharge port 243 made of a rubber member and supplied to the apparatus. The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminate film. In general, the ink cartridge 200 is housed in a plastic cartridge case 244 and is detachably mounted as an ink cartridge 200 on various ink jet recording apparatuses.

FIG. 2 shows an example of the ink jet recording apparatus of the present invention. This recording apparatus forms an image by ejecting ink of four colors (black, cyan, magenta, yellow) onto a recording medium such as printing paper.
The ink jet recording apparatus 1 includes four ink jet heads 11 that eject ink of each color, a carriage 12 on which these heads are mounted, and a carriage 12 that moves in the main scanning direction (left and right in the figure) by a drive system (not shown). A guide rod 13 for guiding the printing paper and a paper transport mechanism 14 for transporting the printing paper P in the sub-scanning direction (vertical direction in the figure). The paper transport mechanism 14 includes a transport roller 15 that is rotated by a drive system (not shown), a tension roller 16, and a transport belt 17 that is stretched between them.
Each inkjet head 11 includes a piezoelectric actuator made of a piezoelectric element. Of course, another actuator for discharging ink, for example, a thermal actuator, a shape memory alloy actuator, or an electrostatic actuator may be provided.
Further, the ink jet recording apparatus 1 includes four ink cartridges 18 that store inks of the respective colors, four sub tanks 19 that are mounted on the carriage 12 and are connected to the ink jet heads 11, each ink cartridge 18, and each sub tank 19. Ink supply tubes (not shown) that communicate with each other are provided so that ink of each color accommodated in each ink cartridge 18 is supplied to each inkjet head 11 via each sub tank 19. That is, the liquid flow path of the ink jet printer 1 is configured by the ink supply tube, the sub tank 19, and the in-head flow path of the ink jet head 11. The ink supply tube is provided with a supply pump (not shown) for supplying the ink in the ink cartridge 18 to the sub tank 19.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples.

<Preparation of pigment dispersion 1>
(Preparation of polymer dispersion)
After sufficiently replacing the inside of the 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas introduction tube, reflux tube and dropping funnel with nitrogen gas, 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer (trade name: AS-6, manufactured by Toagosei Co., Ltd.) and 0.4 g of mercaptoethanol were charged, and the temperature was raised to 65 ° C.
Next, 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxyethyl methacrylate, styrene macromer (trade name: AS-6, manufactured by Toagosei Co., Ltd.) 36 A mixed solution of 0.0 g, mercaptoethanol 3.6 g, azobisdimethylvaleronitrile 2.4 g and methyl ethyl ketone 18 g was dropped into the flask over 2.5 hours.
After completion of dropping, a mixed solution of 0.8 g of azobisdimethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. Next, after aging at 65 ° C. for 1 hour, 0.8 g of azobisdimethylvaleronitrile was added, and further aging was performed for 1 hour.
After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution having a concentration of 50%.

(Preparation of carbon black pigment-containing polymer fine particle dispersion = pigment dispersion 1)
28 g of the polymer solution, 26 g of carbon black pigment (printex 35, manufactured by Degussa), 13.6 g of 1 mol / L potassium hydroxide solution, 20 g of methyl ethyl ketone, and 30 g of ion-exchanged water were sufficiently stirred, and then kneaded using a three-roll mill. did.
The obtained paste was put into 200 g of ion-exchanged water and stirred sufficiently, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a black pigment dispersion 1.

<Preparation of pigment dispersion 2>
A yellow polymer fine particle dispersion = pigment dispersion 2 was obtained in the same manner as pigment dispersion 1 except that the carbon black pigment of pigment dispersion 1 was changed to pigment yellow 74.

<Preparation of pigment dispersion 3>
Magenta polymer fine particle dispersion = pigment dispersion 3 was obtained in the same manner as pigment dispersion 1 except that the carbon black pigment of pigment dispersion 1 was changed to pigment red 122.

<Preparation of pigment dispersion 4>
A cyan polymer fine particle dispersion = pigment dispersion 4 was obtained in the same manner as pigment dispersion 1, except that the carbon black pigment of pigment dispersion 1 was changed to pigment blue 15: 3.

<Preparation of pigment dispersion 5>
After premixing the following mixture, it was circulated and dispersed in a disk type bead mill (KDL type, manufactured by Shinmaru Enterprises, media: zirconia balls having a diameter of 0.3 mm) to obtain a black pigment dispersion 5 .
・ Carbon black pigment (Cabot, Regal 400R) 15% by weight
・ Dispersant: 3% by weight
・ Pure water: remaining amount

<Preparation of pigment dispersion 6>
A yellow pigment dispersion 6 was obtained in the same manner as the pigment dispersion 5 except that the carbon black pigment of the pigment dispersion 5 was changed to pigment yellow 74.

<Preparation of pigment dispersion 7>
A magenta pigment dispersion 7 was obtained in the same manner as the pigment dispersion 5 except that the carbon black pigment of the pigment dispersion 5 was changed to pigment red 122.

<Preparation of pigment dispersion 8>
A cyan pigment dispersion 8 was obtained in the same manner as the pigment dispersion 5 except that the carbon black pigment of the pigment dispersion 5 was changed to pigment blue 15: 3.

Using the pigment dispersions 1 to 8, inks of Production Examples 1 to 26 were prepared according to the formulations shown in Tables 1 to 4. In the table, “Bk” indicates black, “Y” indicates yellow, “M” indicates magenta, and “C” indicates cyan.
After preparing materials in the order of water-soluble organic solvent → surfactant → penetrant → ion exchange water and stirring for 30 minutes, the above pigment dispersions 1 to 8 were added and stirred for 1 hour. The ink was obtained by filtration through an 8 μm membrane filter.
The numbers in the table are “% by weight”, and the surfactants are as follows.
・ Surfactant A
In the structural formula (I), R ³ and R ⁴ are n-butyl groups, r = 5, s = 4. Surfactant B
In the structural formula (I), R ³ is an n-nonyl group, R ⁴ is hydrogen, t = 2, u = 7. Surfactant C
In structural formula (II), m = 3, n = 13. Surfactant D
In structural formula (III), m = 10, n = 4, R ¹ = CH ₂ , R ² = H, a = 6, b = 2. Surfactant E
In Structural Formula (IV), R ⁵ is CH ₃ , R ⁶ is an n-heptyl group, R ⁷ is a perfluoroalkyl group having 3 carbon atoms, R ⁸ is a polyethylene oxide group having 12 carbon atoms, x = 15, y = 6, z = 6

Examples 1-7, Comparative Examples 1-7
The above inks were combined as shown in Tables 5 to 12 to prepare ink sets of Examples and Comparative Examples. “Bk” in the table stands for black.
3 to 11 show the relationship between the dynamic surface tension and the surface life of the ink used in the examples and comparative examples. The dynamic surface tension is a value measured by a maximum bubble pressure method using a dynamic surface tension meter SITA DynaTester (manufactured by SITA Messtechnik). The correspondence between the examples and comparative examples and the respective drawings is as follows.
Fig. 3 = Example 1, Fig. 4 = Example 4, Fig. 5 = Comparative Example 1, Fig. 6 = Comparative Example 2, Fig. 7 = Comparative Example 3, Fig. 8 = Comparative Example 4, Fig. 9 = Comparative Example 5, Fig. 10 = Comparative Example 6, FIG. 11 = Comparative Example 7
As can be seen from the results in Tables 5 to 8, Examples 2, 3, 5, 6, and 7 are almost the same as Example 1, and thus the illustration is omitted. As can be seen from the results in Tables 9 to 11, since the three color inks have almost the same value, FIGS. 3 to 10 show only the yellow ink. As can be seen from the results in Table 7, since magenta ink and cyan ink have almost the same value, only magenta ink is shown in FIG. 4 to 6 is a portion where the lines of black ink and yellow ink overlap.
As can be seen from FIGS. 3 and 4, the ink set of the example satisfies the requirements (1) and (2) defined in the present invention.
On the other hand, the ink sets of Comparative Examples 1 to 7 do not satisfy the requirements in the following points.
Comparative Example 1 = FIG. 5: Both dynamic surface tensions are equal in a long life region.
Comparative Example 2 = FIG. 6: The dynamic surface tension of the color ink is higher in the long life region.
Comparative Example 3 = FIG. 7: The dynamic surface tension of the color ink is larger over the entire region.
Comparative Example 4 = FIG. 8: The dynamic surface tension of the black ink is larger over the entire region.
Comparative Example 5 = FIG. 9: The dynamic surface tension of the black ink is larger over the entire region.
Comparative Example 6 = FIG. 10: The dynamic surface tension of the color ink is larger over the entire region.
Comparative Example 7 = FIG. 11: One type of color ink meets the requirements, but the others do not.

<Color bleed evaluation>
The ink sets of Examples and Comparative Examples were filled in IPSiO GX5000 manufactured by Ricoh, and images were printed using MyPaper as plain paper and Ricoh Business Coat Gloss 100 as coated paper, and black ink and color of the obtained image The bleed at the boundary portion of the ink was visually evaluated according to the following criteria. The results are shown in Tables 5 to 12.
[Evaluation criteria]
(Double-circle): It is a high-definition image with no blur at the boundary part or hardly noticeable.
○: Slight blur is seen at the boundary, but the image has no problem.
(Triangle | delta): A clear blur is seen in the boundary part and it is an image with inferior quality.
X: Extremely blurred at the boundary and very poor quality image.

  As can be seen from the results in Tables 5 to 12, in the examples, the bleed characteristics are excellent regardless of factors such as the combination of surfactants, the type of dispersion, and the amount of penetrant added. In all the examples, the bleed characteristics include those having Δ or less.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 11 Inkjet head 12 Carriage equipped with inkjet head 11 13 Guide rod 14 Paper transport mechanism 15 Transport roller 16 Tension roller 17 Transport belt 18 Ink cartridge 19 Subtank 200 Ink cartridge 241 Ink bag 242 Ink inlet 243 Ink outlet 244 Cartridge case P Printing paper

JP 2006-063322 A

Claims (4)

A set of a plurality of water-based inks containing water, a water-soluble organic solvent, a colorant, and a surfactant, comprising at least a black ink and cyan, magenta, and yellow color inks. An ink set characterized by satisfying the requirements of
(1) The dynamic surface tension of each color ink is greater than or equal to the dynamic surface tension of the black ink in a surface lifetime region of less than 100 ms after landing.
(2) There is a point where the dynamic surface tension of the black ink is equal to the dynamic surface tension of each color ink in the surface life region of 100 to 3000 ms after landing, and the black ink movement in the surface life region after that point. The surface tension is larger than the dynamic surface tension of each color ink.   An ink cartridge containing the ink set according to claim 1 in a container.   An ink jet recording apparatus equipped with the ink cartridge according to claim 2.   An ink record printed using the ink set according to claim 1.

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