JP2008260920A - Method for manufacturing inkjet pigment dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pigment dispersion high in image density, and excellent in ejection stability and liquid stability; dispersion of the pigment; and a technique associated with ink jet ink using it. <P>SOLUTION: The pigment dispersion comprises at least carbon black, a dispersant and water, wherein the carbon black is channel black and/or gas black. A method for manufacturing the inkjet pigment dispersion comprises bead mill dispersion, wherein the diameter of a bead is 0.05 mm ϕ or smaller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing an inkjet pigment dispersion, a pigment dispersion obtained by the production method, and an inkjet ink using the pigment dispersion, and is excellent in storage stability of the pigment dispersion, and further to The present invention relates to an ink jet ink excellent in ejection stability of ink liquid used and ink liquid storage stability. More specifically, the present invention relates to a black ink for ink jet which is improved in clogging of an ink jet head, provides a high image density, and has excellent ink liquid storage stability.

The inkjet recording method is easy to make full color because the process is simpler than other recording methods, and there is an advantage that a high-resolution image can be obtained even with an apparatus having a simple configuration.
As ink-jet inks, dye-based inks in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent are used. Dye-based inks have excellent color tone, but are resistant to light. There was a disadvantage that was inferior in nature. On the other hand, pigment-based inks in which carbon black and various organic pigments are dispersed are actively studied because they are superior in light resistance compared to dye-based inks.
However, pigment-based inks tend to clog nozzles more easily than dye-based inks.
The pigment ink is generally prepared by preparing a dispersion in which a coloring material and a dispersant are pre-dispersed in an aqueous solvent such as water or alcohol, and then using a media-type disperser such as a sand mill. The dispersion is adjusted by performing a dispersion step and then diluting to a predetermined concentration.

  In a pigment-based water-based ink, a surfactant or a water-soluble resin is generally used to disperse a hydrophobic pigment, but the reliability of an obtained image is extremely poor. Thus, a technique for adding film-forming resin fine particles to the ink liquid for the purpose of improving the image quality is disclosed, but it is difficult to disperse a plurality of components finely and stably over a long period of time, and these fine particles are stably dispersed. If a large amount of a dispersing agent such as a surfactant is used for this purpose, problems such as generation of bubbles in the ink tank and the head and deterioration of the image quality may occur. In addition, for the purpose of improving the dispersibility, methods of changing the pigment surface to hydrophilic groups and using resins containing hydrophilic groups are being studied. There is a problem that dispersion becomes unstable and storage stability deteriorates.

  In order to stabilize the dispersion, a method of dispersing a water-dispersible resin having a carboxyl group and a nonionic hydrophilic group in the molecule in water (Japanese Patent Laid-Open No. 5-239392 ... Patent Document 1), water-soluble polymer and surface activity A method of making the same polarity or adding nonions (Japanese Patent Laid-Open No. 8-283633 ... Patent Document 2), a method of making the polarities of the hydrophilic groups of the colored ionic polyester resin and the coloring agent the same in the aqueous recording liquid ( Japanese Patent Laid-Open No. 2000-63727 (Patent Document 3) and a method of making the dispersion polarity of the pigment and the resin fine particles the same (Japanese Patent Laid-Open No. 2001-81366: Patent Document 4) are disclosed.

  Also, pigment particles having a particle size distribution in which at least 70% of the particles in the dispersion have a diameter of less than 0.1 μm and the other particles in the dispersion have a diameter equal to or less than 0.1 μm. A water-based inkjet ink composition containing a pigment dispersion containing aldehyde naphthalene sulfonate dispersant and / or at least one sulfone solvent (Japanese Patent Application Laid-Open No. 08-333531 ... Patent Document 5), and Japanese Patent Application Laid-Open No. 56-147871 The publication (Patent Document 6) discloses a recording liquid comprising an aqueous medium containing a pigment, a polymer dispersant, and a nonionic surfactant. In addition, US Pat. No. 5,085,698 (Patent Document 7) and US Pat. No. 5,221,334 (Patent Document 8) disclose the use of AB or BAB block copolymer as a pigment dispersant. Furthermore, US Pat. No. 5,172,133 (Patent Document 9) discloses the use of a specific pigment, a water-soluble resin, and a solvent.

On the other hand, as a pigment dispersion method that does not use a dispersant, a method of introducing a substituent containing a water-solubilizing group into carbon black is disclosed in US Pat. No. 5,571,311 (Patent Document 10). JP-A-8-81646 (Patent Document 11) discloses a method for polymerizing the carbon black, and JP-A-8-3498 (Patent Document 12) discloses a method for oxidizing carbon black. Also, a method for ensuring water resistance and ejection stability with an ink containing carbon black subjected to oxidation treatment and a terpolymer composed of acrylic acid, styrene, and α-methylstyrene is disclosed in JP-A-9-194775 (Patent Document). 13).
Also disclosed is an ink jet recording liquid (Japanese Patent Laid-Open No. 2000-144028, Patent Document 14), wherein the volume average particle diameter of dispersed particles in the ink jet recording liquid is 30 to 200 nm.
However, although the above-described conventional ink liquid can obtain a high image density with respect to the color pigment ink, the black pigment ink is not yet satisfactory and is not satisfactory.

In addition, an example is disclosed in which beads having a diameter of about 0.05 mm to 1.0 mm are used for bead mill dispersion (Japanese Patent Laid-Open No. 2005-281691, Japanese Patent Laid-Open No. 2005-314528). ... Patent Document 16, Japanese Patent Application Laid-Open No. 2006-188626 ... Patent Document 17) are not sufficient in terms of dispersion stability.
In addition, in Japanese Patent No. 3625595 (Patent Document 18), an anionic surfactant is used as the dispersant, and the molecular weight is preferably in the range of 1000 ≦ m ≦ 30000. This is not sufficient, and pigment types that are weak against strong impacts during dispersion lack stability after dispersion, causing problems such as ejection stability with ink liquid.

JP-A-5-239392 JP-A-8-283633 JP 2000-63727 A JP 2001-81366 A JP-A-08-333531 Japanese Patent Laid-Open No. 56-147871 US Pat. No. 5,085,698 US Pat. No. 5,221,334 US Pat. No. 5,172,133 US Pat. No. 5,571,311 JP-A-8-81646 JP-A-8-3498 JP-A-9-194775 JP 2000-144028 A Japanese Patent Application Laid-Open No. 2005-281691 JP 2005-314528 A JP 2006-188626 A Japanese Patent No. 3625595

  The present invention has been made in view of the circumstances as described above, and has a high image density, a pigment dispersion excellent in ejection stability and liquid stability, and a technology related to the pigment dispersion and an inkjet ink using the pigment dispersion. The purpose is to provide.

  As a result of intensive studies, the present inventors have determined that the dispersion manufacturing method in the carbon black manufacturing method is bead mill dispersion, the bead diameter is 0.05 mm or less, and the production primary particle diameter and the range of the BET surface area. It has been found that the above-mentioned problems can be solved by specifying the range of the degree of naphthalenesulfonic acid condensation of the naphthalenesulfonic acid formalin condensate as a dispersant.

That is, the said subject is solved by (1)-(18) of this invention.
(1) “At least carbon black, a dispersant, and water, wherein the carbon black is channel black and / or gas black, the manufacturing method is bead mill dispersion, and the bead diameter is 0.05 mmφ or less. Manufacturing method of inkjet pigment dispersion "
(2) "The method for producing an inkjet pigment dispersion according to (1) above, wherein the dispersant is sodium naphthalene sulfonate formalin condensate",
(3) “The total content of the dimer, trimer, and tetramer of naphthalenesulfonic acid of the sodium naphthalenesulfonate formalin condensate of the dispersant is 20% to 80%,” “Method for producing inkjet pigment dispersion according to item (2)”,
(4) The pigment dispersion for inkjet according to any one of (1) to (3) above, wherein the carbon black has a BET specific surface area of 100 m ² / g to 400 m ² / g. Liquid manufacturing method ",
(5) "The method for producing an inkjet pigment dispersion according to any one of (1) to (4) above, wherein an average primary particle diameter of the carbon black is 10 nm to 30 nm" ,
(6) “The carbon black has an average particle size (D50) of 70 to 180 nm in the pigment dispersion, and a particle size standard deviation of particle size distribution is ½ or less of the average particle size. The method for producing a pigment dispersion according to any one of (1) to (5) ",
(7) “The dispersant according to any one of (1) to (6) is included in a ratio of 0.1 to 2 with respect to the carbon black 1 on a weight basis. Method for producing inkjet pigment dispersion ",
(8) The method for producing a pigment dispersion for inkjet according to any one of (1) to (7) above, wherein the content of carbon black is 5 to 50% by weight "
(9) "Inkjet pigment dispersion characterized by being produced by the method according to any one of (1) to (8)",
(10) “Inkjet ink characterized by using the inkjet pigment dispersion according to (9)”,
(11) “Ink jet ink, wherein the carbon black content of the ink jet ink according to item (10) is 1 wt% to 20 wt%”;
(12) "Ink cartridge characterized by containing the ink-jet ink according to item (10) or (11)",
(13) “Inkjet printing apparatus, wherein recording is performed by ejecting the inkjet ink according to (10) or (11) onto an image support”,
(14) "Inkjet printing apparatus, wherein the inkjet printing apparatus according to (13) is a piezo system",
(15) "The inkjet printing apparatus according to (14), wherein the inkjet printing apparatus is a thermal system",
(16) "Image forming method characterized in that printing is performed with an inkjet printing apparatus using the inkjet ink according to (10) or (11)",
(17) "Image formed product printed with an inkjet printing apparatus using the inkjet ink according to (10) or (11)",
(18) “Image formation product, wherein the image support of the image formation product according to item (17) is paper”.

  The inkjet ink using the pigment dispersion of the present invention has a high image density, and is superior to conventional ones in ejection stability and ink liquid storage stability.

Hereinafter, the present invention will be described in more detail.
The present invention comprises at least carbon black, a dispersant, and water, wherein the carbon black is channel black and / or gas black, the manufacturing method is bead mill dispersion, and the bead diameter is 0.05 mmφ or less. This is a method for producing an inkjet pigment dispersion.

The beads used in the present invention are usually ceramic beads, and generally zirconia balls are used. The bead diameter is preferably 0.05 mmφ or less, and more preferably 0.03 mmφ or less.
Method for producing carbon black is a gas black method, an average primary particle size of the carbon resulting black is 10.0Nm～30.0Nm, BET surface area is 100m ² / g~400m ² / g.
The average primary particle diameter of preferably carbon black in 15.0nm~20.0nm, BET surface area is 150m ² / g~300m ² / g.
Since the carbon black of the present invention has a small average primary particle size and high structure, it is vulnerable to impact during dispersion, and if the bead diameter exceeds 0.05 mm, the collision energy between the beads is strong and the structure is destroyed. And the resulting stability of the carbon black dispersion is impaired.
Therefore, the bead diameter is preferably 0.05 mm or less.

In the pigment dispersion of the present invention, it is preferable that the dispersant is contained in a ratio of 0.1 to 2 with respect to the carbon black 1 on a weight basis. More preferably, the ratio is 0.25 to 1 with respect to carbon black 1. By adopting such a use amount of the dispersant, the average particle size (D50) of the carbon black of the dispersion of the present invention is 70 nm or more and 180 nm or less, and the particle size standard deviation in the carbon black particle size distribution is the average particle size. The pigment dispersion can be provided with a high image density, ejection stability, and liquid stability.
The gas black that can be suitably used in the present invention is generally a type of carbon. As will be understood from the results of Examples and Comparative Examples described later, the structure is small and has a larger structure than Furnace Black, and is particularly suitable for inkjet in terms of image density. In particular, ink stability, reliability, etc. In view of the above, the primary particle size, the BET specific surface area, and the like are considered important, and the dispersion method is considered to be suitable for fine bead dispersion in carbon in this range. Furthermore, the dispersant described in the above item (2) was optimum in view of the compatibility with the carbon black of the present invention, and at least as far as possible with respect to various dispersants.
In addition, it is difficult to achieve the above effect when the amount of the dispersant used is less than 0.1, and the storage stability of the pigment dispersion and the ink is inferior, and as a result, nozzles tend to clog. If it is greater than 2, the viscosity of the pigment dispersion and the ink tends to be too high, and printing by the ink jet method tends to be difficult.

In the present invention, when the total content of dimer, trimer and tetramer of naphthalene sulfonic acid sodium formalin condensate as a dispersant is less than 20%, the dispersibility is deteriorated and the pigment dispersion and Ink storage stability is poor, and as a result, nozzle clogging tends to occur.
On the other hand, when the content of naphthalenesulfonic acid dimer to tetramer exceeds 80%, the viscosity becomes high and dispersion becomes difficult.

  In the pigment dispersion of the present invention, the pigment concentration is preferably 5% by weight or more and 50% by weight or less based on the total amount of the dispersion. If it is less than 5% by weight, the productivity is inferior, and if it is more than 50% by weight, the viscosity of the pigment dispersion tends to be too high and dispersion tends to be difficult.

  Moreover, various additives other than water can be mix | blended with the pigment dispersion liquid of this invention. For example, as a water-soluble organic medium, alcohols such as methanol, ethanol, 1-propanol and 2-propanol, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and glycerin, N-methylpyrrolidone, 2-pyrrolidone and the like Pyrrolidone derivatives, ketones such as acetone and methyl ethyl ketone, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and nonionic, anionic, cationic and amphoteric surfactants and preservatives.

The carbon black dispersion of the present invention can be obtained by dispersing the carbon black, a dispersant, water, and various additives as necessary with a known disperser such as a sand mill, a ball mill, a roll mill, a bead mill or the like.
At this time, it is preferable that the amount of the dispersing agent is 0.1 to 2 with respect to the pigment 1 on the weight basis as described above, and wet dispersion treatment is employed. The wet dispersion treatment referred to in the present invention is a pulverization / dispersion of a mixture of a pigment, a dispersant, water and, if necessary, a water-soluble organic solvent by a so-called wet dispersion method using the sand mill, ball mill, roll mill, bead mill, etc. It is a process to do.
Also, by pre-processing coarse particles with a homogenizer or the like in the pre-process of the disperser, the particle size distribution can be made sharper, leading to improvements in image density, ejection stability, and the like.

The pigment dispersion of the present invention thus obtained can be suitably used particularly as a pigment-based inkjet ink.
The pigment-based ink-jet ink is a known method, for example, the pigment dispersion of the present invention, water, a water-soluble organic solvent, a surfactant and the like are stirred and mixed, and coarse particles are filtered with a filter, a centrifugal separator or the like. And obtained by degassing. The concentration of carbon black in the ink is preferably 1% by weight or more and 20% by weight or less based on the total amount. If the amount is less than 1% by weight, the image density is low, so that the printing is not clear. If the amount is more than 20% by weight, not only the viscosity of the ink tends to increase but also nozzle clogging tends to occur. Further, the ink can be blended with a material equivalent to the material described as the additive to the pigment dispersion as required.
For example, the content of the water-soluble organic solvent is 0% by weight to 50% by weight, preferably 5% by weight to 40% by weight, and more preferably 10% by weight to 35% by weight with respect to the total amount of the ink.

The pigment-based inkjet ink of the present invention thus obtained can be suitably used for an ink cartridge that accommodates it. The pigment-based ink-jet ink of the present invention can be image-formed by an ink-jet printing apparatus that forms an image by ejecting the ink-jet ink onto an image support such as paper and performing recording (printing).
Examples of the printing method include a continuous jet type and an on-demand type. Examples of the on-demand type include a piezo method, a thermal method, and an electrostatic method.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, this invention is not limited to these examples. In addition, the part in an Example is a basis of weight.

Example 1
・ Prescription 1
Carbon black NIPEX160-IQ (manufactured by degussa: gas black) 150 parts Naphthalene sulfonate sodium formalin condensate 38 parts (Pionin A-45-PN Takemoto Yushi Co., Ltd.)
(Total content of naphthalenesulfonic acid dimer, trimer and tetramer: 49%)
812 parts of distilled water After premixing the above mixture, a peripheral speed of 10 m / s with 0.05 mm zirconia beads (density 6.03 × 10 ⁻⁶ g / m ² ) using a bead mill disperser (UAM-015 manufactured by Kotobuki Industries Co., Ltd.) After dispersion at a liquid temperature of 32 ° C. for 12 minutes, coarse particles were centrifuged with a centrifuge (Model 3600 manufactured by Kubota Corporation) to obtain an average particle size of 121.4 nm and a standard deviation of 48. A dispersion (A) of 3 nm in Table 1 was obtained.

(Examples 2, 3, and 4)
Pigment dispersion (B) in the same manner except that the carbon black of Example 1 was changed to NIPEX150, (degussa: gas black), COLOR BLACK S170, color Black FW18 (degussa: channel black). , (C), (D) were obtained.

(Examples 5 and 6)
Similarly to Table 1, except that the total content of the naphthalenesulfonic acid dimer, trimer and tetramer of Example 1 was changed, the zirconia bead diameter was 0.03 mm, and the dispersion time was 8 minutes. Pigment dispersions (E) and (F) were obtained.

(Example 7)
A pigment dispersion (G) shown in Table 1 was obtained in the same manner except that the zirconia bead diameter of Example 1 was 0.03 mm and the dispersion time was 5 minutes.

(Comparative Examples 1, 2, 3)
Each of the pigment dispersions in Table 1 was prepared in the same manner as in Example 1 except that the carbon black of Example 1 was printed in order, Printex 95, Printex 85, Printex 75 (manufactured by Degussa: Furnace Black), and the zirconia bead diameter was 0.1 mm. Liquids (H), (I), and (J) were obtained.

(Comparative Examples 4 and 5)
The pigment dispersions (K) and (L) in Table 1 were similarly prepared except that the carbon black of Example 1 was sequentially changed to # 850 and # 44 (manufactured by Mitsubishi Chemical Corporation: furnace black) and the zirconia bead diameter was 0.3 mm. )

Using the pigment dispersion liquids (A) to (L) obtained by the above method, an ink liquid was prepared according to the following ink formulation 1, and after stirring for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm and vacuum degassed. Ink liquids of Examples and Comparative Examples (a) to (l) were obtained.
・ Ink formula 1
Pigment dispersion (pigment concentration 15%) 100.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-ethyl-1,3-hexanediol 3.0 parts 2-pyrrolidone 3.0 parts Polyoxyethylene (3) Alkyl (C13) ether sodium acetate 0.45 parts Distilled water 13.55 parts The average particle diameter of the pigment contained in the ink liquids (a) to (l) was measured. Further, printing was performed on a PPC paper 4024 manufactured by Xerox Co., Ltd. using an inkjet printer MJ-930C manufactured by EPSON, and the ejection stability and the printed image were measured with an Xrite densitometer. The ink liquid storage stability was also evaluated by the following test method. The results are shown in Table 1.
In Table 1, the BET specific surface area and the average primary particle diameter of carbon black are manufacturer guaranteed values (catalog values). The average particle diameter (D50) and standard deviation value measurement method of the dispersion and ink are as follows.
[Dispersion, ink liquid particle size measurement conditions]
Measuring instrument: Nikkiso Co., Ltd. particle size distribution meter UPA150
Measurement conditions 1) Solid concentration of measurement solution: 0.1 wt% aqueous solvent 2) Transparent Particles: Yes
3) Spherical Particles: No
4) Part. Refractive Index: 1.86
5) Part. Density: 1.86 (gm / cm ³ )
6) Fluid: Default Fluid
7) Fluid Refractive Index: 1.33
8) Viscosity High 30 ° C: 0.797 cp
9) Viscosity Low 20 ° C .: 1.002 cp
10) Display format: Volume distribution Table 1 describes the average particle diameter (D50) and standard deviation (sd) obtained as a result of measurement under the above conditions.

<Naphthalenesulfonic acid condensate HPLC analysis>
Equipment: LC-10vp (Shimadzu Corporation)
Column: ZORBAX BP-ODS (4.6id. × 150mm) GL Science)
Guard column: ZORBAX BP-ODS (4.0id. × 10mm) GL Science)
Detector: UV (237nm)
Mobile phase: CH ₃ CN / 0.005M PIC aqueous solution = 25/75
Flow rate: 1 mL / min
Sample adjustment: 200ppm soln
Injection volume: 20 μL
<Image density>
The image density is measured with an Xrite densitometer for color measurement of a solid image of an image sample.
<Discharge stability>
As for ejection stability, after printing a printed matter, the printer was left in a 40 ° C. environment for one month with the printer head capped. Whether or not the discharge state of the printer after being left restored to the initial discharge state was evaluated by the following number of cleaning operations.
○: Recovered by one operation.
Δ: Recovered by 2 to 3 operations.
X: No recovery was observed even after three or more operations.
<Ink storage stability>
Each ink was put in a polyethylene container, sealed, stored at 70 ° C. for 3 weeks, and then the particle size, surface tension, and viscosity were measured and evaluated according to the rate of change from the initial physical properties as follows.
A: Change rate is less than 5% in all items of particle size, surface tension, and viscosity.
○: Change rate is less than 10% in all items of particle size, surface tension, and viscosity.
Δ: Change rate is less than 30% in all items of particle size, surface tension, and viscosity.
X: The rate of change is 30% or more in at least one of the particle size, surface tension, and viscosity.

Claims (18)

  An inkjet pigment comprising at least carbon black, a dispersant, and water, wherein the carbon black is channel black and / or gas black, the production method is bead mill dispersion, and the bead diameter is 0.05 mmφ or less. A method for producing a dispersion.   The method for producing an inkjet pigment dispersion according to claim 1, wherein the dispersant is sodium naphthalene sulfonate formalin condensate.   The total content of dimers, trimers and tetramers of naphthalene sulfonic acid in the sodium naphthalene sulfonate formalin condensate of the dispersant is 20% to 80%. A method for producing a pigment dispersion for inkjet. The method for producing an inkjet pigment dispersion according to claim 1, wherein the carbon black has a BET specific surface area of 100 m ² / g to 400 m ² / g.   The method for producing an inkjet pigment dispersion according to any one of claims 1 to 4, wherein the carbon black has an average primary particle size of 10 nm to 30 nm.   The carbon black has an average particle size (D50) of 70 nm to 180 nm in a pigment dispersion, and a particle size standard deviation of particle size distribution is ½ or less of the average particle size. A method for producing a pigment dispersion according to any one of the above.   A method for producing an inkjet pigment dispersion, wherein the dispersant according to any one of claims 1 to 6 is contained in a ratio of 0.1 to 2 with respect to the carbon black 1 on a weight basis.   The method for producing an inkjet pigment dispersion according to any one of claims 1 to 7, wherein the carbon black content is 5 to 50 wt%.   An inkjet pigment dispersion produced by the method according to claim 1.   An ink-jet ink comprising the ink-jet pigment dispersion according to claim 9.   The ink-jet ink according to claim 10, wherein the carbon black content of the ink-jet ink according to claim 10 is 1 wt% to 20 wt%.   An ink cartridge containing the ink-jet ink according to claim 10.   An ink jet printing apparatus that performs recording by ejecting the ink for ink jet according to claim 10 or 11 onto an image support.   The inkjet printing apparatus according to claim 13 is a piezo type.   The inkjet printing apparatus according to claim 14 is a thermal type.   12. An image forming method, wherein printing is performed by an ink jet printing apparatus using the ink jet ink according to claim 10.   An image formed article printed by an inkjet printing apparatus using the inkjet ink according to claim 10.   An image formed article according to claim 17, wherein the image support of the image formed article is paper.