JP2009191222A - Oil-based white dispersion for inkjet recording, method for producing it, and oil-based white ink composition for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil-based white dispersion, which causes no clogging in an inkjet head or no hinderance of ink repellent properties on a discharge nozzle face for allowing stable discharge and prevents sedimentation of pigment and change in viscosity of a solution or a grain size of the pigment for exhibiting long-term storage stability, for inkjet recording. <P>SOLUTION: The oil-based white dispersion for inkjet recording contains 5-60 mass% of white pigment produced by further covering titanium oxide fine particles, which are covered with aluminum oxide and/or silicon oxide and provided with an average primary grain size of 0.15-0.25 μm, with SiH-containing polysiloxane and/or dimethylpolysiloxane at a ratio of 0.01-2.5 mass%, 0.03-5 pts.mass of a straight/branched chain type polyester dispersant having a basic group in the molecule for 1 pts.mass of the white pigment, and glycol ether dialkyl ethers as a solvent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil-based white dispersion for ink jet recording excellent in storage stability and stability over time, a method for producing the same, and an ink composition obtained using the dispersion, the ink ejection surface of an ink jet recording head The present invention relates to an oil-based white ink composition for ink-jet recording, which is excellent in ink repellency and dischargeability, and has excellent concealability with respect to the background of printed matter.

  Conventionally, an ink jet recording method is a recording method in which ink droplets are ejected from a print head or spray nozzle toward a recording material at a high speed in accordance with an electric signal from a computer or the like, and printed on an ink receiving layer of the recording material. It is. This ink jet recording system has been widely used for copying, facsimiles, posters, displays and the like because it has low noise and can be printed at high speed. Ink used in the ink jet recording system does not change with time, can maintain a sufficient density stably for a long time when an image is formed, and the image printed on the recording material has excellent original reproducibility. It is requested. For this reason, it is required that the ink used does not clog the nozzles of the head and the filtration filter that passes from the ink cartridge until it reaches the head. For this purpose, the density, viscosity, particle size, concentration, etc. It is necessary to adjust the ink characteristics.

  The ink is generally prepared by blending a colorant that is a dye or a pigment, a dispersant for dispersing them, a solvent, and, if necessary, an additive. In particular, white ink for ink jet prints with good visibility can be obtained by printing on a black or transparent recording material with low brightness, and is also effective for marking various products. Furthermore, when printing on the recording material with a colored ink other than white ink, printing cannot be reproduced clearly due to the influence of the color of the base. For this reason, after printing, it is required to perform background printing with a white ink having a sufficient concealing property for the background to conceal the empty background, and to print on the white background with other colored ink.

  This white ink generally uses a titanium oxide pigment as a colorant, but the white ink using a conventional titanium oxide pigment is caused by the specific gravity of the pigment particles and the solvent used during storage. When an alcohol solvent is used, the titanium oxide pigment may settle and aggregate over time, and the redispersibility of the titanium oxide pigment may be reduced. In addition, when the titanium oxide pigment is used as a white pigment, it has a property that the aggregation and precipitation of the ink pigment is likely to proceed during storage of the ink. When it is not used, the ejection stability at the time of reuse is lacking, and the printer nozzle is clogged, and in the worst case, the printer head may be forced to be replaced.

  In order to solve such a problem, an alumina-treated titanium oxide pigment that has been dispersed in an alcohol solvent using an acrylic resin having a carboxyl group as a dispersant has been proposed (Patent Document 1). This white pigment composition is intended to improve the redispersibility of the precipitated white pigment, and is used as it is without redispersing the precipitated pigment in actual work (inkjet printing work). It is unsuitable for what it can do. Patent Documents 2 to 5 propose various titanium oxide dispersions, all of which are limited to water-based inks. When dispersed in water, they are stable but dispersed in an organic solvent. In many cases, the ink becomes unstable, and when used as an inkjet ink, precipitation occurs in the ink or nozzle clogging occurs. For this reason, even when an organic solvent is specified, the ink-jet printer has high concealability with respect to the background of the printed matter, and has excellent temporal stability in which the pigment does not settle or the viscosity of the liquid or the particle size of the pigment does not change. There is an urgent need to develop an oil-based white ink composition for recording.

  Further, in an ink jet recording head, it is important that an ink ejection surface on which an ejection port of a nozzle that ejects ink droplets is formed has ink repellency. As a recording head used in an ink jet recording apparatus, there is known a recording head which causes pressure fluctuation in a pressure chamber communicating with a nozzle opening by the action of a pressure generating element, and ejects ink droplets from the nozzle opening by this pressure fluctuation. ing. As this type of recording head, there is a so-called piezoelectric recording head. Piezo-type recording heads use piezoelectric vibrators as pressure generating elements, and deformation of piezoelectric vibrators (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.) The pressure chamber is pressurized and depressurized to eject ink droplets. In such a recording head, as an attempt to further improve the image quality and the recording speed, an attempt is made to further increase the image quality by increasing the types of colors that can be recorded by increasing the number of nozzle rows, Attempts have been made to improve the recording speed by increasing the number of nozzle openings constituting one nozzle row. However, when the nozzles of the head are miniaturized, flying bends and nozzle clogging are likely to be caused by the ink adhered and remaining on the nozzle plate portion. Therefore, the ink repellent treatment is applied to the nozzle plate, but if the ink repellency of the ink ejection surface is inferior, various problems that reduce the head performance such as the flying direction of the ink droplets bend and the image quality deteriorates. Is produced. After the ink droplets are ejected from the nozzles, the ink adhering to the surface of the nozzle plate around the nozzles remains without being returned into the nozzles. Such residual ink is wiped off by wiping, but if the ink repellency is inferior, it remains without being removed even by wiping, and the ink component adheres to the ink ejection surface over a long period of use, causing the ink droplets to fly. There is a problem in that troubles such as bending and lack of discharge occur. In particular, since white ink has strong adhesion of titanium oxide contained to the periphery of the nozzle, this phenomenon tends to occur remarkably. Therefore, there is an urgent need to develop an oil-based white ink composition for ink jet recording that does not cause clogging in the ink jet head and does not impair ink repellency on the surface of the discharge nozzle and can be stably ejected.

The inventors of the present invention previously coated with an oxide of aluminum and / or silicon as the titanium oxide pigment in the oil-based white ink composition for ink jet recording, and has an average primary particle size of 0.15 μm to 0.25 μm. By making certain titanium oxide fine particles a white pigment further coated with SiH-containing polysiloxane and / or dimethylpolysiloxane at a ratio of 0.01% to 2.50% by weight, the concealability of the printed matter on the background is large. In addition, it has been shown that an oil-based white ink composition for ink-jet recording having excellent temporal stability in which the pigment does not settle or the viscosity of the liquid or the particle size of the pigment does not change can be obtained (Patent Document 6). As shown in Fig. 9, the nozzle plate surface layer portion is subjected to fluorine and / or silicone coating treatment. It has been found that there are certain problems in combination with the recording head.
JP-A-6-107964 JP 2006-274214 A JP2002-348513 JP 2004-536923 A Special table 2004-256726 JP 2004-263181 A JP 2006-82363 A JP2007-106050 JP 2006-51808 A

  An object of the present invention is to provide an oil-based white dispersion for ink jet recording which is excellent in long-term storage stability, in which the pigment does not settle, the viscosity of the liquid or the particle size of the pigment does not change, and the white dispersion An oil-based white ink composition for ink-jet recording capable of stable ejection that does not cause clogging in the ink-jet head and does not impair ink repellency on the ejection nozzle surface. It is to provide.

  The oily white dispersion for ink-jet recording of the present invention comprises titanium oxide fine particles coated with an oxide of aluminum and / or silicon and having an average primary particle size of 0.15 μm to 0.25 μm, SiH-containing polysiloxane and And / or 5 to 60% by mass of a white pigment further coated with dimethylpolysiloxane at a ratio of 0.01% to 2.50% by mass, and in the molecule with respect to 1 part by mass of the white pigment A linear or branched polyester-based dispersant having a basic group is contained in an amount of 0.03 to 5 parts by mass, and at least glycol ether dialkyl ether is contained as a solvent.

  The glycol ether dialkyl ether is at least one selected from those represented by the following general formula (1).

R ¹ — (OC ₂ H ₄ ) _n —OR ² (1)
(In the above formula, R ¹ and R ² each independently represent a methyl group or an ethyl group, and n represents an integer of 2 to 4)
The linear or branched polyester dispersant having a basic group in the molecule is at least one selected from an amino group, an amide group, an imide group, an amide-containing group, and an imide-containing group as a basic group. And imparting pigment affinity to the dispersant, and the linear or branched polyester portion imparts affinity for the solvent to the dispersant, and the dispersant is water-soluble. It is characterized by being.

  The method for producing an oily white dispersion for ink jet recording of the present invention comprises titanium oxide fine particles coated with an oxide of aluminum and / or silicon and having an average primary particle diameter of 0.15 μm to 0.25 μm and containing SiH. A white pigment further coated with polysiloxane and / or dimethylpolysiloxane in a proportion of 0.01% to 2.50% by mass is contained in a proportion of 5% to 60% by mass, and 1 part by mass of the white pigment A solvent comprising at least glycol ether dialkyl ether so as to contain a linear or branched polyester-based dispersant having a basic group in the molecule at a ratio of 0.03 to 5 parts by mass. And mixed and dispersed.

  The oil-based white ink composition for ink-jet recording of the present invention contains the above-described oil-based white dispersion for ink-jet recording.

  Further, the oil-based white ink composition for ink jet recording is for a piezo ink jet printer having an ink jet recording head in which a nozzle plate surface layer is subjected to ink repellent treatment with fluorine and / or silicone coating. .

  The oil-based white dispersion for ink-jet recording of the present invention does not interfere with the ink repellency of the ink discharge surface, does not cause clogging in the ink-jet head, can be stably discharged, and is resistant to precipitation of pigments over time. And is suitable for the preparation of an oil-based white ink composition for ink jet recording from which a printed matter with high whiteness on the printing substrate and excellent concealability and a highly visible marking can be obtained.

  The oil-based white dispersion for inkjet recording of the present invention employs titanium oxide having a specific average particle diameter coated with a specific inorganic metal oxide and further coated with a siloxane material as a white pigment, and a dispersant. Ink repellency of the ink ejection surface by dispersing in an organic solvent consisting of glycol ether dialkyl ether solvents using a linear or branched polyester dispersant having a basic group in the molecule Based on the knowledge that oil-based white dispersions for ink-jet recording can be obtained without clogging with the ink-jet head, enabling stable ejection, and excellent long-term storage stability and ejection stability. It has been made.

  Hereinafter, the oil-based white dispersion for inkjet recording will be described. In this specification, the “oil-based white dispersion for inkjet recording” may be simply referred to as “white dispersion” or “dispersion”. The “oil white ink composition for recording” may be simply referred to as “white ink” or “ink”. “Oxide” means an anhydrous oxide, a hydrous oxide, and a mixture of both.

The white pigment in the oily white dispersion for inkjet recording is prepared using titanium oxide (titanium oxide fine particles). Specific examples of titanium oxide include known rutile type and / or anatase type titanium dioxide, preferably rutile type titanium dioxide. In order to obtain a white pigment, the titanium oxide particles are first coated with an oxide of aluminum and / or silicon. Specific examples of these oxides include oxides such as SiO ₂ and Al ₂ O _3, and hydrous oxides such as SiO ₂ · nH ₂ O and Al ₂ O ₃ · nH ₂ O, preferably Al ₂ O ₃ and its hydrated oxide are mentioned. Titanium oxide coated with these oxides has an average primary particle size of 0.15 μm to 0.25 μm, preferably 0.15 μm to 0.21 μm. When this average primary particle size is within this range, the storage stability of the white pigment in the white dispersion or the ink is excellent, the concealability to the base is improved, and the ink is clogged in the print head during printing. It is possible to effectively prevent this. In particular, it is possible to achieve storage stability and concealment with respect to the background when ink is used. The mass ratio of titanium oxide and coating oxide is not particularly limited, but is generally 0.01 to 30 parts by mass per 100 parts by mass of titanium oxide.

  In the present invention, oxide-coated titanium oxide is further coated with SiH-containing polysiloxane and / or dimethylpolysiloxane. Specific examples of the SiH-containing polysiloxane include the following general formula (2):

(In the above formula (2), m is an integer of 0 or more, and n is an integer of 1 or more.)
Methyl hydrogen polysiloxane represented by general formula (2), and derivatives thereof, and methyl hydrogen polysiloxane represented by the above general formula (2) are preferable. Among the methyl hydrogen polysiloxanes, in the above formula (2), (m + n) is preferably an integer of 3 to 500, and more preferably (m + n) is an integer of 10 to 100. When the value of (m + n) is within this range, the dispersibility of the white pigment becomes preferable. This methyl hydrogen polysiloxane is available, for example, from Shin-Etsu Chemical Co., Ltd. under the trade name of methyl hydrogen polysiloxane “KF-99” and can be used in the present invention.

  Specific examples of dimethylpolysiloxane include the following general formula (3):

(In the above formula (3), n represents an integer of 1 or more.)
The linear dimethylpolysiloxane represented by these, its derivative (s), what has them as a main component, etc. are mentioned. Specific examples of dimethylpolysiloxane are available from Shin-Etsu Chemical Co., Ltd. under the trade name of dimethylpolysiloxane “KF-96” and can be used in the present invention.

  In the present invention, if necessary, the polysiloxane compound may be added to methylphenyl silicone oil, polyether-modified silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, mercapto-modified silicone oil, fluorine-modified silicone oil, etc. Silicone oil can be used in combination.

  The coating ratio of SiH-containing polysiloxane and / or dimethylpolysiloxane to the oxide-coated titanium oxide is 0.01% by mass to 2.50% by mass, preferably 0.01% by mass to 1.0% by mass. is there. When the coating amount is within this numerical range, the precipitation of the white pigment in the white dispersion or ink is suppressed, sufficient whiteness is imparted to the white dispersion or ink, and the printed material is concealed from the background. It becomes possible to improve the property.

  The content of the white pigment in the oily white dispersion for inkjet recording is 5% by mass to 60% by mass, preferably 10% by mass to 50% by mass, with respect to the total amount of the white dispersion.

  Next, as the dispersant, an alkyl polyester-based dispersant having a basic group in the molecule and having a linear or branched structure (also simply referred to as a polyester-based dispersant) is added. The basic group is preferably an amino group having a pigment affinity group, an amide group, an imide group, an amide-containing group or an imide-containing group. The polyester portion has an affinity for a solvent composed of glycol ether dialkyl ethers. The polyester dispersant in the present invention is soluble in 20 ° C. water. In addition, for example, the comb-shaped and block-type polymer dispersants are insoluble in water and insoluble, and as shown in Comparative Examples described later, as a dispersant in the oily white dispersion for ink jet recording in the present invention. Is unsuitable. In the present invention, although the detailed reason is unknown, the present inventors have found that a water-soluble dispersant is effective for glycol ether dialkyl ethers which are solvents.

  As the polyester dispersant in the present invention, for example, “Disperbyk-191” manufactured by Big Chemie Japan Co., Ltd., “SOLPERSE 9000” manufactured by Lubrizol, and “SOLPERSE 20000” can be obtained and used in the present invention.

  The polyester-based dispersant in the present invention may be added in a proportion of 0.03 to 5 parts by mass, preferably 0.05 to 5 parts by mass with respect to 1 part by mass of the white pigment. The dispersion may contain 0.1% by mass to 30% by mass, preferably 2% by mass to 20% by mass.

The solvent in this invention consists of glycol ether dialkyl ethers.
As glycol ether dialkyl ethers, the following general formula (1) is preferable.
R ¹ — (OC ₂ H ₄ ) _n —OR ² (1)
(In formula (1), R ¹ and R ² each independently represent a methyl group or an ethyl group, and n represents an integer of 2 to 4]
It is represented by Examples thereof include polyoxyethylene glycol dimethyl ether, polyoxyethylene glycol diethyl ether, and polyoxyethylene glycol ethyl methyl ether. These glycol ether dialkyl ethers can be used alone or in combination of two or more. Since such a glycol ether dialkyl ether has a high boiling point and a low vapor pressure, it has a low odor, a high safety, and an excellent working environment.

  The addition amount of glycol ether dialkyl ethers in all the solvents in the oily white dispersion for inkjet recording of the present invention is 5% by mass to 100% by mass, preferably 10% by mass to 100% by mass.

  The oily white dispersion for ink jet recording is prepared by mixing and dispersing the above-described white pigment and polyester dispersant in a solvent composed of glycol ether dialkyl ethers. As the disperser used in the dispersion step, a known one can be used. For example, in the case of using a media, a paint shaker, a ball mill, a nanomill, an attritor, a basket mill, a sand mill, a sand grinder, a dyno mill, a disperse mat, an SC mill, Examples include spike mills and agitator mills. Examples of media that do not use media include ultrasonic homogenizers, high-pressure homogenizers, nanomizers, resolvers, dispersers, high-speed impeller dispersers, etc. One of these may be used alone, or two or more types of devices May be used in combination. Among these, a disperser using media is preferable because of high dispersibility. In addition, after dispersion | distribution, you may adjust a density | concentration with a solvent as needed. Depending on the type of disperser used, before dispersing (main dispersion) with the disperser, if necessary, a solvent may be added to the kneaded product after completion of the kneading step, mixed and diluted. It is preferable to adjust in advance to a viscosity suitable for processing.

  The order of blending the components and the manner of blending are arbitrary, and can be determined in consideration of, for example, the properties of the blend at each stage of the production process and the ease of production. For example, each component can be blended independently one by one, or supply and blending of each component can be performed together to obtain a blend of each component at once. Moreover, after mix | blending 2 or more types of components previously, it can also mix | blend with the remaining other components. At this time, when two or more components are blended in advance, the amount of the components blended in advance may be the total amount of each component or a part of the required amount of each component.

  Next, the oily white ink composition for inkjet recording will be described. The oil-based white ink composition for ink jet recording is prepared using at least the white dispersion in the present invention, and the weight concentration of the white pigment is 0.5% by mass to 50% by mass, preferably 1% by mass. It may be adjusted to ˜40 mass%, most preferably 5 mass% to 30 mass%. If the pigment content of the ink is less than 0.5% by mass, the print density may be insufficient. On the other hand, if the amount exceeds 50% by mass, the amount of ink additive such as a moisturizing component added to the ink is restricted from the viewpoint of ink viscosity, nozzle clogging of the inkjet head is likely to occur, and the viscosity of the ink increases. Stable discharge may not be obtained. In the oil-based white ink composition for ink-jet recording, the above-described white dispersion liquid may be appropriately diluted with a solvent to make the pigment concentration range in the ink composition. If the pigment concentration in the white dispersion is in the pigment concentration range in the ink composition, it can be used as it is.

  Further, a binder resin can be added to the white ink composition as necessary. Examples of the binder resin include (meth) acrylic resin, styrene (meth) acrylic resin, rosin modified resin, phenol resin, terpene resin, polyester resin, polyamide resin, epoxy resin, vinyl chloride vinyl acetate copolymer resin, cellulose Examples thereof include fiber-based resins such as acetate butyrate, vinyltoluene-α-methylstyrene copolymer resin, and the addition amount is preferably 0.05% by mass to 5% by mass with respect to 1 part by mass of the white pigment. .

  Moreover, stabilizers, surfactants, etc., such as antioxidant and a ultraviolet absorber, can be added as needed. Preferable antioxidants include BHA (2,3-dibutyl-4-oxyanisole), BHT (2,6-di-t-butyl-p-cresol) and the like. 0.01 mass%-3.00 mass% are preferable with respect to the whole thing. Examples of the ultraviolet absorber include benzophenone compounds and benzotriazole compounds, and the addition amount is preferably 0.01% by mass to 0.5% by mass with respect to the total amount of the ink composition. Further, as the surfactant, any of anionic, cationic, amphoteric or nonionic surfactants can be used, and the addition amount thereof is 0.5% by mass to 4.% by mass relative to the total amount of the ink composition. 0% by mass is preferred.

  The ink composition of the present invention is preferably prepared so that the viscosity at 20 ° C. is 2 mPa · s to 20 mPa · s, preferably 3 mPa · s to 15 mPa · s, and the surface tension is 20 mN / m to 50 mN. / M or less is preferable. When the surface tension is within the above range, the wettability of the surface of the printer head for ink jet recording can be controlled, the ink droplets can be easily discharged, and the wettability of the surface of the printed recording medium is controlled. And good printing becomes possible.

  The material of the nozzle plate of the ink jet recording head for discharging the ink composition according to the present invention is not particularly limited, but is preferably formed of metal, ceramics, silicon, glass, plastic, or the like, more preferably titanium, chromium, iron, Single material such as cobalt, nickel, copper, zinc, tin or gold, or alloy such as nickel-phosphorus alloy, tin-copper-phosphorus alloy, copper-zinc alloy or stainless steel, polycarbonate, polysulfone, acrylonitrile-butadiene -It is preferably formed of a styrene copolymer, polyethylene terephthalate, or polysulfone and various photosensitive resins. The method of ink repellent treatment of the nozzle plate is not particularly limited, but the liquid repellent film may be a silicone resin polymer film or a fluororesin polymer film obtained by polymerizing an organic silicon compound such as silicone resin or an organic compound such as fluorinate. preferable.

  The ink composition according to the present invention can be suitably used for an ink jet recording head in which the nozzle plate surface layer portion is subjected to ink repellent treatment with fluorine and / or silicone coating as shown in Patent Documents 7 to 9. . Even when the ink composition according to the present invention is combined with an ink jet recording head subjected to an ink repellent treatment, it is difficult for the ink to be bent, and a good image can be recorded on the recording paper.

  Further, according to the ink composition of the present invention, the surface state of the nozzle plate subjected to the ink repellent treatment can be maintained in a good state for a long time, and long-term ink ejection stability can be realized. . It can be used for a long time, and the liquid repellency can be kept good without replacing the ink jet printer head for a long time.

  EXAMPLES Examples and comparative examples of the present invention will be described below, but these examples are for clarifying the present invention and do not limit the scope of the present invention. In addition, unless otherwise indicated, the part in an Example and a comparative example shall be a mass part. The viscosity of the pigment dispersion is a value measured with a falling ball viscometer (AMVn manufactured by Nippon Sebel Hegner Co., Ltd.). The average particle size (D50) is a value measured using a particle size analyzer Microtrac UPA150 manufactured by Nikkiso Co., Ltd.

Example 1
The following composition components were mixed, dispersed for 1 hour with zirconia beads of φ0.8 mm with a paint shaker, then dispersed with zirconia beads of φ0.3 mm for 3 hours, and a white dispersion (viscosity at 20 ° C. was 8.0 mPa · s) was prepared.
-White pigment {Titanium dioxide with an average primary particle size of 0.21 μm surface-treated with alumina is further treated with methyl hydrogen polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., methyl hydrogen polysiloxane KF-99). 25% by mass treated} ·· 40 parts by mass · Solvent (diethylene glycol diethyl ether) ·· 48 parts by mass · Polyester-based dispersant 1 having a basic group (Disperbyk-191, manufactured by Big Chemie Japan Co., Ltd.) Department.

(Example 2)
The following composition components were mixed in the same manner as in Example 1 to prepare a white dispersion (viscosity at 20 ° C. was 8.5 mPa · s).
-White pigment {Titanium dioxide with an average primary particle size of 0.21 μm surface-treated with alumina is further treated with methyl hydrogen polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., methyl hydrogen polysiloxane KF-99). 75 mass% treated} ·· 40 parts by mass · Solvent (diethylene glycol diethyl ether) · · 48 parts by mass · Polyester-based dispersant 1 having a basic group (Disperbyk-191, manufactured by Big Chemie Japan) · · 12 parts by mass Department.

(Example 3)
A white dispersion (20 ° C.) was used in the same manner as in Example 1 except that polyester-based dispersant 2 having a basic group (SOLBERS 9000, manufactured by Lubrizol Corporation) was used instead of Dispersant 1 used in Example 1. Viscosity at 8.2 mPa · s) was prepared.

Example 4
Instead of the dispersant 1 used in Example 2, a white dispersion (20 ° C.) was used in the same manner as in Example 2 except that a polyester-based dispersant 2 having a basic group (SOLBRASE 9000, manufactured by Lubrizol Corporation) was used. Viscosity at 8.6 mPa · s) was prepared.

(Example 5)
Instead of the dispersant 1 used in Example 1, a white dispersion (20 ° C.) was used in the same manner as in Example 1, except that a polyester-based dispersant 3 having a basic group (SOLSPERSE 20000, manufactured by Lubrizol Corporation) was used. The viscosity was 8.5 mPa · s).

(Example 6)
Instead of the dispersant 1 used in Example 2, a white dispersion (20 ° C.) was used in the same manner as in Example 2, except that a polyester-based dispersant 3 having a basic group (SOLSPERSE 20000, manufactured by Lubrizol Corporation) was used. Viscosity at 9.0 mPa · s) was prepared.

(Example 7)
30 parts by weight of the white dispersion prepared in Example 1 was mixed with 4.4 parts by weight of a binder resin (“Paraloid B-99N” manufactured by Rohm & Haas) and 65.6 parts by weight of diethylene glycol diethyl ether to obtain a white ink. (The viscosity at 20 ° C. is 5.0 mPa · s).

(Comparative Example 1)
In place of Dispersant 1 used in Example 1, Dispersant 4 which is an acrylic copolymer (Big Chemie Japan, Disperbyk-112) was used in the same manner as in Example 1 except that Comparative Example 1 was used. A dispersion (viscosity at 20 ° C. of 7.2 mPa · s) was prepared.

(Comparative Example 2)
It replaced with the dispersing agent 1 used in Example 1, and it carried out similarly to Example 1 except having used the dispersing agent 5 (The Big Chemie Japan company make, Disperbyk-145) which is a phosphate ester salt of a copolymer. A dispersion of Comparative Example 2 (viscosity at 20 ° C. of 7.5 mPa · s) was prepared.

(Comparative Example 3)
It replaced with the dispersing agent 1 used in Example 1, and it was the same as that of Example 1 except having used the dispersing agent 6 (the Big Chemie Japan company make, Disperbyk-166) which is an acrylic-polycaprolactone block copolymer. Thus, a dispersion liquid of Comparative Example 3 (viscosity at 20 ° C. was 7.8 mPa · s) was prepared.

(Comparative Example 4)
A comparative example is carried out in the same manner as in Example 1 except that Dispersant 7 which is an acrylic block copolymer (Disperbyk-2020, manufactured by Big Chemie Japan Co., Ltd.) is used instead of Dispersant 1 used in Example 1. No. 4 dispersion (viscosity at 20 ° C. is 10.0 mPa · s) was prepared.

(Comparative Example 5)
It replaced with the dispersing agent 1 used in Example 1, and it carried out similarly to Example 1 except having used the dispersing agent 8 (The Big Chemie Japan company make, Disperbyk-2050) which is an amine salt of an acrylic copolymer. A dispersion of Comparative Example 5 (viscosity at 20 ° C. of 12.0 mPa · s) was prepared.

(Comparative Example 6)
The dispersion of Comparative Example 6 was performed in the same manner as in Example 1 except that Dispersant 9 (Lubrisol Co., Ltd., SOLPERSE 32000), which is a polycaprolactone copolymer, was used instead of Dispersant 1 used in Example 1. A liquid (viscosity at 20 ° C. of 9.0 mPa · s) was prepared.

(Comparative Example 7)
In place of the white pigment used in Example 1, titanium dioxide particles having an average primary particle diameter of 0.21 μm surface-treated with alumina, methylhydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., methylhydrogenpoly) A dispersion liquid of Comparative Example 7 (viscosity at 20 ° C. of 7.6 mPa · s) was prepared in the same manner as in Example 1 except that a material not treated with siloxane KF-99) was used.

(Comparative Example 8)
In place of the white pigment used in Example 1, titanium dioxide having an average primary particle diameter of 0.21 μm surface-treated with alumina, and methylhydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., methylhydrogenpoly) A dispersion of Comparative Example 8 (viscosity at 20 ° C. of 8.8 mPa · s) was prepared in the same manner as in Example 1 except that 3.0% by mass treated with siloxane KF-99) was used.

Evaluation test The following evaluation was performed using each dispersion liquid and ink of Examples 1 to 7 and Comparative Examples 1 to 8 prepared above. The evaluation results were as described in Table 1 below.

Evaluation 1: Viscosity change 60 ° C./1 Viscosity before and after storage for 1 week was measured under the condition of 20 ° C. and evaluated according to the following criteria. The results are shown in Table 1.
Evaluation criteria Evaluation A: The difference obtained by subtracting the viscosity before storage from the viscosity after storage is less than ± 5% of the viscosity before storage.
Evaluation B: The difference obtained by subtracting the viscosity before storage from the viscosity after storage is ± 5% or more of the viscosity before storage.

Evaluation 2: Particle size change 60 ° C./Number average dispersed particle size before and after storage for 1 week was measured and evaluated according to the following criteria. The results are shown in Table 1.
Evaluation criteria Evaluation A: The difference obtained by subtracting the number average dispersed particle size before storage from the number average dispersed particle size after storage is less than ± 5% of the number average dispersed particle size before storage.
Evaluation B: The difference obtained by subtracting the number average dispersed particle size before storage from the number average dispersed particle size after storage is ± 5% or more of the number average dispersed particle size before storage.

Evaluation 3: Sedimentability was placed in a transparent glass bottle, stored at 60 ° C. for 1 week, visually observed for ink sedimentation, and evaluated according to the following evaluation criteria.
Evaluation criteria Evaluation A: Pigment settling is not observed.
Evaluation B: Sedimentation of the pigment is observed.

Evaluation 4: 1 g of the re-dissolvable ink composition was taken in a petri dish, and the ink was dropped again on the ink that had been left to dry at 60 ° C. for 1 day, and its re-dissolution (dispersion) property was confirmed.
Evaluation criteria Evaluation A: Re-dissolution evaluation B: Not re-dissolved

Evaluation 5: Nozzle-adhesive inkjet printer (MJ-8000C; manufactured by Seiko Epson Corporation) was immersed in each ink composition with a nozzle portion that had been subjected to an ink repellent treatment by fluorine coating, and was treated at 40 ° C. for one week. After standing, the state was observed visually.
Evaluation Criteria Evaluation A: Ink adherence does not occur in the ink-repellent processed portion around the nozzle of the head.
Evaluation B: Ink adheres to an ink repellent processed portion around the nozzle of the head.

  From the evaluation results, the oily white dispersion for ink-jet recording of the present invention has no change in physical properties or sedimentation of the pigment even when left for a long time, and flight bending or clogging at the nozzle occurs during recording. It has been proved that the nozzle surface is difficult to deteriorate. Further, as shown in Example 7, it can be seen that an oil-based white ink composition for ink-jet recording having the same physical properties can be easily prepared.

  The oily white dispersion for ink jet recording of the present invention is excellent in stability over time and storage stability, so that it is not necessary to re-disperse the dispersion during use and continuous printing without clogging the print head. In addition, it can be effectively used to prepare an oily white ink composition for inkjet recording in which the nozzle surface is less likely to deteriorate.

Claims (6)

Titanium oxide fine particles coated with an oxide of aluminum and / or silicon and having an average primary particle diameter of 0.15 μm to 0.25 μm are 0.01% by mass to SiH-containing polysiloxane and / or dimethylpolysiloxane. 2. A linear or branched chain type containing 5% to 60% by weight of a white pigment further coated at a ratio of 50% by weight and having a basic group in the molecule with respect to 1 part by weight of the white pigment An oily white dispersion for ink-jet recording, comprising 0.03 to 5 parts by mass of the polyester-based dispersant and at least glycol ether dialkyl ether as a solvent. 2. The oily white dispersion for ink jet recording according to claim 1, wherein the glycol ether dialkyl ether is at least one selected from those represented by the following general formula (1).
R ¹ — (OC ₂ H ₄ ) _n —OR ² (1)
(In the above formula, R ¹ and R ² each independently represent a methyl group or an ethyl group, and n represents an integer of 2 to 4) The linear or branched polyester dispersant having a basic group in the molecule is at least one selected from an amino group, an amide group, an imide group, an amide-containing group, and an imide-containing group as a basic group. And imparting pigment affinity to the dispersant, and the linear or branched polyester portion imparts affinity for the solvent to the dispersant, and the dispersant is water-soluble. The oily white dispersion for ink-jet recording according to claim 1. Titanium oxide fine particles coated with an oxide of aluminum and / or silicon and having an average primary particle size of 0.15 μm to 0.25 μm are 0.01% by mass to SiH-containing polysiloxane and / or dimethylpolysiloxane. 2. A white pigment further coated in a proportion of 50% by mass in a proportion of 5% by mass to 60% by mass and having a basic group in the molecule with respect to 1 part by mass of the white pigment or For inkjet recording, wherein a branched polyester-based dispersant is added to a solvent comprising at least glycol ether dialkyl ether so as to contain 0.03 to 5 parts by mass, and mixed and dispersed. A method for producing an oily white dispersion. An oily white ink composition for ink-jet recording, comprising the oily white dispersion for ink-jet recording according to claim 1. The oil-based white ink composition for ink-jet recording is for a piezo-type ink-jet printer provided with an ink-jet recording head having a nozzle plate surface layer subjected to ink repellent treatment with fluorine and / or silicone coating. 5. An oily white ink composition for ink-jet recording according to 5.