JP2006249242A - Inkjet ink composition, method for producing the same, and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink composition in which a colorant has particles having a uniform particle size and has a surface uniformly coated with a resin; colorant particles can be stably discharged for a long period of time under electric field conditions of low voltage and low frequency; and dots having high intensity and few smears can be printed at high speed, and to provide a method for producing the same and an inkjet recording method. <P>SOLUTION: The method for producing an ink composition comprises the steps of: (i) mixing a colorant and a resin component to prepare a colored mixture (A); (ii) mixing the colored mixture (A) with an aqueous auxiliary component (B) to prepare a dispersion; (iii) eluting the aqueous auxiliary component (B) from the dispersion to obtain colorant particles (C); and (iv) dispersing the colorant particles (C) in a nonaqueous solvent together with a dispersing agent. The ink composition is produced by the production method. The recording method uses the ink composition to cause ink droplets to fly by an inkjet recording system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink-jet ink composition for forming characters and images on a recording medium such as recording paper, a method for producing the same, and an ink-jet recording method. Particularly, high-density and low-bleed dots are stably printed at high speed. The present invention relates to an inkjet ink composition that can be produced, a method for producing the same, and an inkjet recording method.

  Inkjet recording, which performs printing by flying ink onto a recording medium to form recording dots, is attracting interest as a non-impact recording method that can be easily colored and recorded directly on plain paper. Various printers have been put into practical use. Inkjet recording methods include, for example, Takeshi Aoiin “Real Color Hard Copy” Sangyo Tosho Co., Ltd. (1993), Shin Ohno “Non-impact Printing -Technology and Materials” (CMC) (1986), Takeshi Amari It is described in a book such as “inkjet printer technology and material” CMC Co., Ltd. (1998), and there are on-demand (optional injection) and continuous (continuous injection) systems. Further, a recording method called an electrostatic method (Sweet type, Hertz type) is known for the continuous type, and a piezo piezoelectric method, a shear mode piezo piezoelectric method, or a thermal ink jet method is known for the on-demand type. As one of the on-demand inkjet recording methods, Susumu Ichinose, Yuji Ohba, IEICE Transactions Vol.J66-C (No.1), p.47 (1983), Tadayoshi Ohno, Mamoru Mizuguchi, The Institute of Image Electronics Engineers of Japan There is known a system called electrostatic acceleration type ink jet or slit jet described in magazines Vol. 10, (No. 3), p. 157 (1981). In this method, a voltage is applied to a plurality of recording electrodes arranged opposite to the recording medium and a counter electrode arranged on the back surface of the recording medium, and a potential difference generated between the two electrodes causes a voltage difference between the recording electrodes. An electrostatic force is applied to the supplied ink to cause the ink to fly on the recording medium. Specific modes are disclosed in, for example, Japanese Patent Laid-Open Nos. 56-170, 56-4467, and 57-151374. Etc. are disclosed. In this method, instead of the nozzles in the conventional inkjet head, an elongated slit-like ink discharge port having a large number of recording electrodes on the inner wall is used, and ink is supplied to the slit-like ink chamber, and these electrodes are selected. In particular, by applying a high voltage, recording is performed by ejecting ink in the vicinity of the electrode onto a recording sheet that is in close proximity to the slit.

  For this reason, there is little worry about clogging of ink, and since the head configuration is simple, a reduction in manufacturing cost can be expected, and the so-called long line head has a length that can cover a wide range in the width direction of the recording medium. This is also an effective method for realizing the above.

  An example of a drop-on-demand type full-color recording head constituted by the electrostatic acceleration type ink jet method is disclosed in, for example, Japanese Patent Publication No. 60-59569, Journal of the Institute of Electrical Communication, Vol. J68-C, 2 (1985), pages 93 to 100.

In this electrostatic acceleration type ink jet head, an oil-based ink in which a dye is dissolved in an organic solvent is preferably used. Although the constituent material of the ink is not disclosed in detail, the volume resistivity (electric resistivity) is 10 An ink having physical properties of ⁷ to 10 ⁸ Ω · cm, a surface tension of 22 mN / m, and a viscosity of 3.1 to 6.9 cP is used.

  However, such oil-based ink has a surface tension lower than that of water-based ink generally used in other in-jet methods, and therefore has a very high permeability to recording paper. In particular, printing is performed on plain paper. In some cases, the print density tends to decrease, blur, or show through.

  A coloring material concentration discharge type electrostatic system that does not use a slit-shaped recording head is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 9-193389) and Patent Document 2 (Japanese Patent Laid-Open No. 10-138493). This is a control comprising a plurality of individual electrodes for applying an electrostatic force to a color material component in ink, and an insulating substrate having a through hole and a control electrode formed corresponding to the through hole. It consists of an electrode substrate and a convex ink guide arranged almost at the center of this through hole. The surface of this convex ink guide is transported to the ink droplet flying position by surface tension, and a predetermined voltage is applied to the control electrode. Is applied to cause ink droplets to fly on the recording medium.

  In this color material concentration discharge type electrostatic ink jet system, color material particles are concentrated on the discharge port portion by electrophoresis, and ink droplets are ejected in a form in which the color material particles are concentrated to a high concentration. For this reason, unlike the above-described method, the ink components are not discharged while containing a large amount of liquid components in a uniform state, but are discharged in a state where the color material particles are aggregated and the liquid components are small. This solves the above-mentioned problems. Further, by using a pigment as a coloring material, advantageous results can be obtained in terms of water resistance and light resistance of a printed image as compared with an ink jet head using a conventional dye.

  In such a color material concentration discharge type electrostatic inkjet ink, first, in order to obtain good print characteristics with high print density and no blurring or show-through, the volume resistivity of the ink is sufficiently high. It is necessary. As a result, the electric field formed by the recording electrode and the counter electrode and applied to the ink can reach the colorant particles. Also, if the volume resistivity of the ink is low, the ink is charged and charged by the voltage applied by the recording electrode, and the ink is discharged while containing a large amount of liquid component due to electrostatic repulsion. The tendency becomes stronger. Next, since it is necessary to concentrate the color material particles at the discharge port portion by electrophoresis at a sufficient speed, the color material particles have a sufficient charge amount, that is, the color material particles are positive or negative. It is necessary to have a high particle conductivity.

  In recent years, as the demand for higher speed printers and higher image quality has increased, even in the above-described ink jet heads with concentrated color material discharge, a small amount of ink droplets with high color material concentration can be stably maintained for a long time. There is a need for a technique for printing a higher-definition image at a high speed by discharging the ink at a high speed.

It has been confirmed that such printing performance largely depends on the physical property value of the ink. In order to obtain sufficient printing performance, as described above, when preparing the ink, preferably 10 ⁸ Ω · cm. While maintaining a high volume resistivity as described above, it is necessary to impart a high particle conductivity of 100 pS / cm or more to the colorant particles. If the particle conductivity of the color material particles is less than 100 pS / cm, the color material particles cannot be moved at high speed to the discharge port, that is, the discharge electrode tip by electrophoresis, and the supply of the color material particles becomes insufficient. The cohesiveness of the color material particles is deteriorated and the discharge response frequency is lowered.

  Furthermore, since the electric repulsive force between the surface of the discharge electrode and the color material particles is weak, there may be a case where the color material particles adhere to and accumulate on the discharge electrode and stable discharge cannot be performed. For these reasons, there arise problems that a sufficient print density cannot be obtained and stable and high-speed printing cannot be performed.

The color material particles are preferably composed of a color material such as a pigment and a resin. As a resin for coating the color material, in general, (1) the pigment surface is sufficiently coated to form a colored mixture. It has a suitable fluidity by heat, etc., (2) It is well dispersed in the dispersion medium by coating the color material, (3) It is as transparent as possible, (4) It is fixed to the recording medium by fixing. In addition to having characteristics such as giving sufficient scratch resistance, the electrostatic inkjet ink described above can impart (5) particle conductivity with high positive or negative polarity to the color material particles. It is desired. Color material particles coated with a color material with a resin can be formed by coating a color material with a resin to form a colored mixture, and then dispersing the colored mixture in a non-aqueous solvent. However, in the normal dispersion, coarse color material particles are generated, or fine color material particles of 0.2 μm or less are generated, and the average particle size is about 0.3 to 4 μm and the particle sizes are uniform. In fact, it is difficult to obtain a dispersion with a small amount of fine color material particles of 0.2 μm or less by dispersion.

  On the other hand, as a method for producing resin particles, a method in which a dispersion composed of a resin and a water-soluble auxiliary agent is prepared and resin particles are obtained by eluting the auxiliary component is disclosed in Patent Document 3 (Japanese Patent Application Laid-Open No. 2004-51942). However, there is no description of color material particles for ink jet recording including a color material such as a pigment.

Japanese Patent Laid-Open No. 9-193389 JP 10-138493 A JP 2004-51942 A

  The object of the present invention is that the color material particles have a uniform particle diameter and the surface of the color material is uniformly coated with a resin, so that stable color material particle ejection can be performed for a long time under electric field conditions at low voltage and low frequency. It is possible to provide an ink-jet ink composition capable of printing at high speed dots with high density and little bleeding, a method for producing the same, and an ink-jet recording method.

  As a result of intensive studies to achieve the above object, the present inventor mixed a coloring admixture obtained by mixing a coloring material and a resin with an aqueous auxiliary component, and eluted the auxiliary component therefrom to produce coloring material particles. However, the ink composition obtained by dispersing this in a non-aqueous solvent together with a dispersing agent produces less colorant fine particles compared with the composition obtained by the conventional production method, and the ink composition is excellent over a long period of time. The present invention has been found out that it can be recorded.

That is, the present invention is as follows.
(1) A method for producing an ink-jet ink composition comprising the following steps (i) to (iv):
(I) A step of mixing the coloring material and the resin component to create a colored mixture (A);
(Ii) mixing the colored admixture (A) with the aqueous auxiliary component (B) to form a dispersion;
(Iii) a step of eluting the aqueous auxiliary component (B) from the dispersion to obtain the colorant particles (C); and (iv) a step of dispersing the colorant particles (C) together with the dispersant in a non-aqueous solvent.
(2) An inkjet ink composition produced by the production method described in (1) above.
(3) An ink jet recording method characterized by using the ink jet ink composition described in (2) above and causing ink droplets to fly by an ink jet recording method.

According to the production method of the present invention, the colored admixture (A) is mixed with the aqueous auxiliary component (B) to form a dispersion, and then the aqueous auxiliary component (B) is eluted from the dispersion. Therefore, color material particles (C) having a uniform particle diameter and a color material surface uniformly coated with a resin are obtained. For this reason, the colorant particles having high surface energy are not exposed on the surface, and the particles are stably charged, and stable particle ejection is possible under electric field conditions at low voltage and low frequency. Further, since the color material particles having a high surface energy are not exposed on the surface, the adhesion of fine particles to the piping, nozzle portion, etc. in the apparatus is suppressed, and stable particle ejection can be performed for a long period of time. Therefore, according to the present invention, it is possible to provide an ink-jet ink composition, a manufacturing method thereof, and an ink-jet recording method capable of printing dots with a high density and little bleeding over a long period of time stably and at high speed.

The present invention is described in detail below.
[Color material]
The coloring material is not particularly limited, and all commercially available organic pigments and inorganic pigments, or those in which pigments are dispersed in a resin that is insoluble in a dispersion medium, or the resin is grafted onto the pigment surface. Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Specific examples of organic pigments and inorganic pigments include, for example, C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. Monoazo pigments such as CI Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as CI Pigment Yellow 17; I. Non-benzidine azo pigments such as CI Pigment Yellow 180; I. An azo lake pigment such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow, etc.).

  As a magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as CI Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as CI Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G ′ lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Quinacridone pigments such as C.I. Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as C.I. Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting a cyan color, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (such as Viclotia Pure Blue BO Lake); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

Examples of black pigments include organic pigments such as aniline black pigments such as BK-1 (aniline black), iron oxide pigments, and carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. . Specific examples of the carbon black pigment include MA-8, MA-10, MA-11, MA-100, MA-220, # 25, # 40, # 260, # 2600, # 2700B, manufactured by Mitsubishi Chemical Corporation. # 3230B, CF-9, MA-100R, MA-200RB, Degussa Printex 75, 90, Cabot Monarch 800, 1100, and the like.
Also, metal powder can be used for color reproduction of gold, silver, copper and the like.

  In addition, a processed pigment in which pigment fine particles are dispersed in a rosin ester resin, vinyl chloride-vinyl acetate resin, or the like is commercially available and may be used. Specific examples of commercially available processed pigments include microlith pigments manufactured by Ciba Specialty Chemicals, and preferred examples of processed pigments include Microlith-T pigments in which the pigment is coated with a rosin ester resin.

[Resin component]
Next, the resin component will be described. The resin component of the present invention is preferably a resin that is insoluble in the nonaqueous solvent described later. As the resin insoluble in the nonaqueous solvent, various known natural or synthetic resins can be used. For example, there are acrylic resin, epoxy resin, polyester resin, ethylene-vinyl acetate resin, vinyl chloride-vinyl acetate resin, styrene-butadiene resin, styrene-acrylic resin and the like. As a method for dispersing the pigments in these resins, various known methods such as those found in the production process of electrophotographic toner may be used.
In addition, colorant particles coated with a commercially available resin can be used, and specific examples include Microlith-T pigment in which the pigment is coated with the above-mentioned rosin ester resin.

  As a preferable resin, a resin having a function of adsorbing to a pigment and being well dispersed in a non-aqueous solvent, a part that is solvated in a solvent, a part that is difficult to solvate in a solvent, and a part that has a polar group Is preferred. For example, examples of the monomer that solvates with a solvent after polymerization include lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, and cetyl methacrylate. Examples of monomers that are difficult to solvate with the solvent after polymerization include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, styrene, and vinyl toluene. Monomers containing polar groups include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, styrene sulfonic acid or alkali salts thereof, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, vinyl pyridine, vinyl Examples include basic group monomers such as pyrrolidine, vinylpiperidine, and vinyllactam.

[Preparation of colored admixture (A)]
A process of making a colored admixture by mixing a coloring material such as a pigment and a resin insoluble in a non-aqueous solvent will be described. The colored mixture is prepared by the following method, for example.

(1) A method of obtaining a colored mixture by melting and kneading a pigment or the like (coloring material) and a resin at a temperature equal to or higher than the softening point of the resin using a kneader such as a roll mill, a Banbury mixer, or a kneader, and pulverizing after cooling. .
(2) Dissolve the resin in a solvent, add a coloring material, and wet disperse with a ball mill, attritor, sand grinder, etc., and evaporate the solvent to obtain a colored mixture, or disperse the non-solvent of the resin A method in which the mixture is poured and precipitated to obtain an admixture, and then dried to obtain a colored admixture.
(3) A method in which a water-containing pigment paste (wet cake) is kneaded with a resin or a resin solution by a flushing method, water is replaced with a resin or a resin solution, and then the water and the solvent are dried under reduced pressure to obtain a colored mixture.

[Water-based auxiliary]
The aqueous auxiliary component (B) is a water-soluble compound, and preferable examples thereof include water-soluble polymer compounds (polyvinyl alcohol, polyacrylamide, polyacrylic acid, gelatin, starch, etc.) and water-soluble oligomers (oligosaccharides). Of these, oligosaccharides are more preferred. Hereinafter, an oligosaccharide will be described as an example.

The oligosaccharide (B ₁ ) may exhibit a melting point or softening point at a temperature higher than the heat distortion temperature of the resin component, or may be decomposed. For example, the melting point or softening point of the oligosaccharide (B ₁ ) may be higher than the heat distortion temperature of the colored mixture (A), for example, about 90 to 290 ° C. In addition, the oligosaccharide (B ₁ ) may be an oligosaccharide that does not exhibit a clear melting point or softening point at a temperature higher than the thermal deformation temperature of the colored admixture (A) and decomposes thermally. The thermal deformation temperature of the colored mixture may be measured, for example, as the Vicat softening point specified in JIS K 7206, and the thermal deformation temperature (Vicat softening point) of the colored mixture is, for example, 60 to 300 ° C., preferably May be about 80 to 260 ° C.). The oligosaccharide (B ₁ ) may be composed of disaccharides, trisaccharides, tetrasaccharides, pentasaccharides, hexasaccharides, heptasaccharides, octasaccharides, nine saccharides, decasaccharides, or at least tetrasaccharides. Good. The oligosaccharide (B ₁ ) may be composed of a tetrasaccharide such as malotetraose, isomaltotetraose, stachyose, cellotetraose, scorotose, liquinose, or tetraose in which sugar or sugar alcohol is bound to the reducing end of panose. . The oligosaccharide (B ₁ ) may be composed of an oligosaccharide composition such as starch sugar, galactooligosaccharide, coupling sugar, fructo-oligosaccharide, xylo-oligosaccharide, soybean oligosaccharide, chitin oligosaccharide, chitosan oligosaccharide, the content of tetrasaccharides in such oligosaccharides (B ₁₎ may be 60 mass% or more. The viscosity of the 50% by mass aqueous solution of the oligosaccharide (B ₁ ) may be 1 Pa · s or more (for example, about 3 to 100 Pa · s) when measured with a B-type viscometer at a temperature of 25 ° C.

Furthermore, the aqueous auxiliary component (B) may contain a water-soluble plasticizing component (B ₂ ) for plasticizing the oligosaccharide (B ₁ ). When the oligosaccharide (B ₁ ) and the plasticizing component (B ₂ ) are combined, even if the oligosaccharide (B ₁ ) is an oligosaccharide that is thermally decomposed, it can be effectively plasticized or softened. The melting point or softening point of the plasticizing component (B ₂ ) may be equal to or lower than the heat distortion temperature (the Vicat softening point) of the colored mixture (A). Further, when the melt flow rate defined in JIS K 7210 was measured at a temperature 30 ° C. higher than the heat distortion temperature of the colored admixture (A), the oligosaccharide (B ₁ ) and the plasticizing component (B ₂ ) 1 or more (for example, about 1-40) may be sufficient as the melt flow rate of the comprised aqueous | water-based adjuvant component (B), for example. The plasticizing component (B ₂ ) may be composed of saccharides (for example, monosaccharides, disaccharides, etc.), sugar alcohols, etc., and such saccharides may be composed of reducing sugars. The monosaccharide may be composed of triose, tetrose, pentose, hexose, heptose, octose, nonose, decose, dodecose, etc., and the disaccharide may be composed of homo- and heterodisaccharides of the monosaccharide. Sugar alcohols include tetritol (eg, erythritol), pentitol (eg, pentaerythritol, arabitol, ribitol, xylitol, etc.), hexitol (eg, sorbitol, dulcitol, mannitol, etc.), heptitol, octitol, nonitol, dexitol, doditol, etc. You may comprise. The ratio of the colored admixture (A) and the aqueous auxiliary component (B) is: colored admixture (A) / aqueous auxiliary component (B) = 99/1 to 1/99 (mass ratio). In the aqueous auxiliary component (B), the ratio of the oligosaccharide (B ₁ ) and the plasticizing component (B ₂ ) is as follows: oligosaccharide (B ₁ ) / plasticizing component (B ₂ ) = 99/1 It may be 50/50 (mass ratio).

In order to effectively disperse the colored admixture (A) and the aqueous auxiliary component (B) by kneading, it is desirable that the oligosaccharide (B ₁ ) has a high viscosity. Specifically, when measured at a temperature of 25 ° C. using a B-type viscometer, the viscosity of a 50% by mass aqueous solution of oligosaccharide (B ₁ ) is 1 Pa · s or more (eg, about ₁ to 500 Pa · s), Preferably 2 Pa · s or more (for example, 2 to 250 P
a · s, particularly about 3 to 100 Pa · s), more preferably 4 Pa · s or more (for example, about 4 to 50 Pa · s), particularly 6 Pa · s or more (for example, about 6 to 50 Pa · s), and high It is desirable to use viscosity oligosaccharides.

In addition, the melting point or softening point of the oligosaccharide (B ₁ ) is preferably higher than the heat distortion temperature of the colored admixture (A) (for example, the Vicat softening point defined in JIS K 7206). In addition, depending on the type of oligosaccharide [for example, starch sugar such as reduced starch saccharified product], it does not show melting point or softening point and may be thermally decomposed. In such a case, the decomposition temperature may be the “melting point or softening point” of the oligosaccharide (B ₁ ).

The temperature difference between the melting point or softening point of the oligosaccharide (B ₁ ) and the heat distortion temperature of the colored admixture (A) is, for example, 1 ° C. or higher (for example, about 1 to 80 ° C.), preferably 10 ° C. or higher ( For example, it is about 10-70 degreeC, More preferably, it is 15 degreeC or more (for example, about 15-60 degreeC). The melting point or softening point of the oligosaccharide (B ₁ ) can be selected in the range of 70 to 300 ° C. depending on the type of the colored admixture (A), for example, 90 to 290 ° C., preferably 100 to 280 ° C. ( For example, it may be about 110 to 270 ° C., more preferably about 120 to 260 ° C. (for example, 130 to 260 ° C.). In general, an oligosaccharide anhydride exhibits a high melting point or softening point. For example, in the case of trehalose, the melting point of dihydrate is 97 ° C, while the melting point of anhydride is 203 ° C. When the melting point or softening point of the oligosaccharide is higher than the heat distortion temperature of the colored admixture (A), it is possible not only to prevent a rapid viscosity drop of the oligosaccharide during melt-kneading but also to suppress thermal degradation of the oligosaccharide.

The plasticizing component (B ₂ ) may be liquid (syrup-like) at normal temperature (for example, about 15 to 20 ° C.), but usually it is often a solid from the viewpoint of handleability. When the aqueous auxiliary component (B) is composed of an oligosaccharide (B ₁ ) and a plasticizing component (B ₂ ), the oligosaccharide (B ₁ ) is a thermally decomposable oligosaccharide that does not exhibit a clear melting point or softening point. However, it can be effectively plasticized or softened.

The melting point or softening point of the plasticizing component (B ₂ ) is usually not higher than the heat distortion temperature of the colored admixture (A) (for example, the Vicat softening point defined by JIS K 7206). Note that some plasticizing components have a high melting point (for example, 200 ° C. or higher) and melt at a temperature lower than the actual melting point when coexisting with the oligosaccharide. For example, pentaerythritol exhibits a plasticizing effect on oligosaccharides at a temperature lower than the actual melting point (260 ° C.) (for example, about 160 to 180 ° C.), and itself is in a molten state. Such a high melting point plasticizing component cannot be used because it does not melt at the heat distortion temperature of the resin component alone, but can be effectively used in combination with an oligosaccharide. In addition, in a plasticizing component that exhibits a plasticizing effect on oligosaccharides at a temperature lower than the actual melting point (for example, pentaerythritol, etc.), the temperature at which the plasticizing effect is exerted on oligosaccharides is set at the plasticizing component (B ₂ ) "Melting point or softening point".

  The melting point or softening point of the aqueous auxiliary component (B) may be equal to or higher than the heat distortion temperature of the colored admixture (A), and may be as follows. The colored admixture (A) and the aqueous auxiliary component (B) may be melted or softened at least at the kneading temperature (or molding processing temperature). For example, the temperature difference between the melting point or softening point of the aqueous auxiliary component (B) and the heat distortion temperature of the colored mixture (A) may be selected in the range of 0 to 100 ° C., for example, 3 to 80 It may be about 5 ° C (for example, 3 to 55 ° C), preferably 5 to 60 ° C (for example, 5 to 45 ° C), and more preferably about 5 to 40 ° C (for example, 10 to 35 ° C). When the temperature difference between the melting point or softening point of the aqueous auxiliary component (B) and the heat distortion temperature of the colored admixture (A) is small (for example, when the temperature difference is about 0 to 20 ° C.), it is solidified. There is an advantage that the dispersed form can be fixed in a short time by the aqueous auxiliary component (B) (for example, sugar component) having a high speed.

Further, the melt flow rate of the aqueous auxiliary component (B) (for example, the auxiliary component including the oligosaccharide (B ₁ ) and the plasticizing component (B ₂ )) is, for example, the heat distortion temperature (for example, the resin component) When the melt flow rate specified by JIS K 7210 is measured at a temperature 30 ° C. higher than the Vicat softening point), it is 1 or more (for example, about 1 to 40), preferably 5 or more (for example, about 5 to 30), More preferably, it may be 10 or more (for example, about 10 to 20).

In the aqueous auxiliary component (B), the proportion (mass ratio) of the plasticizing component (B ₂ ) is not localized due to aggregation or the like with the melt kneading, and the oligosaccharide (B ₁ ) An amount that can be efficiently plasticized, for example, oligosaccharide (B ₁ ) / plasticizing component (B ₂ ) = 99/1 to 50/50, preferably 95/5 to 60/40, more preferably 90 It is about / 10 to 70/30.

  The compatibility of the colored admixture (A) and the aqueous auxiliary component (B) is not particularly limited, and may be incompatible or compatible. When the color mixture (A) and the aqueous auxiliary component (B) are compatible, the color mixture (A) and the aqueous auxiliary component (B) may form a uniform single phase at the kneading temperature. In the cooling process after kneading, the colored admixture (A) and the aqueous auxiliary component (B) can be phase-separated by the difference in both surface tension and solidification rate. The reason why the colored admixture (A) and the aqueous auxiliary component (B) can be phase-separated even when the colored admixture (A) and the aqueous auxiliary component (B) are compatible with each other is as follows. The auxiliary component (B) has a low surface tension, can maintain a relatively high viscosity even at the kneading temperature with the colored admixture (A), and has a low molecular weight, so that the solidification rate during cooling is a resin component. It has a unique physical property that is extremely fast compared to the above.

  The ratio (mass ratio) between the colored admixture (A) and the aqueous auxiliary component (B) is the type and viscosity of the resin component and auxiliary component, the colored admixture (A) and the aqueous auxiliary component (B). Although it can be selected according to the compatibility and the like and is not particularly limited, it can be generally selected from a wide range of, for example, a color mixture (A) / aqueous auxiliary component (B) = 99/1 to 1/99, for example, 90/10 to 5/95, preferably 80/20 to 10/90 (for example, 80/20 to 15/85), more preferably 75/25 to 25/75 (especially 60/40 to 25/75) Degree.

[Other additives]
A dispersion is obtained by mixing the colored admixture (A) and the aqueous auxiliary component (B), and various additives such as fillers, plasticizers, or the like can be added to the dispersion as necessary. Contains softeners, lubricants, stabilizers (thermal stabilizers, antioxidants, UV absorbers), thickeners, colorants (titanium oxide, carbon black, etc.), dispersants, flame retardants, antistatic agents, etc. Also good.

  Examples of the filler (or reinforcing agent) include a granular filler or reinforcing agent (mica, clay, talc, silicic acid, silica, calcium carbonate, magnesium carbonate, carbon black, ferrite, etc.), fibrous filler or reinforcing agent ( Organic fibers such as rayon, nylon, vinylon, and aramid, and inorganic fibers such as carbon fiber, glass fiber, metal fiber, and whisker).

  Each of these additives may be an effective amount. For example, the total amount of the additive is about 0 to 50 parts by mass, preferably about 0.1 to 20 parts by mass with respect to 100 parts by mass of the resin component. Preferably, it may be about 0.5 to 10 parts by mass. Each additive may be about 0 to 30 parts by mass, preferably about 0.05 to 20 parts by mass, and more preferably about 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin component. .

In the dispersion of the present invention, the phase separation structure and the dispersion structure are not particularly limited, and the resin component and the auxiliary component may form a sea-island structure or a composite dispersed phase structure, and both components have a continuous phase. It may be formed. When the aqueous auxiliary component (B) forms a continuous phase in the sea-island structure (phase separation structure in which the resin phase is independent) or a co-continuous phase, the auxiliary component can be quickly eluted.

  When the aqueous auxiliary component (B) forms a continuous phase in the sea-island structure, the shape of the dispersed phase composed of the resin component is particulate (for example, spherical, elliptical, polygonal, prismatic) , Columnar shape, rod shape, indefinite shape, etc.). A preferable dispersed phase has a spherical shape. The average particle size of the dispersed phase is not particularly limited, and can be selected from the range of about 0.1 μm to 1 mm depending on the application, and is, for example, 0.1 to 800 μm (for example, 0.1 to 500 μm), preferably 0. It is about 1-100 micrometers (for example, 0.5-80 micrometers), More preferably, it is about 0.5-50 micrometers (for example, 1-40 micrometers).

[Method for producing dispersion]
Next, a method for producing a dispersion from the colored admixture (A) and the aqueous auxiliary component (B) will be described.

  The dispersion can be prepared by kneading the colored admixture (A) and the aqueous auxiliary component (B). Usually, the kneaded composition is molded to prepare a preform. The kneading can be performed using a conventional kneader (for example, a single or twin screw extruder, a kneader, a calender roll, etc.). The kneading time may be selected, for example, from the range of 10 seconds to 1 hour, and is usually about 30 seconds to 45 minutes, preferably about 1 to 30 minutes (for example, 1 to 10 minutes). Prior to kneading, the colored admixture (A) and the aqueous auxiliary component (B) may be preliminarily processed into a powder form with a freeze pulverizer or the like, or premixed with a Henschel mixer, a tumble mixer, a ball mill, or the like. Good.

  Examples of the molding method include extrusion molding, injection molding, blow molding, calendar molding, and the like. Usually, extrusion molding or injection molding is used from the viewpoint of productivity and ease of processing. The shape of the preform is not particularly limited, and is a zero-dimensional shape (such as granular or pellet), a one-dimensional shape (such as a strand or rod), or a two-dimensional shape (such as a plate, sheet, or film). ) It may be a three-dimensional shape (tubular, block shape, etc.). In consideration of the dissolution property of the aqueous auxiliary component (B), it is desirable to process into a strand shape, a rod shape, a sheet shape, or a film shape. Further, the preform may be processed by laminating other base materials in the molding process.

  The kneading temperature and the molding processing temperature can be appropriately set according to the raw materials used (for example, the resin component and the aqueous auxiliary component), and are, for example, 90 to 300 ° C., preferably 110 to 260 ° C. More preferably, it is about 140-240 degreeC (for example, 170-240 degreeC), especially about 170-230 degreeC (for example, 180-220 degreeC). In order to avoid thermal decomposition of the aqueous auxiliary component (B), the kneading temperature and the molding processing temperature may be 230 ° C. or lower.

The dispersion may be formed by appropriately cooling a melt (for example, a kneaded product or a preformed product) after kneading and / or molding. For example, the cooling temperature may be at least about 10 ° C. lower than the heat distortion temperature of the colored admixture (A) or the melting point or softening point of the aqueous auxiliary component (B). The temperature at which the product (A) is heat-deformed or the melting point or softening point of the aqueous auxiliary component (B) is about 10 to 100 ° C., preferably about 15 to 80 ° C., more preferably the temperature. The temperature may be lower by about 20 to 60 ° C. Specifically, for example, the cooling temperature can be selected from a range of 5 to 150 ° C. according to the type of the colored admixture (A) or the aqueous auxiliary component (B), for example, 10 to 120 ° C. (for example, 10 ~ 60 ° C), preferably 15-100 ° C (eg, 15-50 ° C), more preferably about 20-80 ° C (eg, 20-40 ° C). The cooling time can be appropriately set according to the type of the color admixture (A) and the aqueous auxiliary component (B), the cooling temperature, etc., and may be selected from a wide range of 30 seconds to 20 hours, for example, It may be 45 seconds to 10 hours, preferably 1 minute to 5 hours (for example, 1 minute to 1 hour), more preferably about 1.5 to 30 minutes. Even if the colored admixture (A) and the aqueous auxiliary component (B) are compatible with each other by cooling, a dispersion system can be formed in the cooling step due to differences in the solidification rate such as surface tension and crystallization, A dispersion can be obtained.

  When producing colorant particles, the compatibility of the colored admixture (A) with the aqueous auxiliary component (B), the melt viscosity of the colored admixture (A) and the aqueous auxiliary component (B), kneading conditions (for example, By adjusting the kneading time, kneading temperature, etc.), molding processing temperature and cooling conditions (for example, cooling time, cooling temperature, etc.), the average particle diameter of the particles can be changed, and the particle size distribution width is narrow and uniform. Particles having a particle size can be easily obtained.

  The average particle diameter of the color material particles is not particularly limited, and is preferably in the range of about 0.1 μm to 10 μm, more preferably 0.3 to 5 μm, and preferably 0.5 to 3 μm.

  The variation coefficient of the particle diameter ([standard deviation of particle diameter / average particle diameter] × 100) is 60 or less (for example, about 5 to 60), more preferably 50 or less (for example, about 10 to 50).

[Process for producing colorant particles]
A method for producing the colorant particles (C) by eluting the aqueous auxiliary component (B) from the dispersion will be described.
The dispersion obtained as described above is immersed in a solvent [water, a water-soluble solvent (for example, alcohols (methanol, ethanol, propanol, isopropanol, butanol, etc.), ethers (cellosolve, butyl cellosolve, etc.), etc.). Then, the aqueous auxiliary component (B) can be eluted or washed to obtain the colorant particles (C), since the environmental load is small and the industrial cost can be reduced, water is preferable as the solvent. The elution of the agent component (B) can be carried out using a conventional method, for example, under normal pressure (for example, about 1 atm or 100,000 Pa), under reduced pressure, or under pressure. Can be appropriately set according to the components of the dispersion, for example, 10 to 100 ° C., preferably 25 to 90 ° C., more preferably 30 to 80 ° C. (for example, 40 to 80 ° C.). Every time it is.

  The colorant particles can be recovered using a recovery method such as filtration or centrifugation. In the obtained molded product, it is desirable that the aqueous auxiliary component (B) does not remain, but the aqueous composition is used in a range that does not affect the performance from the viewpoint of charge stability and storage stability of the ink composition. A small amount of the auxiliary component (B) may remain in the colorant particles.

[Non-aqueous solvent]
The non-aqueous solvent used in the present invention is preferably a non-polar insulating solvent having a relative dielectric constant of 1.5 to 20 and a surface tension of 15 to 60 mN / m (at 25 ° C.), having low toxicity and flammability. It is good to have less odor and less odor. Examples of such non-aqueous solvents include solvents selected from linear or branched aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, petroleum naphtha, halogen substitution products thereof, and the like. It is done. For example, hexane, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, Isopar E from Exxon, Isopar G, Isopar H, Isopar L, Saltol from Philippe Petroleum, IP Solvent from Idemitsu Petrochemical, Petroleum Naphtha Then, S. of Shell Petrochemical Co., Ltd. B. R. A solvent selected from Shellzol 70, Shellzol 71, Mobil Petroleum Begazole, etc. is used alone or in combination.

Preferred hydrocarbon solvents include high-purity isoparaffinic hydrocarbons having a boiling point in the range of 150 to 350 ° C., and commercially available products such as Isopar G, manufactured by Exxon Chemical Co., Ltd.
H, L, M, V (trade name), Noper 12, 13, 15 (trade name), IP solvent 1620, 2028 (trade name) made by Idemitsu Petrochemical, Isosol 300, 400 made by Nippon Petrochemical (trade name) ), Amsco OMS, Amsco 460 solvent (Amsco; trade name of Spirits), and the like. These products are highly saturated aliphatic saturated hydrocarbons, the viscosity at 25 ° C. is 3 cSt or less, the surface tension at 25 ° C. is 22.5 to 28.0 mN / m, and the specific resistance at 25 ° C. is 10 ¹⁰ Ω. -It is cm or more. In addition, it is characterized by low reactivity and stability, low toxicity, high safety, and low odor.
There is a fluorocarbon solvent as a halogen-substituted hydrocarbon solvent, for example, C ₇ F ₁₆
Perfluoroalkanes represented by C _n F _{2n + 2} such as C ₈ F ₁₈ (Sumitomo 3M “Fluorinert PF5080”, “Fluorinert PF5070” (trade name), etc.), fluorine-based inert liquid (Sumitomo 3M) "Fluorinert FC series" (trade name), etc.), fluorocarbons ("Crytox GPL series" (trade name), etc., manufactured by DuPont Japan Limited), CFCs ("HCFC-141b", manufactured by Daikin Industries, Ltd.) Name), etc.), iodinated fluorocarbons such as [F (CF ₂ ) ₄ H ₂ CH ₂ I], [F (CF ₂ ) ₆ I] (“I-1420”, “I-1600 manufactured by Daikin Fine Chemical Laboratory) (Product name) etc.).

As the non-aqueous solvent used in the present invention, higher fatty acid esters and silicone oil can also be used. Specific examples of silicone oil include low-viscosity synthetic dimethylpolysiloxane, and commercially available products include KF96L (trade name) manufactured by Shin-Etsu Silicone, SH200 (trade name) manufactured by Toray Dow Corning Silicone, and the like. .
The silicone oil is not limited to these specific examples. These dimethylpolysiloxanes are available in a very wide viscosity range depending on the molecular weight, but it is preferable to use those in the range of 1 to 20 cSt. These dimethylpolysiloxanes, like isoparaffinic hydrocarbons, have a volume resistivity of 10 ¹⁰ Ω · cm or more, and are characterized by high stability, high safety, and odorlessness. These dimethylpolysiloxanes are characterized by low surface tension and have a surface tension of 18 to 21 mN / m.

  Solvents that can be used in combination with these organic solvents include alcohols (eg, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, fluorinated alcohol), ketones (eg, acetone, methyl ethyl ketone, cyclohexanone, etc.), carvone Acid esters (eg, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.), ethers (eg, diethyl ether, dipropyl ether, tetrahydrofuran, dioxane, etc.) and halogenated hydrocarbons ( Examples thereof include methylene dichloride, chloroform, carbon tetrachloride, dichloroethane, methyl chloroform, and the like.

[Dispersant]
As the dispersant used in the present invention, a general pigment dispersant applied in the non-aqueous solvent can be used.
For example, any dispersant may be used as long as it is compatible with the non-aqueous solvent and can stably disperse fine particles of pigments. Specific examples include sorbitan fatty acid esters (sorbitan monooleate, sorbitan monolaurate, sorbitan sesquioleate, sorbitan trioleate, etc.), polyoxyethylene sorbitan fatty acid esters (polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan). Monooleate, etc.), polyethylene glycol fatty acid esters (polyoxyethylene monostearate, polyethylene glycol diisostearate, etc.), polyoxyethylene alkyl phenyl ethers (polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, etc.), Nonionic surfactants such as aliphatic diethanolamides and polymer dispersants include polymer compounds having a molecular weight of 1000 or more. For example, styrene-maleic acid resin, styrene-acrylic resin, rosin, BYK-160, 162, 164, 182 (urethane polymer compound manufactured by Big Chemie), EFKA-47, LP-4050 (manufactured by EFKA) Urethane dispersant), Solsperse 24000 (polyester polymer compound manufactured by Zeneca), Solsperse 17000 (aliphatic diethanolamide from Zeneca), and the like.

  In addition to the above, the polymeric dispersants include monomers such as lauryl methacrylate, stearyl methacrylate, 2-ethylhexyl methacrylate, and cetyl methacrylate that are solvated in a solvent, and methyl methacrylate, ethyl methacrylate, and isopropyl methacrylate that are difficult to solvate in a solvent. , A random copolymer comprising a monomer having a polar group and a monomer such as styrene and vinyltoluene, or a graft copolymer disclosed in JP-A-3-188469. Examples of the monomer containing a polar group include an acidic group monomer such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, styrene sulfonic acid or an alkali salt thereof, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and vinylpyridine. And basic group monomers such as vinylpyrrolidine, vinylpiperidine, and vinyllactam. In addition to this, a styrene-butadiene copolymer, a block copolymer of styrene and a long-chain alkyl methacrylate disclosed in JP-A-60-10263, and disclosed in JP-A-6-95436. Examples thereof include block copolymers. Further, it is soluble in the graft copolymer disclosed in JP-A-4-350669 and JP-A-5-188657, or in the non-aqueous solvent containing a graft group disclosed in JP-A-11-43638. Random copolymers, partially crosslinked polymers disclosed in JP-A-10-316920, partially crosslinked polymers containing graft groups at the main chain ends disclosed in JP-A-10-316920, etc. As an agent. Preferred examples of the dispersant for pigment include graft copolymers disclosed in JP-A-3-188469, JP-A-4-350669, and JP-A-5-188657. However, the pigment dispersant is not limited to these.

As for the usage-amount of the dispersing agent used at a dispersion treatment process, 5-50 mass parts is preferable with respect to 100 mass parts of color material particles. A more preferable amount of the dispersant is 5 to 40 parts by mass, and a particularly preferable amount is 5 to 30 parts by mass with respect to 100 parts by mass of the colorant particles.
In the present invention, the concentration of the coloring material (pigment) is preferably 0.5 to 20% by mass, particularly preferably 2 to 15% by mass, based on the total amount of the ink composition. A sufficient printing density can be obtained by setting the density of the color material to 0.5% by mass or more. Further, when the concentration of the color material is 20% by mass or less, stable ink ejection can be performed without significantly increasing the viscosity of the ink composition.

  There is no restriction | limiting in particular as a disperser used at a dispersion | distribution process, A commercially available rotary stirring and mixing apparatus, a shaking type stirring and mixing apparatus, an ultrasonic disperser, a homogenizer, and a wet disperser can be used. For example, a ball mill, a sand mill, an attritor, etc., and a sealed type is generally used to prevent evaporation of the solvent. Sand mills have a vertical type and a horizontal type, and are dispersed by rotating a shaft on which a disk or a pin is attached at a peripheral speed of 3 to 15 m / s. By arranging several continuous sand mills in series and changing the diameter of the media according to the degree of dispersion, the ink composition can be efficiently produced. Further, when a pigment having a large particle size is dispersed by a continuous sand mill, pre-dispersion is required. In this case, a disperser, a ball mill, a batch sand mill, or the like is used as a pre-dispersing machine. Among these dispersers, from the standpoint of maintaining a particle shape and obtaining a stable dispersion, those that do not use a dispersion medium are preferable. A rotary rotary stirring and mixing device, a shaking type stirring and mixing device, an ultrasonic type A disperser and a homogenizer are preferable, and an ultrasonic disperser is more preferable.

[Charge control agent]
Next, as a charge control agent that can be used in the present invention, conventionally known charge control agents can be used. For example, metal salts of fatty acids such as naphthenic acid, octenoic acid, oleic acid, stearic acid, metal salts of sulfosuccinic acid esters, Japanese Patent Publication No. 45-556, Japanese Patent Publication No. 52-37435, Japanese Patent Publication No. 52-37049 Oil-soluble sulfonic acid metal salts disclosed in Japanese Patent Publication No. 45-9594, phosphoric acid ester metal salts disclosed in Japanese Patent Publication No. 45-9594, abietic acid or hydrogenated abietin disclosed in Japanese Patent Publication No. 48-25666 Metal salts of acids, alkylbenzene sulfonic acid Ca salts disclosed in Japanese Patent Publication No. 55-2620, JP-A 52-107837, 52-38937, 57-90643, and 57-139753 Nonionics such as aromatic carboxylic or sulfonic acid metal salts, polyoxyethylated alkylamines, etc. Surfactant, fats and oils such as lecithin and linseed oil, polyvinyl pyrrolidone, organic acid ester of polyhydric alcohol, phosphate ester type surfactant disclosed in JP-A-57-210345, JP-B-56-24944 The sulfonic acid resin etc. which are shown by the gazette can be used. In addition, amino acid derivatives described in JP-A-60-21056 and 61-50951 can also be used. Moreover, the copolymer etc. which contain the maleic acid half amide component described in each gazette of Unexamined-Japanese-Patent No. 60-173558 and 60-179750 are mentioned. Further, quaternized amine polymers described in JP-A-54-31739 and JP-B-56-24944 can be given.

  Among these, preferred are a metal salt of naphthenic acid, a metal salt of dioctylsulfosuccinic acid, a copolymer containing the maleic acid half amide component, lecithin, and the amino acid derivative. As these charge control agents, two or more compounds can be used in combination. The concentration of the charge control agent as described above is preferably in the range of 0.0001 to 2.0 mass% with respect to the total amount of ink. By increasing the concentration of the charge control agent to more than 0.0001% by mass, high specific conductivity can be imparted to the colorant particles, and by setting the concentration to 2.0% by mass or less, the volume resistivity of the ink is lowered. Therefore, the necessary print density can be maintained.

  The basic constituent materials in the present invention are as described above, but various additives may be added to the ink composition of the present invention as desired. The ink composition is arbitrarily selected depending on the material and structure of the ink jet system or the ink jet discharge head, the ink supply unit, and the ink circulation unit, and is contained as an ink composition. For example, additives described in Takeshi Amari “Inkjet Printer Technology and Materials”, Chapter 17, published by CMC Co., Ltd. (1998) are used.

Specifically, fatty acids (for example, C6-C32 monocarboxylic acid, polybasic acid; for example, 2-ethylhexynoic acid, dodecenyl succinic acid, butyl succinic acid, 2-ethylcaproic acid, lauric acid, palmitic acid, elaidin Acid, linolenic acid, ricinoleic acid, oleic acid, stearic acid, enanthic acid, naphthenic acid, ethylenediaminetetraacetic acid, abietic acid, dehydroabietic acid, hydrogenated rosin etc.), resin acid, alkylphthalic acid, alkylsalicylic acid, etc. (As metals of metal ions, Na, K, Li, B, Al, Ti, Ca, Pb, Mn, Co, Zn, Mg, Ce, Ag, Zr, Cu, Fe, Ba, etc.), surface active compounds (For example, as an organic phosphoric acid or a salt thereof, a mono-, di- or trialkylphosphorus composed of an alkyl group having 3 to 18 carbon atoms Organic sulfonic acids or salts thereof such as long chain aliphatic sulfonic acids, long chain alkylbenzene sulfonic acids, dialkylsulfosuccinic acids, etc. or metal salts thereof, amphoteric surface active compounds such as phospholipids such as lecithin and kephalin) , Alkyl group-containing surfactants containing fluorine atoms and / or dialkylsiloxane bonding groups, aliphatic alcohols (for example, higher alcohols comprising branched alkyl groups having 9 to 20 carbon atoms, benzyl alcohol, phenethyl alcohol) Cyclohexyl alcohol, etc.), polyhydric alcohols {for example, alkylene glycols having 2 to 18 carbon atoms (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-he Sundiol, dodecanediol, etc.)}; alkylene ether glycols having 4 to 1000 carbon atoms (diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); fats having 5 to 18 carbon atoms Cyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); C12-C23 bisphenols (bisphenol A, bisphenol F, bisphenol S, etc.) C2-C18 alkylene oxides (ethylene oxide) , Propylene oxide, butylene oxide, α-olefin oxide, etc.) adducts, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol Polyols such as sorbitol; trihydric to octahydric or higher phenols (trisphenol PA, phenol novolac, cresol novolac, etc.); C2-C18 alkylene oxide adducts (additions) of the above trivalent or higher polyphenols 2-20), polyhydric alcohol ether derivatives (polyglycol alkyl ethers, alkylaryl polyglycol ethers, etc.), polyhydric alcohol fatty acid ester derivatives, polyhydric alcohol ether oleate derivatives (eg, ethylene glycol) Monoethyl acetate, diethylene glycol monobutyl acetate, propylene glycol monobutyl propiolate, sorbitan monomethyl dioxalto), alkyl naphthalene sulfonate, alkyl aryl sulfonate It compounds such bets, and the like, but not limited thereto. The amount of each additive used is preferably adjusted so that the surface tension of the ink composition is 15 to 60 mN / m (at 25 ° C.) and the viscosity is 1.0 to 40 cP.

The ink composition obtained in the present invention is particularly useful as an ink for an electrostatic ink jet recording apparatus. Any electrostatic ink jet printer can be used without particular limitation as long as it uses ink using color material particles. A preferable example is a color material concentration discharge type electrostatic ink jet printer. In this embodiment, the volume resistivity of the ink composition at 25 ° C. is preferably 10 ⁸ Ω · cm or more, and the particle conductivity in the ink composition is preferably 100 pS / cm or more. By satisfying these conditions, excellent printing performance can be imparted to the ink composition.

[Inkjet recording apparatus]
The ink composition described above is recorded on a recording medium by an ink jet recording method. In the present invention, it is preferable to use an ink jet recording method utilizing an electrostatic field. An ink jet recording method using an electrostatic field concentrates charged particles of an ink composition to an ejection position by an electrostatic force by applying a voltage between a control electrode and a back electrode on the back of a recording medium, and the recording medium from the ejection position It is a method to fly to. For example, when the charged particles are positive, the voltage applied between the control electrode and the back electrode is such that the control electrode is a positive electrode and the back electrode is a negative electrode. The same effect can be obtained by charging the recording medium instead of applying a voltage to the back electrode.

  As a method of flying ink, for example, there is a method of flying ink from a needle-like tip such as an injection needle. By using the ink composition of the present invention, recording in a short time is possible.

  On the other hand, the ink is circulated in the ink chamber having the ejection opening, and is present in the ejection opening by applying a voltage to the control electrode formed at the periphery of the ejection opening, and the ink guide whose tip is directed to the recording medium side. In the method in which the concentrated ink droplets fly from the front end, the supply of charged particles by the circulation of ink and the meniscus stability at the ejection position can be achieved at the same time, so that recording can be performed stably for a long period of time. Further, in this method, since the portion where the ink is in contact with the outside air is very small with only the discharge opening, the evaporation of the solvent is suppressed and the ink physical properties are stabilized, so that it can be suitably used in the present invention.

A configuration example of an ink jet recording apparatus suitable for applying the ink composition of the present invention is shown below.
First, an outline of an apparatus that performs single-sided four-color printing on a recording medium shown in FIG. 1 will be described.
An ink jet recording apparatus 1 shown in FIG. 1 supplies ink to an ejection head 2 composed of ejection heads 2C, 2M, 2Y, and 2K for four colors for forming a full color image. A head driver 4 for driving the ejection head 2 by an output from an external device such as a computer (not shown) or a RIP, and a position control means 5. Further, the ink jet recording apparatus 1 includes a transport belt 7 stretched around three rollers 6A, 6B, and 6C, a transport belt position detection unit 8 including an optical sensor that can detect the position of the transport belt 7 in the width direction, An electrostatic attraction unit 9 for holding the recording medium P on the conveyance belt, a static elimination unit 10 and a mechanical unit 11 for peeling the recording medium P from the conveyance belt 7 after completion of image formation are provided. Upstream and downstream of the conveying belt 7, the feed roller 12 and the guide 13 that supply the recording medium P from the stocker (not shown) to the conveying belt 7, the ink is fixed to the recording medium P after peeling, and the discharge stocker (not shown). A fixing unit 14 and a guide 15 are arranged to be conveyed. In addition, the inkjet printing apparatus 1 has a recording medium position detecting means 16 at a position facing the ejection head 2 with the conveyance belt 7 interposed therebetween, and further collects the solvent vapor generated from the ink composition. A solvent recovery unit comprising the exhaust fan 17 and the solvent vapor adsorbent 18 is disposed, and the vapor inside the apparatus is discharged outside the apparatus through the recovery unit.

  A known roller can be used as the feed roller 12, and the feed roller 12 is arranged so as to increase the feeding ability to the recording medium. Further, since dirt, paper powder, or the like may adhere on the recording medium P, it is desirable to remove them. The recording medium P supplied by the feed roller is transported to the transport belt 7 through the guide 13. The back surface (preferably metal back surface) of the conveyor belt 7 is installed via a roller 6A. The transported recording medium P is electrostatically attracted onto the transport belt by the electrostatic attracting means 9. In FIG. 1, electrostatic adsorption is performed by a scorotron charger connected to a negative high voltage power source. The recording medium P is electrostatically adsorbed without floating on the transport belt 7 by the electrostatic adsorption means 9 and the surface of the recording medium is uniformly charged. Here, the electrostatic attraction means is also used as a charging means for the recording medium, but may be provided separately. The charged recording medium P is transported to the ejection head portion by the transport belt 7, and electrostatic ink jet image formation is performed by superimposing the recording signal voltage with the charging potential as a bias. The recording medium P on which the image has been formed is discharged by the discharging unit 10, peeled off by the transfer belt 7 by the mechanical unit 11, and transferred to the fixing unit. The peeled recording medium P is sent to the image fixing means 14 and fixed. The fixed recording medium P is discharged through a guide 15 to a discharge stocker (not shown). The apparatus also has a means for recovering the solvent vapor generated from the ink composition. The recovery means is composed of the solvent vapor absorbing material 18, and a gas containing solvent vapor in the apparatus is introduced into the adsorbent by the exhaust fan 17, and after the vapor is adsorbed and recovered, it is exhausted outside the apparatus. The apparatus is not limited to the above example, and the number, shape, relative arrangement, charging polarity, and the like of constituent devices such as rollers and chargers can be arbitrarily selected. In the above system, four-color drawing is described. However, a multicolor system may be combined with light color ink or special color ink.

  The ink jet recording apparatus used in the above ink jet printing method includes an ejection head 2 and an ink circulation system 3. The ink circulation system 3 further includes an ink tank, an ink circulation device, an ink concentration control device, an ink temperature management device, and the like. In addition, the ink tank may include a stirring device.

As the ejection head 2, a single channel head, a multi-channel head, or a full line head can be used, and main scanning is performed by the rotation of the transport belt 7.
An ink jet head suitably used in the present invention is an ink jet method in which charged particles in an ink flow path are electrophoresed to increase the ink density near the opening and discharge, and is mainly a recording medium or a recording target. Ink droplets are ejected by electrostatic attraction caused by the counter electrode disposed on the back surface of the medium. Therefore, if the recording medium or the counter electrode does not face the head, or if no voltage is applied to the recording medium or the counter electrode even at the position facing the head, the voltage is accidentally applied to the ejection electrode. Ink droplets are not ejected even when a pressure is applied or vibration is applied, and the inside of the apparatus is not soiled.

  An ejection head suitably used for the ink jet apparatus is shown in FIGS. As shown in FIGS. 2 and 3, the inkjet head 70 includes an electrically insulating substrate 74 that forms the upper wall of the ink flow path 72 where the ink flow Q in one direction is formed, and the ink to the recording medium P. And a plurality of discharge portions 76 that discharge toward the surface. Each of the ejection portions 76 is provided with an ink guide portion 78 that guides the ink droplet G flying from the ink flow path 72 toward the recording medium P, and the substrate 74 has an opening through which the ink guide portion 78 is inserted. 75 is formed, and the ink meniscus 42 is formed between the ink guide portion 78 and the inner wall surface of the opening 75. The gap d between the ink guide portion 78 and the recording medium P is preferably about 200 μm to 1000 μm. Further, the ink guide part 78 is fixed to the support bar part 40 on the lower end side.

  The substrate 74 includes an insulating layer 44 that electrically isolates two discharge electrodes at a predetermined interval, a first discharge electrode 46 formed above the insulating layer 44, and an insulation that covers the first discharge electrode 46. It has a layer 48, a guard electrode 50 formed on the insulating layer 48, and an insulating layer 52 that covers the guard electrode 50. The substrate 74 includes a second ejection electrode 56 formed below the insulating layer 44 and an insulating layer 58 that covers the second ejection electrode 56. The guard electrode 50 is provided to prevent an electric field from being affected by the voltage applied to the first ejection electrode 46 and the second ejection electrode 56 in an adjacent ejection section.

Further, the ink jet head 70 constitutes the bottom surface of the ink flow path 72, and the ink flow is generated by the induced voltage that is constantly generated by the pulsed discharge voltage applied to the first discharge electrode 46 and the second discharge electrode 56. A floating conductive plate 62 that moves positively charged ink particles (charged particles) R in the path 72 upward (that is, toward the recording medium side) is provided in an electrically floating state. In addition, a coating film 64 that is electrically insulating is formed on the surface of the floating conductive plate 62 to prevent the physical properties and components of the ink from becoming unstable due to charge injection into the ink. The electric resistance of the insulating coating film is preferably 10 ¹² Ω · cm or more, and more preferably 10 ¹³ Ω · cm or more. In addition, the insulating coating film is desirably resistant to corrosion with respect to ink, and this prevents the floating conductive plate 62 from being corroded by ink. Further, the floating conductive plate 62 is covered with the insulating member 66 from below, and the floating conductive plate 62 is completely electrically insulated by such a configuration.

  There are one or more floating conductive plates 62 per head unit (for example, when there are four heads C, M, Y, and K, the number of floating conductive plates is at least one each, and C and M The floating conductive plate is not shared between the head units.

  As shown in FIG. 3, in order to cause ink to fly from the inkjet head 70 and record on the recording medium P, the ink in the ink flow path 72 is circulated to generate an ink flow Q, and the guard electrode A predetermined voltage (for example, +100 V) is applied to 50. Further, a flying electric field that attracts the positive charged particles R in the ink droplet G that has been guided by the ink guide portion 78 and flew from the opening 75 to the recording medium P is generated by the first ejection electrode 46 and the second ejection electrode. A positive voltage is applied to the first ejection electrode 46, the second ejection electrode 56, and the recording medium P so as to be formed between the recording medium P and the recording medium P (1 kV when the gap d is 500 μm). A potential difference of about ~ 3.0 kV is taken as a guide).

In this state, when a pulse voltage is applied to the first ejection electrode 46 and the second ejection electrode 56 in accordance with the image signal, the ink droplet G having an increased charged particle concentration is ejected from the opening 75 (for example, initial charged particles). When the concentration is 3 to 15%, the charged particle concentration of the ink droplet G is 30% or more).
At that time, the ink droplet G is applied to the first ejection electrode 46 and the second ejection electrode 56 so that the ink droplet G is ejected only when the pulse voltage is applied to both the first ejection electrode 46 and the second ejection electrode 56. Adjust the voltage value.

  In this way, when a pulsed positive voltage is applied, the ink droplet G is guided by the ink guide portion 78 from the opening 75 and flies to adhere to the recording medium P, and the first ejection is applied to the floating conductive plate 62. A positive induced voltage is generated by the positive voltage applied to the electrode 46 and the second ejection electrode 56. Even if the voltage applied to the first ejection electrode 46 and the second ejection electrode 56 is pulsed, this induced voltage is a substantially steady voltage. Therefore, the charged particles R that are positively charged in the ink flow path 72 are subjected to the upward movement force by the electric field formed between the floating conductive plate 62 and the guard electrode 50 and the recording medium P, and The concentration of charged particles R increases near the substrate 74. As shown in FIG. 3, when the number of ejection units (that is, channels for ejecting ink droplets) to be used is large, the number of charged particles necessary for ejection increases, but the first ejection electrode 46 and the second ejection electrode to be used are used. Since the number of 56 increases, the induced voltage induced in the floating conductive plate 62 increases, and the number of charged particles R moving to the recording medium side also increases.

  In the above, an example in which the colored particles are positively charged has been described. However, the colored particles may be negatively charged. In that case, all the above-mentioned charging polarities are reversed.

  In the present invention, it is preferable to fix the ink by an appropriate heating means after discharging the ink onto the recording medium. As the heating means used, a contact-type heating device such as a heat roller, a heat block, or a belt heating, and a non-contact type heating device such as a dryer, an infrared lamp, a visible light lamp, an ultraviolet lamp, or a hot air oven may be used. it can. These heating devices are preferably continuous with and integrated with the ink jet recording apparatus. The temperature of the recording medium at the time of fixing is preferably in the range of 40 ° C. to 200 ° C. for ease of fixing. The fixing time is preferably in the range of 1 microsecond to 20 seconds.

[Replenishment of ink composition]
In the ink jet recording method using an electrostatic field, charged particles in the ink composition are concentrated and discharged. Therefore, when ink is ejected for a long time, the amount of charged particles in the ink composition is reduced, and the electrical conductivity of the ink composition is lowered. Further, the ratio between the electric conductivity of the charged particles and the electric conductivity of the ink composition changes. Further, when discharging, charged particles having a larger diameter tend to be discharged preferentially than charged particles having a smaller diameter, so that the average diameter of the charged particles is reduced. Further, since the solid content in the ink composition changes, the viscosity also changes. Due to these changes in physical property values, as a result, ejection failure occurs, the optical density of recorded images decreases, and ink bleeding occurs. For this reason, by reducing the amount of charged particles by replenishing the ink composition having a higher concentration (higher solid content concentration) than the ink composition initially charged in the ink tank, the electrical conductivity of the ink composition The ratio between the electrical conductivity of the charged particles and the electrical conductivity of the ink composition can be kept within a certain range. Also, the average particle diameter and viscosity can be maintained. Further, by maintaining the physical property value of the ink composition within a certain range, the ink discharge is stably and uniformly performed for a long time. The replenishment at this time is preferably performed mechanically or manually, for example, by detecting a physical property value such as the electrical conductivity or optical density of the ink liquid used and calculating the shortage. Further, the amount of the ink composition to be used may be calculated based on the image data, and may be formed mechanically or manually.

[Recording medium]
In the present invention, various recording media can be used depending on the application. For example, if paper, plastic film, metal, and paper on which plastic or metal is laminated or vapor-deposited, plastic film on which metal is laminated or vapor-deposited, etc., printed matter can be directly obtained by ink jet recording. The shape of the recording medium may be planar such as a sheet shape or three-dimensional such as a cylindrical shape.

[Fixing]
In the present invention, it is preferable to fix the ink by an appropriate heating means after the ink is discharged onto the recording medium. As the heating means to be used, a contact-type heating device such as a heat roller, a heat block, or a belt heating and a non-contact type heating device such as a dryer, an infrared lamp, a visible light lamp, an ultraviolet lamp, or a hot air oven may be used. it can. These heating devices are preferably integrated with an inkjet recording apparatus.

  By using the ink composition of the present invention described above, it is possible to stably discharge ink droplets for a long time. Further, by using the above-described ink jet recording apparatus, a high-quality image recorded matter having no ink bleeding and high image density can be obtained for a long time. Although the cause of this effect is not clear, it can be inferred that the charge amount per color material particle is uniform because the particle size distribution of the color material particles is narrow and the number of fine particles is small. Further, since the surface of the colorant particles is uniformly covered with the resin, it can be estimated that the aggregation of particles due to the polar pigment particles is small.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not limited to these examples.

[Example 1: Ink composition IJ-1]
100 parts by mass of Linol Blue FG-7350 (Pigment Blue 15: 3 manufactured by Toyo Ink Co.) as a blue pigment, Styrene / vinyltoluene / lauryl methacrylate / butyl acrylate / trimethylammonium ethyl methacrylate (anion, p-toluenesulfonic acid ion) as a resin A table-type kneader PBV (Irie), 200 parts by mass of copolymer (25/27/2/27/18 mass ratio, mass average molecular weight 11,000), preliminarily pulverized with a trioblender and mixed well, then heated to 100 ° C. Melt-kneaded (120 minutes). The above colored mixture was pulverized with a pin mill. Next, 25 parts by mass of the pulverized colored admixture, oligosaccharide as a water-based auxiliary component (manufactured by Towa Kasei Co., Ltd., reduced starch saccharified product PO-10, 50 mass% aqueous solution viscosity at 25 ° C .: 6.5 Pa · s ) A composition consisting of 55 parts by mass and 20 parts by mass of sugar alcohol (manufactured by Wako Pure Chemical Industries, Ltd., D (−) sorbitol) was set at a set temperature of 140 ° C. by Brabender (manufactured by Toyo Seiki Co., Ltd., Labo Plast Mill). The mixture is melt-kneaded for 10 minutes at 25 ° C., left at 25 ° C. for 15 minutes, and then subjected to a pressure of 140 ° C. and 200 kg / m ² for 3 minutes in a press machine, and then immediately at 30 ° C. and 200 kg / m ² . The mixture was cooled for 3 minutes and then immersed in hot water at 60 ° C. to obtain a dispersion of colorant particles. The volume average particle size of the colorant particles in the dispersion was 1.10 μm as measured with an ultracentrifugal automatic particle size distribution analyzer CAPA700 (Horiba Seisakusho). The proportion of fine particles of 0.2 μm or less was 0% on a volume basis. Next, the concentration of the obtained colorant particle dispersion was adjusted so that the solid content concentration was 15% by mass, and a small high-speed cooling centrifuge (SRX-201 manufactured by Tommy Seiko Co., Ltd.) was used. Centrifugation was performed for 30 minutes under the conditions of a rotational speed of 1000 rpm and a temperature of 23 ° C. to separate the colorant particles. The supernatant liquid was discarded, the precipitated colorant particles were taken out, vacuum-dried at room temperature for 3 days, and pulverized in a mortar.

10. 20% by mass solution prepared by heating 10 parts by weight of the pulverized color material particles, 80 parts by weight of Isopar G, and the following dispersant D-1 (mass average molecular weight 55000) by heating and dissolving in Isopar G. 5 parts by mass were mixed and subjected to ultrasonic irradiation for 3 hours to obtain an Isopar G dispersion of colorant particles. When the particle diameter was measured, the volume average particle diameter was 1,10 μm and the number average particle diameter was 0.62 μm.

Next, the colorant particle dispersion was diluted with Isopar G so that the colorant particle component would be 7.0%. Next, an ink composition IJ-1 was prepared by adding an octadecene-half-maleic acid octadecylamide copolymer as a charge control agent so as to be 0.03% by mass. The viscosity of the obtained ink composition is 1.30 cP (E-type viscometer, measured at a temperature of 25 ° C.), the surface tension is 24 mN / m (automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd., measured at a temperature of 25 ° C.), The relative dielectric constant was 2.48 (LCR meter, measured by Ando Electric Co., Ltd. AG-4311). The ink composition IJ-1 had an overall specific conductivity of 850 pS / cm, a volume resistivity at 25 ° C. of 1.2 × 10 ⁹ Ω · cm, and a clear positive charge. The conductivity of the color material particles was 600 pS / cm.

  The charge amount of the ink composition was measured by using the above-described LCR meter and liquid electrode (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.) and the specific conductivity measured under conditions of an applied voltage of 5 V and a frequency of 1 kHz. The particle conductivity of the colorant particles is obtained by subtracting the specific conductivity of the supernatant obtained by centrifuging the ink composition from the total specific conductivity of the ink composition, and the volume resistivity is the total specific conductivity. Obtained by reciprocal degree. Centrifugation was performed for 30 minutes using a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) under conditions of a rotational speed of 14500 rpm and a temperature of 23 ° C.

<Inkjet recording evaluation>
The ink composition IJ-1 shown in FIGS. 1 to 3 was filled in an ink tank connected to the head. Here, a 150 dpi (three-row staggered arrangement with a channel density of 50 dpi), 833 channel head of the type shown in FIG. 2 was used as the ejection head, and a silicon rubber heat roller incorporating a 1 kW heater was used as the fixing means. As the ink temperature control means, a throw-in heater and a stirring blade were provided in the ink tank, the ink temperature was set to 30 ° C., and the temperature was controlled with a thermostat while rotating the stirring blade at 30 rpm. Here, the stirring blade was also used as a stirring means for preventing precipitation and aggregation. In addition, the ink flow path is partially transparent, and the LED light emitting element and the light detecting element are arranged between them, and the ink dilution liquid (Isopar G) or concentrated ink (the solid content concentration of the ink composition is determined by the output signal). The concentration was controlled by charging. A fine coated paper for offset printing was used as a recording medium. After removing dust on the surface of the recording medium by air pump suction, the ejection head is brought close to the recording medium to the image forming position, image data to be recorded is transmitted to the image data calculation control unit, and the recording medium is rotated by the rotation of the conveyor belt. The ink composition was discharged while sequentially moving the discharge head while transporting the recording medium, and an image was formed with a drawing resolution of 2400 dpi. As the conveyor belt, a metal belt and polyimide film bonded together are used, and a line-shaped marker is placed in the vicinity of one end of the belt along the conveyor direction, and this is optically read by the conveyor belt position detection means. An image was formed by driving the control means. At this time, the distance between the ejection head and the recording medium was kept at 0.5 mm by the output from the optical gap detector. Further, the surface potential of the recording medium was set to −1.5 kV at the time of ejection, and a pulse voltage of +500 V was applied (pulse width 50 μsec) at the time of ejection, and image formation was performed at a driving frequency of 15 kHz. Immediately after image recording, the image was fixed using a heat roller. The temperature of the coated paper at the time of fixing was 90 ° C., and the contact time with the heat roller was 0.3 seconds.

The obtained image recorded matter (printed matter) was a very clear image with no stripe unevenness and ink blur. No image formation failure or the like was observed, and no image deterioration due to dot diameter change or the like was observed even when the outside air temperature changed or the recording time increased, and good image formation was possible. After the end of recording, the ink jet recording apparatus was retracted 50 mm from a position close to the conveying belt in order to protect the ink jet head.
Further, after performing the above recording 100 times, supplying the head with Isopar G instead of ink for cleaning for 1 minute, and then storing the head in a cover filled with vapor of Isopar G for 1 month. In the meantime, a good recorded image could be produced without the need for maintenance work.

[Comparative Example 1: Ink composition IJR-1]
A colored mixture was prepared in the same manner as in Example 1, and pulverized with a pin mill. Next, 10 parts by mass of the pulverized pigment admixture, 80 parts by mass of Isopar G, 12.5 parts by mass of a 20% by mass solution prepared by heating and dissolving the pigment dispersant D-1 in Isopar G, and 3G- After pre-dispersing for 30 minutes with a paint shaker (Toyo Seiki KK) together with 350 parts by mass of X glass beads, using a thermostat NESLAB RTE7 (MS Equipment Co., Ltd.) at 3000 rpm in a Dynomill KDL type (Shinmaru Enterprise Co., Ltd.) The dispersion was wet-dispersed for 10 hours while controlling the liquid temperature of the dispersion at 35 ° C. After the completion of dispersion, the volume average particle diameter of the colorant particles in the dispersion was measured with an ultracentrifugal automatic particle size distribution analyzer CAPA700 (Horiba Seisakusho), and was 0.98 μm. The proportion of fine particles of 0.2 μm or less was 2% on a volume basis. The number average particle diameter was 0.14 μm.

The colorant particle dispersion from which the glass beads were removed by filtration was diluted with Isopar G so that the colorant particle component would be 7.0%. Next, an ink composition IJ-1 was prepared by adding an octadecene-half-maleic acid octadecylamide copolymer as a charge control agent so as to be 0.032% by mass. The viscosity of the obtained ink composition is 1.35 cP (E-type viscometer, measured at a temperature of 25 ° C.), the surface tension is 23 mN / m (automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd., measured at a temperature of 25 ° C.), The relative dielectric constant was 2.50 (LCR meter, measured by Ando Electric Co., Ltd. AG-4311). The ink composition IJ-1 has an overall specific conductivity of 840 pS / cm, a volume resistivity at 25 ° C. of 1.3 × 10 ⁹ Ω · cm, and color material particles exhibiting positive charge. The particle conductivity was 460 pS / cm.

<Inkjet recording evaluation>
Next, in the same manner as in Example 1, the ink composition IJR-1 was discharged, and ink jet recording evaluation was performed. On the first day of the ejection evaluation, the image was very clear with no stripe unevenness and ink bleeding. The ejection stability from the ink head was also good, and there was no clogging. However, ejection failure occurred on the third day, and character blurring began to occur. The comparative ink composition IJR-1 has a wide particle size distribution and is caused by the presence of fine particles, so that the charge amount variation of the color material particles is large, and it can be said that stable ejection cannot be performed for a long time.

[Example 2]
In Example 1, instead of Linol Blue FG-7350, a magenta pigment (coloring material)
Monoazo lake pigments C.I. I. Pigment Red (57: 1) (Dainippon Ink Co., Ltd., Symbol Brillant Carmine 6B229) was used in the same manner as in Example 1 to prepare a pulverized colored mixture.
Next, 30 parts by mass of the pulverized colored admixture, oligosaccharide as an auxiliary component (manufactured by Towa Kasei Co., Ltd., reduced starch saccharified product PO-10, viscosity at 25 ° C. of a 50% by mass aqueous solution: 6.5 Pa · s) A composition consisting of 50 parts by mass and 20 parts by mass of sugar alcohol (manufactured by Wako Pure Chemical Industries, Ltd., D (-) sorbitol) at a set temperature of 140 ° C. with a Brabender (manufactured by Toyo Seiki Co., Ltd., Labo Plast Mill). After melt-kneading for 10 minutes, the mixture is allowed to stand at 25 ° C. for 15 minutes. After that, a pressure of 140 ° C. and 200 kg / m ² is applied for 3 minutes with a press machine, and then immediately under conditions of 30 ° C. and 200 kg / m ^2. The mixture was cooled for a minute and then immersed in hot water at 60 ° C. to obtain a dispersion of colorant particles. It was 1.25 micrometers when the volume average particle diameter of the color material particles in the dispersion was measured with an ultracentrifugal automatic particle size distribution analyzer CAPA700 (Horiba Seisakusho). The proportion of fine particles of 0.2 μm or less was 0% on a volume basis. Next, the concentration of the obtained colorant particle dispersion is adjusted so that the solid concentration is 15% by mass, and a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) is used. Centrifugation was performed for 30 minutes under the conditions of a rotational speed of 1000 rpm and a temperature of 23 ° C. to separate the colorant particles. The supernatant liquid was discarded, the precipitated colorant particles were taken out, vacuum-dried at room temperature for 3 days, and pulverized in a mortar.

10 parts by weight of the pulverized color material particles obtained above, 80 parts by weight of Isopar G, and 12.5 parts by weight of the 20% by weight solution prepared by dissolving the dispersant D-1 in Isopar G by heating are mixed. Ultrasonic irradiation was performed for 3 hours to obtain an Isopar G dispersion of colorant particles. When the particle diameter was measured, the volume average particle diameter was 1,26 μm and the number average particle diameter was 0.60 μm.
Next, the colorant particle dispersion was diluted with Isopar G so that the colorant particle component was 7.0%. Next, an ink composition IJ-2 was prepared by adding an octadecene-half-maleic acid octadecylamide copolymer as a charge control agent so as to be 0.03% by mass. The viscosity of the obtained ink composition is 1.35 cP (E-type viscometer, measured at a temperature of 25 ° C.), the surface tension is 23 mN / m (automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd., measured at a temperature of 25 ° C.), The relative dielectric constant was 2.35 (measured with an LCR meter, AG-4311 manufactured by Ando Electric Co., Ltd.). Ink composition IJ-2 had an overall specific conductivity of 830 pS / cm, a volume resistivity at 25 ° C. of 1.23 × 10 ⁹ Ω · cm, and a clear positive charge. The colorant particle conductivity was 620 pS / cm.

<Inkjet recording evaluation>
In the same manner as in Example 1, the ink composition IJ-2 was discharged and ink jet recording evaluation was performed.
The obtained image recorded matter (printed matter) was a very clear image with no stripe unevenness and ink blur. No image formation failure or the like was observed, and no image deterioration due to dot diameter change or the like was observed even when the outside air temperature changed or the recording time increased, and good image formation was possible. Also, good image recordings could be produced for one month without the need for maintenance work.

Example 3
In Example 1, in place of Linol Blue FG-7350, disazo pigment C.I. I. Pigment Yellow 180 (manufactured by Clariant Co., Ltd., Toner Y HG) was used in the same manner as in Example 1 to prepare a pulverized colored mixture.
Next, 25 parts by mass of the pulverized colored admixture, oligosaccharide as an auxiliary component (manufactured by Towa Kasei Co., Ltd., reduced starch saccharified product PO-10, 50 mass% aqueous solution viscosity at 25 ° C .: 6.5 Pa · s) A composition consisting of 55 parts by mass and 20 parts by mass of sugar alcohol (manufactured by Wako Pure Chemical Industries, Ltd., D (−) sorbitol) was set at a set temperature of 140 ° C. with a Brabender (manufactured by Toyo Seiki Co., Ltd., Labo Plast Mill). After melt-kneading for 10 minutes, the mixture is allowed to stand at 25 ° C. for 15 minutes. After that, a pressure of 140 ° C. and 200 kg / m ² is applied for 3 minutes with a press machine, and then immediately under conditions of 30 ° C. and 200 kg / m ^2. The mixture was cooled for a minute and then immersed in hot water at 60 ° C. to obtain a dispersion of colorant particles. Ultracentrifugal automatic particle size distribution analyzer CAPA700 (Horiba Seisakusho) for volume average particle size of colorant particles in dispersion
It was 1.15 μm when measured with 1. The proportion of fine particles of 0.2 μm or less was 0% on a volume basis. Next, the concentration of the obtained colorant particle dispersion is adjusted so that the solid concentration is 15% by mass, and a small high-speed cooling centrifuge (Tomy Seiko Co., Ltd. SRX-201) is used. Centrifugation was performed for 30 minutes under the conditions of a rotational speed of 1000 rpm and a temperature of 23 ° C. to separate the color material particles. The supernatant liquid was discarded, the precipitated colorant particles were taken out, vacuum-dried at room temperature for 3 days, and pulverized in a mortar.

10 parts by weight of the pulverized color material particles obtained above, 80 parts by weight of Isopar G, and 12.5 parts by weight of the 20% by weight solution prepared by dissolving the dispersant D-1 in Isopar G by heating are mixed. Ultrasonic irradiation was performed for 3 hours to obtain an Isopar G dispersion of colorant particles. When the particle diameter was measured, the volume average particle diameter was 1,14 μm and the number average particle diameter was 0.58 μm.
Next, the colorant particle dispersion was diluted with Isopar G so that the colorant particle component was 7.0%. Next, an ink composition IJ-3 was prepared by adding an octadecene-half-maleic acid octadecylamide copolymer as a charge control agent so as to be 0.03% by mass. The viscosity of the obtained ink composition is 1.30 cP (E-type viscometer, measured at a temperature of 25 ° C.), the surface tension is 22 mN / m (automatic surface tension meter manufactured by Kyowa Interface Science Co., Ltd., measured at a temperature of 25 ° C.), The relative dielectric constant was 2.20 (LCR meter, measured with AG-4311 manufactured by Ando Electric Co., Ltd.). The ink composition IJ-2 had an overall specific conductivity of 780 pS / cm, a volume resistivity at 25 ° C. of 1.20 × 10 ⁹ Ω · cm, and a clear positive charge. The colorant particle conductivity was 580 pS / cm.

<Inkjet recording evaluation>
In the same manner as in Example 1, the ink composition IJ-3 was discharged and ink jet recording evaluation was performed.
The obtained image recorded matter (printed matter) was a very clear image with no stripe unevenness and ink blur. No image formation failure or the like was observed, and no image deterioration due to dot diameter change or the like was observed even when the outside air temperature changed or the recording time increased, and good image formation was possible. Also, good image recordings could be produced for one month without the need for maintenance work.

It is a whole lineblock diagram showing typically an example of an ink jet printer used for the present invention. It is a perspective view which shows the structure of the inkjet head of the inkjet recording device of this invention (In order to make it intelligible, the edge of the guard electrode in each discharge part is not drawn). FIG. 3 is a side sectional view showing a distribution state of charged particles when the number of ejection units of the inkjet head shown in FIG. 2 is large (corresponding to an arrow XX in FIG. 2).

Explanation of symbols

G Ink Drop P Recording Medium Q Ink Flow R Charged Particle 1 Inkjet Recording Device 2, 2Y, 2M, 2C, 2K Discharge Head 3 Ink Circulation System 4 Head Driver 5 Position Control Means 6A, 6B, 6C Roller 7 Conveyor Belt 8 Conveyance Belt position detection means 9 Electrostatic adsorption means 10 Static elimination means 11 Mechanical means 12 Feed roller 13 Guide 14 Image fixing means 15 Guide 16 Recording medium position detection means 17 Discharge fan 18 Solvent vapor adsorbent 38 Ink guide 40 Support bar 42 Ink meniscus 44 Insulating layer 46 First ejection electrode 48 Insulating layer 50 Guard electrode 52 Insulating layer 56 Second ejection electrode 58 Insulating layer 62 Floating conductive plate 64 Coating film 66 Insulating member 70 Ink jet head 72 Ink flow path 74 Substrate 75, 75A , 75B Opening 76, 76A, 76B Discharge section 78 Ink guide

Claims (3)

The manufacturing method of the inkjet ink composition characterized by having the process of following (i)-(iv).
(I) A step of mixing the coloring material and the resin component to create a colored mixture (A);
(Ii) mixing the colored admixture (A) with the aqueous auxiliary component (B) to form a dispersion;
(Iii) a step of eluting the aqueous auxiliary component (B) from the dispersion to obtain the colorant particles (C); and (iv) a step of dispersing the colorant particles (C) together with the dispersant in a non-aqueous solvent.   An inkjet ink composition produced by the production method according to claim 1.   An ink jet recording method comprising using the ink jet ink composition according to claim 2 and causing ink droplets to fly by an ink jet recording method.

Images