JP5607906B2 - Oil-based inkjet ink - Google Patents

Description

  The present invention relates to an oil-based ink suitable for use in an ink-jet recording system, and more particularly to an oil-based ink-jet ink that has excellent repellency to a nozzle plate and can suppress deterioration of the nozzle plate.

It is already known that an oil-based inkjet ink having a low viscosity even at a high pigment concentration can be obtained by using a capsule-type pigment surface-treated with a (meth) acrylic acid copolymer having an acid value of 30 to 60 as the pigment. (See Patent Document 1).
However, this ink has good wettability with respect to the fluororesin film on the surface of the nozzle plate of the head of the inkjet printing apparatus, and tends to adhere to the surface of the nozzle plate. As a result, there is a problem that the ink attached to the surface of the nozzle plate hangs on the paper and stains the image, or the ink attached to the surface of the nozzle plate hinders ink ejection.

In addition, an ink jet printing apparatus using oil-based ink is designed so that a head cleaning operation is periodically performed. This head cleaning operation includes pressure purge for discharging ink from the nozzles and wiping of the nozzle plate.
When ink that adheres easily to the nozzle plate surface as described above is used, when the nozzle plate is wiped, the pigment in the ink becomes an abrasive, scraping off the fluororesin film on the nozzle plate surface, and the ink repellency of the nozzle plate Will be lowered forever.

JP 2007-314651 A

  An object of the present invention is to provide an oil-based inkjet ink that is excellent in repellent properties with respect to a nozzle plate and can suppress deterioration of the nozzle plate.

  As a result of diligent research under the above-mentioned objectives, the present inventors have excellent repellent properties for the nozzle plate by including a capsule-type pigment surface-treated with a specific polymer compound as a coloring material in an oil-based inkjet ink. The present inventors have found that an oil-based inkjet ink that can suppress the deterioration of the nozzle plate can be obtained, and have completed the present invention.

  That is, according to the present invention, an oil-based inkjet ink comprising at least a capsule pigment surface-treated with a polymer compound and a solvent, wherein the polymer compound has an α value of 5 to 60 as a side chain. An oil-based inkjet ink is provided which is a comb-shaped polyurethane compound which is added and miscible with the solvent.

  According to the present invention, as a coloring material to be contained in an oil-based inkjet ink, a capsule type in which a compound having an α value of 5 to 60 is added as a side chain and surface-treated with a comb-shaped polyurethane compound miscible with the solvent of the ink. Since the pigment is used, the ink repellency with respect to the nozzle plate can be improved, and the deterioration of the nozzle plate can be suppressed.

It is a longitudinal cross-sectional view which shows the method of the wet evaluation with respect to the nozzle plate in an Example.

  Hereinafter, the present invention will be described in more detail. In the present specification, “(meth) acryl” and “(meth) acrylate” mean “acryl and / or methacryl” and “acrylate and / or methacrylate”, respectively.

  The inkjet ink of the present invention is composed of at least a pigment and a solvent, and may contain a pigment dispersant and other additives as necessary.

  The solvent used in the present invention is not particularly limited as long as it can be used as a vehicle for oil-based ink, and may be a polar organic solvent or a nonpolar organic solvent. The solvent used in the present invention may be composed of one kind alone, or may be composed of two or more different solvents as long as a single phase is formed.

  The solvent used in the present invention is preferably composed of 20 to 60% by weight of a nonpolar organic solvent and 80 to 40% by weight of a polar organic solvent, and preferably 25 to 55% by weight of a nonpolar organic solvent and 75 to 45%. More preferably, it is composed of a weight% polar organic solvent, and it is particularly preferably composed of 30-50 wt% nonpolar organic solvent and 70-50 wt% polar organic solvent.

  As non-polar organic solvents, petroleum hydrocarbon solvents such as naphthenic, paraffinic and isoparaffinic solvents can be used. Specifically, “Isoper, Exol” (all trade names) manufactured by ExxonMobil, Nippon Oil Corporation “AF Solvent” (trade name) manufactured by the company, “Sansen, Thamper” (both trade names) manufactured by Sun Sekiyu Co., Ltd., and the like. These nonpolar organic solvents can be used alone or in combination of two or more.

  Examples of polar organic solvents include fatty acid ester solvents, higher alcohol solvents, fatty acid solvents, glycol ether solvents, and the like.

  Examples of the fatty acid ester solvent include methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, hexyl palmitate, isostearyl palmitate, isooctyl isopalmitate, methyl oleate, ethyl oleate , Isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate, 2-octyldodecyl pivalate, soybean oil Methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, Propylene glycol caprate, tri 2-ethylhexanoic acid trimethylol propane, tri 2-ethylhexanoic acid glyceryl and the like.

  Examples of the higher alcohol solvent include alcohols having 6 or more carbon atoms, and preferably alcohols having 12 or more carbon atoms. Preferred higher alcohol solvents include isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol and the like.

  Examples of the fatty acid solvent include fatty acids having 9 or more carbon atoms, preferably higher fatty acids having 12 or more carbon atoms. Specific examples of such fatty acids include isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid, isostearic acid and the like.

  Examples of the glycol ether solvent include diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol dibutyl ether and the like.

  These polar organic solvents can be used alone or in combination of two or more. In the present invention, preferred polar organic solvents include fatty acid ester solvents.

  The pigment used in the present invention is not particularly limited, regardless of whether it is an organic pigment or an inorganic pigment, those that are generally used in the technical field of printing. Specifically, carbon black, cadmium red, chrome yellow, cadmium yellow, chromium oxide, viridian, titanium cobalt green, ultramarine blue, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindo Rinone pigments, dioxazine pigments, selenium pigments, perylene pigments, thioindigo pigments, quinophthalone pigments, metal complex pigments and the like can be suitably used. These pigments may be used alone or in appropriate combination.

  In the present invention, the pigment is used in the form of a capsule pigment surface-treated with a specific polymer compound. As the specific polymer compound, a comb-shaped polyurethane compound to which a compound having an α value of 5 to 60 is added as a side chain, which is miscible with a solvent used in ink, is used.

  As such a comb-shaped polyurethane compound, for example, a compound comprising a main chain made of a polyurethane compound and a side chain made of a compound having an α value of 5 to 60 graft-polymerized to the main chain can be mentioned. Here, examples of the polyurethane compound include those obtained by reacting a polyhydric alcohol and a polyvalent isocyanate.

  Preferable specific examples of the comb-shaped polyurethane compound include dihydric alcohol (—O— (XR) —O—) having a side chain (R) and divalent isocyanate (—CONH) as shown in the following formula (1). And a compound having a polyurethane structure in which -Y-NHCO-) are alternately arranged.

式（１）において、Ｘは３価の基を示し、Ｙは２価の基を示し、Rはα値５〜６０の基を示す。

In the formula (1), X represents a trivalent group, Y represents a divalent group, and R represents a group having an α value of 5 to 60.

The comb-shaped polyurethane compound of the above formula (1) can be produced by reacting a dihydric alcohol and a divalent isocyanate.
The dihydric alcohol is preferably a divalent amino alcohol, and more preferably a dialkanolamine represented by the following formula (2).

式（２）において、Rはα値５〜６０の基を示し、ｌは１〜４の整数、ｍは１〜４の整数である。

In the formula (2), R represents a group having an α value of 5 to 60, l is an integer of 1 to 4, and m is an integer of 1 to 4.

  When the dihydric alcohol (—O— (XR) —O—) is a dialkanolamine, it is advantageous in that the side chain (R) can be bonded to the main chain via the nitrogen atom of the dialkanolamine. It is. For example, as shown in the following formula (3), an α, β-unsaturated carbonyl compound (for example, a compound of the formula C═C—COO—R) is graft-polymerized to the nitrogen atom of dialkanolamine by a Michael addition reaction. be able to. The introduction of the side chain (R) by this Michael addition reaction is usually performed on the dialkanolamine monomer before the polymerization, but the dialkanolamine contained in the polyurethane compound at the time after the polymerization. You may go.

  The α, β-unsaturated carbonyl compound (for example, a compound of formula C═C—COO—R) is preferably a (meth) acrylic acid ester having an α value of 5 to 60, more preferably an α value of 5 to 60. Alkyl (meth) acrylate, alkyl group-terminated polyalkylene glycol mono (meth) acrylate or alkylaryl group-terminated polyalkylene glycol mono (meth) acrylate. Specific examples of the alkyl (meth) acrylate include isostearyl (meth) acrylate, lauryl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) acrylate, butyl (meth) acrylate, ethyl (meth) acrylate, Examples thereof include alkyl esters having 1 to 18 carbon atoms of (meth) acrylic acid such as methyl (meth) acrylate. Specific examples of the alkyl group-terminated polyalkylene glycol mono (meth) acrylate include methoxypolyethylene glycol acrylate (average polymerization degree of polyethylene glycol is 2 to 12 mol), lauroxy polyethylene glycol acrylate (average polymerization degree of polyethylene glycol is 2 to 2). 12 moles). Examples of the alkylaryl group-terminated polyalkylene glycol mono (meth) acrylate include nonylphenoxy polypropylene glycol acrylate (the average degree of polymerization of polypropylene glycol is 2 to 20 mol).

  The α value of the side chain of the comb-shaped polyurethane compound is equivalent to the α value of the α, β-unsaturated carbonyl compound as a raw material. The α value of the side chain is preferably 15 to 60, and more preferably 40 to 60. If the α value is too low, the comb-shaped polyurethane compound is easily dissolved in an ink solvent, particularly a non-polar ink solvent. Therefore, the form of the capsule-type pigment cannot be maintained, and the repelling property of the ink on the nozzle plate is not improved. If the α value is too high, the miscibility of the comb-shaped polyurethane compound with an ink solvent, particularly a non-polar ink solvent, is reduced, and the pigment is likely to aggregate, so the repelling property of the ink to the nozzle plate is not improved.

  The α value is a value of α given by tan α = (inorganic value / organic value). Here, the “organic value” and “inorganic value” are based on the concept used in the “Organic Conceptual Diagram” proposed by Satoshi Fujita, and the organic compound is linked to a covalent bond in the carbon region. It is divided into two factors, “organic” due to “organic” and “inorganic” due to electrostatic influence existing in the substituents (functional groups), and each is quantified and obtained from the structure of each compound. Value. Therefore, the α value quantitatively shows the balance between “organic” and “inorganic” of the compound. Matters related to the “Organic Conceptual Diagram” are described in detail in Satoshi Fujita “Systematic Organic Qualitative Analysis (mixture)” Kazama Shobo (1974) and the like.

  In order to prevent the comb-shaped polyurethane compound represented by the above formula (1) from crystallizing in the ink solvent and to make it miscible with the ink solvent, the dihydric alcohol (—O— (XR) —) of the above formula (1) is used. O-) can be partially replaced by other dihydric alcohols (-OXO-) that do not have a side chain (R). Examples of such other dihydric alcohols (—O—X—O—) include alkylene glycols having a branched chain. Such alkylene glycol can be introduced by using an alkylene glycol such as propylene glycol, dipropylene glycol, or polypropylene glycol having a molecular weight of 400 to 900 as the dihydric alcohol.

  The comb-shaped polyurethane compound represented by the above formula (1) preferably contains dialkanolamine and other dihydric alcohol in a molar ratio of 25:75 to 75:25 (dialkanolamine: other dihydric alcohol). .

  The divalent isocyanate is not particularly limited as long as it is used in ordinary polyurethanes. For example, 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate, metaxylene diisocyanate, hexamethylene diisocyanate, Examples include norbornene diisocyanate and naphthalene diisocyanate.

The comb-shaped polyurethane compound of the above formula (1) can be produced by reacting the dihydric alcohol and the divalent isocyanate in a low-boiling aprotic solvent such as methyl ethyl ketone. In the reaction, the dihydric alcohol and the divalent isocyanate are usually used in a molar ratio of 0.95 to 1.05 (dihydric alcohol: divalent isocyanate) to prevent unreacted raw materials from remaining. , Preferably in a molar ratio of 0.98 to 1.02 (dihydric alcohol: divalent isocyanate).
It is preferable that the mass average molecular weight (GPC method, standard polystyrene conversion) of the comb-shaped polyurethane compound used by this invention is 5000-30000. When the weight average molecular weight of the compound is lower than 5000, the compound may float in the ink solvent and cannot maintain the capsule pigment. When the weight average molecular weight of the compound is higher than 30000, the ink viscosity may be too high.

The capsule-type pigment used in the present invention is prepared by mixing the comb-shaped polyurethane compound dissolved in a low-boiling aprotic solvent such as methyl ethyl ketone with a high-boiling solvent for ink and a pigment, and dispersing the mixture with a disperser such as a bead mill. Thereafter, the low boiling point solvent can be volatilized. At this time, the use ratio of the comb-shaped polyurethane compound, the pigment and the high boiling point solvent is
The comb-type polyurethane compound is preferably 0.01 to 10 by weight with respect to the pigment. The use ratio of the high boiling point solvent is preferably 3 to 100 by weight with respect to the pigment. A sufficient amount of the low-boiling aprotic solvent is required so that aggregation does not occur when the comb-type polyurethane compound is mixed with the high-boiling solvent. A preferred amount of the low-boiling point aprotic solvent is 1 to 15 by weight with respect to the comb-type polyurethane compound.
In the capsule type pigment thus obtained, the pigment surface is coated with the comb-shaped polyurethane compound, and the comb-shaped polyurethane compound has a side chain composed of a compound having an α value of 5 to 60, and the nozzle plate It is considered that it has excellent repellent properties.

  The capsule-type pigment is preferably contained in the range of 1 to 15% by weight with respect to the total amount of ink.

  The ink of the present invention may contain a pigment dispersant in order to stabilize the dispersion of the capsule type pigment. Such a pigment dispersant is not particularly limited as long as it can stably disperse a capsule-type pigment in a solvent. Conventionally known pigment dispersants can be used, and among them, a plurality of side chains comprising polyester chains are provided. A comb-type polyamide-based dispersant is preferably used. The comb-type polyamide-based dispersant having a plurality of side chains composed of polyester chains includes a main chain containing a large number of nitrogen atoms, such as polyethyleneimine, and amide-bonded side chains via the nitrogen atoms. A compound comprising a plurality of compounds, wherein the side chain is a polyester chain. For example, as disclosed in JP-A-5-177123 (US Pat. No. 4,645,611), a polyimine such as polyethyleneimine A poly (carbonyl-C3-C6-alkyleneoxy) chain containing 3 to 80 carbonyl-C3-C6-alkyleneoxy groups is bonded as a side chain by an amide bridge. And a dispersant having a structure of Such a comb-shaped dispersant having a comb-shaped structure is available as a commercial product such as Solsperse 11200, Solsperse 28000 (both trade names) manufactured by Nippon Lubrizol.

  The content of the dispersant is sufficient as long as the pigment can be sufficiently dispersed in the ink, and can be appropriately set.

  The ink-jet ink of the present invention can contain, for example, dyes, preservatives, etc., in addition to the above-mentioned solvent, capsule type pigment, and pigment dispersant, as long as the ink repellent property to the nozzle plate is not affected. .

  The ink-jet ink of the present invention can be prepared by, for example, supplying all components into a known disperser such as a bead mill in a batch or divided and dispersing the mixture, and if desired, passing it through a known filter such as a membrane filter. Specifically, after preparing a mixed liquid in which a part of the solvent and the whole amount of the pigment and the dispersant are uniformly mixed in advance and dispersing with a disperser, the remaining components are added to the dispersion and filtered. It can be prepared by passing through a machine.

  The viscosity at 25 ° C. of the inkjet ink of the present invention thus obtained is preferably set in the range of 5 to 30 mPa · s suitable for ejection from the inkjet head nozzle, and is set in the range of 7 to 14 mPa · s. More preferably. Further, the freezing point of the ink is preferably set to −5 ° C. or lower so that the ink does not freeze depending on the storage environment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this Example.

Production Example 1 (Synthesis of diol)
In a 300 mL four-necked flask, 10.51 g of diethanolamine (molecular weight (MW) 105.1) was charged, and the temperature was raised to 110 ° C. while agitating with nitrogen gas. 48.20 g of methoxypolyethylene glycol acrylate (average added mole number of polyethylene glycol chain: 9 mol, molecular weight (MW) 482.0) was added dropwise over 30 minutes. The Michael addition reaction was completed by maintaining at 110 ° C. for 2 hours. After cooling, 58.71 g of methyl ethyl ketone was added and diluted to obtain a diol solution 1 having a solid content of 49.8% by weight.
Diol solutions 2 to 4 were obtained in the same manner as diol solution 1 except that the components shown in Table 1 were used. In Table 1, the blending amount of each component is shown by weight%, and the α value is that of the α, β-unsaturated carbonyl compound used.

Production Example 2 (Synthesis of comb-shaped polyurethane compound)
Into a 300 mL four-necked flask was charged 117.42 g of the diol solution 1 obtained in Production Example 1 and 7.60 g of propylene glycol as another diol component, 0.15 g of dibutyltin dilaurate was added, and nitrogen gas was bubbled. The temperature was raised to 78 ° C. with stirring. Then, a mixture of Takenate 600 (1,3-bis (isocyanatomethyl) cyclohexane, Mitsui Chemicals Polyurethane Co., Ltd.) 38.84 g and methyl ethyl ketone 99.22 g was added dropwise over 30 minutes. After dropping, the mixture was reacted for 24 hours under reflux at a temperature of 78 ° C. to 80 ° C., and then cooled to obtain a resin solution 1 having a solid content of 40.3 wt%. The mass average molecular weight (GPC method, standard polystyrene conversion) was 11,200.
Resin solutions 2 to 4, 6 and 7 were prepared in the same manner as the resin solution 1 except that the components shown in Table 2 were used. In addition, the compounding quantity of each component in Table 2 is shown by weight%.

Production Example 3 (Synthesis of acrylic anionic resin, production of capsule type pigment)
MEK is added to a reaction vessel of an automatic polymerization reaction device (polymerization tester DSL-2AS type, manufactured by Sakai Sangyo Co., Ltd.) having a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device at the top. 1000 parts of (2-butanone) was charged and the inside of the reaction vessel was purged with nitrogen while stirring. After raising the temperature in the reaction vessel to 80 ° C. while maintaining a nitrogen atmosphere, 150 parts of 2-hydroxyethyl methacrylate, 200 parts of styrene, 92.1 parts of methacrylic acid, 370.1 parts of butyl methacrylate, acrylic 157.8 parts of butyl acid, 30.0 parts of glycidyl methacrylate, 40.0 parts of Blemmer TGL (polymerization degree adjusting agent) and perbutyl (registered trademark) O (polymerization initiator, all manufactured by NOF Corporation) 100. 0 part of the mixture was added dropwise over 4 hours. After completion of the dropwise addition, the reaction was further continued at the same temperature for 7 hours to obtain a MEK solution of a copolymer having an acid value of 60, a weight average molecular weight of 5,900, and a nonvolatile content of 46.32%. This acrylic anionic resin solution was designated as resin solution 5. Then, 263 parts of the above copolymer, 30 parts of 25% aqueous potassium hydroxide solution, water and carbon black MA11 250 parts made by Mitsubishi Chemical Co., Ltd., 1064 parts of water were charged into a mixing tank equipped with a cooling jacket, and stirred. Mixed. Here, the amount of each charged is such that the copolymer has a non-volatile content of 50% with respect to the pigment, and the 25% aqueous potassium hydroxide solution has the acid value of the styrene-acrylic copolymer 100% neutralized. Amount.

  The mixed solution was passed through a dispersion apparatus (SC mill SC100 / 32 type, manufactured by Mitsui Mining Co., Ltd.) filled with zirconia beads having a diameter of 0.3 mm, and dispersed for 4 hours by a circulation method. The number of revolutions of the dispersing device was 2700 rpm, and the temperature of the dispersion liquid was kept at 40 ° C. or less through the cooling jacket through cold water. After the dispersion, the dispersion stock solution was extracted from the mixing tank, and then the mixing tank and the dispersion device flow path were washed with 10,000 parts of water, and the diluted dispersion liquid was obtained together with the dispersion stock solution. The diluted dispersion was put into a glass distillation apparatus, and the whole amount of methyl ethyl ketone and a part of water were removed by atmospheric distillation.

  The dispersion from which methyl ethyl ketone was removed was cooled, and then 10% hydrochloric acid was added dropwise with stirring to adjust the pH to 4.5, and then the solid content was filtered with a Nutsche filter and washed with water. The cake was taken in a container and vacuum dried at 50 ° C. and <0.01 mmHg. The obtained solid was pulverized in a mortar to produce a capsule-type pigment. This capsule type pigment was designated as MC5 (control) in Table 3.

  As shown in Table 3, 11.0 g of the obtained capsule pigment MC5, 5.0 g of a pigment dispersant (pigment dispersant Solsperse 28000 manufactured by Lubrizol) and 34.0 g of methyl oleate were mixed, and zirconia beads (diameter 0.5 mm) and dispersed with a rocking mill (Seiwa Giken Co., Ltd.) at 67.50 Hz for 120 minutes. After dispersion, zirconia beads were removed, and the resulting dispersion was cooled and irradiated with ultrasonic waves for 10 minutes using an ultrasonic homogenizer (SONIC & MATERIALS, INC., VC750) while stirring. Thus, a pigment dispersion 5 containing a capsule type pigment was obtained.

Production Example 4 (Production of capsule type pigment)
2.5 g of the resin solution 1 obtained in Production Example 2 above, 10.0 g of pigment (carbon black, MA11 manufactured by Mitsubishi Chemical Corporation), 5.0 g of pigment dispersant (pigment dispersant Solsperse 28000 manufactured by Lubrizol), 34.0 g of methyl oleate and 10.0 g of methyl ethyl ketone were mixed, zirconia beads (diameter 0.5 mm) were added, and dispersed with a rocking mill (manufactured by Seiwa Giken Co., Ltd.) at 67.50 Hz for 120 minutes. After dispersion, the zirconia beads were removed, and the low boiling point solvent (methyl ethyl ketone) of the dispersion was removed using an evaporator while heating and reducing the pressure. Subsequently, the obtained dispersion was cooled and irradiated with ultrasonic waves for 10 minutes using an ultrasonic homogenizer (SONIC & MATERIALS, INC., VC750) while stirring. Thus, a pigment dispersion MC1 containing a capsule type pigment was obtained.
MC2 to MC4, MC6, and MC7 were produced in the same manner except that the components shown in Table 3 were used. In addition, the compounding quantity of each component in Table 3 is shown by weight%.

Production Example 5 (Production of non-capsule type pigment dispersion)
As shown in Table 3, 10.0 g of Pigment MA11 manufactured by Mitsubishi Chemical Corporation, 5.0 g of a pigment dispersant (pigment dispersant Solsperse 28000 manufactured by Lubrizol Corporation), and 35.0 g of methyl oleate were mixed, and zirconia beads ( The diameter was 0.5 mm) and dispersed with a rocking mill (Seiwa Giken Co., Ltd.) at 67.50 Hz for 120 minutes. After dispersion, zirconia beads were removed, and the resulting dispersion was cooled and irradiated with ultrasonic waves for 10 minutes using an ultrasonic homogenizer (SONIC & MATERIALS, INC., VC750) while stirring. Thus, a pigment dispersion 8 containing a non-capsule type pigment was obtained.

In addition, the symbol of the raw material of Table 3 is as follows.
MA11 (trade name): manufactured by Mitsubishi Chemical Corporation Carbon black (nitrogen adsorption specific surface area of 92m ² / g, DBP absorption amount of 64cm ³ / 100g).
S28000: Pigment dispersant Solsperse 28000 (trade name) manufactured by Lubrizol.

Examples 1-4, Comparative Examples 1-4
50.0 g of the pigment dispersion shown in Table 4 was diluted with the solvent shown in Table 4 and sufficiently stirred. By sequentially filtering through a membrane filter of 3.0 μm and 0.8 μm, dust and coarse particles were removed to obtain an inkjet ink (pigment content 10% by weight). In addition, the compounding quantity of each component in Table 4 is shown by weight%.

  The inkjet inks obtained in the above examples and comparative examples were evaluated by the following methods. These evaluation results are shown in Table 4.

(1) Evaluation of wettability with respect to nozzle plate As shown in FIG. 1, an inkjet ink 1 is placed in a 30 ml container 2 and used in an inkjet printer “HC5500” (trade name: Riso Kagaku Kogyo Co., Ltd.). One end of 3 (length 5 cm, width 5 mm) was pinched with tweezers 4 and the other end 2 cm was immersed in ink. Thereafter, the nozzle plate was quickly pulled up, the time until the ink film remaining on the nozzle plate became ink droplets was measured 10 times, the average value was calculated, and the ink repelling time was evaluated according to the following criteria. In addition, the used nozzle plate used the polyimide film as the base material, and the surface was fluorine-processed.
Evaluation criteria:
A: Ink repellent time less than 1 second,
○: Ink repellent time 1 second or more, less than 3 seconds,
Δ: Ink repellent time 3 seconds or more, less than 4 seconds,
X: Ink repellent time 4 seconds or more.

(2) Evaluation of wiping durability Using an inkjet printer “HC5500” (trade name: manufactured by Riso Kagaku Co., Ltd.), the head cleaning was performed 1000 times by normal cleaning of the head maintenance, and the part where the wiping blade was in contact The ink repellency was visually evaluated.
Evaluation criteria:
A: Ink repellency is maintained at all the portions where the wiping blade is in contact. Immediately after the test, the ink is completely repelled.
○: Ink repellency is maintained in all the parts that are in contact with the wiping blade. After the test, it takes a few seconds for the ink to completely repel.
(Triangle | delta): The ink repellency of the part which the wiping blade contacted has fallen.
X: The ink repellency of all the portions which are in contact with the wiping blade is lowered.

(3) Evaluation of ink viscosity The viscosity of the ink is a viscosity when the pigment concentration in the ink is 10% by weight. The viscosity at 10 Pa when the shear stress was increased from 0 Pa at a rate of 0.1 Pa / s at 25 ° C., and measured with a TA Instruments rheometer AR-G2 (cone angle 2 °, diameter 40 mm).

In addition, the symbol of the raw material of Table 4 is as follows.
AF-7 (trade name): Petroleum hydrocarbon solvent manufactured by Nippon Oil Corporation.

From the results in Table 4, the following can be understood.
The oil-based ink-jet inks of Examples 1 to 4 contain capsule-type pigments surface-treated with a comb-shaped polyurethane compound having a compound having an α value of 5 to 60 as a side chain. Also improved.

On the other hand, since Comparative Example 1 contains a capsule-type pigment surface-treated with a (meth) acrylic acid copolymer described in JP-A-2007-314651, the repelling property and wiping durability against the nozzle plate Both were inferior.
Comparative Example 2 is an example in which a comb-shaped polyurethane compound containing ethylene glycol as a diol component was used, and an ink could not be prepared because it was crystallized in an ink solvent.
Comparative Example 3 is an example using a non-comb polyurethane compound having no side chain, and both the repelling property against the nozzle plate and the wiping durability were inferior.
Comparative Example 4 was an example using a pigment that was not encapsulated, and both the repelling property and wiping durability against the nozzle plate were inferior.

  The oil-based inkjet ink of the present invention has good repellency with respect to the nozzle plate, and therefore can suppress deterioration of the nozzle plate, and thus can be used in the field of inkjet printing.

1 ... inkjet ink, 2 ... container, 3 ... nozzle plate, 4 ... tweezers.

Claims (6)

An oil-based inkjet ink comprising at least a capsule-type pigment surface-treated with a polymer compound and a solvent, wherein the polymer compound has a compound having an α value of 5 to 60 added as a side chain, and the solvent is added to the solvent. comb polyurethane compound der miscible is, compounds of the α values 5-60 are alkyl (meth) acrylate, alkyl-terminated polyalkylene glycol mono (meth) acrylate or alkyl aryl group-terminated polyalkylene glycol mono (meth) acrylate oil-based inkjet ink, characterized in der Rukoto (excluding an active energy ray curable ink-jet inks). The polymer compound has a polyurethane structure in which a dihydric alcohol and a divalent isocyanate are alternately arranged as a main chain, the dihydric alcohol has at least a dialkanolamine, and the side chain has the dialkanolamine The oil-based inkjet ink according to claim 1, wherein the oil-based inkjet ink is bonded to the main chain via a nitrogen atom. An alkyl (meth) acrylate, an alkyl group-terminated polyalkylene glycol mono (meth) acrylate or an alkylaryl group-terminated polyalkylene glycol mono (meth) acrylate is formed by Michael addition to the nitrogen atom of the dialkanolamine as the side chain. 2. The oil-based inkjet ink according to 2. The oil-based inkjet according to claim 2, wherein the dihydric alcohol contains dialkanolamine and another dihydric alcohol in a molar ratio of 25:75 to 75:25 (dialkanolamine: other dihydric alcohol). ink. The oil-based inkjet ink according to claim 4 , wherein the other dihydric alcohol is an alkylene glycol having a branched chain. The oil-based inkjet ink according to claim 5 , wherein the alkylene glycol having a branched chain is propylene glycol.

Images