JP5593046B2 - 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 specifically, an oil-based ink-jet ink that is excellent in repelling properties for a nozzle plate, can suppress deterioration of the nozzle plate, and can perform printing at a high printing density. About.

  An ink jet printing apparatus using oil-based ink is designed such that a head cleaning operation is periodically performed in order to prevent ink non-ejection when not in use for a long time or during normal use. This head cleaning operation includes pressure purge for discharging ink from the nozzles and wiping of the nozzle plate.

  However, it is known that if the head cleaning operation is repeated, the fluorine film on the surface of the nozzle plate is damaged, the ink repellency of the nozzle plate is lowered, and problems such as non-ejection, ejection bending, and ink dripping occur.

  Conventionally, in order to suppress a decrease in ink repellency of a nozzle plate, it has been proposed to improve the repellency of the ink to the nozzle plate by adding a long-chain polyaminoamide and a salt of a polar acid ester to the ink. (See Patent Document 1). However, in this technique, in order to sufficiently improve the repellency, it is necessary to contain a salt of a long-chain polyaminoamide and a polar acid ester in an amount of 1% by weight or more, preferably 2 to 20% by weight based on the total amount of the ink. . Further, when a long-chain polyaminoamide and a salt of a polar acid ester are contained in the ink, there is a problem that the penetration of the ink into the printing paper is promoted and the image density is lowered.

JP 2008-274232 A

  Further, according to the study by the present inventors, the reason why the ink repellency of the nozzle plate disappears by the head cleaning operation is that the pigment in the ink attached to the nozzle plate becomes an abrasive and the surface of the nozzle plate is scraped by wiping. In particular, if carbon black with a small primary particle size and a large structure is included as a pigment in the oil-based ink, printing can be performed on plain paper at a high image density. However, when the head cleaning operation is repeated, the hardness of the carbon black particles And the particle size is small, it was found that the ink repellency of the nozzle plate was significantly reduced.

  An object of the present invention is to provide an oil-based inkjet ink that is excellent in repellency to a nozzle plate, can suppress deterioration of the nozzle plate, and can perform printing at a high printing density.

  As a result of diligent research under the above-mentioned objectives, the present inventors have added a specific compound to an oil-based inkjet ink comprising at least a pigment, a pigment dispersant, and a solvent, thereby improving the repellency of the ink to the nozzle plate. It has been found that the nozzle plate can be improved and deterioration of the nozzle plate can be suppressed, and the present invention has been completed.

  That is, according to the present invention, an oil-based inkjet ink comprising at least a pigment, a pigment dispersant, and a solvent, wherein the oil-based inkjet ink further includes (A) a fatty acid or an alkyl phosphate ester and (B) an amine compound. There is provided an oil-based inkjet ink comprising:

  When (A) fatty acid or alkyl phosphate ester and (B) amine compound are added to the ink, both components undergo neutralization reaction in the ink, and are dissolved or dispersed in the ink solvent in a state where the neutralized salt is dissociated. According to the present invention, since the component (A) and the component (B) are added to the oil-based inkjet ink comprising at least a pigment, a pigment dispersant and a solvent, the charge of the ink is adjusted, and the nozzle plate It is considered that the wettability to the surface is suppressed.

  Therefore, according to the present invention, the ink repellency with respect to the nozzle plate can be improved, and the deterioration of the nozzle plate can be suppressed. In addition, since the present invention can suppress deterioration of the nozzle plate even when a pigment such as carbon black having a small primary particle size and a large structure is contained in the ink, a high printing density can be obtained without impairing the durability of the printing apparatus. It is convenient for printing a large amount of printed matter.

Hereinafter, the present invention will be described in more detail.
The inkjet ink of the present invention comprises a pigment, a pigment dispersant, a solvent, (A) a fatty acid or an alkyl phosphate ester (hereinafter, also collectively referred to as “component (A)”), and (B) an amine compound (hereinafter, It is at least comprised from "component (B)"), and can contain another additive as needed.

  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. Such a solvent is preferably a non-volatile water-insoluble solvent having a 50% distillation point of 150 ° C. or higher. The 50% distilling point is measured according to JIS K0066 “Method for Distillation Test of Chemical Products”. It means the temperature when 50% by mass of the solvent is volatilized. From the viewpoint of safety, it is more preferable to use one having a 50% distillation point of 160 ° C or higher, preferably 230 ° C or higher. 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 30 to 70% by weight of nonpolar organic solvent and 70 to 30% by weight of polar organic solvent, and 40 to 60% by weight of nonpolar organic solvent and 60 to 40%. More preferably, it is composed of a 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 the polar organic solvent include fatty acid ester solvents, higher alcohol 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 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, and particularly preferred polar organic solvents include mixtures of fatty acid ester solvents and higher alcohol solvents. When these solvents are used in combination, the mixing ratio of both solvents (fatty acid ester solvent: higher alcohol solvent) is preferably 99: 1 to 50:50, more preferably 95: 5 to 60:40, even more preferably. Is 90: 10-70: 30. When fatty acid ester solvents and higher alcohol solvents are used in this ratio, an image with a high printing density can be obtained and the nozzle plate deteriorates even when pigments such as carbon black with a small primary particle size and a large structure are used. Can be suppressed. This is because the polarities of polar organic solvents, particularly higher alcohol solvents, promote the dissociation of component (A) and component (B) and carbon black surface functional groups, and the components (A) and (B) of carbon black This is probably because the contact between the nozzle plate and the carbon black is suppressed as a result of promoting the adsorption.

  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.

  The pigment is preferably contained in the range of 0.01 to 20% by weight with respect to the total amount of ink.

  The pigment dispersant used in the present invention is not particularly limited as long as the pigment is stably dispersed in the solvent, and a conventionally known pigment dispersant can be used. Examples of such a pigment dispersant include a main chain made of polyalkyleneimine such as polyethyleneimine as disclosed in JP-A-5-177123 (US Pat. No. 4,645,611). In addition to a dispersant having a structure in which poly (carbonyl-C3-C6-alkyleneoxy) chains containing -80 carbonyl-C3-C6-alkyleneoxy groups are bonded as side chains by amide bridges, Nippon Lubrizol Examples include commercial products such as Solsperse 11200, Solsperse 13940, Solsperse 28000 (all trade names).

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

  Examples of the fatty acid used as the component (A) in the present invention 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 decanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid, isostearic acid and the like. The molecular weight of the fatty acid is preferably 170 to 360.

  Examples of the alkyl phosphate used as the component (A) in the present invention include a monoalkyl phosphate represented by the following formula (I) or a dialkyl phosphate represented by the following formula (II).

In the formula (I) or (II), R ₁ and R ₂ represent the same or different alkyl groups having 6 to 22 carbon atoms.

In the present invention, the alkyl phosphate ester is preferably oil-soluble.
Specific examples of the alkyl phosphate ester include isodecyl acid phosphate, 2-ethylhexyl acid phosphate, dibutyl phosphate and the like. The molecular weight of the alkyl phosphate ester is preferably 200 or more.

  Although it will not specifically limit as an amine compound used as a component (B) by this invention if it is an oil-soluble amine compound neutralized by a component (A), A representative is an alkylamine. The alkylamine is preferably a compound containing one amino group in one molecule and one to three alkyl groups bonded to the amino group, that is, a primary to tertiary amine compound. The group is preferably a long-chain alkyl group having 8 or more carbon atoms.

  Specific examples of such alkylamines include dioctylamine, dilaurylmethylamine, trioctylamine, dimethyllaurylamine, dimethylmyristylamine, dimethylpalmitylamine and the like. The molecular weight of the alkylamine is preferably 150 to 800.

  In the present invention, since the component (A) and the component (B) are allowed to coexist in the oil-based ink, the component (A) and the component (B) form a neutralized salt in the ink. It is considered that a pigment such as carbon black used for oil-based ink generally has a carboxyl group or a hydroxyl group introduced to the surface in order to promote the adsorption of the pigment dispersant, and the surface potential is biased negative. According to the present invention, since the neutralized salt coexists in the oil-based inkjet ink comprising at least a pigment, a pigment dispersant, and a solvent, the neutralized salt is adsorbed on the surface of the pigment, and the nozzle plate and the carbon black are mixed. It is thought that contact is suppressed.

  Component (A) and component (B) are preferably blended in an amount of 0.01 to 5% by weight, more preferably, based on the total amount of the ink, in order to exhibit the ink repellent property with respect to the nozzle plate. Is added in an amount of 0.1 to 3% by weight, particularly preferably 0.3 to 1.0% by weight. If the amount added is too large, the printing density may decrease.

  Component (A) and component (B) are preferably blended at a molar ratio (component (A) / component (B)) of 0.1 to 10.0, more preferably 0.3 to 3. It is still more preferable to mix | blend by 0.8-1.2. If the molar ratio is out of this range, the effects of the present invention may not be sufficiently exhibited.

  In addition to the above solvent, pigment, pigment dispersant, component (A) and component (B), the inkjet ink of the present invention, for example, as long as it does not affect the repellency of the ink to the nozzle plate, for example, Dyes, preservatives, etc. can be added.

  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 23 ° C. of the inkjet ink of the present invention thus obtained is preferably set in a range of 5 to 30 mPa · s suitable for ejection from an inkjet head nozzle, and is set in a 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.

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

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

Examples 1-7, Comparative Examples 1-6
After premixing the components of the pigment dispersion shown in Tables 1-2 at the ratios shown in Tables 1-2, pigment dispersions were prepared, and the viscosity adjusting solvents shown in Tables 1-2 were added to Tables 1-2. It mixed in the ratio shown. 30 g of the obtained mixed solution was put in a glass container, 80 g of zirconia beads (φ0.5 mm) was put in this, and it was operated at a frequency of 60 Hz for 2 hours using a rocking mill (RM05S type manufactured by Seiwa Giken) to prepare an inkjet ink. . In addition, the compounding quantity of each component in Tables 1-2 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 Tables 1-2.

(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.
X: Ink repellent time 4 seconds or more,
Δ: Ink repellent time 3 seconds or more and less than 4 seconds,
○: Ink repellent time 2 seconds or more and less than 3 seconds,
A: The ink repellent time is less than 2 seconds.

(2) Evaluation of wiping durability Using an inkjet printer “HC5500” (trade name: manufactured by Riso Kagaku Kogyo Co., Ltd.), the head cleaning was performed a predetermined number of times by normal cleaning of the head maintenance, and the wiping blade contacted. The ink repellency of the part was visually evaluated.
◎: The ink repellency of all the parts in contact with the wiping blade was maintained, and the ink was completely repelled immediately after the head cleaning. ○: The ink repellency of all the parts in contact with the wiping blade was maintained. The ink was completely repelled within 20 seconds after the head cleaning.
(Triangle | delta): The ink repellency of the part which the wiping blade contacted was falling.
X: The ink repellency of all the parts which contacted the wiping blade was lowered.

(3) Evaluation of image density Each ink was loaded into an inkjet printer “HC5500” (trade name: manufactured by Riso Kagaku Co., Ltd.) and plain paper (ideal paper thin end (product name: manufactured by Riso Kagaku Co., Ltd.)). A printed matter was obtained by printing a black solid on the surface, and the OD value of the printed surface (table) of the obtained printed matter was measured with an optical densitometer (RD920, manufactured by Macbeth Co., Ltd.). Evaluation was made with a value of 0.95 or more and less than 1.05 as Δ and a value of less than 0.95 as x.

In addition, the symbol of the raw material of Tables 1-2 is as follows.
MA8 (trade name): Carbon black manufactured by Mitsubishi Chemical Corporation.
S-11200: Pigment dispersant Solsperse 11200 (trade name, solid content 50%) manufactured by Lubrizol.
OLA: oleic acid (reagent).
AP-10: Daihachi Chemical Industry Co., Ltd. isodecyl acid phosphate AP-10 (trade name).
DOA: Dioctylamine (reagent).
DLMA: Dilaurylmethylamine (reagent).
disperbyk-101: a salt of a long-chain polyaminoamide and a polar acid ester manufactured by Big Chemie Japan.
AF-7: Shin Nippon Oil Co., Ltd. naphthenic solvent AF-7 (trade name).
IOP: Isooctyl palmitate (manufactured by Nikko Chemicals).
FOC-140N: Isomyristyl alcohol FOC-140N (trade name) manufactured by Nissan Chemical Co., Ltd.

From the results in Table 1, the following can be understood.
Since the inks of Examples 1 to 7 belonging to the present invention contain (A) fatty acid or alkyl phosphate ester and (B) amine compound, the wiping durability of the nozzle plate can be maintained well, and the ink can be used with respect to the nozzle plate. It can be seen that the repellency is good. In particular, it can be seen from Example 1 that the use of a fatty acid as the component (A) is preferable because the image density increases. Further, from Example 6, it can be seen that it is preferable to use an appropriate amount of a higher alcohol solvent as a polar solvent because the image density is increased.

From the results in Table 2, the following can be understood.
Comparative Example 1 is an example in which neither component (A) nor component (B) is contained, and the ink repelling property with respect to the nozzle plate is inferior, and the wiping durability of the nozzle plate is also inferior. Comparative Examples 2 and 3 are examples in which the additive disclosed in Japanese Patent Application Laid-Open No. 2008-274232 is used, but a large amount of additive is used to improve the repelling property of the ink to the nozzle plate and the wiping durability of the nozzle plate. Necessary and when added in large amounts, the image density decreased. Comparative Examples 4 to 6 are examples containing any one of the component (A) and the component (B), and the ink repellency to the nozzle plate was poor, and the wiping durability of the nozzle plate was also poor.

  The oil-based inkjet ink of the present invention has good repellency to the nozzle plate, so that not only can the deterioration of the nozzle plate be suppressed, but it can also be used in the field of inkjet printing, and can be used in the field of inkjet printing. It can be used in the field of printing using a printer.

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

Claims (6)

Pigment, an oil-based inkjet ink comprising at least a pigment dispersant and a solvent, wherein the oil-based inkjet ink, further characterized by containing a (A) A Rukirurin acid ester and (B) an amine compound Oil-based inkjet ink. An oil-based inkjet ink comprising at least a pigment, a pigment dispersant and a solvent, wherein the oil-based inkjet ink further contains (A) a fatty acid and (B) an amine compound. . The oil-based inkjet ink according to claim 1 or 2 , wherein the component (A) and the component (B) are contained in a total amount of 0.01 to 5% by weight based on the total amount of the ink. The oil-based inkjet ink of Claim 3 formed by mix | blending the said component (A) and the said component (B) by 0.1-10.0 molar ratio (component (A) / component (B)). The oil-based inkjet ink according to claim 4 , wherein the pigment is carbon black. The oil-based inkjet ink according to claim 5 , wherein the solvent contains a fatty acid ester solvent and / or a higher alcohol solvent .

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