JP4897205B2 - Non-aqueous inkjet ink - Google Patents

Description

  The present invention relates to a non-aqueous inkjet ink that is excellent in pigment dispersion stability and excellent in storage stability and ejection stability of ink.

  Inkjet recording methods are broadly classified into on-demand (voluntary ejection) types and continuous (continuous ejection) types, both of which eject high-fluidity inkjet ink as ink particles from fine nozzles and face the nozzles. It is used to record an image on a placed printing medium, and is rapidly spreading in recent years because it can perform high-speed printing with low noise.

  Ink jet inks used in such an ink jet recording system are roughly classified into water-based inks and non-water-based inks. Water-based inks are often used in which water-soluble dyes such as acid dyes, direct dyes, and basic dyes are dissolved in glycol solvents and water. Inkjet recordings using this type of ink are generally water resistant. There is a problem of being inferior.

  In contrast, non-aqueous inks are excellent in water resistance, and are roughly classified into solvent-based inks mainly composed of volatile solvents and oil-based inks mainly composed of non-volatile solvents. In particular, oil-based inks are suitable as inks for high-speed inkjet printers because they are less likely to clog ink nozzles and require less cleaning of the ink nozzles, and many proposals have been made.

  For example, Japanese Patent Application Laid-Open No. 50-84311 discloses an inkjet in which clogging of an inkjet head nozzle is reduced by dissolving an oil-soluble dye in a liquid fatty acid and dissolving or dispersing it in a high-boiling aromatic hydrocarbon solvent. Ink has been proposed (see Patent Document 1). In this ink, the liquid fatty acid is non-volatile and the solubility of the oil-soluble dye is good, so that the liquid fatty acid does not evaporate in the head nozzle and does not precipitate the oil-soluble dye, thereby reducing head nozzle clogging. Is. This ink is effective when an oil-soluble dye is used as a coloring material, but cannot be applied when a pigment having good light resistance is used.

  Japanese Patent Application Laid-Open No. 2003-261808 discloses that a non-aqueous inkjet ink composition having good storage stability contains a polar organic solvent in an amount of 60% by weight or more based on the total amount of the ink, and further 10% by weight of the polar organic solvent. The point which aims at the stability of an ink by making the above into a fatty acid ester solvent is proposed.

JP 50-84311 A JP 2003-261808 A

  However, the non-aqueous ink jet ink according to the above proposal was certainly good in terms of the storage stability of the ink, that is, the change in viscosity and particle size over time, but a starchy foreign matter was generated in the ink, Ink ejection properties sometimes deteriorated. In order to maintain the ejection stability of the ink, it is necessary to suppress changes in physical properties over time and to suppress the occurrence of this starchy foreign matter.

  Accordingly, the present invention solves the above-described problems of the prior art, and provides a non-aqueous inkjet ink that has excellent ink storage stability with no change in physical properties of the ink over time, and that has excellent ejection stability while suppressing the occurrence of foreign matter. The purpose is to provide.

  As a result of intensive studies under the above-mentioned objectives, the present inventors have found that the starch-like foreign substance is a fatty acid salt, and the alcohol-based solvent, ester-based solvent and pigment dispersant used in the ink are in trace amounts. Free fatty acids present and lower saturated fatty acids produced in the process of oxidative degradation of unsaturated fatty acids react with metal ions present in pigments and plastics in ink containers to form fatty acid salts. It has been found that when the solubility in a solvent is low, it is produced as the above-mentioned starchy foreign matter in the ink. Therefore, the polar solvent in the ink contains an unsaturated higher fatty acid and a polar solvent having the same carbon chain structure, and the former is used in combination with a specific composition, so that the generation of starchy foreign substances can be suppressed. Knowledge has been obtained and the present invention has been completed.

  That is, according to the present invention, a non-aqueous ink-jet ink comprising at least a pigment, a pigment dispersant and a solvent, wherein the solvent contains at least 40% by weight of a polar solvent based on the total amount of the solvent, An unsaturated higher fatty acid and a polar solvent having the same carbon chain structure as the unsaturated higher fatty acid, wherein the content of the unsaturated higher fatty acid is less than 8% by weight based on the total amount of the ink, and the unsaturated higher fatty acid The ratio of the content of the unsaturated higher fatty acid to the content of the polar solvent having the same carbon chain structure is less than 2.5.

  According to the present invention, the polar solvent is contained in an amount of 40% by weight or more based on the total amount of the solvent, and the polar solvent contains a specific amount of an unsaturated higher fatty acid and a polar solvent having the same carbon chain structure. Thus, while ensuring the storage stability in the ink, the unsaturated higher fatty acid can preferentially react with the metal ion contained in the pigment or the like, and the metal ion can be captured. In addition, since the ratio of the content of the unsaturated higher fatty acid to the content of the polar solvent having the same carbon chain structure as the unsaturated higher fatty acid is less than 2.5, the metal ions are captured. The unsaturated higher fatty acid salt thus formed can be dissolved in a polar solvent having the same carbon chain structure, and as a result, the unsaturated higher fatty acid salt does not precipitate as a starchy foreign substance. .

  The non-aqueous inkjet ink of the present invention contains at least a pigment, a pigment dispersant, and a solvent, and among these, the solvent is characteristic.

  From the viewpoint of ink storage stability, at least 40% by weight, preferably 50% by weight or more, more preferably 60% by weight or more of the solvent is composed of a polar solvent. Examples of the polar solvent include higher fatty acids, higher fatty acid esters, higher alcohols, glycol ethers and the like. Usually, those that are liquid at room temperature are used, and those that are non-volatile at room temperature are preferred. In the present invention, it is essential that the solvent contains at least an unsaturated higher fatty acid and a polar solvent having the same carbon chain structure. Here, the above “higher” means that any solvent has 9 or more, preferably 12 to 18 carbon atoms in one molecule.

  Specific examples of the unsaturated higher fatty acid include oleic acid, linoleic acid, linolenic acid and the like, and these can be used alone or in combination of two or more. The content of the unsaturated higher fatty acid is less than 8% by weight, preferably 0.1 to 7.5% by weight, more preferably 1 to 5% by weight, based on the total amount of the ink. Higher fatty acids act so as to preferentially capture metal ions contained in pigments and the like. Therefore, the higher content is preferably within the above range. However, when 8% by weight or more is contained in the ink, The acid value of the ink becomes high, the storage stability becomes poor, and the member such as plastic that comes into contact with the ink may be corroded.

  The polar solvent having the same carbon chain structure as that of the unsaturated higher fatty acid is a polar solvent other than the unsaturated higher fatty acid, and the carboxylic acid group of the unsaturated higher fatty acid is subjected to treatment such as reduction or esterification. The compound which can be induced | guided | derived by carrying out, and an unsaturated higher fatty acid ester, an unsaturated higher alcohol, etc. are mentioned specifically ,. When any one of the above-mentioned unsaturated higher fatty acids is used alone in the solvent, either one of an unsaturated higher fatty acid ester or an unsaturated higher alcohol having the same carbon chain structure may be used, These may be used in combination. When two or more types of unsaturated higher fatty acids are used in combination, either one of the unsaturated higher fatty acid and the unsaturated higher fatty acid ester or unsaturated higher alcohol having the same carbon chain structure is used. These may be used in combination, or may be used in combination with other unsaturated higher fatty acids, unsaturated higher fatty acid esters or unsaturated higher alcohols having the same carbon chain structure, or combinations thereof. Also good.

  Specific examples of unsaturated higher fatty acid esters include methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, isobutyl oleate, decyl oleate, oleyl oleate, methyl linoleate, ethyl linoleate, and isopropyl linoleate. Etc. Moreover, you may use mixed fatty acid ester, such as soybean oil methyl, soybean oil isobutyl, and palm oil methyl. These unsaturated higher fatty acid esters can be used alone or in combination of two or more.

  Specific examples of the unsaturated higher alcohol include unsaturated aliphatic higher alcohols such as oleyl alcohol and linolenyl alcohol. These unsaturated higher alcohols can be used alone or in combination of two or more.

  The ratio of the content of the unsaturated higher fatty acid to the content of the unsaturated higher fatty acid and the polar solvent having the same carbon chain structure is less than 2.5, preferably 0.03 to 0.85. When this ratio is 2.5 or more, the fatty acid salt formed by the reaction between the metal ion contained in the pigment or the like and the unsaturated higher fatty acid is not completely dissolved and remains in the ink as a starchy foreign substance. It will be.

  Specific examples of the saturated higher alcohol include isostearyl alcohol, isomyristyl alcohol, isopalmityl alcohol and the like. Specific examples of the glycol ether include diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol dibutyl ether and the like. These can be used alone or in combination of two or more.

  In the present invention, the solvent may contain a nonpolar solvent in addition to the polar solvent. As this non-polar solvent, hydrocarbon solvents such as naphthenic, paraffinic, and isoparaffinic solvents can be used. Specifically, “Isoper, Exol” (all trade names) manufactured by ExxonMobil, manufactured by Nippon Oil Corporation “AF Solvent” (trade name), “Sansen, Thumper” (both trade names) manufactured by Sun Oil Co., Ltd.

  In addition, when using the said unsaturated higher alcohol or saturated higher alcohol, it is especially preferable that these total content shall be 50 weight% or more with respect to the polar solvent whole quantity. When this content is less than 50% by weight, problems may occur in the printed matter in the following cases. That is, some other printing materials use a binder resin to improve the fixability of the colorant. When this resin is brought into contact with a solvent having good solubility, the resin is It swells, the fixing property of the colorant is impaired, and the printed matter is defective. For example, styrene-acrylic resin, polyester resin, epoxy resin, and the like are used as binder resins for toners used in electrophotography. When this toner contains a styrene-acrylic resin, the resin swells when brought into contact with the fatty acid ester. As a result, when the printed matter imaged with the toner and the printed matter imaged using the ink containing the polar solvent are stored in an overlapping manner, the printed matter may adhere to each other due to the swollen resin, or the image may be May be disturbed. In this regard, in the case of higher alcohol, such a problem does not occur, so the content of higher alcohol is preferably set to be in the above range or more.

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, pyridian, 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. Among these, this invention is suitable when using the pigment containing a metallic element.
The pigment is preferably contained in the range of 0.01 to 20% by weight with respect to the total amount of ink.

  Examples of the pigment dispersant used in the present invention include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, Molecular weight unsaturated acid ester, polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonyl phenyl ether Polyester polyamine, stearylamine acetate and the like are preferably used.

  These pigment dispersants are not particularly limited as long as the pigments to be used are stably dispersed in the solvent, and among them, it is preferable to use a polymer dispersant. Specifically, “Solsperse 5000 (phthalocyanine ammonium salt type), 13940 (polyesteramine type), 17000, 18000 (fatty acid amine type), 22000, 24000, 28000” (all trade names), manufactured by Nippon Lubrizol, Efka “Fuka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)” (all trade names), manufactured by CHEMICALS, manufactured by Kao Corporation “Demol P, EP, Poise 520, 521, 530, Homogenol L-18 (polycarboxylic acid type polymer surfactant)” (both trade names), “Disparon KS-860, KS-873N4” manufactured by Enomoto Kasei Co., Ltd. (Amine salt of high molecular polyester) ”(both trade names), No. “Discall 202, 206, OA-202, OA-600 (multi-chain polymer non-ionic)” (all are trade names) manufactured by Ichi Kogyo Seiyaku Co., Ltd.

  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.

  The non-aqueous inkjet ink of the present invention includes, for example, dyes, surfactants, antiseptics in addition to the solvents, pigment dispersants, and pigments as long as the storage stability and oxidation stability of the ink are not affected. An agent or the like can be added.

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

  The viscosity at 23 ° C. of the non-aqueous inkjet ink of the present invention thus obtained is preferably set in the range of 5 to 30 cPs suitable for ejection from the inkjet head nozzle. Further, the freezing point of the ink is preferably set to −20 ° 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.

Used ink material (1) Pigment Carmine 6B (Azo pigment)
(2) Pigment dispersant Solsperse 28000 (trade name, manufactured by Nihon Lubrizol)
(3) Unsaturated higher fatty acid oleic acid (manufactured by Wako Pure Chemical Industries, Ltd.)
Linoleic acid (Wako Pure Chemical Industries, Ltd.)
(4) Unsaturated higher fatty acid ester Ethyl oleate (trade name EOO, manufactured by Nikko Chemical Co., Ltd.)
Ethyl linoleate (trade name VFE, manufactured by Nikko Chemical)
Soybean oil methyl (SE-0120-1, manufactured by Nikka Gosei Co., Ltd., containing 20-35% methyl oleate)
(5) Unsaturated higher alcohol oleyl alcohol (Wako Pure Chemical Industries, Ltd.)
(6) Saturated higher alcohol Isostearyl alcohol (trade name FOC180, manufactured by Nissan Chemical Industries, Ltd.)
(7) Nonpolar solvent AF6 (trade name, manufactured by Nippon Oil Corporation)

Example 1
Carmine 6B is used as an azo pigment having a high metal element content, 5% by weight of this carmine 6B, 3% by weight of Solsperse 28000 (trade name), 10% by weight of ethyl oleate, 10 parts by weight of AF6 (trade name) The mixture was mixed and dispersed in a bead mill for about 20 minutes to prepare a pigment dispersion. The remaining solvent was added to this pigment dispersion while stirring so as to have the composition shown in Table 1, and filtered through a membrane filter to prepare a non-aqueous inkjet ink.

Examples 2-5 and Comparative Examples 1-5
Ingredients shown in Table 1 were mixed and dispersed in the same manner as in Example 1, and then treated with a membrane filter to prepare inks of Examples 2-5 and Comparative Examples 1-6.

For the non-aqueous inkjet inks obtained in the above examples and comparative examples, the storage stability and ejection stability of the ink were evaluated by the following methods. The evaluation results are shown in Table 1.
(1) Ink storage stability After measuring the viscosity immediately after the preparation of each ink as an initial viscosity, each ink was placed in a sealed container and allowed to stand in a 70 ° C. environment for 4 weeks. Was measured. Haake Rheometer RS75 was used for viscosity measurement. From these measurement results, the viscosity change rate (%) was determined based on the following equation. This viscosity change rate was evaluated according to the following criteria.
○ ・ ・ ・ Viscosity change rate of less than 3% × ・ ・ ・ Viscosity change rate of 3% or more

(2) Occurrence of starchy foreign matter After each ink was prepared for 2 weeks in an environment of 70 ° C., each ink was filtered through a # 2000 metal mesh to determine whether or not the foreign matter remained on the metal mesh. Observation was performed using a microscope.
○ ・ ・ ・ Almost no foreign matter is found × ・ ・ ・ There are many foreign matters

(3) Ink ejection stability After each ink was left in a 60 ° C. environment for 1 week, it was introduced into a piezo piezoelectric line-type inkjet head of an inkjet printer “ORPHIS HC5000” (made by Riso Kagaku Kogyo). The operation of stopping the ink after discharging each ink continuously was performed 10 times. The results of this ink ejection test were evaluated according to the following criteria.
○ ・ ・ ・ There is almost no ejection failure.

  From the results of Table 1, in the case of Examples 1 to 7 belonging to the present invention, the polar solvent contains at least 40% by weight with respect to the total amount of the solvent, and the polar solvent contains unsaturated higher fatty acid and the same carbon chain structure as this. The unsaturated higher fatty acid content is less than 8% by weight based on the total amount of the ink, and the unsaturated higher fatty acid content of the unsaturated higher fatty acid and the carbon chain structure. Since the ratio to the content of the polar solvent having the same is less than 2.5, it was confirmed that the storage stability of the ink was excellent, the generation of foreign matter was scarce, and the ejection stability was also good.

  On the other hand, in the case of Comparative Example 1, since the unsaturated higher fatty acid is not contained, the amount of foreign matter generated in the ink is large and the ejection stability of the ink is also inferior. In the case of Comparative Example 2, since the content of unsaturated higher fatty acids relative to the total amount of ink is large, both the storage stability and ejection stability of the ink are inferior. In the case of Comparative Example 3, since the content of the polar solvent is less than 40% by weight of the total amount of the solvent, the storage stability of the ink is inferior. In the case of Comparative Example 4, since the ratio of the content of unsaturated higher fatty acid to the content of unsaturated higher fatty acid ester having the same carbon chain structure as that of the unsaturated higher fatty acid exceeds 2.5, the storage stability of the ink is increased. Both insufficiency and ejection stability are poor, and the amount of foreign matter generated in the ink is large. In the case of Comparative Example 5, the structure of the carbon chain of the unsaturated higher fatty acid ester and the unsaturated higher fatty acid in the polar solvent is different, so that foreign matter is often generated and the ink ejection stability is poor.

The non-aqueous ink-jet ink of the present invention is excellent in ink storage stability, and also when a pigment component having a high metal element content is used or when the ink is stored in an ink nozzle or a plastic container for a long period of time. It is particularly suitable as a high-speed ink-jet ink because it generates less starchy foreign matter and has excellent ink ejection stability.

Claims (3)

A non-aqueous ink-jet ink comprising at least a pigment, a pigment dispersant and a solvent, wherein the solvent contains at least 40% by weight of a polar solvent with respect to the total amount of the solvent, and the polar solvent has 9 to 18 carbon atoms. A saturated higher fatty acid and a compound derived by reducing or esterifying a carboxylic acid group of the unsaturated higher fatty acid, and the content of the unsaturated higher fatty acid having 9 to 18 carbon atoms is based on the total amount of the ink The ratio of the content of the unsaturated higher fatty acid having less than 8% by weight and having 9 to 18 carbon atoms to the content of the compound derived by reducing or esterifying the carboxylic acid group of the unsaturated higher fatty acid is A non-aqueous inkjet ink characterized by being less than 2.5. The non-aqueous inkjet ink according to claim 1, wherein the unsaturated higher fatty acid having 9 to 18 carbon atoms is selected from unsaturated higher fatty acids having 12 to 18 carbon atoms. The non-aqueous inkjet ink according to claim 1, wherein the unsaturated higher fatty acid having 9 to 18 carbon atoms is selected from the group consisting of oleic acid, linoleic acid and linolenic acid.