JP2011046759A - Oil-based inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil-based inkjet ink capable of preventing accumulation of solid materials. <P>SOLUTION: To the oil-based inkjet ink comprising at least a pigment, a dispersing agent, and an organic solvent; at least one compound selected from alkyl silicate represented by general formula of the figure (wherein n is an integer of 2-4), an oligomer of the alkyl silicate of this general formula, and orthocarboxylic esters is added as a chemical dehydrating agent compatible with the organic solvent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an oil-based ink-jet ink, and more particularly to an oil-based ink-jet ink capable of suppressing the accumulation of solid matter.

  The ink jet recording method is a method in which high-fluidity ink jet ink is ejected as ink particles from fine head nozzles, and an image is recorded on a printing medium placed opposite to the nozzles. Since it is possible, it has spread rapidly in recent years. As inks used in such an ink jet recording method, various so-called oil-based ink jet inks in which pigments are finely dispersed in a water-insoluble solvent have been proposed.

  For example, the present inventors have proposed an ink in which a pigment is dispersed in a nonpolar solvent such as an ester solvent, a higher alcohol solvent, or a hydrocarbon solvent in Patent Document 1. This ink has excellent on-machine stability and has an advantage that a print surface that does not stick even when superimposed on a print surface printed by a PPC copying machine or a laser printer can be obtained.

  However, when the ink is used for a long period of time, solid matter accumulates in the vicinity of the nozzles of the ink jet head, preventing normal ink discharge and causing image defects. The solid matter in the vicinity of the nozzle is water-soluble, and the component dissolved in the water contained in a trace amount in the ink raw material (pigment, resin, solvent and other additives) is in contact with the ink due to the evaporation of water, that is, the nozzle This is considered to be caused by the accumulation of solids in the vicinity. In particular, since a high-speed ink jet printer is not provided with a capping mechanism for the head in order to increase the printing start time, it is difficult to suppress solid matter accumulation from the printer side.

  As a method for reducing the water content of an oil-based inkjet ink, for example, Patent Document 2 discloses a series of operations of dehydrating by passing an oil-based inkjet ink through a cylinder packed with a molecular sieve and then filtering with a membrane filter. It is described that the process is repeated until a desired water content is obtained.

JP 2007-126564 A JP 2007-314635 A

  However, the method for reducing the water content using the molecular sieve described in Patent Document 2 is complicated because it creates a new process in the production of oil-based inkjet ink, and the printer forms meniscuses at the head nozzles. Therefore, even if the moisture content is reduced during ink production, the ink absorbs moisture after the printer is introduced, so that solid matter is prevented from depositing near the nozzles of the inkjet head. I found it impossible.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an oil-based inkjet ink capable of suppressing the accumulation of solid matter near the nozzles of an inkjet head by a simple method. .

  The oil-based ink-jet ink of the present invention is an oil-based ink-jet ink comprising at least a pigment, a dispersant, and an organic solvent, and contains a chemical dehydrating agent that is compatible with the organic solvent.

下記一般式（式中、ｎは１〜３の整数、ｍは２〜５の整数）で表されるアルキルシリケートオリゴマー、

およびオルトカルボン酸エステル類の中から選ばれる少なくとも１つであることが好ましい。 The chemical dehydrating agent is an alkyl silicate represented by the following general formula (wherein n is an integer of 2 to 4),

An alkyl silicate oligomer represented by the following general formula (where n is an integer of 1 to 3, and m is an integer of 2 to 5):

And at least one selected from orthocarboxylic acid esters.

The orthocarboxylic acid esters are preferably alkyl orthoformate, alkyl orthoacetate, alkyl orthopropionate or alkyl orthobutyrate (the alkyl group has 1 to 4 carbon atoms).
The organic solvent preferably contains a fatty acid ester and / or a higher alcohol.

  The oil-based ink-jet ink of the present invention contains a chemical dehydrating agent that is compatible with the organic solvent in the oil-based ink-jet ink composed of at least a pigment, a dispersant, and an organic solvent. Since moisture due to moisture absorption can also be reduced, it is possible to suppress the accumulation of solid matter in the vicinity of the nozzles of the inkjet head. Moreover, the oil-based inkjet ink of the present invention only has to add a chemical dehydrating agent that is compatible with an organic solvent, so that new equipment and complicated operations are not necessary for ink production, and it is excellent in production suitability.

  Hereinafter, the oil-based inkjet ink of the present invention will be described in detail. The chemical dehydrating agent that can be used in the oil-based inkjet ink of the present invention is compatible with an organic solvent and can be used without particular limitation as long as it does not react with ink components other than water. . However, in the case of oil-based inkjet ink, it is more preferable to use the following chemical dehydrating agent because it is necessary to consider ejection stability, on-machine stability, etc. in addition to suppressing solid matter accumulation.

下記一般式（式中、ｎは１〜３の整数、ｍは２〜５の整数）で表されるアルキルシリケートオリゴマー

あるいはオルトカルボン酸エステル類を好ましくあげることができる。 Specifically, the alkyl silicate represented by the following general formula (wherein n is an integer of 2 to 4)

Alkyl silicate oligomer represented by the following general formula (where n is an integer of 1 to 3, and m is an integer of 2 to 5)

Alternatively, orthocarboxylic acid esters can be preferably exemplified.

  The orthocarboxylic acid esters are preferably alkyl orthoformate, alkyl orthoacetate, alkyl orthopropionate, or alkyl orthobutyrate (the alkyl group of these orthocarboxylic acid esters has 1 to 4 carbon atoms). The chemical dehydrating agents can be used alone or in combination of two or more.

  The content of the chemical dehydrating agent is 0.1% by mass to 2% by mass with respect to the total amount of ink in the case of alkyl silicate, and 0.1% by mass with respect to the total amount of ink in the case of alkyl silicate oligomer. In the case of ˜2% by mass and orthocarboxylic acid esters, it is preferably 0.1% by mass to 5% by mass with respect to the total amount of the ink. In addition, when it contains the fatty acid ester and higher alcohol which are mentioned later as an organic solvent, it is more preferable to increase 0.5 mass%-5 mass% rather than the said content.

  The organic solvent used by this invention is not specifically limited, For example, water-insoluble organic solvents, such as a hydrocarbon solvent, an ester solvent, an alcohol solvent, a higher fatty acid solvent, can be used. These may be used alone or in combination of two or more. When using 2 or more types mixed, it is necessary for a liquid mixture to form a single continuous phase.

  Examples of the hydrocarbon solvent include aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, and the like. As the aliphatic hydrocarbon solvent and alicyclic hydrocarbon solvent, “Nippon Oil Co., Ltd.“ Tclean N-16, Tclean N-20, Tclean N-22, No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent ” "H, AF-4, AF-5, AF-6, AF-7" (all trade names), "Nisseki Isosol, Naphthezol" (all trade names) manufactured by Nippon Petrochemicals, "Exxon Mobil" IsoparG, IsoparH, IsoparL, IsoparM, ExxolD40, ExxolD80, ExxolD100, ExxolD140, ExxolD140 "(all trade names).

  As ester solvents, methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate, isopropyl oleate, butyl oleate, methyl linoleate, isobutyl linoleate, Ethyl linoleate, isopropyl isostearate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate, trimethylolpropane tri-2-ethylhexanoate And glyceryl tri-2-ethylhexanoate.

Examples of the alcohol solvent include isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol and the like.
Examples of the higher fatty acid solvent include isononanoic acid, isomyristic acid, isopalmitic acid, oleic acid, and isostearic acid.
The amount of the organic solvent used in the present invention is preferably 60% by mass or more, more preferably 70 to 98% by mass, based on the total amount of the ink.

  In the oil-based inkjet ink of the present invention, when the water-insoluble organic solvent contains a fatty acid ester, a higher alcohol, or these two types, the effect of the chemical dehydrating agent becomes more remarkable. In particular, from the viewpoint of the dispersion stability of the pigment, there is a case where it is desired to use a solvent having a high water content such as a fatty acid ester or a higher alcohol, but even if these solvents are used, in the oil-based inkjet ink of the present invention, Accumulation of solid matter in the vicinity of the nozzles of the inkjet head can be suppressed.

  In addition to the water-insoluble organic solvent, the oil-based ink-jet ink of the present invention may be added with a water-soluble organic solvent in a range that is compatible with this and forms a single continuous liquid phase. The water-soluble organic solvent is not particularly limited, and conventionally known solvents such as lower alcohols can be used. Even in this case, in the oil-based inkjet ink of the present invention, it is possible to suppress the solid matter from being deposited near the nozzles of the inkjet head.

  The pigment used in the present invention is not particularly limited, and conventionally known inorganic pigments and organic pigments can be used. Examples of inorganic pigments include titanium oxide, bengara, cobalt blue, ultramarine blue, bitumen, carbon black, calcium carbonate, kaolin, clay, barium sulfate, talc, and silica. Examples of the organic pigment include insoluble azo pigments, azo lake pigments, condensed azo pigments, condensed polycyclic pigments, and copper phthalocyanine pigments. These pigments may be used alone or in appropriate combination. The addition amount of the pigment is preferably 0.5 to 20% by mass with respect to the total amount of the ink.

The pigment dispersant is not particularly limited as long as the colorant to be used is stably dispersed in the solvent, but among them, it is preferable to use a polymer dispersant. Specifically, Nippon Lubrizol Corporation 13940 (polyesteramine type), 17000, 18000 (aliphatic amine type), 22000, 24000, 28000 (all trade names); Efka CHEMICALS, Inc. "Efka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4050, 4055 (modified polyurethane) ”(all trade names);“ Demol P, EP ”manufactured by Kao Corporation, “Poise 520, 521, 530”, “Homogenol L-18 (polycarboxylic acid type polymer surfactant)” (all trade names); “Disparon KS-860, KS-873N4 (polymer polyester) manufactured by Enomoto Kasei Co., Ltd. (All are trade names); “Discall 2” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 02, 206, OA-202, OA-600 (multi-chain polymer nonionic system) "(all trade names).
Examples of the oil-based inkjet ink of the present invention are shown below.

(Preparation of ink)
For Examples 1 to 8 and Comparative Example 1, the raw materials were premixed according to the formulation shown in Table 1 below (the numerical values shown in Table 1 are parts by mass), and then dispersed in a bead mill for about 10 minutes to obtain an inkjet ink. Prepared. Comparative Example 2 was premixed with the formulation shown in Table 1, then dispersed for about 10 minutes in a bead mill, passed through a cylinder packed with molecular sieves, and filtered through a 5.0 μm membrane filter. An ink jet ink was prepared by repeating the process until the amount reached 200 ppm. The adjusted ink was evaluated by the following items.

(Solid matter accumulation nozzle rate)
Each of the prepared inks is introduced into an inkjet printer “Orifice HC5500” (trade name: manufactured by Riso Kagaku Kogyo Co., Ltd.), and the ink is ejected continuously for 100 hours in a 35 ° C. and 85% environment, and then in the same environment. After standing for 2 weeks, it was confirmed with a microscope whether solid matter was deposited on the nozzle, the number of solid matter deposition nozzles for all nozzles (100) was measured, and the following evaluation was performed.
◎: Less than 5% ○: 5% or more and less than 20% △: 20% or more and less than 50% ×: 50% or more

  As is apparent from Table 1, in Examples 1 to 3, 5, and 6 using an alkyl silicate, Example 4 using an alkyl silicate oligomer, and Examples 7 and 8 using orthocarboxylic acid esters. Solid matter accumulation was suppressed. Comparative Example 2 was dehydrated with molecular sieves, but the amount of water immediately after ink preparation was low, but it was not effective in absorbing moisture after the printer was introduced. I couldn't. Example 5 is a case where the amount of the alkyl silicate added is considerably small, but even in this case, solid matter deposition was suppressed as compared with Comparative Example 1 containing no chemical dehydrating agent.

  As described above, since the oil-based inkjet ink of the present invention contains a chemical dehydrating agent that is compatible with an organic solvent, it was possible to suppress the accumulation of solid matter in the vicinity of the nozzles of the inkjet head. In particular, with conventional molecular sieves, it was not possible to reduce moisture due to moisture absorption after the introduction of the printer. I was able to suppress it. In addition, since the oil-based ink-jet ink of the present invention only needs to add a chemical dehydrating agent that is compatible with an organic solvent, new equipment and complicated operations are not necessary for ink production, and it is excellent in production suitability.

Claims (4)

  An oil-based inkjet ink comprising at least a pigment, a dispersant, and an organic solvent, and a chemical dehydrating agent compatible with the organic solvent. An alkyl silicate in which the chemical dehydrating agent is represented by the following general formula (wherein n is an integer of 2 to 4);

An alkyl silicate oligomer represented by the following general formula (where n is an integer of 1 to 3, and m is an integer of 2 to 5):

2. The oil-based inkjet ink according to claim 1, wherein the oil-based inkjet ink is at least one selected from orthocarboxylic acid esters.   3. The oil-based inkjet ink according to claim 2, wherein the orthocarboxylic acid ester is alkyl orthoformate, alkyl orthoacetate, alkyl orthopropionate or alkyl orthobutyrate (the alkyl group has 1 to 4 carbon atoms). .   The oil-based inkjet ink according to claim 1, wherein the organic solvent contains a fatty acid ester and / or a higher alcohol.