JP2013177483A - Water-in-oil (w/o) emulsion ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-in-oil (W/O) emulsion ink showing excellent print density and saturation of a printed material and particularly suitable for inkjet printing.SOLUTION: A water-in-oil (W/O) emulsion ink contains a water-soluble dye and a water-soluble clathrate in an aqueous phase. The water-soluble clathrate comprises preferably cyclodextrins, and more preferably, α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin. The water-soluble clathrate is compounded by 0.02 or more in terms of a mass ratio with respect to the water-soluble dye.

Description

  The present invention relates to a water-in-oil (W / O) emulsion ink containing a dye in an aqueous phase, which is excellent in printing density and chroma of printed matter.

  Inkjet printing is characterized by non-contact printing by ejecting ink droplets from fine nozzles, and each company is developing ink-jet ink with the aim of miniaturizing ink droplets, speeding up printed materials, and increasing the size. Is going.

  As ink-jet ink, water-based ink is generally used for personal and office use. The water-based ink has a high printing density due to the high water absorption of the printing paper fiber, and the show-through, which is the printing density viewed from the back side of the printed matter, is reduced. On the other hand, since the printing paper is dried in a state where pressure is applied when the paper is made, when water adheres, hydrogen bonds between the printing paper fibers are cut and paper curling occurs. This paper curl is conspicuous when a cut sheet is used, and affects the positional accuracy of the ink droplets and the paper conveyance. In particular, in order to aim at high-speed printing, it was necessary to eliminate paper curl.

  A technique for eliminating paper curl includes reducing or eliminating the amount of water in the ink. Therefore, if oil-based ink is used, paper curl does not occur and it is suitable for high-speed printing.

  Business printers that employ a line head type ink jet method are attracting attention because they have a fixed head and are capable of mass printing at high speed and are inexpensive. Oil-based inks are usually used in this high-speed inkjet printer, but the printed matter has a lower print density because the ink penetrates the back of the printed product when printed compared to other types of printers. , It will be a lot of strikethrough.

  One solution to this problem is to emulsify water in an oil-based ink to make a water-in-oil (W / O) emulsion ink. Water-in-oil (W / O) emulsion inks have the characteristics of both oil-based inks and water-based inks, have higher printing density than oil-based inks, reduce show-through, and can curl less than water-based inks. It can be said that the ink has both high-speed transportability and printing performance.

  In a water-in-oil (W / O) emulsion ink, a coloring material may be contained in the oil phase that is the outer phase, but it is preferable that a coloring material is contained in the aqueous phase that is the inner phase. Moreover, as a coloring material contained in the water phase of a water-in-oil (W / O) type emulsion ink, it is desirable to use a dye from the viewpoint of storage stability and dischargeability of the ink.

  However, a water-in-oil (W / O) emulsion ink containing a water-soluble dye in the aqueous phase has a lower print density of the printed matter than the water-based ink, and the chroma also changes to an aggregated color of the dye. There was a technical problem in that respect. With respect to this problem, the present inventors have reported that the printing density of the printed matter of water-in-oil (W / O) emulsion ink can be improved by adding an amino alcohol or an amine-based dispersant to the aqueous phase. However (see Patent Document 1 and Japanese Patent Application No. 2011-066983), the saturation of the printed matter has not been improved sufficiently.

  On the other hand, when a dye is used as a coloring material in water-based ink, it is known that it is inferior in weather resistance and water resistance compared to a pigment, but a compound that includes a dye such as cyclodextrin is used together with a specific dye. It has already been reported that water resistance is improved (see Patent Document 2). However, this report relates to water-based inks, not water-in-oil (W / O) emulsion inks, and does not mention any problem of saturation of printed matter and its improvement effect.

JP 2011-74195 A JP 2005-239822 A

  An object of the present invention is to provide a water-in-oil (W / O) emulsion ink that is excellent not only in print density but also in chroma.

  As a result of intensive studies under the above-mentioned objectives, the present inventors have found that a water-in-oil (W / O) emulsion ink comprising an aqueous phase and an oil phase contains a water-soluble dye and a water-soluble dye in the aqueous phase. By making the inclusion compound coexist, it was found that a water-in-oil (W / O) emulsion ink excellent in both printing density and saturation of the printed matter was obtained, and the present invention was completed.

That is, according to the present invention, there is provided a water-in-oil (W / O) emulsion ink comprising a water-soluble dye and a water-soluble inclusion compound in an aqueous phase.
The water-in-oil (W / O) emulsion ink of the present invention can be suitably used for inkjet applications.

  According to the present invention, since the water phase of the water-in-oil (W / O) emulsion contains a water-soluble dye as a coloring material in the presence of an inclusion compound, the printing density is high, A water-in-oil (W / O) emulsion ink having equivalent saturation is obtained. Moreover, the emulsion ink of this invention is excellent also in the weather resistance and water resistance of printed matter by using the said clathrate compound.

Hereinafter, the present invention will be described in more detail.
The water-in-oil (W / O) emulsion ink of the present invention is obtained by mixing an oil phase and an aqueous phase and dispersing the aqueous phase as fine particles in the oil phase.

  The aqueous phase is mainly composed of water, a water-soluble dye, and a water-soluble inclusion compound, but if necessary, a metal salt, an electrolyte, a moisturizer, a water-soluble polymer, and an oil-in-water (O / W) type resin You may contain other components, such as an emulsion, an antifungal agent, antiseptic | preservative, a pH adjuster, and an antifreezing agent.

  It does not specifically limit as water contained in a water phase, For example, ion-exchange water, distilled water, etc. can be used.

  The water-soluble dye is not particularly limited as long as it is included by the inclusion compound used in the present invention, and various dyes used in the field of printing ink can be used. Specific examples of such dyes include basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes, mordant dyes, reactive dyes, vat dyes, sulfur dyes, etc. Among these, water-soluble ones Those that become water-soluble by reduction or the like can be used. More specifically, examples include azo dyes, rhodamine dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, triphenylmethane dyes, diphenylmethane dyes, and methylene blue. The color of the dye may be not only black but also chromatic colors such as yellow, green, purple, and red. Such dyes can be used alone or in combination of two or more.

  The amount of the water-soluble dye is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and particularly preferably 1 to 10% by mass with respect to the total amount of the ink. Moreover, 5-40 mass% is preferable with respect to the water phase whole quantity, and, as for the compounding quantity of water-soluble dye, 10-30 mass% is more preferable. If the amount of the water-soluble dye is too small, the surface printing density will not be improved, and if it is too much, the ejection property will be deteriorated.

  In the present invention, an inclusion compound (also referred to as a clathrate compound) means that other ions, atoms, or molecules can be incorporated into the structure of a cavity existing in the inclusion molecule or in the molecular assembly. Means a compound. Among these, in the present invention, a water-soluble clathrate compound is used. Examples of the water-soluble clathrate compound include cyclodextrins, water-soluble calixarene, and urea. Examples of cyclodextrins include cyclodextrins represented by α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, and derivatives of these cyclodextrins. Of these, cyclodextrin is preferable, and γ-cyclodextrin is more preferable from the viewpoint of the effect of improving saturation. It is preferable to use cyclodextrins together with a red, black or yellow water-soluble dye having a relatively small dye molecule size, since the effect of improving the saturation is increased.

  The blending amount of the water-soluble clathrate compound is preferably 0.1 to 10% by mass, more preferably 0.15 to 8% by mass, and particularly preferably 0.2 to 6% by mass with respect to the total amount of the ink. Moreover, 0.1-30 mass% is preferable with respect to the water phase whole quantity, and, as for the compounding quantity of a water-soluble clathrate compound, 0.5-25 mass% is more preferable. The mixing ratio of the water-soluble clathrate compound to the water-soluble dye is preferably 0.02 or more, more preferably 0.03 to 1, and still more preferably 0.03 to 0.5. Increasing the blending amount of the water-soluble clathrate compound increases the chroma of the printed matter, but if it is too much, the ejection property may be deteriorated.

  The oil phase is mainly composed of an organic solvent and an emulsifier, but may contain other components as necessary.

  As the organic solvent, any of a nonpolar solvent and a polar solvent can be used. These may be used alone or in combination of two or more as long as they form a single phase.

  As non-polar solvents, petroleum hydrocarbon solvents such as naphthenic, paraffinic, and isoparaffinic solvents can be used. Specifically, aliphatic saturated hydrocarbons such as dodecane, “Isoper, Exol” manufactured by ExxonMobil ( All of them are trade names), “AF Solvent” (trade name) manufactured by JX Nippon Oil & Energy Corporation, “Sansen, Thumper” (all trade names) manufactured by Sun Oil Co., Ltd., and the like. These can be used alone or in combination of two or more.

  Examples of the polar solvent include ester solvents, alcohol solvents, fatty acid solvents, ether solvents and the like. These can be used alone or in combination of two or more.

  Examples of the ester solvent include higher fatty acid esters having 5 or more, preferably 9 or more, and more preferably 12 to 32 carbon atoms in one molecule. For example, isodecyl isononanoate, isotridecyl isononanoate, and isononanoic acid. Isononyl, methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, hexyl palmitate, isostearyl palmitate, isooctyl isopalmitate, methyl oleate, ethyl oleate, isopropyl oleate, oleic acid Butyl, hexyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopate isostearate Pill, 2-octyldodecyl pivalate, soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, diisopropyl sebacate, diethyl sebacate, propylene glycol monocaprate, trimethylol tri-2-ethylhexanoate Examples thereof include propane and glyceryl tri-2-ethylhexanoate.

  Examples of the alcohol solvent include aliphatic higher alcohols having 12 or more carbon atoms in one molecule. Specifically, higher alcohols such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, and oleyl alcohol. Examples include alcohol.

  Examples of the fatty acid solvent include fatty acids having 4 or more, preferably 9 to 22 carbon atoms in one molecule, such as isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid, and isostearic acid. Is mentioned.

  Examples of ether solvents include glycol ethers such as diethyl glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol dibutyl ether, and acetates of glycol ethers.

  The emulsifier is not particularly limited as long as it can form a water-in-oil (W / O) emulsion ink, but a nonionic surfactant is preferably used. Nonionic surfactants include, for example, sorbitan higher fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan sesquioleate, fatty acid glycerides, polyglycerin Examples thereof include fatty acid esters, fatty acid diglycerides, and ethylene oxide adducts such as higher alcohols, alkylphenols, and fatty acids.

  Of these, polyglycerol fatty acid esters are preferably used for inkjet. The polyglycerin fatty acid ester here refers to an esterified product of polyglycerin obtained by dehydration condensation of glycerin and a fatty acid or oxy fatty acid. In the polyglycerin fatty acid ester, the glycerin condensation amount is preferably 4 to 20 mol, more preferably 6 to 16 mol, and even more preferably 4 to 12 mol. The number of added moles of fatty acid or oxyfatty acid per molecule of polyglycerol is preferably 1 to 10 moles, and more preferably 1 to 3 moles. As the higher fatty acid or higher oxy fatty acid, those having 8 to 24 carbon atoms are preferable. Examples of the fatty acid include lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, stearic acid, and isostearic acid. Among these, oleic acid, stearic acid, and isostearic acid are preferable. Examples of the oxy fatty acid include ricinoleic acid, oxylauric acid, oxymyristic acid, oxypalmitic acid, oxystearic acid, oxybehenic acid, and the like, among which ricinoleic acid is preferable.

  Specific examples of preferred polyglyceryl fatty acid esters include tetraglyceryl monooleate, hexaglyceryl monooleate, decaglyceryl trioleate, tetraglyceryl monoisostearate, hexaglyceryl monoisostearate, decaglyceryl diisostearate, hexapolyricinoleate Examples include glyceryl.

  The amount of the emulsifier used in the present invention is preferably 0.5 to 40% by mass, more preferably 1 to 30% by mass, and still more preferably 2 to 20%, based on the solid mass, based on the total amount of the ink. % By mass. When the amount used is less than 0.5% by mass, the storage stability of the emulsion may be lowered. Moreover, when this usage-amount exceeds 40 mass%, a viscosity becomes high and there exists a possibility that it may become unsuitable for an inkjet use. Moreover, it is preferable that it is 3-50 mass% of the quantity of an oil phase, and, as for the usage-amount of an emulsifier, it is more preferable that it is 5-40 mass%.

  The oil phase 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. For example, after preparing a mixed solution in which a part of the solvent and a part of the other components are uniformly mixed in advance and dispersing with a disperser, the remaining solvent and the remaining other components are added to the dispersion. And can be prepared by passing through a filter.

  The water-in-oil (W / O) emulsion ink of the present invention can be produced by mixing and emulsifying the above oil phase and water phase. The aqueous phase and the oil phase may be prepared separately in advance, and then the aqueous phase solution may be added to the oil phase solution to emulsify, or the components constituting the oil phase may be added to the aqueous phase collectively or individually. Thereafter, it may be emulsified. A known emulsifier such as a disper mixer or a homomixer can be used for the production.

  The water-in-oil (W / O) emulsion ink of the present invention is blended so that the oil phase is 40 to 99% by mass and the water phase is 60 to 1% by mass. When the ratio of the water phase exceeds 60% by mass, it becomes difficult to form a water-in-oil (W / O) emulsion. When the ratio of the aqueous phase is less than 1% by mass, the print density may be lowered or the printout may be exposed. In general, since the ink viscosity tends to increase as the ratio of the aqueous phase increases, the blending ratio of both phases is preferably 50 to 98% by mass of the oil phase and 50 to 2% by mass of the aqueous phase, and 55 to 97 of the oil phase. The mass% and the water phase 45 to 3 mass% are more preferable, and the oil phase 70 to 97 mass% and the aqueous phase 30 to 3 mass% are even more preferable.

  The viscosity at 23 ° C. of the water-in-oil (W / O) emulsion ink of the present invention thus obtained is preferably set in the range of 3 to 100 mP · s when used as an inkjet application. More preferably, it is set in the range of 30 mPa · s, and particularly preferably in the range of 10 to 20 mPa · s. The viscosity of the ink can be adjusted by adjusting the type and amount of components of the oil phase and the amount of the aqueous phase. In general, the smaller the amount of aqueous phase and / or the amount of emulsifier, the lower the viscosity of the ink, but the lower the storage stability of the emulsion.

  The recording medium to be printed using the water-in-oil (W / O) emulsion ink of the present invention is not particularly limited, and is surface-treated so as to receive ink in addition to paper such as plain paper and coated paper. Alternatively, a plastic holder on which an ink receiving layer is formed, a plastic product such as a CD or a DVD, and the like. In addition, when performing ink jet printing using the water-in-oil (W / O) emulsion ink of the present invention, the ink jet printer discharges ink from a nozzle of an ink jet toward a recording medium based on a digital signal, There is no particular limitation as long as it reproduces an image such as a photograph, and any method such as a thermal method, a piezo method, or an electrostatic method may be used.

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

Examples 1-10, Comparative Examples 1-8
An emulsifier and a hydrocarbon solvent having a blending amount shown in Table 1 or Table 2 were mixed to obtain an oil phase. Moreover, the ion exchange water of the compounding quantity shown in Table 1 or Table 2, dye, and an additive or an inclusion compound were mixed, and the water phase was obtained. While stirring the oil phase at 5000 rpm using a high-speed homogenizer “Viscotron” (trade name: manufactured by Microtech Nichion), the aqueous phase was added dropwise to the oil phase, and then stirred at 20000 rpm for 5 minutes in the oil. A water (W / O) type emulsion ink was prepared. In addition, the compounding quantity of each component in Table 1 and Table 2 is shown by the mass part.

  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 and 2.

(1) Density / Saturation Evaluation Method for Printed Material Using a line-type inkjet printer “Orifice HC5500” (trade name: manufactured by Riso Kagaku Co., Ltd.), plain paper “ideal paper IJ mat (W) A4” (trade name) : Riso Kagaku Kogyo Co., Ltd.), and measured the surface density and saturation when a solid image was printed on one side.

  The surface concentration was measured using an OD meter “RD920” (trade name: manufactured by Macbeth Co.). The difference between the surface density of the ink to which the clathrate compound was added (Example) and the surface density of the ink to which no clathrate compound was added (control comparative example) was calculated as “density difference: ΔOD”.

The saturation was evaluated based on the measured color difference ΔE using a color difference meter “TC-1800MK-II” (trade name: manufactured by Tokyo Denki Technical Center). The color difference was calculated according to the equation ΔE = √ (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ). ΔL ^* , Δa ^*, and Δb ^* are respectively L ^* , a ^*, and b ^* of the ink to which the inclusion compound was added (Example), and L ^{* of} the ink to which no inclusion compound was added (Control Comparative Example), It is the difference from a ^* and b ^* .

(2) Conveyance performance evaluation method Using a line-type ink jet printer "Olfis HC5500" (trade name: manufactured by Riso Kagaku Kogyo Co., Ltd.) After printing a solid image on the entire surface of one side, the behavior when the paper was immediately passed through the printer was evaluated according to the following criteria. The ink discharge amount per dot was 30 pl.

○: Paper can be passed through the printer, and paper discharge is good.
×: Paper jam occurs in the printer, and paper cannot be passed.

Details of the raw materials described in Tables 1 and 2 are as follows.
Decaglyn 2-ISV (trade name): decaglyceryl diisostearate manufactured by Nikko Chemicals.
Hexaglyn PR-15 (trade name): Polyglycinoyl polyricinoleate manufactured by Nikko Chemicals.
Decaglyn 3-OV (trade name): Decaglyceryl trioleate manufactured by Nikko Chemicals.
AF Solvent No. 6 (trade name): Petroleum hydrocarbon solvent manufactured by JX Nippon Oil & Energy Corporation.
KST Black J-BL Liquid (trade name): A water-soluble black dye aqueous solution manufactured by Nippon Kayaku Co., Ltd.
DAIWA RM400L (trade name): A water-soluble black dye aqueous solution manufactured by Daiwa Kasei Co., Ltd.
KST Yellow J-GX Liquid (trade name): A water-soluble yellow dye aqueous solution manufactured by Nippon Kayaku Co., Ltd.
Solsperse 27000: An amine surfactant Solsperse 27000 (trade name) manufactured by Nippon Lubrizol Corporation.

  As shown in Table 2, in Comparative Examples 1, 4 and 5 containing neither an inclusion compound nor an additive, the print density (OD) of the printed material was 0.72, 0.60 and 0.48, respectively. In the case of Comparative Examples 2 and 3 containing an amino alcohol or an amine dispersant as an additive, the print density (OD) of the printed matter is improved to 0.74 and 0.75, but the color difference (ΔE) is a comparative example. It was almost the same as 1.

  On the other hand, as shown in Table 1, in Example 1 in which the inclusion compound was added, the print density (OD) of the printed material was improved to 0.74 and the color difference (ΔE) was 3.14. The degree of improvement was seen. Further, from Example 2, when the inclusion compound is blended in a mass ratio of 1/25 or more with respect to the dye, the color difference (ΔE) is improved to such an extent that a change in saturation can be visually confirmed (ΔE ≧ 1). From Examples 1, 2 and 4, it can be seen that when the inclusion compound is blended in a mass ratio of 1/10 or more with respect to the dye, the effect of improving the concentration further appears.

In addition, it can be seen from Examples 5 and 6 that even when the emulsifier is changed, the effect of improving the printing density and saturation according to the present invention can be obtained.
In addition, it can be seen from Examples 7 and 8 that even when the dye is changed, the effect of improving the printing density and saturation according to the present invention can be obtained.
In addition, it can be seen from Examples 9 and 10 that even when the type of the water-soluble clathrate compound is changed, the effect of improving the printing density and saturation according to the present invention can be obtained.

On the other hand, in Comparative Example 6 using a water-insoluble clathrate compound, the clathrate compound was not dissolved in water, so the dye could not be clathrated, and neither the printing density nor the saturation was improved.
Further, from the results of Comparative Examples 7 and 8, in the case of water-based ink, even when a water-soluble inclusion compound is blended, neither the printing density nor the saturation is improved, and the curling of the printing paper occurs, and the printer It turns out that the problem of the conveyance performance of printing paper arises.

  The water-in-oil (W / O) emulsion ink of the present invention is excellent in printing density and saturation of printed matter, so it is used as an ink for the field of ink jet printing, particularly for business printers employing a line head type ink jet system. it can.

Claims (3)

A water-in-oil (W / O) emulsion ink comprising a water-soluble dye and a water-soluble inclusion compound in an aqueous phase. The water-in-oil (W / O) emulsion ink according to claim 1, wherein the water-soluble inclusion compound is a cyclodextrin. 3. The water-in-oil (W / O) emulsion ink according to claim 1, wherein the water-soluble clathrate compound is contained in a mass ratio of 0.02 or more with respect to the water-soluble dye.