JP5545533B2 - Radical photocurable ink composition - Google Patents

Description

  The present invention relates to a radical photocurable ink composition.

  In recent years, photocurable ink compositions have been used to form images having excellent water resistance, solvent resistance, scratch resistance, and the like. This photocurable ink composition contains a photopolymerizable compound and a photopolymerization initiator. Then, the ink composition is applied to a recording medium, and the photopolymerizable compound in the ink composition is polymerized by light irradiation to solidify the ink, whereby an image is formed (printing is performed).

  In order to form a high-quality image, it is desired that the photocurable ink composition has good storage stability. Accordingly, various attempts have been made to obtain a photocurable ink composition having excellent storage stability. For example, Patent Document 1 discloses an actinic ray curable ink jet recording ink containing a cationically polymerizable monomer, an initiator, and a pigment having a predetermined range of pH, and having a predetermined moisture content.

Japanese Patent Laying-Open No. 2005-239808

However, the ink disclosed in Patent Document 1 refers to a cationically polymerizable compound. When a general (meth) acrylate monomer is used as a photopolymerizable compound, it is almost described in Patent Document 1. There is no effect. A general (meth) acrylate monomer is a radically polymerizable compound, does not contain water as in the formulation disclosed in Patent Document 1, and a polymerization inhibitor or the like when ensuring storage stability A prescription different from the prescription in Patent Document 1 is selected.
On the other hand, in the ink composition using a general (meth) acrylate monomer, in addition to the storage stability problem, there is also a problem that precipitates are generated.

  Accordingly, an object of the present invention is to provide a radical photocurable ink composition that can prevent the generation of precipitates and has excellent storage stability.

  The inventors of the present application have made extensive studies to solve the above problems. First, the present inventors have developed a phenomenon in which precipitates are generated in a radical photocurable ink composition containing a (meth) acrylate monomer as a photopolymerizable compound (hereinafter also simply referred to as “ink composition”). investigated. As a result, it was found that the acid catalyst used in synthesizing the (meth) acrylate monomer remains, which causes the generation of precipitates. As the acid catalyst, methanesulfonic acid or p-toluenesulfonic acid is mainly used.

  Subsequently, the inventors of the present application manufactured ink compositions containing a (meth) acrylate monomer synthesized using methanesulfonic acid or p-toluenesulfonic acid as an acid catalyst. As a result, in the former case, although the synthesized (meth) acrylate monomer is hardly colored or a by-product is not generated at the time of synthesis, the remaining methanesulfonic acid is the other component in the ink composition. It was found that it can be precipitated by forming a salt with a metal ion such as sodium or potassium. On the other hand, in the latter case, although there is almost no precipitation at the time of salt formation, the synthesized (meth) acrylate monomer is colored or a by-product is generated at the time of synthesis. It was found that there are disadvantages inferior to

  Patent Document 1 refers to improving the storage stability of a cationically polymerizable ink, and does not attempt to solve the problem of precipitation of an acid catalyst in a radically polymerizable ink composition using a (meth) acrylate monomer. In the synthesis of a monomer used in a radically polymerizable ink composition, it is often synthesized by esterification using an acid catalyst such as a (meth) acrylate monomer. However, when the degree of purification is low, the acid catalyst remaining in the monomer may be precipitated. The inventors of the present application paid attention to this point.

  Accordingly, the inventors of the present application have further studied and attempted to contain a predetermined amount of water in a non-aqueous radical photocurable ink composition containing a (meth) acrylate monomer synthesized using methanesulfonic acid. went. As a result, it was found that it was possible to prevent the occurrence of precipitates in the ink composition, and the present invention was completed.

  In other words, the present invention is effective in containing water to prevent the precipitate from being generated from the radical polymerizable ink due to such an acid catalyst, while ensuring the storage stability, As a result of finding the water content that can be prevented by the present inventors, the present invention has been completed.

That is, the present invention is as follows.
[ 1 ]
A method for producing a radical photocurable ink composition, comprising a photopolymerizable compound, a photopolymerization initiator, methanesulfonic acid, less than 10% by mass based on the total amount of the ink composition, and A method for producing a radical photocurable ink composition, comprising mixing at least an amount of water that is at least 1/200 of the total amount of the photopolymerizable compound.
[ 2 ]
The radical photocurable type according to [ 1 ], wherein the water is added to and mixed with a premix obtained by previously mixing the photopolymerizable compound, the photopolymerization initiator, and the methanesulfonic acid. A method for producing an ink composition.
[ 3 ]
Content of the said methanesulfonic acid is a manufacturing method of the radical photocurable ink composition as described in [ 1 ] or [ 2 ] which is 100-500 ppm with respect to the total amount of an ink composition.
[4]
The method for producing a radical photocurable ink composition according to any one of [1] to [3], wherein the photopolymerizable compound contains (meth) acrylate.
[5]
The radical system according to any one of [1] to [4], wherein the photopolymerizable compound includes one or more selected from dipropylene glycol di (meth) acrylate and tripropylene glycol di (meth) acrylate. A method for producing a photocurable ink composition.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not restrict | limited to the following embodiment, A various deformation | transformation can be implemented within the range of the summary.

In the present specification, “(meth) acrylate” means acrylate and its corresponding methacrylate, and “(meth) acryl” means acryl and its corresponding methacryl.
The “oligomer” in the present specification is synthesized by the reaction of about 2 to several tens of monomers, has a relatively small number of repeating units, and has one or more photopolymerizable groups. Means a molecule.

[Radical photocurable ink composition]
One embodiment of the present invention relates to a radical photocurable ink composition. The ink composition includes a (meth) acrylate compound containing methanesulfonic acid as an acid catalyst as a photopolymerizable compound, and a photopolymerization initiator, and the content is 10 with respect to the total amount of the ink composition. It further contains water that is less than mass% and is 1/200 or more based on the total amount of the photopolymerizable compound. Further, the radical photocurable ink composition of the present embodiment is non-aqueous. Hereinafter, each component contained in the ink composition will be described in detail.

[Acid catalyst]
The acid catalyst contained in the ink composition of the present embodiment needs to be methanesulfonic acid. When the acid catalyst is methanesulfonic acid, the ink can be supplied at low cost and the color is excellent. Specifically, by using a monomer synthesized using methanesulfonic acid in the ink composition, the synthesized photopolymerizable compound is different from the case where a monomer synthesized using p-toluenesulfonic acid is used. Compared to the advantage that there is almost no coloration or generation of by-products and the synthesis method that does not use an acid catalyst and the degree of purification at that time, there is an advantage that an equivalent ink can be provided at a lower cost. is there.

  The point which can prevent generation | occurrence | production of a precipitate among the above is demonstrated in detail. In methanesulfonate, methanesulfonic acid used as an acid catalyst in the synthesis of a photopolymerizable compound remains in the obtained photopolymerizable compound, which forms a salt with a metal ion in the ink composition. It has a very good water solubility. On the other hand, methanesulfonate becomes insoluble or hardly soluble in a solvent having a small polarity. Therefore, by utilizing the property that methanesulfonate is water-soluble, and by including water in the solvent, precipitation can be prevented because methanesulfonate is dissolved in water. On the other hand, when a large amount of water is contained in the solvent which is insoluble or hardly soluble, the pigment dispersion designed for the solvent is destroyed and the pigments aggregate. In view of such a situation, the present inventor has found a water content in the ink composition that can achieve both salt precipitation prevention and pigment aggregation prevention. This water content will be described later.

  The content of methanesulfonic acid is preferably 100 to 500 ppm, more preferably 200 to 400 ppm, based on the total amount of the ink composition. The above range is a range in which the storage stability deterioration due to precipitation and residual acid is prevented, and the cost can be suppressed without excessive purification.

〔water〕
The ink composition of this embodiment contains water. As described above, the ink composition of the present embodiment is non-aqueous (solvent-based), but by containing a predetermined amount of water, the generation of precipitates can be prevented, and the ink composition has excellent storage stability. Is obtained.

  Although it does not specifically limit as water contained in the ink composition of this embodiment, For example, deionized water, distilled water, and ultrapure water are mentioned.

  The predetermined amount, that is, the water content in the ink composition is less than 10% by mass with respect to the total amount of the ink composition, and is 1/200 or more with respect to the total amount of the photopolymerizable compound. When the water content is less than 10% by mass with respect to the total amount of the ink composition, aggregation of the pigment can be prevented, and the storage stability of the ink composition can be improved. On the other hand, generation | occurrence | production of a precipitate (sulfonate) can be prevented as the water content is 1/200 or more with respect to the total amount of a photopolymerizable compound.

  The upper limit of the water content is preferably 9% by mass and more preferably 5% by mass with respect to the total amount of the ink composition. On the other hand, the lower limit of the water content is preferably 1/200, more preferably 1/100, based on the total amount of the photopolymerizable compound.

  The water content contained in the aqueous ink composition, which is different from the non-aqueous ink composition of the present embodiment, is usually 50% by mass or more with respect to the total amount of the ink composition.

[Photopolymerizable compound]
The photopolymerizable compound contained in the radical photocurable ink composition of the present embodiment can be polymerized at the time of light irradiation by the action of a photopolymerization initiator described later to cure the printed ink. Since the photopolymerizable compound is contained in the radical photocurable ink composition, it contains at least a photoradical polymerizable compound.

  As the photopolymerizable compound, conventionally known various monomers and oligomers such as monofunctional, bifunctional, and trifunctional or more polyfunctional can be used. Examples of the monomer include compounds having a photopolymerizable group (radical polymerizable group), compounds having an ester bond, and unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid. Examples include acids and their salts or urethanes, amides and anhydrides, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, unsaturated urethanes, and lactams. Moreover, as an oligomer, the oligomer formed from said monomers, such as a linear acrylic oligomer, epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate are mentioned, for example.

Among those listed above, a compound having at least one of a radical polymerizable group and an ester bond is preferable from the viewpoint of curing speed. Although it does not specifically limit as a radically polymerizable group, For example, a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group are mentioned.
Among these, from the viewpoint of curing speed, an ester of (meth) acrylic acid, that is, (meth) acrylate is more preferable.

  Among the (meth) acrylates, monofunctional (meth) acrylates include, for example, isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, and isomyristyl. (Meth) acrylate, isostearyl (meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meta ) Acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate Tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, lactone modified flexibility (Meth) acrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and isobornyl (meth) acrylate.

  Among the (meth) acrylates, examples of the bifunctional (meth) acrylate include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and dipropylene glycol di (meth). ) Acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol Di (meth) acrylate, neopentyl glycol di (meth) acrylate, dimethylol-tricyclodecane di (meth) acrylate, EO (ethylene oxide) adduct di (meth) acrylate of bisphenol A PO bisphenol A (propylene oxide) adduct di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, and polytetramethylene glycol di (meth) acrylate.

  Among the (meth) acrylates, trifunctional or higher polyfunctional (meth) acrylates include, for example, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, Pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate, cowprolactone modified trimethylolpropane tri (meth) acrylate, pentaerythritol ethoxy Examples include tetra (meth) acrylate and caprolactam-modified dipentaerythritol hexa (meth) acrylate.

  Among these, it is preferable that a photopolymerizable compound contains monofunctional (meth) acrylate or bifunctional (meth) acrylate. In this case, the ink composition has a low viscosity, is excellent in solubility of additives such as a photopolymerization initiator, and is easy to obtain ejection stability during recording. Furthermore, it is more preferable to use a monofunctional (meth) acrylate and a bifunctional (meth) acrylate in combination from the viewpoint of increasing the toughness, heat resistance, and chemical resistance of the ink cured layer.

Among the (meth) acrylates listed above, one or more selected from dipropylene glycol di (meth) acrylate and tripropylene glycol di (meth) acrylate are preferable. In this case, the balance of curability, viscosity, and skin irritation is excellent.
The photopolymerizable compound may further contain a conventionally known (meth) acrylate oligomer in addition to the (meth) acrylate monomer.

From another viewpoint, as the photopolymerizable compound, those synthesized using an acid catalyst are preferable in the present invention, and among the acid catalysts, those synthesized using methanesulfonic acid are more preferable. Preferred examples of such a photopolymerizable compound include dipropylene glycol di (meth) acrylate and tripropylene glycol di (meth) acrylate.
Said photopolymerizable compound may be used individually by 1 type, and may use 2 or more types together. The content of the photopolymerizable compound is preferably 60 to 90% by mass with respect to the total amount of the ink composition. When the content is within the above range, a sufficient pigment amount and initiator amount can be contained while maintaining sufficient film fastness.

(Photopolymerization initiator)
The photopolymerization initiator contained in the ink composition of the present embodiment is used for forming an image by curing ink present on the surface of a recording medium by photopolymerization by light irradiation. Here, examples of the light source include γ rays, β rays, electron beams, ultraviolet rays (UV), visible rays, and infrared rays. Among these, ultraviolet rays (UV) are preferable from the viewpoint of safety and cost of the light source lamp. As the photopolymerization initiator, known polymerization initiators such as a radical photopolymerization initiator and a cationic photopolymerization initiator can be used. Especially, since the photocurable ink composition of this embodiment is a radical type, it is preferable to use a photoradical polymerization initiator.

  The above radical photopolymerization initiator is not particularly limited, and examples thereof include aromatic ketones, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds. , Borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon halogen bond, and alkylamine compounds.

  Specific examples of the photo radical polymerization initiator include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine. , Carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) ) -2-Hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethyl Oxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, bis (2,4,6-trimethylbenzoyl) -phenyl Examples include phosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4-diethylthioxanthone and bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide. It is done.

  Examples of commercially available photo radical polymerization initiators include IRGACURE 651 (2,2-dimethoxy-1,2-diphenylethane-1-one), IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone), DAROCUR 1173. (2-hydroxy-2-methyl-1-phenyl-propan-1-one), IRGACURE 2959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- 1-one), IRGACURE 127 (2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl] -2-methyl-propan-1-one}, IRGACURE 907 (2-Methyl-1- (4-methylthiophenyl) -2-morphol Linopropan-1-one), IRGACURE 369 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), IRGACURE 379 (2- (dimethylamino) -2-[(4- Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone), DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis (2, 4,6-trimethylbenzoyl) -phenylphosphine oxide), IRGACURE 784 (bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-) Yl) -phenyl) titanium), IRGACURE OXE 01 (1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]), IRGACURE OXE 02 (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime)), IRGACURE 754 (oxyphenylacetic acid, 2- [2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2- (Mixture of (2-hydroxyethoxy) ethyl ester) (manufactured by Ciba Japan KK), Kayacure DETX-S (2,4-diethylthioxanthone) (Nippon Kayaku Co., Ltd. .)), Lucirin TPO, LR8883, LR8970 (above, manufactured by BASF), and Ubekrill P3 (Manufactured by UCB), and the like.

  Said photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more type. The content of the photopolymerization initiator is preferably 1 to 20% by mass with respect to the total amount of the ink composition. When the content is within the above range, the photocuring speed is sufficiently high, and the photopolymerization initiator is not dissolved and there is almost no coloring derived from the photopolymerization initiator.

[Color material]
The ink composition of the present embodiment may further include a color material. A colorant that can be dissolved or dispersed in the main component of the photopolymerizable compound can be used, and such a colorant is at least one of a pigment and a dye. In addition, when the ink composition of this embodiment is a colorless and transparent clear ink composition, a coloring material is not included.

(Pigment)
In this embodiment, the weather resistance of the ink composition can be improved by using a pigment as the color material. As the pigment, both inorganic pigments and organic pigments can be used.

First, the following pigments can be used for color inks, but are not limited thereto.
Examples of inorganic pigments include carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, iron oxide, and titanium oxide.
Organic pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Polycyclic pigments, dye chelates (for example, basic dye chelates, acid dye chelates, etc.), dye lakes (basic dye lakes, acid dye lakes), nitro pigments, nitroso pigments, aniline black, and daylight A fluorescent pigment is mentioned.

As specific examples, pigments used in yellow ink include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213 and the like.
Examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 9, 12, 22, 38, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168 , 184, 185, 188, 202, 209, C.I. I. Pigment violet 19 and the like.
Examples of pigments used for cyan ink include C.I. I. And CI Pigment Blue 1, 2, 3, 15: 3, 15: 4, 60, 16, and 22.
Examples of pigments used in black ink include C.I. I. Pigment black 7 and the like.
In addition, as orange ink, C.I. I. Pigment Orange-16, 36, 38, green ink, C.I. I. Pigment Green-7, 36.

  Next, a white pigment can be used as a color material used for white ink. The white pigment is not particularly limited as long as it makes the ink composition white, and usually white pigments used in this field can be used. Examples of such a white pigment include a white inorganic pigment and a white organic pigment.

Examples of white inorganic pigments include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicas such as finely divided silicic acid, and synthetic silicates, calcium silicate, alumina, alumina Examples include hydrates, titanium oxide, zinc oxide, talc, and clay. Of these, titanium oxide is preferable from the viewpoints of concealability, colorability, and dispersed particle size.
Examples of the white organic pigment include organic compound salts disclosed in JP-A No. 11-129613 and alkylene bismelamine derivatives disclosed in JP-A Nos. 11-14365 and 2001-234093. Specific examples of the white organic pigment include ShigenoxOWP, ShigenoxOWPL, ShigenoxFWP, ShigenoxFWG, ShigenoxUL, and ShigenoxU (all trade names manufactured by Hackol Chemical Co., Ltd.).
Specific examples of the white pigment include C.I. I. And CI Pigment White 6, 18, and 21.

  When the ink composition contains a pigment as a coloring material, it is preferable to prepare a pigment dispersion in advance before producing the ink composition in order to further prevent the pigment from aggregating. The dispersion medium used for the pigment dispersion may be a photopolymerizable compound (monomer component or oligomer component), or a separately added dispersant. In the latter case, conventionally known components such as polyoxyalkylene polyalkylene polyamine can be used as the dispersant.

(dye)
In the present embodiment, by using a dye as the color material, it is easier to lower the viscosity of the ink, and it is possible to prevent ejection failure due to the adhesion of pigment or a decrease in dispersibility. The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9, 45, 249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive black 3, 4, and 35 are mentioned.

  The above color materials may be used alone or in combination of two or more. The content of the color material is preferably 0.1 to 20% by mass with respect to the total amount of the ink composition. When the content is within the above range, sufficient curability can be maintained while maintaining desired color developability.

[Other ingredients]
The ink composition of this embodiment may contain components other than the components listed above. Such components are not particularly limited, and may include, for example, conventionally known solvents, polymerization accelerators, thermal polymerization inhibitors, slip agents, and other additives. Examples of the other additives include conventionally known penetration enhancers, wetting agents (humectants), fixing agents, antifungal agents, antiseptics, antioxidants, ultraviolet absorbers, chelating agents, pH adjusting agents, and A thickener is mentioned.

[Recording medium]
As the recording medium, for example, a non-absorbing or absorbing recording medium can be cited. The ink composition of the present embodiment can be applied to a recording medium having various absorption performances from a non-absorbing recording medium in which the ink composition is difficult to penetrate to an absorbent recording medium in which the ink composition is easily penetrated. Widely applicable.

  Although it does not specifically limit as a non-absorbable recording medium, For example, plastics, such as polyvinyl chloride, polyethylene, a polypropylene, polyethylene terephthalate (PET), metals, such as iron, silver, copper, aluminum, or those various metals Examples include metal plates produced by vapor deposition, and alloys such as stainless steel and brass.

  The absorbent recording medium is not particularly limited, and examples thereof include plain paper such as electrophotographic copying paper, paper having an ink absorption layer containing silica, alumina, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and the like. Can be mentioned. In addition, art paper, coated paper, cast paper, and the like used for general offset printing can be given as a type of absorbent recording medium having a relatively low ink permeation speed.

  As described above, according to the present embodiment, when the ink composition contains a photopolymerizable compound synthesized with methanesulfonic acid having a small coloring effect as an acid catalyst, a salt due to methanesulfonic acid contained in a trace amount. Precipitation of (sulfonate) can be prevented, and an ink composition excellent in storage stability can be provided. Further, by using this ink composition, it is possible to prevent clogging of the print head due to precipitates, so that it is possible to ensure ink ejection reliability, and it is possible to prevent image disturbance due to precipitates, thereby obtaining good image quality. It is done.

[Method for producing radical photocurable ink composition]
One embodiment of the present invention relates to a method for producing a radical photocurable ink composition. In the production method, the photopolymerizable compound, the photopolymerization initiator, methanesulfonic acid, and the water content are less than 10% by mass with respect to the total amount of the ink composition, and the total amount of the photopolymerizable compound And at least mixing with an amount of water that is 1/200 or more.

  Hereinafter, the present embodiment will be described, but the contents described in the section of the embodiment relating to the radical photocurable ink composition are omitted in order to avoid redundant description.

  When the ink composition is manufactured, the materials may be mixed by mixing all the materials, or by mixing some materials in advance and then mixing the remaining materials.

  Among these, it is preferable to mix a part of the materials in advance and then mix the remaining materials. As one specific example, it is preferable that a photopolymerizable compound, a photopolymerization initiator, and methanesulfonic acid are mixed in advance to obtain a premix, and then water is added to the premix and mixed. In this case, as demonstrated in the examples described later, when water is added and mixed at the end, impurities (for example, metal ions such as sodium ions) contained in other components and methanesulfonic acid are mixed. Since there is a high possibility of being in a salt form, precipitation can be prevented more effectively.

  Hereinafter, although an embodiment of the present invention is described still more concretely by an example, a comparative example, and a reference example, this embodiment is not limited only to these examples.

[Use ingredients]
The components used in Examples, Comparative Examples, and Reference Examples described below are as follows.
[Photopolymerizable compound]
Dipropylene glycol diacrylate (bifunctional monomer, abbreviated as DPGDA in Table 1)
Tripropylene glycol diacrylate (bifunctional monomer, abbreviated as TPGDA in Table 1)

  First, three types of dipropylene glycol diacrylates (DPGDA-1, -2, and -3) were synthesized as follows.

(DPGDA-1)
200 g of dipropylene glycol and 270 g of toluene were added to a 1 L flask equipped with a stirrer and a thermometer, and heated at 60 ° C. The liquid obtained after stirring for 2 hours was placed in a 1 L flask equipped with a stirrer, thermometer, air introduction tube, Dean-Stark trap, and cooling tube, and 430 g of acrylic acid and methanesulfonic acid were added. 30 g and 0.4 g of hydroquinone monomethyl ether were added. The inside of the system was 53 kPa, and the temperature was raised while blowing dry air at a rate of 100 mL / min. The reaction was carried out while adjusting the pressure so that the reaction temperature was 90 ° C. while removing water produced along with the reaction. Three hours later, a theoretical amount of water distilled out, and gas chromatography analysis was conducted. As a result, the area ratio (%) of dipropylene glycol diacrylate as a reaction product was 97%, and thus the reaction was terminated. The obtained reaction solution was cooled, and when it became 40 ° C. or lower, 100 g of 17% by mass saline was added and stirred at 300 rpm. The organic layer was transferred to a separatory funnel and washed with 10% aqueous sodium hydroxide to remove excess methacrylic acid. After removing the aqueous layer, the organic layer was further washed with 300 g of 17% by mass saline to adjust the pH of the aqueous layer to 8. The organic layer was placed in a 1 L eggplant type flask, and toluene was distilled off under reduced pressure using a rotary evaporator, and then the liquid in the eggplant flask was filtered by suction filtration to obtain the desired dipropylene glycol diacrylate (recovery). Rate 89%).
DPGDA-1 contained methanesulfonic acid used as an acid catalyst.

(DPGDA-2)
200 g of dipropylene glycol and 270 g of toluene were added to a 1 L flask equipped with a stirrer and a thermometer, and heated at 60 ° C. The liquid obtained after stirring for 2 hours was placed in a 1 L flask equipped with a stirrer, thermometer, air introduction tube, Dean-Stark trap, and cooling tube, and 430 g of acrylic acid, p-toluenesulfone 60 g of acid and 0.4 g of hydroquinone monomethyl ether were added. The inside of the system was 53 kPa, and the temperature was raised while blowing dry air at a rate of 100 mL / min. The reaction was carried out while adjusting the pressure so that the reaction temperature was 90 ° C. while removing water produced along with the reaction. Three hours later, a theoretical amount of water distilled out, and gas chromatography analysis was conducted. As a result, the area ratio (%) of dipropylene glycol diacrylate as a reaction product was 97%, and thus the reaction was terminated. The obtained reaction solution was cooled, and when it became 40 ° C. or lower, 100 g of 17% by mass saline was added and stirred at 300 rpm. The organic layer was transferred to a separatory funnel and washed with 10% aqueous sodium hydroxide to remove excess methacrylic acid. After removing the aqueous layer, the organic layer was further washed with 300 g of 17% by mass saline to adjust the pH of the aqueous layer to 8. The organic layer was placed in a 1 L eggplant type flask, and toluene was distilled off under reduced pressure using a rotary evaporator, and then the liquid in the eggplant flask was filtered by suction filtration to obtain the desired dipropylene glycol diacrylate (recovery). 82%).
Note that DPGDA-2 contained p-toluenesulfonic acid used as an acid catalyst.

(DPGDA-3)
To a 1 L flask equipped with a stirrer and a thermometer, 200 g of dipropylene glycol and 660 g of methyl acrylate were added and heated at 60 ° C. Stirring was continued for 2 hours as it was, and then insoluble matter was removed by suction filtration. The obtained filtrate was put in a 1 L flask equipped with a stirrer, a thermometer, an air introduction tube, and a rectifying column (15 stages), and 0.22 g of hydroquinone monomethyl ether was further added to adjust the pressure to 40 kPa. While drying air was blown in at an introduction rate of 100 mL / min, the mixture was heated and refluxed to remove moisture in the system. Next, 6.0 g of isopropyl orthotitanate was added to initiate the reaction. During the reaction, the system pressure was adjusted to 69 kPa. When the reaction liquid was heated to reflux and the temperature at the top of the rectifying column (column top temperature) was monitored, it approached the azeotropic boiling point of methanol and methyl acrylate, so that the column top temperature was 60 ° C. The reaction was carried out while adjusting the reflux ratio to distill off methanol as an azeotrope of methyl acrylate. The tower top temperature started to rise from about 2 hours after the addition of the above-mentioned isopropyl orthotitanate as a catalyst, and finally rose to 80 ° C., so that the reaction was continued by gradually increasing the reflux ratio. When the reaction solution 3 hours after the start of the reaction was analyzed by gas chromatography, the area ratio (%) of the reactive product dipropylene glycol diacrylate was 97% or more, so the reaction was terminated. The obtained reaction liquid was cooled, and when the temperature of the reaction liquid reached 75 ° C., 100 g of 17% by mass saline was added to hydrolyze the catalyst. After standing for 30 minutes, the organic layer was taken into a 1 L eggplant-shaped flask by decantation, and excess methyl methacrylate was distilled off under reduced pressure using a rotary evaporator. To obtain the desired dipropylene glycol diacrylate (yield 79%).
Since dipropylene glycol diacrylate was synthesized without using an acid catalyst, DPGDA-3 naturally did not contain an acid catalyst.

  Next, three types of tripropylene glycol diacrylate (TPGDA-1, -2, and -3) were each synthesized as follows.

(TPGDA-1)
280 g of tripropylene glycol and 270 g of toluene were added to a 1 L flask equipped with a stirrer and a thermometer, and heated at 60 ° C. The liquid obtained after stirring for 2 hours was placed in a 1 L flask equipped with a stirrer, thermometer, air introduction tube, Dean-Stark trap, and cooling tube, and 430 g of acrylic acid and methanesulfonic acid were added. 30 g and 0.4 g of hydroquinone monomethyl ether were added. The inside of the system was 53 kPa, and the temperature was raised while blowing dry air at a rate of 100 mL / min. The reaction was carried out while adjusting the pressure so that the reaction temperature was 90 ° C. while removing water produced along with the reaction. Three hours later, a theoretical amount of water was distilled, and gas chromatography analysis was performed. As a result, the area ratio (%) of tripropylene glycol diacrylate as a reaction product was 97%, and thus the reaction was terminated. The obtained reaction solution was cooled, and when it became 40 ° C. or lower, 100 g of 17% by mass saline was added and stirred at 300 rpm. The organic layer was transferred to a separatory funnel and washed with 10% aqueous sodium hydroxide to remove excess methacrylic acid. After removing the aqueous layer, the organic layer was further washed with 300 g of 17% by mass saline to adjust the pH of the aqueous layer to 8. The organic layer was placed in a 1 L eggplant type flask, and toluene was distilled off under reduced pressure using a rotary evaporator, and then the liquid in the eggplant flask was filtered by suction filtration to obtain the desired tripropylene glycol diacrylate (recovery). 88%).
TPGDA-1 contained methanesulfonic acid used as an acid catalyst.

(TPGDA-2)
280 g of tripropylene glycol and 270 g of toluene were added to a 1 L flask equipped with a stirrer and a thermometer, and heated at 60 ° C. The liquid obtained after stirring for 2 hours was placed in a 1 L flask equipped with a stirrer, thermometer, air introduction tube, Dean-Stark trap, and cooling tube, and 430 g of acrylic acid, p-toluenesulfone 60 g of acid and 0.4 g of hydroquinone monomethyl ether were added. The inside of the system was 53 kPa, and the temperature was raised while blowing dry air at a rate of 100 mL / min. The reaction was carried out while adjusting the pressure so that the reaction temperature was 90 ° C. while removing water produced along with the reaction. Three hours later, a theoretical amount of water was distilled, and gas chromatography analysis was performed. As a result, the area ratio (%) of tripropylene glycol diacrylate as a reaction product was 97%, and thus the reaction was terminated. The obtained reaction solution was cooled, and when it became 40 ° C. or lower, 100 g of 17% by mass saline was added and stirred at 300 rpm. The organic layer was transferred to a separatory funnel and washed with 10% aqueous sodium hydroxide to remove excess methacrylic acid. After removing the aqueous layer, the organic layer was further washed with 300 g of 17% by mass saline to adjust the pH of the aqueous layer to 8. The organic layer was placed in a 1 L eggplant type flask, and toluene was distilled off under reduced pressure using a rotary evaporator, and then the liquid in the eggplant flask was filtered by suction filtration to obtain the desired tripropylene glycol diacrylate (recovery). Rate 81%).
TPGDA-2 contained p-toluenesulfonic acid used as an acid catalyst.

(TPGDA-3)
To a 1 L flask equipped with a stirrer and a thermometer, 280 g of tripropylene glycol and 660 g of methyl acrylate were added and heated at 60 ° C. Stirring was continued for 2 hours as it was, and then insoluble matter was removed by suction filtration. The obtained filtrate was put in a 1 L flask equipped with a stirrer, a thermometer, an air introduction tube, and a rectifying column (15 stages), and 0.22 g of hydroquinone monomethyl ether was further added to adjust the pressure to 40 kPa. While drying air was blown in at an introduction rate of 100 mL / min, the mixture was heated and refluxed to remove moisture in the system. Next, 6.0 g of isopropyl orthotitanate was added to initiate the reaction. During the reaction, the system pressure was adjusted to 69 kPa. When the reaction liquid was heated to reflux and the temperature at the top of the rectifying column (column top temperature) was monitored, it approached the azeotropic boiling point of methanol and methyl acrylate, so that the column top temperature was 60 ° C. The reaction was carried out while adjusting the reflux ratio to distill off methanol as an azeotrope of methyl acrylate. The tower top temperature started to rise from about 2 hours after the addition of the above-mentioned isopropyl orthotitanate as a catalyst, and finally rose to 80 ° C., so that the reaction was continued by gradually increasing the reflux ratio. When the reaction solution 3 hours after the start of the reaction was analyzed by gas chromatography, the area ratio (%) of tripropylene glycol diacrylate, which is a reactive organism, was 97% or more, so the reaction was terminated. The obtained reaction liquid was cooled, and when the temperature of the reaction liquid reached 75 ° C., 100 g of 17% by mass saline was added to hydrolyze the catalyst. After standing for 30 minutes, the organic layer was taken into a 1 L eggplant-shaped flask by decantation, and excess methyl methacrylate was distilled off under reduced pressure using a rotary evaporator. Then, the solution in the eggplant flask was filtered by suction filtration. To obtain the desired tripropylene glycol diacrylate (yield 77%).
Since tripropylene glycol diacrylate was synthesized without using an acid catalyst, TPGDA-3 naturally did not contain an acid catalyst.

(Photopolymerization initiator)
・ IRGACURE 819 (Ciba Japan)
・ DAROCUR TPO (Ciba Japan)
・ DETX-S (manufactured by Nippon Kayaku Co., Ltd.)
[Pigment]
・ C. I. Pigment Black-7 (Ciba Specialty Chemicals, abbreviated as Pigment Black-7 in Table 1)
[Dispersant]
Polyoxyalkylene polyalkylene polyamine (abbreviated as dispersant in Table 1)
〔water〕
・ Ultra pure water

[Examples 1 to 10, Comparative Examples 1 to 5, Reference Example 1]
[Production of ink composition]
The components shown in Table 1 below were added so as to have the composition (unit: mass%) shown in Table 1, and this was stirred with a high-speed water-cooled stirrer, whereby a black UV curable ink composition was obtained. Got.

  In Examples 1 to 8, all components except water were mixed to obtain a premix, and then water was added to the premix and mixed. In Examples 9 and 10, first, a photopolymerizable compound (DPGDA, TPGDA) and water were mixed, and then the remaining components were added and mixed. In Comparative Examples 1 to 5, all components except water were mixed to obtain a premix, and then water was added to the premix and mixed. In Reference Example 1, all components except water were mixed to obtain a premix, and then water was added to the premix and mixed.

[Examples 11 to 13, Comparative Examples 6 to 10]
[Production of ink composition]
The components described in Table 3 below were added so as to have the composition (unit: mass%) described in Table 3, and this was stirred with a high-speed water-cooled stirrer to obtain a UV curable clear ink composition. Obtained. In Examples 11 to 13 and Comparative Examples 6 to 10, all the components were added at once and mixed.
The following items are common to Examples 1 to 13, Comparative Examples 1 to 10, and Reference Example 1.

[Evaluation 1: Evaluation of sulfonate precipitation]
The ink composition was left in a bottle at 60 ° C. for 1 week. Then, it left still for one week at room temperature (RT), and 10 cc was collected on the metal filter with a hole diameter of 10 micrometers. The filter was observed by Fourier transform infrared spectroscopy (FTIR) to confirm the contents of the filtered product. Evaluation criteria are as shown in A to C below. The evaluation results are shown in Table 2 below for Examples 1 to 10, Comparative Examples 1 to 5, and Reference Example 1, and are shown in Table 4 below for Examples 11 to 13 and Comparative Examples 6 to 10.
A: A sulfonate was not confirmed.
B: A sulfonate was confirmed. All 10 cc of ink could pass through the filter.
C: A sulfonate was confirmed. In the filtration, all 10 cc of ink could not pass through due to filter clogging with precipitates.

[Evaluation 2: Evaluation of pigment aggregation]
The pigment aggregation was evaluated by measuring the particle size (average particle size) of the pigment dispersed in the ink composition. The average particle diameter was measured by Microtrac UPA manufactured by NIKKISO CO., LTD., And water-free ink was prepared for each composition shown in Table 1 and compared with it. Evaluation criteria are as shown in A to C below. The evaluation results are shown in Table 2 below for Examples 1 to 10, Comparative Examples 1 to 5, and Reference Example 1, and are shown in Table 4 below for Examples 11 to 13 and Comparative Examples 6 to 10.
A: The change in the average particle size was less than twice that of the corresponding water-free ink.
B: The average particle size increased more than twice compared with the corresponding non-water-added ink.
C: Precipitation due to pigment aggregation occurred.

[Manufacture of recorded materials]
The printing method is as follows.

Each ink composition obtained in Examples, Comparative Examples and Reference Examples was filled in a recording device (inkjet printer PX-G920, manufactured by Seiko Epson Corporation), and printed on a PET film to obtain an image. The ink discharge amount was adjusted so that the thickness of each printed material was 10 μm. Each of the ink compositions described above had good ejection properties, and various good images were obtained. The obtained image was cured with a metal halide lamp under an irradiation energy condition of 200 mJ / cm ² per PASS, and after adding the PASS number until the surface tack disappeared, the following evaluation was performed.

[Evaluation 3: Color difference of coating film due to thermal history of ink]
The ink composition produced as described above was divided, one was stored at 60 ° C. for 1 week, and the other was stored at room temperature for 1 week. Thereafter, these were printed and cured to produce recorded matter. Color difference (ΔE *) of the coating film (cured layer) on the recorded material between the recorded material obtained from the ink composition stored at 60 ° C. and the recorded material obtained from the ink composition stored at room temperature Was measured using a colorimeter (Eye-One (manufactured by Gretag)) and evaluated. 5 and Reference Example 1 are shown in Table 2 below, and Examples 11 to 13 and Comparative Examples 6 to 10 are shown in Table 4 below.
A: ΔE * is less than 1 B: ΔE * is 1 or more and less than 1.5 C: ΔE * is 1.5 or more

  From Examples 1 to 10 and Comparative Examples 1 to 5 (Table 1), it was revealed that a predetermined amount of water should be included in order to prevent precipitation when methanesulfonic acid is used. In particular, it became clear that the remaining methanesulfonic acid and sodium ions (impurities) contained in other components take a salt form and are dissolved in a liquid containing a predetermined amount of water. . Therefore, it was found that adding water separately at the end is more likely to be in a salt form, which is advantageous in suppressing precipitation in the ink composition.

Moreover, when the reference example 1 (Table 1) is seen, although the characteristic of an ink composition and its printed matter is equivalent or more compared with the system (Example) using an acid catalyst, it is the time of the synthesis | combination of the photopolymerizable compound. The yield is inferior, so that the cost is remarkably high and not suitable for practical use.
As a supplementary statement, although photopolymerizable compounds synthesized using methanesulfonic acid are excellent in yield, the synthesis method using methanesulfonic acid as an acid catalyst has a problem of precipitation in the prior art. . On the other hand, although the synthesis method using no acid catalyst has no problem of precipitation, the photopolymerizable compound not containing an acid catalyst has a problem of poor yield.

On the other hand, from Examples 11 to 13 and Comparative Examples 6 to 10 (Table 2), when p-toluenesulfonic acid was used as the acid catalyst, the margin of precipitation increased compared to when methanesulfonic acid was used. It was found that the yield decreased during the synthesis of the polymerizable compound, resulting in an increase in impurities and a tendency to be colored by oxidation.
In terms of yield, the photopolymerizable compound synthesized using p-toluenesulfonic acid was superior to the photopolymerizable compound synthesized using a catalyst other than the acid catalyst, and was synthesized using methanesulfonic acid. It was found to be inferior to the photopolymerizable compound. In addition, the synthesis method using p-toluenesulfonic acid as an acid catalyst is less likely to generate precipitates than the synthesis method using methanesulfonic acid as an acid catalyst, but a synthesis method using a catalyst other than an acid catalyst. It was found that precipitates are more likely to occur than in the case of.

Claims (5)

A method for producing a radical photocurable ink composition comprising:
A photopolymerizable compound;
A photopolymerization initiator;
Methanesulfonic acid,
Water in an amount that is less than 10% by mass with respect to the total amount of the ink composition and that is 1/200 or more with respect to the total amount of the photopolymerizable compound;
A method for producing a radical photocurable ink composition, comprising mixing at least. Said photopolymerizable compound, and the photopolymerization initiator, and the methanesulfonic acid, to the pre-mixture obtained by previously mixing the added mixing water, a radical-based light-curing according to claim 1 A method for producing an ink composition. The method for producing a radical photocurable ink composition according to claim 1 or 2 , wherein the content of the methanesulfonic acid is 100 to 500 ppm with respect to the total amount of the ink composition. The manufacturing method of the radical type photocurable ink composition of any one of Claims 1-3 in which the said photopolymerizable compound contains (meth) acrylate. The radical photocuring according to any one of claims 1 to 4, wherein the photopolymerizable compound includes one or more selected from dipropylene glycol di (meth) acrylate and tripropylene glycol di (meth) acrylate. Type ink composition manufacturing method.