JP2010121078A - Photoacid generator for use in active ray-curable type inkjet ink, active ray-curable type inkjet ink, inkjet recording method, method for manufacturing triaryl sulfonium salt, and solid photoacid generator for use in active ray-curable type inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoacid generator to give inkjet ink which has less decrease in the ink discharge stability and is excellent in the storage stability even when stored for a long period. <P>SOLUTION: The photoacid generator for use in active ray-curable type inkjet inks is used in the active ray-curable type inkjet ink containing a cationically polymerizable compound and a photoacid generator, wherein the photoacid generator is the one manufactured by a manufacturing method including the following purification process; the purification process: a process including a heating step of heat-treating a triaryl sulfonium salt at a temperature ranging from higher than 60°C to lower than a decomposition temperature (°C) of the triaryl sulfonium salt and a proton removing step carried out after the heating step, in which process the process meet K-59h≥82, letting a heating temperature at the heat treatment step be t (°C) and letting a heating time be h (hr), and K is a value integrated between from x=0 to x=h in the heating hour-heating temperature curve that is determined with a heating time h as x-axis and with a heating temperature t as y-axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photoacid generator and an actinic ray curable inkjet ink used for an actinic ray curable inkjet ink that is cured by an active energy ray such as an ultraviolet ray or an electron beam.

  Actinic ray curable compositions that are cured by active energy rays such as ultraviolet rays and electron beams are used in various applications such as paints, adhesives, printing inks, inkjet inks, and electrical insulating sealing materials.

  Among these, in applications used as inkjet inks, in particular, ultraviolet curable inkjet inks that are cured with ultraviolet rays have advantages such as quick drying and recording on a recording medium that does not absorb inks. Attention has been paid.

  Among the ultraviolet curable ink-jet inks, an ink using a cationically polymerizable compound is excellent in thin film curability because it is not subjected to polymerization inhibition by oxygen, and is relatively excellent in flexibility of the cured film.

  In addition, as a polymerization initiator used in an ink-jet ink containing a cationic polymerizable compound, an acid generator made of a triarylphosphonium salt having an advantage of being excellent in environmental suitability without generating benzene is known (Patent Document). 1).

  In UV curable inkjet inks, if the ink is stored for a long period of time, the viscosity of the ink will increase, or precipitation including pigment will occur, causing clogging of the ink at the inkjet nozzle port, and ink ejection failure will occur There were problems such as.

  Even in inks using cationically polymerizable compounds, there are problems in the case of long-term storage as described above, and the following techniques are known to improve this.

  For example, a technique is known in which the total content of cationic impurities, metal impurities, and strongly acidic substances in ink is set to 500 ppm or less to suppress thickening and gelation over time (see Patent Document 2).

  In addition, a technique for suppressing an increase in viscosity during storage of an active energy ray-curable resin composition for optical three-dimensional modeling by using a triarylsulfonium compound (photopolymerization initiator) having a purity of 80% or more is known. (See Patent Document 3).

  In recent years, in the field of image formation using an inkjet method, higher sensitivity and higher definition image quality are required, and from the viewpoint of cost, an inkjet ink that can be used in a higher quality state for a longer period is required. .

  However, in response to such a demand, it is not sufficient to use an ink-jet ink in which the content of impurities in the ink is reduced as described above, and a high-sensitivity and high-definition image for a longer period of time. It was difficult to provide an inkjet ink capable of forming the ink.

That is, even when the ink is stored for a long period of time and no increase in viscosity is observed, and no precipitate is observed in appearance, the ink adheres to the vicinity of the inkjet nozzle port, and the trajectory of the ejected droplets There is a problem that there is a case where the lens is bent or the nozzle is not emitted.
JP 2005-139425 A JP 2005-146001 A International Publication No. 04/113396 Pamphlet

  An object of the present invention is an ink jet recording excellent in environmental suitability using an ink jet ink containing a triarylsulfonium compound as a photoacid generator. An object of the present invention is to provide a photoacid generator that provides ink, a method for producing the same, and an inkjet ink and an inkjet recording method using the photoacid generator.

The above object of the present invention is achieved by the following configurations.
1. A photoacid generator for an actinic radiation curable inkjet ink used for an actinic radiation curable inkjet ink containing a cationic polymerizable compound and a photoacid generator, wherein the photoacid generator is a triarylsulfonium salt, The triarylsulfonium salt is a photoacid generator for an actinic ray curable inkjet ink, which is produced by a production method having the following purification step.
[Purification step: a heating step of heating the triarylsulfonium salt at a temperature range of 60 ° C. or higher and lower than the decomposition temperature (° C.) of the triarylsulfonium salt, and a proton removal step performed after the heating step, The heating step is a step of heating the solid of the triarylsulfonium salt and then subjecting the solid of the triarylsulfonium salt to the proton removal step, or dissolving the solid of the triarylsulfonium salt in a solvent to form a solution, After heating the solution, the solution is subjected to the proton removal step. When the heating temperature of the heat treatment step is t (° C.) and the heating time is h (hr), K−59h ≧ 82. Process. K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis. ]
2. An actinic radiation curable inkjet ink comprising the cationic polymerizable compound and the photoacid generator for actinic radiation curable inkjet ink described in 1.
3.2. An inkjet recording method using the actinic ray curable inkjet ink described in 3.2.
4). A method for producing a triarylsulfonium salt for use in an actinic radiation curable inkjet ink containing a cationically polymerizable compound and a triarylsulfonium salt, the method comprising the following purification step: .
[Purification step: a heating step of heating the triarylsulfonium salt at a temperature range of 60 ° C. or higher and lower than the decomposition temperature (° C.) of the triarylsulfonium salt, and a proton removal step performed after the heating step, The heating step is a step of heating the solid of the triarylsulfonium salt and then subjecting the solid of the triarylsulfonium salt to the proton removal step, or dissolving the solid of the triarylsulfonium salt in a solvent to form a solution, After heating the solution, the solution is subjected to the proton removal step. When the heating temperature of the heat treatment step is t (° C.) and the heating time is h (hr), K−59h ≧ 82. Process. K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis. ]
5). A photoacid generator solid for actinic ray curable inkjet ink used for actinic ray curable inkjet ink containing a polymerizable compound and a photoacid generator, wherein the photoacid generator solid contains a triarylsulfonium salt The acid generation amount of the photoacid generator solid (when the 0.02 mol / L dioxane solution of the photoacid generator was refluxed for 20 hours, the difference in hydrogen ion concentration (mol / L) in the solution before and after the reflux was ) Is 1 × 10 ⁻⁴ (mol / L) or less, a photoacid generator solid for actinic ray curable inkjet inks.

In the present invention, an embodiment in which the purification step in 1 above is the following is a preferred embodiment.
[Purification step: There is a heating step in which the triarylsulfonium salt is heated at 60 ° C. or higher and within a range of 10 ° C. or lower than the decomposition temperature (° C.) of the triarylsulfonium salt, and a proton removing step performed after the heating step. The heating step is a step of heating the solid of the triarylsulfonium salt and then subjecting the solid of the triarylsulfonium salt to the proton removal step, or dissolving the solid of the triarylsulfonium salt in a solvent to form a solution, After heating the solution, the solution is subjected to the proton removal step. When the heating temperature in the heat treatment step is t (° C.) and the heating time is h (hr), K−59h ≧ 82 Is the process. K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis. ]

  According to the present invention, in an ink jet recording excellent in environmental suitability using an ink jet ink containing a triarylsulfonium compound as a photoacid generator, the ink jet ink is excellent in storability even when stored for a long period of time with little decrease in the ejection stability of the ink. It is possible to provide a photogenerator that gives ink, a method for producing the photogenerator, and an inkjet ink and an inkjet recording method using the photoacid generator.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The present invention relates to a photoacid generator for actinic radiation curable inkjet ink used for an actinic radiation curable inkjet ink containing a cationic polymerizable compound and a photoacid generator (hereinafter simply referred to as the photoacid generator of the present invention). The photoacid generator is a triarylsulfonium salt, and the triarylsulfonium salt is produced by the production method having the purification step described above.

  In the present invention, an ink jet ink having excellent storage stability can be obtained by using a triarylphosphonium salt produced by the production method having the specific purification step as an acid generator for an actinic ray curable ink jet ink.

  The actinic radiation curable inkjet ink in which the photoacid generator of the present invention is used contains a cationically polymerizable compound and a photoacid generator.

(Photoacid generator)
In the present invention, the photoacid generator used in the actinic ray curable inkjet ink is a triarylsulfonium salt.

  The triarylsulfonium salt according to the present invention is a sulfonium salt having a sulfur atom to which three phenyl groups which may have a substituent are bonded, and particularly represented by the following general formulas [1] to [4]. A compound is preferred from the viewpoint of environmental suitability.

In the formula, R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, R _{4 to} R ₇ do not simultaneously represent a hydrogen atom, and R _{8 to} R ₁₁ do not represent hydrogen atoms at the same time, and R _{12 to} R ₁₇ do not represent hydrogen atoms at the same time. X represents a non-nucleophilic anionic residue.

The substituent represented by R _{1 to} R ₁₇ is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, or a hexyl group, Alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group, hexyloxy group, decyloxy group, dodecyloxy group, acetoxy group, propionyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group, methoxycarbonyl group, ethoxycarbonyl Group, carbonyl group such as benzoyloxy group, halogen atom such as fluorine, chlorine, bromine and iodine, cyano group, nitro group and hydroxy group.

X represents a non-nucleophilic anion residue, for example, a halogen atom such as F, Cl, Br, or I, B (C ₆ F ₅ ) ₄ , R ₁₈ COO, R ₁₉ SO ₃ , SbF ₆ , AsF ₆ , PF ₆ , BF _{4 and the} like.

However, R ₁₈ and R ₁₉ are each an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a halogen atom such as fluorine, chlorine, bromine or iodine, a nitro group, a cyano group, a methoxy group or an ethoxy group. Represents an alkyl group or a phenyl group which may be substituted with an alkoxy group.

Among these, B (C ₆ F ₅ ) ₄ and PF ₆ are preferable from the viewpoint of safety.

  The above compounds can be obtained from THE CHEMICAL SOCIETY OF JAPAN Vol. 71 no. 11, 1998, as well as the photoacid generator described in “Organic Materials for Imaging”, edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), can be easily synthesized by a known method.

  Specific examples of the triarylsulfonium salt are given below.

(Purification process)
The purification step according to the present invention includes a heating step in which the triarylsulfonium salt is heat-treated at a temperature range of 60 ° C. or higher and lower than the decomposition temperature (° C.) of the triarylsulfonium salt, and a proton removal step performed after the heating step. And the heating step is a step of heating the solid of the triarylsulfonium salt and then subjecting the solid of the triarylsulfonium salt to the proton removal step, or dissolving the solid of the triarylsulfonium salt in a solvent to obtain a solution And heating the solution, and then subjecting the solution to the proton removal step. When the heating temperature of the heat treatment step is t (° C.) and the heating time is h (hr), K-59h This is a step of ≧ 82.

  However, K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis.

  The heat treatment in the heating step according to the present invention is a treatment for heating the triarylsulfonium salt.

  A specific method of the heat treatment is a method in which a solid of a triarylsulfonium salt is dissolved in a solvent and a solution is prepared and the solution is heated or a solid of a triarylsulfonium salt is heated. A method of heating a solution in which the solid is dissolved is preferred.

  In the method of heating a solution in which a solid of triarylsulfonium salt is dissolved, the solution is heated and then subjected to a proton removal step.

  Although it depends on the structure of the triarylsulfonium salt, a protic or aprotic polar organic solvent is preferably used as the solvent.

  For example, alcohols such as ethanol and propanol, ethers such as anisole, diethyl ether, dioxane, and tetrahydrofuran, acetals, ketones such as acetone, isophorone, and methyl ethyl ketone, esters such as ethyl acetate, ethyl lactate, and γ-butyrolactone, Polyhydric alcohols such as propylene carbonate, ethylene glycol diacetate and diethylene glycol diethyl ether and derivatives thereof, organic acids such as acetic acid, propionic acid and acetic anhydride and anhydrides thereof, 2-pyrrolidone, N-methylpyrrolidone, N-methylformamide And nitrogen-containing compounds such as diphenylsulfone, dimethyl sulfoxide, and sulfolane. Dioxane and propylene carbonate are preferably used.

  The heating temperature t (° C.) in the heat treatment step is the temperature of the solvent in the method of heating the solvent in which the triarylsulfonium salt is dissolved, and the temperature of the atmosphere to be heated in the method of heating the solid particles. is there.

  When the heating temperature is less than 60 ° C., ejection failure or the like occurs when the inkjet ink is stored for a long period of time.

  In the present invention, when the heating time is h (hr), K−59h ≧ 82.

  However, K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis.

  In the case where K-59h is less than 82, when it is stored for a long period of time, an emission failure or the like occurs.

  In the heat treatment, the heating temperature may be changed within the above range.

  The heating temperature h is 60 ° C. to less than the decomposition temperature of the triarylsulfonium salt, but 60 ° C. to (the decomposition temperature of the triarylsulfonium salt (° C.) − 10 (° C.)) decomposes the triarylsulfonium salt. This is preferable because the treatment can be performed without the treatment.

  The proton removal step according to the present invention is a step of removing protons that are thought to be generated by heating, such as the treatments described below, and is made to be brought into contact with an alkali treatment, a chromatographic separation treatment using various chromatographs, or water. Water treatment etc. are mentioned.

  The alkali treatment is treatment for bringing a triarylsulfonium salt into contact with an alkali agent.

  The alkali treatment is performed by a method of contacting with an alkali agent in a solvent in which a triarylsulfonium salt is dissolved.

  As the solvent for dissolving the triarylsulfonium salt in the alkali treatment, the solvent used in the aforementioned heat treatment is used.

  Examples of the alkali agent include aqueous solutions of alkali metal and alkaline earth metal carbonates such as potassium carbonate and sodium carbonate.

  Examples of the contact method include a method of stirring a mixture of a triarylsulfonium salt solution and an alkali agent.

  The temperature of the alkali treatment is preferably 10 ° C. to the decomposition temperature (° C.)-10 (° C.) of the triarylsulfonium salt, and particularly preferably 10 ° C. to 40 ° C. because a heating or cooling device is unnecessary.

  After the alkali treatment step, it is preferable to have a step of removing water by performing a dehydration treatment using magnesium sulfate or the like.

  Examples of the chromatographic separation treatment include a method in which the alkaline solution is passed through a column filled with a cation exchange resin and then the triarylsulfonium salt solution subjected to the heat treatment is passed.

  Water treatment can be performed by stirring a mixture of a solvent in which triarylsulfonium salt is dissolved and water.

  As described above, the purification step according to the present invention is different from the conventional adsorption method such as activated carbon, basic adsorbent, column chromatography, or the method of phase separation simply by recrystallization, etc. It is characterized in that the protons generated by the change of impurities are removed by heating over a certain temperature and time range as described above.

(Photoacid generator solid)
The triarylsulfonium salt which is the photoacid generator for actinic ray curable inkjet ink of the present invention is a solid.

The acid generator solid for an actinic ray curable inkjet ink of the present invention contains a triarylsulfonium salt, and its acid generation amount (when a 0.02 mol / L dioxane solution of a photoacid generator is refluxed for 20 hours, The difference in hydrogen ion concentration (mol / L) in the solution before and after the flux) is 1 × 10 ⁻⁴ (mol / L) or less.

  By using the solid of triarylsulfonium salt having the above-mentioned acid generation amount, an ink-jet ink excellent in storability can be obtained with little decrease in ink ejection stability even when stored for a long period of time.

  A solid of triarylsulfonium salt having an acid generation amount in the range according to the present invention can be obtained by the production method having the purification step described above.

The thermal acid generation amount of the photoacid generator in the present invention is determined as follows.
(1) Reflux a 0.02 mol / L dioxane solution of a photoacid generator for 20 hours.
(2) About the solution before the reflux and after the reflux, 1 g of the solution and 4 g of pure water are mixed, and the pH of the aqueous layer as the supernatant is measured.
(3) determined by calculating the [H ^+] concentration before and after the reflux from the measurement results of pH, [H ^+] concentration before reflux - the [H ^+] concentration after refluxing, the thermal acid generation amount.

  The reason why the inkjet ink using the triarylsulfonium salt that has undergone the purification process according to the present invention has an effect of suppressing the ball trajectory of the droplet due to adhesion to the nozzle and the ejection failure even when stored for a long period of time is not clear. However, it is guessed as follows.

  Conventionally, when a triarylsulfonium salt is used as an acid generator for inkjet, a method for reducing the impurities contained in the triarylsulfonium salt to be used and incorporating it in the inkjet ink is known.

  Examples of a method for reducing impurities include a method by adsorption on activated carbon, a basic adsorbent, and the like, a method for separating column chromatography, crystallization, recrystallization, and the like.

  However, even if the triarylsulfonium salt is subjected to a method for reducing these impurities, if the ink is stored for a long period of time, problems such as bending of the droplets from the ink jet nozzle and defective emission may occur.

  This problem is that even if the purification method as described above is applied, a very small amount of impurities still remain, and the remaining impurities decompose to generate protonic acid during long-term storage. However, it is assumed that a very small amount of polymer is produced and the presence of this very small amount of polymer is the cause.

  This very small amount of polymer is presumed to be present at a level that does not form a precipitate in appearance and cannot detect thickening by ordinary viscosity measuring methods.

  In the present invention, a very small amount of remaining impurities are decomposed in the heat treatment step to generate a proton acid, and this proton acid is removed in the proton acid removal step. It is presumed that the occurrence is suppressed.

(Cationically polymerizable compound)
The cationically polymerizable compound is a compound that can be cationically polymerized by an acid generated by a photoacid generator upon irradiation with actinic rays.

  Examples of the cationically polymerizable compound used in the present invention include a compound having an oxetane ring (hereinafter referred to as oxetane compound) and a compound having an oxirane ring (hereinafter referred to as oxirane compound).

  The oxetane compound as the cationically polymerizable compound used in the present invention is a compound having one or more oxetane rings in the molecule.

  Specifically, 3-ethyl-3-hydroxymethyloxetane (trade name OXT101 manufactured by Toagosei Co., Ltd.), 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene (OXT121 etc.) ), 3-ethyl-3- (phenoxymethyl) oxetane (OXT211 etc.), di (1-ethyl-3-oxetanyl) methyl ether (OXT221 etc.), 3-ethyl-3- (2-ethylhexyloxymethyl) ) Oxetane (OXT212, etc.) can be preferably used, and in particular, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, di (1-ethyl-3-oxetanyl) methyl Ether can be preferably used.

  These can be used alone or in combination of two or more.

  The oxetane compound is preferably contained in the actinic ray curable inkjet ink in an amount of 5 to 95% by mass, more preferably 20 to 80% by mass.

  Examples of the oxirane compound include epoxy compounds such as the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene oxide thereof. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide or cyclopentene obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Oxide-containing compounds are preferred.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like.

  Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable.

  Examples of the most preferred alicyclic epoxide in the present invention include those described in JP-A Nos. 2004-315778 and 2005-28632.

  Exemplary compounds are described below.

  In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  These oxirane compounds are preferably contained in the actinic ray curable inkjet ink of the present invention in an amount of 5 to 95% by mass, more preferably 20 to 80% by mass.

  In the present invention, a vinyl ether compound may be used in combination as the cationic polymerizable compound.

  Examples of the vinyl ether include ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol. Di- or trivinyl ether compounds such as divinyl ether, cyclohexanedimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, Monovinyl ether compounds such as cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether Etc.

  In the present invention, when the actinic ray curable ink-jet ink contains the oxetane compound and the epoxy compound as the cationic polymerizable compound, the effect of the present invention is particularly large, which is a preferred embodiment.

(Actinic ray curable inkjet ink)
The actinic ray curable inkjet ink of the present invention contains the photoacid generator and a cationically polymerizable compound.

  The content of the acid generator is preferably 0.1 to 15.0% by mass, more preferably 1.0 to 10.0% by mass, and particularly 3.0 to 5%, based on the cationic polymerizable compound. 0.0 mass% is preferable.

  The actinic ray curable inkjet ink of the present invention preferably contains a colorant and a sensitizer, and may further contain other additives such as a basic compound described below.

  As the photoacid generator, a sulfonium salt other than the triarylsulfonium salt according to the present invention, an ammonium salt, a diaryliodonium salt, or the like can be used in combination.

  The content of the photoacid generator that can be used in combination is preferably 0 to 5% by mass with respect to the entire photoacid generator.

  Examples of the acid generator that can be used in combination include those described in JP-A-8-143806 and JP-A-8-283320.

(Colorant)
As the colorant, various dyes and pigments can be used, and pigments are particularly preferably used.

  The pigment is used as a particle having a particle size of approximately 0.01 to 3.0 μm and dispersed in the inkjet ink.

  For the dispersion of the pigment, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used.

  When dispersing the pigment, it is preferable to add a dispersant.

  As the dispersant, a polymer dispersant is preferably used, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series.

  Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.

  The pigments that can be preferably used are listed below.

  C. I Pigment Yellow-1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185, 213, C.I. I Pigment Orange-16, 36, 38, C.I. I Pigment Red-5, 7, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202, C.I. I Pigment Violet-19, 23, C.I. I Pigment Blue-1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60, C.I. I Pigment Green-7, 36, C.I. I Pigment White-6, 18, 21, C.I. I Pigment Black-7, and the like.

(Sensitizer)
In the present invention, a sensitizer can be used in combination according to the wavelength of the light source used.

  As the sensitizer, a polycyclic aromatic compound having at least one hydroxyl group, an optionally substituted aralkyloxy group or an alkoxy group, a carbazole derivative, a thioxanthone derivative, or the like is used as a sensitizer.

  As the polycyclic aromatic compound, naphthalene derivatives, anthracene derivatives, chrysene derivatives, and phenanthrene derivatives are preferable. As an alkoxy group which is a substituent, a C1-C18 thing is preferable and a C1-C8 thing is especially preferable. As the aralkyloxy group, those having 7 to 10 carbon atoms are preferable, and benzyloxy groups and phenethyloxy groups having 7 to 8 carbon atoms are particularly preferable.

  Examples of these sensitizers include 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 1-stearyloxynaphthalene, 2-methoxynaphthalene, 2-dodecyloxynaphthalene, 4-methoxy-1-naphthol, glycidyl- 1-naphthyl ether, 2- (2-naphthoxy) ethyl vinyl ether, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,7-dimethoxynaphthalene, 1,1'-thiobis (2-naphthol), 1,1'-bi-2-naphthol, 1,5-naphthyl diglycidyl ether, 2,7-di (2-vinyloxyethyl) naphthyl ether, 4-methoxy -1-Naphthol, ESN-175 (Epox made by Nippon Steel Chemical Co., Ltd.) Cis-resin) or series thereof, naphthalene derivatives such as condensates of naphthol derivatives and formalin, 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 2-tbutyl-9,10-dimethoxyanthracene, 2,3-dimethyl-9,10-dimethoxyanthracene, 9-methoxy-10-methylanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, 2-tbutyl-9,10 -Diethoxyanthracene, 2,3-dimethyl-9,10-diethoxyanthracene, 9-ethoxy-10-methylanthracene, 9,10-dipropoxyanthracene, 2-ethyl-9,10-dipropoxyanthracene, 2- t-butyl-9,10-dipropoxyanthracene, 2 3-dimethyl-9,10-dipropoxyanthracene, 9-isopropoxy-10-methylanthracene, 9,10-dibenzyloxyanthracene, 2-ethyl-9,10-dibenzyloxyanthracene, 2-tbutyl-9 , 10-dibenzyloxyanthracene, 2,3-dimethyl-9,10-dibenzyloxyanthracene, 9-benzyloxy-10-methylanthracene, 9,10-di-α-methylbenzyloxyanthracene, 2-ethyl- 9,10-di-α-methylbenzyloxyanthracene, 2-tbutyl-9,10-di-α-methylbenzyloxyanthracene, 2,3-dimethyl-9,10-di-α-methylbenzyloxyanthracene, 9- (α-methylbenzyloxy) -10-methylanthracene, 9,10- Anthracene derivatives such as (2-hydroxyethoxy) anthracene and 2-ethyl-9,10-di (2-carboxyethoxy) anthracene, 1,4-dimethoxychrysene, 1,4-diethoxychrysene, 1,4-dipropoxy Chrysene derivatives such as chrysene, 1,4-dibenzyloxychrysene, 1,4-di-α-methylbenzyloxychrysene, phenanthrenes such as 9-hydroxyphenanthrene, 9,10-dimethoxyphenanthrene, 9,10-diethoxyphenanthrene Derivatives and the like can be mentioned. Among these derivatives, 9,10-dialkoxyanthracene derivatives which may have an alkyl group having 1 to 4 carbon atoms as a substituent are particularly preferable, and the alkoxy group is preferably a methoxy group or an ethoxy group.

  Examples of the carbazole derivative include carbazole, N-ethylcarbazole, N-vinylcarbazole, N-phenylcarbazole and the like.

  Examples of the thioxanthone derivative include thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone 2-chlorothioxanthone, and the like.

(Basic compound)
Representative examples of basic compounds include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines.

  Examples of the basic alkali metal compound include alkali metal hydroxides (lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.), alkali metal carbonates (lithium carbonate, sodium carbonate, potassium carbonate, etc.), alkali metals. Alcoholate (sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, etc.).

  Examples of the basic alkaline earth metal compound include alkaline earth metal hydroxides (magnesium hydroxide, calcium hydroxide, etc.), alkali metal carbonates (magnesium carbonate, calcium carbonate, etc.), and alkali metals. Alcoholate (magnesium methoxide, etc.).

  Examples of the basic organic compound include amines and nitrogen-containing heterocyclic compounds such as quinoline and quinolidine.

  Specifically, for example, octylamine, naphthylamine, xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6- Examples include hexamethylenediamine, hexamethylenetetramine, 2- (methylamino) ethanol, and triethanolamine.

  The concentration in the presence of the basic compound is preferably in the range of 10 to 50000 mass ppm, particularly 100 to 5000 mass ppm with respect to the total amount of the photocationically polymerizable compound.

  In addition, a basic compound may be used individually or may be used in combination of multiple.

  The actinic ray curable inkjet ink of the present invention preferably has the following physical property values from the viewpoints of ejection stability, effectiveness, and image quality.

  The viscosity at 50 ° C. is 1 to 30 mPa · s.

  The surface tension (platinum plate method) is preferably 20 to 40 N / m, more preferably 20 to 30 N / m.

(Inkjet recording method)
The ink jet recording method of the present invention is a recording method in which the actinic ray curable ink jet ink of the present invention is ejected onto a recording medium from an ink jet nozzle and then irradiated with actinic rays such as ultraviolet rays to cure the ink.

(Actinic ray irradiation conditions after ink landing)
In the ink jet recording method of the present invention, it is preferable that the actinic ray is irradiated for 0.001 second to 1.0 second after the ink landing, more preferably 0.001 second to 0 as the irradiation condition of the actinic ray. .5 seconds.

  In order to form a high-definition image, it is preferable that the irradiation timing is as early as possible.

  The irradiation method of actinic rays is not specifically limited, For example, it can carry out with the following method.

  As disclosed in JP-A-60-132767, a light source is provided on both sides of a head unit, the head and the light source are scanned by a shuttle method, and irradiation is performed after a certain period of time after ink landing. The curing is completed by another light source without accompanying.

  A method using an optical fiber as described in US Pat. No. 6,145,979, or a method in which a collimated light source is applied to a mirror surface provided on the side surface of a head unit and UV light is irradiated to a recording unit.

  Any of these irradiation methods can be used in the inkjet recording method of the present invention.

  In addition, irradiation with actinic rays is divided into two stages. First, actinic rays are irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further, actinic rays are irradiated after all printing is completed. The method is also a preferred embodiment.

  By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

(Total ink film thickness after ink landing)
In the inkjet recording method of the present invention, the total ink film thickness after the ink has landed on the recording medium and cured by irradiation with actinic rays is 2 to 20 μm. This is preferable in terms of texture change.

  Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording material, and even for a single color, other two colors are superimposed (secondary color), three colors are superimposed, four colors are used. Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

(Ink heating and ejection conditions)
In the ink jet recording method of the present invention, it is preferable from the viewpoint of ejection stability that the actinic ray is irradiated with the actinic ray curable inkjet ink in a heated state.

  The heating temperature is preferably 35 to 100 ° C, and more preferably irradiated with actinic rays while being kept at 35 to 80 ° C, in terms of ejection stability.

  There is no particular limitation on the method of heating and keeping the ink-jet ink at a predetermined temperature.For example, an ink supply system such as an ink tank constituting a head carriage, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, There is a method in which a piezo head or the like is insulated and heated to a predetermined temperature by a panel heater, a ribbon heater, warm water or the like.

  The control range of the ink temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and particularly preferably set temperature ± 1 ° C. from the viewpoint of ejection stability.

  The amount of liquid droplets ejected from each nozzle is preferably 2 to 20 pl from the viewpoint of recording speed and image quality.

(recoding media)
As a recording medium that can be used in the ink jet recording method of the present invention, various non-absorbing plastics and films thereof used for so-called soft packaging can be used in addition to ordinary uncoated paper, coated paper, and the like.

  Examples of plastic films include polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, An acetyl cellulose (TAC) film can be mentioned.

  As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used.

  Moreover, it is applicable also to metals and glass.

  Next, an ink jet recording apparatus (hereinafter simply referred to as a recording apparatus) that can be used in the ink jet recording method of the present invention will be described.

  Hereinafter, the recording apparatus will be described with reference to the drawings as appropriate.

  FIG. 1 is a front view showing a configuration of a main part of the recording apparatus.

  The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like.

  In the recording apparatus 1, the platen unit 5 is installed under the recording medium P.

  The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording medium P.

  As a result, a high-definition image can be reproduced very stably.

  The recording medium P is guided by the guide member 6 and moves from the near side to the far side in FIG. 1 by the operation of the conveying means (not shown). A head scanning unit (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

  The head carriage 2 is installed on the upper side of the recording medium P, and accommodates a plurality of recording heads 3 to be described later according to the number of colors used for image printing on the recording medium P, with the discharge ports arranged on the lower side.

  The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning means.

  In FIG. 1, the head carriage 2 is white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan (Lc). In the drawing, the recording head 3 for light black (Lk) and white (W) is drawn. However, in practice, the number of colors of the recording head 3 stored in the head carriage 2 is appropriately determined. Is.

  The recording head 3 discharges actinic ray curable ink-jet ink (for example, UV curable ink) supplied by an ink supply means (not shown) by the operation of a discharge means (not shown) provided therein. The ink is discharged from the outlet toward the recording medium P.

  During a scan in which the recording head 3 moves from one end of the recording medium P to the other end of the recording medium P in the Y direction in FIG. 1 by driving the head scanning means, a certain area (landing possible area) in the recording medium P On the other hand, UV ink is ejected as ink droplets, and ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and actinic ray curable ink jet ink is ejected toward one landable area. Then, the recording medium P is appropriately moved from the front to the back in FIG. While performing scanning by the scanning unit, the recording head 3 discharges UV ink to the next landable area adjacent to the rearward direction in FIG.

  By repeating the above operation and ejecting the actinic ray curable ink jet ink from the recording head 3 in conjunction with the head scanning means and the conveying means, the recording medium P is composed of an aggregate of actinic ray curable ink jet ink droplets on the recording medium P. An image is formed.

  The irradiation unit 4 includes, for example, an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength.

  Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a hot cathode tube, a black light, an LED (light emitting diode), and the like can be applied. A cathode tube, a hot cathode tube, a mercury lamp or black light is preferred.

  In particular, a low-pressure mercury lamp, a hot cathode tube, a cold cathode tube, and a germicidal lamp that emit ultraviolet light having a wavelength of 254 nm are preferable because they can prevent bleeding and control the dot diameter efficiently.

  By using black light as the radiation source of the irradiation means 4, the irradiation means 4 for curing the UV ink can be produced at low cost.

  The irradiating means 4 has substantially the same shape as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the head scanning means. , Having a shape larger than the landable area.

  The irradiation means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the recording medium P.

  As described above, as a means for adjusting the illuminance of the ink discharge portion, not only the entire recording head 3 is shielded, but in addition, the ink discharge of the recording head 3 is determined from the distance h1 between the irradiation means 4 and the recording medium P. It is effective to increase the distance h2 between the portion 31 and the recording medium P (h1 <h2) or to increase the distance d between the recording head 3 and the irradiation means 4 (d is increased).

  Further, it is more preferable that a bellows structure 7 is provided between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation unit 4 can be changed as appropriate by exchanging the ultraviolet lamp or the filter provided in the irradiation unit 4.

  FIG. 2 is a top view illustrating another example of the configuration of the main part of the ink jet recording apparatus.

  The ink jet recording apparatus shown in FIG. 2 is called a line head system, and a plurality of ink jet recording heads 3 of each color are fixedly arranged on the head carriage 2 so as to cover the entire width of the recording medium P. ing.

  On the other hand, on the downstream side of the head carriage 2, that is, the rear portion of the head carriage 2 in the direction in which the recording medium P is conveyed, the entire width of the recording medium P is also covered so as to cover the entire ink printing surface. Arranged irradiation means 4 are provided.

  As the ultraviolet lamp used in the illuminating means 4, the same one as described in FIG. 1 can be used.

  In this line head system, the head carriage 2 and the irradiation means 4 are fixed, and only the recording medium P is conveyed, and ink ejection and curing are performed to form an image.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Synthesis and Purification of Triarylsulfonium Salt>
A white powder which is a triarylsulfonium salt having the structure of the exemplified compound TAS-1 was obtained by a method similar to the method described in Examples (paragraph 0041) of JP-A-2005-146001.

  The white powder is dissolved in methylene chloride, passed through an alumina column, treated with sodium carbonate, and dehydrated with magnesium sulfate in the same manner as described in the examples (paragraph 0042) of JP-A-2005-146001. Treatment and recrystallization were performed to obtain a triarylsulfonium salt white powder (S-2-a). The decomposition temperature of S-2-a was 180 ° C.

(Purification)
The above S-2-a was dissolved in dioxane, sealed in a sample tube, and stored in a dark place at a heating temperature of 70 ° C. for 8 hours.

  Thereafter, the mixture was passed through an alumina column and then stirred and mixed with an aqueous sodium carbonate solution.

  Next, the organic layer was taken out, dehydrated with magnesium sulfate, dioxane removed under reduced pressure, dried, and recrystallized with methanol to obtain purified triarylsulfonium salt powder (photoacid generator 11).

  The obtained photoacid generator 11 was used as a 50% propylene carbonate solution (photoacid generator solution 11) as a sample for ink-jet ink preparation.

  In the photoacid generator solution 11, the photoacid generators 1 to 10 and 12 to 12 were prepared in the same manner as in the preparation of the photogenerator solution 11, except that the heating temperature and time during purification were those shown in Table 1. 23 was prepared, and photoacid generator solutions 1 to 10 and 12 to 23 were prepared.

  The photoacid generator solution 11 was prepared in the same manner as the photogenerator solution 11 except that the heating temperature at the time of purification was increased from 60 ° C. to 100 ° C. for 4 hours and heated at regular intervals. Thus, a photoacid generator 24 was prepared, and a photoacid generator solution 24 was prepared.

  The triarylsulfonium salt white powder (S-2-a) was heated in the dark at 100 ° C. for 4 hours. After heating, it was dissolved in dioxane, passed through an alumina column, and then stirred and mixed with an aqueous sodium carbonate solution. Subsequently, the organic layer was taken out, dehydrated with magnesium sulfate, dioxane was removed under reduced pressure and dried, and recrystallization was performed with methanol to obtain a purified triarylsulfonium salt powder (photoacid generator 25). A photoacid generator solution 25 was prepared in the same manner as described above.

  Further, the photoacid generator solution 26 was prepared in the same manner as described above, using the above S-2-a that did not undergo the purification step in the present invention as the photoacid generator 26.

<Preparation of actinic ray curable inkjet inks 1-26>
(Preparation of pigment dispersion)
A pigment dispersion containing a pigment was prepared according to the following method.

  The following two compounds were placed in a stainless beaker and dissolved by heating and stirring for 1 hour while heating on a 65 ° C. hot plate.

(Pigment dispersion)
PB824 (manufactured by Ajinomoto Fine Techno Co., Ltd., dispersant) 5 parts OXT-221 (manufactured by Toagosei Co., Ltd., oxetane compound) 80 parts After cooling the above solution to room temperature, carbon black MA-7 (manufactured by Mitsubishi Chemical Corporation) as a pigment to this After adding 15 parts, 200 g of zirconia beads having a diameter of 0.5 mm were placed in a glass bottle and sealed, and after 8 hours of dispersion treatment with a paint shaker, the zirconia beads were removed.

(Preparation of inkjet ink)
Inkjet inks 1 to 27 having the compositions shown below were prepared using the prepared pigment dispersion and the acid generator solution obtained with the above light.

  The obtained ink-jet ink was filtered through a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVATEC.

(Inkjet ink composition)
OXT-221: (di [1-ethyl (3-oxetanyl)] methyl ether, manufactured by Toagosei Co., Ltd.) Amount in which the total of the following components is 100 parts by mass: OXT-212: (3-ethyl-3- (2 -Ethylhexyloxymethyl) oxetane, manufactured by Toagosei Co., Ltd.) 15 parts EPR: (Exemplified Compound EP-17) 15 parts X-22-4272 (Shin-Etsu Silicone, silicone-based nonionic surfactant)
0.1 part 2-methylaminoethanol 0.03 part Photoacid generator solution (described in Table 1) 5 parts DEA (9,10-diethoxyanthracene, manufactured by Kawasaki Kasei Kogyo Co., Ltd.) 2 parts Pigment dispersion 10 parts <Evaluation>
(Storability)
The prepared inkjet ink was stored in a dark place at 70 ° C. for 3 weeks.

  The stored ink-jet ink was subjected to the following ink-jet recording, the ejection stability and the nozzle surface were evaluated, and used as an index of storage stability.

  Using Konica Minolta IJ Co., Ltd. inkjet print unit SP-L2130, each of the stored inkjet inks was used for continuous printing for one month.

  The recording medium uses a roll-shaped white PET having a substrate width of 213 mm and a roll of 180 m, a resolution of 360 dpi in the recording medium width direction (dpi represents the number of dots per 2.54 cm), and a recording medium feed direction. The operation of printing a character image with a printing rate of 18% on a recording medium of 360 m per day (for 2 rolls) at a resolution of 360 dpi at a conveyance speed of 30 m per minute was continued for one month.

A high pressure mercury lamp was used as the irradiation light source, and the ink was cured by irradiating with ultraviolet rays with a light amount such that the integrated light amount was 180 mJ / cm ² .

  After one month of continuous operation, the ink jet nozzles were continuously discharged for 30 minutes, the injection state from each ink jet nozzle was visually observed, and the discharge stability and the state of the nozzle surface were evaluated according to the following criteria.

(Discharge stability)
○: No nozzle missing or bending occurs even after 30 minutes of continuous emission. Δ: No nozzle missing occurs after 30 minutes of continuous emission, but slight bending occurs but there is no problem in practical use. Nozzle occurs at the nozzle of [Nozzle surface condition]
○: Ink deposits are not seen Δ: Ink deposits are slightly seen in the form of droplets, but they do not affect the nozzle opening ×: Many ink deposits are seen on the nozzle surface, The nozzle opening is blocked.

  The results are shown in Table 1.

  From Table 1, it can be seen that the inkjet ink using the acid generator that has undergone the purification step in the present invention is excellent in storage stability.

Example 2
<Preparation of triarylsulfonium salt>
Commercially available product Dow Chemical Japan Co., Ltd. UVI-6992, 8: 2 mixture of bis- [4- (diphenylsulfonio) phenyl] sulfide bishexafluorophosphate and (4-phenylthiophenyl) diphenylsulfonium hexafluorophosphate A 50% aqueous propylene carbonate solution was solidified under reduced pressure to obtain triarylsulfonium hydrochloric acid generator solid S-1-a.

  A triarylsulfonium salt photoacid generator S-3-a having the following structure was obtained in the same manner as described in (3) of Production Example 1 in the examples of the WO2004 / 113396 pamphlet.

  Next, the above triarylsulfonium hydrochloric acid generator solid S-1-a, S-2-a, S-3-a is dissolved in dioxane, sealed in a sample tube, and heated at 100 ° C. in the dark for 4 hours. Heated.

  Thereafter, the mixture was passed through an alumina column and then stirred and mixed with an aqueous sodium carbonate solution.

  Subsequently, the organic layer is taken out, dehydrated with magnesium sulfate, dioxane is removed under reduced pressure, dried, recrystallized with methanol, and purified triarylsulfonium salt photoacid generator solids S-1-b, S-2-b, S-1-b was obtained.

  Also, using S-1-a, the heating temperature was 100 ° C., 4.5 hours, the triarylsulfonium hydrochloric acid generator solid S-1-c was heated to 60 ° C., and the heating time was 10 hours. Triarylsulfonium hydrochloric acid generator solid S-1-d was obtained.

  The acid generation amount of these triarylsulfonium hydrochloric acid generator solids was measured.

  The results are shown in Table 2.

(Preparation of inkjet ink)
Acid generator solutions 2-1 to 2-8 were prepared in the same manner as in Example 1 using S-1-a to d, S-2-a to b, and S-3-a to b. Were used to prepare inkjet inks 2-1 to 2-8.

(Evaluation)
In the same manner as in Example 1, the storage stability of the inkjet inks 2-1 to 2-8 was evaluated.

  The results are shown in Table 2.

  From Table 2, it can be seen that the inkjet ink using the photoacid generator solid of the present invention is excellent in storage stability.

It is a front view which shows an example of a structure of the principal part of the inkjet recording device used for the inkjet recording method of this invention. It is a top view which shows another example of a structure of the principal part of the inkjet recording device used for the inkjet recording method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording device 2 Head carriage 3 Recording head 31 Ink discharge port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure 8 Irradiation light source P Recording medium

Claims (5)

A photoacid generator for an actinic radiation curable inkjet ink used for an actinic radiation curable inkjet ink containing a cationic polymerizable compound and a photoacid generator, wherein the photoacid generator is a triarylsulfonium salt, The triarylsulfonium salt is a photoacid generator for an actinic ray curable inkjet ink, which is produced by a production method having the following purification step.
[Purification step: a heating step of heating the triarylsulfonium salt at a temperature range of 60 ° C. or higher and lower than the decomposition temperature (° C.) of the triarylsulfonium salt, and a proton removal step performed after the heating step, The heating step is a step of heating the solid of the triarylsulfonium salt and then subjecting the solid of the triarylsulfonium salt to the proton removal step, or dissolving the solid of the triarylsulfonium salt in a solvent to form a solution, After heating the solution, the solution is subjected to the proton removal step. When the heating temperature of the heat treatment step is t (° C.) and the heating time is h (hr), K−59h ≧ 82. Process. K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis. ] An actinic radiation curable inkjet ink comprising a cationically polymerizable compound and the photoacid generator for an actinic radiation curable inkjet ink according to claim 1. An inkjet recording method using the actinic ray curable inkjet ink according to claim 2. A method for producing a triarylsulfonium salt for use in an actinic radiation curable inkjet ink containing a cationically polymerizable compound and a triarylsulfonium salt, the method comprising the following purification step: .
[Purification step: a heating step of heating the triarylsulfonium salt at a temperature range of 60 ° C. or higher and lower than the decomposition temperature (° C.) of the triarylsulfonium salt, and a proton removal step performed after the heating step, The heating step is a step of heating the solid of the triarylsulfonium salt and then subjecting the solid of the triarylsulfonium salt to the proton removal step, or dissolving the solid of the triarylsulfonium salt in a solvent to form a solution, After heating the solution, the solution is subjected to the proton removal step. When the heating temperature of the heat treatment step is t (° C.) and the heating time is h (hr), K−59h ≧ 82. Process. K is a value obtained by integrating a heating time-heating temperature curve from x = 0 to x = h with the heating time h as the x-axis and the heating temperature t as the y-axis. ] A photoacid generator solid for actinic ray curable inkjet ink used for actinic ray curable inkjet ink containing a polymerizable compound and a photoacid generator, wherein the photoacid generator solid contains a triarylsulfonium salt The acid generation amount of the photoacid generator solid (when the 0.02 mol / L dioxane solution of the photoacid generator was refluxed for 20 hours, the difference in hydrogen ion concentration (mol / L) in the solution before and after the reflux was ) Is 1 × 10 ⁻⁴ (mol / L) or less, a photoacid generator solid for actinic ray curable inkjet inks.

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