JP2008222864A - Cationic polymerization curable ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationic polymerization curable ink for inkjet recording having excellent ejection stability in continuous printing and curability of the formed image. <P>SOLUTION: The cationic polymerization curable ink for inkjet recording at least contains a cationic polymerization compound, a photopolymerization initiator and a compound expressed by general formula (I). In the formula, R is a 5-15C hydroxyalkyl group or a 9-25C alkyl group, and the hydroxyalkyl group or the alkyl group may have one or more unsaturated bonds. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cationic polymerization curable inkjet ink excellent in emission stability.

  2. Description of the Related Art Conventionally, ink compositions that are cured by radical polymerization by irradiation with active energy rays such as ultraviolet rays are known as quick-drying printing inks. The ink composition has a problem that it is inhibited from curing in the presence of oxygen. Therefore, in recent years, a cation polymerization type ink jet ink composition which is cured by cation polymerization by irradiation with active energy rays has been proposed. As such a cationic polymerization type ink-jet ink composition, a composition composed mainly of an oxetane compound, a photocationic polymerization initiator, and a pigment, to which an epoxy compound is added as required has been proposed (for example, patents). Reference 1).

  Since cationic polymerization is initiated by the presence of a cation generated from a cationic polymerization initiator by irradiation with ultraviolet rays or the like, the polymerization is not inhibited by oxygen, and in particular, it must be carried out in an inert atmosphere. And has the advantage of allowing rapid and complete polymerization in air. However, if the cationic polymerization initiator is added to a cationically polymerizable compound such as an oxetane compound or an epoxy compound and stored for a long period of time, a cation may be spontaneously generated from the cationic polymerization initiator even when the ultraviolet ray is blocked. However, there is a problem in that the polymerization of the cationically polymerizable compound is initiated by this cation, resulting in thickening and gelation.

  The cationic polymerization curable ink jet ink is mainly composed of a colorant, a surfactant and the like in addition to the cationic polymerizable compound and the cationic polymerization initiator. On the other hand, in an ink jet recording apparatus used for ink jet recording, for example, a conductive metal member such as SUS, copper, or aluminum is used as the constituent metal member. It is highly durable against various inks such as water-based ink-jet ink, solvent-based ink-jet ink, oil-based ink-jet ink, ultraviolet curable ink-jet ink, and solid-based ink-jet ink. Yes. However, it has become clear that the cationic polymerization curable ink-jet ink has a problem from the viewpoint of stable ejection.

  That is, it has been found that when the electrically conductive member and the cationic polymerization curable inkjet ink come into contact, an undesirable electrochemical reaction occurs, and a decomposition product or a polymer of the ink component is generated in the flow path or the inkjet head. . When two or more kinds of electrically conductive members are present in the flow path or in the ink jet head, an electromotive force is generated between the different metals due to the contact between the ink and the different metals. Alternatively, metal dissolution occurs. When an ink containing a polymerizable compound is used, this electromotive force or metal dissolution is a trigger, and if the ink is brought into contact with the flow path or the ink jet head for a long period of time, an unexpected ink polymerization reaction occurs. In particular, a cationically polymerizable actinic ray curable inkjet ink using a photoacid generator such as an onium salt as an essential material is likely to cause this problem because the electrical conductivity of the ink is relatively high.

  As means for solving the above problems, it is proposed to improve storage stability without impairing the ring-opening polymerizability of the oxetane compound by adding a basic compound such as an amine to the oxetane compound. (For example, see Patent Document 2). In Patent Document 2, as an amine compound, octylamine, naphthylamine, xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1 , 6-hexamethylenediamine, hexamethylenetetramine, triethanolamine and the like.

  However, even if an amine compound is added according to the above-mentioned proposed method, the polymerization inhibiting effect of the cationic polymerizable compound is still not sufficiently obtained. In particular, the cationic polymerizable compound is not an oxetane compound and an alicyclic compound. When it is a mixed system with an epoxy compound, sufficient storage stability cannot be obtained, and when it is used as an inkjet ink containing a colorant, the colorant aggregates and its dispersion stability is impaired. There was also.

  In addition, an ink-jet ink in which the number of carbon atoms of tertiary alkanolamines or tertiary alkylamines is defined has been proposed (see, for example, Patent Document 3).

However, the amine compound described in Patent Document 3 has a high volatility because it has a low molecular weight as a whole, and since the vicinity of the nozzle plate of the inkjet head is an open system, it is greatly affected during printing. However, at present, the highly volatile amine compound is volatilized from the nozzle interface in the printing pause state, and the effect as a polymerization inhibitor cannot be sufficiently exhibited. As a result, ink polymerization occurs in the vicinity of the nozzle, and precipitates are generated in the vicinity of the nozzle. If the direction of ink ejection during ejection is disturbed or further progressed by the generated precipitate, the nozzle portion is blocked and nozzle missing occurs. In addition, these cationically polymerizable inkjet inks are originally stored in a closed container in order to ensure stable storage, but are often handled in an open system, and in such cases, the amine component is similarly contained. It evaporates and the storage stability in the long term is impaired.
JP-A-8-143806 JP 2000-186079 A JP 2003-292606 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a cationic polymerization curable inkjet ink excellent in emission stability during continuous printing and curability of the formed image.

  The above object of the present invention is achieved by the following configurations.

  1. A cationic polymerization curable ink-jet ink comprising at least a cationic polymerizable compound, a photopolymerization initiator, and a compound represented by the following general formula (I).

[Wherein, R represents a hydroxyalkyl group having 5 to 15 carbon atoms or an alkyl group having 9 to 25 carbon atoms. However, the hydroxyalkyl group or the alkyl group may have one or more unsaturated bonds. ]
2. 2. The cationic polymerization curing according to 1 above, wherein R in the compound represented by the general formula (I) is a hydroxyalkyl group having 5 to 10 carbon atoms or an alkyl group having 9 to 18 carbon atoms. Type inkjet ink.

  3. 3. The cationic polymerization curable inkjet ink according to 1 or 2, wherein the cationic polymerizable compound is at least one selected from an epoxy compound, an oxetane compound having an oxetane ring, and a vinyl ether compound.

  4). 4. The cationic polymerization according to any one of 1 to 3, wherein the content of the compound represented by the general formula (I) is 0.01 to 1.0% by mass with respect to the total mass of the ink. A curable inkjet ink.

  5. 4. The cationic polymerization according to any one of 1 to 3, wherein the content of the compound represented by the general formula (I) is 0.01 to 0.05% by mass with respect to the total mass of the ink. A curable inkjet ink.

  6). The cationic polymerization curable inkjet ink according to any one of 1 to 5, wherein the photopolymerization initiator is a photoacid generator, and the photoacid generator contains a triarylsulfonium salt. .

  According to the present invention, it is possible to provide a cationic polymerization curable inkjet ink that suppresses the generation of precipitates in the vicinity of a nozzle of an inkjet recording head and is excellent in emission stability during continuous printing and curability of a formed image.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventor of the present invention contains at least a cationic polymerizable compound, a photopolymerization initiator, and a compound represented by the general formula (I). Cationic polymerization curable type that suppresses the generation of precipitates in the vicinity of the nozzles of the ink jet recording head during continuous emission or resumption after pause, and has excellent emission stability during continuous printing and curability of the formed image. It has been found that an inkjet ink can be realized, and has reached the present invention.

  That is, the cationic polymerization curable inkjet ink is characterized by containing at least a cationic polymerizable compound and a photopolymerization initiator and a compound represented by the general formula (I) as a polymerization inhibitor. In the dimethylamine compound represented by the general formula (I) according to the present invention, the substituent R is a hydroxyalkyl group having 5 to 15 carbon atoms or an alkyl group having 9 to 25 carbon atoms. In this way, by applying an amine compound having a relatively large molecular weight, the amine compound does not volatilize in the ink even in the open system, and volatilization from the nozzle interface or in the open system container during ejection stoppage. The volatilization of amine during storage can be suppressed, and as a result, excellent ejection stability can be realized, and the storage stability of ink can be maintained over a long period of time. In addition, the ink stored for a long period of time often deteriorates the wettability of the water repellent film provided in the vicinity of the nozzle, but the dimethylamine compound represented by the general formula (I) according to the present invention By applying this, it is possible to maintain excellent wettability with respect to the water-repellent film in the vicinity of the nozzle even for ink after long-term storage.

  Details of the present invention will be described below.

<< Cationic polymerization curable inkjet ink >>
[Compound represented by formula (I)]
First, the compound represented by formula (I) according to the present invention will be described.

  The cationic polymerization curable inkjet ink of the present invention (hereinafter also simply referred to as ink) contains at least a cationic polymerizable compound and a photopolymerization initiator, and contains a compound represented by the general formula (I). Features.

  The cationic polymerization curable inkjet ink of the present invention is an ink having relatively electrical conductivity, and specifically has an electrical conductivity of 0.1 μS / cm or more and 10 μS / cm or less. The electrical conductivity of the ink can be determined using a conductivity meter (for example, conductivity meter SC-51 type: manufactured by Yokogawa Hokushin Electric Co., Ltd.).

  In the cationic polymerization curable ink-jet ink of the present invention, at least one selected from an epoxy compound, a compound having an oxetane ring and a vinyl ether compound is used as a photopolymerizable compound which is a preferred structure, and a sulfonium salt as a photoacid generator. Specifically, when a triarylsulfonium salt is used, the electric conductivity of the ink is higher.

  Even when such a cationic polymerization curable inkjet ink having relatively high electrical conductivity is ejected using an inkjet printer having an electrically conductive member, it is represented by the general formula (I) according to the present invention. By adding dimethylalkylamine or dimethylalkanolamine, even if the ink contacts the electrically conductive member constituting the ink jet printer, it accompanies electrolytic corrosion and corrosion caused by the electrically conductive member due to moisture contained in the ink. The polymerization reaction of the ink can be suppressed and the generation of foreign matters such as a polymer can be prevented.

  Further, when the ink is stored for a long period of time, a cation may be spontaneously generated from the cationic polymerization initiator even in a state where the ultraviolet ray is blocked, and this cation initiates polymerization of the cation polymerizable compound, resulting in a dark reaction. It is possible to effectively suppress the generation of a gel-like substance due to an increase in ink viscosity or an incorrect polymerization reaction.

  In the cationic polymerization curable ink-jet ink of the present invention, the content of the compound represented by the general formula (I) with respect to the total mass of the ink is 0.01 to 1.0 mass from the viewpoint of further achieving the object effect of the present invention. %, Preferably in the range of 0.01 to 0.05% by mass. If the content of the compound represented by the general formula (I) is 0.01% by mass, the effect as a polymerization inhibitor can be exerted, and the gel is caused by an unnecessary reaction during long-term storage or in an inkjet printer. When the amount is 1.0% by mass or less, the desired effect can be exhibited and sufficient curability can be obtained.

  Furthermore, the ink of the present invention is preferably stored in a sealed container in order to maintain the moisture content until it is loaded into an ink jet printer.

  In general, a film pack having an oxygen and moisture barrier property is used as an ink storage container, but the oxygen and moisture barrier effect required for the recent cationic polymerization curable inkjet ink may not be sufficient. For this reason, a container made of a metal member is used. In such a metal container, when a cationic polymerization curable inkjet ink having a water content measured by the Karl Fischer method exceeding 0.3 mass% is stored in a container composed of different kinds of different metals, the different kinds of metals are used. Lewis acid is generated from the contact point of the metal with the elution of the metal, and the Swiss acid is used as a trigger for cationic polymerization, and precipitates are generated in the ink, and the precipitates clog the nozzles of the inkjet head. In some cases, the discharge stability is lowered. For example, ink deposits are likely to occur when stored in a container having a member in which two kinds of aluminum and stainless steel are in contact with each other, or a container made of stainless steel as an alloy. On the other hand, the ink in which the dimethylalkylamine or dimethylalkanolamine of the present invention is added in the range of 0.01 to 1.0% by mass according to the present invention has a water content measured by the Karl Fischer method of 1.5% by mass. If it is in the range of% or less, the above-mentioned phenomenon that lowers the ejection stability can be sufficiently suppressed. Further, from the viewpoint of maintaining these states even after being loaded into the ink jet printer, it is more preferable that the ink supply path from the ink tank to the ink jet head is a sealed system as the ink jet printer.

  In the compound represented by the general formula (I) according to the present invention, the compound represented by the substituent R represents a hydroxyalkyl group having 5 to 15 carbon atoms or an alkyl group having 9 to 25 carbon atoms. However, the hydroxyalkyl group or the alkyl group may have one or more unsaturated bonds.

  In particular, when it cannot be stored in an airtight container and stored in an open system, if it is a hydroxyalkyl group having 5 or more carbon atoms or an alkyl group having 9 or more carbon atoms, it can suppress volatility. In addition, the storability as an ink component can be maintained, and sufficient performance intended by the present invention can be exhibited. In addition, if the hydroxyalkyl group having 15 or less carbon atoms or the alkyl group having 25 or less carbon atoms, the polymerization inhibition effect can be sufficiently maintained, and in addition, the ink jet recording head around the nozzles can be stored during long-term storage. Appropriate wettability with respect to the water-repellent film provided on the substrate can be exhibited.

  In the present invention, from the viewpoint of more exerting the above effects, the compound represented by the substituent R of the compound represented by the general formula (I) has a hydroxyalkyl group having 5 to 10 carbon atoms or a carbon number. More preferably, it is a 9-18 alkyl group.

  Specific examples of the compound represented by the general formula (I) according to the present invention include, for example, dimethylundecanol, dimethyldodecanolamine, dimethyltridecanolamine, dimethyltetradecanolamine, dimethylpentadecanolamine, Examples thereof include dimethylnonadecylamine, dimethylicosylamine, dimethyleicosylamine, dimethylhencosylamine, dimethyldocosylamine, dimethyltricosylamine, dimethyltetracosylamine, and dimethylpentacosylamine.

  Further, preferably the substituent R is a hydroxyalkyl group having 5 to 10 carbon atoms or an alkyl group having 9 to 18 carbon atoms, dimethylpentanolamine, dimethylhexanolamine, dimethylheptanolamine, dimethyloctanolamine, dimethylnona Nolamine, dimethyldecanolamine, dimethylnonylamine, dimethyldecylamine, dimethylundecylamine, dimethyldodecylamine, dimethyltridecylamine, dimethyltetradecylamine, dimethylpentadecylamine, dimethylhexadecylamine, dimethylheptadecylamine, Examples include dimethyloctadecylamine.

[Photopolymerizable compound]
One feature of the cationic polymerization curable ink-jet ink of the present invention is that it contains at least a cationic polymerizable compound and a photopolymerization initiator. Moreover, it is preferable to contain 10-30 mass% of at least 1 type of monofunctional monomer as a cationically polymerizable compound. If the monofunctional monomer is 10% by mass or more, the effect can be sufficiently exerted, and if it is 30% by mass or less, excellent curability can be achieved and image quality problems such as color bleeding can be prevented. be able to.

  In the cationic polymerization curable ink-jet ink of the present invention, the cationically polymerizable compound is at least one selected from an epoxy compound, an oxetane compound having an oxetane ring, and a vinyl ether compound, so that the objective effect of the present invention can be further exhibited. It is preferable from the viewpoint, and further contains at least one monofunctional or bifunctional epoxy compound, at least one monofunctional or bifunctional oxetane compound, or at least one monofunctional or bifunctional vinyl ether compound. Is preferred.

  Examples of these cationically polymerizable compounds include, for example, Kaihei 6-9714, JP 2001-31892, JP 2001-40068, JP 2001-55507, JP 2001-310938, JP 2001-310937. And epoxy compounds, vinyl ether compounds, oxetane compounds and the like exemplified in JP-A-2001-220526.

  Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides described below.

  Preferred as the 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 its Examples thereof include di- or polyglycidyl ethers of alkylene oxide adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, and novolak-type epoxy resins. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is preferable.

  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 epoxy compounds, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable in consideration of fast curability. In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  In the present invention, from the viewpoint of further improving curability and ejection stability, as a photopolymerizable compound, a compound having an oxetane ring is 30 to 95% by mass of a total photopolymerizable compound, and a compound having an oxirane group is 5 to 5. It is preferable to contain 70 mass% and 0-40 mass% of vinyl ether compounds.

  As the oxetane compound that can be used in the present invention, for example, any known oxetane compound described in JP-A Nos. 2001-220526 and 2001-310937 can be used.

  Examples of vinyl ether compounds that can be used in the present invention include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, Di- or trivinyl ether compounds such as cyclohexanedimethanol divinyl ether and trimethylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol Bruno vinyl, n- propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

(Photopolymerization initiator)
In the ink of the present invention, as the photopolymerization initiator, all known photopolymerizations described in “Application and Market of UV / EB Curing Technology” (CMC Publishing Co., Ltd., edited by Yoneho Tabata / Edited by Radtech Research Association), etc. Although an initiator can be used, it is preferable to use a photoacid generator. Among them, in the present invention, it is preferable that the photopolymerization initiator is a photoacid generator, and the photoacid generator contains a triarylsulfonium salt.

  As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), 187. To page 192). Examples of compounds suitable for the present invention are listed below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, phosphonium, etc. be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated substances that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

  In particular, in the ink of the present invention, the photoacid generator is preferably a compound containing a triarylsulfonium salt.

  The photoacid generator is preferably contained at a ratio of 0.2 to 20 parts by mass with respect to 100 parts by mass of the cationic polymerizable compound. If the content of the photoacid generator is less than 0.2 parts by mass, it is difficult to obtain a cured product, and even if the content exceeds 20 parts by mass, there is no further effect of improving curability. These photoacid generators can be used alone or in combination of two or more.

[Color material]
The cationic polymerization curable ink-jet ink of the present invention can contain various known dyes or pigments together with the above-described cationic polymerizable compound and photopolymerization initiator, but as a color material from the viewpoint of excellent weather resistance. It is preferred to apply a pigment.

  Examples of the pigment used in the present invention include carbon pigments such as carbon black, carbon refined, and carbon nanotubes, and metal oxide pigments such as iron black, cobalt blue, zinc oxide, titanium oxide, chromium oxide, and iron oxide. Sulfide pigments such as zinc sulfide, phthalocyanine pigments, pigments composed of salts such as metal sulfates, carbonates, silicates and phosphates, and aluminum powders, bronze powders, and zinc powders Inorganic pigments such as metallic powders, nitro pigments, aniline black, nitroso pigments such as naphthol green B, azo pigments such as Bordeaux 10B, Lake Red 4R, and chromoftal red (azo lakes, insoluble azo pigments, condensed azo pigments, Including chelate azo pigments), Peacock Blue Lake and Rhodamine Ray Rake pigments such as phthalocyanine blue, polycyclic pigments (perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinofuranone pigments), thioindigo red Organic pigments such as selenium pigments such as Indatron Blue, quinacridone pigments, quinacridine pigments, and isoindolinone pigments can also be used.

Specific examples of pigments include
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, 180, 185,
C. I Pigment Orange-16, 36, 38,
C. 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 Pigment Violet-19, 23,
C. I Pigment Blue-1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60,
C. I Pigment Green-7, 36,
C. I Pigment White-6, 18, 21,
C. I Pigment Black-7, and the like.

  The amine value of the pigment is preferably larger than the acid value, and the difference is more preferably 1 mg / g KOH or more and less than 10 mg / g.

  For the dispersion of the pigment, for example, a dispersion device such as 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, or a paint shaker can be used. Moreover, a dispersing agent can also be added when dispersing a pigment. As the dispersant, a polymer dispersant is preferably used. 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 dispersion medium is used using a solvent or a polymerizable compound, but the ink of the present invention is preferably solvent-free because it is reacted and cured after printing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle diameter of the pigment particles is 0.08 to 0.5 μm, and the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained. In the ink of the present invention, the color material concentration is preferably 1% by mass to 10% by mass of the whole ink.

〔Additive〕
Various additives other than those described above can be used in the ink of the present invention. For example, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, for the purpose of improving storage stability, any known basic compound can be used, but representative examples include basic alkali metal compounds, basic alkaline earth metal compounds, amines, fatty acid amine salts, Examples include basic organic compounds such as various rust inhibitors.

[Others]
In the ink of the present invention, when used for inkjet image formation, the viscosity at 25 ° C. is preferably 7 to 50 mPa · s.

"inkjet printer"
Next, an outline of an ink jet printer applicable to the present invention will be described.

  An ink jet printer according to the present invention comprises at least a cationic polymerizable compound and a photopolymerization initiator of the present invention, and a cationic polymerization curable ink jet ink comprising a compound represented by formula (I) An ink tank for storing the ink, an ink supply path for sending ink from the ink tank to the ink jet head, an ink jet head for emitting the ink supplied from the ink supply path onto the recording material, and landed on the recording material An actinic ray irradiation light source for curing ink droplets and a joint for connecting each component member, and the like, and a filter or an intermediate tank are provided in the ink supply path of the ink tank and the inkjet head.

  FIG. 1 is a diagram showing an overall configuration of an inkjet printer including a filter and an intermediate tank applicable to the present invention.

  Reference numeral 1 denotes an ink tank that stores and supplies ink. In FIG. 1, for example, a configuration including a yellow ink tank 1Y, a magenta ink tank 1M, a cyan ink tank 1C, and a black ink tank 1K is shown. J is a joint connecting the ink tank 1 and the ink supply path.

  Reference numeral 2 denotes an inkjet head having nozzles for forming an image by ejecting ink droplets onto a recording material, and is composed of a yellow inkjet head 2Y, a magenta inkjet head 2M, a cyan inkjet head 2C, and a black inkjet head 2K. Reference numeral 3 denotes an active energy ray source that irradiates ink that has landed on the recording material with ultraviolet rays that are active energy rays.

  Reference numeral 4 denotes a carriage. The carriage 4 integrally mounts the inkjet head 2 and the energy ray source 3 and is reciprocated as indicated by arrows WX1 and WX2 by being guided by the carriage guide 5 to scan the recording material P. Then, an image is formed on the recording material P.

  A filter box 6 includes a yellow filter box 6Y, a magenta filter box 6M, a cyan filter box 6C, and a black filter box 6K. An intermediate tank 7 includes a yellow intermediate tank 7Y, a magenta intermediate tank 7M, a cyan intermediate tank 7C, and a black intermediate tank 7K.

  Ink is sent from the ink tank 1 to the intermediate tank 7, and is supplied from the intermediate tank 7 to the inkjet head 2 through the ink supply path 8. The ink supply path 8 is composed of supply paths for yellow ink, magenta ink, cyan ink, and black ink, and each single color ink is independently supplied from the ink tank 1 through the ink supply path 8 and the inkjet head. 2 is supplied.

  A maintenance unit 10 performs a recovery process of the inkjet head 2 and includes a suction cap 9 for capping the inkjet head 2. A waste ink container 12 for storing waste ink receives and stores ink forcedly ejected from the inkjet head 2 during flushing.

  FIG. 2 is a schematic configuration diagram showing an example of an ink supply path configuration of an inkjet printer applicable to the present invention.

  In FIG. 2a, the ink tank 101 is connected to the ink supply path 102 via the joint J1, and the end of the ink supply path 102 is further stored in the carriage 103 via the joint J2. It is connected to the head 104. Ink droplets are ejected onto the recording material from the nozzles N of the inkjet head 104 in accordance with the image formation information, and then the active energy rays are instantaneously irradiated from the active energy ray source L to cure the ink. .

  FIG. 2B shows an example in which an intermediate tank unit 105 with a built-in filter is provided in the middle of the ink supply path 102. The discharge port of the ink tank 101 and the ink supply path 102 are connected by a joint J1, and are connected to the intermediate unit tank 105 through a joint J3. The ink is fed from the joint J3 to the intermediate tank front chamber 106, and then is fed to the intermediate tank 108 by removing a foreign substance or the like by the filter 107. Next, the intermediate tank 108 and the ink supply path 102 are connected via a joint J 4, and an ink supply line that supplies filtered ink stored in the intermediate tank 108 to the inkjet head 104. Note that reference numeral 109 shown in FIG. 2B denotes a filter adjacent portion adjacent to the filter 107.

  FIG. 2c) shows an example in which a filter box 110 is provided in place of the intermediate tank unit 105 in FIG. A filter 107 is provided in a filter box 110 connected to the ink supply path 102 via the joint J5 on the ink entrance side and via the joint J6 on the ink exit side. An ink supply line that supplies ink to the inkjet head 104 after removing foreign matter or the like. 2 indicates a filter adjacent portion adjacent to the filter 107.

  In FIG. 2 described above, for convenience, only lines for supplying ink to the magenta inkjet head are shown. However, as shown in FIG. 1, the same supply lines are used for the yellow inkjet head and the cyan inkjet head. It is also provided in the head and the black inkjet head. Further, FIG. 2 shows only the configuration necessary for the description, and although not shown in FIG. 2, for example, an electromagnetic valve for controlling ink feeding, a branch joint, a liquid feeding pump, an inkjet, etc. A head control unit and the like are provided.

  In the present invention, the ink jet printer has a portion in contact with the cationic polymerization curable ink jet ink of the present invention. In the present invention, a portion in contact with ink (hereinafter also referred to as an ink contact portion) is an ink tank, an ink supply path, an intermediate tank unit, a filter box, and the like, and a joint group connecting them, and is directly connected to the ink of the present invention. In the ink supply line shown in FIG. 2A, for example, the inside of the ink tank 101, the inside of the ink supply path 102, the joints J1 and J2, and the inside 104 of the inkjet head. 2B), the inside of the ink tank 101, the inside of the ink supply path 102, the joints J1 to J4, the filter 107 and the filter adjacent portion 109 of the intermediate tank unit 105, and the inside 104 of the inkjet head. is there. Further, in the ink supply line shown in FIG. 2C, the inside of the ink tank 101, the inside of the ink supply path 102, the joints J1, J2, J5, and J6, the filter 107 in the filter box 110, the filter adjacent portion 111, and the inkjet. This is the inside 104 of the head.

  When different types of electrically conductive members are used as the ink contact member having the above-described configuration, an electromotive force is generated between different kinds of metals, and this electromotive force causes an illegal polymerization reaction with the cationic polymerization curable inkjet ink. It causes a gel-like substance, and the cationic polymerization curable inkjet ink of the present invention containing the compound represented by the general formula (I) according to the present invention is also long in the inkjet printer having the above-described configuration. Even in a state of being stored for a period, stable emission can be realized. In addition, the cationic polymerization curable inkjet ink of the present invention has good wettability with respect to the water-repellent film provided around the nozzles of the inkjet recording head, so that even when continuous emission is performed, oblique emission is performed. And nozzle missing can be effectively suppressed.

<Inkjet recording method>
In the ink jet printer according to the present invention, as described above, the ink jet printer represented by FIGS. 1 and 2 was used to eject the cationic polymerization curable ink jet ink of the present invention onto the recording material from the ink jet head described later. After that, an image is formed by irradiating and curing with actinic rays. A curing method using an inkjet head, an actinic ray irradiation apparatus and actinic ray irradiation will be described below.

  Examples of actinic rays used for curing the cationic polymerization curable inkjet ink of the present invention include ultraviolet rays, X-rays, and electron beams. As the light source that can be used when the ink of the present invention is cured by ultraviolet rays, various light sources can be used, for example, mercury lamp, metal halide lamp, electrodeless lamp, excimer laser, ultraviolet laser, cold cathode tube, heat A cathode tube, black light, LED (light emitting diode), etc. are mentioned. In the case of curing with an electron beam, various irradiation devices can be used, for example, a cockroft-warthin type, a bandegraph type, or a resonance transformer type, and the electron beam has an energy of 50 to 1000 eV. Preferably, it is 100 to 300 eV. In this invention, since an inexpensive apparatus can be used, it is preferable to use an ultraviolet-ray for hardening of an active energy ray hardening composition.

  Next, an inkjet image forming method applicable to the present invention will be described.

  The inkjet image forming method according to the present invention is a method in which the cationic polymerization curable inkjet ink of the present invention is ejected and drawn on a recording material by an inkjet recording method and then irradiated with actinic rays such as ultraviolet rays to cure the ink. is there.

(Ink ejection conditions)
When forming an image using the ink of the present invention, the ink is preferably discharged from the inkjet head and the ink of the present invention at 35 to 100 ° C. for discharge stability. Cationic polymerization curable ink-jet ink has a large viscosity fluctuation range due to temperature fluctuation, and the viscosity fluctuation directly affects the droplet size and droplet ejection speed, causing image quality degradation. Therefore, the temperature is kept constant while raising the ink temperature. It is necessary to keep on. The control range of the ink temperature is a set temperature ± 5 ° C., preferably a set temperature ± 2 ° C., more preferably a set temperature ± 1 ° C. (Light irradiation conditions after ink landing)
In the inkjet image forming method according to the present invention, as the irradiation condition of the actinic ray, it is preferable that the actinic ray is irradiated for 0.001 seconds to 1.0 seconds after the ink has landed on the recording material. More preferably, it is 0.001 second to 0.5 second. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

  As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  Next, an ink jet head and an actinic ray irradiation unit constituting the ink jet printer of the present invention will be described.

  Hereinafter, the ink jet printer of the present invention will be described with reference to the drawings as appropriate. However, the recording apparatus of the drawings is merely one aspect of the recording apparatus of the present invention, and the recording apparatus of the present invention is not limited to this drawing.

  FIG. 3 is a front view showing an example of the configuration of the main part (inkjet head, irradiation means) of the inkjet printer of the present invention.

  The ink jet printer 201 includes a head carriage 202, an ink jet head 203, an irradiation unit 204, a platen unit 205, and the like. In the recording apparatus 201, a platen unit 205 is installed under the recording material P. The platen unit 205 has a function of absorbing actinic rays, for example, ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording material P. As a result, a high-definition image can be reproduced very stably.

  The recording material P is guided by the guide member 206 and moves from the near side to the far side in FIG. 3 by the operation of the conveying means (not shown). A head scanning unit (not shown) scans the inkjet head 203 held by the head carriage 202 by reciprocating the head carriage 202 in the Y direction in FIG.

  The head carriage 202 is installed on the upper side of the recording material P, and accommodates a plurality of recording heads 203 to be described later in accordance with the number of colors used for image printing on the recording material P, with the discharge ports arranged on the lower side. The head carriage 202 is installed with respect to the main body of the ink jet printer 201 so as to reciprocate in the Y direction in FIG. 3, and reciprocates in the Y direction in FIG. 3 by driving the head scanning means.

  In FIG. 3, the head carriage 202 is white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan (Lc). ), Light black (Lk), and white (W) are drawn as being housed. However, the number of colors of the ink-jet head 203 housed in the head carriage 202 is appropriately determined in the implementation. It is what

  The ink-jet head 203 records the cationic polymerization curable ink-jet ink of the present invention supplied by an ink supply means (not shown) from the discharge port by the operation of a plurality of discharge means (not shown) provided therein. Discharge toward the material P. The ink ejected by the inkjet head 203 includes a color material, a photopolymerizable compound, a photoinitiator, and the like, and the photoinitiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by monomer crosslinking and polymerization reactions.

  The inkjet head 203 is a fixed region (landing possible region) in the recording material P during the scanning of moving from the one end of the recording material P to the other end of the recording material P in the Y direction in FIG. Ink is ejected as ink droplets, and the ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and after ejecting ink toward one landable area, the recording material P is appropriately moved from the front to the back in FIG. 3 by the conveying means, and scanning by the head scanning means is performed again. In the meantime, the inkjet head 203 discharges ink to the next landable area adjacent to the landable area in FIG.

  By repeating the above-described operation and ejecting ink from the inkjet head 203 in conjunction with the head scanning unit and the conveying unit, an image composed of an aggregate of ink droplets is formed on the recording material P.

  The irradiation unit 204 includes an ultraviolet lamp that emits active light in a specific wavelength region, for example, ultraviolet light with stable exposure energy, and a filter that transmits ultraviolet light having a specific wavelength. Here, as the ultraviolet lamp, the above-mentioned mercury lamp, metal halide lamp, electrodeless lamp, excimer laser, ultraviolet laser, cold cathode tube, hot cathode tube, black light, LED (light emitting diode), etc. can be applied. is there.

  The irradiating means 204 has the same shape as the largest one that can be set by the ink jet printer 201 among the landable areas where the ink jet head 203 ejects ink by one scan driven by the head scanning means, or is larger than the landable area. Has a large shape.

  The irradiation means 204 is fixed and installed on both sides of the head carriage 202 so as to be substantially parallel to the recording material P.

  Further, as a means for preventing unauthorized irradiation of actinic rays to the ink discharge portion, not only the entire inkjet head 203 is shielded, but in addition, from the distance h1 between the irradiation means 204 and the recording material P, the inkjet head It is effective to increase the distance h2 between the ink discharge portion 231 and the recording material P 203 (h1 <h2) or increase the distance d between the inkjet head 203 and the irradiation unit 204 (d is increased). Further, it is more effective to provide a bellows structure 207 between the inkjet head 203 and the irradiation means 204.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation unit 204 can be appropriately changed by replacing the ultraviolet lamp or filter provided in the irradiation unit 204.

  The ink of the present invention has very excellent ejection stability and is particularly effective when an image is formed using a line head type ink jet printer.

  FIG. 4 is a top view illustrating another example of the configuration of the main part of the inkjet printer.

  The ink jet printer shown in FIG. 4 is called a line head system, and a plurality of ink jet heads 203 of each color are fixedly arranged on the head carriage 202 so as to cover the entire width of the recording material P. .

  On the other hand, an irradiation unit 204 is provided on the downstream side of the head carriage 202 so as to cover the entire width of the recording material P.

  In this line head system, the head carriage 202 and the irradiation means 204 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image.

<Recording material>
As a recording material that can be used in the present invention, in addition to ordinary uncoated paper, coated paper, etc., various non-absorbable plastics and films used for so-called soft packaging can be used. For example, polyethylene terephthalate (PET) film, stretched polystyrene (OPS) film, stretched polypropylene (OPP) film, stretched nylon (ONy) film, polyvinyl chloride (PVC) film, polyethylene (PE) film, triacetyl cellulose (TAC) ) A film etc. can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, polyvinyl alcohol (PVA), rubbers and the like can be used. Moreover, it is applicable also to metals and glass. The actinic ray curable ink of the present invention is particularly suitable as an ink for forming an image on a fibrous material (medium) such as a fabric. The fiber material is not particularly limited, and various materials can be used, but synthetic fibers are preferable. Examples of synthetic fibers applicable to the present invention include commercially available synthetic fibers such as polyester fibers, polyamide fibers, polyvinyl alcohol fibers, polyethylene fibers, polypropylene fibers, and polyaramid fibers. Examples of the fabric made of synthetic fibers include woven fabrics, knitted fabrics, and nonwoven fabrics using the synthetic fibers. Tarpaulins are those in which the surface of a fabric is coated with a polyvinyl chloride resin, and any of those processed by a laminating method, a coating method, a padding method, a topping method, or a combination of these methods may be used. As the vinyl chloride resin, either a paste resin type or a straight resin type can be used. The vinyl chloride resin can be blended with plasticizers, fillers, cryogenic agents, flameproofing agents, ultraviolet absorbers and the like that are generally blended.

  The cationic polymerization curable ink-jet ink of the present invention is suitable as an ink when an image is formed on a polyester fiber material among the above synthetic fibers, and the cured film does not peel off without impairing the texture of the recording material. An image can be formed on a polyester fiber material.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Preparation of pigment dispersion >>
[Preparation of yellow pigment dispersion]
A yellow pigment dispersion was prepared according to the method described below.

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

Azisper PB822 (dispersant manufactured by Ajinomoto Fine Techno Co., Ltd.) 8 parts by mass Aron Oxetane OXT-221 (Oxetane compound manufactured by Toagosei Co., Ltd.) 72 parts by mass Next, after cooling to room temperature, C.I. I. 20 parts by weight of Pigment Yellow 150 was added together with 200 parts of zirconia beads having a diameter of 0.3 mm and sealed in a glass bottle. After a dispersion process for 4 hours with a paint shaker, the zirconia beads were removed, and a yellow pigment was added. A dispersion was prepared.

[Preparation of magenta pigment dispersion]
In the preparation of the yellow pigment dispersion, the pigment is C.I. I. In place of Pigment Yellow 150, C.I. I. A magenta pigment dispersion was prepared in the same manner except that it was changed to Pigment Red 122.

(Preparation of cyan pigment dispersion)
In the preparation of the yellow pigment dispersion, the pigment is C.I. I. In place of Pigment Yellow 150, C.I. I. A cyan pigment dispersion was prepared in the same manner except that it was changed to Pigment Blue 15: 4.

[Preparation of black pigment dispersion]
In the preparation of the yellow pigment dispersion, the pigment is C.I. I. In place of Pigment Yellow 150, C.I. I. A black pigment dispersion was prepared in the same manner except that it was changed to Pigment Black 7.

<Preparation of ink>
[Preparation of Ink 1]
Using the yellow pigment dispersion liquid prepared above (yellow pigment: 20% by mass, dispersant PB822: 8% by mass, photopolymerizable compound OXT-221: 72% by mass) and the following additives, yellow ink was prepared. Prepared.

  Specifically, after mixing all the following additives other than the yellow pigment dispersion and confirming that it was sufficiently dissolved, this mixed solution was added little by little to the yellow pigment dispersion with stirring for 15 minutes. After stirring, filtration was performed with a PP3 μm disk filter manufactured by Loki Techno.

Yellow pigment dispersion 20.0 parts by weight Addis Bar PB822 (manufactured by Ajinomoto Fine Techno) 2.0 parts by weight Oxetane OXT221 (manufactured by Toagosei) 46.0 parts by weight Oxetane OXT212 (manufactured by Toagosei) 5.0 parts by weight Oxetane OXT101 (Toagosei) 5.0 parts by weight Alicyclic epoxy compound 1 18.0 parts by weight Photoacid generator 1 (molecular weight 466, having three aryl groups per molecular weight)
4.0 parts by mass [Preparation of inks 2 to 5]
In the preparation of the ink 1, dimethylaminoethanol (R: hydroxyalkyl group having 2 carbon atoms) is added as a polymerization inhibitor in the amount shown in Table 1, and the amount of oxetane OXT221 added so that the total amount becomes 100 parts by mass. Inks 2 to 5 were prepared in the same manner except that was changed to the amounts shown in Table 1.

[Preparation of inks 6 to 9]
In the preparation of the ink 1, dimethyldecanolamine (R: hydroxyalkyl group having 10 carbon atoms) was added as a polymerization inhibitor in the amount shown in Table 1, and oxetane OXT221 was added so that the total amount was 100 parts by mass. Inks 6 to 9 were prepared in the same manner except that the amount was changed to the amount shown in Table 1.

[Preparation of inks 10 to 13]
In the preparation of the ink 1, dimethyloctadecanolamine (R: hydroxyalkyl group having 18 carbon atoms) was added as a polymerization inhibitor in the amount shown in Table 1, and the total amount of oxetane OXT221 was adjusted to 100 parts by mass. Inks 10 to 13 were prepared in the same manner except that the addition amount was changed to the amount shown in Table 1.

[Preparation of inks 14 to 17]
In the preparation of the ink 1, dimethylpropylamine (R: an alkyl group having 3 carbon atoms) was added as a polymerization inhibitor in the amount shown in Table 1, and the addition amount of oxetane OXT221 was adjusted so that the total amount was 100 parts by mass. Inks 14 to 17 were prepared in the same manner except that the amounts shown in Table 1 were changed.

[Preparation of inks 18 to 21]
In the preparation of the ink 1, dimethylhexadecylamine (R: alkyl group having 16 carbon atoms) is added as a polymerization inhibitor in the amount shown in Table 1, and the amount of oxetane OXT221 added so that the total amount becomes 100 parts by mass. Inks 18 to 21 were prepared in the same manner except that the amount was changed to the amount shown in Table 1.

[Preparation of inks 22 to 25]
In the preparation of the ink 1, dimethyloctacosylamine (R: alkyl group having 28 carbon atoms) is added as a polymerization inhibitor in the amount shown in Table 1, and the amount of oxetane OXT221 added so that the total amount becomes 100 parts by mass. Ink 22 to 25 were prepared in the same manner except that was changed to the amount shown in Table 1.

  The details of the compounds described in abbreviations in Table 1 are as follows.

PB822: Addis Bar PB822 (manufactured by Ajinomoto Fine Techno)
OXT221: a compound having an oxetane ring, oxetane OXT221 (manufactured by Toagosei)
OXT212: Compound having an oxetane ring, Oxetane OXT212 (manufactured by Toagosei)
OXT101: a compound having an oxetane ring, oxetane OXT221 (manufactured by Toagosei)
DMAE: dimethylaminoethanol (R: hydroxyalkyl group having 2 carbon atoms)
DMDA: dimethyldecanolamine (R: hydroxyalkyl group having 10 carbon atoms)
DMODA: Dimethyloctadecanolamine (R: Hydroxyalkyl group having 18 carbon atoms)
DMPA: dimethylpropylamine (R: alkyl group having 3 carbon atoms)
DMHDA: Dimethylhexadecylamine (R: alkyl group having 16 carbon atoms)
DMOCA: Dimethyloctacosylamine (R: C28 alkyl group)
<< Evaluation of each ink >>
〔inkjet printer〕
Evaluation was performed using the ink jet printer described in FIG. 1 and FIG.

  In the ink supply line having the configuration shown in FIG. 2B, the ink tank 101 is made of aluminum, the joints J1, J2 and the filter 107 are made of stainless steel, the filter box 109 is made of aluminum, and the ink supply path 102 is insulated. An ink-resistant Teflon (registered trademark) tube as a member was covered with a black polyolefin tube. The ink jet head 104 is composed of carbon graphite, the number of nozzles is 256, and a multi-size dot of 2 to 20 pl is 720 × 720 dpi (dpi represents the number of dots per 2.54 cm). It was set as the structure which can discharge by the resolution.

  The ink jet printer having such a configuration is a sealed system that does not contact outside air from the ink tank 101 to the nozzle portion of the ink jet head 104. Further, a water-repellent film (nozzle plate) made of a fluororesin was provided around the nozzle portion of the inkjet head.

[Ink preservation processing]
Each ink prepared above and stored in a stainless steel container was quickly loaded into the ink tank of the ink jet printer, and the ink was filled up to the nozzle portion of the ink head.

[Continuous ink discharge]
The ink jet printer 1 was filled with ink, and while the ink jet head was heated to 50 ° C., intermittent discharge was performed for 4 hours per day, and this was continued for one month.

[Evaluation of each characteristic]
After intermittent discharge for one month by the above method, the following evaluations were performed.

(Evaluation of straight discharge performance)
One month later, each ink was ejected from 256 nozzles of the ink jet head, its flying property was visually observed, the number of nozzles with exiting bending was counted, and ejection straightness was evaluated according to the following criteria.

A: All nozzles are normally emitted, and there are no nozzles where the emission curve occurs. O: Extremely weak emission curve is observed with 1 to 5 nozzles. Almost excellent emission property. Δ: 6- Although weak exiting bends are recognized with 10 nozzles, the landing deviation width is within a practically allowable range. X: Generation of strong exiting bends is recognized with 10 to 25 nozzles. Defects occur. XX: With 26 or more nozzles, the occurrence of extremely strong exit bends is not possible.
One month later, each ink is ejected from 256 nozzles of the inkjet head, the occurrence of nozzle missing due to clogging at each nozzle is visually observed, the number of nozzle missing nozzles is counted, and according to the following criteria Nozzle missing resistance was evaluated.

A: All nozzles are emitted normally, and there are no missing nozzles. O: Nozzle missing is observed with 1 to 2 nozzles, but there is no effect on the formed image. Δ: With 2 to 5 nozzles. The occurrence of nozzle missing is recognized, but the image to be formed is within the practically acceptable limit. X: Nozzle missing is recognized with 6 to 15 nozzles, and the formed image is defective. With 16 or more nozzles, nozzle missing occurs and the desired image cannot be obtained (wetability evaluation of water repellent film)
One month later, the ink adhesion state of the water repellent film (nozzle plate) provided on the periphery of the inkjet head was visually observed, and the wettability of the water repellent film was evaluated according to the following criteria.

◎: No ink deposits are observed on the surface of the water repellent film. ○: Slightly lump of ink deposits are observed on the surface of the water repellent film. △: Small lump of ink deposits on the surface of the water repellent film. Although it is recognized, it is within a practically acceptable range. X: Clear lump of ink adhering matter is recognized on the surface of the water repellent film, which causes factors such as oblique emission (curability evaluation).
After filling each ink in an ink jet printer and forming a solid image on a polyethylene terephthalate (PET) film while heating the ink jet head to 50 ° C., the high pressure mercury lamp VZero085 (manufactured by INTEGRATION TECHNOLOGY) is irradiated with ultraviolet rays. Then, the solid image was cured, and the hardness of each cured film was measured according to a method based on JIS K 5400.

  The rank of hardness was (soft) 6B to B, HB, F, and H to 9H (hard), and 6B was the softest, 9H was the hardest, and the harder the harder, the better.

  The results obtained as described above are shown in Table 2.

  As is clear from the results shown in Table 2, the compound represented by the general formula (I) having a hydroxyalkyl group having 5 to 15 carbon atoms or an alkyl group having 9 to 25 carbon atoms defined in the present invention is provided. The ink of the present invention used has excellent discharge straightness, nozzle missing resistance, wettability of the water-repellent film and excellent curability of the formed image even after intermittent emission over a long period of time for the comparative example. I understand that

It is a figure which shows the whole structure of the inkjet printer provided with the filter and intermediate | middle tank which can be applied to this invention. 1 is a schematic configuration diagram illustrating an example of an ink supply path configuration of an inkjet printer applicable to the present invention. 1 is a front view showing a configuration of a main part of an ink jet printer applicable to the present invention. It is a top view which shows an example of a structure of the principal part of a line head type inkjet printer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Ink tank 2,104 Inkjet head 3 Energy ray source 4,103 Carriage 6,110 Filter box 7,108 Intermediate tank 8,102 Ink supply path 105 Intermediate tank unit 106 Intermediate tank front chamber 107 Filter 109, 111 Adjacent to filter Part J1-J6 Joint L Active energy ray source N Nozzle 201 Inkjet printer 202 Head carriage 203 Inkjet head 231 Ink discharge port 204 Irradiation means 205 Platen part 206 Guide member 207 Bellows structure 208 Irradiation light source P Recording material

Claims (6)

A cationic polymerization curable ink-jet ink comprising at least a cationic polymerizable compound, a photopolymerization initiator, and a compound represented by the following general formula (I).

[Wherein, R represents a hydroxyalkyl group having 5 to 15 carbon atoms or an alkyl group having 9 to 25 carbon atoms. However, the hydroxyalkyl group or the alkyl group may have one or more unsaturated bonds. ] 2. The cationic polymerization according to claim 1, wherein R in the compound represented by the general formula (I) is a hydroxyalkyl group having 5 to 10 carbon atoms or an alkyl group having 9 to 18 carbon atoms. A curable inkjet ink. 3. The cationic polymerization curable inkjet ink according to claim 1, wherein the cationic polymerizable compound is at least one selected from an epoxy compound, an oxetane compound having an oxetane ring, and a vinyl ether compound. 4. The cation according to any one of claims 1 to 3, wherein the content of the compound represented by the general formula (I) is 0.01 to 1.0 mass% with respect to the total mass of the ink. Polymerization-curable inkjet ink. 4. The cation according to claim 1, wherein the content of the compound represented by the general formula (I) is 0.01 to 0.05 mass% with respect to the total mass of the ink. Polymerization-curable inkjet ink. The cationic polymerization curable inkjet according to any one of claims 1 to 5, wherein the photopolymerization initiator is a photoacid generator, and the photoacid generator contains a triarylsulfonium salt. ink.

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