JP2009280672A - Active light curing-type ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active light curing-type ink composition capable of recording with stability under various printing circumstances a high-precision image excellent in printed character quality free from color blending and hardened wrinkles even using an ink preserved for long period of time. <P>SOLUTION: The active light curing-type ink composition contains a polymerizable compound having glycidyl ether group, a photoinitiator, and an amine compound, and satisfies at least one of the following conditions, i.e. (a) chlorine content of the polymerizable compound having a glycidyl ether group is not more than 1,000 ppm, (b) electric charge of the nitrogen atom of the amine compound is at least -0.400, and (c) content of the amine compound existing separately in the active light curing-type ink composition is not more than 1,000 ppm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an actinic ray curable ink composition that can stably reproduce a high-definition image even in various printing environments using ink that has been stored for a long period of time for any recording material.

  In recent years, the inkjet recording method can be easily and inexpensively produced images, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, a recording device that emits and controls fine dots, ink that has improved color reproduction gamut, durability, and emission suitability, and ink absorbability, coloring material color development, surface gloss, etc. have been dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper. The image quality improvement of today's ink jet recording system is achieved only when all of the recording apparatus, ink, and special paper are available.

  However, in an inkjet system that requires dedicated paper, the recording medium is limited, and the cost of the recording medium increases. Therefore, many attempts have been made to record on a transfer medium different from dedicated paper by an ink jet method. Specifically, a phase change ink jet method using a wax ink solid at room temperature, a solvent ink jet method using an ink mainly composed of a fast-drying organic solvent, a UV ink jet method in which crosslinking is performed by ultraviolet (UV) light after recording, etc. It is.

  In particular, the UV inkjet method has been attracting attention as an ultraviolet curable inkjet ink in recent years because it has a relatively low odor compared to the solvent-based inkjet method and can be recorded on a recording medium having no quick-drying and no ink absorption.

  However, even if these inks are used, the dot diameter after landing greatly changes depending on the type of recording material and the working environment, and it is not possible to form high-definition images on various recording materials. Is possible.

  In the ultraviolet curable ink-jet ink, an ink using a cationic polymerizable compound is disclosed (for example, see Patent Documents 1 to 5).

Inks using this cationically polymerizable compound are not subject to oxygen inhibition, but inks that have been stored for a long time are particularly susceptible to the effects of moisture (humidity) at the molecular level, and adhere to various recording materials. There is a problem that a sufficiently strong image cannot be formed.
JP 2003-292606 A JP 2005-112937 A JP-A-2005-154738 JP 2005-194357 A JP 2005-320508 A

  The present invention has been made in view of the above problems, and the purpose thereof is excellent in character quality, no color mixing, no generation of cured wrinkles, even in various printing environments using ink that has been stored for a long time, An actinic ray curable ink composition capable of always stably recording a high-definition image is provided.

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

  1. In the actinic ray curable ink composition containing a polymerizable compound having a glycidyl ether group, a photoinitiator and an amine compound, (a) the chlorine content of the polymerizable compound having a glycidyl ether group is 1000 ppm or less, (b) The charge of the nitrogen atom of the amine compound is −0.400 or more, or (c) the content of the amine compound released in the actinic ray curable ink composition satisfies at least one condition of 1000 ppm or less. An actinic ray curable ink composition characterized by the above.

  2. 2. The actinic ray curable ink composition according to item 1, wherein the compound having a glycidyl ether group has a chlorine content of 500 ppm or less.

  3. 2. The actinic ray curable ink composition as described in 1 above, wherein the amine compound is a polymer pigment dispersant.

  4). 4. The actinic ray curable ink composition according to any one of items 1 to 3, wherein the actinic ray curable ink composition has a viscosity at 50 ° C. of 1 to 30 mPa · s.

  5). 5. The actinic ray curable ink composition as described in any one of 1 to 4 above, further comprising a compound having an oxetane ring as the polymerizable compound.

  6). 6. The actinic ray curable ink composition according to any one of 1 to 5, wherein the photoinitiator is an onium salt.

  7. The actinic ray curable ink composition according to any one of 1 to 6, wherein the onium salt is less than 2.5 parts by mass with respect to 100 parts by mass of the polymerizable compound.

  8). 8. The actinic ray curable ink composition as described in any one of 1 to 7 above, wherein the onium salt is a sulfonium salt.

  According to the present invention, it is possible to always stably record a high-definition image with excellent character quality, no color mixing, no generation of curing wrinkles, even when using ink that has been stored for a long time and under various printing environments. An actinic ray curable ink composition capable of achieving the above can be provided.

  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 present inventor has found that in the actinic ray curable ink composition containing a polymerizable compound having a glycidyl ether group, a photoinitiator, and an amine compound, (a) the glycidyl ether group (B) the amine compound has a nitrogen atom charge of −0.400 or more, or (c) the amine free in the actinic ray curable ink composition. An image formed using an actinic radiation curable ink composition that satisfies at least one condition with a compound content of 1000 ppm or less is dramatically stable and robust against various recording materials even when ink that has been stored is used. The present inventors have found that a cured image can be formed and a good image can be formed regardless of the ejection stability and the curing environment (temperature, humidity).

  Conventionally, actinic ray curable ink compositions containing polymerizable compounds having various glycidyl ether groups have been used. However, these ink compositions have problems that their curability tends to fluctuate depending on the type and environment (for example, temperature and humidity) of the photopolymerizable composition, and there is a problem that ejection becomes unstable. It was impossible to form a high-definition and strong image by ink jet recording using.

  In the actinic ray curable ink composition containing a compound having a glycidyl ether group according to the present invention, the compound having a glycidyl ether group has a specific chlorine content, the nitrogen atom of the amine compound has a specific charge and content There is no known actinic ray curable ink composition having:

(Polymerizable compound)
In the present invention, a polymerizable compound having a glycidyl ether group is used as the polymerizable compound.

  It is preferable to contain a compound having a glycidyl ether group having a chlorine content of 1000 ppm or less, and a compound having a glycidyl ether group having a chlorine content of 500 ppm or less.

  Hereinafter, the present invention will be described in detail.

  The compound having a glycidyl ether group according to the present invention is a compound having one or more glycidyl groups, and can be produced, for example, by a reaction between a compound having a hydroxyl group and epichlorohydrin.

  Examples of the compound having a hydroxyl group include butylphenol, 1,6-hexanediol, neopentyl glycol, and the like, and monoglycidyl ether or polyglycidyl ether is obtained by reaction of these with epichlorohydrin.

  The compound having a glycidyl group according to the present invention may be a monofunctional, bifunctional, trifunctional or higher compound, or a combination thereof.

  Exemplary compounds of the compound having a glycidyl group according to the present invention are described below.

  Next, a compound having a glycidyl ether group having a chlorine content of 1000 ppm or less, further 500 ppm or less according to the present invention can be produced, for example, by the method described below.

  The chlorine content can be measured by, for example, oxidative decomposition / coulometric titration.

  A compound represented by the following general formula (1) is added to an alkaline aqueous solution such as sodium hydroxide as a base, heated at 80 to 90 ° C. for about 1 hour, then cooled at 40 to 50 ° C., and then the catalyst tetra. Butyl ammonium bromide is added and allyl chloride is added dropwise while maintaining the reaction temperature at 40-50 ° C. After completion of dropping, the reaction is carried out at 40-50 ° C. for about 5 hours.

  In the formula, R represents a lower alkyl group.

  After completion of the reaction, the reaction solution is cooled to around room temperature and separated by adding an organic solvent such as toluene, and the obtained organic layer is concentrated and further purified by a silica gel short column. ) Can be obtained.

  Examples of the compound represented by the general formula (1) include trihydroxyalkanes such as hydroxymethylpropanediol, trimethylolethane, trimethylolpropane, and pentaerythritol.

  As the base, sodium hydroxide, calcium hydroxide, potassium hydroxide and the like are preferable. The addition amount of the base is preferably 20 to 25 equivalents relative to the starting trihydroxyalkane.

  Moreover, the addition amount of the tetrabutylammonium bromide which is a catalyst has preferable 0.4-0.6 equivalent with respect to a starting material. Furthermore, the addition amount of allyl chloride is preferably 4 to 5 equivalents with respect to the compound represented by the general formula (1).

  Next, after dissolving the allyl ether compound represented by the general formula (2) in an organic solvent such as methylene chloride, the reaction solution is cooled to around 0 ° C., an oxidizing agent such as m-chloroperbenzoic acid is added, and the room temperature is increased. Then, the reaction is performed for 8 to 10 hours.

  After completion of the reaction, neutralization of the oxidizing agent with an aqueous alkaline solution, followed by separation treatment by adding an organic solvent such as toluene, and then concentrating the organic layer, the glycidyl ether group represented by the following general formula (3) The compound which has can be obtained.

  The amount of m-chloroperbenzoic acid added as the oxidizing agent is preferably 4 to 5 equivalents relative to the allyl ether compound represented by the general formula (2). As the solvent, halogen compounds such as methylene chloride and hydrocarbons such as hexane and toluene are preferable, and methylene chloride is particularly preferable. As the addition amount of the allyl ether compound represented by the general formula (2) dissolved in the solvent, a range of 0.2 to 0.6 mol / L is preferable, and a range of 0.3 to 0.5 mol / L is particularly preferable. Is preferred.

  The compound having a glycidyl ether group thus obtained has a small amount of residual chlorine due to side reactions according to the conventional method, and the chlorine content is 1000 ppm or less, more preferably 50 ppm or less.

  In this invention, the epoxidized fatty acid ester and epoxidized fatty acid glyceride which have a glycidyl group in the inside instead of the terminal can also be contained.

  The epoxidized fatty acid ester and the epoxidized fatty acid glyceride are not particularly limited as long as an epoxy group is introduced into the fatty acid ester or fatty acid glyceride.

  The epoxidized fatty acid ester is produced by epoxidizing an oleic acid ester, and examples thereof include methyl epoxy stearate, butyl epoxy stearate, octyl epoxy stearate and the like. Similarly, the epoxidized fatty acid glyceride is produced by epoxidizing soybean oil, linseed oil, castor oil and the like, and epoxidized soybean oil, epoxidized linseed oil, epoxidized castor oil and the like are used. Examples of commercially available epoxidized vegetable oils include Sansizer E-4030 manufactured by Shin Nippon Chemical Co., Ltd., Vf7170, Vf7190, Vf5075, Vf4050, Vf7010, Vf9010, Vf9040, and Vf7040 manufactured by ATOFINA Chemical.

  Moreover, in this invention, it is preferable to contain an at least 1 sort (s) of alicyclic epoxide for the further improvement of sclerosis | hardenability and discharge stability.

  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.

  In the actinic ray curable ink composition of the present invention, the polymerizable compound preferably contains a compound having at least one oxetane ring.

  The oxetane compound that can be used in the present invention is a compound having an oxetane ring, and any known oxetane compound as disclosed in JP-A Nos. 2001-220526 and 2001-310937 can be used. .

  Furthermore, the actinic ray curable ink composition of the present invention preferably contains a vinyl ether compound, and a known vinyl ether compound can be used.

  Examples of the vinyl ether compound 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, cyclohexanedimethanol divinyl ether, and trimethylol. Di- or trivinyl ether compounds such as propane 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 monovinyl ether, n-pro Vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  As a preferable constitution of the actinic ray curable ink composition of the present invention, epoxide having a glycidyl ether group is 5-70% by mass, oxetane compound is 5-60% by mass, alicyclic epoxide is 5-40% by mass, vinyl ether. The structure containing 0-40 mass% of compounds is mentioned.

(Photoinitiator)
The photoinitiator according to the present invention is a compound capable of initiating curing of the actinic ray curable ink composition by irradiation with actinic rays, and an onium salt is preferably used.

  Exemplary compounds of onium salts include, for example, THE CHEMICAL SOCIETY OF JAPAN Voi. 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), etc., can be easily synthesized by a known method.

  The onium salt is preferably a sulfonium salt from the viewpoint of improving ejection stability.

  As a preferable constitution of the actinic ray curable ink composition of the present invention, the onium salt is less than 2.5 parts by mass relative to 100 parts by mass of the polymerizable compound. If it is 2.5 parts by mass or more, the ejection stability is inferior, and a high-definition image may not always be stably recorded.

  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 as a substituent, a carbazole derivative, a thioxanthone derivative, or the like is used.

  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 the sensitizer include carbazole derivatives such as carbazole, N-ethylcarbazole, N-vinylcarbazole, N-phenylcarbazole, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 1-stearyloxynaphthalene, 2-methoxy. Naphthalene, 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-vinyl Xylethyl) naphthyl ether, 4-methoxy-1-naphthol, ESN-175 (epoxy resin manufactured by Nippon Steel Chemical Co., Ltd.) 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-diethoxy Anthracene, 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-tbutyl-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-methyl Benzyloxyanthracene, 9- (α-methylbenzyloxy) -10-methylanthracene, 9,10-di (2-hydroxyethoxy) anthracene, 2-ethyl-9,10-di (2-carboxyethoxy) anthracene, etc. Anthracene derivatives of 1,4-dimethoxychrysene, 1,4-diethoxychrysene, 1,4-dipropoxychrysene, 1,4-dibenzyloxychrysene, 1,4-di-α-methylbenzyloxychrysene, etc. Examples include chrysene derivatives, phenanthrene derivatives such as 9-hydroxyphenanthrene, 9,10-dimethoxyphenanthrene, and 9,10-diethoxyphenanthrene. 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 thioxanthone derivative include thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone 2-chlorothioxanthone, and the like.

(Amine compound)
The charge of the nitrogen atom of the amine compound can be calculated using, for example, WinMOPAC (Fujitsu) software.

  On the other hand, the content of the amine compound released in the actinic ray curable ink composition is determined by subjecting the ink of the present invention to a centrifugal treatment (centrifugal acceleration 645,000 g × 30 min), and then collecting a supernatant, for example, gas It can be measured by chromatography.

  Examples of the amine compound include octylamine, dodecylamine, octadecylamine, naphthylamine, xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, dimethyloctadecylamine, dimethylhexadecylamine, diheptylamine, dimethyl Examples include decylamine, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6-hexamethylenediamine, hexamethylenetetramine, 2-methylaminoethanol, triisopropanolamine, and triethanolamine. Compounds having a nitrogen atom charge of −0.400 or more are triisopropanolamine, diheptylamine, octylamine Dimethyl decyl amine, dimethyl hexadecyl amine, trioctylamine, dimethyl octadecylamine, dodecylamine, octadecyl amine.

  The actinic ray curable ink composition of the present invention preferably contains various known dyes and / or pigments together with the above-mentioned actinic ray curable composition, and particularly preferably contains a pigment.

  The pigments that can be preferably used in the present invention are listed below, but the present invention is not limited thereto.

C. I Pigment Yellow-1, 3, 12, 13, 14, 17, 81, 83, 87, 95, 109, 42, C.I. I Pigment Orange-16, 36, 38, C.I. I Pigment Red-5, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 144, 146, 185, 101, C.I. I Pigment Violet-19, 23, C.I. I Pigment Blue-15: 1, 15: 3, 15: 4, 18, 60, 27, 29, C.I. I Pigment Green-7, 36, C.I. I Pigment White-6, 18, 21, C.I. I Pigment Black-7
In the present invention, it is preferable to use white ink in order to improve the color concealment property on a transparent substrate such as a plastic film. In particular, in soft packaging printing and label printing, it is preferable to use white ink. There is a limit.

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

  Further, a dispersing agent can be added when dispersing the pigment. 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 dispersion medium is used using a solvent or a polymerizable compound. However, the actinic ray curable ink of the present invention is preferably solvent-free because it reacts and cures immediately after ink landing.

  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, when a color material is contained, the color material concentration is preferably 1% by mass to 10% by mass of the entire ink.

  Various additives other than those described above can be used in the ink of the present invention. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  The ink of the present invention preferably has a viscosity of 1 to 30 mPa · s at 50 ° C. in order to stabilize ejection and obtain good curability regardless of the curing environment (temperature / humidity).

  As the recording material that can be used in the image forming method of the present invention, various types of non-absorbable plastics and films used for so-called soft packaging can be used in addition to ordinary uncoated paper and coated paper. Examples of the plastic film 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. Among these recording materials, the structure of the present invention is effective particularly when an image is formed on a PET film, an OPS film, an OPP film, an ONy film, or a PVC film that can be shrunk by heat. These substrates are not only susceptible to curling and deformation of the film due to ink curing shrinkage and heat generation during the curing reaction, but also the ink film is difficult to follow the substrate shrinkage.

  The surface energy of these various plastic films varies greatly depending on the characteristics of the material, and it has been a problem that the dot diameter after ink landing changes depending on the recording material. With the configuration of the present invention, a good high-definition image can be formed on a wide range of recording materials having a surface energy of 35 to 60 mN / m, including OPP films having a low surface energy, OPS films, and PET having a relatively large surface energy. .

  In the present invention, it is more advantageous to use a long (web) recording material in terms of the cost of the recording material such as packaging cost and production cost, the production efficiency of the print, and the ability to cope with printing of various sizes. is there.

  Next, the image forming method of the present invention will be described.

  In the image forming method of the present invention, a method is preferred in which the ink is ejected and drawn on a recording material by an ink jet recording method, and then the ink is cured by irradiation with an actinic ray such as ultraviolet rays.

(Light irradiation conditions after ink landing)
In the image forming method of the present invention, the actinic ray is preferably irradiated for 0.001 second to 1.0 second after the ink landing, more preferably 0.001 second to 0. .5 seconds. 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.

  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.

  Conventionally, in the UV ink jet system, a light source with high illuminance in which the total power consumption of the light source exceeds 1 kW · hr is usually used in order to suppress dot spreading and bleeding after ink landing. However, when these light sources are used, particularly in printing on a shrink label or the like, the shrinkage of the recording material is so large that it cannot be used practically.

  In the present invention, a high-definition image can be formed even when a light source having a power consumption per hour of 1 kW or less is used, and the shrinkage of the recording material is within a practically acceptable level. Examples of light sources that consume less than 1 kW per hour include, but are not limited to, fluorescent tubes, cold cathode tubes, LEDs, and the like.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording material and cured by irradiation with actinic rays is preferably 2 to 20 μm. In the actinic ray curable ink jet recording in the screen printing field, the total ink film thickness currently exceeds 25 μm, but in the flexible packaging printing field where the recording material is often a thin plastic material, the recording material described above is used. In addition to the problem of curling and wrinkles, there is a problem in that the entire printed material is changed in its strain and texture.

  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 image recording method of the present invention, it is preferable to irradiate actinic rays with the actinic ray curable ink heated.

  As one of the methods, it is preferable from the viewpoint of ejection stability that the ink jet recording head and the ink are heated to 35 to 100 ° C. and the ink is ejected onto the recording material in the heated state.

  Further, as a method of the present invention, the ink jet recording head and the ink are respectively heated to 35 to 80 ° C., and after the ink is ejected from the ink jet recording head and the ink has landed on the recording material, the temperature is 35 to 80 ° C. It is preferable from the viewpoint of ejection stability to irradiate with actinic rays in a state maintained in the above.

  In the present invention, the method for heating and keeping the ink jet recording head and ink at a predetermined temperature is not particularly limited. For example, ink supply such as an ink tank constituting a head carriage, a supply pipe, a front chamber ink tank immediately before the head, etc. There is a method in which a system, a pipe with a filter, a piezo head, and the like are insulated and heated to a predetermined temperature by a panel heater, a ribbon heater, warm water or the like.

  In addition, as a method of maintaining a predetermined temperature after the ink has landed on the recording material, for example, a method of incorporating a panel heater in the recording material holding unit, or surrounding the recording material conveying unit and heating with warm air or the like A method can be mentioned.

  Actinic radiation curable ink has a large viscosity fluctuation range due to temperature fluctuations, and the viscosity fluctuations directly affect the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  Moreover, in this invention, it is preferable that the amount of droplets discharged from each nozzle is 2 to 20 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe. According to the present invention, even when the ink is ejected with a small droplet amount such as 2 to 20 pl, the ejection stability is improved and a high-definition image can be stably formed.

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

  The recording apparatus of the present invention will be described below with reference to the drawings as appropriate. Note that 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. 1 is a front view showing the configuration of the main part of the recording apparatus of the present invention. 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 material P. The platen unit 5 has a function of absorbing 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 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 material P, and stores a plurality of recording heads 3 to be described later according to 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 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). Although the drawing is carried out assuming that the recording heads 3 of light black (Lk) and white (W) are accommodated, the number of colors of the recording heads 3 accommodated in the head carriage 2 is determined as appropriate. Is.

  The recording head 3 has a discharge port by operating a discharge means (not shown) provided with a plurality of actinic ray curable inks (for example, UV curable ink) supplied by an ink supply means (not shown). To the recording material P. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer crosslinks when the initiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by a polymerization reaction.

  During the scanning in which the recording head 3 moves from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. 1 by driving the head scanning means, a certain area (landing possible area) in the recording material 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 after UV ink is ejected toward one landable area, the recording material P is appropriately moved from the front to the back in FIG. 1, the recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG.

  By repeating the above operation and ejecting the UV ink from the recording head 3 in conjunction with the head scanning means and the conveying means, an image composed of an aggregate of UV ink droplets is formed on the recording material P.

  The irradiation unit 4 includes 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 material 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 material P. It is effective to increase the distance h2 between the portion 31 and the recording material 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 to provide a bellows structure 7 between the recording head 3 and the irradiation means 4.

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

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

  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 material P. ing.

  On the other hand, on the downstream side of the head carriage 2, that is, the rear part of the head carriage 2 in the direction in which the recording material P is conveyed, the entire width of the recording material P is also covered so as to cover the entire area of the 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 irradiating means 4 are fixed, and only the recording material P is conveyed, and ink ejection and curing are performed to form an image.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

<Preparation of ink composition set>
Ink composition sets 1 to 7 and 1C and 2C (comparative examples) having the compositions shown in Tables 1 to 7 were prepared according to the following method.

  The polymer pigment dispersant and each polymerizable compound described in Tables 1 to 7 were put in a stainless beaker, stirred and mixed for 1 hour while being heated on a hot plate at 60 ° C., and dissolved. Next, after adding the coloring materials described in Tables 1 to 7 to this solution, it was sealed in a plastic bottle together with zirconia beads having a diameter of 1 mm, and dispersed for several hours using a paint shaker. Next, zirconia beads were removed, and various additives such as each photoinitiator, sensitizer, amine compound other than polymer pigment dispersant, and surfactant were added in combinations shown in Tables 1 to 7, and this was added to the printer. Ink composition sets 1 to 7 were prepared by filtering through a 0.8 μm membrane filter to prevent clogging. A part of the ink composition was stored for 4 days in a constant temperature bath at 70 ° C. assuming a storage time of 1 year.

  Details of each ink, each compound, and display described in Tables 1 to 7 are as follows.

K: dark black ink C: dark cyan ink M: dark magenta ink Y: dark yellow ink W: white ink Lk: light black ink Lc: light cyan ink Lm: light magenta ink Ly: light yellow ink Color material 1: C.I. I. pigment Black 7
Color material 2: C.I. I. pigment Blue 15: 3
Color material 3: C.I. I. pigment Red 57: 1
Color material 4: C.I. I. pigment Yellow 13
Colorant 5: Titanium oxide (anatase type, average particle size 0.20 μm)
[Polymerizable compound]
<Compound having glycidyl ether group>
EP-1: Neopentyl glycol diglycidyl ether (viscosity 20 mPa · s / 25 ° C.)
EP-4: 1- (2- {2- [2- (1-hydroxy-ethoxy) ethoxy] ethoxy} ethoxy) ethanol diglycidyl ether (viscosity 40 mPa · s / 25 ° C.)
EP-7: p-tertiarybutylphenyl glycidyl ether (viscosity 20 mPa · s / 25 ° C.)
EP-9: 2-ethylhexyl glycidyl ether (viscosity 4 mPa · s / 25 ° C.)
EP-23: Trimethylolpropane triglycidyl ether (viscosity 130 mPa · s / 25 ° C.)
EP-24: 2-biphenylyl glycidyl ether (viscosity 54 mPa · s / 40 ° C.)
<Alicyclic epoxide>
C2021P: Celoxide 2021P (manufactured by Daicel Chemical Industries)

E-4030: Sunsizer (manufactured by Shin Nippon Rika Co., Ltd.)
<Vinyl ether>
DVE-3: Triethylene glycol divinyl ether (manufactured by BASF)
<Oxetane>
OXT-221: Bifunctional oxetane (manufactured by Toagosei Co., Ltd.)
OXT-212: monofunctional oxetane (manufactured by Toagosei Co., Ltd.)
OXT-101: Monofunctional oxetane alcohol (manufactured by Toagosei Co., Ltd.)
<Photoinitiator>
SP-1: CPI-100P (propylene carbonate 50% solution of triallylsulfonium salt, manufactured by San Apro)
SP-2: UVI6992 (50% propylene carbonate solution of triallylsulfonium salt, manufactured by Dow)

<Amine compound>
N-1: 2-methylaminoethanol (N charge: -0.459)
N-2: Octadecylamine (N charge: -0.350)
N-3: Dodecylamine (N charge: -0.349)
<Surfactant>
KF351: Side chain polyether-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd.)
X-22-4272: Both-end polyether-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd.)
<Polymer pigment dispersant>
PB822: Basic functional group-containing copolymer (Ajinomoto Fine Techno Co., Ltd.)
Solsperse 32000: Basic functional group-containing copolymer (Avisia)
<Sensitizer>
DEA: Diethoxyanthracene << Inkjet image forming method >>
Each ink composition set 1, 4, 5 (invention) and 1C (comparative example) prepared above was loaded into an ink jet recording apparatus having the configuration shown in FIG. The following image recording was continuously performed on each long recording material having a width of 600 mm and a length of 500 m shown in Table 9. The ink supply system was composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, a pipe with a filter, and a piezo head, and was heated from the front chamber tank to the head portion and heated at 50 ° C. The piezo head was driven so that 2 to 15 pl multi-sized dots could be ejected at a resolution of 720 × 720 dpi (), and each ink was ejected continuously. After each ink landed, the ink was cured by irradiating with ultraviolet rays from the irradiation light sources shown in Tables 8 and 9 instantly (less than 0.5 seconds after landing) by the lamp units on both sides of the carriage. When the total ink film thickness was measured after image recording, it was in the range of 2.3 to 13 μm. In the present invention, dpi represents the number of dots per 2.54 cm.

  Next, each image was formed in the same manner using the ink composition sets 2, 3, 6, 7 (present invention) and 2C (comparative example) using the line head type ink jet recording apparatus shown in FIG. . Further, a heat plate was provided in the platen portion, and the heat plate temperature was adjusted so that the surface of each recording material was 40 ° C.

  Printing was performed by the above two methods under three conditions: an environment of 10 ° C. and 20% RH (relative humidity), an environment of 23 ° C. and 50% RH, and an environment of 27 ° C. and 80% RH.

  1 is a low-pressure mercury lamp (manufactured by Heraeus), and FIG. 2 is a high-pressure mercury lamp VZero085 (manufactured by INTEGRATION).

  The details of the abbreviations of the recording materials are as follows.

OPP (Yupo FS): oriented polypropylene (Yupo FS)
PET: Polyethylene terephthalate
PVC: polyvinyl chioride
Art paper: Mitsubishi double-sided art 《Evaluation of inkjet recording image》
Each image recorded by the above image forming method was subjected to the following evaluations.

[Evaluation of character quality]
Using each color ink of Y, M, C, and K, a 6-point MS Mincho character was printed at a target density, and the character roughness was enlarged and evaluated with a loupe, and character quality was evaluated according to the following criteria.

◎: No roughness ○: Slightly gritty △: Slightly visible, but can be recognized as characters, but can be used as barely as possible. ×: Level of rustiness, characters are faint and unusable [Evaluation of color mixing (bleeding, wrinkles) ]
At 720 dpi, printing is performed so that each dot of Y, M, C, and K is adjacent to each other, each adjacent dot is enlarged with a magnifying glass, the degree of bleeding is visually observed, and color mixing is evaluated according to the following criteria. .

◎: Adjacent dot shape maintains a perfect circle and no bleeding occurs. ○: Adjacent dot shape maintains an almost perfect circle and almost no bleeding occurs. Δ: Adjacent dot is slightly blurred and dot shape is slightly. Although it is broken, it is a level that can be used at the end ×: Adjacent dots are blotted and mixed, and wrinkles are observed in the overlapping part, and it is a quality that can not withstand use [Adhesion]
For the printed image produced above, a sample that does not scratch the printed surface at all, and in accordance with JIS K 5400, 11 cuts are made on the printed surface at 1 mm intervals vertically and horizontally, and a 1 mm square grid. 100 samples were prepared, cellotape (registered trademark) was pasted on each printing surface, quickly peeled off at an angle of 90 degrees, and the remaining printed image or grid pattern remaining in accordance with the following criteria evaluated. A sample cured at 25 ° C. and 45% RH was used.

◎: No peeling of the printed image is observed even in the cross cut test. ○: Some ink peeling is recognized in the cross cut test, but almost no peeling is observed even if the ink surface is scratched. △: Cross cut test In FIG. 2, slight ink peeling is recognized, but almost no peeling is observed unless the ink surface is scratched. ×: Easy peeling with cello tape (registered trademark) is recognized under both conditions.

(Discharge stability)
Each of the untreated inkjet ink composition and the inkjet ink composition that has been subjected to the forced deterioration treatment stored in a polypropylene bottle for 7 days at 70 ° C. is continuously applied for 30 minutes from the inkjet nozzle according to the inkjet image forming method. The ejection state was visually observed and the ejection stability was evaluated according to the following criteria.

◎: No nozzle missing even after 30 minutes of continuous emission ○: No nozzle missing occurs after 30 minutes of continuous emission, but a slight satellite is generated but there is no practical problem △: No nozzle missing with 30 minutes of continuous emission Although not generated, satellites are generated. X: Nozzle is missing at several nozzles in continuous emission for 30 minutes Table 7 shows the evaluation results obtained as described above.

  As is apparent from Tables 8 and 9, by using the actinic ray curable composition having the constitution according to the present invention, the characters of the comparative example can be recorded on all recording materials even in various printing environments. It can be seen that a high-definition image with excellent quality and no color mixing (bleeding, wrinkles) can be recorded.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Head carriage 3 Inkjet recording head 31 Inkjet nozzle 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording material

Claims (8)

In the actinic ray curable ink composition containing a polymerizable compound having a glycidyl ether group, a photoinitiator and an amine compound, (a) the chlorine content of the polymerizable compound having a glycidyl ether group is 1000 ppm or less, (b) The charge of the nitrogen atom of the amine compound is −0.400 or more, or (c) the content of the amine compound released in the actinic ray curable ink composition satisfies at least one condition of 1000 ppm or less. An actinic ray curable ink composition characterized by the above. The actinic ray curable ink composition according to claim 1, wherein the chlorine content of the compound having a glycidyl ether group is 500 ppm or less. The actinic ray curable ink composition according to claim 1, wherein the amine compound is a polymer pigment dispersant. The actinic ray curable ink composition according to any one of claims 1 to 3, wherein the actinic ray curable ink composition has a viscosity of 1 to 30 mPa · s at 50 ° C. The actinic ray curable ink composition according to claim 1, further comprising a compound having an oxetane ring as the polymerizable compound. The actinic ray curable ink composition according to claim 1, wherein the photoinitiator is an onium salt. The actinic ray curable ink composition according to claim 1, wherein the onium salt is less than 2.5 parts by mass with respect to 100 parts by mass of the polymerizable compound. The actinic ray curable ink composition according to claim 1, wherein the onium salt is a sulfonium salt.

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