JP2010095583A - Active light-curing type ink composition, image formation method using the same and inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active light-curing type ink composition which gives an excellent letter quality and does not cause the mixing of colors and cured wrinkles even under various printing environments, and can always stably record high precision images, to provide an image formation method using the same, and to provide an inkjet recorder. <P>SOLUTION: There are provided the active light-curing type ink composition comprising a polymerizable compound and a photoinitiator, characterized in that the active light-curing type ink composition contains a compound having at least two glycidyl groups at terminals in an amount of 60 to 95 mass% as the polymerizable compound, and the photoinitiator is contained in an amount of <2.5 pts.mass per 100 pts.mass of the polymerizable compound; the image formation method using the same; and the inkjet recorder. <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 on various recording materials even under various printing environments, an image forming method using the same, and an ink jet recording apparatus.

  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 special paper, the recording material is limited, and the cost of the recording material 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.

  The UV inkjet method has been attracting attention in recent years because it has a relatively low odor compared to the solvent-based inkjet method and can be recorded on a recording material having no quick-drying property and no ink absorption. It is disclosed.

  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.

Among them, the ultraviolet curable cationic polymerizable inkjet inks described in Patent Documents 1 to 3 have a feature that they are not easily affected by moisture (humidity), but their characteristics are insufficient and adhesion to various recording materials. There is a problem that a sufficiently strong image cannot be formed.
WO2006-068010 (Claims, Examples) JP 2005-154738 A (Claims, Examples) JP 2002-188025 A (Claims, Examples)

  The present invention has been made in view of the above problems, and its purpose is to have excellent character quality, no color mixing, no generation of curing defects, and stable high-definition images even under various printing environments. An actinic ray curable ink composition capable of recording, an image forming method using the same, and an ink jet recording apparatus.

  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 and a photoinitiator, the actinic ray curable ink composition comprises at least 60% by mass of a compound having a glycidyl group at at least two terminals as the polymerizable compound. 95% by mass or less, and the photoinitiator is less than 2.5 parts by mass with respect to 100 parts by mass of the polymerizable compound.

  2. 2. The actinic ray curable ink composition as described in 1 above, wherein the compound having a glycidyl group is a compound having a bifunctional glycidyl group.

  3. 3. The actinic ray curable ink composition as described in 1 or 2 above, wherein the photoinitiator is a sulfonium salt.

  4). 4. The actinic ray curable ink composition as described in any one of 1 to 3 above, wherein the actinic ray curable ink composition contains at least one selected from a polyol and a polyphenol compound.

  5. 5. An image forming method in which the actinic ray curable ink composition according to any one of 1 to 4 is jetted onto a recording material from an inkjet recording head, and printing is performed on the recording material, the recording material comprising: Is heated to at least 45 ° C.

  6). 6. An ink jet recording apparatus for use in the image forming method according to 5 above, wherein the actinic ray curable ink composition and the ink jet recording head are heated to 35 to 100 ° C., and then the actinic ray curable ink from the ink jet recording head. An ink jet recording apparatus comprising a mechanism for discharging a composition and a mechanism for heating a recording material to at least 45 ° C.

  According to the present invention, an actinic ray curable ink composition that is excellent in character quality, has no color mixing, does not generate cured wrinkles, and can always stably record a high-definition image even under various printing environments. An image forming method and an ink jet recording apparatus using the same 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 inventors have found that the polymerizable compound and the actinic ray curable ink composition containing the photoinitiator (hereinafter also simply referred to as the ink of the present invention) As described above, an image formed using an actinic ray curable ink composition containing 60% by mass or more and 95% by mass or less of a compound having at least two terminal glycidyl groups is dramatically stable and robust against various recording materials. 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 compounds having various epoxy 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.

  An actinic ray curable ink composition using a compound having a glycidyl group is also known, but the actinic ray curable ink composition having a content and composition of a compound having a glycidyl group and an initiator according to the present invention is also known. Things are not known.

(Polymerizable compound)
In the present invention, as a polymerizable compound, a compound having at least two terminal glycidyl groups is contained in the ink composition in an amount of 60% by mass or more and 95% by mass or less. It is possible to obtain an ink jet image forming method which is excellent in ejection stability and can be formed on various recording materials with high reproducibility and high image quality without depending on the curing environment.

  When the compound having a glycidyl group is less than 60% by mass, the curability tends to fluctuate depending on the environment (for example, temperature and humidity), and discharge becomes unstable.

  Further, by containing a bifunctional glycidyl group as the polymerizable compound, the ejection stability, which is an important characteristic in ink jet recording, can be improved.

  Moreover, in this invention, it is preferable to contain the compound which has a bifunctional glycidyl group as a polymeric compound.

  Hereinafter, the present invention will be described in detail.

  First, the compound having at least two terminal glycidyl groups according to the present invention will be described.

  The compound having at least two terminal glycidyl groups according to the present invention can be produced, for example, by reacting a compound having at least two hydroxyl groups with epichlorohydrin.

  Examples of the compound having at least two hydroxyl groups include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,6-hexanediol, neopentyl glycol, glycerol, pentaerythritol and the like, and reaction of these with epichlorohydrin Gives monoglycidyl ether or polyglycidyl ether.

  Illustrative compounds of the compound having at least two terminal glycidyl groups according to the present invention are described below.

  In this invention, polymeric compounds other than the compound which has at least 2 terminal glycidyl group can also be contained.

For example, a compound having a monofunctional glycidyl group such as 2-ethylhexyl glycidyl ether, decanol glycidyl ether, phenyl glycidyl ether, decyl oxirane, epoxidized fatty acid ester such as methyl epoxy stearate, butyl epoxy stearate, octyl epoxy stearate, Epoxidized fatty acid glycerides such as epoxidized soybean oil, epoxidized linseed oil, and epoxidized castor oil, alicyclic epoxides such as Celoxide 3000 and Celoxide 2021P (manufactured by Daicel Chemical Industries), JP-A No. 2001-220526, 2001- No. 310937, etc., oxetane compounds, 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, trimethylolpropane trivinyl ether, and the like.
(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.

  Examples of the onium salt include, for example, THE CHEMICAL SOCIETY OF JAPAN Vol. 71 no. 11, 1998, as well as the photoacid generator described in “Organic Materials for Imaging”, edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), etc., can be easily synthesized by a known method.

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

  When the photoinitiator of the present invention is less than 2.5 parts by mass with respect to 100 parts by mass of the polymerizable compound, stable and strong cured images can be formed on various recording materials, and the ejection stability and curing can be achieved. The amount is preferably less than 2.0 parts by mass because a good image can be formed regardless of the environment (temperature, humidity).

  When the photoinitiator is 2.5 parts by mass or more with respect to 100 parts by mass of the polymerizable compound, even if the compound having the glycidyl group is contained in the actinic ray curable ink composition by 60% by mass or more, the environment The curability tends to fluctuate depending on (for example, temperature and humidity), and the problem that ejection becomes unstable occurs.

  That is, the effect of the present invention is that the compound having a glycidyl group is contained in an actinic ray curable ink composition in an amount of 60% by mass or more, and the photoinitiator is 2.5% by mass with respect to 100 parts by mass of the polymerizable compound. Less than part, preferably less than 2.0 parts by weight, is expressed for the first time.

  In the present invention, a sensitizer is preferably used in combination for further improving the curability.

  The sensitizer is at least one selected from a polycyclic aromatic compound having at least one hydroxyl group, optionally substituted aralkyloxy group or alkoxy group as a substituent, a carbazole derivative and a thioxanthone derivative, and 330 nm. A sensitizer having an ultraviolet spectrum absorption at a longer wavelength is preferably 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.

  In the present invention, it is preferable to use a basic compound in combination for further improving the ejection stability.

  By containing the basic compound, not only the ejection stability becomes good, but also the generation of wrinkles due to curing shrinkage is suppressed even under low humidity. As the basic compound, any known compounds can be used, and typical examples include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines.

  Examples of basic alkali metal compounds include alkali metal hydroxides (eg, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc.), alkali metal carbonates (eg, lithium carbonate, sodium carbonate, potassium carbonate, etc.), Examples include alkali metal alcoholates (for example, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, and the like).

  As the basic alkaline earth metal compound, similarly, an alkaline earth metal hydroxide (eg, magnesium hydroxide, calcium hydroxide, etc.), an alkali metal carbonate (eg, magnesium carbonate, calcium carbonate, etc.), Examples include alkali metal alcoholates (eg, magnesium methoxide).

  Examples of the basic organic compound include amines and nitrogen-containing heterocyclic compounds such as quinoline and quinolidine. Among these, amines are preferable from the viewpoint of compatibility with the photopolymerization monomer, and examples thereof include octylamine and dodecylamine. , Octadecylamine, naphthylamine, xylenediamine, dibenzylamine, diphenylamine, dibutylamine, dioctylamine, dimethylaniline, quinuclidine, tributylamine, trioctylamine, tetramethylethylenediamine, tetramethyl-1,6-hexamethylenediamine, hexamethylene Examples include tetramine, 2-methylaminoethanol, triisopropanolamine, and triethanolamine.

  The concentration when the basic compound is present is preferably in the range of 10 to 1000 ppm by mass, particularly 20 to 500 ppm by mass relative to the total amount of the polymerizable compound. In addition, a basic compound may be used individually or may be used in combination of multiple.

(Polyol)
As the polyle according to the present invention, known compounds can be used as long as they have at least two alcoholic hydroxyl groups.

  Examples of the polyol compound include glycerin, 1,2-ethanediol, 1,2-propylene glycol, dipropylene glycol, trimethylolpropane, 1,2-ethylene glycol, 1,3-propylene glycol, 1,4-butylene. Examples include glycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyoxyalkylene polyether polyol, poly (oxyalkylene) polyol, and polyoxyalkylene polyether polyol. In the ink of the present invention, the amount of polyol added is preferably 0.5% by mass to 10% by mass of the whole ink.

(Polyphenol)
As the polyphenol according to the present invention, known compounds can be used as long as they have at least two phenolic hydroxyl groups.

  Examples of the polyphenol compound include compounds described in JP-A-2008-209600, JP-A-5-289420, JP-A-2008-189541, and the like. In the ink of the present invention, the amount of polyphenol added is preferably 0.5% by mass to 10% by mass of the whole ink.

  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, 42, 81, 83, 87, 95, 109, 117, 129, 150, 153, 177, 179, 271 C.I. I Pigment Orange-16, 36, 38, 59, 65, 68, C.I. I Pigment Red-5, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 144, 146, 185, 257, 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, 10, 36, C.I. I Pigment White-6, 18, 21, C.I. I Pigment Black-7.

  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.

  In the present invention, the recording material is heated to at least 45 ° C. At that time, the temperature of the recording material on which image formation is performed is controlled within the target set temperature range by the recording material control mechanism. The actinic ray curable ink composition that has landed on the recording material is controlled to a desired temperature, whereby the actinic ray curable ink composition that has landed is cured without being affected by humidity. The target set temperature range is a temperature range at which the actinic radiation curable ink composition is sufficiently cured even in an atmosphere that inhibits the curing of the actinic radiation curable ink composition. However, when the resin material is heated / printed, there is a concern that the resin material may be deformed / softened, and therefore there is an upper limit in the temperature range. For example, with vinyl chloride, the temperature is up to 60 ° C.

  The recording material control mechanism includes a temperature detection unit, a temperature adjustment unit, and a control unit. The temperature detecting means and the temperature adjusting means are connected to the control means.

  The temperature adjusting means is provided at an image forming position or an upstream position upstream of the conveyance path from the image forming position, and heats the recording material by applying heat to the recording material at the image forming position or the upstream position. is there. In addition, when the temperature of the recording material is excessively increased by heating by giving the cooling function to the temperature adjusting means, or when the temperature around the recording material becomes too high at the image forming position, the temperature adjusting means The recording material may be cooled by releasing the heat of the recording material.

  Specifically, the temperature adjusting means is a heat plate or the like that heats the recording material by generating heat to heat the recording material at the image forming position. As another example of the temperature adjusting means, the driven roller disposed on the upstream side of the conveyance path from the image forming position is provided with a heat generating function so that the driven roller is a heat roller and is in contact with the driven roller. The recording material may be heated by applying heat to the material. In addition, a hot air fan that blows a gas heated toward the recording material as warm air is disposed near the image forming position as a temperature adjusting unit, and the recording material is located upstream of the image forming position or the conveyance path from the image forming position. May be heated. In addition, a heating element such as a heater is provided near the image forming position as a temperature control means, and the heat generated by the heating element is conducted, transmitted, and radiated to the recording material, so that it is conveyed more than the image forming position or the image forming position. The recording material may be heated on the upstream side of the path. Furthermore, a Peltier element that exchanges heat between the heat dissipating part (heat dissipating side heat transfer member) and the heat absorbing part (heat absorbing side heat transfer member) when current flows is arranged near the image forming position as a temperature control means. It is also possible to heat the recording material on the upstream side of the conveyance path from the image forming position or the image forming position by providing the heat radiating portion in contact with the recording material.

  When the temperature adjusting means has a cooling function, for example, a heat pump or the like that cools by heat of vaporization, a heat absorbing part of a Peltier element, etc. can be used as the temperature adjusting means, and if it is cooled to about room temperature A cooling fan or the like that blows air at about room temperature onto the recording material can be used as the temperature adjusting means. Here, the Peltier element may be provided so that the heat absorbing portion of the Peltier element contacts the recording material at the image forming position.

  The temperature detecting means is arranged in the vicinity of the image forming position and detects the temperature of the recording material whose temperature is adjusted by supplying and supplying heat by the temperature adjusting means. The temperature detection means outputs the detected temperature (hereinafter referred to as detection temperature) to the control means as an electrical signal.

  The control means is basically a device that controls the temperature adjusting means based on an electric signal representing the detected temperature detected by the temperature detecting means. The control means has a general-purpose CPU (central processing unit) and an arithmetic processing unit comprising a memory or the like, or a dedicated logic circuit, and can detect the detected temperature by the CPU or logic circuit. A control signal can be output to the temperature adjusting means. The control means outputs a control signal based on the detected temperature to the temperature adjustment means, so that the temperature adjustment means according to the control signal, heating operation, cooling operation, heating operation stop, cooling operation stop, heating energy increase / decrease, cooling energy Can be increased or decreased.

  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 the ink is ejected from the ink jet recording head, and after the ink has landed on the recording material, the temperature is 45 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). In the drawing, the recording head 3 for light black (Lk) and white (W) is drawn. However, in practice, the number of colors of the recording head 3 stored in the head carriage 2 is appropriately determined. Is.

  The recording head 3 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. , Has a property of curing by 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 efficiently control the dot diameter. 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, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Preparation of ink composition set>
Ink composition sets 1 to 6 and 1C and 2C having the compositions shown in Tables 1 to 6 were prepared according to the following method.

  3 parts by mass of a dispersant (PB822, manufactured by Ajinomoto Fine-Techno Co., Ltd.) and each polymerizable compound described in Tables 1 to 6 were placed in a stainless beaker and stirred for 1 hour while heating on a hot plate at 60 ° C. Mix and dissolve. Next, after adding the coloring materials described in Tables 1 to 6 to this solution, it was sealed in a plastic bottle together with 200 g of zirconia beads having a diameter of 1 mm, and subjected to a dispersion treatment for 2 hours in a paint shaker. Next, the zirconia beads are removed, and various additives such as photoinitiators, sensitizers, basic compounds, and surfactants are added in the combinations shown in Tables 1 to 6 to prevent clogging of the printer. Ink composition sets 1 to 6 were prepared by filtration through an 8 μm membrane filter.

  Details of each ink, each compound, and display described in Tables 1 to 6 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 group>
A compound corresponding to the number of the exemplified compound.

<Alicyclic epoxide>
C2021P: Celoxide 2021P (manufactured by Daicel Chemical Industries)

<Other epoxides>
E-4030: Sunsizer (manufactured by Shin Nippon Rika Co., Ltd.)
<Vinyl ether>

<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)

<Basic compound>
N-1: 2-methylaminoethanol N-2: Octadecylamine N-3: Triisopropanolamine N-4: Octadecylamine <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.)
<Sensitizer>
DEA: Diethoxyanthracene <Dispersant>
PB822: Ajinomoto Fine Techno Co., Ltd. <Polyol>
Priplast 3191: manufactured by Croda <Polyphenol>
Sumilizer MDP-S: Maruka Rinka M1SP manufactured by Sumitomo Chemical Co., Ltd. Sumilite resin PR-219 manufactured by Maruzen Oil Co., Ltd. “Inkjet image forming method”
Each ink composition set 1-3, 1C, 2C prepared above is loaded into an ink jet recording apparatus having the structure shown in FIG. 1 having a piezo type ink jet nozzle, and a width having each surface energy shown in Table 7 The following image recording was continuously performed on each long recording material having a length of 600 mm and a length of 500 m. 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. The ink was insulated 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-size 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 each irradiation light source shown in Table 7 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 4 to 6 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.

  By the above two methods, printing was performed 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.

  The irradiation light source used is a high-pressure mercury lamp VZero085 (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
<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) ]
Print at 720 dpi so that each dot of Y, M, C, K colors is adjacent to each other, enlarge each adjacent color dot with a magnifying glass, visually observe the degree of bleeding, and evaluate color mixing according to the following criteria It was.

◎: Adjacent dot shape keeps perfect circle and no blurring occurs ○: Adjacent dot shape keeps almost perfect circle and almost no blurring △: Adjacent dots blur slightly and dot shape is a little Although it is broken, it is a level that can be barely used ×: Adjacent dots are blurred and mixed, and wrinkles are observed in the overlapping part, and it is a quality that can not be used.

[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. It is easy to peel off with cello tape (registered trademark).

(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 at 30 minutes of continuous emission, but slightly satellite generated ×: No nozzle missing at several nozzles with 30 minutes of continuous emission Table 7 shows the evaluation results obtained as described above.

  As is apparent from Table 7, by using the actinic ray curable composition having the constitution according to the present invention, the character quality is excellent with respect to all the recording materials even in various printing environments as compared with the comparative example. It can be seen that it is possible to record a high-definition image with no color mixing (bleeding, wrinkles).

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 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording material

Claims (6)

In the actinic ray curable ink composition containing a polymerizable compound and a photoinitiator, the actinic ray curable ink composition comprises at least 60% by mass of a compound having a glycidyl group at at least two terminals as the polymerizable compound. 95% by mass or less, and the photoinitiator 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 compound having a glycidyl group is a compound having a bifunctional glycidyl group. The actinic ray curable ink composition according to claim 1, wherein the photoinitiator is a sulfonium salt. The actinic ray curable ink composition according to claim 1, wherein the actinic ray curable ink composition contains at least one selected from a polyol and a polyphenol compound. An image forming method in which the actinic ray curable ink composition according to any one of claims 1 to 4 is jetted onto a recording material from an ink jet recording head, and printing is performed on the recording material. An image forming method, wherein the material is heated to at least 45 ° C. 6. An ink jet recording apparatus for use in the image forming method according to claim 5, wherein the actinic ray curable ink composition and the ink jet recording head are heated to 35 to 100 ° C. An ink jet recording apparatus having a mechanism for discharging an ink composition and a mechanism for heating a recording material to at least 45 ° C.

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