JP5500168B2 - Actinic ray curable ink jet ink and ink jet image forming method - Google Patents

Description

  The present invention relates to an actinic ray curable ink jet ink, and more particularly to an actinic ray curable ink jet ink having a property of sol-gel phase transition depending on temperature and an ink jet image forming method using the same.

  In recent years, in the office and light printing fields, there is an increasing need for a system that can perform high-speed full-color printing without being restricted by recording media (for example, plain paper, coated paper, art paper, label paper, double-sided printing on plain paper, etc.). is there.

  From the viewpoint of simplicity and running cost of the image recording apparatus, a system using an ink jet recording method is attracting attention. An ink jet method using a water-based ink, a phase change ink jet method using a solid wax ink at room temperature, and after recording. There has been proposed an ultraviolet curable inkjet method in which actinic rays such as ultraviolet (UV) light are irradiated to crosslink.

  Above all, the ultraviolet curable ink jet method has an advantage that a system with reduced energy consumption can be constructed because the drying load is less than that of water-based ink, and the ink is cured by ultraviolet rays to form an image. In recent years, the image has high image robustness even when printed on non-printing media, and when printing on plain paper or coated paper for printing, it has the advantage of suppressing the deformation of paper media such as curling and cockling. Yes.

  However, in the ultraviolet irradiation method, due to the configuration of the apparatus, an interval of several centimeters to several tens of centimeters is generated between the inkjet recording head and the ultraviolet irradiation apparatus, so that the ink emitted from the inkjet recording head is deposited on the recording medium. Then, a time lag of several hundred ms to several seconds occurs between the irradiation of the ultraviolet rays. Since the ink wets and spreads during the time lag, there arises a problem that the size of the recording dot depends on the length of the time lag, that is, the apparatus configuration and the recording speed.

  For this reason, for example, when using two different recording speeds, the low-speed recording mode and the high-speed recording mode, the dot size in the low-speed recording mode is larger than the dot size in the high-speed recording mode. If the image conversion process is applied to the low-speed mode, the gradation property of the shadow portion of the printed image is deteriorated and the color density is changed. Therefore, different image conversions must be performed in each of the low-speed recording mode and the high-speed recording mode, and the image conversion process becomes complicated.

  In addition, when printing on various recording media using the ultraviolet irradiation method, the ink wetting and spreading differs depending on the type of recording medium, resulting in differences in the size of the recording dots depending on the type of recording medium, and the gradation and color of the image. The concentration changes. Therefore, there arises a problem that the image quality depends on the type of the recording medium.

  Furthermore, when the ultraviolet curable ink jet system is applied to a single pass method, ink droplets are coalesced before being irradiated with ultraviolet rays, and there is a problem that density unevenness occurs and image quality deteriorates.

  On the other hand, a method is known in which a low melting point wax is used, a wax ink that is solid at room temperature is heated (for example, 120 ° C. or higher), melted, emitted in the melted state, and instantly solidified on a recording medium. Yes. According to this method, it is possible to obtain an image having a certain quality even with a recording medium having an ink absorbing ability such as plain paper, but the formed image has low scratch resistance, and this scratch resistance is improved. For this purpose, it is necessary to increase the hardness of the solidified wax ink. However, in order to obtain a desired hardness, it is necessary to use a wax having a high melting point. For example, when a wax having a melting point of 120 ° C. or higher is used, the head is heated to a high temperature of 120 ° C. or higher, so that the heat resistance of the head of the ink jet printing apparatus and the members of the ink supply system are overloaded, making the printing apparatus difficult to be durable. There is a problem that the apparatus must be large. In particular, in a method using a piezo element in an ink jet recording head, there is a Curie temperature as a high temperature limit point, and there is an upper limit on the temperature that can be heated by itself.

  Further, a method is disclosed in which an organic gelling agent is contained in the ink and the blurring between the color dots of the ink is improved by utilizing the solidification ability of the gelling agent (see, for example, Patent Documents 1 and 2). .) However, in the method using only the gelling agent as proposed above, when printing on a recording medium with low absorbency such as print-coated paper or a recording medium with no absorbency such as polyethylene terephthalate film, In many cases, the scratch resistance on the printing surface and the adhesion to the recording medium are not sufficient, and there is a problem that the image tends to deteriorate. Moreover, in the said patent documents 1 and 2, no reference is made | formed regarding using an actinic-light curable composition with a gelatinizer in an ink.

  In addition, a technique for improving the quality of a printed image when printing on various recording media by adding an oil gelling agent to an actinic ray curable inkjet ink is disclosed (for example, see Patent Documents 3 and 4). However, depending on the type of gelling agent, when printing on a recording medium having no absorbability such as polyethylene terephthalate film, the sharpness of the image deteriorates and sufficient image quality cannot be obtained, or the printed surface is scratch resistant. Further, there is a case where the adhesion to the recording medium is insufficient, and further improvement is desired.

JP-A-11-315245 US Patent Application Publication No. 2004 / 0065227A1 JP 2005-126507 A JP 2007-63553 A

  The present invention has been made in view of the above problems, and its purpose is to enable printing on various recording media, and in particular to print image quality and adhesion when printing on plain paper, coated paper for printing, and film. An object of the present invention is to provide an excellent actinic ray curable inkjet ink and an inkjet image forming method using the same.

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

  1. An actinic ray curable ink jet ink that reversibly undergoes sol-gel phase transition depending on temperature, comprising a polysaccharide fatty acid ester compound as a gelling agent.

  2. 2. The actinic ray curable ink-jet ink as described in 1 above, wherein the polysaccharide fatty acid ester compound is a dextrin fatty acid ester compound or an inulin fatty acid ester compound.

  3. 3. The actinic radiation curable inkjet ink according to 1 or 2 above, which contains a pigment as a colorant.

  4). 4. The actinic ray curable type according to any one of 1 to 3, wherein the content of the fatty acid ester compound of the polysaccharide is 1% by mass or more and less than 30% by mass with respect to the total mass of the ink. Ink for inkjet.

  5. 5. The actinic ray curable inkjet ink according to any one of 1 to 4 above, which has a gel transition temperature of 20 ° C. or higher and lower than 70 ° C.

  6). 6. The actinic ray curable inkjet ink according to any one of 1 to 5, wherein the fatty acid portion of the polysaccharide fatty acid ester compound has 8 to 24 carbon atoms.

7). The actinic radiation curable inkjet ink according to any one of 1 to 6 above is heated in a temperature range of not less than + 10 ° C and less than + 40 ° C in the gel transition temperature of the actinic radiation curable inkjet ink in an inkjet recording head. An inkjet image forming method comprising: recording the image by ejecting the actinic ray curable inkjet ink from the inkjet recording head onto a recording medium.
8). 8. The inkjet image forming method as described in 7 above, wherein the recording medium is a non-absorbent recording medium.

  According to the present invention, it is possible to print on various recording media, and in particular, an actinic ray curable ink jet ink excellent in print image quality and adhesion when printed on plain paper, coated paper for printing, and film, and the same are used. An ink jet image forming method could be provided.

1 is a front view illustrating an example of a configuration of a main part of an ink jet recording apparatus that can be used in the present invention. It is a top view which shows another example of a structure of the principal part of the line head type inkjet recording device which can be used by this invention.

  Hereinafter, embodiments 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 is an actinic ray curable ink jet ink that undergoes a sol-gel phase transition reversibly depending on temperature, and contains a fatty acid ester compound of a polysaccharide as a gelling agent. The actinic ray curable ink jet ink characterized by the above features enables printing on various recording media, especially actinic ray curing with excellent print image quality and adhesion when printed on plain paper, coated paper for printing, and film. The present inventors have found that a type inkjet ink can be realized, and have reached the present invention.

  The actinic ray curable inkjet ink of the present invention (hereinafter also referred to as inkjet ink or simply ink) has a low viscosity and good fluidity by heating an inkjet recording head (hereinafter also simply referred to as recording head) during emission. Have. However, after landing on the recording medium, the phase transition from sol to gel occurs rapidly mainly due to the decrease in ink temperature, and the fluidity is remarkably lowered. As a result, the action of suppressing the expansion of the recording dots due to wetting and spreading on the recording medium and suppressing the coalescence of the droplets works, and it is considered that the print image quality of the printed matter has been dramatically improved.

  Details of the present invention will be described below.

  The actinic ray curable ink-jet ink of the present invention is characterized by containing at least one polysaccharide fatty acid ester compound. By adding a fatty acid ester compound of a polysaccharide to the ink, the ink can be gelled as the temperature drops.

  Gelation as used in the present invention refers to an independent movement of a substance due to an interaction such as a lamellar structure, a polymer network formed by covalent bonding or hydrogen bonding, a polymer network formed by a physical aggregation state, or an aggregation structure of fine particles. It has a structure that is aggregated by losing and solidified with a sudden increase in viscosity or elasticity, or semi-solidified.

  The mechanism by which the ink of the present invention thickens or gels is not clear, but the present inventor presumes as follows. That is, when the ink of the present invention in a heated state is cooled below the gel transition temperature, the hydroxyl groups present in the sugar chain region of the fatty acid ester compound of the polysaccharide dissolved in the ink form a network by hydrogen bonding, Furthermore, hydrocarbon regions derived from fatty acids are aggregated or crystallized by van der Waals forces to form a fibrous network structure. It is presumed that the entire ink is gelled by incorporating solvent molecules into this network structure.

  In order to exhibit the above effect, it is difficult to add a polysaccharide or a fatty acid independently into the ink, and it is required that the polysaccharide is esterified with a fatty acid.

  As to whether the ink is thickened or gelled, the type of polysaccharide fatty acid ester compound used, the amount of polysaccharide fatty acid ester compound added to the ink, or the actinic ray curable composition used in the ink It is possible to adjust by changing the type. In order to maximize the print quality on the recording medium, the ink of the present invention is preferably gelled on the recording medium.

[Polysaccharide fatty acid ester compound]
Next, details of the fatty acid ester compound of the polysaccharide according to the present invention will be described.

  The fatty acid ester compound of the polysaccharide according to the present invention is present in the ink as a gelling agent, and thickens or gels the ink of the present invention. Any fatty acid can be used as the esterification, but a saturated fatty acid having 8 to 24 carbon atoms is preferable in order to maximize the effect of thickening or gelling. Specific examples of polysaccharide fatty acid ester compounds used in the ink of the present invention are shown below, but the present invention is not limited to these compounds.

  The polysaccharide fatty acid ester compound used in the present invention is obtained by esterifying a polysaccharide containing a disaccharide with a fatty acid. Examples of such a polysaccharide fatty acid ester compound include a dextrin fatty acid ester compound. , Inulin fatty acid ester compounds, sucrose fatty acid ester compounds, and the like. Of these, dextrin fatty acid ester compounds and inulin fatty acid ester compounds are particularly useful.

  The dextrin fatty acid ester compound is preferably an ester compound of a linear or branched saturated or unsaturated fatty acid having 8 to 24 carbon atoms and a dextrin having an average degree of polymerization of 10 to 100, and particularly 8 to 24 carbon atoms. More preferably, it is an ester compound of saturated fatty acid and dextrin.

  Specific examples of dextrin fatty acid ester compounds according to the present invention include palmitic dextrin, palmitic acid / ethylhexanoic acid dextrin, stearic acid dextrin, palmitic acid / stearic dextrin, oleic dextrin, isopalmitic acid dextrin, isostearic acid dextrin, Examples include dextrin myristate. Commercially available products include dextrin palmitate (for example, Leopard KL2, Leopard TL2 manufactured by Chiba Flour Milling Co., Ltd.), dextrin / ethylhexanoic acid dextrin (for example, Leopard TT2 manufactured by Chiba Flour Milling Co., Ltd.) and dextrin myristate ( Examples thereof include Leopard MKL2 manufactured by Chiba Flour Milling Co., Ltd.

  Any inulin fatty acid ester compound can be used, but it is preferably an ester compound with a linear or branched, saturated or unsaturated fatty acid having 8 to 24 carbon atoms, specifically, caproic acid, Caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isodecanoic acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, behenic acid, ricinoleic acid, fatty acid ester compounds of hydroxystearic acid, etc. Is mentioned. Examples of commercially available products include inulin stearate (for example, Leopard ISK2, ISL2 from Chiba Flour Milling Co., Ltd.).

  Any sucrose fatty acid ester compound can be used, but it is preferably an ester compound with a linear or branched saturated or unsaturated fatty acid having 8 to 24 carbon atoms, and saturated with 8 to 24 carbon atoms. More preferably, it is an ester compound with a fatty acid. Specific examples include fatty acid ester compounds of caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isodecanoic acid, myristic acid, palmitic acid, stearic acid, isostearic acid, behenic acid, hydroxystearic acid, and the like. It is done. In addition, the HLB value (Hydrophilic-Lipophilic Balance) of the sucrose fatty acid ester used in the present invention is 0 or more and 5 or less from the viewpoint of solubility in the actinic ray curable composition used in the present invention. Preferably, it is 0 or more and 3 or less.

  These fatty acid ester compounds of polysaccharides can be used alone or in combination of two or more, and other gelling agents such as 12-hydroxystearic acid and behenic acid / eicosane diacid glyceryl, metal soap, Silicic anhydride, N-lauroyl-L-glutamic acid-α, γ-dibutylamide, stearone, and various known waxes such as petroleum wax, preferably paraffin wax, microcrystalline wax, petrolactam, and plant wax , Preferably candelilla wax, carnauba wax, rice wax, wood wax or jojoba oil, jojoba solid wax, animal wax, preferably beeswax, lanolin or whale wax, mineral wax, preferably montan wax, Hydrogenated wax, preferably hardened Mashi oil or hydrogenated castor oil derivative, modified wax, preferably montan wax derivative, paraffin wax derivative, microcrystalline wax derivative or polyethylene wax derivative, higher fatty acid, preferably behenic acid, stearic acid, palmitic acid, myristic acid, lauric acid Acid or oleic acid, higher alcohol, preferably stearyl alcohol or behenyl alcohol, hydroxystearic acid, preferably 12-hydroxystearic acid or 12-hydroxystearic acid derivative, fatty acid amide, preferably lauric acid amide, stearic acid amide, Oleic acid amide, erucic acid amide, ricinoleic acid amide, 12-hydroxystearic acid amide, special fatty acid amide or N-substituted fatty acid amide, amine Desirably dodecylamine, tetradecylamine or octadecylamine, ester, preferably glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester or polyoxyethylene fatty acid ester, polymerized wax, desirably α-olefin You may use it in combination with a maleic anhydride copolymer wax.

  The amount of the fatty acid ester compound of the polysaccharide according to the present invention added to the ink is appropriately adjusted according to the object effect of the present invention, but is 1% by mass or more and less than 30% by mass with respect to the total mass of the ink. It is preferable. In the ink of the present invention, if the addition amount of the fatty acid ester compound of the polysaccharide is 1% by mass or more with respect to the total mass of the ink, the desired thickening and gelation upon landing on the recording medium can be obtained. The print quality on the recording medium is sufficiently satisfied. In addition, when the addition amount of the fatty acid ester compound of the polysaccharide is less than 30% by mass with respect to the total mass of the ink, the emission stability can be maintained, and when the pigment is used as the coloring material, the dispersion of the pigment can be maintained. Stability can be ensured. If the amount of the fatty acid ester compound of the polysaccharide is 1% by mass or more and less than 30% by mass with respect to the total mass of the ink, the desired effect can be obtained, but more preferably 3% by mass or more and less than 25% by mass.

  When two or more types of polysaccharide fatty acid ester compounds according to the present invention are used, the total amount is preferably less than 30% by mass relative to the total mass of the ink.

  When the ink of the present invention causes a sol-gel phase transition depending on the temperature, the gel transition temperature is arbitrarily set, but is preferably 20 ° C. or higher and lower than 70 ° C. When the gel transfer temperature of the ink is 20 ° C. or higher, sufficient gel transition after ink landing according to the recording conditions can be performed, and the print image quality can be sufficiently improved. If it is less than 70 ° C., it is not necessary to heat the ink jet recording apparatus to an excessively high temperature, the load on the head of the ink jet recording apparatus and the members of the ink supply system can be reduced, and good durability of the recording head is realized. be able to.

  The gel transition temperature referred to in the present invention means a temperature at which the viscosity suddenly changes from a fluid solution state to a gel state, and the sol-gel transition temperature, phase transition temperature, sol-gel transition point, It is synonymous with the term called gel point.

  The method for measuring the gel transition temperature in ink is, for example, performing thermal analysis with a differential scanning calorimeter (DSC), measuring the center temperature of the exothermic peak observed when cooling from a high temperature state, and obtaining the gel transition temperature. Can do.

  Further, the gel transition temperature preferably exists between the ink holding temperature in the head and the surface temperature of the recording medium. The gel transition temperature of the ink of the present invention can be adjusted by the addition amount of the polysaccharide fatty acid ester compound according to the present invention.

[Actinic ray curable composition]
The ink of the present invention comprises an actinic ray curable composition that is cured with actinic rays together with a fatty acid ester compound of a polysaccharide and a coloring material.

  The actinic ray curable composition (hereinafter also referred to as a photopolymerizable compound) used in the present invention will be described.

  Examples of the actinic rays in the present invention include electron beams, ultraviolet rays, α rays, γ rays, X rays, etc., but they are dangerous to human bodies and easy to handle, and their use is widespread industrially. Preferred are ultraviolet rays and electron beams.

  In the present invention, the photopolymerizable compound that is crosslinked or polymerized by irradiation with actinic rays can be used without any particular limitation. Among them, it is preferable to use a photocationic polymerizable compound or a radical polymerizable compound, particularly preferably light. It is a cationically polymerizable compound.

  As the photo cationic polymerizable monomer, various known cationic polymerizable monomers can be used. For example, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, JP-A-2001-220526 Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like.

  In the present invention, for the purpose of suppressing the shrinkage of the recording medium during ink curing, it contains at least one oxetane compound as a photopolymerizable compound and at least one compound selected from an epoxy compound and a vinyl ether compound. Is preferred.

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

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

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

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

  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, Di- or trivinyl ether compounds such as methylolpropane 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-propyl Pills vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

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

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

  In the oxetane compound that can be used in the present invention, when a compound having 5 or more oxetane rings is used, the viscosity of the ink composition increases, which makes it difficult to handle, and the glass transition temperature of the ink composition is high. Therefore, the tackiness of the cured product obtained may not be sufficient. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  Examples of the compound having an oxetane ring that can be preferably used in the present invention include compounds represented by general formula (1) described in paragraph No. 0089 of JP-A No. 2005-255821, and also paragraphs of the same publication. Compounds represented by general formula (2), general formula (7) of paragraph number 0107, general formula (8) of paragraph number 0109, general formula (9) of paragraph number 0166 and the like described in number 0092 Can be mentioned.

  Specific examples thereof include the exemplified compounds 1 to 6 described in paragraph numbers 0104 to 0119 and the compound described in paragraph number 0121 of the publication.

  Next, the radical polymerizable compound will be described.

  In the ink of the present invention, the use of the radical polymerizable compound is not limited. Examples of the radical polymerizable compound include JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, A photocurable material using a photopolymerizable composition described in JP-A-10-863 and a cationic polymerization type photocurable resin are known, and recently, a long wavelength longer than visible light. Photo-cationic polymerization type photo-curing resins sensitized to the region are also disclosed in, for example, JP-A-6-43633 and JP-A-8-324137.

  The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and may be any compound as long as it has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. , Oligomers, polymers and the like having a chemical form. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties.

[Each component of ink]
Next, the components of the ink of the present invention excluding the above items will be described.

(Color material)
In the ink of the present invention, a dye or a pigment can be used without limitation as a color material constituting the ink, but a pigment having good dispersion stability with respect to the ink component and excellent weather resistance is used. It is preferable. Although it does not necessarily limit as a pigment, For example, the organic or inorganic pigment of the following number described in a color index can be used for this invention.

Examples of red or magenta pigments include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, and 53: 1. 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13 16, 20, 36,
As the blue or cyan pigment, Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36, 60 ,
Examples of green pigments include Pigment Green 7, 26, 36, 50,
As the yellow pigment, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 137, 138 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193,
As the black pigment, Pigment Black 7, 28, 26 and the like can be used according to the purpose.

  Specific product names include, for example, chromo fine yellow 2080, 5900, 5930, AF-1300, 2700L, chromo fine orange 3700L, 6730, chromo fine scarlet 6750, chromo fine magenta 6880, 6886, 6891N, 6790, 6887. , Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Ku Mofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Red 8040 , C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870 , Seika Fast Bordeaux 10B-430, Seica Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C7 18, A612, cyanine blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seikagaku), KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302 , 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (large Nippon Ink Chemical Co., Ltd.), Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pi gment Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, C USN, Colortex Maroon 601, Colortex Brown B610N, Colortex violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403B, Col. , Lionol lue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink), Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, HostaBem G2 , Hostaperm Pink E, Hostaperm Blue B2G (manufactured by Clariant), carbon black # 2600, # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, MA11, MA100, MA100R, MA77 # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, CF9 (Mitsubishi Chemical) Can be mentioned.

  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. Examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series. Furthermore, the following are mentioned.

  Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, a high molecular weight unsaturated acid ester, Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene nonyl Examples thereof include phenyl ether, stearylamine acetate, and pigment derivatives.

  Specific examples include “Anti-Terra-U (polyaminoamide phosphate)”, “Anti-Terra-203 / 204 (high molecular weight polycarboxylate)” manufactured by BYK Chemie, “Disperbyk-101 (polyaminoamide phosphate). And acid ester), 107 (hydroxyl group-containing carboxylic acid ester), 110 (copolymer containing an acid group), 130 (polyamide), 161, 162, 163, 164, 165, 166, 170 (polymer copolymer) ”,“ 400 ”,“ Bykumen ”(high molecular weight unsaturated acid ester),“ BYK-P104, P105 (high molecular weight unsaturated acid polycarboxylic acid) ”,“ P104S, 240S (high molecular weight unsaturated acid polycarboxylic acid and Silicone) ”,“ Lactimon (long chain amine, unsaturated acid polycarboxylic acid and silicon Down) "and the like.

  In addition, “Efka CHEMICALS” “Efka 44, 46, 47, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766”, “Efka Polymer 100 (modified polyacrylate), 150 (aliphatic) System modified polymer), 400, 401, 402, 403, 450, 451, 452, 453 (modified polyacrylate), 745 (copper phthalocyanine system) "; Kyoei Chemical Co., Ltd." Floren TG-710 (urethane oligomer) "," “Flonon SH-290, SP-1000”, “Polyflow No. 50E, No. 300 (acrylic copolymer)”; “Disparon KS-860, 873SN, 874 (polymer dispersing agent), # 2150, manufactured by Enomoto Kasei Co., Ltd. (Aliphatic polyvalent carboxylic acid), # 7004 (polyether ester type) "and the like That.

  Furthermore, “Demol RN, N (Naphthalenesulfonic acid formalin condensate sodium salt), MS, C, SN-B (aromatic sulfonic acid formalin condensate sodium salt), EP”, “Homogenol L-18 (made by Kao Co., Ltd.) Polycarboxylic acid type polymer) "," Emulgen 920, 930, 931, 935, 950, 985 (polyoxyethylene nonylphenyl ether) "," acetamine 24 (coconut amine acetate), 86 (stearyl amine acetate) "; "Solspers 5000 (phthalocyanine ammonium salt type), 13240, 13940 (polyesteramine type), 17000 (fatty acid amine type), 24000, 32000" manufactured by Nikko Chemical Co., Ltd. "Nikkor T106 (polyoxyethylene sorbitan monooleate), MY" -IEX (polyoxyethylene monostearate), Hexagline4-0 (hexaglyceryl ruthenate Huwei rate) ", and the like.

  These pigment dispersants are preferably contained in the ink in the range of 0.1 to 20% by mass. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound, but the ink of the present invention is preferably solvent-free because it is reacted and cured after printing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

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

  In the ink of the present invention, a conventionally known dye, preferably an oil-soluble dye can be used as necessary. Specific examples of oil-soluble dyes that can be used in the present invention are given below, but the present invention is not limited to these.

<Magenta dye>
MS Magenta VP, MS Magenta HM-1450, MS Magenta HSo-147 (manufactured by Mitsui Toatsu Co., Ltd.), AIZENSOT Red-1, AIZEN SOT Red-2, AIZEN SOTRed-3, AIZEN SOT Pink-1, SPERON Red GE SPECIAL (above, manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN Red FB 200%, MACROLEX Red Violet R, MACROLEX ROT5B (above, manufactured by Bayer Japan), KAYASET Red B, KAYASET Red 130, KAYASET Red Japan 802 ), PHLOXIN, ROSE BENGAL, ACID Red (above, made by Daiwa Kasei), HSR-31, DIARESIN Red K (below) , Manufactured by Mitsubishi Kasei Co., Ltd.), Oil Red (manufactured by BASF Japan Co., Ltd.).

<Cyan dye>
MS Cyan HM-1238, MS Cyan HSo-16, Cyan HSo-144, MS Cyan VPG (manufactured by Mitsui Toatsu Co., Ltd.), AIZEN SOT Blue-4 (manufactured by Hodogaya Chemical Co., Ltd.), RESOLIN BR. Blue BGLN 200%, MACROLEX Blue RR, CERES Blue GN, SIRIUS SUPRATURQ. Blue Z-BGL, SIRIUS SUTRA TURQ. Blue FB-LL 330% (above, Bayer Japan), KAYASET Blue FR, KAYASET Blue N, KAYASET Blue 814, Turq. Blue GL-5 200, Light Blue BGL-5 200 (above, Nippon Kayaku Co., Ltd.), DAIWA Blue 7000, Oleosol Fast Blue GL (above, Daiwa Kasei), DIARESIN Blue P (Mitsubishi Kasei), SUDAN Blue 670, NEOPEN Blue 808, ZAPON Blue 806 (above, manufactured by BASF Japan).

<Yellow dye>
MS Yellow HSm-41, Yellow KX-7, Yellow EX-27 (Mitsui Toatsu), AIZEN SOT Yellow-1, AIZEN SOT YellowW-3, AIZEN SOT Yellow-6 (above, manufactured by Hodogaya Chemical Co., Ltd.), MACROLEX Yellow 6G, MACROLEX FLUOR. Yellow 10GN (above, manufactured by Bayer Japan), KAYASET Yellow SF-G, KAYASET Yellow 2G, KAYASET Yellow AG, KAYASET Yellow EG (above, manufactured by Nippon Kayaku), DAIWA YELLOW 330H HSY-68 (manufactured by Mitsubishi Kasei Co., Ltd.), SUDAN Yellow 146, NEOPEN Yellow 075 (above, manufactured by BASF Japan).

<Black dye>
MS Black VPC (Mitsui Toatsu Co., Ltd.), AIZEN SOT Black-1, AIZEN SOT Black-5 (above, Hodogaya Chemical Co., Ltd.), RESORIN Black GSN 200%, RESOLIN Black BS (above, Bayer Japan Co., Ltd.), KAYASET Black A-N (manufactured by Nippon Kayaku Co., Ltd.), DAIWA Black MSC (manufactured by Daiwa Kasei Co., Ltd.), HSB-202 (manufactured by Mitsubishi Kasei Co., Ltd.), NEPTUNE Black X60, NEOPEN Black X58 (manufactured by BASF Japan) .

  The amount of pigment or oil-soluble dye added is preferably 0.1 to 20% by mass, more preferably 0.4 to 10% by mass. If it is 0.1% by mass or more, good image quality can be obtained, and if it is 20% by mass or less, an appropriate ink viscosity in ink ejection can be obtained. In addition, two or more kinds of colorants can be mixed as appropriate for color adjustment.

(Photopolymerization initiator)
In the ink of the present invention, when ultraviolet rays or the like are used as the active light, it is preferable to contain at least one photopolymerization initiator. However, in the case where an electron beam is used as the actinic ray, a photopolymerization initiator is not required in many cases.

  Photopolymerization initiators can be broadly classified into two types: intramolecular bond cleavage type and intramolecular hydrogen abstraction type.

  Examples of the intramolecular bond cleavage type photopolymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether, benzoin isopropyl ether; 2 , 4,6-Trimethylbenzoindiphenyl Scan fins oxides such acylphosphine oxide of benzil, methyl phenylglyoxylate esters.

  On the other hand, as an intramolecular hydrogen abstraction type photopolymerization initiator, for example, benzophenone, methyl 4-phenylbenzophenone, o-benzoylbenzoate, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl Benzophenones such as diphenyl sulfide, acrylated benzophenone, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 3,3'-dimethyl-4-methoxybenzophenone; 2-isopropylthioxanthone, 2 Thioxanthone series such as 1,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone; amino benzophenone series such as Michler-ketone, 4,4'-diethylaminobenzophenone; 10-butyl- - chloro acridone, 2-ethyl anthraquinone, 9,10-phenanthrenequinone, camphorquinone, and the like.

  The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 10.00% by mass of the actinic ray curable composition.

  Examples of radical polymerization initiators include triazine derivatives described in JP-B-59-1281, JP-B-61-9621, JP-A-60-60104, JP-A-59-1504, and JP-A-59-1504. Organic peroxides described in JP-A-61-243807, JP-B-43-23684, JP-B-44-6413, JP-B-44-6413, JP-B-47-1604, etc., and the United States Diazonium compounds described in Japanese Patent No. 3,567,453, organic azides described in US Pat. Nos. 2,848,328, 2,852,379 and 2,940,853 Compounds, ortho-quinonediazides described in JP-B 36-22062, JP-B 37-13109, JP-B 38-18015, JP-B 45-9610 and the like, Various onium compounds described in JP-A-55-39162, JP-A-59-14023, and the like, and “Macromolecules, Vol. 10, page 1307 (1977); No. 142205, JP-A-1-54440, European Patent No. 109,851, European Patent No. 126,712, etc., “Journal of Imaging Science” (J. Imag. Sci.), Vol. 30, page 174 (1986), (oxo) sulfonium organoboron complexes described in Japanese Patent Nos. 2711491 and 2803454, 61-151197, titanocenes, “Coordination Chemistry Levi (Coordination Chemistry Review), 84, 85-277 (1988) and JP-A-2-182701, transition metal complexes containing transition metals such as ruthenium, JP-A-3-209477 No. 2,4,5-triarylimidazole dimer, carbon tetrabromide, and organic halogen compounds described in JP-A-59-107344. These polymerization initiators are preferably contained in the range of 0.01 to 10 parts by mass with respect to 100 parts by mass of the compound having an ethylenically unsaturated bond capable of radical polymerization.

  In the ink of the present invention, a photoacid generator can also be used as a photopolymerization initiator.

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

First, diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds such as phosphonium ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 -, CF 3 SO 3 - and salts be able to.

  Specific examples of the onium compound that can be used in the present invention include compounds described in paragraph No. 0132 of JP-A No. 2005-255821.

  Specific examples of the sulfonated compound that generates sulfonic acid include compounds described in paragraph No. 0136 of JP-A No. 2005-255821.

  Secondly, halides that generate hydrogen halide can also be used, and specific examples thereof include compounds described in paragraph No. 0138 of JP-A No. 2005-255821.

  Thirdly, an iron allene complex described in paragraph No. 0140 of JP-A-2005-255821 can be mentioned.

(Other additives)
In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as a viscosity modifier, a specific resistance modifier, a film forming agent, an ultraviolet absorber, an antioxidant, a discoloration inhibitor, an antibacterial agent, and a rust inhibitor can be appropriately selected and used.

〔recoding media〕
The recording medium that can be used for image formation with the ink of the present invention is not particularly limited, and is made of a paper base such as plain paper or art paper used for copying, ordinary uncoated paper, base paper, etc. In addition to coated paper, synthetic paper, etc. coated on both sides with resin, various non-absorbable plastics and films used for so-called soft packaging can be used. Examples of various plastic films include PET film and OPS. Examples thereof include a film, an OPP film, an ONY film, a PVC film, a PE film, and a TAC film. Moreover, it is applicable also to metals and glass.

[Inkjet image forming method]
Next, the inkjet image forming method of the present invention will be described.

  In the inkjet image forming method of the present invention, the actinic ray curable inkjet ink is heated in the inkjet recording head at a gel transition temperature of + 10 ° C. or more and less than + 40 ° C. An image is recorded by ejecting the actinic ray curable ink jet ink onto a recording medium from the ink jet recording head.

  By using the ink according to the present invention to form an image by making a difference between the temperature of the ink in the recording head and the temperature of the recording medium, the ink of the present invention that has landed on the recording medium is In this method, the ink is cured by fixing by gelation and then irradiating the recording surface with an actinic ray such as ultraviolet rays or electron beams.

  As the fixing means by thickening or gelation, for example, an inkjet recording apparatus used for inkjet recording is heated on a recording medium after heating the recording head to a predetermined temperature in a relatively low temperature environment such as room temperature. The method of landing on the surface and naturally cooling and fixing by the environmental temperature, the method of cooling the recording medium in advance, or the method of fixing by blowing cold air to the landing part, etc. are appropriately selected and used. However, the ink jet image forming method of the present invention is characterized in that the ink in the recording head is heated to a predetermined temperature range higher than the room temperature. Examples of the method for heating the ink in the recording head include a method for heating the ink directly or indirectly by attaching a heater inside or outside the recording head, a method for utilizing heat generated when the recording head is driven, and the like. I can do it.

  Further, in addition to the method of heating the ink in the recording head to a predetermined temperature, which is a feature of the inkjet image forming method of the present invention, a method of providing an intermediate transfer medium such as a roller between the inkjet recording head and the recording medium, This is one of the preferred embodiments of the present invention. In this method, the ink of the present invention is ejected onto an intermediate transfer medium set at a temperature lower than that of the recording head, the ink is fixed on the intermediate transfer medium by thickening or gelation, and then the fixed ink is used. Transfer to recording medium. For this reason, it is possible to relatively reduce variations in image quality due to temperature changes in the printing environment.

(Total ink film thickness after ink landing)
In the present invention, the total ink film thickness after the ink has landed on the recording medium and cured by irradiation with actinic rays is preferably 2 to 25 μm. Here, “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the recording medium, 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 ejection conditions)
As the ink discharge conditions, it is preferable from the viewpoint of improving discharge stability and image quality that the recording head and the ink are heated at a temperature of 10 ° C. or higher and lower than 40 ° C. than the gel transition temperature of the ink according to the present invention. . By making the ink ejection temperature 10 ° C. or more higher than the gel transition temperature, it is possible to prevent the ink from gelling in the recording head due to temperature fluctuations, and to suppress ejection defects. By setting the temperature below 40 ° C., the time until the ink reaches the gel transition temperature after landing on the recording medium can be shortened, and the gelation speed can be increased. As a result, high image quality can be obtained.

  The ink according to the present invention has a large viscosity fluctuation range due to temperature fluctuation, and the viscosity fluctuation directly affects the droplet size and droplet ejection speed and causes image quality degradation. Therefore, the ink temperature is equal to or higher than the gel transition temperature of the ink + 10 ° C. , And maintaining in a temperature range of less than + 40 ° C. and emitting in that state. The temperature management range is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C. The set temperature here refers to a reference temperature set as the temperature of ink when ink is ejected.

  Further, in the present invention, the amount of liquid droplets ejected from each nozzle of the recording head can be appropriately changed according to the recording image. However, when a high-definition image is formed, it is preferably in the range of 1 pl to 15 pl. .

(Light irradiation conditions after ink landing)
In the inkjet image forming method of the present invention, the active light irradiation condition is preferably irradiation with active light within 10 seconds after ink landing, more preferably 0.001 to 5 seconds, and still more preferably. 0.001 second to 2 seconds.

  A basic method of irradiating actinic rays is disclosed in JP-A-60-132767. Specifically, a light source is provided on both sides of the recording head unit, and the recording head and the light source are arranged in a shuttle system. Scan. 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 surface of the recording head unit and irradiating the recording unit with ultraviolet rays is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  In addition, the irradiation of 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 actinic rays are further 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 medium that occurs during ink curing.

(Electron beam irradiation)
Examples of the irradiation method in the case of using an electron beam as the actinic ray include a scanning method, a curtain beam method, and a broad beam method. The curtain beam method is preferable from the viewpoint of processing capability.

  The acceleration voltage of electron beam irradiation can be set to a range of 30 to 250 kV, and a cured film can be formed. However, it is preferable to set the acceleration voltage to 30 to 100 kV, which can obtain the same curability with a lower irradiation dose. . By irradiating an electron beam with an acceleration voltage of 30 to 100 kV, the electron beam concentrates on the surface of the recording medium where inhibition of curing tends to occur, and the curability can be improved. Therefore, in order to obtain high curability under a high oxygen concentration, it is preferable to irradiate an electron beam with an acceleration voltage of 30 to 100 kV.

  In addition, when the acceleration voltage of electron beam irradiation is set in the range of 30 to 100 kV, the irradiation dose of the electron beam is set to a value lower than normal, energy saving by high energy efficiency, and production efficiency by increasing printing speed. It is also possible to plan upward and downward. In normal electron beam irradiation with an acceleration voltage of 100 to 250 kV, the electron beam irradiation amount is preferably 30 to 100 kGy, more preferably 30 to 60 kGy. In addition, the measurement of the electron beam irradiation amount is performed, for example, by irradiating a 44.5 μm-thick dosimetry film (RADIACHROMIC FILM FWT-60-00 manufactured by FARWEST) with Co60 γ-ray as a standard radiation source, and absorbance due to film coloring. A calibration curve for determining the relationship between the dose and the dose is prepared, and the electron beam irradiation dose can be determined from the calibration curve and the absorbance.

  Examples of electron beam irradiation means that can be used in the present invention include “Curetron EBC-200-20-30” manufactured by Nissin High Voltage Co., Ltd., “Min-EB” manufactured by AIT Co., Ltd., and the like. Can be mentioned.

  In the inkjet image forming method of the present invention, it is preferable to irradiate an electron beam in an oxygen concentration atmosphere of 1000 ppm or less, and more preferably 500 ppm or less. The oxygen concentration of 1000 ppm or less in the present invention includes a concentration range achieved by inerting with an inert gas such as nitrogen or argon.

(UV irradiation)
When ultraviolet rays are used as actinic rays, for example, low-pressure, medium-pressure, high-pressure mercury lamps, metal halide lamps and the like having an operating pressure of several hundred Pa to 1 MPa are used as the ultraviolet irradiation light source. A high-pressure mercury lamp and a metal halide lamp are preferable, and a metal halide lamp is more preferable. Moreover, it is preferable to provide a filter that cuts light having a wavelength of 300 nm or less. The output of the lamp ^{400W~30kW, 10mW / cm 2 ~10kW /} cm 2 as illuminance, preferably 0.1~500mJ / cm ² as irradiation energy, 1 to 100 mJ / cm ² is more preferable.

When the light source wavelength includes ultraviolet rays of 300 nm or less, or when the irradiation energy exceeds 500 mJ / cm ² , the mother nucleus of the actinic ray crosslinkable resin or various coexisting additives are decomposed by ultraviolet rays, and the present invention. In addition to not being able to obtain the above effect, there is a possibility of causing problems such as odor derived from the decomposition product, which is not preferable. When the irradiation energy is less than 0.1 mJ / cm ² , the crosslinking efficiency is insufficient and the effect of the present invention cannot be obtained sufficiently.

Illuminance at the time of ultraviolet irradiation is preferably 0.1 mW / cm ^{2 to 1} W / cm ² . When the illuminance exceeds 1 W / cm ² , the surface curability of the coating film is improved, but the deep curability is lowered and a film having a hard surface only is obtained. In that case, the balance of hardness in the depth direction of the film is lost and curling occurs, which is not preferable.

When the illuminance is lower than 0.1 mW / cm ^{2, the} crosslinking does not proceed sufficiently due to scattering in the film and the effect of the present invention cannot be obtained, which is not preferable.

When giving the same integrated light quantity (mJ / cm ² ), the preferable range of illuminance is due to the change in the light transmittance. When the concentration distribution of the generated cross-linking reactive species is different due to the transmittance of ultraviolet rays, and the UV illuminance is high, a high concentration of cross-linking reactive species is generated on the surface of the coating film, and a tight and dense film is formed on the surface of the coating film. .

(Inkjet recording device)
Next, an inkjet recording apparatus (hereinafter simply referred to as a recording apparatus) that can be used in the inkjet image forming method of the present invention will be described using an ultraviolet irradiation apparatus as an example.

  Hereinafter, a recording apparatus that can be used in the present invention will be described with reference to the drawings as appropriate. Note that the recording apparatus shown in the drawings is merely an embodiment of the recording apparatus that can be preferably used in the present invention, and the present invention is not limited to this drawing.

  FIG. 1 is a front view showing a configuration of a main part of an ink jet recording apparatus that can be used in the present invention. The ink jet recording apparatus 1 includes a recording head carriage 2, a recording head 3, irradiation means 4 as means for irradiating ultraviolet rays, a platen unit 5, and the like. In the recording apparatus 1, the platen unit 5 is installed under the recording medium P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the recording medium P. As a result, a high-definition image can be reproduced very stably.

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

  The recording head carriage 2 is installed on the upper side of the recording medium P, and has a plurality of recording heads 3 to be described later and discharge ports (nozzles) on the lower side according to the number of colors used for image printing on the recording medium P. Store. The recording head carriage 2 is installed on 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 recording head scanning means.

  In FIG. 1, the recording head carriage 2 has white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan ( Although the drawing is carried out in such a manner that the recording heads 3 for Lc), light black (Lk), and white (W) are accommodated, the number of recording heads 3 accommodated in the recording head carriage 2 is The color of the ink accommodated therein can be determined as appropriate.

  In the inkjet image forming method of the present invention, each recording head 3 is heated and kept in a temperature range of the gel transition temperature of each ink to be filled + 10 ° C. or higher and lower than + 40 ° C.

  The recording head 3 is directed from the discharge port toward the recording medium P by the operation of a plurality of discharge means (not shown) provided inside the ink of the present invention supplied by the ink supply means (not shown). Discharge. The ink ejected by the recording head 3 includes a coloring material, a polymerizable monomer, a photopolymerization initiator, and the like in addition to the polysaccharide fatty acid ester compound according to the present invention, and is landed on the recording medium P. Then, it is cooled and gelled, and in this example, it has the property of being cured by crosslinking and polymerization reaction of the monomer when the photopolymerization initiator acts as a catalyst by being irradiated with ultraviolet rays as an irradiation means.

  The recording head 3 moves from one end in the width direction of the recording medium P to the other end of the recording medium P in the Y direction in FIG. The ink of the present invention is ejected as ink droplets onto the landable region), and the ink droplets are landed on the landable region.

  The above scanning is performed as many times as necessary, and after the ink of the present invention is ejected toward one landable area, the recording medium P is appropriately moved from the front to the back in FIG. While performing scanning by the means, the recording head 3 discharges the ink of the present invention to the next landable area adjacent to the rearward direction in FIG.

  By repeating the above operation and ejecting the ink of the present invention from the recording head 3 in conjunction with the recording head scanning means and the conveying means, an image composed of the ink aggregate of the present invention is formed on the recording medium 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 active light 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 the same shape as the largest one that can be set by the recording apparatus 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the recording head scanning means. Has a larger shape.

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

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

  FIG. 2 is a top view illustrating an example of a configuration of a main part of a line head type ink jet recording apparatus that can be used in the present invention. Those having the same functions as those shown in FIG. 1 will be described using the same reference numerals as those in FIG.

  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 fixed to a recording head carriage 2 so as to cover the entire width of the recording medium P. Has been placed.

  On the other hand, on the downstream side of the recording head carriage 2, there is provided irradiation means 4 arranged so as to cover the entire width of the ink printing surface so as to cover the entire width of the recording medium P. As the ultraviolet lamp used in the illuminating means 4, the same one as described in FIG. 1 can be used.

  In the line head system shown in FIG. 2, the recording head carriage 2 and the irradiation means 4 are fixed, and only the recording medium P is transported, and ink is ejected and cured 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. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Preparation of pigment dispersion >>
[Preparation of pigment dispersion 1]
Pigment: Black pigment Pigment Black 7 (Mitsubishi Chemical Corporation # 52) 20 parts Pigment dispersant: PB822 (Ajinomoto Fine Techno Co., Ltd.) 8 parts Polymerizable compound: Oxetane 221 (OXT221 manufactured by Toagosei Co., Ltd.) 72 parts Each of the above additives Was mixed at 60 ° C., dissolved by heating, and then kneaded using a bead mill to prepare Pigment Dispersion Liquid 1. It was 80 nm as a result of measuring the volume average particle diameter of the pigment particle of the pigment dispersion liquid 1 containing this black pigment using Zetasizer 1000 (made by Malvern).

<< Preparation of Ink: Cationic Polymerization Inkjet Ink >>
[Preparation of Ink 1]
The following additives were mixed in sequence, heated to 80 ° C. and stirred, and the resulting liquid was filtered through a # 3000 metal mesh filter under heating and cooled to obtain a cationic polymerization type black ink. Ink 1 was prepared.

Polymerizable compound: Oxetane 221 (OXT221 manufactured by Toagosei Co., Ltd.)
57.5 parts Polymerizable compound: Oxetane 212 (OXT212, manufactured by Toagosei Co., Ltd.)
10.0 parts Polymerizable compound: Alicyclic epoxy compound 1 (EPR) 15.0 parts Photopolymerization initiator: CPI100P (manufactured by Sun Apro) 2.5 parts Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.05 parts Pigment dispersion 1 15.0 parts [Preparation of ink 2]
In the preparation of the ink 1, 30.0 parts of 12-hydroxystearic acid (abbreviated as 12HSA in Table 1) was added as an additive, the addition amount of OXT221 was changed to 27.5 parts, and heating during ink preparation Ink 2 was prepared in the same manner except that the temperature was changed to 90 ° C.

[Preparation of ink 3]
In the preparation of the ink 1, 5.0 parts of N-lauroyl-L-glutamic acid-α, γ-dibutyramide (abbreviated as LGBA in Table 1) was added as an additive, and the amount of OXT221 added was 52.5. Ink 3 was prepared in the same manner except that the heating temperature during ink preparation was changed to 130 ° C.

[Preparation of Ink 4]
In the preparation of the ink 1, 1.0 part of stearone (abbreviated as STR in Table 1) is added as an additive, the addition amount of OXT221 is changed to 56.5 parts, and the heating temperature at the ink preparation is 120. Ink No. 4 was prepared in the same manner except that the temperature was changed to ° C.

[Preparation of ink numbers 5 to 23]
In the preparation of the ink 1, the amount of OXT 221 added, the type and amount of each additive were changed as shown in Table 1, and the heating temperature during ink preparation was changed to 130 ° C. 5-23 were prepared.

  In addition, the detail of each compound described by the abbreviation in Table 1 is as follows.

(Polymerizable monomer)
OXT221: Oxetane compound (di (1-ethyl-3-oxetanyl) methyl ether, manufactured by Toagosei Co., Ltd.)
OXT212: Oxetane compound (3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, manufactured by Toagosei Co., Ltd.)

(Photopolymerization initiator)
CPI100P: photopolymerization initiator (triallylsulfonium salt propylene carbonate 50% solution, manufactured by San Apro)
(Surfactant)
X22-4272: surfactant (both ends polyether-modified silicon, manufactured by Shin-Etsu Chemical Co., Ltd.)
(Additive)
12-HSA: 12-hydroxystearic acid LGBA: N-lauroyl-L-glutamic acid-α, γ-dibutylamide STR: stearone A: dextrin palmitate d (A Leopard KL2 manufactured by Chiba Flour Mills)
B: Dextrin palmitate B (Leopard TL2 manufactured by Chiba Flour Mills)
C: Inulin stearate C (Leopard ISL2 manufactured by Chiba Flour Mills)
D: Inulin stearate D (Leopard ISK2 manufactured by Chiba Flour Mills)
E: Palmitic acid / ethylhexanoic acid dextrin E (Leopard TT2 manufactured by Chiba Flour Mills)
F: Dextrin myristate F (Leopard MKL2 manufactured by Chiba Flour Mills)
G: Sucrose stearate G (Ryoto Sugar Ester S-070 manufactured by Mitsubishi Chemical Foods)
H: Sucrose stearate ester H (Ryoto sugar ester S-270, manufactured by Mitsubishi Chemical Foods)
I: Sucrose palmitate I (Ryoto Sugar Ester P-170, manufactured by Mitsubishi Chemical Foods)
<Measurement of gel transition temperature of ink>
For the inks 2 to 23 prepared as described above, the gel transition temperature was measured by the following method, and the obtained results are shown in Table 1.

(Measurement of gel transition temperature)
20 mg of each sample was set in a differential scanning calorimeter (Seiko Denshi SSC5200), and the calorie change was measured. After the temperature was raised from −15 ° C. to 180 ° C. at a scanning speed of 10 ° C./min, the temperature was cooled from 180 ° C. to −15 ° C. at 20 ° C./min, and the center temperature of the observed exothermic peak was determined as the gel transition temperature of each sample. did.

Example 2
<< Preparation of pigment dispersion >>
[Preparation of pigment dispersion 2]
After the following additives were mixed, the mixture was kneaded using a bead mill to prepare Pigment Dispersion Liquid 2.

Pigment: Black pigment Pigment Black 7 (Mitsubishi Chemical Corporation # 52) 20 parts Pigment dispersant: PB822 (Ajinomoto Fine Techno Co., Ltd.) 8 parts Polymerizable compound: Tetraethylene glycol diacrylate (TEGDA)
72 parts << Preparation of ink: radical polymerization type inkjet ink >>
[Preparation of Ink 24]
The following additives are mixed in order, heated to 80 ° C. and stirred, and the resulting liquid is heated and filtered with a # 3000 metal mesh filter and cooled to produce a radical polymerization type black ink. 24 was prepared.

Polymerizable compound: Tetraethylene glycol diacrylate (TEGDA)
30 parts Polymerizable compound: Lauryl acrylate (RA) 25 parts Polymerizable compound: NK ester (A-400 manufactured by Shin-Nakamura Chemical Co., Ltd.) 25 parts Photopolymerization initiator: IRGACURE907 (I-907 manufactured by Ciba Japan) 5 parts 15 parts of pigment dispersion 2 [Preparation of inks 25 to 30]
In the preparation of the ink 24, the addition amount of each polymerizable compound, the type and addition amount of each additive were changed as shown in Table 2, and the same was performed except that the heating temperature at the ink preparation was changed to 130 ° C. Thus, inks 25 to 30 were prepared.

  In addition, the detail of each additive described by the abbreviation in Table 2 is as follows.

RA: lauryl acrylate TEGDA: tetraethylene glycol diacrylate A-400: NK ester (manufactured by Shin-Nakamura Chemical Co., Ltd.)
I-907: IRGACURE907 (manufactured by Ciba Japan)
A: Dextrin palmitate d (A Leopard KL2 manufactured by Chiba Flour Mills)
B: Dextrin palmitate B (Leopard TL2 manufactured by Chiba Flour Mills)
C: Inulin stearate C (Leopard ISL2 manufactured by Chiba Flour Mills)
D: Inulin stearate D (Leopard ISK2 manufactured by Chiba Flour Mills)
H: Sucrose stearate ester H (Ryoto sugar ester S-270, manufactured by Mitsubishi Chemical Foods)
<Measurement of gel transition temperature of ink>
For each ink prepared above, the gel transition temperature was measured in the same manner as in the method described in Example 1, and the results obtained are shown in Table 2.

Example 3
<< Inkjet image formation >>
A line head type ink jet recording apparatus equipped with a piezo type ink jet nozzle is loaded with inks 1 to 30 described in Examples 1 and 2, and PPC paper (manufactured by J PAPER Konica Minolta Business Solutions), art paper for printing ( SA Kinfuji Oji Paper Co., Ltd.), cast coated paper for printing (mirror coated gold, made by Oji Paper Co., Ltd.), coated paper for printing (OK Matte Coat Green 100, made by Oji Paper Co., Ltd.), and polyethylene terephthalate film (white pet Maru adhesive) A blank character, a solid image, a sharpness evaluation chart, and a dot diameter measurement chart were printed on the product, and images 1 to 30 were obtained, respectively. The ink supply system is composed of an ink tank, a supply pipe, a front chamber ink tank immediately before the recording head, a pipe with a filter, and a piezo head. The ink determined in Examples 1 and 2 is insulated from the front chamber tank to the recording head portion. The gel transition temperature was + 30 ° C. The piezo head also has a built-in heater, and the ink temperature in the recording head is heated to the gel transition temperature + 30 ° C. For the ink that does not cause gelation, the ink was uniformly heated to 70 ° C. The piezo head has a nozzle diameter of 20 μm, the number of nozzles is 512 nozzles (256 nozzles × 2 rows, staggered arrangement, 1 row nozzle pitch 360 dpi), and the droplet speed is about 2.5 pl under each condition. The light was emitted at 6 m / sec and printed at a recording resolution of 1440 dpi × 1440 dpi. Each recording medium was at room temperature (23 ° C.). After each ink landed, the ink was cured by irradiating with ultraviolet rays at an illuminance of 60 mJ / cm ² 0.5 seconds after the ink landed by a high-pressure mercury lamp arranged on the upper part of the carriage. The illuminance of the irradiation light source was measured and displayed by measuring an integrated illuminance of 254 nm using UV PF-A1 manufactured by Iwasaki Electric Co., Ltd. The above image formation was performed in an environment of 23 ° C. and 55% RH. In the present invention, dpi represents the number of dots per 2.54 cm.

<Evaluation of formed image>
About the created images 1-30, according to the following methods, evaluation of plain paper character quality, density unevenness, sharpness, recording medium type compatibility, adhesion, and emission stability was performed.

[Evaluation of plain paper character quality]
According to the above method, with a resolution of 1400 dpi × 1440 dpi on a PPC paper (manufactured by J PAPER Konica Minolta Business Solutions Co., Ltd.), a 3 point, 4 point and 5 point MS Mincho font, the Chinese character “mouth, four, day, times, The characters “Cause, Difficulty, Solid, Country, Eye, Figure, Country” were printed, the printed character image was visually observed, and the character quality was evaluated according to the following evaluation criteria.

◎: All three-point extracted characters are clearly recorded in detail. ○: Only a part of the three-point extracted characters can be read, but all four-point extracted characters can be read. Only a part of the extracted characters can be read, but all the 5-point extracted characters can be read. X: Some 5-point extracted characters cannot be read.

[Evaluation of density unevenness]
By the above method, art paper for printing (SA Kinfuji Oji Paper Co., Ltd.), printing cast coated paper (Mirror Coat Gold Oji Paper Co., Ltd.), printing coated paper (OK Mat Coat Green 100 manufactured by Oji Paper Co., Ltd.), and A solid image of 2 cm × 2 cm printed on a polyethylene terephthalate film (manufactured by White Pet Maru Adhesive Co., Ltd.) was visually evaluated, and density unevenness was evaluated according to the following evaluation criteria.

：: No density unevenness is observed in all recording media observed from a position 15 cm away. ○: Density unevenness is observed in some recording media when observed from a position 15 cm away, but from a position 30 cm away. No density unevenness is observed in all the recording media. Δ: Density unevenness is observed in a part of the recording medium observed from 30 cm. X: All the recording media are observed from the position separated by 30 cm. Concentration unevenness is observed in [Evaluation of sharpness]
According to the above method, a sharpness evaluation chart in which fine lines are arranged at equal intervals is printed on a polyethylene terephthalate film (manufactured by White Pet Maru Adhesion Co., Ltd.), and the printed chart is visually evaluated. Evaluation was performed.

A: The boundary between the image portion and the non-image portion is sharp and has high sharpness. ○: The boundary between the image portion and the non-image portion looks slightly blurred. Δ: The boundary between the image portion and the non-image portion looks clearly blurred. Thin lines stick together, and part of the boundary between the image area and the non-image area is crushed [Evaluation of recording medium type compatibility]
By the above method, printing art paper (SA Kinfuji Oji Paper Co., Ltd.), printing cast coated paper (Mirror Coat Gold Oji Paper Co., Ltd.), printing coated paper (OK Matte Coat Green 100, manufactured by Oji Paper Co., Ltd.) and polyethylene A dot diameter measurement image in which pixels are arranged at an interval of 360 dpi is printed on a terephthalate film (manufactured by White Pet Maru Adhesive Co., Ltd.), and the dot diameter of various papers is set to 20 using an optical microscope (VHX-500, manufactured by KEYENCE). Measurement was made point by point to determine the average dot diameter. Next, using the dot diameter variation index calculated as follows, the recording medium type compatibility was evaluated.

Dot diameter variation index = (average dot diameter of the recording medium having the largest average dot diameter) / (average dot diameter of the recording medium having the smallest average dot diameter)
As the dot diameter variation index is smaller, the same image can be printed regardless of the type of the recording medium, so that it can be said that the recording medium type compatibility is excellent.

A: The dot diameter variation index is 1.00 or more and less than 1.15. O: The dot diameter variation index is 1.15 or more and less than 1.30. Δ: The dot diameter variation index is 1.30 or more. Less than 50 x: The dot diameter variation index is 1.50 or more [Evaluation of Adhesion]
After pasting the cello tape (registered trademark) on the solid image formed on the polyethylene terephthalate film (manufactured by White Pet Maru Adhesive Co., Ltd.), visually observe the image state when peeled off in the vertical method, as follows: Judged.

A: Image peeling is not observed, and the surface property of the image is not changed. ○: Image peeling is not observed, but at least part of the image is cloudy. Δ: Slight peeling at the edge of the image. X: Image peeling was clearly observed.

[Evaluation of output stability]
Ejection was performed with an ink jet recording apparatus equipped with each of the inks prepared as described above, and visual observation was performed for the presence or absence of nozzle missing and emission bending, and the emission stability was evaluated according to the following criteria.

◎: No missing nozzle was observed. ○: Out of all nozzles 512, 1 to 5 nozzles were bent in the emitting direction. △: Out of all nozzles 512, 1 to 5 nozzles had poor emission. X: Outgoing defects were recognized with 6 or more nozzles among all nozzles 512. Table 3 shows the results obtained as described above.

  As is clear from the results in Table 3, the actinic radiation curable inkjet ink of the present invention is superior to the comparative example in the quality of plain paper characters of the formed image, and is excellent in various recording media such as coated paper and films. It can be seen that printing can be performed with quality, adhesion of the formed image is excellent, and in addition, emission stability is high. Moreover, as a result of visually observing the created JIS / SCID N5 “bicycle” image, it was confirmed that there was no image deterioration due to coalescence of droplets, excellent sharpness, and high optical density was obtained. .

Example 4
<< Preparation of pigment dispersion >>
[Preparation of Yellow Pigment Dispersion 1]
Pigment: Yellow pigment (Pigment Yellow 180) 20 parts Pigment dispersant: PB822 (manufactured by Ajinomoto Fine-Techno Co., Ltd.) 8 parts Oxetane compound (OXT221 manufactured by Toagosei Co., Ltd.) 72 parts After heating and mixing the above additives, a bead mill is used. The yellow pigment dispersion 1 was prepared by kneading.

[Preparation of magenta pigment dispersion 1]
Pigment: Magenta pigment (Pigment Red 122) 20 parts Pigment dispersant: PB822 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 8 parts Oxetane compound (OXT221 manufactured by Toagosei Co., Ltd.) 72 parts After heating and mixing the above additives, a bead mill is used. The magenta pigment dispersion 1 was prepared by kneading.

[Preparation of Cyan Pigment Dispersion 1]
Pigment: Cyan pigment (Pigment Blue 15: 4) 20 parts Pigment dispersant: PB822 (manufactured by Ajinomoto Fine Techno Co., Ltd.) 8 parts Oxetane compound (OXT221 manufactured by Toagosei Co., Ltd.) 72 parts The mixture was kneaded to prepare a cyan pigment dispersion 1.

[Black pigment dispersion 1]
The black pigment dispersion 1 described in Example 1 was used.

<Preparation of ink set>
An ink set comprising the following color inks was prepared.

[Preparation of yellow ink]
The following additives were sequentially mixed, heated and stirred at 130 ° C., and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a yellow ink.

Polymerizable compound: Oxetane 221 (OXT221 manufactured by Toagosei Co., Ltd.)
45.5 parts Polymerizable compound: Oxetane 212 (OXT212 manufactured by Toagosei Co., Ltd.)
10.0 parts Polymerizable compound: Alicyclic epoxy compound 1 (supra) 15.0 parts Photopolymerization initiator: CPI100P (manufactured by San Apro) 2.5 parts Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.05 part Yellow pigment dispersion 1 15.0 parts Additive D: Inulin stearate D (Leopard ISK2 manufactured by Chiba Flour Mills) 12.0 parts [Preparation of magenta ink]
The following additives were sequentially mixed, heated and stirred at 130 ° C., and then the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a magenta ink.

Polymerizable compound: Oxetane 221 (OXT221 manufactured by Toagosei Co., Ltd.)
45.5 parts Polymerizable compound: Oxetane 212 (OXT212 manufactured by Toagosei Co., Ltd.)
10.0 parts Polymerizable compound: Alicyclic epoxy compound 1 (supra) 15.0 parts Photopolymerization initiator: CPI100P (manufactured by San Apro) 2.5 parts Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.05 part Magenta pigment dispersion 1 15.0 parts Additive D: Inulin stearate D (Leopard ISK2 manufactured by Chiba Flour Mills) 12.0 parts [Preparation of cyan ink]
The following additives were sequentially mixed, heated and stirred at 130 ° C., and then the resulting liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a cyan ink.

Polymerizable compound: Oxetane 221 (OXT221 manufactured by Toagosei Co., Ltd.)
45.5 parts Polymerizable compound: Oxetane 212 (OXT212 manufactured by Toagosei Co., Ltd.)
10.0 parts Polymerizable compound: Alicyclic epoxy compound 1 (supra) 15.0 parts Photopolymerization initiator: CPI100P (manufactured by San Apro) 2.5 parts Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.05 part Cyan pigment dispersion 1 15.0 parts Additive D: Inulin stearate D (Leopard ISK2 manufactured by Chiba Flour Mills) 12.0 parts [Preparation of black ink]
The following additives were sequentially mixed, heated and stirred at 130 ° C., and then the obtained liquid was filtered with a # 3000 metal mesh filter under heating and then cooled to prepare a black ink.

Polymerizable compound: Oxetane 221 (OXT221 manufactured by Toagosei Co., Ltd.)
45.5 parts Polymerizable compound: Oxetane 212 (OXT212 manufactured by Toagosei Co., Ltd.)
10.0 parts Polymerizable compound: Alicyclic epoxy compound 1 (supra) 15.0 parts Photopolymerization initiator: CPI100P (manufactured by San Apro) 2.5 parts Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) ) 0.05 part Black pigment dispersion 1 15.0 parts Additive D: Inulin stearate D (Leopard ISK2 manufactured by Chiba Flour Mills) 12.0 parts << Measurement of each characteristic value of ink >>
About each color ink prepared by the above, the gel transition temperature was measured like the method of Example 1, and the obtained result is shown in Table 4.

<< Formation and evaluation of inkjet image >>
Using the line head type ink jet printer of the third embodiment, the above four color inks are filled in a line head printer arranged in four rows in the paper transport direction, and the recording conditions are the same as in the third embodiment, and the PPC paper (JPAPER Konica Minolta) is used. Business Solutions Co., Ltd.), Art Paper for Printing (SA Kinfuji Oji Paper Co., Ltd.), Cast Coated Paper for Printing (Mirror Coat Gold Oji Paper Co., Ltd.), Coated Paper for Printing (OK Matt Coat Green 100, Oji Paper Co., Ltd.) And a polyethylene terephthalate film (manufactured by White Pet Maru Adhesive Co., Ltd.) printed with a letter image, a solid image, a sharpness evaluation chart, a dot diameter measurement chart, and a JIS / SCID N5 “bicycle” image. In the same way as the method, evaluation of plain paper character quality, density unevenness evaluation, sharpness evaluation, As a result of evaluating the recording medium type compatibility, the adhesiveness evaluation, and the emission stability evaluation, it was possible to confirm excellent effects in all the evaluation items. Moreover, as a result of visually observing the created JIS / SCID N5 “bicycle” image, it was confirmed that there was no image deterioration due to coalescence of droplets, excellent sharpness, and high optical density was obtained. .

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 2 Recording head carriage 3 Recording head 31 Ink ejection port 4 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P Recording medium

Claims (8)

  An actinic ray curable ink jet ink that reversibly undergoes sol-gel phase transition depending on temperature, comprising a polysaccharide fatty acid ester compound as a gelling agent.   2. The actinic ray curable ink jet ink according to claim 1, wherein the fatty acid ester compound of the polysaccharide is a dextrin fatty acid ester compound or an inulin fatty acid ester compound.   The actinic ray curable ink jet ink according to claim 1, further comprising a pigment as a colorant.   The actinic ray curing according to any one of claims 1 to 3, wherein the content of the fatty acid ester compound of the polysaccharide is 1% by mass or more and less than 30% by mass with respect to the total mass of the ink. Type ink jet ink.   The actinic ray curable inkjet ink according to any one of claims 1 to 4, wherein the gel transition temperature is 20 ° C or higher and lower than 70 ° C.   6. The actinic ray curable ink jet ink according to claim 1, wherein the fatty acid portion of the polysaccharide fatty acid ester compound has 8 to 24 carbon atoms.   The actinic radiation curable inkjet ink according to any one of claims 1 to 6 in a temperature range of not less than + 40 ° C and less than + 40 ° C in the gel transition temperature of the actinic radiation curable inkjet ink in an inkjet recording head. An inkjet image forming method comprising: recording an image by discharging the actinic ray curable inkjet ink from a inkjet recording head onto a recording medium while heating. The ink jet image forming method according to claim 7, wherein the recording medium is a non-absorbent recording medium.