JP2017113944A - Inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method capable of reducing a gloss difference between a region in which an image is formed and a region in which an image is not formed, regardless of a recording medium, when an image is formed by an inkjet method using gel ink. The present invention relates to an inkjet recording method. The method of the present invention includes a step of specifying the type of recording medium, a step of setting a maximum amount of ink that can land on a unit area of the recording medium, and a step of setting an amount not exceeding the maximum amount set in the setting step. A step of landing a droplet of an inkjet ink containing a photopolymerizable compound and a gelling agent and undergoing a solgel phase transition with temperature on the recording medium so that the inkjet ink landed on the recording medium, and landing on the recording medium. The present invention includes a step of irradiating the above-mentioned inkjet ink with active light to cure the above-mentioned inkjet ink. [Selection diagram] Fig. 1

Description

  The present invention relates to an ink jet recording method.

  The ink jet recording method is used in various printing fields because it can form an image easily and inexpensively. As one of the ink-jet inks, an ink containing a photopolymerizable compound that cures when irradiated with actinic rays (hereinafter, also simply referred to as “actinic ray curable ink”) is known. In recent years, actinic ray curable ink has been attracting attention because it can form an image having high adhesion even on a recording medium having low water absorption.

  In recent years, actinic ray curable ink containing a gelling agent and undergoing a sol-gel phase transition with temperature (hereinafter also simply referred to as “gel ink”) has been developed. Gel ink is in a sol state when heated, and can be ejected from the nozzles of an inkjet head, but when ejected onto a recording medium, it cools and gels, so the pinning property after landing is high. Have By irradiating the gel ink pinned on the surface of the recording medium with a sliding light beam, the gel ink is cured on the surface of the recording medium and an image is formed.

  For example, in Patent Document 1, although the specific mechanism of action is unknown, the gel ink in which the gloss on the area on the recording medium where the image is formed and the area where the image is not formed closely matches Is described.

  The ink jet recording method is an image forming method capable of forming an image on various types of recording media. However, even when ink is ejected under the same conditions, the behavior of the ink after landing differs depending on the recording medium, and thus the image quality of the formed image may differ depending on the recording medium. Inkjet recording methods are known in which the amount of ink discharged from the nozzles is changed in accordance with the recording medium in order to form a high-quality image regardless of the recording medium.

  For example, Patent Document 2 describes an ink jet recording method in which the ink discharge amount per unit area is changed between plain paper and a transparent film. According to the method of Patent Document 2, in plain paper having a high ink absorption rate, the amount of ink discharged per unit area can be increased to suppress the occurrence of unclear edges, color mixing and wrinkles due to ink penetration, and ink absorption. In a transparent film with a low rate, it is said that the amount of ink discharged per unit area can be reduced to suppress the occurrence of density unevenness due to solidification of unfixed ink.

  Patent Document 3 describes an ink jet recording method in which the ink ejection amount is changed depending on the air permeability of the recording medium, and the difference in the ink bleeding due to the difference in the quality of plain paper is adjusted. According to Japanese Patent Laid-Open No. 2004-260260, it is said that, on a recording medium having a low air permeability, the occurrence of bleeding during image formation can be suppressed by reducing the ink discharge amount regardless of the type of plain paper.

JP 2009-132919 A JP-A-7-276615 JP 2008-23842 A

  Patent Document 1 describes that if an image is formed with gel ink, there is little difference in gloss between a region where an image is formed and a region where an image is not formed. However, according to the study of the present inventor, the difference in gloss when the image is formed using the gel ink varies depending on the recording medium.

  Patent Document 2 describes a method of changing the ink discharge amount between plain paper and a transparent film, and Patent Document 3 describes a method of changing the ink discharge amount depending on the type of plain paper. Has been. However, these documents are methods for forming an image by absorbing ink in a recording medium, and the same effect cannot be expected in a gel ink that cures ink on the surface of the recording medium. In addition, the inkjet method can form images on various recording media other than plain paper or transparent film, and the recording medium other than plain paper or transparent film targeted by these documents can be formed regardless of the recording medium. There is a demand for a method that can reduce variations in image quality of images.

  The present invention has been made in view of the above problems, and the object thereof is to form an image formed region and an image regardless of a recording medium when an image is formed by an inkjet method using a gel ink. An object of the present invention is to provide an ink jet recording method capable of reducing a difference in glossiness from a region, and an image forming apparatus capable of executing such an ink jet recording method.

The above object of the present invention is achieved by the following means.
[1] With reference to a table that associates the type of recording medium to be recorded with the maximum amount of ink that can land on the unit area of the recording medium, the maximum amount of ink that can land on the unit area of the recording medium is determined. A setting step and a photopolymerizable compound and a gelling agent so that the amount of inkjet ink not exceeding the maximum amount set in the setting step lands on the recording medium, and undergoes a sol-gel phase transition depending on the temperature. A step of ejecting ink-jet ink droplets from nozzles of an ink-jet head and landing on a recording medium; a step of irradiating the ink-jet ink landed on the recording medium with actinic rays to cure the ink-jet ink; An ink jet recording method comprising:
[2] The type of the recording medium is classified based on one or more criteria selected from the coating amount of the resin that the recording medium has, the air permeability of the recording medium, and the Beck smoothness of the recording medium. The method according to [1].
[3] The maximum amount when the resin coating amount of the recording medium is 20 g / m ² or more is 20 g / m ² , and the resin coating amount of the recording medium is 10 g / m ² or more. The maximum amount when it is less than 20 g / m ² is 15 g / m ² , and the maximum amount when the coating amount of the resin layer is 0 g / m ² or more and less than 10 g / m ² is 10 g / m ^2. The method according to [1] or [2], wherein
[4] The maximum amount when the air permeability of the recording medium is 100 seconds or more is 20 g / m ² , and the maximum amount when the air permeability of the recording medium is less than 100 seconds is 10 g / m ^2. The method according to [1] or [2], which is m ² .
[5] The maximum amount when the air permeability of the recording medium is 100 seconds or more and the Beck smoothness of the recording medium is 200 seconds or more is 20 g / m ² , and the recording medium The maximum amount is 15 g / m ² when the air permeability is 100 seconds or more and the Beck smoothness of the recording medium is 1 second or more and less than 200 seconds, according to [4]. Method.
[6] An inkjet head having a nozzle surface provided with a nozzle outlet that includes a photopolymerizable compound and a gelling agent and capable of ejecting droplets of an inkjet ink that undergoes a sol-gel phase transition with temperature. A transport unit that transports the recording medium so that the recording medium facing the inkjet head moves directly below the nozzle outlet, an irradiation unit that irradiates the upper surface of the transport unit with actinic rays from a light source, and recording A storage unit that stores a table that associates the type of medium and the maximum amount of ink that can be landed on a unit area of the recording medium, and the inkjet head, the transport unit, the irradiation unit, and the storage unit are controlled. A control unit that performs recording with reference to the table stored in the storage unit. The maximum amount of ink that can land on the unit area of the recording medium to be set is set, the transport unit is controlled to transport the recording medium, and the ink jet head is controlled to land on the unit area of the recording medium. An image forming apparatus that discharges the inkjet ink so that a maximum amount does not exceed the set maximum amount.

  According to the present invention, when an image is formed by an ink jet method using gel ink, an ink jet recording method capable of reducing a difference in gloss between a region where an image is formed and a region where an image is not formed, regardless of a recording medium, An image forming apparatus capable of performing such an ink jet recording method is also provided.

FIG. 1 is a conceptual diagram showing an inkjet image forming apparatus according to an embodiment of the present invention.

  As a result of diligent research, the inventor of the present invention has a strong pinning property, and since there is little reduction in thickness due to wet spreading after landing on the recording medium, the method described in Patent Document 1 or Patent Document 2 uses gel ink. It has been found that when an image is formed, the difference in gloss between the region where the image is formed and the region where the image is not formed is not sufficiently small. That is, since the pinned gel ink has a large thickness, it covers the irregularities on the surface of the recording medium and flattens the plane of the recording medium. This region where the gel ink has landed and the surface has become flatter is more likely to reflect light and have a higher gloss than the region where the ink has not landed. Therefore, when a large amount of gel ink is landed and cured on a recording medium with large irregularities, the area where the image is formed (area where the ink has landed) becomes flatter and the gloss becomes higher, but on the other hand, no image is formed. It is considered that the difference in gloss of the formed image is increased because the gloss of the remaining area (the area where the ink has not landed) remains low.

  The unevenness of the surface of the recording medium becomes large when the thickness of the resin layer that coats the surface is thin (the amount of resin is small) or when the amount of fibers constituting the recording medium is small. For this reason, in a recording medium with a small amount of resin or a recording medium with a small amount of fibers, it is considered that the difference in gloss can be reduced if the amount of ink landed on the recording medium is reduced.

  In addition, the recording medium with a small amount of resin or the recording medium with a small amount of fibers easily absorbs a component having a low viscosity (for example, a part of a photopolymerizable compound) from the ink into the recording medium. Curing tends to be insufficient, and odor and blocking are likely to occur. Therefore, it is expected that the occurrence of the odor and blocking can be suppressed by reducing the amount of ink landing on these recording media.

  Further, the recording medium with a small amount of resin or the recording medium with a small amount of fibers tends to wet and spread the gel ink landed more than other recording media, so that fine lines are difficult to be reproduced. Therefore, it is expected that the fineness of the formed image can be improved by reducing the amount of ink landing on these recording media.

  According to the present invention, in particular, when an image is formed on various types of recording media by an ink jet recording method using one image forming apparatus, it is possible to adjust various types of recording media only by adjusting the ink discharge amount. Thus, the effect of reducing the gloss difference, the effect of suppressing the generation of odor, the effect of suppressing the generation of blocking, or the effect of increasing the fineness of the image can be easily achieved.

  The recording medium targeted by the present invention may be any medium as long as it can form an image by the ink jet method. For example, art paper, coated paper, lightweight coated paper, coated paper including finely coated paper and cast paper, Consists of absorbent media including uncoated paper, plastics including polyester, polyvinyl chloride, polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate and polybutadiene terephthalate. Non-absorbing recording media (plastic base materials), and non-absorbing inorganic recording media such as metals and glass. Among these, the absorbent medium is more effective in suppressing the occurrence of the odor and blocking. In addition, the effect of reducing the gloss difference, the effect of suppressing the generation of odor and blocking, and the effect of increasing the fineness of the image are more suitably achieved in the coated paper.

  The inkjet ink targeted by the present invention is an inkjet ink that contains a photopolymerizable compound and a gelling agent and undergoes a sol-gel phase transition with temperature (hereinafter also simply referred to as “the ink of the present invention”).

  Hereinafter, the present invention will be described with reference to exemplary embodiments, but the present invention is not limited to the following embodiments.

1. Inkjet recording method An embodiment of the present invention includes a step of setting a maximum amount of ink that can land on a unit area of a recording medium, a step of landing a droplet of ink that does not exceed the maximum amount on a recording medium, and The present invention relates to an ink jet recording method including a step of curing ink.

1-1. Step of setting the maximum amount of ink that can land on the unit area of the recording medium In this step, the maximum amount of ink droplets that can land on the unit area of the recording medium to be recorded is set.

  The types of recording media are classified based on arbitrarily defined criteria such as the amount of change in gloss when an image is formed with gel ink, the amount of odor generation, the degree of occurrence of blocking, or the ease of wetting and spreading of gel ink. be able to. The amount of gloss change, amount of odor generation, degree of blocking, or ease of wetting and spreading of the gel ink correlates with the amount of resin applied to the recording medium and the amount of fibers constituting the recording medium. Therefore, for example, the type of the recording medium may be classified into any number of stages based on the amount of resin applied to the recording medium. At this time, the type of the recording medium may be classified into art paper, coated paper, lightweight coated paper, and finely coated paper (and non-coated paper) that are usually used. The amount of fibers constituting the recording medium correlates with the air permeability and smoothness of the recording medium. Therefore, the type of the recording medium may be classified into any number of stages based on the air permeability and smoothness of the recording medium. The classification of these recording media is preferably set in advance.

  The air permeability is an index representing the resistance of the recording medium to air passage. The air permeability is related to the density, texture, water absorption, printability and the like of the recording medium, and can be used as one scale indicating the porous structure of the recording medium.

  The smoothness is an index representing the flatness and smoothness of the surface of the recording medium. The larger the value, the smoother the recording medium. Smooth soil is greatly affected by surface properties (skin, texture), gloss, ink acceptability, and bulk. As a method for measuring smoothness, the Beck method and the Oken method are generally known, and both measure the smoothness of paper using air. In the present invention, a value measured by either the Beck method or the Oken method may be used as the smoothness.

  The air permeability of the recording medium can be, for example, the air permeability determined by the Gurley method according to JIS P 8117. The Beck smoothness of the recording medium can be, for example, the smoothness obtained according to JIS P 8119.

According to the knowledge newly obtained by the present inventors, in order to obtain the effect of reducing the gloss difference, the effect of suppressing the generation of odor, the effect of suppressing the occurrence of blocking, or the effect of increasing the fineness of the image, When an image is formed on a recording medium (for example, art paper or coated paper) having a resin coating amount of 20 g / m ² or more, the maximum amount is 20 g / m ² , preferably 18 g / m ² , More preferably, it is 16 g / m ^2, and when an image is formed on a recording medium (for example, a light coated paper or a fine coated paper) having a resin coating amount of 10 g / m ² or more and less than 20 g / m ² , The maximum amount is 15 g / m ² , preferably 13 g / m ^2, and an image is formed on a recording medium (for example, non-coated paper) having a resin coating amount of 0 g / m ² or more and less than 10 g / m ² If you want the above maximum amount It may be set to 10 g / ^{m 2.}

In addition, in order to obtain the effect of reducing the gloss difference, the effect of suppressing the generation of odor, the effect of suppressing the generation of blocking, or the effect of increasing the fineness of the image, a recording medium having an air permeability of 100 seconds or more When forming an image on the recording medium, the maximum amount is set to 20 g / m ² , more preferably 16 g / m ^2, and when forming an image on a recording medium having an air permeability of less than 100 seconds, the maximum amount is set to It may be 10 g / m ² . At this time, when an image is formed on a recording medium having an air permeability of 100 seconds or more and a Beck smoothness of 200 seconds or more, the maximum amount is set to 20 g / m ² , more preferably. and 16g / ^{m 2,} air permeability is not more than 100 seconds, and, if the Bekk smoothness forms an image on a recording medium is less than 200 seconds or more second, the maximum amount as 15 g / ^{m 2} Also good.

From the viewpoint of expanding the color gamut of the image to be formed, when forming an image on a recording medium (for example, art paper or coated paper) having a resin coating amount of 20 g / m ² or more, Preferably, the minimum amount is 15 g / m ^2, and an image is formed on a recording medium (for example, light-weight coated paper and fine coated paper) having a resin coating amount of 10 g / m ² or more and less than 20 g / m ^2. In that case, the minimum amount is preferably 10 g / m ² .

Similarly, from the viewpoint of expanding the color gamut of an image to be formed, when the image is formed on a recording medium having an air permeability of 100 seconds or more, the maximum amount is preferably set to 20 g / m ² . Further, when an image is formed on a recording medium having an air permeability of 100 seconds or more and a Beck smoothness of 200 seconds or more, the maximum amount is set to 15 g / m ² and the air permeability is 100. When an image is formed on a recording medium having a second or more and a Beck smoothness of 1 second or more and less than 200 seconds, the maximum amount is preferably 10 g / m ² .

1-2. Step of landing ink droplets on recording medium In this step, the amount of ink droplets that does not exceed the maximum amount of ink droplets that can land on the recording medium determined in the above step (and optionally an amount that is not less than the minimum value) The ink droplets of the present invention are ejected from the nozzles of the inkjet head so as to land on the recording medium, and land on the recording medium. At this time, the ink of the present invention is ejected so that the amount of ink that lands on the unit area of the recording medium does not exceed the set maximum amount.

  The ink jet head may be either an on-demand type or a continuous type ink jet head. Examples of on-demand inkjet heads include single-cavity, double-cavity, vendor-type, piston-type, electro-mechanical conversion methods including shear mode and shared wall types, and thermal inkjet types and bubble jets ( The bubble jet includes an electric-thermal conversion system including Canon (registered trademark) type.

  The adjustment of the amount of ink of the present invention that lands on the recording medium may be performed by changing the amount of ink ejected from the nozzles, or by changing the number of nozzles ejecting ink. These may be combined. The amount of ink ejected from the nozzle can be changed, for example, by changing the vibration width of the piezoelectric element in the electro-mechanical conversion type inkjet head. For example, the number of nozzles from which ink is ejected can be changed without ejecting ink from some of the plurality of nozzles of the inkjet head. In this way, the volume or quantity of the ink droplets ejected from the ink jet head may be changed so that the amount of the ink of the present invention landing on the recording medium is set to a desired value.

1-3. Step of curing ink In this step, the ink is cured by irradiating the landed ink of the present invention with actinic rays. From the viewpoint of enhancing the curability of the ink of the present invention, the actinic ray is preferably applied for 0.001 second or more and 1.0 second or less after ink landing, and from the viewpoint of forming a higher definition image, More preferably, the irradiation is performed for 0.001 second or more and 0.5 second or less.

  Examples of actinic rays that can be applied to the ink in this embodiment include electron beams, ultraviolet rays, α rays, γ rays, and X-rays. Among these, it is preferable to irradiate ultraviolet rays from the viewpoint of easy handling and little influence on the human body. The light source is preferably a light emitting diode (LED) from the viewpoint of suppressing the occurrence of ink curing failure due to melting of the ink of the present invention by the radiant heat of the light source. Examples of LED light sources capable of irradiating actinic rays for curing the ink of the present invention include 395 nm, water-cooled LED, manufactured by Phoseon Technology.

1-4. Other Steps This embodiment may further include a step of characterizing the type of recording medium before the step of setting the maximum amount of ink. The identification may be performed based on information on a recording medium included in print information that the image forming apparatus receives from an external device or the like. In the image forming apparatus that includes a measurement unit upstream of the inkjet head, the measurement unit May be performed based on information obtained by measuring the recording medium. The measurement unit may be any member that can measure, for example, the coating amount of the resin that the recording medium has, or the air permeability of the recording medium and optionally the Beck smoothness of the recording medium. The type of the recording medium is specified in a classification corresponding to the content of the information, for example, based on the information on the recording medium or the information obtained by the measurement.

1-5. Ink of the Present Invention The ink of the present invention is an inkjet ink that contains a gelling agent and undergoes a sol-gel phase transition with temperature. More specifically, the ink of the present invention contains a photopolymerizable compound and a gelling agent, and is a known ink that forms a sol or liquid when heated but gels when cooled. Good. The ink of the present invention may further contain a photopolymerization initiator, a color material and other components.

1-5-1. Gelling agent The content of the gelling agent is preferably 1.0% by mass or more and 10.0% by mass or less with respect to the total mass of the ink. By setting the content of the gelling agent to 1.0% by mass or more, the pinning property of the ink can be sufficiently enhanced and a higher definition image can be formed. By making the content of the gelling agent 10.0% by mass or less, it becomes difficult for the gelling agent to deposit on the surface of the formed image, and the gloss of the image can be made closer to the gloss of the image by other ink, And the ink discharge property from an inkjet head can be improved more. From the above viewpoint, the content of the gelling agent in the ink of the present invention is preferably 1.0% by mass or more and 5.0% by mass or less, and 2.5% by mass or more and 5.0% by mass or less. More preferably, it is 2.5 mass% or more and 4.0 mass% or less.

  From the following viewpoints, the gelling agent is preferably crystallized in the ink at a temperature not higher than the gelation temperature of the ink. When the gelling agent is crystallized in the ink, a structure in which the photopolymerizable compound is included in the three-dimensional space formed by the gelling agent that has been crystallized in a plate shape may be formed (such a structure). , Hereinafter referred to as "card house structure"). When the card house structure is formed, since the liquid photopolymerizable compound is held in the space, the ink droplets are less likely to spread and the pinning property of the ink is further increased. When the pinning property of the ink is increased, the ink droplets that have landed on the recording medium are less likely to coalesce, and a higher definition image can be formed.

  In order to form the card house structure, it is preferable that the photopolymerizable compound dissolved in the ink and the gelling agent are compatible. On the other hand, when the photopolymerizable compound dissolved in the ink and the gelling agent are phase-separated, it may be difficult to form a card house structure.

  Examples of gelling agents suitable for forming a card house structure by crystallization include ketone wax, ester wax, petroleum wax, vegetable wax, animal wax, mineral wax, hydrogenated castor oil, modified wax, and higher fatty acid. Higher alcohols, hydroxystearic acid, fatty acid amides including N-substituted fatty acid amides and special fatty acid amides, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acids and dimer diols.

  Examples of the ketone wax include dilignoceryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dilauryl ketone, dimyristyl ketone, myristyl palmityl ketone and palmityl stearyl ketone. It is.

  Examples of the ester wax include behenyl behenate, icosyl icosanoate, stearyl stearate, palmityl stearate, cetyl palmitate, myristyl myristate, cetyl myristate, myricyl serinate, stearyl stearate, oleyl palmitate, glyceryl fatty acid Esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters and polyoxyethylene fatty acid esters are included.

  Examples of commercially available ester wax products include the Emulex series (“EMALEX” is a registered trademark of the company) manufactured by Nippon Emulsion Co., Ltd., and the Riquemar Series and Poem Series (“Riquemar” and “Poem” manufactured by Riken Vitamin Co. Both are registered trademarks of the company.

  Examples of the petroleum-based wax include petroleum-based waxes including paraffin wax, microcrystalline wax and petrolactam.

  Examples of the plant wax include candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax and jojoba ester.

  Examples of the animal wax include beeswax, lanolin and whale wax.

  Examples of the mineral wax include montan wax and hydrogenated wax.

  Examples of the modified wax include montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, 12-hydroxystearic acid derivatives and polyethylene wax derivatives.

  Examples of the higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.

  Examples of the higher alcohol include stearyl alcohol and behenyl alcohol.

  Examples of the hydroxy stearic acid include 12-hydroxy stearic acid.

  Examples of the fatty acid amide include lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide and 12-hydroxystearic acid amide.

  Examples of commercially available fatty acid amides include Nippon Kasei Co., Ltd., Nikka Amide Series (“Nikka Amide” is a registered trademark of the company), Ito Oil Co., Ltd., ITOWAX Series, and Kao Corporation, FATTYAMID Series. .

  Examples of the N-substituted fatty acid amide include N-stearyl stearamide and N-oleyl palmitate.

  Examples of the special fatty acid amide include N, N'-ethylenebisstearylamide, N, N'-ethylenebis-12-hydroxystearylamide and N, N'-xylylenebisstearylamide.

  Examples of the higher amine include dodecylamine, tetradecylamine and octadecylamine.

  Examples of the ester of sucrose fatty acid include sucrose stearic acid and sucrose palmitic acid.

  Examples of commercially available sucrose fatty acid esters include Ryoto Sugar Ester Series ("Ryoto" is a registered trademark of the company) manufactured by Mitsubishi Chemical Foods.

  Examples of the synthetic wax include polyethylene wax and α-olefin maleic anhydride copolymer wax.

  Examples of commercially available synthetic waxes include the UNILIN series ("UNILIN" is a registered trademark of the company) manufactured by Baker-Petrolite.

  Examples of the dibenzylidene sorbitol include 1,3: 2,4-bis-O-benzylidene-D-glucitol.

  Examples of commercially available products of the above-mentioned dibenzylidene sorbitol include Shinol Rika Co., Ltd., Gelol D (“Gelol” is a registered trademark of the company).

  Examples of commercial products of the dimer diol include the CRIPOR series ("PRIPOR" is a registered trademark of the company) manufactured by CRODA.

  Of these gelling agents, ketone waxes, ester waxes, higher fatty acids, higher alcohols and fatty acid amides are preferable from the viewpoint of further improving pinning properties. From the above viewpoint, ketones represented by the following general formula (G1) A wax and an ester wax represented by the following general formula (G2) are more preferable. The ketone wax represented by the following general formula (G1) and the ester wax represented by the following general formula (G2) may contain only one kind or two or more kinds in the ink of the present invention. It may be. In addition, only one of the ketone wax represented by the following general formula (G1) and the ester wax represented by the following general formula (G2) may be included in the ink of the present invention. May be included.

General formula (G1): R1-CO-R2
In General Formula (G1), R1 and R2 are each a linear or branched hydrocarbon group having 9 to 25 carbon atoms.

General formula (G2): R3-COO-R4
In General Formula (G2), R3 and R4 are each a linear or branched hydrocarbon group having 9 to 25 carbon atoms.

  Since the ketone wax represented by the general formula (G1) or the ester wax represented by the general formula (G2) has 9 or more carbon atoms in the linear or branched hydrocarbon group, it is gelled. The crystallinity of the agent is further increased, and more sufficient space is created in the card house structure. For this reason, the photopolymerizable compound can be easily contained in the space, and the pinning property of the ink becomes higher. Further, since the carbon number of the linear or branched hydrocarbon group is 25 or less, the melting point of the gelling agent does not increase excessively, so that it is not necessary to heat the ink excessively when ejecting the ink. . From the above viewpoint, R1 and R2 are particularly preferably linear hydrocarbon groups having 11 to 23 carbon atoms.

  Further, from the viewpoint of increasing the gelation temperature of the ink and causing the ink to gel more rapidly after landing, the number of carbon atoms is 11 or more in which either R1 or R2 or R3 or R4 is saturated. A hydrocarbon group of less than 23 is preferred. From the above viewpoint, it is more preferable that both R1 and R2 or both R3 and R4 are saturated hydrocarbon groups having 11 to 23 carbon atoms.

  Examples of the ketone wax represented by the general formula (G1) include dilignoceryl ketone (carbon number: 23-24), dibehenyl ketone (carbon number: 21-22), distearyl ketone (carbon number: 17). -18), dieicosyl ketone (carbon number: 19-20), dipalmityl ketone (carbon number: 15-16), dimyristyl ketone (carbon number: 13-14), dilauryl ketone (carbon number: 11) -12), lauryl myristyl ketone (carbon number: 11-14), lauryl palmityl ketone (11-16), myristyl palmityl ketone (13-16), myristyl stearyl ketone (13-18), myristyl behenyl ketone (13) -22), palmityl stearyl ketone (15-18), valmityl behenyl ketone (15-22) and stearyl behenyl ketone 17-22) are included. In addition, the carbon number in the said parenthesis represents the carbon number of each of the two hydrocarbon groups divided by a carbonyl group.

  Examples of commercially available ketone waxes represented by the general formula (G1) include Alfa Aeser, 18-Pentriacontanon and Hentriacontan-16-on, and Kao Corporation, Kao Wax T1.

  Examples of the fatty acid or ester wax represented by the general formula (G2) include behenyl behenate (carbon number: 21-22), icosyl icosanoate (carbon number: 19-20), stearyl stearate (carbon number: 17). -18), palmitic acid stearate (carbon number: 17-16), lauryl stearate (carbon number: 17-12), cetyl palmitate (carbon number: 15-16), stearyl palmitate (carbon number: 15-18) ), Myristyl myristate (carbon number: 13-14), cetyl myristate (carbon number: 13-16), octyldodecyl myristate (carbon number: 13-20), stearyl oleate (carbon number: 17-18) , Stearyl erucate (carbon number: 21-18), stearyl linoleate (carbon number: 17-18), behenyl oleate (carbon number) 18-22) and linoleic acid arachidyl (carbon number: 17-20) are included. The number of carbons in the parenthesis represents the number of carbons of each of the two hydrocarbon groups that are divided by the ester group.

  Examples of commercially available ester waxes represented by the general formula (G2) include NOF Corporation, Unistar M-2222SL and Spal Aceti (“Unistar” is a registered trademark of the company), Kao Corporation, Exepearl SS and Exepal MY-M (“Exepal” is a registered trademark of the company), manufactured by Nippon Emulsion Co., Ltd., EMALEX CC-18 and EMALEX CC-10 (“EMALEX” is a registered trademark of the company) ("Amlepus" is a registered trademark of the company). Since these commercially available products are often a mixture of two or more types, they may be separated and purified as necessary and contained in the ink.

1-5-2. Photopolymerizable compound Examples of the photopolymerizable compound include a radical polymerizable compound and a cationic polymerizable compound. The photopolymerizable compound has a function of crosslinking or polymerizing by being irradiated with the actinic ray to cure the ink. The photopolymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof. Only one kind of photopolymerizable compound may be contained in the ink of the present invention, or two or more kinds thereof may be contained.

  The content of the photopolymerizable compound can be, for example, from 1% by mass to 97% by mass with respect to the total mass of the ink of the present invention.

  The radical polymerizable compound is preferably an unsaturated carboxylic acid ester compound, and more preferably (meth) acrylate. In the present invention, “(meth) acrylate” means acrylate or methacrylate, “(meth) acryloyl group” means acryloyl group or methacryloyl group, and “(meth) acryl” means acrylic. Or methacryl.

  Examples of (meth) acrylates include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl (meth) Acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, Methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meta Acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- ( A simple substance comprising (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid and t-butylcyclohexyl (meth) acrylate Functional acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, poly Pyrene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, dimethylol-tricyclodecane di (meth) acrylate, di (meth) acrylate having bisphenol A structure, neopentyl glycol di (meth) acrylate hydroxypivalate, polytetramethylene glycol di (meth) acrylate, polyethylene glycol di Bifunctional (meth) acrylates including acrylate and tripropylene glycol diacrylate, and trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate Tri- or more functional groups including pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerol propoxytri (meth) acrylate and pentaerythritol ethoxytetra (meth) acrylate (Meth) acrylates, oligomers having (meth) acryloyl groups including polyester acrylate oligomers, and modified products thereof are included. Examples of the modified products include ethylene oxide modified (EO modified) acrylate having an ethylene oxide group inserted therein, and propylene oxide modified (PO modified) acrylate having a propylene oxide inserted therein.

  Examples of the cationically polymerizable compound include epoxy compounds, vinyl ether compounds, and oxetane compounds.

1-5-3. Photopolymerization initiator The photopolymerization initiator includes a photoradical initiator when the photopolymerizable compound is a compound having a radical polymerizable functional group, and the photopolymerizable compound has a cationic polymerizable functional group. When the compound has a photoacid generator. Only one kind of the photopolymerization initiator may be contained in the ink of the present invention, or two or more kinds thereof may be contained. The photopolymerization initiator may be a combination of both a photo radical initiator and a photo acid generator.

  The photo radical initiator includes a cleavage type radical initiator and a hydrogen abstraction type radical initiator.

  Examples of cleavage type radical initiators include acetophenone-based initiators, benzoin-based initiators, acylphosphine oxide-based initiators, benzyl and methylphenylglyoxyesters.

  Examples of hydrogen abstraction type radical initiators include benzophenone-based initiators, thioxanthone-based initiators, aminobenzophenone-based initiators, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10- Phenanthrene quinone and camphor quinone are included.

  Examples of the photoacid generator include the compounds described in Organic Electronics Materials Research Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187-192.

  The content of the photopolymerization initiator may be in a range where the ink can be sufficiently cured, and can be, for example, 0.01% by mass or more and 10% by mass or less with respect to the total mass of the ink of the present invention.

1-5-4. Colorant The colorant includes dyes and pigments. From the viewpoint of obtaining an image having good weather resistance, the color material is preferably a pigment. The pigment can be selected from, for example, a yellow pigment, a red or magenta pigment, a blue or cyan pigment, and a black pigment according to the color of the image to be formed.

1-5-5. Other Components The ink of the present invention may further contain other components including a dispersant, a photosensitizer, a polymerization inhibitor, and a surfactant as long as the effects of the present invention are obtained. Only one kind of these components may be contained in the ink of the present invention, or two or more kinds thereof may be contained.

1-5-6. Physical Properties From the viewpoint of further improving the ejection properties from the inkjet head, the viscosity of the ink of the present invention at 80 ° C. is preferably 3 mPa · s or more and 20 mPa · s or less. Further, from the viewpoint of sufficient gelation of the ink when landed and cooled to room temperature, the viscosity of the ink of the present invention at 25 ° C. is preferably 1000 mPa · s or more.

  The gelation temperature of the ink of the present invention is preferably 40 ° C. or higher and lower than 100 ° C. When the gelation temperature of the ink is 40 ° C. or higher, the ink gels quickly after landing on the recording medium, and therefore the pinning property is further improved. When the gelation temperature of the ink is less than 100 ° C., the ink gelled by heating can be ejected from the inkjet head, so that the ink can be ejected more stably. From the viewpoint of enabling ink to be ejected at a lower temperature and reducing the load on the image forming apparatus, the gelation temperature of the ink of the present invention is more preferably 40 ° C. or higher and lower than 70 ° C.

  The viscosity at 80 ° C., the viscosity at 25 ° C. and the gelation temperature of the ink of the present invention can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink with a rheometer. In the present invention, these viscosity and gelation temperature are values obtained by the following method. The ink of the present invention was heated to 100 ° C., and the shear rate 11.7 was measured while measuring the viscosity by a stress-controlled rheometer Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0 °) manufactured by Anton Paar. The ink is cooled to 20 ° C. under the conditions of (1 / s) and a temperature drop rate of 0.1 ° C./s to obtain a temperature change curve of the viscosity. The viscosity at 80 ° C. and the viscosity at 25 ° C. can be determined by reading the viscosities at 80 ° C. and 25 ° C. in the temperature change curve of the viscosity, respectively. The gelation temperature can be determined as the temperature at which the viscosity becomes 200 mPa · s in the temperature change curve of the viscosity.

  From the viewpoint of further improving the dischargeability from the inkjet head, the average particle diameter of the pigment particles when the ink of the present invention contains a pigment is 0.08 μm or more and 0.5 μm or less, and the maximum particle diameter is 0.3 μm or more. It is preferable that it is 10 micrometers or less. The average particle diameter of the pigment particles in the present invention means a value obtained by a dynamic light scattering method using Data Sizer Nano ZSP, manufactured by Malvern. Note that the ink containing the color material has a high concentration and does not transmit light with this measuring instrument. Therefore, the ink is diluted 200 times before measurement. The measurement temperature is room temperature (25 ° C.).

2. Image Forming Apparatus Another embodiment of the present invention relates to an inkjet image forming apparatus capable of performing the above method. FIG. 1 is a side view showing the concept of an inkjet image forming apparatus 100 according to the present embodiment.

  As illustrated in FIG. 1, the image forming apparatus 100 includes an inkjet head 110, a transport unit 120, an irradiation unit 130, a control unit 140, and a storage unit 150. The image forming apparatus 100 may further include a data input unit 160. The image forming apparatus 100 may further include a measuring unit 170 that measures the type of the recording medium on the upstream side of the inkjet head 110 in the recording medium conveyance direction. In FIG. 1, the arrows indicate the conveyance direction of the recording medium.

2-1. Inkjet head 110
The ink jet head 110 has a nozzle surface 113 provided with an ejection port of the nozzle 111 on a surface facing the transport unit 120 when an image is formed, and the recording head 200 is transported by the transport unit 120. Eject ink. From the viewpoint of improving the discharge performance by solding the ink of the present invention, the inkjet head 110 may have a temperature adjusting means for adjusting the temperature of the ink to adjust the ink to a low viscosity. Examples of the temperature adjusting means include a panel heater, a ribbon heater, and a heating means using warm water.

  The inkjet head 110 may be a scanning inkjet head whose width in the direction perpendicular to the recording medium conveyance direction is smaller than that of the recording medium 200, and a line whose width in the direction orthogonal to the recording medium conveyance direction is larger than that of the recording medium 200. An ink jet head of the type may be used.

  The nozzle 111 has a discharge port on the nozzle surface 113. The number of nozzles 111 should just be more than the number (for example, four) of ink used for image formation. When the inkjet head 110 has a plurality of nozzles 111, from the viewpoint of simplifying the configuration of the apparatus and facilitating control, the plurality of nozzles 111 are provided side by side in the conveyance direction of the recording medium so as to be substantially equally spaced. It is preferred that

  The inkjet head 110 is configured to be able to change the amount of ink that is ejected and landed on a recording medium. For example, the inkjet head 110 is configured to be controlled by the control unit 140 so that the vibration width of the piezoelectric element can be changed or ink can be prevented from being ejected from some nozzles.

2-2. Transport unit 120
When forming an image, the transport unit 120 transports the recording medium 200 so that the recording medium 200 facing the ink jet head 110 moves immediately below the ink jet head 110 in the vertical direction. For example, the conveyance unit 120 includes a driving roller 121, a driven roller 122, and a conveyance belt 123.

  The driving roller 121 and the driven roller 122 are arranged in a state of being spaced apart from each other in the recording medium conveyance direction and extending in a direction orthogonal to the recording medium conveyance direction. The drive roller 121 is rotated by a drive source (not shown).

  The transport belt 123 is a belt for transporting the recording medium 200 placed thereon, and is stretched around the driving roller 121 and the driven roller 122. The conveyor belt 123 can be, for example, an endless belt formed wider than the recording medium 200. At this time, when the driving source rotates the driving roller 121, the conveying belt 123 follows the driving roller 121 and the recording medium 200 on the conveying belt 123 is conveyed. A plurality of suction holes (not shown) may be formed on the belt surface of the conveying belt 123 from the viewpoint of making the recording medium 200 sucked and held to make it difficult to detach the recording medium.

2-3. Irradiation unit 130
The irradiation unit 130 has a light source, and irradiates the upper surface of the transport unit 120 with actinic rays from the light source. As a result, the droplets of the inkjet ink landed on the recording medium 200 to be conveyed can be irradiated with actinic rays to cure the droplets. The irradiation unit 130 can be disposed immediately above the transport unit 120 on the downstream side of the inkjet head 110. The light source is preferably a light emitting diode (LED) from the viewpoint of suppressing the occurrence of ink curing failure due to melting of the inkjet ink by the radiant heat of the light source. Examples of LED light sources that can irradiate actinic rays for curing inkjet inks include 395 nm, water-cooled LEDs, manufactured by Phoseon Technology.

2-6. Control unit 140
The control unit 140 controls the operation of the image forming apparatus 100 during image formation.

2-5. Storage unit 150
The storage unit 150 includes various tables including a table that associates the control program executed by the control unit 140, the type of the recording medium, and the maximum amount (and optionally the minimum amount) of ink that can land on the unit area of the recording medium. Store information so that it can be referenced.

2-7. Data input unit 160
The data input unit 160 transmits and receives various types of information such as data including the type of the recording medium to be printed and the image to be printed with the external device.

2-8. Measuring unit 170
The measurement unit 170 measures the type of recording medium on which an image is formed and transmits the obtained information to the control unit 140. The measuring unit 170 may be any known device that can measure, for example, the coating amount of the resin that the recording medium has, the air permeability of the recording medium, or the Beck smoothness of the recording medium.

2-9. Other Configurations In addition to the above-described configuration, the image forming apparatus 100 includes an ink tank (not shown) for storing inkjet ink before ejection, and an ink flow path that allows ink to communicate between the ink tank and the inkjet head 110. (Not shown) may be included.

2-10. The image forming control unit 140 using the image forming apparatus 100 includes the type of recording medium, the maximum amount of ink that can land on the unit area of the recording medium (and optionally the minimum amount), which are stored in the storage unit 150. The maximum amount of ink that can land on the unit area of the type of the specified recording medium, and optionally the minimum amount are set.

In addition, the control unit 140 controls the transport unit 120 to transport the recording medium 200 and controls the ink jet head 110 so that an image included in the print information is formed on the recording medium 200. The ink droplets of the present invention are ejected from the nozzle 111. At this time, the control unit 140 adjusts the ink discharge amount of the present invention so that the maximum amount of ink that lands on the unit area of the recording medium 200 does not exceed the set maximum amount. The recording medium may be transported after the maximum amount of ink is set or may be performed before the setting.
In addition, the control unit 140 controls the irradiation unit 130 to irradiate the ink of the present invention landed on the recording medium 200 with an actinic ray to cure the ink. At this time, the control unit 140 controls the inkjet head 110 to eject ink, and land the amount of ink not exceeding the maximum amount on the downstream side of the recording medium 200 to simultaneously form the downstream image. You may begin to do.

  Further, the control unit 140 determines the type of the recording medium to be printed from the print information received by the data input unit 160 or the recording medium information measured by the measurement unit 170 before setting the maximum amount of ink that can be landed. May be specified.

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

1. 1. Preparation of ink 1-1. Preparation of Pigment Dispersion Dispersant and dispersion medium of the following types and amounts are placed in a stainless beaker, heated and stirred for 1 hour while heating on a 65 ° C. hot plate, cooled to room temperature, and then added with pigment. And 200 g of zirconia beads having a diameter of 0.5 mm were placed in a glass bottle and sealed tightly. Thereafter, the dispersion treatment was carried out with a paint shaker until the desired particle size was achieved, and then the zirconia beads were removed to prepare a yellow pigment dispersion, a magenta pigment dispersion, a cyan pigment dispersion and a black pigment dispersion, respectively.

(Material for yellow pigment dispersion)
Dispersant 1: EFKA7701 (manufactured by BASF) 5.6 parts by mass Dispersant 2: Solsperse 22000 (manufactured by Nippon Lubrizol Co., Ltd.) 0.4 parts by mass Dispersion medium: tripropylene glycol diacrylate (containing 0.2% UV-10) 80.6 parts by mass Pigment: PY185 (manufactured by BASF, Paliotor Yellow D1155) 13.4 parts by mass

(Material for magenta pigment dispersion)
Dispersant: JET-9151 (manufactured by BYK) 11 parts by mass Dispersion medium: Tripropylene glycol diacrylate (containing 0.2% UV-10) 69 parts by mass Pigment: PV19 / PR202 (manufactured by BASF, D4500J) 20 parts by mass

(Cyan pigment dispersion material)
Dispersant: JET-9151 (manufactured by BYK) 7 parts by weight Dispersion medium: tripropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by weight Pigment: PB15: 4 (manufactured by Dainichi Seika, Chromofine Blue 6332JC) 23 parts by mass

(Black pigment dispersion material)
Dispersant: JET-9151 (BYK) 7 parts by weight Dispersion medium: Tripropylene glycol diacrylate (containing 0.2% UV-10) 70 parts by weight Pigment: PB7 (Mitsubishi Chemical Corporation, MA-7) 23 parts by weight Part

1-2. Preparation of ink According to the composition of the ink described in Table 1 and Table 2 below, the following components and the pigment dispersion were mixed, heated to 80 ° C. and stirred. The obtained solution was heated and filtered through a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVATEC to prepare yellow ink, magenta ink, cyan ink and black ink constituting ink set 1 and ink set 2, respectively. .

(Ink material)
Pigment dispersion Y: Yellow pigment dispersion prepared above Pigment dispersion M: Magenta pigment dispersion prepared above Pigment dispersion C: Cyan pigment dispersion prepared above Pigment dispersion Bk: Black pigment dispersion prepared above Gelation Agent 1: Ketone wax represented by the general formula (G1) (Kao Wax T1 manufactured by Kao Corporation)
Gelling agent 2: ester wax represented by general formula (G2) (manufactured by NOF Corporation, Unistar M-2222SL)
Gelling agent 3: ester wax represented by general formula (G2) (manufactured by NOF Corporation, behenyl stearate)
Photopolymerizable compound 1: Tripropylene glycol diacrylate Photopolymerizable compound 2: Polyethylene glycol # 600 diacrylate Photopolymerizable compound 3: 6EO modified trimethylolpropane triacrylate Photopolymerizable compound 4: 3PO modified trimethylolpropane triacrylate Light Polymerizable compound 5: Polyester acrylate oligomer having an average functional group number of 8 (ETERCURE 6361-100, manufactured by ETERNAL CHEMICAL)
Photopolymerizable compound 6: Polyester acrylate oligomer having an average functional group number of 2 (Sartomer, CN2270)
Photopolymerizable compound 7: amine-modified acrylate oligomer (Sartomer, CN371)
Photopolymerization initiator 1: Acylphosphine oxide radical polymerization initiator (manufactured by BASF, IRGACURE TPO (“IRGACURE” is a registered trademark of the same company))
Photopolymerization initiator 2: Acylphosphine oxide radical polymerization initiator (manufactured by BASF, IRGACURE 819 (“IRGACURE” is a registered trademark of the same company))
Photosensitizer 1: 2-Isopropylthioxanthone (ITX)
Photosensitizer 2: Polymer type thioxanthone (manufactured by Lambson, SPEEDCURE 7010-L)
Polymerization inhibitor: manufactured by BASF, IRGASTAB UV10 ("IRGASTAB" is a registered trademark of the company)
Surfactant: Momentive Performance Materials Japan, TSF-4442

2. Image formation Each ink set 1 was loaded into a drum-type ink jet recording apparatus having an ink jet recording head equipped with a piezoelectric ink jet nozzle. As the ink supply system, an ink tank, an ink flow path, a sub ink tank immediately before the ink jet recording head, a pipe with a metal filter, and a piezo head were used. Heat the ink to 90 ° C from the ink tank to the head. A heater was also incorporated in the piezo head, and the ink temperature in the recording head was heated to 90 ° C. A piezo head having a nozzle diameter of 22 μm, a head having a nozzle resolution of 600 dpi and a nozzle array of 1200 dpi was used.

  Using this ink jet recording apparatus, image formation was continuously performed while each recording medium shown in Table 3 and Table 4 was adsorbed onto a drum and conveyed. A voltage is applied in the order of yellow ink, magenta ink, cyan ink, and black ink so that the amount of droplets becomes two size dots of 3.5 pl and 9.0 pl, and recording is performed on a recording medium at 1200 × 1200 dpi. Set the total amount of ink to be ejected on the medium, and for each total amount of ink, the solid image of Blue, Green, Red and 3C, the positive of the word “excellent” of 5 points and 7 points of MS Mincho Negatives (outlined characters) and natural images were printed. The blue solid image was formed by ejecting magenta ink and cyan ink in this order. The green solid image was formed by discharging yellow ink and cyan ink in this order. A red solid image was formed by discharging yellow ink and magenta ink in this order. The characters were formed by discharging black ink. The natural image was formed by discharging all four colors of ink. The temperature of the drum was controlled so that the surface temperature of the substrate in front of the head was 46 ° C. (dpi represents the number of dots per 2.54 cm).

Within 1 second after printing, the LED layer (395 nm, 8 W / cm ² , manufactured by Phoseon Technology) was irradiated to cure the ink layer. The distance from the tube surface of the LED lamp to the recording medium was 50 mm (irradiation width 100 mm in the transport direction). The conveyance speed of the recording medium was 800 mm / sec.

  For ink set 2, image formation was performed in the same manner.

  The recording media used for image formation are shown in Tables 3 and 4. In addition, "basis weight" described in Tables 3 and 4 is a value published by each manufacturer. In addition, the “air permeability” shown in Table 4 is a value measured using a Oken type smoothness / air permeability tester manufactured by Kumagai Riki Kogyo Co., Ltd., and “Beck smoothness” It is the value measured using Kumagai Riki Kogyo Co., Ltd. make and a Beck smoothness tester.

  The “names” shown in Tables 3 and 4 are the names of the recording media in Tables 6 to 11, and the recording media described as “A class paper” in the “Name” of Table 4 are: A recording medium having an air permeability of 100 seconds or more and a Beck smoothness of 200 seconds or more, and a recording medium described as “B class paper” has an air permeability of 100 seconds or more and a Beck smoothness. Is a recording medium having a gas permeability of less than 100 seconds.

3. Evaluation The above-prepared images were evaluated according to the following criteria.

3-1. Odor For each of the images created above, odor sensory evaluation was performed with six panels (subjects) according to the ratings shown in Table 5. The average of the odor intensity of the 6 persons scored was rounded off to the first decimal place, and the evaluation was made according to the following criteria based on that value.

○: Average 3.0 points or less △: Average 3.1 to 3.9 points ×: Average 4.0 points or more

3-2. Gloss The gloss of each of the solid images and natural images created above was visually compared with the gloss of the surface of the recording medium that was not printed.

○: There is almost no difference in gloss between the printed part and the non-printed part. Δ: There is a part that feels a difference in gloss between the printed part and the non-printed part. ×: The difference in gloss between the printed part and the non-printed part is large. Can't stand

3-3. Curability For each solid image created above, a recording medium cut to an appropriate size is placed on the image according to the method described in “JIS Standard K5701-1-6.2.3 Friction Resistance Test”. Then, they were rubbed together under a load. Thereafter, the degree of image density reduction was visually observed and evaluated according to the following criteria.

A: Image change is not recognized at all even after rubbing 100 times or more. ○: When rubbing 100 times or more, the surface is slightly traced, but the density is not lowered and is practically acceptable. Δ: Stage of rubbing 100 times The image density drop is recognized, but it is in a practically acceptable range. X: The image density is unacceptable in practical use because it is clearly reduced by rubbing less than 50 times.

3-4. Character quality Each character image created above was visually observed and evaluated according to the following criteria.

◎: 5-point character negatives and positives can be reproduced without any loss of detail. ○: Some details are slightly crushed with the 5-point character positive, but it can be fully read. Although the details are crushed in the positive, it is fully readable, and the 7-point characters can be reproduced without being crushed. ×: The details are crushed in the negative and positive of the 7-point characters

  Tables 6 to 11 show the type, basis weight, air permeability and Beck smoothness of the recording medium, and the evaluation results for each ejected ink. Tables 6 to 11 show the evaluation results of the images created using the ink set 1, but the same results were obtained for the images created using the ink set 2.

As apparent from Tables 6 to 8, when an image is formed on a recording medium (art paper and coated paper) having a resin coating amount of 20 g / m ² or more, the ink that lands on the unit area of the recording medium. In the case where an image is formed on a recording medium (light coated paper and fine coated paper) having a maximum amount of 20 g / m ² and a resin coating amount of 10 g / m ² or more and less than 20 g / m ² , the recording medium In the case of forming an image on a recording medium (non-coated paper) in which the maximum amount of ink that lands on a unit area is 15 g / m ² and the resin coating amount is 0 g / m ² or more and less than 10 g / m ² When the maximum amount of ink that landed on the unit area of the recording medium was 10 g / m ² , all of odor, gloss, curability and character quality were evaluated highly.

As is apparent from Tables 9 to 11, when an image is formed on a recording medium (A class paper and B class paper) having an air permeability of 100 seconds or more, the maximum amount of ink that lands on the unit area of the recording medium. When an image is formed on a recording medium (C class paper) having a large amount of 20 g / m ² and an air permeability of less than 100 seconds, the maximum amount of ink that lands on the unit area of the recording medium is 10 g / m ² . As a result, all of odor, gloss, curability and character quality were evaluated highly.

Further, when an image is formed on a recording medium (A class paper) having an air permeability of 100 seconds or more and a Beck smoothness of 200 seconds or more, the ink that lands on the unit area of the recording medium. When the image is formed on a recording medium (B class paper) having a maximum amount of 20 g / m ² , an air permeability of 100 seconds or more, and a Beck smoothness of 1 second or more and less than 200 seconds, When the maximum amount of ink that landed on the unit area of the recording medium was 10 g / m ² , all of odor, gloss, curability, and character quality were evaluated highly.

  According to the ink jet recording method of the present invention, it is possible to form an image with a gel ink with a small gloss difference between a region where an image is formed and a region where an image is not formed, regardless of the type of recording medium. Therefore, the present invention is expected to expand the range of application of gel ink by the ink jet method and contribute to the advancement and spread of technology in the same field.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 110 Inkjet head 111 Nozzle 113 Nozzle surface 120 Conveyance part 121 Drive roller 122 Followed roller 123 Conveyance belt 130 Irradiation part 140 Control part 150 Storage part 160 Data input part 170 Measurement part 200 Recording medium

Claims (6)

A step of setting the maximum amount of ink that can land on the unit area of the recording medium with reference to a table that associates the type of recording medium to be recorded with the maximum amount of ink that can land on the unit area of the recording medium. When,
Ink-jet ink droplets containing a photopolymerizable compound and a gelling agent and undergoing a sol-gel phase transition depending on temperature so that an amount of ink-jet ink that does not exceed the maximum amount set in the setting step lands on the recording medium. Is discharged from the nozzles of the inkjet head and landed on the recording medium;
Irradiating the inkjet ink landed on the recording medium with an actinic ray to cure the inkjet ink.   The type of the recording medium is classified based on one or more criteria selected from the coating amount of the resin that the recording medium has, the air permeability of the recording medium, and the Beck smoothness of the recording medium. Item 2. The method according to Item 1. The maximum amount when the coating amount of the resin that the recording medium has is 20 g / m ² or more is 20 g / m ² ;
The maximum amount when the coating amount of the resin that the recording medium has is 10 g / m ² or more and less than 20 g / m ² is 15 g / m ² ;
The method according to claim 1 or 2, wherein the maximum amount when the coating amount of the resin layer is 0 g / m ² or more and less than 10 g / m ² is 10 g / m ² . The maximum amount when the air permeability of the recording medium is 100 seconds or more is 20 g / m ² ;
The method according to claim 1, wherein the maximum amount when the air permeability of the recording medium is less than 100 seconds is 10 g / m ² . When the air permeability of the recording medium is 100 seconds or more and the Beck smoothness of the recording medium is 200 seconds or more, the maximum amount is 20 g / m ² ,
The maximum amount when the air permeability of the recording medium is 100 seconds or more and the Beck smoothness of the recording medium is 1 second or more and less than 200 seconds is 15 g / m ^2. The method described in 1. An ink jet head having a nozzle surface provided with a discharge port of a nozzle, which contains a photopolymerizable compound and a gelling agent, and which can discharge a droplet of an ink jet ink that undergoes a sol-gel phase transition depending on temperature;
A transport unit that transports the recording medium so that the recording medium facing the ink-jet head moves immediately below the ejection port of the nozzle of the ink-jet.
An irradiation unit that irradiates the upper surface of the transport unit with an actinic ray from a light source,
A storage unit that stores a table that associates the type of the recording medium and the maximum amount of ink that can land on a unit area of the recording medium, and the inkjet head, the transport unit, the irradiation unit, and the storage unit; Control unit to control,
With
The control unit sets a maximum amount of ink that can land on a unit area of a recording medium to be recorded with reference to the table stored in the storage unit, and controls the transport unit to control the recording medium. An image forming apparatus that discharges the inkjet ink so that the maximum amount of ink that is conveyed and controls the inkjet head to land on a unit area of the recording medium does not exceed the set maximum amount.

Images