JP2019130715A - Image forming method and image forming apparatus - Google Patents

Abstract

To provide an image forming method that makes it possible to further increase transfer properties of an ink in an intermediate transfer type image forming method using an ink jet ink.SOLUTION: An image forming method includes: forming a precoat layer by applying a precoat agent onto a front surface of an intermediate transfer body; forming an ink layer by applying an ink onto a front surface of the formed precoat layer, according to an ink jet method; and transferring the formed precoat layer and ink layer to a recording medium, where a contact angle of the precoat agent with respect to the ink-landing surface of the intermediate transfer body is less than a contact angle of the ink with respect to the ink-landing surface of the intermediate transfer body, and a viscosity of the precoat agent is lower than a viscosity of the ink.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming method and an image forming apparatus.

  The ink jet method can easily and inexpensively produce an image, and thus has been applied to various printing fields including special printing such as photographs, various printing, marking, and color filters. In particular, the inkjet method is particularly suitable for applications in which various images are formed in small amounts because digital printing is possible without using a plate.

  In the ink jet method, the dot diameter of the landed ink may be displaced depending on the surface roughness of the recording medium on which the ink is landed or the ink absorbability. On the other hand, in the intermediate transfer type image forming method, ink is applied to an intermediate transfer body in which the dot diameter of the landed ink is easily controlled to form an intermediate image, and the intermediate image is transferred from the intermediate transfer body to a recording medium. Therefore, it is expected that the displacement of the dot diameter will be suppressed and a higher definition image can be easily formed.

  In the image forming method of the intermediate transfer method, there is a demand for further increasing the transfer rate of ink from the intermediate transfer member to the recording medium. From the viewpoint of increasing the transfer rate, a method has been developed in which a precoat agent is applied in advance to an intermediate transfer member to form a precoat layer, and the precoat layer is transferred as a release layer together with ink.

  With respect to the precoat agent, Patent Document 1 discloses that a precoat agent containing a specific siloxane compound is applied to an intermediate transfer member having a contact angle with water of 50 degrees or more and 120 degrees or less. It describes that wettability and releasability can be adjusted.

JP 2013-199114 A

  According to the image forming method using the precoat agent as described in Patent Document 1, the precoat agent is sufficiently wetted and spread on the intermediate transfer member, and the dot diameter of the landed ink is controlled, and the ink transfer property is controlled. It is expected that the effect of the precoat agent, which is improved, will be sufficiently exerted.

  However, according to the study by the present inventors, even in the image forming method described in Patent Document 1 using a precoat agent, the dot diameters of the landed inks still vary, and the ink transferability is sufficient. Was not growing.

  The present invention has been made on the basis of the above knowledge, and in the intermediate transfer type image forming method using inkjet ink, the variation in the dot diameter of the landed ink is further suppressed, and the ink transferability is further improved. An object of the present invention is to provide an image forming method that can be enhanced and an image forming apparatus that can perform the image forming method.

  The above-mentioned problems include a step of applying a precoat agent to the surface of the intermediate transfer member, a step of thickening the applied precoat agent, and a step of applying ink to the surface of the thickened precoat agent by an inkjet method. And a process for transferring the thickened precoat agent and ink to a recording medium.

  In addition, the above-mentioned problems include an intermediate transfer member, a precoat agent applying portion that applies a precoat agent to the surface of the intermediate transfer member, a thickening portion that thickens the applied precoat agent, and the thickened precoat. This is solved by an image forming apparatus having an ink application portion for applying ink to the surface of the agent by an ink jet method and a transfer portion for transferring the thickened precoat agent and ink to a recording medium.

  INDUSTRIAL APPLICABILITY According to the present invention, in an intermediate transfer type image forming method using ink-jet ink, an image forming method capable of further suppressing variation in dot diameter of landed ink and further improving ink transferability, and the image An image forming apparatus capable of performing the forming method is provided.

FIG. 1 is a flowchart illustrating an example of an intermediate transfer type image forming method using inkjet ink according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a configuration of an image forming apparatus for carrying out an image forming method according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing the configuration of another image forming apparatus for carrying out the image forming method according to the embodiment of the present invention.

  The inventors of the present invention diligently studied the above problems, and by suppressing the dispersion of the dot diameter of the landed ink by increasing the viscosity of the precoat agent applied to the surface of the intermediate transfer body before applying the ink, and The inventors have conceived that the transferability of ink can be improved, and have further studied to complete the present invention.

  That is, the precoat agent applied in advance to the surface of the intermediate transfer member is usually a low-viscosity liquid and its surface shape is unstable. For this reason, the variation in dot diameter in the image forming method of the intermediate transfer method is such that when the ink droplets land on the surface of the precoat agent, the surface shape of the precoat agent is disturbed due to the impact of the landing, and the ink liquid thus landed It is considered that the droplet shape is also disturbed.

  In addition, when the precoat agent is in a low-viscosity liquid state, the ink that has landed on the surface of the precoat agent may enter the precoat layer formed by applying the precoat agent. When ink penetrates into the precoat layer, the dot diameter of the ink is more likely to vary, and a part of the precoat agent is separated and moved into the ink layer to which the ink is applied. In some cases, the releasability of the layer is lowered and the ink is not sufficiently transferred.

  On the other hand, in this embodiment, the surface shape of the applied precoat agent is stabilized by increasing the viscosity of the precoat agent when ink is landed. This makes it difficult to disturb the shape of the landed ink droplets and makes it difficult for the landed ink to enter the inside of the precoat layer. It is considered that the decrease in the temperature can be suppressed.

  In addition, although it is thought that the same effect is acquired even if a precoat agent with a high viscosity is provided, it is difficult to apply a precoat agent with a high viscosity uniformly. On the other hand, by applying a precoat agent having the same degree of viscosity as that of a normally applied precoat agent, and increasing the viscosity after the application, the variation in the dot diameter and the releasability of the precoat layer can be more easily performed. Reduction can be suppressed.

  Hereinafter, exemplary embodiments of the present invention will be described.

[Image forming method]
FIG. 1 is a flowchart illustrating an example of an intermediate transfer type image forming method using inkjet ink according to the present exemplary embodiment.

  In the present embodiment, first, a precoat agent is applied to the ink landing surface of the surface of the intermediate transfer member (step S110).

  The precoat agent may be applied to at least a region where ink is landed on the ink landing surface. A method for applying the precoat agent is not particularly limited, and a method using a roll coater or a bar coater, an ink jet method, or the like can be used.

  The precoat agent is applied to the ink landing surface, and is smoothed with a scraper or the like as necessary. The thickness of the applied precoat agent is smaller than the thickness of the ink in the formed image from the viewpoint of suppressing a decrease in transferability due to the ink landed in the subsequent step sinking (penetrating) into the precoat layer. For example, it can be 0.5 μm or more and 1.0 μm or less.

  Next, the formed precoat agent is thickened (step S120). A precoat layer is formed by thickening the precoat agent.

  The precoat agent thickening method may be appropriately selected according to the type of the precoat agent applied.

  For example, when the applied precoat agent is a precoat agent that contains a photopolymerizable compound and is cured by irradiation with active light, the precoat agent may be semi-cured by irradiation with active light. The amount of actinic rays irradiated at this time is, for example, 5% or more and 25% or less with respect to the amount of actinic rays for curing an ink containing a photopolymerizable compound and cured by irradiation with actinic rays. Can do.

  Examples of actinic rays include ultraviolet rays, electron beams, α rays, γ rays, and X-rays. From the viewpoint of safety and from the viewpoint that the polymerization and crosslinking can be generated even with a lower energy amount, the active light is preferably ultraviolet rays or electron beams.

  The actinic ray may be applied to the applied precoat agent from the surface side opposite to the intermediate transfer member, or from the back side, which is the intermediate transfer member side, through the intermediate transfer member. May be. The viewpoint that the back side contacting the intermediate transfer body is cured to some extent to suppress the invasion of the landed ink, and the surface side contacting the recording medium at the time of transfer is not cured so much and the deterioration of the adhesiveness at the time of transfer is suppressed. Therefore, it is preferable that the actinic ray is irradiated from the back surface side through the intermediate transfer member.

  Or you may perform the thickening of a precoat agent by removing the liquid component contained in a precoat agent by volatilization etc. by heating. At this time, when the precoat agent contains a dissolved or dispersed thermoplastic resin, the applied precoat agent may be heated to such an extent that the thermoplastic resin is not completely formed.

  Among these, thickening by irradiation with actinic rays is more preferable because thickening can be performed in a shorter time and the amount of volatile organic compound (VOC) generated can be reduced.

  Semi-cured means a state in which the precoat agent is not completely cured and leaves room for further curing, and the precoat agent has a certain degree of flexibility or fluidity. Regardless of the type of precoat agent, when the precoat agent contains a thermoplastic resin, transferability can be improved by heating and softening the precoat layer in a subsequent transfer step. Therefore, the pre-coating agent may be semi-cured to such an extent that the adhesive property of the pre-coating agent to the recording medium at normal temperature is lowered.

The thickening of the precoat agent is preferably performed so that the viscosity of the precoat agent is 1 × 10 ⁴ CP or more and 1 × 10 ⁸ CP or less, and is performed so that the viscosity is 1 × 10 ⁶ CP or more and 1 × 10 ⁷ CP or less. It is more preferable.

  Next, ink is applied to the surface of the applied precoat agent (formed precoat layer) by an inkjet method (step S130).

  The ink is ejected from the ink jet head and is landed on the surface of the applied precoat agent or landed on the surface of the already landed ink. By ejecting and landing ink of a color corresponding to the image to be formed, an ink layer is formed on the surface of the precoat layer, and an intermediate image is formed on the ink landing surface of the intermediate transfer member.

  Finally, the precoat layer and the ink layer formed by applying the ink are transferred to a recording medium (step S140).

  The precoat layer and the ink layer are transferred to the recording medium by pressing an intermediate transfer body having the precoat layer and the ink layer formed on the surface thereof toward the recording medium that has been conveyed.

  From the viewpoint of improving transferability, the precoat layer and the ink layer may be heated by heating a pressure roller or a conveyance unit disposed to face the pressure roller during transfer. In particular, when the precoat agent thickened (semi-cured) by irradiation with actinic rays has a glass transition point, it is possible to enhance transferability by softening the precoat agent by heating. The heating may be any temperature as long as it is not lower than the softening point of the precoat agent and does not cause deformation of the intermediate transfer member and the recording medium. For example, the heated precoat layer and ink layer have a temperature of 100 ° C. or higher and 130 ° C. The following can be done.

  The image forming method according to this embodiment may include a step of completely curing the precoat agent and the ink after the transfer. Complete curing can be performed, for example, by curing the precoat agent and ink by irradiation with actinic rays. In order to further stabilize the dot diameter of the ink, the ink before irradiation is irradiated with an actinic ray having a light amount that does not completely cure the ink to temporarily cure the ink, and the ink after the transfer has a larger amount of light. The ink may be completely cured by reirradiation with actinic rays.

[Precoat agent]
The precoat agent can be, for example, a liquid containing a photopolymerizable compound.

  Examples of the photopolymerizable compound include a radical polymerizable compound and a cationic polymerizable compound. Among these, a cationically polymerizable compound is preferable from the viewpoint of further improving transferability. The photopolymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof.

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

  Examples of monofunctional (meth) acrylates include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, isomustyl (meth) acrylate, isostearyl (Meth) acrylate, 2-ethylhexyl-diglycol (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meta ) Acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (Meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid and t-butylcyclohexyl (meth) acrylate Is included.

  Examples of polyfunctional (meth) acrylates include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene 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, PO adduct di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) acrylate hydroxypivalate, polytetramethylene glycol di (meth) ) Acrylates, bifunctional (meth) acrylates including polyethylene glycol diacrylate and tripropylene glycol diacrylate, and trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, Trifunctional or higher functional (meth) acrylates including dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, glycerin propoxytri (meth) acrylate and pentaerythritol ethoxytetra (meth) acrylate are included.

  The radical polymerizable compound preferably contains (meth) acrylate modified with ethylene oxide or propylene oxide (hereinafter also simply referred to as “modified (meth) acrylate”). The modified (meth) acrylate has higher photosensitivity. Further, the modified (meth) acrylate is more compatible with other components even at high temperatures. Furthermore, since the modified (meth) acrylate has little curing shrinkage, curling of the printed matter during irradiation with actinic rays is less likely to occur.

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

  Examples of the epoxy compounds include 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, vinylcyclohexene monoepoxide, ε-caprolactone modified 3, 4-epoxycyclohexylmethyl 3 ', 4'-epoxycyclohexanecarboxylate, 1-methyl-4- (2-methyloxiranyl) -7-oxabicyclo [4,1,0] heptane, 2- (3,4 -Cycloaliphatic epoxy resins such as epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexanone-meta-dioxane and bis (2,3-epoxycyclopentyl) ether, diglycidyl ether of 1,4-butanediol 1,6-hexanediol di- One type of aliphatic polyhydric alcohol such as lysidyl ether, triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, diglycidyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, ethylene glycol, propylene glycol, and glycerin Or an aliphatic epoxy compound containing a polyglycidyl ether of a polyether polyol obtained by adding two or more kinds of alkylene oxide (such as ethylene oxide and propylene oxide), and di- or bisphenol A or an alkylene oxide adduct thereof. Polyglycidyl ether, di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, And aromatic epoxy compounds including novolac type epoxy resins.

  Examples of the vinyl ether compounds include ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl. Monovinyl ether compounds including ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether, and the like, as well as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol dibi Ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and the like di- or tri-vinyl ether compounds containing a cyclohexane dimethanol divinyl ether and trimethylolpropane trivinyl ether.

  Examples of the oxetane compound include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-normalbutyloxetane, 3 -Hydroxymethyl-3-phenyloxetane, 3-hydroxymethyl-3-benzyloxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, 3 -Hydroxyethyl-3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxy Cetane, 3-hydroxybutyl-3-methyloxetane, 1,4bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} benzene, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane and di [1-ethyl (3-oxetanyl)] methyl ether and the like are included.

  Content of the said photopolymerizable compound in a precoat agent can be 1.0 mass% or more and 97 mass% or less with respect to the total mass of a precoat agent, for example, is 30 mass% or more and 90 mass% or less. It is preferable.

  The precoat agent may further contain a photopolymerization initiator. The photopolymerization initiator may be any one that can initiate the polymerization of the photopolymerizable compound. For example, when the precoat agent has a radically polymerizable compound, the photopolymerization initiator can be a photoradical initiator, and when the precoat agent has a cationically polymerizable compound, the photopolymerization initiator is a photocationic initiator ( Photoacid generator).

  The content of the photopolymerization initiator can be arbitrarily set within a range where the curing of the precoat agent is started by irradiation with actinic rays. For example, the content of the photopolymerization initiator is 0.1% by mass with respect to the total mass of the precoat agent. It can be made 20 mass% or less, preferably 1.0 mass% or more and 12 mass% or less. In addition, when hardening of a precoat agent is started even if there is no photopolymerization initiator, such as when a precoat agent is semi-cured by irradiation of an electron beam, a photopolymerization initiator is unnecessary.

  Alternatively, the precoat agent can be a liquid containing a liquid component such as water and a water-soluble organic solvent and a surfactant, or a liquid having a low surface tension such as silicone oil. In particular, when the ink landing surface of the intermediate transfer member is a silicone resin, a low-viscosity silicone oil is preferable because it easily spreads onto the ink landing surface of the intermediate transfer member.

  The precoat agent may contain components such as polyvalent metal ions and polyvalent organic acids that precipitate or aggregate the color material contained in the ink. These components can precipitate or aggregate the color material in the ink, and can further stabilize the dot diameter of the ink.

[ink]
The ink is not particularly limited as long as it is a normal ink used for image formation by an inkjet method.

(Ink material)
For example, when the ink is a water-based ink, it can contain water and optionally a water-soluble organic solvent. Further, when the ink is a solvent-based ink, it can contain an organic solvent. Further, when the ink is an actinic ray curable ink, it can contain a photopolymerizable compound that polymerizes and crosslinks upon irradiation with an actinic ray and optionally a photopolymerization initiator.

  If necessary, the above ink further includes coloring materials such as dyes and pigments, a dispersant for dispersing the pigment, a fixing resin for fixing the pigment to the substrate, a surfactant, a polymerization inhibitor, and an ultraviolet absorber. An agent and a gelling agent that causes the ink to undergo a sol-gel phase transition by temperature change may be contained. Only one type of the other components may be contained in the ink, or two or more types may be contained in the ink.

  Examples of the water-soluble organic solvent when the ink is a water-based ink include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, alcohol containing sec-butanol and t-butanol, ethylene glycol, diethylene glycol, triethylene Glycerol, hexanetriol, thiodiglycol, 1,2-butanediol, 1,3-butanediol, including glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, and pentanediol , 2-pentanediol, polyhydric alcohols including 1,2-hexanediol and 1,2-heptanediol, ethanolamine, diethanolamine Amines including triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine and tetramethylpropylenediamine; Amides including formamide, N, N-dimethylformamide and N, N-dimethylacetamide, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone and 1,3-dimethyl-2-imidazolidinone Containing heterocyclic compounds, sulfoxides including dimethyl sulfoxide, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether Ter, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether Ether, propylene glycol diethyl ether, dipropylene glycol diethyl ether, ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono Glycol ethers including butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol monoethyl acetate, diethylene glycol monobutyl acetate, triethylene glycol monobutyl ether are included.

  The content of the water-soluble organic solvent when the ink is a water-based ink can be, for example, 5.0% by mass or more and 30% by mass or less with respect to the total mass of the ink.

  Examples of the organic solvent when the ink is a solvent-based ink include a water-soluble organic solvent and a water-insoluble organic solvent that can be used for the water-based ink.

  Examples of the water-insoluble organic solvents include pentane, hexane, i-hexane, heptane, i-heptane, octane, i-octane, and aliphatic hydrocarbons having 5 to 15 carbon atoms and cyclopentane. , Cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, cycloheptane, and cycloaliphatic hydrocarbons having 5 to 15 carbon atoms, cyclohexene, cycloheptene, cyclooctene, 1,1,3,5,7 -C6-C12 containing cyclooctatetraene, cyclododecene-containing cyclic unsaturated hydrocarbon having 5 to 15 carbon atoms, benzene, toluene, ethylbenzene, cumene, o-xylene, m-xylene and p-xylene. The following aromatic hydrocarbons, heptanol, hexanol , Methyl hexanol, ethyl hexanol, heptanol, octanol, decanol, undecyl alcohol, and monovalent alcohol having 5 to 15 carbon atoms, methyl-i-butyl ketone, di-i-butyl ketone, cyclohexanone, methyl Cyclohexanone, cycloheptanone, and cyclooctanone containing 5 to 15 carbon atoms, alicyclic ketones, methyl acetate, ethyl acetate, propyl acetate, i-propyl acetate, butyl acetate, hexyl acetate, amyl acetate, acetic acid -I-amyl, 2-ethylhexyl acetate, methyl propionate, ethyl propionate, butyl propionate, hexyl propionate, amyl propionate, ethyl valerate, ethyl hexanoate, ethyl heptanoate, ethyl octoate, decanoic acid Ester compounds including til, cyclohexyl acetate, cyclooctyl acetate, phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, butyl benzoate, dimethyl phthalate, diethyl phthalate, and dibutyl phthalate, nitroethane, nitropropane, Nitro compounds including nitropentane, nitrobenzene, dinitrobenzene, nitrotoluene, and nitroxylene, nitriles including acetonitrile, benzonitrile, and lactones including γ-butyrolactone and ε-caprolactone.

  The content of the water-insoluble organic solvent when the ink is a solvent-based ink can be, for example, 1.0% by mass or more and 98% by mass or less, and 20% by mass with respect to the total mass of the ink. It is more preferable to set it as 95 mass% or less, and it is still more preferable to set it as 40 mass% or more and 90 mass% or less.

  Examples of the photopolymerizable compound when the ink is an actinic ray curable ink include the compounds exemplified for the precoat agent. The photopolymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof.

  The content of the photopolymerizable compound when the ink is an actinic ray curable ink can be, for example, 1.0% by mass or more and 97% by mass or less, and 30% by mass with respect to the total mass of the ink. % To 90% by mass is preferable.

  The photopolymerization initiator when the ink is an actinic ray curable ink may be any as long as it can initiate polymerization of the photopolymerizable compound. For example, when the ink has a radically polymerizable compound, the photopolymerization initiator can be a photoradical initiator, and when the ink has a cationically polymerizable compound, the photopolymerization initiator is a photocationic initiator ( Photoacid generator).

  The content of the photopolymerization initiator can be arbitrarily set within a range in which the ink is sufficiently cured by irradiation with actinic rays and does not lower the ink ejection property. For example, it can be 0.1 mass% or more and 20 mass% or less, preferably 1.0 mass% or more and 12 mass% or less with respect to the total mass of the ink. In addition, when the ink can be sufficiently cured without a photopolymerization initiator, such as when the ink is cured by electron beam irradiation, the photopolymerization initiator is unnecessary.

  Examples of the coloring material include dyes and pigments. From the viewpoint of forming an image having good weather resistance, the colorant 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 depending on the color of the image to be formed.

  The dispersant need only be capable of sufficiently dispersing the pigment. Examples of the 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 Nonylphenyl ether, and stearylamine acetate are included.

  The content of the dispersant can be, for example, 20% by mass to 70% by mass with respect to the total mass of the pigment.

  Examples of the fixing resin include (meth) acrylic resin, epoxy resin, polysiloxane resin, maleic acid resin, vinyl resin, polyamide resin, nitrocellulose, cellulose acetate, ethyl cellulose, ethylene-vinyl acetate copolymer, urethane resin, Polyester resins and alkyd resins are included.

  The content of the fixing resin can be, for example, 1.0% by mass or more and 10.0% by mass or less with respect to the total mass of the ink. In addition, since the particles can be amorphized to form a self-film, the ink does not necessarily contain a fixing resin.

  Examples of such surfactants include anionic surfactants, including dialkyl sulfosuccinates, alkyl naphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and poly (ethylene glycols). Includes nonionic surfactants including oxyethylene / polyoxypropylene block copolymers, cationic surfactants including alkylamine salts and quaternary ammonium salts, silicone surfactants, and fluorine surfactants It is.

  The content of the surfactant is preferably 0.001% by mass or more and less than 5.0% by mass with respect to the total mass of the ink.

  Examples of the gelling agent include ketone wax, ester wax, petroleum wax, vegetable wax, animal wax, mineral wax, hydrogenated castor oil, modified wax, higher fatty acid, higher alcohol, hydroxystearic acid, N- Fatty acid amides including 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 are included. Of these, ketone wax, ester wax, higher fatty acid, higher alcohol, and fatty acid amide are preferable from the viewpoint of further improving the pinning property of the ink, and the carbon number of carbon chains arranged on both sides of the keto group or the ester group. Are more preferably ketone waxes or ester waxes of 9 to 25.

  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.

(Ink physical properties)
From the viewpoint of further improving the ejection properties from the inkjet head, when the ink is an ink that does not contain a gelling agent, the viscosity of the ink at 40 ° C. is preferably 3 mPa · s or more and 20 mPa · s or less. When the ink is an ink containing a gelling agent, the viscosity of the ink at 80 ° C. is preferably 3 mPa · s or more and 20 mPa · s or less.

  When the ink contains a gelling agent, it preferably has a phase transition temperature at which a sol-gel phase transition is performed at 40 ° C. or higher and 70 ° C. or lower. When the phase transition temperature of the ink is 40 ° C. or higher, the ink quickly thickens after landing on the base material, so that the degree of wetting and spreading can be adjusted more easily. When the phase transition temperature of the ink is 70 ° C. or less, the ink is less likely to gel when ejected from the ejection head whose ink temperature is usually about 80 ° C., so that the ink can be ejected more stably.

  The viscosity at 40 ° C., the viscosity at 80 ° C. and the phase transition temperature of the ink can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink with a rheometer. In the present specification, these viscosities and phase transition temperatures are values obtained by the following method. While the ink was heated to 100 ° C. and the viscosity was measured with a stress-controlled rheometer (manufactured by Anton Paar, Physica MCR301 (cone plate diameter: 75 mm, cone angle: 1.0 °)), a shear rate of 11.7 ( 1 / s), the ink is cooled to 20 ° C. under the condition of a temperature drop rate of 0.1 ° C./s, and a temperature change curve of the viscosity is obtained. The viscosity at 80 ° C. and the viscosity at 25 ° C. are determined by reading the viscosities at 40 ° C. and 80 ° C. in the temperature change curve of the viscosity, respectively. The phase transition temperature is determined as a temperature at which the viscosity becomes 200 mPa · s in the temperature change curve of the viscosity.

[Image forming apparatus]
FIG. 2 is a schematic diagram showing a configuration of an image forming apparatus for carrying out the image forming method. As shown in FIG. 2, the image forming apparatus 1 is an intermediate transfer type image forming apparatus using an inkjet method. The image forming apparatus 1 includes an ink application unit 10, an intermediate transfer unit 20, a conveyance unit 30, a light irradiation unit 40, a cleaning unit 50, a precoat agent application unit 60, and a thickening unit 70.

  As shown in FIG. 2, the ink application unit 10 includes inkjet heads 11Y, 11C, 11M, and 11K, and applies Y (yellow), M (magenta), C (cyan), and K (black) coatings. Ink as an example is discharged to the intermediate transfer unit 20. Since the inkjet heads 11Y, 11C, 11M, and 11K have the same configuration, in the following description, Y, M, C, and K are omitted for convenience.

  The ink ejected from each ink jet head may be a water-type ink containing water and optionally a small amount of an organic solvent as a liquid component, or contains an organic solvent as a liquid component but substantially contains water. A solvent-based ink, or an actinic ray curable ink containing, as a liquid component, a photopolymerizable compound that polymerizes and crosslinks when irradiated with actinic rays such as ultraviolet rays and electron beams. Also good. In the present embodiment, the ejected ink is actinic ray curable ink.

  The intermediate transfer unit 20 includes an intermediate transfer member 21 and three support rollers 22, 23, and 24. The intermediate transfer member 21 is composed of an endless belt, and is stretched around the three support rollers 22, 23, and 24 in an inverted triangular shape.

  Of the three support rollers 22, 23, 24, at least one roller is a drive roller, and rotates the intermediate transfer member 21 in the A direction (clockwise direction in FIG. 2).

  The intermediate transfer member 21 includes benzene such as aromatic polyimide (PI), aromatic polyamideimide (PAI), polyphenylene sulfide (PPS), aromatic polyetheretherketone (PEEK), aromatic polycarbonate, and aromatic polyetherketone. The substrate layer includes a resin having a structural unit including a ring, polyvinylidene fluoride, and a mixture or copolymer thereof. In addition to the base material layer, the intermediate transfer member 21 has rubber, such as silicone rubber (SR), chloropung rubber (CR), nitrile rubber (NBR), and epichlorohydrin rubber (ECO), an elastomer, and an elastic resin on the ink landing surface side. And / or a surface layer containing a fluororesin such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polyvinylidene fluoride (PVDF), and an acrylic resin. , It may have a laminated structure of at least two layers.

  Alternatively, the intermediate transfer member 21 is a polyethylene terephthalate (PET) film, 1,4-polycyclohexylenedimethylene terephthalate film, polyethylene naphthalate (PEN) film, polyphenylene sulfide film, polystyrene (PS) film, polypropylene (PP). Films, polysulfone films, aramid films, polycarbonate films, polyvinyl alcohol films, cellophane, cellulose derivatives such as cellulose acetate, polyethylene (PE) films, polyvinyl chloride films, nylon films, polyimide films, and ionomer films May be.

  When the precoat agent is thickened (semi-cured) by irradiation with actinic rays, the intermediate transfer member 21 has durability against actinic rays such as ultraviolet rays from the viewpoint of suppressing heat generation and deformation due to absorption of actinic rays. Is preferably high, for example, it is preferable to have ultraviolet transparency. In addition, the intermediate transfer member 21 also has an actinic ray such as an ultraviolet ray when the pre-transfer agent is thickened (semi-cured) by irradiating the intermediate transfer member through the intermediate transfer member and irradiating it with an actinic ray. It is preferable to have transparency to the light, for example, ultraviolet ray transparency. For example, the intermediate transfer member 21 preferably has an ultraviolet transmittance of 70% or more.

  Examples of the material of the intermediate transfer member 21 having ultraviolet transparency include polyolefin-based films such as ethylene-tetrafluoroethylene copolymer (ETFE), polyimide film, and polypropylene (PP) film.

  The portions of the intermediate transfer member 21 that are stretched around the support rollers 22 and 24 positioned at the left and right apex portions of the inverted triangle form the landing surfaces of the ink ejected from the respective ink jet heads. The support roller 23 positioned at the lower apex portion of the inverted triangular shape in the intermediate transfer member 21 is a pressure roller that presses the intermediate transfer member 21 toward the transport unit 30 with a predetermined nip pressure, and each inkjet It functions as a transfer unit that transfers an intermediate image formed by landing of ink ejected from the head onto the recording medium S.

  The conveyance unit 30 is formed of a metal drum, and forms a transfer nip by being pressed by the support roller 23. The transport unit 30 has a claw (not shown) that fixes the leading end of the recording medium S. The conveyance unit 30 fixes the leading end of the recording medium S to the claw and rotates counterclockwise in FIG. 2 to convey the recording medium S as an example of the recording medium to the transfer nip.

  The ink ejected from the respective ink jet heads and landed on the surface of the intermediate transfer member 21 is conveyed to the transfer nip between the support roller 23 and the conveying unit 30 as the intermediate transfer member 21 rotates. The ink transported to the transfer nip is transferred to the recording medium S transported by the transport unit 30.

  The light irradiation unit 40 faces a portion of the transport unit 30 on the downstream side of the transfer nip, and irradiates the ink on the recording medium S with an actinic ray to cure the ink. In addition, when the ink discharged from each inkjet head is water-type ink or solvent-based ink, the light irradiation unit 40 is not necessary.

  The cleaning unit 50 is a cleaning roller such as a web roller or a sponge roller, and contacts the downstream portion of the transfer nip in the intermediate transfer body 21. The cleaning unit 50 is driven and rotated under the control of the control unit to remove residual ink (residual applied material) remaining on the intermediate transfer body 21 without being transferred to the paper S in the transfer nip.

  The precoat agent application unit 60 includes a roll coater 61 whose surface is covered with a sponge, and a scraper 62. The roll coater 61 applies a precoat agent to the ink landing surface side of the intermediate transfer member 21. The scraper 62 removes an excessive amount of the precoat agent, smoothes the surface of the applied precoat agent, and forms a precoat layer in which the precoat agent spreads to a predetermined thickness on the ink landing surface side of the intermediate transfer body 21. . The precoat agent application unit 60 may apply the precoat agent by a method using a bar coater or an ink jet method.

  The thickening section 70 is disposed on the downstream side of the precoat agent application section 60 and the upstream side of the ink application section 10 so as to face the intermediate transfer body 21, and cures the precoat agent on the intermediate transfer body 21.

  When the precoat agent is a precoat agent that is cured by irradiation with actinic rays, the thickening portion 70 irradiates the precoat agent on the intermediate transfer body 21 with actinic rays to semi-cure the precoat agent. At this time, the amount of actinic rays irradiated by the thickening portion 70 is smaller than the amount of actinic rays irradiated by the light irradiating portion to cure the ink.

  The thickening portion 70 may irradiate the applied precoat agent with actinic rays from the surface side opposite to the intermediate transfer member 21 as shown in FIG. 2, or as shown in FIG. Alternatively, the intermediate transfer member 21 may be transmitted through the intermediate transfer member 21 and irradiated with actinic rays from the back side, which is the intermediate transfer member 21 side. The viewpoint that the back side in contact with the intermediate transfer member 21 is cured to some extent to suppress the invasion of the landed ink, and the surface side that contacts the recording medium S at the time of transfer is not cured so much that the adhesion at the time of transfer is not lowered. From the above, it is preferable that the thickening portion 70 transmits the actinic ray from the back surface side through the intermediate transfer member.

  Alternatively, the thickening unit 70 may heat the precoat agent on the intermediate transfer body 21 to remove the liquid component in the precoat agent by volatilization or the like, thereby thickening the precoat agent.

  When the thickening unit 70 irradiates the actinic light, the image forming apparatus 1 is applied from the ink applying unit 10 by the active light from the thickening unit 70 between the thickening unit 70 and the ink applying unit 10. Further, it may have an oblique light portion (not shown) for suppressing the ink from curing.

  Hereinafter, although the specific Example of this invention is described with a comparative example, this invention is not limited to these.

[Example 1]
1. 1. Precoat agent and ink 1-1. Precoat agent The following photopolymerizable compound, photopolymerization initiator, polymerization inhibitor, surfactant, and pigment dispersant 1 were mixed, heated to 100 ° C., and stirred. Thereafter, the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare a precoat agent.
Photopolymerizable compound: bis [1-ethyl (3-oxetanyl)] methyl ether (OXT-221) 10 parts by mass Photopolymerizable compound: 3 ′, 4′-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate 90 mass Part Photopolymerization initiator: Dow Chemicals, UV16992 (triarylsulfonium acid) 10 parts by mass

1-2. Ink The following pigment dispersant, photopolymerizable compound, and polymerization inhibitor were placed in a stainless beaker and stirred with heating for 1 hour while heating on a 65 ° C. hot plate.
Pigment dispersant: Azisper PB824 (Ajinomoto Fine Techno Co., Ltd.) 9 parts by mass Photopolymerizable compound: Tripropylene glycol diacrylate 70 parts by mass Polymerization inhibitor: Irgastab UV10 (Ciba Japan Co., Ltd.) 0.02 parts by mass

  After cooling the mixed solution to room temperature, 21 parts by mass of Pigment Red 122 (manufactured by Dainichi Seika, Chromofine Red 6112JC) was added thereto. The mixed solution was put in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm and sealed, and dispersed with a paint shaker for 8 hours. Thereafter, the zirconia beads were removed to prepare a pigment dispersion 1.

The following photopolymerizable compound, photopolymerization initiator, polymerization inhibitor, surfactant, and pigment dispersant 1 were mixed, heated to 100 ° C., and stirred. Thereafter, the obtained liquid was filtered through a # 3000 metal mesh filter under heating and then cooled to prepare ink 1.
Photopolymerizable compound: Polyethylene glycol # 400 diacrylate 34.9 parts by mass Photopolymerizable compound: 4EO-modified pentaerythritol tetraacrylate 15.0 parts by mass Photopolymerizable compound: 6EO-modified trimethylolpropane triacrylate 23.0 parts by mass Light Polymerization initiator: DAROCUR TPO (manufactured by BASF) 6.0 parts by mass Photopolymerization initiator: ITX (manufactured by DKSH Japan) 1.0 part by mass Photopolymerization initiator: DAROCUR EDB (manufactured by BASF) 1.0 part by mass Surfactant: KF-352 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1 part by mass Pigment dispersion 1: 19.0 parts by mass

2. Image Formation An image was formed under the following conditions using an image forming apparatus having the configuration shown in FIG.

  The precoat agent application part had a roll coater whose surface was coated with a sponge and a scraper, and applied any of the precoat agents to form a precoat layer.

The thickened part was a UV-LED light source having a wavelength of 395 nm, and the irradiation intensity was 1.5 mW / cm ² .

  The ink applicator used was a piezo ink jet head, an ink tank, a supply pipe, a front chamber ink tank immediately before the recording head, and a pipe with a filter. As the inkjet head, a piezo head having a nozzle diameter of 24 μm and a resolution of 512 dpi was arranged in a staggered manner, and a line head type inkjet head having a recording resolution of 1200 dpi × 1200 dpi was installed. Ink is loaded into an ink tank connected to the ink jet head, and 3.5 pl of ink 1 per droplet heated to 80 ° C. is ejected at a droplet ejection speed of 6 m / sec. On the surface of the precoat layer. I landed.

  In the image forming apparatus having the configuration shown in FIG. 2, the intermediate transfer member has a base material layer formed from polyimide (PI) and an elastic material formed from silicone rubber formed on the ink landing surface side of the base material layer. Using an endless belt having an axial length of 800 mm and a surface layer formed of perfluoroalkoxyalkane (PFA), three support rollers (one of which is a pressure roller) are inverted triangles Stretched in shape. As the pressure roller, a roller having a diameter of 100 and a rubber pressure of 10 mm was used. The load on the transfer portion by the pressure roller was 80N.

  In the image forming apparatus having the configuration shown in FIG. 3, the intermediate transfer member is formed on the base layer made of polyimide (PI) and having an ultraviolet transmittance of 70% or more, and the ink landing surface side of the base layer. An endless belt having an axial length of 800 mm having an elastic layer formed from the formed silicone rubber and a surface layer formed from perfluoroalkoxyalkane (PFA) was used. One was stretched in an inverted triangle shape on the pressure roller. As the pressure roller, a roller having a diameter of 100 and a rubber pressure of 10 mm was used. The load on the transfer portion by the pressure roller was 80N.

  The transport unit was a metal drum with a triple cylinder for a printing press, and used a drum that sucks and holds a recording medium by an air suction chuck and transports the recording medium.

The light irradiation unit used a UV-LED light source with a wavelength of 395 nm, and the irradiation intensity was 5 mW / cm ² .

Recording medium, (manufactured by OK top coat rice basis weight of 84.9g / ^{m 2,} Oji Paper Co., Ltd.) coated printing paper A, coated printing paper B (New Age rice basis weight of 104.7g / ^{m 2,} Oji Paper Co., Manufactured) and art paper (SA Kanofuji, US basis weight 104.7 g / m ² , manufactured by Oji Paper Co., Ltd.).

  Each recording medium was conveyed to this image forming apparatus at 600 mm / s to form ten 30 cm × 30 cm solid images and a 10% density halftone image.

2-1. Test 1
Using the image forming apparatus having the configuration shown in FIG. 2, the precoat agent 1 is applied from the precoat agent application portion, and the actinic rays are irradiated from the surface side of the applied precoat agent from the thickening portion. Was semi-cured to form a precoat layer, and ink 1 was loaded into an ink tank communicating with the inkjet head to form the image.

2-2. Test 2
Using the image forming apparatus having the configuration shown in FIG. 3, the precoat agent 1 is applied from the precoat agent application part, and the intermediate transfer member is transmitted from the thickened part through the intermediate transfer member from the back side of the precoat agent. The precoat agent 1 was semi-cured to form a precoat layer, and the ink 1 was loaded into an ink tank communicating with the inkjet head to form the image.

2-3. Test 3
Using the image forming apparatus having the configuration shown in FIG. 2, the precoat agent 1 is applied from the precoat agent application portion, and the precoat agent 1 is not semi-cured without irradiating actinic rays from the thickening portion, and the inkjet head Ink 1 was loaded into an ink tank communicating with No. 1, and the image was formed.

2-4. Test 4
Using the image forming apparatus having the configuration shown in FIG. 2, the precoat agent was not applied from the precoat agent application unit, and ink 1 was loaded into an ink tank communicating with the inkjet head to form the image.

3. Evaluation Images formed on the above three types of recording media were evaluated according to the following criteria. In each test, the same evaluation was obtained for images formed on any recording medium.

3-1. Color blur The shape of the dots in the halftone part was observed.
○: No dot bleed △: The dot boundary bleeds but there is no practical problem ×: The dot bleed is large and is not practical

3-2. Transferability The transferability of a solid image was evaluated from the remaining amount on the image and the transfer body.
◎: No pre-coating agent remains ○: Pre-coating agent remains, but almost no ink remains △: Ink remains on the transfer body (transfer rate 70% or more)
X: Residual ink remains on the transfer body (transfer rate is less than 70%)

3-3. Dot diameter The dot diameter of the halftone part was measured.
○: The dot size is 50 μm or more and 70 μm or less. ×: The dot size exceeds the above range.

  For Test 1 to Test 4, whether or not a precoat agent was applied, the amount of actinic light irradiated to thicken the precoat agent (ratio (%) to the amount of actinic light irradiated to cure the ink) and the irradiation direction, The evaluation results are shown in Table 1.

  Test No. 1 in which ink was applied after thickening the precoat agent applied to the intermediate transfer member. Nos. 1 and 2 had little color blur, high transferability, and a stable dot diameter.

  In particular, Test No. 1 in which the precoat agent was thickened by irradiation with actinic rays from the back side of the intermediate transfer member. No. 2 was more transferable.

[Example 2]
Test No. 1 of Example 1 except that the precoat agent was heated to 40 ° C. or 100 ° C. from the pressure roller during transfer and the amount of actinic rays irradiated from the thickened portion was changed. Test 11 to Test 20 were performed under the same conditions as in 1.

  For Test 11 to Test 20, Table 2 shows the heating temperature during transfer, the amount of actinic light irradiated from the thickened part (ratio (%) to the amount of actinic light irradiated to cure the ink), and the evaluation results. Shown in

  When the temperature at the time of transfer was made higher than the softening point of the resin contained in the precoat agent, a decrease in transferability was suppressed even when the amount of actinic rays irradiated from the thickened portion was increased.

  The evaluations of “color blur” and “dot diameter” in Test 16 to Test 20 were both within the range of the standard “◯”, but Test 19 and Test 20 were more colored than Test 16 to Test 18. It was confirmed that there was little blurring and the variation in dot diameter was further suppressed.

  When the image forming method and the image forming apparatus of the present invention are used, the transferability of ink in the intermediate transfer type image forming method using inkjet ink can be improved. Therefore, the present invention is expected to broaden the range of application of the intermediate transfer type image forming method using inkjet ink and contribute to the advancement and spread of the technology in this field.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Ink application part 11 Inkjet head 20 Intermediate transfer part 21 Intermediate transfer body 22 Support roller 23 Support roller 24 Support roller 30 Conveyance part 40 Light irradiation part 50 Cleaning part 60 Precoat agent provision part 61 Roll coater 62 Scraper 70 Increase Sticky part

Claims (8)

Applying a precoat agent to the surface of the intermediate transfer member;
A step of thickening the applied precoat agent;
A step of applying ink to the surface of the thickened precoat agent by an inkjet method;
Transferring the thickened precoat agent and ink to a recording medium;
Having
Image forming method. The precoat agent is a precoat agent that contains a photopolymerizable compound and is cured by irradiation with actinic rays,
The image forming method according to claim 1, wherein the step of increasing the viscosity of the precoat agent is a step of semi-curing the precoat agent by irradiating the applied precoat agent with actinic rays. The intermediate transfer member has transparency to actinic rays,
The image forming method according to claim 2, wherein the step of increasing the viscosity of the precoat agent is a step of irradiating the applied precoat agent with an actinic ray transmitted through the intermediate transfer member from the back surface side, which is the intermediate transfer member side. .   The image forming method according to claim 1, wherein the ink contains a photopolymerizable compound and is cured by irradiation with actinic rays. The precoat agent is a precoat agent that contains a photopolymerizable compound and is cured by irradiation with actinic rays,
The ink is an ink that contains a photopolymerizable compound and is cured by irradiation with actinic rays,
The step of thickening the precoat agent is a step of semi-curing the precoat agent by irradiating the applied precoat agent with actinic rays,
After the step of transferring the thickened precoat agent and ink to a recording medium, the step of curing the ink by irradiating the transferred ink with actinic rays,
The amount of the active light irradiated in the step of semi-curing the precoat agent is less than the amount of the active light irradiated in the step of curing the ink,
The image forming method according to claim 1. The coating agent after the thickening in the step of thickening has a glass transition point,
The transferring step is performed at a temperature higher than the glass transition point of the thickened coating agent.
The image forming method according to claim 1.   The image forming method according to claim 1, wherein the intermediate transfer member has a laminated structure of at least two layers. An intermediate transfer member;
A precoat agent application portion for applying a precoat agent to the surface of the intermediate transfer member;
A thickening portion for thickening the applied precoat agent;
An ink application portion for applying ink to the surface of the thickened precoat agent by an inkjet method;
A transfer portion for transferring the thickened precoat agent and ink to a recording medium;
Having
Image forming apparatus.

Images