JP2012091387A - Image forming device, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording method high in image uniformity among recording media even when not only a non-absorptive recording medium but also an absorptive recording medium is used, which is capable of suppressing the occurrence of unevenness of line width or color unevenness due to mixing between liquid droplets.SOLUTION: The image forming device includes a conveying unit of a recording medium 2, a pretreatment agent giving unit 3 giving a colorless pretreatment agent including an active energy-ray curable material to the recording medium conveyed by the conveying unit, an ink discharging unit 4 for discharging an ink including the active energy-ray curable material and a color material to the recording medium after pretreatment, and a curing unit 5. The colorless pretreatment agent contains a wax component solid at normal temperature. Moreover, the giving unit includes a temperature adjusting member 6, and the pretreatment agent is given to the recording medium at a temperature equal to or higher than the melting point of the wax component solid at normal temperature in the pretreatment agent.

Description

  The present invention relates to an image forming apparatus using an ink jet system in a copying machine, a printer, a facsimile, or the like.

2. Description of the Related Art Conventionally, an image forming method using an ink jet recording method is known as a copying machine, a printer, a facsimile, or the like.
The ink jet recording technique is a technique that uses a pressure on-demand system, a charge control system, or the like to form ink droplets through fine nozzles and attach them to a recording medium such as paper according to image information. Such an ink jet recording technique is suitably used for image forming apparatuses such as printers, facsimiles, and copying machines. Inkjet recording technology allows images to be formed by directly attaching ink to a recording medium. Therefore, compared to indirect recording using a photoconductor such as electrophotographic recording, recording can be performed with a simple apparatus configuration. Further development is expected as a recording method.

  Such an ink jet recording method is a low-noise printing method, and according to an image signal, ink is directly ejected onto a printing material (recording medium) such as paper, cloth, and a plastic sheet to print characters, images, and the like. The method of printing (also called a direct discharge method) is the mainstream. In addition, since the inkjet recording method does not require a plate for printing, an efficient printed matter can be produced even with a small number of copies, and is a printing method expected from industrial applications. In order to use it for industrial purposes, it is necessary to form an image on various recording media, but the current mainstream direct discharge method cannot satisfy this. That is, the ink jet recording by the direct discharge method is an image forming method in which the limit of the recording medium is large.

One specific limitation is the effect of ink absorbency of the recording medium.
The ink used in the ink jet recording method is mostly a liquid component, and therefore the difference in the absorption and permeability of the recording medium with respect to the ink affects the image reproducibility. In particular, when a recording medium that does not absorb liquid (non-ink-absorbing) is used, ink droplets printed adjacently are mixed (bleeding), and ink droplets that have landed first are attracted to ink droplets that have landed later. Image formation is very difficult due to the tendency to beaded (beading), and furthermore, penetrating drying cannot be used, and evaporation drying results in problems such as set-off when superimposed, especially high speed. It becomes impossible to ensure the drying property. On the other hand, for example, there is a method of printing on a non-absorbable recording medium by using an ink containing an ultraviolet curable resin and irradiating it with ultraviolet rays to solidify after printing.

For example, in Patent Document 1, ultraviolet curable ink is applied as an ink, and ultraviolet curable color ink dots ejected onto a recording medium are irradiated with ultraviolet rays in accordance with the respective ejection timings to increase the viscosity, thereby adjacent dots. Ink jet recording methods have been proposed in which pre-curing is carried out to such an extent that they are not mixed with each other, and then UV-irradiated to further cure.
However, in the method described in Patent Document 1, bleeding is suppressed, but there remains a problem that images between various recording media differ, and line width non-uniformity caused by mixing between droplets remains. It is insufficient for eliminating color unevenness.

In Patent Document 2, a wax layer is formed on a recording medium by applying wax on the recording medium in order to prevent image disturbance due to color material movement even when ink is ejected onto the recording medium. An image forming apparatus is disclosed in which an aggregating agent is applied and then ink is ejected from an ink head onto a recording medium to aggregate the pigment in the ink.
In this method, a wax is used as a pretreatment agent, and further, after adding an aggregating treatment agent, the ink is ejected after drying, and a wax layer is used as a binder for the aggregating treatment. And an operation for assigning each of them.

Further, in Patent Document 3, a radiation-curable white ink is uniformly applied as an undercoat layer on a transparent or translucent non-absorbent recording medium, solidified or thickened by irradiation, and then a radiation-curable color. Techniques have been proposed for improving the problems of color ink visibility, bleeding, and image differences between various recording media by performing ink jet recording using an ink set.
However, the method described in Patent Document 3 is insufficient to eliminate non-uniform line width and color unevenness caused by mixing between droplets.

As a means for solving such a problem, there is a technique for preventing bleeding and mixing between droplets by applying a UV curable clear liquid as an undercoat layer on a recording medium and discharging colored ink there. .
For example, in Patent Document 4, a photocurable undercoat liquid is applied onto a recording medium in order to suppress the occurrence of non-uniform line width and color unevenness due to mixing between droplets. An ink jet recording method has been disclosed in which an image is recorded by ejecting ink that is cured by irradiation of active energy rays onto the surface of a semi-cured undercoat liquid after being brought into a semi-cured state by irradiation. This method prevents the deterioration of the surface state of the coated surface that may occur in the step of applying the undercoat liquid onto the recording medium so that high-quality image formation can be performed. The undercoat layer is semi-cured to prevent excessive spreading of ink droplets, but the curing conditions to create this semi-cured state are difficult, causing unevenness such as complete curing or hardly curing. There is a problem that the unevenness of ink droplets is caused by this unevenness.

  In order to prevent this, a technique for ejecting ink to an uncured layer has also been proposed (Patent Document 5). The ink droplets ejected on the uncured undercoat layer are gradually spread, but the droplets are not bonded or smeared under the influence of the undercoat layer.

These means are effective means for a recording medium that does not absorb liquid (non-ink-absorbing). For example, they absorb liquid such as coated paper for printing, but are difficult to absorb (hard ink). Absorption) In the recording medium, there is a problem that the pretreatment liquid for the undercoat layer is absorbed and absorbed by the recording medium.
That is, there is a risk that the means can be used only with a non-absorbable recording medium.
Regardless of the absorption characteristics of the medium with respect to ink, there is no technique for eliminating the non-uniformity of line width and color unevenness caused by mixing between droplets.

The present invention aims to solve the above problems, and more specifically, the image uniformity between recording media is not limited to non-absorbent recording media, even when an absorbent recording medium is used. An object of the present invention is to provide an image forming apparatus of an ink jet recording system that can suppress the occurrence of non-uniform line width and color unevenness due to ink bleeding and mixing between droplets. Let it be an issue.
In order to solve the above problems, the image forming apparatus of the present invention has a configuration as described below.

(1) Recording medium conveying means, pretreatment agent applying means for applying a colorless pretreatment agent containing an active energy ray curable material to the recording medium conveyed by the conveying means, and active energy ray curable material In addition, in the image forming apparatus having the ink discharge means for discharging the ink containing the color material onto the pre-processed recording medium, and the curing means, the colorless pre-treatment agent contains a wax component that is solid at room temperature, The image forming apparatus is characterized in that the applying unit includes a temperature adjusting unit, and the preprocessing agent is applied to the recording medium at a temperature equal to or higher than the melting point of the wax component that is solid at room temperature in the preprocessing agent.
(2) The image forming apparatus according to (1), further comprising a cooling unit for cooling the recording medium in a conveyance path of the recording medium between the pretreatment agent applying unit and the ink discharge unit.
(3) The image forming apparatus according to (1) or (2), wherein the pretreatment agent application unit is an inkjet discharge unit.

According to the aspect (1) of the present invention, the pretreatment agent containing a wax component that is solid at room temperature is heated to a temperature equal to or higher than the melting point of the wax component and applied to the recording medium, thereby providing a uniform application in a thin layer. Furthermore, by increasing the viscosity on the recording medium, the penetration of the pretreatment agent is suppressed even in the absorbent recording medium, and the uncured pretreatment agent layer is maintained from printing to curing. Therefore, uniform dots without bleeding can be formed, and a high-quality image can be formed.
Moreover, according to the said aspect (2) of this invention, the viscosity of the pre-processing agent after provision on a recording medium can be reliably performed with a cooling means.
Furthermore, according to the aspect (3) of the present invention, if the pretreatment agent contains a wax component, the viscosity can be lowered by adjusting the temperature to a temperature equal to or higher than the melting point of the wax. As a means for applying to the ink, it is possible to apply a pretreatment agent with a general ink jet head. In addition, after discharging, the wax component solidifies and thickens by contact with the recording medium and is cooled, thereby suppressing the permeation rate of the pretreatment liquid even from an absorbent recording medium, from printing to curing Since a thin layer of the pretreatment agent can be maintained on the recording medium for a time level required for this time, uniform dots without bleeding can be formed, and a high-quality image can be formed. Further, since the ejection head can apply the pretreatment agent to the recording medium in a non-contact manner, even if the head is heated to a temperature exceeding the melting point of the wax component of the pretreatment agent, the heat is recorded on the recording medium. This is advantageous in maintaining the temperature of the recording medium at room temperature.

1 is a diagram illustrating one aspect of an image forming apparatus of the present invention. It is a figure which shows the detail of the pretreatment agent provision means in this invention. It is a figure which shows the relationship between the temperature of a wax containing pretreatment agent and the pretreatment agent which does not contain wax, and a viscosity. It is the figure which plotted the relationship between the viscosity of the liquid which passes between the application roller and supply roller shown in FIG. 2, and a passage liquid film thickness. It is a figure which shows the relationship between the thickness of a pretreatment agent layer, and a dot diameter. It is a figure which shows the other aspect of the image forming apparatus of this invention. It is a figure which shows one aspect | mode of the cooling means used in the image forming apparatus of this invention. It is a figure which shows the other aspect of the cooling means used in the image forming apparatus of this invention. It is a figure which shows the example which used the discharge head as a provision means of a pretreatment agent.

An example of an image forming method by the image forming apparatus according to the present invention will be described with reference to FIG.
The recording medium 2 is transported and fed from the paper supply means 1 to a pretreatment agent application section having a pretreatment agent application means 3, where the pretreatment agent is applied to the surface of the recording medium to form a pretreatment agent layer. The Thereafter, ink droplets are ejected from the ink ejection head 4 to the uncured pretreatment agent layer in accordance with the image pattern in the ink ejection unit, and the curing unit 5 that irradiates active energy rays in the curing unit, and the pretreatment agent and the ink. Are cured simultaneously.

Here, the pretreatment agent contains a wax component that is solid at room temperature, and the pretreatment agent application means is provided with a temperature adjustment means 6 for adjusting the temperature to be equal to or higher than the melting point of the wax component. ing.
After the pretreatment agent is applied by the pretreatment agent application means, the pretreatment agent is cooled on the recording medium, so that the viscosity of the pretreatment agent increases rapidly. It is possible to prevent the pretreatment agent from penetrating into the recording medium after the pretreatment agent is applied and before ink ejection after the pretreatment agent is applied. For this reason, it is possible to stably maintain an uncured pretreatment agent layer even on an absorbent recording medium, which causes problems such as non-uniform line width and color unevenness due to mixing between droplets. No image can be obtained.

FIG. 2 shows details of the pretreatment agent applying means 3. The pretreatment agent applying means 3 includes a container 9 that holds the pretreatment agent 8, a supply roller 10 that is partially immersed in the container 9, and an application roller that contacts the supply roller 10 with an appropriate pressure. 11 and an opposing roller 12 for bringing the recording medium 2 into contact with the application roller 11 when applying to the recording medium 2. Further, a heater 13 is built in the supply roller 10, and the temperature of the supply roller 10 can be controlled in combination with a temperature detection means (not shown). The amount of the pretreatment agent pumped up by the supply roller 10 is regulated by the pressure of both rollers at the nip portion with the application roller 11, and a thin layer of the pretreatment agent is formed on the application roller 11. The recording medium 2 is pressed against the application roller 11 and conveyed, whereby the pretreatment agent 8 is applied to the recording medium 2 and a thin layer of the pretreatment agent is formed on the surface. The application amount is determined by the viscosity of the pretreatment agent and the pressure at the nip portion of the application roller 11 and the supply roller 10.
Since the viscosity of the pretreatment agent can be lowered by adjusting the temperature of the supply roller 10 so that the temperature exceeds the melting point of the wax component contained in the pretreatment agent, the amount of the pretreatment agent can be reduced. Granting is possible.

FIG. 3 is a graph showing the relationship between the temperature and viscosity of a wax-containing pretreatment agent and a wax-free pretreatment agent, and shows that the viscosity of the pretreatment agent rapidly decreases when the melting point of the wax is exceeded. ing.
FIG. 4 is a plot of the relationship between the viscosity of the liquid passing between the rollers and the film thickness of the passing liquid.
According to the elastohydrodynamic lubrication theory, the passing film thickness varies depending on the viscosity of the liquid, and the passing film thickness is proportional to the 0.6th power of the viscosity of the liquid. When the viscosity is high, coating in a thin layer becomes difficult. As the application means, the pressure-controlled roller method application method is simple in structure and can be applied uniformly in the width direction, so it is a general means, but the application amount depends on the viscosity of the liquid. There is a problem that changes drastically.

  For example, when the wax-containing pretreatment agent was applied at 60 ° C., the viscosity was about 10 mPa · s, and the amount applied to the recording medium by the applying means was about 2 μm in average film thickness. When this is applied at room temperature and 25 ° C., the viscosity is about 200 mPa · s, the application amount by the application means becomes an average film thickness of 10 μm or more, and application in a thin layer becomes difficult.

  If a pretreatment agent having a viscosity of about 10 mPa · s at room temperature and 25 ° C. is used, an average film thickness of about 2 μm can be applied. In this case, the viscosity of the pretreatment agent on the recording medium after application is possible. Is still about 10 mPa · s, the penetration speed into the recording medium is fast, the average film thickness changes due to the penetration before the image is printed, and the thickness of the pretreatment agent on the recording medium is not sufficient An area is formed, or the thickness of the pretreatment agent is uneven due to uneven absorption of the recording medium. FIG. 5 is a diagram showing the relationship between the thickness of the pretreatment agent layer and the dot diameter. As shown in FIG. 5, the thickness of the pretreatment agent layer affects the way the ink spreads. The thinner the film thickness, the easier the ink droplets to spread, and the thicker the ink, the more difficult it is to spread. Therefore, when the pretreatment agent is absorbed by the recording medium, unevenness in the absorption causes unevenness in the layer thickness of the pretreatment agent, affects the image as the size of the dot diameter, and causes unevenness.

  In the example shown in FIG. 1, an example in which three applying rollers are used as the applying unit has been described. However, the present invention is not limited to this, and applying units having various configurations can be considered. The same applies to the temperature adjusting means associated therewith, and various configurations such as the type and position of the heater and the type and position of the temperature detecting means are conceivable, and any configuration may be used.

  Next, the ink and pretreatment agent used in the image forming apparatus will be described. The pretreatment agent and ink that are cured by absorbing ultraviolet rays, which are a kind of active energy rays, contain at least a polymerizable compound, a photoinitiator, and a coloring material as main components. In addition, additives such as a leveling agent, a reaction accelerator, a reaction inhibitor, and a sensitizer may be included. UV curable inks are broadly classified into radically polymerizable inks containing radically polymerizable compounds and cationically polymerizable inks containing cationically polymerizable compounds as polymerizable compounds. Both types of inks can be applied. There may be used a mixed system thereof.

  In the apparatus of the present invention, a clear material containing no color material is used as a pretreatment agent, and a color ink containing a color material such as black, cyan, magenta, yellow is mainly used. In addition, it is also possible to use a combination of light-color inks that enrich tone expression. Further, the pretreatment agent contains a wax component that is solid at room temperature (about 25 ° C.). The melting point or glass transition point is not particularly specified, but a temperature of about 80 ° C. or lower is desirable in consideration of heating to a temperature higher than that by the applying means. In consideration of curability, the content is preferably 20% by weight or less.

  The wax component that is solid at room temperature (about 25 ° C.) used in the present invention is a substance that is solid (no fluidity) at room temperature (about 25 ° C.) and becomes liquid at 30 ° C. or higher. Any substance can be used as long as it is satisfied. Specifically, pentaerythritol tetrastearate, pentaerythritol distearate, pentaerythritol tristearate, stearyl stearate, stearyl stearate, stearyl stearate, myristyl myristate, cetyl palmitate, ethylene glycol distearate, behenyl alcohol, Microcrystalline wax, paraffin wax, hydrocarbon wax, fatty acid alkyl ester, polyol fatty acid ester, mixture of fatty acid ester and wax, fatty acid ester mixture, glycerin monopalmitate (/ stearic acid monoglyceride), glycerin mono distearate (/ glycerin stearate) Rate), glycerin monoacetomonostearate (/ glycerin fatty acid ester), succinic fat Monoglyceride (/ glycerin fatty acid ester), citric acid saturated aliphatic monoglyceride, sorbitan monostearate, sorbitan fatty acid ester, sorbitan tribehenate, propylene glycol monobehenate (/ propylene glycol fatty acid ester), stearate of pentaerythritol polymer adipic acid Rate, pentaerythritol tetrastearate, dipentaerythritol hexastearate, stearyl citrate, pentaerythritol fatty acid ester, glycerin fatty acid ester, ultralight rosin, rosin-containing diol, ultralight rosin metal salt, hydrogenated petroleum resin, rosin ester, Hydrogenated rosin ester, special rosin ester, novolak, crystalline polyalphaolefin, polyalkylene glycol, polyalkylene group Call esters, and the like as a main component a polyoxyalkylene ether.

  Examples of the epoxy compound used in the cationic polymerization type ink of the present invention include bisphenol A type epoxy, bisphenol BA type epoxy, bisphenol F type epoxy, bisphenol AD type epoxy, phenol novolac type epoxy, cresol novolac type epoxy, alicyclic epoxy, Fluorene type epoxy, naphthalene type epoxy, glycidyl ester compound, glycidyl amine compound, heterocyclic epoxy, α-olefin epoxy and the like can be mentioned.

In particular, the alicyclic epoxy compound can be suitably applied to the cationic polymerization type ink composition of the present invention having a low viscosity and a high curing rate. For example, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate and its epsilon-caprolactone modification, bis- (3,4 epoxycyclohexylmethyl) adipate, 1,2: 8,9 diepoxy Limonene and vinylcyclohexene monooxide 1,2-epoxy-4-vinylcyclohexane can be preferably used.
The oxetane compound used in the cationic polymerization type ink of the present invention may be appropriately selected according to the properties required for the ink, and in particular when 3-ethyl-3- ( Phenoxymethyl) octacene can be preferably used.

  The cationic polymerization type ink of the present invention can be mixed with a vinyl ether compound as necessary. Examples of vinyl ethers that can be suitably added include 2-ethylhexyl vinyl ether, butanediol-1,4-divinyl ether, cyclohexanedimethanol monovinyl ether, diethylene glycol monovinyl ether, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, dipropylene glycol divinyl ether, dodecyl vinyl ether, Ethyl vinyl ether, hexanediol divinyl ether, hydroxybutyl vinyl ether, hydroxyethyl vinyl ether, isobutyl vinyl ether, methyl vinyl ether, octadecyl vinyl ether, propyl vinyl ether, triethylene glycol divinyl ether, vinyl 4-hydroxybutyl ether, vinyl cyclohexyl ether Ether, vinyl propionate, vinyl carbazole, Binirubiroridon and the like.

  As the reactive component of the cationic polymerization type ink of the present invention, propenyl ether and butenyl ether can be blended as necessary. For example, 1-dodecyl-1-propenyl ether, 1-dodecyl-1-butenyl ether, 1-butenoxymethyl-2-norbonene, 1-4-di (1-butenoxy) butane, 1,10-di (1-butenoxy) Decane, 1,4-di (1-butenoxymethyl) cyclohexane, diethylene glycol di (1-butenyl) ether, 1,2,3-tri (1-butenoxy) propane, propenyl ether propylene carbonate, and the like can be suitably applied.

  The cationic polymerization initiator applicable to the cationic polymerization type ink of the present invention may be any compound that generates a substance that initiates polymerization upon receiving energy rays such as ultraviolet rays, and is an onium salt such as arylsulfonium salt or aryl. An iodonium salt can be preferably used. Furthermore, if necessary, photosensitizers such as anthracene compounds such as N-vinylcarbazole, thioxanthone compounds, and 9,10-dibutoxyanthracene can be used in combination.

  The component of the radical polymerization type ink in the present invention is preferably various known radical polymerizable monomers that cause a polymerization reaction with an initiation species generated from a radical polymerization initiator. Examples of the radical polymerizable monomer include (meth) acrylates, (meth) acrylamides, aromatic vinyls, vinyl ethers, and compounds having an internal double bond (such as maleic acid). Hereinafter, monofunctional polymerizable compounds and polyfunctional polymerizable compounds will be exemplified in detail.

  Specific examples of monofunctional (meth) acrylates include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, tert-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) ) Acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-n-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate 2-ethylhexyl diglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyano Chill (meth) acrylate, butoxymethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, alkoxymethyl (meth) acrylate, alkoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 2 -(2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-trifluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butylphenyl (meth) Acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chlorophenyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate, glycidyl (meth) Chlorate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) ) Acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl ( (Meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethyl Rusilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, oligoethylene oxide monomethyl ether (meth) acrylate, polyethylene oxide (meth) acrylate, oligoethylene oxide (meth) acrylate, oligoethylene oxide monoalkyl ether (meth) acrylate, Polyethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl ether (meth) acrylate, oligopropylene oxide monoalkyl ether (meth) acrylate, 2-methacryloyloxyethyl succinic acid, 2- Methacryloyloxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydride Xylpropyl phthalate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, EO-modified phenol (meth) acrylate, EO Examples thereof include modified cresol (meth) acrylate, EO-modified nonylphenol (meth) acrylate, PO-modified nonylphenol (meth) acrylate, EO-modified-2-ethylhexyl (meth) acrylate, and the like.

  Examples of monofunctional (meth) acrylamides that can be used in the radical polymerization type ink used in the present invention include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) ) Acrylamide, Nn-butyl (meth) acrylamide, Nt-butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, (meth) acryloylmorpholine, etc. are mentioned.

  Specific examples of the monofunctional aromatic vinyls that can be used in the radical polymerization type ink used in the present invention include styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, and acetoxy. Styrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3- Butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene, 3-octylstyrene, 4-octylstyrene, 3- (2-ethylhexyl) styrene, 4- (2-ethylhexyl) styrene, allyl styrene Emissions, isopropenyl styrene, butenylstyrene, octenyl styrene, 4-t-butoxycarbonyl styrene, 4-methoxystyrene, and a 4-t-butoxystyrene.

  Examples of monofunctional vinyl ethers that can be used in the radical polymerization type ink used in the present invention include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, Cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxy Ethoxyethyl vinyl ether, Xylethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl Examples include vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, and the like.

  Specific examples of the bifunctional (meth) acrylate include 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and 2,4-dimethyl. -1,5-pentanediol di (meth) acrylate, butylethylpropanediol (meth) acrylate, ethoxylated cyclohexanemethanol di (meth) acrylate, polyethylene glycol di (meth) acrylate, oligoethylene glycol di (meth) acrylate, Ethylene glycol di (meth) acrylate, 2-ethyl-2-butyl-butanediol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, EO-modified bisphenol A di (meth) acrylate Bisphenol F polyethoxydi (meth) acrylate, polypropylene glycol di (meth) acrylate, oligopropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 2-ethyl-2-butylpropanediol di ( Examples include meth) acrylate, 1,9-nonanedi (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, and tricyclodecane di (meth) acrylate.

  Specific examples of trifunctional (meth) acrylates include trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane alkylene oxide-modified tri (meth) acrylate, pentaerythritol tri (meth) acrylate , Dipentaerythritol tri (meth) acrylate, trimethylolpropane tris ((meth) acryloyloxypropyl) ether, isocyanuric acid alkylene oxide modified tri (meth) acrylate, propionate dipentaerythritol tri (meth) acrylate, tris ((meta) ) Acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meth) Acrylate, propoxylated trimethylolpropane tri (meth) acrylate, and ethoxylated glycerin tri (meth) acrylate.

  Examples of polyfunctional vinyl ethers that can be used in the radical polymerization ink used in the present invention include ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, and bisphenol A alkylene. Divinyl ethers such as oxide divinyl ether and bisphenol F alkylene oxide divinyl ether; trimethylol ethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl Ether, dipentaerythritol hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, propylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, propylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether And polyfunctional vinyl ethers such as vinyl ether, propylene oxide-added pentaerythritol tetravinyl ether, ethylene oxide-added dipentaerythritol hexavinyl ether, and propylene oxide-added dipentaerythritol hexavinyl ether.

  As the vinyl ether compound, di- or trivinyl ether compounds are preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and divinyl ether compounds are particularly preferable.

  The colorant that can be used in the present invention is not particularly limited, and can be appropriately selected from known water-soluble dyes, oil-soluble dyes, pigments, and the like. Of these, oil-soluble dyes and pigments that are easily dispersed and dissolved in a water-insoluble medium are preferred.

  Specifically, the photocurable resin monomer accounts for 10 to 70 weight percent in the ink composition, but as an effective one, a relatively low viscosity having an unsaturated double bond capable of radical polymerization in the molecular structure. Resin monomers such as monofunctional 2-ethylhexyl (meth) acrylate (EHA), 2-hydroxyethyl (meth) acrylate (HEA), 2-hydroxypropyl (meth) acrylate (HPA), caprolactone-modified tetrahydrofurfuryl (Meth) acrylate, isobornyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, lauryl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, isodecyl (meth) acrylate, isooctyl (Meta) ak Rate, tridecyl (meth) acrylate, caprolactone (meth) acrylate, ethoxylated nonylphenol (meth) acrylate, bifunctional tripropylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) ) Acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol hydroxypivalate ester di (meth) acrylate (MANDA) and hydroxypivalate neopentyl glycol ester di (meth) acrylate (HPNDA), 1.3-butanediol di ( (Meth) acrylate (BGDA), 1.4-butanediol di (meth) acrylate (BUDA), 1.6-hexanediol di (meth) acrylate (HDDA), 1,9-nonanediol di (meth) acrylate, diethylene glycol di (meth) acrylate (DEGDA), neopentyl glycol di (meth) acrylate (NPGDA), tripropylene glycol di (meth) acrylate (TPGDA), Caprolactone-modified hydroxypivalate neopentyl glycol ester di (meth) acrylate, propoxylated opentyl glycol di (meth) acrylate, ethoxy-modified bisphenol A di (meth) acrylate, polyethylene glycol 200 di (meth) acrylate, polyethylene glycol 400 di ( (Meth) acrylate, polyfunctional trimethylolpropane tri (meth) acrylate (TMPTA), pentaerythritol tri (meth) acrylate (PE) TA), dipentaerythritol hexa (meth) acrylate (DPHA), triallyl isocyanate, (meth) acrylate of ε-caprolactone modified dipentaerythritol, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, ethoxylated tri Methylolpropane tri (meth) acrylate, propoxylated trimethylolpropane tri (meth) acrylate, propoxylated glyceryl tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol hydroxypenta (Meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate, penta (meth) acrylate ester, etc. are preferred

  Specifically, KAYARAD TC-110S, KAYARAD R-128H, KAYARAD R-526, KAYARAD NPGDA, KAYARAD PEG400DA, KAYAARAD MANDA, KAYARAD R-167, KAYARAD HX-220, AD R-712, KAYARAD R-604, KAYARAD R-684, KAYARAD GPO, KAYARAD TMPTA, KAYARAD THE-330, KAYARAAD TPA-320, KAYAARADTPA-330, KAYARAD PET-A, YKARAD RPAR40K DPHA, KAYARAD DPHA 2C, KAYARAD D-310, KAYARAD D-330, KAYARAD DPCA-20, KAYARADDPCA-30, KAYARAD DPCA-60, KAYARAD DPCA-120, KAYARAD DN-0075, KAYARAD DN-2475, KAYAMER PM-2 , KS series HDDA, TPGDA, TMPTA, SR series 256, 257, 285, 335, 339A, 395, 440, 495, 504, 111, 212, 213, 230, 259, 268, 272, 344, 349, 601, 602 610, 9003, 368, 415, 444, 454, 492, 499, 502, 9020, 9035, 295, 355, 399E494, 9041203, 2 08, 242, 313, 604, 205, 206, 209, 210, 214, 231E239, 248, 252, 297, 348, 365C, 480, 9036, 350 (manufactured by Nippon Kayaku), beam set 770 (manufactured by Arakawa Chemical) Etc. can be used.

The vehicle can be used by mixing at least one selected from these, or two or more. All of these have good wettability to a recording medium and have excellent adhesion to a wide variety of adherend materials.
Furthermore, water and a solvent may be added to reduce the viscosity and increase the speed. Any solvent may be used as long as it dissolves all the components of the ink composition and evaporates quickly after printing. The solvent used for this purpose is preferably a ketone and / or alcohol as the main solvent. For example, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, etc. are used alone or as a mixed solvent with water. It is preferable to do this.

The photoinitiator is included in the total vehicle in an amount of 0.01 weight percent to 10 weight percent. For example, there are special groups such as benzoin ether, acetophenone, benzophenone, benzophenone, thioxanthone, acylphosphine oxide, methylphenylglyoxylate, benzoin alkyl ether, benzyl methyl ketal, hydroxycyclohexyl phenyl ketone, p-isopropyl -Α-hydroxyisobutylphenone, 1,1-dichloroacetophenone, 2-chlorothioxanthone and the like are selected.
Examples of the photoinitiator include triethanolamine, ethyl 2-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, and polymerizable tertiary amine.

  Specifically, BYCURE 10, 30, 55 (Stouffer), KAYACURE BP-100, KAYACURE BMS, KAYACURE DETX-S, KAYACURE CTX, KAYACURE 2-EAQ, KAYACURE DMBI, KAYACURE EPA, Japan 184, 907, 369 (Ciba-gigi), Darocur 1173, 1116, 953, 2959, 2273, 1664 (Merck), Sandre 1000 (Sand), Counter Cure CTX, Counter Cure BMS, Counter Cure ITX, Counter Cure PDO, Counter Cure BEA , DMB (Word Brenkin Sopp), Suncure IP, BTTP (Nippon Yushi) and the like are desirable. In addition, a photoinitiator-containing type photocurable resin may be used.

  As the colorant, a pigment that is well dispersed in the vehicle and has excellent weather resistance is desirable. Although not particularly limited, for example, organic or inorganic pigments having the following numbers described in the color index can be used in the present invention.

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

  Specific product names include, for example, chromo fine yellow 2080, 5900, 5930, AF-1300, 2700L, chromo fine orange 3700L, 6730, chromo fine scarlet 6750, chromo fine magenta 6880, 6886, 6891N, 6790, 6887. , Chromofine Violet RE, Chromofine Red 6820, 6830, Chromofine Blue HS-3, 5187, 5108, 5197, 5085N, SR-5020, 5026, 5050, 4920, 4927, 4937, 4824, 4933GN-EP, 4940, 4973, 5205, 5208, 5214, 5221, 5000P, Chromofine Green 2GN, 2GO, 2G-550D, 5310, 5370, 6830, Ku Mofine Black A-1103, Seika Fast Yellow 10GH, A-3, 2035, 2054, 2200, 2270, 2300, 2400 (B), 2500, 2600, ZAY-260, 2700 (B), 2770, Seika Fast Red 8040 , C405 (F), CA120, LR-116, 1531B, 8060R, 1547, ZAW-262, 1537B, GY, 4R-4016, 3820, 3891, ZA-215, Seika Fast Carmine 6B1476T-7, 1483LT, 3840, 3870 , Seika Fast Bordeaux 10B-430, Seica Light Rose R40, Seika Light Violet B800, 7805, Seika Fast Maroon 460N, Seika Fast Orange 900, 2900, Seika Light Blue C7 18, A612, cyanine blue 4933M, 4933GN-EP, 4940, 4973 (manufactured by Dainichi Seikagaku), KET Yellow 401, 402, 403, 404, 405, 406, 416, 424, KET Orange 501, KET Red 301, 302 , 303, 304, 305, 306, 307, 308, 309, 310, 336, 337, 338, 346, KET Blue 101, 102, 103, 104, 105, 106, 111, 118, 124, KET Green 201 (large Nippon Ink Chemical Co., Ltd.), Colortex Yellow 301, 314, 315, 316, P-624, 314, U10GN, U3GN, UNN, UA-414, U263, Finecol Yellow T-13, T-05, Pi gment Yellow 1705, Colortex Orange 202, Colortex Red 101, 103, 115, 116, D3B, P-625, 102, H-1024, 105C, UFN, UCN, UBN, U3BN, URN, UGN, UG276, U456, U457, C USN, Colortex Maroon 601, Colortex Brown B610N, Colortex violet 600, Pigment Red 122, Colortex Blue 516, 517, 518, 519, A818, P-908, 510, Colortex Green 402, 403B, Col. , Lionol lue FG7330, FG7350, FG7400G, FG7405G, ES, ESP-S (manufactured by Toyo Ink), Toner Magenta E02, Permanent RubinF6B, Toner Yellow HG, Permanent Yellow GG-02, HosteBane G2 , # 2400, # 2350, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 850, MCF88, # 750, # 650, MA600, MA7, MA8, MA11, MA100, MA100R , MA77, # 52, # 50, # 47, # 45, # 45L, # 40, # 33, # 32, # 30, # 25, # 20, # 10, # 5, # 44, F9, and the like (manufactured by Mitsubishi Chemical).

  An appropriate amount of pigment is 1 to 20 parts by weight. If the amount is less than 0.1 parts by weight, the image quality is deteriorated. If the amount is more than 20 parts by weight, the ink viscosity characteristics are adversely affected. Further, two or more kinds of colorants can be mixed and used in a timely manner for adjusting the color.

In order to further develop functionality in the ink composition of the present invention, various sensitizers, light stabilizers, surface treatment agents, surfactants, viscosity reducing agents, antioxidants, anti-aging agents, crosslinking accelerators, Polymerization inhibitors, plasticizers, preservatives, pH adjusters, antifoaming agents, humectants, dispersants, dyes, and the like can be mixed.
A bead mill and a homogenizer are optimal for mixing and dispersing the vehicle, colorant and other components described above, but various known grinding or dispersing devices can be used without any particular limitation.

As an ultraviolet light source used as a curing means, an ultraviolet ray is irradiated, and a low-pressure mercury lamp, a high-pressure mercury lamp, a metal halide lamp, a hot cathode tube, a cold cathode tube, an LED, or the like is applicable. Since the UV irradiation lamp may generate heat and the recording medium may be deformed, it is desirable that a cooling mechanism such as a cold mirror, a cold filter, a workpiece cooling, and the like is provided.
For example, when an LED light source is used, it is preferable to use one having an emission wavelength of 200 nm to 420 nm. Considering the cost of the light source and the output intensity, it is more preferable to use an ultraviolet to visible LED having an emission wavelength of 350 nm to 420 nm.

Examples of LED light sources (light emitting diodes) that can be applied to the present invention include UJ20 (peak wavelengths: 365 nm and 385 nm, illuminance: 8 W / cm ^{2 at} maximum) manufactured by Panasonic Electric Works, Ltd. and line type UD80 (peak wavelength: 385 nm, ^illuminance: 4W / cm 2), INTEGRATION manufactured by LED Zero (peak wavelength: 395 nm, illuminance: 1~2.5W / cm ^2), and the like.
In addition, metal halide has a wide wavelength range and is cheaper than LEDs and is often used as a light source. The metal halide is a metal halide such as Pb, Sn, or Fe, and can be selected according to the absorption spectrum of the photoinitiator. Any lamp that is effective for curing can be used without particular limitation.

  In the apparatus of the present invention, a pretreatment agent containing a wax component that is solid at room temperature (about 25 ° C.) is uniformly applied in a thin layer by bringing the pretreatment agent into a low-viscosity state at a temperature equal to or higher than its melting point. In the recording medium, the temperature of the pretreatment agent is lowered to a high viscosity state due to a temperature change, so that the recording medium surface can also be absorbed in the same manner as the non-absorbing recording medium. An uncured pretreatment agent layer can be maintained from printing to curing.

The recording medium provided with the pre-treatment agent tends to be in a state higher than normal temperature due to the influence of the temperature adjusting means of the pre-treatment agent application portion, and the temperature of the pre-treatment agent after application cannot be sufficiently lowered. In some cases, the uncured pretreatment agent layer cannot be sufficiently maintained in the absorbent recording medium without the viscosity being sufficiently high. In order to prevent this, it is preferable to provide a cooling means for the recording medium in the apparatus of the present invention. FIG. 6 is a diagram showing the embodiment. In this image forming apparatus, a recording medium cooling unit 7 is provided in the recording medium conveyance path, and the recording medium to which the pretreatment agent is applied by the applying unit 3 is shown. Is cooled by the cooling means 7 that contacts the back side of the recording medium.
A cooling roller can be used as the cooling means 7. As shown in FIG. 7, the cooling roller 71 is piped to pass cooling water 72, and the cooling water whose temperature is controlled by the cooling unit 73 is circulated by the pump 74. A chiller or a cooling fin can be used as the cooling unit 73.

The cooling means is not limited to this. For example, as shown in FIG. 8, a combination with the heat radiation fins 15 using a heat pipe 14 or cooling to a temperature lower than normal temperature using a Peltier element may be used. Is possible. Here, although the method of cooling from the back surface has been described, for example, cooling from the front surface is possible by blowing air from the surface by a fan or the like. Furthermore, it is desirable that the cooling part be in the vicinity of the application part where time has not elapsed since the application of the pretreatment agent.
The cooling means and the position thereof are not limited to these examples, and any means may be used as long as it has an effect of lowering the temperature of the applied pretreatment agent and increasing the viscosity.

  As described above, the pretreatment agent contains a wax component that is solid at room temperature, and the viscosity of the pretreatment agent at the time of application and after application can be changed by the application means provided with the temperature adjusting means, and the absorbent recording medium In this case, since the penetration of the pretreatment agent layer can be suppressed, ink can be ejected to the uncured pretreatment agent layer as in the case of the non-absorbent medium.

Although FIG. 1 shows an example in which a roller is used as the pretreatment agent application unit, as shown in FIG. 9, a pretreatment agent discharge head 4 ′ can be used as the pretreatment agent application unit. In order to discharge stably with a discharge head, it is necessary to suppress the viscosity at the time of discharge to 20 m · Pas or less. On the other hand, the pretreatment agent having this level of viscosity has a high penetration speed in the recording medium and penetrates into the recording medium during the time from printing to curing, thereby causing image unevenness due to uneven penetration.
If the pre-treatment agent contains a wax component, the temperature can be adjusted to a temperature equal to or higher than the melting point of the wax, and the liquid can be discharged. As the wax component solidifies and thickens, the penetration rate of the pretreatment liquid is suppressed even on an absorbent recording medium, and the amount of time necessary for the time from printing to curing is reduced on the recording medium. A thin layer of treatment agent can be maintained.
Furthermore, since the ejection head can apply the pretreatment agent to the recording medium in a non-contact manner, even if the head is heated to a temperature exceeding the wax melting point of the pretreatment agent, this heat is applied to the recording medium. This is advantageous in maintaining the temperature of the recording medium at normal temperature without being transmitted by conduction.

(Evaluation methods)
In order to confirm the effect of the present invention, an ink dot image was formed under the following conditions, and unevenness of the dot diameter was measured and evaluated.
Use of Oji Paper's OK Topcoat + as the absorbent recording medium, and apply the pretreatment agent by heating the head temperature with the pretreatment agent application means using the Gen4 head manufactured by Ricoh Printing Systems. The amount was applied so as to correspond to a thickness of 2 μm. After that, the black ink (discharged liquid B) was printed with the same Gen4 head discharge device as the pretreatment agent, and cured using Integration Technology Sub Zero 085 (A valve). The time from applying the pretreatment agent to curing is 0.5 seconds.
Nine dot diameters were arbitrarily measured with a microscope VHX-200 manufactured by Keyence Corporation. A case where all were 75 ± 5 μm was evaluated as “◯”, and the other cases were determined as “X”.

Pretreatment agent and ink <Pretreatment agent A-1>
A pretreatment agent A-1 having the following composition was prepared by a conventional method.
・ Polyethoxylated tetramethylol methane tetraacrylate ... 85 parts by mass (trade name: NK ester ATM35E, manufactured by Shin-Nakamura Chemical Co., Ltd.)
Citric acid saturated aliphatic monoglyceride: 5 parts by mass (trade name: Poem K-30, manufactured by Riken Vitamin Co., Ltd., melting point 58.7 ° C.)
Initiator (Ciba, Irgacure 184) ... 10 parts by mass

<Pretreatment agent A-2>
A pretreatment agent A-2 having the following composition was prepared by a conventional method.
・ Polyethoxylated tetramethylol methane tetraacrylate ... 85 parts by mass (trade name: NK ester ATM35E, manufactured by Shin-Nakamura Chemical Co., Ltd.)
Propylene glycol monobehenate: 5 parts by mass (trade name: Riquemar PB-100, manufactured by Riken Vitamin Co., Ltd., melting point 57.6 ° C.)
Initiator (Ciba, Irgacure 184) ... 10 parts by mass

<Pretreatment agent A-3>
A pretreatment agent A-3 having the following composition was prepared by a conventional method.
-Polyethoxylated tetramethylolmethane tetraacrylate ... 90 parts by mass (trade name: NK ester ATM35E, manufactured by Shin-Nakamura Chemical Co., Ltd.)
Initiator (Ciba, Irgacure 184) ... 10 parts by mass

<Ink B-1>
Ink B-1 having the following composition was prepared by a conventional method.
-Mixture of the following composition: 100 parts by mass propoxylation (2) neopentyl glycol diacrylate (Sartomer SR9003)
Tripropylene glycol diacrylate (Nippon Kayaku Kayrad TPGDA)
Other additives Small amount
Photoinitiator (Ciba, Irgacure 379) ... 10 parts by mass Colorant Carbon black (Mitsubishi Chemical Corporation MA-7) ... 5 parts by mass

The pretreatment agent was ejected onto the surface of the recording medium under the conditions shown in Table 1, and then ink was ejected to form a dot pattern and cured.
Table 1 shows the evaluation results for the dots obtained under each condition.

The pretreatment agent containing no wax component (A-3) has a low viscosity even at room temperature, so that the pretreatment agent permeates into the non-recording medium after the pretreatment agent is applied and before curing. The thickness of the layers varied widely and the diameters of the printed dots also varied. On the other hand, the pretreatment agent (A-1, A-2) containing the wax component is thickened after being applied on the recording medium, so that the penetration into the recording medium is suppressed and the pretreatment agent layer is cured. Since the ink can be ejected to the pretreatment agent layer having a uniform thickness, a uniform dot diameter can be obtained.
On the other hand, in the state where it was not heated, any pretreatment agent had a high viscosity and could not be ejected by the inkjet head.
From the above results, it was confirmed that a uniform pixel diameter can be obtained even on an absorbent recording medium by forming an image using the image forming apparatus and method of the present invention.

  The image forming apparatus of the present invention is not limited to non-absorbent recording media, and even when an absorbent recording medium is used, the image uniformity between the recording media is high, and the line width caused by ink bleeding or mixing between droplets is high. Therefore, it can be suitably used as a recording apparatus in a copying machine, a printer, a facsimile, and the like.

DESCRIPTION OF SYMBOLS 1 Paper feed means 2 Recording medium 3 Pretreatment agent provision means 4 Ink discharge head 4 'Pretreatment agent discharge head 5 Curing means 6 Temperature adjustment means 7 Cooling means 8 Pretreatment agent 9 Container 10 Supply roller 11 Application roller 12 Opposite roller 13 Heater 14 Heat pipe 15 Radiation fin 16 Cooling fan

JP 2004-42548 A JP 2009-226853 A JP 2004-42525 A JP 2008-105382 A Japanese Patent Application No. 2010-127192

Claims (3)

Recording medium conveying means, pretreatment agent applying means for applying a colorless pretreatment agent containing an active energy ray curable material to the recording medium conveyed by the conveying means, active energy ray curable material, and coloring material In an image forming apparatus having an ink discharge means for discharging a pre-processed ink to a recording medium and a curing means, the colorless pretreatment agent contains a wax component that is solid at room temperature, and An image forming apparatus, wherein the applying unit includes a temperature adjusting unit, and the preprocessing agent is applied to the recording medium at a temperature equal to or higher than the melting point of the wax component that is solid at normal temperature in the preprocessing agent. The image forming apparatus according to claim 1, further comprising: a cooling unit configured to cool the recording medium in a conveyance path of the recording medium between the pretreatment agent applying unit and the ink discharge unit. 3. The image forming apparatus according to claim 1, wherein the pretreatment agent applying means is an ink jet discharging means.

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