JP2020110965A - Inkjet recording method and inkjet recording device - Google Patents

Abstract

To provide an inkjet recording method that enables excellent printing quality by reducing liquid transfer load of an active ray curable inkjet ink that causes a sol-gel phase transition and an inkjet recording device.SOLUTION: An inkjet recording method according to the present invention is for recording an active ray curable inkjet ink, characterized by using the active ray curable inkjet ink that contains a polymerizable monomer and a liquid composition (A component) containing a photopolymerization initiator and a composition (B component) that can gelate the A component and is a solid at 40°C or lower, and prepared by melting the B component by heating, and by mixing the A component and the B component under heating in a mixing unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inkjet recording method and an inkjet recording apparatus, and more particularly, to an inkjet recording method and an inkjet recording that reduce the liquid-feeding load of an actinic ray-curable inkjet ink that undergoes a sol-gel phase transition and enable excellent print quality. Regarding the device.

The inkjet recording method is used in various printing fields because it can easily and inexpensively form an image. As one of the inkjet inks, an inkjet ink containing a photopolymerizable compound that is cured by being irradiated with actinic rays (hereinafter, also simply referred to as “actinic ray curable ink”) is known. Actinic ray curable inks have recently been attracting attention because they can form images with high adhesion even on recording media with low water absorption.

In recent years, an actinic ray-curable inkjet ink (hereinafter, also simply referred to as “gel ink”) that further contains a gelling agent and undergoes a sol-gel phase transition has been developed. The gel ink is in a sol state when heated and can be ejected from a nozzle of an ink jet head, but when landed on a recording medium after ejection, it is cooled and gelled. When the gelled droplets land on the recording medium, the pinning property is high and the leveling hardly occurs.

Therefore, as compared with the non-gel ink, when a defect at the nozzle (for example, a curved ejection of ink or a defective ejection) occurs, there is a problem that image defects such as streaks and uneven density are more likely to occur.

Further, since the gel ink is a paste having a high viscosity at room temperature, in a device requiring a long flow path such as a large-scale device, the pressure loss of the flow path becomes large and the load of liquid transfer to the inkjet head is large. was there. Further, in the case of heating and sending the liquid in a sol state, it is necessary to heat the entire flow path, which causes a problem that the power consumption of the device becomes enormous.

Furthermore, the ink that undergoes sol-gel phase transition often has the property that the gelling agent separates into two phases when left standing after stirring in the gel state, and the concentration of the gelling agent in the flow path becomes heterogeneous. As a result, there is also a problem that the image quality of the printed matter varies.

For example, in Patent Document 1, there is a mechanism for mixing two types of gel ink having a first gel concentration and a second gel concentration in a heated mixing pot in the apparatus, and recording of a porous or non-porous recording medium is performed. A system is disclosed that forms a high-quality image regardless of the recording medium by changing the mixing ratio of the first ink and the second ink according to the type of medium.

However, none of the above-mentioned problems of gel ink liquid-feeding load and problems of image quality of printed matter due to the high viscosity of the gel ink have been solved.

JP, 2013-233801, A

The present invention has been made in view of the above problems and circumstances, and a problem to be solved is an ink jet that enables a superior print quality by reducing the liquid-feeding load of an actinic ray curable ink jet ink that undergoes a sol-gel phase transition. A recording method and an inkjet recording apparatus are provided.

In order to solve the above problems, the present inventor has studied the causes of the above problems and the like, and found that it is very effective to prepare a gel ink by mixing a monomer component and a gelling agent in the vicinity of an inkjet head. Heading The present invention has been reached.
That is, the above-mentioned subject concerning the present invention is solved by the following means.

1. An inkjet recording method for recording an actinic ray curable inkjet ink, comprising:
The actinic radiation-curable inkjet ink is a liquid composition (component A) containing a polymerizable monomer and a photopolymerization initiator, and a composition (component B) having a melting point of 40° C. or higher capable of gelling the component A. Contains and
An inkjet recording method characterized by using an actinic ray-curable inkjet ink prepared by mixing the component A and the component B in-line under heating in a mixing unit.

2. 2. The ink jet recording method according to item 1, wherein the polymerizable monomer in the component A is a radical polymerizable monomer or a cationic polymerizable monomer.

3. 3. The inkjet recording method according to item 1 or 2, wherein the component A further contains a pigment or a dye as a colorant.

4. 4. The inkjet recording method according to any one of items 1 to 3, wherein the melting point of the component B is in the range of 50 to 130°C.

5. 5. The ink jet recording method according to any one of items 1 to 4, wherein the component B is a waxy gelling agent.

6. The inkjet recording method according to any one of items 1 to 5, wherein the component B does not contain a polymerizable monomer and a photopolymerization initiator.

7. The mass ratio (A:B) of the A component and the B component is within the range of 90.0:10.0 to 99.5:0.5. The inkjet recording method according to any one of 1.

8. An inkjet recording device using an actinic ray curable inkjet ink, comprising:
The actinic radiation-curable inkjet ink is a liquid composition (component A) containing a polymerizable monomer and a photopolymerization initiator, and a composition (component B) having a melting point of 40° C. or higher capable of gelling the component A. Contains and
An inkjet head for ejecting the actinic ray curable inkjet ink toward a recording medium,
A mixing unit for mixing the component A and the component B under heating upstream of the inkjet head;
A means for controlling the mixing amount of the component A and the component B so that the prepared mixture becomes an actinic ray-curable inkjet ink that reversibly undergoes a sol-gel phase transition at a desired temperature. Inkjet recording device.

9. 9. The ink jet recording apparatus according to item 8, further comprising a sub tank downstream of the mixing unit.

10. 10. The inkjet recording device according to item 8 or 9, wherein the mixing unit has a static mixer.

11. A means for mixing under heating, after heating and melting the B component upstream of the mixing unit, and then sending the solution into the heated mixing unit containing the A component by a solution sending pump; The inkjet recording apparatus according to any one of items 8 to 10.

12. 12. The ink jet recording apparatus according to item 11, wherein the liquid feed pump is a diaphragm pump or a syringe pump.

By the above means of the present invention, it is possible to provide an ink jet recording method and an ink jet recording apparatus that reduce the liquid feeding load of an actinic ray curable ink jet ink that undergoes a sol-gel phase transition and enable excellent printing quality.

The mechanism of action or mechanism of action of the present invention has not been clarified, but is presumed as follows.

By mixing the monomer component and the gelling agent in the vicinity of the inkjet head, the flow path of the gel ink to the inkjet head can be greatly shortened, which significantly reduces the load of liquid delivery of highly viscous gel ink. It is presumed that high image quality can be achieved by suppressing the non-uniform concentration of the gelling agent due to separation.

An example of the basic configuration of the ink supply unit used in the inkjet recording apparatus according to the present invention Configuration example 1 of the ink supply unit used in the inkjet recording apparatus according to the present invention Configuration example 2 of ink supply unit used in the inkjet recording apparatus according to the present invention Configuration example 3 of ink supply unit used in the inkjet recording apparatus according to the present invention Configuration Example 4 of Ink Supply Unit Used in Comparative Inkjet Recording Device Configuration Example 5 of Ink Supply Unit Used in Comparative Inkjet Recording Device Example of configuration of inkjet recording apparatus according to the present invention

The inkjet recording method according to the present invention is an inkjet recording method for recording an actinic ray curable inkjet ink, wherein the actinic ray curable inkjet ink contains a polymerizable monomer and a photopolymerization initiator. (Component A) and a composition (component B) having a melting point of 40° C. or higher capable of gelating the component A, and the component A and the component B are mixed in-line under heating with heating. It is characterized by using an actinic ray-curable inkjet ink prepared by mixing the components inside. This feature is a technical feature common to or corresponding to each of the following embodiments (forms).

As an embodiment of the present invention, from the viewpoint of exhibiting the effect of the present invention, it is preferable that the polymerizable monomer in the component A is a radical polymerizable monomer or a cationic polymerizable monomer.
Further, it is preferable that the component A further contains a pigment or a dye as a colorant.
Further, in the present invention, the melting point of the component B is preferably within the range of 50 to 130°C. Thereby, good injection stability can be obtained while achieving high image quality.
As an embodiment of the present invention, from the viewpoint of exhibiting the effects of the present invention, it is preferable that the component B is a waxy gelling agent from the viewpoint of high image quality and injection stability.
Furthermore, in the present invention, it is preferable that the component B does not contain a polymerizable monomer and a photopolymerization initiator from the viewpoint of exhibiting the effects of the present invention.
Further, in the present invention, the mass ratio (A:B) of the A component and the B component is preferably in the range of 90.0:10.0 to 99.5:0.5. Thereby, good injection stability can be obtained while achieving high image quality.

The inkjet recording apparatus of the present invention is an inkjet recording apparatus using an actinic ray curable inkjet ink, wherein the actinic ray curable inkjet ink contains a polymerizable monomer and a photopolymerization initiator (component A). And an ink jet head containing the composition (component B) having a melting point of 40° C. or more capable of gelating the component A, and ejecting the actinic ray-curable inkjet ink toward a recording medium, and the inkjet head. And a mixing unit for mixing the components A and B under heating, and the prepared mixture becomes an actinic ray curable inkjet ink that reversibly undergoes a sol-gel phase transition at a desired temperature. , And means for controlling the mixing amount of the A component and the B component.
As an embodiment of the present invention, from the viewpoint of recording stability, it is preferable to have a sub tank downstream of the mixing unit.

Further, in the present invention, it is preferable that the mixing unit has a static mixer from the viewpoint of recording stability, device cost and power consumption.
Further, it is preferable that the means for mixing under heating heats and melts the component B upstream of the mixing unit, and then feeds the component B into the heated mixing unit containing the component A by a feed pump.
Furthermore, in the present invention, it is preferable that the liquid feed pump is a diaphragm pump or a syringe pump. As a result, a constant amount of A component and B component is stably supplied to the mixing unit without pulsation.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used by the meaning including the numerical value described before and after that as a lower limit and an upper limit.
Further, in the present invention, "mixing the A component and the B component in-line under heating in a mixing unit" means that the A component and the B component, which are raw materials of the gel ink, in the inkjet image forming apparatus. , Mixing under heating.

<Inkjet recording method>
The inkjet recording method according to the present invention is an inkjet recording method for recording an actinic ray curable inkjet ink, wherein the actinic ray curable inkjet ink contains a polymerizable monomer and a photopolymerization initiator. (Component A) and a composition having a melting point of 40° C. or higher (Component B) capable of gelating the Component A, and mixing the Component A and the Component B under heating in a mixing unit. The actinic radiation-curable inkjet ink prepared in this way is used.

The inkjet recording method according to the present invention can be preferably applied to an ink supply method in an ink supply step of supplying an inkjet ink to an inkjet head.

FIG. 1 is an example of a basic configuration of an ink supply unit used in the inkjet recording apparatus according to the present invention.
In the ink supply step, the inkjet ink is supplied by the ink supply unit. The ink supply unit includes a storage tank 1 for storing the A component, a liquid feed passage 2 for the A component, a liquid feed pump 3 for the A component, a storage tank 4 for the B component, a liquid feed pump 5 for the B component, a heating unit 6, It is composed of a mixing unit 7 and a liquid sending channel 12.

The component A and the component B are mixed in the mixing unit 7 in the heating unit 6 to prepare a gel ink. The prepared gel ink is sent from the liquid sending channel 12 to an inkjet head (not shown). The ink can be supplied to the inkjet head through a path 12 that is shorter than the conventional method.

In this way, since the monomer component and the gelling agent are mixed in the vicinity of the inkjet head, the flow path of the gel ink liquid feed can be shortened, so that the liquid feed load can be significantly reduced and the two-phase separation can be performed. By suppressing the non-uniformity of the concentration of the gelling agent, excellent print quality can be achieved.

The mixing amount of the component A and the component B is adjusted by a control unit (not shown) so that the prepared gel ink becomes an actinic ray-curable inkjet ink that reversibly undergoes a sol-gel phase transition at a desired temperature. This can be controlled by controlling the respective liquid feed amounts by the liquid feed pump 3 for the component A and the liquid feed pump 5 for the component B.

FIG. 2 is a configuration example 1 of the ink supply unit used in the inkjet recording apparatus according to the present invention. Configuration example 1 is an example of an ink supply unit that can be used in the present invention. The apparatus of the configuration example 1 includes a storage tank 101 for storing the A component, a liquid feed passage 102 for the A component, a liquid feed pump 103 for the A component, a storage tank 104 for the B component, a liquid feed pump 105 for the B component, and a heating unit. 106, a static mixer 107a as a mixing unit, an electromagnetic valve 108, a sub-tank 109, a float sensor 110, a negative pressure generation pump 111, and a liquid supply passage 112. The prepared inkjet ink is sent to the inkjet head through the liquid sending channel 112.

The B component is heated in the lower part of the storage tank 104 and supplied in a liquid state. The mixing ratio of the A component and the B component is appropriately adjusted depending on the liquid feed amounts of the liquid feed pump 103 and the liquid feed pump 105. A sub-tank 109 is provided downstream of the mixing unit. The sub-tank 109 has a built-in float sensor 110, and when the ink in the sub-tank falls below a certain amount, the sensor is activated and the liquid feed pump 103 and the liquid feed pump 105 are activated to feed a liquid of a certain ratio. The sent components A and B are mixed by passing through the static mixer 107a to form a uniform ink. The solenoid valve 108 opens and closes appropriately in conjunction with the sensor. The ink in the sub tank 109 is delivered to the inkjet head by the pumping capacity of the inkjet head itself during recording. The sub tank 109 has a negative pressure control unit 111 built therein and is controlled at a constant negative pressure so that the ink in the inkjet head is stably ejected. As the inkjet head, for example, an inkjet head having a resolution of 600 npi manufactured by Konica Minolta is used.

FIG. 3 is a second configuration example of the ink supply unit used in the inkjet recording apparatus according to the present invention. Configuration example 2 is an example in which various dynamic mixers 107b are used as mixing units.

FIG. 4 is a configuration example 3 of the ink supply unit used in the inkjet recording apparatus according to the present invention. Configuration example 3 is an example of a method of supplying the B component as a solid. As shown in the enlarged view of FIG. 4B, the B component 113 molded in a stick shape is supplied in a fixed amount at a constant interval into the heated A component supplied from the channel 102 in the mixing unit. , A component.

In the inkjet recording method of the present invention, as the steps other than the above-mentioned ink supply step of supplying the inkjet ink to the inkjet head, a usual known step can be applied.

[Inkjet ink]
The actinic ray-curable inkjet ink according to the present invention comprises a liquid composition (A component) containing a polymerizable monomer and a photopolymerization initiator, and a composition having a melting point of 40° C. or higher capable of gelling the A component ( Component B).

The ink according to the present invention is an inkjet ink that contains a composition (component B) gelling agent having a melting point of 40° C. or higher as a gelling agent and undergoes a sol-gel phase transition depending on temperature. More specifically, the ink according to the present invention may be a known ink that contains a photopolymerizable compound and a gelling agent and turns into a sol or liquefaction when heated, but gels when cooled. Good. The ink according to the present invention may further contain a photopolymerization initiator, a coloring material and other components.

When the mass ratio (A:B) of the A component and the B component is within the range of 90.0:10.0 to 99.5:0.5, pinning is sufficient and uneven density or blank characters It is preferable from the viewpoint of printing with good image quality without crushing.

<A component>
The gel ink according to the present invention contains a liquid composition (component A) containing a polymerizable monomer and a photopolymerization initiator.

(Polymerizable monomer)
The polymerizable monomer is preferably a photopolymerizable monomer (also referred to as a photopolymerizable compound). Among them, the polymerizable monomer is preferably a radical polymerizable monomer or a cation polymerizable monomer. The photopolymerizable compound has a function of crosslinking or polymerizing by being irradiated with the actinic ray to cure the ink. The photopolymerizable compound may be a monomer, a polymerizable oligomer, a prepolymer or a mixture thereof. The photopolymerizable compound may be contained in the ink according to the present invention in only one kind or in two or more kinds. Further, a monomer having both photopolymerizable and thermosetting properties may be contained.

The content of the photopolymerizable compound can be, for example, 1% by mass or more and 97% by mass or less based on the total mass of the ink according to the present invention.

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

Examples of (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstil (meth)acrylate, isostearyl (meth). Acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, Methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth) ) Acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylphthalic acid, 2 -(Meth)acryloyloxyethyl-2-hydroxyethyl-phthalic acid and monofunctional acrylates including t-butylcyclohexyl (meth)acrylate, 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, di(meth)acrylate having a bisphenol A structure, hydroxypivalic acid neopentyl glycol di( (Meth)acrylate, polytetramethylene glycol di(meth)acrylate, bifunctional (meth)acrylate including polyethylene glycol diacrylate and tripropylene glycol diacrylate, and trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate ) Acrylate, Tri- or higher-functional (meth ) Acrylates, oligomers having a (meth)acryloyl group including polyester acrylate oligomers, and modified products thereof. Examples of the modified product include ethylene oxide-modified (EO-modified) acrylate having an ethylene oxide group inserted therein and propylene oxide-modified (PO-modified) acrylate having propylene oxide inserted therein.

In addition, polymerizable oligomers can be blended in the same manner as the monomers. Examples of the polymerizable oligomer include epoxy acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, polyester acrylate, and linear acrylic oligomer. More specifically, Shinzo Yamashita, "Handbook of Crosslinking Agents", (1981, Taiseisha); Kiyomi Kato, "UV/EB Curing Handbook (Materials)" (185, Kobunshi Kogyokai); Radtech Research Society, “Applications and Markets of UV/EB Curing Technology”, page 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun), etc. Commercially available products or radically polymerizable or crosslinkable monomer oligomers and polymers known in the art can be used.

Examples of the cationically polymerizable compound include epoxy compounds, vinyl ether compounds and oxetane compounds.
As the cationic photopolymerizable monomer, various known cationically polymerizable monomers can be used. For example, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and JP-A-2001-220526. The epoxy compounds, vinyl ether compounds, oxetane compounds and the like exemplified in the respective publications are listed.

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

Examples of the photopolymerizable and thermosetting monomer include (meth)acryloyl group as a photopolymerizable functional group and hydroxyl group, carboxyl group, isocyanate group, imino group, epoxy group, oxetanyl as a thermosetting functional group in the molecule. Examples thereof include a monomer having a group, a mercapto group, a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, an oxazoline group and the like.

(Photopolymerization initiator)
The component A according to the present invention contains a polymerizable monomer and a photopolymerization initiator. When the photopolymerization compound is a compound having a radically polymerizable functional group, the photopolymerization initiator contains a photoradical initiator, and the photopolymerizable compound is a compound having a cationically polymerizable functional group. In some cases, a photoacid generator is included. The photopolymerization initiator may be contained in the ink according to the present invention in only one kind or in two or more kinds. The photopolymerization initiator may be a combination of both a photo radical initiator and a photo acid generator.

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

Examples of the cleavage type radical initiator include an acetophenone-based initiator, a benzoin-based initiator, an acylphosphine oxide-based initiator, benzyl and methylphenylglyoxyester.

Examples of the hydrogen abstraction type radical initiator include a benzophenone-based initiator, a thioxanthone-based initiator, an aminobenzophenone-based initiator, 10-butyl-2-chloroacridone, 2-ethylanthraquinone, 9,10-. Includes phenanthrenequinone and camphorquinone.

Examples of the photo-acid generator include compounds described in "Organic Materials for Imaging", edited by Organic Electronics Materials Research Group, Bushin Publishing Co., Ltd. (1993), pages 187 to 192.
The content of the photopolymerization initiator may be within a range in which the inkjet ink can be sufficiently cured, and for example, may be 0.01% by mass or more and 10% by mass or less with respect to the total mass of the inkjet ink according to the present invention. it can.

(Coloring material)
As the component A, a pigment or dye may be further contained as a colorant. Colorants include dyes and pigments. The colorant is preferably a pigment from the viewpoint of obtaining an image having good weather resistance. 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.

<B component>
The component B is a composition having a melting point of 40° C. or higher which allows the component A to gel (hereinafter also referred to as a gelling agent). In the present invention, the melting point of the gelling agent is 40°C or higher. More preferably, the melting point is in the range of 50 to 130°C. When the melting point is 40° C. or higher, a sufficient difference between the phase transition temperature of the ink after mixing with the component A and the temperature of the recording medium can be provided, so that sufficient pinning can be achieved and, as a result, high image quality can be achieved. .. It is preferably 50° C. or higher. Further, the melting point is preferably 130° C. or lower. When the temperature is 130° C. or lower, the sol-gel phase transition temperature of the gel ink after mixing does not increase, so that the injection stability does not decrease.

When the component B contains a plurality of gelling agents, it is preferable that each gelling agent be within the above melting point range.

The melting point can be measured by using an ordinary melting point measuring device. For example, it can be obtained by performing a temperature drop analysis at a rate of 5° C./min with DSC. The melting point is measured at the intersection of the baseline and the rising portion of the precipitation peak.

In the ink after mixing the components A and B, the content of the gelling agent is preferably 1.0% by mass or more and 10.0% by mass or less based on the total mass of the ink. By setting the content of the gelling agent to 1.0% by mass or more, the pinning property of the ink can be sufficiently enhanced and a higher-definition image can be formed. By setting the content of the gelling agent to 10.0% by mass or less, it becomes difficult for the gelling agent to deposit on the surface of the formed image, and the gloss of the image can be brought closer to the gloss of the image by another ink, In addition, the ink ejection property from the inkjet head can be further improved. From the above viewpoint, the content of the gelling agent in the ink according to the present invention is preferably 1.0% by mass or more and 5.0% by mass or less, and 2.5% by mass or more and 5.0% by mass or less. Is more preferable, and 2.5% by mass or more and 4.0% by mass or less is further preferable.

Further, it is preferable that the component B does not contain the polymerizable monomer and the photopolymerization initiator contained in the component A. In particular, it is preferable not to include a polymerizable monomer that is liquid at 40°C. By doing so, it becomes possible to stably supply the B component to the mixing unit. It should be noted that the case where the polymerizable monomer and the photopolymerization initiator are mixed into the component B as impurities, for example, as long as the effects of the present invention are not impaired, is not hindered.

From the following viewpoints, the gelling agent is preferably crystallized in the ink at a temperature not higher than the gelation temperature of the ink. When the gelling agent is crystallized in the ink, a structure in which the photopolymerizable compound is included in the three-dimensional space formed by the plate-like crystallized gelling agent may be formed. , Hereinafter referred to as "card house structure"). When the card house structure is formed, the liquid photopolymerizable compound is held in the space, and thus the ink droplets are more difficult to wet and spread, and the ink pinning property is further enhanced. When the ink pinning property is improved, it becomes difficult for the ink droplets landed on the recording medium to coalesce with each other, and a higher-definition image can be formed.

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

Examples of gelling agents suitable for forming a card house structure by crystallization include waxy gelling agents. As the waxy gelling agent, ketone wax, ester wax, petroleum wax, plant wax, animal wax, mineral wax, hydrogenated castor oil, modified wax, higher fatty acid, higher alcohol, hydroxystearic acid, N-substituted Included are fatty acid amides, including fatty acid amides and specialty fatty acid amides, higher amines, synthetic waxes, dimer acids and dimer diols.

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

Examples of the above-mentioned ester waxes include behenyl behenate, icosyl icosate, stearyl stearate, palmityl stearate, cetyl palmitate, myristyl myristate, cetyl myristate, myrisyl stearate, stearyl stearate, oleyl palmitate, glycerin fatty acid. Esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters and polyoxyethylene fatty acid esters are included.

Examples of commercial products of the above ester waxes include EMALEX series manufactured by Japan Emulsion Co., Ltd. (“EMALEX” is a registered trademark of the same company), and Riken Vitamin Co., Ltd. All include trademarks of the same company.
Examples of the petroleum wax include petroleum waxes including paraffin wax, microcrystalline wax and petrolactam.
Examples of the vegetable waxes include candelilla wax, carnauba wax, rice wax, wax, jojoba oil, jojoba solid wax and jojoba ester.
Examples of the above-mentioned animal wax include beeswax, lanolin and whale wax.

Examples of the mineral wax include montan wax and hydrogenated wax.
Examples of the modified wax include a montan wax derivative, a paraffin wax derivative, a microcrystalline wax derivative, a 12-hydroxystearic acid derivative and a polyethylene wax derivative.
Examples of the higher fatty acids include behenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid.
Examples of the higher alcohols include stearyl alcohol and behenyl alcohol.

Examples of the hydroxystearic acid include 12-hydroxystearic acid.
Examples of the fatty acid amide include lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide and 12-hydroxystearic acid amide.
Examples of commercially available fatty acid amides include Nippon Kasei Co., Ltd., Nikka Amide series (“Nikka Amide” is a registered trademark of the company), Ito Oil Co., ITOWAX series, and Kao Corporation's FATTYAMID series. ..
Examples of the N-substituted fatty acid amide include N-stearyl stearic acid amide and N-oleyl palmitic acid amide.

Examples of the special fatty acid amide include N,N'-ethylenebisstearylamide, N,N'-ethylenebis-12-hydroxystearylamide and N,N'-xylylenebisstearylamide.
Examples of the higher amines include dodecylamine, tetradecylamine and octadecylamine.

Examples of the synthetic waxes include polyethylene wax and α-olefin maleic anhydride copolymer wax.
Examples of commercially available synthetic waxes include UNILIN series manufactured by Baker-Petrolite (“UNILIN” is a registered trademark of the same).
Examples of commercially available products of the above-mentioned dimer diol include PRIPOR series manufactured by CRODA (“PRIPOR” is a registered trademark of the same).

Among these gelling agents, the gelling agent is preferably a wax-based gelling agent such as a ketone wax, an ester wax, a higher fatty acid, a higher alcohol, and a fatty acid amide from the viewpoint of further improving the pinning property. From the above viewpoint, a ketone wax represented by the following general formula (G1) and an ester wax represented by the following general formula (G2) are more preferable. The ketone wax represented by the following general formula (G1) and the ester wax represented by the following general formula (G2) may be contained in the ink according to the present invention in only one kind, or in two or more kinds. It may be. Further, only one of the ketone wax represented by the following general formula (G1) and the ester wax represented by the following general formula (G2) may be contained in the ink according to the present invention, Both may be included.

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

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

The ketone wax represented by the general formula (G1) or the ester wax represented by the general formula (G2) has a linear or branched hydrocarbon group having 9 or more carbon atoms, and therefore gels. The crystallinity of the agent is further enhanced, and more sufficient space is created in the card house structure. Therefore, the photopolymerizable compound is easily included in the space, and the pinning property of the ink is further enhanced. In addition, since the linear or branched hydrocarbon group has 25 or less carbon atoms, the melting point of the gelling agent does not rise excessively, and therefore it is not necessary to excessively heat the ink when ejecting the ink. .. From the above viewpoint, R1 and R2 are particularly preferably a linear hydrocarbon group having 11 or more and less than 23 carbon atoms.

Further, from the viewpoint of increasing the gelation temperature of the ink to cause the ink to gel more rapidly after landing, either R1 or R2, or R3 or R4 is saturated and has 11 or more carbon atoms. It is preferably a hydrocarbon group of less than 23. From the above viewpoint, it is more preferable that both R1 and R2, or both R3 and R4 are saturated hydrocarbon groups having 11 or more and less than 23 carbon atoms.

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

Examples of commercial products of the ketone wax represented by the general formula (G1) include Kaowax T1 manufactured by Alfa Aeser, 18-Pentatria contanon and Hentriacontan-16-on, and Kao Co., Ltd.

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

Examples of commercial products of the ester wax represented by the general formula (G2) include NOF CORPORATION, Unistar M-2222SL and Sperm Aceti (“Unistar” is a registered trademark of the same company), Kao Corporation, Exepearl SS and Exepearl MY-M (“Exepearl” is a registered trademark of the same company), Nippon Emulsion Co., Ltd., EMALEX CC-18 and EMALEX CC-10 (“EMALEX” is a registered trademark of the same company), and High Alcohol Industry Co. Ltd. ("Amreps" is a registered trademark of the same company). Since many of these commercially available products are a mixture of two or more kinds, they may be separated and purified as necessary to be contained in the ink.

As the component B, other low-molecular oil gelling agents described in JP-A-2005-126507, JP-A-2005-255821, and JP-A-2010-111790, N-lauroyl-L-glutamic acid dibutylamide, Amide compounds such as N-(2-ethylhexanoyl)-L-glutamic acid dibutylamide, dibenzylidene sorbitols such as 1,3:2,4-bis-O-benzylidene-D-glucitol, and sucrose fatty acid ester , Various fatty acid dextrins, fatty acid inulin, various gelling agents such as eicosane behenate glyceryl behenate, and various binders may be contained.

<Other ingredients>
The ink according to the present invention contains, as a part of the component A or the component B, a dispersant, a photosensitizer, a polymerization inhibitor, a thermal cross-linking agent, and a surfactant as long as the effects of the present invention can be obtained. It may further include the composition. These components may be contained in the ink according to the present invention in only one kind or in two or more kinds.

<Physical properties>
From the viewpoint of further enhancing the ejection property from the inkjet head, the viscosity of the inkjet ink according to the present invention (hereinafter also simply referred to as ink) at 80° C. is preferably 3 mPa·s or more and 20 mPa·s or less. Further, from the viewpoint of sufficiently gelling the ink when landing and cooling to room temperature, the viscosity of the ink at 25° C. is preferably 1000 mPa·s or more.

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

The viscosity at 80° C., the viscosity at 30° C. and the gelation temperature of the ink according to the present invention can be determined by measuring the temperature change of the dynamic viscoelasticity of the ink with, for example, various rheometers. In the present invention, these viscosity and gelation temperature are values obtained by the following method. The ink according to the present invention was set in a stress-controlled rheometer Physica MCR300 (cone plate diameter: 75 mm, cone angle: 1.0°), manufactured by Anton Paar, and then heated to 100° C., and the temperature decreasing rate was 0.1. C./s, strain 5%, angular frequency 10 radian/s, the temperature of the ink is cooled to 20.degree. The viscosity at 80° C. and the viscosity at 30° C. can be determined by reading the complex viscosities at 80° C. and 30° C. on the dynamic viscoelastic temperature change curve. The gelling temperature can be obtained as a temperature at which the complex viscosity becomes 200 mPa·s or more in the dynamic viscoelastic temperature change curve.

From the viewpoint of further enhancing the ejection property from the inkjet head, the average particle diameter of the pigment particles when the ink according to the present invention contains a pigment is 0.08 μm or more and 0.5 μm or less, and the maximum particle diameter is 0.3 μm. It is preferably 10 μm or less. The average particle diameter of the pigment particles in the present invention means a value obtained by a dynamic light scattering method using Datasizer Nano ZSP, manufactured by Malvern. Since the ink containing the colorant has a high density and light is not transmitted by this measuring instrument, the ink is diluted 200 times before the measurement. The measurement temperature is room temperature (25° C.).

<Inkjet recording device>
The inkjet recording apparatus of the present invention is an inkjet recording apparatus using an actinic ray curable inkjet ink, wherein the actinic ray curable inkjet ink contains a polymerizable monomer and a photopolymerization initiator (component A). And an ink jet head containing the composition (component B) having a melting point of 40° C. or more capable of gelating the component A, and ejecting the actinic ray-curable inkjet ink toward a recording medium, and the inkjet head. And a mixing unit for mixing the components A and B under heating, and the prepared mixture becomes an actinic ray curable inkjet ink that reversibly undergoes a sol-gel phase transition at a desired temperature. , And means for controlling the mixing amount of the A component and the B component.

FIG. 7 is an example showing the concept of the inkjet recording apparatus of the present invention. As shown in FIG. 7, the inkjet recording device 300 includes an inkjet head 310, a transport unit 320, an irradiation unit 330, a control unit 340, an ink supply unit 380, and a storage unit 350. The inkjet recording device 300 may further include a data input unit 360. The inkjet recording apparatus 300 may further include a measuring unit 370 that measures the type of the recording medium on the upstream side of the inkjet head 310 in the recording medium conveyance direction. In addition, in FIG. 7, the arrow indicates the conveyance direction of the recording medium.

[Inkjet head 310]
The inkjet head 310 has a nozzle surface 313 provided with the ejection ports of the nozzles 311 on the surface facing the transporting unit 320 when forming an image, and with respect to the recording medium 400 transported by the transporting unit 320. To eject ink. The inkjet head 310 may include a temperature adjusting unit for adjusting the temperature of the ink to adjust the viscosity of the ink to be low, from the viewpoint of increasing the ejection property by making the ink according to the present invention into a sol. Examples of the temperature adjusting means include a panel heater, a ribbon heater, and a heating means using warm water.

The inkjet head 310 may be a scan type inkjet head whose width in the direction orthogonal to the recording medium conveyance direction is smaller than that of the recording medium 400, and a line whose width in the direction orthogonal to the recording medium conveyance direction is larger than that of the recording medium 400. Type inkjet head may be used.

The nozzle 311 has a discharge port on the nozzle surface 313. The number of nozzles 311 may be the number of inks used for image formation (for example, four) or more. When the inkjet head 310 has a plurality of nozzles 311, the plurality of nozzles 311 are arranged side by side in the transport direction of the recording medium so as to be at substantially equal intervals from the viewpoint of simplifying the configuration of the apparatus and facilitating control. Preferably.

The inkjet head 310 is configured to be able to change the amount of ink ejected and landed on the recording medium. For example, the inkjet head 310 is configured to be controlled by the control unit 340 so that the vibration width of the piezoelectric element can be changed or ink cannot be ejected from some nozzles.

[Conveyor 320]
The transport unit 320 transports the recording medium 400 so that the recording medium 400 facing the inkjet head 310 moves right below the inkjet head 310 when forming an image. For example, the transport unit 320 includes a drive roller 321, a driven roller 322, a transport belt 323, and a heating device 324.

The drive roller 321 and the driven roller 322 are arranged in a state that they are spaced from each other in the transport direction of the recording medium and extend in a direction orthogonal to the transport direction of the recording medium. The drive roller 321 is rotated by a drive source (not shown).

The transport belt 323 is a belt for transporting the recording medium 400 placed on the transport belt 323, and is stretched over the drive roller 321 and the driven roller 322. The conveyor belt 323 can be, for example, an endless belt formed wider than the recording medium 400. At this time, when the drive source rotates the drive roller 321, the conveyor belt 323 follows the drive roller 321, and the recording medium 400 on the conveyor belt 323 is conveyed. A plurality of suction holes (not shown) may be formed on the belt surface of the conveyor belt 323 from the viewpoint of holding the recording medium 400 by suction and making it more difficult to detach the recording medium.
Further, the conveyor belt 323 can be heated by the heating device 324. By appropriately adjusting the temperature of the recording medium according to the type of the recording medium, the pinning of the sol-gel phase transition ink can be adjusted to obtain an optimum image quality.

[Irradiator 330]
The irradiation unit 330 has a light source, and irradiates the upper surface of the transport unit 320 with an actinic ray from the light source. As a result, the droplets of the inkjet ink that have landed on the recording medium 400 being conveyed can be irradiated with actinic rays to cure the droplets. The irradiating section 330 can be arranged on the downstream side of the inkjet head 310 and directly above the conveying section 320. The light source is preferably a light emitting diode (LED) from the viewpoint of suppressing the occurrence of defective curing of the ink due to the ink jet ink being melted by the radiant heat of the light source. Examples of LED light sources that can be irradiated with actinic radiation to cure the inkjet ink include 395 nm, water-cooled LEDs, from Phoseon Technology.

[Control unit 340]
The control unit 340 controls the operation of the inkjet recording apparatus 300 during image formation. Here, it also includes controlling the mixing amount of the component A and the component B so that the gel ink becomes an actinic ray-curable inkjet ink that reversibly undergoes a sol-gel phase transition at a desired temperature.

Hereinafter, an example of means for controlling the flow rate of the A liquid component will be described by taking the liquid feed control method of the A component when using the static mixer of the configuration example 1 shown in FIG. 2 as an example. The control of the supply amount of the B component can be performed similarly.

<Feedback control by flow sensor>
It is possible to control the feed amount of the liquid feed component 103 by the liquid feed pump 103 based on the information from the flow rate sensor provided in the flow passage 102 for the liquid A component.

<Driving time (pulse drive) control with a metering pump>
The driving time of the liquid feed pump 103 for the liquid A component is determined, and a fixed amount of liquid is fed.

<Open/close control by solenoid valve>
The liquid feed pump 103 for the A liquid component is constantly driven, and the flow rate can be controlled by turning on and off a solenoid valve (not shown) provided in the flow passage 102 for the A liquid component.

[Storage section 350]
The storage unit 350 includes various tables including a control program executed by the control unit 340, a type of recording medium, and a table that associates the maximum amount (and optionally the minimum amount) of ink that can land on the unit area of the recording medium. Store information so that it can be referenced.

[Data input section 360]
The data input unit 360 transmits/receives various information such as data including a type of a recording medium to be printed and an image to be printed, to/from an external device.

[Measurement unit 370]
The measuring unit 370 measures the type of recording medium on which an image is formed and transmits the obtained information to the control unit 340.

[Ink supply unit 380]
In the ink supply unit, the component A and the component B are mixed in a mixing unit under heating to prepare a gel ink, which is then sent to the inkjet head 310. It is preferable to have a sub-tank downstream of the mixing unit.

<Heating unit>
The heating unit is composed of a heater and a heat transfer member that transfers heat from the heater, and heats and keeps the temperature of the inkjet ink in the sub-tank 109, each liquid supply channel, and the mixing unit 107 at a predetermined temperature. As the heater, for example, a heating wire that generates Joule heat when energized is used. Further, as the heat transfer member, a member having high thermal conductivity, for example, a heat conductive plate formed of various metals (alloys) is used.

(Heating control by heater)
When heating the gel ink, it is heated from outside the tank, but it is difficult to synchronize the liquid temperature of the gel ink itself and the control of the heater. For this reason, it is common to control the heater temperature while checking the temperature of the ink itself with a liquid contact sensor. Specifically, it is preferable to monitor both the temperature of the heater and the liquid temperature to determine the heater output.

<Mixing unit>
In the mixing unit, the A component and the B component are mixed in the mixing unit under heating, and the mixing amount of the A component and the B component is adjusted so that a gel ink reversibly undergoes a sol-gel phase transition at a desired temperature. To prepare a gel ink. The components A and B are preferably sent to the mixing unit from the respective tanks whose heating is controlled.

The controller 340 controls the mixing amounts of the A component and the B component. As the mixing means, a static mixer as shown in the configuration example 1 can be used. Alternatively, as shown in the configuration example 2, a dynamic mixer can be used.

(Static mixer)
In the present invention, it is preferable that the mixing unit has a static mixer. The static mixer is one type of static mixing/stirring mixer having no moving parts, and is configured by arranging elements in which rectangular plates are twisted 180 degrees in the left and right directions alternately in a pipe. The static mixer can perform mixing by three functions of division, conversion and inversion. As a result of the above effects, it is more reproducible than the conventional batch method, accurate and uniform mixing is possible, and it is also effective in saving maintenance cost, energy and space.

In addition, since the static mixer is a static mixer, it has no drive unit. Therefore, the energy for mixing is provided by consuming the velocity energy of the liquid.

<Feed pump>
The liquid delivery pump used to deliver the A component, the B component, and the gel ink includes a turbo type (non-volume type) pump, a positive displacement type pump, a special type pump, and the like, but the present invention requires quantitativeness. Therefore, it is preferable to use a positive displacement pump. Examples of the positive displacement pump include a piston pump, a plunger pump, a diaphragm pump, a gear pump (gear pump), a vane pump, a screw pump, a syringe pump, and a tube pump, and any pump is preferably used. When the static mixer is used as described in the configuration example 1 of the present invention, due to the characteristics of the static mixer, the mixing in the cross-sectional direction of the pipe is good, but there is almost no mixing in the axial direction of the pipe. Therefore, a metering pump is essential.

Further, not only is it possible to deliver a fixed amount of liquid, but it is also important to change the amount of liquid to be delivered, to accurately turn it on and off, and to work with a pair of pumps. Therefore, a diaphragm pump, a damper pump that suppresses pulsation of the diaphragm pump, and a syringe pump are preferably used.

<Negative pressure controller>
The sub tank 109 is connected to the negative pressure control unit 111 via a ventilation path. The negative pressure control unit 111 adjusts the pressure in the sub tank. Therefore, the pressure in the sub tank changes depending on the degree of the negative pressure applied by the negative pressure control unit (not shown). Further, a float sensor (liquid level sensor) 110 is provided in the sub tank, and the amount of ink stored in the tank can be constantly detected. Since the pressure from the sub tank to the inkjet head is set to a negative pressure state by the pressure control unit, it is possible to prevent ink from leaking from the nozzle when image formation or various maintenances are not performed.

<Transfer channel>
The liquid sending flow path is formed of a tubular member, connects the storage tank to the mixing unit, and communicates the inside. As the ink flow path, for example, a resin material or a metal tube having good heat conductivity is used. An electromagnetic valve and a pump are provided on the flow path.

[Other configurations]
In addition to the above-described configuration, the inkjet recording apparatus 300 includes an ink tank (not shown) for storing inkjet ink before ejection, and an ink flow path (not shown) for communicating the ink between the ink tank and the inkjet head 310. ) May be included.

[Image Formation Using Inkjet Recording Device 300]
The control unit 340 refers to a table, which is stored in the storage unit 350, that associates the type of recording medium with the maximum amount (and optionally the minimum amount) of ink that can land on the unit area of the recording medium, The maximum amount of ink that can land on the unit area of the specified recording medium type, and optionally the minimum amount is set.

Further, the control unit 340 controls the transport unit 320 to transport the recording medium 400 and controls the inkjet head 310 so that the image included in the print information is formed on the recording medium 400. The ink droplets of the present invention are ejected from the nozzle 311 of FIG. At this time, the control unit 340 adjusts the ejection amount of the ink according to the present invention so that the maximum amount of ink landed on the unit area of the recording medium 400 does not exceed the set maximum amount. The conveyance of the recording medium may be performed after setting the maximum amount of the ink, or may be performed before the setting.

In addition, the control unit 340 controls the irradiation unit 330 to irradiate the ink according to the present invention landed on the recording medium 400 with an actinic ray to cure the ink. At this time, the control unit 340 controls the inkjet head 310 to eject ink and land an amount of ink that does not exceed the maximum amount on the downstream side of the recording medium 400 to form an image on the downstream side at the same time. You may start.

In addition, the control unit 340 determines the type of recording medium to be printed from the print information received by the data input unit 360 or the recording medium information measured by the measuring unit 370 before setting the maximum amount of ink that can be landed. May be specified.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “parts” or “%” is used, but unless otherwise specified, “parts by mass” or “% by mass” is shown.

(1) Preparation of Component A and Component B (1-1) Preparation of Component A-1 (1-2) Preparation of Magenta Pigment Dispersion Liquid 1 Dispersant and dispersion medium of the types and amounts shown below were placed in a stainless steel container. The mixture was put into a polypropylene container with a zirconia bead having a diameter of 0.5 mm, and the container was sealed with the zirconia beads having a diameter of 0.5 mm. The mass ratio of the zirconia beads to the following materials was adjusted to 2:1. After that, a dispersion treatment was carried out with a paint shaker until a desired particle size was obtained, and then the zirconia beads were removed to prepare a magenta pigment dispersion liquid 1.

(Material of magenta pigment dispersion liquid)
Dispersant: JET-9151 (manufactured by BYK) 11 parts by mass Dispersion medium: Tripropylene glycol diacrylate (containing 0.2% UV-10)
69 parts by mass Pigment: PV19/PR202 (manufactured by BASF, D4500J) 20 parts by mass (1-3) Preparation of A component A-1 The following components and the pigment dispersion liquid are mixed and heated to 60°C. It was stirred. The resulting solution was filtered through a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVANTEC to prepare A component A-1.

Photopolymerizable compound 1: tripropylene glycol diacrylate 2.0 parts by mass Photopolymerizable compound 2: polyethylene glycol #600 diacrylate
20.0 parts by mass Photopolymerizable compound 3:6 EO-modified trimethylolpropane triacrylate
4.0 parts by mass Photopolymerizable compound 4:3PO-modified trimethylolpropane triacrylate
21.3 parts by mass Photopolymerizable compound 5: Polyester acrylate oligomer having an average number of functional groups of 8 (ETERCURE 6361-100, manufactured by ETERNAL CHEMICAL)
5.0 parts by mass Photopolymerizable compound 6: Polyester acrylate oligomer having an average number of functional groups of 2 (CN2270 manufactured by Sartomer) 13.0 parts by mass Photopolymerization initiator 1: Acylphosphine oxide-based radical polymerization initiator (BASF Corp.) Made by IRGACURE TPO ("IRGACURE" is a registered trademark of the same company)
2.7 parts by mass Photopolymerization initiator 2: Acylphosphine oxide-based radical polymerization initiator (IRGACURE 819, manufactured by BASF Ltd. (“IRGACURE” is a registered trademark of the same company))
3.0 parts by mass Photosensitizer 1:2-isopropylthioxanthone (ITX) 0.5 parts by mass Polymerization inhibitor: manufactured by BASF, IRGASTAB UV10 (“IRGASTAB” is a registered trademark of the company) 0.15 parts by mass Surfactant Agent: Momentive Performance Materials Japan Co., Ltd., TSF-4452 0.02 parts by mass Pigment dispersion: Magenta pigment dispersion 1 26.0 parts by mass

(1-4) Preparation of Component A-2 (1-5) Preparation of Magenta Pigment Dispersion Liquid 2 The following two compounds were placed in a stainless beaker and dissolved by heating with stirring on a hot plate at 65°C for 1 hour. did.

Pigment dispersant: Addisper PB824 (manufactured by Ajinomoto Fine-Techno Co., Inc.)
9 parts by mass Polymerizable compound: OXT221 (Oxetane 221, manufactured by Toagosei Co., Ltd.) 70 parts by mass After cooling to room temperature, 21 parts of the following magenta pigment 1 is added thereto, and a polypropylene container together with zirconia beads having a diameter of 0.5 mm. Pigment dispersion liquid 2 was prepared by removing the zirconia beads after performing a dispersion treatment for 8 hours with a paint shaker.

Magenta pigment 1: Pigment Red 122 (Dainichi Seika Co., Ltd., Chromofine Red 6112JC)

(1-6) Preparation of A component A-2 The following additives were sequentially mixed, heated to 80° C. and stirred, and the obtained liquid was filtered under heating with a #3000 metal mesh filter, Upon cooling, A-2 was prepared.
Polymerizable compound: OXT221 (Oxetane 221, manufactured by Toagosei Co., Ltd.) 44.0 parts by mass Polymerizable compound: Celoxide 2021P (alicyclic epoxy, manufactured by Daicel Chemical Industries, Ltd.)
10.0 parts by mass Photopolymerization initiator: CPI-100P (50% propylene carbonate solution of triallylsulfonium salt, manufactured by San-Apro) 5.0 parts by mass Sensitizer: DEA (diethoxyanthracene, manufactured by Kawasaki Kasei Kogyo Co., Ltd.)
2.0 parts by mass Surfactant: X22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.05 parts by mass Pigment dispersion: Magenta pigment dispersion 2 19.0 parts by mass

(1-7) Preparation of Component B-1 Ester wax (Unistar M-2222SL, manufactured by NOF CORPORATION) was placed in a stainless beaker as a gelling agent and dissolved by heating at 90° C., followed by a #3500 mesh metal filter. Filtered through. Then, the wax liquid was poured into a metal molding container and cooled at 25°C. The solidified component was taken out from the molding container and designated as B component B-1.

(1-8) Preparation of B component B-2 As a gelling agent, 40 parts by mass of an ester wax (manufactured by NOF CORPORATION, Unistar M-2222SL) and 60 parts by mass of a ketone wax (Kao Wax T1 manufactured by Kao Corporation) were used. The mixture was placed in a stainless steel container, heated and dissolved at 90° C., and then filtered through a #3500 mesh metal filter. Then, the wax liquid was poured into a metal molding container and cooled at 25°C. After that, the solidified component was taken out from the molding container and designated as B component B-2.

(1-9) Preparation of B component B-3 100 parts by mass of paraffin wax (Fuji Film Wako Pure Chemical Industries, mp68-70) was placed in a stainless steel container, heated and melted at 90° C., and then a #3500 mesh metal filter. Filtered through. Then, the wax liquid was poured into a metal molding container and cooled at 25°C. Then, the solidified component was taken out from the molding container and designated as B component B-3.

(1-10) Preparation of B component B-4 100 parts by mass of paraffin wax (Fuji Film Wako Pure Chemical Industries, mp42-44) was placed in a stainless steel container, heated and melted at 90° C., and then a #3500 mesh metal filter. Filtered through. Then, the wax liquid was poured into a metal molding container and cooled at 25°C. Thereafter, the solidified component was taken out from the molding container and designated as B component B-4.

(1-11) Preparation of Comparative Inks 1 to 3 The comparative ink was prepared by mixing the components A and B under heating in advance and cooling the gel ink prepared once.
(1-12) Preparation of Ink 1 A component A-1 and B component B-1 were each heated to 90° C. and mixed in advance in a stainless container so that the mass ratio was 98.0:2.0, The mixture was heated and stirred at 90°C for 15 minutes. Then, it was cooled to 25° C. to prepare Ink 1.

(1-13) Preparation of Ink 2 A component A-1 and B component B-2 were each heated to 90° C. and mixed in advance in a stainless container so that the mass ratio was 97.5:2.5, The mixture was heated and stirred at 90°C for 15 minutes. Then, it was cooled to 25° C. to prepare Ink 2.

(1-14) Preparation of Ink 3 A component A-2 and B component B-3 were each heated to 90° C. and mixed in advance in a stainless container so that the mass ratio was 95.0:5.0, The mixture was heated and stirred at 90°C for 15 minutes. Then, it was cooled to 25° C. to prepare Ink 3.

(2) Measurement of Physical Properties (2-1) Measurement of Ink Viscosity The physical properties of Ink 1 and Ink 2 (viscosity at 30° C. and 80° C., gelation temperature) were measured by the following methods.

The obtained ink was set in a stress-controllable rheometer (Physica MCR300, manufactured by Anton Paar) that can control the temperature. Next, after heating the ink to 100° C., it was cooled to 20° C. at a temperature lowering rate of 0.1° C./s, a strain of 5%, and an angular frequency of 10 radian/s, and the dynamic viscoelasticity at the time of temperature lowering was measured. For the measurement, a cone plate (CP75-1, manufactured by Anton Paar) having a diameter of 75.033 mm and a cone angle of 1.017° was used. The temperature control was performed by a Peltier element type temperature control device (TEK150P/MC1) attached to the Physica MCR300.

In the obtained temperature change curve of dynamic viscoelasticity, the complex viscosities at 30° C. and 80° C. were read and defined as “30° C. viscosity” and “80° C. viscosity”. Further, the temperature at which the complex viscosity becomes 200 mPa·s or more was read from the obtained temperature change curve of dynamic viscoelasticity and defined as “gelling temperature (° C.)”.

(2-2) Measurement results Ink 1:30° C. viscosity=1.9×10 ⁴ mPa·s, 80° C. viscosity=10 mPa·s, gelling temperature 63° C.
Ink 2:30° C. viscosity=4.8×10 ⁵ mPa·s, 80° C. viscosity=10 mPa·s, gelling temperature 60° C.
Ink 3: 30° C. viscosity=1.0×10 ⁵ mPa·s, 80° C. viscosity=9 mPa·s, gelling temperature 58° C.

As described above, it was confirmed that all of Ink 1, Ink 2 and Ink 3 undergo a sol-gel phase transition depending on the temperature and are in a gel state at 30°C.
In addition, it was confirmed that the ink composed of A component A-1 and B component B-4 used in Example 10 described later also had a sol-gel phase transition depending on the temperature and was in a gel state at 30°C.

(2-3) Measurement of melting point of B component The melting point of the B component used as the above B component was 3.0 mg of a sample measured by DSC (model name: manufacturer) at a rate of 5°C/min from 120°C to 30°C. It was determined by analyzing the temperature drop. The melting point was defined as the intersection between the baseline and the rising portion of the precipitation peak. The measurement results of the melting point of the gelling agent are shown in Table I.

(3) Example 1
(3-1) Image Formation The inkjet image forming apparatus shown in FIG. 7 was equipped with the ink supply unit of Structural Example 1, and images were continuously formed on the recording medium. A component A-1 and a B component B-1 were set in the ink supply section of the configuration example 1, and the heating unit was heated to 90°C. Then, the liquid feed amounts of the A component and the B component were adjusted so that the mixing mass ratio of the A component and the B component was 98.0:2.0. The ink jet head and the sub-tank-ink jet head channel were also heated to 90°C.

As the recording medium, OK top coated paper (Oji Paper Co., Ltd.) was used. On a recording medium, a solid image of 15 cm×15 cm, a positive and a negative of 5 points of MS Mincho type (excellent) and a negative (white characters) were printed on a recording medium at 600×600 dpi. The temperature of the recording medium was controlled to be 45°C. Within 1 second after printing, the ink layer was cured by irradiation with an LED lamp (395 nm, 8 W/cm ² , manufactured by Phoseon Technology). The conveyance speed of the recording medium was 400 mm/sec.

(3-2) Continuous printing The test for carrying out the above continuous printing for 5 hours a day was repeated for 20 days. At the end of the one-day test, the device was turned off and before the next day's test, the device was turned on.

(4) Example 2
Image formation and continuous printing were carried out in the same manner as in Example 1 except that the B component was replaced with B-2 and the mixing mass ratio of the A component and the B component was changed as shown in Table I.

(5) Example 3
In Example 1, except that the ink supply section was replaced by the configuration example 2, the B component was replaced by B-2, and the mixing mass ratio of the A component and the B component was changed as shown in Table I, Image formation and continuous printing were performed.

(6) Example 4
Image formation and continuous printing were carried out in the same manner as in Example 1 except that the ink supply unit was replaced with the configuration example 3.

(7) Examples 5 and 6
Image formation and continuous printing were carried out in the same manner as in Example 2 except that the mixing mass ratio of the A component and the B component was changed as shown in Table I.

(8) Examples 7-9
Image formation and continuous printing were carried out in the same manner as in Example 1 except that the component A was A-2, the component B was B-3, and the mixing mass ratio was changed as shown in Table I.

(9) Example 10
Image formation and continuous printing were carried out in the same manner as in Example 1 except that the B component was replaced with B-4.

(10) Comparative Example 1
In Example 1, the ink supply unit was replaced with Example 4, and the ink had the same composition as in Example 1, but the ink was prepared in advance outside the inkjet ink image forming apparatus, and image formation and Continuous printing was performed.
FIG. 5 illustrates a configuration example 4 of an ink supply unit of a general inkjet printer used in a comparative inkjet recording device. In the configuration example 4, the gel ink is sent in the state where the gel is broken by being stirred by the ink stirring blade 210 in the ink storage tank 201. The gel ink sent to the sub tank 209 is heated by the heating unit 206 and sent to the head in a sol state.

(11) Comparative example 2
In Comparative Example 1, the ink supply unit was replaced with Configuration Example 5, and the ink 1 was used to perform image formation and continuous printing.
FIG. 6 illustrates a configuration example 5 of an ink supply unit of a general inkjet printer used in a comparative inkjet recording device. In the configuration example 5, when gel ink is used, the entire apparatus is heated by the heating unit 210, and the ink is sent in a liquid state.

(12) Comparative Example 3
In Example 2, the ink supply unit was replaced with Example 4, and the ink had the same composition as that of Example 2, but the ink 2 was prepared in advance outside the inkjet ink image forming apparatus, and image formation and Continuous printing was performed.

(13) Comparative Example 4
In Example 7, the ink supply section was replaced with Example 4, and the ink had the same composition as that of Example 7, but the ink 3 was prepared in advance outside the inkjet ink image forming apparatus, and image formation and Continuous printing was performed.

(14) Evaluation of image quality of printed matter For the printed matter of each Example and Comparative Example obtained by continuous printing described in 3-2 above, the image quality of the first first sheet and the final printed matter after 20 days The image quality was evaluated from the following viewpoints.

⊚: No density unevenness or gloss unevenness is visually observed in the solid part, and the character part is clearly recorded in both positive and negative details.
◯: Density unevenness and gloss unevenness are not visually observed in the solid portion, but the sharpness of the positive portion of the character is slightly reduced.
Δ: A slight density unevenness or gloss unevenness is visually observed in the solid portion, and the negative portion of the character is partially crushed.
Poor: The uneven density and uneven gloss are visually observed in the solid part, and the negative part of the character is crushed.

(15) Evaluation of Continuous Printing Stability The continuous printing stability described in 3-2 above was evaluated for the printed matter obtained in each of Examples and Comparative Examples from the following viewpoints.
◯: No difference in image quality between the first sheet and the final print.
X: The image quality of the final printed matter is deteriorated as compared with the image quality of the first sheet.

(16) Evaluation of power consumption The total value of power consumption required for the continuous printing was recorded. The relative value of the power consumption of each example is described assuming that the power consumption required for continuous printing in Example 1 is 1.0.
The above results are shown in Table I.

From Table I, Examples 1 to 10 of the present invention show excellent image quality even in continuous printing. In particular, when the mass ratio of A component:B component was in the range of 90.0:10.0 to 99.5:0.5, pinning was sufficient and uneven density and crushed characters were not observed. ..

Further, in Comparative Examples 1, 3 and 4, since the ink supply unit of Structural Example 4 is used, the gelling agent is phase-separated in the flow path by repeating ON/OFF of the liquid supply of the ink supply unit. Degradation of the image quality of the final print, which is presumably because of this, was recognized.
In Comparative Example 2, since the main tank and the entire flow path are heated, the power consumption becomes enormous.

1, 101 A component storage tank 2, 102 A component liquid supply flow path 3, 103 A component liquid supply pump 4, 104 B component storage tank 5, 105 B component liquid supply pump 105a B component supply unit 6, 106 Heating Unit 7 Mixing Unit 107a Static Mixer as Mixing Unit 107b Dynamic Mixer as Mixing Unit 108 Solenoid Valve 109 Sub-Tank 110 Float Sensor 111 Negative Pressure Control Unit 112 Liquid Transfer Channel 113 Stick B Component 201 Ink Storage Tank 202 ink delivery channel 203 ink delivery pump 204 solenoid valve 206 heating unit 209 sub tank 210 float sensor 211 negative pressure control section 212 fluid delivery channel 213 inkjet head 210 ink stirring blade 211 heating unit 300 inkjet recording apparatus 310 inkjet head 311 Nozzle 313 Nozzle surface 320 Conveying section 321 Driving roller 322 Driven roller 323 Conveying belt 324 Heating device 330 Irradiating section 340 Control section 350 Storage section 360 Data input section 370 Measuring section 380 Ink supply section 400 Recording medium

Claims (12)

An inkjet recording method for recording an actinic ray-curable inkjet ink, comprising:
The actinic radiation-curable inkjet ink is a liquid composition (component A) containing a polymerizable monomer and a photopolymerization initiator, and a composition (component B) having a melting point of 40° C. or higher capable of gelling the component A. Contains and
An inkjet recording method characterized by using an actinic ray-curable inkjet ink prepared by mixing the component A and the component B in-line under heating in a mixing unit. The inkjet recording method according to claim 1, wherein the polymerizable monomer in the component A is a radically polymerizable monomer or a cationically polymerizable monomer. 3. The inkjet recording method according to claim 1, wherein the component A further contains a pigment or a dye as a colorant. The ink jet recording method according to any one of claims 1 to 3, wherein the melting point of the component B is in the range of 50 to 130°C. The inkjet recording method according to any one of claims 1 to 4, wherein the component B is a waxy gelling agent. The inkjet recording method according to any one of claims 1 to 5, wherein the component B does not contain a polymerizable monomer and a photopolymerization initiator. The mass ratio (A:B) before the A component and the B component is in the range of 90.0:10.0 to 99.5:0.5. The inkjet recording method according to any one of items 1 to 7. An inkjet recording device using an actinic ray curable inkjet ink, comprising:
The actinic radiation-curable inkjet ink is a liquid composition (component A) containing a polymerizable monomer and a photopolymerization initiator, and a composition (component B) having a melting point of 40° C. or higher capable of gelling the component A. Contains and
An inkjet head for ejecting the actinic ray curable inkjet ink toward a recording medium,
A mixing unit for mixing the component A and the component B under heating upstream of the inkjet head;
A means for controlling the mixing amount of the component A and the component B so that the prepared mixture becomes an actinic ray-curable inkjet ink that reversibly undergoes a sol-gel phase transition at a desired temperature. Inkjet recording device. The inkjet recording apparatus according to claim 8, further comprising a sub-tank downstream of the mixing unit. The inkjet recording apparatus according to claim 8 or 9, wherein the mixing unit includes a static mixer. 9. The means for mixing under heating, after heating and melting the B component upstream of the mixing unit, feeds it into the heated mixing unit containing the A component by a feed pump. The ink jet recording apparatus according to any one of claims 1 to 10. The inkjet recording apparatus according to claim 11, wherein the liquid feed pump is a diaphragm pump or a syringe pump.

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