JP2023032078A - Inkjet image forming method and inkjet image forming apparatus - Google Patents

Abstract

To provide an image forming method of a direct drawing method using active energy ray-curable ink in which a mechanism of separating temporary curing and final curing with good controllability is provided, which realizes compatibility of temporary fixing of a stable image and high robustness.SOLUTION: An inkjet image forming method has the steps of: imparting active energy ray-curable ink onto a recording medium to form a first intermediate image; irradiating the first intermediate image with active energy ray to form a second intermediate image; imparting liquid composition containing polymerization initiator onto the second intermediate image to form a third intermediate image; and irradiating the third intermediate image with active energy ray to form a final image, where the ink contains a polymerizable component, a polymerization initiator and a coloring material, the content of the polymerization initiator in the ink is 0.030 to 0.100 mass% for the polymerizable component, and the content of the coloring material in the liquid composition is 1.00 mass % or less.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to an inkjet image forming method and an inkjet image forming apparatus using an active energy ray-curable ink containing a very small amount of a polymerization initiator with respect to a polymerizable component, and a liquid composition different from the ink. .

2. Description of the Related Art Conventionally, a technique of using an active energy ray-curable ink in an inkjet type image forming apparatus is known. As an image forming method using active energy ray-curable ink (hereinafter also simply referred to as "ink"), a direct drawing method in which the ink is applied directly onto a recording medium and then irradiated with an active energy ray to form an ink film. There is an image forming method (direct drawing method). In the direct-writing image forming method, if the ink is rapidly cured by irradiating the active energy ray immediately after applying the ink onto the recording medium, sufficient adhesion to the recording medium cannot be ensured, resulting in high robustness. It may not be possible to obtain sexuality. On the other hand, if the ink is not thickened immediately after being applied to the recording medium, beading and bleeding will occur, resulting in degradation of image quality. To overcome this trade-off, a two-stage curing system is sometimes employed. That is, immediately after the ink is applied onto the recording medium, temporary curing is performed by first irradiation with an active energy ray to the extent that the ink is appropriately thickened, and then a second actinic ray is applied to further advance the curing of the ink. This is a method of performing main curing by irradiation. In Patent Literature 1, an image recording method capable of performing two-stage curing by controlling the integrated light amount of active energy rays irradiated at each stage of temporary curing and main curing, thereby realizing image recording with a certain quality. is proposed.

JP 2013-078862 A

However, in the method described in Patent Document 1, when temporary curing is performed, it is very difficult to uniformly control the progress of curing over the entire image regardless of the color or duty of the ink applied on the recording medium. difficult. For example, if the formed image has a low-duty magenta portion and a high-duty black portion, temporary curing with the same light source will cause the magenta portion to harden too much or the black portion to harden insufficiently. situation will occur. In other words, with this method, it is difficult to clearly separate temporary curing and main curing.

The present invention has been made in view of the above problems. An object of the present invention is to provide a mechanism for separating pre-curing and main curing with good controllability in a direct-drawing image forming method and image forming apparatus using an active energy ray-curable ink, thereby stably forming an image. It is to achieve both temporary fixation (image quality quality) and high robustness.

The present invention comprises a first step of applying an active energy ray-curable ink onto a recording medium to form a first intermediate image, and irradiating the first intermediate image with an active energy ray to remove the ink. a second step of increasing the viscosity to form a second intermediate image; and a third step of applying a liquid composition containing a polymerization initiator to the second intermediate image to form a third intermediate image. and a fourth step of irradiating the third intermediate image with an active energy ray to cure the ink to form a final image, wherein the active energy ray-curable ink is polymerizable component, a polymerization initiator, and a coloring material, and the content of the polymerization initiator in the ink is 0.030% by mass or more and 0.100% by mass or less with respect to the content of the polymerizable component; In the inkjet image forming method, the content of the coloring material in the liquid composition is 1.00% by mass or less.

Further, the present invention provides an ink applying device equipped with an inkjet head for applying an active energy ray-curable ink onto a recording medium to form a first intermediate image, and A first active energy ray irradiation device for forming a second intermediate image by increasing the viscosity of the ink, and applying a liquid composition containing a polymerization initiator to the second intermediate image, a liquid composition applying device for forming a third intermediate image; and a second active energy ray irradiation device for irradiating the third intermediate image with an active energy ray to cure the ink and form a final image. , wherein the active energy ray-curable ink contains a polymerizable component, a polymerization initiator, and a coloring material, and the content of the polymerization initiator in the ink is 0 with respect to the content of the polymerizable component. 0.030% by mass or more and 0.100% by mass or less, and the content of the coloring material in the liquid composition is 1.00% by mass or less.

According to the present invention, in an image forming method and an image forming apparatus of a direct writing system using an active energy ray-curable ink, a mechanism is provided to separate pre-curing and main curing with good controllability, thereby stably forming an image. Both temporary fixation (image quality) and high robustness can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a flow from each step in an inkjet image forming method according to the present invention until a final product is obtained. 1 is a schematic diagram showing the configuration of a direct-writing inkjet recording apparatus according to an embodiment of the present invention; FIG. FIG. 4 is a schematic diagram of an image evaluated for printing in Examples and Comparative Examples.

Hereinafter, the inkjet image forming method and the inkjet image forming apparatus according to the present invention will be described in detail by taking an inkjet recording apparatus as an example. However, the configuration, structure, materials, settings, etc. should be appropriately changed according to various conditions to which the invention is applied, and are not meant to limit the scope of the invention. The inkjet recording apparatus of the present invention is a direct drawing type inkjet recording apparatus to which the inkjet image forming method of the present invention is applied. The inkjet image forming method of the present invention has at least the following first to fourth steps. And the content of the polymerization initiator in the active energy ray-curable ink applied onto the recording medium in the first step is extremely small, and the liquid applied on the ink in the third step The composition is characterized by containing a polymerization initiator.
(First step)
an ink application step of applying an active energy ray-curable ink onto a recording medium to form a first intermediate image;
(Second step)
A temporary curing step of irradiating the first intermediate image with an active energy ray to thicken the ink to form a second intermediate image.
(Third step)
a liquid composition application step of applying a liquid composition containing a polymerization initiator to the second intermediate image to form a third intermediate image;
(Fourth step)
A main curing step of irradiating the third intermediate image with an active energy ray to cure the ink to form a final image.
FIG. 1 is a schematic diagram showing a flow of obtaining a final image, which is a final product, through the above four steps.

FIG. 2 is a schematic diagram showing the configuration of a direct-write ink jet recording apparatus 100 according to one embodiment of the present invention. This recording apparatus is an inkjet recording apparatus that creates a recorded matter by directly applying active energy ray-curable ink onto a recording medium 107 from an ink applying device 101 having an inkjet head. In the present embodiment, the X direction, Y direction and Z direction respectively indicate the full length direction, depth direction and height direction of the inkjet recording apparatus 100 . As shown in FIG. 2, the direct print ink jet recording apparatus 100 of the present invention has the following members.
An ink application device 101 having an inkjet head for applying active energy ray-curable ink onto a recording medium 107 to form a first intermediate image.
A first active energy ray irradiation device 102 that irradiates the first intermediate image formed on the recording medium 107 with an active energy ray to thicken the ink and form a second intermediate image.
A liquid composition application device 103 that applies a liquid composition containing a polymerization initiator to the second intermediate image formed on the recording medium 107 to form a third intermediate image.
A second active energy ray irradiation device 104 that irradiates the third intermediate image formed on the recording medium 107 with an active energy ray to cure the ink and form a final image.
A recording medium conveying device 108 for conveying the recording medium 107
Further, the direct drawing type inkjet recording apparatus 100 may have the following devices as necessary.
A pretreatment liquid applying device 105 for applying a pretreatment liquid onto the recording medium 107
A drying device 106 that promotes drying of the ink or liquid composition applied onto the recording medium 107 by heating or blowing air.
As a matter of course, each of the above members has a length in the Y direction corresponding to the recording medium 107 used.

In the direct drawing type inkjet recording apparatus 100, the recording medium 107 is conveyed in the X direction. If necessary, the pretreatment liquid applying device 105 applies pretreatment liquid onto the transported recording medium 107 , and then the ink applying device 101 applies ink sequentially. The order in which the pretreatment liquid is applied by the pretreatment liquid applying device and the ink is applied by the ink applying device is not limited to this order. Thereby, a first intermediate image is formed on the recording medium 107 . The first intermediate image formed on the recording medium 107 is irradiated with an active energy ray by the first active energy ray irradiation device 102 and thickened to become a second intermediate image. At this time, by making the amount of the polymerization initiator contained in the ink extremely small, even if the first active energy ray irradiation is performed, part of the polymerizable component in the ink remains in an unreacted state. , the ink can be controlled to a temporary hardening state. After that, the liquid composition applying device 103 applies a liquid composition containing a polymerization initiator onto the second intermediate image formed on the recording medium 107 , thereby forming a third intermediate image on the recording medium 107 . An image is formed. By supplying an additional polymerization initiator to the temporarily cured ink and re-irradiating it with active energy rays, the aim is to react unreacted polymerizable components and create a state in which further curing can proceed. be. Then, the third intermediate image formed on the recording medium 107 is irradiated with active energy rays from the second active energy ray irradiation device 104 to progress curing and obtain a final image. In this step, most of the polymerizable components in the ink are polymerized, and the main curing is completed. Further, in the present embodiment, drying may be accelerated by the drying device 106 at any timing between the ink applying process and the main curing process. By volatilizing the ink and the solvent component in the liquid composition with a drying device and then curing by irradiation with active energy rays, it is expected that an image with higher fastness can be obtained.
Each configuration of the direct drawing type ink jet recording apparatus according to the present embodiment will be described below.

<Ink application device>
The ink application device 101 is a device capable of performing the first step, that is, the step of applying active energy ray-curable ink onto the recording medium 107 to form a first intermediate image on the recording medium 107. is. When the pretreatment liquid is applied onto the recording medium 107, the pretreatment liquid and the ink are mixed, and the first intermediate image is formed by the pretreatment liquid and the ink.
In this embodiment, an inkjet head is used as an ink application device that applies ink. As an inkjet head, for example, an electro-thermal transducer causes film boiling in ink to form air bubbles to eject ink, an electro-mechanical transducer ejects ink, and an ink is ejected using static electricity. Examples include a form of discharging. In this embodiment, a known inkjet head can be used. Among them, from the viewpoint of performing high-speed and high-density printing, one using an electric-heat converter is preferably used. Drawing is performed by receiving an image signal and applying the required amount of ink to each position.
The inkjet head in this embodiment is a line head having a length in the Y direction corresponding to the recording medium 107 to be used. may be used. The inkjet head has an ink ejection surface with nozzles open on one surface thereof, and the ink ejection surface faces the surface of the recording medium 107 with a minute gap (of the order of several millimeters).
The ink applying device 101 may have a plurality of inkjet heads to apply each color ink onto the recording medium 107 . For example, when yellow ink, magenta ink, cyan ink, and black ink are used to form respective color images, the ink application device has four inkjet heads that eject the four types of ink onto the recording medium 107, respectively. You may have These are arranged side by side in the X direction.

[Active energy ray-curable ink]
As the active energy ray-curable ink of this embodiment, an ink containing at least a polymerizable component that is cured by irradiation with an active energy ray, a polymerization initiator, and a coloring material is used. Also, the content of the polymerization initiator in the ink is 0.030% by mass or more and 0.100% by mass or less with respect to the polymerizable component in the ink.

(Polymerizable component)
Although the polymerizable component that is cured by irradiation with active energy rays is not particularly limited, it is preferably a polymerizable component having an ethylenically unsaturated group. Examples of polymerizable components are shown in Tables 1-1 to 1-4 below.

In the present invention, the polymerizable component in the ink is preferably liquid at room temperature. Many active energy ray-curable polymerizable components are insoluble in water. It is preferable to have Hydrophilic binding groups include, for example, hydroxyl groups, carboxyl groups, phosphoric acid groups, sulfonic acid groups, salts thereof, ether bonds, amide bonds, and the like. Further, when the ink is a water-based ink, the polymerizable component more preferably has a (meth)acrylamide structure from the viewpoint of hydrolysis resistance. Examples having a (meth)acrylamide structure include M-12 to M-22 in the above table. In addition, the polymerizable component may be further contained in the pretreatment liquid and the liquid composition described below.

(Polymerization initiator)
When the polymerizable component of the ink described above is a radically polymerizable compound and curing is to proceed by irradiation with active energy rays, a polymerization initiator that generates radicals upon irradiation with active energy rays is added. As long as it is such a polymerization initiator, there are no particular restrictions on the structure and the like of the compound. Examples of polymerization initiators are shown in Table 2 below.

Many polymerization initiators are insoluble in water, but when the ink of the present invention is a water-based ink, the polymerization initiator preferably has a hydrophilic binding group in its structure. Hydrophilic binding groups include, for example, hydroxyl groups, carboxyl groups, phosphoric acid groups, sulfonic acid groups, salts thereof, ether bonds, amide bonds, and the like. Examples having a phosphoric acid group or a sulfonic acid group include PI-6 to PI-7 in Table 2. When a thioxanthone-based polymerization initiator such as PI-7 is used as the polymerization initiator, it is preferable to add a hydrogen donor. Examples of hydrogen donors include triethanolamine and monoethanolamine, but are not limited to these. Also, two or more polymerization initiators may be used in combination.
Furthermore, in order to improve the reaction rate, it is also possible to use a sensitizer that has the role of broadening the absorption wavelength of light. A sensitizer may be used in combination with the polymerizable component. Examples of such sensitizers include compounds having skeletons such as α-hydroxyketones, benzyl ketals, acylphosphine, thioxanthone and the like.

(colorant)
Dyes, pigments, and dispersions thereof are generally preferably used as colorants in inks.
The dye is not particularly limited, and commonly used dyes can be used without any problem. For example, C.I. I Direct Blue 6, 8, 22, 34, 70, 71, 76, 78, 86, 142, 199, C.I. I Acid Blue 9, 22, 40, 59, 93, 102, 104, 117, 120, 167, 229, C.I. I Direct Red 1, 4, 17, 28, 83, 227, C.I. I Acid Red 1, 4, 8, 13, 14, 15, 18, 21, 26, 35, 37, 249, 257, 289, C.I. I Direct Yellow 12, 24, 26, 86, 98, 132, 142, C.I. I Acid Yellow 1, 3, 4, 7, 11, 12, 13, 14, 19, 23, 25, 34, 44, 71, C.I. I Food Black 1, 2, C.I. Acid Black 2, 7, 24, 26, 31, 52, 112, 118 and the like.
The pigment is not particularly limited, and any commonly used pigment can be used without any problem. For example, C.I. Pigment Blue 1,2,3,15:3,16,22, C.I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn) 57 (Ca), 112, 122, C.I. Pigment Yellow 1, 2, 3, 13, 16, 83, carbon black #2300, 900, 33, 40, 52, MA7, 8, MCF88 (all trade names, manufactured by Mitsubishi Chemical Corporation), RAVEN1255 (trade name , Columbia), REGAL330R, 660R, MOGUL (all trade names, manufactured by Cabot), Color Black FW1, FW18, S170, S150, Printex35 (all trade names, manufactured by Degussa).

When the ink of the present invention is a water-based ink, a dispersing resin capable of dispersing the dye and pigment is preferably water-soluble and has a weight-average molecular weight of about 1,000 to 15,000. Examples include block copolymers or random copolymers of the following monomers, salts thereof, and the like:
- styrene and its derivatives - vinylnaphthalene and its derivatives - aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids - acrylic acid and its derivatives - maleic acid and its derivatives - itaconic acid and its derivatives - fumaric acid and its derivatives derivative.

Moreover, an active energy ray-curable resin can be used alone without using a dispersion resin. In addition, the present invention is not subject to any limitation as to the form of the ink, and it is possible to appropriately use a self-dispersion type, a resin dispersion type, a microcapsule type, or the like.

(Water and water-soluble organic solvent)
The ink may contain water and/or an organic solvent in order to control the inkjet ejection property and drying property. The water is preferably deionized water such as by ion exchange. As the organic solvent, a water-soluble organic solvent having a high boiling point and a low vapor pressure is preferable. Examples include (poly)ethylene glycols such as ethylene glycol, diethylene glycol and triethylene glycol, (poly)propylene glycols such as propylene glycol and dipropylene glycol, butylene glycol, thiodiglycol, hexylene glycol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, glycerin and the like. Alcohols such as ethyl alcohol and isopropyl alcohol, and various surfactants can also be added as components for adjusting viscosity, surface tension, and the like. When the ink is a water-based ink containing water, it preferably contains water in an amount of 50.0% by mass or more based on the total mass of the ink from the viewpoint of dischargeability.

Regarding the compounding ratio of each component in the ink, this embodiment is characterized in that the content of the polymerization initiator is 0.030% by mass or more and 0.100% by mass or less with respect to the polymerizable component. Moreover, it is preferable that the content of the polymerization initiator is 0.050% by mass or more and 0.080% by mass or less with respect to the polymerizable component. The content of the polymerizable component in the ink is preferably 3.00% by mass or more, more preferably 10.0% by mass or more, relative to the total amount of the ink. The content of the polymerization initiator in the ink is adjusted within the above range according to the content of the polymerizable component. The other components can be adjusted within the ejection range depending on the selected inkjet recording method, head ejection force, nozzle diameter, and the like.

<First active energy ray irradiation device>
A first active energy ray irradiation device (hereinafter also referred to as a “first irradiation device”) irradiates the second step, specifically, the first intermediate image with an active energy ray to irradiate the ink. An apparatus capable of carrying out the step of thickening to form a second intermediate image. As the first irradiation device, any known irradiation device can be used without particular limitation as long as it is a device capable of irradiating an active energy ray capable of promoting polymerization of ink. Examples include mercury lamps, metal hydride lamps, excimer lamps, and LEDs. In addition, the active energy ray irradiated by the first irradiation device is also referred to as "first active energy ray".
In the present invention, in order to cure the ink, at least one or more first irradiation devices are arranged after the ink applying device and before the liquid composition applying device. Upon receiving the active energy ray irradiation from the first irradiation device, the polymerizable component in the ink advances the polymerization reaction. Here, in the present invention, since the amount of the polymerization initiator in the ink is extremely small, a part of the polymerizable component in the ink is intentionally left in an unreacted state so that the ink is temporarily cured. can do. The integrated amount of energy rays irradiated by the first irradiation device is not particularly limited, but is preferably 400 mJ/cm ² or more in order to sufficiently thicken the ink. Conventionally, in order to temporarily cure an active energy ray-curable ink, it was common to set a limit (upper limit) on the cumulative light amount of the active energy ray applied during temporary curing. However, the present invention is characterized in that there is basically no limit to the integrated amount of energy rays emitted by the first irradiation device.

<Liquid composition application device>
The liquid composition application device 103 applies a liquid composition containing a polymerization initiator onto the second intermediate image formed on the recording medium 107 in the second step, and onto the recording medium 107, An apparatus capable of performing a third step of forming a third intermediate image. By applying the liquid composition to the second intermediate image, an additional polymerization initiator is supplied to the temporarily cured active energy ray-curable ink (second intermediate image), and a third intermediate image is formed. is formed.

In this embodiment, an inkjet head is preferably used as the liquid composition application device. As an inkjet head, for example, an electro-thermal transducer causes film boiling in ink to form air bubbles to eject ink, an electro-mechanical transducer ejects ink, and an ink is ejected using static electricity. Examples include a form of discharging. In this embodiment, a known inkjet head can be used. Among them, from the viewpoint of performing high-speed and high-density printing, one using an electro-thermal converter is preferably used. Drawing is performed by receiving an image signal and applying the required amount of liquid composition to each position.
The inkjet head used as the liquid composition applying device in this embodiment is a line head having a length in the Y direction corresponding to the recording medium 107. However, depending on the configuration of the device, the direction perpendicular to the conveying direction of the recording medium may be used. A serial head that scans to The inkjet head has an ejection surface with nozzles open on one surface thereof, and the ejection surface faces the surface of the recording medium 107 with a minute gap (of the order of several millimeters).

[Liquid composition]
(Polymerization initiator)
The liquid composition of this embodiment contains at least a polymerization initiator. The polymerization initiator contained in the liquid composition is basically selected from those that can be used in the ink described above. The polymerization initiator contained in the liquid composition may be the same as that contained in the ink, or may be different. The content of the polymerization initiator in the liquid composition is preferably 0.500% by mass or more of the total amount of the polymerizable components contained in the ink and optionally the polymerizable components contained in the liquid composition. It is more preferably at least 0.000% by mass. As a result, the actinic energy ray-curable ink, which has been temporarily cured in the second step, can be supplied in the third step with a sufficient amount of the polymerization initiator to fully cure the ink.

(colorant)
The liquid composition contains no colorant, or a very low proportion, if any. Specifically, the content of the coloring material in the liquid composition is 1.00% by mass or less, and the liquid composition preferably contains no coloring material.

The liquid composition is not limited except that it contains the polymerization initiator and optionally a colorant. The liquid composition, like the ink, may contain a polymerizable component, may contain water or an organic solvent for controlling the ink jetting property and drying property, and may further contain a surfactant. . Examples of the polymerizable component include those exemplified as the polymerizable component in the ink. When the liquid composition is a water-based liquid composition containing water, it preferably contains water in an amount of 50.0% by mass or more based on the total mass of the liquid composition, from the viewpoint of dischargeability. The water is preferably deionized water such as by ion exchange.

<Second active energy ray irradiation device>
A second active energy ray irradiation device (hereinafter also abbreviated as a “second irradiation device”) irradiates the fourth step, specifically, the third intermediate image with an active energy ray, and finally Apparatus capable of performing the step of forming an image. As the second irradiation device, any known irradiation device can be used without particular limitation as long as it can irradiate an active energy ray capable of further advancing the curing of the temporarily cured ink to which the liquid composition has been applied. be able to. Examples include mercury lamps, metal hydride lamps, excimer lamps, and LEDs. In addition, the active energy ray irradiated by the second irradiation device is also referred to as "second active energy ray".
In the present invention, at least one or more second irradiation devices are arranged after the liquid composition applying device in order to further promote the curing of the temporarily cured ink to which the liquid composition has been applied. The temporarily cured ink to which the liquid composition has been applied is completely cured by the irradiation of the active energy ray by the second irradiation device to reach the main cured state.
When the temporarily cured ink is fully cured by irradiation with active energy rays from the second irradiation device, the integrated light quantity of the irradiated light is preferably 200 mJ/cm ² or more, and is 2000 mJ/cm ² or more. is more preferred.

<Pretreatment liquid application device>
The inkjet recording apparatus 100 of this embodiment may have a pretreatment liquid applying device 105 that applies a pretreatment liquid onto the recording medium 107 . The pretreatment liquid applying device 105 shown in FIG. 2 includes a pretreatment liquid container 105a and pretreatment liquid applying members 105b and 105c for applying the pretreatment liquid in the pretreatment liquid container 105a onto a recording medium. and a roller. For the pretreatment liquid, the configuration of the application device and the components contained therein can be freely selected according to the purpose. For example, the fluidity of a portion of the ink/or ink composition on the recording medium 107 is lowered, and the colorant component in the ink is aggregated for the purpose of helping to suppress bleeding and beading during image formation. It is conceivable to apply a pretreatment liquid containing valent metal ions, cationic components such as cationic resins, organic acids, and the like. As another example, it is conceivable to apply a pretreatment liquid containing a urethane resin emulsion or the like for the purpose of improving the adhesion of the image to the recording medium 107 .
The pretreatment liquid applying device 105 may be any device that can apply the pretreatment liquid onto the recording medium, and various conventionally known devices can be used as appropriate. Specifically, a gravure offset roller, an inkjet head, a die coating device (die coater), a blade coating device (blade coater) and the like can be mentioned. The application of the pretreatment liquid by the pretreatment liquid application device 105 may be performed before or after application of the ink as long as it can be mixed (reacted) with the ink on the recording medium. Preferably, the pretreatment liquid is applied before applying the ink.

<Drying device>
The inkjet recording apparatus 100 of this embodiment has a drying device 106 for the purpose of promoting drying of the pretreatment liquid, the active energy ray-curable ink, and the liquid composition applied onto the recording medium 107. good too. The drying device 106 is introduced at an arbitrary position after the ink application device and before the second active energy ray irradiation device, and at any timing between the first step and the fourth step, It promotes drying of the pretreatment liquid, active energy ray-curable ink, and liquid composition. By evaporating solvent components contained in the pretreatment liquid, ink, and liquid composition by the drying device 106, and then curing by irradiation with active energy rays, it is expected that a final image with higher durability can be obtained. . The drying device is preferably arranged after the liquid composition applying device so that the pretreatment liquid, ink, and solvent components contained in all of the liquid composition can be volatilized at the same time. The drying device 106 may be any device capable of accelerating the drying of the pretreatment liquid, ink, and liquid composition, and conventionally known various devices can be appropriately used.

<Recording medium and recording medium conveying device>
In this embodiment, the recording medium 107 is not particularly limited, and any known recording medium can be used. Examples of the recording medium include a long object wound into a roll or a sheet cut into a predetermined size. Materials include paper, plastic film, wood board, cardboard, and metal film. In FIG. 2, a recording medium conveying device 108 for conveying the recording medium 107 is composed of a recording medium delivery roller 108a, a recording medium take-up roller 108f, and recording medium conveying rollers 108b to 108e. However, as long as the recording medium can be transported, the configuration is not particularly limited to this configuration.

The first intermediate image formed on the recording medium is reliably pre-cured by the first actinic energy ray irradiation by forming an image with the apparatus configuration and process as described above. As a result, it is possible to form a high-quality image in which beading, bleeding, and the like are suppressed. After that, a liquid composition containing a polymerization initiator is applied onto the temporarily cured second intermediate image, and a second active energy ray irradiation is performed to fully cure the third intermediate image, resulting in high fastness. can be expressed. In this manner, in a direct-writing type inkjet image forming method and an inkjet image forming apparatus using an active energy ray-curable ink, provision of a temporary curing mechanism with good controllability enables temporary fixing of an image (image quality). It is possible to achieve both high robustness after main curing.

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. The present invention is by no means limited by the following examples, as long as the gist thereof is not exceeded. Unless otherwise specified below, "parts" represent parts by mass and "%" represents mass%.

(Preparation of pigment dispersion)
When a pigment is used as a water-based ink, a pigment dispersion obtained by dispersing a mixture of the following raw materials is centrifuged to remove coarse particles, and a pigment dispersion having a pigment concentration of 10.0% is used. bottom.
・Pigments (magenta: pigment red 122, black: carbon black): 10.0%
・Aqueous resin solution containing the following resins (pigment dispersant): 15.0%
Resin: styrene-acrylic acid-ethyl acrylate copolymer (acid value 150, weight average molecular weight 8000, solid content 20% aqueous solution, neutralizer KOH)
・Ion-exchanged water: 75.0%

When a pigment was used as the non-aqueous ink, the following components were stirred and mixed to obtain a millbase.
・Pigments (magenta: pigment red 122, black: carbon black): 30.0%
SR9003 (propoxylated (2) neopentyl glycol diacrylate (a compound obtained by diacrylated a 2 mol adduct of neopentyl glycol propylene oxide), trade name, manufactured by SARTOMER): 49.0%
・SOLSPERSE32000 (dispersant, trade name, manufactured by Noveon): 20.0%
・ FIRSTCURE ST-1 (polymerization inhibitor, trade name, manufactured by Chem First): 1.00%

(Preparation of ink and liquid composition)
Inks 1 to 8 and liquid compositions 1 to 5 were prepared with the following compositions. Detailed compositions are shown in Tables 3 and 4. In the table, the units of numerical values are parts. In each water-based ink and liquid composition, the water content was adjusted so that the total amount of all components contained in the ink and liquid composition was 100 parts.
(composition)
Pigment dispersion: any of the above aqueous or non-aqueous pigment dispersions (Tables 3 and 4 describe the mass of the pigment itself, not the pigment dispersion)
-Polymerizable components (from Tables 1-2 to 1-4 above): M-13, M-18, M-23, M-24
- Polymerization initiator (from Table 2 above): PI-1, PI-6
・Surfactant: BYK-307 (trade name, BYK-Chemie)
・Solvent: Water

[Examples 1 to 8, Comparative Examples 1 to 5]
(Formation of image)
In this example and comparative example, an image in which a solid portion, a thin line portion and a check pattern portion as shown in FIG. The recording medium was transported at a transport speed of 300 mm/sec. This direct drawing type ink jet recording apparatus has a drying device that applies warm air at 60° C. for 1 second after applying the liquid composition and before performing the second activation energy irradiation. As a recording medium, an easily adhesive PET film (trade name: HL92W-100μ, manufactured by Toyobo Co., Ltd.) was prepared.
First, any one of the black and magenta inks 1 to 8 having the composition described above was applied onto the recording medium by an ink applying device to form a first intermediate image. When water-based ink was used, an ink-jet head (nozzle row density: 1200 dpi) of a type that ejects ink by an on-demand system using an electro-thermal conversion element was used as the ink application device. Ink was applied at 4 ng/1200 dpi by driving at a frequency of 14.173 kHz. When using an oil-based ink, the same amount of ink was applied using a head mounted on an IJ-DESK-H on-demand inkjet coating device (trade name, manufactured by BMT Co., Ltd.) as an ink applying device. . The amount of ink applied was calculated by measuring the mass of the recording medium before and after application.
Next, the first intermediate image on the recording medium is irradiated with activation energy using a UV-LED irradiation device (trade name: UV-LED Unijet, wavelength 395 nm, manufactured by Ushio Inc.) as a first active energy ray irradiation device. A second intermediate image was obtained by exposing the line and thickening the first intermediate image. At this time, the peak illuminance of the irradiated active energy rays was 2000 mW/cm ² , and the integrated amount of light was individually set for each example and comparative example.
Next, on the second intermediate image on the recording medium, any one of liquid compositions 1 to 5 having the composition described above was applied by a liquid composition applying device to form a third intermediate image. When the liquid composition contained a pigment, the liquid composition was applied so that the ink and the liquid composition applied thereon had the same color (black or magenta). The liquid composition applicator used in the present examples and comparative examples was selected based on the same criteria as the ink applicator. Also, the amount of the liquid composition applied was the same as that of the ink.
Next, the third intermediate image is irradiated with active energy rays using a UV-LED irradiation device (trade name: UV-LED Unijet, wavelength: 395 nm, manufactured by Ushio Inc.) as a second active energy irradiation device. , the third intermediate image was main cured to obtain the final image. At this time, the peak illuminance and integrated light quantity of the irradiated active energy rays were set to 2000 mW/cm ² and 2000 mJ/cm ² , respectively.

(Evaluation of image quality and robustness)
Image quality and fastness of images formed in each example and comparative example were evaluated. Regarding the image quality, the image quality evaluation portion in FIG. 3 was observed using a microscope, and the quality of beading/bleed was evaluated on a three-grade scale from A to C based on the thin line portion and check pattern portion. As for fastness, a surface scratching test was performed using a Gakushin tester on the fastness evaluation portion shown in FIG. The condition of the surface rubbing test was to rub 500 g of dry Kanakin No. 3 back and forth 150 times. Table 5 below shows the active energy ray-curable inks and liquid compositions used in Examples 1 to 8 and Comparative Examples 1 to 5, and the total amount of polymerizable components contained in the inks and liquid compositions. The content of the polymerization initiator, the integrated amount of light in the first actinic energy ray irradiation, and the image quality and fastness evaluation results of the final image are summarized.

In Examples 1 and 2, the amount of polymerization initiator contained in the ink was moderately adjusted. In addition, the integrated amount of light in the first actinic energy ray irradiation was sufficiently high, and the amount of the polymerization initiator supplied to the ink by applying the liquid composition thereafter was also appropriate. As a result, both the magenta and black inks can be temporarily cured to an appropriate viscosity, and the final curing after application of the liquid composition can be ideally performed, and the final image can be highly durable while maintaining image quality. I was able to achieve sexuality.
Example 3 is an example using a non-aqueous ink and liquid composition, unlike the other examples using an aqueous ink and liquid composition. In this example, as in Examples 1 and 2, both the magenta ink and the black ink were appropriately pre-cured, and the amount of the polymerization initiator supplied to the ink by the subsequent application of the liquid composition was also appropriate. As a result, both the magenta and black inks can be temporarily cured to an appropriate viscosity, and the final curing after application of the liquid composition can be ideally performed, and the final image can be highly durable while maintaining image quality. I was able to achieve sexuality.

In Example 4, the amount of polymerization initiator contained in the ink was the minimum amount for practicing the present invention. The integrated amount of light in the first actinic energy ray irradiation was sufficiently high, and the amount of the polymerization initiator supplied to the ink by applying the liquid composition thereafter was appropriate. As a result, both the magenta and black inks were temporarily cured to such an extent that the minimum image quality could be maintained. Further, the main curing after application of the liquid composition could be ideally carried out, and high fastness of the final image could be realized.
In Example 5, the amount of polymerization initiator contained in the ink was the upper limit for practicing the present invention. The integrated amount of light in the first actinic energy ray irradiation was sufficiently high, and the amount of the polymerization initiator supplied to the ink by applying the liquid composition thereafter was appropriate. As a result, both the magenta and black inks were provisionally cured to a level at which image quality can be sufficiently maintained. In addition, the main curing after application of the liquid composition could be carried out satisfactorily, and although inferior to Example 1, high fastness of the final image could be realized.

In Example 6, the amount of the polymerization initiator contained in the ink was appropriately adjusted, and the integrated amount of light in the first active energy ray irradiation was sufficiently high. The amount of polymerization initiator supplied to the ink by subsequent application of the liquid composition was within the preferred range for carrying out the present invention. As a result, both the magenta and black inks could be pre-cured to have appropriate viscosities, and image quality could be maintained. Regarding the main curing after application of the liquid composition, although inferior to Example 1, sufficiently high fastness was able to be exhibited.
In Example 7, the amount of the polymerization initiator contained in the ink was appropriately adjusted, and the integrated amount of light in the first active energy ray irradiation was sufficiently high. Also, the amount of the polymerization initiator supplied to the ink by the subsequent application of the liquid composition was also appropriate. On the other hand, since the liquid composition contained a small amount of coloring material, both the magenta and black inks could be pre-cured to an appropriate viscosity. Then it was inferior. The main curing after application of the liquid composition could be ideally carried out, and high fastness of the final image could be realized.
In Example 8, the amount of the polymerization initiator contained in the ink was appropriately adjusted, and the amount of the polymerization initiator supplied to the ink by the subsequent application of the liquid composition was also appropriate. On the other hand, the integrated amount of light in the first active energy ray irradiation was set lower than in other examples. As a result, both magenta and black inks can be temporarily cured to the extent that the image quality can be maintained at a minimum, and the main curing after application of the liquid composition is ideally performed, realizing high durability of the final image. I was able to

In Comparative Example 1, the amount of the polymerization initiator contained in the ink was less than the lower limit amount specified in the present invention. As a result, both the magenta and black inks could not be pre-cured to a viscosity at which the minimum image quality could be maintained by the first actinic energy ray irradiation, and the image quality was impaired.
In Comparative Example 2, the amount of the polymerization initiator contained in the ink exceeded the upper limit amount specified in the present invention. Therefore, at the stage of the first actinic energy ray irradiation, the easily curable magenta ink was excessively cured, and the fastness of the final image could not be sufficiently ensured.
In Comparative Example 3, the liquid composition contained a coloring material in an amount larger than that specified in the present invention. As a result, both the magenta and black inks could be pre-cured to a suitable viscosity, but the image quality of the final image was remarkably deteriorated.

Comparative Examples 4 and 5 are examples in which the image is temporarily cured by adjusting the cumulative amount of light of the active energy ray irradiated at the time of temporary curing without using the liquid composition. In Comparative Example 4, the magenta ink, which is easy to cure, was temporarily cured to an appropriate viscosity by the first irradiation of the active energy beam, but the black ink, which is difficult to cure, hardly increased in viscosity, and the image quality was sufficiently ensured. I couldn't do it. Further, in Comparative Example 5, the hard-to-cure black ink was temporarily cured to an appropriate viscosity by the first active energy ray irradiation, but the easy-to-cure magenta ink was over-cured, resulting in poor fastness in the final image. could not secure enough.

100 Direct-drawing inkjet recording device 101 Ink applying device 102 First active energy ray irradiation device 103 Liquid composition applying device 104 Second active energy ray irradiation device 107 Recording medium

Claims (14)

a first step of applying an active energy ray-curable ink onto a recording medium to form a first intermediate image;
a second step of irradiating the first intermediate image with an active energy ray to thicken the ink to form a second intermediate image;
a third step of applying a liquid composition containing a polymerization initiator to the second intermediate image to form a third intermediate image;
a fourth step of irradiating the third intermediate image with an active energy ray to cure the ink to form a final image;
has
The active energy ray-curable ink contains a polymerizable component, a polymerization initiator, and a coloring material, and the content of the polymerization initiator in the ink is 0.030% by mass with respect to the content of the polymerizable component. 0.100% by mass or less,
An inkjet image forming method, wherein the content of the coloring material in the liquid composition is 1.00% by mass or less. The content of the polymerization initiator in the active energy ray-curable ink is 0.050% by mass or more and 0.080% by mass or less with respect to the content of the polymerizable component in the active energy ray-curable ink. The inkjet image forming method according to claim 1 . In the third step, the content of the polymerization initiator in the liquid composition to be applied to the second intermediate image is equal to the content of the polymerizable component contained in the active energy ray-curable ink and optionally 3. The inkjet image forming method according to claim 1, wherein the total amount of the polymerizable component contained in the liquid composition is 0.500% by mass or more. In the third step, the content of the polymerization initiator in the liquid composition to be applied to the second intermediate image is equal to the content of the polymerizable component contained in the active energy ray-curable ink and optionally 4. The inkjet image forming method according to claim 3, wherein the total amount of the polymerizable component contained in the liquid composition is 1.000% by mass or more. The inkjet image forming method according to any one of claims 1 to 4, wherein the integrated amount of active energy rays irradiated in the second step is 400 mJ/cm ² or more. The inkjet image forming method according to any one of claims 1 to 5, wherein the liquid composition does not contain a coloring material. The inkjet image forming method according to any one of claims 1 to 6, wherein the active energy ray-curable ink and the liquid composition each contain 50.0% by mass or more of water based on the total mass. an ink application device having an inkjet head for applying active energy ray-curable ink onto a recording medium to form a first intermediate image;
a first active energy ray irradiation device for irradiating the first intermediate image with an active energy ray to thicken the ink to form a second intermediate image;
a liquid composition applying device for applying a liquid composition containing a polymerization initiator to the second intermediate image to form a third intermediate image;
a second active energy ray irradiation device for irradiating the third intermediate image with an active energy ray to cure the ink to form a final image;
with
The active energy ray-curable ink contains a polymerizable component, a polymerization initiator, and a coloring material, and the content of the polymerization initiator in the ink is 0.030% by mass with respect to the content of the polymerizable component. 0.100% by mass or less,
An inkjet image forming apparatus, wherein the content of the coloring material in the liquid composition is 1.00% by mass or less. The content of the polymerization initiator in the active energy ray-curable ink is 0.050% by mass or more and 0.080% by mass or less with respect to the content of the polymerizable component in the active energy ray-curable ink. The inkjet image forming apparatus according to claim 8. The content of the polymerization initiator in the liquid composition applied to the second intermediate image by the liquid composition applying device is determined by the amount of the polymerizable component contained in the actinic energy ray-curable ink and the optional 10. The inkjet image forming apparatus according to claim 8, wherein the total amount of the polymerizable component contained in the liquid composition is 0.500% by mass or more. The content of the polymerization initiator in the liquid composition applied to the second intermediate image by the liquid composition applying device is determined by the amount of the polymerizable component contained in the actinic energy ray-curable ink and the optional 11. The inkjet image forming apparatus according to claim 10, wherein the content is 1.000% by mass or more based on the total amount of polymerizable components contained in said liquid composition. 12. The inkjet image forming apparatus according to any one of claims 8 to 11, wherein the integrated amount of active energy rays irradiated by said first active energy ray irradiation device is 400 mJ/cm2 ^or more. The inkjet image forming apparatus according to any one of claims 8 to 12, wherein the liquid composition does not contain a coloring material. The inkjet image forming apparatus according to any one of claims 8 to 13, wherein the active energy ray-curable ink and the liquid composition each contain 50.0% by mass or more of water based on the total mass.

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