JP6968976B2 - Image recording method - Google Patents

Description

The present disclosure relates to an image recording method.

Conventionally, various methods such as a printing method, an electrophotographic method, and an inkjet recording method have been known as techniques for recording an image. Among them, the inkjet recording method is inexpensive because the device does not require a plate for recording, and ink is ejected only to the required image portion to record the image directly on the recording medium. Can be used efficiently and the running cost is low. Further, the inkjet recording method has less noise and is excellent as an image recording method.
Examples of the ink used in the inkjet recording method include solvent-based inks, ultraviolet-curable inks (hereinafter, also referred to as UV inks), and ultraviolet-curable inks containing a solvent. The solvent-based ink is, for example, an ink in which a colorant is dispersed in an organic solvent. The solvent-based ink is ejected from an inkjet head onto a recording medium, and the organic solvent is volatilized by using a heater or the like to form a recording medium. Record the image.
The UV ink is an ink containing, for example, a colorant, a polymerizable compound (for example, a monomer) and a polymerization initiator. After ejecting the UV ink from an inkjet head onto a recording medium, the ink is cured by irradiating it with active energy rays. The image is recorded on the recording medium.
The UV curable ink containing a solvent is an ink containing, for example, a colorant in which a colorant is dispersed with an organic solvent, a polymerizable compound (for example, a monomer), and a polymerization initiator. Images are recorded on the recording medium by ejecting the ink onto the recording medium and volatilizing the organic solvent using a heater or the like, and by irradiating the ink with active energy rays to cure the ink.
Various image recording methods using these inks have been proposed.

For example, in International Publication No. 2017-104845, as an inkjet recording method capable of forming an image having excellent wear resistance and flexibility, colored ink ejection is performed by ejecting colored ink containing a colorant and an organic solvent onto a recording medium. The step, the colored ink heating step of heating the discharged colored ink while keeping the surface temperature of the recording medium at 40 ° C. or higher, and the polymerizable compound, the photopolymerization initiator, and the photopolymerization initiator on the heated colored ink. A colorless ink ejection step that ejects colorless ink containing an organic solvent, and a colorless ink heating step that heats the colorless ink ejected onto the colored ink after heating while maintaining the surface temperature of the recording medium at 40 ° C. or higher. Disclosed is an inkjet recording method comprising a colorless ink curing step of irradiating a heated colorless ink with active energy rays to cure the colorless ink.

Further, for example, Japanese Patent Application Laid-Open No. 2015-147418 describes, as a method for performing high-speed inkjet recording on a recording medium having a significantly low ink absorption capacity, for the surface of a recording medium having ink non-absorbability and low absorption. A recording head that ejects ink, a medium support portion that faces the recording head and supports the recording medium from the back surface, and a first that evaporates the liquid component of the ink that is ejected from the recording head to the recording medium and adheres to the recording head. A drying portion as a fixing portion and a second fixing portion on the downstream side in the transport direction of the recording medium from the drying portion are provided, and the ink is at least (1) a colorant and (2) a boiling point of 100 ° C. or higher and 250 ° C. In an irradiation device containing the following organic solvent monomers, (3) polymerizable oligomer and / or polymer, and (4) photopolymerization initiator, the second fixing portion irradiates the recording medium with ultraviolet rays or electron beams. There is disclosed an inkjet recording method using an inkjet recording system in which the amount of liquid component evaporated in the dried portion is 40 to 70% by mass of the ink adhering to the recording medium.

Here, when the recording medium is irradiated with active energy rays such as ultraviolet rays and electron beams, the recording medium may be damaged. The damage to the recorded medium tends to increase more when heat is applied to the recorded medium to volatilize the organic solvent in the ink. On the other hand, if the exposure amount of the active energy rays and the heat applied to the recording medium are kept low, the recording medium is not easily damaged, but the wear resistance and glossiness of the recorded image tend to decrease. That is, it may be difficult to achieve both damage to the recording medium and wear resistance and glossiness of the image.

Regarding the thickness of the recording medium, when the thickness of the recording medium is thick, it takes a relatively long time for the heat applied from the back surface for volatilizing the organic solvent to be conducted to the surface of the recording medium, so that the back surface is used. It is necessary to keep the temperature of the applied heat high. However, if the temperature of the heat applied from the back surface is high, the temperature of the recording medium itself rises, and the damage to the recording medium when irradiated with active energy rays tends to increase. Moreover, when the amount of exposure of the irradiated active energy rays is large, the damage to the recording medium tends to be more remarkable.

International Publication No. 2017-104845 describes that deformation of the recording medium can be suppressed when the heating temperature in the coloring ink heating step is 100 ° C. or lower, but the recording is performed by irradiation with active energy rays. No consideration is given to medium damage.

Japanese Patent Application Laid-Open No. 2015-147418 describes that warm air is blown to the ink or the ink is irradiated with an infrared lamp in order to evaporate the liquid component in the ink. No consideration is given to the heat applied to. Therefore, a good recorded medium cannot be expected from the viewpoint of damage to the recorded medium.

An object to be solved by one embodiment of the present disclosure is to provide an image recording method for recording an image in which damage to the recording medium is small and the image is excellent in abrasion resistance and glossiness.

Specific means for solving the problem include the following aspects.
<1> A step of ejecting an ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator onto a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method, and a back surface temperature of the recording medium having a thickness A of A. the B ° C. and held within a range satisfying the following formula 1, heating the ink ejected onto the recording medium, at least ink after ^heating, light emission at an exposure amount of 200mJ / cm ² ~1000mJ / cm 2 It is an image recording method including a step of irradiating active energy rays with a diode to cure at least ink.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Equation 1)
<2> The image recording method according to <1>, wherein the ink is a colored ink further containing a colorant.
<3> As a step of ejecting ink and a step of heating ink, a colorant, an organic solvent, a polymerizable compound, and a photopolymerization initiator are contained on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method. A step of ejecting colored ink, a step of keeping the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying Equation 1 and heating the colored ink ejected onto the recording medium, and a step of coloring after heating. A step of ejecting clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator onto the ink by an inkjet method, and holding the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying the formula 1. The step of heating the clear ink ejected onto the recording medium and the step of curing the heated colored ink and the clear ink according to <1> or <2>. This is an image recording method.
<4> The image recording method according to any one of <1> to <3>, further comprising a step of irradiating the cured ink with active energy rays using a low-pressure mercury lamp.
<5> The image recording method according to any one of <1> to <4>, wherein the content of the organic solvent contained in the ink is 20% by mass to 90% by mass with respect to the total mass of the ink. ..
<6> exposure described ^above, it is 400mJ / cm 2 ~900mJ / cm is ² <1> to image recording method according to any one of <5>.
<7> The image recording method according to any one of <1> to <6>, in which the back surface temperature B ° C. of the recording medium having a thickness A is maintained within a range satisfying the following formula 2.
8 × ln (A) ≦ B ≦ 10 × ln (A) (Equation 2)
<8> The image recording method according to any one of <1> to <7>, wherein the organic solvent contained in the ink has a boiling point of 75 ° C to 300 ° C.
<9> The image recording method according to any one of <1> to <8>, wherein the back surface temperature B ° C. of the recording medium is 30 ° C. to 90 ° C.
<10> The image recording method according to any one of <1> to <9>, wherein the recording medium is a material for a seat for a vehicle.

According to one embodiment of the present disclosure, it is possible to provide an image recording method for recording an image in which damage to the recording medium is small and the image is excellent in abrasion resistance and glossiness.

Hereinafter, an embodiment of the image recording method of the present disclosure will be described in detail.

In the present specification, the numerical range indicated by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value, respectively. In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

In the present specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless otherwise specified, when a plurality of substances corresponding to each component are present in the composition. means.
In the present specification, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. Is done.
In the present specification, the back surface of the recording medium means the surface opposite to the image recording surface of the recording medium. Further, the back surface temperature of the recorded medium means the temperature of the back surface of the recorded medium.

≪Image recording method≫
The image recording method of the present disclosure includes the following aspects.
The image recording method of the present disclosure includes a step of ejecting an ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator onto a recorded medium having a thickness A of 200 μm to 2000 μm by an inkjet method, and a covering of the thickness A. The process of heating the ink ejected onto the recording medium while maintaining the back surface temperature B ° C. of the recording medium within the range satisfying the following formula 1 and at least the ink after heating are 200 mJ / cm ^{2 to} 1000 mJ / cm ^2. It has a step of irradiating active energy rays with a light emitting diode at the exposure amount of the above to cure at least the ink.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Equation 1)
The unit of the thickness A is μm.

In the above-mentioned prior art, in an inkjet recording method using a solvent-type ink, a UV ink, or an ultraviolet curable ink containing a solvent, the recording medium is irradiated with active energy rays such as ultraviolet rays and electron beams, and the organic solvent is volatilized. Applying heat to the recording medium in order to cause the recording may increase the damage of the recording medium. On the other hand, keeping the exposure amount of the active energy rays and the heat applied to the recording medium low is effective in reducing damage to the recording medium, but the wear resistance and glossiness of the recorded image are improved. Easy to drop. As a result, it may be difficult to achieve both damage to the recording medium and abrasion resistance and glossiness of the image.

Further, when the recording medium is thick, it takes time for the heat applied from the back surface of the recording medium to volatilize the organic solvent in the ink to be conducted to the surface of the recording medium. Therefore, it is necessary to keep the temperature of the heat applied from the back surface high, but if the temperature applied to the recording medium is high, the temperature of the recording medium itself rises, and the recording medium is damaged when irradiated with active energy rays. It tends to increase. Moreover, when the active energy rays having a large exposure amount are irradiated, the damage to the recording medium tends to be significant.

Therefore, in the image recording method of the present disclosure, the exposure amount of the active energy ray emitted from the light emitting diode (LED) is specified while using a relatively thick recording medium, and the recording medium generated by heating the recording medium is used. We are paying attention to the point of specifying the relationship between the back surface temperature and the thickness of the recording medium. When a thick recording medium is used, it is necessary to keep the temperature of the heat applied from the back surface of the recording medium relatively high, but the amount of heat required to volatilize the organic solvent in the ink depends on the thickness of the recording medium. However, when the thickness of the recording medium is thick, the required amount of heat is high, and when the thickness of the recording medium is thin, the required amount of heat is low. That is, the amount of heat required to volatilize the organic solvent in the ink varies depending on the thickness of the recording medium. Therefore, from the viewpoint of maintaining good wear resistance and glossiness of the image while suppressing damage to the recorded medium, the relationship between the back surface temperature of the recorded medium generated by heating the recorded medium and the thickness of the recorded medium. It is important to identify.
As described above, it is possible to provide an image recording method for recording an image in which damage to the recording medium is small and the image has excellent wear resistance and glossiness.

The image recording method of the present disclosure will be described in detail below.

[Ink ejection process]
It has an ink ejection step of ejecting ink containing an organic solvent, a polymerizable compound, and a photopolymerization initiator from an inkjet head on a recording medium having a thickness A of 200 μm to 2000 μm.
This makes it possible to record a desired image on the recording medium.
Further, by having the ink ejection process, the abrasion resistance of the recorded image is improved.
In the image recording method of the present disclosure, the ink ejection process can be provided a plurality of times. For example, the embodiment may include a colored ink ejection step and a clear ink ejection step described later.

As the ink ejection method in the ink ejection process, it is preferable to use an inkjet method.
The inkjet method is not particularly limited, and is a known method, for example, a charge control method for ejecting ink by using electrostatic attraction, a drop-on-demand method (pressure pulse method) using the vibration pressure of a piezo element, and the like. An acoustic inkjet method that converts an electric signal into an acoustic beam and irradiates the ink to eject the ink using radiation pressure, and a thermal inkjet method that heats the ink to form bubbles and uses the generated pressure (bubble jet (registered). It may be any of trademark)) methods and the like.

The details of the ink will be described later.
The ink is preferably ejected in a droplet size of less than 100 picolitres, more preferably in a droplet size of less than 50 picolitres, and ejected in a droplet size of less than 30 picolitres. More preferred.
A small droplet size is desirable to record high quality images. Small droplets have a large ratio of surface area to volume compared to large droplet sizes, which facilitates evaporation (removal) of the organic solvent from the ejected ink. Therefore, the small droplet size provides an advantage in the rate of organic solvent removal.

[Recorded medium]
The recording medium in the present disclosure has a thickness (A) of 200 μm to 2000 μm.
When A is 200 μm or more, some heating is required to volatilize the organic solvent in the ink, so that the problem of reducing damage to the recording medium becomes apparent. That is, the present disclosure is an invention that solves the problem of reducing damage to the recording medium, which is a problem when A is 200 μm or more.
When A is 2000 μm or less, the organic solvent in the ink can be volatilized without raising the heating temperature of the recording medium too high, and the glossiness can be improved.
From the above viewpoint, the thickness (A) is preferably 800 μm to 1800 μm, more preferably 1000 μm to 1500 μm.
The thickness (A) of the recorded medium is the thickness of the thickest portion of the recorded medium.

The recording medium can be appropriately selected from materials used for applications where damage and abrasion resistance of the recording medium are required (for example, seats for vehicles, bags, etc.).
For applications where damage and wear resistance of the recording medium are required, a seat for a vehicle is preferable from the viewpoint of more easily exerting the effect of the image recording method of the present disclosure.
Since seats for vehicles are susceptible to damage to the seat surface because humans sit on the seat surface or place luggage on the seat surface, damage to the recorded medium and wear resistance are required at a high level. According to one embodiment of the image recording method of the present disclosure, it is possible to achieve a high level of damage and abrasion resistance of a recorded medium required for a seat for a vehicle.

Examples of the recording medium include leather, cloth, and a polymer film.
Examples of the material constituting the recording medium include natural fibers such as collagen fibers, polyvinyl chloride (PVC), polyurethane (PU), and polyamide (PA).
As the recording medium, leather is preferable from the viewpoint of more easily exerting the effect of the image recording method of the present disclosure. Examples of leather include natural leather, artificial leather, synthetic leather, artificial leather and the like.

Natural leather is composed of collagen fibers, which are mainly composed of a fibrous protein called collagen. Hundreds of fine fibers (fibrils) are bundled to form a fiber (fiber), and several to dozens of fibers are bundled to form a fiber bundle (fiber bundle). The structure of natural leather is a structure in which these fiber bundles are three-dimensionally entwined.
Natural leather is divided into a grain layer on the surface and a net-like layer on the inside from the intermediate layer that follows, forming a continuous structure. The grain layer has a glossy, flexible and excellent feel due to the tightness of collagen fiber bundles. In the net-like layer, the fibers are slightly thick and intricately intertwined to maintain the strength of natural leather.
Synthetic leather is made by applying a foam such as polyurethane to the surface of a woven fabric, a knitted fabric, or a non-woven fabric, and then coating a nylon resin or a polyurethane resin on the surface.
As the artificial leather, a non-woven fabric having a fiber layer having a three-dimensional three-dimensional structure similar to the collagen fiber structure of natural leather is used. Further, by using ultrafine fibers of 0.1 denier or less for the surface portion, a leather-like feel can be obtained.
Artificial leather is composed of a non-woven fabric with a fiber layer called a random three-dimensional three-dimensional structure in which ultrafine fibers of nylon and polyester are interlaced in a bundle, and an elastic polyurethane resin.

[Ink heating process]
The image recording method of the present disclosure includes an ink heating step of maintaining the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying the following formula 1 and heating the ink ejected onto the recording medium.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Equation 1)
In addition, ln represents a natural logarithm.

By having the ink heating step, at least a part of the organic solvent contained in the ink is removed, so that an image having excellent wear resistance and glossiness is recorded.

Since the image recording method of the present disclosure includes an ink heating step, at least a part of the organic solvent contained in the ink can be removed, and poor curing of the ink in the LED irradiation step described later can be suppressed.
In the image recording method of the present disclosure, the ink heating step can be provided a plurality of times. For example, the embodiment may include a coloring ink heating step and a clear ink heating step described later.

The back surface temperature B ° C. of the recording medium satisfies the above formula 1 with respect to the thickness Aμm of the recording medium. In Equation 1, the coefficient of ln (A) is an empirically obtained value.
As a result, damage to the recording medium can be suppressed while maintaining good wear resistance and glossiness of the image.
When B is 6 × ln (A) or more, glossiness can be kept good, and when B is 12 × ln (A) or less, damage to the recording medium can be improved. ..

The back surface temperature B ° C. of the recording medium is preferably in a range satisfying 7 × ln (A) ≦ B ≦ 11 × ln (A).
Further, the back surface temperature B ° C. of the recording medium is more preferably in a range satisfying the following (Equation 2).
8 × ln (A) ≦ B ≦ 10 × ln (A) (Equation 2)

The back surface temperature B of the recording medium is preferably 30 ° C. to 90 ° C.
When the back surface temperature B of the recording medium in the ink heating step is 30 ° C. or higher, the organic solvent contained in the ink can be easily removed and the glossiness can be improved. On the other hand, when the back surface temperature of the recorded medium is 90 ° C. or lower, damage to the recorded medium can be satisfactorily suppressed. From the above viewpoint, the back surface temperature of the recorded medium is more preferably 35 ° C. to 80 ° C.
The back surface temperature of the recording medium can be measured by an infrared radiation thermometer (AD-5616, manufactured by A & D Co., Ltd.).

The organic solvent in the ink heating step is preferably removed so that the organic solvent contained in the ink is 10% by mass or less with respect to the total mass of the ink, and is preferably removed so as to be 3% by mass or less. Is more preferable, and it is particularly preferable to remove (all remove) so as to be 0% by mass.
In the ink heating step, it is preferable that the organic solvent contained in the ink is quickly removed from the viewpoint of suppressing bleeding of the recorded image and improving the glossiness. As a method for rapidly removing the organic solvent contained in the ink, for example, the boiling point of the organic solvent contained in the ink may be set in the range described later.

The heating in the ink heating step is preferably performed for 1 second or longer by keeping the back surface temperature of the recording medium satisfying the above formula 1 at the back surface temperature B ° C. with respect to the thickness Aμm of the recording medium.

When the heating time in the ink heating step is 1 second or longer, the organic solvent contained in the ink can be easily removed, and blurring and fogging of the image can be suppressed.
From the above viewpoint, the heating is preferably performed for 5 seconds or more, more preferably 5 seconds or more and 500 seconds or less, and further preferably 5 seconds or more and 400 seconds or less.
When the heating time is 500 seconds or less, damage to the recording medium can be further suppressed.

The back surface temperature of the recording medium can be adjusted by the heating temperature and the heating time in the ink heating step.
The heating temperature and heating time in the ink heating step may be adjusted according to the boiling point of the organic solvent contained in the ink, the content of the organic solvent, and the transport speed of the recording medium.

As the method for heating the ink in the above-mentioned ink heating step, a method capable of removing the organic solvent contained in the ink can be appropriately selected.

Examples of the heating method include a heating plate (resistance heater, induction heater) arranged under the recording medium, a radiant heater (heating rod, infrared (IR) lamp) arranged on the recording medium, and the like. A method using a solid IR) can be mentioned.
For heating, the ink is heated via the recording medium using the above heating plate, the above radiant heater, and the like.
Further, it is preferable that the heating is performed before the ink is ejected to the recording medium.

Next, the details of the ink will be described.
〔ink〕
The ink contains an organic solvent, a polymerizable compound and a photopolymerization initiator.
Further, the ink may contain components other than the above, if necessary.

The ink in the present disclosure is not particularly limited as long as it is an ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator, contains an organic solvent, a polymerizable compound and a photopolymerization initiator, and substantially does not contain a colorant. It may be an ink (clear ink) or an ink (color curable ink) containing a colorant, an organic solvent, a polymerizable compound and a photopolymerization initiator.
In the present specification, the clear ink is an ink that does not substantially contain a colorant. The term "substantially free of colorant" means that the content of colorant is less than 0.1% by mass with respect to the total amount of ink.
The colored ink may further contain a polymer.

(Organic solvent)
The ink contains at least one of the organic solvents.
The organic solvent is a liquid at an ambient temperature and functions as a dispersion medium or a solvent for the components contained in the ink.
The organic solvent is not particularly limited and can be selected from any organic solvent generally used in the printing industry.

The content of the organic solvent contained in the ink is preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 85% by mass or less, and 40% by mass or more and 80% by mass or less with respect to the total mass of the ink. More preferred.
When the organic solvent in the ink is 20% by mass or more, the ejection property is excellent. On the other hand, when the content is 90% by mass or less, the bleeding of the ink can be suppressed and the glossiness can be improved.

The boiling point of the organic solvent contained in the ink is preferably 75 ° C. or higher and 300 ° C. or lower, more preferably 90 ° C. or lower and 280 ° C. or lower, further preferably 100 ° C. or higher and 260 ° C. or lower, and particularly preferably 120 ° C. or higher and 260 ° C. or lower.
When the boiling point of the organic solvent contained in the ink is 75 ° C. or higher, the volatility of the organic solvent is good, so that damage to the recording medium due to heating is further reduced. On the other hand, when the boiling point is 300 ° C. or lower, the bleeding of the ink is further suppressed and the glossiness is improved.
The boiling point of the organic solvent can be measured using a known method. For example, the measurement can be performed according to JIS K2254.
When the ink contains a plurality of organic solvents, the boiling point of the organic solvent is the product of the ratio of the content of each organic solvent to the total organic solvent (mass% ÷ 100) and the boiling point of each organic solvent. It is a value obtained by calculating the average value.

The organic solvent is not particularly limited and can be selected from any organic solvent generally used in the printing industry.
Examples of the organic solvent include glycol ether, glycol ether ester, alcohol, ketone, ester and pyrrolidone.

Examples of the glycol ether include ethylene glycol monomethyl ether, diethylene glycol diethyl ether, and triethylene glycol monobutyl ether.
Examples of the ketone include methyl ethyl ketone.
Examples of the ester include 3-methoxybutyl acetate and γ-butyrolactone.

Of these, diethylene glycol diethyl ether, ethylene glycol monomethyl ether, 3-methoxybutyl acetate, and γ-butyrolactone are preferable.

(Acrylic modified polyorganosiloxane)
The ink preferably further contains an acrylic-modified polyorganosiloxane having a weight average molecular weight of 20,000 or more and 400,000 or less.

Preferred embodiments and specific examples of the above-mentioned acrylic-modified polyorganosiloxane are the same as those described in International Publication No. 2017/104845 (paragraph Nos. 0122 to 0124).

(Polymerizable compound)
The ink contains at least one polymerizable compound.
The polymerizable compound means a compound in which the polymerization reaction proceeds by irradiation with active energy rays in the presence of a photopolymerization initiator.
The polymerizable compound can include a monomer, an oligomer, or a mixture thereof.
The monomers and / or oligomers can have different functionalities, and mixtures containing monofunctional, bifunctional, trifunctional or higher functional monomers and / or oligomer combinations can be used.
The polymerizable compound preferably contains an oligomer.

The oligomer preferably contains a backbone, eg, a polyester, urethane, epoxy or polyether backbone, and a group that can be polymerized by one or more active energy rays. The polymerizable group may be any group that can be polymerized upon exposure to active energy rays.

The oligomer is preferably polymerized by free radical polymerization. That is, an oligomer having a group capable of free radical polymerization is preferable.
Examples of the group capable of free radical polymerization include a (meth) acryloyl group and the like.
The (meth) acryloyl group is a concept that includes a methacryloyl group and an acryloyl group.

The oligomer preferably has one, two, three, four, five, or six groups capable of free radical polymerization. That is, monofunctional to hexafunctional oligomers are preferable.
From the viewpoint of the flexibility of the ink after curing, the total mass of the monofunctional oligomer and the bifunctional oligomer is preferably 30% by mass or more, more preferably 40% by mass or more, based on the total mass of the oligomer. It is more preferably 50% by mass or more.

The oligomer preferably contains a urethane main chain, and is more preferably a urethane acrylate oligomer, from the viewpoint of having excellent image adhesion and flexibility.
Further, from the viewpoint of having good chemical resistance, the oligomer is a urethane acrylate oligomer having trifunctionality, tetrafunctionality, pentafunctionality, hexafunctionality or higher functionality, particularly a hexafunctional urethane acrylate oligomer. It is preferable to have.

As another example of the oligomer, epoxy-based oligomers such as bisphenol A epoxy acrylate and epoxy novolak acrylate may be used because they have a rapid curing rate and good chemical resistance.

As the oligomer, an oligomer having a weight average molecular weight of 1,000 or more and 30,000 or less is preferable, and an oligomer having a weight average molecular weight of 1,500 or more and 10,000 or less is more preferable.

Weight average molecular weight means a value measured by a gel permeation chromatograph (GPC).
For the above GPC, HLC-8020GPC (manufactured by Tosoh Corporation) is used, and three columns, TSKgel (registered trademark) and Super Multipore HZ-H (manufactured by Tosoh Co., Ltd., 4.6 mm ID × 15 cm) are used for elution. This is done using THF (tetrahydrofuran) as the liquid.
The GPC is performed using a differential refractive index (RI) detector with a sample concentration of 0.45% by mass, a flow velocity of 0.35 ml / min, a sample injection amount of 10 μl, and a measurement temperature of 40 ° C.
The calibration curve is "Standard sample TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A". It is made from 8 samples of "-2500", "A-1000" and "n-propylbenzene".

The oligomer was 0.5 Pa · s to 20 Pa. At 60 ° C. s, more preferably 5 Pa. At 60 ° C. s ~ 15 Pa. s, most preferably 5 Pa. At 60 ° C. s-10Pa. It has a viscosity of s. The viscosity of the oligomer is such that a steel cone with a slope of 40 mm / 2 ° is used at ^{60 ° C. with a shear rate of 25 seconds -1.} A. It can be measured using an ARG2 rheometer manufactured by Instruments.

Free radically polymerizable monomers are well known in the art and include (meth) acrylates, α, β-unsaturated ethers, vinylamides and mixtures thereof.

Monofunctional (meth) acrylate monomers are well known in the art and are preferably acrylic acid esters. Preferred examples are phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), isobornyl acrylate (IBOA), tetrahydrofurfuryl acrylate (THA), 2- (2-ethoxyethoxy) ethyl acrylate, octadecyl acrylate. (ODA), tridecyl acrylate (TDA), isodecyl acrylate (IDA) and lauryl acrylate. Among them, PEA is particularly preferable.

Polyfunctional (meth) acrylate monomers include bifunctional, trifunctional and tetrafunctional monomers. Examples of polyfunctional acrylate monomers that may be contained in the ink include hexanediol diacrylate, trimethyl propantriacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate (eg, tetraethylene glycol diacrylate), dipropylene glycol diacrylate, etc. Tri (propylene glycol) triacrylate, neopentyl glycol diacrylate, bis (pentaerythritol) hexaacrylate, and acrylate or propoxylated glycol and polyol acrylate esters such as propoxylated neopentyl glycol diacrylate, ethoxylated trimethylol. Examples thereof include propanetriacrylates and mixtures thereof.

The polyfunctional (meth) acrylate monomer includes methacrylic acid such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, and 1,4-butanediol dimethacrylate. Esters (ie, methacrylates) are included. A mixture of (meth) acrylates can also be used.

(Meta) acrylate is a concept that includes acrylate and methacrylate. Monofunctional and polyfunctional monomers shall also have their standard meanings, i.e. one and two or more groups used in the polymerization reaction during curing, respectively.

The α, β-unsaturated ether monomers can be polymerized by free radical polymerization and can be useful in reducing the viscosity of the ink when used in combination with one or more (meth) acrylate monomers. Examples are well known in the art and include vinyl ethers such as triethylene glycol divinyl ether, diethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether and ethylene glycol monovinyl ether. A mixture of α, β-unsaturated ether monomers can also be used.

N-vinylamide and N- (meth) acryloylamine can also be used. The N-vinylamide has a vinyl group attached to the nitrogen atom of the amide and may be further substituted in the same manner as the (meth) acrylate monomer. Preferred examples include N-vinylcaprolactam (NVC) and N-vinylpyrrolidone (NVP). Further, the N-acryloylamine also has a vinyl group bonded to the amide, but is bonded via a carbonyl carbon atom, and may be further substituted in the same manner as the (meth) acrylate monomer. Preferred examples include N-acryloyl morpholine (ACMO).

Examples of the polymerizable compound include compounds that can be polymerized by cationic polymerization. Examples of such compounds include oxetane, alicyclic epoxides, bisphenol A epoxides, epoxy novolaks and the like.
A mixture of a cationically curable monomer and an oligomer may be used as the polymerizable compound. For example, the polymerizable compound may contain a mixture of an epoxide oligomer and an oxetane monomer.

As the polymerizable compound, a compound capable of free radical polymerization and a compound capable of cationically polymerizable may be used in combination.

The polymerizable compound that can be contained in the ink is preferably an oligomer having a weight average molecular weight of 1,000 or more and 30,000 or less.
In addition, in this specification, an oligomer means a polymerizable compound having a weight average molecular weight of 1,000 or more and 30,000 or less. Further, the monomer means a polymerizable compound having a weight average molecular weight of less than 1,000.
When the weight average molecular weight of the oligomer is in the above range, the viscosity of the ink containing the oligomer does not become too high, and the ink is excellent in ejectability.
Further, when the ink contains an oligomer having a weight average molecular weight in the above range and is cured, the weight average molecular weight of the structural unit derived from the oligomer in the cured ink is derived from the monomer when the ink containing the monomer is cured. The image is more flexible because it is larger than the weight average molecular weight of the structural unit.
From the above viewpoint, the weight average molecular weight of the oligomer is more preferably 1,500 or more and 10,000 or less, and further preferably 3,000 or more and 5,000 or less.

When the ink contains a polymerizable compound, the content of the polymerizable compound is preferably 15% by mass or more and 30% by mass or less, and more preferably 18% by mass or more and 28% by mass or less with respect to the total mass of the ink.
When the content of the polymerizable compound in the ink is in the above range, the balance between flexibility and abrasion resistance is good, and both flexibility and abrasion resistance can be achieved at a higher level.

The polymerizable compound that can be contained in the ink is preferably an acrylate compound, and more preferably the acrylate compound is an oligomer. When the polymerizable compound is an acrylate compound, an image having more excellent wear resistance can be obtained.

The polymerizable compound that can be contained in the ink is preferably an acrylate compound (acrylate oligomer) having a weight average molecular weight of 1,000 or more and 30,000 or less, and the content of the above acrylate compound is based on the total mass of the ink. It is preferably 15% by mass or more and 30% by mass or less.
When the above-mentioned acrylate compound is contained in the above-mentioned content, the balance between flexibility and abrasion resistance is improved, and both flexibility and abrasion resistance can be achieved at a higher level.
It is more preferable that the ink contains an acrylate compound (acrylate oligomer) having a weight average molecular weight of 1,500 or more and 10,000 or less as a polymerizable compound in an amount of 18% by mass or more and 28% by mass or less with respect to the total mass of the ink. ..

The polymerizable compound that can be contained in the ink contains at least one acrylate compound, and the total mass of the monofunctional acrylate compound and the bifunctional acrylate compound is preferably 50% by mass or more with respect to the total mass of the polymerizable compound.
When the total mass of the monofunctional acrylate compound and the bifunctional acrylate compound is 50% by mass or more with respect to the total mass of the polymerizable compound, the network structure of the cured ink does not become too dense, and the flexibility of the image is further improved. , The adhesion of the image is also improved.

As the polymerizable compound, a commercially available product may be used, and as the commercially available product, CN996 (bifunctional oligomer, urethane acrylate, weight average molecular weight (Mw) = 2850) manufactured by Sartomer, Shin-Nakamura Chemical Industry Co., Ltd. UA-122P (bifunctional oligomer, urethane acrylate, Mw = 1100), Shikou (registered trademark) UV-6630B (bifunctional oligomer, urethane acrylate, Mw = 3000) of Nippon Synthetic Chemical Co., Ltd., Shikou (registered trademark) UV -3310B (bifunctional oligomer, urethane acrylate, Mw = 5000), and oligomers such as Shikou (registered trademark) UV-7630B (six-functional oligomer, urethane acrylate, Mw = 2200), and BASF's N-vinyl caprolactam (single). Functional monomers), SR339C (phenoxyethyl acrylate, monofunctional monomer) from Sartomer, SR506D (isobornyl acrylate, monofunctional monomer), dipropylene glycol diacrylate (polyfunctional monomer) from Sartomer, and the like.

(Photopolymerization initiator)
The ink contains at least one of the photopolymerization initiators.
When the ink contains a free radically polymerizable polymerizable compound, the photopolymerization initiator preferably contains a free radical photopolymerization initiator, and when the ink contains a cationically polymerizable polymerizable compound, the photopolymerization initiator is a cation. It preferably contains a photopolymerization initiator.
When the ink contains a combination of a free radical polymerizable polymerizable compound and a cationically polymerizable polymerizable compound, it is preferable to contain both a free radical photopolymerization initiator and a cationic photopolymerization initiator.

The free radical photopolymerization initiator can be selected from any of those known in the art. For example, benzophenone, 1-hydroxycyclohexylphenyl ketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one, 2-benzyl-2-dimethylamino. -(4-Molholinophenyl) butane-1-one, isopropylthioxanthone, benzyldimethylketal, bis (2,6-dimethylbenzoyl) -2,4,4-trimethylpentylphosphine oxide, or mixtures thereof. These photopolymerization initiators are known and are commercially available, for example, from BASF's IRGACURE® and Darocur® (from Ciba) and Lucerin.

As the cationic photopolymerization initiator, for example, a sulfonium or iodonium-based photopolymerization initiator can be used. For example, Rhodia's Rhodolsil PI 2074; Siber Hegner's MC AA, MC BB, MC CC, MC CC PF, MC SD; Alfa Chemicals' UV9380c; UCB Chemicals' Uvacure 1590; It is commercially available at.

The content of the photopolymerization initiator in the ink is preferably 1% by mass to 20% by mass, more preferably 4% by mass to 10% by mass, based on the total mass of the ink.

(Colorant)
The ink can contain at least one of the colorants. The colorant is not particularly limited, and may be a pigment or a dye.
When the ink is used as a coloring ink, the content of the coloring agent is preferably 0.1% by mass or more with respect to the total mass of the ink.

The pigment is not particularly limited and may be appropriately selected depending on the intended purpose. The pigment can be dissolved or dispersed in the liquid medium of the ink.
The pigment may be either an organic pigment or an inorganic pigment, and the organic pigment and the inorganic pigment may be used in combination.
Examples of the organic pigment include azolake, azo pigment, phthalocyanine pigment, perylene pigment, perinone pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, diketopyrrolopyrrole pigment, thioindigo pigment, isoindolinone pigment, and quinophthalone pigment. Examples thereof include dye lakes such as cyclic pigments, basic dye type rakes, and acidic dye type rakes, nitro pigments, nitroso pigments, aniline blacks, and daylight fluorescent pigments.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow and carbon black.

As the colorant, for example, organic pigments or inorganic pigments having the following numbers listed in the Color Index can be used.
Examples of the blue pigment or cyan pigment include Pigment Blue 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17-1, 22, 27, 28, 29, 36, 60,
Examples of the green pigment include Pigment Green 7, 26, 36, 50, and the like.
Examples of the red pigment or magenta pigment include Pigment Red 3, 5, 9, 19, 22, 31, 38, 42, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53: 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13, 16, 20, 36,
Examples of the yellow pigment include Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120. 137, 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193,
Examples of the black pigment include Pigment Black 7, 28, 26,
Examples of the white pigment include Pigment White 6, 18, and 21.
Further, even pigments not listed in the color index can be appropriately used depending on the purpose. For example, further, a pigment surface-treated with a surfactant, a polymer dispersant, or the like, graft carbon, or the like can also be used.

Examples of the polymer dispersant include polyamide amines and salts thereof, polyvalent carboxylic acids and salts thereof, high molecular weight unsaturated acid esters, modified polyurethanes, and polyether esters.

Commercially available products may be used as the polymer dispersant, and examples of the commercially available products include DisperBYK-101, DisperBYK-102, DisperBYK-103, DisperBYK-106, DisperBYK-111, DisperBYK-161, DisperBYK-162, DisperBYK. -163, DisperBYK-164, DisperBYK-166, DisperBYK-167, DisperBYK-168, DisperBYK-170, DisperBYK-171, DisperBYK-174, DisperBYK-174, DisperBYK-178, DisperBYK-178, EF40A, EF40 EFKA5207, EFKA5244, EFKA6745, EFKA6750, EFKA7414, EFKA745, EFKA7462, EFKA7500, EFKA7570, EFKA7755, EFKA7580 (manufactured by EFKA 7750, EFKA 7750, EFKA 7540, EFKA 7540, EFKA 7745, EFKA 6745, EFKA 7745, EFKA 7445, EFKA 7462, EFKA 7570, EFKA 7580 (manufactured by EFKA Additive) Polymer dispersants such as San Nopco Ltd.); Solsperse 3000, 5000, 9000, 12000, 13240, 13940, 17000, 22000, 24000, 26000, 28000, 32000, 36000, 39000, 41000, 71000, etc. Various polymer dispersants (manufactured by Abyssia); ADEKA PLRONIC L31, F38, L42, L44, L61, L64, F68, L72, P95, F77, P84, F87, P94, L101, P103, F108, L121, P-123 ( ADEKA Corporation) and Ionet (registered trademark) S-20 (Sanyo Chemical Industries, Ltd.), Kusumoto Chemical Industries, Ltd. "Disparon KS-860, 873SN, 874 (Polymer dispersant), # 2150 ( (Adipose polyvalent carboxylic acid), # 7004 (polyether ester type) ”.

The content ratio of the polymer dispersant to the pigment (polymer dispersant: pigment) in the pigment surface-treated with the polymer dispersant is preferably 1: 1 to 1:10, more preferably 1: 1 to 1: 5. It is preferable, and 1: 2 to 1: 3 is more preferable.

Commercially available products can also be used as the colorant. Examples of commercially available products include Pariotor (BASF), Cinquasia, Irgalite (both Ciba Speciality Chemicals), and Hostaparm (Clariant UK).

Among these colorants, phthalocyanine pigments such as phthalocyanine blue 15: 4 as cyan pigments, azo pigments such as pigment yellow 120, pigment yellow 151, and pigment yellow 155 as yellow pigments, and pigment violet 19 as magenta pigments, And quinacridone pigments such as mixed crystal quinacridone such as Cinquasia MAGENTA L4540, and carbon black pigments such as Pigment Black 7 are preferable as the black pigment.

The volume average particle size of the colorant is not particularly limited, but is preferably less than 8 μm, more preferably less than 5 μm, still more preferably less than 1 μm, and particularly preferably less than 0.5 μm from the viewpoint of ink ejection property. The lower limit of the volume average particle size of the colorant is not particularly limited, but from the viewpoint of colorability and light resistance, 0.001 μm or more is preferable, and 0.01 μm or more is more preferable.
The volume average particle size can be measured by a laser diffraction particle size distribution meter (for example, Mastersizer 2000 manufactured by Malvern, or a laser diffraction / scattering type particle size distribution measuring device LA-920 manufactured by HORIBA, Ltd.).

The content of the colorant is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 8% by mass or less, and particularly preferably 1% by mass to 5% by mass, based on the total mass of the ink.

(polymer)
The ink may contain at least one of the polymers. When the ink contains a polymer, the polymer acts as a binder to retain the components contained in the ink.

The ink may further contain a polymer having a molecular weight of 10,000 or more and 150,000 or less (preferably 20,000 or more and 100,000 or less) in an amount of 2% by mass or more based on the total mass of the ink.
Polymers are distinguished from the above-mentioned polymerizable compounds in that they do not contain polymerizable groups when irradiated with active energy rays.

Examples of the polymer include epoxy resin, polyester, vinyl or (meth) acrylic resin.
The (meth) acrylic resin is a concept including a methacrylic resin and an acrylic resin.
Examples of the vinyl resin include vinyl chloride, vinyl acetate, and a copolymer of vinyl chloride and vinyl acetate.
Examples of the (meth) acrylic resin include a copolymer of methyl methacrylate and n-butyl methacrylate.

Of these, vinyl resin and (meth) acrylic resin are preferable.

As the polymer, a commercially available product may be used, and examples of the commercially available product include VINNOL (registered trademark) E15 / 45 (copolymer of vinyl chloride and vinyl acetate, weight average molecular weight (Mw) = 50) manufactured by Wacker Chemie AG. , 000), Elvacite 2013 (polymer of methyl methacrylate and n-butyl methacrylate, Mw = 34,000), Elvacite 2014 (polymer of methyl methacrylate and n-butyl methacrylate), Lucite International. , Mw = 119,000), Elvacite 4099 (polymer of methyl methacrylate and n-butyl methacrylate, Mw = 15,000).

When the ink contains a polymer, the content of the polymer is preferably 2% by mass or more, more preferably 2% by mass or more and 10% by mass or less, and further preferably 5% by mass or more and 7% by mass or less, based on the total mass of the ink. preferable.
When the content of the polymer is 2% by mass or more, the function as a binder is likely to be exhibited. On the other hand, when the content of the polymer is 10% by mass or less, the ejection property of the ink is further improved.

The weight average molecular weight of the polymer is preferably 10,000 or more and 150,000 or less, more preferably 15,000 or more and 120,000 or less, and even more preferably 20,000 or more and 100,000 or less.
When the weight average molecular weight of the polymer is 10,000 or more, the function as a binder is likely to be exhibited. On the other hand, when the weight average molecular weight of the polymer is 150,000 or less, the ink ejection property is further improved.

When the ink contains a polymer, it is preferable that the ink contains a polymer having a weight average molecular weight of 10,000 or more and 150,000 or less in an amount of 2% by mass or more based on the total mass of the ink, and the weight average molecular weight is 20,000 or more and 100,000 or less. It is more preferable to contain the polymer in an amount of 2% by mass or more based on the total mass of the ink.
The weight average molecular weight can be measured by the method described above.

(Other ingredients)
If necessary, the ink may be added with components other than the above components.
Examples of other components include surfactants, polymerization inhibitors, sensitizers, ultraviolet absorbers, antioxidants, anti-fading agents, conductive salts, and basic compounds.

A surfactant may be added to the ink in order to impart stable ejection properties for a long period of time.
Examples of the surfactant include the surfactants described in JP-A-62-173436 and JP-A-62-183457. For example, anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks. Examples thereof include nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts.
The content of the surfactant in the ink is appropriately selected depending on the purpose of use, but is preferably 0.0001% by mass to 1% by mass with respect to the total mass of the ink.

~ Physical characteristics of ink ~
The surface tension of the ink is preferably 20 mN / m or more and 40 mN / m or less, more preferably 22 mN / m or more and 30 mN / m or less, and further preferably 25 mN / m or more and 30 mN / m or less at 25 ° C.

The surface tension can be measured by Automatic Surface Tensiometer CBVP-Z (Kyowa Interface Science Co., Ltd.) in an environment of a temperature of 25 ° C.

The viscosity of the ink at 25 ° C. is preferably 200 mPa · s or less, more preferably 100 mPa · s or less, further preferably 25 mPa · s or less, and particularly preferably 10 mPa · s or less. The viscosity of the ink is preferably 2 mPa · s or more, more preferably 4 mPa · s or more, and even more preferably 5 mPa · s or more at 25 ° C.

The viscosity of the ink is a value measured under the condition of 25 ° C. (± 1 ° C.) using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

[LED irradiation process]
The image recording method of the present disclosure, at least the ink after ^heating, by irradiating an active energy ray with 200mJ / cm ² ~1000mJ / cm 2 exposure amount in the light-emitting diode (LED), a curing the least ink process (Hereinafter, also referred to as an LED irradiation step).
The LED irradiation process reduces damage to the recording medium.

As a method of at least curing the ink in the LED irradiation step, a method of irradiating an active energy ray with an LED to cure at least the ink is used.

As the active energy ray, α ray, γ ray, electron beam, X-ray, ultraviolet light, visible light, infrared light and the like can be used. When a sensitizer is used, the peak wavelength of the active energy ray is preferably, for example, 200 nm to 600 nm, more preferably 300 nm to 450 nm, and 350 nm to 420 nm, although it depends on the absorption characteristics of the sensitizer. Is more preferable.

Since the LED does not easily generate heat in the irradiated portion by irradiation, damage to the recording medium can be further reduced by using the LED as a light source in the LED irradiation step in the present disclosure.
LEDs are compact, have a long life, are highly efficient, and are low in cost, and are expected as light sources for photocurable inkjet light sources.
In particular, if an ultraviolet source is required, an ultraviolet LED (UVLED) can be used. For example, Nichia Corporation has launched a purple LED with a main emission spectrum of wavelengths between 365 nm and 420 nm. If a shorter wavelength is required, the LED can emit an active energy ray having a wavelength center between 300 nm and 370 nm disclosed in US Pat. No. 6,084,250. Can be exemplified. Other UV LEDs are also available and can irradiate radiation in different UV bands.

Exposure of the active energy ray in the LED irradiation step ^{is 200mJ / cm 2 ~1000mJ / cm 2} . When the exposure amount of the active energy ray in the LED irradiation step is 200 mJ / cm ² or more, the polymerizable compound can be polymerized and the abrasion resistance of the image can be improved. When the exposure amount of the active energy ray in the LED irradiation step is 1000 mJ / cm ² or less, damage to the recording medium can be reduced.
Exposure of the active energy ray by the LED is ^{preferably 300mJ / cm 2 ~900mJ / cm 2} , 400mJ / cm 2 ~900mJ / cm 2 is more preferable.

The irradiation time of the active energy ray by the LED is preferably 0.01 seconds to 120 seconds, more preferably 0.1 seconds to 90 seconds.
Irradiation conditions of active energy rays and basic irradiation methods are disclosed in Japanese Patent Application Laid-Open No. 60-132767.
Specifically, an active energy ray irradiation device is provided on a single-scale serial head, and the shuttle method in which irradiation is performed while scanning the head in the width direction of the recorded medium and the activity corresponding to the entire area of one side of the recorded medium are activated. There is a single-pass method in which energy ray irradiation devices are arranged.

Irradiation of the active energy ray by the LED is performed for a certain period of time (preferably 0.01 seconds to 0.5 seconds, more preferably 0.01 seconds to 0.3 seconds, still more preferably 0.01 seconds) after the completion of the ink heating step. ~ 0.15 seconds) is preferable.

[Mercury lamp irradiation process]
In the present disclosure, it is possible to further have a mercury lamp irradiation step of irradiating at least the ink after curing with an active energy ray using a low pressure mercury lamp. By having the mercury lamp irradiation step, the adhesion and abrasion resistance of the image become better.

As a method of at least curing the ink in the mercury lamp irradiation step, a method of irradiating an active energy ray with a low-pressure mercury lamp to cure at least the ink is used.

The active energy ray in the mercury lamp irradiation step is the same as the above-mentioned active energy ray.

Specific examples of the low-pressure mercury lamp include a sterilization lamp GL15 (manufactured by Hitachi Appliances, Inc.).

Exposure of the active energy ray by a low-pressure mercury lamp is preferably ^{50mJ / cm 2 ~100mJ / cm 2} , more preferably ^{65mJ / cm 2 ~85mJ / cm 2} .

The irradiation time of the active energy ray in the mercury lamp irradiation step is preferably 0.01 seconds to 120 seconds, more preferably 0.1 seconds to 90 seconds.
The irradiation conditions of the active energy rays, the basic irradiation method, and the like are the same as those in the LED irradiation step described above.

The irradiation of the active energy beam in the mercury lamp irradiation step is performed for a certain period of time (preferably 0.01 seconds to 0.5 seconds, more preferably 0.01 seconds to 0.3 seconds, still more preferably 0. It is preferable to perform the operation after a interval of 01 seconds to 0.15 seconds).

The image recording method of the present disclosure includes, for example, the following aspects A-1, A-2 and B.

[Aspect A-1]
The image recording method according to the aspect A-1 is a step of ejecting ink and a step of heating ink on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method using a colorant, an organic solvent, and polymerizable. The step of ejecting the colored ink containing the compound and the photopolymerization initiator (colored ink ejection step) and the back surface temperature B ° C. of the recorded medium having a thickness A are maintained within the range satisfying the formula 1 and ejected onto the recorded medium. A step of heating the colored ink (colored ink heating step) and a step of ejecting clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator on the heated colored ink by an inkjet method (clear ink). The ejection step) and the step of holding the back surface temperature B ° C. of the recording medium having a thickness A within the range satisfying Equation 1 and heating the clear ink ejected onto the recording medium (clear ink heating step). In the step of curing the ink, the colored ink and the clear ink after heating are cured by irradiation with active energy rays using an LED (LED irradiation step).
In the LED irradiation step in the aspect A-1, the colored ink and the clear ink after heating may be cured at the same time, or the colored ink and the clear ink after heating may be cured separately and sequentially. When the colored ink and the clear ink after heating are cured at the same time, the work efficiency can be improved and the economical burden can be reduced.

[Aspect A-2]
In the image recording method according to the aspect A-2, before the step of ejecting the clear ink, the colored ink after heating is irradiated with active energy rays, and the clear ink after heating is further irradiated with active energy rays. .. That is, the image recording method according to the aspect A-2 is an aspect in which the colored ink and the clear ink are sequentially cured separately.

[Aspect B]
In the image recording method according to the aspect B, as a step of ejecting ink and a step of heating the ink, colored ink containing a colorant and an organic solvent is put on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method. A step of ejecting (colored ink ejection step) and a step of holding the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying Equation 1 and heating the colored ink ejected onto the recording medium (colored ink). (Heating step), a step of ejecting clear ink containing an organic solvent, a polymerizable compound, and a photopolymerization initiator on the colored ink after heating (clear ink ejection step), and a recording medium having a thickness A. The back surface temperature B ° C. is maintained within the range satisfying the formula 1, and the step of heating the clear ink discharged onto the recording medium (clear ink heating step) is included, and the step of curing is after heating. At least the clear ink is cured by irradiation with active energy rays using an LED (LED irradiation step).

It is preferable that the image recording method of the present disclosure includes a colored ink ejection step and a colored ink heating step in this order before the clear ink ejection step, as in aspects A-1, A-2 and B.
In embodiments A-1 and A-2, which have a colored ink ejection step and a colored ink heating step before the clear ink ejection step, the clear ink can be cured in addition to the colored ink by the LED irradiation step. Images with excellent wear resistance can be obtained.

[Colored ink ejection process]
The image recording method of the present disclosure can include a colored ink ejection step of ejecting colored ink by an inkjet method on a recording medium having a thickness A of 200 μm to 2000 μm before the step of ejecting clear ink. .. The colored inks in aspects A-1 and A-2 are colored curable inks containing a colorant, an organic solvent, a polymerizable compound and a photopolymerization initiator, and the colored inks in aspect B are colored curable inks. It is a colored ink other than.
As a result, a desired image can be recorded by ejecting the colored ink onto the recording medium.

The ink ejection method in the colored ink ejection process is the same as the ink ejection method in the ink ejection process described above.

The droplet size of the colored ink in the colored ink ejection process is the same as the ink droplet size in the ink ejection process described above.

[Colored ink]
Coloring inks include colorants and organic solvents.
The colored ink is preferably a colored curable ink further containing a polymerizable compound and a photopolymerization initiator.
The colored ink may contain components other than the above, if necessary.

(Colorant)
As the colorant contained in the coloring ink, the same compound as the colorant contained in the above-mentioned ink can be used, and the preferred embodiment is also the same.

(Organic solvent)
The colored ink contains at least one of the organic solvents.
The organic solvent is a liquid at an ambient temperature (25 ° C.) and functions as a dispersion medium or a solvent for components contained in the coloring ink such as the above-mentioned colorant.

The preferable range of the content of the organic solvent in the colored ink is the same as the preferable range of the content of the organic solvent in the above-mentioned ink.

The boiling point of the organic solvent contained in the colored ink is the same as the boiling point of the organic solvent contained in the above-mentioned ink.
The boiling point of the organic solvent can be measured by the method described above.
When the colored ink contains a plurality of organic solvents, the boiling point of the organic solvent is the product of the ratio of the content of each organic solvent to the total organic solvent (mass% ÷ 100) and the boiling point of each organic solvent. It is a value obtained by calculating the average value of.

Specific examples and preferred embodiments of the organic solvent contained in the colored ink are the same as those of the organic solvent contained in the above-mentioned ink.

(Polymerizable compound and photopolymerization initiator)
The colored ink preferably further contains a polymerizable compound and a photopolymerization initiator.
As the polymerizable compound and the photopolymerization initiator that can be contained in the colored ink, the same compounds as the polymerizable compound and the photopolymerization initiator contained in the above-mentioned ink can be used, and the preferred embodiments are also the same.

~ Physical characteristics of colored ink ~
The surface tension of the colored ink is preferably 18 mN / m or more and 36 mN / m or less, more preferably 20 mN / m or more and 30 mN / m or less, and further preferably 22 mN / m or more and 26 mN / m or less at a temperature of 25 ° C.
The preferable range of the viscosity of the colored ink is the same as the preferable range of the viscosity of the above-mentioned ink.

[Colored ink heating process]
The image recording method of the present disclosure includes a colored ink heating step of maintaining the back surface temperature B ° C. of a recording medium having a thickness A within a range satisfying the following formula 1 and heating the colored ink ejected onto the recording medium. be able to.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Equation 1)

The back surface temperature B ° C. of the recording medium satisfies the above formula 1 with respect to the thickness Aμm of the recording medium.
The formula 1 is the same as the formula (1) in the ink ejection process described above, and the preferable range of the formula (1) is also the same. The same applies to the back surface temperature B of the recording medium, the heating time, the heating method, and preferred embodiments thereof.

[Clear ink ejection process]
The image recording method of the present disclosure can include a clear ink ejection step of ejecting clear ink by an inkjet method on the colored ink after heating.
As a result, the abrasion resistance can be improved by ejecting the clear ink on the colored ink after heating.

The clear ink ejection method in the clear ink ejection process is the same as the ink ejection method in the ink ejection process described above.

The size of the clear ink droplets in the clear ink ejection process is the same as the ink droplet size in the above-mentioned ink ejection process.
It is preferable that the droplet size of the clear ink is larger than the droplet size of the colored ink, and when the droplet size of the clear ink is larger than the droplet size of the colored ink, the clear ink easily covers the colored ink. Therefore, clear ink is present on the surface of the recorded image, and an image having excellent wear resistance and chemical resistance can be obtained.

[Clear ink]
The clear ink contains an organic solvent, a polymerizable compound and a photopolymerization initiator.
The clear ink may contain components other than the above, if necessary.
The clear ink has the same meaning as the clear ink in the above-mentioned ink.

(Organic solvent)
The clear ink contains at least one of the organic solvents.
The organic solvent is a liquid at an ambient temperature and functions as a dispersion medium or a solvent for the components contained in the clear ink.

The preferable range of the content of the organic solvent in the clear ink is the same as the preferable range of the content of the organic solvent in the above-mentioned ink.

The boiling point of the organic solvent contained in the clear ink is the same as the boiling point of the organic solvent contained in the above-mentioned ink.
The boiling point of the organic solvent can be measured by the method described above.
When the clear ink contains a plurality of organic solvents, the boiling point of the organic solvent is the product of the ratio of the content of each organic solvent to the total organic solvent (mass% ÷ 100) and the boiling point of each organic solvent. It is a value obtained by calculating the average value of.

It is preferable that the boiling point Tbp (T) of the organic solvent contained in the clear ink and the boiling point Tbp (C) of the organic solvent contained in the colored ink satisfy the relationship of the following formula (3).
Tbp (C) ≤ Tbp (T) Equation (3)

When the boiling point Tbp (T) of the organic solvent contained in the clear ink is equal to or higher than the boiling point Tbp (C) of the organic solvent contained in the colored ink (satisfying the relationship of the above formula (3)), the colored ink and the clear ink It is possible to achieve both adhesion and glossiness at a higher level.
The heating temperature and heating time in the clear ink heating step may be adjusted according to the boiling point of the organic solvent contained in the clear ink, the content of the organic solvent, and the transport speed of the recording medium.

Specific examples and preferred embodiments of the organic solvent contained in the clear ink are the same as those of the organic solvent contained in the above-mentioned ink.

(Polymerizable compound and photopolymerization initiator)
As the polymerizable compound and the photopolymerization initiator contained in the clear ink, the same compounds as the polymerizable compound and the photopolymerization initiator contained in the above-mentioned ink can be used, and the preferred embodiment is also the same.

~ Physical characteristics of clear ink ~
The surface tension of the clear ink is preferably 18 mN / m or more and 36 mN / m or less, more preferably 20 mN / m or more and 30 mN / m or less, and further preferably 22 mN / m or more and 26 mN / m or less at a temperature of 25 ° C.
It is preferable that the surface tension γ (T) of the clear ink at a temperature of 25 ° C. is equal to or less than the surface tension γ (C) of the colored ink. The surface tension γ (T) of the clear ink and the surface tension γ (C) of the colored ink at a temperature of 25 ° C. are preferably different by 1 mN / m or more, and more preferably 5 mN / m or more.
Surface tension can be measured by the method described above.

It is preferable that the surface tension γ (C) of the colored ink and the surface tension γ (T) of the clear ink at a temperature of 25 ° C. satisfy the relationship of the following formula (a). The unit of surface tension is mN / m.
γ (T) ≤ γ (C) Equation (a)

When the surface tension γ (T) of the clear ink at a temperature of 25 ° C. is equal to or less than the surface tension γ (C) of the colored ink (satisfying the relationship of the above formula (a)), the colored ink is on the clear ink ejection step. Clear ink is easy to get wet and spread. That is, the clear ink easily covers the colored ink. Therefore, clear ink is present on the surface of the recorded image, and an image having more excellent wear resistance can be obtained.
The surface tension can be measured by the method described above.

The preferred range of the viscosity of the clear ink is the same as the preferred range of the viscosity of the ink described above.

[Clear ink heating process]
The image recording method of the present disclosure includes a clear ink heating step of maintaining the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying the following formula 1 and heating the clear ink discharged onto the recording medium. be able to.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Equation 1)

The back surface temperature B ° C. of the recording medium satisfies the above formula 1 with respect to the thickness Aμm of the recording medium.
The formula 1 is the same as the formula (1) in the ink ejection process described above, and the preferable range of the formula (1) is also the same.

From the viewpoint of adhesion between the colored ink and the clear ink, it is preferable that the organic solvent contained in the clear ink is removed relatively slowly.
Specifically, the time between the drip of the clear ink on the colored ink after heating and the start of heating is preferably 1 second or less, more preferably 0.5 seconds or less. It is preferable to heat at the same time as landing.
The back surface temperature B of the recording medium, the heating time, the heating method, preferred embodiments thereof, and the like are the same as those in the ink ejection step described above.

<Inkjet recording device>
The inkjet recording device is an inkjet recording device that performs the image recording method of the present disclosure, and records a colored ink ejection unit that ejects colored ink onto a recording medium and a colored ink ejected onto the recording medium. A colored ink heating unit that keeps the back surface temperature of the medium at 40 ° C. or higher to heat it, a clear ink ejection unit that ejects clear ink onto the heated colored ink, and a clear ink ejected onto the heated colored ink. A clear ink heating unit that heats the recording medium while maintaining the back surface temperature at 40 ° C. or higher, and an ink curing irradiation unit that irradiates the colored ink after heating and the active energy ray that cures the clear ink. Is preferable.
The inkjet recording apparatus may further include an irradiation unit for curing colored ink that irradiates an active energy ray that cures the colored ink after heating.

The recording method of the inkjet recording device is not particularly limited. As a recording method, a shuttle method that records while scanning the head in the width direction of the support using a single-length serial head and a line head in which recording elements are arranged corresponding to the entire area of one side of the support are used. There is a line method (single pass method) used.

Specific examples of the shuttle system include the devices described in International Publication No. 2017/104845 (paragraph numbers 0133 to 0143). Specific examples of the single-pass method include the devices described in International Publication No. 2017/104845 (paragraph numbers 0144 to 0162) and the like.

Hereinafter, the invention of the present disclosure will be described in more detail by way of examples, but the invention of the present disclosure is not limited to the following examples as long as the gist thereof is not exceeded. Unless otherwise specified, "part" is based on mass.

<Preparation of pigment dispersion>
Ingredients other than the pigments shown in Table 1 below are mixed so as to have the composition shown in Table 1, and stirred with a SILVERSON mixer under the conditions of 2,000 rpm to 3,000 rpm and 10 minutes to 15 minutes. A uniform dispersant diluent was obtained. Each pigment is added to this dispersant diluent in the types and amounts shown in Table 1, and the mixture is further stirred with a mixer under the conditions of 2,000 rpm to 3,000 rpm and 10 minutes to 20 minutes. 500 parts of a uniform preliminary dispersion was obtained.
Then, each of the obtained preliminary dispersions was subjected to a dispersion treatment using a circulation type bead mill device (SL-012C1) manufactured by Dispermat Co., Ltd. to obtain pigment dispersions of each color. The conditions for the dispersion treatment were that the circulating bead mill device was filled with 200 parts of zirconia beads having a diameter of 0.65 mm and the peripheral speed was 15 m / s. The dispersion time was 1 hour to 6 hours.

The details of the components in Table 1 are as follows.
PB15: 4 ... C.I. I. Pigment Blue 15: 4, BASF, HELIGOEN BULE D 7110F,
Mixed quinacridone ... BASF, CINQUASIA MAGENTA L 4540
PY120 ... C.I. I. Pigment Yellow 120, Clariant, NOVOPERM YELLOW H2G
Carbon black ... CABOT, MOGUL E
Sol32000 ... Lubrizol, SOLSERSE 32000
DEGDEE ... Diethylene glycol diethyl ether manufactured by Tokyo Chemical Industry Co., Ltd.

<Ink preparation>
For colored ink, each component is mixed according to the following composition 1, and for clear ink, each component is mixed according to the following composition 2, respectively, with a mixer manufactured by SILVERSON, 2,000 rpm to 3,000 rpm, respectively. Each ink was obtained by stirring under the conditions of 10 to 15 minutes.

-Composition of colored ink 1-
~ Cyan ink ~
Pigment dispersion: Pigment mill base Cyan: 6 parts Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.): 70.9 parts Polymerizable compound: GENOMER4215 (manufactured by Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE819 (BASF) (Manufactured by Co., Ltd.): 2 parts Polymerization initiator: IRGACURE2959 (manufactured by BASF Co., Ltd.): 1 part Surfactant: BYK331 (manufactured by Big Chemie Co., Ltd.): 0.1 parts ~ Magenta Ink ~
Pigment dispersion :: Pigment mill base Magenta: 12 parts Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.): 64.9 parts Polymerizable compound: GENOMER4215 (manufactured by Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE819 ( BASF Co., Ltd.): 2 parts Polymerization initiator: IRGACURE2959 (BASF Co., Ltd.): 1 part Surfactant: BYK331 (Big Chemie Co., Ltd.): 0.1 part ~ Yellow ink ~
Pigment dispersion: Pigment mill base Yellow: 10 parts Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.): 66.9 parts Polymerizable compound: GENOMER4215 (manufactured by Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE819 (BASF) (Manufactured by Co., Ltd.): 2 parts Polymerization initiator: IRGACURE2959 (manufactured by BASF Co., Ltd.): 1 part Surfactant: BYK331 (manufactured by Big Chemie Co., Ltd.): 0.1 parts ~ Black ink ~
Pigment dispersion: Pigment mill base Black: 5 parts Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.): 69.9 parts Polymerizable compound: GENOMER4215 (manufactured by Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE819 (BASF) (Manufactured by Co., Ltd.): 2 parts Polymerization initiator: IRGACURE2959 (manufactured by BASF Co., Ltd.): 1 part Surfactant: BYK331 (manufactured by Big Chemie Co., Ltd.): 0.1 part-Composition of clear ink 2-
Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Kasei Kogyo Co., Ltd.): 70.9 parts Polymerizable compound: GENOMER4215 (manufactured by Rahn Co., Ltd.): 8 parts Polymerizable compound: Shikou UV-7630B (manufactured by Nippon Synthetic Chemical Co., Ltd.): 8 parts Polymerization initiator: IRGACURE819 (manufactured by BASF Co., Ltd.): 3 parts Polymerization initiator: IRGACURE2959 (manufactured by BASF Co., Ltd.): 2 parts Surface active agent: BYK331 (manufactured by BIC Chemie Co., Ltd.): 0.1 parts

<Image recording device>
As an inkjet recording device, an inkjet printer (KEGON) manufactured by Afit, a rubber heater (manufactured by Three High Co., Ltd .:), a UV exposure machine (LED-UV lamp) (LLRG1200FUV, manufactured by Aitec System Co., Ltd.), and , A device equipped with a low-pressure mercury lamp (sterilization lamp GL15, manufactured by Hitachi Appliances Co., Ltd.) was prepared.
The output of the rubber heater was set so that the back surface temperature of the recording medium could be heated between 35 ° C. and 90 ° C. The time from the inkjet droplet to the ultraviolet (LED-UV) exposure corresponds to the heating time of the droplet, and the transport speed (5 m / 5 m /) so that this time can be changed from 0.5 second to 60 seconds. The timing of opening and closing the UV shutter was adjusted to 25 m / min).

<Image recording method>
Images were recorded with the following configuration. Each configuration is as shown below.

(Example 1)
The ink ejection step, the ink heating step, and the LED irradiation step were carried out in this order, and images were recorded. As a recording medium, cappuccino CP-830 (manufactured by Yamaplus Co., Ltd., thickness A: 1500 μm) was used. The values of 6 × ln (A) and 12 × ln (A) are as shown in Table 2.
(1) Ink ejection process:
Inkjet head heated to 35 ° C (Toshiba Tech Co., Ltd., CA4, nozzle diameter 26 μm) to Y (yellow), M (magenta), C (cyan) and K (black) using four colored inks. Y (yellow), M (magenta), C (cyan), and K (black) were repeatedly ejected onto the recording medium in a line shape so as to have an image density of 1200 dpi × 600 dpi (dot per ink). ..
At this time, the voltage was adjusted so that the ejection amount of the colored ink was ^{20 g per 1 m 2.}
(2) Ink heating process:
The recording medium to which the colored ink was discharged was heated with a rubber heater so that the back surface temperature of the recording medium was 45 ° C. The heating time was set to 10 seconds.
The back surface temperature of the recording medium was measured with an infrared radiation thermometer (AD-5616, manufactured by A & D Co., Ltd.).
(3) LED irradiation process:
(2) The entire surface of the side on which the colored ink was ejected was irradiated with ultraviolet rays toward the recording medium after the ink heating step. As a result, the colored inks are cured, and four colored inks are used by each colored ink that is repeatedly ejected in the order of Y (yellow), M (magenta), C (cyan), and K (black) in a line shape. Only 100% solid images were recorded.
A UV exposure machine (LED-UV lamp, wavelength 385 nm) was used as a light source for irradiating the ultraviolet rays, and the ultraviolet rays were irradiated with an exposure amount of ^{800 mJ / cm 2.}

(Examples 2-9, Comparative Examples 1-9)
Images were recorded in the same manner as in Example 1 except that the combination of the thickness A of the recording medium, the back surface temperature B of the recording medium, and the exposure amount of the LED was changed as shown in Table 2.
As the recording medium having a thickness of 2500 μm, 1500 μm, 1000 μm and 200 μm, 2500 μm, 1500 μm, 1000 μm and 200 μm polyurethane leather LUMISH (registered trademark) (manufactured by Kyowa Leather Co., Ltd.) were used, respectively.

(Comparative Example 10)
An image is formed in the same manner as in Example 6 except that the UV exposure machine (LED-UV lamp, wavelength 385 nm) is a low pressure mercury lamp (sterilization lamp GL15, manufactured by Hitachi Appliances, Inc.) and the exposure amount is 200 mJ / cm ^2. (Recorded).

<Examples 10 to 11 and Comparative Example 11>
(Example 10)
As described below, a colored ink ejection step, a colored ink heating step, a clear ink ejection step, a clear ink heating step, an LED irradiation step, and a mercury lamp irradiation step were carried out in this order, and an image was recorded. As the recording medium, the recording medium (thickness A: 1000 μm) obtained by the above method was used. The values of 6 × ln (A) and 12 × ln (A) are as shown in Table 3.
(1) Colored ink ejection process:
Inkjet head heated to 35 ° C (Toshiba Tech Co., Ltd., CA4, nozzle diameter 26 μm) to Y (yellow), M (magenta), C (cyan) and K (black) using four colored inks. Y (yellow), M (magenta), C (cyan), and K (black) were repeatedly ejected onto the recording medium in a line shape so as to have an image density of 1200 dpi × 600 dpi (dot per ink). ..
At this time, the voltage was adjusted so that the ejection amount of the colored ink was ^{20 g per 1 m 2.}
(2) Colored ink heating process:
The recording medium to which the colored ink was discharged was heated with a rubber heater so that the back surface temperature of the recording medium was 60 ° C. The heating time was set to 10 seconds.
(3) Clear ink ejection process:
Clear ink was ejected onto the colored ink from an inkjet head (Toshiba TEC Corporation, CA4, nozzle diameter 26 μm) heated to 35 ° C. so as to have an image density of 1200 dpi × 600 dpi. At this time, the voltage was adjusted so that the amount of the dropped clear ink was ^{10 g per 1 m 2.}
(4) Clear ink heating process:
The recording medium to which the clear ink was discharged was heated with a rubber heater so that the back surface temperature of the recording medium became 60 ° C. The heating time was set to 10 seconds.
(5) LED irradiation process:
(4) The entire surface of the side on which the clear ink was ejected was irradiated with ultraviolet rays toward the recording medium after the clear ink heating step. As a result, the colored ink and the clear ink are cured, and four colors are colored by each colored ink that is repeatedly ejected in the order of Y (yellow), M (magenta), C (cyan), and K (black) in a line shape. A 100% solid image with ink was recorded.
A UV exposure machine (LED-UV lamp, wavelength 385 nm) was used as a light source for irradiating the ultraviolet rays, and the ultraviolet rays were irradiated with an exposure amount of ^{800 mJ / cm 2.}
(6) Mercury lamp irradiation process:
The entire surface of the side on which the clear ink was ejected was irradiated with ultraviolet rays toward the recording medium after the LED irradiation step. As a result, the colored ink and the clear ink were further cured.
A UV exposure machine (low pressure mercury lamp) was used as a light source for irradiating ultraviolet rays, and ultraviolet rays were irradiated at an exposure amount of ^{75 mJ / cm 2.}

(Example 11)
An image was formed in the same manner as in Example 10 except that the mercury lamp irradiation step was not performed.

(Comparative Example 11)
An image was formed in the same manner as in Example 10 except that the LED irradiation step was not performed.

〔evaluation〕
The recorded medium on which the image was formed by the methods of Examples 1 to 11 and Comparative Examples 1 to 11 was used as a sample.
The damage of the recorded medium of the obtained sample, the abrasion resistance and the glossiness of the recorded medium and the image were evaluated by the following evaluation criteria. The evaluation results are shown in Tables 2 and 3.

(Evaluation of damage to recorded media)
The damage of the recorded medium can be evaluated by the amount of deformation of the recorded medium after irradiation with active energy rays. Place the sample on a flat desk with the side opposite to the side on which the image was recorded facing down, and the distance between the back of the sample in the normal direction of the desk and the front of the desk is the back of the sample. Although there are advantages and disadvantages depending on the location, the maximum value of the above distance was measured with a ruler and evaluated according to the following evaluation criteria.
-Evaluation criteria-
3: 1 mm or less 2: 1 mm or more and less than 5 mm 1: 5 mm or more

(Abrasion resistance evaluation)
With a Gakushin tester (AB-301 Gakushin type friction robustness tester, manufactured by Tester Sangyo Co., Ltd.), the images of each sample were abraded 200 times under the condition of 200 g load with canvas, and each was worn. The number of times the image was peeled off from the sample image was recorded and evaluated according to the following evaluation criteria. Two or more have practical wear resistance.
-Evaluation criteria-
The image does not come off even at 5: 200 times.
4: The image was peeled off after 100 times or more and less than 200 times.
3: The image was peeled off after 50 times or more and less than 100 times.
The image was peeled off after 2:10 times or more and less than 50 times.
The image was peeled off less than 1:10 times.

(Evaluation method of gloss)
After measuring the glossiness (%) of the solid image of the above four colors with micro-TRI-gloss (manufactured by BYK-Gardner, 85 °, n = 5), an average value was obtained and evaluated according to the following evaluation criteria.
-Evaluation criteria-
3: The above average value was 4.0% or more.
2: The above average value was more than 2.5% and less than 4.0%.
1: The above average value was 2.5% or less.

In Table 2, the description of "-" in the LED exposure amount and the mercury lamp exposure amount means that the LED and the mercury lamp are not exposed.

As shown in Table 2, without using the clear ink, the case of using only the color ink, the thickness A of the recording medium is a 200Myuemu～2000myuemu, exposure of LED is 200mJ ^/ cm ² ~1000mJ ^/ cm 2 Examples 1 to 9 in which the back surface temperature B of the recording medium is 6 × ln (A) ≦ B ≦ 12 × ln (A) are excellent in damage to the recording medium, wear resistance and glossiness of the image. Was there.
Comparative Examples 1, 3 and 5 having B <6 × ln (A) were inferior in glossiness. On the other hand, Comparative Examples 2, 4 and 6 in which B> 12 × ln (A) were inferior in the damage of the recording medium.
Further, in Comparative Example 7 in which the exposure amount of the LED was ^{less than 200 mJ / cm 2} , the wear resistance of the image was inferior. On the other hand, Comparative Example 8 in which the exposure amount of the LED was ^{more than 1000 mJ / cm 2} was inferior to the damage of the recording medium.
Comparative Example 9 using a recorded medium having a thickness of more than 2000 μm was inferior in glossiness, and Comparative Example 10 exposed to a mercury lamp instead of an LED was inferior in damage to the recorded medium.
Even in Examples 5 to 9 using a thin recording medium, the glossiness was more excellent when the back surface temperature B was in the range of 35 ° C to 60 ° C. In Examples 1-7 the exposure amount of the LED is in the range of 400mJ ^/ cm ² ~900mJ ^/ cm 2 was superior by damage of the recording medium.

As shown in Table 3, Examples 10 and 11 using the clear ink were remarkably superior in wear resistance of the image as compared with Examples 1 to 9 in which the clear ink was not used. Above all, in Example 10 in which the low-pressure mercury lamp was further exposed in addition to the LED exposure, the wear resistance of the image was further excellent.

The disclosure of Japanese Patent Application No. 2018-033964, filed February 27, 2018, is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims (9)

A step of ejecting an ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator onto a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method.
A step of holding the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying the following formula 1 and heating the ink ejected onto the recording medium.
At least in the ink after ^heating, by irradiation with active energy rays by using a light-emitting diode with an exposure amount of ^{200mJ / cm 2 ~1000mJ / cm 2} , and curing the at least ink,
Have a,
Further, an image recording method comprising a step of irradiating the cured ink with active energy rays using a low-pressure mercury lamp.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Equation 1) The image recording method according to claim 1, wherein the ink is a colored ink further containing a colorant. As a step of ejecting the ink and a step of heating the ink,
A step of ejecting a colored ink containing a colorant, an organic solvent, a polymerizable compound and a photopolymerization initiator onto a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method.
A step of holding the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying Equation 1 and heating the colored ink ejected onto the recording medium.
A step of ejecting a clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator onto the colored ink after heating by an inkjet method.
A step of holding the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying Equation 1 and heating the clear ink discharged onto the recording medium.
Have,
The image recording method according to claim 1 or 2, wherein the curing step is to cure the colored ink and the clear ink after heating by the irradiation. The image recording method according to any one of claims 1 to 3 , wherein the content of the organic solvent contained in the ink is 20% by mass to 90% by mass with respect to the total mass of the ink. The exposure ^{amount, 400mJ / cm 2 ~900mJ / cm} 2 The image recording method according to any one of claims 1 to 4. The image recording method according to any one of claims 1 to 5 , wherein the back surface temperature B ° C. of the recording medium having a thickness A is maintained within a range satisfying the following formula 2.
8 × ln (A) ≦ B ≦ 10 × ln (A) (Equation 2) The image recording method according to any one of claims 1 to 6 , wherein the organic solvent contained in the ink has a boiling point of 75 ° C to 300 ° C. The image recording method according to any one of claims 1 to 7 , wherein the back surface temperature B ° C. of the recording medium is 30 ° C. to 90 ° C. The image recording method according to any one of claims 1 to 8 , wherein the recording medium is a material for a seat for a vehicle.