WO2019167769A1

WO2019167769A1 - Image recording method

Info

Publication number: WO2019167769A1
Application number: PCT/JP2019/006408
Authority: WO
Inventors: 中野　良一; 梅林　励
Original assignee: 富士フイルム株式会社
Priority date: 2018-02-27
Filing date: 2019-02-20
Publication date: 2019-09-06
Also published as: JPWO2019167769A1; JP6968976B2

Abstract

This image recording method comprises: a step of ejecting an ink containing an organic solvent, a polymerizable compound, and a photopolymerization initiator onto a medium to be recorded having a thickness A of 200 μm to 2000 μm according to an ink jet technology; a step of maintaining a back surface temperature B°C of the medium to be recorded having the thickness A in a range satisfying the following formula 1, and heating the ink ejected onto the medium to be recorded; and a step of irradiating at least the ink after the heating with activation energy rays using a light-emitting diode at an exposure amount of 200 mJ/cm2 to 1000 mJ/cm2 to cure at least the ink. (Formula 1): 6 × ln(A) ≤ B ≤ 12 × ln(A)

Description

Image recording method

This disclosure relates to an image recording method.

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

For example, in International Publication No. 2017-104845, as an ink jet recording method capable of forming an image having excellent wear resistance and flexibility, a colored ink discharge method for discharging a color ink containing a colorant and an organic solvent onto a recording medium. A colored ink heating step of heating the discharged colored ink while maintaining the surface temperature of the recording medium at 40 ° C. or higher, a polymerizable compound, a photopolymerization initiator, and A colorless ink discharge step for discharging a colorless ink containing an organic solvent, and a colorless ink heating step for heating the colorless ink discharged on the heated colored ink while maintaining the surface temperature of the recording medium at 40 ° C. or higher; And a colorless ink curing step in which the colorless ink after heating is irradiated with active energy rays to cure the colorless ink is disclosed.

Further, for example, in Japanese Patent Application Laid-Open No. 2015-147418, as a method for performing inkjet recording on a recording medium with extremely low ink absorption capability at high speed, the surface of the recording medium with non-ink-absorbing and low-absorbing properties is recorded. A recording head that ejects ink, a medium support that faces the recording head and supports the recording medium from the back surface, and a first liquid component that evaporates the liquid component of the ink ejected and adhered to the recording medium from the recording head. A drying unit as a fixing unit; and a second fixing unit downstream of the drying unit in the conveyance direction of the recording medium, and the ink is at least (1) a colorant, and (2) a boiling point of 100 ° C. or more and 250 ° C. The following organic solvent is a monomer, (3) a polymerizable oligomer and / or polymer, and (4) a photopolymerization initiator. The second fixing unit irradiates the recording medium with ultraviolet rays or an electron beam. An irradiation device for the evaporation of liquid components in the drying section, the ink-jet recording method is disclosed an inkjet recording system is a 40 to 70% by weight of the ink adhered on a 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 of the recording medium tends to increase when heat is applied to the recording medium in order to volatilize the organic solvent in the ink. On the other hand, if the exposure amount of the active energy ray and the heat applied to the recording medium are kept low, the recording medium is less susceptible to damage, but the recorded image tends to have reduced wear resistance and gloss. That is, it may be difficult to achieve both the damage of the recording medium and the wear resistance and glossiness of the image.

In addition, regarding the thickness of the recording medium, when the recording medium is thick, it takes a relatively long time until the heat applied from the back surface for volatilizing the organic solvent is conducted to the recording medium surface. It is necessary to keep the temperature of the applied heat high. However, if the temperature of heat applied from the back surface is high, the temperature of the recording medium itself increases, and the damage to the recording medium tends to increase when irradiated with active energy rays. In addition, when the exposure amount of the active energy ray to be irradiated is large, the damage of the recording medium tends to become more remarkable.

International Publication No. 2017-104845 describes that deformation of the recording medium can be suppressed when the heating temperature in the colored ink heating step is 100 ° C. or less, but recording by irradiation with active energy rays is described. Medium damage is not considered.

Japanese Patent Laid-Open No. 2015-147418 discloses that hot air is applied to the ink or an infrared lamp is applied to the ink in order to evaporate the liquid component in the ink. The heat applied to is not considered. Therefore, a good recording medium cannot be expected from the viewpoint of damage to the recording medium.

A problem to be solved by an embodiment of the present disclosure is to provide an image recording method for recording an image in which the recording medium is less damaged and the image has excellent wear resistance and gloss.

Specific means for solving the problems include the following aspects.
<1> A step of discharging 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 The process of heating the ink ejected on the recording medium while maintaining B ° C. within a range satisfying the following formula 1, and at least the ink after heating emits light at an exposure amount of 200 mJ / cm ² to 1000 mJ / cm ^2. And irradiating active energy rays using a diode to cure at least the ink.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Formula 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 discharging ink and a step of heating ink, a colorant, an organic solvent, a polymerizable compound, and a photopolymerization initiator are included on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method. A step of discharging the colored ink, a step of holding the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying Equation 1, heating the colored ink discharged onto the recording medium, and coloring after the heating On the ink, a step of discharging a clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator by an inkjet method, and maintaining the back surface temperature B ° C. of the recording medium having a thickness A within a range satisfying Formula 1, Heating the clear ink ejected onto the recording medium, and the curing step cures the heated colored ink and clear ink by irradiation <1> or <2 An image recording method according to.
<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, is 400mJ / cm 2 ~ 900mJ / cm is ² <1> to <5> The image recording method according to any one of.
<7> The image recording method according to any one of <1> to <6>, 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) (Formula 2)
<8> The image recording method according to any one of <1> to <7>, wherein a boiling point of the organic solvent contained in the ink is 75 ° C. to 300 ° C.
<9> The image recording method according to any one of <1> to <8>, wherein a 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 vehicle seat.

According to an embodiment of the present disclosure, it is possible to provide an image recording method for recording an image in which damage to a recording medium is small and the image has excellent wear resistance and gloss.

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

In this specification, a numerical range indicated by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value, respectively. In a numerical range described in stages in the present disclosure, an upper limit value or a lower limit value described in a numerical range may be replaced with an upper limit value or a lower limit value in another numerical range. Further, in the numerical ranges 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 values shown in the examples.

In this specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. means.
In this specification, the term “process” is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. It is.
In this specification, the back surface of the recording medium means a surface opposite to the image recording surface of the recording medium. Further, the back surface temperature of the recording medium means the temperature of the back surface of the recording 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 discharging 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, the backside temperature B ° C. of the recording medium held within a range satisfying the following formula 1, heating the ink ejected onto the recording medium, at least ink after ^{heating, 200mJ / cm 2 ~ 1000mJ /} cm 2 Irradiating an active energy ray with a light emitting diode at an exposure amount of at least to cure the ink.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Formula 1)
The unit of thickness A is μm.

In the above prior art, in an ink jet 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. Therefore, applying heat to the recording medium may cause an increase in damage to the recording medium. On the other hand, if the exposure amount of the active energy ray and the heat applied to the recording medium are kept low, it is effective in reducing damage to the recording medium, but the wear resistance and glossiness of the recorded image are reduced. It tends to decline. As a result, it may be difficult to achieve both the damage to the recording medium and the wear resistance and glossiness of the image.

Further, when the recording medium is thick, it takes time until the heat applied from the back surface of the recording medium for volatilizing the organic solvent in the ink is conducted to the surface of the recording medium. Therefore, it is necessary to keep the temperature of the heat applied from the back side high. However, 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. In addition, when the active energy ray having a large exposure amount is irradiated, the damage of the recording medium tends to be remarkable.

Therefore, in the image recording method of the present disclosure, the exposure amount of the active energy ray irradiated 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 recorded. The focus is on identifying the relationship between the back surface temperature and the thickness of the recording medium. When using a thick recording medium, it is necessary to keep the temperature of the heat applied from the back of the recording medium relatively high, but the amount of heat required to volatilize the organic solvent in the ink depending on the thickness of the recording medium However, when the recording medium is thick, the necessary heat amount is high, and when the recording medium is thin, the necessary heat amount is low. That is, the amount of heat necessary for volatilizing 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 recording medium, the relationship between the back surface temperature of the recording medium caused by heating of the recording medium and the thickness of the recording medium It is important to identify
As described above, it is possible to provide an image recording method for recording an image with little damage to the recording medium and excellent image wear resistance and glossiness.

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

[Ink ejection process]
An ink ejection step is performed for ejecting ink containing an organic solvent, a polymerizable compound, and a photopolymerization initiator from an inkjet head onto a recording medium having a thickness A of 200 μm to 2000 μm.
Thereby, a desired image can be recorded on the recording medium.
In addition, by including the ink ejection step, the wear resistance of the recorded image is improved.
In the image recording method of the present disclosure, the ink ejection step can be provided a plurality of times. For example, the aspect including the coloring ink discharge process and the clear ink discharge process which are mentioned later may be sufficient.

As an ink ejection method in the ink ejection process, an ink jet method is preferably used.
The ink jet method is not particularly limited, and is a known method, for example, a charge control method for discharging ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) using vibration pressure of a piezo element, An acoustic ink jet system that converts an electrical signal into an acoustic beam, irradiates the ink with ink, and ejects the ink using radiation pressure, and a thermal ink jet that forms bubbles by heating the ink and uses the generated pressure (bubble jet (registered) Trademark)) method or the like.

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

[Recording 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, a certain amount of heating is required to volatilize the organic solvent in the ink, so that the problem of reducing damage to the recording medium becomes obvious. That is, the present disclosure is an invention that solves the problem of reducing damage to a 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 increasing the heating temperature of the recording medium, and the glossiness can be improved.
From the above viewpoint, the thickness (A) is preferably 800 μm to 1800 μm, and more preferably 1000 μm to 1500 μm.
The thickness (A) of the recording medium is the thickness of the thickest portion of the recording medium.

The recording medium can be appropriately selected from materials used for applications in which the recording medium is required to have damage and wear resistance (for example, vehicle seats, bags, etc.).
As a use in which the recording medium is required to have damage and wear resistance, a vehicle seat is preferable from the viewpoint of easily achieving the effect of the image recording method of the present disclosure.
A seat for a vehicle requires a high level of damage and wear resistance of a recording medium because a person is seated on the seating surface of the seat or puts luggage on the seat because the seat surface is likely to be damaged. According to an embodiment of the image recording method of the present disclosure, it is possible to achieve a high level of damage and wear resistance of a recording medium required for a vehicle seat.

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

Natural leather is composed of collagen fibers whose main component is a fibrous protein called collagen. Hundreds of fine fibers (fibrils) are bundled to form fibers (fibers), and several to tens 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 intertwined three-dimensionally.
Natural leather is divided into a silver layer on the surface, followed by an intermediate net layer from the intermediate layer, and has a continuous structure. The silver layer has a glossy, flexible and excellent feel because the fiber bundle of collagen is intricate. In the net-like layer, the fibers are slightly thick and intricately intertwined to maintain the strength of natural leather.
Synthetic leather is obtained by applying a foam such as polyurethane on the surface of a woven fabric, a knitted fabric, or a non-woven fabric, and coating it with a nylon resin or a polyurethane resin.
As the artificial leather, a non-woven fabric having a fiber layer having a three-dimensional structure similar to the collagen fiber structure of natural leather is used. In addition, a leather-like feel can be obtained by using ultrafine fibers of 0.1 denier or less on the surface portion.
Artificial leather is composed of a nonwoven fabric with a fiber layer called a random three-dimensional structure in which ultrafine fibers of nylon or polyester are combined in a bundle, and an elastic polyurethane resin.

[Ink heating process]
The image recording method of the present disclosure includes an ink heating process in which the back surface temperature B ° C. of a recording medium having a thickness A is maintained within a range satisfying the following formula 1 and the ink ejected on the recording medium is heated.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Formula 1)
Note that 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 the ink heating step, at least a part of the organic solvent contained in the ink is removed, and ink curing failure 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 aspect containing the coloring ink heating process and clear ink heating process which are mentioned later may be sufficient.

The back surface temperature B ° C. of the recording medium satisfies the above formula 1 with respect to the thickness A μm of the recording medium. In Equation 1, the coefficient of ln (A) is an empirical value.
As a result, it is possible to suppress damage to the recording medium while maintaining good wear resistance and glossiness of the image.
When B is 6 × ln (A) or higher, glossiness can be kept good, and when B is 12 × ln (A) or lower, 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 (Formula 2).
8 × ln (A) ≦ B ≦ 10 × ln (A) (Formula 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 recording medium is 90 ° C. or lower, damage to the recording medium can be satisfactorily suppressed. From the above viewpoint, the back surface temperature of the recording 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 removal of the organic solvent in the ink heating step is preferably performed 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 removed so as to be 3% by mass or less. Is more preferable, and removal (all removal) is particularly preferable 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 glossiness. As a method for quickly removing the organic solvent contained in the ink, for example, the boiling point of the organic solvent contained in the ink is set in the range described later.

The heating in the ink heating step is preferably performed for 1 second or more while maintaining the back surface temperature B ° C. of the recording medium satisfying the above formula 1 with respect to the thickness A μm of the recording medium.

When the heating time in the ink heating step is 1 second or longer, it is easy to remove the organic solvent contained in the ink, and bleeding 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 process.
The heating temperature and the 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 conveyance speed of the recording medium.

The ink heating method in the ink heating step can be appropriately selected from methods that can remove the organic solvent contained in the ink.

As a heating method, for example, a heating plate (resistance heater, induction heater) disposed below the recording medium, a radiant heater (heating rod, infrared (IR) lamp) disposed above the recording medium, And a method using solid IR).
In the heating, the ink is heated through the recording medium using the heating plate and the radiation heater.
The heating is preferably performed before the ink is discharged onto the recording medium.

Next, 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 those described above as necessary.

The ink in the present disclosure is not particularly limited as long as the ink includes an organic solvent, a polymerizable compound, and a photopolymerization initiator, and includes an organic solvent, a polymerizable compound, and a photopolymerization initiator, and does not substantially include a colorant. It may be an ink (clear ink) or an ink (colored 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 substantially does not contain a colorant. “Containing substantially no colorant” means that the content of the colorant is less than 0.1% by mass relative to the total amount of the ink.
The colored ink may further contain a polymer.

(Organic solvent)
The ink contains at least one organic solvent.
The organic solvent is liquid at ambient temperature and functions as a dispersion medium or solvent for components contained in the ink.
It does not restrict | limit especially as an organic solvent, It can select from the arbitrary organic solvents generally used in the printing industry.

The content of the organic solvent contained in the ink is preferably 20% by mass to 90% by mass with respect to the total mass of the ink, more preferably 30% by mass to 85% by mass, and more preferably 40% by mass to 80% by mass. Further preferred.
When the organic solvent in the ink is 20% by mass or more, the discharge property is excellent. On the other hand, when the content is 90% by mass or less, ink bleeding can be suppressed and 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 organic solvent has good volatility, 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, ink bleeding is further suppressed and glossiness is improved.
The boiling point of the organic solvent can be measured using a known method. For example, measurement can be performed according to JIS K2254.
In addition, the boiling point of the organic solvent when the ink contains a plurality of organic solvents is the product of the ratio of the content of each organic solvent in the whole organic solvent (mass% ÷ 100) and the boiling point of each organic solvent. It is a value obtained by calculating an average value.

It does not restrict | limit especially as an organic solvent, It can select from the arbitrary organic solvents 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 acrylic-modified polyorganosiloxane are the same as the preferred embodiments and specific examples described in International Publication No. 2017/104845 (paragraph numbers 0122 to 0124).

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

The oligomer preferably comprises a main chain, such as a polyester, urethane, epoxy or polyether main chain, and a group polymerizable by one or more active energy rays. The polymerizable group may be any group that can polymerize 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 preferred.
Examples of groups capable of free radical polymerization include (meth) acryloyl groups.
The (meth) acryloyl group is a concept including 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 with respect to the total mass of the oligomer is preferably 30% by mass or more, more preferably 40% by mass or more, More preferably, it is 50 mass% or more.

The oligomer preferably contains a urethane main chain, more preferably a urethane acrylate oligomer, from the viewpoint of excellent image adhesion and flexibility.
Furthermore, from the viewpoint of having good chemical resistance, the oligomer is a trifunctional, tetrafunctional, pentafunctional, hexafunctional or higher functional urethane acrylate oligomer, particularly a hexafunctional urethane acrylate oligomer. Preferably there is.

As another example of the oligomer, epoxy oligomers such as bisphenol A epoxy acrylate and epoxy novolac acrylate may be used because they have a rapid curing speed 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.

The weight average molecular weight means a value measured by gel permeation chromatography (GPC).
The above GPC uses HLC-8020GPC (manufactured by Tosoh Corp.) and elution using three columns of TSKgel (registered trademark) and Super Multipore HZ-H (manufactured by Tosoh Corp., 4.6 mm ID × 15 cm). This is performed using THF (tetrahydrofuran) as a liquid.
GPC is performed using a differential refractive index (RI) detector with a sample concentration of 0.45 mass%, a flow rate 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 -2500 "," A-1000 ", and" n-propylbenzene ".

The oligomer has a viscosity of 0.5 Pa · s to 20 Pa. s, more preferably 5 Pa. at 60 ° C. s to 15 Pa. s, most preferably 5 Pa. s to 10 Pa. having a viscosity of s. The viscosity of the oligomer is determined by T. using 40 mm slope / 2 ° steel cone at 60 ° C. with a shear rate of 25 sec ⁻¹ . A. Measurements can be made using an ARG2 rheometer from Instruments.

Monomers capable of free radical polymerization 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 esters of acrylic acid. Preferable examples include phenoxyethyl acrylate (PEA), cyclic TMP formal acrylate (CTFA), isobornyl acrylate (IBOA), tetrahydrofurfuryl acrylate (THFA), 2- (2-ethoxyethoxy) ethyl acrylate, octadecyl acrylate (ODA), tridecyl acrylate (TDA), isodecyl acrylate (IDA) and lauryl acrylate. Of these, PEA is particularly preferable.

Multifunctional (meth) acrylate monomers include bifunctional, trifunctional and tetrafunctional monomers. Examples of multifunctional acrylate monomers that can be included in the ink include hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, polyethylene glycol diacrylate (eg, tetraethylene glycol diacrylate), dipropylene glycol diacrylate, Tri (propylene glycol) triacrylate, neopentyl glycol diacrylate, bis (pentaerythritol) hexaacrylate, and acrylate esters of ethoxylated or propoxylated glycols and polyols such as propoxylated neopentyl glycol diacrylate, ethoxylated trimethylol Propane triacrylate, as well as mixtures thereof.

Polyfunctional (meth) acrylate monomers include methacrylic acid such as hexanediol dimethacrylate, trimethylolpropane trimethacrylate, triethylene glycol dimethacrylate, diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, and 1,4-butanediol dimethacrylate. Of esters (ie methacrylates). A mixture of (meth) acrylates can also be used.

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

The α, β-unsaturated ether monomer 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. Mixtures of α, β-unsaturated ether monomers can also be used.

N-vinylamide and N- (meth) acryloylamine can also be used. N-vinylamide has a vinyl group bonded to the nitrogen atom of the amide and may be further substituted in the same manner as the (meth) acrylate monomer. Preferable examples include N-vinylcaprolactam (NVC) and N-vinylpyrrolidone (NVP). 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. A preferred example is N-acryloylmorpholine (ACMO).

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

As the polymerizable compound, a compound capable of free radical polymerization and a compound capable of cationic polymerization 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 the present specification, the oligomer means a polymerizable compound having a weight average molecular weight of 1,000 or more and 30,000 or less. 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 dischargeability.
In addition, the ink contains an oligomer having a weight average molecular weight in the above range and is cured, so that 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 from 1,500 to 10,000, and still more preferably from 3,000 to 5,000.

When the ink contains a polymerizable compound, the content of the polymerizable compound is preferably 15% by mass to 30% by mass and more preferably 18% by mass to 28% by mass 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 the flexibility and the wear resistance becomes good, and both the flexibility and the wear 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 an acrylate compound is an oligomer. When the polymerizable compound is an acrylate compound, an image with more excellent abrasion 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 acrylate compound is based on the total mass of the ink. 15 mass% or more and 30 mass% or less are preferable.
By including the above acrylate compound in the above content, the balance between flexibility and wear resistance is improved, and both flexibility and wear resistance can be achieved at a higher level.
The ink more preferably contains an acrylate compound (acrylate oligomer) having a weight average molecular weight of 1,500 to 10,000 as a polymerizable compound in a content of 18% by mass to 28% by mass 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 based on the total mass of the polymerizable compound.
When the total mass of the monofunctional acrylate compound and the bifunctional acrylate compound with respect to the total mass of the polymerizable compound is 50% by mass or more, the network structure of the ink after curing does not become too dense, and the flexibility of the image is further improved. Also, the adhesion of the image is improved.

As the polymerizable compound, a commercially available product may be used. As a commercially available product, CN996 (bifunctional oligomer, urethane acrylate, weight average molecular weight (Mw) = 2850) of Sartomer, Shin-Nakamura Chemical Co., Ltd. UA-122P (bifunctional oligomer, urethane acrylate, Mw = 1100), Purple light (registered trademark) UV-6630B (bifunctional oligomer, urethane acrylate, Mw = 3000), Nippon Gohsei Co., Ltd., purple light (registered trademark) UV -3310B (bifunctional oligomer, urethane acrylate, Mw = 5000), and Ogure (registered trademark) UV-7630B (hexafunctional oligomer, urethane acrylate, Mw = 2200), as well as N-vinylcaprolactam (single) from BASF Functional monomer), S of Sartomer 339c (phenoxyethyl acrylate, monofunctional monomer), SR506D (isobornyl acrylate, monofunctional monomer), Sartomer Inc., dipropylene glycol diacrylate (polyfunctional monomer) include monomers such as.

(Photopolymerization initiator)
The ink contains at least one photopolymerization initiator.
When the ink contains a polymerizable compound capable of free radical polymerization, the photopolymerization initiator preferably contains a free radical photopolymerization initiator. When the ink contains a polymerizable compound capable of cationic polymerization, the photopolymerization initiator is a cation. It is preferable to include a photopolymerization initiator.
When the ink includes a combination of a polymerizable compound capable of free radical polymerization and a polymerizable compound capable of cationic polymerization, it is preferable to include both a free radical photopolymerization initiator and a cationic photopolymerization initiator.

The free radical photopolymerization initiator can be selected from any known in the art. For example, benzophenone, 1-hydroxycyclohexyl phenyl ketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-benzyl-2-dimethylamino -(4-morpholinophenyl) butan-1-one, isopropylthioxanthone, benzyldimethyl ketal, bis (2,6-dimethylbenzoyl) -2,4,4-trimethylpentylphosphine oxide, or mixtures thereof. These photopolymerization initiators are known, and are commercially available, for example, from IRSFACURE (registered trademark) and Darocur (registered trademark) (from Ciba) manufactured by BASF and Lucerin.

As the cationic photopolymerization initiator, for example, a photopolymerization initiator based on sulfonium or iodonium can be used. For example, Rhodorsil PI 2074 from Rhodia; MC AA, MC BB, MC CC, MC CC PF, MC SD from Siber Hegner; UV9380c from Alfa Chemicals; Uvacure 1590 from UCB Chemicals; Is commercially available.

The content of the photopolymerization initiator in the ink is preferably 1% by mass to 20% by mass and more preferably 4% by mass to 10% by mass with respect to the total mass of the ink.

(Coloring agent)
The ink can include at least one colorant. The colorant is not particularly limited, and may be a pigment or a dye.
When the ink is used as a colored ink, the content of the colorant is preferably 0.1% by mass or more based on the total mass of the ink.

There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably. 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 an organic pigment and an inorganic pigment may be used in combination.
Examples of organic pigments include azo lakes, azo pigments, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples thereof include dye lakes such as cyclic pigments, basic dye lakes, and acid dye lakes, nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments.
Examples of inorganic pigments 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 described 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,
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 described in the color index can be used as appropriate according to the purpose. For example, pigments surface-treated with a surfactant, a polymer dispersant, etc., and graft carbon can also be used.

Examples of the polymer dispersant include polyamidoamine and its salt, polyvalent carboxylic acid and its salt, high molecular weight unsaturated acid ester, modified polyurethane and polyether ester.

Commercially available polymer dispersants may be used. Examples of 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-182, EFK40, EFK40, EFK40, EFK40 EFKA5207, EFKA5244, EFKA6745, EF A6750, EFKA7414, EFKA745, EFKA7462, EFKA7500, EFKA7570, EFKA7575, EFKA7580 (manufactured by Fuka Additive), Disperse Aid 6, Disperse Aid 8, Disperse Aid 15, Disperse Aid 9100 (Sannopco) Polymer dispersing agents such as Solsperse 3000, 5000, 9000, 12000, 13240, 13940, 17000, 22000, 24000, 26000, 28000, 32000, 36000, 39000, 41000, 71000, etc. Adeka Pluronic L31, F38, L42, L44, L61, L64, F68, L72, P95, F77, P 4, F87, P94, L101, P103, F108, L121, P-123 (manufactured by ADEKA Corporation) and Ionette (registered trademark) S-20 (manufactured by Sanyo Chemical Industries, Ltd.), manufactured by Enomoto Kasei Co., Ltd. Disparon KS-860, 873SN, 874 (polymer dispersant), # 2150 (aliphatic polycarboxylic acid), # 7004 (polyether ester type) ”.

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

Commercial products can also be used as the colorant. Examples of commercially available products include Paliotol (BASF), Cinquasia, Irgalite (both Ciba Specialty Chemicals), and Hostaperm (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, As the quinacridone pigment such as mixed crystal quinacridone such as Cinquasia MAGENTA L4540 and the black pigment, carbon black pigment such as pigment black 7 is preferable.

The volume average particle diameter 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. The lower limit of the volume average particle diameter of the colorant is not particularly limited, but is preferably 0.001 μm or more and more preferably 0.01 μm or more from the viewpoint of colorability and light resistance.
The volume average particle size can be measured by a laser diffraction particle size distribution analyzer (for example, Mastersizer 2000 manufactured by Malvern, or a laser diffraction / scattering particle size distribution measuring apparatus 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, still more preferably 8% by mass or less, and particularly preferably 1% by mass to 5% by mass with respect to the total mass of the ink.

(polymer)
The ink may contain at least one polymer. When the ink contains a polymer, the polymer functions as a binder that holds the components contained in the ink.

The ink may further contain 2% by mass or more of a polymer having a molecular weight of 10,000 to 150,000 (preferably 20,000 to 100,000) based on the total mass of the ink.
The polymer is distinguished from the above-described polymerizable compound in that it does not contain a group capable of being polymerized when irradiated with active energy rays.

Examples of the polymer include an 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 resins and (meth) acrylic resins are preferred.

As the polymer, a commercially available product may be used. For example, VINNOL (registered trademark) E15 / 45 manufactured by Wacker Chemie AG (a copolymer of vinyl chloride and vinyl acetate, weight average molecular weight (Mw) = 50) , 000), Lucite International Elvacite 2013 (copolymer of methyl methacrylate and n-butyl methacrylate, Mw = 34,000), Elvacite 2014 (copolymer of methyl methacrylate and n-butyl methacrylate) , Mw = 1119,000), Elvacite 4099 (a copolymer 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 more preferably 5% by mass or more and 7% by mass or less with respect to 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 easily developed. On the other hand, when the polymer content is 10% by mass or less, the ink ejection property is further improved.

The weight average molecular weight of the polymer is preferably 10,000 to 150,000, more preferably 15,000 to 120,000, and still more preferably 20,000 to 100,000.
When the weight average molecular weight of the polymer is 10,000 or more, the function as a binder is easily developed. 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, the polymer having a weight average molecular weight of 10,000 to 150,000 is preferably 2% by mass or more based on the total mass of the ink, and the weight average molecular weight is 20,000 to 100,000. More preferably, the polymer is contained 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)
The ink may contain other components other than the above components as necessary.
Examples of other components include surfactants, polymerization inhibitors, sensitizers, ultraviolet absorbers, antioxidants, antifading agents, conductive salts, and basic compounds.

A surfactant may be added to the ink in order to give stable ejection properties for a long time.
Examples of the surfactant include surfactants described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks 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.

~ Ink physical properties ~
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.

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

The viscosity of the ink 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 at 25 ° C. The viscosity of the ink is preferably 2 mPa · s or more at 25 ° C., more preferably 4 mPa · s or more, and even more preferably 5 mPa · s or more.

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

[LED irradiation process]
In the image recording method of the present disclosure, at least the ink after heating is irradiated with active energy rays using a light emitting diode (LED) at an exposure amount of 200 mJ / cm ² to 1000 mJ / cm ² to cure at least the ink. (Hereinafter also referred to as LED irradiation step).
The LED irradiation process reduces damage to the recording medium.

As a method of curing at least the ink in the LED irradiation step, a method of curing at least the ink by irradiating active energy rays with the LED is used.

As the active energy rays, α rays, γ rays, electron rays, X rays, ultraviolet rays, visible light, infrared rays, or the like can be used. When the sensitizer is used, the peak wavelength of the active energy ray depends on the absorption characteristics of the sensitizer, but is preferably, for example, 200 nm to 600 nm, more preferably 300 nm to 450 nm, and 350 nm to 420 nm. More preferably.

Since the LED hardly generates heat at the place irradiated by irradiation, the damage of the recording medium can be further reduced by using the LED as a light source in the LED irradiation process in the present disclosure.
LEDs are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photocurable inkjets.
In particular, when an ultraviolet light source is required, an ultraviolet LED (UVLED) can be used. For example, Nichia Corporation has launched a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. If even shorter wavelengths are required, the LED can emit active energy rays having a wavelength center between 300 nm and 370 nm as disclosed in US Pat. No. 6,084,250. Can be illustrated. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands.

The exposure amount of the active energy ray in the LED irradiation process is 200 mJ / cm ² to 1000 mJ / 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.
The irradiation conditions of active energy rays and the basic irradiation method are disclosed in JP-A-60-132767.
More specifically, a single serial head is provided with an active energy ray irradiation device, and the shuttle system that irradiates while scanning the head in the width direction of the recording medium and the activation corresponding to the entire area of one side of the recording medium. There is a single pass method in which energy beam irradiation devices are arranged.

The irradiation of the active energy ray by the LED is performed for a certain 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 completion of the ink heating process. It is preferable to be performed after 0.15 seconds).

[Mercury lamp irradiation process]
The present disclosure may further include a mercury lamp irradiation step of irradiating at least the ink after being cured with active energy rays using a low-pressure mercury lamp. By having the mercury lamp irradiation step, the image adhesion and wear resistance are improved.

As a method of curing at least the ink in the mercury lamp irradiation process, a method of curing at least the ink by irradiating active energy rays with a low-pressure mercury lamp is used.

The active energy ray in the mercury lamp irradiation process is the same as the active energy ray described above.

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

The exposure amount of the active energy ray by the low-pressure mercury lamp is preferably 50 mJ / cm ² to 100 mJ / cm ² , more preferably 65 mJ / cm ² to 85 mJ / 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 active energy ray irradiation conditions, the basic irradiation method, and the like are the same as those in the LED irradiation step described above.

The active energy ray irradiation in the mercury lamp irradiation step is performed for a certain period of time after the LED irradiation step is completed (preferably 0.01 seconds to 0.5 seconds, more preferably 0.01 seconds to 0.3 seconds, and still more preferably 0.8. It is preferable to carry out after a period 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]
In the image recording method according to aspect A-1, as a step of ejecting ink and a step of heating ink, a colorant, an organic solvent, and a polymerizable agent are formed on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method. A step of discharging a colored ink containing a compound and a photopolymerization initiator (colored ink discharge step), and a back surface temperature B ° C. of a recording medium having a thickness A are maintained within a range satisfying Equation 1, and discharged onto the recording medium. A step of heating the colored ink (colored ink heating step), and a step of discharging a clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator by an inkjet method onto the heated colored ink (clear ink) A discharge step) and a step of heating the clear ink discharged on the recording medium while maintaining the back surface temperature B ° C. of the recording medium having a thickness A in a range satisfying Equation (1) In the step of curing the ink, the colored ink and the clear ink after heating are cured by irradiation with an active energy ray 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 simultaneously, or the colored ink and the clear ink after heating may be separately cured sequentially. When the colored ink and the clear ink after heating are cured at the same time, the working efficiency is improved and the economic burden can be reduced.

[Aspect A-2]
In the image recording method according to aspect A-2, before the step of discharging the clear ink, the heated colored ink is irradiated with active energy rays, and the heated clear ink 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 separately and sequentially cured.

[Aspect B]
In the image recording method according to aspect B, as a step of ejecting ink and a step of heating ink, a colored ink containing a colorant and an organic solvent is formed on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method. A step of discharging (colored ink discharging step), 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 discharged on the recording medium (colored ink) Heating step), a step of discharging a clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator by an inkjet method on the heated colored ink (clear ink discharging step), and a recording medium having a thickness A And maintaining the back surface temperature B ° C. in a range satisfying Equation 1, and heating the clear ink discharged onto the recording medium (clear ink heating step) In the step, at least the clear ink after heating is cured by irradiation with an active energy ray using an LED (LED irradiation step).

The image recording method of the present disclosure preferably includes a colored ink discharging step and a colored ink heating step in this order before the clear ink discharging step, as in Aspect A-1, Aspect A-2, and Aspect B.
In the aspect A-1 and the aspect A-2 having the colored ink discharging process and the colored ink heating process before the clear ink discharging process, the clear ink can be cured in addition to the colored ink by the LED irradiation process. 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 discharging step of discharging colored ink by an inkjet method on a recording medium having a thickness A of 200 μm to 2000 μm before the step of discharging clear ink. . The colored ink in the embodiment A-1 and the embodiment A-2 is a colored curable ink containing a colorant, an organic solvent, a polymerizable compound and a photopolymerization initiator, and the colored ink in the embodiment B is a colored curable ink. Colored ink other than the above.
Thus, a desired image can be recorded by ejecting colored ink on the recording medium.

The ink discharge method in the colored ink discharge step is the same as the ink discharge method in the ink discharge step described above.

The droplet size of the colored ink in the colored ink discharge step is the same as the droplet size of the ink in the ink discharge step described above.

[Colored ink]
The colored ink contains a colorant and an organic solvent.
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 those described above as necessary.

(Coloring agent)
As the colorant contained in the color ink, the same compound as the colorant contained in the above-described ink can be used, and the preferred embodiment is also the same.

(Organic solvent)
The colored ink contains at least one organic solvent.
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 color ink such as the colorant.

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

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 ink described above.
The boiling point of the organic solvent can be measured by the method described above.
The boiling point of the organic solvent in the case where the colored ink contains a plurality of organic solvents is the product of the ratio of the content of each organic solvent in the whole 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 ink described above.

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

-Physical properties 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 ink described above.

[Colored ink heating process]
The image recording method of the present disclosure includes a colored ink heating 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 colored ink discharged onto the recording medium. be able to.
6 × ln (A) ≦ B ≦ 12 × ln (A) (Formula 1)

The back surface temperature B ° C. of the recording medium satisfies the above formula 1 with respect to the thickness A μm of the recording medium.
About Formula 1, it is the same as Formula (1) in the above-mentioned ink discharge process, and the preferable range of 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 discharge process]
The image recording method of the present disclosure can include a clear ink discharging step of discharging clear ink by an ink jet method on the heated colored ink.
Accordingly, the abrasion resistance can be improved by discharging the clear ink on the heated colored ink.

The clear ink discharge method in the clear ink discharge step is the same as the ink discharge method in the ink discharge step described above.

The clear ink droplet size in the clear ink ejection step is the same as the ink droplet size in the ink ejection step described above.
The droplet size of the clear ink is preferably larger than the droplet size of the colored ink. If the droplet size of the clear ink is larger than the droplet size of the colored ink, the clear ink tends to cover 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 those described above as necessary.
The clear ink is synonymous with the clear ink in the above-described ink.

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

The preferred range of the organic solvent content in the clear ink is the same as the preferred range of the organic solvent content in the ink described above.

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 ink described above.
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 in the entire 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) Formula (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 The adhesiveness and glossiness can be compatible 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 conveyance 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 ink described above.

(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-described ink can be used, and preferred embodiments are also the same.

~ Physical properties 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.
The surface tension γ (T) of the clear ink at a temperature of 25 ° C. is preferably not more 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, more preferably 5 mN / m or more.
The 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 satisfy the relationship of the following formula (a) at a temperature of 25 ° C. The unit of surface tension is mN / m.
γ (T) ≦ γ (C) Formula (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 (satisfies the relationship of the above formula (a)), the clear ink is discharged on the colored ink in the clear ink discharging step. Clear ink easily spreads out. That is, the clear ink tends to cover the colored ink. Therefore, clear ink is present on the surface of the recorded image, and an image with better wear resistance can be obtained.
The surface tension can be measured by the method described above.

The preferable range of the viscosity of the clear ink is the same as the preferable 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 a 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) (Formula 1)

The back surface temperature B ° C. of the recording medium satisfies the above formula 1 with respect to the recording medium thickness A μm.
About Formula 1, it is the same as Formula (1) in the above-mentioned ink discharge process, and the preferable range of 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 from when the clear ink is deposited on the heated colored ink until the heating is started is preferably 1 second or less, more preferably 0.5 seconds or less. Preferably, heating at the same time as landing is more preferable.
The back surface temperature B of the recording medium, the heating time, the heating method, preferred modes thereof, and the like are the same as those in the above-described ink ejection step.

<Inkjet recording apparatus>
An ink jet recording apparatus is an ink jet recording apparatus that performs the image recording method of the present disclosure, and includes a colored ink discharging unit that discharges colored ink onto a recording medium, and a colored ink discharged onto the recording medium. A colored ink heating unit that heats while maintaining the back surface temperature of the medium at 40 ° C. or higher, a clear ink discharge unit that discharges the clear ink onto the heated colored ink, and a clear ink that is discharged onto the heated colored ink A clear ink heating unit that heats the recording medium while maintaining the back surface temperature of the recording medium at 40 ° C. or higher, and an ink curing irradiation unit that irradiates an active energy ray that cures the colored ink and the clear ink after heating. It is preferable.
The ink jet recording apparatus may further include a colored ink curing irradiation unit that irradiates an active energy ray that cures the heated colored ink.

The recording method of the ink jet recording apparatus is not particularly limited. As a recording method, a single serial head is used to perform recording while scanning the head in the width direction of the support, and a line head in which recording elements are arranged corresponding to the entire area of one side of the support. There is a line method (single pass method) used.

As a specific example of the shuttle system, for example, there is an apparatus described in International Publication No. 2017/104845 (paragraph numbers 0133 to 0143). Specific examples of the single-pass method include, for example, an apparatus described in International Publication No. 2017/104845 (paragraph numbers 0144 to 0162).

Hereinafter, the invention of the present disclosure will be described in more detail with reference to examples. However, the invention of the present disclosure is not limited to the following examples unless it exceeds the gist of the invention. 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 mixer of SILVERSON under the conditions of 2,000 rpm to 3,000 rpm and 10 minutes to 15 minutes. To obtain a uniform diluent diluent. Each pigment was added to this diluent diluted solution in the types and amounts shown in Table 1, and further stirred with a mixer under the conditions of 2,000 rpm to 3,000 rpm, 10 minutes to 20 minutes, 500 parts of a uniform preliminary dispersion was obtained.
Thereafter, each of the obtained preliminary dispersions was subjected to dispersion treatment using a circulation type bead mill apparatus (SL-012C1) manufactured by Dispermat Co., thereby obtaining a pigment dispersion of each color. The conditions for the dispersion treatment were such that 200 parts of zirconia beads having a diameter of 0.65 mm were filled in a circulation type bead mill apparatus, and the peripheral speed was 15 m / s. The dispersion time was 1 to 6 hours.

Details of the components in Table 1 are as follows.
PB15: 4 ... C.I. I. Pigment Blue 15: 4, BASF, HELIGOEN BURE 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 ... Luburizol, SOLPERSE 32000
DEGDEE ... Diethylene glycol diethyl ether Tokyo Chemical Industry Co., Ltd.

<Preparation of ink>
The colored ink is mixed with each component according to the following composition 1, and the clear ink is mixed with each component according to the following composition 2, and each is mixed at 2,000 rpm to 3,000 rpm with a mixer manufactured by SILVERSON. The mixture was stirred for 10 to 15 minutes to obtain each ink.

-Composition of colored ink 1-
~ Cyan ink ~
Pigment dispersion: Pigment mill base Cyan: 6 parts Organic solvent: Diethylene glycol diethyl ether (Tokyo Chemical Industry Co., Ltd.): 70.9 parts Polymerizable compound: GENOMER 4215 (Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE 819 (BASF) Co., Ltd.): 2 parts Polymerization initiator: IRGACURE 2959 (BASF Co., Ltd.): 1 part Surfactant: BYK331 (Bic Chemie Co., Ltd.): 0.1 part-magenta ink-
Pigment dispersion :: Pigment mill base Magenta: 12 parts Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.): 64.9 parts Polymerizable compound: GENOMER 4215 (manufactured by Rahn Inc.): 20 parts Polymerization initiator: IRGACURE 819 ( BASF Corporation): 2 parts Polymerization initiator: IRGACURE 2959 (BASF Corporation): 1 part Surfactant: BYK331 (BIC Chemie Corporation): 0.1 part-Yellow ink-
Pigment dispersion: Pigment mill base Yellow: 10 parts Organic solvent: Diethylene glycol diethyl ether (Tokyo Chemical Industry Co., Ltd.): 66.9 parts Polymerizable compound: GENOMER 4215 (Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE 819 (BASF) (Made by Co., Ltd.): 2 parts Polymerization initiator: IRGACURE2959 (made by BASF Corporation): 1 part Surfactant: BYK331 (made by Big Chemie Co., Ltd.): 0.1 part-black ink-
Pigment dispersion: Pigment mill base Black: 5 parts Organic solvent: Diethylene glycol diethyl ether (Tokyo Chemical Industry Co., Ltd.): 69.9 parts Polymerizable compound: GENOMER 4215 (Rahn Co., Ltd.): 20 parts Polymerization initiator: IRGACURE 819 (BASF) Co., Ltd.): 2 parts Polymerization initiator: IRGACURE 2959 (BASF Co., Ltd.): 1 part Surfactant: BYK331 (Bic Chemie Co., Ltd.): 0.1 part-Clear ink composition 2-
Organic solvent: Diethylene glycol diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.): 70.9 parts Polymerizable compound: GENOMER 4215 (manufactured by Rahn Co., Ltd.): 8 parts Polymerizable compound: Purple light UV-7630B (manufactured by Nippon Synthetic Chemical Co., Ltd.): 8 parts Polymerization initiator: IRGACURE819 (manufactured by BASF Corporation): 3 parts Polymerization initiator: IRGACURE2959 (manufactured by BASF Corporation): 2 parts Surfactant: BYK331 (manufactured by BYK Chemie Corporation): 0.1 part

<Image recording device>
As an inkjet recording apparatus, an inkjet printer manufactured by Afit (KEGON), a rubber heater (manufactured by Three High Co., Ltd.), a UV exposure machine (LED-UV lamp) (LLRG 1200 FUV, manufactured by ITEC System Co., Ltd.), and A device equipped with a low-pressure mercury lamp (sterilization lamp GL15, manufactured by Hitachi Appliances, Inc.) 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. In addition, the time from ink jet ejection to ultraviolet (LED-UV) exposure corresponds to the heating time of the droplet, and the conveyance speed (5 m / sec) can be changed between 0.5 seconds and 60 seconds. Min ~ 25m / min) and the timing of UV shutter opening and closing was adjusted.

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

Example 1
An ink ejection process, an ink heating process, and an LED irradiation process were performed in this order, and an image was 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:
Using ink jet head (Toshiba Tec Corporation, CA4, nozzle diameter 26 μm) heated to 35 ° C. with four colored inks of Y (yellow), M (magenta), C (cyan) and K (black) The image was repeatedly ejected on the recording medium in the order of Y (yellow), M (magenta), C (cyan), and K (black) in order of 1200 dpi × 600 dpi (dot per inch). .
At this time, the voltage was adjusted so that the discharge amount of the colored ink was 20 g per 1 m ² .
(2) Ink heating process:
The recording medium on 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 at 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 on the side where the colored ink was discharged was irradiated with ultraviolet rays toward the recording medium after the ink heating step. As a result, the colored ink is cured, and four colored inks are used by the colored inks that are repeatedly ejected in the order of Y (yellow), M (magenta), C (cyan), and K (black). 100% solid image was recorded.
In addition, ultraviolet rays were irradiated with an exposure amount of 800 mJ / cm ² using a UV exposure machine (LED-UV lamp, wavelength 385 nm) as a light source for irradiating ultraviolet rays.

(Examples 2 to 9, Comparative Examples 1 to 9)
An image was 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 recording media 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.

(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) and the exposure amount is 200 mJ / cm ^2. (Recorded).

<Examples 10 to 11 and Comparative Example 11>
(Example 10)
In the following manner, a colored ink ejection process, a colored ink heating process, a clear ink ejection process, a clear ink heating process, an LED irradiation process, and a mercury lamp irradiation process were performed in order, and an image was recorded. The recording medium (thickness A: 1000 μm) obtained by the above method was used as the recording medium. The values of 6 × ln (A) and 12 × ln (A) are as shown in Table 3.
(1) Colored ink ejection process:
Using ink jet head (Toshiba Tec Corporation, CA4, nozzle diameter 26 μm) heated to 35 ° C. with four colored inks of Y (yellow), M (magenta), C (cyan) and K (black) The image was repeatedly ejected on the recording medium in the order of Y (yellow), M (magenta), C (cyan), and K (black) in order of 1200 dpi × 600 dpi (dot per inch). .
At this time, the voltage was adjusted so that the discharge amount of the colored ink was 20 g per 1 m ² .
(2) Colored ink heating process:
The recording medium on 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 at 10 seconds.
(3) Clear ink ejection process:
Clear ink was ejected onto the colored ink so as to obtain an image density of 1200 dpi × 600 dpi from an inkjet head heated to 35 ° C. (Toshiba Tec Corporation, CA4, nozzle diameter 26 μm). At this time, the voltage was adjusted so that the amount of clear ink deposited was 10 g per 1 m ² .
(4) Clear ink heating process:
The recording medium on which the clear 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 at 10 seconds.
(5) LED irradiation process:
(4) The entire surface on the side where the clear ink was discharged 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 of the colored inks repeatedly ejected in a line shape in the order of Y (yellow), M (magenta), C (cyan), and K (black). A 100% solid image using ink was recorded.
In addition, ultraviolet rays were irradiated with an exposure amount of 800 mJ / cm ² using a UV exposure machine (LED-UV lamp, wavelength 385 nm) as a light source for irradiating ultraviolet rays.
(6) Mercury lamp irradiation process:
The entire surface on the side where the clear ink was ejected was irradiated with ultraviolet rays toward the recording medium after the LED irradiation process. Thereby, the colored ink and the clear ink were further cured.
Using a UV exposure machine (low pressure mercury lamp) as a light source for irradiating ultraviolet rays, the ultraviolet rays were irradiated with 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]
A recording medium on which an 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 recording medium of the obtained sample and the wear resistance and glossiness of the recording medium and the image were evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 2 and 3.

(Evaluation of damage to the recording medium)
The damage of the recording medium can be evaluated by the deformation amount of the recording medium after the active energy ray irradiation. Place the sample on a flat desk with the side opposite the image recording side facing down, and the distance between the back of the sample in the normal direction of the desk and the surface of the desk is the back of the sample. The maximum value of the 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)
Using the Gakushin Tester (AB-301 Gakushin Type Friction Fastness Tester, manufactured by Tester Sangyo Co., Ltd.), 200 times of wear was applied to the image of each sample under the condition of 200 g load with the canvas. The number of times the image was peeled from the sample image was recorded and evaluated according to the following evaluation criteria. Two or more have practical wear resistance.
-Evaluation criteria-
5: The image does not peel off even 200 times.
4: The image was peeled off 100 times or more and less than 200 times.
3: The image peeled off 50 times or more and less than 100 times.
2: The image peeled off 10 times or more and less than 50 times.
1: The image peeled off less than 10 times.

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

In Table 2, “-” 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, when only clear ink is used instead of clear ink, the recording medium thickness A is 200 μm to 2000 μm, and the LED exposure is 200 mJ / cm ² to 1000 mJ / cm ² . In Examples 1 to 9, where the back surface temperature B of the recording medium is 6 × ln (A) ≦ B ≦ 12 × ln (A), recording medium damage, image wear resistance, and glossiness are excellent. It was.
Comparative Examples 1, 3 and 5 where B <6 × ln (A) were inferior in gloss. On the other hand, Comparative Examples 2, 4 and 6 where B> 12 × ln (A) were inferior in damage to the recording medium.
Moreover, the comparative example 7 whose exposure amount of LED is less than 200 mJ / cm < ² > was inferior to the abrasion resistance of an image. On the other hand, Comparative Example 8 in which the exposure amount of the LED was over 1000 mJ / cm ² was inferior to the recording medium.
Comparative Example 9 using a recording medium having a thickness of more than 2000 μm was inferior in gloss, and Comparative Example 10 in which a mercury lamp was exposed instead of LED was inferior in damage to the recording 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 exposure amount of the LED is in the range of ^{400mJ / cm 2 ~ 900mJ / cm} 2 1 ~ 7 was superior by damage of the recording medium.

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

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

Claims

A step of discharging an ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator by an inkjet method onto a recording medium having a thickness A of 200 μm to 2000 μm;
Holding the back surface temperature B ° C. of the recording medium having a thickness A in a range satisfying the following formula 1, and heating the ink ejected on the recording medium;
Irradiating at least the ink after heating with active energy rays using a light emitting diode at an exposure amount of 200 mJ / cm 2 to 1000 mJ / cm 2 to cure at least the ink;
An image recording method comprising:
6 × ln (A) ≦ B ≦ 12 × ln (A) (Formula 1)
The image recording method according to claim 1, wherein the ink is a colored ink further containing a colorant.
As a step of discharging the ink and a step of heating the ink,
Discharging a colored ink containing a colorant, an organic solvent, a polymerizable compound, and a photopolymerization initiator on a recording medium having a thickness A of 200 μm to 2000 μm by an inkjet method;
Holding the back surface temperature B ° C. of the recording medium having a thickness A in a range satisfying Equation 1, and heating the colored ink ejected onto the recording medium;
A step of discharging a clear ink containing an organic solvent, a polymerizable compound and a photopolymerization initiator by an inkjet method on the colored ink after heating,
Holding the back surface temperature B ° C. of the recording medium having a thickness A in a range satisfying Equation 1, and heating the clear ink ejected on the recording medium;
Have
The image recording method according to claim 1, wherein in the curing step, the colored ink and the clear ink after heating are cured by the irradiation.
4. The image recording method according to claim 1, 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 claim 1, 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 5 is.
7. The image recording method according to claim 1, 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) (Formula 2)
The image recording method according to any one of claims 1 to 7, wherein a boiling point of the organic solvent contained in the ink is 75 ° C to 300 ° C.
The image recording method according to any one of claims 1 to 8, wherein a 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 9, wherein the recording medium is a material for a seat for a vehicle.