JP2018034316A - Inkjet method and ink jet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet method which has excellent line width uniformity, can form an image in which a difference in glossiness (gloss banding) is suppressed at a high speed, and can reduce the size of a device.SOLUTION: The inkjet device comprises: head groups 11 and 12 being scanned in a main scanning direction and having relative positions changing with respect to a recording medium; a first light source 21; and a second light source 22. The inkjet method includes: a first main scanning step of discharging a radiation-curable composition toward one side in the main scanning direction; a second main scanning step of discharging the radiation-curable composition toward the other side in the main scanning direction; and a sub-scanning step of conveying a recording medium in a sub-scanning direction intersecting with the main scanning direction. A difference between first time from timing when nozzles of a first head face a prescribed position of the recording medium to timing when the prescribed position face the second light source in the first main scanning step and second time from timing when the nozzles of the first head face the prescribed position of the recording medium to timing when the prescribed position face the first light source in the second main scanning step is equal to 100 ms or less.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an inkjet method and an inkjet apparatus.

  The ink jet method is a method of recording an image or modeling a structure by ejecting a small droplet of ink from a fine nozzle and attaching it to a target. This method has a feature that a high-resolution and high-quality image or structure can be created at a high speed with a relatively inexpensive apparatus. In the ink jet method, there are a great number of consideration factors, including the properties of ink used, stability in ejection, and the quality of images and structures obtained. Research not only on ink jet devices but also on the composition (ink) used. Is also thriving.

  In recent years, an ink jet method for forming an image or a pattern on a recording medium using an ultraviolet curable composition that is cured by ultraviolet irradiation has attracted attention. The ultraviolet curable composition has a preferable characteristic as a recording ink, in which the curing is slow until the ultraviolet ray is irradiated and the ultraviolet ray curable composition is rapidly cured when the ultraviolet ray is irradiated. In addition, since it does not contain a solvent that does not participate in the reaction, and it is difficult to generate a volatile solvent even when cured, there is an advantage that the environmental load is small.

  For these reasons, various ink jet devices using photocurable compositions have been proposed (see, for example, Patent Documents 1 and 2). Each of the ink jet devices discharges a photocurable ink containing a photoinitiator and irradiates the ink landed on the recording medium with light to cure the ink and fix it on the recording medium. . In these documents, after ink landing, light is irradiated and cured, so there is little ink permeation and bleeding into the recording medium, and there is no ink receiving layer, and there is no ink absorption at all. In contrast, there is a description that image recording can be performed.

JP 2006-289722 A JP 2012-139655 A

  In a so-called serial type ink jet apparatus, while the head and the light irradiation device are reciprocated in the width direction of the recording medium, ink is ejected and light is irradiated to fix the landed ink. For this reason, the time until the ink ejected from the head is irradiated with light may be different between the forward path and the backward path in the reciprocating movement. In this case, the diameter of each dot, the degree of connection, the degree of spreading, etc. are different. It will be. Then, since the dot diameters are different, the line width becomes non-uniform, and the unevenness of the dots is different, so that there are cases where the color tone and glossiness of the recorded image are different for each part (also referred to as gloss banding). there were. In addition, this phenomenon tends to become more prominent as the ink curability is better and the correlation between the light irradiation time deviation and the dot shape becomes stronger.

  As a technique for avoiding such a problem, two light irradiation devices are arranged symmetrically in the main scanning direction with respect to the head, and from landing to light irradiation in both forward and backward passes in the main scanning direction. It is conceivable to arrange the timings.

On the other hand, the ink jet apparatus is required to be faster than before. As one of means for meeting such a demand, it is conceivable to increase the number of nozzles of the head. However, in order to increase the number of nozzles in the head, the length of the nozzle row is increased, and the size of the material such as the silicon substrate and the manufacturing process are restricted. Have difficulty. Therefore, a method is adopted in which a plurality of heads having short nozzle rows are connected in the sub-scanning direction to increase the length of the nozzle rows as a whole. Further, in this case, if the nozzle rows of adjacent heads are not cut when viewed from the main scanning direction (nozzle spacing is uniform throughout), line omission in one main scanning can be eliminated. This is advantageous.

  However, it is structurally difficult to form the nozzles to the end of the head, and it is difficult to extend the end of the nozzle row to the end of the head, and the head has areas where no nozzles are formed at both ends of the nozzle row. End up. In order to arrange a plurality of such heads in the sub-scanning direction so that no gap in the sub-scanning direction is generated between the nozzle rows, the head position is shifted in the main scanning direction. (Hereinafter, such an arrangement may be referred to as a “staggered arrangement”.) That is, in the staggered arrangement, the heads adjacent in the sub-scanning direction are arranged so as to overlap when projected in the main scanning direction.

  Here, in consideration of the time until the above ink is irradiated with light, in the case of staggered arrangement, there are different heads for the time until the light is irradiated in the forward path and the backward path in the reciprocating movement in the main scanning direction. Will occur. Then, the ink ejected from such a head is likely to have non-uniform line widths in the main scanning direction and gloss banding.

  One of the objects according to some aspects of the present invention is that the uniformity of the line width is good and an image in which the difference in gloss (gloss banding) is suppressed can be formed at high speed, and the apparatus is downsized. It is an object of the present invention to provide an ink jet method and an ink jet apparatus which can be used.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

One aspect of the inkjet method according to the present invention is:
An inkjet method performed using an inkjet device,
The inkjet device
A group of heads that are scanned in the main scanning direction and whose relative positions change with respect to the recording medium;
A first light source disposed on one side of the head group in the main scanning direction, the relative position of which changes relative to the recording medium as the head group scans, and the main scanning direction of the head group A second light source disposed on the other side of
The head group is positioned first from the downstream side in the direction in which the recording medium is transported and second from the downstream side in the direction in which the recording medium is transported, and is projected in the main scanning direction. A second head arranged to overlap the first head, and
The inkjet method includes:
A first main scanning step of discharging a radiation curable composition onto a recording medium while changing the relative position of the head group to the recording medium toward the one side in the main scanning direction;
A second main scanning step of discharging the radiation curable composition onto the recording medium while changing the relative position of the head group to the recording medium toward the other side in the main scanning direction;
A sub-scanning step of transporting the recording medium in the transport direction in the sub-scanning direction intersecting the main scanning direction,
A first time that is a period from when the nozzle of the first head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the second light source in the first main scanning step;
In the second main scanning step, a difference between a second time which is a period from when the nozzle of the first head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the first light source is 100 ms or less.

  According to such an ink jet method, since the difference between the first time and the second time is 100 ms or less, the dot diameters from the first head ejected at a later timing on the recording medium are easily aligned, and the line Recording with little variation in width can be performed. Further, according to the ink jet method, the unevenness of the dots from the first head ejected at a later timing with respect to the recording medium tends to be uniform, and the dots previously attached are covered with the dots. Therefore, gloss banding can also be suppressed.

In the inkjet method according to the present invention,
The irradiation energy of the radiation required for the radiation curable composition discharged from the first head to reach tack-free may be 500 mJ / cm ² or less.

  In such an ink jet method, the radiation curable composition has good curability, and line width variation or gloss banding in the main scanning direction is likely to occur, but there is little variation in line width in the main scanning direction, and gloss banding. Can be suppressed, and the effect is more remarkable.

In the inkjet method according to the present invention,
The radiation curable composition ejected from the first head may be brought into contact with the radiation curable composition ejected from the head other than the first head and adhered to the recording medium.

  According to such an ink jet method, the radiation curable composition discharged from the head other than the first head and attached to the recording medium is attached and disposed so as to cover the radiation curable composition discharged from the first head. It is easy to be done, and gloss banding can be further suppressed.

In the inkjet method according to the present invention,
Another radiation curable composition having a composition different from that of the radiation curable composition discharged from the first head may be discharged from a head other than the first head.

  According to such an ink jet method, gloss banding can be further suppressed.

In the inkjet method according to the present invention,
A radiation curable composition having the same composition as the radiation curable composition discharged from the first head may be discharged from a head other than the first head.

  According to such an ink jet method, the variation in line width can be further suppressed.

In the inkjet method according to the present invention,
The radiation curable composition discharged from the first head is a vinyl ether group-containing (meth) acrylic acid ester represented by the following general formula (I), a vinyl ether group-containing compound represented by the general formula (I) ( It may contain at least one of monofunctional (meth) acrylates having an aromatic ring skeleton other than (meth) acrylic acid esters.
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a monovalent organic atom having 1 to 11 carbon atoms. It is an organic residue.)

  In such an ink jet method, the radiation curable composition has good curability, and line width variation or gloss banding in the main scanning direction is likely to occur, but there is little variation in line width in the main scanning direction, and gloss banding. Can be suppressed, and the effect is more remarkable.

In the inkjet method according to the present invention,
The difference between the first time and the second time may be 70 ms or less.

In the inkjet method according to the present invention,
The difference between the first time and the second time is
In the first main scanning step, a third time period from when the nozzle of the second head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the second light source;
In the second main scanning step, a fourth time period from when the nozzle of the second head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the first light source;
It may be smaller than the difference.

In the inkjet method according to the present invention,
Each of the first light source and the second light source may have an irradiation peak intensity of 200 mW / cm ² or more.

In the inkjet method according to the present invention,
Each of the first light source and the second light source may have an irradiation energy of irradiating the radiation curable composition in one main scanning of 40 mJ / cm ² or more.

In the inkjet method according to the present invention,
Each of the first light source and the second light source may be an ultraviolet light emitting diode.

  According to such an ink jet method, the apparatus to be used can be further downsized.

In the inkjet method according to the present invention,
In the first main scanning step and the second main scanning step, the scanning speed of the head group may be 400 mm / s or more.

  According to such an ink jet method, the radiation curable composition can be irradiated with radiation earlier after being ejected from the head.

In the inkjet method according to the present invention,
The arrangement of the heads used for recording the head group may be asymmetric in the main scanning direction.

One aspect of the inkjet apparatus according to the present invention is as follows.
A head group that is scanned in the main scanning direction and whose relative position changes with respect to the recording medium;
A first light source that is scanned with the head group and disposed on one side of the head group in the main scanning direction, and a second light source that is disposed on the other side of the head group in the main scanning direction. When,
Have
The recording medium is conveyed in the sub-scanning direction intersecting the main scanning direction,
The head group is positioned first from the downstream side in the direction in which the recording medium is transported and second from the downstream side in the direction in which the recording medium is transported, and extends in the main scanning direction. A second head arranged to overlap the first head when projected,
An apparatus for discharging a radiation curable composition from the head group to adhere to the recording medium,
The separation distance in the main scanning direction of the irradiation area of the nozzle of the first head and the first light source, and the separation distance in the main scanning direction of the irradiation area of the nozzle of the first head and the second light source, The difference is 50 mm or less,
The scanning speed of the head group is 400 mm / s or more.

  According to such an inkjet method, the separation distance in the main scanning direction between the irradiation area of the first head nozzle and the first light source and the separation in the main scanning direction of the irradiation area of the first head nozzle and the second light source. Since the difference from the distance is 50 mm or less and the scanning speed of the head group is 400 mm / s or more, recording with little variation in line width can be performed. Further, according to the ink jet apparatus, since the arrangement is made in the first head that applies the radiation curable composition to the recording medium at a later timing, gloss banding can also be suppressed.

In the inkjet device according to the present invention,
The difference in the separation distance in the main scanning direction may be 35 mm or less.

1 is a perspective view schematically showing an ink jet apparatus according to an embodiment. The schematic diagram at the time of seeing through from above the arrangement | positioning of the head group and light source of the inkjet apparatus which concerns on embodiment. FIG. 3 is a schematic diagram when a head group and a light source of the ink jet apparatus according to the embodiment are viewed from the sub-scanning direction. The schematic diagram at the time of seeing through the arrangement | positioning of the head group which concerns on embodiment from upper direction. The schematic diagram at the time of seeing through from above the arrangement | positioning of a head group and a light source for demonstrating an experiment example.

  Several embodiments of the present invention will be described below. Embodiment described below demonstrates an example of this invention. The present invention is not limited to the following embodiments, and includes various modified embodiments that are implemented within a range that does not change the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

1. Ink Jet Device FIG. 1 is a perspective view schematically showing an ink jet device 100 which is an embodiment of an ink jet device capable of performing an ink jet method according to the present invention. FIG. 2 is a schematic diagram when the arrangement of the head group 10, the first light source 21, and the second light source 22 of the inkjet device 100 is seen through from above. FIG. 3 is a schematic diagram when the head group 10, the first light source 21, and the second light source 22 of the inkjet device 100 are viewed from the sub-scanning direction SS. FIG. 4 is a schematic diagram when the arrangement of the head group of the inkjet apparatus 100 is seen through from above.

  In this specification, the main scanning direction is a moving direction of the carriage 50 on which the head group 10 is mounted, and is represented by a symbol MS. One direction of the main scanning direction MS is referred to as a main scanning direction MS1, and the other direction is referred to as a main scanning direction MS2.

In this specification, the sub-scanning direction is a direction that intersects the main scanning direction MS and is a moving direction of the recording medium P, and is represented by a symbol SS. In the sub-scanning direction SS, the moving direction of the recording medium P in printing is referred to as a sub-scanning direction SS1, and the opposite direction is referred to as a sub-scanning direction SS2.

  In any of the reciprocating movement of the carriage in the main scanning direction MS and the movement of the recording medium P in the sub-scanning direction SS, the relative positions of the head group, the light source, and the recording medium P change.

  The ink jet apparatus 100 according to this embodiment includes a head group 10, a first light source 21, and a second light source 22.

1.1. Head Group The head group 10 is mounted on the carriage 50 and is scanned in the main scanning direction MS along with the operation of the carriage 50. As a result, the position relative to the recording medium P is changed. Then, a radiation curable composition to be described later is ejected from the head group 10 and attached to the recording medium P.

  As shown in FIG. 1, the head group 10 includes a plurality of heads. The number of heads included in the head group 10 may be two or more, and is not particularly limited. In the example shown in FIG. 1, the head group 10 includes two heads, and the first head 11 positioned first from the downstream side in the direction SS1 in which the recording medium P is conveyed in the sub-scanning direction SS, and the recording medium And a second head 12 located second from the downstream side in the direction SS1 in which P is conveyed.

  As shown in FIG. 1, the two heads are arranged side by side along the sub-scanning direction SS, and are arranged so that no gap is generated between the nozzle rows N of each head when viewed from the main scanning direction MS. Is done. That is, as shown in FIG. 2, the nozzle rows N of adjacent heads are arranged so that there is no break when viewed from the main scanning direction MS (nozzle hole intervals are uniform throughout).

  In the example of FIG. 1, the first head 11 and the second head 12 are aligned so that the direction along the sub-scanning direction SS is the longitudinal direction, and both are sub-scanned when projected in the main scanning direction MS. It arrange | positions so that it may mutually overlap by the length D in the direction SS (refer FIG. 2). In other words, the second head 12 is arranged so as to overlap the first head 11 when projected in the main scanning direction MS.

  Furthermore, the interval in the sub-scanning direction SS of the nozzle holes in each nozzle row N of the first head 11 and the second head 12 is the interval P1, and the second head 12 is in the main scanning direction MS with respect to the first head 11. It is shifted and arranged. Therefore, a plurality of heads are arranged with their positions shifted from each other in the main scanning direction (hereinafter, such an arrangement may be referred to as a “staggered arrangement”).

  Then, the nozzle holes located at the upstream end (SS2) of the nozzle row N of the first head 11 in the sub-scanning direction SS and the downstream side (SS1) of the nozzle row N of the second head 12 in the sub-scanning direction SS. The interval P2 when viewed from the main scanning direction MS with the nozzle hole located at the end is the same as the interval P1. Accordingly, the nozzle groups 10 are arranged so that the nozzle hole intervals are uniform when viewed from the main scanning direction MS in the entire nozzle group 10.

The head group 10 may include a head other than the first head 11 and the second head 12. That is, when the head group 10 has three or more heads, the third third head is provided on the side closer to the first head 11 in the main scanning direction MS, as shown by the broken line in FIG. (The third head 13A in FIG. 4) (this arrangement may be referred to as “staggered arrangement”), or may be arranged on the side away from the first head 11 (the third head 13B in FIG. 4). (This arrangement is sometimes referred to as “diagonal arrangement”.) Furthermore, when the fourth and subsequent heads are arranged as heads other than the first head 11 and the second head 12, a staggered arrangement and an oblique arrangement can be selected arbitrarily. That is, in the staggered arrangement, adjacent heads are arranged so as to overlap when projected in the main scanning direction.

  By arranging a plurality of heads of the head group 10 in this way, the number of nozzles ejected in one main scan can be increased, the speed can be increased, and the length of the nozzle row N in one head. Compared with the case of increasing the length, it is not necessary to use a material such as a large substrate, and restrictions on the manufacturing process can be made difficult to occur. Furthermore, by arranging the nozzle rows so as not to leave a gap, it is possible to suppress line omission in one main scan.

  As described above, the first head 11 in the head group 10 is positioned first from the downstream side in the direction in which the recording medium P is conveyed (sub scanning direction SS1 side), and the second head 12 is the recording medium P. It is located second from the downstream side (sub scanning direction SS1 side) in the transport direction. Therefore, the radiation curable composition discharged from the nozzle holes belonging to the first head 11 is more than the radiation curable composition discharged from the nozzle holes belonging to the head other than the first head 11 (for example, the second head 12). It will be attached to the recording medium P later. Therefore, the radiation curable composition discharged from the first head 11 can be attached to the recording medium P so as to cover the radiation curable composition discharged from the nozzle holes of the heads other than the first head 11.

  Note that there may be a plurality of first heads 11 positioned first from the downstream side (sub-scanning direction SS1 side) of the head group 10 in the direction in which the recording medium P is conveyed. In that case, the nozzles of the first head when defining the first time and the second time are the nozzle closest to the first head and the first light source closest to the second light source in the main scanning direction, respectively. It is defined as the closest nozzle of the near first head.

  The second light source and the first light source for defining the first time and the second time are the first light source closest to the main scanning direction of the closest nozzle of the first head closest to the second light source. The position of the end of the two light sources is used for definition, and the first light source is the position of the end of the first light source closest to the main scanning direction of the nozzle closest to the first head of the first head. Used for definition.

  Similarly, there may be a plurality of second heads positioned second from the downstream side (sub scanning direction SS1 side) in the direction in which the recording medium P is transported in the head group 10, and the third time in that case The definition of the nozzle of the second head used for the definition of the fourth time is the same. The same applies to the light source used to define the third time and the fourth time. It is the same that there may be a plurality of heads after the third head.

  When the head group 10 is viewed from above with the nozzle surface horizontal, the head of the head group (however, the recording of the recording method of the present embodiment is recorded when the main scanning direction is the left-right direction and the sub-scanning direction is the up-down direction). The present embodiment is particularly useful in that the arrangement of the heads used in the embodiment is asymmetric in the left-right direction (main scanning direction), that is, not line-symmetric with respect to the line extending in the up-down direction (sub-scanning direction). preferable. For example, in FIGS. 2 and 4, the arrangement of the heads in the left-right direction is asymmetric.

Each head included in the head group 10 is not particularly limited as long as the droplets of the radiation curable composition can be ejected from the nozzle holes to adhere the droplets to the recording medium P. Also good. As a head system, for example, a strong electric field is applied between the nozzle and the acceleration electrode placed in front of the nozzle, the composition is continuously ejected in the form of droplets from the nozzle, and the droplets fly between the deflection electrodes. In the meantime, a printing information signal is applied to the polarizing electrode for recording or a droplet is jetted in response to the printing information signal without deflecting (electrostatic suction method), a pressure is applied to the composition with a small pump, A method in which droplets are forcibly ejected by mechanically oscillating the nozzle with a crystal resonator, etc., and a method in which pressure and a print information signal are simultaneously applied to the composition by a piezoelectric element to eject and record droplets (piezo) Method), a method in which the composition is heated and foamed with a microelectrode in accordance with a print information signal, and droplets are jetted and recorded (thermal method).

  Among these, the piezo method can be further classified, and is classified into one having a thin film type piezoelectric element (also referred to as a thin film head) and one having a multilayer type piezoelectric element (also referred to as a multilayer head). can do. The thin film head includes a so-called unimorph type piezoelectric actuator, and discharges the composition from the nozzle by the displacement of the piezoelectric actuator. On the other hand, the laminated head has a mode in which the composition is ejected from the nozzle by pushing the wall of the pressure chamber communicating with the nozzle by the d31 mode driving of the laminated piezoelectric element. The laminated head is also called a longitudinal mode head because the piezoelectric element pushes the wall of the pressure chamber.

  Any of the above-described heads can be used as the head of the head group 10 of the present embodiment, but the longitudinal mode method can relatively increase the ejection force of the radiation curable composition. Thus, it is possible to form a high-quality image at a high speed with less influence of a printing position shift or satellite. On the other hand, when a thin film type head is used, the structure is relatively small and lightweight, so that a high-speed operation is possible and a high-definition high-quality image can be formed at high speed.

  The nozzle holes are formed on the surface of the head group 10 that faces the recording medium P. The head group 10 can eject droplets of the radiation curable composition through the nozzle holes. The number, density (resolution), and arrangement of the nozzle holes are not particularly limited.

  As shown in FIG. 2, in the head group 10 of the present embodiment, the nozzle holes are provided in alignment in the direction (sub-scanning direction SS) orthogonal to the moving direction of the carriage 50 (main scanning direction MS). Two such nozzle rows (nozzle row N) are formed in parallel along the main scanning direction MS of the carriage 50. Note that three or more nozzle rows N may be provided.

  When the head group 10 is moved in the main scanning direction MS along with the movement of the carriage 50, the position of the head group 10 is moved with respect to the recording medium P, and the positional relationship between the two changes. The ink jet apparatus 100 of the present embodiment is a serial type ink jet apparatus as shown in FIG. 1, and the head group 10 moves along the main scanning direction MS by the operation of the carriage 50. Thereby, the radiation curable composition can be adhered to a predetermined position on the recording medium P. The speed at which the head group 10 moves with respect to the recording medium P is the difference in the distance from the nozzle row N closest to the light source of the first head 11 to the position of the end of the light emitting part (LED) of two light sources described later ( (W1-W2: details will be described later). For example, when the difference between the distance W1 and the distance W2 is about 50 mm, the moving speed is preferably 400 mm / s or more, more preferably 500 mm / s or more, further preferably 700 mm / s or more, and still more preferably. 1000 mm / s or more. The upper limit of the moving speed is not limited, but is preferably 5000 mm / s or less, more preferably 4000 mm / s or less, and still more preferably 3000 mm / s or less, from the viewpoint of ease of designing the ink jet device.

The head group 10 can discharge a plurality of types of radiation curable compositions (described later). As the plurality of types of radiation curable compositions, those containing different materials may be used for each radiation curable composition, or the contained materials may be the same for each radiation curable composition. Even if it exists, you may use the thing from which the composition differs. For example, another radiation curable composition having a composition different from that of the radiation curable composition discharged from the first head 11 may be discharged from a head other than the first head 11. This makes it easier to further suppress the gloss banding of the formed image. A radiation curable composition having the same composition as the radiation curable composition discharged from the first head 11 may be discharged from a head other than the first head 11. In this way, it is easier to further suppress variations in line width.

  The amount of liquid droplets ejected from each nozzle hole of the head group 10 is preferably 1 pl or more and 20 pl or less. When the appropriate amount of liquid is within the above range, the ejection stability is good and a high-quality image can be obtained.

1.2. Light Source The ink jet apparatus 100 according to the present embodiment includes a first light source 21 and a second light source 22. The first light source 21 and the second light source 22 are mounted on the carriage 50 and scanned in the main scanning direction MS along with the head group 10 described above.

  The first light source 21 and the second light source 22 move together with the head group 10 described above, and are arranged at both ends of the head group 10 in the scanning direction MS. The first light source 21 and the second light source 22 are used for the radiation curable composition discharged from all nozzle holes of the head of the nozzle group 10 when the head group 10 is scanned in the main scanning direction MS. And configured to be able to irradiate radiation (light).

  The first light source 21 is disposed on one side of the head group 10 in the main scanning direction MS, and the second light source 22 is disposed on the other side of the head group 10 in the main scanning direction MS. 1 to 3, the first light source 21 is on one side MS1 in the main scanning direction MS when viewed from the head group 10, and the second light source 22 is on the other side in the main scanning direction MS when viewed from the head group 10. It is arranged on the direction MS2 side. Accordingly, when the carriage 50 moves in the main scanning direction MS1, the radiation curable composition discharged from the head group 10 is attached to the recording medium P, and the first light source 21 applies the composition to the recording medium P. Radiation is irradiated. Similarly, when the carriage 50 moves in the main scanning direction MS2, the radiation curable composition discharged from the head group 10 is attached to the recording medium P, and the second light source 22 is applied to the composition. The radiation from is irradiated.

  The sizes of the first light source 21 and the second light source 22 in the main scanning direction MS, and the distance between the first light source 21 and the second light source 22 and the recording medium P are the intensity of light to be irradiated, the period of irradiation, and the like. Can be set arbitrarily. In addition, the first light source 21 and the second light source 22 can irradiate light onto a droplet (also referred to as a dot group) of the radiation curable composition attached to the recording medium P. The second light source 22 may continue to generate light, or may blink or increase / decrease the light.

Examples of the light generated from the first light source 21 and the second light source 22 include 400 nm to 200 nm ultraviolet light, visible light, far ultraviolet light, g-line, h-line, i-line, KrF excimer laser light, ArF excimer laser light, or Examples include electromagnetic waves such as X-rays. The light generating means of the first light source 21 and the second light source 22 is not particularly limited. Specific examples of the first light source 21 and the second light source 22 include, for example, a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, a low pressure mercury lamp, a high pressure mercury lamp, an H lamp, a D lamp, and a V lamp ( And the like that can guide light to the first light source 21 by a light guide, an optical fiber, or the like. Further, as another specific mode of the first light source 21 and the second light source 22, for example, a light emitting element such as an ultraviolet light emitting diode (ultraviolet LED) or an ultraviolet light emitting semiconductor laser can be used. When the light generation means of the first light source 21 and the second light source 22 is such a light emitting element, for example, it can include light having a wavelength of 365 nm or more and 410 nm or less. Selecting such a wavelength makes it easy to select a photo (radiation) polymerization initiator in the radiation curable composition. When a light emitting element is selected as the light generating means of the first light source 21 and the second light source 22, the first light source 21 and the second light source 22 can be reduced in size and weight, and the first light source 21 and the second light source can be reduced. The degree of freedom in the arrangement of 22 can be increased. For example, in the example shown in FIGS. 2 and 3, the first light source 21 and the second light source 22 have a configuration in which a plurality of ultraviolet light-emitting diodes (ultraviolet LEDs) (symbol d) are arranged along the direction in which the nozzle row N extends. Have.

  One of the functions of the first light source 21 and the second light source 22 is to perform at least a part of the curing reaction of the droplets of the radiation curable composition attached to the recording medium P. When the recording medium P is non-absorbing, the radiation curable composition droplets spread unnecessarily on the recording medium P or merge with other droplets if the recording medium P is uncured. In some cases, colors may be mixed more than necessary. A part of the radiation curable composition constituting the droplet is cured by irradiating light from the first light source 21 and the second light source 22 that move together with the head group 10 at an early stage after the droplet adheres. In addition, it is possible to prevent the recording medium P from being wetted and spread more than necessary, and to be mixed with other droplets and to be mixed more than necessary.

  In this specification, such an aspect of light irradiation may be referred to as “pinning”. In other words, one of the functions of the first light source 21 and the second light source 22 is to pin the droplets of the radiation curable composition.

At least one of the first light source 21 and the second light source 22, preferably both, has an irradiation peak intensity of preferably 200 mW / cm ² or more, more preferably 300 mW / cm ² or more, and even more preferably 500 mW / cm ^2. As described above, it is particularly preferably 800 mW / cm ² or more. When the irradiation peak intensity is in such a range, the radiation curable composition can be sufficiently pinned by one scanning in the main scanning direction MS (one main scanning). Further, the irradiation peak intensity is preferably at 2000 mW / cm ² or less, more preferably 1700mW / cm ² or less, more preferably 1500 mW / cm ² or less. By setting it as such a range, the freedom degree of design can be raised and waste of energy can be suppressed.

Further, the irradiation energy for irradiating the radiation curable composition with one main scanning (one pass) with the first light source and the radiation curable composition with one main scanning (one pass) with the second light source. the irradiation energy, at least one, preferably both, is preferably 40 mJ / cm ² or more, more preferably 50 mJ / cm ² or more, even more preferably 70 mJ / cm ² or more, particularly more preferably 100 mJ / cm ² or more It is. By setting it as such a range, the radiation-curable composition can be sufficiently pinned by one main scanning in the main scanning direction MS.

1.3. Recording Medium As a recording medium P that can be used in the inkjet apparatus 100 of the present embodiment, when a droplet of a radiation curable composition is attached, light for curing the droplet may reach the droplet. The material is not particularly limited as long as it can be used, and examples thereof include paper, fabric, and film. Further, the recording medium P may have a printing surface that does not absorb or hardly absorbs droplets of the composition. Examples of the recording medium P having such a printing surface include non-absorbing recording media such as metal, glass, and plastic. The recording medium P may be colorless and transparent, translucent, colored and transparent, chromatic color opaque, achromatic color opaque, and the like. Further, the recording medium P may be any of a gloss type, a mat type, and a dull type. Examples of such a recording medium P include a plastic film such as a vinyl chloride sheet or a PET film. Examples of commercially available recording media P include glossy vinyl chloride sheets (for example, trade name SP-SG-1270C: manufactured by Roland DG Corporation), PET films (for example, trade name XEROX FILM <no frame>: manufactured by Fuji Xerox Co., Ltd.), and the like. is there.

The recording medium used in the inkjet apparatus 100 according to the present embodiment is preferably non-ink-absorbing or low-absorbing. When the inkjet apparatus 100 of the present embodiment is used, a good image can be formed even if the recording medium is non-ink-absorbing or low-absorbing.

As a non-ink-absorbing recording medium, for example, a plastic film coated on a substrate such as a plastic film or paper that has not been surface-treated for inkjet printing (that is, an ink-absorbing layer is not formed). And those having a plastic film adhered thereto. Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene. Examples of the recording medium having low ink absorption include printing paper such as art paper, coated paper, and matte paper. Here, in this specification, “ink non-absorbing or low-absorbing recording medium” means “the amount of water absorbed from the start of contact to 30 msec ^1/2 in the Bristow method is 10 mL / m ² or less. Recording medium ". This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method". In the present specification, a non-ink-absorbing or low-absorbing recording medium is also referred to as “plastic medium”.

1.4. Other Configurations In addition to the first light source 21 and the second light source 22, the inkjet device 100 may include an auxiliary light source as necessary. Although not shown, an example of such an auxiliary light source is one that moves with the head group 10 and is disposed at one end of the head group 10 in the sub-scanning direction SS of the recording medium P. . Another example of the auxiliary light source is a light source that is not mounted on the carriage and is arranged downstream of the carriage in the conveyance direction of the recording medium.

  The shape of the auxiliary light source is not particularly limited. The auxiliary light source can emit light for further curing the liquid droplets that have been subjected to at least one of pinning and curing by the first light source 21 and the second light source 22. Therefore, the recording medium P may be provided on the moving direction SS1 side with respect to the head group 10. In other words, the auxiliary light source is on the downstream side in the scanning direction SS of the recording medium P (sub scanning direction SS1 side) (the side on which the radiation of the auxiliary light source can be irradiated after the radiation curable composition has adhered to the recording medium P: FIG. It can be provided at one end of the middle arrow SS1.

  In the case where an auxiliary light source is provided, the droplets of the radiation curable composition may be supplemented as needed after being pinned one or more times by the light from the first light source 21 and the second light source 22 described above. The radiation curable composition can be further cured (main curing) by the light of the light source.

  In addition, although this embodiment includes the form which can fully harden a droplet only by the 1st light source 21 and the 2nd light source 22, even if it does not have an auxiliary light source, in that case, providing an auxiliary light source There is no hindrance, and an auxiliary light source may be provided to achieve a higher curing rate.

  1 includes a motor 30 that feeds the recording medium P in the sub-scanning direction SS1, a platen 40, a head group 10, a carriage 50 on which the first light source 21 and the second light source 22 are mounted. And a carriage motor 60 that moves the carriage 50 in the main scanning direction MS. These configurations can be arbitrarily configured as long as the functions can be exhibited.

The carriage 50 is pulled by a pulling belt 62 driven by a carriage motor 60 and moves along a guide rail 64. The head group 10 is mounted on the carriage 50, and moves in the main scanning direction MS as the carriage 50 moves in the main scanning direction MS. Therefore, the movement of the head group 10 by the carriage 50 and the movement of the recording medium P by the platen 40 can be performed independently.

  Further, a capping device 80 for sealing the nozzle surface of the head group 10 when stopped is provided at the home position of the carriage 50 (the position on the right side in FIG. 1). When the recording job is finished and the carriage 50 reaches above the capping device 80, the capping device 80 is automatically raised by a mechanism (not shown) to seal the nozzle surface of the head group 10. This capping prevents the ink in the nozzles from drying out. The positioning control of the carriage 50 is performed to accurately position the carriage 50 at the position of the capping device 80, for example.

1.5. Operation of Inkjet Device In the inkjet device 100 of the present embodiment, the head group 10 and the recording medium P can operate as follows. As described above, the head group 10, the first light source 21, and the second light source 22 are mounted on the carriage 50 and moved along the main scanning direction MS (the main scanning direction MS1 or the main scanning direction MS2). On the other hand, the recording medium P is moved to one side (scanning direction SS1) of the sub-scanning direction SS crossing the main scanning direction MS.

  In the ink jet apparatus 100 of the present embodiment, the recording medium P is not moved while the head group 10, the first light source 21, and the second light source 22 are moving. In the state where the recording medium P does not move, the head group 10, the first light source 21, and the second light source 22 may move only in one direction of the main scanning direction MS (for example, the main scanning direction MS1). The movement direction may be changed (for example, in the main scanning direction MS2) to reciprocate.

  Next, in the inkjet apparatus 100 of the present embodiment, the recording medium P is in the sub-scanning direction SS1 that intersects the main scanning direction MS with the movement of the head group 10, the first light source 21, and the second light source 22 stopped. After the movement of the recording medium P in the sub-scanning direction SS1 is stopped, the head group 10, the first light source 21, and the second light source 22 are again moved along the main scanning direction MS along with the movement of the carriage 50. Moved.

  The ink jet apparatus 100 according to the present embodiment forms an image on the recording medium P by moving the head group 10, the first light source 21, the second light source 22, and the recording medium P in such a manner. Here, the liquid droplets ejected from the head group 10 are the first light source 21 and the second light source arranged at the rear in the moving direction in one movement (first main scanning step) (one pass) of the carriage 50. 22 receives the first irradiation (pinning). In the ink jet apparatus 100 of the present embodiment, the first light source 21 and the second light source 22 are disposed on both ends of the head group 10 in the main scanning direction MS. Thereby, even if the head group 10 ejects the radiation curable composition while moving in any direction of the main scanning direction MS (main scanning direction MS1 or main scanning direction MS2), the first light source 21 and the second light source 22 Pinning can be performed by either one of the methods.

  Next, the recording medium P is moved by a predetermined distance in the sub scanning direction SS1. Next, by moving the carriage 50 in the direction opposite to the first main scanning step (second main scanning step) (one pass), the liquid droplets ejected from the head group 10 are arranged behind the moving direction. Irradiation (pinning) is received by either one of the first light source 21 and the second light source 22 that has been performed. Note that the recording medium P may not be moved after the first main scanning step and before the second main scanning step. In this way, the second pinning may be performed on the droplets ejected in the first main scanning step.

  Further, in the inkjet apparatus 100 of the present embodiment, even when the recording medium P is moved, the carriage 50 changes the direction of movement after the recording medium P is moved and passes the droplets. The second pinning can be performed by the light source 21 or the second light source 22. That is, in the inkjet apparatus 100 of the present embodiment, the second and third pinning can be performed by adjusting the moving amount of the recording medium P.

  The moving distance of the recording medium P when moved after the movement of the head group 10 may vary depending on the recording mode of the inkjet apparatus 100. That is, the moving distance of the recording medium P varies depending on the printing method within the range of the distance between both ends in the sub-scanning direction SS in the nozzle hole arrangement. Therefore, the movement distance of the recording medium P (which may be referred to as “unit distance” in the movement of the recording medium P) may be different for each recording mode when the recording medium P is moved once.

  By using such an ink jet device 100, droplets of the radiation curable composition can be ejected onto the recording medium P to achieve an effect (pinning). In addition, according to the inkjet apparatus 100, a droplet discharge step of discharging a droplet of the radiation curable composition from the head group 10, and a step of irradiating the droplet with light from the first light source 21 and the second light source 22 Can be performed continuously in one apparatus without being performed in a separate apparatus.

2. Inkjet Method The inkjet method according to the present embodiment is performed using the above-described inkjet device. In the ink jet method of the present embodiment, the radiation curable composition is ejected to the recording medium P while changing the relative position of the head group 10 with respect to the recording medium P toward one side in the main scanning direction. A main scanning step, a second main scanning step of discharging the radiation curable composition onto the recording medium P while changing the relative position of the head group 10 with respect to the recording medium P toward the other side in the main scanning direction; A sub-scanning step of transporting the recording medium P in the sub-scanning direction that intersects the main scanning direction and in the transport direction.

  In other words, the inkjet method of the present embodiment includes discharging the radiation curable composition to adhere to the recording medium P, and irradiating the radiation curable composition with radiation. In the following, using the inkjet device 100 described above, a radiation curable composition is ejected from the head group 10 onto the recording medium P and deposited on the recording medium P to form a dot group. An ink jet method for irradiating radiation from the first light source 21 or the second light source 22 will be described.

  In the inkjet method of the present embodiment, a droplet discharge step of discharging a droplet of a radiation curable composition from the head group 10 and an irradiation step of irradiating the droplet with light from the first light source 21 and the second light source 22 And including.

2.1. Droplet Discharge Step This step is a step in which the radiation curable composition is discharged as droplets from the head group of the ink jet apparatus, and the droplets are adhered onto the recording medium P. In the present embodiment, when the radiation curable composition is adhered to the recording medium, the composition is not limited to being brought into direct contact with the recording medium and is already ejected on the recording medium and already present on the recording medium. Indirect attachment to a recording medium by contacting with a radiation curable composition.

In the ink jet method of the present embodiment, the amount of liquid droplets ejected from one nozzle hole of the head group 10 is preferably 1 pl or more and 20 pl or less. When the amount of droplets is within the above range, the ejection stability is good, and a higher quality image can be obtained. The image formed in this step is not particularly limited, and the resolution and recording mode are not limited at all.

2.2. Irradiation Step This step is a step of irradiating the droplets of the radiation curable composition attached to the recording medium P with the first light source 21 and the second light source 22. With reference to FIG. 2 and FIG. 3, first, this process will be described by taking as an example the case where the head group 10 moves in the main scanning direction MS1.

  As a result of the head group 10 moving in the main scanning direction MS1, the first light source 21 moves to a predetermined position, and the liquid droplets attached to the predetermined position of the recording medium P in the liquid droplet ejection process are separated from the first light source 21. Of radiation (light). Thereby, the curing reaction of the radiation curable composition constituting the droplet occurs, and the first pinning of the droplet is performed. This step can be performed very easily using the above-described ink jet apparatus 100.

  The degree to which the droplets are pinned in this step is 5% or more, preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more as the curing rate of the radiation curable composition constituting the droplets. It is. In this way, it is possible to suppress the liquid droplets from spreading drastically on the recording medium P and to significantly mix the colors, and it is possible to cause controlled wetting spread and color mixing.

  Next, although details are omitted, the same applies to the case where the head group 10 moves in the main scanning direction MS2 of the head group 10, and droplets attached to a predetermined position of the recording medium P in the droplet discharge process. As a result of the head group 10 moving in the main scanning direction MS2, the second light source 22 reaches a predetermined position, and radiation (light) from the second light source 22 is irradiated. Thereby, the curing reaction of the radiation curable composition constituting the droplet occurs, and the first pinning is performed on the droplet. The liquid droplets ejected by the scanning are subjected to the first pinning by the second light source 22, but the second light source 22 performs the second and subsequent pinnings of the liquid droplets ejected by the previous scanning. May be.

  The ink jet method according to the present embodiment includes a first main scanning step of scanning the head group 10 toward one side (for example, the main scanning direction MS1) in the main scanning direction MS, and the other side (for example, the main scanning direction MS). A second main scanning step of scanning the head group 10 in the main scanning direction MS2).

  In the ink jet method of the present embodiment, the first time, which is a period from when the nozzle hole of the first head 11 faces the predetermined position of the recording medium P until the predetermined position and the second light source 22 face each other. And a second time, which is a period from when the nozzle hole of the first head 11 faces a predetermined position of the recording medium P to when the predetermined position and the first light source 21 face each other, can be defined. . That is, in the first main scanning step, the first time, which is a period from when the nozzle of the first head 11 faces a predetermined position of the recording medium P to when the predetermined position and the second light source 22 face each other, In the two main scanning steps, a second time is defined which is a period from when the nozzle of the first head 11 faces a predetermined position of the recording medium P until the predetermined position and the first light source 11 face each other.

  Furthermore, in the ink jet method of the present embodiment, in the first main scanning step, after the nozzles of the second head 12 face a predetermined position of the recording medium P, the predetermined position and the second light source 22 face each other. In the second time of the third time, and in the second main scanning step, the nozzles of the second head 12 face the predetermined position of the recording medium P until the predetermined position and the first light source 12 face each other. The 4th time which is a period is defined.

In the inkjet method of the present embodiment, the difference (absolute value) between the first time and the second time is 12
0 ms or less, preferably 100 ms or less, more preferably 80 ms or less, further preferably 70 ms or less, particularly preferably 50 ms or less. The lower limit value of the difference (absolute value) between the first time and the second time is not particularly limited, but it is preferably 0 ms or more, preferably 10 ms or more, more preferably 20 ms or more, and further preferably 30 ms, from the viewpoint of design freedom. That's it.

  According to such an ink jet method, the difference (absolute value) between the first time and the second time is sufficiently small, and the time difference from landing to irradiation in the reciprocation of main scanning is small, so that there is little variation in line width. It can be performed. Further, since the dot diameters from the first head 11 ejected at a later timing with respect to the recording medium P are easily aligned, the dot diameters of the radiation curable compositions ejected from the heads other than the first head 11 are aligned. Even if not, since it can be covered with the radiation curable composition discharged from the first head 11, the unevenness of the dots can be easily made uniform, and the gloss banding can also be suppressed. That is, in the inkjet method of the present embodiment, the radiation curable composition discharged from the first head 11 is brought into contact with the radiation curable composition discharged from the head other than the first head 11 and attached to the recording medium P. Can be attached. In this way, the radiation curable composition discharged from the head other than the first head 11 and attached to the recording medium is easily attached and disposed so as to cover the radiation curable composition discharged from the first head. Gloss banding can be suppressed.

  Furthermore, in the ink jet method according to the present embodiment, the radiation curable composition that is ejected from a head other than the first head 11 and adhered to the recording medium P, and the radiation curable composition that is ejected from the first head 11 and adhered to the recording medium. The radiation curable composition may be different from each other. In this way, for example, by using radiation curable compositions whose colors that can be colored on the recording medium are different from each other, multi-colored recording is possible, and the variety of recording is rich. Further, in the ink jet method according to the present embodiment, the radiation curable composition discharged from the head other than the first head 11 and attached to the recording medium P, and discharged from the first head 11 and attached to the recording medium P. The radiation curable compositions may have the same composition. In this way, it is possible to increase the recording speed by recording one radiation curable composition using two or more heads. In these cases, the radiation curable composition ejected from the heads other than the first head 11 contacts the radiation curable composition present on the recording medium P, and the radiation curable composition ejected from the first head 11 is applied to the recording medium. When adhering, a difference in line width and gloss banding tend to occur particularly easily, but according to this embodiment, this embodiment is particularly useful in that the difference in line width and gloss banding can be reduced. is there.

  On the other hand, in the inkjet method of the embodiment, the difference (absolute value) between the third time and the fourth time is more than 80 ms, preferably more than 100 ms, more preferably more than 120 ms, still more preferably more than 150 ms, particularly preferably more than 200 ms. It is done to become. In this way, the degree of freedom of arrangement (design) of the second head 12 can be increased. Further, the upper limit value of the difference (absolute value) between the third time and the fourth time is not particularly limited, but is preferably 1000 ms or less, preferably 500 ms or less, more preferably 200 ms or less, further preferably from the viewpoint of downsizing of the apparatus. Is 1000 ms or less.

  Furthermore, it is more preferable that the difference between the first time and the second time is smaller than the difference between the third time and the fourth time. That is, the irradiation timing of radiation from the first head 11 to the radiation curable composition is smaller in the first main scanning process and the second main scanning process in the main scanning direction MS than in the case of other heads. Is more preferable.

The adjustment of the lengths of the first time, the second time, the third time, and the fourth time is, for example, between the first head 11 and the second head 12 and the first light source 21 in the inkjet device 100 described above. It is possible to adjust the distance between the first head 11 and the second head 12 and the second light source 22 and / or adjust the moving speed of the carriage 50. It is.

  Examples of the moving speed of the carriage 50 (scanning speed of the head group 10) are 200 mm / s or more and 2000 mm / s or less, preferably 400 mm / s or more and 1500 mm / s or less, more preferably 500 mm / s or more and 700 mm / s or less. is there. Further, the separation distance (W2 in FIG. 2) in the main scanning direction MS of the nozzle closest to the first light source 21 of the first head 11 and the irradiation region (end of the light emitting unit) of the first light source 21 and the first head 11 The difference (absolute value) between the nozzle closest to the second light source 22 and the distance (W1 in FIG. 2) in the main scanning direction MS of the irradiation region of the second light source 22 (end of the light emitting unit) is, for example, It is 50 mm or less, preferably 40 mm or less, more preferably 35 mm or less, and particularly preferably 30 mm or less. Furthermore, the separation distance (W2 in FIG. 2) in the main scanning direction MS of the nozzle closest to the first light source 21 of the first head 11 and the irradiation region (end of the light emitting unit) of the first light source 21 and the first head 11 The lower limit value of the difference (absolute value) between the nozzle closest to the second light source 22 and the separation distance (W1 in FIG. 2) in the main scanning direction MS of the irradiation region (end of the light emitting unit) of the second light source 22 is , 0 mm, and 10 mm, preferably 20 mm, from the viewpoint of design freedom.

  If the moving speed of the carriage 50 and the arrangement of the first head 11, the first light source 21 and the second light source 22 are within the above range, the difference between the first time and the second time is within the above range. Is easy. Thereby, it is possible to perform recording with little variation in line width. Further, if such a moving speed and arrangement are used in the first head 11 that applies the radiation curable composition to the recording medium P at a later timing, gloss banding can also be suppressed.

3. Radiation-curable composition A radiation-curable composition (hereinafter also simply referred to as “composition”) ejected by the head group 10 of the inkjet device 100 of the present embodiment is a composition that is ejected from an inkjet head by an inkjet method. It is a thing. Hereinafter, a radiation curable (ink jet ink) composition will be described as an embodiment of the radiation curable ink jet composition, but the composition is a composition other than the ink composition, for example, a composition used for 3D modeling. Also good. In addition, as an embodiment of the “radiation curable type”, there are cases where it is described as “ultraviolet curable type”, “photo curable type”, etc., but in this embodiment, the composition is used by being cured by irradiation with radiation. Any curable composition may be used, and an ultraviolet curable composition or an ultraviolet curable composition may be read as a radiation curable composition or a radiation curable composition. Examples of radiation include ultraviolet rays, infrared rays, visible rays, and X-rays. As the radiation, ultraviolet rays are preferable because a radiation source is easily available and widely used, and a material suitable for curing by ultraviolet radiation is easily available and widely used.

  Examples of the radiation curable composition include those containing at least a polymerizable compound and a photopolymerization initiator. In the present specification, “(meth) acryloyl” means at least one of acryloyl and its corresponding methacryloyl, and “(meth) acrylate” means at least one of acrylate and its corresponding methacrylate. “(Meth) acryl” means at least one of acrylic and methacryl corresponding thereto.

3.1. Polymerizable compound The radiation-curable composition of the present embodiment contains a polymerizable compound. Examples of such polymerizable compounds include those having at least one of photocationic polymerizability and photoradical polymerizability. The polymerizable compound contained in the radiation curable composition may have a photocationically polymerizable functional group and a photoradical polymerizable functional group in one molecule. The polymerizable compound includes a monomer as a monomer and an oligomer having a dimer to a quanta or a molecular weight of up to about several thousand. Those contents are adjusted so that it may become the viscosity range which can be used as an inkjet ink.

  Examples of the radical photopolymerizable group include those having a radical having an unsaturated double bond capable of radical radical polymerization, such as acryloyl group, methacryloyl group, acrylamide group, methacrylamide group, allyl group, vinyl ether group, A vinyl thioether group, a vinyl amino group, and a vinyl group are exemplified, and from the viewpoint of particularly high photoradical polymerization reactivity, an acryloyl group, an acrylamide group, a methacryloyl group, and a methacrylamide group are more preferable, and an acryloyl group is more preferable. And acrylamide group.

  Specific examples of the monomer of the radical photopolymerizable compound include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid, and esters thereof, and styrene derivatives such as styrene, vinyltoluene, and dimethylstyrene. N-vinyl compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylformamide, N-vinylacetamide, N-substituted maleimide, acrylonitrile, acryloylmorpholine, and the like.

  Specific examples of oligomers of radical photopolymerizable compounds include polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, oligo acrylate, alkyd acrylate, polyol acrylate, polyester methacrylate, polyurethane methacrylate, epoxy methacrylate, polyether methacrylate, oligo methacrylate. , Alkyd methacrylate, polyol methacrylate and the like.

  Specific examples of the polymerizable compound include (meth) acrylates, (meth) acrylamides, N-vinyl compounds and the like.

Monofunctional (meth) acrylates include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, tert-octyl (meth) acrylate, isoamyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, stearyl (Meth) acrylate, isostearyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-n-butylcyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, 2- Ethylhexyl diglycol (meth) acrylate, butoxyethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 4-bromobutyl (meth) acrylate, cyanoethyl (meth) Acrylate, benzyl (meth) acrylate, butoxymethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, alkoxymethyl (meth) acrylate, alkoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) Acrylate, 2- (2-butoxyethoxy) ethyl (meth) acrylate, 2,2,2-tetrafluoroethyl (meth) acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth) acrylate, 4-butylphenyl (Meth) acrylate, phenyl (meth) acrylate, 2,4,5-tetramethylphenyl (meth) acrylate, 4-chlorophenyl (meth) acrylate, phenoxymethyl (meth) acrylate, phenoxyethyl (meth) acrylate Glycidyl (meth) acrylate, glycidyloxybutyl (meth) acrylate, glycidyloxyethyl (meth) acrylate, glycidyloxypropyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, hydroxyalkyl (meth) acrylate, 2- Hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, dimethylaminoethyl (meth) acrylate , Diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate Acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, trimethoxysilylpropyl (meth) acrylate, trimethylsilylpropyl (meth) acrylate, polyethylene oxide monomethyl ether (meth) acrylate, oligoethylene oxide monomethyl ether ( (Meth) acrylate, polyethylene oxide (meth) acrylate, oligoethylene oxide (meth) acrylate, oligoethylene oxide monoalkyl ether (meth) acrylate, polyethylene oxide monoalkyl ether (meth) acrylate, dipropylene glycol (meth) acrylate, polypropylene oxide monoalkyl Ether (meth) acrylate, oligopropylene oxide Alkyl ether (meth) acrylate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, butoxydiethylene glycol (meth) acrylate, trifluoroethyl ( (Meth) acrylate, perfluorooctylethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, EO-modified phenol (meth) acrylate, EO-modified cresol (meth) acrylate, EO-modified nonylphenol (meth) acrylate, Examples thereof include PO-modified nonylphenol (meth) acrylate and EO-modified-2-ethylhexyl (meth) acrylate.

  As polyfunctional (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate (DPGD (M) A), tripropylene glycol di (meth) acrylate (TPGD (M) A), 2,4-dimethyl-1,5-pentanediol di (meth) acrylate, butylethylpropanediol di (meth) Acrylate, ethoxylated cyclohexanemethanol di (meth) acrylate, triethylene glycol di (meth) acrylate (TEGD (M) A), polyethylene glycol di (meth) acrylate, oligoethylene glycol di (meth) acrylate, ethylene glycol (Meth) acrylate, 2-ethyl-2-butyl-butanediol di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, EO-modified bisphenol A di ( (Meth) acrylate, bisphenol F polyethoxydi (meth) acrylate, polypropylene glycol di (meth) acrylate, oligopropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 2-ethyl-2-butyl-propane Diol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, propoxylated ethoxylated bisphenol A di (meth) acrylate, tricyclodecane di (meth) acrylate, etc. They include a (meth) acrylate.

Furthermore, as polyfunctional (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, alkylene oxide modified tri (meth) acrylate of trimethylolpropane, pentaerythritol tri (meth) acrylate , Dipentaerythritol tri (meth) acrylate, trimethylolpropane tri ((meth) acryloyloxypropyl) ether, isocyanuric acid alkylene oxide modified tri (meth) acrylate, propionate dipentaerythritol tri (meth) acrylate, tri ( (Meth) acryloyloxyethyl) isocyanurate, hydroxypivalaldehyde-modified dimethylolpropane tri (meth) acrylate, sorbitol tri (meth) a Relate, propoxylated trimethylolpropane tri (meth) acrylate, ethoxylated glycerol tri (meth) acrylate: trifunctional, pentaerythritol tetra (meth) acrylate, sorbitol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, Propionic acid dipentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate: tetrafunctional, sorbitol penta (meth) acrylate, dipentaerythritol penta (meth) acrylate: pentafunctional, dipentaerythritol hexa ( (Meth) acrylate, sorbitol hexa (meth) acrylate, phosphazene alkylene oxide modified hexa (meth) acrylate, cap Lactone-modified dipentaerythritol hexa (meth) acrylate or hexafunctional, and the like.

  (Meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide, Nt -Butyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) Examples include acrylamide and (meth) acryloylmorpholine.

The N-vinyl compound has a structure in which a vinyl group is bonded to nitrogen (> N—CH═CH ₂ ). Specific examples of the N-vinyl compound include, for example, N-vinylformamide, N-vinylcarbazole, N-vinylindole, N-vinylpyrrole, N-vinylacetamide, N-vinylpyrrolidone, N-vinylcaprolactam, and their Derivatives, and N-vinylcaprolactam is particularly preferable among these compounds.

Moreover, it is more preferable that the radiation curable composition of this embodiment contains the vinyl ether group containing (meth) acrylate represented by the following general formula (I).
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
(In Formula (I), R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a hydrogen atom or a monovalent having 1 to 11 carbon atoms. This is an organic residue.)
Hereinafter, the vinyl ether group-containing (meth) acrylate represented by the general formula (I) may be simply referred to as “compound of formula (I)”.

  When the composition according to this embodiment contains the compound of formula (I), the curability of the composition can be made excellent. Moreover, it is easy to suppress the viscosity of a composition low by containing the compound of Formula (I). Furthermore, it is more effective to use a compound having both a vinyl ether group and a (meth) acryl group in one molecule than using a compound having a vinyl ether group and a compound having a (meth) acryl group separately. It is preferable for improving the property.

In the general formula (I), the divalent organic residue having 2 to 20 carbon atoms represented by R ² may be linear, branched or cyclic substituted having 2 to 20 carbon atoms. A good alkylene group, an optionally substituted alkylene group having an oxygen atom by an ether bond and / or an ester bond in the structure, and an optionally substituted divalent fragrance having 6 to 11 carbon atoms Group groups are preferred. Among these, C2-C6 alkylene groups such as ethylene group, n-propylene group, isopropylene group, and butylene group, oxyethylene group, oxy n-propylene group, oxyisopropylene group, and oxybutylene group An alkylene group having 2 to 9 carbon atoms having an oxygen atom due to an ether bond in the structure is preferably used. Furthermore, from the viewpoint of lowering the viscosity of the radiation curable composition and further improving the curability, R ² is an oxyethylene group, an oxy n-propylene group, an oxyisopropylene group, and an oxybutylene group. A compound having a glycol ether chain, which is an alkylene group having 2 to 9 carbon atoms having an oxygen atom by an ether bond in the structure such as

In the general formula (I), the monovalent organic residue having 1 to 11 carbon atoms represented by R ³ may be linear, branched or cyclic substituted having 1 to 10 carbon atoms. A good alkyl group and an optionally substituted aromatic group having 6 to 11 carbon atoms are preferred. Among these, C6-C2 aromatic groups, such as a C1-C2 alkyl group which is a methyl group or an ethyl group, a phenyl group, and a benzyl group, are used suitably.

  When each of the organic residues is an optionally substituted group, the substituent is divided into a group containing a carbon atom and a group not containing a carbon atom. First, when the substituent is a group containing a carbon atom, the carbon atom is counted in the carbon number of the organic residue. Examples of the group containing a carbon atom include, but are not limited to, a carboxyl group and an alkoxy group. Next, examples of the group not containing a carbon atom include, but are not limited to, a hydroxyl group and a halo group.

  A plurality of compounds of the formula (I) may be mixed and used. The total content of the compounds of the formula (I) is preferably 10% by mass or more with respect to the total mass (100% by mass) of the composition. The content of the compound of formula (I) is preferably 10% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less, with respect to the total mass (100% by mass) of the composition. More preferably, it is 10 mass% or more and 30 mass% or less, Most preferably, it is 10 mass% or more and 25 mass% or less. When the content of the compound of formula (I) is 10% by mass or more, the curability of the composition can be made sufficient. On the other hand, when the content is 25% by mass or less, the storage stability of the ink can be maintained in a particularly excellent state.

Specific examples of the compound of the formula (I) are not particularly limited. For example, 2-vinyloxyethyl (meth) acrylate, 3-vinyloxypropyl (meth) acrylate, 1-methyl-2- (meth) acrylate Vinyloxyethyl, 2-vinyloxypropyl (meth) acrylate, 4-vinyloxybutyl (meth) acrylate, 1-methyl-3-vinyloxypropyl (meth) acrylate, 1-vinyloxymethylpropyl (meth) acrylate, ( 2-methyl-3-vinyloxypropyl (meth) acrylate, 1,1-dimethyl-2-vinyloxyethyl (meth) acrylate, 3-vinyloxybutyl (meth) acrylate, 1-methyl-2-vinyl (meth) acrylate Loxypropyl, 2-vinyloxybutyl (meth) acrylate, 4-vinyloxycyclohexane (meth) acrylate Sil, 6-vinyloxyhexyl (meth) acrylate, 4-vinyloxymethylcyclohexylmethyl (meth) acrylate, 3-vinyloxymethylcyclohexylmethyl (meth) acrylate, 2-vinyloxymethylcyclohexyl (meth) acrylate Methyl, (meth) acrylic acid p-vinyloxymethylphenylmethyl, (meth) acrylic acid m-vinyloxymethylphenylmethyl, (meth) acrylic acid o-vinyloxymethylphenylmethyl, methacrylic acid 2- (2-vinylic acid) Loxyethoxy) ethyl, 2- (2-vinyloxyethoxy) ethyl acrylate (VEEA), 2- (vinyloxyisopropoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxy) propyl (meth) acrylate, (Meth) acrylic acid 2- (vinyloxyethoxy) isopropyl Pill, 2- (vinyloxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyethoxy) ethyl (meth) acrylate, (meth) 2- (vinyloxyethoxyisopropoxy) ethyl acrylate, 2- (vinyloxyisopropoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyisopropoxyisopropoxy) ethyl (meth) acrylate, (meth) acrylic 2- (vinyloxyethoxyethoxy) propyl acid, 2- (vinyloxyethoxyisopropoxy) propyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) propyl (meth) acrylate, 2- (meth) acrylic acid 2- (Vinyloxyisopropoxyisopropoxy) propyl, 2- (vinyloxyethoxyethoxy) isopropyl (meth) acrylate, 2- (vinyloxyethoxyisopropoxy) isopropyl (meth) acrylate, 2- (vinyloxyisopropoxyethoxy) isopropyl (meth) acrylate, (meth) 2- (vinyloxyisopropoxyisopropoxy) isopropyl acrylate, 2- (vinyloxyethoxyethoxyethoxy) ethyl (meth) acrylate, 2- (vinyloxyethoxyethoxyethoxyethoxy) ethyl (meth) acrylate, (meth) 2- (isopropenoxyethoxyethoxy) ethyl acrylate, 2- (isopropenoxyethoxyethoxy) ethyl (meth) acrylate, 2- (isopropenoxyethoxyethoxyethoxy) ethyl (meth) acrylate, (meth) acrylic acid 2- (Isopropeno Shi ethoxyethoxy ethoxyethoxy) ethyl, and (meth) Polyethylene glycol monovinyl ether acrylate, and (meth) acrylic acid polypropylene glycol monovinyl ether. Among these specific examples, VEEA: 2- (2-vinyloxyethoxy) ethyl acrylate is particularly preferable because it is easy to balance the curability and viscosity of the composition.

  The radiation curable composition of the present embodiment may also contain a monofunctional (meth) acrylate having an aromatic ring skeleton other than the vinyl ether group-containing (meth) acrylate represented by the general formula (I). It is preferable in that it has excellent properties and can make the composition have a low viscosity. In addition, when the radiation curable composition contains a monofunctional (meth) acrylate having an aromatic ring skeleton, the photopolymerization initiator is excellent in solubility, and by reducing the amount of undissolved residue, the curability of the radiation curable composition is improved. It is also preferable in terms of contributing. The content of the monofunctional (meth) acrylate having an aromatic ring skeleton is preferably 10 to 70% by mass or more, more preferably 20% with respect to the total mass (100% by mass) of the composition in the above points. It is -60 mass%, More preferably, it is 30-50 mass%. Examples of the monofunctional (meth) acrylate having an aromatic ring skeleton include, but are not limited to, the above-described monofunctional (meth) acrylates having an aromatic ring skeleton.

  Moreover, the radiation curable composition of this embodiment is other than the vinyl ether group-containing (meth) acrylate represented by the general formula (I) and the vinyl ether group-containing (meth) acrylate represented by the general formula (I). It is also preferable to contain at least one of monofunctional (meth) acrylates having an aromatic ring skeleton in terms of excellent curability and low viscosity of the composition. A vinyl ether group-containing (meth) acrylate represented by the general formula (I), a monofunctional (meth) acrylate having an aromatic ring skeleton other than the vinyl ether group-containing (meth) acrylate represented by the general formula (I), The total content of at least any one of the above is preferably 10 to 80% by mass or more, more preferably 30 to 70% by mass with respect to the total mass (100% by mass) of the composition. More preferably, it is 40-60 mass%.

  On the other hand, examples of the photocationically polymerizable group include an epoxy ring, an oxetane ring, an oxolane ring, a dioxolane ring, and a vinyl ether group. About an epoxy ring, an aromatic type and an alicyclic system are preferable from a viewpoint that it is excellent in a cure rate, and an alicyclic epoxy ring is especially preferable.

  Specific examples of the polymerizable compound having cationic polymerizability include an epoxy compound, a vinyl ether compound, an oxetane compound and the like as the cationic polymerizable compound.

  The content of the polymerizable compound contained in the radiation curable composition is suitably 5% by mass or more and 95% by mass or less, preferably 7% by mass or more and 90% by mass or less, with respect to the entire radiation curable composition. More preferably, it is the range of 10 mass% or more and 80 mass% or less.

3.2. Photoinitiator The radiation curable composition of this embodiment contains a photoinitiator. As a photoinitiator, the substance which produces the active seed | species which causes superposition | polymerization of a polymeric compound by light can be mentioned.
Photopolymerization initiators that generate radicals by light (photoradical polymerization initiators) include arylalkyl ketones, oxime ketones, S-phenyl thiobenzoate, titanocene, aromatic ketones, thioxanthones, benzyl and quinone derivatives, ketocoumarins, etc. Conventional initiators known in the art can be used.

  Specific examples of the photo radical polymerization initiator include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, benzophenone, 2-chlorobenzophenone, p, p′-dichlorobenzophenone, p, p′-bisdiethylaminobenzophenone. Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, benzoin-n-butyl ether, benzyl methyl ketal, 2,2-dimethoxy-1,2- Diphenylethane-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methylpropionyl) benzyl] Enyl} 2-methylpropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1,2-dimethylamino-2- (4-methylbenzyl) -1- ( 4-morpholin-4-yl-phenyl) butan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] 2-morpholinopropan-1-one, thioxanthone, 2-chlorothioxanthone, 2 -Hydroxy-2-methyl-1-phenyl-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-methylbenzoyl fill formate, azo-bis-isobutyronitrile Lilo nitrile, benzoyl peroxide, di -tert- butyl peroxide, and the like.

  Examples of commercially available photo radical polymerization initiators include IRGACURE 651 (2,2-dimethoxy-1,2-diphenylethane-1-one), IRGACURE 184 (1-hydroxy-cyclohexyl-phenyl-ketone), DAROCUR 1173. (2-hydroxy-2-methyl-1-phenyl-propan-1-one), IRGACURE 2959 (1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane- 1-one), IRGACURE 127 (2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one), IRGACURE 907 (2-Methyl-1- (4-methylthiophenyl) -2-morphol Linopropan-1-one), IRGACURE 369 (2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1), IRGACURE 379 (2- (dimethylamino) -2-[(4- Methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1-butanone), DAROCUR TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide), IRGACURE 819 (bis (2, 4,6-trimethylbenzoyl) -phenylphosphine oxide), IRGACURE 784 (bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-) Yl) -phenyl) titanium), IRGACURE OXE 01 (1.2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)]), IRGACURE OXE 02 (ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime)), IRGACURE 754 (oxyphenylacetic acid, 2- [2-oxo-2-phenylacetoxyethoxy] ethyl ester and oxyphenylacetic acid, 2- (Mixture of (2-hydroxyethoxy) ethyl ester) (manufactured by Ciba Japan KK), DETX-S (2,4-diethylthioxanthone) (Nippon Kayaku Co., Ltd. )), Lucirin TPO, LR8883, LR8970 (above, manufactured by BASF), and Ubekrill P36 (manufactured by UCB) ).

  Photopolymerization initiators that generate cations (acids) by light (photocation polymerization initiators) include onium salts such as arylsulfonium salts and aryliodonium salts, o-nitrobenzyl tosylate, and arylsulfonic acid p-nitrobenzyl esters. And an acid generator such as an initiator that generates a sulfonic acid such as a sulfonium acetophenone derivative, an allene-ion complex derivative such as an iron-allene complex, a diazonium salt derivative, a triazine-based initiator, and other halides. Specific examples of the cationic photopolymerization initiator include arylsulfonium salt derivatives such as Syracure UVI-6990, Syracure UVI-6974 manufactured by Union Carbide, Adekaoptomer SP-150, Adekaoptomer manufactured by Asahi Denka Kogyo Co., Ltd. SP-152, Adeka optomer SP-170, Adeka optomer SP-172 and the like are mentioned. As the allyl iodonium salt derivative, RP-2074 made by Rhodia is mentioned, and as the allene-ion complex derivative, Ciba Geigy is made. Irgacure 261 and the like.

  The content of the polymerization initiator contained in the radiation curable composition is preferably 1% by mass or more and 20% by mass or less, and preferably 3% by mass or more and 15% by mass or less with respect to the entire radiation curable composition. More preferably. By setting it as the said range, there exists an effect which maintains sclerosis | hardenability, without reducing the mechanical strength of the radiation-curable composition after hardening. As the photopolymerization initiator, those having sensitivity to irradiated light can be appropriately selected and used. Further, the degree of pinning of the droplets of the radiation curable composition can be adjusted by the type and blending amount of the photopolymerization initiator. For example, when it is desired to reduce the degree of pinning, the degree of pinning can be adjusted by reducing the light amount of the first light source 21 and the second light source 22, but within the above range, the amount of the photopolymerization initiator is reduced. This can also be done.

  As the polymerizable compound and the photopolymerization initiator, a photoradical polymerization initiator is used for photopolymerization of the photoradical polymerizable compound, and a photocationic polymerization initiator is used for photopolymerization of the photocationic polymerizable compound. When using a radical photopolymerizable compound and a cationic photopolymerizable compound together, a radical photopolymerization initiator and a cationic photopolymerization initiator are used in combination.

3.3. Other components 3.3.1. Colorant and Dispersant The radiation curable composition of the present embodiment can contain a colorant and a dispersant.

  In this case, examples of the color material include pigments and dyes, and a color material that can be used for ordinary ink can be used without any particular limitation.

  The radiation curable composition of this embodiment may further contain a coloring material. The coloring material is selected from pigments and dyes, but it is preferable to use pigments from the viewpoint of light resistance. In this embodiment, the light resistance of the radiation curable composition can be improved by using a pigment as the color material. As the pigment, both inorganic pigments and organic pigments can be used. The radiation material is preferably contained in the radiation curable composition in an amount of 1 to 10% by mass, more preferably 1 to 5% by mass.

  Examples of inorganic pigments include carbon blacks such as furnace black, lamp black, acetylene black and channel black (CI Pigment Black 7), iron oxide, titanium oxide (for example, NanoTek (R) Slurry, manufactured by CI Kasei Co., Ltd.). ) Can be used.

Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Polycyclic pigments, dye chelates (for example, basic dye chelates, acid dye chelates, etc.), dye rakes (basic dye rakes, acid dye rakes), nitro pigments, nitroso pigments, aniline black, daytime A photofluorescent pigment is mentioned. The said pigment may be used individually by 1 type, and may use 2 or more types together.

  Speaking of colors, carbon black is an example of an inorganic pigment used for black. Examples of white pigments include C.I. I. Pigment White is a pigment called C.I. I. Pigment Yellow is a pigment called C.I. as a magenta pigment. I. Pigment Red and C.I. I. Pigment Bio Red is a pigment called C.I. I. Pigment Blue is a pigment other than C.I. I. Pigment orange, C.I. I. Pigment Green, C.I. I. Pigment brown and the like.

  In the present embodiment, in addition to the organic pigments listed above, dyes that are insoluble or hardly soluble in water, such as disperse dyes and oil-soluble dyes, can also be suitably used.

  When the above pigment is used as a coloring material for ink jet recording ink, the average particle diameter is preferably 500 nm or less, more preferably 200 nm or less, and further preferably 50 to 100 nm.

  When the radiation curable composition of the present embodiment contains a color material, the amount of the color material added is preferably in the range of about 0.1% by mass or more and 25% by mass or less, more preferably 0.5% by mass or more. It is 15 mass% or less, More preferably, it is 1-7 mass%. Further, the degree of pinning of the droplets of the radiation curable composition can be adjusted by the type and blending amount of the color material. For example, when it is desired to reduce the degree of pinning, the degree of pinning can be adjusted by reducing the light amount of the first light source 21 and the second light source 22, but the type of the color material exemplified above can be selected, This can also be done by changing the blending amount of the colorant within the range.

  Moreover, when making a radiation-curable composition contain a pigment, the pigment dispersion liquid obtained by making it disperse | distribute in a medium with a dispersing agent or surfactant can be used. Furthermore, when a pigment is contained in the radiation curable composition, these pigment and a dispersant or a surfactant can be contained. As a preferable dispersant, a dispersant conventionally used for preparing a pigment dispersion, for example, a polymer dispersant can be used.

  As the dispersant, any dispersant used in ordinary ink can be used. Commercially available products can be used as the dispersant. Specific examples thereof include Hinoact KF1-M, T-6000, T-7000, T-8000, T-8350P, T-8000EL (manufactured by Takefu Fine Chemical Co., Ltd.). ) Polyester polymer compounds such as solsperse 13940, 20000, 24000, 32000, 32500, 33500, 34000, 35200, 36000 (manufactured by Lubrizol Corporation), disperbyk-161, 162, 163, 164, 166, 180, 190, 191, 192 (Bic Chemie), Floren DOPA-17, 22, 33, G-700 (Kyoeisha Chemical Co., Ltd.), Ajisper PB821, PB711 (Ajinomoto Co., Inc.), LP4010, LP4050, LP4055, OLYMER400,401,402,403,450,451,453 can be mentioned those alone, or a mixture (EFKA Chemicals Co., Ltd.).

  The content of the dispersant in the radiation curable composition is 5% by mass or more and 200% by mass or less with respect to the content of the coloring material (especially pigment) in the radiation curable composition, preferably It is 30% by mass or more and 120% by mass or less, and may be appropriately selected depending on the color material to be dispersed.

3.3.2. Additives The radiation curable composition comprising the photoradically polymerizable compound of the present embodiment may contain a polymerization accelerator. In the case of radical photopolymerization, the polymerization accelerator is not particularly limited, and examples thereof include Darocur EHA, EDB (manufactured by Ciba Specialty Chemicals), EBECRYL 7100 (manufactured by Daicel-Cytec).

  Moreover, you may make a radiation curable composition consisting of a photoradical polymerizable compound contain a thermal radical polymerization inhibitor. Thereby, the storage stability of a radiation curable composition can be improved. Specific examples of the thermal radical polymerization inhibitor include methyl ether hydroquinone (MEHQ) (manufactured by Kanto Chemical Co., Inc.), tert-butyl-p-benzoquinone, Irgastab UV-10, UV-22 (manufactured by Ciba Specialty Chemicals). Etc.

  Furthermore, a surfactant (slip agent) can be contained in the radiation curable composition. As the slip agent, a silicone-based surfactant is preferable, and polyester-modified silicone or polyether-modified silicone is more preferable. Examples of the polyester-modified silicone include BYK-347, 348, BYK-UV3500, 3510, 3530 (manufactured by BYK Additives & Instruments) and the like, and examples of the polyether-modified silicone include BYK-3570 (by BYK Additives & Instruments). Can be mentioned. A slip agent may be used individually by 1 type, and may be used in combination of 2 or more type. The total content of the slip agent is preferably 0.01% by mass or more and 2% by mass, more preferably 0.05% by mass or more and 1% by mass or less, with respect to the total mass (100% by mass) of the composition. .

  Furthermore, an ultraviolet absorber, a leveling agent, etc. can be added to the radiation curable composition of this embodiment as needed.

3.4. Physical Properties (1) Viscosity The viscosity at 20 ° C. of the radiation curable composition according to this embodiment is preferably 5 mPa · s to 50 mPa · s, more preferably 20 mPa · s to 40 mPa · s. When the viscosity at 20 ° C. of the radiation curable composition is within the above range, an appropriate amount of the radiation curable composition is ejected from the nozzle, and flight bending and scattering of the radiation curable composition can be further reduced. It can be used suitably for an apparatus. The viscosity is measured by using a viscoelasticity tester MCR-300 (manufactured by Pysica), increasing the Shear Rate to 10 to 1000 in an environment of 20 ° C., and reading the viscosity at Shear Rate 200. be able to.

(2) Surface tension The surface tension at 20 ° C. of the radiation curable composition according to this embodiment is preferably 20 mN / m or more and 30 mN / m or less. When the surface tension at 20 ° C. of the radiation curable composition is within the above range, the radiation curable composition is difficult to get wet with the nozzle subjected to the liquid repellent treatment. Accordingly, an appropriate amount of the radiation curable composition is ejected from the nozzle, and the flight bending and scattering of the radiation curable composition can be further reduced, so that it can be suitably used for an ink jet apparatus. The surface tension can be measured using an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) in a 20 ° C. environment when the platinum plate is wetted with ink. .

3.5. Curing of radiation curable composition The radiation curable composition of the present embodiment contains at least the polymerizable compound and the polymerization initiator. Therefore, the radiation curable composition can be cured by irradiating light from the first light source 21 and the second light source 22.

When ultraviolet rays are used as the light of the first light source 21 and the second light source 22, the irradiation amount of the ultraviolet rays to the radiation curable composition is 10 mJ / cm ² or more and 20,000 mJ / cm ² or less, and preferably 50 mJ / cm ² or more, irradiated at 15,000 / cm ² or less. If the ultraviolet irradiation amount is finally in the above range, the polymerizable compound can be sufficiently cured.

Moreover, it is more preferable that the radiation irradiation energy required for the composition to reach tack-free by adjusting the composition of the radiation curable composition of the present embodiment is 500 mJ / cm ² or less. Such a radiation curable composition has good curability, and when the difference between the first time and the second time is large, variations in line width and gloss banding tend to occur. However, if the ink jet method and the ink jet apparatus of the present embodiment described above are used, the effect that the gloss banding can be suppressed with less variation in line width can be achieved more remarkably. The irradiation energy of the radiation required to reach a tack-free, more preferably 400 mJ / cm ² or less, more preferably 300 mJ / cm ² or less, more preferably 250 mJ / cm ² or less, particularly preferably 200 mJ / cm ² or less, the lower limit Is not limited, but is preferably 50 mJ / cm ² or more, and more preferably 100 mJ / cm ² or more.

The “irradiation energy required to reach tack-free” is an LED (peak wavelength 395 nm, peak intensity 600 mW / cm ² ) applied to a recording medium with ink applied at a coating amount of 10 mg / cm ^2. This is the irradiation energy required for irradiation and reaching tack-free.

4). Experimental Examples Hereinafter, the present invention will be described more specifically with experimental examples (also simply referred to as “examples”), but the present invention is not limited to these examples.

4.1. Preparation of radiation curable composition First, a coloring material, a dispersant, and a part of each monomer are weighed and placed in a pigment dispersion tank, and a ceramic bead mill having a diameter of 1 mm is placed in the tank and agitated. A pigment dispersion was obtained in which was dispersed in a polymerizable compound. Next, the remaining monomer, polymerization initiator (Irgacure819, DarocurTPO), and polymerization inhibitor (MEHQ) are placed in a mixture tank, which is a stainless steel container, and mixed and stirred to achieve the composition shown in Table 1. Then, the pigment dispersion obtained above is added, mixed and stirred at room temperature for 1 hour, and further filtered through a 5 μm membrane filter, so that the radiation curing type of b1, b2, b3 and w1 is obtained. A composition was obtained. In addition, the numerical value of each component shown in Table 1 represents mass%.

表１中で使用した略号の成分は、以下の通りである。

The components of the abbreviations used in Table 1 are as follows.

<Polymerizable compound>
VEEA (trade name, manufactured by Nippon Shokubai Co., Ltd., 2- (2-vinyloxyethoxy) ethyl acrylate)
・ PEA (trade name “Biscoat # 192, manufactured by Osaka Organic Chemical Industry Co., Ltd., phenoxyethyl acrylate”)
・ TPGDA (trade name “APG-200”, manufactured by Shin-Nakamura Chemical Co., Ltd., tripropylene glycol diacrylate)
・ DPHA (trade name, manufactured by Daicel Ornex Co., Ltd., dipentaerythritol hexaacrylate)
<Photopolymerization initiator>
IRGACURE 819 (Irq. 819) (trade name, manufactured by BASF, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide)
・ TPO (trade name “IRGACURE TPO”, manufactured by BASF, 2,4,6-trimethylbenzoyldiphenylphosphine oxide)
<Polymerization inhibitor>
MEHQ (trade name “p-methoxyphenol”, manufactured by Kanto Chemical Co., Inc., hydroquinone monomethyl ether)
<Slip agent>
BYK-UV3500 (trade name, manufactured by BYK Additives & Instruments, polyether-modified polydimethylsiloxane having an acrylic group)
<Color material>
・ Carbon black (trade name “MA-100”, manufactured by Mitsubishi Chemical Corporation)
-Titanium oxide pigment (NanoTek (R) Slurry, manufactured by CI Kasei Co., Ltd., average particle size 250 nm)
(The values in the table are the pigment solid content in the ink)
<Pigment dispersant>
・ Sol Sparse 32000 (made by Lubrizol)

4.2. Evaluation test 4.2.1. Recorded material creation method Recorded materials were created according to the following methods 1 to 4. The method in each example is shown in Table 2.

Method 1:
A modified machine of a printer (SC-S70650) manufactured by Seiko Epson Corporation was used. On the carriage, two heads (first head 11 and second head 12) staggered as shown in FIG. 5 and light sources on both sides (first light source 21 and second light source 22) were provided.

  One head has two nozzle rows, and the nozzle density of each nozzle row is 360 dpi. The nozzles of the two nozzle rows of one head are not overlapped in the sub-scanning direction when projected from the main scanning direction, and the nozzles of the other nozzle rows are located between the nozzles of one nozzle row. The nozzle density was 720 dpi across the two nozzle rows of one head located. In addition, the two heads are arranged side by side in the sub-scanning direction so that the nozzles are arranged at equal intervals in the sub-scanning direction, and the nozzle spacing is maintained at the joint of the heads in the sub-scanning direction. The distance between the rows in the main scanning direction MS of the two nozzle rows in one head is about 1 mm. In the experiment, the distance between the first light source and the first head can be changed by moving the distance between the light source on the left side (first light source 21) in FIG. .

  On the other hand, the position of the end of the light emitting portion of the right light source (first light source 22) in FIG. 5 is a position that is 127 mm away from the nozzle row on the side near the second light source 22 of the first head 11 in the main scanning direction. (W1 = 127 mm in the figure). The time until irradiation in the main scanning in the right direction is 250 ms.

In Method 1, two heads were used, but the composition was set to be discharged from only one nozzle row (nozzle density 360 dpi) of the two nozzle rows of one head. The light source was an LED having a peak wavelength of 395 nm and a peak intensity as shown in Table 2. The irradiation energy by one light source in one scan in the main scanning direction (one pass) was set to be about 100 mJ / cm ² . Therefore, in an example where the irradiation intensity is low, the irradiation energy is reduced.

  The moving speed of the carriage in main scanning during recording was set to 508 mm / s.

  Next, main scanning and sub-scanning are alternately performed to form one dot row dot in the main scanning direction MS in two main scans, and one dot row dot in the sub-scanning direction SS in two sub-scans. Was formed so that the recording resolution was 720 dpi × 720 dpi. The moving distance of the recording medium during the sub-scanning is approximately half the length of the first head 11 in the sub-scanning direction SS (differing by a distance of 1/720 inch). A group of dots was formed. The mass of the composition per dot was set to about 10 ng. The ink composition discharged from the upstream second head first and contacted with the recording medium was brought into contact with the ink composition, and then the ink composition was discharged from the downstream first head and adhered to the recording medium. As the recording medium, a vinyl chloride film “5829R” manufactured by mactac was used.

A post-cure light source (not shown) is also provided downstream of the head on the carriage in the sub-scanning direction SS (LED, peak wavelength and peak intensity are the same as the horizontal light source), and ink discharged from the most downstream nozzle (total Even for the ink with the lowest irradiation energy), the total irradiation energy was set to be equal to or higher than the tack-free energy of the ink used.

  In addition, the upstream second head 12 fixed the distance from the right light source (second light source 22) to the value shown in Table 3 (W4 in the figure). During recording, both the left and right light sources were always lit while the light source was facing the paper surface.

  This recording method is referred to as method 1, and method 1 is used as examples 1 to 4 by changing the conditions for each example. In each example, the position of the end of the light emitting unit of the left light source (first light source 21) in FIG. 5 is represented in the main scanning direction as the distance from the nozzle row on the side closer to the first light source 21 of the first head 11. The position of the first light source was changed to be the position described in 2 (W2 in the figure). As a result, the time difference between the forward and return irradiations (the difference between the first time and the second time) was the value shown in Table 2. Table 2 also shows the difference between the distance to each light source and the time to irradiation for the second head.

Method 2:
Only the downstream head (first head 11) was used, and the two nozzle rows of one head were also used. The nozzle density is substantially 720 dpi. Thus, 720 dpi × 720 dpi dots were formed in one pass in the main scanning direction MS, and all dots within the range of the nozzle array distance were formed in one pass. The moving distance of the recording medium in the sub-scanning direction SS is the length of the head in the sub-scanning direction SS. In the method 2, since recording is performed using only the downstream head without using the upstream head, it is not possible to increase the recording color or increase the recording speed or the image quality using a plurality of heads.

Method 3:
In method 2, two nozzle rows of the upstream head (second head 12) are filled with the composition w1 (see Table 1), the upstream head (nozzle density is substantially 720 dpi and one pass, and the recording resolution is 720 dpi × 720 dpi, A pattern was recorded at a composition amount of about 10 ng per dot), and after sub-scanning, it was superimposed on the pattern and recorded by the downstream head (first head 11) in the same manner as in method 2. The moving distance of the recording medium in the sub-scanning direction SS is the same as that in method 2.

Method 4:
The upstream head (second head 12) and the downstream head (first head 11) are linearly arranged in the sub-scanning direction SS (when viewed from the main scanning direction MS, the two heads do not overlap in the sub-scanning direction). .) That is, the position of the upstream head is shifted upward so that the upstream head does not collide with the downstream head, and the distance between the end nozzle of the downstream head and the end nozzle of the upstream head is the distance of one head. In other words, the first head 11 and the second head 12 are not displaced in the main scanning direction MS. In this method, since both the left and right heads can be positioned in the middle of the two light sources in the main scanning direction, the time difference between the left and right (the difference between the first time and the second time) is zero for the two heads. However, it is necessary to increase the length of the carriage in the vertical direction, which is not preferable because the apparatus becomes large. The heads of the head group were not asymmetrical in the left-right direction but symmetrical.

Method 5:
The separation distance between the upstream head (second head 12) and the right light source (second light source 22) was set to be half that of Method 1. The time difference between the left and right upstream heads (difference between the third time and the fourth time) was larger than that in Method 1.

  In methods 2 to 5, the position of the right light source was changed in the same manner as in examples 2 to 4 of method 1, and the time difference until the left and right irradiation of the first head was changed as shown in Table 3.

  The test pattern was recorded by the above recording method to evaluate the recorded matter. In method 3, the pattern portion of black ink recorded by the first head was used for evaluation.

4.2.2. Evaluation of recorded material <Tack-free test>
A recording medium coated with ink at a coating amount of 10 mg / cm ² is irradiated with an LED (peak wavelength 395 nm, peak intensity 600 mW / cm ² ), and the irradiation energy necessary to reach tack-free is evaluated. It described in Table 1. Whether or not tack-free was reached was determined with a cotton swab (manufactured by Johnson & Johnson Co., Ltd.) with a weight of 100 g and a state where the swab was not soiled and scratched on the recorded portion when rubbed once. The peak intensity was measured using an ultraviolet intensity meter UM-10 and a light receiving unit UM-400 (both manufactured by Konica Minolta Sensing).

<Line width>
Under the conditions of the recording test, the dot amount (line pattern) extending in the main scanning direction with a dot density of 720 dpi was printed with the composition amount per dot being 10 ng. However, printing with only scanning in the right direction and printing with scanning only in the left direction were performed. Two line patterns in the right direction and the left direction were observed with a microscope, and the line width was measured to evaluate the difference between the line widths. The line width was defined as the average value of the line widths measured at 10 points at random in the line. A line width difference of less than 3% was a good level, and 3% or more was a bad level.

<Glossy banding>
Under the conditions of the recording test, the resolution is 720 dpi × 720 dpi and the composition amount per dot is 1.
A 0 mg solid pattern was recorded. The solid pattern is a pattern including a raster line A recorded by scanning in the right direction and a raster line B recorded by scanning in the left direction. A raster line is one dot row extending in the main scanning direction.

  The recorded matter was visually observed from an oblique direction, the reflected light of the fluorescent lamp was observed, evaluated according to the following criteria, and listed in Table 3.

○: Difference in glossiness in the sub-scanning direction (gloss banding) is not observed Δ: Gloss banding is slightly observed ×: Gloss banding is conspicuous.

<Image quality>
The presence or absence of color blurring inside the pattern and the appearance of color unevenness (bleed) was visually observed, evaluated according to the following criteria, and listed in Table 3.
○: No bleed △: Slightly bleed ×: Many bleed

4.3. Evaluation Results Table 3 shows that if the difference between the forward irradiation time and the backward irradiation time (difference between the first time and the second time) is 100 ms or less, the line width difference and the reduction in gloss banding are excellent. In Examples 1 to 4, the difference between the forward and backward irradiation times of the second head is 120 ms or more, and the time difference of the second head is larger in Example 1 than in Example 4, so that the second head is not the second head. It was found that the time difference of one head affects the line width difference and gloss banding.

  Moreover, when Example 8-10 was seen, when the composition which does not contain the vinyl ether group containing (meth) acrylic acid ester shown by general formula (I) was used, it turned out that the influence of a time difference is reduced. However, the image quality deteriorated due to low curability.

  When Example 11-13 was seen, even when the illumination intensity of irradiation was small, it turned out that the influence of a time difference is reduced. Image quality tended to be worse.

  From the comparison between Examples 14 to 16 and Examples 2 to 4, and further from the comparison between Examples 14 to 16 and Examples 17 to 19, the dots hit by the upstream head before the dots hit by the downstream head and hit by the upstream head When the dots are hit by the downstream head in contact with the surface, the influence of the time difference tends to increase, and it has been found that the method according to the present invention is particularly useful.

  Examples 20 to 22 and Examples 23 to 25 differ from Example 2 to 4 in the time difference until irradiation of the second head, but the evaluation results of line width and gloss banding do not change. It was also found that the difference in time until irradiation of the first head affected the line width difference and gloss banding.

  Further, although not shown in the table, further confirmation was made with respect to Examples 8 to 10. When the composition contained phenoxyethyl acrylate, the photopolymerization initiator was excellent in solubility, and acrylic acid 2- (2-vinyl acetate) was obtained. It can be seen that the composition has excellent curability, although not as much as when it contains loxyethoxy) ethyl), whereas the composition contains tripropylene glycol diacrylate or dipentaerythritol hexaacrylate, the composition has excellent curability. I found it inferior.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 10 ... Head group, 11 ... 1st head, 12 ... 2nd head, 21 ... 1st light source, 22 ... 2nd light source, 30 ... Motor, 40 ... Platen, 50 ... Carriage, 52 ... Discharge head, 54 ... Black ink Cartridge, 56 ... color ink cartridge, 60 ... carriage motor, 62 ... traction belt, 64 ... guide rail, 80 ... capping device, 100 ... inkjet device, P ... recording medium

Claims (15)

An inkjet method performed using an inkjet device,
The inkjet device
A group of heads that are scanned in the main scanning direction and whose relative positions change with respect to the recording medium;
A first light source disposed on one side of the head group in the main scanning direction, the relative position of which changes relative to the recording medium as the head group scans, and the main scanning direction of the head group A second light source disposed on the other side of
The head group is positioned first from the downstream side in the direction in which the recording medium is transported and second from the downstream side in the direction in which the recording medium is transported, and is projected in the main scanning direction. A second head arranged to overlap the first head, and
The inkjet method includes:
A first main scanning step of discharging a radiation curable composition onto a recording medium while changing the relative position of the head group to the recording medium toward the one side in the main scanning direction;
A second main scanning step of discharging the radiation curable composition onto the recording medium while changing the relative position of the head group to the recording medium toward the other side in the main scanning direction;
A sub-scanning step of transporting the recording medium in the transport direction in the sub-scanning direction intersecting the main scanning direction,
A first time that is a period from when the nozzle of the first head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the second light source in the first main scanning step;
In the second main scanning step, a difference between a second time which is a period from when the nozzle of the first head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the first light source is An inkjet method that is 100 ms or less. In claim 1,
The inkjet method, wherein the radiation irradiation energy required for the radiation curable composition discharged from the first head to reach tack-free is 500 mJ / cm ² or less. In claim 1 or claim 2,
An inkjet method in which a radiation curable composition ejected from the first head is brought into contact with and adhered to a radiation curable composition ejected from a head other than the first head and adhered to the recording medium. In claim 3,
An inkjet method in which another radiation curable composition having a composition different from that of the radiation curable composition ejected from the first head is ejected from a head other than the first head. In claim 3,
An inkjet method, wherein a radiation curable composition having the same composition as the radiation curable composition discharged from the first head is discharged from a head other than the first head. In any one of Claims 1 thru | or 5,
The radiation curable composition discharged from the first head is a vinyl ether group-containing (meth) acrylic acid ester represented by the following general formula (I), a vinyl ether group-containing compound represented by the general formula (I) ( An inkjet method comprising at least one of monofunctional (meth) acrylates having an aromatic ring skeleton other than (meth) acrylic acid esters.
_{^{CH 2 = CR 1 -COOR 2 -O}} -CH = CH-R 3 ··· (I)
(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a divalent organic residue having 2 to 20 carbon atoms, and R ³ is a monovalent organic atom having 1 to 11 carbon atoms. It is an organic residue.) In any one of Claims 1 thru | or 6,
The ink jet method, wherein a difference between the first time and the second time is 70 ms or less. In any one of Claims 1 thru | or 7,
The difference between the first time and the second time is
In the first main scanning step, a third time period from when the nozzle of the second head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the second light source;
In the second main scanning step, a fourth time period from when the nozzle of the second head is opposed to a predetermined position of the recording medium to when the predetermined position is opposed to the first light source;
An inkjet method that is smaller than the difference. In any one of Claims 1 thru | or 8,
The inkjet method, wherein the first light source and the second light source each have an irradiation peak intensity of 200 mW / cm ² or more. In any one of Claims 1 thru | or 9,
Each of the first light source and the second light source is an inkjet method in which irradiation energy for irradiating the radiation curable composition in one main scanning is 40 mJ / cm ² or more. In any one of Claims 1 thru | or 10,
The inkjet method, wherein each of the first light source and the second light source is an ultraviolet light emitting diode. In any one of Claims 1 thru | or 11,
In the first main scanning step and the second main scanning step, the scanning speed of the head group is 400 mm / s or more, respectively. In any one of Claims 1 thru | or 12,
An inkjet method in which an arrangement of heads used for recording of the head group is asymmetric in a main scanning direction. A head group that is scanned in the main scanning direction and whose relative position changes with respect to the recording medium;
A first light source that is scanned with the head group and disposed on one side of the head group in the main scanning direction, and a second light source that is disposed on the other side of the head group in the main scanning direction. When,
Have
The recording medium is conveyed in the sub-scanning direction intersecting the main scanning direction,
The head group is positioned first from the downstream side in the direction in which the recording medium is transported and second from the downstream side in the direction in which the recording medium is transported, and extends in the main scanning direction. A second head arranged to overlap the first head when projected,
An apparatus for discharging a radiation curable composition from the head group to adhere to the recording medium,
The separation distance in the main scanning direction of the irradiation area of the nozzle of the first head and the first light source, and the separation distance in the main scanning direction of the irradiation area of the nozzle of the first head and the second light source, The difference is 50 mm or less,
An ink jet apparatus, wherein a scanning speed of the head group is 400 mm / s or more. In claim 14,
An ink jet apparatus, wherein a difference in a separation distance in the main scanning direction is 35 mm or less.

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