JP5614529B2 - Inkjet recording apparatus and image forming method - Google Patents

Description

  The present invention relates to an ink jet recording apparatus and an image forming method.

  In recent years, development of photocurable ink compositions that are cured by ultraviolet rays, electron beams, or other light has been promoted. Such a photocurable ink composition is generally composed of a polymerizable compound, a polymerization initiator, a pigment and other additives. In general, when an image is formed using a photocurable ink composition, for example, after being deposited on a recording medium by an ink jet recording apparatus, by irradiating light using an appropriate light source, This is done by curing the composition.

  For example, Patent Document 1 discloses an image forming method for irradiating actinic ray curable ink with actinic rays by two or more irradiation means. In this publication, the degree of curing of the ink by the first actinic ray is set to 6 to 70%, and after all the printing is completed, a sufficient actinic ray is irradiated to completely cure, thereby forming a high-definition image. Is described.

JP 2004-216681 A

  By the way, the photocurable ink composition may be used for recording on a non-absorbing recording medium that does not absorb or hardly absorbs ink such as plastic, glass, and coated paper. In such recording, the photocurable ink composition does not penetrate into the recording medium and is adhered while the shape of the droplet is kept long. In the case where the attached droplets have fluidity, for example, they may merge with adjacent droplets to cause color mixing, or the droplets may get wet and spread, resulting in a reduction in image definition.

  Conversely, if the photocurable ink composition is made to adhere to a non-absorbent recording medium and then irradiated with sufficient light to increase the degree of curing, the fluidity of the droplets will be lost. Therefore, an image is formed with the shape of the droplet as it is attached. In this case, for example, it may not be sufficiently wet and spread, the line width may be insufficient, and the glossiness and texture of the image may deteriorate.

  As described above, it has been relatively difficult to form an image using a photocurable ink composition on a non-absorbing recording medium. For example, in the method described in Patent Document 1 described above, in which the degree of curing is simply 6 to 70% before the ink is completely cured, the fluidity of the droplets is reduced, resulting in higher image definition. Contrary to this, there is a concern that the fluidity is insufficient, the line width is insufficient, and the gloss and texture are not necessarily good.

  One of the objects according to some embodiments of the present invention is that a photocurable ink composition can be used to form an image on a recording medium with little color mixing and good definition and gloss. An inkjet recording apparatus and an image forming method using the apparatus are provided.

  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.

[Application Example 1]
One aspect of the ink jet recording apparatus according to the present invention is:
A head that is moved in the first direction and discharges the droplets of the photocurable ink composition from the nozzle holes to attach the droplets to the recording medium;
A light source that is moved together with the head, is disposed on both ends of the head in the first direction, and irradiates the droplets attached to the recording medium;
With
The light source has a protruding portion arranged to protrude to one side in the second direction rather than the nozzle hole located at one end in the second direction intersecting the first direction,
After the head is moved, the recording medium is moved to one side in the second direction by a unit distance, and then the head is moved in the direction opposite to the first direction. .

  According to the ink jet recording apparatus of this application example, the photocurable ink composition can be pre-cured by providing the light sources at both ends in the scanning direction of the head. Furthermore, according to the ink jet recording apparatus of this application example, since the light source has the protruding portion extending in the second direction, the preliminary curing can be performed twice by the protruding portion. Therefore, it is possible to easily control the color mixture, definition and gloss of the image formed on the recording medium. Thereby, for example, an image with little color mixing and good definition and gloss can be formed on a recording medium using a photocurable ink composition.

[Application Example 2]
In application example 1,
The size of the protruding portion in the second direction can be greater than the unit distance of the recording medium in the second direction.

  According to the ink jet recording apparatus of this application example, it is possible to preliminarily cure the droplets more reliably by the light generated from the protruding portion of the light source.

[Application Example 3]
In application example 1 or application example 2,
The light source may be a light emitting element having an emission wavelength of 365 nm or more and 410 nm or less.

  According to the ink jet recording apparatus of this application example, since the light source is reduced in size and weight, for example, the degree of freedom in arranging them can be increased.

[Application Example 4]
One aspect of the image forming method according to the present invention is:
An image forming method for forming an image on the recording medium with a photocurable ink composition using the ink jet recording apparatus described in any one of Application Examples 1 to 3.
After the photocurable ink composition is attached to the recording medium, the photocurable ink composition is cured to a curing rate of 10% or more and less than 20% by the first light irradiation of the light source, and the second light irradiation of the light source. Is cured to a curing rate of 20% or more and less than 40%.

  According to the image forming method of this application example, at least two preliminary curings are performed before the photocurable ink composition is fully cured, and the curing rate of the first preliminary curing is 10% or more and less than 20%. Then, light is irradiated from the light source so that the curing rate of the second preliminary curing is 20% or more and less than 40%. Thereby, it is possible to form an image with good definition and gloss while suppressing color mixing of the image formed by the photocurable ink composition.

[Application Example 5]
In application example 4,
The time interval between the first light irradiation of the light source and the second light irradiation of the light source may be 1 second or more and 10 seconds or less.

  According to the image forming method of this application example, it is possible to form an image with high definition and glossiness at high speed while suppressing color mixing of the image formed by the photocurable ink composition.

1 is a perspective view schematically showing an ink jet recording apparatus according to an embodiment. The figure which shows typically the side surface of the inkjet recording head and light source of embodiment. The figure which shows typically the lower surface of the inkjet recording head and light source of embodiment.

  Hereinafter, embodiments of the present invention will be described. In addition, the following embodiment demonstrates an example of this invention. Therefore, this invention is not limited to the following embodiment, The various modifications implemented in the range which does not change a summary are also included. Note that not all of the configurations described in the following embodiments are indispensable constituent requirements of the present invention.

1. Inkjet Recording Apparatus FIG. 1 is a perspective view schematically showing an inkjet recording apparatus 100 that is an embodiment of an inkjet recording apparatus according to the present invention. FIG. 2 is a diagram schematically showing the side surfaces of the head 10 and the light source 20 of the present embodiment. FIG. 3 is a diagram schematically showing the lower surfaces of the head 10 and the light source 20 of the present embodiment.

  The ink jet recording apparatus 100 according to this embodiment includes an ink jet recording head 10 and a light source 20.

1.1. Inkjet recording head The inkjet recording head 10 according to the present embodiment is moved in the first direction and ejects droplets of a photocurable ink composition from nozzle holes to attach the droplets to a recording medium. it can. In the present specification, the ink jet recording head 10 may be simply referred to as the head 10.

  The head 10 is not particularly limited as long as the droplets of the photocurable ink composition can be ejected from the nozzle holes 12 to adhere the droplets to the recording medium P, and any system may be used. As a recording method of the head 10, for example, a strong electric field is applied between the nozzle and the acceleration electrode placed in front of the nozzle, the ink is continuously ejected in the form of droplets from the nozzle, and the ink droplets are between the deflection electrodes. A method in which a print information signal is applied to the polarizing electrode for recording during flight, or a method in which ink droplets are ejected in accordance with the print information signal without being deflected (electrostatic suction method). Pressure is applied to the ink liquid with a small pump. , A method of forcibly ejecting ink droplets by mechanically vibrating the nozzle with a crystal resonator, etc., a method of simultaneously ejecting and recording ink droplets by simultaneously applying pressure and a printing information signal to the ink liquid with a piezoelectric element ( Piezo method), a method in which ink liquid is heated and foamed with a microelectrode in accordance with a print information signal, and ink droplets are ejected and recorded (thermal jet method).

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

  Any of the above-described ink jet recording heads can be used as the head 10 of the present embodiment, but the longitudinal mode method can relatively increase the discharge force of the photocurable ink 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, in the case of using a thin-film ink jet recording head, since it has a relatively small and lightweight configuration, it can operate at high speed and can form a high-definition and high-quality image at high speed.

  As the recording medium P that can be used in the ink jet recording apparatus 100 of the present embodiment, when a droplet of the photocurable ink composition is attached, the light for curing the droplet reaches the droplet. There is no particular limitation as long as it is possible. The recording medium P preferably has a printing surface that does not absorb or hardly absorbs ink droplets. 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 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. .

  When the head 10 is moved in the first direction, the position of the head 10 is moved with respect to the recording medium P, and the positional relationship between the two changes. The ink jet recording apparatus 100 of the present embodiment is a serial type ink jet recording apparatus as shown in FIG. 1, and the head 10 moves along the scanning direction MS in the figure by the operation of the carriage 50. Thereby, the photocurable ink composition can be attached to different positions on the recording medium P. The speed at which the head 10 moves with respect to the recording medium P is not particularly limited, but may be, for example, 1 m / min or more and 50 m / min or less.

  The nozzle hole 12 is formed on the surface of the head 10 that faces the recording medium P. The head 10 can eject droplets of the photocurable ink composition through the nozzle holes 12. The number and arrangement of the nozzle holes 12 are not particularly limited. As shown in FIG. 3, in the head 10 of the present embodiment, the nozzle holes 12 are along a direction (second direction: scanning direction SS) perpendicular to the moving direction of the carriage 50 (first direction: scanning direction MS). 8 rows are formed in parallel along the scanning direction MS of the carriage 50.

1.2. Light Source The ink jet recording apparatus 100 according to this embodiment includes a first light source 20.

  The light source 20 is moved in the first direction with respect to the recording medium P together with the head 10 described above. Since the content of the operation of the light source 20 is the same as the content of the reciprocating operation of the head 10 described above, description thereof is omitted.

  The light source 20 moves with the above-described head 10 and is disposed on both ends of the head 10 in the scanning direction MS. Further, the light source 20 has a protruding portion 20A.

  The size of the light source 20 in the scanning direction MS (first direction) and the distance between the light source 20 and the recording medium P are arbitrarily set in consideration of the intensity of light to be irradiated and the period of irradiation. Can do.

  Examples of the light generated from the light source 20 include electromagnetic waves such as 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, and X-rays. It is done. The light generation means of the light source 20 is not particularly limited. Specific examples of the light source 20 include, for example, metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, H lamps, D lamps, and V lamps (available from Fusion System, etc.) ) And the like are guided to the first light source 21 by a light guide, an optical fiber, or the like. Moreover, as a specific aspect of the other light source 20, 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 generating means of the light source 20 is such a light emitting element, for example, the emission wavelength can be 365 nm or more and 410 nm or less. Selecting such a wavelength facilitates selection of the photopolymerization initiator in the photocurable ink composition. When a light emitting element is selected as the light generating means of the light source 20, the light source 20 can be reduced in size and weight, and the degree of freedom in the arrangement of the light source 20 can be increased. For example, in the example of FIG. 3, the light source 20 has a configuration in which a plurality of ultraviolet light emitting diodes (ultraviolet LEDs) (symbol D) are arranged along the row of nozzle holes 12.

  The light source 20 can irradiate the droplets of the photocurable ink composition attached to the recording medium P with light. The light source 20 may continue to generate light, or may blink or increase / decrease the light.

  One of the functions of the light source 20 is to perform a curing reaction of the droplets of the photocurable ink composition attached to the recording medium P. If the recording medium P is non-absorbing, the droplets of the photocurable ink composition may spread unnecessarily on the recording medium P or may merge with other droplets if the recording medium P is uncured. May mix more colors than necessary. After the droplets are attached, a part of the photocurable ink composition constituting the droplets is cured by irradiating light from the light source 20 that moves together with the head 10 at an early stage. It is possible to suppress spreading more than necessary and mixing with other droplets and mixing colors 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 light source 20 is to pin the droplets of the photocurable ink composition.

  The protruding portion 20A protrudes to one side in the second direction from the nozzle hole 12 of the head 10 located at one end in the second direction (scanning direction SS) intersecting the first direction (scanning direction MS). Be placed. In the example shown in FIG. 3, the protruding portion 20 </ b> A protrudes in the feeding direction of the recording medium P (in the drawing, the tip side of the arrow in the scanning direction SS). One of the functions of the protruding portion 20A is to pin the droplets attached to the recording medium P. For details of this function, “1.4. Operation of Inkjet Recording Device” has been described. This will be described in detail later.

1.3. Other configurations 1.3.1. Auxiliary Light Source The inkjet recording apparatus 100 may include an auxiliary light source in addition to the light source 20 as necessary. As an example of such an auxiliary light source, one that moves together with the above-described head 10 and is arranged at one end of the head 10 in the scanning direction SS of the recording medium P can be cited.

  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 light source 20. For this reason, the recording medium P is provided with respect to the head 10 in the moving direction SS side (that is, on the side farther from the protrusion 10A of the light source 20 than the head 10). In other words, the auxiliary light source is the downstream side in the scanning direction SS of the recording medium P (the side on which the light of the auxiliary light source can be irradiated after the photocurable ink composition adheres to the recording medium P: the tip side of the arrow SS in the figure) ) At one end.

  The light generated from the auxiliary light source is the same as that of the light source 20 described above. The auxiliary light source may be different from the light source 20 in type and wavelength. The auxiliary light source may continue to generate light, or may blink or increase or decrease the light. The size of the auxiliary light source in the movement direction (scanning direction SS) of the recording medium P is preferably larger than the distance that is a unit of movement of the recording medium P when the inkjet recording apparatus 100 is operated. In this way, the light of the auxiliary light source can be reliably irradiated onto the droplets of the photocurable ink composition. Further, the size of the auxiliary light source in the moving direction (scanning direction MS) is not limited, and can be designed according to the required light amount, the size of the housing of the apparatus, and the like.

  In the case where an auxiliary light source is provided, the photocurable ink composition droplets are subjected to pinning twice or more by the light from the light source 20, and then the photocurable ink composition is irradiated by the light from the auxiliary light source. Can be sufficiently cured (main curing).

  When the auxiliary light source is provided in the ink jet recording apparatus 100, the light from the auxiliary light source reaches the droplets by the scanning of the head 10 and the scanning of the recording medium P. Accordingly, the droplets are ejected from the head 10 and adhere to the recording medium P, and are subjected to at least two pinnings by the light of the light source 20, and then the recording medium P moves in the scanning direction SS to move the head 10 (carriage). 50) moves in the scanning direction MS and reaches the position of the droplet, the light from the auxiliary light source is irradiated. Although depending on the feed amount (movement distance) of the recording medium P in the scanning direction SS, it is possible to adopt a mode in which the light of the auxiliary light source is irradiated a plurality of times to the position of the droplet. In such a case, the light from the auxiliary light source is intermittently irradiated a plurality of times to the droplets after pinning.

  In the case where an auxiliary light source is provided in the inkjet recording apparatus 100 of the present embodiment, the light of the auxiliary light source can be intermittently applied to the droplets of the photocurable ink composition after being pinned. Accordingly, the progress of the curing reaction of the droplets after pinning can be made more gradual, and for example, effects such as the dot surface becoming closer to smoothness and the shrinkage due to curing can be reduced.

  When the auxiliary light source is provided, the degree of curing after irradiation of the light of the auxiliary light source is preferably, for example, 85% or more and 100% or less in the total of the curing rate combined with the light of the light source 20. If the degree of curing by the auxiliary light source is 85% or more in terms of conversion, sufficient curing is achieved, but more preferably 90% or more. The degree of the main curing by the auxiliary light source includes the light amount of the auxiliary light source, increase / decrease in the light amount, blinking, size in the scanning direction, distance from the recording medium P, and photopolymerization initiator in the photocurable ink composition. The above range can be set by adjusting at least one of the amount of color and the type of color material.

  Note that the present embodiment includes a mode in which droplets can be fully cured only by the light source 20 without having an auxiliary light source, but even in that case, there is no problem in providing the auxiliary light source, and higher curing is achieved. An auxiliary light source may be provided to achieve the rate.

1.3.2. Other Configurations The ink jet recording apparatus 100 according to the present embodiment can have the following configurations.

  In the ink jet recording apparatus 100 exemplified in the present embodiment, as described above, the head 10 is a serial head for full color printing that ejects ink of three or more colors, and includes a large number of nozzle holes 12 for each color. It has been. In addition to the head 10, a plurality of cartridges 52 as ink containers containing various photocurable ink compositions supplied to the head 10 are mounted on the carriage 50 on which the head 10 is mounted. The ink stored in each cartridge 52 is a photocurable ink composition to be described later. The photocurable ink composition ejected by the head 10 may be one color or two or more colors.

  Further, the ink jet recording apparatus 100 shown in FIG. 1 includes a motor 30 that sends the recording medium P in the scanning direction SS, a platen 40, a carriage 50 on which the head 10 is mounted, and a carriage motor that moves the carriage 50 in the scanning direction MS. 60.

  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 10 is mounted on the carriage 50, and moves in the scanning direction MS as the carriage 50 moves in the scanning direction MS. Therefore, the movement of the head 10 by the carriage 50 and the movement of the recording medium P by the platen 40 can be performed independently.

1.4. Operation of Inkjet Recording Device In the inkjet recording device 100 of this embodiment, the head 10 and the recording medium P can operate as follows.

  As described above, the head 10 and the light source 20 are mounted on the carriage 50 and moved along the first direction (scanning direction MS). On the other hand, the recording medium P is moved to one side (scanning direction SS) in the second direction intersecting the first direction.

  In the ink jet recording apparatus 100 of the present embodiment, the recording medium P is not moved while the head 10 and the light source 20 are moving. Further, in a state where the recording medium P does not move, the head 10 and the light source 20 may move only in one direction in the first direction, or may reciprocate by changing the direction of movement.

  Next, in the ink jet recording apparatus 100 of the present embodiment, the recording medium P is moved in one direction in the second direction intersecting the first direction while the movement of the head 10 and the light source 20 is stopped, and recording is performed. After the movement of the medium P in the second direction stops, the head 10 and the light source 20 are moved again along the first direction.

  The ink jet recording apparatus 100 of the present embodiment forms an image on the recording medium P by moving the head 10, the light source 20, and the recording medium P in such a manner.

  Here, in any case, the droplets ejected from the head 10 are subjected to the first pinning by the light source 20 arranged at the rear of the movement direction by the one movement of the carriage 50. In the inkjet recording apparatus 100 of the present embodiment, the light source 20 is disposed on both ends of the head 10 in the first direction. Thereby, even if the photocurable ink composition is ejected while the head 10 moves in any direction of the first direction, the first pinning by the light source 20 can be performed.

  After that, when the recording medium P is not moved, the carriage 50 changes the direction of movement and passes the droplets, so that the light source 20 disposed in front of the moving direction (used for the first pinning). The second light source 20) receives the second pinning, and the light source 20 arranged rearward in the moving direction receives the third pinning.

  In the ink jet recording apparatus 100 according to 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, and the third pinning can be performed by the light source 20 arranged behind the moving direction. That is, in the ink jet recording apparatus 100 of the present embodiment, since the light source 20 has the protruding portion 20A extending in the moving direction of the recording medium P, the moving distance of the recording medium P is the scanning direction SS ( As long as the length is smaller than the length in the second direction, the second and third pinning groups can be reliably performed at least once on the droplet.

  The moving distance of the recording medium P when moved after the movement of the head 10 may vary depending on the printing method of the ink jet recording 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 second direction in the arrangement of the nozzle holes 12. 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) when the recording medium P is moved once may differ for each printing method.

  In the inkjet recording apparatus 100 of the present embodiment, it is more preferable that the size of the protruding portion 20A of the light source 20 in the second direction is larger than the unit distance described above. If the size of the protruding portion 20A is larger than the unit distance, the second pinning can be surely performed for the droplets discharged from any nozzle hole 12. Further, if the size of the protruding portion 20A of the light source 20 in the second direction is equal to or larger than the distance between both ends in the second direction of the arrangement of the nozzle holes 12, the second direction of the arrangement of the nozzle holes 12 will be described. Even in a printing method in which the distance between both ends is a unit distance, the second and third pinning can be reliably performed.

  If the unit distance is a printing method that is smaller than the distance between both ends in the second direction of the arrangement of the nozzle holes 12 of the nozzle holes 12, the droplets attached to the recording medium P are further transferred four times. You can receive the above pinning. Depending on the size of the unit distance, the distance between both ends in the second direction of the arrangement of the nozzle holes 12, and the length in the second direction of the protrusion 20A, the droplet is constituted by four or more pinnings. The curing rate of the photocurable ink composition can be increased to 85% or more. In this way, the auxiliary light source exemplified as the configuration included as necessary, other curing lamps, and the like can be eliminated.

1.5. Embodiment of Pinning by Light Source The degree of pinning by the light source 20 is expressed by the conversion rate (curing rate) of the photocurable ink composition in the droplet, that is, the ratio of the cured composition to the composition of the entire droplet. For example, when expressed in terms of conversion rate (curing rate), it is preferably 10% or more and less than 20% in the first pinning. The first pinning by the light source 20 is performed in order to suppress dripping and spreading of the photocurable ink composition droplets and significant color mixing, and does not completely suppress these phenomena. .

  The degree of the first pinning by the light source 20 is more preferably 10% or more and less than 18%, and further preferably 10% or more and less than 15% in terms of conversion rate in terms of forming large dots quickly.

  The degree of the second pinning by the light source 20 is preferably 20% or more and less than 40% when expressed in terms of curing rate. Similar to the first pinning, the second pinning by the light source 20 is performed in order to prevent the droplets of the photocurable ink composition from spreading significantly wet and remarkably mixing. It is also possible to completely suppress this phenomenon.

  The degree of pinning by the light source 20 depends on the light amount of the light source 20, the increase or decrease of the light amount, blinking, the size in the scanning direction, the distance from the recording medium P, and the photopolymerization in the photocurable ink composition. The above range can be set by adjusting at least one of the amount of the initiator and the type of the color material.

  The time interval between the first pinning and the second pinning is more preferably 1 second or more and 10 seconds or less. In the ink jet recording apparatus 100 of the present embodiment, for example, the time interval between the first pinning and the second pinning is changed by changing the moving speed of the carriage 50 or adjusting the waiting time of the carriage 50. Different printing modes can be provided. When the inkjet recording apparatus 100 according to the present embodiment includes such a printing mode, for example, it is possible to balance the wetting and spreading of droplets and the gloss of an image.

1.6. Photocurable ink composition Examples of the photocurable ink composition ejected by the head 10 of the ink jet recording apparatus 100 of the present embodiment include those containing at least a polymerizable compound and a photopolymerization initiator. It is done.

1.6.1. Polymerizable compound The photocurable ink composition of this 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 photocurable ink 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.

  Among these, as the polymerizable compound of the present embodiment, acrylic acid esters having an acryloyl group, an N-vinyl compound, and acryloylmorpholine are preferable because of excellent photopolymerizability.

  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.

  Examples of the photocationically polymerizable group include an epoxy ring, an oxetane ring, an oxolane ring, a dioxolane ring, and a vinyl ether group. Regarding the epoxy ring, aromatic and alicyclic systems are preferable from the viewpoint of excellent curing speed, and alicyclic epoxy rings are particularly 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 photocurable ink composition is suitably 5% by mass or more and 95% by mass or less, and preferably 7% by mass or more and 90% by mass with respect to the entire photocurable ink composition. Hereinafter, it is more preferably in the range of 10% by mass to 80% by mass.

1.6.2. Photopolymerization initiator The photocurable ink composition of this embodiment contains a photopolymerization initiator. 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 photo radical polymerization initiators 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 aryliodonium salt derivative, RP-2074 made by Rhodia is mentioned. As the allene-ion complex derivative, Ciba Geigy is made. Irgacure 261 and the like.

  The content of the polymerization initiator contained in the photocurable ink 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 with respect to the entire photocurable ink composition. More preferably, it is contained below. By setting it as the said range, there exists an effect of hold | maintaining sclerosis | hardenability, without reducing the mechanical strength of the photocurable ink 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 photocurable ink 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 amount of light from the first light source 21 and the second light source 22, but within this range the amount of 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.

1.6.3. Other components 1.6.3.1. Colorant and Dispersant The photocurable ink 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 normal ink can be used without any particular limitation.

  The ink composition of the present embodiment may further include a color 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 ink 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 ink composition preferably contains 1 to 10% by mass of the color material, and more preferably 1 to 5% by mass.

  As the inorganic pigment, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, iron oxide, and titanium oxide 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.

  More specifically, as an inorganic pigment used for black, the following carbon black, for example, No. manufactured by Mitsubishi Chemical Corporation is used. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, or No2200B, etc .; Columbia-made Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc .; 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc .; or Color Black FW1, Color Black FW2, Bck, Col Black FW2, Cck W200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, or Special Black 4 and the like.

  The yellow organic pigments include CIPigment Yellow 1, CIPigment Yellow 2, CIPigment Yellow 3, CIPigment Yellow 4, CIPigment Yellow 5, CIPigment Yellow 6, CIPigment Yellow 7, CIPigment Yellow 10, CIPigment Yellow 11 , CIPigment Yellow 12, CIPigment Yellow 13, CIPigment Yellow 14, CIPigment Yellow 16, CIPigment Yellow 17, CIPigment Yellow 24, CIPigment Yellow 34, CIPigment Yellow 35, CIPigment Yellow 37, CIPigment Yellow 53 , CIPigment Yellow 55, CIPigment Yellow 65, CIPigment Yellow 73, CIPigment Yellow 74, CIPigment Yellow 75, CIPigment Yellow 81, CIPigment Yellow 83, CIPigment Yellow 93, CIPigment Yellow 94, CIPigment Yellow 95 , CIPigment Yellow 97, CIPigment Yellow 98, CIPigment Yellow 99, CIPigment Yellow 108, CIPigment Yellow 109, C.I.Pigment Yellow 110, CIPigment Yellow 113, CIPigment Yellow 114, CIPigment Yellow 117, CIPigment Yellow 120, CIPigment Yellow 124, CIPigment Yellow 128, CIPigment Yellow 129, CIPigment Yellow 133, CIPigment Yellow 138, CIPigment Yellow 139, CIPigment Yellow 147, CIPigment Yellow 151, CIPigment Yellow 153, CIPigment Yellow 154, CIPigment Yellow 167, CIPigment Yellow 172, CIPigment Yellow 180, and the like.

  As magenta organic pigments, CIPigment Red 1, CIPigment Red 2, CIPigment Red 3, CIPigment Red 4, CIPigment Red 5, CIPigment Red 6, CIPigment Red 7, CIPigment Red 8, CIPigment Red 9 , CIPigment Red 10, CIPigment Red 11, CIPigment Red 12, CIPigment Red 14, CIPigment Red 15, CIPigment Red 16, CIPigment Red 17, CIPigment Red 18, CIPigment Red 19, CIPigment Red 21 , CIPigment Red 22, CIPigment Red 23, CIPigment Red 30, CIPigment Red 31, CIPigment Red 32, CIPigment Red 37, CIPigment Red 38, CIPigment Red 40, CIPigment Red 41, CIPigment Red 42 , CIPigment Red 48 (Ca), CIPigment Red 48 (Mn), CIPigment Red 57 (Ca), CIPigment Red 57: 1, CIPigment Red 88, CIPigment Red 112, CIPigment Red 114, CIPigment Red 122, CIPigment Red 123, C. I.Pigment Red 144, CIPigment Red 146, CIPigment Red 149, CIPigment Red 150, CIPigment Red 166, CIPigment Red 168, CIPigment Red 170, CIPigment Red 171, CIPigment Red 175, CIPigment Red 176 , CIPigment Red 177, CIPigment Red 178, CIPigment Red 179, CIPigment Red 184, CIPigment Red 185, CIPigment Red 187, CIPigment Red 202, CIPigment Red 209, CIPigment Red 219, CIPigment Red 224 , CIPigment Red 245, or CIPigment Violet 19, CIPigment Violet 23, CIPigment Violet 32, CIPigment Violet 33, CIPigment Violet 36, CIPigment Violet 38, CIPigment Violet 43, CIPigment Violet 50, etc. .

  Examples of cyan organic pigments include CIPigment Blue 1, CIPigment Blue 2, CIPigment Blue 3, CIPigment Blue 15, CIPigment Blue 15: 1, CIPigment Blue 15: 2, CIPigment Blue 15: 3, CIPigment Blue 15:34, CIPigment Blue 15: 4, CIPigment Blue 16, CIPigment Blue 18, CIPigment Blue 22, CIPigment Blue 25, CIPigment Blue 60, CIPigment Blue 65, CIPigment Blue 66, CIVat Blue 4 , CIVat Blue 60 and the like.

  Examples of organic pigments other than magenta, cyan and yellow include CIPigment Green 7, CIPigment Green 10, CIPigment Brawn 3, CIPigment Brawn 5, CIPigment Brawn 25, CIPigment Brawn 26, CIPigment Orange 1 , CIPigment Orange 2, CIPigment Orange 5, CIPigment Orange 7, CIPigment Orange 13, CIPigment Orange 14, CIPigment Orange 15, CIPigment Orange 16, CIPigment Orange 24, CIPigment Orange 34, CIPigment Orange 36 , CIPigment Orange 38, CIPigment Orange 40, CIPigment Orange 43, CIPigment Orange 63, 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 average particle diameter of the core substance is within such a range, the ink for ink jet recording is effective in reliability such as ejection stability and dispersion stability, and can output a high-quality image.

  When the photocurable ink composition of the present embodiment contains a color material, the addition amount of the color material 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. The range is about 15% by mass or less. Further, the degree of pinning of the droplets of the photocurable ink 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 amounts 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.

  Further, when a pigment is contained in the photocurable ink composition, a pigment dispersion obtained by dispersing in a medium with a dispersant or a surfactant can be used. Furthermore, when pigments are contained in the photocurable ink composition, these pigments 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 mixed (EFKA Chemicals Co., Ltd.).

  The content when the dispersing agent is contained in the photocurable ink composition is 5% by mass or more and 200% by mass or less with respect to the content of the coloring material (particularly the pigment) in the photocurable ink composition. The content is preferably 30% by mass or more and 120% by mass or less, and may be appropriately selected depending on the color material to be dispersed.

1.6.3.2. Additives The photo-curable ink composition comprising the photo-radical 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).

  The photocurable ink composition comprising a photoradical polymerizable compound may contain a thermal radical polymerization inhibitor. Thereby, the storage stability of the photocurable ink 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.

  Further, the photocurable ink composition may contain a surfactant. The surfactant is preferably dissolved in a photopolymerizable compound, and a silicone-based surfactant or a fluorine-based surfactant can be used. As the silicone surfactant, polyether-modified polydimethylsiloxane or polyester-modified polydimethylsiloxane can be used. Specific examples of the silicone-based surfactant include BYK-347, BYK-348, BYK-UV3500, 3510, 3530, 3570 (manufactured by Big Chemie Japan Co., Ltd.), UV-3500 (manufactured by Ciba Specialty Chemicals). Can be mentioned. These surfactants can also function as slip agents. A preferable addition amount when a surfactant is blended is 0.5% by mass or more and 4.0% by mass or less in the ink composition.

  Furthermore, an ultraviolet absorber, a leveling agent, etc. can be added to the photocurable ink composition of the present embodiment as necessary.

1.7. Curing of Photocurable Ink Composition The photocurable ink composition of the present embodiment contains at least the polymerizable compound and the polymerization initiator. Therefore, the photocurable ink composition can be cured by irradiating light from the light source 20.

When ultraviolet rays are used as the light of the light source 20, the amount of ultraviolet rays applied to the photocurable ink composition is 10 mJ / cm ² or more, 20,000 mJ / cm ² or less, and preferably 50 mJ / cm ² or more. Irradiation is performed in the range of 15,000 mJ / cm ² or less. If the ultraviolet irradiation amount is finally in the above range, the polymerizable compound can be sufficiently cured.

  In the ink jet recording apparatus 100 of this embodiment, the photocurable ink composition is pinned by the light from the light source 20. The curing rate at the time of pinning can be set such that the amount of light irradiation at this point is 100% when the point at which no further curing reaction of the photocurable ink composition occurs is 100%. If a calibration curve of the curing rate with respect to the light irradiation amount is prepared in advance for the photocurable ink composition to be used, the droplets of the photocurable ink composition have a desired curing rate. The light irradiation amount of the light source 20 can be set. In addition, the conversion rate of a photocurable ink composition can be calculated | required from the change value of the light absorbency in the peak of a specific absorption spectrum, for example using FT-IR (Fourier transform infrared spectrophotometer).

1.6. Effects and the like According to the ink jet recording apparatus 100 of the present embodiment, by providing the light sources 20 disposed on both sides in the first direction of the head 10, at least two preliminary curings are performed on the photocurable ink composition. (Pinning) can be performed. Therefore, it is possible to easily control the color mixture, definition and gloss of the image formed on the recording medium. From this, for example, an image with little color mixing and good definition and gloss can be formed on a recording medium using a photocurable ink composition. In addition, according to the ink jet recording apparatus 100 of the present embodiment, the light source 20 is arranged with the protruding portion 20A, so that the above-described pinning can be performed more than once.

2. Image Forming Method The image forming method of the present embodiment includes discharging the above-described photocurable ink composition using the above-described inkjet recording apparatus 100 and attaching it to a recording medium. In the following, an example of an image forming method in which a dot group is formed by ejecting a photocurable ink composition onto a recording medium P using the inkjet recording apparatus 100 and depositing it on the recording medium P will be described.

  The image forming method of the present embodiment includes a droplet discharge step of discharging a droplet of a photocurable ink composition from the head 10, a first pinning step of irradiating the droplet with light from the light source 20, and the light source 20. A second pinning step of irradiating the droplets with light from the second pinning step.

2.1. Droplet Discharge Step This step is a step in which the photocurable ink composition is discharged as droplets from the head 10 of the ink jet recording apparatus 100 and the droplets are deposited on the recording medium P.

  In the image forming method of the present embodiment, the amount of liquid droplets ejected from one nozzle hole 12 of the head 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. FIG. 2 shows the droplet I attached to the recording medium P by this process.

2.2. Pinning process 2.2.1. First Pinning Step This step is a step of irradiating light droplets attached to the recording medium P with the light source 20. Hereinafter, this process will be described by taking as an example the case where the head 10 moves in the direction of arrow A in the scanning direction MS of the head 10 shown in FIG.

  As a result of the head 10 moving in the direction of arrow A in the drawing, the droplet I attached to the recording medium P in the droplet discharge process moves to a position where light on one side of the light source 20 is irradiated. As a result, the light from the light source 20 is applied to the droplet I. By this step, a curing reaction of the photocurable ink composition constituting the droplet I occurs, and the first pinning of the droplet I is performed. In the present embodiment, since the light sources 20 are provided on both sides of the head 10 in the scanning direction, the same process is performed even if the direction of movement of the head 10 and the recording medium P is opposite to the above example. . The first pinning step can be performed very easily using the above-described inkjet recording apparatus 100.

  The degree to which the droplet I is pinned in the first pinning step is set to be 10% or more and less than 20% as the curing rate of the photocurable ink composition constituting the droplet I. In this way, it is possible to prevent the droplet I from being greatly wetted and spread on the recording medium P, and to prevent the color mixture from being noticeably mixed, and to produce controlled wet spread and color mixing. . The degree of pinning of the droplet I in the first pinning step is more preferably 10% or more and less than 18%, and further preferably 10% or more and less than 155% in terms of curing rate.

2.2.2. Second Pinning Step This step is a step of irradiating the droplets attached to the recording medium P with the light source 20. Hereinafter, this process will be described by taking as an example the case where the head 10 moves in the direction of arrow B of the scanning direction MS of the head 10 shown in FIG.

  The droplet I attached to the recording medium P in the droplet discharge process is generated by the light from the light source 20 when the carriage 50 moves in the direction of arrow A and then returns in the direction of arrow B after the first pinning step. The droplet I is irradiated. By this step, a curing reaction of the photocurable ink composition constituting the droplet I occurs, and the second pinning of the droplet I is performed. In the present embodiment, since the light sources 20 are provided on both sides of the head 10 in the scanning direction, the same process is performed even if the direction of movement of the head 10 and the recording medium P is opposite to the above example. . The second pinning process can be performed very easily using the above-described inkjet recording apparatus 100.

  The degree to which the droplet I is pinned in the second pinning step is 20% or more and less than 40% including the curing rate of the first pinning step as the curing rate of the photocurable ink composition constituting the droplet I. To be. In this way, for example, when the droplet I on the recording medium P has a desired shape, or when there are a plurality of droplets I, their color mixture can be set to a desired level. Further, the degree of pinning in the second pinning step is more preferably 20% or more and less than 35%, and further preferably 20% or more and less than 30% in terms of conversion.

  In the image forming method of the present embodiment, the above-described ink jet recording apparatus 100 is used. Therefore, the light source 20 is provided with the protruding portion 20A, and even when the movement of the recording medium P is included between the first pinning step and the second pinning step, the second pinning step can be performed reliably. .

  The time interval between the first pinning step and the second pinning step is more preferably 1 second or longer and 10 seconds or shorter. In the ink jet recording apparatus 100 of the present embodiment, for example, the time interval between the first pinning and the second pinning is changed by changing the moving speed of the carriage 50 or adjusting the waiting time of the carriage 50. Different printing modes can be provided. Thereby, for example, it is possible to balance the wetting and spreading of the droplets and the gloss of the image.

3. Experimental Examples Hereinafter, the present invention will be specifically described with reference to some experimental examples, but these do not limit the scope of the present invention.

3.1. Photocurable Ink Composition A set of photocurable ink compositions common to each experimental example was prepared.

  As the polymerizable compound, 29.5% by mass of phenoxy acrylate (V # 192: manufactured by Osaka Organic Industry Co., Ltd.), 19.7% by mass of dicyclopentenyloxyethyl acrylate (FA512AS: manufactured by Hitachi Chemical Co., Ltd.), di 9. 15.8% by mass of cyclopentenyl acrylate (FA511AS: manufactured by Hitachi Chemical Co., Ltd.), 9.8% by mass of vinylcaprolactam, dimethylol tricyclodecane diacrylate (EBECRYL IRR214K: manufactured by Daicel Cytec Co., Ltd.) 8% by mass, 5% by mass of IRGACURE 819 (manufactured by Ciba Specialty Chemicals), 4% by mass of DAROCURE TPO (manufactured by Ciba Specialty Chemicals), DETX (manufactured by Nippon Kayaku Co., Ltd.) ) 1% by mass, polymerization As an accelerator, EBECRYL 7100 (manufactured by Daicel Cytec Co., Ltd.) is 3% by mass, as a slip agent, BYK-UV3500 (manufactured by Big Chemie Japan Co., Ltd.) is 0.2% by mass, and as a pigment dispersant, solsperse 36000 (rubrisol Was mixed, dissolved and mixed and stirred with a magnetic stirrer at room temperature and normal pressure for 30 minutes.

  As a set of the photocurable ink composition, as the above pigment, a cyan pigment: a product using IRGALITE BLUE GLVO (manufactured by Ciba Specialty Chemicals), a magenta pigment: a pigment using Pigment Red 122, a yellow pigment: A set using Pigment Yellow 180 and a set using carbon black were used.

  After the photocurable ink composition was obtained, methyl ether hydroquinone (manufactured by Kanto Chemical Co., Inc.) and tert-butyl-p-benzoquinone (manufactured by Ciba Specialty Chemicals) were both used as polymerization inhibitors. An ink set common to each experimental example was prepared by adding 2000 ppm.

3.2. Inkjet recording apparatus The evaluation sample of each experimental example was created using a modified inkjet printer PX-G920 (manufactured by Seiko Epson Corporation) as an inkjet recording apparatus. The above-described photocurable ink composition set was introduced into each color ink cartridge of the printer. As a result of the modification, the light source composed of LEDs having a wavelength of 395 nm is provided on both sides in the scanning direction of the head, and is larger than the unit distance of movement of the recording medium P, as described in the above embodiment. A protrusion having a size in the second direction is provided. In each experimental example, the length of the nozzle holes in the head is 2.54 cm, the nozzle holes are arranged in the direction perpendicular to the moving direction of the head, and the number of nozzles in the nozzle holes is 180. The nozzle density in the nozzle hole array (the number of nozzles per unit distance in the direction orthogonal to the moving direction of the head) is (180 / 2.54) / cm, and the length of the protruding portion in the moving direction of the recording medium Is 10 mm, the unit distance of movement of the recording medium is about 6.35 mm, and the recording density in the moving direction (the number of droplets that can be attached per unit distance in the moving direction of the recording medium) is four times the nozzle density. It was.

3.3. Preparation of sample for evaluation The sample of each experimental example was prepared by using a vinyl chloride sheet cut to A4 size as a recording medium, and setting the light amount of each light source so that the curing rate shown in Table 1 was obtained. did.

  In any sample, the printer is set up in the print mode of the media “PVC General 1” and the print quality “Pretty”, and the line width of one dot of each color and the density of the solid part can be evaluated, and color bleeding The test pattern was able to evaluate (mixed color) and gloss. Moreover, the light quantity of the light source in each experimental example was adjusted as shown in Table 1 according to the light quantity of the LED. Although not shown, the curing rate of the photocurable ink composition is determined by preparing a calibration curve showing the relationship between the curing rate of the cyan photocurable ink composition and the amount of light, and the value is shown in Table 1. did. The scanning speed of the head was 30 m / min. Further, the time interval between the first irradiation step and the second irradiation step is set to the time interval shown in Table 1 by adjusting the time to stop at one end of the recording medium in the carriage movement control. Set.

3.4. Evaluation Method The color bleed, line width, and gloss were evaluated for the obtained samples of each experimental example.

  The color bleed was evaluated by visually observing the test pattern with a loupe or the like. “A” indicates no color bleed, “B” indicates that the test pattern color boundary is unclear, and “C” indicates that color mixing occurs at the test pattern color boundary. It described in Table 1.

  The line width was evaluated by visually observing the test pattern with a loupe or the like. “A” indicates that a sufficient line width is obtained and the solid part is filled with dots, and “B” indicates that the solid part is filled with dots although the line width is narrower than A, but the line width is narrow. Those in which the solid part is not buried are listed in Table 1 as “C”.

  The gloss was evaluated by visually observing the test pattern. Table 1 shows “A” for high gloss, “B” for gloss, and “C” for lack of gloss.

3.5. Evaluation results Table 1 shows that in each experimental example, the color bleed, the line width, and the gloss can be significantly changed by changing the curing rate in the first irradiation and the second irradiation. did. That is, it has been found that if the ink jet recording apparatus used in the experimental example is used, the way in which the droplets of the photocurable ink composition attached to the recording medium spread and the surface shape can be changed in a wide range.

  In addition, it was found that the samples of Experimental Examples 1 to 6 were all good in color bleeding, line width, and gloss. That is, the conversion rate of the photocurable ink composition at the time of the first irradiation is 10% or more and less than 20%, and the conversion rate of the photocurable ink composition at the time of the second irradiation is 20% or more. In a sample with less than 40% and a time interval between the first irradiation and the second irradiation within 10 seconds, all of the color bleed, line width, and gloss are good. found.

  Color bleed was observed in the sample of Experimental Example 7 in which the time interval between the first irradiation and the second irradiation was 15 seconds. In the samples of Experimental Examples 8 to 12, the conversion rate of the photocurable ink composition at the time of the first irradiation is less than 10% or 20% or more, and the photocurable type at the time of the second irradiation. A sample in which the conversion rate of the ink composition was less than 20% or 40% or more, and at least one of color bleed, line width, and gloss was inferior to the samples of Experimental Examples 1 to 6. .

  The embodiments and modified embodiments described above can be arbitrarily combined with a plurality of forms. Thereby, combined embodiment can have an effect which each embodiment has, or a synergistic effect.

  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 achieves the same effect 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 ... Inkjet recording head (head), 12 ... Nozzle hole, 20 ... Light source, 20A ... Projection, 30 ... Motor, 40 ... Platen, 50 ... Carriage, 52 ... Cartridge, 60 ... Carriage motor, 62 ... Traction belt, 64 ... guide rail, 80 ... capping device, 100 ... inkjet recording device, P ... recording medium, I ... droplet, MS, SS ... scanning direction

Claims (7)

A head that is moved in the first direction and discharges the droplets of the photocurable ink composition from the nozzle holes to attach the droplets to the recording medium;
A light source that is moved together with the head, is disposed on both ends of the head in the first direction, and irradiates the droplets attached to the recording medium;
A light source projecting portion arranged to project to one side in the second direction from the nozzle hole located at one end in the second direction intersecting the first direction,
After moving the head, an ink jet recording apparatus is used that moves the recording medium to one side in the second direction by a unit distance and then moves the head in the direction opposite to the first direction. An image forming method for forming an image on the recording medium with a photocurable ink composition,
The light source is an ultraviolet light emitting diode having an emission wavelength of 365 nm to 410 nm,
The photocurable ink composition contains phenoxyethyl acrylate as a polymerizable compound,
The photocurable ink composition contains acylphosphine oxide as a photopolymerization initiator in an amount of 3% by mass or more and 15% by mass or less based on the entire ink composition;
After the photocurable ink composition is attached to the recording medium, the photocurable ink composition is cured to a curing rate of 10% or more and less than 20% by the first light irradiation of the light source, and 20% by the second light irradiation. Cured to a cure rate of 40% or less,
The image forming method, wherein a time interval between the first light irradiation of the light source and the second light irradiation is not less than 1 second and not more than 10 seconds.   The image forming method according to claim 1, wherein a size of the protruding portion in the second direction is larger than the unit distance of the recording medium in the second direction. The final light irradiation used for curing is 50 mJ / cm ² or more and 15,000 mJ / cm
The image forming method according to claim 1 , wherein the image forming method is ² or less. The image forming method according to claim 1, wherein the photocurable ink composition contains a polymerizable compound in an amount of 10% by mass to 95% by mass with respect to the entire ink composition. The photocurable ink composition, a switch Okisanton as a photopolymerization initiator, the sum of said acylphosphine oxide, containing 3 wt% to 15 wt% with respect to the entire ink composition, according to claim 1 The image forming method according to claim 4 . The image forming method according to claim 1, wherein the photocurable ink composition is a non-aqueous ink composition. An ink jet recording apparatus that performs recording by the image forming method according to claim 1 .

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