JP2009285854A - Inkjet recorder and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder and an inkjet recording method, capable of recording quickly a satisfactory image reduced in ink spreading between respective colors and reduced in deterioration of image quality, while reducing the generation of a stripe-like defect even in different kinds of recording media and ink, when carrying out multicolor printing at a high speed by a single path system. <P>SOLUTION: This inkjet recorder 10 is provided with an irradiation energy quantity setting means for setting an irradiation energy quantity of an active energy ray for semi-curing based on the kind of recording medium, the kind of first ink and the kind of second ink. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus and an inkjet recording method, and more particularly to a single-pass inkjet recording apparatus having a semi-curing light source that irradiates active energy rays, and performs multicolor printing using an energy beam curing reaction. The present invention relates to an ink jet recording apparatus and an ink jet recording method.

  In recent years, the ink jet recording method can create images more easily and cheaply than the gravure printing method, and thus has been applied to various printing fields such as special printing such as photography, various printing, marking, and color filters. In particular, in the ink jet recording system, ink jet recording devices that eject and control fine dots, ink with improved color gamut, durability, ejection suitability, etc., ink absorbency, colorant coloring, surface gloss, etc. Combined with specially improved special paper, it is possible to obtain image quality comparable to silver halide photography.

  In general, an ink jet recording apparatus performs image recording by ejecting ink from a line head in which a plurality of ejection openings arranged in a scanning direction orthogonal to the transport direction is formed on a recording medium transported in the transport direction. There are a single-pass method and a scan method in which image recording is performed by moving a recording head mounted on a carriage in the scanning direction and discharging ink from an ejection port of the recording head while the recording head is moving.

  The scanning method is a method that is particularly widely used in home inkjet recording apparatuses and performs drawing by reciprocating the head several times. However, the scanning method is generally low in speed and low in productivity. Therefore, in the field of industrial use, a single-pass method that is high speed and excellent in productivity has recently attracted attention.

  However, as described above, the single-pass method is a method of printing by a single scan (relative movement of the head and the recording medium) and can be printed at high speed and has excellent productivity. However, ink ejected from each nozzle at that time However, streak-like defects after printing greatly affect the image quality due to the influence of conveyance and nozzle accuracy.

  Until now, single-pass printing has been produced by single-color printing, for example, monochrome printing of labels, but as the market expands, more colorful and high-quality multicolor printing is being demanded from the market.

  However, when multi-color printing is performed by inkjet using a single-pass method, ink ejection, subsequent fixing or solidification cannot be performed in time, and thus “bleeding” occurs in which inks of different ink colors are mixed. I understand that. In other words, in order to perform multicolor printing with a single-pass inkjet, the conflicting performance of spreading the droplets to suppress the generation of streaks, but also suppressing the bleeding without spreading the droplets too much to eliminate the streaks It is necessary to devise so that a high-definition image can be printed by controlling the image quality.

  As a conventional technique, Patent Document 1 discloses a dot resolution of a dot when it collides with a receiving layer medium that absorbs ink by a single-pass method in order to suppress ink aggregation, which is one of the causes of streaks. Has been disclosed in which the ink and the diffusion coefficient are defined in a certain relationship to prevent the ink from aggregating, but streaks occur on a substantially non-absorbent recording medium, and this is used for multicolor printing. Bleeding also occurred greatly and was not useful.

  Inkjet recording apparatuses can be classified according to the type of ink. The conventional phase change inkjet method using a solid wax ink at room temperature, the solvent-based inkjet method using an ink mainly composed of a fast-drying organic solvent, and the ultraviolet light exposure. Examples include an ultraviolet curable ink jet method using an ultraviolet curable ink that is cured by irradiation.

  Among these, the ultraviolet curable ink jet method has been attracting attention because it can record on a recording medium having no quick drying property and ink absorbability other than dedicated paper, and has started to be widely used in the single pass method.

  Patent Document 2 discloses a scanning ink jet technique that includes an active energy ray-curable ink and a semi-curing light source that irradiates active energy rays using these advantages. In this technology, an attempt is made to reduce streak-like defects by controlling an appropriate amount of liquid from the recording head based on the distance between the recording head and the semi-curing light source. When the single pass method is combined, it is a problem that bleeding between the inks printed in order cannot be suppressed.

On the other hand, Patent Document 3 newly adds a step of applying an undercoat liquid on a recording medium in advance and then semi-curing the ink when the ink that is cured by irradiation with active energy rays is discharged onto the recording medium. Attempts to reduce ink bleed on a semi-cured primer have been disclosed. However, this method is inferior in productivity because it requires a new step of applying an undercoat liquid. In addition, in the actual market, the undercoat liquid and a wide variety of curable inks are used. However, when the compatibility with the ink is poor, a chemical reaction such as agglomeration also occurs and the prescription of the undercoat liquid needs to be changed. In some cases, bleeding could not be controlled well, and it was not able to withstand actual use including productivity in the market.
JP 2004-114688 A JP 2007-320120 A JP 2008-23980 A

  In an ink jet recording apparatus that uses ink that is cured by irradiation with active energy rays, image formation is performed using a wide variety of recording media and inks.

  Here, especially in a multi-color superimposed image, the characteristics such as the curing characteristics of the first ink on the recording medium and how to ride the second ink superimposed thereon differ depending on the type of the ink and the recording medium. When the types of ink and recording medium are different, the extent of the dots of the second ink changes, and a desired image may not be realized due to the occurrence of streak-like defects or bleeding.

  The object of the present invention is to reduce the occurrence of streak-like defects and reduce ink bleeding between each color ink even when the recording medium and the ink type are different in high-speed multicolor printing by the single pass method. It is an object to provide an ink jet recording apparatus and an ink jet recording method capable of recording a good image with little image quality degradation and high speed.

  The above problems are solved by the following inventions.

1. A transport unit for transporting the recording medium in the transport direction;
A head portion in which a plurality of full-line-type ink jet heads that discharge active energy ray-curable inks of different colors to the recording medium are arranged in the transport direction;
Disposed between the inkjet heads disposed between the inkjet heads and ejected from the inkjet heads on the upstream side in the transport direction and landed on the recording medium and ejected from the inkjet heads on the downstream side in the transport direction A semi-curing light source for irradiating an active energy ray for semi-curing the first ink before the second ink lands,
Irradiation energy amount for setting the irradiation energy amount of the active energy ray to be referred to during recording based on at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink Setting means;
An ink jet recording apparatus comprising:

2. Irradiation energy amount storage means for storing at least one of the recording medium identification information, the first ink identification information, and the second ink identification information in association with the irradiation energy amount;
The irradiation energy amount setting means outputs the irradiation energy amount corresponding to at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink from the irradiation energy amount storage means. 2. The inkjet recording apparatus according to 1 above, wherein the read irradiation energy amount is set as the irradiation energy amount referred to during recording.

3. A determination print output means for outputting a determination print of a superimposed image in which the image of the second ink is formed on the image of the first ink having a plurality of regions each having a different amount of irradiation energy;
The irradiation energy amount setting means selects one irradiation energy amount to be referred to during recording between the minimum value and the maximum value of a plurality of types of irradiation energy amounts used for the determination print, and the recording medium used for the determination print 3. The inkjet according to claim 1, wherein the irradiation energy amount storage unit stores the identification information in association with at least one of identification information of the first ink, identification information of the first ink, and identification information of the second ink. Recording device.

  4). As the active energy ray curable ink, a cationic polymerization type ultraviolet curable ink is used. The viscosity at 25 ° C. is 25 mPa · s or more and 500 mPa · s or less, and the viscosity when discharged is 8 mPa · s or more and 20 mPa · s. The inkjet recording apparatus according to any one of 1 to 3, wherein:

5. 5. The inkjet recording apparatus according to any one of 1 to 4, wherein the irradiation energy amount is set in a range of 5 mJ / cm ^{2 to} 50 mJ / cm ² .

6). The head unit is an array of three or more full-line type ink jet heads that discharge active energy ray-curable inks of different colors to the recording medium, in the transport direction,
The irradiation energy amount setting means is adjacent to the identification information of the recording medium, the identification information of the first ink ejected from the inkjet head on the upstream side in the transport direction adjacent to the semi-curing light source, and the semi-curing light source Then, the irradiation energy amount is set based on at least one of identification information of the second ink ejected from the ink jet head on the downstream side in the transport direction. The inkjet recording apparatus according to Item.

7). The head unit is an array of three or more full-line type ink jet heads that discharge active energy ray-curable inks of different colors to the recording medium, in the transport direction,
The semi-curing light source is disposed between the inkjet heads of the respective colors,
The irradiation energy amount setting means includes a semi-curing light source based on at least one of the identification information of the recording medium, the identification information of the first ink and the identification information of the second ink corresponding to each semi-curing light source. 7. The ink jet recording apparatus according to any one of 1 to 6, wherein the irradiation energy amount is set every time.

  8). 8. The ink jet recording apparatus according to any one of 1 to 7, wherein the recording medium is a recording medium that substantially does not absorb ink.

9. Using a plurality of full-line type ink jet heads that discharge active energy ray-curable inks of different colors onto a recording medium, the first ink was ejected onto the recording medium and then landed on the recording medium. An ink jet recording method for performing image recording by irradiating an active energy ray for semi-curing the first ink, ejecting and landing a second ink on the semi-cured first ink,
Irradiation energy amount for setting the irradiation energy amount of the active energy ray to be referred to during recording based on at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink A setting process;
Performing the image recording with the set irradiation energy amount;
An ink jet recording method comprising:

10. In the irradiation energy amount setting step, the irradiation energy amount corresponding to at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink is set as the identification information of the recording medium. And reading from the irradiation energy amount storage means for storing the irradiation energy amount in association with at least one of the identification information of the first ink and the identification information of the second ink, and the read irradiation energy amount is referred to during recording. 10. The inkjet recording method according to 9, wherein the irradiation energy amount is set.

11. Before the irradiation energy amount setting process,
A determination print output step of outputting a determination print of a superimposed image in which the image of the second ink is formed on the image of the first ink having a plurality of regions each having a different amount of irradiation energy; and
One irradiation energy amount to be referred to at the time of recording is selected between the minimum value and the maximum value of the plurality of types of irradiation energy amounts used for the determination print, and the identification information of the recording medium used for the determination print, the first Storing in the irradiation energy amount storage means in association with at least one of identification information of one ink and identification information of the second ink;
The inkjet recording method according to the above 9 or 10, characterized by comprising:

  12 As the active energy ray curable ink, a cationic polymerization type ultraviolet curable ink is used. The viscosity at 25 ° C. is 25 mPa · s or more and 500 mPa · s or less, and the viscosity when discharged is 8 mPa · s or more and 20 mPa · s. The inkjet recording method according to any one of 9 to 11, wherein:

13. The inkjet recording method according to any one of the 9 to 12 and sets the amount of irradiation energy in the range of ^{5mJ / cm 2 ~50mJ / cm 2} .

14 The image recording is performed using an active energy ray curable ink of three or more colors,
The irradiation energy amount setting step includes identification information of the recording medium, identification information of the first ink used for image recording performed immediately before the semi-curing process, and image recording performed immediately after. 14. The inkjet recording method according to any one of 9 to 13, wherein the irradiation energy amount is set based on at least one of the identification information of the two inks.

15. The image recording is performed using an active energy ray curable ink of three or more colors,
The semi-curing process is performed between the image recording of each color,
In the irradiation energy amount setting step, each semi-curing is based on at least one of the identification information of the recording medium, the identification information of the first ink and the identification information of the second ink corresponding to each semi-curing process. The inkjet recording method according to any one of 9 to 14, wherein the irradiation energy amount is set for each of the processes.

  16. 16. The ink jet recording method according to any one of 9 to 15, wherein the recording medium is a recording medium that is substantially non-absorbing ink.

  According to the present invention, even when performing multi-color printing at a high speed by a single pass method, a good image with less ink bleeding between each color ink and less image quality deterioration while reducing the occurrence of streak-like defects. Can be recorded at a high speed, and an ink jet recording method can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The description in this column does not limit the technical scope of the claims or the meaning of terms. Further, the assertive description in the following embodiments of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.
<Inkjet recording apparatus>
Hereinafter, an ink jet recording apparatus and an ink jet recording method according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a plurality of inkjet heads (heads) provided corresponding to yellow (Y), magenta (M), cyan (C), and black (K) inks. (Hereinafter referred to as a head) 12Y (yellow), 12M (magenta), 12C (cyan), 12K (black) and an ink storage for storing ultraviolet curable ink (so-called UV ink) supplied to each head / Loading portion 14, semi-curing light sources 16A, 16B, 16C, 16D respectively disposed downstream of each head, and pressure fixing disposed downstream of semi-curing light source 16D after the final head (black head 12K) Unit 17, complete curing light source 18 disposed after pressure fixing unit 17, paper feeding unit 22 for supplying recording medium 20, and anti-car for removing curl of recording medium 20 The processing unit 24 and the head surfaces 12Y, 12M, 12C, and 12K are arranged to face the nozzle surfaces (ink ejection surfaces) and the light emitting surfaces of the semi-curing light sources 16A to 16D, and maintain the flatness of the recording medium 20. In addition, an adsorption belt conveyance unit 26 that conveys the recording medium 20 and a paper discharge unit 28 that discharges a recorded recording medium (printed material) to the outside are provided.

  The UV curable ink is an ink containing a component (UV curable component such as monomer, oligomer, low molecular weight homopolymer or copolymer) that is cured (polymerized) by application of UV energy and a polymerization initiator. When it receives light, it starts polymerization, thickens with the progress of polymerization, and eventually hardens.

  The ink storage / loading unit 14 includes ink tanks 14Y, 14M, 14C, and 14K that store inks of colors corresponding to the heads 12Y, 12M, 12C, and 12K. The heads 12Y, 12M, 12C, and 12K communicate with each other. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  In FIG. 1, a magazine 32 in which the recording medium is in a roll state (continuous paper) is shown as an example of the paper supply unit 22, but a plurality of magazines having different paper widths, recording paper quality, and the like may be provided side by side. Further, instead of the roll-shaped magazine or in combination with this, the cut-shaped magazine may be supplied by a cassette loaded in a stacked manner.

  When a plurality of types of recording media can be used, an information recording body such as a barcode or a wireless tag in which identification information such as the type of recording medium is recorded is attached to the magazine, and the information on the information recording body is read in a predetermined manner. By reading with the device, identification information such as the type of recording medium to be used is automatically determined, and ink ejection control is performed so as to realize appropriate ink ejection according to the identification information such as the type of recording medium Is preferred.

  The recording medium 20 delivered from the paper supply unit 22 retains curl due to having been loaded in the magazine 32. In order to remove the curl, heat is applied to the recording medium 20 by the heating drum 34 in the direction opposite to the curl direction of the magazine 32 in the anti-curl processing unit 24. At this time, the heating temperature can be controlled so that the printed surface is slightly curled outward.

  In the case of an apparatus configuration used in a roll shape, a cutter 38 is provided as shown in FIG. 1, and the recording medium is cut into a desired size by the cutter 38. The cutter 38 includes a fixed blade 38A having a length equal to or greater than the conveyance path width of the recording medium 20, and a round blade 38B that moves along the fixed blade 38A.

  After the anti-curl process, the cut recording medium 20 is sent to the suction belt conveyance unit 26. The suction belt conveyance unit 26 has a structure in which an endless belt 43 is wound between rollers 41 and 42, and at least a portion facing each of the nozzle surfaces of the heads 12Y, 12M, 12C, and 12K forms a flat surface. It is configured.

  The belt 43 has a width that is wider than the width of the recording medium 20, and a plurality of suction holes (not shown) are formed on the belt surface. Inside the belt 43 spanned between the rollers 41 and 42, an adsorption chamber or the like is provided, and the recording medium 20 is adsorbed and held on the belt 43 by sucking it with a fan to obtain a negative pressure. good.

  The power of the motor (not shown) is transmitted to at least one of the rollers 41 and 42 around which the belt 43 is wound, so that the belt 43 is driven in the counterclockwise direction in FIG. The recording medium 20 is conveyed from right to left along the conveyance direction (sub-scanning direction A) indicated by the arrow in FIG. The conveyance speed is preferably 20 mm / sec to 1000 mm / sec, and is set to 200 mm / sec in this embodiment.

  Each of the heads 12Y, 12M, 12C, and 12K has a length corresponding to the maximum paper width of the recording medium 20 targeted by the inkjet recording apparatus 10, and at least one side of the maximum size recording medium 20 is provided on the nozzle surface. This is a full-line head in which a plurality of nozzles for ejecting ink are arranged over a longer length (the full width of the drawable range).

  The heads 12Y, 12M, 12C, and 12K are arranged in the order of colors of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side along the feeding direction of the recording medium 20. The heads 12Y, 12M, 12C, and 12K are arranged so as to extend along a direction (main scanning direction) substantially orthogonal to the conveyance direction of the recording medium 20. The head arrangement order may be arranged as necessary in view of curing sensitivity and ink transmittance as long as the effects of the present invention are not impaired.

  A color image can be formed on the recording medium 20 by ejecting ink of each color from each of the heads 12Y, 12M, 12C, and 12K while conveying the recording medium 20 by the suction belt conveyance unit 26.

  As described above, the single-pass inkjet recording apparatus 10 uses yellow (Y), magenta (M), cyan (C), and black (K) of a full-line head having a nozzle array that covers the entire paper width. According to the configuration provided for each color, the recording medium 20 can be moved by moving the recording medium 20 relative to the heads 12Y, 12M, 12C, and 12K in the conveyance direction of the recording medium 20 only once by performing a single pass. An image can be recorded on the entire surface.

  In this example, the configuration using a combination of YMCK standard color (four colors) ink is exemplified, but the combination of the ink color and the number of colors is not limited to this embodiment, and the number of colors may be two or more. Light ink and dark ink may be added as necessary. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta.

  The semi-curing light sources 16 </ b> A to 16 </ b> D arranged downstream of each head have a length corresponding to the maximum paper width of the recording medium 20 like the head, and extend in a direction substantially orthogonal to the conveyance direction of the recording medium 20. To be fixed. As the semi-curing light sources 16A to 16D, LED elements or LD elements having a light emission wavelength region narrower than that of the fully-curing light source 18 disposed downstream of the head portion are preferably used. However, the center wavelength and emission wavelength region of the semi-curing light sources 16A to 16D and the complete curing light source 18 are selected according to the design of the ink used.

  Each semi-curing light source 16 is disposed between two adjacent heads 12 and is transported on the first ink ejected from one inkjet head on the upstream side in the transport direction and landed on the recording medium. Before the second ink ejected from the other ink jet head on the downstream side in the direction is landed, an active energy ray for semi-curing the first ink is irradiated.

  Before the recording medium 20 passes through the upstream head and enters under the next head, light is irradiated from the semi-curing light sources 16A to 16C to make the ink on the recording medium 20 in a semi-cured state, and the next stage different color A droplet is ejected by the head.

  In the example of FIG. 1, droplets are ejected by the yellow head 12Y, and after yellow ink is semi-cured through light irradiation by the semi-curing light source 16A, droplets are ejected by the magenta head 12M. Similarly, after droplet ejection by the magenta head 12M, droplet ejection by the cyan head 12C is performed through light irradiation by the semi-curing light source 16B, and droplet ejection by the black head 12K is performed by light irradiation by the latter half curing light source 16C. After droplet ejection by the black head 12K, light irradiation is performed by the semi-curing light source 16D. In addition, it is good also as a structure which does not provide the semi-curing light source 16D.

  The ink ejected from the head existing upstream in the conveyance direction of the recording medium 20 is semi-cured by the irradiation of ultraviolet rays, and the ink on the recording medium 20 can be maintained in a semi-cured state. At the stage of passing through the semi-curing light source 16D, the ink on the recording medium 20 is in a semi-cured state in which the progress difference between the colors is small and leveled.

  The pressure fixing unit 17 (smoothing means) provided at the subsequent stage of the final semi-curing light source 16D includes a roller 45 whose surface is coated with a resin having high peelability. The roller 45 has a hollow structure and is provided with a heater 46 such as a halogen lamp in the center to pressurize the image surface of the recording medium 20 while applying heat. The ink surface is heated and pressed by the pressure fixing unit 17 to flatten the unevenness of the ink surface. Moreover, when smoothing is possible only by pressurization without applying heat, it is not necessary to heat. In addition, when printing on porous paper with dye-based ink, the weather resistance of the image is prevented by closing the paper hole by pressurization and preventing contact with ozone or other substances that cause dye molecules to break. Has the effect of improving.

  The pressure fixing unit 17 has a mechanism (for example, a variable structure that applies a pressing force of the roller 45 by a spring load) that can adjust the pressure, and pressurizes appropriately according to the thickness of the recording medium 20 and the amount of ink. Controlled by pressure.

  A complete curing light source 18 is provided after the pressure fixing unit 17. As the complete curing light source 18, a metal halide lamp, a mercury lamp, or the like having a wider emission wavelength range and a larger irradiation light amount than the semi-curing light sources 16 </ b> A to 16 </ b> D is used.

  The recording medium 20 that has been subjected to the smoothing process by the pressure fixing unit 17 is irradiated with light sufficient to completely cure the ink by the complete curing light source 18, and the main fixing is performed.

  Further, the roller 45 of the pressure fixing unit 17 is configured to be moved to a predetermined retreat position that does not contact the recording medium 20 by a moving mechanism (not shown). When performing the smoothing process of the ink surface, the roller 45 is placed at a predetermined position (smoothing process position) where it contacts the recording medium 20, and pressurization is performed. On the other hand, when the flattening process of the ink surface is unnecessary, the roller 45 is retracted to the retracted position and cured and fixed by the complete curing light source 18 without applying pressure. As a result, it is possible to perform drawing with the unevenness of the ink surface remaining.

  Note that, as a means for switching between pressurization / non-pressurization with respect to the pressure fixing unit 17, a structure in which the pressure fixing unit 17 can be detached (detached) instead of the above-described retraction mechanism may be employed. In other words, when the smoothing process is unnecessary, it is also possible to remove the pressure fixing unit 17 (or a part thereof) from the inkjet recording apparatus 10 and omit the smoothing process.

  In this way, the printed matter generated through the complete curing process by the complete curing light source 18 (the process of curing and fixing to such an extent that the image quality is not deteriorated due to ink rubbing or the like in the transport handling) is discharged from the paper discharge unit 28. Although not shown in FIG. 1, the paper discharge unit 28 is provided with a sorter for collecting images according to orders.

  Next, the semi-curing light source will be described. The semi-curing light source 16 includes a plurality of semi-curing light sources arranged in a line in a light-shielding enclosure (not shown) using a low-pressure mercury lamp or the like.

  A slit-like opening (not shown) or the like serving as a light exit is formed at the bottom of the semi-cured light source surrounded by the light shielding. By controlling the light emission amount of each element, it is possible to realize a desired irradiation range and light amount (intensity) distribution for the ultraviolet irradiation area.

  At this time, the light emission position and light emission amount of the semi-curing light source are appropriately controlled according to the size of the recording medium 20, the droplet ejection range by the head 12 and the ink amount, and adverse effects on the head 12 (curing of ink in the nozzle, etc.). As much as possible, the necessary light emission can be performed.

  In addition, as the semi-curing light source, an ultraviolet LED, an LD (laser diode), a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a black light, a hot cathode tube, or a cold cathode tube can be used.

  For example, the type of the recording medium, the type of the first ink ejected to the recording medium, the first ink, and the like are influenced by the image quality when forming a multicolor image using the ultraviolet curable ink. Examples include the type of the second ink ejected on the top.

  The amount of irradiation energy when the first ink is semi-cured is the amount of irradiated energy that the first ink receives when it is cured. Since this amount of irradiated energy affects, the surface of the landed first ink is thickened. State or semi-cured state. The surface energy of the first ink changes depending on the degree of thickening, and the leveling behavior of the second ink hit on the landed first ink changes, so the dot diameter of the second ink changes. By increasing the amount of irradiation energy, the surface energy of the landed first ink is increased, the surface wettability is improved, and the second ink hit on the landed first ink is likely to spread. As a result, the second ink landed on the first ink spreads, and the dot diameter increases. If the optimum condition is not satisfied due to such a change in the dot diameter, bleeding and streak-like defects occur.

  The curing sensitivity of the ultraviolet curable ink varies depending on the type (composition). By changing the curing sensitivity, when the irradiation amount is constant, the surface energy of the landed ink changes according to the type of the first ink. Therefore, since the leveling behavior of the second ink hit from above the landed ink changes as the surface energy changes, the dot diameter of the second ink changes. For example, the sensitivity of the ultraviolet curable ink increases as the amount of the polymerizable compound increases. When the irradiation amount is constant, the larger the amount of the polymerizable compound, the higher the surface energy of the ink, the higher the surface energy of the first ink that has landed, and the surface wettability is improved. The second ink hit from above tends to spread. That is, since the ink on the surface spreads, the dot diameter increases.

  Further, the semi-curing of the first ink and the state of the dot diameter (2R) of the second ink are exemplified in the case where the first color ink is used as the first ink and the second color ink is overlapped as the second ink. Will be described. In FIG. 6, the irradiation energy amount of the semi-curing light source 16 is the smallest in (a) and increases in the order of (b), (c), and (d). As shown in FIG. 6, when the first color ink is ejected onto the recording medium, the recording medium hardly penetrates. Therefore, if the degree of semi-curing is changed, the second color ink is trapped and spread as shown in FIG. Surprisingly, the dot diameter increases as the amount of irradiation energy increases. 6A to 6C, the second color ink penetrates to the recording surface of the recording medium. In such a state, the contact angle θ determined by the combination of the second color ink and the recording medium affects the dot diameter of the second color ink, and the smaller the contact angle θ, the larger the dot diameter.

  In this way, if the second color ink is ejected while the first color ink is not yet fully cured, it will sink deeply into the lower side of the first color ink, and conversely, as shown in FIG. It has been found for the first time that it is easy to get on and is fixed in this state with complete curing.

  Next, the control system of the inkjet recording apparatus 10 will be described.

  FIG. 2 is a block diagram of the main part of the ink jet recording apparatus.

  The system controller 112 includes a central processing unit (CPU) and its peripheral circuits. The system controller 112 executes a program in the ROM 115 to control communication with the host computer 130, read / write control of the image memory 114, and the like. Then, a control signal for controlling the motor 134, the pressure fixing unit 17 and the like of the conveyance system of the recording medium 20 is generated.

  The print control unit 120 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the image memory 114 under the control of the system controller 112, and the generated print A control unit that supplies a control signal (dot data) to the head driver 124. The print control unit 120 performs necessary signal processing, and controls the ink discharge amount and discharge timing of the head 12 for each color via the head driver 124 based on the image data.

  The head driver 124 drives an ejection drive actuator (not shown) of each head 12 based on the dot data given from the print control unit 120. The head driver 124 may include a feedback control system for keeping the head driving condition constant.

  Image data to be printed is input from the outside via the communication interface 110 and stored in the image memory 114. At this stage, for example, RGB image data is stored in the image memory 114. The image data stored in the image memory 114 is sent to the print control unit 120 via the system controller 112, and the print control unit 120 converts it into dot data for each ink color by a known dither method, error diffusion method, or the like. Converted.

  In this way, each head 12 is driven and controlled based on the dot data generated by the print control unit 120, and ink is ejected from each head 12. An image is formed on the recording medium 20 by controlling ink ejection from each head 12 in synchronization with the conveyance speed of the recording medium 20.

  At this time, the droplet radius at the time of flight (droplet radius in the combined state of the multi-droplet) can be obtained by using a multi-droplet method that can discharge liquid in several steps at a time. It is particularly preferable to control and predict the landing radius. In particular, high-definition images with less bleeding and less streaking can be printed in color in a single pass. Preferably, as the multi-droplet, the appropriate amount of liquid can be adjusted in at least three stages.

  A recording medium detection unit 126 serving as a recording medium recognition unit is means for detecting identification information such as the paper type of the recording medium 20. For example, means for reading information such as a barcode attached to the magazine 32 of the paper feed unit 22 and sensors (such as sensors for detecting reflectivity) disposed at appropriate locations in the paper transport path are used. Appropriate combinations are possible. Further, the recording medium recognition unit may be configured to specify identification information such as a paper type by an input from a predetermined user interface instead of or in combination with these automatic detection means.

  The ink detection unit 127 serving as an ink recognition unit is a unit that detects identification information such as the type of ink. For example, a means for reading information such as a barcode attached to the ink tank 14 and a sensor arranged at an appropriate place where identification information such as the type of ink can be detected are used, and an appropriate combination thereof is also possible. In addition, instead of or in combination with these automatic detection means, the ink recognition unit can also be configured to specify information relating to identification information such as the type of ink by input from a predetermined user interface.

  The identification information acquired by the recording medium detection unit 126 and the ink detection unit 127 is sent to the irradiation energy amount setting unit 129 and notified to the system controller 112 and / or the print control unit 120, and the ink ejection control and pressure fixing unit. 17 and semi-curing light sources 16A, 16B, 16C, and 16D.

  The light source control unit 128 includes a semi-curing light source control circuit that controls lighting (ON) / extinguishing (OFF) of the semi-curing light source 16 and a lighting position, a light emission amount at the time of lighting, and lighting (ON) / And a complete curing light source control circuit for controlling the light-off (OFF) and the light emission amount at the time of lighting. The light source control unit 128 controls the light emission of each light source (16, 18) according to a command from the print control unit 120. At this time, it is preferable to control the irradiation energy amount of the semi-curing light source 16 by changing the irradiation intensity or the irradiation time.

  That is, the irradiation energy amount of the semi-curing light source 16 is the energy amount irradiated to the recording medium, and the irradiation intensity is changed by changing the light emission amount of the semi-curing light source 16 or the irradiation time of the semi-curing light source 16 is changed. By changing the irradiation time, the irradiation energy amount is controlled. In order to change the irradiation time, the conveyance speed of the recording medium may be changed. In the embodiment, the conveyance speed is constant at 200 mm / sec, and the irradiation energy amount is changed by changing the light emission amount of the semi-curing light source 16. Control is easier than changing the conveyance speed of the recording medium.

  Further, by optimizing the pressure heating condition of the pressure fixing unit 17 and the irradiation energy amount condition of the complete curing light source 18 based on the information of the characteristics of the recording medium and the amount of ink landing, stable fixing processing becomes possible. Ink peeling and cracking can be prevented. If necessary, a similar pressure fixing unit may be provided behind the complete curing light source 18.

  The data stored in the irradiation energy amount storage unit 122 includes, for each of the semi-curing light sources 16A, 16B, and 16C, identification information of the recording medium used for image recording, identification information of the first ink, and identification of the second ink. There is a table of optimum irradiation energy amounts set so as to correspond to each combination with information.

  The irradiation energy amount table determines an optimum irradiation energy amount for semi-curing the first ink ejected from the upstream heads 12Y to 12C so as to correspond to the semi-curing light sources 16A to 16C. is there.

  The table is set for each combination of identification information such as the type of the recording medium, identification information such as the first ink type, and identification information such as the second ink type, by experiment or simulation. For example, in the case of a semi-curing light source 16A that semi-cures yellow ink, the amount of irradiation energy for each combination of the type of recording medium, the type of yellow ink that is the first ink, and the type of magenta ink that is the second ink. A multi-color image is recorded while differentiating each, and the dot diameter, streaks, and blur of the magenta image are measured to determine the amount of irradiation energy that becomes a desired image. Similarly, in the case of the semi-curing light source 16B for semi-curing magenta ink, the irradiation energy is different for each combination of the type of recording medium, the type of magenta ink that is the first ink, and the type of cyan ink that is the second ink. The amount of irradiation energy to be a desired image is determined by recording a multicolor image while varying the amount and measuring the dot diameter, streaks, and blur of the cyan image.

  Since it is not easy to automatically measure image streaks and blurs, in this embodiment, the image streaks and blurs output under each condition are visually evaluated, and the following conditional expression ( The dot diameter was set from the range satisfying 1), and the optimum irradiation energy amount was set.

  Thereby, the dot diameter of the second color of the test pattern (hereinafter may be referred to as a judgment print) is automatically measured, and the irradiation energy amount of the semi-curing light source 16 is adjusted based on the dot diameter data, As a result, it is possible to record an image with less streaking and bleeding nearing a predetermined dot diameter, and work efficiency is improved.

The ink jet recording apparatus of the present embodiment sets an optimum irradiation energy amount within a range that satisfies the following conditional expression (1).
1 ≦ R / r ≦ 0.0013θ ² −0.1θ + 3.8 (1)
However, 10 ° ≦ θ ≦ 40 °. Note that 1 ≦ R / r means that R / r is not substantially less than 1.

  Here, R is the dot radius after the second color ink is completely cured, r is the droplet radius when the second color ink is flying, and θ is the contact angle between the second color ink and the recording surface of the recording medium.

A description will be given of the results of an experiment in which image recording was performed using the ink and recording medium described below, and image evaluation was performed under conditions outside and within the range of the conditional expression (1).
<Ink>
As the ink, a cationic polymerization type ultraviolet curable ink was used. The viscosity was 10 cp for each of Y, M, C, and K colors (measured value at 50 ° C.), and the surface tension was about 28 dyn / cm ² (measured value at 25 ° C.).

  In addition, although the display of "part" or "%" is used in the following experimental results, "part by mass" or "mass%" is expressed unless otherwise specified.

<Preparation of dispersion>
[Preparation of Dispersion A]
Each of the following compounds was placed in a stainless beaker and dissolved by stirring and heating for 1 hour while heating on a hot plate at 65 ° C.

PB821 (dispersant manufactured by Ajinomoto Fine-Techno Co., Ltd.) 9 parts OXT221 (Oxetane compound manufactured by Toa Gosei Co., Ltd.) 71 parts Then, 200 g of 3 mm zirconia beads were placed in a glass bottle and sealed, and after a dispersion treatment for 4 hours with a paint shaker, the zirconia beads were removed to prepare dispersion A.

[Preparation of dispersions B to D]
In the preparation of the above dispersion A, Pigment Black 15: 4 (Cyanine Blue 4044 manufactured by Sanyo Dye Co., Ltd.), Pigment Red 122 (CFR321 manufactured by Dainichi Seika Co., Ltd.), and Pigment Yellow 180 (Large) were used instead of Pigment Black 7 Dispersion B, dispersion C, and dispersion D were prepared in the same manner except that CFY313-2) manufactured by Nissei Kasei was used.

<Preparation of ink set>
[Preparation of ink set]
Inks K, C, M, and Y having the configurations shown in Table 1 were prepared using the dispersions A to D (cationically polymerizable compounds) prepared above, and this was used as an ink set.

  In addition, the numerical value of the said Table 1 represents a mass part.

  The details of the compounds described in abbreviations in Table 1 are as follows.

<Cationically polymerizable compound>
2021P: Celloxide 2021P (alicyclic epoxy compound, bifunctional, manufactured by Daicel Chemical Industries)
OXT212: Monofunctional oxetane compound, manufactured by Toagosei Co., Ltd. OXT221: Bifunctional oxetane compound, manufactured by Toagosei Co., Ltd. <Modified silicone oil>
SDX-1843: Modified silicone oil SDX-1843, manufactured by Asahi Denka Kogyo Co., Ltd. <Photopolymerization initiator>
I-907: Irgacure 907 Ciba Japan Co., Ltd. UVI6992: Triarylsulfonium salt, UVI6992, Dow Chemical Co., Ltd. <sensitizer>
CPTX: 1-chloro-4-propoxythioxanthone AHC: 3-acetyl-7-hydroxycoumarin <recording medium>
As the recording medium, three types having a contact angle θ of 12, 20, and 35 ° were used. The Y, M, C, and K inks were adjusted using a surface tension adjusting agent so as to have the same contact angle.

The contact angle θ was measured using a commercially available automatic contact angle meter (Kyowa Interface Science DM300).
<Inkjet head>
Four heads of share mode type (AL = 3 μsec, nozzle pitch: 180 dpi, number of nozzles: 256, nozzle taper angle 6 degrees, nozzle diameter 26 μm, ink droplet amount: 7 pl) were prepared for each color. The nozzle rows of each head are shifted from each other by ¼ pitch, and each of the heads bonded together so as to be arranged in a staggered manner is a 180 dpi head, so by shifting the nozzle pitch by ¼, A recording head of 720 dpi was produced. The evaluation was performed using a DRR driving waveform and 3 cycle driving and a driving cycle of 22 kHz.
<Inkjet recording apparatus>
The single-pass ink jet recording apparatus having the configuration shown in FIG. 1 having the share mode type head is loaded with the ink, and the ink is ejected onto each recording medium transported at a transport speed of 200 mm / sec. The image was formed.

  As energy irradiation for curing, a low-pressure mercury lamp was used for the semi-curing light sources 16A to 16D for semi-curing, and a high-pressure mercury lamp was used for the light source 18 for complete curing.

<< Image formation and evaluation >>
Hereinafter, examples satisfying the conditional expression (1) are referred to as examples, and those outside the range are referred to as comparative examples.
(Examples 1-13, Comparative Examples 1-6)
Each evaluation shown below was performed about each image formed as shown below.

[Streak]
First, a solid image of C ink is directly printed on the above three recording media at 720 dpi, and this is semi-cured by changing the amount of irradiation energy in the range of 10 mJ to 1000 mJ / cm ² with a semi-curing light source 16C, and then After printing a solid image with K ink, the solid image was fixed and completely cured to create a C + K two-color solid image, and the presence or absence of streaks in the K image was examined.

  Judgment criteria are as follows. Δ is not practically problematic, but ○ is preferable.

○: Occurrence ratio is less than 5% △: Occurrence ratio is 5 to 10%
×: The generation ratio exceeds 10% and cannot be evaluated <bleed>
First, a solid image of C ink is directly printed on the above three recording media at 720 dpi, and this is semi-cured by changing the amount of irradiation energy in the range of 10 mJ to 1000 mJ / cm ² with a semi-curing light source 16C, and then After printing characters and lines with K ink, the images were fixed and completely cured to produce images, and the presence or absence of bleeding was visually evaluated.

  Judgment criteria are as follows. Δ is not practically problematic, but ○ is preferable.

○: Occurrence ratio is less than 5% △: Occurrence ratio is 5 to 10%
×: The generation ratio exceeds 10% and cannot be evaluated <overall evaluation>
From the gist of the present invention, the following bleeding and streak compatibility was evaluated.

  Judgment criteria are as follows. Even if Δ, there is no practical problem, but ○ or more is preferable.

◎: Bleeding and streaks are both better than ○ ○: One is △ and one is ○
△: Both △
X: There is one x. Note that r is a high-speed video, and R is observed and measured with a microscope (Example 14).
Using ink whose contact angle θ with the recording medium is adjusted to 20 ° and printing a judgment print, R and r are measured, and the control unit sets the target R / r = 1.76 to automatically control. did.

First, a determination print is printed using the ink and recording medium of the second embodiment, and is automatically photographed by the high-speed video camera of the determination print measurement unit 200A, while r is K ink and a droplet diameter measurement unit. Measurement was performed with a 200B high-speed video camera, and the ratio of R and r was calculated. Then, the amount of irradiation energy for semi-curing was automatically set to 10 mJ / cm ² and the same evaluation was performed.
(Example 15)
The same procedure as in Example 14 was performed except that a determination print was printed, read with a scanner, and R was measured.

  The results obtained as described above are shown in Table 2, FIG. 3, and FIG.

  In the correlation diagram between the contact angle θ and R / r in FIG. 3, ◯, ●, and △ indicate data of Examples 1 to 9, and x indicates data of Comparative Examples 1 to 3, respectively. Corresponds to the number.

  Similarly, in the correlation diagram between the contact angle θ and R / r in FIG. 9, Δ indicates the data of Examples 7 to 9, ○ indicates the data of Examples 14 and 15, and the subscript corresponds to the number of the Example. ing.

  As is clear from Table 2, by setting the irradiation energy amount of the semi-curing light source so as to satisfy the conditional expression (1), it is possible to obtain good print quality and image quality with little image quality deterioration due to streaking and bleeding. Very good results were obtained.

  The effects of the present invention could be confirmed without any problem in Examples 14 and 15 in which the irradiation energy amount was automatically set.

  The same evaluation was carried out for other color combinations such as Y + M, M + C, etc., but there was no difference with respect to streaking / bleeding, and the effect of the present invention could be confirmed.

  From these experimental results, reference is made at the time of recording based on at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink so as to satisfy the conditional expression (1). By setting the irradiation energy amount of the active energy ray, it is possible to reduce the occurrence of streak-like defects and reduce the occurrence of streak-like defects even when the type of recording medium or ink is different when printing at high speed using the single pass method. It was found that good images with little ink bleeding between them and little deterioration in image quality can be recorded at high speed.

It is preferable that the following conditional expression (2) is satisfied,
1 ≦ R / r ≦ 0.0013θ ² −0.1θ + 3.6 (2)
It is more preferable that the following conditional expression (3) is satisfied.
0.0013θ ² −0.1θ + 3.1 ≦ R / r (3)
As described above, the contact angle θ is 10 ° or more and 40 ° or less, and more preferably 10 ° or more and 30 ° or less.

  The contact angle θ between the second color ink and the recording surface of the recording medium is a static contact angle on the recording medium and in a state where the ink is uncured. It can be measured using a known contact angle meter.

  The radius r of the droplet ejected from the nozzle of the head in the flying state is directly observed by the droplet diameter measuring unit 200B arranged in the vicinity of the head, and the radius of the spherical droplet is obtained by image processing. It can be calculated.

  In this embodiment, an image is obtained by strobe synchronization in the flying state of the droplet 101 shown in FIG. 4 using a high-speed video camera as the droplet diameter measuring unit 200B, and is measured at a point close to a perfect circle (A in FIG. 4). A value obtained by averaging the radii r1 and r2 of the ellipsoid was used.

R is an image pattern (so-called solid), in which the first color ink is printed on a recording medium with a predetermined resolution on one side in advance, by appropriately changing the amount of irradiation energy to a semi-cured state. This is a value obtained by measuring the radius of the ink dot of the second color with the determination print measuring unit 200A after applying the energy for complete curing and then completely curing, and is a value that does not pressurize. The complete curing may be 70% or more when the reaction rate of the polymerizable compound in the formed image is measured. A Fourier transform infrared spectrophotometer (FT-IR, for example, IR Prestinge-21 manufactured by Shimadzu Corporation) , IRAffinity-1, etc.). Speaking of the irradiation energy amount, 150 mJ / cm ² or more is sufficient. Conversely, semi-curing means a state where the reaction rate is measured and 50% or less.

  In the present embodiment, the determination print measurement unit 200A is photographed using a high-speed video camera, and measurement data is obtained from the image. In addition, you may measure manually using well-known microscope observation or a high magnification magnifier. Further, the determination print may be automatically taken in with a commercially available scanner, and measurement data may be obtained from the image.

  r is preferably 20 μm or less. If R / r is too small, bleeding does not occur, but streaks are likely to occur. If the R / r is large, the maximum droplet radius upon landing increases, and the line width is also clean by the liquid close to each other and subsequent receding and moving. Unable to draw.

  R can be adjusted by adjusting the balance of the viscosity, density, and surface tension of the first and second color inks. However, as a factor that can be controlled with high accuracy and has a large influence, an increase in the degree of cure and viscosity due to the irradiation energy of the first color ink deposited immediately before landing the second color ink greatly influences.

  When the resolution in the direction substantially orthogonal to the recording medium conveyance direction of the second color image is X (dpi: dot / inch, number of dots per inch), R (mm) ≦ 1.4 (25.4 / X) is preferred. More preferably, it is 0.8d-1.2d. If it is small, streaks tend to appear from the point of position, and if it exceeds 1.4, bleeding tends to occur.

  In addition, as a system, there are various types of recording media, and the characteristics may differ depending on the recording media. In the case of printing Y, M, C, and K inks, the viscosity, density, surface tension, and the like can be balanced by various combinations.

  On the other hand, considering that the viscosity range of the ink that can be ejected from the nozzles of the inkjet head is limited, actually adjust the physical properties of the ink to some extent, and then take full advantage of using the cured reaction ink to the maximum, It is realistic and most important by appropriately adjusting the degree of semi-curing of the first color ink.

  In order to adjust the R / r so as to satisfy the conditional expression (1), it can be adjusted by changing the amount, type, and component ratio of the curing reaction component in the ink. This can be achieved by adjusting the amount of irradiation energy.

The irradiation energy amount can be determined by changing the irradiation energy amount for the first color ink so as to satisfy the conditional expression (1). From the viewpoint of achieving both bleeding and color mixing prevention, it is preferably 5 mJ / cm ^{2 to} 50 mJ / cm ² .

  Further, the number of times that the ink ejected from the head 12 existing on the upstream side in the conveyance direction of the recording medium 20 passes through the semi-curing light source 16 increases. For example, the combination of the first color and the second color printed on the recording medium is once for Y + M, M + C, and C + K, twice for Y + C and M + K, and three times for Y + K.

  Thus, it is preferable to adjust the amount of irradiation energy so as to maintain a desired semi-cured state even when irradiated by the semi-cured light source 16 a plurality of times and to satisfy the conditional expression (1).

  Next, the determination print will be described. R is measured from a judgment print in which the second color ink is printed on an image pattern in which the irradiation energy of ultraviolet rays to be irradiated is changed in a plurality of stages after the first color ink is solid-printed on the recording medium. The R data obtained is used.

  The recording medium for obtaining R indicates a recording medium to be printed. Particularly preferably, when R is measured from the judgment print, it is automatically measured, and thereafter, an optimum irradiation energy amount is calculated and controlled so that R / r satisfies the conditional expression (1). .

  The determination print measurement is performed by the determination print measurement unit 200A as described above.

5A to 5C show examples of R determination patterns. The four R determination patterns shown in FIG. 5C are solidly printed with Y ink, and then the amount of emitted light is changed by the semi-curing light source 16A to change the half-curing irradiation energy to 5, 10, 50. , 100 mJ / cm ² , M, C, and K inks are printed at half resolution so that the dot diameter can be easily measured, and then completely cured by the complete curing light source 18. Similarly, in the case of (b), Y, C, K is printed on the M ink, and in the case of (a), the pattern is printed with Y, M, K ink on the C ink.

  In the present invention, other various patterns and combinations of irradiation energy amounts can be considered, and the present invention is not limited to three colors. What is important is to print the first color solid and the second color dots in order, and print the pattern at intervals that allow R to be measured so that the dots do not overlap. In this embodiment, the judgment print is printed by using the adjacent heads (12Y and 12M, 12M and 12C, 12C and 12K), and semi-curing with the solid Y-printing late curing light source 16A to print M dots. Fully cured pattern, M solid printing Half-curing treatment with the latter-half curing light source 16B, printing C dots and completely curing C, Semi-curing treatment after 16 C solid printing and printing with K dots, complete A determination print of three types of patterns to be cured is created, and the amount of irradiation energy of each of the semi-curing light sources 16A, 16B, and 16C is set.

  Accordingly, the identification information of the recording medium, the identification information of the first ink ejected from the inkjet head on the upstream side in the transport direction adjacent to the semi-curing light source, and the downstream in the transport direction adjacent to the semi-curing light source It becomes possible to set the irradiation energy amount of each semi-curing light source based on the identification information of the second ink ejected from a certain ink-jet head, and the setting of the irradiation energy amounts of a plurality of semi-curing light sources is performed conveniently. be able to.

  The judgment print output means 148 generates judgment pattern data as shown in FIG. 5, or calls it from a predetermined memory and sends the judgment pattern data to the heads 12Y, 12C, 12M, and 12K through the head driver 124. This is output as a judgment print.

  The output determination print of FIG. 5 is subjected to density measurement by the determination print measuring unit 200A as described above. The measurement result is sent to the irradiation energy amount setting means 129 in correspondence with the measurement result of r measured by the droplet diameter measuring unit 200B.

  Then, the irradiation energy amount setting means 129 is based on the contact angle θ data measured in advance with the recording medium and the ink and stored in correspondence with the combination of the recording medium and the ink, and the calculated R / r. The irradiation energy amount of the semi-curing light source 16 is set so that R / r satisfies the conditional expression (1), and the combination of the identification information of the recording medium, the identification information of the first color ink, and the identification information of the second color ink And stored in the irradiation energy amount storage unit 122 for storing the optimum irradiation energy amount and sent to the print control unit 120. The print control unit 120 sends an instruction to the light source control unit 128 to control the light emission amount of the corresponding semi-curing light source 16 based on the set value of the irradiation energy amount sent.

  As described above, the irradiation energy amount storage unit 122 sets an optimum irradiation energy amount for each recording medium and each ink, and this irradiation energy amount is stored in the recording medium 20 sent from the recording medium detection unit 126 and the ink detection unit 127. The identification information such as the type and the identification information such as the ink type can be stored in association with each other.

  When the target value of R / r is set within a range that satisfies the above (1), when the irradiation energy amount and r are constant, basically, the contact angle θ between the recording medium and the second color ink is relatively Since the smaller the smaller, the higher the curing sensitivity of the first color ink, the larger the R tends to be. Therefore, a table for setting the irradiation energy amount relatively small in such a combination of the recording medium and the ink is stored.

  Next, the operation of the inkjet recording apparatus 10 of the present embodiment will be described with reference to the flowchart of FIG.

  First, in step S <b> 100 of FIG. 7, a paper feed unit 22 for supplying the recording medium 20 to the inkjet recording apparatus 10 is loaded. As described above, the paper feed unit 22 reads identification information such as the type of the recording medium 20 loaded. The identification information read by the recording medium detection unit 126 is sent to the irradiation energy amount setting means 129. On the other hand, the ink detection unit 127 detects the type of ink, and identification information such as the detected ink type is similarly sent to the irradiation energy amount setting means 129.

  In the next step S110, the irradiation energy amount setting unit 129 determines whether or not the optimum irradiation energy amount corresponding to the sent medium type identification information has already been set and stored in the irradiation energy amount storage unit 122. If there is an optimum irradiation energy amount corresponding to the identification information such as the medium type, the process proceeds to step S120, and the optimum irradiation energy amount stored in the irradiation energy amount storage unit 122 is called to print. The data is sent to the control unit 120. The print control unit 120 sets the semi-curing light sources 16A, 16B, and 16C through the light source control unit 128 so that the light emission amount corresponds to the optimum irradiation energy amount.

In this way, the irradiation energy amount setting means determines the irradiation energy amount corresponding to the recording medium identification information, the first ink identification information, and the second ink identification information as the recording medium identification information. The irradiation information is read from the irradiation energy amount storage means for storing the identification information of the first ink and the identification information of the second ink in correspondence with the irradiation energy amount, and the read irradiation energy amount is referred to at the time of recording. By setting the energy amount, the reliability of the irradiation energy amount setting can be improved.

  On the other hand, if there is no optimal irradiation energy amount corresponding to the detected medium type or the like, the process proceeds to step S130 in order to create a determination pattern for setting the optimal irradiation energy amount.

  In step S130, the print control unit 120 reads the determination print data from the determination print output unit 148, and uses the adjacent heads (12Y and 12M, 12M and 12C, and 12C and 12K). By changing the amount of emitted light, the amount of irradiation energy is changed in a plurality of stages, and each image is output to execute image recording of a judgment print. At this time, the irradiation energy amount setting means 129 controls the droplet diameter measuring unit 200B so that the radius r in the flying state of the droplets ejected from the nozzles of the M, C, and K heads for the second color is directly set. The flying state is observed with a high-speed video camera of the droplet diameter measuring unit 200B, and the radius r of the spherical droplet is calculated by image processing. The measurement result is sent to the irradiation energy amount setting means 129 in association with r and the irradiation energy amount for each ink color.

  Next, in step S140, the irradiation energy amount setting unit 129 controls the determination print measurement unit 200A to cause each high-speed video camera of the determination print measurement unit 200A to shoot each print of the determination print from above and process the image. Thus, the dot radius R of the second color image is measured. The measurement result is sent to the irradiation energy amount setting means 129 in association with R and the irradiation energy amount for each color of ink.

Next, in step S150, the irradiation energy amount setting means 129 constructs correlation data as shown in FIG. 8, and is previously measured for the recording medium and ink and stored in association with the combination of the recording medium and ink. Based on the data of the contact angle θ, the R / r target value is set from the range of R / r that satisfies the conditional expression (1). For example, when R / r is set to 1.76, it is calculated that an irradiation energy amount of 10 (mJ / cm ² ) is necessary. The measured correlation data can be integrated as necessary to increase the accuracy.

  In addition, it is preferable that the correlation data of FIG. 8 is made uniform among the inks of the respective colors from the viewpoint that the irradiation energy of the semi-curing light sources 16A to 16C can be made uniform. It becomes easy to control so as to satisfy the conditional expression (1) even when irradiated multiple times as described above. For the same reason, the irradiation energy amount is preferably set within the range of 1 to 2 which is the lower limit of R / r. FIG. 8 shows data corresponding to Examples 13 and 14 to be described later. For example, when the irradiation energy amount is set to 10 in FIG. Conditional expression (1) can be satisfied without exceeding the upper limit of r of 2.32.

  Next, in step S160, the irradiation energy amount setting means includes the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink using these optimum irradiation energy amounts for the determination print. The data is stored in the irradiation energy storage unit in association with the data, and the data is sent to the print controller 120. The print control unit 120 obtains the light emission amount of the semi-curing light source 16 corresponding to the set value of the irradiated irradiation energy amount, and sets it to each semi-curing light source 16A, 16B, 16C through the light source control unit 128.

  In this way, the irradiation energy amount setting means selects one irradiation energy amount to be referred to during recording between the minimum value and the maximum value of the plurality of types of irradiation energy amounts used for the determination print, and is used for the determination print. This information is stored in the irradiation energy storage means in association with at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink. Since the set value can be used as it is, the work efficiency of setting the irradiation energy amount can be improved.

  In step S170, image recording (printing) is performed using these optimum irradiation energy amounts. Also, in step S110, even when the optimum irradiation energy amount is set in step S120 assuming that the optimum irradiation energy amount exists, printing is performed in step S170. However, if the condition is greatly deviated or if a conditional branch that increases the number of N is set, the determination print in S130 can be performed again after setting the optimum irradiation energy amount in S120.

  As a result, the irradiation energy amount of the semi-curing light source 16 is adjusted based on the dot diameter of the second color of the test pattern, and it is possible to record an image with less streaking and blurring closer to a predetermined dot diameter. It becomes.

  As described above, according to the present embodiment, the irradiation energy amount of the semi-curing light source is set based on the recording medium identification information, the first ink identification information, and the second ink identification information during image recording. Therefore, the second ink is superimposed on the first ink that is semi-cured by the amount of irradiation energy determined so as to obtain a desired image, and a multicolor image is recorded. Thereby, the difference in the spread of the second ink depending on the type of the recording medium and the ink is suppressed, and a desired multicolor image with less streak-like defects and bleeding can be recorded. In particular, the reliability of the irradiation energy amount setting can be improved by setting based on the identification information.

  The irradiation energy amount setting means includes the active energy ray that is referred to during recording based on at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink. What is necessary is just to set the amount of irradiation energy. For example, in the case where recording is performed using a plurality of types of recording media with respect to one type of YMCK ink set in FIG. 1, for example, the irradiation energy of the active energy rays referred to during recording based on the identification information of the recording media What is necessary is just to set quantity. In this case, the irradiation energy amount storage means stores the identification information of the recording medium and the irradiation energy amount of each semi-curing light source in association with each other.

  Table 3 shows the value of the optimum irradiation energy amount when recording is performed using three types of recording media having contact angles of 12 °, 20 °, and 35 ° with respect to one type of YMCK ink set. An example of a table is shown. The irradiation energy amount storage means stores the identification information of the three types of recording media and the irradiation energy amount of each semi-curing light source in association with each other.

From Table 3, when recording an image on a recording medium having a contact angle of 12 °, the irradiation energy amounts of the semi-curing light sources 16A, 16B, and 16C are set to 46, 50, and 58 mJ / cm ² , respectively, and the contact angle is 20 °. When recording an image on the recording medium, the irradiation energy amounts of the semi-curing light sources 16A, 16B, and 16C are set to 52, 58, and 64 mJ / cm ² , respectively, and the image is recorded on the recording medium having a contact angle of 35 °. In this case, the irradiation energy amounts of the semi-curing light sources 16A, 16B, and 16C are set to 59, 68, and 74 mJ / cm ² , respectively. These irradiation energy amounts are set so as to satisfy the conditional expression (1).

<Multiple active energy ray curable inks>
Next, the active energy ray-curable ink according to the present invention will be described.

  A plurality of active energy ray-curable inks (hereinafter, also simply referred to as inks) according to the present invention constitute an ink set composed of two or more kinds of inks having different hues, and at least one kind of ink contains photopolymerization initiation The constitution of the agent group is different from the constitution of the photopolymerization initiator group of other inks.

  The ink constituting the ink set according to the present invention is preferably at least two types selected from yellow ink, magenta ink and cyan ink, and further includes four types of yellow ink, magenta ink, cyan ink and black ink. It is preferable to include. Further, if necessary, the ink set according to the present invention may have a configuration in which light color ink (for example, light magenta ink, light cyan ink, light black ink, etc.) or white ink using a white pigment is added. .

  Each active energy ray-curable ink according to the present invention is mainly composed of an active energy ray-polymerizable compound (hereinafter also simply referred to as a polymerizable compound), a constituent compound of a photopolymerization initiator group, and a color material. The constitution of the photopolymerization initiator group referred to in the present invention is a single photopolymerization initiator, a plurality of photopolymerization initiators, a combination of a photopolymerization initiator and a sensitizer, and a photopolymerization initiator and a sensitizer. The photopolymerization initiator group is different in composition between at least two types of ink.

[Active energy ray polymerizable compound]
Examples of the active energy ray polymerizable compound applicable to the active energy ray curable ink according to the present invention include a radical polymerizable compound and a cationic polymerizable compound. In particular, cationic polymerization UV curable inks have a wider range of irradiation energy amounts of active energy rays that are semi-cured than radical polymerization UV curable inks, making it easier to set the irradiation energy amount. preferable.

(Radically polymerizable compound)
The radically polymerizable compound applicable to the present invention is a compound having an ethylenically unsaturated bond capable of radical polymerization, and any compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. In other words, those having chemical forms such as monomers, oligomers and polymers are included. Only one kind of radically polymerizable compound may be used, or two or more kinds thereof may be used in combination at an arbitrary ratio in order to improve desired properties. A polyfunctional compound having two or more functional groups is more preferable than a monofunctional compound. More preferably, two or more polyfunctional compounds are used in combination for controlling performance such as reactivity and physical properties.

  Examples of compounds having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid and their salts, esters, urethanes, amides. And radically polymerizable compounds such as various anhydrides, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. Specifically, acryloylmorpholine, phenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate Bis (4-acryloxypolyethoxyphenyl) propane, EO-modified bisphenol A diacrylate, polyethylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerin epoxy acrylate, neopentyl glycol diacrylate, 1,6-hexane Diol diacrylate, ethylene glycol dia Relate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, Acrylic acid derivatives such as tetramethylol methane tetraacrylate, oligoester acrylate, N-methylol acrylamide, diacetone acrylamide, epoxy acrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, allyl methacrylate, glycine Methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane Examples include methacrylic derivatives such as trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, and other derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, and triallyl trimellitate. , Yamashita Shinzo, “Crosslinking agent handbook” (Taisei, 1981); Kato Kiyomi, “UV / EB Curing Han” Dobook (raw material edition) "(1985, Polymer publication society); Radtech study edition," Application and market of UV / EB curing technology ", p. 79, (1989, CMC); Eiichiro Takiyama," Polyester Commercially available products described in “Resin Handbook”, (1988, Nikkan Kogyo Shimbun), or radically polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used. The amount of the radical polymerizable compound added is preferably 1 to 97% by mass, more preferably 30 to 95% by mass.

(Cationically polymerizable compound)
Examples of the cationic polymerizable compound applicable to the present invention include an epoxy compound, an oxetane compound, and a vinyl ether compound that can be polymerized by cationic polymerization.

  Examples of the epoxy compound that can be used in the present invention include JP-A No. 2001-220526, JP-A No. 2002-188025, JP-A No. 2002-317139, JP-A No. 2003-55449, and JP-A No. 2003-73481. Any known epoxy compound described in 1. can be used, and a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring is epoxidized with a suitable oxidizing agent such as hydrogen peroxide or peracid. A cyclohexene oxide or cyclopentene oxide-containing compound obtained by this is preferable.

  As the oxetane compound that can be used in the present invention, for example, any known oxetane compound as disclosed in JP-A Nos. 2001-220526 and 2001-310937 can be used.

  Examples of the vinyl ether compound that can be used in the present invention include ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, and dipropylene glycol divinyl ether. , Butanediol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether and other di- or trivinyl ether compounds, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether Monomers such as octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether Examples include vinyl ether compounds.

  One of the polymerizable compounds may be used alone, but two or more may be used in appropriate combination.

  In addition, as a means for preventing a decrease in sensitivity due to the light-shielding effect due to the ink color material, it is possible to combine a cationically polymerizable monomer having a long initiator lifetime with an initiator to obtain a radical-cation hybrid curable ink.

[Configuration of photopolymerization initiator group]
Examples of the additive constituting the photopolymerization initiator group according to the present invention include radical polymerization initiators, cationic polymerization initiators, initiation assistants, and sensitizers. The added amount of these photopolymerization initiator groups in the ink is required to be 1 to 10 parts by mass of the whole ink.

  Various known compounds can be used for the photopolymerization initiator group according to the present invention, and the photopolymerization initiator group is selected from those soluble in the polymerizable compound.

(Photopolymerization initiator)
<Radical polymerization initiator>
Examples of the radical polymerization initiator include triazine derivatives described in JP-B-59-1281, JP-A-69-1621, and JP-A-60-60104, JP-A-59-1504 and JP-A-61-2243807. And other publications such as JP-B Nos. 43-23684, 44-6413, 44-6413, and 47-1604, and US Pat. No. 3,567,453. Diazonium compounds described in the specification, organic azide compounds described in U.S. Pat. Nos. 2,848,328, 2,852,379 and 2,940,853, Japanese Patent Publication No. 36-22062, Ortho-quinonediazides described in JP-A-37-13109, JP-A-38-18015, JP-A-45-9610, JP-B-55-39162, JP-A-59-1 No. 023 etc. and various onium compounds described in “Macromolecules, Vol. 10, Volume 1307 (1977)”, azo compounds described in JP-A-59-142205, 1-54440, European Patent Nos. 109,851 and 126,712, “Journal of Imaging Science” (J. Imag. Sci.), Vol. 30, No. 174 Page (1986), metal allene complexes described in JP-A-4-2133861 and JP-A-4-255347, organoboron complexes described in JP-A-4-151197, and titanocene described in JP-A-61-151197. "Coordination Chemistry Review" ry Review), 84, 85-277 (1988) and JP-A-2-182701, transition metal complexes containing transition metals such as ruthenium, JP-A-3-209477 Examples include 2,4,5-triarylimidazole dimer, carbon tetrabromide, and organic halogen compounds described in JP-A-59-107344. These polymerization initiators are preferably contained in the range of 0.01 to 10 parts by mass with respect to 100 parts by mass of the compound having an ethylenically unsaturated bond capable of radical polymerization.

<Cationic polymerization initiator>
The active energy ray-curable ink according to the present invention preferably contains a cationic polymerization initiator as a photopolymerization initiator together with the cationic polymerizable compound.

  Specific examples of the cationic polymerization initiator include a photoacid generator and the like. For example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “ Organic materials for imaging ", Bunshin Publishing (1993), see pages 187-192). Examples of compounds suitable for the present invention are listed below.

First, diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds of phosphonium such as ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 -, CF 3 SO 3 - and salts be able to.

  Specific examples of onium compounds that can be used in the present invention are shown below.

  Secondly, sulfonated compounds that generate sulfonic acid can be mentioned, and specific compounds thereof are exemplified below.

  Thirdly, halides that generate hydrogen halide can also be used, and specific compounds thereof are exemplified below.

  Fourthly, an iron allene complex can be mentioned.

(Sensitizer)
In the active energy ray-curable ink according to the present invention, it is preferable to use a sensitizer having ultraviolet spectrum absorption at a wavelength longer than 300 nm. For example, a hydroxyl group, an optionally substituted aralkyloxy group or A polycyclic aromatic compound having at least one alkoxy group, a carbazole derivative, a thioxanthone derivative, and the like can be given.

  As the polycyclic aromatic compound that can be used in the present invention, naphthalene derivatives, anthracene derivatives, chrysene derivatives, and phenanthrene derivatives are preferable. As an alkoxy group which is a substituent, a C1-C18 thing is preferable and a C1-C8 thing is especially preferable. As the aralkyloxy group, those having 7 to 10 carbon atoms are preferable, and benzyloxy groups and phenethyloxy groups having 7 to 8 carbon atoms are particularly preferable.

  Examples of these sensitizers that can be used in the present invention include carbazole derivatives such as carbazole, N-ethylcarbazole, N-vinylcarbazole, N-phenylcarbazole, 1-naphthol, 2-naphthol, 1-methoxynaphthalene, 1-stearyloxynaphthalene, 2-methoxynaphthalene, 2-dodecyloxynaphthalene, 4-methoxy-1-naphthol, glycidyl-1-naphthyl ether, 2- (2-naphthoxy) ethyl vinyl ether, 1,4-dihydroxynaphthalene, 1, , 5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 2,7-dimethoxynaphthalene, 1,1′-thiobis (2-naphthol), 1,1′-bi-2-naphthol, 1,5-naphthyl diglycid Ether, 2,7-di (2-vinyloxyethyl) naphthyl ether, 4-methoxy-1-naphthol, ESN-175 (epoxy resin manufactured by Nippon Steel Chemical Co., Ltd.) or its series, condensate of naphthol derivative and formalin, etc. Naphthalene derivatives, 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 2-tbutyl-9,10-dimethoxyanthracene, 2,3-dimethyl-9,10-dimethoxyanthracene, 9-methoxy -10-methylanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, 2-tbutyl-9,10-diethoxyanthracene, 2,3-dimethyl-9,10-di Ethoxyanthracene, 9-ethoxy-10-methylanthracene, 9, 0-dipropoxyanthracene, 2-ethyl-9,10-dipropoxyanthracene, 2-tbutyl-9,10-dipropoxyanthracene, 2,3-dimethyl-9,10-dipropoxyanthracene, 9-isopropoxy- 10-methylanthracene, 9,10-dibenzyloxyanthracene, 2-ethyl-9,10-dibenzyloxyanthracene, 2-tbutyl-9,10-dibenzyloxyanthracene, 2,3-dimethyl-9,10 -Dibenzyloxyanthracene, 9-benzyloxy-10-methylanthracene, 9,10-di-α-methylbenzyloxyanthracene, 2-ethyl-9,10-di-α-methylbenzyloxyanthracene, 2-tbutyl -9,10-di-α-methylbenzyloxyanthracene, 2,3- Dimethyl-9,10-di-α-methylbenzyloxyanthracene, 9- (α-methylbenzyloxy) -10-methylanthracene, 9,10-di (2-hydroxyethoxy) anthracene, 2-ethyl-9,10 -Anthracene derivatives such as di (2-carboxyethoxy) anthracene, 1,4-dimethoxychrysene, 1,4-diethoxychrysene, 1,4-dipropoxychrysene, 1,4-dibenzyloxychrysene, 1,4- Examples include chrysene derivatives such as di-α-methylbenzyloxychrysene, phenanthrene derivatives such as 9-hydroxyphenanthrene, 9,10-dimethoxyphenanthrene, and 9,10-diethoxyphenanthrene. Among these derivatives, 9,10-dialkoxyanthracene derivatives which may have an alkyl group having 1 to 4 carbon atoms as a substituent are particularly preferable, and the methoxy group and ethoxy group are preferable as the alkoxy group.

  Examples of the thioxanthone derivative include thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone 2-chlorothioxanthone, and the like.

(Starting aid)
An initiator is a substance that acts as a sensitizing dye that improves the radical or acid generation efficiency of an initiator by donating energy to the initiator by light irradiation, electron donation, electron attraction, heat generation, etc. Yes, applied in combination with initiator.

  Examples of the initiator include xanthene, thioxanthone dye, ketocoumarin, thioxanthene dye, cyanine, phthalocyanine, merocyanine, porphyrin, spiro compound, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane , Triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrylium compound, pyromethene compound, pyrazolotriazole compound, benzothiazole compound, barbituric acid derivative, thiobarbituric acid derivative and the like can be applied.

  In addition to the above-mentioned compounds, it is well known that the initiator acts as a sensitizing dye in documents such as “Development technology of polymer additives” (CMC Publishing Co., Ltd., supervised by Junichi Daikatsu). The substance may be applied. The initiation assistant can also be regarded as a component that forms part of the photopolymerization initiator.

  In addition to these photoinitiators, an accelerator aid may be added to accelerate the photopolymerization (curing) reaction. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  Examples of a combination of a radical polymerization initiator and an initiator that are applied to the radical polymerizable composition include a peracid ester as a radical polymerization initiator and xanthene, a thioxanthone dye, a ketocoumarin, a thiopyrylium salt as an initiator. And a combination of an onium salt such as diphenyliodonium salt which is a radical polymerization initiator and a thioxanthene dye which is an initiation assistant are well known.

  Further, when applying titanocenes as radical polymerization initiators, as initiators for sensitizing the titanocenes from visible light to near infrared light corresponding to lasers or LEDs, for example, cyanine, phthalocyanine, merocyanine, porphyrin, Spiro compound, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrylium compound, pyromethene compound, pyrazolotriazole A compound, a benzothiazole compound, a barbituric acid derivative, a thiobarbituric acid derivative, or the like can be applied.

  As the starting aid used in combination with titanocene, further, European Patent No. 568,993, US Patent Nos. 4,508,811, 5,227,227, JP 2001-125255 A, JP 11-271969 A, etc. The compounds described in (1) are also applicable. Specific examples of the combination of such a titanocene radical polymerization initiator and an initiation assistant include combinations described in JP-A Nos. 2001-125255 and 11-271969.

[Color material]
The coloring material used for the active energy ray-curable ink according to the present invention may be a pigment or a dye. From the viewpoint of the weather resistance of the image, it is preferable to use a pigment.

  The pigments that can be preferably used in the present invention are listed below.

C. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 150, 151, 154, 180, 185,
C. I. Pigment Red 5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202,
C. I. Pigment Violet 19, 23,
C. I. Pigment Blue 1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60,
C. I. Pigment Green 7, 36,
C. I. Pigment White 6, 18, 21,
C. I. Pigment Black 7.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Further, a dispersing agent can be added when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used, and examples of the polymer dispersant include Avecia's Solsperse series and Ajinomoto Fine-Techno's PB series. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound. However, the radiation curable ink used in the present invention is preferably solvent-free because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle diameter of the pigment particles is 0.08 to 0.2 μm, and the maximum particle diameter is 0.3 to 10 μm, preferably 0.3 to 3 μm. The selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  In the ink according to the present invention, the color material concentration is preferably 1% by mass to 30% by mass of the entire ink. For inks other than white, the content is more preferably 1% by mass to 10% by mass.

[Other additives]
A polymerization inhibitor can be added to the ink according to the present invention in an amount of 200 to 20000 ppm from the viewpoint of improving the storage stability. Since the ink according to the present invention is preferably ejected by heating and lowering the viscosity in the range of 40 to 80 ° C., it is preferable to add a polymerization inhibitor in order to prevent head clogging due to thermal polymerization.

  In addition to this, surfactants, leveling additives, matting agents, polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes are added to adjust film properties as necessary. can do.

  The viscosity at 25 ° C. is preferably 25 mPa · s or more and 500 mPa · s or less from the viewpoint of ease of fixing of the droplet after landing, and the viscosity at the time of discharge is 8 mPa · s or more and 20 mPa · s or more due to the driving voltage and stability at the time of discharge. The following is preferred. The free surface tension of the ink is preferably 30 mN / m or less because the retraction after landing is small and the line outline drawing property is good.

  As described above, the contact angle with the recording medium is preferably 10 to 30 ° from the viewpoint that the receding after landing due to the liquid is small and the drawing of the outline of the line is good and fixing on the recording medium is easy.

  In the present embodiment, image recording is performed using ink that is cured by irradiation with ultraviolet rays. However, the ink is not necessarily limited thereto, and examples thereof include electron beams, X-rays, visible rays, infrared rays, and the like. The ink may be cured by irradiating activation energy rays other than ultraviolet rays such as electromagnetic waves. In this case, a polymerizable compound that is polymerized and cured with an activation energy ray other than ultraviolet rays and a photoinitiator that initiates a polymerization reaction between the polymerizable compounds with an activation energy ray other than ultraviolet rays are applied to the ink. The Moreover, when using the photocurable ink which hardens | cures with activation energy rays other than an ultraviolet-ray, it replaces with an ultraviolet light source and the light source which irradiates the activation energy ray is applied.

  Further, as ink droplet ejection methods of the inkjet head 12, electro-mechanical conversion methods (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), electro- Specific examples include thermal conversion methods (for example, thermal ink jet type, bubble jet (registered trademark) type), electrostatic attraction methods (for example, electric field control type, slit jet type, etc.), discharge methods (for example, spark jet type, etc.), etc. An example can be given. The present invention may be of any ejection method, but a share mode type as described in JP-A No. 2004-122760 is particularly preferable. The driving waveform is preferably a so-called DRR driving method in which the volume of the pressure chamber is expanded and held for a predetermined time and then restored, and subsequently the volume is contracted and held for a predetermined time and then restored.

  Next, the “recording medium” used in the present embodiment will be described.

  As a recording medium used in the present embodiment, recording made of various papers such as plain paper, recycled paper, glossy paper, etc., various fabrics, various non-woven fabrics, resin, metal, glass and the like applied to a normal ink jet recording apparatus. The medium is applicable. As a form of the recording medium, a roll shape, a cut sheet shape, a plate shape, or the like is applicable. Further, as the recording medium used in the present embodiment, various known papers such as various types of paper whose recording surface is coated with a resin, a film containing a pigment, and a foam film can be applied.

In addition, as a guideline of “a recording medium substantially non-absorbing ink” that exhibits the effect particularly remarkably in the configuration of the present invention, the following two criteria are:
1) There is no penetration of ink deeper than 2 μm into the recording medium.
2) More than 20% of the 50 pL droplets jetted on the surface of the recording medium do not disappear in the recording medium within 5 seconds,
This means a case where at least one of the above is satisfied. One of ordinary skill in the art can use standard analytical methods to determine whether a recording medium is included in either or both of the above criteria. For example, after jetting ink onto the surface of the recording medium, a section of the recording medium is taken and examined with a transmission electron microscope to determine whether the ink penetration depth is greater than 2 μm or not Can do. Thus, an appropriate analysis method can be taken as appropriate.

  Next, examples of the substantially non-water-absorbing recording medium used in the present embodiment include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, ceramics, and surface-treated wood. Can be mentioned. In the present invention, a recording medium obtained by combining a plurality of these materials can be used for the purpose of adding functions. The term “substantially small amount of ink penetrating downward from the printing surface of the recording medium” includes a support on which UV curable ink is generally printed on the market.

  As the synthetic resin, any synthetic resin or resin film processed for printing can be used. For example, polyesters such as polyethylene terephthalate and polybutadiene terephthalate, polyolefins such as polyvinyl chloride, polystyrene, polyethylene, polyurethane, and polypropylene. , Acrylic resin, polycarbonate, acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, celluloid and the like. The thickness and shape of the recording medium when using a synthetic resin are not particularly limited, and may be any of a film shape, a label shape, a card shape, and a block shape, and either transparent or opaque. There may be.

  The synthetic resin is preferably used in the form of a film used for so-called soft packaging, and various non-absorbable plastics and films thereof can be used. Examples of the plastic film include a PET film, an OPS film, an OPP film, a PNy film, a PVC film, a PE film, a TAC film, and a PP film. Other plastics that can be used include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers.

  Examples of the resin-coated paper include a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both surfaces of paper are laminated with a polyolefin resin. Particularly preferred is a paper support in which both sides of the paper are laminated with a polyolefin resin. In the case of synthetic paper, YUPO, peach coat, Karel, over paper, etc. are also hit.

  There is no restriction | limiting in particular as said metal, For example, aluminum, iron, gold | metal | money, silver, copper, nickel, titanium, chromium, molybdenum, silicon, lead, zinc, stainless steel, etc., and these composite materials are suitable.

  Furthermore, a read-only optical disk such as a CD-ROM or DVD-ROM, a write-once optical disk such as a CD-R or DVD-R, or a rewritable optical disk can be used, and ink jet recording is performed on the label surface side. be able to.

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. It is a block diagram showing the main control structure of an inkjet recording device. It is a correlation diagram of contact angle (theta) and R / r. It is a schematic diagram which shows the flying state of the ink drop at the time of measuring r. It is a figure which shows the example of the determination pattern of R. It is a schematic diagram for demonstrating the relationship between the semi-hardening of an ink and R. FIG. 3 is a flowchart illustrating an example of the operation of the ink jet recording apparatus. It is a correlation diagram of irradiation energy amount and R / r. It is a correlation diagram of contact angle (theta) and R / r.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet recording device 12Y, 12C, 12M, 12K Head 14 Ink storage / loading part 16, 16A, 16B, 16C, 16D Semi-curing light source 17 Pressure fixing part 18 Complete curing light source 20 Recording medium 22 Paper feeding part 26 Adsorption belt conveyance Section 32 Magazine 45 Roller 46 Heater

Claims (16)

A transport unit for transporting the recording medium in the transport direction;
A head portion in which a plurality of full-line-type ink jet heads that discharge active energy ray-curable inks of different colors to the recording medium are arranged in the transport direction;
Disposed between the inkjet heads disposed between the inkjet heads and ejected from the inkjet heads on the upstream side in the transport direction and landed on the recording medium and ejected from the inkjet heads on the downstream side in the transport direction A semi-curing light source for irradiating an active energy ray for semi-curing the first ink before the second ink lands,
Irradiation energy amount for setting the irradiation energy amount of the active energy ray to be referred to during recording based on at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink Setting means;
An ink jet recording apparatus comprising: Irradiation energy amount storage means for storing at least one of the recording medium identification information, the first ink identification information, and the second ink identification information in association with the irradiation energy amount;
The irradiation energy amount setting means outputs the irradiation energy amount corresponding to at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink from the irradiation energy amount storage means. 2. The inkjet recording apparatus according to claim 1, wherein the irradiation energy amount read out and set is set as the irradiation energy amount referred to during recording. A determination print output means for outputting a determination print of a superimposed image in which the image of the second ink is formed on the image of the first ink having a plurality of regions each having a different amount of irradiation energy;
The irradiation energy amount setting means selects one irradiation energy amount to be referred to during recording between the minimum value and the maximum value of a plurality of types of irradiation energy amounts used for the determination print, and the recording medium used for the determination print 3. The irradiation energy amount storage unit stores the identification information in association with at least one of the identification information of the first ink, the identification information of the first ink, and the identification information of the second ink. Inkjet recording device. As the active energy ray curable ink, a cationic polymerization type ultraviolet curable ink is used, the viscosity at 25 ° C. is 25 mPa · s or more and 500 mPa · s or less, and the viscosity when discharged is 8 mPa · s or more and 20 mPa · s. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is the following. The inkjet recording apparatus according to claim 1, wherein the irradiation energy amount is set in a range of 5 mJ / cm ^{2 to} 50 mJ / cm ² . The head unit is an array of three or more full-line type ink jet heads that discharge active energy ray-curable inks of different colors to the recording medium, in the transport direction,
The irradiation energy amount setting means is adjacent to the identification information of the recording medium, the identification information of the first ink ejected from the inkjet head on the upstream side in the transport direction adjacent to the semi-curing light source, and the semi-curing light source The irradiation energy amount is set based on at least one of identification information of the second ink ejected from the inkjet head on the downstream side in the transport direction. 2. An ink jet recording apparatus according to item 1. The head unit is an array of three or more full-line type ink jet heads that discharge active energy ray-curable inks of different colors to the recording medium, in the transport direction,
The semi-curing light source is disposed between the inkjet heads of the respective colors,
The irradiation energy amount setting means includes a semi-curing light source based on at least one of the identification information of the recording medium, the identification information of the first ink and the identification information of the second ink corresponding to each semi-curing light source. The inkjet recording apparatus according to claim 1, wherein the irradiation energy amount is set every time. The ink jet recording apparatus according to claim 1, wherein the recording medium is a recording medium that is substantially non-absorbing ink. Using a plurality of full-line type ink jet heads that discharge active energy ray-curable inks of different colors onto a recording medium, the first ink was ejected onto the recording medium and then landed on the recording medium. An ink jet recording method for performing image recording by irradiating an active energy ray for semi-curing the first ink, ejecting and landing a second ink on the semi-cured first ink,
Irradiation energy amount for setting the irradiation energy amount of the active energy ray to be referred to during recording based on at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink A setting process;
Performing the image recording with the set irradiation energy amount;
An ink jet recording method comprising: In the irradiation energy amount setting step, the irradiation energy amount corresponding to at least one of the identification information of the recording medium, the identification information of the first ink, and the identification information of the second ink is set as the identification information of the recording medium. And reading from the irradiation energy amount storage means for storing the irradiation energy amount in association with at least one of the identification information of the first ink and the identification information of the second ink, and the read irradiation energy amount is referred to during recording. The inkjet recording method according to claim 9, wherein the irradiation energy amount is set. Before the irradiation energy amount setting process,
A determination print output step of outputting a determination print of a superimposed image in which the image of the second ink is formed on the image of the first ink having a plurality of regions each having a different amount of irradiation energy; and
One irradiation energy amount to be referred to at the time of recording is selected between the minimum value and the maximum value of the plurality of types of irradiation energy amounts used for the determination print, and the identification information of the recording medium used for the determination print, the first Storing in the irradiation energy amount storage means in association with at least one of identification information of one ink and identification information of the second ink;
The inkjet recording method according to claim 9, wherein: As the active energy ray curable ink, a cationic polymerization type ultraviolet curable ink is used, the viscosity at 25 ° C. is 25 mPa · s or more and 500 mPa · s or less, and the viscosity when discharged is 8 mPa · s or more and 20 mPa · s. The inkjet recording method according to any one of claims 9 to 11, wherein: The inkjet recording method according to claim 9, wherein the irradiation energy amount is set in a range of 5 mJ / cm ^{2 to} 50 mJ / cm ² . The image recording is performed using an active energy ray curable ink of three or more colors,
The irradiation energy amount setting step includes identification information of the recording medium, identification information of the first ink used for image recording performed immediately before the semi-curing process, and image recording performed immediately after. The inkjet recording method according to claim 9, wherein the irradiation energy amount is set based on at least one of the identification information of the two inks. The image recording is performed using an active energy ray curable ink of three or more colors,
The semi-curing process is performed between the image recording of each color,
In the irradiation energy amount setting step, each semi-curing is based on at least one of the identification information of the recording medium, the identification information of the first ink and the identification information of the second ink corresponding to each semi-curing process. The inkjet recording method according to claim 9, wherein the irradiation energy amount is set for each process. The ink jet recording method according to claim 9, wherein the recording medium is a recording medium that is substantially non-absorbing ink.

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