JP2004042548A - Ink jet recording method and recording apparatus - Google Patents

Abstract

An object of the present invention is to prevent the occurrence of mottle and bleed and to prevent a deterioration in image quality.
Kind Code: A1 It is assumed that ultraviolet rays curable ink, which cures when irradiated with ultraviolet rays from different nozzles, is shifted at a predetermined time to record dots on a recording medium. The ultraviolet curable ink 12 ejected onto the recording medium 13 is irradiated with ultraviolet rays from the ultraviolet irradiator 18 in accordance with the respective ejection timings to increase the viscosity and pre-cure so that adjacent dots do not mix with each other. Further, ultraviolet rays are irradiated from an ultraviolet irradiation device 19 to perform full curing.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording method and a recording apparatus for recording an image on a recording medium by discharging an ultraviolet curable ink which cures when irradiated with ultraviolet light.
[0002]
[Prior art]
Water-based inks, oil-based inks, solvent inks, and ultraviolet-curable inks that cure when irradiated with ultraviolet rays are used as inks for inkjet recording apparatuses that record images by discharging liquid ink from nozzles of an inkjet recording head. . For these various inks, a recording medium suitable for each is selected from the difference in fixing mechanism, and is used in different applications.
[0003]
Water-based inks and oil-based inks are generally used for absorptive recording media that absorb ink, and their fixing mechanisms are different from one another. In the case of the aqueous ink, it is governed by both the evaporation of the solvent and the penetration into the recording medium. In the case of oil-based ink, penetration into a recording medium is dominant. That is, the water-based ink or the oil-based ink has poor fixability to a non-absorbing recording medium that does not absorb the ink, for example, a plastic film such as OHP.
[0004]
For this reason, solvent inks have often been used for non-absorbing recording media, but the fixing mechanism is dominated by the evaporation of the solvent, and a system for collecting the generated volatile organic compounds is needed. It becomes. In addition, solvent ink has high volatility, and the frequency of clogging due to evaporation and drying of the solvent at the nozzle formed in the ink jet recording head is high, often causing non-ejection, and frequent maintenance such as spits and purging is required. is there.
[0005]
The fixing mechanism of the ultraviolet curable ink is a photo-curing reaction, that is, an ultraviolet-curing reaction. The photo-polymerization initiator reacts with the reactive monomer or oligomer by the ultraviolet rays to be polymerized, so that the non-absorbing recording medium is used. Can be reliably fixed. Further, these reactions are performed in a very short time and do not generate a volatile organic solvent. Furthermore, it has a very low volatility and very little clogging due to evaporation and drying at the nozzle, which is a problem with solvent ink. Due to such an excellent fixing mechanism, low volatility and low viscosity of the ink, there is a demand for an ink jet recording apparatus using an ultraviolet curable ink for a non-absorbing recording medium.
[0006]
[Problems to be solved by the invention]
However, a problem arises when the ultraviolet curable ink is ejected from different nozzles at a temporally shifted timing and recorded on an adjacent portion on a recording medium. For example, when printing monochrome dots, as shown in FIG. 6A, the dots n11 and n12 in the first row land on the recording medium 1 first, and then after a predetermined time, the dots in FIG. As shown in FIG. 6B, when the dots n21 and n22 in the second row are landed on the recording medium 1, the dots n11, n12, n21 and n22 are not cured, and are shown in FIG. 6C. Thus, for example, on the upper side, a phenomenon occurs in which the dot n11 is attracted to the dot n21, and on the lower side, the dot n22 is attracted to the dot n12, and the finally cured dot is a black dot in FIG. As shown by, a dot n31 is formed by combining the dot n11 with the dot n21, and a dot n32 is formed by combining the dot n22 with the dot n12.
[0007]
As a result, there is a problem that a difference in shading occurs in the dots, and a mottled pattern called mottle is recorded, resulting in a decrease in image quality. Further, when printing dots of different colors in the first column and the second column when recording color dots, so-called bleeding occurs in which ink is mixed at the boundary surface between the dots in the first column and the second column. However, there is a problem that image quality is reduced.
[0008]
The present invention has been made in order to solve such a problem, and in the case of performing recording using an ultraviolet curable ink, inkjet recording that can prevent deterioration in image quality by preventing occurrence of mottle and bleeding It is intended to provide a method and a recording device.
[0009]
[Means for Solving the Problems]
The present invention is based on the premise that dots are recorded on a recording medium by ejecting an ultraviolet curable ink that cures when irradiated with ultraviolet rays from different nozzles at a predetermined time interval. The ultraviolet-curable ink dots ejected on the recording medium are irradiated with ultraviolet rays at the respective ejection timings to increase the viscosity and pre-cure so that the adjacent dots do not mix with each other. Let it cure.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First Embodiment)
FIG. 1 is a schematic sectional view showing an ink jet recording apparatus. The ultraviolet curable ink 12 used in the ink jet recording apparatus 11 has a property of being cured by irradiating ultraviolet rays.
[0011]
Examples of the UV-curable ink 12 include 1 to 3 wt% of a pigment or dye as a coloring material, 50 to 70 wt% of a radically polymerizable acrylic monomer having a cyclic structure, and a radically polymerizable aliphatic urethane acrylate oligomer. A mixture of 10 to 20 wt%, a trifunctional acrylate oligomer of 10 to 20 wt%, a radical photopolymerization initiator of 3 to 5 wt%, and an organic polymer dispersion of 0.5 to 3 wt% is used. .
[0012]
The ink jet recording apparatus 11 includes a paper supply unit 14 on which a recording medium 13 arranged below the apparatus is set, a paper supply unit 15 for supplying the recording medium 13 from the paper supply unit 14, and a paper supply unit 15. And a medium conveying means 16 for conveying the recording medium 13 fed from the printer.
[0013]
The inkjet recording apparatus 11 includes a color inkjet recording head mechanism 17 that is disposed at the center of the apparatus and discharges the ultraviolet curable ink 12 to the recording medium 13 transported by the medium transport unit 16. An ultraviolet irradiation device 18 as a pre-curing means for pre-curing by irradiating ultraviolet rays to the ultraviolet curing ink 12 landed on the recording medium 13 by the mechanism 17 and an ultraviolet curing ink 12 pre-cured by the ultraviolet irradiation device 18 Further, there are provided an ultraviolet irradiation device 19 as a main curing unit for performing main curing by irradiating ultraviolet rays, and a discharge unit 20 for discharging the recording medium 13 which has been completely cured by the ultraviolet irradiation device 19.
[0014]
The feeding unit 15 separates the recording medium 13 set in the sheet feeding unit 14 one by one from a top by a separation roller 21, and the medium conveying unit 16 is separated by two pairs of sheet feeding rollers 22 a, 22 b, 22 c, and 22 d. To be fed to
[0015]
The medium transport unit 16 forms a transport path by extending a medium transport belt 26 between a driving roller 24 driven by a stepping motor 23 and a driven roller 25. A plurality of tension rollers 27 are provided inside the transport belt 26 so as to loosen the transport belt 26 and maintain a predetermined tension.
[0016]
Further, the recording medium 13 is sandwiched between the driven roller 25 and the conveying roller 28 and is conveyed in a direction indicated by an arrow in the drawing while being adsorbed on the medium conveying belt 26, and passes through a position facing the color ink jet recording head mechanism 17. The discharge unit 20 discharges the sheet to a discharge sheet storage unit 20f by discharge rollers 20a, 20b, 20c, and 20d.
[0017]
The color inkjet recording head mechanism 17 is disposed above the medium transport belt 26, and is an ultraviolet curable type of four colors of yellow, magenta, cyan, and black in order from upstream to downstream in the transport direction of the recording medium 13. The inkjet recording heads 17a, 17b, 17c, and 17d for storing the ink 12 are provided.
[0018]
The ink jet recording heads 17a, 17b, 17c, and 17d have a large number of fine liquid ejection ports in a direction intersecting the conveyance direction of the recording medium 13 over a width that can sufficiently cover the entire width of the recording medium 13, that is, , Nozzles 29 are arranged in a line-type head, and discharge the ultraviolet curable ink 12 of each color from the nozzles 29. Each of the ink jet recording heads 17a, 17b, 17c and 17d uses a pressure generating means composed of an electromechanical transducer such as a piezo element for discharging the ink 12 from the nozzle 29.
[0019]
The ultraviolet irradiation device 18 is installed on the downstream side near each of the ink jet recording heads 17a, 17b, 17c, and 17d so as to face the medium transporting means 16, respectively, and irradiates the entire width of the recording medium 13 with ultraviolet light. The ultraviolet curable ink 12 can be pre-cured. The ultraviolet irradiation device 18 is provided with, for example, an ultraviolet (UV) lamp such as a high-pressure mercury lamp or an excimer lamp, and irradiates ultraviolet rays with the ultraviolet lamp.
[0020]
The ultraviolet irradiation amount for pre-curing of the ultraviolet irradiation device 18 is determined when dots ejected from each of the inkjet recording heads 17a, 17b, 17c, and 17d onto the recording medium 13 are adjacent to each other (for example, the inkjet recording head 17a). (When the dots from the ink jet recording head 17b are adjacent to each other), the light amount is adjusted to increase the viscosity so that the dots are not mixed.
[0021]
FIGS. 2A and 2B are graphs showing the relationship between the integrated amount of ultraviolet light and the degree of polymerization (the degree of solidification of the ink) for two types of ultraviolet curable inks. In the case of the ink of FIG. When the light quantity is 50 mJ / cm ^2, the degree of polymerization is about 40%, and in the case of the ink (b), the polymerization degree is about 60% when the integrated light quantity is 50 mJ / cm ² . This degree of polymerization is suitable for pre-curing. Therefore, the irradiation amount of the ultraviolet light for pre-curing the ultraviolet irradiation device 18 is adjusted, for example, so that the integrated light amount becomes about 50 mJ / cm ² .
[0022]
The ultraviolet irradiation device 19 is installed at the rearmost end on the downstream side of the medium transport belt 26, that is, further downstream of the ultraviolet irradiation device 18 installed on the downstream side of the black inkjet recording head 17d. The ultraviolet curable ink 12 can be fully cured by irradiating the entire width of the ink with ultraviolet rays. Similarly to the ultraviolet irradiation device 18, the ultraviolet irradiation device 19 is provided with, for example, an ultraviolet (UV) lamp such as a high-pressure mercury lamp or an excimer lamp, and irradiates the ultraviolet light with the ultraviolet lamp.
[0023]
Next, the operation of the present embodiment will be described.
First, image processing for recording is started by an image processing means (not shown), and data for recording is supplied to each of the inkjet recording heads 17a to 17d. On the other hand, the recording medium 13 set in the paper feeding section 14 is separated one by one by a separation roller 21 at a predetermined timing, and is fed to the medium conveying means 16 by paper feeding rollers 22a, 22b, 22c, and 22d. Then, the recording medium 13 is attracted onto the medium transport belt 26 by the driven roller 25 and the transport roller 28, and is transported to a position facing each of the inkjet recording heads 17a, 17b, 17c, 17d.
[0024]
First, the yellow ink jet recording head 17a operates to discharge the ultraviolet curable ink 12 from the nozzle 29 to land a dot on the recording medium 13. The dots are irradiated with ultraviolet rays by an ultraviolet irradiation device 18 immediately downstream, and are pre-cured to increase the viscosity.
[0025]
Subsequently, the magenta ink jet recording head 17b is operated to discharge the ultraviolet curable ink 12 from the nozzle 29 and land a dot on the recording medium 13. The dots are irradiated with ultraviolet rays by an ultraviolet irradiation device 18 immediately downstream, and are pre-cured to increase the viscosity.
[0026]
Subsequently, the cyan ink jet recording head 17c is operated, and the ultraviolet curable ink 12 is discharged from the nozzle 29 to land dots on the recording medium 13. The dots are irradiated with ultraviolet rays by an ultraviolet irradiation device 18 immediately downstream, and are pre-cured to increase the viscosity.
[0027]
Finally, if there is black printing, the black ink jet recording head 17d operates to discharge the ultraviolet curable ink 12 from the nozzle 29 to land dots on the recording medium 13. The dots are irradiated with ultraviolet rays by an ultraviolet irradiation device 18 immediately downstream, and are pre-cured to increase the viscosity.
[0028]
The pre-cured dots recorded on the recording medium 13 are finally finally cured by the ultraviolet irradiation device 19. The recording medium 13 that has been completely cured is discharged to a discharge sheet storage section 20f by discharge rollers 20a, 20b, 20c, and 20d.
[0029]
As described above, the dots of the ultraviolet curable ink 12 discharged from each of the ink jet recording heads 17a, 17b, 17c, and 17d onto the recording medium 13 are immediately pre-cured and thickened by the ultraviolet irradiation device 18, so that, for example, FIG. As shown in FIG. 3A, the dots n11 and n12 in the first row are recorded by the yellow ink jet recording head 17a, and then, by the magenta ink jet recording head 17b, as shown in FIG. When the dots n21 and n22 in the column are recorded, the dots n11 and n12 in the first column are pre-cured as indicated by the black circles in the figure, and therefore are not drawn to the dots n21 and n22 in the second column.
[0030]
Accordingly, as shown in FIG. 3C, ink does not mix with the yellow dots n11 and n12 in the first column and the magenta dots n21 and n22 in the second column. That is, the occurrence of bleeding is prevented, and the deterioration of image quality is prevented. Then, an image excellent in light resistance, scratch resistance, and water resistance inherent to the cured resin of the ultraviolet curable ink can be recorded.
[0031]
(Second embodiment)
The same parts as those in the first embodiment are denoted by the same reference numerals, and different parts will be described. FIG. 4 is a schematic side view of the ink jet recording apparatus according to the present embodiment.
[0032]
In the first embodiment, the ultraviolet irradiating device 18 which is a pre-curing unit for pre-curing the ultraviolet curable ink 12 is provided for each of the inkjet recording heads 17a to 17d. As shown in FIG. 4, the recording device 41 is provided with one ultraviolet irradiation device 18 as a pre-curing means on the downstream side near the black ink jet recording head 17d. An ultraviolet irradiation device 19 as a curing means is provided.
[0033]
Further, the medium conveying means 16 is of a driving method of moving forward or reverse, and the driving roller 25 is rotated forward and reverse by a stepping motor 23 so that the conveying belt 26 can move in the direction of the arrow A and the direction of the opposite arrow B. Has become.
[0034]
The operation of this embodiment will be described.
First, the dots are recorded on the recording medium 13 by discharging the yellow ultraviolet curable ink 12 from the nozzles 29 of the yellow ink jet recording head 17a. Next, in order to pre-cure the recorded dots, the medium conveyance belt 26 is conveyed in the direction of arrow A, and the recorded dots are moved to the position of the ultraviolet irradiation device 18 and irradiated with ultraviolet light from the ultraviolet irradiation device 18 to perform pre-curing. .
[0035]
Next, the drive roller 24 is rotated in the reverse direction to move the medium transport belt 26 in the direction indicated by the arrow B in the opposite direction, and after returning the recording medium 13, the magenta ultraviolet curable ink is discharged from the nozzle 29 of the magenta inkjet recording head 17 b. 12 is ejected, and dots are recorded on the recording medium 13. Then, similarly to the case of yellow, the conveyor belt 26 is conveyed in the direction A, and the magenta dots are irradiated with ultraviolet rays from the ultraviolet irradiation device 18 to be pre-cured.
[0036]
These operations are repeated, and when dot recording on the recording medium 13 and pre-curing thereof are all completed, the recording medium 13 is finally conveyed to an ultraviolet irradiation device 19 and irradiated with ultraviolet rays to be fully cured.
[0037]
Therefore, also in this embodiment, since the dot recording and the pre-curing are repeated, the adjacent inks are not mixed. That is, the occurrence of bleeding is prevented, and the deterioration of image quality is prevented. Further, since the number of the ultraviolet irradiation device 18 as the pre-curing means is one, the size can be reduced.
[0038]
(Third embodiment)
The same parts as those in the above-described embodiment are denoted by the same reference numerals, and different parts will be described. FIG. 5 is a schematic side view of a main part of the ink jet recording apparatus.
[0039]
As shown in FIG. 5, the ink jet recording apparatus 51 of the present embodiment differs from the medium conveying means 16 of the above-described embodiment in that a rotary drum 52 is used for medium conveyance.
[0040]
That is, a rotary drum 52 is provided for rotating and transporting the recording medium 13 in the direction of the arrow in a state in which the recording medium 13 is wrapped, and opposed to the rotary drum 52, from the upstream side to the downstream side in the transport direction of the recording medium 13, yellow, Four inkjet recording heads 17a, 17b, 17c and 17d of magenta, cyan and black are arranged side by side.
[0041]
Then, an ultraviolet irradiation device 18 as a pre-curing means is arranged on the downstream side near the black inkjet recording head 17d arranged on the most downstream side, and ultraviolet irradiation as a main curing means is further downstream of the ultraviolet irradiation device 18. The device 19 is arranged.
[0042]
Next, the operation of the present embodiment will be described.
The rotating drum 52 rotates at a constant speed in a direction indicated by an arrow in the drawing while the recording medium 13 is wound. First, the yellow ultraviolet curable ink 12 is ejected from the nozzles 29 of the yellow inkjet recording head 17a to record dots on the recording medium 13. Then, the recorded dots are pre-cured by the ultraviolet irradiation device 18.
[0043]
Next, the magenta ultraviolet curable ink 12 is ejected from the nozzles 29 of the magenta ink jet recording head 17b to record dots on the recording medium 13. Then, the recorded dots are pre-cured by the ultraviolet irradiation device 18. Similarly, dot recording and pre-curing with cyan ink and dot recording and pre-curing with black ink are performed. When dot recording with all inks and pre-curing are completed, main curing is performed by the ultraviolet irradiation device 19 and printing is completed. I do.
[0044]
Therefore, also in this embodiment, since the dot recording and the pre-curing are repeated, the adjacent inks are not mixed. That is, the occurrence of bleeding is prevented, and the deterioration of image quality is prevented. In addition, since the number of the ultraviolet irradiation device 18 as the pre-curing means is one, it is possible to reduce the size. Furthermore, since the dot recording is performed while the recording medium 13 is in close contact with the rotary drum 52, the ink landing position on the recording medium 13 is stabilized, and a highly accurate image can be recorded.
[0045]
In addition, in the ink jet recording apparatus using this rotary drum, for example, a monochrome ink jet recording apparatus in which only the black ink jet recording head 17d is arranged, and the ink jet recording head 17d is rotated by one rotation of the rotary drum. A method is known in which the same line is printed while being shifted by a half pitch of the nozzle pitch in a direction intersecting with the rotation direction, and printing is performed at twice the resolution of the nozzle pitch of the inkjet recording head 17d. If the pre-curing is performed by the ultraviolet irradiation device 18 in the same manner as in the above-described embodiment, it is possible to prevent adjacent inks of the same color from attracting each other. Accordingly, it is possible to prevent the dots from being shifted due to the adjacent dots being attracted to each other, which is expressed as a difference in shading.
[0046]
【The invention's effect】
As described above, according to the present invention, in the case where recording is performed using an ultraviolet curable ink, deterioration in image quality can be prevented by preventing occurrence of mottle and bleed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an inkjet recording apparatus according to a first embodiment of the present invention.
FIG. 2 is a graph showing a relationship between an integrated light amount and a degree of polymerization when the ultraviolet curable ink is irradiated with ultraviolet light in the same embodiment.
FIG. 3 is a schematic diagram showing recording dots formed by an ultraviolet curable ink according to the embodiment.
FIG. 4 is a schematic side view of an ink jet recording apparatus according to a second embodiment of the present invention.
FIG. 5 is a schematic side view of an ink jet recording apparatus according to a third embodiment of the present invention.
FIG. 6 is a schematic diagram for explaining a problem of recording dots formed by a conventional ultraviolet curable ink.
[Explanation of symbols]
12 ... ultraviolet curable ink 13 ... recording media 17a, 17b, 17c, 17d ... inkjet recording head 18 ... ultraviolet irradiation device (pre-curing means)
19 ... Ultraviolet irradiation device (main curing means)
29 ... Nozzle

Claims (5)

When recording a dot on a recording medium by ejecting an ultraviolet curable ink that cures when irradiated with ultraviolet light from different nozzles at a predetermined time interval, the ultraviolet curable ink ejected onto the recording medium from each nozzle is An ink jet recording method comprising: irradiating the dots with ultraviolet rays in accordance with their respective ejection timings to increase the viscosity, pre-curing the dots to such an extent that the adjacent dots do not mix with each other, and then irradiating the dots with ultraviolet rays to perform full curing. From a plurality of ink jet recording head nozzles arranged at different positions, when recording a dot on a recording medium by discharging an ultraviolet curable ink that is cured by irradiating ultraviolet rays, the nozzles of the respective ink jet recording heads The ultraviolet curable ink dots ejected on the recording medium are irradiated with ultraviolet rays in accordance with the respective ejection timings to increase the viscosity, pre-curing to the extent that adjacent dots do not mix with each other, and then further irradiating ultraviolet rays to the main body. An ink jet recording method characterized by curing. When recording dots on a recording medium by discharging ultraviolet curable ink of a corresponding color which is cured by irradiating ultraviolet rays from the nozzles of the ink jet recording head for each color arranged at different positions, the respective ink jet recording heads The nozzles of the ultraviolet-curable ink ejected onto the recording medium from the nozzles are irradiated with ultraviolet rays in accordance with the respective ejection timings to increase the viscosity, pre-curing to the extent that adjacent dots do not mix with each other, and then further apply ultraviolet rays. An ink jet recording method characterized by irradiating and fully curing. A plurality of ink-jet recording heads which are arranged at different positions for each color and which eject ultraviolet-curable ink of a corresponding color which is cured by irradiating ultraviolet rays from a nozzle to record dots on a recording medium; A pre-curing means for pre-curing by irradiating ultraviolet rays for each head to the dots of the ultraviolet-curable ink discharged from the nozzles of the head onto the recording medium, and further irradiating the ultraviolet rays to the dots pre-cured by the pre-curing means And a main curing unit for performing main curing. The ink jet recording apparatus according to claim 4, wherein the pre-curing means is provided for each of the plurality of ink jet recording heads.

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