Printing apparatus using radiation-curable ink and method for promoting ink curing thereof

Abstract

To provide a printing device suitable for forming a printing area using a radiation-curable ink on a surface of a container being transported.SOLUTION: A printing device 1 that forms a printing area with a radiation-curable ink on a surface of each of a plurality of bottles 2 transported by a transport device 10 includes: an irradiation unit 15 that irradiates the printing area coated with ink of each bottle 2 with radiation such as ultraviolet light to promote curing of the ink; and a gas supply device 20 that supplies gas such as nitrogen gas that is inert to the ink to the irradiation area by the irradiation unit 15 from an upstream side in a transportation direction TD of the transport device 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an apparatus and the like for forming a printing area on the surface of a container using a radiation-curable ink.

Background Art

[0002] As a printing apparatus for forming a printing area by utilizing an inkjet printing technique on a continuously running film sheet, a printing apparatus has been proposed in which radiation having a curing acceleration effect on the ink, such as ultraviolet light, is irradiated onto the printing area of the film after the ink is applied to promote early curing of the ink (see, for example, Patent Documents 1 to 3). A radiation-curable ink has the property that monomers in the ink rapidly polymerize and instantaneously cure by radiation such as ultraviolet light. However, when irradiated with ultraviolet light or the like in the air, oxygen may inhibit the polymerization reaction, and this tendency is particularly high in radical polymerization type inks. When the polymerization reaction is inhibited, some of the monomers contained in the ink remain unreacted, which causes inconveniences such as being a cause of odor. Therefore, in the apparatus described in the above-mentioned patent documents, in a part of the running path of the film after ink application, an inert gas such as nitrogen is supplied to the ink to provide a low-oxygen region in which oxygen is replaced, and radiation is irradiated within the low-oxygen region to suppress the occurrence of polymerization inhibition.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding containers such as resin bottles and glass bottles, instead of using shrink films as labels, it has been considered to directly form various displays as printing areas on the surfaces of the containers using radiation-curable inks. In manufacturing lines where such containers are filled with contents such as beverages, it is common for a large number of containers to be continuously conveyed at high speed. The process of accelerating the curing of the ink by irradiation with radiation also needs to be continuously carried out in synchronization with the conveyance of the containers. All of the printing devices described in the above-mentioned patent documents are targeted at continuously running roll films and not at a large number of individually and independently conveyed containers. And no technology or method suitable for sequentially irradiating each container being conveyed with radiation under a low oxygen concentration to accelerate the curing of the ink has been studied so far.

[0005] Therefore, an object of the present invention is to provide a printing device suitable for forming a printing area with a radiation-curable ink on the surface of a conveyed container, and an ink curing acceleration method used therefor.

Means for Solving the Problems

[0006] A printing device according to an aspect of the present invention has a conveying means for continuously conveying a plurality of containers, and is a printing device for forming a printing area with a radiation-curable ink on the surface of each of the plurality of containers conveyed by the conveying means. The printing device includes an irradiation means for irradiating radiation for accelerating the curing of the ink onto the printing area where the ink is applied on each container conveyed by the conveying means, and a gas supply means for supplying an inert gas to the ink from the upstream side in the conveying direction of the conveying means with respect to the irradiation area of the radiation by the irradiation means.

[0007] An ink curing acceleration method according to an aspect of the present invention is an ink curing acceleration method applied to a printing apparatus having a conveying means for continuously conveying a plurality of containers, and forming a printing area with a radiation-curable ink on the surface of each of the plurality of containers conveyed by the conveying means. The method includes a step of irradiating radiation for accelerating the curing of the ink on the printing area where the ink is applied to each container conveyed by the conveying means, and a step of supplying an inert gas to the ink from an upstream side in the conveying direction of the conveying means with respect to the irradiation area of the radiation.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] With reference to FIGS. 1 to 3, a printing apparatus according to an embodiment of the present invention and a printing method using the same will be described. The printing apparatus 1 of the present embodiment uses, as an example of a container, the bottle 2 shown in FIG. 3 as a printing target, and directly forms a printing area PA on at least a part of the outer periphery of the body portion 2a of the bottle 2. The bottle 2 is, for example, a resin bottle made of a material such as PET resin, and is formed in a shape having rotational symmetry (including the case of axial symmetry) with respect to its axis AX. Note that the container to be printed is not limited to a resin bottle, and various other containers such as glass bottles may be targeted. The bottle 2 is filled with various liquid types such as beverages, but the contents are not limited to liquids.

[0010] As shown in Fig. 1, the printing apparatus 1 includes a printing unit 3 and a curing unit 4. Note that Fig. 1 shows the printing unit 3 in a simplified manner while enlarging the curing unit 4, and does not represent the positional relationship or size relationship between the two units 3 and 4. The printing unit 3 is configured as an inkjet printer that forms a printing area PA on the outer periphery of the body portion 2a of each of a plurality of bottles 2 continuously conveyed by a predetermined conveying device by discharging radiation-curable ink. For example, the printing unit 3 includes nozzle groups of three colors (CMY) (or four colors CMYK may also be used) arranged along the conveying direction of the bottle 2, and discharges inks of respective colors in an appropriate pattern from these nozzle groups to perform desired color printing on the outer periphery of the body portion 2a of the bottle 2. Note that the printing in the printing unit 3 is not limited to color printing, and may be monochromatic printing.

[0011] The configuration of the printing unit 3 may be the same as that of an inkjet printing apparatus configured for roll film, etc., and its details are omitted. The ink used for printing is, as an example, an ultraviolet-curable ink. However, in addition to radiation in the ultraviolet region, or instead of it, radiation in other wavelength regions may be used for curing the ink. The printing unit 3 may be provided with an irradiation unit that irradiates radiation such as ultraviolet light having a curing promoting effect on the inks of respective colors applied to the bottle 2 to semi-cure the inks of respective colors.

[0012] The printing area PA formed in the printing unit 3 may, as an example, replace a display such as a label realized by a shrink film wound around the bottle 2. However, various displays may be printed in the printing unit 3, and the position, size, and shape of the printing area PA may be appropriately changed. The printing in the printing unit 3 may be performed while rotating the bottle 2 around its axis AX.

[0013] The curing unit 4 includes a conveying device 10 that conveys each bottle 2 that has passed through the printing unit 3. The conveying device 10 is configured as a rotary-type conveying device that supports the bottle 2 in a rotatable state about its axis AX at support portions 12 provided at regular intervals on the outer periphery of a wheel 11 that rotates around a predetermined rotation center RC, and continuously conveys each bottle 2 at a predetermined speed in the turning direction TD of the wheel 11. The turning direction TD corresponds to the conveying direction of the bottle 2, and may be expressed as the conveying direction TD hereinafter. The support portion 12 is provided, as an example, by a support structure such as a support base or a support frame provided at equal intervals on the outer periphery of the wheel 11 so as to support the bottle 2 in a rotatable state about the axis AX. When supporting the body portion 2a of the bottle 2, for example, the support position of the bottle 2 may be set while avoiding the printing area PA so as not to contact the ink before curing.

[0014] The conveying device 10 further includes a rotation mechanism that rotates each bottle 2 about the axis AX. The rotation mechanism may be realized by a configuration similar to the rotation mechanisms in various known rotary-type conveying devices. For example, a rotating body such as a belt or a roller is brought into contact with the bottle 2 supported by the support portion 12 to transmit a rotational motion to the bottle 2, or the bottle 2 is rotated by means such as rotating a member such as a support base or a support frame that serves as the support portion 12 of the bottle 2 about the axis AX of the bottle 2. The rotation direction of the bottle 2 is defined such that, as shown by the arrow RD, when observing the bottle 2 from the outer peripheral side of the wheel 11 toward the rotation center RC, the bottle 2 rotates from the upstream side to the downstream side in the conveying direction TD. [[ID=,6]]

[0015] The conveying device 10 may be shared with the conveying device in the printing unit 3, or may be provided as a separate device from the conveying device in the printing unit 3. When sharing the conveying device 10 between the printing unit 3 and the curing unit 4, the nozzle groups of each color in the printing unit 3 may be arranged at a position upstream of the curing unit 4 shown in FIG. 1. On the other hand, when separating the conveying devices between the printing unit 3 and the curing unit 4, an intermediate conveying device or the like for delivering the bottle 2 may be interposed between the conveying device in the printing unit 3 and the conveying device 10.

[0016] A plurality of irradiation areas RA are set at regular intervals in the conveying direction TD on the outside of the wheel 11 of the conveying device 10. In the illustrated example, three irradiation areas RA are set. Each irradiation area RA is provided with an irradiation unit 15, which is an example of an irradiation means. The irradiation unit 15 is arranged to face the outer periphery of the body portion 2a of the bottle 2 in the irradiation area RA. Therefore, when viewed from the irradiation unit 15 side, the bottle 2 is conveyed downstream in the conveying direction TD while rotating from the upstream side to the downstream side in the conveying direction TD.

[0017] The irradiation unit 15 irradiates the bottles 2 with ultraviolet light as radiation to promote curing of the ink applied to the bottles 2 by the printing unit 3. As an example, the irradiation unit 15 is configured as a lighting device that uses an LED element that emits ultraviolet light as a light source. The irradiation direction of the irradiation unit 15 is directed toward the rotation center RC of the wheel 11 of the conveying device 10. In other words, the irradiation direction of the irradiation unit 15 roughly coincides with the radial direction of the wheel 11. As an example, the ultraviolet light emitted from the irradiation unit 15 is a bundle of rays that is roughly parallel to the radial direction of the wheel 11, and the irradiation area RA of the ultraviolet light is set so that it is roughly even on both the upstream and downstream sides of the conveying direction TD, sandwiching the position where the bottles 2 and the irradiation unit 15 are closest to each other.

[0018] The curing unit 4 is provided with a gas supply device 20 as an example of a gas supply means for supplying a predetermined gas to each irradiation area RA. As shown in Fig. 2, the gas supply device 20 ejects gas introduced from a predetermined gas source 21 toward the irradiation area RA from nozzles 22 provided for each irradiation area RA, thereby replacing the air in the irradiation area RA with the gas from the gas source 21. Between the gas source 21 and the nozzles 22, ancillary devices such as a control circuit 23 for adjusting the pressure, flow rate, etc. of the gas distributed to each nozzle 22 may be provided as appropriate.

[0019] The gas from the gas source 21 is a gas that is inert to the ink applied to the bottle 2 in the printing unit 3. That is, the gas from the gas source 21 is a gas that does not inhibit the polymerization reaction of the ink by the irradiation of ultraviolet light from the irradiation unit 15. As an example, nitrogen gas is supplied from the gas source 21. By replacing the air in the irradiation region RA with a gas, the oxygen concentration in the irradiation region RA can be reduced to less than that in the air, and the occurrence of polymerization inhibition of the ink due to the presence of oxygen can be suppressed. Thereby, it is possible to sufficiently draw out the ink curing acceleration effect by ultraviolet light and cure the ink early.

[0020] The nozzle 22 is adjusted in its position and orientation so as to supply gas to the irradiation region RA from the upstream side in the conveyance direction TD of the conveyance device 10. Further, as is clear from FIG. 3, the nozzle 22 is provided so as to extend along the printing region PA with respect to the axial direction of the bottle 2 (the direction of the axis AX). Therefore, with respect to the axial direction of the bottle 2, gas can be supplied so that the entire printing region PA is evenly touched by the gas ejected from the nozzle 22, and the homogenization of the oxygen concentration reduction effect by the gas can be achieved. Note that the total length of the nozzle 22 with respect to the axial direction of the bottle 2 (precisely, the total length of the opening of the nozzle 22) does not necessarily have to be equal to or longer than the total length of the printing region PA in the same direction. As long as the oxygen concentration in the irradiation region RA can be reduced to a level where polymerization inhibition does not occur, the total length of the nozzle 22 may be set appropriately.

[0021] In order to cure the ink in the printing area PA of the bottle 2 by the cured part 4 having the above configuration, the bottle 2 coated with the ink is sequentially fed into the irradiation area RA by the conveying device 10, and while supplying gas from the nozzle 22 to the irradiation area RA, ultraviolet light may be irradiated from the irradiation unit 15 toward the printing area PA of the bottle 2. In that case, since the gas is supplied from the upstream side in the conveying direction TD with respect to the irradiation area RA, the gas can be efficiently drawn into the irradiation area RA by utilizing the entrainment effect accompanying the conveyance of the bottle 2, and the oxygen concentration in the irradiation area RA can be effectively reduced. In addition, since the bottle 2 is rotated so as to move from the upstream side to the downstream side in the conveying direction TD, the entrainment effect of the gas can be further enhanced, and the oxygen in the irradiation area RA can be more efficiently replaced with the gas.

[0022] A plurality of irradiation areas RA are set along the conveying direction TD, and ultraviolet light is irradiated from the irradiation unit 15 while the oxygen concentration in each irradiation area RA is reduced by the gas supply device 20. Therefore, each time a plurality of continuously conveyed bottles 2 pass through the irradiation area RA, the curing promoting action by the ultraviolet light gradually occurs, and the ink can be efficiently cured. Therefore, compared with the case where only a single irradiation area RA is set, it is possible to surely and smoothly cure the ink applied to the bottle 2. Thus, it is possible to realize the printing device 1 suitable for forming the printing area PA on a large number of bottles 2 conveyed at high speed and continuously.

[0023] FIG. 4 shows an example of the result of confirming the oxygen concentration reduction effect by simulation when nitrogen gas is supplied from the nozzle 22 of the gas supply device 20 to the irradiation region RA. The simulation conditions were as follows: a PET bottle with a capacity of 450 mL was used as the bottle 2, the gap (shortest distance) between the bottle 2 and the irradiation unit 15 in the irradiation region RA was set to 10 mm, the flow rate of nitrogen gas discharged from the nozzle 22 was set to 79.2 L per minute, and the rotation speed of the bottle 2 was set to 200 rotations per minute. The shape, size, and position of the nozzle 22 were appropriately set to perform the simulation, and the reduction effect of the oxygen concentration was evaluated by measuring the concentration of nitrogen gas on the outer periphery of the bottle 2. FIG. 4 is an example, and it is assumed that nitrogen gas is supplied from the right side in the figure. That is, in FIG. 4, the right side is the upstream side in the conveyance direction, and the left side is the downstream side in the conveyance direction. The white rectangular region shown in FIG. 4 indicates the range irradiated with ultraviolet light. In FIG. 4, the concentration of nitrogen gas is shown in grayscale, and the closer to black, the higher the concentration of nitrogen gas. In this example, the nitrogen gas concentration is approximately 100% by volume at the portion closest to black, and the nitrogen gas concentration is ensured to be about 95% by volume even at the outer edge of the grayscale region. Therefore, it was confirmed that almost complete substitution with nitrogen gas is realized in the ultraviolet light irradiation range, and it was found that the oxygen concentration can be reduced to about 0.1% by volume or even lower concentrations.

[0024] The present invention is not limited to the above-described form and may be implemented in an appropriately modified or changed form. For example, in the above form, the transport device 10 in the curing part 4 is configured as a rotary type transport device. However, even when a linear transport type transport device that linearly transports the bottle 2 is used, the nozzle 22 is arranged upstream in the transport direction with respect to the ultraviolet light irradiation region RA to supply nitrogen gas, and further, the bottle 2 is rotated so as to move from the upstream side to the downstream side in the transport direction as viewed from the irradiation unit 15. Thus, it is possible to irradiate the ink with ultraviolet light under a low oxygen concentration and effectively bring out its curing acceleration effect in the same manner as in the above form.

[0025] In the above-described embodiment, the bottle is rotated while being conveyed in a predetermined direction. However, if it is possible to include the entire printing area within the irradiation range of radiation such as ultraviolet light even without rotating the bottle, the rotation of the bottle may be omitted. Even in such a case, by supplying an inert gas such as nitrogen gas from the upstream side in the conveyance direction, it is possible to reduce the oxygen concentration in the irradiation area of ultraviolet light or the like and suppress the polymerization inhibition with respect to the curing of the ink.

[0026] Various aspects of the present invention derived from each of the above-described embodiments and modifications will be described below. In the following description, corresponding components illustrated in the accompanying drawings are appended in parentheses in order to facilitate understanding of each aspect of the present invention. However, the present invention is not limited to the illustrated forms by this.

[0027] A printing apparatus (1) according to an aspect of the present invention includes a conveying unit (10) that continuously conveys a plurality of containers (2), and forms a printing area (PA) by radiation-curable ink on the surface of each of the plurality of containers conveyed by the conveying unit. The printing apparatus is an irradiation unit (15) that irradiates radiation for promoting curing of the ink on the printing area where the ink is applied to each container conveyed by the conveying unit, and an inert gas with respect to the ink, from the upstream side in the conveying direction of the conveying unit with respect to the irradiation area (RA) of the radiation by the irradiation unit. And a gas supply means (20) for supplying.

[0028] According to the printing apparatus of the above aspect, by supplying gas from the upstream side in the conveyance direction of the container, a gas entrainment effect occurs as the container is carried into the irradiation area. Therefore, it is possible to replace the air in the irradiation area with an inert gas with respect to the ink, reduce the oxygen concentration in the area, suppress the occurrence of polymerization inhibition, and cure the ink at an early stage. Therefore, it is possible to realize a printing apparatus suitable for forming a printing area on the surface of continuously conveyed containers.

[0029] In the printing apparatus according to the above aspect, the irradiation means may be arranged to face the outer periphery of the container, and the conveying means may convey the container while rotating it so as to move from the upstream side to the downstream side in the conveying direction as viewed from the irradiation means side. According to this, the effect of entraining the gas into the irradiation area can be enhanced by utilizing the rotation of the container.

[0030] The gas supply means may supply the gas from a nozzle (22) provided so as to extend along the printing area in the axial direction of the container. According to this, with respect to the axial direction of the container, the gas can be supplied so that the entire printing area is evenly touched by the gas ejected from the nozzle, and the homogenization of the oxygen concentration reduction effect by the gas can be achieved.

[0031] A plurality of irradiation areas may be set along the conveying direction, the irradiation means may be provided in each of the plurality of irradiation areas, and the gas supply means may be provided to supply the gas to each of the plurality of irradiation areas. According to this, each time the container passes through a plurality of irradiation areas, the curing acceleration action by radiation can be gradually generated to efficiently cure the ink.

[0032] An ink curing acceleration method according to an aspect of the present invention is an ink curing acceleration method applied to a printing apparatus (1) having a conveying means (10) for continuously conveying a plurality of containers (2), and forming a printing area (PA) by radiation-curable ink on the surface of each of the plurality of containers conveyed by the conveying means, and includes a procedure of irradiating radiation for accelerating the curing of the ink to the printing area where the ink is applied to each container conveyed by the conveying means, and a procedure of supplying an inert gas to the ink from the upstream side in the conveying direction of the conveying means with respect to the irradiation area (RA) of the radiation.

[0033] According to the ink curing acceleration method of the above aspect, similar to the printing apparatus of the above-described aspect, the effect of entraining the gas is generated as the container is carried into the irradiation area, the oxygen concentration in the irradiation area is reduced, the occurrence of polymerization inhibition is suppressed, and the ink can be cured early.

[0034] Also in the method for promoting ink curing of the above aspect, it may have additional features similar to those of the printing apparatus of the above aspect. That is, in the irradiation procedure, the radiation may be irradiated from irradiation means (15) arranged so as to face the outer periphery of the container, and the conveying means may convey the container while rotating it from the upstream side to the downstream side in the conveying direction as viewed from the irradiation means side. In the supply procedure, the gas may be supplied from a nozzle (22) provided so as to extend along the printing area in the axial direction of the container. A plurality of irradiation areas (RA) may be set along the conveying direction, and in each of the plurality of irradiation areas, the procedure of irradiating the radiation and the procedure of supplying the gas may be carried out. The advantages of adding those features are the same as those of the printing apparatus of the above aspect.

Explanation of Signs

[0035] 1 Printing apparatus 2 Bottle (container) 10 Conveying device (conveying means) 15 Irradiation unit (irradiation means) 20 Gas supply device (gas supply means) 22 Nozzle PA Printing area RA Irradiation area RD Rotation direction TD Conveying direction

Claims

1. A printing apparatus having a conveying means for continuously conveying a plurality of containers, and forming a printing area by a radiation-curable ink on the surface of each of the plurality of containers conveyed by the conveying means, an irradiation means for irradiating radiation for promoting curing of the ink onto the printing area coated with the ink of each container conveyed by the conveying means; a gas supply means for supplying an inert gas to the ink from the upstream side in the conveying direction of the conveying means with respect to the irradiation area of the radiation by the irradiation means; comprising: a plurality of irradiation areas are set along the conveying direction; the irradiation means is provided for each of the plurality of irradiation areas; the gas supply means is provided to supply the gas to each of the plurality of irradiation areas. A printing apparatus.

2. The irradiation means is arranged to face the outer periphery of the container, The conveying means conveys the container while rotating it from the upstream side to the downstream side in the conveying direction as viewed from the irradiation means side. The printing apparatus according to claim 1.

3. The gas supply means supplies the gas from a nozzle provided to extend along the printing area in the axial direction of the container. The printing apparatus according to claim 1.

4. An ink curing acceleration method applied to a printing apparatus having a conveying means for continuously conveying a plurality of containers, and forming a printing area by a radiation-curable ink on the surface of each of the plurality of containers conveyed by the conveying means, a procedure of irradiating radiation for promoting curing of the ink onto the printing area coated with the ink of each container conveyed by the conveying means; a procedure of supplying an inert gas to the ink from the upstream side in the conveying direction of the conveying means with respect to the irradiation area of the radiation; comprising: a plurality of irradiation areas are set along the conveying direction; An ink curing acceleration method in which the procedure of irradiating the radiation and the procedure of supplying are carried out in each of the plurality of irradiation areas.

5. In the procedure of irradiating, the radiation is irradiated from an irradiation means arranged to face the outer periphery of the container, The conveying means conveys the container while rotating it from the upstream side to the downstream side in the conveying direction as viewed from the irradiation means side. The ink curing acceleration method according to claim 4.

6. The ink curing acceleration method according to claim 4, wherein in the supplying procedure, the gas is supplied from a nozzle provided so as to extend along the printing region in the axial direction of the container.

Images