JP7316486B2 - Inkjet printing device and inkjet printing method - Google Patents

Description

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

2. Description of the Related Art Conventionally, an inkjet printing apparatus that prints by an inkjet method has been widely used (see, for example, Patent Document 1).

2. Description of the Related Art An inkjet printing apparatus forms an image by applying ink droplets of a plurality of colors, mainly cyan, magenta, yellow, and black, onto a recording medium to form ink dots.

By the way, in recent years, in inkjet printing, there is an increasing demand for performing high-quality printing on sheet-shaped thin long webs, especially synthetic resin films formed of resins such as polypropylene (OPP), polyethylene terephthalate (PET), and nylon. are doing.

Such synthetic resin films often have the property of transmitting light, such as being transparent or translucent. Therefore, when printing on a synthetic resin film, in order to make the printed image easy to see and to make it difficult to see the back side of the synthetic resin film by making it difficult for light to pass through, the front or back of the printed image is used. In addition, there is a method of concealing a printed image by applying solid printing in which background ink such as white ink is printed without gaps.

Among such printing methods, after printing a predetermined image, solid printing of the ink for the background of the image is carried out on the printed image, and the completed printed material is the ink of the recording medium. There is a printing method (so-called reverse printing method) in which a printed image is printed through the recording medium itself from the side to which is not applied.

JP-A-60-132767

However, when such printing is carried out, there is a problem in that the ink dots forming the image and the ink applied by the solid printing are mixed in color, resulting in deterioration of the image.

The present invention has been made in view of the above problems, and provides an inkjet printing apparatus that solves the above problems and performs high-quality printing on a long web, and an inkjet printing method that realizes the same. is.

In order to achieve the above object, the inventor of the present invention discovered the following configuration as a result of diligent ingenuity.

That is, in the present invention, in an inkjet printing apparatus that applies ink to a recording medium by ejecting ink from an inkjet head,
a conveying means for conveying the recording medium;
For forming an ink image layer, which is a layer of ink formed as a mirror image in which a predetermined image is inverted by applying a plurality of different color inks to the surface of the recording medium, an ink image layer forming unit having an inkjet head;
a first ink curing unit for accelerating and curing the ink image layer formed by the ink image layer forming unit;
an inkjet for forming an image hiding layer for partially or entirely hiding the surface of the ink image layer by applying ink to the surface of the ink image layer cured by the first ink curing unit; an image hiding layer forming unit having a head;
and a second curing unit for accelerating and curing the image hiding layer formed by the image hiding layer forming unit.

Further, in the present invention, in the inkjet printing method in which ink is applied to a recording medium by ejecting ink from an inkjet head,
an ink image layer forming step of applying a plurality of inks of different colors to the surface of the recording medium to form an ink image layer representing an inverted mirror image of a predetermined image;
a first ink curing step of curing the ink image layer;
Formation of an image hiding layer for forming an image hiding layer for hiding part or all of the surface of the ink image layer by applying ink to the surface of the ink image layer cured by the first ink curing step. a step;
and a second ink curing step of curing the image hiding layer.

In the present invention, by adopting the above configuration, the above problems can be solved, and an inkjet printing apparatus that performs high-quality printing on a long web and an inkjet printing method that realizes the same can be provided. .

1 is an overall view showing the configuration of an inkjet printing apparatus that is an embodiment of the present invention; FIG. FIG. 2 is an overall view showing another configuration of an inkjet printing apparatus that is an embodiment of the present invention; 4 is a flow chart showing a printing sequence performed by the inkjet printing apparatus that is one embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration around the image concealing layer forming unit and the marker recognition sensor in the inkjet printing apparatus that is one embodiment of the present invention; FIG. 4 is a schematic diagram showing the state of formation of an ink image layer and measurement markers at the time when flow 3 in FIG. 3 ends. FIG. 4 is a schematic diagram showing the state of formation of an ink image layer, a measurement marker, and an image concealing layer at the time when flow 6 in FIG. 3 is completed; FIG. 7 is a cross-sectional view taken along the line AA of FIG. 6; FIG. 8 is a schematic diagram when viewing FIG. 7 by reversing it;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, a configuration example of an inkjet printing apparatus according to a first embodiment of the present invention will be described. FIG. 1 is an overall view showing the configuration of an inkjet printer that is one embodiment of the present invention.

The same composition is used for water-based inks that use water as a solvent, water-based latex inks that use water as a solvent and resin is dispersed with pigments, and solvent inks that use a solvent as a solvent. This configuration is suitable for performing inkjet printing using ink that dries and cures. Among them, water-based inks and water-based latex inks, which use water as a solvent and are less harmful to the environment and the human body, are particularly suitable.

Further, the same configuration is used for so-called reverse printing, in which the above-described solid printing is performed on the printed image after mirror image printing of a predetermined image is performed. A printed matter printed by reverse printing is viewed from the side where printing is not performed and ink is not applied, through the recording medium and the printed image is viewed visually.

A long roll-shaped sheet member is used as the recording medium used in the following configuration. Paper such as coated paper can be assumed as the material of the sheet member, but transparent or translucent synthetic resin films made of resins such as polypropylene (OPP), polyethylene terephthalate (PET), and nylon are suitable. .

First, the recording medium 10 is transported and supplied from the unwinding section 11 that supplies the recording medium 10 in a roll shape.

The supplied recording medium 10 is transported to the transport heating belt 15 and placed on its outer peripheral surface. A heater is incorporated in the conveying heating belt 15, and has a function of heating a predetermined portion of the outer peripheral surface on which the recording medium 10 is placed. By placing the recording medium 10 on the transport heating belt 15, the recording medium 10 is preheated (preheated) to a predetermined temperature by thermal conduction before printing is performed by the ink image layer forming unit 12, which will be described later. be done. In this embodiment, the conveying heating belt 15 is shown as a belt having a heating function for both heating and conveying the recording medium 19. A heating device can be mounted, and a plurality of them may be mounted as necessary.

The preheated recording medium 10 is transported to the bottom of the ink image layer forming unit 12 .

The ink image layer forming unit 12 is usually an inkjet head for ejecting four colors of ink, cyan (C), magenta (M), yellow (Y), and black (K), corresponding to the number of inks. 13 are mounted on the first carriage 14 in plurality. In addition, the first carriage 14 may optionally be equipped with an inkjet head 13 for ejecting special color inks required for image expression, or when multiple colors are not required. can be omitted.

The inkjet head 13 has a nozzle surface in which a plurality of nozzles for ejecting ink are arranged in a predetermined row.

When the recording medium 10 passes through a position facing the nozzle surface of the lower portion of the ink image layer forming unit 12 , ink is ejected from the nozzles arranged on the nozzle surface of the inkjet head 13 . The ink image layer 51 is formed on the surface of the recording medium 10 by the ejected ink landing on and being applied to the surface of the recording medium 10 .

In addition, the ink image layer forming unit can print and form measurement markers 53 on the surface of the recording medium 10 to be recognized by the marker recognition sensor 19 described later. Of course, a separate unit for forming the measurement marker 53 may be separately mounted.

After the ink image layer 51 is formed on the surface of the recording medium 10 by the ink image layer forming unit 12 , the recording medium 10 is transported to the first drying drum 17 and wound around the outer peripheral surface of the first drying drum 17 . is turned.

A driving motor is connected to the first drying drum 17 to rotate the recording medium 10 to roll and transport the recording medium 10, and the outer peripheral surface of the drying drum 17 is heated to a predetermined target temperature to wind the recording medium 10. A heater is built in to heat the medium.

The recording medium 10 is wound around the first drying drum 17 and conveyed while being heated to a predetermined temperature by thermal conduction, thereby drying the ink image layer 51 .

After passing through the first drying drum, the recording medium 10 is conveyed to a place where the marker recognition sensor 19 is arranged.

The marker recognition sensor 19 must have a function of reading the above-described measurement marker 53 attached to the recording medium 10, and a laser sensor, camera, or the like is appropriately applied. By reading the measurement marker 53 attached to the recording medium 10 by the marker recognition sensor 19, the formation position of the ink image layer 51 on the recording medium 10 is measured, and the image hiding layer forming unit 21 is operated. It can send a signal.

Further, the marker recognition sensor 19 can be provided with a moving means capable of moving in a direction intersecting the conveying direction of the recording medium 10 . That is, it may be necessary to appropriately move the position of the measurement marker 53 in the direction crossing the transport direction with respect to the image to be printed. Furthermore, the position and shape of the measurement marker 53 may be limited by the image to be printed and the final use shape of the printed matter. Therefore, by providing such a moving means, the measurement marker 53 can recognize the marker according to the arrangement position of the measurement marker 53 regardless of the image or the shape of the measurement marker 53. It can be conveyed through the sensor 19 to enable the marker recognition sensor 19 to recognize the measurement marker 53 .

Then, the recording medium 10 is conveyed to the image concealing layer forming unit 21 after passing through the marker recognition sensor 19 .

The image hiding layer forming unit 21 ejects ink of a color having a high hiding property such as white (W) onto the surface of the recording medium 10 to form an ink image layer 51 formed on the surface of the recording medium 10. The inkjet head 13 for forming the image hiding layer 55 that covers all or part of the image is mounted on the second carriage 22 .

In this embodiment, the image hiding layer forming unit 21 is controlled to operate when the marker recognition sensor 19 transmits a signal indicating that the measurement marker 53 has been recognized. Then, the image forming layer forming unit 21 ejects ink from above the ink image layer 51 formed on the surface of the recording medium 10 so as to cover all or part of the ink image layer 51 to form an image hiding layer. 55 is formed.

After the image hiding layer 55 is formed on the surface of the recording medium 10 by the image hiding layer forming unit 21 , the recording medium 10 is transported to the second drying drum 23 and wound around the outer peripheral surface of the second drying drum 23 . is turned.

Like the first drying drum 17, the second drying drum 23 is connected to a drive motor that rotates it to roll and convey the recording medium 10, and heats the outer peripheral surface to a predetermined temperature. A heater is built in to heat the wound recording medium.

While the recording medium 10 is wound around the second drying drum 23 and conveyed, it is heated to a predetermined temperature by heat conduction, and the drying of the image hiding layer 55 is completed.

After drying of the image hiding layer 55 by the second drying drum 23 is completed, the recording medium 10 is taken up by the take-up unit 24 for recovery, and printing is completed. If necessary, it is possible to provide means for cutting the recording medium 10 that has been printed instead of winding it by the winding section 24 .

In order to control the transport path of the recording medium 10, a transport roller may be appropriately arranged on the transport path of the inkjet drawing apparatus according to the present embodiment, if necessary. In addition, by arranging a device for improving the surface adhesion of the recording medium 10 (such as a corona discharger) at an appropriate position on the conveying path, the surface of the recording medium 10 that has not been subjected to the adhesion improving means in advance can be used. Even so, the adhesion improving means can be applied efficiently. Furthermore, the first drying drum 17 and the second drying drum 23 are embodiments of the first ink curing unit and the second ink curing unit, respectively, and may be modified in configuration form as necessary.

Here, the arrangement configuration of each unit described above in the present embodiment will be described.

In the inkjet printing apparatus of the present embodiment, as shown in FIG. 1, the transport heating belt 15, the ink image layer forming unit 12, and the image concealing layer forming unit 21 are arranged at the unwinding section 11, the first It is arranged vertically above the positions where the first drying drum 17, the second drying drum 23 and the winding section 24 are arranged.

This is because, when using the inkjet printing apparatus according to the present embodiment, the user sets the recording medium 10, which is a roll-shaped long web, in the unwinding section 11, and after printing is completed, the recording medium 10 is set in the winding section 24. This is because it is necessary to remove the wound recording medium 10 after printing. Therefore, by configuring each unit as described above, the user of the inkjet printing apparatus can easily install and remove the heavy roll-shaped recording medium 10 without lifting it to a high place.

The surface of the first drying drum 17 opposite to the surface of the recording medium 10 on which the ink image layer 51 is formed is in contact with the uppermost point in the vertical direction of the outer peripheral surface of the first drying drum 17. , is disposed vertically below the passage position of the recording medium 10 facing the nozzle surface of the inkjet head 13 constituting the ink image layer forming unit 12 .

Further, the second drying drum 23 is arranged so that the surface opposite to the surface of the recording medium 10 on which the image hiding layer 55 is formed is in contact, and the vertical highest point of the outer peripheral surface of the second drying drum 23 is , is arranged vertically below the passage position of the recording medium 10 facing the nozzle surface of the inkjet head 13 constituting the image hiding layer forming unit 21 .

By arranging the first drying drum 17 and the second drying drum 23 as described above, the side opposite to the side provided with the ink image layer 51 or the image hiding layer 55 can be brought into contact with the first drying drum. 17 or the outer peripheral surface of the second drying drum 23 and the printed surface of the recording medium 10 can be prevented from damaging the applied ink image layer 51 or the image hiding layer 55 .

Furthermore, by setting the arrangement relationship as described above, the space below the conveying heating belt 15, the ink image layer forming unit 12, and the image concealing layer forming unit 21 can be utilized, and the unwinding section 11 and the first drying drum can be arranged. 17, the second drying drum 23 and the take-up unit 24 can be arranged, thereby making it possible to realize a highly practical inkjet printing apparatus while achieving miniaturization of the apparatus. Due to the miniaturization of the inkjet printing apparatus, the installation area can be saved, and the user's operation cost can be suppressed.

The inkjet printing sequence of the first embodiment shown in FIG. 1 will be described below.

FIG. 3 is a flow chart of inkjet printing according to the first embodiment. Hereinafter, description will be made with appropriate reference to the flow chart of FIG.

In the following description, water-based inks that use water as a solvent, water-based latex inks that use water as a solvent and resin is dispersed together with pigments, and solvent inks that use a solvent as a solvent are mainly used. It is assumed that ink jet printing is performed using ink that dries and hardens as the solvent evaporates.

First, the recording medium 10 conveyed and supplied from the unwinding section 11 is conveyed and mounted to the outer peripheral surface of the conveying heating belt 15, and the preheating step of flow 1 is started.

At this time, the temperature of the outer peripheral surface of the conveying heating belt 15 is controlled so as to reach a predetermined target temperature, and the mounted recording medium 10 reaches a predetermined temperature due to heat conduction of the heated belt. warmed up.

Here, the purpose of heating the recording medium 10 in the preliminary heating step will be described. When the ink is ejected from the inkjet head and lands on the surface of the recording medium, a phenomenon occurs in which the ink spreads on the surface of the recording medium due to the interfacial tension of the ink. Ink jet printing involves forming a plurality of very small ink dots on the surface of a recording medium using ink droplets and combining them to form an image. Therefore, in order to ensure the print image quality, it is effective to appropriately control the wetting and spreading of the ink applied to the surface of the recording medium to maintain the shape of the ink dots.

Therefore, in the case of ink that dries and cures by evaporating the solvent, by heating the recording medium before printing, the ink that has landed on the surface of the recording medium is heated by the heat of the recording medium and the solvent is removed. Evaporation is accelerated. As a result, although the ink does not completely cure immediately after landing on the surface of the recording medium, it cures to an extent that the ink does not spread due to interfacial tension, and the shape of the ink dot can be maintained.

In the present embodiment, the transport heating belt 15 having a heater built into the belt for placing and transporting the recording medium 10 is configured to heat the mounted recording medium 10 . At the same time as heating by heat conduction from the belt, it is configured to play a role of a platen capable of fixing the recording medium 10 at the time of printing.

The target temperature of the conveying heating belt 15 is appropriately controlled depending on the performance of the ink, the required print conveying speed, etc., and is assumed to be controlled at about 20 degrees Celsius to 70 degrees Celsius.

The pre-heating step of Flow 1 is completed by heating the recording medium 10 to a predetermined temperature while being placed on and being transported by the transport heating belt 15 .

Next, the image forming sequence of flow 2 is performed on the recording medium 10 heated to a predetermined temperature by the preheating sequence of flow 1 .

In flow 2, as described above, from the ink image layer forming unit 12, CMYK and other special color inks are appropriately ejected from the plurality of inkjet heads 13 so as to form an intended predetermined image, and onto the recording medium 10. A plurality of ink dots are formed by landing. As a result, an ink image layer 51 is formed on the recording medium 10, which is an aggregate of ink dots formed by ink-jet printing to express a predetermined image for appreciation.

At this time, in the present embodiment, the ink image layer 51 is formed on the surface of the recording medium 10 as a mirror image in which the image intended for viewing is reversed. In the present embodiment, a reverse printing method is performed in which the printed material is viewed through the recording medium itself from the side of the recording medium to which ink is not applied. Therefore, by forming the ink image layer 51 as a mirror image, the ink image layer 51 can be recognized as a normal image when the recording medium 10 is turned over.

At this time, as described above, the ink that has landed on the surface of the recording medium 10 is heated by the heat of the heated recording medium 10, and is dried and cured to the extent that it does not spread.
In this way, wetting and spreading of the ink applied to the recording medium is suppressed, and high-quality printing can be realized.

As for the type of inkjet printing method used in this embodiment, an appropriate one can be selected. A so-called one-pass method is suitable in which all the inks necessary for image formation are applied to complete printing when the recording medium passes once.

Before, after, or at the same time as the formation of the ink image layer 51 in flow 2, measurement markers 53 to be read by the marker recognition sensor 19, which will be described later, are applied.

Any appropriate method can be assumed for the application method. can also be granted.

The shape, color, etc. of the measurement marker 53 are desirably selected appropriately so as to be easily recognized by the marker recognition sensor 19, but the color, shape, etc. are not particularly limited. In this embodiment, the measurement marker 53 is set as a black substantially square image.

In addition, it is preferable that the measurement marker 53 is arranged downstream of the ink image layer 51 in the conveying direction of the recording medium 10 .

It is also possible to arrange the measurement marker 53 upstream of the ink image layer 51 in the transport direction. However, in this embodiment, as will be described later, the marker recognition sensor 19 is arranged on the transport path of the recording medium 10, and the image hiding layer is formed in response to the marker recognition sensor 19 recognizing the measurement marker 53. The configuration is such that the unit 21 is operated. Therefore, if the length of the image to be printed in the transport direction is longer than the arrangement distance of the marker recognition sensor 19 and the image concealing layer forming unit 21 with respect to the transport direction, the measurement marker 53 will be detected before reaching the marker recognition sensor 19 . Then, the ink image layer 51 is conveyed to the image hiding layer forming unit 21 . In this case, the image hiding layer forming unit 21 cannot be operated to form the image hiding layer 55 in response to the marker recognition sensor 19 recognizing the measurement marker 53 .

Therefore, the arrangement position of the measurement marker 53 is desirably arranged downstream of the ink image layer 51 in the transport direction.

In this embodiment, by operating the ink image layer forming unit 12, the measurement marker 53 is located at a position downstream of the ink image layer 51 on the surface of the recording medium 10 in the transport direction, and also by a marker recognition sensor described later. 19.

FIG. 5 is a schematic diagram showing the printed state of the ink image layer 51 and the measurement marker 53 when the flow 2 is finished.

In FIG. 5, diagonal lines indicate that the recording medium 10 is a transparent substrate.
An ink image layer 51 is formed by applying ink to the surface of the recording medium 10 .
In addition, a substantially square black measurement marker 53 is provided on the upstream side in the conveying direction.
As described above, the characters "Tritek" and "TriJet" forming the ink image layer 51 are reversed to form a mirror image. As a result, when the recording medium 10 is reversed and viewed after all the printing sequences are completed, the image can be viewed as a normal image.

After the ink image layer forming step of flow 2 and the application of the measurement marker 53 are completed, the first ink curing step of flow 3 is performed.

In the present embodiment, the recording medium 10 is wound around the first drying drum 17 and transported, so that the recording medium 10 is heated to a predetermined temperature by thermal conduction, and the heat causes the ink image layer 51 to be formed. Water, which is a solvent contained in the ink, evaporates, accelerates drying and curing, and completes the passage of the recording medium 10 through the first drying drum 17, completing the drying of the ink image layer 51.

The drying drum 17 is appropriately set to a temperature that does not damage the recording medium 10 and allows the ink image layer 51 to be completely dried. Although it is set in consideration of the properties of the ink and the printing speed, in this embodiment, it is set to be approximately 80 degrees Celsius or more and 160 degrees Celsius or less.

Here, the purpose of completely drying the ink image layer 51 in Flow 3 before performing the image concealing layer forming step in Flow 5, which will be described later, will be described.

When the ink image layer 51 is formed by Flow 2, it is not completely dried and cured. Before the ink image layer 51 is completely dried, the image hiding layer forming step of flow 6 is performed, and a large amount of hiding ink is applied on the ink image layer 51 by solid printing. , and the ink for concealing are in contact with each other, resulting in marked color mixture. This color mixture leads to image quality deterioration. In particular, when white (W) ink, in which the specific gravity of the pigment dispersed in the ink is relatively high, is used for concealment, the W ink is applied on the ink image layer 51, so that the W pigment spreads over the ink image layer 51. It tends to settle in the constituent inks, and color mixing occurs particularly remarkably.

Therefore, in the present embodiment, the ink image layer 51 is preliminarily dried and cured by performing the first ink curing step. As a result, even if the ink for the image hiding layer is applied onto the ink image layer 51, color mixture of the inks does not occur, and the above problem can be avoided.

Next, the marker recognition step of flow 4 will be described.

First, in the present embodiment, the formation of the ink image layer 51 and the formation of the image concealing layer 55 are not performed at the same time. A sequence is adopted in which the formation of the concealing layer 55 is performed. Therefore, in order to print an intended image, the ink image layer 51 and the image hiding layer 55 are aligned so that the ink image layer 51 and the image hiding layer 55 are aligned on the surface of the recording medium 10 . It is necessary to intentionally control the positional relationship of

However, as described above, the synthetic resin film used for the recording medium 10 is thin and has the property of being relatively easy to expand and contract. There is As a result, the recording medium 10 is slightly stretched and deformed after the ink image layer 51 is formed on the surface thereof by the ink image layer forming unit 12 until it is conveyed to the image concealing layer forming unit 21, which will be described later. end up Although the degree of expansion and contraction depends on the properties of the recording medium 10 and the continuous conveying distance, expansion and contraction of several millimeters to several centimeters can be assumed.

However, for example, the start timing of the operation of the image hiding layer forming unit 21 is theoretically determined from when the recording medium 10 passes through the ink image layer forming unit 12 to when it is conveyed to the image hiding layer forming unit 21 and reaches it. The expansion and contraction of the recording medium 10 cannot be reflected in the operation start timing of the image hiding layer forming unit 21 depending on the method of controlling according to the distance.

In particular, as shown in FIG. 6, a part of the image hiding layer 55 is hollowed out to form a window, and characters and images ("Tritek" in FIG. 6) are printed in the window. However, in this case, alignment between the image hiding layer 55 and the ink image layer 51 is particularly important.

Therefore, in the marker recognition step of flow 4, a step of confirming the position of the measurement marker 53 by the marker recognition sensor 19 is performed immediately before the formation of the image hiding layer 55 by the image hiding layer forming unit 21 is started.

As in this embodiment, when the recording medium 10 is a long web and a plurality of images are continuously printed on the surface of the recording medium 10, the step of reading the measurement marker 53 for each image. to implement.

In the present embodiment, when the recording medium 10 is transported and the measurement markers 53 applied to the surface of the recording medium 10 pass the marker recognition sensor 19, the marker recognition sensor 19 operates to detect the measurement marker 53. It can be recognized that it has passed through and reached just before the conveying route of the image concealing layer forming unit 21 .

As described above, the measurement marker 53 is arranged for each ink image layer 51 to be formed. can initiate the formation of As a result, regardless of the expansion and contraction of the recording medium 10, the ink image layer 51 and the image concealing layer 55 can be aligned to avoid misalignment.

Then, with the completion of flow 5 as a trigger, the image hiding layer forming step of flow 6 is performed.

That is, in order to confirm the formation position of the ink image layer 51 on the recording medium 10 by the measurement marker recognition step of flow 5, and to form the image hiding layer 55 having the intended shape according to this, the image hiding layer Ink ejection from the inkjet head 13 constituting the forming unit 21 is started. Thereby, the image hiding layer 55 can be formed so as to hide part or all of the ink image layer 51 and to match the positional relationship with the ink image layer 51 .

Depending on the design of the printed image required, the formation of the image hiding layer 55 may be started from the downstream side of the ink image layer 51 in the conveying direction of the surface of the recording medium 10. can also be completed upstream of the ink image layer 51 in the transport direction. By doing so, the image hiding layer 55 is applied to a wider range in the conveying direction than the ink image layer 51 on the surface of the recording medium 10, so that the ink image layer 51 more reliably hides the image. It can be printed so that the layer 55 is all covered.

Here, the electrical configuration around the image concealing layer forming unit and the marker recognition sensor will be described with reference to the block diagram of FIG.

The inkjet printing apparatus according to this embodiment includes a control computer 41 . The control computer 41 includes, for example, a CPU and memory. The memory is composed of, for example, a RAM and a ROM, and the RAM temporarily stores the calculation results of the CPU and print image data. In addition, the ROM stores an execution program for the inkjet printing sequence according to the present embodiment, a control program for driving and controlling the inkjet head 13 and various other structural units, and the like.

The control computer 41 is connected to and communicates with the controller 43 via an interface such as a LAN. A programmable controller (PLC), for example, is used as the controller 43 to control various types of connected drivers, including those not shown.

In this embodiment, the marker recognition sensor 19 monitors passage of the measurement marker 53 by its action. By recognizing the measurement marker 53 formed on the recording medium 10 , the marker recognition sensor 19 communicates a signal to that effect to the controller 43 . Using this signal as a trigger, the controller 43 starts forming the image hiding layer 55 by operating the inkjet head 13 via the driver 45 to eject ink.
When there are a plurality of images to be formed on the recording medium 10, the marker recognition sensor 19 recognizes the measurement marker 53 for each image, communicates the signal to the controller 43, and operates the driver 45 to operate the inkjet head 13. The sequence of starting the formation of the image concealing layer 55 by ejecting ink from .

In this way, by carrying out the flow 4 for each image to be formed and carrying out the flow 5 while monitoring the position of the ink image layer 51 in real time, the conveyance of the recording medium 10 and the Regardless of the presence or absence of deformation due to heating, it is possible to avoid misalignment of the printing positions of the ink image layer 51 and the image hiding layer 55 .

Through the above steps, the step of forming the image hiding layer in flow 5 is completed.

FIG. 6 is a schematic diagram showing the state of the printing surface at the completion of the image hiding layer forming step of flow 5, and FIG. 7 is a sectional view taken along the line AA of FIG.

By completing the above steps, the image hiding layer 55 could be printed while avoiding misalignment with the ink image layer 51 . Furthermore, as shown in FIG. 7, it can be seen that the ink image layer 51 is partially concealed by the image concealing layer 55 and partially not concealed. As described above, the ink image layer 51 is completely cured, so that the ink of the image hiding layer 55 is not mixed with the ink, and the ink image layer 51 and the image hiding layer 55 are not misaligned.

Then, after the image hiding layer forming step of flow 5 is completed, the second ink curing step of flow 6 is performed by the second curing unit.

In this embodiment, as in the first curing step, the recording medium 10 is wound around the second drying drum 23 and conveyed, so that the recording medium 10 is heated to a predetermined temperature by heat conduction. The heat evaporates water, which is a solvent contained in the ink of the image hiding layer 55, and drying and curing is accelerated. is completed.

Among the present embodiments, water-based inks that use water as a solvent, and water-based latex inks that use water as a solvent and in which a resin is dispersed together with a pigment, differ from solvent inks in that the solvent evaporates and dries. is slow, it is important to properly dry the ink in the second ink curing step.

In flow 6, drying and hardening of the image concealing layer 55 is accelerated and sufficiently dried to prevent damage to the printing surface due to rubbing during transportation of the recording medium 10 for which printing has been completed, and to execute the printing sequence. Since the time can be shortened and the productivity can be improved, the flow 6 is appropriately performed to completely cure the image hiding layer 55, thereby stably continuing printing on the recording medium 10. be able to.

By going through the above flow, the print sequence according to the present embodiment is completed.

The relationship between the print resolution of the ink image layer 51 and the print resolution of the image concealing layer 55 will be described.

First, the printing resolution indicates the number of ink dots per unit area that are applied by ejection from the inkjet head.

If the print resolution of the ink image layer 51 and the print resolution of the image concealing layer 55 do not match when performing the above printing sequence, a difference occurs in the diameter of the ink dots applied per unit area. Due to such a difference in ink dot diameter, the contact surface between the ink image layer 51 and the image hiding layer 55 may have fine unevenness. These minute unevenness appear in the print quality, and the print quality may be degraded.

Therefore, by controlling the ink image layer forming unit 12 and the image hiding layer forming unit 21 so that the printing resolution of the ink image layer 51 and the printing resolution of the image hiding layer 55 match, the ink image layer 51 and In some cases, such a phenomenon can be avoided by matching the ink dot diameter with that of the image hiding layer 55 .

By turning over the recording medium 10 and viewing it as illustrated in FIG. 8, the printed image can be viewed through the recording medium 10 .

Further, another configuration example of the inkjet printing apparatus will be described as a second embodiment of the present invention.

FIG. 2 is an overall view showing the configuration of an inkjet printing apparatus that is one embodiment of the present invention.

Similar to the configuration shown in FIG. 1, this configuration includes water-based ink using water as a solvent, water-based latex ink using water as a solvent and resin dispersed together with a pigment, and solvent using a solvent as a solvent. It can also be applied to inkjet printing using an ink that dries and hardens when the solvent evaporates, such as a solvent ink in which the solvent is vaporized.

Moreover, the same configuration is also applicable to actinic radiation curable ink that contains a polymerizable substance that is polymerized by irradiation with actinic rays and that is cured by irradiation with actinic rays.
Examples of actinic radiation curable ink include UV curable ink that is cured by ultraviolet (UV) irradiation and EB curable ink that is cured by electron beam (EB) irradiation.

Also, as the recording medium used in the following configuration, a long roll-shaped sheet member is used in the same manner as in the configuration of FIG. Paper such as coated paper is assumed as the material of the sheet member, but a synthetic resin film made of a resin such as polypropylene (OPP), polyethylene terephthalate (PET), or nylon is suitable.

First, the recording medium 10 is transported and supplied from the unwinding section 11 that supplies the recording medium 10 in a roll shape.

The supplied recording medium 10 reaches the heating unit 25, and before printing by the ink image layer forming unit 12 described later, the recording medium 10 is preheated (preheated) to a predetermined temperature. )do. Here, the above flow 1 is performed. As the heating unit 25, for example, a warm air generator, an infrared (IR) irradiation device, or the like is assumed, but other configurations may be used, and a plurality of units may be mounted as necessary. Also, when using ink that does not need to be heated for drying and curing, such as UV curing ink and EB curing ink, the mounting of the heating unit 25 may be omitted.

After that, the recording medium 10 is transported to the lower portion of the ink image layer forming unit 12 which is composed of a plurality of inkjet heads 13 mounted on the first carriage 14 . The details of the configuration are the same as those of the ink image layer forming unit 12 in FIG. Here, the above flow 2 is performed.

When the recording medium 10 passes under the ink image layer forming unit 12, ink is ejected from the nozzle surface side of the inkjet head 13 and applied to the surface of the recording medium 10, thereby forming the ink image layer 51. It is formed. At the same time, the measurement marker 53 can also be printed on the surface of the recording medium 10 to be recognized by the marker recognition sensor 19, which will be described later, similarly to the description in FIG.

When the ink to be used is an actinic ray curable ink, an actinic ray irradiation device is appropriately arranged along with the inkjet head 13 on the first carriage 14 to temporarily cure the ink applied to the surface of the recording medium 10, It is also envisioned to replace the pre-warming step of Flow 1.

After the ink image layer 51 is formed on the surface of the recording medium 10 by the ink image layer forming unit 12 , the recording medium 10 is transported to the first curing unit 27 . The first curing unit 27 has a function of drying and curing the ink image layer 51 formed on the surface of the recording medium 10 . Here, the above flow 3 is performed.

When using water-based ink, water-based latex ink, solvent ink, etc., it is assumed that a mechanism for heating the recording medium 10 such as a hot air generator or an infrared (IR) irradiation device is applied. Further, when using UV curable ink, EB curable ink, or the like, it is also assumed that a UV irradiation device such as a UV lamp, an electron beam irradiation device, or the like is applied.
By passing the recording medium 10 through the first curing unit 27, drying and curing of the ink image layer 51 is completed.

After that, the recording medium 10 is conveyed to a place where the marker recognition sensor 19 is arranged, as in the description of FIG. Here, flow 4 is performed.

1, the position where the ink image layer 51 is formed on the recording medium 10 is measured by reading the measurement marker 53 provided on the recording medium 10 by the marker recognition sensor 19. FIG.

Then, the recording medium 10 reaches the image hiding layer forming unit 21 after passing through the marker recognition sensor 19 . The description of the configuration of the image hiding layer forming unit 21 is the same as in FIG. Here, the above flow 5 is performed.

1, the image hiding layer forming unit 21 operates by recognizing the measurement marker 53 with the marker recognition sensor 19, and the ink image layer 51 formed on the surface of the recording medium 10 is covered with the ink image layer 51. , ink is ejected so as to cover all or part of the ink image layer 51 to form an image masking layer 55 .

After the formation of the image hiding layer 55 on the surface of the recording medium 10 by the image hiding layer forming unit 21 is completed, the recording medium 10 is conveyed to the second curing unit 29 . Here, flow 6 is performed.

The configuration of the second curing unit is the same as the description of the first curing unit above, and suitable means is selected according to the characteristics of the ink.
By passing the recording medium 10 through the second curing unit 29, drying and curing of the image hiding layer 55 is completed.

After drying and curing of the image hiding layer 55 by the second curing unit 29 is completed, the recording medium 10 is wound up by the winding section 24, and the entire printing sequence is completed.

As in the description of FIG. 1, a transport roller may be appropriately arranged in the configuration of the inkjet drawing apparatus according to the present embodiment in order to control the transport path of the recording medium 19 as necessary.

11 unwinding section 12 ink image layer forming unit 13 inkjet head 14 first carriage 15 transport heating belt 17 first drying drum 19 marker recognition sensor 21 image concealing layer forming unit 22 second carriage 23 second drying drum 24 winding section 25 heating unit 27 first curing unit 29 second curing unit 41 control computer 43 controller 45 driver 51 ink image layer 53 measurement marker 55 image hiding layer

Claims (24)

In an inkjet printing apparatus that applies ink to a long recording medium by ejecting ink from an inkjet head,
a conveying means for conveying the recording medium in a predetermined conveying direction ;
a first inkjet head that ejects inks of a plurality of different colors; and a plurality of inks of different colors are applied from the first inkjet head to the recording medium conveyed in the conveying direction by the conveying means. Forming an ink image layer corresponding to a mirror image in which a predetermined image is reversed by applying it to the surface of a recording medium, and using the ink ejected from the first inkjet head to form the ink on the surface of the recording medium an ink imaging layer forming unit for forming measurement markers at locations relative to the image layer ;
The ink image layer is formed by heating the recording medium provided downstream of the ink image layer forming unit in the conveying direction and having the ink image layer formed by the ink image layer forming unit and the measurement marker. a first ink curing unit for curing ;
marker recognition means provided downstream of the first ink curing unit in the conveying direction for recognizing the measurement marker on the recording medium heated by the first ink curing unit;
A second inkjet head is provided on the downstream side of the first ink curing unit in the conveying direction and ejects concealing ink for concealing an ink image layer onto the surface of the recording medium, and the marker recognizing means detects the By applying the concealing ink from the second inkjet head to the surface of the ink image layer cured by the first ink curing unit in accordance with recognition of the measurement marker , a part of the surface of the ink image layer is formed. or an image hiding layer forming unit for forming an image hiding layer for hiding all,
a second ink curing unit provided downstream of the image hiding layer forming unit in the conveying direction for curing the image hiding layer formed by the image hiding layer forming unit;
An inkjet printing device, comprising: 2. The image hiding layer forming unit according to claim 1, wherein said image hiding layer forming unit is controlled to start forming said image hiding layer in response to recognition of said measurement marker by said marker recognition means. Inkjet printing device. 2. The measurement marker is formed on the surface of the recording medium at a position downstream in the transport direction from a position where the ink image layer is formed . Item 3. The inkjet printing apparatus according to item 2. 3. The marker recognizing means has a moving means for moving in a direction intersecting the conveying direction in accordance with the position of the measurement marker on the surface of the recording medium. The inkjet printing device according to any one of claims 1 to 3. The formation of the image hiding layer is started from a position on the surface of the recording medium downstream in the conveying direction from a position where the ink image layer is formed on the surface of the recording medium. The inkjet printing apparatus according to any one of Claims 1 to 4. The first ink curing unit and the second ink curing unit both have heaters for heating the ink applied to the recording medium. The inkjet printing device according to claim 5 . The ink is a water-based ink in which the main component of the solvent is water, a solvent ink in which the main component of the solvent is an organic solvent, or a latex ink in which a resin is dispersed in the solvent. The inkjet printing device according to any one of claims 6 . 8. The target temperatures of both the first ink curing unit and the second ink curing unit are controlled to be 80 degrees Celsius or more and 160 degrees Celsius or less. The inkjet printing device according to any one of 1. 2. The apparatus further comprises a recording medium heating unit for heating the recording medium to a predetermined temperature before or at the same time that the ink image layer forming unit starts forming the ink image layer. The inkjet printing device according to any one of claims 8 to 10. The recording medium heating unit has an endless belt that conveys the recording medium while adsorbing and fixing the recording medium, and a heating member is arranged to face an inner peripheral surface of the endless belt. 10. The inkjet printing device according to claim 9, wherein: 11. The inkjet printing apparatus according to claim 9 , wherein the temperature of said recording medium warming unit is controlled to be 30 degrees Celsius or more and 80 degrees Celsius or less. The inkjet printing apparatus according to any one of claims 1 to 11 , wherein the printing resolution of the ink image layer and the printing resolution of the image hiding layer are the same. The inkjet printing apparatus according to any one of claims 1 to 12 , wherein the recording medium is a synthetic resin film. a medium supply unit for supplying the recording medium; and a medium collection unit for collecting the recording medium on which the formation of the ink image layer and the image concealing layer has been completed,
The medium supply unit, the first ink curing unit, the second ink curing unit, and the medium collection unit are all vertically below the arrangement positions of the ink image layer forming unit and the image hiding layer forming unit. 4. An ink jet printing device according to any one of claims 1 to 13 , characterized in that it is arranged in the . In an inkjet printing method in which ink is applied to a long recording medium by ejecting ink from an inkjet head,
An ink image corresponding to a mirror image obtained by applying a plurality of different color inks to the surface of the recording medium using a first inkjet head that ejects a plurality of different color inks, thereby inverting a predetermined image. an ink image layer forming step of forming a layer and applying ink ejected from the first inkjet head to a position related to the ink image layer on the surface of the recording medium to form a measurement marker;
a first ink curing step of curing the ink image layer by heating the recording medium having the ink image layer formed in the ink image layer forming step and the measurement marker;
a marker recognition step of recognizing the measurement marker of the recording medium heated in the first ink curing step;
In accordance with the recognition of the measurement marker in the marker recognition step, a concealing ink is applied from a second inkjet head to the surface of the ink image layer cured in the first ink curing step to obtain the ink image. an image hiding layer forming step of forming an image hiding layer for hiding part or all of the layer surface;
a second ink curing step of curing the image hiding layer formed in the image hiding layer forming step ;
An inkjet printing method, comprising : 16. The inkjet printing method according to claim 15 , wherein said image hiding layer forming step is initiated upon recognition of said measurement marker in said marker recognition step. The measurement marker is provided on the surface of the recording medium at a position downstream of the position where the ink image layer is formed in the direction in which the recording medium is conveyed . 17. The inkjet printing method according to 16 . The formation of the image hiding layer is started from a position on the surface of the recording medium downstream in the conveying direction from a position where the ink image layer is formed on the surface of the recording medium. The inkjet printing method according to any one of claims 1-5 to 1-7 . 15. The ink is a water-based ink in which the main component of the solvent is water, a solvent ink in which the main component of the solvent is an organic solvent, or a latex ink in which a resin is dispersed in the solvent. 19. The inkjet printing method of any one of claims 18 to 18. A target temperature for heating the recording medium when performing the first ink curing step and the second ink curing step is both 80 degrees Celsius and 160 degrees Celsius. 19. The inkjet printing method of any one of claims 15-19 . 21. The method according to any one of claims 15 to 20, wherein before or at the same time as performing the ink image layer forming step, a recording medium warming step of heating the recording medium to a predetermined temperature is performed. inkjet printing method. 22. The inkjet printing method according to claim 21 , wherein the temperature for heating the recording medium in the recording medium heating step is 30 degrees Celsius or more and 80 degrees Celsius or less. The inkjet printing method according to any one of claims 15 to 22, wherein the printing resolution of the ink image layer and the printing resolution of the image hiding layer are the same . The inkjet printing method according to any one of claims 15 to 23 , wherein the recording medium is a synthetic resin film.

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