JP7500041B2 - Drying device and inkjet drawing device - Google Patents

Description

The present invention relates to a drying device for ink applied to a recording medium and an inkjet printing device using the same.

As a drying device for drying the ink after applying and printing onto a recording medium such as a long roll of film, there is a device that dries the ink by contacting the recording medium with the outer surface of a heat drum containing a heater and transporting it while heating it.

Furthermore, in recent years, there has been an increasing demand for the use of so-called water-based inks in printing, which use water as a solvent and have less impact on the environment and human body, and the demand for water-based inks in inkjet printing is also increasing. Water-based inks differ from actinic radiation curable inks, which instantly harden and dry when exposed to actinic radiation such as UV, in that the main component is water, and therefore all of the water contained in the water-based ink must be evaporated in order to dry it, necessitating the application of an efficient drying method.

In a drying device using the above-mentioned heat drum that is applied to a printing system for printing with such water-based ink, in order to increase the drying efficiency, an outer wall is formed around the periphery of the heat drum, and a mechanism for blowing hot air or other air onto the outer wall and a mechanism for exhausting air between the periphery of the heat drum and the outer wall are disposed. These drying devices are disclosed in the following Patent Documents 1 and 2.

Japanese Patent Publication No. 37-3054 JP 2014-152964 A

However, water-based ink generates a large amount of water vapor when it dries, and the amount of water vapor in the air between the outer periphery of the heat drum and the outer wall quickly reaches saturated water vapor, so it is necessary to efficiently replace the air in the space formed between the outer periphery of the heat drum and the outer wall.

In this regard, when a configuration is used in which there is only one mechanism for introducing hot air (air) and one mechanism for exhausting it, as disclosed in Patent Documents 1 and 2, the air in the space cannot be efficiently supplied and exhausted, and a large amount of water vapor remains in the space formed between the outer periphery of the heat drum and the outer wall. As a result, the air in this space remains saturated with water vapor, the ink does not dry, and the generated water vapor leaks out from places other than the exhaust mechanism and adheres to the drying device and printing device. These problems are particularly pronounced when performing high-speed printing, since it is necessary to dry a large amount of ink at high speed.

The present invention has been made in consideration of the above problems, and aims to provide a drying device that can reliably discharge water vapor generated during drying and reliably dry ink, and an inkjet printing device that uses this drying device.

In order to achieve the above objective, the inventors of the present invention have, through extensive ingenuity, discovered the following configuration.

That is, in the present invention, there is provided a drying device for drying ink applied to a surface of a recording medium, comprising:
a conveying means having an outer peripheral surface that winds the recording medium to which ink has been applied while contacting the outer peripheral surface, and conveying the recording medium in contact with the outer peripheral surface along a conveying path along the outer peripheral surface while heating the recording medium;
a cover member disposed opposite the outer circumferential surface to define a predetermined space along the conveying path between the cover member and the outer circumferential surface;
An air supply port for supplying air to the predetermined space;
an exhaust port for discharging air from the predetermined space;
The exhaust port is characterized in that a plurality of the exhaust ports are arranged opposite to each other on the outer circumferential surface.

Furthermore, in the present invention, the exhaust port is characterized in that one or more exhaust ports are arranged on the upstream side of the conveying direction of the conveying path and one or more exhaust ports are arranged on the downstream side of the conveying direction with respect to the vertical lowest point of the outer peripheral surface.

Furthermore, the present invention is characterized in that the volume of air exhausted from the specified space by the exhaust port is controlled to be greater than the volume of air supplied to the specified space by the air intake port.

Furthermore, in the present invention, the temperature of the heat drum is controlled to be equal to or higher than 80 degrees Celsius and equal to or lower than 160 degrees Celsius.

The present invention is also characterized in that the opening of the air intake or exhaust port is provided with a straightening member for controlling the air flow.

Furthermore, in the present invention, the recording medium is a synthetic resin film, and the ink is a water-based ink that contains water.

Furthermore, the present invention may be configured as an inkjet drawing device having an unwinding section for supplying and transporting the roll-shaped recording medium, a preheating section for heating the recording medium supplied and transported from the unwinding section, a printing section for printing by ejecting ink onto the recording medium, a drying device as described above for drying the recording medium on which printing has been performed, and a winding section for winding up the recording medium, characterized in that the preheating section is disposed vertically above the unwinding section, the drying device, and the winding section, and the printing section is disposed vertically above the preheating section.

By adopting the above-mentioned configuration, the present invention is able to provide a drying device that can reliably discharge water vapor generated during drying and reliably dry ink, and an inkjet printing device that employs the drying device.

FIG. 2 is an overall view showing a configuration example of a drying device. FIG. 4 is a diagram showing an example of the arrangement of an air inlet and an exhaust port. FIG. 13 is a diagram showing the layout pattern of the air inlet and exhaust port verified in the water vapor discharge verification. FIG. 2 is an enlarged view of a portion within the dashed line b in FIG. 5A to 5C are schematic diagrams illustrating an example of the configuration of a flow straightening member. FIG. 2 is a cross-sectional view showing an example of the structure of a heat drum. 1 is a configuration example of an inkjet printing apparatus using a drying device of the present invention.

The following describes in detail an embodiment of the present invention with reference to the drawings.

First, an inkjet printing device equipped with a drying device will be described as an embodiment of the present invention with reference to FIG. 7.

Figure 7 is a schematic diagram of the overall configuration of an inkjet printing device equipped with a drying device.

First, the recording medium 19 is transported from the unwinding section 71, which supplies the recording medium 19 in a roll. The supplied recording medium 19 reaches the preheating section 72, where it is preheated to a predetermined temperature. Preheating prevents the ink from bleeding unintentionally and ensures print image quality. In this embodiment, the preheating section 72 is shown as a belt with a heating function that both heats the recording medium 19 and transports it, but a heating device can be installed separately from the transport belt, and multiple heating devices can be installed as necessary.

The preheated recording medium 19 passes under the printing section 73, and ink is ejected from the inkjet heads 74 mounted on the printing section 73 to print on it. The printing section 73 is usually equipped with inkjet heads 74 for ejecting four colors of ink, cyan (C), magenta (M), yellow (Y), and black (K), corresponding to the number of inks, and additional inkjet heads 74 for ejecting special color inks such as white are additionally mounted as appropriate, but this is not limited to this, and inkjet heads 74 for ejecting the required inks may be arranged as appropriate.

After printing on the recording medium 19 by the printing unit 73 is completed, the recording medium 19 is transported to the drying device 10 according to this embodiment, and the ink applied to the recording medium 19 is dried by the action described above. After the recording medium 19 passes through the drying device 10 and is completely dried, it is wound up by the winding unit 75, and printing is completed. Note that, if necessary, a suitable transport roller may be arranged within the configuration of the inkjet drawing device according to this embodiment in order to control the transport path of the recording medium 19. Also, multiple drying devices 10 may be installed if necessary.

Here, in this embodiment, the preheat unit 72 is located above the unwinding unit 71, the drying device 10, and the winding unit 75, and the printing unit 73 is located above the preheat unit 72. This is because, in order to achieve both space saving and maintenance performance, the unwinding unit 71 and the winding unit 77 are located below the preheat unit 72 in order to replace the recording medium 19, and it is also desirable to locate the drying device 10 below the preheat unit 72 in order to turn the printing surface of the recording medium 19 to the front and bring the back surface into contact with the heater drum 11, and because the printing unit 73 is located above the preheat unit 72, it can eject ink appropriately to print.

Please note that this embodiment is merely one example of a possible configuration of an inkjet printing device, and that other configurations can be set as appropriate.

Next, a drying device according to an embodiment of the present invention will be described with reference to the drawings as appropriate.

Figure 1 is an overall view showing an example of the configuration of a drying device according to this embodiment.

As a conveying means applied to the drying device 10 in this embodiment, which has an outer peripheral surface that rolls up while contacting the recording medium 19 to which ink has been applied, and which conveys the recording medium 19 in contact with the outer peripheral surface along a conveying path along the outer peripheral surface while heating it, a heat drum 11 shown in FIG. 1 is assumed. The heat drum 11 has a built-in heater that can heat the surface to a predetermined temperature, and is arranged to be rotatable around the rotation axis 11a. The shape of the heat drum 11 is preferably cylindrical because the recording medium needs to be conveyed efficiently without wrinkles. In addition, since the surface needs to be heated uniformly throughout the recording medium, it is basically desirable that the surface of the heat drum 11 is smooth so that the surface of the recording medium 19 contacts the entire surface of the recording medium. However, if necessary, some processing such as groove processing or crown processing can be appropriately performed on the surface to impart a predetermined function such as preventing meandering and wrinkles. In addition, the material is preferably a metal material with high thermal conductivity to efficiently and uniformly heat the recording medium, and stainless steel is preferable for ease of handling, but is not limited to this. In the example shown in FIG. 1, the heat drum rotates around the rotation axis 11a from upstream to downstream of the transport path in the direction of the solid arrow, transporting and heating the recording medium 19. Note that the transport means is not limited to a cylindrical drum shape like the heat drum 11 of this embodiment, and may be configured to have the above-mentioned transport and heating functions, and may be configured like a belt that has transport and heating functions.

A cover member 13 is arranged facing the outer peripheral surface of the heat drum 11 to form a predetermined space between the heat drum 11 and the outer peripheral surface along the transport path of the recording medium 19. In the example of FIG. 1, the cover member 11 is formed in a curved U-shape along the heat drum 11, but in order to reduce processing costs, it may be formed in a polygonal shape formed by connecting multiple flat plates, or any other method that can form the above-mentioned space may be used. The cover member 13 is a member provided to prevent a decrease in temperature on the outer peripheral surface of the heat drum 11 while preventing water vapor generated during drying of the recording medium 19 from flowing to parts other than the drying device and affecting other parts of the printing device. In particular, since water vapor is generated by drying the recording medium 19 in the part where the recording medium 19 and the heat drum 11 come into contact and are wound, it is more preferable to arrange the cover member 13 in the part facing this part. By disposing the cover member 13, as described above, not only is it possible to prevent a temperature drop on the outer peripheral surface of the heat drum 11 while preventing the water vapor generated during drying from flowing to parts other than the drying device, but it is also expected that the cover member 13 will have the effect of insulating the heat generated by the heat drum 11 from the outside of the drying device 10. This heat insulating effect is also expected to have the effect of preventing damage (such as damage due to high heat) to parts (printing unit, etc.) other than the drying device 10 that make up the printing device. This heat insulating effect makes it possible to arrange the drying device 10 close to other components, which contributes to space saving for the entire printing device.

On the cover member 13, an air inlet 15 for supplying air to a predetermined space between the heat drum 11 and the cover member 13, and a plurality of exhaust ports 17 for discharging air containing water vapor generated when drying the ink on the recording medium present in the predetermined space between the heat drum 11 and the cover member 13 are arranged opposite the outer circumferential surface of the heat drum 11. In this manner, by adopting a configuration in which the air inlet and a plurality of exhaust ports are arranged opposite the heat drum 11, air containing water vapor generated by drying the recording medium 19 in the space formed along the conveying path between the outer circumferential surface of the heat drum 11 and the cover member can be efficiently replaced. This makes it possible to prevent the air from reaching a saturated water vapor amount, and therefore it is possible to provide a drying device that can reliably and quickly dry the recording medium 19. The air supplied from the air inlet may be heated hot air, but it may not be particularly heated in order to reduce the space required for mounting a device that generates hot air. In the example shown in FIG. 1, one or more air inlets 15 and multiple exhaust ports 17 are arranged on the surface of the cover member opposite the side where the heat drum 11 is located, facing the heat drum 11. However, the air inlets 15 and exhaust ports 17 may be attached by connecting them to the cover member as in this embodiment, or may be arranged separately from the cover member.

In the drying device of this embodiment, a long roll-shaped sheet member is used as the recording medium 19. The material of the sheet member may be paper such as coated paper, but a synthetic resin film made of resin such as polypropylene (OPP), polyethylene terephthalate (PET), or nylon is basically suitable. Ink applied to the recording medium may be a solvent ink that requires drying by heating, but water-based ink, which uses water as a solvent and has a low impact on the environment and human body, is more suitable.

Figure 2 shows an example of the arrangement of the air intake vent 15 and the exhaust vent 17 in this embodiment. Here, the details of the arrangement method of the air intake vent 15 and the exhaust vent 17 will be described.

As a premise, in the drying device of this embodiment, as described above, not only is it necessary to properly exhaust the water vapor generated when the ink is dried by the heat drum so that the air in the specified space does not reach a saturated water vapor amount, but it is also desirable that the generated water vapor is exhausted only from the exhaust port 17 arranged, and does not leak from anywhere other than the exhaust port 17, such as the opening of the cover member 13. This is to avoid problems that occur when water vapor leaks from anywhere other than the exhaust port 17, such as the water vapor adhering to other parts of the drawing device and causing damage to the device, and problems such as the leakage of odors contained in the water vapor.

Here, regarding specific examples of the arrangement of the air inlets 15 and the exhaust ports 17, for example, as shown in FIG. 2α, the air inlets 15 and the exhaust ports 17 may be arranged alternately, as shown in FIG. 2β, and a random arrangement method in which the air inlets 15 are arranged next to the exhaust port 17 and then the exhaust port 17 may be assumed for reasons of mechanical design, and a case in which the opening of the cover member 13 does not face upward in the vertical direction in the first place as shown in FIG. 2γ may also be assumed. However, in any case, it is preferable that one or more exhaust ports 17 are arranged on the upstream and downstream sides of the transport path of the recording medium 19 that is transported by contacting the surface of the heat drum 11 and wrapping around it with respect to the vertical lowest point of the outer circumferential surface of the heat drum 11. In the example of FIG. 2, the lowest point is the point d where the dashed line c that passes vertically through the rotation axis a of the heat drum 11 and the outer circumferential surface of the heat drum 11 intersect, and at least one exhaust port 17 is arranged on the upstream and downstream sides of the transport path based on this lowest point.

The reason for this arrangement of the exhaust port 17 will be explained. The water vapor generated when drying the ink rises vertically upward because the specific gravity of the water vapor is lighter than that of air, which is mainly composed of nitrogen and oxygen. Therefore, if the exhaust port 17 is arranged only on either the upstream or downstream side of the conveying path, the air flow in the space formed between the heat drum 11 and the cover member 13 is not formed to flow from the air supply port 15 to the exhaust port 17, and the water vapor does not flow from the exhaust port 17. Due to this problem, the water vapor may remain in the specified space, or may leak from other than the exhaust port 17 (such as the opening of the cover member 13). Ultimately, not only does the amount of water vapor in the air in the space reach the saturated water vapor amount, causing the recording medium 19 to be unable to be dried, but the water vapor may leak from other than the exhaust port 17, resulting in damage to the drawing device. To solve this problem, the exhaust port 17 in this embodiment is positioned as described above, which allows for an appropriate air flow within the space and ensures that air containing water vapor is exhausted from the exhaust port 17 efficiently and reliably.

The inventor conducted the following experiment on the arrangement of the exhaust ports 17 and the water vapor exhaust status. Figure 3 shows the arrangement pattern of the exhaust ports 17 in this experiment. Figure 3α is a pattern in which the exhaust ports 17 are arranged only on one side of the downstream side of the transport path, Figure 3β is a pattern in which the exhaust ports 17 are arranged only at the lowest point in the vertical direction of the outer circumferential surface of the heat drum 11, and Figure 3γ is a pattern in which one exhaust port 17 is arranged on each of the upstream side and downstream side. In this experiment, the temperature of the heat drum 11 was controlled to 110 degrees Celsius, and the amount of ink applied to the recording medium 19 was controlled to 22.3 cc/m2, and the drying state of the ink applied to the recording medium 19 and the water vapor exhaust performance were verified for each of the arrangement patterns of Figures 3α to 3γ when the printing (transport) speed was 20 m/min and 30 m/min. In each case, the water vapor discharge performance and the drying performance of the ink applied to the recording medium 19 were evaluated in the order of ○, △, and × from the best side.

First, in the arrangement pattern of Figure 3α, at both the printing speeds of 20 m/min and 30 m/min, the water vapor generated during the drying of the ink was not properly discharged, with a large amount of water vapor leaking out of the drying device 10 and the ink applied to the recording medium 19 not being completely dry, resulting in an overall evaluation of water vapor discharge performance and ink drying state of x.

Next, in the arrangement pattern of Figure 3β, at a printing speed of 20 m/min, although there was some water vapor leakage, the ink applied to the recording medium 19 was somewhat dry and was rated as △, but at a printing speed of 30 m/min, the overall rating of the water vapor exhaust performance and ink dryness was ×. This is thought to be because the amount of ink that needs to be dried at one time in the drying device 10 increases, which in turn generates a large amount of water vapor, resulting in insufficient exhaust of the generated water vapor.

Finally, with the arrangement pattern of Figure 3γ, water vapor was properly discharged from the exhaust port 17 at both the printing speeds of 20 m/min and 30 m/min, and the ink applied to the recording medium 19 was completely dry, resulting in an overall evaluation of water vapor discharge performance and ink drying state of ◯.

The above experimental results show that by arranging one or more exhaust ports 17 on both the upstream and downstream sides of the transport path of the recording medium 19, the water vapor exhaust performance and the ink drying state are improved.

Here, we will explain the method for controlling the supply air volume and exhaust air volume of the drying device 10. Note that the air volume refers to the amount of air moved per unit time. Also, the supply air volume refers to the amount of air supplied per unit time from all the air supply ports 15 mounted on the drying device 10 to a specified space along the transport path of the recording medium 19 formed between the heat drum 11 and the cover member 13. Also, the exhaust air volume refers to the amount of air exhausted per unit time from the specified space by all the exhaust ports 17 mounted on the drying device 10.

In the drying device 10, it is desirable to appropriately control the air volume of all the air inlets 15 and exhaust ports 17 installed, thereby controlling the exhaust air volume to be greater than the supply air volume and controlling the air pressure in the specified space to be in a negative pressure state lower than the air pressure outside the space. When the air pressure in the specified space is in a positive pressure state controlled to be higher than the air pressure outside the space, the air in the specified space is not discharged from the exhaust port 17, but is likely to leak out of the specified space, where the air pressure is lower, through gaps such as the opening of the cover member. This causes the water vapor generated when drying the ink on the recording medium to leak out of the drying device 10, so in order to avoid this, it is possible to control the exhaust air volume to be greater than the supply air volume so that the air pressure in the specified space is controlled to be negative. This allows the water vapor to be properly discharged from the exhaust port 17 without leaking. The method of controlling the air volume of the air intake ports 15 and exhaust ports 17 can be any suitable method, including adjusting the number of air intake ports 15 and exhaust ports 17, controlling the air volume by switching the rotation speed of the fans connected to each of the air intake ports 15 and exhaust ports 17, using both methods in combination, or other methods.

Next, the structure of the air intake 15 and exhaust 17 will be described in detail with reference to Figures 4 and 5.

Figure 4 is an enlarged view of the area within the dashed line b in Figure 1. Straightening members 31 for controlling the flow of air are arranged at the openings of the air inlet 15 and the exhaust port 17 on the heat drum 11 side. In order to efficiently exchange the air in the space between the heat drum 11 and the cover member 13, it is effective to straighten the air flow from the air inlet 15 to the exhaust port 17. Specifically, it is desirable to form the straightening member 31 so that the air supplied from the air inlet 15 flows to the exhaust port 17 between the adjacent or nearby air inlet 15 and exhaust port 17, as shown by the solid arrow in Figure 3. Note that the shapes of the air inlet 15 and the exhaust port 17 themselves may be the same or different as long as they are equipped with the functions of suctioning and discharging air, respectively.

Figure 5 shows an example of a configuration in which a straightening member 31 is attached to the air intake or exhaust port. A straightening plate can also be attached to the opening, as in Figure 5α. It can also be configured as a nozzle with a straightening member that controls the air flow, as in Figure 5γ.

Figure 6 is a cross-sectional view showing an example of the configuration of the heat drum 11. As mentioned above, it is desirable to provide a heater unit on the heat drum 11 in order to heat the recording medium 19 in contact with the surface of the heat drum 11. As shown in Figure 6, it is preferable that multiple heater units 51 are arranged along the outer surface of the heat drum 11 in terms of thermal conductivity, and as mentioned above, it is necessary to make the surface temperature of the heat drum 11 as uniform as possible, so it is preferable to appropriately arrange the heater units 51 with adjusted output. However, depending on the machine configuration, the heater units 51 may be arranged other than on the outer surface of the heat drum 11, such as only on the shaft portion of the heat drum 11.

Next, we will explain the temperature control of the heat drum 11. The set temperature of the heat drum 11 is mainly determined by conditions such as the type of recording medium 19, the drying performance of the ink, and the required printing (conveying) speed (rotation speed of the heat drum 11).

For example, when the recording medium 19 is a coated paper having a receiving layer with high ink fixing stability on its surface, the recording medium 19 can be dried even when the controlled temperature of the heat drum 11 is about 80 degrees Celsius. As described above, water is used as the solvent in water-based ink, so in order to dry the ink in a short time, it is basically desirable to set the temperature at or above 100 degrees Celsius, which is the boiling point of water. However, even with water-based ink, it is possible that the ink can be dried at a lower temperature depending on the properties of the additives contained therein. Basically, the higher the set temperature of the heat drum 11, the faster the ink can be dried, and as a result, the printing speed (transport speed) for the recording medium 19 can be increased.

However, the recording medium 19 has a heat resistance temperature that indicates the maximum temperature at which the recording medium 19 can maintain its properties and shape. For example, in the case of synthetic resin films formed from resins such as polypropylene (OPP), polyethylene terephthalate (PET), and nylon as described above, if the temperature of the heat drum 11 is set too high, the recording medium 19 will shrink and be damaged, so there is an upper limit to the set temperature. In the case of these synthetic resin films, it is usually assumed that the heat resistance temperature is at most 160 degrees Celsius or less. In view of this, by controlling the temperature of the heat drum 11 to be between 80 degrees Celsius and 160 degrees Celsius, it is possible to ensure drying properties and drying speed without damaging the recording medium 19.

10 Drying device 11 Heat drum 11a Rotating shaft 13 Cover member 15 Air inlet 17 Exhaust port 19 Recording medium 31 Flow straightening member 71 Unwinding section 72 Preheat section 73 Printing section 74 Inkjet head 75 Winding section

Claims (8)

A drying device for drying ink applied to a surface of a recording medium, comprising:
a cylindrical drum member having an outer circumferential surface that winds around the recording medium to which ink has been applied while contacting the recording medium, and which rotates around a predetermined axis to heat the recording medium in contact with the outer circumferential surface while transporting the recording medium along a transport path along the outer circumferential surface in a predetermined transport direction;
a cover member disposed on the outer periphery of the drum member so as to face the outer periphery of the drum member, in a first rotation section during one rotation of the drum member, to cover the outer periphery of the drum member over a length exceeding half the circumference of the drum member, thereby forming a predetermined space along the transport path between the cover member and the outer periphery of the drum member, and in a second rotation section different from the first rotation section, to provide an opening for introducing the recording medium onto the outer periphery of the drum member;
having
the first rotation section is a section in which the recording medium is wound while contacting the outer peripheral surface of the drum member, and includes a winding section from an upstream side in the transport direction with respect to a vertical lowest point of the drum member, through the lowest point, to a downstream side in the transport direction with respect to the lowest point ,
the cover member covers a section extending from a section beyond the winding section to the winding section on the upstream side in the conveying direction with respect to the lowest point, to form the predetermined space,
the recording medium is introduced through the opening located vertically above the lowest point and transported along the transport path, and the ink applied to the surface of the recording medium is dried by heating the recording medium with the drum member;
Furthermore,
a plurality of air supply ports arranged in an area on the transport path corresponding to the winding section , for supplying air to the predetermined space;
a plurality of exhaust ports arranged in an area on the transport path corresponding to the winding section and configured to exhaust air from the predetermined space;
having
the air supply port and the air exhaust port are disposed on the upstream side and the downstream side of the conveying path in the conveying direction with respect to the lowest point , respectively ;
Furthermore, on the upstream side in the conveying direction, the air supply port is disposed upstream of the exhaust port in the conveying direction, and air is supplied from the upstream side in the conveying direction to the predetermined space to form an air flow toward the exhaust port on the downstream side in the conveying direction,
A drying device characterized in that the volume of air discharged from the specified space through the multiple exhaust ports is set to be greater than the volume of air supplied to the specified space through the multiple air intake ports. The drying device according to claim 1, characterized in that the cover member further covers a section extending from the winding section to a section beyond the winding section on the downstream side in the conveying direction relative to the lowest point, thereby forming the specified space. 3. The drying device according to claim 1, wherein the opening portion further conveys the recording medium wound around the outer circumferential surface of the drum member from the outer circumferential surface. 4. The drying device according to claim 1, wherein the number of the exhaust ports is greater than the number of the air inlets. 5. The drying device according to claim 1, wherein the temperature of the drum member is controlled to be in the range of 80 degrees Celsius or more and 160 degrees Celsius or less. 6. The drying device according to claim 1, wherein a straightening member for controlling the flow of air is provided in a ventilation opening that opens to allow air to flow in the air intake port or the exhaust port. 7. The drying device according to claim 1, wherein the recording medium is a synthetic resin film, and the ink is a water-based ink containing water. An inkjet drawing device comprising: an unwinding section for supplying and transporting a roll-shaped recording medium; a preheating section for heating the recording medium supplied and transported from the unwinding section; a printing section for printing by ejecting ink onto the recording medium; a drying device described in any one of claims 1 to 7 for drying the recording medium on which printing has been performed; and a winding section for winding up the recording medium, wherein the preheating section is positioned vertically above the unwinding section, the drying device and the winding section, and the printing section is positioned vertically above the preheating section.

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