Medium treatment apparatus and liquid imparting system

Abstract

Provided are a medium treatment apparatus and a liquid imparting system that are able to realize both durability performance and suppression of liquid attachment in a member that comes into contact with a medium that has undergone a drying treatment. This medium treatment apparatus (60) comprises: a drying device (34) that applies drying treatment to a medium (S); and a contact member (31) with which a liquid attachment surface of the medium having undergone the drying treatment comes into contact first after the drying treatment. The drying treatment device applies drying treatment so that the liquid attachment surface of the medium will have a liquid mass of 200 μg / cm2 or less per unit area thereof. The contact member has a cooling structure. The adhesion work of a contact surface, which comes into contact with the liquid attachment surface, with respect to a liquid imparting region of the liquid attachment surface is 80 mN / m or less. The contact surface has a Vickers hardness of 450-600 Hv.

Description

Media processing device and liquid application system

[0001] The present invention relates to media processing devices and liquid application systems.

[0002] Inkjet printing devices dry an image after forming it on a recording medium. Drying is performed to volatilize the ink adhering to the recording medium and reduce the stickiness of the image. Even if a certain level of drying is performed to reduce stickiness, the temperature of the printed surface of the recording medium immediately after the drying process is close to the temperature of the drying process, and depending on the configuration of the printing device, there is a risk that the printed surface of the recording medium will come into contact with components of the printing device during transportation of the recording medium. Note that the recording medium is the medium used for printing, and examples include paper media. Recording media are also called printing media, printing paper, printing paper, recording paper, and recording paper.

[0003] When the printed surface of a printed recording medium comes into contact with a component of a printing device, a portion of the image printed on the printed surface of the recording medium may adhere to the component, potentially causing a portion of the image to peel off from the printed surface of the recording medium. Once ink adheres to a component, the affinity between the ink adhered to the component and the ink constituting the image can lead to frequent image defects, such as the image peeling off from the printed surface of the recording medium when it is subsequently transported. In particular, images that have not yet been dried for a certain period of time have weak surface film quality, and components that the image comes into contact with within a certain period of time after the drying process are prone to ink adhesion.

[0004] Examples of members that the image may come into contact with within a certain period after the drying process include a paper feed roller in a perfecting printer that uses a sheet-type recording medium and a cooling roller in a roll printer. Examples of methods for preventing ink from adhering to members of a printing device that the image may come into contact with include coating the surface of the member and cooling the image.

[0005] Examples of coatings on the surface of a component include the application of an anti-fouling film, a fluororesin coating, and a silicone coating. Examples of cooling the image include a water-cooling method in which a cooling roller that circulates a refrigerant is brought into contact with the image, and an air-cooling method in which cool air is blown onto the image. When the latex contained in the ink is cooled and a latex film is formed on the surface of the image, the film quality of the image surface is strengthened and adhesion of the ink to the surface of the component is suppressed.

[0006] Patent Document 1 describes an image forming system that forms images on a first side and a second side of a recording medium. The device described in this document has a conveying member whose surface energy in contact with the first side of the recording medium is lower than the surface energy of ink that forms the image on the surface. Examples of materials with low surface energy include fluororesin-based materials such as PTFE, ETFE, and FDTS resin.

[0007] PTFE is an abbreviation for Poly Tetra Fluoro Ethylene, which is an English term that represents polytetrafluoroethylene. ETFE is an abbreviation for Ethylene Tetra Fluoro Ethylene, which is an English term that represents ethylene tetrafluoroethylene copolymer. FDTS stands for 1H,1H,2H,2H-perfluorodecyltrichlorosilane.

[0008] U.S. Patent No. 5,999,623 describes a printer that prints on a continuous web using organic solid phase change inks. The document describes that ink offset onto an aluminum roller occurs when the adhesive force between the ink image and the aluminum roller is stronger than the cohesive force of the ink itself. The document also describes maintaining the aluminum roller at a relatively low temperature of around 30°C as a method for minimizing ink offset. The document also describes low-adhesion coatings and phobic coatings.

[0009] JP 2021-154658 A JP 2011-31615 A

[0010] When an image is printed and then dried, the film quality of the image surface is weak immediately after the drying process. In particular, the first-touch member that first comes into contact with the image after the drying process is the most susceptible to ink adhesion.

[0011] Coating the surface of a component that comes into contact with an image prevents ink from adhering to the component surface, but the coating has poor durability and a short lifespan. Conventionally, components have been configured to be removable, and the component surface has been periodically coated to maintain the ability to prevent ink from adhering, but periodic coating of components poses a problem in terms of labor costs.

[0012] When cooling components that come into contact with an image, the air cooling method is less efficient than the water cooling method, and the water cooling method has an advantage in that it has a relatively high cooling efficiency.However, with the water cooling method, it is difficult to remove the cooling roller due to its structure.

[0013] In other words, members that come into contact with the image, such as first-touch members, are required to have low surface adhesion, be stain-resistant, have a certain level of durability, and not require periodic replacement or require periodic replacement relatively infrequently.

[0014] Patent Document 1 does not describe the durability of a conveying member to which a low surface energy material is applied. Generally, a fluorine-based material coating lacks durability as a member that constantly comes into contact with a recording medium. In other words, the conveying member to which the low surface energy material described in Patent Document 1 is applied does not achieve both the ability to suppress image adhesion and durability.

[0015] The aluminum roller described in Patent Document 2 does not specify a material hardness. In other words, the aluminum roller described in this document does not have any measures in place to ensure durability. The above-mentioned problems with inkjet printing devices can also exist in media processing devices that include a drying process after liquid application in a liquid application system that applies liquid to a medium.

[0016] The present invention has been made in consideration of these circumstances, and aims to provide a media processing device and liquid application system that achieves both suppression of liquid adhesion and durability in components that come into contact with the media after drying processing.

[0017] A media processing device according to a first aspect of the present disclosure comprises a drying device that performs a drying process on a medium to which a liquid has been applied, and a contact member that comes into contact first with the liquid-adhering surface of the medium to which the liquid is applied after the drying process has been performed using the drying device, wherein the drying device performs the drying process on a medium in which the mass of liquid per unit area on the liquid-adhering surface of the medium is 200 micrograms per square centimeter or less, the contact member has a cooling structure that cools the medium, and the work of adhesion of the contact surface that comes into contact with the liquid-adhering surface relative to the liquid-application area on the liquid-adhering surface of the medium to which the liquid is applied is 81 millinewtons per meter or less, and the Vickers hardness of the contact surface is 450 Hv or more and 600 Hv or less.

[0018] According to this aspect, the contact member that first comes into contact with the liquid-adhered surface of the medium after drying has a work of adhesion of 81 millinewtons per meter or less on the contact surface that comes into contact with the liquid-adhered surface of the medium, thereby suppressing liquid adhesion. Furthermore, the Vickers hardness of the contact surface is set to 450 Hv or more and 600 Hv or less, thereby achieving a certain level of durability. This achieves both suppression of liquid adhesion and durability on the contact member.

[0019] The media processing device may include a transport device that transports the media. The transport device may use a roller transport system that includes one or more rollers that support the media. The transport device may use a transport system that includes one or more support members that have a surface that supports the media.

[0020] The drying device can perform a drying process such that the mass of liquid per unit area on the liquid-adhered surface of the medium after the drying process is 105 micrograms per square centimeter or more.

[0021] The work of adhesion at the contact surface of the contact member is preferably 35 millinewtons per meter or more.

[0022] The contact member may be disposed inside the drying device or outside the drying device.

[0023] A media processing device according to a second aspect of the present disclosure is the media processing device according to the first aspect, wherein the contact members have contact surfaces that are subjected to eutectoid plating.

[0024] According to this aspect, by applying a eutectoid plating process as the surface treatment of the contact member, it is possible to realize the contact surface of the contact member having a specified work of adhesion and a specified Vickers hardness.

[0025] A media processing device according to a third aspect of the present disclosure is the media processing device according to the first or second aspect, wherein the contact surfaces of the contact members may be subjected to a fluorine-based resin eutectoid plating process.

[0026] According to this aspect, by applying a fluororesin eutectoid plating process as the surface treatment of the contact member, it is possible to realize the contact surface of the contact member having a specified adhesion work and a specified Vickers hardness.

[0027] A fourth aspect of the present disclosure is a media processing device according to the third aspect, wherein the plating film applied to the contact surface of the contact member may contain 4.0 mass percent or more and 9.0 mass percent or less of a fluorine-based resin.

[0028] According to this embodiment, it is possible to optimize both the adhesive work and the Vickers hardness.

[0029] A media processing device according to a fifth aspect of the present disclosure is the media processing device according to any one of the first to fourth aspects, wherein the contact member has a roller shape.

[0030] In this embodiment, the roller-shaped contact member is preferably a driven roller that moves in accordance with the movement of the medium.

[0031] A media processing device according to a sixth aspect of the present disclosure is a media processing device according to any of the first to fifth aspects, wherein the cooling structure may be a system that circulates a liquid adjusted to a specified temperature range.

[0032] According to this aspect, the contact member has excellent durability and therefore requires relatively low replacement frequency, and although the cost of the replacement work is high, a system of circulating a liquid with excellent cooling performance can be adopted.

[0033] A media processing device according to a seventh aspect of the present disclosure is a media processing device according to the sixth aspect, which includes one or more processors and one or more memories in which programs to be executed by the one or more processors are stored, and the one or more processors may execute instructions of the programs to adjust the liquid applied to the cooling structure to 25°C or below.

[0034] According to this aspect, the hardening of the liquid applied to the medium is accelerated, and preferable hardening of the liquid is achieved.

[0035] A media processing device according to an eighth aspect of the present disclosure is a media processing device according to the sixth aspect, which includes one or more processors and one or more memories in which programs to be executed by the one or more processors are stored, and the one or more processors execute instructions of the programs to perform cooling on a liquid-adhered surface cooled using a cooling structure such that the temperature difference between before and after cooling is 60°C or more.

[0036] According to this aspect, the hardening of the liquid applied to the medium is accelerated, and preferable hardening of the liquid is achieved.

[0037] A media processing device according to a ninth aspect of the present disclosure is a media processing device according to any one of the first to sixth aspects, which includes one or more processors and one or more memories storing programs to be executed by the one or more processors, and the one or more processors may execute instructions of the programs to adjust the temperature of the media after drying processing to between 90°C and 180°C using a drying device.

[0038] According to this aspect, insufficient drying and excessive drying are suppressed, and the dry state of the medium is optimized.

[0039] A liquid application system according to a tenth aspect of the present disclosure comprises a liquid application device that applies liquid to a liquid-adhering surface of a medium, a drying device that performs a drying process on the medium having the liquid applied to its liquid-adhering surface, and a contact member that comes into contact first with the liquid-adhering surface of the medium that has been dried using the drying device and to which the liquid is applied after the drying process, wherein the drying device performs the drying process on the medium such that the mass of liquid per unit area on the liquid-adhering surface of the medium is 200 micrograms per square centimeter or less, the contact member has a cooling structure that cools the medium, and the work of adhesion of the contact surface that comes into contact with the liquid-adhering surface relative to the liquid-application area on the liquid-adhering surface of the medium where the liquid is applied is 81 millinewtons per meter or less, and the Vickers hardness of the contact surface is 450 Hv or more and 600 Hv or less.

[0040] The liquid application system according to the tenth aspect can achieve the same effects as the media processing device according to the first aspect. The components of the media processing device according to the second to ninth aspects can also be applied to the liquid application systems according to the other aspects.

[0041] A liquid application system according to an eleventh aspect of the present disclosure is a liquid application system according to the tenth aspect, in which a moisture content adjustment device is arranged at a position upstream of the liquid application device in the transport direction of the medium, and includes a moisture content adjustment device that performs a moisture content adjustment process on the medium as it enters the liquid application device, one or more processors, and one or more memories that store programs to be executed by the one or more processors, and the one or more processors may execute instructions of the program to use the moisture content adjustment device to adjust the moisture content of the medium to 1.2 percent or more and 14.3 percent or less as it enters the liquid application device.

[0042] According to this aspect, the moisture content of the medium when it enters the liquid deposition device is adjusted, thereby optimizing the performance of the drying device.

[0043] A liquid application system according to a twelfth aspect of the present disclosure is the liquid application system according to the tenth or eleventh aspect, and includes, as the liquid application device, a printing device that applies ink to a medium to form an image on the medium, and the ink may contain wax having a melting point of 90°C or higher.

[0044] According to this aspect, stickiness of the cured liquid is suppressed.

[0045] According to the present invention, the contact member that first comes into contact with the liquid-adhered surface of the medium after drying has a work of adhesion of 81 millinewtons per meter or less on the contact surface that comes into contact with the liquid-adhered surface of the medium, thereby suppressing liquid adhesion. Furthermore, the Vickers hardness of the contact surface is set to 450 Hv or more and 600 Hv or less, thereby achieving a certain level of durability. This achieves both suppression of liquid adhesion and durability on the contact member.

[0046] FIG. 1 is an overall configuration diagram of a printing system according to an embodiment. FIG. 2 is a configuration diagram showing the general configuration of a main print drying unit shown in FIG. 1. FIG. 3 is a schematic diagram showing an example configuration of a cooling roller. FIG. 4 is a functional block diagram showing the electrical configuration of the printing system shown in FIG. 1. FIG. 5 is a block diagram showing an example electrical configuration hardware configuration of a control device of the printing system shown in FIG. 4. FIG. 6 is a table showing the performance of cooling rollers due to differences in surface treatment. FIG. 7 is a table showing evaluation results of the amount of solvent on a substrate. FIG. 8 is a configuration diagram showing the general configuration of a main print drying unit according to a first modified example. FIG. 9 is a configuration diagram showing the general configuration of a main print drying unit according to a second modified example. FIG. 10 is a configuration diagram showing the general configuration of a main print drying unit according to a third modified example.

[0047] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the following, the direction in which the substrate S travels is referred to as the transport direction, and the direction perpendicular to the transport direction and parallel to the recording surface of the substrate S is referred to as the width direction. The substrate described in the embodiment is an example of a medium.

[0048] [Example of Printing System Configuration] Figure 1 is a diagram showing the overall configuration of a printing system according to an embodiment. The printing system 10 shown in the figure is a printing system that transports a substrate S, which is a long paper medium, using a so-called roll-to-roll method and forms an image using a single-pass method. The printing system 10 includes a paper feed unit 12, a preliminary drying unit 14, a main drying unit for front side printing 16, a reversing unit 18, a main drying unit for back side printing 20, and a paper discharge unit 22.

[0049] The paper feed unit 12 houses a feed roll on which the substrate S before printing is wound in a roll shape. The paper feed unit 12 drives a motor connected to the rotation shaft of the feed roll to rotate the feed roll, and supplies the substrate S before printing to a transport path for the substrate S. The substrate S supplied from the feed roll is transported to the preliminary drying unit 14. The feed roll and the motor connected to the rotation shaft of the feed roll are not shown in the drawing.

[0050] The preliminary drying unit 14 includes a preliminary drying conveying device that conveys the substrate S in the preliminary drying unit 14 and a heating device that heats the substrate S. The preliminary drying unit 14 adjusts the moisture content of the substrate S that enters the front surface printing main drying unit 16. The preliminary drying conveying device and heating device are not shown in the figure. The preliminary drying unit 14 heats and pre-dries the substrate S being conveyed.

[0051] The pre-drying unit 14 can apply at least one of heat conduction, convection, radiation, and dielectric heating as a method of pre-drying treatment to the substrate S. The substrate S discharged from the pre-drying unit 14 is transported to the front surface printing main drying unit 16. Note that the pre-drying unit 14 described in the embodiment is an example of a moisture content adjustment device that performs moisture content adjustment treatment on the medium when it enters the liquid application device.

[0052] The front surface printing main drying unit 16 includes a front surface printing transport device, a front surface printing device, and a front surface main drying device. The front surface printing transport device transports the substrate S along a transport path of the substrate S in the front surface printing main drying unit 16.

[0053] The surface printing device employs an inkjet system equipped with one or more inkjet heads. The surface printing device ejects droplets of aqueous ink from the inkjet heads onto the substrate S transported along a specified transport path to print an image on the surface of the substrate S. The surface of the substrate S is indicated by the symbol SA in FIG. 2 .

[0054] The main front surface drying device dries the aqueous ink applied to the substrate S. The configuration of the main front surface drying device is shown in Figure 2. The main front surface drying device may use the same drying method as the preliminary drying unit 14. The substrate S discharged from the main front surface printing drying unit 16 is transported to the reversing unit 18. Note that the main front surface printing transport device, printing device, and main front surface drying device are not shown in Figure 1. The main front surface printing transport device, printing device, and main front surface drying device are shown in Figure 2.

[0055] The reversing unit 18 includes a turn bar. The turn bar turns the substrate S over. The substrate S, whose front and back sides have been turned over, is transported to the backside printing main drying unit 20. For example, the printing surface of the substrate S on which an image is printed in the frontside printing main drying unit 16 may be referred to as the front side, and the supporting surface on which the substrate S is supported in the frontside printing main drying unit 16 may be referred to as the back side. The front side and back side referred to here represent the relative relationship between one side and the other side of the substrate S. The back side of the substrate S is illustrated in FIG. 2 using the symbol SB.

[0056] The rear surface printing main drying unit 20 may have the same configuration as the front surface printing main drying unit 16. The rear surface printing main drying unit 20 uses a rear surface printing transport device to transport the substrate S along a specified transport path.

[0057] The back surface printing main drying unit 20 uses a back surface printing device to eject droplets of aqueous ink from an inkjet head onto the substrate S being transported along a specified transport path, thereby printing an image on the back surface, which is the printing surface of the substrate S.

[0058] The rear surface printing main drying unit 20 uses a rear surface main drying device to dry the water-based ink applied to the substrate S. The substrate S discharged from the rear surface printing main drying unit 20 is transported to the paper discharge unit 22.

[0059] The paper discharge unit 22 stores a delivery roll on which printed substrate S is wound in a roll. The paper discharge unit 22 has the same configuration as the paper feed unit 12. The paper discharge unit 22 may also include a cutter that cuts the continuous sheet of substrate S, and store the cut sheets of substrate. Each unit provided in the printing system 10 will be described in detail below.

[0060] [Configuration Example of Printed Book Drying Unit] The front printed book drying unit 16 and the back printed book drying unit 20 are collectively referred to as the printed book drying unit. The front printed book drying unit 16 and the back printed book drying unit 20 may have the same configuration. Here, the front printed book drying unit 16 will be described as the printed book drying unit 60.

[0061] Figure 2 is a diagram showing a schematic configuration of the printed book drying unit shown in Figure 1. The printed book drying unit 60 includes a plurality of pass rollers 30, an inkjet head 32, a radiant heating section 34, and a drying drum 36. The plurality of pass rollers 30 are components of a print transport device, the inkjet head 32 is a component of a printing device, and the radiant heating section 34 and the drying drum 36 are components of the main drying device.

[0062] The printing transport device is a general term for the front printing transport device and the back printing transport device, the printing device is a general term for the front printing device and the back printing device, and the main drying device is a general term for the front main drying device and the back main drying device.

[0063] A plurality of pass rollers 30 are arranged on the transport path of the substrate S in the printed book drying unit 60. The substrate S brought into the printed book drying unit 60 is supported and transported using the pass rollers 30, and is discharged to the outside of the printed book drying unit 60. One or more of the plurality of pass rollers 30 may function as tension rollers that generate tension on the substrate S. A tension pickup that detects the tension applied to the substrate S may be arranged on the transport path of the substrate S.

[0064] The inkjet head 32 is disposed at a position facing the surface SA of the substrate S transported along the transport path of the substrate S. The inkjet head 32 ejects aqueous ink onto the surface SA of the substrate S to print an image.

[0065] The printing device may include inkjet heads corresponding to a plurality of ink colors. That is, the printing device may include a plurality of inkjet heads, and may eject ink of different colors from the plurality of inkjet heads. Examples of the plurality of ink colors include cyan, magenta, yellow, and black. The printing device may also include inkjet heads 32 that eject special color inks such as white and clear.

[0066] The inkjet head 32 is a line head in which a plurality of nozzles are arranged over a length corresponding to the entire width of the substrate S in the width direction perpendicular to the transport direction of the substrate S. The printing device may employ a single pass method in which the substrate S and the inkjet head 32 are scanned relative to each other once to print an image over the entire surface of the substrate S.

[0067] The inkjet head 32 may have a configuration in which a plurality of head modules are connected in the width direction of the substrate S. The arrangement of the plurality of nozzles may be such that the plurality of nozzles are aligned in a row in the width direction of the substrate S. Or the arrangement may be such that the plurality of nozzles are aligned two-dimensionally. As the arrangement in which the plurality of nozzles are aligned two-dimensionally, a two-row zigzag arrangement or a matrix arrangement may be used.

[0068] Aqueous ink refers to ink in which a coloring material such as a dye or pigment is dissolved or dispersed in water and a water-soluble solvent. In this example, aqueous pigment ink is used as the aqueous ink. The aqueous ink may also contain wax.

[0069] The substrate S is guided by the path rollers 30 and transported from a position facing the inkjet head 32 to a position facing the radiant heating section 34. The arrow line shown in Figure 2 indicates the transport direction of the substrate S in the printed book drying unit 60.

[0070] The radiant heating unit 34 includes an infrared heater. The infrared heater radiates infrared rays toward the surface SA of the substrate S to heat the substrate S. The radiant heating unit 34 may also include a hot air fan that supplies hot air to the surface SA of the substrate S. The infrared heater and the hot air fan are not shown in the drawings.

[0071] The substrate S is guided by the pass rollers 30 and transported from a position facing the radiant heating section 34 to the drying drum 36. The substrate S is wrapped around the outer peripheral surface 36B of the drying drum 36.

[0072] The drying drum 36 has a cylindrical shape and a rotary shaft 36A is rotatably supported. SUS is used as the material for the outer peripheral surface 36B of the drying drum 36. SUS is an abbreviation for Steel Use Stainless.

[0073] The drying drum 36 includes a heater 36C therein. The heater 36C heats the outer peripheral surface 36B. The drying drum 36 heats the substrate S by bringing the substrate S into contact with the outer peripheral surface 36B. A rotating shaft 36A of the drying drum 36 is connected to a rotating shaft of a motor 36D. A connecting member such as a gear is used to connect the rotating shaft 36A of the drying drum 36 to the rotating shaft of the motor 36D.

[0074] When the motor 36D is operated, the drying drum 36 is driven to rotate around the rotation shaft 36A. The drying drum 36 rotates with its outer peripheral surface 36B in contact with the back surface SB of the substrate S, which is opposite to the front surface SA on which the image is printed, and heats and transports the substrate S from the back surface SB. In the case of the back surface printing main drying unit 20, the surface of the substrate S on which the image is printed is the back surface SB of the substrate S, and the surface of the substrate S opposite to the surface on which the image is printed is the front surface SA of the substrate S. The substrate S heated using the drying drum 36 is guided by the path rollers 30 and discharged from the drying drum 36 to the outside of the printing main drying unit 60.

[0075] Of the members arranged downstream of the drying drum 36 in the transport direction of the substrate S, the first member to come into contact with the ink application area of ​​the image-printed surface of the dried substrate S when the ink application area separates from the drying drum 36 is the first-touch member. The cooling roller 31 that is closest to the drying drum 36 in the transport path of the substrate S can be understood as a first-touch roller, which is the first-touch member.

[0076] In the case of the surface printing and drying unit 16 shown in Figure 1, the first-touch member is the member that comes into contact first with the surface SA of the substrate S, which has been printed using the inkjet head 32 and has been subjected to a drying process, when it leaves the drying drum 36.

[0077] In the case of the backside printing main drying unit 20, the first-touch member is the member that is first contacted when the backside SB of the substrate S, which has been printed using the inkjet head 32 and has been subjected to a drying process, separates from the drying drum 36.

[0078] In the printed book drying unit 60 shown in FIG. 2, the first-touch member is the cooling roller 31 whether it is the front-side printed book drying unit 16 or the back-side printed book drying unit 20.

[0079] The cooling roller 31, which functions as a first-touch member, has a cylindrical shape and a surface 31A made of SUS. The surface 31A of the cooling roller 31 is plated to adjust its physical properties.

[0080] The cooling roller 31 has a cooling structure for cooling the substrate S that has been subjected to the drying treatment. The cooling structure of the cooling roller 31 employs a water-cooling system in which water adjusted to a specified temperature range is circulated as a refrigerant.

[0081] The front surface SA of the substrate S in the front-surface printing main drying unit 16 described in the embodiment is an example of a liquid-adhering surface of a medium to which a liquid is applied, and the back surface SB of the substrate S in the back-surface printing main drying unit 20 is an example of a liquid-adhering surface of a medium to which a liquid is applied. The cooling roller 31 described in the embodiment is an example of a contact member. The ink application area described in the embodiment is an example of a liquid application area.

[0082] [Configuration example of cooling roller] Fig. 3 is a schematic diagram showing a configuration example of a cooling roller. Fig. 3 schematically illustrates the internal structure of a cooling roller 31. A cooling water flow path is formed inside the cooling roller 31, and cooling water 31E that flows in from a cooling water inlet 31C passes through a cooling water flow path 31B and is discharged from a cooling water outlet 31D. The cooling roller 31 circulates cooling water adjusted to a specified temperature range, adjusting the temperature of the surface 31A to the specified range. The cooling roller 31 may use a gas as a refrigerant. The cooling water inlet 31C and the cooling water outlet 31D are connected to a temperature adjustment device that adjusts the temperature of the cooling water.

[0083] [Electrical Configuration of Printing System] Figure 4 is a functional block diagram showing the electrical configuration of the printing system shown in Figure 1. The printing system 10 includes an overall control unit 50. The overall control unit 50 performs overall control of the printing system 10. The overall control unit 50 functions as a memory controller that controls reading and storing of data from and to storage devices such as memory 51.

[0084] The overall control unit 50 acquires a sensor signal transmitted from the sensor 53. The overall control unit 50 transmits a command signal to various control units based on the information represented by the sensor signal, and controls the operation of each unit via the various control units.

[0085] The printing system 10 includes a transport control unit 52. The transport control unit 52 controls a transport device 55 that transports the substrate S based on a command signal transmitted from the integrated control unit 50. The transport device 55 shown in Fig. 4 includes a paper feed unit 12, a reversing unit 18, and a paper discharge unit 22. The transport device 55 includes a preliminary drying transport device provided in the preliminary drying unit 14 shown in Fig. 1, a front printing transport device provided in the front printing main drying unit 16, and a back printing transport device provided in the back printing main drying unit 20.

[0086] The transport control unit 52 controls the operation of the motor of the paper feed unit 12, the turn bar of the reversing unit 18, the motor of the paper discharge unit 22, etc., and transports the substrate S at a specified transport speed. The transport control unit 52 applies a specified transport tension to the substrate S and transports the substrate S. The transport control unit 52 controls the rotational drive of the drying drums 36 provided in the front surface printing main drying unit 16 and the back surface printing main drying unit 20.

[0087] The printing system 10 includes a pre-drying control unit 54. Based on a command signal transmitted from the overall control unit 50, the pre-drying control unit 54 applies specified pre-drying conditions and controls the operation of the heating device of the pre-drying unit 14 to pre-dry the substrate S.

[0088] The printing system 10 includes a print control unit 56. The print control unit 56 controls the inkjet heads 32 provided in the front-side printing main drying unit 16 and the back-side printing main drying unit 20, respectively, to print an image on the substrate S.

[0089] The print control unit 56 includes an image processing unit that generates a halftone image of the print image from the print data. The print control unit 56 includes a drive voltage generation unit that generates a drive voltage to be supplied to the inkjet head 32 based on dot arrangement information and dot size information based on the halftone image. The print control unit 56 includes a drive voltage supply circuit that supplies a drive voltage to the inkjet head 32. The print control unit 56 includes a correction processing unit that performs various correction processes.

[0090] The printing system 10 includes a drying control unit 58. The drying control unit 58 controls the operation of the radiant heating unit 34 and the drying drum 36 provided in each of the front-side printing book drying unit 16 and the back-side printing book drying unit 20, thereby drying the ink applied to the substrate S.

[0091] The printing system 10 includes a cooling control unit 59. The cooling control unit 59 controls the temperature, flow rate, etc. of the cooling water in the cooling roller 31, and cools the substrate S immediately after the drying process.

[0092] Fig. 5 is a block diagram showing an example of the electrical and hardware configuration of the control device of the printing system shown in Fig. 4. The control device 100 provided in the printing system 10 includes a processor 102, a computer-readable medium 104 which is a non-transitory tangible entity, a communication interface 106, and an input / output interface 108.

[0093] A computer is applied to the control device 100. The computer may be in the form of a server, a personal computer, a workstation, a tablet terminal, or the like.

[0094] The processor 102 includes a central processing unit (CPU) and may include a graphics processing unit (GPU). The processor 102 is connected to a computer-readable medium 104, a communication interface 106, and an input / output interface 108 via a bus 110. An input device 112 and a display device 114 are connected to the bus 110 via the input / output interface 108.

[0095] The computer-readable medium 104 includes a memory 116 serving as a main storage device and a storage 118 serving as an auxiliary storage device. The computer-readable medium 104 may be a semiconductor memory, a hard disk drive, a solid-state drive, or the like. The computer-readable medium 104 may be any combination of multiple devices.

[0096] A hard disk drive may be referred to as an HDD, which is an abbreviation of the English term Hard Disk Drive, and a solid state drive may be referred to as an SSD, which is an abbreviation of the English term Solid State Drive.

[0097] The control device 100 is connected to a network via a communication interface 106, and is communicably connected to external devices. The network may be a local area network (LAN), etc. The network is not shown in the figure.

[0098] The computer-readable medium 104 stores a transport control program 120, a print control program 122, a drying control program 124, and a cooling control program 126. The transport control program 120 is applied to the transport control unit 52 shown in FIG. 4 and realizes the function of transporting the substrate S of the transport device 55. The print control program 122 is applied to the print control unit 56 and realizes the printing function of the front surface printing device of the front surface printing main drying unit 16 and the back surface printing device of the back surface printing main drying unit 20.

[0099] The drying control program 124 is applied to the drying control unit 58. The drying control program 124 realizes the drying functions of the preliminary drying unit 14, the main front surface drying device of the main front surface printing drying unit 16, and the main rear surface drying device of the main rear surface printing drying unit 20.

[0100] The cooling control program 126 is applied to the cooling control unit 59. The cooling control program 126 realizes a cooling function for cooling the substrate S after the drying process using the cooling roller 31 has been performed.

[0101] The various programs stored in the computer-readable medium 104 include one or more instructions. Various data, various parameters, etc. are stored in the computer-readable medium 104. Note that the memory 51 shown in Fig. 4 may be included in the memory 116 of the computer-readable medium 104 shown in Fig. 5.

[0102] In the printing system 10, the processor 102 executes various programs stored in a computer-readable medium 104 to realize various functions of the printing system 10. Note that the term "program" is synonymous with the term "software."

[0103] The control device 100 performs data communication with an external device via a communication interface 106. The communication interface 106 may be compliant with various standards such as USB (Universal Serial Bus). The communication form of the communication interface 106 may be either wired communication or wireless communication.

[0104] The control device 100 is connected to an input device 112 and a display device 114 via an input / output interface 108. The input device 112 is implemented by input devices such as a keyboard and a mouse. The display device 114 displays various information applied to the control device 100.

[0105] A liquid crystal display, an organic EL display, a projector, etc. may be used as the display device 114. Any combination of multiple devices may be used as the display device 114. Note that the EL in the organic EL display is an abbreviation for Electro-Luminescence.

[0106] Examples of the hardware structure of the processor 102 include a CPU, a GPU, a programmable logic device (PLD), and an application specific integrated circuit (ASIC). The CPU is a general-purpose processor that executes programs and functions as various functional units. The GPU is a processor specialized for image processing.

[0107] A PLD is a processor whose electrical circuit configuration can be changed after the device is manufactured. An example of a PLD is an FPGA (Field Programmable Gate Array). An ASIC is a processor with dedicated electrical circuitry designed specifically to perform a specific process.

[0108] A processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types. Examples of combinations of various processors include a combination of one or more FPGAs and one or more CPUs, and a combination of one or more FPGAs and one or more GPUs. Another example of a combination of various processors is a combination of one or more CPUs and one or more GPUs.

[0109] A single processor may be used to configure multiple functional units. An example of using a single processor to configure multiple functional units is a configuration in which a single processor is configured by applying a combination of one or more CPUs and software, such as a SoC (System On a Chip) that is typified by a computer such as a client or server, and this processor operates as multiple functional units.

[0110] Another example of using one processor to configure multiple functional units is to use a processor that uses one IC chip to realize the functions of an entire system including multiple functional units. Note that IC is an abbreviation for Integrated Circuit.

[0111] In this way, the various functional units are configured as hardware structures using one or more of the various processors described above.More specifically, the hardware structures of the various processors described above are electric circuits (circuitry) that combine circuit elements such as semiconductor elements.

[0112] The computer-readable medium 104 may include semiconductor devices such as read-only memory (ROM), random access memory (RAM), and solid-state drives (SSD). The computer-readable medium 104 may include magnetic storage media such as hard disks. The computer-readable medium 104 may comprise multiple types of storage media.

[0113] [Operation of the Printing System] The substrate S supplied from the paper feed unit 12 is transported to the preliminary drying unit 14, where it is subjected to a preliminary drying process. After the preliminary drying process, the substrate S is transported to the front side printing main drying unit 16.

[0114] In the front surface printing main drying unit 16, the substrate S is guided by path rollers 30 and transported to a position facing the inkjet head 32. The inkjet head 32 ejects droplets of aqueous ink toward the front surface SA of the substrate S. The ejected droplets adhere to the front surface SA of the substrate S, and an image is printed on the front surface SA of the substrate S.

[0115] Next, the substrate S is transported to a position facing the radiant heating unit 34. The radiant heating unit 34 uses an infrared heater to heat the substrate S. This promotes drying of the aqueous ink applied to the surface SA of the substrate S.

[0116] Furthermore, the substrate S is guided by the path rollers 30 and transported from a position facing the radiant heating unit 34 to the drying drum 36. The substrate S is wrapped around the outer peripheral surface 36B of the drying drum 36. The drying drum 36 rotates with the outer peripheral surface 36B in contact with the back surface of the substrate S, heating the substrate S from the back surface and transporting it. This promotes drying of the aqueous ink applied to the front surface SA of the substrate S.

[0117] The surface SA of the substrate S on which the ink has been dried is cooled by contact with the cooling roller 31. The substrate S on which the surface SA has been cooled is guided by the path roller 30 and discharged to the outside of the front surface printing main drying unit 16.

[0118] The substrate S discharged from the front surface printing main drying unit 16 is transported to the reversing unit 18, where it is turned over using a turn bar. The turned over substrate S is transported to the back surface printing main drying unit 20.

[0119] In the rear surface printing main drying unit 20, the substrate S is guided by path rollers 30 and transported to a position facing the inkjet head 32. The inkjet head 32 ejects droplets of aqueous ink toward the rear surface SB of the substrate S. The ejected droplets adhere to the rear surface SB of the substrate S, and an image is printed on the rear surface SB of the substrate S.

[0120] Next, the substrate S is transported to a position facing the radiant heating unit 34. The radiant heating unit 34 uses an infrared heater to heat the substrate S. This promotes drying of the aqueous ink applied to the back surface SB of the substrate S.

[0121] Furthermore, the substrate S is guided by the path rollers 30 and transported from a position facing the radiant heating unit 34 to the drying drum 36. The substrate S is wrapped around the outer peripheral surface 36B of the drying drum 36. The drying drum 36 rotates with the outer peripheral surface 36B in contact with the front surface SA of the substrate S, heating the substrate S from the front surface SA and transporting it. This promotes drying of the aqueous ink applied to the back surface SB of the substrate S.

[0122] The back surface SB of the substrate S on which the ink has been dried is cooled by contact with the cooling roller 31. The substrate S whose back surface SB has been cooled is guided by the path roller 30 and discharged to the outside of the back surface printing main drying unit 20. The substrate S discharged from the back surface printing main drying unit 20 is transported to the paper discharge unit 22 and taken up onto a take-up roll.

[0123] As described above, the printing system 10 transports the substrate S through the paper feed unit 12, the preliminary drying unit 14, the front printing main drying unit 16, the reversal unit 18, the back printing main drying unit 20, and the paper discharge unit 22 in that order, and performs each process on the substrate S to produce a printed matter.

[0124] [Detailed Description of Cooling Drum] Next, the cooling drum 31 that functions as a first-touch roller will be described in detail. The first-touch roller described in the embodiment is an example of a first-touch member.

[0125] The cooling roller 31 shown in Fig. 3 and other figures prevents ink from adhering to the substrate S immediately after the drying process. This makes it possible to prevent image defects in which ink is partially peeled off from the printed matter. The cooling roller 31 has the following two features.

[0126] The following description will be given for the case where an image is printed on the front surface SA of the substrate S shown in Fig. 2. When an image is printed on the back surface SB of the substrate S, the front surface SA of the substrate S in the following description means the back surface SB of the substrate S.

[0127] [Surface Stain-Preventing Coating] The surface free energy γ of the cooling roller 31 s and the surface free energy γ of the image lThe adhesive work W calculated from sl The smaller the value, the less likely the image is to peel off when the cooling roller 31 comes into contact with the image.

[0128] With reference to the Owens and Wendt equation, the surface free energy γ of the cooling roller 31 is s The variance component is γ s d and the polar component is γ s p Then, γ s = γ s d +γ s p ...expressed as Equation 1. Similarly, the surface free energy γ l The variance component is γ l d and the polar component is γ l p Then, γ l = γ l d +γ l p ...expressed as Equation 2. The surface free energy γ sl is γ sl = {(γ s d ) 0.5 + (γ l d ) 0.5} 2 + {(γ s p ) 0.5 + (γ l p ) 0.5} 2 ...Equation 3. Using Equations 1, 2, and 3, the adhesion work W between the cooling roller 31 and the image is calculated. sl Is W sl = γ s +γ l -γ s = 2 × (γ s d ×γ l d ) 0.5 +2 × (γ s p ×γ lp ) 0.5 ...expressed as Equation 4. The unit of surface free energy and work of adhesion is millinewtons per meter.

[0129] The plating treatment applied to the surface treatment of the cooling roller 31 was changed, and the surface free energy, work of adhesion, and hardness were calculated for each plating treatment. Under specified conditions, an image was brought into contact with the surface 31A of the cooling roller 31, and the occurrence of white dots and the durability of the surface treatment film of the cooling roller 31 were evaluated. The results of the evaluation test are shown below.

[0130] 6 is a table showing the performance of cooling rollers due to different surface treatments. Five types of cooling rollers 31 were prepared, each with a different surface treatment. The surface treatments applied were anodized aluminum, hard chrome plating, electroless nickel plating, PTFE coating, and PTFE nickel plating.

[0131] The surface free energy of the surface 31A of the cooling roller 31 was measured using a double drop handy contact angle, surface free energy analyzer, MSA, manufactured by KRUSS. MSA is the trade name of the device. The measurement method involved dropping 2 microliters of diiodomethane and pure water to measure the contact angle, calculating the components of the surface free energy from the measured contact angle, and then calculating the work of adhesion from the calculated values ​​of the components of the surface free energy.

[0132] The surface free energies of the surface 31A of the cooling roller 31 that has been subjected to the above-described surface treatment are 50.1 millinewtons per meter, 70.0 millinewtons per meter, 33.9 millinewtons per meter, 18.5 millinewtons per meter, and 24.5 millinewtons per meter.

[0133] The surface free energy of the image, γ l The variance component of γ l d The range is 25.0 millinewtons per meter < γ l d <55.0 millinewtons per meter, and the surface free energy γ l The polar component γ l pThe range is 4.0 millinewtons per meter < γ l p <15.0 millinewtons per meter.

[0134] Furthermore, the adhesion work of the surface 31A of the cooling roller 31 calculated from the surface free energy of the surface 31A of the cooling roller 31 described above is 94.2 millinewtons per meter, 109.5 millinewtons per meter, 80.3 millinewtons per meter, 59.4 millinewtons per meter, and 68.3 millinewtons per meter.

[0135] The hardness listed in the table of Fig. 6 refers to the Vickers hardness of the surface 31A of the cooling roller 31, and is a measured value obtained by measuring the surface 31A of the cooling roller 31 using a Vickers hardness tester. The Vickers hardness tester used is one that complies with the Vickers hardness test method specified in JIS Z 2244. The Vickers hardness tester may also be one that complies with the method for understanding the hardness level of metallic materials specified in ISO 6507-1 or ISO 6507-4.

[0136] JIS is an abbreviation for Japanese Industrial Standards, and ISO is an abbreviation for International Organization for Standardization.

[0137] For the evaluation of white dots, an image printed on the surface of printing paper was brought into contact with the surface 31A of five types of cooling rollers 31 with different surface conditions, and the image was visually inspected after a specified time had passed to confirm the presence or absence of white dots. When the printing paper was brought into contact with the surface 31A of the cooling roller 31, a specified tension was applied to the printing paper using the cooling roller 31. The image was a 100% solid image using black ink, the contact time was 10 seconds, and the tension was 100 Newtons.

[0138] The durability evaluation was carried out by applying a specified tension to the printing paper using the cooling roller 31, continuously conveying the printing paper, and visually inspecting the condition of the plating film on the surface 31A of the cooling roller 31 using a microscope. The tension was 100 Newtons, and the continuous printing time was 1,000 hours.

[0139] A rating of A in the white dot evaluation column and durability performance evaluation column indicates that each aspect is very good. A rating of B indicates that it is inferior to A but is good. A rating of C indicates that it is inferior to B but can be used as a product. A rating of D indicates that it cannot be used as a product.

[0140] From the viewpoint of white dots, the preferable range of the work of adhesion is 80.3 millinewtons per meter or less. A more preferable range of the work of adhesion is 68.3 millinewtons per meter or less. Taking into consideration the measurement error and significant figures of the measured surface free energy, the preferable range of the work of adhesion is 81.0 millinewtons per meter or less, and a more preferable range of the work of adhesion is 69.0 millinewtons per meter or less.

[0141] The smaller the work of adhesion, the less likely the surface 31A of the cooling roller 31 is to become soiled. Considering the practical lower limit of the work of adhesion for the surface 31A of the cooling roller 31 from the viewpoint of soiling. Hexafluoropropylene, which has the highest hydrophobicity among fluororesins, is used as the material for the plating film. Considering the case where the surface free energy of the image is relatively low, the lower limit of the work of adhesion can be set to 35 millinewtons per meter.

[0142] In order to relatively reduce the adhesive work of the surface 31A of the cooling roller 31, it is effective to devise a method for the surface 31A of the cooling roller 31. One example of such a method is to attach a glass bead sheet to the surface 31A of the cooling roller 31. However, the glass bead sheet needs to be replaced periodically. The interior of the printed book drying unit 60 shown in Figure 2 is narrow, and replacing the glass bead sheet requires removing the cooling roller 31, which makes the work difficult.

[0143] Examples of materials that do not require periodic replacement include coatings of fluororesin such as PTFE and silicone resin on the surface 31A of the cooling roller 31. On the other hand, coatings such as fluororesin have poor durability and a short lifespan compared to glass bead sheets. The surface treatment of the surface 31A of the cooling roller 31 is preferably electroless nickel plating or PTFE-nickel plating. The PTFE-nickel plating described in the embodiment is an example of a fluororesin eutectoid plating process.

[0144] Furthermore, the cooling roller 31 can achieve sufficient durability if the surface 31A has a Vickers hardness of 450 Hv or more. A relatively high hardness is preferable for the surface 31A, but the practical upper limit for hardness is 1000 Hv when hard chrome plating, a common surface treatment for industrial products, is applied. From the viewpoint of durability, the surface 31A of the cooling roller 31 preferably has a Vickers hardness in the range of 450 Hv or more and 600 Hv or less.

[0145] The cooling roller 31 is required to have a surface 31A with a relatively low adhesive work, be stain-resistant, and have a relatively high durability so that periodic replacement is not required. To satisfy these conditions, fluorine-based plating in which a fluorine-based resin is co-deposited is effective as the surface treatment for the surface 31A of the cooling roller 31.

[0146] The PTFE nickel plating shown in the table in Figure 6 has the stain resistance of a fluorine-based material and the hardness of nickel plating. When the PTEF content in the plating film is 4.0 mass percent or more and 9.0 mass percent or less, it is possible to achieve an appropriate range for both hardness and surface free energy.

[0147] [Water-Cooled Cooling Roller] From the viewpoint of preventing image defects and contamination of the surface 31A of the cooling roller 31, the influence of friction between the image printed on the substrate S and the surface 31A of the cooling roller 31 should be minimized so that the ink film constituting the image does not peel off from the substrate S. Based on this viewpoint, sliding between the image and the surface 31A of the cooling roller 31 is avoided, and the cooling roller 31 rotates in response to the movement of the substrate S. When the cooling roller 31 shown in Fig. 2 is a plate-shaped member, the plate-shaped member moves in the transport direction of the substrate S in response to the movement of the substrate S.

[0148] Cooling the image suppresses adhesion of ink that constitutes the image to the surface 31A of the cooling roller 31. Therefore, a cooling roller whose internal structure is shown in Fig. 3 is used as the cooling roller 31. The cooling water 31E flowing through the cooling water flow path 31B of the cooling roller 31 is adjusted to a temperature of 25°C or less.

[0149] It has been confirmed that when the above-described cooling water temperature conditions are applied and the surface temperature of the substrate S before passing over the surface 31A of the cooling roller 31 is 90° C. or higher and 180° C. or lower, the difference in the surface temperature of the substrate S before and after passing over the surface 31A of the cooling roller 31 is 60° C. or higher. In other words, the cooling roller 31 can perform a cooling treatment on the substrate S such that the difference in temperature between the surface temperature of the substrate S before cooling and the surface temperature of the substrate S after cooling is 60° C. or higher.

[0150] The surface pressure, which is the pressure per unit area acting between the cooling roller 31 and the substrate S, should be relatively small from the viewpoint of suppressing ink adhesion to the surface 31A of the cooling roller 31. The diameter of the cooling roller 31 is preferably 280 mm or more. The upper limit of the diameter of the cooling roller 31 is determined depending on the conditions of the space in which the cooling roller 31 is arranged and the constraints of the surface treatment treatment device, etc.

[0151] [Moisture Content of Substrate] The printing system 10 shown in Fig. 1 employs an inkjet method in which an aqueous ink without a pretreatment liquid is applied. The substrate S is in a continuous form, and a roll-to-roll method is employed as the transport method for the substrate S. The moisture content of the substrate S in an untreated state may be 1.2% or more and 14.3% or less. The pre-drying unit 14 shown in Fig. 1 can adjust the moisture content of the substrate S in an untreated state to fall within the above range.

[0152] [Melting Point of Wax] The melting point of the wax contained in the aqueous ink is important for reducing the stickiness of the image. From the viewpoint of reducing the stickiness of the image, the melting point of the wax should be 90°C or less. As long as the wax does not start to weep at room temperature, it is preferable that the melting point is relatively low. As a wax with a low melting point, paraffin wax with a melting point of 47°C is appropriate.

[0153] [Amount of Solvent on Substrate] As shown in Figure 2, the substrate S on which an image has been printed is dried by the action of heat energy radiated from the radiant heating unit 34 and heat energy conducted using the drying drum 36. If the image printed on the substrate S is not dried sufficiently, the image may become very sticky, and the cooling roller 31 alone may not be sufficient. Therefore, in the drying process for the substrate S using the radiant heating unit 34 and the drying drum 36, it is important that the amount of solvent, expressed as the mass of solvent per unit area of ​​the substrate S to which the penetration medium is applied, is 250 micrograms per square centimeter or less. A drying process in which the amount of solvent on the substrate S is 148 micrograms per square centimeter is more preferred.

[0154] Fig. 7 is a table showing the evaluation results of the amount of solvent on the substrate. In Fig. 7, the amount of solvent on the substrate S was changed stepwise by changing the parameters of the drying process, and the occurrence of white spots and blisters was evaluated for six different solvent amounts.

[0155] The amounts of solvent in the substrate S were 300 micrograms per square meter, 250 micrograms per square meter, 200 micrograms per square meter, 148 micrograms per square meter, 105 micrograms per square meter, and 50 micrograms per square meter.

[0156] The amount of solvent in the substrate S was calculated by measuring the mass of the substrate S before and after the drying treatment, subtracting the mass of the substrate S after the drying treatment from the mass of the substrate S before the drying treatment, and dividing the subtracted value by the area of ​​the substrate S.

[0157] Two types of cooling rollers 31 with different surface treatments were used, and an image was brought into contact with the surface 31A of the cooling roller 31 under specified conditions, and the image was visually inspected for the presence or absence of white dots and blisters. The image was a 100% solid image using black ink, the contact time was 10 seconds, and the tension was 100 Newtons.

[0158] A rating indicates that each aspect is very good. B rating indicates that it is inferior to A rating but still good. C rating indicates that it is inferior to B rating but still usable as a product. D rating indicates that it cannot be used as a product. The surface 31A of the cooling roller 31 is surface treated by applying PTFE nickel plating and electroless nickel plating.

[0159] When the surface treatment is PTFE nickel plating, the amount of solvent in the substrate S is in the range of 50 micrograms per square centimeter or more and 300 micrograms per square centimeter or less, and this is favorable for both white spots and blisters.

[0160] On the other hand, when the surface treatment is electroless nickel plating, the amount of solvent in the substrate S is preferably in the range of 50 micrograms per square centimeter or more and 200 micrograms per square centimeter or less from the viewpoint of preventing white spots. On the other hand, when the amount of solvent in the substrate S is in the range of 50 micrograms per square centimeter or more and 300 micrograms per square centimeter or less, blisters are favorable.

[0161] That is, the preferred range of the amount of solvent in the substrate S is 200 micrograms per square centimeter or less, and the more preferred range of the amount of solvent in the substrate S is 148 micrograms per square centimeter or less.

[0162] It is preferable that the amount of solvent in the substrate S be as small as possible, but excessive drying treatment of the substrate S can cause problems in image quality, such as the occurrence of blisters. From the viewpoint of avoiding excessive drying treatment, the practical lower limit of the amount of solvent in the substrate S can be set to 105 micrograms per square centimeter.

[0163] In summary, when the surface treatment of the cooling roller 31 is PTFE nickel plating, the preferable range of the amount of solvent in the substrate S is 105 micrograms per square centimeter or more and 250 micrograms per square centimeter or less. The more preferable range of the amount of solvent in the substrate S is 105 micrograms per square centimeter or more and 148 micrograms per square centimeter or less.

[0164] When the surface treatment of the cooling roller 31 is electroless nickel plating, the amount of solvent in the substrate S is preferably in the range of 105 micrograms per square centimeter or more and 200 micrograms per square centimeter or less. The amount of solvent in the substrate S is more preferably in the range of 105 micrograms per square centimeter or more and 148 micrograms per square centimeter or less.

[0165] The above-described amount of solvent in the substrate S is achieved when the surface temperature of the substrate S immediately before contacting the cooling roller 31 is 90° C. or higher and 180° C. or lower. This has been confirmed by conducting tests on combinations of multiple types of substrate S commonly used in inkjet printing and multiple printing conditions.

[0166] [Variations of First-Touch Member] Next, variations of the first-touch member will be described. The first-touch member is the member that first comes into contact with the image printed on the substrate S after the substrate S has been dried. In the case of the print drying unit 60 shown in Fig. 2 , the first-touch member is the cooling roller 31, which is the member that comes into contact first when the surface of the substrate S that has been subjected to the drying process and on which the ink has been applied and the image has been printed comes into contact when it leaves the drying drum 36.

[0167] 8 is a schematic diagram showing the configuration of a printed matter drying unit according to a first modified example. The printed matter drying unit 60A shown in the figure includes inkjet head 32C, inkjet head 32M, inkjet head 32Y, inkjet head 32K, and a print drum 38. The printed matter drying unit 60A also includes a drying drum 390.

[0168] A plurality of pass rollers 30 are arranged on the transport path of the substrate S in the printed matter drying unit 60A. The substrate S that has been carried into the printed matter drying unit 60 is supported by the pass rollers 30 and transported to the print drum 38. The substrate S is wrapped around the outer peripheral surface of the print drum 38.

[0169] The print drum 38 has a cylindrical shape, and a rotating shaft is supported so as to be freely rotatable. The rotating shaft of the print drum 38 is connected to the rotating shaft of a motor, which is the drive source for the print drum 38. The print drum 38 is driven to rotate about the rotating shaft in response to the drive of the motor, which is the drive source. The rotating shaft of the print drum 38 and the motor are not shown in the figure.

[0170] The print drum 38 is driven to rotate while holding the support surface opposite the printing surface of the substrate S on its outer circumferential surface, and transports the substrate S in the transport direction of the substrate S along the outer circumferential surface of the print drum 38. The outer circumferential surface of the print drum 38 may be provided with suction holes used to support the substrate S by suction.

[0171] The inkjet head 32C, the inkjet head 32M, the inkjet head 32Y, and the inkjet head 32K use water-based inks of cyan, magenta, yellow, and black, respectively.

[0172] The inkjet heads 32C, 32M, 32Y, and 32K are arranged at regular intervals along a transport path of the substrate S using the print drum 38.

[0173] Here, an example is shown of a configuration using four colors of ink: cyan, magenta, yellow, and black. However, the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink may be added as needed.

[0174] The substrate S, which has been transported by the printing drum 38 and on whose printing surface an image has been printed by the inkjet heads 32C, 32M, 32Y, and 32K, is then transported to the drying drum 390.

[0175] The drying drum 390 has the same configuration as the drying drum 36 shown in FIG. 2. Here, a description of the configuration of the drying drum 390 is omitted. The term "same" as used here may mean substantially the same, even though there are differences. Note that in FIG. 8, the rotating shaft of the drying drum 390, the heater provided inside the drying drum 390, and the motor connected to the rotating shaft, which are shown in FIG. 2, are not shown.

[0176] The cooling roller 310 closest to the drying drum 390 along the transport path of the substrate S functions as the first-touch member. The cooling roller 310 shown in Fig. 8 has the same configuration as the cooling roller 31 shown in Fig. 2. The term "same" here may mean "substantially the same" as described above.

[0177] 9 is a diagram showing the schematic configuration of a main print drying unit according to a second modified example. The main print drying unit 60B according to the second modified example performs printing on a sheet of base material S. The main print drying unit 60B includes a first drying drum 361, a second drying drum 362, and a cooling section 40.

[0178] The substrate S is transported using the printing drum 38 and has an image printed on its printing surface using inkjet head 32C, inkjet head 32M, inkjet head 32Y, and inkjet head 32K, and is then transferred from the printing drum 38 to the first drying drum 361.

[0179] The first drying drum 361 rotates about its rotation axis with its outer peripheral surface 361B in contact with the printed surface of the substrate S to transport the substrate S and heats the printed surface of the substrate S. The substrate S, in which the drying of the aqueous ink has been accelerated, is transferred from the first drying drum 361 to the second drying drum 362.

[0180] The second drying drum 362 rotates about its rotation axis with its outer peripheral surface 362B in contact with the support surface opposite the printed surface of the substrate S, thereby transporting the substrate S and heating the support surface of the substrate S. The substrate S, in which the drying of the aqueous ink has been accelerated, is transferred from the second drying drum 362 to the cooling section 40.

[0181] The cooling section 40 includes a jaw portion 42, a sliding cooling member 44, and a cold air fan 46. The jaw portion 42 jaws the leading end of the substrate S delivered from the second drying drum 362, and transports the substrate S along a transport path along the sliding cooling member 44. The substrate S transported using the jaw portion 42 has its printed surface sliding against the sliding cooling member 44. The sliding cooling member 44 is cooled using the cold air fan 46 from the surface opposite to the sliding surface 44A on which the substrate S slides. Therefore, the printed surface of the substrate S in contact with the sliding surface 44A of the sliding cooling member 44 is cooled and discharged outside the printed book drying unit 60B.

[0182] In the printed book drying unit 60B, the sliding cooling member 44 functions as a first-touch member. A sliding surface 44A of the sliding cooling member 44 is subjected to the same surface treatment as the surface 31A of the cooling roller 31 shown in FIG.

[0183] 10 is a schematic diagram showing the configuration of a printed matter drying unit according to a third modified example. The printed matter drying unit 60C shown in the figure includes a hot air drying device 364 that blows hot air onto the substrate S, instead of the drying drum 36 shown in FIG.

[0184] The printed book drying unit 60C also includes a first nip roller pair 366 and a second nip roller pair 368. The first nip roller pair 366 is disposed upstream of the hot air drying device 364 in the transport direction of the substrate S. The second nip roller pair 368 is disposed downstream of the hot air drying device 364 in the transport direction of the substrate S.

[0185] The printing surface of the substrate S, which is supported and transported using the first nip roller pair 366 and the second nip roller pair 368, is acted upon by hot air blown from the hot air drying device 364, thereby accelerating the drying of the aqueous ink. The printing surface of the substrate S, which has been subjected to a drying process using the hot air drying device 364, first comes into contact with the first roller 368A of the second nip roller pair 368.

[0186] That is, the first roller 368A of the second nip roller pair 368 functions as a first-touch member. The surface of the first roller 368A is subjected to the same surface treatment as the surface 31A of the cooling roller 31 shown in FIG.

[0187] The first-touch member may have a roller shape such as the cooling roller shown in Fig. 2, or a non-roller shape such as the sliding cooling member 44 shown in Fig. 9. The non-roller shape may be a prism such as a triangular prism or a quadrangular prism, or may be a sphere.

[0188] [Fourth Modification] The cooling roller 31 shown in Fig. 2 may be a cooling roller group in which a plurality of cooling rollers are arranged in series. Of the cooling roller group, the cooling roller arranged at the most upstream position in the transport direction of the substrate S may be subjected to the same surface treatment as the cooling roller 31 shown in Fig. 2. All of the plurality of cooling rollers may be subjected to the same surface treatment as the cooling roller 31, or half of the cooling rollers on the upstream side in the transport direction of the substrate S may be subjected to the same surface treatment as the cooling roller 31.

[0189] An example of an arrangement in which a plurality of cooling rollers are arranged in succession is an embodiment in which the distance between adjacent cooling rollers is greater than the radius of the cooling roller and less than the diameter of the cooling roller.

[0190] Effects of the Embodiment The printing system 10 according to the embodiment can achieve the following effects.

[0191] [1] After the substrate S has been dried, the first-touch member that first comes into contact with the image printed on the substrate S has a contact surface that comes into contact with the image with a work of adhesion of 81.0 millinewtons per meter or less, and a Vickers hardness of the contact surface that is 450 Hv or more and 600 Hv or less. This prevents the occurrence of image defects such as white spots. Furthermore, a certain level of durability is ensured, eliminating the need to replace the first-touch member, and improving the workability of maintenance of the printing system 10.

[0192] [2] The first-touch member has a function of cooling the substrate S after the drying process has been performed. This improves the strength of the image printed on the substrate S and enables further measures to prevent contamination of the first-touch member.

[0193] [3] The surface treatment of the first-touch member is performed by PTFE nickel plating, which is a eutectic plating process using a fluorine-based resin. This allows the first-touch member to be subjected to a desired surface treatment.

[0194] [4] The amount of solvent in the substrate S after drying is adjusted to 250 micrograms per square centimeter or less. This prevents the image from becoming sticky.

[0195] [5] The temperature of the printed surface of the substrate S after the drying process, on which the image is printed, is adjusted to 90° C. or more and 180° C. or less. This prevents the substrate S from being excessively dried.

[0196] [6] The ink used for printing contains wax with a melting point of 90° C. or less. This prevents the image from becoming sticky.

[0197] [Variations of the printing system] Figure 1 illustrates a printing system 10 that performs double-sided printing, printing images on both sides of the substrate S, but the system may also be a single-sided printing device that prints an image on one side of the substrate S and does not have the reversing unit 18 and the back-side printing drying unit 20 shown in Figure 1.

[0198] Furthermore, the printing system 10 may be configured as a liquid application system that applies an inkjet method to eject a functional liquid onto the substrate S and form a pattern on the pattern formation surface of the substrate S. That is, the printing system 10 may be configured as a liquid application system that includes a liquid application device, a drying device, and a transport device that transports the substrate S.

[0199] [Variations of Substrate] In the present embodiment, the substrate S is described as being paper, but the substrate S can be a resin sheet, a film, or any other medium of any material or shape.

[0200] [Example of application to a media processing device] The printed book drying unit 60 shown in Figure 2 may not be equipped with an inkjet head 32, but may be a media processing device that includes a drying device that performs a drying process on the substrate S and a conveying device that conveys the substrate S.

[0201] The technical scope of the present invention is not limited to the scope described in the above embodiments. The configurations and the like in each embodiment can be appropriately combined with each other within the scope that does not deviate from the spirit of the present invention.

[0202] REFERENCE SIGNS LIST 10 Inkjet recording device 12 Paper feed unit 14 Preliminary drying unit 16 Front side printing main drying unit 18 Reversing unit 20 Back side printing main drying unit 22 Paper discharge unit 30 Pass roller 31 Cooling roller 31A Surface of cooling roller 31B Cooling water flow path 31C Cooling water inlet 31D Cooling water outlet 31E Cooling water 32 Inkjet head 32C Inkjet head 32K Inkjet head 32M Inkjet head 32Y Inkjet head 34 Radiant heating unit 36 ​​Drying drum 36A Rotating shaft 36B Outer circumferential surface 36C Heater 36D Motor 38 Print drum 40 Cooling unit 42 Grip portion 44 Sliding cooling member 44A Sliding surface of sliding cooling member 46 Cool air fan 50 Overall control unit 51 Memory 52 Conveyance control unit 53 Sensor 54 Preliminary drying control unit 55 Conveying device 56 Printing control unit 58 Drying control unit 59 Cooling control unit 60 Main print drying unit 60A Main print drying unit 60B Main print drying unit 60C Main print drying unit 310 Cooling roller 361 First drying drum 361B Outer circumferential surface of first drying drum 362 Second drying drum 362B Outer circumferential surface of second drying drum 364 Warm air drying device 366 First nip roller pair 368 Second nip roller pair 368A First roller 390 Drying drum S Substrate

Claims

1. A drying device that performs a drying process on the medium to which the liquid has been applied; a contact member that is brought into contact first with a liquid adhering surface of the medium that has been subjected to a drying process using the drying device, the liquid being adhered to the liquid, after the drying process; Equipped with the drying device performs a drying process on the medium such that a mass of liquid per unit area on the liquid-adhered surface of the medium becomes 200 micrograms per square centimeter or less; The contact member is A cooling structure for cooling the medium is provided. a work of adhesion of a contact surface of the medium in contact with the liquid application surface with respect to a liquid application area on the liquid application surface to which the liquid is applied is 81 millinewtons per meter or less; The contact surface has a Vickers hardness of 450 Hv or more and 600 Hv or less.

2. The media processing device according to claim 1 , wherein the contact surface of the contact member is subjected to eutectoid plating.

3. The media processing device according to claim 1 , wherein the contact surface of the contact member is subjected to a fluororesin eutectoid plating process.

4. The media processing device according to claim 3 , wherein the plating film applied to the contact surface of the contact member contains 4.0 mass percent or more and 9.0 mass percent or less of a fluorine-based resin.

5. A media processing device as described in claim 1, wherein the medium is paper, a resin sheet, or a film.

6. The media processing device according to claim 1 , wherein the contact member has a roller shape.

7. The media processing device according to claim 1 , wherein the cooling structure uses a method of circulating a liquid whose temperature is adjusted to a specified range.

8. one or more processors; One or more memories in which programs to be executed by the one or more processors are stored; Equipped with The one or more processors execute instructions of the program, The media processing device according to claim 7 , wherein the liquid applied to the cooling structure is adjusted to 25° C. or lower.

9. one or more processors; One or more memories in which programs to be executed by the one or more processors are stored; Equipped with The one or more processors execute instructions of the program, The media processing device according to claim 7 , wherein the liquid-adhered surface is cooled using the cooling structure such that the temperature difference between before and after cooling is 60° C. or more.

10. one or more processors; One or more memories in which programs to be executed by the one or more processors are stored; Equipped with The one or more processors execute instructions of the program, The media processing device of claim 1 , wherein the drying device is used to adjust the temperature of the media after drying processing to 90° C. or higher and 180° C. or lower.

11. A liquid application device that applies liquid to a liquid application surface of a medium; a drying device that performs a drying process on the medium having the liquid applied to the liquid-adhering surface; a contact member that is brought into contact first with a liquid adhering surface of the medium that has been subjected to a drying process using the drying device, the liquid being adhered to the liquid, after the drying process; Equipped with the drying device performs a drying process on the medium such that a mass of liquid per unit area on the liquid-adhered surface of the medium becomes 200 micrograms per square centimeter or less; The contact member is A cooling structure for cooling the medium is provided. a work of adhesion of a contact surface of the medium in contact with the liquid application surface with respect to a liquid application area on the liquid application surface to which the liquid is applied is 81 millinewtons per meter or less; A liquid application system, wherein the contact surface has a Vickers hardness of 450 Hv or more and 600 Hv or less.

12. A liquid application system as described in claim 11, wherein the medium is paper, a resin sheet, or a film.

13. a moisture amount adjustment device that is disposed at a position upstream of the liquid application device in a transport direction of the medium, the moisture amount adjustment device performing a moisture amount adjustment process on the medium when the medium enters the liquid application device; one or more processors; One or more memories in which programs to be executed by the one or more processors are stored; Equipped with The one or more processors execute instructions of the program, The liquid application system according to claim 11 , wherein the moisture amount regulator regulates the moisture amount of the medium when it enters the liquid application device to be between 1.2 percent and 14.3 percent.

14. A liquid application system as described in claim 13, wherein the moisture content adjustment device adjusts the moisture content of the medium in an untreated state.

15. a printing device that applies ink to the medium to form an image on the medium, The liquid application system according to claim 11 , wherein the ink contains a wax having a melting point of 90° C. or higher.