Inkjet printing apparatus and drying method thereof

Abstract

An inkjet printing apparatus and a drying method of the inkjet printing apparatus, the inkjet printing apparatus including, in the following order: a first image forming unit configured to form an image by applying a first ink to a print medium; a first drying unit configured to heat the print medium to which the first ink has been applied; a second image forming unit configured to form an image by applying a second ink to the print medium; and a second drying unit configured to heat the print medium to which the second ink has been applied, a drying temperature T1 of the second drying unit in a case where the second ink is applied on a region where the first ink has been applied is different from a drying temperature T2 of the second drying unit in a case where the second ink is applied on a region where the first ink is not applied.

Description

Technical Field

[0001] The invention relates to an inkjet printing device and a drying method for the inkjet printing device. Background Art

[0002] In recent years, inkjet printing has been increasingly used in the fields of signage and display technology, such as for printing posters and large advertisements. In this field, polyvinyl chloride sheets and polyethylene terephthalate (PET) sheets are widely used as printing media due to their durability and cost-effectiveness. These printing media have little to no ink-receptive layer on their printing surfaces and are referred to as non-absorbent printing media (printing media with no ink absorbency) or low-absorbent printing media (printing media with low ink absorbency). Hereinafter, printing media with little or no ink absorbency on their surfaces will sometimes be collectively referred to as "low to non-absorbent printing media."

[0003] For example, as discussed in Japanese Patent Application Laid-Open No. 2015-071738, printing by applying ink to a non-absorbent printing medium and then applying another ink onto the applied ink is widely used.

[0004] In many cases, a print medium to which ink has been applied is heated and dried regardless of whether it is an absorbent print medium or a non-absorbent print medium. In conventional technology, a drying unit indiscriminately dries an area of ​​the print medium to which a single ink has been applied and an area to which multiple inks have been applied using the same power. Summary of the Invention

[0005] The present invention aims to provide an inkjet printing device capable of setting appropriate drying conditions and a drying method of the inkjet printing device.

[0006] According to an aspect of the present invention, an inkjet printing apparatus includes, in the following order: a first image forming unit configured to form an image by applying a first ink to a printing medium; a first drying unit configured to heat the printing medium to which the first ink has been applied; a second image forming unit configured to form an image by applying a second ink to the printing medium; and a second drying unit configured to heat the printing medium to which the second ink has been applied, wherein each of the first ink and the second ink is an ink containing a colorant, and wherein, when measured using the Bristol method, a liquid transfer amount (mL / m2) to the printing medium within 2 seconds from the start of contact is 2 ) is 10mL / m 2 or less, and wherein a drying temperature T1 of the second drying unit when the second ink is applied to an area to which the first ink has been applied is lower than a drying temperature T2 of the second drying unit when the second ink is applied to an area to which the first ink has not been applied.

[0007] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram illustrating the internal configuration of an inkjet printing apparatus.

[0009] Figure 2 is a perspective view illustrating a sheet conveying portion housing of a printing unit according to the first exemplary embodiment.

[0010] Figure 3 is a perspective view illustrating a print head lifting mechanism according to the first exemplary embodiment.

[0011] Figure 4 is a block diagram illustrating an example of the overall system configuration.

[0012] Figures 5A to 5F : is a diagram illustrating the state of the first ink layer and the penetration of the second ink.

[0013] 6A to 6D are diagrams illustrating penetration of the second ink into different types of print media in different print modes.

[0014] Figure 7 is a diagram illustrating a drying temperature setting flow according to the first exemplary embodiment. DETAILED DESCRIPTION

[0015] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The constituent elements described in the following exemplary embodiments are merely examples, and the configuration and various conditions of the device to which the present invention is applied may be appropriately modified or changed without departing from the spirit of the present invention, and the present invention is not limited to the following exemplary embodiments. For example, the size, material, shape, relative arrangement, etc. of the components described in the following exemplary embodiments may be appropriately changed according to the configuration and various conditions of the device to which the present invention is applied, and unless otherwise specified, the present invention is not limited to the following exemplary embodiments.

[0016] A first exemplary embodiment will be described below. Figure 1 In the figure, the top of the printing apparatus 1 is defined as the top, the left-right direction is defined as the longitudinal direction, and the front-back direction on the paper surface perpendicular to the direction in which the print medium is conveyed is defined as the sheet width direction. The printing apparatus 1 according to this exemplary embodiment is a high-speed line printer that uses a continuous sheet wound into a roll as the print medium.

[0017] <Inkjet Printing Equipment>

[0018] Figure 1: is a schematic cross-sectional view illustrating the internal configuration of the printing apparatus 1. The printing apparatus 1 according to this exemplary embodiment includes a take-out roller unit 2, a first slack adjusting unit 3, a first main conveying unit 4, a skew correction unit 5, a conveying detection unit 6, a printing unit 7, a conveying tension detection unit 9, a printed image position detection unit 10, a scanner unit 11, a second main conveying unit 12, a second slack adjusting unit 13, a take-up roller section 14, a maintenance unit 15, a drying unit 40, and a cooling unit 50. A continuous sheet S as a printing medium is fed along a path formed by Figure 1 The sheet is conveyed along the conveying path indicated by the solid line in FIG and processed by each unit.

[0019] The printing apparatus 1 according to this exemplary embodiment includes a first image forming unit and a second image forming unit along a sheet conveyance path (sheet S). The first image forming unit prints an image fixed on the sheet S by the first printing unit 7a, the first drying unit 40, and the first cooling unit 50a. The second image forming unit prints an image fixed on the sheet S by the second printing unit 7b, the second drying unit 40b, and the second cooling unit 50b. As described above, the printing apparatus 1 continuously prints images on the sheet S by passing the sheet S through the first and second image forming units. Alternatively, the printing apparatus 1 can select one image forming unit based on printing conditions. In this case, the image is printed on the sheet S using only the selected image forming unit.

[0020] The unwinding roller unit 2 is a unit for holding and feeding a continuous sheet wound into a roll. The unwinding roller unit 2 is configured to accommodate a winding roller and unwind and feed a sheet S. The number of rollers that can be accommodated in the unwinding roller unit 2 is not limited to one, and a configuration in which two, three, or more rollers are accommodated and the sheet S is unwound and fed from one of the accommodated rollers may be employed.

[0021] The first dancer unit 3 is a unit for applying a constant sheet tension to the sheet S between the unwind roller unit 2 and the first main conveying unit 4. The first dancer unit 3 applies the sheet tension using a tension applying unit (not shown).

[0022] The first main conveying unit 4 is a unit for conveying the sheet S to a unit provided along the sheet conveying path (sheet S) and for applying sheet tension to the sheet S between the first main conveying unit 4 and the second main conveying unit 12. The first main conveying unit 4 rotates as a motor (not shown) is driven, and conveys the sheet S under tension.

[0023] The skew correction unit 5 is a unit for performing skew correction in the width direction of the sheet while conveying the sheet S under tension. In the present exemplary embodiment, the skew correction unit 5 includes a first skew correction unit 5a and a second skew correction unit 5b. The first skew correction unit 5a is arranged upstream of the image forming unit on the sheet conveying path. The skew correction unit 5 includes a skew correction roller and a skew detection sensor (not shown) configured to detect the skew of the sheet S. The skew correction roller changes its angle relative to the sheet S using a motor (not shown) and performs skew correction on the sheet S based on the measurement value obtained from the skew detection sensor. Winding the sheet S around the skew correction roller enhances the skew correction function.

[0024] The conveyance detection unit 6 is a unit for detecting the conveyance speed of the sheet S and pre-printed marks on the sheet S in order to control the timing of image formation in the printing unit 7. In this exemplary embodiment, the conveyance detection unit 6 includes a first conveyance detection unit 6a and a second conveyance detection unit 6b. The first conveyance detection unit 6a is arranged upstream of the image forming unit in the sheet conveyance path. The first conveyance detection unit 6a is used to control the timing of image formation in the first printing unit 7a, and the second conveyance detection unit 6b is used to control the timing of image formation in the second printing unit 7b.

[0025] The printing unit 7 is a sheet processing unit configured to form an image on a conveyed sheet S by applying a liquid component (ink) to the sheet S from above via the print head 22. In the printing unit 7, a guide roller 23 configured in an upwardly protruding arc forms a conveying path, and applies constant tension to the sheet S to maintain a gap with the print head 22. In the print head 22, a plurality of print heads are arranged along the conveying direction. In the present exemplary embodiment, the first printing unit 7a includes two line print heads corresponding to white (W) ink and reaction liquid. The second printing unit 7b includes eight line print heads corresponding to four colors (black (Bk), yellow (Y), magenta (M), and cyan (C)), reaction liquid, and three special colors.

[0026] A reaction liquid refers to a liquid containing a component that increases ink viscosity. The phrase "increases ink viscosity" refers to a phenomenon in which the colorant and resin that make up the ink come into contact with the component that increases ink viscosity and undergoes a chemical reaction or physical adsorption, causing the ink viscosity to increase. This increase in ink viscosity refers not only to an increase in the viscosity of the entire ink, but also to a localized increase in viscosity caused by partial coagulation of the components that make up the ink (such as the colorant and resin). The component that increases ink viscosity (reactant) is not particularly limited and can be a polyvalent metal ion, a cationic component such as a cationic resin, or an organic acid. Any material that causes a pH change in the ink and induces coagulation of the colorant in the ink can be used. Applying the reaction liquid before applying the ink to the sheet S allows the ink to be fixed immediately upon reaching the sheet S. This minimizes color bleeding between adjacent inks. The type of color, number of colors, and number of print heads 22 are not limited. Inkjet methods such as those utilizing heating elements, piezoelectric elements, electrostatic elements, or microelectromechanical system (MEMS) elements can be employed. Ink is supplied to the print head 22 from an ink tank (not shown) via an ink tube. Because the print head 22 is a full-line print head extending across the sheet S in the sheet width direction, so-called one-pass printing is performed. In one-pass printing, ink is applied to each unit area in a single scan of the print head 22 and the print medium to improve productivity. Specifically, the first image forming unit applies the first ink to the print medium in a single pass, and the second image forming unit applies the second ink to the print medium in a single pass. In this case, the drying load may increase further due to the increased amount of ink applied per unit time. However, by adopting the configuration according to the present exemplary embodiment described below, the power required for drying is reduced.

[0027] like Figure 2 As shown, the sheet conveying portion housing 71 of the printing unit 7 includes a plurality of print head positioning members 711 for positioning the print head 22. For each print head 22, one print head positioning member 711 is provided at the front and two print head positioning members 711 are provided at the rear in the sheet width direction across the sheet S. Figure 3As shown, the print head 22 is supported by the print head support shaft 27 on the print head holding portion 26, with the print head 22 providing support from below. The print head holding portion 26 holds and moves the print head 22 up and down. The print head holding portion 26 moves up and down along a rail 29 for moving up and down (the rail 29 is included in a frame 28 for moving the print head 22 up and down) using a drive mechanism (not shown) included in the print head holding portion 26. Although the ink is applied to the sheet S using an inkjet head in the present exemplary embodiment, this is not a limiting method of applying ink to the sheet S using the printing unit 7. For example, in the present exemplary embodiment, when the reaction liquid is applied by the print head 22, the reaction liquid may be applied by a roller, a die coating device (die coater), or a doctor coating device (doctor coater).

[0028] like Figure 1 As shown, the conveyance tension detection unit 9 is a unit for detecting tension during conveyance under tension between the first main conveyance unit 4 and the second main conveyance unit 12. The print image position detection unit 10 is a unit for detecting misalignment of the image formed on the sheet S by the printing unit 7 during printing and correction printing.

[0029] The winding guide roller R1 is a roller around which the surface of the sheet S, located downstream of the second printing unit 7b in the conveyance direction, opposite the ink-applied surface of the sheet S, is wound at a constant winding angle. In this exemplary embodiment, two winding guide rollers R1 are arranged between the second printing unit 7b and the second drying unit 40b, and the sheet S is folded so that the folded portions at the top and bottom of the printing apparatus 1 are substantially parallel to each other. The second drying unit 40b is arranged below the printing unit 7b at the bottom of the printing apparatus 1.

[0030] The drying units 40 (first drying unit 40a, second drying unit 40b) are units that reduce the liquid content contained in the liquid applied to the sheet S by the printing unit 7 and enhance the adhesion between the sheet S and the ink. The drying units 40 dry the applied ink at a predetermined drying temperature by blowing air heated by a heater onto the printed sheet S. In the drying units 40, air is blown onto the passing sheet S, at least from the ink-applied surface, to dry the ink-applied surface of the sheet S. Alternatively to the air-blowing drying method, methods that irradiate the surface of the sheet S with electromagnetic waves (such as ultraviolet and infrared rays), conductive heat exchange methods that contact heating elements, or a combination thereof can be employed. In this specification, the drying temperature is defined as follows. For example, in the air-blowing method described above, the drying temperature refers to the temperature of the air. This temperature can be measured by placing a temperature sensor near the drying unit 40, or it can be set by the user as the set temperature of the drying unit 40. In other methods, the drying temperature can be determined based on a set temperature.

[0031] The cooling unit 50 (the first cooling unit 50a and the second cooling unit 50b) cools the sheet S fixed by the drying unit 40, solidifies the softened ink, and suppresses temperature changes in the sheet S at a downstream position in the printing apparatus 1. In the cooling unit 50, air having a lower temperature than that of the sheet S is blown onto the passing sheet S from at least the ink application surface side to cool the ink application surface of the sheet S. The cooling method is not limited to the air blowing method; a conductive heat exchange method using a heat dissipation member in contact with the sheet S, or a combination thereof, may be employed.

[0032] The scanner unit 11 is a unit for reading a test image formed on the sheet S by the printing unit 7 before main printing, detecting image misalignment and density, and correcting the main printing.

[0033] The second main conveying unit 12 is a unit that conveys the sheet S while applying tension to the first main conveying unit 4 and the sheet S, and adjusts the tension of the sheet S. The second main conveying unit 12 rotates as a motor (not shown) is driven, and a tension control unit (not shown) controls the speed of the second main conveying unit 12 based on the tension value detected by the conveying tension detection unit 9. As an additional configuration for adjusting the tension of the sheet S, a clutch (not shown) for torque control in the drive connection may be added to adjust the tension of the sheet S. In this case, two tension control methods, namely, a torque control method for controlling the torque value transmitted from the clutch and a speed control method for controlling the roller speed of the second main conveying unit 12, may be included and switched or used simultaneously based on the intended purpose.

[0034] The second dancer unit 13 is a unit for applying constant sheet tension between the second main conveying unit 12 and the take-up roller portion 14. The second dancer unit 13 applies sheet tension using a tension applying unit (not shown).

[0035] The take-up roller section 14 is a unit for taking up the printed sheet S around a core. The number of rollers that can be collected is not limited to one, and a configuration including two, three, or more cores and one core being selected and used to collect the sheet S may be employed. Depending on the details of post-printing processing, a configuration in which a continuous sheet S is cut using a cutter and the cut sheets S are stacked may be employed instead of a configuration in which the sheet S is wound around a core.

[0036] The control unit 31 controls the various units of the entire printing apparatus 1. The control unit 31 includes a central processing unit (CPU), a storage device, a controller including various control units, an external interface, and an operation unit 32 through which a user performs input and output. The operation of the printing apparatus 1 is controlled based on instructions from the controller or a host device 33 (such as a host computer) connected to the controller via the external interface.

[0037] The maintenance unit 15 is a unit that includes a mechanism for restoring the discharge performance of the print head 22. Examples of such a mechanism include a cover mechanism that protects the ink discharge surface of the print head 22, a wiper mechanism that wipes the ink discharge surface, and a suction mechanism that uses negative pressure to suck ink in the print head 22 from the ink discharge surface. The maintenance unit 15 includes a drive mechanism (not shown) and a track along which the maintenance unit 15 can reciprocate horizontally. During maintenance operations on the print head 22, the maintenance unit 15 moves directly under the print head 22. When maintenance is not being performed, the maintenance unit 15 retreats to a position away from directly under the print head 22. In this example, a first maintenance unit 15a and a second maintenance unit 15b are arranged corresponding to the first printing unit 7a and the second printing unit 7b, respectively.

[0038] <System Configuration>

[0039] Figure 4 1 is a block diagram illustrating the entire system configuration including the image forming apparatus 100 according to the present exemplary embodiment. Figure 4 As shown, the system according to this exemplary embodiment includes Figure 1 Shown are an image forming apparatus 100 and an information processing apparatus (personal computer (PC)) 300 as its host apparatus.

[0040] The information processing device 300 includes a CPU 301, a read-only memory (RAM) 302, a hard disk drive (HDD) 303, a communication interface (communication I / F) 304, an input device interface (input device I / F) 305, and a display device interface (display device I / F) 306. The functional units of the information processing device 300 are connected to each other via an internal bus for communication. The CPU 301 executes processing based on programs and various types of data stored in the HDD 303 or RAM 302. The RAM 302 is a volatile memory and temporarily stores programs and data. The HDD 303 is a non-volatile memory and stores programs and data.

[0041] The communication I / F 304 is an interface that manages communication with external devices and controls data transmission and reception to and from the image forming apparatus 100. As a connection method for data transmission and reception, a wired connection such as a universal serial bus (USB), Institute of Electrical and Electronics Engineers (IEEE) 1394, or a local area network (LAN) or a method such as a wireless communication interface can be used. or The input device I / F 305 is an interface for controlling a human interface device (HID) such as a keyboard or a mouse, and receives user input from the input device. The display device I / F 306 controls display on a display device such as a display (not shown).

[0042] Although the information processing device 300 is described below as a PC separate from the image forming device 100, there are no specific limitations on these implementations as long as the same processing can be performed. For example, the information processing device 300 may be a device built into the image forming device 100, or may be a server. Furthermore, the information processing device 300 may be, for example, a mobile terminal such as a smartphone, a tablet terminal, or an imaging device.

[0043] Image forming apparatus 100 includes a CPU 311, RAM 312, ROM 313, a communication I / F 314, a head controller 315, and a heater controller 316. Furthermore, the functional units of image forming apparatus 100 are connected to one another via an internal bus for communication. CPU 311 executes the processing according to the exemplary embodiment described below based on programs and various types of data stored in ROM 313 or RAM 312. RAM 312 is a volatile memory that temporarily stores programs and data. ROM 313 is a non-volatile memory that stores various types of data, such as table data and programs, used in the processing described below.

[0044] The communication I / F 314 is an interface that manages communication with external devices and controls data transmission and reception to and from the information processing apparatus 300. The head controller 315 controls the head based on the formed data. Figure 1 The print head 22 is shown. Specifically, the head controller 315 may be configured to read control parameters and formation data from a predetermined address of the RAM 312. The heater controller 316 controls Figure 1 The drying unit 40 is shown. The heater controller 316 can control the drying temperature and air speed of the first drying unit 40a and the second drying unit 40b independently of each other. The printed ink is dried at the drying temperature and air speed set for each print medium used in printing.

[0045] <Print Media>

[0046] In the printing method and printing apparatus 1 according to the present invention, not only absorbent printing media but also low-absorbent or non-absorbent printing media (low to non-absorbent printing media) can be used. Low to non-absorbent printing media refers to printing media that has a liquid transfer amount (mL / m2) measured within 2 seconds from the start of contact using the Bristow method specified in "Test Method for Liquid Absorption of Paper and Paperboard" of Japan Pulp and Paper Industry Technical Association (JAPAN TAPPI) Paper and Pulp Test Method No. 51. 2 ) is 0mL / m 2 Up to 10 mL / m 2In the present invention, a printing medium that satisfies the above-mentioned water absorption condition is defined as a "low to non-absorbent printing medium". A printing medium for inkjet printing (such as glossy paper or matte paper) including a coating layer (ink receiving layer) formed of inorganic particles and plain paper without a coating layer is a printing medium having a liquid transfer amount greater than 10 mL / m 2 When using low to non-absorbent print media, it is expected that the liquid transfer volume is 1mL / m 2 Hereinafter, so-called non-absorbent printing media are used. Examples of such printing media include polyethylene terephthalate (PET) films and polyvinyl chloride (PVC) films, but any printing media that satisfies the above-mentioned liquid transfer amount may be used.

[0047] As a low to non-absorbent print medium, a plastic film, a print medium having a plastic film bonded to a substrate's print surface, or a print medium having a resin coating on the print surface of a substrate containing cellulose pulp can be used. Of the above, a plastic film is desirable. A print medium having a resin coating on the print surface of a substrate containing cellulose pulp is also desirable.

[0048] In this specification, the term "printing medium" refers to a printing medium on which an image is printed as a finished material, rather than a transfer medium.

[0049] <Drying Unit>

[0050] In this exemplary embodiment, drying conditions are predetermined for each combination of print medium and print mode. When a user selects the print medium and print mode to use, the corresponding drying conditions are automatically set. The print modes include a first mode, a second mode, and a third mode. In the first mode, the first print unit 7a is used solely for ink application. In the second mode, the second print unit 7b is used solely for ink application. In the third mode, both the first print unit 7a and the second print unit 7b are used for printing.

[0051] (down to dry conditions for non-absorbent print media)

[0052] In this exemplary embodiment, the drying conditions differ between the various modes. First, the drying conditions for non-absorbent print media will be described below. In the second mode, the second ink is applied directly to the print medium, so that the areas containing the second ink are dried by the second drying unit 40b to evaporate the liquid components of the second ink. On the other hand, in the third mode, the second ink is applied to overlap the first ink layer dried by the first drying unit 40a. As a result, in the areas where the second ink overlaps the first ink layer, some of the liquid components of the second ink seep into the first ink layer, significantly reducing the amount of liquid components that need to be dried by the second drying unit 40b.

[0053] For the above reasons, the drying temperature T1 of the second drying unit 40b (corresponding to the second drying unit) in the third mode can be set to be lower than the drying temperature T2 of the second drying unit 40b (corresponding to the second drying unit) in the second mode. Therefore, not only can appropriate drying conditions be set, but also the power required for drying can be reduced.

[0054] In the third mode, the second ink may not be applied over the first ink layer. In this case, the drying temperature T1 of the second drying unit 40b in the third mode is the same as the drying temperature T2 of the second drying unit 40b in the second mode. An example of a situation where the second ink is applied over the first ink layer is when the first ink is applied to the entire surface of the print medium. Alternatively, a separate determination unit configured to determine whether the first ink has been applied to the area to which the second ink is to be applied may be provided. The user may be prompted to select a mode for overlapping application. Specifically, it is desirable to include a control unit configured to control a first printing mode and a second printing mode. In the first printing mode, the second ink is applied to overlap areas where the first ink has already been applied, and in the second printing mode, the second ink is applied to areas where the first ink has not yet been applied. The second printing mode includes a situation where the second ink is applied to at least some areas without overlapping the first ink layer, as well as a situation where only the second ink is applied. In this situation, the drying temperature T1 of the second drying unit 40b in the first printing mode is lower than the drying temperature T2 of the second drying unit 40b in the second printing mode. The control unit may control the drying temperature of the second drying unit 40b.

[0055] The effect of reducing the electric power used for drying can be improved by the following factors. Figures 5A to 5F 4 is a schematic diagram illustrating the penetration of the first ink layer and the second ink after being dried by the first drying unit 40a. Figures 5A to 5F , a low to non-absorbent printing medium 108, a first ink layer 109, and a second ink 110 before being dried are illustrated. Also illustrated is an agglomerate 111 formed by agglomerating particulate components such as pigments. In order to reduce the amount of liquid components in the second ink to be dried, the liquid components in the second ink need to penetrate into the first ink layer more effectively. Therefore, measures are taken to promote the penetration of the liquid components in the second ink into the first ink layer. Specifically, it is desirable to set the amount of first ink applied per unit area to be greater than or equal to the amount of second ink applied per unit area. In the case where the amount of first ink applied is low ( Figure 5A ), it may not be possible to achieve sufficient penetration of the liquid component in the second ink ( Figure 5B On the other hand, in the case where the first ink application amount is high ( Figure 5C ), the first ink layer 109 may have a large thickness, allowing the liquid component in the second ink to fully penetrate ( Figure 5D ). This further reduces the electricity used for drying.

[0056] (Drying conditions for absorbent printing media)

[0057] The following will refer to 6A to 6D Describe the drying conditions for absorbent print media, 6A to 6D A comparison of behavior between down to non-absorbent print media and absorptive print media is illustrated. Figure 6A and Figure 6C 4 is a schematic diagram showing a state after only the second ink is applied and before drying is performed by the second drying unit 40b. Figure 6B and Figure 6D 4 is a schematic diagram illustrating a state after the first ink layer is formed and the second ink is applied on the first ink layer and before drying is performed by the second drying unit 40b. Figure 6A and Figure 6B , printing is performed on a low to non-absorbent printing medium 401, and a second ink 402 before being dried, a first ink layer 403, and an aggregate 404 formed by agglomerating particulate components such as pigments are illustrated. Figure 6C and Figure 6D , printing is performed on the absorptive printing medium 405.

[0058] When a liquid such as ink is applied to the absorptive print medium 405, the liquid component permeates through the spaces between the fibers 406. Figure 6A and Figure 6C As shown in the comparison between , although the same amount of ink is applied, the drying load is lower in the case where printing is performed on the absorptive printing medium 405. In other words, Figure 6C The drying temperature in the case shown can be set below Figure 6A Drying temperatures for the cases shown.

[0059] On the other hand, in Figure 6D In the case of the third mode shown, the second ink is applied to the first ink layer formed in such a manner that the spaces between the fibers 406 are filled with the particle components (agglomerates 404) such as the pigment of the first ink layered on the absorptive printing medium 405. Therefore, when comparing Figure 6C and Figure 6D When the second ink is applied to the first ink layer, the drying load is higher than the drying load when only the second ink is applied, which is a phenomenon opposite to the phenomenon observed in the case of the non-absorbent printing medium 401. By setting the first ink application amount per unit area to be larger than the second ink application amount per unit area as described above, the increased drying load of this phenomenon can be reduced to a certain extent.

[0060] Thus, the drying temperature T1 of the second drying unit 40b (corresponding to the second drying unit) in the third mode is set to be higher than the drying temperature T2 of the second drying unit 40b (corresponding to the second drying unit) in the second mode, which allows setting appropriate drying conditions based on the printing mode also for the absorptive printing medium 405. Specifically, with the configuration according to this exemplary embodiment, appropriate drying conditions can be set based on whether the printing medium is low to non-absorbent printing medium and the printing mode.

[0061] In this exemplary embodiment, each of the first and second inks can be an aqueous ink containing water or a water-soluble organic solvent, or an oil-based ink containing a water-insoluble organic solvent. When the first and second inks are aqueous inks, the drying load is likely to be high due to the high power required to dry the water. However, the configuration according to this exemplary embodiment effectively reduces the power required for drying.

[0062] In this exemplary embodiment, the first ink is preferably white ink, and the second ink is a colored ink, so that the liquid component of the second ink can easily penetrate into the first ink layer. An example of a colorant contained in white ink is titanium oxide. This colorant has a larger particle size than colorants typically used in colored inks. Therefore, in the first ink layer, the agglomerates of titanium oxide, a component with a large particle size, are expected to contain many voids due to their size. This allows the liquid component of the second ink to penetrate efficiently through these voids, further reducing the power required for drying.

[0063] In this exemplary embodiment, the first image forming unit and the second image forming unit apply a first reaction liquid and a second reaction liquid containing a reactant that reacts with the ink, respectively. Specifically, including a first reaction liquid applying unit and a second reaction liquid applying unit, the first reaction liquid applying unit is configured to apply a first reaction liquid that reacts with the ink before applying the first ink, and the second reaction liquid applying unit is configured to apply a second reaction liquid that reacts with the ink before applying the second ink. The reactants in the first reaction liquid and the second reaction liquid may be the same or different. A single reaction liquid can be used as the first reaction liquid and the second reaction liquid. When the first ink and the first reaction liquid are mixed, it is expected to increase the viscosity. Hereinafter, this viscosity will also be referred to as mixed viscosity. By increasing the mixed viscosity, the coagulant ( Figure 5E ), and contains many voids in the layer. Desirably, the viscosity of the mixture of the first reaction liquid and the first ink is higher than the viscosity of the mixture of the second reaction liquid and the second ink. In the exemplary embodiment described below, the viscosity of a mixed solution prepared by mixing the reaction liquid and the ink at a ratio of 7:100 (mass %) was measured with the reaction liquid and the ink applied to a print medium, the ratio being a condition that takes reactivity in image printing into consideration.

[0064] <Drying Temperature Setting Process>

[0065] The following will refer to Figure 7 The drying temperature setting process according to this exemplary embodiment will be described. In step S701, a print medium is selected. Specifically, the user selects the type of media to be used for printing on a display device, such as a monitor, of the printing apparatus 1. In this exemplary embodiment, when the user selects the type of media to be used for printing as described above, a sensor for identifying the print medium type may be disposed on the unwinding roller unit 2 to select the print medium type.

[0066] In step S702 , a printing mode is selected. Specifically, the user selects a printing mode for printing via a display device such as a display of the printing apparatus 1 (from the first mode to the third mode).

[0067] In step S703, the CPU 311 determines whether to use the first ink based on the print mode selected by the user. If the CPU 311 determines that the first ink is to be used (Yes in step S703), printing is performed in the first mode or the third mode, and the process proceeds to step S708. If the CPU 311 determines that the first ink is not to be used (No in step S703), printing is performed in the second mode, and the process proceeds to step S704.

[0068] In step S704, since the first ink is not being used, the CPU 311 turns off the power of the first drying unit 40a. Although this exemplary embodiment is configured to reduce power consumption by turning off the first drying unit 40a, it is not necessary to turn off the first drying unit 40a, considering the effort required to turn it on again for the next printing. Therefore, step S704 can be omitted.

[0069] In step S705, based on the information regarding the print medium selected by the user, the CPU 311 determines whether the print medium to be used for printing is a low to non-absorbent print medium. If the CPU 311 determines that the print medium is a low to non-absorbent print medium (YES in step S705), the process proceeds to step S706. If the CPU 311 determines that the print medium is an absorptive print medium (NO in step S705), the process proceeds to step S707.

[0070] In step S706, the CPU 311 sets the drying temperature of the second drying unit 40b to T2. Specifically, if the second drying unit 40b performs drying by blowing air, the temperature of the air is set to T2. Then, the drying temperature setting process ends.

[0071] In step S707, the CPU 311 sets the drying temperature of the second drying unit 40b to T3. T3 is a temperature lower than the above-mentioned T2. This is because, as mentioned above, Figure 6A and Figure 6C As described above, when using an absorbent printing medium, the ink penetrates and the drying load is reduced compared to when using a non-absorbent printing medium. Then, the drying temperature setting process is ended.

[0072] In step S708 , the CPU 311 sets the drying temperature of the first drying unit 40 a to T1 .

[0073] Step S709 is similar to step S705. If the print medium is determined to be non-absorbent (Yes in step S709), the process proceeds to step S710. If the print medium is determined to be absorbent (No in step S709), the process proceeds to step S711.

[0074] In step S710, the CPU 311 sets the drying temperature of the second drying unit 40b to T2'. T2' is a temperature lower than T2. ​​This is because, as mentioned above, Figures 5A to 5F 、 Figure 6A and Figure 6B As described, in the case where the first ink layer is formed on a low non-absorbent printing medium, some liquid components in the second ink penetrate into the first ink layer, and the drying load is reduced. Then, the drying temperature setting process is ended.

[0075] In step S711, the CPU 311 sets the drying temperature of the second drying unit 40b to T3'. T3' is a temperature higher than T3. This is because, as mentioned above, Figure 6C and Figure 6D As described, in the case where the first ink layer has been formed on the absorptive printing medium, the liquid component in the second ink is prevented from penetrating, and the drying load increases. Then, the drying temperature setting process ends.

[0076] By performing the aforementioned drying temperature setting according to this exemplary embodiment, an appropriate drying temperature can be set for the print medium and the print mode. In particular, even when using low to non-absorbent print media that are likely to have a high drying load, power consumption is effectively reduced.

[0077] [Example]

[0078] The present invention will be further described in detail below by giving examples and comparative examples. It should be noted that the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. Unless otherwise specified, the amount of ingredients expressed as "parts" or "%" is based on mass.

[0079] <Measurement of physical properties>

[0080] (Viscosity of mixed solution)

[0081] The viscosity of each mixture of the reaction liquid and ink was measured as follows. First, the reaction liquid and ink were mixed at a ratio of 7:100 (mass ratio). Then, after stirring the mixture at 1500 rpm for 10 seconds using a stirrer, the viscosity of the mixed solution was measured. For viscosity measurement, an E-type viscometer (product name "RE-80L", manufactured by Toki Sangyo) was used.

[0082] <Reaction Solution Preparation>

[0083] (Reaction solution 1)

[0084] 15.0 parts of magnesium sulfate heptahydrate, 15.0 parts of 1,2-butanediol, 0.3 parts of acetylenol E100, and 69.7 parts of ion-exchanged water were mixed, stirred thoroughly, and then pressure-filtered using a cellulose acetate filter (manufactured by ADVANTEC) having a pore size of 3.0 μm to prepare a reaction liquid 1. "Acetylenol E100" is the product name of a surfactant manufactured by Kawakane Fine Chemicals.

[0085] (Reaction solution 2)

[0086] Reaction liquid 2 was prepared using the same procedure as that of reaction liquid 1 except that 5.0 parts of magnesium sulfate heptahydrate and 79.7 parts of ion-exchanged water were used.

[0087] The above method was used to mix the following inks with each of Reaction Liquids 1 and 2, and the viscosity of the mixtures was measured. Each ink exhibited a higher viscosity when mixed with Reaction Liquid 1. In other words, Reaction Liquid 1 had a higher ink cohesion than Reaction Liquid 2.

[0088] <Pigment Dispersion Preparation>

[0089] (Pigment dispersion 1)

[0090] A styrene-ethyl acrylate-acrylic acid copolymer (Resin 1) having an acid value of 150 mgKOH / g and a weight-average molecular weight of 8000 was prepared. 20.0 parts of Resin 1 were neutralized with an equimolar amount of potassium hydroxide corresponding to the acid value of Resin 1, and a sufficient amount of pure water was added to prepare an aqueous solution of Resin 1 having a resin (solid content) content of 20.0%. 10.0 parts of a pigment (CI Pigment Blue 15:3), 15.0 parts of the aqueous solution of Resin 1, and 75.0 parts of pure water were mixed to obtain a mixture.

[0091] The resulting mixture and 200 parts of zirconia beads having a diameter of 0.3 mm were placed in a batch vertical sand mill (manufactured by AMX) and dispersed for 5 hours while cooling with water. After centrifugation to remove coarse particles, pressure filtration was performed using a cellulose acetate filter (manufactured by ADVANTEC) having a pore size of 3.0 μm to prepare a pigment dispersion 1 having a pigment content of 10.0% and a resin dispersant (Resin 1) content of 3.0%.

[0092] (Pigment dispersion 2)

[0093] Pigment Dispersion Liquid 2 having a pigment content of 10.0% and a resin dispersant (Resin 1) content of 3.0% was prepared using the same procedure as that of Pigment Dispersion Liquid 1, except that the pigment was changed to CI Pigment Red 122.

[0094] (Pigment dispersion 3)

[0095] Pigment Dispersion Liquid 3 having a pigment content of 10.0% and a resin dispersant (Resin 1) content of 3.0% was prepared using the same procedure as that of Pigment Dispersion Liquid 1, except that the pigment was changed to CI Pigment Yellow 74.

[0096] (Pigment dispersion 4)

[0097] Pigment Dispersion Liquid 4 having a pigment content of 10.0% and a resin dispersant (Resin 1) content of 3.0% was prepared using the same procedure as that of Pigment Dispersion Liquid 1 except that the pigment was changed to carbon black.

[0098] (Pigment dispersion 5)

[0099] Pigment Dispersion Liquid 5 having a pigment content of 40.0% and a resin dispersant (Resin 1) content of 12.0% was prepared using the same procedure as that of Pigment Dispersion Liquid 1, except that the pigment was changed to CI Pigment White 6.

[0100] <Ink Preparation>

[0101] The components (unit: %) shown in Table 1 were mixed, stirred thoroughly, and then filtered under pressure using a cellulose acetate filter (manufactured by ADVANTEC) having a pore size of 3.0 μm to prepare an ink. A liquid containing acrylic resin particles (product name "VINYBLAN 2685", manufactured by Nissin Chemical Industry, resin particle content: 30%) was used as the aqueous dispersion of the resin particles in Table 1.

[0102] Table 1: Ink components

[0103] Black ink Cyan ink Magenta ink Yellow ink White ink Pigment dispersion 1 35.0 Pigment dispersion 2 35.0 Pigment dispersion 3 35.0 Pigment dispersion 4 35.0 Pigment dispersion 5 30.0 Aqueous dispersion of resin particles 24.0 24.0 24.0 24.0 24.0 1,2-Propanediol 15.0 15.0 15.0 15.0 15.0 Acetyleno E100 0.5 0.5 0.5 0.5 0.5 Ion exchange water 25.5 25.5 25.5 25.5 30.5

[0104] <Print Media Preparation>

[0105] Use the following print media.

[0106] - Printing medium 1: Product name "PET50(A)PAT1 8LK", manufactured by LINTEC, adhesive label, material: PET, when measured using the Bristol method, liquid transfer amount within 2 seconds from the start of contact = 0 mL / m 2 Up to 1 mL / m 2 the following.

[0107] - Print medium 2: Product name "PVC80M P11K SHIRO (white)", manufactured by LINTEC, adhesive label, material: polyvinyl chloride, when measured using the Bristol method, liquid transfer amount within 2 seconds from the start of contact = 0 mL / m 2 Up to 1 mL / m 2 the following.

[0108] - Printing medium 3: Product name "ART E PW 8K", manufactured by LINTEC, when measured using the Bristol method, the amount of liquid transferred within 2 seconds from the start of contact = more than 10 mL / m 2 .

[0109] <Evaluation>

[0110] Use under the conditions specified in Table 2 Figure 1 The inkjet-type printing device 1 shown prints a 5 cm×5 cm solid image. White ink is used as the first ink, and black ink is used as the second ink. In the case of using the first reaction liquid, the first reaction liquid is applied before applying the first ink, and in the case of using the second reaction liquid, the second reaction liquid is applied before applying the second ink. The first drying unit 40a and the second drying unit 40b blow air as a drying method. In Table 2, the drying temperature of each heating unit represents the temperature of the blown air. The drying temperature of the first drying unit 40a and the second drying unit 40b is set so that the residual solvent content of the image is maintained at or below a specified percentage, and in the following example, if the conveying speed is the same, the heating time is also the same.

[0111] The following method is used as an indirect method for determining whether the residual solvent content of an image is a specified percentage or less. First, a Gakushin-type friction fastness tester (product name "AB-301," manufactured by Tester Industry) conforming to JIS K 5701 is used. A 50-cycle rubbing test is performed on the printed image surface using a 500g load using a rubbing white cloth (cotton) specified in JIS L0803. The image after the rubbing test is then visually inspected, and sufficient drying of the image is confirmed by checking that the substrate surface of the printed medium is no longer visible.

[0112] The first example is an example in which the second ink is applied without applying the first ink, with the drying temperature (air temperature) of the second drying unit 40b set to 90°C. Furthermore, the example is an example in which the second ink is applied over the first ink, and even if the drying temperature of the second drying unit 40b is set lower than that of the first exemplary embodiment, the target image can be printed. In other words, the power required for drying can be reduced.

[0113] Comparison of the second and third examples shows that increasing the amount of first ink applied enhances the power consumption reduction effect. Of the fourth to sixth examples, which vary the type of reaction liquid, the fifth example demonstrates the most significant power consumption reduction effect. Considering that the mixed viscosity of the first reaction liquid and the first ink is higher than the mixed viscosity of the second reaction liquid and the second ink, voids are easily created in the first ink layer, which facilitates the penetration of the liquid component of the second ink.

[0114] In the examples, in addition to the printing mode, the drying temperature of the second drying unit 40b can also be changed according to the print medium to be used. Specifically, as specified in the sixth and seventh examples, when using a print medium 2 having a heat resistance temperature lower than that of the print medium 1, the drying temperature is set to a low temperature. Even in this case, the drying temperature when the second ink is applied to the first ink can be set to be lower than the drying temperature when the second ink is applied without applying the first ink. In other words, the power required for drying can be reduced. In the eighth example, except that black ink is used as the first ink and white ink is used as the second ink, the image is printed using the same procedure as in the second example. Compared with the second example, the effect of reducing the power used for drying in the eighth example is less effective. It is taken into account that when another ink is used as the first ink instead of white ink, gaps that allow the penetration of the liquid component in the second ink are less likely to form.

[0115] The same evaluation was performed using cyan, magenta, and yellow inks as the second inks instead of black ink, and it was found that the power required for drying was similarly reduced. Then, except that synthetic paper (product name "YUPO 60PAT 18K", manufactured by LINTEC Corporation, when measured using the Bristol method, the amount of liquid transferred within 2 seconds from the start of contact = 2 mL / m 2 Up to 3 mL / m 2 ) as the printing medium, the evaluation was performed under the same conditions as in the second example. As a result, the effect of lowering the drying temperature was less effective than in the second example.

[0116] Next, the same evaluation conditions as in the first and second examples were performed, except that print medium 3 was used as the print medium in each of the ninth and tenth examples. As a result, the image in the tenth example was not sufficiently dried at the drying temperature (60°C) of the second drying unit 40b in the ninth example. This is because, as described above, the drying load is high when the first ink layer is formed in advance in an absorptive recording medium.

[0117] Table 2: Evaluation conditions

[0118]

[0119]

[0120] <Other exemplary embodiments>

[0121] The exemplary embodiment described above features a preset temperature condition selected based on the print medium type and print mode. However, the present invention also encompasses the automatic detection of temperature conditions when feeding sheets. For example, a device can be employed that uses an optical sensor to read the surface of the dried image and determines the drying temperature based on changes in reflectivity.

[0122] The present invention provides an inkjet printing device capable of reducing electricity used for drying and a drying method of the inkjet printing device.

[0123] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An inkjet printing device comprising, in the following order: a first image forming unit configured to form an image by applying a first ink to a printing medium; a first drying unit configured to heat the printing medium to which the first ink has been applied; a second image forming unit configured to form an image by applying a second ink to the printing medium; and a second drying unit configured to heat the printing medium to which the second ink has been applied, wherein each of the first ink and the second ink is an ink containing a colorant, Wherein, when measured using the Bristol method, the amount of liquid transferred to the printing medium within 2 seconds from the start of contact (mL / m 2 ) is 10mL / m 2 or smaller, and The drying temperature T1 of the second drying unit when the second ink is applied to the region to which the first ink is applied is lower than the drying temperature T2 of the second drying unit when the second ink is applied to the region to which the first ink is not applied.

2. The inkjet printing device according to claim 1, wherein When measured using the Bristol method, the amount of liquid transferred to the print medium within 2 seconds from the start of contact (mL / m 2 ) is 1mL / m 2 or smaller.

3. The inkjet printing apparatus according to claim 1, wherein Each of the first ink and the second ink is an aqueous ink.

4. The inkjet printing device according to claim 1 further includes a control unit, which is configured to control a first printing mode and a second printing mode, wherein in the first printing mode, the second ink is applied to an area to which the first ink has been applied, and in the second printing mode, the second ink is applied to an area to which the first ink has not been applied.

5. The inkjet printing apparatus according to claim 1, wherein An application amount of the first ink per unit area is greater than or equal to an application amount of the second ink per unit area.

6. The inkjet printing apparatus according to claim 1, wherein The first image forming unit applies a first reaction liquid containing a reactant that reacts with ink, and the second image forming unit applies a second reaction liquid containing a reactant that reacts with ink.

7. The inkjet printing apparatus according to claim 6, wherein The viscosity of the mixture of the first reaction liquid and the first ink is higher than the viscosity of the mixture of the second reaction liquid and the second ink.

8. The inkjet printing apparatus according to claim 1, wherein The first ink is white ink, and the second ink is color ink.

9. The inkjet printing apparatus according to claim 1, wherein The first image forming unit applies the first ink to the print medium in a single pass, and the second image forming unit applies the second ink to the print medium in a single pass.

10. An inkjet printing device comprising, in the following order: a first image forming unit configured to form an image by applying a first ink to a printing medium; a first drying unit configured to heat the printing medium to which the first ink has been applied; a second image forming unit configured to form an image by applying a second ink to the printing medium; and a second drying unit configured to heat the printing medium to which the second ink has been applied, wherein each of the first ink and the second ink is an ink containing a colorant, Wherein, when measured using the Bristol method, the amount of liquid transferred to the printing medium within 2 seconds from the start of contact (mL / m 2 ) greater than 10 mL / m 2 ,as well as The drying temperature T1 of the second drying unit when the second ink is applied to the region to which the first ink is applied is higher than the drying temperature T2 of the second drying unit when the second ink is applied to the region to which the first ink is not applied.

11. The inkjet printing apparatus according to claim 10, wherein Each of the first ink and the second ink is an aqueous ink.

12. The inkjet printing device according to claim 10 further includes a control unit, which is configured to control a first printing mode and a second printing mode, wherein in the first printing mode, the second ink is applied to an area to which the first ink has been applied, and in the second printing mode, the second ink is applied to an area to which the first ink has not been applied.

13. The inkjet printing apparatus according to claim 10, wherein An application amount of the first ink per unit area is greater than or equal to an application amount of the second ink per unit area.

14. The inkjet printing apparatus according to claim 10, wherein The first image forming unit applies a first reaction liquid containing a reactant that reacts with ink, and the second image forming unit applies a second reaction liquid containing a reactant that reacts with ink.

15. The inkjet printing apparatus according to claim 14, wherein The viscosity of the mixture of the first reaction liquid and the first ink is higher than the viscosity of the mixture of the second reaction liquid and the second ink.

16. The inkjet printing apparatus according to claim 10, wherein The first ink is white ink, and the second ink is color ink.

17. The inkjet printing apparatus according to claim 10, wherein The first image forming unit applies the first ink to the print medium in a single pass, and the second image forming unit applies the second ink to the print medium in a single pass.

18. A drying method for an inkjet printing device, the drying method comprising: a first image forming device for forming an image by applying a first ink to a printing medium; a first drying step for heating the printing medium to which the first ink has been applied; a second image forming device for forming an image by applying a second ink to the printing medium; and second drying for heating the printing medium to which the second ink has been applied, wherein each of the first ink and the second ink is an ink containing a colorant, Wherein, when measured using the Bristol method, the amount of liquid transferred to the printing medium within 2 seconds from the start of contact (mL / m 2 ) is 10mL / m 2 or smaller, and Here, the drying temperature T1 of the second drying when the second ink is applied to the region to which the first ink is applied is lower than the drying temperature T2 of the second drying when the second ink is applied to the region to which the first ink is not applied.

19. A drying method for an inkjet printing device, the drying method comprising: a first image forming step for forming an image by applying a first ink to a printing medium; a first drying step for heating the printing medium to which the first ink has been applied; a second image forming device for forming an image by applying a second ink to the printing medium; and second drying for heating the printing medium to which the second ink has been applied, wherein each of the first ink and the second ink is an ink containing a colorant, Wherein, when measured using the Bristol method, the amount of liquid transferred to the printing medium within 2 seconds from the start of contact (mL / m 2 ) greater than 10 mL / m 2 ,as well as The drying temperature T1 of the second drying when the second ink is applied to the region to which the first ink is applied is higher than the drying temperature T2 of the second drying when the second ink is applied to the region to which the first ink is not applied.

Images