Drying device, printing device, and drying method

Abstract

To provide a drier capable of determining a dry condition of each solvent for a printing medium coated with coating liquid including a plurality of kinds of solvents, a printer and a dry method.SOLUTION: A control part 51 controlling a drier and a printer comprises dry means for drying a printing medium coated with coating liquid including a plurality of kinds of solvents and a dry strength of the dry means, an absorbance sensor control part 511 for controlling an absorbance measurement device 26 measuring the absorbance of the printing medium in a predetermined wavelength band, and obtaining the measured absorbance and a temperature sensor control part 512 for controlling a temperature measurement device 27 measuring the temperature of the printing medium, and obtaining the temperature of the measured printing medium. The control part 51 determines the dry condition of each solvent on the basis of the absorbance obtained at the absorbance sensor control part 511 and the temperature of the printing medium obtained at the temperature sensor control part 512 and controls the dry strength on the basis of the determined dry condition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a drying device, a printing device, and a drying method, and more particularly to a drying device and a drying method for drying a coating liquid containing multiple types of solvents that has been applied to a printing medium. [Background technology]

[0002] Conventionally, inkjet printing devices that eject ink onto long print media such as paper or plastic film to perform printing, dry laminating devices that apply an adhesive to the media to bond the media, etc. For example, in inkjet printing, in which ink, which is a coating liquid, is applied to a web, ink containing a solvent is used to maintain printing performance.

[0003] The solvent is dried by a drying device to fix the resin, pigment, etc. in the coating liquid onto the print medium. Specifically, the print medium coated with the coating liquid is heated using hot air or a heat roller, etc., to evaporate the solvent contained in the coating liquid and dry the print medium.

[0004] If the drying is insufficient, the resins, pigments, etc. contained in the coating liquid will not adhere, resulting in problems such as bleeding, smearing, and blocking. Furthermore, if the drying is excessive, problems such as shrinkage of the printing medium, paper, or plastic film will occur. Therefore, it is necessary to appropriately control the drying strength according to the solvent used.

[0005] For example, Patent Document 1 proposes a drying device that uses multiple dryers and dries a water-soluble coating liquid by adjusting the temperature inside the dryers to control the drying strength. Also, Patent Document 2 proposes a drying device that measures the absorption strength of infrared light and controls the drying strength based on the measurement results. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-246306 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-54423 Summary of the Invention [Problem to be solved by the invention]

[0007] In coating fluids such as inks and adhesives, components such as pigments and resins, solvents, etc. are carefully adjusted to optimize them for conditions such as the type of printing medium, coating method, printing accuracy, etc. Furthermore, various solvents are designed for use in coating fluids to accommodate these complex coating conditions, and multiple types of solvents are often mixed and used to design coating fluids with higher performance.

[0008] When using a coating liquid containing multiple types of solvents, the evaporation temperature differs for each solvent, making it difficult to grasp the drying state of each solvent using the drying strength control method using temperature measurement in Patent Document 1. Furthermore, when the absorbance wavelength band representing the drying state is the same, such as in the case of a mixed solvent of water and a glycol, both of which have hydroxy groups, it is difficult to grasp the drying state of each solvent using the drying strength control method using absorbance measurement in Patent Document 2.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a drying device, printing device, and drying method that are capable of determining the drying state of each solvent for a printing medium coated with a coating liquid containing multiple types of solvents. [Means for solving the problem]

[0010] In order to achieve the above object, a drying device according to a first aspect of the present invention comprises: a drying means for drying a printing medium coated with a coating liquid containing multiple types of solvents; a control unit for controlling the drying intensity of the drying means; an absorbance sensor control unit that controls an absorbance measurement device that measures the absorbance of the print medium in a predetermined wavelength band and acquires the measured absorbance; a temperature sensor control unit that controls a temperature measurement device that measures the temperature of the print medium and acquires the measured temperature of the print medium; The control unit determining a dryness state of each of the solvents based on the absorbance acquired by the absorbance sensor control unit and the temperature of the printing medium acquired by the temperature sensor control unit; The drying intensity is controlled based on the determined dryness state.

[0011] In addition, the control unit determining the type of the remaining solvent based on the temperature of the print medium; determining the final remaining amount of the solvent based on the absorbance, thereby determining the dryness state of each of the solvents; This may also be the case.

[0012] In addition, the control unit determining the remaining amounts of the plurality of types of solvents based on the absorbance; determining the type of the remaining solvent based on the temperature of the print medium, and thereby determining the drying state of each of the solvents; This may also be the case.

[0013] Further, the plurality of types of solvents have the same wavelength band of absorbance representing a dry state. This may also be the case.

[0014] Moreover, the plurality of types of solvents are water and propylene glycol. This may also be the case.

[0015] A printing device according to a second aspect of the present invention comprises: A drying device according to a first aspect; and a coating device that applies the coating liquid to the print medium.

[0016] In addition, in a drying method according to a third aspect of the present invention, drying the printing medium coated with the coating liquid containing multiple types of solvents; measuring the absorbance of the print medium in a predetermined wavelength range; measuring the temperature of the print medium; determining a dryness state for each of the solvents based on the measured absorbance and the temperature of the print medium; The drying strength of the print medium is controlled based on the determined dryness state. [Effects of the Invention]

[0017] The drying device of the present invention measures the absorbance and temperature of the print medium coated with the coating liquid to determine the drying state for each solvent, making it possible to dry coating liquids containing multiple types of solvents with an appropriate drying strength. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating a printing device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a functional block diagram of a control unit according to the first embodiment. [Figure 3] 4 is a flowchart showing the flow of a drying process according to the first embodiment. [Figure 4] 4 is a graph showing the transmittance of a solvent for each wavelength according to the first embodiment. [Figure 5] (A) is the absorption spectrum of water, and (B) is the transmission spectrum of propylene glycol. [Figure 6] FIG. 1(A) is a graph showing an example of the temperature and drying rate versus drying time for a mixed solvent of water and propylene glycol, and FIG. 1(B) is a schematic diagram of the measurement system for FIG. [Figure 7] 1 is a graph showing an example of the relationship between absorbance and the residual amount of propylene glycol in a mixed solvent of water and propylene glycol. [Figure 8] 10 is a flowchart showing the flow of a drying process according to the second embodiment. [Figure 9] 10 is a graph showing an example of the relationship between the print medium feed speed, temperature, and absorbance according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] (Embodiment 1) Hereinafter, a drying device according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a drying device 2 will be described as an example in which ink containing a mixed solvent of water and propylene glycol is used as a coating liquid to perform inkjet printing on a printing medium that is a plastic film web W.

[0020] 1, the drying device 2 according to this embodiment is attached to an inkjet printing section 23 that performs inkjet printing as a coating device, and constitutes a printing apparatus 1. As shown in the schematic diagram of FIG. 1, the printing apparatus 1 includes an unwinding device 11, an in-feed roll 12, a precoat section 21, a precoat drying section 22, an inkjet printing section 23, a suction roll 24, a drying device 2, an absorbance measuring device 26, a temperature measuring device 27, an out-feed roll 14, a winding device 15, and a control unit 50 (not shown).

[0021] The web W is a long print medium. The material of the web W is not particularly limited, but the web W in this embodiment is a plastic film such as biaxially oriented polypropylene (OPP) or polyethylene terephthalate (PET), which are commonly used in food packaging films and the like. The web W, which is a plastic film, is less likely to absorb solvents than paper print media. Therefore, even if a small amount of propylene glycol remains on the web W due to insufficient drying, problems such as bleeding and insufficient laminate strength may occur.

[0022] The unwinding device 11 is a device that delivers the web W set in a roll state to the precoat section 21.

[0023] The in-feed roll 12 transports the web W unwound from the unwinding device 11 to the precoat section 21. The in-feed roll 12 is equipped with a drive device and transports the web W at a set feed speed.

[0024] The precoat unit 21 applies a precoat liquid to the coating surface of the web W unwound from the unwinding device 11 to form a precoat layer on the coating surface.

[0025] The precoat drying section 22 is disposed downstream of the precoat section 21 in the transport direction of the web W. The precoat drying section 22 dries the precoat liquid applied to the coated surface of the web W in the precoat section 21.

[0026] The inkjet printing unit 23 is disposed downstream of the precoat drying unit 22 in the transport direction of the web W. The inkjet printing unit 23 includes a plurality of print heads 231 that perform printing for each color. The inkjet printing unit 23 forms a pattern by depositing ink ejected from the print heads 231 onto the coated surface of the web W (more specifically, onto the precoat layer formed on the coated surface).

[0027] The inkjet printing unit 23 according to this embodiment includes four print heads 231, and prints images on the web W in four colors: cyan (C), magenta (M), yellow (Y), and black (K).

[0028] The inkjet-printed web W is transported to the downstream drying device 2 by a suction roll 24. The suction roll 24 transports the web W by suction, so the web W can be transported stably without coming into contact with the printed surface.

[0029] The drying device 2 includes a drying oven as a drying means, and dries the ink on the surface of the web W by blowing hot air onto the web W passing through the drying oven. The dried web W is delivered from the drying device 2.

[0030] The absorbance measuring device 26 is connected to the control unit 50 and is disposed downstream of the drying device 2. The absorbance measuring device 26 measures the absorbance by irradiating light from a light source onto the web W delivered from the drying device 2. By measuring the absorbance in a predetermined wavelength band with the absorbance measuring device 26, the amount of remaining solvent in the coating liquid can be measured.

[0031] The temperature measuring device 27 is connected to the control unit 50 and is disposed downstream of the drying device 2 and near the absorbance measuring device 26. The temperature measuring device 27 according to this embodiment is disposed downstream of the absorbance measuring device 26. The temperature measuring device 27 may be a non-contact measuring device such as a thermograph, or a contact measuring device using a thermocouple. In this embodiment, a contact type temperature measuring device 27 is used, which is less restricted by conditions such as the type of web W and coating liquid.

[0032] The outfeed roll 14 is disposed downstream of the temperature measuring device 27. The outfeed roll 14 transports the inkjet-printed web W to the winding device 15.

[0033] The winding device 15 is a device that winds up the web W fed by the outfeed roll 14.

[0034] 2, the control unit 50 includes a control unit 51, a storage unit 52, a display unit 53, and an input unit 54. In this embodiment, the control unit 51, which is included in the drying device 2 and controls the drying device 2, is configured as a part of the control unit 50 that controls the entire printing device 1.

[0035] The control unit 51 is composed of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and controls the drying device 2. The control unit 51 also determines the drying state of the coating liquid based on the absorbance measured by the absorbance measuring device 26 and the temperature measuring device 27 and the temperature of the web W, and controls the drying intensity.

[0036] The control unit 51 loads various operation programs and data stored in the ROM, storage unit 52, etc. of the control unit 51 into the RAM and operates the CPU, thereby realizing each function of the control unit 51 shown in Fig. 2. As a result, the control unit 51 operates as an absorbance sensor control unit 511, a temperature sensor control unit 512, an arithmetic unit 513, and a drying device control unit 514.

[0037] The absorbance sensor control unit 511 controls the absorbance measurement device 26 to measure the absorbance of the coating liquid applied to the web W, and obtains data on the measured absorbance.

[0038] The temperature sensor control unit 512 controls the temperature measuring device 27 to measure the temperature of the web W coated with the coating liquid, and acquires data on the measured temperature.

[0039] The calculation unit 513 determines the drying state of the coating liquid, more specifically, the drying state of the solvent in the coating liquid, based on the absorbance acquired by the absorbance sensor control unit 511 and the temperature of the web W acquired by the temperature sensor control unit 512.

[0040] The drying device control unit 514 controls the drying device 2 based on the determination result of the calculation unit 513, and adjusts the drying intensity of the drying oven.

[0041] The storage unit 52 is a nonvolatile memory such as a hard disk or flash memory, and stores measurement data from the absorbance measurement device 26 and the temperature measurement device 27, a determination program for determining the drying state of the coating liquid from these measurement data, and the like.

[0042] The display unit 53 is a display device, such as a liquid crystal panel, provided in the control unit 50, which is a computer device. The display unit 53 displays the measurement data of the absorbance measuring device 26 and the temperature measuring device 27, the drying state of the coating liquid, which is the determination result of the calculation unit 513, etc.

[0043] The input unit 54 is an input device for inputting instructions to start and stop printing in the printing device 1, settings of various printing conditions, settings of operating conditions of the drying device 2, etc. The input unit 54 is a keyboard, a touch panel, a mouse, etc. provided in the control unit 50.

[0044] Next, a temperature measurement method using the drying device 2 will be described with reference to the flowchart of FIG.

[0045] When the operation of the printing device 1 is started, the web W is unwound from the unwinding device 11 and transported by the in-feed roll 12 to the precoat section 21 and the precoat drying section 22 (step S11). Furthermore, the web W, which has been precoated and the precoat liquid dried, is sent to the inkjet printing section 23. Then, a pattern stored in advance in the memory section 52 is inkjet printed onto the web W (step S12). More specifically, ink is ejected from the four print heads 231 so as to correspond to the pattern of each color, and the pattern is printed onto the web W.

[0046] The ink, which is the coating liquid according to the present embodiment, contains multiple types of solvents. Specifically, the ink contains a mixed solvent of water and propylene glycol. Water and propylene glycol have different vaporization temperatures, and when the web W on which the ink has been printed is heated and dried, the timing and amount of vaporization differ. Details of the drying state due to the vaporization of the mixed solvent will be described later.

[0047] The web W, on which a four-color pattern of CMYK has been printed by the inkjet printing unit 23, is transported to the drying device 2 by the suction roll 24 (step S13). The web W, on whose surface the ink has dried in the drying device 2, is then sent out from the drying device 2.

[0048] The absorbance sensor control unit 511 controls the absorbance measuring device 26 to measure the absorbance of the web W sent out from the drying device 2 and acquire the measured absorbance data (step S14). Specifically, the absorbance measuring device 26 measures the absorbance at a predetermined wavelength that is set in advance based on the absorbance wavelength band that indicates the drying state of the coating liquid. FIG. 4 shows an example of the absorbance spectrum of a coating liquid containing a mixed solvent of water and propylene glycol. As shown in FIG. 4, in the wavelength band around 3.0 μm, the difference in absorbance between a good drying state and a bad drying state is large. Therefore, by measuring the absorbance at a wavelength of 3.0 μm, the drying state of the coating liquid can be determined.

[0049] However, as can be seen from the spectral characteristics of the absorbance of water shown in FIG. 5(A) and the spectral characteristics of the transmittance of propylene glycol shown in FIG. 5(B), the absorbance of both water and propylene glycol is high in the 3.0 μm wavelength band. This is because the absorbance at 3.0 μm indicates the presence of hydroxyl groups contained in both water and propylene glycol. Therefore, it is difficult to determine the amount of water or propylene glycol remaining by simply measuring the absorbance in the 3.0 μm wavelength band. Therefore, the drying device 2 according to this embodiment also uses temperature data of the web W.

[0050] The temperature sensor control unit 512 controls the temperature measuring device 27 to measure the temperature of the web W whose absorbance has been measured, and acquires the measured temperature data (step S15).

[0051] Figure 6(A) is a graph showing an example of the relationship between the elapsed time and the temperature of the print medium measured in the drying device with the simple configuration shown in the schematic diagram of Figure 6(B). This example shows the change in the temperature of the print medium over drying time when the mixing ratio of water to propylene glycol is changed for a two-solvent mixed solvent containing water and propylene glycol.

[0052] As shown in Figure 6(A), the smaller the proportion of water in the solvent, the steeper the temperature rise. Water evaporates first in the initial stage of drying. As water evaporation progresses, the temperature of the print medium rises, and propylene glycol evaporation progresses. Therefore, by measuring the temperature of the print medium, the proportion of remaining solvent can be estimated. However, when the temperature remains constant, as in the cases of water only and propylene glycol only in the graph of Figure 6(A), it is difficult to estimate the amount of remaining solvent.

[0053] The calculation unit 513 according to the present embodiment determines the drying state of each solvent based on the absorbance measured in step S14 and the temperature of the web W measured in step S15 (step S16). Specifically, the calculation unit 513 determines which of the following states 1 to 3 the coating liquid is in based on the measured temperature of the web W. State 1 is a state in which solvents with low vaporization temperatures remain and both solvents remain (insufficient drying state). State 2 is a state in which the vaporization of solvents with low vaporization temperatures progresses, causing the temperature of the web W to rise, and mainly solvents with high vaporization temperatures remain (insufficient drying state). State 3 is a state in which the vaporization of solvents with low vaporization temperatures progresses and solvents with high vaporization temperatures remain (insufficient drying state), or a state in which the vaporization of both solvents progresses (good drying state).

[0054] The calculation unit 513 also estimates the remaining amount of solvent in State 3 based on the measured absorbance. As shown in FIG. 7, there is a correlation between absorbance and the remaining amount of solvent. In this example, when the absorbance at a wavelength of 3.0 μm is 0.29 or less, the remaining amount of propylene glycol is estimated to be 0.35 g / m 2 and this range can be determined as a good dry state. Therefore, in the case of the above state 3, the calculation unit 513 determines that when the absorbance is greater than 0.29 it is state 3-1 (insufficient dry state), and when the absorbance is 0.29 or less it is state 3-2 (good dry state).

[0055] If the state determined in step S16 is state 1 or state 2 (YES in step S17), it is considered that all of the multiple types of solvents remain. Therefore, the drying device control unit 514 significantly increases the drying intensity (step S18). For example, the drying device control unit 514 controls the drying device 2 to perform operations such as increasing the set temperature of the hot air in the drying oven, increasing the volume of the hot air, and reducing the feed speed of the web W. The adjustment of the drying intensity may be divided into levels for state 1 and state 2, and the drying intensity may be increased more significantly in the case of state 1.

[0056] If the determined state is State 3-1 (YES in step S19), it is considered that the evaporation of the solvent with a low evaporation temperature has been completed and the solvent with a high evaporation temperature remains. Therefore, the drying device control unit 514 increases the drying intensity (step S20). The degree of increase in the drying intensity in this case may be smaller than the increase in the drying intensity in step S18.

[0057] If the determined state is state 3-2 (NO in step S19), all of the solvents are considered to have been sufficiently vaporized and the drying state is satisfactory. Therefore, the drying device control unit 514 does not change the drying intensity.

[0058] The control unit 51 continues measuring the absorbance and temperature until printing is completed (NO in step S22). At this time, if the operating conditions are changed to change the drying intensity, the control unit 51 may resume measuring the absorbance and temperature after a predetermined time, taking into consideration the time required for the operating conditions after the change to stabilize (step S21).

[0059] The web W dried in the drying device 2 is sent out from the drying device 2 and fed to the winding device 15 by the outfeed roll 14. The winding device 15 winds up the web W fed from the outfeed roll 14.

[0060] When printing by the printing device 1 is completed (YES in step S22), the drying device 2 stops operating and the drying process ends.

[0061] As described above in detail, the drying device 2 according to this embodiment determines the dryness state of each solvent by measuring the temperature of the printing medium and the absorbance in a predetermined wavelength band for a printing medium coated with a coating liquid containing multiple types of solvents. Specifically, the control unit 51 determines the type of remaining solvent based on the temperature of the web W, and determines the final amount of remaining solvent based on the absorbance, thereby determining the dryness state of each solvent. This makes it possible to control the drying device with high accuracy. In particular, even if the web W contains multiple solvents whose absorbance spectral characteristics indicate the same dryness state in the same wavelength band, the drying state of each solvent can be determined based on the measured temperature of the web W, making it possible to control the drying device with high accuracy.

[0062] Specifically, although the coating liquid according to the present embodiment contains water and propylene glycol as solvents, it may contain, for example, water and glycol as solvents. In this case, since glycol has a hydroxyl group like propylene glycol, the wavelength band of absorbance that indicates the dry state of the coating liquid is the same, but the dry state of each solvent can be determined by the same method as in the case of propylene glycol described above.

[0063] Furthermore, in this embodiment, the drying state of a coating liquid containing two types of solvents is determined, but the present invention is not limited to this, and the coating liquid may contain three or more types of solvents.

[0064] Furthermore, in the present embodiment, the case where the wavelength band of absorbance indicating the dry state is the same for multiple solvents has been described as an example, but this is not limited to this. The wavelength band of absorbance to be measured may be a wavelength band based on the absorbance spectrum characteristics of a solvent with a high vaporization temperature. This allows the amount of solvent remaining at the end of the drying process to be estimated, making it possible to accurately determine the dry state of each solvent.

[0065] Furthermore, in this embodiment, multiple types of solvents contained in the ink printed by the inkjet printing unit 23 are dried, but multiple types of solvents contained in the precoat liquid applied by the precoat unit 21 may also be dried. In this case, an absorbance measuring device 26 and a temperature measuring device 27 may be disposed downstream of the precoat drying unit 22 to determine the drying state of the precoat liquid and control the drying strength of the precoat drying unit 22.

[0066] In addition, although the present embodiment has been described with reference to a case where the drying intensity is increased depending on the dryness state, this is not limiting. For example, when the dryness state determined by the calculation unit 513 is the above-mentioned state 3, if the remaining amount of solvent estimated based on the absorbance is considered to be too small, the drying device control unit 514 may decrease the drying intensity of the drying device 2.

[0067] (Embodiment 2) In the first embodiment, the evaporation of the solvent progresses depending on the drying strength of the drying device 2, i.e., the amount of heat applied to the coating liquid on the print medium, and the temperature of the print medium changes. However, there are also cases where the drying strength affects the temperature of the print medium regardless of the state of evaporation of the solvent. In this embodiment, we will explain a case where the drying strength is adjusted by changing the feed speed of the print medium, and the temperature of the print medium changes as a result of the adjustment of the drying strength.

[0068] In this embodiment, the method of determining the dryness state based on the measured absorbance and temperature of the print medium differs from that in embodiment 1. Other components, such as the drying device 2 and the printing device 1, are similar to those in embodiment 1, so the same reference numerals are used and detailed descriptions are omitted.

[0069] The drying method according to this embodiment will be described below with reference to the flowchart of FIG.

[0070] When the operation of the printing device 1 is started, the web W is unwound from the unwinding device 11 and sent by the in-feed roll 12 to the precoat section 21 and the precoat drying section 22, where a precoat layer is formed on the web W (step S31). The precoated web W is sent to the inkjet printing section 23. Then, a design stored in advance in the memory section 52 is inkjet printed on the web W (step S32).

[0071] The ink, which is the coating liquid according to this embodiment, contains a mixed solvent of water and propylene glycol, which have different vaporization temperatures, as in the first embodiment.

[0072] The web W, on which a four-color pattern of CMYK has been printed by the inkjet printing unit 23, is transported by the suction roll 24 to the drying device 2, where it is dried (step S33). The web W, on whose surface the ink has been dried by the drying device 2, is sent out from the drying device 2.

[0073] The absorbance sensor control unit 511 controls the absorbance measuring device 26 to measure the absorbance of the web W sent out from the drying device 2 and acquire the measured absorbance (step S34). The wavelength of the measured absorbance is 3.0 μm, as in the first embodiment.

[0074] Furthermore, the temperature sensor control unit 512 controls the temperature measuring device 27 to measure the temperature of the web W whose absorbance has been measured, and acquires the measured temperature data (step S35).

[0075] 9 is a graph showing an example of the temperature and absorbance of the web W when the drying intensity control according to the present embodiment, i.e., the feed speed V of the web W, is changed. As shown in FIG. 9, the residual state of the solvent is divided into three regions (region 1 to region 3) as the feed speed V increases.

[0076] In region 1, the absorbance is below a predetermined threshold (0.3 in this example), indicating that evaporation of the solvent has progressed and the coating liquid has sufficiently dried. In region 2, the absorbance exceeds the threshold, indicating that a large amount of solvent remains and drying is insufficient. In regions 1 and 2, the temperature of the web W increases as the feed speed V increases. This is thought to be because the amount of heat dissipated between the outlet of the drying device 2 and the temperature measuring device 27 decreases. That is, in this embodiment, although heat dissipation occurs between the outlet of the drying device 2 and the temperature measuring device 27, the wet-bulb temperature of propylene glycol is high, and therefore, the increase in the amount of propylene glycol remaining on the web W makes it difficult for the temperature of the web W to decrease.

[0077] In region 3, the absorbance is much higher than the threshold value compared to region 2, and a large amount of solvent remains, indicating insufficient drying. Region 3 indicates that water remains in addition to the solvent propylene glycol. Here, the temperature is lower in region 3 compared to region 2. This is thought to be because the wet-bulb temperature of water is lower than that of propylene glycol. Therefore, in regions 2 and 3 where drying is insufficient, it is possible to determine whether the solvent water remains based on the measured temperature of the web W.

[0078] The calculation unit 513 according to the present embodiment determines the dryness state for each solvent based on the absorbance measured in step S34 and the temperature of the web W measured in step S35 (step S36). Specifically, the calculation unit 513 determines which of region 1 to region 3 represents the dry state based on the absorbance and the temperature of the web W, as described above.

[0079] If the determined state is in region 3 (YES in step S37), it is considered that multiple types of solvents remain. Therefore, the drying device control unit 514 significantly increases the drying intensity (step S38). For example, the drying device control unit 514 reduces the feed speed V of the web W.

[0080] If the determined state is in region 2 (YES in step S39), it is considered that the evaporation of the solvent with a low evaporation temperature has been completed and the solvent with a high evaporation temperature remains. Therefore, the drying device control unit 514 increases the drying intensity (step S40). The degree of increase in the drying intensity in this case may be smaller than the increase in the drying intensity in step S37.

[0081] If the determined state is in region 1 (NO in step S39), it is considered that all of the multiple types of solvents have been sufficiently vaporized and the drying state is satisfactory. Therefore, the drying device control unit 514 does not change the drying intensity.

[0082] The control unit 51 continues measuring the absorbance and temperature until printing is completed (NO in step S42). At this time, if the operating conditions are changed to change the drying intensity, the control unit 51 may resume measuring the absorbance and temperature after a predetermined time, taking into consideration the time required for the operating conditions after the change to stabilize (step S41).

[0083] The web W dried in the drying device 2 is sent out from the drying device 2 and fed to the winding device 15 by the outfeed roll 14. The winding device 15 winds up the web W fed from the outfeed roll 14.

[0084] When printing by the printing device 1 is completed (YES in step S42), the drying device 2 stops operating and the drying process ends.

[0085] As described above, the drying device 2 according to this embodiment determines the drying state of each solvent by measuring the temperature of the printing medium and the absorbance in a predetermined wavelength band for a printing medium coated with a coating liquid containing multiple types of solvents. More specifically, the total remaining amount of solvent is determined by measuring the absorbance, and the remaining state of each solvent is determined by measuring the temperature of the printing medium. Therefore, even if the measured temperature changes due to a change in the feed speed V of the web W, it is possible to accurately control the drying device.

[0086] In the above-described embodiments, the position at which absorbance is measured by the absorbance measuring device 26 is not specified, but this is not limiting. For example, absorbance may be measured at a position where the coating fluid is applied in large amounts, i.e., at a position where the total ink amount (TAC value: Total Area Coverage) is large. This makes it possible to prevent insufficient drying and properly dry the solvent, even when coating a printing pattern with large variations in TAC values. The method for setting the measurement position is not particularly limited. For example, the control unit 51 may calculate a position with a large TAC value from the printing data and preset the calculated position as the absorbance measurement position. [Industrial Applicability]

[0087] The drying device, printing device, and drying method according to the present invention are suitable for drying a coating liquid containing multiple types of solvents, and are particularly suitable for drying a coating liquid containing multiple solvents whose absorbance wavelength ranges, which indicate the dry state, are the same. [Explanation of symbols]

[0088] 1 printing device, 2 drying device, 11 unwinding device, 12 infeed roll, 14 outfeed roll, 15 winding device, 21 precoat section, 22 precoat drying section, 23 inkjet printing section, 231 print head, 24 suction roll, 26 absorbance measuring device, 27 temperature measuring device, 50 control unit, 51 control section, 511 absorbance sensor control section, 512 temperature sensor control section, 513 calculation section, 514 drying device control section, 52 memory section, 53 display section, 54 input section, V feed speed, W web

Claims

1. a drying means for drying a printing medium coated with a coating liquid containing multiple types of solvents; a control unit for controlling the drying intensity of the drying means; an absorbance sensor control unit that controls an absorbance measurement device that measures the absorbance of the print medium in a predetermined wavelength band and acquires the measured absorbance; a temperature sensor control unit that controls a temperature measurement device that measures the temperature of the print medium and acquires the measured temperature of the print medium; The control unit determining the type of the remaining solvent based on the temperature of the print medium acquired by the temperature sensor control unit; determining the final remaining amount of the solvent based on the absorbance acquired by the absorbance sensor control unit, thereby determining the dryness state of each of the solvents; controlling the drying intensity based on the determined dryness state; A drying device characterized by:

2. a drying means for drying a printing medium coated with a coating liquid containing multiple types of solvents; a control unit for controlling the drying intensity of the drying means; an absorbance sensor control unit that controls an absorbance measurement device that measures the absorbance of the print medium in a predetermined wavelength band and acquires the measured absorbance; a temperature sensor control unit that controls a temperature measurement device that measures the temperature of the print medium and acquires the measured temperature of the print medium; The control unit determining the remaining amounts of the plurality of types of solvents based on the absorbance acquired by the absorbance sensor control unit; determining the type of the remaining solvent based on the temperature of the print medium acquired by the temperature sensor control unit, thereby determining the dryness state of each of the solvents; controlling the drying intensity based on the determined dryness state; A drying device characterized by:

3. the plurality of types of solvents have the same wavelength band of absorbance representing a dry state; 3. The drying device according to claim 1 or 2.

4. The plurality of solvents are water and propylene glycol.

4. The drying device according to claim 3.

5. The drying device according to claim 1 or 2; a coating device that applies the coating liquid to the print medium, A printing device characterized by:

6. drying the printing medium coated with the coating liquid containing multiple types of solvents; measuring the absorbance of the print medium in a predetermined wavelength range; measuring the temperature of the print medium; determining the type of the remaining solvent based on the measured temperature of the print medium; determining the final remaining amount of the solvent based on the measured absorbance, thereby determining the dryness state of each solvent; controlling the drying strength of the print medium based on the determined dryness state; A drying method characterized by:

7. drying the printing medium coated with the coating liquid containing multiple types of solvents; measuring the absorbance of the print medium in a predetermined wavelength range; measuring the temperature of the print medium; determining the remaining amounts of the plurality of types of solvents based on the measured absorbance; determining the type of the remaining solvent based on the measured temperature of the printing medium, and determining the drying state of each of the solvents; controlling the drying strength of the print medium based on the determined dryness state; A drying method characterized by:

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