Drying device and method for storing plasma-containing gas

Abstract

The present invention addresses the problem of obtaining a drying device (1) which can rapidly dry and cure a recording composition after printing, can reduce energy consumption, and suppresses a volatile organic solvent and plasma from being released into the atmosphere. To solve the problem, provided is a drying device provided with: a plasma addition part (2) which adds plasma to a gas; and a drying part (3) in which a plasma-containing gas, obtained by adding the plasma in the plasma addition part, is sprayed on a printed printing medium (P) discharged from a printing device.

Description

[Technical field]

[0001] The present invention relates to a drying device. The present invention also relates to a method for preserving a plasma-containing gas, and more particularly to a method for preserving a plasma-containing gas used to maintain activity of plasma (plasma active species) contained in the plasma-containing gas sprayed onto a printed material from a drying unit of a printing press. [Background technology]

[0002] In recent years, environmental initiatives such as the SDGs (Sustainable Development Goals) and the problem of marine plastics have been progressing rapidly. In product development, low carbonization and recyclability have become extremely important, and efforts to use biomass and conserve energy are becoming more common in the printing market. A printed matter in which the recording composition has been sufficiently fixed can be post-processed or stacked, but if the fixing is insufficient, there is a risk that offset will occur when stacking, that the printed surface will be scratched during post-processing, or that the equipment will be contaminated during post-processing. As a method for fixing a recording composition attached to the surface of a printing medium, a heat set printing method using a drying device having a drying chamber is known. In the drying chamber, hot air is blown from a hot air nozzle of a drying dryer unit onto the printed surface of the printing medium discharged from the printing press, and the solvent in the recording composition is evaporated and removed. Since the exhaust gas from the drying chamber contains VOC components such as volatile organic solvents, it is sent to a deodorizing chamber, where the solvent is decomposed by heating, combustion, etc. Such drying devices are known from Patent Documents 1 and 2. The method using a drying device is effective in evaporating the solvent in the printed recording composition because hot air is blown onto the print medium. However, the recording composition has low curing ability, and a lot of energy is required for rapid drying and curing. However, the heatset printing method consumes a lot of energy to generate hot air in the drying dryer section and to deodorize VOC components, so environmental impact and running costs are major issues.

[0003] As environmental awareness has grown rapidly in recent years, the inks used in printing have also become a major issue, as they contain large amounts of petroleum-derived mineral oil components. Therefore, biomass-based design of heat-set inks has become a major challenge. The inventors have been developing a technology that is useful for a new printing system that is highly environmentally friendly and energy-saving, and that can replace heatset printing methods, by applying a quick-drying technology for ink that utilizes the oxidation-promoting properties of plasma. As a result, they have found that a printing method that includes plasma irradiation is promising. Printing methods including plasma irradiation are effective for chemically reacting and curing the recording composition printed on the print medium. Among them, the remote plasma irradiation method is a method in which a gas plasmatized in a discharge space is brought into contact with an object to be irradiated outside the discharge space, and the contact between the plasma and the recording composition is adjusted according to the printing speed.

[0004] As printing methods involving plasma irradiation, for example, the methods disclosed in Patent Documents 3 to 6 are known. For example, Patent Document 4 proposes a new drying and fixing method for sheet-fed offset ink, in which negative ions generated by atmospheric pressure plasma are brought into contact with the printed surface. However, since it takes time for the ink to dry and fix, there is a problem with quick drying, and it is difficult to apply this method to a method of printing large quantities quickly. Patent Documents 5 and 6 describe the use of atmospheric pressure plasma to dry and cure ink after inkjet printing.

[0005] Here, the plasma-containing gas used in the printing methods described in Patent Documents 3 to 6 does not consider the duration of plasma activity. In addition, there is no consideration of long-distance transportation or cyclical use of the plasma-containing gas. Furthermore, there is no description of obtaining a plasma-containing gas with a high plasma concentration at low cost in order to quickly dry at the printing speed (e.g., 400 m / min) of a heat-set rotary press. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-52754 A [Patent Document 2] JP 2009-56702 A [Patent Document 3] JP 2007-106105 A [Patent Document 4] JP 2007-54987 A [Patent Document 5] JP 2008-12919 A [Patent Document 6] JP 2020-11460 A Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide an apparatus capable of quickly drying and curing a recording composition after printing, reducing energy consumption, and further, a drying apparatus which suppresses emission of volatile organic solvents and plasma into the atmosphere. In addition, the problem to be solved by the present invention is to obtain a plasma-containing gas that contains a high concentration of plasma and can maintain high plasma activity by extending the life of the plasma (plasma active species) in the plasma-containing gas, thereby suppressing a decrease in the plasma concentration in the plasma-containing gas. Another challenge is to improve the degree of freedom in designing drying devices that use plasma-containing gas in printing machines by enabling long-distance transport and circulating use of plasma-containing gas, etc. Another challenge is to establish a highly versatile printing system that can simultaneously achieve quick drying at the printing speed of a heatset rotary press (e.g., 400 m / min) and reduce drying costs, and apply drying and curing of printing inks using plasma-containing gas to conventional oil-based sheet-fed printing. [Means for solving the problem]

[0008] As a result of extensive investigations aimed at solving the above problems, the present inventors have completed the following invention. [1] A plasma addition unit that adds plasma to a gas; a drying section that blows the plasma-containing gas obtained by adding plasma in the plasma adding section onto the printing medium after printing and discharged from the printing device; A drying device comprising: [2] The drying apparatus according to [1], wherein the plasma application unit is provided with a plasma generator that converts a plasma raw material gas into plasma. [3] The drying device according to [2], wherein the plasma generator generates atmospheric pressure plasma. [4] The drying device according to any one of [1] to [3], wherein the drying unit includes one or more spray nozzles arranged at a predetermined interval across a transport path of the print medium. [5] A drying device described in any of [1] to [4], wherein the drying section has two or more drying chambers, and exhaust air from a drying chamber located downstream in the transport direction of the printing medium is supplied to a drying chamber located upstream in the transport direction of the printing medium. [6] A drying apparatus according to any one of [1] to [5], further comprising a deodorizing section for deodorizing exhaust gas from the drying section, the deodorizing section comprising a gas processor for decomposing the gas to be treated discharged from the drying chamber to produce a treated gas and / or a plasma processor for treating the plasma in the gas. [7] The drying device according to [6], wherein at least a portion of the gas treated in the deodorizing section is reused as a gas to which plasma is added. [8] The drying apparatus according to any one of [1] to [7], further comprising a means for storing the obtained plasma-containing gas at -25 to 100°C. [9] A method for storing plasma-containing gas, comprising storing the plasma-containing gas at -25 to 100°C.

[10] The method for storing a plasma-containing gas according to [9], wherein the plasma-containing gas is stored at 0 to 65°C.

[11] The method for storing a plasma-containing gas according to [9] or

[10] , wherein the plasma-containing gas is an atmospheric pressure plasma-containing gas generated at a pressure of 0.1 to 10 atmospheres and a temperature of 150°C or lower. Effect of the Invention

[0009] According to the present invention, it is possible to obtain an apparatus capable of quickly and sufficiently drying and curing a recording composition after printing, reducing energy consumption, and further, a drying apparatus capable of suppressing the release of volatile organic solvents and plasma into the atmosphere. Also, according to the present invention, it is possible to obtain a plasma-containing gas that contains plasma at a high concentration and can maintain high plasma activity, since it is possible to extend the life of the plasma (plasma active species) in the plasma-containing gas and to suppress a decrease in the plasma concentration in the plasma-containing gas. This enables long-distance transport and recycling of plasma-containing gas, and improves the degree of freedom in designing drying devices using plasma-containing gas in printing machines. This allows for both quick drying at the printing speed of a heatset rotary press (e.g., 400 m / min) and reduced drying costs, making it possible to apply plasma-containing gas to drying and curing printing ink in conventional oil-based sheet-fed printing and build a highly versatile printing system. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an embodiment of a drying device according to the present invention; [Diagram 2] FIG. 1 is a schematic diagram showing another embodiment of a drying device according to the present invention; [Diagram 3] FIG. 1 is a schematic diagram showing another embodiment of a drying device according to the present invention; [Figure 4] FIG. 1 is a schematic diagram showing another embodiment of a drying device according to the present invention; [Diagram 5] FIG. 1 is a schematic diagram showing another embodiment of a drying device according to the present invention; [Figure 6] 1 is a schematic diagram of a plasma application unit provided in a drying apparatus according to the present invention; [Figure 7] FIG. 2 is another schematic diagram of the plasma application unit included in the drying apparatus according to the present invention. [Figure 8] Schematic diagram of plasma-containing gas production device (plasma generator) [Figure 9] Another schematic diagram of a plasma-containing gas production device (plasma generation device) [Figure 10] FIG. 1 is a graph showing the color change (color difference ΔE) over time for each storage temperature of the plasma-containing gas according to the present invention. [Explanation of symbols]

[0011] 1 Drying device 2. Plasma addition section 20 Air supply machine 21, 21a, 21b Plasma-containing gas production device (plasma generator) 211 Plasma Production Room 212 Plasma generation chamber housing 213 Introduction 214 Plasma-containing gas outlet 22 Power supply 231a, 231b electrode 232 Coil 233 Electrode core 3 Drying section 30 Case 301 Print media entrance 302 Print media exit 303 Heating chamber forming partition 304 Cooling chamber forming partition 305 Bulkhead 31 Drying room 31x upstream drying room 31y Downstream drying room 311, 311n, 311x, 311y air supply machine 312, 312p, 312x, 312y spray nozzle 312a, 312pa, 312xa, 312ya Upper spray nozzle 312b, 312pb, 312xb, 312yb Lower Spray Nozzle 313, 313x, 313y exhaust 32 Heating chamber 321 Air supply machine for heating chamber 322 Hot air nozzle 322a Upper hot air nozzle 322b Lower hot air nozzle 323 Exhaust Machine 33 Cooling room 331 Cooling room air supply machine 332 Cold air nozzle 332a Upper cold air nozzle 332b Lower cold air nozzle 333 Exhaust Machine 34 Outdoor air supply 4. Deodorizing section 41 Gassing Machine 42 Plasma treatment machine 43 Exhaust Fan 44 Heat exchanger 5 Printing media inlet gas recovery section 51 Exhaust Fan 6 Printing media outlet gas recovery section 61 Exhaust Fan 70 Plasma raw gas supply unit P Print media G1 Plasma source gas PL Plasma DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described. Note that the present invention is not limited to the following embodiment, and can be practiced by making appropriate modifications within the scope of the present invention.

[0013] [Drying equipment] An embodiment of a drying device of the present invention will be described with reference to Figs. 1 to 5 are schematic diagrams showing an embodiment of a drying device according to the present invention. The drying device 1 is disposed downstream of a printing device (not shown). The drying device 1 includes a plasma adding section 2 that adds plasma to a gas, and a drying section 3 that blows the plasma-containing gas obtained by adding plasma in the plasma adding section onto a printing medium P having a wet recording composition on its surface that has been discharged from the printing device. The drying device 1 may include a deodorizing section 4 that deodorizes the exhaust gas from the drying section 3. Further, the drying device 1 may be provided with a printing media inlet gas recovery section 5 for recovering gas flowing out from the printing media inlet 301 of the drying section 3, and / or a printing media outlet gas recovery section 6 for recovering gas flowing out from the printing media outlet 302 of the drying section 3.

[0014] <Plasma addition section> 1 to 5, the plasma adding section 2 adds plasma to at least a part of the gas supplied from the air feeder 20 and / or the treatment gas returned from the deodorizing section 4. The plasma-containing gas obtained by adding plasma in the plasma adding section 2 has its temperature adjusted as necessary and is sent to the air feeder 311 of the drying section 3. In one embodiment, as shown in FIG. 2, a plasma-containing gas generated from a plasma-containing gas manufacturing device (plasma generator) 21 can be mixed with gas (which may contain plasma) recovered from any portion of the drying section 3, one or more portions of the printing medium inlet gas recovery section 5, and the printing medium outlet gas recovery section 6. 6, a plasma raw material gas is supplied from a plasma raw material gas supplying device 70 to a plasma-containing gas producing device (plasma generator) 21. The plasma-containing gas producing device (plasma generator) 21 converts at least a part of the plasma raw material gas into plasma to produce a plasma-containing gas. The plasma-containing gas is added to at least a part of the gas supplied from the air supplying device 20 and / or the treatment gas returned from the deodorizing section 4. As one embodiment, as shown in FIG. 7, at least a portion of the gas supplied from the air supply unit 20 and / or the treatment gas returned from the deodorization section 4 can be directly supplied as a plasma raw material gas to a plasma-containing gas manufacturing device (plasma generator) 21 to add plasma. As an embodiment, as shown in FIG. 6 , from the viewpoints of stable operation, ease of changing the type of plasma raw material gas, reliable addition of plasma, etc., it is preferable to supply plasma raw material gas from a plasma raw material gas supply device 70 to a plasma-containing gas production device (plasma generator) 21, and add the generated plasma-containing gas to at least a part of the gas supplied from the air supply device 20 and / or the treatment gas returned from the deodorization section 4.

[0015] <Plasma> As the plasma in the present invention, any scientifically defined plasma can be used without limitation. Plasma is a gaseous state of high energy containing charged particles generated by ionization, and may be in an electrically neutral or nearly neutral state with the same or nearly equal numbers of ions and electrons. Plasma can be generated by various methods such as discharge between electrodes spaced apart from each other. The plasma in the plasma-containing gas immediately after generation is in a high-energy state accompanied by light emission of a color according to the type of plasma raw material gas. After that, the plasma in the plasma-containing gas becomes invisible by losing or taking away part of its energy, but even in the invisible state, it is possible to induce various chemical reactions and processes. In the present invention, by storing the plasma-containing gas at a specific temperature (-20 to 100°C), loss and deactivation of the plasma (plasma active species) in the plasma-containing gas can be effectively suppressed.

[0016] The present inventors observed the plasma concentration in the plasma-containing gas by evaluating discoloration (ΔE evaluation) using a plasma indicator (PLAZMARK (registered trademark) manufactured by Sakura Color Products Corporation). As a result, they found that even after about one hour, the plasma concentration in the plasma-containing gas was sufficient to exhibit the plasma treatment effect, and that even when using plasma-containing gas in which about one hour had passed since plasma generation, ink could be dried and cured without any particular problems. This eliminated the need to provide the plasma addition section 2 and the plasma-containing gas production device (plasma generator) 21 inside the drying section 3 (drying chamber 31), improving the degree of freedom in designing the drying device.

[0017] <Plasma-containing gas> The plasma-containing gas is a gas (vapor) containing plasma generated in a plasma generation chamber of the plasma-containing gas production apparatus (plasma generator) 21. By supplying a plasma raw material gas to the plasma-containing gas production apparatus (plasma generator) 21, at least a part of the plasma raw material gas is converted into plasma, whereby the plasma-containing gas can be obtained. The plasma-containing gas of the present invention includes a plasma immediately after generation that is in a high-energy state accompanied by light emission of a color according to the type of plasma raw material gas (also referred to as a plasma modified gas), and / or a plasma that was in a high-energy state accompanied by light emission but has lost energy and become quenched and invisible (also referred to as a plasma quenching gas), and can induce various chemical reactions.

[0018] When performing various treatments utilizing the characteristics of plasma, the use of plasma-containing gas is advantageous in that it does not require any additional operations (e.g., cleaning, removal of components other than plasma, etc.) after the treatment, and therefore has a wide range of applications. For this reason, it can be preferably used, for example, when drying and hardening printed matter. However, when using a plasma-containing liquid, it may be necessary to remove the liquid after the treatment (e.g., drying by heat), which limits the range of applications. The plasma-containing gas of the present invention can be used for various purposes. For example, it is useful for contacting a printed matter (for printed matter) in a drying device of a printing press to dry and harden the printing ink, but is not particularly limited thereto. The means for contacting the printed matter is not particularly limited, and for example, the plasma-containing gas may be sprayed onto the printed matter, or the printed matter may be moved in a plasma-containing gas atmosphere.

[0019] The plasma-containing gas in the present invention preferably has a low temperature (150°C or less) when it leaves the plasma-containing gas production device (plasma generator) 21. A plasma-containing gas that has a high temperature (over 150°C) when it leaves the plasma-containing gas production device (plasma generator) 21 has poor cooling efficiency and is disadvantageous in terms of cost. In addition, if the temperature is high, the plasma may be lost or deactivated, making it difficult to increase the plasma concentration in the plasma-containing gas. The plasma-containing gas that leaves the plasma-containing gas production device (plasma generator) 21 generally contains high-temperature electrons that are generated by ionization and have relatively high energy, and components other than the electrons (ions, plasma raw material gas, etc.) that are relatively low temperature compared to the high-temperature electrons. Here, the degree of ionization of the plasma is usually less than 0.1%, and the temperature of the plasma-containing gas itself is determined by the presence rate of components other than the high-temperature electrons and the relatively low-temperature electrons.

[0020] <Storage temperature of plasma-containing gas> The storage temperature in the method for storing a plasma-containing gas of the present invention is −20 to 100° C., preferably −5 to 65° C., more preferably 0 to 65° C., and further preferably more than 10° C. and 55° C. or less. Below -20°C, cooling costs are high, the equipment becomes bulky, and there is a risk of the moisture in the gas freezing. Furthermore, when it comes into contact with printed matter, the ink may take a long time to dry and harden because the gas temperature is too low. In particular, below 10°C, although this depends on the type of ink, there is a risk that the ink's drying and hardening properties, especially the removal of volatile components in the ink, may become difficult, or the ink's reactive hardening properties may decrease. If the temperature exceeds 100° C., the amount of deactivated plasma increases, the plasma concentration in the plasma-containing gas decreases, and the effect of the plasma treatment, for example, the drying and hardening of the ink, may be adversely affected.

[0021] In the present invention, the plasma-containing gas in which plasma is generated at atmospheric pressure is one in which plasma exists in a gaseous state, and by setting the storage temperature at -20 to 100°C, loss and deactivation of the plasma (plasma active species) in the gas can be effectively suppressed. The method for maintaining the plasma-containing gas at a predetermined storage temperature is not particularly limited, and examples thereof include a method using a thermostatic bath, a heating device, a cooling device, or the like.

[0022] In the present invention, "storing at -25 to 100°C" means keeping the plasma-containing gas at -20 to 100°C. This makes it possible to suppress loss and deactivation of plasma (plasma active species) in the plasma-containing gas. The storage temperature refers to the temperature of the plasma-containing gas during storage. In the present invention, the plasma-containing gas can be stored, for example, as follows: (i) When the plasma-containing gas is recycled, the storage temperature is set to -20 to 100°C from the time the plasma-containing gas is used and recovered until it is recycled and used again. (ii) When transporting the plasma-containing gas from the generation source to the place of use, the storage temperature is set to -20 to 100°C, for example, by providing a temperature control means (cooling mechanism, etc.). (iii) When storing the plasma-containing gas in a container or the like, the storage temperature is set to -20 to 100°C; These include, but are not limited to, the following:

[0023] <Plasma-containing gas manufacturing equipment (plasma generator)> In the present invention, the plasma-containing gas production device (plasma generator) 21 may have a structure as shown in FIG. 8 or FIG. 8 or 9, the plasma-containing gas production apparatus (plasma generator) 21 includes a plasma generation chamber 211 for generating plasma therein, and the plasma generation chamber 211 is formed by a plasma generation chamber housing 212. The plasma-containing gas production apparatus (plasma generator) 21 at least includes an inlet 213 for introducing a plasma raw material gas G1 into the plasma generation chamber 211, a means for forming an electric field in the plasma generation chamber 211 to cause discharge, and a plasma-containing gas outlet 214 for discharging the plasma-containing gas containing the plasma PL generated in the plasma generation chamber 211 from the plasma generation chamber 211 to the outside.

[0024] The plasma generation chamber housing 212 forming the plasma generation chamber 211 can be made of a dielectric material such as glass or ceramic. Dielectrics with a dielectric constant of 2000 or less, such as barium titanate, silicon oxide, aluminum nitride, silicon nitride, and silicon carbide, can also be used. By making at least a part of the plasma generation chamber housing 212 out of a conductive material, the plasma generation chamber housing 212 itself can be used as an electrode. The shape of the plasma generation chamber case 212 forming the plasma generation chamber 211 is not particularly limited, and may be any shape such as a cylinder, a sphere, a box, etc. The plasma generation chamber case 212 forming the plasma generation chamber 211 may be processed to become thinner as it approaches the plasma-containing gas outlet 214, to have a nozzle shape.

[0025] The means for forming an electric field in the plasma generation chamber 211 to cause discharge is not particularly limited, and any known means can be used. In the plasma-containing gas production apparatus (plasma generator) 21a of FIG. 8, which is one embodiment of the plasma-containing gas production apparatus (plasma generator) 21, a pair of electrodes 231a and 231b having different polarities are formed on the outer or inner surface of the plasma generation chamber housing 212, facing each other at a distance from each other, and each of the electrodes 231a and 231b is connected to a power source 22 to form an electric field and discharge the electric field. The pair of electrodes 231a and 231b may be provided facing each other inside the plasma generation chamber housing 212 that forms the plasma generation chamber 211. In addition, at least one of the pair of electrodes 231a and 231b having a layer of an insulator or the like formed on the surface can be provided. The interval between the discharge electrodes is not particularly limited and may be appropriately set in consideration of the voltage and the like, and may be, for example, about 0.5 to 5.0 mm. When discharging using the electrodes, the plasma concentration can be increased.

[0026] 9, which is one embodiment of the plasma-containing gas manufacturing apparatus (plasma generator) 21, has a coil 232 provided on the outer or inner circumference of the plasma generation chamber housing 212, an electrode core 233 provided in the plasma generation chamber 211, and the coil 232 and the electrode core 233 connected to a power source 22 to form an electric field and cause discharge. The interval, winding length, winding diameter, wire diameter, interval between the electrode core 233 and the coil 232, shape of the electrode core 233, and the like of the coil 232 are not particularly limited and are appropriately optimized in consideration of the voltage, etc. For example, when a plasma generation chamber housing 212 having an elongated cylindrical shape from an inlet 213 to a plasma-containing gas outlet 214 is configured, and discharge is generated using a coil 232 and a corresponding electrode core 233 provided on the outer or inner circumference of the plasma generation chamber housing 212, the discharge density is relatively low, but the discharge volume through which the plasma raw material gas G1 passes becomes large, and a large amount of plasma can be generated, and therefore this is preferably used as the plasma-containing gas manufacturing apparatus (plasma generator) 21 of the present invention. In order to obtain a stable plasma discharge, it is preferable that the electrodes 231a, 231b or the coil 232 are configured not to come into direct contact with the plasma raw material gas G1. For this reason, an insulating coating made of a glassy material such as quartz or alumina, or a ceramic material may be provided on the surface of one or more of the electrodes 231a, 231b, the coil 232, and the electrode core 233 by a known method such as coating.

[0027] The plasma raw material gas G1 is exemplified by, but not limited to, one or more selected from the group consisting of air, oxygen gas, carbon dioxide gas, nitrogen gas, argon gas, water vapor, etc. Among these, one or more gases selected from the group consisting of air, oxygen gas, nitrogen gas, and carbon dioxide gas are preferred.

[0028] The plasma raw material gas G1 is supplied from the air feeder 20 or the plasma raw material gas source GP, and is introduced into the plasma generation chamber 211 through the inlet 213. The air feeder 20 or the plasma raw material gas source GP may be a container (gas cylinder) for storing the plasma raw material gas, and when the plasma raw material gas G1 is air, the air feeder 20 may be an outside air intake blower. Furthermore, the treated gas from the deodorization section 4 may be used as part of the plasma raw material gas G1. In this case, the high-temperature treated gas discharged from the gas treatment device in the deodorization section 4 may be used, or the treated gas after heat exchange by the heat exchanger 44, which is optionally provided, may be used.

[0029] The plasma raw material gas G1 is blown into the plasma generation chamber 211 from the inlet 213. The supply amount of the plasma raw material gas G1 is not particularly limited, but is preferably 0.1 to 100 m 3 / min, preferably 0.5 to 30 m 3 / min. A high frequency wave, a pulse wave, a microwave, or the like is applied from the power source 22 to the electrodes 231a, 231b, or the coil 232 and the electrode core 233, and when the discharge start voltage is exceeded, an electric field is formed in the plasma generation chamber 211. The plasma raw material gas G1 is turned into plasma in the plasma generation chamber 211, and then discharged as a plasma-containing gas from the plasma-containing gas discharge port 214. The plasma-containing gas includes all gases obtained by turning at least a part of the raw material gas into plasma.

[0030] The plasma-containing gas production device (plasma generator) 21 generates plasma (atmospheric pressure plasma) in a pressure range of 0.1 to 10 atm, preferably 0.7 to 1.5 atm, and is exemplified by a remote type. The temperature at which the plasma is generated is not particularly limited, but in consideration of handling and the like, it is preferable to set it to a low temperature (150°C or lower, preferably 100°C or lower, more preferably 50°C or lower).

[0031] In the present invention, it is preferable to apply a pulse wave in order to shorten the time required for the electric field to rise and fall (rising and falling means that the voltage increases or decreases continuously). The time required for the electric field to rise and fall is 10 μs or less, and preferably 50 ns to 5 μs. The electric field strength generated in the plasma generation chamber 211 is not particularly limited. It can be 1 kV / cm or more, preferably 20 kV / cm or more. It can also be 1000 kV / cm or less, preferably 300 kV / cm or less. The frequency when applying the electric field by the pulse wave is not particularly limited. It is preferably 0.5 kHz or more, and can be about 10 to 20 MHz or about 50 to 150 MHz. The power can be 40 W / cm or less, preferably 30 W / cm or less.

[0032] <Drying section> As shown in FIGS. 1 to 5, the drying section 3 is formed by a housing 30 that covers at least a part of the transport path of the print medium P. The housing 30 is provided with a print medium inlet 301 for introducing the print medium P into the drying section 3, and a print medium outlet 302 for discharging the print medium P from the drying section 3. The interior of the drying section 3 may be divided into a drying chamber 31 on the upstream side of the transport path of the print medium P, and a heating chamber 32 and / or a cooling chamber 33 on the downstream side, by using a heating chamber forming partition 303 and / or a cooling chamber forming partition 304 as needed. The heating chamber 32 and / or the cooling chamber 33 are provided as necessary, and the heating chamber 32 and / or the cooling chamber 33 may not be provided. 1 to 5, the heating chamber 32 is located upstream of the transport path of the printing medium P, but the cooling chamber 33 may be located upstream of the transport path of the printing medium P. Furthermore, one or more heating chambers 32 and / or cooling chambers 33 may be provided, and in that case, the positional relationship between the heating chamber 32 and the cooling chamber 33 can be designed as desired.

[0033] By minimizing the opening area of ​​the print medium inlet 301 and the print medium outlet 302, the drying section 3 (drying chamber 31) can be made closer to a closed space, and the plasma concentration and thermal efficiency of the drying section 3 can be easily adjusted. In particular, the plasma concentration in contact with the recording composition on the surface of the print medium P can be increased, improving the efficiency of drying and curing. The minimum opening area is determined taking into consideration the size of the print medium P, the size of the mechanism for transporting the print medium P, and clearance to prevent paper jams, etc. 2, a printing medium inlet gas recovery section 5 equipped with an exhauster 51 can be provided to recover gas flowing out from the printing medium inlet 301. Furthermore, a printing medium outlet gas recovery section 6 equipped with an exhauster 61 can be provided to recover gas flowing out from the printing medium outlet 302. Both the printing medium inlet gas recovery section 5 and the printing medium outlet gas recovery section 6 can be provided, or either one may be provided, or neither may be provided.

[0034] It is preferable that the housing 30, the heating chamber forming partition 303, and the cooling chamber forming partition 304 have thermal insulation properties. This can further improve the thermal efficiency of the drying section 3, the drying chamber 31, the heating chamber 32, and the cooling chamber 33, and reduce the energy consumption. The length of the drying section 3 (drying chamber 31) (the distance between the print medium inlet 301 and the print medium outlet 302) is not particularly limited as long as the recording composition on the surface of the print medium P is sufficiently dried and cured. For example, it may be about 1 to 20 m. The width and height of the drying section 3 (drying chamber 31) may be appropriately determined taking into consideration the installation space for various devices such as the spray nozzle 312, the plasma concentration, energy consumption, etc. The length, width and height of the heating chamber 32 and the cooling chamber 33 may also be appropriately determined taking into consideration similar requirements.

[0035] The drying section 3 is equipped with at least an air supply device 311 that supplies plasma-containing gas to the drying chamber 31, a spray nozzle 312 that sprays the plasma-containing gas onto the printing medium P transported within the drying chamber 31, and an exhaust device 313 that exhausts exhaust gas generated in the drying section 3 (drying chamber 31). The air supply unit 311 and the exhaust unit 313 can be provided at any position in the drying chamber 31, taking into consideration the efficiency of air supply and the efficiency of exhaust. The air supply volume of the air supply unit 311 and the exhaust volume of the exhaust unit 313 can be appropriately determined, taking into consideration the pressure inside the drying chamber 31, etc. It is preferable to set the exhaust volume so that it is equal to or slightly larger than the air supply volume. If the exhaust volume is larger than the air supply volume, problems such as negative pressure occurring inside the drying chamber 31 may occur.

[0036] The gas sprayed from the spray nozzle 312 contains the plasma added in the plasma adding section 2. The plasma-containing gas comes into contact with the surface of the printing medium P transported in the drying chamber 31, and dries, hardens, and fixes the recording composition adhering to the surface of the printing medium P immediately after printing. The temperature of the plasma-containing gas sprayed onto the printing medium P is not particularly limited, and the gas may or may not be heated. When spraying heated plasma-containing gas, for example, a heating device can be provided between the air feeder 311 and the spray nozzle 312.

[0037] As shown in Figs. 1 to 4, the blow nozzle 312 may be composed of one or more upper blow nozzles 312a and one or more lower blow nozzles 312b arranged at a predetermined interval across the transport path of the print medium P. In this case, the upper blow nozzles 312a and the lower blow nozzles 312b are preferably arranged in a staggered manner across the transport path of the print medium. This allows the print medium P to be transported in the drying section 3 (drying chamber 31) while being air floated. The number of nozzles in each of the upper blow nozzles 312a and the lower blow nozzles 312b is not particularly limited. For example, it can be about 20 each. The blow nozzles 312 may be provided only on one side of the print medium. In that case, the other side can be a roller, a support plate, or the like.

[0038] In the drying device shown in Figures 1 and 2, the plasma-containing gas obtained by adding plasma in the plasma adding section 2 is supplied from the air feeder 311 to the spray nozzle 312p and sprayed onto the printing medium P. The spray nozzle 312p is provided at the most upstream position of the transport path of the printing medium P in the drying chamber 31, and may be composed of one or more upper spray nozzles 312pa and one or more lower spray nozzles 312pb. The spray nozzle 312p may also be provided on only one side of the printing medium. In that case, the other side may be a roller, a support plate, or the like. In this embodiment, since a plasma-containing gas with a high plasma concentration can be sprayed onto the print medium immediately after printing, it becomes possible to more efficiently dry and harden the recording composition. The plasma-containing gas fills the drying chamber 31 after being sprayed from the spray nozzle 312p. Then, the plasma-containing gas filling the drying chamber 31 can be supplied to the spray nozzle 312 by an air supply device 311n optionally provided in the drying chamber 31, and sprayed again onto the printing medium P, thereby more reliably drying and curing the recording composition.

[0039] 3, the plasma-containing gas obtained by adding plasma in the plasma adding unit 2 is introduced into the drying chamber 31 by the air feeder 311. The plasma-containing gas filling the drying chamber 31 is then supplied to the spray nozzle 312 by the air feeder 311n provided in the drying chamber 31, and sprayed onto the printing medium P, where the recording composition is dried and cured.

[0040] 4, the plasma-containing gas obtained by adding plasma in the plasma adding unit 2 is supplied from the air feeder 311 to the spray nozzle 312 and sprayed onto the printing medium P. In this embodiment, the plasma-containing gas with a high plasma concentration can be sprayed evenly onto the printing medium P transported inside the drying chamber 31.

[0041] 5, the drying unit 3 may include two drying chambers, an upstream drying chamber 31x on the upstream side in the transport direction and a downstream drying chamber 31y on the downstream side in the transport direction, separated by a partition 305 having a transport opening for the print medium P. Furthermore, the downstream drying chamber 31y may be provided with a heating chamber 32 on the upstream side of the end of the transport path of the print medium P and a cooling chamber 33 on the most downstream side by using a heating chamber forming partition 303 and a cooling chamber forming partition 304 as needed. The heating chamber 32 and / or the cooling chamber 33 are provided as needed, and the heating chamber 32 and / or the cooling chamber 33 may not be provided. In this embodiment, the gas used in the downstream drying chamber 31y is sent to the upstream drying chamber 31x and used therein, thereby reducing the flow rate (air volume) of gas required for drying and curing. Since the drying and curing of the recording composition on the surface of the print medium P transported through the downstream drying chamber 31y is relatively advanced, the plasma-containing gas used in the downstream drying chamber 31y can be sent to the upstream drying chamber 31x and reused. In particular, when using a recording composition containing a volatile organic solvent, this is a preferred embodiment from the viewpoint of treatment of exhaust gas containing the volatile organic solvent.

[0042] The upstream drying chamber 31x is equipped with an air supply unit 311x that supplies gas to the spray nozzles 312x, a spray nozzle 312x that sprays gas onto the print medium P, and an exhaust unit 313x that exhausts exhaust gas generated in the upstream drying chamber 31x. The downstream drying chamber 31y is equipped with an air supply 311y that supplies plasma-containing gas obtained by adding plasma in the plasma addition section 2 to the spray nozzle 312y, a spray nozzle 312y that sprays gas onto the printing medium P, and an exhauster 313y that sends the gas filling the downstream drying chamber 31y to the air supply 311x of the upstream drying chamber 31x. The spray nozzles 312x, 312y may be composed of one or more upper spray nozzles 312xa, 312ya and one or more lower spray nozzles 312xb, 312yb arranged at a predetermined interval on either side of the transport path of the printing medium P. The upper spray nozzles 312xa, 312ya and the lower spray nozzles 312xb, 312yb are preferably arranged in a staggered pattern on either side of the transport path of the printing medium P. This allows the printing medium P to be transported while being air-floated in the upstream drying chamber 31x. The number of nozzles in each of the upper spray nozzles 312xa, 312ya and the lower spray nozzles 312xb, 312yb is not particularly limited. For example, it can be about 10 nozzles each. The spray nozzles 312x, 312y may be provided on only one side of the print medium. In that case, the other side can be a roller, a support plate, or the like.

[0043] 1 to 5, the shape of the gas outlet of the blowing nozzles 312, 312p, 312x, and 312y (upper blowing nozzles 312a, 312pa, 312xa, and 312ya, lower blowing nozzles 312b, 312pb, 312xb, and 312yb) is not particularly limited as long as it can blow gas evenly onto the surface of the printing medium P, particularly in the width direction. For example, it can be a slit shape that opens in the width direction of the printing medium P, or a shower shape with a large number of holes lined up at least in the width direction of the printing medium P. The gas blowing direction of the gas blowing nozzles 312, 312p, 312x, and 312y can be adjusted by directing them in any direction. For example, the gas blowing direction can be directed to any of the following directions: the transport direction of the print medium P, the direction opposite to the transport direction of the print medium P, the direction intersecting the transport direction of the print medium P (the width direction of the print medium P), the direction toward the surface of the print medium P, etc. The amount of gas sprayed from the spray nozzles 312, 312p, 312x, and 312y is not particularly limited. For example, the amount is 1 to 200 m 3 / min, preferably 30 to 100 m 3 / min. It is also possible to adjust the amount of gas sprayed for each individual nozzle. There is no particular limitation on the transport speed of the print medium P. For example, it can be set to 1 to 1000 m / min, and preferably 10 to 600 m / min.

[0044] In the drying apparatus shown in Figures 1 to 5, when gas heated by an optional heating device (not shown) is sprayed from the spray nozzle 312 or when a heating chamber 32 is provided, a cooling chamber 33 can be provided in the drying chamber 31 or the downstream drying chamber 31y. The heating chamber 32 may include a heating chamber air supply unit 321 that supplies hot air, and a hot air nozzle 322 that blows the hot air supplied from the heating chamber air supply unit 321 onto the print medium P. As a heating means in the heating chamber 32, in addition to a heating means using hot air, a heating means using infrared rays or the like may also be used. The heating chamber 32 may also include an exhaust unit 323 for exhausting air. The air supply unit 321 for the heating chamber is supplied with gas supplied from the outside air supply unit 34 and / or treated gas recycled from the deodorizing section 4, and supplied to the heating chamber. The gas may be heated by a heating device (not shown) before being supplied to the air supply unit 321 for the heating chamber, or may be heated by any means before being supplied to the hot air nozzle 322 or in the hot air nozzle 322.

[0045] The hot air nozzle 322 may have at least one upper hot air nozzle 322a and at least one lower hot air nozzle 322b, or may have only one of them. Also, depending on the material and shape of the heating chamber forming partition 303 and the cooling chamber forming partition 304, an exhaust machine (not shown) for discharging exhaust air from the heating chamber 32 may be provided. By blowing hot air to the printing medium P from at least one upper hot air nozzle 322a and at least one lower hot air nozzle 322b, the printing medium P conveyed through the drying chambers 31, 31x, and 31y can be heated. When blowing hot air, the angle of at least one upper hot air nozzle 322a and at least one lower hot air nozzle 322b, the hot air blowing speed, etc. can be adjusted. By heating the print medium P in the heating chamber 32, the recording composition can be dried and cured more reliably, and gas and the like accompanying and adhering to the print medium P can be removed and peeled off. For example, when a recording composition containing a volatile organic solvent is used, by removing and peeling off the gas and the like containing the volatile organic solvent accompanying the print medium P, it is possible to reduce the volatile organic solvent and the like discharged from the print medium outlet 302 and to remove odors accompanying and adhering to the print medium. Furthermore, by providing an exhaust machine 323, gas and the like accompanying and adhering to the print medium P can be more reliably removed and peeled off.

[0046] The cooling chamber 33 may include a cooling chamber air supply unit 331 that supplies cold air, and a cold air nozzle 332 that blows the cold air supplied from the cooling chamber air supply unit 331 onto the print medium P. As the cooling means in the cooling chamber 33, a cooling means using a refrigerant or the like may be used in addition to the cooling means using cold air. The cooling chamber 33 may also include an exhaust unit 333 for exhausting air. The cooling chamber air supply unit 331 is supplied with gas supplied from the outside air supply unit 34 and / or treated gas recycled from the deodorizing section 4, and supplies the gas to the cooling chamber 33. The gas may be cooled by a cooling device (not shown) before being supplied to the cooling chamber air supply unit 331, or may be cooled by any means before being supplied to the cold air nozzle 332 or in the cold air nozzle 332.

[0047] The cold air nozzle 332 may have at least one upper cold air nozzle 332a and at least one lower cold air nozzle 332b, or may have only one of them. Also, depending on the material, shape, etc. of the cooling chamber forming partition 304, an exhaust machine (not shown) for discharging exhaust air from the cooling chamber 33 may be provided. By blowing cold air to the printing medium P from at least one upper cold air nozzle 332a and at least one lower cold air nozzle 332b, the printing medium P that has been transported through the drying chamber 31, 31x, 31y and the heating chamber 32 can be cooled. Also, by adjusting the angle, cold air blowing speed, etc. of at least one upper cold air nozzle 332a and at least one lower cold air nozzle 332b, gas and the like that accompanies and adheres to the printing medium P can be removed and peeled off. For example, when a recording composition containing a volatile organic solvent is used, it is possible to reduce the amount of volatile organic solvent discharged from the print medium outlet 302 and remove odors that have adhered to the print medium by removing and peeling off the gas containing the volatile organic solvent that has accompanied and adhered to the print medium P. Furthermore, by providing an exhaust fan 333, it is possible to more reliably remove and peel off the gas, etc., that has accompanied and adhered to the print medium P.

[0048] [Printing device] The printing device (not shown) is a device that uses a recording composition to print on the transported printing medium P. As such a printing device, a known device can be used, for example, an offset printing device, a flexographic printing device, a gravure printing device, an inkjet printing device, an electrophotographic device, etc. In addition, each printing device may be a sheet-fed type in which the printing medium P is supplied one sheet at a time, or a rotary type in which a continuous printing medium P is wound up. In the present invention, a rotary offset printing device can be suitably used as the printing device.

[0049] [Print media] Examples of the printing medium P include various printable media, such as coated paper, plain paper, various resin films, metal films, and laminated films having a metal layer or a metal compound layer. The printing medium may be in the form of a long web or in the form of sheets. The printing medium P discharged from the drying device is further cooled as necessary, and then subjected to necessary processing such as folding and cutting to become a printed product such as a book or a poster.

[0050] [Recording composition] The recording composition may be selected from those suitable for the printing machine included in the printing section. For example, in the case of an offset printing machine, ink for offset sheet-fed printing, ink for offset rotary printing, ink for newspaper printing, etc. are used. In the case of a flexographic printing machine, ink for flexographic printing, etc. can be used; in the case of a gravure printing machine, ink for gravure printing, etc. can be used; in the case of an inkjet printing machine, ink for inkjet printing, etc. can be used; and in the case of an electrophotographic device, a toner composition for developing an electrostatic image (powder (toner composition) that adheres to an electrostatic image formed on a photosensitive drum to form an image) can be used. The recording composition is a known one that contains one or more selected from a pigment component, a binder component, a solvent component, etc. Also, a recording composition that does not contain a volatile organic solvent can be used. The recording composition used may be transparent, one color, or multiple colors. In the present invention, it is preferable to use a plasma curable recording composition that is reactive to plasma and does not contain a volatile organic solvent.

[0051] [Deodorizing section] The drying apparatus of the present invention may have a deodorizing section 4 as necessary. The deodorizing section 4 includes a gas processor 41 and an exhauster 43 that discharges the treated gas treated by the gas processor 41. The gas processor 41 decomposes the gas to be treated discharged from the drying section 3 by the exhauster 313 to produce a treated gas. The deodorizing section 4 may include, as necessary, a plasma processor 42 for treating the plasma in the gas to be treated and / or a heat exchanger 44 for recovering heat from the gas to be treated and preheating the low-temperature gas to be treated.

[0052] The gas to be treated, which contains volatile organic solvents, is decomposed and deodorized / purified by the gas treatment device 41. Any known method can be used as the treatment method. For example, any of thermal decomposition methods, such as a method of directly burning the gas to be treated or a method of using an oxidation catalyst, a treatment by adsorption, and chemical decomposition methods can be used. The plasma treatment device 42, which is provided as necessary, treats plasma and the like in the gas to be treated and / or the treatment gas discharged into the atmosphere by the exhaust device 43. The gas to be treated and / or the treatment gas may contain not only plasma, but also various radicals and ozone generated by discharge when generating plasma or by plasma. Therefore, the volatile organic solvent in the gas to be treated is also deodorized by decomposition treatment with plasma (and one or more of various radicals and ozone that may be contained), so that the deodorization effect is further enhanced. As a means for treating plasma and the like in the plasma treatment device 42, a known method can be used without limitation. For example, the treatment of plasma and the like includes a treatment of removing electric charge from charged particles, a treatment of adsorbing to a catalyst, and the like. In addition, the treatment of ozone includes one or more treatments such as activated carbon adsorption, catalytic decomposition, and water washing. In these treatments, an appropriate treatment method can be used in consideration of the concentration of plasma and the like in the gas, the amount of released gas, maintenance costs, and the like.

[0053] The heat exchanger 44, which is provided as necessary, recovers heat from the high-temperature gas to be treated that has been pyrolyzed in the gas processor 41, and preheats the low-temperature gas to be treated. This makes it possible to increase the temperature of the gas to be treated that is introduced into the gas processor 41, and to reduce the amount of energy consumed by the fuel, etc., used in the gas processor 41. It also makes it possible to suppress thermal deterioration of the plasma processor 42, and to reduce running costs. Furthermore, the heat exchanger 44 can also be used as a heat source when heat is required.

[0054] The gas to be treated discharged by one or more of the exhauster 313 of the drying chamber 31, the exhauster 323 of the heating chamber 32, the exhauster 333 of the cooling chamber 33, the exhauster 51 of the printing medium inlet gas recovery section 5, and the exhauster 61 of the printing medium inlet gas recovery section 5 is preheated by a heat exchanger 44 provided as necessary, and then decomposed in the gas treatment device 41 to become a treatment gas. At least a portion of the treatment gas is returned to the drying section 3 directly or via the plasma addition section 2 for reuse. At least a portion is sent to a plasma treatment device 42 provided as necessary, and after treatment with plasma or the like in the treatment gas, is released from the exhauster 43. In addition, in cases where there is no need to treat the gas (vapor) discharged by one or more of the exhauster 313 of the drying chamber 31, the exhauster 323 of the heating chamber 32, the exhauster 333 of the cooling chamber 33, the exhauster 51 of the printing medium inlet gas recovery section 5, and the exhauster 61 of the printing medium inlet gas recovery section 5 using the gas treatment device 41, it is also possible to recycle and reuse the discharged gas (vapor) as shown in Figure 2.

[0055] Although the embodiments of the drying device of the present invention have been described above, the present invention is not limited to these embodiments, and can be practiced by making appropriate modifications within the scope of the technical concept of the present invention.

[0056] As an embodiment of the drying device of the present invention, for example, the following can be mentioned. By providing a temperature regulator at a desired location, such as between the plasma application section and the spray nozzle, it is possible to adjust the temperature of the gas at a desired location within the drying apparatus. Optionally, sensors such as a flow meter, a thermometer, a pressure gauge, a concentration meter, etc. can be provided, and depending on the measured values, operation control, opening / closing control, and change / control of the gas flow path and flow rate of the exhauster, air supplyer, plasma adder, gas processor, valves, etc. can be performed. Also, a heating chamber can be provided downstream of the drying chamber in the print medium transport path. EXAMPLES

[0057] The method for storing a plasma-containing gas will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0058] [Evaluation method] A certain amount of plasma-containing gas obtained from a plasma-containing gas production device is injected into a bag and placed in a thermostatic chamber set at 4°C, 20°C (room temperature), 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C and stored for a certain period of time. After storage for a certain period of time, a plasma indicator is introduced and the mixture is shaken for 1 minute. The ΔE of the discolored plasma indicator (PLAZMARK (registered trademark) manufactured by Sakura Color Products Corporation) is measured.

[0059] The change in ΔE of the plasma indicator over time (minutes) for each storage temperature (temperature of the thermostatic bath) is shown in FIG. From FIG. 10, it can be seen that the activity of the plasma-containing gas can be maintained for a long period of time by storing the plasma-containing gas at a low temperature.

Claims

1. a plasma adding unit that adds plasma to the gas; a drying section that blows the plasma-containing gas obtained by adding plasma in the plasma adding section onto the printing medium after printing and discharged from the printing device; A drying device comprising: the plasma adding unit is provided with a plasma generator that converts air, which is a plasma raw material gas, into plasma; The plasma generator generates atmospheric pressure plasma, the drying unit includes two or more drying chambers, and exhaust air from a drying chamber located downstream in a transport direction of the print medium is supplied to a drying chamber located upstream in the transport direction of the print medium; The drying apparatus further comprises a deodorizing section for deodorizing exhaust gas from the drying section, the deodorizing section comprising a plasma treatment device for treating plasma in the gas to be treated discharged from the drying chamber.

2. 2. The drying device according to claim 1, wherein the drying section is provided with one or more spray nozzles arranged at a predetermined interval across the transport path of the printing medium, and the temperature of the plasma-containing gas emitted from the plasma generator is 150°C or less.

3. 3. The drying device according to claim 1, wherein at least a part of the gas treated in the deodorizing section is reused as a gas to which plasma is added.

4. 4. The drying apparatus according to claim 1, further comprising a means for storing the obtained plasma-containing gas at -25 to 100.degree.

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