JP6718390B2 - Printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus that prints on both sides of a print medium, and particularly relates to temperature control of the print medium.

In a printing apparatus that prints on both sides of a printing sheet, such as an inkjet printing apparatus, it is an important issue to manage the temperature of the printing sheet during printing. When the paper surface temperature of the printing paper dried after the surface printing in the front surface printing device becomes higher than the head temperature of the printing section of the back surface printing device, the radiant heat from the printing paper raises the head temperature and causes ink clogging. As a result, nozzle breakage easily occurs in the nozzles that are not ejecting. Therefore, the paper surface temperature of the printing paper needs to be lower than the head temperature of the printing unit.

Therefore, after printing and drying the surface, the printing paper is cooled using a cooling roller (for example, refer to Patent Document 1). The temperature of the printing paper can be lowered by cooling the printing paper after the surface drying with the cooling roller. The coolant cooled by the chiller unit flows inside the cooling roller.

JP, 2016-186342, A

However, the conventional example having such a configuration has the following problems.
That is, in the printing apparatus including the conventional chiller device, there is a problem that a difference in gloss occurs between the front surface and the back surface of the printed matter. Then, as a result of investigating the gloss property of the printed matter, it was clarified that it has the temperature characteristics as shown in FIG.

As shown in FIG. 13, the glossiness changes according to the temperature of the print medium. This is because as the temperature of the print medium increases, the spread of the ink surface increases and the glossiness increases. In the relationship between the ink and the print medium shown in FIG. 13, the glossiness sharply increases until the temperature of the print medium reaches 30° C., and gradually increases immediately before the temperature exceeds 30° C.

Thus, the difference in the temperature of the print medium leads to the difference in the quality of the printed matter. That is, a difference in temperature between the front surface and the back surface of the print medium causes a difference in gloss between the front surface and the back surface. As shown in FIG. 13, the change in gloss is sensitive to the temperature difference. Contrary to the example shown in FIG. 13, depending on the type of combination of the ink and the print medium, when the temperature of the print medium rises, the penetration of the ink into the print medium progresses, and the glossiness may decrease.

The temperature of the print medium during printing on the front surface and the temperature of the print medium during printing on the back surface are different in the following cases. The temperature of the front surface of the print medium is often the same as the ambient temperature, but the back surface of the print medium may be cooled after drying the front surface print, such as when printing at high speed or when printing on thick paper. The temperature is often higher than the ambient temperature.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a printing apparatus in which the difference in gloss between the front surface and the back surface is reduced.

The present invention has the following configuration in order to achieve such an object.
That is, the invention according to claim 1 is a printing apparatus that prints on the front and back of a print medium, the temperature adjusting roller changing the temperature of the print medium, and the printing device arranged downstream of the temperature adjusting roller. A first printing unit that prints on one side of a medium, a drying unit that is arranged downstream of the first printing unit and dries the printing medium, and a printing unit that is arranged downstream of the drying unit. Cooling roller, a second printing unit arranged on the downstream side of the cooling roller for printing on the other surface of the printing medium, the temperature of the printing medium at the time of printing one surface, and the other surface The temperature control unit controls the temperature of the temperature control roller so that the temperature of the print medium during printing is the same.

According to the invention described above, by adjusting the temperature of the temperature adjusting roller so that the temperature of the print medium when printing on one side and the temperature of the print medium when printing on the other side are the same, The temperature of the print medium when printing on one side can be matched to the temperature of the print medium when printing on the other side. This can reduce the difference in gloss between the front surface and the back surface due to the temperature difference of the print medium. Further, by using the temperature adjusting roller, the temperature of the print medium can be changed by directly contacting the print medium. As a result, not only the surface of the print medium but also the internal temperature can be changed, so that the uniformity of the temperature distribution on the print medium can be improved. As a result, the gloss quality after printing in the first and second printing units can be stabilized.

Further, in the present invention, it is preferable that the temperature adjusting unit is a chiller unit with a heater that heats and cools the heat medium flowing through the temperature adjusting roller to a first set temperature.

By using the chiller unit with a heater as the temperature control unit, both heating and cooling can be performed on the heat medium. Further, by flowing the heated and cooled heat medium to the temperature adjusting roller, it is not necessary to provide separate temperature adjusting rollers for heating and cooling. Thereby, it is possible to realize both heating and cooling while saving space on the printing line.

Further, in the present invention, a first temperature sensor for measuring the temperature of the print medium is provided on the downstream side of the temperature adjusting roller and on the upstream side of the first printing unit, and the first temperature sensor is provided on the downstream side of the cooling roller, A second temperature sensor that measures the temperature of the print medium and a chiller unit that cools the coolant flowing to the cooling roller to a second preset temperature are provided on the upstream side of the second printing unit, and the temperature adjusting unit includes: Control for controlling the first set temperature so that the detected temperature of the first temperature sensor becomes the target temperature, and controlling the second set temperature so that the detected temperature of the second temperature sensor becomes the target value temperature. It is preferable to provide a part.

By measuring the temperature of the print medium and controlling the temperatures of the heat medium of the chiller unit with a heater and the refrigerant of the chiller unit, the temperature of the print medium can be controlled with higher accuracy. Since the control unit controls the chiller unit with a heater so that the temperature of the print medium reaches the target temperature based on the measurement result of the first temperature sensor, it is possible to control the print quality of gloss on one surface. Further, the control unit controls the chiller unit so that the temperature of the print medium becomes the same target temperature based on the measurement result of the second temperature sensor, so that the print quality of the other surface can be controlled. Therefore, it is possible to improve the print quality on both sides of the print medium. Further, it is possible to maintain the temperature at which the gloss is most beautiful according to the type of print medium. In particular, the effect can be expected in an inkjet printing apparatus in which the spread of dots on the print medium greatly affects the quality.

Further, in the present invention, a first temperature sensor for measuring the temperature of the print medium is provided on the downstream side of the temperature adjusting roller and on the upstream side of the first printing unit, and the first temperature sensor is provided on the downstream side of the cooling roller, A second temperature sensor that measures the temperature of the print medium and a chiller unit that cools the refrigerant flowing through the cooling roller to a second preset temperature are provided on the upstream side of the second printing unit, and the temperature adjusting unit includes the second temperature sensor. The first setting temperature is controlled so that the temperature detected by the first temperature sensor is the same as the temperature detected by the second temperature sensor, and the second setting is performed so that the detection value of the second temperature sensor becomes the target temperature. It is preferable to include a control unit that controls the temperature.

By measuring the temperature of the print medium and controlling the temperatures of the heat medium of the chiller unit with a heater and the refrigerant of the chiller unit, the temperature of the print medium can be controlled with higher accuracy. The control unit controls the chiller unit with a heater and the chiller unit so that the temperature of the print medium during printing on one side becomes the temperature of the print medium during printing on the other side. As a result, even if the temperature of the print medium during printing on the other side rises, the temperature of the print medium on one side rises, thereby reducing the difference in gloss between the one side and the other side. it can.

Further, in the present invention, a supply unit that supplies the print medium wound in a roll shape on the most upstream side, and a paper discharge unit that collects the print medium in a roll shape on the most downstream side may be provided. ..

By applying the present invention to a long print medium that can be wound into a roll, even if the temperature of the print medium at the time of printing on the other side increases due to long-time printing, at the time of printing on one side By adjusting the temperature of the print medium to the temperature of the print medium at the time of printing on the other surface, it is possible to reduce the difference in gloss between the one surface and the other surface.

Further, in the present invention, a pretreatment device which raises the temperature of the print medium by performing a predetermined treatment on the print medium may be provided on the upstream side of the temperature adjusting roller.

Even if the temperature of the print medium on one side before printing rises by the pretreatment device, the temperature of the print medium is adjusted by the temperature adjusting roller, so the temperature difference between the print medium on one side and the other side is reduced. be able to. Thereby, the difference in gloss between the one surface and the other surface can be reduced.

According to the printing apparatus of the present invention, the temperature of the temperature adjusting roller is adjusted so that the temperature of the printing medium when printing on one side is the same as the temperature of the printing medium when printing on the other side. As a result, the temperature of the print medium during printing on one side can be matched with the temperature of the print medium during printing on the other side. This can reduce the difference in gloss between the front surface and the back surface due to the temperature difference of the print medium. Further, by using the temperature adjusting roller, the temperature of the print medium can be changed by directly contacting the print medium. As a result, not only the surface of the print medium but also the internal temperature can be changed, so that the uniformity of the temperature distribution on the print medium can be improved. As a result, it is possible to stabilize the gloss quality after printing in the first and second printing units, and to provide a printing apparatus in which the difference in gloss between the front surface and the back surface is reduced.

FIG. 1 is an overall configuration diagram showing a schematic configuration of an inkjet printing apparatus according to a first embodiment. It is a longitudinal cross-sectional view of a temperature control unit. It is a figure which shows the connection of the chiller unit with a heater, and a temperature control unit. It is a longitudinal cross-sectional view of a temperature adjusting roller. It is a perspective view of a lateral vortex flow forming part. It is a longitudinal cross-sectional view of a cooling unit. It is a figure which shows the connection of a chiller unit and a cooling part. It is a graph which shows the relationship between concentration and temperature. It is a graph which shows the relationship between concentration and temperature. 6 is a functional block diagram showing a control configuration of an inkjet printing apparatus according to a second embodiment. FIG. FIG. 6 is an overall configuration diagram showing a schematic configuration of an inkjet printing apparatus according to a third embodiment. It is a block diagram of a pretreatment apparatus. It is a graph which shows the relationship between gloss and temperature.

Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram showing a schematic configuration of the inkjet printing apparatus according to the first embodiment.

The inkjet printing apparatus 1 includes a paper feeding unit 3, a temperature control device 4, a front surface printing device 5, a reversing device 7, a cooling device 8, a back surface printing device 9, and a paper ejection unit 11.

The paper feeding unit 3 holds the roll-shaped continuous paper WP rotatably around a horizontal axis, and unwinds and supplies the continuous paper WP to the temperature control device 4. The temperature of the continuous paper WP supplied is almost the same as the environmental temperature in which the paper feeding unit 3 is installed. Here, for example, it is 25°C. The temperature control device 4 is a device capable of both heating and cooling the continuous paper WP. The front surface printing device 5 is, for example, an ink jet type printing device that ejects ink droplets to form an image, and prints on the surface of the continuous paper WP. The reversing device 7 includes a plurality of turn bars (not shown), and reverses the back surface of the continuous paper WP to the upper side. The cooling device 8 cools the continuous paper WP printed by the front surface printing device 5 and reversed by the reversing device 7. The back surface printing device 9 has, for example, the same configuration as the front surface printing device 5 and performs printing on the back surface of the continuous paper WP. The paper discharge unit 11 winds the continuous paper WP processed by the front surface printing device 5 and the back surface printing device 9 in a roll shape around the horizontal axis.

The front surface printing device 5 is provided with a drive roller 13 on the upstream side for taking in the continuous paper WP from the temperature adjusting device 4. The continuous paper WP heated and cooled by the temperature adjusting device 4 is transported to the downstream side by the drive roller 13 along the plurality of transport rollers 15. The surface printing device 5 includes a drive roller 17 at the most downstream side. A temperature sensor 18, a first printing unit 19, a first heat roller 21, and an inspection unit 23 are arranged between the drive roller 13 and the drive roller 17 from the upstream side. By installing the temperature sensor 18 between the temperature adjusting roller 39 and the first printing unit 19, the paper surface temperature of the continuous paper WP during front surface printing is measured. Examples of the temperature sensor 18 include a non-contact type temperature sensor. The first printing unit 19 includes an inkjet print head 25. The first control unit 20 adjusts the first set temperature of the temperature adjusting device 4 based on the measured temperature of the temperature sensor 18 and controls so that the measured temperature of the continuous paper WP becomes the target temperature. The first set temperature is the set temperature of the heat medium, and the target temperature is, for example, 30°C. The first heat roller 21 has a built-in heat source and heats the continuous paper WP wrapped around the outer peripheral surface to dry the printing surface. The inspection unit 23 inspects the image printed on the continuous paper WP.

The first printing unit 19 includes, for example, four print heads 25. Specifically, in order from the upstream side, the print head 25 for black (K), the print head 25 for cyan (C), the print head 25 for magenta (M), and the print for yellow (Y). And a head 25. The print heads 25 are arranged at predetermined intervals along the transport direction of the continuous paper WP.

The back surface printing device 9 has almost the same configuration as the front surface printing device 5 described above. Here, only the configuration different from that of the front surface printing device 5 will be described.

The drive roller 13 of the back surface printing device 9 takes in the continuous paper WP whose surface temperature has been cooled by the cooling device 8. The second printing unit 19 ′ of the back surface printing device 9 is in a posture with the back surface facing upward, and prints on the back surface of the continuous paper WP cooled by the cooling device 8. The second printing unit 19 ′ includes four print heads 25, like the first printing unit 19. By installing the temperature sensor 26 between the cooling roller 83 and the second printing unit 19', the paper surface temperature of the continuous paper WP at the time of back surface printing is measured. The second controller 27 adjusts the second set temperature of the cooling device 8 based on the detected value of the temperature sensor 26, and controls the detected temperature of the continuous paper WP to be the target temperature. The second set temperature is the temperature of the refrigerant. As a result, the continuous paper WP dried by the first heater roller 21 and having a temperature of 40° C., for example, is cooled to 30° C. The second set temperature of the cooling device 8 in this case is set to 20°C. The second heat roller 21' has a built-in heat source and heats the continuous paper WP wound around the outer peripheral surface to dry the printing surface.

The first printing unit 19 corresponds to the "first printing unit" in the present invention, and the second printing unit 19' corresponds to the "second printing unit" in the present invention. The first control unit 20 and the second control unit 27 correspond to the "control unit" in the present invention. The first control unit 20 and the second control unit 27 are configured by a PC or a microprocessor having an input unit such as a touch panel display and a display unit. The first control unit 20 and the second control unit 27 may be integrated as one control unit.

Here, the temperature adjusting device 4 will be described with reference to FIGS. 2 and 3. 2 is a vertical cross-sectional view of the temperature adjustment unit, and FIG. 3 is a view showing the connection between the chiller unit with a heater and the temperature adjustment unit.

As shown in FIG. 3, the temperature control device 4 includes a temperature control unit 29 and a chiller unit 31 with a heater.

First, the temperature adjustment unit 29 shown in FIG. 2 will be described. The temperature adjustment unit 29 includes a housing 33, introduction rollers 35 and 37, seven temperature adjustment rollers 39, and discharge rollers 41 and 43. These rollers 35, 37, 39, 41, 43 are provided with a rotation shaft in the front direction on the paper surface of FIG. 2, and are attached to the housing 33 rotatably around the rotation shaft.

The housing 33 has an inlet 45 formed on one side of the side surface and an outlet 47 formed on the other side of the side surface. The introduction port 45 introduces the continuous paper WP before temperature adjustment, and the discharge port 47 discharges the continuous paper WP after temperature adjustment. The introducing rollers 35 and 37 are arranged downstream of the introducing port 45 and guide the continuous paper WP to the seven temperature adjusting rollers 39. Among the seven temperature adjusting rollers 39, four temperature adjusting rollers 39 are arranged in the lower part and three temperature adjusting rollers 39 are arranged in the upper part. Each of the temperature adjusting rollers 39 is arranged such that the outer periphery of the upper three temperature adjusting rollers 39 is located more centrally than the outer periphery of the lower four temperature adjusting rollers 39 in a plan view so that the winding angle becomes large. Has been done. This increases the contact area between the outer peripheral surface and the continuous paper WP, which is advantageous for temperature control of the continuous paper WP. The continuous paper WP that has passed through the seven temperature adjusting rollers 39 is guided to the discharge port 47 by the discharge rollers 41 and 43.

Assuming that the temperature adjusting rollers 39 are 39a to 39g in order from the introduction port 45 side for convenience, the continuous paper WP has seven temperature adjusting rollers 39 in a zigzag shape, that is, the temperature adjusting rollers 39a, 39b, 39c,. 39d, 39e, 39f, and 39g are wound in this order to change the temperature.

Each temperature adjusting roller 39 is connected to the chiller unit 31 with a heater as shown in FIG. The chiller unit 31 with a heater stores water as a heat medium, and measures the temperature of the water with a built-in temperature sensor. The water is heated by the heater and cooled by the chiller so as to reach the first set temperature. The first set temperature is set by an instruction from the first controller 20. As a result, the chiller unit 31 with a heater adjusts the temperature of the temperature adjusting roller 39 so that the temperature of the continuous paper WP during printing on the front surface and the temperature of the continuous paper WP during printing on the back surface are the same. Here, "the temperature of the continuous paper WP during printing on the front surface and the temperature of the continuous paper WP during printing on the back surface are the same" means that the temperature of the continuous paper WP during printing on the front surface and the continuous paper during printing on the back surface. Not only the temperature of WP is completely the same, but also the range of plus or minus 1°C is included. The chiller unit 31 with a heater includes a feed part 49 and a return part 51. The temperature-controlled water is sent out from the feed part 49, and the water heat-exchanged by the temperature adjustment unit 29 is returned to the return part 51. As the heat medium, a solvent-based heat medium other than water may be used.

The water described above corresponds to the "heat medium" in the present invention. Further, the “temperature adjusting section” of the present invention corresponds to the chiller unit 31 with a heater.

The feeding unit 49 is connected to the distribution unit 55 via a pipe 53. The distributor 55 is connected to one end of each of the seven temperature adjusting rollers 39. However, the temperature adjusting rollers 39 that are adjacent to each other on the transport path of the continuous paper WP are connected so that water is supplied from the opposite ends. In other words, in the direction of FIG. 3, the temperature adjusting rollers 39a, 39c, 39e, 39g are supplied with water from the left side. Water is supplied to the temperature adjusting rollers 39b, 39d, 39f from the right side. The water that has flowed through each temperature adjusting roller 39 is collected in the water collecting portion 57 and returned to the return portion 51 through the pipe 59.

As described above, since the adjacent temperature control rollers 39 are alternately supplied with water from the opposite directions on the conveyance path, the temperature of one end of the continuous paper WP is prevented from being excessively changed from that of the other end. ing.

Next, the above-mentioned temperature adjusting roller 39 will be described with reference to FIGS. 4 and 5. 4 is a vertical cross-sectional view of the temperature adjusting roller, and FIG. 5 is a perspective view of the horizontal vortex flow forming portion.

The temperature adjusting roller 39 includes a roller body 59, lid members 61 and 63, and lateral vortex flow forming portions 65 and 67. The roller body 59 has a tubular shape with a flow path formed inside, and both ends are open. The roller body 59 has an outer diameter of about 100 mm, for example. The roller body 59 is made of a heat conductive member so that heat is exchanged with the continuous paper WP by heat conduction. The lid members 61 and 63 are provided at both ends of the roller body 59, and one of them serves as a supply unit and the other serves as a discharge unit. Here, it is assumed that the lid member 61 constitutes the supply portion 69 and the lid member 63 constitutes the discharge portion 71.

The supply part 69 has a shaft part 73 fixed to an inner ring of a bearing (not shown) and a flow path 75 to which water is supplied. The lateral vortex flow forming portion 65 is integrally attached to the roller body 59 side of the supply portion 69. The supply part 69 is integrally screwed and fixed to one end side of the roller body 59 together with the lateral vortex flow forming part 65.

Similar to the supply unit 69, the discharge unit 71 is provided with a shaft 73 and a flow path 75. The discharge part 71 is integrally screwed and fixed to the other end side of the roller body 59 together with the lateral vortex flow forming part 67.

In the lateral vortex flow forming portions 65 and 67, for example, four through holes 77 are formed at equal intervals around the central axis of the supply portion 69 (discharge portion 71). Each through hole 77 has an angle θ toward the inner wall of the roller body 59 with reference to a line connecting the centers of the supply unit 69 and the discharge unit 71 (two-dot chain line drawn in the horizontal direction in FIG. 4). Has been formed. The angle θ is, for example, 30°. This angle θ is an angle that forms a lateral vortex in which the cooling water is reflected and flows on the inner wall of the roller body 59. The angle θ is preferably set in the range of about 20° to 45°, and is set based on the flow path length of the roller body 59 from the relationship of the formation of the lateral vortex flow.

In the horizontal vortex flow forming unit 65 having the above-described configuration, the water supplied from the supply unit 69 is reflected by the inner wall of the roller body 59 and becomes a horizontal vortex flow and is discharged from the discharge unit 71, as shown by a two-dot chain line in FIG. To be done. Therefore, the water does not mainly flow through the central portion of the flow path of the roller body 59, but flows around the center of the flow path while being reflected by the inner wall located on the outer side. Are agitated and the temperature of the roller body 59 is forcibly adjusted. As a result, the efficiency of heat exchange between the water flowing through the flow path of the roller body 59 and the continuous paper WP in contact with the roller body 59, particularly the efficiency in the central portion, is improved. The temperature difference between the portion 69 side and the central portion can be reduced. As a result, the uniformity of the temperature distribution in the continuous paper WP can be improved relatively inexpensively without using a complicated structure such as a heat pipe.

The inkjet printing apparatus 1 including the temperature adjusting roller 39 having the above-described configuration in the temperature adjusting unit 29 can improve the uniformity of the paper surface temperature of the continuous paper WP in the width direction and adjust the temperature, thereby improving the print quality. can do.

Next, the cooling device 8 will be described with reference to FIGS. 6 and 7. 6 is a vertical sectional view of the cooling unit, and FIG. 7 is a diagram showing the connection between the chiller unit and the cooling unit.

The cooling device 8 includes a cooling unit 79 and a chiller unit 81 as shown in FIG. 7. The cooling device 8 has the same basic configuration as the temperature adjusting device 4. Since the temperature control device 4 is provided with a chiller with a heater, it is possible to perform both heating and cooling of the heat medium, but since the cooling device 8 is provided with the chiller unit 81, it is possible to cool the refrigerant. it can.

The cooling unit 79 shown in FIG. 6 will be described. The cooling unit 79 includes a housing 33, introduction rollers 35 and 37, seven cooling rollers 83, and discharge rollers 41 and 43. Each of these rollers 35, 37, 83, 41, 43 has a rotation axis in the front-back direction on the paper surface of FIG. 2, and is attached to the housing 33 rotatably around the rotation axis.

The housing 33 has an inlet 45 formed on one side of the side surface and an outlet 47 formed on the other side of the side surface. The inlet 45 introduces the continuous paper WP before cooling, and the outlet 47 discharges the continuous paper WP after cooling. The introduction rollers 35 and 37 are arranged downstream of the introduction port 45 and guide the continuous paper WP to the seven cooling rollers 83. The continuous paper WP that has passed through the seven cooling rollers 39 is guided to the discharge port 47 by the discharge rollers 41 and 43.

Each cooling roller 83 is connected to the chiller unit 81 as shown in FIG. The chiller unit 81 stores cooling water as a refrigerant, and the cooling water is cooled according to an instruction from the second controller 27. The chiller unit 81 includes a feed section 49 and a return section 51. The cooled cooling water is sent out from the feed section 49, and the cooling water heat-exchanged by the cooling unit 79 is returned to the return section 51. As the refrigerant, a solvent-based refrigerant may be used in addition to the cooling water. The other configuration of the cooling unit 79 is the same as that of the temperature adjustment unit 29, and thus the description thereof is omitted. Further, the structure of the cooling roller 83 is the same as that of the temperature adjusting roller 39, and therefore its explanation is omitted.

The cooling water described above corresponds to the "refrigerant" in the present invention.

The inkjet printing apparatus 1 having the above-described configuration heats and cools the continuous paper WP by using the first controller 20 and the temperature controller 4. The first control unit 20 controls the first set temperature of the chiller unit 31 with a heater so that the temperature measured by the temperature sensor 18 becomes a target temperature (for example, 28° C. to 33° C., preferably 30° C.). The temperature of the water as is controlled. When the temperature-controlled water passes through the temperature-adjusting roller 39, the temperature of the temperature-adjusting roller 39 is also adjusted. Since the temperature of the continuous paper WP is changed by such a temperature adjusting roller 39, the paper surface temperature of the continuous paper WP can be accurately adjusted to the target temperature. Further, the inkjet printing apparatus 1 cools the continuous paper WP by using the second controller 27 and the cooling unit 8. The second controller 27 controls the second set temperature of the chiller unit 81 so that the temperature measured by the temperature sensor 26 becomes the target temperature, so the temperature of the cooling water as the refrigerant is controlled. By passing the cooled cooling water through the temperature adjusting roller 83, the temperature adjusting roller 83 is also cooled. Since the temperature of the continuous paper WP is cooled by such a temperature adjusting roller 83, the paper surface temperature of the continuous paper WP can be accurately adjusted to the target temperature.

Accordingly, it is possible to control the temperature at the time of printing on the front surface and the temperature at the time of printing on the back surface of the continuous paper WP to be the same target temperature. As a result, the difference between the temperature at the time of printing on the front surface and the temperature at the time of printing on the back surface can be kept within 1° C., the difference in glossiness between the front surface and the back surface can be reduced, and the glossiness can be made almost the same. be able to. Therefore, the print quality can be matched between the front surface and the back surface. Note that the target temperature at this time is preferably set to a temperature at which the "paste" of the ink droplets improves according to the characteristics of the continuous paper WP, and "printing" appears on the print to improve the print quality. .. In particular, in the inkjet printing apparatus 1, since the temperature of the continuous paper WP affects the spread of dots of ink droplets, it is possible to control the quality of the product printed matter by adjusting the target temperature.

The inkjet printing apparatus 1 having the above-described configuration also reduces the difference in density between the front surface and the back surface of the product printed matter. The effect of the inkjet printing apparatus 1 on the density will be described with reference to FIGS. 8 and 9. 8 and 9 are graphs showing the relationship between concentration and temperature.

FIG. 8 is a graph showing the difference in density of yellow when the paper surface temperature during front surface printing is 25° C. and when the paper surface temperature during back surface printing is 30° C. in the conventional inkjet printing apparatus. FIG. 9 is a graph showing the difference in black density between when the paper surface temperature during front surface printing is 25° C. and when the paper surface temperature during back surface printing is 30° C. in the conventional inkjet device.

In the case where the ink color is yellow, as shown in FIG. 8, the spread of the ink becomes larger as the paper surface temperature becomes higher, so that the halftone density increases. Therefore, the density of yellow is higher on the back surface than on the front surface. Further, when the ink color is black, as shown in FIG. 9, the solid density at a printing rate of 100% increases as the paper surface temperature increases. Conventionally, in order to reduce these density differences, the density differences have been reduced by image processing that shifts the density of the image to be printed according to each ink color. According to the inkjet printing apparatus 1 of the present embodiment, since the difference in the paper surface temperature between the front surface and the back surface is reduced, the density difference between the front surface and the back surface can be reduced, and the image processing of the original image is omitted. be able to.

Further, according to the inkjet printing apparatus 1 of the first embodiment, the front surface of the continuous paper WP is temperature-controlled and the rear surface is cooled so that the paper surface temperature does not become too high. It is possible to prevent the temperature from becoming higher than the head temperature of each print head 25 of the apparatus 5 and the back surface printing apparatus 9. Therefore, ink clogging due to radiant heat from the printing paper is prevented, and the occurrence of nozzle chipping is suppressed.

Further, when the continuous paper WP is heated by an IR heater or heated air, the heating effect is limited to the surface of the paper, so the temperature of the paper may change during printing. On the other hand, according to the inkjet printing apparatus 1 of the first embodiment, since the temperature adjusting roller 39 directly contacts the continuous paper WP to heat and cool it, it is possible to sufficiently heat and cool the inside of the paper. .. As a result, it is possible to prevent temperature changes on the paper surface during printing.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 10 is a block diagram illustrating the control configuration of the inkjet printing apparatus according to the second embodiment. In FIG. 10, the portions denoted by the same reference numerals as those of the first embodiment have the same configuration as that of the first embodiment, and therefore the description thereof is omitted here. Further, the configuration of the inkjet printing apparatus 1 other than the following is the same as that of the first embodiment.

In the first embodiment, the temperature control device 4 is individually temperature-controlled by the first controller 20, and the cooling device 8 is individually temperature-controlled by the second controller 27. In the second embodiment, a configuration in which the first control unit 20 and the second control unit 27 are interlocked to control the temperature of the temperature adjusting device 4 is added to the configuration of the first embodiment.

When the second control unit 27 detects that the paper surface temperature is higher than the target temperature, the second control unit 27 outputs the detected temperature of the second temperature sensor to the first control unit 20. When the detected temperature is input from the second controller 27, the first controller 20 controls the first set value of the chiller unit 31 with a heater by using the detected temperature of the second temperature sensor as a target value. Accordingly, the paper surface temperature during front surface printing can be controlled according to the paper surface temperature during back surface printing, and the difference in gloss between the front surface and the back surface can be reduced.

The inkjet printing apparatus 1 according to the second embodiment is particularly effective when the paper surface is long. In the case of a long paper, the printing time may exceed 1 hour. Due to such continuous printing for a long time, the temperature inside the front surface printing device 5 may be raised by the drying device 23, and the paper surface temperature of the continuous paper WP after the surface drying may be higher than that at the start of printing. As a result, the cooling water may not be cooled to the second set value even if the cooling function of the cooling device 8 is maximized. As a result, the temperature of the continuous paper WP at the time of printing on the back surface is higher than the temperature at the time of printing on the back surface at the start of printing. Even in such a state, the temperature of the continuous paper WP at the time of the back surface printing, which is higher than that at the time of the start of printing, can be raised to the temperature of the continuous paper WP at the time of the front surface printing. Although not, it is possible to reduce the difference in gloss between the front surface and the back surface.

The inkjet printing apparatus 1 according to the second embodiment is also effective for printing thick continuous paper WP. When the thickness of the continuous paper WP is large, heat is stored inside the paper surface, so that cooling of the cooling water by the cooling device 8 may not catch up. As a result, the temperature of the continuous paper WP may not be cooled to the target temperature. Even in such a case, it is possible to reduce the difference in gloss between the front surface and the back surface by raising the paper surface temperature during the front surface printing to the paper surface temperature during the back surface printing.

In the second embodiment described above, after the second controller 27 detects that the paper surface temperature is higher than the target temperature, the first controller 20 adjusts the temperature according to the detection value of the second temperature sensor. Controlled device 4. Alternatively, the first control unit 20 may control the temperature adjustment device 4 from the beginning of printing with the detection value of the second temperature sensor as the target value.

Next, a third embodiment of the present invention will be described with reference to FIGS. 11 and 12. FIG. 11 is an overall configuration diagram showing a schematic configuration of the inkjet printing apparatus according to the third embodiment. FIG. 12 is a configuration diagram of the pretreatment device. In FIG. 11, the portions denoted by the same reference numerals as those of the first embodiment have the same configuration as that of the first embodiment, and therefore the description thereof is omitted here. Further, the configuration of the inkjet printing apparatus 1 other than the following is the same as that of the first embodiment.

The third embodiment has a configuration in which a pretreatment device is added to the configuration of the first embodiment. The pretreatment device 91 is provided between the paper feed unit 3 and the temperature control device 4. The pretreatment device 91 is, for example, a precoat device that applies the treatment liquid to the continuous paper WP.

The pre-processing device 91 includes a driving roller 93, a conveying roller 95, a discharging unit 97 that discharges a processing liquid, a heat roller 99 that dries, and a driving roller 101. The continuous paper WP taken in by the drive roller 93 is guided to the ejection portion 97 by the transport roller 95. The ejection unit 97 ejects, for example, a treatment liquid for improving the familiarity of the ink onto the continuous paper WP. The continuous paper WP from which the treatment liquid has been discharged is dried by the heat roller 99. As a result, the temperature of the continuous paper WP becomes higher than the target temperature. The dried continuous paper WP having an increased temperature is conveyed to the outside by the drive roller 101.

The temperature adjusting device 4 cools the continuous paper WP heated by the heat roller 99 to the target temperature. This allows the temperature of the front surface and the temperature of the back surface of the continuous paper WP to be controlled to the same target temperature. As a result, it is possible to reduce the difference in gloss between the front surface and the back surface and to realize high-quality gloss.

The pretreatment device 91 may be an undercoat device or a calendering device other than the precoat device. The calendering device is a device that scrapes the surface of the paper in order to give the gloss of the paper itself. By scraping the surface of the paper, frictional heat causes the temperature of the paper to rise above the target temperature. The temperature controller 4 cools the paper surface temperature to the target temperature. As a result, the difference in gloss between the front surface and the back surface can be reduced, and high quality gloss can be realized. It should be noted that double-sided printing may be performed by a configuration that combines the second embodiment and the third embodiment.

The present invention is not limited to the above embodiment, but can be modified as follows.

(1) In the above-described embodiment, the temperature adjusting roller connected to the chiller with the heater is provided as the temperature adjusting unit for heating and cooling the continuous paper WP, but the present invention is not limited to such a form. .. That is, it may be a temperature adjusting unit including a thermoelectric cooling roller and a roller with a heater. Further, although the cooling unit is provided with the cooling roller connected to the chiller, the present invention is not limited to such a form. That is, a cooling unit including a thermoelectric cooling roller may be used.

(2) In the above-described embodiment, the first controller 20 controls the temperature of the chiller unit 31 with the heater so that the temperature of the continuous paper WP during printing on the front surface and the temperature of the continuous paper WP during printing on the back surface are the same. 1 The set temperature was controlled, but the present invention is not limited to such a form. An operator empirically sets the first set temperature of the chiller unit 31 with a heater so that the temperature of the continuous paper WP during printing on the front surface and the temperature of the continuous paper WP during printing on the back surface are the same. The temperature of the roller 39 may be adjusted. The second set temperature of the chiller unit 81 at this time may also be set empirically by the operator.

(3) In the embodiment described above, the cooling device 8 is arranged on the downstream side of the reversing device 7, but the cooling device 8 may be arranged on the upstream side of the reversing device 7.

(4) In the above-described embodiment, the ink jet type printing apparatus is taken as an example, but the present invention uses another method as long as it is an apparatus that heats the print medium after the front surface is printed and then prints the back surface. For example, it can be applied to an electrophotographic printing apparatus.

(5) In the above-described embodiment, the continuous paper WP is illustrated as the print medium, but the present invention can be applied to print media such as films other than paper.

DESCRIPTION OF SYMBOLS 1... Inkjet printing device 3... Paper feeding part 5... Front surface printing device 9... Back surface printing device 11... Paper ejection part 18... Temperature sensor 19... 1st printing part 19'... 2nd printing part 20... 1st control part 21... 1st heat roller 26... Temperature sensor 27... 2nd control part 31... Chiller unit with a heater 39... Temperature adjustment roller 81... Chiller unit 83... Cooling roller 91... Pretreatment device WP... Continuous paper

Claims (6)

A printing device that prints on the front and back of a print medium,
A temperature adjusting roller for changing the temperature of the print medium,
A first printing unit which is arranged on the downstream side of the temperature adjusting roller and prints on one surface of the printing medium;
A drying unit that is arranged on the downstream side of the first printing unit and dries the print medium;
A cooling roller arranged on the downstream side of the drying unit for cooling the print medium,
A second printing unit which is arranged on the downstream side of the cooling roller and prints on the other surface of the printing medium;
A temperature control unit for controlling the temperature of the temperature control roller so that the temperature of the print medium when printing on one side and the temperature of the print medium when printing on the other side are the same. Printing device. The printing apparatus according to claim 1,
The printing apparatus, wherein the temperature control unit is a chiller unit with a heater that heats and cools the heat medium flowing through the temperature control roller to a first set temperature. The printing apparatus according to claim 2,
A first temperature sensor that measures the temperature of the print medium on the downstream side of the temperature adjusting roller and on the upstream side of the first printing unit;
A second temperature sensor that measures the temperature of the print medium on the downstream side of the cooling roller and on the upstream side of the second printing unit;
A chiller unit that cools the refrigerant flowing through the cooling roller to a second preset temperature,
The temperature controller controls the first set temperature so that the temperature detected by the first temperature sensor reaches a target temperature, and the second temperature sensor controls the second set temperature so that the temperature detected by the second temperature sensor reaches the target temperature. A printing apparatus comprising a control unit that controls a set temperature. The printing apparatus according to claim 2,
A first temperature sensor that measures the temperature of the print medium on the downstream side of the temperature adjusting roller and on the upstream side of the first printing unit;
A second temperature sensor that measures the temperature of the print medium on the downstream side of the cooling roller and on the upstream side of the second printing unit;
A chiller unit for cooling the coolant flowing through the cooling roller to a second preset temperature,
The temperature controller controls the first set temperature so that the temperature detected by the first temperature sensor is the same as the temperature detected by the second temperature sensor, and the detected value of the second temperature sensor is the target temperature. A printing apparatus comprising a control unit that controls the second set temperature so that The printing apparatus according to any one of claims 1 to 4,
A supply unit that supplies the print medium wound in a roll shape on the most upstream side,
A paper discharge unit that collects the print medium in a roll shape on the most downstream side,
A printing apparatus comprising: The printing apparatus according to any one of claims 1 to 5,
A printing apparatus, comprising: a pretreatment device, which is provided on the upstream side of the temperature control unit to raise the temperature of the print medium by performing a predetermined process on the print medium.

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