JP2019048406A - Inkjet recording device, inkjet recording method and computer program - Google Patents

Abstract

An inkjet recording apparatus capable of performing double-sided printing without interruption. In an inkjet recording apparatus, after recording on a first surface of a printing paper, recording is performed on a second surface of the printing paper. Specifically, in the ink jet recording apparatus 100, while the first surface of the printing paper P is opposed to the ejection surface 13A of the recording head 13, the printing paper P is adsorbed to the transport unit 11 while water-based ink is printed on the printing paper. While discharging to the 1st surface of P, the liquid S is supplied to at least one part of the supply area | region in the 1st surface of the printing paper P. FIG. Further, in the ink jet recording apparatus 100, while the printing paper P is adsorbed to the transport unit 11 with the second surface of the printing paper P facing the ejection surface 13 </ b> A of the recording head 13, water-based ink is applied to the printing paper P. The second surface is discharged. [Selection] Figure 1

Description

  The present invention relates to an inkjet recording apparatus, an inkjet recording method, and a computer program.

  When printing is performed on printing paper using aqueous ink, the printing paper after printing may curl. As a method of preventing curling of the printing paper after printing, for example, it has been proposed to discharge aqueous ink onto the printing paper to which the pretreatment liquid has been applied (see Patent Document 1 described later). Patent Document 1 describes that each of the aqueous ink and the pretreatment liquid contains polyethylene glycol (PEG), and the content of PEG in the pretreatment liquid is compared to the content of PEG in the aqueous ink. Many are described.

JP, 2012-207061, A

  It has been found that, when printing is performed on printing paper according to the method described in Patent Document 1, curling is easily maintained even when time passes on printing paper after printing. Therefore, printing may be interrupted when recording is performed on both sides of the printing paper according to the method described in Patent Document 1.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an ink jet recording apparatus, an ink jet recording method, and a computer program which can be carried out without interrupting double-sided printing.

  The inkjet recording apparatus according to the present invention performs recording on a printing sheet using an aqueous ink. Specifically, in the inkjet recording apparatus according to the present invention, a conveyance unit that conveys the printing paper while suctioning it, a recording head that discharges the aqueous ink onto the printing paper, and a distribution coefficient LogP of 0.0 or more and 1.5 The printing apparatus includes a liquid supply unit that supplies the following liquid to the printing sheet, and a control unit that controls the transport unit, the recording head, and the liquid supply unit. The distribution coefficient LogP is a common logarithm value of the n-octanol / water distribution coefficient. The control unit is configured to perform the recording on the first side of the printing sheet, and then perform the recording on the second side of the printing sheet positioned opposite to the first side. And the liquid supply unit. The control unit is configured to discharge the water-based ink to the first surface while the print sheet is adsorbed by the transport unit in a state where the first surface faces the discharge surface of the recording head. Controlling the recording head and controlling the liquid supply unit such that the liquid is supplied to at least a part of the supply area on the first surface. The control unit is configured to perform the recording so that the water-based ink is discharged to the second surface while the printing sheet is adsorbed by the transport unit with the second surface facing the discharge surface. Control the head. The supply area is located at the periphery of the first surface and extends along the longitudinal direction of the printing paper.

  In the inkjet recording method according to the present invention, recording is performed on a printing sheet using an aqueous ink. More specifically, in the inkjet recording method according to the present invention, after performing recording on the first side of the printing paper, and after performing recording on the first side, the printing located on the opposite side to the first side Recording on the second side of the sheet. In the recording on the first surface, the water-based ink is discharged to the first surface while the printing paper is adsorbed by the transport unit with the first surface facing the discharge surface of the recording head. And supplying liquid to at least a portion of the supply area on the first surface. The recording on the second surface discharges the water-based ink to the second surface while the printing paper is adsorbed by the transport unit with the second surface facing the discharge surface. Including. The distribution coefficient LogP of the liquid is 0.0 or more and 1.5 or less. The distribution coefficient LogP is a common logarithm value of the n-octanol / water distribution coefficient. The supply area is located at the periphery of the first surface and extends along the longitudinal direction of the printing paper.

  The computer program according to the present invention comprises recording on the first side of the printing paper, and recording on the first side, in a computer constituting an ink jet recording apparatus for recording on printing paper using aqueous ink. And performing recording on the second side of the printing paper located opposite to the first side. In the recording on the first surface, the water-based ink is discharged to the first surface while the printing paper is adsorbed by the transport unit with the first surface facing the discharge surface of the recording head. And supplying liquid to at least a portion of the supply area on the first surface. The recording on the second surface discharges the water-based ink to the second surface while the printing paper is adsorbed by the transport unit with the second surface facing the discharge surface. Including. The distribution coefficient LogP of the liquid is 0.0 or more and 1.5 or less. The distribution coefficient LogP is a common logarithm value of the n-octanol / water distribution coefficient. The supply area is located at the periphery of the first surface and extends along the longitudinal direction of the printing paper.

  According to the present invention, double-sided printing can be performed without interruption.

FIG. 1 is a view showing the configuration of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram showing a control system of the ink jet recording apparatus according to an embodiment of the present invention. (A)-(c) is a top view which shows the 1st surface of printing paper, respectively. It is a flowchart which shows the procedure of the process which the inkjet recording device which concerns on one Embodiment of this invention performs.

  Hereinafter, an ink jet recording apparatus, an ink jet recording method, and a computer program according to an embodiment of the present invention will be sequentially described with reference to the drawings. In the drawings, the same reference numerals represent the same or corresponding parts. The dimensional relationships such as length, width, thickness, depth and the like have been changed as appropriate for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships.

[Ink jet recording apparatus]
The configuration of the inkjet recording apparatus 100 will be described with reference to FIG. FIG. 1 is a view showing the configuration of the ink jet recording apparatus according to the present embodiment. In FIG. 1, the upper side in the vertical direction is described as Z1, and the lower side in the vertical direction is described as Z2. The direction from Z1 to Z2 is orthogonal to the direction from X1 to X2.

  The inkjet recording apparatus 100 performs recording on the printing paper P using an aqueous ink. The inkjet recording apparatus 100 may be a monochrome printer or a color printer as long as double-sided printing is possible. The printing paper P may be, for example, any of plain paper, copy paper, recycled paper, thin paper, thick paper, or glossy paper.

  Specifically, the inkjet recording apparatus 100 includes a first conveyance unit (conveyance unit) 11, a recording head 13, a second conveyance unit 15, a sheet reversing unit 17, a liquid supply unit 19, and a sheet feeding cassette 21; The manual feed tray 23, the discharge tray 25, and the control unit 51 are provided. Hereinafter, the configuration of the inkjet recording apparatus 100 will be specifically described.

  The first conveyance unit 11 conveys the print sheet P supplied from the sheet feeding cassette 21 or the manual feed tray 23 along a sheet conveyance direction (direction from X2 side to X1 side) while adsorbing. Specifically, the first conveyance unit 11 includes a drive roller 111, a driven roller 113, an endless conveyance belt 115, and a suction unit 117. The conveying belt 115 is rotatably stretched by the driving roller 111 and the driven roller 113. The transport belt 115 is formed with a large number of suction holes. A suction unit 117 is provided on the inner side of the conveyance belt 115 (the back side of the conveyance surface 115A of the conveyance belt 115). As the drive roller 111 and the driven roller 113 rotate, the transport belt 115 rotates. In addition, the negative pressure is generated by the suction unit 117, whereby the print sheet P is attracted to the conveyance surface 115 </ b> A of the conveyance belt 115. In this manner, the printing paper P attracted to the conveyance surface 115A of the conveyance belt 115 is conveyed along the paper conveyance direction.

  The recording head 13 is provided above the first conveyance unit 11 (more specifically, the conveyance surface 115A of the conveyance belt 115) in the vertical direction, and water ink is used as the printing paper P based on the image data and the printing conditions. Discharge on one side. More specifically, the recording head 13 discharges the water-based ink onto one side of the printing paper P attracted to the conveyance surface 115A of the conveyance belt 115 based on the image data and the printing conditions. For example, in the recording head 13, a plurality of nozzles are formed. The nozzles are respectively opened at the lower surface (ejection surface) 13A of the recording head 13 and eject the aqueous ink onto one surface of the printing paper P. The aqueous ink is stored in a tank (ink tank) of the inkjet recording apparatus 100, and supplied from the ink tank to the recording head 13 when necessary.

  The second conveyance unit 15 conveys the printing paper P conveyed from the first conveyance unit 11 along a paper conveyance direction (a direction from the X2 side to the X1 side) while suctioning. The second conveyance unit 15 is configured in the same manner as the first conveyance unit 11 and functions in the same manner as the first conveyance unit 11. Specifically, the second conveyance unit 15 includes a drive roller 151, a driven roller 153, an endless conveyance belt 155, and a suction unit 157. The conveyance belt 155 rotates as the drive roller 151 and the driven roller 153 rotate. Further, as the suction unit 157 generates a negative pressure, the print sheet P is attracted to the conveyance surface of the conveyance belt 155. In this way, the printing paper P attracted to the conveyance surface of the conveyance belt 155 is conveyed along the paper conveyance direction.

  The aqueous ink discharged onto the printing paper P dries while the printing paper P passes through the second conveyance unit 15. The print sheet P that has passed through the second conveyance unit 15 is discharged to the discharge tray 25 or conveyed to the sheet reversing unit 17.

  When duplex printing is performed, the sheet reversing unit 17 reverses the front and back of the printing sheet P on which aqueous ink is discharged only on one side. Specifically, when the sheet reversing unit 17 reverses the sheet conveyance direction of the printing sheet P, the front and back of the printing sheet P is reversed. The print sheet P with the front and back reversed by the sheet reversing unit 17 is conveyed to the first conveyance unit 11.

  The liquid supply unit 19 supplies a predetermined liquid (hereinafter, described as “liquid S”) to one side of the printing paper P. More specifically, the liquid supply unit 19 supplies the liquid S to one side of the printing paper P adsorbed on the conveyance surface 115 A of the conveyance belt 115. Preferably, the liquid supply unit 19 is provided above the first conveyance unit 11 (more specifically, the conveyance surface 115A of the conveyance belt 115) in the vertical direction. More preferably, the liquid supply unit 19 is provided upstream of the recording head 13 in the sheet conveyance direction. The liquid S is preferably accommodated in a tank (liquid tank) of the inkjet recording apparatus 100, and is preferably supplied from the liquid tank to the liquid supply unit 19 when necessary.

The aqueous ink and the liquid S will be described.
As the water-based ink, a water-based ink known as a water-based ink used when recording on printing paper using an ink jet recording apparatus can be used without particular limitation. Therefore, the aqueous ink preferably contains an aqueous medium containing water and a plurality of pigment particles dispersed in the aqueous medium.

  The liquid S is a liquid having a distribution coefficient LogP of 0.0 or more and 1.5 or less. Partition coefficient Log P is a common logarithm value of n-octanol / water partition coefficient P, and it is described in JIS Z 7260-107: 2000 [Measurement of partition coefficient (1-octanol / water)-flask shaking method] Measured in compliance. Since the distribution coefficient LogP of the liquid S is 0.0 or more and 1.5 or less, the liquid S has stronger hydrophobicity than the aqueous ink. When the liquid S is composed of two or more kinds of liquids, it is preferable that the distribution coefficient LogP of each of the two or more kinds of liquids constituting the liquid S be 0.0 or more and 1.5 or less.

  The control system of the inkjet recording apparatus 100 will be described with reference to FIG. FIG. 2 is a block diagram showing a control system of the ink jet recording apparatus according to the present embodiment. The control system of the inkjet recording apparatus 100 includes a storage device 31, an input display unit 33, an interface 41, and a control unit 51.

  The storage device 31 is configured of non-volatile memory. For example, the storage device 31 is preferably a hard disk. The storage device 31 preferably stores, for example, image data for printing, a control program related to various controls, and data used in the control program. As the control program, for example, a program for controlling recording on the printing paper P (hereinafter, referred to as "recording control program") can be mentioned. Preferably, the recording control program includes a liquid supply program and a recording execution program. The liquid supply program means a program for supplying the liquid S to the printing paper P adsorbed on the first conveyance unit 11 (more specifically, the conveyance surface 115A of the conveyance belt 115). The recording execution program means a program for executing recording on the printing paper P. As data used in the control program, for example, the discharge amount of the aqueous ink to the printing area or the supply amount of the liquid S to the supply region (hereinafter simply referred to as “supply amount of the liquid S”) may be mentioned. Can.

  The input display unit 33 has an input unit 35 and a display unit 37. The input unit 35 receives a signal input by the user. The display unit 37 displays various types of information.

  The interface 41 can communicate the control unit 51 with each of the storage device 31, the input display unit 33, the recording head 13, the sheet reversing unit 17, the liquid supply unit 19, the first conveyance unit 11, and the second conveyance unit 15. Connect to The interface 41 communicably connects the control unit 51 and an external device. Here, the “external device” means a device connected to the control unit 51 via a communication network. As a communication network, the Internet or LAN is mentioned, for example.

  The control unit 51 includes a CPU 53, a ROM 55, and a RAM 57. The CPU 53 is a processor that performs various arithmetic processing. The ROM 55 is a non-volatile memory. A control program for causing the CPU 53 to execute various arithmetic processing is stored in advance in the ROM 55. The recording control program may be stored in the ROM 55 instead of the storage device 31. The RAM 57 is a volatile memory and temporarily stores various kinds of arithmetic processing executed by the CPU 53. The control unit 51 controls the operation of the inkjet recording apparatus 100 by the CPU 53 executing a control program (a control program stored in advance in the storage device 31 or the ROM 55).

  The control unit 51 is configured to control recording on the printing paper P, and more specifically, is configured to control at least the first conveyance unit 11, the recording head 13, and the liquid supply unit 19. ing. The control unit 51 is preferably embodied by the CPU 53 capable of executing the recording control program. Further, at the time of a request for recording on the printing paper P, the control unit 51 preferably initializes various parameters used to control the recording on the printing paper P. When the user operates the input unit 35 of the input display unit 33, recording on the printing paper P may be requested. Recording on the print paper P may be requested by the user operating an external device (for example, a personal computer). Examples of the request for recording on the printing paper P include when the power of the inkjet recording apparatus 100 is switched from OFF to ON or when the inkjet recording apparatus 100 returns from the power saving mode.

  Hereinafter, the control unit 51 will be described more specifically. In the following, the side of the printing paper P on which recording is first performed in duplex printing will be referred to as the “first side of the printing paper P”. The surface of the printing paper P located on the opposite side to the first surface of the printing paper P is referred to as “the second surface of the printing paper P”. Recording on the first side of the printing paper P using an aqueous ink is referred to as “front side printing”. Printing on the second side of the printing paper P using water-based ink after front side printing is referred to as “back side printing”.

  The control unit 51 controls at least the first conveyance unit 11, the recording head 13, and the liquid supply unit 19 to perform recording on the first side of the printing paper P when the double-sided printing is requested, and then performs the second printing paper P It is configured to record on the surface.

  Specifically, while the printing paper P is being attracted to the first conveyance unit 11 in a state where the first surface of the printing paper P faces the ejection surface 13A of the recording head 13 (hereinafter, “the front side printing The recording head 13 is controlled to discharge the water-based ink onto the first surface of the printing paper P). In addition, while the printing paper P is adsorbed by the first conveyance unit 11 in a state where the second surface of the printing paper P faces the ejection surface 13A of the recording head 13 (hereinafter, “the printing in the reverse side printing is performed The recording head 13 is controlled to discharge the water-based ink onto the second surface of the printing paper P). The control unit 51 may be configured to eject aqueous ink based on image data and printing conditions stored in the storage device 31 or the ROM 55, or based on image data and printing conditions input from an external device. It may be configured to eject a water-based ink.

  Further, the control unit 51 controls the liquid supply unit 19 to supply the liquid S to at least a part of the supply area on the first surface of the printing paper P while the printing paper P is adsorbed in front surface printing. Is configured. The supply area is located at the periphery of the first surface of the printing paper P, and more specifically, at each of both ends of the first surface of the printing paper P in the lateral direction. Thus, the supply area is a band-like area extending in the longitudinal direction of the printing paper P. The control unit 51 may be configured to continuously supply the liquid S in the longitudinal direction of the supply area, or may be configured to intermittently supply the liquid S in the longitudinal direction of the supply area. Hereinafter, supplying the liquid S to at least a part of the supply area on the first surface of the printing paper P may be referred to simply as “supplying the liquid S”.

  Generally, when recording on printing paper using an inkjet recording apparatus, the use of water-based ink has been proposed from the viewpoint of reducing the environmental load. However, when recording is performed on printing paper using an aqueous ink, water is absorbed by the printing paper, and therefore swelling of cellulose fibers contained in the printing paper (hereinafter simply referred to as "swelling of cellulose fibers"), or Cleavage of intermolecular hydrogen bonds of cellulose fibers is likely to occur. Therefore, curling (convex curling) that protrudes in the direction from the non-printing surface toward the printing surface is likely to occur on the printing paper on which the aqueous ink is discharged.

  When the reverse side printing is performed on the printing sheet in which the convex curling has occurred, the peripheral edge of the printing sheet conveyed to the first conveyance unit is likely to be positioned vertically above the center. Therefore, when the print sheet is conveyed to the first conveyance unit, the front end in the sheet conveyance direction of the print sheet may collide with the recording head. If the recording head is damaged due to the printing paper colliding with the recording head, it may be difficult to eject the aqueous ink. Therefore, printing may be interrupted (occurrence of feeding failure: first failure). In addition, when the print sheet passes through the first transport unit, the trailing edge of the print sheet in the sheet transport direction may rub the ejection surface. As a result, the aqueous ink may contaminate the ejection surface. When the water-based ink that contaminates the ejection surface blocks the opening of the nozzle, printing is interrupted (occurrence of feeding failure: first failure). In addition, the water-based ink contaminating the discharge surface may adhere to the non-printing area of the printing paper P (occurrence of image defect: second failure).

  As a method of preventing the occurrence of the first and second defects, for example, it is conceivable to separate the discharge surface from the conveyance surface (more specifically, the conveyance surface of the conveyance belt included in the first conveyance unit). However, in this method, image defects may occur. Also, satellite drops may occur. When the generated satellite droplets adhere to the non-printing area of the printing paper, an image defect occurs. When the generated satellite droplets adhere to electrical connection sites in the ink jet recording apparatus, an electrical short circuit occurs.

  Another possible method of preventing the occurrence of the first and second defects is to mechanically crease the printing paper after surface printing. However, in this method, paper jams are likely to occur, and therefore, sheet feeding defects are likely to occur.

  On the other hand, in the inkjet recording apparatus 100, while the printing paper P is adsorbed in front side printing, the aqueous ink is discharged onto the first surface of the printing paper P, and the liquid S is supplied. Here, since the liquid S has stronger hydrophobicity than the water-based ink, it easily penetrates in the planar direction of the printing paper P and in the thickness direction of the printing paper P as compared with the water-based ink. Therefore, supplying the liquid S prevents the aqueous ink from being localized in the printing paper P (hereinafter referred to as "the printing paper P after surface printing") in which the aqueous ink is discharged to the first surface. it can.

  If localization of the water-based ink can be prevented in the printing paper P after surface printing, the water-based ink is easily dried on the printing paper P after surface printing. Thereby, even if the cellulose fiber swells due to water being absorbed by the printing paper P, the swollen cellulose fiber is in its original state (before surface printing) in a relatively short time (for example, within 30 seconds). State) easy to return to. In addition, even if the intermolecular hydrogen bond of the cellulose fiber is broken due to water being absorbed by the printing paper P, the broken intermolecular hydrogen bond is likely to be recombined in a relatively short time. From these things, even if the printing paper P after surface printing is curled due to the water-based ink being discharged to the first surface, the printing paper conveyed to the first conveyance unit 11 at the time of back surface printing It is possible to prevent the curl from remaining in P. Therefore, it is possible to prevent the occurrence of the first and second defects when the back side printing is performed. Therefore, if the inkjet recording apparatus 100 is used, it can implement without interrupting double-sided printing (hereinafter, this effect may be described as “desired effect”). For example, if the inkjet recording apparatus 100 is used, double-sided printing can be performed at high speed and continuously.

  As described above, in the inkjet recording apparatus 100, even if the printing paper P after surface printing is curled due to the water-based ink being discharged to the first surface, the curling is performed in a relatively short time. It can be removed from the printing paper P later. Therefore, after surface printing, it is possible to transport the printing paper P with almost no remaining curl. Therefore, unlike the case where the printing paper is mechanically creased after surface printing, the occurrence of paper jam during conveyance of the printing paper P can be prevented.

  When a liquid having a distribution coefficient LogP too small (for example, a liquid having a distribution coefficient LogP of less than 0.0) is used as the liquid supplied to at least a part of the supply region, the liquid is more hydrophobic than the aqueous ink. Since it is difficult to have the property, it is difficult to penetrate the printing paper P. Therefore, when the liquid having a distribution coefficient LogP too small is supplied, the aqueous ink may be localized in the printing paper P after surface printing. Therefore, it may be difficult to obtain a desired effect (refer to the evaluation result of the inkjet recording apparatus D-4 in Experimental Example 1 described later). On the other hand, when a liquid having a distribution coefficient LogP too large is used as the liquid supplied to at least a part of the supply area, the liquid has very strong hydrophobicity compared to the aqueous ink, and thus the aqueous ink in the printing paper P Easy to repel. Therefore, when the liquid having a distribution coefficient LogP too large is supplied, the ink may blur in the obtained image (see the evaluation result of the inkjet recording apparatus D-3 in Experimental Example 1 described later).

  Preferably, the control unit 51 controls the liquid supply unit 19 to supply the liquid S while discharging the water-based ink to the first surface of the printing paper P while the printing paper P is adsorbed in front side printing. It is configured to If the liquid S is supplied before the aqueous ink is discharged to the first surface of the printing paper P, the liquid S is printed compared to the case where the liquid S is supplied after the aqueous ink is discharged to the first surface of the printing paper P It easily penetrates in the plane direction of the sheet P and the thickness direction of the printing sheet P. This can effectively prevent the aqueous ink from being localized in the printing paper P after surface printing. Therefore, if the liquid S is supplied before the aqueous ink is discharged to the first surface of the printing paper P, a desired effect can be easily obtained. This control can be easily realized by arranging the liquid supply unit 19 upstream of the recording head 13 in the sheet conveyance direction.

  The supply area is specifically described with reference to FIGS. 3 (a) to 3 (c). FIG. 3A is a plan view showing the first surface of the printing paper P. FIG. FIGS. 3B and 3C are each a plan view showing a part of the first surface of the printing paper P in an enlarged manner. In each of FIGS. 3A to 3C, the longitudinal direction of the printing paper P is described as D1, and the lateral direction of the printing paper P is described as D2. Below, supply area R1 is first demonstrated using Fig.3 (a).

  Preferably, as shown in FIG. 3A, the supply area R1 has a length extending inward in the short direction of the printing paper P from each end of the printing paper P in the short direction of the printing paper P, as shown in FIG. It is located at a site separated by L1 or more and L2 or less. An example of a preferable combination of the length L1 and the length L2 is a combination in which the length L1 is 3 mm and the length L2 is 40 mm regardless of the size of the printing paper P.

  As a result of experiments conducted by the present inventors, when the water-based ink is discharged to a predetermined printing area (hereinafter referred to as "printing area Rp") on the first side of the printing paper, the printing paper after surface printing curls. It was easy to do. The print area Rp is positioned at a portion of the first surface of the print sheet P, which is spaced from the at least one end in the short direction of the print sheet P to the inner side of the print sheet P by 3 mm to 40 mm. Thus, the print area Rp is included in the supply area R1. Therefore, if the liquid S is supplied to at least a part of the supply area R1, localization of the aqueous ink in the print area Rp can be effectively prevented. Therefore, a desired effect can be easily obtained. Therefore, the supply area R1 may be located at a portion of the first surface of the printing paper P which is spaced 3 mm or more and 40 mm or less away from each end of the printing paper P in the width direction preferable.

More preferably, the control unit 51 controls the liquid supply unit when the discharge amount of the aqueous ink to the print area Rp (hereinafter referred to simply as the “discharge amount of the aqueous ink”) is 10 cm ³ / m ² or more. It is configured to control 19 to supply the liquid S. As a result of experiments conducted by the present inventors, when the ejection amount of the aqueous ink is 10 cm ³ / m ² or more, the printing paper P after the surface printing is significantly curled. Therefore, if the liquid S is supplied when the discharge amount of the aqueous ink is 10 cm ³ / m ² or more, the desired effect is easily obtained. The control unit 51 is preferably configured to determine whether the discharge amount of the aqueous ink is 10 cm ³ / m ² or more based on the image data. Thereby, this control can be easily realized. The image data used for the determination may be image data stored in the storage device 31 or the ROM 55, or may be image data input from an external device.

The present inventors consider the following matters as the reason why the printing paper P after surface printing tends to curl when the aqueous ink is discharged to at least a part of the printing region Rp.
Specifically, when the water-based ink is discharged to the vicinity of the short-side end of the printing paper on the first surface of the printing paper, the portion where the water-based ink is recorded (recording portion) and the width direction of the printing paper The length between the end (hereinafter simply referred to as "length L") is too short. Therefore, even if the printing sheet after front surface printing curls, the first and second defects hardly occur when back surface printing is performed.

  On the other hand, when the water-based ink is discharged to the inside in the width direction of the printing paper of the first surface of the printing paper, the length L is too long. As a result, the mass of the portion of the printing sheet located on the short side end portion side of the printing sheet rather than the recording portion becomes too large, which makes it difficult to maintain the shape of the portion. Therefore, in this case, the print sheet after surface printing is unlikely to curl.

  However, when the aqueous ink is ejected to at least a part of the print area Rp, the length L is not too short or too long. Therefore, the print sheet after surface printing is likely to curl.

  The relationship between the supply region R1 and the supply location R2 will be described with reference to FIGS. 3 (b) and 3 (c). The supply point R2 means a point in the supply area R1 where the liquid supply unit 19 actually supplies the liquid S. In each of FIG. 3B and FIG. 3C, the supply point R2 is hatched.

  Supply point R2 may be located in a part in the longitudinal direction of supply area R1. In this case, the liquid S is preferably supplied to a portion of the supply region R1 including both longitudinal ends of the supply region R1. More specifically, the liquid S may be supplied to a part of the supply area R1 excluding the longitudinal center of the supply area R1 (FIG. 3 (b)), or the liquid S may be spaced apart from each other in the longitudinal direction of the supply area R1. It may be supplied open (FIG. 3 (c)). Supply point R2 may be located in a portion in the lateral direction of supply area R1. The inventors have confirmed that if the dimension W of the supply location R2 in the short direction of the printing paper P is about 25 mm, it is easy to obtain the desired effect. The control unit 51 controls the liquid supply unit 19 to change the position of the supply location R2 in the supply region R1. In addition, the planar shape of supply location R2 in the 1st surface of printing paper P is not limited to the shape shown to each of FIG.3 (b) and FIG.3 (c).

Hereinafter, the control unit 51 will be described more specifically.
Preferably, the control unit 51 is being conveyed based on the size of the printing paper P selected when the user requests duplex printing, or based on the position of the paper guide in the manual feed tray 23 adjusted by the user when duplex printing is requested. The longitudinal direction and the lateral direction of the printing paper P are determined. Thereby, the liquid S can be accurately supplied to at least a part of the supply region R1. When the inkjet recording apparatus 100 has a sensor for detecting the size of the printing paper P, the control unit 51 determines the longitudinal direction and the lateral direction of the printing paper P being conveyed based on the detection result by the sensor. It may be configured.

  Preferably, the control unit 51 is configured to control the liquid supply unit 19 so that the liquid S is not supplied while the printing paper P is adsorbed in the back surface printing. As a result, the supply amount of the liquid S can be minimized, so that the ink can be effectively prevented from bleeding in the obtained image. In addition, if the liquid S is not supplied while the printing paper P is adsorbed in the back side printing, the consumption amount of the liquid S can be minimized, so that the cost required for the double-sided printing can also be suppressed low. The present inventors believe that the first and second defects are unlikely to occur even if the printing paper P after backside printing curls due to the water-based ink being discharged to the second side. ing.

Preferably, the control unit 51 is configured to set the supply amount of the liquid S to a numerical value selected from the range of 0.2 g / m ² or more and 1.2 g / m ² or less based on the type of printing paper P. There is. More preferably, the control unit 51 is configured to set the supply amount of the liquid S to a relatively large value when the thickness of the printing paper P is relatively small, and the thickness of the printing paper P is relatively large. In this case, the supply amount of the liquid S is set to a relatively small value. More preferably, the control unit 51 is configured to set the supply amount of the liquid S to a relatively large value when the basis weight of the printing paper P is relatively small, and the basis weight of the printing paper P is compared In the case of a large value, the supply amount of the liquid S is set to a relatively small value.

For example, the control unit 51 may be configured to set the supply amount of the liquid S based on the type of the printing paper P input by the user. This control can be easily realized if a table indicating the correspondence between the product number of the printing paper P and the thickness and basis weight of the printing paper P is stored in the storage device 31 or the ROM 55. When the inkjet recording apparatus 100 has a sensor that detects the type of the printing paper P, the control unit 51 may be configured to set the supply amount of the liquid S based on the detection result by the sensor. The type of printing paper P includes the thickness of the printing paper P and the basis weight of the printing paper P. The control unit 51 is configured to set the supply amount of the liquid S to a numerical value selected from the range of 0.2 g / m ² or more and 1.2 g / m ² or less based on the supply amount of the liquid S input by the user. It may be When the supply amount of the liquid S is too small, it may be difficult to obtain a desired effect. If the supply amount of the liquid S is too large, the ink may blur in the obtained image.

  The liquid supply unit 19 may be, for example, a roller having the liquid S adhered to the circumferential surface, or a sponge impregnated with the liquid S, but is preferably a sprayer containing the liquid S. If the liquid supply unit 19 is a sprayer, the liquid S can be supplied to a desired position even when the size of the printing paper P is changed. In addition, if the liquid supply unit 19 is a sprayer, the liquid S can be supplied without sandwiching the printing paper P with a predetermined member, so that the portion of the printing paper P which is not the supply region R1 (for example, the printing paper P It is possible to prevent adhesion to the second surface). More preferably, the liquid supply unit 19 is a nozzle head that discharges the liquid S to at least a part of the supply region R1. Thereby, the supply accuracy of the liquid S can be further enhanced. The nozzle head is preferably configured in the same manner as the recording head 13. When the liquid supply unit 19 is a nozzle head, it is preferable to use, of the liquid S, a liquid having a viscosity of 1 mPa · s to 10 mPa · s. The viscosity of the liquid S means the viscosity of the liquid S at 25 ° C., and is measured in accordance with the method described in “JIS Z 8803: 2011 (Method of measuring viscosity of liquid)”.

  The inkjet recording apparatus 100 may further include a curl correction unit on the downstream side of the second conveyance unit 15 in the sheet conveyance direction and on the upstream side of the sheet reversing unit 17 in the sheet conveyance direction. Even if the inkjet recording apparatus 100 includes a curl correction unit, a desired effect can be easily obtained by supplying the liquid S while the printing paper P is adsorbed in surface printing.

  Moreover, the implementation method of the control part 51 is not limited to the above-mentioned method. For example, the control unit 51 may be embodied in cooperation with an electronic circuit and / or a program provided outside the inkjet recording apparatus 100. More specifically, the control unit 51 may be embodied as a user executes or downloads a print job control program held in a predetermined server on a communication network.

[Ink jet recording method]
Hereinafter, an inkjet recording method using the inkjet recording apparatus 100 will be described. When the user requests double-sided printing, the control unit 51 executes a recording control program. Specifically, when the user requests double-sided printing, the control unit 51 sequentially executes front-side printing and back-side printing. When the CPU 53 executes the recording control program (the recording control program stored in the storage device 31 or the ROM 55), the front side printing and the back side printing can be performed in order.

  Hereinafter, an example of the recording control program will be described with reference to FIG. FIG. 4 is a flowchart showing a preferable example of the procedure of the recording control program. The CPU 53 can execute the recording control program to perform the process shown in FIG.

  Specifically, when the user requests double-sided printing, the control unit 51 performs front-side printing. Specifically, first, the control unit 51 supplies the print sheet P from the paper feed cassette 21 or the manual feed tray 23 into the inkjet recording apparatus 100. Next, the control unit 51 transports the printing paper P supplied into the inkjet recording apparatus 100 to the first conveyance unit 11 and then causes the suction unit 117 to adsorb the printing paper P. Subsequently, the process proceeds to step S101.

  In step S101, the control unit 51 controls the liquid supply unit 19 to supply the liquid S from the liquid supply unit 19 to at least a part of the supply region R1. Subsequently, the process proceeds to step S102.

  In step S102, the control unit 51 controls the recording head 13 to discharge the aqueous ink from the recording head 13 to the first surface of the printing paper P. Subsequently, the control unit 51 causes the printing paper P after the front surface printing to be transported from the first transport unit 11 to the second transport unit 15 and then transported to the paper reversing unit 17. Thereafter, the process proceeds to step S103.

  In step S103, the control unit 51 controls the paper reversing unit 17 to reverse the front and back of the printing paper P after front surface printing. Thereafter, the process proceeds to step S104.

  In step S104, the control unit 51 performs back side printing. Specifically, the control unit 51 first causes the suction unit 117 to adsorb the printing paper P after the front surface printing after being conveyed to the first conveyance unit 11. Next, the control unit 51 controls the recording head 13 to discharge the aqueous ink from the recording head 13 to the second surface of the printing paper P. Subsequently, the control unit 51 transports the printing paper P after duplex printing from the first transport unit 11 to the second transport unit 15, and then discharges the printing paper P to the discharge tray 25. Thus, the process shown in FIG. 4 ends.

  Note that step S101 may be performed after step S102. However, if step S102 is performed after step S101, a desired effect can be easily obtained.

Also, a predetermined determination step may be performed before step S101. In the predetermined determination step, the control unit 51 determines whether the discharge amount of the aqueous ink in step S102 is to be 10 cm ³ / m ² or more. Then, when it is determined that the discharge amount of the aqueous ink in step S102 is to be 10 cm ³ / m ² or more, it is difficult to obtain the desired effect unless the liquid S is supplied, so the process proceeds to step S101. move on. On the other hand, if it is determined that the discharge amount of the aqueous ink in step S102 is not scheduled to be 10 cm ³ / m ² or more, the desired effect may be obtained without supplying the liquid S. It progresses to S102.

[Computer program]
The function related to control of the inkjet recording apparatus 100 may be realized by a computer program (software). The computer program according to the present embodiment causes a computer constituting the inkjet recording apparatus 100 to execute a recording control program.

  The program (recording control program) executed by the control unit 51 may be stored in a computer readable recording medium and may be distributed. Further, the recording control program may be held by a predetermined server on the communication network so that the user can execute or download the recording control program.

  When the recording control program includes a liquid supply program and a recording execution program, both the liquid supply program and the recording execution program may be stored in a computer readable recording medium, or a predetermined server on a communication network. May be held by Further, one of the liquid supply program and the recording execution program may be stored in a computer readable recording medium, and the other may be held by a predetermined server on the communication network.

[Example of experiment]
Hereinafter, experimental examples 1 and 2 will be described. In Example 1, the function and effect of the ink jet recording apparatus were verified by changing the material of the liquid S. In Experimental Example 2, the operation and effects of the ink jet recording apparatus were verified by changing the amount of liquid S supplied.

  In Experimental Examples 1 and 2, the evaluation results (values indicating the shape, physical properties, etc.) of the powder containing a plurality of particles are not limited, and the number average of the values measured for a considerable number of particles. It is. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic mean of the obtained measurement values is used as the evaluation value.

<Preparation Method of Aqueous Ink>
Below, the preparation method of the water-based ink used by each of Experimental example 1 and 2 is demonstrated first.

(Synthesis of Coating Resin A)
First, a coating resin A (hereinafter simply referred to as "resin A") was synthesized. Specifically, a stirrer, a nitrogen inlet tube, a condenser (agitator), and a dropping funnel were set in a four-necked flask (volume: 1000 mL). Next, the flask was charged with 100 g of isopropyl alcohol and 300 g of methyl ethyl ketone. Heated reflux at 70 ° C. while bubbling nitrogen through the contents of the flask.

  In addition, 40.0 g of styrene, 10.0 g of methacrylic acid, 40.0 g of methyl methacrylate, 10.0 g of n-butyl acrylate, and 0.4 g of azobisisobutyronitrile (AIBN, The polymerization initiator was mixed to obtain a monomer solution. While heating to reflux at 70 ° C., the monomer solution was dropped into the flask over about 2 hours. After the dropwise addition, the mixture was heated to reflux at 70 ° C. for 6 hours.

  A methyl ethyl ketone solution containing 0.2 g of AIBN was dropped into the flask over 15 minutes. After the dropwise addition, the mixture was heated to reflux at 70 ° C. for 5 hours. Thus, resin A (styrene-acrylic acid resin) was obtained. The obtained resin A had a mass average molecular weight (Mw) of 20000 and an acid value of 100 mg KOH / g.

The mass average molecular weight of the resin A was measured using gel filtration chromatography (“HLC-8020 GPC” manufactured by Tosoh Corporation) under the following conditions.
Column: "TSKgel SuperMultipore HZ-H" (4.6 mm ID × 15 cm semi-micro column) manufactured by Tosoh Corporation
Number of columns: 3 Eluent: Tetrahydrofuran Flow rate: 0.35 mL / min Sample injection amount: 10 μL
Measurement temperature: 40 ° C
Detector: IR detector The standard curve is F-40, F-20, F-4, F-1, A-5000, A-2500, and A-1000 from TSKgel standard polystyrene manufactured by Tosoh Corporation. Were selected from the following 7 and n-propylbenzene.

  Moreover, the acid value of the resin A is described in “JIS (Japanese Industrial Standard) K 0070-1992 (Test method of acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical product)”. Asked in accordance with the method.

(Preparation of pigment dispersion L)
Next, pigment dispersion L was prepared using resin A. Table 1 shows the composition of the pigment dispersion L.

Specifically, 15.0% by mass of resin A and 25.0% by mass of a vessel (volume: 0.6 L) of a media type dispersing machine ("Dinomill" manufactured by Willy-e-Bachkofen (WAB)) Carbon black ("MA100" manufactured by Mitsubishi Chemical Corporation), 10.0% by mass of glycerin and ion-exchanged water (remaining amount) were charged. Next, 1.5 times the mass media (0.5 mm diameter glass beads) to the mass of the contents of the vessel was added to the vessel. While cooling the vessel with water at a temperature of 10 ° C and a peripheral speed of 8 m / s, the media type disperser is set so that the volume median diameter (D ₅₀ ) of the pigment particles falls within the range of 70 nm to 130 nm. The contents of the vessel were kneaded using this. Thus, pigment dispersion L was obtained.

(Mixing of pigment dispersion L with other ink components)
Subsequently, the pigment dispersion L and the other ink components were mixed. Table 2 shows the composition of the aqueous ink. In Table 2, surfactant means "Orfin (registered trademark) E1010" manufactured by Nisshin Chemical Industry Co., Ltd. "Olfin E1010" contains an ethylene oxide adduct of an acetylene diol.

  Specifically, the materials described in Table 2 were added to the beaker in the amounts described in Table 2. The contents of the beaker were stirred at a rotational speed of 400 rpm using a stirrer ("Three-One Motor BL-600" manufactured by Shinto Scientific Co., Ltd.) to uniformly mix the contents of the beaker. The mixture was filtered using a filter (pore diameter 5 μm) to remove foreign matter and coarse particles contained in the mixture. Thus, an aqueous ink was obtained.

Experimental Example 1
In Experimental Example 1, each of the inkjet recording apparatuses D-1 to D-4 was prepared by the method shown below. Then, it was verified whether each of the inkjet recording apparatuses D-1 to D-4 had a desired effect.

(Preparation of inkjet recording device)
Each of the inkjet recording apparatuses D-1 to D-4 was a prototype manufactured by KYOCERA Document Solutions Inc. Each of the prototypes was modified to be able to supply the liquid S while the printing paper is adsorbed in surface printing. More specifically, each of the inkjet recording apparatuses D-1 to D-4 has a liquid supply unit. The liquid supply was a sprayer. In the inkjet recording apparatuses D-1 to D-4, the liquid S is supplied from the liquid supply unit to at least a part of the supply area while the printing paper is adsorbed in the surface printing. The supply area is positioned at a portion of the first surface of the printing paper, which is spaced 3 mm or more and 40 mm or less away from each end of the printing paper in the short direction toward the inside of the short direction of the printing paper P. In the inkjet recording apparatuses D-1 to D-4, the supply amount of the liquid S could be changed. In Experimental Example 1, the supply amount of the liquid S was set to 0.5 g / m ² .

  The inkjet recording apparatuses D-1 to D-4 each include an ink tank and a liquid tank. The aqueous ink obtained by the above-mentioned method was housed in the ink tank, and the liquid S (more specifically, each of the liquids S shown in Table 3) was housed in the liquid tank. After that, installation operation was done. Thus, the aqueous ink was supplied from the ink tank to the recording head. In addition, the liquid S was supplied from the liquid tank to the liquid supply unit. Thus, each of the inkjet recording devices D-1 to D-4 was prepared.

  Table 3 shows the configuration of each of the inkjet recording apparatuses D-1 to D-4. In Table 3, "apparatus" means an inkjet recording apparatus. "LogP" means distribution coefficient LogP.

(Evaluation of inkjet recording device)
Double-sided printing was performed using each of the inkjet recording apparatuses D-1 to D-4. The presence or absence of ink bleeding in the obtained image was examined. Moreover, the presence or absence of the adhesion of the ink in the non-printing area of the paper after duplex printing was examined.

(Evaluation: presence or absence of ink bleeding in the obtained image)
Barcodes (JAN code with a reduction ratio of 80%) were recorded on both sides of paper ("IJW Fantas" manufactured by Oji Paper Co., Ltd., A4 size) using each of the inkjet recording apparatuses D-1 to D-4. . Each barcode was tried to be recognized in a state where a barcode reader ("H. H. 220HT-6" manufactured by Panasonic Corporation) was separated from each of the recorded barcodes by 20 cm. Then, it was checked whether the barcode reader recognized each of the barcodes. Evaluation criteria are shown below. When the barcode reader recognizes the barcode, it is determined that the ink does not blur in the obtained image. On the other hand, when the barcode reader does not recognize the barcode, it is determined that the ink is blurred in the obtained image.
Good: The barcode reader recognized each of the barcodes.
Bad: The barcode reader did not recognize each of the barcodes.

  The evaluation results are shown in "ink smear" in Table 4. In Table 4 “Ink Bleeding”, if the bar code reader recognizes each bar code, it indicates “recognizable”, and if the bar code reader does not recognize each bar code “ It is described as "not recognized."

(Evaluation: presence or absence of ink adhesion)
Whether or not the ink is adhered to the non-printing area of the printed matter (paper after double-sided printing) obtained in the above-mentioned (Evaluation: presence or absence of ink bleeding in the obtained image) was visually examined. Evaluation criteria are shown below.
Good: No adhesion of ink was found in the non-printing area.
Poor: Ink adhesion was confirmed in the non-printing area.

  The evaluation results are shown in “ink adhesion” in Table 4. In the "ink adhesion" in Table 4, "No" is described when the ink adhesion is not confirmed in the non-printing area, and "Available" when the ink adhesion is confirmed in the non-printing area. .

<Experimental Example 2>
In Experimental Example 2, the supply amount of the liquid S was changed to the value shown in Table 5 in the inkjet recording apparatus D-1, and each of the inkjet recording apparatuses D-11 and D-12 was prepared. Further, the supply amount of the liquid S was changed to the value shown in Table 5 in the inkjet recording device D-2, and each of the inkjet recording devices D-21 and D-22 was prepared. Table 5 shows the configurations of the inkjet recording apparatuses D-11, D-12, D-21, and D-22. In Table 5, "apparatus" means an inkjet recording apparatus. "LogP" means distribution coefficient LogP.

  Each of the inkjet recording devices D-11, D-12, D-21, and D-22 was evaluated by the method described in <Experimental Example 1> described above. The evaluation results are shown in Table 6. Table 6 also shows the evaluation results of the inkjet recording apparatuses D-1 and D-2. In Table 6, "apparatus" means an inkjet recording apparatus. In "ink blur" in Table 6, "recognizable" means that the barcode reader has recognized each of the barcodes. In "ink adhesion" in Table 6, "absent" means that no ink adhesion was confirmed in the non-printing area.

  The present inventors can implement double-sided printing without interruption by using each of the inkjet recording apparatuses D-1, D-11, D-12, D-2, D-21, and D-22. Have confirmed that.

Preferred Configuration of Water-Based Ink
Hereinafter, a preferable configuration of the water-based ink in the present embodiment will be described without referring to the drawings. The aqueous ink preferably comprises an aqueous medium and a plurality of pigment particles dispersed in the aqueous medium.

  The aqueous medium preferably contains, for example, water, glycerin and / or glycol, and alcohol and / or glycol ether. If the aqueous medium contains glycerin and / or glycol, drying of the aqueous ink can be prevented. If the aqueous medium contains alcohol and / or glycol ether, the permeability of the aqueous ink to the printing paper can be enhanced. The water contained in the aqueous medium is preferably ion exchange water.

The pigment particles each comprise a pigment core and a coating resin.
The pigment core contains a pigment. As a pigment, for example, a yellow pigment, an orange pigment, a red pigment, a blue pigment, a violet pigment or a black pigment can be used. Examples of yellow pigments include C.I. I. Pigment yellow 74, 93, 95, 109, 110, 120, 128, 138, 139, 151, 154, 155, 173, 180, 185, or 193. As an orange pigment, for example, C.I. I. Pigment orange 34, 36, 43, 61, 63, or 71. Examples of red pigments include C.I. I. Pigment red 122 or 202. Examples of blue pigments include C.I. I. Pigment blue 15 or 15: 3. Examples of purple pigments include C.I. I. Pigment violet 19, 23, or 33. Examples of black pigments include C.I. I. Pigment black 7.

  The content of the pigment core in the aqueous ink is preferably 4% by mass or more and 8% by mass or less. Thereby, an image having a desired image density can be easily obtained. Moreover, it is easy to ensure the permeability of the water-based ink to the printing paper. When the content of the pigment core is too low, an image having a desired image density may not be obtained. On the other hand, when the content of the pigment core is too large, the permeability of the aqueous ink to the printing paper may not be secured. In addition, since the fluidity of pigment particles may not be secured in an aqueous ink, an image having a desired image density may not be obtained.

The volume median diameter (D ₅₀ ) of the pigment core is preferably 30 nm or more and 200 nm or less. As a result, the color density, hue, and stability of the water-based ink can be easily improved. More preferably, the volume median diameter (D ₅₀ ) of the pigment core is 70 nm or more and 130 nm or less. The measured value of the volume median diameter (D ₅₀ ) of the pigment core is a value measured using a laser diffraction type particle size distribution measuring apparatus (“Zetasizer nano-ZS (Zetasizer nano ZS)” manufactured by Malvern Co., Ltd.).

  The coating resin is provided on the surface of the pigment core. The coating resin preferably has an anionic property, for example, a styrene-acrylic acid resin, a styrene-maleic acid copolymer, a styrene-maleic acid half ester copolymer, a vinyl naphthalene-acrylic acid copolymer, and a vinyl naphthalene. -It is preferable that it is at least one selected from the group consisting of a maleic acid copolymer. More preferably, the coating resin is a styrene-acrylic acid resin. When the coating resin is a styrene-acrylic acid resin, pigment particles can be easily produced. In addition, the dispersibility of the pigment particles can be enhanced.

  The styrene-acrylic acid based resin is a resin containing a unit derived from styrene and a unit derived from acrylic acid, methacrylic acid, an acrylic ester, or a methacrylic ester. Preferably, the styrene-acrylic acid resin is a copolymer of styrene, acrylic acid and alkyl acrylate, a copolymer of styrene, methacrylic acid, alkyl methacrylate and alkyl acrylate, styrene and acrylic acid At least one of: a copolymer of styrene, a copolymer of styrene, maleic acid and alkyl acrylate, a copolymer of styrene and methacrylic acid, and a copolymer of styrene and methacrylic alkyl ester is there. More preferably, the styrene-acrylic acid based resin is a copolymer of styrene, methacrylic acid, methacrylic acid alkyl ester and acrylic acid alkyl ester. More specifically, the styrene-acrylic acid resin is a copolymer of styrene, methacrylic acid, methyl methacrylate and n-butyl acrylate.

  The content of the coating resin is preferably 15 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the pigment core. As a result, it is easy to prevent the occurrence of the strike-through in the printing paper after recording. In addition, an image having a desired image density can be easily obtained. If the content of the coating resin is too low, the printing paper after recording may be punched. On the other hand, when the content of the coating resin is too large, an image having a desired image density may not be obtained.

[Preferred Material of Liquid S]
Hereinafter, preferable materials of the liquid S in the present embodiment will be described without reference to the drawings. The liquid S is preferably a liquid having a distribution coefficient LogP of 0.02 or more and 1.50 or less. More specifically, the liquid S is preferably at least one selected from the group consisting of monohydric alcohols, dihydric alcohols (diols) and polyhydric alcohol alkyl ethers.

  The monohydric alcohol is preferably, for example, a monohydric alcohol having 3 to 5 carbon atoms. The monohydric alcohol may be a branched alcohol but is preferably a straight chain alcohol. Examples of monohydric alcohols include 1-propanol (0.34), isopropyl alcohol (2-propanol, 0.28), 1-butanol (0.88), 2-butanol (0.60) and 1-pentanol It is preferably at least one selected from the group consisting of (1.40) and 2-pentanol (1.19). Here, the numerical value in parentheses is the distribution coefficient LogP of each monohydric alcohol. The viscosity of the aforementioned monohydric alcohols is relatively low.

  The dihydric alcohol is preferably, for example, a dihydric alcohol having 4 to 8 carbon atoms. The dihydric alcohol may be a straight chain alcohol or a branched alcohol. The straight chain alcohols include, for example, 1,4-butanediol (0.50), 1,5-pentanediol (0.27), 1,2-hexanediol (0.70) and 1,2-heptanediol ( It is preferable that it is at least one selected from the group consisting of 1.50) and 1,2-octanediol (1.30). The branched alcohol is, for example, at least one selected from the group consisting of 3-methyl-1,3-butanediol (0.16) and 2-methylpentane-2,4-diol (0.88) Is preferred. Here, the numerical value in parentheses is the distribution coefficient LogP of each dihydric alcohol. The viscosity of the aforementioned dihydric alcohols is relatively high.

  The polyhydric alcohol alkyl ether may be a polyhydric alcohol monoalkyl ether or a polyhydric alcohol dialkyl ether. Examples of polyhydric alcohol monoalkyl ethers are propylene glycol monoethyl ether (0.30), propylene glycol monopropyl ether (0.62), dipropylene glycol monopropyl ether (0.87) and ethylene glycol monobutyl ether (0 .83), diethylene glycol monobutyl ether (0.56), triethylene glycol monobutyl ether (0.02), propylene glycol monobutyl ether (1.15), dipropylene glycol monobutyl ether (1.50) and tripropylene glycol monobutyl ether It is preferable that it is at least one selected from the group consisting of (1.34). The polyhydric alcohol dialkyl ether is preferably, for example, at least one selected from the group consisting of dipropylene glycol dimethyl ether (0.81) and diethylene glycol diethyl ether (0.39). Here, the numerical value in parentheses is the distribution coefficient LogP of each polyhydric alcohol alkyl ether. The viscosity of the aforementioned polyhydric alcohol alkyl ethers is relatively low.

  The ink jet recording apparatus according to the present invention can be used, for example, as a printer capable of double-sided printing.

11 First transport unit (transport unit)
13 recording head 19 liquid supply unit 51 control unit 100 inkjet recording apparatus P printing paper R1 supply area Rp print area

Claims (9)

An inkjet recording apparatus for recording on printing paper using aqueous ink, comprising:
A conveyance unit that conveys the printing sheet while suctioning the sheet;
A recording head for discharging the aqueous ink onto the printing sheet;
A liquid supply unit that supplies a liquid having a distribution coefficient LogP of 0.0 or more and 1.5 or less to the printing paper;
A control unit that controls the transport unit, the recording head, and the liquid supply unit;
Equipped with
The distribution coefficient LogP is a common logarithm value of n-octanol / water distribution coefficient,
The control unit is configured to perform the recording on the first side of the printing sheet, and then perform the recording on the second side of the printing sheet positioned opposite to the first side. And the liquid supply unit,
The control unit is configured to discharge the water-based ink to the first surface while the print sheet is adsorbed by the transport unit in a state where the first surface faces the discharge surface of the recording head. Controlling the recording head and controlling the liquid supply unit such that the liquid is supplied to at least a portion of the supply area on the first surface;
The control unit is configured to perform the recording so that the water-based ink is discharged to the second surface while the printing sheet is adsorbed by the transport unit with the second surface facing the discharge surface. Control the head,
The ink jet recording apparatus, wherein the supply area is located at the periphery of the first surface and extends along the longitudinal direction of the printing paper.   The inkjet apparatus according to claim 1, wherein the control unit controls the liquid supply unit such that the liquid is supplied to at least a part of the supply area before the aqueous ink is discharged to the first surface. Recording device. The control unit sets the supply amount of the liquid to the supply area to a numerical value selected from the range of 0.2 g / m ² or more and 1.2 g / m ² or less based on the type of the printing paper. An ink jet recording apparatus according to claim 1 or 2.   The supply area is located in a portion of the first surface, which is separated by 3 mm or more and 40 mm or less from each of both ends of the print paper in the short direction toward the inside of the print paper in the short direction. The inkjet recording device as described in any one of these. The control unit is configured to supply the liquid to at least a part of the supply area when the discharge amount of the aqueous ink to the printing area on the first surface is 10 cm ³ / m ² or more. Control
The printing area is located in a portion of the first surface at a distance of 3 mm or more and 40 mm or less from the at least one end of the printing paper in the width direction to the inside in the width direction of the printing paper. The inkjet recording device described in.   The control unit controls the liquid supply unit such that the liquid is not supplied to the print sheet while the print sheet is adsorbed by the transport unit in a state where the second surface faces the discharge surface. The inkjet recording device as described in any one of Claims 1-5. The liquid supply unit is a nozzle head that discharges the liquid to at least a part of the supply area,
The ink jet recording apparatus according to any one of claims 1 to 6, wherein the viscosity of the liquid is 1 mPa · s to 10 mPa · s. An inkjet recording method for recording on printing paper using a water-based ink, comprising:
Recording on the first side of the printing paper;
Performing recording on the second side of the printing paper positioned opposite to the first side after recording on the first side;
Including
In the recording on the first surface, the water-based ink is discharged to the first surface while the printing paper is adsorbed by the transport unit with the first surface facing the discharge surface of the recording head. And supplying liquid to at least a portion of the supply area on the first surface,
The recording on the second surface discharges the water-based ink to the second surface while the printing paper is adsorbed by the transport unit with the second surface facing the discharge surface. Including
The distribution coefficient LogP of the liquid is 0.0 or more and 1.5 or less,
The distribution coefficient LogP is a common logarithm value of n-octanol / water distribution coefficient,
The inkjet recording method, wherein the supply area is located at the periphery of the first surface and extends along the longitudinal direction of the printing paper. In a computer constituting an inkjet recording apparatus that performs recording on printing paper using aqueous ink,
Recording on the first side of the printing paper;
Performing recording on the second side of the printing paper positioned opposite to the first side after recording on the first side;
To run
In the recording on the first surface, the water-based ink is discharged to the first surface while the printing paper is adsorbed by the transport unit with the first surface facing the discharge surface of the recording head. And supplying liquid to at least a portion of the supply area on the first surface,
The recording on the second surface discharges the water-based ink to the second surface while the printing paper is adsorbed by the transport unit with the second surface facing the discharge surface. Including
The distribution coefficient LogP of the liquid is 0.0 or more and 1.5 or less,
The distribution coefficient LogP is a common logarithm value of n-octanol / water distribution coefficient,
The computer program, wherein the supply area is located at the periphery of the first surface and extends along the longitudinal direction of the printing paper.

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