JP5365650B2 - Liquid ejection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a test pattern to be expressly generated easily. <P>SOLUTION: A printer includes: an inkjet head which discharges an ink; a print quality-improving head which discharges a colorless clear print quality-improving liquid; a conveyance mechanism which conveys a thermosensitive paper; and a control device which controls them. The print quality-improving liquid contains an alkaline neutralizing agent which neutralizes an acidic developer contained in a thermosensitive layer of the thermosensitive paper, the concentration of the alkaline neutralizing agent being at least a concentration able to neutralize the developer in a region attached with the print quality-improving liquid, of the thermosensitive paper. The control device controls the conveyance mechanism and the print quality-improving head so that they form a test pattern by conveying the thermosensitive paper and discharging the print quality-improving liquid on the thermosensitive paper. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a liquid ejection device that ejects liquid from ejection ports.

  Patent Document 1 discloses an ink jet recording in which colorless and transparent ink is ejected onto thermal paper, the thermal paper is heated within a predetermined temperature range to develop an ink landing area on the thermal paper, and the ejection state is visually inspected. A head ejection inspection method is described.

JP 2009-208336 A

  However, in the technique described in Patent Document 1, it is necessary to perform temperature control for heating the thermal paper with very high accuracy. When the thermal paper is heated beyond a predetermined temperature range, the area around the ink landing area is also increased. Discolor. Then, the ink landing state becomes unclear, and the discharge state cannot be visually inspected.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid ejecting apparatus that can easily specify a test pattern.

  The liquid ejection apparatus according to the present invention includes a transport mechanism that transports a recording medium in the transport direction, a first liquid discharge head in which a plurality of first discharge ports that discharge a first liquid containing a dye component are formed, A second liquid discharge head formed with a plurality of second discharge ports for discharging a colorless and transparent second liquid containing a component for aggregating or precipitating the pigment component in the first liquid; Control means for controlling the transport mechanism and the first and second liquid discharge heads so as to form an image by discharging two liquids. In the second liquid, an alkaline neutralizing agent that neutralizes the acidic developer contained in the heat-sensitive layer of the thermal paper is present in the region where the second liquid is attached to the thermal paper. The second liquid is contained so as to have a concentration that can neutralize the colorant, and the control means discharges the second liquid onto the thermal paper transported by the transport mechanism to form a test pattern. Control the ejection head.

  According to this, when the test pattern is formed on the thermal paper, the developer in the region where the test pattern of the thermal layer is formed is neutralized, so that the color does not change even when the region is heated. For this reason, by simply heating the thermal paper above the temperature at which the area where the test pattern of the thermal layer is not formed is discolored, the area other than the test pattern of the thermal paper is discolored (for example, changed to black). It is possible to specify a test pattern.

  In the present invention, the image forming apparatus further includes a heating mechanism that is provided downstream of the second liquid discharge head in the transport direction and that heats the recording medium. The control means controls the heating mechanism such that the thermal paper on which the test pattern is formed is heated to a temperature equal to or higher than a minimum temperature at which the region of the thermal layer where the test pattern is not formed is discolored. Is preferred. As a result, the area other than the test pattern on the thermal paper changes color, and is discharged from the apparatus with the test pattern clearly shown. For this reason, it is not necessary to heat the thermal paper on which the test pattern is formed by a heating mechanism different from the apparatus.

  Further, in the present invention, with respect to the transport direction, a reading unit provided downstream of the heating mechanism and reading the test pattern formed on the thermal paper, and the reading data read by the reading unit, It is preferable that the apparatus further includes a discharge determination unit that determines whether or not the second liquid is discharged from the second discharge port. As a result, it is possible to accurately determine whether or not the second liquid is being discharged from the second discharge port.

  In the present invention, there is further provided discharge means for forcibly discharging the second liquid from all the second discharge ports. The control means causes the liquid to be discharged from all the second discharge ports when the discharge determination unit determines that the second liquid is not discharged from the plurality of the second discharge ports. It is preferable to control the discharging means. Thereby, it becomes possible to recover the ejection failure of the second liquid ejection head.

  Further, in the present invention, the control means has a second predetermined number in which the number of the second discharge ports that are not discharged from the second liquid determined by the discharge determination unit is equal to or more than a first predetermined number. If the amount of liquid discharged from all of the second discharge ports is less than the second predetermined number, the amount of liquid discharged from all of the second discharge ports is not less than the second predetermined number. It is preferable to control the discharge means so that the amount of liquid discharged from the two discharge ports is smaller. Thereby, the amount of liquid to be discharged can be changed according to the number of second discharge ports from which the second liquid is not discharged. For this reason, useless consumption of the second liquid can be suppressed.

  In the present invention, the control unit controls the transport mechanism and the first liquid ejection head so that the test pattern is formed by ejecting the first liquid onto a recording medium, and the ejection determination unit includes: When determining whether or not the first liquid is being ejected from the first ejection port based on the test pattern read data read by the reading unit, the test pattern read data is determined. It is preferable to determine the read data of the test pattern formed on the recording medium using the inverted data obtained by inverting the information of the determination data. As a result, it is possible to determine the presence or absence of ejection failure of the first and second liquid ejection heads by simply inverting the information of one determination data.

  According to the liquid ejection apparatus of the present invention, when the test pattern is formed on the thermal paper, the color developer in the region where the test pattern of the thermal layer is formed is neutralized. do not do. For this reason, by simply heating the thermal paper above the temperature at which the area where the test pattern of the thermal layer is not formed is discolored, the area other than the test pattern of the thermal paper is discolored (for example, changed to black). It is possible to specify a test pattern.

1 is a schematic side view showing an internal structure of an ink jet printer according to an embodiment of a liquid ejection apparatus of the present invention. It is a top view which shows the flow-path unit and actuator unit of the inkjet head contained in the printer of FIG. FIG. 3 is an enlarged view showing a region surrounded by an alternate long and short dash line in FIG. 2. It is a fragmentary sectional view of the ink jet head shown in FIG. It is a block diagram which shows schematic structure of the control apparatus shown in FIG. It is a figure which shows the test pattern printed by the test pattern printing part shown in FIG. It is a flowchart which shows the control content of the discharge test | inspection which the control apparatus of a printer performs. It is an operation | movement condition diagram for demonstrating purge operation | movement and wiping operation | movement.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  First, an overall configuration of an inkjet printer 101 according to an embodiment of the liquid ejection apparatus of the present invention will be described with reference to FIG.

  The printer 101 has a rectangular parallelepiped housing 101a. A paper discharge unit 15 is provided on the top plate of the housing 101a. The internal space of the housing 101a can be divided into spaces A, B, and C in order from the top. In the spaces A and B, a paper transport path from the paper feed unit 101b to the paper discharge unit 15 is formed. In the space A, image formation on the paper P and conveyance of the paper P to the paper discharge unit 15 are performed. In the space B, the paper P is fed to the conveyance path. From the space C, ink is supplied to the four inkjet heads 1 in the space A, and image quality improving liquid is supplied to the image quality improving head 2 in the space A.

  In the space A, four inkjet heads 1 (first liquid ejection head: hereinafter referred to as head 1), an image quality improvement head 2 (second liquid ejection head: hereinafter referred to as head 2), and a sheet P in the transport direction ( In FIG. 1, a conveyance mechanism 16 that conveys the sheet P from the left to the right), a guide unit that guides the paper P, a heating unit (heating mechanism) 31 that heats the paper P, an image sensor (reading unit) 30, and a head lift A mechanism 33 (see FIG. 5), a wiper unit 36 (see FIG. 5), a cleaner unit 37, a control device 100, and the like are arranged.

  The four heads 1 eject yellow, cyan, magenta, and black ink droplets, respectively. The head 2 is arranged upstream of the four heads 1 in the transport direction, and ejects droplets of image quality improving liquid. These four heads 1 and 2 have the same structure, are arranged at a predetermined pitch in the sub-scanning direction, and are supported by the casing 101a via the head holder 35. The lower surfaces of the heads 1 and 2 are discharge surfaces 1a and 2a in which a plurality of discharge ports (first and second discharge ports) 108 (see FIG. 3) are arranged. The head holder 35 holds the heads 1 and 2 so that a predetermined gap suitable for recording is formed between the ejection surfaces 1 a and 2 a of the heads 1 and 2 and the transport belt 8.

  The transport mechanism 16 includes two belt rollers 6 and 7, a transport belt 8, a tension roller 10, a platen 18, a nip roller 4, and a peeling plate 5. The conveyor belt 8 is an endless belt wound between both rollers 6 and 7, and tension is applied by a tension roller 10. The platen 18 is disposed to face the five heads 1 and 2 and supports the upper loop of the conveyor belt 8 from the inside. The belt roller 7 is a driving roller that is rotated clockwise in FIG. 1 by a motor (not shown), and causes the conveyor belt 8 to travel. The belt roller 6 is a driven roller that rotates as the conveyor belt 8 travels. A weak adhesive silicon layer is formed on the outer peripheral surface of the conveyor belt 8. The nip roller 4 presses the sheet P conveyed from the sheet feeding unit 101 b against the outer peripheral surface of the conveying belt 8. The pressed sheet P is held on the conveyor belt 8 by the silicon layer. The peeling plate 5 peels the paper P that has been transported by the transport belt 8 from the transport belt 8.

  The guide unit has an upstream guide unit and a downstream guide unit that are arranged with the transport mechanism 16 interposed therebetween in the transport direction. The upstream guide unit includes guides 13 a and 13 b and a feed roller pair 14, and connects the paper feed unit 101 b and the transport mechanism 16. The image forming paper P is transported toward the transport mechanism 16. The downstream guide unit includes guides 29 a and 29 b and two feed roller pairs 28, and connects the transport mechanism 16 and the paper discharge unit 15. The paper P after image formation is conveyed toward the paper discharge unit 15.

  In the space B, the paper feeding unit 101b is arranged. The paper feed unit 101 b includes a paper feed tray 11 and a paper feed roller 12. Among these, the paper feed tray 11 is detachable from the housing 101a. The paper feed tray 11 is a box that opens upward, and can store a plurality of papers P. The paper feed roller 12 sends out the uppermost paper P in the paper feed tray 11.

  Here, the sub-scanning direction is a direction parallel to the transport direction when the paper P is transported by the transport mechanism 16, and the main scanning direction is a direction orthogonal to the sub-scanning direction and along the horizontal plane. .

  In the space C, the tank unit 101c is detachably attached to the housing 101a. The tank unit 101c is detachably mounted with four ink tanks 17a and one image quality improving liquid tank 17b. Each ink tank 17a stores cyan, magenta, yellow, and black ink (first liquid), and is connected to the corresponding head 1 via a tube (not shown) and a pump 32 (see FIG. 5). Has been. Similarly, the image quality improving liquid tank 17b stores a colorless and transparent image quality improving liquid (second liquid) and is connected to the head 2 via a tube (not shown) and a pump 32 (see FIG. 5). . Each pump 32 is driven by the control device 100 only when ink or image quality improving liquid is forcibly sent to the corresponding heads 1 and 2 (that is, when purge operation or initial introduction of liquid is performed).

  Generally, an image quality improving liquid that aggregates pigment pigments is used for pigment ink, and an image quality improving liquid that precipitates dye pigments is used for dye ink. The material of the image quality improving liquid can be appropriately selected from a liquid containing a polyvalent metal salt such as a cationic polymer or a magnesium salt. When such an image quality improving liquid and ink are mixed, a polyvalent metal salt or the like acts on a dye or pigment that is a colorant of the ink, so that an insoluble or hardly soluble metal complex or the like is formed by aggregation or precipitation.

  Further, the image quality improving liquid contains an alkaline neutralizing agent. An amine is employed as the neutralizing agent in the present embodiment, but in addition to this, an alkaline inorganic hydroxide (for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.) can be employed. is there. Further, the image quality improving liquid contains a neutralizing agent at a concentration that can neutralize the acidic developer contained in the heat sensitive layer in the adhesion area when the image quality improving liquid droplets adhere to the thermal paper. Yes.

  Next, the control device 100 will be described. The control device 100 controls the operation of each part of the printer 101 and controls the operation of the entire printer 101. The control device 1p controls an image forming operation based on image data supplied from an external device (such as a PC connected to the printer 101). Specifically, the control device 100 controls the supply / conveyance / discharge operation of the paper P, the ink discharge operation synchronized with the transport of the paper P, and the like. The control device 100 also controls a maintenance operation for the heads 1 and 2. Furthermore, the control device 100 also performs an inspection of the ejection state of the heads 1 and 2 (that is, ejection inspection). In the ejection inspection, when the head 1 is inspected, a test pattern is formed on thermal paper or plain paper. On the other hand, when the head 2 is inspected, a test pattern is formed on the thermal paper. Details of the discharge inspection will be described later.

  The control device 100 drives the paper feed unit 101b, the transport mechanism 16, each pair of feed rollers 14, 28, etc. based on a recording command received from an external device. The paper P sent out from the paper feed tray 11 is guided by the upstream guide unit and sent to the transport mechanism 16. When the paper P transported by the transport mechanism 16 passes immediately below the head 2, the head 2 is controlled by the control device 100, and an image quality improving liquid droplet is ejected to an area on the paper P where an image is formed. Is done. Thereafter, when the paper P passes immediately below the four heads 1, the head 1 is controlled by the control device 100, and the ink of each color is transferred from each head 1 to the area where the image quality improving liquid is attached on the paper P. Drops are ejected in order. Thereby, a desired color image is formed on the paper P. At this time, when the ink droplets land on the image quality improving liquid on the paper P, the image quality improving liquid causes the pigment component of the ink droplets to aggregate or deposit, so that ink bleeding on the paper P is prevented. Note that the image quality improving liquid and ink ejection operations are performed based on a detection signal from a paper sensor (not shown) that detects the leading edge of the paper P. The paper P on which the image is formed is peeled off from the transport belt 8 by the peeling plate 5, guided by the downstream guide portion, and discharged from the opening 22 at the top of the housing 101 a to the paper discharge portion 15.

  The control device 100 recovers and maintains the ink ejection characteristics of the heads 1 and 2 through a maintenance operation. The maintenance operation includes a purge operation, a wiping operation for the discharge surfaces 1a and 2a, a capping operation for the discharge surfaces 1a and 2a, and the like.

  In the purge operation, the pump 32 is driven and ink is forcibly discharged from all the ejection ports 108. In the wiping operation, the discharge surfaces 1a and 2a are wiped by the wiper 36a (see FIG. 8). The wiping operation is performed after the purge operation, and residual ink and foreign matters on the ejection surfaces 1a and 2a are removed. In the capping operation, the discharge space (the space facing the discharge surfaces 1a and 2a) is isolated from the external space by a cap (not shown).

  The purge operation is accompanied by a wiping operation, and the foreign matter in the heads 1 and 2 and the thickened ink near the ejection port 108 are discharged. Then, the discharge characteristics of the discharge port 108 are restored, and the discharge surfaces 1a and 2a are cleaned. The capping operation suppresses meniscus drying. The purge operation is performed, for example, immediately after the printer 1 is turned on, after a paper jam (clogging) in the transport path, after image formation that has continued for a predetermined period, or after non-ejection that has continued for a predetermined period of time. The purge operation and the wiping operation are also executed based on the determination result of the discharge inspection. The capping operation is performed, for example, when the printer 1 is stopped or stopped.

  Next, the heads 1 and 2 will be described in detail with reference to FIGS. Since both the heads 1 and 2 have the same structure, only the head 1 will be described and the description of the head 2 will be omitted. In FIG. 3, for convenience of explanation, the pressure chamber 110, the aperture 112, and the discharge port 108 that are to be drawn with broken lines below the actuator unit 21 are drawn with solid lines.

  As shown in FIG. 2, the head 1 is a laminated body in which four actuator units 21 are fixed to the upper surface 9 a of the flow path unit 9. The actuator unit 21 includes a plurality of unimorph actuators corresponding to the pressure chambers 110 and selectively applies ejection energy to the ink in the pressure chambers 110. Although not shown, the heads 1 and 2 are a flexible printed circuit board (Flexible Printed Circuit Board) that supplies a drive signal to a reservoir unit and actuator unit 21 that store ink (or image quality improving liquid) supplied to the flow path unit 9. Circuit: FPC), and a control board for controlling a driver IC mounted on the FPC.

  As shown in FIG. 4, the flow path unit 9 is a laminated body in which nine metal plates 122 to 130 made of stainless steel are laminated. As shown in FIG. 2, a total of ten ink supply ports 105 b communicating with the reservoir unit are opened on the upper surface 9 a of the flow path unit 9. As shown in FIGS. 2 to 4, a manifold channel 105 having an ink supply port 105 b as one end and a plurality of sub-manifold channels 105 a branched from the manifold channel 105 are formed inside the channel unit 9. Has been. Furthermore, a plurality of individual ink flow paths 132 are formed in the flow path unit 9 from the outlets of the sub-manifold flow paths 105a to the discharge ports 108 of the discharge surface 1a through the pressure chambers 110. A large number of ejection ports 108 formed on the ejection surface 1a are arranged in a matrix, and are arranged at intervals of 600 dpi, which is the resolution in the main scanning direction with respect to the main scanning direction.

  The ink flow in the flow path unit 9 will be described. As shown in FIGS. 2 to 4, the ink supplied from the reservoir unit to the ink supply port 105 b flows into the manifold channel 105 (sub-manifold channel 105 a). The ink in the sub-manifold channel 105 a is distributed to each individual ink channel 132 and reaches the ejection port 108 via the aperture 112 and the pressure chamber 110.

  The pump 32 forcibly supplies liquid (ink or image quality improving liquid) to the flow path unit 9 via the reservoir unit in the corresponding head 1 and head 2. Although one pump 32 is shown in FIG. 5, the printer 101 has five pumps 32 corresponding to each head 1 and head 2.

  The heating unit 31 is provided as a constituent member of the guide 29b downstream of the heads 1 and 2 in the transport direction. The heating unit 31 includes a heater and a heating surface 31a. The heating surface 31a is a part of the inner surface of the guide 29b. When the heater is energized under the control of the control device 100, the heating surface 31a has a printing surface (thermal layer) of the thermal paper that is higher than a predetermined temperature (the lowest temperature at which the thermal layer portion to which no image quality improving liquid is attached changes). Heat to. As a result, the heat-sensitive layer is discolored outside the region where the image quality improving liquid of the heat-sensitive paper is attached. On the other hand, the area of the thermal paper to which the image quality improving liquid is attached does not change color.

  As a modification, the heating unit 31 may be configured by a heat roller pair and a pull roller pair. The paper P is heated by the heat roller pair and cooled while being pulled in the direction of the paper discharge unit by the pull roller pair. As a result, the curling phenomenon due to the heating of the paper P is reduced.

  In the thermal paper, a thermal layer is generally formed on a base paper. The heat-sensitive layer includes a color former and a developer in a holding agent. The color former is mainly a leuco dye, and the developer is mainly an acidic phenol compound. In addition, the heat-sensitive layer includes a sensitizer and the like. The basic principle of color development of the thermal paper is that when the thermal layer is heated to a predetermined temperature or higher, the color former, the developer, etc. are dissolved, and the color develops by reacting with the developer. As the thermal paper, for example, PA-C-412 manufactured by Brother Industries, FAX-1010 manufactured by KOKUYO, WP-4AS6 manufactured by Sharp, and FXP-A4T100 manufactured by Sanyo Electric Co., Ltd. are used. Is possible.

  The image sensor 30 is provided downstream of the heating unit 31 in the transport direction and is provided in the guide 29b. The image sensor 30 is a line sensor having a detection area having a substantially paper width. The detection surface 30a faces the printing surface, and a plurality of sensor elements are arranged in the main scanning direction. Thereby, the image sensor 30 can read at least the maximum width of the image in the main scanning direction. Each sensor element has a light emitting unit that irradiates the paper P with light and a light receiving unit that receives the light reflected from the paper P. Then, the image sensor 30 outputs the received light amount detected by each light receiving unit from the paper P on which the image is formed to the control unit 100 as read data.

  In the main scanning direction, the distance between the sensor elements is the same as the distance between the ejection ports 108 of the heads 1 and 2. That is, the image sensor 30 can read an image formed on the paper P with the same resolution as the print resolution of the heads 1 and 2 in the main scanning direction. Therefore, it is possible to detect for each dot area where the image quality improving liquid and ink ejected from the heads 1 and 2 have landed.

  The head lifting mechanism 33 moves the head holder 35 up and down, and the five heads 1 and 2 move between the printing position and the retracted position. At the printing position, the five heads 1 and 2 face the conveyor belt 8 at an interval suitable for printing. At the retracted position, the five heads 1 and 2 are separated from the conveyance bell 8 at an interval equal to or larger than the printing position. In the retracted position, the wiper unit 36 can move in the space between the five heads 1 and 2 and the conveyor belt 8.

  The wiper unit 36 has five wipers 36a (see FIG. 8) for wiping the discharge surfaces 1a and 2a. The wiper 36a is a plate-like elastic member such as rubber. In FIG. 8, only one wiper 36a is shown. The wiper unit 36 wipes the ejection surfaces 1a and 2a by moving the wiper 36a along the main scanning direction while contacting the ejection surfaces 1a and 2a of the heads 1 and 2.

  The cleaner unit 37 includes a cleaning liquid application member 37 a and a blade 37 b and cleans the outer peripheral surface of the transport belt 8. As shown in FIG. 1, the cleaner unit 37 is disposed on the lower right side of the conveyor belt 8 and opposed to the belt roller 7. The cleaning liquid application member 37 a is composed of a porous body (for example, a sponge) that holds the cleaning liquid and a support member that supports the porous body, and the porous body can contact over the entire width of the transport belt 8. The cleaning liquid is supplied from a cleaning liquid tank (not shown). The blade 37b is made of a plate-like elastic member such as rubber, and is disposed immediately downstream of the porous body in the traveling direction of the transport belt 8. The blade 7b can also be contacted over the entire width of the conveyor belt 8 in the same manner as the porous body.

  The cleaning liquid application member 37a and the blade 37b selectively take a contact position and a separation position by a moving mechanism (not shown). At the abutting position, the porous body and the blade 37b abut on the outer peripheral surface of the transport belt 8 at the abutting position, and are separated from the outer peripheral surface at the separation position. In the cleaning operation described later, the cleaner unit 37 moves the cleaning liquid application member 37a and the blade 37b to the contact positions. At this time, the conveying belt 8 rotates clockwise, the cleaning liquid is applied from the porous body to the outer peripheral surface of the conveying belt 8, and dirt on the outer peripheral surface is scraped off together with the cleaning liquid by the blade 37b. The cleaning liquid scraped off by the blade 37b flows into a waste liquid tank (not shown).

  Next, the control device 100 will be described with reference to FIG. The control device 100 includes a CPU (Central Processing Unit), a program executed by the CPU and a ROM (Read Only Memory) that stores data used in these programs in a rewritable manner, and temporarily stores data when the program is executed. RAM (Random Access Memory). Each functional unit constituting the control device 100 is constructed by cooperation of these hardware and software in the ROM. As shown in FIG. 5, the control device 100 includes a transport control unit 131, an image data storage unit 132, a head control unit 133, a purge control unit 134, a head lifting control unit 135, a wiper control unit 136, A cleaner control unit 137, a test pattern printing unit 138, and a discharge determination unit 139 are provided.

  The transport control unit 131 controls the paper feed unit 101b, each pair of feed rollers 14, and the transport mechanism 16 so that the paper P is transported from the paper feed unit 101b to the paper discharge unit 15. The image data storage unit 132 stores image data relating to an image (including a test pattern) formed on the paper P transferred from an external device.

  The head control unit 133 drives the actuator unit 21 of the head 2 based on the image data stored in the image data storage unit 132 to discharge the image quality improving droplet from the discharge port 108 at a desired timing. The actuator unit 21 of each head 1 is driven to eject a desired volume of ink droplets from the ejection port 108 at a desired timing.

  The purge controller 134 drives each pump 32 so that liquid (ink and image quality improving liquid) is discharged from the ejection ports 108 of the heads 1 and 2. The purge control unit 134 has a number of discharge ports 108 detected by a discharge determination unit 139 (described later) equal to or greater than a first predetermined number (for example, 1) and less than a second predetermined number (for example, 10). When it is determined, the pump 32 is driven so that the liquid discharge amount becomes the first predetermined amount. In addition, when the purge control unit 134 determines that the number of ejection ports 108 detected by the ejection determination unit 139 is equal to or greater than the second predetermined number, the second discharge amount of the liquid is greater than the first predetermined amount. The pump 32 is driven so as to be a predetermined amount.

  The head elevating control unit 135 controls the elevating operation of the head holder 35 by the head elevating mechanism 33 so that the five heads 1 and 2 move between the printing position and the retracted position. The wiper control unit 136 controls the wiper unit 36 so that the ejection surfaces 1a and 2a are wiped by the wiper 36a in the wiping operation.

  In the maintenance operation, the cleaner controller 137 causes the conveyor belt 8 to travel clockwise via the conveyor controller 131 at the same time that the wiper 36a starts wiping the ejection surfaces 1a and 2a. Further, the cleaner control unit 137 moves the cleaning liquid application member 37a and the blade 37b to the contact positions. As a result, the cleaning liquid is applied to the outer peripheral surface of the conveyor belt 8, and the ink and the image quality improving liquid on the outer peripheral surface are scraped off together with the cleaning liquid by the blade 37b.

  The test pattern printing unit 138 causes the heads 1 and 2 to print the test patterns 91 and 92 via the head control unit 133 and the conveyance control unit 131 based on a discharge inspection command from the user. FIG. 6 shows an example of a test pattern. The head 1 may form the test pattern 91 on either the plain paper or the thermal paper P, but the head 2 forms the test pattern 92 on the thermal paper. For example, when the test pattern 91 is formed by the head 1, the test pattern printing unit 138 sequentially selects the ejection ports 108 to be ejected from the ejection ports 108 that are arranged at equal intervals in the main scanning direction. Ink droplets are ejected simultaneously at all selected ejection ports 108. Thereby, a linear pattern having a predetermined length in the transport direction is formed side by side in the main scanning direction. The test pattern printing unit 138 repeats such an ejection operation three times while changing the ejection port 108 to be selected one by one from the one side to the other side. In the present embodiment, three linear pattern groups are sequentially arranged in the transport direction while being shifted at the same regular intervals as the ejection ports 108 in the main scanning direction. The same applies when the test pattern 92 is formed. In particular, at this time, the test pattern printing unit 138 controls the heating unit 31 to heat the heating surface 31 a as the test pattern 92 is formed. As a result, the heat-sensitive layer of the heat-sensitive paper is heated to a predetermined temperature or higher, and colors other than the adhesion region 92a to which the image quality improving liquid adheres, as will be described later, are colored (for example, black). As shown in FIG. 6B, the test pattern 92 is clearly shown as a white portion in the coloring area. In addition, since the test pattern 92 before heating is formed of a colorless and transparent image quality improving liquid, the adhesion region 92a cannot be distinguished from other regions.

  The ejection determination unit 139 causes the image sensor 30 to read the test patterns 91 and 92 formed on the paper P, and detects each straight line of the test patterns 91 and 92 from the read result. The ejection determination unit 139 detects the non-ejection ejection port 108 by comparing the test data stored in advance (determination data) with the detection data. At the time of detection, the number of non-ejection ejection ports 108 is compared with two threshold values (a first predetermined number and a second predetermined number), and the degree of ejection failure in the heads 1 and 2 is determined. At this time, the ejection determination unit 139 uses inverted data obtained by inverting the information of the determination data for the test pattern 92 as the determination data for the test pattern 91. This is because the test pattern 92 drawn by the head 2 is an image obtained by inverting the test pattern 91 drawn by the head 1.

  Next, a discharge inspection method for the head 2 will be described below with reference to FIGS. When the ejection inspection of the head 2 is performed, the user sets thermal paper as the paper P in the paper supply unit 101b in advance. As shown in FIG. 7, the printer 101 first receives an ejection inspection command for the head 2 from an external device (S1). When the ejection inspection command is received, in step 2 (S2), the test pattern printing unit 138 causes the paper feed unit 101b, each of the feed roller pairs 14, 28, and the like via the transport control unit 131 so that the thermal paper is transported. The transport mechanism 16 is controlled. At this time, the test pattern printing unit 138 controls the head control unit 132 and the heating unit 31 so that the test pattern 92 is formed on the conveyed thermal paper. As a result, an image quality improving liquid adhering region 92a is formed in the pattern of the test pattern 92 on the thermal paper. In the adhesion region 92a, the developer of the heat sensitive layer is neutralized by the neutralizer of the image quality improving liquid. For this reason, in the adhesion region 92a, there is no developer used for the reaction with the color former, and even if the developer 31 is heated to a predetermined temperature or higher, the color former does not develop color. Therefore, the adhesion area 92a maintains the color before heating, and the areas other than the adhesion area 92a are colored.

  Next, in step 3 (S3), the test pattern 92 on the thermal paper is read by the image sensor 30. In step 4 (S4), the ejection determination unit 139 detects each straight line of the test pattern 92 from the read result, compares the detected data with the determination data, and causes the non-ejection of the image quality improving droplet. The discharge port 108 is detected. At this time, if there is a non-ejection outlet 108, the process proceeds to step 5 (S5), and if not, the process proceeds to step 11 (S11).

  In step 5, the control device 100 determines whether or not the number of non-ejection outlets 108 is greater than or equal to a second predetermined number, and if it is greater than or equal to the second predetermined number, the process proceeds to step 6 (S6). If it is less than the second predetermined number, the process proceeds to step 7 (S7). In step 6, as shown in FIG. 8A, the purge control unit 134 controls the pump 32 corresponding to the head 2 to discharge the second predetermined amount of image quality improving liquid from all the discharge ports 108. (Strong purge operation) On the other hand, in step 7, as shown in FIG. 8A, the purge control unit 134 controls the pump 32 corresponding to the head 2, and the first predetermined amount of image quality improving liquid is discharged from all the discharge ports 108. Is discharged (weak purge operation). Thereby, it becomes possible to recover the ejection failure of the head 2. Further, the amount of the image quality improving liquid to be discharged can be changed according to the number of ejection ports 108 that have caused non-ejection. For this reason, useless consumption of the image quality improving liquid can be suppressed.

  After step 6 or step 7, the head elevating control unit 135 controls the head elevating mechanism 33 to move the five heads 1 and 2 from the printing position to the wiping position as shown in FIG. The wiping position is closer to the printing position than the retracted position, and is a position where the tip of the wiper 36a can be brought into contact with the ejection surface 2a only by moving the wiper unit 36 in the main scanning direction. Then, the wiper control unit 136 controls the wiper unit 36 and wipes the ejection surface 2a with the wiper 36a (wiping operation: step 8 (S8)). In this way, the image quality improving liquid adhering to the ejection surface 2a can be removed.

  In the present embodiment, in step 8, the cleaner control unit 137 starts running of the conveyance belt 8 via the conveyance control unit 131 and brings the cleaner unit 37 into contact with the outer peripheral surface of the conveyance belt 8. At this time, the cleaner control unit 137 makes the traveling speed of the conveyor belt 8 slower than that during image formation. Thereby, the waste liquid adhering to the outer peripheral surface by the purge operation or the wiping operation is surely removed. The conveyor belt 8 travels several times after the wiping operation is completed, and the cleaning of the outer peripheral surface by the cleaner unit 37 is continued. Thereafter, the cleaner control unit 137 returns the cleaner unit 37 to the separation position.

  After step 8, the head lifting control unit 152 controls the head lifting mechanism 33 to move the five heads 1 and 2 from the wiping position to the retracted position, and the wiper control unit 136 controls the wiper unit 36, The wiper 36a is returned to the original position (the standby position of the wiper 36a) (step 9: S9). Thereby, the wiper 36a can be returned to the original position without contacting the discharge surface 2a. After step 9, the head lifting control unit 152 controls the head lifting mechanism 33 to move the five heads 1 and 2 to the printing position as shown in FIG. 8C (step 10: S10).

  After step 10, the control device 100 capping the ejection surfaces 1 a and 2 a of the heads 1 and 2 with a cap (not shown) (capping operation: step 11).

  Next, a discharge inspection method for the head 1 will be described below. The ejection inspection of the head 1 is almost the same as the ejection inspection of the head 2 and only the sheet P is not heated. In other words, the test pattern 91 is formed on the paper P by the ink ejected from the head 1, the paper P is read by the image sensor 30 without being heated, and the purge operation is performed as necessary as in the ejection inspection of the head 2. Do.

  Specifically, when performing a discharge inspection of the head 1, the printer 101 first receives a discharge inspection command of the head 1 from an external device (step 1). When the ejection inspection command is received, in step 2, the test pattern printing unit 138 causes the paper feeding unit 101b and each feed roller pair to be fed via the conveyance control unit 131 so that the paper P (plain paper or thermal paper) is conveyed. 14 and 28 and the transport mechanism 16 are controlled. At this time, the test pattern printing unit 138 controls the head control unit 132 so that the test pattern 91 is formed on the conveyed paper P. As a result, a test pattern 91 is formed on the paper P.

  Next, in step 3, the test pattern 91 on the paper P is read by the image sensor 30. In step 4, the ejection determination unit 139 detects each straight line of the test pattern 91 from the read result, compares the detection data with the determination data, and detects the ejection port 108 causing the ink ejection failure. To do. At this time, the ejection determination unit 139 detects the ejection state of each ejection port 108 using the inverted data obtained by inverting the information of the determination data for ejection inspection for the head 2. As a result, it is possible to determine the presence or absence of ejection failure of the head 1 and the head 2 only by inverting the information of one determination data.

  If there is a non-ejection outlet 108, the process proceeds to step 5, and if not, the process proceeds to step 11. The subsequent processing steps 5 to 11 are the same as the ejection inspection of the head 2. Thus, the ejection inspection of the head 1 is completed.

  As described above, according to the inkjet printer 101 of the present embodiment, when the test pattern 92 is formed on the thermal paper when performing the ejection inspection of the head 2, the region where the test pattern 92 of the thermal layer is formed (that is, Further, since the developer in the adhesion region 92a) where the image quality improving liquid is adhered is neutralized, the color does not change even when the region is heated. For this reason, the area other than the test pattern 92 of the thermal paper is discolored (for example, changed to black) simply by heating the thermal paper above the temperature at which the area where the test pattern 92 of the thermal layer is not formed is discolored. The test pattern 92 can be easily specified. In the present invention, it is not necessary to perform temperature control in a narrow temperature range below the temperature at which the heat-sensitive layer changes color. Therefore, the test pattern 92 can be clearly specified with high accuracy under easy temperature control.

  Further, since the heating unit 31 is provided in the printer 101, the area other than the test pattern 92 on the thermal paper is changed in color, and the test pattern 92 is discharged from the printer 101 in a state where the test pattern 92 is clearly indicated. For this reason, it is not necessary to heat the thermal paper on which the test pattern 92 is formed by a heating mechanism different from the printer 101. Further, since the image sensor 30 is provided in the printer 101, it is possible to accurately determine whether or not the image quality improving liquid is being discharged from the discharge port 108 of the head 2.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims. For example, the heating unit 31 and the image sensor 30 may not be provided. In this case, the test pattern 92 can be clearly shown by heating the thermal paper on which the test pattern 92 is printed using a heating mechanism (for example, a dryer) different from the printer 101. Then, the user visually checks the thermal paper on which the test pattern 92 is clearly specified, so that it is possible to determine whether or not there is a discharge failure at the discharge port 108. In addition, when the test pattern 92 is visually confirmed by the user without providing the image sensor 30, the test pattern 92 is configured by a white area (that is, the test pattern formation portion is inverted). ) Visual confirmation of the test pattern 92 by the user is extremely easy. That is, it is possible to easily find missing patterns.

  If the number of ejection ports 108 causing non-ejection is one or more, a predetermined amount of liquid may be discharged from the head regardless of the number. Further, the pump 32 for performing the purge operation may not be provided. The ejection inspection of the head 1 that does not eject the image quality improving liquid may not be performed.

  The present invention can be applied to both a line type and a serial type, and is not limited to a printer, and can also be applied to a facsimile, a copier, and the like. In addition, although a piezoelectric actuator is used to discharge droplets, other methods (for example, a resistance heating method or an electrostatic method) may be used.

  Further, a colorless and transparent second liquid containing a component that causes the head 1 to discharge a first liquid containing a dye component other than ink and causes the head 2 to aggregate or deposit the dye component in the first liquid other than the image quality improving liquid. The present invention is also applicable to a liquid ejecting apparatus that performs recording by ejecting liquid. If the thermal paper is used only for the ejection inspection of the head 2, the recording medium other than this is not particularly limited to the paper P, and various recording media may be used. Moreover, the head 1 may be provided 1-3 and 5 or more. Two or more heads 2 may be provided. Moreover, the head 2 may be arrange | positioned downstream from the head 1 regarding the conveyance direction.

1 Inkjet head (first liquid ejection head)
2 Image quality improvement head (second liquid ejection head)
16 Conveyance mechanism 30 Image sensor (reading unit)
31 Heating part (heating mechanism)
32 Pump 91, 92 Test pattern 100 Control device (control means)
101 Inkjet printer (liquid ejection device)
108 Discharge port 139 Discharge determination unit

Claims (6)

A transport mechanism for transporting the recording medium in the transport direction;
A first liquid discharge head formed with a plurality of first discharge ports for discharging a first liquid containing a pigment component;
A second liquid discharge head formed with a plurality of second discharge ports for discharging a colorless and transparent second liquid containing a component for aggregating or precipitating the pigment component in the first liquid;
Control means for controlling the transport mechanism and the first and second liquid ejection heads so as to form an image by ejecting the first and second liquids onto a recording medium;
In the second liquid, an alkaline neutralizing agent that neutralizes an acidic developer contained in a heat-sensitive layer of the thermal paper is in the adhesion region of the thermal paper to which the second liquid is adhered. Is contained in a concentration that can neutralize
The control means controls the second liquid discharge head so as to form a test pattern by discharging the second liquid onto the thermal paper transported by the transport mechanism. . A heating mechanism provided on the downstream side of the second liquid discharge head for heating the recording medium with respect to the transport direction;
The control means controls the heating mechanism such that the thermal paper on which the test pattern is formed is heated to a temperature equal to or higher than a minimum temperature at which the region of the thermal layer where the test pattern is not formed is discolored. The liquid ejection device according to claim 1. A reading unit that is provided downstream of the heating mechanism with respect to the transport direction and reads the test pattern formed on the thermal paper;
The apparatus according to claim 2, further comprising: a discharge determination unit that determines whether or not the second liquid is discharged from the second discharge port based on read data read by the reading unit. The liquid discharge apparatus as described. A discharge means for forcibly discharging the second liquid from all the second discharge ports;
The control means is configured to cause the liquid to be discharged from all the second discharge ports when the discharge determination unit determines that the second liquid is not discharged from a plurality of the second discharge ports. The liquid discharging apparatus according to claim 3, wherein the discharging means is controlled.   The control means is configured so that the number of the second discharge ports that are not discharged from the second liquid determined by the discharge determination unit is greater than or equal to a first predetermined number and less than a second predetermined number. The amount of liquid discharged from the second discharge ports is discharged from all the second discharge ports when the number of the second discharge ports from which the second liquid is not discharged is equal to or greater than the second predetermined number. The liquid discharging apparatus according to claim 4, wherein the discharging unit is controlled so as to be less than a liquid amount. The control means controls the transport mechanism and the first liquid discharge head so as to form the test pattern by discharging the first liquid onto a recording medium;
When the discharge determination unit determines whether or not the first liquid is discharged from the first discharge port based on the read data of the test pattern read by the reading unit, the read data of the test pattern The read data of the test pattern formed on the recording medium is determined using inverted data obtained by inverting the information of the determination data for determining whether or not The liquid discharge apparatus as described.

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