WO2022039065A1 - Head control device, head control method and program, liquid ejection device, and printing device - Google Patents

Abstract

Provided are a head control device for inspecting a liquid ejection head without excessively detecting abnormality, a head control method and a program, a liquid ejection device, and a printing device. A liquid is caused to be ejected from an ejection port of an ejection element of a liquid ejection head on the basis of printing data to print a user image on a base material. When a deteriorated state of the ejection element is below an index for securing inspection accuracy of the ejection element, an inspection pattern having substantially no influence on image quality is formed in a region of the user image by the ejection element, a reading result obtained by reading the inspection pattern with a scanner is acquired, the reading result is analyzed, an abnormality degree of the ejection element is calculated, and treatment is performed on the ejection element according to the abnormality degree.

Description

Head control device, head control method and program, liquid discharge device, printing device

The present invention relates to a head control device, a head control method and program, a liquid discharge device, and a printing device, and particularly relates to a technique for inspecting a liquid discharge head.

A printing machine that prints an image by ejecting a liquid such as ink from a liquid ejection head onto a printing substrate is known. The discharge element that discharges the liquid of the liquid discharge head from the discharge port may deteriorate in the discharge state during printing. In order to grasp the ejection state, there is a method of printing an inspection pattern that does not affect the image quality on the printing substrate, reading it with a scanner, and analyzing it to determine whether an ejection abnormality has occurred (patented). Refer to Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2005-313625 Patent No. 5899222

When the ejection element waits during printing and there is no opportunity to eject the liquid, the ink viscosity inside the ejection port increases, and the analysis result by the inspection pattern becomes worse as a result. The ejected element deteriorated in this way recovers its state by ejecting a predetermined amount of liquid and can be used for printing, so that there is a problem that an abnormality is detected excessively. rice field.

The present invention has been made in view of such circumstances, and provides a head control device, a head control method and program, a liquid discharge device, and a printing device that inspect a liquid discharge head without detecting an excessive abnormality. With the goal.

One embodiment of the head control device for achieving the above object comprises a memory for storing instructions to be executed by the processor and a processor for executing instructions stored in the memory, and the processor is used for print data. Based on this, the liquid is discharged from the discharge port of the discharge element of the liquid discharge head to print a user image on the base material, and when the deterioration state of the discharge element is equal to or less than the index for ensuring the inspection accuracy of the discharge element, it is substantially. An inspection pattern that does not affect the image quality is formed in the area of the user image by the ejection element, the reading result obtained by reading the inspection pattern by the scanner is obtained, the reading result is analyzed, the degree of abnormality of the ejection element is obtained, and the ejection element is obtained. It is a head control device that takes measures according to the degree of abnormality.

According to this aspect, the liquid discharge head can be inspected without detecting an excessive abnormality.

The index is preferably defined as a value at which an abnormality in the discharge element due to deterioration of the liquid in the discharge port is not detected. As a result, the degree of abnormality of the discharge element can be appropriately detected.

It is preferable that the index is determined from the deteriorated volume of the liquid for each standby time by changing the standby time during which the discharge element does not discharge the liquid continuously. As a result, the index can be appropriately acquired.

It is preferable that the processor discharges the liquid until the deterioration state of the discharge element becomes equal to or less than the index. As a result, the deterioration state of the discharge element can be set to the index or lower.

It is preferable that the processor discharges the liquid into the area of the user image in an amount that does not substantially affect the image quality. As a result, the liquid can be discharged without affecting the image quality.

It is preferable that the processor acquires image data representing a user image, generates print data in which an inspection pattern is arranged on the image data, and forms the inspection pattern on the base material by the print data. As a result, the inspection pattern can be appropriately formed in the area of the user image.

One aspect of the liquid discharge device for achieving the above object is a liquid discharge device including a liquid discharge head and the above head control device. According to this aspect, the liquid discharge head can be inspected without detecting an excessive abnormality.

The liquid is preferably a water-based ink. This aspect is suitable for a liquid ejection head that ejects water-based ink whose viscosity increases due to evaporation of water from the ejection port of the ejection element.

The liquid discharge head includes a supply flow path for supplying the liquid to the discharge element and a recovery flow path for collecting the liquid supplied to the discharge element, and the recovery flow path is preferably provided around the discharge port. .. This aspect is suitable for a liquid discharge head provided with a recovery flow path around the discharge element.

One aspect of the printing device for achieving the above object is to relatively move the liquid ejection device, the scanner that reads the inspection pattern and generates the reading result, and the substrate, the liquid ejection head, and the scanner. A printing device including a mobile device. According to this aspect, the liquid discharge head can be inspected without detecting an excessive abnormality.

One aspect of the head control method for achieving the above object is a user image printing step of ejecting liquid from the ejection port of the ejection element of the liquid ejection head to print a user image on a substrate based on print data. When the deterioration state of the ejection element is equal to or less than the index for ensuring the inspection accuracy of the ejection element, an inspection pattern forming step of forming an inspection pattern substantially unaffected by the image quality in the area of the user image by the ejection element. A reading result acquisition process for acquiring the reading result obtained by scanning the inspection pattern with a scanner, an abnormality degree calculation process for analyzing the reading result and obtaining the abnormality degree of the ejection element, and a treatment according to the abnormality degree for the ejection element. It is a head control method including a treatment step.

According to this aspect, the liquid discharge head can be inspected without detecting an excessive abnormality.

One aspect of the program for achieving the above object is a program for causing a computer to execute the head control method described above. A computer-readable non-temporary storage medium on which this program is recorded may also be included in this embodiment.

According to this aspect, the liquid discharge head can be inspected without detecting an excessive abnormality.

According to the present invention, the liquid discharge head can be inspected without detecting an excessive abnormality.

FIG. 1 is an overall configuration diagram of an inkjet printing apparatus. FIG. 2 is a plan perspective view showing a structural example of the inkjet head. FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. FIG. 4 is a block diagram showing a configuration of a control system of an inkjet printing apparatus. FIG. 5 is a diagram showing an example of a paper on which an abnormality nozzle detection pattern is printed. FIG. 6 is a diagram showing an example of a paper on which only a user image is printed. FIG. 7 is a diagram showing an example of printing an inspection pattern in a user image. FIG. 8 is an enlarged view of the nozzle portion shown in FIG. FIG. 9 is a graph for explaining the transition of the deteriorated volume of a certain nozzle. FIG. 10 is a graph showing the relationship between the discharge drop amount of the nozzle waiting for 10 seconds and the discharge speed. FIG. 11 is a graph showing an example of the relationship between the deteriorated volume of the inkjet head and the number of abnormal inspection nozzles. FIG. 12 is a diagram showing a paper on which a reference dot pattern for acquiring a dot diameter and a dot shape in a normal state is printed. FIG. 13 is a flowchart showing each step of the head control method.

Hereinafter, preferred embodiments of the present invention will be described in detail according to the accompanying drawings.

[Structure of inkjet printing device]
FIG. 1 is an overall configuration diagram of the inkjet printing apparatus 10 according to the present embodiment. The inkjet printing apparatus 10 is a printing machine that prints an image on a web-shaped paper 1 by a single pass method. General-purpose printing paper is used as the paper 1. The general-purpose printing paper is not a so-called inkjet-only paper, but a paper mainly composed of cellulose such as coated paper used for general offset printing and the like.

As shown in FIG. 1, the inkjet printing apparatus 10 includes a transport unit 20, a feed unit 30, a pretreatment liquid application unit 40, a printing unit 50, a drying unit 70, and a winding unit 80. It is composed.

[Transporting section / Sending section / Winding section]
The transport section 20 transports the paper 1 from the feed section 30 to the take-up section 80 along the transport path. The transport unit 20 includes a plurality of pass rollers 22 that function as guide rollers.

The delivery unit 30 includes a delivery roll 32. The feed roll 32 includes a reel (not shown) that is rotatably supported. Paper 1 before the image is printed is wound on the reel in a roll shape.

On the other hand, the take-up unit 80 includes a take-up roll 82. The take-up roll 82 includes a rotatably supported reel (not shown). One end of the paper 1 is connected to the reel. The take-up roll 82 includes a take-up motor (not shown) for rotationally driving the reel.

The paper 1 is conveyed by the conveying unit 20 in a roll-to-roll manner along the conveying path from the sending roll 32 to the take-up roll 82. In this specification, the transport path of the paper 1 may be simply referred to as a “transport path”.

[Pretreatment liquid application part]
The pretreatment liquid application unit 40 is arranged on the upstream side of the transport path with respect to the printing unit 50. The pretreatment liquid application unit 40 applies the pretreatment liquid to the printed surface of the paper 1. The pretreatment liquid is a liquid containing water and a component that aggregates, insolubilizes, or thickens the color material component in the water-based ink, and thickens by reacting with the water-based ink.

The pretreatment liquid coating unit 40 includes a coating roller 42, an opposing roller 44, and a pretreatment liquid drying unit 46. The paper 1 conveyed from the feeding section 30 is guided by the pass roller 22 and conveyed to a position facing the coating roller 42.

The coating roller 42 is rotated by a motor (not shown). A pretreatment liquid is supplied to the surface of the coating roller 42 from a coater (not shown), and then excess pretreatment liquid is scraped off by a blade (not shown). The coating roller 42 sandwiches the paper 1 with the facing roller 44, brings the surface to which the pretreatment liquid is supplied into contact with the printing surface of the paper 1, and causes the pretreatment liquid supplied to the surface to come into contact with the printing surface of the paper 1. Apply to.

The method of applying the pretreatment liquid to the printed surface of the paper 1 is not limited to the method using a coating roller, and may be, for example, a method using a liquid ejection head.

The paper 1 coated with the pretreatment liquid is conveyed to the pretreatment liquid drying unit 46. The pretreatment liquid drying unit 46 includes a hot air heater (not shown). The pretreatment liquid drying unit 46 blows warm air from the warm air heater toward the printing surface of the paper 1 to dry the pretreatment liquid.

The paper 1 on which the pretreatment liquid has been dried is guided by the pass roller 22 and conveyed to the printing unit 50.

[Printing section]
The printing unit 50 prints an image on the printing surface of the paper 1. The printing unit 50 includes a printing drum 52, inkjet heads 54K, 54C, 54M, 54Y, and a scanner 56.

The paper 1 conveyed from the pretreatment liquid application unit 40 is guided by a plurality of pass rollers 22 and conveyed to the printing drum 52.

The print drum 52 is rotated by a motor (not shown), and the paper 1 is held on the outer peripheral surface and conveyed. The print drum 52 has a plurality of suction holes (not shown) on the outer peripheral surface. The print drum 52 sucks the paper 1 on the outer peripheral surface by sucking the suction holes by a pump (not shown).

The paper 1 conveyed by the print drum 52 is conveyed to a position facing the inkjet heads 54K, 54C, 54M, 54Y.

The inkjet heads 54K, 54C, 54M, and 54Y eject water-based inks (examples of liquid) of black (K), cyan (C), magenta (M), and yellow (Y), respectively. The water-based ink refers to an ink in which a coloring material such as a dye or a pigment is dissolved or dispersed in water and a solvent soluble in water. Water-based ink is supplied to each of the inkjet heads 54K, 54C, 54M, and 54Y from an ink tank of a corresponding color (not shown) via a piping path (not shown).

The inkjet heads 54K, 54C, 54M, and 54Y are each composed of a line-type recording head that can be printed by scanning once with respect to the paper 1 conveyed by the printing drum 52. The inkjet heads 54K, 54C, 54M, and 54Y may be configured by connecting a plurality of head modules in the X direction. The nozzle surfaces of the inkjet heads 54K, 54C, 54M, and 54Y are arranged so as to face the printing drum 52, respectively. The inkjet heads 54K, 54C, 54M, 54Y are arranged at regular intervals along the transport path.

The scanner 56 includes an image pickup device that captures an image printed on the print surface of the paper 1 and converts it into an electric signal. A color CCD (Charge Coupled Device) linear image sensor can be used as the image pickup device. A color CMOS (Complementary Metal Oxide Semiconductor) linear image sensor can also be used instead of the color CCD linear image sensor.

The printing unit 50 ejects droplets of water-based ink from at least one of the inkjet heads 54K, 54C, 54M, and 54Y toward the printing surface of the paper 1 conveyed by the printing drum 52. The ejected droplets of the water-based ink adhere to the paper 1, so that an image is printed on the printing surface of the paper 1.

Further, the scanning result is acquired by scanning the printed surface of the paper 1 conveyed by the printing drum 52 with the scanner 56.

As described above, the transport unit 20 corresponds to a moving device that relatively moves the paper 1 and the inkjet heads 54K, 54C, 54M, 54Y, and the scanner 56.

[Dry part]
The drying unit 70 dries the ink on the printing surface of the paper 1. The drying unit 70 includes a drying drum 72.

The paper 1 conveyed from the printing unit 50 is conveyed to the drying drum 72. The drying drum 72 is rotated by a motor (not shown) to hold and convey the paper 1 on the outer peripheral surface. The drying drum 72 has a plurality of suction holes (not shown) on the outer peripheral surface. The drying drum 72 sucks the paper 1 on the outer peripheral surface by sucking the suction holes by a pump (not shown).

The drying unit 70 is provided with a hot air heater (not shown) around the drying drum 72. The drying unit 70 blows warm air from the hot air heater toward the printing surface of the paper 1 to dry the ink.

[Inkjet head configuration]
The structures of the inkjet heads 54K, 54C, 54M, and 54Y will be described. Since the structures of the inkjet heads 54K, 54C, 54M, and 54Y are common, the inkjet head 54 will be described here.

FIG. 2 is a plan perspective view showing a structural example of the inkjet head 54 (an example of a liquid ejection head), and FIG. 3 is a sectional view taken along the line 3-3 of FIG.

The inkjet head 54 includes a nozzle plate 130 in which a nozzle 102, which is an ink droplet ejection port, is formed, and a flow path plate 132 in which an ink flow path is formed. The nozzle plate 130 and the flow path plate 132 are laminated and joined. The flow path plate 132 has a structure in which one or a plurality of substrates are laminated. The nozzle plate 130 and the flow path plate 132 can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

The inkjet head 54 is provided with a plurality of nozzles 102 on the nozzle surface 100 which is the bottom surface. Further, a plurality of ink chamber units 106 (an example of an ejection element) composed of pressure chambers 104 and the like provided corresponding to each nozzle 102 are two-dimensionally arranged in a fixed arrangement pattern. As a result, a substantially high density of nozzle spacing is achieved, which is projected so as to line up along the X direction.

The pressure chamber 104 communicates with the supply tributary 110 (an example of the supply flow path) via the supply throttle 108, and each supply tributary 110 communicates with the common flow path 112. Further, the descender 114 communicating with each pressure chamber 104 is communicated with the circulation common flow path 120 via the ink circulation path 116 (an example of the recovery flow path) and the recovery tributary 118. The inkjet head 54 is provided with a supply port 122 and a discharge port 124, the supply port 122 communicates with the common flow path 112, and the discharge port 124 communicates with the circulation common flow path 120.

As described above, the supply port 122 and the discharge port 124 of the inkjet head 54 have a common flow path 112, a supply tributary 110, a supply throttle 108, a pressure chamber 104, a descender 114, an ink circulation path 116, a recovery tributary 118, and a circulation common flow. It is configured to be communicated via the road 120.

Therefore, the ink supplied to the supply port 122 flows through the common flow path 112, the supply tributary 110, the supply throttle 108, the pressure chamber 104, and the descender 114, a part of the ink is discharged from each nozzle 102, and the remaining ink is ink. It is discharged from the discharge port 124 via the circulation path 116, the recovery tributary 118, and the circulation common flow path 120.

The ink circulation path 116 is preferably configured to be provided around the nozzle 102. Here, the ink circulation path 116 is provided in a region communicating with the descender 114 and in contact with the nozzle plate 130 of the flow path plate 132. As a result, the ink circulates in the vicinity of the nozzle 102, so that the ink thickening inside the nozzle 102 is prevented and stable ejection is possible.

Further, an actuator 128 having an individual electrode (not shown) is joined to the diaphragm 126 which constitutes the top surface of the pressure chamber 104 and is also used as a common electrode. When a predetermined voltage is applied to the individual electrodes, the actuator 128 is deformed in the direction of contracting the pressure chamber 104. As a result, ink is ejected from the nozzle 102. After that, the actuator 128 is deformed in the direction of expanding the pressure chamber 104. As a result, new ink is supplied to the pressure chamber 104 from the common flow path 112 through the supply tributary 110 and the supply throttle 108.

Here, the actuator 128 is applied as a means for generating the ejection force of the ink ejected from the nozzle 102, but a thermal method is provided in which a heater is provided in the pressure chamber 104 and the ink is ejected by using the pressure of the film boiling due to the heating of the heater. It is also possible to apply.

The arrangement structure of the nozzle 102 is not limited to the illustrated example, and various nozzle arrangement structures such as an arrangement structure having one row of nozzles in the X direction can be applied.

[Control system for inkjet printing equipment]
FIG. 4 is a block diagram showing a configuration of a control system of the inkjet printing apparatus 10. The inkjet printing apparatus 10 includes a transport control unit 150, a pretreatment liquid application control unit 152, a print control unit 154, a drying control unit 156, a general control unit 158, and a user interface 164.

The transport control unit 150 unwinds the paper 1 from the feed roll 32 by rotationally driving the take-up roll 82 with a motor (not shown). The transport unit 20 guides the paper 1 by a plurality of pass rollers 22, and the take-up unit 80 winds the printed paper 1 on the take-up roll 82. As a result, the paper 1 is conveyed to the feeding unit 30, the pretreatment liquid application unit 40, the printing unit 50, the drying unit 70, and the winding unit 80.

The transport control unit 150 controls a pump (not shown) to attract the paper 1 to the outer peripheral surface of the printing drum 52. The transport control unit 150 rotates the print drum 52 by a motor (not shown). Further, the transfer control unit 150 acquires an encoder value from a rotary encoder (not shown) arranged on the print drum 52.

The transport control unit 150 controls a pump (not shown) to attract the paper 1 to the outer peripheral surface of the drying drum 72. The transport control unit 150 rotates the drying drum 72 by a motor (not shown).

The pretreatment liquid application control unit 152 applies the pretreatment liquid to the printed surface of the paper 1 by the coating roller 42. Further, the pretreatment liquid application control unit 152 dries the pretreatment liquid applied to the printed surface of the paper 1 by a warm air heater (not shown) of the pretreatment liquid drying unit 46.

The print control unit 154 controls the ejection of ink by the inkjet heads 54K, 54C, 54M, 54Y based on the print data. The print control unit 154 directs black, cyan, magenta, and yellow ink droplets toward the paper 1 by the inkjet heads 54K, 54C, 54M, and 54Y, respectively, in synchronization with the encoder value acquired via the transport control unit 150. And discharge. As a result, a color image is printed on the printed surface of the paper 1, and the paper 1 becomes a "printed matter".

The print control unit 154 causes the scanner 56 to read the image printed on the paper 1 in synchronization with the encoder value acquired via the transport control unit 150, and acquires the reading result.

The inkjet printing apparatus 10 may acquire information on the location of the nozzle 102 with a ejection defect by forming a detection pattern by the print control unit 154 and analyzing the reading result read by the scanner 56. The print control unit 154 may output information on the location of the nozzle 102 having a ejection failure to the control unit 158.

Further, the print control unit 154 may have a compensation function of correcting the print data and compensating for the print area of the nozzle 102 having a ejection defect. As an example, there is a compensation function for compensating for a nozzle 102 with defective ejection by increasing the volume of ink droplets of a plurality of adjacent nozzles 102. The print control unit 154 outputs information on the portion compensated by the compensation function of the printed matter to the integrated control unit 158.

The drying control unit 156 controls heating by a hot air heater (not shown), so that the drying unit 70 dries the paper 1.

The integrated control unit 158 controls the operation of the inkjet printing device 10 by controlling the transfer control unit 150, the pretreatment liquid application control unit 152, the print control unit 154, and the drying control unit 156, respectively. The integrated control unit 158 includes a processor 160 and a memory 162. The processor 160 executes an instruction stored in the memory 162.

The hardware structure of the processor 160 is various processors as shown below. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and acts as various functional units, and a GPU (Graphics Processing Unit), which is a processor specialized in image processing. A circuit specially designed to execute specific processing such as PLD (Programmable Logic Device), ASIC (Application Specific Integrated Circuit), which is a processor whose circuit configuration can be changed after manufacturing FPGA (Field Programmable Gate Array), etc. A dedicated electric circuit or the like, which is a processor having a configuration, is included.

One processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same type or different types (for example, a plurality of FPGAs, or a combination of CPU and FPGA, or with a CPU. It may be composed of a combination of GPUs). Further, a plurality of functional units may be configured by one processor. As an example of configuring a plurality of functional units with one processor, first, one processor is configured by a combination of one or more CPUs and software, as represented by a computer such as a client or a server. There is a form in which the processor acts as a plurality of functional parts. Secondly, as typified by SoC (System On Chip), there is a form of using a processor that realizes the functions of the entire system including a plurality of functional units with one IC (Integrated Circuit) chip. As described above, the various functional units are configured by using one or more of the above-mentioned various processors as a hardware-like structure.

Furthermore, the hardware-like structure of these various processors is, more specifically, an electric circuit (circuitry) in which circuit elements such as semiconductor elements are combined.

The memory 162 stores an instruction to be executed by the processor 160. The memory 162 includes a RAM (RandomAccessMemory) and a ROM (ReadOnlyMemory) (not shown). The processor 160 uses the RAM as a work area, executes software using various programs and parameters including a head control program stored in the ROM, and uses the parameters stored in the ROM or the like to perform inkjet printing. Various processes of the device 10 are executed.

The integrated control unit 158 corresponds to the head control device. Further, the integrated control unit 158 and the inkjet heads 54K, 54C, 54M, 54Y correspond to a liquid ejection device.

The user interface 164 includes an input unit (not shown) for the user to operate the inkjet printing device 10 and a display unit (not shown) for presenting information to the user. The input unit is, for example, an operation panel that receives input from a user. The display unit is, for example, a display that displays image data and various types of information. The user can have the inkjet printing device 10 print a desired image by using the user interface 164.

[Problems with inkjet printing machines]
In an inkjet printing machine such as the inkjet printing apparatus 10, since tens of thousands of ejection elements are controlled to form a printed image, it is inevitable that an ejection element causing an abnormality will occur during printing. Therefore, the inkjet printing machine reads the "abnormal nozzle detection pattern" printed in the gap between the user images by the scanner installed inside the device, and determines whether the ejection element is operating normally from the read abnormal nozzle detection pattern. Technology is used.

FIG. 5 is a diagram showing an example of paper 1 on which an abnormality nozzle detection pattern is printed. In the example shown in FIG. 5, a plurality of user images _GU are printed along the transport direction of the paper 1, and an abnormality nozzle detection pattern _PN is printed between the user image _GU and the user image _GU . ing.

However, there is a problem that the area where the abnormality nozzle detection pattern _PN of the paper 1 is printed becomes a loss. Further, when the printed roll is post-processed, there is a problem that it is necessary to remove this abnormality nozzle detection pattern _PN . Therefore, it is preferable that the abnormality nozzle detection pattern _PN is not printed between the user image _GU and the user image _GU .

FIG. 6 is a diagram showing an example of paper 1 on which only the user image _GU is printed. As shown in FIG. 6, if the abnormality nozzle detection pattern _PN is not printed and there is no gap between the user images _GUs , there is no loss area and post-processing is easy.

However, in the example shown in FIG. 6, the abnormality of the nozzle cannot be detected by utilizing the abnormality nozzle detection pattern _PN . Therefore, it is conceivable to perform ejection at a level permitted by the user in the area of the user image _GU and read it with a scanner to determine whether or not there is an abnormality in the nozzle.

FIG. 7 is a diagram showing an example of printing the inspection pattern _PD in the user image _GU . F7A shown in FIG. 7 shows paper 1 on which a plurality of user images _GU are printed. Further, _F7B shown in FIG. 7 is an enlarged view of one of the plurality of user image _GUs .

As shown in F7A, a plurality of user images _GU are printed on the paper 1 along the transport direction of the paper 1. The abnormality nozzle detection pattern _PN is not printed on the paper 1, and there is no gap between the user images _GU . Further, as shown in _F7B , an inspection pattern PD composed of a plurality of dots _D is arranged on the user image GU. Here, for the sake of explanation, the dot _D is expressed in a size relatively larger than the actual size, but the inspection pattern PD is not visible to the human eye and has virtually no effect on the image quality.

Especially when water-based ink is used, the viscosity of the ink in the nozzle increases due to water evaporation during the waiting time during printing. Therefore, the discharge state is deteriorated by the standby, and if an abnormality inspection is attempted after the standby, there is a possibility that an abnormality is detected excessively.

If the abnormality nozzle detection pattern _PN shown in FIG. 5 can be arranged between the user images _GU , a certain amount of space can be secured, so that the ink ejection amount can be increased and the influence of water evaporation can be ignored. However, when the abnormality of the nozzle is detected by the inspection pattern PD composed of the dots _D shown in FIG. 7, the ink ejection amount cannot be increased and the viscosity of the ink may increase. Such a phenomenon may occur even in oil-based inks and UV (UltraViolet) inks.

On the other hand, in the inkjet head 54 of the inkjet printing apparatus 10, as shown in FIGS. 2 and 3, fresh ink is continuously sent around the nozzle 102 by ink circulation to prevent an increase in the viscosity of the ink in the nozzle 102. is doing.

FIG. 8 is an enlarged view of the nozzle 102 portion shown in FIG. The nozzle 102 has a minute constricted region 102A in which ink is not circulated. Here, the region formed by the nozzle plate 130 is applicable. Ink circulation cannot flow in the volume of the narrowed region 102A (hereinafter referred to as the nozzle volume), and the ink becomes thickened. Therefore, there is a case where a technique of moving the actuator 128 (see FIG. 3) to the extent that the ink is not ejected and stirring the ink in the nozzle 102 is adopted. However, the technique of stirring the ink in the nozzle 102 may not be applicable because the power consumption increases and the stirring operation leads to unstable ejection depending on the ink. Therefore, it is necessary to consider the ink thickening corresponding to the nozzle volume on the premise that it can occur.

On the other hand, there is known a technique of discarding ink on paper at predetermined time intervals so that the state of ink in the nozzle does not deteriorate during standby (see Patent Document 2). Combining this discarding technique with the reading inspection of the inspection pattern _PD in the user image _GU described above, it is conceivable to discard before the reading inspection.

However, in order to create a good nozzle condition in the dark clouds, it is necessary to increase the amount of ink discarded on the user image before inspection, and the ink dots on the user image _GU become easily visible. Further, even a nozzle in a good condition needs to be thrown away, and the amount of the nozzle in a bad condition is thrown away.

Therefore, the present invention defines a parameter that allows printing of an inspection pattern, and proposes an inkjet printing apparatus 10 that forms an inspection pattern when the condition is better than that.

[Deteriorated volume]
Here, in order to have a more quantitative discussion, the idea of deteriorated volume [pL] is introduced. The deteriorated volume is the volume of the ink in the nozzle whose state has deteriorated, and is defined in the range from 0 [pL] to the nozzle volume Vn [pL] which is the volume of the narrowed region of the nozzle.

Also, the deterioration volume speed [pL / s] is defined. This is the ink volume that deteriorates per second. It is considered that the ink corresponding to the deteriorated volume is discharged by ejecting the ink from the nozzle.

FIG. 9 is a graph for explaining the transition of the deteriorated volume of a certain nozzle. In FIG. 9, the horizontal axis represents time [s] and the vertical axis represents deterioration volume [pL].

_{In FIG} . ₉ , the period from time T1 to time T2 _, the period from time T3 to time _T4 , the period from time _T6 to time T7, and the period from time _T9 to time _T10 are It shows how the deteriorated volume of the ink in the nozzle increases at a constant rate because the ink is not ejected from the nozzle. In addition, during the period from time T ₂ to time T ₃ , the period from time T ₄ to time T ₅ , and the period from time T ₇ to time T ₈ , the ink in the nozzle is ejected by ejecting the ink. It shows how the deteriorated volume decreases.

In addition, during the period from time T ₅ to time T ₆ and the period from time T ₈ to time T ₉ , the ink in the nozzle is not deteriorated and is in a fresh state by continuously ejecting ink from the nozzle. It shows how to maintain. Further, the period after the time _T10 shows that the deterioration state is saturated.

In FIG. 9, when the deterioration volume on the vertical axis is close to 0, the ink in the nozzle is in a fresh state. This shows the state of the nozzle used for normal printing, and in this case, ejection failure due to deterioration of ink does not occur.

On the other hand, when the nozzle is not used and stands by (non-ejection state continues), it deteriorates at the deterioration volume speed defined above. This deterioration is saturated with the nozzle volume Vn during the continuous printing time performed by a normal inkjet printing machine.

As an example, the deterioration volume speed is 5 [pL / s], the ink ejection amount from the nozzle is 1 [pL] to 100 [pL] per shot (1 dot), and the nozzle volume is 10 [pL] to 1000 [pL]. ].

[Measurement method of deterioration volume speed]
The deterioration volume speed can be measured by the following method.

The deterioration state of the ink in the nozzle can be measured by using the ink ejection speed as an example. The discharge rate can be measured with a light source and a camera.

FIG. 10 is a graph showing the relationship between the discharge drop amount of the nozzle waiting for 10 seconds and the discharge speed. In FIG. 10, the horizontal axis represents the ejection droplet amount [pL], and the vertical axis represents the ink ejection speed [m / s]. The amount of ejected drops is the product of the number of droplets [emitted] of the ejected ink and the amount of droplets [pL] per drop. Here, the ejection speed of the ink that has not deteriorated is defined as _VF [m / s].

As shown in FIG. 10, the ink in the nozzle deteriorated by waiting for 10 seconds is then ejected by repeating the ink ejection. When 50 [pL] is discharged, the discharge speed becomes _VF [m / s], and it can be seen that the inside of the nozzle is completely fresh. Here, it is considered that the deteriorated state of the nozzle is eliminated by ejecting 50 [pL] of ink. Since the deterioration is 50 [pL] after waiting for 10 seconds, the deterioration volume speed is 5 [pL / s].

When a plurality of ink droplet sizes are used for image formation, the ejection droplet amount may be defined by the ejection droplet amount of a typical size.

[Measurement method of index]
The index Vth for ensuring the inspection accuracy of the nozzle can be determined by the following method.

As a way of thinking, the causes of nozzles with poor ejection conditions are divided into the following two types.

One is a nozzle whose ejection condition has deteriorated due to deterioration of ink due to standby (cause a). Since this type of nozzle can be recovered by discharging to some extent, it is not preferable to detect it as an abnormality.

The other is a nozzle with a poor ejection condition for a reason different from the deterioration of ink due to standby (cause b). This type of nozzle does not recover when ejecting ink.

It is the nozzle of type b that should detect the abnormality in the inspection pattern in the user image in this embodiment. Therefore, the state in which the nozzle detected by the cause a becomes zero (value at which the abnormality is not detected) can be defined as the index Vth.

FIG. 11 is a graph showing an example of the relationship between the deteriorated volume of the inkjet head and the number of abnormal inspection nozzles. In FIG. 11, the horizontal axis shows the deteriorated volume [pL], and the vertical axis shows the number of abnormal inspection nozzles [pieces].

The deteriorated volume can be controlled by the waiting time. For example, as described with reference to FIG. 10, the deteriorated volume after waiting for 10 seconds is 50 [pL]. In the graph shown in FIG. 11, the deteriorated volume for each waiting time is obtained while changing the waiting time, the abnormal nozzle inspection is performed during the waiting time, and the number of detected abnormal nozzles is plotted on the vertical axis. be.

From this graph, the index Vth can be obtained. The index Vth is, for example, 100 [pL]. Of course, the calculation of the index Vth is performed before the actual printing. As shown in FIG. 11, the number of abnormal nozzles due to cause b is constant regardless of the deteriorated volume. On the other hand, the number of abnormal nozzles due to cause a is not detected until the deterioration volume reaches the index Vth, but increases as the deterioration volume increases when the deterioration volume exceeds the index Vth.

Here, the abnormality nozzle inspection can be realized by reading the inspection pattern with a scanner and analyzing the read inspection pattern. In this case, it is common to compare the inspection pattern with the normal dot diameter and dot shape. Alternatively, normality or abnormality may be determined based on whether or not there is a dot at the position observed by the scanner, whether or not the landing position of the line deviates from the target position, and the like.

FIG. 12 is a diagram showing a paper 1 on which a reference dot pattern _PR for acquiring a dot diameter and a dot shape in a normal state is printed. _F12A shown in FIG. 12 shows the discarded area A and the reference dot pattern PR. Further, _F12B shown in FIG. 12 is an enlarged view of the reference dot pattern PR.

As shown in _F12A , the discarding area A is located on the upstream side of the reference dot pattern PR in the transport direction of the paper 1. The discarding area A is an area where a sufficient amount of discarding is performed for each nozzle. Each nozzle is thrown away until the deteriorated volume becomes equal to or less than the index Vth.

As shown in _F12B , in the reference dot pattern PR, dots formed by ejection from each nozzle are regularly arranged. The inkjet printing machine reads the reference dot pattern _PR by a scanner, and obtains the dot diameter and the dot shape formed by the ejection from each nozzle in the normal state from the reading result.

In addition, if it should be in a state of deterioration volume lower than the index Vth before using it for actual printing instead of inspection, it is necessary to intentionally increase the amount of waste to ensure a more appropriate state. Can be done. That is, the ink may be ejected until the deteriorated volume of the nozzle becomes equal to or less than the index Vth.

[How to apply Vth]
When the nozzle volume Vn is 200 [pL] and the index Vth is 100 [pL], the following idea is obtained when the present invention is applied.

Suppose that the deterioration condition of a certain nozzle is saturated and you want to carry out an inspection. In that case, an inspection pattern is formed after discarding ink for Vn-Vth = 200 [pL] -100 [pL] = 100 [pL]. It is not necessary to discard more ink because it increases the risk of image quality deterioration.

Also, for example, assuming that there is a nozzle in a fresh state with a deteriorated volume of 0 [pL], after leaving it unattended, an attempt is made to determine whether or not the inspection can be carried out without discarding. In this case, if the deterioration volume speed is 5 [pL / s], it can be seen that the inspection pattern may be formed without discarding within 20 seconds.

[Head control method]
A method of controlling the head by the inkjet printing apparatus 10 will be described. FIG. 13 is a flowchart showing each step of the head control method.

In step S1, the processor 160 of the integrated control unit 158 acquires image data representing the user image _GU to be printed on the paper 1.

In step S2, the processor 160 acquires the deterioration state of each nozzle 102 of the inkjet heads 54K, 54C, 54M, 54Y. Here, the deteriorated volume is acquired as the deteriorated state.

In step S3 (an example of the user image printing process), the processor 160 controls the inkjet printing device 10 to print the user image _GU on the paper 1.

In step S4 (an example of the inspection pattern forming step), the processor 160 determines the inkjet heads 54K, 54C, 54M when the deterioration state of the nozzle 102 is equal to or less than the index Vth for ensuring the inspection accuracy (an example of the inspection pattern or less). , _54Y causes an inspection pattern P _D that has substantially no effect on image quality to be formed in the region of the user image GU. Since the inkjet printing apparatus 10 prints an image by a single-pass method, steps S3 and _S4 print the user image _GU and the inspection pattern PD in one transfer of the paper 1.

That is, the processor 160 generates print data in which the inspection pattern PD composed of the dots _D formed by the nozzle 102 whose deterioration volume is the index Vth or less is arranged in the image data acquired in step S1. Further, the processor 160 forms the user image _GU and the inspection pattern _PD on the paper 1 on the base material by the print data.

The processor 160 can calculate the deteriorated volume of the nozzle 102 from the nozzle volume Vn [pL], the time [s] from the previous ejection, and the deteriorated volume speed [pL / s].

When the deteriorated volume of the nozzle 102 to be inspected is larger than the index Vth, the processor 160 may eject (discard) the ink until the deteriorated state of the nozzle 102 becomes equal to or less than the index Vth. In this case, the processor 160 ejects ink to the area of the user image _GU in an amount that does not substantially affect the image quality.

Here, the inspection pattern P _D that has substantially no effect on the image quality is a distinction between the user image _GU including the inspection pattern P _D and the user image _GU not including the inspection pattern P _D when visually viewed by the user. _Refers to the inspection pattern PD that does not work.

In step S5 (an example of the reading result acquisition process), the processor 160 causes the scanner 56 to read the inspection pattern P _D together with the user image _GU , and acquires the reading result of the inspection pattern P _D.

In step S6 (an example of the abnormality degree calculation step), the processor 160 analyzes the reading result of the inspection pattern _PD and obtains the abnormality degree of the nozzle 102.

In step S7 (an example of the treatment step), the processor 160 treats the nozzle 102 according to the degree of abnormality.

For example, if the amount of ink ejected from the nozzle 102 is not appropriate, the drive voltage of the corresponding actuator 128 is controlled. When ink is not ejected from the nozzle 102 (it is a non-ejection nozzle), the ejection amount of the adjacent nozzle 102 in the X direction is increased to correct the streaks caused by the non-ejection nozzle.

In this way, by using the index Vth, it is possible to inspect the inkjet heads 54K, 54C, 54M, 54Y in an appropriate state.

〔others〕
Here, the inkjet head 54 that circulates ink around the nozzle 102 has been described as an example, but the present embodiment can also be applied to an inkjet head that does not circulate ink.

The technical scope of the present invention is not limited to the scope described in the above embodiment. The configurations and the like in each embodiment can be appropriately combined between the embodiments without departing from the spirit of the present invention.

1 ... Paper 10 ... Inkjet printing device 20 ... Conveying unit 22 ... Pass roller 30 ... Feeding unit 32 ... Feeding roll 40 ... Pretreatment liquid coating unit 42 ... Coating roller 44 ... Opposing roller 46 ... Pretreatment liquid drying unit 50 ... Printing unit 52 ... Printing drum 54 ... Inkjet head 54C ... Inkjet head 54K ... Inkjet head 54M ... Inkjet head 54Y ... Inkjet head 56 ... Scanner 70 ... Drying unit 72 ... Drying drum 80 ... Winding unit 82 ... Winding roll 100 ... Nozzle surface 102 ... Nozzle 102A ... Narrowing region 104 ... Pressure chamber 106 ... Ink chamber unit 110 ... Supply tributary 112 ... Common flow path 114 ... Decender 116 ... Ink circulation path 118 ... Recovery tributary 120 ... Circulation common flow path 122 ... Supply port 124 ... Discharge port 126 ... Vibrating plate 128 ... Actuator 130 ... Nozzle plate 132 ... Flow path plate 150 ... Transfer control unit 152 ... Pretreatment liquid application control unit 154 ... Print control unit 156 ... Drying control unit 158 ... General control unit 160 ... Processor 162 ... Memory 164 ... User interface A ... Area D ... Dot _GU ... User image P _D ... Inspection pattern _PN ... Abnormal nozzle detection pattern _PR ... Reference dot pattern S1 to S7 ... Each step of the head control method

Claims (13)

1. A memory that stores instructions for the processor to execute,
   A processor that executes instructions stored in memory, and
   Equipped with
   The processor
   Based on the print data, the liquid is discharged from the discharge port of the discharge element of the liquid discharge head to print the user image on the base material.
   When the deterioration state of the ejection element is equal to or less than the index for ensuring the inspection accuracy of the ejection element, an inspection pattern having substantially no effect on the image quality is formed in the region of the user image by the ejection element.
   The reading result of reading the inspection pattern with a scanner is acquired, and
   The reading result is analyzed, and the degree of abnormality of the discharge element is obtained.
   The discharge element is treated according to the degree of abnormality.
   Head control device.
2. The head control device according to claim 1, wherein the index is defined as a value at which an abnormality of the discharge element due to deterioration of the liquid in the discharge port is not detected.
3. The head control device according to claim 2, wherein the index is determined from the deteriorated volume of the liquid for each standby time by changing the standby time in which the discharge element continuously discharges the liquid.
4. The head control device according to any one of claims 1 to 3, wherein the processor discharges the liquid until the deterioration state of the discharge element becomes equal to or less than the index.
5. The head control device according to claim 4, wherein the processor discharges the liquid into the area of the user image in an amount that does not substantially affect the image quality.
6. The processor
   The image data representing the user image is acquired, and the image data is obtained.
   Print data in which the inspection pattern is arranged on the image data is generated.
   The head control device according to any one of claims 1 to 5, wherein an inspection pattern is formed on the substrate by the print data.
7. With the liquid discharge head,
   The head control device according to any one of claims 1 to 6.
   A liquid discharge device equipped with.
8. The liquid ejection device according to claim 7, wherein the liquid is a water-based ink.
9. The liquid discharge head is
   A supply flow path for supplying the liquid to the discharge element,
   A recovery flow path for recovering the liquid supplied to the discharge element, and a recovery flow path.
   Equipped with
   The liquid discharge device according to claim 7 or 8, wherein the collection flow path is provided around the discharge port.
10. The liquid discharge device according to any one of claims 7 to 9,
    A scanner that reads the inspection pattern and generates a reading result,
    A moving device that relatively moves the base material, the liquid discharge head, and the scanner.
    A printing device equipped with.
11. A user image printing process in which a liquid is discharged from a discharge port of a discharge element of a liquid discharge head based on print data to print a user image on a base material.
    When the deterioration state of the ejection element is equal to or less than the index for ensuring the inspection accuracy of the ejection element, an inspection pattern that causes the ejection element to form an inspection pattern that does not substantially affect the image quality in the area of the user image. The formation process and
    A reading result acquisition process for acquiring a reading result obtained by scanning the inspection pattern with a scanner, and
    An abnormality degree calculation step of analyzing the reading result and obtaining an abnormality degree of the discharge element, and
    A treatment step of treating the discharge element according to the degree of abnormality, and
    Head control method.
12. A program for causing a computer to execute the head control method according to claim 11.
13. A non-temporary, computer-readable recording medium on which the program according to claim 12 is recorded.

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