JP5680362B2 - Inkjet recording apparatus and method - Google Patents

Description

  The present invention relates to an ink jet recording apparatus and method, and more particularly, to an ink jet recording apparatus and method for drawing an image on a traveling belt-like continuous paper (web) with a line type ink jet head.

  In an inkjet recording apparatus that prints by transporting roll paper (web wound in a roll) at high speed, a large amount of paper is lost when printing is started after the paper speed is constant. Printing is also required during acceleration / deceleration.

  Conventionally, printing is possible even during acceleration / deceleration of a sheet by detecting the speed of the sheet during printing and controlling the ejection interval of ink droplets ejected from the inkjet head in accordance with the speed of the sheet.

  However, there is a problem in that when the ink droplet ejection interval is changed in this way, the density of the drawn image becomes non-uniform.

  Japanese Patent Application Laid-Open No. 2004-133867 proposes that the cause of non-uniform density is regarded as a change in discharge amount due to a change in discharge interval, and control is performed so that ink droplets are always discharged at a constant discharge amount.

JP 2010-36447 A

  However, the cause of the density change is the fluctuation of landing interference accompanying the fluctuation of the ejection interval, and there is a problem that the density change cannot be completely corrected even if the ink droplets are ejected with a constant ejection amount. That is, in the case of the ink jet method, when the ejection interval changes, the interference state between the ink droplets that have landed on the paper changes, so the ink landing shape changes, and even if the same amount of ink droplets are ejected, it looks macro And the image density changes. In addition, since ink droplets that should originally become a plurality of dots are united, there is a problem that a large dot is formed and graininess is deteriorated.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an ink jet recording apparatus and method capable of drawing a high-quality image without density unevenness even during acceleration / deceleration of a sheet. .

In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a sheet conveying unit that conveys a sheet composed of a continuous belt- like sheet , and an ink droplet in synchronization with the traveling of the sheet conveyed by the sheet conveying unit. eject, and a line type inkjet head even during acceleration or deceleration of the paper draws an image on the sheet, and reading means for reading an image drawn by the inkjet head from the paper conveyed by the paper conveying means, wherein From the image read by the reading means, the position of the dots of a plurality of droplets drawn so as to come in contact along the paper transport direction or the paper transport speed changes as the paper transport speed changes. along the conveying direction of the sheet by detecting the size of the dots drawn connected multiple droplets of dots in the printing conditions defined as a standard state A measuring unit that measures the amount of deviation from the position or size, and a correction that corrects the drawing condition of the image by the inkjet head based on the amount of deviation measured by the measuring unit so that the image is drawn at a constant density And an ink jet recording apparatus.

  According to the present invention, the position of a plurality of dots drawn so as to come into contact with an image actually drawn on paper or the size of a dot drawn by connecting a plurality of drops is detected and defined as a standard state. The amount of deviation from the dot size under measured printing conditions is measured. Then, based on the deviation amount, the image drawing condition by the ink jet head is corrected. In the case of the ink jet system, ink droplets are ejected in synchronization with paper conveyance, and when the paper conveyance speed changes, the ink droplet ejection interval is changed accordingly. On the other hand, when the ink droplet ejection interval fluctuates, the interference state between dots drawn in contact with each other changes. As a result, even if the same amount of ink is ejected, the image density changes when viewed macroscopically. Therefore, in the present invention, the position of a plurality of dots drawn so as to come into contact with an image actually drawn on paper or the size of a dot drawn by connecting a plurality of drops is detected and set as a standard state. The amount of deviation from the dot size under the printing conditions is measured, and the image drawing condition by the inkjet head is corrected based on the amount of deviation, thereby preventing the density from fluctuating. In other words, by measuring the amount of deviation from the dot size under the printing conditions determined as the standard state, the variation in the discharge interval (= the variation in the conveyance speed of the paper) is detected, and the density variation based on that is corrected. Correct image drawing conditions by inkjet head.

  Here, the standard state refers to a state of dots when a sheet is conveyed and drawn at a constant conveyance speed. Various drawing conditions are set to draw an image so that an optimal image is drawn when the paper is transported at a steady transport speed. The average state of the dots is set as the standard state. Alternatively, this standard state may be set to coincide with the theoretical dot state (dot position and size) on the dot arrangement data. Therefore, even if the amount of deviation from the dot state on the dot arrangement data is measured, the same purpose can be achieved.

  In order to achieve the above-mentioned object, the invention according to claim 2 includes storage means for storing correction information corresponding to a deviation amount, and the correction means refers to the correction information stored in the storage means. The inkjet recording apparatus according to claim 1, wherein an image drawing condition by the inkjet head is corrected.

  According to the present invention, correction information of drawing conditions corresponding to the amount of deviation is prepared in advance, and the drawing conditions are corrected with reference to the correction information prepared in advance. The correction information is set based on, for example, an image drawn by changing the paper conveyance speed and the drawing result. That is, how the deviation amount changes when the sheet conveyance speed is changed, and the correction information is set so as to correct the density variation based on the deviation amount change. This correction information is defined as information on the correction amount of the drawing conditions, for example.

  In order to achieve the above object, the invention according to claim 3 comprises information acquisition means for acquiring at least one information of paper to be used, ink status, environmental temperature and humidity of the paper, and landing error of the inkjet head, The ink jet recording apparatus according to claim 2, wherein the correcting unit corrects an image drawing condition by the ink jet head in consideration of information acquired by the information acquiring unit.

  According to the present invention, the drawing condition of the image by the inkjet head is corrected in consideration of at least one information of the paper to be used, the state of the ink, the environmental temperature and humidity of the paper, and the landing error of the inkjet head. The interference state of dots drawn on paper varies depending on the paper used, ink status, paper environmental temperature and humidity, ink jet head landing error, and so on. The drawing conditions can be corrected more appropriately, and an image having a uniform density can be stably drawn.

  The invention according to claim 4 is the inkjet according to any one of claims 1 to 3, wherein the correcting means corrects dot arrangement data of an image to be drawn in order to achieve the object. A recording device is provided.

  According to the present invention, the dot arrangement data of the image to be drawn is corrected according to the amount of deviation. That is, the dot arrangement / density is corrected so as to correct the density fluctuation.

  The invention according to claim 5 is characterized in that, in order to achieve the object, the correction information is information of a gradation curve representing a relationship between a dot appearance rate and a density of an input image. An ink jet recording apparatus described in 1) is provided.

  According to the present invention, the gradation curve information representing the relationship of the dot appearance rate to the density of the input image is defined as the correction information, and this gradation curve is set according to the amount of deviation. The correcting means corrects the dot arrangement data based on the gradation curve.

  The invention according to claim 6 is characterized in that, in order to achieve the object, the correcting means corrects the ejection amount of the ink droplet per dot. An inkjet recording apparatus as described is provided.

  According to the present invention, the ejection amount of ink droplets per dot is corrected in accordance with the amount of deviation so that density fluctuations are corrected.

  According to a seventh aspect of the present invention, in order to achieve the above object, the correcting means corrects at least one of a peak value and a pulse width of a drive signal applied to the actuator of the ink jet head, thereby correcting per dot. The inkjet recording apparatus according to claim 6, wherein the ejection amount of the ink droplet is corrected.

  According to the present invention, at least one of the peak value and the pulse width of the drive signal applied to the actuator of the inkjet head is corrected, and the ejection amount of the ink droplet per dot is corrected.

  According to an eighth aspect of the present invention, in order to achieve the above object, the reading means performs a reading operation at a constant reading cycle and reading time, and reads the image from the paper conveyed by the conveying means. A reading paper speed detecting means for detecting the paper conveyance speed when the image is read by the reading means as a reading paper speed, and a predetermined correction function set in accordance with the reading paper speed. 8. A read image correction unit that corrects blur of a read image caused by a change in paper speed during reading by correcting the read image using the read image correction unit. 8. An ink jet recording apparatus described in 1) is provided.

  According to the present invention, the read image is corrected according to the reading paper speed, and the fluctuation of the blurred state of the read image caused by the fluctuation of the reading paper speed is corrected. Accordingly, a stable read image can be obtained even if reading is performed during acceleration / deceleration of the paper.

  In the invention according to claim 9, in order to achieve the above object, the correction function includes a 1 × n filter matrix for correcting a read image with respect to the paper transport direction, where n is a paper speed at the time of reading. The ink jet recording apparatus according to claim 8 is provided.

  According to the present invention, the correction function used for correcting the read image is configured by a 1 × n predetermined filter matrix that corrects the read image in the paper conveyance direction, and performs a filter process on the read image to read the read image. Is corrected. n is set according to the paper speed at the time of reading, and the number of read pixels corresponding to the amount of movement of the paper during the reading time of one pixel is set (where n is an odd number). For example, if the paper moves by 3 pixels during the reading time of one pixel, n = 5 is set so that one pixel is added in consideration of that the reading target is in the middle of the pixel, and the odd number is set to an odd number. The In this way, by correcting the read image by the filter process, the read image can be corrected by a simple calculation process.

  In the invention according to claim 10, in order to achieve the above object, the filter parameters of the filter matrix are set so as to realize a spatial frequency characteristic opposite to that when blurring occurs, and the total number of images before and after the processing is set. The inkjet recording apparatus according to claim 9, wherein the energy is set to be substantially the same.

  According to the present invention, the filter parameters of the filter matrix are set so as to realize a spatial frequency characteristic opposite to that when blurring occurs, and the total energy of the image before and after processing is set to be substantially the same. Is done. As a result, it is possible to appropriately correct the blur occurring in the read image.

  Note that “the total energy of the image is substantially the same before and after the processing” means that the average value of the data of each pixel of the image is substantially the same before and after the processing. That is, the average density of the images is almost the same. For this purpose, the filter parameter of the filter matrix, that is, the total value of each element of the matrix only needs to be approximately 1.

  According to an eleventh aspect of the present invention, in order to achieve the above object, the filter parameters of the filter matrix and n are set in consideration of the characteristics of the optical system of the reading means. Alternatively, the inkjet recording apparatus according to 10 is provided.

  According to the present invention, the filter parameter of the filter matrix for correcting the read image is set in consideration of the characteristics of the optical system of the reading unit, for example, the characteristics related to the blurring state such as the MTF of the optical system of the reading unit. The As a result, the read image can be corrected more appropriately.

  In order to achieve the above object, the reading means is a reading means for periodically reading an image, and an illuminating means for illuminating a sheet on which an image is read by the reading means; A reading paper speed detecting means for detecting the paper conveyance speed when the image is read by the reading means as a reading paper speed, and a period of one reading period becomes longer as the reading paper speed becomes slower. The inkjet recording apparatus according to claim 1, further comprising: a reading control unit that controls an image reading operation by the reading unit.

  According to the present invention, when a reading unit (for example, a line scanner) that periodically reads an image recorded on a sheet is read, the sheet conveyance speed (sheet speed at reading) is detected, and the reading sheet speed is determined according to the reading sheet speed. Thus, the time of one cycle of reading by the reading means is varied. In other words, if the reading paper speed is slow, the time for one reading period is set to be long, and if the reading paper speed is high, the time for one reading period is set to be short. As an example, the time of one reading cycle is set in inverse proportion to the reading paper speed. Alternatively, the time for one reading period is set to be longer stepwise as the paper speed at the time of reading decreases. Thereby, it is possible to prevent the image from being blurred and read during high-speed conveyance, and a good image can be read.

  According to a thirteenth aspect of the present invention, in order to achieve the above object, the reading control means causes the reading means to perform a reading operation in a predetermined reading time when the reading paper speed is equal to or lower than a predetermined paper speed. An ink jet recording apparatus according to claim 12 is provided.

  According to the present invention, when the reading paper speed is equal to or lower than a predetermined speed, reading is performed with a constant reading time. In the present invention, the reading time is set to become longer as the reading paper speed decreases. On the other hand, a solid-state imaging device (CCD, CMOS, etc.) constituting the reading unit may be saturated when exposed for a long time. Therefore, when the reading paper speed is equal to or lower than a predetermined speed, reading is performed with a constant reading time, and saturation of the solid-state imaging device constituting the reading unit is prevented. Thereby, a good image can be obtained even during acceleration / deceleration.

  In order to achieve the above object, the invention according to claim 14 is provided with a read image correction means for correcting a read image read in a predetermined reading time when the reading paper speed becomes equal to or lower than a predetermined paper speed. The read image correction unit acquires information on the reading paper speed when the read image is read, and corrects the read image using a predetermined correction function set in accordance with the reading paper speed. The inkjet recording apparatus according to claim 13, wherein blurring of the read image caused by fluctuations in paper speed during reading is corrected.

  According to the present invention, when the reading paper speed is reduced and an image is read in a fixed reading time, the read image is corrected according to the reading paper speed. In other words, if an image is read from the accelerating / decelerating paper in a certain reading time, the blurred state of the read image fluctuates. To do. As a result, a good image can be stably obtained even during acceleration / deceleration.

  In the invention according to claim 15, in order to achieve the object, the correction function includes a 1 × n filter matrix for correcting the read image with respect to the paper transport direction, where n is a paper at the time of reading. The inkjet recording apparatus according to claim 14, wherein the inkjet recording apparatus is set according to a speed.

  According to the present invention, the correction function for correcting the read image is composed of a 1 × n filter matrix for correcting the read image in the paper transport direction. As a result, the read image can be appropriately corrected by simple filter processing.

  In the invention according to claim 16, in order to achieve the above object, the filter parameters of the filter matrix are set so as to realize a spatial frequency characteristic opposite to that when blur occurs, and the total of the images before and after the processing is set. 16. The ink jet recording apparatus according to claim 15, wherein the energy is set to be substantially the same.

  According to the present invention, the filter parameters of the filter matrix constituting the correction function are set so as to realize a spatial frequency characteristic opposite to that when blurring occurs, and the total energy of the image is almost the same before and after processing. Is set to be Thereby, the read image can be corrected appropriately.

  The invention according to claim 17 is characterized in that, in order to achieve the object, the filter parameter of the filter matrix and n are set in consideration of the characteristics of the optical system of the reading means. Alternatively, an ink jet recording apparatus according to 16 is provided.

  According to the present invention, the filter parameter of the filter matrix constituting the correction function, and n take into account the characteristics of the optical system of the reading unit, for example, the characteristics related to the blurring state such as the MTF of the optical system of the reading unit. Is set. As a result, the read image can be corrected more appropriately.

  In order to achieve the above object, the invention according to claim 18 is a reading means for periodically reading an image, wherein the reading means illuminates a paper on which an image is read; A reading paper speed detecting means for detecting the paper conveyance speed when the image is read by the reading means as a reading paper speed, and a light emission control means for controlling a light emitting operation of the light emitting means, The illumination means is caused to emit light intermittently in synchronization with a reading cycle, and in each light emission, the light emission time is controlled so that the light emission time becomes longer as the paper speed at the time of reading becomes slower, and the light emission amount within one reading cycle The ink jet recording according to any one of claims 1 to 7, further comprising: a light emission control unit that controls a light emission amount so that an integrated value of the light emission becomes substantially constant. To provide a location.

  According to the present invention, the image is read by causing the illumination means to emit light intermittently. At this time, light emission is performed in synchronization with the reading cycle of the reading means. In addition, the light emission time and the light emission amount are controlled so that the light emission time becomes longer as the paper speed at the time of reading decreases, and the light emission amount is set so that the integrated value of the light emission amount within one reading cycle is substantially constant. Be controlled. Thereby, it is possible to prevent the image from being blurred and read during high-speed conveyance, and a good image can be read. Since the light emission is performed in synchronization with the reading cycle, the maximum light emission time is set shorter than the reading time of one cycle.

  In order to achieve the above-mentioned object, the reading means is a reading means for periodically reading an image, and an illuminating means for illuminating a sheet on which an image is read by the reading means, The illumination means comprises: a light emission control means for controlling a light emission operation of the illumination means so as to emit light intermittently at a constant light emission time and a light emission quantity in synchronization with a reading cycle of the reading means, and the illumination 8. The light emission time and light emission amount of the means are set to a light emission time and light emission amount capable of reading an image by the reading means when the sheet is conveyed at a maximum conveyance speed. An ink jet recording apparatus according to any one of the above is provided.

  According to the present invention, reading of an image is performed by causing the illumination unit to emit light intermittently with a constant light emission time and light emission amount. At this time, light emission is performed in synchronization with the reading cycle of the reading means. Further, the light emission time and the light emission amount are set to the light emission time and the light emission amount at which the image can be read by the reading unit when the sheet is conveyed at the maximum conveyance speed. For example, when the paper is transported at the maximum transport speed, the light emission time is set to be equal to the time for one pixel to move the reading unit of the reading means, and the amount of light necessary for reading the image is emitted by the light emission time. Set as the amount of light. Thereby, it is possible to prevent the image from being blurred and read during high-speed conveyance, and a good image can be read.

  According to a twentieth aspect of the invention, in order to achieve the object, the reading paper speed detecting means reads a predetermined reading paper speed detection mark recorded on the paper at a predetermined distance interval. 20. The inkjet recording apparatus according to claim 1, wherein an hour sheet speed is detected.

  According to the present invention, the reading paper speed is detected by reading the reading paper speed detection marks recorded on the paper at constant distance intervals. As a result, the reading paper speed can be detected easily and accurately.

  The invention according to claim 21 is the inkjet according to claim 20, wherein, in order to achieve the object, a part or all of the reading paper speed detection mark is configured by a pattern indicating an order. A recording device is provided.

  According to the present invention, a part or all of the reading paper speed detection marks are constituted by a pattern indicating the order. Thereby, the order of the paper speed detection marks at the time of reading can be recognized.

  The invention according to claim 22 is the ink jet recording according to claim 20 or 21, wherein the reading paper speed detection mark is recorded on the paper by the ink jet head in order to achieve the object. Providing equipment.

  According to the present invention, the reading paper speed detection mark is recorded on the paper by the image recording means. Thereby, even when an image is recorded on a plain paper, the paper speed at the time of reading can be detected. In addition, it is not necessary to provide a dedicated recording means separately, and the apparatus configuration can be simplified.

The invention according to claim 23, in order to achieve the above object, in any one of claims 1 to 22, characterized in that it comprises a sheet feed means for continuously feeding while replenishing said for paper An inkjet recording apparatus as described is provided.

  According to the present invention, the paper is constituted by a belt-like continuous paper (web) and is continuously fed while being added. In the case of an inkjet recording apparatus that records images on continuous paper, a large amount of damaged paper is generated if images are not recorded even during acceleration / deceleration of the paper, so that a good image can be appropriately recorded even during acceleration / deceleration of the paper. The invention works particularly effectively in the ink jet recording apparatus that records images on continuous paper in this way.

According to a twenty-fourth aspect of the present invention, in order to achieve the above object, ink droplets are ejected from a line-type ink jet head in synchronization with the travel of a sheet composed of a continuous belt-shaped sheet, In the ink jet recording method for drawing an image on the paper, the step of reading the image drawn by the ink jet head and the contact along the paper transport direction by changing the paper transport speed from the read image The size of dots drawn by connecting a plurality of drops along the paper transport direction by changing the position of the dots of the plurality of drops drawn on the paper or the transport speed of the paper was determined as a standard state. The step of measuring the amount of deviation from the position or size of the dots under the printing conditions and the measurement are performed so that the image is drawn at a constant density. Based on the record amount, an inkjet recording method is characterized in that and a step of modifying the drawing condition of the image by the ink jet head.

  According to the present invention, the position of a plurality of dots drawn so as to come into contact with an image actually drawn on paper or the size of a dot drawn by connecting a plurality of drops is detected and defined as a standard state. The amount of deviation from the dot size under measured printing conditions is measured. Then, based on the deviation amount, the image drawing condition by the ink jet head is corrected. Thereby, the density change based on the fluctuation of the sheet conveyance speed can be corrected, and a good image can be stably recorded.

  The invention according to claim 25 is characterized in that, in order to achieve the object, the paper is a continuous belt-like paper, and the paper is continuously fed while the paper is added. The inkjet recording method described is provided.

  According to the present invention, the sheet is composed of a continuous belt (web) and continuously fed while being added, so that an efficient printing operation can be performed.

  According to the present invention, it is possible to draw a high-quality image without density unevenness even during acceleration / deceleration of a sheet.

Overall configuration of inkjet printer Block diagram showing schematic configuration of control system of inkjet printer The figure which shows an example of the waveform of the drive signal applied to the actuator of an inkjet head The figure which shows an example of the waveform of the drive signal applied to the actuator of an inkjet head Diagram explaining landing interference due to difference in paper speed during recording Diagram showing an example of a gradation curve The figure which shows an example of the waveform of the drive signal applied to the actuator of an inkjet head The figure which shows an example of the waveform of the drive signal applied to the actuator of an inkjet head Explanatory drawing of inspection / correction method based on printing result when web is switched The perspective view which shows schematic structure of a scanner Diagram for explaining blur of read image due to difference in paper speed during recording Conceptual diagram of correction processing applied to scanned image Graph showing the relationship between reading paper speed and reading time Timing chart showing the relationship between reading paper speed and reading time Graph showing the relationship between reading paper speed and reading time Graph showing the relationship between reading paper speed and reading time Graph showing the relationship between the paper speed during reading and the light emission time Graph showing the relationship between light emission time and light intensity Timing chart showing the relationship between reading and light emission Diagram explaining printing on the web The figure which shows an example of the paper speed detection mark at the time of recording, and the paper speed detection mark at the time of reading The figure which shows an example of the paper speed detection mark at the time of recording, and the paper speed detection mark at the time of reading The figure which shows an example of the paper speed detection mark at the time of recording, and the paper speed detection mark at the time of reading The figure which shows an example of the paper speed detection mark at the time of recording, and the paper speed detection mark at the time of reading

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

  Here, a case where the present invention is applied to an ink jet printer that prints on a web by an ink jet method using an ultraviolet curable aqueous ink will be described as an example.

≪Inkjet printer configuration≫
FIG. 1 is an overall configuration diagram of an inkjet printer 1. The inkjet printer 1 includes a paper feeding unit 10 that feeds the web 2, an infeed unit 20 that feeds the web 2, a processing liquid coating unit 30 that coats a predetermined processing liquid on the printing surface of the web 2, and a processing liquid applied A first drying unit 40 that dries the web 2 that has been printed, a printing unit 50 that records (draws) an image on the web 2, a second drying unit 60 that dries the web 2 on which the image is recorded, and an image recorded on the web 2 And a fixing / reading unit 70 for reading a recording result, an outfeed unit 80 for feeding the web 2, and a collecting unit 90 for winding the web 2.

  The web 2 fed from the paper feeding unit 10 is fed by the infeed unit 20 and the outfeed unit 80 and travels along a predetermined conveyance path, and the treatment liquid coating unit 30 installed in the middle of the conveyance path. The first drying unit 40, the printing unit 50, the second drying unit 60, and the fixing / reading unit 70 perform necessary processing, and the collecting unit 90 winds up.

<web>
The web 2 as a recording medium is provided in the form of a paper feed roll wound around a winding core in a roll shape. The type of the web 2 is not particularly limited, but in the inkjet printer 1 of the present embodiment, the general printing paper (so-called high-quality paper, coated paper, art paper, etc. used in general offset printing) Paper mainly composed of cellulose).

<Paper Feeder>
The paper feeding unit 10 feeds the web 2 continuously. The paper feed unit 10 is provided with a reel stand 14 for mounting a paper feed roll and a paper splicing device (not shown) for connecting old and new webs when the paper feed roll is replaced.

  The reel stand 14 is configured to be capable of mounting a plurality of paper feed rolls, and automatically switches the paper feed rolls that feed the web 2. The reel stand 14 in this example includes three arms extending radially, and a mounting portion for a paper feed roll is provided on each arm. Therefore, three paper feed rolls can be attached at a time. The three arms are driven and rotated by a motor (not shown), whereby the position of the paper feed roll is switched. Then, by switching the position of the paper feed roll, the paper feed roll for feeding the web 2 is switched. In FIG. 1, reference numeral 11 denotes a paper feeding roll that is feeding paper, reference numeral 12 denotes a paper feeding roll to be fed next, and reference numeral 13 denotes a used paper feeding roll. The three arms rotate clockwise to switch the paper feed roll that feeds the web 2. Each mounting unit is provided with a motor (not shown), and a paper feed roll mounted on each mounting unit is driven by this motor to rotate.

  A paper splicing device (not shown) connects old and new webs when switching between old and new paper feed rolls. That is, the leading end of the web 2 drawn out from the paper feed roll 12 to be used next is connected to the web 2 drawn out from the paper feed roll 11 in use to form a continuous web 2. Thereby, the web 2 is continuously fed.

  The replacement of the old and new paper feed rolls is performed as follows. First, the arm of the reel stand 14 is rotated to bring the new paper feed roll 12 close to the travel line of the web 2. Next, the peripheral speed of the new paper feed roll 12 is synchronized with the conveyance speed of the web 2. Next, a paper splicing device (not shown) is operated to pull out the web 2 from the new paper feed roll 12 and connect it to the web 2 drawn from the paper feed roll 11 in use. Here, a gluing portion is provided at the tip of the web 2 drawn out from the new paper feed roll 12, and the paper splicing device applies the gluing portion to the web 2 drawn out from the paper feed roll 11 in use. Press to connect the old and new webs. After the connection, the paper splicing device cuts the web 2 drawn from the paper feed roll 11 in use with a cutter and separates it from the newly joined web 2. Thereby, the old and new paper feed rolls are switched.

  The old and new paper feed rolls are automatically replaced. That is, the remaining amount of the web 2 is measured by a remaining amount measuring means (not shown), and is replaced with a new sheet feeding roll immediately before the remaining amount. Alternatively, the paper feed roll is replaced in accordance with a command from the operator.

<Infeed part>
The infeed unit 20 pulls out the web 2 from the paper supply roll of the paper supply unit 10 and feeds the web 2 toward the printing unit 50. The infeed unit 20 includes an infeed roller pair 21 that sandwiches and feeds the web 2, and a dancer roller 22 that adjusts the tension of the web 2.

  The infeed roller pair 21 is driven to rotate by a motor (not shown). The rotational speed of the infeed roller pair 21 can be arbitrarily set, and the feeding speed of the web 2 is adjusted by adjusting the rotational speed of the infeed roller pair 21.

  The dancer roller 22 is rocked and held by an actuator (not shown). The tension of the traveling web 2 is adjusted by the dancer roller 22. When the paper feed roll is replaced, the web 2 is temporarily stored by the dancer roller 22 to secure the time required for paper splicing. Further, when the conveyance speed of the web 2 changes, the dancer roller 22 absorbs the tension fluctuation.

<Processing liquid application part>
The treatment liquid application unit 30 applies a predetermined treatment liquid to the printing surface of the web 2. As described above, in the inkjet printer 1 of the present example, printing is performed on a general printing paper by an inkjet method using water-based ink. In general printing paper mainly composed of cellulose, when ink-jet printing is performed using water-based ink, ink (coloring material) is likely to move after droplet ejection, and image quality is likely to deteriorate. Therefore, in the ink jet printer 1 of this example, a treatment liquid that causes an agglomeration reaction with the ink ejected by the printing unit 50 is applied to the printing surface of the web 2 in advance. In this way, by applying a treatment liquid that causes an agglomeration reaction with ink and then ejecting ink droplets, it is possible to prevent bleeding after ink landing, landing interference (unification), and color mixing, and high-quality images. Can be recorded.

  The treatment liquid application unit 30 includes a treatment liquid application device 31 that applies the treatment liquid, and applies the treatment liquid to the printing surface of the web 2 that travels by the treatment liquid application device 31. For example, the processing liquid coating device 31 applies a processing liquid to the printing surface of the web 2 with a certain thickness by bringing a coating roller having a processing liquid applied to the peripheral surface thereof into contact with the printing surface of the web 2.

  Note that the configuration of the treatment liquid coating apparatus is not limited to this, and for example, a configuration in which coating is performed using a line-type inkjet head or a configuration in which coating is performed by spraying may be employed.

  The treatment liquid contains an aggregating agent that aggregates the components in the ink composition. The flocculant may be a compound that can change the pH of the ink composition, a polyvalent metal salt, or a polyallylamine. Preferred examples of the compound capable of lowering the pH include highly water-soluble acidic substances (phosphoric acid, oxalic acid, malonic acid, citric acid, derivatives of these compounds, or salts thereof). An acidic substance may be used individually by 1 type, and may use 2 or more types together. Thereby, cohesion can be improved and the whole ink can be fixed. The pH (25 ° C.) of the ink composition is 8.0 or more, and the pH (25 ° C.) of the treatment liquid is preferably in the range of 0.5-4. As a result, it is possible to increase the image density, resolution, and speed of inkjet recording. Further, the treatment liquid may contain an additive. For example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, anti-fungal agents, pH adjusters, surface tension adjusters, antifoaming agents, viscosity adjusters, Known additives such as a dispersant, a dispersion stabilizer, a rust inhibitor, and a chelating agent can be contained.

<First drying section>
The first drying unit 40 dries the treatment liquid applied to the web 2. The first drying unit 40 includes a dryer (not shown). The dryer sprays heated air on the printing surface of the traveling web 2 to heat and dry the web 2.

  In addition, the first drying unit 40 includes a dancer roller 42 for temporarily storing the web 2 necessary for changing the paper joining time and the conveyance speed. The dancer roller 42 is swingably held by an actuator (not shown) and adjusts the tension of the traveling web 2.

<Printing section>
The printing unit 50 applies ink of each color of magenta (M), black (K), cyan (C), and yellow (Y) from the inkjet head 51 (51M, 51K, 51C, 51Y) to the printing surface of the traveling web 2. A color image is recorded by ejecting ink droplets. The printing section 50 includes an inkjet head 51M that ejects magenta ink droplets, an inkjet head 51K that ejects black ink droplets, an inkjet head 51C that ejects cyan ink droplets, and yellow ink droplets. And an inkjet head 51Y for discharging.

  Each color inkjet head 51 is composed of a line-type inkjet head corresponding to the width of the web 2, and records an image on the traveling web 2 in a single pass.

  The configuration of the drive unit for ejecting ink droplets from the nozzle is not particularly limited, and it may be ejected by a thermal ink jet method using a heating element, or a piezo ink jet method using a piezoelectric element. You may make it discharge by. In this example, an ink jet is used in which ink droplets are ejected from a nozzle by a piezo ink jet method using a piezoelectric element.

  The conveyance path of the web 2 in the printing unit 50 has a convex shape that curves upward, and a certain tension is applied to the web 2 to ensure clearance between the inkjet heads 51.

  Further, the speed at which the web 2 traveling through the printing unit 50 passes through the drawing unit immediately below the inkjet head, that is, the speed at which an image is recorded (recording paper speed) is not shown. Detected by mechanism.

  The recording paper speed detection mechanism, for example, installs a rotation amount detecting means such as a rotary encoder on the shaft of the roller that conveys the web 2, and detects the recording paper speed from the rotation amount of the shaft. Further, for example, the recording paper speed is detected by a laser Doppler velocimeter. Further, for example, a speed detection pattern is printed in an area outside the printing range of the web 2 (for example, the ears on both sides of the web), and the movement of this pattern is detected by an optical sensor or the like. Detect paper speed.

  Information on the detected recording paper speed is used for ejection control of the inkjet head 51, analysis of a recorded image read by the scanner 74, and the like. This point will be described in detail later.

  The ink used in the ink jet printer 1 of this example is a water-based ultraviolet curable ink, and contains a pigment, polymer particles, and a water-soluble polymerizable compound that is polymerized by active energy rays. The water-based ultraviolet curable ink can be cured by irradiating with ultraviolet rays, and has a property that it has excellent observation resistance and high film strength.

  As the pigment, a water dispersible pigment in which at least a part of its surface is coated with a polymer dispersant is used.

  As the polymer dispersant, a polymer dispersant having an acid value of 25 to 1000 (KOHmg / g) is used. The stability of self-dispersibility is good, and the cohesiveness when the treatment liquid comes into contact is good.

  As the polymer particles, self-dispersing polymer particles having an acid value of 20 to 50 (KOHmg / g) are used. The stability of self-dispersibility is good, and the cohesiveness when the treatment liquid comes into contact is good.

  As the polymerizable compound, a nonionic or cationic polymerizable compound is preferable in that it does not interfere with the reaction between the flocculant, the pigment, and the polymer particles, and the solubility in water is 10% by mass or more (more preferably 15% by mass or more). It is preferable to use a polymerizable compound.

  The ink also contains an initiator that initiates polymerization of the polymerizable compound by active energy rays. The initiator can appropriately contain and contain a compound capable of initiating a polymerization reaction by active energy rays. For example, an initiator that generates active species (radicals, acids, bases, etc.) by radiation, light, or electron beams. (For example, a photoinitiator etc.) can be used. The initiator can be contained in the treatment liquid, and may be contained in at least one of the ink and the treatment liquid.

  The ink contains 50 to 70% by mass of water. The ink may contain an additive. For example, water-soluble organic solvents, drying inhibitors (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, antiseptics, antifungal agents, pH adjusters, surface tension adjusters, antifoaming agents , Known additives such as viscosity modifiers, dispersants, dispersion stabilizers, rust inhibitors and chelating agents can be contained.

<Second drying section>
The second drying unit 60 dries the ink deposited on the web 2. The second drying unit 60 is provided with a dryer (not shown). The dryer sprays heated air on the printing surface of the traveling web 2 to heat and dry the web 2.

  In addition, the second drying unit 60 includes a dancer roller 62 for temporarily storing the web 2 necessary for changing the paper joining time and the conveyance speed. The dancer roller 62 is swingably held by an actuator (not shown) and adjusts the tension of the web 2 that travels.

<Fixing / reading section>
The fixing / reading unit 70 fixes an image recorded on the web 2 and reads a recording result with a scanner. The fixing / reading unit 70 includes an ultraviolet irradiation light source 71 that applies ultraviolet light to the printing surface of the web 2 on which an image is recorded, a cooling device 72 that cools the web 2, and a scanner 74 that reads a recorded image.

  The ultraviolet irradiation light source 71 irradiates the printing surface of the web 2 on which an image is recorded with ultraviolet rays to solidify the aggregate of the treatment liquid and the ink.

  The cooling device 72 includes a plurality of cooled cooling rollers 73, and the cooling roller 73 cools the web 2 to an appropriate temperature to fix the recorded image.

  The scanner 74 includes a line sensor camera, an optical system for forming an image on the light receiving surface of the line sensor camera, and an illuminating device that illuminates the reading unit by the line CCD, and records an image recorded on the traveling web 2. The line sensor camera periodically reads each line. The image data read by the scanner 74 is output to a system controller 100 (see FIG. 2) that controls the overall operation of the inkjet printer 1. The system controller 100 analyzes this image data, inspects for defects in the print unit 50 (such as non-ejection and ejection direction failure) and print quality (such as image density, color, unevenness, etc.), and performs necessary corrections. Make adjustments.

  The speed at which the web 2 traveling on the fixing / reading unit 70 passes through the reading unit by the scanner 74, that is, the speed at which the image is read by the scanner 74 (reading paper speed) is a reading paper speed (not shown). It is detected by a detection mechanism.

  Similarly to the recording paper speed detection mechanism, the reading paper speed detection mechanism is provided with, for example, a rotation amount detecting means such as a rotary encoder on the shaft of the roller that conveys the web 2, and the reading paper is determined from the rotation amount of the shaft. Detect speed. Further, for example, the reading paper speed is detected by a laser Doppler velocimeter. Further, for example, a speed detection pattern is printed in an area outside the printing range of the web 2 (for example, the ears on both sides of the web), and the movement of this pattern is detected by an optical sensor or the like. Detect paper speed.

  Information on the detected paper speed at the time of reading is used for analysis of a recorded image read by the scanner 74 and the like. This point will be described in detail later.

<Outfeed section>
The outfeed unit 80 pulls the web 2 and feeds it toward the collection unit 90. The outfeed unit 80 includes an outfeed roller pair 81 that sandwiches and feeds the web 2, and a dancer roller 82 that adjusts the tension of the web 2.

  The outfeed roller pair 81 is driven to rotate by a motor (not shown). The rotational speed of the outfeed roller pair 81 can be arbitrarily set, and the feeding speed of the web 2 is adjusted by adjusting the rotational speed of the outfeed roller pair 81.

  The dancer roller 82 is rocked and held by an actuator (not shown). The tension of the traveling web 2 is adjusted by the dancer roller 82. When the core for winding the web 2 is replaced, the dancer roller 82 temporarily stores the web 2 to secure the time required for the replacement. Further, when the conveyance speed of the web 2 changes, the dancer roller 82 absorbs the tension fluctuation.

<Recovery Department>
The collection unit 90 winds the web 2 on which an image is recorded on a winding core. The collection unit 90 includes a reel stand 94 for mounting the core and a core joining device (not shown) that joins the tip of the web 2 to the core when the core is replaced.

  The reel stand 94 is configured to be capable of mounting a plurality of cores, and automatically switches the core around which the web 2 is wound. The reel stand 94 of this example includes three arms extending radially, and a winding core mounting portion is provided on each arm. Therefore, three cores can be attached at a time. The three arms are driven and rotated by a motor (not shown), whereby the position of the core is switched. And the core which winds up the web 2 is switched by switching the position of this core. In FIG. 1, reference numeral 91 is a winding core that is winding the web 2, reference numeral 92 is a winding core that winds the web 2 next, and reference numeral 93 is a winding core that has already been wound. The three arms rotate counterclockwise to switch the winding core around which the web 2 is wound. Each mounting portion is provided with a motor (not shown), and the winding core mounted on each mounting portion is driven by this motor to rotate.

  A core joining apparatus (not shown) cuts the web 2 being wound up and switches the tip of the cut web 2 to a new core 92 when switching the winding core for winding the web 2. Thereby, the web 2 can be wound on a continuous enemy.

  The winding core is exchanged as follows. First, the arm of the reel stand 94 is rotated to bring the new core 92 close to the travel line of the web 2. Next, the peripheral speed of the new core 92 is synchronized with the conveyance speed of the web 2. Next, a core joining device (not shown) is operated to join the web 2 to a new core 92. Here, the new core 92 is provided with an adhesive portion on the outer periphery thereof, and the core joining device presses the web 2 against the adhesive portion to join the web 2 to the new core 92. After the joining, the core joining apparatus cuts the web 2 on the front side of the joining portion with a cutter and separates it from the new core 92. Thereby, the winding core which winds up the web 2 is switched.

  Note that the winding core is automatically replaced. That is, the winding amount of the web 2 is measured by a winding amount measuring means (not shown), and when a predetermined amount of the web 2 is wound up, it is automatically switched to a new winding core.

  In addition, in the inkjet printer 1 of this example, it is set as the structure wound up in roll shape around a core, However, It can also be set as the structure which collect | recovers the web 2 with which the image was recorded with a well-known folding machine.

<Control system>
FIG. 2 is a block diagram illustrating a schematic configuration of a control system of the inkjet printer 1.

  As shown in the figure, the inkjet printer 1 includes a system controller 100, a communication unit 102, an image memory 104, a conveyance control unit 110, a paper feed control unit 112, a treatment liquid application control unit 114, a first drying control unit 116, The printing control unit 118, the second drying control unit 120, the fixing / reading control unit 122, the collection control unit 124, the operation unit 130, the display unit 132, and the like are provided.

  The system controller 100 controls each unit of the inkjet printer 1 by executing a predetermined control program. Further, the system controller 100 executes various arithmetic processes necessary for execution of printing by executing a predetermined control program. The system controller 100 includes a CPU, a ROM, and a RAM. The ROM stores a control program and various data necessary for executing printing.

  The communication unit 102 includes a required communication interface, and transmits / receives data to / from the host computer 200 connected to the communication interface.

  The image memory 104 functions as a temporary storage unit for various data including image data, and data is read and written through the system controller 100. Image data captured from the host computer 200 via the communication unit 102 is stored in the image memory 104.

  The conveyance control unit 110 controls the operations of the infeed unit 20 and the outfeed unit 80 according to a command from the system controller 100 to control the conveyance of the web 2. That is, by controlling the operations of the infeed roller pair 21 provided in the infeed unit 20 and the outfeed roller pair 81 provided in the outfeed unit 80, the web 2 is directed from the paper supply unit 10 toward the collection unit 90. While running, the movement of the dancer roller 22 provided in the infeed part 20 and the operation of the dancer roller 82 provided in the outfeed part 80 are controlled to control the tension fluctuation of the web 2.

  The paper feed control unit 112 controls the operation of the paper feed unit 10 in accordance with a command from the system controller 100 and feeds paper from a paper feed roll. That is, the operation of the reel stand 14 provided in the paper feed unit 10 is controlled to switch the paper feed roll, and the operation of a paper splicing device (not shown) provided in the paper feed unit 10 is controlled. Paper splicing at the time of roll replacement.

  The processing liquid application control unit 114 controls the operation of the processing liquid application unit 30 in accordance with a command from the system controller 100 and applies the processing liquid to the web 2. That is, the operation of the treatment liquid application device 31 provided in the treatment liquid application unit 30 is controlled to apply the treatment liquid to the web 2.

  The first drying control unit 116 controls the operation of the first drying unit 40 according to a command from the system controller 100 to dry the processing liquid applied to the web 2. That is, the operation of the dryer provided in the first drying unit 40 is controlled to control the temperature and air volume of the heating air applied to the web 2, and the treatment liquid applied to the web 2 is dried.

  The print control unit 118 controls the operation of the printing unit 50 in accordance with a command from the system controller 100 and records an image on the web 2. That is, by controlling the drive of each inkjet head 51M, 51K, 51C, 51Y provided in the printing unit 50, the ejection of ink droplets from each inkjet head 51M, 51K, 51C, 51Y is controlled, and desired on the web 2 Record images.

  The second drying control unit 120 controls the operation of the second drying unit 60 in accordance with a command from the system controller 100 and dries the ink deposited on the web 2. That is, the operation of the dryer provided in the second drying unit 60 is controlled to control the temperature and air volume of the heated air applied to the web 2, and the ink ejected onto the web 2 is dried.

  The fixing / reading control unit 122 controls the operation of the fixing / reading unit 70 in accordance with a command from the system controller 100 to fix the image recorded on the web 2 and to read the image recorded on the web 2. Do. That is, the operation of the ultraviolet irradiation light source 71 provided in the fixing / reading unit 70 is controlled to control the irradiation of the ultraviolet rays onto the web 2 to solidify the aggregate of the processing liquid and the ink on the web. Further, the operation of the cooling device 72 provided in the fixing / reading unit 70 is controlled to control the cooling of the web 2 and to fix the image recorded on the web 2. Further, the operation of the scanner 74 provided in the fixing / reading unit 70 is controlled to read the image recorded on the web 2.

  The collection control unit 124 controls the operation of the collection unit 90 according to a command from the system controller 100 and collects the web 2. That is, the operation of the reel stand 94 provided in the collection unit 90 is controlled to switch the winding core around which the web 2 is wound, and the core joining device (not shown) provided in the collection unit 90 is switched. The operation is controlled to perform core joining at the time of core replacement.

  The operation unit 130 includes necessary operation means (for example, operation buttons, a keyboard, a touch panel, and the like), and outputs operation information input from the operation means to the system controller 100. The system controller 100 executes various processes in accordance with operation information input from the operation unit 130.

  The display unit 132 includes a required display device (for example, an LCD panel) and outputs required information to the display device in accordance with a command from the system controller 100.

  Image data to be printed on the web 2 is taken into the inkjet printer 1 from the host computer 200 via the communication unit 102. The image data captured by the inkjet printer 1 is stored in the image memory 104. The system controller 100 performs necessary signal processing on the image data stored in the image memory 104 to generate dot arrangement data. Then, the drive of each inkjet head 51 (51M, 51K, 51C, 51Y) is controlled according to the generated dot arrangement data, and the image represented by the image data is printed on the web 2.

  The dot arrangement data is generally generated by performing color conversion processing and halftone processing on image data. The color conversion process is a process for converting image data expressed in sRGB or the like (for example, RGB 8-bit image data) into color data for each ink color used in the inkjet printer 1 (in this example, MKCY color data). It is. The halftone process is a process for generating dot arrangement data for each ink color (in this example, MKCY dot arrangement data) by performing error diffusion or the like on the color data for each ink color generated by the color conversion process. It is.

  The system controller 100 performs color conversion processing and halftone processing on the image data to generate dot arrangement data for each color of MKCY. Then, each inkjet head 51 (51M, 51K, 51C, 51K) is driven according to the generated dot arrangement data of each color, and an image represented by the image data is printed on the web 2.

  In this example, dot arrangement data composed of large size, medium size, and small size dots is generated, and an image represented by the image data is printed. Therefore, the inkjet head 51 is configured to be able to form dots of large, medium, and small sizes. That is, an ink droplet (large droplet) that forms a large-sized dot when it is hit on the web 2, an ink droplet (medium droplet) that forms a medium-sized dot, and an ink droplet that forms a small-sized dot. (Small droplets) can be discharged.

  In the case of a piezo ink jet type ink jet head, an ink droplet is ejected from each nozzle by applying a predetermined drive signal to a piezoelectric element (actuator) provided corresponding to each nozzle. This drive signal is applied at a predetermined recording cycle, and the size (dot diameter) of the ink droplet ejected onto the medium can be changed by changing the waveform.

  FIG. 3 is a diagram illustrating an example of a waveform of a drive signal in the case where the size of the ink droplet is changed by changing the peak value of the ejection pulse incorporated within one recording cycle.

  FIG. 4A shows a driving waveform when a small-sized ink droplet is ejected, FIG. 5B shows a driving waveform when a medium-sized ink droplet is ejected, and FIG. 4C shows a large-sized ink droplet. The drive waveform in the case of hitting a drop is shown. As shown in the figure, the size of the ink droplet to be ejected can be changed by changing the peak value (voltage) of the ejection pulse. In this way, gradation recording can be performed by making it possible to eject ink droplets of different sizes.

  FIG. 4 is a diagram showing an example of the waveform of the drive signal when the size of the ink droplet is changed by changing the number of ejection pulses incorporated in one recording cycle.

  FIG. 4A is a drive waveform when ejecting a small size, FIG. 4B is a drive waveform when ejecting a medium size, and FIG. 4C is a drive waveform when ejecting a large size ink droplet. Is shown.

  As shown in the figure, the ejection pulses are incorporated at regular intervals. Then, by incorporating only one, small-sized ink droplets, by incorporating two, medium-sized ink droplets, and by incorporating four, large-sized ink droplets are ejected.

  As shown in FIG. 4, when the ejection pulse is incorporated so that the peak value gradually increases, the ink droplet ejected later catches up with the previously ejected ink droplet and is landed on the recording medium in a single droplet state. (So-called aerial coalescence).

  In the example shown in FIG. 4, the crest value of each ejection pulse is changed, but the crest value of each ejection pulse can be made constant, and the number of ejection pulses to be incorporated can be varied to change the size of the ink droplets to be ejected. . In this case, ink droplets sequentially land at the same location, and dots of a predetermined size are formed.

  The recording cycle is switched in synchronization with the travel of the web 2. That is, while the web 2 is traveling at a constant speed, the recording period is also constant, but during the acceleration / deceleration of the web 2, the recording period is switched in synchronization with the change in the traveling speed of the web 2. As a result, printing can be performed even while the web 2 is accelerated or decelerated.

≪Outline of printing operation of inkjet printing machine≫
The web 2 is fed by the infeed unit 20 and the outfeed unit 80 and travels between the paper feed unit 10 and the collection unit 90.

  The web 2 drawn out from the paper supply roll of the paper supply unit 10 first passes through the treatment liquid application unit 30. And the processing liquid is apply | coated to a printing surface at the time of the passage.

  The web 2 that has passed through the treatment liquid application unit 30 then passes through the first drying unit 40. And the heating air is sprayed on the printing surface at the time of the passage, and the process liquid apply | coated to the printing surface is dried.

  The web 2 that has passed through the first drying unit 40 then passes through the printing unit 50. Then, ink droplets ejected from the inkjet heads 51M, 51K, 51C, and 51Y during the passage are ejected onto the printing surface, and an image is recorded on the printing surface.

  The web 2 that has passed through the printing unit 50 then passes through the second drying unit 60. Then, heating air is blown onto the printing surface during the passage, and the ink deposited on the printing surface is dried.

  The web 2 that has passed through the second drying unit 60 then passes through the fixing / reading unit 70. Then, ultraviolet rays are applied to the printing surface during the passage, and the aggregate of the ink and the treatment liquid is solidified. Further, after solidification, the image is cooled and the image recorded on the printing surface is fixed on the web 2. Further, after fixing, the image recorded on the printing surface is read by the scanner 74.

  The web 2 that has passed through the fixing / reading unit 70 is then fed toward the collecting unit 90, and is wound around the winding core in a reel shape by the collecting unit 90.

  Thus, the inkjet printer 1 of this example prints an image on the web 2 continuously fed out from the paper feeding unit 10 by the inkjet method, and sequentially winds the web after printing by the collecting unit 90, Images are continuously printed on the web 2.

  The paper feed roll that feeds the web 2 is automatically switched to a new paper feed roll immediately before the web 2 disappears. Thereby, the web 2 can be continuously fed. The same applies to the winding core for winding the printed web 2. When a predetermined amount of the web 2 is wound, the winding core is automatically switched to a new winding core. Thereby, the web 2 can be continuously collected.

  Printing is also performed during acceleration / deceleration of the web 2. Thereby, even when the web 2 is transported and printed at a high speed (for example, the steady transport speed is 300 (m / min)), it is possible to prevent the occurrence of damaged paper.

≪Correction of printing conditions based on printing results≫
[First method]
As described above, in the ink jet printer of this example, printing is performed even during acceleration / deceleration of the web 2. In order to perform printing even during acceleration / deceleration of the web 2, it is necessary to synchronize the ejection of ink droplets with the travel of the web 2. That is, when the web 2 transport speed (paper speed during recording) increases, the ink droplet ejection interval is shortened accordingly, and when the web 2 transport speed (paper speed during recording) decreases, it is adjusted accordingly. Increase the ink droplet ejection interval.

  However, when the discharge interval fluctuates in this way, the interference state of dots drawn so as to come into contact with each other changes, and the image density changes. That is, as shown in FIG. 5, when the conveyance speed of the web 2 (recording paper speed) is slow and the discharge interval is long, the next dot is ejected after the previously ejected dots aggregate, It is difficult to cause interference, and vertically long dots are drawn. However, when the web 2 is transported at a high speed (paper speed during recording) and the discharge interval is shortened, before the dots that have been previously ejected completely aggregate, Since the dots are ejected, landing interference occurs, resulting in a dot that is close to a circle. As a result, even when the same amount of ink droplets is ejected, the density of the drawn image varies.

  Therefore, in the ink jet printer 1 of this example, the state of the dot drawn so as to come in contact with the image (read image) read by the scanner 74 of the fixing / reading unit 70 is detected, and based on the detection result, Correct the printing conditions.

  In the first method, the size of a dot drawn by connecting a plurality of drops from a read image is detected. Then, the amount of deviation from the dot size under the printing conditions determined as the standard state is measured, and the dot arrangement data is corrected based on the measurement result.

  Here, the standard state refers to a state of dots drawn when the web 2 is conveyed at a steady conveyance speed (for example, 300 (m / min)). Various printing conditions (dot arrangement data, driving signal driving waveforms, etc.) in the printing unit 50 are set so that an optimum image is drawn when the web 2 is conveyed at a steady conveying speed. The web 2 is conveyed at the conveyance speed, and the dot state when drawing is set to the standard state. Alternatively, this standard state may be set so as to substantially match the theoretical dot state (dot position and size) on the dot arrangement data. Therefore, even if the amount of deviation from the dot state on the dot arrangement data is measured, the same purpose can be achieved.

  As shown in FIG. 5, the dot size is measured by measuring the aspect ratio (a / b) of a dot (actual dot) drawn on the web 2 and setting this as the dot size (vertical (a): web transport direction. , Side (b): direction orthogonal to the web conveyance direction). The dot size decreases as the web 2 conveyance speed increases, and conversely increases as the web 2 conveyance speed decreases.

  The dot size information in the standard state is acquired from the image obtained by actually transporting the web 2 at a steady transport speed and drawing an image, for example, by drawing a test image of a specific pattern. The obtained dot size information in the standard state is stored in the ROM.

  The system controller 100 detects a size of a dot drawn by connecting a plurality of drops (for example, two drops) from a read image by executing a predetermined image processing program. Then, the amount of deviation is calculated by comparison with the dot size in the standard state stored in the ROM. Based on the measurement result, the dot arrangement data is corrected.

  Here, the dot arrangement data is corrected based on correction information set according to the amount of deviation. That is, correction information is prepared for each deviation amount in advance, and the dot arrangement data is corrected according to the correction information prepared for each deviation amount.

  The correction information is obtained, for example, by drawing an image of the same dot arrangement data (for example, a test image of a specific pattern) by changing only the conveyance speed of the web 2 and the drawing result. That is, by changing the conveyance speed of the web 2, the size of the dots drawn by connecting a plurality of droplets changes (this changes the amount of deviation), and the density changes, so the density is kept constant for each amount of deviation. Conditions (= conditions for making the density almost the same as the density at the time of drawing at a steady conveyance speed) are obtained and defined as correction information.

  In this example, dot appearance rate information according to the density of the input image (image to be drawn) is defined as correction information, and dot arrangement data is corrected accordingly. In the inkjet printing machine 1 of this example, since an image is recorded with dots of three sizes, large, medium, and small, information on the appearance rate of each size according to the density of the input image is defined as correction information, and for each deviation amount To be prepared.

  The dot appearance rate according to the density of the input image can be defined as a gradation curve. FIG. 6 is a diagram illustrating an example of a gradation curve. FIG. 4A shows an example of a gradation curve at a steady recording paper speed, and FIG. 4B shows a floor when the shift amount is small (lower than the steady recording paper speed). An example of a tone curve is shown.

  Such gradation curve information is prepared for each shift amount. The information of the gradation curve for each prepared deviation amount is stored in the ROM. The system controller 100 reads the information of the gradation curve corresponding to the measured deviation amount, performs predetermined data processing, and corrects the dot arrangement data.

<About gradation curve>
By defining the gradation curve information in detail according to the amount of deviation, it is possible to print a high-quality image with a more stable density.

  On the other hand, when the number of information on the gradation curve is increased, the capacity of the memory (ROM in this example) necessary for storage increases.

  Therefore, the gradation curve information is prepared by thinning out to some extent, and if there is no gradation curve information corresponding to the detected deviation amount, the dot arrangement is performed using the gradation curve information in the vicinity of the value. Data may be corrected. In addition, the gradation curve corresponding to the detected displacement amount is estimated in consideration of the gradation curve for the displacement amount before and after the detected displacement amount, and the dot arrangement data is corrected using the estimated gradation curve. You may make it do.

  As a result, it is possible to print a high-quality image while reducing the memory capacity necessary for storing the gradation curve information.

  The gradation curve is preferably set so that the appearance rate of small dots increases as the amount of deviation increases, and the appearance rate of large dots increases as the amount of deviation decreases. That is, when the amount of deviation is large, it is presumed that landing interference has occurred, so the proportion of small-sized dots is increased to reduce the possibility of landing interference. On the other hand, when the amount of deviation is small, it is presumed that landing interference does not occur, so the appearance rate of large dots is increased. Thereby, since the number of ejections is reduced, the load applied to the ink jet head can be reduced, and the life of the head can be extended.

  The change in density also changes depending on the paper to be used, the state of the ink, the environmental temperature and humidity of the paper, the landing error of the ink jet head, and the like, so it is preferable to prepare a gradation curve for each of these conditions. When a gradation curve is prepared for each of these conditions, information on these conditions is acquired together with the amount of deviation of the dot size, and the corresponding gradation curve is determined. Therefore, when acquiring information on these conditions and selecting a gradation curve, a means for detecting information on these conditions is installed.

<Dot arrangement data correction>
The dot arrangement data can be uniformly corrected for all areas, but can also be performed only for necessary areas. Thereby, it can correct efficiently.

  For example, the dot arrangement data is corrected only for an area having a predetermined density or higher. That is, in the low density area, the gap between the dots is wide and there is little possibility of causing landing interference, so the correction is not performed and the original arrangement is recorded. On the other hand, in the dark area, the gap between dots is narrow, and if the recording paper speed fluctuates, there is a risk of landing interference, so the dot arrangement is corrected.

  Thus, by correcting only the dot arrangement data in the necessary area, the correction processing speed can be improved, and the dot arrangement data can be corrected efficiently.

  In addition, since the density change based on the fluctuation in the web 2 conveyance speed is largely due to the distance between dots when droplets are ejected onto the web 2, only the dot arrangement data in the area where the dots are deposited adjacently is corrected. You may make it do. For example, among adjacent dots, 4 dots or 8 dots (upper, lower, right, left), [upper left, upper right, lower right, lower left] or [upper right, upper left] , Upper left, left, lower left, lower, lower right, right]) is corrected. Thereby, since only a necessary area can be corrected, the processing speed of the correction can be improved.

  In the above example, the size of the dots drawn by connecting a plurality of drops from the image read by the scanner 74 is detected, but the positions of the dots of the plurality of drops drawn so as to come into contact with each other are detected. The same purpose can be achieved by measuring the amount of deviation of the dot position from the standard state.

[Second method]
In the second method, the dot arrangement data is not changed, and the ejection amount of ink ejected from the nozzles is changed according to the deviation amount. That is, when the dot size is displaced, the amount of ink droplets ejected from the nozzles is adjusted according to the amount of displacement so that the density does not change.

  The correction of the discharge amount is performed using correction information obtained in advance, as in the first method. The correction information is obtained, for example, by drawing an image of the same dot arrangement data while changing the conveyance speed of the web 2 and the drawing result. That is, by changing the conveyance speed of the web 2, the size of the dots drawn by connecting a plurality of droplets changes (this changes the amount of deviation), and the density changes, so the density is kept constant for each amount of deviation. A discharge amount correction amount (= a correction amount of the discharge amount for making the density almost the same as that at the time of drawing at a steady conveyance speed) is obtained, and this is defined as correction information.

  In the inkjet printer 1 of this example, since an image is recorded with dots of three sizes, large, medium, and small, discharge amount correction information is obtained for each size.

  The discharge amount is adjusted by changing the waveform of the drive signal applied to the piezoelectric element. For example, the ejection amount is adjusted by changing either the peak value of the ejection pulse, the pulse width of the ejection pulse, or both.

  FIG. 7 is a diagram illustrating an example of a drive signal when changing the discharge amount by changing the peak value. (A-1) to (c-1) in FIG. 5 show examples of drive signals at the normal recording paper speed, and (a-2) to (c-2) in FIG. An example of the drive signal is shown when is large. As shown in the figure, when the amount of deviation is large, it is presumed that landing interference has occurred, so the crest value is increased (the applied voltage is increased) so that the discharge amount increases for each size. .

  FIG. 8 is a diagram illustrating an example of a drive signal when the ejection amount is changed by changing the pulse width. (A-1) to (c-1) in FIG. 5 show examples of drive signals at the normal recording paper speed, and (a-2) to (c-2) in FIG. An example of the drive signal when is large is shown. As shown in the figure, when the amount of deviation is large, it is estimated that landing interference has occurred. Therefore, the pulse width is widened so that the ejection amount increases for each size.

  In the examples shown in FIGS. 7 and 8, the discharge amount is adjusted by changing the crest value or the pulse width. However, the discharge amount may be adjusted by changing both the crest value and the pulse width.

  Similarly, when the size of the ink droplet is changed by changing the number of ejection pulses incorporated in one recording cycle (see FIG. 4), either the peak value of the ejection pulse or the pulse width of the ejection pulse, or By changing both, the discharge amount can be adjusted.

  In this way, the ejection amount is adjusted by changing the waveform of the drive signal applied to the piezoelectric element.

  As described above, for example, the correction information is acquired based on the image obtained by recording the image of the same dot arrangement data while changing the conveyance speed of the web 2. In other words, when the dot size deviates from the dot size under the printing condition determined as the standard state, how the density (gradation) is displaced is measured, and a condition for correcting this is acquired as correction information.

  The obtained correction information is stored in, for example, a ROM. The system controller 100 reads the correction information stored in the ROM, obtains the ejection amount corresponding to the amount of deviation of the dot size from the standard state, and causes the print control unit 118 to drive the inkjet head 51.

  Thereby, it is possible to print a stable and high-quality image without density fluctuation.

<Discharge amount correction information>
The discharge amount correction information is defined in detail according to the amount of dot size deviation from the standard state, so that a high-quality image with a more stable density can be printed.

  On the other hand, when the number of discharge amount correction information is increased, the capacity of the memory (ROM in this example) required for storage increases.

  Therefore, the discharge amount correction information is prepared by thinning out to some extent, and when there is no discharge amount information corresponding to the detected deviation amount, the discharge amount information corresponding to the neighboring deviation amount is used. Also good. In addition, the correction amount corresponding to the detected deviation amount is estimated in consideration of the correction amount information corresponding to the deviation amount before and after the detected deviation amount, and the discharge amount is estimated using the estimated correction amount information. May be corrected. As a result, it is possible to print a high-quality image while reducing the memory capacity required to store the correction amount information.

  The change in density also changes depending on the paper to be used, the state of the ink, the environmental temperature and humidity of the paper, the landing error of the ink jet head, etc., so it is preferable to prepare correction information for each of these conditions. When correction information is prepared for each of these conditions, the information is also acquired together with the amount of deviation of the dot size, and the corresponding gradation curve is determined.

  The change in density varies depending on the printing conditions such as the type of ink used and the type of paper used. Therefore, it is preferable to prepare correction amount information for each printing condition of the image.

  Similarly to the gradation curve, the correction amount of the discharge amount is set by printing a predetermined image (for example, a test image of a predetermined pattern) by changing the recording paper speed and analyzing the printed image. However, the image data for this analysis is acquired from the scanner 74 installed in the fixing / reading unit 70.

  In the above example, the size of the dots drawn by connecting a plurality of drops from the image read by the scanner 74 is detected, but the positions of the dots of the plurality of drops drawn so as to come into contact with each other are detected. The same purpose can be achieved by measuring the amount of deviation of the dot position from the standard state.

<About correction of discharge amount>
The correction of the ejection amount (drive waveform) can be performed uniformly for all regions, but can also be performed only for necessary regions. Thereby, it can correct efficiently.

  For example, the ejection amount is corrected only for a region having a predetermined density or higher. That is, in the low density area, there are many gaps between dots and there is little possibility of causing landing interference, so that correction is not performed and recording is performed with the original arrangement. On the other hand, in a region having a high density, if the gap between dots is narrow and the recording paper speed fluctuates, landing interference may occur, so the ejection amount is corrected.

  By correcting only the discharge amount in the necessary region in this way, the correction processing speed can be improved, and the discharge amount (drive waveform) can be corrected efficiently.

  In addition, since the density change due to the change in the paper speed during recording is largely due to the interval between dots when droplets are ejected onto the web 2, only the ejection amount (drive waveform) of the region where the dots are ejected adjacent to each other is determined. You may make it correct. For example, the discharge amount of the area where 4 dots or 8 dots around the top, bottom, left and right of the adjacent droplets are ejected is corrected. Thereby, since only a necessary area can be corrected, the processing speed of the correction can be improved.

  In addition, the correction of the ejection amount can be performed whenever the dot size deviation is detected, but can also be performed in units of images.

[Control when the web type is switched]
As described above, in the inkjet printer 1 of this example, even when one paper feed roll is used up, printing can be continued by switching to the next paper feed roll without stopping printing. In this case, the web 2 (paper feed roll) to be switched is not necessarily the same as that before the switching, and there are cases where the web 2 is switched to a web 2 with a different type, paper thickness, production lot, and the like.

  On the other hand, in printing performed by the printing unit 50, image printing conditions are set in consideration of the type of web 2 (paper), paper thickness, manufacturing lot, and the like.

  Therefore, if the print result of the image printed previously is fed back and the print condition of the image is corrected as described above, when the type of the web 2 is switched, the correct correction can be made with the few images immediately after the switch. On the contrary, the image quality may be deteriorated. That is, when the paper feed roll is switched, some images immediately after the switching are corrected based on the inspection result of the image printed on the web 2 before the switching. As described above, since the printing conditions of the image are set in consideration of the type of the web 2 and the like, the image printed on the web 2 after switching using the inspection result of the image printed on the web 2 before switching. If the printing conditions are corrected, it is not possible to correct the printing conditions properly, and the image quality may be deteriorated.

  Therefore, when correcting the image printing conditions based on the printing result as described above, when the paper feed roll is switched, the correction based on the image printed on the web before switching is performed on the web after switching. Prevent it from being reflected in the printed image.

  Specifically, as shown in FIG. 9, when the last image is recorded on the web 2 before switching, the inspection of the print result and the correction of the print condition of the image based on the inspection result are temporarily stopped. Then, when the first image is recorded on the switched web 2 ′ and the first image is read by the scanner 74, inspection / correction based on the read image is resumed.

  As described above, the inspection of the printing result and the correction of the printing condition of the image based on the inspection result are performed only while printing on the same web.

  As a result, it is possible to prevent the printing condition from being erroneously corrected with the correction amount derived under the different conditions, and the image quality to be deteriorated.

  When correction by feedback is stopped, printing is performed without correction during that period, and the image is printed under standard printing conditions.

  Even if the web is switched, if it is switched to the same type of web (same paper type, paper thickness, production lot), the correction should be continued without stopping. Also good. In this case, it is detected whether or not the switched webs are of the same type, and it is determined whether or not to stop the correction based on the detection result. The detection of whether or not the switched web is the same type is performed by installing a sensor that automatically detects the type of the web, for example. Or it determines based on the information which the operator input.

<When inspecting and correcting ejection abnormalities based on print results>
As described above, it is possible to inspect from the printing results for ejection abnormalities (non-ejection, ejection bending (landing position deviation), ink droplet volume defect, splash, etc.).

  The correction of the ejection abnormality is a correction that is preferably performed even when the web is switched regardless of the type of the web.

  Therefore, when the ejection abnormality is inspected from the printing result and the image printing condition is corrected based on the inspection result, the inspection / correction is continuously performed even when the web is switched. .

  That is, when correcting the dot arrangement data or ink droplet ejection amount from the print result, and also performing the ejection abnormality inspection / correction at the same time, the ejection abnormality inspection / correction is performed even when the web is switched. Continue to implement. On the other hand, the correction of the dot arrangement data or the ejection amount of the ink droplet is temporarily stopped when the last image is recorded on the web 2 before switching, and the first image is recorded on the web 2 ′ after switching. Is resumed when read by the scanner 74.

  As described above, regarding the ejection abnormality, even when the web is switched, a high-quality image can be printed by continuously inspecting and correcting.

  In the above example, the deviation of the image density from the target and the discharge abnormality are detected from the print result. However, from the print result, the deviation from the color target, the presence / absence of unevenness, the dot, Deviation from the target of diameter and line width, presence / absence of fixing of drawing dots, presence / absence of satellite dots accompanying drawing dots, abnormal drawing (for example, dot bleeding due to non-uniformity of the paper surface, color / density deviation, paper (Abnormalities due to paper problems such as wrinkles or rubbing due to floating) can be detected, and corrections associated therewith can also be performed.

<Detection of web switching>
For web switching, for example, a sensor for detecting web switching is installed in the printing unit 50 and the fixing / reading unit 70, and a web switching point is detected based on the detection result of the sensor.

  Alternatively, the operator may input a web switching point from the operation unit 130 and detect the web switching based on the input information.

≪How to obtain print results≫
As described above, in the inkjet printer 1 of the present example, the fixing / reading unit 70 reads the printing result (the image actually printed on the web 2) with the scanner 74, and the read image (read image) is read. Analysis is performed, and the printing state is inspected in the printing unit 50. Then, necessary corrections are performed based on the inspection result.

  FIG. 10 is a perspective view showing a schematic configuration of the scanner. As shown in the figure, the scanner 74 mainly includes a line sensor camera 74A, an optical system 74B that forms an optical image of an image on the web 2 on the light receiving surface of the line sensor camera 74A, and the line sensor camera 74A. It is comprised with the illuminating device 74C which proves a reading part.

  The line sensor camera 74A incorporates a line sensor (line CCD, line CMOS, etc.) and reads an image recorded on the web conveyed by the line sensor line by line. The line sensor is arranged orthogonal to the traveling direction of the web 2.

  The optical system 74B is mounted on the line sensor camera 74A and forms an optical image of an image recorded on the web on the light receiving surface of the line sensor.

  The illuminating device 74C is configured by line illumination, emits illumination light from the line-shaped illumination unit toward the reading unit by the line sensor camera 74A, and illuminates the reading unit. In this example, the illumination device 74C is configured by a white lamp, and continuously irradiates white illumination light toward the reading unit.

  The operation of the scanner 74 is controlled by the fixing / reading control unit 122, and the fixing / reading control unit 122 controls the operation of the scanner 74 in accordance with a command from the system controller 100.

  By the way, in the case of a printing machine that prints on the web 2 like the ink jet printing machine 1 of this example, if printing is not performed even during the acceleration / deceleration of the web 2, a large amount of waste paper is generated. For this reason, in this type of printing machine, printing is performed even during acceleration / deceleration of the web 2.

  In a printing machine that performs printing by the inkjet method, in order to print even while the web 2 is accelerated, ink droplets are ejected from the inkjet head 51 in synchronization with the traveling of the web 2.

  On the other hand, when printing is performed during acceleration / deceleration of the web 2 as described above, it is necessary to read the printing result while the web 2 is accelerated / decelerated.

  As described above, the printing result is read by the scanner 74, and this scanner 74 normally assumes the web 2 conveyed at a steady conveyance speed (for example, 300 (m / min)). Reading conditions (reading cycle, exposure conditions (light quantity of the light source, reading time of one pixel (so-called shutter speed (exposure time)), CCD optical aperture size, etc.)) are set.

  However, assuming the web 2 conveyed at a steady conveyance speed as described above, when the reading conditions are set and the image is read, the web is rotated at a speed faster than the regular conveyance speed as shown in FIG. When 2 is conveyed, there is a problem that a read image is blurred and a good image cannot be obtained.

  Therefore, in the inkjet printer 1 of the present example, an image without blur is obtained by reading the image as follows.

  Note that “blurring” refers to blurring of a subject on a read image that occurs when reading is performed by an image sensor at a predetermined shutter speed (exposure time) in a state where the web that is the subject is moving. An image obtained by blurring and reading a subject is called a blurred state. Furthermore, if the shutter speed is constant even if the web speed changes, the blur amount of the read subject changes, so this blur state changes. This change can be said to be a difference in the extent and range of contrast reduction in the read image.

<First method>
In the first method, the image data of the read image read by the scanner 74 is corrected according to the paper speed at the time of reading, and the blurred state of the read image due to the fluctuation of the paper speed at the time of reading is corrected. Specifically, the read image is corrected by performing a required calculation process on the read image using a correction function set according to the paper speed at the time of reading.

  The correction function is composed of, for example, a 1 × n filter matrix that corrects the read image with respect to the conveyance direction of the web 2, and n is determined according to the paper speed when the web 2 is read. That is, n is selected so that the number of read pixels is a length corresponding to the amount of movement of the web 2 during the read time (exposure time) of one pixel (where n is an odd number of 3 or more).

  The filter parameter is a value that realizes a spatial frequency characteristic opposite to that when blur occurs, and is determined so that the total energy of the image is substantially the same before and after the arithmetic processing.

  Note that the fact that the total energy of the image is substantially the same before and after the arithmetic processing means that the average value of the data of each pixel of the image is substantially the same before and after the arithmetic processing. That is, the average density of the images is almost the same. For this purpose, the filter parameter of the filter matrix, that is, the total value of each element of the matrix only needs to be approximately 1.

  The correction processing of the read image is performed by the system controller 100. Also, the set filter matrix information is stored in the ROM. The system controller 100 obtains information on the reading paper speed when the read image is read from the reading paper speed detection mechanism, and reads out information on the filter matrix corresponding to the obtained reading paper speed from the ROM. Then, a necessary filter process is performed on the read image using the filter matrix to correct the read image. That is, since the value of n is automatically determined according to the reading paper speed, the corresponding filter matrix information is read from the ROM, and the read image is filtered using the read filter matrix.

  FIG. 12 is a conceptual diagram of the correction process performed on the read image. The image data (A) of the original read image is filtered using the filter matrix (X) corresponding to the paper speed at the time of reading, and the corrected image (B) is acquired. In the example shown in the figure, n = 3 is shown. In this case, the filter matrix (X) is composed of 1 column × 3 rows. Using this filter matrix (X), the read image is corrected in the web 2 conveyance direction.

  Of course, n is not limited to 3, and 5 or 7 or even a larger filter matrix may be used.

  Thereby, the fluctuation of the read image based on the fluctuation of the paper speed at the time of reading can be corrected. Then, by performing image analysis based on the corrected read image and inspecting the printing state by the printing unit 50, it is possible to accurately detect abnormality, etc., and to correct printing conditions more appropriately. Can do. Thereby, a high-quality image can be printed stably.

  Note that the blurring state also varies depending on the characteristics of the optical system 74B of the scanner 74. Therefore, it is preferable to determine the filter parameter and n in consideration of the characteristics of the optical system. Specifically, the filter parameter and n are determined in consideration of characteristics related to the blurring state such as MTF of the optical system 74B. Thereby, the read image can be corrected more appropriately, and a better read image can be obtained.

  Further, in this example, the correction function is configured by a 1 × n filter matrix that corrects the read image with respect to the conveyance direction of the web 2, but the configuration of the filter matrix is not limited to this. For example, it may be configured by an m × n filter matrix (m is a constant and an odd number of 3 or more), and filter processing may be performed in consideration of pixel information in a direction orthogonal to the transport direction.

  Further, the reading is not limited to the line CCD, but may be a CMOS image sensor or an image sensor of another principle. The sensor is not limited to the line type, and may be a two-dimensional type sensor.

<Second method>
First, in the second method, the conveyance speed of the web 2 at the time of reading (paper speed at reading) is detected, and the reading condition of the scanner 74 is varied according to the paper speed at reading. Specifically, setting is made such that the reading time (exposure time) of one pixel becomes longer as the reading paper speed becomes slower (= the reading time of one pixel becomes shorter as the reading paper speed becomes faster). Set) and scan the image.

  Here, as shown in FIG. 13, the reading time of one pixel is made inversely proportional to the paper speed during reading. Therefore, when the reading paper speed is increased, the reading time is set accordingly.

  The system controller 100 acquires information on the reading paper speed from the reading paper speed detection mechanism, and varies the reading time by the line sensor camera 74A so as to be inversely proportional to the reading paper speed. That is, as shown in FIG. 14, if the reading paper speed is increased, the reading time of one pixel is shortened accordingly, and if the reading paper speed is reduced, the reading time of one pixel is increased accordingly. .

  In this way, by varying the reading time (exposure time) according to the paper speed at the time of reading, even when the web 2 is conveyed at a high speed, it is recorded on the web 2 without causing blur. The image can be read.

  By the way, as described above, the scanner 74 reads an image by a line sensor (line CCD or the like) mounted on the line sensor camera 74A. However, when the line sensor constituted by a solid-state imaging device is exposed for a long time. Saturates, making accurate reading impossible.

  Therefore, as shown in FIG. 15, in a region where the paper speed during reading is equal to or lower than a preset lower limit value, reading is performed with a constant reading time to prevent sensor saturation. In other words, if the reading time is further increased, the sensor will saturate in a region where the sensor is saturated without changing the reading time according to the paper speed at the time of reading. To prevent it. Thereby, a good image can be obtained even in a low speed region.

  Note that the reading time (exposure time) at which the sensor is saturated varies depending on the sensor used, illumination, and the like. Accordingly, the lower limit value of the reading paper speed is set in consideration of these conditions. Specifically, the time during which the sensor saturates under the actual usage environment is obtained, and the upper limit value of the reading time (the maximum value of the reading time that can be read without the sensor being saturated) is set. The web conveyance speed corresponding to the upper limit value of the reading time is set as the lower limit value of the reading paper speed. When the sheet speed during reading becomes lower than the lower limit, reading is performed with the reading time fixed at the upper limit.

  If reading is performed with a constant reading time in this way, the blurred state of the read image changes when the reading paper speed fluctuates.

  Therefore, as described in the first method, the read image read with a constant reading time is subjected to a necessary correction process according to the paper speed at the time of reading, and the read image due to the fluctuation of the paper speed at the time of reading is applied. Correct the blurred condition. That is, using a correction function set according to the paper speed at the time of reading, the read image is subjected to necessary signal processing to correct blur.

  In the above example, the reading time is continuously changed according to the reading paper speed. However, as shown in FIG. 16, the reading time is changed stepwise according to the reading paper speed. May be.

  Further, the reading cycle may be varied according to the paper speed at the time of reading, or may be constant. When the reading cycle is constant, the reading time is varied within one cycle according to the reading paper speed. In this case, one pixel can be read even when the web 2 is conveyed at high speed by setting the reading cycle so that one pixel can be read when the paper speed during reading is maximum.

<Third method>
In the third method, the conveyance speed of the web 2 at the time of reading (paper speed at reading) is detected, and the light emission condition of the illumination light is varied according to the paper speed at reading. Specifically, reading is performed at a constant reading cycle and reading time, and illumination light is intermittently emitted in synchronization with the reading cycle. In each light emission, the light emission time and the light emission amount are varied according to the reading paper speed.

  Here, as shown in FIG. 17, the light emission time is inversely proportional to the reading paper speed. Accordingly, when the reading paper speed is increased, the light emission time is shortened accordingly, and when the reading paper speed is decreased, the light emission time is increased accordingly.

  On the other hand, when imaging is performed with a constant amount of emitted light, underexposure occurs when the emission time is short, and overexposure or saturation occurs when the emission time is long. Therefore, as shown in FIG. 18, the amount of emitted light (the intensity of emitted light) is adjusted so that the integrated value of the amount of emitted light is constant. That is, the light emission amount is set to be smaller as the light emission time becomes longer, and the integrated value of one light emission amount is adjusted to be constant.

  As a result, it can be read with an exposure time (reading time) substantially corresponding to the paper speed at the time of reading, and a read image without blur can be obtained. That is, when the paper speed at the time of reading is high, it is possible to photograph with a substantially short exposure time (short light emission time), and it is possible to obtain a read image without blur. In addition, since the intensity of light emission is adjusted according to the light emission time, an image with no unevenness in brightness can be obtained.

  Since the light emission is performed in synchronization with the reading cycle, the maximum light emission time is set shorter than the reading time of one cycle.

  Further, as described above, in the third method, the illumination light is intermittently emitted, and the emission time and the amount of emitted light are also adjusted. Therefore, the illumination device 74C can emit intermittently and emit light. A device capable of adjusting the time and the amount of emitted light is used. For example, an illumination device using an LED light source that emits white light can be used.

  The system controller 100 executes a predetermined control program to control the light emission of the lighting device 74C. That is, information on the reading paper speed is acquired from the reading paper speed detection mechanism, a predetermined control program is executed, and the light emission time and the light emission amount corresponding to the reading paper speed are calculated. Then, the fixing / reading control unit 122 is instructed so that illumination light is emitted with the obtained light emission time and light emission amount, and the illumination device 74C is caused to emit light.

  FIG. 19 is a timing chart showing the relationship between reading (exposure) and light emission. As shown in the figure, illumination light is intermittently emitted in synchronization with the reading cycle for reading performed at a constant reading cycle and a constant reading time. Then, the light emission time and the amount of light emitted are adjusted in accordance with the reading paper speed. That is, the light emission amount is adjusted so that the light emission time is shortened as the reading paper speed increases, while the integrated value of the light emission amount is substantially constant.

  Thereby, even when the web 2 is conveyed at a high speed, an image recorded on the web 2 can be read without causing blur.

  In this method, the light emission time may be changed stepwise instead of continuously changing according to the paper speed at the time of reading.

<Fourth method>
Also in the fourth method, the image is read by intermittently emitting illumination light in synchronization with the reading cycle. At this time, without changing the light emission time and the light emission amount, the illumination light is intermittently emitted with the constant light emission time and the light emission amount, and the image is read. That is, even if the paper speed at the time of reading is changed, the image is read by emitting illumination light under illumination conditions that allow reading. Specifically, even when the web 2 is conveyed at the maximum reading paper speed, the illumination light is emitted under the light emission conditions (light emission time, light emission amount) capable of reading the image, and the image is read. Do.

  Here, when the web 2 is conveyed at the maximum reading paper speed, the light emission time is set to be equal to the time for one pixel to pass through the reading unit of the line sensor camera 74A, and the image is read with the light emission time. Is set as the amount of emitted light.

  Information on the set light emission conditions is recorded in the ROM. The system controller 100 reads information on the light emission conditions recorded in the ROM and instructs the fixing / reading control unit 122 to cause the illumination device 74C to emit light under the set light emission conditions.

  Thereby, it is possible to prevent the image from being blurred and read during high-speed conveyance, and a good image can be read.

  In this way, in this method, since it is required to emit light necessary for imaging in a short time, the illumination device 74C is capable of emitting a large amount of illumination light.

  Further, since the maximum reading paper speed may vary depending on printing conditions such as paper to be used and images to be recorded, it is preferable to set the light emission conditions according to the printing conditions of the image. In this case, information on the light emission conditions for each set printing condition (light emission conditions for each maximum paper speed at the time of reading) is stored in the ROM and read appropriately to set the light emission conditions.

≪Print control during web acceleration and deceleration≫
As described above, the ink jet printer 1 of this example appropriately corrects the printing conditions based on the printing result, but according to the speed fluctuation of the web 2 so that a higher quality image is stably printed. Then, the printing conditions are corrected as follows.

[First method]
In the first method, dot arrangement data of an image to be recorded is changed according to the recording paper speed of the web 2. That is, the dot arrangement of the image to be recorded is changed so that an image with a constant density is recorded even when the recording paper speed of the web 2 fluctuates.

  The dot arrangement data is corrected using correction information obtained in advance. For example, the image of the same dot arrangement data is recorded while changing the web 2 conveyance speed (recording paper speed), and a condition for making the density constant for each speed is obtained and used as correction information. The condition for making the density constant is defined by the dot appearance rate, and the dot appearance rate according to the density of the input image is changed according to the recording paper speed. In the ink jet printer 1 of this example, an image is recorded with dots of three sizes, large, medium, and small, so that the appearance rate of dots of each size according to the density can be changed according to the recording paper speed.

  Information on the appearance rate of dots according to the density is defined as a gradation curve as described above (see FIG. 6). The gradation curve information is prepared for each recording paper speed, and the dot arrangement data is corrected according to the recording paper speed measured by the printing unit 50.

  The dot arrangement data generated from the image data (RGB) is the dot arrangement data at the normal recording paper speed, and when the web 2 speed changes, at the normal recording paper speed. Necessary correction processing is applied to the dot arrangement data. This process is executed by the system controller 100 according to a predetermined control program. That is, the system controller 100 acquires information on the recording paper speed from the recording paper speed detection mechanism of the printing unit 50 using the gradation curve information stored in the ROM, and determines the steady recording paper speed. Correct the dot arrangement data. Then, based on the corrected dot arrangement data, the printing unit 50 prints an image.

  Thereby, it is possible to print on the web 2 even when the web 2 is accelerated and decelerated, and it is possible to print a stable and high-quality image without density fluctuation. In addition, in the inkjet printer 1 of the present example, as described above, density correction is appropriately performed according to the printing result, so printing with less density fluctuation can be performed.

<About gradation curve>
The gradation curve information is defined in detail within the range in which the recording paper speed varies, so that a high-quality image with a more stable density can be printed. For example, when the normal recording paper speed is 300 (m / min) and the recording paper speed fluctuates in the range of 0 to 350 (m / min), the speed of each speed is 1 (m / min). Prepare gradation curve information.

  On the other hand, when the number of information on the gradation curve is increased, the capacity of the memory (ROM in this example) necessary for storage increases.

  Therefore, the gradation curve information is prepared by thinning out to some extent. If there is no gradation curve information corresponding to the detected speed, the dot arrangement data is obtained by using the gradation curve information of the nearby speed. May be corrected. For example, gradation curve information is prepared at an interval of 10 (m / min), and when a speed is detected between them, the information of the gradation curve corresponding to the speed closer to the speed is used ( For example, when the recording paper speed is 52 (m / min), information on the gradation curve when 50 (m / min) is used. Alternatively, information on the gradation curve corresponding to the faster or slower speed is used (for example, when the recording paper speed is 52 (m / min), 50 (m / min) or 60 (Use gradation curve information at (m / min)).

  In addition, the gradation curve information corresponding to the detected recording paper speed is estimated in consideration of the gradation curve information at speeds before and after the detected recording paper speed, and the estimated gradation curve information is estimated. The dot arrangement data may be corrected by using. For example, when gradation curve information is prepared at an interval of 10 (m / min), if a recording paper speed of 52 (m / min) is detected, the gradation at 50 (m / min) Using the curve information and the gradation curve information at 60 (m / min), the gradation curve information at 52 (m / min) is estimated.

  As a result, it is possible to print a high-quality image while reducing the memory capacity necessary for storing the gradation curve information.

  The gradation curve is set so that the appearance rate of small dots increases as the recording paper speed increases, and the appearance rate of large dots increases as the recording paper speed decreases. It is preferable. That is, as the recording paper speed increases, landing interference is more likely to occur. Therefore, as the recording paper speed increases, the proportion of small-sized dots is increased to reduce the possibility of landing interference. On the other hand, when the recording paper speed is low, landing interference is unlikely to occur, so the appearance rate of large dots is increased to reduce the load on the inkjet head. Thereby, a higher quality image can be printed.

  The change in density also changes depending on the printing conditions such as the type of ink used and the type of paper used, so it is preferable to prepare a gradation curve for each printing condition.

<Dot arrangement data correction>
The dot arrangement data can be uniformly corrected for all areas, but can also be performed only for necessary areas. Thereby, it can correct efficiently.

  For example, the dot arrangement data is corrected only for an area having a predetermined density or higher. That is, in the low density area, there are many gaps between dots and there is little possibility of causing landing interference, so that correction is not performed and recording is performed with the original arrangement. On the other hand, in the dark area, the gap between dots is narrow, and if the recording paper speed fluctuates, there is a risk of landing interference, so the dot arrangement is corrected.

  Thus, by correcting only the dot arrangement data in the necessary area, the correction processing speed can be improved, and the dot arrangement data can be corrected efficiently.

  Further, as described above, the density change when the recording paper speed changes is largely due to the interval between the dots when the droplets are ejected onto the web 2, so that the dot arrangement in the region where the dots are ejected adjacent to each other is large. Only the data may be corrected. For example, among adjacent dots, 4 dots or 8 dots (upper, lower, right, left), [upper left, upper right, lower right, lower left] or [upper right, upper left] , Upper left, left, lower left, lower, lower right, right]) is corrected. Thereby, since only a necessary area can be corrected, the processing speed of the correction can be improved.

  Further, the dot arrangement data can be performed at any time as the recording paper speed changes, but can also be performed in units of images. In this case, for example, the dot arrangement data may be corrected according to the average speed when passing through the drawing unit, or the dot arrangement data may be corrected according to the speed when entering the drawing unit. May be. Thereby, it is not necessary to correct the dot arrangement data as needed, and an image can be recorded efficiently.

  Also, the dot arrangement data is corrected according to the average recording paper speed only when the change amount of the recording paper speed when recording one image is equal to or less than a predetermined value (first reference value). May be. That is, when the recording paper speed changes slowly, such as when the web 2 is slowly accelerated or decelerated, the density change is small, so the dot arrangement data is corrected with the average recording paper speed. As a result, excessive correction can be prevented, and an image can be recorded efficiently.

  When the web 2 travels more slowly, the dot arrangement data may be corrected at the recording paper speed averaged among a plurality of images. That is, when the amount of change in the recording paper speed when recording one image is equal to or smaller than the second reference value that is further smaller than the first reference value (= the recording paper while printing a plurality of images) When the speed change amount is equal to or smaller than a predetermined value), the dot arrangement data of each image is corrected according to the recording paper speed averaged among a plurality of images. Thereby, an image can be recorded more efficiently.

  Since the first reference value and the second reference value vary depending on the image printing conditions (such as ink and paper used), it is preferable to set them according to the image printing conditions.

[Second method]
In the second method, the dot arrangement data is not changed, and the ejection amount of ink ejected from the nozzles is changed according to the recording paper speed of the web 2. That is, the amount of ink droplets ejected from the nozzles is adjusted according to the recording paper speed so that the density does not change even if the recording paper speed of the web 2 fluctuates.

  The correction of the discharge amount is performed using correction information obtained in advance. For example, images of the same dot arrangement data are recorded at different speeds (paper speed at the time of recording), a discharge amount condition for making the density constant for each speed is obtained, and this is used as correction information.

  In the ink jet printer 1 of this example, since an image is recorded with dots of three sizes, large, medium, and small, a discharge amount correction condition is obtained for each size.

  The adjustment of the discharge amount is performed by changing the waveform of the drive signal applied to the piezoelectric element, similarly to the adjustment of the discharge amount based on the printing result described above. For example, the ejection amount is adjusted by changing either the peak value of the ejection pulse, the pulse width of the ejection pulse, or both.

  When adjusting the crest value, if the recording paper speed is slow, the crest value is less affected by landing interference, so the crest value is lowered (the applied voltage is lowered) so that the discharge amount is reduced for each size. .)

  Further, when adjusting the pulse width, when the recording paper speed is low, the pulse width is narrowed so that the ejection amount is small for each size because it is not easily affected by landing interference.

  As described above, the correction information is acquired based on the obtained image, for example, by recording an image of the same dot arrangement data while changing the recording paper speed. That is, how the density (gradation) is displaced when the recording paper speed is changed is measured, and conditions for correcting this are acquired as correction information.

  The obtained correction information is stored in, for example, a ROM. The system controller 100 reads the correction information stored in the ROM, obtains the ejection amount corresponding to the recording paper speed, and causes the print control unit 118 to drive the inkjet head 51.

  Thereby, it is possible to print on the web 2 even when the web 2 is accelerated and decelerated, and it is possible to print a stable and high-quality image without density fluctuation. In addition, in the inkjet printer 1 of the present example, as described above, density correction is appropriately performed according to the printing result, so printing with less density fluctuation can be performed.

<Discharge amount correction information>
The discharge amount correction information is defined in detail within a range in which the recording paper speed varies, so that a high-quality image with a more stable density can be printed. For example, when the normal recording paper speed is 300 (m / min) and the recording paper speed fluctuates in the range of 0 to 350 (m / min), the discharge amount is changed at an interval of 1 (m / min). Prepare correction information.

  On the other hand, when the number of discharge amount correction information is increased, the capacity of the memory (ROM in this example) required for storage increases.

  Accordingly, the discharge amount correction information may be prepared by thinning out to some extent, and when there is no information on the discharge amount corresponding to the detected speed, information on the discharge amount at a speed in the vicinity thereof may be used. For example, correction information on the discharge amount is prepared at intervals of 10 (m / min), and when the speed is detected during that interval, information on the correction amount corresponding to the speed closer to the front and rear of the speed is used (for example, When the recording paper speed is 52 (m / min), the correction amount information at 50 (m / min) is used. Alternatively, the correction amount information corresponding to the faster or slower speed is used (for example, when the recording paper speed is 52 (m / min), 50 (m / min) or 60 ( m / min)).

  In addition, the correction amount corresponding to the detected recording paper speed is estimated in consideration of the correction amount information before and after the detected recording paper speed, and ejection is performed using the estimated correction amount information. The amount may be corrected. For example, when correction amount information is prepared at intervals of 10 (m / min), when a recording paper speed of 52 (m / min) is detected, the correction amount at 50 (m / min) is detected. Using the information and the information of the correction amount at 60 (m / min), the information of the correction amount at 52 (m / min) is estimated.

  As a result, it is possible to print a high-quality image while reducing the memory capacity required to store the correction amount information.

  The change in density varies depending on the printing conditions such as the type of ink used and the type of paper used. Therefore, it is preferable to prepare correction amount information for each printing condition of the image.

<About correction of discharge amount>
The correction of the ejection amount (drive waveform) can be performed uniformly for all regions, but can also be performed only for necessary regions. Thereby, it can correct efficiently.

  For example, the ejection amount is corrected only for a region having a predetermined density or higher. That is, in the low density area, there are many gaps between dots and there is little possibility of causing landing interference, so that correction is not performed and recording is performed with the original arrangement. On the other hand, in a region having a high density, if the gap between dots is narrow and the recording paper speed fluctuates, landing interference may occur, so the ejection amount is corrected.

  By correcting only the discharge amount in the necessary region in this way, the correction processing speed can be improved, and the discharge amount (drive waveform) can be corrected efficiently.

  Further, as described above, the density change when the recording paper speed changes is largely due to the interval between the dots when the droplets are ejected onto the web 2, and therefore the discharge amount of the region where the dots are ejected adjacent to each other. Only (driving waveform) may be corrected. For example, the discharge amount of the area where 4 dots or 8 dots around the top, bottom, left and right of the adjacent droplets are ejected is corrected. Thereby, since only a necessary area can be corrected, the processing speed of the correction can be improved.

  Further, the correction of the ejection amount can be performed at any time as the recording paper speed changes, but can also be performed in units of images. In this case, for example, the discharge amount may be corrected according to the average speed when passing through the drawing unit directly under the head, or the discharge amount may be corrected according to the speed when entering the drawing unit. It may be. As a result, it is not necessary to correct the ejection amount at any time, and an image can be recorded efficiently.

  Further, only when the amount of change in the recording paper speed when recording one image is equal to or less than a predetermined value (first reference value), the ejection amount is corrected according to the average recording paper speed. Also good. That is, when the recording paper speed changes slowly, such as when the web 2 is slowly accelerated or decelerated, the density change is small, so the ejection amount is corrected with the average recording paper speed. As a result, excessive correction can be prevented, and an image can be recorded efficiently.

  Further, when the web 2 travels more slowly, the ejection amount may be corrected at the recording paper speed averaged among a plurality of images. That is, when the amount of change in the recording paper speed when recording one image is equal to or smaller than the second reference value that is further smaller than the first reference value (= the recording paper while printing a plurality of images) When the speed change amount is equal to or smaller than a predetermined value), the ejection amount of each image is corrected according to the recording paper speed averaged among a plurality of images. Thereby, an image can be recorded more efficiently.

  Since the first reference value and the second reference value vary depending on the image printing conditions (such as ink and paper used), it is preferable to set them according to the image printing conditions.

As an example, the first reference value is the maximum value of image density and color shift in one recorded image expressed in L *, a *, b * color space (specified in JIS Z 8729) And the slowest change in the paper speed, where ΔE = (Δa * ² + Δb * ² + ΔL * ² ) ^1/2 ≦ 2. Similarly, the second reference value is the slowest paper speed change in which the image density and color shift in a plurality of recorded images are ΔE ≦ 2.

  By doing so, correction of the ejection amount of each image can be simplified and an image can be efficiently recorded within a range in which a change in image quality is not recognized.

≪Measurement method of reading paper speed≫
As described above, when correcting the read image and controlling reading according to the reading paper speed, accurate information on the reading paper speed is required. Further, when analyzing the read image, it is necessary to accurately know information on the recording paper speed when the image is recorded.

  As described above, the reading paper speed is directly measured by a method of obtaining rotation amount detecting means such as a rotary encoder on the shaft of the roller that conveys the web 2 and obtaining the rotation amount of the shaft, or by a laser Doppler velocimeter. There are methods.

  These methods can directly measure the reading paper speed when reading an image, but cannot know the recording paper speed of the read image. That is, in the inkjet printer 1 of this example, the distance between the printing unit 50 and the fixing / reading unit 70 is long, and the dancer roller 62 is also installed, so that the reading paper speed is not necessarily the same as the recording paper speed. Not limited to this, the web 2 may be conveyed at a different speed.

  Therefore, the reading paper speed when reading a recorded image and the recording paper speed of the read image are measured by the method described below.

  As shown in FIG. 20, when printing on the web 2 in general, both ends of the web 2 in the width direction are non-printing areas, and an area excluding the width-direction both ends (so-called ear portions) is the printing range. Set to

  When the web 2 passes through the drawing section directly below the inkjet head, as shown in FIG. 21, predetermined reading paper speed detection marks are recorded at a certain distance interval in one non-printing area (the recording paper speed is set to the recording paper speed). In addition to recording in synchronism), a predetermined recording paper speed detection mark is recorded at regular time intervals.

  The reading paper speed detection mark and the recording paper speed detection mark are configured by, for example, a line segment orthogonal to the conveyance direction of the web 2 (= a line segment orthogonal to the longitudinal direction of the web 2) as shown in FIG. , M, K, C, and Y (for example, recording with a black inkjet head 51K).

  The fixing / reading unit 70 is provided with a speed detection mark reading device (not shown) in the vicinity of the reading unit by the scanner 74 for reading the reading paper speed detection mark and the recording paper speed detection mark. This speed detection mark reader measures the time interval for reading the speed detection mark during reading, and outputs the measurement result to the system controller 100. In addition, the reading distance interval of the recording paper speed detection mark is measured, and the measurement result is output to the system controller 100.

  The system controller 100 reads the paper speed at the time of reading and the image read by the scanner 74 from the time interval of reading the speed detection mark at the time of reading read by the speed detection mark reader and the distance interval of the reading of the paper speed detection mark at the time of recording. The paper speed during recording is calculated.

  That is, since the reading speed detection mark is sequentially recorded on the web 2 at a constant distance interval regardless of the web 2 conveyance speed, the reading paper speed is obtained by measuring the reading time interval. Can do.

  On the other hand, since the recording paper speed detection mark is recorded on the web 2 at regular time intervals, the recording paper speed when an image to be read by the scanner 74 is recorded is measured by measuring the reading distance interval. Can be sought.

  Thus, the reading paper speed can be accurately measured, and the recording paper speed of the read image can be acquired.

  In the above example, the reading paper speed detection mark and the recording paper speed detection mark are recorded in parallel in one non-printing area. However, the reading paper speed detection mark is provided in one non-printing area. A recording paper speed detection mark may be recorded in the other non-printing area.

  In the above example, the reading paper speed detection mark and the recording paper speed detection mark are recorded by the ink jet head that records an image in the printing unit 50 (in the above example, the ink jet head 51K that discharges the black ink). However, the recording may be performed using a separate dedicated recording unit (for example, an ink jet head different from the ink jet head for recording an image). In this case, both the reading paper speed detection mark and the recording paper speed detection mark can be recorded by the dedicated recording means, or only one of them can be recorded by the dedicated recording means. You can also

  Further, since the paper speed detection mark at the time of reading is recorded on the web 2 at a constant distance interval, it may be recorded on the web 2 in advance. In other words, printing may be performed using the web 2 on which the paper speed detection mark for reading is recorded in advance. In this case, the reading speed of the paper speed detection mark at the time of reading is provided in the printing unit or the like, and by measuring the reading time interval, the conveyance speed of the web 2 can be measured also in the printing unit or the like.

  By the way, since the recording paper speed detection mark is recorded at a constant time interval, when the conveyance speed of the web 2 is extremely reduced, the marks may be overlapped and recorded.

  Therefore, in the speed range where the web 2 is transported at a low speed and the marks are overlapped, the recording paper speed detection mark is thinned and recorded, and when calculating the speed, the thinning state is detected and the recording paper is recorded. Try to find the speed.

  The thinning state is detected by, for example, recording information for identifying the thinned number together with a recording paper speed mark and reading the information with a speed detection mark reader.

  For example, as shown in FIG. 22, the information for identifying the thinned number is encoded by a pattern in which dots are turned ON / OFF, and this pattern is recorded together with a recording paper speed mark to be recorded next. In the example shown in the figure, the thinned number is coded by a 4-bit pattern and recorded in parallel with the recording paper speed mark. In this case, up to 16 lines can be thinned out. In addition, the number of thinned-out lines can be represented by a known barcode or two-dimensional barcode and recorded.

  In the above example, the recording paper speed detection mark and the reading paper speed detection mark are both line segments orthogonal to the conveyance direction of the web 2, but the recording paper speed detection mark and the reading paper are used. The shape of the speed detection mark is not limited to this. In addition, a point, a pattern image, a figure with a specific shape, or the like can be used.

  Further, a serial number is assigned to the recording paper speed detection mark and the reading paper speed detection mark, and information of the serial number can be recorded simultaneously. For example, as described above, the serial number information is coded with a pattern in which dots are turned ON / OFF, and is recorded together with the recording paper speed detection mark and the reading paper speed detection mark. Alternatively, recording is performed together with a recording paper speed detection mark and a reading paper speed detection mark represented by a known barcode or two-dimensional barcode.

  FIG. 23 shows an example in which the serial number of the recording paper speed detection mark is recorded as a barcode, and the serial number of the reading paper speed detection mark is recorded as a two-dimensional barcode.

  In the example shown in the figure, a barcode indicating the serial number of the recording paper speed detection mark is recorded in parallel with the recording paper speed detection mark, and a two-dimensional barcode indicating the serial number of the reading paper speed detection mark is read. Although the recording is performed in parallel with the hourly paper speed detection mark, the position where the serial number information is recorded is not limited to this. In addition, it is also possible to record at a position close to the recording paper speed detection mark and the reading paper speed detection mark, for example, above or below each mark.

  In the example shown in the figure, a barcode representing the serial number of the recording paper speed detection mark is recorded in parallel with the recording paper speed detection mark, and a two-dimensional barcode representing the serial number of the reading paper speed detection mark. However, the serial number information may be formed as part of the recording paper speed detection mark and the reading paper speed detection mark. Further, the recording paper speed detection mark itself or the reading paper speed detection mark itself may be represented by information indicating a serial number.

  The recording paper speed detection mark shown in FIG. 24 is partially barcoded, and the barcode represents the serial number. Further, the reading paper speed detection mark shown in the figure has a structure in which the mark itself is a bar code and the serial number is represented by the bar code.

  In this way, by adding information indicating the serial number to the recording paper speed detection mark and the reading paper speed detection mark, for example, when the mark is recorded by thinning, the information on the number of thinned pieces can be acquired. it can.

<< Other embodiments >>
In the above embodiment, a line-type reading unit using a line sensor camera is used as a unit for reading a printed image. However, the unit for reading a printed image is not limited to this. However, in the case of a reading unit configured to periodically read an image, such as a line-type reading unit, a good image can be obtained by reading with the above-described reading method.

  In the above embodiment, the case where the present invention is applied to an image recording apparatus that prints on a continuously fed web by an inkjet method has been described as an example. However, an image recording apparatus that prints an image on a sheet of paper is also described. The same can be applied.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet printing machine, 2 ... Web, 10 ... Paper feed part, 11-13 ... Paper feed roll, 14 ... Reel stand, 20 ... Infeed part, 21 ... Infeed roller pair, 22 ... Dancer roller, 30 ... Processing Liquid coating unit, 31... Treatment liquid coating device, 40... First drying unit, 42 .. dancer roller, 50 .. printing unit, 51 (51M, 51K, 51C, 51Y). ... dancer roller, 70 ... fixing / reading unit, 71 ... ultraviolet light source, 72 ... cooling device, 74 ... scanner, 74A ... line sensor camera, 74B ... optical system, 74C ... illumination device, 80 ... outfeed unit, 81 ... Pair of outfeed rollers, 82 ... dancer roller, 90 ... collection unit, 91-93 ... core, 94 ... reel stand, 100 ... system controller, 1 DESCRIPTION OF SYMBOLS 2 ... Communication part, 104 ... Image memory, 110 ... Conveyance control part, 112 ... Paper feed control part, 114 ... Treatment liquid application control part, 116 ... 1st drying control part, 118 ... Print control part, 120 ... 2nd drying Control unit 122 ... Fixing / reading control unit 124 ... Collection control unit 130 ... Operation unit 132 ... Display unit 200 ... Host computer

Claims (25)

Paper transport means for transporting paper composed of strip-shaped continuous paper ;
Said eject ink droplets in synchronism with the travel of the sheet conveyed by the sheet conveying means, the ink-jet head of line type, also during acceleration and deceleration of the paper draws an image on the sheet,
A reading unit that reads an image drawn by the inkjet head from a sheet conveyed by the sheet conveying unit;
From the image read by the reading unit, the position of the dots of a plurality of droplets drawn so as to come in contact along the paper conveyance direction or the paper conveyance speed changes as the paper conveyance speed changes. Measuring means for detecting a size of a dot drawn by connecting a plurality of droplets along the paper transport direction and measuring a deviation amount from the position or size of the dot under a printing condition determined as a standard state;
Correction means for correcting the drawing condition of the image by the inkjet head based on the amount of deviation measured by the measuring means so that the image is drawn at a constant density;
An ink jet recording apparatus comprising:   The image processing apparatus includes a storage unit that stores correction information corresponding to a shift amount, and the correction unit refers to the correction information stored in the storage unit and corrects an image drawing condition by the inkjet head. The inkjet recording apparatus according to claim 1.   Information acquisition means for acquiring at least one information of paper to be used, ink status, paper environmental temperature and humidity, and ink jet head landing error; and the correction means takes into account information acquired by the information acquisition means The ink jet recording apparatus according to claim 2, wherein an image drawing condition by the ink jet head is corrected.   4. The ink jet recording apparatus according to claim 2, wherein the correcting unit corrects dot arrangement data of an image to be drawn.   5. The ink jet recording apparatus according to claim 4, wherein the correction information is information on a gradation curve representing a relationship between a dot appearance rate and an input image density.   The inkjet recording apparatus according to claim 1, wherein the correcting unit corrects an ejection amount of the ink droplet per dot.   The correction means corrects the ejection amount of the ink droplet per dot by correcting at least one of a peak value and a pulse width of a drive signal applied to an actuator of the inkjet head. Item 7. The ink jet recording apparatus according to Item 6. The reading unit is a reading unit that performs a reading operation at a predetermined reading cycle and reading time and reads an image from a sheet conveyed by the sheet conveying unit,
A reading paper speed detecting means for detecting, as a reading paper speed, a conveyance speed of the paper when an image is read by the reading means;
A read image correction unit that corrects a blur of the read image caused by a change in the paper speed during reading by correcting the read image using a predetermined correction function set according to the paper speed during reading;
An ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is provided.   9. The correction function includes a 1 × n filter matrix that corrects a read image with respect to a conveyance direction of the sheet, and n is set according to a reading sheet speed. Inkjet recording apparatus.   The filter parameter of the filter matrix is set so as to realize a spatial frequency characteristic opposite to that when blur occurs, and is set so that the total energy of the image is substantially the same before and after processing. The ink jet recording apparatus according to claim 9.   11. The ink jet recording apparatus according to claim 9, wherein a filter parameter of the filter matrix and n are set in consideration of characteristics of an optical system of the reading unit. The reading means is a reading means for periodically reading an image,
Illuminating means for illuminating a sheet on which an image is read by the reading means;
A reading paper speed detecting means for detecting, as a reading paper speed, a conveyance speed of the paper when an image is read by the reading means;
A reading control means for controlling an image reading operation by the reading means so that the time of one reading period becomes longer as the reading paper speed becomes slower;
An ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is provided.   13. The inkjet recording apparatus according to claim 12, wherein the reading control unit causes the reading unit to perform a reading operation at a constant periodic reading time when the reading paper speed is equal to or lower than a constant paper speed.   Read image correction means for correcting a read image read at a constant periodic reading time when the reading paper speed becomes equal to or less than a constant paper speed, and the read image correction means reads the read image. Information on the reading paper speed at the time of reading, and correcting the read image using a predetermined correction function set in accordance with the reading paper speed, thereby causing the reading caused by fluctuations in the reading paper speed. The inkjet recording apparatus according to claim 13, wherein blurring of an image is corrected.   15. The correction function includes a 1 × n filter matrix that corrects the read image with respect to a conveyance direction of the paper, and n is set according to a reading paper speed. The ink jet recording apparatus described.   The filter parameter of the filter matrix is set so as to realize a spatial frequency characteristic opposite to that when blur occurs, and is set so that the total energy of the image is substantially the same before and after processing. The ink jet recording apparatus according to claim 15.   The inkjet recording apparatus according to claim 15 or 16, wherein a filter parameter of the filter matrix and n are set in consideration of characteristics of an optical system of the reading unit. The reading means is a reading means for periodically reading an image,
Illuminating means for illuminating a sheet on which an image is read by the reading means;
A reading paper speed detecting means for detecting, as a reading paper speed, a conveyance speed of the paper when an image is read by the reading means;
A light emission control means for controlling a light emission operation of the illumination means, wherein the illumination means is caused to emit light intermittently in synchronization with a reading cycle of the reading means, and light emission is performed as the paper speed during reading decreases in each light emission. A light emission control means for controlling the light emission time so as to increase the time, and for controlling the light emission quantity so that the integrated value of the light emission quantity within one reading period is substantially constant;
An ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is provided. The reading means is a reading means for periodically reading an image,
Illuminating means for illuminating a sheet on which an image is read by the reading means;
A light emission control means for controlling a light emission operation of the illumination means so that the illumination means emits light intermittently at a constant light emission time and light emission amount in synchronization with a reading cycle of the reading means;
The light emission time and the light emission amount of the illumination means are set to the light emission time and the light emission amount at which an image can be read by the reading means when the paper is conveyed at the maximum conveyance speed. Item 8. The ink jet recording apparatus according to any one of Items 1 to 7.   19. The reading paper speed detecting means detects a reading paper speed by reading predetermined reading paper speed detection marks recorded on the paper at predetermined distance intervals. The ink jet recording apparatus according to any one of the above.   21. The inkjet recording apparatus according to claim 20, wherein a part of or all of the reading paper speed detection marks are configured by a pattern indicating an order.   The inkjet recording apparatus according to claim 20 or 21, wherein the reading sheet speed detection mark is recorded on the sheet by an inkjet head. The ink-jet recording apparatus according to any one of claims 1 to 22, characterized in that it comprises a sheet feed means for continuously feeding while replenishing the for paper. In an ink jet recording method in which ink droplets are ejected from a line-type ink jet head in synchronization with the travel of a sheet composed of a belt-like continuous sheet, and an image is drawn on the sheet even during acceleration / deceleration of the sheet .
Reading an image drawn by the inkjet head;
From the read image , the position of a plurality of droplets drawn so as to come in contact along the paper conveyance direction by changing the paper conveyance speed , or the paper conveyance speed changes by changing the paper conveyance speed. Detecting the size of a dot drawn by connecting a plurality of drops along the transport direction, and measuring the amount of deviation from the position or size of the dot under the printing conditions determined as a standard state;
Correcting the image drawing conditions by the inkjet head based on the measured amount of deviation so that the image is drawn at a constant density;
An ink jet recording method comprising:   25. The ink jet recording method according to claim 24, wherein the paper is a belt-like continuous paper, and the paper is continuously fed while the paper is added.