JP2006326984A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease visibility of non-uniformity of stripes and to improve the quality of an image. <P>SOLUTION: A method for forming an image forms the image on a recording medium by attaching a liquid for improving reproducibility of the image on the recording medium and hitting at least one kind of ink. The problem is solved by providing the method for forming the image characterized by attaching the liquid for improving reproducibility of the image on a line pattern basic tone. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming method and an image forming apparatus, and in particular, an image that forms an image on a recording medium by depositing an image reproducibility improving liquid (processing liquid) on the recording medium and ejecting ink. The present invention relates to a forming method and an image forming apparatus.

  Conventionally, an image is recorded by ejecting ink from a plurality of nozzles formed on the print head while moving the print head (discharge head) and the recording medium relatively to form dots on the recording medium. An inkjet recording apparatus (inkjet printer) that performs inkjet image recording is known.

  The heads used in the ink jet recording apparatus include a shuttle system that performs recording while a short head is scanned in the paper width direction (main scanning direction) perpendicular to the paper feeding direction (sub-scanning direction) of the recording medium, and the paper width direction (main scanning direction). There is a line system using a line head in which a large number of nozzles are arranged in the scanning direction). In the line method, an image can be recorded on the entire surface of the recording medium by relatively moving the recording medium and the head in the paper feed direction, and high-speed recording is possible compared to the shuttle method.

  Further, as an ink ejection method in an ink jet recording apparatus, a heating element (electrical / thermal energy converting means) is provided in the vicinity of the nozzle, and an electric signal is applied to the heating element to locally heat the ink so as to change the pressure. This is a thermal method that causes ink to be ejected from the nozzle, and a piezoelectric method that causes the ink to be ejected from the nozzle by applying mechanical pressure to the ink using an electrical / pressure converting means such as a piezoelectric element (piezo element). Method).

  By the way, in the ink jet recording apparatus, normally, only two gradations of dot on / off can be expressed for each pixel. Therefore, image recording is performed after performing image processing for expressing input multi-tone image information by dot distribution, so-called halftone processing. As a method for realizing the halftone process, a dither method and an error diffusion method are widely known.

  In the dither method, a dither matrix (threshold matrix) consisting of threshold values arranged in a matrix is prepared, and one-to-one image comparison between each threshold value and each pixel of input data is performed to determine dot on / off. To do. On the other hand, in the error diffusion method, a diffusion coefficient is assigned to a peripheral pixel for a target pixel, and a quantization error generated in the target pixel is distributed to the peripheral pixels according to the diffusion coefficient. As a result, the density of the entire image is preserved, and favorable gradation expression is possible. In general, the image quality tends to be lower in the dither method than in the image to which the error diffusion method is applied. However, since the error diffusion method cannot move to the next pixel processing until the error propagates, high-speed processing is difficult.

  As a halftone processing method different from the dither method and the error diffusion method, a line for controlling the thickness of the line is known. The line is a halftone processing method used in the electrophotographic method and the like, and has the effect of reducing the visibility of stripes in the direction perpendicular to the line direction.

  Patent Document 1 describes an image processing method in which a line feature is added to the error diffusion method. According to this document, in order to reduce pitch unevenness (straight unevenness in the main scanning direction) generated in the sub-scanning direction (paper feeding direction), the periodic component perpendicular to the main scanning direction is perpendicular to the sub-scanning direction. By using a stronger dither matrix, a line basic tone that is a periodic line component perpendicular to the main scanning direction is generated, and pitch unevenness in the sub-scanning direction is reduced.

  Patent Document 2 describes an image processing method in which a line feature is added to the dither method. According to this document, a dither matrix (threshold matrix) having a high-pass filter characteristic for a portion of the density of an input multi-tone image that is formed in a line tone (line tone) in a predetermined direction and a portion other than the tone. ) To prevent image quality from being degraded at low resolution.

By the way, in the ink jet recording apparatus, for example, as described in Patent Document 3, in order to improve the image quality, the ink fixing property is provided on the entire surface of the recording medium, the ink landing position, or the vicinity thereof. What discharges the processing liquid (image reproducibility improvement liquid) for improving is known. In Patent Document 3, in order to reduce the visibility of uneven stripes caused by abnormal nozzles (e.g. landing position misalignment nozzles, undischarge nozzles), the printability is improved in the dots corresponding to the abnormal nozzles and in the vicinity thereof (that is, in the vicinity of the streaks). Image recording is performed without applying ink.
JP-A-11-215376 Japanese Patent Laid-Open No. 2004-80065 JP 2002-67296 A

  However, the image processing methods described in Patent Document 1 and Patent Document 2 described above are effective when the line frequency (line density) is sufficiently lower than the droplet ejection density, but other than that In some cases, there are the following problems. In other words, for the purpose of high-quality printing, if you want to realize a line tone at 300 lpi (line per inch) so that the structure of the line is not visible, the line density is about 1200 dpi (dot per inch). There is an amount that can be controlled only by 4 dots (= 1200/300) in the width direction. For this reason, in the image processing method of Patent Document 1, the contact between adjacent lines and the separation probability in the direction of the lines increase, and the line tone is lost and noise characteristics are deteriorated. Further, in the image processing method of Patent Document 2, it becomes impossible to give high-pass filter characteristics because isolated dots cannot be hit at portions other than the line. As described above, the image processing methods described in Patent Document 1 and Patent Document 2 cannot realize high-quality prints that are resistant to unevenness due to the high number of lines.

  In order to solve these problems, it is conceivable to increase the droplet ejection density to reduce the dot size. However, while it is possible to improve the droplet ejection density (for example, 4800 dpi) with the latest technology, The size limit is about 25 μm, and it is difficult to achieve a dot size that matches the droplet ejection density (it is impossible to control the amount smaller than the dot diameter. Even if the droplet ejection position is controlled, the ink amount increases. )

  Further, in the ink jet recording apparatus described in Patent Document 3, an abnormal nozzle specifying unit is required, which complicates the apparatus, lowers the processing speed, and further increases the cost. In addition, the ejection state of each nozzle may change during printing, and it is difficult to identify abnormal nozzles during printing.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming method and an image forming apparatus that reduce the visibility of uneven stripes and improve the image quality.

  In order to achieve the above object, the invention according to claim 1 forms an image on the recording medium by depositing an image reproducibility improving liquid on the recording medium and ejecting at least one kind of ink. There is provided an image forming method, characterized in that the image reproducibility improving liquid is adhered in a line tone.

  According to the present invention, not the ink but the image reproducibility improving liquid is adhered to the whole line so that the ink (dot) smearing or the droplet ejection interference is applied to the portion where the image reproducibility improving liquid is not adhered. By using it, the visibility of stripes can be reduced, and the image quality is improved.

  Furthermore, since the lines are made of the image reproducibility improving liquid, the line tone can be easily maintained from highlight to shadow, and the line tone does not deteriorate or nozzle characteristics are not deteriorated at a specific gradation.

  A second aspect of the present invention is the image forming method according to the first aspect, wherein a line direction of the image reproducibility improving liquid is a direction substantially perpendicular to a direction in which stripe unevenness occurs. And

  The aspect of Claim 2 improves the suppression effect of a stripe unevenness.

  A third aspect of the present invention is the image forming method according to the first aspect, wherein a line direction of the image reproducibility improving liquid is an oblique direction with respect to a direction in which stripe unevenness occurs. To do.

  The aspect of Claim 3 is effective when the stripe unevenness has arisen in several directions.

  A fourth aspect of the present invention is the image forming method according to any one of the first to third aspects, wherein a line frequency of the image reproducibility improving liquid is 250 lpi or more. And

  The aspect of claim 4 improves the image quality because the visibility of the line structure is reduced.

  A fifth aspect of the present invention is the image forming method according to any one of the first to fourth aspects, wherein the line width of the image reproducibility improving liquid is varied according to the characteristics of the recording medium. , Changing at least one of the line frequency and line intensity.

  According to the fifth aspect of the present invention, an optimum image quality can be obtained even when the degree of bleeding and droplet ejection interference varies depending on the characteristics of the recording medium.

  A sixth aspect of the present invention is the image forming method according to any one of the first to fifth aspects, wherein the image reproducibility improving liquid has a line width of 10,000, tens of thousands according to the strength of the stripes. It is characterized in that at least one of the line frequency and the line strength is changed.

  According to the aspect of the sixth aspect, it is possible to obtain an optimum image quality in accordance with the intensity of the uneven stripe.

  A seventh aspect of the present invention is the image forming method according to any one of the first to sixth aspects, wherein the image reproducibility improving liquid is further adhered to a portion corresponding to an edge portion of the image. It is characterized by that.

  According to the aspect of the seventh aspect, it is possible to prevent bleeding and disturbance of the edge portion of the image.

  The invention according to claim 8 is the image forming method according to any one of claims 1 to 7, wherein the recording medium is permeable to such an extent that ink does not penetrate or landing interference occurs. In contrast to the number of dots in which the center of dots formed by ink landing on the recording medium does not land on the image reproducibility improving liquid, the dots themselves are completely absent from the image reproducibility improving liquid. The number of non-contact dots is 1/3 or less.

  According to the aspect of the eighth aspect, it is possible to apply a certain restriction to the movement of the ink (dots) landed on the recording medium, and it is possible to suppress the unevenness while suppressing the deterioration of the granularity due to the droplet ejection interference.

  The invention according to claim 9 is the image forming method according to any one of claims 1 to 8, wherein the at least one kind of ink is ejected so as to have a blue noise characteristic. It is characterized by.

  According to the ninth aspect of the present invention, it is possible to maintain a high line number of all lines from highlights to shadows, good gradation connection, and high resolution.

  In order to achieve the above object, the invention according to claim 10 is a first discharge head for ejecting ink onto a recording medium and a second ejection head for ejecting an image reproducibility improving liquid onto the recording medium. First control means for controlling droplet ejection of the ink by the first ejection head, second control means for controlling droplet ejection of the image reproducibility improving liquid by the second ejection head, and the recording medium; Conveying means for relatively conveying the first ejection head and the second ejection head, wherein the first ejection head and the second ejection head have a plurality of lengths corresponding to the entire width of the recording medium. An image forming apparatus comprising: a line head in which nozzles are arranged, wherein the second control unit controls the second discharge head so that the image reproducibility improving liquid is ejected in a line-basis. I will provide a.

  According to the tenth aspect of the present invention, it is possible to reduce the visibility of the stripe unevenness caused by the abnormal nozzle of the second discharge head that is a line head.

  An eleventh aspect of the present invention is the image forming apparatus according to the tenth aspect, in which the second control unit is configured such that a direction substantially perpendicular to a relative conveyance direction of the recording medium is a line direction. The second ejection head is controlled so as to eject the basic image reproducibility improving liquid.

  According to the aspect of the eleventh aspect, it is possible to effectively suppress the unevenness in the relative conveyance direction.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to the tenth aspect, the second control unit is configured such that a direction inclined obliquely with respect to a relative conveyance direction of the recording medium is a line direction. The second discharge head is controlled so as to eject the liquid reproducibility improving liquid having the basic line.

  According to the aspect of the twelfth aspect, it is possible to effectively suppress the unevenness in the relative conveyance direction and the unevenness in the direction orthogonal to the relative conveyance direction.

  According to the present invention, not the ink but the image reproducibility improving liquid is adhered to the whole line so that the ink (dot) smearing or the droplet ejection interference is applied to the portion where the image reproducibility improving liquid is not adhered. By using it, the visibility of stripes can be reduced, and the image quality is improved.

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

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus as an embodiment of an image forming apparatus according to the present invention. As shown in FIG. 1, the ink jet recording apparatus 10 includes a print unit 12 having a plurality of print heads 12P, 12K, 12C, 12M, and 12Y, and liquid supplied to the print heads 12P, 12K, 12C, 12M, and 12Y. A liquid storage / loading unit 14 for storing (processing liquid or ink), a paper feeding unit 18 for supplying the recording paper 16, a decurling unit 20 for removing curl of the recording paper 16, and the printing unit 12. An adsorption belt conveyance unit 22 that is arranged opposite to the nozzle surface (ink ejection surface) and conveys the recording paper 16 while maintaining the flatness of the recording paper 16, and a print detection unit 24 that reads a printing result by the printing unit 12; And a paper discharge unit 26 for discharging the printed recording paper (printed matter) to the outside.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  In the case of an apparatus configuration using roll paper, a cutter 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is arranged on the print surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least a portion facing the nozzle surface of the printing unit 12 and the sensor surface of the printing detection unit 24 is flat ( Flat surface).

  The belt 33 has a width that is greater than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, an adsorption chamber 34 is provided at a position facing the nozzle surface of the print unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. Then, the suction chamber 34 is sucked by the fan 35 to be a negative pressure, whereby the recording paper 16 on the belt 33 is sucked and held.

  The power of a motor (not shown) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, so that the belt 33 is driven in the clockwise direction in FIG. The recording paper 16 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blowing method of spraying clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip transport mechanism instead of the suction belt transport unit 22 is also conceivable, when the print area is transported by a roller / nip, the roller comes into contact with the print surface of the paper immediately after printing, so that the image blurs. There is a problem that it is easy. Therefore, as in this example, suction belt conveyance that does not contact the image surface in the printing region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 12 is a so-called full-line type head in which line-type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) orthogonal to the paper transport direction (sub-scanning direction). That is, as shown in FIG. 2, the print heads 12P, 12K, 12C, 12M, and 12Y constituting the printing unit 12 have a length that exceeds at least one side of the maximum size recording paper 16 targeted by the inkjet recording apparatus 10. It is composed of a line head in which a plurality of discharge ports (nozzles) are arranged.

  A print head (processing liquid droplet ejection head) 12P corresponding to the processing liquid (P) is disposed on the upstream side (left side in FIG. 1) along the transport direction (paper transport direction) of the recording paper 16, and the downstream side thereof. Are arranged with print heads (ink ejection heads) 12K, 12C, 12M, and 12Y corresponding to the respective color inks in the order of black (K), cyan (C), magenta (M), and yellow (Y). While transporting the recording paper 16, the processing liquid is ejected from the processing liquid droplet ejection head 12 </ b> P, and then the color ink is ejected from each of the ink ejection heads 12 </ b> K, 12 </ b> C, 12 </ b> M, 12 </ b> Y. A color image can be formed on top.

  As the ink used in this example, for example, a color ink containing an anionic polymer that is a polymer containing negatively charged surface active ions is used. Further, for the treatment liquid used in this example, for example, a transparent reaction accelerator containing a cationic polymer which is a polymer containing positively charged surface active ions is used.

  When the ink and the treatment liquid are mixed, the color material in the ink is insolubilized and / or the fixing reaction proceeds by a chemical reaction. The term “insolubilization” includes, for example, a phenomenon in which a color material is precipitated and precipitated from a solvent, a phenomenon in which a liquid in which a color material is dissolved changes to a solid phase (solidification), and a phenomenon in which the liquid thickens and hardens. included. “Fixing” includes an aspect in which the color material is held on the surface of the recording paper 16, an aspect in which the color material penetrates and is held inside the recording paper 16, or a combination thereof.

  The reaction speed and the physical properties (contact angle, surface tension, etc.) of each liquid can be adjusted by adjusting the composition of each ink and the treatment liquid and the concentration of the substance that contributes to the reaction. Insolubility and / or ink penetration rates can be achieved. The physical properties of the treatment liquid and ink used in this embodiment will be described later.

  Thus, according to the printing unit 12 provided with a plurality of full line heads covering the entire area of the paper width, the operation of relatively moving the recording paper 16 and the printing unit 12 in the paper conveyance direction (sub-scanning direction). An image can be recorded on the entire surface of the recording paper 16 only once (that is, in one sub-scan). Accordingly, high-speed printing is possible as compared with a shuttle type head in which the print head reciprocates in a direction (main scanning direction) orthogonal to the paper transport direction, and productivity can be improved.

  In this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink and dark ink are added as necessary. May be. For example, a configuration in which an ink droplet ejection head for ejecting light-colored ink such as light cyan and light magenta can be added. Further, the number of treatment liquid droplet ejection heads is not limited to one, and may be plural.

  As shown in FIG. 1, the liquid storage / loading unit 14 stores the processing liquid corresponding to the processing liquid droplet ejection head 12P and the inks of the respective colors corresponding to the ink droplet ejection heads 12K, 12C, 12M, and 12Y. The tanks communicate with the print heads 12P, 12K, 12C, 12M, and 12Y through conduits (not shown). In addition, the liquid storage / loading unit 14 includes notifying means (display means, warning sound generating means, etc.) for notifying that when the remaining amount of liquid (processing liquid or ink) is low, and an error between processing liquids and colors. It has a mechanism for preventing loading.

  The print detection unit 24 includes an image sensor (line sensor or the like) for imaging the droplet ejection result of the print unit 12, and means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor. Function as.

  The print detection unit 24 of this example is configured by a line sensor having a light receiving element array that is wider than at least the ejection width (image recording width) of each print head 12P, 12K, 12C, 12M, 12Y. The line sensor includes an R sensor row in which photoelectric conversion elements (pixels) provided with red (R) color filters are arranged in a line, a G sensor row provided with green (G) color filters, The color separation line CCD sensor includes a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 24 reads the test patterns printed by the ink droplet ejection heads 12K, 12C, 12M, and 12Y for each color, and detects the ejection of each head. The ejection determination includes the presence / absence of ejection, measurement of the dot size, and the like.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  When printing on porous paper with dye-based ink, the weather resistance of the image is improved by preventing contact with ozone or other things that cause dye molecules to break by blocking the paper holes by pressurization. There is an effect to.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined uneven surface shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. ing. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B.

  Although not shown, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

[Print head structure]
Since the structures of the print heads 12P, 12K, 12C, 12M, and 12Y are common, the structure of the treatment liquid droplet ejection head 12P will be described below as a representative of these structures.

  FIG. 3 is a plan view showing the nozzle arrangement of the treatment liquid droplet ejection head 12P, and FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. The treatment liquid droplet ejection head 12P is provided with a nozzle row in which a plurality of nozzles 51 are arranged along the longitudinal direction of the head (see FIG. 3). Each nozzle 51 communicates with the common liquid chamber 55 via the flow path 60 (see FIG. 4). The common liquid chamber 55 is connected to a tank (not shown) and stores the processing liquid discharged from each nozzle 51.

  A heating element 58 is provided in the vicinity of the nozzle 51. Specifically, the heating element 58 is disposed in the partition wall of the flow path 60 so as to face the nozzle 51. The heat generating element 58 is connected to a processing liquid droplet ejection head driver (not shown in FIG. 4, described as reference numeral 85 in FIG. 5) via a wiring (not shown). Is supplied to the heating element 58.

  With this configuration, when the processing liquid is supplied from the common liquid chamber 55 to the flow path 60 and the drive signal is supplied to the heating element 58, bubbles are generated in the processing liquid in the flow path 60 due to heat generated by the heating element 58, A part of the processing liquid is discharged from the nozzle 51 by the pressure when the bubbles are generated.

  In this embodiment, the thermal type head is exemplified, but the present invention is not limited to this, and various types such as a piezoelectric type (piezo type) may be used. Further, it may be a matrix type head in which nozzles are arranged in a two-dimensional form (matrix form).

[Explanation of control system]
Next, the control system of the inkjet recording apparatus 10 will be described.

  FIG. 5 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, an ink droplet ejection head driver 84, and a treatment liquid droplet ejection head. A driver 85 and the like are provided.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet, and wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 is a control unit that controls each unit such as the communication interface 70, the image memory 74, the motor driver 76, and the heater driver 78. The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 86, read / write control of the image memory 74, and the like, as well as a transport system motor 88 and heater 89. A control signal for controlling is generated.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heaters 89 of the post-drying unit 42 and other units in accordance with instructions from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print It is a control unit that supplies ink droplet placement data (dot data), which is a control signal, and processing liquid droplet placement data, which will be described later, to the ink droplet ejection head driver 84 and the processing liquid droplet ejection head driver 85, respectively. The required signal processing is performed in the print control unit 80, and the ink ejection amounts of the ink droplet ejection heads 12K, 12C, 12M, and 12Y of the respective colors via the ink droplet ejection head driver 84 based on the ink ejection arrangement data The ejection timing is controlled, and the treatment liquid ejection amount and ejection timing of the treatment liquid droplet ejection head 12P are controlled via the treatment liquid ejection head driver 85 based on the treatment liquid ejection arrangement data. This realizes a desired dot size and dot arrangement.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. In FIG. 5, the image buffer memory 82 is shown in a form associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  The ink droplet ejection head driver 84 drives the ink droplet ejection heads 12K, 12C, 12M, and 12Y of the respective colors based on the ink droplet arrangement data (dot data) given from the print controller 80. Further, the processing liquid head driver 85 drives the processing liquid droplet ejection head 12 </ b> P based on the processing liquid droplet placement data supplied from the print controller 80. The ink droplet ejection head driver 84 and the treatment liquid droplet ejection head driver 85 may include a feedback control system for keeping the head driving conditions constant.

  As described with reference to FIG. 1, the print detection unit 24 is a block including a line sensor, reads an image printed on the recording paper 16, performs necessary signal processing, and the like to perform a print status (whether ejection is performed, droplet ejection And the detection result is provided to the print control unit 80. The reading start timing of the line sensor is determined from the distance between the sensor and the nozzle and the conveyance speed of the recording paper 16.

  The print control unit 80 performs various corrections for the ink droplet ejection heads 12K, 12C, 12M, and 12Y based on information obtained from the print detection unit 24 as necessary. Further, the print control unit 80 determines whether or not the nozzle 51 is ejected based on the detection information obtained through the print detection unit 24, and performs a predetermined recovery operation when a non-ejection nozzle is detected. I do.

  FIG. 6 is a block diagram showing details of the print control unit 80 of FIG. As shown in FIG. 6, the print control unit 80 mainly includes a processing liquid droplet ejection method determining unit 90, a processing liquid droplet ejection arrangement data setting unit 92, an image analysis unit 94, and an ink droplet ejection arrangement data setting unit 96. The

  The print control unit 80 is configured such that external information such as the characteristics of the recording medium (medium type and blur level) and the intensity of unevenness are input from the external information input unit 98. Specifically, this external information is input to the treatment liquid droplet ejection method determining unit 90 and the ink droplet arrangement data setting unit 96. The external information input unit 98 may be used also as, for example, an input unit (not shown) of the host computer 86 in FIG. 5 or may be provided separately. As an input form of the external information, the user may input according to the result of the test print, or a means for automatically identifying the external information may be provided.

  The treatment liquid droplet ejection method determining unit 90 determines a droplet ejection method (droplet ejection pattern) of the treatment liquid to be ejected onto the recording paper 16 (recording medium) based on the input external information. The determined droplet ejection method is sent to the treatment liquid droplet arrangement data setting unit 92. Note that the method of depositing the treatment liquid will be described in detail later.

  The image analysis unit 94 performs image analysis of the input image data, generates information (image edge information) related to the edge portion of the image, and sends the information to the processing liquid droplet placement data setting unit 92. The image edge information is used to eject the treatment liquid onto the edge portion of the image.

  The treatment liquid droplet placement data setting unit 92 is configured to process the liquid droplet placement data based on the treatment liquid droplet ejection method determined by the treatment liquid droplet ejection method determination unit 90 and the image edge information generated by the image analysis unit 94. Is set (generated). The treatment liquid droplet placement data is sent to the treatment liquid droplet ejection head driver 85 of FIG. 5, and the treatment liquid droplet ejection head 12P is driven based on the treatment liquid placement data.

  The ink droplet arrangement data setting unit 96 sets ink droplet arrangement data (dot data) for each ink color by a known method such as a dither method or an error diffusion method based on the input image data and external information ( Generated). The ink droplet placement data is sent to the ink droplet placement head driver 86 in FIG. 5, and the ink droplet ejection heads 12K, 12C, 12M, and 12Y are driven based on the ink droplet placement data.

  The ink droplet placement data preferably has a blue noise characteristic. That is, it is preferable to use a blue noise mask as a threshold matrix used in the dither method or the error diffusion method, and it is possible to obtain a good image quality. In particular, when the image component of the input image is mainly a low-frequency component, a high-quality result can be obtained due to the blue noise characteristics. Then, by combining with a treatment liquid droplet ejection pattern, which will be described later, it is possible to maintain the high line number of all lines from highlight to shadow, and to improve the gradation connection and resolution.

[Method of spraying treatment liquid]
First, as an example of a conventional treatment liquid droplet deposition method (droplet ejection pattern), a case where a treatment liquid is deposited on the entire surface of a recording medium will be described with reference to FIG. In the upper side of FIG. 7, the eight nozzles 51 (51-1,..., 51-8) of an arbitrary ink droplet ejection head (12K, 12C, 12M, 12Y) are shown as a representative. A plurality of dots 100 on the recording paper 16 (recording medium) formed by the ink ejected from each nozzle 51 is shown. Here, it is assumed that the nozzle 51-6 is an abnormal nozzle in which the landing position deviation occurs on the right side of FIG. The nozzles of the treatment liquid droplet ejection head 12P are not shown. The same applies to FIGS. 8 to 16 shown below.

  In the droplet ejection pattern of FIG. 7, each dot 100 ejected from each nozzle 51 is ejected onto the treatment liquid 110, and the spread of each dot 100 is suppressed by the effect of the treatment liquid 110. Therefore, when there is an abnormal nozzle such as the nozzle 51-6, a stripe unevenness extending in the sub-scanning direction is visually recognized at a portion (S portion) corresponding to the abnormal nozzle. As a representative example, the case where the treatment liquid 110 is ejected onto the entire surface of the recording medium has been described. However, the same applies to the case where the treatment liquid is ejected at a position corresponding to each dot 100 or the vicinity thereof. is there.

  On the other hand, in the present invention, in order to reduce the visibility of uneven stripes, the treatment liquid is ejected in a line. As described above, the treatment liquid droplet ejection method (droplet ejection pattern) is determined by the treatment liquid droplet ejection method determination unit 90 in FIG. 6 based on the external information.

  FIG. 8 is an example of a droplet ejection pattern of the treatment liquid in the present invention. The figure shows a state where penetrating paper (bleeding paper) is used. In the droplet ejection pattern of FIG. 8, the treatment liquid 110 is ejected in a line-basis tone in the main scanning direction perpendicular to the sub-scanning direction corresponding to the direction in which the uneven stripes are formed (straight stripe direction) in FIG. In other words, a large number of linear processing liquids 110 in the main scanning direction having a predetermined width (in this example, two dots) in the sub scanning direction are arranged in the sub scanning direction. Here, with respect to the multi-line processing liquid 110 configured as described above, the main scanning direction as the direction of each line is “line direction”, and the width of each line (width in the sub-scanning direction) is “line width”. ”, The interval, number and density of lines in the main scanning direction arranged in the sub-scanning direction are referred to as“ line spacing ”,“ number of lines ”and“ line frequency (or line density) ”, respectively. The amount of the basic processing liquid 110 will be referred to as “line strength”. The same applies to the following.

  As shown in FIG. 8, when penetrating paper is used, the dot 100 </ b> A where the treatment liquid 110 is ejected is prevented from spreading, while the dot where the treatment liquid 110 is not ejected. Since 100B spreads and spreads, the visibility of the stripe unevenness is reduced in the S portion of FIG. 8 as compared with the case where the treatment liquid 110 is ejected onto the entire surface of the recording medium (FIG. 7).

  Further, as described above, since the spread of the dots 100A in the portion where the treatment liquid 110 is ejected is suppressed as compared with the case where the treatment liquid 110 is not ejected at all, the resolution and the density (ink consumption) are reduced. Increase in amount) can be prevented.

  In addition, the line frequency (line density) of the line-tone processing liquid 110 is desirably 250 lpi or more, and there is almost no sensitivity in a region higher than about 10 cycles / mm from the spatial frequency characteristics of the human eye. The visibility of the line structure is reduced and the image quality is improved.

  In addition, unevenness can be suppressed by droplets of processing liquid instead of ink, so that even when multiple colors of ink are used, it is possible to realize a high-quality image without causing inter-color moire. it can.

  FIG. 9 shows a state where non-penetrating paper (or weakly penetrating paper) is used for the droplet ejection pattern of FIG. As shown in the figure, in the case of non-penetrating paper, the dot 100B in the portion where the treatment liquid 110 has not been ejected does not spread and spread, and is affected by the previously ejected dot (the previous dot). . That is, when the dot 100B comes into contact with the previous dot, the dot 100B is deformed (moved) so as to be attracted to the previous dot. Note that the spread of the dot 100A in the portion where the treatment liquid 110 is ejected is suppressed as in FIG.

  Here, paying attention to part B in FIG. In this embodiment, it is a thermal print head 50 (see FIG. 4), and each nozzle 51 (51-1,..., 51-8) is in order from the left in FIG. Each dot 100B is ejected in a short time. The numbers described in each dot 100B represent the droplet ejection order in the B portion. Hereinafter, by combining the droplet ejection orders, the dots 100B in the B portion are expressed as 100B-1, 100B-2,..., 100B-13, respectively.

  First, the dots 100B-1 and 100B-2 are ejected in order, but these dots are not in contact with each other, and other dots are not ejected in the portion B, so that they are substantially unaffected. Become. Next, the dots 100B-3, 100B-4, and 100B-5 are ejected in order. The dots 100B-3, 100B-4, and 100B-5 come into contact with the previously ejected dots (the previous dots) and are attracted to these dots. Deforms into an ellipse that is long in the main scanning direction. For example, the dot 100B-3 is deformed so as to be attracted to the previous dot 100B-2. Dot 100B-6 does not contact the previous dot and is substantially circular. The dot 100B-7 is deformed into an ellipse that is long in the sub-scanning direction so as to be attracted to the previous dot 100B-1. The dot 100B-8 is attracted to the previous dot 100B-7. The dot 100B-9 is attracted to both the previous dots 100B-2 and 100B-8. The dot 100B-10 is attracted to the previous dot 100B-4. The dot 100B-11 is attracted to the previous dots 100B-4, 100B-5, and 100B-10. Subsequently, the dot 100B-12 ejected from the abnormal nozzle 51-6 is attracted to the previous dot 100B-11 and becomes an ellipse that is long in the main scanning direction. The dot 100B-13 that is finally ejected in the portion B is attracted to the previous dots 100B-6 and 100B-12 and becomes an obliquely inclined ellipse.

  When non-penetrating paper (or weakly penetrating paper) is used, the dot 100B of the portion where the treatment liquid 110 is not ejected is perpendicular to the stripe direction (sub-scanning direction), as represented by the dot 100B-12. The direction of movement (in the main scanning direction) has a high degree of freedom of movement, and has the effect of reducing the visibility of uneven stripes.

  Further, each dot 100B (100B-1,..., 100B-13) does not spread to the portion where the treatment liquid 110 is ejected. Further, in the case of FIG. 9, at least a part of each dot 100 </ b> B is configured to contact the processing liquid 110. Specifically, the line width and line interval of the line-basis processing liquid 110, the size of dots formed by ink, and the like are determined so as to satisfy the above-described configuration. As a result, each dot 100B is deformed (moved) so as to be attracted to the previously ejected dot (previous dot), while the movement thereof is limited by contact with the treatment liquid 110. Therefore, as compared with the case where the treatment liquid 110 is not ejected at all, it is possible to reduce the visibility of the stripe unevenness in FIG. 7 while preventing the deterioration of the granularity in the portion where the treatment liquid 110 is not ejected.

  In FIG. 9, as a preferred embodiment, a configuration in which at least a part of each dot 100 </ b> B is in contact with the treatment liquid 110 is illustrated, but the following configuration may be used in order to prevent the granular deterioration. . That is, with respect to the number of dots whose dot center is not on the processing liquid 110, the number of dots in which the dots themselves do not contact the processing liquid 110 is set to 1/3 or less. As the ink movement due to droplet ejection interference increases, the mottle-like granular deterioration is visually recognized. However, by setting the number of dots that do not contact the processing liquid 110 to 1/3 or less, three or more that do not contact the processing liquid 110 at all. Since the probability of contact of these dots is very small, large ink movement does not occur, and unevenness can be suppressed while preventing deterioration in graininess.

  FIG. 10 is an example of a droplet ejection pattern in the case where the bleeding of the penetrating paper is severe. When the penetration of the penetrating paper is severe, the spread of the dots 100B where the treatment liquid 110 is not ejected is larger than that in FIG. 8, and the visibility of the stripes is weak. Therefore, from the viewpoint of ensuring resolution and concentration, it is preferable to increase the amount of the treatment liquid 110 as a whole. Specifically, as shown in FIG. 10, the line width of the line-basis processing liquid 110 is increased. At this time, it is preferable to narrow the line spacing. Although not shown, the line frequency (line density) may be increased by increasing the number of lines. When the line frequency is increased, the total amount of the processing liquid does not increase, but since the line interval is narrowed, the degree of bleeding of the dot portion that does not contact the processing liquid 110 can be suppressed. Note that it is effective to apply the same droplet ejection pattern even when droplet ejection interference is severe when non-penetrating paper (or weakly penetrating paper) is used.

  When bleeding or droplet ejection interference is intense, bleeding or droplet ejection interference occurs not only in the portion where the treatment liquid 110 is not ejected but also in the portion where the treatment liquid 110 is ejected, but the treatment liquid 110 is deposited. The degree of bleeding and droplet ejection interference in the portion where the treatment liquid 110 is ejected is sufficiently smaller than that in the portion where the treatment liquid 110 is not formed. Furthermore, by configuring the range of the portion where the treatment liquid 110 is not ejected narrowly, the influence on the resolution and density can be sufficiently reduced.

  Further, when the penetration of the penetrating paper and the droplet ejection interference are severe, as shown in the droplet ejection pattern shown in FIG. 11, the portion where the treatment liquid 110 is large and the portion where the treatment liquid 110 is small are alternately repeated in the non-uniform direction (sub-scanning direction) of FIG. The line strength may be increased as described above. In FIG. 11, the dots ejected from the nozzles 51 (51-1,..., 51-8) are not shown.

  Next, a treatment liquid droplet ejection pattern according to the intensity of the stripe unevenness will be described. FIG. 12 shows a conventional droplet deposition pattern in which the treatment liquid 110 is deposited on the entire surface of the recording medium. Compared with FIG. 7, the amount of landing position deviation by the abnormal nozzle 51-6 is large, and the unevenness in the S portion is uneven. This shows the case where the intensity is intense (when the visibility of the streak is strong). In the present invention, droplets are ejected so that the amount of the treatment liquid 110 is reduced as a whole when the unevenness is intense.

  FIG. 13 is an example of a droplet ejection pattern in the case where the unevenness is intense. Here, a state where penetrating paper is used is shown. In the droplet ejection pattern of FIG. 13, the line width of the line-based processing liquid 100 is narrower by one dot and the line spacing is wider by one dot than in FIG. 8. That is, the amount of the processing liquid 110 is reduced as a whole. As a result, the number of dots 100 in the portion where the treatment liquid 110 is not ejected increases, and the visibility of the stripe unevenness is reduced by the spread of the dots 100B.

  Furthermore, when the unevenness is intense, as shown in FIG. 14, it is preferable that the line strength is weakened by applying droplets so that the line-basis processing liquid 110 becomes discontinuous in the main scanning direction. In this case, the number of dots in the portion where the treatment liquid 110 is not ejected increases, and the visibility of the stripe unevenness can be further reduced.

  Further, not only the unevenness in the sub-scanning direction (paper feeding direction) as shown in FIG. 7 and FIG. 12, but also the unevenness in the main scanning direction perpendicular to the sub-scanning direction may be visually recognized due to unevenness of the paper feeding amount. is there. In such a case, as shown in the droplet ejection pattern shown in FIG. 15, a line-basis tone process in which the direction of the line is 45 degrees in the oblique direction (45 degrees in this example) with respect to the sub-scanning direction (paper feed direction). By ejecting the liquid 100, the visibility of uneven stripes in both directions can be effectively reduced.

  Further, although the visibility of the stripes is reduced by using blurring of dots 100B in the area where the line-basis processing liquid 110 is not ejected and droplet ejection interference, bleeding and disturbance of the edge portion of the image are conspicuous on the contrary. It may become like this. In such a case, it is preferable that the treatment liquid 110 is not only ejected in a single line as shown in the treatment liquid ejection arrangement data shown in FIG. More preferably, the treatment liquid 110 is ejected onto the edge portion of the substrate. As a result, it is possible to prevent bleeding and disturbance of the edge portion of the image.

[Specific examples of treatment liquid and ink]
In the present embodiment, for example, the following aqueous solution can be used as the treatment liquid.

(Processing liquid)
・ Daiichi Kogyo Seiyaku Co., Ltd. Charol DC-902P 1-20% by weight
・ Nonionic surfactant as a surface active agent: Olfin E1010 from Nissin Chemical Industry Co., Ltd. 0.05 to 0.1% by weight
In addition, in the case of cationic surfactants, Sanyo Chemical Co., Ltd. Cationic G50 0.1 to 0.2 wt%
An aqueous solution containing at least the above, and in addition, 0-30% by weight of glycerin as a high boiling point solvent
・ As a pH adjuster, triethanolamine 0 to 10% by weight
May be included.

  On the other hand, as an ink containing a color material, for example, the following aqueous solution can be used.

(ink)
An anionic dye compound,
For example, 1 to 30% by weight having a structure represented by the following general formula

・表面活性剤として、
日信化学工業株式会社製 オルフィンＥ１０１０ ０．１〜１０重量％
・ポリスチレンスルホン酸ナトリウム ０〜２０重量％
・高沸点溶媒として、グリセリン ０〜３０重量％
・ｐＨ調整剤として、トリエタノールアミン ０〜１０重量％
を含んでもよい。

・ As a surfactant
Nissin Chemical Industry Co., Ltd. Olfin E1010 0.1 to 10% by weight
-Sodium polystyrene sulfonate 0-20% by weight
・ Glycerin 0-30% by weight as high boiling point solvent
・ As a pH adjuster, triethanolamine 0 to 10% by weight
May be included.

  The inkjet recording apparatus 10 configured as described above deposits ink based on image data onto a recording medium to which a treatment liquid is attached, insolubilizes the ink to generate a color material aggregate, and the color material aggregation. The physical properties of the processing liquid and the ink are determined so that the contact angle of the processing liquid with respect to the recording medium, the contact angle of the ink, and the contact angle of the mixed liquid of the ink and the processing liquid are 60 degrees or more. The treatment liquid and the ink can be surely reacted on the recording medium, and a preferable dot having a desired density is formed. In addition, by reliably reacting the treatment liquid and the ink, it is possible to suppress the penetration of the mixed liquid of the treatment liquid and the ink into the recording medium, and dots without bleeding are formed on the recording medium.

  Furthermore, since the ink physical properties are determined so that the contact angle of the ink with respect to the recording medium is 60 degrees or more, even when the ink lands on a portion where the treatment liquid is not attached, the ink penetration is suppressed. In other words, it is possible to suppress bleeding to a certain amount in dots formed by ink alone.

  As described above, in the present invention, the treatment liquid, not ink, is ejected in all directions, and the ink (dots) of the portion where the treatment liquid is not ejected is used for bleeding or droplet ejection interference. The visibility of the stripe unevenness can be reduced. Thereby, even when a plurality of color inks are used, inter-color moire does not occur, and the image quality is improved.

  In particular, the treatment liquid is preferably formed such that the direction substantially perpendicular to the direction of the stripe unevenness is the line direction, and the effect of suppressing stripe unevenness can be improved. In addition, by varying the line width, line interval, line interval, etc. of the line-basis processing liquid according to the characteristics of the recording medium and the intensity of the stripe unevenness, the stripe unevenness can be effectively suppressed and optimized. Image quality can be achieved.

  Further, in the present invention, it is only necessary to drop the processing liquid with the basic line as described above without specifying an abnormal nozzle, so that the apparatus is realized at a low cost without complicating the apparatus and reducing the processing speed. can do.

  In this embodiment, the mode in which the processing liquid is ejected by the processing liquid droplet ejection head 12P is exemplified, but the present invention is not limited to this, and the processing liquid is allowed to adhere onto the recording medium. Any method can be used. For example, various methods such as a transfer method and a printing method can be used.

  The image forming method and the image forming apparatus of the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.

1 is an overall schematic diagram of an ink jet recording apparatus. It is a principal part top view of the printing part periphery of an inkjet recording device. It is the top view which showed nozzle arrangement | positioning of the head for process liquid droplet ejection. FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. It is a principal block diagram showing the system configuration of the ink jet recording apparatus. FIG. 6 is a block diagram illustrating details of a print control unit in FIG. 5. It is explanatory drawing showing an example of the hitting pattern of the conventional process liquid. It is a droplet ejection pattern of the process liquid in this invention, and is explanatory drawing showing a mode when permeation paper is used. It is explanatory drawing showing a mode when the non-penetrating paper (or weakly permeable paper) is used with respect to the droplet ejection pattern of FIG. This is a droplet ejection pattern when the spread of the penetrating paper is severe. This is another droplet ejection pattern in the case where the bleeding of the penetrating paper is severe. It is an explanatory view showing the case where it is a conventional droplet ejection pattern of processing liquid and the stripes are intense. This is a droplet ejection pattern when the stripes are intense. Further, this is a droplet ejection pattern in the case where the unevenness is intense. This is a droplet ejection pattern in the case where stripes are visually recognized in a plurality of directions. This is a droplet ejection pattern for preventing bleeding and disturbance of an edge portion of an image.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12P ... Print head (treatment liquid droplet ejection head), 12K, 12M, 12C, 12Y ... Print head (ink droplet ejection head), 16 ... Recording paper, 51 ... Nozzle, 58 ... Heating element , 80... Print control unit, 84... Ink ejection head driver, 85... Treatment liquid ejection head driver, 90... Treatment liquid ejection method determination unit, 92 .. treatment liquid ejection arrangement data setting unit, 94. Analysis unit 96 ... Ink droplet arrangement data setting unit 98 ... External information input unit 100, 100A, 100B ... Dot, 110 ... Treatment liquid

Claims (12)

An image forming method in which an image reproducibility improving liquid is attached to a recording medium and at least one type of ink is ejected to form an image on the recording medium.
An image forming method, wherein the image reproducibility improving liquid is adhered to a line.   The image forming method according to claim 1, wherein a line direction of the image reproducibility improving liquid is a direction substantially perpendicular to a direction in which unevenness occurs.   The image forming method according to claim 1, wherein a line direction of the image reproducibility improving liquid is an oblique direction with respect to a direction in which unevenness occurs.   The image forming method according to claim 1, wherein the number of lines of the image reproducibility improving liquid is 250 lpi or more.   The line width, line frequency and line intensity of the image reproducibility improving liquid are changed according to the characteristics of the recording medium, according to any one of claims 1 to 4. The image forming method described in 1.   6. The apparatus according to claim 1, wherein at least one of a line width, a line frequency, and a line intensity of the image reproducibility improving liquid is changed according to the intensity of the stripe unevenness. Image forming method.   The image forming method according to claim 1, wherein the image reproducibility improving liquid is further adhered to a portion corresponding to an edge portion of the image. The recording medium is a medium having a low permeability so that ink does not penetrate or landing interference occurs.
The number of dots where the center of dots formed by ink landing on the recording medium does not land on the image reproducibility improving liquid is 1 / The image forming method according to claim 1, wherein the image forming method is 3 or less.   9. The image forming method according to claim 1, wherein the at least one kind of ink is ejected so as to have a blue noise characteristic. A first ejection head that ejects ink onto a recording medium;
A second ejection head that ejects an image reproducibility improving liquid onto the recording medium;
First control means for controlling droplet ejection of the ink by the first ejection head;
Second control means for controlling droplet ejection of the image reproducibility improving liquid by the second ejection head;
Conveying means for relatively conveying the recording medium and the first and second ejection heads;
The first ejection head and the second ejection head are line heads in which a plurality of nozzles are arranged over a length corresponding to the entire width of the recording medium,
The image forming apparatus according to claim 2, wherein the second control unit controls the second ejection head so that the image reproducibility improving liquid is ejected in line.   The second control means controls the second ejection head so as to eject a line-based image reproducibility improving liquid in which the direction substantially perpendicular to the relative conveyance direction of the recording medium is a line direction. The image forming apparatus according to claim 10. The second control means controls the second ejection head so as to eject a line-basis image reproducibility improving liquid in which the direction inclined obliquely with respect to the relative conveyance direction of the recording medium is a line direction. The image forming apparatus according to claim 10, wherein the image forming apparatus is controlled.

Images