JP4845651B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming equipment, especially the ink and the treatment liquid and detecting the discharge state of suitable imaging techniques and liquid jet recording apparatus for forming a high-quality image on a recording medium by using a comprising a coloring material Related to technology.

  In the ink-jet printing technology field, a method of using an ink containing a color material and a treatment liquid in combination in order to form a high-quality image is known. In this method using the treatment liquid, the treatment liquid and the ink must react reliably on the recording medium, so that the treatment liquid is not ejected or the adhesion position (landing position) of the ink and the treatment liquid is shifted. If it gets loose, the effect cannot be obtained sufficiently. With respect to such a problem, a technique in terms of detecting discharge of a transparent liquid has been proposed (Patent Documents 1 to 3).

  Patent Document 1 discloses a technique that uses a discharge inspection film as means for inspecting the discharge state of a colorless and transparent treatment liquid. Patent Document 2 discloses a technique for recording a test pattern by mixing with another type of liquid as a technique for confirming the discharge of a nozzle that discharges a liquid that is difficult to visually recognize. Patent Document 3 discloses a technique for detecting from a difference in the degree of light scattering caused by the fine surface state of a recording medium as a technique for detecting a missing dot of a liquid that is difficult to visually recognize.

On the other hand, Patent Document 4 discloses a technique related to ink having spectral absorption in the infrared region, and discloses a drying method characterized by heating with infrared rays after drawing. Further, Patent Document 5 discloses a technique for providing an invisible pattern using an infrared absorbing material from the viewpoint of design restrictions on printed matter or prevention of counterfeiting.
JP 2000-168106 A JP 2004-276314 A JP 2004-314362 A JP 2001-226618 A JP 2002-146254 A

  In Patent Document 1, as a technique for detecting the discharge state of the transparent processing liquid, a method using a discharge inspection film whose color changes depending on the processing liquid is disclosed, but a special medium (discharge inspection film) is used for inspection. Necessary. In addition, the method disclosed in Patent Document 2 has a problem that detection is not stable depending on the state of mixing different liquids. The method disclosed in Patent Document 3 requires a detector having high-precision optical path adjustment and high-sensitivity detection capability.

  Japanese Patent Application Laid-Open No. H10-228707 discloses a technique for containing an infrared absorbing material and quickly drying ink containing a color material, but does not disclose a technique relating to a two-component reaction system transparent processing liquid. In Patent Document 5, it is disclosed to draw an invisible pattern by including an infrared absorbing material in the ink. However, simply providing an invisible pattern using a specific material has been a problem. There is no disclosure of the idea of application to drying and drying acceleration.

The present invention has been made in view of such circumstances, and provides a technique for detecting the discharge status of a nozzle that discharges a transparent liquid by a simple method, and is capable of reliable 2 inks including a transparent processing liquid and a coloring material. and to provide an image forming equipment which can realize the liquid reaction.

In order to achieve the above object, an image forming apparatus according to the invention of claim 1 includes an ink discharge means for discharging an ink containing a color material, and a colorless and transparent having an action of insolubilizing or aggregating the color material of the ink. A liquid or a colorless and transparent liquid that prevents diffusion of the color material of the ink, and a processing liquid discharge means that discharges a processing liquid containing an infrared absorbing material, and an infrared ray on the processing liquid discharged from the processing liquid discharge means Infrared irradiating means for irradiating, a processing liquid detecting means including a photoelectric conversion element having sensitivity in the infrared region, and the number of discharge failure nozzles of the processing liquid discharging means based on a detection signal obtained from the photoelectric conversion element; The ink droplet ejection arrangement is determined so as to reduce the usage rate of the nozzle of the ink discharge means corresponding to the position of the discharge failure nozzle of the treatment liquid discharge means and the treatment liquid discharge means for determining the position. Characterized by comprising an image processing means.

The colorless and transparent treatment liquid is difficult to visually recognize the droplet ejection result as it is, but in the present invention, the treatment liquid contains an infrared absorbing material, and absorbs infrared rays irradiated from the infrared irradiation means, whereby infrared rays are absorbed. Identification can be made by a photoelectric conversion element having sensitivity in a region. Thereby, the discharge state (for example, non-discharge, discharge direction abnormality, discharge liquid amount abnormality, etc.) of the processing liquid discharge means can be easily detected.
When there is a discharge failure nozzle (a nozzle that cannot be discharged), the treatment liquid does not adhere to the position where droplets should be ejected by the nozzle, and the drawing result of the treatment liquid varies depending on the presence or absence of the discharge failure nozzle. Since the detection signal obtained from the photoelectric conversion element is a signal corresponding to the drawing state, the position and number of undischarge nozzles can be grasped by processing this detection signal.
According to the present invention, the ink ejection position (dot arrangement) of ink dots is corrected so as to reduce the amount of ink ejected to a position where the processing liquid is insufficient, by specifying the non-discharge position of the processing liquid. Dropping is controlled. As a result, it is possible to suppress image quality deterioration due to non-ejection of the processing liquid and realize high-quality image formation.
For example, based on the position information of the discharge failure nozzle of the processing liquid discharge means, the image data is corrected from the viewpoint of suppressing the occurrence of uneven stripes corresponding to the discharge failure position, and the halftone process ( A halftoning process is performed to obtain droplet placement data. Further, by controlling the droplet ejection by the ink ejection means in accordance with the droplet ejection arrangement data, it is possible to form a good image.

  A second aspect of the present invention is an aspect of the image forming apparatus according to the first aspect, wherein the processing liquid is drawn so as to draw a predetermined test pattern on a recording medium or on an intermediate transfer member by droplet ejection of the processing liquid. Test pattern droplet ejection control means for controlling the ejection operation of the ejection means is provided, and the photoelectric conversion element detects a drawing state of the predetermined test pattern.

  When grasping the discharge state of the processing liquid, a predetermined test pattern is drawn, and the drawing state is detected by a photoelectric conversion element, so that detection accuracy can be improved as compared with detection in a practical image. it can.

  A third aspect of the present invention is an aspect of the image forming apparatus according to the first or second aspect, wherein the processing liquid ejected from the processing liquid ejecting unit and the ink ejected from the ink ejecting unit are attached. The image forming apparatus includes a drying accelerating unit that accelerates drying of the recording medium by irradiating the medium with infrared rays.

  According to the third aspect of the present invention, the heat absorption efficiency is increased by the infrared absorption function of the treatment liquid, and the drying of the recording medium after droplet ejection can be promoted. Printing can be realized.

The invention according to a fourth aspect is an aspect of the image forming apparatus according to any one of the first to third aspects, wherein the number of undischarge nozzles of the processing liquid discharge unit exceeds a first threshold value. And a first recovery control means for performing control to perform a maintenance operation for recovering the discharge performance of the processing liquid discharge means.

According to the aspect of claim 4 , since the maintenance operation is performed when the number of discharge failure nozzles exceeds the allowable value, a reliable two-liquid reaction can be realized. In addition, the number of maintenance operations can be minimized, and print productivity can be improved.

  Examples of the “maintenance operation” include preliminary ejection, nozzle suction, nozzle surface wiping, or an appropriate combination thereof.

The invention according to claim 5 is an aspect of the image forming apparatus according to claim 4 , and includes ink detection means including a photoelectric conversion element having sensitivity in the visible region, and detection obtained from the photoelectric conversion element of the ink detection means. An ink discharge failure determination unit that determines the number and position of discharge failure nozzles of the ink discharge unit based on a signal; and a second threshold value in which the number of discharge failure nozzles of the ink discharge unit is smaller than the first threshold value. And a second recovery control means for performing a control for performing a maintenance operation for recovering the ejection performance of the ink ejection means.

According to the fifth aspect of the present invention, the means for detecting the discharge state of the ink discharge means (ink detection means) is provided in the same manner as the means for detecting the discharge state of the treatment liquid discharge means. According to the number of discharge nozzles, the maintenance operation of the ink discharge means is performed. Compared with colorless and transparent processing liquid, colored ink has high visibility and has a large effect on image quality. Therefore, the allowable number of undischarge nozzles in the ink discharge means is larger than the allowable number of undischarge nozzles in the treatment liquid discharge means. Is also small. From this point of view, the threshold value (second threshold value) for determining whether or not the maintenance operation (recovery process) for the ink discharge unit needs to be performed determines whether or not the maintenance operation (recovery process) for the processing liquid discharge unit needs to be performed. It is set to a value smaller than the threshold (first threshold). In other words, the first threshold value is set to a value larger than the second threshold value.

A sixth aspect of the present invention is an aspect of the image forming apparatus according to the fourth or fifth aspect, wherein the medium type specifying means for specifying the type of the recording medium, and the first threshold value according to the type of the recording medium. And a threshold value setting means for changing and setting.

The invention according to claim 7 is an aspect of the image forming apparatus according to claim 5 , wherein the medium type specifying means for specifying the type of the recording medium, and the first threshold value according to the type of the recording medium. And a threshold value setting means for changing and setting the second threshold value.

Since the liquid permeability and the behavior of the landing droplet on the recording medium differ depending on conditions such as the material, thickness, and dielectric constant of the recording medium, the recording medium type specifying means is used as shown in claims 6 and 7. It is preferable to grasp the type of the recording medium and variably set the first threshold value and the second threshold value according to the medium type. This makes it possible to form an image under optimum conditions corresponding to the recording medium.

  For example, when using a medium with high penetrability (penetrating medium), the allowable number of discharge failure nozzles is set large, and print productivity is emphasized. On the other hand, when a medium with low permeability (non-penetrating medium or low-penetrating medium) is used, the allowable number of undischarge nozzles is set small with an emphasis on image quality.

  The recording medium type specifying means includes, for example, means for measuring the reflectance of the recording medium, means for reading the type of recording medium used from the ID of the supply magazine, and the like. The recording medium type specifying means is not limited to a form in which information is automatically acquired by a sensor, an information reading means, or the like, but a user inputs information such as the paper type of the recording medium by a predetermined input device (user interface) or the like. A configuration is also possible in which the input is performed by operating.

As the processing liquid discharge means in the image forming apparatus according to the first to seventh aspects, for example, means for discharging the processing liquid into droplets using an ink jet type discharge head is suitably used. As the ink discharge means, an ink jet type liquid discharge head that discharges ink based on drawing image information (print data) is preferably used.

  An ink jet recording apparatus as an aspect of the image forming apparatus of the present invention includes a nozzle that discharges ink droplets (or processing liquid) for forming dots and a pressure generating unit that generates discharge pressure (such as a piezoelectric element or a heating element). A liquid discharge head (corresponding to “ink discharge means” or “processing liquid discharge means”) having a liquid drop discharge element array in which a plurality of liquid drop discharge elements are arranged, and droplet ejection arrangement data generated from image data And droplet ejection control means for controlling ejection of droplets from the liquid ejection head, and forms an image on the recording medium or on the intermediate transfer member by the droplets ejected from the nozzle.

  As a configuration example of the liquid discharge head used in the treatment liquid discharge means and the ink discharge means, a full-line head in which a plurality of nozzles are arranged over a length corresponding to the entire width of the recording medium or the intermediate transfer member can be used. . In this case, a plurality of relatively short recording head modules having nozzle rows that do not have a length corresponding to the entire width of the recording medium or the intermediate transfer member are combined, and these are combined to correspond to the entire width of the recording medium. There exists an aspect which comprises the nozzle row of length.

  A full-line type head is usually arranged along a direction perpendicular to the relative feeding direction (relative conveyance direction) of the recording medium, but has a certain angle with respect to the direction perpendicular to the conveyance direction. There may be a mode in which the recording head is arranged along the oblique direction.

  The “recording medium” is a medium to which liquid ejected from the liquid ejection head adheres, and receives an image recording by the action of the liquid ejection head. That is, the “recording medium” can be called a printing medium, an image forming medium, a recording medium, an image receiving medium, an ejected medium, and the like, a continuous sheet, a cut sheet, a seal sheet, a resin sheet such as an OHP sheet, It includes various media, regardless of the material and shape, such as a printed board on which a film, cloth, wiring pattern or the like is formed.

  The “conveying means” is an aspect in which the recording medium or the intermediate transfer body is conveyed to the stopped (fixed) liquid ejection head, an aspect in which the liquid ejection head is moved relative to the stopped recording medium or intermediate transfer body, or Any of the modes in which both the liquid discharge head and the recording medium or the intermediate transfer member are moved is included.

  When forming a color image with an inkjet head, a head may be arranged for each color and type of ink (recording liquid), or multiple colors of ink and processing liquid can be ejected from one head. It is good also as a simple structure.

  In addition, the present invention is not limited to the full-line type head described above, but a shuttle scan type recording head (a recording head that ejects droplets while reciprocating in a direction substantially perpendicular to the conveyance direction of the recording medium or intermediate transfer member) Is also applicable.

According to the present invention, it is possible to detect the discharge state of a colorless and transparent processing liquid by placing an infrared absorbing material in the processing liquid. Moreover, since the heat absorption efficiency is increased by this infrared absorbing material, the energy required for drying can be reduced as compared with the prior art.
According to the present invention, it is possible to suppress deterioration in image quality due to non-ejection of the processing liquid and to realize high-quality image formation.

  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 showing an embodiment of an image forming apparatus according to the present invention. As shown in the figure, the ink jet recording apparatus 10 is a two-component image forming apparatus that forms an image using processing liquid and ink, and discharges the first processing liquid (pre-processing liquid). Treatment liquid head 11 (corresponding to “treatment liquid discharge means”) and black (K), magenta (M), cyan (C), and yellow (Y) inks (second liquid). A plurality of ink ejection heads (corresponding to “ink ejection means”, hereinafter referred to as “ink heads”) 12K, 12M, 12C, and 12Y, and processing liquid supplied to the processing liquid head 11 are provided. A processing liquid storage / loading unit 13 for storing the ink, an ink storage / loading unit 14 for storing the color ink supplied to the ink heads 12K, 12M, 12C, and 12Y, and a medium for supplying the recording medium 16 Supply unit 18 and recording medium 16 A decurling unit 20 that removes curl, a belt conveyance unit 22 that conveys the recording medium 16 while maintaining the flatness of the recording medium 16, a print detection unit 24 that reads a print result, and a print detection area on the recording medium 16 A light source for detection 26 (corresponding to “infrared irradiating means”) and a heating / drying section 28 as means for accelerating drying after printing.

  The processing liquid storage / loading unit 13 includes a processing liquid tank that stores the processing liquid, and the processing liquid tank is communicated with the processing liquid head 11 via a required pipe line. The processing liquid storage / loading unit 13 includes notifying means (display means, warning sound generating means) for notifying when the remaining amount of the processing liquid is low, and for preventing erroneous loading between liquid types. It has a mechanism.

  The ink storage / loading unit 14 includes ink tanks that store inks of colors corresponding to the ink heads 12K, 12M, 12C, and 12Y, and the tanks 12K, 12M, and 12C are connected to the ink tanks via necessary pipe lines. , 12Y. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  Although the composition example of the treatment liquid and ink used in the present embodiment will be described in detail later, the treatment liquid of this example is a colorless and transparent liquid and contains an infrared absorber. When the ink and the treatment liquid are mixed, the color material in the ink is insolubilized or aggregated by the reaction of the two liquids, or the diffusion of the color material is suppressed by the color material diffusion inhibitor in the treatment liquid. Examples of “insolubilization or aggregation” include, for example, a phenomenon in which a color material is precipitated and precipitated from a solvent, a phenomenon in which a liquid in which the color material is dissolved changes (solidifies), and a liquid in which the color material is in a dispersed state. A phenomenon in which the dispersion becomes unstable and the color material aggregates, and a phenomenon in which the liquid thickens and hardens are included.

  The reaction rate and physical properties (surface tension, viscosity, etc.) of each liquid can be adjusted by adjusting the composition of each ink and the treatment liquid and the concentration of a substance that contributes to the reaction. Alternatively, ink fixability (curing speed, fixing speed, etc.) can be realized.

  In FIG. 1, a roll paper (continuous paper) magazine 19 is shown as an example of the media 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.

  The recording medium 16 delivered from the media supply unit 18 retains curl due to having been loaded in the magazine 19. In order to remove the curl, heat is applied to the recording medium 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine 19 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.

  In the case of an apparatus configuration using roll paper, as shown in FIG. 1, a cutter 38 is provided, and the roll paper is cut into a desired size by the cutter 38. The cutter 38 includes a fixed blade 38A having a length equal to or greater than the conveyance path width of the recording medium 16, and a round blade 38B that moves along the fixed blade 38A. The fixed blade 38A is provided on the back side of the print. The round blade 38B is arranged on the print surface side with the conveyance path interposed therebetween. Note that the cutter 38 is not necessary when cut paper is used.

  After the decurling process, the cut recording medium 16 is sent to the belt conveyance unit 22. The belt conveyance unit 22 has a structure in which an endless belt 43 is wound between rollers 41 and 42, and at least the nozzle surfaces of the heads 11, 12K, 12M, 12C, and 12Y and the sensor surface of the print detection unit 24. The part which opposes is comprised so that the horizontal surface (flat surface) may be made.

  The belt 43 has a width that is greater than the width of the recording medium 16, and a plurality of suction holes (not shown) are formed on the belt surface. A suction chamber (not shown) is provided on the inner side of the belt 43 spanned between the rollers 41 and 42, and the recording medium 16 is placed on the belt 43 by sucking the suction chamber with a fan to obtain a negative pressure. Is adsorbed and retained. In place of the suction adsorption method, an electrostatic adsorption method may be adopted.

  The power of the motor (reference numeral 138 in FIG. 9) is transmitted to at least one of the rollers 41 and 42 around which the belt 43 is wound, so that the belt 43 is driven in the counterclockwise direction in FIG. The recording medium 16 held in is conveyed from the right to the left in FIG.

  Although it is possible to use a roller / nip conveyance mechanism instead of the belt conveyance unit, if the roller / nip conveyance is performed in the printing area, the roller is brought into contact with the printing surface of the sheet immediately after printing, so that the image tends to blur. There is. Therefore, as in this example, suction belt conveyance that does not bring the image surface into contact with each other in the print region is preferable.

The treatment liquid head 11 and the ink heads 12K, 12M, 12C, and 12Y have a length corresponding to the maximum paper width of the recording medium 16 targeted by the ink jet recording apparatus 10, and the nozzle surface has a maximum size. The recording medium 16 is a full-line type head in which a plurality of nozzles (ejection ports) are arranged over a length exceeding at least one side (full width Wm of the drawable range) (see FIG. 2).

  As shown in FIG. 1, the ink heads 12K, 12M, 12C, and 12Y are black (K), magenta (M), cyan (C), yellow (Y from the upstream side along the feeding direction of the recording medium 16. ) And the processing liquid head 11 is arranged further upstream of the ink head 12K. Each of the heads 11, 12K, 12M, 12C, and 12Y is fixedly installed so as to extend along a direction substantially orthogonal to the conveyance direction of the recording medium 16.

  With such a head arrangement, the treatment liquid is attached to the recording surface (printed surface) of the recording medium 16 by the treatment liquid head 11 before ink droplets of the respective colors are ejected by the ink heads 12K, 12M, 12C, and 12Y. Can do. In addition, while the recording medium 16 is conveyed at a constant speed by the belt conveyance unit 22, inks of different colors are ejected from the ink heads 12K, 12M, 12C, and 12Y toward the recording medium 16 to which the processing liquid is attached. Thus, a color image can be formed on the recording medium 16.

  As described above, according to the configuration in which the full-line heads 12K, 12M, 12C, and 12Y having nozzle rows covering the entire paper width are provided for each color, the recording medium 16 is moved to the head 12K in the paper feeding direction (sub-scanning direction). , 12M, 12C, and 12Y, the image can be recorded on the entire surface of the recording medium 16 by performing the operation of moving relative to the recording medium 16 only once (that is, by one sub-scanning). Such a single-pass inkjet recording apparatus 10 can perform high-speed printing as compared with a shuttle scan system that performs drawing while reciprocating the recording head in the main scanning direction, and can improve print productivity.

  In this example, the configuration of CMYK 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, dark ink, special color ink, etc. are used as necessary. May be added. For example, it is possible to add a head for ejecting light-colored ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited.

  The detection light source 26 arranged at the subsequent stage of the final color ink head 12Y has a length corresponding to the maximum paper width of the recording medium 16, like each of the heads 11, 12K, 12M, 12C, and 12Y. The recording medium 16 is installed so as to extend in a direction substantially orthogonal to the conveyance direction of the recording medium 16. As the light source 26 for detection, a light source (for example, a halogen lamp) having a light emission wavelength range including a visible light region and an infrared region is used. In addition, the aspect which comprises the light source for a detection combining the some light source from which light emission wavelength range differs like the combination of infrared LED and visible LED, for example is also possible.

  The print detection unit 24 includes an image sensor for imaging the droplet ejection results from the treatment liquid head 11 and the ink heads 12K, 12M, 12C, and 12Y, and nozzles are clogged from the droplet ejection image read by the image sensor. It functions as a means for checking other ejection defects.

The print detection unit 24 of this example is composed of a line sensor having a light receiving element array wider than at least the droplet discharge width (image recording width in the main scanning direction) by each of the heads 11, 12K, 12M, 12C, and 12Y. The 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, A B sensor array provided with a blue (B) color filter, and a CCD sensor in which photoelectric conversion elements (pixels) having sensitivity in an infrared (Ir) region are arranged in a line. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used. Further, the method of the image sensor is not limited to the CCD, and other image sensors such as CMOS can be used.

  The print detection unit 24 reads the test pattern or practical image of the treatment liquid ejected by the treatment liquid head 11 and the test pattern or practical image printed by the ink heads 12K, 12M, 12C, and 12Y for each color, The ejection of each head is detected. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  The heat drying unit 28 is means for promoting drying of the recording medium 16 by infrared irradiation. As a specific example, a halogen lamp, a ceramic heater, a carbon dioxide laser, an electric resistor such as tungsten, or the like can be used. The heating and drying unit 28 also has a length corresponding to the maximum paper width of the recording medium 16 and is installed so as to extend in a direction substantially perpendicular to the conveyance direction of the recording medium 16. A mode in which the detection light source 26 is also used as an infrared source of the heating and drying unit 28 is also possible.

  Thus, the recording medium 16 (generated printed matter) that has passed through the heating and drying unit 28 is discharged from the paper discharge unit via a toothed driven roller and a nip roller (not shown). Although not shown in FIG. 1, the paper discharge unit is provided with a sorter for collecting images according to orders.

[Head structure]
Next, the structure of the ink heads 12K, 12M, 12C, and 12Y will be described. Since the structure of each head provided for each ink color is common, the head for ink will be represented by reference numeral 50 in the following.

  FIG. 2A is a plan perspective view showing an example of the structure of the ink head 50, and FIG. 2B is an enlarged view of a part thereof. In order to increase the dot pitch printed on the recording medium 16, it is necessary to increase the nozzle pitch in the ink head 50. As shown in FIGS. 2 (a) and 2 (b), the ink head 50 of this example is an ink chamber unit comprising a nozzle 51 as an ink droplet ejection port, a pressure chamber 52 corresponding to each nozzle 51, and the like. It has a structure in which 53 (droplet discharge elements as recording element units corresponding to one nozzle) are arranged in a staggered matrix (two-dimensionally), and thereby the head longitudinal direction (perpendicular to the paper feed direction) The density of the substantial nozzle interval (projection nozzle pitch) projected so as to be aligned along the (direction) is achieved.

  A configuration in which nozzle arrays having a length corresponding to the full width Wm of the recording medium 16 are configured in a direction (arrow M direction; main scanning direction) substantially orthogonal to the feeding direction (arrow S direction; sub-scanning direction) of the recording medium 16. Is not limited to this example. For example, instead of the configuration of FIG. 2 (a), as shown in FIG. 3, a short head unit 50 'in which a plurality of nozzles 51 are two-dimensionally arranged is arranged in a staggered manner and connected to form a recording medium. You may comprise the line head which has a nozzle row of the length corresponding to the full width of 16.

  The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape (see FIGS. 2 (a) and 2 (b)), and is connected to the nozzle 51 at both corners on a diagonal line. An outlet and an inlet (supply port) 54 for supply ink are provided. The shape of the pressure chamber 52 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon and other polygons, a circle, and an ellipse.

  FIG. 4 is a cross-sectional view (a cross-sectional view taken along line 4-4 in FIG. 2A) showing a three-dimensional configuration of a droplet discharge element for one channel (an ink chamber unit corresponding to one nozzle 51). . As shown in FIG. 4, each pressure chamber 52 communicates with a common flow channel 55 through a supply port 54. The common channel 55 communicates with an ink tank (not shown in FIG. 4, not shown in FIG. 6 and indicated by reference numeral 60) serving as an ink supply source, and the ink supplied from the ink tank 60 passes through the common channel 55 in FIG. Then, it is distributed and supplied to each pressure chamber 52.

  An actuator 58 having an individual electrode 57 is joined to a pressure plate (vibrating plate that also serves as a common electrode) 56 constituting a part of the pressure chamber 52 (the top surface in FIG. 4). By applying a drive voltage between the individual electrode 57 and the common electrode, the actuator 58 is deformed and the volume of the pressure chamber 52 is changed, and ink is ejected from the nozzle 51 due to the pressure change accompanying this. The actuator 58 is preferably a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate. After the ink is ejected, when the displacement of the actuator 58 returns to its original state, new ink is refilled into the pressure chamber 52 from the common channel 55 through the supply port 54.

  As shown in FIG. 5, the ink chamber unit 53 having such a structure is latticed in a fixed arrangement pattern along a row direction along the main scanning direction and an oblique column direction having a constant angle θ not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in the shape.

  That is, with a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along a certain angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to be aligned in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 51 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, a high-density nozzle array can be realized.

  When driving a nozzle with a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially moved from one side to the other. (3) The nozzles are divided into blocks, and the nozzles are sequentially driven from one side to the other for each block, etc., and one line (1 in the width direction of the paper (direction perpendicular to the paper conveyance direction)) Driving a nozzle that prints a line of dots in a row or a line consisting of dots in a plurality of rows is defined as main scanning.

  In particular, when driving the nozzles 51 arranged in a matrix as shown in FIG. 5, the main scanning as described in (3) above is preferable. That is, nozzles 51-11, 51-12, 51-13, 51-14, 51-15, 51-16 are made into one block (other nozzles 51-21,..., 51-26 are made into one block, The nozzles 51-31,..., 51-36 as one block,...), And the nozzles 51-11, 51-12,. One line is printed in 16 width directions.

  On the other hand, by relatively moving the above-mentioned full line head and the paper, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) formed by the above-described main scanning is repeatedly performed. Defined as sub-scan.

  The direction indicated by one line (or the longitudinal direction of the belt-like region) recorded by the main scanning is referred to as a main scanning direction, and the direction in which the sub scanning is performed is referred to as a sub scanning direction. In other words, in the present embodiment, the conveyance direction of the recording medium 16 is the sub-scanning direction, and the direction orthogonal to it is the main scanning direction.

  In implementing the present invention, the nozzle arrangement structure is not limited to the illustrated example. In the present embodiment, a method of ejecting ink droplets by deformation of an actuator 58 typified by a piezo element (piezoelectric element) is adopted. However, in the practice of the present invention, the method of ejecting ink is not particularly limited. Instead of the piezo jet method, various methods such as a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure can be applied.

  The structure of the treatment liquid head 11 is substantially the same as that of the ink head 50 described above, although not shown. However, since the treatment liquid has only to be deposited substantially uniformly (substantially uniformly) on the area where ink is ejected on the recording medium 16, formation of high-density dots is not required as compared with ink. Therefore, the treatment liquid head 11 can be configured to have a smaller number of nozzles (lower nozzle density) than the ink head 50. Further, a configuration in which the nozzle diameter of the treatment liquid head 11 is larger than the nozzle diameter of the ink head 50 is also possible.

[Configuration of ink supply system]
FIG. 6 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 10. The ink tank 60 is a base tank that supplies ink to the ink head 50 and is installed in the ink storage / loading unit 14 described with reference to FIG. That is, the ink tank 60 in FIG. 6 is equivalent to the ink storage / loading unit 14 in FIG. In the form of the ink tank 60, there are a system that replenishes ink from a replenishing port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink is low. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type.

  As shown in FIG. 6, a filter 62 is provided between the ink tank 60 and the ink head 50 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter. Although not shown in FIG. 6, a configuration in which a sub tank is provided in the vicinity of the ink head 50 or integrally with the ink head 50 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 10 is provided with a cap 64 as a means for preventing the nozzle 51 from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 66 as a means for cleaning the nozzle surface 50A. . The maintenance unit (recovery means) including the cap 64 and the cleaning blade 66 can be moved relative to the ink head 50 by a moving mechanism (not shown), and can be moved from a predetermined retraction position to a position below the ink head 50 as required. Moved to the maintenance position.

  The cap 64 is displaced up and down relatively with respect to the ink head 50 by an elevator mechanism (not shown). The cap surface 64A is covered with the cap 64 by raising the cap 64 to a predetermined raised position when the power is turned off or during printing standby, and bringing the cap 64 into close contact with the ink head 50.

  The cleaning blade 66 is made of an elastic member such as rubber, and can slide on the nozzle surface 50A (nozzle plate surface) of the ink head 50 by a blade moving mechanism (not shown). When ink droplets or foreign matter adheres to the nozzle plate surface, the nozzle plate surface is wiped by sliding the cleaning blade 66 on the nozzle plate.

  During printing or standby, when a specific nozzle is used less frequently and the ink viscosity in the vicinity of the nozzle increases, preliminary ejection is performed toward the cap 64 (also used as an ink receiver) to discharge the deteriorated ink. .

  If the ink head 50 is not ejected for a certain period of time, the ink solvent near the nozzles evaporates and the viscosity of the ink near the nozzles increases, and the nozzles 51 even when the ejection driving actuator 58 operates. Ink can no longer be discharged. Therefore, before this state is reached (within the range of viscosity at which ink can be discharged by the operation of the actuator 58), the actuator 58 is operated toward the ink receiver to discharge the ink in the vicinity of the nozzle whose viscosity has increased. "Preliminary discharge" is performed. In addition, after the dirt on the surface of the nozzle plate is cleaned by a wiper such as a cleaning blade 66 provided as a cleaning means for the nozzle surface 50A, the foreign matter is prevented from entering the nozzle 51 by the wiper rubbing operation. Also, preliminary discharge is performed. Note that the preliminary discharge may be referred to as “empty discharge”, “purge”, “spitting”, or the like.

  On the other hand, if bubbles are mixed into the nozzle 51 or the pressure chamber 52 or if the viscosity of the ink in the nozzle 51 rises above a certain level, ink cannot be ejected by the preliminary ejection. In such a case, the cap 64 serving as a suction means is brought into contact with the nozzle surface 50A of the ink head 50, and the ink in the pressure chamber 52 (ink mixed with bubbles or thickened ink) is sucked by the suction pump 67. Ink removed by the suction operation is sent to the collection tank 68. The ink collected in the collection tank 68 may be reused, or may be discarded if it cannot be reused.

  Since the above suction operation is performed on the entire ink in the pressure chamber 52, the amount of ink consumption is large. Therefore, when the increase in viscosity is small, it is preferable to perform preliminary discharge as much as possible. The above suction operation is also performed when the ink is initially loaded into the ink head 50, or at the start of use after a long stop.

  Although not shown, the processing liquid supply system and the processing liquid head cleaning (maintenance) means are substantially the same as the ink supply system and ink head cleaning (maintenance) means described in FIG. .

[Description of ink set]
Next, an ink set (processing liquid and ink) applied to the inkjet recording apparatus 10 according to the present embodiment will be described in detail.

  As the treatment liquid and ink used in this example, the treatment liquid contains water as a solvent, a surfactant, a water-soluble solvent, a cationic polymer, and an infrared absorber, and the ink contains water as a solvent, a coloring material (dye ), A surfactant, and a water-soluble solvent. Further, the ink may further include an anionic polymer. In general, since the coloring material becomes a negative ion (anion) in the solvent (water), the dye itself can be a reactive substance that reacts with the cationic polymer in the processing liquid. In the case of this ink set, the color material of the ink is insolubilized by the reaction between the cationic polymer of the treatment liquid and the color material.

  The infrared absorbent contained in the treatment liquid is preferably one that has little absorption of light in the visible light region and particularly high absorption of light wavelength in the infrared region. Preferably, it is a dye or pigment having an absorption maximum at a wavelength of 750 nm to 1200 nm. For example, as the dye, a commercially available dye and a known dye described in literature (for example, “Dye Handbook” edited by the Society of Synthetic Organic Chemistry, published in 1970) Can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarilium dyes, bililium salts, metal thiolate complexes Is mentioned. In addition, what can be applied as an infrared absorber is not limited to what was illustrated here.

  As examples of the material of the cationic polymer contained in the treatment liquid, polyallylamine, polyaminesulfone, polyvinylamine, chitosan, neutralized products of these acids, and the like can be used.

  Moreover, as a material example of the anionic polymer added to the ink as needed, polyacrylic acid, shellac, styrene-acrylic acid copolymer, styrene-maleic anhydride copolymer, and the like can be used.

  As another example of the ink set, the treatment liquid includes water as a solvent, a surfactant, a water-soluble solvent, a color material flocculant, and an infrared absorber, and the ink includes water as a solvent and a color material. (Pigment), a surfactant, and a water-soluble solvent.

  As the color material flocculant, a pH adjuster or a polyvalent metal salt can be used.

  Examples of materials for the pH adjuster include inorganic acids (hydrochloric acid, sulfuric acid, phosphoric acid, etc.), organic acids (acids containing carboxylic acid, sulfonic acid, etc., more specifically, acetic acid, methanesulfonic acid, etc.) Can be used.

  As the polyvalent metal salt, various polyvalent metal ions, aluminum, calcium, magnesium, iron, zinc, tin and the like can be used.

  As another example of the ink set, the treatment liquid contains a color material diffusion inhibitor, water or oil or monomer as a solvent, and an infrared absorber, and the ink is a color material (pigment or dye) or solvent. Water, oil or monomer.

  In the present embodiment, the color material diffusion preventing agent refers to a substance contained in the treatment liquid for the purpose of preventing the diffusion and bleeding of the ink having the colorant ejected onto the treatment liquid.

  The colorant diffusion inhibitor is at least selected from the group consisting of a polymer having an amino group, a polymer having an onium group, a polymer having a nitrogen-containing heterocycle, a metal compound, and a fluorine-based surfactant. One type can be used.

  By adjusting the composition and concentration of substances that contribute to the reaction of the treatment liquid and ink, the reaction speed and physical properties (surface tension, viscosity, etc.) of each liquid can be adjusted, and the desired reactivity and physical properties can be adjusted. Can be realized.

  The coloring material (coloring agent) used in the present embodiment is not particularly limited, and any known water-soluble dye, oil-soluble dye, and pigment can be used as long as the hue and color density suitable for the intended use of the ink can be achieved. It can be appropriately selected and used.

  The colorant may be used alone or in combination of two or more. Further, different colorants may be used for each liquid, or the same may be used.

[Configuration example of print detection unit]
Next, a detailed configuration example of the print detection unit 24 described in FIG. 1 will be described. An upper view (a) of FIG. 7 is a plan view of the periphery of the print detection unit 24, and a lower view (b) of FIG. 7 is a side view.

  As illustrated, the print detection unit 24 includes an R sensor array 24R, a G sensor array 24G, a B sensor array 24B, and an Ir sensor array 24Ir having high detection sensitivity in each wavelength region of R, G, B, and Ir. It is configured. In this example, the RGB sensor rows 24R, 24G, and 24B correspond to “ink detection means”, and the Ir sensor row 24Ir corresponds to “processing liquid detection means”.

  Light is irradiated to the detection area on the recording medium 16 by the detection light source 26 arranged upstream of the print detection unit 24, and the reflected light is received by each sensor array (24R, 24G, 24B, 24Ir).

  The infrared light contained in the light emitted from the detection light source 26 is absorbed by the infrared absorbent in the processing liquid, whereby the treatment liquid adhesion pattern (arrangement pattern of the processing liquid dots) is detected by the Ir sensor array 24Ir. .

  Further, the adhesion pattern of each color ink (ink dot arrangement pattern) is detected by the RGB sensor array (24R, 24G, 24B). Note that the arrangement sequence of the sensor rows and the location of the detection light source 26 are not limited to the illustrated example. For example, a mode in which the detection light source 26 is arranged on the downstream side of the print detection unit 24 is also possible.

  FIG. 8 is a schematic diagram illustrating a print example of a test pattern (nozzle check pattern) for detecting the discharge state. As shown in the figure, a check pattern 70 is printed on the recording medium 16 by dividing the area for each head. In the same figure, the processing liquid (Pre) nozzle check pattern area 71, black (K) ink nozzle check pattern area 72, magenta (M) ink nozzle check pattern area 73, cyan (from the right) as in the head arrangement order. C) A check pattern is printed so that each area is arranged on the recording medium 16 in the order of the check pattern area 74 of the ink nozzle and the check pattern area 75 of the yellow (Y) ink nozzle.

The check pattern in each of the areas 71 to 74, as shown in the partially enlarged view of FIG. 7, performs a plurality of continuous droplet ejections for one nozzle (for example, the i-th nozzle in the head) and performs the sub-scanning direction. It is assumed that a line segment (referred to as a “check pattern line segment”) 76-i in which dots of a predetermined number of dots are arranged in the (horizontal direction in the drawing) is formed. Further, the main check pattern line segments 76-i, 76- (i + 1),... Are not overlapped between nozzles that eject droplets to pixels adjacent in the main scanning direction (vertical direction in the figure). The droplet ejection timing is shifted between nozzles that deposit droplets on pixels adjacent in the scanning direction (for example, between the i-th nozzle and the (i + 1) -th nozzle). In this way, the check pattern line segments 76-i, 76- (i + 1),... Of adjacent nozzles are shifted from each other in the sub-scanning direction on the recording medium 16 to thereby check pattern line segments corresponding to each nozzle. 76-i and 76- (i + 1) are separated, and reading by the print detection unit 24 becomes easy. As a result, the presence / absence of ejection from each nozzle, the dot size, the dot landing position, and the like can be easily measured.

  For example, if there is a nozzle that cannot be ejected, the check pattern line segment corresponding to the nozzle is not printed. Therefore, the position of the non-discharge nozzle is specified by finding the location where the check pattern line segment is missing (missing location). In addition, the number of discharge failure nozzles can be identified from the number of missing portions of the check pattern line segment.

  Alternatively, if there is a nozzle with an abnormal ejection direction (flying direction), the check pattern line segment corresponding to the nozzle is printed at a position shifted from the original recording position (ideal droplet ejection position). By measuring the amount of deviation of the droplet position, it is possible to determine whether there is an abnormality in the ejection direction. As described above, the print state of the test pattern is read by the print detection unit 24 and the image pickup signal (image signal of the print result) obtained from the print detection unit 24 is analyzed to detect the discharge state of each nozzle. .

  The drawing result of the processing liquid is read by the Ir sensor array 24Ir, and the drawing result of each color ink is grasped from the combination of signals (RGB signals) for each color channel obtained from the RGB sensor arrays 24R, 24G, and 24B.

  In this example, from the viewpoint of easily detecting the drawing state of each head, a check pattern is drawn in a separate area for each head. However, a plurality of different liquids are deposited at the same position on the recording medium. A check pattern is also possible.

[Explanation of control system]
FIG. 9 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 100, a system controller 102, an image memory 104, a ROM 106, a media type detection unit 108, a motor driver 116, a heater driver 118, a discharge detection unit 120, a print control unit 130, an image buffer memory 132, and a process. A liquid control unit 133, a head driver 134, and the like are provided.

  The communication interface 100 is an interface unit (image input unit) that functions as an image input unit that receives image data sent from the host computer 136. As the communication interface 100, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a 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 136 is taken into the inkjet recording apparatus 10 via the communication interface 100 and temporarily stored in the image memory 104. The image memory 104 is a storage unit that temporarily stores an image input via the communication interface 100, and data is read and written through the system controller 102. The image memory 104 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 102 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. .

  That is, the system controller 102 is a control unit that controls the communication interface 100, the image memory 104, the motor driver 116, the heater driver 118, the discharge detection unit 120, the print control unit 130, and the like, and is connected to the host computer 136. In addition to performing communication control, read / write control of the image memory 104, etc., a control signal for controlling the motor 138, the heater 139, etc. of the transport system is generated.

  The ROM 106 stores programs executed by the CPU of the system controller 102 and various data necessary for control (nozzle check pattern data, discharge determination threshold table, and the like). The ROM 106 may be a non-rewritable storage unit or a rewritable storage unit such as an EEPROM. The image memory 104 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The media type detection unit 108 is a means for acquiring information on the media type (corresponding to “medium type specifying means”), and is a means for detecting the paper type, wettability, size, etc. of the recording medium 16 (for example, the optical type of the paper). A sensor for detecting the reflectance, a sheet width detecting sensor, a sensor for detecting the thickness of the sheet, or an appropriate combination thereof. The media type detection unit 108 automatically determines the type of the recording medium, and performs control so as to realize appropriate treatment liquid application and ink ejection according to the media type.

  Note that the means for acquiring information about the media type is not limited to the above configuration. For example, an information recording body such as a barcode or a wireless tag that records media type information is attached to the magazine 19 of the media supply unit 18 described in FIG. 1, and the information of the information recording body is read by a predetermined reading device (information reading). It is also possible to automatically determine the type of media to be used by reading by the above means. Further, instead of or in combination with these automatic detection means, it is also possible to specify recording medium information such as paper type, wettability, and size by input from a predetermined user interface.

  Information obtained from the media type detection unit 108 shown in FIG. 9 is sent to the system controller 102. The system controller 102 sets a determination threshold value in the ejection detection unit 120 based on information obtained from the media type detection unit 108 and printing image data, and also performs ejection control of processing liquid and ejection of ink. .

  The motor driver 116 is a driver (drive circuit) that drives the motor 138 in accordance with an instruction from the system controller 102. The heater driver 118 is a driver that drives the heater 139 of the heating drum 30 (see FIG. 1) and other parts in accordance with instructions from the system controller 102.

9 includes a light source control circuit that controls lighting (ON) / extinguishing (OFF) of the light source 26 for detection and a light emission amount at the time of lighting, and a drive for driving the CCD of the print detection unit 24. The circuit includes a circuit and a signal processing circuit that processes a signal output from the CCD. The discharge detection unit 120 controls the light emission of the light source 26 for detection according to a command from the system controller 102, and controls the reading operation by the print detection unit 24 and analyzes the signal obtained from the print detection unit 24.

  The print controller 130 generates various signals for generating an ink discharge control signal and a processing liquid discharge control signal from image data (multi-valued input image data) in the image memory 104 according to the control of the system controller 102. It functions as signal processing means for performing processing such as processing and correction. In addition, the print control unit 130 functions as an ink discharge control unit that controls the discharge drive of the ink head 50 by supplying the generated ink discharge data to the ink head driver 134 and cooperates with the processing liquid control unit 133. In this way, data for processing liquid discharge is generated and functions as processing liquid application control means for controlling the discharge driving of the processing liquid head 11.

  The head driver 134 drives the ejection driving actuator 58 of each head 50 based on the ink ejection data given from the print control unit 130. The head driver 134 may include a feedback control system for keeping the head driving conditions constant.

  The required signal processing is performed in the print control unit 130, and the discharge amount and discharge timing of the processing liquid from the processing liquid head 11 are controlled via the processing liquid control unit 133 based on the image data. Control of the discharge amount and discharge timing of ink from the ink head 50 for each color is performed via the driver 134. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 130 includes an image buffer memory 132, and image data, parameters, and other data are temporarily stored in the image buffer memory 132 when image data is processed in the print control unit 130. In FIG. 9, the image buffer memory 132 is shown in a mode accompanying the print control unit 130, but it can also be used as the image memory 104. Also possible is an aspect in which the print controller 130 and the system controller 102 are integrated and configured with one processor.

  An overview of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 100 and stored in the image memory 104. At this stage, for example, RGB multi-value input image data is stored in the image memory 104.

In the ink jet recording apparatus 10, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the image memory 104 is sent to the print control unit 130 via the system controller 102, and ink color is obtained by halftoning processing using a dither method, an error diffusion method, or the like. Converted into dot data (droplet placement data).

  That is, the print control unit 130 performs a process of converting the input RGB image data into dot data of four colors K, C, M, and Y. Thus, the dot data generated by the print control unit 130 is stored in the image buffer memory 132. The dot data for each color is converted into CMYK droplet ejection data for ejecting ink from the nozzles of the ink head 50, and the ink ejection data to be printed is determined.

  The ink head driver 134 outputs a drive signal for driving the actuator 58 corresponding to each nozzle 51 of the ink head 50 based on the ink ejection data given from the print control unit 130.

  Similarly, the processing liquid control unit 133 uses the processing liquid head 11 based on the processing liquid ejection data generated from the image data (processing liquid dot data generated in correlation with the ink ejection amount). A drive signal for driving an actuator corresponding to each nozzle is output. That is, the processing liquid control unit 133 includes means as a head driver for processing liquid.

  When the driving signal output from the processing liquid control unit 133 is applied to the processing liquid head 11, the processing liquid is discharged from the corresponding nozzle. In addition, when the drive signal output from the ink head driver 134 is applied to the ink head 50, ink is ejected from the corresponding nozzle 51. By controlling the processing liquid ejection from the processing liquid head 11 and the ink ejection from the ink head 50 in synchronization with the conveyance speed of the recording medium 16, an image is formed on the recording medium 16.

  As described above, the ejection amount and ejection timing of the droplets from the processing liquid head 11 and the ink head 50 based on the processing liquid ejection data and the ink ejection data generated through the required signal processing in the print control unit 130. Is controlled. Thereby, a desired dot size and dot arrangement are realized.

  In this example, image data is corrected in consideration of ejection failure nozzles in the previous stage of halftoning processing (intermediate gradation processing), so that unevenness due to ejection failure nozzles can be accurately corrected. it can.

  As described with reference to FIG. 7, the print detection unit 24 is a block including an image sensor. The print detection unit 24 reads a test pattern or a practical image printed on the recording medium 16, performs necessary signal processing, etc. Presence / absence, droplet landing position variation, optical density, etc.) are detected, and the detection results are provided to the system controller 102.

  The system controller 102 and the print control unit 130 perform various corrections for the processing liquid head 11 and the ink head 50 based on information obtained from the print detection unit 24 as necessary, and perform preliminary ejection and suction as necessary. Control for performing a cleaning operation such as wiping (maintenance operation for restoring the discharge performance of the nozzles) is performed.

  In this example, the system controller 102 corresponds to a “first recovery control unit”, a “second recovery control unit”, and a “threshold setting unit”, and the system controller 102, the print control unit 130, and the processing liquid control unit 133. This combination corresponds to “test pattern droplet ejection control means”. Further, the combination of the system controller 102 and the print control unit 130 corresponds to “image processing means”, and the combination of the ejection detection unit 120 and the system controller 102 becomes “processing liquid non-discharge determination means” and “ink non-discharge detection means”. Equivalent to.

  Each processing function of the system controller 102 and the like can be realized by ASIC, software, or an appropriate combination thereof.

  FIG. 10 is a flowchart showing a control procedure of the inkjet recording apparatus 10 according to the present embodiment. As shown in the figure, first, media type determination processing is performed (step S10). For this determination method, for example, automatic detection by optical reflectivity detection of the recording medium 16, magazine detection, menu designation by a user interface, or the like is used.

Based on the media type determination result in step S10, a determination value = M corresponding to the type of recording medium 16 to be used is determined (step S12). The ink jet recording apparatus 10 includes information storage means (internal memory or external memory) that stores data of a media type table in which a media type is associated with a determination value (M). Refer to the media type table. Thus, the determination value is determined.

  The reason for changing the judgment value depending on the type of media is that the level of undischargeable nozzles that are allowed varies depending on the type of media, for example, printing on ink-jet paper with small penetration blur. In this case, streak unevenness due to nozzle omission becomes more conspicuous, so the threshold value for the number of allowable non-discharge nozzles becomes small, and the threshold value for the number of allowable non-discharge nozzles becomes large when printing on plain paper or the like having a large penetration blur. .

  Next, the discharge detection of the treatment liquid is performed (step S14), and the discharge detection of the ink is performed (step S16). In the process liquid discharge detection process in step S14, a check pattern is drawn by the process liquid head 11, and a process of reading the drawing result by the Ir sensor array 24Ir of the print detection unit 24 is performed. Is implemented. Similarly, in the ink ejection detection step in step S16, check patterns are drawn by the ink heads 12K, 12M, 12C, and 12Y for each color, and the drawing results are displayed on the RGB sensor rows 24R and 24G of the print detection unit 24. , 24B, and detection signal processing is performed.

  The processing on the processing liquid side will be described. From the detection result in step S14, it is determined whether or not there is an undischarge nozzle for the processing liquid head 11 (step S18). If there is an undischarge nozzle, the process proceeds to step S20, and whether or not the number of undischarge nozzles exceeds a determination threshold value (corresponding to a “first threshold value”) A = T1 (M) for processing liquid head maintenance determination. Is judged.

The determination threshold A is variably set according to the type of the recording medium 16. The ink jet recording apparatus 10 includes information storage means (internal memory or external memory) that stores data of a threshold table T1 in which a media determination value (M) and a determination threshold A are associated with each other. The determination threshold A = T1 (M) is determined with reference to T1.

  In step S20, the number of ejection failure nozzles is compared with the determination threshold A. If the number of ejection failure nozzles exceeds the determination threshold A, it is determined that head maintenance processing is necessary, and the process proceeds to step S22. Maintenance operation of the treatment liquid head 11 is performed.

  The maintenance operation includes preliminary discharge, nozzle suction, nozzle surface wiping, and the like. In this example, the number of discharge failure nozzles and the determination threshold A are compared. However, instead of using the discharge failure nozzle number itself, a function having a correlation with the discharge failure nozzle number, etc. It is also possible to obtain an evaluation value (maintenance evaluation value reflecting the number of discharge failure nozzles) determined from the above and compare this evaluation value with a threshold for determination.

  After performing the maintenance operation in step S22, the process returns to step S14, and detection of the discharge state of the processing liquid is performed again.

  If it is confirmed in step S18 that there is no discharge failure nozzle, the process proceeds to step S48, and the print output preparation is completed after completion of an ink discharge detection routine (step S16, steps S38 to S44) described later.

If the number of undischarge nozzles does not exceed the determination threshold A in step S20, the process proceeds to step S24. In this case, although the discharge failure nozzles are recognized, the number of discharge nozzles is relatively small, and it is determined that the range is acceptable from the viewpoint of image quality, and the maintenance operation is avoided. That is, in step S24, it is set to perform image processing (correction of droplet ejection arrangement) for determining the droplet ejection arrangement so as to reduce the usage rate of the nozzles of the ink head 50 corresponding to the position of the treatment liquid ejection failure nozzle. The In the case of this example, the halftoning process is performed for all ink colors in a sequence that reduces the usage rate of the corresponding nozzle position, and the droplet ejection arrangement is determined. After step S24, the process proceeds to step S48.

  Next, processing on the ink side will be described. From the detection result of step S16, it is determined whether or not there is an undischarge nozzle for each of the ink heads 50 of K, C, M, and Y (step S38). If there is a discharge failure nozzle, the process proceeds to step S40, and the number of discharge failure nozzles for each color exceeds the determination threshold value for ink head maintenance determination (corresponding to the “second threshold value”) B = T2 (M). It is determined whether or not.

The determination threshold B is variably set according to the type of the recording medium 16. The ink jet recording apparatus 10 includes information storage means (internal memory or external memory) that stores data of a threshold table T2 in which a media determination value (M) and a determination threshold B are associated with each other. The determination threshold B = T2 (M) is determined with reference to T2.

  The determination threshold B = T2 (M) is set to a value different from the determination threshold A = T1 (M) for the processing liquid. That is, since the colorless and transparent processing liquid itself has low visibility, the influence on the image quality due to non-discharge is smaller than that of the ink. Therefore, the determination threshold A that is a criterion for determining whether to perform the maintenance operation is relatively low. A large value increases print productivity. On the other hand, since the color ink is noticeably deteriorated due to non-discharge, the high-quality image output is prioritized by setting the determination threshold B to a relatively small value.

  In step S40, the number of undischargeable nozzles is compared with the determination threshold B. If the number of undischargeable nozzles exceeds the determination threshold B, it is determined that head maintenance processing is necessary, and the process proceeds to step S42. Maintenance operation of the ink head 50 is performed.

  The maintenance operation includes preliminary discharge, nozzle suction, nozzle surface wiping, and the like. However, the maintenance operation of the treatment liquid head 11 and the maintenance operation of the ink head 50 do not necessarily have the same contents. That is, the maintenance operation sequence may be changed between the treatment liquid head 11 and the ink head 50. Further, the processing content of the maintenance operation, the number of times of processing, and the like may be set in accordance with the number of undischarge nozzles.

  After performing the maintenance operation in step S42, the process returns to step S16 to detect the ink ejection state again.

  If it is confirmed in step S38 that there is no discharge failure nozzle, the process proceeds to step S48, and the process proceeds to step S48, where the preparation of print output is completed after the processing liquid discharge detection routine (steps S14 to S24) described above is completed. To do.

  If the number of undischargeable nozzles does not exceed the determination threshold B in step S40, the process proceeds to step S44. In this case, although the discharge failure nozzles are recognized, the number of discharge nozzles is relatively small, and it is determined that the range is acceptable from the viewpoint of image quality, and the maintenance operation is avoided. That is, in step S44, it is set to perform image processing (correction of droplet ejection arrangement) for determining the ink droplet arrangement so as to increase the usage rate of neighboring nozzles without using the non-discharge nozzle. In the case of this example, the halftoning process is performed under the condition that the discharge failure nozzle is not used, and the droplet ejection arrangement is determined. After step S44, the process proceeds to step S48.

  When the print output preparation is completed in step S48, the print operation corresponding to the input image data is executed thereafter.

[Modification 1]
In the above embodiment, the aqueous processing liquid and ink are exemplified, but the present invention can also be applied to an oil-based processing liquid and ink. In the above embodiment, the example of mixing the two liquids of the pretreatment liquid and the ink has been described. However, the present invention can also be applied to a case where three or more kinds of liquids are mixed. Furthermore, a mode in which a plurality of types of processing liquids are prepared and one or two or more appropriate processing liquids are selected according to the type of recording medium is also possible.

[Modification 2]
In the above-described embodiment, the configuration in which the first treatment liquid is deposited on the recording medium and then the second ink is ejected onto the treatment liquid has been described. Is not limited to this example, and there may be an aspect in which ink is first ejected and then a treatment liquid is ejected, or an aspect in which the treatment liquid and the ink are simultaneously deposited on the medium.

  In the above embodiment, the liquid ejected from the processing liquid head 11 and the ink head 50 is directly landed on the recording medium 16. A mode in which the treatment liquid or ink is attached to the recording medium by transfer from the transfer medium is also possible.

[Modification 3]
The ink jet recording apparatus 10 described with reference to FIG. 1 has a configuration in which the treatment liquid head 11 is disposed only on the upstream side (right side in FIG. 1) of the ink head 12K in the recording medium conveyance direction. A configuration in which the processing liquid heads are arranged upstream of the ink heads 12K, 12M, 12C, and 12Y is also possible. With this configuration, it is possible to apply an appropriate amount of processing liquid for each ink color.

[Modification 4]
In each of the above embodiments, an ink jet recording apparatus using a page-wide full-line head having a nozzle array with a length corresponding to the entire width of the medium (recording medium) has been described. However, the present invention is also applicable to an inkjet recording apparatus that uses a shuttle head that records an image while reciprocating a short recording head.

[Modification 5]
In the above embodiment, an ink jet recording apparatus of a method (direct recording method) in which an ink droplet is directly formed on a recording medium such as recording paper has been described. However, the scope of application of the present invention is not limited to this.

  FIG. 11 is a block diagram of the main part of an ink jet recording apparatus showing another embodiment of the image forming apparatus according to the present invention. The form of the ink jet recording apparatus 210 shown in FIG. 11 does not directly form an image on a recording medium, but once forms an image on the intermediate transfer member 212, and the image is transferred to the recording medium 16 at the transfer unit 214. The image forming apparatus performs final image formation by transferring. 11, elements that are the same as or similar to those in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

  In the ink jet recording apparatus 210 shown in FIG. 11, an endless belt member is used as the intermediate transfer member 212. The intermediate transfer member 212 made of an endless belt member is wound between a plurality of stretching rollers 218 and 219 and opposing rollers 220 and 221 for transfer pressure, and at least the heads 11, 12 </ b> K, and 12 </ b> M. , 12C, 12Y and the belt surface range facing the sensor surface of the print detection unit 24 are configured to form a horizontal surface (flat surface).

  In the present embodiment, a test pattern (similar to FIG. 8) is drawn on the intermediate transfer member 212, and the test pattern on the intermediate transfer member 212 is detected by the print detection unit 24, as shown in the figure. In addition, a print detection unit 24, a detection light source 26, and a heating and drying unit 28 are provided along the belt surface of the intermediate transfer member 212 that forms a horizontal plane.

  The transfer unit 214 is opposite to the image forming surface of the flat intermediate transfer body 212 facing the nozzle surfaces of the heads 11, 12K, 12M, 12C, and 12Y and the sensor surface of the print detection unit 24 (a position directly below in FIG. 11). Provided. The transfer unit 214 is provided with a belt pressure conveying mechanism 236 having a configuration in which an endless belt member 234 is wound between a plurality of pressure rollers 230 and 231 and a stretching roller 232.

  A color image (primary image) formed on the intermediate transfer member 212 by discharging the processing liquid or ink from each of the heads 11, 12C, 12M, 12Y, and 12K is shown in FIG. It is moved counterclockwise.

  The recording medium 16 is conveyed in synchronism with the conveyance of the intermediate transfer body 212, and in the transfer unit 214, the pressure rollers 230 and 231 of the belt pressure conveyance mechanism 236 and a pressure nip for the pressure nip disposed opposite thereto are used. The intermediate transfer member 212, the recording medium 16, and the belt member 234 are sandwiched between the opposing rollers 220 and 221, and the primary image on the intermediate transfer member 212 is transferred to the recording medium 16 by applying a predetermined pressure (nip pressure). It has a configuration.

  Thus, an image (secondary image) is transferred and formed on the recording medium 16 through the transfer unit 214, and the generated printed matter (the recording medium 16 on which the image is formed) is discharged from a print discharge unit (not shown).

  As illustrated in FIG. 11, the present invention can be applied to an intermediate transfer type inkjet recording apparatus.

1 is an overall configuration diagram of an ink jet recording apparatus showing an embodiment of an image forming apparatus according to the present invention. Plane perspective view showing a structural example of an ink head Plane perspective view showing another configuration example of a full-line head Sectional drawing which shows the three-dimensional structure of the droplet discharge element (ink chamber unit corresponding to 1 nozzle) for 1 channel FIG. 2 is an enlarged view showing the nozzle arrangement of the ink head shown in FIG. Schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus of this example Main part configuration diagram around the print detection unit Schematic diagram showing a print example of a test pattern (nozzle check pattern) for detecting the discharge status Main part block diagram which shows the system configuration | structure of the inkjet recording device which concerns on this embodiment. A flowchart showing an example of control of the ink jet recording apparatus according to the present embodiment. The principal part block diagram of the inkjet recording device which concerns on other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 11 ... Processing liquid head, 12K, 12M, 12C, 12Y ... Ink head, 16 ... Recording medium, 24 ... Print detection part, 26 ... Light source for detection, 28 ... Heat drying part, 50 ... Ink head, 51 ... Nozzle, 52 ... Pressure chamber, 58 ... Actuator, 102 ... System controller, 108 ... Media type detection unit, 120 ... Discharge detection unit, 133 ... Treatment liquid control unit, 212 ... Intermediate transfer member, 214 ... Transcription part

Claims (7)

Ink ejection means for ejecting ink containing a color material;
Discharge of a processing liquid containing a colorless and transparent liquid having an action of insolubilizing or aggregating the ink coloring material or a colorless and transparent liquid for preventing diffusion of the ink coloring material and containing an infrared absorbing material Means,
Infrared irradiation means for irradiating the processing liquid discharged from the processing liquid discharge means with infrared rays;
Treatment liquid detection means including a photoelectric conversion element having sensitivity in the infrared region;
Treatment liquid discharge failure determination means for determining the number and position of discharge failure nozzles of the treatment liquid discharge means based on a detection signal obtained from the photoelectric conversion element;
Image processing means for determining the ink droplet ejection arrangement so as to reduce the usage rate of the nozzle of the ink ejection means corresponding to the position of the non-ejection nozzle of the processing liquid ejection means;
An image forming apparatus comprising: Comprising test pattern droplet ejection control means for controlling the ejection operation of the treatment liquid ejection means so as to draw a predetermined test pattern on a recording medium or an intermediate transfer member by droplet ejection of the treatment liquid,
The image forming apparatus according to claim 1, wherein the photoelectric conversion element detects a drawing state of the predetermined test pattern.   A drying accelerating unit is provided that irradiates the recording medium to which the processing liquid ejected from the processing liquid ejecting unit and the ink ejected from the ink ejecting unit adhere to each other, and accelerates drying of the recording medium. The image forming apparatus according to claim 1 or 2. First recovery control means for performing control to perform a maintenance operation for recovering the discharge performance of the processing liquid discharge means when the number of undischarge nozzles of the processing liquid discharge means exceeds a first threshold value is provided. The image forming apparatus according to claim 1 , wherein the image forming apparatus is an image forming apparatus. Ink detection means including a photoelectric conversion element having sensitivity in the visible region;
An ink discharge failure determination means for determining the number and position of discharge failure nozzles of the ink discharge means based on a detection signal obtained from a photoelectric conversion element of the ink detection means;
A second recovery for performing control to perform a maintenance operation for recovering the discharge performance of the ink discharge means when the number of undischarge nozzles of the ink discharge means exceeds a second threshold value smaller than the first threshold value. Control means;
The image forming apparatus according to claim 4, further comprising: Medium type specifying means for specifying the type of recording medium;
Threshold setting means for changing and setting the first threshold according to the type of the recording medium;
The image forming apparatus according to claim 4, further comprising: Medium type specifying means for specifying the type of recording medium;
6. The image forming apparatus according to claim 5, further comprising a threshold setting unit configured to change and set the first threshold and the second threshold according to the type of the recording medium.

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