JP2010076224A - Inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve image quality by setting, when continuously jetting a plurality of ink droplets to a recording medium in an overlapping manner after uniformly giving a processing liquid containing a coagulant thereto in a planar form in a two-liquid aggregation system, the dot diameter of the aggregated ink to a set dot diameter matched to the discharge volume of the ink droplet, and minimizing the dot diameter difference between the ink droplets. <P>SOLUTION: The method includes: a processing liquid giving step of uniformly giving the coagulant-containing processing liquid onto the recording medium 22 in a planar form; an ink jetting step of jetting droplets of ink which is aggregated by the processing liquid onto the recording medium 22 with the processing liquid applied thereto to form an image; a drying step of drying the ink given to the recording medium 22; and a fixing step of fixing the ink by nipping the recording medium with the ink being dried by fixing rollers 86 and 88. In the fixing step, a fixing condition is controlled according to the dot diameter of the ink before the fixing treatment. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inkjet recording method, and more particularly, to a two-liquid aggregation type inkjet recording method in which a treatment liquid is applied to a recording medium and ink is applied thereon to cause aggregation.

  An ink jet recording apparatus is an apparatus that forms an image by continuously ejecting ink onto a recording medium. Since the apparatus configuration is simple and image recording with good image quality is possible, the home recording apparatus is used for personal use. It is widely used as an office printer for business use including printers. Particularly in office printers for business use, higher processing speed and higher image quality are further demanded.

  In such an ink jet recording apparatus, when ink dots are deposited adjacent to each other, the ink droplets on the recording medium are united by their surface tension, and a desired dot cannot be formed (landing interference). Problems occur. Bleed occurs when the dots are the same color, and the dot shape is lost. When the dots are between different colors, the problem of color mixing also occurs.

  Therefore, a two-liquid aggregation method has been proposed in which a treatment liquid containing an aggregation component is first applied to a recording medium, and ink is then ejected and aggregated. For example, Patent Document 1 discloses a method of controlling pigment aggregation on paper by making one of processing liquid and ink acidic and the other alkaline. According to this method, interference between dots is suppressed, and sharp recording without density unevenness can be performed. Further, it is said that the penetration of the color material in the ink into the paper can be suppressed, and a high resolution can be obtained.

  However, after the treatment liquid is uniformly applied on the surface of the recording medium by a coating apparatus or the like, droplets are ejected so that a plurality of inks (for example, CMYK different color inks or dark and light inks) are superimposed (so that the respective inks overlap). In the case of droplet ejection), there is a problem that the dot diameter of ink droplets that are ejected later increases as the dot diameter increases. For example, when the secondary color ink to be ejected next is deposited on the 100% solid image formed by the primary color ink to be ejected first, the dot diameter formed by aggregation of the secondary color ink However, there is a problem that the diameter of the primary color ink is remarkably enlarged compared to the dot diameter formed. Further, when the tertiary ink is deposited on the 100% solid image of the primary color ink and the secondary color ink, the dot diameter enlargement becomes more remarkable. Even if the primary color ink is not a 100% solid image, this phenomenon increases as the image area ratio% of the primary color ink increases, that is, the dot diameter of the secondary color ink increases as the primary color ink approaches 100% solid. Become. The dot diameter of the ink has an appropriate dot diameter range depending on the ejection volume of the ink droplet to be ejected, and the image quality deteriorates if the dot diameter is out of this range.

  As a method of solving this problem, increasing the amount of the treatment liquid applied or increasing the concentration of the coagulant in the treatment liquid to enhance the ink cohesive force makes it easier for the ink to be ejected later to be easily aggregated. Therefore, it is conceivable to suppress the enlargement of dots. However, the expansion of the dot diameter of the secondary color ink or the tertiary ink that is ejected later may be suppressed, but this time, the cohesive force of the primary color ink becomes too large, and the dot diameter of the primary color ink is increased. A new problem arises that will shrink.

  Increasing the dot diameter of the ink causes deterioration in image quality such as a decrease in resolution, character reproducibility, graininess, and color unevenness in the recording medium surface. On the other hand, the reduction in the dot diameter of the ink causes a decrease in image density in a 100% solid image portion.

  As described above, since the optimum amount of the flocculant applied to each ink varies depending on the total droplet ejection amount of the plurality of inks, the processing liquid containing the flocculant is uniformly applied to the recording medium by a coating device such as roller coating. In the case where the ink is applied in the form of a sheet and droplets are ejected so as to superimpose a plurality of inks thereon, it is necessary to accept that a difference occurs in the dot diameters of the plurality of inks. As a countermeasure against this, it is conceivable to apply the treatment liquid as droplets from the ink jet nozzle, but there is a problem that the treatment liquid droplets land and interfere with each other and the treatment liquid cannot be uniformly applied in the application region. When landing interference occurs between the processing liquids, it is natural that unevenness occurs in the agglomeration reaction and the image quality of the obtained image is deteriorated.

  Therefore, in order to improve the image quality of the obtained image, it is important to make the dot diameter suitable for the predetermined ejection volume of a plurality of ink droplets, and it is important to make the dot diameter difference of each ink as small as possible become.

Patent Document 2 proposes that the temperature of a recording medium on which ink is ejected is kept constant, and that the amount of heat applied during image fixing is kept constant, thereby suppressing dot diameter fluctuations caused by temperature unevenness.
JP 2004-10633 A JP 2003-191452 A

  However, Patent Document 2 does not control the dot diameter of the ink in the two-liquid aggregation method, and in the case of the two-liquid aggregation method, the temperature of the recording medium is kept constant or the amount of heat applied during image fixing is constant. It is not possible to increase the dot diameter of the secondary color ink or the tertiary ink when a plurality of inks are ejected, and to reduce the dot diameter difference between the inks.

  The present invention has been made in view of such circumstances, and in a two-liquid aggregation method, a treatment liquid containing an aggregating agent is uniformly applied to a recording medium in a continuous form, and a plurality of inks are continuously superimposed. Ink-jet recording that can improve the image quality because the dot diameter of the aggregated ink can be set to a set dot diameter that matches the ejection volume of the ink droplets and the difference in todd diameter between the inks can be reduced when droplets are ejected It aims to provide a method.

  In the case of image formation by a two-liquid aggregation method in which ink is aggregated with a processing liquid containing an aggregating agent, the dot diameter of the ink after aggregation depends on the intensity of the aggregation reaction of the aggregating agent contained in the processing liquid. The dot size is enlarged or reduced from an appropriate dot diameter corresponding to the droplet discharge volume. As a result, the following problem occurs. That is, from the viewpoint of eliminating a white background in a solid image, it is not preferable that the dot diameter of the ink droplet formed on the recording medium after ink ejection is too small, and a certain spread is required for the dot diameter. As an adverse effect of the dot diameter being too small, it is necessary to increase the ink droplet ejection amount in order to form a solid image, which adversely affects other properties such as curling, cockling, and fixability of the recording medium. Conversely, if the dot diameter is too large, the resolution is lowered and the sharpness of the image is impaired. For example, when the ejection volume of the ink droplet is 2 pL, it is preferably 28 μm or more and less than 40 μm (more preferably 30 to 38 μm), and there is an appropriate dot diameter corresponding to the ejection volume. However, when a plurality of inks are superimposed and continuously ejected, the amount of the flocculant corresponding to the total amount of the ink fluctuates. It is actually difficult to control strength. Unless otherwise specified, the dot diameter in the present invention refers to the dot diameter of the ink after being agglomerated with the treatment liquid.

  Thus, as a result of earnestly researching countermeasures in the case of deviating from an appropriate dot diameter, the inventor obtained knowledge that it is possible to easily and accurately adjust the appropriate dot diameter by controlling the fixing conditions in the fixing process. It was.

  In order to achieve the above object, claim 1 of the present invention provides a treatment liquid application step for uniformly applying a flocculant-containing treatment liquid onto a recording medium, and a recording medium provided with the treatment liquid. An ink droplet ejecting process for forming an image by ejecting ink droplets aggregated by the treatment liquid, a drying process for drying the ink applied to the recording medium, and fixing the recording medium after the ink is dried And a fixing step of fixing the ink by nipping with a roller. In the fixing step, a fixing condition is controlled according to the dot diameter of the ink before the fixing process. .

  Claim 1 is the basic technical idea of the present invention. In the fixing step, the fixing conditions are controlled in accordance with the dot diameter of the ink before the fixing process, so that an appropriate dot diameter can be obtained after fixing. it can. Thereby, the image quality of an image obtained by ink jet recording can be improved, and other performances such as curling, cockling, and fixing properties are not adversely affected.

  According to a second aspect of the present invention, in order to achieve the above object, a treatment liquid application step for uniformly applying a flocculant-containing treatment liquid onto a recording medium in a sheet form, and a recording medium provided with the treatment liquid, An ink droplet deposition step for forming an image by continuously ejecting a plurality of N-order inks from the primary color ink agglomerated by the treatment liquid so as to overlap at the same predetermined discharge volume; A drying step for drying the ink, and a fixing step for fixing the ink by nipping the recording medium on which the ink has been dried with a fixing roller, wherein the treatment liquid applying step includes: When adjusting the amount of the flocculant applied to the recording medium so that the dot diameter of the ink to be superimposed last before the fixing process does not exceed the preset dot diameter range corresponding to the predetermined ejection volume. In the fixing step, the dot diameters after the fixing process of all the inks from the primary color ink to the N-th order ink fall within the set dot diameter range, and the dot diameter difference between the inks is a predetermined value or less. There is provided an ink jet recording method characterized by controlling fixing conditions as described above.

  Here, the set dot diameter set in advance according to the predetermined discharge volume means an appropriate dot diameter corresponding to the discharge volume for the above image quality and other performances. For example, the discharge volume of the ink droplet is 2 pL (pico In the case of (liter), the dot diameter is 28 to 40 μm. The dot diameter is more preferably 30 to 38 μm.

  A second aspect of the present invention is a case in which a plurality of N-order inks are continuously ejected onto a recording medium to which a treatment liquid is applied so as to overlap with a predetermined discharge volume from primary color inks aggregated by the treatment liquid. is there. In this case, since the strength of the agglutination reaction is weakened as the ink is ejected later from among the plurality of superimposed inks, the dot diameter is increased and is likely to be larger than the set dot diameter.

According to the second aspect of the present invention, in the treatment liquid application step, the dot diameter before the fixing process of the ink to be superimposed last among the plurality of inks exceeds the preset dot diameter range corresponding to the predetermined ejection volume. The amount of the flocculant applied to the recording medium is adjusted so as not to be present. As the adjustment of the amount of the flocculant, for example, in the case of using two colors of primary color ink and secondary color ink, the content of the flocculant is 5.19 (mol · valence / valence / m ^{2 of} recording medium). kg) or more.

  In the fixing step, the dot diameters after the fixing process of all the inks from the primary color ink to the Nth order ink are within the set dot diameter range, and the dot diameter difference between the inks becomes a predetermined value or less. Control the fixing conditions. For example, it is possible to satisfy the set dot diameter by flattening and expanding the diameter of the plurality of inks that have not reached the set dot diameter by controlling the fixing conditions to be strong in the fixing process.

  In addition, when droplets are ejected so as to overlap a plurality of inks, it is necessary to reduce the dot diameter difference between the inks in addition to satisfying the set dot diameter for all the inks after fixing. By controlling this, it is possible to reduce the dot diameter difference between the inks. For example, an appropriate dot diameter difference is 4 μm or less when the ejection volume of each ink droplet is 2 pL (picoritter).

  Thereby, the image quality of an image obtained by ink jet recording can be improved, and other performances such as curling, cockling, and fixing properties are not adversely affected.

  In the present invention, the fixing condition factor (variable) is at least one of the nip pressure of the fixing roller, the number of nips, the temperature of the fixing roller, the nip time, and the elapsed time from the ink droplet ejection process to the fixing process. Preferably there is. In particular, it is preferable to control the nip pressure of the fixing roller, the number of nips, and the temperature of the fixing roller.

  As a further aspect of the present invention, a detection step for detecting the dot diameter is provided between the ink droplet ejection step and the fixing step, and based on the dot diameter before the fixing process detected in the detection step. It is preferable to control the fixing conditions.

  In the case of the present invention, a relational expression or a relational table is created by obtaining a fixing condition for setting the ink dot diameter to be a setting condition by an offline experiment or an online preliminary experiment, and based on that. Fixing conditions can be controlled (set). However, it has a detection process that detects the dot diameter, and it can handle various disturbances that affect the dot diameter by controlling the fixing conditions online based on the dot diameter detected in the detection process. Can do. Disturbances affecting the dot diameter include, for example, the amount of flocculant contained in the processing liquid, the film thickness of the processing liquid applied to the recording medium, the recording medium temperature at the time of ink ejection, the image area ratio of the lower layer, and the recording medium In the detection step, the resulting dot diameter including these disturbances is detected. In addition, since the detection process is provided, online feedback control is possible, so that the control can be automated.

  As a detection means used in the detection process, for example, a CCD camera can be suitably used. There is a method in which a spot where an ink droplet has landed is captured by a CCD camera, captured in an electronic image, binary processing is performed using a luminance value as a threshold value, and a dot diameter is calculated from the number of pixels.

  As a further aspect of the present invention, it is preferable to control the fixing conditions in accordance with the image area ratio% of the N-1 primary color ink formed on the recording medium to which the processing liquid has been applied.

  Here, the N-1 primary color ink image corresponds to, for example, primary color ink that is first ejected onto a recording medium when two types of ink are superimposed. When superimposing three types of ink, when focusing on the dot diameter of the secondary color ink, the primary color ink image corresponds to the N-1 primary color ink image, and when focusing on the dot diameter of the tertiary ink The secondary color ink image corresponds to the N-1 primary color ink image.

  This affects the enlargement of the dot diameter because the remaining area of the flocculant in the processing liquid used for the ink to be ejected next changes as the image area ratio% of the N-1 primary color ink image changes. That is, the image area ratio% of the N−1 primary color ink image is a disturbance that affects the enlargement / reduction of the dot diameter of the N primary color ink. Therefore, it is necessary to control (set) the fixing conditions in consideration of the image area ratio% of the N-1 primary color ink image. In the case where the detection step is provided, since the dot diameter as a result including the image area ratio% of the N-1 primary color ink image is detected, it is not necessary to consider the image area ratio%.

  As a further aspect of the present invention, it is preferable to control the fixing conditions according to the type of the recording medium.

  This is because the penetrability of the treatment liquid differs depending on the type of the recording medium, so that the dot diameter increases or decreases depending on the type of the recording medium, and the fixing conditions need to be changed accordingly. It should be noted that there is no need to consider when a dot diameter detection step is provided.

  As a further aspect of the present invention, it is preferable to control the fixing conditions in accordance with the film thickness of the treatment liquid applied onto the recording medium in the treatment liquid application step.

This is because the film thickness of the processing liquid applied on the recording medium also affects the dot diameter, and it is necessary to control (set) the fixing conditions in consideration of the film thickness of the processing liquid. The film thickness of the treatment liquid is preferably 1 g / m ² or more and 3.5 g / m ² or less. It should be noted that there is no need to consider when a dot diameter detection step is provided.

  As a further aspect of the present invention, it is preferable to control the fixing conditions according to the temperature of the recording medium at the time of ink droplet ejection in the ink droplet ejection step.

  This is because the temperature of the recording medium at the time of ink ejection in the ink ejection process also affects the dot diameter, and it is necessary to control (set) the fixing conditions in consideration of the temperature of the recording medium. A preferable temperature is 30 ° C. or higher and 45 ° C. or lower. It should be noted that there is no need to consider when a dot diameter detection step is provided.

  As a further aspect of the present invention, in the ink droplet ejection step, it is preferable that droplets are ejected in order from an ink having a small solid content among the plurality of inks.

  This is because the solid content in the ink is related to the amount of flocculant consumed in the treatment liquid, and consequently affects the dot diameter. This is because the amount of ink increases and the dot diameter of ink to be ejected later is difficult to expand. This preferred embodiment is also necessary when a dot diameter detection step is provided.

As a further aspect of the present invention, the ink is a water-based ink, and the amount of residual water of the ink that has been ejected in the ink ejection process is in the range of ² to 4 g / m ² and the ink ejection. It is preferable to perform the fixing step in a satisfied state within 10 seconds.

  This is because it is easier to flatten the dot diameter and the fixability is improved if the fixing process is performed while the image formed by ink droplets is moderately soft.

  According to the ink jet recording method of the present invention, in the two-liquid aggregation method, in the two-liquid aggregation method, the treatment liquid containing the aggregating agent is uniformly applied to the recording medium in a continuous form, and a plurality of inks are continuously superimposed. In the case of droplet ejection, the dot diameter of the ink after agglomeration can be set to a set dot diameter corresponding to the ejection volume of the ink droplets, and the difference in the todd diameter between the inks can be reduced, so that the image quality can be improved.

Hereinafter, preferred embodiments of the ink jet recording method of the present invention will be described in detail with reference to the accompanying drawings. In the present invention, an image can be formed using an ink jet recording apparatus described below.
[Overall configuration of inkjet recording apparatus]
First, the overall configuration of an ink jet recording apparatus to which the present invention is applied will be described.

  FIG. 1A is a configuration diagram schematically showing the ink jet recording apparatus 1 of the present embodiment. An inkjet recording apparatus 1 shown in FIG. 1 is an apparatus that forms an image on a recording surface of a recording medium 22, and mainly includes a paper feeding unit 10, a processing liquid application unit 12, a drawing unit 14, a drying unit 16, a fixing unit 18, and a discharge unit. 20.

  A recording medium 22 (sheets) is stacked on the paper supply unit 10, and the recording medium 22 is sent from the paper supply unit 10 to the treatment liquid application unit 12, and the treatment liquid application unit 12 processes the treatment liquid on the recording surface. Is applied to the recording surface by the drawing unit 14. The recording medium 22 to which the ink has been applied is dried by the drying unit 16 and the image is fastened by the fixing unit 18, and then conveyed by the discharge unit 20.

  Intermediate conveyance units 24, 26, and 28 are provided between the units, and the recording medium 22 is transferred by the intermediate conveyance units 24, 26, and 28. That is, a first intermediate transport unit 24 is provided between the processing liquid application unit 12 and the drawing unit 14, and the recording medium from the processing liquid application unit 12 to the drawing unit 14 by the first intermediate transport unit 24. 22 delivery is performed. Similarly, a second intermediate transport unit 26 is provided between the drawing unit 14 and the drying unit 16. The recording medium 22 is transferred from the drawing unit 14 to the drying unit 16 by the second intermediate transport unit 26. Is done. Further, a third intermediate transport unit 28 is provided between the drying unit 16 and the fixing unit 18, and the third intermediate transport unit 28 transfers the recording medium 22 from the drying unit 16 to the fixing unit 18. Done.

  Hereinafter, each unit of the inkjet recording apparatus 1 (the paper feeding unit 10, the processing liquid applying unit 12, the drawing unit 14, the drying unit 16, the fixing unit 18, the discharging unit 20, the first to third intermediate conveying units 24, 26, and 28). ) Will be described.

(Paper Feeder)
The paper feed unit 10 is a mechanism that supplies the recording medium 22 to the drawing unit 14. The paper feed unit 10 is provided with a paper feed tray 50, and the recording medium 22 is fed from the paper feed tray 50 to the processing liquid application unit 12 one by one.

(Processing liquid application part)
The processing liquid application unit 12 is a mechanism that applies the processing liquid to the recording surface of the recording medium 22. The treatment liquid includes a color material aggregating agent that agglomerates or deposits the color material (pigment) in the ink applied by the drawing unit 14. When the treatment liquid comes into contact with the ink, the ink Separation from the solvent is promoted, and the ink aggregates. A more detailed description of the treatment liquid will be described later.

  As shown in FIG. 1A, the treatment liquid application unit 12 includes a transfer drum 52, a treatment liquid drum 54, a treatment liquid application device 56, a hot air blowing nozzle 58, and an IR heater 60. The transfer drum 52 is disposed between the paper feed tray 50 and the processing liquid drum 54 of the paper feed unit 10 and is driven to rotate. The recording medium 22 fed from the paper feed unit 10 is received by the transfer drum 52 and transferred to the processing liquid drum 54. In addition, instead of the transfer drum 52, an intermediate conveyance unit described later may be provided.

  The treatment liquid drum 54 is a drum that holds and rotates the recording medium 22 and is driven to rotate. Further, the processing liquid drum 54 is provided with a claw-shaped holding means on its outer peripheral surface, and the leading end of the recording medium 22 can be held by this holding means. The recording medium 22 is rotated and conveyed by rotating the processing liquid drum 54 with the tip held by the holding means. At that time, the recording medium 22 is conveyed so that the recording surface faces outward. Note that suction holes may be provided on the outer peripheral surface of the treatment liquid drum 54, and suction may be performed from the suction holes. As a result, the recording medium 22 can be held in close contact with the peripheral surface of the treatment liquid drum 54.

  A processing liquid coating device 56, a hot air blowing nozzle 58 and an IR heater 60 are provided outside the processing liquid drum 54 so as to face the peripheral surface thereof. The processing liquid coating device 56, the hot air blowing nozzle 58, and the IR heater 60 are sequentially arranged from the upstream side in the rotation direction of the processing liquid drum 54 (counterclockwise direction in FIG. 1A), and the recording medium 22 is disposed. First, the processing liquid is applied to the recording surface by the processing liquid coating device 56. As a result, the treatment liquid is uniformly applied to the recording surface of the recording medium 22 in a planar shape.

  In the treatment liquid application unit 12, the recording medium 22 is arranged so that the dot diameter before the fixing process of the ink to be superimposed last among a plurality of inks does not exceed the preset dot diameter range corresponding to the ejection volume of the ink droplets. The amount of the flocculant applied to is adjusted. This is because the dot diameter is corrected by flattening (expanding) the dots by strengthening the fixing conditions in the fixing unit 18 described later. Therefore, if the dot diameter before the fixing process of the ink to be superimposed last exceeds the upper limit of the set dot diameter range, it cannot be kept within the set dot diameter range even if the fixing conditions are controlled.

In adjusting the amount of the flocculant, the amount of flocculant applied per 22 m ² of the recording medium is preferably 5.19 (mol · valence / kg) or more.

The configuration of the processing liquid coating apparatus 56 is not particularly limited. For example, the processing liquid container in which the processing liquid is stored, an anix roller partially immersed in the processing liquid in the processing liquid container, anix The squeegee is in contact with the roller and performs measurement, and an anix roller and a rubber roller that is pressed against the recording medium 22 on the processing liquid drum 54 and transfers the measured processing liquid to the recording medium 22. According to the processing liquid application device 56, the processing liquid can be applied to the recording medium 22 while being measured with a squeegee. The film thickness of the treatment liquid is desirably sufficiently smaller than the droplet diameter of ink ejected from the ink jet heads 72M, 72C, 72Y, 72K of the drawing unit 14. For example, when the ink droplet ejection volume (discharge volume) is 2 pL (picolitta), the average droplet diameter is 15.6 μm. At this time, when the film thickness of the processing liquid is large, the ink dots float in the processing liquid without contacting the surface of the recording medium 22. Therefore, in order to make the landing dot diameter 28 μm or more and less than 40 μm, which is a preferable range when the ink droplet ejection amount is 2 pL, the film thickness of the treatment liquid is 1 to 3.5 g / m ² (1 to 3.5 μm). ) Is desirable.

The recording medium 22 coated with the treatment liquid by the treatment liquid application device 56 is conveyed to the position of the hot air blowing nozzle 58 and the IR heater 60. The hot air blowing nozzle 58 is configured to blow high temperature (for example, 70 ° C.) warm air toward the recording medium 22 at a constant air volume (for example, 9 m ³ / min), and the IR heater 60 has a high temperature (for example, 180 ° C.). Be controlled. By the heating by the hot air blowing nozzle 58 and the IR heater 60, water in the solvent of the processing liquid is evaporated, and a thin film layer of the processing liquid is formed on the recording surface. By thinning the treatment liquid in this way, the dots of ink that are ejected by the drawing unit 14 come into contact with the recording surface of the recording medium 22 to obtain the required dot diameter, and the thinned treatment liquid component Reacts with the colorant to cause aggregation of the coloring material, and an effect of fixing to the recording surface of the recording medium 22 is easily obtained. The processing liquid drum 54 may be controlled to a predetermined temperature (for example, 50 ° C.).
(Drawing part)
As shown in FIG. 1A, the drawing unit 14 includes a drawing drum 70 and ink heads 72C, 72M, 72Y, and 72K that are arranged close to the outer peripheral surface of the drawing drum 70. The ink heads 72C, 72M, 72Y, and 72K correspond to four colors of ink of cyan (C), magenta (M), yellow (Y), and black (K), respectively, and are upstream in the rotation direction of the drawing drum 70. Arranged in order from the side.

  The drawing drum 70 is a drum that holds the recording medium 22 on its outer peripheral surface and rotates and conveys the recording medium 22 and is driven to rotate. Further, the drawing drum 70 is provided with a claw-shaped holding means (not shown) on its outer peripheral surface, and the leading end of the recording medium 22 can be held by this holding means. The recording medium 22 is rotated and conveyed by rotating the drawing drum 70 with the tip held by the holding means. At that time, the recording medium 22 is conveyed so that the recording surface faces outward, and ink is applied to the recording surface from the ink heads 72C, 72M, 72Y, 72K.

  Each of the ink heads 72C, 72M, 72Y, and 72K is a full-line type ink jet recording head (ink jet head) having a length corresponding to the maximum width of the image forming area in the recording medium 22, and the ink discharge surface thereof has an ink ejection surface. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each of the ink heads 72C, 72M, 72Y, 72K is fixedly installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 22 (the rotation direction of the drawing drum 70).

  A corresponding color ink cassette is attached to each of the ink heads 72C, 72M, 72Y, 72K. Each color ink preferably contains at least pigment particles (A), a dispersant polymer (B) for coating the pigment, and self-dispersing polymer fine particles (C).

  The ink droplets configured as described above are ejected from the ink heads 72C, 72M, 72Y, 72K toward the recording surface of the recording medium 22 held on the outer peripheral surface of the drawing drum 70. As a result, the ink comes into contact with the processing liquid that has been uniformly applied to the recording surface in advance by the processing liquid application unit 12, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. . Thereby, the color material flow on the recording medium 22 is prevented, and an image is formed on the recording surface of the recording medium 22. At that time, since the drawing drum 70 of the drawing unit 14 is structurally separated from the processing liquid drum 54 of the processing liquid applying unit 12, the processing liquid may adhere to the ink heads 72C, 72M, 72Y, and 72K. In addition, the cause of ink ejection failure can be reduced.

  In this ink droplet ejection, a plurality of inks (for example, CMYK different color inks or dark and light inks) are continuously deposited on the recording medium 22 to which the treatment liquid is applied in a planar shape (each ink overlaps). In general, the droplets are ejected in the same manner.

  In addition, as an example of the reaction between the ink and the treatment liquid, using a mechanism in which an acid is contained in the treatment liquid and the pigment dispersion is destroyed and aggregated by lowering the pH, the color material bleeds, the color mixture between the inks of each color, and the liquid upon landing of the ink droplets It is conceivable to avoid droplet ejection interference due to coalescence.

  Further, the droplet ejection timings of the ink heads 72C, 72M, 72Y, and 72K are synchronized with an encoder that detects the rotational speed disposed on the drawing drum 70. Thereby, the landing position can be determined with high accuracy. In addition, the fluctuation of the speed due to the deflection of the drawing drum 70 is learned in advance, and the droplet ejection timing obtained by the encoder 91 is corrected to obtain the deflection of the drawing drum 70, the accuracy of the rotation axis, and the speed of the outer peripheral surface of the drawing drum 70. Irregular droplet ejection can be reduced without depending on it.

  Further, maintenance operations such as cleaning the nozzle surfaces of the ink heads 72C, 72M, 72Y, and 72K and discharging the thickened ink may be performed by retracting the head unit from the drawing drum 70.

  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, and special colors are used as necessary. Ink may be added. For example, it is possible to add an ink head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

(Drying part)
The drying unit 16 is a step of drying moisture contained in the solvent separated by the color material aggregating action. The drying drum 76 and a first IR heater disposed at a position facing the outer peripheral surface of the drying drum 76. 78, a hot air jet nozzle 80, and a second IR heater 82. The first IR heater 78 is provided on the upstream side in the rotation direction of the drying drum 76 (counterclockwise direction in FIG. 1A) with respect to the hot air jet nozzle 80, and the second IR heater 82 is It is provided on the downstream side of the hot air jet nozzle 80.

  The drying drum 76 is a drum that holds the recording medium 22 on its outer peripheral surface and rotates and conveys the recording medium 22 and is driven to rotate. Further, the drying drum 76 includes a claw-shaped holding unit on the outer peripheral surface thereof, and the leading end of the recording medium 22 can be held by the holding unit. The recording medium 22 is rotated and conveyed by rotating the drying drum 76 with the tip held by the holding means. At that time, the recording surface of the recording medium 22 is conveyed so that the recording surface 22 faces outward, and a drying process is performed on the recording surface by the first IR heater 78, the hot air jet nozzle 80, and the second IR heater 82. Is called.

The hot air jet nozzle 80 is configured to blow hot air controlled to a predetermined temperature (for example, 50 ° C. to 70 ° C.) toward the recording medium 22 at a constant air volume (12 m ³ / min). The IR heater 78 and the second IR heater 82 are each controlled to a predetermined temperature (for example, 180 ° C.). By the first IR heater 78, the hot air jet nozzle 80, and the second IR heater 82, water contained in the ink solvent on the recording surface of the recording medium 22 held on the drying drum 76 is evaporated, and a drying process is performed. Is done. At that time, since the drying drum 76 of the drying unit 16 is structurally separated from the drawing drum 70 of the drawing unit 14, the head meniscus portion is dried by thermal drying in the ink heads 72 </ b> C, 72 </ b> M, 72 </ b> Y, 72 </ b> K. Ink ejection failure can be reduced. Moreover, there is a degree of freedom in setting the temperature of the drying unit 16, and an optimal drying temperature can be set.

  It is preferable to control the temperature so as to satisfy the relationship of Td <Tp, where Td is the temperature reached on the image surface in the drying step and Tp is the softening point of the self-dispersing polymer fine particles of the ink. By controlling Td <Tp, it is possible to prevent the dot diameter from being reduced and to prevent the occurrence of image curvature (the state in which the image is curved in a curved shape). Decrease in rubbing and image gloss can be prevented. Here, the softening temperature Tp of the self-dispersing polymer fine particles is preferably 30 ° C. or higher and 70 ° C. or lower. This is because when Tp is less than 30 ° C., offset due to insufficient drying occurs, and when Tp exceeds 70 ° C., the film property is insufficient under high-speed recording.

  The evaporated water may be discharged out of the apparatus together with air by a discharge means (not shown). Further, the recovered air may be cooled by a cooler (radiator) or the like and recovered as a liquid.

  Further, the drying drum 76 is preferably controlled at a predetermined temperature (for example, 60 ° C. or lower) on the outer peripheral surface thereof.

  Further, the drying drum 76 may be provided with suction holes on the outer peripheral surface thereof and connected to suction means for performing suction from the suction holes. As a result, the recording medium 22 can be held in close contact with the peripheral surface of the drying drum 76.

(Fixing part)
The fixing unit 18 includes a fixing drum 84, a first fixing roller 86, a second fixing roller 88, and an inline sensor 90. The first fixing roller 86, the second fixing roller 88, and the inline sensor 90 are disposed at a position facing the peripheral surface of the fixing drum 84, and are sequentially disposed from the upstream side in the rotation direction of the fixing drum 84. Although FIG. 1A shows an example in which the first and second fixing rollers 86 and 88 are provided, the first fixing roller 86 is replaced as shown in FIG. 1B. An IR heater 89 may be provided. By providing the IR heater 89, the flattening effect at the fixing nip by the fixing roller 88 can be increased by heating and softening the surface of the image before fixing. In this case, the surface heating temperature of the image by the IR heater 89 can be set to 60 ° C., for example.

  The fixing drum 84 is a drum that rotates and conveys the recording medium 22 while holding the recording medium 22 on the outer peripheral surface thereof, and is driven to rotate. Further, the fixing drum 84 is provided with a claw-shaped holding means on its outer peripheral surface, and the leading end of the recording medium 22 can be held by this holding means. The recording medium 22 is rotated and conveyed by rotating the fixing drum 84 with the tip held by the holding means. At that time, the recording surface of the recording medium 22 is conveyed so that it faces outward, and the recording surface is subjected to fixing processing by the first fixing roller 86 and the second fixing roller 88 and inspection by the inline sensor 90. Done.

  The first fixing roller 86 and the second fixing roller 88 are roller members for welding the self-dispersing polymer fine particles in the ink by heating and pressurizing the dried ink to form a film of the ink. The medium 22 is configured to be pressurized and heated. Specifically, each of the first fixing roller 86 and the second fixing roller 88 is disposed so as to be in pressure contact with the fixing drum 84, and constitutes a nip roller with the fixing drum 84. ing. As a result, the recording medium 22 is sandwiched between the first fixing roller 86 and the fixing drum 84 and between the second fixing roller 88 and the fixing drum 84 and is nipped at a predetermined nip pressure to be fixed. Processing is performed.

  Each of the first fixing roller 86 and the second fixing roller 88 is configured to be able to adjust the nip pressure. FIG. 2 shows an example of the nip pressure adjusting mechanism. 2 shows the nip pressure adjusting mechanism of the second fixing roller 88, the nip pressure adjusting mechanism of the first fixing roller 86 is configured similarly.

  As shown in FIG. 2, the second fixing roller 88 is supported by a frame 81, and this frame 81 is supported by a pressure bar 83. The pressure bar 83 is in contact with the pressure cam 85, and a motor 87 is connected to the pressure cam 85. By rotating the pressure cam 85 by the motor 87, the holding position of the pressure bar 83 is controlled and the nip pressure is adjusted. Further, the nip pressure can be released by separating the second fixing roller 88 from the fixing drum 84.

  The nip pressure adjusting mechanism of the first fixing roller 86 and the second fixing roller 88 is not limited to the pressure bar, and for example, a cylinder (not shown) that extends and contracts the rod in the radial direction of the fixing drum 84. May be used. Also in this case, the nip pressure can be adjusted and the nip pressure can be released. The nip pressure is preferably configured to be adjustable in the range of 0 MPa to 2 MPa.

  The fixing conditions of the first fixing roller 86 and the second fixing roller 88 are such that the dot diameter of the ink after being ejected and agglomerated by the drawing unit is equal to the ejection volume of the ink droplet ejected from the ink head. It is set so that the set dot diameter matches. Here, the set dot diameter is preferably 28 to 40 μm, and more preferably 30 to 38 μm, when the ink droplet discharge volume is 2 pL (picoliter). Moreover, it is preferable that the dod diameter difference between several inks is 4 micrometers or less.

  Various rollers can be used as the fixing rollers 86 and 88, but those having elasticity (easily deformable) are preferable. As an example, a roller having a single layer structure in which the core material of the fixing rollers 86 and 88 is covered with an elastic layer, a roller having a two-layer structure in which the elastic layer is further covered with a release layer, and an elastic layer between the release layer and the release layer. A three-layer roller having an intermediate layer can be mentioned.

  As the core material of the fixing rollers 86 and 88, various core materials having sufficient strength against pressure can be used, but those made of a material having good thermal conductivity are preferable. Specifically, aluminum rollers such as A5056, A5052, A5083, and A6063, nonmagnetic stainless steel rollers such as STKM11, and the like are preferably used.

  Since the fixing rollers 86 and 88 incorporate a heating source (lamp heater), a hollow cylindrical body is used. The elastic layer may be formed of synthetic rubber such as silicone rubber or fluorine rubber. In particular, in the case of a single layer configuration, LTV (low temperature vulcanization type) silicone rubber having excellent releasability from the recording medium after image recording can be preferably used. A preferred example of the fluororubber is Viton (manufactured by DuPont). Moreover, in order to improve the thermal conductivity at the time of heat-fixing, it is preferable that these synthetic rubbers contain 5 to 30% by mass of a metal oxide powder such as silica, alumina or magnesium oxide as a filler. For the same reason, conductive carbon black may be used as the filler. In this case, the electrical resistance of the elastic layer can be reduced to prevent charging. The elastic layer has a thickness of 1 to 8 mm. The rubber hardness is adjusted to a value suitable for the present invention within a range of 10 to 80, which is a value (hereinafter referred to as JIS A) measured using a type A durometer defined in JIS K 6253-1997. The release layer is for improving release properties from the recording medium. The release layer may be formed, for example, by covering the elastic layer with a tube made of PFA (fluororesin), or by forming a fluororesin paint such as PTFE, PFA, FEP or the like on the surface of the elastic layer. Also good. The release layer is preferably formed to a thickness of 10 to 100 μm. In this embodiment, a silicone rubber having a rubber hardness of 30 and a thickness of 4 mm is used as the elastic layer, and a PFA tube having a release layer of 30 μm is used. Further, by forming an intermediate layer formed by mixing fluororubber and fluororesin on the surface of the elastic layer and forming the release layer thereon, the elastic layer and the release layer are formed. A fixing roller having a three-layer structure is also preferable in order to improve adhesion to the layer and prevent damage to the release layer (crack generation, etc.) due to the buffering action of the intermediate layer.

  Furthermore, an HTV (high temperature vulcanization type) silicone rubber excellent in heat resistance is used as an elastic layer, and a fluororubber layer for preventing swelling of the elastic layer is provided thereon as an intermediate layer, and a release layer is provided on the intermediate layer. A fixing roller having a three-layer structure in which an LTV silicone rubber layer is provided is also suitable. In the present embodiment, as the configuration of the fixing rollers 86 and 88, the diameter and thickness of the core material, the width, the diameter and length of the shaft, and the like may be appropriately designed. In particular, as for the shape of the axial cross section of the fixing rollers 86 and 88, the thickness of the core material and the elastic layer is usually made constant, but the thickness depends on the axial position in consideration of the deflection of the roller and the paper sheet. The height may be changed, and a so-called crown shape or inverted crown shape may be used. As the fixing rollers 86 and 88, in addition to the above, the core material is a soft material obtained by coating a core material with a sponge-like foam rubber layer using a foam material such as a silicone rubber layer, a fluorine rubber layer, or silicone rubber. A roller can also be suitably used. Further, a hard roller in which the core material is covered with a fluororesin such as PTFE, PFA, or FEP, a PFT tube, or the like can be suitably used. As the fixing rollers 86 and 88, various known rollers can be used as long as they can withstand the pressing force for heat fixing. Needless to say, the roller incorporating the heat source is preferably formed of a material having high thermal conductivity.

  When the recording medium 22 is pressurized and heated by the first fixing roller 86 and the second fixing roller 88 configured as described above, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex contained in the ink. Is applied and the latex particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 22, and the unevenness on the surface of the image is leveled to obtain glossiness.

  In addition, since the nip pressure between the first fixing roller 86 and the second fixing roller 88 is set according to the dot diameter before fixing, an appropriate set dot corresponding to the ejection volume of the ejected ink is set. The diameter can be set.

  In the above-described embodiment, an example in which both heating and pressurization are performed is shown, but only one may be performed. Further, the first fixing roller 86 and the second fixing roller 88 may be provided in a plurality of stages depending on the thickness of the image film and the Tg characteristics of latex particles. Further, the surface of the fixing drum 84 may be controlled to a predetermined temperature (for example, 60 ° C.).

  On the other hand, the in-line sensor 90 is a measuring unit for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 22, and a CCD line sensor or the like is applied. The fixing drum 84 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 22 can be held in close contact with the peripheral surface of the fixing drum 84.

  In the fixing unit 18 configured as described above, the dot diameters after the fixing process of all inks ejected onto the recording medium 22 fall within the set dot diameter range, that is, 28 to 40 μm, and the dot diameters between the inks. The fixing conditions are controlled so that the difference is 4 μm or less. For example, by controlling so that the fixing conditions become stronger, it is possible to satisfy the set dot diameter by flattening and expanding the diameter of the ink that has not reached the set dot diameter among the plurality of inks.

  In addition, when droplets are ejected so as to overlap a plurality of inks, it is necessary to reduce the dot diameter difference between the inks in addition to satisfying the set dot diameter for all the inks after fixing. By controlling this, it is possible to reduce the dot diameter difference between the inks. For example, an appropriate dot diameter difference is 4 μm or less when the ejection volume of each ink droplet is 2 pL (picoritter).

  Further, as a further aspect of the present invention, ink dots that are ejected onto the recording medium 22 between the drawing unit 14 and the fixing unit 18, for example, above the intermediate conveyance body 30 between the drying unit 16 and the fixing unit 18. It is preferable to provide detection means (not shown) for detecting the diameter, and to control the fixing conditions in the fixing unit 18 based on the detected dot diameter before the fixing process.

  In the case of the present invention, a relational expression or a relational table is created by obtaining a fixing condition for setting the ink dot diameter to be a setting condition by an offline experiment or an online preliminary experiment, and based on that. Fixing conditions can be controlled (set). However, it is possible to cope with various disturbances that affect the dot diameter by providing a detecting means for detecting the dot diameter and controlling the fixing condition online based on the dot diameter detected by the detecting means. Can do. Disturbances affecting the dot diameter include, for example, the amount of flocculant contained in the processing liquid, the film thickness of the processing liquid applied to the recording medium, the recording medium temperature at the time of ink ejection, the image area ratio of the lower layer, and the recording medium In the detection step, the resulting dot diameter including these disturbances is detected. In addition, since the feedback control can be performed online by providing the detection means, the control can be automated.

  As a detection means to be used, for example, a CCD camera can be suitably used. There is a method in which a spot where an ink droplet has landed is captured by a CCD camera, captured in an electronic image, binary processing is performed using a luminance value as a threshold value, and a dot diameter is calculated from the number of pixels.

  Thus, in the two-liquid aggregation method, when the recording liquid 22 is uniformly coated with a treatment liquid containing an aggregating agent and is continuously ejected so as to superimpose a plurality of inks, The dot diameter can be set to a set dot diameter commensurate with the ink droplet ejection volume, and the tod diameter difference between the inks can be reduced, so that the image quality can be improved.

  In the present invention, the fixing condition factor (variable) is at least one of the nip pressure of the fixing roller, the number of nips, the temperature of the fixing roller, the nip time, and the elapsed time from the ink droplet ejection process to the fixing process. Preferably there is. In particular, it is preferable to control the nip pressure of the fixing roller, the number of nips, and the temperature of the fixing roller.

(Discharge part)
As shown in FIG. 1A, a discharge unit 20 is provided following the fixing unit 18. The discharge unit 20 includes a discharge tray 92, and a transfer drum 94, a conveyance belt 96, and a tension roller 98 are provided between the discharge tray 92 and the fixing drum 84 of the fixing unit 18 so as to be in contact therewith. It has been. The recording medium 22 is sent to the transport belt 96 by the transfer drum 94 and discharged to the discharge tray 92.

(Intermediate transport section)
Next, the structure of the first intermediate transport unit 24 will be described. Note that the second intermediate conveyance unit 26 and the third intermediate conveyance unit 28 have the same configuration as the first intermediate conveyance unit 24, and a description thereof will be omitted.

  The first intermediate transport unit 24 includes an intermediate transport body 30. The intermediate conveyance body 30 is a drum for receiving the recording medium 22 from the preceding drum, rotating and conveying it to the subsequent drum, and is rotatably attached. Further, the intermediate transport body 30 is rotated by a motor (not shown).

  Claw-shaped holding means are provided at 90 ° intervals on the outer peripheral surface of the intermediate conveyance body 30. The holding unit rotates while drawing a circular locus, and the tip of the recording medium 22 is held by the operation of the holding unit. Accordingly, the recording medium 22 can be rotated and conveyed by rotating the intermediate conveyance body 30 with the holding means holding the tip of the recording medium 22. The recording surface of the recording medium may be conveyed in a non-contact manner by providing a plurality of air outlets on the surface of the intermediate carrier 30 and blowing out air from the air outlets.

  The recording medium 22 transported by the first intermediate transport unit 24 is transferred to the subsequent drum (that is, the drawing drum 70). At this time, the recording medium 22 is delivered by synchronizing the holding means of the intermediate transport unit 24 and the holding means of the drawing unit 14. The transferred recording medium 22 is held and drawn by the drawing drum 70.

(Ink head structure)
Next, the structure of each ink head will be described. Since the ink heads 72C, 72M, 72Y, and 72K for each color have the same structure, the ink heads are represented by the reference numeral 100 in the following.

  3A is a plan perspective view showing an example of the structure of the ink head 100, and FIG. 3B is an enlarged view of a part thereof. In order to increase the dot pitch printed on the recording medium 22, it is necessary to increase the nozzle pitch in the ink head 100. As shown in FIGS. 3A and 3B, the ink head 100 according to this example includes a plurality of ink chamber units (a plurality of ink chamber units) each including a nozzle 102 serving as an ink discharge port, a pressure chamber 104 corresponding to each nozzle 102, and the like. It has a structure in which droplet ejection elements 108 as recording element units are arranged in a zigzag matrix (two-dimensionally), and thereby, in the longitudinal direction of the head (direction perpendicular to the conveyance direction of the recording medium 22). A high density of substantial nozzle intervals (projection nozzle pitch) projected so as to be aligned along the line is achieved.

  One or more nozzle rows are formed over a length corresponding to the entire width of the image forming area of the recording medium 22 in a direction (arrow M in FIG. 3) substantially orthogonal to the conveyance direction of the recording medium 22 (arrow S in FIG. 3). The form is not limited to the illustrated example. For example, instead of the configuration of FIG. 3A, as shown in FIG. 4, long head modules 100 ′ in which a plurality of nozzles 102 are two-dimensionally arranged are arranged in a staggered manner and connected to each other. Therefore, a line head having a nozzle row having a length corresponding to the entire width of the image forming area of the recording medium 22 as a whole may be configured.

  The pressure chamber 104 provided corresponding to each nozzle 102 has a substantially square planar shape (see FIGS. 3A and 3B), and the nozzle 102 is provided at one of the diagonal corners. An outlet for supplying ink (supply port) 106 is provided on the other side. The shape of the pressure chamber 104 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, other polygons, a circle, an ellipse, and the like.

  FIG. 5 is a cross-sectional view showing a three-dimensional configuration of a droplet ejection element for one channel (an ink chamber unit corresponding to one nozzle 102) serving as a recording element unit in the ink head 100 (X in FIG. 3A). FIG.

  As shown in FIG. 5, each pressure chamber 104 communicates with the common flow path 110 via the supply port 106. The common flow path 110 communicates with an ink tank (not shown) as an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 104 via the common flow path 110.

  An actuator 116 having an individual electrode 114 is joined to a pressure plate (a diaphragm used also as a common electrode) 112 constituting a part of the pressure chamber 104 (the top surface in FIG. 5). By applying a driving voltage between the individual electrode 114 and the common electrode, the actuator 116 is deformed to change the volume of the pressure chamber 104, and ink is ejected from the nozzle 102 due to the pressure change accompanying this. For the actuator 116, a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate is preferably used. When the displacement of the actuator 116 returns to the original state after ink ejection, new ink is refilled into the pressure chamber 104 from the common flow path 110 through the supply port 106.

  By controlling the driving of the actuator 116 corresponding to each nozzle 102 in accordance with dot data generated by digital halftoning processing from the input image, ink droplets can be ejected from the nozzle 102. A desired image can be recorded on the recording medium 22 by controlling the ink ejection timing of each nozzle 102 in accordance with the conveyance speed while conveying the recording medium 22 in the sub-scanning direction at a constant speed.

  As shown in FIG. 6, the ink chamber units 108 having the above-described structure are 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, the pitch P of the nozzles projected (orthographically projected) so as to be aligned in the main scanning direction by a structure in which a plurality of ink chamber units 108 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction. D × cos θ, and in the main scanning direction, each nozzle 102 can be handled equivalently as a linear array with a constant pitch P. With such a configuration, it is possible to realize a substantial increase in the density of nozzle rows projected so as to be aligned in the main scanning direction.

  When the nozzles are driven by 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 each block is sequentially driven from one side to the other, etc., and one line (by one row of dots) in a direction perpendicular to the conveyance direction of the recording medium 22 Driving a nozzle that prints a line or a line composed of a plurality of rows of dots is defined as main scanning.

  In particular, when driving the nozzles 102 arranged in a matrix as shown in FIG. 6, the main scanning as described in (3) above is preferable. That is, nozzles 102-11, 102-12, 102-13, 102-14, 102-15, 102-16 are made into one block (other nozzles 102-21,..., 102-26 are made into one block, , 102-36 as one block,..., And by sequentially driving the nozzles 102-11, 102-12,. One line is printed in a direction orthogonal to the 22 conveyance direction.

  On the other hand, by moving the full line head and the recording medium 22 relative to each other, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) formed by the main scanning described above is repeatedly performed. This is defined as sub-scanning.

  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. That is, in the present embodiment, the conveyance direction of the recording medium 22 is the sub-scanning direction, and the direction orthogonal to the recording medium 22 is the main scanning direction. In implementing the present invention, the nozzle arrangement structure is not limited to the illustrated example.

  In this embodiment, a method of ejecting ink droplets by deformation of an actuator 116 typified by a piezo element (piezoelectric element) is employed. However, the method of ejecting ink is not particularly limited in implementing the present invention. 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.

(Description of control system)
FIG. 7 is a principal block diagram showing the system configuration of the inkjet recording apparatus 1. The ink jet recording apparatus 1 includes a communication interface 120, a system controller 122, a print controller 124, a treatment liquid application controller 126, a first intermediate transport controller 128, a head driver 130, a second intermediate transport controller 132, and a drying controller 134. A third intermediate transport control unit 136, a fixing control unit 138, an inline sensor 90, an encoder 91, a motor driver 142, a memory 144, a heater driver 146, an image buffer memory 148, a suction control unit 149, and the like.

  The communication interface 120 is an interface unit that receives image data sent from the host computer 150. As the communication interface 120, 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 150 is taken into the inkjet recording apparatus 1 via the communication interface 120 and temporarily stored in the memory 144.

  The system controller 122 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 1 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 122 includes the communication interface 120, the treatment liquid application controller 126, the first intermediate transport controller 128, the head driver 130, the second intermediate transport controller 132, the drying controller 134, and the third intermediate transport controller 136. , Fixing control unit 138, memory 144, motor driver 142, heater driver 146, suction control unit 149, and the like to control communication with host computer 150, read / write control of memory 144, etc. A control signal for controlling the motor 152 and the heater 154 is generated.

  The memory 144 is a storage unit that temporarily stores an image input via the communication interface 120, and data is read and written through the system controller 122. The memory 144 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The ROM 145 stores programs executed by the CPU of the system controller 122 and various data necessary for control. The ROM 145 may be a non-rewritable storage unit, or may be a rewritable storage unit such as an EEPROM. The memory 144 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 motor driver 142 is a driver that drives the motor 152 in accordance with an instruction from the system controller 122. In FIG. 7, the motors arranged in the respective units in the apparatus are represented by reference numeral 152 as a representative. For example, the motor 152 shown in FIG. 7 includes a motor for driving rotation of the transfer drum 52, the treatment liquid drum 54, the drawing drum 70, the drying drum 76, the fixing drum 84, the transfer drum 94, and the like shown in FIG. A drive motor for the pump 75 for sucking negative pressure from the suction hole of the drum 70, a motor for a retraction mechanism for the head units of the ink heads 72C, 72M, 72Y, 72K, and the like are included.

  The heater driver 146 is a driver that drives the heater 154 in accordance with an instruction from the system controller 122. In FIG. 7, a plurality of heaters provided in the inkjet recording apparatus 1 are represented by reference numeral 154 as a representative. For example, the heater 154 shown in FIG. 7 includes a preheater (not shown) for heating the recording medium 22 to an appropriate temperature in the paper feeding unit 10 in advance.

  The print control unit 124 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 144 under the control of the system controller 122, and the generated print. It is a control unit that supplies data (dot data) to the head driver 130. Necessary signal processing is performed in the print control unit 124, and the ejection amount and ejection timing of the ink droplets of the ink head 100 are controlled via the head driver 130 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 124 includes an image buffer memory 148, and image data, parameters, and other data are temporarily stored in the image buffer memory 148 when image data is processed in the print control unit 124. In FIG. 7, the image buffer memory 148 is shown in a mode associated with the print control unit 124, but it can also be used as the memory 144. Also possible is an aspect in which the print control unit 124 and the system controller 122 are integrated to form a single processor.

  An outline 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 120 and stored in the memory 144. At this stage, for example, RGB image data is stored in the memory 144.

  In the ink jet recording apparatus 1, 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 memory 144 is sent to the print control unit 124 via the system controller 122, and the print control unit 124 performs halftoning processing using a threshold matrix, an error diffusion method, or the like. Is converted into dot data for each ink color.

  That is, the print control unit 124 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 124 is stored in the image buffer memory 148.

  The head driver 130 is a drive signal for driving the actuator 116 corresponding to each nozzle 102 of the ink head 100 based on print data (that is, dot data stored in the image buffer memory 148) given from the print control unit 124. Is output. The head driver 130 may include a feedback control system for keeping the head driving condition constant.

  When the drive signal output from the head driver 130 is applied to the ink head 100, ink is ejected from the corresponding nozzle 102. An image is formed on the recording medium 22 by controlling the ink ejection from the ink head 100 while conveying the recording medium 22 at a predetermined speed.

  Further, the system controller 122 includes a processing liquid application control unit 126, a first intermediate conveyance control unit 128, a second intermediate conveyance control unit 132, a drying control unit 134, a third intermediate conveyance control unit 136, a fixing control unit 138, and suction control. The unit 149 is controlled.

  The treatment liquid application control unit 126 controls the operation of the treatment liquid application device 56 of the treatment liquid application unit 12 in accordance with an instruction from the system controller 122.

The first intermediate conveyance control unit 128 controls the operation of the intermediate conveyance body 30 of the first intermediate conveyance unit 24 in accordance with an instruction from the system controller 122. Specifically, in the intermediate transport body 30, the rotational drive of the intermediate transport body 30 itself, the rotation of the holding means provided in the intermediate transport body 30, and the like are controlled. The second intermediate transfer control unit 132 and the third intermediate transfer control unit 136 also perform the same control as the first intermediate transfer control unit 128.
(Other forms of inkjet recording apparatus)
The inkjet recording apparatus 1 described above is an example in which the recording medium 22 is conveyed by a drum, but may be conveyed by a belt. FIG. 8 schematically shows the configuration of the belt conveyance type inkjet recording apparatus 2. Note that members having substantially the same configuration and function as those of the ink jet recording apparatus 1 shown in FIG.

  The ink jet recording apparatus 2 shown in FIG. 8 mainly includes a processing liquid application unit 12, a drawing unit 14, a drying unit 16, and a fixing unit 18, and the recording medium 22 is conveyed by the suction belt conveyance device 200.

  The suction belt conveyance device 200 includes a pair of rollers 202 and an endless belt 204 wound around the rollers 202, and at least one of the pair of rollers 202 is rotationally driven by a motor or the like (not shown). As a result, the belt 204 travels between the pair of rollers 202.

  The belt 204 has a width wider than that of the recording medium 22, and a plurality of suction ports (not shown) are formed on the upper surface of the belt 204. An adsorption chamber (not shown) is provided inside the belt 204. The adsorption chamber is provided at a position facing the processing liquid application unit 12 and the drawing unit 14, and the suction chamber is sucked with a pump (not shown) or the like to make a negative pressure, thereby recording medium 22 on belt 204. Can be adsorbed and held.

  Although a mechanism using a nip conveyance mechanism with a roller may be used in place of the suction belt conveyance device 200, if the 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 is easily stained. There's a problem. 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.

  By the suction belt conveyance device 200 described above, the recording medium 22 is conveyed from the paper supply unit (not shown) to the treatment liquid application unit 12. The processing liquid application unit 12 includes a nozzle-like recording head 206, and is configured to discharge the processing liquid from the recording head 206 toward the recording medium 22. As a result, the treatment liquid is applied to the recording medium 22 to form a treatment liquid layer. The treatment liquid application unit 12 is not limited to the method of discharging from the nozzle-shaped recording head 206, and an application method using an application roller can also be adopted.

  The recording medium 22 to which the treatment liquid is applied is heated by a hot air supply device 208 that supplies hot air to the upper surface of the recording medium 22 and a heating panel 210 disposed below the recording medium 22. The heating temperature at that time is preferably a temperature equal to or higher than the softening point temperature of the solid particles or a temperature equal to or higher than the melting point temperature.

  The recording medium 22 subjected to the drying process is sent to the drawing unit 14, and ink is ejected from each of the inkjet heads 72M, 72C, 72Y, 72K.

  A drying unit 16 is provided following the drawing unit 14. The drying unit 16 is a device that removes a solvent component remaining on the recording medium 22 on which each color ink is ejected. A hot air supply device 212 that supplies hot air to the upper surface of the recording medium 22, and a lower part of the recording medium 22. A heating panel 214 is provided. The solvent on the recording medium 22 is removed by the drying unit 16.

  A fixing unit 18 is provided following the drying unit 16. The fixing unit 18 includes fixing rollers 216 and 218 arranged with the recording medium 22 interposed therebetween. By pressing and heating with the fixing rollers 216 and 218, an image on the recording medium 22 is recorded. To be established.

  At least one of the fixing rollers 216 and 218 is supported so as to be movable forward and backward with respect to the other fixing roller 216 and 218. Accordingly, the nip pressure by the fixing rollers 216 and 218 can be adjusted, and the nip pressure can be released. The nip pressure by the fixing rollers 216 and 218 is adjusted according to the surface roughness of the recording medium 22.

  Also in the case of the ink jet recording apparatus 2 configured as described above, in the two-liquid aggregation method, the treatment liquid containing the aggregating agent is uniformly applied to the recording medium 22 and the continuous printing is performed so that a plurality of inks are superimposed. In the case of droplets, the dot diameter of the ink after aggregation can be set to a set dot diameter corresponding to the ejection volume of the ink droplets, and the difference in todd diameter between inks can be reduced, so that the image quality can be improved.

  The above has described the ink jet recording apparatus and the ink jet recording method of the present invention in detail. However, the present invention is not limited to the above examples, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

[recoding media]
The recording medium used in the present invention is not particularly limited, but a particularly preferable result can be obtained with respect to the coated paper for printing in which the penetration of the ink solvent is slow.

  Examples of the support that can be suitably used for coated paper include: chemical pulp such as LBKP and NBKP; mechanical pulp such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP; wood pulp such as waste paper pulp such as DIP And a pigment as a main component, and one or more kinds of additives such as a binder, a sizing agent, a fixing agent, a yield improver, a cationizing agent, and a paper strength enhancer are mixed together to produce a long net paper machine, circular net paper machine. Base paper manufactured using various machines such as a machine, twin-wire paper machine, base paper provided with size press or anchor coat layer using starch, polyvinyl alcohol, etc., or of these size press or anchor coat layer Examples thereof include coated paper such as art paper, coated paper, cast coated paper and the like, on which a coating layer is provided.

The basis weight of the support is usually about 40 to 300 g / m ² , but is not particularly limited. The coated paper used in the present invention is coated with a coating layer on the support as described above. The coating layer is composed of a coating composition mainly composed of a pigment and a binder, and is coated on at least one layer on the support.

  As the pigment, a white pigment can be preferably used. Examples of such white pigments include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc sulfide, zinc carbonate, satin white, aluminum silicate, Inorganic pigments such as diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, hydrous halloysite, magnesium hydroxide; styrene plastic pigments, Examples thereof include organic pigments such as acrylic plastic pigment, polyethylene, microcapsule, urea resin, melamine resin.

  Examples of the binder include starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein, gelatin, soybean protein, polyvinyl alcohol or derivatives thereof; various saponification degrees Polyvinyl alcohol or various derivatives thereof such as silanol-modified products, carboxylated products, and cationized products thereof; conjugated diene copolymer latexes such as polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer, and methyl methacrylate-butadiene copolymer Acrylic polymer latex such as polymer or copolymer of acrylic acid ester and methacrylic acid ester; vinyl polymer latex such as ethylene vinyl acetate copolymer; Functional group-modified polymer latex with functional group-containing monomers such as xy groups; water-based adhesives such as thermosetting synthetic resins such as melamine resins and urea resins; acrylics such as polymethyl methacrylate; acid esters; Polymer or copolymer resin; Synthetic resin adhesives such as polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, alkyd resin, and the like. The blending ratio of the pigment and binder in the coating layer is 3 to 70 parts by weight, preferably 5 to 50 parts by weight, based on 100 parts by weight of the pigment. When the blending ratio of the binder with respect to 100 parts by weight of the pigment is less than 3 parts by weight, the coating strength of the ink receiving layer made of such a coating composition may be insufficient. On the other hand, when the blending ratio exceeds 70 parts by weight, the absorption of the high boiling point solvent becomes extremely slow.

  Further, the coating layer includes, for example, a dye fixing agent, a pigment dispersant, a thickener, a fluidity improver, an antifoaming agent, a foam suppressor, a release agent, a foaming agent, a penetrating agent, a coloring dye, a coloring pigment, Various additives such as a fluorescent whitening agent, an ultraviolet absorber, an antioxidant, an antiseptic, an antibacterial agent, a water resistant agent, a wet paper strength enhancer, and a dry paper strength enhancer can be appropriately blended.

The coating amount of the ink receiving layer varies depending on the required gloss, ink absorbability, type of support, etc., and cannot be generally stated, but is usually 1 g / m ² or more. Further, the ink receiving layer may be applied by dividing a certain coating amount into two portions. When coating is performed in two steps in this way, the gloss is improved as compared with the case where the same coating amount is applied once.

  Coating of the coating layer is performed by using various devices such as various blade coaters, roll coaters, air knife coaters, bar coaters, rod blade coaters, curtain coaters, short dwell coaters, and size presses on-machine or off-machine. be able to. Further, after coating the coating layer, the ink receiving layer may be flattened using a calendar device such as a machine calendar, a TG calendar, or a soft calendar. In addition, the number of coat layers can be appropriately determined as necessary.

The coated paper includes art paper, high-quality coated paper, medium-quality coated paper, high-quality lightweight coated paper, medium-sized lightweight coated paper, and fine-coated printing paper. The coating amount of the coating layer is art paper and both sides are 40 g / m ^2. Front and back, high-quality coated paper, medium-sized coated paper, double-sided around 20 g / m ² , high-quality lightweight coated paper, medium-sized light-weight coated paper, both sides around 15 g / m ² , fine-coated printing paper both sides 12 g / m ² or less It is. Examples of art paper include Tokuhishi Art, Ulite as high-quality coated paper, Tohoku Art (made by Mitsubishi Paper Industries), satin Kinto (made by Oji Paper Co., Ltd.), etc. as art paper, Examples of coated paper include OK Top Coat (Oji Paper Co., Ltd.), Aurora Coat (Nippon Paper Co., Ltd.), and Recycle Coat T-6 (Nippon Paper Co., Ltd.). , New V mat (Mitsubishi Paper Co., Ltd.), New Age (Oji Paper Co., Ltd.), Recycle Mat T-6 (Nihon Paper Co., Ltd.), Pisum (Nihon Paper Co., Ltd.). Examples of the fine coated printing paper include Aurora L (manufactured by Nippon Paper Industries Co., Ltd.), Kinmari Hi-L (manufactured by Hokuetsu Paper Industries Co., Ltd.) and the like. Further, examples of the cast coated paper include SA Kanto Plus (manufactured by Oji Paper Co., Ltd.), Hi McKinley Art (manufactured by Gojo Paper Co., Ltd.), and the like.

[Water-based ink]
Hereinafter, although the water-based ink used by embodiment of this invention is demonstrated in detail, this invention is not limited to a water-based ink, It can apply also to oil-based ink.

  The aqueous ink includes at least a resin dispersant (A), a pigment (B) dispersed by the resin dispersant (A), self-dispersing polymer fine particles (C), and an aqueous liquid medium (D). Yes.

<Resin dispersant (A)>
The resin dispersant (A) is used as a dispersant for the pigment (B) in the aqueous liquid medium (D), and any resin that can disperse the pigment B may be used. The structure of the agent (A) preferably has a hydrophobic structural unit (a) and a hydrophilic structural unit (b). If necessary, the resin dispersant (A) can include a structural unit (c) different from the hydrophobic structural unit (a) and the hydrophilic structural unit (b).

  The composition of the hydrophilic structural unit (b) and the hydrophobic structural unit (a) depends on the degree of hydrophilicity and hydrophobicity of each, but the hydrophobic structural unit (a) is the entire resin dispersant (A). It is preferable to contain more than 80 mass% with respect to the mass of, and 85 mass% or more is more preferable. That is, the hydrophilic structural unit (b) needs to be 15% by mass or less, and when the hydrophilic structural unit (b) is more than 15% by mass, the aqueous liquid medium alone does not contribute to the dispersion of the pigment. The component dissolved in (D) increases, which deteriorates various properties such as the dispersibility of the pigment (B), and causes the discharge properties of the inkjet recording ink to deteriorate.

  Specific preferred examples of the resin dispersant (A) in the present invention are shown below, but the present invention is not limited to the following.

〈顔料（Ｂ）と樹脂分散剤（Ａ）の比率〉
顔料（Ｂ）と樹脂分散剤（Ａ）の比率は、重量比で１００：２５〜１００：１４０が好ましく、さらに好ましくは１００：２５〜１００：５０である。樹脂分散剤が１００：２５以上の場合は分散安定性と耐擦性が良化する傾向となる。樹脂分散剤が１００：１４０以下の場合も、分散安定性が良化する傾向となる。

<Ratio of pigment (B) to resin dispersant (A)>
The weight ratio of the pigment (B) and the resin dispersant (A) is preferably 100: 25 to 100: 140, and more preferably 100: 25 to 100: 50. When the resin dispersant is 100: 25 or more, the dispersion stability and the abrasion resistance tend to be improved. When the resin dispersant is 100: 140 or less, the dispersion stability tends to be improved.

<Pigment (B)>
In the present invention, the pigment (B) is a colored substance (inorganic) which is almost insoluble in water and organic solvents, as described on page 518 of the Chemical Dictionary 3rd edition published on April 1, 1994 (edited by Michinori Oki et al.). In the present invention, organic pigments and inorganic pigments can be used.

  In the present invention, the “pigment (B) dispersed by the resin dispersant (A)” means a pigment dispersed and held by the resin dispersant (A), and the resin dispersed in the aqueous liquid medium (D). The pigment is preferably used as a pigment dispersed and held using the agent (A). The aqueous liquid medium (D) may or may not contain a dispersant.

  In the present invention, the pigment (B) dispersed by the resin dispersant (A) is not particularly limited as long as it is a pigment dispersed and held by the resin dispersant (A). From the viewpoint of ejection stability, a microencapsulated pigment produced by a phase inversion method is more preferable.

  A preferred example of the pigment (B) contained in the present invention is a microencapsulated pigment. The microencapsulated pigment is a pigment in which the pigment is coated with the resin dispersant (A).

  The resin of the microencapsulated pigment needs to use the resin dispersant (A), and is a polymer having self-dispersibility or solubility in water and an anionic group (acidic). It is preferable to use the compound for a resin other than the resin dispersant (A).

  Examples of the pigment usable in the present invention include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 14C, 16, 17, 24, 34, 35, 37, 42, 53, 55, 65, 73, 74, 75, 81, 83, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 128, 129, 138, 150, 151, 153, 154, 155, 180 etc. are mentioned.

  Examples of magenta ink pigments include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 48 (Ca), 48 (Mn), 48: 2, 48: 3, 48: 4, 49, 49: 1, 50, 51, 52, 52: 2, 53: 1, 53, 55, 57 (Ca), 57: 1, 60, 60: 1, 63: 1, 63: 2, 64, 64: 1, 81, 83, 87, 88, 89, 90, 101 (Bengara) ), 104, 105, 106, 108 (cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 163, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 209, 2 9 and the like, in particular, C. I. Pigment Red 122 is preferable.

  Further, as pigments for cyan ink, C.I. I. Pigment blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, 17: 1, 22, 25, 56, 60, C.I. I. Bat blue 4, 60, 63 and the like. I. Pigment Blue 15: 3 is preferable.

  Examples of other color ink pigments include C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, C.I. I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19 (quinacridone red), 23, 38, and the like. In addition, processed pigments such as graft carbon whose surface is treated with a resin or the like can also be used.

An example of the black type is carbon black. Specific examples of such carbon black include No. 1 manufactured by Mitsubishi Chemical. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, No2200B, etc. are Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc., manufactured by Columbia, Regal 400R, Regal 330R, Regal 800R, Mal 80 , Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. are color blacks manufactured by Degussa.
FW1, ColorBlack FW2, Color Black FW2V, Color Black FW18, Color Black FW200, ColorBlack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black4A , Special Black 4 and the like.

  The above pigments may be used alone or in combination of a plurality selected from the above-mentioned groups or between the groups.

  The content of the pigment (B) in the aqueous ink in the present invention is preferably 1 to 10% by mass, more preferably 2 to 8% by mass, and 2 to 6% by mass from the viewpoint of dispersion stability and concentration of the aqueous ink. % Is particularly preferred.

<Self-dispersing polymer fine particles (C)>
The water-based ink used in the present invention contains at least one kind of self-dispersing polymer fine particles. The self-dispersing polymer fine particles in the present invention are water-insoluble which can be dispersed in an aqueous medium by a functional group (particularly an acidic group or a salt thereof) of the pr resin itself in the absence of other surfactant. It refers to fine particles of a water-insoluble polymer which is a polymer and does not contain a free emulsifier.

  Here, the dispersed state refers to both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in an aqueous medium in a solid state. It includes the state of.

  The water-insoluble polymer in the present invention is a water-insoluble polymer that can be in a dispersed state in which the water-insoluble polymer is dispersed in a solid state from the viewpoint of ink aggregation rate and ink fixability when contained in a water-soluble ink. preferable.

  The self-dispersing polymer fine particles in the present invention include a structural unit derived from an aromatic group-containing (meth) acrylate monomer, and the content is preferably 10% by mass to 95% by mass. When the content of the aromatic group-containing (meth) acrylate monomer is 10% by mass to 95% by mass, the stability of the self-emulsification or dispersion state can be improved, and further the increase in ink viscosity can be suppressed.

  In the present invention, from the viewpoints of stability in a self-dispersing state, stabilization of particle shape in an aqueous medium due to hydrophobic interaction between aromatic rings, and reduction in the amount of water-soluble components due to appropriate hydrophobicization of particles. More preferably, the content is from mass% to 90 mass%, more preferably from 15 mass% to 80 mass%, and particularly preferably from 25 mass% to 70 mass%.

  The self-dispersing polymer fine particles in the present invention can be composed of, for example, a structural unit composed of an aromatic group-containing monomer and a structural unit composed of a dissociable group-containing monomer. Can further be included.

  The molecular weight range of the water-insoluble polymer constituting the self-dispersing polymer fine particles in the present invention is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. More preferably it is. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less. The weight average molecular weight can be measured by gel permeation chromatography (GPC).

  From the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer, the water-insoluble polymer constituting the self-dispersing polymer fine particles in the present invention comprises an aromatic group-containing (meth) acrylate monomer as a copolymerization ratio of 15 to 90% by mass, a carboxyl group-containing monomer, And an alkyl group-containing monomer, preferably having an acid value of 25 to 100 and a weight average molecular weight of 3000 to 200,000, and an aromatic group-containing (meth) acrylate monomer as a copolymerization ratio of 15 to 80 mass. %, A carboxyl group-containing monomer, and an alkyl group-containing monomer, an acid value of 25 to 95, and a weight average molecular weight of 5000 to 150,000 are more preferable.

  The average particle size of the self-dispersing polymer fine particles in the present invention is preferably in the range of 10 to 400 nm, more preferably 10 to 200 nm, and further preferably 10 to 100 nm. Manufacturability is improved when the average particle diameter is 10 nm or more. Moreover, storage stability improves by setting it as an average particle diameter of 400 nm or less.

  Further, the particle size distribution of the self-dispersing polymer fine particles is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Further, two or more kinds of water-insoluble particles may be mixed and used.

  The average particle size and particle size distribution of the self-dispersing polymer fine particles can be measured using, for example, a light scattering method.

  The self-dispersing polymer fine particles of the present invention can be suitably contained in, for example, an aqueous ink composition, and can be used alone or in combination of two or more.

<Aqueous liquid medium (D)>
In the inkjet recording water-based ink, the aqueous liquid medium (D) represents a mixture of water and a water-soluble organic solvent. Water-soluble organic solvents (hereinafter also referred to as “water-soluble organic solvents”) are used for the purpose of drying inhibitors, wetting agents or penetration enhancers.

  The ink composition uses a water-soluble solvent for the purpose of an anti-drying agent, a wetting agent or a penetration accelerator. In particular, when used as an aqueous ink composition of an ink jet recording system, a water-soluble organic solvent is preferably used for the purpose of a drying inhibitor, a wetting agent or a penetration accelerator.

  Anti-drying agents and wetting agents are used for the purpose of preventing clogging due to drying of the ink-jet ink at the nozzles, and the anti-drying agents and wetting agents are water-soluble organic compounds having a vapor pressure lower than that of water. Solvents are preferred.

  In addition, a water-soluble organic solvent is suitably used as a penetration accelerator for the purpose of allowing the ink composition (particularly, the ink-jet ink composition) to permeate the paper better.

  In the present invention, for the purpose of suppressing curling, (a) the water-soluble solvent contains 90% by mass or more of a water-soluble solvent having an SP value of 27.5 or less, and is represented by the following structural formula (1). Containing compounds. Here, the “water-soluble solvent having an SP value of 27.5 or less” and the “compound represented by the structural formula (1)” may be the same or different.

  The solubility parameter (SP value) of the water-soluble solvent referred to in the present invention is a value represented by the square root of the molecular cohesive energy. F. It can be calculated by the method described in Fedors, Polymer Engineering Science, 14, p147 (1967), and this numerical value is adopted in the present invention.

  The water-soluble solvent (a) used in the present invention may be used alone or in combination of two or more.

  (A) The content of the water-soluble solvent is preferably 1% by mass or more and 60% by mass or less, and more preferably 5% by mass or more and 40% by mass or less from the viewpoint of ensuring stability and ejection reliability in the entire ink composition. Preferably, 10 mass% or more and 30 mass% or less are used especially preferably.

  The amount of water (c) used in the present invention is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less from the viewpoint of ensuring stability and ejection reliability in the entire ink composition. More preferably, they are 30 mass% or more and 80 mass% or less, More preferably, they are 50 mass% or more and 70 mass% or less.

<Surfactant>
It is preferable to add a surfactant (hereinafter also referred to as a surface tension adjusting agent) to the water-based ink in the invention. Examples of the surfactant include nonionic, cationic, anionic and betaine surfactants. The addition amount of the surface tension adjusting agent is preferably an amount for adjusting the surface tension of the water-based ink in the present invention to 20 to 60 mN / m, more preferably 20 to 45 mN / m, in order to eject ink droplets well by inkjet. More preferably, the amount can be adjusted to 25 to 40 mN / m.

  As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively. Anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant Any of the surfactants can be used. Furthermore, the above-mentioned polymer substance (polymer dispersing agent) can also be used as a surfactant.

<Other ingredients>
The water-based ink used in the present invention may contain other additives. Other additives include, for example, ultraviolet absorbers, anti-fading agents, anti-mold agents, pH adjusters, rust inhibitors, antioxidants, emulsion stabilizers, preservatives, antifoaming agents, viscosity modifiers, and dispersion stabilizers. Known additives such as agents and chelating agents are included.

[Treatment solution]
The aqueous treatment liquid in the present invention contains at least one fixing agent for fixing components in the aqueous ink. The fixing agent in the present invention can fix (aggregate) water-based ink by contacting with water-based ink on paper. For example, by applying an aqueous treatment liquid, when the aqueous ink is deposited and contacted in the state where the fixing agent is present on the paper, the components in the aqueous ink can be aggregated and immobilized on the paper. it can.

  Since it is desirable that the water-based ink can be fixed (aggregated), it is preferable that the material be easily dissolved in the water-based ink when coming into contact with the water-based ink. In this respect, the highly water-soluble polyvalent metal salt is more An acidic substance having a high water solubility is more preferable. Further, from the viewpoint of fixing the entire ink by reacting with the aqueous ink, an acidic substance having a valence of 2 or more is particularly preferable. Moreover, a cationic compound can also be used as a fixing agent.

  Here, the aggregation reaction of the water-based ink can be achieved by reducing the dispersion stability of particles dispersed in the water-based ink (colorant (for example, pigment), resin particles, etc.) and increasing the viscosity of the entire ink. it can. For example, by reducing the surface charge of particles such as pigments and resin particles in inks that are stabilized by weakly acidic functional groups such as carboxyl groups by reacting with acidic substances with lower pKa, the dispersion stability is lowered. can do. Therefore, the acidic substance as the fixing agent contained in the aqueous treatment liquid preferably has a low pKa, a high solubility, and a valence of 2 or more, and a functional group that stabilizes the dispersion of particles in the ink. More preferably, it is a divalent or trivalent acidic substance having a high buffering capacity in a pH range lower than the pKa (for example, carboxyl group).

  Specific examples include phosphoric acid, oxalic acid, malonic acid, succinic acid, citric acid, and phthalic acid. In addition, other acidic substances having pKa and solubility similar to these can be used.

  Among these acidic substances, citric acid is preferably used in a system that has a high water retention ability and tends to increase the physical strength of the aggregated ink, and requires more mechanical properties. On the other hand, malonic acid is preferably used when the water retention is low and it is desired to speed up drying of the treatment liquid.

  As described above, the fixing agent can be appropriately selected and used depending on a secondary factor different from the fixing ability of the water-based ink.

  Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and Group 13 of the periodic table. Mention may be made of salts of cations (for example, aluminum) and lanthanides (for example, neodymium).

  Preferred examples of the cationic compound include cationic surfactants. As the cationic surfactant, for example, a primary, secondary, or tertiary amine salt type compound is preferable. In addition, amphoteric surfactants that are cationic in the desired pH range can also be used.

  The said fixing agent can be used individually by 1 type or in mixture of 2 or more types.

  The content of the fixing agent for fixing the water-based ink in the aqueous treatment liquid is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, and still more preferably 10 to 25% by mass. is there.

  The aqueous treatment liquid in the present invention can generally contain a water-soluble organic solvent in addition to the fixing agent, and can be constituted by using various other additives in the same manner as the water-based ink.

  As the water-soluble organic solvent, it is preferable to add a water-soluble solvent having an SP value of 27.5 or less for the purpose of suppressing curling similarly to the water-based ink.

  In addition, said organic solvent may be used independently and may use 2 or more types together. Moreover, it is preferable that these organic solvents are contained 1-50 mass% in a process liquid.

The application amount of the fixing agent is not particularly limited as long as it is an amount sufficient to stabilize the water-based ink, and is preferably 0.25 g / m ² or more, in that the water-based ink is easily fixed by aggregation. It is more preferably 0.30 g / m ² or more and less than 2.0 g / m ² , and further preferably 0.40 g / m ² or more and less than 1.0 g / m ² .

  The surface tension (25 ° C.) of the aqueous treatment liquid is preferably 20 mN / m or more and 60 mN / m or less. More preferably, it is 25 mN / m or less and 50 mN / m or less, More preferably, it is 25 mN / m or more and 45 mN / m or less.

The surface tension is measured using an automatic surface tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) and a water-based ink at 25 ° C.

In addition, the viscosity of the aqueous treatment liquid at 25 ° C. is 1.2 mPa · s or more and 15.0 mPa · s or less from the viewpoint of stably applying in the range of 0.5 to 3.5 ml / m ^2. It is preferably 2 mPa · s or more and 12 mPa · s or less, and more preferably 2 mPa · s or more and 8 mPa · s or less. In particular, when the aqueous treatment liquid is applied on paper, the viscosity (25 ° C.) is preferably 2 to 8 mPa · s, and more preferably 2 to 6 mPa · s.

  The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under an aqueous treatment solution at 25 ° C.

  The treatment liquid and ink were prepared as described below, and ink jet recording was performed under the following test conditions, and the relationship between the dot diameter of the ink after being deposited and aggregated on the recording medium and the fixing conditions was examined.

[Treatment solution]
・ Malonic acid 22.5% by mass
・ Diethylene glycol monoethyl ether 20% by mass
・ Surfactant 1% by mass
・ Ion-exchanged water balance The surfactant has the following chemical structure.

［インク組成］
・顔料 ５ 質量％
・分散剤ポリマー ２．５質量％
・自己分散性ポリマー微粒子 ４．５質量％
・グリセリン １５ 質量％
・オルフィン１０１０（日信化学工業製） １ 質量％
・イオン交換水 残部
顔料は、チバ・スペシャリティーケミカルズ社のCromophtal Jet MagentaＤＭＱ（PR-122）を使用した。

[Ink composition]
・ Pigment 5% by mass
・ Dispersant polymer 2.5% by mass
・ Self-dispersing polymer fine particles 4.5% by mass
・ Glycerin 15% by mass
・ Olfin 1010 (manufactured by Nissin Chemical Industry) 1% by mass
-Ion-exchanged water balance The pigment used was Cromophtal Jet Magenta DMQ (PR-122) manufactured by Ciba Specialty Chemicals.

The dispersant polymer was benzyl methacrylate / methyl methacrylate / methacrylic acid 60/30/10 (mass ratio).
As the self-dispersing polymer fine particles, methyl methacrylate / phenoxyethyl acrylate / benzyl acrylate / acrylic acid 50/30/15/5 (mass ratio) were used.

[recoding media]
Special Rhihoku art (basis weight 104.7 g / m ² ) manufactured by Mitsubishi Paper Industries was used.

[Test conditions]
-Paper feeding speed: 500 mm / s
Treatment liquid application: A sheet coating was applied uniformly on a recording medium using a bar coating apparatus. The amount of the flocculant was adjusted by the coating amount of the treatment liquid, the concentration of the flocculant in the treatment liquid and the like.
Ink droplet ejection: droplets were ejected at a discharge volume of 2 pL, and dots and images with an image area ratio of 20, 40, 60, 80, 100 were formed on the recording medium.
Ink drying: The back surface of the recording medium was heated at 60 ° C., and the front surface (recording surface) was dried with hot air at 70 ° C. for 2 seconds.
Ink fixing: The fixing roller used was a hollow aluminum roller having a diameter of 40 mm coated with silicon rubber having a predetermined rubber hardness and thickness. Then, the following four conditions were set according to the application conditions of the flocculant (coating amount, time until drying, drying), image data (single color, secondary color ink, image area ratio%), and the like.

    Fixing condition A: normal fixing conditions in which the nip pressure is 0.15 MPa, the fixing roller temperature is 70 ° C., the number of nips is one, and dot flattening is not actively performed.

    Fixing condition B: A nip pressure of 0.45 MPa, a fixing roller temperature of 70.degree.

    Fixing condition C: A nip pressure of 0.45 MPa, a fixing roller temperature of 70 ° C., a nip frequency of 2 times, and a stronger fixing condition for flattening dots.

    Fixing condition D: The image is heated to 60 ° C. with an IR heater in advance of fixing condition B to promote flattening of dots.

    Fixing condition E: Before the fixing condition A, the image is preheated to 60 ° C. with an IR heater to promote dot flattening.

[Evaluation methods]
In addition to mainly evaluating the size of the dot diameter, the curl degree, the offset degree, and the ejection stability were also evaluated.

<Evaluation of dot diameter>
From the viewpoint of eliminating a white background in a solid image, it is not preferable that the dot diameter of the ink droplet formed on the recording medium after ink ejection is too small, and a certain spread is required for the dot diameter. As an adverse effect of the dot diameter being too small, it is necessary to increase the ink droplet ejection amount in order to form a solid image, which adversely affects other properties such as curling, cockling, and fixability of the recording medium. Conversely, if the dot diameter is too large, the resolution is lowered and the sharpness of the image is impaired.

  Thus, there is an appropriate dot diameter, and when the ink droplet discharge volume is 2 pL as in this embodiment, it is 28 μm or more and less than 40 μm (more preferably 30 to 38 μm). Is preferred.

  From the above viewpoint, assuming the drawing at 1200 dpi (dot pitch: 21.2 μm), the following determination was made for the dot diameter. In addition, the measurement for evaluating a dot diameter measured the dot diameter with the dot analyzer made from Oji Scientific Instruments using the optical microscope. The dot diameter of 40 dots was measured, and the average value was adopted as the dot diameter.

(Criteria for dot diameter)
・ Determines that the dot diameter is too large for 40 μm or more. ・ Determines that the dot diameter is appropriate for 28 μm or more and less than 40 μm (corresponding to the set dot diameter). ・ Determines that the dot is too small for less than 28 μm. Secondary color ink, tertiary ink Of course, the above criteria also apply to the dot diameter of the ink, but the dot diameter difference between the primary color ink and the secondary color ink, or the primary color ink and the tertiary ink, the secondary color ink and the tertiary ink It is desirable that the difference is as small as possible. If the dot diameter difference is large, there will be a difference in sharpness between the primary color part and the secondary color part, resulting in an uncomfortable image. Thus, there is an acceptable level in the dot diameter difference, and the dot diameter difference between the inks is preferably 4 μm or less.

(Dot diameter difference criteria)
・ If the dot diameter difference between the inks exceeds 4 μm, it is determined that the dot diameter difference is too large. ・ If the dot diameter difference between the inks is 4 μm or less, it is determined that there is no problem with the dot diameter difference.
The recording medium after the solid droplet ejection with an ink droplet ejection amount of 13.4 g / m ² was cut into 5 × 50 mm so that the curl direction was 50 mm to prepare a sample. Thereafter, the sample was allowed to stand under conditions of a temperature of 23 ° C. and a humidity of 50%, and the curvature C of the sample was measured. Note that the curl value is expressed as in Equation 1, assuming that the curl is an arc of a circle with a radius R.

C = 10 / R (cm) Formula 1
◎: C value is less than 0.5 and there is almost no curling ○: C value is 0.5 or more and 2.5 or less, there is curl, but there is no particular problem ×: C value is 2.5 or more, curl Has developed to a problem level <Evaluation of offset>
The offset is a sensory evaluation of the degree of color material adhesion to the fixing roller after the fixing process. The evaluation criteria are as follows.

  ○: Adherence of coloring material is not visually confirmed.

  Δ: Slightly adhering coloring material, but acceptable in practice.

  X: Adhering to the coloring material is severe and the white background of the recording medium is exposed, which is not acceptable.

<Evaluation of ejection stability>
◎: The ink can be ejected from all nozzles after opening the nozzles for 10 minutes in the temperature environment of the evaluated room. ○: The ink can be ejected from all nozzles after opening the nozzles for 5 minutes in the evaluation temperature environment. △: Under the evaluation temperature environment. Ink can be ejected from all nozzles after opening the nozzles for 1 minute. ×: There is a nozzle that does not eject ink after opening the nozzles for 1 minute under the evaluation temperature environment (Example A)
In Example A, the primary color ink (primary color ink) is ejected (not superimposed) on the recording surface of the recording medium on which the treatment liquid is uniformly applied, and the formed dot diameter satisfies the fixing condition. It was investigated whether it was possible to adjust to an appropriate set dot diameter (28 μm or more and less than 40 μm) by controlling. In addition, Experiment No. demonstrated below. Of the same experiment No. Indicates that the conditions are the same.

  In Experiments 1 to 6, in order to change the dot diameter of the ink before fixing (before the fixing process), the amount of the coagulant in the processing liquid applied to the recording medium is changed from 2.77 (mol · valence / kg). It was changed to 14.41 (mol · valence / kg). The experimental results are shown in the table of FIG. 9 and indicated as primary color dot diameter X.

  As can be seen from FIG. 9, the agglomeration reaction becomes stronger as the amount of the aggregating agent increases, so the dot diameter before fixing becomes smaller. That is, Experiments 1 to 4 are within the appropriate set dot diameter range before fixing, but Experiments 5 and 6 are below the lower limit of the set dot diameter range.

  Since the dots within the set dot diameter do not need to be flattened any further, they are controlled by the fixing condition A which is a normal fixing condition. Thereby, the dot diameter after fixing (after performing the fixing process) hardly fluctuates, and the set dot diameter range is maintained.

  On the other hand, in Experiment 5 and Experiment 6 in which the amount of the flocculant is large, the dot diameter before fixing becomes 27.2 μm and 25.6 μm, and the dot diameter is too small. Control. Thereby, the dot diameter after fixing (after performing the fixing process) is flattened and expanded to the set dot diameter.

  Thus, by controlling the fixing conditions according to the dot diameter before fixing, the dot diameter can be adjusted to a preset dot diameter.

(Example B)
In Example B, two types of inks were formed by ejecting droplets so that two types of ink, primary color ink and secondary color ink, were superimposed on the recording surface of the recording medium to which the treatment liquid was uniformly applied. It was investigated whether the dot diameter can be adjusted to an appropriate set dot diameter (28 μm or more and less than 40 μm) by controlling the fixing conditions. Furthermore, it was investigated whether the dot diameter difference between the two types of inks could be reduced to 4 μm or less by controlling the fixing conditions.

  In Experiments 7 to 18, as in Example A, the dot diameter before fixing was changed by changing the amount of the flocculant in the treatment liquid. The experimental results are shown in the table of FIG.

  As can be seen from FIG. 10, when the dot diameter before fixing in Experiment 7 and Experiment 8 using the processing liquid having a small amount of the flocculant of 2.77 to 3.84 (mol · valence / kg), the recording medium Although the dot diameter X of the primary color ink that is first ejected falls within the set dot diameter range, the dot diameter Y of the secondary color ink superimposed on the primary color ink exceeds the set dot diameter range. It will expand significantly. Further, the dot diameter difference (Y−X) before fixing between the inks becomes significantly larger than 4 μm.

  As described above, when the dot diameter Y before fixing the secondary color ink exceeds the set dot diameter because the amount of the flocculant is too small, the dot diameter can be increased by increasing the fixing conditions to promote flattening. Will expand. Therefore, in this case, it is necessary to increase the amount of the flocculant so that the dot diameter of the secondary color ink falls within the set dot diameter. This is because the amount of flocculant applied to the recording medium is set so that the dot diameter before the fixing process of the ink to be superimposed last among a plurality of inks does not exceed a preset dot diameter range corresponding to a predetermined discharge volume. It will be necessary to adjust. This is the same when the number of inks to be superimposed is 3 or more.

Specifically, in Experiment 9 in which the amount of the flocculant was increased to 5.19 (mol · valence / kg) per m ² of the recording medium, the dot diameter of the secondary color ink before fixing was 38.2 μm and the set dot Since it falls within the range of the diameter, it can be seen that the necessary amount of the flocculant when two inks are superimposed is 5.19 (mol · valence / kg) or more.

  Further, in Experiments 9 to 11 in which the amount of the flocculant is close to the lower limit of the required amount, the dot diameter Y of the secondary color ink before fixing is within the set dot diameter range, but the dots before fixing between the inks are fixed. The diameter difference (Y-X) becomes significantly larger than 4 μm. In this case, the difference in dot diameter after fixing is increased to 4 μm by strengthening from fixing condition B in Experiment 9 to fixing condition C in Experiment 10 so that the amount of flocculant can be seen by comparison between Experiment 9 and Experiment 10. It can be: Similarly, by strengthening from the fixing condition B of Experiment 9 to the fixing condition C of Experiment 11, the dot diameter difference after fixing can be reduced to 4 μm or less.

  Further, Experiment 14 and Experiment 15 in which the amount of the flocculant is increased to 10.81 (mol · valence / kg) suppresses the expansion of the dot diameter of the secondary color ink before fixing, and thus falls within the set dot diameter range. However, the dot diameter of the primary color ink before fixing is conversely reduced below the lower limit of the set dot diameter range. Also, the dot diameter difference before fixing between the inks before fixing becomes larger than 4 μm. Also in this case, as can be seen from the comparison between Experiment 14 and Experiment 15, by strengthening from the fixing condition A of Experiment 14 to the fixing condition B of Experiment 15, flattening of the dot diameter of the primary color ink is promoted. The dot diameter after fixing the secondary color ink and the secondary color ink can be kept within the range of the set dot diameter. Furthermore, the dot diameter difference between the fixed inks can be reduced to 1 μm, which is significantly smaller than 4 μm.

  Looking at Experiments 16 to 18 in which the amount of the flocculant was further increased to 14.41 (mol · valence / kg), the dot diameter before fixing for both the primary color ink and the secondary color ink was lower than the lower limit of the set dot diameter range. Is also shrinking. In this case as well, as can be seen from the comparison of Experiments 16 to 18, the fixing condition A of Experiment 16 is strengthened to the fixing condition B of Experiment 17, and the flattening of the primary color ink is positively promoted. The dot diameter after fixing the color ink and the secondary color ink can be kept within the set dot diameter. Further, as in Experiment 18, when the fixing condition C is strengthened, the dot diameter difference between the dots after fixing can be made smaller than in Experiment 17.

  Experiments 10b, 11b, and 18b in FIG. 10 are cases in which the fixing conditions C (the number of nips is 2 times) in Experiments 10, 11, and 18 are changed to the fixing condition D (IR heating + fixing condition B), respectively. It can be seen that the dot flattening effect is the same between the fixing condition C and the fixing condition D.

  As described above, when droplets are ejected so as to overlap a plurality of inks, the amount of the flocculant of the processing liquid used in the processing liquid application process is appropriately adjusted, and the fixing conditions in the fixing process are appropriately controlled. As a result, the dot diameter after fixing a plurality of inks can be kept within the range of the set dot diameter, and the dot diameter difference between the inks after fixing can be reduced to 4 μm or less.

  In addition, Example B was implemented using two types of inks of primary color ink and secondary color ink, but the case of three types of inks of primary color ink, secondary color ink, and tertiary color ink is also possible. The basic idea about the dot diameter is the same. In this case, it is the same that the dot diameter difference between the primary color ink and the tertiary color ink and the dot diameter difference between the secondary color ink and the tertiary color ink are set to 4 μm or less.

  It is also desirable to adjust the amount of treatment liquid applied based on the image data formed on the recording medium so that the set dot diameter can be obtained without strengthening the fixing conditions. If the frequency of strengthening the fixing conditions is reduced, the life of the fixing roller is extended.

(Example C)
In Example C, an image area ratio (also referred to as halftone dot density) of a primary color ink image (described as a primary color image in FIG. 11) located in the lower layer of the secondary color ink is used before fixing the secondary color ink. We examined how the dot diameter was affected. The result is shown in FIG.

  As can be seen from the results of Experiments 15, 19, and 20 to 22 in FIG. 11, the dot diameter Y before fixing the secondary color ink tends to increase as the image area ratio of the primary color ink image increases. Further, as the dot diameter Y before fixing of the secondary color ink increases, the dot diameter difference (Y−X) before fixing between the inks also increases as the image area ratio increases. This is because the higher the image area ratio of the primary color ink image, the greater the amount of aggregating agent consumed for the aggregation of the primary color ink, and the agglomeration reaction of the secondary color ink becomes slower. It is considered to expand. In addition, the dot diameters of the primary color ink before fixing in Experiments 15 to 22 are all smaller than the lower limit of the set dot diameter range. In Experiments 21 and 22, the dot diameter before fixing of the secondary color ink is also set dots. It is smaller than the lower limit of the diameter range.

  However, in Experiments 15, 19, and 20, by performing the fixing process under the fixing condition B, it is possible to satisfy the set dot diameter for both the primary color ink and the secondary color ink, and the difference in dot diameter after fixing between the inks. Becomes 4 μm or less. In Experiments 21 and 22, by performing the fixing process under the fixing condition C, both the primary color ink and the secondary color ink can satisfy the set dot diameter, and the dot diameter difference between the inks after fixing is also 4 μm. It becomes the following.

  As described above, the dot area before fixing the primary color ink and the secondary color ink and the dot diameter difference before fixing between the inks are affected by the image area ratio of the lower layer ink. It can be seen that it is preferable to control (set) the fixing conditions.

  Further, the image area ratio existing in the same image data is in a narrow range of, for example, 80 to 100% in FIG. 12, and the dot diameter before fixing and the dot diameter difference (0.8 μm) are the set dot diameter. If it is within the range and 4 μm or less, it is not necessary to strengthen the fixing conditions. However, since the image area ratio extends over a wide range such as 20 to 100% in FIG. 12, the dot diameter before fixing and the dot diameter difference (5.1 μm) are within the set dot diameter range and 4 μm or less. If not, it is necessary to reduce the difference in dot diameter by strengthening the fixing conditions and actively flattening the dots in the target portion that deviate from the set dot diameter to increase the dot diameter.

  FIG. 13 shows a case where an image area ratio is large (referred to as a large area ratio), medium (referred to as a medium area ratio), and small (referred to as a small area ratio) in the same data image. FIG. 13A is a top view of the recording surface of the recording medium before and after the fixing process. FIG. 13B shows a case where the recording surface of the recording medium before and after the fixing process is viewed from the side. In FIG. 13, S1 is a primary color ink dot (droplet) forming the lower layer, and S2 is a secondary color ink dot (droplet) deposited on the primary color ink. .

  Thus, when large, medium, and small image area ratios exist in the same data image, the dot diameter before fixing the secondary color ink in the large area ratio portion is the largest, and the small area ratio is 2 The dot diameter before fixing the next color ink is the smallest.

  In this case, as can be seen from the comparison before and after the fixing in FIGS. 13A and 13B, by strengthening the fixing conditions, the dot with the smallest area ratio can be flattened. The flattening of the medium area rate dot is promoted a little, and then the flattening of the large area rate dot is hardly promoted. As a result, even when large, medium, and small image area ratios exist in the same data image, the fixed dot diameter can be kept within the set dot diameter by controlling the fixing conditions. In addition, the dot diameter difference between the inks can be 4 μm or less.

(Example D)
In Example D, it was examined how the dot diameters before fixing of the primary color ink and the secondary color ink are affected by the film thickness of the treatment liquid at the time of ink ejection. The film thickness of the treatment liquid is indicated by the number of grams of treatment liquid per recording medium m ² . Moreover, the result of Experiment 23, 13, and 24-29 is shown in FIG. In Experiment 13, the film thickness condition of the treatment liquid in Experiment 13 performed in Example B was set to 0.5 g / m ² .

As can be seen from Experiments 23, 13, and 24 in FIG. 14, when the film thickness of the treatment liquid at the time of ink ejection is less than 1 g / m ² , the dot diameter before fixing the primary color ink is expanded to the set dot diameter. Absent. The reason for this is that when the liquid film thickness is 1 g / m ² or more, the dot diameter increases due to the effect of ink dots (droplets) spreading over the liquid film, but when the liquid film thickness is less than 1 g / m ² . It is considered that the effect is not so manifested. In Experiments 23, 13, and 24, the dot diameter difference between the inks before fixing exceeds 4 μm.

On the other hand, as in Experiment 29, the dot diameter before fixing the primary color ink does not expand to the set dot diameter even when the film thickness of the treatment liquid at the time of ink ejection is too thick, 9 g / m ² . In this way, if the liquid film thickness is made too thick, the dot diameter tends to decrease. The ink droplets land on the liquid film, which promotes the reaction in the liquid phase and aggregates before spreading. It is considered that the reaction proceeds. Further, as can be seen from Experiment 29, the curl of the recording medium increases as the amount of the processing liquid increases.

In contrast to these experimental results, in Experiments 25, 26, and 27 where the film thickness of the treatment liquid is 1.0 to 3.5 g / m ² , both the primary color ink and the secondary color ink are within the set dot diameter. The dot diameter between the inks is also 4 μm or less. Furthermore, the evaluation of curl is good with 〜 to ◎.

Therefore, in order to keep the dot diameter before fixing the primary color ink within the range of the set dot diameter within a range where the curl is not deteriorated, the film thickness of the treatment liquid is 1.0 g / m ² or more and 3.5 g / m. ^It is preferable to make it ² or less. Further, it goes without saying that even if the dot diameter of the primary color ink is smaller than the set dot diameter outside this range, the dots can be enlarged to fit within the set dots by strengthening the fixing conditions.

(Example E)
Example E examines how the temperature of the recording medium during ink ejection affects the dot diameter of the primary color ink and the secondary color ink before the fixing process. The temperature of the recording medium was controlled by providing a heating mechanism on the back support member and heating. The results of Experiments 8 and 30 to 34 are shown in FIG. In Experiment 8, the temperature condition of the recording medium in Experiment 8 described in Example B was set to 25 ° C.

  As can be seen from FIG. 15, the higher the temperature of the recording medium is, the more the dot diameter can be prevented from expanding before the secondary color ink is fixed. It is considered that this is because the spread of ink dots (droplets) is suppressed by promoting the aggregation reaction due to the temperature increase during the aggregation reaction.

  More specifically from FIG. 15, in Experiments 8, 30, and 31 in which the temperature of the recording medium was set to a low value of 25 to 35 ° C., the dot diameter spread before fixing the secondary color ink was large. In Experiment 8, the upper limit of the set dot diameter range is exceeded, and in Experiments 8, 30, and 31, the dot diameter difference before fixing exceeds 4 μm.

  However, as can be seen from the comparison between Experiments 8, 30 and 31, the dot diameter difference after fixing can be reduced to 4 μm or less by strengthening the fixing condition A in Experiment 8 to the fixing condition C in Experiments 30 and 31. . This means that even if the dot diameter difference between the primary color ink and the secondary color ink before fixing exceeds 4 μm, the dot diameter before fixing the secondary color ink which is easy to enlarge after being ejected is set dots. If the upper limit of the diameter range is not exceeded, it means that it can be dealt with by strengthening the fixing conditions.

  On the other hand, in the experiments 32, 33, and 34 where the temperature of the recording medium is as high as 40 to 50 ° C., the expansion of the dot diameter before fixing of the secondary color ink can be suppressed, so that both the primary color ink and the secondary color ink are fixed. The previous dot diameter satisfies the set dot diameter, and the dot diameter difference is 4 μm or less.

  As described above, by appropriately adjusting the temperature of the recording medium, it is possible to suppress the dot diameter expansion of the secondary color ink, so that the set dot diameter can be obtained without strengthening the fixing conditions as in Experiments 32, 33, and 34. be able to. However, as in Experiment 34, when the temperature of the recording medium reaches 50 ° C., the ink volatilization proceeds at the head nozzle portion, which adversely affects the ejection stability.

  Therefore, it can be seen that the temperature of the recording medium during ink ejection is preferably adjusted to a range of 30 ° C to 45 ° C.

(Example F)
In Example F, when the primary color ink and the secondary color ink having different solid contents are used, the order in which the ink is ejected depends on the dot diameter before fixing the primary color ink and the secondary color ink. It was investigated whether it affected. The amount of solid content was controlled by increasing or decreasing the amount of self-dispersing polymer fine particles in the ink. The solid content refers to the total amount of pigment, dispersant polymer and self-dispersing polymer fine particles contained in the ink.

  The results of Experiments 37, 13, 38, and 39 are shown in FIG. In the “droplet order” in FIG. 16, “12 → 10” indicates that the ink having a solid content of 12% by mass was first ejected and then the ink having a solid content of 10% was ejected.

  As can be seen from the comparison between Experiments 38 and 39 and Experiments 37 and 13 in FIG. 16, the earlier the ink is ejected with a small solid content, the more the dot diameter before fixing of the primary color ink is promoted. This has the effect of suppressing the expansion of the dot diameter before fixing the secondary color ink. Accordingly, it can be understood that the dot diameter difference between the inks can be reduced as the ink having a small solid content is ejected first. It is considered that the reason why the dot diameter of the primary color ink is expanded is that the amount of solid content is small and the wetting and spreading to the surface of the recording medium is promoted. Moreover, it is considered that the expansion of the dot diameter of the secondary color ink is suppressed because the surface energy of the lower ink layer is reduced and the expansion is suppressed.

  Therefore, in the ink droplet ejection process, droplets are ejected in order from the least solid amount of the plurality of inks, so that the dot diameter before fixing falls within the set dot diameter range without strengthening the fixing conditions. And the dot diameter difference can be reduced to 4 μm or less. Accordingly, if the frequency of strengthening the fixing conditions can be reduced, the life of the fixing roller can be extended. Further, even if the dot diameter before fixing either the primary color ink or the secondary color ink is reduced from the lower limit of the set dot diameter range, it can be kept within the set dot diameter range by strengthening the fixing conditions. Needless to say, you can.

(Example G)
Example G is a case where water-based ink is used, and the amount of residual water of ink that has been ejected onto the recording medium and the elapsed time from the ink ejection process to the fixing process (hereinafter simply referred to as “elapsed time”) are: This is an investigation of how dots are flattened (expanded diameter) by the fixing process. The results of Experiment 15 and Experiments 40 to 48 are shown in FIG. In Example G, in order to examine the flattening effect, the dot diameter before fixing was set to be lower than the lower limit of the set dot diameter range for both the primary color ink and the secondary color ink.

As can be seen from the results of Experiments 41, 42, 43, 46b, 47a, 47b, and 48 in FIG. 17, the amount of residual water after ink ejection is dried to ² to 4 g / m ² in the drying step, and ink dots ( When the fixing process is performed in a state in which the liquid droplets) have an appropriate elasticity and the elapsed time is set to 10 seconds or less, the dot diameter after fixing can be expanded for both the primary color ink and the secondary color ink. .

On the other hand, in Experiment 15 in which the residual water amount is less than 2 g / m ² and the elapsed time is 10 seconds, the residual water amount is too small and the image becomes too hard, and the flattening effect is insufficient. As a result, the dot diameter after fixing cannot be satisfied with the set dot diameter.

Further, in Experiment 40 in which the remaining water amount exceeds 4 g / m ² and the elapsed time is 10 seconds, the dots (droplets) become too soft, and the image strength is insufficient with respect to the nip during the fixing process. An offset phenomenon in which ink adheres occurs.

Further, the elapsed time is to satisfy the following 10 seconds 5 seconds, the offset phenomenon in Experiment 46a which residual water content exceeds 4.0 g / ^{m 2} at 4.3 g / ^{m 2} occurs.

Further, as can be seen from Experiments 44 and 45, even when the residual water amount satisfies ² to 4 g / m ² , if the elapsed time exceeds 10 seconds and becomes 12 seconds, the effect of flattening the dots is insufficient. Become. In particular, the secondary color ink is hardly flattened. This is because when the time from ink droplet ejection to the fixing process exceeds 10 seconds and the remaining water amount is in the range of ^{2 to 4} g / m ² , the penetration into the recording medium proceeds. It is considered that the droplet) becomes too hard and is difficult to flatten.

Based on the above results, the remaining water amount after ink ejection was dried to 2-4 g / m ² in the drying process, and the normal fixing condition A that does not strengthen the fixing condition was performed by setting the elapsed time to 10 seconds or less. Even so, the dot diameters after fixing the primary color ink and the secondary color ink can be within the set dot diameter range, and the dot diameter difference between the inks can be 4 μm or less.

  Further, as can be seen from the comparison between the experiment 46a and the experiment 46b and the comparison between the experiment 47a and the experiment 47b, the flattening of the dots is promoted by setting the fixing condition A to the fixing condition E (IR heating + fixing condition A). Not only can this be done, but offset can be suppressed. This is considered that the offset at the time of nip is suppressed by heating and drying the image with an IR heater in the front stage of the nip as in the fixing condition E.

(Example H)
Example H examines how the type of solvent used for dissolving the color material affects dot flattening (expansion) by the fixing process. The experimental results are shown in FIG. Incidentally, the elapsed time from the ink ejection to the fixing process was unified to 12 seconds. Moreover, although the solvent material of FIG. 18 is described in an abbreviated name, the official name is as follows. In Example H as well as Example G, both the primary color ink and the secondary color ink were set so that the dot diameter before fixing was lower than the lower limit of the set dot diameter range.
-DEGmEE: Diethylene glycol monomethyl ether-DEGmBE: Diethylene glycol monobutyl ether-TEGMBE: Triethylene glycol monobutyl ether-GP-250 (manufactured by Sanyo Chemical Industries): Trioxypropylene glyceryl ether-GP-400 (Sanyo Chemical Industries ( Co., Ltd.): Hexaoxypropylene glyceryl ether As can be seen from Experiments 51, 52, 54, 55, and 56 in FIG. 18, a solvent having a molecular weight of 200 or more was used as the solvent contained in the ink, and 10 to 30% by mass. It turns out that the flattening effect can be accelerated | stimulated by setting it as less than% content. The reason for promoting the flattening effect is that if the molecular weight of the solvent is greater than 200, the viscosity of the solvent increases, so that the solvent is not absorbed by the recording medium and tends to stay in the dots, which is the ink dot (droplet). This is considered to promote flattening by moderately softening.

  However, as can be seen from Experiment 57, even when the molecular weight is 200 or more, if the solvent content is 30% by mass or more, the film becomes too soft and the image strength is insufficient, and the coloring material adheres to the fixing roller during the fixing process. The offset phenomenon will occur.

  On the other hand, in Experiments 49 and 50 using a solvent having a molecular weight of less than 200, the flattening effect in the fixing process is hardly exhibited. Further, as can be seen from Experiment 53, even when the solvent content is less than 10% by mass, the flattening effect in the fixing process is similarly insufficient. As a result, the dot diameter after fixing the primary color ink does not satisfy the set dot diameter.

  From the above results, the primary color ink and the primary color ink can be obtained even when the normal fixing condition A that does not reinforce the fixing condition is performed by using a solvent having a molecular weight of 200 or more and a content of 10% by mass or more and less than 30% by mass. The dot diameter of the secondary color ink can be set within the range of the set dot diameter.

1 is an overall configuration diagram schematically showing an example of an ink jet recording apparatus for carrying out the ink jet recording method of the present invention. Schematic diagram showing another embodiment of the fixing unit in FIG. Schematic diagram showing the structure of the fixing roller Plane perspective view showing the internal structure of the head Plan view showing another configuration example of the head Sectional drawing which follows the XX line in FIG. Plan view showing an example of nozzle arrangement of the head Main block diagram showing the system configuration of the inkjet recording apparatus Overall configuration diagram schematically showing an inkjet recording apparatus having a configuration different from that shown in FIG. Table showing results of Example A Table showing results of Example B Table showing the results of Example C Table showing the image area ratio and dot diameter difference existing in the same image data Explanatory drawing explaining the effect | action of a fixing process when different image area ratios exist in the same image data Table showing the results of Example D Table showing results of Example E Table showing results of Example F Table showing the results of Example G Table showing the results of Example H

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus, 10 ... Paper feed part, 12 ... Processing liquid provision part, 14 ... Drawing part, 16 ... Drying part, 18 ... Fixing part, 20 ... Discharge part, 22 ... Recording medium, 54 ... Processing liquid drum, 56 ... Processing liquid coating device, 61 ... Processing liquid container, 62 ... Measuring roller, 63 ... Belt, 64-66 ... Roller, 67 ... Doctor blade, 68 ... Doctor blade, 69 ... Roller, 70 ... Drawing drum, 71 ... Roller 72C, 72M, 72Y, 72K ... ink head, 76 ... drying drum, 84 ... fixing drum, 86 ... first fixing roller, 88 ... second fixing roller, 89 ... IR heater

Claims (11)

A treatment liquid application step for uniformly applying a flocculant-containing treatment liquid onto a recording medium in a surface shape;
An ink droplet ejection step of forming an image by ejecting ink droplets aggregated by the treatment liquid on the recording medium to which the treatment liquid is applied; and
A drying step of drying the ink applied to the recording medium;
A fixing step of fixing the ink by niping the recording medium on which the ink has been dried with a fixing roller,
In the fixing step, the fixing condition is controlled according to the dot diameter of the ink before the fixing process. A treatment liquid application step for uniformly applying a flocculant-containing treatment liquid onto a recording medium in a surface shape;
On the recording medium to which the treatment liquid is applied, an image is formed by continuously ejecting a plurality of inks of the N-order ink from the primary color ink aggregated by the treatment liquid so as to overlap with the same predetermined discharge volume. An ink ejection process;
A drying step of drying the ink applied to the recording medium;
A fixing step of fixing the ink by niping the recording medium on which the ink has been dried with a fixing roller,
In the treatment liquid application step, the recording medium is arranged such that the dot diameter before the fixing process of the ink superimposed last among the plurality of inks does not exceed a preset dot diameter range corresponding to the predetermined ejection volume. While adjusting the amount of flocculant applied to the
In the fixing step, the dot diameter after the fixing process of all the inks from the primary color ink to the N-th order ink is within the set dot diameter range, and the dot diameter difference between the inks is equal to or less than a predetermined value. An ink jet recording method characterized by controlling fixing conditions as described above.   A detection step for detecting the dot diameter is provided between the ink droplet ejection step and the fixing step, and the fixing condition is controlled based on the dot diameter before the fixing process detected in the detection step. The ink jet recording method according to claim 1 or 2, characterized in that   The fixing condition is at least one of a nip pressure of the fixing roller, a number of nips, a temperature of the fixing roller, a nip time, and an elapsed time from the ink ejection to the fixing process. The ink jet recording method according to claim 1.   5. The set dot diameter is 28 μm or more and less than 40 μm when the predetermined ejection volume of the ink droplet is 2 pL, and the predetermined value or less of the dot diameter difference is 4 μm or less. Any one of the inkjet recording methods.   6. The inkjet according to claim 2, wherein the fixing condition is controlled in accordance with an image area ratio% of N-1 primary color ink formed on the recording medium to which the processing liquid is applied. Recording method.   The ink jet recording method according to claim 1, wherein the fixing condition is controlled according to a type of the recording medium.   8. The ink jet recording method according to claim 1, wherein the fixing condition is controlled in accordance with a film thickness of the processing liquid applied on the recording medium in the processing liquid applying step.   9. The ink jet recording method according to claim 1, wherein the fixing condition is controlled according to the temperature of the recording medium at the time of ink droplet ejection in the ink droplet ejection step.   The ink jet recording method according to any one of claims 1 to 9, wherein, in the ink droplet ejection step, ink droplets are ejected in order from an ink having a small solid content among the plurality of inks. The ink is water-based ink, and the fixing is performed in a satisfied state within a range of ² to 4 g / m ² of the remaining water amount of the ink ejected in the ink ejection process and within 10 seconds after ink ejection. The inkjet recording method according to claim 1, wherein a process is performed.

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