JP2010201714A - Inkjet recorder and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder and an inkjet recording method which can perform drying efficiently while being able to inhibit a cockle efficiently. <P>SOLUTION: The inkjet recorder includes an ink discharge means which drops ink on a recording medium and forms an image therein, and the first drying means 80 for drying the ink given to the recording medium. The first drying means 80 includes a blower means 81 for blasting dried air on the recording medium, heating means 82, 83 for heating the dried air, and a steam supply means 85 for feeding steam to the dried air. The inkjet recording method is applied to the inkjet recorder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method, and more particularly, to an ink jet recording apparatus and an ink jet recording method capable of efficiently suppressing drying and effectively suppressing cockle.

  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 an image can be recorded with good image quality, the home for personal use is used. It is widely used as an office printer for business use including printers. Particularly in office printers for business use, there is a further demand for higher processing speed and higher image quality.

  In an inkjet recording apparatus, when printing on general printing paper, the amount of water absorbed by the paper fibers in the area where the ink is attached (image part) and the area where the ink is not attached (non-image part) Therefore, there is a problem that unevenness (cuckling) occurs on the paper.

  In order to solve such a problem, the following Patent Document 1 discloses that the amount of moisture absorbed in the non-image area paper fiber by applying a substantially transparent liquid mainly composed of water to the non-image area. It is described that cuckling is suppressed by bringing the amount close to the amount of water in the image area.

  Further, in Patent Document 2 below, the temperature and humidity of the apparatus are measured, the value, the saturated water vapor amount, and the actual water vapor amount are calculated to calculate the vapor amount that can be evaporated, and the drying is controlled accordingly. It is described that highly efficient drying is performed. Thus, by providing an efficient drying means, it is possible to suppress the amount of cockle to some extent.

JP 2005-212371 A JP 2008-119998 A

  However, the method described in Patent Document 1 requires a liquid to be applied to the non-image portion and a liquid application device, and thus has a problem of cost increase. Further, in the apparatus described in Patent Document 2, the moisture in the non-image area is also reduced by the drying means, so that the moisture content in the image area and the non-image area still exists and the cockle can be sufficiently suppressed. It wasn't done.

  The present invention has been made in view of such circumstances, and provides an ink jet recording apparatus and an ink jet recording method capable of performing drying with high efficiency and effectively suppressing cockle. Objective.

  According to a first aspect of the present invention, in order to achieve the above-mentioned object, ink is ejected onto a recording medium to form an image, and the first ink that is applied onto the recording medium is dried. The first drying means includes a blowing means for blowing dry air onto the recording medium, a heating means for heating the drying air, and a water vapor supply for supplying water vapor to the drying air. And an ink jet recording apparatus.

  According to the first aspect of the present invention, when drying air is blown to the recording medium in drying after ink ejection, the drying air is heated and water vapor is supplied. Thereby, the relative humidity which fell by heating air can be raised.

  Here, the amount of water contained in the recording medium is almost uniquely determined by the relative humidity of the air in contact with the recording medium (the higher the relative humidity, the larger the amount of water).

  After drawing, the recording medium has different moisture content in the image portion and the non-image portion, but when air with a constant relative humidity is blown, the moisture content contained in the recording medium in both the image portion and the non-image portion is: Asymptotically approach a certain value.

  Here, the time during which the amount of water contained in the recording medium asymptotically approaches a certain value in both the image portion and the non-image portion is determined by the air temperature (the higher the air temperature, the shorter the time). Therefore, according to the first aspect, compared to the case where the air is blown without changing the temperature and humidity of the air, the amount of water in the image portion and the non-image portion can be made asymptotic to a constant value in a short time.

  A second aspect of the present invention includes the temperature and humidity measuring means for measuring the temperature and relative humidity of the air around the apparatus according to the first aspect, and the difference between the relative humidity of the dry air and the relative humidity of the air around the apparatus is substantially equal. As described above, it is characterized by comprising control means for controlling the water vapor supply means.

  According to claim 2, since the difference between the relative humidity of the dry air and the relative humidity of the air around the apparatus is substantially equal, the amount of water contained in the recording medium is balanced with the air in the environment where the apparatus is installed. Asymptotic to the value. Therefore, even if the recording medium is transported outside the apparatus after the printing is completed, the change in the amount of moisture contained in the recording medium can be reduced, so that the occurrence of cockle can be suppressed.

  A third aspect of the present invention is the method according to the first or second aspect, wherein the water vapor supply means includes a water storage section that stores water, and a heating element that heats the water to form water vapor, and the flow path section through which the dry air passes, The water vapor supply means is separated by an openable / closable shutter, and the control means controls at least one of an opening ratio of the shutter and a current supplied to the heating element.

  A fourth aspect of the present invention includes the drying air temperature / humidity measuring unit that measures the temperature / humidity of the drying air according to the third aspect, and the control unit performs feedback control based on the temperature / humidity of the drying air so as to perform the shutter and the heat generation. Actuating at least one of the bodies.

  Claims 3 and 4 define a method for controlling the temperature and humidity of the drying air. According to Claims 3 and 4, the opening ratio of the shutter provided in the water vapor supply means is provided in the water. By controlling the current supplied to the heating element, the amount of water vapor supplied to the drying air can be controlled.

  A fifth aspect according to any one of the first to fourth aspects is characterized in that the air around the apparatus is used as the drying air.

  By using the air around the apparatus as the gas used for the drying air, the cost can be reduced.

  A sixth aspect of the present invention provides the method according to any one of the first to fifth aspects, wherein a treatment liquid application unit that applies a treatment liquid having a function of aggregating or thickening the components in the ink onto the recording medium, and drying the treatment liquid. Treatment liquid drying means, and the treatment liquid drying means comprises: a treatment liquid blowing means for blowing a drying air onto the recording medium; a treatment liquid heating means for heating the drying air; and the drying air. A treatment liquid water vapor supply means for supplying water vapor to the treatment liquid, the treatment liquid water vapor supply means so that the difference between the relative humidity of the drying air and the relative humidity of the air around the apparatus is substantially equal. A processing liquid drying control means for controlling is provided.

  According to the sixth aspect, even in the drying after the treatment liquid is applied, the drying air is heated and the drying air that is substantially equal to the relative humidity of the air around the apparatus is blown. Therefore, when the treatment liquid is applied, the amount of water contained in the recording medium can be made equal to the amount of water in contact with the air around the apparatus. The time for equilibrating the moisture contained in can be shortened.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a second drying unit is provided between the ink discharge unit and the first drying unit, and the second drying unit generates a drying air. It is characterized by comprising a second blowing means for supplying and a second heating means for heating the drying air.

  According to the seventh aspect, the second drying means is provided, and in the second drying means, the drying is performed by blowing the drying air which is only heated. Therefore, since the drying air has a high temperature and low humidity, drying can be promoted, and the amount of water can be reduced in both the image portion and the non-image portion. However, the water in the image area is mainly water as an ink solvent, and remains on the paper surface, so that it is easy to dry. For this reason, although both the image portion and the non-image portion of the recording medium have a small amount of water, the moisture in the image portion is easier to dry, so that the difference in the amount of water between the image portion and the non-image portion can be reduced.

  And since the difference in the moisture content between the image area and the non-image area has already been reduced, the water content contained in the recording medium of the image area and the non-image area is balanced by the first drying means thereafter. The time can be shortened.

  An eighth aspect according to any one of the first to seventh aspects further comprises ink amount measuring means for measuring an ink amount per unit area of the ink applied to the recording medium, wherein the first amount is determined according to the ink amount. And a drying control means for adjusting the strength of the second drying means.

  According to the eighth aspect of the invention, the ink amount measuring means is provided, the ink amount applied to the recording medium is measured, and the strengths of the first drying means and the second drying means are adjusted according to the ink amount. , Can promote drying.

  A ninth aspect of the present invention is characterized in that, in the eighth aspect, the drying control means controls to use only the first drying means when the ink amount is lower than a reference value.

  According to the ninth aspect, when the ink amount is lower than a predetermined reference value, the moisture amount contained in the image portion and the non-image portion of the recording medium is balanced only by drying by the first drying portion. Can do. Therefore, since the second drying unit is not used, the running cost can be reduced.

  A tenth aspect of the present invention is characterized in that, in the ninth aspect, the reference value is determined from a relative humidity of air around the apparatus measured by the temperature and humidity measuring means.

  According to the tenth aspect, the reference value of the ink amount is determined from the relative humidity of the air around the apparatus. When the relative humidity of the air around the apparatus is high, the amount of moisture contained in the recording medium after drying can be increased, and the amount of moisture dried from the recording medium can be reduced. Therefore, even if the amount of ink is small, it can be dried only by the first drying means. On the other hand, when the relative humidity of the air around the apparatus is low, drying of moisture from the image portion can be promoted, so that even if the amount of ink is large, only the first drying portion is dried to achieve an equilibrium state. can do. Thus, the reference value can be changed by the relative humidity of the air around the device.

  According to an eleventh aspect of the present invention, in order to achieve the above object, an ink discharge step of forming ink on the recording medium to form an image, and a first drying of the ink applied on the recording medium. And the first drying step supplies the water vapor and supplies the water vapor to the recording medium to provide an ink jet recording method.

  A twelfth aspect of the present invention relates to the eleventh aspect, wherein the temperature and humidity measuring step for measuring the temperature and relative humidity of the air around the device, the relative humidity of the drying air blown in the first drying step, and the air around the device are measured. And a control step for controlling the difference from the relative humidity to be substantially equal.

  A thirteenth aspect of the present invention provides the processing liquid applying step according to the eleventh or twelfth aspect, wherein the processing liquid is applied to the recording medium with a processing liquid having a function of aggregating or thickening components in the ink, and the processing liquid is dried. And the treatment liquid drying step heats the drying air and supplies water vapor so that the difference between the relative humidity of the drying air and the relative humidity of the air around the apparatus is substantially the same. It has the process liquid drying control process to control.

  According to a fourteenth aspect of the present invention, in any one of the eleventh to thirteenth aspects, an ink amount measuring step of measuring an ink amount per unit area of the ink applied to the recording medium is provided before the first drying step. And a second drying step of supplying heated drying air in accordance with the ink amount.

  A fifteenth aspect is characterized in that, in the fourteenth aspect, whether to perform the second drying step is determined based on a reference value determined by a relative humidity of air around the apparatus.

  The eleventh to fifteenth aspects are developed from the invention of the ink jet recording apparatus as an ink jet recording method. According to the eleventh to fifteenth aspects, the same effects as those of the ink jet recording apparatus can be obtained.

  According to the ink jet recording apparatus and the ink jet recording method of the present invention, the moisture contained in the recording medium is increased between the image portion and the non-image portion of the recording medium by increasing the temperature of the drying air during drying and increasing the relative humidity. The amount can be a constant value. Therefore, the moisture contained in the recording medium can be brought into an equilibrium state between the image portion and the non-image portion, the occurrence of cockle can be suppressed, and the time until the equilibrium state is reached can be shortened. , Drying can be performed efficiently.

1 is a schematic configuration diagram of an ink jet recording apparatus according to the present invention. It is an enlarged view of a 1st drying means (1st warm air ejection nozzle). 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

  Hereinafter, preferred embodiments of an ink jet recording apparatus according to the present invention will be described with reference to the accompanying drawings.

[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. 1 is a configuration diagram schematically showing an inkjet recording apparatus 1 according to 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 ink is applied is transported by the discharge unit 20 after the ink is dried by the drying unit 16 and the image is fastened by the fixing unit 18.

  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 treatment liquid application unit 12 is a mechanism for applying the treatment liquid to the recording surface of the recording medium 22, and the treatment liquid contains a component that aggregates or thickens a coloring material (pigment or dye) in the ink described later. Yes. Specific methods for agglomerating or thickening the color material include a treatment liquid that reacts with the ink to precipitate or insolubilize the color material in the ink, and a semi-solid substance (gel) containing the color material in the ink. And the like. The means for causing the reaction between the ink and the treatment liquid is a method of reacting the anionic coloring material in the ink and the cationic compound in the treatment liquid, or by mixing the ink and the treatment liquid having different pHs with each other. A method of agglomerating the pigment by causing dispersion destruction of the pigment in the ink by changing the pH of the ink, a method of causing the dispersion destruction of the pigment in the ink by reaction with the polyvalent metal salt in the treatment liquid, and the like. is there.

  Examples of the treatment liquid application method include droplet ejection using an inkjet head, application using a roller, and uniform application using a spray. For example, the treatment liquid application unit 12 illustrated in FIG. 1 includes a transfer drum 52, a treatment liquid drum 54, a treatment liquid application device 56, and a hot air ejection nozzle 58. 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.

  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, and 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 72C, 72M, 72Y, 72K of the drawing unit 14. For example, when the ink droplet ejection amount is 2 pl, 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 obtain a landing dot diameter of 30 μm or more when the ink droplet ejection amount is 2 pl, it is desirable that the film thickness of the treatment liquid is 3 μm or less.

The recording medium 22 coated with the processing liquid by the processing liquid coating device 56 is conveyed to the position of the hot air jet nozzle 58. The warm-air blow-out nozzle 58 can be a high temperature (e.g. 50 ° C.), such as blown toward the recording medium 22 by the hot air constant air volume of (e.g. 9m 3 ^/ min) configuration. As the hot air ejection nozzle 58, the same configuration as that of the first hot air ejection nozzle 80 in the drying section described later can be used. The humidity is preferably increased to the relative humidity of the air around the device. By performing such processing, the amount of water contained in the recording medium after drying the treatment liquid becomes substantially equal to the amount of water contained in the recording medium when in equilibrium with the atmosphere around the apparatus. When the ink is dried, the water content difference between the image area and the non-image area is made closer (the water content when both the image area and non-image area in the recording medium are in equilibrium with the atmosphere around the device) Time asymptotically) can be shortened.

The solvent component of the treatment liquid is dried by heating with the hot air jet nozzle 58. As described above, by drying the treatment liquid applied to the recording medium 22 before the ink is ejected, the ink coloring material can be prevented from floating in the treatment liquid. It is not always necessary to completely evaporate the solvent of the treatment liquid, and the total film thickness after drying (the total of non-drying components [flocculating agent, etc.] in the treatment liquid and the dry residual liquid) is about 1 What is necessary is just to dry so that it may become a thickness of 0.0 g / m < ² > or less.

  Further, in FIG. 1, the treatment liquid is heated by the hot air jet nozzle 58, but drying can be performed using an IR heater. Drying can be promoted by performing drying using an IR heater. However, when an IR heater is used, the atmosphere around the recording medium during drying changes, and drying is performed with air whose relative humidity is lower than that of the apparatus atmosphere. Whether or not an IR heater is used is preferably determined as appropriate based on drying conditions.

(Drawing part)
The drawing unit 14 is a mechanism for drawing an image corresponding to an input image by ejecting ink using an inkjet method. The drawing unit 70 and an inkjet arranged close to a position facing the outer peripheral surface of the drawing drum 70. The heads 72C, 72M, 72Y and 72K are configured. The inkjet heads 72C, 72M, 72Y, and 72K correspond to four colors of ink of magenta (M), cyan (C), 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 with its recording surface facing outward, and ink is applied to the recording surface from the ink jet heads 72C, 72M, 72Y, 72K.

  The inkjet heads 72C, 72M, 72Y, and 72K are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 22, and the ink ejection surfaces thereof are arranged on the 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 inkjet head 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 inkjet heads 72C, 72M, 72Y, 72K.

  From the respective ink jet heads 72C, 72M, 72Y, 72K configured as described above, ink droplets are discharged 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 on 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 jet heads 72C, 72M, 72Y, 72K. In addition, the cause of ink ejection failure can be reduced.

  The droplet ejection timings of the inkjet 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, it learns the speed fluctuation due to the deflection of the drawing drum 70 in advance, corrects the droplet ejection timing obtained by the encoder, and depends on 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. In this case, it is possible to reduce the droplet ejection unevenness.

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

  Further, 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 inkjet 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 the solvent (water) separated by the color material aggregating action, and includes a drying drum 76 and a first drying unit disposed at a position facing the outer peripheral surface of the drying drum 76. It comprises a certain first hot air jet nozzle 80 and a second hot air jet nozzle 95 as the second drying means. The second warm air ejection nozzle 95 is provided upstream of the first warm air ejection nozzle 80 in the rotation direction of the drying drum 76 (counterclockwise direction in FIG. 1).

  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 as to face outward, and a drying process is performed on the recording surface by the first hot air ejection nozzle 80 and the second hot air ejection nozzle 95. .

  In FIG. 2, the block diagram which shows a 1st drying means typically is shown. The first drying means takes in air around the apparatus and blows air from the first hot air jet nozzle 80 onto the recording medium 22 and a fan 81 that heats the air that becomes the drying air. The heater 82, the second heater 83, and a water vapor supply means 85 for supplying water vapor to the air.

  The first hot air ejection nozzle 80 can blow air over substantially the entire surface of the recording medium 22. The temperature of the air around the apparatus is T0, the relative humidity is H0, the temperature of the air ejected from the first hot air ejection nozzle 80 is Tu, and the relative humidity is Tu. The air taken in by the fan 81 is heated to the temperature T1 by the first heater 82. The heating of air here is T0 <T1 <Tu. The amount of saturated water vapor can be increased by heating the air with the first heater 82. The air heated to the temperature T1 is given water vapor by the water vapor supply means, and the amount of water in the air is increased.

  The water vapor supply means 85 includes a water tank 87 in which a certain amount of water is held, a heating element 89 provided in the water tank 87, and a shutter 97 provided between the water tank 87 and the first hot air jet nozzle 80. Composed. The amount of moisture supplied to the air is adjusted by controlling the opening ratio of the shutter 97 and the current supplied to the heating element 89 provided in the water.

  The air to which the water vapor has been applied is further heated by the second heater 83, reaches a desired temperature, and is jetted onto the recording medium 22.

  In this way, the time taken to dry the ink can be shortened by warming the air taken from around the apparatus. In addition, by increasing the relative humidity in the drying air, moisture contained in the ink solvent in the image area formed in the drawing area is evaporated, and drying of moisture in the non-image area can be suppressed or increased. In addition, the amount of water contained in the image portion and the non-image of the recording medium can be balanced, and the occurrence of cockle can be suppressed.

  In addition, as shown in FIG. 2, dry air temperature / humidity measuring means 93 can be provided at the outlet of the first hot air ejection nozzle 80. The dry air temperature and humidity measuring means 93 can measure the temperature and humidity of the sprayed dry air. By feeding this measurement value back to each other, air having a desired temperature and humidity can be created. Preferably, temperature / humidity measuring means 68 for measuring the temperature and humidity of the air around the apparatus is provided, and the temperature Tu of the drying air is preferably controlled to be 50 ° C. or higher and 70 ° C. or lower. More preferably, it is 60 degreeC or more and 65 degrees C or less. As described above, when the temperature of the drying air is increased, the moisture contained in the air does not change, so that the relative humidity decreases. Therefore, it is preferable to adjust the humidity of the drying air so as to be approximately equal to the relative humidity Hu of the air around the apparatus. The difference between the relative humidity H0 of the dry air and the relative humidity Hu of the air around the apparatus is substantially equal to that it is in the range of −5% <Hu−H0 <+ 5%.

  In the control of the drying air, the current value or the energization timing of the second heater 83 is adjusted so that the temperature of the air of the drying air becomes a desired temperature Tu. Further, the opening degree of the shutter 97 and the current of the heating element 89 are adjusted so that the relative humidity Hu of the air after jetting becomes H0. Further, when the saturated water vapor amount at the temperature T is SH (T), SH (T1)> SH (Tu) × Hu / 100 (ie, the saturated water vapor amount at the temperature T1> the water vapor at the temperature Tu and the relative humidity Hu) The current value of the first heater 82 or the energization timing is adjusted so as to satisfy (quantity).

  By making the relative humidity Hu of the drying air substantially equal to the relative humidity H0 of the air around the apparatus, the atmosphere during drying can be made substantially equal to the atmosphere around the apparatus. Even if discharged, the change in the amount of water vapor contained in the recording medium can be reduced, so that the occurrence of cockle can be suppressed.

  In addition, although the structure which takes in the air around an apparatus was demonstrated in the above, the gas supplied as a dry wind is not limited to the air around an apparatus, Another gas can also be used. For example, gas can be supplied from a gas cylinder.

  Further, in the drying section, the drying can be performed by the second warm air jet nozzle 95 as the second drying means before the first drying means 80 performs the drying. In the second drying means 95, it is preferable that drying is performed by increasing the temperature and not adjusting the moisture content (humidity) or by supplying air with a reduced moisture content. Since the relative humidity is low in the second drying means, drying can be promoted. In the second drying means, the amount of water decreases in both the image area and the non-image area. However, the moisture in the image area is mainly the moisture as the ink solvent and remains on the paper surface, so it is easy to dry. Therefore, by performing drying by the second drying means 95, the water content in both the image area and the non-image area is reduced, but since the drying proceeds particularly in the image area, the difference between the two can be reduced. . And after that, since the image formed on the recording medium is dried by the first drying means 80, the difference in the amount of water contained in the recording medium between the image portion and the non-image portion is small. When drying by the first drying means, it is possible to shorten the time until the moisture in the recording medium reaches equilibrium between the image portion and the non-image portion. The drying by the second drying means 95 can be appropriately changed depending on the drying conditions of the ink, but it is preferable that the ink droplets are dried until the water content of the ink is about half dried.

  The first drying unit 80 and the second drying unit 95 preferably adjust the strength according to the amount of ink per unit area of ink applied on the recording medium.

  Specifically, when the amount of droplet ejection is small, the amount of water contained in the image portion and the non-image portion is small, so that the moisture amount reaches an equilibrium state by drying only with the first drying means 80. Can do. On the contrary, when the amount of droplet ejection is large, if drying is performed only with the first drying unit 80, it takes time to reach the equilibrium state. It is preferable to reduce the difference in water content in the non-image area.

  Whether the drying is performed only by the first drying means 80 or the drying is also performed using the second drying means 95 can be made asymptotically efficient by changing the temperature and humidity of the apparatus environment. For example, when the average ink amount is equal to or less than a predetermined reference amount corresponding to the relative humidity in the table shown below, only the first drying means is used, and when the predetermined ink amount is exceeded, the second drying means is also used. By using and drying, the difference in moisture content can be reduced and drying can be performed efficiently.

  In Table 1 below, when the relative humidity is low, drying can be facilitated. Therefore, even if the average ink amount is large, it can be dried only by the first drying means. If the relative humidity is high, drying is difficult to proceed. Therefore, it is preferable to use the second drying means 95 if the amount of ink is not smaller than when the relative humidity is low. Table 1 shown below is an example, and it is preferable to change the predetermined reference value as appropriate depending on the temperature and humidity of the device environment.

  The amount of ink can be determined by the following formula and compared with the reference amount to determine the drying method.

When the total amount of ink in a predetermined area is V [pL], the number of pixels in a predetermined area (the total number of dots that can be ejected onto the predetermined area) is N [pieces],
Average ink amount m = V / N
Can be calculated.

  Further, since the drying drum 76 of the drying unit 16 is structurally separated from the drawing drum 70 of the drawing unit 14 during the drying process, the head meniscus by thermal drying is used in the inkjet heads 72C, 72M, 72Y, and 72K. Ink ejection due to drying of the portion 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 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.

  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 come into pressure contact with the fixing drum 84 at a predetermined pressure (for example, 0.3 MPa). A nip roller is configured between the two. 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 at a predetermined nip pressure (for example, 1 MPa). The nipping is performed and the fixing process is performed.

  When the recording medium 22 is pressurized and heated by the first fixing roller 86 and the second fixing roller 88, 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. Is 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, although the example which performs both heating and pressurization was shown in the above, you may make it perform only one side. 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 layer and the Tg characteristics of the 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.

  According to the fixing unit 18 configured as described above, latex particles in the thin image layer formed by the drying unit 16 are pressed and heated by the first fixing roller 86 and the second fixing roller 88. Since it is melted, it can be fixed and fixed on the recording medium 22. Further, according to the fixing unit 18, the fixing drum 84 is structurally separated from the other drums. Therefore, the temperature setting of the fixing unit 18 can be freely set separately from the drawing unit 14 and the drying unit 16. be able to.

  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.

(Discharge part)
As shown in FIG. 1, 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 carrier)
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.

(Inkjet head structure)
Next, the structure of each inkjet head will be described. Since the structures of the ink-jet heads 72C, 72M, 72Y, and 72K for each color are common, the ink-jet heads are represented by the reference numeral 100 in the following.

  FIG. 3A is a plan perspective view showing an example of the structure of the inkjet 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 inkjet head 100. As shown in FIGS. 3A and 3B, the ink jet head 100 of this example includes a plurality of ink chamber units (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 (X in FIG. 3A) showing a three-dimensional configuration of a droplet discharge element for one channel (an ink chamber unit corresponding to one nozzle 102) serving as a recording element unit in the inkjet head 100. 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 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. A drive motor for the pump 75 for sucking negative pressure from the suction hole, a motor for a retracting mechanism for the head units of the ink jet 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 inkjet 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 inkjet 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 inkjet 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 inkjet 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 processing liquid application control unit 126 controls operations of the processing liquid application device 56 and the hot air drying device (hot air ejection nozzle) 58 of the processing liquid application unit 12 in accordance with an instruction from the system controller 122. In the treatment liquid application apparatus, the amount of treatment liquid applied to the recording medium 22 is controlled. In the hot air drying device controller 162, the temperature and humidity of the hot air supplied to the recording medium 22 are controlled by the first heater 164, the second heater 166, and the water vapor supply means 168.

  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 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.

  The drying control unit 134 performs drying of the ejected ink according to the control of the system controller 122, and therefore the first hot air drying device (first hot air ejection nozzle) control unit 170, the second warm air. Control is performed by an air drying device (second hot air ejection nozzle) control unit 172. The first hot air drying device controller 170 controls the first heater 174, the second heater 176, and the water vapor supply means 178 for adjusting the humidity of the drying air. Further, the drying control unit 134 uses the second hot air drying device based on the temperature and humidity of the air around the device measured by the temperature / humidity measuring unit 68 and the ink amount measured by the ink amount measuring unit 74. The controller 172 controls the second hot air drying device (second hot air jet nozzle).

  The drying air temperature and humidity of the drying air controlled by the first hot air drying device are measured by the drying air temperature / humidity measuring means 93. Based on the measured temperature and humidity of the drying air, feedback control is performed to control the shutter opening ratio of the water vapor supply means, the current supplied to the heating element, and the like, thereby adjusting the relative humidity of the drying air. In addition, the ROM 145 stores the amount of water vapor supplied to the drying air after heating corresponding to the temperature and humidity of the air around the apparatus, and the shutter opening ratio and the heating element are determined by the amount of water vapor supplied. The amount of electricity to be energized can also be controlled.

  Note that the measured temperature, humidity, and ink amount can be directly input by a personal computer (not shown), or can be input from the outside via the communication interface 120 and controlled based on this information.

  Even when the temperature and humidity of the drying air are controlled by the treatment liquid application control unit, the first heater 164, the second heater 166, and the water vapor supply means 168 are driven based on the temperature and humidity acquired by the same method. Control can be performed with.

[recoding media]
In the present invention, drying is performed by increasing the humidity of the drying air, and the amount of water contained in the recording medium is in an equilibrium state. Therefore, any recording medium having liquid permeability can be used without any particular limitation. Plain paper, coated paper, etc. can be used.

[ink]
As the ink used, a dye ink in which a color material is dissolved in a molecular state (may be in an ionic state) in a liquid solvent, or a pigment ink in which a color material is dispersed in a minute mass in a liquid solvent Etc.

  Hereinafter, the water-based ink will be described in detail, but the present invention is not limited to the water-based ink, and can be applied to an 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.

<Pigment (B)>
Pigment (B) is a colored substance that is almost insoluble in water and organic solvents as described on page 518 of the 3rd edition of the Chemical Dictionary, 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).

  The upper pigments may be used alone or in combination of two or more selected.

  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.

<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.

<Self-dispersing polymer fine particles (C)>
The water-based ink 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 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 uses a water-soluble solvent for the purpose of an anti-drying agent, a wetting agent or a penetration enhancer. In particular, when used as an ink jet recording ink, a water-soluble organic solvent is preferably used for the purpose of an anti-drying agent, 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.

  (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 added is not particularly limited, but is preferably 10% by mass or more and 99% by mass or less, and more preferably 30% by mass or more and 80% by mass, from the viewpoint of ensuring stability and ejection reliability in the entire ink composition. % Or less, and more preferably 50% by mass or more and 70% by mass or less.

<Surfactant>
It is preferable to add a surfactant to the water-based ink. 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 contains at least one fixing agent that fixes components in the aqueous ink. The immobilizing agent can immobilize (aggregate) ink by contacting with ink on paper. For example, when the treatment liquid is applied and ink is deposited and brought into contact with the fixing agent on the paper, the components in the ink can be aggregated and fixed on the paper.

  Since it is desirable that the fixing agent can fix (aggregate) the water-based ink, it is preferable that the fixing agent is a material that easily dissolves in the water-based ink when it comes into contact with the water-based ink. A valent metal salt is more preferable, and an acidic substance having 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. Cationic compounds can also be used.

  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, it is preferable that the acidic substance as a fixing agent contained in the treatment liquid has a low pKa, high solubility, and a valence of 2 or more, and a functional group that stabilizes the dispersion of particles in the ink ( For example, a divalent or trivalent acidic substance having a high buffering capacity in a pH range lower than the pKa of the carboxyl group) is more preferable.

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

  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, 24 ... 1st middle Conveying section, 26 ... second intermediate conveying section, 28 ... third intermediate conveying section, 30 ... intermediate conveying body, 68 ... greenhouse degree measuring means, 70 ... drawing drum, 72C, 72M, 72Y, 72K ... inkjet head, 74: Ink amount measuring means, 76 ... Drying drum, 80 ... First drying means (first hot air jet nozzle), 81 ... Fan, 82 ... First heater, 83 ... Second heater, 84 ... Fixing drum, 85 ... water vapor supply means, 86 ... first fixing roller, 87 ... water tank, 88 ... second fixing roller, 89 ... heating element, 93 ... drying air temperature and humidity measuring means, 95 ... second drying means (Second hot air ejection nozzle), 97 ... shutter

Claims (15)

An ink ejection means for ejecting ink onto a recording medium to form an image; and
First drying means for drying the ink applied on the recording medium,
The first drying means includes a blowing means for blowing dry air onto the recording medium, a heating means for heating the drying air, and a water vapor supply means for supplying water vapor to the drying air. An inkjet recording apparatus. Equipped with temperature and humidity measuring means to measure the temperature and relative humidity of the air around the device,
2. The inkjet recording according to claim 1, further comprising a control unit that controls the water vapor supply unit so that a difference between a relative humidity of the dry air and a relative humidity of the air around the apparatus is substantially equal. apparatus. The water vapor supply means comprises a water storage section for storing water, and a heating element that heats the water to form water vapor,
The flow path section through which the dry air passes and the water vapor supply means are separated by an openable / closable shutter,
The inkjet recording apparatus according to claim 1, wherein the control unit controls at least one of an opening ratio of the shutter and a current supplied to the heating element. A drying air temperature and humidity measuring means for measuring the temperature and humidity of the drying air;
4. The ink jet recording apparatus according to claim 3, wherein the control unit performs feedback control based on temperature and humidity of the dry air to operate at least one of the shutter and the heating element.   The inkjet recording apparatus according to any one of claims 1 to 4, wherein air around the apparatus is used as the drying air. Treatment liquid application means for applying a treatment liquid having a function of aggregating or thickening components in the ink onto the recording medium;
A treatment liquid drying means for drying the treatment liquid,
The treatment liquid drying means includes a treatment liquid blow means for blowing dry air onto the recording medium, a treatment liquid heating means for heating the dry air, and a treatment liquid steam supply for supplying water vapor to the dry wind. Means, and
The process liquid drying control means for controlling the steam supply means for the process liquid is provided so that the difference between the relative humidity of the dry air and the relative humidity of the air around the apparatus is substantially equal. The inkjet recording apparatus according to any one of 1 to 5. A second drying unit provided between the ink discharge unit and the first drying unit;
The said 2nd drying means is provided with the 2nd ventilation means which supplies drying air, and the 2nd heating means which heats this drying air, The any one of Claim 1 to 6 characterized by the above-mentioned. The ink jet recording apparatus described. An ink amount measuring means for measuring an ink amount per unit area of the ink applied to the recording medium;
The inkjet recording apparatus according to claim 1, further comprising a drying control unit that adjusts strength of the first drying unit and the second drying unit according to the ink amount.   9. The inkjet recording apparatus according to claim 8, wherein the drying control unit controls to use only the first drying unit when the ink amount is lower than a reference value.   10. The ink jet recording apparatus according to claim 9, wherein the reference value is determined from a temperature of air around the apparatus and a relative humidity measured by the temperature / humidity measuring unit. An ink ejection process for forming an image by ejecting ink onto a recording medium; and
A first drying step of drying the ink applied on the recording medium,
In the ink jet recording method, the first drying step heats drying air, supplies water vapor, and blows air on the recording medium. A temperature and humidity measurement process for measuring the temperature and relative humidity of the air around the device;
And a control step of controlling the difference between the relative humidity of the drying air blown in the first drying step and the relative humidity of the air around the apparatus to be substantially equal. 11. An ink jet recording method according to item 11. A treatment liquid application step of applying a treatment liquid having a function of aggregating or thickening components in the ink onto the recording medium;
A treatment liquid drying step for drying the treatment liquid,
The treatment liquid drying step heats the drying air and supplies water vapor,
The ink jet recording method according to claim 11, further comprising a treatment liquid drying control step of controlling the difference between the relative humidity of the drying air and the relative humidity of the air around the apparatus to be substantially equal. . Before the first drying step,
An ink amount measuring step of measuring an ink amount per unit area of the ink applied to the recording medium;
The inkjet recording method according to claim 11, further comprising a second drying step of supplying heated drying air in accordance with the ink amount.   15. The ink jet recording method according to claim 14, wherein whether to perform the second drying step is determined based on a reference value determined by a relative humidity of air around the apparatus.

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