JP5276384B2 - Inkjet recording method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method and an inkjet recording device capable of obtaining a desired dot diameter in all inks and preventing the inks from floating in the case of providing the plurality of inks. <P>SOLUTION: The inkjet recording device 1 has a treatment liquid applying device 56 providing a treatment liquid containing a coagulant to a recording medium 22 and a plurality of inkjet heads 72M, 72C, 72Y, 72K arranged in the rear step of the treatment liquid applying device 56 for hitting the inks to the treatment liquid on the recording medium 22. The plurality of inkjet head 72M, 72C, 72Y, 72K hit the inks having different surface tension and arranged from the upstream side of the traveling direction of the recording medium 22 in the order of the smaller surface tension of the hit inks. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an ink jet recording method and apparatus, and more particularly to a direct drawing type ink jet recording method and apparatus for forming an image by directly applying ink to a recording medium.

  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 the surface tension, and a bleed (landing interference) in which a desired dot cannot be formed. ) Problem occurs. 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, as a method for solving the problem of bleeding, a two-liquid mixing method is proposed in which a treatment liquid containing an aggregating component is applied to a recording medium, and then ink is ejected and aggregated. According to this method, since the color material component of the ink that has been ejected onto the recording medium is aggregated by the processing liquid on the recording medium, it is difficult for the dots to interfere with each other, and the bleeding problem can be improved.

  However, in the above-described two-component mixing method, the secondary color (ink ejected on the primary color dot) is larger than the dot diameter of the primary color (ink first ejected on the treatment liquid on the recording medium). This causes a problem that the dot diameter increases. For this reason, if the dot diameter setting value is adjusted to the primary color dot, the secondary color dot becomes too large and noticeable. Conversely, if the dot diameter setting value is adjusted to the secondary color dot, the primary color dot becomes small. There is a problem that the solid portion due to the primary color dots is not filled. When a line drawing is drawn, the line width changes at the boundary between the primary color and the secondary color (that is, at the boundary between the portion having the primary color dot below the line drawing and the portion not having the primary color dot). This problem occurs.

  As a method for solving such a problem, a method of determining whether the dot is a primary color dot or a secondary color dot and reducing the ink discharge amount in the case of a secondary color dot can be considered. However, this method has a problem that control is very difficult.

As another method, a method using special ink jet dedicated paper as in Patent Document 1 can be considered. In the ink jet exclusive paper of Patent Document 1, at least one solid fine particle-containing ink receiving layer is provided on a support, and the solid fine particles are synthesized in the presence of a water-soluble organic polymer. This ink jet dedicated paper has excellent ink absorbability and can prevent the secondary color ink from expanding.
JP-A-7-9755

  However, in recent years, not only special inkjet dedicated paper as in Patent Document 1, but also drawing on a recording medium such as coated paper with low permeability is desired.

  Further, even when the ink jet exclusive paper of Patent Document 1 is used, if the ink droplet ejection time interval is short, there is a problem that the dot diameter cannot be completely prevented from being enlarged. For example, when the shuttle scan method is changed to the one-pass method, the ink droplet ejection time interval becomes very short, and the secondary color ink is ejected before the primary color ink penetrates. There was a problem that the increase in diameter could not be prevented.

  Furthermore, in the two-liquid mixing method described above, ink is ejected onto the recording medium to which the processing liquid is applied, so that the ink does not contact the recording medium and floats on the processing liquid, and the dot formation position is large. There was a problem of being disturbed, and there was a request to prevent this.

  The present invention has been made in view of such circumstances, and in the case of applying a plurality of inks, an ink jet capable of obtaining a desired dot diameter with all the inks and preventing ink floating. It is an object to provide a recording method and apparatus.

In order to achieve the above object, a first aspect of the present invention provides a treatment liquid application step for applying a treatment liquid containing a flocculant onto a recording medium, and a plurality of different colors on the recording medium to which the treatment liquid is applied. An ink droplet ejecting step for ejecting ink of a different color from an ink jet head in ascending order of surface tension. The ink droplet ejecting step deposits inks of different colors on the previously deposited ink and continuously The ink jet recording method is characterized in that the difference in surface tension between the two inks ejected is greater than 1 mN / m .

  According to the present invention, ink is ejected in order of increasing surface tension, so that the ink deposited later has a large surface tension and a low wettability. For this reason, the ink that has been ejected later is difficult to wet and spread, and the dot expansion of the secondary color ink can be prevented.

According to a second aspect of the present invention, in the first aspect of the invention, an ink drying step for drying the ink on the recording medium and a fixing for fixing the dried ink are performed after the ink droplet ejection step. And the ink droplet ejection step is characterized in that the difference in surface tension between the plurality of ink droplets ejected is less than 5 mN / m. When the surface tension difference of the entire ink is large, an offset occurs in which the ink adheres to the fixing roller in the fixing step. However, in the present invention, the surface tension difference of the plurality of inks is less than 5 mN / m. Can be prevented.
In order to achieve the above object, a third aspect of the present invention provides a treatment liquid application step for applying a treatment liquid containing a flocculant on a recording medium, and a recording medium to which the treatment liquid is applied. An ink droplet ejection process for ejecting the ink from the inkjet head in ascending order of surface tension, an ink drying process for drying the ink on the recording medium, and fixing the dried ink after the ink droplet ejection process. A fixing step, wherein the ink droplet ejection step deposits ink of different colors on the previously deposited ink, and a difference in surface tension between the plurality of ink droplets ejected is less than 5 mN / m An ink jet recording method is provided.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the ink includes self-dispersing polymer fine particles, the temperature reached on the image surface in the ink drying step is Td, and the ink self When the softening point of the dispersible polymer particles is Tp, the temperature is controlled so as to satisfy the relationship of Td <Tp.
In invention any one of the invention of claim 2 to 4 according to claim 5 of the present invention, it said ink comprising a self-dispersible polymer microparticles, the temperature reached the image surface at the fixing step and the Tf In this case, the softening point Tp of the self-dispersing polymer fine particles of the ink is set so as to satisfy the relationship of Tp <Tf.
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the treatment liquid on the recording medium is dried between the treatment liquid application step and the ink droplet ejection step. A treatment liquid drying step is provided. According to the present invention, since the ink is ejected after the treatment liquid is dried, it is possible to prevent the ejected ink from floating.

According to a seventh aspect of the present invention, in the sixth aspect , the treatment liquid drying step is characterized in that the total thickness of the treatment liquid on the recording medium is 1.0 g / m ² or less. . According to the present invention, it is possible to reliably prevent colorant floating by defining the total thickness of the treatment liquid.

According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, in the ink droplet ejection step, the landing time interval between two inks that are ejected in succession is 100 ms or less. It is characterized by. When the landing time interval is 100 ms or less, secondary color ink dot expansion tends to occur. However, in the present invention, droplets are ejected in order of increasing surface tension, and therefore secondary color ink dot expansion can be prevented.
According to a ninth aspect of the present invention, in order to achieve the above object, a treatment liquid application step for applying a treatment liquid containing a flocculant on a recording medium, and a recording medium to which the treatment liquid is applied are provided with a plurality of different colors. An ink droplet ejecting step for ejecting ink of a different color from an ink jet head in ascending order of surface tension. The ink droplet ejecting step deposits inks of different colors on the previously deposited ink and continuously The ink jet recording method is characterized in that the landing time interval between the two inks to be ejected is 100 ms or less.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the recording medium is a coated paper for printing. The coated paper for printing has low penetrability and is likely to cause dot expansion of the secondary color ink. However, since the droplets are ejected in order of increasing surface tension in the present invention, the dot expansion of the secondary color ink can be prevented.

According to an eleventh aspect of the present invention, in order to achieve the above object, a treatment liquid application device for applying a treatment liquid containing an aggregating agent to a recording medium, and a stage subsequent to the treatment liquid application device, are provided on the recording medium. A plurality of inkjet heads that eject ink onto a treatment liquid; a drying drum that dries the ink on the recording medium; and a fixing drum that fixes the dried ink after the plurality of inkjet heads. , wherein the plurality of inkjet heads, Ri Do different surface tension different colors from each other, the difference in surface tension of the plurality of ink droplet ejection is hitting the ink is less than 5 mN / m, on the ink ejected earlier There is provided an ink jet recording apparatus which is disposed from the upstream side in the traveling direction of the recording medium in the order of decreasing surface tension of ink to be ejected.

  According to the present invention, ink is ejected in ascending order of surface tension. For this reason, since the ink that has been ejected later has a large surface tension and a low wettability, it is possible to prevent the dot expansion of the secondary color ink.

  According to the present invention, since ink is ejected in order of increasing surface tension, it is possible to prevent an increase in the dot diameter of the ink.

  Hereinafter, preferred embodiments 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. 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 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. A more detailed description of the treatment liquid will be described later.

  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, 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.

  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 72M, 72C, 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 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. The solvent component of the processing liquid is dried by heating with the hot air blowing nozzle 58 and the IR heater 60. 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 thickness of 0.0 g / m < ² > or less.

(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 72M, 72C, 72Y, and 72K are configured. The inkjet heads 72M, 72C, 72Y, and 72K correspond to inks of four colors, 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 so that the recording surface faces outward, and ink is applied to the recording surface from the ink jet heads 72M, 72C, 72Y, 72K.

  The inkjet heads 72M, 72C, 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 72M, 72C, 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 72M, 72C, 72Y, 72K. Each color ink contains at least pigment particles, a dispersant polymer for coating the pigment, and self-dispersing polymer fine particles.

  Further, the ink jet heads 72M, 72C, 72Y, and 72K are configured to eject ink having a smaller surface tension toward the upstream side of the recording medium 22 in the traveling direction. That is, each color ink is adjusted so that the surface tension satisfies the relationship of magenta (M) <cyan (C) <yellow (Y) <black (K). The surface tension is adjusted by changing the composition such as the amount of the surfactant. As a result, when ink is ejected by the one-pass method, the ink is ejected in ascending order of surface tension.

  The surface tension of the color ink is set so that the surface tension difference between adjacent color inks exceeds 1 mN / m. That is, the surface tension difference between magenta (M) and cyan (C), the surface tension difference between cyan (C) and yellow (Y), and the surface tension difference between yellow (Y) and black (K) each exceed 1 mN / m. Set to This is because if the surface tension difference is 1 mN / m or less, the dot expansion preventing effect described later cannot be sufficiently obtained.

  Further, the surface tension of each color ink is set so that the surface tension difference in the whole ink is less than 5 mN / m. That is, the surface tension difference between the first color magenta (M) and the final color yellow (Y) is set to less than 5 mN / m. This is because dots are repelled when color inks having a surface tension difference exceeding 5 mN / m are adjacent to each other. Further, when the overall surface tension difference exceeds 5 mN / m, an offset occurs in the fixing roller at the subsequent stage.

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

  Further, in this embodiment, since ink is ejected in order of increasing surface tension, the ink deposited afterward has a large surface tension and a low wettability. For this reason, ink that has been ejected later is difficult to wet and spread, and dot expansion of the secondary color ink can be prevented.

  The droplet ejection timing of each of the inkjet heads 72M, 72C, 72Y, and 72K is 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. Further, the fluctuation of the speed due to the fluctuation of the drawing drum 70 or the like is learned in advance, and the droplet ejection timing obtained by the encoder 91 is corrected to obtain the fluctuation 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.

  In addition, maintenance operations such as cleaning the nozzle surfaces of each of the inkjet heads 72M, 72C, 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. However, it is necessary to arrange the recording medium 22 from the upstream side in the traveling direction in the order of the ink having the smallest surface tension. A more detailed description of the ink jet heads 72M, 72C, 72Y, and 72K and a detailed description of ink will be described later.

(Drying part)
The drying unit 16 is a step of drying the solvent (water) separated by the color material aggregation action. The drying unit 16 and a first IR heater 78 disposed at a position facing the outer peripheral surface of the drying drum 76. , A hot air jet nozzle 80 and a second IR heater 82. The first IR heater 78 is provided upstream of the hot air jet nozzle 80 in the rotation direction of the drying drum 76 (counterclockwise direction in FIG. 1), and the second IR heater 82 is jetted of hot air. Provided downstream of the 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. The residual water amount of the ink-derived water after the drying treatment is preferably 1 g / m ² or more and 4 g / m ² or less.

  During the drying process, the drying drum 76 of the drying unit 16 is structurally separated from the drawing drum 70 of the drawing unit 14, so that the head meniscus portion of the ink jet heads 72M, 72C, 72Y, and 72K is thermally dried. Ink ejection failure due to drying 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.

  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.

  Note that an elastic layer may be formed on one surface of the first fixing roller 86, the second fixing roller 88, and the fixing drum 84 to have a uniform nip width with respect to the recording medium 22. For example, the surface of the first fixing roller 86 and the surface of the second fixing roller 88 have a two-layer structure, and the first layer on the surface layer side is formed of a releasable material, and the second layer (inner layer). Is preferably made of a rubber elastic material. By using the first layer as a releasable material, the roller is less likely to become dirty, and the cleaning load on the roller can be reduced. The second layer is preferably a rubber elastic body having a rubber hardness of 50 ° or less. By making the second layer a rubber elastic body having a hardness of 50 ° or less, it is possible to gain time for nipping the recording medium 22, which is advantageous for forming a film in high-speed recording. Further, by setting the second layer to a hardness of 50 ° or less, it is possible to reduce the pressure when contacting the recording medium 22, and the life of the roller can be improved. On the other hand, the roller surface hardness of the first fixing roller 86 and the second fixing roller 88 is preferably 70 ° or less. By reducing the surface hardness of the roller, the followability to image irregularities (in a certain time) is improved, which is advantageous for coating at high speed recording.

  The first fixing roller 86 and the second fixing roller 88 are constituted by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good heat conductivity, and have a predetermined temperature (for example, 60 to 80 ° C.). Controlled. In this case, when the arrival temperature on the image surface is Tf, it is preferably set so as to satisfy the relationship of Tp <Tf with respect to the softening point Tp of the self-dispersing polymer fine particles of the ink.

  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 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 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 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.

(Inkjet head structure)
Next, the structure of each inkjet head will be described. Since the structures of the ink-jet heads 72M, 72C, 72Y, and 72K for each color are the same, the ink-jet head will be denoted by reference numeral 100 as a representative of them.

  FIG. 2A is a plan perspective view showing an example of the structure of the inkjet head 100, and FIG. 2B 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. 2A and 2B, the ink jet head 100 of the present example includes a plurality of ink chamber units (including ink nozzles 102, pressure chambers 104 corresponding to the nozzles 102, etc.). 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. 2) substantially orthogonal to the conveying direction of the recording medium 22 (arrow S in FIG. 2). The form is not limited to the illustrated example. For example, instead of the configuration of FIG. 2 (a), as shown in FIG. 3, a long head module 100 ′ in which a plurality of nozzles 102 are two-dimensionally arranged is arranged in a staggered manner and joined together to form a long one. 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. 2A and 2B), 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. 4 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 inkjet head 100 (X in FIG. 2A). FIG.

  As shown in FIG. 4, 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 (vibrating plate also serving as a common electrode) 112 constituting a part of the pressure chamber 104 (the top surface in FIG. 4). 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. 5, the ink chamber unit 108 having the structure described above is latticed in a fixed arrangement pattern along a row direction along the main scanning direction and an oblique column direction having a constant angle θ not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in the shape.

  That is, 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 driving a nozzle with a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially moved from one side to the other. (3) The nozzles are divided into blocks, and 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 the nozzles 102 arranged in a matrix as shown in FIG. 5 are driven, 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 adopted. However, in the practice of the present invention, a method of ejecting ink is not particularly limited. Instead of the piezo jet method, various methods such as a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure can be applied.

(Description of control system)
FIG. 6 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. 6, a motor 152 disposed in each part in the apparatus is represented by reference numeral 152. For example, the motor 152 shown in FIG. 6 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 retraction mechanism for the head units of the ink jet heads 72M, 72C, 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. 6, a plurality of heaters provided in the ink jet recording apparatus 1 are represented by reference numeral 154 as a representative. For example, the heater 154 shown in FIG. 6 includes a preheater (not shown) for heating the recording medium 22 to an appropriate temperature in the paper supply 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. 6, 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 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. Specifically, in the treatment liquid application device 56, a rubber roller rotation drive unit 156 that drives rotation of the rubber roller, an anilox roller rotation drive unit 158 that drives rotation of the anilox roller, and a liquid feed pump that supplies the treatment liquid to the treatment liquid container 160 and the like are controlled by the processing liquid application control unit 126.

  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.

(Effects unique to inkjet recording devices)
Since the ink jet recording apparatus 1 configured as described above ejects ink in order of increasing surface tension, it can prevent the dot diameter of the second and subsequent inks from increasing. The mechanism will be described below.

  When the first ink (hereinafter referred to as “primary color ink”) is ejected onto the recording medium 22, a thin film of a treatment liquid that is substantially solid by drying is formed on the recording medium 22. For this reason, since primary color ink spreads in a substantially solid state, the wetting and spreading speed is relatively slow. In addition, when a primary color ink is ejected, a sufficient amount of aggregating agent (treatment liquid) is present on the recording medium 22, so that the aggregating reaction is fast. Accordingly, the primary color ink deposited on the recording medium 22 has a low wetting and spreading speed and aggregates at the initial stage of the wetting and spreading, so that the dot diameter of the primary color ink becomes small.

  On the other hand, when another ink (hereinafter referred to as secondary color ink) is ejected onto the primary color ink, substantially liquid primary color ink exists on the recording medium 22. Therefore, the secondary color ink wets and spreads with respect to the liquid primary color ink, so that the wet spreading speed is relatively fast. Further, when the secondary color ink is ejected, the aggregating agent (processing liquid) on the recording medium 22 is reduced by the agglomeration reaction of the primary color ink, so the agglomeration speed is slow. Accordingly, the secondary color ink ejected onto the recording medium 22 has a high wet spreading speed and aggregates at a later stage of the wet spreading, so that the dot diameter of the secondary color ink becomes large.

  Therefore, in the present embodiment, ink is ejected in ascending order of surface tension. That is, the secondary color ink having a surface tension larger than that of the primary color ink is subsequently ejected. Since the secondary color ink having a large surface tension has a slow wetting and spreading speed, the secondary color dot diameter can be prevented from being enlarged, and the difference in dot diameter between the primary color ink and the secondary color ink can be eliminated.

  In the above-described embodiment, the ink droplets are ejected in ascending order of the surface tension. Therefore, the inkjet heads 72M, 72C, 72Y, and 72K are arranged from the upstream side in the running direction of the recording medium 22 in ascending order of the surface tension of the ink. However, the present invention is not limited to this. For example, the traveling means of the recording medium 22 may be controlled so that ink is ejected in ascending order of surface tension.

  In addition, as described above, since the primary color ink is ejected onto the thin film of the treatment liquid that has become substantially solid by drying, it is possible to prevent the color material from floating in the primary color ink. Conversely, when the treatment liquid is not dried, the primary color ink does not adhere to the recording medium, and dots are not formed at desired positions.

(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. 7 schematically shows the configuration of the belt conveyance type inkjet recording apparatus 2. Note that members having substantially the same configuration and operation as those of the ink jet recording apparatus 1 shown in FIG.

  The ink jet recording apparatus 2 shown in FIG. 7 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-shaped 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. The ink jet heads 72M, 72C, 72Y, and 72K are arranged so as to eject ink in ascending order of surface tension, as in the case of the ink jet recording apparatus 1 of FIG.

  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 has been ejected. A hot air supply device 212 that supplies hot air to the upper surface of the recording medium 22 and a lower portion 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.

  Also in the case of the ink jet recording apparatus 2 configured as described above, since the ink is ejected in order of increasing surface tension, it is possible to prevent the secondary color dot diameter from being increased.

As described above, the ink jet recording apparatus and the ink jet recording method of the present invention have been described in detail. However, the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.
[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 pulps such as LBKP and NBKP; mechanical pulps such as GP, PGW, RMP, TMP, CTMP, CMP, and CGP; wood pulps such as waste paper pulp such as DIP And a pigment as a main component, and at least one binder such as 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 and 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.

  In the method of the present invention, these base papers or coated papers may be used as they are, or for example, a calendar process is performed using a machine calendar, a TG calendar, a soft calendar, or the like, and the flattening is controlled. May be used.

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.

The recording medium in the present invention is not limited to coated paper, and the following recording media can also be used. That is, glossy or matte paper such as commercially available paperboard, cast-coated paper, art paper, high-quality paper, copy paper, recycled paper, synthetic paper, medium-quality paper, pressure-sensitive paper, embossed paper, etc. is suitably used, and ink jet dedicated paper Can also be used. Resin films and metal vapor deposited forms can also be used. Examples of recording media include OK L Card + (Oji Paper Co., Ltd.), SA Kinto + (Oji Paper Co., Ltd.), Satin Kinto N (Oji Paper Co., Ltd.), OK Top Coat + (Oji Paper Co., Ltd.), New Age (made by Oji Paper Co., Ltd.), Tokuhishi Art Double Sided N (Mitsubishi Paper Co., Ltd.), Tokuhishi Art Single Sided N (Mitsubishi Paper Co., Ltd.), New V Matt (Mitsubishi Paper Co., Ltd.), Aurora Coat (made by Nippon Paper Industries Co., Ltd.) , Aurora L (manufactured by Nippon Paper Industries), Ulite (manufactured by Nippon Paper Industries), Recycle Coat T-6 (manufactured by Nippon Paper Industries), Recycle Mat T-6 (manufactured by Nippon Paper Industries), iBest W (Nippon Paperboard Company) ), Invar Coat M (manufactured by SPAN CORPORATION), Hi McKinley Art (manufactured by Gojo Paper Co., Ltd.), Kinmari Hi-L (manufactured by Hokuetsu Paper Co., Ltd.), Signature True (manufactured by Newpage corporation), Sterling Ultra (manufactured by Newpage corporation) ), Anthem (manufactured by Newpage corporation), Hanno Art Silk (manufactured by Sappi), Han no Art gross (Sappi), Consort Royal Semimatt (Scheufelen), Consort Royal Gross (Scheufelen), Zanders Ikono Silk (m-real), Zanders Ikono Gross (m-real) Those having a basis weight of 60 to 350 g / m ² are preferably used.

[Water-based ink]
Hereinafter, the water-based ink used in the present invention will be described in detail. 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.

<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 pigments that can be used 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 Black made 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 preferably used as a penetration accelerator for the purpose of allowing the ink composition (particularly, the ink-jet ink composition) to penetrate into 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.

    In the structural formula (1), l, m, and n are each independently an integer of 1 or more and represent 1 + m + n = 3-15.

  When l + m + n is less than 3, the curl suppressing force is small, and when it exceeds 15, the discharge property is deteriorated.

  Among the above, l + m + n is preferably 3 to 12, and more preferably 3 to 10.

  In the structural formula (1), AO represents ethyleneoxy and / or propyleneoxy, and among them, a propyleneoxy group is preferable.

Each AO of (AO) ₁ , (AO) _m , and (AO) _n may be the same or different.

  Examples of the water-soluble solvent having an SP value of 27.5 or less and the compound represented by the structural formula (1) are shown below together with the SP value (in parentheses). However, the present invention is not limited to this.

Diethylene glycol monoethyl ether (22.4)
Diethylene glycol monobutyl ether (21.5)
Triethylene glycol monobutyl ether (21.1)
Dipropylene glycol monomethyl ether (21.3)
Dipropylene glycol (27.2)

_{· NC 4 H 9 O (AO} ) 4 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1)
(20.1)
_{· NC 4 H 9 O (AO} ) 10 -H ( in AO = EO or PO, the ratio of EO: PO = 1: 1) (18.8)
HO (A′O) ₄₀ −H (A′O = EO or PO, the ratio is EO: PO = 1: 3) (18.7)
HO (A ″ O) ₅₅ −H (A ″ O = EO or PO, the ratio is EO: PO = 5: 6) (18.8)
HO (PO) ₃ -H (24.7)
・ HO (PO) _7- H (21.2)
・ 1,2-Hexanediol (27.4)
In the present invention, EO and PO represent an ethyleneoxy group and a propyleneoxy group.

  The proportion (content) of the compound of the structural formula (1) in the (a) water-soluble solvent is preferably 10% or more, more preferably 30% or more, and further preferably 50% or more. Even if the value is high, no problem arises.

  By setting it in the above range, curling can be suppressed without deteriorating the stability and dischargeability of the ink, which is preferable.

  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, the surface charge of particles such as pigments and resin particles in inks that are dispersed and stabilized with weakly acidic functional groups such as carboxyl groups is reduced by reacting with acidic substances having a lower pKa, thereby reducing dispersion stability. can do. Therefore, the acidic substance as a 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.

(Synthesis of resin dispersant P-1)
According to the following scheme, a resin dispersant P-1 (Chemical Formula 8), which is one embodiment of the resin dispersant (A), was synthesized.

  To a 1000 ml three-necked flask equipped with a stirrer and a condenser, 88 g of methyl ethyl ketone was added and heated to 72 ° C. under a nitrogen atmosphere. A solution in which 10 g of methacrylic acid and 30 g of methyl methacrylate were dissolved was dropped over 3 hours. After the completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2'-azobisisobutyrate dissolved in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess of hexane, and the precipitated resin was dried to obtain 96 g of a resin dispersant P-1.

  The composition of the obtained resin dispersant P-1 was confirmed by H-NMR, and the weight average molecular weight (Mw) determined by GPC was 44600. Furthermore, when the acid value of this polymer was calculated | required by the method of JIS specification (JISK0070: 1992), it was 65.2 mgKOH / g.

(Synthesis of self-dispersing polymer fine particles B-01)
According to the following scheme, self-dispersing polymer fine particles B-01, which is one embodiment of the self-dispersing polymer fine particles (C), were synthesized.

  That is, 360.0 g of methyl ethyl ketone was charged into a reaction vessel formed of a 2 liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, and the temperature was raised to 75 ° C.

  Next, while maintaining the temperature in the reaction vessel at 75 ° C., 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (Wako Pure Chemical Industries, Ltd.) (Manufactured) A mixed solution consisting of 1.44 g was added dropwise at a constant speed so that the addition was completed in 2 hours.

  After completion of the dropwise addition, a solution consisting of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added, stirred for 2 hours at 75 ° C., and then a solution consisting of 0.72 g of “V-601” and 36.0 g of isopropanol was added. After stirring at 75 ° C. for 2 hours, the temperature was raised to 85 ° C. and stirring was further continued for 2 hours.

  The weight average molecular weight (Mw) of the obtained copolymer was 64000, and the acid value was 38.9 (mgKOH / g). The weight average molecular weight (Mw) was calculated in terms of polystyrene by gel permeation chromatography (GPC). The columns used were TSKgel SuperHZM-H, TSKgel SuperHZ4000, and TSKgel SuperHZ200 (manufactured by Tosoh Corporation).

  Next, 668.3 g of the copolymer solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the reaction vessel was depressurized, and isopropanol, methyl ethyl ketone, and distilled water totaled 913. 7 g was distilled off. As a result, an aqueous dispersion (emulsion) of self-dispersing polymer fine particles (B-01) having a solid content concentration of 28.0% was obtained.

  The chemical structural formula of self-dispersing polymer fine particles B-01 is shown below. The number of each structural unit represents a mass ratio.

(Creation of dispersion of cyan pigment-containing resin particles)
CI Pigment Blue 15: 3 (Phthalocyanine-A220 manufactured by Dainichi Seika Co., Ltd.), 5 parts by mass of the resin dispersant (P-1) shown in Table 1, 42 parts by mass of methyl ethyl ketone, and 1 N aqueous NaOH solution 5.8 parts by mass and 86.9 parts by mass of ion-exchanged water were mixed and dispersed with a bead mill using 0.1 mmΦ zirconia beads for 2 to 6 hours.

  Methyl ethyl ketone was removed from the obtained dispersion at 55 ° C. under reduced pressure, and a part of water was further removed to obtain a dispersion of cyan pigment-containing resin particles having a pigment concentration of 10.2% by mass.

(Making a dispersion of magenta pigment-containing resin particles)
Pigment Blue 15: 3 (Phthalocyaniburu-A220 manufactured by Dainichi Seika Co., Ltd.) used in the preparation of the cyan pigment dispersion was replaced with Cromophtal Jet Magenta DMQ (PR-122) manufactured by Ciba Specialty Chemicals. In a similar procedure, a dispersion of magenta pigment-containing resin particles was obtained.

(Ink composition)
Magenta ink M1 and cyan inks C1 to C6 were prepared with the following compositions using the dispersion of resin dispersant P-1, self-dispersing polymer fine particles B-01, and cyan pigment-containing resin particles.

(Magenta ink M1 creation)
Dispersion of magenta pigment-containing resin particles 39.2 parts by mass Aqueous dispersion of self-dispersing polymer fine particles (B-01) 28.6 parts by mass Trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part by mass Ion-exchanged water balance
The surface tension of M1 was measured and found to be 35.0 mN / m.

(Cyan ink C1 creation)
Dispersion of cyan pigment-containing resin particles 39.2 parts by mass Self-dispersing polymer fine particles (B-01) in water 28.6 parts by mass of trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0 parts by mass ion-exchanged water balance The surface tension of C1 prepared with this composition was measured and found to be 33.5 mN / m.

(Cyan ink C2 creation)
Dispersion of cyan pigment-containing resin particles 39.2 parts by mass Self-dispersing polymer fine particles (B-01) in water 28.6 parts by mass of trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 parts by mass ion-exchanged water balance The surface tension of C2 prepared with this composition was measured and found to be 35.5 mN / m.

(Cyan ink C3 creation)
Dispersion of cyan pigment-containing resin particles 39.2 parts by mass Self-dispersing polymer fine particles (B-01) in water 28.6 parts by mass of trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.5 parts by mass ion-exchanged water balance The surface tension of C3 prepared with this composition was measured and found to be 36.2 mN / m.

(Cyan ink C4 creation)
Dispersion of cyan pigment-containing resin particles 39.2 parts by mass Self-dispersing polymer fine particles (B-01) in water 28.6 parts by mass of trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olfin E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.3 parts by mass ion-exchanged water balance The surface tension of C4 prepared with this composition was measured and found to be 37.9 mN / m.

(Cyan ink C5 creation)
Dispersion of cyan pigment-containing resin particles 39.2 parts by mass Self-dispersing polymer fine particles (B-01) in water 28.6 parts by mass of trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.2 parts by mass of ion-exchanged water balance The surface tension of C5 prepared with this composition was measured and found to be 39.8 mN / m.

(Cyan ink C6 creation)
Dispersion of cyan pigment-containing resin particles 39.2 parts by mass Self-dispersing polymer fine particles (B-01) in water 28.6 parts by mass of trioxypropylene glyceryl ether (Sanix GP250 (manufactured by Sanyo Chemical Industries, Ltd.)) 15.0 parts by mass Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.1 parts by mass ion-exchanged water balance The surface tension of C6 prepared with this composition was measured and found to be 41.3 mN / m.

(Composition of treatment liquid)
Malonic acid (manufactured by Wako Pure Chemical Industries) 20.0 mass parts diethylene glycol monomethyl ether (manufactured by Wako Pure Chemical Industries) 20.0 mass parts Zonyl FSN-100 1.0 mass part ion-exchanged water remainder <Results>
Ink jet recording was performed using the magenta ink M1 and the cyan inks C1 to C6, and the dot diameter, color material floating, and offset were examined. Test conditions and evaluation methods were performed as follows.

(Dot diameter)
Magenta ink M1 was ejected with dots at intervals of 150 dpi, and the dot diameter was measured. Then, cyan inks C1 to C6 were ejected with dots at intervals of 150 dpi on magenta solid droplets (1200 * 1200 dpi * 4 pL droplets), and the dot diameter was measured. The dot diameter was measured using a dot analyzer DA-6000 manufactured by Oji Scientific Instruments.

  The time from the time when the magenta dots were deposited to the time when the cyan dots were deposited (time intervals between colors) was changed to 20 ms, 100 ms, 200 ms, 500 ms, and 1000 ms, and the dot diameter was measured in the same manner. Moreover, in each condition, the test was done in the case of the presence or absence of drying of a process liquid.

(Color material floating)
When dots having an interval of 150 dpi were ejected and the average deviation amount of the distance between dots was 5% or more (that is, 8.5 μm or more), x was less than 5% (less than 8.5 μm). .

(offset)
After using the above ink and treatment liquid to perform 1200 * 1200 dpi * 4 pL droplet ejection * 2 colors (magenta → cyan), the dried water is dried until the residual water amount becomes about 3 g / m ² , and the hot pressure roller (temperature 75 ° C., 0.3 MPa). When contacted, the color material does not adhere to the roller and the image surface does not deteriorate, ○, the color material adheres to the roller, but the image surface does not deteriorate, Δ, the color material to the roller Is attached, and deterioration is recognized on the image surface as x.

  The above conditions and results are shown in Table 1.

  As can be seen from Table 1, in Test Examples 1 to 4, there is almost no difference in surface tension between magenta and cyan. Therefore, when droplets are ejected at intervals of 200 ms, the difference in dot diameter (primary color dot diameter-secondary color dot diameter) is significant. (5 μm or more).

  On the other hand, since the surface tension difference between magenta and cyan is larger than 1 mN / m in Test Examples 5 to 12, even when droplets are ejected at intervals of 200 ms, the dot diameter difference is very small, 3.0 μm or less. It was good. In addition, about the time difference, it turned out that it was improved especially in 100 ms-200 ms.

  In addition, as can be seen by comparing Test Examples 1, 3, 5, 7, 9, and 11 and Test Examples 2, 4, 6, 8, 10, and 12, when ink is ejected without drying the treatment liquid In contrast, the color material floating occurred, but when the ink was ejected after the treatment liquid was dried, the color material floating was prevented.

  Further, as can be seen by comparing Test Examples 1 to 10 and Test Examples 11 and 12, in Test Examples 11 and 12 having a surface tension difference of 5 mN / m or more, an offset occurred, whereas 5 mN / m In Test Examples 1 to 10 that are less than m, occurrence of offset could be prevented.

Overall configuration diagram schematically showing the inkjet recording apparatus of the present embodiment 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 1 is an overall configuration diagram schematically showing an inkjet recording apparatus having a configuration different from that of FIG.

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, 24 ... 1st middle Conveying section, 26 ... second intermediate conveying section, 28 ... third intermediate conveying section, 30 ... intermediate conveying body, 70 ... drawing drum, 72M, 72C, 72Y, 72K ... ink jet head, 76 ... drying drum, 84 ... Fixing drum, 86 ... first fixing roller, 88 ... second fixing roller

Claims (11)

A treatment liquid application step for applying a treatment liquid containing a flocculant on the recording medium;
An ink ejection step of ejecting a plurality of inks of different colors from an inkjet head in ascending order of surface tension on a recording medium provided with the treatment liquid;
Equipped with a,
In the ink droplet ejection step, different color inks are ejected onto the previously deposited ink, and the difference in surface tension between the two inks ejected successively is greater than 1 mN / m. An inkjet recording method. An ink drying step for drying the ink on the recording medium and a fixing step for fixing the dried ink after the ink ejection step;
2. The ink jet recording method according to claim 1 , wherein in the ink droplet ejection step, a difference in surface tension between the plurality of ink droplets ejected is less than 5 mN / m.   A treatment liquid application step for applying a treatment liquid containing a flocculant on the recording medium;
  An ink ejection step of ejecting a plurality of inks of different colors from an inkjet head in ascending order of surface tension on a recording medium provided with the treatment liquid;
  With
  An ink drying step for drying the ink on the recording medium and a fixing step for fixing the dried ink after the ink ejection step;
  In the ink droplet ejection step, inks of different colors are ejected onto the previously ejected ink, and the difference in surface tension between the plurality of ink droplets ejected is less than 5 mN / m. Recording method. The ink contains self-dispersing polymer fine particles, and satisfies the relationship of Td <Tp, where Td is the temperature reached on the image surface in the ink drying step and Tp is the softening point of the self-dispersing polymer fine particles of the ink. The inkjet recording method according to claim 2 or 3, wherein the temperature is controlled as described above. When the ink contains self-dispersing polymer fine particles and the temperature reached on the image surface in the fixing step is Tf, the relationship of Tp <Tf is satisfied with respect to the softening point Tp of the self-dispersing polymer fine particles of the ink. the ink jet recording method according to any one of claims 2-4 that is set to satisfy.   The process liquid drying process of drying the process liquid on the recording medium is provided between the process liquid application process and the ink droplet ejection process. Inkjet recording method. The ink jet recording method according to claim 6, wherein in the treatment liquid drying step, the total thickness of the treatment liquid on the recording medium is 1.0 g / m ² or less.   The ink jet recording method according to any one of claims 1 to 7, wherein, in the ink droplet ejection step, a landing time interval between two inks ejected in succession is 100 ms or less.   A treatment liquid application step for applying a treatment liquid containing a flocculant on the recording medium;
  An ink ejection step of ejecting a plurality of inks of different colors from an inkjet head in ascending order of surface tension on a recording medium provided with the treatment liquid;
  With
  Ink-jet recording is characterized in that, in the ink droplet deposition step, inks of different colors are deposited on the previously deposited ink, and the landing time interval between the two inks that are successively deposited is 100 ms or less. Method. The ink jet recording method according to any one of claims 1-9, wherein the recording medium is a coated paper for printing. A treatment liquid applying apparatus for applying a flocculant-containing treatment liquid on a recording medium;
A plurality of inkjet heads that are provided at a subsequent stage of the treatment liquid application apparatus and that eject ink onto the treatment liquid on the recording medium;
A drying drum for drying the ink on the recording medium after the plurality of inkjet heads;
A fixing drum for fixing the dried ink ,
Wherein the plurality of inkjet heads, Ri Do different surface tension different colors from each other, the difference in surface tension of the plurality of ink droplet ejection is droplet of ink is less than 5 mN / m, on the ink ejected earlier In addition, the ink jet recording apparatus is arranged from the upstream side in the running direction of the recording medium in ascending order of surface tension of the ink to be ejected.

Images