JP2014148143A - Liquid discharge head, image forming apparatus and manufacturing method of liquid discharge head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a liquid discharge head which prevents liquid from infiltrating into a gap between head modules, improves chemical durability of a water repellent film on a side surface neighboring a nozzle-side surface and, when exchanging a head module, causes no trouble occurring on the water repellent film on the side surface of the head module; an image forming apparatus; and a manufacturing method of the liquid discharge head.SOLUTION: A side surface 202 of a head module 72-i, which opposes a neighboring head module with a gap 160 interposed therebetween, includes a water repellent film 204. The water repellent film 204 on the side surface 202 is formed in such a manner as to be thick at the side of a nozzle surface 72A and become thinner stepwise or continuously as it moves away from the side of the nozzle surface 72A.

Description

  The present invention relates to a liquid discharge head, an image forming apparatus, and a method for manufacturing a liquid discharge head, and more particularly, to a liquid discharge head formed by connecting a plurality of head modules and a method for manufacturing the liquid discharge head.

  In order to realize high-speed printing with a liquid discharge head, it is necessary to adopt a one-pass scanning method using a line head in which a plurality of head modules are connected. In order to put this line head into practical use at a low cost, it is necessary to make it possible to replace individual head modules. Thereby, for example, when one module is defective, a low maintenance cost can be realized by replacing only the target module without replacing the entire line head.

  If each head module is configured to be replaceable, a gap is naturally generated between the head modules. When a gap is generated between the head modules, ink mist discharged from the nozzles enters the gap during printing, or ink on the nozzle surface is pushed into the gap by wiping the nozzle surface during maintenance. The ink that has entered the gap causes ink dripping when in the liquid state, and causes the recording medium to become dirty during printing. In addition, when the ink is dried, thickened and solidified, the ink is scraped out during maintenance and becomes a cause of clogging the nozzle. Therefore, it is desired that the ink does not enter the gap between the head modules.

  For example, Patent Document 1 below describes that a plurality of head modules are connected to form a line head, and a tape is applied to prevent ink from entering the gap between the head modules. .

  Japanese Patent Application Laid-Open No. H10-228688 describes that a water repellent is applied to the side surface of a unit in a configuration in which a plurality of recording head units are arranged and mounted on a carriage, although they are not line heads.

JP 2008-30361 A Japanese Patent Laid-Open No. 3-136854

  However, the line head as disclosed in Patent Document 1 prevents the ink from entering the gap between the head modules by sealing and fixing the gaps between the individual head modules, so that the individual head modules Is not a replaceable configuration.

  By the way, in a line head in which a plurality of head modules are connected, a phenomenon in which the liquid penetrates deeper due to capillary action occurs as the gap between the head modules is smaller. In addition, the rising height h (m) of the liquid level due to the capillary force is given by the following formula.

[However, T = surface tension (N / m), θ = contact angle, ρ = liquid density (kg / m ³ ), g = gravity acceleration (m / s ² ), r = inner diameter (radius) of the tube ( m)]
As can be seen from the above equation, the higher the surface tension T of the liquid, the more significant the liquid intrusion due to the capillary force. In particular, when a water-based ink having a high surface tension is used as the liquid, the surface tension of the water-based ink is about 40 mN / m, and the surface tension is higher than 20 mN / m of a general solvent-based ink, so that capillary action is likely to occur. .

  Further, as can be seen from the above equation, it is effective to increase the contact angle θ (decrease cos θ) in order to suppress this capillary phenomenon. That is, the capillary phenomenon can be suppressed by performing water repellent treatment as in Patent Document 2 on the side surface of the head module in the gap between the head modules.

  However, in order to perform water repellent treatment on the side of the head module in the gap, a certain distance is required between the head modules. However, if the gap between the head modules is large, it may cause printing failure in the line head. Therefore, in order to correct the gap portion, the nozzle arrangement is a parallelogram, and the head module is arranged in a staggered arrangement. Since the width in the feed direction is large, the system was enlarged.

  As described above, it is necessary to narrow the gap between the head modules. However, in order to narrow the gap between the head modules, the thick coating surface treatment cannot be performed on the side surface of the head module. In particular, in a head having a high-density nozzle with high image quality, there is a limit to the film thickness formed by the surface treatment because the interval between modules is narrow.

  Since the side surface of the head module is always exposed to an alkaline liquid such as ink and nozzle cleaning liquid, like the nozzle surface, chemical durability against the ink and nozzle cleaning liquid is important. In this case, the nozzle surface is subjected to an immersion chemical attack from one end. Therefore, the water repellent material on the side surface in the vicinity of the nozzle surface side needs to have chemical durability.

  Also, if the water repellent film on the side of the head module is uniformly thick, the water repellent films on the side of the head module come into contact with each other when the head module is replaced because the distance between adjacent head modules is short. Problems occur such as the water-repellent film being dragged and peeled off.

  The present invention has been made in view of such circumstances, while preventing the liquid from entering the gap between the head modules, and improving the chemical durability of the water-repellent film on the side surface near the nozzle surface side, It is an object of the present invention to provide a liquid discharge head, an image forming apparatus, and a method for manufacturing the liquid discharge head that do not hinder the water-repellent film on the side of the head module when the head module is replaced.

  In order to achieve the above object, the present invention provides a liquid ejection head in which a plurality of head modules each having a nozzle surface on which a plurality of nozzles for ejecting liquid are arranged are connected to each other. The side of the head module facing each other has a water-repellent film, and the water-repellent film on the side surface is thicker on the nozzle surface side, and the film thickness decreases stepwise or continuously as the distance from the nozzle surface side increases. Provided is a liquid discharge head that is formed.

  According to the present invention, a side surface of each head module of a liquid discharge head in which a plurality of head modules are connected has a water-repellent film, and the water-repellent film on the side surface has a thick film on the nozzle surface side. Since the film thickness is thinly formed stepwise or continuously as the distance from the surface side increases, the capillary phenomenon can be suppressed and the liquid can be prevented from entering the gap between the head modules. Accordingly, it is possible to prevent the liquid from dripping from the gap between the head modules, the liquid entering the gap being dried, and solidified solid matter coming out at the time of wiping or the like to cause nozzle clogging.

  Further, according to the present invention, the water-repellent film on the side surface has a thick film on the nozzle surface side, and the film thickness is formed to be thin stepwise or continuously as the distance from the nozzle surface side increases. The chemical durability of the side water-repellent film is improved.

  Furthermore, according to the present invention, the water-repellent film on the side surface has a thick film on the nozzle surface side and is formed to be thin stepwise or continuously as the distance from the nozzle surface side increases. The water repellent films on the side surfaces of the head module are prevented from contacting each other.

  Therefore, according to the present invention, the liquid can be prevented from entering the gaps between the head modules, and the chemical durability of the water-repellent film on the side surface near the nozzle surface side is improved. It is possible to provide a liquid discharge head that does not hinder the water repellent film.

  In the liquid ejection head according to another aspect of the present invention, the gap between the head modules is preferably 200 μm or less.

  The present invention is particularly effective in the case of a very narrow gap of 200 μm or less.

  In the liquid ejection head according to another aspect of the present invention, the maximum film thickness of the water repellent film is preferably 20 μm or less.

  If the maximum film thickness of the water repellent film is 20 μm or less, it is possible to suitably suppress contact between the water repellent films on the side surface of the head module when the head module is replaced.

  In the liquid discharge head according to another aspect of the present invention, the water repellent film is preferably formed on the entire side surface.

  In general, when a part of the head module side surface near the nozzle surface is subjected to water repellency, the liquid that has entered the gap is sucked up by capillary force, and the liquid accumulates in the hydrophilic part of the side of the head module that has not been subjected to water repellency. End up. If there is a hydrophilic surface in the vicinity of the water repellent surface, the liquid that has entered the water repellent portion generally tends to move to the hydrophilic portion. Therefore, in order to further suppress the liquid suction due to the capillary force, it is preferable to perform water repellent treatment on the entire side surface.

  In the liquid discharge head according to another aspect of the present invention, the liquid is preferably water-based ink containing water as a main solvent.

  A water-based ink containing water as a main solvent has a high surface tension and is prone to capillary action. The present invention is particularly effective when an aqueous ink having a high surface tension is used.

  A liquid discharge head according to another aspect of the present invention is a liquid discharge head in which a head module is installed to be inclined with respect to a horizontal plane, and the water-repellent film on the side surface is thicker on the lower side with an inclination. It is preferable that the film thickness is thinned stepwise or continuously toward the upper side.

  In many cases, the head module is used while being tilted. In this case, the liquid tends to adhere and stay on the nozzle surface on the lower side of the tilt. Accordingly, the amount of liquid that enters the gap between the head modules when performing maintenance by wiping or the like also relatively increases on the side surface on the lower side of the inclination. Therefore, a relatively high chemical durability is required for the water-repellent film on the lower side of the inclination. Therefore, the chemical durability can be further improved by forming the film thickness stepwise or continuously thicker on the lower side of the inclination than on the upper side of the inclination.

  In the liquid discharge head according to another aspect of the present invention, the surface roughness Ra of the water repellent film is preferably 10 nm or less.

  According to the liquid ejection head according to another aspect of the present invention, since the surface roughness Ra of the water repellent film is 10 nm or less, a film having good water repellency can be formed. Further, by setting the surface roughness Ra of the water-repellent film within the above range, for example, even when mist-like liquid enters the gap between the head modules, the surface roughness is low, so that the dynamic water-repellent ( (Sliding property) can be improved, so that the liquid on the water-repellent film can easily flow. Therefore, liquid can be prevented from entering between the head modules.

  In order to achieve the above object, the present invention provides an image forming apparatus including a liquid ejection head according to an aspect of the present invention.

  According to the image forming apparatus of the present invention, the liquid is prevented from entering the gap between the head modules, and the chemical durability of the water-repellent film on the side surface in the vicinity of the nozzle surface side is improved. It is possible to provide an image forming apparatus in which the side water-repellent film is not hindered.

  In order to achieve the above object, the present invention is a method of manufacturing a liquid ejection head in which a plurality of head modules having nozzle surfaces on which a plurality of nozzles for ejecting liquid are arranged are continuously connected, and adjacent head modules And a step of applying a water-repellent material to the side surface of the head module facing through a gap with a thick film on the nozzle surface side and gradually decreasing in thickness as the distance from the nozzle surface side increases. And a step of forming a water-repellent film to provide a method for manufacturing a liquid discharge head.

  According to the present invention, the water repellent film is provided on the side surface of the head module facing the adjacent head module through a gap, and the water repellent film on the side surface is thick on the nozzle surface side, from the nozzle surface side. A liquid discharge head having a thin film thickness that is stepwise or continuously formed with increasing distance can be manufactured. Therefore, according to the present invention, the liquid can be prevented from entering the gaps between the head modules, and the chemical durability of the water-repellent film on the side surface near the nozzle surface side is improved. It is possible to provide a method of manufacturing a liquid discharge head that does not cause a problem in the water repellent film.

  In the method of manufacturing a liquid discharge head according to another aspect of the present invention, in the step of applying, when the water repellent material is applied in a stepwise manner as the distance from the nozzle surface decreases, the number of times the dispenser is applied stepwise. It is preferable to apply the water repellent material while changing to the above.

  By applying the water repellent material by changing the number of times of application of the dispenser stepwise, the water repellent material can be applied in a stepwise manner with decreasing film thickness as the distance from the nozzle surface side increases. Therefore, according to the present invention, the liquid can be prevented from entering the gaps between the head modules, and the chemical durability of the water-repellent film on the side surface near the nozzle surface side is improved. It is possible to provide a method of manufacturing a liquid discharge head that does not cause a problem in the water repellent film.

  In the method of manufacturing a liquid discharge head according to another aspect of the present invention, in the step of applying, when applying a water-repellent material with a film thickness that is continuously reduced as the distance from the nozzle surface increases, the application speed of the dispenser is gradually increased. It is preferable to apply the water repellent material in a changed manner.

  By applying the water-repellent material while gradually changing the application rate of the dispenser, the water-repellent material can be applied continuously with a thinner film thickness as the distance from the nozzle surface side increases. Therefore, according to the present invention, the liquid can be prevented from entering the gaps between the head modules, and the chemical durability of the water-repellent film on the side surface near the nozzle surface side is improved. It is possible to provide a method of manufacturing a liquid discharge head that does not cause a problem in the water repellent film.

  According to the liquid ejection head, the image forming apparatus, and the liquid ejection head manufacturing method of the present invention, the liquid is prevented from entering the gap between the head modules, and the chemical durability of the water-repellent film on the side surface near the nozzle surface side is prevented. It is possible to provide a liquid discharge head, an image forming apparatus, and a method of manufacturing the liquid discharge head that improve the performance and do not cause a problem with the water-repellent film on the side surface of the head module when the head module is replaced.

1 is an overall configuration diagram of an ink jet recording apparatus. It is a perspective view of an inkjet head. It is a top view which shows the structural example of the inkjet head shown in FIG. FIG. 4 is a partially enlarged view of FIG. 3. FIG. 4 is a plan perspective view of the head module shown in FIG. 3. It is sectional drawing of the head module which concerns on this invention. It is a perspective view of the side of a head module concerning the present invention. It is sectional drawing of the head module which concerns on this invention. It is a side view of a head module.

  Hereinafter, preferred embodiments of a liquid discharge head and a method of manufacturing a liquid discharge head according to the present invention will be described with reference to the accompanying drawings. Hereinafter, an ink jet head will be described as an example of the liquid discharge head. An ink jet recording apparatus having this ink jet head will be described.

<< Overall configuration of inkjet recording apparatus >>
First, the overall configuration of the ink jet recording apparatus will be described. FIG. 1 is a configuration diagram showing the overall configuration of the ink jet recording apparatus.

  The inkjet recording apparatus 10 includes a plurality of colors from inkjet heads 72M, 72K, 72C, and 72Y on a recording medium 24 (sometimes referred to as “paper” for convenience) held on an impression cylinder (drawing drum 70) of the drawing unit 16. Is an impression cylinder direct drawing type ink jet recording apparatus that forms a desired color image by applying ink droplets of the ink. A treatment liquid (here, an aggregating treatment liquid) is applied onto the recording medium 24 before ink droplet ejection, This is an on-demand type image forming apparatus to which a two-liquid reaction (aggregation) method for forming an image on a recording medium 24 by reacting a treatment liquid and an ink liquid is applied.

  As shown in the figure, the ink jet recording apparatus 10 mainly includes a paper feed unit 12, a treatment liquid application unit 14, a drawing unit 16, a drying unit 18, a fixing unit 20, and a discharge unit 22.

(Paper Feeder)
The paper supply unit 12 is a mechanism that supplies the recording medium 24 to the treatment liquid application unit 14, and a recording medium 24 that is a sheet is stacked on the paper supply unit 12. The paper feed unit 12 is provided with a paper feed tray 50, and the recording medium 24 is fed from the paper feed tray 50 to the processing liquid application unit 14 one by one.

  In the inkjet recording apparatus 10 of this example, a plurality of types of recording media 24 having different paper types and sizes (paper sizes) can be used as the recording medium 24. A mode is also possible in which a plurality of paper trays (not shown) are provided in the paper feed unit 12 to separately collect various recording media and the paper to be sent to the paper feed tray 50 is automatically switched from among the plurality of paper trays. In addition, a mode is also possible in which the operator selects or replaces the paper tray as necessary. In this example, a sheet (cut paper) is used as the recording medium 24, but a configuration in which continuous paper (roll paper) is cut to a required size and fed is also possible.

(Processing liquid application part)
The processing liquid application unit 14 is a mechanism that applies the processing liquid to the recording surface of the recording medium 24. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) applied in the ink provided by the drawing unit 16, and the ink comes into contact with the colorant when the treatment liquid comes into contact with the ink. And the solvent are promoted.

  As shown in FIG. 1, the treatment liquid application unit 14 includes a paper feed drum 52, a treatment liquid drum 54, and a treatment liquid application device 56. The treatment liquid drum 54 is a drum that holds and rotates and conveys the recording medium 24. The processing liquid drum 54 is provided with a claw-shaped holding means (gripper) 55 on the outer peripheral surface thereof, and the recording medium 24 is sandwiched between the claw of the holding means 55 and the peripheral surface of the processing liquid drum 54 to thereby remove the recording medium 24. The tip can be held. The treatment liquid drum 54 may be provided with suction holes on the outer peripheral surface thereof and connected to suction means for suction from the suction holes. As a result, the recording medium 24 can be held in close contact with the peripheral surface of the treatment liquid drum 54.

  A processing liquid coating device 56 is provided outside the processing liquid drum 54 so as to face the peripheral surface thereof. The processing liquid coating device 56 includes a 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 the recording medium 24 on the anix roller and the processing liquid drum 54. And a rubber roller that transfers the measured processing liquid to the recording medium 24. According to the processing liquid application device 56, the processing liquid can be applied to the recording medium 24 while being measured.

  The recording medium 24 to which the processing liquid is applied by the processing liquid applying unit 14 is transferred from the processing liquid drum 54 to the drawing drum 70 of the drawing unit 16 via the intermediate transport unit 26.

(Drawing part)
The drawing unit 16 includes a drawing drum (second transport body) 70, a sheet pressing roller 74, and inkjet heads 72M, 72K, 72C, and 72Y. The drawing drum 70 includes a claw-shaped holding means (gripper) 71 on the outer peripheral surface thereof, like the processing liquid drum 54. The recording medium 24 fixed to the drawing drum 70 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 72M, 72K, 72C, 72Y.

  Each of the inkjet heads 72M, 72K, 72C, and 72Y is preferably a full-line inkjet recording head (inkjet head) having a length corresponding to the maximum width of the image forming area in the recording medium 24. On the ink ejection surface, a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area is formed. Each inkjet head 72M, 72K, 72C, 72Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 24 (the rotation direction of the drawing drum 70).

  The droplets of the corresponding color ink are ejected from the respective ink jet heads 72M, 72K, 72C, 72Y toward the recording surface of the recording medium 24 held tightly on the drawing drum 70. The ink comes into contact with the treatment liquid previously applied to the recording surface, 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 24 is prevented, and an image is formed on the recording surface of the recording medium 24.

  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.

  The recording medium 24 on which an image is formed by the drawing unit 16 is transferred from the drawing drum 70 to the drying drum 76 of the drying unit 18 via the intermediate conveyance unit 28.

(Drying part)
The drying unit 18 is a mechanism for drying moisture contained in the solvent separated by the color material aggregation action, and includes a drying drum 76 and a solvent drying device 78 as shown in FIG.

  Similar to the treatment liquid drum 54, the drying drum 76 includes a claw-shaped holding unit (gripper) 77 on the outer peripheral surface thereof, and the holding unit 77 can hold the leading end of the recording medium 24.

  The solvent drying device 78 is disposed at a position facing the outer peripheral surface of the drying drum 76, and includes a plurality of IR heaters 82 and hot air ejection nozzles 80 disposed between the IR heaters 82.

  Various drying conditions can be realized by appropriately adjusting the temperature and air volume of the hot air blown toward the recording medium 24 from each hot air jet nozzle 80 and the temperature of each IR heater 82.

  The surface temperature of the drying drum 76 is set to 50 ° C. or higher. Drying is accelerated by heating from the back surface of the recording medium 24, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 76 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 76 (preventing burns due to high temperature). It is preferably set to 75 ° C. or lower (more preferably 60 ° C. or lower).

  The recording drum 24 is held on the outer peripheral surface of the drying drum 76 so that the recording surface of the recording medium 24 faces outward (that is, in a state where the recording surface of the recording medium 24 is convex), and is dried while being rotated and conveyed By doing so, it is possible to prevent the recording medium 24 from being wrinkled or lifted, and to reliably prevent uneven drying due to these.

  The recording medium 24 that has been dried by the drying unit 18 is transferred from the drying drum 76 to the fixing drum 84 of the fixing unit 20 via the intermediate conveyance unit 30.

(Fixing part)
The fixing unit 20 includes a fixing drum 84, a halogen heater 86, a fixing roller 88, and an inline sensor 90. Like the processing liquid drum 54, the fixing drum 84 includes a claw-shaped holding unit (gripper) 85 on its outer peripheral surface, and the holding unit 85 can hold the leading end of the recording medium 24.

  With the rotation of the fixing drum 84, the recording medium 24 is conveyed with the recording surface facing outward. The recording surface is preheated by the halogen heater 86, fixed by the fixing roller 88, and by the inline sensor 90. Inspection is performed.

  The halogen heater 86 is controlled to a predetermined temperature (for example, 180 ° C.). Thereby, the recording medium 24 is preheated.

  The fixing roller 88 is a roller member for heating and pressurizing the dried ink to weld the self-dispersing thermoplastic resin fine particles in the ink to form a film of the ink. The fixing roller 88 is configured to heat and press the recording medium 24. Composed. Specifically, the fixing roller 88 is disposed so as to be in pressure contact with the fixing drum 84, and constitutes a nip roller with the fixing drum 84. As a result, the recording medium 24 is sandwiched between the fixing roller 88 and the fixing drum 84 and nipped at a predetermined nip pressure (for example, 0.15 MPa), and a fixing process is performed.

  The fixing roller 88 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and is controlled to a predetermined temperature (for example, 60 to 80 ° C.). By heating the recording medium 24 with this heating roller, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the thermoplastic resin fine particles contained in the ink is applied, and the thermoplastic resin fine particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 24, and the unevenness of the image surface is leveled to obtain glossiness.

  In the embodiment of FIG. 1, only one fixing roller 88 is provided. However, a configuration in which a plurality of fixing rollers 88 are provided may be employed depending on the thickness of the image layer and the Tg characteristics of the thermoplastic resin fine particles.

  On the other hand, the in-line sensor 90 is a measuring means for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 24, and a CCD line sensor or the like is applied.

  According to the fixing unit 20 configured as described above, the thermoplastic resin fine particles in the thin image layer formed by the drying unit 18 are heated and pressurized by the fixing roller 88 and melted. Can be fixed and fixed. Further, by setting the surface temperature of the fixing drum 84 to 50 ° C. or higher, drying is promoted by heating the recording medium 24 held on the outer peripheral surface of the fixing drum 84 from the back surface, thereby preventing image destruction during fixing. In addition, the image intensity can be increased by the effect of increasing the image temperature.

  In addition, when a UV curable monomer is contained in the ink, after the water is sufficiently volatilized in the drying unit, the image is irradiated with UV at the fixing unit equipped with a UV irradiation lamp. The monomer can be cured and polymerized to improve the image strength.

(Discharge part)
As shown in FIG. 1, a discharge unit 22 is provided following the fixing unit 20. The discharge unit 22 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 20 so as to be in contact therewith. It has been. The recording medium 24 is sent to the conveying belt 96 by the transfer drum 94 and discharged to the discharge tray 92.

  Although not shown in the drawing, the ink jet recording apparatus 10 of this example has an ink storage / loading unit for supplying ink to each of the ink jet heads 72M, 72K, 72C, and 72Y, and a treatment liquid application, in addition to the above-described configuration. A means for supplying a processing liquid to the unit 14, and a head maintenance unit for cleaning each of the inkjet heads 72M, 72K, 72C, 72Y (wiping, purging, nozzle suction, etc. of the nozzle surface), A position detection sensor for detecting the position of the recording medium 24, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

[Configuration of inkjet head]
FIG. 2 is a perspective view of the inkjet head. FIG. 2 illustrates a state in which the ejection surface is looked up from below the ink jet head 72 (obliquely downward direction). The ink-jet head 72 is a print head installed in a drawing section of an ink-jet recording apparatus, and is a full-line bar head (single-line head) in which a plurality of head modules 72-i are aligned and connected in the paper width direction. Page wide head with pass printing). Here, an example in which 17 head modules 72-i are connected is shown, but the configuration of the modules, the number of modules, and the arrangement form are not limited to the illustrated examples. Reference numeral 104 denotes a housing (housing for constituting a bar-shaped line head) serving as a frame for fixing a plurality of head modules 72-i, and reference numeral 106 denotes a flexible member connected to each head module 72-i. It is a substrate.

  FIG. 3 is a plan view showing a structural example of the head 72, and is a view of the head 72 as seen from the nozzle surface 72A side. FIG. 4 is a partially enlarged view of FIG.

  As shown in FIG. 3, the head 72 has n head modules 72-i (i = 1, 2, 3,..., N) perpendicular to the transport direction of the longitudinal direction (recording medium 24 (see FIG. 1)). ), And a plurality of nozzles (not shown in FIG. 3) are provided over a length corresponding to the entire width of the recording medium.

  Each head module 72-i is supported by a head module support member 72B from both sides of the head 72 in the short direction. Further, both end portions of the head 72 in the longitudinal direction are supported by a head support member 72D.

  As shown in FIG. 4, each head module 72-i (n-th head module 72-n) has a structure in which a plurality of nozzles are arranged in a matrix. In FIG. 4, an oblique solid line denoted by reference numeral 151A represents a nozzle row in which a plurality of nozzles are arranged in a row.

  Fig.5 (a) is a plane perspective view of the head module 72-i, and FIG.5 (b) is the one part enlarged view.

  In order to increase the dot pitch formed on the recording medium 24, it is necessary to increase the nozzle pitch in the head 72. As shown in FIGS. 5A and 5B, the head module 72-i of this example includes a plurality of ink chamber units each including a nozzle 151 that is an ink discharge port, a pressure chamber 152 corresponding to each nozzle 151, and the like. (Droplet discharge elements as recording element units) 153 has a structure in which the zigzag is arranged in a matrix (two-dimensionally), and thereby, the head longitudinal direction (direction orthogonal to the transport direction of the recording medium 24); High density of the substantial nozzle interval (projection nozzle pitch) projected along the main scanning direction is achieved.

  The pressure chamber 152 provided corresponding to each nozzle 151 has a substantially square planar shape, the nozzle 151 is provided at one of the diagonal corners, and the supply port 154 is provided at the other. ing. The shape of the pressure chamber 152 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, and an ellipse.

  As shown in FIG. 5B, the ink chamber units 153 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of this example is realized.

  That is, with a structure in which a plurality of ink chamber units 153 are arranged at a constant pitch d along the direction of an angle θ with respect to the main scanning direction, the pitch P of the nozzles projected in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 151 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which the number of nozzle rows projected so as to be aligned in the main scanning direction is 2400 per inch (2400 nozzles / inch).

<Configuration of head module side>
Next, the configuration of the side surface of the head module will be described. 6 is a cross-sectional view of the head module, and FIG. 7 is a side perspective view.

  As shown in FIG. 6, a water repellent film 204 is formed on the side surface 202 facing the adjacent head module. In the present invention, the “water repellent film” is a film having a static contact angle of water of 60 ° or more.

  The method for forming the water repellent film is not particularly limited, and the film can be formed by applying and drying a water repellent material. Specifically, film formation can be performed by a method described later.

  As a material for the water repellent film, a fluorocarbon water repellent material can be used.

  The film thickness of the water repellent film is determined by the distance between the head modules 72-i.

  When the distance between the head modules 72-i becomes large, the nozzles must be arranged so as to correct the gap, and therefore the allowable distance between the head modules is 2/3 or less of the distance between the nozzles. For example, in the case of a 1200 dpi high-density head, the minimum inter-nozzle distance is 300 μm, so the allowable inter-module distance is 200 μm or less, and preferably 100 μm or less.

  Therefore, the water-repellent film is preferably thinner than 100 μm, and is formed on both sides of the head module. Therefore, the water-repellent film is preferably 50 μm or less, which is 1/2 or less of the distance between modules, and 20 μm which is 1/5 or less. More preferably, it is as follows.

  The water repellent film 204 on the side surface 202 of the head module 72-i has a thick film thickness on the nozzle surface 72A side, and is formed to be thin stepwise or continuously as the distance from the nozzle surface 72A side increases. 6 and 7 show a case where the water repellent film 204 is formed so that the film thickness on the nozzle surface 72A side is thick and the film thickness is continuously reduced as the distance from the nozzle surface 72A side increases.

  As can be seen from FIG. 6, the film thickness on the nozzle surface 72A side is thick and the water repellent film 204 is formed thinly stepwise or continuously as the distance from the nozzle surface 72A side increases. The gap 160 spreads stepwise or continuously from the nozzle surface 72A side.

  Since the gap 160 between the head modules spreads stepwise or continuously from the nozzle surface 72A side, the capillary phenomenon can be suppressed, and the liquid can be prevented from entering the gap between the head modules. Accordingly, it is possible to prevent the liquid from dripping from the gap between the head modules, the liquid entering the gap being dried, and solidified solid matter coming out at the time of wiping or the like to cause nozzle clogging.

  Since the water repellent film 204 is formed with a large film thickness on the nozzle surface 72A side, chemical durability against the ink and nozzle cleaning liquid in the vicinity of the nozzle surface side is ensured.

  Further, the water repellent film 204 has a thick film on the nozzle surface side and is formed to be thin stepwise or continuously as the distance from the nozzle surface is increased. It is suppressed that water films contact.

  This prevents liquid from entering the gaps between the head modules, improves the chemical durability of the water-repellent film on the side surface near the nozzle surface, and interferes with the water-repellent film on the side surface of the head module when replacing the head module. A liquid discharge head that does not occur can be provided.

  6 and 7, as shown in FIG. 8A, the film thickness on the nozzle surface 72 </ b> A side is thick, and the water repellent film 204 is formed to be continuously thinner as the distance from the nozzle surface 72 </ b> A is increased. However, as shown in FIGS. 8B and 8C, the film thickness on the nozzle surface 72A side is thick, and the film thickness is gradually reduced as the distance from the nozzle surface 72A side increases. ) Prevents the liquid from entering the gap between the head modules and improves the chemical durability of the water-repellent film on the side surface near the nozzle surface. It is possible to provide a liquid discharge head in which the side water-repellent film is not hindered.

  Here, the water repellent film 304 in FIG. 8B has two stages and the water repellent film 404 in FIG. 8C has five stages, but the water repellent film has two stages or more. The film thickness on the nozzle surface 72A side should be thick, and the film thickness should be gradually reduced as the distance from the nozzle surface 72A side increases.

  The water repellent film 204 (304, 404) is preferably formed on the entire surface of the head module side surface 202.

  In general, when a part of the head module side surface near the nozzle surface is subjected to water repellency, the liquid that has entered the gap is sucked up by capillary force, and the liquid accumulates in the hydrophilic part of the side of the head module that has not been subjected to water repellency. End up. If there is a hydrophilic surface in the vicinity of the water repellent surface, the liquid that has entered the water repellent portion generally tends to move to the hydrophilic portion. Therefore, in order to further suppress the liquid suction due to the capillary force, it is preferable to perform water repellent treatment on the entire side surface.

  The surface roughness Ra of the water repellent film 204 (304, 404) is preferably 10 nm or less.

  Since the surface roughness Ra of the water repellent film is 10 nm or less, a film having good water repellency can be formed. Further, by setting the surface roughness Ra of the water-repellent film within the above range, for example, even when mist-like liquid enters the gap between the head modules, the surface roughness is low, so that the dynamic water-repellent ( (Sliding property) can be improved, so that the liquid on the water-repellent film can easily flow. Therefore, liquid can be prevented from entering between the head modules.

  Further, as shown in the side view of the head module in FIG. 9, when the head module 72-i is installed with an inclination with respect to the horizontal plane, the lower side is thicker and the upper side is higher. It is preferable that the film thickness is formed thin stepwise or continuously.

  In many cases, the head module 72-i is used while being tilted. In this case, the liquid 210 tends to adhere and stay on the nozzle surface on the lower side of the tilt. Accordingly, the amount of liquid that enters the gap between the head modules when performing maintenance by wiping or the like also relatively increases on the side surface on the lower side of the inclination. Therefore, a relatively high chemical durability is required for the water-repellent film on the lower side of the inclination. Therefore, the chemical durability can be further improved by forming the thin film stepwise or continuously as the inclination is thicker on the lower side and on the upper side of the inclination.

<Method for forming water-repellent film>
Next, a method for forming a water repellent film will be described. The manufacturing method described below is an example, and the present invention is not limited to this. As described above, the water-repellent film has a large film thickness on the nozzle surface 72A side, and is formed to be thin stepwise or continuously as the distance from the nozzle surface 72A side increases.

  Examples of the head module include a high-density nozzle and a nozzle plate having a high-density flow path structure, and an epoxy resin material on a silicon substrate on which a substrate on which a high-density piezoelectric body and driving electrode wiring are formed is disposed adjacent to the head module. A head module including a head housing to which a flow path member is attached is used. This head module can be subjected to water repellent treatment on the side surfaces by, for example, the following materials and methods.

  As the water repellent material, a silane coupling type fluorocarbon water repellent (trade name Daikin Optool, F tone, Harves Durasurf, etc.) can be used. This dispenser can sequentially feed out liquids by applying pressure to the Teflon (registered trademark) tube from outside with a roller. Therefore, when applying a low-viscosity liquid, the liquid amount can be easily controlled.

  When applying with this dispenser, the tube tip is placed close to the side of the head module, and the tube is moved while the tip of the droplet surface is always in contact with the side of the head module. Thereby, the water repellent material can be uniformly applied.

  As a target for the maximum film thickness, 12.5% between module gaps (25% between head module gaps as a total film thickness with adjacent modules) was set as the maximum value. If the film thickness becomes thicker than this, it will be damaged by coming into contact with the side surface of the head facing when the module is replaced. For example, when the gap specification of the head is assumed to be 150 μm, the target coating thickness is set to Max 20 μm or less.

  For example, the water repellent film can be formed as follows.

[A. Formation of multi-stage film thickness]
Multistage film thickness control is performed by changing the number of times of coating stepwise.

  For example, the side closest to the nozzle surface is applied 10 times, and the number of times of application is reduced toward the side farther from the nozzle surface. The number of coatings varies depending on the material used, but in the case of Daikin OPTOOL, the film thickness after 20 coatings is about 0.7 μm. In addition, when apply | coating several times, although drying is performed between application | coating, the drying time at room temperature shall be about several minutes. The number of times of application is decreased as the distance from the nozzle surface is gradually increased at four levels of 20, 15, 10, 5 times. After the side surfaces are applied, they are left in the air at room temperature for 24 hours for complete drying and fixing. In addition, when the water repellent film was formed in this way, when the static contact angle evaluation and the sliding property evaluation with water were performed after standing, the contact angle was 100 ° and the sliding angle was 30 ° in the Daikin optool.

[B. Formation of single-stage film thickness]
Similar to the control of the multi-stage film thickness, the single-stage film thickness is controlled by controlling the number of coatings at two levels.

  For example, only the side closest to the nozzle surface and the second line from that side are subjected to 20 layers of coating, and thereafter the coating is performed 5 times. Note that there is an effect of reducing the coating time as compared with the control of the multistage film thickness.

[C. Formation of graded film thickness]
The stepless gradient film thickness is controlled by gradually changing the application speed of the dispenser.

  For example, the side near the nozzle surface has a coating speed of v = 0.5 mm / sec, and increases by Δv = 3 mm / sec per side as the distance from the nozzle surface increases. In the case of 10 line application, the maximum application speed is 27.5 mm / sec, gradually increasing from 0.5 mm / sec. The film thickness was about 0.3 μm at the maximum part.

  Assuming that the head module is used obliquely, the coating can be performed so that the film thickness becomes the thickest on the lower side and the nozzle surface side. In this case, the film thickness on the line can be changed by changing the coating speed on the same line. For example, coating is started from v = 0.1 mm / sec on the side surface corresponding to the lower side of the tilt and close to the nozzle surface, and the coating speed is gradually increased. Since the application is scanned in the reverse direction on the adjacent line, the application speed is programmed so that the speed change is in the reverse direction at the turning point.

  A simple line head connected with a head module was prototyped, and an endurance evaluation test was conducted by immersion in water-based pigment ink. Four modules were connected, and the gap between the modules was adjusted to 150 μm.

  The ink was immersed in the nozzle surface of the connection module and left to stand. The ink temperature was 60 ° C. The ink was replenished at regular intervals, and the ink was always immersed in the nozzle surface. A method was also tested in which the ink was circulated and a constant amount was always immersed in the nozzle surface.

(Sample 1)
The above simple line head was prototyped with a head module having no water repellent treatment on the side.

(Sample 2)
The above-mentioned simple line head was prototyped with a head module in which a single-layer film having a film thickness of about 0.1 μm was formed without controlling the thickness of the side water-repellent film.

(Sample 3)
As described above in the Daikin Optool [A. The above simple line head was prototyped with a head module in which a multi-stage film was formed by the method of “Formation of multi-stage film thickness”.

(Sample 4)
The above simple line head was prototyped with a head module in which a pressure film having a film thickness of 20 μm or more was formed using Durasurf manufactured by Harves.

[Evaluation and results]
First, when the head modules were arranged side by side and the line head was prototyped, Samples 1 to 3 were able to proceed to the line head without any particular problem. However, the thick sample 4 was in contact with the adjacent module during the handling of the adjacent module. As a result, scratches or rubbing traces occurred on both water-repellent surfaces. The contact mark was observed with a microscope. The contact mark portion is likely to be filled with ink afterwards due to the shape effect, and the thinness of the film or the absence of the water-repellent film causes the surrounding water-repellent deterioration preferentially in an accelerated manner. In practical use, it is assumed that this module replacement operation is performed by the user. Therefore, the form of the sample 4 that easily contacts the adjacent module is less practical in terms of design specifications, and it has been determined that adoption is severe.

  When the invasion state of the ink into the gap was visually observed with respect to the immersion time of the ink, in the sample 1 without the side water repellent treatment, the invasion of the ink into the gap was already confirmed at the time of immersion for 50 hours. Then, it was confirmed that the ink entered the gap of Sample 2 where the single-layer film was formed when immersed for 150 hours. Further, in the sample 3 on which the multi-stage film was formed, no invasion of ink was confirmed until the time of immersion for 500 hours.

  In this test, not only visual confirmation but also a static contact angle (unit: °) by water of the water repellent film provided on the side surface is measured. The measurement was performed on the side surface close to the nozzle surface. The measurement results are shown in the following table.

  Based on the above test results, a gap between the head modules is formed by forming a water-repellent film on the side surface of the head module. It can be seen that the liquid can be prevented from entering the surface, and the chemical durability of the water-repellent film on the side surface in the vicinity of the nozzle surface side can be improved.

  Next, an embodiment in which the head module is used tilted will be described. Since the head module is arranged in the ink jet head recording apparatus so that the nozzle surfaces are close to each other in parallel with the tangential direction of the drawing drum, the head module is used by being inclined. When printing is performed with the head module tilted, it is confirmed that the ink ejected from the nozzles flows downward from the nozzle surface due to gravity, and the ink is naturally in contact with the side of the head module on the tilted lower side. It was. When the printing operation was continued while the head module was tilted, the head module in which a single layer film having a film thickness of about 0.1 μm was formed on the side surface as in the case of the sample 2 described above. It was confirmed that it deteriorated. The deterioration of water repellency was judged by how the ink got wet. It was confirmed that the environmental temperature was about 10 months at room temperature and the water repellency deteriorated on the lower side of the slope and the ink was wet and spread, and the ink was difficult to flow and remained attached (water repellency). When the ink drops, the ink spreads and hardly flows). Based on this result, the film thickness of the lower part of the side of the side of the head module was increased and the film thickness treatment similar to that of Sample 3 was performed. As a result, the side water repellency was not deteriorated even in the same 10 months. It was confirmed.

  The tilt was verified in two cases of about 10 ° and about 25 °, and the same effect was confirmed at both tilt angles.

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 12 ... Paper feed part, 14 ... Processing liquid provision part, 16 ... Drawing part, 18 ... Drying part, 20 ... Fixing part, 22 ... Discharge part, 24 ... Recording medium, 70 ... Drawing drum, 72 ... Inkjet head, 72A ... Nozzle surface, 72-i ... head module, 160 ... gap, 202 ... side surface (head module), 204, 304, 404 ... water repellent film, 210 ... liquid

Claims (11)

A liquid discharge head in which a plurality of head modules each having a nozzle surface on which a plurality of nozzles for discharging liquid are arranged are continuously connected,
On the side of the head module facing the adjacent head module through a gap, a water repellent film is provided,
The water repellent film on the side surface is a liquid discharge head in which the film thickness on the nozzle surface side is thick and the film thickness is gradually or continuously decreased as the distance from the nozzle surface side increases.   The liquid ejection head according to claim 1, wherein a gap between the head modules is 200 μm or less.   3. The liquid ejection head according to claim 1, wherein a maximum film thickness of the water repellent film is 20 μm or less.   4. The liquid ejection head according to claim 1, wherein the water repellent film is formed on an entire surface of the side surface. 5.   The liquid discharge head according to claim 1, wherein the liquid is water-based ink having water as a main solvent.   The liquid ejection head in which the head module is installed to be inclined with respect to a horizontal plane, and the water-repellent film on the side surface is thicker on the lower side with an inclination, and the film thickness is stepwise as it becomes an upper side with an inclination. Or the liquid discharge head of any one of Claim 1 to 5 currently formed thinly.   The liquid discharge head according to claim 1, wherein the water-repellent film has a surface roughness Ra of 10 nm or less.   An image forming apparatus comprising the liquid ejection head according to claim 1. A method of manufacturing a liquid discharge head in which a plurality of head modules having a nozzle surface on which a plurality of nozzles for discharging liquid are arranged are continuously connected,
The water repellent material is applied to the side surface of the head module facing the adjacent head module with a gap, and the film thickness on the nozzle surface side is thick and the film thickness is gradually or continuously reduced as the distance from the nozzle surface side increases. Process,
And a step of drying the water repellent material to form a water repellent film. In the step of applying, when applying a water repellent material in a stepwise thin film thickness away from the nozzle surface side,
The method of manufacturing a liquid ejection head according to claim 9, wherein the water repellent material is applied by changing the number of times of application of the dispenser stepwise. In the step of applying, when applying a water repellent material with a thin film thickness as it gets away from the nozzle surface side,
The method for manufacturing a liquid discharge head according to claim 9, wherein the water-repellent material is applied by gradually changing the application speed of the dispenser.