JP2006062166A - Recording head device and inkjet recorder having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording head device capable of effectively preventing degrading in printing quality due to harmful increase of a viscosity of ink or clogging in an ejection nozzle by adequately keeping an ejection face of a recording head to be wet in a simple structure. <P>SOLUTION: A humidifying region 130 for vaporizing a humidifying liquid bleeding from a humidifying liquid supply hole 121 is formed on a predetermined region of the ejection face 100 of the recording head device 10. The ejection face 100 can be humidified by the vaporization of the humidifying liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a recording head device for recording ink on a recording medium by discharging ink from an ejection port provided on an ejection surface facing the applied recording medium, and the recording head apparatus. The present invention relates to an ink jet recording apparatus.

  One of the recording systems using an ink jet recording apparatus is an on-demand system in which recording is performed by selecting an ink ejection port that ejects ink droplets and an ejection port that does not eject ink droplets. In this on-demand method, unlike a continuous ink jet recording apparatus that always ejects ink droplets, ink droplets are ejected at appropriate timing only from the necessary nozzles according to print data.

  When recording by the on-demand method, there may be a discharge port where the non-discharge state lasts for a relatively long time. In such a case, the ink viscosity increases due to evaporation of the ink solvent at the discharge port. When the ink is ejected next time, the landing position of the ink droplet is shifted, the ink ejection amount is changed, or in the worst case, the recording quality is deteriorated. As measures against the above-described problems, it has already been proposed to apply an ink that does not contain a volatile component as an ink while the diameter of the ink discharge port of the nozzle is set to 12 μm or more and 22 μm or less (see, for example, Patent Document 1).

  In addition, by operating the non-ejection nozzle in an ejection operation that does not contribute to recording (flushing), or by performing an ink suction operation (head cleaning) from the ejection port during or before and after recording, The measures for preventing the deterioration of the discharge state are as already adopted in the existing apparatus. Cover the discharge surface of the recording head with a suction cap and suck the ink that causes the clogging by sucking with the pump through this suction cap, and then use a wiper member made of a plate-like elastic body. It has already been proposed to remove ink on the ejection surface and to cover the recording head with a moisture retention cap when the recording head is at a specific position that does not contribute to recording (for example, patents). Reference 2).

  In an on-demand and line-type ink jet recording apparatus, means for wiping the nozzle opening surface without moving the ink jet head (recording head) from the printing position is provided, and ink droplets are formed by drying ink on the nozzle surface and adhering foreign matter. Techniques for preventing printing defects due to so-called dot omission due to ejection failure of the ink and bending of the ejection direction of ink droplets and adding a means for supplying ink solvent to the means for wiping the nozzle surface have already been proposed. In one proposal of this type, a cloth or the like impregnated with an ink solvent is applied to the surface of the belt-like wiping member that comes into contact with the discharge nozzle, and the wiping member is disposed in the gap between the nozzle surface and the printing medium. By inserting a nozzle and wiping the nozzle surface, the dried and solidified ink is dissolved (see Patent Document 3).

In addition, in order to reduce the effect of ink viscosity change of non-ejection nozzles, maintain recording quality, and prevent a decrease in recording speed, temperature detection is performed on the recording head carriage near the ejection section of the recording head. Means and a humidity detecting means, and based on the temperature and humidity values detected by these detecting means, a preliminary ejection operation that does not affect recording on the recording medium is performed and the temperature and humidity around the recording head are controlled. Has been proposed. In this proposal, the waste ink is vaporized by the heat of the heating element, and the ejection portion of the recording head is humidified by the vaporized waste ink (see Patent Document 4).
Japanese Patent Laying-Open No. 2004-090223 (paragraphs 0005 to 0007, FIG. 3) Japanese Patent Laying-Open No. 2004-034662 (paragraphs 0004 to 0007, FIG. 5) JP 2003-21680 (paragraphs 0011, 0024, 0035, FIG. 2) JP 2000-190528 A (paragraphs 0014, 0028, 0029, FIG. 6)

  The conventional technology described above still has various problems as described below. In other words, the technique of Patent Document 1 that applies a specific size to the diameter of the ink discharge port of the nozzle or that does not include a volatile component as the ink has strict conditions relating to manufacturing accuracy and does not use a special ink. Cannot be expected to be effective. Also, the method of performing flushing and head cleaning as in existing products, or the recording head is moisturized only when the recording head is in a home position that is a specific position that does not contribute to recording as in Patent Document 2. In the method, the recording operation is interrupted during the flushing or cleaning period, or during the period in which the recording head is shifted to the home position, and the time required for recording is extended.

  Originally, it is desirable that the number of times of these flushing and cleaning operations is smaller. Reducing the number of flushing and cleaning operations is a more important issue especially in a line type ink jet recording apparatus. That is, in the line type, recording is performed by conveying the recording paper (recording medium) at a high speed in a state of being fixed facing the sheet conveying means, but neither flushing nor head cleaning can be performed during the recording operation. Print quality may be reduced during recording. Further, even when flushing or cleaning is performed, it takes time to move the head to the operating position, and the overall recording speed is reduced.

  On the other hand, as disclosed in Patent Document 3, when a structure is adopted in which a wiping member is inserted into the gap between the nozzle surface and the printing medium and brought into contact with the nozzle surface, the gap between the nozzle surface and the printing medium is inserted into the wiping member. Therefore, it is not always advantageous to realize high-quality recording because the flying distance of the ink droplets may increase and the positioning accuracy related to the landing of the droplets may decrease. Absent.

  In the technique disclosed in Patent Document 4, waste ink is vaporized by the heat of the heating element, and the discharge portion of the recording head is humidified by the vaporized waste ink. It depends on the humidity in the vicinity of the ejection surface where the ink is in contact with the solvent, and even if the humidity around the head is increased, the moisture retention in the vicinity of the ejection surface is not necessarily perfect. Further, in a line-type printer, if the atmosphere around the large head unit is set to high humidity, excessive steam may be generated in the apparatus, resulting in malfunction of each part.

  The present invention has been made by paying attention to the problems in the prior art as described above, and is capable of undesired ink by appropriately moisturizing the ejection surface of the recording head with a simple configuration while enabling high-speed recording. An object of the present invention is to provide a recording head device capable of effectively avoiding deterioration of recording quality due to an increase in viscosity or clogging of an ejection port, and an ink jet recording device including the recording head device.

In order to solve the above-described problems, the present application proposes the following techniques.
(1) A recording head device for performing recording on a recording medium by discharging ink from an ejection port provided on an ejection surface facing the recording medium,
A humidifying liquid supply port for supplying and exuding the humidifying liquid to a predetermined portion in the discharge surface is provided, and a wet region for vaporizing the humidifying liquid exuding from the humidifying liquid supply port is formed along the discharge surface. A recording head device.
In the apparatus of (1), with a simple configuration, by appropriately moisturizing the ejection surface of the recording head, it is possible to effectively avoid undesired increase in ink viscosity and deterioration in recording quality due to clogging of ejection ports. Can do.

(2) The humidifying liquid can be guided to the humidifying liquid supply port through a predetermined humidifying liquid supply path from a humidifying liquid reservoir provided to store the humidifying liquid (1). 2. A recording head device according to 1.
In the apparatus of (2), sufficient humidification liquid can be guided to the humidification liquid supply port through a predetermined humidification liquid supply path from a humidification liquid reservoir that can be separate from the recording head unit itself. With such a configuration, by appropriately moisturizing the ejection surface of the recording head, it is possible to effectively avoid an undesirable increase in ink viscosity and deterioration in recording quality due to clogging of the ejection ports.

(3) A hydrophobic region is formed around the ink discharge port, and the wet region is formed so as to exclude the hydrophobic region. (1) or (2) Recording head device.
In the apparatus of (3), the meniscus of the ink is adjusted by the action of the hydrophobic area in addition to the action and effect of the recording head apparatus described in (1) or (2), and adhesion of unnecessary ink is prevented, and the wet area The inconvenience that the humidifying liquid and the ink at the discharge port are connected and mixed together is avoided.

(4) The wet area is set so that the area of the upstream area from the position of the ink discharge port is larger than the area of the downstream area along the sub-scanning direction related to the recording operation by the recording head. The recording head device according to any one of (1) to (3), wherein:
In the apparatus of (4), the ink discharge port is effectively moisturized by the vapor held in the relatively large volume space in the wet area upstream of the position of the ink discharge port.

(5) The recording according to any one of (1) to (4), wherein a cleaning member for cleaning the discharge surface can be brought into contact with the discharge surface side. Head device.
In the apparatus of (5), in addition to the effects of the apparatus described in any of (1) to (4) above, the viscosity attached to the ink discharge port and its peripheral area is high and the print quality is lowered. The ink residue is wiped out to maintain the recording quality.

(6) The recording head device according to any one of (1) to (5), wherein a heat generating member is provided in a predetermined portion on the ejection surface side.
In the apparatus of (6), in addition to the effects of the apparatus described in any of (1) to (5) above, the temperature of the wet area is lowered by the heat of vaporization of the humidifying liquid, and the temperature of the ink at the ejection port In comparison, it is avoided that the temperature of the humidifying liquid is lowered and effective moisturizing cannot be performed.

(7) The wet area is set so that the ink discharge port and the humidifying liquid supply port are disposed within the self area, and the wet area is a sub-scanning related to a recording operation by the recording head. The area of the upstream region from the position of the ink discharge port along the direction is set to be large relative to the area of the downstream region, and the hydrophobicity formed around the ink discharge port Set to exclude the region:
The dimension along the sub-scanning direction of the upstream region in the wet region is L,
The conveyance speed of the recording medium is V,
G represents a gap between the ejection surface and the recording medium,
The recording head device according to any one of (1) to (2), wherein the recording head device is set to satisfy a relationship of 2.30E-5 ≧ G ² V / L.
In the apparatus of (7), in addition to the effects of the apparatus described in any of (1) to (2) above, the moisture retention at the ink discharge port and its vicinity is further improved.

(8) An ink jet recording apparatus comprising the recording head device according to any one of (1) to (7).
In the ink jet recording apparatus of (8), the recording quality due to an undesired increase in ink viscosity or clogging of the discharge port can be achieved by appropriately moisturizing the discharge surface of the recording head with a simple configuration while enabling high-speed recording. Can be effectively avoided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings referred to below, for the sake of convenience, the main part that is the subject of the description is appropriately exaggerated.
FIG. 1 is a plan view showing an outline of a line type ink jet recording apparatus to which the present invention is applied.
The recording paper 20 as a recording medium is conveyed by the recording paper conveyance unit 30 so that the recording surface of the line-type head unit 10 is close to and opposed to the ejection surface of the line head unit 10, and recording is performed while passing under the head unit 10. The recorded recording paper 20 is discharged from the discharge unit 31 to the outside.

  That is, first, the recording paper 20 is led out from the paper feeding unit 32 and guided to the recording paper transport unit 30 by the gate roller 33. In accordance with the general recognition of those skilled in the art, in this specification, the conveyance direction of the recording paper 20 is also referred to as the sub-scanning direction (Y direction), and the direction orthogonal thereto, that is, the arrangement direction of the discharge ports, which will be described in detail later, is the main. This is called the scanning direction (X direction).

  In the head unit 10, a black head unit 11, a magenta head unit 12, a cyan head unit 13, and a yellow head unit 14 each having an inkjet discharge port arranged in the X direction are arranged in parallel as shown in the figure. It is configured to be supported by a single unit. The black head unit 11, the magenta head unit 12, the cyan head unit 13, and the yellow head unit 14 are respectively provided with a black ink cartridge 41, a magenta ink cartridge 42, a cyan ink cartridge 43, and Ink is supplied from the yellow ink cartridge 44 through ink supply tubes 51, 52, 53, and 54, respectively.

  The black ink cartridge 41, the magenta ink cartridge 42, the cyan ink cartridge 43, and the yellow ink cartridge 44 are arranged as a group of ink cartridges 40 as shown in the figure. In addition to this, a humidifying liquid tank 60 is provided as a humidifying liquid reservoir for storing the humidifying liquid. The humidifying liquid in the humidifying liquid tank 60 is distributed and supplied to the black head unit 11, the magenta head unit 12, the cyan head unit 13, and the yellow head unit 14 through a humidifying liquid supply tube 61 that forms a humidifying liquid supply path.

  The black head unit 11, the magenta head unit 12, the cyan head unit 13, and the yellow head unit 14 include a black cleaning unit 71, a magenta cleaning unit 72, a cyan cleaning unit 73, and a yellow cleaning unit 74, respectively. A cleaning unit 70 is provided. In FIG. 1, the cleaning unit 70 is conceptually expressed by being surrounded by a broken line, but the configuration and operation will be described later with reference to FIG. 7. The head unit 10, the recording paper transport unit 30, and other units are controlled in an integrated manner from a control means (CPU) not shown.

The ink color types need not be limited to K (black), M (magenta), C (cyan), and Y (yellow). Besides these, light cyan (LC), light magenta (LM), red Of course, (R), blue (B), resin for ink layer coating, and the like may be added, and the arrangement of the line type heads is not necessarily limited to the order of KMCY.
FIG. 2 is a side view showing an outline of the line-type ink jet recording apparatus of FIG. 2 corresponding to those in FIG. 1 are denoted by the same reference numerals.

  In FIG. 2, as described above with reference to FIG. 1, each ink supply tube 51 is added to the head unit 10 including the black head unit 11, the magenta head unit 12, the cyan head unit 13, and the yellow head unit 14. , 52, 53 and 54, ink is supplied. Further, the humidifying liquid is supplied through the humidifying liquid supply tube 61. The recording paper 20 is led out from the paper supply unit 32, guided to the recording paper transport unit 30 by the gate roller 33, and transported to the discharge unit 31 through under the head unit 10.

  This conveyance is performed by placing the recording paper 20 on the conveyance belt 34 and rotating the conveyance belt 34 counterclockwise from the driven roller 35 side to the drive roller 36 side. The tension of the conveyor belt 34 is appropriately maintained by a tension roller 37. On the other hand, air blowing means 70 for sending outside air into the apparatus is attached, and after the recording operation is completed, the humidity in the apparatus is appropriately adjusted by the air blowing thereby to maintain the quality of recording (printing).

  FIG. 3 is a front view schematically showing the external appearance of the recording head apparatus according to the embodiment of the present invention. In FIG. 3, corresponding parts to those in FIGS. 1 and 2 are denoted by the same reference numerals. What is schematically represented in FIG. 3 is a black head unit 11, a magenta head unit 12, a cyan head unit 13, and four colors (K, M, C, and Y) constituting a reference color of one line. An ink nozzle row group (a discharge surface having a printing length L, which will be described later) composed of a set of yellow head units 14 is divided into 12 in the line direction (main scanning direction) as shown in the drawing (that is, each unit width L has a unit width L). Twelve recording head ejection surfaces are arranged in the line direction so as to cover the entire effective printing width of 12L, and the head units 11, 12, 13, and 14 of each color (each line) are printed with a width of 12L. It is configured as possible.

  As shown in the drawing, the ink nozzle row group (each recording head ejection surface drawn with diagonal lines) of each of the four color (K, M, C, Y) head units 11, 12, 13, and 14 is, for example, With respect to the black head unit 11, each of the six recording heads 11a, 11a,..., 11a in the first group is discontinuously arranged in the main scanning direction at intervals corresponding to the widths of the ejection surfaces. , 11b are arranged in parallel with the arrangement of the recording heads 11a, 11a,..., 11a of the first group and are displaced in the main scanning direction. As a whole, twelve recording heads are arranged in a staggered manner in the main scanning direction to cover the entire effective printing width 12L.

  As illustrated, the above-described configuration is the same for the magenta head unit 12, the cyan head unit 13, and the yellow head unit 14. That is, the magenta head unit 12 is configured by arranging the six recording heads 12a, 12a,..., 12a in the first group and the six recording heads 12b, 12b,. The cyan head unit 13 is composed of a first group of six recording heads 13a, 13a,..., 13a and a second group of six recording heads 13b, 13b,. The yellow head unit 14 is composed of six recording heads 14a, 14a,..., 14a in the first group and six recording heads 14b, 14b,. Has been.

  In the present specification, the embodiment is described using a head unit having a print area in the main scanning direction in which twelve monochrome print heads are arranged in a staggered manner. However, the monochrome has a print area width in the main scanning direction. When the long recording head is used, the configuration is the same as that of the individual staggered recording heads.

  4 is a front view schematically showing one ejection surface 100 of the recording head device 10 according to the first embodiment of the present invention, and FIG. 5 is a (A-A line) of the recording head device of FIG. FIG. The illustrated recording head device 10 includes recording heads 11a, 11a,..., 11a that are constituent elements of the head units 11, 12, 13, and 14 that are line heads described with reference to FIG. 11b; 12a, 12a, ..., 12a; 12b, 12b, ..., 12b; 13a, 13a, ..., 13a; 13b, 13b, ..., 13b; 14a, 14a, ..., 14a; 14b, 14b, ..., 14b About one of them, the code | symbol 10 is attached typically and the structure common to each piece is represented.

  The nozzle plate 101 forming the discharge surface 100 is provided with a plurality of discharge ports 110, 110,... (Corresponding to any of the four colors of inks K, M, C, and Y) aligned in the main scanning direction. In addition, a plurality of humidifying liquid supply ports 121, 121,... Are arranged in parallel to the row of the plurality of discharge ports 110, 110,... And spaced apart in the sub-scanning direction (upstream as viewed in the paper feed direction). (In FIG. 5, the reference numeral 120 is representatively attached).

  In addition, a vibration plate 103 that is vibrated and displaced by a pressure generating means 102 made of a known piezoelectric element or the like is provided in parallel with the nozzle plate 101. The predetermined area along the discharge surface 100 is formed as a wet area 130 for vaporizing the humidified liquid that has exuded from the humidified liquid supply ports 121, 121,.

  In FIG. 4, the alignment direction of the plurality of discharge ports 110, 110,... Is represented by a broken line connecting the center positions of the discharge ports 110, 110,. Such display of the alignment direction by the broken line is the same in FIGS. 9, 10, 11, and 12, which will be described later. This broken line is also a boundary line between the upstream side and the downstream side along the sub-scanning direction when viewed from the aligned position of the discharge ports 110, 110,.

  As understood from FIG. 4, in this embodiment, the wet region 130 has a larger area in the upstream region than the boundary line than the area in the downstream region. By forming the wet region 130 in such a form, the wet region 130 is relatively large in area upstream of the position of the ink discharge port, and therefore has a large amount of moisture held in a space having a large volume for moisture retention. The ink discharge port is effectively moisturized by the steam. Ink supply tubes from the ink cartridge 40 (any one of the black ink cartridge 41, the magenta ink cartridge 42, the cyan ink cartridge 43, and the yellow ink cartridge 44) described with reference to FIG. The ink supplied to the ink reservoir 140 through 50 (any of 51, 52, 53, 54) is guided through the ink supply port 141 communicating with the ink reservoir 140.

  On the other hand, the humidifying liquid in the humidifying liquid tank 60 described with reference to FIG. 1 is supplied to the humidifying liquid reservoir 150 through the humidifying liquid supply tube 61, and the humidifying liquid in the humidifying liquid reservoir 150 is supplied to the humidifying liquid supply ports 121, 121,. It evaporates from the gas and vaporizes in the wet region 130, and a humidifying action due to this vaporization occurs. In particular, annular hydrophobic surfaces 111, 111,... Are formed around the respective discharge ports 110, 110,. A hydrophobic surface 112 is also formed on the outermost peripheral side of the wet region 130 so as to surround the wet region 130.

  These hydrophobic surfaces 111, 111,... Adjust the ink meniscus, prevent the unnecessary ink from adhering, and the humidified liquid in the wet region 130 and the ink at the discharge ports 110, 110,. Avoid inconveniences. Each of the discharge ports 110, 110,... Can supply the humidifying liquid quickly after wiping, and does not cause the gravity acting on the humidifying liquid at the supply port to fall above the surface tension. In addition, their diameter is preferably 20 μm to 500 μm. However, the size and arrangement of 121, 121,... Are not limited to the above.

  FIG. 6 shows a state in which the humidifying liquid is supplied from the humidifying liquid tank 60 serving as the humidifying liquid reservoir to the discharge surface 100 of the recording head 10 (where the above-described wet region 130 is formed) in the embodiment of the present invention. FIG. The humidifying liquid is guided from the humidifying liquid tank 60 to the recording head 10 by the illustrated water head difference H and capillary force. The humidifying liquid tank 60 is provided with a liquid level switch 63 having a float 62.

  When the level position of the float 62 changes according to the liquid level in the humidifying liquid tank 60, the magnet provided on the support portion of the float 62 is displaced according to this change, and the liquid level switch 63 according to the position of this magnet. The internal reed switch opens and closes. When the liquid level in the humidifying liquid tank 60 reaches a predetermined lower limit level, the liquid level switch 63 is activated and a warning is displayed on a display means (not shown).

  FIG. 7 is a diagram illustrating a state of the wiping operation in the embodiment described with reference to FIG. 1, and FIG. 7A illustrates a state where the recording head and the blade to be wiped are separated from each other. A state in which the protrusion amount of the blade is made variable is shown, and a portion (b) shows a state in which the blade wipes the recording head. As shown in FIG. 7A, with respect to the recording head 10 (nozzle surface thereof), the blade 104 is variable in the amount of protrusion toward the nozzle surface by the lifting means 105 (in the vertical direction as shown). The tip of the blade 104 can project to a level position higher than the level position of the nozzle surface by d as shown in the figure.

  When the blade 104 is displaced relative to the recording head 10 (nozzle surface thereof) with the blade 104 protruding in this manner (displaced in the horizontal direction of the paper surface in the illustrated example), the blade 104 is illustrated in FIG. 7B. As described above, the blade 104 wipes the nozzle surface while being bent. A blade cleaning means 106 is attached to wipe off ink or the like adhering to the blade 104 itself. By the above-described wiping operation, the ink residue that has a high viscosity adhering to the ink discharge port and its peripheral region and causes a decrease in print quality is wiped out, and the recording quality is maintained.

  FIG. 8 is a schematic diagram for analytically explaining the operation of the present invention in relation to the portion B indicated by the broken line in FIG. 4 in the recording head device of the embodiment of the present invention. That is, the discharge surface 100 described with reference to FIG. 4 is sandwiched between a portion B indicated by a broken line (FIG. 4) and a conveyance belt (paper conveyance surface) divided by a width corresponding to the outer diameter of one discharge port 110. FIG. As described above, the wet region 130 vaporizes the humidified liquid exuded from the humidified liquid supply ports 121, 121,... Provided in the region, and the humidified region 130 is generated by evaporating the humidified liquid. The water vapor is supplied to the discharge port 110 by diffusion and air flow.

Here, since the conveyance speed of the paper, which is the recording medium, is larger than the movement speed in one direction due to the diffusion, a model in which water vapor is supplied to the discharge port 110 by the air flow generated by the conveyance will be considered. In order to obtain the effect of suppressing the evaporation of the ink solvent at the discharge port 110 by the evaporation (humidification) of the humidified liquid at the wet region 130, the upstream of the paper feed direction in the paper feed direction from the discharge port 110 of the wet region 130. Necessary conditions are obtained for the length L, the distance (gap) G between the print medium (paper) conveyance surface 300 and the ejection surface, and the print medium conveyance speed Vp.
The preconditions for this model are set as follows:

(1) The length L on the upstream side of the print medium (paper) feed direction, and only the air humidified by a part of the wet area having the width of the discharge port diameter R in the discharge port arrangement direction is the paper feed direction by the air flow. It passes through the discharge port and the paper transport surface 300 from the upstream side. The air flow between the discharge surface and the paper transport surface 300 is equal to the transport speed Vp and uniform.
(2) The temperature range of the operating environment is 5 to 50 ° C., and the humidity range is 0 to 90%. The humidity distribution in the space to be humidified is saturated in the wet area on the ejection surface and operating humidity on the transport surface.

(3) The ink is water-based ink, and the humidifying liquid is water.
(4) The evaporation of the humidified liquid that has exuded from the humidifying section (humidified liquid supply port) is constantly performed, and the diffusion speed of the water vapor diffusing in the vicinity of the water surface is the water vapor supply speed by the evaporation from the humidifying section. To do. Diffusion is based on Fick's law, and the water supply rate takes a certain value depending only on the initial humidity distribution.

Formulate the above assumptions. The amount of water vapor M required to saturate the air in the space (Δl × R × G) obtained by dividing the air flowing from the upstream side in the paper feeding direction into a minute length Δl in the paper conveyance direction is:
M = (C _S −C _X ) × R × G × Δl (1)
However, C _s : saturated vapor density, C _x : water vapor density of the operating environment, R: diameter of the discharge port (length in the direction of the discharge port array in a finely divided space), G: gap, Δl: finely divided The length of the space in the paper feed direction.
On the other hand, the amount of water vapor m supplied when the air passes through the wet region is:
m = {D (C _S -C _X ) × R × Δl / G} × (L / V _P ) (2)
Where L: length in the paper feeding direction upstream of the paper outlet in the wet area, Vp: paper feeding speed, D: diffusion coefficient of water vapor in the operating environment.
In the formulas (1) and (2), if m−M ≧ 0, evaporation of the discharge port can be suppressed.
Furthermore, in the precondition temperature range (5 ° C to 50 ° C),
Since 2.30E-5 ≦ D ≦ 3.02E-5,
2.30E-5 ≧ G ² V _P / L (3)
Should be satisfied.
From Expression (3), for example, when the conveyance speed Vp = 200 mm / s and the gap G = 1.0 mm, L needs to be 8.7 mm or more. By selecting the positional and dimensional relationship of each part so as to satisfy the expression (3), the moisture retention at the ink discharge port and its vicinity is further enhanced.

  Further, the area of the wet region may be appropriately changed for each head unit of the black head unit 11, the magenta head unit 12, the cyan head unit 13, and the yellow head unit 14 in the paper feeding direction. That is, the wet area of the head unit on the most upstream side in the paper feed direction is the maximum area, and from the remaining head units, the area of the wet area of the head on the upstream side in the paper feed direction is the area on the downstream side. It is formed so as to be equal or larger than With such a configuration, it is possible to increase the evaporation amount even in the head unit on the most upstream side in the paper feeding direction in which the air with the lowest humidity is sent.

  The distance L between the wet region 130 and the ejection port 110 is preferably as short as possible in consideration of the humidification effect due to evaporation and diffusion from the wet region 130. However, if the distance L is shorter, the distance L between the wet region 130 and the discharge port 110 is different from the wet region 130 during ink droplet ejection or wiping. Ink or humidifying liquid is easily connected at the ejection port 110, and the shortest distance with respect to the distance L is preferably 20 μm or more and 100 μm or less, for example. When the nozzle plate 101 is a hydrophilic material, the wet region 130 is formed by forming a hydrophobic material on the ejection surface 100 and then exposing the nozzle plate surface by etching, laser processing, or the like.

  Alternatively, even when the nozzle plate is a hydrophobic material, the wet region and the hydrophobic surface of the hydrophilic material are formed by an anisotropic film formation method such as sputtering. As the hydrophilic material, a hydrophilic oxide such as titanium dioxide or aluminum oxide, a metal having a surface of these oxides, or a hydrophilic polymer material such as PVA can be used. Examples of the hydrophobic material include fluorine-based resins and polymer hydrocarbons.

  By using these hydrophilic materials, wetting of the wet area with respect to the humidifying liquid is improved, so that the humidifying liquid can be uniformly supplied to the entire surface of the wet area. Furthermore, unevenness may be formed on the surface, and the contact angle may be made smaller than in the case of a flat surface to improve wetting. The humidification liquid is supplied to the wet region 130 so that 80 to 100% of the wet region is wetted with a liquid layer that can be visually judged to the extent that droplets are not formed. H is set so that the capillary force of the humidifying liquid supply path including the humidifying liquid tank 60) and the head pressure due to the height H of the liquid level of the humidifying liquid tank 43 and the discharge surface 100 are balanced, and the wet area automatically 130 is moistened (see FIG. 6).

  In order to prevent the dampening liquid from dripping onto the printing medium or the paper conveying means, the surface of the wet area by electropolishing, brush polishing or the like has, for example, a groove having a width of 20 μm or more and 500 μm or less, or a diameter in an equivalent range. The hole which has is formed and a humidification liquid is hold | maintained by capillary force. Furthermore, in order to prevent the humidified liquid in the wet region from being inclined and dripped in the inclined direction due to the inclination of the head in the horizontal direction, the unevenly humidified liquid is held at the boundary portion with the hydrophobic surface outside the humidified part. For example, a desirable effect can be obtained by forming a groove having a diameter of 20 μm or more and 500 μm or less or a hole having an equivalent diameter range.

  The humidifying liquid is composed of a component having the highest component ratio among the components of the ink excluding the color material and the drying inhibitor, or a solution containing the remaining component as a main component. That is, as the humidifying liquid, water which is the main component of the liquid or an aqueous solution containing components such as a penetrating agent, a pH adjusting agent and an antiseptic and antifungal agent constituting the ink is suitable. In particular, in the case of pigment ink, it is desirable that the pH of the aqueous solution is approximately the same as that of the ink in order to prevent a decrease in dispersibility due to a change in pH of the ink at the ejection port. Furthermore, in order to improve the wetness with the wet region, the surface tension of the humidifying liquid may be adjusted with a surfactant, alcohol or the like.

FIG. 9 is a front view schematically showing one ejection surface of the recording head apparatus according to the second embodiment of the present invention. In FIG. 9, corresponding parts to those in FIG. 4 described above are denoted by the same reference numerals, and detailed description thereof is omitted.
A plurality of discharge ports 110, 110,... (Corresponding to any of four color inks K, M, C, Y) are arranged on the discharge surface 100 in the main scanning direction. A plurality of humidifying liquid supply ports 121, 121,... Are arranged in parallel to the rows of the discharge ports 110, 110,. The predetermined area of the discharge surface 100 becomes a wet area 130 that is humidified by vaporizing the humidified liquid that has oozed from the humidified liquid supply ports 121, 121,.

  In this embodiment, in particular, the arrangement of the discharge ports 110, 110,... Instead of the annular hydrophobic surfaces 111, 111,. A series of hydrophobic surfaces 111c as shown in the figure continuous in the direction are formed. This hydrophobic surface 111c, like the hydrophobic surfaces 111, 111,... Described above, adjusts the ink meniscus and prevents the adhesion of unnecessary ink, and the humidifying liquid in the wet region 130 and the discharge ports 110, 110,. This works to prevent the inconvenience of being connected to and mixed with the other ink.

  FIG. 10 is a front view schematically showing one ejection surface of the recording head apparatus according to the third embodiment of the present invention. 10, the corresponding parts to those in FIG. 9 described above are denoted by the same reference numerals, and detailed description thereof will be omitted. A plurality of discharge ports 110, 110,... (Corresponding to any of four color inks K, M, C, Y) are arranged on the discharge surface 100 in the main scanning direction. , 110,..., A series of hydrophobic surfaces 111c continuous in the arrangement direction are formed as shown.

  This hydrophobic surface 111c, like the previously described hydrophobic surfaces 111, 111,... Prepares the ink meniscus and prevents the unnecessary ink from adhering, and the humidified liquid in the wet region 130 and the discharge ports 110, 110,. This works to prevent the inconvenience of being connected to and mixed with the other ink. In this third embodiment, in particular, instead of arranging the plurality of humidifying liquid supply ports 121, 121,... As in the embodiment of FIGS. As described above, a grooved humidifying liquid supply line 122 is provided in the wet region 130 so as to surround the belt-like region including the discharge ports 110, 110,... And a series of hydrophobic surfaces 111c continuous in the arrangement direction. Is provided.

  The humidifying liquid supply line 122 is formed as a groove having a hydrophilic surface on the surface in the area of the wet region 130, and the humidifying liquid supplied from the humidifying liquid supply port 121 a is caused to vaporize around the wet area 130. It acts to maintain a substantially uniform moisturizing state. By adopting such a configuration, the structure of the humidifying liquid supply path of the recording head can be simplified. The shape of the hydrophobic surface is not limited to that shown in the figure. For example, as shown in FIG. 4, an annular hydrophobic surface 111, 111,. The grooved humidifying liquid supply line may be formed so as to surround the plurality of island-shaped regions.

  FIG. 11 is a front view schematically showing one ejection surface of the recording head apparatus according to the fourth embodiment of the present invention. In FIG. 11, the corresponding parts to those in FIG. 4 described above are denoted by the same reference numerals, and detailed description thereof is omitted. A plurality of discharge ports 110, 110,... (Corresponding to any of four color inks K, M, C, Y) are arranged on the discharge surface 100 in the main scanning direction. A plurality of humidifying liquid supply ports 121, 121,... Are arranged in parallel to the row of the discharge ports 110, 110,... And spaced apart in the sub-scanning direction (that is, upstream in the paper feed direction). .

  In the fourth embodiment, the wet region 130 is provided only on the upstream side in the paper feed direction from the arrangement of the discharge ports 110, 110,. A hydrophobic surface 111d is formed over the entire region on the downstream side in the paper feeding direction and a slight region on the upstream side in the paper feeding direction from the arrangement of the discharge ports 110, 110,. By forming the hydrophobic surface 111d in this way, when wiping the discharge surface by wiping, the humidification liquid is not touched until the blade passes through the discharge port, and therefore the inconvenience of mixing the ink and the humidification liquid is avoided. In addition, the number of flushing operations after wiping can be reduced.

  FIG. 12 is a front view schematically showing one ejection surface of the recording head device according to the fifth embodiment of the present invention. Also in FIG. 12, the corresponding parts in FIG. 4 described above are denoted by the same reference numerals, and detailed description thereof is omitted. A plurality of discharge ports 110a and 110a (corresponding to any of four color inks K, M, C, and Y) are arranged on the discharge surface 100 so as to be separated in the sub-scan direction and aligned in two rows in the main scan direction. ,... Are provided, and the discharge ports 110a, 110a,...; Each of these rows are positioned (phase) by a distance of half the arrangement pitch in the main scanning direction. These discharge ports are arranged in a staggered manner as a whole. These plural outlets 110a, 110a,...; Are parallel to the outlets 110b, 110b,... And separated in the sub-scanning direction (that is, upstream in the paper feed direction). Are arranged.

  As shown in the figure, annular hydrophobic surfaces 111a, 111a,...; 111b, 111b,... Are formed around the discharge ports 110a, 110a,. These hydrophobic surfaces 111a, 111a,...; 111b, 111b,... Also adjust the ink meniscus, prevent the adhesion of unnecessary ink, and the humidified liquid in the wet area and the ink at the discharge port are connected and mixed. Prevent inconvenience. The position, number (arrangement pitch), and size of the humidifying liquid supply port are not limited to the illustrated example.

  FIG. 13 is a cross-sectional view of a recording head device according to the sixth embodiment of the present invention. In FIG. 13, corresponding parts to those in FIG. 5 described above are denoted by the same reference numerals, and detailed description of these parts is omitted. A plurality of discharge ports 110 are arranged on the nozzle plate 101 forming the discharge surface 100 so as to be aligned in the main scanning direction (in the direction perpendicular to the paper surface in this figure), and are parallel to the row of the discharge ports 110 and in the sub-scanning direction. A plurality of humidifying liquid supply ports 120 are provided apart from each other (that is, on the upstream side in the paper feeding direction).

  In addition, a vibration plate 103 that is vibrated and displaced by a pressure generating means 102 made of a known piezoelectric element or the like is provided in parallel with the nozzle plate 101. The predetermined area of the discharge surface 100 becomes a wet area 130 that is humidified by vaporizing the humidified liquid that has oozed from the humidified liquid supply port 120 provided in this area. The ink supplied to the ink reservoir 140 through the ink supply tube 50 is guided to the ejection port 110 through the ink supply port 141 communicating with the reservoir 140.

  Further, the humidified liquid is supplied to the humidified liquid reservoir 150 through the humidified liquid supply tube 61, and the humidified liquid in the humidified liquid reservoir 150 oozes out from the humidified liquid supply port 120 and is vaporized in the wet area 130, and is discharged by the vaporized humidified liquid. Surface 100 is humidified. An annular hydrophobic surface 111 is formed around each ejection port 110, and the meniscus of ink is adjusted by the hydrophobic surface 111 to prevent unnecessary ink from being attached. This is also the same as described with reference to FIG. 5 in that the inconvenience of being connected to and mixed with the other ink is prevented.

  In this embodiment, in particular, a heater 104 and a temperature detector 105 for detecting the temperature of the humidifying liquid are attached to a partial region of the nozzle plate 101. The heater 104 is heated by Joule heat of resistance, and the heating is adjusted by voltage control. Further, the heater 104 is formed in a strip shape extending upstream in the paper feed direction in the discharge port arrangement direction (in the direction perpendicular to the paper surface in this figure), and is discharged by the air flow caused by the paper feed of the paper transport means. Wet air is sent to the outlet 110.

  In addition, the area of the heater is changed in association with each of the four color (K, M, C, Y) head units 11, 12, 13, 14 (see FIG. 1) arranged side by side in the paper feed direction. Also good. In other words, the head area on the most upstream side in the paper feed direction is set to the maximum area, and from the remaining head units, the heater area of the head on the upstream side in the paper feed direction is equal between the adjacent heads compared to the area on the downstream side. Or larger. With such a configuration, it is possible to ensure a sufficient amount of evaporation even in the head unit on the most upstream side in the paper feed direction in which air with the lowest humidity is sent.

  The heater 104 heats the humidified liquid for the purpose of preventing the temperature of the wet region 130 from being lowered by the heat of vaporization of the humidified liquid and lowering the temperature of the humidified liquid compared to the temperature of the ink at the ejection port 110. Act on. Therefore, it is avoided that effective moisturizing cannot be performed due to the temperature drop of the humidifying liquid. The temperature detector 105 that detects the temperature of the humidifying liquid and an ink temperature detector (not shown) control the humidifying liquid temperature to be higher than the ink temperature by a temperature in the range of 0 ° C. to 15 ° C.

In addition, in order to prevent the humidified liquid from boiling due to excessive heating and soiling the paper and the printer device, control is also performed to stop the heating of the heater at 80 ° C. or higher. In the sixth embodiment, the wet region 130 and the hydrophobic surface 111 of the discharge surface 100 can take any of the forms described above for the first to fifth embodiments.
In general, according to the technique proposed in the present application, the conditions relating to the manufacturing accuracy are not so strict, so that the manufacturing is easy and good printing can be performed without using special inks or the like. Further, since the recording head is moisturized and maintained in a good state without frequent flushing and cleaning, it is not necessary to interrupt the recording operation, and the time required for recording is shortened. This effect is remarkable when the line type recording head is used.

  Furthermore, it is not necessary to set the gap between the nozzle surface and the print medium large enough to allow the wiping member to be inserted, and this gap can be shortened to ensure sufficient positioning accuracy for ink droplet landing. High quality recording can be realized. Furthermore, since sufficient humidification can be performed on the discharge port of the head that originally needs to be moisturized and the vicinity thereof, undesired increase in ink viscosity and clogging of the discharge port can be effectively avoided to improve the recording quality. Can be maintained.

It is a top view which shows the outline | summary of the line-type inkjet recording device to which this invention is applied. It is a side view which shows the outline | summary of the line-type inkjet recording device of FIG. 1 is a front view schematically showing an appearance of a recording head device according to an embodiment of the present invention. FIG. 2 is a front view schematically showing one ejection surface of the recording head device according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view of the recording head device in FIG. 4. It is a figure showing a mode that humidification liquid is supplied from a humidification liquid storage device in the embodiment of the present invention. It is a figure showing the mode of the wiping operation | movement in embodiment of this invention. FIG. 5 is a schematic diagram for analytically explaining the operation of the present invention in relation to the portion indicated by the broken line in FIG. 4 of the recording head device of the embodiment of the present invention. FIG. 6 is a front view schematically showing one ejection surface of a recording head device according to a second embodiment of the present invention. FIG. 10 is a front view schematically showing one ejection surface of a recording head device according to a third embodiment of the invention. FIG. 10 is a front view schematically showing one ejection surface of a recording head device according to a fourth embodiment of the invention. FIG. 10 is a front view schematically showing one ejection surface of a recording head device according to a fifth embodiment of the invention. It is sectional drawing of the recording head apparatus which is the 6th Embodiment of this invention.

Explanation of symbols

10 ... head unit, 11 ... black head unit, 12 ... magenta head unit,
DESCRIPTION OF SYMBOLS 13 ... Cyan head unit, 14 ... Yellow head unit, 20 ... Recording paper, 30 ... Recording paper conveyance unit, 31 ... Discharge part, 32 ... Paper feed part, 33 ... Gate roller, 34 ... Conveyor belt, 35 ... Driven roller, 36 ... Drive roller, 37 ... Tension roller, 40 ... Ink cartridge, 41 ... Black ink cartridge, 42 ... Magenta ink cartridge, 43 ... Cyan ink cartridge, 44 ... Yellow ink cartridge, 50, 51, 52, 53, 54 ... Ink Supply tube, 60 ... humidified liquid tank, 61 ... humidified liquid supply tube, 62 ... float, 63 ... liquid level switch, 70 ... cleaning section, 71 ... black cleaning section, 72 ... magenta cleaning section, 73 ... cyan cleaning section, 74 ... Yellow cleaning section, 100 ... discharge surface, 101 Nozzle plate, 102 ... Pressure generating means, 103 ... Vibration plate, 110 ... Discharge port, 111 ... Hydrophobic surface, 120, 121 ... Humidification liquid supply port, 130 wet region, 140 ... Ink reservoir, 141 ... Ink supply port, 150 ... Humidifying liquid reservoir, 300 ... Paper transport surface

Claims (8)

A recording head device for performing recording on a recording medium by ejecting ink from an ejection port provided on an ejection surface facing the recording medium,
A humidifying liquid supply port for supplying and exuding the humidifying liquid to a predetermined portion in the discharge surface is provided, and a wet region for vaporizing the humidifying liquid exuding from the humidifying liquid supply port is formed along the discharge surface. A recording head device.   The humidification liquid can be guided to the humidification liquid supply port through a predetermined humidification liquid supply path from a humidification liquid reservoir provided to store the humidification liquid. Recording head device.   The recording head device according to claim 1, wherein a hydrophobic region is formed around the ink ejection port, and the wet region is formed so as to exclude the hydrophobic region. The wet area is set so that the area of the upstream area from the position of the ink discharge port is larger than the area of the downstream area along the sub-scanning direction related to the recording operation by the recording head. The recording head device according to claim 1, wherein the recording head device is a recording head device.   The recording head device according to claim 1, wherein a cleaning member for cleaning the ejection surface can be brought into contact with the ejection surface side.   The recording head device according to claim 1, wherein a heat generating member is provided in a predetermined portion on the discharge surface side. The wet region is formed such that the ink discharge port and the humidifying liquid supply port are disposed within the self region, and the wet region is along a sub-scanning direction related to a recording operation by the recording head. The area of the upstream area from the position of the ink discharge port is set to be large relative to the area of the downstream area, and the hydrophobic area formed around the ink discharge port is excluded. Is set up like this:
The dimension along the sub-scanning direction of the upstream region in the wet region is L,
The conveyance speed of the recording medium is V,
G represents a gap between the ejection surface and the recording medium,
3. The recording head device according to claim 1, wherein the recording head device is set so as to satisfy a relationship of 2.30E−5 ≧ G ² V / L.   An ink jet recording apparatus comprising the recording head device according to claim 1.

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