JP2008221580A - Liquid drop ejection head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress increase in viscosity of a liquid being ejected from a nozzle. <P>SOLUTION: A moistening liquid circulating through a second moistening liquid channel 42 is supplied from the second moistening liquid channel 42 to a through hole 43 and thence supplied through a groove 45 to an opening 40, thus filling the opening 40 with the moistening liquid. The moistening liquid filling the opening 40 is held in the opening 40 by surface tension of the moistening liquid, and evaporates naturally from the surface of the moistening liquid held in the opening 40. A recess 15, i.e. a space surrounded by the sidewall, is moistened and thereby the vicinity of a nozzle 22 is moistened, thus suppressing increase in viscosity of liquid being ejected from the noise 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a droplet discharge head and an image forming apparatus.

  As a droplet discharge head, an ink jet recording head that records an image by discharging ink droplets is known. As an ink jet recording head, an ink jet recording head disclosed in Patent Document 1 is known.

  In the ink jet head of Patent Document 1, a holder made of rayon, polyester, or the like is provided near the nozzle on the surface of the orifice plate, and is held via a tube by a capillary phenomenon or a pump from a tank containing a solvent used for water-based ink. Supply solvent to the body.

As a result, the humidity in the space near the nozzle opening becomes the saturated vapor pressure level at the head installation environment temperature, and the solvent can be prevented from drying at the nozzle opening even when the installation is in a low humidity environment.
JP 2003-145783 A

  In a droplet discharge head and an image forming apparatus, it is desired to suppress an increase in the viscosity of a liquid discharged from a nozzle.

  In consideration of the above-described facts, an object of the present invention is to humidify the vicinity of a nozzle and suppress an increase in the viscosity of a liquid discharged from the nozzle.

  A droplet discharge head according to claim 1 of the present invention includes a nozzle that discharges a droplet, a pressure chamber that communicates with the nozzle, a first flow path that supplies liquid to the pressure chamber, and a periphery of the nozzle. A concave portion formed by a surrounding side wall and a nozzle surface on which the nozzle is formed, an opening opening in the concave portion, and a second flow path for supplying a humidifying liquid to the opening, To do.

  According to a second aspect of the present invention, there is provided the liquid droplet ejection head according to the first aspect, wherein a plurality of the nozzles are opened in the recess.

  A droplet discharge head according to a third aspect of the present invention is characterized in that, in the configuration of the first or second aspect, a plurality of the second flow paths are formed and are connected to each other.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: the droplet discharge head according to the third aspect; and a circulation unit that circulates the humidified liquid flowing through the second flow path. .

  According to the structure of Claim 1 of this invention, compared with the case where it does not have this structure, the nozzle vicinity can be humidified and the increase in the viscosity of the liquid discharged from a nozzle can be suppressed.

  According to the configuration of the second aspect of the present invention, the vicinity of the plurality of nozzles can be humidified at a time and the increase in the viscosity of the liquid ejected from the plurality of nozzles can be suppressed as compared with the case where the configuration is not provided. .

  According to the structure of Claim 3 of this invention, compared with the case where it does not have this structure, two or more paths which supply humidification liquid are ensured, and humidification liquid can be supplied to an opening part without a stagnation.

  According to the structure of Claim 4 of this invention, compared with the case where it does not have this structure, a fresh humidification liquid can be supplied to an opening part.

  Below, an example of an embodiment concerning the present invention is described based on a drawing.

  In this embodiment, an ink jet recording head that discharges ink droplets and records an image on a recording medium will be described as an example of a droplet discharging head that discharges droplets.

  Note that the droplet discharge head is not limited to the one that records an image, and the liquid to be discharged is not limited to ink. As the droplet discharge head, for example, a droplet discharge head for manufacturing a color filter by discharging ink or the like onto a film or glass, or a liquid for forming a bump for mounting a component by discharging molten solder onto a substrate It may be a droplet discharge head, a droplet discharge head that discharges a liquid containing metal to form a wiring pattern, or a droplet discharge head for various film formation that discharges a droplet to form a film. Anything that discharges may be used.

(Configuration of inkjet recording head according to this embodiment)
The configuration of the ink jet recording head according to this embodiment will be described. FIG. 1B is a schematic diagram illustrating the configuration of the ink jet recording head according to the embodiment. 1A is a cross-sectional view taken along line 1A-1A in FIG. FIG. 2 is an exploded perspective view in which a portion A in FIG. 1B is enlarged. FIG. 3 is an enlarged plan view of a portion A in FIG. 4 is a cross-sectional view taken along line 4-4 in FIG.

  As shown in FIG. 1A, FIG. 2 and FIG. 4, the ink jet recording head 10 according to this embodiment includes a counterbore plate 13, a nozzle plate 12, a humidifying liquid passage plate 14, a flow passage plate 16, and a pressure chamber plate. 18 and a diaphragm 20 are provided.

  The counterbore plate 13, the nozzle plate 12, the humidifying liquid channel plate 14, the flow channel plate 16, the pressure chamber plate 18, and the vibration plate 20 are laminated in this order, and the plates are joined.

  A plurality of nozzles 22 for ejecting ink droplets are formed on the nozzle plate 12. The nozzles 22 are circular holes that penetrate the nozzle plate 12 and are arranged in a row on the nozzle plate 12 as shown in FIG.

  The counterbore plate 13 is joined to the nozzle surface 12A of the nozzle plate 12 on which the nozzles 22 are formed. In the counterbore plate 13, a circular hole having a diameter larger than the nozzle diameter is formed at a position below the nozzles 22.

  The inner wall of the circular hole surrounds the periphery of the nozzle 22, and a recess 15 having the inner wall as a side wall and the nozzle surface 12 </ b> A as a bottom surface is formed below the nozzle 22. The concave portion 15 is called a counterbore portion, and protects the nozzle 22 by preventing the cleaning member from directly contacting the opening of the nozzle 22 when the nozzle surface 12A is cleaned by the cleaning member.

  In the humidifying liquid flow path plate 14 and the flow path plate 16, flow paths 24 each having a circular hole having a diameter larger than the nozzle diameter are formed in the upper position corresponding to the nozzles 22 of the nozzle plate 12. The flow path 24 communicates with the nozzle 22, and ink as an example of a liquid can flow from the flow path 24 to the nozzle 22.

  In the pressure chamber plate 18, a pressure chamber 26 having a predetermined size is formed above the flow passage 24 of the flow passage plate 16.

  One end of the pressure chamber 26 communicates with the flow passage 24, and ink can flow from the pressure chamber 26 to the flow passage 24. That is, the pressure chamber 26 communicates with the nozzle 22 through the flow passage 24.

  Further, as shown in FIGS. 1A and 1B, the pressure chamber plate 18 is provided with a supply path 28 as an example of a first flow path that communicates with the other end of the pressure chamber 26. . The supply path 28 communicates with an ink pool 30 that stores ink, and is configured to supply ink sent from the ink pool 30 to the pressure chamber 26. The passage width of the supply passage 28 is formed to be narrower than the width of the space of the pressure chamber 26.

  As shown in FIG. 1A, a driving unit 32 made of a piezoelectric element is provided on the upper surface of the diaphragm 20. The drive unit 32 is applied with a drive signal, deforms the diaphragm 20 so as to reduce the volume in the pressure chamber 26, and applies pressure to the ink in the pressure chamber 26. Thus, ink droplets are ejected from the nozzle 22 communicating with the pressure chamber 26.

(Configuration to humidify the vicinity of the nozzle 22)
Next, a configuration for humidifying the vicinity of the nozzle 22 will be described.

  As shown in FIGS. 2, 3, and 4, the nozzle plate 12 has an opening 40 that opens into the recess 15. A plurality of (for example, eight) openings 40 are formed around each nozzle 22.

  Further, the nozzle plate 12 is formed with a first humidifying liquid channel 41 as an example of a second channel that communicates with the opening 40 and supplies the humidifying liquid to the opening 40. The first humidifying liquid channel 41 includes a through hole 43 that penetrates the nozzle plate 12 and a groove 45 that is formed in the nozzle plate 12 from the through hole 43 toward the nozzle 22.

  By joining the counterbore plate 13 to the nozzle plate 12, the groove 45 formed in the nozzle plate 12 becomes a tubular flow path for supplying the humidifying liquid.

  Two through holes 43 are formed around the nozzle 22 so as to sandwich the nozzle 22 between the nozzles 22. The groove 45 is formed so as not to penetrate the nozzle plate 12, and as shown in FIG. 3, a linear straight portion 45A extending from the two through holes 43 toward the nozzle 22 and a straight portion 45A. Each arcuate arc portion 45B extending along the outer periphery of the nozzle 22 from the front end portion thereof, and a connecting portion 45C for connecting the arc portion 45B and the opening 40 to each other. The arc portions 45 </ b> B extend from the straight portions 45 </ b> A and are connected to each other, are formed in a circular shape along the outer periphery of the nozzle 22, and surround the entire periphery of the nozzle 22.

  45 C of communication parts are extended toward the recessed part 15 from the circular arc part 45B, and are connected with the some opening part 40, respectively. As described above, a plurality of paths for supplying the humidifying liquid to the opening 40 is ensured by connecting the arc portions 45B.

  A humidification liquid is supplied to the opening 40 from the through-hole 43 through the groove 45 by a capillary phenomenon, and the humidifying liquid supplied to the opening 40 is held in the opening 40 by the surface tension.

  As shown in FIG. 2, two humidifying liquid flow paths 42 that supply the humidifying liquid to the through holes 43 are formed in the humidifying liquid flow path plate 14 above the through holes 43. Each of the second humidifying fluid channels 42 is a channel of a different system from the ink channel (the channel configured by the ink pool 30, the supply channel 28, the pressure chamber 26, the flow channel 24, and the nozzle 22) through which the ink flows. As shown in FIG. 1 (B), it is formed in a wavy line shape as a whole. A part of the second humidifying liquid channel 42 is curved along the outer periphery of the nozzle 22, and has an arc shape extending about a half of the outer periphery of the nozzle 22.

  The second humidifying fluid channel 42 is formed along a direction (specifically, a direction orthogonal) intersecting the direction in which ink is supplied from the supply channel 28 to the pressure chamber 26. The flowing humidifying liquid flows in a direction crossing the ink supply direction.

  Moreover, the through-hole 43 is formed directly under the 2nd humidification liquid flow path 42, as shown in FIG. For example, in the case where the through hole 43 is formed not at a position directly below the second humidifying fluid channel 42 but at an obliquely lower position shifted from the second humidifying fluid channel 42, the second humidifying fluid channel 42 and the through hole 43 are formed. It is necessary to form a laterally extending flow path connecting the two.

  Moreover, as a humidifying liquid supplied to the opening part 40, water (specifically pure water), alcohol, etc. are used, for example. In addition, any liquid that does not increase in viscosity even when solvent evaporation occurs may be used.

  Further, as shown in FIG. 1B, a humidifying liquid supply port 44 to which a humidifying liquid is supplied is formed at one end of the two second humidifying liquid channels 42. At the other end, a humidifying liquid discharge port 46 for discharging the humidifying liquid is formed.

  The humidifying liquid supply port 44 and the humidifying liquid discharge port 46 are supplied as an example of a circulation means for supplying the humidifying liquid from the humidifying liquid discharge port 46 to the humidifying liquid supply port 44 through a circulation pipe 47 such as a tube. A pump 48 is connected. The liquid feed pump 48 sucks up the humidified liquid from the humidified liquid discharge port 46 and sends it to the humidified liquid supply port 44 so that the humidified liquid circulates through the second humidified liquid channel 42.

(Operation according to this embodiment)
According to the configuration of the present embodiment, the humidifying liquid is circulated through the second humidifying liquid channel 42 by the liquid feeding pump 48. The humidifying liquid circulating through the second humidifying liquid channel 42 is supplied from the second humidifying liquid channel 42 to the first humidifying liquid channel 41. The humidifying liquid supplied to the first humidifying liquid channel 41 is supplied to the opening 40 through the through hole 43 and the groove 45 constituting the first humidifying liquid channel 41, and the opening 40 is filled with the humidifying liquid. Is done. The humidifying liquid filled in the opening 40 is held in the opening 40 by the surface tension of the humidifying liquid, and the humidifying liquid spontaneously evaporates from the liquid level of the humidifying liquid held in the opening 40. Thereby, the recessed part 15 which is the space enclosed by the side wall is humidified, and the nozzle 22 vicinity is humidified.

  Here, FIG. 5 shows the relationship between the distance between the humidifying liquid and the nozzle 22 and the drop speed of the first drop after waiting for discharge. The area X in FIG. 5 does not have the configuration of the present embodiment, that is, does not have the groove 45 extending from the through hole 43 to the nozzle 22, and evaporates the humidifying liquid from the through hole 43. The distance to the nozzle 22 is shown. In this configuration, the distance L between the through hole 43 and the nozzle 22 is obtained in order to obtain the rigidity of the partition wall between the flow passage 24 and the second humidifying liquid passage 42 in order to secure the bonding area of each plate (see FIG. 4). Needs a predetermined length, and the lower limit of the distance between the humidifying liquid filled in the through-hole 43 and the nozzle 22 is X1.

  In the area of Y in FIG. 5, the distance between the humidifying liquid filled in the opening 40 and the nozzle 22 in the configuration according to the present embodiment in which the groove 45 is formed is shown. In this configuration, since the humidifying liquid is held in the opening 40, the humidifying liquid approaches the nozzle 22.

  For this reason, the vicinity of the nozzle 22 becomes a higher humidity environment, an increase in viscosity at the nozzle 22 is suppressed, and the drop speed of the first drop after waiting for discharge approaches an ideal value. Note that the ideal value is the droplet speed when discharging continuously, and is the droplet speed that is essentially required.

(Modified example in which the groove shape of the groove 45 is changed)
Next, a modification in which the groove shape of the groove 45 is changed will be described.

  As shown in FIG. 6, the groove portion 55 according to the present modification includes linear straight portions 55 </ b> A that extend from the two through holes 43 toward the nozzles 22, and along the outer peripheral part of the nozzle 22 from the straight portions 55 </ b> A. And an arcuate arc portion 55B that extends and a communication portion 55C that communicates the arc portion 55B and the opening 40.

  In the present modification, the arc portions 55B are not connected to each other and are independent from each other, and the humidifying liquid is supplied to the opening 40 through one path. Thus, the shape of the groove part 45 can be changed into an arbitrary shape.

(Modification in which the opening position of the opening 40 is changed)
In the above embodiment, the opening 40 is formed in the bottom surface of the recess 15, that is, the nozzle plate 12, but the opening 50 according to this modification is as shown in FIGS. 7A and 7B. The recess 15 is formed on the side wall, that is, the counterbore plate 13.

  In this modification, a plurality of (for example, eight) openings 50 are formed around each nozzle 22. The nozzle plate 12 is formed with a first humidifying liquid channel 51 that communicates with the opening 50 and supplies the humidifying liquid to the opening 50. The first humidifying fluid channel 51 includes a through hole 53 that penetrates the nozzle plate 12 and a groove 55 that is formed in the counterbore plate 13 from the through hole 53 toward the nozzle 22.

  When the counterbore plate 13 is joined to the nozzle plate 12, the groove portion 55 formed in the counterbore plate 13 becomes a tubular flow path for supplying the humidifying liquid.

  Two through-holes 53 are formed around the nozzle 22 so as to sandwich the nozzle 22 between the nozzles 22. The groove portion 55 is formed so as not to penetrate the counterbore plate 13, and the linear straight portion 55 </ b> A that extends from the two through holes 53 toward the nozzle 22, and the nozzle 22 from the tip portion of the straight portion 55 </ b> A, respectively. An arcuate arc part 55B extending along the outer periphery of the arc and a connecting part 55C that communicates the arc part 55B and the opening 40 are provided. The arc portions 55B extend from the straight portions 55A and are connected to each other, are formed in a circular shape along the outer periphery of the nozzle 22, and surround the entire periphery of the nozzle 22.

  The connecting portion 55C extends from the arc portion 55B toward the recess 15 and communicates with the plurality of openings 50, respectively. By connecting the arc portions 55B, a plurality of paths for supplying the humidifying liquid to the openings 50 are secured.

  A humidifying liquid is supplied to the opening 50 from the through hole 53 through the groove 55 by capillary action, and the humidifying liquid supplied to the opening 50 is held in the opening 50 by the surface tension.

(Variation of nozzle arrangement)
In the above embodiment, the nozzles 22 are arranged in a line, but as shown in FIG. 8, the nozzles 22 may be arranged in a two-dimensional manner. Also in this case, similarly to the above, the vicinity of the nozzle 22 is humidified by forming the second humidifying liquid channel 42 and the opening 40. In FIG. 8, the liquid feed pump 48 that feeds the humidified liquid from the humidified liquid discharge port 46 to the humidified liquid supply port 44 via the flow pipe 47 such as a tube is omitted.

(Modified example of the number of nozzles opening into the recess)
In the above embodiment, one nozzle 22 is open to one recess 15, but as shown in FIG. 9, a plurality of nozzles 22 are open to one recess 15. It may be.

  In this modification, the groove 45 extending from the through hole 43 is formed so as to surround the periphery of the recess 15, and extends to the opening 40 to supply the humidifying liquid to the opening 40.

  In this configuration, the concave portions 15 opened by the plurality of nozzles 22 are humidified, and the vicinity of the plurality of nozzles 22 is humidified at a time.

(Configuration in which the humidifying liquid passing through the groove 45 is circulated)
In the above embodiment, the humidifying liquid flowing through the groove 45 is not circulated. However, as shown in FIG. 10, the humidifying liquid flowing through the groove 45 is circulated from one through hole 43 to the other through hole 43. There may be.

  In this configuration, as shown in FIG. 10, a humidifying liquid supply port 44 to which the humidifying liquid is supplied is provided at one end portion of one of the two second humidifying liquid channels 42. Is formed. A humidifying liquid discharge port 46 through which the humidifying liquid is discharged is formed at the other end of the other second humidifying liquid channel 42 out of the two second humidifying liquid channels 42.

  A tank 39 for storing the humidifying liquid is connected to the humidifying liquid supply port 44. The tank 39 and the humidified liquid discharge port 46 are connected to a liquid feed pump 48 for supplying the humidified liquid from the humidified liquid discharge port 46 to the tank 39 via a circulation pipe 47 such as a tube. The liquid feed pump 48 sucks the humidified liquid from the humidified liquid discharge port 46 and sends it to the tank 39, so that the humidified liquid flows from the tank 39 through one of the second humidified liquid flow paths 42. The humidifying liquid that has flowed into one second humidifying liquid flow path 42 flows to the other second humidifying liquid flow path 42 through the groove 45 so that the humidifying liquid circulates.

(Overall configuration of inkjet recording apparatus according to this embodiment)
In addition, as an example of an image forming apparatus droplet to which the ink jet recording head according to the present embodiment is applied, the ink jet recording head according to the present embodiment is provided, and an ink droplet is ejected from the ink jet recording head to form an image on a recording medium. An ink jet recording apparatus for recording will be described. FIG. 11 is a schematic diagram showing the overall configuration of the ink jet recording apparatus according to the present embodiment.

  The ink jet recording apparatus 102 according to the present embodiment includes a carriage 104 on which the ink jet recording head 10 is mounted, a main scanning mechanism 106 that scans the carriage 104 along the main scanning direction M, and a sub scanning of a recording medium P such as paper. A sub-scanning mechanism 108 that transports along the direction S and a maintenance unit 110 are provided. The flow pipe 47, the liquid feed pump 48, and the tank 39 are not shown. Moreover, it has the control part which is not shown in figure which controls the liquid feeding pump 48 and a maintenance part.

  In this ink jet recording apparatus 102, a predetermined band is obtained by selectively ejecting ink droplets from the nozzles 22 of the ink jet recording head 10 to the recording medium P while the carriage 104 is moved in the main scanning direction M by the main scanning mechanism 106. A part of the image based on the image data is recorded in the region BE.

  When one movement in the main scanning direction is completed, the recording medium P is conveyed by a predetermined pitch in the sub-scanning direction S by the sub-scanning mechanism 108, and the inkjet recording head 10 is again moved in the main scanning direction (the direction opposite to the above). ) While moving to M, a part of the image based on the image data is recorded in the next band area. By repeating such an operation a plurality of times, the image data is recorded on the recording medium P. The entire image based is recorded in full color.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made.

1A is a cross-sectional view taken along line 1A-1A in FIG. FIG. 1B is a schematic diagram illustrating the configuration of the ink jet recording head according to the present embodiment. FIG. 2 is an exploded perspective view in which a portion A in FIG. 1 (B) is enlarged. FIG. 3 is an enlarged plan view of a portion A in FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. FIG. 5 is a graph showing the relationship between the distance between the humidifying liquid and the nozzle and the drop speed of the first drop after waiting for discharge. FIG. 6 is a view showing a modification in which the groove shape of the groove part according to the present embodiment is changed. FIG. 7 is a view showing a modification in which the opening position of the opening according to the present embodiment is changed. FIG. 8 is a diagram illustrating a configuration in which nozzles are two-dimensionally arranged in the ink jet recording head according to the present embodiment. FIG. 9 is a diagram illustrating a configuration in which a plurality of nozzles according to the present embodiment are opened in the recess. FIG. 10 is a diagram illustrating an overall configuration in the configuration in which the humidifying liquid passing through the groove portion according to the present embodiment is circulated. FIG. 11 is a schematic configuration diagram illustrating an ink jet recording apparatus to which the ink jet recording head according to the present embodiment is applied.

Explanation of symbols

10 Inkjet recording head (droplet ejection head)
15 Recess 22 Nozzle 26 Pressure chamber 28 Supply path (first flow path)
40 opening 41 1st humidification liquid flow path (2nd flow path)
48 Liquid feed pump (circulation means)
102 Inkjet recording apparatus (image forming apparatus)

Claims (4)

A nozzle for discharging droplets;
A pressure chamber leading to the nozzle;
A first flow path for supplying liquid to the pressure chamber;
A recess formed by a side wall surrounding the periphery of the nozzle and a nozzle surface on which the nozzle is formed;
An opening that opens into the recess;
A second flow path for supplying a humidifying liquid to the opening;
A liquid droplet ejection head comprising:   The droplet discharge head according to claim 1, wherein the nozzle has a plurality of openings in the recess.   The droplet discharge head according to claim 1, wherein a plurality of the second flow paths are formed and are connected to each other. A droplet discharge head according to claim 3;
Circulating means for circulating the humidifying liquid flowing in the second flow path;
An image forming apparatus comprising:

Images