JP5510536B2 - Liquid ejection device - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus that performs drawing by ejecting a liquid, such as an inkjet printer, a display manufacturing apparatus, an electrode forming apparatus, or a biochip manufacturing apparatus.

  2. Description of the Related Art Conventionally, an ink jet printer suitable for printing on paper is known as a liquid ejecting apparatus, and generally an ejecting head that ejects liquid (ink) from a minute nozzle to a carriage that reciprocates in a certain direction. It is a configuration equipped with. The paper is fed in one direction, and the ejection head is reciprocated (scanned) perpendicular to the paper feeding direction to eject ink droplets on the paper to form an image.

  Ink droplets ejected from ink jet printers have been miniaturized in recent years, and such micronized ink droplets lose their speed due to the influence of air resistance and are likely to float (mist). . The generated mist spreads in the aircraft by riding on the airflow generated by the movement of the carriage, causing a problem of so-called in-machine dirt.

  In recent years, an inkjet printer that performs so-called borderless printing that performs printing without providing a margin at the outer edge of the paper has also appeared (for example, Patent Document 1), and the occurrence of the mist described above has become more prominent. That is, ink droplets that are ejected from the outer edge of the paper in borderless printing are received by an absorber (such as a sponge) disposed on the back side of the paper. It is easy to mist due to its length.

  In view of such a problem, an ink jet printer has been proposed in which generation of mist is suppressed by the action of electrostatic force (for example, Patent Document 2). That is, in this printer, by generating an electric field between the nozzle opening formation surface (nozzle surface) and the absorber surface, the ink droplet is charged and an electrostatic force is applied to the ink droplet to force the ink droplet. Is trying to attract.

Japanese Patent Laid-Open No. 2002-103586 JP 2004-216877 A

  By the way, depending on the ejection control method, the ink droplet ejected from the nozzle may be divided into a leading portion (main droplet) and a subsequent portion (satellite droplet) in the flight process. In such a case, when the above-described electric field is generated, the inventors have obtained the knowledge that the main droplet and the satellite droplet are charged with opposite polarities. As a result, an acceleration force toward the absorber acts on the main droplet, while a reverse deceleration force acts on the satellite droplet, and as a result, the satellite droplet mists. is there.

  Incidentally, Patent Document 2 also discloses a modified example in which the direction of the electric field generated between the nozzle surface and the absorber surface is periodically switched. In this case, by reversing the direction of the electric field, the effect of attracting the already-misted satellite droplets cannot be expected.

  However, this modification does not show any positive means for effectively collecting the satellite droplets. In particular, it is not possible to prevent the mist-like satellite droplets from being caught in the airflow (upward airflow) generated behind the scanning of the ejection head without waiting for the electric field to be reversed, and diffusing and adhering in the apparatus.

  SUMMARY An advantage of some aspects of the invention is to provide a liquid ejection apparatus that can suitably reduce in-machine contamination due to liquid droplets.

The liquid ejection apparatus according to the present invention includes: an ejection head having a nozzle surface on which nozzles for ejecting liquid are formed; a scanning unit that scans the ejection head; and the nozzle surface and a facing region facing the nozzle surface . An electric field generating means for generating an electric field therebetween, wherein the counter area includes a discharge target area where the discharge head discharges the liquid, and an area where the discharge head faces the discharge target in the discharge target area. And the non-opposing region, wherein the electric field generating means discharges liquid in a region where the discharge head does not face the discharge target and periodically inverts the electric field.

  According to the liquid ejecting apparatus of the present invention, the positively and negatively charged droplets discharged in the immediate vicinity of the inversion of the electric field are attracted in a time-sharing manner before the influence of the air flow relating to the scanning of the ejection heads. can do. Thus, it is possible to suitably suppress the droplets from being mist and further diffusing the mist droplets into the apparatus.

Preferably, the electric field generating means periodically inverts the electric field during one scanning pass .
According to the liquid ejection apparatus of the present invention, it is possible to reduce the machine in dirt more effectively.

Preferably, the counter area has a preliminary discharge area for performing preliminary discharge, and the electric field generating means reverses the electric field in the preliminary discharge operation .
According to the liquid ejection apparatus of the present invention, it is possible to more effectively reduce in-machine dirt.

Preferably, the counter area is provided with a liquid storage means capable of storing the liquid.
According to the liquid ejecting apparatus of the present invention, the attracted liquid droplets can be accommodated and held.

Also preferably, in the liquid ejection device including the liquid storage means, the liquid storage means.
Is characterized by including an absorber having conductivity.

According to the liquid ejection apparatus of the present invention, since the absorber constituting the liquid storage means has a function as a part of the electricity generation means, the apparatus configuration can be simplified by sharing the parts.
Can do.

The perspective view which shows schematic structure of a liquid discharge apparatus. Schematic which shows the planar structure of a platen part. The figure which shows the side cross-section of a platen part, and the electrical structure around a platen part. (A)-(c) is a sectional side view which shows the mode of the discharge which concerns on an outer peripheral area | region. (A)-(c) is a sectional side view which shows the mode of the discharge which concerns on an outer peripheral area | region. Schematic which shows the planar structure of the platen part which concerns on the modification 1. FIG. The figure which shows the electrical constitution of the platen part which concerns on the modification 2. As shown in FIG.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
The embodiment described below is a preferred specific example of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.

First, the overall configuration of the liquid ejection apparatus will be described with reference to FIG.
FIG. 1 is a perspective view illustrating a schematic configuration of the liquid ejection apparatus.

  In FIG. 1, a printer 1 as a liquid ejection apparatus is an apparatus that draws (prints) an image or the like by ejecting ink as a liquid onto a sheet 2 as an ejection target. The printer 1 includes a frame base 6 formed of a steel plate, an ejection head 3 that ejects ink droplets, a carriage 4 on which the ejection head 3 is mounted, and a carriage 4 that reciprocates (scans) in a certain direction. A scanning mechanism 5 for transporting the paper 2, a transport roller 14 for transporting the paper 2, and a maintenance unit 16 for performing maintenance of the ejection head 3. Here, the frame base 6 forms the basis of the entire apparatus by its rigidity and weight, and also functions as an electrical ground.

  For example, four colors of black, magenta, cyan, and yellow are used as the ink ejected from the ejection head 3, and are accommodated in ink cartridges 7 a to 7 d mounted on the carriage 4, respectively. At the bottom of the ink cartridges 7a to 7d, a lead-out portion (not shown) for leading out ink is provided, and coupled to an ink introduction portion (not shown) provided on the discharge head 3, Ink is supplied to the printer.

  A scanning mechanism 5 serving as a scanning unit includes a motor (not shown) that generates a driving force, a driving belt 8 that transmits the driving force to the carriage 4, and a guide rod that supports the carriage 4 and defines the moving direction thereof. 10. Thus, the ejection head 3 mounted on the carriage 4 reciprocates (scans) on the paper 2 along the extending direction (X-axis direction) of the guide rod 10.

  The paper 2 is stocked in a paper tray (not shown) provided on the back side of the frame base 6 and is transferred (paper fed) one by one to the transport roller 14 by a paper feeding mechanism (not shown). The transport roller 14 rotates by driving the transport motor 15 and transports the paper 2 in a direction (Y-axis direction) orthogonal to the scanning direction.

  A platen portion 11 for supporting the paper 2 from the back surface 2b side is provided at a position facing the nozzle surface 3a of the ejection head 3. The structure of the platen part 11 will be described in detail later.

  The ejection head 3 is mounted on the carriage 4 so that the nozzle surface 3a, which is one surface on which nozzles are formed in a predetermined arrangement, is opposed to the surface 2a of the paper 2. The ejection head 3 ejects ink (ink droplets) from the nozzles by ejection control for each nozzle synchronized with the scanning of the carriage 4. The nozzle surface 3a of the discharge head 3 is formed of a conductive member such as SUS, and also serves as an electrode for generating an electric field (details will be described later).

  The maintenance unit 16 includes a cap member 17 that can be sealed around a certain area of the nozzle surface 3a. The cap member 17 serves to protect the nozzle from dust and drying by covering the nozzle surface 3a, and operates a suction pump connected to the communication port on the bottom surface while covering the nozzle surface 3a to remove the nozzle from the nozzle. It is also used when sucking ink (suction operation).

  The maintenance unit 16 also has a wiper blade 18 that is a plate-like member formed of rubber or the like. The wiper blade 18 is used for wiping off ink adhering to the nozzle surface 3a after the suction operation.

Next, the peripheral configuration of the platen unit will be described with reference to FIGS.
FIG. 2 is a schematic view showing a planar structure of the platen portion. FIG. 3 is a diagram showing a side sectional structure of the platen portion and an electrical configuration around the platen portion.

  As shown in FIG. 2 and FIG. 3, the platen unit 11 is a box-shaped case 20 having an opening on the side facing the nozzle surface 3 a, and liquid storage means stored in a recess formed in the case 20. Absorber 21 (shown by shading for convenience) is provided. Further, a support member 22 is provided on the exposed surface of the absorber 21 for contacting and supporting the paper 2.

  As the absorber 21, a conductive material such as carbon mixed with polyethylene or polyurethane and foamed to impart conductivity is used. Thereby, the absorber 21 functions as an electrode facing the nozzle surface 3a as well as a function of absorbing ink.

  The so-called borderless printing is performed in a state in which the ejection target area 23 is extended to the outside of the paper 2 as illustrated. At this time, since the ink droplets ejected to the outer peripheral areas 23a and 23a on the outside of the side edges are accommodated in the absorber 21 located on the back side of the paper 2, the support of the paper 2 The surface is not soiled.

  A preliminary ejection receiving area 24 for receiving ink droplets related to preliminary ejection is provided beside the ejection target area 23 in the platen unit 11. Preliminary ejection refers to ejection performed on an area other than the sheet 2 for the purpose of discharging the dried ink in the nozzle, and is performed periodically, for example, during a printing operation. The preliminarily ejected ink droplets are accommodated in the absorber 21.

  The printer 1 includes a high voltage generation circuit 30 that outputs a positive potential (+) with a ground potential (GND) as a reference, and a potential inversion circuit 31 that outputs a negative potential (−). The printer 1 includes a switch circuit 32 that is connected to the output terminals of the high voltage generation circuit 30 and the potential inversion circuit 31 and selects and outputs either the positive potential (+) or the negative potential (−). I have.

  The nozzle surface 3 a is connected to the ground, and the absorber 21 is connected to the output terminal of the switch circuit 32, whereby an electric field is formed between the nozzle surface 3 a and the absorber 21. Further, the direction of the formed electric field can be reversed by switching the output of the switch circuit 32. That is, the nozzle surface 3a, the absorber 21, the high voltage generation circuit 30, the potential inversion circuit 31, and the switch circuit 32 constitute an electric field generation means in the present invention.

Next, the electrostatic force acting on the ink droplet will be described with reference to FIGS. 4 and 5.
4 and 5 are side cross-sectional views showing a state of discharge related to the outer peripheral region. Note that the imaginary line arrows in the figure indicate lines of electric force, and the signs of + and − indicate the potential polarity of the absorber and the charging polarity of the ink droplets.

  FIGS. 4A to 4C show, in chronological order, the manner of ejection when the ejection head 3 (nozzle surface 3a) moves from the inside to the outside of the paper 2. FIG.

  As shown in FIGS. 4A and 4B, the ejection head 3 allows ink droplets from the nozzle 3b to the paper 2 and the outer peripheral area 23a in a state where the absorber 21 is at a positive potential (+). Discharge. As shown in the figure, the ejected ink droplets are split into a main droplet 25a in the leading portion and a satellite droplet 25b in the trailing portion, and are charged to the negative electrode (-) and the positive electrode (+), respectively. As a result, the electrostatic force in the acceleration direction acts on the main droplet 25a and reliably reaches the sheet 2 or the absorber 21.

  On the other hand, an electrostatic force in the deceleration direction acts on the satellite droplet 25b. In this case, the satellite droplets 25b ejected onto the paper 2 can reach the paper 2 before losing speed, but the satellite droplets 25b ejected onto the outer peripheral region 23a are applied to the absorber 21. You will lose speed before you reach it.

  Therefore, in the present embodiment, after the ink droplets (main droplet 25a and satellite droplet 25b) are ejected to the outer peripheral region 23a, the potential polarity of the absorber 21 is switched after a predetermined delay time. As a result, as shown in FIG. 4C, the direction of the electric field formed between the nozzle surface 3a and the absorber 21 is reversed, and an electrostatic force directed toward the absorber 21 acts on the satellite droplet 25b. To do.

  Thus, the satellite droplet 25b reaches the absorber 21 without being misted and is accommodated in the absorber 21. In FIG. 4 (c), the electrostatic force in the deceleration direction acts on the main droplet 25a in flight. However, a sufficient acceleration force is applied to the main droplet 25a during the delay time described above. By setting, it is possible to avoid the mist formation of the main droplet 25a.

  FIGS. 5A to 5C show, in chronological order, the state of ejection when the ejection head 3 (nozzle surface 3a) moves from the outside to the inside of the paper 2. FIG.

  Also in the case shown in FIG. 5, after the ejection head 3 ejects ink droplets to the outer peripheral region 23a, the potential polarity of the absorber 21 is switched after a predetermined delay time, and the direction of the electric field formed is changed. Inverted. Thereby, both the main droplet 25a and the satellite droplet 25b in the outer peripheral region 23a are collected by the absorber 21.

  As described above, the ink droplets ejected in the immediate vicinity of the inversion of the electric field are attracted in a time-division manner regardless of the charge polarity before being affected by the air flow generated behind the scanning of the ejection head 3, and the absorber 21. It is collected at. In particular, in the present embodiment, the electric field is switched at a timing during which the ejection head 3 (nozzle surface 3a) passes through the outer peripheral region 23a, and ink droplets in the outer peripheral region 23a where mist formation easily occurs are effectively performed. It is supposed to be collected. Thereby, what is called in-machine dirt is reduced suitably.

  In addition, the inversion of the electric field as described above is also performed when the ejection head 3 is performing preliminary ejection in the preliminary ejection receiving area 24, thereby favorably misting ink droplets related to preliminary ejection. It has been reduced. In the prior art, a weight is provided after the preliminary discharge to suppress the mist winding caused by the preliminary discharge, and the discharge head scanning is resumed after waiting for the mist to settle. In the embodiment, it is possible to reduce the weight and increase the operation speed.

(Modification 1)
Next, with reference to FIG. 6, the modification 1 of this invention is demonstrated centering around difference with previous embodiment. FIG. 6 is a schematic diagram illustrating a planar structure of the platen portion according to the first modification.

  As shown in FIG. 6, the platen portion 11 in the first modification includes conductive wires 26 arranged in a predetermined pattern on the exposed surface of the non-conductive absorber 27. Here, the conductive wire 26 is formed by forming an insulating film for preventing a short circuit and corrosion on a linear conductor (metal or the like). The conducting wire 26 is connected to the output terminal of the switch circuit 32 (see FIG. 3).

Thus, the conductive wire 26 functions as an electrode and plays a role as part of an electric field generating means for generating an electric field between the nozzle surface 3a (see FIG. 3) and the absorber 27. As in this modification, the electrode for generating an electric field can be partially formed of a conductor different from the absorber.
(Modification 2)
Next, with reference to FIG. 7, the modified example 2 of this invention is demonstrated centering on difference with previous embodiment. FIG. 7 is a diagram illustrating an electrical configuration of the platen unit according to the second modification.

  As shown in FIG. 7, the printer 1 according to the second modification example selectively outputs a potential with one of the nozzle surface 3a and the absorber 21 as a ground potential (GND) and the other as a positive potential (+). A switch circuit 33 is provided. As a result, an electric field is formed between the nozzle surface 3 a and the absorber 21, and the direction of the electric field can be reversed by switching the connection path in the switch circuit 33. That is, the switch circuit 33 constitutes the electric field generating means of the present invention.

  As in this modification, the electric field generating means of the present invention can be configured without using a potential inverting circuit.

The present invention is not limited to the above-described embodiment.
For example, the inversion of the electric field may be periodically performed in one scanning pass or in the preliminary ejection operation.
Further, the electric field generating means may be configured to generate an electric field between the nozzle surface 3a and the paper 2 using a charging means for charging the paper 2 by corona discharge or the like.
In addition, each configuration of each embodiment can be appropriately combined, omitted, or combined with other configurations not shown.

  DESCRIPTION OF SYMBOLS 1 ... Printer as a liquid discharge apparatus, 2 ... Paper as discharge target object, 2a ... Front surface, 2b ... Back surface, 3 ... Discharge head, 3a ... Nozzle surface as one surface of discharge head which comprises electric field generation means, 3b ... Nozzle, 4 ... Carriage, 5 ... Scanning mechanism as scanning means, 6 ... Frame base, 11 ... Platen part, 20 ... Case, 21 ... Absorber as liquid storage means constituting electric field generating means, 22 ... Support member, DESCRIPTION OF SYMBOLS 23 ... Discharge object area | region, 23a ... Outer periphery area | region, 24 ... Preliminary discharge receiving area | region, 25a ... Main drop, 25b ... Satellite drop, 26 ... Conductor which comprises electric field generation means, 27 ... Absorber, 30 ... Constitution of electric field generation means A high voltage generation circuit, 31... A potential inversion circuit constituting electric field generation means, 32... A switch circuit constituting electric field generation means, 33... A switch circuit constituting electric field generation means.

Claims (5)

An ejection head having a nozzle surface on which nozzles for ejecting liquid are formed ;
Scanning means for scanning the ejection head;
An electric field generating means for generating an electric field between the nozzle surface and a facing region facing the nozzle surface ,
The facing region includes a discharge target region where the discharge head discharges the liquid, a region where the discharge head faces a discharge target in the discharge target region, and a region which does not face the discharge target region,
The electric field generating means discharges a liquid in a region where the discharge head does not face an object to be discharged, and periodically reverses the electric field. 2. The liquid ejecting apparatus according to claim 1, wherein the electric field generating unit periodically inverts the electric field during one scanning pass. 2. The liquid ejecting apparatus according to claim 1, wherein the counter area includes a preliminary discharge area for performing preliminary discharge, and the electric field generating unit reverses an electric field in the preliminary discharge operation. Before Symbol pair countercurrent region, the liquid ejecting apparatus according to claims 1 to 3, characterized in that it comprises a liquid containment means capable of containing the liquid. The liquid ejecting apparatus according to claim 4 , wherein the liquid storage unit includes a conductive absorber.

Images