JP2010241003A - Liquid droplet delivering head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet delivering head which can stably deliver even a high-viscosity liquid. <P>SOLUTION: A delivering liquid is pressurized and supplied to a cavity 23 which communicates with a nozzle 22, and at the same time, the nozzle 22 is can be blocked with a pin 24 and the pin 24 is can be isolated from and contacted with the nozzle 22 by an actuator 25. The actuator 25 is controlled by a controller 12. By the constitution, the delivering liquid supplied under pressure is delivered as liquid droplets from the nozzle 22 only while the pin 24 is isolated from the nozzle 22. Moreover, the actuator 25 can be reduced in size by constituting the actuator 25 with a piezoelectric element. In consequence, the integration level of the nozzles 22 is enhanced, enabling delivering of more minute liquid droplets. In addition, the cavity 23 is formed to communicate with a plurality of the nozzles 22 in common, eliminating the need of forming the cavity for every nozzle as conventionally. Constitution becomes easy and costs can be reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a droplet discharge head that discharges minute droplets from a plurality of nozzles. For example, by forming fine particles (dots) on a print medium, a predetermined character or image is printed. The present invention is suitable for a droplet discharge type printing apparatus.

Since the droplet discharge type printing apparatus is generally inexpensive and easily obtains a high-quality color printed matter, it has been widely used not only in offices but also in general users with the spread of personal computers and digital cameras.
Among such droplet discharge type printing apparatuses, a device that moves a droplet discharge head on which droplet discharge nozzles are formed on a moving body called a carriage in a direction crossing the conveyance direction of the print medium is generally referred to as “multiple”. It is called a “pass-type printing device”. On the other hand, a device capable of performing printing in a so-called one pass by disposing a long droplet discharge head in a direction crossing the conveyance direction of the print medium is generally called a “line head type printing apparatus”.

  In this type of droplet ejection printing apparatus, a plurality of nozzles for ejecting liquid are formed on the droplet ejection head, and each nozzle is connected to a pressure chamber for pressurizing the ejected liquid. A nozzle actuator such as a piezoelectric element is disposed in the chamber, and a droplet is ejected from the corresponding nozzle toward the print medium by applying a drive signal to each nozzle actuator. In the following Patent Document 1, a storage chamber for storing the discharge liquid is provided on the front side in the discharge liquid supply direction of the pressure chamber, and an island portion is formed in a flow path that connects the storage chamber and the pressure chamber. With this flow resistance, excessive discharge liquid supply and excessive return to the pressure chamber are simultaneously suppressed and prevented.

JP 2003-334951 A

By the way, in such a droplet discharge device, the discharge liquid has a high viscosity, including a printing device. For example, a polymer polymer liquid has a high viscosity, and it is difficult to stably discharge a droplet from a nozzle. For example, when the nozzle actuator is composed of a piezoelectric element, there is a limit to the pressure applied to the pressure chamber, and as a result, the physical property (viscosity) of the liquid that can be discharged is limited. In such a case, if a high-viscosity liquid is to be ejected, it is necessary to dilute the liquid or to reduce the viscosity of the liquid by heating. In the case of heating, various problems occur, such as the addition of heating means, an increase in power consumption, and the effect on the surrounding parts due to heating.
The present invention has been developed by paying attention to these problems, and an object of the present invention is to provide a droplet discharge head that can stably discharge even a highly viscous liquid.

In order to solve the above problems, a droplet discharge head according to the present invention is a droplet discharge head by discharging droplets from a plurality of nozzles, and a liquid pressurizing apparatus that pressurizes and supplies discharge liquid to the nozzles. A nozzle closing member disposed on the nozzle, a nozzle opening / closing driving means for separating and contacting the nozzle closing member with respect to the nozzle, and a nozzle opening / closing control means for controlling the nozzle opening / closing driving means. To do.
According to this droplet discharge head, the discharge liquid is pressurized and supplied to the nozzle, and in this state, the nozzle closing member is moved away from the nozzle to pressurize only while the nozzle closing member is separated from the nozzle. Since the supplied discharge liquid is discharged as droplets from the nozzle, even a highly viscous liquid can be discharged stably.
Further, the nozzle opening / closing driving means is constituted by a piezoelectric element.

According to this droplet discharge head, it is possible to reduce the size of the nozzle opening / closing drive means. As a result, it is possible to increase the integration degree of the nozzles and to discharge finer droplets.
In addition, a liquid storage section that communicates in common with the plurality of nozzles is provided.
According to this droplet discharge head, it is not necessary to form a conventional pressure chamber for each nozzle, the configuration is easy, and the cost can be reduced.

1 is a front view of a schematic configuration of a droplet discharge printing apparatus showing an embodiment of a droplet discharge head of the present invention. It is a block diagram of the control apparatus of the droplet discharge type printing apparatus of FIG. It is a schematic block diagram of the droplet discharge head of FIG. It is explanatory drawing of the nozzle obstruction | occlusion member and nozzle opening / closing actuator of FIG. FIG. 4 is a detailed view of a nozzle closing member and a nozzle in FIG. 3.

Next, an embodiment of a droplet discharge type printing apparatus using the droplet discharge head of the present invention will be described.
FIG. 1 is a schematic configuration diagram of a printing apparatus according to the present embodiment. In the drawing, a print medium 1 is conveyed in the direction of an arrow from the left to the right in the figure, and is printed in a printing area in the middle of the conveyance. It is a line head type printing apparatus.
Reference numeral 2 in FIG. 1 denotes a droplet discharge head provided above the transport line of the print medium 1 and is fixed to a fixed plate 11. A large number of nozzles are formed on the lowermost surface of the droplet discharge head 2, and this surface is called a nozzle surface. The nozzles are arranged in a row in the direction intersecting the print medium conveyance direction for each color of the liquid to be ejected, and the row is called a nozzle row or the row direction is called a nozzle row direction. A line head extending over the entire width in the direction intersecting the transport direction of the print medium 1 is formed by all the nozzles arranged in the direction intersecting the print medium transport direction. When the print medium 1 passes below the nozzle surface of the droplet discharge head 2, droplets are discharged from a large number of nozzles and printing is performed.

  For example, liquids such as yellow (Y), magenta (M), cyan (C), and black (K) inks are supplied to the droplet discharge head 2 from liquid tanks of respective colors (not shown) via liquid supply tubes. Supplied. Then, by ejecting a necessary amount of liquid droplets from a nozzle of the liquid droplet ejection head 2 to a necessary location at the same time, minute dots are output on the print medium 1. By performing this for each color, it is possible to perform printing by so-called one-pass only by passing the print medium 1 conveyed by the conveyance unit 4 once.

  Below the droplet discharge head 2, a transport unit 4 for transporting the print medium 1 in the transport direction is provided. The conveying unit 4 is configured by winding a conveying belt 6 around a driving roller 8 and a driven roller 9, and an electric motor (not shown) is connected to the driving roller 8. An adsorption device (not shown) for adsorbing the print medium 1 to the surface of the conveyance belt 6 is provided inside the conveyance belt 6. As this adsorption device, for example, an air suction device that adsorbs the print medium 1 to the conveyance belt 6 by negative pressure, an electrostatic adsorption device that adsorbs the print medium 1 to the conveyance belt 6 by electrostatic force, or the like is used. Accordingly, when only one sheet of the printing medium 1 is fed from the sheet feeding unit 3 to the conveying belt 6 by the sheet feeding roller 5 and the driving roller 8 is rotationally driven by the electric motor, the conveying belt 6 is rotated in the printing medium conveying direction. The print medium 1 is adsorbed to the conveyance belt 6 by the adsorption device and conveyed. While the printing medium 1 is being conveyed, printing is performed by ejecting droplets from the droplet ejection head 2. The print medium 1 that has finished printing is discharged to the paper discharge unit 10 on the downstream side in the transport direction. The transport belt 6 is attached with a printing reference signal output device composed of, for example, a linear encoder. This printing reference signal output device pays attention to the fact that, for example, the transport belt 6 and the print medium 1 that is attracted and transported are synchronously moved, and after the print medium 1 has passed a predetermined position in the transport path. Outputs a pulse signal corresponding to the printing resolution required in accordance with the movement of the conveyor belt 6 and outputs a drive signal from a drive circuit, which will be described later, to an actuator in accordance with the pulse signal, whereby a predetermined signal on the print medium 1 is output. A droplet of a predetermined color is ejected at a position, and a predetermined image is drawn on the print medium 1 by the dot.

  A control device for controlling itself is provided in the printing apparatus. For example, as shown in FIG. 2, the control device 12 controls a printing device, a paper feeding device, and the like based on print data input from a host computer 60 such as a personal computer or a digital camera. A printing process is performed. Then, an input interface 61 for reading print data input from the host computer 60 and a control unit 62 configured by, for example, a microcomputer that executes arithmetic processing such as print processing based on the print data input from the input interface 61. A paper feed roller motor driver 63 for driving and controlling the paper feed roller motor 17 connected to the paper feed roller 5, a head driver 65 for driving and controlling the droplet discharge head 2, and the drive roller 8. An electric motor driver 66 for driving and controlling the electric motor 7, a paper feed roller motor driver 63, a head driver 65, an electric motor driver 66, an external paper feed roller motor 17, the droplet discharge head 2, and the electric motor 7. And an interface 67 to be connected.

  The control unit 62 temporarily stores a CPU (Central Processing Unit) 62a that executes various processes such as a print process, and print data input through the input interface 61 or various data when the print data print process is executed. A random access memory (RAM) 62c that temporarily stores a program such as a print process or a nonvolatile semiconductor memory that stores a control program executed by the CPU 62a. ) 62d. When the control unit 62 obtains print data (image data) from the host computer 60 via the interface 61, the CPU 62a executes a predetermined process on the print data, and from any nozzle of the droplet discharge head 2. Nozzle selection data for discharging droplets or how much droplets to discharge is calculated, and based on the print data, nozzle selection data, and input data from various sensors, the paper feed roller motor driver 63, head Control signals are output to the driver 65 and the electric motor driver 66. A drive signal for driving the actuator is output from the paper feed roller driver 63, the head driver 65, and the electric motor driver 66, and the paper feed roller motor 17, the electric motor 7, the actuator in the droplet discharge head 2, etc. are operated. As a result, the feeding, transporting and discharging of the printing medium 1 and the printing process on the printing medium 1 are executed. Each component in the control unit 62 is electrically connected through a bus (not shown).

  FIG. 3 shows a schematic configuration of the droplet discharge head of the present embodiment. The figure shows a part of the nozzles in the droplet discharge head 2. Reference numeral 21 in the drawing is a nozzle plate attached to the lower surface of the droplet discharge head 2, and a number of nozzles 22 are provided on the nozzle plate 21. Above the nozzle plate 21, a cavity 23 is provided as a storage chamber for storing the discharge liquid in common with the plurality of nozzles 22. Within this cavity 23, a pin 24 as a nozzle closing means for closing the nozzle 22 is disposed above each nozzle 22, and its lower end faces the nozzle 22.

  The upper end portion of the pin 24 is connected to an actuator 25 as nozzle opening / closing drive means via the mounting plate 20. The actuator 25 is composed of, for example, piezoelectric elements stacked in the left-right direction in the figure, and an upper end portion of the actuator 25 is connected to the control device 12 via an electrode. The drive signal for driving the actuator 25 from the control device 12 is provided. COM is output. The actuator 25 composed of a piezoelectric element, for example, expands and contracts in the vertical direction in the figure, so that the pin 24 is moved in the vertical direction along with the expansion and contraction, and when the pin 24 is lowered, it contacts the opening of the nozzle 22 and When the nozzle 22 is closed and the pin 24 is raised, the nozzle 22 is opened away from the opening of the nozzle 22. Since the pin 24 is lightweight and has low inertia, the pin 24 can be sufficiently driven even if the actuator 25 is a piezoelectric element.

  A liquid is pressurized and supplied into the cavity 23 from a pump 27 as a liquid pressurizing device via a liquid supply path 26. The pump 27 sucks the liquid stored in the liquid tank 28, pressurizes it, and supplies it to the cavity 23 from the liquid supply path 26. In this state, when the actuator 25 made of a piezoelectric element is contracted and the pin 24 is separated from the opening of the nozzle 22, a droplet is ejected from the nozzle 22. The pump 27 stops when the pressure of the liquid inside the cavity 23 reaches a predetermined value.

  The drive signal COM of the actuator 25 may be a simple rectangular wave voltage signal, and the contraction amount of the actuator 25 can be changed simply by changing the voltage value. When the contraction amount of the actuator 25 changes, the nozzle 22 and the pin 24 are changed. Since the gap between the liquid crystal and the gap changes, the discharge amount of the liquid droplets changes. For example, when the droplet discharge amount is increased, the gap between the nozzle 22 and the pin 24 may be increased. Therefore, the voltage value of the drive signal COM may be increased so that the contraction amount of the actuator 25 is increased. . For example, in the case of a droplet discharge type printing apparatus that discharges droplets from a nozzle by changing the pressure of the cavity previously proposed by the applicant with a piezoelectric element, a precise trapezoidal wave voltage signal is required, In the liquid discharge printing apparatus according to the present embodiment, a rectangular wave voltage signal is used as a drive signal, so that a drive signal can be easily generated.

  FIG. 4 shows details of the relationship among the actuator 25, the mounting plate 20, the pin 24, and the nozzle 22. The pin 24 is separate from the cavity 23 and is made of a metal material such as nickel or stainless steel. The diameter of the pin 24 is the same as the diameter of the nozzle 22. The nozzle plate 21 was also made of a metal material such as nickel or stainless steel. A minute gap 29 is provided between the mounting plate 20, that is, the actuator 25 and the constituent members of the cavity 23. When pressure is applied to the liquid in the cavity 23, the constituent members of the cavity 23 swell outward. In order to avoid the influence of the swelling of the constituent members of the cavity 23, a minute gap 29 is interposed between the mounting plate 20, that is, the actuator 25 and the constituent members of the cavity 23. If this minute gap 29 is not present, the actuator 25 is displaced as the constituent members of the cavity 23 swell, the amount of movement of the pin 24 changes, and the droplet discharge amount changes.

  FIG. 5 shows details of the relationship between the nozzle 22 and the pin 24. The lower end of the pin 24 inserted into the nozzle 22 may be flat or rounded as shown in the figure. Further, when the nozzle 22 has an upper tapered portion 22a and a lower cylindrical portion 22b as shown in the figure, the lower end portion of the pin 24 contacts only the tapered portion 22a, and the tapered portion 22a and the cylindrical portion 22b It is preferable not to touch the ridgeline. If the lower end of the pin 24 is in contact with the ridgeline between the tapered portion 22a and the cylindrical portion 22b, biting may occur between them. Further, by coating the lower end portion of the pin 24 with a metal material having high lubricity and an elastic resin material having a thickness of several tens of μm, the effect of preventing biting is improved. As a result, the nozzle clogging effect is increased.

  Further, in the conventional droplet discharge type printing apparatus using the pressure change in the cavity, it is necessary to partition the cavity for each nozzle. However, in this embodiment, it is not necessary to partition the cavity 23 finely. The structure of the member becomes easier, and the cost can be reduced accordingly. Further, in a conventional droplet discharge type printing apparatus using a change in pressure in the cavity, it is necessary to thin a portion that comes into contact with the actuator of the cavity, for example, a portion called a vibration plate. It is not necessary to reduce the thickness of the wall, and the overall rigidity is increased to suppress deformation of the constituent members of the cavity 23, thereby preventing breakage and a decrease in internal pressure.

As described above, in the droplet discharge head of this embodiment, the discharge liquid is pressurized and supplied to the nozzle 22, and the nozzle 22 can be closed by the pin 24, and the pin 24 is separated from the nozzle 22 by the actuator 25. Since the actuator 25 is configured to be controlled by the control device 12, the discharge liquid supplied under pressure is discharged as a droplet from the nozzle 22 only while the pin 24 is separated from the nozzle 22. Even a highly viscous liquid can be discharged stably.
Further, by configuring the actuator 25 with a piezoelectric element, the actuator 25 can be reduced in size, and as a result, the degree of integration of the nozzles 22 can be increased and finer droplet discharge can be performed.
In addition, since the cavity 23 communicates in common with the plurality of nozzles 22, it is not necessary to form a cavity for each nozzle as in the prior art, and the configuration is easy and the cost can be reduced.

In accordance with these, the force required for droplet discharge is uniformly given in advance over the entire area of the cavity 23 by the pump 27, so that variations in droplet discharge due to each nozzle or nozzle position are unlikely to occur.
In addition, since the pressure in the cavity 23 is always maintained at a level higher than the atmospheric pressure, the outside air does not enter (suck) from the nozzle 22 and no ejection failure due to bubbles occurs.
In addition, since a rectangular wave voltage signal can be used as the drive signal of the actuator 25, it is easy to generate a drive signal, and there are effects such as simplification of the circuit and reduction of power consumption.

In addition, liquids with higher viscosity than liquids used for normal printing can be ejected as droplets, so it is also applicable to liquids such as metal particle dispersion solutions, UV curable inks, and polymer compound solutions used in industrial applications. it can.
In the above embodiment, only the case where the liquid droplet ejection head of the present invention is used in a line head type liquid droplet ejection printing apparatus has been described in detail. The present invention can be similarly applied to a droplet discharge type printing apparatus. Moreover, printing apparatuses other than these printing apparatus forms may be used. For example, the present invention can be similarly applied to apparatuses that perform printing by discharging droplets in the industrial field, the medical field, and the like.

  In the above embodiment, the liquid droplet ejection head of the present invention is embodied as one that ejects a liquid such as ink. However, the present invention is not limited to this, and liquid other than ink (in addition to liquid, particles of functional material) Or a liquid droplet discharge head that ejects or discharges a fluid other than a liquid (including a solid that can be ejected by flowing as a fluid). it can. For example, a liquid discharge head that discharges a liquid containing a material such as an electrode material or a color material used in the manufacture of a liquid crystal display, an EL (electroluminescence) display, a surface emitting display, a color filter, or the like in a dispersed or dissolved form. Also, a droplet discharge head for discharging a bio-organic material used for biochip manufacturing, or a droplet discharge head for discharging a liquid as a sample used as a precision pipette may be used. In addition, transparent resins such as UV curable resins for forming droplet ejection heads that eject lubricant oil to precision machines such as watches and cameras, and micro hemispherical lenses (optical lenses) used in optical communication elements. Droplet discharge head for discharging liquid onto the substrate, droplet discharge head for discharging etching liquid such as acid or alkali to etch the substrate, etc., fluid discharge head for discharging gel, powder such as toner For example, a fluid discharge type recording head that discharges a solid may be used. The present invention can be applied to any one of these discharge heads.

1 is a print medium, 2 is a droplet discharge head, 3 is a paper feed unit, 4 is a transport unit, 5 is a paper feed roller, 6 is a transport belt, 7 is an electric motor, 8 is a drive roller, 9 is a driven roller, 10 Is a discharge plate, 11 is a fixed plate, 20 is a mounting plate, 21 is a nozzle plate, 22 is a nozzle, 23 is a cavity, 24 is a pin, 25 is an actuator, 26 is a liquid supply path, 27 is a pump, 28 is a liquid tank , 29 is a minute gap

Claims (3)

  A liquid discharge device that discharges liquid droplets from a plurality of nozzles to supply pressure to the nozzles, a nozzle closing member disposed on the nozzle, and the nozzle closing member A droplet discharge head, comprising: a nozzle opening / closing driving means for separating and contacting the nozzle; and a nozzle opening / closing control means for controlling the nozzle opening / closing driving means.   The droplet discharge head according to claim 1, wherein the nozzle opening / closing driving means is constituted by a piezoelectric element.   The liquid droplet ejection head according to claim 1, further comprising a liquid storage unit that communicates in common with the plurality of nozzles.

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