JP2007516876A - Droplet ejection assembly - Google Patents

Abstract

A fluid drop delivery device is disclosed. The device includes a plurality of nozzle openings from which fluid is ejected and a waste control aperture.

Description

  The present invention relates to droplet ejection.

  An ink jet printer is a type of apparatus for depositing droplets on a substrate. Ink jet printers generally include an ink path from an ink source to a nozzle path. The nozzle path terminates at a nozzle opening through which ink droplets are ejected. Ink droplet ejection is typically controlled by applying pressure to the ink in the ink path with an actuator, which can be, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatic deflection element. A typical print assembly has an array of ink paths with corresponding nozzle openings and associated actuators. Droplet ejection from each nozzle opening can be controlled independently. In an on-demand droplet firing print assembly, the print assembly and the printed circuit board are moved relative to each other and the respective actuators are activated to selectively eject droplets at specific pixel locations in the image. . In high performance print assemblies, the nozzle openings are generally 50 μm or smaller, for example about 25 μm in diameter, separated by a pitch of 100-300 nozzles / inch (3.9-11.8 nozzles / mm); It has a resolution of 100 to 3000 dpi (3.9 to 118.1 dots / mm) or higher and provides droplets with a volume of about 1 to 120 picoliters (pL) or less. The droplet ejection frequency is generally 10 kHz or higher.

U.S. Pat. No. 6,057,037 to Hoisington et al. Describes a printed assembly having a semiconductor structure and a piezoelectric actuator. The structure is made of silicon with an ink chamber defined by etching. The nozzle openings are defined by individual nozzle plates attached to the silicon structure. Piezoelectric actuators have a layer of piezoelectric material that changes shape, ie, bends, in response to an applied voltage. The bending of the piezoelectric layer exerts pressure on the ink in the pump chamber located along the ink path. Piezoelectric inkjet print assemblies are also described in US Pat. Nos. 4,099,086, Fishbeck et al., US Pat. The entire contents of these patent documents are hereby incorporated by reference.
US Pat. No. 5,265,315 US Pat. No. 4,825,227 US Pat. No. 4,937,598 US Pat. No. 5,659,346 US Pat. No. 5,757,391

  SUMMARY OF THE INVENTION An object of the present invention is to provide a means for enhancing droplet ejection performance in a print head of an ink jet printer.

  In one aspect, a feature of the present invention is a droplet ejector that includes a flow path in which pressure is applied to a liquid to eject the droplet from a nozzle opening formed in a substantially planar substrate. A channel is also formed in the substrate in the vicinity of the nozzle opening. The channel is separated from the nozzle opening by a distance of about 20% or more of the nozzle opening width.

  In another aspect, a feature of the present invention is a method of liquid ejection comprising providing a droplet ejector comprising a flow path within which pressure is applied to the liquid for ejection through a nozzle opening formed in the substrate. It is. A channel is also formed in the substrate in the vicinity of the nozzle opening. The channel is separated from the nozzle opening by a distance of about 20% or more of the nozzle opening width. The method also includes the step of supplying liquid that is sucked by capillary action force into the space defined by the channel and ejecting the liquid through the nozzle opening by applying pressure to the liquid in the flow path.

Other aspects or embodiments may have the features of the above aspects and / or combinations of one or more of the following characteristics. The nozzle opening is surrounded by a channel. The channel is annular. The channel extends radially from the nozzle opening. The channel has a width of about twice or less than the nozzle opening width. The channel has a width of about 100 μm or less. The channel is about 2 μm to about 50 μm. The substrate is a silicon material. The planar substrate has a plurality of nozzle openings and channels near the nozzle openings. The nozzle opening width is about 200 μm or less. The droplet ejector includes a piezoelectric actuator. The liquid has a surface tension of about 20-50 dynes / cm (1 dynes / cm = 10 ⁻³ N / m). The liquid has a viscosity of about 1 to 40 centipoise (1 centipoise = 10 ⁻¹¹ N · sec / m ² ).

  Embodiments can have one or more of the following advantages. Printhead operation is robust and reliable because the waste ink liquid around the surface of the nozzle plate is controlled to reduce interference with drop formation and ejection. In high performance printheads where a large array of small nozzles must eject ink accurately at precise locations on the substrate, drop velocity and trajectory linearity are maintained. The channels control the waste ink liquid and allow the head to change the desired jetting characteristics and various pressure characteristics at the nozzle openings, such as inks that vary in viscosity and surface tension characteristics. The channel is robust, requires no moving parts, and can be implemented economically, for example in semiconductor materials such as silicon materials, by machining, for example laser machining or etching.

  Further aspects, features and advantages are set forth below. For example, certain aspects have channel dimensions, characteristics and operating conditions as described below.

  Referring to FIG. 1, the ink jet device 10 includes a liquid reservoir 11 containing supply ink 12 and a liquid passage 13 that leads from the liquid reservoir 11 to the pressure chamber 14. An actuator 15, for example a piezoelectric transducer, overlaps the pressure chamber 14. The actuator can be used to apply ink force to eject ink droplets 19 from the nozzle 17 toward the substrate 20 through the liquid passage 16 leading from the pressure chamber 14 to the nozzle openings 17 of the nozzle plate 18. In operation, the inkjet device 10 and the substrate 20 can be moved relative to each other. For example, the substrate can be a continuous web that is moved between rolls 22 and 23. The desired image is produced on the substrate 20 by selective ejection of droplets from the array of nozzles 17 on the nozzle plate 18.

  The ink jet device also controls the operating pressure at the ink meniscus near the nozzle opening when the system is not ejecting droplets. Variations in meniscus pressure can cause variations in drop volume or velocity that can cause print errors and drops. In the illustrated embodiment, pressure control is provided by a vacuum source 30 such as a mechanical pump that provides a vacuum to the headspace 9 above the ink 12 in the reservoir 11. The vacuum is transmitted to the nozzle opening 17 through the ink to prevent ink from dripping through the nozzle opening 17 due to gravity. A controller 32, such as a computer controller, monitors the vacuum above the ink in the reservoir 11 and adjusts the vacuum source 30 to maintain the reservoir at the desired vacuum. In another embodiment, a vacuum source is provided by placing an ink reservoir below the nozzle opening to create a vacuum near the nozzle opening. An ink level monitor (not shown) detects the ink level, which drops as ink is consumed during the printing operation, thus increasing the vacuum at the nozzle. The controller monitors the ink level and refills the reservoir from the bulk container to maintain the vacuum within the desired operating range when the ink drops below the desired level. In another embodiment, a reservoir is located below the nozzle that is sufficiently separated from the meniscus vacuum to overcome the capillary force of the nozzle, in another embodiment, pressure is applied to the ink to maintain the meniscus near the nozzle opening. be able to. In an embodiment, the vacuum is maintained at about 0.5 to about 10 inches of water column (1 inch water column = 249 Pa).

  Referring to FIGS. 2 to 2A, the nozzle plate part 40 has a plurality of nozzle openings 42 formed in a substantially planar substrate 41. The substrate 41 is also formed with a cleaning structure in the form of a channel 44 in the vicinity of each nozzle opening 42. Channel 44 controls unwanted ink on the nozzle plate that could affect nozzle performance. For example, ink accumulates on the nozzle plate during ink ejection. Over time, the ink can form liquid masses that cause print errors. For example, liquid mass near the edge of the nozzle opening can affect the trajectory, velocity or volume of the ejected droplet. Also, the liquid mass could be large enough to drop on the printed substrate 20 to produce a meaningless mark. The liquid mass may protrude sufficiently far from the surface of the nozzle plate 40 and come into contact with the print substrate 20 to cause contamination on the print substrate 20. Channel 44 collects, localizes and directs waste ink fluid. With particular reference to FIG. 2A, the channel 44 completely surrounds each nozzle opening 42 located in the center of the platform region 43. Channels 44 are connected by radial channels 46 and 48 exiting channel 44 to form a connected channel network that guides and holds unwanted liquid on the nozzle plate.

  With particular reference to FIG. 3, a nozzle opening 42 is shown adjacent to a channel 44 prior to droplet ejection. Referring to FIGS. 3A and 3B, the waste ink liquid 38 accumulates on the platform area 43 and is drawn into the channel 44 by capillary action force. Referring to FIG. 3C, the waste ink liquid 38 enters the channel 44 and is spread around the nozzle opening 42 by the channel 44. Upon encountering the radial channel 46 or 48, the ink moves into the space defined by the radial channel and then moves radially away from the nozzle opening 42 under capillary action forces to induce and retain unwanted liquid. Into the connected channel network (see FIG. 2). When the nozzle plate is arranged in the vertical direction, the waste ink liquid moves through the channel network in a macroscopic single direction under the influence of both gravity and capillary forces. If the nozzle plate is positioned horizontally, a vacuum source or wicking material can be used to remove ink from the channel.

Channel spacing, dimensions, and placement are selected to control the waste ink fluid. In embodiments, the spacing S from the edge of the channel to the edge of the nozzle openings is from about 20% to greater than that of the nozzle opening width W _N, for example 30% to greater, also from about 5-fold of the nozzle opening width It is smaller than that, for example, 3 times or less than the nozzle opening width. The channel width W _C and depth D are selected to prevent excessive ink accumulation on the nozzle surface and to allow the liquid to be drawn and retained by capillary forces into the space defined by the channel. . In an embodiment, the channel width is twice or less than the nozzle opening width and about 10% or more of the nozzle opening width. In certain embodiments, the channel width _{W C,} for example from about 100μm to less than, for example, 5 to 20 [mu] m, channel depth D, for example about 2~10μm to greater, such as 50 [mu] m. In the embodiment, the nozzle opening width W _N is, for example, 200 μm or less, for example, 25 to 100 μm, and the distance S from the nozzle opening to the edge of the channel is, for example, 40 μm or more, for example, 100 μm. In embodiments, the nozzle pitch is about 25 nozzles / inch (about 0.98 nozzles / mm) or less, such as about 300 nozzles / inch (about 11.8 nozzles / mm), and the ink droplet volume is about The pressure is applied to the liquid by the piezoelectric actuator. In an embodiment, the jet liquid has a viscosity of about 1-40 centipoise (1 centipoise = 10 ⁻¹¹ N · sec / m ² ) and about 20-50 dynes / cm (1 dynes / cm = 10 ⁻³ N / ^second ). m) surface tension. In an embodiment, the jetting liquid is ink. In embodiments, the channel can have a wicking material and / or a non-wetting coating (eg, Teflon fluoropolymer) can be applied to the nozzle plate surface between the nozzle and the channel. The channel network can also communicate with a vacuum source (not shown). The waste ink liquid can be returned to the main ink supply or a separate suction system. In embodiments, the channels are arranged in a ring shape. In another embodiment, the channels are arranged in a waveform.

  In any of the embodiments described above, the channels and / or nozzle openings can be formed by machining, electroforming, laser ablation, and chemical or plasma etching. The channel can also be formed by molding, for example an injection molded plastic channel. In an embodiment, the channel, nozzle opening and pressure chamber are formed in a common structure. The structure can be an etchable material such as metal, carbon, or a silicon material such as silicon or silicon dioxide. The formation of printhead components using an etching method is described in US patent application Ser. No. 10/189947, filed Jul. 3, 2002, and US Pat. And the entire contents of each specification are hereby incorporated by reference.

  Channels are described in US patent application Ser. No. 10/749829 filed on Dec. 30, 2003, US patent application Ser. No. 10 / 769,622 filed Dec. 30, 2003. In combination with other waste control aspects such as wells described in the literature and / or protrusions described in US patent application Ser. No. 10 / 479,816, filed Dec. 30, 2003. it can. For example, a series of protrusions can be provided on the nozzle surface near the channel.

  In embodiments, the droplet ejection system can be utilized to eject liquids other than ink. For example, the deposited droplets can be UV curable or other radiation curable materials, or other materials that can be delivered as droplets, such as chemical or biological liquids. For example, the described device could be part of a precision dispensing system. The actuator can be an electromechanical actuator or a thermal actuator. The cleaning structure can be combined with a manual or automatic cleaning and wiping system in which cleaning liquid is applied to the nozzle plate and wiped off. The cleaning structure can collect cleaning liquid and waste, not waste ink liquid after jetting.

  Other embodiments are within the scope of the appended claims.

FIG. 1 is a schematic diagram of a droplet ejection assembly. FIG. 2 is a perspective view of the nozzle plate. 2A is an enlarged view of region A in FIG. FIG. 3 is a cross-sectional view of the nozzle taken along line 3-3 of FIG. 2A showing droplet ejection. 3A is a cross-sectional view of the nozzle taken along line 3-3 of FIG. 2A showing droplet ejection. 3B is a cross-sectional view of the nozzle taken along line 3-3 of FIG. 2A showing droplet ejection. 3C is a cross-sectional view of the nozzle taken along line 3-3 of FIG. 2A showing droplet ejection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Head space 10 Inkjet apparatus 11 Liquid reservoir 12 Ink 13, 16 Liquid path 14 Pressure chamber 15 Actuator 17 Nozzle 18 Nozzle plate 19 Ink droplet 20 Substrate 22, 23 Roll 30 Vacuum source 32 Controller 44 Channel

Claims (14)

In droplet ejector,
A flow path in which pressure is applied to the liquid in order to eject droplets from a nozzle opening substantially formed in the planar substrate, and a channel formed in the substrate in the vicinity of the nozzle opening, from the opening Channels separated by a distance of about 20% or more of the width of the nozzle opening;
A droplet ejector comprising:   The droplet ejector according to claim 1, wherein the nozzle opening is surrounded by the channel.   The droplet ejector according to claim 2, wherein the channel is annular.   The droplet ejector of claim 1, wherein the channel extends radially from the nozzle opening.   The drop ejector of claim 1, wherein the channel has a width of about twice or less than a width of the nozzle opening.   The droplet ejector according to claim 1, wherein the channel has a width of about 100 μm or less.   The droplet ejector of claim 1, wherein the channel has a depth of about 2 μm to about 50 μm.   The droplet ejector according to claim 1, wherein the substrate is a silicon material.   The droplet ejector according to claim 1, wherein the planar substrate has a plurality of nozzle openings and a channel in the vicinity of the nozzle openings.   The droplet ejector according to claim 1, wherein the nozzle opening has a width of about 200 μm or less.   The droplet ejector according to claim 1, further comprising a piezoelectric actuator. In the method of liquid injection,
A flow path in which pressure is applied to the liquid therein for injection through a nozzle opening formed in the substrate, and a channel formed in the vicinity of the nozzle opening in the substrate, the channel extending from the nozzle opening to the nozzle opening Providing a droplet ejector that is separated by a distance of about 20% or more of the width of the nozzle opening;
Supplying liquid sucked by capillary action force into a space defined by the channel, and ejecting the liquid through the nozzle opening by applying pressure to the liquid in the flow path;
A method comprising the steps of: The method of claim 12, wherein the liquid has a surface tension of about 20-50 dynes / cm (1 dynes / cm = 10 ⁻³ N / m). The method of claim 12, wherein the liquid has a viscosity of about 1 to 40 centipoise (1 centipoise = 10 ⁻¹¹ N · sec / m ² ).

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