JP2009269220A - Liquid droplet discharge device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a change of an ink property caused by the cohesion of particulates in an ink in a liquid droplet discharge device for discharging the ink containing the particulate. <P>SOLUTION: When the zeta potential of a pigment particle and metal nanoparticle contained in the ink is negative polarity, a coating layer 8 of a fluoride such as a tetra-fluoroethylene perfluoroalkyl vinyl ether copolymer (PFA) is formed in a liquid chamber 4 and an outlet port 1 with which the ink contacts. Since the absolute value of the zeta potential of the fluoride is larger than the particulate in the ink, the cohesion of the particulates in the liquid chamber 4 and the outlet port 1 can be prevented by the fluoride. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a droplet discharge device that discharges ink containing nanometer-sized fine particles.

  In recent years, a droplet discharge apparatus such as an ink jet recording apparatus has been used for outputting electronic data such as documents and photographs created by a computer, and has been widely spread to general households due to low price and high image quality. Colored inks containing dyes or pigments are mainly used as printing inks on paper.

  In recent years, there have been many reports on cases where inkjet technology is deployed for industrial use. For example, it can also be used for commercial printing, wiring formation for electronic devices, element formation for organic semiconductor devices, development of displays related to color filters and organic EL, genetic diagnosis in the medical field, trial production of three-dimensional objects, etc. is doing.

  With the widespread use of inkjet technology, a wide range of inks are used. In addition to colored inks containing dyes and pigments used in conventional printing applications, inks containing metal nanoparticles or conductive polymer material inks Functional inks such as these are also used.

  Inks containing fine particles, for example, printing inks, those in which the primary particle diameter of the pigment is finely divided to a size of 100 nm or less have become mainstream.

  Moreover, in the metal nanoparticle ink used for wiring of an electronic device or the like, fine particles having a primary particle size of several nm to 50 nm or less are used.

  The ink containing these nanometer-sized fine particles is designed to exhibit a desired function when discharged and landed in a state where the fine particles are uniformly dispersed. Therefore, many inks consider the surface potential of the particles in order to improve and stabilize the dispersibility of the fine particles. A zeta potential is used as an index of the surface potential. The zeta potential is used as an index because it is difficult to directly measure the surface potential of the particles, so the surface potential is approximated by the zeta potential.

  The zeta potential of fine particles in a solution generally varies depending on the pH, temperature, and additives of the solution. In addition, when the absolute value of the zeta potential is large, aggregation of particles can be suppressed by electrical repulsion between particles, and the dispersibility can be stabilized.

  When an inkjet is developed for industrial use, it is required with high accuracy that the functional ink has a small discharge amount, a stable discharge amount, and an accurate discharge direction.

  Patent Document 1 discloses that in an ink jet recording apparatus that discharges ink containing a pigment as a colorant, the zeta potential on the surface of a member in contact with the ink and the ink have the same polarity in order to prevent clogging caused by pigment deposition and adhesion. Is disclosed.

  Since the negative potential is obtained when the pigment is an anionic pigment and the positive potential is obtained when the pigment is a cationic pigment, the polarity of the surface of the member in contact with the liquid is defined by the type of the pigment.

Japanese Patent Laid-Open No. 2003-266685

  However, if the polarity of the zeta potential is just the same, fine particles agglomerate with the ink flow while the ink passes from the ink supply system through the ink flow path and discharge port, and physical properties such as viscosity and surface tension are present. In some cases, the discharge speed and the discharge amount of the droplets may change.

  In this case, two or more kinds of substances are in contact between the ink and the ink jet recording apparatus, and charge transfer occurs between the substances in contact with the flow of the ink, and static electricity is charged. Examples of the charging phenomenon include fluid charging by movement of ink, friction charging generated by friction, induction charging generated by electrostatic induction, and ejection charging accompanying ejection from an ink ejection port. As the electrostatic charge amount, when the contact area is large, the pressure is large, or the friction is large, the generated amount is large and the charge amount is large. For this reason, the fine particles in the ink are electrically influenced by the liquid contact member and the ink flowing conditions.

  Also in the ink jet recording apparatus, the absolute value of the zeta potential of the fine particles changes due to the flow of the ink, and when the absolute value decreases, the particles dispersed in the ink are likely to aggregate together. Physical properties such as surface tension change. As a result, there is a problem that the discharge state such as the discharge speed and the discharge amount of the droplets as described above changes. If the ejection speed changes during ejection / drawing, there is a problem that the landing position shifts from the desired position. Further, if the discharge amount changes, a desired image and function expression cannot be achieved. Furthermore, adhesion and precipitation of fine particles are likely to occur on the surface of the member.

  An object of the present invention is to provide a droplet discharge device capable of preventing changes in physical properties of ink caused by aggregation of fine particles.

  In order to solve the above-described problems, a droplet discharge device of the present invention is a droplet discharge device that discharges ink containing fine particles, and supplies ink to the droplet discharge device and discharges the ink. An ejection port; a channel for guiding ink supplied by the supply unit to the ejection port; and an ejection driving unit for ejecting ink from the ejection port. The ejection port and an inner surface of the channel Has a coating layer made of a material having the same polarity as the zeta potential of the fine particles in the ink and having a zeta potential larger than the absolute value of the zeta potential.

  Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) is a fluorine-based compound, and has an absolute value of zeta potential larger than that of pigment particles and metal nanoparticles.

  In such a potential relationship, the electrical interaction of the fine particles contained in the ink with the flow of the ink is controlled, and aggregation caused by the decrease in the surface potential of the fine particles due to the charging due to the flow of the ink is suppressed. Thus, changes in physical properties such as ink viscosity and surface tension can be prevented.

  Since the ink physical properties do not change, it is possible to ensure ejection stability such as ejection amount and ejection speed for a long time.

  In particular, it is effective in preventing aggregation of nanometer-sized particles having a larger surface area effect than the volume of fine particles, and can prevent an increase in viscosity and a change in surface tension due to aggregation.

  Furthermore, it is possible to prevent fine particles from adhering to and depositing on the discharge port of the droplet discharge device in contact with the ink or the inner surface of the flow path.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  1A and 1B show an ink jet type droplet discharge apparatus according to an embodiment, in which FIG. 1A is a schematic diagram for explaining a main part thereof, and FIG. 1B is a schematic partial sectional view showing an enlarged vicinity of a discharge port. is there.

  The discharge port 1 is a nozzle having a diameter of about 10 μm to 50 μm formed in the nozzle plate 3 having the water repellent film 2. The substrate of the nozzle plate 3 may be insulating or conductive, and the insulating substrate may be a polymer film such as polyimide. As the conductive base material, a foil-like material such as metal may be used. A water repellent film 2 corresponding to the physical properties of the ink is formed on the nozzle plate.

  The nozzle plate 3 is joined to a liquid chamber (flow path) 4 in which a volume change occurs when a voltage is applied by a discharge driving means (not shown). These joined bodies are connected to a manifold (common flow path) 5, and an ink supply tube 6 and an ink discharge tube 7 as supply means are connected to the manifold 5.

  In an ink containing fine particles having a negative zeta potential, particles of tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) are formed into a film on the inner surface of the liquid chamber 4 or the discharge port 1 which is a member in contact with the ink. A coating layer 8 for controlling the surface potential is provided.

  Other materials for forming the coating layer 8 include tetrafluoroethylene / hexafluoropropylene copolymer (4, 6 fluoride) (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), graphite fluoride, and fullerene fluoride. Etc. can also be used.

  Although the nanoparticle jet is used for the method of forming the coating layer 8, the present invention is not limited to this, and other film forming methods may be used. Nanoparticle jet is a method of forming a film by jetting ultrafine particles onto a substrate at high speed. There are a gas deposition method and an aerosol method for evaporating materials.

  Since these materials also have water repellency, they can also be used as materials for the water repellent film 2.

  Thus, by providing the coating layer 8 made of a material having the same polarity as the zeta potential of the fine particles contained in the ink and a large absolute value on the surface in contact with the ink, the fine particles in the ink are aggregated. prevent.

  As a past example, polytetrafluoroethylene (PTFE) has been used in tubes and the like as a material with a negative polarity and a large zeta potential, but its purpose is to improve durability against ink and gas barrier properties from the viewpoint of the present invention. There is no use.

  With respect to polytetrafluoroethylene (PTFE), an experiment was conducted again after forming a film on a member in contact with ink other than the tube, and the effect of the zeta potential could be confirmed as in the present invention.

  However, in actual use, a film in which polytetrafluoroethylene (PTFE) is formed on the flow path or the like has poor adhesion, does not satisfy a desired function, and lacks reliability.

  Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) is good in film formability including adhesion. Further, tetrafluoroethylene / hexafluoropropylene copolymer (4, 6 fluoride) (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), graphite fluoride, and fullerene fluoride are preferable.

  As the primary particle diameter of the fine particles contained in the ink, particularly when the influence of the surface area is larger than the volume of 200 nm or less compared with the volume, a great effect is obtained for preventing aggregation according to the present invention.

  Even when the fine particles contained in the ink have a positive zeta potential, if the surface of the member in contact with the ink has the same polarity as the zeta potential of the fine particles contained in the ink and the absolute value is increased, The effects of the invention can be obtained.

  When the fine particles contained in the ink have a positive polarity zeta potential, a layer for controlling the surface potential can be provided by forming aluminum oxide particles or the like.

  As for the fine particles contained in the ink, in addition to the insulating fine particles, conductive fine particles such as metal nanoparticles can achieve the same effect.

  The nanoparticle jet gas deposition method consists of an ultrafine particle generation chamber, a film formation chamber, a transfer tube, etc., and materials such as arc, resistance heating, high frequency induction heating, and laser in an inert gas atmosphere in the ultrafine particle generation chamber Is heated, melted and evaporated to collide with an inert gas. The dry type composition that draws the pattern directly by guiding the generated ultrafine particles to the film formation chamber through the transfer tube due to the pressure difference between the ultrafine particle generation chamber and the film formation chamber, and spraying at high speed from the nozzle connected to the end of the transfer tube. It is a membrane method.

  In the aerosol method, a container containing ultrafine particles is vibrated into an aerosol, and this aerosol is transported as helium or oxygen gas as a carrier gas, guided to a film formation chamber, and from a nozzle connected to the end of the transport pipe A film is formed by drawing at a high speed.

  A tubular material such as a tube can be formed by applying a dispersion of tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) particles in a paint to the inner wall.

  Tetrafluoroethylene / hexafluoropropylene copolymer (4, 6 fluoride) (FEP), tetrafluoroethylene / ethylene copolymer (ETFE), fluorinated graphite, fluorinated fullerene, and the like can be formed in the same manner.

  In the present invention, the zeta potential of the ink containing fine particles was measured using a ZETERSIZER Nano-Z manufactured by MALVERN.

  Measurement of the zeta potential at the discharge port of the droplet discharge device and the inner surface of the flow path was performed using SurPASS manufactured by Anton Paar.

  In addition, droplets were continuously ejected under a desired driving condition, and the state of the droplet flying was observed by synchronizing the state with the driving condition and emitting a strobe light.

  In the apparatus of FIG. 1, inorganic pigment ink (primary particle size 10 nm, solid content concentration 20 wt.%, Prepared in 80% water) was used as the ink. The prepared ink had a pH of 6.8, and the zeta potential of the pigment particles contained in the ink was measured and found to be -30 mV.

  In order to confirm the effect of providing the coating layer 8 on the surface of the droplet discharge device that contacts the ink, the following two types of devices were manufactured.

  As Configuration 1, a droplet discharge device was manufactured using a material whose absolute value of zeta potential is smaller than the zeta potential of the fine particles contained in the ink on the surface in contact with the ink. This configuration is applicable because there is no particular rule in the conventional example. The ink supply tube 6 is a polyvinyl chloride tube often used in consumer inkjet printers, and the manifold 5 is made of a plastic mainly composed of 4-methylpentene-1. Silicon oxide was formed as a protective film on the surface of the liquid chamber 4, and a polyimide film was used for the nozzle plate 3. The zeta potential of these members alone was PVC tube -20 mV, manifold -21 mV, polyimide -24 mV, and silicon oxide surface -25 mV.

  As Configuration 2, a droplet discharge device according to this example was manufactured. A film of tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) was formed as the coating layer 8. The zeta potential on the film surface of the tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) formed this time was −53 mV.

  In the droplet discharge device having the above two configurations, the ink was introduced from the ink supply tube 6 and flowed through the manifold 5 and the liquid chamber 4 and collected from the discharge port 1. When the zeta potential of the pigment particles contained in the recovered ink was measured, it was −20 mV in the droplet discharge device of Configuration 1 manufactured as a comparative example, and the zeta potential (−30 mV) of the initial ink was There was a 33% reduction in zeta potential. In the droplet discharge device of Configuration 2 according to this example, it was −26 mV, which was a 13% decrease in the zeta potential amount with respect to the initial zeta potential (−30 mV) of the ink.

  As described above, in the case where the coating layer 8 of tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) was formed on the member in contact with the ink, the change in the zeta potential of the pigment particles in the ink was small. From this, it is presumed that the aggregation of particles has not progressed.

  In configuration 1, a tendency for the ink particle size distribution to increase was observed by measuring the particle size distribution.

  In addition, when droplets were discharged under the same driving conditions (driving frequency 3 kHz), the droplet discharge device of Configuration 1 compared to the discharge speed of 7.0 m / s of the droplet discharge device of Configuration 2 of this example. The discharge speed was 6.0 m / s, and the speed was reduced by about 14%.

  Furthermore, in the droplet discharge device of configuration 2, there is one satellite at the time of discharge, whereas in the droplet discharge device of configuration 1, a plurality of satellites are observed and at the same strobe observation timing, The satellite position was not stable. When discharge was performed continuously for 2 hours, the discharge amount did not vary in the droplet discharge device of Configuration 2, but in the droplet discharge device of Configuration 1, the discharge amount was 12 after 2 hours from the initial discharge amount. % Decrease.

  In this example, a coating layer of tetrafluoroethylene / hexafluoropropylene copolymer (4, 6 fluoride) (FEP) was formed on the ink contact portion. The zeta potential on the film surface of the tetrafluoroethylene / hexafluoropropylene copolymer (4, 6 fluoride) (FEP) formed this time was −53 mV.

  Ink was introduced from the ink supply tube in the same manner as in Example 1, and flowed through the manifold and the liquid chamber, and was collected from the discharge port. When the zeta potential of the pigment particles contained in the recovered ink was measured, it was −25 mV in the droplet discharge device of this example, and 17% of the zeta potential of the initial ink (−30 mV). The amount of potential was decreased.

  As described above, the structure 1 shown in Example 1 is the one in which the coating layer of the tetrafluoroethylene / hexafluoropropylene copolymer (4, 6 fluoride) (FEP) is formed on the surface of the member in contact with the ink. The amount of change was small compared to the amount of decrease in zeta potential. From this, it is presumed that the aggregation of particles has not progressed.

  Further, when droplets were ejected under the same driving conditions (driving frequency 3 kHz), the ejection speed of the droplet ejection device of this example was 7.0 m / s, and at the same strobe observation timing, satellites and ejection speeds were obtained. Was also stable. There was no decrease in the discharge rate.

  In this example, a coating layer of tetrafluoroethylene / ethylene copolymer (ETFE) was formed on the ink contact part. The zeta potential on the film surface of the tetrafluoroethylene / ethylene copolymer (ETFE) formed this time was −51 mV.

  Ink was introduced from the ink supply tube in the same manner as in Example 1, and flowed through the manifold and the liquid chamber, and was collected from the discharge port. When the zeta potential of the pigment particles contained in the collected ink was measured, it was -24 mV in the droplet discharge device of this example, and 20% of the zeta potential of the initial ink (-30 mV). The amount of potential was decreased.

  Thus, what formed the coating layer of the tetrafluoroethylene-ethylene copolymer (ETFE) on the surface of the member which contacts ink changes compared with the reduction amount of the zeta potential of the structure 1 shown in Example 1. The amount was small. From this, it is presumed that the aggregation of particles has not progressed.

  Further, when droplets were ejected under the same driving conditions (driving frequency 3 kHz), the ejection speed of the droplet ejection device of this example was 6.9 m / s, and at the same strobe observation timing, satellites and ejection speeds were obtained. Was also stable. There was no decrease in the discharge rate.

  In this example, a coating layer of graphite fluoride was formed on the ink contact part. The zeta potential of the surface of the graphite fluoride film formed this time was −50 mV.

  Ink was introduced from the ink supply tube in the same manner as in Example 1, and flowed through the manifold and the liquid chamber, and was collected from the discharge port. When the zeta potential of the pigment particles contained in the recovered ink was measured, it was −25 mV in the droplet discharge device of this example, and 17% of the zeta potential of the initial ink (−30 mV). The amount of potential was decreased.

  As described above, in the case where the graphite fluoride coating layer was formed on the surface of the member in contact with the ink, the amount of change was small compared to the amount of decrease in the zeta potential of Configuration 1 shown in Example 1. From this, it is presumed that the aggregation of particles has not progressed.

  Further, when droplets were ejected under the same driving conditions (driving frequency 3 kHz), the ejection speed of the droplet ejection device of this example was 6.9 m / s, and at the same strobe observation timing, satellites and ejection speeds were obtained. Was also stable. There was no decrease in the discharge rate.

  Table 1 below shows the zeta potential of the ink fine particles, the zeta potential of the coating layer, and the ink fine particles after passing through the liquid chamber and the decreasing rate described in Examples 1 to 4.

  The droplet discharge device of the present invention can be used for an inkjet head that discharges colored ink, and can also be used for an industrial inkjet head that accurately discharges a functional ink containing metal nanoparticles or the like. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a droplet discharge device according to an embodiment, in which (a) is a schematic diagram illustrating a main part thereof, and (b) is a schematic partial cross-sectional view illustrating an enlarged vicinity of a discharge port of (a).

Explanation of symbols

1 discharge port 2 water repellent film 3 nozzle plate 4 liquid chamber 5 manifold 6 ink supply tube 7 ink discharge tube 8 coating layer

Claims (5)

In a droplet discharge device that discharges ink containing fine particles,
Supply means for supplying ink to the droplet discharge device;
An ejection port for ejecting ink;
A flow path for guiding the ink supplied by the supply means to the ejection port;
An ejection driving means for ejecting ink from the ejection port,
The droplets characterized in that the discharge port and the inner surface of the flow path have a coating layer made of a material having the same polarity as the zeta potential of the fine particles in the ink and having a zeta potential larger than the absolute value of the zeta potential. Discharge device. The droplet discharge device according to claim 1, wherein a coating layer of a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer is formed on an inner surface of the discharge port and the flow path. The droplet discharge device according to claim 1, wherein a coating layer of a tetrafluoroethylene / hexafluoropropylene copolymer is formed on an inner surface of the discharge port and the flow path. 2. The droplet discharge device according to claim 1, wherein a coating layer of a tetrafluoroethylene / ethylene copolymer is formed on an inner surface of the discharge port and the flow path. The droplet discharge device according to claim 1, wherein a coating layer of graphite fluoride is formed on an inner surface of the discharge port and the flow path.

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