JP2008119843A - Recorder of high-viscosity ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which can stabilize ejection by the same driving condition as that of a low-viscosity ink by expanding a selection range of materials of a high-viscosity ink and stably controlling ink physical properties. <P>SOLUTION: A nozzle is formed using a cylinder tube. A cylinder type piezoelectric element is arranged in the periphery of the nozzle tube. A cooling mechanism is set outside the element. A heating medium is disposed at the center part in the nozzle in a direction from an ink supply port towards an ejection opening. The ink is directly heated to perform a precise control of the ink physical properties. The ink is ejected by the same driving condition regardless of the materials. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a recording apparatus that forms an image pattern on a recording medium by ejecting and flying ink droplets, and more particularly to an ink jet recording apparatus that uses high-viscosity ink.

  In recent years, non-impact ink jet recording apparatuses have been widely used in offices and homes as recording and printing systems for computers and the like due to features such as low noise and high-speed recording of photographic image quality.

  In a conventional ink jet recording apparatus, an electromechanical conversion means, for example, a piezoelectric element is disposed around the pressure generating chamber, and a voltage pulse is applied to the polarized piezoelectric element to rapidly reduce the volume of the pressure generating chamber. A method of ejecting ink droplets is widely used.

  As another pressure generation method, a bubble jet (registered trademark) method (thermal method) is used in which a heat generating medium disposed in a pressure generation chamber is heated and ink droplets are ejected by the pressure of the generated bubbles.

These ink jet recording apparatuses are required to have stable meniscus control near the discharge port, uniform discharge amount, and stability during high-speed recording in order to stabilize discharge.
In order to achieve these, the ink to be used uses an ink composition mainly composed of water or alcohol, and in particular, a low-viscosity ink having a viscosity of 10 mPs · s or less is mainly used.

  Regarding the use of high-viscosity ink, an inkjet recording method using hot-melt ink has been proposed as a solid material used as ink. In this method, wax is used as a main component of ink, and the ink is heated at around 100 ° C. to dissolve the ink, thereby reducing the viscosity and discharging the ink. In particular, since the ink does not contain a solvent component, an image having no blur is formed after ejection and landing. However, depending on the background, there are cases where the permeability of the ink component to the background may be poor, and the desired fixing performance may not be obtained.

  As a recording head, the entire head part or a part of the head is locally heated, and in order not to cause deterioration or destruction of the piezoelectric element, in actual use, at a temperature higher than the polarization treatment temperature. In order to avoid use, the heating temperature is also limited.

In recent years, there have been many reports of developing an inkjet recording method for industrial use as a material-saving and high-precision patterning tool due to the features of inkjet on-demand and high-precision landing performance of small droplets.
For example, Japanese Patent Laid-Open No. 06-071870 discloses a method used for printing on an electric circuit board.

  Japanese Patent Application Laid-Open No. 07-072325 discloses a method for forming pixels by ejecting colored inks of red (R), green (G), and blue (B) with an inkjet as a method for forming a color filter used in a liquid crystal display or the like. It is disclosed.

  Japanese Patent Application Laid-Open No. 10-12377 discloses a method of applying a polymer organic EL material by ink jet.

  Japanese Patent Application Laid-Open No. 11-297947 discloses a method of forming a semiconductor element by applying a semiconductor material or a dielectric material by inkjet.

  These materials used in industrial applications are mainly organic polymer materials and fine particles of metals, etc., and inks that are dissolved or dispersed in a solvent to be ejected using an inkjet head Therefore, it is necessary to formulate a low viscosity together.

When formulating an ink with a low viscosity, the amount of solvent generally exists in a large amount with respect to the solid content in the ink. When such ink is ejected and landed, the ink is dried on the substrate surface. Without strictly controlling, it is difficult to form a desired function or shape.
Japanese Unexamined Patent Publication No. 06-071870 Japanese Unexamined Patent Publication No. 07-072325 Japanese Patent Laid-Open No. 10-12377 JP-A-11-297947

  When considering the needs of high-definition image recording by ink jet or industrial applications, the material can be used as it is or with a small amount of solvent in order to expand the range of physical properties of the material that can be used and to acquire the function and shape characteristics of the material. There is a need to discharge and land in a mixed state.

  In order to meet such technical needs, a recording apparatus for high-viscosity ink is desired to control the physical properties of the high-viscosity ink to make the discharge amount constant and improve the landing accuracy.

  Actually, in the past, ink jet recording methods applied to industrial applications have often been difficult to formulate inks, and materials that can be used in particular from the viewpoint of viscosity are often limited.

  Accordingly, the present invention has been made to solve the above-mentioned problems, and the purpose thereof is to widen the selection range of ink materials that can be used, stably control ink physical properties, and drive conditions similar to those of low-viscosity inks. To provide an ink jet recording apparatus capable of stabilizing ejection.

  In order to solve the above problem, the present invention provides an ink jet recording apparatus in which a heating medium is arranged in the center of a nozzle from the ink supply port toward the discharge port, and the ink is directly heated.

  As the nozzle, a glass or metal cylindrical tube is used, and a cylindrical piezoelectric element is arranged on the outer periphery thereof. Furthermore, a cooling mechanism for preventing overheating is provided outside the cylindrical piezoelectric element.

  The tip diameter of the nozzle tube is smaller than the inner diameter of the ink flow path and has a tapered shape, and the temperature can be varied for each nozzle tube.

(Function)
In the high-viscosity ink recording apparatus as described above, a nozzle is formed using a cylindrical tube, a cylindrical piezoelectric element is disposed on the outer periphery of the nozzle tube, a cooling mechanism is disposed outside the nozzle tube, and an ink is disposed at the center of the nozzle. By disposing a heating medium from the supply port toward the discharge port, it is possible to precisely control the ink physical properties, expanding the range of materials that can be used, and stabilizing ink droplets under the same drive conditions regardless of the material. It becomes possible to discharge.

  As described above, according to the present invention, in a high-viscosity ink recording apparatus, a heating medium is arranged from the ink supply port toward the discharge port in the center of the nozzle, and the ink is directly heated. As the nozzle, a cylindrical tube made of glass or metal is used, a cylindrical piezoelectric element is disposed on the outer periphery thereof, and a cooling mechanism for preventing overheating is provided outside the cylindrical piezoelectric element.

  The nozzle tube tip diameter is smaller than the inner diameter of the ink flow path and has a tapered shape, and the temperature can be varied for each nozzle tube by a heating medium disposed inside the nozzle tube.

  As a result, precise control of the ink physical properties is possible, the range of materials that can be used is expanded, and ink droplets can be stably ejected under the same driving conditions regardless of the material.

  The present invention relates to a recording apparatus for discharging high-viscosity ink whose ink viscosity is reduced by heating. Since the present invention solves the problem of controlling the ejection of high-viscosity ink, only the portion including the inkjet head will be described in detail.

  Embodiments of the present invention will be described below.

  FIG. 1 is a cross-sectional view of an ink jet head according to an embodiment of the present invention.

  FIG. 2 is a schematic view of an ink jet head provided with a cooling mechanism according to an embodiment of the present invention.

  The nozzle of the inkjet head was formed by stretching a glass tube or a metal tube to have an inner diameter of 120 μm, and the discharge port was further stretched to reduce the inner diameter and processed to have an inner diameter of 50 μm to produce a tapered nozzle tube.

  For the metal tube, Kovar containing Fe, Ni, and Co as metal components was used.

  Quartz was used for the glass tube.

  The nozzle tube may be either glass or metal.

  As a heating medium, a metal wire having a diameter of 50 to 70 μm was placed inside the nozzle tube, and was used while being energized.

  A cylindrical piezoelectric element having electrodes attached thereto was disposed on the outer periphery of the nozzle tube. The piezoelectric element was subjected to polarization treatment at 120 ° C. for 1 hour under the condition of 3 kV / mm.

  A cooling mechanism was provided outside the cylindrical piezoelectric element to prevent overheating. As a cooling mechanism, an air cooling method or a water cooling method may be used, and any method can be used as long as it can be controlled to a temperature lower than the polarization temperature at the time of manufacturing the piezoelectric element.

  Regarding the discharge performance of high-viscosity ink, the discharge state at the time of ink droplet flight was observed, and the ink droplet discharge speed was obtained from the measurement of the flight distance by the strobe timing at the time of observation.

As a high viscosity ink, an ink was formulated using the following resist material.
The resist material was prepared by adding a solvent to an acrylic copolymer having the following composition.
The acrylic copolymer is composed of the following monomer composition, which is ink A.

N-methylolacrylamide 20 parts by weight
N, N-dimethylaminoethyl methacrylate 10 parts by weight Methyl methacrylate 25 parts by weight 2-hydroxyethyl methacrylate 40 parts by weight Acrylic acid 5 parts by weight The following solvent was added to 20 parts by weight of the above acrylic copolymer to prepare an ink.

Ethylene glycol monoethyl ether 15 parts by weight Ethylene glycol 20 parts by weight Isopropyl alcohol 2 parts by weight Pure water 43 parts by weight The ink formulated with the above composition is referred to as ink A.

  When the physical properties of ink A were measured with a rheometer CVO-120HR manufactured by BOHLIN, the viscosity at a shear rate of 10 1 / s was 24 mPa · s.

  Ink B was formulated with the following composition.

N-methylolacrylamide 20 parts by weight
N, N-dimethylaminoethyl methacrylate 10 parts by weight Methyl methacrylate 25 parts by weight 2-hydroxyethyl methacrylate 40 parts by weight Acrylic acid 5 parts by weight The following solvent was added to 80 parts by weight of the above acrylic copolymer to prepare an ink.

Ethylene glycol monoethyl ether 5 parts by weight Ethylene glycol 3 parts by weight Isopropyl alcohol 2 parts by weight Pure water 10 parts by weight When ink B formulated with the above composition was measured in the same manner as ink A, the viscosity at a shear rate of 10 1 / s was measured. Was 1020 mPa · s.

  The ink A was supplied to the nozzle tube and heated to 60 ° C. by a metal wire heater disposed inside the nozzle tube. The outside of the cylindrical piezoelectric element was cooled with water (FIG. 2) so that the piezoelectric element portion did not rise above 50 ° C.

  When a voltage of 15 V was applied to the electrode of the cylindrical piezoelectric element, stable ink droplet flight was observed. At this time, the ejection speed of the ink droplets was measured and found to be 5.7 m / s.

  Next, ink B was supplied to the nozzle tube and heated to 150 ° C. by a metal wire heater disposed inside the nozzle tube. The outside of the cylindrical piezoelectric element was cooled with water so that the piezoelectric element portion did not rise above 50 ° C.

  As with ink A, when a voltage of 15 V was applied to the electrode of the cylindrical piezoelectric element, ink droplets were observed to fly. At this time, the ejection speed of the ink droplets was measured and found to be 5.5 m / s.

  Further, when the ink A was heated to 80 ° C. (on the Peltier element stage attached to the rheometer) and the physical properties were measured with a rheometer, the viscosity was 12 mPa · s at a shear rate of 10 1 / s.

  Ink B was also measured by heating to 150 ° C., and the viscosity was 13.5 mPa · s.

  As described above, by controlling the heating of inks having different physical properties, the ink physical properties in the nozzle tube can be made the same, and ink droplets can be stably ejected without changing the driving conditions.

(Comparative Example 1)
Ink A and ink B were supplied to the nozzle tube in the same manner as in the example. However, the heater arranged inside the nozzle tube was not heated.

  When a voltage of 15 V was applied as in the example, ink droplets were observed to fly in the initial stage of ejection in ink A, but no flying was observed after several seconds.

  Ink B, no ink droplet flying was observed.

(Comparative Example 2)
In the same manner as in the example, ink A and ink B were supplied to the nozzle tube, and ejection driving was performed.

  However, it heated so that it might become the temperature similar to an Example with warm air from the exterior of a nozzle tube.

  Ink droplets were observed to fly in both ink A and ink B, but when the ejection speed was measured, ink A varied from 2.2 to 4.5 m / s, and ink B varied from 2.0 to 3.8 m / s. The flight direction was not constant and unstable.

(Comparative Example 3)
In the same manner as in the example, ink A and ink B were supplied to the nozzle tube, and ejection driving was performed.

  However, the tip diameter of the nozzle tube was the same as that of the ink supply tube.

  Ink drops were observed in both ink A and ink B, but when the ejection speed was measured, ink A was 2.5 to 3.8 m / s, ink B was 2.1 to 3.1 m / s, and the speed was slow, and It fluctuated and the flight direction was not constant and unstable.

Sectional drawing of an inkjet head. Schematic of the inkjet head provided with the cooling mechanism.

Explanation of symbols

1 Heating medium 2 Nozzle tube 3 Cylindrical piezoelectric vibrator 4 Cooling medium inlet

Claims (9)

  In an inkjet recording apparatus that records an image using ink whose viscosity is lower at a temperature higher than normal temperature, a heating medium is arranged in the center of the nozzle from the ink supply port toward the discharge port, and the ink is directly heated. An ink jet recording apparatus.   2. The ink jet recording apparatus according to claim 1, wherein a cylindrical piezoelectric element is arranged on the outer periphery of the nozzle in an ink jet recording apparatus for recording an image using an ink having a viscosity lower than a normal temperature.   3. The ink jet recording apparatus according to claim 1, wherein a cooling mechanism is provided on an outer periphery of the cylindrical piezoelectric element in an ink jet recording apparatus for recording an image using an ink having a viscosity lower than a normal temperature.   An ink jet recording apparatus, wherein the nozzle according to claim 1 or 2 uses a cylindrical tube.   5. An ink jet recording apparatus according to claim 4, wherein the cylindrical nozzle tube is glass.   5. An ink jet recording apparatus according to claim 4, wherein the cylindrical nozzle tube is made of metal.   5. An ink jet recording apparatus according to claim 4, wherein the nozzle tip diameter is smaller than the inner diameter in the ink flow path and is tapered toward the ejection port.   An ink jet recording apparatus for recording an image using an ink whose viscosity is lowered at a temperature higher than normal temperature, wherein the temperature can be varied for each nozzle tube by a heating medium arranged inside the nozzle tube.   An ink jet recording apparatus for recording an image using an ink whose viscosity is lowered at a temperature higher than normal temperature, wherein the ink having an ink viscosity at room temperature of 20 mPa · s or more is used.

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