JP2008119845A - Inkjet head and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply form an inkjet head by reducing and simplifying working and assembling of piezoelectric materials through reconsideration of an ejection method and a head structure in the piezo inkjet head, and to form a highly durable inkjet head. <P>SOLUTION: In the piezo inkjet head, the piezoelectric material 1 is used for an ink chamber partition part material and is constructed to contract and expand in an ink ejection direction. The same and continuous piezoelectric material as that of the partition part material is used also for an orifice member 5. Ink chambers, nozzle holes, etc. are formed by cutting or the like. Moreover, a high water-repellency can be given to an orifice surface by carrying out plating using a driving electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet head, and more particularly to an ink jet head using an electrical actuating means. A typical example of such an ink jet head is a piezo jet head. The present invention also relates to a pulse droplet deposition apparatus equipped with a piezo jet head. A typical example is what is called a “drop-on-demand” inkjet printer.

  Inkjet heads that record by discharging ink include bubble jet (registered trademark) heads that eject ink droplets by instantaneously evaporating ink using a heater, and piezo jet heads that eject ink using piezoelectric elements It has been known. In particular, the piezo jet head has a piezoelectric element that deforms in response to a signal on a member that forms an ink chamber, and causes the ink to fly as a droplet by the pressure generated at the time of deformation, and the piezoelectric element is placed in the ink reservoir facing the nozzle. In addition, there are known ones that cause ink droplets to fly by generating dynamic pressure in the nozzle region by expansion or contraction or deformation of this piezoelectric element, and those that cause ink droplets to fly by propagating vibration waves from the piezoelectric element to the nozzle part. . As shown in Japanese Examined Patent Publication No. 6-6375, the side wall of the ink chamber is sheared as a piezoelectric element that deforms in response to a signal is provided in a container forming the ink chamber and the ink is ejected as a droplet by the pressure generated at the time of deformation. It is known that the mode flow path is deformed sideways. Japanese Patent Publication (Kokoku) No. 7-33089 discloses that a piezoelectric element is installed in the ink reservoir so as to oppose the nozzle, and a dynamic pressure is generated in the nozzle region by deformation of the piezoelectric element to cause ink droplets to fly. Ink ejection systems having pressure chambers with shear transducers are known. JP-A-5-508 and JP-A-2000-218787 are known for causing ink droplets to fly by vibration waves.

Furthermore, a method for forming stable ink droplets by forming an orifice plate on the front surface of an ink jet head block in order to form an orifice surface that is important in forming ink droplets with high accuracy is known.
Japanese Patent Publication No. 6-6375 Japanese Patent Publication No. 7-33089 JP-A-5-508 JP 2000-218787 A

  However, since a conventional piezoelectric element that deforms in response to a signal in a container that forms an ink chamber and causes the ink to fly as droplets by the pressure generated at the time of deformation has a complicated head structure, the piezoelectric material that becomes the head member There was a problem that processing and assembly were difficult. Moreover, since it is difficult to form the orifice member integrally with the head member due to the structure of the head, there is a problem that it is difficult to reduce the head cost.

  Furthermore, in the case where ink droplets are ejected by generating dynamic pressure in the nozzle region by expansion or contraction or deformation of the piezoelectric element, the ink chamber must be formed separately from the formation of the piezoelectric element and the ink chamber. There is a problem that it is difficult to form, to process and assemble the piezoelectric element, and it is difficult to easily assemble due to high accuracy during assembly.

  In addition, depending on the characteristics of the ink medium, there has been a problem that strength and durability are not sufficient for repeated ejection after joining the orifice member to the head member.

The above problems have been solved by the present invention described below.
(1) In an ink jet head using electrical actuating means, the side wall of the ink chamber is made of a piezoelectric material, and electrodes are provided at both ends of the side wall portion piezoelectric material on the nozzle side and the ink supply path side. An ink jet head that ejects liquid droplets by expanding and contracting to change the volume of the ink chamber.
(2) In an ink jet head using an electrical actuating means, the side wall and the orifice member are made of an integral piezoelectric material, and the ink chamber side wall is made of a piezoelectric material, and the side wall portion piezoelectric material nozzle side and ink supply path side An ink jet head that has electrodes at both ends of the, and expands and contracts in the ejection direction when an electric field is applied, thereby changing the volume of the ink chamber and ejecting droplets.
(3) In an inkjet head using electrical actuating means, the side wall and the orifice member are made of an integral piezoelectric material, and the orifice member has an electrode on the orifice surface, and a water repellent film is formed on the electrode by plating. An inkjet head made of a piezoelectric material in which a side wall and an orifice member are integrated.

  As described above, according to the present invention, a piezo ink jet head can be easily assembled and produced. Further, by integrating the head, a durable piezo ink jet head can be produced.

  In the ink jet head of the present invention, the ink chamber side wall is made of a piezoelectric material. The ink chamber side wall portion is made of a piezoelectric material, and has electrodes for driving the piezoelectric side wall portion at both ends of the nozzle side end portion and the ink supply path side end portion of the piezoelectric side wall portion. By applying an electric field to the piezoelectric side wall portion, the piezoelectric side wall portion expands and contracts in the ejection direction, thereby causing a change in volume of the ink chamber. As the volume change of the ink chamber, it is appropriate to discharge the droplets by extending the piezoelectric side wall portion in advance and contracting the piezoelectric side wall portion by changing the electric field direction. The voltage for applying the electric field is preferably changed according to the characteristics of the ink filled in the ink chamber. Further, it is preferable to change the time for changing the voltage according to the characteristics of the ink. For example, when ejecting highly viscous ink droplets, it is necessary not only to increase the voltage change but also to shorten the voltage change time.

  As a specific example, FIG. 1 shows a configuration diagram of an inkjet head. The ink chamber side wall is made of a piezoelectric material, and electrodes for driving the piezoelectric material are formed at the upper and lower ends. Due to the application of the electric field, the piezoelectric body expands and the volume of the ink chamber increases. By reversing the electric field, the piezoelectric body is reduced, and when the volume of the ink chamber is reduced, droplets are ejected from the nozzle. Reference numeral 1 denotes a piezoelectric body, which is a sintered body made of barium titanate or lead zirconate. The piezoelectric body is subjected to polarization treatment with a high electric field. Electricity is maintained by applying a voltage to the electrode by polarization treatment, and the electrode expands and contracts in the direction of the double arrow in the drawing. The thickness of the piezoelectric body 1 in the expansion / contraction direction is not particularly limited, but preferably has a thickness of 1 to 10 mm in order to eject ink droplets. An electrode 2 is used to apply a voltage for expanding and contracting the piezoelectric body. The electrode 2 may be formed after the piezoelectric body is processed into a head member, or may be formed into a head member together with the piezoelectric body after an electrode is formed in advance. Although it can be changed according to the electrode material and the head size, in a normal formation, in consideration of the polarization treatment of the piezoelectric body, an electrode formed in advance is processed into a head member together with the piezoelectric body. The electrode material is not particularly limited as long as it is a highly conductive material such as Au, Ag, or Cu. In addition, as a method for forming the electrode, there are various methods such as paste application and vapor deposition, but the method is not particularly limited. An ink chamber 3 is replenished and filled with ink from an ink supply path, and ink in the ink chamber is ejected as ink droplets as the volume of the ink chamber changes due to displacement of the piezoelectric body. Reference numeral 4 denotes a nozzle port from which ink droplets are ejected. The size of the nozzle opening may be adjusted according to the desired amount of ink liquid desired, and it is preferably 5-100 μmφ for ejecting ink droplets, and preferably has a circular shape. Reference numeral 5 denotes an orifice member, which has a nozzle opening and is joined to the head member to form an ink jet head. The thickness of the orifice member is preferably 30 to 100 μm. As a method of increasing the amount of ink droplets ejected from the nozzle, the displacement amount of the ink chamber side wall must be changed after increasing the nozzle diameter. As a method of changing the displacement amount of the ink chamber side wall portion, there are a method of increasing the voltage applied to the side wall portion, which is a piezoelectric material, and a method of using a piezoelectric body having a laminated structure in the piezoelectric material constituting the side wall portion of the ink chamber. . FIG. 2 shows a structural diagram of a piezoelectric material having a laminated structure. In particular, when increasing the change amount of the ink chamber volume, it is simple and desirable to adopt a laminated structure. Electrodes for expanding and contracting the piezoelectric body are alternately formed in the piezoelectric material, and a voltage can be applied by taking out the electrodes to both sides of the ink chamber side wall. There are various methods for forming a piezoelectric material having a laminated structure, and a method of obtaining a laminate in which a sheet of piezoelectric material and electrode material is laminated is suitable. It is possible to take out the electrodes alternately by adjusting the electrode positions in advance when the sheets are laminated.

  The orifice member of a conventional inkjet head is configured separately from the head member and integrated by pasting the orifice member and the head member. However, the inkjet head of the present invention can be configured as a single structure from the same member. is there. An example in which the orifice member and the head member are formed from the same piezoelectric material is shown in FIG. The piezoelectric member can be formed so that the orifice member is integrated with the same piezoelectric member as the head member. As a method for forming the piezoelectric member, the shape is controlled by processing the material before sintering the piezoelectric body into a desired shape in advance, and the piezoelectric body that is a sintered body is processed into a desired shape by a cutting method. It is possible to control the shape by doing so. It is also possible to perform fine shape control by using both methods in combination. The thickness of the orifice member is not particularly limited as long as it does not interfere with nozzle opening formation and ink droplet ejection, but it may be about 0.1 to 2 mm in consideration of ink droplet ejection properties. preferable. In addition to taking out the electrodes from the side wall portions on both sides of the ink chamber as the electrodes of the piezoelectric body, one electrode for driving the piezoelectric body is formed on the front surface of the orifice member. One electrode can be integrated with the orifice member, so that the electrode for driving the ink chamber side wall can be made common, and the assembly of the head can be simplified. Ink chamber side wall drive controls the discharge of ink droplets by applying voltages individually to the electrodes on the ink supply path side and changing them.

  An orifice surface having high water repellency and durability can be formed by using an electrode on the front surface of the orifice member formed of a piezoelectric member. As a method for forming the orifice surface, a method of performing an electroplating process using an electrode formed on the orifice member is preferable. As a material formed by electrolytic plating, eutectoid plating of a fluorine resin material and a metal material such as nickel is preferable. The thickness of the treatment layer for water repellency and durability treatment on the orifice surface varies depending on the treatment material, but is 10 to 2000 μm. This stabilizes the characteristics of the orifice surface and stabilizes ink droplet ejection.

  The ink jet head formed in this way is an ink jet head that is inexpensive and simple, and is less restricted by ink characteristics.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  Barium titanate was used as the piezoelectric material for the inkjet head partition. The barium titanate sintered body was cut to a thickness of 5 mm in the polarization direction. A sheet-like piezoelectric material having a thickness of 5 mm was cut to have a width of 2 mm and a length of 10 mm. Gold previously formed by sputtering film formation was used for the electrodes. The cut and formed piezoelectric material blocks were arranged in parallel so that the width of the ink chamber was 1 mm, and then bonded to a stainless steel block in which the flow path was previously formed so as to form an ink flow path. At the time of bonding, a circuit was formed so that a voltage could be applied to the electrode for driving the piezoelectric material, and the circuit was arranged so as to be energized. A stainless steel block was bonded to both ends of the parallel piezoelectric materials in the same manner. After bonding, the circuit was connected to the other electrode for driving the piezoelectric material. An adhesive for forming the ink chamber was applied to the piezoelectric material on the side wall of the ink chamber and the stainless steel block, and the orifice member was bonded to produce an ink jet head. At the time of bonding of the orifice member, adjustment was performed so that the nozzle port was positioned at the center of the ink chamber, and pasting was performed. Further, a polyimide sheet having a plasma surface processing treatment applied to the head member side adhesive surface was used as the orifice member.

  Thus, a piezo ink jet head was produced. When ink was filled in the ink flow path and a pulse voltage was applied to the piezoelectric material, ink droplets could be ejected.

  A barium titanate laminated sintered body was used as the piezoelectric material for the inkjet head partition. A barium titanate laminated sintered body having a thickness of 5 mm in the lamination direction, a width of 3 mm in the electrode extraction direction, a length of 10 mm, and a 10-layer structure was used. As a piezoelectric material, heating was performed while applying an electric field so as to be polarized in the stacking direction, and polarization treatment was performed. The ink chamber was formed by adhering a stainless steel member as in Example 1. The electrode was taken out from the orifice member side for the electrode inside the ink chamber, and from the ink flow path forming side for the opposite side. After connecting each to the drive circuit, the orifice member was bonded in the same manner as in Example 1.

  In this way, a piezoelectric ink jet head in which the piezoelectric material is a laminated structure piezoelectric sintered body was produced. When ink was filled in the ink flow path and a pulse voltage was applied to the piezoelectric material, ink droplets could be ejected.

  As in Example 1, barium titanate was prepared as a piezoelectric material for the inkjet head partition. The barium titanate sintered body was cut to have a thickness of 10 mm, a width of 15 mm, and a length of 30.5 mm in the polarization direction. Gold was deposited on both sides of the 10 mm thick barium titanate sintered body by sputtering so that an electric field was applied in the polarization direction. Cutting was performed so that a groove in the width direction was formed on the deposited gold electrode. The grooves were processed to a depth of 8 mm and a groove width of 1.5 mm so that the interval between adjacent grooves in the length direction was 4 mm. The center of the formed groove was processed until the thickness became 0.5 mm. Further, a nozzle hole having a diameter of 20 μmφ was formed at the center of the groove by the FIB processing method. After processing the driving circuit connection to the gold electrode, a water-repellent film was formed by electrolytic plating on the gold electrode on the side where the nozzle holes were formed. As a water-repellent film, a nickel-Teflon (registered trademark) eutectoid plating film was formed by electrolytic plating. After the electrodes for driving the piezoelectric body were connected to the circuit, the stainless steel member for forming the ink chamber and the ink flow path was bonded.

  Thus, a piezo ink jet head was produced. When ink was filled in the ink flow path and a pulse voltage was applied to the piezoelectric material, ink droplets could be ejected.

It is a mimetic diagram showing an ink jet head concerning one embodiment of the present invention. It is a schematic diagram which shows the inkjet head which concerns on other embodiment of this invention. It is a schematic diagram which shows the inkjet head which concerns on other embodiment of this invention.

Explanation of symbols

1 Piezoelectric material 2 Electrode 3 Ink chamber 4 Nozzle hole 5 Orifice member

Claims (3)

  In an ink jet head using an electrical actuating means, the ink chamber side wall is made of a piezoelectric material, and electrodes are provided at both ends of the side wall piezoelectric material on the nozzle side and the ink supply path side, and expands and contracts in the ejection direction by applying an electric field. An ink jet head that changes the volume of the ink chamber due to the discharge and ejects droplets.   2. The ink jet head according to claim 1, wherein the side wall and the orifice member are made of an integral piezoelectric material.   3. The ink jet head according to claim 2, wherein the orifice member has an electrode on the orifice surface, and a water repellent film is formed on the electrode by plating.

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