JP5012257B2 - Inkjet head - Google Patents

Description

  The present invention relates to an ink jet head, and more specifically, formed by forming a plurality of grooves and a plurality of partition walls, and aligning and bonding two actuator plates each having an electrode formed in each groove. The present invention relates to an inkjet head.

  In Patent Document 1, as shown in FIG. 10, a plurality of grooves 101 and a plurality of partition walls 102 are juxtaposed in a piezoelectric material subjected to polarization treatment, and an electrode 103 is formed from the side surface of each partition wall 102 to the zenith portion 102a. The actuator plate 100 formed and the electrodes 103 adjacent to each other at the zenith portion 102a are electrically separated from each other, and a plurality of grooves 201 corresponding to the grooves 101 are formed on a similarly polarized piezoelectric material, A plurality of partition walls 202 corresponding to the partition walls 102 are juxtaposed, electrodes 203 are formed from the side surfaces of the partition walls 202 to the zenith portion 202a, and the adjacent electrodes 203 in the zenith portion 202a are electrically connected to each other. The separated actuator plate 200 is aligned with the partition wall 102 and the partition wall 202, and the electrode 103 provided on the zenith portion 102 a of the partition wall 102 is arranged. The ink jet head in which the ink chamber 300 formed of the groove 101 and the groove 201 is formed by joining the portion 103a and the end portion 203a of the electrode 203 provided at the zenith portion 202a of the partition wall 202 so as to be electrically connected. Are listed.

  This ink jet head comprises both drive walls (partition walls 102 and 202) disposed on the left and right sides of the ink liquid chamber 300 and drive electrodes (electrodes 103 and 203) on the side surfaces thereof by joining the partition walls 102 and 202 together. Therefore, when a driving voltage is applied to each driving electrode, the entire driving wall can be shear-deformed in a U-shape so that a high pressure can be applied to the ink in the ink liquid chamber 300, and sufficient ink can be obtained with a low driving voltage. It has the advantage that the discharge speed can be obtained.

Further, since the electrodes 103 and 203 are formed over the zenith portions 102a and 202a of the partition walls 102 and 202, respectively, the electrodes 103 and 203 are located at the zenith portions 102a and 202a of the electrodes 103 and 203 when the partition walls 102 and 202 are joined to each other. The electrical connection between the electrodes 103 and 203 can be ensured using the ends 103a and 203a.
JP-A-8-276580 JP-A-3-150348

  In the case of such an ink jet head, the separation distance L1 between the end portions 103a and 203a of the electrodes 103 and 203 provided on the zenith portions 102a and 202a is shorter than the width L2 of the partition walls 102 and 202. For this reason, the capacitance of the drive wall in the vicinity of the end portions 103a and 203a of the electrodes 103 and 203 is increased, and the deformation speed of the drive wall when the drive voltage is applied to each of the electrodes 103 and 203 is reduced. There was a problem that the ink discharge speed could not be obtained.

  In addition, in order to obtain the desired ink discharge speed, it is necessary to further increase the drive voltage, and there is a problem that the power consumption increases accordingly.

  Furthermore, if the area of the end portions 103a and 203a of the electrodes 103 and 203 is increased in order to increase the reliability of the electrical connection between the electrodes 103 and 203, the separation distance L1 is further shortened, so that the capacitance is further increased. turn into.

  Therefore, it has been difficult to ensure the reliability of the electrical connection of the electrodes between the actuator plates and at the same time reduce the capacitance of the drive wall.

  Therefore, an object of the present invention is to provide an ink jet head that can ensure the reliability of electrical connection of electrodes between actuator plates and can reduce the capacitance of a drive wall.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

According to the first aspect of the present invention, a plurality of first grooves and a plurality of first partition walls are juxtaposed, and at least a part of the first partition walls is made of a piezoelectric material, and the plurality of first grooves A first actuator plate in which a first electrode is formed from a side surface of the partition wall to the zenith portion, and ends of the first electrodes adjacent to each other at the zenith portion are electrically separated from each other; A plurality of second grooves corresponding to the first groove and a plurality of second partitions corresponding to the first partition are arranged in parallel, and at least a part of the second partition is made of a piezoelectric material. In addition, a second electrode is formed on the plurality of second partition walls from the side surface to the zenith portion, and ends of the second electrodes adjacent to each other at the zenith portion are electrically separated from each other. A second actuator plate, and the first actuator plate The first partition of the first partition and the second partition of the second actuator plate are aligned, and the end of the first electrode provided at the zenith of the first partition and the second In the inkjet head formed so as to be electrically connected to the end portion of the second electrode provided at the zenith portion of the partition wall, the zenith portion of the first partition wall in the first actuator plate; SiO ₂ or Al ₂ having a relative permittivity smaller than that of the piezoelectric material used for the first partition and the second partition, respectively, at the top of the second partition in the second actuator plate. The inkjet head is provided with a coating layer made of O ₃ , and an end portion of the first electrode and an end portion of the second electrode are provided on the upper surface of the coating layer.

  The invention according to claim 2 is the ink jet head according to claim 1, wherein the coating layer has a thickness of 100 mm or more.

  The invention according to claim 3 is the ink jet head according to claim 1 or 2, wherein the coating layer has a relative dielectric constant of 20 or less.

A fourth aspect of the invention is the ink jet head according to the first , second, or third aspect, wherein the first partition and the second partition have the same height.

Invention of claim 5, wherein the first actuator plate and the second actuator plate, claim 1-4, characterized in that it is joined by an adhesive containing conductive particles It is an inkjet head as described in above.

  ADVANTAGE OF THE INVENTION According to this invention, while ensuring the reliability of the electrical connection of the electrode between actuator plates, the inkjet head which can reduce the electrostatic capacitance of a drive wall can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view showing a head chip structure of an ink jet head according to the present invention, and FIG. 2 is a partial enlarged cross-sectional view of a joining portion of partition walls.

  In FIG. 1, 1 is a head chip, 10 and 20 are actuator plates, respectively.

  The actuator plates 10 and 20 are each made of a piezoelectric material. As the piezoelectric material, a known piezoelectric material that deforms when an electric field is applied can be used. Among them, lead zirconate titanate (trade name: PZT) has a large packing density, a large piezoelectric constant, and a workability. Is preferable. After firing, PZT suddenly changes its crystal structure when the temperature is lowered, and becomes a collection of fine crystals in the form of dipoles in which atoms are displaced, one side is positive, and the other side is negative. Such spontaneous polarization is random in direction and cancels the polarities of each other, so further polarization processing is required. The arrow in the figure indicates the polarization direction. The polarization treatment is performed by sandwiching a PZT thin plate between electrodes and immersing it in silicon oil and applying a high electric field of about 10 to 35 kv / cm.

  One actuator plate 10 (first actuator plate) has a plurality of grooves 11 (first grooves) and a plurality of partition walls 12 (first partition walls) separating the grooves 11. Each groove 11 and each partition 12 are arranged in parallel with each other.

  The zenith part 12a of the partition wall 12 is provided with a coating layer 13 made of an insulating material having a relative dielectric constant smaller than that of the piezoelectric material used for the partition wall 12, respectively.

  Further, an electrode 14 (first electrode) for applying a driving voltage is formed in close contact with the inner surface of the groove 11, that is, the side surface of the partition wall 12 and the bottom surface of each groove 11. These electrodes 14 are further formed over the upper surface of the coating layer 13 provided on the top 12 a of the partition wall 12 continuously from the side surface of the partition wall 12, but adjacent electrodes 14 on the upper surface of the coating layer 13. The end portions 14a, 14a are electrically separated from each other.

  The other actuator plate 20 (second actuator plate) has a plurality of grooves 21 (second grooves) and a plurality of partition walls 22 (second partition walls) separating the grooves 21. Each groove 21 and each partition wall 22 are arranged in parallel with each other.

  The zenith part 22a of the partition wall 22 is provided with a coating layer 23 made of an insulating material having a relative dielectric constant smaller than that of the piezoelectric material used for the partition wall 22, respectively.

  On the inner surface of the groove 21, that is, on the side surface of the partition wall 22 and the bottom surface of the groove 21, an electrode 24 (second electrode) for applying a drive voltage is formed in close contact with each other. These electrodes 24 are further formed over the upper surface of the coating layer 23 provided on the zenith portion 22a of the partition wall 22 from the side surface of the partition wall 22, but are adjacent to each other on the upper surface of the coating layer 24. The end portions 24a, 24a are electrically separated from each other.

  The actuator plates 10 and 20 are aligned so that the partition walls 12 and 22 are aligned, and are overlapped so that the end portions 14a and 24a of the electrodes 14 and 24 are electrically connected to each other, and are joined by an adhesive. The drive walls are constituted by the joined partition walls 12 and 22, the drive electrodes are constituted by the joined electrodes 14 and 24, and the space formed by the grooves 11 and 21 sandwiched between the two drive walls is the ink liquid chamber 30. It becomes.

  The height h1 of the partition wall 12 of the actuator plate 10 is preferably equal to the height h2 of the partition wall 22 of the actuator plate 20, and the thickness of the coating layer 13 of the actuator plate 10 and the thickness of the coating layer 23 of the actuator plate 20 are the same. Are preferably equal. Since the displacement amounts of the partition walls 12 and 22 are the same, the driving efficiency can be improved, and the actuator plates having the same structure can be used for the actuator plates 10 and 20, so that only one type of actuator plate can be used. Manufacturing costs are low.

  The heights h1 and h2 of the partition walls 12 and 22 are heights including the covering layers 13 and 23.

  An example of the manufacturing method of the inkjet head which has such a head chip 1 is shown in FIGS.

  First, a polarization-treated piezoelectric material substrate 40 is prepared, and a coating layer 41 is formed on its surface by a sputtering method or the like with an insulating material (FIG. 3A).

  Next, a narrow dry film 42 is formed on the surface of the coating layer 41 in a pattern corresponding to the top of the partition wall in parallel (FIG. 3B). The patterning of the dry film 42 can be performed through known exposure and development processes. Depending on the width of each dry film 42, as shown in FIG. 2, for example, the distance L between the end portions 14 a and 14 a of the adjacent electrodes 14 and 14 on the upper surface of the coating layer 13 is determined.

  After the dry film 42 is formed by patterning, the gap between the adjacent dry films 42 and 42 is ground at a depth from the surface of the coating layer 41 to the middle part of the piezoelectric material substrate 40 using a rotary grinding tool such as a dicing blade. Thus, the plurality of grooves 43 are formed in parallel. The groove 43 is formed in a straight shape by grinding at the same depth from one end to the other end of the piezoelectric material substrate 40. As a result, the portion of the piezoelectric material substrate 40 left uncut becomes the partition wall 44, and its height is determined by the grinding depth of the groove 43 (FIG. 3C). This partition 44 becomes a partition of the actuator plate.

  After the grooves 43 are formed, a metal film 45 serving as an electrode is formed on the entire inner surface of each groove 43 and the upper surface of the coating layer 41 on the upper surface of each partition wall 44 (FIG. 3D).

  The metal for forming this electrode is preferably gold, aluminum, nickel, chromium, tantalum, titanium or the like from the viewpoints of electrical characteristics, corrosion resistance, and workability. The metal film 45 for forming the electrode can be formed by using such a metal by vapor deposition, sputtering, plating, or the like. Of these, the plating method is preferable in that an electrode having no pinhole can be formed. As the plating method, electroless plating is preferable. Moreover, although thickness is not specifically limited, Generally it can be 0.5-5 micrometers.

  After the metal film 45 is formed, the dry film 42 is removed, so that a part of the metal film 45 formed on the upper surface of the coating layer 41 is removed together with the dry film 42, and the adjacent metal film on the upper surface of the coating layer 41 is removed. 45 are separated from each other (FIG. 3E). Each of the metal coatings 45 becomes an electrode of the actuator plate.

  After the two grooved substrates 40A and 40B having the same structure are formed in this way, the other substrate 40B is repeated above one substrate 40A, and the partitions 44 and 44 of each substrate 40A and 40B are aligned with each other. Then, the end portions of the metal coating 45 provided on the zenith portions are overlapped so as to be electrically connected to each other and joined by an adhesive (FIG. 4). By repeatedly overlapping the other substrate 40B, the polarization directions of the substrates 40A and 40B are opposite to each other.

  As the adhesive, in order to improve the reliability of electrical connection of the metal coating 45, it is preferable to use an adhesive containing conductive particles.

  The inside of the grooves 43 and 43 formed by joining the substrates 40A and 40B is an ink liquid chamber.

  After joining the substrates 40A, 40B, a plurality of head chips 1, 1,... Are created by full cutting along a plurality of cutting lines C1, C2,... Along the direction orthogonal to the length direction of each groove 43. (FIG. 5). Thereby, the head chip 1 having the structure shown in FIG. 1 is obtained. The head chip 1 is arranged so that the ink outlet and the ink inlet of each ink liquid chamber 30 are opposed to the front and rear surfaces of the head chip 1, and becomes a straight ink liquid chamber 30 from the ink inlet to the ink outlet. It becomes a harmonica type head chip.

  Thereafter, the nozzle plate 2 on which the nozzles 2 a communicating with the respective ink liquid chambers 30 are joined to the front surface of the obtained head chip 1 and the rear surface of the head chip 1 is common to the respective ink liquid chambers 30. An ink jet head is formed by joining ink manifolds 3 for forming ink supply chambers for supplying ink (FIG. 6).

  According to the inkjet head, since the top portions 12a and 22a of the partition walls 12 and 22 have the coating layers 13 and 23 having a relative dielectric constant smaller than that of the piezoelectric material of the partition walls 12 and 22, Even if the end portions 14a and 24a of the electrodes 14 and 24 are provided on the upper surfaces of the covering layers 13 and 23, the capacitance on the zenith portions 12a and 22a side of the partition walls 12 and 22 can be reduced. Therefore, the loss of drive energy can be reduced, and the problem that the displacement speed of the drive wall decreases is solved.

  Thereby, when the same drive voltage as the conventional one is applied, the displacement speed of the drive wall can be increased, and the ink discharge speed can be improved.

  In addition, since the capacitance on the zenith portions 12a and 22a side of the partition walls 12 and 22 is small, the separation distance L between the end portions 14a and 24a of the electrodes 14 and 24 can be further shortened. As a result, the areas of the end portions 14a and 24a of the electrodes 14 and 24 can be increased, and the reliability of electrical connection can be further improved accordingly.

  The insulating material constituting the covering layers 13 and 23 may be an insulating material having a relative dielectric constant smaller than that of the piezoelectric material used for the partition walls 12 and 22, but driving energy by driving voltage is driven. It is preferable that the relative permittivity is 20 or less because it can be converted into wall displacement without waste.

Specific examples of the insulating material include SiO ₂ , Si ₃ N ₄ , and Al ₂ O ₃ . Since these have a low relative dielectric constant and good adhesion to the electrodes 14 and 24, they can be suitably used in the present invention.

  The thickness of the covering layers 13 and 23 is preferably 100 mm or more because there is no increase in capacitance even when the electrode separation distance L is short, and the object of the present invention can be suitably achieved.

  Although the upper limit value of the thickness of the coating layers 13 and 23 can be determined as appropriate depending on the relationship with the height of the partition walls 12 and 22, it is 1/50 or less of the heights h1 and h2 of the partition walls 12 and 22 shown in FIG. It is preferable that The heights h1 and h2 of the partition walls 12 and 22 are the heights including the covering layers 13 and 23. When the thickness of the covering layers 13 and 23 exceeds 1/50 of the heights h1 and h2 of the partition walls 12 and 22, the effect of reducing the loss of driving energy is not improved beyond a certain level. The ratio of the covering layers 13 and 23 occupying the entire wall increases, which may affect the displacement of the drive wall itself.

  The covering layers 13 and 23 are not limited to being formed on the entire surfaces of the zenith portions 12a and 22a of the partition walls 12 and 22, but may be provided on a part of the zenith portions 12a and 22a of the partition walls 12 and 22. In this case, as shown in FIG. 7, the covering layers 13 and 23 are provided at least at portions corresponding to the lower surfaces of the end portions 14 a and 24 a of the electrodes 14 and 24 in the zenith portions 12 a and 22 a of the partition walls 12 and 22. Is preferred.

  In the above description, the head chip 1 is exemplified as a so-called harmonica type, but is not limited to this. For example, as shown in FIG. 8, from one end of each actuator plate 10, 20 to the front of the other end. A so-called chopper traverse type head chip 1 may be used in which grooves are ground using a rotary grinding tool such as a dicing blade. In this case, the ink supply hole 4 can be formed so as to penetrate the bottom surface of each groove of one actuator plate 20, and ink can be supplied from the ink manifold 3 to each ink liquid chamber 30.

  The actuator plates 10 and 20 are all formed of a piezoelectric material substrate that is polarized. However, the polarized piezoelectric material may be at least part of the partition walls 12 and 22.

  Hereinafter, the effect of the present invention will be illustrated by examples.

A surface of a polarized 720 μm thick PZT substrate (relative permittivity = 3000) is coated with SiO ₂ (relative permittivity = 4) by sputtering to form a cover layer having a thickness of 1 μm. On the surface of the coating layer, a substrate was prepared by forming a narrow dry film in a portion corresponding to the top of the partition wall and patterning them in parallel so that the electrode separation distance was adjusted as shown in Table 1. Thereafter, from the surface, using a dicing blade, 256 grooves having a width of 85 μm and a depth of 310 μm and a partition wall having a width of 56 μm are paralleled from one end to the other end of the substrate. It was installed side by side.

  After that, an electrode having a thickness of 2 μm made of aluminum was formed by electroless plating over the inner surface of each groove and the upper surface of the dry film, and the dry film was removed to separate the adjacent electrodes on the upper surface of the partition wall. .

  After the substrates formed in the same manner were aligned with the partition walls and joined with an adhesive containing conductive particles (Epotech 353ND manufactured by Epoxy Technology Co., Ltd.) so that the electrodes were electrically connected to each other, A harmonica type head chip No. 1 is cut in a full cut along a direction perpendicular to the length direction of the groove and the length of the ink chamber becomes 2.5 mm. 1-4 were produced.

  On the other hand, a substrate with the electrode separation distance adjusted as shown in Table 1 was prepared in the same manner as in the above example except that the coating layer was not provided. 5-8 were produced.

  The capacitance of the partition walls of each head chip was measured using an LCR meter (“3522 LCR HiTESTER” manufactured by HIOKI). The measurement results are shown as a ratio (%) of change in capacitance when the capacitance (400 pF) of the head chip (No. 1, No. 5) on which no electrode is formed up to the upper surface of the partition is 100.

  The results are shown in Table 1 and FIG.

  In the absence of a coating layer, the capacitance increases in proportion to the electrode separation distance becoming narrower, whereas by providing the coating layer, the capacitance is reduced even if the electrode separation distance is reduced. The effect of the present invention was demonstrated without increasing.

1 is a partial cross-sectional view showing a head chip structure of an inkjet head according to the present invention. Partial enlarged sectional view showing the junction of the partition walls (A)-(e) is a figure which shows an example of the manufacturing method of an inkjet head A figure showing an example of a manufacturing method of an inkjet head A figure showing an example of a manufacturing method of an inkjet head A figure showing an example of a manufacturing method of an inkjet head Partial expanded sectional view which shows the other aspect of a coating layer Sectional drawing which shows the other aspect of an inkjet head Graph showing the relationship between electrode distance and capacitance Partial sectional view showing a head chip structure of a conventional inkjet head

Explanation of symbols

1: Head chip 10, 20: Actuator plate 11, 21: Groove 12, 22: Partition 12a, 22a: Zenith part 13, 23: Cover layer 14, 24: Electrode 14a, 24a: End part of electrode 30: Ink liquid chamber

Claims (5)

A plurality of first grooves and a plurality of first partition walls are juxtaposed, at least a part of the first partition wall is made of a piezoelectric material, and from the side surface of the plurality of first partition walls to the zenith portion A first electrode is formed over the first electrode plate, and the ends of the first electrodes adjacent to each other at the zenith portion correspond to the first groove and the first groove. A plurality of second grooves and a plurality of second partition walls corresponding to the first partition walls are arranged side by side, and at least a part of the second partition walls is made of a piezoelectric material, and the plurality of second partition walls. A second actuator plate in which a second electrode is formed on the partition wall from the side surface to the zenith portion, and ends of the second electrodes adjacent to each other at the zenith portion are electrically separated from each other And the first partition wall of the first actuator plate; The second partition of the second actuator plate is aligned with the second partition, and is provided at the end of the first electrode provided at the top of the first partition and at the top of the second partition. In the inkjet head formed by joining so as to be electrically connected to the end of the second electrode,
Piezoelectric materials used for the first partition and the second partition, respectively, at the zenith of the first partition in the first actuator plate and the zenith of the second partition in the second actuator plate, respectively. A coating layer made of SiO ₂ or Al ₂ O ₃ having a relative dielectric constant smaller than the relative dielectric constant is provided, and the end portions of the first electrode and the second electrode are formed on the upper surface of the coating layer. An ink jet head, wherein each is provided.   The inkjet head according to claim 1, wherein the coating layer has a thickness of 100 mm or more.   The inkjet head according to claim 1, wherein the coating layer has a relative dielectric constant of 20 or less. The inkjet head according to claim 1 , wherein the first partition and the second partition have the same height. Wherein the first actuator plate and the second actuator plate, the ink-jet head according to any one of claims 1 to 4, characterized in that it is joined by an adhesive containing conductive particles.

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