JP2004349688A - Ceramic substrate, piezo-electric actuator substrate, piezo-electric actuator, and manufacturing method for them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic substrate capable of preventing the occurrence of warp or waviness even when it is thin, and being manufactured at a low baking temperature, a piezo-electric actuator substrate and a piezo-electric actuator having stable piezo-electric characteristics, and manufacturing method for them. <P>SOLUTION: The piezo-electric actuator substrate 17 is obtained by baking a laminated body 17 wherein a plurality of green sheets 12, 13, 14, with ceramic raw material powders as main components are laminated to a thickness of not more than 100 μm. In the laminated body 17, higher contraction layers 15, 16, with electrically conductive materials as main components having an average particle diameter of not more than 2 μm, have contraction factors larger than those of the green sheets 12, 13, 14 in the direction parallel to the surface upon baking. The higher contraction layers 15, 16 are laminated with the green sheets 12, 13, 14 so that, in the cross-section in the thickness direction of the laminated body 17, the layers 15, 16 are disposed to be symmetric about a line passing through a middle point of the thickness of the laminated body 17 and parallel to the surface of the laminated body 17. The piezo-electric actuator 11 is obtained by forming individual electrodes 18 on one surface of the piezo-electric actuator substrate 17. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a ceramic substrate suitably used in the electronics industry, a piezoelectric actuator substrate and a piezoelectric actuator used for positioning or pressing various devices by generating a minute displacement, and particularly used for an ink jet recording head. And a method for producing them.

  In general, a ceramic substrate obtained by firing a laminate obtained by laminating a plurality of green sheets mainly composed of ceramic raw material powder is used for an electronic component substrate or the like. In particular, in recent years, with the spread of personal computers and the development of multimedia, the use of an ink jet printer as a recording device for outputting information to a recording medium has been rapidly expanding, and the printer is mounted on an ink jet recording head of such a printer. Ceramic substrates are also widely used for piezoelectric actuators. The piezoelectric type ink jet recording head using the piezoelectric actuator is excellent in that the head can be easily reduced in size and thickness and high-precision printing can be performed.

  FIG. 5 is a sectional view showing an ink jet recording head provided with a conventional piezoelectric actuator. As shown in FIG. 5, in this ink jet recording head, a plurality of ink flow paths 33a are arranged in parallel, and a piezoelectric actuator 34 is provided on a flow path member 33 in which a partition wall 33b is formed as a wall separating each ink flow path 33a. It has an attached structure (see Patent Document 1).

  The piezoelectric actuator 34 is formed by laminating a piezoelectric ceramic layer 35 on a conductive common electrode 36 also serving as a vibration plate to form a piezoelectric actuator substrate 34a, and an individual electrode 37 is formed on one surface of the piezoelectric actuator substrate 34a. Are arranged in a plurality. In the piezoelectric actuator 34, a plurality of piezoelectric displacement portions 38 are formed by the individual electrodes 37, the piezoelectric ceramic layer 35 immediately below the individual electrodes 37, and the common electrode 36. Further, the piezoelectric actuator 34 is mounted on the flow path member 33 such that the individual electrode 37 is located on the ink flow path 33a.

  The ink jet recording head as described above applies a voltage between the common electrode 36 and a predetermined individual electrode 37 to displace the piezoelectric ceramic layer 35 immediately below the individual electrode 37, thereby causing the ink in the ink flow path 33a to be displaced. To discharge ink droplets from the ink discharge holes 33 c opened in the bottom surface of the flow path member 33.

  However, since the ceramic substrate such as the piezoelectric actuator substrate 34a is manufactured by sintering and densifying the ceramic raw material powder during firing, the size of the ceramic substrate after firing is smaller than the size of the green sheet before firing. Shrinks and shrinks. With the shrinkage during firing, the ceramic substrate may be warped or undulated.

  Therefore, Patent Document 2 discloses a ceramic in which two or more types of insulating ceramic substrate compositions having different sintering temperatures are laminated in layers so that the firing shrinkage in the surface direction is smaller than the firing shrinkage in the thickness direction. A green sheet for a substrate and a ceramic substrate obtained by firing the green sheet have been proposed. According to Patent Literature 2, it is described that a ceramic substrate with less undulation can be provided.

However, in the ceramic substrate described in Patent Literature 2, when the thickness of the laminate is as thin as 100 μm or less, the effect of suppressing warpage and undulation is not sufficient, and warpage and undulation are significantly generated due to a difference in firing shrinkage. Was a problem. In general, when a ceramic substrate is manufactured, it is necessary to fire at a very high temperature. Therefore, it is required to lower the firing temperature from the viewpoint of cost and the like.
Japanese Patent Application Laid-Open No. 11-34321 JP-A-6-172017

  A main object of the present invention is to provide a ceramic substrate and a method of manufacturing the same, which can be manufactured at a low firing temperature while suppressing warpage and undulation even when the substrate is thin.

  It is another object of the present invention to provide a piezoelectric actuator substrate, a piezoelectric actuator, and a method of manufacturing the same, which are thin and suppress generation of warpage and undulation and have stable piezoelectric characteristics.

The ceramic substrate of the present invention for solving the above problems has the following configuration.
(1) A ceramic substrate obtained by firing a laminate having a thickness of 100 μm or less in which a plurality of green sheets containing a ceramic raw material powder as a main component are laminated, wherein the laminate has a conductivity of an average particle size of 2 μm or less. A high-shrink layer having a substance as a main component and having a large shrinkage ratio in a direction parallel to the surface than the green sheet at the time of firing, in a cross section in the thickness direction of the laminate, a half of the thickness of the laminate. A ceramic substrate, wherein the ceramic substrate is stacked on the green sheet so as to be line-symmetric with respect to a line passing through a position and parallel to a surface of the laminate.
(2) a plurality of the high shrinkage layers are arranged, a distance between the high shrinkage layers, a distance between an upper surface of the uppermost layer of the high shrinkage layer and an upper surface of the laminate, and the higher shrinkage of the lowermost layer; The ceramic substrate according to (1), wherein a distance between a lower surface of the layer and a lower surface of the laminate is 30 μm or less.
(3) The ceramic substrate according to (1) or (2), wherein the thickness of the high shrinkage layer is 0.5 to 5 μm.
(4) The ceramic substrate according to any one of (1) to (3), wherein the ceramic raw material powder is a piezoelectric ceramic raw material powder.
(5) The ceramic substrate according to any one of (1) to (4), wherein the high shrinkage layer is a conductor layer.

The above ceramic substrate is particularly suitable for a piezoelectric actuator substrate and a piezoelectric actuator. That is, the piezoelectric actuator substrate and the piezoelectric actuator of the present invention have the following configurations.
(6) In the ceramic substrate according to any one of (1) to (5), the ceramic raw material powder is a perovskite compound powder containing Pb, Zr, and Ti, and the high-shrink layer is a conductor layer containing Ag. A piezoelectric actuator substrate, characterized in that:
(7) The piezoelectric actuator substrate according to (6), wherein the conductor layer contains 80% by mass or more of Ag.
(8) A piezoelectric actuator, wherein an electrode is formed on one surface of the piezoelectric actuator substrate according to (6) or (7).
(9) The piezoelectric actuator according to (8), wherein a plurality of the electrodes are arranged on the surface.

A method for manufacturing a ceramic substrate, a piezoelectric actuator substrate, and a piezoelectric actuator according to the present invention includes the following configurations.
(10) A green sheet having a ceramic raw material powder as a main component, and a high-shrink layer having a large shrinkage ratio in a direction parallel to the surface than the green sheet during firing is laminated with the green sheet to form a laminate. A method for manufacturing a ceramic substrate, comprising forming and firing the laminate while accelerating firing shrinkage of the green sheet by firing shrinkage by the high shrinkage layer.
(11) A green sheet mainly composed of ceramic raw material powder, and a high-shrinkage layer having a large shrinkage ratio in a direction parallel to the surface than the green sheet during firing is laminated with the green sheet to form a laminate. Forming a green body, and firing the laminate at a temperature lower than the firing temperature of the green sheet alone.
(12) The method for producing a ceramic substrate according to (10) or (11), wherein the thickness of the laminate is 100 μm or less.
(13) The high shrinkage layer, in a cross section in the thickness direction of the laminate, passes through a position of １ ／ of the thickness of the laminate, and is symmetric with respect to a line parallel to the surface of the laminate. The method for producing a ceramic substrate according to any one of (10) to (12), wherein the ceramic substrate is arranged so as to be laminated with the green sheet.
(14) The method for producing a ceramic substrate according to any of (10) to (13), wherein a plurality of the high shrinkage layers are provided inside and / or on the surface of the laminate.
(15) The method for producing a ceramic substrate according to any one of (10) to (14), wherein the laminate includes a component having high volatility at a firing temperature of the green sheet alone.
(16) A method of manufacturing a ceramic substrate by firing a laminate having a thickness of 100 μm or less in which a plurality of green sheets mainly composed of ceramic raw material powders are laminated, wherein a conductive material having an average particle size of 2 μm or less is mainly used. And a high-shrinkage layer having a large shrinkage ratio in a direction parallel to the surface of the green sheet during firing, and passing through a position corresponding to a half of the thickness of the laminate in a cross section of the laminate in the thickness direction. Laminated with the green sheet so as to be line-symmetric with respect to a line parallel to the surface of the laminate, and sintering the laminate at a temperature lower than the firing temperature of the green sheet alone. Of manufacturing a ceramic substrate.
(17) The method for producing a ceramic substrate according to any one of (10) to (16), wherein the laminate is fired at a temperature of 1100 ° C. or lower.
(18) The method for producing a ceramic substrate according to any one of (10) to (17), wherein the laminate is fired at a temperature lower by at least 50 ° C. than a firing temperature of the green sheet alone.
(19) In the method for manufacturing a ceramic substrate according to any one of (10) to (18), the ceramic raw material powder is a perovskite compound powder containing Pb, Zr, and Ti, and the high shrinkage layer is made of Ag. A method of manufacturing a piezoelectric actuator substrate, comprising:
(20) The method for manufacturing a piezoelectric actuator substrate according to (19), wherein the oxygen concentration in the firing atmosphere at the time of firing the laminate is 90% or more.
(21) A method of manufacturing a piezoelectric actuator, further comprising forming an electrode on one surface of the piezoelectric actuator substrate in addition to the method of manufacturing a piezoelectric actuator substrate according to (19) or (20).

  According to the ceramic substrate according to the above (1), in the laminate, a conductive material having an average particle size of 2 μm or less as a main component, and a large shrinkage ratio in a direction parallel to the surface than the green sheet at the time of firing. By having the high shrinkage layer laminated on the green sheet, the driving force for firing the green sheet increases, and the sintering start temperature of the green sheet decreases. Thereby, the firing temperature of the laminate can be reduced. In the laminate, the high-shrinkage layer is line-symmetric with respect to a line that passes through a position that is a half of the thickness of the laminate and is parallel to a surface of the laminate in a cross section in a thickness direction of the laminate. By being arranged, the amount of shrinkage in the thickness direction of the laminate becomes uniform. Thereby, it is possible to prevent the ceramic substrate after firing from being warped or undulated.

  The average particle size of the conductive material is set to 2 μm or less, the thickness variation of the laminate can be reduced to 100 μm or less, and the thickness variation can be reduced. This is because sintering becomes easier and the firing temperature can be lowered. Further, it is supposed that the driving force for firing the green sheet is increased because the activation energy of the green sheet is increased by applying the shrinking force of the high shrinkage layer to the green sheet during firing.

  Further, in the ceramic substrate according to (2), the distance between the high-shrinkage layers, the distance between the upper surface of the uppermost high-shrinkage layer and the upper surface of the laminate, and the lower part of the lowermost high-shrinkage layer The distance between the lower surface and the lower surface of the laminate is 30 μm or less, respectively, and the rigidity is low.If there is a difference in the amount of shrinkage in the thickness direction of the laminate, warpage and undulation are affected by the difference. Although it is easy to cause, since the high shrinkage layer is arranged symmetrically in the thickness direction as described above, it is possible to suppress the occurrence of warpage and undulation.

  According to the ceramic substrate described in (3), since the thickness of the high shrinkage layer is within the above range, the effect of increasing the firing driving force of the green sheet can be sufficiently obtained, and the appropriate rigidity can be obtained. Therefore, when this ceramics substrate is applied to, for example, a piezoelectric actuator, the rigidity does not become excessively high, so that a large displacement can be obtained.

  As described in (4) and (5), in the ceramic substrate of the present invention, the ceramic raw material powder may be a piezoelectric ceramic raw material powder, and the high shrinkage layer may be a conductor layer. The ceramic substrate having such a configuration is suitable for a piezoelectric actuator substrate.

  In general, a piezoelectric actuator using a perovskite compound containing Pb as a raw material is obtained by firing at a temperature exceeding 1100 ° C. In this temperature range, the evaporation of Pb becomes remarkable, and the piezoelectric characteristics after firing deteriorate. Or variations occur in the piezoelectric characteristics. In particular, these problems become remarkable when the thickness of the laminate is as thin as 100 μm or less.

  On the other hand, according to the piezoelectric actuator substrate described in the above (6), the high shrinkage layer, which is a conductor layer containing a conductive substance having Ag as a main component and having an average particle diameter of 2 μm or less, contains the perovskite compound powder as a main component. The green sheet is stacked and disposed, whereby the driving force for firing the green sheet is increased, and the sintering start temperature of the green sheet is lowered. Thereby, since the firing temperature of the laminate can be lowered, the evaporation of Pb from the green sheet can be suppressed. For this reason, it is possible to obtain a piezoelectric actuator substrate having stable piezoelectric characteristics while suppressing a decrease or variation in the piezoelectric characteristics. Further, the high shrinkage layer is disposed so as to be line-symmetric with respect to a line that passes through a position equal to ２ of the thickness of the laminate and is parallel to the surface of the laminate in a cross section in the thickness direction of the laminate. Thereby, the amount of shrinkage in the thickness direction of the laminate becomes uniform. Thereby, it is possible to prevent the piezoelectric actuator substrate after firing from being warped or undulated. Further, in the piezoelectric actuator substrate, since the perovskite compound is used as a raw material, a large displacement can be obtained. Since the high shrinkage layer is a conductor containing Ag, the high shrinkage layer is also used as a common electrode. And the number of manufacturing steps can be reduced.

  According to the piezoelectric actuator substrate described in the above (7), since the conductor layer, which is the high shrinkage layer, contains 80% by mass or more of Ag, the volume diffusion of the piezoelectric body is promoted by the diffusion of Ag at the time of sintering. Since the contraction of the contraction layer is further promoted, the activation energy is further increased as described above, and the firing driving force is further increased. In addition, the cost can be reduced by increasing the ratio of Ag.

  The piezoelectric actuator according to the above (8) and (9) is obtained by forming an electrode on one surface of the piezoelectric actuator substrate. This piezoelectric actuator has a stable piezoelectric characteristic while suppressing warpage and undulation even if it is thin.

  According to the method for manufacturing a ceramic substrate according to (10), a high-shrink layer having a large shrinkage ratio in a direction parallel to the surface than the green sheet is laminated with the green sheet, and the green is shrunk by the high-shrink layer to reduce the green. Since the laminate is fired while accelerating the firing shrinkage of the sheet, the firing driving force of the green sheet can be increased, and the firing temperature of the green sheet can be lowered to lower the firing temperature of the laminate.

  In the method for manufacturing a ceramic substrate according to the above (11), a high-shrinkage layer having a large shrinkage ratio in a direction parallel to the surface than the green sheet is laminated with the green sheet to form a laminate, and the high shrinkage is performed. By lowering the sintering start temperature of the green sheet by the effect of the firing shrinkage of the layer, the sintering temperature of the laminate is lower than the sintering temperature of the green sheet alone. Thereby, the manufacturing cost of the ceramic substrate can be reduced.

  According to the method for manufacturing a ceramic substrate according to the above (12), since the thickness of the laminate is reduced to 100 μm or less, it becomes easier to shrink each green sheet by the action of firing shrinkage of the high shrinkage layer, firing temperature Can be further reduced in temperature. In particular, the smaller the thickness of each green sheet, the greater the shrinkage effect.

  According to the method for manufacturing a ceramic substrate according to the above (13), in the cross section in the thickness direction of the laminate, the high shrinkage layer passes through a position that is １ ／ of the thickness of the laminate and is parallel to the surface of the laminate. By being disposed so as to be line-symmetrical with respect to, the amount of shrinkage in the thickness direction of the laminate becomes uniform, so that occurrence of warpage and undulation in the fired ceramic substrate can be suppressed.

  As described in the above (14), by providing a plurality of high shrinkage layers, a large shrinkage force of the high shrinkage layer acting on the green sheet can be obtained, so that the laminate can be easily shrunk, and the firing temperature can be further lowered. Can be planned.

  As described in the above (15), even when the laminate contains a highly volatile component at the firing temperature of the green sheet alone, according to the production method of the present invention, the firing temperature of the laminate , The amount of highly volatile components that are easily evaporated can be reduced, and the composition can be easily controlled.

  According to the method for manufacturing a ceramic substrate according to (16) to (18), the sintering start temperature of the green sheet is reduced, and the firing temperature of the laminate can be reduced. In addition, the amount of shrinkage in the thickness direction of the laminate can be equalized, so that the ceramic substrate after firing can be prevented from warping or undulating. Thereby, a high-quality ceramic substrate can be obtained at low cost.

  According to the method for manufacturing a piezoelectric actuator substrate according to the above (19), the high-shrink layer, which is a conductor containing Ag, is disposed so as to be laminated with a green sheet containing a perovskite-type compound powder as a main component. , The firing temperature of the green sheet can be lowered to lower the firing temperature of the laminate. Thereby, it is possible to suppress evaporation of Pb from the green sheet, to suppress a decrease or variation in piezoelectric characteristics, to obtain a piezoelectric actuator substrate having stable piezoelectric characteristics, and to obtain a piezoelectric actuator substrate in the thickness direction of the laminate. Since the amount of shrinkage can be made uniform, it is possible to prevent the piezoelectric actuator substrate after firing from being warped or undulated. Thereby, a high quality piezoelectric actuator substrate can be obtained.

  According to the method for manufacturing a piezoelectric actuator substrate according to the above (20), the decomposition of PbO in the laminate at the time of firing can be suppressed by increasing the oxygen partial pressure in the firing atmosphere. Evaporation of Pb from the body can be further suppressed. Thus, a piezoelectric actuator substrate having more stable piezoelectric characteristics can be obtained.

  According to the method of manufacturing a piezoelectric actuator described in (21), a high-quality piezoelectric actuator having stable piezoelectric characteristics and suppressing occurrence of warpage and undulation can be obtained.

  Hereinafter, a piezoelectric actuator according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing the piezoelectric actuator of the present embodiment.

  As shown in FIG. 1, a piezoelectric actuator 11 has a ceramic actuator having a ceramic layer 12, 13, 14 and a high-shrinkage layer 15, 16 laminated and disposed between the ceramic layers. A plurality of individual electrodes 18 are arranged. The piezoelectric actuator 11 can generate piezoelectric vibration in the ceramic layer 12 immediately below the individual electrode 18 by applying a voltage between the individual electrode 18 and the high shrinkage layer 15 serving as a common electrode.

As the ceramic layer 12, for example, a piezoelectric ceramic raw material of a perovskite-type compound such as a lead zirconate titanate compound containing Pb, Zr and Ti (PbZrTiO ₃ -based compound (PZT-based)), a lead titanate compound, and a barium titanate compound Is preferably used. Among these, it is preferable to use a PZT system in that a large displacement can be obtained. The ceramic layers 13 and 14 are preferably made of the same material as the ceramic layer 12. The ceramic layers 12 are polarized in directions opposite to each other in the thickness direction.

  The high-shrink layers 15 and 16 are made of a conductor (conductive substance) made of Ag, Cu, Pd, Pt, Rh, Au, or Ni alone or in combination of two or more, preferably a conductor containing Ag, and more preferably Ag-. It is preferably formed of a Pd-based alloy. The high shrinkage layers 15 and 16 are preferably conductor layers containing 80% by mass or more of Ag, more preferably 90 to 95% by mass. Further, it is preferable that the high shrinkage layers 15 and 16 are formed of the same material. It is more preferable to use the same material as the ceramic layer 12 for the high shrinkage layers 15 and 16.

  As the individual electrode 18, a conductor made of Ag, Cu, Pd, Pt, Rh, Au-based material, Ni alone or a combination of two or more kinds is used, and high conductivity can be obtained even when the thickness is reduced. It is preferable to be formed of an Au-based material.

  Next, a method for manufacturing the piezoelectric actuator 11 of the present invention will be described. FIG. 2 is a cross-sectional view illustrating a manufacturing process of the piezoelectric actuator 11. First, a piezoelectric ceramic raw material powder containing the above-described lead zirconate titanate compound, lead titanate compound, barium titanate compound or the like as a main component is prepared. This ceramic raw material powder has an average particle size of 2 μm or less, preferably 0.7 μm or less, and more preferably 0.5 μm or less. By setting the average particle size of the ceramic raw material powder to 2 μm or less, uniform firing shrinkage during sintering can be obtained, so that uniform ceramic layers 12, 13 and 14 can be obtained by firing. The ceramic raw material powder and the organic binder component are mixed to prepare a slurry. Then, three green sheets that become the ceramic layers 12, 13, and 14 after firing are manufactured by using the slurry by a general sheet forming method such as a roll coater method, a slit coater method, and a doctor blade method (FIG. 2 (a): molding step). In FIG. 2, these green sheets are referred to as green sheets 12, 13, and 14, respectively, for convenience.

  Next, the green sheets 12, 13, and 14 obtained in the forming step are pressed (pressing step). Although a known method can be employed as the pressing method, a roll pressing method, a flat pressing method, a hydrostatic pressing method, and the like can be particularly used for pressing in that it is easy to obtain a uniform thickness. . As described above, by performing the pressing process on the green sheet after the sheet is formed, the density of the sheet can be increased, and the thickness variation and the density variation can be reduced. The pressing pressure varies depending on the material composition, the amount of the organic binder, the thickness of the green sheet and the like, but is preferably 10 to 100 MPa, particularly preferably 20 to 50 MPa, and more preferably 30 to 40 MPa.

  As described above, according to the present invention, the green sheets 12, 13, and 14 mainly composed of the ceramic raw material powder and the shrinkage greater in the direction parallel to the surface than the green sheets 12, 13, and 14 at the firing temperature. It is important to form the high-shrink layers 15 and 16 having a high modulus as a coating layer or a green sheet, form a laminate of these layers, and fire it. In firing, since the high shrinkage layers 15 and 16 shrink more than the green sheets 12, 13, and 14, the shrinkage of the green sheets 12, 13, and 14 is promoted, and the firing is performed at a temperature lower than the firing temperature of the green sheet alone. Can be fired.

The firing state in the present invention will be described with reference to the graph shown in FIG. FIG. 3 is a graph showing shrinkage curves of the green sheet and the high shrinkage layer. The shrinkage curve shown in FIG. 3 can be obtained by elevating the temperature of the powder compact to a specific temperature, holding the powder at the specific temperature for a certain period of time, cooling the powder, and measuring the sample size. As shown in FIG. 3, the shrinkage rate of the high shrinkage layer shown by the solid line is larger than that of the green sheet shown by the broken line. For example, shrinkage of the high shrinkage layer is constant at a temperature above T _1, shrinkage of the green sheet does not become constant until T _0. Therefore, in the case of a laminate that does not include a high shrinkage layer, it is necessary to set the firing temperature to T ₀ or higher. it can be sintered sheet temperature lower than T _0, for example, T _1.

  In order to obtain such a laminate, for example, it can be achieved by adjusting the density of the green compact or the powder compact of the high shrink layer. The density of the powder compact depends on the amount of the binder, the pressure applied during molding, the drying temperature, the drying time, and the like, and the production conditions thereof are adjusted. The setting of the firing temperature is determined in consideration of the shrinkage of the high shrinkage layer and the shrinkage of the green sheet, but is lower than the firing temperature of the laminate including the green sheet and not including the high shrinkage layer. It is preferable to fire at a temperature higher than the firing temperature.

Also, before reaching the firing temperature, the firing temperature lower temperatures than, for example, in FIG. 3, larger than the shrinkage starting temperature T ₃ of the high-shrink layer, a certain holding time at temperature T ₂ between shrinkage completion temperature T ₁ of This is a preferable treatment for stabilizing the shrinkage of the green sheet, that is, the shrinkage of the laminate. In particular, T ₂ is greater shrinkage near T ₁ high shrink layer, and is preferably set shrinkage of the green sheet is small temperature.

  The above-described shrinkage curve can be easily obtained in the case of a bulk body such as a green sheet or a laminate, but when the high shrinkage layer is formed of a coating layer or the like on the green sheet, the shrinkage of the coating layer alone. It can be difficult to get a curve. In that case, the shrinkage of the green sheet alone or the laminate not including the high shrink layer is measured, and the shrinkage of the laminate of the high shrink layer and the green sheet is measured. When it becomes larger, it can be determined that the coating layer (high shrinkage layer) has a larger shrinkage ratio than the green sheet.

  Next, one of the green sheets 13 and 14 that become the ceramic layer 13 and the ceramic layer 14 after firing among green sheets obtained in the pressing step using the conductor paste made of the above-described electrode material (conductive substance). A high shrinkage layer 15 and a high shrinkage layer 16 are formed on the surface of (FIG. 2 (b)). The average particle size of the electrode material in the conductive paste is preferably 2 μm or less.

  Next, the green sheets 12, 13, and 14 are laminated in the order shown in FIG. 2C and are brought into close contact with each other to obtain a laminate (lamination step). In FIG. 2, this laminate is referred to as a laminate 17 for convenience. Examples of the method of performing the adhesion include a method using an adhesion liquid containing an adhesive component, a method of applying adhesiveness to an organic binder component in a green sheet by heating, and a method of applying adhesion only by applying pressure. .

  In the present invention, the thickness Z of the laminate 17 is preferably 100 μm or less, more preferably 80 μm or less, and more preferably 50 μm or less, in that the displacement of the piezoelectric actuator 11 is increased. On the other hand, the lower limit of the thickness Z has a mechanical strength that does not break during handling or operation, and is preferably 20 μm or more, more preferably 25 μm or more, so as to withstand the applied voltage. More preferably, it is 30 μm or more.

  In the laminate 17, the high shrinkage layers 15, 16 are located on a line that passes through a position の of the thickness of the laminate 17 and is parallel to the surface of the laminate 17 in a cross section in the thickness direction of the laminate 17. The green sheets 12, 13, and 14 are stacked so as to be symmetrical. That is, the high shrinkage layers 15 and 16 are each separated by a distance t from a line that passes through a position that is の of the thickness of the laminate 17 and is parallel to the surface of the laminate 17 in a cross section in the thickness direction of the laminate 17. Is arranged.

  The distance between the high-shrinkage layers 15 and 16, the distance between the upper surface of the uppermost high-shrinkage layer 15 and the upper surface of the laminate 17, and the lower surface of the lowermost high-shrinkage layer 16 and the laminate The distance from the lower surface 17 (that is, the thickness of the green sheets 12, 13, 14) is not particularly limited, but is preferably 30 μm or less, since a large displacement can be obtained as a piezoelectric body. Preferably, the thickness is 10 to 30 μm. The thickness variation of each green sheet is preferably 15% or less, particularly preferably 10% or less. Thereby, the thickness variation of the ceramic layers 12, 13, and 14 formed after firing can be reduced, and warpage and undulation can be suppressed more reliably. Further, in order to obtain shrinkage at a lower temperature, the thickness of the green sheets 12, 13, 14 is preferably 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less. Further, in order to sufficiently exert the driving force of the high shrinkage layer, the thicknesses of the high shrinkage layers 15 and 16 and the green sheets 12, 13 and 14 may be approximately the same.

  The thickness of the high shrinkage layers 15 and 16 is 0.5 to 5 μm, preferably 1 to 2 μm. When the thickness of the high shrinkage layers 15 and 16 is less than 0.5 μm, the shrinkage force of the high shrinkage layers 15 and 16 decreases, and the effect of lowering the firing start temperature by increasing the firing driving force of the green sheets 12, 13 and 14. There is a possibility that it cannot be obtained sufficiently. On the other hand, if the thickness of the high shrinkage layers 15 and 16 exceeds 5 μm, the compliance (reciprocal of the Young's modulus) of the fired ceramic layers 12, 13 and 14 becomes small, and a sufficient displacement amount may not be obtained.

  The shrinkage ratios of the high shrinkage layers 15 and 16 are not particularly limited, and may be larger than those of the green sheets 12, 13 and 14. For example, the shrinkage of the perovskite-type compound is about 85% to 95%, so that the shrinkage of the high shrink layers 15 and 16 in this case may be less than 85%. The high-shrink layers 15 and 16 may be formed into green sheets, and then the green sheets (high-shrink layers 15 and 16) may be disposed on the surfaces of the green sheets 13 and 14, respectively. The present invention is not limited to this as long as the shrinkage ratio at the time is larger than that of the green sheets 12, 13, and 14, and may be a coating layer formed by printing or the like or another form. The shrinkage ratio can be measured by heating a sheet or a bulk body to be a high shrinkage layer and taking a curve of a heating temperature and a shrinkage amount at that time.

  Next, the laminate 17 obtained in the lamination step is degreased to remove organic components in the laminate 17, and then fired in an oxygen atmosphere. During firing of the laminate 17, the firing shrinkage of the green sheets 12, 13, 14 is accelerated by firing shrinkage by the high shrinkage layers 15, 16, so that the sintering start temperature of the green sheets 12, 13, 14 is lowered. The firing temperature of the laminate 17 can be reduced. The sintering temperature is lower than the sintering temperature of the green sheet alone, preferably 50 ° C. or lower, more preferably 70 to 100 ° C. lower. Specifically, when a perovskite-type compound containing Pb is used as a raw material, firing is generally performed at a temperature exceeding 1100 ° C., but in the present invention, firing can be performed at 1100 ° C. or lower. Thereby, even if the laminate 17 contains Pb, which is highly volatile at the firing temperature of the green sheet alone, the firing temperature of the laminate 17 can be lowered as described above. The amount of evaporation can be reduced, and the composition can be easily controlled. Thus, the piezoelectric actuator substrate 17 can be obtained (firing step). In this firing step, the oxygen concentration is set to 90% or more, preferably 95 to 99%.

  In the firing step of manufacturing the piezoelectric actuator substrate 17, the laminate obtained in the laminating step is stacked in a plurality of stages via a sample base plate made of zirconia or magnesia, and further stacked on the stacked body. It is desirable to bake with a weight. By doing so, the warpage of the piezoelectric actuator substrate 17 is further suppressed.

  Finally, an individual electrode 18 can be formed by printing a conductive paste on one surface of the piezoelectric actuator substrate 17 by screen printing, vapor deposition, or the like, and baking it at about 600 to 800 ° C. Thereby, the piezoelectric actuator 11 shown in FIG. 2D can be obtained. As described above, the method of obtaining the piezoelectric actuator substrate 17 by firing the laminated body 17 in a state of having symmetry is effective for preventing warpage and undulation at the time of firing.

  As described above, the embodiment of the present invention has been described. However, it is needless to say that the present invention is not limited to the above-described embodiment, and can be applied to a modified or improved one without departing from the gist of the present invention.

  For example, in the above embodiment, the case where two layers of the high shrinkage layer are provided in the laminate has been described, but one layer or three or more layers may be provided. However, also in these cases, the high shrinkage layer needs to be arranged at the above-mentioned line-symmetric position in the laminate.

  Further, in the above embodiment, the piezoelectric actuator substrate has been described as an example, but the present invention can be similarly applied to various ceramic substrates suitably used in the electronics industry.

[Example 1]
First, as a ceramic raw material, a slurry prepared by mixing a lead zirconate titanate compound powder having an average particle diameter (D50) of 0.5 μm, an organic solvent, an organic binder, and a surfactant is prepared. A green sheet having a thickness of 20 μm was formed by a method. Next, the shrinkage ratio of the conductive paste alone was measured in advance, and an organic binder and an organic solvent were adjusted so that the shrinkage ratio was larger than that of the green sheet. Ag-Pd (Ag: Pd = 80: A high-shrink layer having a thickness of 5 μm was formed on one surface of two green sheets of the green sheet by a screen printing method using the conductive paste of 20). Next, the green sheet on which the high shrinkage layer was not formed was placed on the upper layer, and the green sheet on which the high shrinkage layer was formed was placed on the middle layer and the lower layer, and laminated. Next, the laminated body was subjected to a degreasing treatment at 600 ° C. for 3 hours in the air, and then baked at a temperature of 1100 ° C. for 2 hours in an atmosphere having an oxygen concentration of 95% to obtain a piezoelectric actuator substrate.

  A piezoelectric actuator was obtained by forming 10 conductor patterns on one surface of the obtained piezoelectric actuator substrate by vapor deposition. For this piezoelectric actuator, the capacitance at each point was measured using a capacitance measuring device (LCR meter), and the conductor pattern area and the piezoelectric material thickness were measured using an image recognition length measuring device. The relative permittivity was calculated from.

  As a result, the average value of the relative dielectric constants at 10 points was 2030, the maximum value was 2110, the minimum value was 1940, and the variation in the relative dielectric constant was within ± 5%. In addition, the amount of warpage of the piezoelectric actuator substrate was measured using a non-contact laser three-dimensional shape measuring instrument. As a result, the amount of warpage was as small as 16 μm. Here, the amount of warpage indicates a difference between the maximum height and the minimum height in the substrate plane with respect to the reference plane.

[Example 2]
First, as a ceramic raw material, a slurry prepared by mixing a lead zirconate titanate compound powder having an average particle diameter (D50) of 0.5 μm, an organic solvent, an organic binder, and a surfactant is prepared. It was formed into a green sheet having a thickness of 15 μm by the method. Next, using a slurry made of Ag-Pd (Ag: Pd = 80: 20) having an average particle diameter of 1 μm, a high-shrink sheet having a thickness of 5 μm was similarly formed by a roll coater method. The shrinkage curve of the high shrinkage sheet was measured, and it was confirmed that the high shrinkage sheet had a larger shrinkage ratio than the green sheet. Then, as shown in FIG. 4, four high-shrink layers (high-shrink sheets) 21 and five green sheets 22 were laminated, and pressed and adhered to obtain a laminate. Next, the laminated body was subjected to a degreasing treatment at 600 ° C. for 3 hours in the air, and then baked at a temperature of 1100 ° C. for 2 hours in an atmosphere having an oxygen concentration of 95% to obtain a piezoelectric actuator substrate.

  The obtained piezoelectric actuator substrate was evaluated in the same manner as in Example 1. As a result, the average value of the relative permittivity at 10 points was 2075, the maximum value was 2167, the minimum value was 1980, and the variation of the relative permittivity was within ± 5%. In addition, the amount of warpage of the piezoelectric actuator substrate was measured using a non-contact laser three-dimensional shape measuring instrument. As a result, the amount of warpage was as small as 21 μm.

[Comparative Example 1]
A piezoelectric actuator substrate was prepared in the same manner as in Example 1 except that a high shrinkage layer was not formed on the surface of the green sheet and the sintering temperature was 1200 ° C., and vapor deposition was performed on one surface of the obtained piezoelectric actuator substrate. Thus, a piezoelectric actuator was obtained by forming 10 conductor patterns and forming a high shrinkage layer on the other surface. The relative permittivity and the amount of warpage of this piezoelectric actuator were measured in the same manner as in the example.

  As a result, the average value of the relative permittivity at 10 points was 1880, the maximum value was 2090, the minimum value was 1740, and the variation of the relative permittivity was ± 10% or more. The amount of warpage was as small as 16 μm.

[Comparative Example 2]
A high-shrinkage layer was formed only on one green sheet, a green sheet having no high-shrinkage layer was arranged on the upper and lower layers, and a green sheet having the high-shrinkage layer was arranged on the middle layer. A piezoelectric actuator was manufactured in the same manner as in Example 1, and the relative permittivity and the amount of warpage were measured.

  As a result, the average value of the relative dielectric constants at 10 points was 1990, the maximum value was 2070, the minimum value was 1900, and the variation in the relative dielectric constant was within ± 5%. The warpage was as large as 100 μm or more.

  As described above, in the piezoelectric actuators of Examples 1 and 2, it was found that the dispersion of the piezoelectric characteristics was small and the warpage and undulation were also small.

FIG. 1 is a cross-sectional view illustrating a piezoelectric actuator according to one embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a manufacturing process of the piezoelectric actuator of FIG. 1. It is a graph which shows a contraction curve of a green sheet and a high contraction layer. FIG. 9 is a cross-sectional view illustrating a configuration of a laminate manufactured in Example 2. FIG. 11 is a cross-sectional view illustrating an inkjet recording head including a conventional piezoelectric actuator.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 11 Piezoelectric actuator 12, 13, 14 Ceramic layer 15, 16 High shrinkage layer 17 Piezoelectric actuator board 18 Individual electrode

Claims (21)

  A ceramic substrate obtained by firing a laminate having a thickness of 100 μm or less in which a plurality of green sheets mainly composed of ceramic raw material powder are laminated, wherein the laminate mainly includes a conductive material having an average particle size of 2 μm or less. As a component, the high shrinkage layer having a larger shrinkage ratio in a direction parallel to the surface than the green sheet at the time of firing passes through a position corresponding to a half of the thickness of the laminate in a cross section in the thickness direction of the laminate. A ceramic substrate, wherein the ceramic substrate is disposed so as to be line-symmetric with respect to a line parallel to a surface of the laminate, with the green sheet being laminated.   A plurality of the high shrinkage layers are arranged, a distance between the high shrinkage layers, a distance between an upper surface of the uppermost layer of the high shrinkage layer and an upper surface of the laminate, and a lower side of the lowermost high shrinkage layer. 2. The ceramic substrate according to claim 1, wherein a distance between the first surface and the lower surface of the laminate is 30 μm or less.   The ceramic substrate according to claim 1, wherein the thickness of the high shrinkage layer is 0.5 to 5 μm.   The ceramic substrate according to any one of claims 1 to 3, wherein the ceramic raw material powder is a piezoelectric ceramic raw material powder.   The ceramic substrate according to claim 1, wherein the high shrinkage layer is a conductor layer.   6. The ceramic substrate according to claim 1, wherein the ceramic raw material powder is a perovskite compound powder containing Pb, Zr, and Ti, and the high shrinkage layer is a conductor layer containing Ag. Piezoelectric actuator substrate.   7. The piezoelectric actuator substrate according to claim 6, wherein the conductor layer contains 80% by mass or more of Ag.   8. A piezoelectric actuator, wherein an electrode is formed on one surface of the piezoelectric actuator substrate according to claim 6.   9. The piezoelectric actuator according to claim 8, wherein a plurality of the electrodes are arranged on the surface.   A green sheet containing a ceramic raw material powder as a main component, and a high-shrink layer having a large shrinkage ratio in a direction parallel to the surface than the green sheet during firing is laminated with the green sheet to form a laminate, A method for manufacturing a ceramic substrate, comprising firing the laminate while accelerating firing shrinkage of the green sheet by firing shrinkage by the high shrinkage layer.   A green sheet containing a ceramic raw material powder as a main component, and a high-shrink layer having a large shrinkage ratio in a direction parallel to the surface than the green sheet during firing is laminated with the green sheet to form a laminate, A method for manufacturing a ceramic substrate, comprising firing the laminate at a temperature lower than the firing temperature of the green sheet alone.   The method according to claim 10, wherein the thickness of the laminate is 100 μm or less.   The green is formed such that the high shrinkage layer is line-symmetric with respect to a line parallel to the surface of the laminate and passing through a position corresponding to a half of the thickness of the laminate in a cross section in a thickness direction of the laminate. The method for manufacturing a ceramic substrate according to any one of claims 10 to 12, wherein the ceramic substrate is arranged so as to be laminated with a sheet.   The method for manufacturing a ceramic substrate according to claim 10, wherein a plurality of the high shrinkage layers are provided inside and / or on the surface of the laminate.   The method for manufacturing a ceramic substrate according to claim 10, wherein the laminate includes a component having high volatility at a firing temperature of the green sheet alone.   This is a method of manufacturing a ceramic substrate by firing a laminate having a thickness of 100 μm or less in which a plurality of green sheets mainly composed of ceramic raw material powders are laminated. Forming a high-shrinkage layer having a higher shrinkage ratio in a direction parallel to the surface than the green sheet, in a cross section in the thickness direction of the laminate, at a position which is １ ／ of the thickness of the laminate, and A ceramic laminated on the green sheet so as to be symmetrical with respect to a line parallel to the surface of the green sheet, and firing the laminated body at a temperature lower than a firing temperature of the green sheet alone. Substrate manufacturing method.   The method for producing a ceramic substrate according to claim 10, wherein the laminate is fired at a temperature of 1100 ° C. or lower.   The method for manufacturing a ceramic substrate according to claim 10, wherein the laminate is fired at a temperature lower by at least 50 ° C. than a firing temperature of the green sheet alone.   19. The method for manufacturing a ceramic substrate according to claim 10, wherein the ceramic raw material powder is a perovskite compound powder containing Pb, Zr, and Ti, and the high shrinkage layer is a conductor layer containing Ag. A method for manufacturing a piezoelectric actuator substrate, comprising:   20. The method for manufacturing a piezoelectric actuator substrate according to claim 19, wherein the oxygen concentration in the firing atmosphere when firing the laminate is 90% or more. 21. A method for manufacturing a piezoelectric actuator, further comprising forming an electrode on one surface of the piezoelectric actuator substrate in addition to the method for manufacturing a piezoelectric actuator substrate according to claim 19.

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