JP4889197B2 - Actuator, manufacturing method thereof, and print head - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention provides an actuator made of a thin sintered body mainly composed of a piezoelectric ceramic layer containing Pb, Zr, and Ti, a manufacturing method thereof, and a printing suitably used for an ink jet recording apparatus used for printing characters and images. Regarding the head.

  In recent years, with the spread of personal computers and the development of multimedia, the use of ink jet recording apparatuses as recording apparatuses that output information to recording media is rapidly expanding.

  Such an ink jet recording apparatus is equipped with a print head, and this type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, and heats the ink with the heater. A thermal head system that boiles and pressurizes ink with bubbles generated in the ink flow path and discharges it as an ink flow from the ink discharge hole, and a part of the wall of the ink flow path filled with ink is bent by a displacement element A piezoelectric method is generally known that displaces, pressurizes ink in an ink flow path mechanically, and discharges the ink as an ink flow from an ink discharge hole.

  For example, as shown in FIG. 3A, a print head used in an inkjet recording apparatus using a piezoelectric method has a plurality of grooves arranged in parallel as ink flow paths 23a, and a partition wall as a wall that partitions each ink flow path 23a. The actuator is provided on the flow path member 23 in which the 23b is formed.

  That is, an actuator in which a common electrode 25 is formed on one main surface of the piezoelectric ceramic layer 24, a plurality of individual electrodes 26 are formed on the other main surface, and a plurality of displacement elements 27 are provided is provided as a flow path member. The actuator and the flow path member 23 are bonded so that the individual electrode 26 is disposed immediately above the ink flow path 23 a that is the opening of the flow path 23.

  By applying a voltage between the common electrode 25 and the individual electrode 26 to vibrate the displacement element 27, the ink in the ink flow path 23 a is pressurized, and the ink discharge hole 28 opened on the bottom surface of the flow path member 23. It is structured to eject ink droplets.

Further, as shown in FIG. 3B, a print head in which a large number of individual electrodes 26 are arranged in parallel on the piezoelectric ceramic layer 24 at an equal pitch and a large number of displacement elements 27 are provided is formed. This can contribute to speeding up and high accuracy of the ink jet printer.
Japanese Patent Laid-Open No. 10-151739

  However, when such an actuator is used as a print head for an ink jet printer, it is important to suppress the variation in the actuator displacement. However, when a sintered body is used as the piezoelectric ceramic layer, the characteristic variation is large. There is a problem that the variation becomes large and, as a result, variation occurs in the ink ejection, resulting in variations in the characters and images to be recorded and the sharpness, and further high-speed printing is impossible.

  The displacement element 7 needs to have a thickness of 100 μm or less in order to obtain a sufficiently large displacement as an actuator, but the piezoelectric ceramic layer made of a piezoelectric sintered body containing Pb evaporates Pb during firing. As a result, there is a problem that the composition of the obtained sintered body varies, and as a result, it is not sufficient to suppress the characteristic variation of the actuator.

  Furthermore, in order to obtain an actuator having a thickness of 100 μm or less, the surface portion where Pb is evaporated is removed from the thick piezoelectric ceramic obtained by sintering, and even if an attempt is made to use the uniform composition inside, the thin ceramic is ground to a thickness of 100 μm or less This is difficult in practice, and it has been difficult to produce an actuator composed of a thin layer of porcelain with no composition variation.

  It is an object of the present invention to provide an actuator having a thickness of 100 μm or less, a manufacturing method thereof, and a print head made of piezoelectric ceramics having no composition variation.

In the actuator of the present invention, a displacement element having a lower electrode, a piezoelectric ceramic layer provided on the lower electrode, and an upper electrode provided on the piezoelectric ceramic layer is provided on the upper surface of the substrate. , the main component an overall thickness of less 100μm actuator from the lower surface of the substrate to the top surface of the upper electrode, the substrate and the piezoelectric ceramic layer is at least Pb, Zr, the perovskite crystal containing and Ti and then, the maximum difference in composition ratio Pb / (Ti + Zr) in the previous SL the upper electrode is not provided the surface of the piezoelectric ceramic layers and internal of the substrate, characterized in that 0.02 or less.

Further, the displacement element, it is preferable to provide a plurality in the upper surface of the substrate.

The porosity of the substrate and the piezoelectric ceramic layer is preferably 1% or less.

  The print head of the present invention includes a flow path member and the actuator provided on the flow path member, and ink provided on the flow path member by displacement of the displacement element constituting the actuator. The ink filled in the flow path is ejected.

  In the present invention, in the actuator using a piezoelectric material mainly composed of a perovskite crystal containing Pb, Zr and Ti, the composition variation generated in the thickness direction from the surface is greatly controlled by controlling the Pb / (Ti + Zr) ratio. As a result, an actuator with small variation in characteristics was realized, and as a result, the variation in displacement of the actuator can be reduced. In addition, it is possible to provide a print head capable of high-speed printing with high clarity and no variation in images and images.

  Further, since a plurality of the displacement elements are provided on the surface of the substrate, the displacement element can be applied to a print head that can cope with higher speed and more precise printing.

  Furthermore, since the porosity of the substrate and the piezoelectric ceramic layer is 1% or less, defects due to ink soaking into the porcelain can be suppressed.

  In the manufacturing method of the actuator of the present invention, when the laminate is stored in a firing slag made of a porous sintered body and fired, the amount of Pb contained in the green sheet is the stoichiometric composition of the perovskite crystal. The actuator of the present invention can be manufactured by increasing the amount of Pb corresponding to that.

  In particular, since the A / B molar ratio A / B of the perovskite crystal in the green sheet is 1.01 to 1.05, it is possible to effectively suppress the composition variation and further reduce the characteristic variation. It becomes possible.

  In another method of manufacturing an actuator of the present invention, a laminate composed of a perovskite crystal having a molar ratio A / B of A site to B site of 0.99 to 1.04 is formed in a fired mortar composed of a dense sintered body. The actuator of the present invention can be manufactured because it is stored and fired.

Moreover, it is preferable that the density of the said green sheet is 4.2 g / cm < ² > or more. Thereby, it becomes possible to further reduce the composition variation.

  Furthermore, it is preferable to fire the laminate at 900 ° C. to 1100 ° C. Thereby, Pb evaporation can be suppressed effectively.

  Furthermore, it is preferable that the high concentration oxygen atmosphere contains 98% or more of oxygen. Thereby, in order to suppress decomposition | disassembly of lead oxide, it becomes possible to make a characteristic variation smaller as an actuator.

  The print head of the present invention includes a flow path member and the actuator provided on the flow path member, and is provided on the flow path member by displacement of the displacement element constituting the actuator. Ink filled in the ink flow path is ejected. Thereby, high-speed and high-precision ink ejection can be realized.

  In the actuator of the present invention, for example, as shown in FIG. 1, a displacement element 7 is formed on a surface of a substrate 2 so that a piezoelectric ceramic layer 4 is sandwiched between a common electrode 5 and an individual electrode 6. Thus, the thickness of the actuator 1 is represented by T.

  It is important that the piezoelectric ceramic layer 4 constituting the displacement element 7 is mainly composed of a perovskite crystal containing at least Pb, Zr and Ti. For example, it is a crystal containing Pb as an A site constituent element and Zr and Ti as a B site constituent element. With such a composition, a piezoelectric ceramic layer having a high piezoelectric constant can be obtained.

Specific examples of the perovskite crystal include PbZrTiO ₃ . Further, other oxides may be mixed, and as a subcomponent, other elements may be substituted at the A site and / or the B site as long as the characteristics are not affected. For example, Zn, Sb, Ni and Te may be added as subcomponents, and a solid solution of Pb (Zn _1/3 Sb _2/3 ) O ₃ and Pb (Ni _1/2 Te _1/2 ) O ₃ may be used. .

  According to the present invention, it is desirable to further contain an alkaline earth element as the A site constituent element in the perovskite crystal. Examples of alkaline earth elements include Ba, Sr, and Ca, and Ba and Sr are particularly preferable because high displacement can be obtained. As a result, the dielectric constant is improved, and as a result, a higher piezoelectric constant can be exhibited.

_{Specifically, Pb 1-x-y Sr} x Ba y (Zn 1/3 Sb 2/3) a (Ni 1/2 Te 1/2) b Zr 1-a-b-c Ti c O 3 + α Mass% Pb _1/2 NbO ₃ (0 ≧ x ≧ 0.14, 0 ≧ y ≧ 0.14, 0.05 ≧ a ≧ 0.1, 0.002 ≧ b ≧ 0.01, 0.44 ≧ c ≧ 0.50, α = 0.1 to 1.0).

  In addition, perovskite-type crystals containing Pb, Zr and Ti such as lead magnesium niobate (PMN) and lead nickel niobate (PNN) can be used.

  In the actuator 1 of the present invention, it is important that the maximum difference between the Pb / (Ti + Zr) ratio on the surface of the piezoelectric ceramic layer 4 and the Pb / (Ti + Zr) ratio inside the substrate 2 is suppressed to 0.02 or less. . If this maximum difference is larger than 0.02, characteristic variation of the displacement element 7 occurs due to a deviation in the composition of the surface portion.

  When the actuator with the composition controlled as described above is applied as a print head in a piezoelectric ink jet printer, it is possible to suppress variations in ink ejection and greatly contribute to improvement in printer characteristics such as printing speed and sharpness. .

  According to the present invention, the single electrode 6 may be single, but a plurality of the individual electrodes 6 are preferably present in order to increase the printing speed and printing accuracy.

  The material of the common electrode 5 and the individual electrode 6 may be any material as long as it has conductivity, and Au, Ag, Pd, Pt, Cu, Al, and alloys thereof are used.

Further, the thicknesses of the electrodes 5 and 6 need to be conductive and do not hinder displacement, and are preferably about 0.5 to 5 μm, particularly about 1 to 3 μm.

  The thickness T of the actuator 1 of the present invention is 100 μm or less, which is important in that a large displacement can be obtained and the characteristics as the actuator 1 can be sufficiently exerted. Particularly, the thickness is 80 μm or less, more preferably 65 μm or less. Is preferably 50 μm or less. The thickness T of the actuator 1 indicates the layer thickness of the substrate 2 and the displacement element 7. The lower limit value of the thickness T of the actuator 1 is 3 μm, particularly 5 μm, more preferably 10 μm, and more preferably 20 μm in order to have sufficient mechanical strength and prevent breakage during handling and operation. preferable.

  The displacement element 7 preferably has a porosity of 1% or less, particularly 0.5% or less. By reducing the porosity, the strength of the actuator 1 is increased, and when used as an ink jet print head, ink leakage due to ink soaking into the porcelain can be effectively suppressed.

When the actuator of the present invention is used as a print head of an inkjet printer, for example, a d ₃₁ mode can be used as a piezoelectric strain constant. It exhibits sufficient discharge performance as a printing head of an ink jet printer, in order to realize a fine high-speed _{printing, d 31} is 200 pm / V or more, particularly 225pm / V or more, and further preferably not 250 pm / V or more .

Next, the method for manufacturing the actuator of the present invention will be described by taking as an example a case where a PbZrTiO ₃ -based perovskite crystal is applied to a print head of an inkjet printer.

First, Pb ₂ O ₃ , ZrO ₂ , TiO ₂ , BaCO ₃ , ZnO, SrCO ₃ , Sb ₂ O ₃ , NiO, and TeO ₂ are prepared as raw material powders. These are adjusted to a composition corresponding to the stoichiometric composition of the perovskite crystal and mixed. In particular, when the laminate is stored in a firing slag made of a porous sintered body and fired, the amount is larger than the Pb amount corresponding to the stoichiometric composition of the perovskite crystal, and the molar ratio A / B is 1. In addition, when the laminate is stored in a fired mortar made of a dense sintered body and fired such that the molar ratio A / B is 0.99 to 1.04, particularly 0. It is preferable that the adjustment is made to be .995 to 1.01 in terms of reducing characteristic variation and expressing more excellent piezoelectric characteristics.

  Here, in the case where a fired mortar made of a porous sintered body is used, Pb as a volatile component is evaporated and discharged out of the mortar, so Pb in the sintered body is the amount of Pb in the green sheet. Less than. For this reason, it is preferable to provide a Pb evaporation source inside or outside the firing mortar.

  Further, when a fired slag made of a dense sintered body is used, Pb as a volatile component evaporates, but since it is saturated in the slag and the amount of Pb evaporated from the green sheet is suppressed, An actuator having excellent characteristics can be obtained with a smaller Pb content than when using a bowl.

  The porous sintered body has an open porosity, and the volatile components in the green sheet can be discharged out of the mortar through the open pores, and the porosity is about This means a sintered body of 10% by volume or more, and a porosity of 20 to 40% by volume is desirable in order to sufficiently allow volatile components to aerate.

In addition, the dense sintered body has a density higher than a level at which volatile components do not pass from one main surface of the sintered body to the other main surface opposite to the main surface. This means a sintered body having a rate of about 8% by volume or less, and in order to have sufficient airtightness, a porosity of 3% or less, more preferably 1% or less is desirable.

  The molar ratio A / B is obtained by dividing the sum of the number of moles of all components of the A site by the sum of the number of moles of all components of the B site. The A / B ratio is a perovskite type of stoichiometry. When the A / B ratio is more than 1 in the oxide, the A site has a larger molar ratio than the B site, and the A / B ratio is more than 1. Is smaller, it means that the molar ratio of the B site is larger than that of the A site.

  The obtained mixed powder is molded into a tape composed of a piezoelectric ceramic layer and an organic composition by a general tape molding method such as a roll coater method or a slit coater to produce a green sheet. In this green sheet, the Pb content is larger than the Pb amount corresponding to the stoichiometric composition of the perovskite crystal, so that the composition variation of the ceramic after firing can be greatly reduced, and the actuator of the present invention is obtained. Is important for.

  A common electrode and individual electrodes are formed on a part of the green sheet by a printing method or the like. If desired, a via hole is formed in a part of the green sheet, and a via conductor is inserted into the via hole.

  Next, a desired green sheet is laminated to prepare a laminate, and a restraint sheet obtained by adding an organic composition to substantially the same composition as the green sheet is disposed on both sides or one side of the laminate, and pressure-tight Do wearing.

  The laminated body after pressure adhesion is placed inside a firing furnace, fired at a firing temperature of 900 ° C. or higher, particularly 940 to 1100 ° C. in a high-concentration oxygen atmosphere, and the composition is formed by evaporation of Pb in the laminated body. It is possible to prevent Pb from becoming deficient as compared to the perovskite composition, and as a result, it is possible to obtain a piezoelectric ceramic having a maximum difference in the composition ratio Pb / (Ti + Zr) ratio of 0.02 or less.

The green sheet green density after pressure contact is 4.2 g / cm ² or more, especially 4.5 g / cm ² or more, which reduces Pb evaporation from the inside, and thus makes Pb composition variation easier. This is preferable because it can be suppressed.

  Further, the oxygen concentration in the oxygen atmosphere at the time of firing is preferably 98% or more, particularly 99% or more. As a result, decomposition of the lead oxide can be suppressed, the amount of evaporation of Pb can be further reduced, the composition variation can be suppressed, and the displacement variation as an actuator can be further reduced.

  The actuator manufactured as described above can obtain an actuator made of a piezoelectric ceramic of 100 μm or less without composition variation, and it is easy to suppress displacement variation to 10% or less, and an actuator used for a print head of an ink jet printer Can be suitably used.

  The print head of the present invention includes a flow path member and the actuator provided on the flow path member, and ink provided on the flow path member by displacement of the displacement element constituting the actuator. The ink filled in the flow path is ejected.

  An example of the print head of the present invention will be described with reference to FIG. A flow path member 13 having a structure in which a plurality of ink flow paths 13a is partitioned by a partition wall 13b is bonded to the actuator 11 of the present invention. That is, the substrate 12 is bonded to the surface of the flow path member 13 with an adhesive, and a plurality of displacement elements 17 are provided on the substrate 12. And the part which contact | abuts the displacement element 17 of the board | substrate 12 is each provided so that the ink flow path 13a which is the opening part of the flow path member 13 may overlap.

  The displacement element 17 has a structure in which a common electrode 15 is formed on one main surface of the piezoelectric ceramic layer 14 and an individual electrode 16 is formed on the other main surface, and the piezoelectric ceramic layer 14 is sandwiched between a pair of electrodes 15 and 16. ing.

  Further, the common electrode 15 and the individual electrode 16 of the displacement element 17 are electrically connected to an external drive circuit, and when a voltage is applied between the common electrode 15 and the individual electrode 16 from the drive circuit, FIG. As shown in b), the ink in the ink flow path 13a corresponding to the displacement element 17 displaced by applying a voltage is pressurized, and the ink droplets are ejected from the ink discharge holes 18 opened at one end surface of the flow path member 13. Can be discharged.

  In the printing head of the present invention, as shown in FIG. 3B, a plurality of displacement elements are arranged on the substrate, and the individual displacement elements are independently controlled to be individually displaced. Needless to say.

  By adopting such a configuration, it is possible to stably perform high-speed and high-precision ink ejection, and it is possible to realize a print head suitable for a printer that realizes a clear image at high speed.

Each raw material powder of high-purity Pb ₂ O ₃ , ZrO ₂ , TiO ₂ , BaCO ₃ , ZnO, SrCO ₃ , Sb ₂ O ₃ , NiO, TeO _{2 is used as} the raw material powder, and the sintered body is Pb _{1-xy sr x Ba y (Zn 1/3 Sb} 2/3) a (Ni 1/2 Te 1/2) b Zr 1-a-b-c Ti c O 3 (x = 0.04, y = 0.02 , A = 0.075, b = 0.005, c = 0.4.2), a predetermined amount is weighed, and the quantitative ratio shown in Table 1 with respect to this composition Excess Pb was added.

  The above prepared powder was wet-mixed for 20 hours by a ball mill, and then the mixture was dehydrated and dried. Thereafter, the mixture was calcined at 900 ° C. for 3 hours, and the obtained calcined product was wet pulverized again with a ball mill.

  Thereafter, an organic binder, water, a dispersing agent and a plasticizer are mixed into the pulverized product to prepare a slurry, and the thickness after firing is determined by a roll coater method generally used for forming a thin green sheet. A green sheet was prepared in consideration of the shrinkage rate in advance so as to have the size shown in the table.

  Thereafter, the green sheet was punched into a short shape using a mold to prepare a plurality of short sheets. Next, the electrode was apply | coated to the green sheet surface by screen printing on this short-shaped sheet | seat surface using the electrode paste which consists of Ag-Pd for a common electrode and an individual electrode.

  Next, the green sheet coated with the electrode and the green sheet coated with no electrode are stacked so that the structure shown in FIG. 1 is formed, that is, a plurality of displacement elements are formed on the surface of the substrate, and heat is applied. The laminated actuator molded body was manufactured by pressure bonding.

  Finally, this molded body was degreased at 400 ° C. and then fired for 2 hours under the conditions shown in Table 1. The restrained sheet was removed from the obtained sintered body by ultrasonic cleaning to obtain an actuator. .

  The thickness of the obtained actuator was measured with a micrometer, and Pb / (Ti + Zr) was obtained by cutting the sintered body and observing the cross section with EPMA, and Pb, Ti, Zr on the surface of the piezoelectric ceramic layer and the inside of the substrate. The quantitative measurement was performed and the difference was calculated.

The porosity was calculated by cutting the sintered body and processing the cross section into a mirror surface state, then observing with a microscope, and determining the area of the pores within a predetermined area. The d ₃₁ of the actuator was measured at 10 points by the resonance method using an impedance analyzer, the average value was calculated, and the absolute value is shown in Table 1.

  Next, the actuator was applied to an inkjet print head. Displacement variation at that time was measured with a laser Doppler vibrometer, and the displacement amount of 10 displacement elements was measured, and the variation from the average value was calculated. In addition, the largest value of the difference between each displacement amount and the average value was divided by the average value, and the percentage displayed was the variation. The results are shown in Table 1.

As the support, zirconia, spinel, magnesia, mullite, alumina, bismuth layered compound, tungsten bronze structure compound, Pb-based perovskite structure compound, Nb-based perovskite structure compound, Ta-based perovskite structure compound were used.

Sample No. of the present invention. 2-15 and 17-19 and _{21-25, d 31} is 200 pm / V or more, the displacement variation was below 2%. These values were confirmed to function sufficiently as an ink jet printer.

On the other hand, sample No. 2 in which Pb was prepared as a stoichiometric composition. In No. 1, since the maximum difference of the composition ratio Pb / (Ti + Zr) was as large as 0.04, d ₃₁ was as low as 190 pm / V, and the displacement variation was as large as 8%.

Further, the thickness of the actuator is as large as 150 μm, and sample No. No. 16 had a d _{31 as} low as 150 pm / V, and the characteristics were not sufficient for a print head of an inkjet printer.

  Furthermore, since the firing temperature is as high as 1200 ° C., the sample No. 5 outside the scope of the present invention has a maximum difference of 0.035 in the composition ratio Pb / (Ti + Zr). No. 20 had a large displacement variation of 5.5%.

It is a schematic sectional drawing which shows the actuator of this invention. The structure of the printing head of this invention is shown, (a) is a schematic sectional drawing, (b) is a schematic sectional drawing which shows the state which the displacement element displaced. The structure of the conventional print head is shown, (a) is a schematic sectional drawing, (b) is a schematic plan view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 ... Actuator 2, 12 ... Board | substrate 4, 14 ... Piezoelectric ceramic layer 5, 15 ... Common electrode 6, 16 ... Individual electrode 7, 17 ... Displacement element 13 ... -Channel member 13a ... Ink channel 13b ... Partition 18 ... Ejection hole

Claims (4)

A displacement element having a lower electrode, a piezoelectric ceramic layer provided on the lower electrode, and an upper electrode provided on the piezoelectric ceramic layer is provided on the upper surface of the substrate. An actuator having a total thickness up to the upper surface of the upper electrode of 100 μm or less,
The substrate and the piezoelectric ceramic layer, at least Pb, Zr, the main component a perovskite crystal containing and Ti,
Actuator maximum difference in composition ratio Pb / (Ti + Zr) in the previous SL the upper electrode is not provided the surface of the piezoelectric ceramic layers and internal of the substrate, characterized in that 0.02 or less. The displacement element has a plurality provided in the upper surface of the substrate The actuator of claim 1. Porosity of the substrate and the piezoelectric ceramic layer is 1% or less, according to claim 1 or actuator according to 2. Comprising: a flow path member, and an actuator according to claim 1 provided on the flow path member, provided in the flow path member by the displacement of the displacement elements constituting the actuator It was to discharge ink filled in the ink flow path, the print head.

Images