JPS5821883A - Manufacturing method of composite piezoelectric material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a piezoelectric material that is a composite of a piezoelectric material and an organic material. When applying piezoelectric materials to ultrasonic transducers, especially medical ultrasonic transducers for the human body, it is necessary to use a material that is soft and has a low acoustic impedance, as well as a high conversion efficiency between electricity and ultrasonic waves, that is, an electromechanical coupling coefficient. or desirable. However, inorganic materials with a large electromechanical coupling coefficient, such as PZT ceramics, are hard and have high acoustic impedance, making them difficult to match with the human body. Furthermore, soft materials such as organic materials have the disadvantage that they do not have piezoelectricity, or even if they do have them, they have a small electromechanical coupling coefficient. There is currently no material that satisfies both conditions. Therefore, we made a complete composite of an inorganic material such as PZT and an organic ml material,
More and more attempts are being made to create mating materials that have the characteristics of each material at the same time. A pioneering attempt was made by Newham in the United States, and its usefulness is described, for example, in Material Research Press, Vol. 13, pp. 525-536. It is stated that the combination shown in FIG. 1 is effective. That is, there are many columnar PZ'l'12 in the organic matter 11.
By using a dimensionally embedded layer, the piezoelectric voltage constant can be increased without significantly lowering the electromechanical coupling coefficient compared to that of PZT. Here, the piezoelectric voltage constant is a material constant that defines the magnitude of the voltage that appears when receiving ultrasonic waves, and the larger the piezoelectric voltage constant, the higher the reception sensitivity. Further, the composite material has a compliance of 7". These pressure 1#f, voltage constant and compliance can be controlled by bulking PZT and organic matter.

In order to realize this, Newham et al.
A method is used in which ZT ceramics are sintered, bundled in large numbers in an orderly manner, immersed in molten organic matter, and then solidified. However, this method has the following problems: (1) It is difficult to produce thin PZT fibers; (2)
Polarization treatment is required after compounding, but there are drawbacks such as: (3) it is difficult to apply a high voltage uniformly, and (3) it is difficult to process thin plates, making it difficult to obtain high-frequency converters.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate these drawbacks and provide a simple method for manufacturing a composite piezoelectric material, particularly a method for manufacturing a composite piezoelectric material suitable for use in high-frequency transducers.

In the manufacturing method of the present invention, first, a PZT ceramic plate, which has been polarized in the thickness direction, is bonded onto a substrate having a flat surface using a meltable adhesive, and then the ceramic plate is completely attached to the ceramic plate. A large number of grooves are formed to separate the two. Next, after filling the grooves with an organic substance and solidifying it, the adhesive is dissolved and peeled off from the substrate, making it possible to easily obtain a composite material in the form of a thin plate. Moreover, the volume ratio of piezoelectric ceramics to organic matter and the fineness of the structure can be freely changed by selecting the thickness of the groove-making blade and the cutting pitch. Furthermore, since ceramics have already been polarized, there is no need to polarize them after forming the composite material. The resulting composite material is sufficiently flexible and can be deformed into any desired shape.

The present invention will be explained in detail below with reference to Examples.

FIG. 2 is a diagram for explaining one embodiment of the present invention.

Example 1 As shown in FIG. 2A, a PZT ceramic 4-layer 21 having a length t of 10 mm, a width W of 10 mm, and a thickness 1 of 400 μm, which has been polarized in the thickness direction, is placed on a ferrite substrate 23 using electron wax 22. The grooves 24 were formed by cutting the PZT in a mesh pattern as shown in FIG. 2B at a pitch P of 300 μm using a diamond blade having a thickness of 90 μm. In this embodiment, the pitch in the length direction and the pitch in the width direction are made equal, but it goes without saying that they may be made different.

Through the above process, two
This means that a large number of PZT ceramic prisms 25 each having a square size of 10 μm and a height of 400 μm were obtained. Next, polyurethane was filled into the grooves 24 between the prisms 25 and solidified, and then the electron wax 22 was melted and the I) ZT plate was peeled off from the ferrite substrate 23. As a result, a composite material 30 with a volume ratio of PZT 25 and polyurethane 26 of about 1=1 and a thickness of 1(h+m+square plate of 400 μm) as shown in FIG. 2C was obtained. This composite material 301-j: It can be freely formed into any shape.As an electrode, the electromechanical coupling coefficient of 1, the piezoelectric constant dl, the dielectric constant ε, 3, etc. of a composite material 30 in which chromium and gold were vapor-deposited on both sides were measured.

The results obtained were used to produce composite materials I)
Table 1 shows the characteristics of ZT.

Compared to PZT, the dielectric constant ε33 is about half, and the electromechanical coupling coefficient is about 1.5 times larger. The piezoelectric constant d33 has hardly changed. Therefore, the piezoelectric voltage constant expressed by g*s"du/εI3, which is a measure of reception sensitivity, is approximately twice that of PZTVc.Furthermore, since the frequency constant, that is, the velocity V of the sound wave, does not change much, the density The acoustic impedance, expressed as the product of ρ and V, decreases as the density decreases.

Example 2 Polarization treatment in the thickness direction (10m square, 400μ
A PZT ceramic plate with a thickness of m is bonded onto a ferrite substrate using electron wax, and a PZT ceramic plate with a thickness of 300 μm is bonded onto a ferrite substrate in a mesh pattern using a diamond blade with a thickness of 150 μm.
T was cut. Through this process, 15
This means that a large number of PZT ceramic prisms with a square size of 0 μm and a height of 400 μm were obtained. Next, silicone rubber was filled into the grooves between the prisms and solidified, and then electron wax was applied to peel off the PZT' plate. As a result,
The volume ratio of PZT and silicone rubber is 1 = 4, and the plate thickness is 40.
The 0μn1 composite material was more flexible than in Example 1. After depositing chromium and gold on both sides of the composite material as electrodes, the material constants were measured in the same manner as in Example 1.The results are also shown in Table 1.The dielectric constant was reduced to about 1/4. However, the piezoelectric constant dll is only slightly smaller, so the electric voltage constant becomes larger (about 3 times).

Table 1 Characteristics of Composite Piezoelectric Materials of Examples As explained above, by using the manufacturing method of the present invention, a thin plate-shaped composite piezoelectric material suitable for cylindrical frequency ultrasonic technology can be obtained.
+ru. This thin plate-like composite material is flexible enough to be deformed into any shape, and its piezoelectric voltage constant, which is a measure of reception sensitivity, is several times larger than that of PZT-based ceramics.

When cutting a piezoelectric thin plate 21 such as a PZT ceramic plate into a matrix shape, as the cutting pitch P becomes smaller, it becomes difficult to fix the piezoelectric thin plate 21, and the cut piezoelectric prisms 25 may peel off from the substrate 23. be. A possible solution to this problem is to use a strong adhesive when bonding the piezoelectric thin plate 21 to the substrate 23, but this may make it difficult to peel the material to be bonded from the substrate. Furthermore, when cutting the piezoelectric thin plate 21, grooves 24 are also formed in the grooves of the substrate 23, as shown in FIG. may be difficult to remove.

A manufacturing method that also solves these problems will be described below.

FIGS. 4A to 4F are diagrams for explaining other embodiments of the present invention. As shown in FIG. 4A, a polarized piezoelectric thin plate 41 is adhered to a cutting substrate 43 with an adhesive 42, and as shown in FIG. 4B, the piezoelectric plate 41 is cut into a matrix shape with a diamond cutter or the like. Next, the organic material 44 is filled and hardened. This adhesive 42 is applied to the piezoelectric material 4 during cutting.
1 must have sufficient adhesive strength to prevent it from peeling off from the cutting substrate 43. In addition, in FIG. 4, first, the case where the cutting groove is formed on the cutting table 43 will be described.

Next, as shown in FIG. 4C, the piezoelectric material 4 filled with an organic substance 44 is
1 is adhered to a substrate 45 with an adhesive 46. At this time, the board 4
5 is a stand for fixing to a tensioning machine (not shown), and the adhesive 46 must have a stronger adhesive strength than the adhesive 42. Next, it is peeled off using a tensioning machine and the result is as shown in Fig. 4D.

That is, since the adhesive 42 has a weaker adhesive force than the adhesive 46, the adhesive 42 is damaged. When the material in the state shown in FIG. 4D is soaked in a solvent 47 as shown in FIG. 4E and the adhesive 46 is removed, a composite material 48 as shown in FIG. 4F is obtained.

The properties required of these materials are as follows. The adhesive 42 does not clog the diamond cutter,
It must have adhesive strength sufficient to withstand cutting, and must have less adhesive strength than the adhesive 46. The organic substance 44 must be made of a material such as polyurethane or silicone rubber, which has a low adhesive strength (9) and is hardly affected by the bath agent 47 at t-5. Adhesive 46 is adhesive 4
2. It needs to have stronger adhesive force than the organic substance 44 and be soluble in the bath agent 47. In this embodiment, the adhesive 42 is an epoxy adhesive (trade name [Ecobond 45 Clear]), the adhesive 46 is an epoxy adhesive (trade name [Ecobond 45LVj)', and the solvent 47 is trichlorethylene. It was used. Note that in the state shown in FIG. 413, even if an attempt is made to apply a solvent to the adhesive 42, the organic matter 44 causes the adhesive 42 to overlap four times, making it impossible to apply the solvent directly to the adhesive 42. but,
If it is possible to cut without forming the groove 24 on the cutting table 23 as shown in FIG. 2B, apply a bath agent to the adhesive 22 to remove the material 30.
Of course, it is possible to create At this time, the organic material 26 needs to be a material that is not affected by the solvent used. To get from Figure 4C to the 4D bad state,
Either tensile force or shear force may be used.

Moreover, one unit 45 is a rectangular parallelepiped (10
) There is no need to This embodiment is characterized by using an adhesive having predetermined properties and including a step of peeling it off with a tensioner and a step of peeling it off with a solvent. Next, another embodiment of the present invention will be described.

This embodiment is characterized in that an adhesive (for example, electron wax) that becomes soft when heated is used when attaching the piezoelectric material to the cutting table. In this example, the second
It is desirable to cut without creating grooves on the cutting table as shown in Figure B. Then, after filling the cutting groove with an organic substance and curing it, it is heated to melt the heat-softening adhesive and peel off the composite material f'')'.1. When a ditch is formed, fill it with organic matter and harden it, then
It is also possible to use a tensioner as in the method described above to remove the adhesive from the cutting table.
Soften the metal piece 49 of about 10 to 100 μm.
A more preferable method is to put the organic substance 44 into the adhesive layer 50, cut off the entire organic substance 44, and then peel off the skeleton from the cutting table 43. At this time, if a soft material such as polyurethane or silicone rubber is used as the organic substance 44, (11) the organic substance can be easily cut with the metal piece 49. FIG. 6 is a diagram showing another embodiment of the awn of the present invention.

This embodiment is particularly effective when producing a composite material with a higher tube density without piezoelectric material being peeled off even when cutting as finely as 100 μm at a cutting pitch. 6th
As shown in FIG. 8, a piezoelectric material 61 is attached to a cutting table 63 with an adhesive 62, and the piezoelectric material 61 is cut in the X direction shown in the figure.
4 is filled and hardened.

In addition to the properties required for the above-mentioned method, the organic substance 64 is preferably one that does not cause clogging of the cutter. Next, as shown in FIG. 146B, it is cut in the X direction shown in the figure, and filled with a second organic substance 65 and hardened. The first organic substance 64 and the second organic substance may be the same or different. After this, which of the above methods should I use to peel off the composite material from the table 63? May be used.

As described above, by utilizing the thermal properties, adhesive strength, and chemical properties of the materials used, it is possible to easily produce composite materials that are difficult to process, and the effect is significant.

(12) In the above description, the directions in which the piezoelectric materials are cut are directions in which they are directed to each other, but it is needless to say that the directions are not limited to this.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional composite material, FIGS. 2A to 2C are diagrams showing an embodiment of the present invention, and FIG. 3 is a diagram for explaining another embodiment of the present invention. 4A to 4F are views showing another embodiment of the present invention, FIG. 5 is a view showing another embodiment of the invention, and FIGS. 6A and 6B are still another embodiment of the invention. FIG. (13) Z11 Separate 4 A Fig. 48 Concave foil 4 D Fig. 4 E Fig. Δ5 %4c, Fig.

Claims (1)

[Claims] 1. Cutting a pre-polarized piezoelectric thin plate bonded onto the substrate to form a large number of grooves, filling the pot with organic matter, and peeling it off from the substrate. A method for manufacturing a composite piezoelectric material characterized by: