JPS61753A - Laminated high polymer piezo-electric type ultrasonic probe - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic probe with a higher resolution and the like preventing bulging of a bent part, by bending a high polymer piezo-electric body having electrodes formed on both sides thereof in more than one layers after provided with fine holes along the crease thereof to position a strips-shaped electrode formed on the one side thereof easily and accurately. CONSTITUTION:A common electrode 16 made of silver or the like is formed on one side of a fluorine-containing high polymer such as polyvinylidene fluoride or other organic high polymer piezo-electric body 14 while a strips-shaped electrode 15 on the other side thereof. Fine holes 17a and 17b are arranged on the piezo-electric body 14 in two rows in such a manner as to be perpendicular to the length of the electrode 15. The piezo- electric body 14 is coated with an adhesive 18 beforehand and bent, laminated and solidified along the fine holes 17a and 17b to build a piezo-electric body 13. The piezo- electric body 13 is fixed on a copper plate 12 concurrently serving as a sound reflector and an electrode section on a support 11 made of acrylic resin. This facilitates the positioning of the electrode 16 while preventing the bulging of the bent part to obtain a highly reliable ultrasonic probe with a high resolution along with an even thickness of the adhesive between the laminated piezo-electric bodies 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a laminated polymer piezoelectric ultrasonic probe formed by folding and laminating a polymer piezoelectric material a plurality of times.

[Technical background of the invention and its problems] Linear array type ultrasonic probes conventionally used in linear electronic scanning methods are made of lead titanate, titanium zirconium
An array type is used in which a ceramic piezoelectric material such as lead is cut into strips. However, such ceramic piezoelectric bodies are hard and brittle, and are easily damaged or cracked when cut and divided. Furthermore, it is difficult to precisely form many strip-shaped electrodes, and there are many costs and costs involved. There was a problem.

On the other hand, polyvinylidene fluoride (hereinafter referred to as PVF2)
Fluorine-containing polymers such as polyvinylidene fluoride-ethylene trifluoride copolymer (hereinafter abbreviated as PVF2/TrFE) or other organic synthetic polymers are
It is known that it exhibits piezoelectricity and pyroelectricity when polarized under a high electric field. Further, in recent years, development of ultrasonic probes that utilize the thickness vibration of the piezoelectric polymer has been actively conducted. These polymer piezoelectric materials have a specific acoustic impedance close to that of a living body and a small elastic modulus, so when applying polymer piezoelectric materials to linear array type ultrasound probes, ceramic piezoelectric materials are preferred. However, it is said that it is not necessarily necessary to cut and separate the polymer piezoelectric material itself into strips.

However, the M electric constant of a polymer piezoelectric material is generally about 10 orders of magnitude, which is significantly lower than that of a ceramic piezoelectric material.Moreover, the area of the driving element of a linear array ultrasonic probe is small, so the electrical impedance is low. Usually, electrical matching with a 50Ω power supply (emitting/receiving circuit) is poor, and the loss of the ultrasonic probe is significantly reduced.

For this reason, it has been proposed to appropriately laminate a plurality of polymeric piezoelectric materials to make the thickness substantially equivalent to that of a thick film and to lower the electrical impedance. As an example, as shown in FIG. 3, a plurality of polymer piezoelectric materials 3 each having a strip-shaped electrode 1 and a common electrode 2 formed on both sides are prepared.
These piezoelectric bodies 3 are stacked so that the same electrodes face each other, and the facing identical electrodes (for example, the strip-shaped electrodes 1 are connected to each other in the first and second layers) are soldered or conductive adhesive 4
A laminated polymer piezoelectric ultrasonic probe is known in which the electrical impedance is lowered by connecting the ultrasonic probe through the . For example, if the electrical impedance of a single layer having a resonant frequency f is Zo, then the laminated layer 1lli shown in FIG.
In construction, it is expressed as Z=Zo/n2 (where rl is the number of laminated layers), and 2M! The electrical impedance is 1/4 for f4R and 1'9 for three-layer stacking, improving electrical matching with the power source. However, in the structure shown in FIG. 3, the lead wire 5a is
, 5b and connect them with each other, it is difficult in practice.

Therefore, as shown in Fig. 4, a single continuous polymeric piezoelectric material 3' is appropriately folded to form a laminate with a desired thickness, thereby reducing electrical impedance and making it easier to take out lead wires. A child is proposed. Although such an ultrasonic probe is simple and can be expected to have great practical effects, it has the following problems.

That is, when folding one continuous polymeric piezoelectric material 3', it is difficult to align the strip-shaped electrodes 1 with each other accurately;
The electrode 1 shifts vertically.

If such a shift occurs, a difference in electrical impedance of the driving elements may occur or a short circuit between the driving elements may occur. This problem becomes more noticeable as the number of folds (the number of stacked layers) of the polymer piezoelectric material 3- increases.

Furthermore, in the ultrasonic probe shown in FIG. 4 described above,
When the polymeric piezoelectric material 3' is folded and laminated, the bent portion of the polymeric piezoelectric material 3' appears to swell significantly, causing electrical loss and ultrasonic radiation at the swollen portion. Beam disturbances, etc. appear. Generally, when folding a polymer piezoelectric material with a thickness of about 100 μm to several μm, in addition to the folding unevenness of the polymer piezoelectric material and the restoring force of the polymer piezoelectric material, the polymer piezoelectric material This is thought to be the result of the adhesive used for lamination adhesion gathering within the tip of the bent portion of the polymer piezoelectric material. In particular, as the number of laminated layers of the polymer piezoelectric material increases, the above phenomenon becomes more noticeable, and when the number of laminated polymer piezoelectric materials is three or more, as shown in FIG. The above phenomenon tends to occur at the bent portion of the body 3-. That is, when a desired laminate is constructed by appropriately folding one continuous polymeric piezoelectric material, an adhesive such as epoxy resin or cyanoacrylic resin is applied to at least one of the polymeric piezoelectric materials. However, a method is adopted in which the bent polymer piezoelectric material is bonded by uniformly applying pressure. In this case, it is important from the viewpoint of improving the characteristics of the ultrasound probe that a thin and uniform adhesive layer be interposed between the 471 layers of polymer piezoelectric materials. However, as shown in FIG. 5(b), the adhesive tends to gather at the bend 6 at 3' of the polymer piezoelectric material as described above (arrow A in the figure), and the adhesive Since it is difficult to cast the adhesive to the outside even when the piezoelectric body 3- is pressurized (arrow B in the figure), the adhesive layer is thin and uneven, and its bent portion 6 bulges out.

In order to eliminate the above-mentioned drawbacks, adhesive is applied to a continuous piece of polymeric piezoelectric material in advance, the piezoelectric material i is appropriately folded, and then the folded high-molecular-weight piezoelectric material is A possible method is to minimize the amount of adhesive between the molecular piezoelectric materials and uniformly press the laminated polymer piezoelectric materials. However, with this method, it is not only difficult to accurately maintain the gap between the rotating rolls, but also due to slight unevenness in the rotation of the rotating rolls or misalignment of the laminated polymer piezoelectric material, strips facing each other formed on the polymer piezoelectric material may This results in problems such as misalignment between the shaped electrodes.

[Purpose of the invention]

The present invention makes it easy to fold the polymer piezoelectric material, and when folding the polymer piezoelectric material, it is possible to easily and accurately align the strip-shaped electrode formed on one side of the polymer piezoelectric material.
Furthermore, it is an object of the present invention to provide a laminated polymer piezoelectric ultrasonic probe that can prevent bulges at bent portions and make the adhesive between laminated polymer piezoelectric bodies uniform.

[Summary of the invention]

The present invention provides a laminated polymer piezoelectric ultrasonic probe in which a polymer piezoelectric material having electrodes formed on both sides is folded to form at least two layers, in which According to the present invention, as described above, the polymer piezoelectric material can be easily folded, and when the polymer piezoelectric material is folded, - A laminated structure that allows for easy and accurate alignment of strip-shaped electrodes formed on one side, prevents bulges at bent parts, and evens out the adhesive between laminated polymer piezoelectric bodies. A polymer piezoelectric ultrasonic probe can be obtained.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 and 2.

Reference numeral 11 in the figure is a support made of, for example, acrylic resin, and on the support 11 is fixed a copper plate 12 having a thickness of, for example, 2.0 μm and serving both as an acoustic reflection plate and an electrode portion of the common electrode. On this copper plate 12, a laminated piezoelectric body 2 which is folded once is arranged. This laminated piezoelectric body unit includes a PVF2 piezoelectric body 14. One surface of this piezoelectric body 14 is coated with silver.

a strip-shaped electrode 15 made of silver, and a common electrode 1 made of silver on the other side.
6 are formed respectively. Said PVF2 piezoelectric body 1/l
Two rows of fine holes 17a and 17b are provided between the strip-shaped electrodes 15 so as to be perpendicular to the length direction of the strip-shaped electrodes 15. Then, the piezoelectric body 14 is
4 with adhesive applied in advance, those micropores 1
The laminated piezoelectric body 1β is fixed and laminated with the adhesive layer 18 by folding twice along the lines 7a and 17b and laminating the piezoelectric body 1β.
− is configured. Note that by placing the laminated piezoelectric body 1β- on the copper plate 12, the laminated piezoelectric body 13
The common electrode 16 comes into contact with the copper plate 12.

The laminated piezoelectric body unit is manufactured by the following method.

First, silver layers with a thickness of about 1 μm are deposited on both sides of a uniaxially stretched PVF2 film with a thickness of 50 μm, for example, by vacuum evaporation.
After time polarization, the PVF2 piezoelectric body 14 is produced by cooling to air temperature.

As shown in FIG. 2, the silver layer on one side of the PVF2 piezoelectric material 14 is patterned to be parallel to its uniaxial stretching direction to form a strip-shaped electrode 15.

These strip-shaped electrodes 15 have a unit element electrode width of 0.9 mm,
The electrode length is 458, the unit element gap is 0.1 mm, and 64 elements are formed. Subsequently, after patterning the silver layer on the opposite side of the rf+fftl electrode 15 as necessary to form a common electrode 16, a portion of the piezoelectric body 14 corresponding to the folded portion between the strip electrodes 15 is patterned. Approximately 50mm in diameter
1 im microscopic holes 17a and 17b are formed by laser processing. Next, after folding the PVF2 piezoelectric body 14 twice along the fine holes 17a and 17b, an epoxy resin adhesive (trade name: 301, manufactured by Botefri Co., Ltd.;
-2> was applied and laminated firmly using a pressure press.
The laminated piezoelectric unit shown in the figure is manufactured.

Further, a lead wire 19a is connected to the copper plate 12, and a lead wire 19b is connected to each strip-shaped electrode 15 of the laminated piezoelectric body unit. Further, the entire layer including the laminated piezoelectric I413 is covered with a polyester film 20 having a thickness of 12 μm, for example.
Is it covered? At the same time, an Epoquine resin layer (trade name 301.-2, manufactured by Epotec Co., Ltd.) 21 is injected and filled into the film 20 to fix the laminated pressure N body to the support 11.

Therefore, the ultrasonic probe of the present invention has a PV to be folded.
Since the F2 piezoelectric body 14 is provided with fine holes 17a and 17b, the adhesive previously applied to the piezoelectric body 14 is cast to the outside through the fine holes 17a and i7b as shown in FIG. As a result, it is possible to prevent the bent portion of the PVF2 piezoelectric body 14 from bulging out, and the piezoelectric body 1 of the laminated piezoelectric body 13 can be prevented from expanding.
The excess adhesive between the adhesive layers 18 can be removed, and an extremely uniform and thin adhesive layer 18 can be formed. As a result, when the ultrasonic probe is operated, the effects of acoustic coupling and electrical strokes on the non-voltage applied portions of the strip electrode 15 adjacent to the eight elements of the strip electrode 15 can be extremely reduced. Ru. Therefore, a probe with excellent performance can be obtained.

Further, by providing the fine holes 17a and 17Ll in the PVF2 piezoelectric body 14 and folding it twice along each of the fine holes 17a and 17b, the piezoelectric body 14 can be easily folded and folded. This allows the opposing strip-shaped electrodes 15 to be accurately aligned vertically. As a result, it is possible to prevent differences in the electrical impedance of the drive elements due to misalignment of the strip-shaped electrodes 15 and short circuits between the drive elements, resulting in a highly reliable linear array type ultrasonic probe. You can get tentacles. In fact, in the linear array type ultrasonic probe of this embodiment, there is no difference in electrical impedance between the unit elements, and moreover, there is no difference in electrical impedance between the 8 elements in the middle element part of the probe and the common electrode 16. When a pulse voltage was applied to the device, it was confirmed that it operated at a low frequency of 5 MHz.

Furthermore, a linear array type ultrasonic probe with low electrical impedance is made by folding the PVF2 piezoelectric material 14 many times.
Even when doing so, the folding operation can be performed extremely easily.

Furthermore, micro holes 17a are formed in the bent portion of the PVF2 piezoelectric body 14.
17b is provided, and excess adhesive is flowed outside through the fine holes 17a and 17b when the piezoelectric body 14 is laminated and bonded, so that not only integral molding is possible, but also the PVF2 piezoelectric body can be formed into, for example, a concave cylindrical shape. Modified integral molding such as this is also possible.

Note that in the above embodiment, the opening of the microholes in the PVF2 piezoelectric body was performed by laser processing, but the present invention is not limited to this. For example, the micropores may be opened by a melting method or a mechanical processing method. In addition, it is desirable that the position of the microhole be opened in the non-operating part of the piezoelectric body as in the above embodiment.
If the shape of the strip-shaped electrode does not affect the operation of closing the ultrasonic probe, a fine hole may be formed on the strip-shaped electrode. Furthermore, when the gap between the strip-shaped electrodes is narrow, micropores may be opened across both the electrodes and the gap (non-operating portion).

In the above example, a PV F2 piezoelectric material was used as the polymeric piezoelectric material, but fluorine-containing synthetic polymers such as PVF2 and TrFE, other organic polymers exhibiting piezoelectricity, or lead titanate, A so-called composite piezoelectric material in which a ceramic piezoelectric material powder such as titanium/lead zirconate is mixed into a polymer resin can also be used.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to easily fold the polymer piezoelectric material, and when folding the polymer piezoelectric material, it is possible to easily and accurately align the strip-shaped 1tl formed on one side of the polymer piezoelectric material. In addition to preventing bulges at bent parts, it also makes it possible to make the adhesive between laminated polymer piezoelectric bodies uniform, which in turn improves manufacturability, reduces variations in electrical impedance, and reduces acoustic and electrical problems. We provide a laminated polymer piezoelectric ultrasonic probe that achieves improved resolution by suppressing the effects of coupling and cross-hake.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a linear array type ultrasonic probe showing an embodiment of the present invention, FIG. Figures 3 and 4 are sectional views of main parts of a conventional ultrasonic probe, and Figure 5(a)
, (b) is a cross-sectional view of k-5 illustrating the problems of the laminated piezoelectric material of the conventional ultrasonic probe. 11...Support body, 13-...Laminated piezoelectric body, 14...P
VF2rf electric body, 15:... strip-shaped electrode, 16... common electrode, 17a, 17b... micropore, 18... adhesive layer, 20... film. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a laminated polymer piezoelectric ultrasonic probe formed by folding and laminating at least two layers of a polymer piezoelectric material having electrodes formed on both sides, micropores are provided along the folds of the polymer piezoelectric material. A laminated polymer piezoelectric ultrasonic probe characterized by: