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DESCRIPTION JPH09294300

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DESCRIPTION JPH09294300
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe for use in an ultrasonic endoscope and a method of manufacturing the same.
[0002]
[0002] An ultrasonic probe for an ultrasonic endoscope applies an electric signal to electrodes
provided on both sides of a piezoelectric element, like ultrasonic probes used in various medical
fields. The ultrasonic wave is oscillated by emitting the ultrasonic wave into the examination
medium, and the ultrasonic wave reflected from the examination medium is received by the
piezoelectric element, converted into an electric signal and taken out by the electrode, from the
electric signal It is designed to explore the structure in the test medium. In this case, since the
ultrasonic probe used for the ultrasonic endoscope is provided in the insertion portion to be
inserted into the body cavity, the miniaturization, in particular, the reduction in diameter is
required.
[0003]
FIG. 3 shows a longitudinal sectional view of a conventional ultrasonic probe described in
Japanese Patent Application Laid-Open No. 1-291844. Reference numeral 1a denotes a
piezoelectric element made of a piezoelectric substance such as PZT. A front surface electrode 2a
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and a back surface electrode 3a are provided on both sides of the piezoelectric element 1a, and
an electric signal (particularly, a pulse signal) is applied between the electrodes 2a and 3a to
vibrate the piezoelectric element 1a to transmit ultrasonic waves. It oscillates. A lens layer 4a
having an acoustic matching function is provided on the surface electrode 2a of the piezoelectric
element 1a to focus ultrasonic waves.
[0004]
On the other hand, a back load member 5a is provided on the back electrode 3a side of the
piezoelectric element 1a. The back load member 5a is formed, for example, by mixing an
electroconductive substance such as powder tungsten into an epoxy resin, and absorbs the
vibration from the back electrode 3a side of the piezoelectric element 1a. The back load member
5a is mounted in the insulating layer 7a made of plastic or the like.
[0005]
On the other hand, the piezoelectric element 1a is attached to the stepped portion 13a of the
insulating layer 7a. The cable 9a applies an electrical signal to the piezoelectric element 1a. The
cable 9a is electrically connected to the back surface electrode 3a via the cable line 10a. On the
other hand, the surface electrode 2a is electrically connected to the housing 6a by the cable 11a,
and is electrically connected from the housing 6a through the cable 12a.
[0006]
Since the back load member 5a has conductivity, it is necessary to prevent a short circuit
between the front surface electrode 2a and the back surface electrode 3a. Therefore, the
insulating layer 8a is provided on the back surface side of the back load member 5a. These
insulating layers 7a and 8a have a withstand voltage of at least 300V.
[0007]
The ultrasonic probe of FIG. 3 as described above includes a housing 6a connected to the front
surface electrode 2a, and a back load member 5a containing powder tungsten or the like having
conductivity and being in contact with the back electrode 3a and the back electrode 3a. While
the insulating layer 7a performs the prevention of the short circuit, the insulating layer 7a
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positions the piezoelectric element 1a, and the structure is simplified by having both of these
functions.
[0008]
However, the insulating layer 7a needs to have a thickness of at least 0.2 mm in order to ensure
that it has the stepped portion 13a and the strength necessary for fitting it into the housing 6a.
This caused the diameter of the probe to increase by 0.5 mm or more.
[0009]
Further, in order to perform high resolution diagnosis in ultrasonic diagnosis, it is essential that
the ultrasonic wave oscillated from the piezoelectric element 1a be properly converged by the
lens layer 4a. For that purpose, the sound axes of the piezoelectric element 1a and the lens layer
4a Need to be precisely aligned.
However, since the insulating layer 7a for determining the position of the piezoelectric element
1a is a plastic molded product, the dimensional tolerance is increased to ± 100 μm or more,
which causes the sound axis of the piezoelectric element 1a to deviate with respect to the sound
axis of the lens layer 4a. The
In addition to this, the step of bonding the insulating layer 7a to the housing 6a is also a cause of
the axis deviation.
[0010]
On the other hand, when the shape of the insulating layer 7a is changed, it is necessary to
manufacture a mold for molding the changed shape, which is troublesome and the cost of the
mold is expensive. For this reason, the design change of the probe can not be easily performed,
and it is difficult to cope with various products.
[0011]
The present invention has been made in consideration of the above problems, and it is possible to
reduce the diameter, and further to improve the accuracy of ultrasonic diagnosis based on the
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improvement of the assembly accuracy of the housing and the piezoelectric element. It aims at
providing a probe and its manufacturing method.
[0012]
SUMMARY OF THE INVENTION An ultrasonic probe according to the present invention
comprises a piezoelectric element, an acoustic matching layer and a back load member laminated
on the upper and lower sides of the piezoelectric element, and a conductive housing into which
these are inserted. In the ultrasonic probe, the insulating resin film is formed on the inside or
both the inside and the outside of the housing.
[0013]
In this case, the insulating resin film has a thickness of 5 to 100 μm, and has a withstand
voltage of 100 V to 1000 V.
[0014]
By forming the resin film having a thickness of 5 to 100 μm on the inner side or the inner and
outer sides of the housing as described above, the diameter of the probe can be reduced while
maintaining the required withstand voltage, and the assembly accuracy of the housing and the
piezoelectric element Can be improved.
The thickness of the resin film is preferably in the range of 5 to 100 μm.
If it is 5 μm or less, it becomes difficult to maintain the necessary withstand voltage, but if it is
100 μm or more, the diameter of the probe becomes large and the film thickness tends to be
nonuniform.
[0015]
In consideration of having a withstand voltage of 100 V to 1000 V as the type of resin of the
resin film formed on the inner side or both the inner and outer sides of the housing, a resin
which does not cause dielectric breakdown in an electric field of 1 to 200 kV / mm is used.
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As this resin, for example, epoxy resin (16-22 kV / mm), silicone resin (10-11 kV / mm),
polyimide (22 kV / mm), phenol resin (12-13 kV / mm), polyurethane (18-20 kV) / Mm), acrylic
resin (16kV / mm), polyamide (15 to 19kV / mm), polyethylene (18 to 28kV / mm), polyvinyl
chloride (17 to 50kV / mm), polyacetal (20) Thermoplastic resins such as ∼8080 kV / mm) can
be selected. In addition, a resin in which these resins are reinforced with glass fibers, a resin in
which they are reinforced by crosslinking such as crosslinked polyethylene (65 to 75 kV / mm), a
modified resin in which fluorine or the like is added thereto, and polytetrafluoroethylene (20 kV
/ Fluorine-based resins such as mm) can be selected.
[0016]
In the method of manufacturing an ultrasonic probe according to the present invention, the
method of manufacturing an ultrasonic probe in which the piezoelectric element, the acoustic
matching layer, and the back load member are fixed in a stacked state inside the conductive
housing It is characterized in that an insulating resin film is formed by electrodeposition coating
on the inside or both inside and outside.
[0017]
By applying the electrodeposition coating to the inside or both the inside and outside of the
housing in this manner, a thin resin film of uniform thickness can be formed, and the diameter of
the probe can be reduced while maintaining the required withstand voltage. The assembling
accuracy of the piezoelectric element can be improved.
[0018]
The electrodeposition paint used in the electrodeposition coating of the present invention is an
anionic or cationic resin paint.
Anion-type resin paint is an aqueous paint in which an acidic resin having many carboxyl groups
in the resin skeleton is neutralized with a low molecular weight amine or the like, and a cationtype resin paint is basic resin having many amino groups such as carboxylic acid It is an aqueous
paint neutralized with a low molecular weight organic acid.
In the coating process, in the case of the anion type resin paint, the object to be coated is the
anode, and in the case of the cation type resin paint, the object to be coated is the cathode, and
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voltage is applied to migrate the resin to deposit on the surface of the object It is done by
[0019]
For polymers used in anionic resin paints, curing is achieved by initiating oxidation or addition
polymerization by heating the acrylic or methacrylic resin that has been converted to a polyanion
by introducing a carboxyl group as an electrophoretic hydrophilic group. What introduce |
transduced the acryl group etc. which have a vinyl bond etc. into a side chain as a functional
group to accelerate | stimulate, what produces | generates and hardens methylol melamine, etc.
are used. Although it is desirable to use acrylic resin and methacrylic resin or its modified resin
from the viewpoint of stability against hydrolysis as a resin used for this anion type resin paint, it
is not particularly limited.
[0020]
Polymers used in cationic resin coatings include curing by initiating oxidation or addition
polymerization by heating an epoxy resin or acrylic resin that has been converted into a
polycation by introducing an amino group as an electrophoretic hydrophilic group. As a
functional group to be promoted, those having an allyl group having a vinyl bond or a styryl
group introduced into the side chain, or those cured by a urethane bond formed by the
polyaddition reaction of blocked isocyanate and dihydric alcohol are used. Although it is
desirable to use an epoxy resin having an amino group introduced from the viewpoint of
corrosion resistance as the resin used for the cationic resin paint, it is not particularly limited.
[0021]
In the above-described coating, a colorant, a pH adjuster, a solvent and the like are added as
needed. As a coloring agent, a pigment or a dye is used, but in order to disperse in a water
system, it is preferable to select carbon black, titanium oxide, phthalocyanine or the like which is
insoluble in water system and has good pH stability and good heat resistance. As the pH adjuster,
a low molecular weight amine such as triethylamine can be used in the case of an anionic resin
coating, and a low molecular organic acid such as propionic acid can be used in the cationic resin
coating. As solvents, alcohols, ketones, and esters can be used, and as other additives, curing
catalysts, leveling agents, surfactants, etc. can be used.
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[0022]
DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a longitudinal
sectional view of an ultrasonic probe according to a first embodiment of the present invention. A
piezoelectric element 1 is formed of lead zirconate titanate. Reference numerals 2 and 3 denote
front and back electrodes provided on the front and back surfaces of the piezoelectric element 1,
respectively. Reference numeral 4 denotes a lens layer as an acoustic matching layer provided on
the surface electrode 2 of the piezoelectric element 1.
[0023]
A housing 6 is made of stainless steel such as SUS304, and a resin film 14 is applied to both the
inside and the outside. A stepped portion 13 is provided on the inner surface of the housing 6,
and the piezoelectric element 1, the front electrode 2, the back electrode 3 and the lens layer 4
are fixed to the formation portion of the stepped portion 13.
[0024]
A back load member 5 is provided on the side of the back electrode 3 in the housing 6 and has
conductivity by mixing powder tungsten into an epoxy resin. The back load member 5 is
insulated from the housing 6 by the resin film 14.
[0025]
A cable 9 passes through the housing 6 and is connected to a power supply and observation
device (not shown). Reference numerals 10 and 11 are cable wires from the cable 9, the cable
wire 10 is conducted to the back electrode 3, and the cable wire 11 is unpainted on the lower
surface uncoated portion 16 on the inner surface of the housing 6, housing 6 The surface
electrode 2 is conducted via the portion 15 and the cable wire 12. An insulating layer 8 is
provided on the back surface side of the back load member 5 to prevent a short circuit of the
cable wires 10 and 11. The insulating layer 8 and the resin film 14 have a withstand voltage of
1000V.
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[0026]
The resin film 14 is formed by fixing four unpainted portions 15, 16, 17 and 18 on the inner
surface of the housing 6 with a stainless steel wire, and using this as a contact point, the trade
name "Activator S (Shinzu Co., Ltd.)" C.) at a liquid temperature of 40.degree. C. and a current
density of 5 A / m @ 2 for 120 seconds. After that, using an electrolytic chromate treating agent
consisting of trade name "Elecoat connector (manufactured by Shimizu Co., Ltd.)", cathodic
electrolysis at a concentration of 100 ml / l at 40 ° C and a current density of 1 A / m2 for 60
seconds Then, using an acrylic resin-based anionic electrodeposition paint consisting of trade
name “Elecoat AM-1 (manufactured by Shimizu Co., Ltd.)”, the solution is treated at a liquid
temperature of 25 ° C. for 85 V for 2 minutes. Then, the unelectrodeposited paint is removed by
washing with water, and after preliminary drying at 100 ° C. for 10 minutes, heat curing is
performed at 180 ° C. for 30 minutes. After these treatments, unpainted parts 15, 16, 17 and
18 are formed on the inner surface of the housing 6 by removing the contact points. The
thickness of the resin film 14 produced as described above was measured with a high-frequency
film thickness meter, and was 10 ± 2 μm.
[0027]
In the above configuration, a pulse voltage is applied from the power supply between the front
electrode 2 and the back electrode 3 via the cable 9 to vibrate the piezoelectric element 1. The
vibration on the surface electrode 2 side of the piezoelectric element 1 is increased by an amount
that the vibration on the back surface electrode 3 side is suppressed by the back surface load
member 5 and transmitted as an ultrasonic pulse. The ultrasonic pulse is converged by the lens
layer 4 and oscillated to the outside. By driving the probe with a drive mechanism (not shown),
an ultrasonic beam consisting of an oscillated ultrasonic pulse train is scanned along an arbitrary
path. The ultrasonic pulse reflected from the inspection medium is transmitted to the
piezoelectric element 1 through the lens layer 4 to vibrate it. An electrical signal generated by
the vibration of the piezoelectric element 1 is transmitted to the observation device via the cable
9.
[0028]
In such an embodiment, the resin film 14 can be made thin by electrodeposition coating to be an
insulating film having a necessary and sufficient withstand voltage. Further, by determining the
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positions of both the piezoelectric element 1 and the lens layer 4 by the stepped portion 13 of
the housing 6, the sound axes of the piezoelectric element 1 and the lens layer 4 can be
accurately aligned, whereby the ultrasonic beam is accurate It can be well focused.
[0029]
As described above, since the thin resin film 14 is responsible for the prevention of the short
circuit between the housing 6 and the front surface electrode 2 and the back surface electrode 3,
the diameter of the probe and hence the ultrasonic endoscope can be reduced Insertion at the
site and relief of the patient's pain from the insertion can be achieved.
[0030]
Conventionally, as shown in FIG. 3, since the piezoelectric element 1a is bonded to the housing
6a through the insulating layer 7a having a large dimensional tolerance, the assembling accuracy
of the piezoelectric element 1a to the housing 6a is consequently lowered. In this embodiment,
since the resin film 14 having a small dimensional tolerance of film thickness is used, the
accuracy of ultrasonic diagnosis is improved.
[0031]
Furthermore, since the outside of the conductive housing 6 is coated by electrodeposition
coating, leakage from the housing 6 can be prevented, and safety can be improved.
In addition, since no mold is required for forming the resin film 14, design changes of the probe
become easy, and it becomes possible to cope with various types and small amount production.
[0032]
Second Embodiment FIG. 2 shows a second embodiment of the present invention, in which the
same reference numerals as in the first embodiment denote the same parts in FIG.
In this embodiment, the peripheral portion of the back surface electrode 3 is removed and made
slightly smaller than the piezoelectric element 1. The reference numeral 19 denotes a resin film
applied to the inner surface of the housing 6, and the reference numeral 20 denotes an end of
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the resin film 19. The piezoelectric element 1, the surface electrode 2 and the lens layer 4 a are
fixed to the formation portion of the end portion 20 of the resin film 19. The resin film 19 has a
withstand voltage of 1000V.
[0033]
The resin film 19 is formed by forming a chromate film on the housing 6 as in the first
embodiment, and then covering the upper and lower end portions of the outer and inner surfaces
of the housing 6 with a silicone rubber cap. It spray-paints using the epoxy-type paint of Olga
1000HT primer (made by Nippon Paint Co., Ltd. product), and heat-cures at 110 degreeC for 45
minutes. By removing the cap, the upper and lower end portions of the inner surface of the
housing 6 become unpainted portions. The thickness of the resin film 19 was measured by a
high-frequency type membrane pressure meter, and was 40 μm ± 10 μm.
[0034]
In this embodiment, the resin film 19 can be made relatively thin by spray coating to be an
insulating film having a necessary and sufficient withstand voltage. Further, by determining the
positions of both the piezoelectric element 1 and the lens layer 4 by the end portion 20 of the
resin film 19, the sound axes of the piezoelectric element 1 and the lens layer 4 can be accurately
aligned, whereby the ultrasonic beam is It is possible to focus accurately.
[0035]
In such an embodiment, the thin resin film 19 bears the prevention of the short circuit between
the housing 6, the front surface electrode 2 and the back surface electrode 3, thereby making it
possible to reduce the diameter of the probe and hence the ultrasonic endoscope. Insertion in a
narrower site in the body cavity and relief of the patient's pain by insertion are possible.
[0036]
Conventionally, as shown in FIG. 3, since the piezoelectric element 1a is bonded to the housing
6a through the insulating layer 7a having a large dimensional tolerance, the assembling accuracy
of the piezoelectric element 1a to the housing 6a is consequently lowered. In this embodiment,
since the resin film 19 having a small dimensional tolerance of film thickness is used, the
accuracy of ultrasonic diagnosis is improved.
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[0037]
Furthermore, since no mold is required for forming the resin film 19, the design change of the
probe becomes easier, and it becomes possible to cope with various types and small amount
production.
In addition, since the stepped process of the housing 6 becomes unnecessary, the manufacture
becomes easy and the cost can be reduced.
[0038]
As described above, the ultrasonic probe according to the present invention can be reduced in
diameter, and can be easily applied to the production of various types and small amounts, and
the ultrasonic wave based on the improvement of the assembly accuracy of the housing and the
piezoelectric element A structure capable of improving the accuracy of diagnosis can be made.
Further, in the manufacturing method of the present invention, this ultrasonic probe can be
manufactured favorably.
[0039]
Brief description of the drawings
[0040]
1 is a longitudinal sectional view of the first embodiment.
[0041]
2 is a longitudinal sectional view of the second embodiment.
[0042]
3 is a longitudinal sectional view of a conventional ultrasonic probe.
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[0043]
Explanation of sign
[0044]
Reference Signs List 1 piezoelectric element 2 front surface electrode 3 back surface electrode 4
lens layer 5 back surface load member 6 housing 14 resin layer 19 resin layer
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