JPH0686395A - Piezoelectric sounding body and piezoelectric diaphragm for the same - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric sounding body in which a frequency-sound pressure characteristic can be improved without changing the dimension of a piezoelectric diaphragm and a sounding body case by providing the resin coating film of a characteristic hardness at the other main face of a piezoelectric element board. CONSTITUTION:A resin finishing piezoelectric diaphragm 12 with a lead is fixed to a sounding body case 1 by coating a silicon adhesive (having an alphaand omega-dihydroxydimethyl polysiloxane as a main component) 13, and drying it at room temperature, so that a piezoelectric sounding body 15 can be formed. Then, a resin coating film 12g of the hardness less than JIS A50 is provided at the main face opposed to the diaphragm of the piezoelectric diaphragm 12. Thus, the sound pressure level of a low frequency side can be improved, and the frequency-sound pressure characteristic in which the flat part of the sound pressure level is enlarged can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric sounding body used in, for example, a piezoelectric buzzer, a piezoelectric transmitter / receiver, etc., with improved frequency-sound pressure characteristics.

[0002]

2. Description of the Related Art A piezoelectric sounding body having a structure in which a piezoelectric vibrating plate is attached to a sounding body case is used for a piezoelectric buzzer, a piezoelectric transmitter / receiver, and the like. For example, in the piezoelectric receiver, as shown in FIG. 6, a step portion is formed on the inner wall of a bottomed cylindrical speaker case 1 made of a synthetic resin molding, and the piezoelectric diaphragm 2 shown in FIG. 7 is formed on this step portion. Is attached with an adhesive, and a piezoelectric damper 4 is created by sealing a film-shaped damper 3 having a large number of fine holes in a through hole formed in the center of the bottom of the speaker case 1, while the telephone chassis 5 A double cylindrical portion having a step is provided around the sound output holes 6, 6 ... And the tip surface of the sounding body case 1 is attached to the O-ring 8 on the lower inner cylindrical portion 7.
And the end face of the outer cylindrical portion 9 and the collar portion 1a provided on the bottom portion of the piezoelectric speaker 4 with the screws 10 and 1.
The structure stopped by 0 is mentioned.

The piezoelectric vibrating plate 2 has electrodes 2b and 2c provided on both main surfaces of a piezoelectric ceramic plate 2a, and a metallic vibrating plate 2d is adhered to the electrode 2b on one side by an adhesive. After the lead terminals 2e and 2f are soldered to the diaphragm 2d and the other electrode 2c, they are attached to the sounding body case 1. Then, in the piezoelectric receiver of FIG. 1, when the electric signals sent from the transmitter side are input to these lead terminals, the piezoelectric diaphragm 2 vibrates, whereby the electric signals are converted into voice and the sound output holes are produced. 6,
It will be heard through 6 ...

In such a piezoelectric handset, it is preferable that the sound pressure level becomes flat in a band of 300 to 3.4 KHz as a generally audible voice frequency. About diaphragm, thickness of piezoelectric ceramic plate, outer diameter, material of diaphragm, outer diameter, thickness, sounder case, material of damper, number, size and arrangement of sound emission holes, phone chassis,
Adjust the size, number, placement, etc. of the sound output holes to obtain the desired frequency
I tried to get the sound pressure characteristic.

[0005]

However, the piezoelectric ceramic plate, the vibrating plate, and the sounding body case of the piezoelectric vibrating plate are
The standardization of molds for manufacturing these is progressing, and it is difficult to change the dimensions, and it is desired to realize preferable frequency-sound pressure characteristics in the standard dimensions.

The above is the case of the piezoelectric sounding body used in the piezoelectric receiver, but there is a similar problem in other piezoelectric acoustic devices such as a piezoelectric buzzer, and its solution has been desired.

An object of the present invention is to provide a piezoelectric sounding body which can improve frequency-sound pressure characteristics without changing the dimensions of the piezoelectric diaphragm and the sounding body case.

[0008]

According to the present invention, in order to solve the above problems, a vibration plate is attached to one main surface side of a piezoelectric element plate composed of a piezoelectric ceramic plate and electrodes provided on both main surfaces thereof. A piezoelectric sounding body having a structure in which the attached piezoelectric vibrating plate is attached to a sounding body case, the piezoelectric sounding body having a resin coating film having a hardness of JIS A 50 or less on the other main surface of the piezoelectric element plate. Is.

The present invention also provides a piezoelectric vibrating plate used for the above-mentioned piezoelectric sounding body.

The resin coating film used in the present invention has a hardness of J
It has an IS A of 50 or less and, for example, a silicone resin is used for this. For this, a curable one or the like can be used, and the means for curing is not limited, but for example, an ultraviolet curable silicone resin or a quick-drying silicone resin is preferable. As a silicone resin,
Regardless of the name, it refers to a polymer having an alkyl group or a phenyl group with silicon and oxygen as the skeleton, and examples thereof include a polycondensate of silanol. It can be used in combination with other resins.

Other acrylate-based, varnish-based, epoxy-based and other materials may be used alone or in combination with other materials such that the hardness thereof is JIS A.
A material having a hardness of 50 or less can be used, but a material having a hardness higher than this is not sufficient for improving the frequency-sound pressure characteristics described above. The preferred hardness is JIS A 18-
29. In the present invention, the resin includes what is called rubber.

Since the vibration plate is attached to one main surface of the piezoelectric element plate obtained by forming electrodes on the piezoelectric ceramic plate,
The resin coating film is formed on the other main surface, but is partially or entirely formed concentrically. At this time, when the electrode is formed leaving a side margin of the piezoelectric ceramic plate, it may be formed on a part or the whole surface of the electrode, and at that time, may be formed on a part or the whole side margin. It need not be formed. The resin coating film may be formed only on the side margin. The thickness of the resin coating film is 5
˜500 μm is preferred.

To form the resin coating film, a piezoelectric element plate having electrodes formed on a piezoelectric ceramic plate or a vibrating plate is further adhered to the piezoelectric ceramic plate, and the resin liquid is applied to the surface to be coated with a dispenser or the like. It can be applied and dried.

The above-mentioned piezoelectric diaphragm is made up of PZT, PLZT, P
A punched piece of a piezoelectric material such as a T-based or PZT-based three-component piezoelectric material is fired, and a piezoelectric ceramic plate obtained by the firing is subjected to Ag, Pd, Pt, N.
It is formed by vacuum deposition, sputtering, electroless plating of a metal material such as i, Cu or Co, or by applying an electrode material paste prepared by mixing these metal materials with a binder to form a paste (also when glass is used as a fixing agent. In addition, it is created by joining metal plates such as nickel, brass, stainless steel, etc. as a vibrating plate with a conductive adhesive (inorganic type including glass, etc., containing metal powder and organic binder, etc.) To be done.

Examples of the speaker case used in the present invention include resin moldings such as polyester, PBT and ABS.

[0016]

[Function] Hardness JI is applied to the main surface of the piezoelectric diaphragm opposite to the diaphragm.
By providing the resin coating film with S A of 50 or less, the sound pressure level on the low frequency side of the piezoelectric diaphragm is improved.

[0017]

EXAMPLES Examples of the present invention will be described below. Example 1 As shown in FIG. 1, a speaker case 1 similar to that shown in FIG.
The resin-processed piezoelectric vibrating plate 12 shown in FIG. 6 is coated with a silicone adhesive (having α, ω-dihydroxydimethylpolysiloxane as a main component) 13 as in the case of FIG.
The piezoelectric sounding body 15 is prepared by drying and mounting at room temperature for 3 minutes.

The resin-processed piezoelectric vibrating plate 12 was prepared as follows. A PZT ceramic material is used to produce a green sheet by the doctor blade method, and the punched pieces are fired at 1300 ° C. for 2 hours to produce a piezoelectric ceramic plate 12a having a thickness of 50 μm and a diameter of 15 mm. Side margins of 1 mm on both main surfaces of the piezoelectric ceramic plate 12a
, The silver paste for piezoelectric (Ag powder, vehicle, solvent, etc.) is applied by the screen printing method, and the temperature is 800 ° C.
Then, heat treatment is performed for 15 minutes to form the electrodes 12b and 12c.

Next, the vibrating plate 12 made of stainless steel and having a thickness of 50 μm and a diameter of 20 mm was formed on the electrode 12b on the one side.
d is attached by using an adhesive (containing a modified acrylate resin as a main component) and irradiating the adhesive with ultraviolet rays to cure the adhesive. The lead wire 12e was connected to the electrode 12c on the other side by soldering, and the lead wire 12f was connected to the peripheral portion of the main surface of the vibration plate 12d on the piezoelectric ceramic plate 12a side by soldering. Furthermore, 1
An electric field was applied in an atmosphere of 00 ° C. to perform polarization treatment.
Next, an ultraviolet curable silicone resin solution (containing a material obtained from vinyl siloxane thiol as a raw material) is applied on the electrode 12c to the entire surface of the electrode and the side margin with a dispenser, and cured by ultraviolet irradiation. 12 g of a resin coating film having a thickness of about 50 μm is formed. The hardness of this coating film was JIS A 18.

The resin-processed piezoelectric sounding body 1 with lead obtained
The result of measuring the frequency-sound pressure characteristic for No. 2 is shown by the dotted line in FIG. The solid line in the figure is the result of the same measurement for a piezoelectric sounding body prepared in the same manner except that the resin coating film was not provided.

From these graphs, the resonance frequency of the product with the above resin coating film is 1.3 KHz, which is 0.5 from the resonance frequency of 1.8 KHz without the coating film.
The low frequency side can be shifted by KHz (Δf).

With respect to the above resin coating film, when the coating area was kept constant at 1.77 mm 2 and the thickness was changed, a shift to the low frequency side as compared with the case where this resin coating film was not provided Fig. 4 shows the result of measuring the amount (Δf).
Shown in. Further, the thickness of the resin coating film was set to 0.
FIG. 5 shows the results of measuring the shift amount (Δf) to the low frequency side in comparison with the case where this resin coating film was not provided, when the coating film area was successively increased concentrically while keeping it constant at 1 mm. From these results, it can be seen that the thicker the resin coating film and the larger the area, the larger Δf.

Example 2 In Example 1, a quick-drying silicone resin liquid (having α, ω-dihydroxydimethylpolysiloxane as a main component) was used in place of the ultraviolet curable silicone resin coating film,
Resin coating (JIS A 2
A piezoelectric sounding body was prepared in the same manner except that the hardness (9) was formed, and the same measurement was performed on the piezoelectric sounding body. As a result, almost the same measurement result as the dotted line in FIG. 3 was obtained.

Comparative Example 1 A piezoelectric sounding body was prepared in the same manner as in Example 1 except that an ultraviolet curable acrylic resin coating film having a hardness of D75 (hardness of JIS A50 or more) was provided in place of the above resin coating film. When this was also measured in the same manner, a measurement result was obtained in which the sound pressure level was lower than the solid line in FIG. 3 over the entire measurement frequency (not shown).

[0025]

According to the present invention, in a piezoelectric sounding body having a structure in which a piezoelectric vibrating plate is attached to a sounding body case, JIS A 50 is provided on the main surface of the piezoelectric vibrating plate opposite to the vibrating plate.
Since the resin coating film having the following hardness is provided, the sound pressure level on the low frequency side can be improved, whereby the frequency-sound pressure characteristic in which the flat portion of the sound pressure level is expanded can be obtained. In this way, the frequency-sound pressure level characteristic can be improved without changing the dimensions of the sounding body case and the piezoelectric diaphragm, and the productivity can be increased.

[Brief description of drawings]

FIG. 1 is a front sectional view of an embodiment of a piezoelectric speaker according to the present invention.

FIG. 2 is a sectional view of the piezoelectric diaphragm.

FIG. 3 is a graph showing frequency-sound pressure characteristics of the piezoelectric speaker of FIG.

4 is a graph showing a relationship between a thickness of a resin coating film of the piezoelectric speaker of FIG. 1 and a shift of resonance frequency.

5 is a graph showing the relationship between the area of the resin coating film of the piezoelectric speaker of FIG. 1 and the shift of the resonance frequency.

FIG. 6 is a partial cross-sectional view of a piezoelectric receiver.

FIG. 7 is a sectional view of a piezoelectric diaphragm of the piezoelectric speaker.

[Explanation of symbols]

 1 .... Sounding body case 4, 12 ... Piezoelectric diaphragm 2a, 12a .. Piezoelectric ceramic plate 2b, 2c, 12b, 12c .. Electrode 2d, 12d .. Vibration plate 12g.・ Resin coatings 4, 15 ... Piezoelectric sounder

[Procedure amendment]

[Submission date] December 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Added

[Correction content]

The resin coating film used in the present invention has a hardness of JIS A 50 (JIS K 6301 A type).
Hardness is 50, other parts of the same type are also in accordance with this)
The following are used, and for example, a silicone resin is used. For this, a curable one or the like can be used, and the means for curing is not limited, but for example, an ultraviolet curable silicone resin or a quick-drying silicone resin is preferable. The silicon-based resin, regardless of its name, refers to a polymer having an alkyl group or a phenyl group with silicon and oxygen as the skeleton, and includes a polycondensate of silanol. It can be used in combination with other resins.

Claims (2)

[Claims] 1. A piezoelectric device having a structure in which a piezoelectric vibrating plate having a vibrating plate attached to one principal surface side of a piezoelectric element plate composed of a piezoelectric ceramic plate and electrodes provided on both principal surfaces thereof is attached to a sounding body case. In the sounding body, a piezoelectric sounding body in which a resin coating film having a hardness of JIS A50 or less is provided on the other main surface of the piezoelectric element plate. 2. A piezoelectric vibration plate used for the piezoelectric speaker according to claim 1.