JP2007174453A - Piezoelectric speaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric speaker for which sound pressure characteristics are improved by improving flexibility of a piezoelectric resin complex in the connection of the piezoelectric resin complex composed of a plurality of piezoelectric element chips having the same rectangular parallelepiped shape and an organic resin around the piezoelectric element chips and a speaker frame body. <P>SOLUTION: In the piezoelectric speaker comprising the piezoelectric resin complex composed of the plurality of piezoelectric element chips having the same rectangular parallelepiped shape and the organic resin around the piezoelectric element chips, a frame body connected with the piezoelectric resin complex and a conductive electrode film, a connection part and a non-connection part are provided in the connection of the piezoelectric resin complex and the frame body and the flexibility of the piezoelectric resin complex is improved. The piezoelectric resin complex has a form which can be approximated to a curved surface selected from one or more kinds of a part of a columnar curved surface, a part of a conical curved surface, a part of a spherical curved surface and a part of an ellipsoidal curved surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric speaker using a piezoelectric element chip, and more particularly to a piezoelectric speaker capable of improving sound pressure characteristics.

In general, a speaker causes a voice cone to mechanically vibrate due to the interaction between the current of this coil and the magnetic field of a permanent magnet by flowing a voice electrical signal through a voice coil connected to the voice cone that plays the role of a diaphragm. The sound is reproduced by vibrating the air.
In the reproduction of audio, it is ideal that the reproduction is performed efficiently over a wide range from a human audible frequency of several tens of Hz to several tens of kHz so as not to cause distortion. However, since it is difficult to cover a wide frequency range with one speaker, generally, a plurality of speakers corresponding to each region are used.

By the way, in recent years, there has been a great demand for reduction in size, weight, and thickness of audio devices such as stereo devices, televisions, and surround sound. In response to such demands, extremely thin and lightweight piezoelectric speakers have been developed.
This piezoelectric speaker is disclosed in, for example, Patent Documents 1, 2, 3, etc., and is composed of an epoxy resin and a large number of, for example, lead zirconate titanate (PZT) piezoelectric element chips, conductive electrode films, By using the piezoelectric element chip and the organic resin, the piezoelectric effect of the piezoelectric element and the elasticity of the organic resin are used.

JP 7-327298 A JP 2000-324598 A JP 2003-348692 A

However, in the conventional piezoelectric speaker described above, for example, the sound pressure characteristic at 1 kHz to 10 kHz is not good.
The present invention has been created in order to effectively solve the above-described problems.
An object of the present invention is to devise the shape of a piezoelectric resin composite composed of a plurality of piezoelectric element chips having the same rectangular parallelepiped shape and an organic resin around the piezoelectric element chip, and the coupling between the piezoelectric resin composite and the speaker frame. Accordingly, an object of the present invention is to provide a piezoelectric speaker in which the flexibility of the piezoelectric resin composite that plays the role of a speaker diaphragm is increased and the sound pressure characteristics at 1 kHz to 10 kHz are improved.

The present invention provides a plurality of piezoelectric element chips having the same rectangular parallelepiped shape, a piezoelectric resin portion made of an organic resin filled on the side surface excluding the electrode surface of the piezoelectric element chip, and only an organic resin around the piezoelectric resin portion. A piezoelectric resin composite formed with a surrounding resin portion, a frame coupled with the surrounding resin portion, and a piezoelectric speaker comprising conductive electrode films provided on both surfaces of the piezoelectric resin portion. The body has an approximate curved surface, and the surrounding resin portion and the frame are formed by a coupling portion and a non-coupling portion.
The approximate curved surface can be approximated to a curved surface selected from one or more of a part of a cylindrical curved surface, a part of a cone curved surface, a part of a spherical curved surface, and a part of an ellipsoidal curved surface. This is a piezoelectric speaker.

As the piezoelectric element chip, in addition to lead zirconate titanate (PZT) PZT, other composite material ceramics may be used. Specifically, lead zinc niobate titanate (PZNT) or magnesium magnesium niobate titanate (PMNT) whose piezoelectric strain constant is about three times larger than PZT can be used.
As the organic resin, an epoxy resin, a polyurethane resin, or the like can be used. The frame body may be a material capable of fixing and supporting the piezoelectric resin composite, requires superior strength characteristics as compared to the piezoelectric resin composite, and has no particular limitation on the conductive characteristics.
As the conductive electrode film, a vapor-deposited film on a piezoelectric element chip of a conductive material such as carbon, aluminum, gold, silver, copper or the like having excellent conductivity characteristics, or an organic resin film containing the conductive substance or the vapor-deposited film And a composite of the organic resin film is preferable.
In order to protect the conductive electrode film provided on the upper part of the piezoelectric resin part and improve the speaker output characteristics, an organic resin film such as polyurethane resin, polyethylene resin, epoxy resin or the like is provided on one or both surfaces of the conductive electrode film. It may be provided.

  According to the piezoelectric speaker of the present invention, the sound pressure characteristics at 1 kHz to 10 kHz can be improved by increasing the flexibility of the piezoelectric resin composite that plays the role of a speaker diaphragm.

  Hereinafter, embodiments of the piezoelectric speaker according to the present invention will be described in detail.

FIG. 1 is an enlarged cross-sectional view of a main part showing a piezoelectric speaker of the present invention. FIG. 2 is a cross-sectional view of the piezoelectric speaker shown in FIG.
As shown in the figure, the piezoelectric speaker has a piezoelectric resin portion 13 in which an organic resin 12 is filled between a plurality of piezoelectric element chips 11 having the same rectangular parallelepiped shape and many piezoelectric element chips 11 are coupled, and around the piezoelectric resin portion 13. It is composed of a piezoelectric resin composite 15 formed of a peripheral resin portion 14 made of only organic resin, a frame 16 coupled to the peripheral resin portion 14, and conductive electrode films 17A and 17B provided on both surfaces of the piezoelectric resin portion 13. The
Audio is obtained by connecting the conductive electrode films 17A and 17B and the audio signal source 18 with lead wires 18A and 18B and energizing the audio electric signal.
As shown in FIG. 1, in this embodiment, two linear end portions of the piezoelectric resin composite 15 and two upper side portions of the frame body 16 are joined by epoxy resins 19A, 19a, 19B, and 19b. Yes. However, as shown in FIG. 2, the two arcuate ends of the piezoelectric resin composite 15 and the frame 16 are not coupled. In the coupling between the piezoelectric resin composite 15 and the frame body 16, the formation of the coupling part and the non-bonding part increases the flexibility of the piezoelectric resin complex 15 and improves the sound pressure characteristics.

Further, details of the embodiment will be specifically described.
The piezoelectric resin composite 15 of the piezoelectric speaker was produced by the method disclosed in Japanese Patent Application Laid-Open No. 2003-348692. The used piezoelectric element chip 11 is a lead zirconate titanate (PZT) type piezoelectric element, and has dimensions of a rectangular parallelepiped having a length of 2 mm, a width of 2 mm, and a thickness of 0.2 mm. In addition, an epoxy resin was used as the organic resin 12 to be filled for bonding a plurality of piezoelectric element chips.
Since a 2 mm vertical and 2 mm horizontal plane is used as the electrode surface of the piezoelectric element chip, the thickness of the piezoelectric resin composite 15 is approximately the same as that of the piezoelectric element chip 11.
A front view of the produced piezoelectric resin composite 15 is shown in FIG. 3, and a side view (a piezoelectric element chip is not shown) is shown in FIG. In FIG. 3, the opening angle, the radius of curvature, and the width dimension of the piezoelectric resin composite 15 are θ, R, and D, respectively. In FIG. 4, the length dimension of the piezoelectric resin composite 15 is L.

The piezoelectric element chips 11 are arranged in a lattice shape along a curved surface with an average interval of 0.4 mm between the piezoelectric element chips. In other words, along the R curved surface of FIG. 3, the 14 pieces are arranged so that the distance between the position of the long side of the piezoelectric element chip 11 and the arcuate end of the piezoelectric resin composite 15 is the same in the angle θ direction. The piezoelectric element chips 11 are arranged at regular intervals of an average of 0.4 mm. The arrangement in which the above 14 arrangements in the θ direction are translated in the L direction in FIG. 4 at regular intervals of an average of 2.4 mm is repeated along the R curved surface, and a total of 196 piezoelectric element chips 11 are arranged.
The dimensions of the obtained piezoelectric resin composite 15 are a width D = 37.1 mm, a length L = 37.6 mm, and an average curvature radius R = 45 mm. The dimensions of the piezoelectric resin portion 13 excluding the peripheral resin portion 14 from the piezoelectric resin composite 15 were a width of 33.1 mm, a length of 33.6 mm, and an average curvature radius of 45 mm. FIG. 5 shows an enlarged plan view of a main part of a part of the piezoelectric resin composite 15 according to the first embodiment.
As shown in FIG. 5, 196 piezoelectric element chips 11 are arranged in a lattice pattern at equal intervals of 0.4 mm on average, 14 pieces in the X direction (see FIG. 5) and 14 pieces in the Y direction (see FIG. 5). The

Next, a frame 16 to be bonded to the piezoelectric resin composite 15 is prepared with an acrylic resin having a thickness of 5 mm. The outer dimension of the frame body 16 is a rectangular parallelepiped having a length of 60 mm, a width of 60 mm, and a thickness of 5 mm, and a gap of 37.3 mm in length and 37.8 mm in width is provided at the center.
The piezoelectric resin composite 15 (width 37.1 mm, length 37.6 mm) is placed in the gap (length 37.3 mm, width 37.8 mm) of the frame 16, and two linear ends of the piezoelectric resin composite 15. The part (length 37.6 mm part) was matched with the two upper side parts (length 37.8 mm part) of the frame space, and the meeting parts were bonded with epoxy resins 19A, 19a, 19B and 19b.
FIG. 6 shows a perspective view (a piezoelectric element chip is not shown) of a part of the coupling state of the piezoelectric resin composite 15 and the frame 16. As shown in FIG. 6, in this embodiment, the linear end of the piezoelectric resin composite 15 and the frame 16 are joined by the epoxy resin 19 </ b> A, but the two arc-shaped ends of the piezoelectric resin composite 15 It is not coupled to the frame body 16. In other words, the piezoelectric resin composite 15 and the frame 16 are formed of a coupling portion and a non-coupling portion.

The piezoelectric resin composite 15 combined with the frame 16 was cured at 60 ° C. for 1 hour. After the curing process, the piezoelectric resin composite 15 combined with the frame body 16 is washed, and the conductive aluminum electrode film 17A and the conductive aluminum electrode film 17A formed by vacuum deposition are formed on both surfaces of the piezoelectric resin portion 13 where the electrode surface of the piezoelectric element chip 11 exists. 17B was provided. The thicknesses of the aluminum electrode films 17A and 17B were almost the same and averaged 0.4 μm.
After connecting the two lead wires 18A and 18B to the electrode films 17A and 17B, a sound electric signal was applied to the lead wires, and the sound pressure characteristics with respect to the frequency of the piezoelectric speaker were evaluated. The evaluation results of the sound pressure characteristics are shown in Table 1.
As shown in Table 1, it can be seen that the sound pressure characteristic of Example 1 is 38 to 65 relative sound pressure dB in the frequency range of 1 kHz to 10 kHz.
Evaluation results of sound pressure characteristics of piezoelectric speakers

As a comparative example, a round piezoelectric resin composite 25 was produced by the method disclosed in Japanese Patent Application Laid-Open No. 2003-348692. The used piezoelectric element chip 21 is a lead zirconate titanate (PZT) type piezoelectric element having a rectangular parallelepiped shape with a length of 2 mm, a width of 2 mm, and a thickness of 0.2 mm, which is the same as that of the first embodiment. The organic resin 22 for bonding the piezoelectric element chip is also an epoxy resin, which is the same as in the first embodiment.
Since a 2 mm vertical and 2 mm horizontal plane is used as the electrode surface of the piezoelectric element chip 21, the thickness of the round piezoelectric resin composite 25 is approximately the same as that of the piezoelectric element chip 21.
FIG. 7 shows a side view of a round piezoelectric resin composite 25 produced as a comparative example (illustration of the piezoelectric element chip is omitted). In FIG. 7, the diameter and curvature radius of the round piezoelectric resin composite 25 are d and r, respectively. FIG. 8 shows an enlarged plan view of a main part of the round piezoelectric resin composite 25. As shown in FIG.

The arrangement of the piezoelectric element chips 21 is a grid-like arrangement along the r-curved surface with the intervals between the piezoelectric element chips being equal intervals of 0.4 mm on average. That is, the distance between the position of the long side of the piezoelectric element chip 21 and the bisector curve passing through the center O (see FIG. 8) of the r curved surface along the r curved surface of FIGS. 7 and 8 is 0.2 mm. Thus, 16 piezoelectric element chips 21 are arranged at regular intervals of 0.4 mm on average in the X direction (see FIG. 8). The 16 arrangements described above are further moved along the r-curved surface in parallel with the Y-direction (see FIG. 8) at an average interval of 2.4 mm, and 16 piezoelectric element chips 21 are arranged.

As a result of repeatedly performing such an arrangement of parallel movement at an equal interval of 2.4 mm on the curved surface half of the r-curved surface, 16, 16, 14, 14, 12, 12, 6, A total of 96 piezoelectric element chips 21 are arranged in a lattice pattern at regular intervals of an average of 0.4 mm along the r curved surface. The same arrangement as the above arrangement is also performed on the remaining half curved surface, and finally 6, 6, 12, 12, 14, 16, 16 to the end, center, and end of the r curved surface, 16, 16, 16, 14, 12, 12, 6, 6, 6, a total of 192 piezoelectric element chips 21 have an average interval between the piezoelectric element chips along the r-curved surface They are arranged in a lattice shape with an equal interval of 0.4 mm.
The obtained round piezoelectric resin composite 25 has a diameter d = 42.9 mm and an average curvature radius r = 43 mm. The dimensions of the piezoelectric resin portion 23 excluding the peripheral resin portion 24 from the round piezoelectric resin composite 25 were a diameter of 38.9 mm and an average curvature radius of 43 mm.

Next, a frame body 26 to be coupled to the round piezoelectric resin composite 25 was produced from an acrylic resin cylinder having a diameter of 60 mm and a thickness of 5 mm by providing a gap having a diameter of 43.1 mm at the center.
The round piezoelectric resin composite 25 (diameter 42.9 mm) is placed in the gap (diameter 43.1 mm) of the frame 26, and the outer peripheral end (diameter 42.9 mm portion) of the round piezoelectric resin composite 25 is the frame. The meeting portion was bonded with epoxy resins 29A and 29B in accordance with the upper side portion of the void portion. FIG. 9 shows a coupled state of the round piezoelectric resin composite 25 and the frame body 26 in an enlarged cross-sectional view of a main part (a piezoelectric element chip is not shown except for a cut surface). As shown in FIG. 9, in this comparative example, the outer peripheral end portion of the round piezoelectric resin composite 25 and the frame body 26 are combined with epoxy resins 29A and 29B on the entire periphery, and a non-bonded portion is formed. Not.

The round piezoelectric resin composite 25 combined with the frame 26 was subjected to curing treatment at 60 ° C. for 1 hour. After the curing process, the round piezoelectric resin composite 25 combined with the frame body 26 is washed, and the vacuum evaporation method is applied to both surfaces of the piezoelectric resin portion 23 where the electrode surface of the piezoelectric element chip 21 is present in the same manner as in the first embodiment. Conductive aluminum electrode films 27A and 27B were provided. The thickness of the aluminum electrode film was substantially the same and averaged 0.4 μm.
After connecting the two lead wires 28A and 28B to the electrode films 27A and 27B, the sound pressure characteristics with respect to the frequency of the piezoelectric speaker were evaluated in the same manner as in Example 1. The evaluation results of the sound pressure characteristics of the round piezoelectric resin composite 25 are shown in Table 1 as a comparative example.
As shown in Table 1, the comparative example shows 35 to 61 relative sound pressure dB in the frequency range of 1 kHz to 10 kHz, and it can be seen that the sound pressure characteristic of the comparative example is inferior to that of the first embodiment.

Round piezoelectric resin composite 25 manufactured in the comparative example, ie, 6, 6, 12, 14, 14, 16, 16, from the end to the center of the curved surface 16 pieces, 14 pieces, 14 pieces, 12 pieces, 12 pieces, 6 pieces, 6 pieces, a total of 192 pieces of piezoelectric element chips, and 6 pieces and 6 at the end portions from the round piezoelectric resin composite 25 arranged. The pseudo-round piezoelectric resin composite 35 excluding the individual pieces was produced. Therefore, the piezoelectric element chip 31 of the pseudo-round piezoelectric resin composite 35 has six, twelve, twelve, fourteen, fourteen, sixteen, sixteen, six, twelve, twelve, twelve, fourteen, sixteen, 16, 16, 14, 14, 12, 12, 6 in total, 180 in total, and a lattice shape in which the intervals between the piezoelectric element chips are equally spaced with an average distance of 0.4 mm along the r curved surface Placed in.
The used piezoelectric element chip 31 and organic resin 32 are the same as those in the first embodiment. FIG. 10 shows a plan view of the pseudo-round piezoelectric resin composite 35 (illustration of the piezoelectric element chip is omitted), and FIG. 11 shows a side view (illustration of the piezoelectric element chip is omitted). In FIG. 10, the width and diameter of the pseudo-round piezoelectric resin composite 35 are w and d, respectively. In FIG. 11, the radius of curvature of the pseudo-round piezoelectric resin composite is r.

The dimensions of the obtained pseudo-round piezoelectric resin composite 35 are a width w = 37.0 mm, a diameter d = 42.8 mm, and an average curvature radius r = 43 mm. The dimensions of the piezoelectric resin portion 33 excluding the surrounding resin portion 34 from the pseudo-round piezoelectric resin composite 35 were a width of 33.0 mm, a diameter of 38.8 mm, and an average curvature radius of 43 mm.

Next, a frame body 36 to be coupled with the pseudo-round piezoelectric resin composite 35 was produced from an acrylic resin cylinder having a diameter of 60 mm and a thickness of 5 mm by providing a gap of 43.0 mm in diameter at the center thereof. A pseudo-round piezoelectric resin composite 35 (width 37.0 mm, diameter 42.8 mm) is placed in a gap (diameter 43.0 mm) of the frame 36, and an outer peripheral end (diameter 42) of the pseudo-round piezoelectric resin composite 35. .8 mm portion) was aligned with the upper side of the frame void, and only the meeting portion was bonded with epoxy resins 39A, 39a, 39B and 39b. FIG. 12 is a plan view (piezoelectric element chip is not shown) showing the coupled state of the pseudo-round piezoelectric resin composite 35 and the frame 36.
In FIG. 12, it can be seen that the pseudo-round piezoelectric resin composite 35 and the frame 36 are bonded by epoxy resins 39A and 39a.
FIG. 13 shows an enlarged cross-sectional view of the main part taken along the line B-B shown in FIG.
As shown in FIGS. 12 and 13, in Example 2, the outer peripheral end portion of the pseudo-round piezoelectric resin composite 35 and the frame body 36 are only partially joined by epoxy resins 39A, 39a, 39B, and 39b. In addition, the outer peripheral end (width 37.0 mm portion) of the pseudo-round piezoelectric resin composite 35 and the frame 36 are not joined. In other words, the pseudo piezoelectric resin composite 35 and the frame 36 are formed of a coupling portion and a non-coupling portion.

The pseudo-round piezoelectric resin composite 35 bonded to the frame body 36 was subjected to a curing process at 60 ° C. for 1 hour. After the curing process, the pseudo-round piezoelectric resin composite 35 bonded to the frame body 36 is cleaned, and vacuum deposition is performed on both surfaces of the piezoelectric resin portion 33 on which the electrode surface of the piezoelectric element chip 31 is present in the same manner as in the first embodiment. Conductive aluminum electrode films 37A and 37B were provided by the method. The thickness of the aluminum electrode film was substantially the same and averaged 0.4 μm.
After connecting the two lead wires 38A and 38B to the electrode films 37A and 37B, the sound pressure characteristics with respect to the frequency of the piezoelectric speaker were evaluated in the same manner as in Example 1. The evaluation results of the sound pressure characteristics of the pseudo-round piezoelectric resin composite 35 are shown in Table 1 as Example 2.
As shown in Table 1, Example 2 shows a relative sound pressure dB of 36 to 62 in the frequency range of 1 kHz to 10 kHz, and it can be seen that the sound pressure characteristic of Example 2 is superior to that of the comparative example.

Table 2 shows the shape, approximate dimensions, formation state with the frame, number of piezoelectric element chips, and sound pressure characteristics of the piezoelectric resin composites in Example 1, Comparative Example, and Example 2. From Table 2, it can be seen that the sound pressure characteristics of Examples 1 and 2 according to the present invention are superior to those of the comparative example.
In other words, when the frame and the surrounding resin portion of the piezoelectric resin composite are bonded all around as in the comparative example, the flexibility of the piezoelectric resin composite is reduced and the sound pressure characteristics are considered to be reduced. I can get off. On the other hand, when the surrounding resin part and the frame body of the piezoelectric resin composite are formed with a joined part and a non-joined part as in the present invention, the flexibility of the piezoelectric resin composite is increased and the sound pressure characteristics are improved. I think.
Shape of piezoelectric resin composite, formation with frame, number of chips, sound pressure characteristics

なお、近似曲面として実施例１では円柱体曲面の一部の例を示し、実施例２では球体曲面の一部の例を示したが、他の円錐体曲面の一部及び楕円体曲面の一部などの近似曲面も適用可能である。
すなはち、前記近似曲面として、円柱体曲面の一部、円錐体曲面の一部、球体曲面の一部及び楕円体曲面の一部の内の１種以上から選ばれた曲面に近似できる形態においても本発明の効果は失はれない。

As an approximate curved surface, an example of a part of a cylindrical curved surface is shown in the first embodiment, and a part of a spherical curved surface is shown in the second embodiment. Approximate curved surfaces such as parts can also be applied.
That is, the approximate curved surface can be approximated to a curved surface selected from one or more of a part of a cylindrical curved surface, a part of a conical curved surface, a part of a spherical curved surface, and a part of an ellipsoidal curved surface. However, the effect of the present invention is not lost.

It is a principal part expanded sectional view which shows the piezoelectric speaker of this invention. It is AA arrow sectional drawing of the piezoelectric speaker shown in FIG. 1 is a front view of a piezoelectric resin composite in Example 1. FIG. 1 is a side view of a piezoelectric resin composite in Example 1. FIG. 3 is an enlarged plan view of a main part showing a part of the piezoelectric resin composite in Example 1. FIG. FIG. 3 is a perspective view showing a part of a combined state of the piezoelectric resin composite and the frame in Example 1. It is a side view of the round type piezoelectric resin composite in a comparative example. It is a principal part enlarged plan view of the round type piezoelectric resin composite in a comparative example. It is a principal part expanded sectional view which shows the combined state of the round-shaped piezoelectric resin composite_body | complex in a comparative example, and a frame. 6 is a plan view of a pseudo-round piezoelectric resin composite in Example 2. FIG. 6 is a side view of a pseudo-round piezoelectric resin composite in Example 2. FIG. It is a top view which shows the coupling | bonding state of the pseudo | simulation round type piezoelectric resin composite_body | complex in Example 2, and a frame. It is a principal part expanded sectional view of the BB arrow shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Piezoelectric element chip | tip, 12 ... Organic resin, 13 ... Piezoelectric resin part, 14 ... Ambient resin part,
15 ... piezoelectric resin composite, 16 ... frame, 17A ... conductive electrode film, 17B ... conductive electrode film,
18A ... Lead wire, 18B ... Lead wire, 19A ... Epoxy resin, 19a ... Epoxy resin,
19B ... epoxy resin, 19b ... epoxy resin,

Claims (2)

  A plurality of piezoelectric element chips having the same rectangular parallelepiped shape, a piezoelectric resin portion made of an organic resin filled on a side surface excluding an electrode surface of the piezoelectric element chip, and a peripheral resin portion made of only an organic resin around the piezoelectric resin portion The piezoelectric resin composite is formed of a conductive resin film provided on both surfaces of the piezoelectric resin composite formed on the both sides of the frame resin coupled to the surrounding resin part, and the piezoelectric resin composite is an approximate curved surface The piezoelectric speaker is characterized in that the peripheral resin portion and the frame are formed of a coupling portion and a non-coupling portion. The approximate curved surface can be approximated to a curved surface selected from one or more of a part of a cylindrical curved surface, a part of a conical curved surface, a part of a spherical curved surface, and a part of an ellipsoidal curved surface. The piezoelectric speaker according to claim 1, wherein:

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