Piezoelectric speaker and methods of making the same

Abstract

A piezoelectric speaker includes a diaphragm and a piezoelectric layer disposed over the diaphragm. A thickness of the piezoelectric layer can be in a range from 20 micrometers to 120 micrometers. A width of the piezoelectric layer can be 50 millimeters or more, and a length of the piezoelectric layer can be 100 millimeters or more. The piezoelectric layer can further include a pair of electrodes in electrical contact with the piezoelectric layer and configured to drive the piezoelectric layer. Methods of making a piezoelectric speaker include attaching a single piezoelectric layer and a pair of electrodes to a diaphragm using an adhesive.

Description

PIEZOELECTRIC SPEAKER AND METHODS OF MAKING THE SAME

[0001] This application claims the benefit of priority under 35 U.S. C. § 119 of U.S. Provisional Application Serial No. 63 / 535,416, filed on August 30, 2023, the content of which is relied upon and incorporated herein by reference in its entirety.TECHNICAL FIELD

[0001] The present disclosure relates to a piezoelectric speaker and methods of making the same, and more particularly, to a piezoelectric speaker comprising a piezoelectric layer with a thickness from 20 micrometers to 120 micrometers and methods of making the same.BACKGROUND

[0002] Speakers are used to convey audio to a user of an electronic device, which can increase an aesthetic enjoyment associated with using the electronic device. It is known to generate sound (e.g., audio) using piezoelectric, which can be cheaper than conventional speakers. Such piezoelectric devices are commonly referred to as “buzzers” due to their tinny sound, which is a result of poor low-frequency performance - especially when compared to the high-frequency performance of such buzzers. Consequently, there is a need to develop a piezoelectric speaker with improved low-frequency performance.SUMMARY

[0003] The present disclosure provides a piezoelectric speaker and methods of making the same. The piezoelectric speaker can achieve high values of the average low-frequency amplitude (e.g., 60 dB or more or 64 dB or more). Also, the piezoelectric speaker can exhibit a low difference between the average high-frequency amplitude and the average low-frequency amplitude (e.g., 24 dB or less, 20 dB or less, or 10 dB or less). As demonstrated by the Examples here, the dimensions (e.g., thickness of 120 pm or less and / or dimensions corresponding to an area greater than 5000 mm2or more) of the piezoelectric sheet can enable unexpectedly improved low-frequency performance of the piezoelectric speaker. The piezoelectric speaker can have a single, sintered ceramic (e.g., ribbon) as the piezoelectric. Without wishing to be bound by theory, sintered ceramic ribbons can have increased mechanical strength and / or dimensional stability that other methods of forming a layer (e.g., physical vapor deposition, sputtering).

[0004] Some example aspects of the disclosure are described below with the understanding that any of the features of the various aspects may be used alone or in combination with one another.

[0005] Aspect 1. A piezoelectric speaker comprising:a diaphragm; a piezoelectric layer disposed over the diaphragm, a thickness of the piezoelectric layer is in a range from 20 micrometers to 120 micrometers, a width of the piezoelectric layer is 50 millimeters or more, and a length of the piezoelectric layer is 100 mm or more; and a pair of electrodes in electrical contact with the piezoelectric layer and configured to drive the piezoelectric layer.

[0006] Aspect 2. The piezoelectric speaker of aspect 1 , wherein the width of the piezoelectric layer is from 50 millimeter to 200 millimeters, and the length is greater than or equal to the width.

[0007] Aspect 3. The piezoelectric speaker of any one of aspects 1-2, wherein the length of the piezoelectric layer is from 100 millimeters to 200 millimeters.

[0008] Aspect 4. The piezoelectric speaker of any one of aspects 1-3, wherein the piezoelectric layer comprises a lead zirconate titanate or an alkali metal niobate.

[0009] Aspect 5. The piezoelectric speaker of any one of aspects 1-4, wherein the piezoelectric layer is a single piezoelectric layer.

[0010] Aspect 6. The piezoelectric speaker of any one of aspects 1-5, wherein the piezoelectric layer is a sintered ceramic ribbon.

[0011] Aspect 7. The piezoelectric speaker of any one of aspects 1-6, wherein the piezoelectric layer is attached to the diaphragm by an adhesive layer.

[0012] Aspect 8. The piezoelectric speaker of any one of aspects 1-7, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an average low-frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is within 25 deciBels of an average high-frequency amplitude of sound averaged over frequencies from 1000 Hertz to 20000 Hertz.

[0013] Aspect 9. The piezoelectric speaker of aspect 8, wherein the average low-frequency amplitude of sound is within 20 deciBels of the average high-frequency amplitude of sound.

[0014] Aspect 10. The piezoelectric speaker of any one of aspects 8-9, wherein the average low- frequency amplitude of sound is within 10 deciBels of the average high-frequency amplitude of sound.

[0015] Aspect 11. The piezoelectric speaker of any one of aspects 1-7, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speakerexhibits an average low-frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is 60 deciBels or more.

[0016] Aspect 12. The piezoelectric speaker of aspect 11, wherein the average low-frequency amplitude of sound is 64 deciBels or more.

[0017] Aspect 13. A consumer electronic device comprising: a housing comprising a front surface, a back surface, and side surfaces; and electrical components at least partially within the housing, the electrical components comprise a controller, a memory, a display, and the piezoelectric speaker of any one of aspects 1 - 12.

[0018] Aspect 14. A method of making a piezoelectric speaker comprising: attaching a single piezoelectric layer and a pair of electrodes to a diaphragm using an adhesive to form the piezoelectric speaker, wherein a thickness of the single piezoelectric layer is in a range from 20 micrometers to 120 micrometers, a width of the single piezoelectric layer is 50 millimeters or more, and a length of the single piezoelectric layer is 100 mm or more.

[0019] Aspect 15. The method of aspect 14, further comprising sintering a green tape to form the single piezoelectric layer.

[0020] Aspect 16. The method of any one of aspects 14-15, wherein the width of the single piezoelectric layer is from 50 millimeter to 200 millimeters, and the length is greater than or equal to the width.

[0021] Aspect 17. The method of any one of aspects 14-16, wherein the length of the single piezoelectric layer is from 100 millimeters to 200 millimeters.

[0022] Aspect 18. The method of any one of aspects 14-17, wherein the single piezoelectric layer comprises a lead zirconate titanate or an alkali metal niobate.

[0023] Aspect 19. The method of any one of aspects 14-18, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an average low-frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is within 20 deciBels of an average high-frequency amplitude of sound averaged over frequencies from 1000 Hertz to 20000 Hertz.

[0024] Aspect 20. The method of any one of aspects 14-18, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an averagelow-frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is 60 deciBels or more.

[0025] Aspect 21. The method of any one of aspects 14-20, wherein the piezoelectric speaker is the piezoelectric speaker of any one of aspects 1-13.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other features and advantages of aspects of the present disclosure are better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0027] FIG. 1 is a schematic cross-sectional view of a piezoelectric speaker in accordance with aspects of the present disclosure;

[0028] FIG. 2 is a schematic cross-sectional view of a piezoelectric speaker taken along line 2 — 2 of FIG. 1;

[0029] FIG. 3 is a schematic plan view of an example consumer electronic device according to aspects;

[0030] FIG. 4 is a schematic perspective view of the example consumer electronic device of FIG. 3;

[0031] FIG. 5 schematically illustrates experimental results of Examples 1-2 in accordance with aspects of the disclosure; and

[0032] FIG. 6 schematically illustrates simulated results of Examples 3-5 in accordance with aspects of the disclosure.DETAILED DESCRIPTION

[0033] As shown in FIGS. 1-2, a piezoelectric speaker 101 includes a piezoelectric device 102 having a piezoelectric layer 103 attached to a diaphragm 153. As shown in FIG. 1, the piezoelectric device 102 can have a pair of electrodes 123 and 133 in electrical contact with the piezoelectric layer 103 and configured to drive the piezoelectric layer 103. Also, as shown in FIG. 1, the piezoelectric layer 103 can be attached to the diaphragm 153 by an adhesive layer 143. Unless otherwise noted, a discussion of features of aspects of one piezoelectric speaker can apply equally to corresponding features of any aspects of the disclosure. For example, identical part numbers throughout the disclosure can indicate that, in some aspects, the identified features are identical toone another and that the discussion of the identified feature of one aspect, unless otherwise noted, can apply equally to the identified feature of any of the other aspects of the disclosure.

[0034] As shown in FIG. 1, the piezoelectric layer 103 of the piezoelectric device 102 comprises a first major surface 105 and a second major surface 107 opposite the first major surface 105 with a thickness 109 defined as an average distance therebetween. In aspects, the thickness 109 can be about 10 micrometers (pm) or more, about 15 pm or more, about 20 pm or more, about 25 pm or more, about 30 pm or more, about 35 pm or more, about 40 pm or more, about 200 pm or less, about 160 pm or less, about 120 pm or less, about 100 pm or less, about 80 pm or less, about 60 pm or less, about 50 pm or less, or about 40 pm or less. In aspects, the thickness 109 can be in a range from about 10 pm to about 200 pm, from about 10 pm to about 160 pm, from about 15 pm to about 120 pm, from about 15 pm to about 100 pm, from about 20 pm to about 80 pm, from about 20 pm to about 60 pm, from about 20 pm to about 50 pm, from about 25 pm to about 50 pm, from about 30 pm to about 50 pm, or any range or subrange therebetween. In further aspects, preferred ranges for the thickness 109 can be from about 10 pm to about 200 pm, from about 20 pm to about 50 pm, or from about 30 pm to about 50 pm. The thickness 109 of the piezoelectric layer 103 can be determined from a scanning electron microscope (SEM) image of a cross-section of the piezoelectric layer 103, for example with the view shown in FIG. 1.

[0035] As shown in FIG. 2, the piezoelectric layer 103 of the piezoelectric device 102 comprises a length L and a width W that are measured in directions that are orthogonal to one another and the thickness 109. As used herein, “length” refers to the maximum dimension of the piezoelectric layer measured in a direction perpendicular to the thickness, and “width” refers to the maximum value of a dimension that is perpendicular to both the thickness and the length. Consequently, the length L is greater than or equal to the width W. While FIG. 1, depicts a quadrilateral (e.g., rectangular) piezoelectric layer, it is to be understood that the piezoelectric layer can of any shape (e.g., curved, curvilinear, or other polygons) in other aspects. In aspects, the length L can be about 100 millimeters (mm) or more, about 120 mm or more, about 140 mm or more, about 150 mm or more, about 160 mm or more, about 170 mm or more, about 180 mm or more, about 190 mm or more, about 200 mm or more, about 500 mm or less, about 200 mm or less, about 180 mm or less, about 160 mm or less, about 150 mm or less, or about 140 mm or less. In aspects, the length L can be in a range from 100 mm to 500 mm, from about 100 mm to about 200 mm, from about 120 mm to about 180 mm, from about 140 mm to about 170 mm or more, from about 150 mm to about 160mm, or any range or subrange therebetween. In aspects, the width W can be about 50 mm or more, about 70 mm or more, about 80 mm or more, about 90 mm or more, about 100 mm or more, about 110 mm or more, about 120 mm or more, about 130 mm or more, about 150 mm or more, about 170 mm or more, about 200 mm or less, about 180 mm or less, about 160 mm or less, about 140 mm or less, about 120 mm or less, about 100 mm or less, about 90 mm or less, or about 80 mm or less. In aspects, the width W can be in a range from about 50 mm to about 200 mm, from about 70 mm to about 180 mm, from about 70 mm to about 160 mm, from about 80 mm to about 140 mm, from about 90 mm to about 120 mm, from about 100 mm to about 110 mm, or any range or subrange therebetween. Example dimensions (length by width) include 100 mm by 50 mm, 150 mm by 75 mm, and 200 mm by 100 mm. Consequently, an area of the first major surface 105 or the second major surface 107 can be 5000 mm2or more, 7000 mm2or more, 10000 mm2or more, 15000 mm2or more, 20000 mm2or more, 25000 mm2or more, 30000 mm2or more, 35000 mm2or more, or 40000 mm2or more. As demonstrated by the Examples here, the dimensions (e.g., thickness of 120 pm or less and / or dimensions corresponding to an area greater than 5000 mm2or more) of the piezoelectric sheet can enable unexpectedly improved low-frequency performance of the piezoelectric speaker.

[0036] In aspects, as shown in FIG. 1, the piezoelectric device 102 of the piezoelectric speaker 101 can have a single piezoelectric layer as the piezoelectric layer 103. In aspects, as shown in FIG. 1, the piezoelectric layer 103 can be a single ceramic ribbon. In aspects, the piezoelectric layer 103 can be sintered ceramic ribbon. As used herein, “sintered” refers to ceramic-based materials that have been heated at a temperature below their melting point, where the material is able to diffuse across the boundary between adjacent particles to form a mechanical bond therebetween. Without wishing to be bound by theory, sintered ceramic ribbons can have increased mechanical strength and / or dimensional stability that other methods of forming a layer (e.g., physical vapor deposition, sputtering). Further, the piezoelectric device 102 of the piezoelectric speaker 101 can have a single piezoelectric layer as the piezoelectric layer 103 that is a single, sintered ceramic ribbon.

[0037] Throughout the disclosure, “piezoelectric” refers to a material that can convert applied electrical energy into mechanical energy (e.g., vibrations). For example with reference to FIG. 1, the application of electrical energy to the piezoelectric layer 103 by the pair of electrodes 123 and 133 can drive the piezoelectric to vibrate, which in combination with the diaphragm 153 cangenerate sound that can be recognized and / or aesthetically appreciated by a user. In aspects, the piezoelectric layer 103 can comprise a lead zirconate titanate (PZT), lead magnesium niobate-lead titanate (PMN-PT), an alkali metal niobate (e.g., sodium and / or potassium niobates (KNN)), zinc oxide (ZnO), aluminum nitride (AIN), quartz, tourmaline, topaz, langasite, gallium orthophosphate, lithium niobate, lithium tantalate, berlinite, barium titanate, bismuth titanate, alkali bismuth titanate, potassium niobate, sodium tungstate, barium alkali niobates, lead alkali niobates, bismuth ferrite, or combinations thereof. In further aspects, the piezoelectric layer comprises a ceramic material, for example, lead zirconate titanate (PZT), lead magnesium niobate- lead titanate (PMN-PT), barium titanate, bismuth titanate, alkali bismuth titanate, an alkali metal niobate (e.g., sodium and / or potassium niobates (KNN)), potassium niobate, sodium tungstate, barium alkali niobates, lead alkali niobates, zinc oxide (ZnO), bismuth ferrite, or combinations thereof. In aspects, the piezoelectric layer 103 can be a transition metal dichalcogenide (TMD), for example a ceramic TMD including one or more of the materials mentioned above in the previous sentence. Exemplary aspects of the piezoelectric layer include lead zirconate titanate (PZT) and an alkali metal niobate (e.g., sodium and / or potassium niobates (KNN)). As used herein, “ceramic-based” has one or more crystalline phases and includes both ceramics and glassceramics, wherein glass-ceramics have one or more crystalline phases and an amorphous, residual glass phase.

[0038] As shown in FIG. 1, a first electrode 123 of the pair of electrodes 123 and 133 is in electrical contact with the piezoelectric layer 103. The first electrode 123 can include a third major surface 125 and a fourth major surface 127 opposite the third major surface 125. In aspects, as shown, the fourth major surface 127 of the first electrode 123 can be disposed over and / or physically contact the first major surface 105 of the piezoelectric layer 103. Also, as shown in FIG. 1, a second electrode 133 of the pair of electrodes 123 and 133 is in electrical contact with the piezoelectric layer 103. The second electrode 133 can include a fifth major surface 135 and a sixth major surface 137 opposite the fifth major surface 135. In aspects, as shown, the fifth major surface 135 of the second electrode 133 can be disposed over and / or physically contact the second major surface 107 of the piezoelectric layer 103. In aspects, as shown in FIG. 1, the pair of electrodes 123 and 133 can be positioned on opposite sides of the piezoelectric layer 103 (e.g., sandwiching the piezoelectric layer 103), although other arrangements are possible. In aspects, one or more of the electrodes of the pair of electrodes 123 and 133 can be a metallic conductor (e.g.,copper, aluminum, silver, gold, a platinum-group material, or alloys thereof) and / or a conductive polymer (e.g., poly(p-phenylene vinylene) (PPV), poly(3,4-ethylenedioxythiophene) (PEDOT), a polyacetylene, a polypyrrole, a polyaniline, a polythiophene). In aspects a thickness of the first electrode 123 and / or a thickness of the second electrode 133 can be about 500 nanometers (nm) or more, about 1 pm or more, about 2 pm or more, about 5 pm or more, about 20 pm or less, about 15 pm or less, about 10 pm or less, about 8 pm or less, or about 5 pm or less, for example in a range from about 500 nm to about 20 pm, from about 1 pm to about 15 pm, from about 2 pm to about 10 pm, from about 5 pm to about 8 pm, or any range or subrange therebetween.

[0039] As shown in FIG. 1, the piezoelectric layer 103 (e.g., piezoelectric device 102) is disposed over the diaphragm 153. In aspects, as shown, the piezoelectric layer 103 (e.g., piezoelectric device 102) can be attached to the diaphragm 153 by an adhesive layer 143. The adhesive layer 143 comprises a first contact surface 145 and a second contact surface 147 opposite the first contact surface 145. As shown, the first contact surface 145 can face and / or contact the diaphragm 153. In aspects, as shown, the second contact surface 147 of the adhesive layer 143 can face and / or contact the third major surface 125 of the first electrode 123. Although not explicitly shown in FIG. 1, it is to be understood that the first electrode 123 may not extend for the entire area of the first major surface 105 such that the second contact surface 147 of the adhesive layer 143 can face and / or contact the first major surface 105 of the piezoelectric layer 103. In aspects, a thickness of the adhesive layer 143 can be about 500 nanometers (nm) or more, about 1 pm or more, about 2 pm or more, about 5 pm or more, about 20 pm or less, about 15 pm or less, about 10 pm or less, about 8 pm or less, or about 5 pm or less, for example in a range from about 500 nm to about 20 pm, from about 1 pm to about 15 pm, from about 2 pm to about 10 pm, from about 5 pm to about 8 pm, or any range or subrange therebetween.

[0040] In aspects, the adhesive layer 143 can comprise one or more of a polyolefin, a polyamide, a halide-containing polymer (e.g., polyvinylchloride or a fluorine-containing polymer), an elastomer, a urethane, phenolic resin, parylene, polyethylene terephthalate (PET), and polyether ether ketone (PEEK). Example aspects of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene (PP). Example aspects of fluorine-containing polymers include polytetrafluoroethylene (PTFE), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), a perfluoroalkoxy (PFA), fluorinatedethylene propylene (FEP) polymers, and ethylene tetrafluoro ethylene (ETFE) polymers. Example aspects of elastomers include rubbers (e.g., polybutadiene, poly isoprene, chloroprene rubber, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high-impact polystyrene, poly(dichlorophosphazene)). In further aspects, the adhesive layer 143 can comprise an optically clear adhesive. In even further aspects, the optically clear adhesive can comprise one or more optically transparent polymers: an acrylic (e.g., polymethylmethacrylate (PMMA)), an epoxy, silicone, and / or a polyurethane. Examples of epoxies include bisphenol-based epoxy resins, novolac-based epoxies, cycloaliphatic-based epoxies, and glycidylamine-based epoxies. In even further aspects, the optically clear adhesive can comprise, but is not limited to, acrylic adhesives, for example, 3M 8212 adhesive, or an optically transparent liquid adhesive, for example, a LOCTITE optically transparent liquid adhesive. Exemplary aspects of optically clear adhesives comprise transparent acrylics, epoxies, silicones, and polyurethanes. For example, the optically transparent liquid adhesive could comprise one or more of LOCTITE AD 8650, LOCTITE AA 3922, LOCTITE EAE-05MR, LOCTITE UK U-09LV, which are all available from Henkel.

[0041] As shown in FIGS. 1-2, the diaphragm 151 can comprise a seventh major surface 157 facing the piezoelectric layer 103 of the piezoelectric device 102. In aspects, as shown in FIG. 1, the seventh major surface 157 of the diaphragm 153 can face the first major surface 105 of the piezoelectric layer 103 of the piezoelectric device 102 and / or the third major surface 125 of the first electrode 123. In aspects, as shown, in FIG. 1, the seventh major surface 157 of the diaphragm 153 can face and / or contact the adhesive layer 143 (e.g., first contact surface 145). As shown, the diaphragm 153 can comprise an eighth major surface 155 opposite the seventh major surface 157 with a thickness defined as an average distance therebetween. In aspects, a thickness of the diaphragm 153 can be about 60 pm or more, about 100 pm or more, about 200 pm or more, about 300 pm or more, about 400 pm or more, about 500 pm or more, about 800 pm or more, about 1 mm or more, about 2 mm or more, about 10 mm or less, about 5 mm or less, about 2 mm or less, about 1 mm or less, about 800 pm or less, about 600 pm or less, about 500 pm or less, or about 400 pm or less. In aspects, a thickness of the diaphragm 153 can be in a range from about 60 pm to about 5 mm, from about 100 pm to about 2 mm, from about 200 pm to about 1 mm, from about 300 pm to about 800 pm, from about 400 pm to about 600 pm, or any range or subrange therebetween. In aspects, a thickness of the diaphragm 153 can be greater than the thickness 109 of the piezoelectric layer 103. Also, as shown in FIGS. 1-2, an area of the diaphragm 153 (e.g.,seventh major surface 157 or eighth major surface 155) can be greater than an area of the piezoelectric layer 103 (e.g., first major surface 105 or second major surface 107). Although not shown, it is to be understood that the diaphragm is attached to and / or supported by a comparatively rigid component of a larger device (e.g., consumer electronic device discussed below) such that the diaphragm 153 can vibrate and generate sounds that can be perceived and / or aesthetically appreciated by a user.

[0042] In aspects, materials of the diaphragm 153 are not particularly limited and can include a glass-based material, a metallic material, a ceramic-based material, a polymer-based material, or natural materials (e.g., paper, wood, cotton, bamboo). As used herein, “glass-based” includes both glasses and glass-ceramics, wherein glass-ceramics have one or more crystalline phases and an amorphous, residual glass phase. A glass-based material (e.g., glass-based substrate) may comprise an amorphous material (e.g., glass) and optionally one or more crystalline materials (e.g., ceramic). Exemplary glass-based materials, which may be an alkali-free glass and / or comprise a low content of alkali metals (e.g., R2O of about 10 mol% or less, wherein R2O comprises Li2O Na2O, and K2O). In aspects, polymer-based materials can include one or more of a polyolefin, a polyamide, a halide-containing polymer (e.g., polyvinylchloride or a fluorine-containing polymer), an elastomer (e.g., rubber or block copolymer), a urethane, phenolic resin, parylene, polyethylene terephthalate (PET), and polyether ether ketone (PEEK). Example embodiments of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene (PP). Example embodiments of fluorine-containing polymers include polytetrafluoroethylene (PTFE), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), a perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoro ethylene (ETFE) polymers. Example embodiments of elastomers include rubbers (e.g., polybutadiene, polyisoprene, chloroprene rubber, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high-impact polystyrene, poly(dichlorophosphazene)). In aspects, the polymer-based material can include polystyrene, poly(methyl methacrylate), or poly(ethylene terephthalate). Exemplary aspects of the diaphragm include glass-based materials, rubbers, polystyrene, poly(methyl methacrylate), and poly(ethylene terephthalate).

[0043] As used herein, the amplitude of sound with various frequencies is measured using a sound level meter, which is reported as a sound pressure level (SPL) in deciBels (dB) at a distance of 50 centimeters (cm) from the diaphragm. Unless otherwise indicated and as discussed in the Examples below, the piezoelectric device 102 was affixed to a diaphragm comprising a glass-based material with a thickness of 500 pm and dimensions of 241 mm by 170 mm. Unless otherwise indicated, the piezoelectric speaker is drive with a voltage from 10 Volts to 20 Volts (e.g., 10 V or 20V). As used herein, an average “low-frequency” amplitude refers to an arithmetic average (i.e., mean) of at least 20 amplitude measurements at frequencies from 100 Hertz (Hz) to 1000 Hz that are equally spaced on a logarithmic (log) scale. As used herein, an average “high-frequency” amplitude refers to an arithmetic average (i.e., mean) of at least 25 amplitude measurements at frequencies from 1000 Hz (1 kHz) to 20000 Hz (20 kHz). In aspects, the average low-frequency amplitude can be the mean of 40 amplitude (SPL) measurements that are equally spaces on a log scale. In aspects, the average high-frequency amplitude can be the mean of 40 amplitude (SPL) measurements that are equally spaces on a log scale.

[0044] In aspects, when the piezoelectric speaker is drive with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker can exhibit an average low-frequency amplitude of about 60 dB or more, about 62 dB or more, about 64 dB or more, about 65 dB or more, about 66 dB or more, about 68 dB or more, about 70 dB or more, about 71 dB or more, about 73 dB or more, about 75 dB or more, about 78 dB or more, or about 80 dB or more. In aspects, when the piezoelectric speaker is drive with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker can exhibit an average low-frequency amplitude in a range from 60 dB to 90 dB, from 62 dB to 88 dB, from 64 dB to 86 dB, from 65 dB to 84 dB, from 66 dB to 83 dB, from 68 dB to 82 dB, from 70 dB to 81 dB, from 71 dB to 80 dB, from 73 dB to 79 dB, from 73 dB to 78 dB, or any range or subrange therebetween. In further aspects, the average low-frequency amplitude can be measured with a voltage of 10 Volts that can be within one or more of the ranges discussed above in this paragraph. In even further aspects, the average low-frequency amplitude of the piezoelectric speaker when driven with a voltage of 10 Volts can be in a range from 60 dB to 85 dB, from 62 dB to 83 dB, from 64 dB to 80 dB, from 65 dB to 78 dB, from 66 dB to 75 dB, from 68 dB to 72 dB, or any range or subrange therebetween. In further aspects, the average low-frequency amplitude can be measured with a voltage of 20 Volts that can be within one or more of the ranges discussed above in this paragraph. In even further aspects, the average low-frequency amplitude of the piezoelectric speaker whendriven with a voltage of 20 Volts can be in a range from 60 dB to 90 dB, from 63 dB to 88 dB, from 65 dB to 86 dB, from 68 dB to 85 dB, from 70 dB to 84 dB, from 73 dB to 83 dB, from 75 dB to 83 dB, or any range or subrange therebetween. Consequently, the piezoelectric speaker of the present disclosure can unexpectedly improve the frequency response, amplitude, and / or sound quality of the low-frequency signals.

[0045] As used herein, “A” being within “X” units of “B” means that | A — B| < X, which includes B - A < X. In aspects, when the piezoelectric speaker is drive with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker can exhibit an average low-frequency amplitude and an average high-frequency amplitude, where the average low-frequency amplitude can be within 25 dB or less, 22 dB or less, 21 dB or less 20 dB or less, 19 dB or less, 18 dB or less, 16 dB or less, 14 dB or less, 12 dB or less, 10 dB or less, or 8 dB or less of the average high-frequency amplitude. In aspects, a difference between the average high-frequency amplitude and the average low- frequency amplitude (i.e., average high-frequency amplitude minus average low-frequency amplitude) can be in a range from 0 dB to 25 dB, from 1 dB to 22 dB, from 2 dB to 21 dB, from 3 dB to 20 dB, from 4 dB to 19 dB, from 5 dB to 18 dB, from 6 dB to 16 dB, from 7 dB to 14 dB, from 8 dB to 12 dB, or any range or subrange therebetween. Consequently, the piezoelectric speaker of the present disclosure can unexpectedly improve the frequency response, amplitude, and / or sound quality of the low-frequency signals relative to the performance with high-frequency signals. In further aspects, the average low-frequency amplitude and the average high-frequency amplitude can be measured with a voltage of 10 Volts, and the difference therebetween (i.e., average high-frequency amplitude minus average low-frequency amplitude) can be within one or more of the ranges discussed above in this paragraph. In further aspects, when the piezoelectric speaker is driven with a voltage of 10 Volts, a difference between the average high-frequency amplitude and the average low-frequency amplitude can be in a range from 0 dB to 25 dB, from 1 dB to 22 dB, from 2 dB 11 dB, from 3 dB to 20 dB, from 4 dB to 18 dB, from 5 dB to 16 dB, from 6 dB to 15 dB, from 8 dB to 14 dB, from 10 dB to 13 dB, or any range or subrange therebetween. In further aspects, the average low- frequency amplitude and the average high-frequency amplitude can be measured with a voltage of 20 Volts, and the difference therebetween (i.e., average high- frequency amplitude minus average low-frequency amplitude) can be within one or more of the ranges discussed above in this paragraph. In further aspects, when the piezoelectric speaker is driven with a voltage of 20 Volts, a difference between the average high-frequency amplitude andthe average low-frequency amplitude can be in a range from 0 dB to 25 dB, from 1 dB to 20 dB, from 2 dB 19 dB, from 3 dB to 18 dB, from 4 dB to 14 dB, from 5 dB to 10 dB, from 6 dB to 8 dB, or any range or subrange therebetween.

[0046] Aspects of the disclosure can comprise a consumer electronic product. The consumer electronic product can comprise a front surface, a back surface, and side surfaces. The consumer electronic product can further comprise electrical components at least partially within the housing. The electrical components can comprise a controller, a memory, and a display. The display can be at or adjacent to the front surface of the housing. The display can comprise a liquid crystal display (LCD), an electrophoretic display (EPD), an organic light-emitting diode (OLED) display, or a plasma display panel (PDP). In aspects, the consumer electronic product can comprise a cover substrate disposed over the display. In aspects, the electric components can include the piezoelectric speaker 101 of the present disclosure. The consumer electronic product can comprise a portable electronic device, for example, a smartphone, a tablet, a wearable device, or a laptop. Given the dimensions of the speaker, the consumer electronic product can be incorporated into a laptop, a television, a monitor, appliances, an automobile, a train, a plane, or other relatively large device.

[0047] The piezoelectric speaker disclosed herein may be incorporated into another article, for example, an article with a display (or display articles) (e.g., consumer electronics, including mobile phones, tablets, computers, televisions, monitors, and the like), architectural articles, transportation articles (e.g., automotive, trains, aircraft, sea craft, etc.), or appliance articles. An exemplary article incorporating the piezoelectric speaker disclosed herein is shown in FIGS. 3-4. Specifically, FIGS. 3-4 show a consumer electronic device 300 including a housing 302 having front 304, back 306, and side surfaces 308. Although not shown, the consumer electronic device can comprise electrical components that are at least partially inside or entirely within the housing. For example, electrical components include at least a controller, a memory, and a display. As shown in FIGS. 3-4, the display 310 can be at or adjacent to the front surface of the housing 302. The consumer electronic device can comprise a cover substrate 312 at or over the front surface of the housing 302 such that it is over the display 310. In aspects, the electrical components can include the piezoelectric speaker of the present disclosure. In further aspects, the piezoelectric speaker can include the cover substrate as the diaphragm of the piezoelectric speaker.

[0048] Aspects of methods of making a piezoelectric speaker 101 will now be discussed. In aspects, methods can comprise forming a green tape, sintering the green tape to form a sintered piezoelectric layer, and attaching the piezoelectric layer (e.g., sintered piezo electric layer) (and a pair of electrodes) to a diaphragm (e.g., using an adhesive layer) to form the piezoelectric speaker. It is to be understood that one of more of the these actions can be omitted, for example, is a green tape of a sintered piezoelectric layer is already present (e.g., acquired by purchase or otherwise manufactured). In aspects, a single sintered ribbon ceramic can be used as the piezoelectric layer and / or a single piezoelectric layer can be used in forming the piezoelectric speaker.

[0049] In aspects, forming a green tape can comprise forming a slip by mixing raw materials (e.g., ceramic particles, binder, solvent, dispersant, defoamer, and / or plasticizer) that is cast to form the green tape. In further aspects, the binder can comprise one or more polymeric materials. The binder can provide mechanical strength to the green tape before and / or during the sintering. In aspects, the binder can be a polymer compatible with the solvent, for example, an acrylic polymer, a methacrylate polymer, a carbonate-containing polymer, a vinyl acetate resin, a maleic acid polymer, a vinyl butyral resin, a vinyl formal resin, a vinyl alcohol resin, a cellulose resin, or copolymers or combinations thereof. In aspects, the solvent can be a polar protic solvent, for example water or alcohols (e.g., methanol, ethanol, isopropyl alcohol, acetic acid), or a polar aprotic solvent, for example a ketone (e.g., methyl ethyl ketone, acetone), N,N- dimethylformamide, dimethyl sulfoxide, dimethyl sulfoxide, dimethyl carbonate, methyl ethyl ketone, toluene, anisole, dioxolane, methoxy propyl acetate, or combinations thereof. As used herein, a “dispersant” refers to a material that improves a separation of particles, improves a uniformity of a distribution of particles, decreases particle aggregation, and / or reduces settling of particles. In aspects, the dispersant can comprise a fish oil or commercial dispersants, for example, the Hypermer line of dispersants (available from Croda Energy Technologies). As noted above, additional components in the slip can include a defoamer and / or a plasticizer. For example, plasticizers can include a dibutyl carboxylic acid ester. Plasticizers can include dibutyl phthalate, dibutyl adipate, dibutyl maleate, poly(ethylene glycol), and combinations thereof. In further aspects, the viscosity modifier can comprise dibutyl phthalate. Casting can comprise using a doctor blade or other methods known in the art.

[0050] In aspects, sintering the green tape to form the piezoelectric layer can comprise heating the green tape with one or more heaters to remove organic materials from the green tape followed bysintering the particles from the green tape to form the piezoelectric layer. In further aspects, the green tape can be heated in one or more ovens (e.g., lehrs), for example, being conveyed on a setter plate, although long green tapes can be conveyed through using a rollers system spanning a distance greater than one or more of the ovens. In even further aspects, a temperature profile that the green tape is exposed to can be controlled using one or more spatial zones in the one or more ovens.

[0051] In aspects, the pair of electrodes can be attached to the piezoelectric layer by melting a metal foil or otherwise adhering the electrode material to the piezoelectric layer. In aspects, as discussed above, methods can comprise attaching a single piezoelectric layer (e.g., single sintered piezoelectric layer) and a pair of electrodes (e.g., already attached to the piezoelectric layer) to a diaphragm using an adhesive layer to form the piezoelectric speaker (e.g., see FIG. 1).EXAMPLES

[0052] Various aspects will be further clarified by the following examples. Examples 1-2 were experimentally made and measured, which the results reported in Table 1 and FIG. 5. In Example 1, the piezoelectric layer was a sintered ribbon ceramic of PZT with a thickness of 60 pm with dimensions of 50 mm by 100 mm attached to a glass-based material with a thickness of 500 pm and dimensions of 241 mm by 170 mm. The piezoelectric speaker of Example 1 was driven with a with a voltage of 10 Volts. The piezoelectric speaker of Example 2 was the same as in Example 1 except that the thickness of the piezoelectric layer was 100 pm and was driven with a voltage of 20 Volts.Table 1 : Performance of Examples 1 -2

[0053] In FIG. 5, the horizontal axis 501 (e.g., x-axis) is frequency is Hertz (Hz), and the vertical axis 503 (e.g., y-axis) is the amplitude measured as a sound pressure level in deciBels (dB). Curve 505 corresponds to Example 1, and curve 507 corresponds to Example 2. As shown in Table 1 and FIG. 5, Example 1 (curve 505) has an average low-frequency amplitude of greater than 60 dB (e.g., greater than 64 dB or about 66 dB). For Example 1, the difference between the average high- frequency amplitude and the average low-frequency amplitude is less than 24 dB (e.g., less than20 dB, less than 18 dB, less than 15 dB, or about 13 dB). As shown in Table 1 and FIG. 5, Example 2 (curve 507) has an average low-frequency amplitude of greater than 60 dB (e.g., about 64 dB). For Example 2, the difference between the average high-frequency amplitude and the average low- frequency amplitude is less than 24 dB (e.g., less than 20 dB or about 18 dB).

[0054] The performance of Example 1 is slightly better than Example 2, although the differences in both piezoelectric layer thickness and driving voltage make it difficult to draw direct conclusions. However, it would be expected that amplitude would increase with driving voltage. So, the higher low-frequency amplitude (and smaller difference) for Example 1 (with a driving voltage of 10 Volts) relative to the corresponding properties of Example (with a driving voltage of 20 Volts) suggests that decreasing the thickness of the piezoelectric layer further improves the low- frequency performance of the piezoelectric layer and / or piezoelectric speaker.

[0055] Examples 3-5 were simulated for a piezoelectric layer PZT with an elastic modulus of 129 GigaPascals and the dimensions stated in Table 2 attached to a glass-based diaphragm with an elastic modulus of 71 GigaPascals with a thickness of 500 pm and dimensions of 241 mm by 170 mm. Examples 3-5 were simulated with a driving voltage of 20 Volts, as indicated in Table 2. The results for Examples 3-5 are presented in Table 2, and the results for Examples 3-5 are plotted in FIG. 6. The simulations were performed using ALITA FEM.Table 2: Performance of Examples 3-5

[0056] In FIG. 6, the horizontal axis 601 (e.g., x-axis) is frequency is Hertz (Hz), and the vertical axis 603 (e.g., y-axis) is the amplitude measured as a sound pressure level in deciBels (dB). Curve 605 corresponds to Example 3, curve 607 corresponds to Example 4, and curve 609 correspond to Example 5. As shown in Table 2 and FIG. 6, Example 3 (curve 605) has an average low- frequency amplitude of greater than 60 dB (e.g., greater than 64 dB, greater than 70 dB, or about 73 dB). For Example 3, the difference between the average high-frequency amplitude and the average low- frequency amplitude is less than 24 dB (e.g., less than 20 dB or about 19 dB). As shown in Table2 and FIG. 6, Example 4 (curve 607) has an average low-frequency amplitude of greater than 60 dB (e.g., greater than 64 dB, greater than 70 dB, or about 80 dB). For Example 4, the difference between the average high-frequency amplitude and the average low-frequency amplitude is less than 24 dB (e.g., less than 20 dB or about 14 dB). As shown in Table 2 and FIG. 6, Example 5 (curve 609) has an average low- frequency amplitude of greater than 60 dB (e.g., greater than 64 dB, greater than 70 dB, or about 82 dB). For Example 5, the difference between the average high- frequency amplitude and the average low-frequency amplitude is less than 24 dB (e.g., less than 20 dB, less than 10 dB, or about 8 dB).

[0057] As shown in FIG. 6 and Table 2, increasing the area of the piezoelectric layer (going from Example 3 to Example 5) increases the average low-frequency amplitude. Specifically, increasing the area by a factor of 4 (from Example 3 to Example 5) results in an ~10 dB increase in the average low-frequency amplitude. Also, increasing the area of the piezoelectric layer (going from Example 3 to Example 5) decreases the difference between the average high-frequency and the average low-frequency amplitude, namely, going from 19.1 dB to 7.7 dB.Table 2: Performance of Example 6 and Comparative Examples AA-BB

[0058] Comparative Examples AA-BB and Example 6 were simulated for a piezoelectric layer PZT with an elastic modulus of 129 GigaPascals and the dimensions stated in Table 3 attached to a glass-based diaphragm with an elastic modulus of 71 GigaPascals with a thickness of 500 pm and dimensions of 241 mm by 170 mm. Comparative Example AA was simulated with a driving voltage of 10 Volts while Comparative Example BB and Example 6 was simulated with a driving voltage of 16 Volts.

[0059] Comparative Example AA has a much greater thickness (1 mm in Comparative Example AA is 10 times greater than the 100 pm in Examples 2-3 and ~17 time greater than the 60 pm in Example 1) and a much smaller area (8 times smaller than Examples 1-3). Comparing the 10V results of Example 1 (see Table 1) and Comparative Example AA (Table 3), Comparative Examplehas a worse (i.e., greater) difference between the average high-frequency amplitude and the average low-frequency amplitude. This demonstrates that the piezoelectric speaker of the present invention improves the low-frequency behavior, as observed in relation to the high-frequency behavior.

[0060] Table 3 also presents the dimensions and average low-frequency amplitude of Example 6 and Comparative Example BB. The volume of the single piezoelectric layer in Example 6 (400 mm3) is the same as the stack of four piezoelectric sheets stacked together in Comparative Example BB (also 400 mm3). Since the driving voltage and volume is the same, Example 6 and Comparative Example BB are directly comparable. The average low-frequency amplitude of Example 6 is more than 13 dB higher than that for Comparative Example BB. Additionally, although not shown, it was observed that the difference in amplitude for frequencies less than 200 Hz was 20 dB or more. This demonstrates that the thinner, larger area piezoelectric layer of the piezoelectric speaker of the present disclosure increases the average low-frequency amplitude compared to a thicker, smaller area piezoelectric.

[0061] The piezoelectric speaker can achieve high values of the average low-frequency amplitude (e.g., 60 dB or more or 64 dB or more). Also, the piezoelectric speaker can exhibit a low difference between the average high-frequency amplitude and the average low-frequency amplitude (e.g., 24 dB or less, 20 dB or less, or 10 dB or less). As demonstrated by the Examples here, the dimensions (e.g., thickness of 120 pm or less and / or dimensions corresponding to an area greater than 5000 mm2or more) of the piezoelectric sheet can enable unexpectedly improved low-frequency performance of the piezoelectric speaker. The piezoelectric speaker can have a single, sintered ceramic (e.g., ribbon) as the piezoelectric. Without wishing to be bound by theory, sintered ceramic ribbons can have increased mechanical strength and / or dimensional stability that other methods of forming a layer (e.g., physical vapor deposition, sputtering).

Claims

CLAIMSWhat is claimed is:

1. A piezoelectric speaker comprising: a diaphragm; a piezoelectric layer disposed over the diaphragm, a thickness of the piezoelectric layer is in a range from 20 micrometers to 120 micrometers, a width of the piezoelectric layer is 50 millimeters or more, and a length of the piezoelectric layer is 100 mm or more; and a pair of electrodes in electrical contact with the piezoelectric layer and configured to drive the piezoelectric layer.

2. The piezoelectric speaker of claim 1, wherein the width of the piezoelectric layer is from 50 millimeter to 200 millimeters, and the length is greater than or equal to the width.

3. The piezoelectric speaker of any one of claims 1-2, wherein the length of the piezoelectric layer is from 100 millimeters to 200 millimeters.

4. The piezoelectric speaker of any one of claims 1-3, wherein the piezoelectric layer comprises a lead zirconate titanate or an alkali metal niobate.

5. The piezoelectric speaker of any one of claims 1-4, wherein the piezoelectric layer is a single piezoelectric layer.

6. The piezoelectric speaker of any one of claims 1-5, wherein the piezoelectric layer is a sintered ceramic ribbon.

7. The piezoelectric speaker of any one of claims 1-6, wherein the piezoelectric layer is attached to the diaphragm by an adhesive layer.

8. The piezoelectric speaker of any one of claims 1 -7, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an averagelow-frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is within 25 deciBels of an average high-frequency amplitude of sound averaged over frequencies from 1000 Hertz to 20000 Hertz.

9. The piezoelectric speaker of claim 8, wherein the average low-frequency amplitude of sound is within 20 deciBels of the average high-frequency amplitude of sound.

10. The piezoelectric speaker of any one of claims 8-9, wherein the average low-frequency amplitude of sound is within 10 deciBels of the average high-frequency amplitude of sound.

11. The piezoelectric speaker of any one of claims 1 -7, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an average low-frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is 60 deciBels or more.

12. The piezoelectric speaker of claim 11, wherein the average low-frequency amplitude of sound is 64 deciBels or more.

13. A consumer electronic device comprising: a housing comprising a front surface, a back surface, and side surfaces; and electrical components at least partially within the housing, the electrical components comprise a controller, a memory, a display, and the piezoelectric speaker of any one of claims 1- 12.

14. A method of making a piezoelectric speaker comprising: attaching a single piezoelectric layer and a pair of electrodes to a diaphragm using an adhesive to form the piezoelectric speaker, wherein a thickness of the single piezoelectric layer is in a range from 20 micrometers to 120 micrometers, a width of the single piezoelectric layer is 50 millimeters or more, and a length of the single piezoelectric layer is 100 mm or more.

15. The method of claim 14, further comprising sintering a green tape to form the single piezoelectric layer.

16. The method of any one of claims 14-15, wherein the width of the single piezoelectric layer is from 50 millimeter to 200 millimeters, and the length is greater than or equal to the width.

17. The method of any one of claims 14-16, wherein the length of the single piezoelectric layer is from 100 millimeters to 200 millimeters.

18. The method of any one of claims 14-17, wherein the single piezoelectric layer comprises a lead zirconate titanate or an alkali metal niobate.

19. The method of any one of claims 14-18, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an average low- frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is within 20 deciBels of an average high-frequency amplitude of sound averaged over frequencies from 1000 Hertz to 20000 Hertz.

20. The method of any one of claims 14-18, wherein when the piezoelectric speaker is driven with a voltage from 10 Volts to 20 Volts, the piezoelectric speaker exhibits an average low- frequency amplitude of sound averaged over frequencies from 100 Hertz to 1000 Hertz that is 60 deciBels or more.

21. The method of any one of claims 14-20, wherein the piezoelectric speaker is the piezoelectric speaker of any one of claims 1-13.

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