Touch Sensing Using Polyvinylidene Fluoride Piezoelectric Film

Abstract

A piezoelectric sensing module comprising: a polyvinylidene fluoride (PVDF) piezoelectric film, a first electrode layer including a plurality of receiver electrodes arranged in a first pattern that enables sensing of a position of an input object on a touch surface using the PVDF piezoelectric film, and a second electrode layer including at least one common electrode, wherein the second electrode layer is between the PVDF piezoelectric film and the touch surface, and the PVDF piezoelectric film is disposed between the first electrode layer and the second electrode layer.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 63 / 316,904, filed March 4, 2022. U.S. Provisional Patent Application No. 63 / 316,904 is incorporated by reference herein in its entirety. [Background technology]

[0002] Input devices including touch sensor devices (e.g., touch pads or touch sensor devices) are widely used in various electronic systems. Touch sensor devices generally include a sensing area, often bounded by a surface, in which the touch sensor device determines at least one of the presence, location, and motion of one or more input objects. Touch sensor devices may be used to provide an interface to electronic systems. For example, touch sensor devices are often used as input devices for larger computer systems (e.g., opaque touch pads integrated into or peripheral to notebook or desktop computers). Touch sensor devices may be used in different environments with unique challenges, such as exposure to different types of noise, moisture, etc. Summary of the Invention [Means for solving the problem]

[0003] This Summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

[0004] In general, in one aspect, an embodiment relates to a piezoelectric sensing module including a polyvinylidene fluoride (PVDF) piezoelectric film, a first electrode layer including a plurality of receiver electrodes arranged in a first pattern that enables sensing of a position of an input object on a touch surface using the PVDF piezoelectric film, and a second electrode layer including at least one common electrode, wherein the second electrode layer is between the PVDF piezoelectric film and the touch surface, and the PVDF piezoelectric film is disposed between the first electrode layer and the second electrode layer.

[0005] In general, in one aspect, an embodiment relates to a piezoelectric input device including a piezoelectric sensing module and a processing system, the piezoelectric sensing module including a polyvinylidene fluoride (PVDF) piezoelectric film and a first electrode layer including a plurality of receiver electrodes arranged in a first pattern enabling detection of a position of an input object on a touch surface using the PVDF piezoelectric film, the PVDF piezoelectric film and the first electrode layer being disposed beneath the touch surface in a substantially transparent laminate, and the processing system being for determining the position of the input object based on resultant signals obtained from the plurality of receiver electrodes.

[0006] In general, in one aspect, an embodiment relates to a method for piezoelectric touch sensing that includes obtaining a first force signal from a piezoelectric sensing module including a polyvinylidene fluoride (PVDF) piezoelectric film, recording a start of a touch event based on determining that an amplitude of the first force signal is greater than a first predetermined threshold, obtaining a second force signal, and recording an end of the touch event based on determining that an amplitude of the second force signal is greater than a second predetermined threshold and that the first and second force signals are opposite in polarity.

[0007] Other aspects and advantages of the claimed subject matter will become apparent from the following description and the appended claims.

[0008] Certain embodiments of the disclosed technology will now be described in detail with reference to the accompanying drawings, in which, for purposes of consistency, like elements in the various drawings are designated by like reference numerals. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an input device in accordance with one or more embodiments. [Diagram 2] FIG. 1 illustrates a touch sensing system in accordance with one or more embodiments. [Figure 3A-B] FIG. 1 illustrates an electrode pattern according to one or more embodiments. [Figure 4A-C] 1A-1C are diagrams illustrating examples of stacking of sensing display modules according to one or more embodiments. [Fig. 4D-F] 1A-1C are diagrams illustrating examples of stacking of sensing display modules according to one or more embodiments. [Figure 4G-I] 1A-1C are diagrams illustrating examples of stacking of sensing display modules according to one or more embodiments. [Diagram 5] 1 is a flow diagram illustrating a method for piezoelectric touch sensing in accordance with one or more embodiments. [Figure 6] FIG. 1 illustrates an example implementation according to one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the following detailed description of the embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail in order to avoid unnecessarily complicating the description.

[0011] Throughout this application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in this application). The use of ordinal numbers is not intended to imply or create any particular order of elements, nor to limit any element to being only a single element, unless expressly disclosed, e.g., by using "before," "after," "single," and other such terms. Rather, the use of ordinal numbers is to distinguish elements. By way of example, a first element is different from a second element, and a first element may encompass two or more elements and may follow (or precede) a second element in the ordering of elements.

[0012] Generally, embodiments of the present disclosure include systems and methods for touch sensing using polyvinylidene fluoride (PVDF) piezoelectric films. One or more embodiments of the present disclosure enable touch sensing that provides the location of an input object present within a sensing area of ​​an input device based on piezoelectric sensing. The touch sensing may further provide the amplitude of the force applied by the input object. One or more embodiments of the present disclosure do not use additional sensing techniques (such as, for example, capacitive touch sensing) to determine the location of the input object. Thus, embodiments of the present disclosure have various advantages. For example, the described methods and systems are less costly because they do not require additional touch sensing techniques. Furthermore, the described methods and systems do not have the limitations of other touch sensing techniques. For example, compared to capacitive touch sensing, methods and systems using piezoelectric touch sensing are more robust against environmental influences, such as moisture. Thus, embodiments of the present disclosure are particularly suitable for wet or underwater environments, such as touch interfaces in kitchens, bathrooms, outdoors, industrial, manufacturing, and medical environments, digital signs, appliances, and the like. Embodiments of the present disclosure further include features that improve robustness against noise, such as high frequency noise and pyroelectric noise. Thus, the probability of false touch detection (false positives and false negatives) is greatly reduced. Thus, embodiments of the present disclosure are highly suitable for safety-related applications, such as military, aerospace, automotive, industrial, and medical applications. In general, embodiments of the present disclosure are suitable for harsh environments and applications that require high reliability. A detailed description is provided below.

[0013] FIG. 1 is a block diagram of an example of a piezoelectric input device (100) according to one or more embodiments. The piezoelectric input device (100) may be configured to provide input to an electronic system (not shown). The term "electronic system" (or "electronic device") as used in this document broadly refers to any system that may process information electronically. Some non-limiting examples of electronic systems include personal computers, such as desktop computers, laptop computers, tablets, machines and medical devices having at least some computing power, and the like. Further examples of electronic systems include peripherals, such as data input devices (including remote controls, mice, tactile input devices, or sensing devices including robotic probes, hands, pressure measuring devices, and the like), and data output devices (including display screens and printers). Other examples include remote terminals, kiosks, and video game machines (such as video game consoles and portable game devices, and the like). Other examples include communication devices (including mobile phones, such as smartphones, and the like) and media devices (including recorders, editors, and players, such as televisions, set-top boxes, music players, digital photo frames, and digital cameras, and the like). In addition, the electronic system can be a host or a slave to the input device.

[0014] 1, the piezoelectric input device (100) is shown as a touch sensitive device (e.g., a "touch pad" or "touch sensitive device") configured to sense input provided by one or more input objects within a sensing area (120). Examples of input objects include a stylus, a finger (140), etc.

[0015] The sensing region 120 encompasses any space on, around, in, and / or near the input device 100 in which the input device 100 may detect user input (e.g., user input provided by one or more input objects). The size, shape, and location of a particular sensing region may vary widely from embodiment to embodiment.

[0016] The input device (100) may use any combination of sensor components and technologies to detect user input within a sensing area (120). The input device (100) includes one or more sensing elements for detecting user input. The sensing elements may be piezoelectric. When a force load is applied to a piezoelectric material (e.g., a non-centrosymmetric material with a polarization that moves in a positive or negative direction according to the direction of the applied force), the charge balance in the piezoelectric material changes. By measuring the induced voltage, a touch event associated with the force load may be determined and the applied force may be calculated.

[0017] Some piezoelectric implementations use an array of receiver electrodes or other regular or irregular patterns to pick up induced voltages at different locations across a piezoelectric material associated with the sensing area (120), and the location of a touch event within the input area (120) may be determined accordingly.

[0018] In Figure 1, the processing system (110) is shown as part of the input device (100). The processing system (110) is configured to operate the hardware of the input device (100) to detect input in the sensing area (120). The processing system (110) may include some or all of one or more integrated circuits (ICs) and / or other circuit components. For example, the processing system (110) may include the circuit components described below with reference to Figure 2.

[0019] In some embodiments, the processing system (110) also includes electronically readable instructions, such as at least one of firmware code and software code. In some embodiments, the components that make up the processing system (110) are located together, such as near the sensing element(s) of the input device (100). In other embodiments, the components of the processing system (110) are physically separated, with one or more components in close proximity to the sensing element(s) of the input device (100) and one or more components elsewhere. For example, the input device (100) may be a peripheral device coupled to a computing device, and the processing system (110) may include software configured to run on a central processing unit of the computing device and one or more ICs (possibly with associated firmware) separate from the central processing unit. As another example, the input device (100) may be physically integrated within a mobile device, and the processing system (110) may include circuitry and firmware that is part of the main processor of the mobile device. In some embodiments, the processing system (110) is dedicated to implementing the input device (100). In other embodiments, the processing system (110) performs other functions as well, such as operating a display screen (155) or driving haptic actuators.

[0020] The processing system (110) may be implemented as a set of modules that handle different functions of the processing system (110). Each module may include circuitry, firmware, software, or a combination thereof that is part of the processing system (110). Different combinations of modules may be used in various embodiments. For example, as shown in FIG. 1, the processing system (110) may include a determination module (150) and a sensor module (160). The determination module (150) may include functionality for determining at least one of a signal-to-noise ratio, position information and / or force information of the input object, a gesture, an action to be taken based on the gesture or a combination of gestures or other information, and other operations when at least one input object is within a sensing area.

[0021] The sensor module (160) may include functionality for determining a touch event. For example, as described further below, the sensor module (160) may include sensing circuitry coupled to receiver electrodes. The sensor module (160) may receive one or more result signals from the receiver electrodes disposed on the layer of piezoelectric material. The result signals may include at least one of a desired signal, e.g., a component caused by an input object exerting a force at the sensing region (120), and an undesired signal, e.g., noise or interference.

[0022] Although FIG. 1 shows a decision module (150) and a sensor module (160), alternative or additional modules may be present in accordance with one or more embodiments. Examples of alternative or additional modules include a hardware operation module for operating hardware such as the sensor electrodes and the display screen (155), a data processing module for processing data such as, for example, the sensor signals and position information and / or force information, a reporting module for reporting information, an identification module configured to identify gestures such as, for example, a mode change gesture, and a mode change module for changing the operating mode. Furthermore, various modules may be combined in separate integrated circuits. For example, a first module may be at least partially included in a first integrated circuit and another module may be at least partially included in a second integrated circuit. Furthermore, portions of a single module may span multiple integrated circuits. In some embodiments, a processing system may perform the operations of the various modules as a whole.

[0023] In some embodiments, the processing system (110) responds directly to user input (or lack of user input) at the sensing area (120) by triggering one or more actions, such as changing an operational mode or graphical user interface (GUI) actions, such as cursor movement, selection, menu navigation, and other functions. In some embodiments, the processing system (110) provides information about the input (or lack of input) to a portion of the electronic system (e.g., to a central processing system of the electronic system separate from the processing system (110), if such a central processing system exists). In some embodiments, a portion of the electronic system processes the information received from the processing system (110) and acts in response to the user input, such as facilitating any action, including mode change actions and GUI actions.

[0024] In some embodiments, the input device (100) includes a touch screen interface, and the sensing region (120) overlaps at least a portion of the active area of ​​the display screen (155). For example, the input device (100) may include a substantially transparent sensor electrode overlaid on the display screen to provide a touch screen interface to an associated electronic system. The display screen may be any type of dynamic display capable of displaying a visual interface to a user, and may include any type of light emitting diode (LED), organic LED (OLED), cathode ray tube (CRT), liquid crystal display (LCD), plasma, electroluminescence (EL), or other display technology. The input device (100) and the display screen (155) may share physical components. For example, some embodiments may use some of the same electrical components for display and sensing. In various embodiments, one or more display electrodes of the display device may be configured for both display updates and input sensing. As another example, the display screen (155) may be operated in part or in whole by the processing system (110).

[0025] Although Figure 1 illustrates an arrangement of components, other arrangements may be used without departing from the scope of the present disclosure. For example, various components may be combined to create a single component. As another example, the functionality performed by a single component may be performed by two or more components.

[0026] Turning to Figure 2, a piezoelectric touch sensing system (200) is shown in accordance with one or more embodiments. The piezoelectric touch sensing system (200) includes a piezoelectric sensing module (210). The piezoelectric sensing module (210) may output one or more result signals (280) in response to the presence or absence of a touch, such as by a finger (298) or any other input object. The result signal(s) (280) may be processed by touch circuitry (220), as described below.

[0027] The piezoelectric sensing module (210) may be used to provide touch sensing for all or a portion of the sensing area (120) shown in Figure 1. The piezoelectric sensing module (210) may also provide display for all or a portion of the display screen (155). The touch circuitry (220) may be a component of the processing system (110).

[0028] In one or more embodiments, the piezoelectric sensing module (210) has multiple layers including a display (212) or substrate (when no display is present), various layers (214, 215, 216) for piezoelectric touch sensing, and a cover layer (218). In one embodiment, the display (212) is an OLED display. Multiple display layers may form the display (212). For example, an OLED display may include an organic light-emitting layer, an anode layer, a cathode layer, one or more conductive layers that may include a thin-film transistor (TFT) layer, and the like. The display layer stack may also include a display substrate. The display substrate may be a rigid or flexible glass or plastic substrate. Alternatively, the display (212) may be a micro LED display, a TFT display, or any other type of display including the corresponding layers.

[0029] In one or more embodiments, the layers (214, 215, 216) for piezoelectric touch sensing include a receiver electrode layer (214), a piezoelectric film (215), and a common electrode layer (216). A cover layer (218) may provide a touchable surface. The functions of these layers are described below. Additional details regarding these layers are provided with reference to Figures 4A-I, which show different possible stackups that may be used to arrange these layers.

[0030] In one or more embodiments, the receiver electrode layer (214), the piezoelectric film (215), and the common electrode layer (216) are arranged in a sandwich architecture with the piezoelectric material sandwiched between the two electrode layers. Due to the piezoelectric effect associated with the piezoelectric material, when a force load is applied to the piezoelectric film (215), the charge balance across the piezoelectric film (215) changes. This change in charge balance may be recorded as a voltage between the receiver electrode of the receiver electrode layer (214) and the common electrode of the common electrode layer (216). In one embodiment, the piezoelectric film is a polyvinylidene fluoride (PVDF) piezoelectric film. Other piezoelectric materials, such as copolymers of PVDF, may be used without departing from this disclosure. The piezoelectric film may have certain characteristics. For example, the sensitivity (expressed as a charge in response to an applied force) may be in the range of 5 to 40 pC / N. To increase the signal-to-noise ratio (SNR), the sheet resistance of the PVDF piezoelectric film with electrodes may be kept low. The sheet resistance may be 300 ohms / sq. or 100 ohms / sq. or less. In addition, the piezoelectric film may have any thickness, such as, for example, in the range of 5 to 200 μm. Additional layers may be added to the piezoelectric film. The additional layers may include, for example, one or more of a hard coat layer, an index matching layer, an antistatic layer, and the like. A description of the piezoelectric film is provided in PCT Patent Application No. PCT / JP2021 / 013199, the entirety of which is incorporated herein by reference.

[0031] In one or more embodiments, both the receiver electrode layer (214) and the common electrode layer (216) include one or more electrodes configured to detect a change in charge balance across the piezoelectric film (215). The electrodes may be made of a transparent conductive coating, such as a transparent conductive oxide (TCO), e.g., indium tin oxide (ITO), or other transparent or transparent-appearing structures, e.g., metal nanowires, carbon nanotubes, graphene, PEDOT polymer blends, and the like. For opaque applications, additional electrode materials may be considered. For example, metals, inorganic oxides, carbon, conductive polymers, and the like may be used. The common electrode(s) of the common electrode layer (216) may be held at a reference potential, e.g., signal ground, while the receiver electrode(s) of the receiver electrode layer (214) may float with respect to a reference potential based on the charge balance across the piezoelectric film (215). The receiver electrode layer (214) and possibly the common electrode layer (216) may include patterned electrodes to enable detection of the location of a force applied to the piezoelectric film (215). The use of patterned electrodes to detect the location of a force applied to the piezoelectric film (215) is described below with reference to FIG.

[0032] In one or more embodiments, the cover layer (218) provides a protective surface for the sensing display module. The cover layer (218) may be a thin glass or plastic layer with mechanical characteristics that allow for the transmission of forces applied by an input object (e.g., a finger (298)) to the piezoelectric film (215).

[0033] In one or more embodiments, the receiver electrode layer (214), the piezoelectric layer (215), the common electrode layer (216), and the cover layer (218) are substantially transparent, thereby allowing a user to view the visual content displayed by the display (212).

[0034] Turning now to the touch circuitry (220), in one or more embodiments, the touch circuitry (220) receives a result signal (280) reflecting the charge balance across the piezoelectric film relative to a reference potential (270). In one or more embodiments, a charge integrator (230) is used to convert the measured charge balance (or the change in charge balance when a force is applied) into a voltage (force signal (290)). A low pass filter (240) may be applied to the force signal (290) to reduce or eliminate higher frequency noise on the force signal (290) and also to avoid aliasing by the analog-to-digital converter (ADC) (260). The cutoff frequency of the filter may be set, for example, at 20 Hz, 30 Hz, or 40 Hz, etc., to suppress noise while avoiding interference with the actual touch event. Any suitable cutoff frequency may be used. Considerations for selecting the cutoff frequency may include reducing or eliminating power supply noise, such as at 50 Hz or 60 Hz, and / or eliminating other higher frequency noise. A digital force signal indicative of the force applied to the piezoelectric film (215) may be available at the output of the ADC (260). An example of a force signal (290) obtained in response to the application of a force is shown in FIG. 6.

[0035] 2 shows a single touch circuit (220), in one or more embodiments, multiple touch circuits may be used in conjunction with multiple receiver electrodes in the receiver electrode layer (214), as discussed with reference to Figures 3A and 3B. Alternatively, multiplexing may be used to read multiple receiver electrodes with a single touch circuit.

[0036] Turning to FIG. 3A, an electrode pattern (300) is shown. The electrode pattern includes rows of receiver electrodes (302) and columns of common electrodes (304). In the sensor pattern (300), the receiver electrodes (302) and the common electrodes (304) have a rectangular shape. The electrodes may have different shapes without departing from the present disclosure. For example, interconnected diamond-shaped electrode pads may be arranged in rows or columns. Although not shown, a piezoelectric film (215) may be disposed between the receiver electrodes (302) disposed on one surface of the piezoelectric film and the common electrodes (304) disposed on the other surface of the piezoelectric film.

[0037] In one embodiment, the common electrode (304) may be set to a reference potential, such as signal ground, while the receiver electrode (302) is floating. A result signal may be obtained for each receiver electrode (302) and common electrode (304) pair, such as using the touch circuitry (220).

[0038] At the intersection of the receiver electrode (302) and the common electrode (304), a local voltage measurement (corresponding to the force signal (290)) may be performed to determine the local effect of the force acting on the piezoelectric film (215). This area of ​​local voltage measurement may be termed a "sensing element" (306). Although only a single sensing element (306) is identified in FIG. 3A, there may be a sensing element (306) at each intersection of the receiver electrode (302) and the common electrode (304). By performing a sensing operation on each sensing element (306), the local effect of the force acting on the piezoelectric film (215) may be evaluated across the entirety (or a portion) of the piezoelectric film (215). The sensing operations may be performed in a scanning operation, e.g., row-by-row or column-by-column, until an entire frame of the sensing operation is completed. Each sensing operation may be performed by the touch circuitry (220) as described above. The result may be a set of force signals each indicative of the force at a corresponding sensing element. The location where the input object is actually exerting a force on the piezoelectric element may then be estimated. For example, it may be determined that the location is at the sensing element having the force signal with the highest voltage or highest voltage change over time. To increase accuracy, spatial interpolation between multiple sensing elements may be performed based on the corresponding force signals.

[0039] Turning to Figure 3B, an electrode pattern 350 is shown. The sensor pattern includes a pattern of receiver electrodes 352 and a single common electrode 354 that spans the area of ​​the receiver electrodes 352. Each receiver electrode 352 in the sensor pattern 350 is a pad that may have any shape.

[0040] In one embodiment, the common electrode 354 may be set to a reference potential, such as signal ground, while the receiver electrodes 352 are floated. A result signal may be obtained for each receiver electrode 352, such as using the touch circuitry 220.

[0041] A sensing element 356 is formed at each receiver electrode 352. Although the design of electrode pattern 350 differs from that of electrode pattern 300, the force signals (one for each receiver electrode 352) are obtained in a similar manner.

[0042] 3A and 3B show two types of electrode patterns, other types of electrode patterns may be used without departing from this disclosure. Additionally, the size and / or resolution of the electrode patterns may be adjusted without departing from this disclosure.

[0043] 4A-4I, various examples of possible stackups of a piezoelectric sensing module according to one or more embodiments are shown. The stackups in Figures 4A-4I show how the aforementioned layers may be arranged and further how additional layers may be included in the stackup.

[0044] Referring to FIG. 4A, the stack (400) includes a display or substrate (401), a patterned electrode (403), a piezoelectric film (404), a common electrode (405), and a cover layer (407). The display or substrate (401) may be as described above. The patterned electrode (403) may include a set of receiver electrodes as described above. The patterned electrode (403) may be disposed directly on the piezoelectric film (404). An air gap or a direct bond may be provided between the patterned electrode (403) and the display or substrate (401). The piezoelectric film (404), the common electrode (405), and the cover layer (407) may be as described above. In the stack (400), the common electrode (405) is connected to a signal ground. The common electrode may be disposed directly on the piezoelectric film (404). An adhesive (406) may secure the cover layer (407) on top of the stack (400).

[0045] Referring to FIG. 4B, the laminate (410) includes the components of the laminate (400) of FIG. 4A, plus a polyethylene terephthalate (PET) layer (411) and an adhesive (412). The PET layer (411) may be used to facilitate fabrication of the piezoelectric sensing module. Specifically, instead of disposing the patterned electrodes (403) on the piezoelectric film (404), the patterned electrodes (403) may be disposed on the PET layer (411). The adhesive (412) may permanently bond the PET layer (411) with the patterned electrodes (403) to the piezoelectric film (404). The laminate (410) may otherwise be similar to the laminate (400).

[0046] Referring to FIG. 4C, the laminate (420) includes the components of the laminate (410) of FIG. 4B, plus a PET layer (422) and an adhesive (421). The PET layer (422) may be used to facilitate fabrication of the piezoelectric sensing module. Specifically, instead of disposing the common electrode (405) on the piezoelectric film (404), the common electrode (405) may be disposed on the PET layer (422). The adhesive (421) may permanently bond the PET layer (422) with the common electrode (405) to the piezoelectric film (404). The laminate (420) may otherwise be similar to the laminate (410).

[0047] Referring to FIG. 4D, the stack (430) includes the components of the stack (400) of FIG. 4A. However, instead of the cover layer (407), the stack (430) includes a shield layer (432). The shield layer (432) may be conductive and may be connected to a ground potential, such as a system or device ground. Thus, the shield layer (432) may reduce interference that may be caused by external noise that may affect the force signal. The shield layer (432) may have similar mechanical characteristics as the cover layer (407) and may be transparent. Unlike the cover layer (407), the shield layer (432) may be conductive. For example, the shield layer may include a conductive coating, such as an ITO coating.

[0048] Referring to Figure 4E, stack (440) includes the components of stack (430) of Figure 4D. However, in stack (440), the locations of the patterned electrode (403) and the common electrode (405) within the stack are reversed. Stack (440) may otherwise be similar to stack (430).

[0049] Referring to Figure 4F, stack (450) includes the components of stack (440) of Figure 4E. However, in stack (450), shielding layer (452) provides multi-directional shielding. More specifically, in stack (452), shielding layer (452) surrounds other layers (e.g., at least patterned electrode (403), piezoelectric film (404), and common electrode (405)) from multiple sides. Shielding layer (452) may surround these layers from multiple or all sides.

[0050] Referring to FIG. 4G, in addition to the components of the stack (400) of FIG. 4A, the stack (460) includes a shielding layer (462) that can block or reduce electromagnetic interference from the display (401). This shielding layer may be located between the display (401) and the layers used for touch sensing (the patterned electrode (403), the piezoelectric film (404), and the common electrode (405)). The shielding layer (462) may be conductive and may be connected to a ground potential, such as a system or device ground. ITO or other conductive coatings may be used for the shielding layer (462). Thus, the shielding layer (462) may reduce interference that may be caused by external noise that may affect the force signal. To ensure visibility of the display (401), the shielding layer (432) may be transparent.

[0051] Referring to FIG. 4H, the laminate (470) includes the components of the laminate (460) of FIG. 4G, plus a PET layer (411) and an adhesive (412). The PET layer (411) may be used to facilitate fabrication of the piezoelectric sensing module. Specifically, instead of disposing the patterned electrodes (403) on the piezoelectric film (404), the patterned electrodes (403) may be disposed on the PET layer (411). The adhesive (412) may permanently bond the PET layer (411) with the patterned electrodes (403) to the piezoelectric film (404). The laminate (410) may otherwise be similar to the laminate (460).

[0052] Referring to FIG. 4I, the laminate (480) includes the components of the laminate (470) of FIG. 4H, plus a PET layer (422) and an adhesive (421). The PET layer (422) may be used to facilitate fabrication of the piezoelectric sensing module. Specifically, instead of disposing the common electrode (405) on the piezoelectric film (404), the common electrode (405) may be disposed on the PET layer (422). The adhesive (421) may permanently bond the PET layer (422) with the common electrode (405) to the piezoelectric film (404). The laminate (480) may otherwise be similar to the laminate (470).

[0053] 4A-4I show various stacks, other stacks may be implemented without departing from this disclosure. For example, any component shown in one of the stacks may also be present in any of the other stacks.

[0054] The selection of a particular stack-up may be based on various considerations. For example, a more basic stack-up (fewer layers) may be more cost-effective and / or more compact. Other stack-ups may be easier to manufacture. For example, instead of having electrodes directly on the surface of the piezoelectric film, an additional PET layer may be used to support the electrodes. Additionally, certain stack-ups may be less susceptible to noise than others. In particular, a shielding layer between the display and electrode layers may reduce display interference. By placing the common electrode towards the top of the stack, the effect of external electromagnetic interference on the resulting signal obtained from the patterned electrodes may be reduced, for example, when the common electrode is connected to a system ground, an actively driven shield potential, etc. The materials in any stack-up may be selected to achieve a high level of transparency for transparent applications. For example, the combination of a PVDF piezoelectric film and adjacent electrode layers may have a transparency of at least 90%, at least 80%, or any other level of transparency deemed sufficient for a given application. Thus, the various features and advantages offered by these stack-ups may be utilized without significantly interfering with the display quality in a touch display configuration.

[0055] Also, although not specifically shown, in one or more embodiments, the stack includes a thermal layer. Piezoelectric materials may have thermal drift due to the pyroelectric properties of these materials. Such thermal drift may affect force measurements, for example, when the temperature of the piezoelectric material increases during prolonged touch by a finger. The thermal layer may be an existing layer (e.g., a cover layer) in the stack or may be a dedicated layer. To stabilize the temperature of the piezoelectric material, the thermal layer may be placed on top of the piezoelectric film to provide a thermal barrier between the touch surface, which may be in contact with an object (e.g., a finger) having a different temperature, and the piezoelectric film. The thermal layer may be designed as a thermal insulation layer that limits the transfer of heat to the piezoelectric film. Alternatively, the thermal layer may be designed as a heat sink or heat spreader that absorbs heat and / or conducts heat towards other components. Thermally conductive materials that may be used include, for example, metals (e.g., Cu, Al, etc.), ceramics (e.g., AlN, Al, etc.), and / or other suitable materials. 2 O 3 , Si 3 N 4 Thermal insulation materials that may be used include, for example, glass wool, rock wool, cellulose fibers, wool, etc. For applications requiring transparency, silica gel, aerogel, etc. may be used. Use of the described thermal layer may reduce the presence of pyroelectric noise, so that other measures to address pyroelectric noise may not be necessary. For example, it may not be necessary to use software processing to offset temperature changes.

[0056] FIG. 5 illustrates a flow diagram of a method for piezoelectric touch sensing in accordance with one or more embodiments.

[0057] Performance of one or more steps in Figure 5 may involve one or more components of the systems described in Figures 1, 2, 3, and 4A-4I. Although the various steps in Figure 5 are presented and described sequentially, one skilled in the art will recognize that some or all of the blocks may be performed in a different order, may be combined or omitted, and some or all of the blocks may be performed in parallel. Additionally, the steps may be performed actively or passively.

[0058] Turning to FIG. 5, in one or more embodiments, the method (500) operates on a force signal. Although not shown in FIG. 5, additional steps may be performed to obtain the force signal by performing sensing operations as described above. These sensing operations may include obtaining a resultant signal, integrating the resultant signal with a charge integrator to obtain a force signal, and further low pass filtering and analog to digital conversion of the force signal. The sensing operations may be performed by the components shown in FIG. 2. The sensing operations may be performed at a set rate, such as, for example, 10 times per second, 100 times, 1,000 times per second, or any other rate. As described with reference to FIGS. 3A and 3B, the sensing operations may be performed on any number of sensing elements.

[0059] In step 502, a force signal baseline is obtained. The force signal baseline may reflect the force signal under a no-touch condition (i.e., when there is no input object present within the sensing region). The no-touch condition may be detected statistically over time. The force baseline may be a single value, such as, for example, an offset voltage, or may be a range, such as, for example, a combination of the offset voltage and a standard deviation to quantify the noise level of the force signal baseline.

[0060] In step 504, a force signal is obtained. The obtained force signal may be the most recent force signal available during operation of the piezoelectric touch sensing system shown in Figure 2. The force signal may be adjusted relative to a force signal baseline. For example, an offset voltage may be subtracted.

[0061] In step 506, a test is performed to determine whether the amplitude of the force signal exceeds a first predetermined threshold. The first predetermined threshold may be set such that it may be used to distinguish touch events from other events that may be considered noise. Thus, when the force baseline exhibits low baseline noise, a lower threshold may be preferred, while when the baseline noise is higher, a higher threshold may be necessary. When the amplitude of the force signal exceeds the first predetermined threshold, execution of the method may proceed to step 508. Alternatively, when the amplitude of the force signal does not exceed the first predetermined threshold, execution of the method may continue by returning to step 504 to obtain a new force signal or returning to step 502 to determine a new force signal baseline. Execution of step 506 is illustrated in the example shown in FIG. 6.

[0062] In step 508, the start of a touch event is recorded based on the force signal exceeding a first predetermined threshold, or in other words, it is concluded that a touch is present within the sensing area of ​​the piezoelectric input device.

[0063] In step 510, a force signal is obtained. Step 510 may be performed similarly to step 504.

[0064] In step 512, a test is performed to determine whether the amplitude of the force signal exceeds a second predetermined threshold. Similar to the first predetermined threshold, the second predetermined threshold may be set to account for baseline noise. When the amplitude of the force signal exceeds the second predetermined threshold, execution of the method may proceed to step 514. Alternatively, when the amplitude of the force signal does not exceed the first predetermined threshold, execution of the method may continue back to step 510 to obtain a new force signal. Execution of step 512 is shown in the example shown in FIG. 6.

[0065] In step 514, a test is performed to determine the polarity of the force signal (i.e., it is determined whether the amplitude of the force signal is positive or negative). If the polarity of the force signal is the same as the polarity of the force signal that caused the initiation of the touch event (step 508), then the method may proceed to perform step 516. Otherwise, the method may proceed to perform step 518.

[0066] In step 516, the start of another touch event is recorded, which may be the result of an increased touch force. An example is provided below with reference to FIG.

[0067] In step 518, the end of the touch event is recorded based on the force signal exceeding the second predetermined threshold and the polarity of the force signal obtained in step 510 being opposite to the polarity of the force signal obtained in step 504. In other words, it is concluded that the touch event that started with the performance of step 508 ends. When multiple touch events are detected (e.g., after the performance of step 516), the multiple touch events may be considered to end based on the performance of step 518.

[0068] Steps 502-518 may be performed repeatedly, for example in a loop, to allow for continuous detection of touch events over time.

[0069] Although the steps described are for detecting a touch event, other steps may be taken, such as steps to determine the location of the detected touch within a sensing area and / or determine the force amplitude of the detected touch.

[0070] Turning now to Figure 6, an example of touch event detection in accordance with one or more embodiments is shown. This example (600) is based on a force profile (610) that indicates the force that may be applied by an input object within a sensing area over time. 0 From 1 During this time, the force varies from 0 to F 1 , which may correspond to a finger beginning to touch a piezoelectric input device within the sensing area. This force increases to t 2 This may correspond to a finger continuing to touch the piezoelectric input device. 2 From 3 During this time, the force F 2 This force increases to t 4 It is constant up to t 4 From 5 During this time, the force decreases to 0 as the finger touch ends.

[0071] This embodiment (600) also includes a force signal profile (620). The force signal profile (620) corresponds to the force signal (i.e., voltage) obtained by the piezoelectric input device during exposure to the force profile (610). The force signal obtained from the piezoelectric material responds to the initial touch with a significant downward transient. Referring back to FIG. 5, this downward transient exceeds a first predetermined threshold, resulting in the detection of the start of a touch event. As the force remains constant, the transient decays. t 2 From 3Depending on the adjustment of the force between the first and second touch events, a smaller downward transient may be observed. This smaller downward transient may trigger the detection of a second touch event because it is in the same direction as the first downward transient. When the finger stops applying pressure to the piezoelectric input device within the sensing area, a noticeable upward transient is caused. In the method of FIG. 5, the upward transient will cause the end of the touch event to be detected.

[0072] Although only a few example embodiments have been described in detail above, those skilled in the art will readily recognize that many modifications are possible in these example embodiments without substantially departing from the present invention. Accordingly, all such modifications are intended to be included within the scope of the present disclosure as defined in the following claims. Any means-plus-function clause in the claims is intended to encompass structures described herein as performing the described function(s) and equivalents of those structures. Similarly, any step-plus-function clause in the claims is intended to encompass acts described herein as performing the described function(s) and equivalents of those acts. It is the express intent of the applicants not to invoke 35 U.S.C. 112(f) on any limitation of any claim herein, unless the claim expressly uses the words "means for" or "step for" with the relevant function.

Claims

1. 1. A piezoelectric sensing module, comprising: a polyvinylidene fluoride (PVDF) piezoelectric film; a first electrode layer including a plurality of receiver electrodes arranged in a first pattern that enables sensing of a position of an input object on a touch surface using the PVDF piezoelectric film; a second electrode layer including at least one common electrode; a piezoelectric sensing module, the second electrode layer being between the PVDF piezoelectric film and the touch surface, the PVDF piezoelectric film being disposed between the first electrode layer and the second electrode layer;

2. 2. The piezoelectric sensing module of claim 1, wherein the at least one common electrode is one selected from the group consisting of a signal ground potential and a device ground potential.

3. 2. The piezoelectric sensing module according to claim 1, The piezoelectric sensing module further comprising a shielding layer, the shielding layer being at device ground potential.

4. 4. The piezoelectric sensing module of claim 3, wherein the shielding layer at least partially surrounds the PVDF piezoelectric film, the first electrode layer, and the second electrode layer.

5. 4. The piezoelectric sensing module of claim 3, wherein the shield layer is in the stack between the first electrode layer and a display screen.

6. 10. The piezoelectric sensing module of claim 1 further comprising a thermal layer disposed within the stack between the PVDF piezoelectric film and the touch surface; The piezoelectric sensing module, wherein the thermal layer is one selected from the group consisting of a thermal insulation material and a heat spreader material.

7. 2. The piezoelectric sensing module of claim 1, wherein the plurality of receiver electrodes are disposed directly on the PVDF piezoelectric film.

8. 2. The piezoelectric sensing module according to claim 1, The piezoelectric sensing module further includes a display screen disposed in the stack below the PVDF piezoelectric film.

9. 10. The piezoelectric sensing module of claim 1, wherein the combined PVDF piezoelectric film, first electrode layer, and second electrode layer have a transparency of at least 80%.

10. 10. The piezoelectric sensing module of claim 1, wherein the touch surface provides a button-less touch interface for one selected from the group consisting of appliances, automotive applications, and industrial applications.

11. 1. A piezoelectric input device, comprising: a piezoelectric sensing module and a processing system; The piezoelectric sensing module includes: a polyvinylidene fluoride (PVDF) piezoelectric film; a first electrode layer including a plurality of receiver electrodes arranged in a first pattern that enables sensing of a position of an input object on a touch surface using the PVDF piezoelectric film; the PVDF piezoelectric film and the first electrode layer are disposed beneath the touch surface in a substantially transparent laminate; The processing system is a processing system for determining the position of the input object based on resultant signals obtained from the plurality of receiver electrodes.

12. 12. The piezoelectric input device of claim 11, wherein the processing system comprises: a charge integrator for determining a force signal from a resultant signal obtained at one of the plurality of receiver electrodes; and a low pass filter for reducing noise in the force signal.

13. 12. The piezoelectric input device of claim 11, wherein the piezoelectric sensing module further comprises a display screen disposed in the stack below the PVDF piezoelectric film.

14. 12. The piezoelectric input device of claim 11, wherein the piezoelectric sensing module further comprises a shielding layer disposed between the touch surface and the first electrode layer.

15. 1. A method for piezoelectric touch sensing, comprising: obtaining a first force signal from a piezoelectric sensing module including a polyvinylidene fluoride (PVDF) piezoelectric film; recording a start of a touch event based on determining that an amplitude of the first force signal is greater than a first predetermined threshold; Obtaining a second force signal; and recording an end of the touch event based on determining that an amplitude of the second force signal is greater than a second predetermined threshold and that the first and second force signals are opposite in polarity.

16. 16. The method of claim 15, The method further comprising determining a force signal baseline.

17. 17. The method of claim 16, The method, further comprising adjusting the first and second force signals relative to the force signal baseline.

18. 16. The method of claim 15, wherein obtaining the first force signal comprises: receiving a result signal from a receiver electrode disposed on the PVDF piezoelectric film; and integrating the resultant signal to obtain the first force signal.

19. 20. The method of claim 18, The method, further comprising low pass filtering the first force signal.

20. 16. The method of claim 15, The method further comprising analog-to-digital converting the first force signal.

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