PATENT DOCUMENT

Publication Number: US-9466018-B2
Application Number: US-201514699417-A
Country: US
Kind Code: B2

Title: Displays with radio-frequency identifiers

Abstract:
A display may have an active area surrounded by an inactive border area. The display may be a liquid crystal display having a liquid crystal layer sandwiched between a color filter layer and a thin-film transistor layer. An upper polarizer may have a polarized central region that overlaps the active area of the display. The upper polarizer may also have an unpolarized portion in the inactive border area overlapping the border structures. The border structures may include colored material such as a white layer on the inner surface of the thin-film transistor layer. Binary information may be embedded into an array of programmable resonant circuits. The binary information may be a display identifier or other information associated with a display. The programmable resonant circuits may be tank circuits with adjustable capacitors, fuses, or other programmable components.

Claims:
What is claimed is: 
     
       1. Apparatus, comprising:
 a display substrate; and 
 wireless identification circuitry on the display substrate, wherein the wireless identification circuitry comprises resonant circuits each having a different respective resonant frequency, wherein the resonant circuits are programmed to store embedded binary information in the resonant circuits, and wherein the resonant circuits comprise tank circuits that include capacitors formed from thin-film transistors with programmable threshold voltages. 
 
     
     
       2. The apparatus defined in  claim 1  wherein the display substrate comprises a glass substrate. 
     
     
       3. The apparatus defined in  claim 2  wherein the wireless identification circuitry is formed on the glass substrate. 
     
     
       4. The apparatus defined in  claim 3  wherein the glass substrate is a thin-film transistor layer. 
     
     
       5. A display, comprising:
 display layers; 
 a layer of liquid crystal material interposed between the display layers; 
 polarizer layers, wherein the display layers and the layer of liquid crystal material are sandwiched between the polarizer layers; and 
 thin-film transistor circuitry in the display layers, wherein the thin-film transistor circuitry comprises programmable circuitry with a plurality of programmable resonant circuits that are programmed to embed binary information in the display layers. 
 
     
     
       6. The display defined in  claim 5  wherein the binary information comprises a display identifier and wherein the display layers include a color filter layer. 
     
     
       7. The display defined in  claim 5  wherein the binary information comprises information selected from the group consisting of: test results, information on faults, manufacturing parameters, and a display identifier. 
     
     
       8. The display defined in  claim 5  wherein the programmable resonant circuits comprise tank circuits. 
     
     
       9. A method of embedding information in an array of tank circuits formed from circuitry on a display layer in a display, wherein the tank circuits each have an associated unprogrammed resonant frequency, the method comprising:
 with a programmer, adjusting components in the tank circuits so that a first subset of the tank circuits are programmed to adjust their resonant frequencies and a second subset of the tank circuits are unprogrammed and retain their unprogrammed resonant frequencies. 
 
     
     
       10. The method defined in  claim 9  wherein adjusting the components comprises blowing fuses. 
     
     
       11. The method defined in  claim 9  wherein adjusting the components comprises adjusting capacitors. 
     
     
       12. The method defined in  claim 11  wherein adjusting the capacitors comprises applying bias stress to thin-film transistor capacitors. 
     
     
       13. The method defined in  claim 9  wherein adjusting the components comprises embedding binary display identifier information within the tank circuits.

Description:
This application claims the benefit of provisional patent application No. 62/002,720, filed May 23, 2014, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, cellular telephones, computers, and televisions have displays. 
     The center of a display such as a liquid crystal display contains an array of pixels. This portion of the display, which is sometimes referred to as the active area of the display, is used to display images to a user. Peripheral circuits and other portions of the display that do not display images form a border that surrounds the inactive area. This border is sometimes referred to as the inactive area of the display. 
     To ensure that a display has an appealing appearance, it is generally desirable to hide internal components such as signal traces and other structures in the inactive area from view by the user. Accordingly, displays are often provided with plastic bezel structures that overlap the internal components in the inactive region. Bezel structures can be bulky and unsightly, so some displays are provided with a black ink border. The black ink border can be printed on the underside of a protective cover glass layer within the inactive area. The black ink border is thinner than a plastic bezel and helps hide internal display components in the inactive area of the display from view by the user. 
     Use of a display cover layer can introduce undesirable thickness and weight into a display. Some displays therefore dispense with the display cover layer and instead ensure that other display layers such as a color filter layer are sufficiently thick to provide the display with desired structural integrity. Black ink in this type of display may be incorporated under an upper polarizer layer in the inactive area of the display. 
     This type of arrangement poses challenges due to the presence of the polarizer. The polarizer reduces light transmission by half, resulting in reduced light reflection from the ink in the inactive area. If care is not taken, the border to have an unsightly appearance. For example, a white ink border would have an unsightly gray appearance rather than a desired white appearance. 
     As displays are manufactured and tested, it may be desirable to laser engrave an identifier within the border of the display. The identifier may be used to identify the display in the event that the display is later serviced. In some devices, there may be insufficient room available to engrave an identifier into the display or it may not be practical to form the identifier in an accessible location. These challenges may make it difficult to label a display with an identifier. 
     It would therefore be desirable to be able to provide electronic devices with improved display structures such as improved border masking structures and identifiers. 
     SUMMARY 
     An electronic device may be provided with a display. The display may have an active area and an inactive area. The active area may have a rectangular array of display pixels to produce images for viewing by a user. The inactive area may have the shape of a rectangular ring that surrounds the active area and that serves as a border for the display. 
     Border structures such as opaque masking structures may be used to provide the border with a desired appearance. An array of resonant circuits may be formed from thin-film transistor circuitry or other circuits in the inactive area under the opaque masking structures. The resonant circuits may be programmed so that they store embedded binary data. The resonant circuits may be wirelessly probed using a wireless reader. The resonant circuits may be used in storing a display or device serial number, test results, manufacturing parameters involved in forming display  14 , or other information associated with the manufacturing and testing of display  14  or device  10 . The resonant circuits may be tank circuits formed from parallel inductors and capacitors. 
     Each resonant circuit may have an associated unprogrammed resonant frequency. The resonant frequency of each resonant circuit can be programmed by making a bias stress change to the capacitance of the capacitor in the resonant circuit, by blowing a fuse associated with the resonant circuit, or by otherwise changing the electrical performance of the resonant circuit. A wireless reader can probe an array of resonant circuits to determine which resonant circuits have been programmed and which resonant circuits remain unprogrammed. The pattern of programmed and unprogrammed resonant circuits can be used to store binary information regarding the display or can store other information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with display structures in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with display structures in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with display structures in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a display for a computer or television with display structures in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of a liquid crystal display in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of a polarizer in accordance with an embodiment. 
         FIG. 7  is a top view of a display having a polarizer with a rectangular ring-shaped unpolarized region that runs along the rectangular periphery of the display and that serves as part of the border of the display in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative display showing how border structures may be provided in an inactive region on the underside of a display layer such as a thin-film transistor layer and may be overlapped by an unpolarized border portion of a polarizer layer in accordance with an embodiment. 
         FIG. 9  is a flow chart of illustrative steps involved in forming a display of the type shown in  FIG. 8  in accordance with an embodiment. 
         FIG. 10  is a diagram showing how a radio-frequency identifier may be formed from an array of programmable resonant circuits on a display in accordance with an embodiment. 
         FIG. 11  is a graph showing how application of bias stress may shift the threshold voltage and associated capacitance characteristic of a thin-film transistor that is being used to form a thin-film transistor capacitor in accordance with an embodiment. 
         FIG. 12  is a diagram of an illustrative resonant circuit in accordance with an embodiment. 
         FIG. 13  is a top view of an illustrative corkscrew inductor in accordance with an embodiment. 
         FIG. 14  is a side view of the illustrative inductor of  FIG. 13  in accordance with an embodiment. 
         FIG. 15  is a graph in which the response of an array of resonant circuits has been plotted as a function of frequency in accordance with an embodiment. 
         FIG. 16  is a top view of an illustrative programmable resonant circuit prior to programing of the circuit to blow a fuse in accordance with an embodiment. 
         FIG. 17  is a flow chart of illustrative steps involved in using an array of programmed resonant circuits to provide a component such as a display with a wireless identifier in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative electronic devices that have housings that accommodate displays are shown in  FIGS. 1, 2, 3, and 4 . 
     Electronic device  10  of  FIG. 1  has the shape of a laptop computer and has upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  has hinge structures  20  (sometimes referred to as a clutch barrel) to allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  is mounted in housing  12 A. Upper housing  12 A, which may sometimes be referred to as a display housing or lid, is placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows an illustrative configuration for electronic device  10  based on a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  has opposing front and rear surfaces. Display  14  is mounted on a front face of housing  12 . Display  14  may have an exterior layer that includes openings for components such as button  26  and speaker port  28 . 
     In the example of  FIG. 3 , electronic device  10  is a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  has opposing planar front and rear surfaces. Display  14  is mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  has an external layer with an opening to accommodate button  26 . 
       FIG. 4  shows an illustrative configuration for electronic device  10  in which device  10  is a computer display or other display, a computer that has an integrated computer display, or other electronic equipment. Display  14  is mounted on a front face of housing  12 . With this type of arrangement, housing  12  for device  10  may be mounted on a wall or may have an optional structure such as support stand  30  to support device  10  on a flat surface such as a table top or desk. 
     Display  14  may be a liquid crystal display or a display formed using other display technologies (e.g., a plasma display, an organic light-emitting diode display, an electrophoretic display, an electrowetting display, a hybrid display that incorporates multiple display types into a single display structure, etc.). Liquid crystal display structures for forming display  14  are sometimes described herein as an example. 
     A cross-sectional side view of an illustrative configuration that may be used for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4  or other suitable electronic devices) is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may include backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 5 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  may illuminate images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). 
     Display layers  46  may include a liquid crystal layer such a liquid crystal layer  52 . Liquid crystal layer  52  may be sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  may be interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer by forming transistor circuits on a glass layer and to form a color filter layer by patterning color filter elements on a glass layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, layer  56  may be a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Layer  58  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. 
     During operation of display  14  in device  10 , control circuitry (e.g., one or more integrated circuits on a printed circuit board) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed to display driver integrated circuit  62  and/or thin-film transistor circuitry on one or more display layers  46  using a signal path such as a signal path formed from conductive metal traces in flexible printed circuit  64  (as an example). 
     Display driver integrated circuit  62  may be mounted on thin-film-transistor layer  56  or elsewhere in device  10 . Signal lines in flexible printed circuit  64  may be used in routing signals between control circuitry in device  10  and thin-film-transistor layer  56 . If desired, display driver integrated circuits such as circuit  62  may be mounted on a printed circuit. Printed circuits in device  10  may include rigid printed circuit boards (e.g., layers of fiberglass-filled epoxy) and flexible printed circuits (e.g., flexible sheets of polyimide or other flexible polymer layers). 
     Backlight structures  42  may include a light guide plate such as light guide plate  78 . Light guide plate  78  may be formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  may generate light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from light source  72  may be coupled into edge surface  76  of light guide plate  78  and may be distributed in dimensions X and Y throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  may include light-scattering features such as pits or bumps. The light-scattering features may be located on an upper surface and/or on an opposing lower surface of light guide plate  78 . 
     Light  74  that scatters upwards in direction Z from light guide plate  78  may serve as backlight  44  for display  14 . Light  74  that scatters downwards may be reflected back in the upwards direction by reflector  80 . Reflector  80  may be formed from a reflective material such as a layer of white plastic or other reflective materials. 
     To enhance backlight performance for backlight structures  42 , backlight structures  42  may include optical films  70 . Optical films  70  may include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  may overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint in the X-Y plane of  FIG. 5 , optical films  70  and reflector  80  may have a matching rectangular footprint. If desired, optical films may be incorporated into other layers of display  14 . For example, compensation films may be incorporated into polarizer  54  (as an example). 
     Polarizers such as upper (outer) polarizer  54  and lower (inner) polarizer  60  may be formed from multiple layers of material that are laminated together. An illustrative laminated polarizer is shown in the cross-sectional side view of  FIG. 6 . As shown in  FIG. 6 , polarizer  54  (i.e., an upper polarizer in this example) may have polarizer film (layer)  92 . Film  92  may be formed from a stretched polymer such as stretched polyvinyl alcohol (PVA) and may therefore sometimes be referred to as a PVA layer. A dichroic dye such as iodine or dichroic organic pigments may be added to the stretched PVA film to provide polarizer  54  with the ability to polarize light. Iodine may, for example, be coated onto the surface of layer  92  or may otherwise be used to dope layer  92 . Molecules of iodine align with the stretched film of layer  92  and form the active polarizing layer of polarizer  54 . Other polarizer films may be used if desired. 
     Polarizer film  92  may be sandwiched between layers  90  and  94 . Layers  90  and  94  may be formed from clear polymers. For example, layer  90  may be formed from a material such as tri-acetyl cellulose (TAC) and may sometimes be referred to as a TAC film. The TAC film or other supporting substrate may help support and protect the PVA film. Other films may be laminated to film  92  if desired. For example, lower film(s)  94  may be formed from one or more compensation films  94 A and  94 B (i.e., birefringent films that help enhance off-axis viewing performance for display  14 ). Adhesive layers may be used to hold laminated films together. Functional layers such as antiscratch layers, antismudge layers, antireflection layers, and/or other layers may be coated on a polarizer (e.g., on the upper surface of layer  90 ), if desired. 
     The presence of polarizer material over the entire surface of display  14  may create challenges in forming desired border regions and in mounting components behind display  14 . In the presence of polarizer material, light transmittance is cut in half. The presence of polarizer material around the edge of display  14  may affect the appearance of the border of display  14 , because reduced light transmittance can affect the appearance of underlying border structures. As an example, when border material such as white ink is used to form the border for display  14 , the presence of overlapping polarizer material may cause the white ink to have an undesirable gray appearance. Border structures of other colors may also be adversely affected. 
     To ensure that the border of display  14  has a desired appearance, polarizer  54  can be provided with a central rectangular polarized portion  98  surrounded by an unpolarized border such as border  96 , as shown in  FIG. 7 . Unpolarized border  96  may overlap border structures in display  14  such as a layer of white border material or other border material. Other unpolarized areas may be provided within polarizer  54 , if desired. The example of  FIG. 7  in which polarizer  54  has been provided with a rectangular ring-shaped unpolarized region (unpolarized region  96 ) is merely illustrative. 
     Polarizer  54  can be chemically treated (e.g., with a strong base such as KOH) to change the chemical properties of the polarizer (i.e., to disrupt the iodine of the PVA layer) and thereby create the unpolarized region. If desired, laser bleaching may be used to form unpolarized regions in polarizer  54 . A bleached polarizer region can be stabilized by adding a moisture barrier and/or stabilizing chemicals to the bleached region. 
     In a typical display configuration, display  14  may be provided with a rectangular array of display pixels that provide images for a user (see, e.g., display pixels  100  in  FIG. 7 ). This rectangular portion of display  14  is sometimes referred to as the active area AA of display  14 . An inactive border region, sometimes referred to as inactive area IA, may run along some or all of the peripheral edges of the active area AA. For example, display  14  may have an inactive area IA that has the shape of a rectangular ring and that forms a border running along all four sides of a central rectangular active area AA, as shown by inactive border area IA in  FIG. 7 . 
     To hide signal traces and other internal device structures from view by a user, inactive area IA may be provided with opaque border structures. The border structures may include a visible layer such as a layer of white material or a layer of material having other colors and may optionally include one or more additional layers (e.g., a layer of black material) to ensure that the border structures are sufficiently opaque to block internal components from view and/or to help prevent stray backlight from leaking out of display  14 . 
     Particularly in scenarios in which the border of display  14  has a color that would be degraded by the presence of overlapping polarizer, it may be desirable to form unpolarized regions such as unpolarized border  96  in inactive area IA of  FIG. 7  or to otherwise provide display  14  with a configuration that avoids placement of polarizer material on top of the border structures. 
     Consider, as an example, the configuration of  FIG. 8 . In this type of arrangement, polarizer  54  has been provided with a polarized region  98  that overlaps active area AA of display  14  and an unpolarized border region  96  that lies within the inactive area IA along the border of display  14  (e.g., a rectangular border of the type shown in  FIG. 7 ). Thin-film transistor layer  56  has substrate layer  152  (e.g., a clear glass layer, a transparent plastic substrate, or other substrate material). Border structures  104  are formed on lower (inner) surface  154  of substrate  152 . Polarizer  54  is attached to the opposing outer surface of substrate  152 . 
     Border structures  104  include layer  104 A and optional layer  104 B. Layer  104 A may be a layer of colored material having a color that is appropriate for viewing by user  48  through transparent border portion  56 ′ of thin-film transistor layer  56  and unpolarized border  96 . As an example, layer  104 A may be a layer of white material or a material of other suitable colors (silver, gold, black, red, green, blue, etc.). Layer  104 A may be an Al 2 O 3  layer that is formed by depositing a layer of aluminum and anodizing the deposited aluminum layer, may be a ZnS layer, may be a Ta 2 O 5  layer, may be other metal oxides, may be other inorganic layer(s), or may be formed using other materials. In some scenarios, layer  104 A may be translucent or may otherwise be insufficiently opaque to block light. In these situations, one or more additional layers of material such as layer  104 B may be deposited on the underside of layer  104 A. Layer  104 B may, for example, be a layer of black ink or other opaque masking material. The presence of layer  104 B on layer  104 A helps ensure that border structures  104  in inactive area IA are opaque. In configurations in which layer  104 A is opaque, layer  104 B may be omitted in inactive border area IA. In active area AA, layer  104 B may form a black matrix having a series of openings associated with respective pixels  100 . Each opening in the black matrix on thin-film transistor substrate layer  152  may be aligned with a respective color filter element  156  in color filter layer  58 . 
     Thin-film transistor black masking material  102 B may be formed from a photoimageable material such as black photoresist. The black photoresist may be formed from a polymer such as polyimide. To withstand the elevated temperatures involved in subsequent thin-film transistor fabrication steps, the polymer that is used in forming black masking material  102 B preferably can withstand elevated temperatures (e.g., temperatures of 350° C. or higher or other suitable elevated temperatures). Opaque filler materials such as carbon black and/or titanium black may be incorporated into the polyimide or other polymer of layer  102 B, so that layer  102 B is opaque. 
     Thin-film transistor layer  56  includes thin-film transistor circuitry  166 . Planarization layer  106  is used to planarize layer  102 B so that thin-film transistor structures  166  can be formed on the lower side of thin-film transistor substrate layer  152 . With one suitable arrangement, planarization layer  106  is formed from a black mask compatible material having a low dielectric constant such as a spin-on glass (SOG). For example, planarization layer  106  may be formed from a spin-on glass such as a silicon oxide based spin-on glass (e.g., a silicate spin-on glass) or other silicate layer. 
     During thin-film transistor formation, thin-film transistor structures and associated routing circuitry in layer  166  may be subjected to elevated processing temperatures (e.g., temperatures of 350° C. or higher). Layer  102 A, layer  102 B, and spin-on glass planarization layer  106  are preferably able to withstand processing at these elevated temperatures (i.e., spin-on glass layer  106  will not experience diminished transparency and layers  102 A and  102 B will not degrade). 
     Liquid crystal layer  52  may be interposed between thin-film transistor layer  56  and color filter layer  58 . A peripheral ring of epoxy or other sealant  164  may be used to retain liquid crystal material  52  in the center of display  14 . 
     Color filter layer  58  may have a clear glass or plastic layer such as color filter layer substrate  160 . An array of color filter elements  156  (e.g., red, green, and blue color filter elements or color filter elements of other colors) may be formed for display pixels  100 . Color filter elements  156  may be formed in openings in color filter layer black matrix  158 . A clear polymer planarization layer such as overcoat layer  162  may be used to cover color filter elements  156  and black matrix  158  on color filter layer substrate  160 , thereby planarizing color filter layer  58 . 
     Illustrative steps involved in forming display  14  are shown in  FIG. 9 . At step  170 , polarizer layer  54  may be formed. For example, chemical bleaching, laser bleaching, or other techniques may be used to form unpolarized border  96  in a rectangular ring shape around the periphery of a rectangular polarizer layer  54 . Polarizer  60  (i.e., the lower polarizer for display  14 ) need not be provided with any unpolarized regions. 
     At step  172 , opaque border structures  104  may be formed in inactive border area IA around the periphery of thin-film transistor substrate layer  152 . For example, colored material  104 A may be formed on lower surface  154  of substrate  152  in inactive area IA. Optional black layer  104 A may be deposited in area IA and black matrix  104 B in active area AA may be deposited during the operations of step  174 . Deposition operations for layers  104 A and/or  104 B may be performed using screen printing, pad printing, ink jet printing, metal deposition followed by anodization, blanket deposition followed by etching, shadow mask deposition, physical vapor deposition, atomic layer deposition, chemical vapor deposition, electrochemical deposition, or other suitable deposition and patterning techniques. 
     After forming opaque border structures  104  during the operations of step  172  and  174 , planarization layer  106  may be deposited at step  176 . 
     During the operations of step  178 , thin-film transistor circuitry  166  may be formed on planarization layer  106 . Some of the thin-film transistor circuitry of layer  166  may lie within active area AA (e.g., thin-film transistors for controlling electric fields applied to liquid crystal layer  52  by pixel electrodes in pixels  100 ). Other thin-film transistor circuit structures in layer  166  may lie within inactive area IA (e.g., gate drivers and other display driver circuitry, etc.). If desired, some of the circuitry in inactive area IA of layer  166  may include radio-frequency identifier circuits for storing serial number information or other information. 
     At step  180 , layers  56 ,  52 , and  58  are assembled using sealant  164 . Polarizer  54  is attached to the upper surface of thin-film transistor layer  56  and polarizer  60  is attached to the lower surface of color filter layer  58 . Backlight unit  42  is incorporated into display  14  and display  14  is mounted within device  10 . When attaching upper polarizer layer  54  to display  14 , unpolarized border region  96  is aligned with border structures  104 , so that border structures  104  are overlapped by unpolarized region  96 . Border structures  104  and unpolarized border region  96  of polarizer  54  may have the shape of rectangular rings (e.g., rings made of four strips running along the four edges of display  14 ). The presence of layer  104 A in the border can be used to adjust the color of inactive area IA as observed by an external viewer such as viewer  48 . Layer  104 A is visible through transparent unpolarized border region  96  in polarizer  54  and transparent border region  56 ′ in thin-film transistor substrate layer  152 . 
       FIG. 10  is a diagram of illustrative wireless identification circuitry (radio-frequency identification circuitry) that may be incorporated into thin-film transistor circuitry  166  in inactive area IA of display  14 . Wireless identification circuitry  200  can be used to store display-specific information such as a display serial number, manufacturing date information or other manufacturing parameters, display type, test results (e.g., a defect list), process conditions used to manufacture parts of display  14 , or other information associated with display  14 . Wireless identification circuitry  200  can be programmed so that each individual display  14  (or set of displays  14 ) that is manufactured and tested is customized and contains appropriate embedded information for that display (or set of displays). 
     Wireless identification circuitry  200  can be programmed with embedded information such as display identification information or other information during manufacturing (e.g., using contact probes and programming equipment). At another stage of the manufacturing process, or later, following assembly of display  14  and device  10  and delivery to an end user, display  14  can be placed in proximity to a wireless reader. The wireless reader can apply radio-frequency signals to wireless identification circuitry  200  to read the information that was embedded (stored) within circuitry  200  during programming. 
     As shown in  FIG. 10 , circuitry  200  can include an array of resonant radio-frequency circuits  200 - 1 ,  200 - 2 ,  200 - 3 , . . .  200 -N. There may be any suitable number of resonant circuits in circuitry  200  (e.g., one or more, two or more, five or more, ten or more, or twenty or more (as examples). The resonant circuits may be LC circuits (sometimes referred to as tank circuits) or other circuits that resonate at radio frequencies (e.g., MHz or GHz). In configurations in which the resonant circuits are LC circuits, each resonant circuit has an inductor coupled in parallel with a capacitor. The values of the inductance and capacitance in each resonant circuit are preferably selected so that the resonant circuits resonate at discrete non-overlapping frequencies. 
     In the example of  FIG. 10 , each resonant circuit has the same inductance L, but has a unique respective capacitance Cl, C 2 , C 3 , . . . CN. Configurations in which the inductance values of the resonant circuits vary may also be used, if desired. 
     The resonant circuits are programmable. Initially, when unprogrammed, resonant circuit  200 - 1  resonates at frequency f 1  (e.g., 12 GHz), resonant circuit  200 - 2  resonates at frequency f 2  (e.g., 15 GHz), resonant circuit  200 - 3  resonates at frequency f 3  (e.g., 18 GHz), etc. During programming operations, the resonant frequencies of selected resonant circuits are altered, so that they no longer lie at their original unprogrammed frequency values. For example, the resonance of circuit  200 - 1  may be shifted from an unprogrammed value of 12 GHz to a programmed value of 40 GHz. Programming operations may involve adjusting the capacitance of a capacitor, adjusting the inductance of an inductor, blowing a fuse, or otherwise adjusting the resonant circuits of circuitry  200 . During reading operations, the wireless behavior of circuitry  200  can be characterized and the pattern of programmed resonant circuits can be obtained. The presence or absence of programming for each of the resonant circuits in circuitry  200  can be used to digitally encode information such as a display identifier or other information into circuitry  200 . Information may be encoded using binary encoding. An unprogrammed resonant circuit (i.e., a resonant circuit that has retained its initial unprogrammed resonant frequency) represents a binary “1” and a programmed resonant circuit (i.e., a resonant circuit that has been altered so that its resonant frequency lies out of band or is otherwise not as initially set) represents a binary “0”. 
     With one suitable arrangement, capacitors in the resonant circuits of circuitry  200  may be formed from thin-film transistors. Programming of a resonant circuit may be accomplished by applying a programming bias to the thin-film transistor in that resonant circuit. The programming bias may stress the thin-film transistor and may shift the threshold voltage of the transistor (e.g., by populating traps in the semiconductor layer and other structures in the transistor). The shifted threshold voltage will, in turn, shift the capacitance-voltage characteristic of the transistor. 
     Consider, as an example, the scenario of  FIG. 11 . In the graph of  FIG. 11 , a transistor is initially characterized by C-V curve  202 . Following application of bias stress, curve  202  shifts to curve  206 . As a result, the capacitance of the thin-film transistor shifts (e.g., from high capacitance CH at point  204  to low capacitance CL at point  208 ). When the capacitance is lowered by programming, the resonant frequency of the resonant circuit in circuitry  200  (f˜(LC) −1/2 ) will increase beyond the normal range of frequencies f 1  . . . fn that are associated with the resonant circuits of circuitry  200 . 
       FIG. 12  is a top view of an illustrative resonant circuit. As shown in  FIG. 12 , resonant circuit  200 -N has an inductor L and a capacitor C formed from a thin-film transistor. Programming electrodes  210  and  212  may be used to apply programming signals to circuit  200 -N. In the absence of programming, capacitor C may have a capacitance of CH. Following programming (e.g., by applying a voltage of 20 volts to electrode  210  and a voltage of 0 volts to electrode  212  or using other suitable programming signals), capacitor C will have a capacitance of CL. As a result, the resonant frequency of circuit  200 -N will shift from fn to fn′, where fn′&gt;&gt;fn. 
     Once a desired subset of resonant circuits in circuitry  200  have been patterned to embed desired binary data in circuitry  200 , programming electrodes  210  and  212  may, if desired be removed (e.g., by scribing and breaking the display layer on which circuitry  200  is formed (e.g., thin-film transistor layer  56 ) along scribe line  214 . Because circuitry  200  need not be visible to wirelessly read information from circuitry  200 , circuitry  200  may be formed in small and inaccessible locations within display  14  such as the portion of layer  166  in inactive area IA (as an example). 
     In the example of  FIG. 12 , inductor L is a spiral inductor formed from two metal layers: lower metal layer M 1  and upper metal layer M 2 .  FIGS. 13 and 14  show how inductor L may be formed using a corkscrew inductor layout.  FIG. 13  is a top view of an illustrative corkscrew inductor. As shown in  FIG. 13 , a corkscrew-shaped conductive line for inductor L may be formed by connecting a series of parallel M 1  metal lines to respective diagonal M 2  metal lines.  FIG. 14  shows how M 1  and M 2  metal lines may be joined to form a continuous corkscrew conductor using vias such as via  216  in dielectric layer  218 . 
       FIG. 15  is a graph in which the readout from a wireless reader (signal S) has been plotted as a function of frequency f. The wireless reader may have a near-field communications antenna (e.g., an inductor) that is coupled to inductor L in each resonant circuit in circuitry  200  by inductive coupling (i.e., near-field electromagnetic coupling). Signal S may be the real part of the impedance of circuitry  200  as measured by the reader or may be another signal that is sensitive to the presence and absence of circuit resonances in circuitry  200 . The wireless reader may scan across all frequencies f of interest (i.e., frequencies from low frequency f 1  to high frequency fn). In a typical scenario, the resonances at some of the unprogrammed resonant frequencies for circuitry  200  will be present because the resonant circuits associated with those frequencies will not have been programmed and the resonances at other unprogrammed resonant frequencies for circuitry  200  will no longer be present because the resonant circuits associated with those frequencies will have been programmed by the programming tool (e.g., by applying a bias to resonant circuit programming electrodes such as electrodes  210  and  212  of  FIG. 12 ). 
     In the example of  FIG. 14 , there are four resonant circuits in circuitry  200  associated with four respective unprogrammed resonant frequencies f 1 , f 2 , f 3 , and f 4 . During programming, the resonant circuit for frequency f 3  was programmed (i.e., capacitor C 3  was stressed to reduce its capacitance value). As a result, the resonant frequencies for the first, second, and fourth resonant circuits are unchanged (f 1 , f 2 , and f 4 ), whereas the resonant frequency for the third resonant circuit is changed sufficiently to no longer be present within the frequency range covered by the reader (i.e., frequency f 3  has been shifted out of band to a significantly higher frequency due to the programming of capacitor C 3 ). The wireless reader can detect the binary pattern associated with unprogrammed and programmed resonant circuits (i.e.,  1111  before programming and  1101  following programming in the example of  FIG. 15 ). Using this binary information, the reader can extract information about display  14  or other components in device  10  (e.g., display identification number information, test results for the display, manufacturing parameters for the display, etc.). 
       FIG. 16  is a top view of an illustrative resonant circuit having an inductor that can be programmed by applying a programming current to fuse portion  220  of inductor L. Capacitor C in the  FIG. 16  example may be formed from parallel rectangular plates separated by a dielectric such as silicon oxide. Inductor L may be formed from a spiral of metal in a first metal layer M 1  and metal in a second metal layer M 2 , may be formed from a corkscrew inductor structure, or may be formed from other inductor structures. If desired, resonant circuits such as circuit  200 -N of  FIG. 12  may be programed by applying a voltage to capacitor C in excess of the dielectric breakdown voltage for the oxide layer. 
     A flow chart of illustrative steps involved in using resonant circuits to embed binary information in a display or other portion of device  10  are shown in  FIG. 17 . 
     At step  300 , display  14  may be manufactured. Manufacturing parameters may be associated with the manufacturing process such as the identity of subcomponents, the temperatures, times, and other process variables associated with process steps, etc. 
     At one or more testing operations (step  302 ), tests may be performed on one or more portions of display  14  to characterize display  14  and/or the components of display  14 . 
     During the operations of step  304 , circuitry  200  may be programmed using a programmer. The programmer may have probes that contact electrodes such as electrodes  210  and  212  for each resonant circuit within circuitry  200 . The programmer may apply programming signals (currents and voltages) that blow fuses, that change the threshold voltage and therefore the capacitance of thin-film transistor capacitors, that alter the capacitance exhibited by parallel plate capacitors, or that otherwise adjust the circuitry of one or more resonant circuits in circuitry  200 . The pattern of programmed resonant circuits in circuitry  200  can be used to embed binary information into circuitry  200 . The information that is embedded within circuitry  200  may include manufacturing parameters from step  300 , test results from step  302 , display numbers, dates, times, display types, fault information, etc. If desired, scribe and break techniques or other techniques may be used to remove the programming electrodes from circuitry  200  or may otherwise be used to process circuitry  200  in a way that makes the programming electrodes inaccessible to subsequent direct programming. 
     Display  14  and, if desired, device  10 , may be assembled following programing of circuitry  200  (step  306 ). 
     After display  14  and device  10  have been assembled, display  14  and device  10  may be used by a user in the field. In the event of a need for servicing, display  14  and device  10  can be taken to a service center. At the service center, a wireless reader may be used to read out the binary information that was embedded in circuitry  200 . The wireless reader may include circuitry (e.g., one or more inductors and associated radio-frequency circuitry) for inductively coupling to the resonant circuits of circuitry  200 . The wireless reader sweeps across all frequencies of interest (i.e., from lowest unprogrammed frequency f 1  to highest unprogrammed frequency fn). Expected resonances that are present correspond to binary “1” values and missing resonances correspond to binary “0” values (or vice versa). The binary information gathered by the reader this way may be used by personnel at the service center (e.g., to log a display into a database, to retrieve display-specific repair instructions, to access other database information associated with the embedded information in circuitry  200 , etc.). 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20150429
Publication Date: 20161011
Grant Date: 20161011
Priority Date: 20140523
Inventors: PARK KWANG SOON
HUNG MING-CHIN
HUANG CHUN-YAO
CHANG SHIH CHANG
HSU MING-YUH
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/13306", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1368", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06K19/0772", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133528", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2001/133388", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06K7/10198", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133388", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133388", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1368", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06K7/10198", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06K19/0772", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13306", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 54555947