PATENT DOCUMENT

Publication Number: US-9450203-B2
Application Number: US-201414580052-A
Country: US
Kind Code: B2

Title: Organic light-emitting diode display with glass encapsulation and peripheral welded plastic seal

Abstract:
A display may have thin-film transistor circuitry that includes organic light-emitting diodes. The thin-film transistor circuitry may be formed on a substrate. First and second thin-film inorganic moisture barrier layers may be deposited on top of the thin-film transistor circuitry. An organic planarization layer may be interposed between the first and second thin-film inorganic moisture barrier layers. A moisture barrier glass layer may be attached to the second thin-film inorganic moisture barrier layer with a layer of liquid adhesive. The display may have functional layers such as a touch sensor and circular polarizer that are interposed between a cover glass layer and the moisture-barrier glass layer. A thermoplastic polymer moisture barrier ring that runs around the peripheral edge of the display may be laser welded between the moisture barrier glass layer and the substrate.

Claims:
What is claimed is: 
     
       1. A display having a peripheral edge, comprising:
 first and second display layers; 
 thin-film transistor circuitry between the first and second display layers, wherein thin-film transistor circuitry comprises light-emitting diodes; 
 a moisture-barrier ring of thermoplastic polymer that is attached between the first and second display layers to prevent moisture from reaching the thin-film transistor circuitry, wherein the first display layer comprises a substrate layer on which the thin-film transistor circuitry is formed; and 
 a polarizer, wherein the second display layer is interposed between the polarizer and the first display layer, and wherein the moisture-barrier ring extends between the substrate layer and the second display layer to seal the peripheral edge of the display. 
 
     
     
       2. The display defined in  claim 1 
 wherein the second display layer comprises a moisture-barrier glass layer, wherein the moisture-barrier ring is laser welded between the substrate layer and the moisture-barrier glass layer. 
 
     
     
       3. The display defined in  claim 2  further comprising a layer of liquid adhesive between the moisture-barrier glass layer and the thin-film transistor circuitry. 
     
     
       4. The display defined in  claim 3  further comprising first and second moisture barrier layers interposed between the thin-film transistor layer and the moisture-barrier glass layer. 
     
     
       5. The display defined in  claim 4  further comprising an organic layer between the first and second moisture barrier layers. 
     
     
       6. The display defined in  claim 5  wherein the first and second moisture barrier layers are deposited thin-film inorganic layers. 
     
     
       7. The display defined in  claim 6  wherein the first and second moisture barrier layers are silicon nitride layers. 
     
     
       8. The display defined in  claim 6  wherein the moisture barrier glass layer comprises a layer of bulk glass having a thickness of 10 to 50 microns. 
     
     
       9. The display defined in  claim 1  wherein the light-emitting diodes comprise organic light-emitting diodes. 
     
     
       10. The display defined in  claim 9  wherein the second layer comprises a moisture-barrier glass layer, the display further comprising:
 a thin-film inorganic moisture barrier layer between the moisture-barrier glass layer and the thin-film transistor circuitry; and 
 a layer of liquid adhesive between the moisture-barrier glass layer and the thin-film transistor circuitry. 
 
     
     
       11. The display defined in  claim 10  wherein the layer of liquid adhesive includes index-matched microspheres. 
     
     
       12. The display defined in  claim 10  further comprising:
 a cover glass layer. 
 
     
     
       13. The display defined in  claim 12  further comprising at least one layer of optically clear adhesive interposed between the cover glass layer and the moisture-barrier glass layer. 
     
     
       14. The display defined in  claim 12  further comprising:
 a touch sensor between the cover glass layer and the moisture-barrier glass layer, wherein the polarizer comprises a circular polarizer between the cover glass layer and the moisture-barrier glass layer. 
 
     
     
       15. The display defined in  claim 14  further comprising optically clear adhesive that attaches the cover glass layer to the touch sensor, that attaches the touch sensor to the circular polarizer, and that attaches the circular polarizer to the moisture-barrier glass layer. 
     
     
       16. A method of forming a display that has a peripheral edge, comprising:
 forming thin-film transistor circuitry on a display substrate, wherein the thin-film transistor circuitry includes organic light-emitting diodes; 
 depositing an inorganic moisture barrier layer over the thin-film transistor circuitry; 
 applying a layer of adhesive to a moisture-barrier glass layer; 
 attaching the moisture-barrier glass layer to the inorganic moisture barrier layer with the layer of adhesive such that the inorganic moisture barrier layer is interposed between the moisture barrier glass layer and the thin-film transistor circuitry; and 
 attaching a thermoplastic ring around the peripheral edge between the moisture-barrier glass layer and the display substrate so that the thermoplastic ring surrounds the organic light-emitting diodes. 
 
     
     
       17. The method defined in  claim 16  wherein attaching the thermoplastic ring comprises laser welding the thermoplastic ring around the peripheral edge, the method further comprising:
 depositing the inorganic moisture barrier layer over the thin-film transistor circuitry; 
 depositing an organic planarization layer over the inorganic moisture barrier layer; and 
 depositing an additional inorganic moisture barrier layer over the organic planarization layer. 
 
     
     
       18. The method defined in  claim 17  further comprising:
 attaching the moisture-barrier glass layer to the additional inorganic moisture barrier layer with a layer of adhesive. 
 
     
     
       19. An organic light-emitting diode display, comprising:
 a substrate layer; 
 thin-film transistor circuitry including organic light-emitting diodes on the substrate layer; 
 a first thin-film moisture barrier layer on the thin-film transistor circuitry; 
 an organic planarization layer on the first thin-film moisture barrier layer; 
 a second thin-film moisture barrier layer on the thin-film transistor circuitry; 
 a moisture-barrier glass layer; and 
 a thermoplastic polymer moisture-barrier ring that is attached between the substrate layer and the moisture-barrier glass layer and that surrounds the thin-film transistor circuitry. 
 
     
     
       20. The display defined in  claim 19  wherein the thermoplastic polymer moisture-barrier ring is laser welded between the moisture-barrier glass layer and the substrate, the display further comprising:
 a layer of liquid adhesive that attaches the moisture barrier glass layer to the second thin-film moisture-barrier layer; 
 a cover glass layer; and 
 functional layers interposed between the cover glass layer and the moisture-barrier glass layer. 
 
     
     
       21. The display defined in  claim 20  wherein the functional layers include a touch sensor layer attached to the cover glass layer with optically clear adhesive.

Description:
BACKGROUND 
     This relates generally to electronic devices with displays, and, more particularly, to encapsulating displays to protect display components from moisture. 
     Electronic devices often include displays. Displays such as organic light-emitting diode displays contain organic emissive materials and other structures that are sensitive to moisture. To prevent moisture intrusion, some organic light-emitting diode displays include deposited thin-film moisture barrier layers. The thin-film moisture barrier layers may be formed from materials such as silicon nitride that are impermeable to water. 
     A display may also contain an inorganic barrier layer that is attached to underlying display layers with a layer of pressure sensitive adhesive. Inorganic barrier layers formed on pressure sensitive adhesive in this way tend to exhibit poor water blocking capabilities. Pressure sensitive adhesive is associated with high water diffusivity and low water solubility, so large amounts of moisture can also intrude into a display through the edges of a pressure sensitive adhesive layer. Moisture barrier layers that are not formed on pressure sensitive adhesive may be better able to withstand moisture, but are not perfect and can still allow moisture to penetrate to sensitive organic material layers in a display. For example, these moisture barrier layers may not be able to block all moisture that has penetrated through the edges of a pressure sensitive adhesive layer and the inorganic moisture barrier layer on top of the pressure sensitive adhesive layer. 
     It would therefore be desirable to be able to provide moisture barrier structures for preventing moisture intrusion into a display such as an organic light-emitting diode display. 
     SUMMARY 
     A display may have thin-film transistor circuitry that includes an array of organic light-emitting diodes. The thin-film transistor circuitry may be formed on a substrate. The thin-film transistor circuitry may be covered with moisture barrier structures, functional layers, and a cover glass layer. A moisture-barrier ring that is formed from a thermoplastic polymer may surround the thin-film transistor circuitry. 
     The moisture barrier structures may include first and second inorganic thin-film moisture-barrier layers such as layers of silicon nitride. The first and second thin-film inorganic moisture barrier layers may be deposited on top of the thin-film transistor circuitry. An organic planarization layer may be interposed between the first and second thin-film inorganic moisture barrier layers. 
     A moisture barrier glass layer may be attached to the second thin-film inorganic moisture barrier layer with a layer of liquid adhesive. The moisture barrier glass layer may be a layer of bulk glass such as silica glass with a thickness of 10-50 microns. The display may have functional layers such as a touch sensor and circular polarizer that are interposed between a cover glass layer and the moisture-barrier glass layer. The thermoplastic polymer moisture barrier ring may run around the peripheral edge of the display and may be laser welded between the moisture barrier glass layer and the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is a top view of an illustrative display in an electronic device in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a portion of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG. 4  is cross-sectional side view of a portion of an illustrative organic light-emitting diode display that includes a glass moisture barrier layer in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an edge portion of an illustrative organic light-emitting diode display having a welded plastic moisture barrier ring to block moisture in accordance with an embodiment. 
         FIG. 6  is a flow chart of illustrative steps involved in forming a display in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  16  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  12  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. 
     Control circuitry  16  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  16  may display images on display  14  using an array of pixels in display  14 . 
     Device  10  may be a tablet computer, laptop computer, a desktop computer, a display, a cellular telephone, a media player, a wristwatch device or other wearable electronic equipment, or other suitable electronic device. 
     Display  14  may be an organic light-emitting diode display or may be a display based on other types of display technology. Configurations in which display  14  is an organic light-emitting diode display are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display may be used, if desired. 
     Display  14  may have a rectangular shape (i.e., display  14  may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint) or may have other suitable shapes. Display  14  may be planar or may have a curved profile. 
     A top view of a portion of display  14  is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may have an array of pixels  22 . Pixels  22  may receive data signals over signal paths such as data lines D and may receive one or more control signals over control signal paths such as horizontal control lines G (sometimes referred to as gate lines, scan lines, emission control lines, etc.). There may be any suitable number of rows and columns of pixels  22  in display  14  (e.g., tens or more, hundreds or more, or thousands or more). Each pixel  22  may have a light-emitting diode  26  that emits light  24  under the control of a pixel control circuit formed from thin-film transistor circuitry such as thin-film transistors  28  and thin-film capacitors). Thin-film transistors  28  may be polysilicon thin-film transistors, semiconducting-oxide thin-film transistors such as indium zinc gallium oxide transistors, or thin-film transistors formed from other semiconductors. 
     A cross-sectional side view of an illustrative organic light-emitting diode display is shown in  FIG. 3 . As shown in  FIG. 3 , display  14  may include a substrate layer such as substrate layer  30 . Substrate  30  may be a planar layer or a non-planar layer and may be formed from plastic, glass, ceramic, sapphire, or other suitable materials. Configurations for display  14  in which substrate  30  is formed from a material such as plastic are sometimes described herein as an example. 
     Thin-film transistor circuitry  44  may be formed on substrate  30 . Thin film transistor circuitry  44  may include anode structures such as anode  36  on layers  34 . Layers  34  may include semiconductor layers, metal layers, and dielectric layers that form circuitry  32 . Circuitry  32  may include transistors and capacitors for controlling light-emitting diodes such as light emitting diode  26  of  FIG. 3 . During operation, light-emitting diode  26  may emit light  24 . 
     Light-emitting diode  26  may be formed within an opening in pixel definition layer  40 . Pixel definition layer  40  may be formed from a patterned photoimageable polymer. In each light-emitting diode, organic emissive material  38  is interposed between a respective anode  36  and cathode  42 . Anodes  36  may be patterned from a layer of metal on circuitry  32 . Cathode  42  may be formed from a common conductive layer that is deposited on top of pixel definition layer  40 . Cathode  42  is transparent so that light  24  may exit light emitting diode  26 . 
     Organic light-emitting diode display structures such as emissive material  38  and other thin-film transistor circuitry  44  may be sensitive to moisture. Accordingly, thin-film transistor circuitry  44  may be covered with a layer of moisture barrier structures. For example, thin-film transistor circuitry  44  may be covered with moisture barrier structures  46 . Structures  46  may include one or more moisture barrier layers, planarization layers, adhesive layers, buffer layers, and other structures. To help minimize moisture permeation, the use of pressure sensitive adhesive in structures  46  may be minimized. Moisture may also be blocked by incorporating a thin layer of glass into structures  46 . The glass layer may be formed from a bulk glass material rather than a thin-film layer deposited using thin-film deposition techniques. This helps eliminate defects and thereby enhances moisture resistance. 
     Display  14  may have a protective outer display layer such as cover glass layer  50 . The outer display layer maybe formed from a material such as sapphire, glass, plastic, clear ceramic, or other transparent material. Configurations in which the outermost layer of display  14  is formed from a clear layer of glass are sometimes described herein as an example. This is merely illustrative. In general, the outermost layer of display  14  may be formed from any suitable material and may be formed form a thickness sufficient to provide display  14  with damage from scratches, etc. For example, cover glass  50  may have a thickness of 0.05 to 2 mm, 0.1 to 0.5 mm, etc. 
     If desired, display  14  may include functional layers  48 . Functional layers  48  may include a touch sensor layer, a circular polarizer layer, and other layers. A circular polarizer layer may help reduce light reflections from metal traces in thin-film transistor circuitry  44 . A touch sensor layer may be formed from an array of capacitive touch sensor electrodes on a flexible polymer substrate. The touch sensor layer may be used to gather touch input from the fingers of a user, from a stylus, or from other external objects. Layers of optically clear adhesive may be used to attach cover glass layer  50  and functional layers  48  to underlying display layers such as moisture barrier structures  46 , thin-film transistor circuitry  44 , and substrate  30 . 
     A cross-sectional side view of display  14  in a configuration in which a thin layer of glass is used to help prevent moisture permeation is shown in  FIG. 4 . As shown in  FIG. 4 , thin-film transistor circuitry  44  may be formed on substrate  30 . Moisture barriers structures  46  may be formed on cathode layer  42  and other thin-film transistor circuitry. Functional layers  48  may be interposed between cover glass layer  50  and moisture barrier structures  46 . 
     Moisture barrier structures  46  may include a thin layer of glass such as glass layer  66 . Glass layer  66  may be formed from bulk glass material and may have a thickness of 10-50 microns, 5-100 microns, less than 70 microns, more than 2 microns, more than 5 microns, less than 30 microns, or other suitable thickness. 
     Cathode  42  maybe covered with a capping layer such as capping layer  52 . Capping layer  52  may be a transparent inorganic layer that helps protect cathode  42 . A first inorganic moisture barrier layer such as moisture barrier layer  54  may be deposited on capping layer  52 . Moisture barrier layer  54  may be formed from silicon nitride or other inorganic materials that are impermeable to moisture. 
     An organic buffer layer such as organic planarization layer  56  may be formed on moisture barrier layer  54 . Planarization layer  56  serves as a compliance layer that covers particles in the lower layers of display  14 , but does not block moisture. A second moisture barrier layer such as moisture barrier layer  58  may be formed on planarization layer  56 . Moisture barrier layer  58  maybe a thin-film silicon nitride layer or a layer of other inorganic material that is deposited on the layers of display  14  after depositing planarization layer  56 . 
     Moisture barrier glass layer  66  may be attached to the other layers of structures  46  such as moisture barrier layer  58  using a thin layer of adhesive such as adhesive layer  60 . Adhesive layer  60  may have a thickness of about 3 microns, 1 to 5 microns, more than 1 micron, less than 10 microns, or other suitable thickness. Layer  60  may be formed from a layer of liquid adhesive  62  that contains index-matched microspheres  64 . Microspheres  64  may have an index of refraction that is the same as that of liquid adhesive  62  so that microspheres  64  do not scatter light  24 . The diameter of microspheres  64  may be selected to adjust the thickness of adhesive layer  60  to a desired value. For example, if adhesive layer  60  is to have a thickness of 3 microns, microspheres  64  may be selected that have diameters of 3 microns. Liquid adhesive  62  may be optically clear epoxy that is cured using exposure to ultraviolet light or other suitable adhesive. 
     Layers of optically clear adhesive  68  may be used to attach functional layers  48  between cover glass  50  and moisture barrier structures  46 . As shown in  FIG. 4 , for example, layers such as touch sensor layer  72  and circular polarizer  70  may be attached to the lower surface of cover glass  50  using optically clear adhesive  68 . Optically clear adhesive  68  may also be used to attach functional layers  48  to the upper surface of moisture barrier glass layer  66 . Optically clear adhesive  68  may be a liquid optically clear adhesive or maybe an optically clear adhesive film. Functional films  48  may have a thickness of about 500 microns or other suitable thickness. 
     To help ensure that moisture does not penetrate display  14  through the edges of display  14 , the peripheral edge of display  14  may be provided with a solid plastic moisture barrier ring. This type of arrangement is shown in the cross-sectional side view of display  14  in  FIG. 5 . As shown in  FIG. 5 , thin-film transistor circuitry  44  may be formed on the upper surface of substrate  30 . Moisture barrier structures  46  may be formed on top of thin-film transistor circuitry  44 . Functional layers  48  may be interposed between cover glass layer  50  and glass layer  66  of moisture barrier structures  46 . Adhesive layer  64  may be used to attach glass layer  66  to underlying structures such as moisture barrier layer  58 . 
     The periphery of display  14  may be sealed against moisture using moisture barrier ring  76 . Ring  76  may have a rectangular ring shape that surrounds pixels  22  ( FIG. 2 ) and that runs along the periphery of display  14  between layer  66  and substrate  30  (and/or layers on substrate  30 ). Ring  76  may be formed from a polymer that is impervious to moisture such as a dense thermoplastic polymer. Light  24  does not pass through ring  76 , so the plastic material that makes up ring  76  need not be transparent. Ring  76  may have a thickness of 0.5 mm to 2 mm, 1.0 mm to 2 mm, more than 1 mm, less than 3 mm, or other suitable thickness. Techniques such as laser welding techniques may be used to attach ring  76  within display  14 . 
     A flowchart of illustrative steps involved in forming display  14  is shown in  FIG. 6 . 
     At step  80 , plastic moisture barrier ring  76  may be formed on glass moisture barrier layer  66 . For example, plastic moisture barrier ring  76  may be attached along the edges of glass layer  66  by heating ring  76  and glass layer  66  in an oven. Because sensitive structures such as the emissive material and other structures of thin-film transistor circuitry  44  are not present during the operations of step  80 , the plastic material that forms ring  76  may, if desired, have a relatively high melting temperature (e.g., 250-350° C., 300° C., more than 275° C., less than 400° C., etc.). 
     At step  82 , a thin layer of adhesive such as adhesive layer  64  may be applied to the underside of glass moisture barrier layer  66 . Adhesive layer  64  may be applied in liquid form and may, if desired, contain index-matched microparticles that serve as spacers to help ensure that glass layer  66  is separated from moisture barrier layer  58  by a desired amount of adhesive. Following application of a thin liquid layer of adhesive  64 , layer  64  may be exposed to ultraviolet light to activate adhesive layer  64 . 
     After adhesive layer  64  has been applied, glass layer  66  and ring  76  may be attached to the other layers of display  14  (step  84 ). Adhesive  64  may be cured at room temperature and/or adhesive  64  may be cured by exposing adhesive  64  to heat and/or light (as examples). 
     During the operations of step  86 , a laser may be used to weld ring  76  between glass layer  66  and substrate  30 . The laser may emit light that passes through transparent display layers during welding. For example, laser light may pass through glass layer  66  during welding. The laser welding process preferably only produces heat locally in the vicinity of the applied laser beam and ring  76 , thereby avoiding heat-induced damage to thin-film transistor circuitry  44 . 
     After ring  76  has been welded into place to seal the periphery of display  14  against moisture, the remaining portions of display  14  may be assembled. In particular, optically clear adhesive  68  may be use to attach touch sensor  72 , circular polarizer  70 , or other functional films  48  between cover glass layer  50  and glass layer  66  (step  88 ). 
     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: 20141222
Publication Date: 20160920
Grant Date: 20160920
Priority Date: 20141222
Inventors: KIM JINKWANG
LEE JUNGMIN
Assignee: APPLE INC
CPC Classifications: [{"code": "H01L51/5253", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/323", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/56", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/3262", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5246", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01L51/5237", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/87", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K71/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/84", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/86", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/40", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K50/8426", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K50/844", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/1213", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/841", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/8791", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/873", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K71/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/8722", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 56130485