PATENT DOCUMENT

Publication Number: US-10707282-B1
Application Number: US-201816000725-A
Country: US
Kind Code: B1

Title: Organic light-emitting diode display panels

Abstract:
A display may have organic light-emitting diode pixels formed from thin-film circuitry. An organic layer including planarization layers and a pixel definition layer may overlap the thin-film circuitry. Thin-film encapsulation may overlap the organic layer. The thin-film encapsulation may be formed from an organic dielectric layer interposed between two layers of inorganic dielectric material. A strip of peripheral crack-stopper structures may run along an edge of the display and may surround the array of pixels. The crack-stopper structures may include parallel inorganic lines formed from a first inorganic layer such as an inorganic layer of the thin-film circuitry. A strip of the organic layer may overlap the parallel inorganic lines. The crack-stopper structures may have parallel tapered polymer lines. The polymer lines may be overlapped by a second inorganic dielectric layer formed from the inorganic material of the thin-film encapsulation layer.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 a substrate having a peripheral edge; 
 thin-film circuitry on the substrate that is configured to form pixels, wherein the thin-film circuitry includes a first inorganic dielectric layer and an organic layer that overlaps the first inorganic dielectric layer; 
 thin-film encapsulation that covers the thin-film circuitry, wherein the thin-film encapsulation includes at least a second inorganic dielectric layer; and 
 a crack-stopper structure that runs along the peripheral edge and surrounds the pixels, wherein the first and second inorganic dielectric layers overlap the crack-stopper structure, the crack-stopper structure comprising:
 a portion of the organic layer; and 
 a polymer line with tapered sidewalls, wherein the tapered sidewalls form an overhang that overlaps the portion of the organic layer. 
 
 
     
     
       2. The display defined in  claim 1  wherein the pixels comprise organic light-emitting diode pixels and wherein the polymer line with the tapered sidewalls comprises one of a plurality of polymer lines on the portion of the organic layer, wherein each of the polymer lines has tapered sidewalls. 
     
     
       3. The display defined in  claim 2  wherein the crack-stopper structure includes a strip-shaped portion of the first inorganic dielectric layer that runs parallel to the peripheral edge. 
     
     
       4. The display defined in  claim 3  wherein the polymer lines with the tapered sidewalls have lower portions and upper portions, wherein the lower portions are closer to the portion of the organic layer than the upper portions, and wherein the lower portions of each polymer line are narrower than the upper portions of that polymer line. 
     
     
       5. The display defined in  claim 4  wherein the strip-shaped portion of the first inorganic dielectric layer is patterned to form a plurality of first inorganic dielectric layer lines, each adjacent pair of the first inorganic dielectric layer lines being separated by a respective slot-shaped opening in the strip-shaped portion of the first inorganic dielectric layer. 
     
     
       6. The display defined in  claim 5  wherein the portion of the organic layer comprises a strip-shaped portion of the organic layer that runs parallel to the peripheral edge. 
     
     
       7. The display defined in  claim 6  wherein each of the polymer lines with the tapered sidewalls runs parallel to the peripheral edge and wherein the second inorganic dielectric layer overlaps the polymer lines with the tapered sidewalls. 
     
     
       8. The display defined in  claim 7  wherein the polymer lines include at least five polymer lines. 
     
     
       9. The display defined in  claim 7  wherein the polymer lines each have a first width, wherein the polymer lines are separated from each other by slot-shaped openings that each have a second width, and wherein the second width is less than the first width. 
     
     
       10. A display, comprising:
 a substrate having a peripheral edge; 
 thin-film transistor circuitry on the substrate that is configured to form pixels, wherein the thin-film transistor circuitry includes a first inorganic dielectric layer; 
 thin-film encapsulation that covers the thin-film transistor circuitry, wherein the thin-film encapsulation includes at least a second inorganic dielectric layer; and 
 a line of crack-stopper structures that surrounds the pixels, wherein the line of crack stopper structures comprises a plurality of parallel polymer lines that are overlapped by the second inorganic dielectric layer, wherein the second inorganic dielectric layer has a first density in regions overlapping the polymer lines and a second density that is less than the first density in regions interposed between each of the polymer lines. 
 
     
     
       11. The display defined in  claim 10  wherein the pixels comprise organic light-emitting diode pixels, wherein each of the polymer lines has tapered sidewalls, wherein the polymer lines with the tapered sidewalls each have a lower portion and an upper portion, and wherein the lower portion of each of the polymer lines is narrower than the upper portion of that polymer line. 
     
     
       12. The display defined in  claim 11  wherein the line of crack-stopper structures includes a plurality of lines formed from the first inorganic dielectric layer and wherein the lines formed from the first inorganic dielectric layer are separated from each other by slot-shaped openings and run parallel to the peripheral edge. 
     
     
       13. The display defined in  claim 12  wherein the thin-film transistor circuitry further comprises an organic layer that overlaps the first inorganic dielectric layer, wherein the line of crack-stopper structures includes a strip of the organic layer that overlaps the lines of the first inorganic dielectric layer and that extends parallel to the peripheral edge. 
     
     
       14. The display defined in  claim 13  wherein the polymer lines each have a first width, wherein the polymer lines are separated from each other by gaps, wherein each gap has a second width, and wherein the second width is less than the first width. 
     
     
       15. The display defined in  claim 14  wherein the second inorganic dielectric layer comprises first and second silicon nitride layers. 
     
     
       16. A display, comprising:
 a substrate having a peripheral edge; 
 thin-film circuitry on the substrate that is configured to form pixels, wherein the thin-film circuitry includes a first inorganic dielectric layer and includes an organic layer that overlaps the first inorganic dielectric layer; 
 thin-film encapsulation that covers the thin-film circuitry, wherein the thin-film encapsulation includes a second inorganic dielectric layer; and 
 a crack-stopper structure that surrounds the pixels, wherein the crack stopper structure comprises parallel polymer lines that are overlapped by the second inorganic dielectric layer, wherein the polymer lines include first and second polymer lines, wherein the polymer lines each have a first surface and a second surface and a first width from the first surface to the second surface, wherein the polymer lines are separated from each other by a gap that extends from a first surface of the first polymer line to the second surface of the second polymer line and wherein the gap has a second width that is less than the first width. 
 
     
     
       17. The display defined in  claim 16  wherein the pixels comprise light-emitting diode pixels and wherein each of the polymer lines has tapered sidewalls with upper portions and lower portions that are narrower than the upper portions. 
     
     
       18. The display defined in  claim 17  wherein the crack-stopper structure includes a plurality of inorganic lines formed from the first inorganic dielectric layer. 
     
     
       19. The display defined in  claim 18  wherein the organic layer has a strip-shaped portion in the crack-stopper structure that overlaps the plurality of inorganic lines. 
     
     
       20. The display defined in  claim 19  wherein the second width is less than half of the first width.

Description:
This application claims the benefit of provisional patent application No. 62/556,232, filed Sep. 8, 2017, 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 such as cellular telephones, computers, and other electronic devices often contain displays. A display includes an array of pixels for displaying images to a user. In an organic light-emitting diode display, pixels are formed from thin-film circuitry. A thin-film encapsulation layer is used to protect the pixels from damage due to environmental exposure. The thin-film encapsulation layer includes inorganic dielectric. 
     The thin-film circuitry for multiple display panels can be fabricated on a common substrate. Following fabrication, individual display panels can be cut from the common substrate using a laser. The inorganic dielectric is prone to cracking as display panels are cut from the common substrate. To prevent cracking and to ensure that structures such as bond pads are not coated with inorganic dielectric, chemical vapor deposition shadow masks are used to block inorganic dielectric deposition around the periphery of each display panel where the panels are cut from the substrate. This type of arrangement places a premium on shadow mask accuracy and may create inactive border areas on the display panels that are larger than desired. 
     SUMMARY 
     A display may have an array of pixels. Each pixel may have a light source so that the array of pixels may display images. The pixels may be organic light-emitting diode pixels formed from a layer of thin-film circuitry or other suitable pixels. An organic layer including planarization layers and a pixel definition layer may overlap the thin-film circuitry. 
     Thin-film encapsulation may overlap the organic layer. The thin-film encapsulation may be formed from a layer of material in which organic dielectric material is interposed between two layers of inorganic dielectric material. 
     A strip of peripheral crack-stopper structures may run along an edge of the display and may surround the array of pixels. The crack-stopper structures may include parallel inorganic lines formed from a first inorganic dielectric layer such as an inorganic dielectric layer of the thin-film transistor circuitry. A strip of the organic layer may overlap the parallel inorganic dielectric lines and may run parallel to the edge of the display. The crack-stopper structures may have parallel polymer lines. The polymer lines may be overlapped by a second inorganic dielectric layer formed from the inorganic dielectric material of the thin-film encapsulation layer. 
    
    
     
       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 cross-sectional side view of a portion of an illustrative display in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative edge portion of an illustrative display with crack stopper border structures in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of illustrative crack stopper structures in accordance with an embodiment. 
         FIG. 5  is a top view of an illustrative chemical vapor deposition shadow mask having elongated openings overlapping an illustrative display panel area in accordance with an embodiment. 
         FIGS. 6 and 7  are top views of illustrative displays with crack-stopper border structures in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a tablet computer, laptop computer, a desktop computer, a monitor that includes an embedded computer, a monitor that does not include an embedded computer, a display for use with a computer or other equipment that is external to the display, a cellular telephone, a media player, a wristwatch device or other wearable electronic equipment, or other suitable electronic device. 
     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 . 
     Display  14  may be an organic light-emitting diode display or other suitable display. Configurations in which display  14  is an organic light-emitting diode display are sometimes described herein as an example. 
     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. 
     As shown in  FIG. 1 , display  14  may have an array of pixels  18  configured to display images for a user. Pixels  18  may each include one or more thin-film transistors  22  for forming a pixel control circuit and may each include a respective organic light-emitting diode  20  that is controlled by the pixel control circuitry of that pixel  18 . Display driver circuitry  24  may be formed from thin-film transistor circuitry and/or integrated circuit(s) and may be used in supplying image data and control signals to pixels  18  during operation of display  14 . 
       FIG. 2  is a cross-sectional side view of a portion of an illustrative inorganic light-emitting diode display such as display  14 . As shown in  FIG. 2 , display  14  may include a substrate such as substrate  30 . Substrate  30  may be formed from polymer (e.g., polyimide), glass, or other material. A layer of thin-film transistor circuitry for forming pixel circuits such as thin-film transistor circuitry  32  may be formed on substrate  30 . Circuitry  32  may include layers of material  34  such as buffer layers, semiconductor layers (e.g., a layer of polysilicon for forming silicon thin-film transistors, a layer of semiconducting oxide such as indium gallium zinc oxide for forming semiconducting-oxide thin-film transistors, or other suitable semiconductor layers), metal layers (e.g., metal traces for routing, vias, transistor terminals, capacitors, etc.), and dielectric layers (e.g., gate insulator, interlayer dielectric, and/or other inorganic dielectric layers and, if desired, organic dielectric layers). The thin-film circuitry of display  14  also includes organic layers of material such as organic layer  36 . Organic layer  36  may be formed on the circuitry of thin-film transistor layer  32 . Layer  36  may include one or more planarization layers such as planarization layers  38  and  40  and pixel definition layer  42 . Layers  38 ,  40 , and  42  may be formed from polymer. Pixel  18  may include organic light-emitting diode  20 . Diode  20  may have an anode  52  formed from a conductive layer on layer  40  within an opening in pixel definition layer  42 , may have organic emissive material  54  in the opening in pixel definition layer  42 , and may have a conductive cathode formed from cathode layer  44 . Via  56  may couple the thin-film circuitry of diode  20  to other thin-film transistor circuitry such as the circuitry of thin-film circuitry layer  32 . 
     To prevent degradation of the array of pixels  18  in display  14 , display  14  may be covered with a layer of thin-film encapsulation such as thin-film encapsulation layer  52 . Encapsulation layer  52  may help prevent intrusion of moisture and oxygen to the thin-film circuitry forming pixels  18 . Thin-film encapsulation layer  52  may include one or more inorganic layers and one or more organic layers. In the example of  FIG. 2 , thin-film encapsulation layer  52  includes an organic layer such as polymer layer  48  that is sandwiched between opposing upper and lower layers of inorganic dielectric  46 . Inorganic dielectric  46  may be formed from a material such as silicon nitride (as an example). The presence of polymer layer  48  helps decouple the upper silicon nitride layer in layer  52  from the lower silicon nitride layer in layer  52  and reduces degradation of encapsulation layer  52  due to cracking. 
       FIG. 3  is a cross-sectional side view of an edge portion of display  14 .  FIG. 3  shows how pixels  18  may be formed in an active area AA of display  14  (e.g., a central portion of display  14  that is configured to display images for a user) and shows how inactive border area IA, which runs around the periphery of display  14 , is free of pixels  18  and does not display images. 
     Thin-film circuitry layer  32  contains inorganic dielectric layers that extend into inactive area IA. Inorganic dielectric layer  46  of thin-film encapsulation layer  52  ( FIG. 2 ) also extends into inactive border area IA. In the absence of crack prevention structures, these two layers of inorganic dielectric may be vulnerable to cracking along the edge of display  14 . 
     Dam structures  36 D may help contain thin-film encapsulation layer  52  within the center of display  14  and may be formed from concentric peripheral lines that are patterned from layer  36 . 
     To prevent cracks and delamination of layers  46  and  32 , display  14  may be provided with a peripheral crack-stopper structure (sometimes referred to as a crack prevention structure, crack-stopper strip, crack-stopper line, etc.) such as peripheral crack-stopper structure  68 . Crack-stopper structure  68  may be used to prevent crack propagation and film delamination in layers of display  14  such as layer  32  and  46 . As shown in  FIG. 3 , crack stopper structures  68  may include a series of parallel lines  32 L of the inorganic dielectric layer in layer  32 . Lines  32 L form line-shaped gaps such as slots  62  in the inorganic dielectric layer portion of layer  32  that extends into inactive area IA. Each slot  62  may be interposed between a pair of adjacent lines  32 L in layer  32 . Slots  62  and lines  32 L may run parallel to peripheral edge E of display  14  (e.g., into the page in the orientation of  FIG. 3 ). 
     Crack-stopper structure  68  may include a portion of organic layer  36  such as peripheral strip  36 L. Strip  36 L may extend along peripheral display edge E and may cover slots  62  and lines  32 L. 
     Crack-stopper structure  68  may include one or more tapered lines  70  (lines with tapered cross-sectional profiles) on the strip of layer  36  that covers lines  32 L and slots  62  of crack-stopper structure (line)  68 . Lines  70  may run parallel to edge E and may be formed from a layer of organic material (e.g., polymer) such as a layer of negative photoresist that has been exposed and developed to form tapered sidewalls. The sidewalls of lines  70  taper outwardly at increasing distances from the surface of layer  36  (e.g., lines  70  have lower portions near layer  36  that are narrower than their upper portions). 
     Due to the presence of lines  70 , dielectric layer  46  is weaker (e.g., less dense and/or thinner) in areas such as gap  72  between a pair of adjacent lines  70  (e.g., where chemical reactions are starved for reactant) and/or is entirely missing in gaps such as gap  72  and/or other areas under the overhangs created by the tapered sidewalls of lines  70 . The presence of these weaker regions of layer  46  helps prevent cracks from propagating from the edge E of display  14  inwardly past crack-stopper structure  68  towards active area AA. At the same time, the presence of slots  62  in layer  32  helps prevent cracks in the inorganic dielectric of layer  32  in inactive area IA from propagating from the edge E of display  14  inwardly past crack-stopper structures  68 . Cracks-stopper structure  68  is patterned photolithographically, which relieves the burden that would otherwise be placed on the accuracy of the location of the edge of chemical vapor deposition mask  74 . As a result, the amount of margin required to accommodate chemical vapor deposition shadow mask  74  may be reduced and the size of the inactive border of display  14  may be reduced. 
     As shown in  FIG. 4 , lines  32 L may be characterized by width W 1 . Lines  32 L may be characterized by height H 1 . Each line  70  may have a width W 2  and a height H 2  and may be separated by a gap  72  of width W 3 . Crack stopper structures  68  may include any suitable number of lines  70  (e.g., 1-10, at least 3, at least 5, fewer than 15, etc.). Height H 1  of lines  32 L may be 0.8 microns, at least 0.4 microns, less than 1.2 microns, or other suitable height. Width W 1  may be 4 microns, at least 2 microns, less than 6 microns, or other suitable width. Slots  62  may have widths of 6 microns, at least 3 microns, less than 9 microns, or other suitable width. The height H 2  of lines  70  may be 3 microns, at least 2 microns, less than 4 microns, or other suitable height. The width W 2  of lines  70  may be 5 microns, at least 3 microns, less than 7 microns, or other suitable width. Width W 3  may be 5 microns, at least 2 microns, less than 8 microns, or other suitable width. The thickness of layer  36  may be, for example, 1-2 microns or other suitable thickness. 
     For satisfactory crack stopping, it may be desirable for the value of W 3  to be less than W 2 , or, more preferably less than half of W 2 . Other ratios of W 3  to W 2  may be used, if desired. 
     An illustrative chemical vapor deposition shadow mask that may be used to pattern layer  46  during chemical vapor deposition operations is shown in  FIG. 5 . As shown in  FIG. 5 , mask  74  may have a series of elongated rectangular openings  86  through which layer  46  is deposited. A common substrate layer (e.g., substrate  30 ) corresponding to an array of display panels may be overlapped by mask  74 , so that each opening  86  overlaps a corresponding row of pixel arrays (arrays of pixels  18 ). Each pixel array may be surrounded by a peripheral line of crack-stopper structures  68 . As shown by illustrative display area  14 ′ of  FIG. 5 , mask  74  may overlap the edge portion of each display that contains bond pads  80 . If desired, tape-based masking or other dielectric patterning schemes may be used in ensuring that bond pads  80  are not covered with dielectric. The configuration of  FIG. 5  is merely illustrative. By using an arrangement of the type shown in  FIG. 5  in which each panel has a peripheral crack-stopper structure  68  (crack-stopper line) surrounding its pixel array, it is not necessary to use an array of individual rectangular openings in mask  74 , thereby reducing the challenges associated with creating and aligning the edges of panel-sized mask openings with the structures of each display  14 . 
     The shape of crack-stopper structure  68  can be defined photolithographically, so a variety of potentially complex shapes can be used for the edge of the pixel array, as shown in the examples of  FIG. 6  (e.g., a rectangular display panel having rounded corners  90  and a peripheral strip of crack-stopper structures with corresponding rounded corners) and  FIG. 7  (e.g., a rectangular display panel and corresponding strip of crack-stopper structures having curved corners  90  and curved edge portions  92 ). 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20180605
Publication Date: 20200707
Grant Date: 20200707
Priority Date: 20170908
Inventors: YANG, CHIH JEN
MANDLIK, PRASHANT
CHANG, CHIA-HAO
WANG, CHIEN-CHUNG
TENG, TE-HUA
CHEN, YU CHENG
Assignee: APPLE INC
CPC Classifications: [{"code": "H10K59/122", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K50/84", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/88", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/131", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/1213", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/122", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/1213", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/3262", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/323", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5237", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/3246", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K59/8731", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 71408375