Patent Application
20240278533
This relates generally to electronic devices, and, more particularly, to electronic devices with displays.
Electronic devices often have displays. Portability may be a concern for some devices, which tends to limit available real estate for displays.
Electronic devices may be provided with displays. Displays may be used for displaying images for users. Displays may be formed from arrays of light-emitting diode pixels or other pixels. A device may have an organic light-emitting diode display or a display formed from an array of micro-light-emitting diodes (e.g., light-emitting diodes formed from crystalline semiconductor dies).
The displays may include flexible displays. Flexible displays may be bent about a bend axis to allow an electronic device to be folded and/or may be rolled around rollers. This allows the flexible display to be stored in an electronic device housing when a compact device arrangement is desired and to be pulled from within the electronic device housing when an enlarged display area is desired.
In devices with flexible displays, multilayer adhesive stacks may also be included. For example, a multilayer adhesive may attach a flexible display panel to the display cover layer in an electronic device. Including multiple layers of adhesive in the adhesive stack (as opposed to a single layer) provides more degrees of freedom for the tuning and optimization of the properties of the adhesive stack. The multilayer adhesive stack therefore has better performance than if only a single layer of adhesive is used.
The multilayer adhesive stack may include one or more layers of soft adhesive, hard adhesive, hard elastomer, hard polymer, and/or glass to optimize the mechanical and optical performance of the multilayer adhesive stack. Soft adhesive layers may be included to optimize lateral decoupling (e.g., during folding and unfolding) of the adhesive stack. Harder layers may be included to provide rigidity and prevent denting during impact events. One more adhesive layers may be included that are optimized for low temperature performance. One or more adhesion promotion layers may be included in the adhesive stack.
The multilayer adhesive stack may have different, coplanar materials in addition to different materials in the thickness direction. Softer materials may be included in a strip that overlaps a bend axis of the device, as one example.
Electronic devices may be provided with displays. Displays may be used for displaying images for users. Displays may be formed from arrays of light-emitting diode pixels or other pixels. For example, a device may have an organic light-emitting diode display or a display formed from an array of micro-light-emitting diodes (e.g., light-emitting diodes formed from crystalline semiconductor dies).
The displays may include flexible displays. Flexible displays may be bent about a bend axis to allow an electronic device to be folded and/or may be rolled around rollers. This allows the flexible display to be stored in an electronic device housing when a compact device arrangement is desired and to be pulled from within the electronic device housing when an enlarged display area is desired. An electronic device may incorporate both foldable and scrollable displays or may have foldable displays and/or scrollable displays in a housing that also includes one or more rigid displays.
A schematic diagram of an illustrative electronic device having a flexible display is shown in
Device 10 may include control circuitry 20. Control circuitry 20 may include storage and processing circuitry for supporting the operation of device 10. The storage and processing circuitry may include storage such as 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 20 may be used to gather input from sensors and other input devices and may be used to control output devices. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors and other wireless communications circuits, power management units, audio chips, application specific integrated circuits, etc. During operation, control circuitry 20 may use a display and other output devices in providing a user with visual output and other output.
To support communications between device 10 and external equipment, control circuitry 20 may communicate using communications circuitry 22. Circuitry 22 may include antennas, radio-frequency transceiver circuitry (wireless transceiver circuitry), and other wireless communications circuitry and/or wired communications circuitry. Circuitry 22, which may sometimes be referred to as control circuitry and/or control and communications circuitry, may support bidirectional wireless communications between device 10 and external equipment over a wireless link (e.g., circuitry 22 may include radio-frequency transceiver circuitry such as wireless local area network transceiver circuitry configured to support communications over a wireless local area network link, near-field communications transceiver circuitry configured to support communications over a near-field communications link, cellular telephone transceiver circuitry configured to support communications over a cellular telephone link, or transceiver circuitry configured to support communications over any other suitable wired or wireless communications link). Wireless communications may, for example, be supported over a Bluetooth® link, a WiFi® link, a wireless link operating at a frequency between 6 GHz and 300 GHz, a 60 GHz link, or other millimeter wave link, cellular telephone link, wireless local area network link, personal area network communications link, or other wireless communications link. Device 10 may, if desired, include power circuits for transmitting and/or receiving wired and/or wireless power and may include batteries or other energy storage devices. For example, device 10 may include a coil and rectifier to receive wireless power that is provided to circuitry in device 10.
Device 10 may include input-output devices such as devices 24. Input-output devices 24 may be used in gathering user input, in gathering information on the environment surrounding the user, and/or in providing a user with output. Devices 24 may include one or more displays such as display 14. Display 14 may be an organic light-emitting diode display, a liquid crystal display, an electrophoretic display, an electrowetting display, a plasma display, a microelectromechanical systems display, a display having a pixel array formed from crystalline semiconductor light-emitting diode dies (sometimes referred to as microLEDs), and/or other display. Configurations in which display 14 is an organic light-emitting diode display or microLED display are sometimes described herein as an example.
Display 14 may have an array of pixels configured to display images for a user. The pixels may be formed as part of a display panel that is flexible. A flexible display (e.g., an organic light-emitting diode display formed on a sheet of polymer or other flexible substrate and/or other flexible display pixel array structures) may be used to permit device 10 to be bent and/or stretched to allow display 14 to be folded and/or scrolled (e.g., to allow the visible area of display 14 to be expanded by moving display 14 in or out of a housing using a roller). A flexible display may be folded and unfolded about a bend axis. For example, a flexible (bendable) display in device 10 may be folded so that device 10 may be placed in a compact shape for storage and may be unfolded when it is desired to view images on the display.
Sensors 16 in input-output devices 24 may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into display 14, a two-dimensional capacitive touch sensor overlapping display 14, and/or a touch sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. If desired, sensors 16 may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors, depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices that capture three-dimensional images), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, and/or other sensors. In some arrangements, device 10 may use sensors 16 and/or other input-output devices to gather user input. For example, buttons may be used to gather button press input, touch sensors overlapping displays can be used for gathering user touch screen input, touch pads may be used in gathering touch input, microphones may be used for gathering audio input, accelerometers may be used in monitoring when a finger contacts an input surface and may therefore be used to gather finger press input, etc.
If desired, electronic device 10 may include additional components (see, e.g., other devices 18 in input-output devices 24). The additional components may include haptic output devices, audio output devices such as speakers, light-emitting diodes for status indicators, light sources such as light-emitting diodes that illuminate portions of a housing and/or display structure, other optical output devices, and/or other circuitry for gathering input and/or providing output. Device 10 may also include a battery or other energy storage device, connector ports for supporting wired communication with ancillary equipment and for receiving wired power, and other circuitry.
Display 14 may be mounted in housing 12. Housing 12 may form front and rear housing walls, sidewall structures, and/or internal supporting structures (e.g., a frame, an optional midplate member, etc.) for device 10. Glass structures, transparent polymer structures, and/or other transparent structures that cover display 14 and other portions of device 10 may provide structural support for device 10 and may sometimes be referred to as housing structures. For example, a transparent housing portion such as a glass or polymer housing structure that covers and protects a pixel array in display 14 may serve as a display cover layer for the pixel array while also serving as a housing wall on the front face of device 10. In configurations in which a display cover layer is formed from glass, the display cover layer may sometime be referred to as a display cover glass or display cover glass layer. The portions of housing 12 on the sidewalls and rear wall of device 10 may be formed from glass or other transparent structures and/or opaque structures. Sidewalls and rear wall structures may be formed as extensions to the front portion of housing 12 (e.g., as integral portions of the display cover layer) and/or may include separate housing wall structures.
Housing 12 may have flexible structures (e.g., bendable housing wall structures) and/or hinge structures such as hinge 30. Hinge 30 may have a hinge axis aligned with device bend axis 28. Hinge 30 and/or flexible housing structures that overlap bend axis 28 may allow housing 12 to bend about bend axis 28. For example, housing 12 may have a first portion on one side of bend axis 28 and a second portion on an opposing side of bend axis 28 and these two housing portions may be coupled by hinge 30 for rotational motion about axis 28.
As housing 12 is bent about bend axis 28, the flexibility of display 14 allows display 14 to bend about axis 28. In an illustrative configuration, housing 12 and display 14 may bend by 180°. This allows display 14 to be folded back on itself (with first and second outwardly-facing portions of display 14 facing each other). The ability to place device 10 in a folded configuration in this way may help make device 10 compact so that device 10 can be stored efficiently. When it is desired to view images on display 14, device 10 may be unfolded about axis 28 to place device 10 in the unfolded configuration of
Device 10 of
As shown in
Display cover layer 14CG may be formed from polymer, glass, crystalline materials such as sapphire, other materials, and/or combinations of these materials. To locally increase flexibility, a portion of layer 14CG that overlaps and extends along bend axis 28 may be locally thinned (e.g., this portion may be thinned relative to portions of layer 14CG that do not overlap bend axis 28). The thickness of layer 14CG (e.g., the non-thinned portions of layer 14CG) may be 50-200 microns, 70-150 microns, 100-200 microns, 100-600 microns, at least 100 microns, at least 200 microns, less than 600 microns, less than 400 microns, less than 250 microns, less than 150 microns, less than 100 microns, at least 50 microns, or other suitable thickness.
In the example of
Electrical components 32 may be mounted in the interior of device 10 (e.g., between display 14 and the rear of housing 12. Components 32 may include circuitry of the type shown in
In the example where display 14 is a foldable display (e.g., that bends around a bend axis as in
When the multilayer adhesive is formed above the light-emitting portion of display panel 14P (e.g., as in
The multilayer adhesive stack may be formed from a repeating unit of two or more adhesive layers.
The example in
In another example, shown in
If desired, the final repeating unit in the multilayer stack may not be included in its entirety.
In general, the multilayer adhesive 42 may include any desired number of adhesive layers (e.g., two layers, three layers, four layers, five layers, six layers, seven layers, eight layers, nine layers, ten layers, more than ten layers, more than twelve layers, more than twenty layers, more than forty layers, less than fifty layers, less than twenty layers, less than ten layers, less than six layers, between (inclusive) two and ten layers, etc.). The adhesive layers in multilayer adhesive may include a repeating unit of any desired number of layers (e.g., two layers, three layers, four layers, more than four layers, etc.). The final repeating unit on one side of the multilayer stack may optionally include less than all of the layers of the repeating unit.
In addition to including multiple layers in the thickness direction, the multilayer adhesive stack may be heterogenous within the XY-plane.
In yet another possible arrangement, the adhesive stack may include only a single layer in the thickness direction but may be heterogeneous within the XY-plane. Within the single adhesive layer, adhesive of a first material may overlap a bend axis of a foldable display (as one example). The adhesive of the first material may be surrounded (within the XY-plane) by an adhesive layer of a second material that is different than the first material. The first material may be softer than the second material.
Any of the multilayer adhesive stacks in
Generally, materials may be characterized by Young's modulus and tensile modulus (E) that measure tensile stress and tensile strain behavior and shear modulus (G) that measure shear stress and sheer strain. Modulus is a complex number with a real part characterizing the elastic behavior and an imaginary part characterizing viscous behavior. For example, tensile modulus (E) is a complex modulus (E*) with a real part (storage modulus E′) and an imaginary part (loss modulus E″). Shear modulus (G) is a complex modulus (G*) with a real part (storage modulus G′) and an imaginary part (loss modulus G″). Each layer in the multilayer adhesive stack may have a modulus (E′, E″, E*, G′, G″, or G*) (e.g., at room temperature and an oscillation frequency of 1 Hz) of less than 1 megapascal (MPa), less than 0.5 Mpa, less than 0.1 MPa, less than 0.05 MPa, between 0.01 MPa and 0.5 MPa, between 0.001 MPa and 0.1 MPa, between 0.1 MPa and 0.2 MPa, greater than 1 MPa, between 1 MPa and 1 gigapascal (GPa), between 1 MPa and 500 MPa, between 500 MPa and 1 GPa, between 500 MPa and 1.5 GPa, greater than 1 GPa, greater than 10 GPa, greater than 20 GPa, etc. Each layer in the multilayer adhesive stack may have a modulus at various other temperatures (e.g., −20 degrees Celsius, −40 degrees Celsius, 65 degrees Celsius, 80 degrees Celsius, greater than −20 degrees Celsius, greater than 0 degrees Celsius, greater than 20 degrees Celsius, between (inclusive) −20 degrees Celsius and 70 degrees Celsius, less than 70 degrees Celsius, less than 20 degrees Celsius, less than 0 degrees Celsius, less than −20 degrees Celsius, less than −40 degrees Celsius, etc.) of less than 1 megapascal (MPa), less than 0.5 Mpa, less than 0.1 MPa, less than 0.05 MPa, between 0.01 MPa and 0.5 MPa, between 0.001 MPa and 0.1 MPa, between 0.1 MPa and 0.2 MPa, greater than 1 MPa, between 1 MPa and 1 gigapascal (GPa), between 1 MPa and 500 MPa, between 500 MPa and 1 GPa, between 500 MPa and 1.5 GPa, greater than 1 GPa, greater than 10 GPa, greater than 20 GPa, etc.
Modulus characterizes small deformation behavior in the linear regime. Materials (e.g. materials used in the adhesive stack) may also be characterized by large deformation behavior. For example, each layer in the multilayer adhesive stack may have a shear stress (at room temperature and 500% shear strain using 200%/min strain rate) of between 5 kPa and 50 kPa, less than 1 kPa, less than 0.1 kPa, less than 10 kPa, less than 100 kPa, less than 1000 kPa, less than 1 GPa, more than 1 kPa, more than 0.1 kPa, more than 10 kPa, more than 100 kPa, more than 1000 kPa, more than 1 GPa, between 1 kPa and 100 kPa, etc. This example of shear stress test conditions is merely illustrative. In general, at any desired temperature (e.g., −20 degrees Celsius, −40 degrees Celsius, 65 degrees Celsius, 80 degrees Celsius, greater than −20 degrees Celsius, greater than 0 degrees Celsius, greater than 20 degrees Celsius, between (inclusive) −20 degrees Celsius and 70 degrees Celsius, less than 70 degrees Celsius, less than 20 degrees Celsius, less than 0 degrees Celsius, less than −20 degrees Celsius, less than −40 degrees Celsius, etc.), any desired strain level (e.g., 500%, 200%, 2000%, less than 200%, less than 500%, less than 2000%, more than 200%, more than 500%, more than 2000%, between 200%and 2000%, etc.), and any desired strain rate (e.g., 200%/min, 2000%/min, 50,000%/min, more than 200%/min, more than 2000%/min, more than 50,000%/min, less than 200%/min, less than 2000%/min, less than 50,000%/min, between 200%/min and 2000%/min, between 200%/min and 50,000%/min, etc.), each layer in the multilayer adhesive stack may have a shear stress of between 5 kPa and 50 kPa, less than 1 kPa, less than 0.1 kPa, less than 10 kPa, less than 100 kPa, less than 1000 kPa, less than 1 GPa, more than 1 kPa, more than 0.1 kPa, more than 10 kPa, more than 100 kPa, more than 1000 kPa, more than 1 GPa between 1 kPa and 100 kPa, etc.
Large strain behavior for materials used in the adhesive stack may be characterized by the secant modulus Esec (e.g., using the ASTM D412-16 test). The secant modulus is equal to, for any given strain, the engineering stress divided by the engineering strain. For each material herein, the secant modulus may be equal to 0-400% that material's E′ and/or G′.
Each layer in the multilayer adhesive stack may have a glass transition temperature that is greater than −20 degrees Celsius, greater than 0 degrees Celsius, greater than 20 degrees Celsius, between (inclusive) −20 degrees Celsius and 70 degrees Celsius, less than 70 degrees Celsius, less than 20 degrees Celsius, less than 0 degrees Celsius, less than −20 degrees Celsius, less than −40 degrees Celsius, etc. Each layer in the multilayer adhesive stack may have a transparency to visible light that is greater than 99.9%, greater than 99%, greater than 95%, greater than 90%, greater than 80%, less than 80%, less than 70%, less than 50%, between (inclusive) 90%and 100%, etc. Each layer in the multilayer adhesive stack may have a thickness that is less than 200 microns, less than 100 microns, less than 50 microns, less than 40 microns, less than 30 microns, less than 20 microns, less than 10 microns, less than 5 microns, less than 1 micron, greater than 1 micron, greater than 5 microns, between 1 and 40 microns, between 3 and 25 microns, etc. The total thickness of multilayer adhesive stack 42 may be less than 200 microns, less than 100 microns, less than 75 microns, less than 50 microns, greater than 35 microns, between 25 microns and 75 microns, between 25 microns and 200 microns, etc.
One illustrative multilayer adhesive stack may include alternating layers of soft adhesive and hard polymer. For example, adhesive layer 42A in
The hard polymer layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The hard polymer layers 42B may have a greater shear modulus at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The hard polymer layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events. The hard polymer material may be polyimide or polyethylene terephthalate, as examples.
Properties of the overall multilayer adhesive stack may be tuned by tuning the thicknesses of each individual layer within the stack. For example, the shear modulus of the multilayer adhesive stack at a given frequency may be determined according to the equation 1/P0=a/(P1)+b/(P2)+c/(P3)+d/(P4) . . . , where P0 is the shear modulus for the overall multilayer stack at the given frequency, P1 is the shear modulus for the first layer in the stack at the given frequency, a is the coefficient of linear combination for the first layer in the stack (e.g., a is equal to the thickness of the first layer divided by the total thickness of the stack), P2 is the shear modulus for the second layer in the stack at the given frequency, b is the coefficient of linear combination for the second layer in the stack (e.g., b is equal to the thickness of the second layer divided by the total thickness of the stack), etc.
The thicknesses of the individual layers may therefore be tuned to tune the overall properties of multilayer adhesive stack 42. Layers of the same material may have different thicknesses or the same thicknesses (e.g., a first layer 42A may have the same thickness or a different thickness than a different layer 42A). Layers of different materials may have different thicknesses or the same thicknesses (e.g., a layer 42A may have the same thickness or a different thickness than a layer 42B).
Another illustrative multilayer adhesive stack may include alternating layers of soft adhesive and hard elastomer. For example, adhesive layer 42A in
The hard elastomer layers 42B may have a greater modulus at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, etc.). The hard elastomer layers 42B may have a greater modulus at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The hard elastomer layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events.
Another illustrative multilayer adhesive stack may include alternating layers of soft adhesive and glass. For example, adhesive layer 42A in
The glass layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The glass layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The glass layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events.
Another illustrative multilayer adhesive stack may include alternating layers of soft adhesive and hard adhesive. For example, adhesive layer 42A in
The hard adhesive layers 42B may have a greater modulus at 1 Hz (E′, E″, E*, G′, G″, or G*) than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, etc.). The hard adhesive layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, etc.).
As one specific example, soft adhesive layers 42A may have a modulus of less than 1 MPa (e.g., between 0.5 MPa and 1 MPa) at an oscillation frequency of 10 kHz whereas hard adhesive layers 42B may have a modulus of greater than 1 MPa (e.g., between 1 MPa and 6 MPa) at an oscillation frequency of 10 KHz.
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The hard adhesive layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events.
Another illustrative multilayer adhesive stack may include alternating layers of adhesive optimized for normal temperatures (e.g., room temperature) and adhesive optimized for low temperatures (e.g., temperatures below 0 degrees Celsius). For example, adhesive layer 42A in
The glass transition temperature for adhesive layers 42B may be lower than the glass transition temperature for adhesive layers 42A (e.g., by 5 degrees Celsius or more, by 20 degrees Celsius or more, by 40 degrees Celsius or more, by 60 degrees Celsius or more, by 100 degrees Celsius or more, etc.).
The layers optimized for low temperatures may have shear stress (at room temperature and 500% shear strain using 200%/min strain rate) of between 1 kPa and 30 kPa, between 1 kPa and 50 kPa, less than 1 kPa, less than 0.1 kPa, less than 10 kPa, less than 100 kPa, less than 1000 kPa, less than 1 GPa, more than 1 kPa, more than 0.1 kPa, more than 10 kPa, more than 100 kPa, more than 1000 kPa, more than 1 GPa between 1 kPa and 100 kPa, etc. The layers optimized for low temperatures may have shear stress (at −20 degrees Celsius and 500% shear strain using 200%/min strain rate) of between 1 kPa and 30 kPa, between 1 kPa and 50 kPa, less than 1 kPa, less than 0.1 kPa, less than 10 kPa, less than 100 kPa, less than 1000 kPa, less than 1 GPa, more than 1 kPa, more than 0.1 kPa, more than 10 kPa, more than 100 kPa, more than 1000 kPa, more than 1 GPa between 1 kPa and 100 kPa, etc. The layers optimized for low temperatures may have shear stress (at 0 degrees Celsius and 500% shear strain using 200%/min strain rate) of between 1 kPa and 30 kPa, between 1 kPa and 50 kPa, less than 1 kPa, less than 0.1 kPa, less than 10 kPa, less than 100 kPa, less than 1000 kPa, less than 1 GPa, more than 1 kPa, more than 0.1 kPa, more than 10 kPa, more than 100 kPa, more than 1000 kPa, more than 1 GPa between 1 kPa and 100 kPa, etc.
Including adhesive layers that are optimized for different temperatures may optimize the performance of the multilayer adhesive stack across a wide range of temperatures.
Another illustrative multilayer adhesive stack may include alternating layers of soft adhesive and ceramic. For example, adhesive layer 42A in
The ceramic layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The ceramic layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The ceramic layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events.
The alternating adhesive layers and ceramic layers may be formed by alternating adhesive and ceramic lamination. Alternatively, the alternating adhesive layers and ceramic layers may be formed by alternating ceramic thin film deposition and adhesive lamination.
Another illustrative multilayer adhesive stack may include alternating layers of soft adhesive and fiber-doped polymer. For example, adhesive layer 42A in
The fiber-doped polymer layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The fiber-doped polymer layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The fiber-doped polymer layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events (e.g., fast impact events or slower impact events caused by a pencil and/or fingernail). The stiffer fiber-doped polymer layers may also protect the underlying display layers from damage.
Another illustrative multilayer adhesive stack may include alternating layers of soft adhesive and optical epoxy. For example, adhesive layer 42A in
The optical epoxy layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The optical epoxy layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The optical epoxy layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events (e.g., fast impact events or slower impact events caused by a pencil and/or fingernail). The stiffer fiber-doped polymer layers may also protect the underlying display layers from damage.
Another property that may vary between the layers in the multilayer adhesive stack (instead of or in addition to modulus) is dielectric constant. The dielectric constants between different adhesive layers in the multilayer adhesive may differ by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 3 or more, a factor of 5 or more, etc.).
In addition to modulus and/or dielectric constant, another property that may vary between the layers in the multilayer adhesive stack is color. In particular, dye and/or pigment may be added to some or all of the adhesive layers in the adhesive stack for color correction. When dye and/or pigment is included in an adhesive layer, the dye and/or pigment may be uniformly distributed throughout the adhesive layer or may be more concentrated in a first portion of the adhesive layer than a second portion of the adhesive layer.
In addition to modulus and/or dielectric constant, other properties that may vary between the layers in the multilayer adhesive stack are optical diffusivity, transmittance, reflectance, and haze.
In a multilayer adhesive stack that varies in the lateral direction (within the XY-plane) in addition to the thickness direction (e.g., as in
In
The example in
In yet another possible arrangement, the adhesive stack may include only a single layer in the thickness direction (e.g., in the Z-direction in
The example of two high-adhesion layers of the same type being used in the multilayer adhesive stack is merely illustrative. If desired, high-adhesion layers formed from different materials may be included in the multilayer adhesive stack. As one specific example, a first high-adhesion layer at the top of the stack may be optimized to adhere to a glass layer that is formed above the multilayer adhesive stack. A second high-adhesion layer at the bottom of the stack may be optimized to adhere to a polymer layer that is formed below the multilayer adhesive stack. The first and second high-adhesion layers may be formed from different materials.
Each adhesive layer 42A may be thinner than adhesive layer 42B. Each adhesive layer 42A may have a thickness that is less than 50% of the thickness of adhesive layer 42B, may have a thickness that is less than 30% of the thickness of adhesive layer 42B, may have a thickness that is less than 15% of the thickness of adhesive layer 42B, may have a thickness that is less than 10% of the thickness of adhesive layer 42B, may have a thickness that is less than 5% of the thickness of adhesive layer 42B, etc. Adhesive layer 42B may be formed from a softer material (e.g., having smaller modulus at the same conditions) than adhesive layers 42A. As one specific example, soft adhesive layer 42B may have a modulus of less than 0.1 MPa (e.g., between 0.01 MPa and 0.1 MPa) at an oscillation frequency of 1 Hz whereas adhesive layers 42A may have a modulus of greater than 0.1 MPa (e.g., between 0.1 MPa and 0.3 MPa) at an oscillation frequency of 1 Hz.
In some applications, it may be desirable for the multilayer adhesive stack to block ultraviolet light. In these cases, a thin layer of ultraviolet light blocking adhesive may be included in addition to a soft adhesive layer.
Soft adhesive layer 42A may be optimized for the desired mechanical properties of the multilayer adhesive stack. Ultraviolet light blocking adhesive layer 42B, meanwhile, is optimized for the desired optical properties of the multilayer adhesive stack. Ultraviolet light blocking adhesive layer 42B may block more than 30% of ultraviolet light, more than 50% of ultraviolet light, more than 70% of ultraviolet light, more than 80% of ultraviolet light, more than 90% of ultraviolet light, more than 95% of ultraviolet light, more than 99% of ultraviolet light, etc. Said another way, ultraviolet light blocking adhesive layer 42B may transmit less than 70% of ultraviolet light, less than 50% of ultraviolet light, less than 30% of ultraviolet light, less than 20% of ultraviolet light, less than 10% of ultraviolet light, less than 5% of ultraviolet light, less than 1% of ultraviolet light, etc. This may prevent ultraviolet light from damaging an underlying display panel (e.g., as in
Adhesive layer 42B may be thinner than adhesive layer 42A. Adhesive layer 42B in
In the example of
Adhesive layers 42A and 42B (optimized for normal temperatures) in the multilayer adhesive stack may have a glass transition temperature that is greater than −20 degrees Celsius, greater than 0 degrees Celsius, greater than 20 degrees Celsius, between (inclusive) −20 degrees Celsius and 70 degrees Celsius, less than 70 degrees Celsius, etc. Adhesive layers 42C (optimized for low temperatures) in the multilayer adhesive stack may have a glass transition temperature that is less than 0 degrees Celsius, less than −20 degrees Celsius, less than −40 degrees Celsius, etc.
To further optimize the multilayer adhesive stack, the multilayer adhesive stack may also include an adhesive layer that is optimized for high damping and cushioning performance under high frequency of stress to reduce the impact force to the delicate layers in the display during impact events.
Adhesive layer 42B in
To ensure adequate adhesion between adjacent layers within the multilayer adhesive stack, one or more adhesion promoting layers may be included in the multilayer adhesive stack.
Adhesion promoting layer 42B may be formed from a material that has a high adhesion to both adhesive layers 42C and 42A. With the presence of adhesion promoting layer 42B, the adhesion between adhesive layers 42A and 42C may be stronger than if adhesive layers 42A and 42C were attached directly together (e.g., as in
The order of the layers in the multilayer adhesive stacks shown herein are merely illustrative. The orders of the layers within the multilayer adhesive stacks may be changed if desired.
It should be understood that the interface between layers within adhesive 42 may not necessarily be a sharp interface with a well defined boundary. Instead, the interface between layers 42 within adhesive 42 may sometimes follow a composition gradient.
The gradient can be in the vertical direction and/or in the horizontal direction.
Gradient interface layer 421 may be formed naturally due to inter-diffusion between adjacent layers (e.g., immediately after fabrication and/or slowly over time). Alternatively, gradient interface layer 421 may be introduced by design to achieve certain performance benefits.
The gradient may be a material/chemistry gradient (e.g., a gradient of additive concentration such as a nanoparticle concentration, material type, molecular weight, polymer cross-linking level, polymer chain branching, etc.) and/or a property gradient (e.g., a gradient of modulus, glass transition temperature, refractive index, etc.).
Gradient interface layer 421 has a thickness 52 (in the direction of the gradient). Thickness 52 may be less than 1 centimeter, less than 1 millimeter, less than 1 micron, less than 1 nanometer, greater than 1 centimeter, greater than 1 millimeter, greater than 1 micron, greater than 1 nanometer, etc.). The gradient across thickness 52 may be linear or non-linear.
As shown in
The magnitude of the gap between first and second adhesive layers 42A in
Any of the multilayer adhesive stacks in
In any of the adhesive stacks shown in
If desired, any of the adhesive stacks described herein may include an edge sealant to enclose the periphery of the main body of the adhesive stack.
The multilayer adhesive stack may be formed from a repeating unit of two or more adhesive layers.
In
Edge sealant 102 may be formed by attaching a separate material to the periphery of the adhesive stack. The material of edge sealant 102 may be an adhesive material or may be a non-adhesive material. When edge sealant 102 is an adhesive material, the edge sealant may be in direct contact with the edge of layers 42A and 42B. When edge sealant 102 is a non-adhesive material, the edge sealant may be attached to the edge of layers 42A and 42B with a separate edge adhesive layer or may be attached to the edge of layers 42A and 42B directly without a separate edge adhesive layer (e.g., layers 42A and/or 42B may adhere the non-adhesive edge sealant to the edge of layers 42A and 42B).
In another possible arrangement, edge sealant 102 may be formed by an edge surface modification of layers 42A and 42B. As one example, a chemical agent may be exposed to the edge of layers 42A and 42B to modify layers 42A and 42B and create edge sealant 102. As another example, the edge of layers 42A and 42B may be plasma treated to modify layers 42A and 42B and create edge sealant 102.
Edge sealant 102 may have a similar modulus (E′, E″, E*, G′, G″, or G*) at 1 KHz as adhesive layers 42A (e.g., the modulus of edge sealant 102 may be within 5% of the modulus of adhesive layers 42A at 1 Hz, the modulus of edge sealant 102 may be within 10% of the modulus of adhesive layers 42A at 1 Hz, the modulus of edge sealant 102 may be within 20% of the modulus of adhesive layers 42A at 1 Hz, the modulus of edge sealant 102 may be within 50% of the modulus of adhesive layers 42A at 1 Hz, the modulus of edge sealant 102 may be within 100% of the modulus of adhesive layers 42A at 1 Hz, etc.). Edge sealant 102 may have a similar modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz as adhesive layers 42A (e.g., the modulus of edge sealant 102 may be within 5% of the modulus of adhesive layers 42A at 10 kHz, the modulus of edge sealant 102 may be within 10% of the modulus of adhesive layers 42A at 10 kHz, the modulus of edge sealant 102 may be within 20% of the modulus of adhesive layers 42A at 10 kHz, the modulus of edge sealant 102 may be within 50% of the modulus of adhesive layers 42A at 10 kHz, the modulus of edge sealant 102 may be within 100% of the modulus of adhesive layers 42A at 10 kHz, etc.).
The example in
In another example, shown in
In general, any of the adhesive stacks described herein may optionally have an edge sealant of the type described in connection with
In another possible arrangement, shown in
In
illustrative and other non-linear interfaces may be used if desired (e.g., a sinusoidal interface, an interface with rectangular protrusions instead of triangular protrusions as in
In
The diagonal interface of
Due to the diagonal interface 108 between layers 42A and 42B, each one of layers 42A and 42B has a varying thickness at the interface. In
In addition to multilayer adhesive 42, one or more perimeter coatings 112 may be included between display cover layer 14CG and display panel 14P.
Adhesive stack 42 may have a tile pattern or a wire frame to improve reworkability.
High-index nanoparticles may optionally be included in one or more layers within multilayer adhesive 42 to mitigate a refractive index difference between layers of different types. Consider an example (shown in
The ceramic layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The ceramic layers 42B may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42A provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The ceramic layers 42B make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events.
The alternating adhesive layers and ceramic layers may be formed by alternating adhesive and ceramic lamination. Alternatively, the alternating adhesive layers and ceramic layers may be formed by alternating ceramic thin film deposition and adhesive lamination.
The bulk material 116 of soft adhesive layers 42A may have an index of refraction that is lower than the index of refraction of ceramic layers 42B. This refractive index difference may cause undesired total internal reflection that prevents some or all of the light from display panel 14P from being emitted through the adhesive stack.
To mitigate the refractive index difference between bulk material 116 and ceramic layers 42B, soft adhesive layers 42A may include high-index nanoparticles 118 in addition to the bulk material 116. The high-index nanoparticles 118 (sometimes referred to as particles 118, high-index particles 118, etc.) may have a greater refractive index than bulk material 116 and/or ceramic layers 42A. When the high-index nanoparticles 118 are included in bulk material 116, the effective refractive index of layers 42A (sometimes referred to as the total refractive index, overall refractive index, average refractive index, etc.) is increased (e.g., to a magnitude that is equal to or similar to the refractive index of layers 42B), thus mitigating the undesired total internal reflection at the interfaces between layers 42A and 42B.
As specific examples, bulk material 116 may have a refractive index of 1.5 whereas ceramic layers 42B may have a refractive index of 1.77. The high-index nanoparticles 118 may have a refractive index of 1.9. The high-index nanoparticles may be included in bulk material 116 at a concentration that causes the soft adhesive layers 42A to have an effective refractive index of 1.77.
The difference in refractive index between bulk material 116 and ceramic layers 42B may be greater than 0.05, greater than 0.10, greater than 0.15, greater than 0.20, greater than 0.25, greater than 0.30, etc. The difference in refractive index between bulk material 116 and high-index nanoparticles 118 may be greater than 0.05, greater than 0.10, greater than 0.15, greater than 0.20, greater than 0.30, greater than 0.40, etc. The difference in refractive index between layers 42A and 42B may be less than 0.10, less than 0.05, less than 0.03, less than 0.01, etc.
The example herein of nanoparticles 118 having a higher index of refraction than bulk material 116 is merely illustrative. If desired, nanoparticles 118 may have a lower index of refraction than bulk material 116 to lower the total index of refraction of layer 42A.
Examples have been described herein where a multilayer adhesive stack is interposed between display panel 14P and display cover layer 14CG. Instead or in addition, any multilayer adhesive stack of the type described herein may be interposed between display cover layer 14CG and a hard coat (HC) layer.
As shown in
The soft adhesive layer 42B may have a modulus (E′, E″, E*, G′, G″, or G*) (e.g., at room temperature and an oscillation frequency of 1 Hz) of less than 1 megapascal (MPa), less than 0.5 Mpa, less than 0.1 MPa, less than 0.05 MPa, between 0.01 MPa and 0.5 MPa, between 0.001 MPa and 0.1 MPa, between 0.1 MPa and 0.2 MPa, etc. The PET layer 42B may have a modulus (E′, E″, E*, G′, G″, or G*) (e.g., at room temperature and an oscillation frequency of 1 Hz) of greater than 50 GPa, greater than 100 GPa, greater than 200 GPa, greater than 250 GPa, greater than 300 GPa, etc.
The PET layers 42A may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 1 Hz than soft adhesive layers 42A (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.). The PET layers 42A may have a greater modulus (E′, E″, E*, G′, G″, or G*) at 10 kHz than soft adhesive layers 42B (by a factor of 1.2 or more, a factor of 1.5 or more, a factor of 2 or more, a factor of 10 or more, a factor of 100 or more, a factor of 1,000, a factor of 10,000 or more, a factor of 100,000 or more, etc.).
The soft adhesive layers 42B provide a low shear modulus in the lateral direction in order to optimize decoupling during folding of the display. The PET layers 42A make the multilayer adhesive stack more rigid in the thickness direction to prevent denting of the adhesive stack during impact events.
To avoid film yielding, each PET layer 42A may have a thickness that is less than 50 microns, less than 40 microns, less than 30 microns, less than 25 microns, less than 20 microns, etc. Each soft adhesive layer 42B may have a thickness that is less than 50 microns, less than 40 microns, less than 30 microns, less than 25 microns, less than 20 microns, etc. As shown in
One or more layers may be included below display panel 14P in
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.
This application is a continuation-in-part of U.S. non-provisional patent application Ser. No. 17/716,911, filed Apr. 8, 2022, which claims the benefit of U.S. provisional patent application No. 63/197,882, filed Jun. 7, 2021, which are hereby incorporated by reference herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 63197882 | Jun 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17716911 | Apr 2022 | US |
| Child | 18653598 | US |
